Me ctiani c s De ID t .
The Penton Publishing Co.
Cleveland, O., U. S. A.
Publishers of
The Foundry The Iron Trade Review
Marine Review Daily Metal Trade
Power Boating Abrasive Industry
AMERICAN
MALLEABLE
CAST IRON
By H. A. Schwartz
First Edition
Published by
The Penton Publishing Co.
Cleveland, Ohio
1922
Library
Copyright in the United States
and
Entered at Stationers' Hall, London
1922
The Penton Publishing Co.
Cleveland, Ohio
THE PENTON PRESS CO., CLEVELAND
THE MEMORY OF
ALLEN SMITH BIXBY
Wi:OSE INSTRUCTION, CO-OPERATION AND ADVICE I OWE THE EARLY
OPPORTUNITIES WHICH MADE THIS BOOK POSSIBLE
IT IS AFFECTIONATELY DEDICATED
588565
PREFACE
THE literature of malleable cast iron, in the American sense
of that term, is limited to a single book first issued about
10 years ago and now out of print, and to a series of articles
of great diversity of character and quality in the technical publi-
cations of this country and Europe. Much of the most valuable
scientific matter is buried in the purely scientific press, frequently
under titles which do not suggest its application to any one
not a specialist in metallurgy.
Under these circumstances the preparation of a new book
dealing with American malleable cast iron in theory and
practice may serve a useful purpose as summarizing and rec-
ording, so far as any book can, the contemporary state of the
art in the metallurgy of this product.
If in the following pages the specialist finds much which ap-
pears to him elemental or trivial or the non technical reader finds
matter which appears too complex, the author must plead in ex-
tenuation his desire to prepare a book to suit many kinds of
readers.
This has necessitated the inclusion of much elementary
matter both in metallurgy and mechanics which will be useful
only in acquainting -the lay reader with the interpretation of
terms and data which form the every day vocabulary of the
technician.
On the other hand it has seemed that in order that the
reader might secure full value from a reading of these
pages no known fact or theory should be excluded merely in the
interest of simplicity.
Feeling that no single individual is justified in the belief that
his own views are final in so complex a subject the author
has not hesitated to refer freely to the literature and even to
record opinions contrary to his own. So far as possible due
credit has been given in all such cases.
Guided by the injunction of Leonardo da Vinci, "Con-
firm your statements by examples and not by assertions", it has
VII
been the author's constant effort to- record facts rather than
opinions wherever possible. This has been particularly true
in the chapters dealing with manufacturing methods. In these
chapters the record is one of what has been rather than of what
might be accomplished. Much of the experimental work re-
ferred to is the work of the author's associates. In this connec-
tion special recognition must be given to the very unusual micro-
graphs which are the work of Harrie R. Payne, chief chemist
and metallographer of the author's laboratory.
Many of the author's friends within the malleable industry,
in the organization of which he has the honor to be a member,
and among the business connections of that association have
contributed valuable information.
Whenever possible credit has been assigned. In some cases
where for obvious reasons it was- improper to identify the in-
formation the latter has consented to the anonymous presenta-
tion of his material. The co-operation of the American Malle-
able Castings Association in furnishing statistics and of the
late Thos. Devlin of Philadelphia, and Alfred E. Hammer,
Branford, Conn., in contributing historic matter from their long
experience is especially worthy of grateful acknowledgment.
If the following pages contain any information calculated
to dispel the many misconceptions as to malleable cast iron and
to acquaint the interested reader accurately with the proper-
ties and methods of manufacture of this interesting, valuable and
characteristically American product, the author's labor will
have been richly repaid.
H. A. SCHWARTZ
VIII
CONTENTS
CHAPTER I
Early History of Ironmaking 1
CHAPTER II
Development of Malleable Industry in the United States 15
CHAPTER III
Metallurgy of Malleable Iron 41
CHAPTER IV
General Manufacturing and Plant 71
CHAPTER V
Melting Stock 91
CHAPTER VI
Fuel and Refractories 109
CHAPTER VII
Air Furnace Melting 135
CHAPTER VIII
Electric Furnace Melting 159
CHAPTER IX
Cupola and Open-hearth Melting 175
CHAPTER X
Annealing Practice 189
CHAPTER XI
Principles of Annealing 213
CHAPTER XII
Molding and Patternmaking .* 233
CHAPTER XIII
Cleaning and Finishing 249
CHAPTER XIV
Inspecting and Testing " 267
CHAPTER XV
Tensile Properties 287
CHAPTER XVI
Compression, Bending and Shear 303
CHAPTER. XVII
Fatigue, Impact, Hardness and Wear 315
CHAPTER XVIII
Plastic Deformation 339
CHAPTER XIX
Thermal and Electrical Properties 371
Selected Bibliography 385
Index 403
IX
LIST OF ILLUSTRATIONS
PAGE
Fig. 1 — A meteorite - in the American Museum of Natural History,
New York, brought from Greenland by Admiral Peary 2
Fig. 2 — A primitive furnace, 1500 B. C. The illustration was re-
produced from an Egyptian wall painting
Fig. 3 — One of the earliest blast furnaces 4
Fig. 4 — An early American blast furnace 7
Fig. 5 — Reaumur's foundry in 1724. One furnace has just been
emptied and the blast is being applied to the other
Fig. 6 — Statue of Seth Boyden, erected in the city park of Newark,
N. JM by citizens in memory of the man who laid the founda-
tion for the malleable industry in the United States 12
Fig. 7— Seth Boyden 16
Fig. 8 — J. H. Barlow, Boyden's successor 16
Fig. 9 — Distribution of malleable iron foundries in the United
States. The dots represent the location of malleable foundries
according to data compiled for government use : . . . . 20
Fig. 10 — Map showing location of principle sellers of malleable iron
castings in the United States 22
Fig. 11 — Comparison of production of steel and malleable iron
castings 24
Fig. 12 — Familiar figures in the development of the malleable in-
dustry in the United States 28
Fig. 13 — Three metallurgists who have been closely identified with
the technical advancement of the industry 32
Fig. 14 — The names of these men are linked with the rise of the
American malleable industry 34
Fig. 15 — Austenite and ledeburite in manganiferous white cast iron 42
Fig. 16 — Martensite in quenched white cast iron 42
Fig. 17— Troostite in steel 43
Fig. 18 — Pearlite in incompletely annealed malleable 43
Fig. 19 — Spheroidized pearlite 44
Fig. 20 — Graphite in gray iron 44
Fig. 21 — Soft gray cast iron 45
Fig. 22 — Malleable cast iron 45
Fig. 23 — Benedict's diagram recording the equilibrium conditions in
terms of temperature and agraphic (non graphitic) carbon.
It is based on Benedict's principle, somewhat modified 47
Fig. 24— A further modification of Benedict's diagram indicating
the results of recent research work 51
Fig. 25 — Graphite crystals in malleable made from hard iron con-
taining graphite 54
Fig. 26 — Unannealed hard iron. The structure is always dendritic
but varies slightly with the carbon content 55
XI
LIST OF ILLUSTRATIONS— Continued
PAGE
Fig. 27 — Effect of silicon in relation to carbon on malleable. This
graph is based on data from Thrasher's determinations 56
Fig. 28 — Beginning of graphitization after one half hour at 1700
degrees Fahr 58
Fig. 29 — Progress of graphitization after \l/2 hours at 1700 degrees
Fahr 58
Fig. 30 — Progress of graphitization after 3l/2 hours at 1700 de-
grees Fahr 60
Fig. 31 — Equilibrium at 1700 degrees Fahr. after 70 hours 60
Fig. 32 — Imperfect attainment of equilibrium below A± due to too
short a time 62
Fig. 33 — Normal malleable iron, metastable equilibrium below At . . 62
Fig. 34 — Graphite crystals produced by annealing at 2100 degrees
Fahr , 64
Fig. 35 — Manganese sulphide in a malleable cast iron. The arrows
point to MnS 64
Fig. 36 — Chart showing conversion of combined carbon into temper
carbon 66
Fig. 37 — Changes of metallographic composition during the freezing
and annealing of white iron 69
Fig. 38 — Organization chart for malleable foundry 72
Fig. 39 — A good example of the approved style of architecture for
a malleable foundry built a generation ago 74
Fig. 40 — Exterior view of a large malleable plant built about 1917 76
Fig. 41 — Coreroom of a modern malleable plant showing roof con-
struction designed to facilitate removal of fumes and gases
and to afford good natural lighting 78
Fig. 42 — Interior of the annealing department of a modern
malleable foundry 80
Fig. 43 — Chart showing cycle of principal operations in a malle-
able plant 83
Fig. 44 — Chart showing division of labor in a typical foundry .... 84
Fig. 45 — Molding floor in a well organized American malleable
foundry 86
Fig. 45 — The stock yard usually is served by a traveling crane 92
Fig. 47— Map showing location of principal ore fields, and coke and
charcoal blast furnace producing malleable pig iron 95
Fig. 48 — An open pit iron ore mine on the Mesabi range. Ores in
this district are suitable for making malleable pig 98
Fig. 49 — An ore loading dock at one of the ports on Lake
Superior 100
XII
LIST OF ILLUSTRATIONS— Continued
PAGE
Fig. 50 — An ore unloading dock at a Lake Erie port, where the
ore is transferred from ore carrier to railroad car 102
Fig. 51 — A charcoal blast furnace in Michigan where malleable pig
iron is made 104
Fig. 52 — A typical coke blast furnace in the Mahoning valley 106
Fig. 53 — Map showing location of principal resources of metallurgi-
cal fuel in the United States .' 110
Fig. 54 — A modern coal tipple in West Virginia 112
Fig. 55 — Picking table in a coal tipple showing facilities for remov-
ing slate, sulphur, etc., by hand 114
Fig. 56 — Adjustable loading boom which places coal in car without
breakage 114
Fig. 57 — A modern by-product coke plant which is engaged in
making foundry fuel 116
Fig. 58 — A typical scene at a beehive coke oven plant in- the Con-
nellsville region 118
Fig. 59 — Cross section of a modern gas producer 120
Fig. 60 — A scene in an important oil field in Oklahoma 122
Fig. 61 — Operations in a molding sand pit 125
Fig. 62 — Hauling sand from a pit 125
Fig. 63 — Map showing the principal sources of molding sand, fire-
clay and brick in the United States 126
Fig. 64 — Open fireclay pit covering over 10 acres and with bed
of clay from 25 to 40 feet thick '. 128
Fig. 65 — A plant in Missouri showing round, down-draft kilns,
factory and stock sheds 130
Fig. 66 — A repress room in a Missouri firebrick plant, showing
machines in which stiff mud firebrick are made 132
Fig. 67 — Firebrick and special fireclay shapes in kiln ready to be
burned 133
Fig. 68 — Sectional drawings showing construction of typical air
furnace 136
Fig. 69 — Graph showing recombination of carbon in pig iron,... 139
Fig. 70 — The roof of the modern air furnace is almost straight.. 140
Fig. 71 — A waste heat boiler connected to two air furnaces. Note
that coal for auxiliary firing is on hand 142
Fig. 72 — Gray sprue 148
Fig. 73 — Gray sprue showing white patches. Characteristic of less
but still excessive carbon and silicon 148
Fig. 74 — Moderately mottled sprue characteristic of carbon, silicon
and temperature suited to very small work 148
XIII
LIST OF ILLUSTRATIONS— Continued
PAGE
Fig. 75 — Normal sprue for metal of the higher carbon ranges of
specification metal in average work 149
Fig. 76 — Similar to Fig. 74 but lower in carbon 149
Fig. 77 — Similar to Fig. 76 but quite low carbon 149
Fig. 78 — ''High" iron i.e. metal low in carbon, silicon and man-
ganese. Fracture granular throughout and edge showing blow-
holes 149
Fig. 79 — Changes of metal after tapping 151
Fig. 80 — A powdered coal atatchment for an air furnace 155
Fig. 81 — Cupola producing molten iron — the starting point of the
Kranz triplex process 160
Fig. 82 — Two-ton side-blow converter producing liquid steel from
cupola metal in triplex process 162
Fig. 83. — Transfer train consisting of electric motor car and
trailer with' crane ladle. This equipment is used in carrying
cupola and converter metal to the electric furnaces 165
Fig. 84 — Heroult electric furnace in which cupola and converter
metal is charged for final step in triplex process 168
Fig. 85 — Heroult furnace tilted for pouring 170
Fig. 86 — Pouring side of open-hearth furnace for malleable iron.. 176
Fig. 87 — Charging side of open-hearth furnace in malleable plant . . 178
Fig. 88 — Design of a modern, stationary open-hearth steel furnace. 180-181
Fig. 89 — Separator plate designed to eliminate use of packing
with annealing pots 190
Fig. 90 — A view of the annealing department in a modern malleable
castings plant 194
Fig. 91 — Charging trucks facilitate the handling of pots to and
from the annealing furnaces 195
Fig. 92 — The interior of the powdered coal mill of a modern malle-
able plant 197
Fig. 93 — While most of the plants in the United States employ
annealing furnaces similar to those shown in Fig. 90, a few
plants use the pit type, illustrated above 198
Fig. 94 — Diagram showing the distribution of heat in a continuous-
type annealing furnace 200
Fig. 95 — Interior of continuous-type annealing furnace looking
toward the entrance end 200
Fig. 96 — Single section of combustion chamber of continuous type
annealing furnace 201
Fig. 97 — A sectional plan and elevation of a double-chamber, car-
type tunnel kiln for annealing malleable iron castings. The fir-
XIV
LIST OF ILLUSTRATIONS— Continued
PAGE
ing zones are diagonally opposite each other 202
Fig. 98 — Rim of a casting containing most of the usual defects
due to annealing. Etched with picric acid, magnified 100 diam- '
eters and subsequently reduced one-fourth on erfgraving ....216,217
Fig. 99 — Increase in carbon content at increasing depths below' the
surface of malleable cast iron .........'... 223
Fig. 100— Graph showing effect of removing one-sixteenth inch,
decarborized surface in specimens of various diameters on the
tensile properties of the metal 225
Fig. 101 — Graph showing effect of varying degrees of decarburi-
zation on tensile properties of malleable cast iron 226
Fig. 102 — Equilibrium curves illustrating the reactions between car-
bon, iron and oxygen, after the data of Matsubara 230
Fig. 103 — Methods of mounting patterns 234
Fig. 104 — Squeezer-type molding machine and mold and pattern
equipment in place 236
Fig. 105 — Stripper and rollover -type molding machines 238
Fig. 106 — Curve showing contraction in cooling from solidification
to room temperature 238
Fig. 107 — Graph showing the per cent of contraction of malleable
from pattern size 240
Fig. 108 — Graphs showing relation of annealing upon the density
of the metal 241
Fig. 109 — Casting with thin disk and thick hub, showing probable
point of rupture 242
Fig. 1-10 — Type of casting with thin disk center and thick rim.. 242
Fig. Ill — Dendrite (about half size) from shrink in hard iron
ingot 8 inches in . diameter by 20 inches high which was
poured without feeding 244
Fig. 112 — Typical gate for malleable castings showing strainer, core
and skimmer gates for furnishing clean metal for feeders and
producing sound castings 246
Fig. 113 — Tumbling barrels are used for cleaning castings 250
Fig. 114 — Sand blast equipment is used for removing sand from
castings 252
Fig. 115 — Sorting and inspecting small castings are important opera-
tions in many plants 252
Fig. 116 — When machine center and casting center are not concen-
tric apparent hard spots may be found .-...- 255
Fig. 117— (left) — Cementite persisting near a shrink. The metal in
porous areas is somewhat oxidized 257
XV
LIST OF ILLUSTRATIONS— Continued
PAGE
Fig. 118 — (Right) — Hard slag inclusions just below the surface
which may dull cutting tools rapidly 257
Fig. 119 — Malleable casting effectively arc welded with Swedish iron.
The changes visible microscopically were insufficient to make
notable difference in metal. Area A is soft iron but very slightly
recarburized from the malleable; B is an oxide or slag film,
and C is the malleable showing but little resolution of carbon
due to close confinement 258, 259
Fig. 120 — Hard iron casting successfully acetylene welded with hard
iron and then annealed. Note metallurgical homogeneity of
casting except for presence of slag. A is the original casting,
B the slag, C the material of weld as noted by larger grain
size, and D the material of weld as noted by persistence of a
little pearlite due to decarburization 258, 259
Fig. 121 — Ineffective hard weld of malleable casting using ingot
iron wire and acetylene method. Neither material has its
original structure. A is the soft iron filler converted into hard
iron by migration of carbon from the malleable. B is the
original malleable iron, the background of which has become
sorbitic due to recombination of carbon at temperature the
metal reached in welding 258, 259
Fig. 122 — Photomicrograph showing heavy pearlitic rim which may
cause machining difficulties 262
Fig. 123 — (Left) — An effective acetylene weld, malleable becoming
sorbitic due to resolution of carbon. A is gray iron converted
into white cast iron by remelting. B is malleable 263
Fig. 124 — (Right) — Tobin bronze weld in malleable. Note absence
of oxides and slag in weld and absence of recombination of
carbon due to relatively low melting point of breeze. A is .
bronze, B is malleable 263
Fig. 125 — Analytical laboratory in malleable plant 268
Fig. 126 — Apparatus for determining carbon 269
Fig. 127 — Inverted types of metallographic microscope 272
Fig. 128 — Detail of inverted type of metallographic microscope
(Bausch & Lomb) 272
Fig. 129— A. S. T. M. tension test specimen 274
Fig. 130 — Dimensions of proposed tension test bar 276
Fig. 131 — A 200,000-pound Olsen universal testing machine 278
Fig. 132 — Ewing-type extensometer for determining elongation under
load ...".... 279
Fig. 133 — Olsen-type torsion testing machine 280
Fig. 134 — Leeds & Northrup Co. apparatus for determining critical
XVI
LIST OF ILLUSTRATIONS— Continued
PAGE
points by Roberts-Austin method 281
Fig. 135 — Apparatus for measuring magnetic properties of metal.. 281
Fig. 136 — Farmer fatigue testing machine 282
Fig. 137 — Charpy hammer for impact tests 283
Fig. 138— Brinell hardness tester 284
Fig. 139 — Stress-strain diagram of malleable cast iron in tension 289
Fig. 140 — Tensile strength and elongation plotted from specimens
submitted by members of American Malleable Castings As-
sociation 291
Fig. 141 — Effect of carbon on tensile properties of malleable iron.. 293
Fig. 142 — Relation between tensile strength and elongation of malle-
able cast iron 295
Fig. 143 — Comparison of tensile properties of machined and cast
specimens of equal diameters 296
Fig. 144 — Results of tests on specimens not machined 298
Fig. 145— V groove in bar 300
Fig. 146 — Necked specimens of steel (left) and malleable (right) 301
Fig. 147 — Stress strain diagram of malleable cast iron in com-
pression 304
Fig. 148 — Malleable (center) and cast iron (right) in compression
each specimen before testing was of the size and shape shown
at the left 305
Fig. 149 — Diagram of stresses in cross bending of malleable iron 308
Fig. 150 — Displacement of planes by linear shear and (at right) by
torsional shear 310
Fig. 151 — Stress strain diagram of malleable cast iron in torsion.... 311
Fig. 152 — Diagram showing factors to be considered in deter-
mining torsion stresses 312
Fig. 153 — Effect of elongation of specimen on the resistance to
dynamic tensile loads 319
Fig. 154— Walker test wedges 321
Fig. 155 — Behavior of malleable iron under fatigue as a rotating
beam 322
Fig. 156 — Separation of grains by repeated cross bendings 323
Fig. 157 — Relation between Brinell number and strength of malleable
iron specimens 325
Fig. 158 — Graph showing comparison of Brinell and Shore numbers
indicating relation between them is not definite 326
Fig. 159 — Tests of machining properties of malleable cast iron 330
Fig. 160 — Graph showing values of a in drilling formula 332
XVII
LIST OF ILLUSTRATIONS— Continued
PAGE
Fig. 161 — Graph showing values of'fc in drilling formula 333
Fig. 162 — Relation of torque and thrust to ultimate strength 334
Fig. 163 — Relation of torque and thrust to Brinell number 335
Fig. 164 — Slip bands in ferrite of malleable iron 341
Fig. 165 — Intragranular fracture of a ferrite grain in malleable.. 342
Fig. 166 — Intergranular failure of malleable 343
Fig. 167 — Ferrite grains in malleable, showing slip in two planes
at right angles 344
Fig. 168 — Slip bands due to plastic compression in malleable iron 345
Fig. 169 — Plastic deformation of malleable in compression 345
Fig. 170. — Same specimen as shown in Fig. 169 347
Fig. 171 — Path of cross bending rupture through malleable 348
Fig. 172 — Malleable iron compressed about one half. Annealed
5 hours at 650 degrees Cent 349
Fig. 173. — Stress strain diagram of malleable iron in tension for
two rates of loading 352
Fig. 174 — Changes of strain with time at small increments of stress 353
Fig. 175 — Changes of strain with time under considerable increment
of stress (about 70 per cent of ultimate strength) 354
Fig. 176 — Stress strain diagram of malleable iron in repeated tension
under increasing loads 355
Fig. 178 — Behavior of malleable under cyclic cross bending at con-
stant maximum stress 358
Fig. 179 — Maximum deflection and permanent set under cyclic cross
bending at constant maximum stress 359
Fig. 180 — Stress deflection diagram of malleable in cross bending
with and without previous cold work 362
Fig. 181 — Effect of torsional deformation upon subsequent tensile
strength of malleable 363
Fig. 182 — Absorption of energy from successive impacts 364
Fig. 183 — Load deformation diagram of specimen subjected to al-
ternate impact , 367
Fig. 184 — Magnetization and permeability curves of malleable cast
iron .' 373
Fig. 185 — Magnetic properties of malleable cast iron 375
Fig. 186 — Variation of electrical resistance of malleable cast iron
with temperature 377
Fig. 187 — Expansion of malleable cast iron 379
Fig. 188 — Heat transfer from machined malleable to still water for
various temperature differences 380
Fig. 189— Effect of temperature upon tensile properties of mal-
leable . 382
Fig. 190 — Thermal conductivity of malleable cast iron 383
XVIII
American Malleable
Cast Iron
I
EARLY HISTORY OF IRONMAKING
SINCE the dawn of civilization man has continuously
labored to use the natural resources of the world for
his own well being. He first adapted to his needs the
materials most easily obtained and as his knowledge and
skill grew he sought to find or make other materials which
would better suit his requirements.
Copper and gold, being found in the metallic state in
nature, were the first metals to attract his attention. More-
over, being malleable, these metals were readily fashioned
into the shapes desired. Far beyond even legendary his-
tory the mound builders used copper utensils while the Incas
and Montezumas used gold in domestic articles as well as
in ornaments. Of the various metals found as compounds in na-
ture, lead, silver and tin are fairly easily reduced from their
ores ; hence prehistoric metallurgists soon added these to
the list of available materials. Thus the age of copper was
succeeded by the age of bronze.
The only free iron found in nature is that of meteoric
origin, usually existing in small fragments which easily rust
away. However, in a few cases, notably the three large
siderites brought from Greenland by Admiral Peary and
now in the American Museum of Natural History in New
York, meteoric iron has been put to industrial use. Peary's
siderites, which are the largest ever discovered, constituted
the only source of iron for the Esquimaux of northern
Greenland.
Approximately five thousand years ago, one of Pharoah's
2 c *" AnteriCcirtm^M(ikletfble Cast Iron
Courtesy of American Museum of Natural History
Fig. 1 — A meteorite in the American Museum of Natural History,
New York, brought from Greenland by Admiral Peary
masons carelessly left one of his tools lying on the masonry
where a new stone was being set in building the pyramids.
Thus packed in lime, this earliest known piece of man-made
iron was preserved for posterity. The method doubtless
used by the Egyptian iron masters still persists in many
semicivilized communities.
As shown in Fig. 2 it consisted of heating rather finely
divided ore in a charcoal fire blown by a hand or foot bel-
lows in a shallow basin in the ground. The charcoal acted
both as fuel and as a reducing agent, liberating metallic iron.
The temperature being low, the iron did not combine much
with the carbon nor did it melt freely. The pasty bloom
which accumulated in the hearth was removed and crudely
hammered into the desired shape. Obviously the process
was laborious, yet it was practiced on a considerable scale.
It is believed that the famous pillar of Delhi was made by
welding together blooms of the kind just described. ,
Metal of this kind possessed some of the properties of
wrought iron or unusually soft steel of the present day.
Early History of fronmaking
However, it doubtless was variable in quality since the
carbon content must have fluctuated considerably due to
the changing and uncontrolled temperature conditions. Not-
withstanding this lack of uniformity, it was decidedly a bet-
ter metal for tools and arms than the copper and bronze
preceding it.
Still before the era of written history there lived a
primitive Carnegie whose very name has been lost. This
early steel master, probably a native of Greece, determined
to engage in the quantity production of iron. He substituted
a stack or shaft for the shallow hearth then in use with the
hope of rendering the operation continuous instead of in-
termittent. He introduced blast from the bellows at the
bottom, started a fire of charcoal and then began to add
alternate layers of charcoal and ore until the shaft was full.
Presumably he expected to dig out blooms of iron from the
bottom of the furnace at frequent intervals and to supply
V
##
m
.r^.
Fig. 2 — A primitive furnace, 1500 B. C. The illustration was repro-
duced from an Egyptian wall painting
-•I ntcr icon Malleable Cast Iron
charcoal, ore and air continuously. Doubtless he was much
surprised when on some occasion instead of iron blooms ap-
pearing, molten metal ran from the opening in the stack.
Such was the first production of cast iron. The better
utilization of heat in the shaft furnace had produced a tem-
perature high enough to more completely carburize the
product. The decreased melting point, coupled with the
higher temperature reached, produced a liquid metal prob-
Fig. 3 — One of the earliest blast furnaces
•\
ably of white or mottled fracture. Unconsciously this
primitive artisan discovered the blast furnace. Even today
the process of smelting iron ore is governed by the same
general principles which obtained in the early days in Greece.
Only the technique has been perfected.
The earliest known blast furnace purposely to make pig iron
is said to have operated in the Rhine provinces of Germany
in 1311. The industry spread over the rest of Europe dur-
ing the succeeding century.
With the development of the crude blast furnace, one
Early History of Irontnaking
of which is illustrated in Fig. 3, there existed two kinds of
iron. The one had to be forged to shape and was rather
soft although not easily broken and the other, which could
be cast into shape, was rather hard but too brittle and
fragile to use. Obviously, a metal of either of these limita-
tions was not exactly adapted to the making of swords, the
manufacture of which constituted a most important pro-
fession in the early days. Therefore, the most important
metal for that age was one not soft enough to be bent
and blunted by armor nor so brittle as to be shattered by
a sharp blow. In the search for a material to better meet
the requirements of the armorer some pioneer found that if
the soft iron produced in the forge were heated in charcoal,
the surface of the metal could be made harder — in fact the
metal could be hardened throughout if the treatment were
continued long enough. It was learned that in this man-
ner tools and weapons could be produced with a superior
edge.
For many centuries this "blister" or cementation steel
was the only steel available. One of its principal shortcom-
ings was its lack of uniformity across the section. How-
ever, this was later overcome by remelting the carburized
steel in crucibles, thus rendering it homogeneous. The
crucible process also was modified by melting wrought iron
mixed with sufficient charcoal or cast iron to give the desired
properties to the metal. The amount added was determined em-
pirically, for at that time chemical control from the viewpoint of
carbon content was unkown.
Thus at the beginning of the eighteenth century three
kinds of iron were known to the world. These were wrought
iron, soft and worked only by forging; cast iron, brittle and
worked by casting; and crucible or cementation steel, some-
times melted in the process of manufacture but always
forged to shape, not brittle but hard enough to hold an
edge and be tempered.
Steel, however, could only be made from wrought iron,
wrought iron only from ore, and neither could be made
from the relatively cheap cast iron. The next forward step
in the metallurgy of iron and in fact the first since the dark
American Malleable Cast Iron
ages, was the invention by Cort of the puddling furnace for
converting molten cast iron into blooms of wrought iron by
treatment with ore. This invention made possible the reduc-
tion of the metal from its ore in the cheaply and efficiently
operated blast furnace and its later conversion into mal-
leable and ductile wrought iron.
Steel was sitill made by using wrought iron, now ob-
tained by puddling, as the raw material. This continued
to be the only source of steel until the discovery of the
bessemer process in the middle of the nineteenth century and
the invention of the open-hearth furnace by Siemens about
15 years later. Both of these processes, which depend for
their success on the increased temperatures available, pro-
duce liquid steel of nearly any desired carbon content. The
former process uses the carbon and silicon content of the
molten pig iron for fuel, burning these within the charge by
a blast of air. By the removal of the carbon, the cast iron
becomes steel which is kept liquid by the heat of combus-
tion of the carbon and silicon.
Siemen's was practically a modified reverberatory fur-
nace fired by gas, the fuel and air for combustion being
heated in regenerators by the waste heat of the escaping
products of combustion. The oxidation *of carbon was ac-
complished, as in the puddling furnace, by the oxygen of
the hematite iron ore added to the slag. The essential dif-
ference between Cort's and Siemen's invention was that the
latter worked at temperatures sufficiently high to keep the
resulting product molten.
A review of the industrial world at about the close of the
American civil war indicates that five well established types of
iron and steel were being used. Charcoal iron was made directly
from ore and charcoal on the same principle used in pre-
historic "times. This material resembled wrought iron and
was practically obsolete from a production viewpoint.
Wrought iron was made from cast iron in the puddling fur-
nace. It was a pasty mass and was shaped by rolling and
hammering only. This material was soft, malleable and
ductile. The railroad iron of which the MONITOR'S armor
Early History of Ironmaking
was made was of this character. A third material was
cast iron made in the blast furnace and cast to shape in
molds. This iron was incapable of being bent without
breaking. The fourth material was blister or cementation
steel made from wrought iron in unimportant amounts.
This steel had to be forged to the shape desired. The
Fig. A — An early American blast furnace
fifth and most important metal was steel made in liquid
form by the crucible, bessemer or open-hearth process from
cast iron. This had so high a melting point that it
was incapable of casting any but large molds, hence
it was usually cast into the latter form and rolled or
forged to shape. When desired it could be produced of a
composition permitting of hardening and tempering.
A sixth product, then just coming into use is the subject of
this volume.
It will be observed that in none of the first five products
are combined the properties of malleability of wrought iron
and fusibility as found in cast iron. In other words, no ma-
terial has been described which could be cast into intricate
American Malleable Cast Iron
a
bb
Early History of Ironniaking 9
shapes and which would be in any degree malleable when
complete. The problem of producing a malleable cast iron
to fulfill these requirements had long occupied the minds of
the iron masters. Since Cort had produced wrought iron
by the use of ore, a modification of his process which would
not involve the melting of the cast iron now seems to us a
logical conclusion. In 1722 Reaumur, a French physicist,
described a process, not necessarily original with him, for
producing malleable cast iron by packing small castings of
(presumably white) cast iron in pulverized hematite ore
and heating them to bright redness for many days. This
method evidently was suggested by the cementation process
for making steel from wrought iron, substituting for the
charcoal which adds carbon in that process, ore which removed
carbon, the same reaction later discovered by Cort as applied to
molten cast iron.
Reaumur's discovery, or better disclosure, actually grew
into an industry in Europe. It happened that European
white cast irons, except in Sweden, were relatively low in man-
ganese and high in sulphur, owing to the available fuels and ores.
Being white, it also was low in silicon.
Such conditions are all unfavorable to the formation of
free carbon and consequently Reaumur's reaction was never
complicated by the formation of temper carbon or graphite.
In intention, at least, the annealing removed from his thin
castings all the carbon which burned from the carbide of
iron.
The amount of the carbon originally present was im-
material, in any event the resulting casting, if the anneal
was successful, had only traces of carbon but contained all
the other chemical elements originally present. Having
been only moderately heated it retained its original cast
form but approximated the chemical and physical properties
of wrought iron. The shortcomings arose mainly from the
fact that since carbon was removed through the surface,
the process oould not be commercially applied to moderately
thick sections owing to the prohibitive annealing time.
Moreover, a casting having both thick and thin parts nat-
American Malleable Cast Iron
Urally would be completely decarburized in the former while
still retaining much carbon in the center of the heavier por-
tions. If the process were continued to completion in the
thick sections, trouble from oxidation and scaling of the
thinner parts would be encountered. Furthermore, it was
difficult to be sure that the castings were annealed clear
through, since the interior is not available for inspection.
Any castings not annealed through would be brittle owing
to the remaining undecarburized core.
Hatfield in his "Cast Iron in the Light of Recent
Research" says of this process as practiced in England :
"Essentially, the materials used in Britain in the production
of malleable castings, are high in sulphur, necessitating a
somewhat lengthy anneal at a fairly high temperature with
a view to annealing largely in decarburization. These re-
marks apply also to the practice in France, Switzerland,
Belgium and Germ.any."
Production of "White Heart" Limited
The industry thus was limited to comparatively small
tonnages and hence to crude methods. As practiced then,
and still practiced in England, Germany and France, the
product is used largely for harness parts 'and small and un-
important work. Melting is frequently done on a small
scale either in crucibles or cupolas. The total volume of
production is relatively insignificant in the iron production
of Europe aUhough there are said to be 126 white heart
malleable foundries in Great Britain.
Reaumur's publication was productive of only the most
meager commercial results from an American viewpoint.
Boyden and his immediate successors attempted to anneal
by decarburization. The metal made by the Philadelphia
Hardware and Malleable Iron Works before the Civil war
was "white heart", as was that of at least a number of its
contemporaries. About 1861, however, the manufacture of
this product in America practically ceased. A single job-
bing manufacturer of white heart malleable continued op-
erations until a few years ago, operating largely on European
Early History of Ironmaking
pig iron. At least one plow manufacturer continues to
operate on the basis of European cupola practice and to
turn out white heart malleable of high strength and low
elongation.
Many of the stock phrases regarding malleable which
have gone the rounds for many years originated with
"white heart" metal. For instance, the fairly widespread
belief that malleablization takes place from the surface in,
that the material is not annealed clear through and that
the material cannot be used in heavy sections because of
the unannealed center, are among the common fallacies
handed down from Reaumur's time. Even though the
"white heart" or Reaumur's process never has possessed any
tonnage significance in the United States, and has been
practically discontinued for 60 years, its faults have been
frequently assumed to apply to the American or "black
heart" metal by those not conversant with the facts.
The art of making malleable castings, as that term is
understood in America, was discovered probably uncon-
sciously by Seth Boyden while attempting to practice
Reaumur's method in Newark, N. J., in 1826.
Boyden was a manufacturer rather than a scientist.
Probably for this reason no formal announcement of a new
discovery was made. It is presumed that in attempting to
duplicate European practice with American pig iron, which
is low in sulphur and high in manganese, he inadvertently
discovered an alloy which when heated to produce deear-
burization, graphitized instead. The product possessed all
the properties of the best white heart metal and was more
easily made and more uniform. Not realizing that he had
discovered a new art, Boyden continued this work along
the lines he found empirically most likely of success.
Boyden left a diary covering his experiments from
July 4, 1826, to Sept. 1, 1832. It shows that he was at-
tempting to duplicate Reaumur's process. Under date of
Oct. 20, 1826, he writes : "I have a piece so good it will
not harden any more than copper". Yet from his third ex-
12
American Malleable Cast Iron
Fig. 6 — Statue of Seth Boyden, erected in the city park of Newark
N. J., by citizens in memory of the man who laid the foun-
dation for the malleable industry in the United States
Early History of Ironmaking 13
periment on there are allusions to graphitization. In the
report on the third experiment he states, "Much blacker in-
side and not half so good". Again in Experiment No. 5 he
refers to a piece "which had been done totally well before
rendering dark in the middle". An entry on the eighth ex-
periment is: "Quite gray; none of the above bend or are
good for anything". In the ninth experiment he comments :
"Hard iron melted in coal dust from the air received no
change but in scoria and coal dust became soft gray iron.
A piece of Sterling (grade of pig iron) without W (prob-
ably wrought iron) in soft gray state done (annealed) eight
times remains gray and unmalleable".
Boyden had been unconsciously recording the first ob-
servation of the formation of temper carbon and its dis-
tinction from graphite. Being still convinced that he was
striving to produce a steely decarburized iron he refers in
Experiment No. 11 to the fact that "the iron was tough
when broken and was rather too dark in color". Yet in the
next experiment he writes, "Experiment in the foundry.
Sterling the toughest but very dark. Sprues and Sterling
dark and good". On Sept. 10, 1826, he notes that "some
of the pieces were tough, gray and very good". On Oct. 20
of the same year he makes the peculiar observation that
"the best piece I have ever seen.... was pale blue in the
middle".
For many years neither he nor his successors realized
that decarburization was not essential to the process. He
and his associates laid great stress on packing materials and
their chemical effect upon the product.
Inasmuch as the graphitizing reaction discovered by
Boyden forms the metallurgical basis of the present indus-
try, its consideration in detail will be reserved for a later
chapter. Black heart or American malleable cast iron bears
no metallurgical relation to the European product and its
history begins not with Reaumur but with Seth Boyden.
II
DEVELOPMENT OF MALLEABLE INDUSTRY IN THE
UNITED STATES
SETH BOYDEN began business as an iron founder in
1820 at 26 Orange street, Newark, N. J. Being inter-
ested in malleable castings, he attempted to duplicate
European practice at a time when metallurgy was prac-
tically unknown. After six years of continuous experiment
he succeeded in producing malleable castings, but not of the
kind he attempted to make.
Due presumably to the raw material available, he hit
upon the practical operation of the graphitizing anneal and
thus founded a new industry. Boyden operated the plant
under his own name until 1835 when it became known as
the Boston Malleable Cast Iron and Steel Co. The foundry
continued under this management for two years, after which
it was operated under various firm names by Daniel Condit,
J. H. Barlow and others, becoming in 1907 the Barlow
Foundry Co. This company occupied the original site until
May, 1914, when it removed to another location and the
birthplace of black heart malleable was razed.
Quite naturally the early development of the industry
centered about its discoverer and its birthplace. At one
time Newark had eight malleable foundries, and three of
Boyden's brothers — Otis, Alexander and Frank — engaged in
the malleable founder's art. Otis operated a foundry in
Newark from 1835 until 1837, when it was absorbed by the
Boston Malleable Cast Iron & Steel Co. Alexander and
Frank engaged in the business in East Boston during the
same interval, after which Alexander was employed by
Frederick Fuller, of the Easton (Mass.) Iron Foundry, es-
tablished in 1752. The business later came into the hands
of Daniel Belcher and was continued by his descendents.
Two plants were started in Elizabethport about 1840
and in 1841 David Meeker began to manufacture malleable
16
American Malleable Cast Iron
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Development of Malleable Industry 17
in the Hedenburgs Works. The New Jersey Malleable
was founded at Newark in 1841.
The information regarding the activities of the Boyden
brothers and their contemporaries and associates is derived
from a paper presented before the Philadelphia Foundry-
men's association by George F. Davis.
It would be exceedingly interesting to trace back to its
beginnings the present, highly developed industry. Un-
fortunately written records of the early days survive, if at
all, only in the account books and the minutes of stock-
holders' and directors' meetings of the older corporations.
Such records are not open to public scrutiny and therefore
it is difficult in sketching the early history of the industry
to do full justice to all.
The writer has been unable to trace in complete detail
the early history of the industry, other . than through
Boyden's activities. This may be due to the fact that
these older plants did not survive or may be caused by in-
adequate search. It seems to be of common knowledge that
during the first half of the nineteenth century, a number of
persons entered into the business, the plants being mainly
located in New England and New York, at least one as far
west as Buffalo.
Thomas Devlin has informed the writer that when the
Philadelphia Hardware & Malleable Iron Works, now the
Thomas Devlin Mfg. Co., was 'founded in 1852, the com-
pany officials knew of the existence of the Westmoreland
(N. Y.) Malleable Works, of a plant in Worcester, Mass.,
and also of the M. Greenwood Co., of Cincinnati, which
was founded in or possibly before 1850 and later was taken
over by James L. Haven.
In the early fifties, Isaac Johnson established a mal-
leable foundry at Spuyten Duyvil. In 1872 he, together
with J. H. Whittemore of NaugatUck and W. S. Nichols, a
brother-in-law and representative of Walter Wood, organ-
ized the Hoosick Malleable Iron Works at Hoosick Falls,
New York. Some years later, Johnson also organized the
malleable plant bearing his name in Indianapolis, which in
18 American Malleable Cast Iron
1883 passed into the control of the group which later be-
came the National Malleable Castings Co.
In the early eighties, the Walter Wood Mowing &
Reaping Machine Co. absorbed the Hoosick Malleable Iron
Works, enlarging the plant from time to time. The same
organization under the style of the Walter Wood Har-
vester Co. started the business in St. Paul which, after a
failure during the panic of 1893 and one or two changes of
ownership, became the Northern Malleable Iron Co. under
Frank J. Otis.
Much of the early development centered in New
England, particularly in the state of Connecticut. Among
the oldest malleable plants is what is now the Naugatuck
works of the Eastern Malleable Iron Co. at Union City.
Here the development work of J. H. Whittemore and B. B.
Tuttle was done beginning in 1858. From that plant and
that of the ^Bridgeport Malleable Iron Co. were recruited
many of the executives who established the industry in the
Middle West.
The Naugatuck and Bridgeport plants, with those at
Troy, Wilmington and New Britain became the present
Eastern Malleable Iron Co. At a later date the village of
Hoosick Falls, N. Y., also sent westward a group of mal-
leable iron foundrymen. G. H. Thompson went to Colum-
bus, John Haswell to Marion, and later to Dayton, O.
Sidney Horsley, superintendent of the Northern Malleable Iron
Co., and others also graduated from Hoosick Falls.
In 1854 Duncan Forbes, a Scotchman who had previously
resided in western New York, removed to Rockford, 111., and
with his son Alexander Duncan Forbes, established a gray
iron foundry. In 1859 Forbes installed an annealing oven
and intermittently produced cupola malleable castings in
connection with the production of gray iron stoves which
constituted the larger part of this business. In 1864 the
gray iron portion of the business was definitely abandoned
in favor of malleable castings alone.
Duncan Forbes, the first manufacturer of malleable
castings west of Cincinnati, died in 1870. The business was
__ Development of Malleable Industry 19
continued and enlarged by others of his family. In 1890
the company was incorporated as the Rockford Malleable
Iron Works and in 1907 removed to a new location in
Rockford, where it continues to be operated by descendants
of the original founder.
In 1866 Charles Newbold and Peter Loeb started a
malleable and gray iron foundry in the east end of Day-
ton, O., which was incorporated as the Dayton Malleable
Iron Co. in 1869. In 1872 the business was removed to its
present location on West Third street/ and from time to
time the capital stock and plant equipment were increased.
In 1916 the plant of the Ironton Malleable Iron Co.
was purchased, and has since been operated' as the Ironton
works of the Dayton Malleable Iron Co. In February, 1922,
the Dayton Malleable also took over the foundry of the Timken
Co. at Canton, Ohio.
In August, 1868, the Cleveland Malleable Iron Co.
was incorporated and in 1869 Alfred A. Pope became inter-
ested in the business and immediately thereafter its presi-
dent. In 1873 John C. Coonley, sometime of Louisville,
and a number of men in the Cleveland company, started the
Chicago Malleable Iron Co. The same organization, which
in 1891 became the National Malleable Castings Co. ac-
quired by purchase or construction, plants in Indianapolis,
Toledo, O., and Cicero and East St. Louis, 111., besides
steel plants whic'h are not of interest in the present con-
nection.
A. A. Pope and J. H. Whittemore were leading factors
in the early growth of- the industry, the institutions over
which they presided now being the two largest in the
country. Many other manufacturers of malleable cast iron
have honorable histories extending back into the sixties
and seventies of the last century. The writer has not had
the opportunity he could have wished to do full justice to
the histories of some of these smaller companies.
The industry has the distinction of numbering on its
rolls a president of the United States, Mr. Harding having
been one of the original stockholders of the American Mai-
20
American Malleable Cast Iron
111
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Development of Malleable Industry 21
leable Castings Co., organized in 1905 under the leadership
of Charles L. LaMarche.
In this as in other industries, the growth has been
largely in accord with the survival of the fittest. Many
plants have been started on a moderate scale especially at
times of great industrial activity. Some of these failed to
survive the first period of depression encountered ; others,
particularly in New England, continued a 'small but often
prosperous existence, catering to a limited trade, usually in
their immediate neighborhoods. A number of the organiza-
tions grew in size and influence, and by sound business and
technical methods, coupled with an aggressive policy, at-
tained position of prominence in their fields.
Another type of malleable foundry has sprung up in the
history of the industry. This is the foundry which pro-
duces a given specialty not for the open market but as a
department of an organization manufacturing a finished
product. Many of these foundries also have branched out
into jobbing work when not fully employed for their own
requirements, but are primarily operated to furnish castings
for the product made by the parent company. In this class
are the malleable foundries of the General Electric Co,.,
American Radiator Co., International Harvester Co. of
America, Ebefhard Mfg. Co., Link-Belt Co., and a number
of others." These foundries, having a definitely established
outlet for their product and the financial and administrative
support of a well organized industry, usually have survived
and grown successful. However, in at least one case a found-
ry of this character has been sold to a malleable founder
in pereference to its continued operation by the consumer.
The organization of a special foundry is only possible
where the requirements of the parent company run up to
a sufficient tonnage to make possible operations on a large
enough scale to warrant the best operating conditions and
supervision. The malleable industry, involving more expen-
sive equipment and greater technical skill than the gray
iron industry, cannot well be operated in small units on
account of excessive overhead. Therefore, unless an in-
dustry is large enough to operate'quite an extensive foundry,
22
American Malleable Cast Iron
Development of Malleable Industry 23
castings of better quality usually can be obtained more
cheaply by purchase from established jobbing foundries.
The present extent and distribution of the malleable
industry is shown in Fig. 9. Each dot on this map repre-
sents the approximate location of a producer of malleable
castings. The list" is as complete as possible, having been
compiled from the data of the American Malleable Cast-
ings association and from information gathered for the
government during the war. There are a number of plants
marked as producing malleable where there is reason to
doubt whether they have actually done so. The most recent lists
include between 20 and 30 more plants than are shown on the
map. In part this may be due to incomplete returns, and to a
less degree to new foundries of very small capacity. It is un-
likely that any important plant has been omitted. It will be
noted that the plants are largely in the territory north of
the Ohio and east of the Mississippi rivers, their locations
following closely the various divisions of the Pennsylvania,
New York Central and New York, New Haven and Hart-
ford lines, with an additional development near Milwaukee
and in southern Michigan. These locations were largely
determined by the fact that they are coincident with the
important manufacturing districts of the country, present
good shipping facilities and are conveniently near the
sources of fuel and pig iron.
A more interesting compilation from the viewpoint of
the user of malleable cast iron is the map shown in Fig. 10,
showing the principal sellers of malleable cast iron. This
has been prepared from the previous map by the elimination
of foundries primarily operated as departments of larger in-
dustries producing finished products, as for example harness
parts, pipe fittings, etc., and of foundries whose tonnage is
not of sufficient magnitude to be an important consideration
from the viewpoint of the consuming interests. It will be
seen that the distribution is almost identical, although the
number of plants has been considerably reduced.
Annual Production of Malleable
The plant capacity of the United States as of 1920 is
estimated at 1,286,300 tons annually, divided by states as
24
American Malleable Cast Iron
in
Fig. 11— Comparison of production of steel and malleable iron castings
in the United States
The production of steel castings is charted from the statistics compiled by the
American Iron and Steel institute. The production of malleable iron castings is
carefuDy estimated on the basis of the known production of plants whose output
constitutes the majority of the annual tonnage of the country. No definite figures
ever have been compiled showing the actual production of malleable castings and
in the absence of such information, it is believed that the above charted values are
as accurate as any that can be obtained under existing circumstances.
follows: Illinois, 297,700; Ohio, 202,700; New York, 167,-
500; Pennsylvania, 133,100; Wisconsin, 116,600; Michigan,
108,400; Indiana, 88,300; Connecticut, 58,200; and all others,
113,800.
The most complete information at the writer's disposal
indicates that there are between 176 and 204 manufacturers of
malleable castings in the United States. In this list, however, are in-
cluded a considerable number of manufacturers with whom
the production of malleable castings is only incidental to
other operations. Some of these produce malleable only
intermittently or in small quantities, as their own need«
require, and are included here in the interest of complete-
ness rather than: because of their importance to the job-
Development of Malleable Industry 25
bing trade. About 85 per cent of the tonnage of the country
is produced by 76 manufacturers having a capacity in ex-
cess of 5000 tons annually each. Sixty-two and one-half
per cent is produced by 33 owners having capacities over
10,000 tons per annum. No single manufacturer can be
said to exercise anything approaching a monopoly, as the
five largest interests together have only 28 per cent of the
capacity of the country. Each of these five can produce
30,000 tons per annum or more. The eight additional manu-
facturers, having individual capacities from 20,000 to 30,000
tons, account for an additional 14.2 per cent.
Data as to the production of malleable castings in the
United States go back only to 1913 when the American
Malleable Castings association began the accumulation of
statistics on this point. Fig. 11 shows the production of mal-
leable castings by years since 1913, compared with the
production of steel castings by years since 1904, as recorded
by the American Iron and Steel institute. The production
of malleable pig in 1913 was about 5l/> times that in 1900.
This would imply a production of only about 127,000 tons
of malleable castings in that year.
It will be noticed that the annual production is con-
siderably below the annual plant capacity. The recent fig-
ures on production of course are based on manufacturing
operation in times of great industrial activity. Under these
conditions, a deficit in production compared with capacity
seems at first glance unlikely. This deficit is due to two
causes ; first the fact that the reported capacities are doubt-
less a little higher than the facts warrant and second that
most of the malleable foundries had been unable to obtain
either sufficient labor or fuel to permit the realization of
their full production. In other words, plants apparently
were built in excess of the available labor supply and no
material increase in the country's maximum output of castings
could be expected as a consequence of the erection of ad-
ditional plants.
In view of the lack of productivity in all lines of manu-
facture before the 1921 depression, it is unlikely that the manpower
of this or any other industry could be largely increased except by
26 American Malleable Cast Iron
increasing the productivity of the individual employe. The
only visible remedy seems to be an increase in tonnage per
man by the introduction of every possible mechanical aid.
A considerable improvement may be possible by some
means tending toward a decreased loss of time by the in-
dividual worker, and an increase in his skill. Data based on con-
ditions since the summer of 1921 are of course valueless on
account of the very small production in all lines.
The commercial development of the industry was par-
alleled by steady progress in the technical details of malle-
able production. As has been stated earlier in the discus-
sion, Boyden's discovery was not the result of a logical
metallurgical development but was the accidental outgrowth
"of an attempt to practice a theoretically distinct art. When
it is realized that all of this work was done at a time when
even the chemical analysis of iron was an unusual thing and
that Boyden and his successors blazed the way without any
knowledge of variations in raw material and product, save
what might be gathered by the crudest of inspection, we
cannot but marvel at their courage and persistence in estab-
lishing the empirical basis for the present great industry.
Boyden, however, having a truly technical mind, left behind
complete notes of his experiments and the results attained.
Some of his notes already have been quoted. He recog-
nized the presence of carbon but only in the free state, be-
lieving white iron to contain none. He made many experi-
ments with various packings and under different annealing
conditions, finally concluding that red iron ore was the best
material. He records the belief that the annealing temper-
ature should be at least the melting point of silver. He
considered the presence of silicon and sulphur but knew
nothing of analysis. Under date of Jan. 23, 1829, he records
observations as to the effect of additions of phosphorus,
clay, lead, zinc, tin and antimony.
Boyden's brother, Alexander, seems to have been the
earliest mystery monger in the trade, it being related by
Davis, on the authority XD£ Horace Spaulding, the last sur-
vivor of the Easton foundry, that Alexander had a little
pump with which he squirted something into the stack
Development of Malleable Industry 27
and also that he used to throw some metal into the furnace,
creating a great volume of smoke and doubtless an equally
great awe in the mind of the spectator.
In 1872 Alfred E. Hammer, of the Malleable Iron Fit-
tings Co., began to study the chemistry of black heart
malleable at Branford, Conn. This company in 1864 had
succeeded to the business of an earlier one, 'the Totoket
Co. founded in 1854 for the purpose of practicing Boyden's
method.
In 1875 Mr. Hammer had established a chemical lab-
oratory which was, so far as he is aware, the first in con-
nection with the malleable iron industry. Writing of this
laboratory he says :
"I found that I was practically in an unknown country.
For that reason, 'however, the work was not only interest-
ing but positively exciting — so much so that I had a mat-
tress laid in my laboratory and with the aid of an alarm
clock, I was able to follow the then tedious chemical oper-
ations through the night without much loss of sleep."
As a result of this work, he found it possible to lay
down "a chemical ratio as between carbon and silicon, and
manganese and sulphur," thus being the first one "to bring
the malleable process down to a chemical proposition. "
Among Hammer's difficulties, not the least was that at
this period, pig iron was not made and sold by analysis.
However, he soon applied his chemical ideas to the selection
and mixing of irons, irrespective of brands and grades.
The work of this pioneer metallurgist seems to have
escaped adequate recognition since his conclusions \vere
thought to be too valuable" trade"* secrets to 'warrant publi-
•;*
cation.
He certainly came to correct quantitative conclusions
as to manganese and sulphur at a date long before the the-
oretical explanation was even thought of. His views as to
carbon also seem to have been far in advance of later inves-
tigators who gained much greater general recognition.
While not a technically trained metallurgist, A. A.
Pope from his earliest association, with the industry strove
by every means in his power to collect and interpret ex-
28
American Malleable Cast Iron
> •*->
Development of Malleable Industry 29
perimental data bearing on the processes and products of
his plants. These investigations were conducted by Em-
merton, Benjamin and others and resulted in an accumulation
of valuable data during the seventies and eighties.
It is interesting to note that especially with reference
to manganese and sulphur, Mr. Pope's conclusions were very
similar in application to those reached at about the same
time by Mr. Hammer.
Among the most progressive of the malleable manufac-
turers was the late B. J. Walker, of Erie, Pa., who pursued
a most liberal policy with regard to the exchange of in-
formation and did much to develop the industry.
In 1893 McConway & Torley established in Pittsburgh
what is frequently said to have been the first laboratory in
the malleable industry. It was under the direction of Dr.
Richard Moldenke, who not long thereafter severed his
connection with that company to become associated with
another in the Pittsburgh district. H. E. Diller, now metal-
lurgical editor of The Foundry, was associated with Doctor
Moldenke at this time.
In the autumn of 1893, James Beckett, after a tour
covering all of the malleable foundries then producing agri-
cultural implement parts, found that none of them had es-
tablished a chemical laboratory for works control. This
statement does not apply necessarily to plants not engag-
ing primarily in this specialty which were not visited by
Mr. Beckett.
In 1894 the Wood Mowing & Reaping Machine Co.,
Hoosick, Falls, N. Y. employed Enrique Touceda as a
consultant and established a well equipped laboratory.
In 1903 when the National Malleable Castings Co.,
established a works and experimental laboratory at Indian-
apolis, the author was unable to find by diligent search of
the literature available any adequate information of a
definite and quantitative character regarding the chemical
fundamentals of the process. Therefore it was decided to
disregard precedent and to establish a sound theoretical
basis for works control, using the information accumulated
by Mr. Pope as a nucleus. In this connection the quantita-
30 American Malleable Cast Iron
tive effect of carbon, a sine qua non in the works control
of the product, was worked out in 1904, the conclusion
reached being apparently new to a number of the best in-
formed malleable men with whom it was discussed at the
time. A little later the effect, or rather lack of effect of
manganese sulphide was also worked out. This offers the
theoretical explanation of the practical observations of Mr.
Hammer and Mr. Pope.
These facts were certainly discovered independently by
other observers, including W. R. Bean now of the Eastern
Malleable Iron Co. In the absence of contemporary publi-
cation it is impossible to state whether these discoveries
preceded or followed the Indianapolis investigations. So
far as the writer has been able to learn the Indianapolis laboratory
was the first to successfully exercise complete works control
on the basis of the total carbon content being the determin-
ing factor in the quality of the product.
During all of this time the results of none of these in-
vestigations became publicly available and therefore it is
difficult to accurately chronicle the scientific development
of the art. The organizations collecting scientific and re-
search data of value did not feel it to be sound business pol-
icy to make public disclosures of their work. Regardless
of whether or not this policy was fundamentally sound from
the manufacturers' viewpoint, it certainly proved a handi-
cap to the consumer, who remained in ignorance both of the
theoretical principles and practical applications of the manu-
facture of malleable castings.
Having again severed his business connection and es-
tablished himself as a consultant. Dr. Moldenke began to
contribute voluminously to the technical press. Unfortu-
nately the only sources of information open to him seem to
have been the work in which he personally participated.
Furthermore he was presumably handicapped by the con-
fidential character of his relations with his clients and ap-
parently felt constrained to speak only in somewhat gen-
eral terms. Nevertheless he did yeoman service in striving
for a better interchange of ideas and information, and also
in advocating suitable technical control of the industry.
Development of Malleable Industry 31
His services in this direction are probably of even greater
importance than the actual informative value of his literary
output. The earlier literature of the subject was derived di-
rectly or indirectly almost entirely from his publications.
There still persisted in the engineer's handbooks and in
the technical press a mass of ill-supported conceptions
largely predicated on a confusion with the white heart
process. For example, great weight was attached to the
oxidizing action of the packing and its effect on the proper-
ties of the product was unduly emphasized. Great dif-
ferences also were supposed to exist between the heart and
surface of the same casting. Similarly there was an im-
pression that malleablizing proceeded from the surface in-
ward and was complete at the surface before it had pro-
gressed far at the center. A corollary to this belief was
that very thick castings could not be annealed clear through.
Since none of those who knew better felt called upon
to publicly combat statements of this character, it is not
surprising that the engineering public was left in ignorance
and hence in distrust of the qualities of the material. More-
over it is not surprising that in the absence of guidance by
those better informed, some of the less intelligent and
progressive manufacturers did not clearly understand the
principles of the process they practiced and therefore pro-
duced unsatisfactory castings.
A few of the larger producers maintained adequate
laboratory facilities to investigate and control their methods.
The smaller manufacturers, however, had to get on as best
they could with their own resources until the American
Malleable Castings association undertook as one of its ac-
tivities to carry on extensive research work for the benefit
of its members. Prof. Enrique Touceda, of Rensselaer
Polytechnic institute, was employed as consulting engineer
and since 1913 has labored unceasingly to instruct the mem-
bers of the association in sound practice and -correct funda-
mental principles. This work was largely confidential in
character and added little to the user's knowledge but con-
32
American Malleable Cast Iron
Development of Malleable Industry 33
tributed immensely to his satisfaction in the use of the
product.
At about this time, Oliver Storey published the results
of some research work at the University of Wisconsin, deal-
ing with the fundamentals of the graphitizing reaction. In
the writer's opinion this was the first scientific American
contribution to the literature of- the metallurgy of malleable
iron. The problem has been since investigated by Archer
and White, Merica and by the writer. A few years earlier,
Hatfield thoroughly investigated the less important subject
of decarburization. The theoretical aspects of graphitization
have been studied abroad rather thoroughly. In 1881
Forquignon published in the Annals de Chemie et de
Physique a contribution dealing with his tests in the an-
nealing of malleable iron and steel. Unfortunately the au-
thor has been unable to familiarize himself with this pub-
lication, which is said to have dealt very adequately with
the subject.
In 1902 Charpy and Grenet published a study of the
graphitization of white cast iron which covers the ground
very fully and accurately, even in the light of present
knowledge. This publication seems to be almost if not en-
tirely unknown in this country. Howe, in the Transactions
of the American Institute of Mining and Metallurgical En-
gineers in 1908, discussed critically and exhaustively the
evidence then available bearing on graphitization. Hatfield
in 1910 discussed the chemical physics of the precipitation
of free carbon from iron carbon alloys in a paper before the
Royal society. In 1911 Rueff and Goecke published a
study of the solubility of carbon in iron and in the same
year Ruer and Iljin discussed the stable system of iron
carbon. Heyn summarized the contemporary knowledge of
the iron carbon alloys at the New York congress of the
International Society for Testing Materials in 1912. That
these technical investigations have been of so little service
to the American manufacturer seems a reflection upon the
34
American Malleable Cast Iron
<n
II
I js
o ^
fcfl
Development of Malleable Industry 35
American literature of the subject no less than on the in-
dustry as a whole.
Honda and Murakami in the Journal of the Iron and
Steel Institute, of Great Britain, (1920) advanced the theory
that graphitization does not take place directly but is a
consequence of oxidation of carbon by CO2 and the sub-
sequent decomposition of CO formed with liberation of free
carbon. In the light of his present knowledge, the author
cannot agree with' this conclusion ; nevertheless it is a most
interesting contribution to the theory of the subject.
The officers of the malleable association soon realized
that while some of the work of its consulting engineer was
properly of a confidential character, there existed a necessity
for the publication of authoritative information regarding
malleable cast iron. Accordingly the association encouraged
participation in the programs of the technical societies by its
consulting engineer and by others qualified to speak on the
subject. It also established an educational committee to co-
operate with .institutions of learning and with engineering
organizations in the dissemination of information regarding
the product.
Through these various activities a fund of reliable in-
formation regarding the properties of a well made product
is being made available to engineers. The cloud of mystery
surrounding the manufacture of malleable castings is being
penetrated and the conscientious manufacturer now can pro-
duce reliable metal by availing himself of the research facil-
ities offered by the association.
The larger manufacturers have found it desirable to
continue research departments under their own control for
the investigation of their individual problems and for the
prosecution of research in subjects beyond the scope- of the
investigations made by the association.
A further step forward in the industry was made when
the American Society for Testing Materials began the de-
36 American Malleable Cast Iron
velopment of a specification for malleable cast iron. The
first specification was adopted in 1904 in a perfunctory man-
ner and apparently was dictated by a single individual. This
specification lay dormant for 11 years but later was actively
studied and revised until 1919 when it assumed its present
status.* All the requirements of the specification now in
use have been given adequate attention by a well informed
and competent group of men and are eminently calculated
to safeguard the interests of the consumer without being an
undue burden upon the producer. It may be assumed that
such future revisions of this specification will be made as
advancing knowledge and new requirements may warrant.
The necessities of the war also served as a great stimulus
in this as in other industries. The limitations of labor and
fuel and the exacting requirements of war material forced
the attention of all manufacturers toward a closer study of
their operations and better control of the product.
Probably the earliest application of malleable cast iron
was in the manufacture of buckles and harness parts. This
was a rather natural consequence resulting from white heart
practice where only thin cross sections could be readily de-
carburized. Subsequently malleable castings for wagon and
carriage parts were produced, and as the design of agricul-
tural implements progressed malleable iron was the major
material of construction. In fact, it almost can be said that
this material made possible the production of agricultural
implements at moderate prices. The use of chain belt in
implement work and more especially the invention of the
Ewart link started the manufacture of malleable chain belt
as an important development in the industry.
The railroads also became important users of mal-
leable in the form of couplers and smaller car details. For
many years it was possible to divide the malleable industry
of the country roughly between agricultural implement and
railway material plants. Indeed, this classification still sur-
Tentative changes were proposed at the 1922 meeting. See
Chap. XIV.
Development of Malleable Industry 37
vives in the malleable scrap market. Increasing train loads
forced the abandonment of the malleable coupler for rail-
way use about 20 years ago, although it survives on certain
mine car and similar equipment.
There remained, however, a considerable tonnage of
malleable car parts. Influenced partially by unfortunate ex-
periences with foundries selling purely on a price basis, and
partly by the introduction of the steel underframe to over-
come difficulties encountered with wooden details, the mas-
ter car builders restricted the use of malleable so that the
production of railway malleable rather rapidly decreased.
Peculiarly enough, while malleable castings were
viewed with disfavor by the car builders, practically all the
standard draft gears were still made of malleable and largely
continue to be made of that product. There is an obvious
contradiction, for the draft gear not only is of vital impor-
tance but is subject to more violent stresses than any other
car part. This is explained by the fact that in general the
manufacturers of draft rigging dealt with competent found-
ries and secured a uniformly good product. By tests of
their output they assured themselves against buying and
reselling inferior materials. The agricultural implement
trade meanwhile was largely withdrawn from the open mar-
ket with the establishment of foundries of their own by the
International Harvester Co. and others.
The manufacture of malleable pipe fittings also has
become largely the business of plants producing the finished
product instead of the castings. These developments and
the changed industrial conditions of the last seven or eight
years have very largely altered the selling field for mal-
leable castings.
The handicap under which the railroads operated, in-
volving curtailment of purchases, for a time reduced them
to an almost negligible factor in the market, although jour-
nal boxes, car wedges, derailers, draft gears, rail anchors and
many car parts now are made of malleable cast iron.
_38 American Malleable Cast Iron
The automobile and allied industries entered the field
at just about the time the railroad business began to
wane, and are among the heaviest consumers of malleable
castings. The applications are found in many vital de-
tails as in rear axles, spring shackles, and hubs, as well as
in less critical parts such as lamp and wind shield brackets
etc.
Another application is in some of the highest grade
electrical starting equipment for automotive use.
Applications in truck and tractor design of similar
character have been made. The use of malleable castings
for kitchen ranges has also become standardized in the
highest grades of this product. In hot water and steam
heating systems radiators are assembled almost exclusively
by the use of one of three types of malleable nipples, and
malleable pipe fittings are standard.
During the war the industry was kept at high pitch by
the exacting requirements of the allied governments. In
addition to the obvious peacetime applications, such as
railway equipment and automobile parts which were mere-
ly increased by war conditions, several entirely new uses
were developed.
Among the applications in ordnance material were
hand and rifle grenades, trench mortar shells and 75-milli-
meter shrapnel noses. The air service required fragmen-
tation bombs of malleable castings and the tank service
equipment and artillery tractors developed applications
analogous to ordinary automotive equipment but involving
greater difficulty in manufacture.
There is an extremely prevalent impression that the
manufacture of woodworking and other cutting tools of mal-
leable iron is a common commercial practice and that the
resulting product masquerades as steel. Some material of
this character must have been niade in times gone by, al-
though the writer in 18 years of rather intimate acquaintance
with the product of the largest producer and a fair familiar-
Development of Malleable Industry 39
ity with the output of some of the other principal manufac-
turers has never seen any of this product. A well known con-
sumer of malleable for other purposes states that hatchets con-
tinue to be made from malleable iron by at least two important
producers.
One important manufacturer of vises is a large con-
sumer of malleable and several concerns have made shear
blades to which steel cutting edges are welded. This, with
some business in the form of small hammers, and many
wrenches, seems to be the extent of tool applications.
Just what the future may hold in store can hardly be
foretold. The trend toward a critical study of the proper-
ties of all materials and comparison with the service require-
ments of engineering details without doubt will produce
occasional adjustment of the present conventional designs.
The railroad business doubtless is destined to return and
the automotive applications to increase. The opportunities
for malleable for radiator nipples, pipe fittings, etc., where
resistance to rust and to shocks is the determining factor,
are great. Applications in the electromagnetic field also
give promise of a bright future. This is equally true of
agricultural appliances, although carriages, wagons and har-
ness are permanently decreasing as the automotive appli-
cations increase. The shipbuilding field also holds consid-
erable possibilities.
Foreign Production of Malleable
The production of malleable iron in the Dominion of
Canada is of fair magnitude, there being 10 plants having in
1920 a production of about 30,000 tons in the aggregate.
In Europe the black heart industry seems to have been
limited for many years to a single British producer, the
Leys Malleable Castings Co., which began the manufacture
of black heart malleable some time between 1878 and 1880,
and the European factories of the International Harvester
Co. and the American Radiator Co. It is possible that rela-
tively recently other plants have started the manufacture
of black heart malleables in England, more especially during
40 American Malleable Cast Iron
the war period. It has been said that some ten or twelve
plants now engage in that operation, but the author has so
far been unable to obtain data as to tonnage which might
serve as a check on the magnitude of the British industry.
At the May 24, 1921, meeting of the British Iron Research
association Professor Thomas Turner declared that the
United States makes 10 times the number of malleable cast-
ings made in Great Britain.
Malleable Industry in Europe and Asia
The author's most recent information regarding the mal-
leable production of continental Europe is derived from
conversation with Raymond Gailly, of Gailly Freres, Charle-
ville, France. According to M. Gailly at present there is no
production of black heart malleable in France or Belgium.
However, many small and medium sized plants for the pro-
duction of the European type of product are being devel-
oped. In the larger plants, the mechanical equipment, espe-
cially for sand handling, is in accord with the most ad-
vanced practice.
Lower sulphur metal is becoming available, and an
increasing interest in the American process is developing.
Marcel Remy of Herstal, near Liege, Belgium, has been ac-
tive in an attempt to organize joint action by French and
Belgian foundries toward the study of the process, having in
mind the introduction of the American product. M. Remy
has submitted a report on malleable iron to an association
of" founclrymen at Liege which briefly summarizes the pres-
ent state of the art.
Commander Kawahigashi of the Imperial Japanese navy
advises that there is one malleable foundry in Japan operat-
ing on European principles and none making American
malleable. It seems probable that this constitutes the ex-
tent of the malleable industry of Asia.
Ill
METALLOGRAPHY OF MALLEABLE IRON
A~,L,of the ferrous materials used commercially may be
considered as alloys of iron and carbon. Their proper-
ties are determined primarily by the character of the in-
dividual constituents present. The possible entities or materials
present in commercial iron and steel are as follows :
Ferritc — -Carbon free iron.
Ccmcntite — Iron carbide having the formula FezC.
Austenite — A solid solution of iron carbide in iron, homo-
geneous in character and of indefinite carbon content.
Pearlite — A mechanical mixture composed of alternate
layers of cementite and ferrite in such a proportion as to con-
tain about 0.89 per cent carbon.
Martcnsite, troosite, sorbitc, etc — Various intermediate prod-
ucts between austenite and pearlite.
^Graphite — Free carbon in flat crystalline plates.
Temper carbon — Free carbon in an amorphous condition.
The common irons of commerce are all composed of various
combinations of these ingredients, thus:
Wrought iron is nearly pure ferrite.
Cast and annealed steel is ferrite and pearlite.
Tool steel (0.90 per cent carbon) when annealed is prac-
tically pure pearlite.
Steels which have been hardened and tempered are mar-
tensite, troostite or sorbite with or without the presence of
excess ferrite.
White cast iron is pearlite and cementite, as are also the
very high carbon tool steels (over 0.90 per cent carbon) when
annealed.
Gray cast iron is pearlite and graphite, usually containing
also more or less ferrite and sometimes cementite, depending
on the combined carbon content.
.42
American Malleable Cast Iron
Fig. 15 — Austenite and ledeburite in manganiferous white cast iron
Large gray areas, austenite; speckled white and gray areas, ledeburite, the
eutectic of cementite and austenite
Etched with picric acid x 2000
Fig. 16 — Martensite in quenched white cast iron is shown by inter-
lacing needle structure
Etched with picric acid x 2000
Metallography of Malleable Iron
43
Fig. 17 — Troostite in steel. The dark spots are troostite
Etched with nitric acid
x 2000
Fig. 18— Pearlite in incompletely annealed malleable
Alternate bands of ferrite and cementite are shown
Etched with picric acid x 2000
44
American Malleable Cast Iron
Fig. 19 — Spheroidized pearlite
Lamina of cementite in a matrix of ferrite are shown, the lamina being in
part changing to globules by surface tension
Etched with picric acid x 4000, but reduced one-half in reproduction
Fig. 20 — Graphite in gray iron
Unetched
Metallography of Malleable Iron
45
Fig. 21 — Soft gray cast iron
Black represents graphite flakes, the white areas surroundng the black are
ferrite, the speckled areas are iron carbon phosphorus eutectic, and the gray areas
pearlite
Etched with picric acid x 20U
Fig. 22 — Malleable cast iron
The black represents temper carbon nodules and the white ferrite
x 200
46 American Malleable Cast Iron
Malleable cast iron is ferrite and temper carbon.
It will be noted that the latter product differs from all the
others in containing only free carbon and free iron. Further it
is the only material containing temper carbon and the only
cast material containing ferrite and no pearlite or other form
of combined carbon.
It owes its properties to this combination of constituents,
and in turn it owes its metallographic composition to the peculiar
circumstances under which it is produced. In this case, as in
all others, the particular metallographic entities present are
determined by the chemical composition and heat treatment of
the alloy.
The particular substances which are stable at different
temperatures and concentrations of carbon were first sys-
tematically recorded by Roberts-Austin. The Roberts- Austin
diagram has since been modified in accord with later and more
accurate quantitative observations, and in the light of new
knowledge by many contributors.
It can be shown that there are two typically distinct series
of alloys. In one, cementite and iron are the components
present, either free or in solution in each other, while in the
second free carbon enters to more or less replace the carbon
of the cementite. On the basis of X-ray spectrograms, Jeffries
and Archer have concluded that cementite itself cannot be dis-
solved in solid iron. Alexander has taken exception to this rea-
soning. Without wishing to attempt an expression of opinion
as to the merits of the controversy in a field with which he is
but slightly familiar the author is definitely sure that two dis-
tinct types of solid solutions exist — one of or in equilibrium
with cementite and the other of or with carbon.
It has been clearly shown by Cesaro that molten cast iron or
steel is a solution of cementite, Fe.£, in iron, Fe2. Volumes have
been written to prove or to disprove the thesis that all graphite is
derived from the decomposition of solid, or frozen cementite.
However this may be, temper carbon is always a decomposition
product of previously formed cementite, since the casting before
anneal consists only of cementite and pearlite.
Metallography of Malleable Iron
20 % CARBON
Fig. 23 — Benedict's diagram recording the equilibrium conditions in
terms of temperature and agraphic (non graphitic) carbon.
It is based on Benedict's principle, somewhat modified
In this case, at least, we may base our conclusions on the
conditions as outlined by the Benedicks in the form of a double
diagram. Fig. 23 sums up the principles of Benedick's views
with sufficient accuracy for the present purpose.
In this diagram the absissae or horizontal dimensions, rep-
resent carbon content in per cent, the ordinates or vertical
dimensions represent temperatures in degrees centigrade. The
conditions of equilibrium are then represented by various lines
and fields on the diagram. Thus above ABD the metal is a
homogeneous liquid. A,BD marks the relation between car-
bon content and the beginning of freezing, while AEBC marks
the relation of carbon content and completion of freezing. In
the area AEB and DBC the metal consists of a mixture of
homogeneous liquid and theoretically a homogeneous solid. In
the former area the solid has all the properties usually associat-
ed with a solution except fluidity, hence the term 'solid solu-
48 American Malleable Cast Iron
tion/ The alloy of lowest freezing- point B, carbon 4.3 per cent,
is known as the eutectic and alloys having a higher carbon con-
tent than E, carbon just under 2 per cent, are said to be eutectif-
erous, that is, their freezing is completed by the solidification of
a liquid eutectic at constant temperature of 1130 degrees, Cent.
Davenport has pointed out that the massive character of ce-
mentite in commercial white cast iron is an evidence of super-
cooling below the eutectic freezing point followed by the separa-
tion of pro-eutectic cementite in addition to the cementite ot
ledeburite. This point is of interest to the metallographer, but
may be disregarded for the present discussion. The solidifica-
tion of noneutectiferous alloys to the left of E is completed
by the freezing of a solid solution of composition dependent
on the original carbon content at temperatures marked by the
line AE. Below the freezing point, other rearrangements
o£cur, in the solid metal.
These transformations occur at definitely fixed temperatures
dependent on carbon concentration. These temperatures are
known as thermal critical points, and four important distinct
critical points have been studied, although more are believed to
exist. A critical point is marked by the symbol A. The four
important ones are distinguished from one another by suffixes,
the points being named Aif A2) Az and Acm. The numerals
represent their relative location as to temperature, Al being the
lowest, A3 the highest. Acm is not strongly marked thermally,
but represents the solubility above A^ of cementite contracted to
cm. Critical points vary in position according as they are meas-
ured on a rising or falling temperature. A point determined
on a falling temperature has the letter r preceding the suffix,
while c designates a critical point determined on a rising tem-
perature. Thus Ac^ is the lowest critical point found on heat-
ing from room temperature, and Art the same point as de-
termined in cooling. A c point is always located as high or
higher than the same r point due to lag phenomena. The des-
ignations c and r originated as the initial letter of the French
terms for heating and cooling. The A^ point represents the
temperature below which cementite becomes insoluble. The A2
and Az points represent molecular changes within the iron not
Metallography of Malleable Iron 49
pertinent to our present discussion. These changes are called
allotropic. Incidentally, however, the line COS marks the
minimum solubility of cementite in the solid solution or perhaps
better the maximum solubility of iron in the solid solution.
Alloys below and to the left of this line are mixtures of ferrite
and saturated solid solutions Alloys in the angle GOSE are
homogeneous solid solutions and alloys below and to the right
of ES are solid solutions mixed with cementite.
For a full discussion of the iron carbon diagram, which
is impossible in this connection, the interested' reader is referred
to Dr. Howe's monumental work, "The Metallography of
Steel and Cast Iron."
The exact location of some of the lines has been ques-
tioned on the basis of accuracy of observation. The solid lines
of the figure indicate the equilibrium conditions in the metastable
system FezC — Fe.
Freezing of White Cast Iron
Confining attention to that area between the values carbon=
2.00 per cent and carbon— 3.00 per cent, marked at the lower
part of the diagram as the range for commercial white cast
iron, it is found that molten iron begins to freeze when it
reaches the temperature corresponding to the intersection of the
line A B with the vertical line corresponding to its carbon
content. Thus for a carbon content of 2.50 per cent indicated
by the line x-x on the diagram, the freezing point is at a.
The solid material is lower in carbon than the liquid material
remaining, thus at a temperature b the alloy x-x has a solid
phase of the carbon content r and a liquid phase of the carbon
content d. At the temperature e, constant for all alloys of more
than 2 per cent total carbon, the remaining liquid or eutectic
freezes as an alloy containing 4.3 per cent carbon. The solid
formed just before the eutectic freezes, contains about 2 per
cent of combined carbon. In freezing, the eutectic breaks up
into cementite and austenite containing 2 per cent combined
carbon identical with the solid portion' formed just before the
freezing of the eutectic. This eutectic when frozen is known
as ledeburite.
50 American Malleable Cast Iron
As the temperature decreases further, austenite is saturated
with less than 2 per cent combined carbon, the solubility de-
creasing with the temperature as shown by the line E S. Thus
when the alloy x-x is at the temperature / it consists of cementite
and a decomposition product of austenite of a carbon content ' g.
When the temperature falls to A± at the point h the solubility
• of cementite in iron becomes nil and the remaining solid solution
then containing about 0.90 per cent carbon, is converted into
pearlite consisting of a mixture of cementite and ferrite in
such proportion as to give a carbon content of 0.90 per cent.
It must be remembered that while these various transformations
of the solid solution are going on, there exists also the cemen-
tite formed during freezing so that below A± the metal con-
sists of cementite, pearlite (cementite + ferrite) and the socalled
proeutectoid cementite separating along Acm. This is the actual
course of events during the freezing of the ordinary white cast
iron of the malleable industry.
The system has been described as metastable, in other words,
it is permanent as regards its components, not because actual
final equilibrium has been attained but because further re-
arrangement is impossible under the temperature conditions
obtaining. If the iron be maintained sufficiently long at high
temperature, either in cooling or by reheating, the cementite
directly or indirectly will be converted into free carbon.
This reaction is due to the fact that at a given tempera-
ture carbon is less soluble when not combined with iron than
in the form of Fe^C. The equilibrium conditions in the sLable
system Fe — C, are approximately shown by the dotted lines.
Ruef and Bowman have located the line E'B' at 1138 degrees
Cent. — 1 degree (about eight degrees above the eutectic freez-
ing point of the metastable alloys). The solubility of free car-
bon, as distinguished from cementite is shown by the line
B'E'S' although there is room for argument as to its inter-
section with the line of nil carbon content and with A± line.
If the alloy marked xx be maintained at / a very long time,
free carbon will precipitate and cementite dissolve until none of
the latter remains and the system consists of free carbon and an
alloy having an agraphitic (not free) carbon content /. If now
Metallography of Malleable Iron
51
cooling be very slow the carbon can be progressively precipi-
tated with decreasing temperature until at, or about, Alf no
agraphitic carbon will remain. Archer maintains the solubility
at A!, to be about 0.7 "per cent carbon and graphitization to be
complete below that point only.
Recent work under the writer's supervision by Austin,
Payne and Gorton since the preceding paragraphs were written
has demonstrated the existence of a solid solution which we
f/? Presence OS* An Ex-
cess 0/*
Fig. 24. — A further modification of Benedict's diagram indicating the
results of recent research work
have named boydenite. It bears the same relation to the
stable system which austenite, in its generic sense, bears to
the metastable. Carbon has been shown to have a defi-
nite solubility as boydenite immediately above Alt confirming
Archer's views as to the existence of a eutectoid of carbon and
iron. The relation of the carbon concentration of that eutectoid
as now determined to that of pearlite is contradictory to
Archer's opinion. The solubility of carbon in boydenite has been
accurately determined and the probable locus of the Alm line
E'S' determined. The necessary revisions in the equilibrium
diagram are shown in Fig. 24, which represents the best.informa-
52 American Malleable Cast Iron
tion now at hand on the matter. The diagram also has been modi-
fied to take cognizance of the fact that the alloys are not binary
but ternary containing carbon, silicon and iron. The liquidus in-
dicated is derived from Gontermann's data interpreted in the
light of additional experiment by Hird in the author's laboratory.
Graphite and Temper Carbon
Graphite and temper carbon are chemically identical and
differ only in geometric form. Which one is formed depends
only upon the temperature at which graphitization occurs.
lokiche has demonstrated by radiographic means that their crys-
talline and atomic structure is identical. If carbon forms at
a temperature near the eutectic freezing point, hence in a nearly
liquid medium, it can spread out into crystalline flakes of
graphite. If it is formed in nearly solid iron at relatively
low temperature it remains in the "amorphous" temper form.
The terms "crystalline" and "amorphous" in this connec-
tion are survivals of earlier concepts and in a measure
are misleading in the light of present knowledge of what
constitutes crystallinity. Temper carbon is actually possessed
of crystalline structure, i. e. orientation of its atoms, but
has not grown into a geometric crystalline form. It corres-
ponds to graphite which has been crushed to powder and bears
the same relation to graphite that powdered sugar does to rock
candy.
The function of malleable metallurgy is to produce a gra-
phite-free casting and then graphitize this at temperatures such
that temper carbon results. The terms "graphitize" or "graphitiza-
tion" apply to the separation of free carbon irrespective of its geo-
metric form.
To this end the foundry must produce a white cast iron
of such a composition as to be readily graphitized. The ten-
dency to graphitization both during cooling and in annealing
is affected greatly by the chemical composition of the product.
Thus silicon and some of the rarer elements, notably aluminum,
promote the formation of the stable system while sulphur, man-
ganese, and some rarer metals retard the formation of the
stable system. It can be seen that the properties of malleable
Metallography of Malleable Iron 53
iron depend largely on the total carbon present, because the
more carbon is present the more will the ferrite matrix, of
which the product is mainly composed, be interrupted by that
element. Since the carbon possesses no strength, every temper
carbon granule decreases by that much the strength of the
product. In the early days much malleable was made high in
carbon, owing to the advantage of a lower melting point with
correspondingly greater fluidity. At times the carbon was
so high, as compared with the silicon, that some graphite formed
in freezing, making a bad matter worse, for obviously, a thin
flake of carbon will do more damage than a spherical nodule of
equal weight. From this practice resulted much of the "rotten"
iron sold 10 years ago. Fig. 25 shows such a metal, in which
' 'primary" graphite present in the original hard iron persists
unaltered after annealing in the form of thin flakes. These are
located between ferrite grains and cut up the structure badly.
Use of Silicon
Most of the malleable iron made by the better manufac-
turers today ranges from 2.30 to 2.70 per cent carbon before
annealing. An average for a high grade product in castings of
fair size would probably be between 2.40 and 2.50 per cent.
Small work, especially where the highest strength- is not needed,
still is often made of higher carbon content, even up to 3 per
cent, although this is not good practice from the viewpoint of
the best physical properties. Since the size of the casting affects
the rate of cooling it also affects the tendency to graphitize on
freezing and hence the chemical composition required to pre-
vent this occurrence.
Quite generally, this tendency is held in check by controlling
the silicon content. When little or no silicon is present, graphi-
tization in the annealing process is retarded to a commercially
prohibitive degree. When too much is present graphitization
may be so much promoted as to take place during freezing.
Most classes of work have a silicon content of from 0.60 to
0.80 per cent.
It is general practice and sound metallurgy to vary the
silicon inversely with the carbon and for a given carbon, in-
54
American Malleable Cast Iron
Fig. 25 — Graphite crystals in malleable made from hard iron con-
taining graphite
Black grains represent temper carbon ; heavy black lines, graphite ; thin black
lines, grain boundaries ; white, ferrite
Etched with alcoholic nitric acid x 100
versely with the cross section of the castings. The purpose of
this practice is to select the silicon for a given carbon that the
castings will be absolutely free from graphite.
For rather low carbons, say between 2.10 and 2.40 per
cent, it may be good practice to let the silicon vary at nearly
the same rate as the carbon. For instance, 2.40 carbon and
0.75 silicon metal has practically the same tendency to be
graphitic in the casting or to mottle as 2.10 carbon and 1.05
per cent silicon. In higher ranges of carbon, say from 2.40
to 2.80 per cent the silicon may vary only three-fourths as fast
as the carbon, .2.80 carbon and 0.45 silicon corresponding to
2.40 and 0.75 per cent silicon.
Extremely Low Silicon Undesirable
The reduction of silicon to values as low as 0.45 per cent
is not usually good foundry practice because such iron is easily
oxidized in melting and produces pin holes and similar diffi-
culties due to the liberation of carbon monoxide while the metal
Metallography of Malleable Iron 55
Fig. 26 — Unannealed hard iron. The structure is always dendritic but
varies slightly with the carbon content
White is cementite; gray is pearlite.
Etched with picric acid x 100
is freezing. A casting which would prove large enough to re-
quire the carbon 'and silicon referred to above probably could
not be successfully made with less than 0.55 or 0.60 per cent
silicon, thus setting a limit for maximum carbon distinct from
consideration of strength. The maintenance of proper relation-
ship between carbon, silicon and size of casting is usually pos-
sible only on the basis of foundry experience and constant at-
tention to results ; consequently these matters cannot be briefly
and adequately dealt with in any terms of general application.
From the consumers' viewpoint, any attempt to embody them
in specifications would be the height of folly, because the prac-
tice of no two plants, in matters of casting temperature, sand
preparation, etc., would be nearly enough alike to make any one
specification generally applicable even on a single class of work.
The problem would be further complicated by variations in
the size of castings. The figures previously given may be un-
derstood, to apply to fairly heavy castings and represent nearly
minimum values of silicon for a given carbon. Light work may
56
American Malleable Cast Iron
possibly run 0.20 to 0.30 silicon higher and unusually small
work even beyond that. On such extremely light work the
carbon also is occasionally well above 2.80, as previously ex-
plained, sometimes going over 3 per cent.
It is not necessary to lower the silicon for 3 per cent carbon
2J0 ^.00
Fig. 27 — Effect of silicon in relation to carbon on malleable. This
graph is based on data from Thrasher's determinations
far below that used at 2.80, partly because the tendency to
mottle in very high carbon alloys is relatively little affected by
the silicon. In alloys of this character the graphitization ten-
dency is dependent mainly on the cooling rate. They should
never be used in metal sections of any thickness since their
Metallography of Malleable Iron 57
freedom from graphite is dependent primarily on their rapid
cooling.
Sulphur and manganese have been referred to as opposing
graphitization. These two elements unite to form manganese
sulphide. This compound apparently has no effect on the
formation of temper carbon. Accordingly, the absolute amounts
of the two elements in the metal are unimportant provided they
are in the proper proportion. It is found impracticable to fol-
low the theoretical proportion of the two elements exactly, a
slight excess in manganese always being necessary.
Effect of Manganese Sulphide
A low sulphur can be had only by very close selections of
fuel and melting stock and is impossible of practical attainment
except in electric furnace practice. The low manganese re-
quired for low sulphur also presents difficulty on account of the
manganese content of the available ores. The presence of a
moderate amount of manganese sulphide does no harm and is
sometimes a manufacturing advantage. The user need there-
fore have no fear of sulphur. The only harm this element can
do is to prevent complete graphitization in the anneal. A physi-
cal specification for tensile properties will protect the consumer
adequately in this point and leave the foundryman to operate
his process to the best advantage with the fuel and stock avail-
able.
The value for sulphur, .06 per cent maximum, written into
the 1904 specifications of the American Society for Testing
Materials, and abandoned at its first revision, is particularly ill
founded in view of the fact that very little malleable is made
in the air furnace which does not contain about that amount
before annealing. During the anneal there always is an in-
crease in sulphur ranging from 0.005 to 0.03 per cent. It
therefore is practically impossible to -produce from commercial
raw material a product which would continuously pass this
specification. The highest grade annealed product of com-
merce has from 0.065 per cent to 0.10 per cent sulphur, thus
indicating the unsoundness of the 0.06 per cent limit.
58
American Malleable Cast Iron
Fig. 28 — Beginning of graphitization after one half hour at 1700
degrees Fahr.
Black represents temper carbon ; white, cementite ; gray, martensite to sorbitic mixed
crystals. Etched with picric acid x 100
Fig. 29 — Progress of graphitization after ll/2 hours at 1700 degrees
Fahr.
Black represents temper carbon; white, cementite; gray, martensite to sorbitic mixed
crystals. Etched with picric acid x 100
• Metallography of Malleable Iron 59
Electric furnace metal can be produced as low as 0.01 per
cent sulphur before annealing. The application of the desul-
phurizing process is controlled by one producer through the
Kranz patents. No particular advantage has been found to re-
sult from these very low values as compared with slightly higher
amounts and the triplex process usually is not operated to
secure desulphurization to a point below 0.04 per cent.
Phosphorus also has been regarded with more fear than is
warranted. In small amounts it has no effect on the product;
for example, iron containing 0.05 and iron with 0.15, per cent
phosphorus would have commercially identical properties.
When this element is increased to about 0.25 per cent it
no longer is completely soluble in the ferrite of the finished
product. It then has a direct effect on the properties of the
metal. In this respect phosphorus differs from all the other
common elements, in that its effect is not due to its action on
the graphitizing process.
The exact point where phosphorus begins to exert a harm-
ful effect depends to some extent on the heat .treatment em-
ployed. Commercial melting stock and pig iron grading are
such that the commercial product contains from 0.15 to 0.20
per cent of the element, usually about 0.18 or 0.19 per cent,
which is amply safe.
The microstructure of the unarinealed product is practi-
cally independent of chemical composition, unless the latter be
strikingly abnormal. The structure is always dendritic, con-
sisting of hard white cementite and a darker ground mass of
more or less well developed pearlite, as shown in Fig. 26. Of
course, there are miner differences of structure as between
different samples, lower carbon iron containing relatively less
cementite and higher carbon more. The coarseness or fineness
of crystalline structure is dependent upon the rate of freezing.
In very rapidly chilled metal it may happen that a mesh struc-
ture is substituted for the dendritic. This condition is unusual
in castings.
60
American Malleable Cast Iron
Fig. 30. — Progress of graphitizatoin after 3^2 hours at 1700 degrees
Fahr.
Black represents temper carbon ; white, cementite ; gray, martensite to sorbitic mixed
crystals. Etched with picric acid x 10(1
Fig. 31 — Equilibrium at 1700 degrees Fahr. after 70 hours
Black represents temper carbon; gray and white, martensitic mixed crystals
Etched with picric acid x 100
Metallography of Malleable Iron 61
Turning now to the second metallurgical step in the process,
let us consider the changes taking place during graphitization
in the so-called annealing of castings.
This process has for its object, not the elimination of car-
bon as many appear to believe, but the conversion of a
metastable alloy containing Fe3C and Fe into the stable system,
consisting only of Fe and C. This reaction involves no changes
of the ultimate chemical composition. All of the elements re-
main unaltered in quantity, the carbon only being converted
from the combined to the free state, according to the reaction,
Fe3C=3Fe+C.
That a certain amount of carbon is oxidized is a mere in-
cident in the process. The elimination of carbon is of prac-
tical significance but is not in any sense the purpose for which
the annealing operation is conducted. In this theoretical dis-
cussion of the principles of malleable iron metallurgy this de-
carburization will be disregarded and only the essential graphitiz-
ing reaction will be considered.
In the early part of the chapter the conversion of the
metastable into the stable system was touched upon and the
mechanism of the change described. The equilibrium in the lat-
ter system is not as clearly understood as that of the former.
This is due largely to the fact that steel and white cast iron
furnish commercially important examples of the metastable
system in which equilibrium frequently is attained. Consequent-
ly there was material ready to hand and also a commercial
necessity for the study of the system.
Commercial Application
Malleable cast iron furnishes the only commercial application
of material involving the attainment of equilibrium conditions
in the stable system. .Because the output of malleable is small
compared with that of steel and also because the product was
not always known and understood, even by the more progres-
sive engineers, the theoretical aspects of the problems of mal-
leable metallurgy received inadequate attention and the studies
made in the laboratories of some of the universities lacked the
advantage of contact with the commercial aspects of the problem.
62
.-hnerican Malleable Cast Iron
Fig. 32 — Imperfect attainment of equilibrium below AI due to too short
a time
Same as Fig. 31, followed by three hours at 1200 degrees Fahr. Black areas
surrounded by white represent temper carbon ; white, ferrite ; gray, pearlite.
Etched with picric acid x TOO
Fig. 33 — Normal malleable iron, metastable equilibrium below
Black represents temper carbon ; white ierrite
Etched with alcoholic nitric acid
x 100
Metallography of Malleable Iron 63
Significant work leading toward the establishment of a cor-
rect equilibrium diagram for the system Fe-C was done by
Storey at the University of Wisconsin, Archer and White at
Michigan and Merica at the United States bureau of stand-
ards. Howe also gave adequate attention to the mechanism of
graphitization in his "Metallography of Steel and Cast Iron."
It has been pointed out a number of times in this text
that the conversion of cementite into free carbon results purely
from the fact that the solubility of carbon in the stable system
is less than in the metastable. That is, solid iron will dissolve
less free carbon than carbon in the form of iron carbide.
When a white cast iron is maintained at a temperature
higher than the lower critical point, Ac± (1350 to 1400 degrees
Fahr.) free carbon is slowly formed and combined carbon is re-
duced to a corresponding degree. The rate at which this change
takes place, while depending upon the chemical composition of the
metal, is greater the higher the temperature. However for each
temperature there is a definite value of combined carbon prac-
tically independent of the total carbon content, when the re-
action ceases completely. These values of "combined" carbon,
measuring the solubility of carbon as distinguished from iron
carbide in solid iron, have for their locus the line E'Sf in Fig. 24.
The word "combined" is used in the preceding sentence in
what may be a somewhat inaccurate sense. It is intended to
differentiate free carbon from carbon which is not in the free
state. Whether the combined carbon corresponding to the line
E'S' is actually combined with iron is very problematical. Quite
possibly it is in solid solution and is not actually combined with
iron.
Microstructure of Malleable
Fig. 26 shows the. structure of. a normal piece of hard iron
as cooled in the mold. When white cast iron is raised to a
temperature well above the Acl point, say 1700 degrees Fahr.,
a decrease in cementite and an increase in the constituent forming
the gray background, called "mix crystal" or solid solution,
is observed. (See Fig. 28.) This results from the greater
solubility of cementite at the higher temperature.
64
American Malleable Cast Iron
Fig. 34— Graphite crystals produced by annealing at 2100 degrees Fahr.
Black represents graphite; white, pearlite. Unetched x 100
Fig. 35 — Manganese sulphide in malleable cast iron. The arrows
joint to MnS
Etched with picric acid x 500
Metallography of Malleable Iron 65
As the heating at 1700 degrees is continued, temper carbon
begins to form at the expense of cementite, as shown in Figs.
29 and following, and finally equilibrium is attained by the
destruction of all cementite. The structure then consists of
temper carbon and solid solution of carbon in iron, as shown
in Fig. 31 and is incapable of further change as long as the tem-
perature remains unchanged. The product then is still whitish
in fracture and very brittle. .
If the temperature is allowed to decrease the solubility of
carbon grows less and more temper carbon will form if the ma-
terial is held sufficiently long at the lower temperature. How-
ever, no ferrite will be formed at any temperature above the
critical point. The ground mass above this point will remain a
homogeneous .solid solution, differing only in carbon concentra-
tion from that remaining at higher temperatures.
If the temperature is carried down to 1300 degrees, that
is, below Arlf the carbon is completely insoluble, though
equilibrium may not be reached unless the approach to this
temperature is very slow. In case the time at 1300 degrees is
not very long, a structure as shown in Fig. 32 will result, con-
sisting of temper carbon surrounded by ferrite which in turn
has a background of still incompletely decomposed mix crystal
persisting from the higher temperature. At temperatures above
the critical point, this ferrite separation does not occur, the
structure strongly resembling Fig. 31, except as to detail in the
metallic matrix.
Still further treatment at or slightly below Ai\ will result in
the complete graphitization of the product as shown in Fig. 32
which represents the structure of malleable cast iron. Accord-
ing to Archer's views as to the solubility of carbon at A±
graphitization is always completed only by treatment below A±
as outlined above. Graphitization is accomplished commercially
by just such a heat treatment, that is, by heating first to a
fairly high temperature for a considerable period and then cool-
ing sufficiently slowly to a temperature below the lower critical
point of the stable system.
The maximum temperatures and time chosen are largely a
matter of individual judgment. The exact location of this line
66
American Malleable Cast Iron
on the equilibrium diagram unfortunately has not been the
subject of adequate research. Much remains to be done in map-
ping its course exactly. Our last knowledge is summarized in the
revised diagram Fig. 24. Since there is no microscopic evidence
of an iron carbon eutectoid it is somewhat doubtful whether Atrn
should be interpreted as ending at S' or whether there is a
sharp inflection at 5', Atm running nearly parallel to A: to or
toward Pr . The significance of A2 and As in the stable system
has so far eluded experiment, and nothing final has been ac-
I I I
Diagramatic Representat on
£00%
.._cti _,.-..-
inversion in
>ined Carbon
1.002
\
5
^JlE^
£03
Time Scale Will Depend On Chemical Composition
Fig. 36 — Chart showing conversion of combined carbon into temper
carbon
The graphs show the relation between the carbon remaining combined and the
lapse of time at each of five temperatures. Note the increasing velocity and
higher carbon content of the conclusion at high temperatures as compared with low.
complished toward the location of 5"' as affected by variations
in other elements than carbon.
These points are of very great academic interest, but from
an operating viewpoint are inconsequential. No operating
errors will be involved in considering the line to be straight and
joining the two points mentioned.
Fig. 36 showrs in diagrammatic form the decrease in com-
Metallography of Malleable Iron 67
bined carbon according to the time of exposure to various
temperatures. It will be noted graphs are given for each- 'of
a number of temperatures. The horizontal or time ordinates
have been plotted to scale ; however, the values given for this
dimension are suggestive only, since the rate of graphitization
and hence the time to attain equilibrium at various temperatures
is dependent on the chemical composition with respect to other
elements in addition to carbon. The figure is given as an ex-
ample of what may happen rather than for quantitative inter-
pretation.
Speed is promoted by graphitizing the cementite at the
highest possible temperature but to a certain extent at the ex-
pense of quality. Temper carbon differs from graphite only in
form. It has been pointed out that these differences of geo-
metric form are due to the temperature of the metal in which
the free carbon is formed. Accordingly, the two forms, temper
and graphitic, shade over into each other by infinitesimal degrees
and the temper carbon formed at high temperatures may grow
so coarse and flaky as to be almost graphitic. Fig. 34 shows the
carbon produced by graphitization at 2100 degrees Fahr. far
above any commercially possible temperature. It will be seen
that this carbon is purely graphitic and bears no resemblance
to the temper form. Also the matrix of malleable iron is not a
continuous mass but consists of an assemblage of individual
grains as shown in Fig. 33. The character and size of this grain
structure is influenced by changes of heat treatment, introducing
another viewpoint for the selection of annealing temperatures.
Moreover, high temperature may cause operating difficulties
due to the deformation of castings, destruction of pots and
fusing of packing material. An attempt to reduce the annealing
period too far by a rise in temperature therefore is usually
inadvisable.
Commercial practice involves a maximum temperature of
the castings of between 1500 and 1800 degrees Fahr. The time
for maintaining the maximum temperature varies from 24 to
American Malleable Cast Iron
60 hours, or even longer, the longer periods properly accompany-
ing lower temperatures. The commercial rates of cooling are
variable, ranging from 5 to 12 degrees per hour.
In general the best practice is opposed to the highest tem-
peratures, the minimum time of holding and the fastest cooling
and favors a maximum temperature not far above 1600 degrees,
a time not less than 40 hours near that temperature, and an aver-
age cooling rate certainly not faster than 10 degrees per hour;
preferably less, more particularly near the critical point.
.When properly heat treated, malleable cast iron contains no
combined carbon except just under the surface.- It is prac-
tically impossible to entirely eliminate these last traces of
pearlite from the casting, but this ingredient can and should
be reduced to the point where it is equivalent to not more than
0.15 per cent of combined carbon as referred to the total weight
of the casting.
Approximately six years ago Thrasher published in
graphic form the relation between carbon and silicon in
while iron for constant tendencies to mottle. Based on the form
of Thrasher's curves and known points near the middle of the
range of composition for various classes of work, Fig. 27 has
been prepared indicating the approximate relation between car-
bon and silicon for various classes of work, based on the ten-
dency to primary graphitization only.
• No attention has been given to the weakening effect of car-
bon which sets limiting values on that element nor on pouring
temperatures or other variables which may affect graphitization.
The data presumably apply to ordinary air furnace practice and
doubtless are subject to a certain amount of modification accord-
ing to other variables.
The more or less unavoidable oxidizing conditions in an-
nealing remove some carbon from the surface. The extreme sur-
face of malleable generally contains about 0.40 or 0.50 per cent
combined carbon, while metal more than 0.1 -inch below the
Metallography of Malleable Iron
69
surface is but little affected. Malleable castings sampled so as
to include no material less than 1/8-inch below the surface will
have nearly the ultimate composition of the original hard iron,
except for the absence of combined and the presence of free
carbon. If the sample is taken to include the entire cross sec-
tion of metal the total carbon will vary with the thickness of
Fig. 37 — Changes of metallographic composition during the freezing
and annealing of white iron
the casting and will range from 0.40 per 'cent or even less up to
the original carbon of the hard iron. In Fig. 37 the changes in
carbon distribution during freezing of the hard iron and during
its subsequent annealing are summarized in diagrammatic form.
Time (estimated) is plotted as abscissae. At the top of the
diagram the assumed temperature-time curve is plotted. At the
bottom the relative weights of the various metallographic en-
tities are recorded, the sum of course always being 100 per
cent. Along the middle of the diagram the carbon concen-
tration of the various homogeneous solutions (solid and liquid)
is plotted for convenient reference.
IV
GENERAL MANUFACTURING AND PLANT
TODAY all malleable foundries in the United States
and Canada operate upon the same general principles
although, of course, the manner of execution of the in-
dividual operations varies with the ideas of the individual
operator and the facilities at his disposal.
Physically the foundries of the country differ widely
both in size and type of buildings. The range in capacity
of plants is probably from 50,000 tons per year down to 1000
tons or less. If plants making malleable only as a side issue
are included, the minimum capacity is considerably less than
1000 tons. The plants range from antiquated structures of
brick with low wood roofs to modern brick, concrete and
steel buildings.
A similar range exists in the facilities available in the
form of mechanical equipment and, unfortunately, also in
the personnel. It does not necessarily follow that the larg-
est production is coupled with the best buildings, mechan-
ism and talent although in this as in other industries, many
things are possible for the large operator which are not a-
vailable to the smaller. Large scale operations generally in-
volve conditions better suited to the procurement of men
and machinery of the highest order.
In a previous chapter there have been outlined the prin-
ciples upon which malleable cast iron depends for its proper-
ties. It was there shown that the metal is the product of two
distinct operations — the making of castings of white iron
and the malleablizing of the castings by a subsequent gra-
phitizing or annealing process. This divides the process in-
to two distinct stages and, generally, the plants into two
separate parts — the foundry and the annealing departments.
Centered around each of these major departments are
others of a contributing character such as the stockyard,
mason's department, flask shop, patternshop, coreroom, melt-
ing department, and chemical laboratory as foundry adjuncts
72
American Malleable Cast Iron
bfi
u>
o
bb
General Manufacturing and Plant 73
and cleaning, trimming, inspection and shipping depart-
ments, engineering and metallographic laboratories as ad-
juncts to annealing. Plant maintenance also requires the
operation of a power station, machine shop, electrical de-
partment, etc. There are additional departments not direct-
ly of a manufacturing character, including those pertaining
to sales, purchase, accounting, labor, costs, first aid and
others.
The actual shop organization by which the departments
are subdivided between groups of executives differs widely
in different companies. Even the largest producer, operat-
ing- seven malleable plants, finds it wise to use a somewhat
different organization scheme in each of its foundries.
Small plants usually are practically "one-man" shops. One
executive, often the proprietor, exercises supervision over
all works activities. The scheme is simple, but incapable of
any very great growth.
A common method is to divide the duties among three
major foremen or superintendents. One has charge of the
foundry and is responsible for everything up to the delivery
of hard castings to the trimming room; another converts
these into the finished product; and the third is in charge
of power plant, carpenter, machine and pattern shops, etc.
Sometimes the last two are co ordinated under one head,
making only a foundry and finishing department. A much
more highly organized and efficient system is represented in
the organization chart shown in Fig. 38, which is applicable
only to a fairly large organization and incidentally is not
exactly followed in any plant of which the writer has
knowledge.
The raw material purchased by a malleable plant con-
sists of pig iron and scrap as melting stock ; coal, coke and
sometimes oil, gas and electric power as fuel ; molding and
core sand for the foundry and refractories for the furnaces.
In addition a wide variety of general supplies is used in
more limited quantities.
In almost all plants the melting operation is executed
in air furnaces which generally make two heats a day. In
74
American Malleable Cast Iron
K *i-ir
General Manufacturing and Plant 75
some plants only one heat is made and in a very few two or
three heats every other day and none on the intervening day.
The latter practice is a survival of a practice in vogue 15
or 20 years ago. Heats vary considerably in size. On a
two-heat a-day basis, they vary in different plants from
seven tons to 24 tons each ; on a one-heat basis, from about
18 to 35 tons, and on a three-heat basis from five to 10 tons.
In a few plants the cupola is employed 'for melting but
this practice is not recommended for important work. Open-
hearth melting has been tried by a number of producers
and while not well adapted except to continuous operation
and large tonnages is in successful use in a limited number
of plants. A few small furnaces each having a capacity of
about five tons are said to have been tried. The charge in
most successful open-hearth installations averages from 14
to 20 tons.
A single producer operates electric furnaces at two
different plants. From 10 to 12 heats and even more when
molds are available, are 'made in 24 hours, but the metal
is delivered to different molders so that generally a given
molder only pours off twice per shift. In these plants heats
range from five to seven tons and from eight to fifteen tons
in weight depending on furnace capacity. Six and twelve
tons are the nominal furnace capacities.
Molding still is done by hand in many shops as it
was in all plants 15 years ago. The patterns being small,
many are mounted on a single gate. The pattern is pro-
vided with a match part and the mold made in a snap flask.
Hand operated squeezers 'have been in use for many years,
the air-operated devices apparently not having met with
general favor, although used in some plants.
Recently the trend has been strongly toward patterns
mounted on plates and vibrated by air when the cope is
being lifted or the pattern drawn.
In many localities no labor now is available capable
of commercially producing molds fro'tn other than plate pat-
terns. Consequently this form of mounting which requires
less skill of the molder than any other, is practically forced
76
Malleable Cast Iron
be
£
General Manufacturing and Plant 77
on the industry. Nearly all of the more complicated me-
chanical devices have been tried, but so far they are not
used extensively except for floor work, in which case various
types of roll-over, roll-over drop and stripper plate ma-
chines are successfully employed.
As already stated the stna-le; molds are usually made
in- snap flasks. Sometimes, when there is clanger of breaking
out when pouring, the molds are strengthened with mold
bands of strap ircn. 1 he use of jackets to prevent break-
outs also is prevalent. The larger molds are made in box
flasks, iron flasks being very common and desirable for use
on machines.
All malleable castings are made in green sand except
for cored holes. Since only relatively unskilled help is avail-
able, the use of three-part or other multiple-part flasks and
loose pieces on patterns is practically impossible. Any pat-
tern equipment which cannot be drawn straight out or rolled
out on a flask hinge is incapable of quantity production
under the conditions existing in most foundry centers.
Cores generally are made of local sharp or lake sands
using rosin, oil or some of the wood sugars as binders. As
a rule, the work is of such character that large and complex
cores are not required.
A few foundries are beginning to prepare and deliver
molding sand by mechanical means. One device for cutting
sand on the floor is coming into fairly extended use, since
human sand cutters are no longer available.
Molds are commonly set on the floor by hand, although
at least two semi-automatic devices for removing' molds have
been tried, one of which offers prospects of successful oper-
ation.
No methods of molding, involving successive operations
by a number of workers, have proved entirely successful
thus far. Pouring is done either from hand ladles or from
shank or "bull" ladles handled by two men, the former being
more common. In cupola or air furnace practice molders
catch directly from the stream as it flows from the furnace,
the* tap hole being only infrequently closed by a clay stopper
or iron bar.
78
American Malleable Cast Iron
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General Manufacturing and Plant 79
In electric furnace practice and sometimes also in open-
hearth practice the heat is tapped into one or at most a few
large crane ladles. Pouring is only rarely done from these
ladles, the metal being transferred to hand ladles or shank
ladles for pouring into the mold.
For relatively heavy work the metal is sometimes re-
moved from air furnaces by ladles of 200 to 300-pounds ca-
pacity, mounted on two wheels and pushed and tilted by one
laborer. These so-called "sulky" ladles can be used to pour
work, but this is not often done.
The molds are shaken out by laborers who also re-
move large cores and break off the gates. This is easily
possible because the white cast iron is extremely brittle ;
indeed great care must be exercised to avoid accidental
breakage.
The castings are usually cleaned in tumbling barrels,
although pickling or sand blasting is sometimes employed.
The cleaned castings are inspected and gates and fins are
trimmed off with light hammers. This department is re-
ferred to as the trimming room, from this operation.
Materials for Packing
The castings then go to the annealing department where
they are packed into pots, either with or without packing,
or occasionally stacked directly into muffle furnaces. If
stacked in pots, the pots are usually introduced into the an-
nealing ovens by mechanically operated trucks.
A great variety of materials is used as packing. The
original process was thought to depend on the use of hem-
atite ore for this purpose. Later on "squeezer" and "roll"
scale from puddling mills came into use and great care was
exercised to keep this rusty by the use of salamoniac solu-
tion. At present air furnace slag is the commonest ma-
terial, although blast furnace slag, silicaquartz, ground
brick and many other materials can be used. A refractory
material in granular form to support the castings is the prin-
cipal requirement. Also the access of flame to the castings
80
4mcrican Malleable Cast Iron
= 2°.
•~ £ t/T
General Manufacturing and Plant
must be prevented by using a fairly fine packing and by
keeping the pots tightly luted with clay.
In general the pots are from 15 to 18 inches wide, 18 to
24 inches long and 12 to 14 inches 'high, being approxi-
mately rectangular in shape. In some cases the size of the
work being annealed requires pots as large as 30 to 36
inches. Large pots usually are shallow (about 6 inches
high) on account of their great 'weight. A larger number
of pots are used to produce the desired height of stack. A
few plants prefer circular pots on account of their freedom
from distortion under heat. This advantage is offset by
their being uneconomical of floor space in the ovens. The
pots have neither tops nor bottoms, the bottom of a stack
being made by a special casting. The stack of bottoms and
pots thus forms a single large container.
Annealing
Annealing ovens vary greatly in size and 'hold from 50
to 350 pots arranged in stacks either three or four pots high.
The largest type of furnace has inside floor area of
about 625 square feet and a height of from 7 to 9 feet to
the spring line of the arch. Such furnaces obviously hold
enormous tonnages depending largely on how closely the
pot space can be occupied by castings. Moderate sized
ovens accommodate about 15 tons of castings, while the larg-
est ovens when worked to full capacity can handle from two
to four times as much. Some small commercial furnaces do
not hold much over 5 tons.
Furnaces generally are heated with coal, fired by hand
or by stoker or burned in pulverized form. Oil, producer
gas, and natural gas have also been used to a limited degree.
Continuous furnaces of the tunnel kiln type, which are
just coming into use, seem to promise great advantages, both
economically and from the standpoint of control.
While the heat cycle for complete graphitization de-
pends upon certain definite scientific facts and is fixed for
a given class of material, in practice the cycle is also de-
pendent upon the firing conditions, the circulation of gas
in the furnace, weight of furnace contents, etc., since these
82 American Malleable Cast Iron
affect the practical means for attaining the desired thermal
cycle.
Theoretically the cycle can be reduced to, about 100
hours under the conditions most favorable to rapid graphi-
tization. However, the production of the highest grade of
metal under operating conditions always necessitates a cycle
of at least seven days even under conditions most favorable
to speed. Cycles of 12 to 14 days are not uncommon with
large furnaces.
Incidentally the consumer should be warned against a
product made by any of the means which permit of cycles
occupying only three or four days. Conditions can be ar-
ranged so as to produce merchantable work in that period ;
in fact, the writer has had practical experience with emer-
gency annealing intended to turn out two charges a week
from a 'given furnace, and actually doing so. However, the
process is so tricky and the chance of inaccurate control so
great that he is prepared to unqualifiedly condemn the prac-
tice. Furthermore when the process works exactly right the
conditions are such as to preclude the use of sufficiently low
carbon iron to produce a product of the highest quality.
The consumer should bear in mind that it is naturally
to the manufacturer's interest to use the shortest practicable
cycle on the score of fuel economy and decreased overhead
for the use of furnaces. The producer therefore requires no
outside stimulus to hurry this portion of his process and
such a stimulus will only react against the purchaser. The
conscientious manufacturer takes sufficient time at "a cost
to himself, in order to produce a high grade of work and
should not be driven from this laudable position by the ef-
forts of "stock chasers" whose only thought is of quantity
and time.
When the work leaves the ovens it is separated from
the packing, cleaned by rolling or sand blasting, subjected
to any required machining or grinding operations, inspected
and shipped. These operations are of a 'general character
and are not especially characteristic of this particular in-
dustry. Some special operations will be discussed in detail
later. The diagram in Fig. 43 summarizes the processes by
General Manufacturing and Plant
83
which the raw material is trans formed intp the finished cast-
ings. It is evident that the process of manufacture is so
complex that the cost *of operating a malleable foundry is
much greater than that of a gray iron shop. The first cost of a
malleable plant of given capacity greatly exceeds that of a gray
iron foundry of the same size.
The foundry buildings and operations are approximately
identical in character and cost with tho.-e for gray iron, ex-
Fig 43 — Chart showing cycle of principal operations in a malleable
plant
cept that the cupola is a cheaper melting apparatus, usually
in operation and in first cost than any of its competitors.
When a gray iron casting passes the trimming room it is in
a salable condition, except for some additional grinding. A
malleab1e casting, however, still has to be packed, annealed,
cleaned and straightened. In this process over half as much
fuel is used, in many plants, as was used in the original
{netting. The overhead also is burdensome because the in-
84
American Malleable Cast Iron
vestment in annealing ovens is much greater per unit of capacity
than the investment in melting equipment.
The division of labor between the several departments
may be represented with some pretense at accuracy by the
diagram shown in Fig. 44. To a certain extent the char-
acter of product manufactured alters the proportion shown.
For example, a plant making small castings uses fewer la-
borers per molder than are employed in making heavy cast-
ings. Moreover, in a plant completely developed along me-
/io/der& and
Coremokers
^6%
Fig. 44 — Chart showing division of labor in a typical foundry
chanical lines, the ratio of unskilled .to skilled men and of
employes to product is greatly reduced.
It has been estimated from data gathered for use of the
fuel administration during the war that the country's plant
capacity for malleable castings was about 1,000,000 tons per
annum, and the labor requirements for operation at capacity
were 20,000 molders and coremakers and 36,000 others. This
is in the ratio of 1.8 employes other than coremakers and
molders to 1 of the latter group. The writer's data indicate
a ratio of about 2.2 to 1. Both sets of figures are based on
estimates so that an exact agreement is impossible. The
General Manufacturing and Plant 85
government estimate indicates further that the production of
1000 tons of malleable requires the employment of 56 men
for one year, or roughly that a ton of malleable represents
a labor expenditure of about 155 hours. In the writer's
judgment the figure is probably low as an average through-
out the country.
The amount of labor involved in the mere handling of
material mechanically or manually in a foundry is seldom
realized by those not conversant with the trade.
Conditions vary, o>f course, very widely, depending on
character of work, plant layout and so on, but the following
table may be regarded as suggestive at least of the labor
consumed in handling material for . production of one ton of
castings :
Table I
MATERIAL HANDLED TO PRODUCE 1 TON OF CASTINGS
No. of
Tons of times Total tons
material handled handled
Melting stock 2.2 3 6.6
Molten metal 2.0 3 6.0
Sprue 1.0 3 3.0
Slag 1 6 .6
Castings 1.0 19 19.0
New molding sand 35 2 .7
Used molding sand 5.0 25.0
Core materials .25 10 2.5
Fuel 1.2 3 5.1
Cinders 175 2 .35
Annealing pots 1.5 6 9.0
Packing 5 2.5
Refractories 15 6 .9
ll925 81.25
Add 1/3 for handling supplies and equipment 27.08
108.33
The items in the above table are based entirely upon
estimates. The writer knows of no attempt to actually de-
termine the several items. Also, evidently the expense of
handling a ton of material can have no unit cost assigned,
for the term "handling" may mean picking up the material
and transporting it by a crane; picking it up to inspect,
piece by piece, or the laborious operation of firing a ton of
86
American Malleable Cast Iron
bfl
£
General Manufacturing and Plant 87
coal in an air furnace, or wheeling a ton of sand a consid-
erable distance by hand. The table is here presented pri-
marily .to show the importance of reducing the number of
handlings each material undergoes and facilitating each by
every available means.
The 'history of labor in the malleable industry has been
that of labor in all similar work. In the early days the
workers were practically native Americans, supplemented by
thoroughly Americanized English, Irish, Germans and Scan-
dinavians. Later the two latter groups increased consider-
ably, and still later toward the end of the last century the
influx of Balkan immigration began. The native American
and the original foreign 'groups meanwhile drifted almost
entirely out of the labor and molding groups, though a few
remain principally in the coremakers' trade. Most of these
men and their sons headed toward the machinists, carpen-
ters and patternmakers' trades, or toward other employment
of similar character but requiring less skill.
Type of Workmen Available
Meanwhile the Hungarians, Bohemians, Poles and Aus-
trian-Slavs began as laborers and gradually worked upward
through the various grades of skill, being supplanted in the
lower grades by Italians and later by Bulgarians, Greeks and
Russians, and still later by Turks and Armenians. In some
few plants the negro long has been employed in all but the
highest skilled trade1- and the northward migration of the
southern negro farm laborer is rapidly enlarging this condi-
tion. Postwar developments meanwhile are making for the
return of many former subjects of Austro-Hungary, Bulgaria
and Russia to their native lands. He were a rash prophet
who would attempt to discuss the net effect on the Amer-
ican labor market of this emigration, the European tendency
toward immigration to America, the discontent of those who
returned to Europe, the industrial stagnation of Austria and
Russia, all in the light of the American immigration laws
and shipping facilities. Natural clannishness of foreign races
has produced a segregation of nationalties in different parts
88 American Malleable Cast Iron
of the country. The lines of course are not rigidly drawn
but the Scandinavian still persists in (the northwest and
to some degree in the St. Louis district. In the terri-
tory extending from St. Louis to Terre Haute the Armenian
is relatively prevalent ; the Russian and the Pole have set-
tled in the Chicago district, as also the older class of Bo-
hemians. The region around Indianapolis is manned by
Greek, Bulgarian and Austrian-Slav foundry workers, while
in northern Ohio Poles, Bohemians and Italians dominate.
The latter element is very prevalent through the Pittsburgh
district and through the Shenango and Mahoning valleys.
New England and New York, being gateways to the in-
terior, probably have a more mixed population than the Mid-
dle West.
Foundries of all kinds have been confronted with these
conditions : First, a growing disinclination on the part of
all labor to do foundry work; second, a trend toward less
and less skilled and intelligent help; third, a more and more
turbulent character of help from which the required force
must be recruited. The trend toward negro labor repre-
sents a turn in the tide at least in the latter respect.
The industry is confronted with growing labor problems
the solution) of which requires the best efforts of its ablest
executives. These efforts will have to continue for a long
time to come in order that the decreasing productivity of
labor may be prevented from being reflected in the product
in the form of prohibitive rates.
The solution is in the utilization of mechanical aids to
the utmost and in an enlightened labor policy.
Metallurgy of Malleable Is Complicated
Furthermore the malleable process is metallurgically more
complicated' than that of either gray iron or steel foundry
practice, and the chemical range consistent with good results
is smaller than in the former.
The most successful means of overcoming these handi-
caps in manufacturing cost is to operate upon a sufficiently
large scale and on more or less specialized products in order
General Manufacturing and Plant 89
to take advantage of those manufacturing economies asso-
ciated with such production methods.
By inference the malleable industry is not well fitted
for the manufacture of so-called short orders, that is, orders
involving only a few pieces from a given pattern and small
tonnages for a given consumer. It attains its greatest suc-
cess when operating on orders of sufficient magnitude for each
type of casting to warrant investment in the best possible
pattern equipment and close study of each step in the
manufacturing.
V
MELTING STOCK
THE raw materials of the malleable industry may be
classified as melting stock, fuel and refractories. The
remaining materials are not peculiar to the malleable
industry and therefore are not important in the present dis-
cussion.
Regardless of what melting process is employed in
making malleable, the melting stock is selected from the
same general classes of material. Sprue, which includes
the feeders, runners and defective castings produced inci-
dentally to the plant operation, is seldom if ever sold and
never is bought by a malleable foundry. Being a product
of the foundry-man's own plant, its composition and condi-
tion are known to him and the material requires no "further
description.
Malleable scrap is a material derived in part from the
work condemned at the plant after annealing. Also it is
an article of commerce in the form of scrap material con-
sisting of worn out malleable parts. The* scrap yard of a
malleable foundry is shown in Fig. 46. Scrap has been some-
what roughly divided into "railroad malleable" and "agri-
cultural malleable." The distinction is actually one based
on size of castings rather than on the former use. "Auto-
mobile malleable" is regarded by some users as a legiti-
mate subdivision but really does not differ materially from
the railway malleable scrap from a metallurgical standpoint.
Pipe fittings, often classed separately, could equally well be
included with agricultural malleable scrap.
The composition of purchased malleable of course is
entirely conjectural and there is therefore a limit beyond
which its use introduces serious uncertainties as to compo-
sition of charge. It is safe to assume that railway and auto-
mobile malleable, before annealing had a carbon content
92
American Malleable Cast Iron
i
Melting Stock 93
averaging about 2.50 per cent. No two pieces are alike in
carbon, depending both on the original carbon and the de-
gree of decarburization in the anneal, but the remaining car-
bon in work of these heavier classes is likely to be around
2.00 per cent or a little under. The silicon is likely to av-
erage around 0.70 per cent and in malleable scrap consist-
ing of castings worn out in service the sulphur is from 0.06
to 0.10, the manganese 0.25 to 0.35 and the phosphorus from
0.16 to 0.20 per cent. In the case of agricultural and other
light work, the initial carbon may have been considerably
higher, but in view of the lightness of cross section this ele-
ment may have been much reduced, possibly to 1 per cent
and under. The silicon generally is somewhat higher than
in the heavier materials, usually averaging about 85 per
cent. The other elements are about as in railway malleable.
Malleable scrap is open to the objection that when used
as a considerable percentage of the mix in air furnace or
open-hearth practice, serious errors may be introduced in the
chemical composition of the charge. This condition is ag-
gravated if the malleable scrap includes gray iron scrap rich
in carbon, silicon and phosphorus. It is a most reprehen-
sible practice of a number of junk dealers either to purposely
mix or to not properly separate the two materials, thus
practically destroying the value of the malleable scrap to
the malleable founder. This separation can be readily made
only 'at the point of origin as the user has no commercially
effective method of inspection. Equally harmful in the op-
posite direction is the admixture 'of steel.
Another source of -trouble is the introduction of un-
known amounts of rust into the charge when melting scrap
that has been exposed to weather. Some scrap may con-
tain 5 per cent or more of rust which of course is a dead loss
in melting. It also forms a highly oxidizing slag which in
turn strongly acts on the silicon and carbon causing unpre-
dictable changes of composition in melting. The -effects of
this evil can be minimized by the use of clean scrap, which
unfortunately cannot be purchased and by the purchase of
94 American Malleable Cast Iron
scrap of such form that it presents little surface to rusting.
For this reason and because of the high labor cost of
handling small scrap, agricultural material is not a satis-
factory melting stock in air furnace or open-hearth mal-
leable practice. Heavy malleable scrap stored out doors
but not extremely heavily rusted usually behaves as though
it contained about 1.75 per cent carbon and 0.47 per cent
silicon. The presence of adulterations, except of high phos-
phorus material, is of less consequence in electric furnace
melting than with air furnaces or open 'hearths. Malleable
scrap is used not because it is a means of cheapening the
metal but for the definite purpose of regulating the carbon
content of the mix. Successful air furnace practice requires
a c'harge averaging around 3 per cent in carbon, hence some
low carbon stock must be used to mix with pig iron which
is always of much 'higher percentage of carbon content.
Sprue is available in a quantity dependent on the found-
ry practice but not usually sufficient to bring down the car-
bon as far as necessary. Hence recourse is had to mal-
leable or steel scrap. The use of scrap for the purpose of
making up different 'amounts of sprue has been practiced for
more than 30 years. The Chicago Malleable Iron Works
has purchased scrap for air furnace charges on a commer-
cial scale since 1885 and in 1888 the practice was well es-
tablis'hed. Possibly others adopted it still earlier.
Steel scrap is an article of commerce. What has been
said of -malleable regarding freedom from rust and from ad-
mixture of other forms of scrap applies equally well to steel.
In addition there is a certain danger from the possible pres-
ence of alloy steels which may introduce entirely unexpected
elements. A case in point is the high manganese steel used
in frogs, switch points and cross overs and containing up to
about 13 per cent manganese.
The carbon content of all steels is relatively low, rang-
ing from around 0.90 to 1.00 per cent in some spring steels
down to 0.25 or 0.30 per cent in castings. The silicon is
always low and the manganese averages around 0.50 or 0.60
Melting Stock 95
per cent. The sulphur and phosphorus values are always
lower than in any other ingredient in the charge. Consid-
ering the fact that the material is always somewhat rusty it
may be classed as pure iron in calculating a mix.
Heavy steel scrap is preferable to the lighter material
as is the case with malleable scrap. Thin sheet, small clip-
pings, rods, pipe and light structural material are particu-
larly objectionable when rusty or burned.
Steel, as in the case of malleable scrap, is used to reduce
the carbon content of the mix. Being lower in carbon a
less percentage suffices for a given purpose ; therefore there
is less danger of introducing large errors of calculation in ,
computing the mix or of large amounts of rust to compli-
cate the reactions.
Steel is rarely used in making cupola or electric furnace
malleable. Its general use was adopted more recently than
that of malleable scrap, but the old records of the Indian-
apolis plant of the National Malleable Castings Co. show that for
an extensive period, beginning in August, 1887, steel was
regularly vised in the mix, and that the practice continued
as circumstances warranted. The author has no facts to in-
dicate whether this practice was original with the late
James Goodlet, then in charge thei;e, or copied from some
other plant.
Wrought iron, which chemically is merely an extremely
low carbon steel, was used at the inception of the industry,
Boyden referring to it in his notes. At a later date it was
regarded as harmful arid at present it is not available in
sufficient quantity to possess interest.
Pig iron is the raw material which makes up the bulk
of the tonnage from which malleable cast iron is made. In
the days of the fathers of the industry charcoal iron was
generally if not universally used. Then, as now, it was
made from relatively low phosphorus ores. In the early
days, before the Civil war, the references are mostly to
irons smelted in New Jersey arid Connecticut from eastern
ores using charcoal from local forests. Bovden used such
96
American Malleable Cast Iron
Melting Stock 97
irons. Alfred Hammer used New Jersey coke arid anthra-
cite pig as early as 1878. In about 1885 there was 'a no-
ticeable trend toward the use of coke-melted pig iron, first,
as far as the author can judge, in the case of very soft pig
iron. This was high in silicon, and was unusual in furnaces
operating as cold as did the usual cold blast charcoal fur-
naces of the period.
The impression is quite general among the older found-
rymen that, apart from differences of composition, there
are differences in properties as between the products of
different furnaces. Many also believe that it is preferable
to use iron from several producers in each heat. It is not
clear to the author upon what metallurgical considerations
such differences could be based. Undoubtedly before the
days of analyzed pig iron, these beliefs were based on sound
reason; at present they would seem to be little more than
prejudice as applying to malleable practice.
A similar situation is encountered in a somewhat gen-
eral feeling that the use of malleable scrap is in some way
connected with the substitution of coke for charcoal pig.
It has been only relatively recently that interest in the
control of the product by limiting the total carbon content
became at all general. Dr. Moldenke in his book, "The
Production of Malleable Castings" (1911), recommends for
instance that the carbon be not below 2.75 per cent and
may range up to 3 per cent. Presumably this represents
the best general understanding of the time. While since 1906
certain manufacturers realized the relation between carbon
and strength and acted on this knowledge, it is not sur-
prising that in the days when the substitution of coke for
charcoal iron began the mixes used never were based on
considerations of carbon content.
With low silicon charcoal iron available it was easy to
secure silicons low enough to produce a white fracture by
the use of pig and sprue alone. Hot blast coke irons always
contained enough silicon so that some material other than
the available amount of sprue was required to reduce the
98
American Malleable Cast Iron
Tf
bb
Melting Stock . 99
silicon content sufficiently to avoid "mottled" castings. The
effect of this change of practice on carbon content was totally
disregarded except by a very few observers.
The general observation that charcoal iron malleable
could and should be made lower in silicon than malleable
for the same purpose made from coke iron probably was
true. However, it originated merely from the reduction in
carbon which unconsciously accompanied the changed prac-
tice and not from the method of making the pig.
Where malleable was made from charcoal .and coke
iron of the same silicon content the former was somewhat the
stronger, due to its somewhat lower carbon content, which
in turn was due to lower furnace temperature.
In view of such former experiences great caution should
be used in regarding as cause and effect phenomena without
apparent logical connection.
The transition from charcoal to coke iron has extended
over many years and is not yet complete. In the early
ninety's coke iron was used very sparingly, but 10 years
later the coke iron was far in the ascendant. At present
comparatively few manufacturers continue the use of char-
coal pig and they employ it only in limited quantity.
To the writer it has seemed that this retention of char-
coal iron results either from sentiment pure and simple or
from a superstitious belief that for some unexplained rea-
son a modicum of charcoal pig imparts a mysterious virtue
of unknown character to the resulting product. Being
smelted at a lower temperature, charcoal iron differs from
coke iron in being generally lower in carbon. On account
of the low sulphur fuel, it is always lower in sulphur. Also
the range of silicon values commonly available run lower in
charcoal than in coke iron. Again, this is the result of the
furnace temperature.
The lowest silicon charcoal pig irons commercially
made contain less silicon than the lowest silicon grades of
coke iron. Moreover, high silicon coke iron is more com-
monly obtainable than charcoal iron with the same con-
100
American Malleable Cast Iron
be
c
'-5.
rt
O
Melting' S-otk : 101
tent, in spite of the fact that the "Scotch" grades of charcoal
pig have a high silicon content.
The writer has never been able to see any theoretical
reason why charcoal iron should make a better product than
coke iron, given a correct final composition. The late J. B.
Johnson Jr., who dealt at length with the subject from the
blast furnace viewpoint, ascribed the differences to the in-
direct effect of oxygen. For the best available opinions in
this subject, the interested reader is referred to the pub-
lished reports on Johnson's pioneer wrork on this subject in
the Transactions of the American Institute of Mining and
Metallurgical Engineers. In view of the radical alterations
made in the raw material during the malleable process it is
difficult to see how any differences, such as the form of
crystallization of graphite in the pig iron, could survive the
chemical and physical changes involved. The trade as a
whole seems to look upon the matter in this light and from
a tonnage viewpoint, charcoal iron is of little importance in the
malleable industry.
The production of malleable cast iron requires the use
of relatively low phosphorus ores, those of the Lake Superior
region being the most available for the purpose. Conse-
quently, many of the blast furnaces producing malleable pig
are situated along the lake ports. The proximity to the
Pennsylvania coal fields producing coking coals, has formed
another area extending from Pittsburgh down the Ohio river
and up the Mahoning and Shenango valleys. The charcoal
furnaces are located near the ore fields in heavily wooded
districts. The ore fields of Minnesota, Wisconsin and north-
ern Michigan are shown in the form of a shaded area in
Fig. 47. Immediately adjacent to this section are the prin-
cipal charcoal furnace plants, shown on the map by open
circles. The coke furnace plants are shown as solid circles.
Most blast furnaces do not make pig iron for one purpose
only, but the map is intended to include all important pro-
ducers of this class of metal in considerable quantities. An
open pit mine on the Mesabi range "is shown in Fig. 48.
102
Matictiblc Cast Iron
Melting Stock 103
The ores from which malleable pig iron is made 'have ap-
proximately the following composition :
Per cent
Fe 51.5, present as Fe3O3 . . 75.57
P .086, present as P2O5 19
Mn. .40 to .70, present as MnO ' 77*
Si02 9.50
A1203 2.75
CaO 70
MgO bO
H2O, CO2 and undetermined 10.02
^Average.
Malleable pig iron is sold with ti guaranteed maximum
of 0.05 per cent in sulphur, usually of either 0!19 or 0.20
per cent in phosphorus and is furnished with from about
1.00 to 2.00 per cent silicon, although 'higher values are
sometimes required. The manganese varies from about 0.50
to .about 0.90 per cent, the lower and higher values being
encountered frequently. The average carbon content for the
country is now and lias been for at least 15 years close to
4.10 per cent, individual lots running normally from 3.85 to
4.40 per cent, 'i he carbon content practically is fixed by the
blast furnace temperature.
Pig iron may be either sand, chill or machine cast. The
former1 carries with it a certain amount of sand fused into
the surface. The chill and machine cast irons are free from
this foreign matter, which fact presents a certain advantage
both because nothing but iron is paid for and because less
dirt is carried into the furnaces. The two latter classes,
being rapidly cooled, contain more combined and less free
carbon than the former, other things being equal. The
melting point and, presumably, the latent heat of fusion are
thereby decreased. It is claimed that a material fuel econ-
omy results. On all accounts the use of machine cast iron
can present no disadvantages to compensate for the advan-
tages outlined above and its greater uniformity of size and
form.
Recently there his been a decided tendency toward
changes in chemical composition of commercial pig iron.
Up to 1914 the sulphur content, while guaranteed as 0.05,
was nearly invariably under 0.03 in the Ohio and Illinois
104
American Malleable Cast Iron
Melting Stock 105
irons. Since then fuel conditions have so far deteriorated
the quality of coke available that at present sulphur is usually
only a little under 0.05 per cent and occasionally exceeds
that figure. Ten or 15 years ago iron often was sold with
a maximum phosphorus of 0.16 per cent, no extra price be-
ing charged as compared with a 0.19 or 0.20 per cent maxi-
mum specification. The gradual increase in the ratio of
phosphorus to iron in the product of the Mesabi ore fields
has, however, forced an increase to the latter figures as a
phosphorus maximum.
For about five or six years there has been a decided
trend toward lower carbon malleable, brought about by the
demand for increased quality of product. This results in
lower percentages of pig iron in the mixes than formerly
and therefore requires increasingly a higher silicon content
to maintain the former silicon values in the product and in
some cases raise them -slightly. Accordingly the metal con-
taining under 1.25 per cent silicon is now almost useless
and most -plants require some pig iron up to 2 per cent and
possibly over in silicon. The average silicon content in all
the pig iron consumed in the malleable industry is doubtless
between 1.60 and 1.70 per cent.
There seems to be increasing difficulty in getting any
low manganese pig. However, this stringency has been
somewhat counteracted by the decreased amount of pig re-
quired and the increased sulphur content. Coke pig iron
under 1 per cent in silicon and usually high in sulphur, is
generally the product of an abnormal furnace condition, re-
sulting in cold working and is not of a composition suitable
to modern requirements.
High, silicon pig, or blast furnace ferrosilicon is a metal
usually running about 10 per cent in silicon. Its principal
source is Jackson, O. The phosphorus, sulphur and carbon
are kept low. The metal is used as a source of silicon when
suitable pig is not available. In the electric furnace process,
it may furnish most of the silicon of the cupola charge.
Ferromanganese is a blast furnace product made from
manganese ores. It usually contains from 70 to 85 man-
ganese and nearly 6 per cent carbon. Silicon, sulphur and
106
American Malleable Cast Iron
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Melting Stock 107
phosphorus are low, iron being the principal element, other
than manganese and carbon. Ferromanganese is used gen-
erally in -the form of an addition to the molten metal to
supply a deficiency in manganese.
Electric furnace ferrosilicon contains nominally 15, 50,
75 and 95 per cent silicon. The 50 per cent alloy, actually
running from 48 to 54 per cent silicon, is most commonly
used. In addition to silicon and iron the metal contains
phosphorus, sulphur, aluminum and calcium. These elements
are not usually present in important amounts.
Ferrosilicon, being readily oxidized, is not suitable for
cupola use. When charged into an air furnace with the
melting stock it must be protected from contact with fur-
nace gases as far as possible. It is generally used as addi-
tions to the molten heat.
VI
FUEL AND REFRACTORIES
THUS far we have dealt with the raw material actually
entering the product. There remain two other classes
of raw materials which, although they form no part of
the finished product, are used in such quantities and so affect
the shop operation as to be of decided industrial importance.
The first of these groups is fuel.
The fuels used in the malleable industry may be classi-
fied as melting fuel, annealing fuel and power plant fuel.
The latter, although it may be used in large quantites, as
in electric furnace plants, should be considered from the
viewpoint of power plant practice rather than from a
metallurgical angle. Melting fuels not only furnish heat but
also very distinctly affect the composition of the resulting
product. On the other hand, annealing fuels need be consid-
ered only from the standpoint of combustion.
The original source of almost all the heat used in melting
and annealing malleable is coal, although it may be convert-
ed before use into coke, illuminating gas, water gas, or
producers gas. Oil and natural gas are also industrially im-
portant in some localities and for some purposes.
Bituminous coal is very widely distributed throughout
the country, as indicated in Fig. 53. Anthracite and lignite
are not important metallurgical fuels and are therefore omit-
ted from the map. Anthracite was formerly used as a cupola
fuel and at an early date, possibly 1838 was used for anneal-
ing by Belcher. It is still used in at least one plant for
this purpose.
Coal from practically any of the bituminous fields shown
may be used for annealing, the choice generally being based
on geographic and commercial considerations rather than
on the properties of the fuel from any given field. Mine run
fuel is generally used in annealing for hand firing. The crite-
rion of quality is the absence of ash and water, these fac-
110
American Malleable Cast Iron
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ex
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I
Fuel and Refractories 111
tors representing increased cost and operating trouble and
not metallurgical suitability. -A low ash fuel is sometimes
preferred for use with pulverized fuel annealing equipment
in order to avoid trouble from the ash settling in the fur-
naces and flues. The requirements of a crushing plant prac-
tically necessitate a fuel either quite dry as received or
dried artificially before crushing.
- Since lump coal is of no advantage, pulverized fuel
plants buy the smaller commercial sizes of fuels. However,
the selection of fuel for crushing in annealing practice is not
well standardized. The author knows of two large and ably
managed plants within a few miles of each other, both an-
nealing with pulverized fuel. One buys a high ash local coal
and removes about 10 to 12 per cent of water by drying be-
fore crushing, while the other obtains coal in the eastern
fields hundred of miles distant which runs under 2 per cent
in water. and around 3 to 4 per cent in ash. The subject
of coal for 'annealing is therefore easily dismissed with the
statement that practically any local fuel can be employed,
economical conditions alone governing the selection.
In the case of the melting coals conditions are quite
different. Here, in addition to the purely economic prob-
lems, there enter many other considerations which narrow
down the choice. Coal burned in the air furnace is expected
to furnish heat units as economically as may be practicable,
and must have certain other definite characteristics. It must
burn with a long luminous flame jof sufficient volume to en-
tirely fill the air furnace. It must be so low in sulp'hur as not
to prohibitively raise the content of- that element in the met-
al.
Its character must be such that none of the constituents
will melt and run to a tarry mass at the temperature of the
fire. Its ash must be fairly low in amount and of such char-
acter as not to fuse together into clinker's at fire ibox tem-
peratures. Its moisture content must -be reasonably low in
order to maintain good flame conditions.
These characteristics are found in coal from a very limit-
ed geographical area which is shown in black in Fig. 53.
112
American Malleable Cast Iron
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'Fuel and Refractories 113
In the writer's experience the fuel varies even within this
district, 'being in general better in the southern portion of the
area.
No entirely satisfactory method of judging the quantity
of a melting coal, except by actual test is available. This
arises, in part, from the fact that the behavior of the fuel is
dependent on the actual combustion conditions encountered
which differ with different furnaces. The composition of a
few good melting fuels is shown in Table II.
Table II
ANALYSES OF MELTING GOALS
Origin
Sulphur
Moisture
Pennsylvania
0.70
062
West
Virginia
0.45
0.76
West
Virginia
1.55
1.34
Kentucky
0.45
1.10
Vol. Comb. .
35.63
37.15
41.70
33.95
Fixed carbon . . .
Ash
, . . . 58.32
5.43
55.64
6.45
52.40
4.56
60.68
4.27
B.t.u. per pound.... 13,902 13,434 14,058 14,276
There is a general preference for coal under 1 per cent
sulphur, although the sulphur which the melt takes up de-
pends not only on the •sulphur content of the fuel but also
on the form in which it is present. Some fuels, moderately high
in sulphur, produce metal lower in sulphur than other fuels,
much lower in that element. Many coals exist, even some in the
Illinois, Indiana and central Kentucky fields which based on
composition should work admirably. The expectation, however,
is not borne out in practice.
What makes a long flame coal has never been definitely
determined. The flaming coals are in general the coals best
adapted to making illuminating gas. The flaming quality
is associated with the distillation products of the fuel when
heated in the fire box. The running of the coal is a phenome-
non of the same character. The low moisture seems to be
a necessary characteristic. Goals of this character artificial-
ly wetted behave differently from the naturally wetter In-
diana-Illinois fuels.
The clinkering of the ash is largely a matter of chemical
composition. Strictly speaking it depends on the com-
114
American Malleable Cast Iron
Fig. 55 — Picking table in a coal tipple, showing facilities for removing
slate, sulphur, etc., by hand.
Fig. 56 — Adjustable loading boom which places coal in car without
breakage
Fuel and Refractories 115
pounds formed in the ash under the temperature and chem-
ical conditions existing in the fuel bed. Therefore, analyses
made on laboratory preparations of as-h are not correct state-
ments of what may happen in the fuel bed, but are of some
value as indicating what may be expected. An ash of a
very satisfactory fuel had the following composition :
SiO2
Per Cent
44 52
A12O,
43 75
Fe.O,
1 32
CaO
5 72
MgO
. . . . 1 05
Na2O
)
K?O
. ( 3.64
The analysis is of a laboratory preparation of the ash.
On the grates the Fe,O3 would be largely reduced to FeO.
The fusing point of the ash of eastern coals is 2400 to
2850 degrees Fahr. Above 2600 degrees Fahr. is preferable.
In general, the absence of iron oxide, alkalies and lime
in the order given is considered a desideratum.
The ash and sulphur contents of coal are considerably
affected by the method of preparation and in recent years
mining conditions have been such as to make for a steady
deterioration along these lines.
Air furnaces require a lump coal for their fuel 'but com-
mercial practice varies as to the size of screen over which
the coal should be passed before shipment. Some foundry-
men desire coal not finer than that which will not pass a
4-inch mesh, while others tolerate all that will pass over a
^4-inch screen. The beslt practice probably is a little nearer
the latter figure than the former — say about 1^2-inch screened
lump.
When fuel is to be burned in pulverized form in melt-
ing furnaces the quality of coal required is the sam'e as for
direct combustion on the grates, except that the smaller
sizes of coal can be utilized.
A number of engineering concerns have developed
highly specialized plants for grinding and pulverizing coal.
The sequence of operations in all of them is substantially the
116
American Malleable Cast Iron
•d
o
be
rt
be
S3
o
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Fuel and Refractories 117
same. The coal, crus'hed to fairly small size or purchased
after screening, passes through a device where it is dried by
a current of warm air. A favorite method is to feed it in at
one end of a rather long narrow cylinder rotating on its
axis, whic'h is slightly inclined to the horizontal. As the
cylinder revolves the coal rolls over and over and travels
toward and finally out of the lower end of the cylinder. A
current of warm air passes through the cylinder, usually in
the direction opposite the flow of coal.
From the end of the dryer the coal is automatically de-
livered to a grinder, one type of Whic'h consists of an ar-
rangement like the "fly balP' or centrifugal governor of a
steam engine. The weights are in the form of rollers whic'h
run against a surrounding ring when the mechanism is ro-
tated. The fuel is ground to flour between these rollers 'and
the ring, but if any hard lump such as a piece of scrap iron
should fail to have been removed it merely crowds through
between the roller and track and does no damage.
Means are usually provided for screening or otherwise
separating insufficiently ground material and returning it to
be reground.- The product should be reground to pass a 100-
mesh sieve and 75 per cent to pass a 200-mesh sieve^ When
ground to size it is transported by belt or screw r<5onveyor
to bins. A pulverizing plant is shown in Fig. 92.
In -general it is well to store only limited qu#fitities of
ground coal- -'owing to the fire hazards. Dried pulverized coal
absorbs moisture readily, and sticks together and^feeds to
the 'burner in a lump condition if it has an opportunity to
take up water before being used.
The transportation of coal dust by carrying it in a cur-
rent of air is dangero;us, the mixture being highly explosive.
In the best installations the air and coal are mixed just as
near the point of fen fry- into the furnace as possible to min-
imize the danger.
Gas as a fuel is only an indirect application of the com-
bustion of coal, indeed it might well be maintained that any
use of coal for this purpose involves its gasification even
though that process may be carried out in the fire box in-
stead of in a separate apparatus.
118
American Malleable Cast Iron
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Fuel and Refractories 119
Gas fuels are classified as illuminating gas or producer
gas. The former is either a distillation product of coal, or a
mixture of hydrogen, carbon monoxide and hydrocarbons,
called water gas and made by the action of steam on red
hot coke. Producer gas is a mixture of carbon monoxide
and hydrogen.
Illuminating gas is too costly for extensive metallurgical
operations. Its use is limited to crucible furnaces for brass
melting, etc., and small core ovens. If the gas is a by-prod-
uct in the manufacture of coke, it is commercially available
and then only in the plant operating the coke ovens or in
neighboring plants. If the gas is to 'be piped any distance it
can generally be more profitably sold for public consump-
tion for domestic requirements.
The operation of a gas producer is simple in principle.
A gas producer is merely a firebox in which a deep bed of
fuel is burned with a limited supply of air, the intention
being to burn the carbon of the fuel to carbon monoxide.
Theoretically, the producer gas is air in which the oxy-
gen has been converted to carbon monoxide and should con-
tain about one-third carbon monoxide and two-thirds nitro-
gen. In practice the water from the combustion of the hy-
drogen of the fuel, the moisture of the fuel itself and the
steam which is introduced with the air supply to avoid
clinkering all react with carbom, liberating some hydrogen.
Also the fuels rich in volatile matter distill off more or
less hydrocarbon gases. Furthermore, if the fuel bed is
allowed to get uneven permitting air to come through, some
of the carbon monoxide is burned to dioxide. The latter
constituent is more prevalent in producers blown with steam
than in those blown with air alone.
As a general statement of the composition of commer-
cial producer gas, the following figures are quoted from Wyer:
Table III
COMPOSITION OF PRODUCER GAS
H CH4 C2H4 N CO O C6a
Gas from hard coal 20.0 .. .. 49.5 25.0 0.5 5.0
Gas from soft coal 10.0 3.0 0.5 58.0 23.0 0.5 5.0
Gas from coke 10.0 .. .. 56.0 29.0 0.5 4.5
Gas air blast 4.43 .. . . 62.12 33.04 .. 0.41
Gas same as above with air
and steam blast . . 14.00 53.3 27.2 5.5
120 American Malleable Cast Iron
The CO2 values are rather high, an attempt usually be-
ing made to hold CO2 to 3 per cent.
It is obvious that the 'heat value of the gas from a pound
of coal cannot be greater than the heat value of the original
Fig. 59 — Cross section of a modern gas producer
pound of fuel. The combustion of carbon to CO liberates
4450
— or roughly 30 per cent of the heat of combustion of
carbon to CO2. This heat is transmitted to the incoming
fuel and to the products of combustion as well as to the
producer structure. It finally leaves the producer by radia-
Fuel and Refractories 121
tion from the walls and also as the sensible heat of the gas.
it therefore is of advantage, except in open hearth practice,
to make the gas as near the furnace as possible to avoid the
loss of 'heat units by coo. ing the gas stream in passing
through long ducts.
Where the gas is to be widely distributed or burned in
small accurately controlled burners a cleaned gas from which
tar and heavy hydrocarbons have been removed is desirable.
As stated before, gasification adds nothing to the heat
value of the fuel ; it may, however, result in heat economy
due to the better control and more economical combustion
conditions possible with gas fuel as compared with solid
fuels.
Producer gas being a fuel of rather low calorific power
usually is burned with hot air. The use of cold air does
not give sufficiently hot flames for melting operations ; in-
deed the temperature m'ay not be high enough to maintain
combustion unless a warm or hot air supply is provided or
the gas itself be fairly hot.
Producer gas usually is made from bituminous coal, al-
though wood, peat, lignite, coke and anthracite can be used.
The requirements for producer gas fuel in general are simi-
lar to those for >air furnace fuel. The coal should be rea-
sonably low in ash and the ash should not clinker. The
coal must not soften or swell on heating and preferably
should be low in moisture and high in volatile matter. Fur-
ther, it should be fairly uniform in size and, for melting op-
erations, low in sulphur. However, there are many bitumin-
ous coals giving good results in producers which do not
•work satisfactorily in the air furnace.
Coke is used as ;a metallurgical fuel in the malleable
industry in cupola practice only. As everyone knows, it is
gas 6r similar coal from which the volatile matter, includ-
ing moisture, has been distilled in retorts, beehive ovens or
by-product ovens. It contains all the ash in the coal from
which it was made and is therefore from 50 to 100 per cent
higher in ash than gas coals. The remainder of the coke is
practically pure carbon. All coke contains sulphur and
there is a general feeling1 in favor Of foundry cokes con-
taining less than 1 per cent of this element. Sulphur is
122
American Malleable Cast Iron
Fuel and Refractories 123
taken up by the metal more readily in cupola practice than
in the air furnace, owing to the fact that fuel and metal
come into actual contact with each 'other. Moreover coke
must not be too fine and must be fairly strong to make a
suitable fuel. The ash should be as low as practicable and,
if possible, siliceous in character, since it is easier to add
basic materials to flux with the ash than to add acid 'materials.
The as'h is similar in composition to that of coal and
corresponds to low grade fire clay. Cupola fuel is not of
great interest hi this discussion, owing to the general aban-
donment of cupola malleable. In the case of electric fur-
nace practice in which cupola metal is the raw material for
the electric furnaces it is, of course, an important material.
Oil is found rather widely distributed throughout the
country. Fig. 53 shows the oil areas, exclusive of oil shales.
Oil has many advantages as a fuel, including cleanliness, rel-
ative freedom from sulphur, convenience of distribution and
accuracy of control of combustion conditions.
Twenty or 30 years ago it was customary to burn local
crude oils just as they came from the ground. The need for
gasoline and lubricating oils has caused the abandonment of
this practice and today the fuel oil used consists of the
residue remaining after the distillation of the commercially
important products. Nearly all the petroleum products are
hydrocarbons of the methane series having the general
formula —
CrH2I1 + 2
All have nearly the same 'heat value per pound, because
n being a fairly large quantity, the atomic ratio of carbon to
hydrogen is in all of them very nearly 1 to 2 corresponding
to a ratio by weight of 6 to 1. The more volatile com-
pounds such as gasoline, kerosene, etc., are the members of
low molecular weight in which n is from 5 up.
Fuel oil has been applied to 'annealing furnaces very
conveniently. It is a useful fuel in open-hearth practice and
has been successfully used in that connection in the malle-
able industry. Under favorable circumstances it can some-
times compete for this purpose with producer gas -and pul-
verized coal. Furthermore, it is easy to arrange open-hearths
124 American Malleable Cast -Iron
to permit the use of either oil or gas or oil or pulverized
coal, which is a convenient arrangement.
Attempts have been made to burn fuel oil in air fur-
naces. No particular difficulty exists in actually doing the
melting, but generally the process has not been either eco-
nomically or metallurgically successful. J. P. Pero reports*
what he regards as satisfactory results at an Illinois plant,
but even there it is admitted that excessive oxidization losses
were not overcome and 'the fuel cost was high. A plant in
Michigan is said to 'have operated successfully with oil melt-
ing, even at a high unit cost for fuel. The details are not
available to the writer.
Natural gas is actually the first member of the petro-
leum series methane CH4, corresponding to n=l. It is
found associated with petroleum. Its rapid exhaustion by
wasteful use is one of the scandals of our economic system.
It formerly was used for annealing.
There remain for consideration '-the raw materials which
are grouped under the heading of refractories. These mate-
rials include molding sand, fire sand, fire clay, fire brick and,
to 'a limited degree magnesite, magnesite 'brick, silica brick,
dolomite, gannister and sands'tone.
Molding sands are somewhat widely distributed in na-
ture and -consequently each plant generally uses a local sand.
Molding sands are generally derived from granite which has
weathered and are frequently found in glaciated areas. Mold-
ing sands differ among themselves and each purpose requires
a sand of specific characteristics.
In the malleable foundry a sand is desired consisting of
well rounded quartz grains, of nearly- uniform and fairlv
small size, coated evenly with a moderate amount on\y of
fairly plastic but also reasonably refractory clay. The actual
size of grain and amount of clay desired will vary with the
character of the work. The heavier castings require coarser
and clavier sands than the lighter.
The uniformity of grain size and -roundness of grain
are desired in order to give the greatest possible opportun-
ity for the g-as to escape from the molds. If too much clay
*Vol. XXVIIT. p. 316, Transactions. American Fonndrymen's asso-
ciation.
Fuel and Refractories
125
Fig. 61. — Operations in a molding sand pit
is present or if the 'Sand consists of grains differing largely
in size the clay or small silica grains partly obstruct what
should be openings between the grains.
The clay is needed 'to hold the sand in place. The silica
grain is very refractory, so that the refractoriness of the
sand depends upon the property of the clay coating. If the
clay contains lime or iron oxide the refractoriness is much
decreased. Most sands contain vestiges of feldspar from
Fig. 62. — Hauling sand from a pit
126
American Malleable Cast Iron
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Fuel and Refractories 127
the original granite and these sands are relatively easily
fusible.
The analysis and screen test of sand does not furnish
a good guide to its usefulness, as they are difficult to in-
terpret.
The United States bureau of standards and the Ameri-
can Foundrymen's association have gathered extensive data
w'hich are available to the interested reader.
Tests for porosity, strength of bond, imperviousness and
fusibility are more valuable, but a discussion of these proper-
ties and their relationships would be too technical to interest the
general reader and in the present state of our knowledge
would be largely speculative.
Frequently sand free of clay is wanted in coremaking,
the binder furnishing all the cohesion desired and preventing
cores growing too hard, due to the burning of the clay. For
such purpose wind-blown lake or sea sands, nearly pure
quartz, are generally used.
Fire sands are very pure silica sands usually in uniform
rounded grains. They seldom contain over 2 per cent of im-
purities and are used for the bottoms of acid open-hearth
and air furnaces. The presence of a small amount of basic
material is required to cause the sand to sinter properly.
Sandstone is a naturally compacted mass of silica sand
occasionally used in cupola and other furnace linings. Gan-
nister is a siliceous sedimentary rock of highly refractory
character used in furnace linings usually in crushed form.
Fire clays are refractory silicates of aluminum occurring
in nature. They contain as impurities oxides of iron, cal-
cium and the alkalies as well as some of the rarer metals.
The very pure and refractory flint clays possess little
plasticity. Other varieties are more plastic and also more
fusible. Fire clay is seldom used alone, being mixed with
water and crushed fire brick or silica sand to form a mate-
rial for patching furnace walls. Fig. 63 shows the location
of the principal supplies of molding sand and high grade fire
clay in the United States. Clay fire brick, made from fire
clay usually at or near the source of clay, consist merely
of mixtures of refractory and hard flint clays, ground fire
128
American Malleable Cast Iron
jS^^v ^jH^S;
$m
Fuel and Refractories 129
brick, ground gannister and a plastic fire clay formed into
shapes and burned at high temperatures.
The manufacture of fire brick is one of the most im-
portant ceramic industries and cannot be more than casually
referred to here. Brick differs in the material used, the
fineness or coarseness of grind, the density to which the ma-
terial is compressed and the temperature at which it is
burned.
The material used -largely determines the refractoriness or
melting point. Fine grained, fairly dense and not too hard
brick possess great strength. Coarse, open, lightly burned
brick resists rapid changes of temperature. Fine, dense, hard
burned brick resist penetration of slags, hence every use has
special requirements. A noteworthy feature is that all clay
brick shrink when first heated.
Fire Clay Refractories for Malleable Iron Works
The chief deposits of high grade flint fire clays are lo-
cated in Pennsylvania, Kentucky and Missouri. These clays
are formed from the weathering of feldspar and feldspathic
rocks which have the formula K2O, A12O3 6 SiO2. Pure
kaolins should be A12O3 2SiO2, 2H2O, the potassium silicate
having been dissolved. The flint fire clays approach this
pure clay or kaolin in chemical composition except that they
contain some iron oxide 'which gives the burnt product a
yellow tint. They are a secondary or transported clay de-
posited in still water and are found in the carboniferous
areas or coal measures.
Where the coal is thick the clay is generally thin, and
when the coal 'thins out to almost nothing the clay thickens
up to workable deposits eight to 20 feet in thickness.
These flint clays usually are mined in the Pennsylvania
and Kentucky districts, also occasionally in Missouri, but
the Missouri flint clays often lie in pockets. In certain dis-
tricts, such as at Mexico, Missouri, extensive deposits are
worked 'by stripping the overburden and then mining in an
open pit.
The following chemical analysis of raw clay and burnt
130
American Malleable Cast Iron
Fuel and Refractories 131
bricks will illustrate typical compositions for malleable fur-
nace work:
Table IV
BURNT BRICK ANALYSES
Pennsylvania Missouri Kentucky
SiO3 53.05 55.29 54.41
A12O3 41.16 40.18 . 36.20
Fe2O3 2.65 2.44 2.10
TiO, 1.80 0.00 0.00
CaO 0.00 0.00 2.13
MgO 0.00 0.71 5.16
Alkalies' 1.34 0.76 9.39
Fluxes 5.79 3.91
Cones 32-33 34 31
Ram' Clay Analysis Missouri Flint Clays
Per Cent
Loss on ignition 12.66
Si02 49.08
Al,0, 35.67
Fe3O3 1.28
CaO -. 0.00
MgO .:.... 0.63
Alkalies , ., 0.68
Fluxing parts , , -...,.;; 2.59
Free silica 7.6
The clay is ground and screened in a dry pan in some'
plants while others put the raw clay in a wet pan and add
excess water making the clay plastic and then introduce the
correct per cent of coarse grog, chamotte or calcine. The]
latter is simply burnt clay crushed to coarse .sizes •£© 'help
take care of strains occurring in brick in malleable iron
practice.
The clays are all pugged in a wet pan as this process
develops the greatest placticity. This mud is carried to the
molder who works up portions of it into long (soft mud)
bricks and then throws them with great force into the molds
which are bumped several times to cause the clay to fill the
molds and give good sharp corners. These brick then are
carefully dried on a steam-heated floor.
In a num'ber of plants and for certain purposes brick
instead of being molded as described are pressed hard be-
fore drying giving increased density.
When thoroughly dried the brick are trucked to kilns
where they are set as shown, Fig. 67, leaving spaces for
heat and draft. The kilns are down draft, fired with coal,
132
American Malleable Cast Iron
Fuel and Refractories 133
natural or producer gas, the gas being used more on con-
tinuous kilns.
Silica brick, used for very high temperatures, as in the
roofs of open-hearth and electric furnaces, is a brick made
like a clay brick in which the material is nearly all silica,
using only enough clay to permit the brick to be burned to
hold together. They are very hard, very dense, and possess
an enormous coefficient of thermal expansion. They are
strong, almost infusible, but will not withstand sudden tem-
perature changes.
ft W
Hi l| !
::. ~ -^t, •S-^W- »~ W^ W^*: ju^fr., M
Fig. 67. — Firebrick and special fireclay shapes in a kiln ready to be
burned
Magnesia consisting of MgO, obtained by heating the
mineral magnesite, whic'h is MgCOa, to expel the car'bon
dioxiide, is used both ground and as brick in basic furnace
linings. • In the malleable industry it is used only in electric
furnaces. It is very refractory and resists basic slags. It
conducts heat readily and must be backed up by a layer of
clay brick if heat losses are to be made a minimum. It has
relatively little strength.
Dolomite, a double carbonate of calcium and mag-
nesium, is used in electric furnace bottoms. It is burned
before use, resulting in a mixture of CuO-f-MgO in the ratio
of about 1.4 to 1.0. The commercial preparations may contain
134 American Malleable Cast Iron
from 8 per cent to 25 per cent of other oxides, namely SiCX,
A12O3, and Fe2O3. Some producers purposely add iron oxides
(or silicates) feeling that the material then deteriorates less in
storage and sinters better.
Chromite, zirkite, and bauxite, oxides of chromium, of zir-
conium, and of aluminum respectively, possess no commercial
significance in the malleable industry, although they are well
known refractories. Carborundum, silicon carbide, is another
refractory which has not found application.
VII
AIR FURNACE MELTING
THE air furnace is the commonest device employed for
melting malleable iron, having supplanted the cupola
on the score of quality and the crucible furnaces of
early days on the score of production and economy.
The air furnace is of the reverberatory type in which
the metal, in the form of a fairly shallow bath, is melted by
the flame from fuel burning in a firebox at one end of the
hearth. The flame is drawn over the hearth by a stack at
the opposite end from the firebox. In the earliest type, the
stack was at one side with a charging door at the end op-
posite the firebox. The present arrangement is similar in
character to that of a puddling furnace.
The early air furnaces were very small; some of the
first are said by Davis on the authority of George Belcher
to have had capacities of 800 or 1000 pounds, a 1500-pound
charge being viewed with alarm. Modern furnaces 'have
been, continually growing in size, and now five-ton heats
are unusual, capacities from 10 tons to 15 tons being most
common in practice. Furnaces have been built and oper-
ated with capacities beyond 30 tons, but there are relatively
few in use with capacities far above 20 tons.
Design Is Simple
The construction of an air furnace is relatively simple.
Fig. 68 shows an air furnace in side elevation and cross sec-
tion.
The furnace walls are of fire brick, usually 13 to 18
inches thick, supported and enclosed by cast iron side and
end plates about 1 inch thick. The 'bottom or the hearth
A is built of silica sand or more. rarely paved with fire brick.
Coal is burned in the firebox B, the air being forced through
the fire by a blower discharging into the ash pit C '; the ash pit
doors D being kept closed. Air is also admitted through the
tuyeres E to complete the combustion of the gas and flame com-
ing over the front or fire bridge Avail F. The roof of the
136
American Malleable Cast Iron
.;^y>'^l
Air Furnace Melting 137
furnace consists of a series of removable fire brick arches,
or bungs, supported in cast iron frames. A sufficient number
of these are removed to permit the introduction of the melt-
ing stock.
When charging the furnace, the sprue to be melted is
introduced first in the form of a. layer of fairly uniform
thickness extending nearly the full length of the hearth.
On this is placed malleable or steel scrap, the latter usually
being kept well forward toward the front bridge wall. Pig
iron is placed on top of this in two piles, one well forward,
the other further back.
Most well designed furnaces are of such dimensions as
to be nearly full to the roof when a heat of normal size is
charged. Care therefore must be taken to leave an oppor-
tunity for the free passage of flame from F to the rear
bridge wall.
The bungs are then put on and firing commenced. The
iron soon begins to heat, naturally first at the top and in
front. The firing is so conducted as not to cause much melt-
ing to occur until the lower part of the charge is well
heated through to a gO'od red.
Of the ingredients in the mix, sprue has the lowest
melting point, pig iron next, then malleable scrap, and steel
the highest. The melting points vary inversely as the com-
bined carbon, although the conclusions are slightly compli-
cated by the reabsorption or recombination of the carbon of
malleable scrap below the melting point.
Through the courtesy of H. W. Highriter, the author
has been furnished data as to the recombination of carbon
in pig iron when heated under circumstances comparable
with melting conditions. The data 'have been shown graphi-
cally in Fig. 69. Highriter observes a rapid increase in combined
carbon at the expense of graphitic carbon above 2000
degrees Fahr. The author has calculated the temperature of
the solidus for the observed combined carbon and plotted
these temperatures in a dotted line. When this temperature
falls below that of the specimen, incipient fusion has com-
menced. Melting is complete when the temperature reaches
the liquidus which is dependent on the total carbon and
calculated by Highriter as 2372 degrees Fahr. The metal by
138 American Malleable Cast Iron
observation fused at 2362 degrees Fahr. It will 'be observed
that the melting point referred to by the author is that
where melting is begun, above this temperature presumably
the graphite is rapidly destroyed by solution.
Moldenke many years ago published data as to the re-
lation between combined carbon and melting point of cast
iron and Dyer* refers to the same facts.
In interpreting the author's statements, and presumably
Moldenke's and Dyer's, confusion between the beginning
and completion of melting must be avoided.
If the firing is properly managed, it is not necessary to
melt the steel, the molten pig iron dissolving the steel as it
runs down before the steel actually melts. Some melters ad-
vocate introducing the steel only after the rest of the charge
is melted.
The sprue melts fairly, readily even under all the other
material due to its high combined carbon content. As the
iron melts the surface oxidizes so that there results both liquid
iron and liquid iron oxide, probably Fe2O3. The latter floats on
top of the former and reacts with the carbon, silicon, and
manganese of the metal, oxidizing those to CO2, CO, SiO2 and
MnO and being itself reduced to FeO almost or quite com-
pletely.
The oxides of manganese and iron combine with the silici
to form an acid silicate which also dissolves some of the
refractories in the furnace lining. The resulting slag .soon
covers the surface of the molten metal protecting it from
further action of the furnace gases.
As pools of iron covered with slag form, a good melter
will endeavor to roll unmelted pig iron and steel into these
pools so as to bring the entire charge under the slag blanket as
soon as possible, thus minimizing oxidation losses.
The flame conditions also are carefully regulated by atten-
tion to the dampers in the blast lines to the firebox and top
blast tuyeres and by keeping the openings over the bridge walls
and the channel or neck H to the stack of the right dimensions.
When the charge is all melted it is well mixed by rabbling
with a skimmer bar. The slag is then skimmed off by raking
*lron Age, Nov. 17, 1921.
Air Furnace Melting
139
it out through the skim holes, the skimmer bar consisting of a
1-inch iron bar having a flat plate, say % x 3 x 9 inches
affixed by its center to the end of the round bar. The other
end of the bar is bent into a ring to form a handle.
Meanwhile the fire is being constantly worked with a
poker to keep up active combustion. The heat has to be skim-
med at intervals in order to make rapid heating possible
Fig. 69. — Graph showing recombination of carbon in pig iron
and also to keep the final product fairly clean. One producer
does not remove the slag, but drains it off after the metal
has all been run -out of the furnace.
The progress of the heat is judged as to temperatitre and
composition by 'the inspection of a freshly broken surface of a
not too rapidly cooled ' sample and of the molten metal in the
ladle. For satisfactory work a knowledge of the composition
of previous heats also is necessary. In a few plants more or
less complete preliminary analyses are attempted before tapping.
This chemical practice is attended with a certain amount of un-
140
American Malleable Cast Iron
Air Furnace Melting 141
certainty as to further changes of composition between sampling
and tapping and is therefore less effective than the correspond-
ing practice in electric melting. When the metal is hot and of
proper composition the clap stopper in the tap hole / is cut
through and the metal runs out in a stream into the molders'
ladles.
In the early days of the art the profile of the furnace
roof longitudinally was given very complex, almost fantastic
curves. These usually had a sharp dip in the roof just beyond
the front bridge, then a rise forming a sort of hump over the
hearth, then a drop toward the rear bridge. wall and then a rise
directed toward the stacks.
Furnaces of the older type had sloping roofs but recently the
tendency has been toward a nearly straight roof, lower at the
rear bridge than at the front and sometimes rising again into
the stack as a matter of convenience. A modern design is
shown in Fig. 70.
The flame in flowing through the furnace obeys laws
similar to those governing the flow of water in channels.
These laws 'have been completely investigated by Crum-Grzimai-
lo of Petrograd, (Stahl und Eiscn, Dec. 7, and 11, 1911), who
developed the mathematical formulae and coefficients applying
to the problem in great detail. The discussion is much too
technical in character to be even abstracted here beyond the
statement that the laws are those which would apply to the
flow of one fluid through another, if the two were not mixable
and differed in density as does the hot flame and cold at-
mosphere-
This investigation coupled with a knowledge of combustion
and temperature conditions to be expected forms the only logi-
cal basis for furnace design. In practice actual furnace design
is generally based on modifications of previous designs. This is
in many respects sound policy as tending to avoid erratic prac-
tices. On the other hand, there is a great tendency toward per-
petuation of obsolete features inherent in such a process of ev-
olution.
An inspection of the designs of many furnaces shows a
wide variation on some apparently vital points. These dif-
ferences, however, are not always as little justified as may
142
American Malleable Cast Iron
appear on the surface for the viewpoint of different designers
may not be the same.
Thus, for example, it is undoubtedly sound metallurgical
practice to make but one heat a day on a furnace and make
Fig. 71. — A waste heat boiler connected to two air furnaces. Note that
coal for auxiliary firing is on hand
that a very large one, for ithe brger the capacity the greater
is the melting economy, other things being equal. On the
other hand, consideration must be given to the space re-
quired for molds, to the physical ability of the men to pour,
Air Furnace Melting 143
etc- Thus it is that this practice may not be feasible. If
heats are required at given time intervals it may be more
important to keep the time schedule correct than to get the
maximum of economy, hence fuel consumption may be sacri-
ficed to melting speed. Such a consideration also may limit
the practicable size of heat. Also many furnaces are built
in existing buildings, or under other conditions which handi-
cap the designer by limiting him to certain dimensions from
these causes.
A general idea of the usual dimensions of air furnaces
can be gained from the following: The volume of the hearth,
(the volume of the basin below the level of the skim holes)
is directly dependent on the amount of metal to be melted
and is not subject to any discretion. One pound of melted
cast iron, together with its accompanying slag occupies about 5
cubic inches; therefore 10,000 cubic' inches of hearth must
be provided for each net ton of furnace capacity.
There are certain practical limits to the depth of molten
metal in the hearth which can be successfully worked. Shal-
low baths presenting to the flame a large surface per unit
weight of metal, heat easily and quickly but also oxidize easily
and quickly. Extremely deep baths are difficult to heat, but the
great weight per unit of surface favors the rapid transfer of
heat from flame to metal per unit of hearth area.
Moreover, large capacities coupled with shallow baths may
involve impracticable dimensions. Again, the bottom of the
furnace must have sufficient slope to assure. complete drainage
to the tap hole. Even in unusually short furnaces this slope
produces a difference in depth at the tap hole and rear
bridge of perhaps 5 inches so that an average depth of less
than 2l/2 inches is not workable in any event, because it neces-
sitates a "feather edge" of metal next the bridge.
In practice the average depth of metal ranges from about
5 to 9 inches, the greater depths usually occurring in furnaces
of the greater capacities. The depth at the tap hole may be
from 2l/2 to 5 or 6 inches greater than the average depth de-
pending largely on the furnace length. These depths correspond
to hearth areas running from about 13% square feet per ton
down to less than 8 square feet per ton.
144 American Malleable Cast Iron
The requirements of firing, skimming, etc., as well as the
maintenance of roof arches sets a maximum inside width of
between 5 and 6 feet for air furnaces of the usual design, a
few large furnaces of special design have a clear width of 7
feet. When the maximum width is reached the capacity of the
furnace can be increased only by increasing the hearth length.
Extremely shallow baths are impracticable when large capac-
ities are desired because they necessitate long furnaces- For
example, 2Oto>n furnaces with a hearth area of IS1/-* square
feet per ton would be about 45 feet long between the bridge
walls. Hearths from 14 to 27 feet long are in common use,
and in a few unusually large furnaces they are several feet
longer. A certain length of hearth is desirable because it
insures a better contact of flames and charge. Excessive lengths
cannot be had with small capacities as the furnace would be
too narrow. The practicable length also depends on the fuel
and firing conditions since a length which does not allow the
flame to reach to the rear bridge wall is unworkable.
The firebox is almost fof necessity of the same widths as
the hearth. The grate area required depends on the rate of
combustion of fuel desired and this in turn depends on the
furnace capacity and on the relative importance of quick as
against economical heating. Air furnace grates burn from 43 to
77 pounds of coal per hour depending on firing' conditions.
Values of from 67 to 77 pounds are more common than those
near the lower limit.
Reported tests indicate that air furnaces use from slightly
under 500 to about 1200 pounds of coal per ton of charge.
These are extreme ranges* the usual commercial range being
from 750 to 900 pounds per ton, depending largely on the size
of the furnace- These figures give some indication of grate
areas required under various conditions, having in mind also the
fact that an attempt to melt rapidly is often uneconomical.
• It seems to be usual practice to provide from 2 to 21/2 square
feet of grate per ton of charge although a number of fur-
naces exceed this rate.
Many designers do not agree on the correct height of an
air furnace roof. From 15 to 17 cubic feet per ton from
Air Furnace Melting 145
hearth to roof are unavoidably necessary in order to accom-
modate the unmelted charge. This sets a minimum of height
for any given hearth area per ton of charge.
Quantity of Air Varies
Almost invariably the roof slopes downward toward the
rear bridge. The old humpback furnaces had a somewhat great-
er average height than the more modern straight-roofed
furnaces. The average height of roof above the metal at
the side walls is about 24 inches. A pound of ordinary melt-
ing coal requires about 12j4 pounds of air for combustion under
usual operating conditions. The relative amount of air entering
the furnace through the top blast tuyeres and through the
grates varies in practice, but the average ratio seems to be
about 28 to 100. Therefore a pound of coal requires about
10 pounds of air through the grates and 2j4 pounds of air
through the top blast in ordinary operating practice.
The firebox is operated so that it produces a poor grade
producer gas which is then burned with a sufficient amount
of air for theoretical combustion. A typical gas leaving the
firebox is composed of 1.2 per cent oxygen; 8.0 carbon dioxide;
12.1 carbon monoxide; and 78.7 per cent nitrogen. The gas
leaving the stack contains 1.1 per cent oxygen; 12.7 carbon
dioxide ; 3.6 carbon monoxide ; and 82.6 per cent nitrogen. The
analyses take no account of the water from the combustion
of the hydrogen of the fuel. The oxygen in this water and
that used in the oxidation of silicon and manganese account
for the relatively high value of the nitrogen. The flame gases
also contain unburned hydrocarbons of unknown character and
amount which escape sampling.
Any attempt to further reduce the carbon monoxide content
by adding additional oxygen, probably would result in a pro-
hibitively high excess of oxygen in the gas, causing heavy
oxidation during the melting process. •
The mechanism of this oxidation has already been re-
ferred to as consisting of the oxidation of the iron to the Fe2O3
followed by the subsequent reduction of the Fe2O3 to FeO
by the silicon, carbon and manganese of the bath. The amount
of oxidation varies widely depending upon the furnace at-
146 American Malleable Cast Iron
mosphere and similar conditions. Over an extended period,
however, it seems nearly constant for any successfully operat-
ing plant. The losses expressed in percentage of the total
weight of original charge and in percentage of the amount
of each element present are generally about as follows:
Table V
LOSSES OF ELEMENTS IN MELTING IN AIR FURNACE
Total amount
Total charge of element
100 -per cent 100 per cent
Carbon 0.62 15.8
Silicon 0.33 31.4
Manganese 0.26 48.1
Phosphorus 0.00 0.00
Sulphur —0.01 —22.2
Iron 1.14 1.2
2.37
The results of the figures in the second column form an in-
teresting comparison of the "oxidizability" of the different ele-
ments when melted in an acid furnace.
Oxygen Absorbed During Melting
A more interesting method of clearly showing the relative
affinity for oxygen of the different metals is to calculate the oxy-
gen combined with each one of the elements during melting.
This calculation has been made using the preceding data and
the results are shown in the table below. In the first column
is shown the oxygen combined with each of the four oxidiza-
ble elements in terms of the weight of original charge and in
the second column in terms of the weight of the oxidized ele-
ment present in the charge.
Table VI
OXYGEX ABSORBED BY EACH OF THE OXIDIZABLE ELEMENTS DURING AIR
FURNACE MELTING
Element present in
Total charge original charge
100 per cent 100 per cent
Carbon 1.60 50
Silicon 0.38 36
Manganese 0.06 11
Iron ..... 0.32 34
2.36
Air Furnace Melting 147
It will be seen that carbon combines much more greedily
with oxygen than any other element, silicon coming next, man-
ganese oxidizing much less readily and iron only slightly. Of
course the results would differ with variations in gas com-
position and furnace lining.
It will be seen that the melting process oxidizes a total of
2.34 per cent of the original charge, and combines there with
oxygen weighing 2.36 per cent of the original charge. There
should thus result a weight of slag equal to 2.5 per cent of the
metal charged and of gas equal to 2.2 per cent of the metal
charged, were there no contamination from molten refractories.
A typical sample of air furnace slag showed the following com-
position :
Analysis of Air Furnace Slag
Per cent
FeO 28.80
Fe2O3 1.16
MnO 4.85
Si02 (etc) 50.42
A12O3 14.77
100.00
The metallic oxides aggregate 34.81 per cent of the weight of
the slag. From the preceding tables, this corresponds to 13.8
per cent SiCX. Therefore the above slag consists of a mix-
ture of 58.70 per cent oxidation products and 41.30 per cent
molten refractories and since the weight of slag oxidation prod-
ucts was computed to be 2.5 per cent of the weight of the
charge the actual slag weight should be slightly more than
4.2 per cent of the original metal charged into the furnace. It
is not assumed that these data are absolutely correct but they
furnish a fair guide to what may be expected in practice.
Refractories Destroyed by Melting
Since every ton of iron melted destroys 34 pounds of re-
fractories by melting, it is evident that frequent furnace repairs
are necessary. The furnace parts most strongly exposed to
heat usually are relined at intervals of from 10 to 20 heats.
The roof over the hearth lasts usually from 16 to 24 heats
and the sand bottom from 10 to 20 heats. In one instance the
writer saw a furnace make 34 heats without relining, and
148
American Malleable Cast Iron
Fig. 72. — Gray sprue; characteristic of high carbon and silicon and
sometimes of low pouring temperature (full size)
Fig. 73. — Gray sprue showing white patches; characteristic
of less but still excessive carbon and silicon. Note "in-
verted chill," i.e. greater grayness near the surface
than at center (full size)
Fig. 74. — Moderately mottled sprue; characteristic of carbon, silicon
and temperature suited to small work (fulj size)
in another saw a bottom last 120 heats as a result of careful
attention. However, this record is believed to be exceptional.
The charge going into the furnace can be computed by
adding to the final composition wanted the expected melting
losses and then arranging a mixture from the available melting
stock conforming to these requirements- The process is one
Air Furnace Melting
149
Fig. 75. — Normal sprue for metal of the higher carbon ranges of
specification metal in average work. Note leaf-shaped bright
crystal facets radiating from center (full size)
Fig. 76. — Similar to Fig. 74 but lower in carbon. Note decrease in
leaf-shaped crystals (full size)
Fig. 77. — Similar to Fig. 76 but quite low carbon. Note finely gran-
ular fracture from which the leaf-shaped crystal has almost
- disappeared (full size)
Fig. 78. — "High" iron, i.e. metal low in carbon, silicon and manganese;
fracture granular -throughout and edge showing blowholes
(full size)
of simple arithmetic and the great mystery made of the matter
by the older melters was not justified.
However, the -skill of ' the melter is important in main-
150 American Malleable Cast Iron
taming furnace conditions so that the oxidation losses are uni-
form and as small as practicable. The appearance of the flame
in the furnace, the eddy currents in the bath and the appear-
ance of the slag, whether viscous or liquid, indicate to the
skillful melter what is going on in the furnace. Similarly the
color and fluidity of the metal and the appearance of the frac-
ture after cooling permit of close inferences regarding its
composition.
Interpreting Appearance of Fracture
Among the more obvious indications of the fracture are
the presence of graphitic areas or mottles indicative of too
high a silicon or carbon or both, larger leafy crystals radiat-
ing from the center indicating moderately high carbons de-
creasing to very fine granular structures as the carbon falls
to near 2 per cent. There also is the rim of fine blow holes
and the spray of oxidizing iron arising from the surface of the
metal in cases of "burnt" heats very low in silicon.
The actual conditions are not even capable of illustration
photographically since some of the fractures do not show up
clearly except by looking at them in light falling in various
directions.
It can be shown that by far the largest part of the oxida-
tion losses, occurring in practice, is complete, when the metal
is melted down and ready to skim.
From the time the iron is all melted, before skimming, un-
til the moment of tapping no marked changes of composition
occur as to carbon and manganese although the silicon will
decrease perhaps 0.1 per cent during the removal of the first
slag. This presupposes a properly operated furnace.
Composition May Vary During Heat
Samples taken from the last of a heat frequently show
a considerably lower carbon, silicon and manganese content
than those taken at the first of the heat. However, this is due,
not to a progressive oxidation which would have affected the
entire heat to that extent had it been left in the furnace, but
to the effect of oxidation on the very thin layer of metal
Air Furnace Melting
151
left in the furnace as the last metal is being withdrawn. Only
a small weight of metal is of a composition different from
the bulk of the heat. A feature that frequently is misunder-
stood is the elimination of graphite. Often it is supposed
that the fact that the longer the heat is left in the fur-
Fig. 79. — Changes of metal after tapping
nace the lower the graphite is due to oxidation of carbon and
silicon. As a matter of fact the elimination of graphite is
largely a function of the pouring temperature and time, and
metal will show progressively clearer fractures during the
progress of the pouring of a heat without any accompany-
ing change of ultimate chemical composition. Fig. 79 shows
such a condition.
In this figure the composition of the metal with respect
to total carbon, graphitic carbon, silicon and manganese is
152 American Malleable Cast Iron
shown for samples in the form of 1^-inch sand-cooled cyl-
inders poured at intervals of three minutes each while the heat
was running out of the furnace. It should be said in ex-
planation that this was not a normal malleable iron heat but
one for a special class of work requiring great perfection
of surface on castings on thin sections, hence the high values of
silicon and carbon. However, the curve shows strikingly the
rapid decrease in combined carbon as the metal is exposed longer
to high temperatures.
Temperature of Furnace
Temperature conditions in air furnaces are not accurately
established. The metal flowing from the spout has a tem-
perature from 2100 to 2500 degrees Fahr, as measured by
radiation pyrometers. Such determinations involve a correction
for coefficient of radiation since clean metal does not radiate heat
as rapidly as would a theoretical black body. The use of optic-
al pyrometers involves a similar correction for emissivity which
is however of much smaller magnitude. Optical pyrometer
measurements coupled with observations of metal at known
temperatures suggest that true values are probably more nearly from
2500 to 2700 degrees Fahr. and that the radiation coefficient
is not well established. The flame in the neck when the
heat is melted has a temperature of about 2500 degrees. The
furnace roof and the flame under it seem to . reach temper-
atures up to 3000 degrees or somewhat higher, the average
being about 2800 degrees. In the firebox the temperatures
are about the same as in the neck, 2500 degrees, Fahr. The
latter figures are probably more accurate than those on the
flowing metal since black body conditions are more nearly
approached. They are if anything somewhat low.
The following heat balance gives a general idea of fuel
consumption in an air furnace. Since there is considerable
variation in furnace practice the correction of heat values
for the actual temperature of fuel and air entering the fur-
nace was believed an unnecessary refinement.
While based only on estimates, this balance gives a fairly
comprehensive idea of what becomes of the heat delivered
Air Furnace Melting 153
Table VII
HEAT BALANCE OF A TYPICAL AIR FURNACE
B.t.u. per B.t.u. per
ton ton
charged charged
Heat value coal burned 11,200,000
Heat from oxidation of charge 219,400
Heat of formation of basic silicates 30,000
Total 11,449,400
Latent and sensible heat of metal 878,940
Sensible heat of flue gas 6,112,000
Loss to incomplete combustion of C to CO only 1,232,000
Evaporation of water in coal 10,000
Heat value of unburned combustible in ash 37,335
Sensible heat of slag 42,000
Latent heat of slag (est.) 30,000
Sensible heat of furnace structure 600,000
Radiation conduction and unaccounted for 2,507,125
Totals 11,449,400 11,449,400
to the melting furnace. The values may be summarized on a
percentage basis shown in Table. VIII.
This indicates clearly that the larger part of the waste is
in the sensible heat of the flue gas. This heat occasionallv
is recovered by the use of waste heat boilers which gen-
erate steam with the heat of the gases leaving the furnaces.
The difficulties encountered are largely of a steam engineering
character and arise from the intermittent supply of heat avail-
able.
Prof. Touceda in a paper before the American Foundry-
men's Association in 1920, has given tentative suggestions for
the utilization of waste heat from air furnaces. These sug-
gestions are for various double hearth furnaces in which the
waste heat from one hearth is used to preheat the charge in
Table VIII
HEAT BALANCE IN TERMS OF HEAT VALUE OF COAL FIRED
Per cent Per cent
Heat value of coal fired. . . 100 Heat in metal 7.81
Heat from reactions in Heat in flue gas . . 54.70
furnace 2.2 Heat in slag 0.64
Incomplete combustion.. 11.30
Heating furnace walls. . . . 5.35
Radiation and conduction 22.40
Total input 102.2 Total output 102.20
154 American Malleable Cast Iron
the other. The mechanical means are somewhat complicated
involving movable hearths and also somewhat continuous op-
eration. From a thermal viewpoint, however, they are most
interesting.
Reference has been made to the use of forced draft- in
air furnaces. The air supply is usually at low pressure,
about 4 ounces per square inch, although a few plants use
pressures of a pound. In such cases the furnaces must be
equipped with doors at the fire 'hole and skim holes. At
least one important producer operates on natural draft alone,
using no blowers and consequently no top blast. This partic-
ular plant depends on extremely high stacks. Many air
furnace stacks are from 45 to 85 feet high, and have internal
diameters from 24 to 48 inches. The lack of agreement is
unaccountable except on the basis of poor design. Nearly
all air furnace stacks have capacities far beyond their actual
requirements.
It has been stated in the general discussion of fuels that
both oil and pulverized coal fuel have been tried in air fur-
nace practice. As far as the author knows, the use of oil
never has been generally satisfactory, owing to difficulties
in maintaining the proper furnace atmosphere, free from excess
of air or CO2.
The chemical changes in melting depend entirely upon
the temperature and composition of gas in contact with
the metal. The use of producer gas entailed similar diffi-
culties and was never commercially adopted, except of course
in open-hearth practice. Similar difficulties have been encoun-
tered in the use of pulverized coal but have been successfully
overcome, at least by a few combustion engineers.
A successful equipment of this character is shown in Fig.
80 and consists of a hopper containing the pulverized fuel pro-
vided with screw conveyors for feeding a stream of coal
into the current of air from the blower shown in the lower
right hand corner of the picture. The ends of the con-
veyor shafts are shown under the numbers 1-2-3-4-5 painted
on the hopper.
The current of air loaded with coal dust enters the
furnace through three burners in the head wall of the fire
Air Furnace Melting
155
box, which is blocked up; and through two burners through
the roof at the point where the top blast usually enters.
By proper manipulation of the relative supply of coal and
air to these several burners, proper control may be main-
tained and satisfactory working insured. The entire problem
Fig. 80. — A po'.vclercd coal attachment for an air furnace
is merely the design of a burner capable of so feeding the
fuel into the air as to maintain uniform combustion conditions
with coal and air supply capable of regulation through a fairly
wide range.
Such a set of burners operated to duplicate furnace atmos-
pheres corresponding to the best air furnace practice will
produce results superior in control and economy to results
under hand firing. The improvement results primarily from
the constancy of ratio of coal to air throughout the heat, thus
156 American Malleable Cast Iron ^
avoiding the losses due to alternately incomplete combustion
and excess air w'hich occur even with the best hand firing
when the average condition is perfectly controlled.
. Table IX
CHEMICAL CHANGES IN AIR FURNACE
Metal charged
pounds
Fe .1901.3
C 62.0
Si 21.6
Mn 11.0
S 0.9
P 3.2
Clay
O
N
H
Ash
Water
Refrac-
Coal Air tories
14
Total
[olten metal
Slag Flue gas
1878.5 22.8
49.6 ... 617.0
15 0 66
Cin-
ders
4.4
6090
671.0
21.6
11.0
5.9
3.2
34.0
1918.0
7243.0
39.0
21.0
14.0
"5.6 '.'.'.'.'. '.'.'.
5.8 5.2
1.1 1.2 2.0
32
V.6
. 34.0
.... 1918.0 ...
.... 7243.0 ...
39.0
21.0
14.0
34.0
.... 15.0 1903.0
7243.0
2l'.0
39.0
'.'.','. '.'.'. ' 'l4.0
Total. 2000.0 Ibs. 688.0 9161.0 34.0 11,883.0 1953.2 84.8 9818.0 27.0
The author has seen the results of many tests on this
type of equipment but it is doubtful whether data have yet
been accumulated which warrant a definite conclusion as to
economy of operation due to pulverized fuel.
The tests which he has seen seem to indicate that the
requirements as to furnace atmosphere are such that no direct
saving on coal is practicable. The economies may rather be
expected to result from decreased labor and refractory costs,
and greater independence in using poor coal.
The data at hand point also to a lower and much more
constant loss by oxidation of the several metals than is nor-
mal to ordinary air furnace practice, but insufficient experience
is available to be sure whether this condition always exists.
As a skeleton outline of the metallurgy involved in the
operation of an air furnace the outline of the chemical changes
shown in Table IX may be interesting. The summary is typical
only and does not necessarily apply exactly to any given case.
The summary is based on the weights of each material
and each element entering into the reactions for one net ton
of charge.
Air furnaces usually are operated by a crew of either
two or three men exclusive of those doing the charging.
Air Furnace Af citing 157
bringing in fuel and stock, etc. The majority of air fur-
naces make a heat in 20 to 30 minutes per ton plus about
one half hour if the furnace is hot to begin with, or plus
one and one half hours if the furnace is cold at the start of
the melting operations.
Large furnaces melt faster, per ton, than small ones,
but large heats still take longer to make. It is said that one
plant, using oil fuel made heats around 30 tons in three and
one half or four hours, although the writer is not prepared to
vouch for this statement. Another plant making heats of
this size with coal runs 16 to 18 hours to a heat, it is said.
In most plants skimming begins when the heat is well
melted which will be from one and one half to two hours
before the heat is ready. In a plant where instead of skim-
ming the slag is tapped out after the iron is poured it is
claimed that no loss of time or fuel is incurred due to this meth-
od. The operation is on fairly large furnaces. In spite of
the obvious desirability of this operation, if practicable, it has
not been adopted elsewhere. The author does not know
whether or not this conservatism is justified. The feeling seems
to be one of suspicion as to the general economy and practica-
bility of the operation.
VIII
ELECTRIC FURNACE MELTING
PRACTICALLY the only radical change in melting prac-
tice which has been introduced into the malleable indus-
try in the last half century is the use of electric furnaces.
So far only one producer operates under this method, which is
protected by patents covering the conditions necessary to com-
mercial success.
In electric operation, increased accuracy of chemical con-
trol is made possible and the success of the melting operation
is largely independent of variations in quality of stock and fuel
and of blast and similar conditions. The belief that electric
melting is adopted because it permits the manufacture of al-
loys of compositions unattainable in the air furnace is not
founded on fact. While it is possible, for example, to make
iron as low as .017 per cent in sulphur, if desired, there is
no engineering advantage in such an operation.
Electric melting as practiced today is conducted by the
triplex process, developed by W. G. Kranz, which, as the name
indicates, is conducted in three distinct stages. This process
supplements the advantages of the electric furnace with the
use of a cupola and a bessemer converter to assist the elec-
tric furnace in operations to which it is not so well suited.
The rationale of the process is as follows :
The electric furnace alone is suitable for melting or heating
metal with slight contact with air or any other substance ex-
cept the furnace lining and slag. Therefore, it is suited rather
to keep the composition of its contents unaltered than to make
changes in composition.
Chemical changes occur therein only as a consequence of
the addition of various alloys of slag-making ingredients and
the effect of such additions can be quantitatively controlled. The
changes of chemical composition easiest of attainment in the
electric furnace are increases in silicon, manganese, or phos-
phorus and decreases in sulphur and oxygen. Carbon can be
added or removed, or silicon removed with greater difficulty
160
American Malleable Cast Iron
but the removal of phosphorus is not practicable under the
usual operating conditions in malleable melting.
'Whereas the electric furnace is an expensive source of hear
energy, the cupola is the cheapest known method for merely
Fig. 81. — Cupola producing molten iron — The starting point of the
Kranz triplex process
melting cast iron, composition being no object. . Cupola melt-
ing always removes at least part of the silicon and manganese
and adds sulphur, leaving the phosphorus unaltered. The car-
bon content is nearly independent of the mix used depending
only on the condition of the fuel bed. The carbon content
always is relatively high.
Electric Furnace Melting 161
The bessemer converter furnishes an easy and economical
way to remove all carbon silicon and manganese from iron but
adds a great deal of oxygen.
The three units form an ideal team, each possessing good
qualities to supplement the weak points of its mates. The
cupola furnishes cheaply a supply of liquid iron of high and
approximately constant carbon content which readily can be
controlled as to its maximum silicon, manganese and phos-
phorus content, but may have high sulphur from the fuel.
Carbon, silicon and manganese can be removed from this
metal in the bessemer converter, although oxygen may be
added. By taking the proper relative amounts of cupola and
bessemer metal a mixture can be produced having a 'carbon
content close to any desired value, and which also is below
any desired fixed values in silicon, manganese and phosphorus.
However, it contains an indefinite and relatively large amount
of sulphur and oxygen.
This molten mixture can be given its final heating in the
electric furnace without too great expense, and"*.iby the use of
suitable slags the sulphur and oxygen can be removed without
any -effect on the silicon, manganese, or phosphorus. Guided
by the analysis of the molten charge, silicon and manganese
can be added to adjust these values as desired and a product-
made without prohibitive cost, adjusted to chemical specifica-
tions on each of the five common elements and freed from
oxygen. .
These are the steps in the Kranz process, which since
passing through the experimental stage in 1913-1914 has pro-
duced many thousands of tons of malleable cast iron in two plants
of the largest producer of malleable in the world. The proc-
ess as outlined comprises melting in the cupola ; decarburizing in
the converter; heating, desulphurizing and deoxidizing and
raising the manganese and silicon in the electric furnace; and, if
desired, adding sulphur in the ladle. For still greater uniform-
ity it was once suggested that the cupola and converter metal
be stored in a mixer prior to its introduction into the electric
furnace, but practice has proved that this step is not nec-
essary.
It has been found that a product varying from dead soft
162
American Malleable Cast Iron
steel to" gray iron, and including alloy steels can be made by
this, process at the will of the operator. If dephosphorization
is desired, for example in steel-making, an extra step is re-
quired in the electric furnace, involving the formation of a
dephosphorizing slag and its removal before proceeding with
the desulphurizing and deoxidizing.
Fig. 82. — Two-ton side-blow converter producing liquid steel from
cupola metal in triplex process
Metallurgy of Triplex Process
It may be well to consider the individual steps involved
in greater metallurgical detail. In general, the melting stock
consists of sprue and malleable scrap and high silicon pig iron.
The mix is calculated only to be close to the desired value in
silicon content. The manganese automatically remains low and
with a little care the phosphorus can be kept below about 0.19
per cent, which is all that is required.
Electric Furnace Melting 163
It is intended that the cupola metal shall run slightly under
1 per cent silicon. Too low a value causes trouble from gum-
ming' up the cupola taphole and spout and the ladle. The maxi-
mum is determined by the metal to be made. The composition
of the metal leaving the cupola under ordinary working condi-
tions is approximately as follows: Carbon, 3.10; silicon, 0.80 to
0.95; manganese, 0.12 to 0.19; sulphur, 0.09 and up, and phos-
phorus, 0.14 to 0.19 per cent. The dimensions of the cupola
are such as to allow the unit to run continuously to produce
the metal required by the electric furnaces. Interruptions and
intermissions are undesirable because they affect the tempera-
ture of the fuel bed and consequently the carbon content.
The ratio of iron to coke in the cupola may average 7 to
1, varying somewhat with operating conditions. Two cupolas
are provided and are used alternately to permit repairs.
'i he converter easily reduces the molten metal to a composi-
tion about as follows : Carbon, 0.20 and under ; silicon, trace ;
manganese, trace; sulphur, 0.12 and up; and phosphorus, 0.17
per cent and up. A considerable oxidation of iron also occurs,
which together with the mechanical loss in the form of fine
drops amounts to from 8 to 15 per cent of the converter charge.
If a carbon content of say 2.60 per cent is desired, cupola and
converter metal in the ratio of 240 to 50 will be required and the
mixture will have a composition as follows: Carbon, 2.60; sili-
con, 0.66 to 0.78; manganese, 0.10 to 0.16; sulphur, .095 and
up; and phosphorus 0.14 to 0.19 per cent.
Since each furnace heat is handled as a unit, it will be seen
that the converter charge is dependent on the capacity of the
electric furnace and the carbon content of the cupola metal. In
the illustration chosen the converter must deliver 50/290 or
about 17 per cent of the capacity of the electric for each
blow. The metal introduced must exceed this amount by the
expected oxidation and mechanical losses.
The electric furnaces actually in use have a rated capacity
of six and 15 tons, respectively so that when working at capac-
ity the converter would have to deliver 1.02 and 2.35 tons
respectively.
The electric furnaces used are of the Heroult type, operat-
ing on 3-phase, alternating current. The 6-ton units consume
164 American Malleable Cast Iron
800 kilovolt-amperes of power at 80 to 100 volts and the 15 -ton
units from 18,000 to 22,000 kilovolt-amperes at from 90 to
110 volts.
Handling Charge in Furnace
The internal diameter of the larger units is approximately
10 feet. In all cases the bottoms are dolomite and the lining
of the side walls magnesite. The molten metal is introduced
into the furnace, the arc formed, and a lime slag made on the
surface. The slag-making ingredients are lime, fluorspar and
coke; in amounts determined by the working conditions and not
by weight. About 150 pounds of lime and coke and 100 pounds
of fluorspar may be used in a 12-ton heat, the active ingredient
of the resulting* slag being calcium carbide, CaC2. The ac-
tual amounts of slag-making ingredients are however not de-
termined by weight but by the appearance of the slag and
the "operating conditions of the furnace. This carbide reacts
energetically with any metallic oxides present. For instance
3 FeO + CaC2 = GaO -f 3 Fe + 2 CO
No appreciable amounts of CaC2 are formed until the oxy-
gen is practically completely eliminated. At that stage the
elimination of sulphur begins, the products being CaS and
carbon, which dissolves in the metal. This process can not
be conducted under any but a reducing condition for CaS
is easily oxidized to CaO, the sulphur unfortunately not burn-
ing to SO2 but dissolving in the iron. This introduces certain
difficulties in lowering the silicon content. For example silicon
is easily and almost quantitatively oxidized by ore, the reaction
presumably being
Si + 2 FeaO3 = SiO2 + 4 FeO
Unfortunately the FeO of the resulting slag immediate-
ly reacts as follows :
FeO + CaS = FeS + CaO
and the desulphurizing must be recommenced. The removal
of silicon can be conducted in this way, but it is a cause
of difficulty in the maintenance of the desired slag.
Fortunately the high carbon alloys occurring in malle-
able practice do not take up carbon from the carbide slags
used to any appreciable extent, nor does the CaC2 reduce a
Electric Furnace Melting 165
considerable amount of silicon from any calcium silicates which
may be present.
A sample is taken for analysis after the metal is thor-
oughly mixed in the furnace and should show a correct
amount of carbon and phosphorus, and a deficiency in sili-
con and manganese. These latter two elements are added as
ferrosilicon, ferromanganese, Spiegel or similar alloys. Carbon
can be added as pig, cupola iron, or in very 'hot heats as coke
or can be reduced by steel additions. Silicon can be removed
with ore as previously described but it is not intended that this
Fig. 83.— Transfer train consisting of electric motor car and trailer
with crane ladle. This equipment is used in carrying cupola
and converter metal to the electric furnaces
be done in regular practice. The removal of phospohrus from
malleable heats is so expensive that it is cheaper to scrap such
heats than to attempt to correct them.
Temperature Limited by Operations
The temperature to which electric metal can be heated
depends only on the refractories used and in commercial prac-
tice is from 2600 to 3000 degrees Fahr. The figures are by
radiation pyrometer and in the writer's judgment are likely
to be lower than the correct values. More recent data by optical
pyrometer show temperatures from 2900 degrees to 3000 de-
grees Fahr. It appears therefore that the figures around 2600
166 American Malleable Cast Iron
degrees arose from an improper correction for coefficient of ra-
diation. The relative merits of the two systems of pyrometry
have been discussed in connection with air furnace melting. It is
customary to take a heat away in one or two large ladles and to
proceed immediately with another heat. The advantages of the
process already have been pointed out and all point back to ac-
curacy of control. The most serious limitation is the expensive
first cost of the melting installation, which places it beyond the
reach of the small producer. Furthermore the process is not
suited to intermittent operation involving the banking of cupolas
and filling of electric furnaces with coke. To obtain success-
ful results a 24-hour day during the working week is neces-
sary. Counting iy2 hours per heat or 16 heats per day and
allowing for some loss of time for repairs between heats, and
bearing in mind possible reductions in economy where very
small units are used, a simple calculation will indicate that suc-
cessful operation can be had only in plants of fair capacity.
The two plants now in operation are equipped with three
small and two large furnaces, respectively, and are intended
to operate on large tonnages. Furthermore, the crane service
required for the handling of hot metal, etc., almost precludes the
introduction of hot melting into any but an especially built plant,
thus further limiting its general introduction.
All this is in addition to the limitations to the general use
of the process due to its control through patent protection. Fur-
nace repairs are relatively much less frequent in electric fur-
naces than in air furnaces. The bottom is taken care of after
each heat. The magnesia side walls and silica roof each last
from 120 to 240 heats, while the basic bottom, being repaired
after each heat, lasts indefinitely.
The cost of heat in the electric furnace is high, but on the
other hand the utilization of heat reaches an extremely high
efficiency owing to the elimination of the losses in fuel-fired
furnaces arising from the escape of the hot products of com-
bustion. The current is on about one hour for each heat.
Charging, tapping and patching consume up to 45 min-
utes of time. Cupolas are intended to run a week on each
lining but usually are repaired at 24 to 72-hour intervals.
Electric Furnace Melting 167
The converters are of the side-blown type of a capacity
suited to the Heroult furnace they serve and are lined with
ganister. Converter bottoms last about a week, and the tops
nearly indefinitely.
It will be instructive to follow quantitatively the chemical
changes occurring. The following analysis is typical of the
slag produced by the cupola.
Per cent
SiO, -52.90
A1,O, 12.80
FeO 5.10
FeaO 00
MnO 2.60
CaO 21.30
MgO 3.70
S 0.20
Undetermined and .error 1.40
100.00
This is practically a mixture of molten refractory and
limestone, little oxidation of the metal having occurred under
the strongly reducing conditions of the cupola.
Assuming that the cupola charge consists of 10 per cent
silicon pig, sprue and malleable scrap, the two latter averaging
0.70 silicon, in order to have a mixture at 1.10 silicon the mix
will contain 4.3 per cent pig iron and, for example, 40 per
cent sprue and 55.7 per cent malleable scrap. The average
analysis of such a mixture figures out carbon, 2.68;
silicon, 1.10; manganese, 0.27; sulphur, 055 and
phosphorus, 0.177 per cent. This metal, when melted
and leaving the cupola has a composition of carbon, 3.10; sili-
con, 0.85; manganese, 0.15; sulphur, 0.09 and phosphorus, 0.177
per cent. This change of composition coupled with the pre-
viously given slag analysis amounts to a net loss by oxidation
of 0.166 per cent of the total weight charged.
The oxidation of silicon, manganese and iron is nearly
balanced by the gain in sulphur and carbon from the fuel. In
practice there is a loss of noticeable magnitude due to me-
chanical causes. By calculation the slag corresponds to 5.8 per
cent of the weight of the charge; 1684 per cent is derived
from oxidation of the metal ; 25 per cent from the lime-
stone added as a flux ; and the balance from the fusion of the
168
American Malleable Cast Iron
furnace lining, coke ash, impurities in stone, etc. Assuming
the limestone to have been 90 per cent CaCO3, the weight of the
limestone added was about 50 per cent of the slag weight or
2.9 per cent of the weight of metal charged. The limestone
lost to the flue gas an amount of CO2 equal to 11 per cent of
the slag weight.
When the cupola metal is blown in the converter it be-
Fig. 84. — Heroult electric furnace in which cupola and converter
metal is charged for final step in triplex process
comes a steel containing, for example: Carbon, 0.10; sulphur,
0.095; and phosphorus, 0.187 per cent. The slag formed has a
composition of which the following is typical :
Per cent
SiO3 57.50
A12O3 1.43
FeO 34.41
Fe,O, 1.45
M-nO 3.80
OaiO 0.25
M-gO 0.34
Error and undetermined 0.82
100.00
Electric Furnace Melting 169
A loss in weight of 5.36 per cent of the weight charged
into the converter is indicated. In practice a larger loss is
noted due to mechanical losses and to considerable amounts
of iron oxide which escape as fume and are not taken into ac-
count in the analysis.
The slag is equivalent in weight to 4.86 per cent of the
metal charged. Of this slag 50.08 per cent is an oxidation prod-
uct of the metal and 49.92 per cent is fused refractory.
In the electric furnace no oxidation takes place, the only
elements affected being sulphur and oxygen which leave the
metal to become calcium sulphide and carbon monoxide, respec-
tively. The former remains in the slag, while the latter escapes
as a gas. Therefore the slag in the electric furnace is not in
any material degree derived from the elements in the iron, but
depends for its quantity and largely for its composition on the
slag forming additions used. These are lime (CaO) fluor-
spar (CaF2) and coke. The supposition is that the coke and
lime form .calcium carbide which removes both sulphur and
carbon.
However the slags never are nearly pure mixtures of CaC2
and CaF2. Typical slag obtained under conditions which would
possibly have destroyed "any CaC2 by the action of the atmos-
pheric moisture had a composition as follows :
Per cent
SiO, 29.80
A1,O3 2.85
FeO 0.50
Fe2O3 nil
M.nO 0.18
CaF2 0.70
CaO 44.51
MigO 7.55
CaiS 7.20
Undetermined '6.71
100.00
From the behavior of the slag it seems reasonable that
most of the lime is combined with silica and that there is but
little free CaO as Ca(OH)2 either normally present or derived
from the decomposition of carbides. Possibly the CaO from
these sources may run to 5 per cent or similar undetermined
amounts.
170
American Malleable Cast Iron
Possibly the MnO s'hown is MnS floating up from the met-
al, in which case the CaS would be reduced and CaO increased
to allow for the S combined with Mn. The fluorine apparently
is largely eliminated in the furnace. Data as to slag quan-
tities are uninteresting as having no connection with the metal-
lurgical principles. The additions may amount in the aggre-
gate to perhaps 1 or 1.5 per cent of the weight of the metal.
Fig. 85. — Heroult furnace tilted for pouring
Metallurgy of the Slag
Assuming a desulphurization of .07 per cent, the slag
composition referred to and excluding sulphur from the coke
amounts to around 44 pounds of slag per ton of metal. Of
the slag the SiO2 A12O3 and MgO are primarily derived from
the furnace lining. Those comprise 40.2 per cent of the en-
tire slag. Therefore for each ton of metal 17.6 pounds of re-
fractory are melted and 26.4 pounds of slag is formed from
lime, fluorspar and carbon and from the metal itself. Of the
ingredients from the metal the principal item in weight is 1.4
Electric Furnace Melting 171
Table X
BALANCE SHEET FOR DISTRIBUTION OF METALLOIDS IN ELECTRIC FURNACE
PRACTICE
In pounds per ton of cupola charge
From From
In cupola cupola converter
charge coke air Total
C . 53.6 8.3 61£
Si 22.0
Mn 5.4
P 3.54
S 1.10 0.7
O ... .. 0.60* * 0.60
Fe 1914.36 1914.36
22.0
5.4
.3.54
1.80
In electric To electric
In final In cupola In con- In con- furnace furnace
product slag verter slag verter gas slag atmosphere
C 51.90 ... ..Q> 10.0 0.00*
Si 14.17 5.0 2.83 '. . . 0.00*
Mn 2.46 2.4 0.50 . . . 0.04
P 3.54 ... ... ... 0.00*
S 0.08 ... ... ... 1.00
O ...* ...* ...* ...* 0.60
Fe 1904.84 4.8 4.60 ... 0.12
*Includes only those amounts at some stage alloyed with the
molten metal.
pounds of sulphur, the MnO and FeO being only about 0.3
pounds per ton. • Deducting these two, the slag has 24.7
pounds of material per ton of metal derived from
the slag-forming additions. All of these figures men-
tioned are to be considered as suggestive only. A
balance sheet of the elements concerned in the triplex process is
shown in Table X. It must be understood, however, that the
process has not been quantitatively investigated to the point
where all the reactions are clearly worked out. The figures in
the balance sheet for oxygen are merely estimates. The sulphur
data are not based on a complete series of tests, but are in
accord with current practice. The table neglects oxygen in ori-
ginal metal and final product. Ferromanganese and ferrosilicon
are not supposed to be added. If charged into the electric,
these alloy quantitatively with the charge.
Heat Balance of Triplex Process
A heat balance for the triplex process is extremely inter-
esting as giving an insight into the character of heat losses re-
172
American Malleable Cast Iron
Table XI
GENERAL HEAT BALANCE OF TRIPLEX PROCESS
Cupola
B.t.u. B.t.u.
Heat value fuel 3,718,000
Total heat, metal 1,692,000
Sensible heat, slag 63,800
Sensible heat, flue gas 180,000
Heat value of Fe, CO in flue gas 744,000
Radiation and unaccounted for 1,038,200
Total output 3,718,000
Converter
Total heat of metal charged 282,000
Heat of combustion of C, Si, Mn 93,400
Total input 375,400
Total heat, metal 292,800
Sensible heat, slag , 10,900
Sensible heat, gas and undetermined 71,700
Total output 375,400
Electric Furnace
Total heat metal charged 1,690,800
Heat equivalent of electric input 564,200
Total input 2,255,000
Total heat, metal 1,865,000
Sensible heat, slag 23,000
Radiation and undetermined 367,000
Total output 2,255,000
maining. Unfortunately the results of complete tests of the
process including all the factors involved are not available. Also
the heat of formation of some of the compounds entering into
the reaction, more particularly in the electric furnace are not
known. In the absence of this information the following bal-
ance has been built up on estimates from other sources of the
composition of gas leaving the cupola and converter, and of
the temperature of the cupola gas, and of the metal at various
stages. Also the heat of formation of the slag has not been
considered a source of energy nor has allowance been made
for the latent heat of fusion of slags and refractories.
The presence of oxygen in the metal, at various stages has
not been followed quantitatively so. that no account of the
thermal effect of the formation and reduction of FeO can be
taken. The latter items are included among the undetermined
Electric Furnace Melting 173
Table XII
HEAT BALANCE OF UNITS IN TRIPLEX PROCESS
B.t.u. B.t.u.
Heat value of coke 3,718,000
Heat value of current 564,200
Heat combination of Fe Si, Mn and C 93,400
Total heat input 4,375,600
Incomplete combustion in cupola. . . . .x 744,000
Sensible heat, slag : 63,800
Sensible heat, flue gas 180,000
Radiation and undetermined 1,038,200
Total cupola loss 2,026,000
Sensible heat, converter slag. 10,900
Sensible heat, gas and undetermined 71,700
Total converter loss 82,600
Ladle loss by radiation (preheated ladle) 12,000
Sensible heat, slag 23,000
Radiation and undetermined 367,000
402,000
Total heat, metal 1,865,000
Total output 4,375,600
losses at the various stages of the process. However, the
balance in Table XI, based on one ton of metal charged into
the cupola and on temperatures above atmospheric may be
regarded as indicative of the major items.
The cupola utilizes 45.5 per cent of the heat of the fuel.
The converter delivers 77.7 per cent of the total heat sup-,
plied, using 11.5 per cent of the heat of combus-
tion of the 'elements burned in further heating the
metal. The ladle loss in transferring the metal, not
shown above, amounts to less than 1 per cent. The electric
furnace delivers in the metal 82.7 per cent of all the heat
furnished it, using 30.9 per cent of the thermal equivalent of
the electric input in heating the metal.
Heat Balance in Per -Cent
A summary of the heat balance based on the process as a
whole appears in Table XII. The tabulation may be condensed
174 American Malleable Cast Iron
somewhat further and expressed in percentages of the total
heat supplied by fuel and power as follows :
— Per cent —
Heat of combustion fuel 86.5
Heat equivalent of power 13.5
Heat of combustion of elements in converter 2.2
Heat loss in cupola 47.3
Heat loss in converter 1.9
Heat loss in ladle 0.3
Heat loss in electric furnace 9.1
Total heat metal 43.6
Totals 102.2 102.2
The figures show the relatively very great thermal effi-
ciency of the process as compared with air furnace or open-
hearth melting. A heat made from cold stock in the electric
furnace would show a still hig'her thermal efficiency, approxi-
mating that of the electric furnace alone. This would not, how-
ever, correspond to a greater economic efficiency in view of the
greater cost of a 'heat unit as electric energy than as coke.
From the viewpoint of fuel consumption a vast consideration
of the electric, furnace is not complete without pointing out that a
consumption of 21/2 pounds of coal per kilowatt-hour is an ex-
tremely economical figure, attainable only in unusually large
turbine-driven plants.
There would be superimposed on this further transformer
and line' losses so that the electric furnace may get from 4
per cent to 8 per cent of the energy of the boiler fuel as
electric energy.
This consideration, coupled with the high overhead for the
powder plant, accounts for the great cost of heat energy derived
from electric power as compared with that of an equal amount
of heat energy potentially present in the fuel.
IX
CUPOLA AND OPEN-HEARTH MELTING
IX ADDITION to air and electric furnace melting, which
was discussed in Chapters VII and VIII, there are two com-
mercial methods of melting malleable. That which employs
the cupola can he dismissed with a few words, since its use for
producing specification metal has been prohibited by the specifica-
tions of the American Society for Testing Materials since their
first revision.
The objections to cupola metal are based on lack of uni-
formity of product and lack of control. Because of construc-
tion of the cupola and its method of operation, no large amount
of liquid iron is accumulated at one time; therefore there is no
assurance that successive taps will be even nearly the same in
composition unless the charge consists of only one material,
which manifestly is impracticable.
These variations are of no consequence in the general run
of gray iron castings, but in malleable practice with its much
reduced practicable range of composition they are prohibitive,
especially for large work.'- Furthermore, since the cupola runs
continuously for several hours there is no means of judging the fit-
ness of the iron for its intended purpose either by analysis or
fracture before it is poured.
Control of Metal Limited
Even when the best possible uniformity is secured the cu-
pola process has limitations of control which render it unsuitable
in the production of a general run of malleable castings. The
molten iron runs down through a mass of' incandescent coke,
meeting in the spaces between the coke a stream of gas,
originally air, but converted by the fuel into a mixture of car-
bon dioxide, carbon monoxide and nitrogen.
Under any given operating condition, especially as to tem-
perature, a definite equilibrium exists which determines the com-
position of the products of combustion in contact with mean-
176
American Malleable Cast
bo
Cupola and Open Hearth Melting 177
descent carbon at that temperature. The descending liquid iron
thus passes into a zone in which temperature and gas composi-
tion are adapted to equilibrium with molten iron of only one
specific carbon content and capable of adding or removing car-
bon easily if the metal comes down lower or higher than this
value in equilibrium with the gas phase. Therefore a cupola
produces metal of a carbon content almost independent of that
of the charge and dependent solely on the combustion conditions.
The possible range of working conditions is such as to
produce metal containing from about 2.70 to 3.25 per cent carbon
— a value too high for the production of a high class product
except in small work. The sulphur content of cupola metal also
is invariably high in view of the intimate contact of molten
metal and fuel.
Some cupola metal made for extremely small work thus is
converted into white heart malleable, possibly without the full
understanding of the operator, and the work is annealed by de-
carbonization of the thin sections and not by graphitization.
The surviving successful application of the cupola process
to black heart malleable is in the manufacture of pipe fittings
where the product usually does not have the greatest possible
strength.
The metallurgy of cupola melting has been considered in Chap-
ter VII in connection with the triplex process. However, a
higher fuel ratio is common in ordinary cupola melting than in
the triplex process because the iron must leave the cupola at a
higher temperature in order to run into molds than if it is to be,
handled only by a crane ladle.
A ratio of metal to fuel of between 4 to 1 and 6 to 1 may
represent operating practice, and this represents the one great
advantage of the cupola — cheapness both of construction and
operation, the utilization of heat being about two or two 'and
one-half times as efficient as in the air furnace.
Open-hearth melting, especially when large tonnages and
continuous operation are involved, should be a desirable method
of operation. That its practice is confined to relatively few
178
American Malleable Cast Iron
o
O
'o
o
°c7)
U)
'5;
v-
U
oo
fcio
Cupola and Open Hearth Melting 179
plants may be due to the conservatism of the industry and to
the tonnage limitation.
In general, the open-hearth furnaces used in the malleable"
industry are similar in construction to those used in steel making
and in size represent the lower limits of capacity used* in that
industry. Some experimental heats have been made in basic
furnaces but acid-lined furnaces apparently are used for com-
mercial operation.
The melting operation is similar in principle to aar furnace
melting, except in the application of the heat.
Furnaces ranging in capacity from 5 to 20 tons have been
used, the larger units being preferred when practicable. The
furnace roofs are of silica brick and the bottoms of silica sand.
The regenerative system upon which the operation depends is
so well known as hardly to require description. The products of
combustion leaving the hearth pass through checkers of fire
brick and impart their heat to these brick. When the brick is
thoroughly heated the direction of gas passage is reversed, the
air being drawn into the furnace through the previously heated
checkers. The products of combustion pass out through check-
ers at the opposite end of the furnace. When producer gas
is used it also is preheated. The incoming air gradually cools
the hot set of checker work while the products of combustion
heat the checker at the outlet end when the latter grow hot the
direction of passage is again reversed, this operation being
continued.
Using Heat of Flue Gases
The period of reversal depends upon the heat capacity of
the checker work and in ordinary design a reversal every 15 to
30 minutes may be contemplated. The object is to utilize the
sensible heat of the flue gases. The gases leaving the iron can-
not impart heat thereto unless their temperature is above that of
the metal. However, their heat can be imparted to the furnace
content by using it to preheat the air and sometimes the fuel
used before the combustion begins. In this way a higher furnace
temperature and lower heat loss are maintained.
The heat loss depends upon the temperature of the out-
ISO
American Malleable Cast Iron
f^&TSfa^W^ffifflfliXfff'.
Cupola and Open Hearth Melting
181
flfrf
4) C <*« O M
^ !3
cj jn<
rt •=
G H
jc -^rt £ o ^ 0-5
S- ^Ilil1
s SS'sIl s
- S
-a Z X
182 American Malleable Cast Iron
going gases and this in turn upon the volume of the regenerator
chambers and the period of reversals. In theory the outgoing
temperature might be reduced to that of the incoming air and
gas but this is practically impossible.
Campbell states that open-hearth steel furnaces should be
capable of operation without the stack gases attaining a red heat.
However, this result is not often attained. Assuming this red
heat to be 900 degrees and the gas composition to be the same
as in air furnace melting the sensible heat of the out-going gases
is only 9/25 of that of the air furnace, counting from 0 degree
Fahr. as a basis (which is not strictly correct). Therefore the
heat value saved in the regenerators is 17/25 of that lost in
the stack in air furnace practice. Using the heat loss in sensible
heat of gases, leaving the air furnace as 7800 B.t.u. per pound
of coal, and counting again from 0 degrees Fahr., the heat saved
per pound of coal would be 5304 B.t.u. or over one-third the
heat value of the fuel.
Quoting Campbell in Manufacture and Properties of Struc-
tural Steel> for a given sized chamber the escaping gases are
a certain number of degrees hotter than the gases that go into it.
If this difference is 300 degrees, then if the entering gas is 400
degrees, the escaping gases will be 700 degrees, and if the en-
tering gases are 700 degrees the outgoing gases will be 1000
degrees. It will be seen that this reasoning implies that no
change of economy results from changes of temperature in pro-
ducer gas passing from the producer to the furnace. If
no heat is lost in the gas while passing from the producer to
the regenerator a loss corresponding to this saving is incurred
in the outlet gases.
Since open-hearth furnaces are much less common in the
malleable industry than air furnaces, correspondingly less is
known of their design and operation. For general information
on open-hearth operation the interested reader is referred to
the literature of the subject regarding steel melting.
By kindness of Messrs. Lanihan and Fulton; the writer has
been given access to a certain amount of data accumulated in
the successful operation of open-hearth furnaces by the Fort
Cupola and Open Hearth Melting 183
Pitt Malleable Iron Co., Pittsburgh. Much of what follows is
based on that practice supplemented where necessary by con-
clusions drawn from other sources.
Malleable melting in the open hearth differs metallurgically
in one essential respect from steel melting. The steel maker
operates to greatly reduce the carbon and silicon content of the
bath by oxidation. In malleable practice this oxidation must
be kept down as much as practicable to insure control and re-
duce melting losses. Therefore the furnace atmosphere is sub-
ject to the same limitations as to composition as in air furnace
practice. In view of the fact that this oxidation is actually kept
down to about the same limits as in air furnace practice it seems
reasonable in the absence of direct figures to assume that the CO,
CO2, O and N in the products iof combustion should be about
the same as is given in Chapter VI. An essential difference,
however, will be the presence of a greater proportion of steam
or water, since these furnaces are operated on natural gas and
oil.
In the chapter on air furnace melting, the flue gas analysis
was given as oxygen, 1.1; carbon dioxide, 12.7; carbon mon-
oxide, 3.6; and nitrogen, 82.6 per cent. Assuming the gas in
the present case to have this composition and assuming that the
formula of the petroleum is Cn H2n + 2 the ratio of C to H
in the fuel will vary from 3 to 1 to 6 to 1, depending on the
molecular weight of the hydrocarbon being burned. We can
calculate the flue gas per pounds of fuel closely.
Assuming a ratio of C to H of 5 3/4 (which probably is a
little high but will compensate for the inaccuracy introduced
by neglecting the carbon burned from the metal) we may con-
clude that one pound of fuel will require nearly 17.1 pounds of air
for combustion, yielding 18.1 pounds of gas made up of the
following amounts of the several constituents:
Pounds
<?• .152
£0, 2.430
CO 435
H2o .'..'.'.':::::::::: 1:322
N 13.76
184 American Malleable Cast Iron
If a gas analysis were ma.de, the water would not be found,
being condensed to a liquid in sampling for analysis. The com-
position by volume apparently would be :
Per cent
O 0.8
CO, 9.7
CO 2.8
N , ..86.7
Total 100.0
In the absence of actual analyses this may be taken as
representing a near approach to the combustion conditions to be
expected using oil fuel. The differences using gas fuel are
probably insignificant as compared with the probable inac-
curacies in some of the assumptions made.
The chemical changes occurring in the bath are identical in
character and similar in magnitude to those occurring in the air
furnace.
The oxidation losses in open-hearth melting have been in-
vestigated, in the light of the changes of composition during the
process as determined at the Fort Pitt foundry. Typical re-
sults are given both in per cent of the original charge and in per
cent of the original amount of the element present :
Loss in Open-Hearth Melting
Total charge Amount of element
100 per cent
16.9
22.9
40.5
0.0
—10.00
1.6
Total 2.51
It will be noted that the oxidizing conditions are similar to
those encountered in air furnace practice and described under
that heading. The gain in sulphur and loss of carbon, silicon
and manganese are less in open-hearth practice than in air fur-
nace practice. However the oxidation of iron is sufficiently
greater to keep the net loss at nearly the same figure as in air
furnaces.
c
100 per cent
... 0 49
Si
Mn
0.29
0 154
P
s
0.00
— 004
Fc .
. 1.58
Cupola and Open Hearth Melting 185
*
These conditions can be further followed by a consideration
of the composition of open-hearth slag. A representative sample
of this material had the following analysis :
Per cent
FeO 37.6
Fe,03 2.7
MnO 3.87
SiO, 51.30
Al,,63 1.95
Undetermined 2.58
100.00
The greater oxidation of iron as compared with manganese
is evident. The decrease in A12O3 also is apparent, since the
refractory lining is largely silica instead of largely alumina as
in fire brick structures. The silicon entering, the slag from the
metal corresponds to 12.1 per cent of the weight of the slag.
Therefore, the slag consists of 56.27 per cent compounds de-
rived from the oxidation of the charge and 43.73 per cent melted
refractories.
Comparing the iron content of the slag with the iron oxi-
dized we find that apparently about 101 pounds of slag, or
5.05 per cent of the weight of the metal are formed per ton
charged and hence by calculation 44 pounds of refractories or
2.2 per cent are melted per ton of metal charged. These figures
again are similar in order of magnitude to those determined by
more exhaustive study on air furnaces.
Heat Balance Based on Assumed Data
The heat balance of an open hearth can be calculated
readily from a knowledge of the reactions occurring. Unfortu-
nately we have not a complete record of tests involving all the
factors to be considered. From the preceding assumptions and
the fact that the average natural gas consumption of the furnace
in question was about 8200 cubic feet per ton when regularly
operated, the balance in Table XIII may be considered as an ap-
proximation, no claim to precision being warranted by the char-
acter of the data.
Expressing results in per cent of the heat value of fuel
186
American Malleable Cast Iron
used and summarizing a little further the data may be expressed
as in the summary in Table XIII.
In comparison with air furnace practice it will be noted
that a general increase in economy is shown, 10.22 per cent
of the heat of the fuel being effective instead of 7.81 per cent.
The waste in sensible heat of flue gas and the loss due to in-
Table XIII
HEAT BALANCE OF OPEN-HEARTH FURNACE
B.t.u. B.t.u.
Heat value of fuel 8,514,000
Heat value of metal oxidized 294,000
Heat formation of silicates (estimated) 36,000
Total heat input , 8,844,000
Latent heat of fusion and sensible heat of metal 879,000
Sensible heat of flue gas t 3.007,000
Loss due to uncomplete combustion of C to CO only.... 545,000
Sensible heat slag 51,000
Latent heat fusion slag estimated 36,000
Radiation conduction and stand by losses 4,326,000
Total heat output 8,844,000
Summary of Pleat Balance of Open-Hearth Furnace
.Per Pei-
cent cent
Heat value of fuel 100.00
Heat reactions in bath 3.86
Totals 103.86
Heat in metal 10.22
Heat in flue gas 35.33
Heat in slag 1.02
Incomplete combustion , 6.41
Radiation and standby losses 50.88
103.86
complete combustion are decreased because, being gaseous or
liquid, the fuel is all consumed and because hydrogen is present.
Since the furnace constantly is kept hot, there is no perceptible
heat loss due to sensible heat of furnace wall. However,
there is a large loss due to the need of keeping some heat on the
furnace during, idle periods.
This loss, increasing with the idle time, makes 24-hour
a day operation highly desirable. With such operation it seems
that possibly 25 per cent of the present fuel could be saved.
Radiation and conduction losses would still exist but stand bv
Cupola and Open Hearth Melting 187
and sensible heat losses would be eliminated. Under such
conditions an economy of about 14 per cent in the use of fuel
might be reached as against about 8 per cent in air furnace
practice in 24 hour operation.
Open-hearth furnace heats range in size from 14 to 20
tons or more, preferably at- least two heats a day being made on
a furnace. Fuel in the plant in question is natural gas or
oil. The gas consumption varies from 8200 to 9100 cubic feet
per ton.
Oil fuel runs from 43 to 62 gallons per ton. In both cases
the results depend on whether or not the furnace operates con-
tinuously or intermittently and on the condition of the furnace.
For heats from 15 to 18 tons in size about 5 to ST/2 hours
are consumed in melting; 20-ton heats take around six hours.
The efficiency of design is largely dependent on the checker
arrangement' with its corresponding effect on the utilization of
waste heat. Unlike an air furnace, the open hearth requires
rather infrequent but very extensive repairs. Furnace bottoms
and banks are of course continuously watched and patched be-
tween heats. One furnace operated two years and two months,
making 1282 heats with no repairs except cleaning the checkers
and changing doors. The same furnace has since made 2051
heats with one cleaning of the checkers, a new roof, front, back
and bridgewalls, an unusual record.
On the other hand, another furnace, running on one heat
a day and frequently cooled ran only 200 heats before extensive
repairs were required, showing the extreme destruction from
unequal expansion in heating and cooling of the brick.
The labor to operate an open hearth consists of either three
or two and one half men per furnace. Charging is not included
in this labor. The 'work of charging into a furnace through
doors is prohibitively heavy and charging machines are almost
a necessity.
No data as to the use of pulverized coal or producer gas
are available for malleable melting, although both of these fuels
are -used in steelmaking with great success.
X
ANNEALING PRACTICE
THUS far in the discussion of malleable foundry practice
the various methods of producing molten white cast iron
have been considered. The next step is converting the
hard iron casting into the malleable casting of commerce.
Unfortunately this process still is most widely known as
annealing instead of the better terms, heat treating, graphi-
tizing, or converting. It is the intention to describe mainly
the practical execution of the process in this chapter.
The process primarily is only an effect of time and tem-
perature, and not a chemical one in the sense of a change
of composition. Therefore a general consideration of the
subject should begin with the viewpoint of the general meth-
ods of application of temperature to the product, leaving for
later discussion the practical limitations of temperature and
time and the incidental change of chemical composition in-
volved.
The practice of annealing as originally developed con-
templated packing the castings in a chemically active pack-
ing material in cast iron containers and transferring them
into an oven where the desired heat treatment was executed.
This method of operation still is used conveniently, although
it is now thoroughly recognized that the use of packing is
by no means an essential in the process. In addition to its
control over the chemical changes occurring in the product
by oxidation, the packing has the important function of sup-
porting the casting while hot.
Packing Supports Castings
Commercial annealing contemplates the attainment of
maximum temperatures of from 1500 to 1850 degrees Fahr.
and the maintenance of such temperatures for days at a time.
Obviously iron at this temperature will be fairly soft and a
190
American Malleable Cast Iron
casting of any intricacy would be irretrievably ruined by
sagging if not supported. Except in such special cases as
may arise w'here the design of the part is such as to be prac-
tically self supporting, some method therefore must be
adopted for preventing the distortion of the casting either
under its own weight or under the weight of the castings in
the pots above it.
A second function of packing, in its present application
is to hinder rather than to accelerate oxidation. If a casting
r
Fig. 89. — Separator plate designed to eliminate
with annealing pots
use of packing
be exposed directly to the products of combustion of the fuel
at these high temperatures it will come out badly scaled and
possibly ruined for the purpose intended. There are few
better means of protecting the casting from furnace gases
than enclosing it in a fine inert packing.
How Castings Are Packed
The process of packing is carried out in malleable an-
nealing as follows. First a bottom which is practically a
heavy cast iron bench with legs 4 or 6 inches high is set on
the floor. On this is set a pot which is an approximately
rectangular or round frame, usually about 12 inches deep.
Annealing Practice 191
The size and form of pot depends largely on the work
handled and to some extent on the whim .of the annealer.
Unusually large pots fill the space in the furnace more
completely than smaller pots but heat slowly and rather un-
evenly due to the low conductivity of the packing 'material.
Round pots do not distort as much due to the sagging of
the contents as do those with flat sides. However, they heat
more slowly and do not utilize the furnace capacity as ef-
ficiently as the latter. Furthermore in most places the pots
are handled by hand so that too great weight must be
avoided. The pots must be about 1 inch thick to have a
commercial life and hence extremely large pots can not be
made as deep as smaller ones. Also when large they are not
easily stacked very high and therefore a waste of oven ca-
pacity may result.
The writer has seen rectangular pots as large as 30 x 36-
inches inside used where the character of the castings made
this size unavoidable. Round pots frequently are 24 to 30
inches inside diameter. Rectangular pots running from
about 14 x 18 inches to 16 x 24 inches inside are common.
AY here the work is of such character as to stack solidly
together, a pot of the smaller size or only a little larger will
give a stack as heavy as can be readily moved or uniformly
heated. In thin, sprawly work larger sizes may be unavoid-
able. The pots are made of white cast iron either like that
in the castings or of a cheap cupola iron high in sulphur
and low in manganese which will not graphitize.
Method of Packing Pots
After the pot has been placed upon the stool, the first
step is to put in a layer of packing from one to three inches
thick. On this are shoveled or packed sufficient castings to
nearly fill the pot. Small castings, for example link belt
parts, are shoveled in. Large castings usually are set in reg-
ularly to conserve space, care being -taken to fill the spaces
remaining inside or between large castings with smaller ones
as far as practicable. As much packing is shoveled in from
time to time as can be made to run down into the spaces
192 American Malleable Cast Iron
still remaining. Extremely complicated work must be placet!
carefully so that it may be perfectly supported at all
points. This sometimes necessitates the use of special plates
and other supporting devices designed particularly for the
part in question.
Factors Affecting Heights of Stack
When the first pot is nearly full a second one is set on
it and the packing continued as before. The building up
is continued until the stack of pots is from 3^ to 6 or 7 feet
high above the top of the stool depending on the height of
furnace and the ideas of the annealer. Care is taken that
the top pot be finished Avith several inches of packing into
which no castings project and usually the top is covered with
a plate or with fire clay, or both. A reasonable height must
be attained to secure economy, of space. On the other hand,
stacks of excessive height are not only difficult to heat uni-
formly but are subject to careless packing since the packet-
must stand on a stool and pack in an inconvenient position.
High stacks also are easily upset in handling. The writer
favors a stack four pots high where the individual pots are
12 to 15 inches deep, thus making a maximum height of
stack of 60 inches above the top of the stool.
In any event, after the packing is complete and before
the cover is put on, the stack of pots is rapped with a heavy
hammer or otherwise jarred to settle the packing solidly. It
is easy to leave 20 to 30 per cent of voids due to careless
packing. This not only reduces the capacity but permits the
ingress of furnace gases and also lets the charge settle, usu-
ally unevenly. The result is badly warped castings, scaly iron
.and possibly some completely burned castings in the top
pots where the packing has sunk away.
The life of an annealing pot depends somewhat upon
its composition, but more largely upon the furnace atmo-
sphere to which it is exposed. Pots which crack from in-
ternal stresses do so in the first or at least in an early ex-
posure in the furnace. Thereafter failure is by oxidation of
the surface, which depends on the thickness of the pot. tern-
Annealing Practice 193
perature of the furnace, time the pot is in the furnace, and
combustion conditions. A life of from only 10 to 12 passes
is frequent, but the average probably lies between 15 and
25 passes. Under favorable conditions a pot m'ay survive
from 30 to 50 trips through the furnace.
Pots are made either of the same metal used for castings
or of white cast iron from a cupola operated for that pur-
pose. In the latter case the mix is usually such as to pro-
duce a sulphur-manganese ratio which nearly prevents
graphitization. This is an advantage as reducing the growth
of pots in use.
The heating of an annealing furnace is invariably from
the top down. This causes the top of a stack of pots to heat
first. It is customary to counteract this tendency by pack-
ing the light work in the bottom and the heavy work in the
top so that the greatest thermal capacity is nearest the source
of heat.
The packing of castings is a fairly expensive operation
involving considerable skill which if slighted is productive of
bad work and loss of castings.
Various schemes have been suggested for working in
empty pots to avoid packing. These take1 the general form
of a set of plates between the several pots so that the ma-
trial in the bottom pot does not have to carry the entire
weight of metal above. Such methods were employed suc-
cessfully for many years but require careful exclusion of air.
J. H, Fryer recently introduced a design of separator
plate as shown in Fig. 89 which by its flanged construction
permits the making of a good clay seal. While particularly
important in pots where packing is not used, 'this sealing
also is required in the usual practice.
The pots prepared by any of these methods are intro-
duced into annealing ovens, which are merely fire brick
chambers capable of being heated to the desired tempera-
ture. Some idea of the dimensions of these ovens has already
been given in ithe general description of a malleable foundry.
Ovens may hold from 25 to 100 stacks of pots, neither ex-
treme being common. Nearly all ovens are deeper than they
194
American Malleable Cast Iron
Annealing Practice 195
are wide, and the flame usually travels from back to front.
A number of exceptions exist more particularly in pulverized
fuel or oil-fired furnaces. The older ovens, and particularly
the smaller units frequently were builit in sets of two to
eight ovens. In this way the loss of heat through the side
walls and the waste of floor space was minimized. Heavy
walls about 32 inches thick sometimes were employed to
serve as heat insulators. More recently, with the advent
of various types of heat insulating brick the actual wall
thickness has been reduced.
Fig. 91. — Charging trucks facilitate the handling of pots to and
from the annealing furnaces
Many designers laid great stress on heating the anneal-
ing furnace floors by elaborate systems of checkers or flues
through which the waste heat of the furnace passed. Other
designers preferred to use only the necessary flues to carry
off the flame from the furnace.
Large Ovens More Economical
Large ovens are economical of fuel as they present rela-
tively little wall surface per unit of metal content. However,
they usually are harder to heat uniformly, and therefore re-
quire greater skill in design. A number of engineers feel
196 American Malleable Cast Iron
that wide arches are expensive to maintain. The relative
importance of these factors in the mind of the designer usu-
ally influences the construction chosen in any given case.
It is not likely that any wide difference in performance is
to be expected from the possible variations in furnace di-
mensions. Economy usually dictates the use of a local coal
for annealing fuel. The firebox design generally is extremely
simple, consisting merely of an area fenced off in a back
corner of the furnace by two walls a little higher than the
stack of pots used. The grates, within this area, are fired
through the rear Avail. Occasionally, instead of providing an
inside firebox, the firebox is built outside the furnace against
the rear wall and communicates with the furnace chamber
through a fire 'hole, which is like a window through a wall.
Various stoking devices, including automatic coal feeds',
shaking grates, etc., have been used, but none of these seems
to have commended itself sufficiently to gain a firm foothold
in the industry. Possibly the explanation is that the firing
operation in ' annealing does not require as careful control
as in melting.
It is desirable both in the interest of economy and in
order to avoid rapid burning of the annealing pots that an
excess of air be prevented from entering the furnace. How-
ever with well packed pots the process will be operative,
though uneconomical, if this precaution is neglected. Thus
there has been little incentive to control annealing firing as
closely as the melting operation where the making of good
iron is impossible with poorly controlled fires.
Many producers of whom B. J. Walker is considered the
pioneer, have experimented with pulverized fuel in anneal-
ing and a good measure of success has attended their efforts.
The arrangements employed are of the same character as in
air furnace firing, although the problem is slightly les:;>
difficult.
The standard design of annealing oven contemplates the
introduction of the pots at the front of the furnace. The
opening is closed by doors, usually made in sections which
are equivalent to a front wall.
Annealing Practice
197
At an early date attempts were made to render the pro-
cess approximately continuous. Seth Boyden built a "shov-
ing" furnace of which G. H. Kings land of the Wilmington
Malleable Iron Works writes as follows :
"The furnace was torn down under my direction. The
pots were 12 inches high and 10 inches wide each way, with
Fig. 92. — The interior of the powdered coal mill of a modern
malleable plant. The horizontal cylinder at the left is the dryer
a bottom just like a box without a cover. These were placed
on rollers, pots being pushed in at one end and shoved out
at the other. I believe the furnace held 30 of these boxes,
five wide and six deep. One row of five was shoved out each
working day and a row of five pushed in. The furnace was
about 2 feet high at the crown of the arch, with flues under
198
American Malleable Cast Iron
3 O
M- ,0
<u ^
•5 v
C rt
Annealing Practice 199
the floor and in the side walls running to a stack about 25
feet away through a vitrified pipe. The Barlow people later
charged the entire furnace at one time instead of at the rate
of five pots daily."
Limitations of Removable Roof
In order to permit the loading of annealing furnaces by
cranes the design is sometimes modified by forming the roof
of removable arch-shaped sections, like the bungs in an air
furnace. In this case no doors are required and the furnace
is usually submerged in the ground almost to the spring line
of the arch.
The heat insulation of the side walls in such furnaces
is unusually good but heat losses 'through the roof are large
since the limits of weight prevent the use of a roof of suffi-
cient thickness. Moreover, the construction involves a great
number of joints in the roof which are difficult to seal.
The wid'th of furnaces of this type is restricted
because of the prohibitive weight of long roof sections.
Therefore the design is along the lines of a relatively long
and narrow unit, as compared with the nearly square floor
plan of the ordinary furnace.
It is important that the furnace structure be protected
from the effect of moisture if water is present in the soil
in which the furnace is set. A story regarding a battery of
furnaces built near a river subject to spring floods is well
known in the mallealble industry. To the astonishment of
their builder, these furnaces became miniature lakes when
the back water from the first flood rose to a level higher
than the furnace floor.
The practice thus far described involves the use of pots
either with or without packing. Since pots' and packing are
expensive, efforts have been made to dispense with con-
tainers, muffle annealing being the outgrowth of these at-
tempts.
Muffle-type Furnaces
Muffle furnaces — not "muffled" as frequently pro-
nounced and even spelled — are constructed so that the flame
from the fire box or burner does not come in contact with
200
American Malleable Cast Iron
Fig. 94. — Diagram showing the distribution of heat in a contin-
uous-type annealing furnace
Fig. 95. — Interior of continuous-type annealing furnace looking
toward the entrance end
Annealing Practice 201
the castings to be annealed. In their general design muffle
furnaces represent the usual oven with the addition of a
separate interior chamber or chambers. As usual, the flame
enters the oven but instead of filling the entire space it
merely passes through the spaces between the interior cham-
bers or muffles and the walls, floor and roof. The
muffles are built as thin as possible usually 4^ inches thick,
Fig. 96. — Single section of combustion chamber of continuous-type
annealing furnace
in the interest of low thermal capacity and good heat con-
ductivity. The castings to be annealed, which must be of a
character not to distort easily when hot, are stacked in the
muffles, the front of the muffles bricked up and the oven
proper closed with the usual doors. The heat treatment is
identical with that in the ordinary annealing furnace.
At the conclusion of the treatment the castings are re-
moved by hand ; consequently the furnace cannot be "pulled"
until the contents are well cooled. Therefore the output
of the furnace is decreased by the time taken for cooling to
202
American Malleable Cast Iron
Ecr
£ o
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*oj o
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A
rt u
X! C
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bo.
tu
Annealing Practice 203
this temperature as compared with the time to cool suffi-
ciently to pull pots mechanically. The thermal efficiency
also is decreased since the heat must be transmitted to the
castings through the intervening brick wall. On the other
hand, the cost of pots and packing and the cost for heating
pots and packing are saved.
In view of the fact that the efficiency of annealing fur-
naces is largely determined by the 'heat insulation of the
walls and roofs and is consequently widely different in dif-
ferent plants, it is difficult to speak with assurance as to the
relative economy of muffle and pot furnaces. The general
impression toward muffle-type furnaces seems to be favor-
able. Reliable tests can only be made by weighing coal
and iron on a series of runs in each of two furnaces of
identical exterior construction, one loaded with pots the
other having a muffle built within it.
The coal consumption for annealing varies greatly in
commercial practice. .Plants of good reputation burn around
1000 pounds of coal per ton of iron annealed, although with
well-built furnaces and particularly with pulverized fuel
much better records should be obtained. A quantitative
idea of the heat values involved may be obtained from Table
XIV, which is based on the theoretical heat requirements of
the various reactions involved.
These figures are for the minimum possible use of fuel,
making no allowance for incomplete or other imperfect com-
bustion conditions, radiation from furnace walls, heat car-
ried out by convection currents of cold air when the fur-
nace is supposed to be cooling slowly, conduction of heat
into the ground, etc. All of these losses exist and are of
large magnitude. The aggregate of all losses is what makes
up the difference between the theoretical coal consumption
of 274 pounds per ton and the actual commercial figures
of 600 pounds to 1000 pounds per ton.
Another way of approximating the radiation and similar
losses is by considering the fact that an annealing furnace
of ordinary construction will cool from 1500 to 1300 degrees
204
American Malleable Cast Iron
Table XIV
HEAT REQUIREMENTS OF ANNEALING FURNACES
Available Heat of Fuel
B.t.u. B.t.u.
Heat value per pound coal 12,500
Flue gas from 1 pound coal theoretical combustion conditions:
3.8 pound COa
0.4 pound H2O
13.2 pound N
17.4 Total
Total sensible and latent heat in flue gas from 1
pound coal at 1100 degrees above atmosphere 5,000
Total heat in cinders from 1 pound coal, sensible heat
and heat of combustion of unburned fuel 160
Maximum available heat per pound of coal (12,500-
5,160) 7,340
Total 12,500 12,500
Thermal Capacity Oven and Charge
Total heat 1 ton castings at 1650 degrees above atmosphere 389,400
Total heat in \l/2 tons pots and 1125 pounds packing at
above temperature 955,350
Total heat wall, floor and roof 3900 pounds, brick per ton
charge raised average of 1200 degrees. Fahr 624,000
Total sensible heat furnace contents per 1 ton casting
(of this 19.8 per cent only is in castings) 1,968,750
Heat from Chemical Reactions
Heat from decarburi.zation 1 ton castings l/2 per cent or
10 pounds carbon burned to CO2 142,200
Heat absorbed by reaction (10, pounds carbon) 6 FeO + 5C =
CQ2 + 4 CO + 6 Fe , 136,360
Heat evolved by decarburizing per ton of castings 5,840*
Heat absorbed by graphitization of 2 per cent carbon per ton
castings. Reaction Fe3C = 3 Fe -j- C 53,640
Heat required to maintain chemical reaction per 1 ton of
castings 47,800
Resume Based on 1 Ton Product
Sensible heat castings 389,400
Heat of reaction 47,800
Useful heat 437,200
Sensible heat furnaces, pots and packing 1,579,350
Total heat 2,016,550
Total heat required in oven at 7340 B.t.u. per pound of coal = 274
pounds coal per ton.
*Exact decarburizing reactions unknown. Assumption made on
basis of known composition of resulting gases.
Annealing Practice 205
Fahr. in from 25 to 50 hours, depending mainly on the size
of furnace and the heat insulating ability of the walls.
The area of walls and roof of an annealing furnace totals
about 35 to 40 square feet per ton of capacity. With the
foregoing figures it can be calculated that about 239,000
B.t.u. per ton of castings must be radiated to cool the furnace
200 degrees. This at the rate in round numbers of 6800
B.t.u. per square foot of oven surface (average furnace tem-
perature 1400 degrees Fahr.) which in turn is at a rate of
between 136 and 272 B.t.u. per square foot per hour.
Table XV
DISPOSITION OF HEAT IN ANNEALING FURNACE
Total heat in 900 pounds coal at 12,500 B.t.u. = 11,250,000 B.t.u. per ton
of castings ~ 100 per cent
B.t.u. Per cent
Heat for chemical reaction in 1 ton of castings . . 47,800 0.52
Sensible heat in 1 ton of castings 389,400 3.46
Sensible heat in pots and packing 955,350 8.48
Sensible heat in furnace structure 624,000 5.54 .
Radiation and conduction, furnace structure .... 750,000 6.66
Sensible and latent heat flue gas (theoretical
combustion) 4,500.000 40.00
Heat loss in cinders and air leakage . . . . = 144,000 1.24
Sensible heat, excess air. error and unaccounted
for (excess temperature, etc.) 3,839.450 34.10
Total ' 11,250,000 100.00
Assuming that 1400 degrees is the approximate mean
inside temperature while the furnaces is under fire, the oven
loses heat by radiation and conduction at the rate of be-
tween 5000 and. 10,000 B.t.u. per hour per ton of contents.
Therefore with poor insulation the heat lost per ton
from these sources will be 10,000 B.t.u. per hour that the
furnace is fired, or 80,000 to 1,200,000 B.t.u. which figure may
be halved by good insulation. This is equivalent to from
55 to 165 pounds of coal per ton, an amount insufficient to
account for all the coal frequently used. The remaining
losses presumably are due to intake of cold air, excess air
for complete combustion, excess temperature of outgoing
air, etc., and other similar losses to be determined only as
the result of experimental investigation.
206 American Malleable Cast Iron
An idea of the heat balance may be obtained from Table
XV, which is based on an assumed coal consumption of 900
pounds per ton of castings with only fair insulating and
combustion conditions. The last item of the table is equiva-
lent to a little less than 50 per cent excess air.
It will be noted from the table that only about J^ per
cent of the heat of the fuel is expended usefully in the chemi-
cal- changes, which are the purpose of the annealing opera-
tion, 0.01 per cent in producing the accompanying change in
volume and only 3j/2 per cent additional in heating the cast-
ings themselves to the requisite temperature for the reaction
to take place.
Obviously the thermal efficiency of the process is ex-
tremely low, due to the great heat capacity of the oven and
its contents and to the great amount of heat which is car-
ried out by the avoidably large mass of gas at fairly high
temperature. If the alternate heating and cooling of the
furnace structure could be avoided, if the furnace gases could
leave the chamber at temperatures lower than that of the
pots at their maximum and if the sensible heat of the pots
after anneal could be transmitted to other pots just heating,
greater economy could be effected. Attempts to do this have
been shaped in various continuous annealing processes using
tunnel-shaped kilns.
The Dressier-type kiln originally designed for use in an-
nealing sheets and also for use in the ceramic industries
is just entering the field. Only 3 of these have so far been
constructed .and, owing to business conditions only one has
operated for a considerable continuous period of time. The
principle of operation is that the heat treatment is accom-
plished by passing the furnace charge, on cars, slowly through
a long tunnel of relatively small cross section. The tunnels
are about 300 feet long and the cars of castings or pots pass
through in- the time required for one annealing cycle.
Any given part of the tunnel remains constantly at one
temperature. The temperature varies along the length of
the furnace to correspond to the changes in temperature
Annealing Practice 207
which may be desired as the castings pass through the op-
eration. Special forms of heating units have been developed
using oil, gas or pulverized coal which are conducive to
efficient circulation of the hot furnace atmosphere without
necessarily contaminating it by admitting the flame itself.
Heaters Installed for High Temperatures
The heaters are installed where the highest temperatures
are required and the products of combustion, leaving them
at a temperature low enough to make the further transfer
of heat to pots at their highest temperature impossible, pass
on and are further used to begin the heating of pots just en-
tering the furnace and to preheat the air for combustion.
Further details of construction involve the use pi air
locks to permit the work to enter and leave the kiln
without admitting air, the mechanical means of moving cars
through the furnace, etc. In the absence of any operating
data on such kilns in malleable practice the effect on fuel
saving can only be surmised. The principal sources of fuel
economy which may be expected in a continuously operated
kiln are the following:
First, the fact that the furnace structure is neither
heated nor cooled results in a saving on the basis of our
previous figures of 624,000 B.t.u. per net ton. Second, the
fact that since the flue gases and also the product being
annealed impart much of their heat to the incoming material,
the loss in sensible heat of flue gases and of pot packing and
so on should be considerably reduced. Third, the furnaces now
in use being oil or gas fired, should permit of more economical
use of fuel than can be had in furnaces fired with coal.
Fourth, it should be possible to reduce air leakage in a kiln
of this type far below what could be done in the case of a
furnace through which the products of combustion are forced
to pass.
Offsetting these economies the long slender furnace pre-
sents a somewhat greater surface per ton of content so that
radiation losses would increase considering an equal degree
of heat insulation in the tunnel furnace and in an oven. In
208 American Malleable Cast Iron
practice this loss is largely counteracted by efficient heat in-
sulation on the walls and roof of the structure.
On the basis of entirely arbitrary assumptions as to exit
temperatures, flue gas composition, etc., the writer has calcu-
lated that it might be possible to anneal a ton of castings in a
kiln of this type with the expenditure of about 2,100,000 B.t.u.
It must be clearly understood that these figures are speculative
only, and in no sense founded upon experimental results.
At the time this is written only one furnace of this type
has been operated sufficiently long to be considered beyond the
experimental stage. The best information at the author's dis-
posal is that in the furnace in question about four million
B.t.u. 's were required for annealing a ton of product.
As in the case of electric melting furnace equipment it must
be remembered that the entire plant layout must be adapted to
the use of the continuous kiln and suitable provisions be made
for the transportation of trucks and the mechanical handling
of material in connection therewith. Also as in the case of the
electric furnace a very considerable first cost is involved as com-
pared with the simpler units. Again as in the case of the elec-
tric melting operation one of the hoped for advantages from
the use of the more elaborate method is a better control of the
product, in this case arising from the greater uniformity of
the heat cycle to be expected in a tunnel kiln operation as com-
pared with the operation of a furnace which has temperatures
varying widely, not only from time to time, but also from place
to place in the furnace. Touceda has designed annealing fur-
naces of the usual form in which attempts are made to carry
the elimination of heat Josses as far as practicable. He has
also suggested a furnace heated by fuel in which the tempera-
ture Once reached would be maintained electrically by nearly au-
tomatic means. Such a furnace if practicable would be very
interesting. At least one concern is attempting to introduce
an electrically heated furnace. This, however, is decidedly in
the experimental stage. So much for the practical execution
of the annealing operation.
Controlling Annealing Temperatures
In any annealing operation pyrometric control will be required.
Thermocouples are somewhat frequently introduced in nichrome or
Annealing Practice 209
ceramic tubes through the furnace wall or roof. The practice
has the advantage of a quick response to changes of firing con-
ditions and is the only one possible in the continuous furnace.
However, it does not give any data as to the temperature of
the metal itself and accordingly it is advantageous to have one
or more couples actually within the pot. The interior of a
good sized pot 'may lag 15 or 20 hours behind the furnace
temperature. The lag is less the more solidly the pot is filled
with iron and more the greater the per cent of packing. These
figures apply when the furnace temperature is known and uni-
form. If the space into which the couple penetrates is filled
with flame then the flame temperatures, varying as they may
several hundred degrees in a quarter of an hour or less, are
absolutely meaningless. Theoretically it may be possible to
mount a couple in a protection having the same temperature
lag as an average pot.
Many satisfactory pyrometric equipments are on the mar-
ket. Provision for automatic recording is virtually essential.
The writer's preference is for potentiometer recorders. He fur-
ther prefers a tape record to a disk record. In large plants
multiple point recorders are convenient. Noble element couples
seem commercially undesirable at the temperatures involved, both
on account of expense and the low electromotive force. In
oxidizing atmospheres, couples of the chromel type have a good
life but neither these nor platinum will survive reducing condi-
tions. Iron-constantan is perhaps most satisfactory under those
conditions.
For data on the construction, operation, and characteristics
of various types of pyrometric equipment reference is suggested
to Technologic Paper 170 of the United States bureau of stand-
ards, "Pyrometric Practice" by Foote, Fairchild & Harrison.
A very brief exposition of principles must here suffice.
Any thermocouple sets up at its terminals a difference of
potential, or mill i voltage, depending upon the difference in tem-
perature existing at the junction of the two dissimilar wires and
the temperature where these wires are joined to the copper of
the instrument or distributing system. To know the tempera-
ture of the hot end we must know that of the cold end. We
210 American Malleable Cast Iron
may read this with a thermometer or else keep it constant either
by burying the cold end in the ground, circulating around it
water at constant temperature or introducing it into a ther-
mostat kept at a controlled temperature above that of the room
by electric heaters automatically switched on and off to main-
tain a fixed temperature. Boiling water, kept supplied to re-
place evaporation may be used.
There are. also electric devices for compensating for "cold
end temperature."
The thermocouple electromotive force is measured by a
millivoltmeter which however actually measures the current
set up by the electromotive force through the assured constant re-
sistance of the instrument and external circuit. Since current
is the quotient of electromotive force divided by resistance the
readings may be affected just as 'much by changes of resistance
as by changes of electromotive force. Such changes are coun-
teracted by making the resistance of the instrument high as
related to that of the thermocouple and leads. Accidental changes
of resistance external to the apparatus may be small or even
negligible fractions of the total. Such high resistance instru-
ments are difficult to make rugged. Another course is to use
low resistance instruments and take pains to keep the total re-
sistance constant. This is possible but troublesome. All indicat-
ing instruments depend for their accuracy on ,come torsion mem-
ber, springs or suspension exactly retaining its elastic .prop-
erties unaltered.
The only available means for directly measuring an electro-
motive force is to oppose it to another variable and constantly
known potential using a galvanometer only to indicate, by the
absence of any current when the t\vo are exactly equal. The
apparatus for doing this is called' a potentiometer. Its use is
usually slightly less convenient than that of a millivoltmeter
but avoids all errors except those due to variations in tempera-
ture of the cold ends. This can also be electrically compen-
sated. The potentiometer also can be built with a more open
scale than a millivoltmeter nor need the scale begin at zero, so
that the scale length available can be used for only that range
Annealing Practice 211
of temperature of interest in the process, say 1000 degrees to
2000 degrees "Fahr. Either type of apparatus can be made au-
tographic. Although this is slightly more complex for the poten-
tiometer type this system has the advantage that the motion of
the pointer is rectilinear and not a circular arc as in the gal-
vanometer type instruments.
XI
PRINCIPLES OF ANNEALING
A THOUGH the general principles of graphitization and
decarburization as applied to annealing and the commer-
cial methods of applying heat treatment to 'castings have
been considered in preceding chapters, it may be well to correlate
the scientific principles and commercial equipment with a view
to providing a more definite practical understanding of the art
of annealing.
It has been repeatedly stated in the chapters of this book
that annealing consists primarily of the conversion of the
metastable system Fe-Fe3C into the stable system Fe-C. This
involves no change of chemical composition and is not the
effect of any chemical action on the iron by packing, furnace
gas or other substances. The only chemical reaction involved
takes place within the iron carbide or cementite of the iron
and involves only the chemical elements present within the iron,
in unaltered amount before and after the reaction :
Fe3C = 3Fe + C
The reaction involves the absorption of heat (8940 small
calories per gram molecule) and hence the reaction will con-
tinue only if heat be supplied. Recent published articles have
cast grave doubt on the heat of formation of Fe3C. Different ob-
servers do not even agree on whether it is positive or negative.
In Chap. Ill a detailed discussion of the acceleration of
the reaction with increasing temperature was given and it was
pointed out that the reaction is necessarily incomplete at all
temperatures above the lower critical point of the final alloy.
The best and most recent data available to the writer has been
summarized in Fig. 24 in Chapter III and point to a solubility of
free carbon at Alf considerably less than the eutectoid ratio of the
metastable system. Below A^ the solubility apparently becomes
negligibly small but still existant. No evidence of a eutectoid of C
and Fe as a metallographic entity has been found.
Metallurgically the purpose of the annealing treatment is to
•cause the iron to traverse such a temperature cycle as will
214 American Malleable Cast Iron
completely and most expeditiously transform it into ferrite and
temper carbon, having due regard to the resultant grain
structure of the ferrite. The actual heat cycle required to ac-
complish this result depends upon the chemical composition
and previous thermal history of the product annealed,
The control of the annealing oven to produce a given cycle
is further influenced by the design of the furnace, the uniform-
ity of temperature throughout, rate of heating, etc. Therefore
the. art of annealing cannot be taught adequately in a chapter
of a book. At most the general principles may be outlined,
it being understood that in practice the operations are shaped
toward the desired end in accordance with the skill and exper-
ience of the annealer.
It already has been shown that the graphitizetion of cemen-
tite occurs more rapidly the higher the temperature and that the
rate of this reaction decreases as the reaction approaches its
end point. Consequently at first glance, it would seem advan-
tageous to conduct the process in the beginning at the highest
possible temperature. However, there are practical and the-
oretical objections to this procedure. The practical objections
in order of importance are as follows :
1. The extreme warping or distortion of castings when
softened by the high temperature.
2. The sintering or fusion of any available packing ma-
terial from the same cause.
3. The wear and tear on the fire brick of the oven.
4. The decreased service obtained from annealing pots.
5. The increased fuel cost of attaining extremely high
temperatures.
The theoretical reasons are even more important, being:
1. The large flaky character of the free carbon crystalliz-
ing out at the higher temperatures.
2. The poor ferrite structure set up under these circum-
stances.
Accordingly the metallurgist must determine for himself
where the best balance between speed and quality may lie, hav-
ing regard to the alloys with which he has to work. Opinions
vary somewhat but the advantageous maximum of temperature
of castings, as distinguished from furnace atmosphere or wall
Principles of Annealing 215
temperature, lies between 1500 and 1700 degrees Fahr. While
graphitization can be initiated at temperatures far below 1500
degrees, the reaction at these lower temperatures is prohibitively
slow without any compensating advantages. Few packings can
be found which will withstand temperatures in excess of those
occurring when heating castings to above 1700 degrees Fahr.
Moreover, the effect on grain structure begins to make itself
felt at this temperature.
The reaction at 1800 or 1900 degrees Fahr, is not sufficient-
ly faster to warrant incurring the increasing difficulties which
present themselves above 1700 degrees. Many malleable oper-
ators feel that the extra time required to anneal at temperatures
not exceeding 1600 degrees is well spent.
A safe maximum temperature having been determined for
the particular product under consideration, the annealer first
directs his attention to attaining this temperature as rapidly as
possible consistent with a reasonable uniformity of temperature
throughout the oven. It is here that oven design influences the
economy and quality of the annealing operations.
It is unavoidable that those pots nearest the source of heat
will heat more rapidly than the rest. However, if a furnace is
designed to permit the rapid and free circulation of flame, the
differences of temperature will be far less than where such cir-
culation is hindered to some extent.
All commercial furnaces have the heat supplied above the
pots and all well designed furnaces have a sufficient height of
roof to permit the flame to reach freely to the tops of the
farthest pots. The author has never heard any annealer ques-
tion the reason for introducing tlie heat at the top, all seeming
to take this arrangement for granted. However, there is a
good scientific reason for this design. The heating of the fur-
nace contents is accomplished mainly by the vertical gas currents
in the spaces between the several stacks of pots and to a minor
extent by conduction downward through the pot and contents.
If two of the vertical passages between the pots are at different
temperatures, a gas current will be set up rising in the hotter
and descending in the colder of the two. Therefore, if the hot
216
American Malleable Cast Iron
Principles of Annealing
217
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218 American Malleable Cast Iron
gas enters at the top, this circulation will tend to divert the
descending hot gas from the hotter passages toward the colder
spaces and thus heat the latter more rapidly. Were the heat
admitted at the bottom the. circulation described would cause an in-
crease in the difference of temperature between the hot and cold
passages since the ascending current in the hotter space would
draw the hot incoming gases with it.
Time of Heating Varies Widely
The rapidity with which an oven can be heated uniformly
depends entirely upon its construction. A number of observers
have recorded heating, cycles with pulverized fuel as short as
18 hours, whereas the author frequently has witnessed periods
as long as 100 hours and over, usually under adverse fuel condi-
tions. In some cases the increased time is due to the impos-
sibility of burning the coal rapidly, while in others the rate of
downward distribution of the heat in the furnace is the limiting
factor. In the latter case it sometimes is necessary almost to
cease firing and allow the heat to equalize by conduction and
radiation in order to avoid overheating the top pots. This pro-
cedure is sound metallurgically but necessarily involves a waste
of time.
The desired maximum temperature having been reached
as uniformly and rapidly as possible, the next step is to main-
tain this temperature until the reactions within the castings
have attained a state of equilibrium. This time depends upon
the temperature chosen and upon the chemical and structural
characteristics of the metal. In experimental determinations the
time to reach actual equilibrium is long. Under favorable con-
ditions it may be 20 or 30 hours at 1900 degrees, 100 to 150
hours at 1500 degrees and several hundred hours at 1400 de-
grees. In practice the times are materially shorter because a
slight graphitization of cementite may be relied upon in cooling
through the higher ranges of temperature and also because
equilibrium is approached more rapidly during the earlier stages
than when it is nearly attained. Indeed it might be said that
actual equilibrium is attained only in infinite time at any tem-
perature. Under fairly favorable conditions in well conducted
plants the time to reach equilibrium within commercial limits
Principles of Annealing 219
may be roughly as follows: 1700 degrees, 25 hours; 1500,
50 hours, and 1450, 80 hours or possibly 50 per cent more
under less favorable conditions.
These general relationships already have been indicated in
graphic form in Fig. 36 in Chap. III. The time required
is approximately inversely proportional to the temperature
above A^ for alloys high in carbon or silicon the time required
is less than for those lower in these elements. The presence of
excessive manganese or sulphur, or of some of the more un-
usual elements may prolong the time considerably. Also it is
believed that the rate of freezing and possible other variables
in the previous thermal history of the metal have an effect upon
the rate of graphitization.
The combined carbon content at equilibrium is greater
the higher the temperature, therefore the iron is not completely
annealed at the expiration of the required time at the maximum
temperature chosen. The carbon content, or solubility of carbon,
as dependent on temperature has been definitely determined for
metal containing about 1 per cent silicon. The relation is shown
in Fig. 24. Therefore the anneal will not be complete unless the
reaction is allowed to progress to equilibrium at or just under
A\\. The Ar-L point in commercial iron probably is between 1340
and 1375 degrees Fahr.
Approach Temperature Slowly
One way to accomplish the desired result would be to drop
the temperature quickly from the maximum to just under Ar± when
the reaction at the former temperature is complete and to main-
tain that temperature below Ar^ as long as may be required to
re-establish equilibrium at the lower temperature. This opera-
tion will readily yield perfectly annealed material but is difficult
to execute in practice except possibly in tunnel furnaces. Under
commercial conditions, equilibrium can be attained more
readily just under Ar^ by approaching this slowly from above
at a rate permitting the graphitization to just keep pace with
the falling temperature than by a quick drop and a long wait to
establish equilibrium. Rates of cooling between four and 10
degrees per hour usually are desired and most operators prefer
to cool more and more slowly as the temperature drops.
220 American Malleable Cast Iron
To make sure of attaining equilibrium a number of an-
nealers wisely attempt to hold a constant temperature just under
Ar± for some time. Nothing is gained by additional slow cool-
ing after the reaction at Ar± is complete.
In many plants the cooling rate is determined by the heat
radiation of the furnace. In these cases the annealer merely
seals the furnace at the high temperature and lets it take care
of itself. Fortunately, since the rate of cooling decreases as the
temperature of the oven falls, a well insulated furnace cooling
naturally will fall in temperature at a steadily decreasing rate,
as the metallurgical theory required. Therefore the results of
this practice often are much better than might be expected.
Difficulties begin to arise when the cooling is accelerated by
some unforeseen or unknown cause and the illogical operator
is no longer able to account for his results.
It will be noticed that a complete annealing cycle may be
subdivided into five distinct intervals as follows: Heating to
maximum temperature, maintaining maximum temperature till
equilibrium is attained in graphitization of cementite, cooling
to critical point, holding just under the critical point, and further
cooling to permit handling.
The first and last periods have no metallurgical significance
and can be accelerated as much as is convenient. However,
the second and the combination of the third and fourth, are
determined by the product being manufactured and cannot be
reduced below definite minimum values. The minimum cycle
is divided as follows: Heating to 1600 degrees, 30 hours;
holding at 1600 degrees 45 hours; cooling to Ar^ and holding
there, 35 hours; and cooling to handle, 5 hours. The total is
115 hours, which would make a six-day annealing cycle as an
absolute minimum, the time above 115 hours being spent in
charging and pulling. However, few plants are able to insure
success in so short a cycle and seven days may be considered
as the commercial minimum. Cycles of nine days and more are
not uncommon with large furnaces in order to secure the best
results.
The minimum annealing time is fixed by natural laws which
cannot be changed to suit the wishes of the manufacturer or
Principles of Annealing 221
the consumer. Any attempt on the part of the user to hurry
the producer is misguided. The response to such pressure will
be in inverse ratio to the conscientiousness and intelligence of
the particular manufacturer concerned. It would seem that
self interest will drive the malleable founder to adopt the
shortest workable annealing cycle in order to avoid the in-
vestment in additional ovens and their fuel supply. Nevertheless
the author has known many purchasers of malleable who
seemed to regard the operation of a long cycle as an arbitrary
wish of the manufacturer imposed upon his customer without
any adequate reason.
For many years the larger producing interests have been
approached from time to time by frequently sincere but always
poorly informed inventors claiming either to much reduce an-
nealing time or sometimes to do away with annealing entirely.
As a rule, those in the former class expect to accomplish results
by changes either in furnace design, methods of heating, etc., or
by some unusual and often secret packing. Being an atomic re-
arrangement within the metal itself, the annealing reaction can-
not be accelerated or retarded by the material surrounding the
casting.
The laws governing graphitization have been investigated
by a number of entirely competent experimenters and depend
on clearly known chemical fundamentals. The design of heat
treating furnaces also is well understood. Changes in furnace
design could only reduce the annealing time by accelerating the
time of heating, since as already explained, the times and tem-
peratures during the rest of the cycle are fixed by the metal be-
ing annealed. All of these patented or secret annealing methods
therefore are foredoomed to failure.
It is conceivable, although improbable, that someone will
discover an alloy with a carbon content, similar to that now
used, of such a character that graphitization. will be suppressed
at temperatures above 1600 degrees Fahr. but which will graphi-
tize easily or even spontaneously at lower temperatures. Such
an invention would accelerate or eliminate the present annealing
process. Since the alloys of iron with most of the reasonably
common elements are constantly being investigated and no indi-
222 American Malleable Cast Iron
cations have been found of any elements with properties pro-
ducing the complex effect here described in any degree, it
seems most unlikely that any greatly accelerated annealing meth-
od for producing black heart malleable will be found.
Therefore producers and consumers should admit the
necessity of adequate time for annealing and conduct their
several operations in accordance. The author is still waiting
to hear from a most enthusiastic engineer who, three months
before this was written, offered to demonstrate the manufacturer's
ignorance of annealing principles by taking home a sample of
hard iron in the evening, annealing it over night and returning
it completely annealed the next day.
Other incidental changes are produced in the metal while
graphitization is going an. The clearest evidence that these
changes are only incidental is the fact that the process of
graphitization can be carried on perfectly without any gain or
loss of weight. To prove this, an accurately weighed speci-
men of hard iron can be enclosed in a tube of difficultly fusible
glass, the air displaced by hydrogen, the hydrogen pumped out
to a fairly low pressure and the tube then sealed, so that the
metal can be annealed surrounded by nothing but a trace of a
reducing gas. Samples of 10 or 12 grams weight annealed in
such a tube in accordance with the heat cycle of commercial
practice, are unaltered in weight to 1/10 milligram. In other
words, the weight remains constant to 1/1000 of 1 per cent.
Migration of Carbon
However, under commercial conditions the castings always
are in an atmosphere having oxidizing possibilities. This at-
mosphere may be the atmospheric air remaining in the spaces
not otherwise occupied or it may be the products of combustion
or gases arising from reactions with packing materials. There-
fore there always is a tendency toward burning out the surface
carbon. The mechanism of the removal is interesting. Only
the carbon in the outer layer of molecules can combine directly
with any oxygen in the surrounding gas. Therefore unless
either the gas can penetrate the solid metal or the carbon can
migrate to the surface, decarburization would be limited to the
Principles of Annealing
223
infinitesimally small amount produced by burning out the car-
bon one molecule deep.
At one time it was generally believed that the gas penetrates
but the migratory action certainly exists and is probably the
.01 .oa .03 .04 .05- .06 .07 .06 .09 .10 .//
Inches Be/ow Surface
Fig. 99— Increase in carbon content at increasing depths below the sur-
face of malleable cast iron
major method by which carbon and oxygen are brought to-
gether. Carbon exists in iron at any temperature above Acz
in part, as a solid solution of a definite saturation value at any
given temperature. If the carbon concentration is locally low-
ered below saturation, diffusion will enrich this area at the ex-
pense of the more highly carburized areas. So long as ce-
mentite, or undissolved iron carbide remains, the deficit will
224 American Malleable Cast Iron :
be made up by solution of additional amounts of this element
in such a quantity as to maintain the solid solution in a saturated
state.
This migration requires considerable time so that in gen-
eral, carbon is oxidized at the surface much more rapidly than
diffusion can equalize the carbon content. The result is a ma-
terial poorer in carbon at the surface than in the center. As
we go further toward the center, the increase in carbon content
corresponds to a sort of gradient which is sufficient to feed the
carbon to the surface as fast as it is removed.
Fig. 99 shows the increase in carbon content at increasing
depths below the surface. The graphs represent various de-
grees of decarburization under commercial operating conditions.
It will be noted that the graphs vary both as to carbon con-
centration at the surface and as to the depth of penetration.
The former depends somewhat on the oxidizing medium em-
ployed, the latter on the length of time, the medium is applied,
and on its activity.
The effect of this decarburization on the physical properties
of the product are relatively small. Fig. 100 shows graphically
the results of careful tests made to determine the effect of the
removal of 1/16 inch of carburized surface in specimens of
various diameters on the tensile properties of the metal. The
experiments were conducted by casting tensile specimens to a
series of diameters, grinding one specimen of each size truly
cylindrical, removing about 1/16 inch of stock. The ground
specimens then were annealed with rough specimens from
the same heat and turned to size after annealing. The graphs
show the amount by which the properties of the specimen ground
before annealing exceeds the corresponding properties of the
turned specimens.
The experiment was conducted in this form to eliminate
variations due to cooling rate and original rough surface which
variables are included in the data given in the chapter on tensile
strength.
The tests were conducted on one lot of metal, all annealed
together. Therefore they correspond to one set of decarburiz-
Principles of Annealing
225
ing conditions only. Since decarburization varies, as the an-
nealing conditions vary, another series of investigations was
made to determine the changes in properties in iron of initially
similar composition by variable decarburization.
D/omefer Of Specimen Inches
Fig. 100 — Graph showing effect of removing 1/16 inch decarburized
surface in specimens of various diameters on the tensile
properties of the metal
- Results of 50 Tests
In Fig. 101 have been plotted the results of some 50 such
tests on iron having from 2.40 to 2.60 per cent carbon, 0.70 to
0.80 per cent silicon before anneal, which correlate the tensile
properties with the carbon content after annealing. The graph
226
American Malleable Cast Iron
is plotted from average values. Individual tests depart con-
siderably from the average since small differences of carbon con-
tent in the hard iron affect the results much more than much
larger variations in this element due to decarburization.
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Fig. 101 — Graph showing effect of varying degrees of decarburization
on tensile properties of malleable cast iron
Figs. 100 and 101 serve to show that the final properties are
relatively little affected by the decarburization process. Be-
ing measured on surface metal the elongation probably depends
only in the carbon content near the surface and but little on
the depth of decarburization. The tensile properties are some-
what more consistently affected by decarburization.
Decarburization is controlled in practice by the character of
the packing material. Perhaps it would be more accurate to
say that the results in practice depend on the packing used, there
Principles of Annealing 227
being but little available information with regard to the action
of packing.
The commercial packings depend for their activity chemically
on the reduction of ferric oxide, Fe2O3 to FeO, ferrous oxide.
It is not to be understood that they actually liberate oxygen on
heating as for instance potassium chlorate does.
Four Possible Reactions
The process is a chemical reaction in which the oxygen never
appears as such but merely combines with carbon. Four re-
actions are possible, depending upon the circumstances:
3 Fe2O3 + Fe3C = 2 Fe3O4 + CO + 3 Fe
6 Fe2O3 + Fe3C = 4 Fe3O4 -f CO2 + 3 Fe
Fe3O4 + Fe3C = 3 Fe O + CO -f 3 Fe
2 Fe3O4 + Fe3C = 6 Fe O + CO2 + 3 Fe
The two reactions 'FeO+Fe3C=Fe+CO+3Fe and 2 FeO
-J-Fe3C=2Fe+CO2+3Fe are theoretically possible but occur
only under unusual circumstances, if at all.
The reaction 3FeO+50O— Fe3C+4CO2 can probably oc-
cur under certain unusual conditions.
The fact that the analysis of packings is expressed as a
rule in terms of the Fe2O3 FeO, SiO2 and possibly A12O3 and
other oxides has given rise to the unfortunate conception that
they are mixtures of two oxides of iron with other inert oxides.
As a matter of fact all packings in use, as distinguished from
the raw packing, have become complex silicates. The practical
annealer unconsciously acts on this knowledge where he limits
his additions of roll scale, or other raw material to small
amounts at any one time, for a packing containing any large
amount of free oxides is not a workable material.
The raw material from which packing is built up usually
is roll scale or squeezer scale from rolling mills, pot scale (the
oxide from the. outer surface of the annealing pots after they
are drawn from the furnace) or air furnace slag. Iron ore was
once used but probably is now obsolete. Table XVI shows the
composition in the usual terms, of these several materials.
It should be understood, however, that only the first three
are actually oxides. Ore is nearly pure ferric oxide contam-
228 American Malleable Cast Iron
Table XVI
COMPOSITION OF TYPICAL PACKINGS
FeO Fe203 MnO SiO, A1,O,
Ore 00 91.43 8.57
Pot scale 37.10 53.11 9.79
Roll Scale 61.47 31.99 6.54
Squeezer scale 69.74 9.34 .80 14.95 5.17
Slag 28.80 1.16 4.85 50.42 14.77
inated somewhat with silica minerals. Pot scale is a more or
less impure magnetic oxide, Fe3O4 contaminated by sand adher-
ing to the pots. Roll scale is magnetic and ferrous oxide
originally nearly pure, but contaminated in gathering it up and
shipping. Squeezer scale is a mixture of basic silicates of iron
and manganese with some iron oxides, mainly ferrous oxide
dissolved in bibasic ferrous silicates. Slag is a neutral silicate
contaminated with fused brick, etc.
Some typical analyses of packings as actually used are
shown in Table XVII both in terms of the usual proximate
analysis and in terms of the compounds apparently present.
It will be seen that the packings contain little free oxide
and are mainly silicates. The ferrous silicates are incapable of
reduction to metallic iron under the usual annealing conditions
so that the oxygen for oxidizing the carbon is derived primarily
from the reduction of Fe2O3 to FeO although the ferrous oxide
of pot and roll scale may enter into the reaction.
The relative amounts of carbon monoxide and carbon di-
oxide formed depend on the temperature and the packing used.
With the materials and temperature of commercial practice the
ratio is fairly constant; approximately 12J^ per cent of the car-
bon being burned to CO2 the remainder to CO.
The principal reaction involved, assuming Fe2O3 as the ac-
tive medium, corresponds to the equation:
9 Fe2O$ -f 8 Fe8C = 18 FeO + 7 CO + COa + 24 Fe
The actual mechanism of the decarburizing reaction forms
an interesting though complex problem in physical' chemistry.
The oxidation of the carbon in the iron and reduction of the
Principles of Annealing 229
packing are accomplished by the gas surrounding both. To be
operative, a system must be chosen so that at the temperature
and pressure in the .annealing pot the gas phase present is such
that the reactions
Fe3C + COa = 2 CO + 3 Fe
Fe2O3 + CO + = 2 FeO + COa
FeO + CO =Fe + COa
can all proceed from left to right. In other words the system
must be one in which a ratio of CO to CO2 can be maintained
which will at the same time oxidize Fe3C, reduce Fe2O3, and
reduce FeO.
If the relative concentration of CO and CO2 be such that
the first reaction ceases or reverses no decarburization will
occur. If the reaction is initiated it would soon cease, due to the
conversion of all available CO2 to CO, unless the second re-
action continuously reconverted CO to CO2. If the last re-
action reversed, the iron of the casting would be oxidized in
addition to the carbon in the consequent scaling . Only some
of the more usual reactions have been considered there being a
Table XVII
ANALYSES OF PACKINGS
Source Pot scale Roll scale Squeezer scale Slag
Fe 4.04 6.88
FeO 54.36 57.33 58.49 38.25
Fe20s 9.04 5.97 3.14 1.03
MnO 1.50 3.03
SiO, 21.02 26.16 24.92 43.60
AlaO, and undetermined ..11.54 9.66 11.95 14.09
Proximate Composition of Above
Per* cent
Fe 4.04 6.88
FeO . 23.40 31.34 21.00 12.60
Fe203 5.97 1.00
(FeO)2 SiO, 40.90 56.90
(Fe203)2 (Si02)3 ..14.10 5.40
(FeO), (Si02)a 27.91 .....
FeO Si02 45.20
Fe20, (SiO,), .... 5.40
Various inert silicates by
difference . ..17.56 27.90 16.70 35.80
230
American Malleable Cast Iron
number of others possible between the components of such a
system.
Scientific investigations of the subject matter involved would
be based on determination of the composition of the gas phase
in equilibrium with the several oxides of iron and carbon con-
cerned and a location as to temperature and concentration cor-
Fig. 102 — Equilibrium curves illustrating the reactions between carbon,
iron and oxygen, after the data of Matsubara
responding to the reactions proceeding in the desired directions.
The subject has been but imperfectly studied, the available in-
formation being mainly due to Schenks' summary "Physical
Chemistry of the Metals." Matsubara, in a paper presented
before the American Institute of Mining and Metallurgical
Engineers, February, 1921, amplifies and checks Schenks' data,
particularly with respect to the reactions into which the cementite
enters in the presence of CO and CO2.
Principles of Annealing 231
Fig. 102 is drawn from Matsubara's paper, based on his own
results as well as those of Boucourd, Bauer, Schenk and others.
It represents the percentage of CO in a mixture of CO and CO2
for various temperatures at which the several reactions will
proceed equally rapidly in both directions — or at which they
will cease and equilibrium will be established. The graphs are
plotted for a pressure of one atmosphere as the sum of the
partial pressures of CO and CO2. For other pressures the
equilibria can be calculated from the equilibrium constants of
the several reactions. Letting P be the pressure exerted by
CO and CO2, X the amount of CO in the mixture of these
gases and Klf K2 and K3 the equilibrium constants for equations
1, 2 and 3, respectively, then
X*
K,= P i
1— X
X*
K2= P
\—X
Xs
K,- P
d—xy
KI K2 and K3 can be calculated from Fig. 102 for any giv-
en temperature and hence the change produced in X by changes
of pressure at that temperature can be calculated and a dia-
gram similar to Fig. 102 constructed for other pressures.
Reaction (4) and (5) are independent of pressure. Un-
fortunately nothing is known as to the locus of the curves cor-
responding to (4) and (5) for the silicates forming commer-
cial packings. The interpretation of the equilibrium diagram
to determine what reactions occur is as follows:
On areas below (3) cementite is oxidized to FeO and CO;
in areas above (4) FeO is reduced to Fe with the formation
of CO2, hence in any region below (3) and above (4), FeO
will oxidize the carbon of cementite. Such regions exist only
above 700 degrees Cent., therefore the reaction cannot be main-
tained at lower temperatures. That the lines (1), (2), (3) and
(4) should intersect at one point is curious, and indicates that
at that temperature, pressure and composition, C, Fe, FeO and
Fe3C or any two or more of these radicals can exist together
232 American Malleable Cast Iron
in equilibrium. Almost any question as to the course of the
annealing reaction or the behavior of packings could be answered
.by the construction of such diagrams for the particular packing
material. Many conclusions as to the reactions of the pure ele-
ments and their oxides and carbides will present themselves on
further study of the diagrams.
XII
PATTERNMAKING AND MOLDING
IN MANY respects, patternmaking and molding practice in
malleable plants does not differ from that in other branches
of the foundry industry. The various devices adopted for
repetitive work in gray iron or brass also are found in use in
the malleable shop. Indeed, since the producers of malleable
engage largely in the manufacture of small and moderate sized
parts in large numbers the development perhaps is further ad-
vanced than in gray iron practice. However, there are certain
vital differences between patternmaking and molding for mal-
leable cast iron as distinguished from the same operations in
the gray iron trade. These differences arise from the metal-
lurgical properties of the two materials.
The two essential distinctions between white iron and gray
iron lies in the melting point and shrinkage of the two metals.
Gray iron castings of moderate size are made of metal con-
taining, for example, 3.25 per cent carbon, 2.00 silicon and 0.50
phosphorus as compared with the composition of white cast iron
which approximates 2.50 per cent carbon, 0.75 silicon and 0.19
phosphorus. The equilibrium diagram for the iron carbon
alloys shows that all alloys above 2 per cent in carbon finish,
freezing at the same temperature — 1130 degrees Cent, or 2066
degrees Fahr. It shows further that the point where freezing
begins varies with the carbon, decreasing nearly uniformly from
1550 to 1130 degrees Cent, as the carbon increases from nothing
to 4.3 per cent.
Leaving the other elements out of consideration, the white
iron should begin to freeze at roughly 1310 degrees Cent, or
2390 degrees Fahr. and the gray iron at 1220 degrees Cent, or
2250 degrees Fahr.
Thus gray iron will be completely liquid at a temperature
140 degrees Fahr. lower than that at which white cast iron has
begun to solidify and .the range of partial solidification or pasti-
234
American Malleable Cast Iron
ness is larger by that amount in white cast iron than in gray
iron.
The presence of silicon still further accentuates this point.
According to Gontermann's data, metal of the composition as-
sumed for gray iron should begin to freeze at about 1200 de-
Fig. 103— (Above) Two gates of metal patterns in match part; (below)
Pattern mounted on match plate and gated pattern
mounted on vibrator frame
grees Cent, or 2190 degrees Fahr. and be completely frozen al
1140 degrees Cent, or 2080 degrees Fahr., whereas white cast
iron should begin to freeze at 1330 degrees Cent, or 2420 de-
grees Fahr. and finish the process at 1170 degrees Cent, or 2140
degrees Fahr.
The data are not exactly in accord with those based on car-
Patternmaking and Molding 235
bon alone, due to minor differences in the observations on which
the data were based. The point to be clearly brought 'out is
the higher point of incipient freezing and longer partially frozen
range for white cast iron than for gray iron. The presence
of phosphorus in larger amount in the latter still further
accentuates the difference, although the writer has no available
data on the freezing conditions in the system Fe-Si-P-0.
The data given show clearly that white cast iron must be
poured at a much higher temperature than gray iron, since
the latter will be liquid at a temperature perhaps 230 degrees
Fahr. below that where the former has begun to set. Further-
more, it is quite possible that the fluidity of white iron when
at a temperature say 100 degrees Fahr. above its freezing point
is materially less than that of gray iron at the same temperature
above its freezing point.
Within the author's knowledge data on this point are
lacking. A further corollary of the difference in freezing
conditions is that other things being equal there will be more
shrinks or porous areas in white than in gray iron castings.
This arises from the longer freezing range of the former corres-
ponding to a larger fluid contraction of the still liquid alloy
between the time and temperature of incipient and complete
solidification. The consequence of this increased fluid, contrac-
tion is that as the temperature of complete freezing is ap-
proached there no longer remains a sufficient volume of liquid
to fill the voids in the previously formed solid skeleton.
Therefore, in the last freezing areas, voids remain between
the dendritic crystals of the first frozen solid.
The shorter the freezing range the less of this contraction
can occur. It has been shown by Cesaro that liquid iron is
a solution of cementite in iron and Wust and Peterson have
demonstrated that all such alloys freeze as cementite and
austenite. However, in the temperature interval just under
freezing the higher silicon and carbon metals graphitize by
the conversion of cementite into iron and carbon.
236
American Malleable Cast Iron
Fig. 104 — Hand operated squeezer-type molding machine and (below)
mold and pattern equipment in position on machine. Heavier
machines operated by air also are used in the industry
Patternmaking and Molding 237
The iron resulting from this reaction occupies almost
the same volume as the original cementite. The total volume
therefore is increased almost by the volume of carbon liberated.
As a consequence there is a tendency to expansion at these high-
er temperatures. A number of observers especially Turner have
recorded actual increase in linear dimensions while the metal
was cooling and therefore contracting, just under the freezing
point.
The expansion due to graphitization is important in two
respects. It causes the casting to be only about 1 per cent
smaller in linear dimensions (3 per cent by volume) than the
pattern instead of double these values for white iron, and also
tends to fill up in part the voids left by fluid contraction.
The difference in pattern equipment and molding methods
in the malleable as compared with gray iron industries is due
to the necessity for providing against the following differences
in the properties of the two metals.
1. The higher melting point and lower fluidity of white
iron.
2. Its greater tendency to internal shrinkage due to fluid
contraction.
3. Its greater shrinkage from pattern size.
It will be noticed that the noun "shrinkage" has two
distinct but related meanings to foundrymen. One refers to
the reduction in the overall dimensions of the casting as com-
pared with the pattern and the other to the production of
porosities due to voids left by the contraction of the fluid metal.
A distinction based on the words "solid contraction" and
"fluid contraction" seems desirable but has not- gained favor
among foundrymen. Accordingly one must be constantly on
the alert to avoid confusion due to the indiscriminate use of the
term "shrinkage."
Speaking first of this property in the sense of solid con-
traction, the fact that the shrinkage of white iron is about ^4 -inch
238
American Malleable Cast Iron
Fig. 105 — Stripper and roll-over molding machines
(Top) Plain stripper plate molding machine and equipment for cope and drag.
(Center) Roll-over machine for drag. The cope is rammed up from a plain plate.
(Bottom) Stripper plate machine for cope and a roll-over machine for the drag.
Patternmaking and Molding
239
per foot instead of ^ -inch per foot as in gray iron does not cause
any difficulty in patternmaking, except that a proper allowance
must be made by using a "double" or 54 -inch shrink rule in
laying out the work in case the casting is to be used hard. This
shrink rule is merely a rule graduated in feet and inches and
fractions of inches — usually sixteenths — in which the distance
marked as one foot is 12.25 inches. A casting from this pattern
will come from the mold about true to size.
Experiment has shown that the solid contraction of white
n Length in Per Cent of Length at 75 °F.
Co KJ O^ O
/
/
.
/
^sV/
/
*4
\Y
^
^
c
SL
Total Contraction Independent
of Chemical Composition.Data
on Samples of at>out 2^Tbtal
Carbon No Graphite
C7*
§0.4
£0
/
/
7
00 1600 IZOO 800 400 0
Temperatures, Deq. Fahr.
Fig. 106. — Curve showing contraction in cooling from solidifica-
tion to room temperature
cast iron (metastable carbon iron alloys) is substantially the
same irrespective of composition. The contraction in cooling
from solidification to room temperature, is graphically shown
in Fig. 106.
On annealing the casting expands due to the fact that tem-
per carbon and ferrite occupy a considerably greater volume
than the cementite from which they are formed. The increase
in volume and in linear dimensions, depends primarily on the
original total carbon and to a less degree on the heat treatment
240
American Malleable Cast Iron
by which the graphitization is attained and possibly on other
more obscure circumstances.
Some conclusion as to the changes of dimensions produced
by graphitization can be formed from the following density
data: Ferrite 7.90, cementite 7.438, carbon 2.30 to 2.70.
Dimensions Determined by Trial
The expansion in annealing is usually assumed to be one-
half the original contraction making the net "shrinkage" allow-
ance Y% inch per foot as for gray iron. This conclusion can be
correct for only one particular carbon content. It was probably
3.10
500
0?QO
\
^X,
\
\.
>s
\
"O
|2BO
c
c270
0
_Q
5260
25C
3.40
X
\
"S
\
\
\,
I
5
i
!
f3
\
\
1.0 1.10 1.20 130 1.40 1.50 1.60
Per Cent Contraction of Malleable Specimanfrom Pattern Size
Fig. 107 — Graph showing the per cent of contraction of malleable
from pattern size
fairly accurate in the days when high carbon iron was prevalent.
W. L. Woody has given the writer data obtained in a study
of over 1000 heats from which test specimens were cast from
a pattern 12 inches long, the specimens being micrometered
after annealing. The results are shown graphically in Fig. 107.
The percentage of net shrinkage of unconstrained specimens
can.be read from this graph.
The author has determined the density of hard iron and
malleable cast iron made therefrom for various carbon contents.
Patternmaking and Molding
241
The data are shown in Fig. 108 calculations as to change of di-
mensions in annealing from these changes in density yield re-
sults apparently in error in the direction of too much expansion
in anneal, i.e. to too small a shrinkage allowance.
In determining pattern dimensions consideration must also
be given to the fact that, due to rapping, the molds always are
larger than the pattern, except on ''stripper plate" equipment.
On vibrator plates this "rappage" will be small and uni-
form, in bench and floor molding by hand it will be variable and
may be large.
Very small parts may actually require a negative "shrink-
7.7
d
75
y
74
CD
Q.
^73
7.2
2.3 2.5 2.7 2.9
Per Cent Carbon In Hard Iron
3.IO
Fig. 108 — Graphs showing relation of annealing upon the density
of the metal
age allowance" "the rappage" exceeding the solid contraction.
Further it may happen that in irregular and intricate cast-
ings some parts constrain others when freezing and leave shrink-
age strains. The relief of these strains during the annealing
may cause unexpected changes of form.
Therefore it often is necessary to arrive at the pattern size
for important dimensions by actual trial and even then the
castings will come true to size only so long as temperature of
242
American Malleable Cast Iron
Pro£o£>/e for/7?or/bn Of Crock
Fig. 109 — Casting with thin disk and thick hub, showing probable
point of rupture
pouring, chemical composition, and sometimes even the solidity
cff sand and cores are maintained exactly constant.
The heavy solid contraction of the white cast iron also im-
poses a number of difficulties which would not be clear to the
reader were he to consider the problem altogether from the
standpoint of the net shrinkage of the finished product. It
has been said that the total contraction of all white cast iron is
constant. However, it is at least unusual that all parts of a
given casting cool at the same rate. In other words, in prac-
tically every casting some parts arrive at their final temperature,
and therefore final size, ahead of others. This may develop ex-
cessive stresses or even distort or disrupt the casting.
Consider a casting having the form of a thin disk with a
heavy hub at the center, as shown in Fig. 109. The hub will be
hot and possibly almost fluid when the light disk has already
set and cooled to nearly room temperature. The contraction of
the disk during the cooling has met but little resistance from
the hot plastic center. However, when the latter begins to cool
its reduction in dimensions will be resisted by its attachment to
Fig. 110 — Type of casting with thin disk center and thick rim
Pafternmaking and Molding 243
the solid thin flange. Sometimes this attachment will be so se-
cure as to permanently stretch the pasty mass within. If this
cannot occur the flange may be torn loose from the hub
at one or more places or may even be entirely detached.
In the reverse case of a thin plate surrounded by a thick
rim, as shown in Fig. 110, the contraction of the rim would be
opposed by the previously solidified center, either crushing
the center or producing a radial tear in the rim. Generally
the point of failure is at or near the hottest part of the -casting
Where the strength is the least. Occasionally no external de-
fect results due to the welding up of such defects by molten
metal from the center. Then the consequence is a pipe or other
void.
The magnitude of the stresses from this source may be
enormous, depending only on how rigidly the last cooling por-
tions are held by their solid surroundings. In gray iron the
difficulty is less pronounced due to the lower magnitude of
the contraction and to the fact that the solid portions can be
deformed slightly without breaking, whereas practically no dis-
tortion is possible in the hard iron.
Effect on Design of Castings
The practical application of this reasoning is that, in the
design of parts to be made of malleable cast iron great care
must be used to avoid such forms and proportions as will rigidly
connect parts of widely different cross section. All sections
should merge uniformly into each other, avoiding abrupt changes
of thickness. Fairly thin ribs intended to rigidly brace heavier
sections, spoked wheels with hubs heavier than the rim and in
general any design in which unequal rates of cooling can set up
opposing stresses should be avoided. If such designs are suc-
cessfully executed by the foundryman it is only by methods 'of
gating or chilling calculated to accelerate the cooling of the
heavier sections and retard that of the lighter. This calls for
the exercise of great skill and judgment and may produce pro-
hibitively higher losses with a corresponding increase in cost.
We may now consider the shrinkage produced by fluid con-
traction and resulting in porous material in the areas freezing
244
American Malleable Cast Iron
last. It is impossible to suppress these so called shrinks in any
casting. Their formation is inseparably connected with selective
freezing over a temperature interval and hence always occur in
every casting.
Depending on particular conditions, these shrinks may be
widely distributed in insignificant amount at any one place,
or they may be concentrated in one spo't, aggregating a consid-
erable volume. A casting freezing at a nearly uniform rate
throughout, due to equality of section, etc., and freezing almost
as rapidly as the iron enters the mold may have the porosity
so uniformly distributed and so nearly filled up from the ladle
during pouring as to be practically sound. On the other hand,
a casting having a heavy cross section in some one place which
Fig. Ill — Dendrite (about half size) from shrink in hard iron ingot
8 inches in diameter by 20 inches high which
was poured without feeding
is fluid long after pouring ceases will show a great shrink,
especially if the heavy section is high up in the mold.
Two remedies are employed for this trouble. The older is
the application of iron chills, which are pieces of cast iron
buried in the mold so that they form its inner surface at the
points where shrinkage is prevalent. By accelerating freezing
they suppress the shrink in their immediate vicinity. However,
since the reduction in volume still exists an equal volume of
shrinkage will develop elsewhere. This practice is good if
the shrink in the new location does no harm, or if in that lo-
cation it can be suppressed by feeding ; otherwise it is merely
camouflage. Continuously supplying molten iron until the en-
tire casting is frozen is the only actual preventive of shrinks.
Patternmaking and Molding 245
The shrink always is found in the slowest freezing locality.
Therefore, if to the pattern there is attached a feeder of still
slower cooling rate so located that metal can flow from it to
the location in which the shrink was found, then the shrink
will be transferred to this feeder and be of no consequence,
since the feeder is not a part of the finished product. The
actual design of feeders, to meet a given set of conditions may
require much skill and experience, but the operating principle is
simple. t
Feeders are expensive, not only from the molding view-
point but also because they involve the melting of much ad-
ditional iron. Nevertheless their use is the safest possible found-
ry practice to insure sound castings.
The high freezing point of white cast iron necessitates
much greater care in gating than is requisite for gray iron. The
relatively thin gates commonly used for that metal do not admit
of a sufficiently rapid flow to prevent freezing before the mold
is filled. Most castings must have metal admitted at a number
of points in order to permit the mold to fill sufficiently rapidly.
Because of the large gates, it is necessary to use special means
to exclude slag or sand floating with the current of metal. The
thin knife gates of the gray iron industry will choke the stream
enough to permit these impurities to rise to the surface and be
trapped in the runners. The same principle is used in malleable
foundry but greater care is necessary in making the runners
large and providing places for the ascending slag to be trapped
on account of the rapid flow of iron required.
Frequently the iron is poured through a strainer core placed
at the bottom of the riser, which is intended to cause the latter
to remain full of metal and allow the slag to accumulate and
float up.
(Because of the quick filling of the mold, necessitated by
the quick freezing of the iron, great care must be used in se-
lecting molding sands, and in venting the mold. The air and
gas must be able to escape rapidly enough to allow the iron
to enter at the rate required to keep it from freezing before
the mold is filled.
The selection of molding and core sands of core binders,
246
American Malleable Cast Iron
as well as the actual ramming of the sand are further influ-
enced by the high solid contraction of white cast iron. The
mold and cores must be made so as to give readily under the
heavy contraction of the casting in freezing. If for instance,
a core be so hard as not to disintegrate before the metal begins
Fig. 112— Typical gate for malleable castings showing strainer, core
and skimmer gates for furnishing clean metal for feeders
and producing sound castings
to shrink it may set up such a strain in the casting as to actu-
ally cause rupture.
The patternmaker can frequently save the customer money by
a judicious selection of the number of pieces made in one mold.
A reasonable increase in the castings per mold is good economy.
f Any attempt to increase the weight per mold by putting in
so many pieces as to cause pouring difficulties or to prohibitively
increase the dimensions of the mold it not justifiable.
Patternmaking and Molding 247
In general the steps in the improvement of molding meth-
ods have been as follows:
Starting with a plain pattern as the simplest equipment,
the first step was to permanently attach thereto models or pat-
terns of the gates, feeders, etc., in order that these need not
be the subject of separate operations. In the case of small
parts this leads to the mounting of several patterns on one gate.
To avoid the labor of producing a parting by hand for each
mold, match parts were introduced, which are merely a semi-
permanent duplicate of one half of the mold (generally the
cope).
In the interests of greater stability plate patterns were
developed, consisting of fairly thin flat plates, usually of alumi-
num with the patterns mounted on one or both sides to-
gether with the gates, etc. The plate being at least as large as
the exterior of the flask separates the cope and drag by its own
thickness. Each half of the mold being rammed up off its
own side of the plate, the mold when closed corresponds in form
to the parts mounted on the plate.
To do away with hand-rapping the pattern to withdraw it
from the mold; air or electric vibrators often are attached. In
some cases, especially for heavy work, the pattern is with-
drawn, usually by a lever motion, without rapping, through
a stripper plate. The stripper plate is merely a plate represent-
ing the parting of the mold having an opening exactly fitting
the contour of the pattern at the parting. When drawing the
pattern downward through this plate the latter supports the
sand and prevents its following the pattern.
Unless the cope and drag are duplicates, two machines are
requisite for each job as the construction is evidently such as
to be applicable to one-half the mold only for each unit.
Extremely heavy work is frequently handled on a roll-over
machine which is especially available for making the drag. After
the drag is rammed up, necessarily parting downward, the ma-
chine facilitates turning it over to its proper position by sustain-
ing and counter balancing most of the weight of the mold and
pattern by springs. The pattern is sometimes withdrawn
248 American Malleable Cast Iron
through a stripper plate and sometimes by letting the mold sink
away from under the pattern by a suitable lever motion. The
sand is compacted by hand ramming, by the use of hand or air
operated squeezers, and by jolt ramming. The latter operation
consists of mechanically raising the mold repeatedly and allow-
ing it to come down on a solid support which uses the inertin
of the sand itself for compressing it. On floor work pneumatic
rammers sometimes are used.
XIII
CLEANING AND FINISHING
OPERATIONS of cleaning and finishing malleable iron
castings are conducted in part by the manufacturer, but
frequently also by the consumer. Some of the simpler
operations may be dismissed almost with a word but certain
others such as machining, welding, galvanizing, etc., which are
performed usually after the castings are delivered to the buyer
merit more extended discussion.
Castings generally are cleaned of sand as the first step on
leaving the foundry. An exception to this is found in some
cases of large muffle annealed castings where the finish is
relatively unimportant. Such castings are often annealed with
out cleaning. In most cases, the hard iron castings are cleaned
in tumbling barrels, using any of the standard equipment. The
operation is in no sense distinctive, the only peculiarity being
the brittleness of the castings. To avoid breakage greater care
must be used in handling the material and packing the barrels
than would be needed in gray iron practice.
Castings of a very fragile character can not be cleaned in
this manner without breakage. Therefore, it is usual to pickle
or sand blast them, usually the former. Pickling may be in
dilute sulphuric acid which loosens the sand largely by the ac-
tion of the hydrogen gas formed on the surface of the metal or
less commonly in hydrofluoric acid which dissolves the silica sand
with but little action on the iron. If the latter acid is to be
used, economy will dictate the mechanical removal of as much
sand as possible before pickling to avoid -the needless exhaustion
of the acid through the dissolving of loose sand.
Castings Must Be Cleaned
Large castings are sometimes sand blasted one at a time by
hand more easily and safely than they could be cleaned by
rolling. A second cleaning is practically always necessary after
annealing and this may be by rolling, often using scraps of
leather, old shoes, etc. to impart a polish. If clean cut edges
250
American Malleable Cast Iron
Fig. 113 — Tumbling barrels are used for cleaning castings
Cleaning and Finishing 251
are required, sand blasting is often resorted to either in barrels
or by hand. Pickling is not common except as a preliminary
to plating. Sulphuric acid, hydrochloric acid, and a hot solu-
tion of acid sodium sulphate may be used to remove the oxide
scale left by annealing.
Since the castings are very likely to become warped during
the anneal a straightening operation is often necessary if the
castings are at all complex in shape.
In many cases, especially on complex and thin work, no
better method can be used than the hand method. When pos-
sible a drop hammer fitted with suitable dies may be employed.
Since the development of arc and acetylene welding, the practice
of reclaiming defective material by this process has received at-
tention both by the producer and the consumer. The operation
of welding has two entirely different aspects, the repair of me-
chanically unimportant faults of surface and finish in the pro-
ducer's plant and the repair of castings broken in service.
Reference will be made later to the latter process, that is welding
by or for the ultimate consumer. Limiting ourselves for the
moment to welding as practiced in the malleable foundry, we may
start with the premise that the founder should deliver to the
buyer no casting which is not high-grade malleable iron through-
out.
In welding, the material of the weld is melted and the cast-
ing, in part at least, is brought to this same temperature. Thus
in welding with iron, regardless of whether the filler is
wrought iron, soft gray iron or any other material, the casting
will be heated to a point far above the critical point and hence
on cooling will revert to the condition of white iron.. No in-
genuity in the selection of a filler therefore will overcome the
presence of a glass hard spot at the weld. This condition can
be obviated only by using for a filler either white cast iron or
malleable, more conveniently the former, although both will be
white after remelting. If the welded casting is then annealed,
or re-annealed precisely as in the regular practice the material
in the weld will be the same as that throughout the casting.
The temperature of the arc is so high that a thin layer of
metal can be melted and the operation completed before the un-
252
American Malleable Cast Iron
Fig. 114 — Sand blast equipment is used for removing sand from castings
Fig. 115 — Sorting and inspecting small castings are important operations
in many plants
Cleaning and Finishing 253
derlying metal is much heated. The author once had the op-
portunity to observe the work of an expert arc welder. Work-
ing on castings retaining their original ferrite surface, this oper-
ator was able to weld so rapidly using Swedish iron wire, that the
heat was confined to the ferrite layer and hence a perfectly soft
weld resulted. Such a result presupposes two conditions not
usually existing; the first, the use of an extremely skillful
artisan and the second, a character of repair which does not re-
quire welding to" a part of the casting below the decarburized
skin; The latter condition, depending as it does on the char-
acter of defect to be repaired, is entirely beyond control.
All Faults Not Cured by Welding
Whether or not the casting is annealed before welding has
no effect on the final product and may be left to the welder's
discretion. Welds made in the above manner by a skilled ar-
tisan will render the product equal in quality to an initially
perfect casting. Since the element of skill enters, however,
it may be a measure of safety to exclude from repair by welding,
faults which if not perfectly repaired would be the cause of
serious failures.
Generally, snagging or the grinding away of gates, fins, etc.,
is the duty of the producer. The operation is performed either
with the casting in the hard state or after annealing. Usually
most of these imperfections can be broken off with a light ham-
mer before annealing and the final finish produced by grinding.
Grinding before annealing is slower and more expensive than
if performed on the finished product. But since the former
method produces somewhat better looking castings, especially
on sand blasted work, it is sometimes specified when the con-
sumer feels that this feature is worth the extra cost.
Hard iron is ground on a very hard and rather fine grained
emery wheel; malleable is ground on a soft and coarse wheel.
The size of casting and finish required influence the selection
of the exact grade of wheel. For malleable grinding wheels of
artificial alumina, 14 and 16 grit, in a hard grade are used ex-
tensively.
The preceding discussion covers the usual finishing opera-
tions which the malleable foundry performs for its customers,
254 American Malleable Cast Iron
however, the customer may perform a number of additional oper-
ations. Disk grinding, machining, straightening, welding, tin-
ning, galvanizing, electro-plating, occasionally local hardening
and possibly other operations come into this category. Since
the customer's requirements and method are likely to be peculiar
to his individual conditions, he is better informed as to his
processes than is the manufacturer of the castings. It will be
well, therefore, to confine the present discussion to considera-
tions of the producer's attitude toward these several operations.
Of the technique of disk grinding little need be said, the
one essential point to be observed being that in this as in all
other forms of grinding the operation be not crowded to the
point where the temperature of the surface metal reaches Ac^
Many grinding operations will readily raise the metal in con-
tact with the wheel to a red heat. A portion of a malleable cast-
ing which has risen to such a temperature has had some of its
carbon recombined and has been locally hardened to a degree
which may render it brittle or unmachinable.
Should Allow for Finish
Theoretically, tool life should be long and cutting
speeds high for malleable cast iron, since the material be-
ing cut is a dead soft steel which is one of the easiest ma-
terials to machine. Moreover, the presence of temper carbon
should favor machining both by breaking up the chip and by
acting as a lubricant for the chip and tool.
That this conclusion is correct is indicated by the con-
ditions under which malleable is machined in practice. In ma-
chining malleable cast iron not much over 1/16-inch of stock is
removed at one cut. Only in rare cases are cuts of %-inch to
5/32-inch necessary in practice. The commercial speeds in lathe
operation seem to run from 70 up to 160 or 170 feet per
minute. The heavier cuts usually are run at the lower speeds.
Fine feeds are commonly used, ranging from .01 to .02 inches
per revolution. Although generally these conditions are suc-
cessfully met in operation, machining troubles sometimes are
encountered. Therefore there is definite reason to believe, either
that there exists a fairly wide range of machinability in nor-
mal malleable or that in individual cases an abnormal product
Cleaning and Finishing
255
is unexpectedly encountered in a small amount mixed in with
a large mass of normal material.
In the absence of systematic study on the point, no recom-
mendations are possible by the producer. It is well, however, to
point out some special features influencing machining. If any pearl-
ite remains in the finished casting, it is generally very near the sur-
•Pearl/te
Norma/Structure
Center of Rotation
in lathe
-Finish ed Diameter
Original Diameter-
Fig. 116 — When machine center and casting center are not concentric,
apparent hard spots may be found
face. It is therefore well to design malleable parts with a con-
siderable amount of "finish" for it is usually easier to remove
1/16 to 3/32 inches of metal by turning or planing than to
take a very light cut which may be almost entirely in this
slightly pearlitic area. At the same time this allowance is a
256 American Malleable Cast Iron
necessity to take care of the variations of expansion in annealing
which are not yet entirely under control of the metallurgist.
The film of pearlite just referred to sometimes gives the
misleading impression of hard spots in an otherwise sound
casting. If the finished surface is not concentric with the sur-
face of the rough casting is may be that in only a few places
the lathe tool cut traverses the pearlitic areas which then act as
hard spots. The fact is that this same area of pearlite exists
over the entire surface and had it not been that the eccentricity
in machining threw the cut alternately into ferrite and pearlite,
no trouble would have been encountered.
Fig. 116 illustrates this condition on an exaggerated scale.
Such metal as this, of course, is not of the best quality; the
manufacturer should and does usually remove this pearlitic lay-
er. Howeve'r, attention is called to it here to explain the cause
of complaints sometimes made and to suggest means of using
such metal which is identical internally with a normally an-
nealed product when the pearlite is removed by a cutting tool.
Hard spots in malleable, in the sense of microscopic areas
containing ungraphitized carbon, and scattered irregularly
through the mass of a perfect casting are rare indeed. So rare
is the occurrence that complaints of this fault are found to be
almost always based on erroneous observation. The symmetri-
cal pearlite rim just discussed is the most common cause and
represents not a hard spot at one or two points but a tough
area of little more than microscopic thickness parallel to the
surface throughout.
Shrunken Areas Cause Trouble
Occasionally, also, a defective casting which for- some rea-
son has failed of complete graphitization is soft enough to
machine, though with difficulty. If after most of the machining
is complete, a tool fails on the casting, the machinist is apt to
feel that a hard area has just been encountered. In addition
it occasionally happens that in castings made without suitable
feeder heads, a machining operation may penetrate a shrink.
Such areas always show a bright cut and are mistaken for hard
spots. Cementite in fine granules frequently is present in the
Cleaning and Finishing
257
shrunken areas and dulls the cutting tool if much of the cut
is in the shrink.
If the turning operation which penetrates the shrink is
thread cutting, the threads will crumble away and the metal
may be regarded as defective when the fault is with the feeding
of the individual casting. (Both items are to be controlled by
the foundry but frequently the character of the complaint is
misleading as to the cause of failure. In the case of threading
and reaming operations, it is not uncommon to encounter diffi-
Fig. 117 — (left) — Cementite psrsisting near a shrink. The metal in
porous areas is somewhat oxidized. Fig. 118 — (right)
Hard slag inclusions just below the surface
which may dull cutting tools rapidly
culties with perfectly normal metal. A metal which has been
decarbonized considerably may have the entire thread, especially
if of fine pitch, cut into the pure ferrite rim. Ferrite cuts
freely, but in rather long chips, hence the flutes in dies, taps
or reamers may become clogged and prevent a clean cut. In
work of this character too deep a decarbonization is objection-
able.
An interesting operation other than machine tooling occa-
sionally may be practiced on malleable. This consists of press
fitting and is accomplished by applying sufficient pressure to a
casting to bring it to the desired dimensions and perfection of
surface. To produce reasonable perfect finishes a pressure of
100,000 pounds per square inch is required. The method is
258
American Malleable Cast Iron
Fig. 119 — Malleable casting effectively arc welded with Swedish iron. The changes
A is soft iron but very slightly recarburized from the malleable; B is an
carbon due to
Fig. 120 — Hard iron casting successfully acetylene welded with hard iron and
slag. A is the original casting, B the slag, C the material of weld as noted
of a little pearlitc
Fig. 121— Ineffective hard weld of malleable casting using ingot iron wire and
filler converted into hard iron by migration of carbon from the malleable.
bitic due to recombination of carbon at
Cleaning and Finishing
259
visible microscopically were insufficient to make notable difference in metal. Area
oxide or slag film, and C is the malleable showing but little resolution of
close confinement
then annealed. Note metallurgical homogeneity of casting except for presence of
by larger grain size, and D the material of weld as noted by persistence
due to decarburization
acetylene method. Neither material has its original structure. A is the soft iron
B is the original malleable iron, the background of which has become sor-
temperature the metal reached in welding
260 American Malleable Cast Iron
particularly applicable where relatively small objects have to be
brought to an exact thickness. It is also possible to form
small objects, for example, radiator nipples in press dies. The
method is sometimes preferred where it is desired to retain a
ferrite surface.
Welding Is Limited
Welding of broken or defective castings by the user is of
course subject to the limitations which apply to this operation
when carried on by the producer with the additional difficulty
that reannealing is impracticable. Had the consumer facilities
for the long accurately controlled heat treatments required, he
could of course weld in the same manner as does the malleable
founder. During annealing finished surfaces would suffer and
warping might possibly occur. Under ordinary conditions,
therefore, welding with iron is not to be regarded as practicable
as a repair operation. Thus no repair can be made, irrespective
of the welder's skill, which will restore the original strength of
the casting.
The only resource is to braze, that is, to use bronze as the
welding material. The melting point of bronze is low enough
to permit operating below the critical point for iron hence
if care is used a weld can be made without heating the metal
to a dangerous degree. This, however, involves great skill and
care on the part of the welder. Ordinary brass, Tobin bronze
and Parsons' manganese bronze has been suggested as suitable
for this work. Of course, welds made with nonferrous metals
do not permit of the complete merging into one another of the
metal used as filler with the material being repaired.
They apparently fail invariably by tearing apart between
the iron and bronze, thus the entire strength of either material
is not developed. The strongest welds of this type ever tested
by the writer were made by an expert operator using Parsons'
bronze. These welds developed an adhesion between iron and
bronze of substantially 45,000 pounds per square inch thus
producing a tensile strength of the welded part approximately
equal to the American Society for Testing Materials, specifica-
tions for malleable iron.
The failure occuring entirely along the plane of contact
'Cleaning and Finishing 261
between bronze . and iron produced a failure with only a
negligible elongation, as might be expected. If the circumstances
are such as to permit making a joint similar in form to the
wiped lead joint of the plumber, running the bronze up on the
side of the iron part some distance each way, welds occasionally
can be made with this metal which develop the full strength of
the original metal, elongation excepted. Such welds are seldom
made. A manufacturer of alternating current arc welding
equipment claims that with his apparatus and a nickel filler small
machineable welds can be made in malleable cast iron. The
writer has not yet personally investigated this procedure.
Work of this character can be intrusted only to very skillful
artisans. Unusual care and ability are required to produce me-
chanically perfect welds without even momentary overheating of
the surrounding metal. Theoretically, there should be no rea-
son for preferring electric to acetylene welding or vice versa,
T)ut the writer's observation has been that better work is obtained
with the gas torch. Possibly this observation may be due to
the relative skill of the operators whose work has been observed.
Of straightening operations little can be said here, since
these operations are in general entirely mechanical. Occasionally
there comes to the malleable manufacturer's attention heavy
castings which have been bent in service and straightened in a
blacksmith's fire. Such castings originate more particularly in
the repair shops of railroads. Hot straightening is an extremely
dangerous operation and in general should be avoided by the
consumer since even severe punishment under a heavy hammer
will do the castings less permanent harm than an instantaneous
heating above the lower critical point. The best practice is to
straighten in a screw or hydraulic press.
Must Use Accurate Temperatures
Next to this the use of the lightest hammer blows which
will accomplish the result is to be recommended. Some castings
are of such shape that nothing short of a steam hammer will
do any good. In the absence of properly fitting dies such
a hammer may so mar the casting as to destroy its utility. Un-
der these circumstances hot straightening is an advantage but
-can be executed only under conditions permitting of the use of
262
American Malleable Cast Iron
accurately known and controlled temperatures. Such straight-
ening should be done at temperatures between 1000 and 1100
degrees Fahr. At temperatures below 900 degrees Fahr. the
metal is not sufficiently more ductile than when cold to justify
the heating operation and at temperatures over 1200 degrees,
the danger of accidentally overstepping the critical point is so
great as to be unwarranted. In the absence of pyrometer con-
trol, hot straightening of castings whose failure would cause
loss of life or heavy loss of property is almost criminal.
Application of protective coatings to malleable iron to in-
crease its rust resistance yet remains for consideration. Pro-
jection is obtained by a coating of metallic zinc, applied molten
Fig. 122 — Photomicrograph showing heavy pearlitic rim which may cause
machining difficulties
as in hot dip galvanizing; by a peculiar form of penetration at
temperatures below the melting point of zinc, as in sherardizing ;
and by electroplating as in so-called electrogalvanizing. The
relative merits of the three systems is so much in controversy
that it is hardly within the province of the article to attempt any
decision as between them. It is of course essential to apply
such a coating as will furnish the maximum protection under
service conditions.
The prevalent opinion seems to be that the results of hot
dipping are in this respect superior to the two competitive
processes. On the other hand, the author is informed that a
large consumer of malleable in the form of trolley parts after
exhaustive tests determined to his own satisfaction the superi-
ority of the sherardized coating. Another extensive user of
Cleaning and Finishing
263
malleable, who applied his own coating decided upon the electro-
plating method as being equally satisfactory in service and the
least liable to injure the product to be coated.
Hot galvanizing can and should be done without heating
the metal to be coated above 900 degrees Fahr. Under such
circumstances there is no reason to fear any recombination of
the carbon. Unfortunately, however, there are on record a
number of well established instances in which originally
perfect malleable castings were seriously impaired by galvanizing.
Fig. 123 — (Left) — An effective acetylene weld, malleable becoming sor-
bitic due to resolution of carbon. A is gray iron converted into
white cast iron by remelting. B is malleable. .Fig. 124 —
(Right) — Tobin bronze weld in malleable. Note absence
of oxides and slag in weld and absence of recom-
bination of carbon due to relatively low melting
point of bronze. A is bronze, B is malleable
Such castings are white in fracture and quite brittle. The fault is
believed to arise from careless galvanizing resulting in overheat-
ing of the iron to the point of recombination of the carbon. It
seems questionable whether a zinc bath could be heated commer-
cially to above Ax. W. R. Bean, as a result of extensive in-
vestigation, believes that such . recombination of carbon never
occurs in practice. The writer, and apparently some galvanizers,
feel that although rare, it can not be said that such a recom-
bination is commercially impossible.
However, a very similar variation in quality has been ob-
264 American Malleable Cast Iron
served where it was positively determinable that no such over-
heating has occurred. Indeed, it is sometimes though rarely
observed in tinning where the temperature is never too high.
The cause of this well established fact is still obscure. Attempts
to correlate it with the absorption of hydrogen during pickling,
with heat treatment alone and with the action of the zinc in
alloying with iron have all been inconclusive. One malleable
metallurgist in a preliminary private communication to the au-
thor expressed the belief that similar deterioration was caused
in steel and pure iron but escaped notice since the difference
in the accompanying fractures is less visibly marked than in
malleable castings.
Some experiments with various heat treatments at tempera-
tures far below the critical point would indicate the possibility
that the phenomenon is associated with the grain structure of
the material. How these structural changes are produced or
overcome is still entirely too little understood to permit useful
conclusions as to operating practice. It appears, however, that
these faults are rare in sherardized material and have not been
observed in the electric galvanized product. On the other hand,
hot galvanizing is so generally successful that it may be con-
cluded this operation is not necessarily harmful to the physical
properties of the iron. In the absence of all definite knowledge,
the malleable founder as yet is unable to do anything to assure
the success of the operation nor can it be said that any one
grade of malleable is better adapted to hot galvanizing than
another.
The difference in results is more likely to arise from vari-
ations in the coating process than from the metallurgical char-
acteristics of the castings. Most manufacturers take the ground
that they can assume no responsibility for galvanized material
beyond the delivery of acceptable castings to the galvanizer.
From time to time also tinners and galvanizers think that they
observe differences in the way different lots of castings take the
coating. Occasionally the claim has been made that entire ship-
ments could not be galvanized or tinned, that is, that the coating
Cleaning and Finishing 265
could not be made to adhere. No logical reason for such a phe-
nomenon seemed evident. All malleable castings consist of the
same metallographic ingredients, indeed the surface metal is
in all cases practically pure iron which can be tinned or galvan-
ized successfully.
Careful following up of material complained of for this
reason has disclosed that in no case was the fault with the metal
itself. Cases occur where the castings have not been cleaned
properly and hence do not present suitable surface conditions
for coating. This is at times the fault of improper cleaning
after annealing and also occasionally due to the formation of a
rust or grease coating while the castings are handled in
the consumer's plant. In some cases also the fault has been
found due to oxidized and dirty zinc or tin baths and to the use
of tinning alloys too impure to give good coatings. A manufac-
turer for "many years producing malleable castings which he
tinned himself in large quantities has assured the writer that
no cases have ever been found where castings would not take
the coating perfectly if proper tinning practice is maintained.
In all that has gone before in this chapter, great stress has
been laid on the necessity of avoiding even momentary heating
of malleable castings above the critical point. If such heating
does occur the carbon instantaneously recombines with iron and
can be caused to separate again only by a slow cooling equiva-
lent to that at completion of the annealing process.
In some few cases advantage is taken of this process to
reharden malleable purposely. The combined carbon content
after reheating is a function of the temperature attained; the
hardness depends on the cooling rate adopted. The result of
course is a metal of entirely different character from malleable
iron, the malleability and ductility being entirely lost and a
new product obtained having some of the general characteris-
tics of hardened tool steel. Unless conditions are accurately
controlled, the properties of the resulting metal may be quite
erratic. To the writer's knowledge, the process has not been
applied to any important work. Case hardening is said to have
266 American Malleable Cast Iron
been applied to malleable, particularly when used for wood
working tools, but the author is unfamiliar with any such
practice. However, he has been assured by a consumer that
quite recently at least two producers still furnished castings for
edged tools.
XIV
INSPECTING AND TESTING
INSPECTION and testing of the finished product falls some-
what naturally into two subdivisions, the examination of the
material as to its metallurgical properties, and the inspection
of the individual castings for perfection of form, etc. The
first examination is made generally on the' basis of a system-
atic control of the works operations without reference to any
particular castings. Insofar as this inspection is conducted by
the manufacturer for his own information, but one satisfactory
system is used.
This system consists as a minimum in the chemical
analysis of every heat, either before or at any rate promptly
after casting and the breaking in tension of at least one test
specimen from each heat. The chemical analyses are of no
interest to the consumer. The permanent recording of a test
from each heat is required by specification A47-19, section lib,
of the American Society for Testing Materials.
The maintenance of a systematic record of chemical
analyses is an almost unavoidable necessity to insure the found-
ryman against making heats which will not pass the specifica-
tions. Since test specimens will not come through the an-
nealing process for 10 to 14 days after casting, they would not
give warning of bad furnace practice in time to prevent the
manufacture of a considerable quantity of bad iron. Some dif-
ference of opinion may exist as to just what constitutes ade-
quate chemical control of the product, but the greatest weight
must be laid of course on the control of those elements most
likely to be subject to dangerous fluctuations.
Color Method Unreliable
Carbon and silicon certainly should be determined in every
heat. The determination of manganese seems urgent in view
of the fact that in air furnace practice this element is oxidized
in considerable amounts. The determination of these three ele-
ments will furnish a check on the mix, or charge, being fed into
268
American Malleable Cast Iron
the furnaces. The fact that in hard iron all the carbon should
be in the combined state has lead some chemists to the poor
practice of determining total carbon by color. Since the ad-
vent of the cheap and rapid direct-combustion methods there re-
mains no excuse for such a practice. The color method cannot
be relied upon to give correct values on high carbon metal and
now survives mainly in consulting laboratories doing cheap
Fig. 125 — Anatytical laboratory in malleable plant
contract work. While occasional expert operators can consist-
ently check the correct values to perhaps less than 0.05 per cent
the author has seen results emanating from supposedly reputable
laboratories as much as 0.50 per cent in error. An expert
observer can guess more closely by inspection of a broken
sprue. Carbon values to be. useful must be within 0.05 per
cent of correct and should be better. This is only possible by
combustion methods. Results by color should be disregarded as
inaccurate.
With good coal and melting stock, sulphur does not vary
much from one heat to the next; with poor fuel, however, a
close control must be kept. It must be remembered that while
Inspecting and Testing 269
considerations of speed usually necessitate sulphur being deter-
mined by evolution, the results on white cast iron seldom are
exact due to the formation of compounds of carbon, hydrogen
and sulphur. Oxidation methods also may fail due to the evolu-
tion of gaseous sulphur compounds. Chrome, in the Aug. 10,
1921 issue of Chemical and Metallurgical Engineering, presented
data on this point. The writer's experience is that evolution
methods seldom give accurate results and may be short 25 per
Fig. 126 — Apparatus for determining carbon
cent of the total sulphur. Oxidation methods executed carefully
give the total sulphur but only at the expense of much time.
The phosphorus content of the metal, in a commercial sense,
can be predicted exactly from the analyses of the stock, there-
fore the attention to this element as required by the finished
product varies inversely as the supe'rvision given the raw ma-
terial. Prudence will dictate the determination of silicon and
usually also that of manganese at least in every carload of pig
iron. The carbon content of pig iron is fairly constant but
must not be neglected entirely. Sulphur and phosphorus being
270 American Malleable Cast Iron
subject to specifications should be watched closely. It seems
hardly necessary to describe in detail the methods of iron
analysis which are applicable to hard and malleable iron. The
procedure of iron analysis is becoming so well standardized
that mere reference to accepted methods will doubtless give
the chemist reader the information he requires without burden-
ing the nonchemical reader with uninteresting data.
Carbon should always be determined by direct combustion
in oxygen, determining the CO2 formed either by direct weigh-
ing in soda lime or preferably by absorption in standard
Ba(OH)2 solution and titration of the excess alkali with stand-
ard HC1.
Solutions in which 1 cubic centimeter =^0.10 per cent on a
1.0000 gram sample are convenient. It is sometimes an ad-
vantage to add to the sample about 1 gram of carbon-free iron
before burning to secure better combustion. The use of CuO
or of platinum black to complete the oxidation is superfluous.
Silicon is invariably determined by a modification of
Brown's method substituting a mixture of HNO3, HC1 and
H2SO4 for Drown's method of solution. The major precaution
is to bake well till SO3 no long comes off to render SiO2
insoluble.
For manganese the persulphate method of Walters is com-
mon, finishing the determination either by color or arsenite titra-
tion. It is well to destroy "combined carbon," that is, the
colored nitro compounds produced in the reaction of cementite,
with HNO3 by oxidation with persulphate before adding any
silver solution.
Phosphorus may best be determined by solution in HNO3 ;
oxidation, in solution, with KMnO4; precipitation as "phospho-
molybdate"; and finishing by alkali titration, all in the usual
manner. Where very few determinations are to be made direct
weighing of the "yellow precipitate" in Gooch crucibles is con-
venient.
Evolution sulphurs are made in the usual way. Rapid
solution in rather concentrated acid tends toward complete
conversion of S into H2S. It is also a valuable precaution to
heat the weighed sample for one hour under graphite and
Inspecting and Testing 271
allow to cool slowly before dissolving. The graphite must be
sulphur free. The writer prefers KIo3 to iodine as a titrating
solution.
If the oxidation method is used, concentrated acid and slow
.solution in a capacious and well covered vessel are desirable.
This should be followed by evaporation and subsequent bak-
ing for one hour at not over 400 degrees Fahr. Precipitation
is made in a cold solution not exceeding 100 cubic centimeters
in volume containing besides the 5-gram sample 6 cubic centi-
meters of concentrated HC1 using 10 per cent BaQ2 solution.
The solution and filtrate should stand one or two days to allow
the latter to crystallize. In view of the length of the process care
must be used to avoid contamination by the laboratory atmos-
phere.
Supervise Sulphur Content
Aside from economic considerations sound metallurgical
practice would dictate a supervision over the sulphur content of
the fuel. Taking into consideration the commercial variations
in fuel, stock and furnace operations, a minimum standard for
good laboratory control will include the determination of car-
bon, silicon and manganese in each heat, silicon and manganese
in each car of pig iron, sulphur in all fuel taking an average
sample from each group of 5 to 15 cars where coal is delivered
in large shipments, and occasional determinations of sulphur
and phosphorus in the product.
Extending the work to include sulphur in each heat and
carload of iron, and phosphorus and carbon in each car of
pig iron sometimes may be well repaid. The analysis of scrap
material usually is not of value since no means exists for ob-
taining a true sample. Analytical investigation of steel scrap
suspected of containing unusual elements is sometimes justified
when buying scrap direct from the producer.
Determination of the tensile properties of one bar from
each heat already has been referred to. The best type of works
control to insure uniformity of metallurgical quality will in-
clude a permanent automatic record of all annealing oven
temperatures. The progressive manufacturer will further avail
himself of microscopic methods in seeking the cause for defec-
272
American Malleable Cast Iron
Fig. 127 — Inverted types of metallographic microscope
Fig. 128 — Detail of inverted type of metallographic microscope (Bausch
& Lomb)
Inspecting and Testing 27 Z
tive material. Methods of metallography yield much valuable
information relative to the cause of any failures when these
are due to mischances in heat treatment.
The metallographic characteristics of hard and malleable
iron already have been discussed in connection with the metal-
lurgy of the product. Extended discussion here would amount
to little more than needless repetition. Messrs. Bean, Highright-
er and Davenport presented in a paper before the American
Foundrymen's association in 1920 an extended description of
"Fractures of Microstructures of American Malleable Cast
Iron," showing some 40 illustrations mainly of typical micro-
structures. The interested metallographer may well consult
the original publication.
The technique of the microscopy of these materials is in no
respect unusual. Hard iron is rough ground on an emery wheel
polished further upon fine emery cloth and finished upon broad-
cloth charged with rouge. Some operators conduct the inter-
mediate stages of polishing upon broadcloth charged with F. F.
F. emery flour and then upon broadcloth and tripoli. The etch-
ing medium is almost invariably alcoholic picric acid.
Method of Polishing
In polishing malleable care is necessary to prevent undue
deformation of the soft material and the "smudging" of the
temper carbon. Polishing speeds above 600 feet per minute
seem undesirable. The specimen is best flattened by milling or
planing followed by filing and finished as previously indicated.
Suspended alumina has occasionally been used as the polish-
ing medium.
The etching may be with picric acid if pearlite is to be
examined or usually better, especially if grain boundaries are
important, with 10 per cent alcoholic nitric acid. A solution of
nitric acid in amyl alcohol sometimes overcomes a tendency to
stain. Special reagents such as alkaline picrate or Stead's are
occasionally required for particular investigations.
It is well to begin the examination of malleable at 50 or
100 diameters, to obtain an idea of the form and distribution of
temper carbon pearlite, etc. At 200 diameters grain size can
274 American Malleable Cast Iron
conveniently be studied. The identification of solid solutions
may require 500 to 1000 diameters and the finer details such' as
the boundary structures, minute residues of cementite, crystals
of titanium cyanonitride or nitride can be seen only at 1000 to
2000 diameters.
From the manufacturer's viewpoint, inspection and control
of his product in a metallurgical sense involves chemical
analyses of raw materials and finished- castings to insure uni-
formity of product, autographic pyrometer records to insure uni-
formity of heat treatment, systematic testing of tensile specimens
to determine the quality attained and metallographic work to seek
the cause of otherwise unexplainable faulty material. Inspection
for physical properties of the product when conducted by or
for the -consumer best can be made in accordance with the Amer-
ican Society for Testing Materials, specification A47-19, adopted
„ „ I
-12-
Fig. 129 — A. S. T. M. Tension test specimen
Sept. 1, 1919. For completeness these specifications are quoted
in full as follows:
1 — These specifications cover malleable castings for railroad, motor
vehicle, agricultural implement, and general machinery purposes.
I — MANUFACTURE
2 — The castings shall be produced by either the air-furnace, open-
hearth or electric-furnace process.
II — PHYSICAL PROPERTIES AND TESTS
3 — The tension test specimens in Section 5 shall conform to the
following minimum requirements as to tensile properties :
Tensile strength, pound per square inch 45,000
Elongation in 2-inch, per cent 7.5
A — (a) All castings, if of sufficient size, shall have cast thereon test
lugs of a size proportional to the thickness of the casting, but not ex-
ceeding $/& x %-inch in cross-section. On castings which are 24 inches or
over in length, a test lug shall be cast near each end. These test lugs
shall be attached to the casting at such a point that they will not interfere
with the assembling of the castings, and may be broken off by the in-
spector.
(b) If the purchaser or his reperesentative so desires, a casting
may be tested to destruction. Such a casting shall show good, tough
malleable iron.
Inspecting and Testing 275
5 — (a) Tension test specimens shall be of the form and dimensions
shown in Fig. 129. Specimens whose mean diameter at the smallest
section is less than 19/32-inch, will not be accepted for test.
(b) A set of three tension test specimens shall be cast from each
melt, without chills, using heavy risers of sufficient height to secure sound
bars. The specimens shall be suitably marked for identification with the
melt. Each set of specimens so cast shall be placed in some one oven
containing castings to be annealed.
6 — (a) t After annealing, three tension test specimens shall be selected
by the inspector as representing the castings in the oven from which
these specimens are taken.
(b) If the first specimen conforms to the. specified requirements,
or if, in the event of failure of. the first specimen, the second and third
specimens conform to the requirements, the castings in that oven shall be
accepted, except that any casting may be rejected if its test lug shows
that it has not been properly annealed. If either the second or third
specimen fails to conform to the requirements the contents of that
oven shall be rejected.
7 — Any castings rejected for insufficient annealing may be rean-
nealed at once. The reannealed castings shall be inspected and if the
remaining test lugs or castings broken as specimens, show the castings
to be thoroughly annealed, they shall be accepted; if not, they shall be
finally rejected.
Ill — WORKMANSHIP AND FINISH
8 — The castings shall conform substantially to the patterns or draw-
ings furnished by the purchaser, and also to gages which may be specified
in individual cases. The castings shall be made in a workmanlike man-
ner. A variation of ^-inch per foot will be permitted.
9 — The castings shall be free from injurious defects.
IV — MARKING
10 — The manufacturer's identification mark and the pattern numbers
assigned by the purchaser shall be cast on all of sufficient size, in such
positions that they will not interfere with the service of the castings.
V — INSPECTION AND REJECTION
11 — (a) The inspector representing the purchaser shall have free
entry, at all times while work on the contract of the purchaser is being
performed, to all parts of the manufacture's works which concern the
manufacture of the castings ordered. The manufacturer shall afford
the inspector, free of cost, all reasonable facilities to satisfy him that the
castings are being furnished in accordance with these specifications. All
tests and inspection shall be made at the place of manufacture prior to
shipment, unless otherwise specified, and shall be so conducted as not to
interfere unnecessarily with the operation of the works.
(b) The manufacturer shall be required to keep a record of each
melt from which castings are produced, showing tensile strength and
elongation of test specimens cast from such melts. These records shall
be available and shown to the inspector whenever required.
12 — Castings which show injurious defects subsequent to their accept-
ance at the manufacturer's works may be rejected, and, if rejected, shall
be replaced by the manufacturer free of cost to the purchaser.
These specifications contain a number of points which
perhaps may be subject to criticism, nevertheless representing
276 American Malleable Cast Iron
as they do the consensus of opinion of a committee acting for
all interested parties and having the approval of a large body
of able engineering specialists, the specifications* may be con-
sidered the best practicable solution of the problem of inspec-
tion of malleable.
The specifications further have the approval of the Ameri-
can Foundrymen's association and of the American Malleable
Castings association. Therefore, it would seem to the best in-
terests of all that this specification, together with its further
authorized versions, should be adopted by all producers and
consumers as a universal guide to quality. Any attempt to modi-
fy or adapt it to supposed special conditions as a rule will be
? ' "
o i " * &
? ' "
3
*-t
£• 1
3J
1
1
|D.a.
ft
2
i"
Fig. 130 — Dimensions of proposed tension test bar
productive of intolerable confusion and secure no compensating
advantage. The benefits of standardization will be lost and the
resulting specification, not having the foundation of mature
consideration by many minds is likely to be less satisfactory than
the standard. If in any special case it is agreed by buyer and
seller that it is to their mutual interest to waive the specifica-
tions, of course no objections can be made to that course
provided the understanding is clear to both parties.
It will be seen that inspection by means of test lugs is prov-
ided for in the specification. This is a valuable check on the
^Revisions in the specifications quoted on pages 274 and 275 were
adopted as tentative at the 1922 meeting of the A. S. T. M. Section 3,
is tentatively changed to read :
"The tension test specimens specified in section 5 shall conform to the following
minimum requirements as to tensile properties :
Tensile strength, pounds per square inch 50,000
Elongation in 2-inch, per cent 10.0
In Section 6 (b}. the following sentence is added:
"In case one of the retest specimens contains a flaw which results in the
failure of the bar to meet the specifications, at the discretion of the inspector
additional test specimens from the same oven may be tested, or test specimens may
be cut from castings."
It is further recommended that the standard test specimen be modified
to conform to the dimensions shown in Fig. 130.
Inspecting and Testing 277
quality of individual castings. Test lugs are projections in the
form of a frustum, of a rectangular pyramid, or of a cone which
are broken off by the works inspector or by the consumer to
determine the quality of the metal in the casting. The size of
these test lugs depends upon the size and thickness of the cast-
ings to which they are attached. Thus it is impracticable to
lay down definite rules for their size, form and location. In
general, lugs should be applied to all castings where quality is
important. Pieces weighing less than 3 pounds or heavier of
thin cross section are usually too small to permit of putting on
a lug and breaking it off without damage to the casting.
The round test lug is much affected in appearance by
shrinks and is quite deceptive at times. The author's preference
is for rectangular test lugs in which the smaller dimension at the
point of fracture is ^4-inch less than the layer. Generally the
height of a test lug should be about equal to the larger dimen-
sion at the point of fracture, and the taper about 1/32 to
1/16-inch per 1 inch on each side.
Useful sizes of lugs are specified as follows :
Dimensions at Dimensions
breaking point at top Height
in inches in inches in
Class of work Length Width Length Width inches
Very heavy sections 1^4 -inch thick
and over -K ^ H Jz -K
Intermediate 5/g ^ -ft •& y&
Light castings up to ^-inch thick.. TS ~fs Yz Y$> . A
Test lugs, to represent the metal properly, must be free
from shrinks; hence in general should be located in the drag
of the mold. In inspecting castings by test lugs, care should
be used that the lug is not bent in opposite directions to break
it off. The practice of nicking lugs with a chisel before break-
ing also interferes with a correct interpretation of the result.
Under such circumstances the lug breaks off "shorter," that is,
shows less toughness than it should.
Three factors must be given consideration in determining
the quality of a casting from test lug inspection. These items
are the effort required to break off the lug, the distortion it
sustains before breaking, and the appearance of the resulting
278
American Malleable Cast Iron
fracture. While the effort cannot be measured and recorded
in figures, after a time it becomes simple to compare different
results fairly accurately. In general the hammer should not
be so heavy as to break off a good lug with one or two blows.
A fair idea of the energy consumed can be formed from the
number of blows required to produce fracture.
The amount of distortion in breaking usually increases
with the blows required to do the breaking. Test lugs should
Fig. 131— A 200,000-pound Olsen universal testing machine
bend out of line materially before fracture. All conditions be-
ing equal, small test lugs will bend further than large ones. On
small work where small lugs may be unavoidable, they will often
hammer over flat before breaking. On heavy lugs a displace-
ment of 30 degrees will indicate very good material. The inter-
mediate and smaller sizes listed in the table may bend some-
what more, even up to 60 degrees. Distortion is greater when
the break is made by frequent light blows than by a few heavy
Inspecting and Testing
279
blows. Striking the lug alternately on opposite sides of course
will produce no distortion and hence is valueless.
The fracture of normal malleable iron, in the absence of
much compression, is of a velvety black appearance, having a
mouse gray rim of fair depth. Occasionally two bands are ob-
served, the outer one being somewhat lighter than the inner.
The outer rim in such cases, however, is never steely in ap-
pearance. In bending the lug over, the concave side is of course
considerably compressed and this compression so distorts the
crystal structure of the ferrite as to materially alter its appear-
Pig. 132 — Ewing-type extensometer for determining elongation under load
ance. Toward the concave side of such a lug the fracture will
be silver white in color and rather fine in grain, that is, not
coarsely crystalline. This structure may occupy half or even
more of the entire fracture. However, a band free from any
steely rim and of normal appearance will always be found
toward the convex side.
.When the so-called "compression fracture" is but slightly
developed, danger exists for mistaking it for a rim unless it is
280
American Malleable Cast Iron
observed that the white edge is along one boundary of the frac-
ture only instead. of uniformly around it. Lugs broken by being
struck on opposite sides may show this compression edge on the
two opposite boundaries and may be difficult of interpretation.
.They may even be clear white.
'- Occasionally fractures are encountered which have a so-
called "picture frame" rim or ''shuck." This is a rim, usually
•of crystalline appearance, completely surrounding the fracture as
Fig. 133 — Olsen-type. torsion testing machine
a band of uniform width. If the rim is narrow, the material
may be strong and will bend fairly well. Such rims usually con-
tain pearlite and the resulting metal is not readily machinable.
Where machining is no object, a reasonably narrow edge of this
character need not condemn the product if the lug withstood
punishment well. Where machining is involved, the inspector
should use discretion in taking any material with edges in order
to exclude this condition.
Entirely white fractures somewhat rarely occur. These may
be due to an anneal so incomplete that the original hard iron
Inspecting and Testing
281
Fie;. 134 — Leeds & Northrup Co. apparatus for determining critical
points by Roberts Austens method
structure is but slightly altered, in which case the castings should
be returned for reannealing. Occasionally the fracture is com-
posed entirely of steely brilliant facets surrounded by a narrow
rim of a more gray color. Such iron is useless from the Ameri-
can viewpoint, being that normal to white heart malleable. It
is due to radical faults of chemical composition and cannot be
saved by any ordinary reannealing.
A further type of white fracture sometimes met with
Fig. 135 — Apparatus for measuring magnetic properties of metal
282
American Malleable Cast Iron
resembles in color and texture the compression fracture men-
tioned before but extends over the entire fracture. Such lugs
usually bend but litlte though they are decidedly tougher than
those defective on account of an incomplete anneal. This ma-
terial is normal under the microscope and contains no combined
carbon. The fault lies with the crystalline structure of the fer-
rite and can be remedied by suitable further heat treatment.
A coarse black center surrounded by a slate-colored rim
accompanies weak lugs and is characteristic of poor, high carbon
material. Considerable experience is necessary to interpret ab-
normal fractures properly. Indeed, those who pretend off hand
and from inspection alone to solve all problems as to quality
of material and causes of failure, usually overestimate their own
abilities.
In many cases all the resources of a chemical and metal -
lographic laboratory are required to diagnose troubles. Since
the consumer's inspector is not interested in the cause of trou-
Fig. 136 — Farmer fatigue testing machine
Inspecting and Testing
283
Fig. 1.37 — Charpy hammer for impact tests
bles he may be guided in the acceptance of material by the
following considerations :
1. — Deformation of the lugs must be up to standard.
2. — Bending should require a fair degree of effort.
3. — Irrespective of the fracture, reject all material in which
the lugs snap off sharply.
4. — Irrespective of a fracture, accept any material in
which the lug has sustained much more than average punish-
ment as a result of which indications are rendered worthless due
to the heavy distortion.
5. — Where machining is to be done, reject any castings
which have more than a paper thin rim.
6. — Where machining is no object, accept castings with a
wide steely edge only if the performance of 'the lug under pun-
ishment is unquestionable.
7. — Reject all castings having a coarse structure and the
slate colored rim. Such lugs generally are defective with respect
to the first three tests also.
8. — Return for annealing all condemned castings in which
the fracture is partially or entirely silver or steely in color.
284
American Malleable Cast Iron
It may be well also for the inspector to assure himself of
the absence of injurious shrinkage by breaking hard or annealed
castings from time to time and by watching the fracture of
heavy unannealed castings for the presence of primary graphite
f 1
Fig. 138 — Brinell hardness tester
"mottles." Both shrinks and mottles are found preferentially in
the last cooling sections.
Occasionally questions are raised as to inspection for vari-
ous purposes after arrival of the product at the consumer's plant.
Except in very exceptional cases, inspection and condemnation
of entire lots on the basis of faults observed on individual pieces
cannot be resorted to fairly. As the average malleable found-
ry is operated, it is quite possible that no two castings in a
Inspecting and Testing 285
given sack, or barrel, are representative of the same heat in
the melting department and oven in annealing.
The fact that in an impartially drawn sample a certain small
number of defective pieces are, or are not found proves nothing
as to the remaining pieces. Therefore, only an inspection piece
by piece is equitable after the castings can no longer be identified
with certain specific lots made in the foundry. The test lug
inspection was devised for this very purpose. Upon occasion
the problem has arisen of selecting from a large and indiscrim-
inate mass of castings those too hard to machine.
Brinell and Shore tests are useless for the purpose unless
the material is practically unannealed. Some inspectors feel
that the behavior under a preliminary drilling operation is suit-
able as a means of weeding out hard castings. Others have used
the ring of the casting, that is, the pitch of its musical note
when struck. However, none of these methods are as cheap, as
simple, or as conclusive as the breaking of a test lug.
Occasionally it is desired to inspect the finished or semifin-
ished article to make sure of its fitness for the intended loads.
Where the maximum loads do not require a proof load beyond
the yield point of the article, the application of such a load is
an ideal test. Thus a link belt can be loaded in tension to about
the yield point and defects which would result in failure under-
service conditions can be discovered.
Castings which are straightened after a material deforma-
tion receive of course a test similar in principle to such a proof
test. It is therefore hardly necessary to deal with them here in
any detail. Inspection of castings as to their being true to size
and form, etc., has not been discussed but this is done by the
usual methods of gaging and is not different from similar inspec-
tion on any other product.
XV
TENSILE PROPERTIES
TENSION is the simplest stress which can be applied to a
material. The ease of execution ,of this form of loading has
made tensile tests a favorite means of judging the quality
of a metal even though relatively few structural details are sub-
jected to pure tension in service. When an elastic material is
stretched it first lengthens in exact proportion to the applied
load, in other words, it follows Hook's law of the proportionalit/
of stress to strain. Beyond a certain definite loading the stretch
increases more rapidly than the applied load. The point where
this occurs, beyond which the material no longer obeys Hook's
law, is always referred to as the proportional limit.
In many materials the increasing rate of 'Stretch is at first
so slight as to escape detection by any but the most sensitive
of measuring instruments. As more and more load is applied a
point is usually readied, however, where the material begins to
elongate very rapidly with practically no increase in the load
applied. This load is called the yield point and is more easily
recognized than defined. The term elastic limit, frequently used
and also frequently misused, signifies that stress up to which the
material is not permanently deformed. In other words, a
material may be loaded to any amount up to, its elastic limit and
when the load is removed will return to exactly its original
length. This test is seldom employed. Like the proportional limit,
the elastic limit depends largely on the sensitiveness of the
available means of measurement.
Explanation of Terms
Frequently the three points are confused and used as if
they were identical- The proportional limit is necessarily below
the yield point ; how much below depends on the material
288 American Malleable Cast Iron
being tested and the accuracy of the measurements. The elastic
and proportional limits may be considered identical in principle,
but up to the yield point the permanent set, or elongation, might
be so small as to escape recognition.
The reader should remember that by the very definition of
the proportional and elastic limits the apparent location of these
points will vary with the available methods of measurement, the
proportional limit being the largest load the material will sustain
without visible departure from Hook's Law, and the elastic
limit the largest load it will sustain without taking a permanent
set. The greater the precision of the measurement, the lower will
be the stress corresponding to these definitions. Doubt is fre-
quently expressed whether cast metals actually have any propor-
tional limit larger than zero, the thought being that with suf-
ficiently delicate extensometer measurements, the graph would be
a curve from the origin. In view of these facts an attempt to
find the elastic limit by watching the drop of the testing machine
beam will give apparently higher values than determining this
point by the divider method and the divider method will give
materially higher results than the extensometer. The engineer
will therefore require to know how these points have been
determined in making intelligent use of the information.
Action of Metals in Tension
Most ductile materials when loaded in tension beyond the
yield point do not stretch uniformly at all points of their length.
The larger part of the deformation usually occurs quite close to
the point of failure. The specimens accordingly neck in and finally
break at the smallest portion of the necks. The per cent of elonga-
tion is therefore less the longer the gage length in which it is meas-
ured. The difference between the area at the point of fracture and
the original cross-sectional area, expressed in per cent, is called
the reduction in area. A high reduction in area is even more indi-
cative of a very ductile material than a high elongation. The ratio
of stress to strain, below the proportional limit, is known as the
modulus of elasticity- These various constants, proportional
limit, yield point, elongation, reduction in area, modulus of
elasticity, and ultimate strength and the relationships between
them give a very good picture of the behavior of any material
Tensile Properties
289
under static loads. These constants also yield some information
regarding its behavior under dynamic stresses. The application
of each constant is fairly evident. The proportional limit is
useful when the deflection must be temporary and predictable.
The yield point limits the stresses which may be applied with-
50000
40000
b 30000
c.
20000
10000
Curve A' 0
Curve B- 0
Specimen;
Diameter = 0.
Gage length* 5
004
0.0004
0.06
0.0006
0.08
0.0006
0.10
00010
O.IZ
o.oo ie
Unit" Elongation
Fig. 139 — Stress-strain diagram of malleable cast iron in tension
out producing visible 'permanent changes of shape in the mater-
ial. Elongation and reduction of area are indicative of the amount
of distortion a material can stand without fracture. The ultimate
strength measures the load that can be sustained without failure,
although with permanent deformation. The modulus of elasticity
serves to determine the elastic deflection under relatively small
loads. The behavior of a material under tension is most con-
veniently expressed by means of a stress-strain diagram, in
which the elongation in per cent in some definite gage length is
plotted against the increasing load in pounds per square inch.
Fig. 139 shows a graph of this kind somewhat typical of malle-
290 American Malleable Cast Iron
able cast iron. The various constants are marked in the graph in
the appropriate places. The curve is made from a malleable
casting about the tensile strength .prescribed by the A. S. T. M.
specifications.
Malleable iron of higher tensile strength would have the
proportional limit, elastic limit, and yield point raised very
closely in the same proportion as the tensile strength increased. In
other words, fhe proportional limit would always be about one-
third of the ultimate strength and the yield point as measured
by extensometer about six-tenths the ultimate strength. The
yield point determined by the divider method will be about two-
thirds of the ultimate strength.
The tensile strength of malleable cast iron, as measured in
a test specimen of specified form and dimensions s'hould be
45,000 pounds per square inch and its elongation in 2 inches
7l/2 per cent according to the 1919 specincatioins of the American
Society for Testing Materials. The specimen is to be of the
form and dimensions shown in Fig. 129. The apparent tensile
strength of this, as of any other cast product, is affected by the
gating of the castings forming the test specimen. This is not
due to any effect on the properties of the metal as such, but
on the degree of soundness wlhich is secured in the casting.
Obviously, to give representative results it is necessary to take
such precautions as may insure the freedom of the specimen
from shrinkage.
Specimens Must Be Representative
The point seems worthy of discussion in this chapter be-
cause criticism and confusion often arise when specimens cut
from castings or parts of castings do not conform in properties
to the American Society for Testing Materials specimens from
the same heat. The discrepancy frequently is due mainly to inter-
nal defects of the castings from which specimens are taken.
Failure of 'such specimens to pass the test indicates im-
properly fed castings ratiher than weak metal. The tensile
strength and elongation of malleable as made today by the lead-
ing manufacturers exceed the American Society for Test-
ing Materials specification by a safe margin, the metal now
Tensile Properties
291
sold by reputable makers rarely being under 48,000 pounds per
square inch' in tensile strength and 10 per cent in elongation.
The product probably averages about 51,000 pounds ultimate
strength and 12 per cent elongation.
The tensile strength and elongation of daily specimens
submitted by all of the more than 60 members of the American
Malleable Castings association have been averaged by months
and the results plotted as shown in Fig. 140. The recent data
average better than the author's personal estimate.
Occasional record performances have been noted. The
highest grade malleable known to the writer was a single piece
having a strength of 58,000 pounds per square inch, and an
elongation of 34 per cent. A strength of 64,000 pounds coupled
with an elongation of 18 per cent was once noted. These were
single isolated cases and in no sense typical of a routine product.
One plant produced castings over 57,000 pounds ultimate
strength and 20 per cent elongation continuously for about a
month.
As might be expected from its microstructure, the tensile
strength of malleable cast iron is largely dependent upon its
carbon content, since the more carbon the greater the interrup-
tion to the mechanical continuity of the casting. This applies
rather to the original carbon content than to that after anneal.
Carbon once liberated has accomplished its destruction of con-
tinuity and even if it can be removed after formation, it leaves
behind the hole it occupied.
Furthermore, the other elements present besides carbon
may affect the physical properties of the ferrite just as they affect
Fig. 140 — Tensile strength and elongation plotted from specimens
submitted by members of American Malleable
Castings Association
292 American Malleable Cast Iron
the properties of a dead soft steel. This, however, is of less
practical importance than the variations due to carbon, since
within 'the limits capable of commercial annealing none of the
other dements are likely to have an effect of the order of
magnitude of those due to the latter element. The writer in the
past has had occasion to make comparisons of the tensile proper-
ties of many thousands of 'heats with their chemical composi-
tions. As a rule investigations of this character are influenced by
so many variables that a summary which is strictly accurate as
well as fairly simple is hardly possible, save at the expense of
space for detailed technical explanation which could be spared
only in a monograph upon that one subject.
Increased Carbon Lowers Strength
In general it may be said that an increase in carbon always
carries with it a decrease in strength and elongation. The de-
crease in strength per unit increase in carbon is greater the
greater the total amount of carbon and the higher the silicon-
Manganese and sulphur when present in correct relative
proportion and within anything resembling commercial limits
have relatively little effect. Phosphorus up to about 0.20 or 0.25
per cent strengthens the metal without decreasing its ductility.
The considerations just /outlined would seem to furnish a
basis for a graphical or tabular summary of the relation be-
tween tensile strength and chemical composition. The great dif-
ficulty is that even though the effect of each element may be
well established, there remain variables due to the form of test
specimen, the soundness of the specimen and the effect of the
previous thermal history on the physical and grain structure of
the ferrite.
Accordingly the presentation of such a summary might be
misleading to the interested user of malleable and would serve
:no useful purpose as a guide to specifications or to successful
practice, unless the other variables could also be successfully
defined and prescribed. As a guide to the general order of
magnitude of the effect of carbon and silicon on normal
malleable iron, Fig. 141 shows the average tensile strength of
malleable of varying carbon content but of constant silicon as
Tensile Properties
293
averaged from a large number of heats. An increase of 0.01 per
cent silicon decreases the tensile strength about 20 pounds per
square inch for low-carbon iron (about 2.25 per cent), and
about 75 pounds per square inch high-carbon iron (about 3.25
per cent). From these data it would seem that a simple arith-
metical calculation should show what the strength of malleable
54000
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235 £.40 £45 £.50 £.55 I.
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5il
icoi
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t
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43000
Fig. 141 — Effect of carbon on tensile properties of malleable iron
cast iron in pounds per square inch measured in the American
Society for Testing Materials test specimen should be for any
given composition.
Any attempt, however, to apply these figures literally is
not likely to be productive of results, since the formula is purely
an empirical one and since no account is taken of some of the
other variables, notably of the effect of heat treatment in the
properties of ferrite.
Malleable iron, when completely annealed, stands alone
among the ferrous materials in that variations of composition
294 American Malleable Cast Iron
affect the elongation in the same direction as the strength.
That is, malleable cast iron has a higher elongation the greater
its strength.
The reader should not lose sight of the fact that what has
just been said concerning the proportionality of tensile strength
and elongation is only true of completely graphitized 'products.
For many years and up to relatively recently misguided
efforts were made by ill-informed or careless manufacturers
to produce a metal of great strength by using a chemical com-
position or heat treatment calculated to produce incomplete de-
composition of the combined carbon. The resulting metal is, of
course, stronger than good malleable cast iron, since the matrix
is more or less pearlitic instead of pure ferrite; and also since
less temper carbon is formed by the amount remaining combined
in the matrix. However, the relative lack of ductility of the
pearlite, interrupted as it is in addition by temper carbon, ac-
counts for the lack of elongation shown by material of this
character. The elongation may fall as low as 2 per cent in such
cases-
High Strength May Be Deceptive
Material in which a strength approaching or exceeding 60,-
000 pounds per square inch is observed, without a correspond-
ingly good elongation (at least up to the average or preferably
as high as 12 per cent or 15 per cent) should be looked on with
grave suspicion as not being the product of well controlled
malleable practice.
Each circle in Fig. 142 shows a group of heats of a given
analysis, the different circles representing different analysis.
They are located according to the strength and elongation of
the resulting product. It is plainly evident that increasing
strength is accompanied by higher elongation. This graph fur-
nishes some basis for conclusions as to the effect of chemical
compositions on elongations by demonstrating the approximate
proportionality of f the two properties. An exception has been
noted in that while silicon slightly decreases tensile strength
and hence should decrease elongation, the reverse is true for
very low silicons, especially in the presence of low carbons. The
Tensile Properties
295.
departure may perhaps be explained in the light of minor inter-
ferences with complete graphitization.
The tensile strength of malleable iron further varies with
the cross-^sectional area of the piece under ; consideration. This
phenomenon is not due to the long-exploded thought that the;
strength of malleable iron its only in the skin. This thought
persisted from the days when malleable iron was made;
JWUU
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Elprrcjation in 2 in T percent
Fig. 142 — Relation between tensile strength and elongation of mal-
leable cast iron
"malleable" by decarburization only, as is the case with the so-
called "white heart" product of Europe.
The skin of normal American or black heart nfalleable dif-
fers only in degree from the center. W. R. Bean* gave figures
indicating that specimens from the same heats tested in their
condition as cast and after machining off at least 1-16 inch, and
sometimes % inch of the surface, had practically the same
strength. Tests made by the writer indicate that on 'sections 'up
to one inch in diameter, after machining, the ultimate strength
*Piaper -presented at the annuad meeting of American Society for
Testing Materials, 1919.
296
American Malleable Cast Iron
8000
7000
"I 6000
ISOOG
f-4000
^ 3000
c
Jzooo
1000
0
0
^ o - ro ^ ^
Percent j
Not
?. Data Plotted are the Difference -
v<?w Constants for Rough Specimens
1 Constants for Turned Specimens. —
^^
2si
beh
1
%s
'-
^i
%\
%s
~^T^
^v
^6
^v
Z^feg,
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Sw
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Diameter as Tested, »n.
Fig. 143 — Comparison of tensile properties of machined and cast
specimens of equal diameters
of bars with the original skin is about 4000 pounds per square
inch higher than on bars from which the skin has been turned.
The value given varies with the size of the specimen, as shown
graphically in Fig. 143.
The yield point is not affected measurably by turning off
the surface. The elongation, however, is materially affected,
being decreased 3 or 4 per cent by the removal 'of the surface.
In the case of thin sections, turning off the surface reduces the
reduction of area 5 or 6 per cent and in extremely thin speci-
mens considerably more. It will be seen that these differences,
although not by any means negligble, are not of an order of
magnitude to warrant the conclusion that the properties of the
surface metal are all that gives malleable cast iron its value.
The difference in unit strength between large and small cross
sections may be due to either of three general reasons. The
large specimen may not be so molded and poured as to be free
from shrink. This difficulty usually can be avoided in castings by
proper feeders, unless the casting be of especially intricate de-
sign. In test specimens this remedy can always be applied because
in this case commercial molding restrictions affecting produc-
tion never apply. Even when this difficulty is entirely overcome
Tensile Properties 297
there remain two other variables which always prevent a large
section from having the same strength in pounds per square
inch possessed by a small one of the same metal.
Both of these variations arise from the cooling rate of the
casting. The rate of cooling of the casting in the molds affects
the final product by its effect on the formation of primary
graphite and by its effect on the grain structure in the hard iron.
The former difficulty is easily suppressed by making the
chemical composition such that no graphite will form on freez-
ing, even when the cooling is as slow as any to be expected. Even
when it is completely overcome, as is usually the case, the effect
on grain structure persists. The size of the ferrite grains in
malleable in a large measure is determined by the graphitizing
heat treatment, although perhaps not to the exclusion of the
freezing conditions. However the size and distribution of the
temper carbon nodules is largely an expression of the concensus
of fineness of the original dendritic structure of the hard iron.
Iron alloys in crystallizing while freezing obey the same
laws as do all other crystalline solids in that slowly growing
crystals are larger whereas quickly formed crystals are small.
Consequently a large casting always has a coarser structure
than a small one made of the same metal and to a slight extent
the surface of any casting will be of finer grain than the center.
These differences are carried over into the annealed product
since the form and distribution of the cementite will more or less
affect the distribution of the ferrite and temper carbon into
which it breaks up, hence the quickly cooled casting will have
finer and more uniformly distributed grains of free carbon than
one cooled more slowly. Fig. 144 shows the strength and elonga-
tion of specimens varying in diameter from % to 1.5 inches.
A further word of caution may be necessary. It has just
been explained that of the same metal a small specimen is
stronger than a large one. It is quite possible, at least within
limits, to produce a metal of any desired strength in any given
section even if that section be large. Thus castings having a
cross section 4l/2 x 9 inches have been produced experimentally
with the material at the center having properties conforming to
298
American Malleable Cast Iron
55000
50000
e
Or
? 45 000
&
40000
35000
Diameter, in., as Cast.
Fig. 144 — Results of tests on specimens not machined
the American Society for Testing Materials requirements. Re-
duction of airea is not frequently determined on malleable cast
iron since the material is tested without machining. The im-
possibility of determining the area of a comparatively rough
specimen before testing precludes the determination of this
constant under standard conditions. Occasionally the author has
determined this constant for specimens ground truly cylindrical
before annealing. The following table give's an idea of w'hat
. Tensile Properties 299
may be expected when the specimens are a'bout ^ inch in
diameter.
Ultimate strength in Per icemt of -elonlgation Reduction in area
pounds per square indhi in 2 iniches in per oent
51,600 21 18
51,500 20 17
55,200 19 18
55,100 13 20
55,200 17 23
In malleable cast iron, as in other materials, the reduction in
area decreases as the diameter of the specimen increases. It is
a general principle that the reduction is greater the fewer grains
of iron are contained in the cross section.
In a certain series of tests on a given metal the following
results were observed:
Diameter Reduction in area
indies per cent
*/4 28
M 20
*A 18
M 14
Castings Not in Tension
In engineering design malleable castings are seldom sub-
jected to pure tension. Loads in cross bending, compression
and in shear are much more common. Indeed, where tension is
applied to malleable castings the load usually is transmitted to
the casting by screwing the latter into a nut or similar detail.
Typical cases are malleable eyebolts in turnbuckles. Although
the -shank of the bolt may be in tension, consideration must also
be given to the shearing strength of the threads where
strength calculations are requisite. Unless the design of
such bolt-like details is such that the threaded end has
an outside diameter sufficiently larger than the shank's diameter
so that the area at the root of the thread exceeds that of the
cross section of the cylindrical body of the bolt a further com-
plication enters.
This complication is not limited to malleable castings, but
is common to all structural materials. Nevertheless, it is not
300
American Malleable Cast Iron
infrequently overlooked. Tensile properties are measured on
test specimens usually cylindrical, but at any rate of as nearly
uniform cross section as can be produced. So measured, they do
accurately define the material. However, if the form of the
actual structural detail is such that the area of minimum cross
section is decidedly less than the maximum and is localized in a
relatively short portion of the axial length of the detail, the
Fig. 145 — V groove in bar
loading conditions are not comparable to those obtaining in the
testing ma/chine.
Thus if a cylindrical bar has a sharp V groove turned into
it as illustrated in Fig. 145, fracture will take place in the area at
the root of the groove. However, there will be no significant
elongation of the piece as a whole, for if the total carrying
capacity of the section at A- A at the smallest part of the
bar is not such that when distributed over the area
of the body of the bair at B, an intensity of loading
above the yfeld point is obtained, the piece will tear apart at A-A
without any deformation to each -side of the groove. Even if
the area A-A is sufficiently near that at B so that the body
is stressed beyond the yield point the intensity of stress at B
must be less than in A-A and an inspection of the stress strain
diagram will show the localization of stretch to be expected due
Tensile Properties
301
to the rapid increase in rate of deformation at the higher stress
intensities.
Furthermore the minimum area of cross section apparently
receives some support from the much larger areas immediatel}r
adjacent. The net result of both phenomena is that a grooved
specimen shows an abnormally low elongation and high strength,
as calculated on the basis of the area of fracture.
1
Fig. 146 — Necked specimens of pure iron (left) and malleable (right)
This condition exists in all bolts in which the thread is not
cut on an upset end. The magnitude of the departure from the
results wihich would be expected from tension tests is shown in
the following comparison. Pairs of malleable test specimens of
the American Society for Testing Materials taken from each of
six heats were annealed together. One specimen of each pair
was broken, the other had a sharp V thread turned into it, 20
threads per one inch, to produce a diameter at the root of the
thread of 0.505 inch. These specimens were then broken, the
elongation being measured in the threaded portion of the bar.
302 American Malleable Cast Iron
The standard specimens showed a tensile strength of 52,080
pounds per square inch and an elongation of 15 per cent, and the
threaded specimens a strength of 60,130 pounds per square inch
and an elongation of 6^2 per cent. Therefore, in the design of
threaded members a calculation based on the normal ultimate
strength distributed over the area at the root of a thread will
give very safe results. Such threaded details, however, will not
elongate and inferentially will have their resistance to longitu-
dinal dynamic tension loads much reduced.
XVI
COMPRESSION, CROSS BENDING AND SHEAR
COMPRESSION is exactly the reverse of tension and is
a stress often applied to malleable cast iron. In the
absence of free carbon, in products such as steel and
wrought iron, the elastic properties in compression are very
nearly the same as those in tension. In cast iron the resistance
to compression is considerably higher than that to tension, as
may be expected from the fact that the graphite flakes com-
pletely enclosed in iron are less harmful under compression loads
than under tension.
Difficulty With Ductile Metals
Ordinary cast iron specimens fail in compression by shatter-
ing into fragments, usually with but little bulging at the
center. It therefore is possible to determine definitely the ulti-
mate strength of a given specimen. The ductile metals, soft
steel for instance, are not so definite in their behavior. Instead
of reaching a load where they fail completely by shearing on
planes at 45 degrees to the direction of applied stress or by
rupturing into fragments and ceasing to sustain any load, these
ductile metals merely flow as the load is applied and never reach
a point of complete rupture. Thus a cylindrical specimen of
steel takes a barrel-shaped form, increasing in diameter and de-
creasing in length. The increased diameter reduces the in-
tensity of the applied stress and more load therefore can be
applied. No actual point of failure can be established, but there
is a limit beyond which distortion of a commercial detail would
be equivalent to failure.
Malleable least iron, being capable of .great plastic deforma-
tion, behaves in this manner under compression, as indicated in
the two stress strain diagrams in Fig. 147. Curve B in this dia-
gram indicates the behavior of the same material but not the
304
American Malleable Cast Iron
same specimen from which the diagram, Fig. 142, was charted.
It will be seen that no definite point of failure can be found
up to a load of 90,000 pounds per square inch. The permissible
100 000
80000
f
If, 60 000
f
*
1
cMOOOO
i
i/j
'E
o
20000
0
Curve AJ (
Curve B:
12000
10000 ^
3
O
c
I*
8000 b
a.
£
8
£
i/5
6000 |
4000
7
_
Specimen
A:
Diameteri-**
Height: /"
^x
'^ o
•f
x
^
X
7
/
X
/
/
Mod
E-?
u/usoft
2000001.
'lastich
llb.persq
y J
in. 7
o
/
/
/
f
i
f
D
/
J
Specimen
B:
Area • Bsq.in,
Height: 1334 in.
I
/
f
1
/
) 0.04 0.08 0.12 0.16
0.0004 0.0006 0.000ft
— Unit Compression. —
Fig. 147 — Stress 'Strain diagram of malleable cast iron in compression.
The apparent deflection of 0.00043 at 0 load, Curve B, represents lost
motion in the machine.
intensity of compressive stress depends therefore on the per-
manent set which can be tolerated. The graph readily permits
of the selection of the load corresponding to any assumed con-
dition of this kind. Note the general similarity of the elastic
constants in tension and compression. The proportional limit is
15,000 pounds per square inch in tension and somewhere above
13,000 pounds per square inch in compression. The modulus of
elasticity in tension is 25,000,000 pounds per square inch as
Compression, Cross Bending and Shear
305
compared with 22,000,000 pounds per square inch in (compres-
sion. Therefore the material behaves in a manner very similar
to soft steel under the two systems of loading.
Stresses More Complex
The foregoing applies only to pure compression loads,
which exists only in specimens in which the height is not much
greater than the diameter. In longer columns it is practically
impossible to keep the axis of the specimen exactly in line with
the direction of load; the column springs out of line and the
stresses become more complex. Tests on columns with fixed
ends 5/8-inch in diameter and 10.6 inches high indicated that up
to the proportional limit the modulus of elastidty is about
I!
Fig. 148 — Malleable (center) and cast iron (right) in compression.
Each specimen before testing was of the size and shape
shown at the left
16,000,000 pounds per square inch. The fact that this figure is
materially less than that obtained in pure compression would
seem to indicate that even below the proportional limit the stress
is not a purely concentric compressive one. ' In this column a
very definite failure at 30,000 pounds per square inch was ob-
served.
Stresses in Columns
The yield point is quite definitely marked at 25,000 pounds
per square inch. Insufficient data are at hand to warrant the
definite acceptance of any special column formula for malleable
cast iron. The columns tested have a ratio of length to diam-
eter of about 17 and therefore are more slender than the average
column in actual usf Hence calculations based on an ultimate
306 American Malleable Cast Iron
strength of 25,000 pounds per square inch for strut details
should be amply safe.
A well known formula for cast iron columns with safety
factor of 6 is:
13,333 x area of column
Safe load=
(column length)2
266 x (diameter of column)*
This formula is equivalent to the statement that the ultimate
strength for cast iron columns is equal to
80,000 pounds per square inch
i U* '
1 + —
266
The ultimate strength of the malleable columns tested was
30,000 pounds per square inch, the ratio L/D being 17. If a
malleable column is subject to the same general laws as a gray
iron column then to conform to the observed conditions the ulti-
mate strength of a malleable column will be
62,000 pounds per square inch
LV
266 [D
This formula applied to the specimens tested in pure com-
pression would give a breaking load of nearly 62,000 pounds per
square inch at which figure the material was still carrying load
but had badly deformed.
On the basis of a safety factor of 6 on which the formulas
were, developed the safe crushing strength of malleable comes
out 10,300 pounds per square inch, which is well below the
proportional limit.
It is the writer's opinion that the foregoing formula can be
safely used as a basis of design. The safety factor could
probably be reduced readily to 5 and possibly to 4 without
serious risk. For hollow cylinders Kidder uses the value 1-400
instead of 1-266 in the above formula; 1-500 for a rectangle
and 1-135 for an equal armed cross. In any case D is the least
diameter of the column section.
Compression, Cross Bending and Shear 307
When the material is used in the form of a beam, it is sub-
ject to cross bending stresses. This type of loading is very
common in practice and is readily reproduced in a testing
machine. The specifications of the American Society for Test-
ing Materials before 1918 and of the United States railway
administration provided for cross bending test results about
equivalent to a modulus of rupture or apparent maximum fiber
stress of 64,000 pounds per square inch. This value is decidedly
too low to correspond to the required tensile strength. The
modulus of rupture seems to be about twice the ultimate tensile
strength of the product, the proportional limit corresponding
to a fiber stress about equal to the ultimate strength in tension.
While not absolutely exact quantitatively, the foregoing state-
ments do express the general relationship. Thus a specimen
cast from metal having a tensile strength of about 51,000 pounds
per square inch, showed a proportional limit of 50,500 pounds
per square inch, a yield point of 72,000 pounds per square inch
and a modulus of rupture of 113,000 pounds per square inch.
The specimen was rectangular in cross section, ^-inch deep, 1
inch wide and 12 inches long between supports. The constants
on specimens of different form might be somewhat different.
Stresses in Cross Bending
It is interesting to discuss why the modulus of rupture can
be higher than either the tensile or compression strength of
the material. When a specimen is bent there is a tendency to
compress the material on one side and to stretch it on the other.
Somewhere between there is a so-called neutral axis where there
is no change of length. In material in which the elastic be-
havior in tension and compression is the same the neutral axis
is midway across the section. The surface fibers of the speci-
men are strained most under such a condition, the compression
or stretch decreasing uniformly as the neutral axis is approached.
As long as the material is perfectly elastic the intensity of stress,
being proportional to intensity of strain, also varies uniformly
each way from the neutral axis. Accordingly the material be-
haves as a perfectly elastic body as long as the outer fiber is not
loaded beyond the proportional limit. However, after that load-
ing is passed part of the specimen is subject to plastic de-
308
American Malleable Cast Iron
Fig. 149 — Diagram of stresses in cross bending of malleable iron
formation. The intensity of stress then no longer varies uni-
formly from O at the neutral axis to a maximum at the top and
bottom of the cross-section, but there is a band of 'considerable
width next to the upper and lower boundaries of the cross-
section in which the stress is fairly uniform. It is only below
this area, where the stress is below the proportional limit,
that the uniform decrease is observed.
The stress in the outer fibers is then not so great as would
be calculated, since the permanent deformation of the specimen
has transmitted some of the stress from the outer fiber to those
further in. Therefore the modulus of rupture is a purely the-
oretical value not corresponding to any stress actually occurring
in the specimen. It is merely the extreme fiber stress which
would be produced at the breaking load if the material be-
haved as an elastic solid up to the breaking point.
In Fig. 149 the stresses in a beam are indicated in diagra-
inatic form. In a beam of depth xx; having its neutral axis O ,
compression stress is measured to the right from xx and tension
to the left. The proportional limit assumed to be the same
Compression, Cross Bending and Shear 309
under either stress is shown by y and 3,'. Loads which do not
stress the beam above the proportional limit produce a distribii"
tion of stresses within the beam as shown byAOA. If the load
is sufficient to produce plastic deformation the stresses may be
as indicated by Bbob'B' , which is straight only between b and
br. If OC is drawn so that the area XOC equals the area
ObB, the C marks the modulus of rupture if Bbob'B' corres-
ponds to the load when failure occurs.
Value Unexpectedly High
In the cross-bending tests a load of 700 pounds at the
center of a 12-inch span produced in a l/2 x 1-inch beam a de-
flection of 0.076 inch at the proportional limit. Up to this
point the deflection of the beam has been elastic, hence tlie
value of the modulus of elasticity can be readily calculated.
Letting W be the load = 700 pounds
X — deflection at center = .076 inches
L = span of beam = 12 inches
b = width of beam = 1 inch
d = depth of beam = ^ inch
W L3
E= — — =31,800,000-{-pounds per square inch
x4bd3
The value is unexpectedly high both as compared with fig-
ures for the tension and compression experiments, and as com-
pared with the value for steel, which is about 29,000,000 pounds
per square inch. It is barely possible that the error is due
to slight errors in the uniformity of d in the above formula.
Furthermore the proportional limit and cognate elastic constants
are . necessarily somewhat obscured in a beam specimen owing
to the fact that a relatively small portion only of the beam is
subjected to maximum stress. Only metal near the surface and
in the plane of maximum bending moment actually is sub-
jected to maximum strain, hence the observations are largely
influenced by the behavior of the much larger mass of metal
subjected to a much lower intensity of stress. It is probable
therefore that the elastic constants will be apparently too high
in specimens of. such form that a considerable amount of material
is located close to the neutral axis. The departure of the ap-
parent elastic properties in cross bending from those determined
310 American Malleable Cast Iron
in tension will be greater the greater the ratio of the area of
cross section of the beam to its moment of inertia of that area
about the neutral axis. For purposes of calculation a conserva-
tive value probably would be below 29,000,000 and possibly as
low as 25,000,000 pounds per square inch to conform to the
tensile results for the modulus of elasticity.
Shear and Torsion
Shear and torsion are the two remaining static stresses to
be considered. They are closely related with one another and
Disp/Qcemenf of P/anes
by Tors/onal Shear.
D/'sp/Qcemeni- of P/anes
by L/near Shear
Fig. 150 — Displacement of planes by linear shear and (at right) by
torsional shear
involve the sliding of the metal on itself, the slip taking place
along a series of planes within the material. Shear involves a
linear diplacement, while in torsion the displacement is angu-
lar. Rivets, bolts or pins are subject to shear when an attempt
is made to slide the parts they hold together in a direction at
right angles to the axis of the pin. It also is the shearing
strength of a material which resists the punching or cutting
in a die in a pun'ch press. A knowledge of the shearing strength
of malleable therefore is important both in the design of the
shackle pins and similar details and in the selection of punch
presses to be used in fabricating the product. Determinations
made by driving a punch of known diameter through a plate
of known thickness and measuring the force exerted in a testing
Compression, Cross Bending and Shear
311
machine have shown the shearing strength of malleable to be
about 45,000 pounds per square inch. Similar experiments made
by shearing off a cylindrical pin (double shear) gave values on
the same metal of a little more than 41,000 pounds per square
28000
Yield Point Z3000to.persq.in.
Proportional Limit
14000 Ib.persq. in.
Specimens;
Diameter —--O."90
Gage Length— 5"
0.002
0.004- 0.006 O.OOS 0.010 0.012 0.014
Unit Shearing Strain in Extreme Fiber.
Fig. 151 — Stress strain diagram of malleable cast iron in torsion
inch. The first mentioned experiments probably are the more
trustworthy. The experiments were made on metal having a
probable tensile strength of 50,000 to 52,000 pounds per square
inch. Therefore the shearing strength apparently is about 15 or
20 per cent less than the tensile strength of the product.
In the case of elements in a design subject to twisting loads
there is a tendency to shear — not by a sliding motion of the
planes within a solid — but by a rotating a'ction, one plane over
312
American Malleable Cast Iron
another as shown in Fig. 150. Evidently the action is of exactly
the same character in both cases. A twisting load is measured
by the product of the force applied and its distance from the
axis of rotation. This product is called the moment -of the
force about the axis of rotation, or more briefly the torque, and
is measured usually in inch pounds. An inch pound is the
moment of a force of one pound applied one inch from the
Fig. 152 — Diagram showing factors to be considered in determining
torsion stresses
axis of the specimen. When a shaft is twisted the metal is
evidently deformed or strained more at the surface than at the
center, the strain being proportional to the distance from the
axis. As long as the metal obeys Hook's law of the propor-
tionality of stress to strain — that is, as long as it is not stressed
beyond the proportional limit — the stress also is proportional to
the distance from the tenter and mathematical analysis will de-
fine the moment of torsional resistance of a section of given
geometric form in terms of the dimensions of the cross section
and of the shearing stress in the outside fiber.
The condition is similar in character to that existing under
cross-bending stresses. When the intensity of stress in the
outside fiber passes the proportional limit a mathematical analysis
of the load condition is no longer possible, since the distribu-
Compression, Cross Bending and Shear 313
tion of stress is no longer proportional to the distribution of
strain. The modulus of rupture in shear or the apparent stress
in the extreme fiber when breaking occurs is higher than the
true value, since these layers stressed above the proportional
limit carry a stress more nearly equal than their distance from
the axis of rotation would indicate.
Fig. 151 shows a stress strain diagram of the behavior of the
material in torsion. The load is recorded in terms of intensity
of shearing stress in pounds per square inch. This is calculated
from the known dimensions of the specimen and the measured
torque. The intensity of shearing strain is determined in terms
of the ratio of the linear displacement of a point on the surface
to the gage length. If within a gage length of 5 inches a given
load has produced a twist such that a point on the surface has
advanced .07 inch the shearing strain is .07/5=.014. In other
words, the intensity of shearing strain is measured by the tangent
of the angle * through which an originally straight element of
the cylindrical surface is displaced. Thus in Fig. 151, if W is the
load and D its distance from the center, the torque is WB.
S is the stress in the outer fiber, L the gage length of the
specimen, F in linear measure is the displacement of the point
by twisting under the torque WD from its original position, A
to A'. The intensity of the shearing strain is F/L, the value of F
being determined from the known radius of the specimen R
and the angle e, through which one end of the gage length
has been twisted with respe'ct to the other.
R
e (in radians) being — •
F
if e is in degrees. The value of S is computed from the couple
WD and the moment of inertia of the circle of radius R about
its center on the supposition that the stress increases uniformly
from the center to circumference,
2WD
this giving S== -- .
TR3
It will be seen from Fig. 151 that the proportional limits and
314 American Malleable Cast Iron
yield points are not very different from those in tension and
compression. The shearing modulus of elasticity, however, is
not the same as Young's modulus. The course of the curve
during plastic deformation is riot very instructive, since it is
considerably influenced by the testing speed. The preceding dis-
cussion summarizes the available information with regard to
the resistance of malleable cast iron to the various well known
forms of static loading.
XVII
FATIGUE, IMPACT, HARDNESS AND WEAR
THUS far only static loads have been considered in the
discussion of the mechanical properties of malleable cast
iron. There are many industrial applications of castings
in which the structural detail, instead of merely sustaining a
steady load of some specific character, is subjected to blows,
shock, or repeated reversals of the applied stress. Unfortunate-
ly, our knowledge of the principles underlying the behavior of a
material under dynamic stress still is imperfect. A great deal
of experimental work of this character has been done and the
results published but no method is as yet available for systema-
tically correlating the data and deriving general principles.
In general the energy of rupture of a given specimen and
material can be calculated from its stress strain diagram, the
area below the graph representing the product of stress and
strain measuring the energy, in foot pounds, for example. The
specimen may absorb this amount of kinetic energy from an im-
pact or other dynamic stress. This however, does not tell the
entire story for the possibility of a time factor enters. Assume
that the impact is due to a weight moving with a given velocity.
The specimen absorbs energy from the weight by retarding, and
ultimately stopping its motion. Energy is measured as a prod-
uct of mass and therefore acceleration in the energy absorbed
by the specimen is measured by the product of the mass of
the weight and its (negative) acceleration when being stopped
by the weight. If we have means of knowing the maximum
rate of retardation while the weight is being stopped, we
M
can calculate the maximum stress as being — and where M
G
is the mass of the hammer; A, its maximum retardation and
G, the acceleration due to gravity. Obviously this value cannot
be greater than the ultimate strength of the specimen without
producing failure.
316 American Malleable Cast Iron
Dynamic Stresses in Two Groups
Two groups of dynamic stresses may be recognized.
One of these results from impact or blows.' In general such
stresses are in one direction only and usually are of considerable
intensity. They may be applied axially, either in tension or com-
pression to 'the detail involved, or may be applied to a cantilever
beam or to one supported at both ends. Occasionally the load-
ing is even more complex.
The other group of stresses results from repeated, usually
rapid, reversals of stress, sometimes of small magnitude, and
usually through an extended period of time. The stresses in a
rotating shaft acting also as a beam are of this character, as
are also the stresses in the leaves of an automobile spring,
those in the couplers of a train while in motion, and those
resulting from vibration.
In the former group a mathematical analysis of the service
conditions is almost impossible. The material usually is stressed
beyond its elastic limit by each blow so that it is impossible
to determine the stress distribution within the metal. The energy
absorbed by a given specimen before breaking is frequently
less if the energy be delivered by a single impact than if deliv-
ered by a series of equal smaller impacts whose
sum is equal to the energy of the single impact required
for fracture. If fracture takes place under a series of
blows the energy absorbed depends on whether the successive
blows are of the same intensity or increase in intensity with
each succeeding blow. The subject will be discussed more fully
in the next chapter.
Thus it is seen that practically no two cases are alike
in practice and that the problem is so complex as to prevent
generalization from the results of different groups of tests by
mathematical analysis.
Therefore it is impossible to furnish quantitative data
to be used as a basis of computation for mechanical details
subject .to impact.
The comparison of the behavior of several materials under
impact is easier since the tests of all can be made under the
same circumstances and on geometrically similar specimens.
Fatigue, Impact Hardness and Wear 317
To avoid the complication resulting from -the cumulative effect
of repeated stresses each insufficient to produce failure, the
experiment usually is designed to break the specimen at the
first blow and to measure the energy absorbed in breaking by
taking the difference in -the kinetic energy of the system be-
fore and after failure. The tests so made on various types
of machines do not give comparable data; the results differ
with the design of the hammer, the shape of the specimen
and its manner of support.
It is said that on the Charpy machine, which takes a speci-
men 10 millimeters square by 53.3 millimeters long, with a
45-degree V notch 3 millimeters deep at the center, about 7l/2
foot pounds are absorbed in breaking a specimen of normal
malleable cast iron. On similar specimens except that the notch
is made by a thin saw cut running into a hole 1 millimeter in
diameter, 7l/2 to 8^2 foot pounds of energy usually produce
rupture in tests in the author's laboratory. On the Olsen ma-
chine breaking a round cantilever specimen with a 45-degree V
notch 0.122 inch deep 1.10 inches from one end and with the
notch clamped even with the vice jaws holding the specimen and
the hammer striking 0.625 inch above the notch, the indicated
energy absorption in breaking is 13 foot pounds.
Testing Tensile Impact Stresses
Impact tests may also be made in tension- In such cases
the test is made on a screw-end tensile piece, one end of which
screws into the hammer of the Oharpy machine. The other end
of the specimen carries a yoke which strikes a fixed portion of
the frame of the machine just as the hammer is at the lowest
point of its travel. The dimensions are so chosen that the
energy of the hammer is sufficient to rupture the piece.
Evidently, for a given material the energy to produce
rupture varies as the cross sectional area and as the length
of the specimen. Upon the area depends the resistance of the
material to tensile loads, and the length is a factor, since ob-
viously twice as much work is done in stretching a piece two
inches long a given percentage of its length as in stretching a
piece one inch long an equal percentage.
318 American Malleable Cast Iron
Speaking more technically, the expression for work is
fs where / is the force exerted and .? is 'the distance through
which the hammer moves while the specimen is breaking. If
a is the area of the specimen, E its elongation and / its
length, and if t is its ultimate tensile strength:
f = Kta
s = El
fs = Kta El = KtEv
where K is a constant depending upon the form of the stress
strain diagram and v the volume of the specimen equal to a I.
The resistance to tensile impact is thus to be expressed
not in pounds per square inch of section but in foot pounds
per cubic inch of metal deformed.
It is noteworthy that while in static tension a defect op-
erates to reduce the strength rather less than in proportion
to its area and the elongation considerably, in dynamic test-
ing practically absolute soundness of specimen is required. If
a notch or shrink exists sufficiently large to so far reduce
the area as to localize the stretch wiithiii its own length the
gage length upon which the work is expended becomes only
the axial length of the shrink. This may be only 10 per cent or
even only 1 per cent -of the apparent gage length and the foot
pounds absorbed if calculated on the intended gage length
would be only 10 or 1 per cent, respectively, of the correct
values. Care must further be used to see that the specimen
increases in size immediately beyond the gage length. Any
stretch outside the gage length erroneously credits additional
energy to the specimen.
Sound specimens of good malleable iron 0.1 square inch
in area and 2 inches long showed results as follows when
tested :
Energy •df rupture Elongation
(foot pounds iper (per cent an
cubic inidh) 2 imdh-es)
755 15
640
999 20
930
The relation between resistance to dynamic tension and
elongation is plainly 'Shown and is still more plainly visible
Fatigue, Impact Hardness and Wear
319
by examining -the following tests on good malleable containing
small shrinks.
Energy of iruiptuire
(ifioiolt (pounds per
icu'bic indh)
102
115
345
Elongation
(per 'cent in
2 inic'hes)
The graph in Fig. 153 which summarizes these data indicates
the almost direct proportionality of elongation and resistance
to tensile impact even when the former is artificially affected
by mechanical defects.
1000
900
JC
OflflO
^^
*
^
.*
^
couo
o700
"S
3«»
km
tnAQO
lm
0
^ZOQ
100
;
»^
.*
^
^~
S
^
^
^
^
^
s*
^
^
*
^
5 t
3 10 15 20
Per Cent Elonqation
Fig. 153. — Effect of elongation of specimen on the resistance to dynamic
tensile loads
The presence of temper carbon nodules operates just like
any other mechanical discontinuity. Accordingly it is almost im-
possible to obtain consistent results in tensile impact from mal-
leable. All the results doubtless are lower than the correct value
and since they are far from concordant their practical interpre-
tation is doubtful. At best the test is poorly suited to so hetero-
geneous a material.
From 'the energy of rupture, the measured elongation and
the known dimensions of the specimen we can calculate a
modulus of rupture as the average intensity of tensile • stress in
pounds per square inch developed during rupture of the ma-
terial. Disregarding the very small elastic deformation which
320 American Malleable Cast Iron
has disappeared when the permanent elongation is measured
we can proceed in the light of the previous formulas to solve
the equation:
fs = KtEv
for K t, the modulus of rupture. The values of js, corre-
sponding to given value of /, are shown in the preceding tables
on the basis of v being unity.
The average value of Kt on the four sound specimens
previously quoted was 58,600 pounds per square inch, the three
imperfect ones showing in order 3500, 4700, and 5500 pounds
per square inch.
Unfortunately the static tensile properties of the material
were not actually determined. From the stress strain curve
shown in Fig. 139 in Chapter XV, we may derive an
approximation of the value of K. The average abscissa (stress
ordinate) of that graph is about 0.88 times the stress
art rupture. Using K as 0.14 we can calculate t in the ex-
pression
Kt — 58,600 pounds per square inch
with the result that t has an approximate value of 66,600
pounds per square inch.
While the data are both too few and too inaccurate for
definite conclusion there is a presumption at least that in ten-
sion the material fails under impact at materially higher stresses
than under static loads but that the elongation is not greatly
different in the two conditions.
The effect of velocity of impact on maximum stress is
among the most interesting but least understood phenomena
in the utilization of materials. It is hoped that work in pre-
paration under the author's direction will be productive of
more accurate and useful conclusions.
A number of tests have been devised in which repeated
impact is applied. Such tests must be closely standardized
as to the form of specimen and the energy of the blow. The
amount by which the stresses set up by a single blow exceed
the yield point greatly affects the results of the tests.
Any variable in design or material which affects the yield point
Fatigue, Impact Hardness and Wear
321
of the specimen as a whole therefore profoundly alters the re-
sult of such a test.
A dynamic test developed especially for application to mal-
leable iron was devised at the general suggestion of the late B.
J. Walker and is sometimes known by his name. In this test
a wedge specimen 6 inches long by 1 inch wide, tapering from
J/2 to 1-16 'inch thick is used. The specimen is set on its
thicker end on the anvil of a drop hammer and subjected to
Fig. 154. — Walker test wedges
blows of 70 foot pounds. The first blow is struck straight
down on the point of the wedge, curling it over, and for each
succeeding blow the specimen must be held so that
the point which will be struck by the hammer is
directly over the point of support. This is a difficult
requirement to fulfill and the test, while measuring a very
useful property, is almost incapable of quantitative reproduc-
tion and is accordingly of only slight interest to the consumer.
A normal malleable is supposed to survive 20 blows (ag-
gregating 1400 foot pounds) in this test and to break not
more than 1% inches from the thick end of the wedge. A
better mechanical execution of this test possibly would yield
322
American Malleable Cast Iron
Fig. 155. — Behavior of malleable iron under fatigue as a rotating beam
results of value and has been studied by the writer for some
time.
The writer has been informed that tests by the Humphrey
static notched bar method yield valuable data as to brittleness
but has not personally investigated the matter.
Tests can readily be made under dynamic stresses of the
second type, involving repeated reversals of direction under
rather small loads. Machines of the Upton Lewis type,
especially when equipped for alternate torsion, are valuable for
this purpose, particularly when considerable intensity of stress
is desired. Machines of the Wohler, Whiter Souther, or Far-
mer-type apply well to the repetition of smaller stresses existing
in rotating specimens subjected to bending.
W. W. Flagle in the author's laboratory has determined the
relation between maximum fiber stress and life of a typical
malleable, using the Farmer-type machine. The results of his
investigation are shown in Fig. 155 in which life is plotted
against stress to a logarithmic scale as suggested by Moore. It
will be seen that the fatigue or endurance limit of malleable is at
25,000 pounds per square inch. Malleable will resist alterations
of stress of this magnitude indefinitely — certainly hundreds of
millions of times. Reference should be made to Moore's data
for similar information on a variety of rolled products.
Prof. H. F. Moore is quoted to the effect that ingot iron
(ferrite) will withstand 100,000,000 repetitions of a stress 1.6
times its proportional limit, as determined in tension. This
would indicate the probable great endurance of the matrix
of malleable.
Fatigue, Impact Hardness and Wear
323
It will be seen that much remains to 'be done in the quan-
titative investigation of the resistance of malleable to fatigue
and to impact. Fortunately, qualitative information of this
character is readily accessible in view of the long continued
application of malleable iron in the industrial arts. The prac-
tical experience which attracted consumers to this product
when searching for a 'shock resisting material and in a period
when methods of tests and metallography were practically un-
known seems to have been well founded.
A logical reason now is available for this quality. Being
largely ferrite, malleable is soft and ductile, as are all other
materials in which ferrite predominates. Wrought iron is a
conspicuous example of such materials; malleable is not as
ductile as wrought iron because of the temper carbon present.
Its resistance to deformation and shock, however, depend upon
this principle.
Malleable lias a further great advantage over many other
materials in that the temper carbon granules, while of a form
to affect the physical properties only to a relatively slight ex-
Fig. 156. — Separation of grains by repeated cross bendings
324 American Malleable Cast Iron
tent, operate as a hindrance to failure under alternating stresses
by fatigue. Such failures frequently occur by the penetration
of a crack 'between adjacent grains of the metal. When such
a crack begins to form in malleable it does not penetrate
far before it strikes one or more carbon granules. These
stop its further progress just as a hole drilled at the end of
a crack in a bell prevents the growth of the crack.
The best evidence available as to the shock resisting quali-
ties of the material are derived from the years of service which
properly made malleable, has given in draft gears, rail anchors,
automobile hubs and spring brackets, car couplers (until high
train loads forced the 'adoption of a material capable of higher
unit stresses), and an indefiniite number of similar applications.
For some kinds of service the fitness of a material for the
use intended may depend not so much upon its strength under
load as upon its machineability, resistance to abrasion, co-
efficient of friction and similar properties.
The property which enables a material to resist cutting or
wear is somewhat loosely called hardness. Unfortunately
this term is not clearly defined and often it is misinterpreted.
Moreover, the commercial methods for measuring hardness in
metals actually measure resistance to penetration under defined
conditions' — a property bearing no practical or theoretical rela-
tion to hardness as understood in 'the definition given above.
Two methods of measuring so called hardness a'fe in com-
mon use- In Brinell's method, hardness is determined by the
depth to which a 10-millimeter ball will penetrate under a
load of 3000 kilograms. In Shore's method, the rebound of a
hammer falling from a fixed height measures, in effect, the
work absorbed by the plastic deformation of the material un-
der a standard load. The results of the Brinell test bear
a fairly close relationship to the ultimate strength of the
material, while the data obtained by the Shore method should
conform to the elastic limit.
The Brinell number of normal malleable cast iron is from
about 101 to 145 and increases as does the tensile strength
with decreasing carbon. Common values are around 110-120.
Fig. 157 shows the relation between the Brinell number and
Fatigue, Impact Hardness and Wear
325
the strength of a wide range of malleable iron. The heavy
line indicates the probable relationship and the shaded area the
limits of variation from the probable value. The scleroscope
number is somewhat erratic, running from about 15 to about 20.
The Shore nurriber actually is surprisingly constant in
malleable of quite variable tensile properties. Some experi-
mental data as to the relation between this hardness number
I
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Fig. 157. — Relation between Brinell number and strength of malleable iron
specimens
and the Brinell number are presented in Fig. 158. The explana-
tion of the approximate constancy of the Shore number is as
follows :
The variation in physical properties of malleable are due
primarily to the ratio of ferrite to temper carbon and not to
variations 'in -the properties of the ferrite. The Shore test
being made on an almost microscopic area determines only the
properties of the ferrite. If by accident a temper carbon
grain is struck no rebound at all is observed- The composition
of the ferrite is not sufficiently variable to alter its physical
properties.
326
American Malleable Cast Iron
Neither of -the hardness numbers bears any particular re-
lation to completeness of anneal. White iron is harder than
malleable so that the effect of annealing is to soften the metal
under both tests. Under commercial conditions, however, an-
nealing is almost never so far from complete that this fact
is of any value in inspecting material. Malleable castings which
are sufficiently annealed to pass any ordinary inspection usually
/v*
/7
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/4
W-
tf/'/sy^'// M&s-t/sy&^s
Fig. \*&. — Graph showing comparison of Brinell and Shore numbers
indicating relation between them is not definite
contain only very small amounts of ungraphitized carbides. The
remaining combined carbon is either found as cementite in very
minute grains scattered throughout the castings or as a thin
layer of pearlite just under the surface.
The former condition would have no effect on the Brinell
hardness and would affect the scleroscope hardness only if
the hammer struck such a grain by accident. The thin sheet
of pearlite does not increase the <,Brinell hardness appreciably,
since the pearlite layer is merely crushed down upon the deeper
material which is soft. The Shore number may be affected by
Fatigue, Impact Hardness and Wear 327
pearl ite if this 'be present at the finished surface of this
sample and if the layers are heavy enough to absorb the im-
pact. Neither of these conditions usually exists for the pear-
lite is originally covered with ferrite and if in producing a
finished flat surface for test any considerable amount of ma-
terial is removed the pearlite layer may be completely de-
stroyed. The point 'has been emphasized by Prof. Touceda
and also by W. R. Bean.
Therefore these tests are not directly applicable to the
commercial valuation of malleable with reference to its cutting
properties. The important considerations in industrial uses of
malleable involve cutting hardness which is undesirable in
fabricating the product in the machine shop, and wearing hard-
ness or resistance to abrasion, which resists the destruction of
a bearing or similar detail where subjected to friction.
These two conditions are different manifestations of near-
ly the same property. Ease of machining and resistance to
wear are incompatible with one another. No direct means of
measuring cutting hardness are known. The hardness of min-
erals is measured by comparison with an arbitrary scale rang-
ing from talc, having a 'hardness designated as V to diamond,
with a hardness of 10. Any given mineral can be rated by
determining between which two numerals its hardness lies.
Thus, pyrite, which scratches feldspar, hardness 6, but is
scratched by quartz, hardness 7, is given an intermediate num-
ber, in this case 6.3. On this 'scale iron has a hardness
of about 4 or 5 and steel a hardness of from 5 to 8.5. This
test besides being very unsensitive can be applied only to the
extreme surface of a metal. In the case of malleable this
always is ferrite, which shows a hardness of 4.
Turner has devised a method based on cutting a line
into the surface of the material. This is done by pressing the
V-shaped nose of a diamond against the metal under a def-
inite pressure. The cross section of the furrow cut, as meas-
ured by the width of the groove, is intended to be the measure
of cutting hardness. This method is applicable only to the sur-
face of an article. Since the surface must be smooth, it is diffi-
cult to apply this test to malleable containing a pearlite layer, as
328 American Malleable Cast Iron
pointed out in the discussion of the Shore hardness. The
test is not used extensively, and the writer knows of no data
obtained from its application to malleable iron-
Similar tests, made by scratching polished samples and
examining the scratch under the microscope indicate that the
hardness of the micro-constituent present in normal hard iron
and malleable iron is in the following order: Ferrite, pearlite,
cementite. Ferrite is soft and cementite nearly as hard as
carborundum, as measured by resistance to scratching.
Study of Cutting of Metals
The principles underlying the machining of metals have
been investigated by a number of experimenters, notably, Nich-
olson, Frederick Taylor and Herbert. The special case of
machining by twist drills has been still more fully investi-
gated— for example, in the engineering experiment station of
the University of Illinios.
While these studies have thrown much light upon the prin-
ciples underlying the cutting of metals and liave served in
some cases, notably in Herbert's experiments, to test the qual-
ity of cutting tools, they were not generally conducted so as
to develop any technique for the testing of a material for
machineability. Accordingly, no method is yet available for
determining how readily an existing structural detail can be
machined. Therefore it is not surprising that there are no
means for quantitatively comparing the machining properties
of malleable cast iron with those of similar materials.
However the fundamental relationships involved are eas-
ily summarized. To the consumer, machineability means the
removal of the required amount of metal in the minimum
of time and with the minlimium of tool destruction. Many
investigations have approached the subject by measuring the
load on the nose of the lathe tool. Nicholson measured this
load parallel to three rectangular co-ordinates — radial, tangential,
and axial — with reference to the revolving specimen and used
only two materials, soft and medium steel. His work resulted
in a mass of data concerning the relation between the cutting
angles of the tool and the direction and magnitude of the
Fatigue, Impact Hardness and Wear 329
resultant forces. He also made a limited number of tests
on *he effect of cutting angles on tool life.
For 'the present purpose his work may be summarized as
having demonstrated that the tangential thrust on the tool
is independent of the cutting speed and that the life of the
tool increases as the cutting angle increases. Taylor in his
monumental monograph "The Art of Cutting Metals," covered
exhaustive investigations on feeds, depth of cut, form of tool,
cutting speed load on the tool point and tool life. He deduced
the fact that the load on the tool point is dependent only
on the area of the chip being removed and the material
being cut and independent of the cutting speed, form of tool,
relation between depth of cut and feed, or any other varia-
ble.
This seems to indicate that the load on the tool point
per unit area of cut is a constant, readily determined for a
given material. This is true, 'but unfortunately the deter-
mination of this constant has no practical use since Taylor
also proved conclusively that no determinable relationship ex-
ists between this constant and tool wear or economical cut-
ting speed.
Herbert has shown from Taylor's data that tool failure re-
sults from the heat evolved in cutting and has deduced a for-
mula for determining the relation between the tool temperature
and feed, cut, and speed. He also has proved that the most
economical tool service corresponds to a definite tempera-
ture which is a function of the tool steel used.
From this it will foe seen that all of the work pre-
viously done has not resulted in conclusions applicable to the
defining of the machineability of a given material in terms
of permissible cutting speeds.
Consumer Wants Cutting Speed
In general the consumer is not interested in the load at
the tool point, since he is quite willing to adopt machine and
tool designs capable of sustaining any loads which may be
developed, providing only -he is informed as to the probable
stress to be encountered. The power consumed in removing
330
American Malleable Cast Iron
the material also is of little interest, since this is not a major
item of expense and can be met by the installation of a suffi-
ciently heavy drive. His chief requirement is a fast cutting
speed with long tool life. Tool life when determined by nor-
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Fig. 159. — Tests of machining properties of malleable cast iron
The curves are plotted from data presented by Edwin K. Smith and
William Barr, Milwaukee, in a paper prepared for the American Found-
rymen's association, 1919.
mal conditions is fixed by the working temperature of the tool,
determined by cutting conditions and the material being ma-
chined. Suitable investigation by Herbert's methods should
yield useful results in the relative rating of different metals,
but the data are not available.
Smith and Barr have attempted to determine the relative
Fatigue, Impact Hardness and Wear 331
machineability of different samples of malleable and to com-
pare the data with that for other materials. Their experiments
were based on the torque required to cut threads into the dif-
ferent samples with two dies taken as standards and also by
measuring the penetration per revolution of a standard drill
under a standard load.
Unfortunately the data are incapable of conversion into
absolute figures. Smith and Barr apparently felt that they had
secured evidence pointing toward the fact that iron high in
tensile strength is relatively difficult to machine. The author
does not feel that this conclusion is necessarily justified by the
observed facts. Fig. 159 shows graphically the results of their in-
vestigations and in the writer's opinion they indicate that the
machineability of normal malleable is within the limit of error
of the data.
However these investigators have accumulated useful data
comparing the resistance to drilling of malleable cast iron, gray
cast iron and steel- Their results indicate that the penetration
of a drill under standard conditions is at the rate of 0.249
inch per minute and 0.196 inch per minute in two specimens
of gray iron; 0.209 to 0.240 inch per minute in 17 samples
of malleable and 0.052 to 0.085 inch per minute in three
samples of steel. This proves the general thesis that malleable
is comparatively easy to machine.
An exhaustive study of all types of machining operations,
using the best equipment known, is in progress under the
writer's direction. In connection with this work, W. W. Flagle
has gathered data as to the load on twist drills of standard form-
when drilling fully annealed malleable.
The investigation included a study of the effect of drill
diameter, feed, -speed and character of metal being cut. The
effect of drill form, of lubricants and the life of drills is
being further investigated.
The work is far too voluminous for presentation in detail
in the present connection and is reserved for publication, in
a more appropriate place. A few of tbe more interesting
conclusions may be abstracted as follows.
332
American Malleable Cast Iron
The torque on a drill, cutting malleable iron varies as
the square of the diameter and approximately directly as the
feed. The thrust varies directly as the feed and approximate-
ly as 'the drill diameter. The effect of speed on torque and
thrust is but small for rates from 40 to 640 revolutions
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Fig. 160. — Graph showing values of a in drilling formula
per minute. Both loads decrease slightly with increasing
speed and are more nearly constant with variations in speed
at high speeds than at low.
Representing by Tv the torque and by Tt the thrust
of a drill of diameter df running at s revolutions per minute
with a feed, /, in a certain uniform iron
and
Tt = bfd
Fatigue, Impact Hardness and Wear
333
in which a and b are constants depending on sf t, and d.
The values of a and b can 'be interpolated from the graphs
in Fig. 160 and 161 respectively.
The drilling properties are further affected by variations
in the character of the metal- The investigation disclosed
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Fig. 161. — Graph showing values of b in drilling formula
that machining stresses were not related to either Brinell num-
ber or strength as effect to cause. However, there is a gen-
eral coincidence between the three properties in completely
annealed malleable.
The data of Figs. 160 and 161 were obtained from malle-
able equivalent to a tensile strength of 52,000 pounds per square
inch and a Brinell number of 120. In Figs. 162 and 163 the
effect of Brinell number and strength on Tv and Tt are plotted
in the form of coefficients for reducing, the previously calcu-
lated values to suit other tensile or hardness properties.
334
American Malleable Cast Iron
The observations in a measure substantiate Smith and
Barr's ideas as to the increased machining difficulty of stronger
metal. Apparently there is a variation of from 25 to 30 pet-
cent in the stresses developed as between the weakest and
strongest malleable.
These variations are not nearly sufficient to bridge the
gap between malleable and even the softest steel.
90
to
LX
Fig. 162. — Correction factor for drill torque and thrust in terms of
ultimate strength
It is again to be emphasized that neither the author's data
nor that of Smith and Barr can be interpreted in terms of
tool life. Furthermore, it must be clearly remembered that the
data were all obtained on completely graphitized material and
that nothing heretofore sajid has any relation whatever to white
edged or white material resulting from mischances in annealing.
The subject has already been referred to in connection with
Fatigue, Impact Hardness and Wear
335
the discussion of Brinell numbers where it was shown that
such mischances do not necessarily influence the hardness test.
They do, however, greatly affect machineability both with re-
spect to tool life and stresses.
The machining difficulties occasionally encountered might
be explained on either of three grounds. First, the material
/.SO
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93
.90
.83
.80
Fig. 163. — Correction factor for drill torque and thrust in terms of
Brinell number
may be so tough 'that the heat developed per unit of time causes
the tool temperature to increase rapidly. The tool fails for per-
fectly normal causes but under much accelerated conditions.
Second, the material may contain particles sufficiently hard to
work as an abrasive and so destroy the cutting edge. Third,
336 American Malleable Cast Iron
the material may set up so heavy a tangential load in the
tool point as to cause it to break off irrespective of the failure
of the cutting edge.
A study of abnormally early tool failures seems to indi-
cate the occurrence of failures of all three types- Since all
malleable cast iron consists only of ferrite and temper carbon
it is difficult to see how any great difference could exist between
different products varying only in the percentage of temper
carbon present. This is all the more true since in general the
cutting is in a region where relatively little carbon remains due
to decarburization in anneal-
In the case of imperfectly 'annealed iron a condition ac-
counting fof any or all these causes of failure may exist.
White cast iron is known to exert very heavy unit stress on the
tool point, hence a metal so imperfectly annealed as to retain
much of its original pearlite-cementite dendritic structure would
set up abnormal tool loads and cause a failure of the third
class.
Material in which cooling 'has been so slow that all pearlite
is graphitized but in which some cementite persists would pro-
duce failures of the second class. Cementite is an exceedingly
hard ingredient, the hardest of any carbon-iron alloy. Its hard-
ness on the mineralogical scale is between 8 and 9, since it
is harder than the hardest steels. In imperfect malleable of
this kind it would be found scattered as granules through the
ferrite. Being present In very small amount only, it could
hardly exert any very great effect on the ferrite mass in
which it is imbedded and therefore is not likely to either in-
crease the tool temperature or the load thereon. The tool edge
however, will encounter those granules lying in the finished
surface and these grains will rapidly wear away the cutting
edge which rubs against them.
Failures of the first class are very largely due to so
called "picture frame" iron in which there remains a consider-
able pearlite layer just under the surface. This layer is identical
in composition and properties with annealed tool steel. As
such the cutting speed will not be great before sufficient heat
is generated to rapidly destroy the tool. Unusually bad cases
Fatigue, Impact Hardness and Wear 337
of this character may also produce failures of the third class.
It should 'be remembered that all normally made malleable
is easily machined, there being minor differences only between
the machineability of malleable of varying composition. When
machining difficulties are encountered the explanation general-
ly is due to failures of execution in individual cases rather
than to the character of the product as a whole.
Resistance to Friction
To all intents and purposes, resistance to frictional wear
obviously is the converse of machineability. Experience seems
to indicate that the most successful bearing metals are those
consisting of fairly soft matrix in which a relative hard con-
stituent is imbedded. The hard constituent takes the wear and
is supported by the soft. Further, the soft constituent wearing
down a little, furnishes the certainty of a supply of lubricant to
the bearing. The soft ingredient is further desirable since if a
grain of abrasive enters the bearing and lodges tightly in
the bearing metal it will >soon cut away the rotating mem-
ber where the latter rubs against it. With a soft bearing metal
the grit will at most cut a groove in the easily replaced bearing
without damage to the shaft.
Since malleable does not contain the hard skeleton or
grain required to promote long life it cannot be regarded as
suitable metal to resist wear. By 'analogy also with gray iron
this conclusion seems warranted. Extremely soft gray irons,
which resemble malleable more closely than those containing
more combined carbon, are inferior to the harder irons as
bearing materials.
Malleable is not a suitable material of construction, where
the major requirement is resistance to wear, as for instance
in journal bearing's.
It will of course resist minor friction incident to other
service. . Under such circumstances, the conditions as to hard-
ness and smoothness of the material rubbing against it is of
prime importance in determining the service to be expected.
Determinations of the coefficient of friction for the metal are
not available. While they would be highly interesting, they
338 American Malleable Cast Iron
are not of great practical application because of the general
unsuitability of malleable for friction service and because under
normal lubricating conditions in machine parts there is not
metallic contact between shaft and bearing. Therefore the
friction losses depend mainly upon the lubricant and not
upon the material of the shaft and its support.
XVIII
PLASTIC DEFORMATION
IN CONSIDERING the behavior of malleable cast iron under
mechanical stress we have noted that like most other materials
its deformation, or strain, under load is of two entirely
distinct characters, depending upon the intensity of the stress.
Under light loads the deformation is elastic; that is, it is pro-
portional to the applied stress and is not permanent, the metal
returning to its original dimensions upon the removal of the load.
At higher stresses the strain increases very rapidly and the spe-
cimen becomes permanently deformed.
This change of form is termed "plastic" deformation as dis-
tinguished from "elastic," and especially characterizes ductile
metals. Much interesting work has been done in the investiga-
tion of the phenomenon of plastic flow, the property by virtue of
which a material is malleable and ductile. The property is
usually measured in terms of yield point, reduction in area and
elongation.
Nutting has developed the thesis that plastic strain may be
expressed as the product of constant and exponential functions
of the stress and time. In other words, the strain is measured
by the expression ASxty where S is stress, t time and A, x and -v
characteristics of the material. Hook's law is a special case of
this formula when x=\ and y==0.
The author has no desire, in the present connection, to at-
tempt any exposition of the theoretical aspects of plastic flow.
However, since malleable cast iron is in quite a marked degree
capable of plastic deformation, and in fact, owes many of its
most valuable properties to this property, it seems well to sum-
marize the effect of plastic deformation on the metal.
Summary of Theory
As has been shown, malleable is in effect a mass of ferrite
made up of individual grains. Each grain is made up of many
crystals all oriented in space in the same direction. The several
340 American Malleable Cast Iron
grains are held together, according to the now generally accept-
ed view, by a thin layer of amorphous (non-crystalline) iron
acting as a cement. This amorphous iron is supposed to be
stronger than the crystalline variety and is supposed to behave
like a very viscous liquid. It is also supposed that crystalline
iron will go over into amorphous iron under heavy stresses.
The behavior of a metal under even the simplest stresses
is as a rule complex. Even when a stress is applied in only
one direction the behavior of the material indicates that com-
plex systems of forces result. While we speak of the elonga-
tion or compression of a metal these terms are in a sense mis-
nomers, since solids are but slightly compressible in the sense
of a decrease in volume or mutatis mutandis capable of elonga-
tion. Metals compressed or lengthened by plastic deforma-
tion do not materially gain or lose bulk. For example a speci-
men compressed until it was only one-fourth its original height
had its density reduced from 7.206 to 7.196 in the process, a
change in the opposite direction to what might be expected.
Behavior of Specimens
The increase or decrease of dimensions parallel to the di-
rection of applied stress is made up by decreases or increases of
cross section in a plane normal to the axis of stress; the tensile
specimen necks in, the compression specimen becomes barrel
shaped.
We note also that plastic materials do not fail in tension or
compression in a plane normal to the stress. The tension speci-
men shows a cup shaped fracture, at least on one side of the
break. The compression specimen tears apart either in a plane
approximately at 45 degrees to the direction of stress, or more
rarely on a conical surface whose axis of symetry coincides with
the direction of load.
From these observations it is evident that there is a consid-
erable motion of translation within the stressed material in di-
rections at right angles to the direction of the applied stress.
This rearrangement may conceivably be of two kinds in a ma-
terial composed of crystalline grains either a deformation of
the individual grain (intragranular) or a separation and
Plastic Deformation 341
rearrangement of the grains at their boundaries (intergranular).
Both phenomena are easily recognized. A deformation of
the grain itself is accomplished by a shearing of the grain along
Fig. 164. — Slip bands in ferrite of malleable iron
Nitric acid etch 1000 diameters
Note that there is but little evidence of any separation at grain boundaries
mtragranular crystal boundaries. Such a slip, if occurring in
a grain in a polished surface, shows a series of parallel lines
on the polished surfate which are fine grooves and ridges in
the originally plane surface.
Fig. 164 shows a micrograph at 1000 diameters of such slip
bands in a ferrite grain in malleable cast iron. Such a deforma-
342
American Malleable Cast Iron
tion, increased in magnitude, may result in the rupture of the
grain itself at right angles to the slip bands, as shown in Fig. 165,
or by producing such a distortion of the grains that it can no
longer articulate with the surrounding grains closely enough to
be held to them by the cement of amorphous iron at the bound-
aries.
Change of Structure When Deformed
On the other hand examination of the originally polished
plane surface of a specimen parallel to the direction of stress
which had failed by primary intergranular fracture would show
Fig. 165. — Intragranular fracture of a ferrite grain in malleable
Nitric acid etch 1000 diameters
Note that the path of rupture has advanced about two-thirds through the
grain at right angles to the slip bands
no slip bands but a considerable displacement of the polished
surfaces of the individual grains from their initial location in
the polished plane provided the failure was due to shear at
the grain boundaries. On the other hand, if failure was due
to forces having a tensile component normal to the grain
boundary, the separation of originally adjacent grains would
be shown.
Where the conditions have been such as to produce fairly
great plastic deformation it may even be possible to note the
effect of intragranular flow in the changed orientation of the
polygons marking the individual grains.
Plastic Deformation
343
In unworked ductile metal there is no preference as to the
direction of the longer diameters of the grains in any given
surface nor are the diameters in various directions widely
different. After plastic deformation however the originally
equi-axed grains may be flattened into sheets, drawn out into
threads, etc., etc., depending upon the character of the stress
and the direction of the stress with reference to the polished
Fig. 166. — Intergranular failure of malleable
Nitric acid etch 400 diameters
Note that the surfaces of the different grains no longer seem to be in the same plane
surface under examination. Of course it is obviously necessary
that such changes of form can be detected best in a plane
parallel to the direction of load and are visible only as changes
of grain size in a plane normal to the deforming stress.
Microscopic examination of the path of rupture through a
metal, of the deformation of grains under load or, when applied
to surfaces prepared before the application of the stresses, of
intragranular slip and intergranular displacements is capable of
344 American Malleable Cast Iron
interesting disclosures as to the mechanism of plastic deforma-
tion or ultimate failure under various types of stress.
Shows Two Systems of Slip Bands
A very cursory summary of the changes in malleable is at-
tempted in the accompanying photomicrographs. .Fig. 166 shows
an unusual failure of intergranular type. It will be seen that
at several points the grains have the appearance of being above
or below the general surface. These grains have slipped not
Fig. 167. — Ferrite grains in malleable, showing slip in two planes at right
angles
Nitric acid etch 400 diameters
Note the cohesion at grain boundaries even after severe plastic deformation
on the crystal faces within the grains but at the surface of
contact of adjacent grains. The field of view is near the com-
pression side of a piece distorted by cross bending and it is pos-
sible that this slip at grain boundaries produces the white so
called compression fracture. The comparative absence of slip
bands is interesting.
Fig. 167 is reproduced from the tension side of the same piece
and shows well developed bands. In some grains two sys-
tems of bands are seen due to slip along two directions. The
fact that the adjacent grains are not separated even under
heavy strain shows the strength and ductility of the amor-
phous boundary.
Fig. 168, taken from a piece loaded in pure compression,
shows that the structure of Fig. 166 is not always characteristic
Plastic Deformation
345
of this type of loading and also shows plainly two systems of
slip bands in practically every grain. In all of these photo-
mi'crographs, note that the direction of slip is constant in any
given grain, but is not usually the same in adjacent grains. The
direction of slip has no direct relation to the direction of the
stress but is determined by the direction of the crystallographic
axis of the ultra microscopic crystals making up the individual
grains.
Figs. 169 and 170 show the distortion of grains in compres-
Fig. 168. — Slip bands due to plastic compression in malleable iron
Nitric acid etch 500 diameters
sion as seen on a polished section parallel to the direction of
stress prepared after the distortion has occurred. The grains
are much flattened as are the nodules of temper carbon. The
grain boundaries are nearly obliterated but there is no separation
of the adjacent grains. The effect is more strongly marked
at the axis of the specimen than near the surface due to the
fact that the barreling out of the specimen has permitted part
of the reduction in height to be made by bending the outer
fibers instead of upsetting them. The specimen from which these
illustrations were made was compressed to a little less, than
one-half of its original height.
The effects of plastic deformation upon the grain structure
can be destroyed by somewhat prolonged heat treatment below
the critical point. By such treatment a new series of equi-axed
346
American Malleable Cast Iron
Fig. 169. — Plastic deformation of malleable in compression
Nitric acid etch 100 diameters
Field near axis of the specimen in a plane parallel to the stress. Note the flattening
of ferrite grains, faint grain boundaries and distortion of temper carbon
grains is formed, whose size depends upon the degree of the
previous plastic deformation and the heat treatment adopted.
Fig. 172 shows an axial section of a specimen similar to that shown
in Fig. 169, after about five hours at 650 degrees Cent. While
the ferrite becomes equi-axed and fine grained the deformation
of the temper carbon still persists.
Path of Rupture Shown
Fig. 171 shows the path of rupture of malleable broken in
cross bending. It was prepared by breaking a wedge-shaped
piece by bending it over until fracture occurred. The fracture
was then plated with copper, the specimen sawed in two at
right angles to the ruptured surface and parallel to the cross
bending stress and the exposed surface polished.
Plastic Deformation
347
Fig. 170. — Same specimen as shown in Fig. 169
Nitric acid etch 100 diameters
Field near surface of specimen in plane parallel to stress. Note the difference from
Fig. 169 in lessened intensity of all changes
It is particularly interesting to note how the path of rupture
goes far out of its way to include temper carbon nodules. This
makes many deep depressions in the broken surface and due to
the shadows in the bottom of these depressions produces the
characteristic black fracture of the product. It is not often
recognized that the presence of temper carbon is not a suffi-
cient explanation of the black fracture -for this material, rep-
resenting about 6 per cent of an average cross section, would
not be nearly sufficient to darken the surrounding silver white
metal.
It is only due to the fact that the plane of rupture takes
in many more nodules of carbon than would be found in an
average section and in so doing produces a ,sort of "nap" that
348
American Malleable Cast Iron
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Plastic Deformation
349
the fracture appears as dark as it does. A fracture running
at random along grain boundaries would be steely and crystalline
in character.
The mechanical effects of plastic deformation offer a most
interesting field of investigation. Most engineers are acquainted
with the effects produced by cold rolling on steel and brass rods
and sheets, and by cold drawing on copper and iron wires ; the
Fig. 172. — Malleable iron compressed about one-half. Annealed 5 hours
at 650 degrees Cent.
hardening is a consequence of the distortion of the metallic
grains.
Beilby's theory suggests that the change in properties is caused
by formation of amorphous iron due to the partial destruction of
the normal crystal structure when this becomes distorted. In
this view the greater the coldwork the more nearly does the ma-
terial as a whole assume the properties of this noncrystalline
iron, Jeffries and Archer have dealt ably with the relation be-
tween slip and hardness in an article appearing on page 1057
350 • American Malleable Cast Iron __
of the June 15, 1921 issue of Chemical and Metallurgical En-
gineering.
For the purpose of the present study we may dismiss from
consideration the more abstruse theoretical considerations and
assume it to be an experimentally determined fact that metal
which has suffered plastic deformation has become permanently
altered as to its physical properties.
As a matter of fact this premise is of far reaching effect.
Although it is becoming more and more usual to base engineer-
ing design upon the elastic limit rather than upon ultimate
strength, still there always remains the possibility that a struc-
tural detail will be subjected, during manufacture or in use, to
stresses which although insufficient to produce rupture will
produce plastic deformation and the accompanying changes in
physical properties.
In utilizing a given specimen of a ductile metal we must
consider not only the normal physical properties of that metal
but its entire previous history with respect to applied stress
and also its subsequent service in so far as that is predictable.
In the case of pure iron chemical means are available for de-
tecting the presence of plastic deformation. The products of
the reaction between nitric acid and unstrained iron differ from
those if the iron has suffered strain. An analysis of the reaction
products thus will permit of conclusions as to the conditions of
the metal. The method has not yet been applied to malleable
owing to the disturbing effect of the residue of graphitic car-
bon.
We might assure ourselves of the absence of cold work by
a heat treatment just, before use but this is impracticable. For
the purpose of the designer and manufacturer we must assume
that the behavior of any ductile material in service involves each
stress applied in its previous history and not single stresses.
It is possible that the entire problem is so complex that a
clear understanding of the effects of sequences of stress is be-
yond our grasp. Four cases can be distinguished:
1. The stresses in the sequence differ neither in character,
Plastic Deformation 351
magnitude or sign. This may be illustrated by a load which is
alternately applied and removed.
2. The stresses do not differ in character or sign, but differ
in magnitude. A load that is constantly applied but varies in
intensity is an example.
3. The stresses do not vary in character but vary in mag-
nitude and algebraic sign. Such a condition could be caused by
alternate compression and tension, crossbending in opposite direc-
tions as in rotating beam test, torque in opposite directions etc.
4. The stresses vary with respect to all three characteristics.
This would be the case if torque were followed or preceded by
tension or compression or if compression in one direction were
followed by tension or compression at right angles thereto, etc.
The ever increasing complexity possible will be readily ob-
served. To this complexity must be added the fact that ac-
cording to Nutting's conclusions the stress under plastic deforma-
tion is a function of the time of application.
A formal study of the entire phenomenon therefore is
scarcely possible by any individual or laboratory; indeed the
vast amount of work which has been done in impact and fatigue
testing has but incompletely studied a small portion of this im-
mense field.
New Data Is Available
It is therefore with humility that the author ventures to
record certain observations, not much better than qualitative in
character, on some of the mechanical effects of plastic deforma-
tion of malleable. According to the Nutting formula the strain
under plastic flow is proportional to a higher power than unity
of the applied stress and to a fractional power of the time of
application.
Up to the proportional limit, the deformation is elastic and
proportional to the stress. The exponent of the stress is unity
and not greater than unity and the strain does not depend upon
time. The exponent of time is zero. The course of the usual
stress strain diagram, in tension, for malleable seems to in-
dicate that, for rather quickly increasing stresses the plastic
deformation of malleable is approximately proportional to the
sixth power of the applied stress. There is a surprisingly
352
/Inter lean Malleable Cast Iron
Slow Is At The Rote Of .0000157 Per Minute
FasMsM Thetfate Of .Ob" Per Minute
.02 .04 .06 .08 .10 .12 .14 .16 .18 .20 .22
fc"0 .0004 .0008 .0012 0016 .0020 .0024 .0028 .0031 .0036 .0040 .0044 .0046
Eionqotion
Fig. 173. — Stress strain diagram .of malleable iron in tension for two
rates of loading
short transition range between the point where the strain is
directly proportional to the stress and the point where it begins
to be proportional to the sixth power.
Stress Exponent Changes
During the transition range the exponent of stress obviously
changes progressively from 1 to 6. To illustrate the effect of
time on plastic deformation two stress strain diagrams are
shown in Fig. 173. In one of these the diagram was made rapidly
as extensometer readings could be taken while in the other each
increment of load was maintained till no further increment of
length was observed. In the former case the time was perhaps
four or five minutes ; in the latter case it was 250 hours.
It is obvious that if quickly loaded, to moderate stress,
the metal will be stiff er than if the stress must be endured in-
definitely. The ultimate strength and elongation are unaffected
however. In Fig. 174 is shown the progress of deformation
Plastic Deformation
353
with time at two intensities of stress, in each case the last 500
pounds increment of load having been applied only after equili-
brium had been attained under the previous load. In Fig. 175
a similar graph is plotted for behavior under a quickly applied
load well above the yield point. Below the proportional limit
no increment of strain with time is observed stress being
constant.
Having thus given concrete examples of the application
of the Nutting hypothesis to this particular metal we may turn
£8,500 Lb5. Per 5o. In.
29,500 Lb5. Per So.
Chances of Strain with Time
at Small Increment of Stress
0 .001 .002, .003 .004 .005 .006 .007 .008 .009 .010 .Oil
Elongation in Inches Over 6"
Fig. 174. — Changes of strain with time at small increment of stress
354
American Malleable Cast Iron*
to the effect of previous tensile stresses to the stress-strain re-
lationships during subsequent stresses of the same character.
It is well known that a material to which a tensile strength
in excess of the elastic limit has been applied, thereafter has
an elastic limit equal to the previous load. The stress-strain
diagram under successive increasing tensile stress is shown in
Fig. 176. It will be seen that up to the proportional limit the
stress leaves no permanent effect. On releasing a stress which
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Fig. 175. — Changes of strain with time under considerable increment of
stress (about 70 per cent of ultimate strength)
has produced plastic deformation the material contracts elastic-
ally, retaining a permanent set. Under a subsequent load it
stretches elastically up to the previous maximum and then be-
yond that deforms according to a typical plastic deformation
curve.
A similar cycle is repeated for each subsequent load, pro-
vided the previous load is exceeded. If not, then the metal
merely deforms elastically. A corollary seems to be that no
work is absorbed by the metal except during the plastic defor-
mation, hence it is difficult to see how the material could fail
Plastic Deformation
355
in fatigue by repetitions of any tensile stress which is of suf-
ficient intensity to cause rupture on its first application. Dalby
finds that although the speciman appears perfectly elastic on
successive loadings actually no part of the curve on unloading
or reloading is a straight line but the two form a series of
loops one for each repetition which of course amount to an ab-
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Fig. 176. — Stress strain diagram of malleable iron in repeated tension
under increasing loads
sorption of energy. Similar loops can be observed in malleable
if the magnification be sufficient. They are barely visible in
the diagram.
The simplest case of stress reversing in algebraic sign is that
alternating between tension and compression of equal intensity
although alternate torsional shear is also of considerable im-
portance. We have seen in the earlier chapters of this series
that the behavior, at least within the elastic limit, of malleable
356 American Malleable Cast Iron
in tension and compression, is similar; the proportional limit,
being about 15,000 pounds per square inch and the modulus
of elasticity about 25 x 106 pounds per square inch. Thus there
is an elastic range of about 30,000 pounds per square inch,
one half on each side of the neutral or unloaded condition
through which the intensity of stress can be varied without
plastic deformation.
Applying Alternate Tension and Compression
One of the simplest experimental methods of applying
alternate tension and compression to a specimen is that of
bending a beam to and fro in opposite directions. The be-
havior of malleable under cross bending stresses has already
been fully considered, notably the fact that ultimate strength
and elastic limit determined in this manner bear no direct re-
lation to these constants as determined in pure tension and com-
pression. The explanation of this observation has also been
detailed.
The graph in Fig. 176 indicates the response of a malleable
beam nominally J/£ -inch' wide and 1-inch deep on supports 10-
inches apart to alternations of stress. The deflections are plot-
ted against apparent maximum fibre stress, as calculated from
the known dimensions of the specimen and the applied load.
When as the apparent proportional limit is not exceeded, the
stress-strain diagram under this cyclic cross bending is merely
a straight line through the origin at an angle depending upon
the modulus of elasticity o£ the metal. However,, when the
load in either direction exceeds the proportional limit the stress
strain diagram becomes a curve, plastic deformation taking
iplace. As the specimen is unloaded the elastic deformation
alone is removed and at zero a certain permanent set equal
to the plastic deformation remains.
Elastic Limit Increases
The effect of this plastic deformation is represented not
only by the measurable permanent set but also by the increased
elastic limit in the direction of the previously applied load.
On reversing the direction of stress the elastic limit is en-
countered sooner than it should be and the plastic deformation
Plastic Deformation
357
begins at a lower stress than was the case in the unstrained
metal.
When an intensity of stress equal. to the previous maximum
but of opposite sign is attained in a perfectly homogeneous
specimen, an equal and opposite strain would ensue although
in the present case the negative deflections all seem somewhat
•°?»25 50 37.5 W l£5 0 12.5 £5 57.9 50 62.5"
6tre55ln Thousand Pounds Per SOuare Inch
Fig. 177. — Behavior of malleable under cyclic bending under increas-
ing loads
less than the corresponding positive ones.
Action of Specimen
On unloading the specimen it straightens out first elas-
tically, retaining a negative set at zero load. Under reversed
loads it finally .deforms plastically until at the stress corres-
ponding to the first (positive maximum) it has the original
deflection.
358
American Malleable Cast Iron
Thus the cyclic cross bending stress-strain diagram is a
spindle shaped loop whose area represent? the work done1 in
plastic deformation. Plastic deformation in a given direction
raises the elastic limit in that direction and decreases the abso-
lute value of this constant in the opposite direction, the elastic
range remaining approximately constant. With successively
increasing intensities of stress the area of this mechanical
hystersis loop grows larger and larger as shown in Fig. 177.
If instead of applying cyclic cross bending in a manner so
that each cycle oscillates through a wider range of stress than
the preceding one we merely repeat a given cycle indefinitely,
it is found that the hysteresis loop decreases in area with suc-
cessive cycles. Fig. 178 shows the first and tenth loops of such
c.03
bl.5 50 37.5 25 125 0 12-5 £5 315 50 625
Stress In Thousand Pounds Per Square IncH
Fig. 178. — Behavior of malleable under cyclic cross bending at constant
maximum stress
Plastic Deformation
359
,160
Maximum Deflection
2,345 6 789
No. of Applications
Fig. 179. — Maximum deflection and permanent set under cyclic cross bend-
ing at constant maximum stress
a series. The decrease in work per cycle is due to the smaller
plastic deformation in each successive cycle due to the hardening
of the metal from the cumulative effect of all the slip produced.
The decrease in deflection and permanent set is not at constant
rate but decreases with each successive loading as shown in Fig.
179 and approaches a fixed minimum of finite size. The deflections
and sets are shown to be different according to which half the
specimen is in tension. This is presumably due to lack of com-
plete symmetry about the neutral axis. The work done by a
great number of such alternations will finally rupture the speci-
men. This constitutes the phenomenon of fatigue. The phe-
nomenon of fatigue of metals so far as it is known has been
discussed in another chapter. The experiments just re-
corded having shown the approximate extent to which tensile
or compressive loads strengthen the material for subsequent loads
360 American Malleable Cast Iron
in the same direction and weaken it for loads of opposite sign.
From these experiments we can gain at least a qualitative insight
upon the effect of a previous cross bending upon subsequent
tension or compression in a direction parallel to the length of
the specimen and vice, versa. The quantitative interpretation is
impractical — perhaps impossible — owing to the difficulty of ac-
counting for the distribution of stress in a plastically strained
material.
Behavior of Specimen
Consequently under the subsequently applied longitudinal
stress the elastic limit will be first exceeded on that edge of the
specimen which is experiencing a reversal of stress. As the
applied longitudinal load is increased a greater and greater por-
tion of the area experiences plastic deformation until finally the
elastic limit also is reached at the opposite edge.
At intermediate intensities of stress in a portion of the spe-
cimen elastic strain exists, in another portion plastic strain. From
the nature of the case the ratio of strain to stress is greater for
plastic than elastic deformation. The side experiencing a re-
versal of stress will stretch or compress more rapidly and an
eccentricity of loading will result from the unequal strain dis-
tribution. Such an eccentricity in the case of compression will
result in the superposition of a bending moment on the longi-
tudinal stress, as in the case of columns which are eccentrically
loaded and a given load will produce far greater unit stresses
than might be expected.
In the case of tension the eccentricity of loading will re-
sult in the transfer of a disproportionate amount of load to a few
of the stiffer fibers with an accompanying high unit stress.
Conversely the effect of a previous longitudinal stress upon
subsequent cross bending loads is to shift the neutral axis to-
ward that surface of the specimen which is being stressed in the
same sense as the first load. This shift goes on until the
moment of resistance of the portion of the specimens in opposite
sides of the axis about the axis are equal.
The sum of the two moments, constituting the moment of
resistance is thereby decreased. In either event, although we
may not be able to solve numerically the complex mechanics we
Plastic Deformation 361
may draw the conclusion that cross bending weakens the ma-
terial for subsequent tension or compression and vice versa.
The practical application of this conclusion is that a detail
which in fabrication has been subjected to severe cold work
cannot be expected to be as strong under loadings involving a
reversal of the stress previously encountered as unworked metal
would be. This conclusion applies equally to all ductile materials
and should serve as a warning against needlessly energetic
straightening or beading operations. Many malleable castings
are cast to a simpler form than intended and then bent to the
more complex shapes demanded. Air brake hose clamps are
examples of this practice. Such parts will never develop the
full strength of the original metal.
In all the preceding cases the loadings have been such as
to set up strains parallel to the subsequent stresses. A variety
of circumstances are possible in which the final load has no
component parallel to that producing the plastic deformation.
Two typical cases are torsional shear followed by tension
and compression followed by tension or compression in a di-
rection normal to the first compression. Compression followed
by a cross bending load parallel to the direction of compression
is, of course, a special case of the preceding involving both
tension and compression.
The combination of compression followed by tension, com-
pression, or both, normal to the original strain is the condition
which may arise where a piece is reduced to the desired dimen-
sions by compression in a press rather than by machining. In
Fig. 180 are shown two stress-strain diagrams on specimens
nominally ^>-inch square subjected to cross bending load on
supports 10 inches apart. One specimen, A, is of normal metal
in its original condition, while the other, C, was produced from
a thicker bar by compressing it to a final depth of J/£ inch.
The compressed dimension is vertical, that is, parallel to the
direction of the load in the final test. The effect of relatively
heavy compression under these circumstances can be learned by
a comparison of the two graphs.
A few scattering tests of the effect of shear upon subse-
quent tensile stress have been made.
362
American Malleable Cast Iron
In Fig. 180 certain tests of this character are tabulated.
Standard A. S. T. M. tension specimens were twisted through
various angles and then broken in tension. In the illustration the
angle of twist under load is plotted against the tensile properties
of the resulting metal.
It will be noted that a rapid and continuous decrease in
elongation is encountered with increasing torsional deformation.
The tensile strength first rises rapidly to a maximum and then
decreases still more rapidly. The location* of the maximum
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Fig. 180. — Stress deflection diagram of malleable in cross bending with
and without previous cold work
tensile strength corresponds approximately to the torsional yield
point, as may be seen from the torsional stress strain diagram.
The curve suggests a hardening of the metal due to the forma-
tion of amorphous metal followed at higher strains by disrup-
tion at the grain boundaries.
Failure in tension after great torsional strain did not result
approximately normal to the axis but in a spiral surface ap-
proximately normal to the helix angle into which the originally
straight elements of the specimen have been strained. There is
a suggestion here that distortion is not due to pure shear.
We have considered the effect of a series of stresses of
known intensity and direction upon a ductile material. Another
Plastic Deformation
363
important condition is that in which, instead of a series of
known stresses the specimen is required to undergo a series of
known increments of energy.
Impact testing by a series of equal or increasing blows,
is the principal application of this type of plastic deformation.
90 180 £70 360 450 540 680 7EO 6)0 900 990 1080
Angle Of Torsion (Degrees) In 4' Goqe Length
Fig. 181. — Effect of torsional deformation upon subsequent tensile strength
of malleable
In this case the intensity of maximum stress is a function both
of the energy input of the blow and the elastic and plastic de-
formation of the specimen. The latter factor depends upon the
previous plastic deformation of the specimen and hence is a
function of the magnitude and number of the preceding series
of inputs of energy.
364
American Malleable Cast Iron
Since malleable is often subjected to repeated impact in serv-
ice and occasionally in testing, this condition is of special im-
portance in connection with a study of that metal.
If the load deformation curve of a given specimen under
plastice deformation were capable of mathematical definition in
terms of its dimensions and properties and the rate of applica-
tion of the load, a mathematical study of this problem would
be feasible although probably quite complex.
However, the problem may be simplified by assuming that
Pef/ecfrtn
Fig. 182. — Absorption of energy from successive impacts
we have experimentally determined the load-deformation dia-
gram of a given specimen under given conditions. The load-
deformation diagram in every respect is similar to a stress-
strain diagram except that the co-ordinates are actual load
and actual deflection instead of unit stress and unit strain. We
can conceive that for a given specimen such a graph might be
autographically produced under rates of application of load
as rapid as are encountered in impact testing.
Referring to Fig. 182 let OLU represent the load-deforma-
tion curve described above, L being the elastic limit and U , the
ultimate strength and tan 0 the modulus of elasticity. Then the
energy imparted to the specimen at any given load and deforma-
tion for instance is the area below the curve beginning at O
Plastic Deformation 365
and ending at an. For example, OLa±a2 etc., anbn. If this energy
input be large enough the point an will then reach U, the energy
being the represented by OLa^a2 etc., UV and this energy will
produce rupture under impact.
Therefore, if impact is produced by a single blow, the en-
ergy of rupture is measured by the entire area below the curve
as shown above. A blow having an energy of impact of OLM
or less will not produce a plastic deformation, the specimen will
return to its original form after the load is removed and will
have absorbed no energy. If the energy of impact be equal to
OLaJ)i for example, when the load is removed the deformation
will decrease along a^ (parallel to OL) and a permanent set
Oci will remain. The energy OLa^c^ will have been used up
in plastic deformation and the elastic limit will be raised to a1
and the deflection at the elastic limit to c-J)^. The new load de-
flection curve becomes caa etc., UV. Thereafter any impact of
energy not greater than c^ajb^ will produce elastic deformation
only. Suppose the second impact is equal to C1a1a262 then by
similar measuring the new load deflection curve becomes C2a2a3an
etc., UV the third impact moves it to c3a4an etc., UV and so on,
and after n blows it becomes cnan UV and finally perhaps WUV
in which case a blow equal to or greater than WUV will break
the specimen.
Suppose now that we assume an equal energy input with
each blow. Then OLaJb^ — C1a1a2&2 = C2a2a3b3 etc., —
cn-1an-1an bn. It is obvious by inspection that up to the point
of maximum load G each succeeding one of the similar tri-
angles caji, C2a2b2 etc., is of larger area than its predecessor.
These triangles represent the portion of the energy of impact
expended on elastic deformation. Consequently a smaller per-
centage of the constant increment of energy is available for
plastic deformation with each succeeding blow up to that pro-
ducing maximum deflection. Beyond this point an inqreasing-
ly larger amount of each energy increment is available for plastic
deformation.
Finally if ^c^a2c2 + C2a2a3c3 — cn.^an ^an cn etc., is com-
mensurate with OLGUW the specimen absorbs on the last blow
energy equivalent to UVW '.
366 American Malleable Cast Iron
The specimen has then absorbed plastically the energy
OLGUV which it would have absorbed if broken by a single
impact. Since, however, the area Cn-^n^an cn is always less
than the area c,,.^,.^^ b» the energy absorbed by the metal
at each blow is measurably less than the total energy of im-
pact, a large part of the energy of impact being returned by the
specimen during its elastic recovery.
Obviously since there is a definite amount of energy not ab-
sorbed by the specimen at each blow a smaller percentage of the
energy of impact is absorbed the lighter the blow. If the energy
of rupture be measured by the aggregate of the energy of the
entire number of blows to produce rupture this sum will be
higher the smaller the individual blows. Consequently testing
a metal by successive impacts can yield quantitatively compar-
able results when all the specimens are identical in form and
quality in addition to the constancy of the hammer blow. Of
course this condition is impracticable of attainment, the quality
being unknown before the test.
In practice this means that only carefully prepared speci-
mens of similar material are capable of fairly accurate com-
parison by repeated impact test.
One or two further conclusions may be gained from the
study of the diagram. Energy equivalent to the area OLM
is absorbed by the specimen elastically. The material will with-
stand an indefinite number of impacts of this magnitude with-
out permanent deformation.
Were a similar triangle FGH drawn with its apex at G ,
this area will represent the maximum elastic absorption of
energy the specimen can sustain when by repeated impact the
elastic limit has been raised to the ultimate strength. Any
increment of energy less than this will never fracture the
piece but will produce a maximum deflection after a given
number of blows which will not be further increased by further
repetitions of the impact.
The area OLM— LM. LM tan 0=modulus of elasticity X
square of elastic limit.
The area FGH = GH. CH tan 0=modulus of elasticity
Plastic Deformation
367
X square of ultimate strength.
From the above we may calculate the blows required to
make an impact test workable on a given specimen.
The deflection at each successive blow can be determined
graphically under given conditions from the diagram. An
impact test in which the energy increment increases with each
blow can be studied in a similar manner. In that case there is
no possibility of coming to a maximum deflection without frac-
Fig. 183. — Load deformation diagram of. specimen subjected to alternate
impact
ture for the increased energy of the succeeding blow would
carry the deformation beyond G. In such a test there is great
danger that the last blow will be equivalent to far more than the
energy WUV and the unabsorbed energy of the blow will be
credited also to the specimen.
We may generalize to the effect that no method of repeated
impact can correctly measure the energy of rupture of a duc-
tile metal. In a similar manner we may study graphically the
368 American Malleable Cast Iron
effect of alternate impact in opposite directions, although we
may be confronted with the difficulty of securing the necessary
load deformation curves. In Fig. 183 U^L^OLU is the original
curve for the specimen. An increment of energy Oa^b^ de-
forms it to a± and raises the elastic limit to that point. The
load-deformation diagram then becomes a-lO-lLLJJ'1^ and an in-
crement of energy in the opposite direction to the first OlL11a2b.2
produces a load of a2b2 and a deformation O^b^ The new
elastic limit becomes a2 and the new diagram a2O2U2.
The next increment of energy is diagramed as O2a3B3 and
so on. It will be seen that each impact in one direction appar-
ently decreases both the ultimate load and elongation in the op-
posite direction an expression of the weakening caused by a
negative plastic deformation.
In the absence of stress strain diagrams under dynamic
loads we may turn as the best available substitute to the vari-
ous stress strain diagrams given throughout these chapters and
from them and the dknensions of the specimens estimate the
probable load deformation curves to be used.
It is obvious that those materials in which the elastic limit
is quite high accompanied by a high elongation are these which
will well resist repeated impact. The high elastic limit will dissi-
pate a large amount of energy in elastic deformation at each
blow while the high elongation provides a large amount of re-
serve energy for plastic deformation before rupture takes place.
The Young's modulus of all ferrous materials is practically
the same, hence the deformation at the elastic limit is in direct
proportion to the elastic limit. In steel high elastic ratio is ob-
tained only at the expense of elongation and vice versa. The
various graphs for malleable, indicating a constant and high
elastic ratio and an elongation increasing with strength account
for its excellent behavior under repeated impact even when of
sufficient magnitude to produce plastic flow.
In this connection, incidentally the yield point of metal
is the governing factor in ferrous materials for the small reduc-
tion in the area representing energy clue to the curvature of
the stress-strain diagram between the proportional limit and
yie!cl point is negligible.
Plastic Deformation 369
Plastic deformation has been discussed mainly because of
its great importance in the utilization of malleable. No one
realizes more than the author the unsatisfactory state of
knowledge and the lack of precise numerical data. If this
chapter has enabled the reader to form even a qualitative image
of the resistance of the metal above the elastic limit that is all
that can be expected. An infinite amount of further study will
be required before concrete mathematical analyses will be
possible.
XIX
THERMAL AND ELECTRICAL PROPERTIES
WHILE it is true that materials of construction in gen-
eral are used to resist mechanical stress, yet there are
service conditions when other properties, such as ther-
mal, chemical or electrical, for instance, are of greater conse-
quence.
The most important condition of this kind arises in the
use of malleable as a material for field frames of electrical
apparatus, where the magnetic characteristics of the metal
are much more important than the mechanical strength. It
is a well known fact that if a coil o£ wire is wound around
a piece of iron and a current is passed through the coil, the
iron becomes magnetic. This property of iron, which it shares
in a very limited degree with a few other metals, is of im-
portance in electrical machinery. If the power to become
magnetic is the quality desired, evidently the metal which forms
the strongest magnet with the same coil and current is the
most valuable. Therefore it is desirable to determine the de-
gree to which a given material possesses this valuable property.
Avoiding a discussion of the electrical principles and of the
mathematical reasoning involved in the study of magnetism, it
is sufficient to say that the intensity of magnetization, repre-
sented by the symbol Hf and expressed in gausses (lines per
square centimeter) can be calculated from the dimensions of a
magnetizing coil and measurement of the current. When an
iron core is inserted in the coil it will be found that the inten-
sity of magnetic field is much greater than the calculated value
H. This higher value, known as magnetic induction, is sym-
bolized as B and is measured in the same units as H. The
ratio of B to H, that is, the number of times stronger the
magnet is with the iron core than without any core, using the
coil only, is called the permeability of the material and is the
variable represented by the Greek letter /*.
It is further found that the value of /* depends not only
372' American Malleable Cast Iron
upon the material 'being used but also on the value of H at
which the experiment is made. In general, the permeability
of a material first increases as H increases, soon reaches a
maximum and then falls off, first rapidly and then more and
more slowly.
The value of /* for an indefinitely strong field is prob-
ably 1 for all materials. Owing to experimental difficulties
determinations close to the zero value of B are not very
reliable. The behavior of a magnetic material is usually repre-
sented by a so-called magnetization or "B-H" curve in which
the value of H, the strength of the magnetic field, is plotted
horizontally and the magnetic induction in the iron, B,, which
is equal to v-H, is plotted vertically. The fact that /* is vari-
able, depending on B and hence on H, gives this curve a gen-
eral form which rises from the origin (H = 0, B =0) first
ait a rapidly increasing rate as H increases and then more
slowly until it becomes horizontal when H is infinite. As a
matter of fact the curve becomes nearly horizontal fairly
soon, and /the "knee" in the curve, somewhat resembling the
yield point in a tensile stress strain diagram, represents practi-
cally the maximum flux density which can be attained in a
given metal. This value varies widely in different metals and
is quite definite in each metal having almost the significance of
a physical constant. This characteristic for malleable iron is
shown in curve A, Fig. 184. The specimen was in the form of a
closed ring about 6 inches in diameter and having a rectangular
section 0.33-inch thick radially and 0.9-inch wide. The per-
B
meability, A* = —
H
for various values of //based on the data for the ring described
above, is shown in curve B. The values of /* as related to B
are plotted in curve C.
When a material has been magnetized and the magnetic
field H is then reduced, the magnetic induction B in the
iron decreases but not at the same rate as it increased with
increasing values of H. When H is reduced to 0 there usually
remains a considerable magnetic induction and it is only
Thermal and Electrical Properties
373
after H has reached a definite value in the opposite direction
to that first developed that B falls to 0.
This lag of induction behind magnetizing force is due to
hysteresis. The value of B when H is reduced from a high
500
10000
CO 5000
500
10 20 3 40
H in C.G. 5. Units
Fig. 184. — Magnetization and permeability curves of malleable cast iron
value to 0 is called residual magnetism, and the negative value
of H required to bring B to 0 is called the coercive force.
It is quite possible to plot a curve, similar to a B-H curve
beginning with a fairly high value of H, lowering H gradually
to 0, then increasing it in the opposite direction until a nega-
tive value is reached equal in magnitude to the original posi-
tive value, then back through 0 to the starting point. Such a
374 American Malleable Cast Iron
curve forms a closed loop of distinctive form called a 'hysteresis
loop. The area of this loop represents energy consumed in
magnetizing and demagnetizing the specimen. Materials strong-
ly retaining their magnetism, and therefore suitable for per-
manent magnets have a larger hysteresis loop due to great
residual magnetism and coercive force. Material for electro-
magnets, especially where frequent changes in magnitude or
sign are required in field strength have the opposite characteris-
tics.
This energy is dissipated as heat, either in raising the tem-
perature of the iron or radiated to the surroundings. The
loss is of industrial importance for service involving reversals
of magnetism in that it involves a waste of energy and may re-
sult in inadmissably high temperatures being reached in the
magnetic circuit, possibly sufficient to destroy the insulation on
the coils. The energy is lost once for each cycle of magnetiza-
tion so that for alternating currents the loss depends on the
frequency.
It can be shown mathematically that the energy dissipated
per cycle of magnetization per cubic centimeter of metal is
the area of the hysteresis loop divided by 471", regard being had
of course to the scale to which B and // are plotted. This
value is necessarily dependent on the magnetic induction ob-
tained. In Fig. 185 a condition is plotted in which saturation
has practically been attained, hence calculations based on
this graph would give the energy dissipated by a complete
cycle. The area actually corresponds to a value of 11,388
ergs per cubic centimeter of metal. Cyclic magnetization of
malleable to an inductance of 13,200 centimeter-gram-second
units by the usual 60-cycle alternating current would raise the
temperature of the iron a little over 2 degrees Fahr. per minure,
assuming no radiation of heat.
Steinmetz has determined empirically that the work done
in a cycle of magnetization on any given material is approxi-
mately proportional to the highest magnetic induction, B reached
(in the cycle raised to a power between 1.66 and 1.70. This
formula serves to derive the work done on the same material
by cycles ending at different inductions. Therefore, the uv«-
Thermal and Electrical Properties
. 375
/» Current in Ampere^
n* Number of Turn;,
12000
20 0 - 20
Intensity of Magnetization, H
40
Fig. 185. — Magnetic properties of malleable cast iron
teresis loss on any given material, is a constant times J51-68
when B is the maximum induction reached in the cycle. This
constant varies with different materials and is designated by
the Greek letter ^. Calculation from the preceding data gives
a value of 0.00136 for Steinmetz's constant.
This very low value is logically due to the fact that the
376 American Malleable Cast Iron
bulk of a malleable casting is a fairly pure ferrite contaminated
mainly by silicon whose presence is an advantage and also to
the fact that the anneal involves a heat treatment consistent
with the very softest condition of ferrite possible. So far, the
writer knows of no case where the electrical resistance of mal-
leable is of commercial importance. It has been roughly deter-
mined to be 0.000044 ohm per centimeter cube. More recent
and accurate data indicate the specific resistance to be 0.0000295
ohms per centimeter cube. A part of this descrepancy no doubt
is due to the heterogenous character of the material. The
newer value however is much more reliable. Presumably the
resistance decreases with the carbon content.
The change in resistance with temperature is shown in
Fig. 186, the resistance at room temperature being taken as
unity.
Where metal parts are exposed to weather or to the action
of water or steam, circumstances arise in which the resistance
of the material to rusting is of prime importance. This is
particularly true under circumstances which preclude the use of
paint, galvanizing and similar means for protecting the metal.
This opens up the moot subject of corrosion of iron and
the relative merits of accelerated tests in dilute acid as com-
pared with service tests. All commercial iron alloys, except
a few high-silicon metals, dissolve in acids more or less rapidly.
While not at the same rate for all forms of iron and steel
the deterioration is rapid enough to preclude the use of ordinary
ferrous materials for corrosion resisting services.
A great many acid corrosion tests have been conducted on
malleable but the results are hardly applicable to the present
discussion. It is generally admitted that since corrosion is an
electrolytic phenomenon, the more nearly homogeneous a metal
is the better it will resist corrosive action either of the elements
or of acids, salt water, etc.
Manganese sometimes is alleged to be an offender in start-
ing corrosion. The surface of a malleable casting is always
nearly carbon free; it contains rather small amounts of man-
ganese, less than any material except wrought and ingot iron.
Silicon is supposed to dissolve in ferrite, when present in mod-
Thermal and Electrical Properties
377
erate amount. It would appear therefore that malleable should
resist rusting moderately well. This general conclusion is
borne out by the fact that malleable has been used for many
years in the manufacture of pipe fittings, radiator nipples, etc.,
and complaints that the material has failed by rusting are very
rare.
Resistance at Temperature tr Resistance at Room Temp.
o o b
f
S
/
/
/
i
^
j
/
4
/
/
f
f
c
y
/
iY
Q
f
{
/
/
/
6
I
/
tff
.,
x"
&1
x-*
-X1
x*
100 200 300 400 500 600 TOO
Degrees Cent.
Fig. 186. — Variation of electrical resistance of malleable cast iron with
temperature
There is also of record the case of a malleable iron harness
part which was found in excavating for a foundation. The
circumstances were such as to make it certain that the article
had been in the soil over 40 years, yet it had suffered buft little
injury to the surface. The only service test with which the
writer is familiar was conducted to determine the relative life of
malleable and steel railway tie plates. Plates of both ma-
terials were laid in the same track at the same time. When
378 American Malleable Cast Iron
the steel plates had completely rusted away the malleable plates
were still practically in their original condition. It seems rather
doubt full whether in the present state of our knowledge any
quantitative method exists of measuring resistance to corrosion
other than a direct comparison under the conditions expected
in practice.
In a great many cases mechanism is required to function
under temperature conditions either abnormally high or ab-
normally low. The principles to which malleable owes its
properties indicate obviously that malleable cannot be ex-
posed to temperatures above Ac^ even momentarily, without
being permanently destroyed.
The question of its use at high temperature cannot be
dismissed merely with the statement that it should never be
exposed, even momentarily to temperatures higher than say
1300 degrees Fahr. lest by chance Ac± be overstepped and a
permanent change be produced in the metal. There are many
cases where castings are to be used at temperatures considerably
below the danger point and the designer -must guide himself
by the effect of temperature on the properties of the material.
Even so simple a property as the dimensions of a casting are
affected by variations of temperature. Experiments by the
author have shown that if L0 be the length of a malleable cast-
ing at 0 degrees Cent, when the casting is raised to a tem-
perature of t degrees Cent, its length Lt will be given by the
equation
Lt = L0 (1-KOQ0006 H- -0000000125 t2)
Translating into terms of Fahrenheit temperature the re-
vised formula becomes
Lt=L32 [1+. 0000033 (/•— 32)+. 00000000385 (t— 32 )2]
These figures are somewhat cumbersome. For engineering
purposes it may be more convenient to take the expansion at
various 'Fahrenheit temperatures in per cent of the length at
75 degrees Fahr. from the graph, Fig. 187. It is to be noted
that the change in size of large castings where raised to mod-
erately high temperatures is quite significant. Thus a cast-
ing 3 feet long when raised to 600 degrees Fahr. expands
over 0.1 inch which may be very important where clearances
Thermal and Electrical Properties
379
are to be allowed.
The author is not aware of any actual or experimental
determinations of the specific heat of malleable cast iron. Since
the material is a mechanical mixture of graphitic carbon and
nearly pure iron we may use provisionally data calculated from
the known constants of the two elements.
The conductivity of a metal for heat represented by the
0.30
0.60
§
&
i
|0.40
a.
K
UJ
s
* Jj
0.20
0
C
DC
— m
£
ir
I
tted Curve Plate the V
•the Equation if=L0(
where L0- Length a
Lf - » »
•pansion Measured '/
Percentage of Leng
ilue 0.
l+0.<
to*c
t°c
nS'Re
that 7
000006
700006
corded
'5'F
t + O.OOL
t+o.oa
\
1000012
OOOOOli
st*
>5r2;
/
(
/
^
/
/
/
/
[/•
V
2
/
^i
/
X
^o*
'
X
) 200 400 600 800 1000 1200
Temperature, dcg Fanr
Fig. 187. — Expansion of malleable cast iron
symbol k is defined as "the quantity of heat, in small calories
transmitted through a plate 1 centimeter thick per square centi-
meter of surface when the difference in temperature between
the faces is 1 degree Cent.
The heat transmitted through a plate of metal varies di-
rectly as its area and as the difference in temperature between
the faces and inversely as the thickness.
The value of k varies slightly with the temperature, de-
380
American Malleable Cast Iron
creasing for iron and increasing for carbon as the temperature
rises. At room temperature (17 or 18 degrees Cent.) the values
for k for iron and graphite are .161 and .037, respectively.
(Smithsonian Physical Tables, 1921.)
At that temperature malleable cast iron of 2 per cent to
.006
005
X
or
05
0'
Fig. 188. — Heat transfer from machined malleable to still water for various
temperature differences
total carbon should have a value of k between .1578 and .1585,
depending on how readily heat can be transmitted from car-
bon to iron and vice versa.
On the same authority for the interval between 100 and
720 degrees Cent, the value of k becomes .202 for iron, .306
for graphite, and between .198 and .204 for malleable iron.
The values are higher than certain approximate experimental
values determined in the author's laboratory. Malleable heated
above A, will have its thermal conductivity permanently de-
Thermal and Electrical Properties 381
creased since this constant decreases with the combined car-
bon content.
The specific heat of a substance is the quantity of heat in
small calories to raise the temperature of one gram 1 degree
Cent.
Iron at 37 degrees Cent, has a specific heat of .1092 (loc.
cit.) and graphite at 11 degrees Cent, a specific heat of .160.
As a mechanical mixture of 98 per cent iron and 2 per cent
graphite and neglecting corrections for a change of specific heat
with temperature, the specific heat of malleable at room tem-
perature should be .1102. The value probably is quite accurate,
since cast iron of about 3%. per cent Cent, has a specific
heat of .1189, The specific heat rises with the temperature.
In view of the approximate character of these deductions
and of their intended application a detailed study of the rela-
tion between temperature, thermal conductivity and specific heat
seems "unwarranted.
All ferrous metals grow softer and weaker at elevated
temperatures. Accordingly it becomes important to know the
quantitative effect of temperature upon strength in order that
where very high temperatures are unavoidable, due allowance
may be made in design for the changed physical properties at
the higher tempera Lures.
Since the tensile properties can be more definitely measure.'l
than any other, studies on the effect of temperature on strength
have usually been made on tensile specimens. The author has
conducted experiments of this character by breaking very care-
fully made specimens at temperatures from — 80 to 1450 de-
grees Fahr.
The data up to 1200 degrees Fahr. — the highest commer-
cially safe temperature to provide against the possibility of
heating up to a temperature which will permanently affect
the product — are shown in Fig. 189. It will be seen that malle-
able cast iron has tensile properties equal to those it possesses
at room temperature at all temperatures from — 100 to 800
degrees Fahr. Above 900 degrees the strength decreases rapid-
ly and at 1200 degrees the maximum allowable temperature, the
382
American Malleable Cast Iron
metal is onfy one-fifth as strong as at room temperatures. Pre-
sumably very 'similar relationships will be observed under other
loads, compression cross bending, etc.
Temperature affects the magnetic properties of iron. For
large values of H, B decreases as the temperature increases;
the reverse is true for very small values of H. The effect
of the temperatures is not strongly marked at room tempera-
-100 0 200 400 600 800 1000 1200
Temperature j deg. Fahr
Fig. 189. — Effect of temperature upon tensile properties of malleable
tures but increases rapidly as' the temperature goes beyond 1200
degrees Fahr. Presumably the behavior of malleable is in ac-
cord with these principles. Actual measurements are lacking.
The specific heat of malleable, that is the number of heat
units required to raise a given weight of that material 1 de-
gree in temperature as compared with the heat units to raise an
equal weight of water 1 degree varies from 0.11 at 75 degrees
to 0.165 at 800 degrees Fahr. The intervening curve is near-
ly straight, being but slightly concave upward. The values are
calculated from the specific heats of iron and carbon. Malle-
able, being a mechanical mixture of these two elements, can
have this constant calculated in that way.
As the name implies, the thermal conductivity of a metal
Thermal and Electrical Properties
383
is the rate at which it will conduct heat. The constant is de-
fined in terms of the quantity of heat conducted per unit of
time through a cross section of unit area of a slab of unit
thickness whose opposite sides differ by unity in temperature.
The quantity of heat conducted varies directly as the area of
the conductor and as the temperature difference between its
ends and inversely as its length. However the thermal conduc-
SJ&
%
J36
4
./<?£>
-^La6<?r<?/&s-\
Ht
Fig. 190. — Thermal conductivity of malleable cast iron
tivity is not constant but varies with the temperature.
It will be seen that the flow of heat obeys the same law
as the flow of electric current ; indeed in a given metal the ratio
of thermal to electrical conductivity is nearly constant at all
temperatures.
The determination of thermal conductivity is not alto-
gether easy especially at high temperatures and consequently
data on this constant are somewhat infrequent and not con-
cordant.
The British Aeronautical Research committee gives data
on an annealed gray iron (1.84 per cent silicon) containing very
little combined carbon but much free carbon as determined in
the National physical laboratory. The committee determined
384 American Malleable Cast Iron
the conductivity between 40 degrees Cent, and various tempera-
tures up to 700 degrees Cent. The data, translated into mean
temperatures, have been plotted in Fig. 190. The conductivity
of pure iron is shown for comparison.
Both on account of the lower carbon content and the geo-
metric form of the free carbon, malleable should have a higher
conductivity than a cast iron specimen, but a lower than pure
iron.
The black dots in Fig. 190 give a number of observations
by Dr. Gorton in the author's laboratory, by Wilkes' method.
The data, while made as carefully as possible, have not always
appeared above criticism. From the mean value of Gorton's
data the conductivity can be taken as near .135 at 100 degrees
-Cent. The conductivities at other temperatures have been cal-
culated from the known thermal coefficients of electrical re-
sistance and plotted as a line which follows very well the gen-
eral direction of our observations. From these facts we are
led to believe that our data may be concordant enough to have
some utility.
The density of malleable cast iron is occasionally of im-
portance in the calculation of weights. This varies as does the
shrinkage allowance on patterns, with the composition of prod-
uct. The specific gravity of malleable, that is, the ratio of its
density to that of water is between 7.25 and 7.45 and de-
pends on the temperature at which the experiment is made.
The metal made to pass the specifications of the American
Society of Testing Materials will have a specific gravity of
about 7.40. The "shrinkage allowance" referred to under such
circumstances should be about 0.9 to 1 per cent, agreeing rather
well with the usual ^-inch per foot used by patternmakers.
It should be noted in passing that the differences in "shrink-
age" between metal differing in carbon content is actually an-
nealing.
All white cast iron shrinks very nearly the same amount
in cooling from the molten state (*4-inch per foot) but iron
high in carbon increases in size more when the carbon is lib-
erated than those low in that element.
Selected Bibliography
I— GENERAL INFORMATION
Chronology of -Iron and Steel, by Stephen L. Goodale, Pittsburgh Iron &
Steel Foundries Co. (1920.) •
A chronology of important discoveries, developments, etc., in iron and
steel industry dating from prehistoric times to 1919. 294 pages.
Pcnton's Foundry List; published by The Penton Publishing Go., Cleve-
land. (1922.)
A list of all of the foundries in the United States and Canada,
arranged by class of products. A separate list of malleable iron
foundries is included. 896 pages.
The Romance of Modern Manufacture, by Charles R. Gibson; published
by Seeley & Co., Ltd.
A popular account of the marvels oir manufacturing. Malleable iron
is included. 320 pages, illustrated.
Index of the Transactions of the American Foundrymen's Association;
American Foundrymen's Association, Chicago. (1921.)
An index of all volumes of Transactions from IX to XXIX inclusive,
containing hundreds of references to articles on malleable iron. An
author's . index also is given. 192 pages.
Foundrymen's Handbook; published by the Penton Publishing Co. (1922.)
Contains data on malleable iron, as well as on all other branches of
the foundry industry. 309 pages.
Iron and Steel, by J. H. Stansbie ; published by ^Constable & Co., Ltd.
(1915.)
This book is a comprehensive treatise on the modern aspects of iron
and steel manufacture together with an account of its history. Mal-
leable castings are included in the text. 375 pages, illustrated.
The Founder's Manual, by David W. Payne; published by D. Van Nos-
trand Co., New York. (1920.)
A handbook for foundrymen, with tables on mathematics, weights and
measures, materials, alloys, foundry fuels, cupola practice, sand,
molding practice, etc. One brief chapter is devoted exclusively to mal-
leable cast iron. 676 pages, 245 illustrations, and list of coke and
anthracite pig irons by trade names.
Foundry Cost Accounting, by Robert E. Belt; published by the Penton
Publishing Co. (1919.)
The twelve chapters cover every phase of accurate cost methods
and their various application to different branches of the foundry
industry. The principles and forms used, the classification of accounts,
386 Selected Bibliography
the methods of distributing overhead expenses, the procedures used to
determine the cost of individual jobs or classes of work, are such that
they can be easily adopted to fit the requirements of any foundry —
gray iron, malleable, steel or nonferrous. 262 pages, 75 forms and
charts.
Co-operation Between the Engineer and the Malleable Iron Foundry, by
G. F. Meehan.
A discussion of the need of teamwork between engineers and mal-
leable foundrymen to insure better design of castings. 1000 words.
Transactions, A. F. A., Vol. XXV, p. 221.
The Commercial Side of the Malleable Iron Industry, by W. G. Kranz.
A brief historical sketch of the industry, followed by an account of
recent developments (1916) and a statement covering erroneous con-
ceptions of the properties of malleable that are being corrected.
1000 words. Transactions, A. F. A., Vol. XXV, p. 501.
British and American Malleable Cast Iron, by T. Turner.
Theory and practice are discussed and futures of industries in Eng-
land and the United States are predicted. Iron Age, Vol. 102, p. 970.
Improvements in Making Malleable Iron.
A review of recent progress (1919) based on research and develop-
ment work of American Malleable Castings association. Raw Mate-
rials, Vol. 1 (1919), p. 443-8.
II— PRODUCTION
The A B C of Iron and Steel, edited by A. O. Backert; published by the
Penton Publishing Co., Cleveland. (1921.)
Twenty-six chapters by eminent authorities covering manufacture of
iron and steel from mine to finished product. Contains chapters on
making gray iron, steel and malleable castings, the latter product being
covered by H. A. Schwartz. 408 pages, 269 illustrations, numerous
statistical tables and index.
The Production of Malleable Castings, by Richard Moldenke. (1910.)
(Out -of print.)
The first book published covering the production of malleable, includ-
ing history, characteristics of malleable, testing, patternmaking, mold-
ing, melting, equipment, casting, annealing and cost of malleable.
125 pages, 35 illustrations.
International Library of Technology; published by International Text-
book Co.
Volume on "the manufacture of gas, iron, steel and cement." Con-
tains information on malleable iron.
Non-Technical Chats on Iron and Steel, by L. W. Spring; F. Stokes Co.
(1917.)
A review, in popular manner, of methods of producing iron and
Selected Bibliography 387
steel products, with a reference to the making of malleable cast iron.
Malleable Cast Iron, by S. J. Parsons; Constable & Co., Ltd. (Tem-
porarily out of print.) Reprinting.
Melting, molding, annealing and cleaning operations are explained ;
equipment is described, and principles of design and method of making
patterns discussed. 182 pages, 86 illustrations.
Iron and Steel, Vol. I, by William Henry Greenwood; Henry Carey Baird
& Co. I -jifi
Refractory materials, iron ores, metallurgical chemistry of iron, pig
iron, blast furnace operation, malleable cast iron, production of mal-
leable in open hearth. 255 pages, illustrated.
Notes on Foundry Practice, by J. J. Morgan; published by Charles Grif-
fin & Co., Ltd. (1912.)
This work gives a general description of the methods of founding
and provides condensed and reliable information as to the material
used and its methods followed in more particularly iron founding.
The subject of malleable castings is included. 104 pages, 24 illus-
trations.
International Library of Technology; published by International Text-
book Co.
Volume on "machine molding, foundry appliances, malleable castings,
etc." Contains a complete chapter of 36 pages on the properties and
composition of malleable cast iron.
General Foundry Practice, by William Roxburgh; Constable & Co., Ltd.
(1919.)
A treatise on general iron founding with notes on metallurgy, melt-
ing, molding, heat treatment, cleaning, etc. Malleable castings are
mentioned. 308 pages, 161 illustrations.
General Foundry Practice, by A. McWilliam and Percy Longmuir ; Chas.
Griffin & Co., Ltd. (1920.)
Molding sands, foundry equipment, refractories, mixing, pouring, heat
treatment, testing, etc., as applied to general foundry work. Reference
is made to malleable cast iron. 384 pages illustrated.
Malleable Cast Iron, by Bradley Stoiighton.
A brief outline of the methods of manufacture and properties of mal-
leable cast iron, as known in 1908. School of Mines Quarterly
(Columbia Univ.), Vol. 29, p. 54.
The Production of Malleable Castings, by Richard Moldenke.
A brief treatise including history of the industry, properties of mal-
leable, metallurigcal principles, and methods of production. 4500
words. An address before Connecticut Valley Section of the Amer-
ican Chemical Society, Jan. 4, 1913. Transactions, A. F. A., Vol. 21,
p. 815.
388 Selected Bibliography
Some of the Factors in the Manufacture of High Grade Malleable Cast-
ings, by J. G. Garrard.
A brief discussion of the difficulties in making malleable castings of
heavy section. Results of iron produced by practically eliminating top
blast are given. 800 words. Transactions, A. F. A., Vol. XXVII,
p. 370.
Malleable Iron — Its Manufacture, Characteristics and Uses, by J. P. Pero.
Development of the industry, method of melting, distinction between
shrinkage and contraction, annealing practice and specifications are
the principal topics covered in this paper. 3600 words. Transactions,
A. F. A, Vol. XXIII, p. 451.
An Outline to Illustrate the Inter-dependent Relationship of the Variable
Factors in Malleable Iron Production, by L. E. Gilmore.
A discussion of the chemical analysis and miscrostructure of white
iron, types of furnaces employed, quality of fuel, control of combus-
tion, ideal mixtures, heat-treating and annealing, etc. 2800 words
and one control chart of operations. Transactions, A. F. A., Vol.
XXIVi p. 233.
Progress in Manufacture of Malleable Iron, by Enrique Touceda.
A progress report of recent advances in the technical development of
the malleable industry as of 1920, with a discussion of future possi-
bilities. Furnace design and melting practice, and improved prop-
erties of product are discussed. 4500 words. Transactions, A. F. A.,
Vol. XXIX, p. 354.
Fuel and Materials
Burning Liquid Fuel, by W. N. Best ; published by U. P. C. Book Co.,
Inc. (1922.)
History, theory and applications of oil fuel in 28 chapters, one of
which (3500 words, 17 illustrations) is devoted to malleable iron,
gray iron and brass foundry practice. 341 pages, 316 illustrations.
Foundry Irons, by Edward Kirk; Henry Carey Baird & Co. (Out
of print.)
History of ironmaking, pig iron production, mixing irons, casting by
direct process, foundry chemistry, analysis, etc., as applied to cast iron
and malleable cast iron. Three chapters are devoted to malleable. 276
pages ; illustrated.
Blast Furnace and the Manufacture of Pig Iron, by Robert Forsythe ;
published by the U. U. C. Book Co. (1922.)
An elementary treatise for the use of the metallurgical students and
the furnaceman. Several pages are devoted to malleable pig iron,
castings and specifications. 368 pages.
Fuel and Combustion, by Max Sklovsky.
A general . article on economy of combustion which in conclusion
Selected Bibliography 389
touches on tunnel kilns for annealing malleable iron castings. 2500
words, 9 illustrations. Transactions, A. F. A., Vol. XXIX, p. 367.
Coal — Its Origin and Use in the Air Furnace, by F. Van O'Linda.
The properties of coal for air furnace melting are described and
suggestions for firing given. Cost per .B.t.u. is stated. 1600 words.
Transactions, A. F. A., Vol. XXIV, p. 251.
Pulverized Coal for Melting Malleable Iron, by W. R. Bean.
An explanation of the factors controlling the use of powdered coal
in malleable melting. Foundry, Vol. 45, p. 487.
Powdered Coal as a Fuel in the Foundry, by A. J. Grindle.
Uses in the foundry, problems of feeding and burning, carburization,
economy, kind of coal to use, preparing fuel, and cost, are the
principal topics discussed. 4000 words. Transactions, A. F. A., Vol.
XXVIII, p. 303.
Efficient Use of Pulverized Coal in Malleable Foundry Practice, by
Milton W. Arrowood.
The author discusses methods of preparing pulverized fuel, mixing
it with the air, introducing it into the furnace, and controlling furnace
conditions. The theory of combustion receives considerable attention.
8400 words, 9 illustrations. Transactions, A. F. A., Vol. XXVIII,
p. 277.
Plant and Equipment
Foundry Molding Machines and Pattern Equipment, by Edwin S. Carman;
published by the Penton Publishing Co., Cleveland. (1920.)
A treatise showing the use- of molding machines in all types of
foundries. Parts of the book are of particular interest to malleable
foundrymen. 225 pages, 220 illustrations.
Electric Furnaces in the Iron and Steel Industry, by Rodenhauser-
Schoenawa-Von Baur; published by John Wiley & Sons. (1920.)
This book answers clearly and untechnically every question that may
arise in the electric steel industry. Malleable iron is included. 460
pages, 133 illustrations.
A Study of the Malleable Furnace, by Harbison-Walker Refractories Co.
98 pages, illustrated.
A Continuous Malleable Foundry.
An illustrated description of the new (1911) foundry of the Crane
Co., Chicago. Foundry, Vol. 38, p. 1.
Making Large Castings from Air Furnace Iron, by H. E. Diller.
A description of a foundry of the Westinghouse company equipped
with two 40 and one 15-ton air furnaces. Foundry Vol 48 (1920)
p. 973-77.
A New Annealing Furnace.
Description of malleable annealing furnace operated by the Arcade
390 Selected Bibliography
Malleable Iron Co. Foundry, Vol. 48 (1920), p. 769-71.
Foundry Plant and Machinery, by J. Horner.
A chapter of a series. This chapter is devoted to the equipment and
practice in malleable foundries. Engineering, Vol. 90, pp. 787-91.
Annealing Furnaces, by George Rietkolter.
A description, with drawings, of malleable annealing furnaces. Stahl
und Risen, Vol. 27 (1908), p. 1652.
Malleable Cast Iron and the Open-Hearth Furnace, by G. A. Blume.
A description of two open-hearths built in a malleable plant in Fin-
land in 1910-11. The operation is discussed in detail. 8000 words,
3 illustrations. Transactions, A. F. A., Vol. 21, p. 431.
How an Oil Fired Malleable Furnace Operates.
A description of an oil fired air furnace with data on consumption,
costs, etc. Foundry, Vol. 45, p. 503.
The 25-Ton Air Furnace, by F. C. Rutz.
A brief description of a 25-ton furnace, with dimensions, operating
expense, melting ratio, flexibility of operation, etc. 800 words. Trans-
actions, A. F. A., Vol. XXV, p. 522.
The Waste Heat Boiler for Malleable Furnaces.
The author believes waste heat installations in the foundry will be
justified by results. Foundry, Vol. 46, p. 220.
The Theory of the Modern Waste-Heat Boiler and the Possible Applica-
tion of Such Boilers to Malleable Melting Furnaces, by Arthur D.
Pratt.
An explanation of the theory of the waste heat boiler and a descrip-
tion of the installation of one attached to an air furnace at the Mc-
Cormick works of the International Harvester Co. The performance
of this boiler is given and results tabulated. 600 words, 6 drawings
and charts. Transactions, A. F. A., Vol. XXVI, p. 349.
Pointers from the -Practice of a Malleable Iron Foundry.
A description of the installation of waste heat boilers on air furnaces
at the plant of the Buhl Malleable Co., Detroit (1909), 1500 words,
11 illustrations. Castings, Vol. Ill, p. 196.
A Modern Coreroom, by Donald S. Barrows.
A description of the coreroom built in 1918 at the malleable plant
of the T. H. Symington Co., Rochester, N. Y. 2000 jyords, 10 illus-
trations. Transactions, A. F. A., Vol. XXVII, p. '429.
A New Research Department for a Large Malleable Plant, by H. A.
Schwartz.
A description of the laboratory built in 1919-20 by the National Mal-
leable Castings Co., Cleveland. The laboratory is for the research
requirements of a group of scattered foundries and the article lists
and describes the apparatus and outlines the arrangement of depart-
Selected Bibliography 391
ments. 3700 words, 4 illustrations. Transactions, A. F. A., Vol.
XXIX, p. 380.
Early Laboratories in Malleable Industry.
Discussion by Richard Moldenke and H. A. Schwartz of the pioneer
laboratories of 1891 to 1903, with reference to the work of Dr.
Moldenke, H. E. Diller, A. A. Pope and others. 1200 words.
Transactions, A. F. A., Vol. XXVII, p. 400.
Melting Practice
Calculating Mixtures for Malleable Cast Iron, by Harrold Hemenway.
A system of calculating mixtures is fully explained and the impor-
tance of the various constituents emphasized. 8000 words, 27 tables.
Transactions, A. F. A., Vol. XXIII, p. 413.
Influence of Changing the Composition of Malleable Castings, by P.
Rodigin.
Results of tests showing effects of additions of manganese, silicon,
aluminum, titanium, antimony and tin, copper, bismuth and lead,
sulphur and phosphorus to malleable. 1000 words. Transactions, A.
F. A, Vol. XXII, p. 201.
Malleable Troubles, by Richard Moldenke.
A discussion of melting problems, particularly those related to the
selection of iron, use of scrap, etc. Annealing also is discussed.
3500 words. Transactions, A. F. A., Vol. XXII, p. 251.
Effect of Varying Silicon and Carbon in Malleable Iron Mixtures, by
A. L. Pollard.
A discussion based on records of analyses and tests covering a period
of 8 months, during which time the silicon and carbon contents were
varied. 1200 words. Transactions, A. F. A., Vol. XXIII, p. 437.
Titanium for Malleable Iron, by C. H. Gale.
Ferro-titanium was added to malleable- in the ladle and tests of the
resulting product made. The paper is a discussion of the results.
2400 words, 5 tables. Transactions, A. F. A., Vol. 20, p. 271.
Malleable Castings by a New Process (1908), by E. C. Origley.
Wrought iron and soft steel are melted in a crucible, the metal is
quieted by additions, and poured. Iron Age, Vol. 81, p. 1312-13.
Standardization of Air Furnace Practice, by A. L. Pollard.
A discussion of design, touching on length of hearth, depth of bath,
length of firebox, height of roof, opening at neck and wall thick-
nesses. Advantages and disadvantages are compared and notes on
operation presented. 1800 words. Transactions, A. F. A., Vol.
XXIV, p. 245.
Melting in an Air Furnace with Fuel Oil, by J. P. Pero.
Disadvantages are compared with advantages, and data on oil-operated
392 Selected, Bibliography
air furnaces in three plants are given in parallel. 2000 words, 1 table.
Transactions, A. F. A., Vol. XXVIII, p. 316.
The Equipment of Air Furnaces Using Oil as Fuel, by W. N. Best.
Method of changing air furnace from coal firing to oil firing, with
suggestions regarding design of burners and method of operation.
1500 words. Transactions, A. F. A., Vol. XX, p. 421.
The Application of Pulverized Coal to Malleable Melting Furnaces, by
Joseph Harrington.
The author discusses factors affecting successful use of pulverized
coal in air furnaces, covering rapidity of heating, temperature, effect
on furnace lining, amount of carbon burned out, etc. 2600 words.
Transactions, A. F. A, Vol. XXVI, p. 394.
Application of Pulverized Coal to the Air Furnace, by W. R. Bean.
A discussion of the disadvantages of hand firing and of the possi-
bilities of overcoming some of them by using pulverized coal. Meth-
ods of altering air furnaces for this fuel and results of tests are
given. 2800 words. Transactions, A. F. A., Vol. XXVI, p. 337.
The Triplex Process of Making Electric Furnace Malleable, by H. A.
Schwartz.
A complete description of the triplex process invented by W. G.
Kranz and employed by -the National Malleable Castings Co. This
process involves the use of the cupola, converter and electric furnace.
3200 words, 5 illustrations. Transactions, A. F. A., Vol. XXIX,
p. 342.
The Refining of Cupola Malleable Iron in the Electric Furnace, by A. W.
Merrick.
The advantages of cupola melting of malleable are recounted, and the
results of experiments in refining the cupola metal electrically are
presented and discussed. 2400 words, 3 illustrations. Transactions,
A. F. A, Vol. XXVIII,. p. 322.
Molding
Foundry Work, by Burton L. Gray ; published by the American Technical
Society. (1920.)
A practical handbook on standard foundry practice, including hand
and machine molding, cast iron, malleable iron, steel and brass cast-
ing, foundry managements, etc. 224 pages, 191 illustrations.
The Control of Chill in Cast Iron, by G. M. Thrasher.
Bulletin, A. I. M. E. (1915), p. 2129.
Malleable Cast Iron, by F. Erbreich.
Methods of molding and annealing are described and illustrated.
Stahl und Eisen, Vol. 35, pp. 549-53, 652-58, 773-81.
Producing Machinable Malleable Iron Castings, by A. T. Jeflfery.
The author explains how to avoid common machining difficulties by
Selected Bibliography 393
adopting good foundry practice. Foundry, Vol. 45, p. 449.
Gating Malleable Iron Castings, by A. M. Fulton.
Methods of properly gating malleable castings with various typical sec-
tions, avoiding chills wherever possible. Shrinkage defects are dis-
cussed. 2100 words, 9 illustrations. Transactions, A. F. A., Vol.
XXV, p. 239.
Annealing
A Study of the Annealing Process for Malleable Castings, by E. L.
Leasman.
A review of the metallography of white cast iron is followed by a
description of tests to study the effects of different packing materials,
of different annealing temperatures, of different times of annealing
and different rates of cooling. 3200 words, data on 23 experiments,
15 micrographs. Transactions, A. F. A., Vol. XXII, p. 169.
Experiments in Annealing Malleable Iron, by H. E. Diller.
The author discusses the two actions occurring in the anneal, and
describes tests made to ascertain proper temperatures, time, rate of
cooling, etc. 3000 words, 4 illustrations. Transactions, A. F. A.,
Vol. XXVII, p. 404.
Continuous Tunnel Annealing, by Philip d'H. Dressier.
A description of the Dressier type tunnel annealing furnace for
malleable castings, on the basis of its development in 1918. 2400
words, 5 illustrations. Transactions, A. F. A., Vol. XXVII, p. 414.
The Application of Powdered Coal to Malleable Annealing Furnaces, by
Charles Longnecker.
Following a brief historical sketch of the subject, the author describes
the installation at the plant of the Pressed Steel Car Co., comparing
results with those obtained by the use of natural gas and fuel oil.
2100 words, 3 illustrations. Transactions, A. F. A., Vol. XXVIII,
p. 270.
Effects of Annealing Gray and Malleable Iron Bars in Copper Oxide
Packing, by H. E. Diller.
Malleable iron bars were packed in black oxide of copper and annealed
in an experimental furnace. In one case the copper soaked through,
the bar analyzing 21.4 per cent copper. Similar tests at various
annealing temperatures are described. 1600 words, 8 illustrations.
Transactions, A. F. A., Vol. XXVIII, p. 261.
Malleable Annealing Experiments, by S. B. Chadsey.
Results of tests of malleable subjected to repeated annealing. Foundry,
Vol. 37, p. 215.
Reducing the Malleable Iron Annealing Period, by A. E. White and R. S.
Archer.
Time can be saved by raising the annealing temperature slightly above
394 Selected Bibliography
the critical point and maintaining it at 700 degrees long enough to
change 0.70 per cent combined carbon to graphitic carbon. Foundry,
Vol. 47, p. 61.
Graphitization of White Cast Iron upon Annealing, by Paul D. Merica and
Louis J. Gurevich.
A description and discussion of experiments in which the graphitiza-
tion ranges of temperatures for three compositions for car wheels
were determined. Light is thrown on certain moot questions of the
metallurgy of annealing. 2400 words, 7 illustrations. Transactions,
A. I. M. M. E., Vol. LXII, p. 509.
The Annealing of Malleable Castings, by A. E. White and R. S. Archer.
Following a discussion of the constituents of malleable castings, the
authors describe experiments with white iron, covering the time of
annealing, the temperature and method of treatment. In conclusion,
the authors state an ideal heating cycle is impossible, each case depend-
ing on local requirements. Transactions, A. F. A., Vol. 27, p. 351.
Researches in the Annealing Process for Malleable Castings, by Oliver
W. Storey.
A discussion of research work on packing materials, temperature of
annealing, time of annealing, and rate of cooling, with important con-
clusions. 4400 words, 10 micrographs. Transactions, A. F. A., Vol.
XXIII, p. 460.
Copper Diffuses Through Cast Iron, by H. E. Diller.
An investigating effect of oxidizing packings in annealing malleable, it
was found that copper penetrated bar packed in copper oxide. Foundry,
Vol. 47 (1919), p. 779-80.
Production of Malleable Castings, by Richard Moldenke.
An extensive discussion of the principles of annealing, with data
on operation and description of apparatus. The Iron Trade Review,
Vol. 44 (1910), pp. 540, 776.
Notes on Malleable Cast Iron, by R. Namias.
A discussion of composition of metal, rate of cooling during anneal,
etc. Engineering, Vol. 88, p. 669.
Finishing
Oxy-Acetylene Welding Manual, by Lorn Campbell, Jr., John Wiley &
Sons, Inc.
Apparatus and methods of oxy-acetylene welding of various materials,
including malleable. Glossary of welding terms.
Oxy-Acetylene Welding Practice, by Robert J. Kehl, published by Amer-
ican Technical Society.
A practical presentation of the modern processes of welding, cutting
and lead burning with special attention to welding technique of
different metals. Simple and complex cases of expansion and con-
Selected Bibliography 395
struction — preheating steel, cast iron, malleable iron, aluminum, cop-
per, brass and bronze welding. 110 pages, 117 illustrations, diagrams
and tables.
Oxy- Acetylene Welding, by S. W. Miller ; Industrial Press.
Twelve chapters on oxy -acetylene welding of various materials, in-
cluding malleable cast iron. 287 pages, 192 illustrations.
Troubles Encountered in Machining Malleable Iron: Causes and Reme-
dies, by A. T. Jeffery.
A discussion of machining difficulties due to pure hard white iron,
under-annealed iron, iron cooled too quickly, burned iron, and "tough
and stringy" iron. The use of test lugs, effect of low silicon, etc.,
are considered and in summary, the author urges co-operation between
founder and user of castings. 2400 words, 7 illustrations. Transac-
tions, A. F. A, Vol. XXVI, p. 383.
Ill— METALLURGY AND METALLOGRAPHY
The Chemical and Metallographic Examination of Iron, Steel and Brass,
by Hall and Williams; published by McGraw-Hill Book Co. (1921.)
Malleable iron is included in the volume. 500 pages, illustrated.
Cementation of Iron and Steel, by Frederico Giolitti ; published by Mc-
Graw-Hill Book Co. (1915.)
Information on the theory of malleablized castings. 407 pages, illus-
trated.
Cast Iron in the Light of Recent Research, by William H. Hatfield;
Charles Griffin & Co., Ltd.
The iron-carbon alloys and cast iron from the standpoint of the
equilibrium diagram, with chapters on the influences of silicon, phos-
phorus, sulphur, manganese, etc. Malleable iron is given considerable
attention, the heat treatment of white iron, influence of sulphur on
the stability of iron carbide in the presence of silicon, and the phos-
phorus content permissible in malleable being discussed. Mechanical
properties of malleable are outlined. 292 pages, 199 illustrations.
An Outline of the Metallurgy of Iron and Steel, by A. H. Sexton and
J. S. G. Primrose; Scientific Publishing Co.
An outline of processes of iron and steelmaking, with a discussion of
• metallurgy involved. Malleable iron is included. 587 pages, 271 illus-
trations.
An Elementary Textbook of Metallurgy, by A. Humbolt Sexton; pub-
lished by Charles Griffin & Co., Ltd.
This work is intended for the use of students, both for those com-
mencing the study of metallurgy and those who are already engaged
in metallurgical industries and who desire some knowledge of the
principles on which the processes they are using are based. Mai-
396 Selected Bibliography
leable iron is taken up in Part I under metallurgical processes. 263
pages, 71 illustrations.
Principles of Metallography, by Robert S. Williams; published by Mc-
Graw-Hill Book Co. (1920.)
Malleablizing is included in this text. 158 pages.
Practical Metallography of Iron and Steel, by John S. G, Primrose;
published by Scientific Publishing Co.
Contains information on malleable cast iron. 129 pages, illustrated.
Methods of Chemical Analysis and Foundry Chemistry, by Frank L.
Crobaugh; Penton Publishing Co. (1910.)
Sampling and preparation of samples; determination of iron, phos-
phorus, sulphur, etc.; analysis, etc., as applied to white and chilled
castings, malleable castings, gray iron castings, etc. 110 pages.
The Metallurgy of Iron and Steel, by Bradley Stoughton ; McGraw-Hill
Book Co. "(1913.)
Iron and carbon, manufacture of pig iron, bessemer process, open-
hearth process, defects in ingots and castings, treatment of steel, iron
and steel founding, constitution of cast iron, malleable cast iron, intro-
duction to metallurgy, etc. 539 pages, illustrated.
Metallurgy of Iron and Steel, by A. Humbold Sexton ; published by Scien-
tific Publishing Co.
This book covers in one volume the whole field of metallurgy of iron
and steel. Method of making malleable iron is described. 600 pages,
270 illustrations.
Metallurgy of Iron, by Thomas Turner ; published by Charles Griffin &
Co, Ltd. (1920.)
Contains information on the production of malleable cast iron. 486
pages, illustrated.
The Metallography of Steel and Cast Iron, by Henry Marion Howe;
McGraw-Hill Book Co., New York. (1916.)
A finished treatise on general metallography, with numerous references
to malleable iron. 641 pages, hundreds of illustrations, numerous
tables and diagrams, and complete indices.
The Metallography and Heat Treatment of Iron and Steel, by Albert
Sauveur; Sauveur and Boylston, Cambridge, Mass. (1916.)
A thorough study of metallography covering all types of iron and
steel. One chapter is devoted exclusively to malleable cast iron, and
several others are pertinent to malleable producers and users. 486
pages, 437 illustrations.
Metallography Applied to Siderurgic Products, by Humbert Savoia; pub-
lished by E. & F. N; Spon, Ltd.
A complete chapter of 23 pages is devoted to malleable cast iron. 180
pages, illustrated.
Selected Bibliography 397
Metallography, by Arthur H. Hiorus ; published by Macmillan & Co.
(1902.)
An introduction to the study of the structure of metals chiefly by the
aid of the microscope. Several pages are given over to malleable cast
iron. 158 pages, illustrated.
Iron and Steel, by O. F. Hudson; Constable & Co., Ltd.
An introductory textbook for engineers and metallurgists. Methods of
production are not covered in this book. Metallurgy of malleable cast
iron is discussed briefly. 184 pages, 47 illustrations.
Fractures and Microstructures of American Malleable Cast Iron, by W. R.
Bean, H. W. Highriter and E. S. Davenport.
A discussion of typical specimens of malleable cast iron based on
chemical, miscroscopic and mechanical examination. 6500 words, 40
illustrations. Transactions, A. F. A., Vol. XXIX, p. 306.
Some Remarks Regarding the Permissible Phosphorus Limit in Malleable
Iron Castings, by Enrique Touceda.
Dynamic tests of malleable containing .181, .252, .325 and .388 per
cent phosphorus were made, and the author interprets the results for
the guidance of malleable foundrymen. 3500 words, 5 illustrations, 2
tables. Transactions, A. F. A., Vol. XXIV, p. 209.
Report on Methods of Etching Malleable Iron for Visual Investigation of
Structure, by E. Heyn.
The author recommends a solution of 1 gram of copper-ammonium
chloride in 12 grams of water. Etching requires a minute. 1500
words, 8 illustrations. International Association of Testing Materials,
Brussels, 1906.
Change of Structure in Iron and Steel, by William Campbell.
Review of iron-carbon equilibrium diagram, illustrated by photomi-
crographs of irons and steels. Journal, Franklin institute, Vol. 163,
pp. 407-34.
Constitution of the Iron-Carbon Alloys.
A discussion of Sauveur's article in Journal of Iron and Steel insti-
tute by Benedicts, who upholds Roozeboom's application of phase rule.
Also discussed by Howe, Stansfeld, Stead and others. Mctallurgie,
Vol. 4, pp. 216-41.
Influence of Silicon upon the Iron-Carbon System.
Author determines amount of carbon remaining in solution after
adding definite amounts of silicon to molten pig iron. Influence of
silicon upon solidification point also determined. Stahl und Eiscn,
Vol. 27, 482-87.
Note on the Liquids in the Iron-Carbon Diagram, by G. Cesaro.
Discussion of an attempt to determine the course of the curve joining
the points at which molten iron-carbon alloys begin to solidify. Jour-
nal, Iron and Steel Institute. (1919.)
398 Selected Bibliography
The Alloys of Iron and of Carbon, by Georges Charpy.
A lecture on the iron-carbon system, in which the author reviews the
knowledge of the subject as of 1909. Bulletin de la Socicte Chimique
de France, Vol. 3, p. i-xlvi.
Some Iron-Silicon-Carbon Alloys, by W. Gontermann.
A review of binary systems contributing to the above equilibrium,
with the author's theory on the Fe-C system. Zeitschrift fur anor-
gische Chemie. Vol. 59 (1909), p. 373-414.
Development of the Fusion Diagram of Iron-Carbon Alloys, by F. Wust
An explanation of the theory underlying the construction of the fusion
diagram. The author proposes the term "Ledeburite." Zeitschrift
fur Elektrochimie, Vol. 15 (1910), p. 565-584.
Chemical Equilibrium in the Reduction and Cementation of Iron, by Ru-
dolph Schenck.
Zeitschrift fur Elektrochimie, Vol. 21 (1915), p. 37; Vol. 22 (1916),
p. 121; Vol. 24 (1918), p. 248.
Separation of Graphite in White Cast Iron Heated under Pressure, by
Georges Charpy.
Change of carbide to graphite when the metal is subjected to high
pressure and a temperature of from 700 to 1000 degrees. Cotnptes
Rendus, Vol. 148 (1909), p. 1767.
The Stable System: Iron-Carbon, by Rudolf Ruer and Nikolaus Iljin.
A thorough discussion covering the solubility of carbon in solid iron
and the separation of temper carbon. Metallurgie, Vol. 8, p. 97.
The System Iron-Carbon, by A. Baikov.
A study of the solidification of iron showing that separation of
graphite and cementite follows the same line on the diagram. Revue
de Metallurgie, Vol. 8, p. 315.
The Solubility of Carbon in Iron, by O. Ruff and O. Goecke.
A discussion attending the determination of the solubility of carbon
in iron at temperatures between 1200 and 2600 degrees Cent. Metal-
lurgie, Vol. 8, p. 417.
The Equilibrium Diagram of Iron-Carbon Alloys, by Otto Ruff.
Metallurgie, Vol. 8, pp. 456-64, 497-508.
A Study of the Annealing Process for Malleable Castings, by Oliver W.
Storey.
The effects of packing material, temperature of annealing, time of
annealing and rate of cooling are studied. A thorough and original
discussion on annealing. Metallurgical and Chemical Engineering,
Vol. 12, p. 383.
The Nature of the A2 Transformation in Iron, by K. Honda.
A study of recent investigations. Scientific Reports, Tohoku Imperial
University, Vol. 4 (1915), p. 169.
Selected Bibliography 399
Phosphorus Limit in Malleable Castings, by Enrique Touceda.
The author describes tests which showed that when combined carbon
was low, evil effects of phosphorus were slow to make themselves
felt. Iron Age, Vol. 96, p. 92.
Sulphur in Malleable Cast Iron, by R. H. Smith.
The author concludes that sulphur is not removed in the annealing,
process and does not appear to have evil effects below 0.15 per cent.
Journal, Iron and Steel Institute. Vol. 92, p. 141.
Recrystallization after Plastic Deformation, by H. M. Howe.
Bulletin, A. I. M. E. (1916), p. 1851-60.
Decarburization of Iron-Carbon Alloys, by W. H. Hatfield.
The author opposes theory that carbon must be in the form of temper
carbon before it can be removed by oxidation. Engineering., Vol. 87
(1910), p. 801.
Graphitization of Iron-Carbon Alloys, by Kotaro Honda and Takejiro
Murakanu.
In pure iron carbon alloys, graphitization is caused by the decom-
position of the cementite solidified during cooling from the melt.
Journal, Iron and Steel Institute (Sept.). (1920.)
Graphitizing of White Cast Iron, by R. S. Archer.
The author draws conclusions regarding the initiation of graphitiza-
tion below the A point and completion near or at that point. Foundry,
Vol. 48 (1920), p. 192-4.
Concerning the Solubility of Graphite in Iron, by Carl Benedicts.
Tests show that graphite is appreciably soluble in ferrite at 940
degrees Cent., therefore, iron-carbon diagram should be drawn as pro-
posed by LeChatelier, Stansfield and Charpy. Metallurgie, Vol. 5
(1908), p. 41-45.
Influence of Phosphorus on the Iron-Carbon System, by F. Wust.
The subject is brought up to date (1908) and results of tests and
experiments are given. Metallurgie, Vol. 5, p. 73-87.
The Nature of the Cast Irons, by G. B. Upton.
Discussion of Fe-C diagram, relating particularly to liquidus and
solidus lines. Journal of Physical Chemistry, Vol. 13 (1909), p.
388-416.
The Effect of Foreign Substances Upon the Fusion Diagram of Iron-
Carbon Alloys, by P. Goerens.
An investigation of the iron-manganese-carbon and iron-phosphorus-
carbon systems. Metallurgie, Vol. 6 (1910), p. 537-50.
Theory of Malleablizing, by W. H. Hatfield.
The European and American methods of making malleable castings
are described. From a lecture before Institution of Engineers and
Shipbuilders of Scotland. Foundry, Vol. 36, p. 30.
400 Selected Bibliography
Graphitization in Iron-Carbon Alloys, by Kunlichi Tawara and G. Ashara.
Twenty-seven iron-carbon alloys were melted and after slight cooling
cast into molds and cooled at varying rates. Deductions from these
tests are discussed. Journal, Iron and Steel Institute (1919).
The Theory of Annealing, by F. Wust.
A discussion of the metallurgy of annealing with special reference to
the migration of carbon. Metallurgie, Vol. 5 (1908), p. 7-12.
The Evolution of the Malleable Iron Process, by J. P. Pero and J. C.
Nulsen.
An account of the advance in metallurgy of malleable practice, touch-
ing upon the importance of sulphur and phosphorus, "steely" iron,
uses of the microscope, value of strength tests, fatigue failure, and
properties of malleable. 4000 words. Transactions, A. F. A., Vol.
XXV, p. 222.
What Is the Normal Fracture of Good Malleable Iron? by Enrique
Touceda.
The author explains how the test lug should be secured and describes
the appearance of various fractures, interpreting the significance of
each. 2000 words, 6 illustrations. Transactions, A. F. A., Vol. XXV,
p. 506.
Judging Malleable by Fracture, by Richard Moldenke.
Photographs of typical fractures, with suitable explanation of each.
Foundry, Vol. 37, p. 237.
IV — PROPERTIES AND USES
Materials of Construction, by Adelbert P. Mills ; published by John Wiley
& Sons, Inc., New York. (1922.)
Manufacture and uses of cements, clay products, ferrous and non-
ferrous metals, timber, rope and mechanical fabrics. One chapter
(2500 words), devoted to malleable cast iron, describes methods of
production and lists properties and uses.
Materials of Construction, by M. O. Withey and James Aston ; John Wiley
& Sons, Inc. (1918.)
Principles of mechanics of materials including timber, stone, cement,
metals, etc. Constitution of iron and steel and the properties of metal
products, including malleable cast iron. 840 pages, illustrated.
Machinability of Malleable Cast Iron.
A discussion of the paper by Messrs. Smith and Barr (A. F. A. Vol.
XXVIII, p. 330), covering threading tests and data on cutting
speeds. 1700 words. Transactions, A. F. A., Vol. XXVIII, p. 338.
Relation Between Machining Qualities of Malleable Castings and Physical
Tests, by Edwin K. Smith and William Barr.
A discussion of the effect of higher physical properties of malleable
upon its machinability, based on the results of tests and replies to a
Selected Bibliography 401
questionnaire. 2100 words, 2 drawings and 5 tables. Transactions,
A. F. A., Vol. XXVIII, p. 330.
Some Physical Constants of American Malleable Cast Iron, by H. A.
Schwartz.
A review of the properties of malleable with detailed data and
charts showing the behavior of the metal under various stresses and
physical conditions. 5000 words, 12 diagrams. Proceedings, A, S. T.
M., Vol. XIX, Part II, p. 248.
Physical Properties of American Malleable Cast Iron, by W. R. Bean.
A discussion of the strength, elongation, resistance to bending, hard-
ness, machinability, density, etc., of malleable. 2400 words, 3 illus-
trations, 3 tables. Proceedings, A. S. T. M., Vol. XIX Part II, p.
266.
Testing Hardness of Malleable, by Enrique Touceda.
The author explains why hardness tests are inadequate as a measure
of machinability. 1000 words, 2 illustrations. Proceedings, A. S. T.
M., Vol. XIX; Part II, p. 273.
Effect of Machining and of Cross Section on the Tensile Properties of
Malleable Cast Iron, by H. A. Schwartz.
A description of tests made to determine the effect of decarbonization,
grain structure, area of cross section, rate of cooling, shrinkage, etc.,
on the relative strength of a specimen. The results are discussed and
conclusions drawn. 2400 words, 6 diagrams. Proceedings, A. S. T.
M., Vol. XX ; Part II, p. 70.
Standard Specifications for Malleable Castings (A 47-19).
The standard specifications adopted in 1919 by the American Society
for Testing Materials. 800 words, 1 illustration. A. S. T. M.
Standards, 1921, p. 354.
Some Needs of the Malleable Iron Industry, by W. P. Putnam.
The author explains that research must be extended and equipment
improved before malleable practice attains a high standard of 'excel-
lence. 1500 words. Transactions, A. F. A., Vol. XXVIII, p. 257.
Malleable Iron as a Material for Engineering Construction, by H. A.
Schwartz.
A review of certain objections to malleable held by engineers in 1918,
followed by a brief outline of the malleable process, a detailed account
of metallurgical principles involved, and a description of the actual
properties of malleable as an engineering material. 7500 words, 15
illustrations. Transactions, A. F. A., Vol. XXVII, p. 373.
Malleable Iron and Its Uses, by Henry F. Pope.
A brief outline of the characteristics of malleable and its principal
applications as an engineering material. 1500 words. Year Book,
A. I. and S. I., 1917, p. 353.
Remarks on the Strength and Ductility of Malleable Cast Iron After the
402 Selected Bibliography
Skin Has Been Removed, by Enrique Touceda.
An expose of the fallacy that after the skin of a malleable casting
has been removed, the remaining metal is of inferior quality. 4000
words, 3 illustrations. Transactions, A. F. A., Vol. XXIII, p. 440.
Chemical and Physical Properties of Malleable Iron, by W. P. Putnam.
The annealing process is discussed and charts are shown to empha-
.size the importance of closely controlling annealing temperatures. 500
words, 5 charts, 2 tables, 4 micrographs. Transactions, A. F. A., Vol.
20, p. 363.
The Physical Properties of Malleable Castings as Influenced by the
Process of Manufacture, by Richard Moldenke.
An argument for the adoption of standard specifications for malleable,
particularly to control time of annealing, 1100 words, Proceedings,
A. S. T. M., Vol. 3, p. 204.
Physical Constants for Malleable Cast Iron by H. A. Schwartz.
Results of tests on the physical properties of malleable. Foundry,
Vol. 47, p. 462.
Properties of Malleable Cast Iron, by H. A. Schwartz.
An outline of the mechanical, thermal and electrical properties of
American malleable. Engineering Nezvs-Record, Vol. 83, p. 132.
The Use to Which Malleable Iron Castings Can Be Applied in Car
Construction, by Frank J. Lanahan.
A historical sketch covering the types of castings used in construc-
tion of American railroad cars, followed by a discussion of the
merits of malleable castings for this work. 3200 words. Transac-
tions, A. F. A., Vol. XXV, p. 489.
Advantages of Malleable Iron Versus Steel for Agricultural Castings,
by P. A. Paulson.
An explanation of the increased use (in 1918) of malleable castings
in agricultural machinery, with reference to the tensile strength of
malleable, uniformity of metal, and ratio of elastic limit to the
tensile strength. 1200 words. Transactions, A. F. A., Vol. XXVII,
p. 425.
The Integrity of the Casting, by Enrique Touceda.
A discussion of the value of tests to determine the properties of
malleable, with comments on the production of sound castings. 2400
words. Transactions, A. F. A., Vol. XXVII, p. 438.
Effect of Machining and of Cross-Section on the Tensile Properties of
Malleable Cast Iron, by H. A. Schwartz.
A study of tensile properties of malleable. Proceedings, American
Society for Testing Materials, Vol. 20 (1921), p. 70-79.
Tests for Hardness, by T. Turner.
An investigation to compare results obtained by Turner, Shore, Brinell
and Keep methods. Engineering, Vol. 87 (1909), p. 835.
INDEX
Agricultural implements, applications of malleable for 37
Air Furnace:
Action of flame in 141
Amount of air required for combustion 145
Analysis of slag in 147
Chemical changes in melting in 146
Chemistry of combustion in 146
Coal consumption of 144
Consumption of refractories 147
Depth of metal in 143
Design of 125, 136
Dimensions of 143
Heat balance of 153
Historical notes on early 135
Method of firing and melting in *. 138
Rate of melting in 157
Roof construction of 141
Use of forced draft 154
Use of pulverized coal in - 154
Temperature of metal in 152
Variation in composition at different periods of heat in 150
Alexander 46
American Malleable Castings Association:
Research work of 31, 35
Tensile properties of specimens submitted by members of 291
American Malleable Castings Co 19
American Radiator Co 21
American Society for Testing Materials:
Adoption of specifications for malleable 36
Specifications for malleable castings 274, 276
Annealing:
Changes of metallographic composition of white iron during.... 69
Cycle, length of 218
Effect of type of packing for 228
Factors affecting the rate of cooling during 220
Factors affecting height of, stacks of pots 192
Function of packing in 190
404 Index ,
Annealing :
Furnace, consumption of coal in 203
Furnace, description and use of pit type of 199
Furnace, design of 194
Furnace, disposition of heat in 205
Furnace, economy of large 195
Furnace, electric heating arrangement suggested by Touceda
for use in 208
Furnace, heat requirements of 204
Furnace, pyrometer equipment for 209, 210
Furnace, thermal efficiency of 206
Furnace, use of powdered coal for 196
Limitations on minimum time of 221
Metallurgy of 61, 230
Method of packing castings for 190
Objections to high temperature at beginning of 214
Operations, outline of 81
Pots, construction of 193
Pots, life of 192
Pots, separator plate for 193
Practice, early conception of 189
Principles of 213
Range of temperatures in 189
Safe maximum temperature for 215
Temperature, controlling 209
Archer, R. S 33, 46, 63, 65, 349
Ash, analysis of, of suitable coal for melting 115
Austenite, definition of 41
Austin 51
Automotive industry, use of malleable in 38
Barlow, J. H., successor of Boyden 16
Barr, William - 330, 331, 334
Bauer, 0 231
Bean, W. R ' 30, 32, 263, 273, 295
Beams, strength of malleable castings when used as 307
Beckett, James 29
Beilby 349
Belgium, production of malleable in 40
Benedick's diagram 47, 51
Index 405
Bessemer process, effect of discovery of 6
Bibliography 385
Black heart malleable, discovery of, by Boyden 11
Blast furnace:
Pig iron first made in, in Germany 4
Probable facts surrounding introduction of first, in prehistoric
period 3
Blast furnaces, location of, making malleable pig iron 96
Boyden:
As a metallurgist 26
Extracts from diary kept by 11
Foundry career of 15
Statue of, erected by citizens of Newark, N. J. . 12
Successors of 16
Boyden, Seth 95, 197
Bourcoud, A. E 231
Brick:
Analysis of burnt 131
Manufacture of fire 131
Bridgeport Malleable Iron Co. 18
Brinell method of measuring hardness '. . 324
Brittleness, tests by Humphrey on 322
Building requirements, comparison of, for gray iron and malleable
plants .- 83
Campbell, H. H 182
Canada, production of malleable in 39
Capacity of malleable plants in United States 84
Carbon:
Conversion of combined, into temper 66,67
Definition of temper r 41
Effect of, on tensile properties of malleable 292
Graphite and temper, in graphitization 52
Methods of determining, content 270
Migration of, during annealing process 222, 224
Recombination of, in pig iron, under melting conditions 137, 139
Relation between silicon and, in malleable 55, 68
Solubility of 65
Study of quantitative effect of, by author in 1904 30
Cast iron, first production of, in early stack or blast furnace 4
406 Index
Cementite, definition of 41
Cesaro 46, 235
Charpy 33
Chicago Malleable Iron Co 19, 94
Chrome 269
Clay:
Analysis of raw refractory. 131
Location of deposits of refractory 126, 127, 129
Use of refractory, in malleable industry 127, 129
Cleaning castings, methods of 249
Cleveland Malleable Iron Co 19
Coal:
Analysis of melting 113
Consumption of, in annealing 203
Consumption of, in air furnace melting 144
Distribution of sources of 109, 1 10
Factors to be considered in selecting, for melting 113
Grades of, used in malleable foundries Ill
Method of preparing pulverized 117
Precautions to be taken in transporting pulverized 117
Requirements in, for pulverizing 115
Size of, for air furnace fuel 115
Use of pulverized, in air furnace melting 154
Coke, use of, in making malleable in cupola 121
Color method, unreliability of, for determining carbon and silicon 267
Columns, strength of malleable cast 305
Combustion, discussion of, in air furnace 145
Compression, behavior of malleable under 303, 304
Contraction :
Effect of size and shape of casting on, of metal 242
Use of terms "fluid," and "solid" 237
Converter, type of, used in triplex process 167
Coonley, John C 19
Corrosion of malleable - 376
Cort, invention of puddling, furnace by 6
Cross bending:
Behavior of malleable under cyclic 357, 358
Results of tests on, of malleable 309
Stresses in, of malleable 307
Index 407
Crum-Grzimailo 141
Cupola:
Control of metal in, melting 175
Metallurgy of melting in 163, 177
Ratio of metal to fuel in 177
Cutting hardness, method of measuring 327
Dalby : .355
Davenport, E. S 273
Dayton Malleable Iron Co .' 19
Decarburization:
Control of, in annealing 226
Extent of, during annealing process 224
Definitions of entities in alloys of iron and steel 41
Density of malleable 384
Design, factors to be considered in, of malleable castings 243
Devlin, Thomas 17, 28
Diller, H. E 29
Dolomite, use of, in malleable industry 133
Dressier-type tunnel kiln for annealing 202, 206
Drill tests, conclusions drawn from, of malleable 331, 332
Dyer, C. D 138
Eastern Malleable Iron Co 18
Eberhard Mfg. Co 21
Elastic Limit:
Definition of 287
Increase in, of malleable by plastic deformation 356
Electric Furnace:
Chemical advantages of 160
Chemical reactions in 164
Description of, used in triplex furnace 163
Distribution of metalloids in 171
Use of, in malleable industry 160
Electrical properties of malleable 371
Electrical resistance of malleable, effect of temperature on 376, 377
Elongation, effect of, on resistance of malleable to dynamic ten-
sile loads 319
England, production of malleable in 39
Equilibrium diagram for iron carbon system 47, 48, 49, 63
408 Index
Equipment, principal, used in malleable foundries 73
Expansion of malleable 378, 379
Fairchild 209
Fatigue, resistance of malleable to 323
Feeders, use of, in molding malleable castings 245
Ferrite, definition of 41
Ferromanganese, use of, in making malleable 105
Ferrosilicon, use of, in making malleable 107
Fire brick, manufacture of 131
Foote 209
Forbes, Alexander Duncan 18
Forbes, Duncan 18, 28
Forquignon 33
Fort Pitt Malleable Iron Co 183
Foundries :
Distribution of malleable, in United States ....20,23
Number of malleable, in the United States 24
Range in size and capacity of malleable 71
Fracture :
Interpreting appearance of 148, 149, 150
Normal, of malleable iron 279
France, production of malleable in 40
Freezing, changes of metallographic composition of white iron
during , 69
Friction, resistance of malleable to 336
Fryer, J. H 193
Fuel, classification of, used in making malleable 109
Fulton, A. M 182
Furnace, primitive iron, used by early Egyptians 2, 3
Furnace, shoveling, built by Seth Boyden 197
Galvanizing, method of hot, of malleable 263
Gas:
Analysis and properties of, for melting purposes 119
Composition of producer 119
Location of producing fields of natural 110
Gailly, Raymond 40
Gates, proper use of, in molding malleable 245
General Electric Co. , 21
Index 409
Goecke •**
Gontermann . . ; 52, 234
Goodlet, James 95
Gordon • 51
Graphite, definition of 41
Graphitization:
Effect of chemical composition on 52
Relation of time and temperature in 68
Research on, by Storey 33
Theory advanced by Honda and Murakami 35
Theory of 61
Grenet 33
Grinding, precautions to be taken in disk, of malleable castings.. 254
Grinding as a method of removing gates, fins, etc 253
Hammer, Alfred E 27, 29, 30, 34, 97
Harding, Warren G 19
Hardness:
Method of measuring cutting 328
Methods of measuring 324
Relation of Brinell and Shore, numbers 326
Relation of, to completeness of anneal 326
Relation of, to wear of malleable 324
Significance of cutting, of malleable 327
Harness, early application of malleable for, parts 36
Harrison 209
Haswell, John 18
Hatfield, W. H 10, 33
Heat balance of triplex process 171, 172, 173
Heat, disposition of, in annealing furnace 205
Heat treatment of malleable at temperatures below critical point.. 264
Herbert 328, 329
Heyn, E 33
Highriter, H. W 137, 273
Hird 52
Honda, Kotaro 35
Hoosick Malleable Iron Works 17, 18
Horsley, Sidney 18
Howe, H. M 33, 49, 63
Iljin 33
410 Index
Impact:
Effect of, on malleable 315
Machines for testing 322
Testing malleable for, by series of equal or increasing blows.. 363
Testing malleable for resistance to 316, 317
Inspecting, methods of, malleable 267
Inspecting, factors to be considered in, malleable for acceptance
by consumer 283
International Harvester Co 21
Iron and steel in us'e at time of American civil war, review of
types of 6
Iron-carbon alloys, theories on 46
Iron-carbon diagram 47, 48, 49, 51, 63, 66
Ironton Malleable Iron Co % 19
Japan, production of malleable in 40
Jeffries, Zay 46, 349
Johnson, Isaac ; 17
Johnson, J. B., Jr 101
Kawahigashi, Commander 40
Kingsland, G. H ' , 197
Kranz, W. G 160
Labor, division of, in typical malleable plant 84
Labor, types of, available in various foundry centers of the United
States 87
Laboratory, A. E. Hammer establishes first chemical, in American
malleable industry 27
Laboratory, McConway & Torley establish 29
LaMarche, Charles L 21
Lanahan, Frank J 182
Link-Belt Co 21
Load-deformation curves for malleable under plastic deforma-
tion 364, 367, 368
Loeb, Peter 19
Machineabilit}', investigations on, of malleable 328
Machining:
Factors contributing to, difficulties 256
Factors governing, of malleable castings 254
Properties of malleable 330, 331
Index 411
Magnesia, use of, as refractory in malleable industry 133
Magnetic properties of malleable 374, 375
Magnetization of 'malleable 373
Malleable:
Contraction from pattern size 240
Discovery of black heart, by Boyden in 1826 11
Early uses of 36
Industry, extent of, in Europe 10
Industry in Europe resulting from Reaumur's discovery 9
Industry, number of foundries in United 'States 24
Industry, present extent and distribution of foundries in 20, 23
Iron, first described by Reaumur in 1772 9
Location and distribution of principal sellers of, in United
States 22, 23
Metallurgical characteristics of 46
Misconceptions regarding 31
Pig iron, guarantees of analyses of 103
Production of, in foreign countries 39, 40
Production of, in United States 23, 24
Scrap, description of grades of 91
Use of, for electrical apparatus 371
Uses of, in war 38
Manganese, method of determining, consent 270
Manganese sulphide, effect of 57
Martensite, definition of 41
Material, amount handled to produce one ton of castings 85
Material, raw, used in malleable foundry 73
Matsubara 230, 231
McConway & Torley, establish laboratory 29
Melting operations, outline of . 77
Melting stock used in making malleable 91
Merica, P. D 33, 63
Metallography, employment of, for testing malleable 273
Metallography, method of polishing specimens for 273
Metallurgy, brief history of contributions to, of malleable 33
Metallurgy, role of, in development of American malleable industry 26
Metals used by prehistoric metallurgists 1
Meteoric iron discovered by Admiral Peary 1
Microstructure of malleable 59, 63
Moldenke, Dr. Richard . .29, 30, 32, 97, 138
412 Index
Molding, comparison of considerations in, of gray iron and mal-
leable castings 233
Molding machines, types used for malleable castings 247
Molding methods, improvements in 247
Molding sands, location of beds of, in United States 124, 126
Muffle furnace, description of, for annealing 199, 200, 201
Murakami, T ' 35
Mystery in malleable industry 26
National Malleable Castings Co 19, 29, 95
New Jersey Malleable Works 17
Newbold, Charles -....' 19
Nichols, W. S 17
Nicholson 328
Northern Malleable Iron Co 18
Nutting 351, 353
Oil:
Location of supplies in the United States 110
Use of, for melting and annealing 123
Use of fuel, in open-hearth furnace 187
Open-Hearth Furnace:
Advantages and disadvantages of melting in ' 177
Design of 179, 180, 181
Effect of invention of, by Siemens 6
Heat balance of melting in 185, 186
Labor required to operate 187
Losses in melting in 184
Metallurgy of 183
Ordnance, applications of malleable for 38
Ore, analysis of, used for malleable 103
Ore, location of fields supplying, for malleable industry 96, 101
Operations, sequence of, in malleable foundries 77, 83
Organization of malleable foundry 72, 73
Otis, Frank J 18
Oxidation, effect of, during annealing 68
Packing:
Analyses of various types of, for annealing 229
Composition of, used for annealing 228
For annealing, metallurgical effect of use of 227
Index 413
Patterns for malleable, factors to be considered in making 241
Payne .. . . , 51
Pearlite, definition of 41
Permeability of malleable 372, 373
Personnel of malleable foundry organization 73
Peterson 235
Phosphorus, effect of, in malleable 59
Phosphorus, method of determining, content 270
Pig Iron:
Discussion of merits of coke and charcoal 97
First made in blast furnace in Germany in 1311 : 4
Grades of, used in making malleable 95
Guarantees of analyses of malleable 103
Location of furnaces making malleable 96
Tendency toward change in sulphur and phosphorus content of 105
Pipe fitting, use of malleable for 37
Plastic Deformation:
Action of specimen under test for 360
Behavior of malleable when tested for 340
Change of structure of malleable when deformed under 342
Destroying effect of, by heat treatment 345
Effect of, on elastic limit ._ 356
Effect of, on grain structure of 343
Mechanical effects of 349,351
Theory of 339
Pope, Alfred A 19, 27, 29, 30, 34
Press fitting, method of, malleable 257
Production of malleable in foreign countries. . , 39
Production of malleable in United States by states 23, 24
Production of steel and malleable castings compared 24
Proportional limit, definition of 287
Protecting coatings, comparative value of galvanizing, sherardizing
and electrogalvanizing 262
Protective coatings, methods of applying, .to malleable 262
Puddling furnace, effect of invention of, by Cort 6
Pulverized coal, use of, in annealing ovens 196
Pyrometers for annealing furnaces 209, 210
Railroad, application of malleable for, rolling stock 36
Reaumur, malleable cast iron described by 9
414 Index
Reduction in area, relation of, to diameter of tensile test specimen 298
Refractories, consumption of, in air furnace melting 147
Refractories, use of, in malleable industry 127, 129
Remy, Marcel 40
Roberts-Austin diagram 46
Rockford Malleable Iron Works 19
Ruff 33
Ruer, R 33
Sand:
Properties of molding 124
Selection of core and molding, for malleable 245
Tests for molding. . 127
Schenk 230, 231
Scrap, kinds of, used in making malleable 91
Shear, behavior of malleable when subjected to 310
Shore method of measuring hardness 325
Shrinkage, allowance for, in malleable 239
Shrinkage, use of term in molding and patternmaking 237
Shrinks, methods of avoiding 243
Siemens, effect of development of open-hearth furnace by 6
Silicon:
Influence of, on graphitization 53
Method of determining, content 270
Range of, best suited to foundry requirements 54
Relation between carbon and, in malleable 55, 68
Smith, Edwin K 330, 331, 334
Sorbite, definition of . . , 41
Specific heat of malleable 381
Sprue, use of, as melting charge 94
Steel scrap, selection of, for charging melting furnace 94
Steel, use of "blister" or cementation, in early centuries 5
Steinmetz, Charles P 374
Storey, Oliver 33
Straightening, methods of, malleable castings 261
Sulphur,, influence of, in malleable 57
Sulphur, method of determining, content 270
Taylor, F. W 328, 329
Temperature:
Effect of, on dimensions of malleable 378
Index 415
Temperature :
Influence of, on graphitization 65
Pouring, for malleable 235
Use of malleable under high 378
Tensile properties of malleable, effect of temperature on 382
Tensile strength:
Calculating safe, for threaded malleable 301
Effect of carbon on, of malleable 292
Effect of cross sectional area of specimen on 295, 297
Relation of, of cast and machined specimens 295, 296
Tension :
Applying alternate, stress to malleable 356
Behavior of malleable iron under 290
Behavior of metals under 288
Stress-strain diagram of malleable under successive increas-
ing 354, 355
Test, dynamic, for malleable developed by B. J. Walker 321
Test lugs, preparation of 277
Testing machines, types of impact 322
Thermal conductivity of malleable 379, 380, 383,384
Thermo-couples, use of, in annealing furnaces 210
Thompson, G. H 18
Thrasher 68
Time element in graphitization 68
Timken Roller Bearing Co., foundry of 19
Tool failures, causes of, in machining malleable 335
Torsion and tension, effect on malleable of combined 362
Torsion, behavior of malleable when subjected to 311, 312, 313
Touceda, Enrique 29, 31, 32, 153, 208
Triplex Process:
Description of 161
Developed by W. G. Kranz .' 160
Heat efficiency of 174
Metallurgy of 162
Metallurgy of slag in 170
Troosite, definition of 41
Tunnel-kiln, Dressier, for annealing. 202, 206
Turner, Thomas 40, 237, 327
Tuttle, B. B. . 18
416 Index
University of Illinois 328
Walker, B. J 29, 34, 196, 321
Wear, relation of hardness of malleable to 324
Welding, factors to be considered in, malleable castings 251
Welding, suggestions to user of malleable castings on 260
White, A. E 33, 63
White cast iron, changes of metallographic composition during
freezing and annealing . . .' 69
White cast iron, freezing of . 49
White heart malleable, early production of, in United States 10
Whittemore, J. H ' ....17, 18, 19
Wilmington Malleable Iron Works 197
Wood Harvester Co., Walter 18
Wood Mowing & Reaping Machine Co., Walter 18, 29
Wood, Walter ? 17, 28
Woody, W. L 240
Woodworking tools, impression malleable is widely used for 38
Wrought iron, early use of, in making malleable 95
Wust 235
Yield point, definition of 287
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