THE PRINCIPLES AND PRACTICE
OF
IRON AND STEEL MANUFACTURE
BY THE SAME AUTHOR.
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< i
THE PRINCIPLES AND PRACTICE
OF
IRON AND STEEL
MANUFACTURE
BY
WALTER MACFARLANE, F.I.C.
PRINCIPAL OF THE STAFFORDSHIRE COUNTY iMETALLURGICAL AND ENGINEERING
INSTITUTE, WEDNESBURY
PAST PRESIDENT, STAFFORDSHIRE IRON AND STEEL INSTITUTE
FORMERLY BURSAR IN TECHNICAL CHEMISTRY, ANDERSON'S COLLEGE
ASSESSOR IN METALLURGY, ROYAL TECHNICAL COLLEGE, GLASGOW; AND
VICE-PRESIDENT WEST OF SCOTLAND IRON AND STEHL INSTITUTE
.tfiftb
LONGMANS, GREEN, AND CO.
39 PATERNOSTER ROW, LONDON
NEW YORK, BOMBAY, AND CALCUTTA
1917
-r
PREFACE.
THE author of this book was for fourteen years
engaged on the technical staff of iron and steel works,
a fact which may account for the attention given to
practical details throughout its pages. The intention
is to provide — as far as the scope of the work permits —
sound instruction and reliable information for technical
students, metallurgists, engineers, and others engaged in
the various branches of the iron and steel trades.
In plan the book differs from others on the subject.
Hitherto it has been usual to consider, firstly, the iron
ores, and then the several processes for the production
of finished articles. The author has, however, found it
better to begin with a consideration of the finished
products, as they are more simple in composition and
much more familiar than the ores. Some years' experi-
ence of each system has convinced the author that the
new method is superior to the old. But as each chapter is
self-contained, the reader, student, or teacher may follow
either plan without inconvenience.
The plant illustrated and described is in use in well-
conducted works at the present day.
Several chapters have been revised by acknowledged
experts having intimate practical experience of their
branches of manufacture. To friends who so kindly
helped in this direction the author is grateful. He
desires to thank the firms from whom he had permission
to take works photographs, and also the firms to whose
generosity he is indebted for sketches, blocks, &c.
VI PREFACE.
Thnnks are tendered to the Councils of the Institution
of Mechanical Engineers, the Iron and Steel Institute
(London), the Staffordshire Iron and Steel Institute, the
West of Scotland Iron and Steel Institute, and the
Cleveland Institution of Engineers; also to the Editors
of Gassier s Magazine and the Foundry Trade Journal
for permission kindly granted to copy extracts from their
publications.
Special thanks are due to Professor A. Humboldt
Sexton, and to Messrs. Alfred Harvey, Westminster;
Joseph H. Harrison, Middlesbrough ; and Robert
Buchanan, Birmingham, for valuable suggestions.
THE MUNICIPAL SCIENCE SCHOOL,
WKDNESBURY, February, 1906.
PREFACE TO THE FIFTH EDITION.
A FEW alterations have been made in the text, arid new
matter has been added.
STAFFORDSHIRE COUNTY INSTITUTE,
WEDNESBURY, Sept. 1917.
CONTENTS.
CHAPTER PAOR
I. Introduction, ......... 1
II. Preliminary Considerations, 3
III. The Puddling Process for the Production of Wrought
Iron, 11
IV. Crucible Cast Steel, 35
V. Treatment of Tool Steel, . . . . . .51
VI. Mild Steel, 57
VII. Acid Bessemer Plant, 64
VIII. The Acid Bessemer Process, 75
IX. The Basic Bessemer Process, 84
X. Acid Siemens Plant, 97
XI. The Acid Siemens (Open-hearth) Process, . . .116
XII. The Basic Open-hearth Process, 127
XIII. Bessemer and Siemens Steel Ingots, . . . .134
XIV. Mechanical Testing of Steel and Iron 142
XV. Foundry Practice — Iron and Steel Castings, . . .148
XVI. Malleable Castings, 167
XVII. Case-hardening, 171
XVIII. Iron Ores : their Composition, &c., .... 174
XIX. Preparation of Ores for Smelting, 182
XX. The Blast Furnace and its Equipment, .... 188
XXI. Working a Blast Furnace, 203
XXII. The Products of the Blast Furnace, . . . .213
XXIII. Notes on Fuels, Fluxes, Kefractory Materials, &c., . 224
APPENDIX.
Analyses of Finishing Materials and Softeners, .... 237
Table of Various Grades of Pig Iron, 239
Typical Analyses ot Pig Iron, 240
Composition of Scotch Pig Iron, 241
Composition of Cleveland Pig Iron, 241
Analyses of British Iron Ores, 242
Analyses of Bilbao Ores, 243
Analyses of Mediterranean Ores, 244
Analyses of Bricks, 246
V11I CONTENTS.
PAGE
Analyses of Gases, 246
American Iron Ores, 247
American Ore Supplies, ........ 258
Modern Hoisting Machinery, 251
Handling Pig Iron at Blast Furnaces, 253
Mixers, . .254
Tilting Furnaces, ... 255
Charging Machines, 256
Electrical Applications, 257
Syllabus of "Iron and Steel Manufacture/'' City and Guilds of
London Institute, . xiii
LIST OF ILLUSTRATIONS.
FHJ. NO. PAGJi
1. Puddling Furnace, General View, . . . . .14
2. ,, Longitudinal Section. . . . .15
3. ,, Plan, . . . . . . .15
4. ,, Crosa Section through Grate, . . 16
5. „ ,, ,, Fettling, . . 16
6. Charging a Puddling Furnace, ...... 19
7. Pig Iron in Puddling Furnace, ...... 20
8. Puddler Rabbling a Charge, 21
9 Drawing Puddled Ball from Furnace, .... 22
10. Tapping Cinder from Furnace, ...... 24
11. Helve, 29
12. Steam Hammer, 30
13. Forge Train (Mill for Puddled Bars), 31
14. ,, End View, 32
15. Merchant Bar Mill, 33
16. Cementation Furnace, General View, .... 36
17. „ Section, 37
18. „ Plan, 38
19. Crucible for Steel Melting, 42
20. Steel-melting House, General View, 43
21. ,, Hole, Section, 44
22. Bessemer Converter, 65
23. Tuyere for Converter, 66
24. Arrangement for Ramming Converter, .... 67
25. Bessemer Ladle, &c., 69
26. Ingot Mould, 70
27. Steel-work Cupola 72
28. Mounted Ladle for Hot Metal, 73
29. Pouring " Metal" into a Converter, 75
30. Bessemer Converter while Blowing, 78
31. Pouring Metal from a Converter, ..... 76
32. Steel Ingot and Dogs, 77
33. Arrangement for Ramming Basic Plug, .... 88
34. Bogey Ladle Crane, 89
35. Charging Lime into a Bessemer Converter, . . .90
36. Wilson Gas Producer, Section, 98
X. LIST OP ILLUSTRATIONS.
PIG. HO. PAGE
37. Wilson Gas Producer, \vith Water Bottom, ... 99
38. „ ,, with Discharging Screw, . . .101
39. Duff Gas Producer, 102
40. Siemens Open-hearth Furnace, Front View, . . 104
41. „ „ Longitudinal Section, . 106
42. „ „ Cross Section, . . .108
43. „ ,, Back View, . . .109
44. Siemens Casting Pit, with Ladle, Ill
45. Large Steel Ladle 112
46. Tapping a Siemens Furnace, . . . . . .114
47. Peel for Charging, 116
48. Men Charging Steel Furnace, 117
49. Steel and Slag being Tapped from Furnace, . . .118
50. Teeming Steel into Ingot Moulds, 119
51. Stripping Steel Ingots, 120
52. Empty Steel Ladle 121
53. Neutral Rib in Basic Steel Furnace, 129
54. "Feeding" a Steel-melting Furnace, 130
55. Steel Ingot in Course of Cooling, 135
56. Reheating Furnace, . 137
57. Gjers' Soaking Pit, . . . . . . . .139
58. Soaking Furnace, ........ 140
59. Flat Test Piece, 142
60. Cylindrical Test Piece, 143
61. Foundry Cupola with Solid Bottom, 151
62. „ „ Drop „ 152
63. ,, ,, ,, ,, Section, . . . 153
64. „ ,, „ Receiver, 154
65. Roots' Blower, 155
66. ,, Section, 155
67. Moulder's Hand-shank Ladle, 157
68. „ Double Hand-shank Ladle, . . . .157
69. „ Geared Crane Ladle, 158
70. „ Ladle on Wheels, 159
71. Chill Casting, . • -163
72. Iron Casting, 164
73. „ 1«4
74. „ 164
75. „ 164
76. „ 164
77. „ 165
78. Annealing Furnace for Malleable Castings, . . .168
79. Scotch Calcining Kiln, 186
LIST OP ILLUSTRATIONS. ti
ne. NO. PAGE
80. Gjers* Calcining Kiln, 186
81. Range of Iron-smelting Blast Furnaces, , . , .189
82. Modern Blast Furnace, 191
83. Scotch Tuyere, , . . .194
84. Staffordshire Tuyere, . 194
85. Lloyd's Spray Tuyere 194
86. Cast-iron Hot-blast Stove, . 197
87. Cowper's ,, „ 198
88. ,, ,, ., Plan, 199
89. Blast-furnace Pig-bed, 208
90. Grey Pig Iron, Fracture 218
91. Mottled „ ,, -2 IS
92. White „ ,, 218
93. Grey and White Pig Iron. Fracture, 218
94. Front of Boilers Fired with Blast-furnace Gas, . . . 222
95. Arrangement for Utilising Blast-furnace Gas— Section, . 223
96. Gas Engine, 223
97. Transport Car with two Charging Buckets, . . . 251
98. Charging Bucket at top of Blast Furnace, .... 252
Tilting Furnace, Frontispiece,.
Bogey Ladle Crane, ...... facing page, 89
Crane Locomotive, . . . . . . ,, 111
Map showing the British Iron-making Zones, . ,, 180
Blast-furnace Hoisting Plant, .... „ 251
Overhead Crane with Comb „ 253
Tilting Furnace, „ 255
Charging Machine, „ 156
Charging Machine, „ 257
Electric Furnace, „ 258
Babcock & Wilcoi Boiler 221
THE PKINCIPLES AND PBACT1CE
OF
IRON AND STEEL MANUFACTURE.
CHAPTER I.
INTRODUCTION.
IRON is the most plentiful and most useful of the metals.
In what a variety of useful forms do we daily, hourly, meet
with it ! In stately steamships, whose records of capacity and
of swiftness constitute one of the marvels of our time; in
the powerful locomotive careering along the iron way; in
machinery, ponderous and powerful, or nimbly delicate and
deft ; in hammer and anvil, in cannon and shot : the pen, the
sword, the ploughshare, and a thousand things more, from the
proverbial "needle to an anchor," are fashioned for us from
this most useful metal. Our terrible battleships with their
tremendous guns and engines are composed mostly of iron.
The newest world's wonders have iron for their backbone.
The stupendous bridge which spans the Forth; the Eiffel
Tower, of " solid yet graceful construction, which rears aloft
its fairy-like form, an elegant example of scientific powers and
the imaginative genius of French engineering,"* and the
Tower Bridge have become possible because of progress in
iron (or mild steel) manufacture.
The New World also abounds in stupendous structures of
steel and ironk The magnificent bridge at Poughkeepsie, the
* Sir James Kitson, Bart., M.P.
2 JPON A>P STeftL MANUFACTURE.
splendid span of ^ll-nigh 1,600 feet in the Brooklyn Bridge,
the Williamsburg and other bridges at New York, the
majestic bridge over the St. Lawrence at Quebec, the
towering buildings in the chief cities, the appliances and
plant for dealing quickly with a gigantic turnover of materials
— all these attest the usefulness of iron and steel.
Iron is extensively used for so many purposes, not only
because it is abundant, but because of its adaptability to a
great range of requirements. It can, with comparative ease,
be caused to enter into chemical union with other substances
with most remarkable results.
Wrought iron is pliant, tough, and reliable. Mild steel is
strong and flexible, and, like wrought iron, can be hammered,
rolled, or drawn into serviceable shapes, and can be welded.
With more carbon in its composition, medium steels suited for
other purposes, such as rails, axles, and wheels, are produced,
while, with still more carbon, tool steel, which can be hardened
and tempered, is made. Who can count the service to
civilisation rendered by tool steel ? Iron with still more
carbon is adapted to the formation of castings of utility and
beauty.
When iron is alloyed with such metals as chromium,
manganese, nickel, or tungsten, its range of usefulness be-
comes vastly extended, and if articles consisting mostly of
iron are subjected to modified heat treatment during manu-
facture, wonderful additional strength and endurance are
developed.
In its magnetic properties iron is unique among the
metals.
Because it has been endowed with so many good qualities
in well-balanced proportion IRON is the MASTER METAL.
CHAPTER II.
PRELIMINARY CHEMICAL CONSIDERATIONS:
DEFINITIONS.
THE great gaseous envelope — the atmosphere — which sur-
rounds the globe we inhabit is made up chiefly of two gases,
called oxygen and nitrogen, in proportion nearly approaching
to 4 measures of nitrogen to 1 measure of oxygen. There is
also a vast amount of oxygen in the rocks and minerals which
compose the crust of the earth.
Oxygen is the active agent in the atmosphere. When
oxygen enters into chemical union with fuel in our furnaces
a high temperature is created, by which the extracting,
refining, and working of metals are effected. Its chemical
symbol is 0.
To extract iron from ore a high temperature is necessary,
and if a mass of chemically combined iron-and-oxygen, or
iron oxide (which forms the essential constituent of our iron
ores), is brought into contact with carbon, or substances which
contain much carbon (such as charcoal, coal, coke, or carbon
monoxide), at a high temperature, the oxygen leaves the iron
and unites with the carbon to form gases which ultimately
find their way into the atmosphere. The oxide of iron is
reduced to the metallic state when that transfer of oxygen
takes place.
For the extraction of iron we require ore containing iron ;
we need substances (fuel) which will combine readily with
oxygen and evolve a high temperature,* and we must also
have substances which withstand chemical action even at a
high temperature. The latter constitutes the refractory
materials with which our furnaces are lined. Associated
with the iron oxide in the ores we find other matters
* Electricity generated from water power places n» to some extent
in an independent position with regard to this.
4 IRON AND STEEL MANUFACTURE.
(gangue) such as sand, lime, clay, &c. Fluxes are required
to cause such substances to melt more readily and so become
fluid at the furnace temperature.
Three substances have already been mentioned — namely,
oxygen, iron, and carbon. Each is an element. An element
is a substance which has not been split up into other sub-
stances. It has not been found possible to transmute or
change any element into another. There are about 7 8
elements known, and with the advance of science the number
is from time to time added to.
Each metal is an element : no one metal can be changed
into another. Copper, for example, cannot be changed into
tin ; tin cannot be changed into copper, or zinc, or any other
metal. But two or more metals may be melted together so as
to form an alloy differing in its character and qualities from
the metals of which it is composed.
There are other elements which are not metals. When a
non-metal enters into union with a metal, or when two or
more non-metals unite chemically, a compound is formed.
Compounds, too, differ in character, or properties, from the
elements of which they are composed. For example, a piece
of iron left exposed is attacked by chemical compounds in the
air and is changed into iron rust. The brown, powdery rust
differs from the bright, solid metal.
The elements to be considered in this book are not
numerous.
Iron (the Latin name for which is ferrum) is designated by
the symbol Fe. It is a metal of great chemical activity — -one
which is so quick to combine with substances which come into
contact with it that it is difficult to prepare in a state of
purity. Chemically pure iron is scarce and costly, and is not
of commercial importance.
Three oxides of iron are known :
(a) Ferrous oxide, a compound in the proportion of one
atom of iron with one atom of oxygen. It is therefore
represented by the chemical symbol FeO.
PBELIMINAEY CHEMICAL CONSIDERATIONS. 5
(b) Ferric oxide, a compound in the proportion of two
atoms of iron with three atoms of oxygen. Its chemical
symbol is Fe903.
(c) Magnetic oxide, a compound in the proportion of three
atoms of iron with four atoms of oxygen, and represented by
the chemical symbol Fe304. It has magnetic properties.
The student should make a point of seeing and handling
samples of iron ores containing these oxides.
Arithmetically, the iron oxides ma,y, for purposes of com-
parison, be represented thus :
Ferrous oxide, . . FeO or Fe6O6
Magnetic oxide, . . Fe304 or Fe608
Ferric oxide, .V . Fe203 or Fe609
Ferrous oxide is eager to absorb oxygen and become con-
verted into ferric oxide. If ferric oxide is heated strongly it
loses oxygen and is changed into magnetic oxide.
The chemical symbol for carbon is C. Carbon and oxygen
enter into chemical combination with each other in two well-
defined proportions, forming either carbon monoxide or
carbon dioxide. In the former, the proportions are one
atom of carbon to one atom of oxygen, the resulting com-
pound having the formula CO. In the latter the pro-
portions are one atom of carbon to two atoms of oxygen, the
resulting compound being correctly represented by the formula
CO,.
When abundance of air is present in a furnace which is
hot with glowing fuel containing carbon, the carbon becomes
oxidised (or to use the every-day term, " burned ") 'to its
fullest extent, and carbon dioxide (CO^) is formed. But if
the air supply is limited, the carbon dioxide, on coming into
contact with more hot carbonaceous fuel, is reduced to carbon
monoxide (CO). The following equation represents the
reaction : —
C02 + C = 2CO
Carbon dioxide and carbon yield carbon monoxide. ,
Carbon monoxide is very useful in many metallurgical
6 IRON AND STEEL MANUFACTURE.
operations, because, at ordinary furnace temperatures, it readily
unites with oxygen, as indicated by the equation —
2CO + 02 2C02
Carbon monoxide and oxygen yield carbon dioxide.
The importance of these statements will be apparent on
reading the following chapters.
Chemical combination .takes place in definite proportions — a
number of atoms of one element entering into chemical combination
with a definite number of atoms of another element.
Each element has a relative value with regard to each other
element ; or, to state the fact in other words, each element has
its own exchange value or equivalent. And there need be no
more mystery in the exchange value of an element than there
is in the common fact that 1 shilling is equivalent, or of
equal value, to 12 pence, or that 1 pound equals 20
shillings.
The exchange values, or atomic weights, of the elements
already named are: — Carbon, 12; oxygen, 16; iron, 56.
12 Ibs.* of carbon unite with 16 Ibs. of oxygen to form 28
Ibs. of carbon monoxide ; 12 Ibs. of carbon unite with twice 16
Ibs. of oxygen to form 44 Ibs. of carbon dioxide. The former
is represented as CO, the latter as C02. 72 Ibs. of ferrous
oxide (FeO) contain 56 Ibs. of iron and 16 Ibs. of oxygen. 80
Ibs. of ferric oxide contain 56 Ibs. of iron and &£ Ibs. of
oxygen. Ferric oxide might therefore be represented as
Fe014. But to obtain the most simple formula for ferric
oxide we must double each element and represent ferric oxide
as Fe203. For similar reasons magnetic oxide is represented
by the formula Fe304. The iron and oxygen in magnetic
oxide exist in the proportion of
Iron, 3 times 56 parts, by weight.
Oxygen, 4 „ 16 „ „
The elements to be considered in the earlier chapters of
this book and their symbols and equivalent values are —
*Any other weight may be substituted for Ibs., but that one weight,
or unit, must be kept throughout a comparison or calculation.
PRELIMINARY CHEMICAL CONSIDERATIONS.
METALS.
NON-METALS OR METALLOIDS.
Name.
Symbol.
Atomic
Weights.
Name.
Symbol.
Atomic
Weights.
Iron, .
Fe
56
Carbon,
C
12
Manganese, .
Mn
55
Hydrogen,
Nitrogen,
H
N
1
14
Oxygen,
0
16
Phosphorus,
P
31
Silicon,
Si
28
Sulphur,
S
32
The chief constituents of our fuels are (a) carbon, (&)
hydrogen, and (c) compounds of carbon and hydrogen. The
heat effects of their combustion are dealt with in Chapter
xxiii.
SILICON. — This is an element of much interest to iron and
steel-makers. It is easily oxidised. The only known oxide
of silicon is called silica and has the formula Si02, which
means that each atom of silicon has entered into chemical
union with two atoms of oxygen; or, to express the same
truth in another way, chemical combination has been effected
in the proportion, or ratio, of 28 parts (say 28 Ibs.) of silicon
with twice 16 parts (say 32 Ibs.) of oxygen.
Pure white sand, or quartz, may be taken as fair examples
of silica — the oxide of silicon. Silica is the most plentiful
substance in the earth's crust. All iron ores, as got from
the earth, contain silica. In the process of extracting iron
from ores some of the silica is caused to part with its oxygen,
and the silicon, thus freed by reduction, associates with the
metallic iron. In refining the iron, in subsequent stages,
such silicon requires to be removed.
MANGANESE is a metal the oxides of which are frequently
found in iron ores. Metallic manganese is a constituent of
irons and steels. The readiness with which it combines
chemically with oxygen, and with sulphur, is a most useful
quality which is freely applied in steel-making.
IKON, when pure, is a silver-white, tough metal which can
show the peculiar brightness known as metallic lustre. Its
8 IRON AND STEEL MANUFACTURE.
melting point is very high. When melted, or even heated
highly, where air has free access to it, the metal becomes
oxidised — that is to say, oxygen unites with the iron forming
a crumbling mass of " burnt iron." Pure iron (a very rare
substance) is more .easily burned or oxidised than impure iron ;
a fact which can be understood when it is remembered that
the impurities usually present in ordinary iron are more easily
oxidised when hot than iron itself is.
The worst impurities in many manufactured iron masses
are sulphur and phosphorus.
SULPHUR tends to produce red-shortness in iron. The term
" red-short " means that it is brittle when at a red heat.
PHOSPHORUS tends to produce cold-shortness in iron, the
term " cold-short " meaning that the mass is brittle when
cold ; that is, at ordinary temperature.
SILICON in certain proportions was formerly believed to
induce both red-shortness and cold-shortness, but recent
researches have shown that silicon cannot be classed among
the highly injurious elements.
Iron or steel which is burnt, or is red-short or cold-short, is
brittle and unreliable. Burnt iron, or iron which is red-short,
cannot be welded — at least not in a satisfactory manner.
Although there are objections to the use of iron or steel
containing certain proportions of silicon, sulphur, or phos-
phorus, it must be kept in mind that presence of these
elements in proper proportions is beneficial. For example,
some mild steels containing a little over one-tenth of a per
cent, of sulphur roll into sheets better than some makes
of purer steel. Certain cast irons may be strengthened by
judicious addition of sulphur. Pig iron containing a notable
amount of phosphorus is more fluid than purer pig iron,
and so takes a sharper impression in the mould in which
it may be cast.
The common elements which are usually present in mild
gteel — if not in undue amount — increase the power of the
steel to resist rupture by stress.
Arsenic, copper, and other elements were formerly looked
on with disfavour, or were held to condemn the steel which
contained them, but experiments carried out on a practical
DEFINITIONS. 9
scale in works amply disproved the notions held by inspecting
engineers. The marvellous qualities imparted to steel by the
prudent introduction of chromium, nickel, manganese, tungsten,
molybdenum, and other metals have proved most helpful to
all classes of engineers. The amount of carbon which is
combined with iron has most marked effects on the nature of
the steel produced by such combination.
There are certain qualities, or properties, possessed in a
marked degree by iron and steel which may, with advantage,
be defined here.
Malleability. — The quality which enables a substance to
withstand hammering, rolling out, dishing, or flanging, without
being cracked or broken.
Extensibility is the term applied to the stretching which
takes place before rupture when a metal is subjected to a
pulling force in a testing machine, or which may take place
when the metal is in use as part of a structure.
Elongation is the term used to denote the act of lengthening,
or the length to which a metal has been stretched by the
testing machine.
Elasticity is the power which enables a metal to resume its
original form on being released from a force tending to alter
its form. Thus, a piece of tempered steel may be considerably
bent, but, by virtue of its elasticity, it will straighten itself
when released from the bending force. A piece of steel may
be stretched to a slight extent, and its elasticity will enable it
to return to its original length when freed from the power
which stretched it. If, however, the stretching is carried to a
certain further point, the limit of elasticity is reached, per-
manent set occurs, and the piece of steel cannot go back to its
original dimensions.
Ductility. — The quality which enables a metal, or an alloy,
to hold together and conform to intended shape when subjected
to squeezing and stretching while being drawn into wire. In
practice the wire is drawn through a series of holes, which
dimmish in size, one by one, in a draw plate. Sometimes a
metal which rolls out well is spoken of as ductile.
Tenacity* is the quality which enables a substance to hold
*From the Latin tenax = to hold.
10 IRON AND STEEL MANUFACTURE.
together when subjected to a force which tends to stretch it.
In Britain the tenacity, or tensile strength, of a metal is
generally computed in tons per square inch of section, in
America in pounds per square inch, while on the European
Continent it is usual to state the tensile strength in kilo-
grammes per square millimetre. Mild steel is more tenacious
— has greater tensile strength — than wrought iron. In other
words, mild steel will remain unbroken under a tensile stress,
or pull, which would rupture wrought iron. For information
regarding the mechanical testing of metals see Chapter xiv.
Toughness is that quality which enables a substance to
withstand oft-repeated bendings or twistings without breaking.
Welding is the operation by which wrought iron, and the
milder varieties of steel, may be firmly joined by placing
clean ends together and hammering or pressing while the
pieces are at a proper temperature. Wrought iron is at the
correct temperature when in a plastic condition.
In a brisk fire, which is urged by a blast of air from a
bellows or a fan, the iron pieces which are to be welded are
heated till white hot. The surfaces are apt to be more or less
oxidised or "burnt," and the oxidised particles must be
removed. Some sand is therefore thrown over the white-hot
parts in order to flux off the oxides of iron. Sand, as already
explained, is essentially silica (Si02), which has a strong
affinity (or liking) for ferrous oxide (FeO), and, although
neither of these substances, separately, could be melted at a
temperature far above that of the white-hot iron, they readily
combine with each other, at a moderate temperature, to form
a compound (ferrous silicate = 2FeO, Si02) which easily
melts and flows off, carrying with it the ferric oxide (Fe203),
and leaving clean surfaces to be welded.
11
CHAPTER III.
THE PUDDLING PROCESS FOR THE PRODUCTION
OP WROUGHT IRON.
WROUGHT iron possesses many valuable qualities. It is
strong, tenacious, tough, malleable, and ductile;* it possesses
that remarkable and valuable property which enables it to be
welded. It is not altogether free from the slag 'which
accompanies its production, but even that is an advantage, as
it enables. arrows structure to be developed, and this fibrous
structure hinders dangerous crystallisation. For certain im-
portant purposes it is unsurpassed, and it commands a higher
price than is paid for mild steel. For these and other reasons
its manufacture continues, although its practical extinction
was prophesied many years ago.
Wrought iron — often called malleable iron — is still pro-
duced, although in amount which is relatively small, by
methods which have the attractive title of direct processes.
But by far the greater quantity of wrought iron is made by
the indirect method. In the latter-named method pig iron is
first produced, which is afterwards, by the puddling process,
converted into wrought iron. Pig iron is the chief product of
the blast furnace • in it is concentrated more than 90 per cent,
of iron — even if the ore from which it was extracted con-
tained only 33 per cent, of that metal. It is the business
of the puddler to purify the pig iron, and thereby change it
from a somewhat brittle, unweldable mass into metal having
the useful qualities mentioned at the opening of this chapter.
Present-day puddling is of two kinds — (a) dry puddling,
and (b) wet puddling.
Wet Puddling or Pig Boiling. — A comparison of the per-
centage composition of the pig iron used and the wrought
* These terms are explained in the previous chapter.
12
IRON AND STEEL MANUFACTURE.
iron produced may convey an idea of the work to be done by
the puddler : —
Constituents
Chemical
Symbols.
Forge
Pig Iron.
Wrought Iron
Produced.
Graphitic carbon, . . . (
Combined carbon, .
c
c
2-0
1-5
6-05
Total carbon,
c
Si
3-5
1*3
0-05
0'20
Phosphorus, ....
Sulphur, . '< >$ " ' Y* i ' !.
Manganese, . " . . .
Cinder or slag,
Iron (by difference), .
P
s
Mn
Fe
1-3
o-i
0-5
none
A
0-15
0-03
o-oi
2-80
A
100-0
100-00
Graphitic Carbon is not in chemical combination. From
rich, grey pig iron it is sometimes possible to detach flakes of
graphite (which, chemically, is carbon) from a fractured part.
Combined carbon cannot be separated in this manner.
These figures show that the impurities in the pig iron are
largely, indeed in some instances almost entirely, removed
during puddling. The removal is effected by burning out the
impurities, or, to express the idea more scientifically, the
impurities are removed by oxidation. Fortunately, the
oxidising action is selective; the impurities which we wish to
eliminate* are, under the conditions set up by the puddler,
more readily oxidised than the iron, and they therefore
become separated from the iron.
Briefly put, the puddling process consists in melting suitable
pig ironf in a properly-prepared puddling furnace, and stirring
and rubbing it, or, to use the trade term, " rabbling" it, so as
to bring the melted pig iron into intimate contact with the
oxides (chiefly oxides of iron) which constitute the "fettling"
— including the fluxing oxide — in the furnace. The carbon,
*This long word is from the Latin, and, in plain English, means "to
thrust out of doors. "
tit is one of the merits of the puddling process that a great range,
or variety, of pig iron can be successfully dealt with during the
process.
THE PUDDLING PROCESS. 13
silicon, manganese, phosphorus, and sulphur are, as previously
stated, attacked by oxygen and almost completely removed
from the pig iron. The products resulting from the oxidation
of the carbon, being gaseous, escape by the chimney; the
other oxidised products enter into the slag.
It may be accepted as one of the fundamental principles in
metallurgy that when an element — such as carbon, silicon,
sulphur, or phosphorus — existing in chemical union with a
metal, combines chemically with oxygen, the resulting oxidised
product must, when melted, separate itself from the remaining
metallic portion. Metals which become oxidised are subject
to the same general law. To this principle, or law, there are
a few well-known and easily explained exceptions.
And if oxidised metal parts with its oxygen — becomes
deoxidised, or reduced to the metallic state — the newly
liberated portion joins the metal in the furnace.
These are important points. If, for instance, a pig iron
contains 1 per cent, of silicon, it is clear that there must be
1 per cent, less iron in the pig iron, and it might be inferred
that, provided the other impurities are the same in amount in
each case, the yield of wrought iron from a pig iron containing
2 per cent, of silicon must be less than the yield from a pig
iron with only 1 per cent, of silicon. That is not so,
however. One ton of pig iron containing 1J(= 1 '2 5) per
cent, of silicon is theoretically capable of liberating nearly 1
cwt. of iron from the ferrous oxide in the fettling, or the
cinder, in the furnace, and pig iron with double that per-
centage of silicon is capable of liberating 2 cwts. of iron. The
theoretical increase in yield is never attained in practice.
But if the greater part of the oxygen for purifying the
pig iron is obtained from metallic oxides, such as in the
fettling and the cinder, the weight of wrought iron produced
will be considerably greater than the weight of pig iron
charged.
The silic^, (Si02) formed by the oxidation of silicon (Si)
unites with iron oxide (FeO) and together they go into the
slag. Certain pig irons are known as " hungry pigs," because
they "eat" so much of the fettling. The yield from such
14
IRON AND STEEL MANUFACTURE.
pig iron is great, the consumption of fettling is great, and the
labour is severe.
The oxidation of carbon and of phosphorus by oxide of iron
also leads to increased yield.
The Puddling Furnace is an oblong structure of firebrick
strengthened by cast-iron plates, and tied by iron rods which
extend along and across the furnace, and are fastened by large
nuts at each end. Each plate is thus tightly braced against
Fig. 1. — General View of Puddling Furnace.
the brickwork. The furnace is of the type which is known
as reverberatory — that is, one in which the fuel is burned in
the fire-grate at one end and the flame from which is drawn
towards the chimney at the other end. The under surface of
the brick roof — which is a slanting one — is thus heated, and
it is chiefly the heat which is reflected from the roof, or, as
the word reverberatory means, is beat, back, which causes
the high temperature in the working part of the furnace.
The fuel does not come into contact with the "metal" in
THE PUDDLING PROCESS.
15
the furnace — an arrangement which leads to substantial
advantages.
« n
CO F G H
/ / /•••/ I. /
Fig. 2.— Vertical Longitudinal Section of Puddling Furnace
A, Damper. B, Stack.
C, Nut at end of tie-rod.
D, Flue-bridge. E, Plates.
F, Working door.
G, Fettling.
H, Reverberatory roof.
J, Fire-bridge. K, Staff-hole.
L, Coal-firing opening.
M, Grate-bars.
N, Buckstave. 0, Ashpit ^
Fig. 3.— Plan of Puddling Furnace.
A, Flue. B, Forehearth. I D, Iron plating.
C, Working part. E, Ashpit.
At a convenient height above the ground level the iron
castings which support the fettling of the working bed of the
16
IRON AND STEEL MANUFACTURE.
furnace are so laid that air can circulate freely underneath to
keep the iron- work cool. Separating the fire-grate from the
working bed is the fire-bridge — a hollow iron casting under
which air can be caused to pass. At the other end of the
working bed is the fine -bridge, which is of similar design.
The flue, which is a sloping passage, connects with the
chimney, or stack, as it is often called. The chimney, which
is sometimes 50 feet high, is built of bricks braced by angle
Fig. 4. — Puddling Furnace —
Cross - section through
Grate.
Fig. 5. — Puddling Furnace—
Cross-section between Fire-
bridge and Flue-bridge.
irons up the corners : these are bound to each other by tie-
rods and nuts. It is surmounted by a damper which is
hinged and controlled by means of a chain, the lower end
of which can be easily reached.
Instead ot a heavy brick stack for each furnace it is now
not unusual to arrange for four puddling furnaces to be
worked by one stack consisting of a tall cylindrical steel
casing lined with suitable bricks.
THE PUDDLING PROCESS. 17
As a high temperature is required in the puddling furnace
the area of the fire-grate is larger in proportion to the
working part than is usual in reverberatory furnaces. The
area of the grate is generally more than one-third the area of
the working part. The grate-bars are of wrought iron, and
are supported on iron bearers. The bars are rolled in long
lengths of suitable section, and are cut into shorter pieces to
fit the grate. They can be readily removed when required.
An injector — a pipe with a widened end into which a jet of
steam is injected — may be provided. The force of the steam
induces air to enter the pipe, through which it is conveyed
to the furnace.
In front of the furnace are four openings known respectively
as the firing-hole, the staff-hole, the door, and the cinder-notch
or cinder-hole. These are all shown on figs. 1 and 2.
Through the firing-hole fuel is fed to the fire-grate. It is
customary to partly close it by placing lumps, and some small
pieces, of coal on the sill. A useful purpose is served by the
gases from the gentle distillation of this coal. These gases
are drawn into the furnace.
The largest opening — the one for the door — has a heavy
iron projecting sill, called the foreplate. The working door
consists of large firebricks or slabs set in an iron frame
suspended from one end of a lever. It is raised when
required by pulling down the other end of the lever by
means of a chain. When the chain is released the door
slides down and closes the opening. At the centre of the
lower part of the door is a small opening known as the
stopper hole or stopper notch. Under the foreplate is the
cinder-hole, and through it the cinder or slag is tapped off.
The surface of the fire-bridge and flue-bridge, and the
plates which support the working bottom, are all carefully
covered with firebrick, or with fettling, where they would be
otherwise exposed to the heat of the furnace.
The chief materials used for fettling are : —
Best Tap, the cinder or slag from reheating furnaces which
are worked with (basic) cinder bottoms ;
Bull-dog, puddler's cinder or slag which has undergone
roasting to render it less fusible (not so easily melted) ;
Purple Ore, the rich residue of ferric oxide (with about
2
18
IRON AND STEEL MANUFACTURE
4 per cent, of other compounds) left after the treatment of
iron and copper pyrites ;
Hematite Ore, a rich hematite ore mined in the North-west
of England ; *
Pottery Mine, f an iron ore mined in the pottery district of
North Staffordshire.
AVERAGE COMPOSITION OF FETTLING MATERIALS.
Constituents.
Chemical
. Formulae.
Best Tap.
Bull Dog.
"'")
Purple Ore
(Dried).
Ferrous oxide,
FeO
68-1
3-8
Ferric oxide, .
Fe203
26-5
69-6
96-0
Manganous oxide, .
MnO
1-2
0-7
...
Silica, .
Si02
2-9
24-3
2-0
Phosphoric acid ,
Po05
0-9
0-8
Sulphur, .
Lime,
Magnesia,
S
CaO
MgO
0:3
0-1
I o-s:
Other
constituents
in small
quantities.
100-0
100-0
lOO'O
Metallic iron, .
Fe
71-52
51-68
07-20
Preparation of the Puddling Furnace for Work — On the
top of the iron bed-plates little lumps of " best tap " are
charged so as to form a coating about 3 inches thick.
The temperature of the furnace is then raised to such a pitch
that the best tap begins to soften. The coating is covered
over with a layer, about 2 inches thick, of scale or other
fettling, such as ground bull dog, purple ore, or hematite ore.
These are varied to suit the class of pig iron which is used,
and the quality or the purpose for which the wrought iron is
to be produced. The purer the pig iron the more fusible
must the fettling be : the less pure or more " hungry " the
pig-iron the less fusible must be the fettling. The sides are
also well fettled, the fettling being firmly rammed into the
recesses formed by the firebricks which project over the fire-
and flue-bridges. A light charge of scrap iron is then charged,
* See analysis on p. 178. f See analysis on p. 242. - ^
JBy difference.
THE PUDDLING PROCESS. 19
raised to a welding heat, oxidised, and rolled over the fettling
so as to glaze it with rich oxide of iron.
The Puddling Process. — The furnace, when fettled and hot,
is ready for charging. Through the open door about f cwt.
of hammer slag, or other fusible iron oxide, and 4^ or 5
cwts. of pig iron are thrown as shown in fig. 6. The door
is then lowered, a small iron plate is set in front of the
Pig. 6. — Charging a Puddling Furnace.
stopper hole, and a little quantity of fine ore is placed on
the foreplate so as to prevent access of air through any worn-
out parts.
The puddling process may conveniently be described as
divided into four stages. The first stage merges quietly' into
the second stage, which in its turn glides into the succeeding
one.
The First or Melting-down Stage.— In the course of about
20 IRON AND STEEL MANUFACTURE.
20 minutes after charging, the exposed parts of the pig iron
will have become red hot. The "pigs" are then turned over so
as to be heated more uniformly. Melting begins soon after, and
the melted portions drip and flow into the lowest part of the
working bed, where it is well stirred. The tools for turning
over the pig iron and for stirring the melted materials are
inserted through the stopper notch.
During the melting down much silicon and manganese are
Fig. 7. — Pig Iron in Puddling Furnace.
oxidised, and a considerable quantity of phosphorus is also
oxidised All the oxidised products leave the pig iron and
combine with some of the melted fettling to form the slag or
cinder. This stage occupies about 30 minutes in all.
The Second or Clearing Stage occupies about 10 minutes.
In it the remainder of the silicon and manganese and a
further quantity of the phosphorus are oxidised and removed
THE PUDDLING PROCESS.
from the pig iron. A high temperature is maintained, and
the charge is vigorously rabbled (that is, stirred or worked
with an iron tool called a rabble), so as to promote a more
rapid and intimate contact between the pig iron and the slag
and fettling; thus hastening the oxidation of the impurities
in the pig iron by the oxides in the fettling and the fluxes,
and by the air which is passing through the furnace.
Fig. 8.— Puddler Rabbling a Charge.
In the Third or Boiling Stage, which occupies about 30
minutes, nearly all the carbon is removed and most of the
remaining phosphorus is eliminated. The temperature is
regulated as required, and the charge is still vigorously
rabbled. As the carbon at this stage is oxidised and forms
carbon monoxide (CO), which is a gas, the efforts of the gas
to reach the surface of the now somewhat pasty mass cause
repeated risings and subsidings and an appearance suggestive
of boiling. When the bubbles of carbon monoxide reach the
22 IRON AND STEEL MANUFACTURE.
surface, they are met by a current of air which oxidises the
carbon monoxide (CO) into carbon dioxide (C02). The blue
flames seen at the surface of the bath of metal and slag, when
the burning of the monoxide takes place, are known as
"puddlers' candles." The charge swells considerably, and
"boilings" — the most frothy part of the cinder — are tapped
off. It is at this stage that the metal "comes to nature."
Bright specks of metal appear, and become more numerous
and larger.
Pig. 9. — Drawing Puddled Ball from Furnace.
The Last or Balling Stage occupies about 20 minutes.
It is the heavy duty of the puddler to gather together the
metal, with only a little slag, into balls of convenient size.
He, therefore, raises the metal, which is now in a spongy
condition, and divides it into pieces of about 75 to 100 pounds
each. He then rolls each piece into a ball, and as each
puddled ball is finished it is kept away from oxidising
influences as much as possible, and, while as hot as the
furnace can be kept, is withdrawn by means of tongs over
THE PUDDLING PROCESS. 23
the foreplate, and is usually dropped on to an iron trolley
which is ready to receive it. If, however, the furnace is not
far from the site of the next operation no trolley is used, but
the hot puddled ball is bodily dragged across the well-swept
"race" — the iron plates which constitute part of the flooring
The puddled balls are quickly conveyed to the shingler, whose
business it is to shingle the ball either by squeezing or
hammering. The appliances for shingling are described on
pp. 29 and 30.
During shingling there is a copious flow of cinder from the
mass. The compressing of a porous lump of metal (such as a
puddled ball) causes a great rise in the temperature of th<?
mass. This favours expulsion of the slag, but the expulsion
is never complete. If the puddled ball is shingled by a
hammering action, the shingler turns over the mass from time
to time between the strokes. Sometimes an additional ball,
or balls, are welded together during shingling. This operation
is known as " doubling." When the mass has been sufficiently
worked and shaped into a somewhat rough, oblong block, it is
taken to the forge rolls, where it is rolled into a puddled bar.
The further treatment of the puddled bar is described on
p. 28, and the forge rolls (or forge train) on p. 32.
The foregoing-is but a brief and bare outline of a process
which is most interesting to watch. The procedure varies
somewhat according to the pig iron provided, and the whole
operation is one which calls for strength of arm and soundness
of judgment.
The furnace requires to be fettled before each charge, but
especially at the commencement of each shift. Slag is tapped
off, when required, into a suitable little truck — the cinder
truck — as shown in fig. 10. The waggon is also shown, full
of cinder, in the foreground of fig. 1.
A puddler and his underhand between them work through
six heats of about 5 cwts. each in the course of a working
day, with a yield of about 30 cwts. of puddled balls.
The fuel used is a bituminous coal (see analysis on p. 226),
which yields a long flame. About 24 cwts. are required for
each ton of puddled balls produced.
24 IRON AND STEEL MANUFACTURE.
In many, probably most, instances the weight of puddled
balls produced is about equal to the weight of pig iron
charged, but there is often a notable increase of iron,
especially when the pig iron and the fettling are judiciously
selected so as to suit each other. It is clear that the in-
crease of iron is derived from the iron oxides with which
the furnace is liberally fettled, and especially from that
which the puddler looks on as a flux — namely, from the
Fig. 10.— Tapping Cinder from Puddling Furnace.
hammer scale or other iron oxides which are thrown into the
furnace before charging the pig iron. And it is also clear
from the composition of tap cinder, and the quantity sold,
that the ferric oxide (Fe203) which predominates in much of
the fettling material must, during the puddling process, have
been reduced to magnetic oxide ; the liberated oxygen doing
useful work in oxidising the metalloids, as substances such as
silicon, phosphorus, &c., are called. The composition of
THE PUDDLING PROCESS.
25
magnetic oxide is Fe304, which is sometimes looked on as
Fe203, FeO. Adopting the formula introduced, for convenience
of comparison, on p. 5, ferric oxide may be regarded, for
purposes of comparison, as Fe609. This, on giving up oxygen,
is reduced to magnetic oxide, which may be noted as Fe608.
There is good reason for believing that some part of the
fettling, or the flux, acts as an oxygen carrier — the lower iron
oxide becoming highly oxidised (peroxidised) by the oxygen
of the air passing through the furnace, and readily giving np
the newly -acquired oxygen. See chemical equations on
pp. '21 and 28.
AVERAGE COMPOSITION OF SLAGS OR CINDERS FROM THE
PUDDLING PROCESS.
Constituents.
Chemical
Formula;..
Average
Tap Cinder.
Boilings.
Hammer
Slay.
Ferrous oxide,
FeO
61-5
62-7
54-6
Ferric oxide, .
Fe203
8-3
7-1
19-5
Manganous oxide,
MnO
2 "2
2-6
2-1
Silica,
SiO.
20-3
20-9
17-5
Phosphoric acid,
PA
5-3
6-2
5-1
Sulphur, .
S
0-7
}
Lime,
CaO
1-5
1-5*
1-4*
Magnesia,
MgO
0-2
I
100-0
100-0
100-0
Metallic iron, .
Fe
53-64
53-74
56-12
THEORETICAL CONSIDERATIONS.
Of the elements eliminated during puddling the only one
to become gasified is carbon, which, combining with oxygen,
forms carbon dioxide (C02), and escapes by the stack into the
air. All the other elements, when oxidised, go into the
cinder. The cinder must be of such a composition that it
will become, and remain, fluid, or at least semi-fluid, during
the operation. One of the first elements to be eliminated is
silicon (Si), which is easily oxidised and forms silica f (Si02).
*Bv difference.
t White sand is almost pure silica.
26 IRON AND STEEL MANUFACTURE.
Now, silica is prone to unite with oxide of iron (FeO). The
union, or chemical combination, of the two results in the
formation of ferrous silicate (2FeO . Si02) ; a compound which
fuses, or melts, with comparative ease. Hence some of the
fettling or cinder must contain excess of ferrous oxide in
order that free silica may not interfere with the process. The
quaint idea of the late W. Mattieu Williams, that the fluid
cinder may be compared to soap suds, and assists in the
cleansing of the pig iron, is not far-fetched.
Into the intricacies of acids and bases the size and scope ot
this book forbids entrance, but it may convey sufficiently
clear ideas at this point to say that the bases commonly met
with in metallurgy can enter into chemical union with the
metallurgical acids, and that the resulting compound has a
much lower melting point than either the acid alone or the
base alone. The union of the acid silica (Si02) with the
basic ferrous oxide (FeO) is a case in point.
The following are classed as acids by metallurgists : —
Phosphoric acid or phosphoric anhydride, (I^s)
Titanic oxide, (Ti09)
Silica, . . . (Si02)
Carbonic acid (carbonic anhydride or
carbon dioxide), . . • . (C02)
The chief bases which are of interest to the iron and steel
metallurgist are —
Ferrous oxide, (FeO)
Manganous oxide, ..... (MnO)
Lime, (CaO)
Magnesia, ,*. (MgO)
Alumina (A1203) may act either as an acid or a base,
according to circumstances.
The method by which phosphorus is eliminated during
puddling was discovered by Geo. J. Snelus in 1872, and his
theory is now universally accepted. It is this : The phosphorus
(P2) is oxidised to phosphoric acid (P206), which enters into
THE PUDDLING PROCESS. 27
chemical union with the basic ferrous oxide (FeO) in the
cinder, and is held there.
Dephosphorisation, or the elimination of phosphorus, cannot
be successfully conducted unless under oxidising conditions,
and in presence of plenty of hot material of a basic nature.
The manganese (Mn) which is oxidised becomes converted
into manganous oxide (MnO), which increases the .basic nature
of the slag. The sulphur which becomes oxidised may
escape in the gases or be caught in the
The functions of the fettling and cinder are h've-fold.
(a) To protect the iron plates and other castings at the
working bed.
(b) To supply oxygen for removal of the impurities.
(c) To bind the grains together and to prevent the oxida-
tion of the surface of the grains — " to nourish the iron."
(d) To provide a base for the phosphorus and other
impurities.
(e) To increase the output.
The chief chemical reactions which take place during
puddling are —
OXIDATION BY ATMOSPHERIC OXYGEN.
C + 02 C02
Carbon and oxygen yield carbon dioxide.
Si + 02 Si02
Silicon and oxygen yield silica.
2Mn + 02 2MnO
Manganese and oxygen yield oxide of manganese.
4P + 502 2P2O5
Phosphorus and oxygen yield phosphoric acid.
The phosphoric acid unites with the (basic) ferrous oxide in
the cinder or slag.
OXIDATION BY FERRIC OXIDE, WITH PRODUCTION OF MAGNETIC OXIDE.
C + 3Fe,03 CO + 2Fe3O4
Carbon and ferric oxide yield carbon monoxide and magnetic oxide.
28 IRON AND STEEL MANUFACTURE.
Si -f 6Fe2O3 = Si02 + 4Fe804
Silicon and ferric oxide yield silica and magnetic oxide.
Mn + 3Fe203 MnO + 2Fe304
Manganese and ferric oxide yield manganous oxide and magnetic oxide.
2P + 15Fe203 = P205 + 10Fe304
Phosphorus and ferric oxide yield phosphoric acid and magnetic oxide.
Other chemical reactions also take place.
Treatment of Puddled Bars. — The puddled bar* formed,
as described in previous pages, by rolling the hammered or
squeezed puddled ball, is rough on the surface and ragged at
the edges. The slag which it contains is in splatches and not
well distributed throughout the bar. To remedy these defects
and to produce a bar more uniform in composition, with less
slag, and the remaining slag more evenly distributed — in fact,
of a quality sufficiently good for smiths and engineers — the
puddled bars are cut into short lengths, made into oblong
piles, reheated to a welding pitch in a reheating or mill fur-
nace, and rolled out to a finished section in a set of rolls
known as the " mill train " into " merchant bar."
Piles for reheating are built up on puddled bars, or
merchant bar, or old wrought iron, and the pile is
arranged with due regard to the intended shape of the
finished material.
Scrap wrought iron is piled, brought to a welding heat
in a ball furnace or scrap furnace, and hammered into a
half -finished mass called a bloom. The bloom is reheated
in a mill furnace and rolled in the mill train into finished
Best best and treble best iron is specially made from care-
fully selected materials which are puddled, shingled, rolled,
cut, piled, reheated, and rerolled. The products are systemati-
cally tested, and the iron is of superior quality.
FORGE PLANT.
For consolidating puddled balls and expelling slag squeezers
are sometimes employed. Of these, the crocodile squeezer
* Known in America as " muck bar."
THE PUDDLING PROCESS. 29
may be taken as an example. There are other appliances,
but squeezing is a system which does not appear to be in
favour.
A primitive, but effective, appliance for shingling the
puddled ball is the helve (fig. 11), which has a heavy iron
beam carrying a hammer head which can be easily replaced.
The beam rests on a fulcrum at one end, and the other end is
lifted by projections (cams) on a rotating cylinder. When
the nose of the beam has been raised to the highest point to
which a projection can carry it, the beam and hammer head
Fig. 11.— Helve.
A, Flywheel. C, Hammer head
B, Cam. D, Anvil.
fall heavily on the puddled ball which has been placed on the
anvil block. The next projection on the revolving cylinder
quickly raises the beam and hammer head, and again a heavy
blow is dealt when the hammer head falls on the puddled
ball. The nose may be raised about 20 inches, and about 60
blows per minute are delivered. The shingler keeps turning
over the puddled ball between the strokes. To stop the
working of the helve a prop or sprag is inserted, which keeps
the nose of the beam above the action of the arms or pro-
jections. When a fresh ball has been placed on the anvil
block, a piece of iron is laid on the upcoming arm. This
causes the nose to be lifted higher ; the prop is withdrawn,
thereby allowing the helve to resume work.
30
IRON AND STEEL MANUFACTURE.
The Steam Hammer (fig. 12) consists essentially of an
upright stem or frame supporting a vertical steam cylinder, in
which works a piston having a long rod with a hammer head
Fig. 12.— Steam Hammer.
THE PUDDLING PROCESS.
31
Hii
i^
* isn
o ^ «
j^ H fa O B
bo
g ti)
.^
32
IRON AND STEEL MANUFACTURE.
or tup at its lower end. By means of 'a lever controlling the
admission of steam to the upper or the lower part of the
cylinder, the rate and force of the blows can be easily regu-
lated. An anvil block is set immediately below the tup.
Both block and tup can be readily replaced when required.
The Forge Train, in which the shingled blooms from the
helve or hammer are rolled into puddled bars, is sketched
in fig. 13. This train comprises helical-teeth pinions fitted in
enclosed housings, also one pair of forge rolls with housings,
chocks, brasses, pins, boxes, couplings, &c., and the whole
train is mounted upon a massively-designed girder-section bed
Fig. 14.
plate. The advantages of this design are that the mill is
always kept perfectly in line, and the time occupied in
changing rolls is considerably reduced.
Fig. 14 shows an end view of the forge train.
Fig. 15 illustrates a 10-inch merchant bar mill, or guide
mill, so called because a set of guides are provided for guiding
the oval section into the finishing round groove of the finish-
ing rolls. The merchant mill is designed for the purpose
of rolling wrought iron from a pile of 4-inch puddled bars
into any desired section. The rolls shown are for flats, 1J-
inch and If -inch broad, of such thickness as may be required.
For producing rounds or squares, the rolls for flats marked D
THE PUDDLING PKOCESS.
33
would be removed and a set of rolls with oval and diamond
openings substituted.
60
a
03 'O
!•§
1
S ,«
i I
&b ^' -5
S 2 f
SO O tiC^
2 W^T!
(3>iS 9
'-S £-3
f o S^
34 IRON AND STEEL MANUFACTURE.
The mill comprises flanged couplings, leading spindle and
carriage, double helical-teeth pinions fitted into housings, with
a separate gland cover constituting an oil bath in which the
pinions revolve. The bolting rolls and strand rolls are fitted
with housings, chocks, brasses, and necessary wrought-iron
work, guides, guards, &c., and two pairs of chilled guide rolls
are provided for giving a good finish to round and square
bars. These guide rolls also are fitted with necessary housings,
glands, stools, brasses, wrought-iron work, guides, sfec., and the
whole mill is mounted on a girder-section bed-plate. For the
sake of clearness, some of the usual fittings have been omitted
from the sketch.
These mills are of the type manufactured by Messrs. Akrill,
Limited, West Bromwich.
Best Yorkshire Iron is made from special (cold blast) pig
iron which undergoes a refining process before being puddled
in small charges. Its manufacture is conducted with great
care, the puddled iron is conscientiously examined, the blooms,
&c., are heated well, and a large amount of work is put upon
the iron. The qualities which have given it a world- wide
reputation are its reliability even under most exacting condi-
tions, its capability of standing repeated reheatings, and its
power of enduring without deterioration much punishment in
the hands of the smith and engineer.
35
CHAPTER IV.
STEEL: CRUCIBLE CAST STEEL FOR TOOLS AND
CUTLERY.
OF the services rendered to civilisation by the production of
good tool steel, it would be difficult to speak too highly.
Steel is essentially a compound of iron and carbon. It
contains other elements, some intentionally added to confer
certain qualities on the steel ; others are unavoidably present,
but cannot be tolerated in more than small percentages.
The best quality steel for tools and for cutlery is known as
crucible cast steel. The process is still carried on — chiefly
in Sheffield — with slight variations in the details of the
system devised, after many trials, by Benjamin Huntsman
about the year 1740.
High-class crucible cast steel is made by the application of
intelligent experience to the correct treatment of carefully-
selected materials of high quality — of such experience as has
been practically acquired through generations of skilful
working.
Outline of the Process of Manufacture. — The iron used is
brought from Sweden,* where the pig iron is smelted from
the purest ores by the purest fuel. The pig iron is worked
into wrought iron in a type of furnace which originated in
the north-west of England, and, being adapted to Swedish
requirements, is named the Swedish-Lancashire hearth, f
The wrought iron is hammered into long flat bars, and these
bars are supplied to steel-making firms. From the bars
crucible cast steel is manufactured in two definite stages.
Firstly, the bars are subjected to a cementation process by
being heated for several days in contact with charcoal in
boxes, the tops of which are cemented to exclude air.
* Some American steel-makers believe that Swedish iron is not
necessary. A high degree of purity is always required.
t The famous Dannemora bar iron is produced from pig iron by the
old Walloon fining method.
1
STEEL FOR TOOLS AND CUTLERY.
37
Secondly, in order to produce steel in masses which are free
from slag arid of the same composition and qualities through-
out, the "cemented bars" are broken, graded, melted in a
crucible at a white heat, and, with proper precautions, poured
into prepared moulds so as to form ingots which can be
worked into the shapes desired.
The cementation furnace is externally a tall, tapering
structure (the stack), which is sometimes square at the
Fig. 17. — Cementation Furnace — Elevation and Section.
A, Stack.
B, Arch.
C, Chimney.
D, Manhole.
E, Cementation pots.
F, Fire-grate.
G, Ashpit.
and circular towards the top. Fig. 16 shows a view of the
stacks of steel furnaces at Messrs. Thomas Firth & Sons'
Norfolk Works, Sheffield.
Inside the stack, at its base, a fire-grate extends from front
to back; and alongside the fire-grate two long troughs — or
" cementation boxes " — are placed. These are shown in
00 IRON AND STEEL MANUFACTURE.
section on fig. 17, and a plan is shown on fig. 18. In order
that the heat from the fire-grate may find free and fairly
equal access to all parts of the outside of the cementation
boxes, they are set on bearers, and passages are arranged
leading to short chimneys. Between the walls in which the
short chimneys are set, a brick arch is built at some little
distance above the boxes, or "pots," as they are sometimes
called.
The inner walls and arch are of good firebrick ; the lower
part of the stack is also of good firebrick, while the upper
part may be of more common bricks. The stack — which is
Fig. 18. — Cementation Furnace— Plan.
A, Cementation pots. | B, Passage to flues. | C, Fire-grate.
generally about 50 feet high — prevents excessive radiation
from the arch, and also serves the usual purposes of a chimney.
A manhole is provided in the brickwork, and " trial holes "
are left in the brickwork, which correspond to similar holes in
the ends of the boxes.
The Cementation Boxes, or Pots, are of firestone slabs
cemented with a mortar of good fireclay. They are from 8 to
16 feet in length, a fair average size being 12 feet long, 4
feet deep, and 4 feet wide. The capacity of a furnace is from
15 to 30 tons. The boxes are packed by placing in each a
layer of selected hardwood charcoal, which has been sifted to
STEEL FOR TOOLS AND CUTLERY. 39
exclude pieces generally smaller than half -inch. Some old
charcoal is used along with the new. A layer of the flat
bars — which are frequently 3 inches broad by three-quarters
of an inch thick — is placed on the charcoal, and completely
covered at sides, ends, and on top with charcoal. Alternate
layers of flat bars and charcoal are packed in. the upper-
most one being of charcoal. This is covered with a thick
coating of clay or of wheelswarf. Wheelswarf is collected
from the troughs of the Sheffield grindstones, and consists of
the worn-away material of the grindstones, mixed with the
steel dust which has been ground away. The dust " sparks "
as it is ground ; that is, it becomes oxidised, so that the
wheelswarf is really a mixture containing iron, iron oxide,
and silica from the grindstone. A coating of wheelswarf is
sufficiently porous to permit the escape of air from the pots
while the contents are being heated, but which readily fuses
even at a rnoderately-high temperature, and so forms an air-
tight cover. Iron (or steel) in the wheelswarf is incidentally
oxidised during the rise of temperature, and iron oxide and
silica, when heated, easily fuse, as mentioned in the paragraph
on welding and the chapter on puddling.
When the pots are packed and duly covered, the front of
the furnace is bricked up, and a fire is kindled in the grate.
The long grate of the furnace is fed from both ends; a free-
burning coal which does not "clinker being used. A
non-clinkering coal is one which leaves a white ash in fine
powder. In the course of 24 hours or so a red heat is
attained, and the full heat, a bright orange (about 2,120° R,
or 1,160° C.), is reached in about 48 hours. The full heat
may be maintained for a week or more, according to the
degree of carburisation, or "temper," aimed at. The chief
effect of this treatment is the penetration of carbon into the solid
iron bars.
While packing a box, a few " tap bars," or " trial bars," are
set with their ends protruding through the slot left in one end
of the box. When there is reason to believe that the correct
carbonisation (or conversion) has been arrived at, one of the
tap bars is withdrawn, and the vacated space in the end slab
of the box is carefully filled with white coal ash or other
suitable material. The tap bar, when cold, is broken, and the
40 IRON AND STEEL MANUFACTURE.
fracture is examined. The experienced eye can judge such
fractures with great accuracy. When conversion is thus
judged to have gone far enough— allowance being made for
further carburisation during part of the time of cooling — the
firing, or stoking, is stopped, and the fire is banked. The
furnace cools slowly, as otherwise the pots would be liable to
crack, and in the course of a week or more the furnace is cold
enough to allow the entrance of the workmen by the manhole,
which has been opened. The wheelswarf cover is broken and
removed, and the bars are taken out of the pot.
The charging, converting, and unpacking occupy about
three weeks : for higher carbonisation more time is required
than for lower temper bars. About 25 tons of coals will be
consumed during the conversion of an ordinary 30-ton lot of
bars.
During conversion the bars gain in weight through carbon
being taken up. The " converted " or " cemented " bars
differ in appearance from the bars as packed. Originally
they were fibrous and tough. As taken from the boxes they
are crystalline* and brittle, and are covered with blisters —
hence the name " blister steel." If the blisters are small and
evenly distributed over the surface, it is assumed that the
iron was good and that the conversion is satisfactory.
The blister steel bars are broken across; the fracture is
examined, and each piece is stacked according to its " temper "
or degree of carburisation. The bars which were nearest to
the fire are more highly carburised than those which were in
the centre of the pot, and there must necessarily be more
than one temper from each pot.
In the trade the blister steel is classed thus —
No. 1 or spring heat, containing £ or *5 per cent, of carbon.
2 country heat, , | „ '625
single shear heat, ,
double shear heat, ,
steel- through heat, ,
"75
1'25
melting heat,
No. 1 is not called " spring heat " to indicate that it is
suitable for making springs (it is not suitable), but because of
* In the lower tempers the centre portion remains uncarbonised and
is called "sap"; the crystals of sap have lost their brilliancy — the
sap is said to be killed and no longer looks " raw " or " stares." "
STEEL FOR TOOLS AND CUTLERY. 41
so much "sap." The term "Irish temper" is also applied
and the term " country heat," by which No. 2 is known, are
all suggestive of verdancy. In the lower numbers the con-
version has not proceeded far, and the broken bars show
much unaltered iron in the centre. In " double shear heat "
bars about one-half of the area, in the centre, has not been
changed, while in the highest number the whole of the bar
has been converted, all the fibre has gone, and the entire
area of the fracture is crystalline.
Even with experience and the exercise of care accidents
occasionally happen, and the cemented bars are more or less
spoiled. Aired bars are those to which air has had access
through a crack or cracks in the pot or the covering. Glazed
bars are those which, during conversion, have been over-
heated, and the edges of which are generally melted in the
converting pot. Flushed bars are those resulting from over-
hurried conversion, and which show too plainly the lines
dividing converted from unconverted portions. Tradition
tells of " pots " which were so badly cracked that the charcoal
had been burned and the intense local heat had caused the
bars to become welded together. But the bars, as a rule,
successfully run the gauntlet of possible mishaps, and the
product is good for the intended purpose. The majority of
the blister steel bars are meant to be melted in crucibles.
Some, however, are to be used otherwise, and they are sub-
jected to different treatment.
" Bar Steel is the name given to blister steel which has been
tilted or rolled down to the size required.
"Single Shear Steel is produced by welding six bars of
blister steel which are unconverted in the centre, and rolling
them down so as to have a fairly uniform mixture of iron and
steel — a material which combines great tenacity with the
capability of carrying a moderately hard shearing or cutting
edge." Or bars of blistered steel may be heated and ham-
mered into plates, an operation known as plating. Seven or
eight plates are piled together, heated, and hammered into
shape. In some instances they are finally rolled down into
single shear blades.
"Double Shear Steel is produced by rolling down single
shear steel to suitable-sized bars and rewelding two of them
42 IRON AND STEEL MANUFACTURE.
together so that the mixture of iron and steel may be more
perfect."* Or hammered shear steel is bent over on itself,
and again hammered down.
The bars or plates require to be raised to a welding heat,
and must be protected to prevent undue and uneven loss of
carbon. For this purpose the bars or piles are covered with
gypsum or other suitable material which will melt and form
an even coating capable of remaining intact while in the
furnace.
Cast or Crucible Steel. — Blister steel bars contain slag, and
no bar is uniform in composition throughout. The outer
portions of each contain more carbon than
the inner portions. To obtain a homo-
geneous! steel, from which the slag has
become separated, it is necessary to melt the
blister steel.
Melting is carried on in crucibles or
"pots," which are carefully made from
judicious mixtures of suitable fireclay. A
crucible is about 1 7 inches high and 7 or 8
inches diameter at the top. They are
seasoned for a fortnight or so and "annealed"
before being used.
Fig. 19.— Crucible*
Stand.Lld and The "steel-melting house," in which the
making of crucible cast steel is carried on,
is a building which contains a number of " steel-melting
holes," and the necessary arrangements for casting the steel
into ingots. Fig. 20 shows a view of a steel-melting house
at the works of Messrs. Samuel Osborn & Co., Sheffield—
so long associated with the Mushets. The steel-melting holes
are ranged along the sides of the building but under the
floor level. They are covered, as shown in the illustration,
by covers composed of firebrick slabs set in iron frames and
having iron handles.
A section of a steel-melting hole is shown in fig. 2 1 . Each
"hole," or furnace, is lined with ganister so as to form an
* Seebohm, Iron and Steel Inst. Journal, 1 884, ii. , p. 379.
fFrom Greek words signifying of one kind.
44
IRON AND STEEL MANUFACTURE.
oval of about 36 inches in depth, 26 inches in its longest
diameter, and 19 inches across, so as to hold two crucibles or
pots. Access to the fire-bars, &c., is from the cellar. Ten
or more holes constitute a set, the flues from which lead to
long stacks.
The fuel used is a specially hard burned coke, and the
draught from the furnace is regulated in a simple manner
Fig. 21.— Section of Steel-melting Hole.
A, Crucible being gently dried.
B, Shelf and, support.
C, Stack.
D, Cover of melting-hole.
E, Handle of cover.
F, Furnace.
G, Lid.
H, Crucible.
I, I, Flues.
J, Stand.
Fire-bar.
Bearer.
K,
L,
M, Brick for regulating the
draught.
which is quite effective. If the temperature requires to be
moderated, the brick which is used for closing the inlet* from
the cellar flue (see fig. 21) is removed, thus allowing an
inrush of cold air through the flue to the chimney. The
STEEL FOB TOOLS AND CUTLERY. 45
" draught " is thereby lessened. When a higher temperature
is needed the brick is inserted in the inlet. Only hot
products of combustion, or hot air which has passed between
masses of glowing coke, can enter the flue, and, as the chimney
thereby becomes and continues to be filled with hot gases, the
draught is increased. Live coals are used to kindle the coke
required as fuel in the melting holes.
The crucibles employed in steel melting are carefully
prepared beforehand, and are subjected to a long course of
gentle drying. Before being used they are kept, mouth
downwards, in an annealing furnace which is at a red heat.
The pot, which has thus been tempered, is set on a stand
in a hot melting hole and coke is packed round it. In the
course of an hour the pot is ready for the charge. To
charge the pot, one workman holds a wrought-iron funnel
or charger, while another empties a weighed charge of blister
steel — of selected temper — which is in small pieces. The
charge also contains some fluxing material and some " physic."
Physics are compounds containing manganese, a metal which
acts beneficially in steel-making. The lid is then put on the
crucible. The next one is charged in like manner, the re-
mainder of the hole is filled in with coke, the cover is placed
over the hole, and the draught is regulated. When the fire
has burned some time the remainder of the coke in the hole is
pottered down towards the fire-bars, and more coke is added.
From time to time the head melter examines the condition
of the furnaces and gives orders for the further making-up of
the fires, the regulation of the draught, &c. By and bye he
has the covers moved, and, feeling with an iron rod the
contents of the crucibles, he gives final instructions with
regard to the fires and the time of teeming. The head
melter must have ripe experience and sound judgment.
When ready, the " puller-out," wrapped in " clothes " which
are soaked in water to protect him from the heat, lowers
a pair of tongs, with a broadened and ribbed ending, into
the furnace and with them grips one of the crucibles, pulls
it up, and sets it on the floor of the melting house. The
slag is quickly skimmed off, and the steel is poured into
the moulds. The moulds are of cast iron and each formed of
two halves tightly held together by rings and wedges. The
46 IRON AND STEEL MANUFACTURE.
moulds must be previously "reeked" (smoked) or covered
with a fine deposit of soot by exposing the inner surfaces to
the smoky flame of burning coal tar. Or the steel may be
prevented from adhering to the moulds by wiping the inner
parts with oil or with fireclay in water. The moulds must
be dry and warm before teeming the steel into them. They
are set in a slanting position in recesses — known as " teeming
holes " — in the floor, and the steel is poured into them. The
crucible is then put back into the furnace, or hole, and heated
before receiving the next charge.
The first crucible charge for the day may be 60 Ibs., the
second one 54 Ibs., and the third one 48 Ibs. These three
charges constitute the round for the day and finish the life of
the crucible, which cannot, with a reasonable degree of safety,
be trusted to melt more. Each crucible is placed in a hot
oven about 24 hours before being required so that it may be
well annealed before receiving its charge. Owing to chemical
action which cuts a groove into the crucible where the slag is —
on the top of the melted steel — it is necessary to diminish the
weight of the second and third charges in each pot.
Inferior steel must be " teemed " into tfye mould as soon as
possible after it has become perfectly fluid and as hot as the
pot is likely to stand the strain of "pulling out." Higher
class steel requires " killing " — that is, it requires to be kept in
the furnace for about half an hour (more or less as the judg-
ment of the head melter decides) after it has become fluid,
and it must be poured at a proper temperature. The higher
the quality of the steel the more killing it will require. If
not " killed," or if too hot when poured, the steel boils over
in the mould, the fracture of the ingot when cold shows a
series of bubbles like a sponge. "If the steel be not long
enough in the fire, it will teem fiery and produce a honey-
combed ingot, and the 'same result will follow if it be too hot
when it is poured. If it remain too long in the fire it will
teem ' dead,' the fracture of the ingot will look scorched, and
though exceptionally sound it will be brittle if hard, and
wanting in tensile strength if mild. If the molten steel be
chilled before it is poured into the mould, which may be
detected by the stream skimming over as it is teemed, the
STEEL FOR TOOLS AND CUTLERY.
47
fracture of the ingot will appear dull in colour, and full of
small holes and honeycombs." *
The steel ingots are carefully reheated and hammered or
rolled into the bars required. Bars for certain purposes are
straightened by reeling.
The lest crucible cast steel is made from Swedish iron, smelted
from ores containing a small quantity of phosphorus.
There are four methods of making crucible steel, and they
are as under : —
I. Select cut bar iron and "fetch it up" by addition of
charcoal. Melt and teem.
II. Use broken pig iron and " let it down " to the required
temper with cut bar iron. Melt and teem.
III. Select or "take up" blister steel of the desired per-
centage of carbon. Melt, dead melt or kill, and teem.
IV. Select blister steel which is a little too hard and " let
it down" with a small quantity of milder cast steel scrap.
Melt, dead melt or kill, and teem.
Some steel-makers believe that only by methods III. and
IV. can best quality steel be made in crucibles.
TABLE OF THE COMPOSITION OF THE "METAL" IN THE VARIOUS
STAGES OF THE MANUFACTURE OF CRUCIBLE CAST STEEL.
Chemi-
Swedish
Cemented
Constituents.
cal
Sym-
Swedish
Pig Iron.
Wrought-
iron
Bars,
or Blister
Crucible
Cast Steel.
bols.
Bars.
Steel.
Graphitic carbon,
c
0-12
Combined carbon,
c
3-86
6-05
variest
variest
Silicon,
Si
0-15
002
0-02
0-17
Phosphorus,
P
0-03
0-02
0-02
0-02
Sulphur,
s
0-02
o-oi
o-oi
0-05
Manganese,
Mn
0-29
0-07
0-07
0-18
Iron, .
Fe
A
A
A
A
100-00
100-00
100-00
100-00
* Seebohm, Iron and Steel Institute Journal, ii., 1884, p. 385.
fThe percentage of carbon varies according to the treatment in the
cementation process, as previously explained.
48 IRON AND STEEL MANUFACTURE.
The chief points in the foregoing table are : —
The Swedish pig-iron contains little phosphorus and
less sulphur. The carbon, silicon, and manganese — and
to a slight extent the sulphur — are reduced in amount
during the working of the pig iron into wrought-iron
bars, and it may here be explained that it is absolutely
necessary to remove the excess silicon, which is un-
avoidably present in the pig iron. It is not practicable
to get rid of even that small quantity of silicon without
removing carbon and manganese.
The only change effected during the cementation stage
is the combination of carbon with the iron — with pro-
duction of blister steel. While in the crucible the steel
is increased in manganese, sulphur, and silicon.
The increase in sulphur arises from the presence of that
element in the coke used as fuel. Sulphur can, singularly
enough, penetrate the hot crucible, and combine with the
metal. The additional manganese is derived from the ferro-
manganese* or other physic / used. Manganese acts on the
oxide of iron remaining in the steel, liberating the iron
and becoming oxide of manganese — a reaction indicated by
the equation —
FeO + Mn = Fe + MnO
Iron oxide and manganese yield iron and -j oxir e J
The oxide of manganese rises to the top of the metal and
attacks the silica of the crucible, manganese silicate being
formed. During dead melting or killing, this silicate is acted
on by carbon in the steel with liberation of silicon. The
reaction may be represented thus —
2MnO,SiO2 + C Si + CO2 + 2MnO
«ietd
This silicon passes into the steel, and effects, or at least
hastens, the elimination of gases. The small quantity of
silicon which is taken up is beneficial, but more than that
* See composition on p. 237.
STEEL FOR TOOLS AND CUTLERY 49
amount would be deleterious. The small percentage of
manganese does not adversely affect the quality of the steel,
while it is helpful in keeping down the evil influence of the
sulphur which has entered the steel. Good crucible steel
cannot be made from iron containing more than '03 per cent,
of phosphorus ; hence the great value of the comparatively
pure Swedish irons.
For cheap cutlery or for constructive purposes "steel" is often
made in crucibles from materials other than cemented bars
with a judicious addition of black oxide of manganese along
with a little carbon, or the addition of spiegel-eisen — which is
a fairly pure white pig iron containing much manganese — or
the still richer ferro-manganese. Then there is the un-
challenged statement of the late Sir Henry Bessemer that
" at least one-half of the crucible steel made in Sheffield is
made from Bessemer scrap, simply remelted."* For some pur-
poses such steel scrap is remelted in graphite (plumbago)
crucibles. Puddled steel — a semi-puddled product — is also
used in making crucible steel, and steel is made from un-
converted bars by melting a charge and adding carbon and
spiegel-eisen.
Besides such "physics" as spiegel-eisen and ferro-manganese,
quite a number of nostrums have been proposed at various
times and used in attempting to make superior steels from
common iron.
A large quantity of steel is made, the chief quality of which
is the possession of an enduring cutting edge. Some crucible
steel ingots are required to be solid ; some mild steels must
be weldable.
The first successful attempt to improve the quality of
crucible cast steel for tools was made by 11. F. Mushet,
whose "self-hardening" tool steels (steels containing chro-
mium, tungsten, and a notable amount of manganese) held
the field until the advent of the " rapid - cutting " tools
of Messrs, Taylor & White, of the Bethlehem Company's
Works, Pennsylvania, U.S.A., paved the way for further
considerable advances in the quality of quick-cutting tools.
* Iron and Steel Journal, 1884, vol. ii., p. 397.
60 IBON AND STKEL MANUFACTURE.
Analysis of Special Tool Steels. — Mushet's self-hardening tool
steel contains carbon, 1'65 ; silicon, 1'36 ; manganese, 2'12 ;
tungsten, 5 '80 ; and chromium, 0'45 per cent.
Quick-cutting steel, as made by Messrs. Whitworth, Arm-
strong & Co., Manchester, contains carbon, 0'55 ; tungsten,
13 *5 ; and chromium, 3*5 per cent.
To all steel users the good advice given in Metcalfe's excel-
lent Manual for Steel Users can be commended : " The best
way for a steel user to do is to tell the steel-maker what he
wants to accomplish and put upon him the responsibility of
selecting the best temper. It costs no more to make and to
provide one temper than another ; therefore the one induce-
ment of the steel-maker is to give his patron that which is
best adapted to his use."
The most useful tempers of tool steel are included in the
following list, compiled by the late Mr. H. Seebohm : —
Razor Temper (1£ per cent. Carbon). — This steel is so easily burnt
by being overheated that it can only be placed in the hands of a very
skilful workman. When properly heated, it will do twice the work of
ordinary tool steel for turning chilled rolls, &c.
SawJUe Temper (If per cent. Carbon). — This steel requires careful
treatment ; and, although it will stand more fire than razor-steel,
should not be heated above a cherry-red.
Tool Temper (1£ per cent. Carbon). — The most useful temper for
turning tools, drills, and planing- machine tools in the hands of ordinary
workmen.f It is possible to weld cast steel of this temper, but only
with the greatest care and skill.
Spindle Temper (1£ per cent. Carbon). — A very useful temper for
circular cutters, very large turning tools, taps, screwing dies, &c.
This temper requires considerable care in welding.
Chisel Temper (1 per cent. Carbon). — An extremely useful temper,
combining, as it does, great toughness in the unhardened state with
the capacity of hardening at a low heat. It is consequently well
adapted for tools when the unhardened part is required to stand the
blow of a hammer without snipping, but where a hard cutting edge is
required, such as cold chisels, hot setts, &c.
Sett Temper (§ per cent. Carbon). — This temper is adapted for tools
where the chief punishment is on the unhardened part, such as cold
setts, which have to stand the blows of a very heavy hammer.
Die Temper (f per cent. Carbon). — The most suitable temper for
tools where the surface only is required to be hard, and where the
capacity to withstand great pressure is of importance, such as stamping
or pressing dies, boiler cups, &c. Both the two last tempers may be
easily welded by a mechanic accustomed to weld cast steel.
CHAPTER V.
TREATMENT OF TOOL STEEL.
SPECIAL CHAPTER BY H. W. WALDRON.
WHEN a steel containing more than about 0'2 per cent, of
carbon is heated to. redness, and suddenly cooled by quenching
in water or other suitable medium, it becomes hard. The
degree of hardness depends to a certain extent upon the
rapidity of cooling and the temperatures used, but to a much
greater extent upon the percentage of carbon contained in the
steel. Steels containing 0'2 per cent, of carbon can only be
slightly hardened by the above treatment, while those con-
taining from I'OO to 1'75 per cent, become intensely hard
and somewhat brittle.
Several theories have been advanced in explanation of the
phenomenon of hardening, but whatever may be the precise
function of the carbon, it is agreed that the presence of that
element is essential to the hardening of ordinary commercial
steel.
The changes observable during the heating and cooling of
steel may be thus briefly summarised : — When a piece of
almost carbonless iron, heated to about 900° C. (full cherry
red), is allowed to cool slowly, and its temperature continually
recorded by a sensitive pyrometer, it is found that a " retarda-
tion " in the rate of cooling takes place at three distinct points,
indicating that a chemical or physical change has taken place
with evolution of heat. These critical points — which occur at
temperatures of about 825° C. (cherry red), 720° C. (low red),
and 650° C.* — are known by the formulae Ar 3, Ar 2, and
Ar 1. In the case of steels containing a considerable per-
centage of carbon, there is only one critical point, Ar 1, at
about 670° C.* The reverse changes take place during the
heating up of steel, there being an absorption of heat at the
* 825° Centigrade = 1,517° on the ordinary (Fahrenheit) thermometer.
720° „ =1,328"
670° „ =1,238°
650° =1,202°
52 IRON AND STEEL MANUFACTURE.
points Ac 1, Ac 2, Ac 3, which occur about 30° C. above
those observable on cooling down the steel.
The retardation taking place at Ar 1 is accompanied by a
change in the condition of the carbon from the state of
" hardening carbon," as it exists in hardened steel, to that of
" cement carbon," or the definite carbide, Fe3C, which is pre-
sent in normal and annealed steel. In order to convert
cement carbon into hardening carbon, it is necessary to heat
the steel to a temperature above the critical point Ac 1.
Brinell, in his famous researches on the heat treatment of
steel, used the terms W and V to indicate the points Ac 1 and
Ar 1 respectively, and, for the sake of simplicity, BrmeH's
formulae will be used in the remainder of this chapter, which
will deal only with steels containing '7 per cent, and upwards
of carbon, unless otherwise stated.
If steel, heated to any temperature above W,* is suddenly
cooled by quenching, the carbon is retained as "hardening
carbon" (no time being given for the change to "cement
carbon " to take place), and hardened steel is the result.
Hardening of Steel in Practice. — It would appear from the
preceding paragraph that the process of hardening steel by
quenching from any temperature above a red heat is an ex-
tremely simple operation. It is true that steel containing a
sufficient amount of carbon may be made quite hard by the
above means without any precautions whatever, but nothing
has yet been said about the strength, durability, freedom from
defects, and general fitness of a tool so hardened. As a
matter of fact, for the successful hardening of tool steel con-
siderable skill and care are needed.
Brinell noted that when steel is heated to the temperature
W, and either quenched or slowly cooled, an extremely fine
grain is produced, and that, if heated to any temperature
above W, the grain becomes coarser and coarser with each
increment of heat. No matter how coarse the fracture is
before the treatment, it becomes as fine as it is possible for
that steel to be when it is heated to the temperature W.
In hardened steel the finest structure is accompanied by the
greatest strength.
* The temperature indicated by W is about 700° C. with steels con-
taining 1£ to 1 ^ per cent, of carbon, and gradually rises as the percentage
of carbon decreases.
TREATMENT OF TOOL STEEL. 53
The following experiment is very instructive : — Take a bar
of tool steel (•§- inch x f inch x 12 inches long is a convenient
size), notched with a chisel at intervals of 1 inch throughout
its length, and heat it in such a manner that one end is at a
bright yellow heat, gradually decreasing to a temperature
below redness at the other end. Then quench the bar in
cold water, break off at the notches, and compare the frac-
tures. It will be found that the part which has been heated
to the highest temperature will have a coarse granular frac-
ture, and that the size of the grains gradually decreases in the
parts less highly heated, until the point heated to the tempera-
ture W is reached, when a fine fracture like that of porcelain
will be exhibited.
Although steel may be hardened by quenching from any
temperature above W, it will be readily understood that the
temperature which gives the finest grain and the greatest
strength, together with sufficient hardness, must be the best to
quench from. The correct hardening heat for any steel may
easily be experimentally determined by quenching samples
from different temperatures and observing the fractures.
For the successful hardening of tool steels, means must be
at hand for gradually bringing up the metal to the required
temperature, allowing sufficient time for it to become uniformly
heated throughout, but without permitting any part of it to
exceed the correct hardening heat. Excessive oxidation
should be carefully avoided.
The means used for heating are too numerous to be detailed
here ; any appliances may be used which will bring about the
conditions named above. They include various forms of coal-
and gas-fired furnaces and muffles, lead baths, charcoal and
" breeze " fires. The temperature may be judged with the eye
with surprising accuracy by an experienced hardener, but in
some cases a pyrometer may be used with advantage. If a
pyrometer is not used, the light in the hardening shop should
be subdued and as uniform as possible, all bright sunlight being
carefully excluded. Steel which looks red hot in diffused day-
light will appear almost black in bright sunlight. Excellent
hardening is continually being done from an ordinary black-
smith's hearth, but much experience and judgment are
necessary in order to obtain good results by this method.
54 IRON AND STEEL MANUFACTURE.
Quenching. — For most purposes, water is the best quenching
medium. The tool should be kept moving rapidly in the
water, otherwise bubbles of steam may collect on the surface
of the steel, and greatly retard the cooling action. The water
should be, as near as is practicable, to the temperature which
is known to give good results with the class of steel being
hardened. Hardening in very cold water at the commencement
of a day's work will often result in an unusual number of
cracked tools.
Brine has a greater quenching power than pure water, and
with some tools (notably files) gives better results.
Mercury is a quicker cooling medium than either water or
brine, and is sometimes used for small articles required to be
extremely hard.
Quenching in Oil. — Some articles, such as springs and saws,
which are required to be very elastic and tough without
possessing very great hardness, are quenched in oil. Whale
oil and lard oil are frequently used for the purpose.
Defects Produced by Hardening. — Improper hardening, or
the use of inferior steel, will often cause "water cracks."
These cracks are the direct result of the enormous stresses to
which the hardened steel is subjected by contraction during
the sudden cooling. The stresses vary in extent and direction
according to the shape and size of the tool, the temperature of
the steel and of the quenching medium. Sometimes a corner
of the steel will fly off when in the water, while in other cases
the cracks can only be detected by a very minute examination
of the polished surface of the metal. If the steel has been
tempered before the crack is detected, the surface of the
fracture where the water crack occurs will be covered with an
oxide film of the usual temper colour, even if the crack is so
minute as to require the aid of a magnifying glass to see it.
The necessary conditions for the prevention of water cracks
may be obtained —
(1) By the use of steel of such a quality as to give the
greatest strength, together with sufficient hardness.
(2) By minimising, by careful treatment in the forging
and hardening processes, the magnitude of the
stresses to which the steel is subjected by sudden
contraction when quenched.
TREATMENT OP TOOL STEEL. 55
Tool steel should be low in phosphorus and manganese.
The effect of phosphorus in causing brittleness in mild steels
is well known, and this effect is much accentuated in high
carbon steels, in which about O02 per cent, only is permissible.
It is quite usual to have 0'4 or 0'5 per cent, of manganese
present in mild steel, but in steel containing 1 per cent, of
carbon, 0'2 per cent, of manganese is sufficient for most pur-
poses, and in some cases an additional O'l or 0*15 per cent,
of manganese will lead to numerous water cracks, although
the forging qualities of such a steel may be excellent.
Assuming that the quality of the steel is right, and that the
forging has been carefully done, it is for the hardener to see
that the steel is in the best possible condition to resist the
stresses put upon it, at the moment it is put into the water.
If water cracks are to be avoided, the steel should be quenched
at that temperature which gives the finest fracture — i.e., the
lowest temperature at which the steel will properly harden — as
it is then in the best possible condition to resist the contraction
stresses. The corners of a tool should not be allowed to reach
a higher temperature than the rest of the steel. If by
accident any part of the tool is got too hot, it should not be
allowed to cool down to the proper temperature and afterwards
quenched, as the steel will then have a coarse grain corre-
sponding to the highest temperature reached, with a
proportionate loss of strength. The remedy in this case is to
let the steel cool down slowly and completely, and then again
gradually bring it up to the correct hardening heat, by which
means the grain will be restored to the required degree of
fineness. With a tool that has thick and thin parts, it is
advantageous to heat the thick part first, in order to prevent
the thin part becoming overheated, and the method of putting
it into the water may also be modified to suit various shapes.
Tempering. — The hardness produced by quenching in water
is generally accompanied by an undesirable amount of brittle-
ness, which may be removed by the process of " tempering."
This is effected by reheating the hardened steel to a
temperature very much below that required for hardening,
and varying in practice between about 220° C. and 320° C.*
*220° C. = 428° on the ordinary (Fahrenheit) thermometer.
320° C. = 608°
56 IRON AND STEEL MANUFACTURE.
The degree of temper is generally judged by an observation
of the oxidation tints which appear on the bright surface of
the metal when heated, and which succeed each other in the
following order : — Light straw, dark straw, brown, brown with
purple (pigeon wing), purple, blue. Professor Turner* has
shown that the whole of these tints may be produced in
succession by keeping the metal at a constant temperature as
low as 220° C. for a sufficient length of time, a very light
straw being produced in two minutes, and a dark blue in l'2S
minutes, at that temperature.
After tempering, the article may either be allowed to cool
naturally in the air, or may be quenched in water. With
some tools, such as chisels, the point only is hardened, and
the tempering is effected by allowing the heat from the hot,
unhardened portion to travel to the point until the desired
colour is obtained, when the tool is quenched to prevent the
point becoming softened. The tint cannot therefore be re-
garded as a reliable indication of the temperature obtained
when tempering a tool, and the use of a thermometer is to be
preferred where practicable.
Oil-hardened tools are usually tempered by heating up until
the oil begins to char or burn, this being an indication of the
temperature reached.
* Trans, of the Birmingham Philosophical Society, vol. vi. , Part 2.
57
CHAPTER VI.
MILD STEEL.
MILD steel contains much less carbon than is found in tool
steel. To avoid cold-shortness and red-shortness (see p. 8),
the percentage of phosphorus and of sulphur must each be
kept under 0'05 per cent, for good quality steel. In regard
to these elements, mild steel is not so pure as steel for
cutlery and tools, which, it may be remembered, contain only
0*03 per cent, of each of these.
It differs from wrought iron in percentage composition, and,
in a more marked degree, in its structure. Mild steel is finely
crystalline, and is free from slag ; wrought iron is fibrous, and
contains a considerable bulk of slag in a state of irregular
intermixture. Owing to the high temperature at which mild
steels are finished, the metal is so fluid as to allow of the
ready separation of the slag ; indeed, it was owing to its being
" poured " in a state of fluidity that the term " steel " was
applied to it. The name "ingot iron" was proposed, but did
not prove acceptable.
COMPOSITION OF WROUGHT IRON COMPARED WITH STEEL.
Mild Steel
Constituents.
Chemical
Symbols.
Good
Wrought-Iron
Shaft.
for General
Engineering
Purposes.
Carbon, .
c
trace.
0-18
Silicon, .
Si
0-12
0-02
Sulphur, .
s
0-04
0-05
Phosphorus,
p
0-21
0-05
Manganese,
Cinder or slag,
Mn
trace.
1-30
0-50
none.
Iron (by difference),
Fe
A
A
100-00
100-00
Phosphorus in the Cinder, 0'05.
58 IRON AND STEEL MANUFACTURE.
Sir William Siemens showed the relative bulk of iron and
cinder in wrought iron by a cube of 4 i -inch side representing
the iron, and one of 2-inch side representing the cinder.
Presence of cinder seriously impairs the tensile strength of
wrought iron. Wrought iron has considerable compensation
in its fibrous character, which cannot be imparted in the
absence of cinder.
Mild steel is produced in large quantities by the following
processes : —
Bessemer process, . . \ either
Siemens process, . . I acid
Martin process, . . . f or
Siemens-Martin process, . ; basic.
It has largely taken the place of wrought iron because —
(a) It can be produced in larger masses,
(&) It is more uniform in composition throughout its
mass,
(c) It has greater tensile strength, and
(d) Its price is lower.
BESSEMER PROCESS. — The history of the Bessemer process
is most interesting, but cannot be dealt with here further
than to state that BESSEMER at first intended to improve
the strength and character of cast iron for cannons. His
investigations led him to attempt to make tool steel. That,
however, was not continued. The manufacture of a material
suited to general engineering purposes offered a much larger
field, which he proceeded to occupy. Signal failure followed
his first success, but by persevering he ultimately triumphed,
and produced the useful material now known as mild steel.
We must admire in Sir HENRY BESSEMER his ingenuity in
following up and improving on the results of his investigations,
the genius displayed in devising suitable contrivances for
carrying on the process, his quiet determination, his honesty,
thoroughness, and business capacity, as well as his generous
acknowledgment of the assistance of R. F. MUSHET and WM.
HENDERSON in helping him to perfect his method of making
mild steel.
MILD STEEL. 59
Briefly, the Bessemer Process consists in blowing air
through fluid pig iron, and "finishing" the metal according
to requirements. The metalloids (see p. 7) are oxidised, and
thereby separated from the iron. It is a beautiful process,
and is fully described in the following chapters.
Sir Henry Bessemer.
The Siemens Process consists in melting pig iron, and,
when the silicon and, incidentally, the manganese have been
oxidised, feeding suitable ore into the mass of melted metal
in the furnace. The oxygen in the ore hastens the burning
out of the carbon. At the same time the iron oxide in the
ore is reduced, the iron thereof adding to the weight of ingot
produced.
The skilful adaptation of the regenerative system intro-
duced in the open-hearth furnace designed by Mr. FREDERICK
SIEMENS (brother of Sir WILLIAM SIEMENS) has deservedly
won most hearty commendation.
60 IRON AND STEEL MANUFACTURE.
Martin Process. — The steel-making process with which the
name of M. Martin is associated consists in melting together
scrap steel, or good scrap wrought iron, with a quantity of
pig iron, and allowing oxidation to proceed. It may have
been suggested by the method devised by Reaumur in the
year 1722.
The Siemens-Martin process is a combination of the two
methods briefly described above. Siemens-Martin steel is
often called Siemens steel, and as it is always produced in
open-hearth furnaces it is known as open-hearth steel.
Sir William Siemens.
Unless basic steel is specified it is generally understood
that acid steel is meant — just as Mr. Smith (the senior) is
meant unless Mr. Smith, junior, is mentioned. This remark
applies alike to Bessemer and Siemens steels.
SIEMENS-MARTIN STEEL is in great demand because it is
a reliable material possessing valuable properties. It is made
from the same class of pig iron as acid Bessemer steel ; and,
so far as the content of carbon, phosphorus, sulphur, and
manganese is concerned, the two steels are frequently identical
in composition.
MILD STEEL. 61
Owing to the comparative slowness of the working of a
Siemens-Martin charge (which may occupy about ten hours)
the Siemens-Martin process is well under control and may be
more deliberately finished ; it has also been urged that it is
not, during manufacture, so highly oxidised as Bessemer steel.
Siemens-Martin steel is in high repute and favour in
Britain, while in the United States of America Bessemer steel
is more abundantly produced.
ACID STEEL. — Both Bessemer and Siemens processes were
originally conducted in plant lined with material in which
silica largely predominated. Chemically, silica (Si02) is of an
acid nature (see p. 26), and only those pig irons which
contained small quantities of phosphorus (and sulphur) could
be converted into good mild steel under these conditions.
BASIC STEEL. — As most of the iron ores at home and
abroad contain a notable amount of phosphorus, and as the
phosphorus is, with few exceptions, all carried into the pig
iron during the smelting in the blast furnace, it was most
desirable that a workable process should be found for expelling
the phosphorus, so that a good steel (not cold-short) might be
obtained from phosphoric pig iron. It has already been
explained (see p. 27) that if phosphorus is to be got out
of pig iron, certain conditions must be complied with,
including the presence of plenty of base. A basic slag is neces-
sary, and that slag must, during the process, be contained in
a basic-lined plant, or disastrous results would follow. (See
p. 84 for further information on this important point.)
Good acid steel, whether Bessemer-acid or Siemens-acid,
is made from pig irons, scrap, &c., comparatively low in
phosphorus. Only pure, costly ores can be used in the
manufacture of such pig irons, and the supplies are not
equal to the fast-growing demand for more steel.
On the other hand, good basic steel may be made from pig
iron produced from cheap and plentiful materials containing
much phosphorus, but the phosphorus must, during conver-
sion into steel, be eliminated, so that less than "05 per cent,
of phosphorus remains.
The pursuit of a process by which steel could be made from
highly phosphoric materials was most fascinating, and the
62 IRON AND STEEL MANUFACTURE.
promised results were most important. For not only would
the output of trustworthy steel be vastly increased, but large
deposits of iron ores could then be utilised. The problem,
and its importance, were fully realised in the latter seventies.
Some of the best metallurgists in the chief countries of the
world were at work on the question. Success was won in a
most unexpected quarter. SIDNEY GILCHRIST THOMAS, who
had sought relaxation from his prosaic duties as clerk in an
East London police court by attending evening classes, solved
Sidney Gilchrist Thomas.
the problem.* He was assisted by his cousin, PERCY CARLYLE
GILCHRIST, who was then metallurgist at Blaenavun, and he
had most kindly encouragement from E. P. MARTIN and E.
WINDSOR RICHARDS, who arranged for trials of the process
on a practical scale. The embodying of the ideas of GKO. J.
SNELUS and EDWARD RILEY completed the success of the
method.
*See the interesting Memoir of Sidney Gilchriat rJ homos, by
R. W. Burnie.
MILD STEEL. 63
Steel-making flourishes in certain districts because local
raw materials have been made available by the working of
the basic, or Thomas-Gilchrist, process.
The great rise in the German steel trade is due to the
successful working out of the basic process on a commercial
scale by the untiring perseverance of SIDNEY GILCHRIST
THOMAS. America, also, has profited immensely by the work
of the same genius. Vast ore-bearing territories in the
United States have been developed lor the supply of ore for
the manufacture of pig iron, which is worked into steel by
the basic open-hearth system.
Basic steel, corresponding in chemical composition to acid
iteel, is regularly made.
64
CHAPTER VII
PLANT AND APPLIANCES FOR THE ACID BESSEMER
PROCESS OF STEEL-MAKING.
THIS process aims, in the first instance, at the purifying of
melted pig iron (of selected quality) by quickly blowing air
through it in a vessel called a converter. At the hands of
Bessemer the converter underwent many changes in design.
At first he tried a fixed converter; afterwards he employed
converters which could be rotated into positions which
facilitated the charging and discharging of the metal. In
shape, too, the converter has been modified. In the earlier
forms the upper part (the hood or nose) was very much con-
tracted and sloped, with the idea of preventing, as far as
practicable, the ejection of metal and slag during the
" blow."
Improvements were introduced by Alexander Lyman
Holley, of New York, who arranged that the mouth should be
concentric, so as to permit of charging from two positions — a
distinct advantage for steel-making. He also carried into
practice the idea of building up the converter of three
separate parts fixed together by means of hinged flaps and
cotter bolts — an arrangement which helps in the quick
replacement of rapidly-worn parts by corresponding ones
which have been lined anew, properly dried, and got into
good condition for work.
The modern Bessemer converter is a capacious vessel of
mild steel plates firmly rivetted together and lined with a
refractory material to withstand the very high temperature,
the intense chemical action, and the wear and tear incidental
to the work done. The converter is somewhat barrel-shaped.
At one end is the opening through which it is charged and
discharged ; at the other end are numerous openings (the
tuyere holes) through which the strong air-blast is injected.
ACID BESSEMER PLANT.
65
Encircling the converter at its widest part is a heavy cast-steel
ring, to which two trunnions are firmly attached. The
trunnions may be said to be short axles. They rest on
suitable bearings, and not only support the converter but
serve other useful purposes. Attached to one is a large
toothed wheel which gears into a horizontal rack.* The rack
Fig. 22.— Bessemer Converter— Part Elevation, part Section.
I,
A, Toothed wheel.
B, Trunnion belt.
C, Ganister lining.
D, Iron shell.
E, Brackets for bolts.
F, Pin for cotter bolt.
G, Trunnion belt.
H, Blast pipe.
Support for blast-pipe
trunnion.
J, Blast-box plate.
K, Blast box.
L, Guard plate for keeping
tuyeres in position.
M, Tuyere.
is, when required, actuated by a horizontal double-acting
hydraulic ram, and as the rack is moved backwards or for-
wards it causes the toothed wheel to revolve, and with it the
converter to rotate to any desired inclination or position.
The other trunnion forms part of the blast pipe through
which the tremendous air-blast is sent from the blowing
* Sometimes the rack is vertical.
66
IRON AND STEEL MANUFACTURE.
engine to the tuyere box (under the bottom of the converter)
to be distributed to the several tuyeres.
The Tuyeres, with the necessary number and size of tuyere
holes for acid-lined converters, are carefully moulded, dried,
and kiln-fired, and are supplied ready-made to most steel-
works. They are slightly tapered so that they may be more
easily fitted into, and held fast in, the openings which are left
in the tuyere plug of the converter bottoms. The tuyeres
are pushed into the openings, luted with
moistened fireclay or ganister, and held firmly
in position by means of the guard plate, which
is a large disc with openings corresponding to,
but a little smaller than, the larger end of each
tuyere. The tuyeres may be held in position
by metal "lugs" which can be turned round on
their pivot studs to permit removal.
In one works the 18-ton converters have
each 24 tuyeres, and each tuyere has 19 holes
of T5F inch diameter. This equals 35 square
inches of tuyere hole area, and may be accepted
as fairly representing British Bessemer (acid)
practice in this particular. The bottom may
last for twenty blows, and the hood and body
of the converter may need relining after twelve
months ; these figures representing average
working.
Fig. 23.
Bessemer
Tuyere.
The material used for lining the converter is good ganister,
which may have the following composition : —
Constituents.
Chemical Formulae.
Percentage.
Silica,
Si02
94-3
Alumina,
Iron oxide,
ALA*
FeO
CaO
1-5
1-2
0-5
Magnesia,
Alkalies,
Water, .
MgO
Na.,0 and K2O
" H2O
0-2
O'l
2-2
100-0
ACID BESSEMER PtANT. 67
To line a vessel with ganister the three pieces — namely,
the hood or nose, body, and bottom — are each dealt with
separately. The rivetted sheathing for the hood or nose is
inverted on a platform ; a wooden core or plug of the internal
size and shape is placed correctly, and the space between the
plug and the sheathing is filled and rammed with crushed
and moistened ganister ; or tar may be used as a binding
material. The bottom part is also rammed with ganister,
openings being left for the insertion of the fireclay tuyeres.
The body is generally lined with suitably curved silica bricks.
These arc built within the rivetted plates which make up
the shell, and are carefully cemented with a thin slurry of
J
Fig. 24. — Arrangement for Ramming Converter.
A, Platform. C, Ganister lining.
B, Iron shell. D, Plug.
ganister. The body is lined while the shell is in its ordinary
position ; the other parts are rammed in a separate building
in the work. The parts are placed in position by overhead
cranes, or by trolleys carrying hydraulic lifting (and lowering)
appliances, and are fastened by hinged, slotted flaps and
cotter bolts.
The several parts having been lined and bolted, each to its
adjoining part, live coal may be put into the converter and a
gentle air current sent through it so as to thoroughly dry the
lining. The converter having been thus dried and warmed, is
rotated till the month is downwards and the ash and unburnt
fuel fall out. It is then ready to receive the charge.
68 IRON ANJ) STEEL MANUFACTURE.
The Air-blast is urged by powerful blowing engines and is
delivered at a pressure of 25 Ibs. per square inch.
On an elevated platform, or pulpit, as the workmen call it,
is a range of levers — like those in a railway signal box — by
which the " pulpit man " controls the duration of the blow, the
position of the converters, and the pouring of steel and slag as
directed by the " blower " who is in charge.
The Bessemer Ladle enables the steel free from slag to be
poured into the ingot moulds, even if steel and slag have been
poured into it from the converter. These, by reason of the
fluidity of each, and of the decided difference in density, soon
separate from each other ; the slag, being much lighter, rising
to the top. A layer of slag floating on the top of the steel
protects the latter from chilling and from oxidation. Then,
when the steel is run out through the nozzle in the bottom
of the ladle, it is — all except the last of it at least — free
from slag.
The Bessemer ladle consists of a shell or sheath of mild
steel plates rivetted together. It is lined within with
rammed ganister or with thin firebricks of good quality
which are carefully cemented in position by a mortar
of ganister. At the lowest part of the ladle there is a
space for receiving the fireclay nozzle through which the
metal is poured. Into this a fireclay stopper at the end
of a rigid iron or steel rod is carefully adjusted. The
rod is covered with fireclay sleeves, in short lengths,
which are fitted to each other from the stopper up to above
the lip of the ladle (see fig. 25). These are all fitted with
care and well-dried before being attached to the arrangement
at the top for actuating the rod, and adjusted to the nozzle at
the bottom. The arrangement at the top may consist of
cranks worked by the action of an outside rod which is guided
by sockets fixed on the outside of the ladle. The outside rod
is moved up or down, as required, by means of a hand lever
fitted to a pivot stud. Instead of the crank arrangement the
outer rod may be bent over so that the inner rod, with the
sleeves, &c.. can be attached.
The ladle must be hot and the stopper rod arid nozzle
ACID BESSEMER PLANT.
69
set to a nicety before the steel is poured into it. The ladle
is carried at the end of a platform which is pivoted at or near
the centre so that it can be swung in a circle from its point
Fig. 25. — Teeming Bessemer Steel into Ingot Moulds.
A,
0,'
t>,
E,
F,
G,
H,
Ladle.
Trunnion.
Support for rod.
Sleeves covering iron rod.
Nozzle or outlet.
Top of crane stem project-
ing through roof support.
Brackets for crane stem.
Stay rod.
I, Hydraulic ram.
J, Staging.
K, Piston of crane stem.
L, Ingot mould.
M, Trolley.
N, Arrangement for regulating
the position of the trolley
during teeming.
0, Cylinder.
under the converter to the semi-circular casting pit where a
set of ingot moulds have been placed to receive the steel
The nozzle of the ladle having been brought ove? the centre
70
IRON AND STEEL MANUFACTURE.
of the first mould of the series, the hand lever is unfastened
and the free end is moved so as to push the rod upwards,
thus opening a passage between the stopper and the nozzle
and permitting the outflow of the steel into the ingot mould.
When the mould is sufficiently filled the stopper is pressed
down and the ladle is swung over the next ingot mould, which
in turn is filled with the steel. And so the " teeming " is
continued till all the steel has been poured. The ladle is
then turned over so that the slag is emptied out. The nozzle
is then knocked out and a new one fitted in,
to which, in due course, a covered stopper
rod will be carefully set.
Instead of the ladle being swung over each
individual mould, it is not an unusual arrange-
ment to have the moulds mounted on low
trolleys (see fig. 25) and to push the trolleys
one by one up to the pointer which regu-
lates the position under the ladle. The
" teeming " from the ladle is regulated by
the stopper as described above.
Ingot Moulds are strong hematite-iron
castings with wrought-iron or steel lugs at
the upper end, as shown in fig. 26. They
are usually open both at top and bottom,*
and they are broader at the bottom than at
the top so that they may be more easily
stripped from the steel ingot when the latter
is cool enough. Stripping is performed by inserting in the
lugs hooks attached to a chain which is moved by a crane,
as shown in fig. 51, p. 120.
The Bessemer Crane, for lifting and conveying ingots,
moulds, &c., is worked on the hydraulic system, and is in
principle similar to the hydraulic ram, &c., shown in fig. 25.
It consists essentially of a strong hydraulic cylinder in which
a long upright stem works smoothly without being too loose.
The stem sometimes extends to the roof by which it is braced ;
* The moulds are set on heavy cast-iron slabs before "teeming" the
steel into them.
Fig. 26.— Ingot
Mould.
ACID BESSEMER PLANT. 71
if not, a counterpoise is fitted to another arm corresponding
to the jib. From the stem there projects an arm or jib along
which a little trolley runs easily. From a hook attached to
the trolley the ingot or mould to be moved is suspended.
By admitting water under the bottom of the stem the stem
may be raised, lifting with it the weight, be it ingot or
mould, which can then be swung round and run along the jib.
Then on allowing the water to escape from the cylinder the
suspended article can be lowered.
There are other kinds of cranes in extensive use in steel
works. Hydraulic and electric arrangements for stripping
the moulds from off the ingots are also used.
The fluid metal required for the Bessemer process may be
obtained by remelting the pig iron in a cupola, or by conveying
in a ladle the molten pig iron,* in the condition in which it
comes from the blast furnace, direct to the converter.
There is a newer and a better method — namely, that of
conveying the pig iron as it runs from the blast furnace into
a metal mixer — which may be described as a cistern — and
taking off from the mixer, in such quantities and at such
times as needed, the fluid metal for use in the converter.
Storing in a mixer tends to yield a more uniform quality of
metal throughout the working week.
A cupola is a shaft furnace open at the top. It is of mild
steel plates rivetted together, and is lined with firebricks set in
a grouting or mortar of fireclay. A working bottom is made
by ramming sand or ganister into the required shape.
Near the top is a platform and an opening for charging.
On one side, near the bottom, is an openingf by which the
slag and unburnt coke may be drawn when the cupola has
ceased work ; it is also useful for repairs, for making up the
sand bottom, and for putting in the coke and the kindling
material when beginning or resuming work.
When a cupola is in working order, pig iron and coke are
* As a matter of convenience, we consider the "metal" which is
tapped from an iron-smelting blast furnace to be pig iron whether it is
formed into " pigs " or not. With regard to " pigs " see p. 208.
fThis opening is closed, and is covered with an iron plate during the
melting of the charge.
C, Air or blast belt.
D, Charging platform.
E, Charging door.
F, Iron shell.
G, Angle iron for supporting
bricks.
Fig. 27.— Steel Work Cupola— Half Elevation, Half Section.
A, Slag spout.
B, Blast pipe from blower.
H, Firebrick lining.
J, Tuyere.
K, Taphole.
L, Spout or lander for melted
metal
ACID BESSEMER PLANT.
73
charged in, along with a little limestone. An air-blast is
forced in through tuyeres, which may be in one row or more.
The burning of the coke raises the temperature, and melts the
pig iron and the slag which is formed. These descend, and
are taken off through their respective tapholes.
74 IRON AND STEEL MANUFACTURE.
During the descent a little loss occurs through oxidation of
iron, manganese, and silicon, and the "metal" takes up a
small amount of sulphur from the fuel.
The cupola shown in lig. 27 is of the following
dimensions : —
Height to charging platform, . . .22 feet.
Internal diameter at widest part, . 8 „
„ middle „ 5 „
„ „ „ lower „ 6 „
There arc seven tuyeres, each 5 inches diameter, set 4 feet
6 inches above the floor level, and the blast is supplied at a
pressure of about If Ibs. per square inch. The slaghole is
3 inches below the tuyeres.
Such a cupola melts 500 tons of pig iron in 24 hours, and
requires repairs to its lining after working about 60 hours.
When needed, the melted pig iron is tapped from the
cupola into a ladle of the kind shown in fig. 28, which
conveys it to the Bessemer gantry — that is, the platform at
the converters — and by a side lip it is poured into the
converter.
75
CHAPTER VIII.
THE ACID BESSEMER PROCESS.
BY the successful working of this process, suitable molten pig
iron is purified and converted into either medium or mild
steel by the action of a rapid current of air which is forced
through it. This causes the oxidation, or burning, of certain
elements, which are thereby removed from the pig iron. The
"blown metal" is then finished by the judicious addition of
hot spiegel-eisen or ferro-manganese. The steel is then poured
Fig. 29.— Pouring "Metal" into a Converter.
from the converter into a ladle, from which it is tapped into
ingot moulds. The steel ingots are afterwards rolled into the
shapes required — such as plates, angles, girders, bars, springs,
tyres, axles, &c.
Working an Acid Bessemer Blow, — The Bessemer con-
verter, lined as described in the previous chapter, being
76
IRON AND STEEL MANUFACTURE.
in good condition and hot, is rotated till it is nearly
horizontal. The position must be such that the melted metal
cannot flow into the holes of the tuyeres. The charge of
Fig. 30.— Bessemer Converter while Blowing.
Fig. 31.— Pouring Steel from Converter.
THE ACID BESSEMER FROCESSl
77
fluid pig iron is run into the converter* from the ladle which
conveyed it, and, if too hot, scrap steel is thrown in. An
alarm — a loud whistle from a jet — is sounded, so as to warn
the workmen to get out of the way of the flame and sparks
which are ejected when the blast is turned on. The vessel
is then rotated till nearly vertical, the blast being continued
until it is judged that the silicon and carbon have been
oxidised — a point indicated by a change in the sound of the
blow and by the difference in the flame when it "drops."
The alarm is again heard, and the converter
is turned down to a safe horizontal position.
The converter then contains metal and slag.
By reason of its much lower density, the slag
soon separates by rising to the surface. The
metal at this stage is highly oxygenated.
Addition of a weighed quantity of hot ferro-
manganese or spiegel-eisen soon deoxidises the
metal, and converts it into mild, medium, or
hard steel by giving to it the desired percen-
tage of carbon. All being ready, the steel is
poured into a Bessemer ladle, and from thence
it is teemed into the ingot moulds.
When the steel ingot has become cold enough
to safely bear removal, the mould is stripped
off (as shown in fig. 51), and the ingot is
gripped by "dogs" on the end of a chain,
hoisted by a crane, and conveyed to be re-
heated or stocked. The weight of the ingot
tends to pull the dogs, and the grip is thereby
tightened. The ingot is thus firmly held
until released when it ceases to be suspended.
The further treatment of steel ingots is dealt
with in Chapter xiii.
Fig. 32. — Steel
Ingot and
Dogs.
The Principles of the Bessemer Process may be gathered
from a study of the appended table of composition, and a
consideration of the chemical changes which take place during
the course of conversion into mild steel : —
historic reasons the old-fashioned type of hood is shown.
78
IRON AND STEEL MANUFACTURE.
JMtM Steel
Constituents.
Chemical
Symbols.
Hematite
Pig Iron
before Blowing.
Hematite
Pig Iron
after Blowing.
Produced
after Addition
of Ferro-
M auganese.
Graphitic carbon,
c
3-42
None
None
Combined carbon,
c
0-46
Trace
0-20*
Silicon,
Si
2-20
None
0-02
Phosphorus,
P
0-045
0-048
0-05
Sulphur,
s
0-045
0-048
0-04S
Manganese, .
Mn
0-47
Trace
0-50
Oxide of iron,
None J
Present, but
not estimated.
| None
Iron, .
Fe
A
A
A
Total, .
100-000
100-000
100-000
Chemical Considerations. — The force and volume of the
powerful air-blast, which is urged by the blowing engine at
high pressure into the tuyeres, can support the heavy mass
of metal, and keep it dancing, as it were, on a cushion of
air, so that it cannot run down and choke the tuyere holes.
The air finds its way up through the mass of hot, fluid
metal ; there is a violent commotion and sharp chemical
action. Even in that brief passage the oxygen of the air
exerts its chemical power with much effect. Fortunately, it
is selective in its action.
For, as in the puddling process, one metalloid is attacked
by oxygen in preference to another, so is it in the Bessemer
process. Generally the silicon is first attacked ; nearly at the
same rate the carbon is also attacked. The manganese in due
course is also oxidised, so that at the time the flame " drops "
these three elements are all practically absent. Considering
the large quantity of iron present the oxidation of that metal
is small. It is more than probable that the resulting oxides
of iron assist in the rapid oxidation of other elements.
There is no elimination of phosphorus or of sulphur, and,
as the quantity of these elements originally present is, at the
end, concentrated in a smaller weight of metal, the percentage
of each of these elements is higher. The percentage increase
is slight but is important.
* The percentage of carbon is easily adjusted so as to suit the purpose
for which the steel is made,
THE ACID BESSEMER PROCESS. 79
The chemical reactions involved may briefly be explained
thus : —
(a) Carbon (C) is oxidised, partly into carbon monoxide
(CO) and partly into carbon dioxide (C02), and the
changes may be concisely indicated by chemical
symbols : —
C + 0, COo
Carbon and oxygen yield carbon dioxide.
2C + 0, 2CO
Carbon and oxygen yield carbon monoxide.
The gases, carbon monoxide and carbon dioxide,
escape into the air.
(b) Silicon (Si) is oxidised into silica (Si09) — a reaction
noted in the chemical equation : —
Si + 02 Si02
Silicon and oxygen yield silica.
Silica forms the chief component of the slag.
(c) Manganese (Mn) is oxidised to manganous oxide (MnO),
as symbolised in the following equation : —
2Mn + 0., 2MuO
Manganese and oxygen yield manganous oxide.
The manganous oxide goes into the slag.
(d) The iron which suffers oxidation is changed partly into
ferrous oxide (FeO) and ferric oxide (Fe203) — changes
represented in chemical symbols thus —
2Fe + 02 2FeO
Iron and oxygen yield ferrous oxide.
4Fe + 302 . = 2FeA
Iron and oxygen yield* ferric oxide.
These oxides find their way into the slag.
Oxidation and Deoxidation of Bessemer Metal.— A belief is
current that a lower oxide of iron exists, and that the lower
80
IRON AND STEEL MANUFACTURE.
oxide clings to the melted iron and causes that condition
which makes ordinary blown Bessemer metal worthless. The
existence of that lower oxide has not been proved. There
is also a belief that oxygen is dissolved in blown Bessemer
metal. In either case the mischievous oxygen is removed by
the addition of hot manganese which takes over the oxygen
from the iron and becomes converted into oxide of manganese,
which is quickly carried into the slag.
In the absence of definite information concerning the com-
position of the supposed lower oxide of iron, the chemical
change by which deoxidation is effected may be represented
thus —
FeO + Mn MnO + Fe
Iron oxide and manganese yield manganous oxide and iron.
The following table shows the composition of certain
grades of the " triple compounds of manganese, carbon, and
iron " used in the manufacture of Bessemer and other steels.
Constituents
Chemical
Symbols.
Spiegel-
eisen.
Medium
Ferro-
Manganese.
High Grade
Ferro-
Manganese.
Manganese,
Mn
15-12
53-36
79-85
Carbon (combined), .
C
4-43
6-12
6-64
Silicon,
Si
0-47
0-46
0-71
Sulphur,
S
0-02
0-01
o-oi
Phosphorus,
P
0-23
0-11
0-20
Iron, ....
Fe
A
A
A
100-00
100-00
100-00
For additional analyses see p. 237.
Spiegel-eisen is generally known in works as "spiegel";
ferro-manganese is known as " ferro " or " manganese." All
such materials are known in works by the common name
of "physic."
THE ACID BESSEMER PROCESS. 81
In the Bessemer process the functions of these materials
are threefold.
(a) To " restore the nature " of the metal by removing the
combined or dissolved oxygen.
(b) To add the necessary amount of carbon required in the
steel to suit its intended purpose.
(c) To add a certain amount of manganese to the finished
steel — in which it acts to some slight extent as a
" corrective " to the phosphorus, and more especially
to the sulphur which is always present.
Recarburising. — The quantity and kind of material added
are determined by the percentage of carbon required in the
finished steel. Thus, if a mild steel (that is, one low in
carbon) is ordered, ferro-manganese is used ; if a steel con-
taining a higher percentage of carbon is wanted, spiegel-eisen
is used. Why this is so is explained in Chapter xxiii.
Coke and other substances rich in carbon are occasionally
used for recarburising.
The ferro-manganese is broken into little lumps (say about
4 inch cubes or even smaller pieces), and is usually red hot
when charged into the molten metal in the converter. It
soon melts, and time is allowed for its diffusion through
the " metal." When spiegel-eisen is used it is charged into
the converter in the fluid condition, as such a large quantity
would, with difficulty and uncertainty, melt in the metal in
the converter.
If the blow is stopped before all the carbon is burned out,
less recarburising material will of course be needed. Swedish
Bessemer practice is interesting in this particular. Carbon
may be added directly to the metal at the end of a blow, or
grey hematite pig iron may to some extent be used. Other
materials for promoting soundness in steel contain aluminium
or silicon in notable proportions.
Heat evolved during a Bessemer Blow.— The molten pig
iron which is run into the converter is red hot, and, although
6
82 IRON AND STEEL MANUFACTURE.
a large volume of ordinary cold air is forced through it, the
metal is much hotter at the end of the blow. The decided
rise in temperature is due to the rapid burning of the carbon,
the manganese, some of the iron, and especially the burning
of the silicon. Much of the heat evolved by the oxidation of
the carbon is carried quickly away in the gases which escape
by the mouth of the converter, whereas the silica resulting
from the oxidation of the silicon remains in the converter (as
a component of the slag) until it is poured off after the end of
the blow. The silica, it may be well to explain, unites
chemically with oxide of iron and other bases, forming at the
high temperature attained during a " blow " a slag so very
fluid that it can contain a considerable quantity of chemically
free silica and yet remain fluid.
The British Bessemer blower mainly relies on the percentage
of silicon for the maintenance of the heat needed to keep
his metal in the condition 6f fluidity required.
When the metal is too hot at the finish it is apt to be
" wild " in the moulds and to produce unsound ingots. On
the other hand, metal which is too cold is apt to lead to an
insufficient intermingling of the ferro-manganese or spiegel-
eisen ; there is also a serious risk of steel solidifying in the
ladle and forming a " skull," of the teeming not being smooth,
and the ingots being unsatisfactory.
The best cure for cold blows is hotter and more highly
siliceous pig iron. If a supply of such cannot be had a
greater volume of blast through wider tuyeres should be
arranged for.
For blows which finish too hot, quite the contrary con-
ditions should be set up, and a plentiful supply of suitable
scrap steel, which should be liberally thrown into the con-
verter before running in the melted pig iron, would go far to
remedy matters.
THE ACID BESSEMER PROCESS.
83
Bessemer Slag from the blowing of ordinary Hematite Fig
Iron may contain the following components in the percentages
stated : —
Constituents.
Chemical Formulae.
Percentage.
Ferrous oxide,
Ferric oxide, .
Oxide of manganese,
Silica, .
Alumina,
FeO
FeA
MnO
Si02
10-4
0-5
14-4
69-8
2-9
1*7
Magnesia, ....
MgO
0-3
100-0
Although slag of this composition contains 8' 3 4 per cent,
of iron and 1 T15 per cent, of manganese — each in an oxidised
state — no profitable method of extracting these metals has
yet been devised, and the slag is thrown down as worthless
on slag heaps.
The percentage of oxide of manganese (MnO) given in the
above analysis is much lower than that stated in many text
books, but it accurately represents present day practice.
CHAPTER IX.
THE BASIC BESSEMER PROCESS.
THE intention of the basic Bessemer process is to produce
good malleable metal (mild steel) from pig iron containing
much phosphorus.
In the ordinary (acid) Bessemer process all the phosphorus
in the pig iron is concentrated in the steel which is made
from it. Presence of more than 0'05 per cent, (that is, equal
to 5 in 10,000 parts) of phosphorus in steel makes it "cold
short " and therefore useless for some purposes for which steel
is used. Clearly, then, if good, reliable steel is to be made
from pig iron containing a high percentage of phosphorus
some means must be found for eliminating phosphorus from
the metal.
The conditions for dephosphorising pig iron are : —
(a) Fluid metal, and, when formed, fluid slag.
(5) An active oxidising atmosphere.
(c) Intimate intermixture of metal and slag during working.
(d) Abundance of suitable base to hold the phosphorus
which is liberated from the pig iron. [Phosphorus
when liberated is oxidised and forms phosphoric acid
WV-]
(e) The presence of abundance of highly heated base
necessitates a basic lining for the chamber in which
the operation is conducted.
Because basic Bessemer slag contains all the phosphorus
from the pig iron the slag has a high commercial value.
The chief difference in the basic Bessemer plant, as
contrasted with the acid Bessemer plant, is the lining of
the converter for the former with basic material. And
as a much greater bulk of slag results from the basic pro-
THE BASIC BESSEMER PROCESS.
85
cess, the converter, for a given amount of metal, must be
larger.
The cupolas and ladles are the same in size and in lining
as for the acid process, and the blowing engines, cranes, ingot
moulds, &c., are also the same. They are described in
Chapter vii.
For the manufacture of basic steel, machinery and appli-
ances are required for making basic bricks and for preparing
the basic linings. Machinery for grinding the slag from the
basic process is also required unless the slag is sold in its
rough state to merchants.
Materials for Lining. — The basic Bessemer converter is
generally lined with a prepared mixture of ground calcined
dolomite and special tar free from water.
When limestone, which contains calcic carbonate (CaCO3 or
CaO, C02 ), is calcined, or, as the works' phrase goes, " burnt,"
the carbon dioxide is liberated, and lime (or quicklime) is left.
Lime mixed with tar would make a tolerably good basic
lining, but magnesia — which is left on strongly calcining
magnesite or magnesic carbonate — is a better substance. It
is, however, much more costly. Fortunately there exist
large accessible deposits of dolomite* (or magnesian lime-
stone), which is a compound carbonate of lime and magnesia.
Prepared dolomite is freely used as the material for lining the
basic converter. Where magnesite is plentiful and cheap,
magnesia is used. In Russia, chrome iron ore is used and a
lining of that substance lasts a very long time.
COMPOSITION OF BASIC REFRACTORY MATERIALS.
Chief Constituents.
Chemical
Formulae.
Calcined
Limestone.
Calcined
Magnesite.
Calcined
Dolomite.
Lime, ....
Magnesia, .
Alumina,
Silica,
CaO
MgO
A1A
Si02
95'7
1-2
0-9
1-9
1-8
94'4
2-3
0-6
59-5
33-1
2-8
3-7
99-7
99-1
99/1
Named after Dolomieu, a famous French geologist.
86 IRON AND STEEL MANUFACTURE.
These are derived from —
Chief Constituents.
Chemical
Formulae.
Limestone.*
Magnesite.*
Dolomite.*
Carbonic acid and other)
volatile matters, . /
C02, fto.
42-7
51-2
46-3
Lime, ....
CaO
54-8
0-9
31-9
Magnesia, .
MgO
0-5
46-3
17'8
Alumina,
ALA
0-5
1-1
1-5
Silica,.
Si62
1-2
0'3
2-1
99-7
99-8
99-6
Preparation of the Materials for Lining. — The dolomite, in
lumps as quarried, or broken into smaller pieces, is calcined by
being placed in a kiln, along with the necessary fuel, which,
when burning, expels the carbon dioxide. The calcined
dolomite — which shrinks very much during the "burning" —
is ground in a pan mill, and enough hot anhydrous f tar (or
pitch) to make a mass of the proper consistency is added, and
thoroughly mixed with it in the pan mill. About 8 per cent.,
by weight, of the water-free tar may be needed. The tar acts
as a binding material, and protects, to some extent at least,
the lime, which would otherwise quickly take up moisture
from the air.
The mixture of calcined and ground dolomite and water-free
tar (or pitch) is known in the works as basic material — a
term sometimes applied to the burnt dolomite without the tar
addition. It may be used in the form of bricks, or may be
hand-pressed by hot rammers.
To make basic bricks a press is employed. The press has
a table which can be rotated about its centre. The table
carries three moulding boxes, which are arranged at equal
distances from the centre and from each other. Each box in
turn is filled with the basic material, a strong iron plate is
placed over it, and the table is moved until a box is right
under the hydraulic ram, which descends and presses the basic
* These are not basic until calcined,
f Anhydrous means "free from water."
THE BASIC BESSEMER PROCESS. 87
material until it half fills the box. The table is moved again
till the first box is over another but less powerful ram; the
ram, on rising, lifts the pressed brick, which is moved by hand
and carried to a warm place. Meanwhile, the other boxes
have been filled, and the second one has been under the press.
And so the succession is kept up, three bricks being on
the way at one time. The bricks, having been kept in a
warm place for some days, may then be packed in a kiln
and kept at a high temperature for a few days, or they may,
while in the green state, be built into position in the
converter.
Lining the Basic Converter. — The converter is of three
parts— the hood or nose, the body, and the bottom.
The body is generally lined with basic bricks, made as
previously described, and set in plenty of basic material.
The hood, being the part least subjected to severe usage, is
often lined with a mixture made from clean portions of old
lining ground fine and mixed with more anhydrous tar.
When in need of renewal the hood is turned upside down
on a platform, and detached by undoing the cotter bolts.
It is then taken to that part of the works — popularly called
the plug shop — where relining is done. The old lining is
removed, and a core or pattern is placed in position.
Kammers — long iron bars with flattened enlargements "at one
end — are made hot at the broad end. Some of the mixture
is thrown in between the shell and the core, and workmen
press firmly the hot rammers on it, and cause it to cohere.
More of the mixture is supplied and similarly pressed, relays
of hot rammers being supplied to the men.
The bottom is similarly rammed, but in two parts. In the
first place, a " plug" is prepared, and, secondly, the plug is
fixed in the centre of a converter bottom. To prepare the
plug, an iron plate or disc, surrounded by an iron cylinder, is
provided. Round, tapered iron rods about 21 inches long, of
the number and diameter of the intended tuyere holes, are
fixed to the plate (see fig. 33). Between these upright rods a
small quantity of ground burnt dolomite, mixed with melted
anhydrous tar, is thrown in, and carefully pressed with hot
iron rammers of a special shape. More of the mixture is
88
IRON AND STEEL MANUFACTURE.
emptied in, and cemented to the previous portion by means
of the hot irons. In this manner, little by little, the plug is
built up, generally to a thickness of about 1 8 inches. When
completed, the plug is lifted up on the iron bottom plate and
the upright iron rods are each struck a smart blow. As they
are slightly tapered they are easily caused to fall, and each
leaves a vacant space for a tuyere hole. The plug, contained
in the metal cylinder, is then carefully dried and kiln-fired.
It is then set in the centre of the space enclosed by the iron
work which constitutes the sheathing of the " bottom," and
the space between the sheath and the plug is filled in with
basic material, which is cemented by ramming in the
usual way.
The size and number of the tuyere holes vary in different
works, but 70 openings, each f inch diameter — giving an area
Fig. 33.— Plate, Cylinder, and Rods for Basic Plug.
of 31 inches — may be accepted as a fair average for a 15-ton
basic converter.
The plug, as a whole, may be rammed by hydraulic pressure
instead of by hand. At the North-Eastern Works, Middles-
brough, this is regularly done, and with most advantageous
results. In some works fireclay tuyeres — same as for the acid
Bessemer process — are used. They soon become worn, but
are easily replaced by pushing them into a setting of basic
material in the tuyere openings of the plug.
A plug lasts, as a rule, about 17 blows; the body needs
relining after about 120 blows; and the nose may stand from
50 to 300 blows before requiring relining.
ft- i-
C/D ,
O
<u
>« 'So
h o
u w o PQ o
< <-• . *^
u 3
THE BASIC BESSEMER PROCESS. 89
The three parts of the converter are fixed to each other
by means of cotter bolts, a junction of basic material in a
plastic condition being placed between each before pressing
the parts together prior to fixing.
A fire is kindled and kept going in the converter till it is hot.
The regular supply of fairly uniform "metal" to the
converters conduces to smooth working and helps in the
production of steel of uniform quality. As in the acid
process, the pig iron may be , re-melted in cupolas, or the
" metal " as tapped from the blast furnace may be taken
directly to the converter, or it may be supplied through a mixer.
Many mixers are shaped like open-hearth tilting furnaces,
and have gas producers and regenerators. In some instances
a considerable diminution in the percentage of silicon and of
sulphur takes place in the mixer. Scrap steel can be melted
in the mixer and "metal" sufficiently hot for comfortable
flowing may be delivered as required.
Mechanical contrivances which facilitate the conveyance of
metal are advantageously adopted. The more rapid pro-
duction resulting from their adoption more than compensates
for the cost of installing and working. Fig. 34 shows a
double-bugey ladle crane of the substantial type made by
Messrs. Thomas Broadbent and Sons, Huddersfield. This
crane is fitted with five electric motors. The illustration
shows the molten metal being poured into a converter, the
rear chain and pulley being brought into action to tilt the ladle.
Working a Basic Bessemer Blow. — When a basic-lin^d
converter is in good working condition, and hot, it is turned
with its mouth towards the upper gantry, from which a
quantity of calcined or "burnt" lime is shot into it (see
fig. 35 on next page). The converter is then rotated until it
is in a proper position to receive the charge of melted basic
pig iron which is poured into it from a side- tipping ladle, as
shown in fig. 35. The alarm is sounded and the air-blast is
turned on. The vessel is rotated until in a nearly upright
position and the blowing is continued until the flame drops and
90 IRON AND STEEL MANUFACTURE.
for a further period, the length of which is decided by the
" blower " who is in charge. There is therefore in the basic
Bessemer process the period of the blow — till the flame
"drops" — and a further period called the " after-blow." It
is during the after-blow that nearly all the phosphorus is eliminated,
and the length of that period is a matter for cool judgment.
When the blower thinks the after-blow has continued long
enough he has the vessel turned down arid the blast stopped.
As soon as the "metal" and the slag have separated from
each other — and as they are both very fluid and the difference
Fig. 35. — Charging Lime into a Bessemer Converter.
in density is great, separation is soon effected — a sample is
withdrawn by means of a long-handled ladle and the " metal "
sample is poured into an open mould where it quickly
solidifies. The sample is flattened under a steam hammer,
water-cooled, and broken across. The blower examines the
fracture and judges by the size of the crystals on the fractured
parts whether or not the process of dephosphorisation<- has
proceeded far enough. If not, he signals for the continuance
of the blow. Another sample is taken and similarly tested.
If. in the judgment of the blower, this is still unsatisfactory
THE BASIC BESSEMER PROCESS.
91
the blowing is resumed — perhaps for some seconds. When
he concludes that the metal is right (due allowance being
made for the slight rephosphorising which occurs on the
addition of ferro-manganese or spiegel-eisen) some of the slag
may be run off. The necessary amount of ferro-manganese
or spiegel-eisen is then charged, and, when it has had time to
mix well with the metal, the steel is poured into the hot,
mounted ladle and duly teemed into the moulds which have
been carefully set in the casting pit. The treatment of steel
ingots is dealt with in Chapter xiii.
Additions of lime, of scrap, or of iron oxide may be made
at a certain stage or stages of the blow.
The Chemical Changes which occur during the basic Bes-
semer blow may be gathered from the following table : —
Com position of
Constituents.
Chemical
Symbols.
Pig Iron
Charged.
Metal at
End of
Blow.
Metal at
End of
After-blow
Finished
Steel.
Graphitic carbon,
Combined carbon,
c
c
0-82
2-83
0-05
Trace.
6:14*
Silicon,
Si
0-63
0-03
0-005
001
Phosphorus,
P
2-75
2-38
0-04
0-04
Sulphur, .
s
0-07
0-07
0-05
0-05
Manganese,
Mn
1-75
0-13
o-io
0-45
Iron, .
Fe
A
A
A
A
100-00
100-00
100-00
100-00
Chemical Considerations. — The elements which are required
to be removed from the pig iron are oxidised by the oxygen
of the air which is forced in such large volume through the
pig iron in the converter. Silicon and carbon are vigorously
attacked, manganese is freely acted on, and when these are
nearly all removed iron begins to be burned, and, lastly, the
phosphorus is oxidised. Where abundance of hot lime is
present a steady diminution of the amount of sulphur in the
* The percentage of carbon is varied according to requirements.
A By difference.
92 IRON AND STEEL MANUFACTURE.
metal takes place. Prolonging the blow, which is not gener-
ally advisable, may lead to a further diminution of sulphur.
If the pig iron charged contained much sulphur, part of it
may be easily " gasified " or volatilised and carried off" in the
escaping gases. Hot blows tend to lead to sulphur elimina-
tion. Where only a moderate amount of sulphur is present
it appears that that which is removed during the after-blow
all goes into the slag. In one British Bessemer work about
33 per cent, of sulphur is regularly eliminated during blowing.
The Chemical Reactions may be indicated by the following
equations : —
Si + 02 Si02
Silicon and oxygen yield silica,
which combines with bases in the slag.
Carbon is oxidise4, forming carbon monoxide (CO) and
carbon dioxide (C02), thus —
2C + 02 = 2CO
Carbon and oxygen yield carbon monoxide.
C + 02 = C02
Carbon and oxygen yield carbon dioxide.
These oxides being gaseous escape by the open mouth of the
converter.
S + 02 S02
Sulphur and oxygen yield sulphur dioxide.
The sulphur dioxide escapes with the other gases.
Sulphur trioxide (S03) may be formed by the action of
ferric oxide— -
9Fe203 + S 6Fe3O4 + S03
The sulphur trioxide combines with lime in the slag.
S03 + CaO = CaS04
Sulphur trioxide and lime form calcic sulphate.
THE BASIC BESSEMER PROCESS. 93
Manganese is oxidised, and the resulting oxide goes into
the slag : —
Mn + 0 = MnO
Manganese, and oxygen yield manganous oxide.
Two oxides of iron are formed, and they constitute part of
the slag : —
2Fe + O2 2FeO
Iron and oxygen yield ferrous oxide.
4Fe + 302 2Fe203
Iron and oxygen yield ferric oxide.
Phosphorus when oxidised forms phosphoric acid (more
correctly named phosphoric anhydride) : —
4P + 502 2P206
Phosphorus and oxygen yield phosphoric acid.
The phosphoric compound unites with lime to form tetra-
calcic phosphate : —
P206 + 4CaO = 4CaO.PflO5
Phosphoric acid and lime form tetra-calcic phosphate.
Tetra-calcic phosphate was discovered simultaneously by
Hilgenstock in Germany, and Stead & Bidsdale in England.
So far it has not been found in nature.
The acids in the basic slag are silica (Si02) and phosphoric
anhydride (P206). The bases present are lime (CaO),
magnesia (MgO), manganous oxide (MnO), and ferrous
oxide (FeO). To carry on the process a decided excess
of base must be present in the converter.
At the end of the after-blow the " metal " is in a highly
oxidised state, and the addition of suitable material containing
manganese and carbon is necessary. The finishing material
is added as in the acid Bessemer process, and the reactions —
detailed on pp. 78, 79, and 80 — and effects are similar.
Recarbnrising. — There is danger of reduction of some
phosphorus from the slag during recarburising. To lessen
this risk the slag is freely poured off before " finishing." As
94
IRON AND STEEL MANUFACTURE.
the bath of metal is highly oxidised it is not unusual to add
grey hematite pig iron (which is rich in carbon and silicon)
before adding ferro-manganese or spiegel-eisen.
In the basic Bessemer, as in other modern steel-making
processes, ferro-manganese is used for mild steels, while
spiegel-eisen is employed when higher carbon steels are being
made. Carbon is added directly in some instances. The
carbon, or molten spiegel-eisen, is added to the metal which
had been poured into the ladle with the smallest workable
quantity of slag.
Comparison of the composition of the pig iron used for the
respective processes : —
Constituents.
Chemical
Symbols.
Acid
Bessemer.
Basic
Bessemer.
Per cent.
Per cent.
Graphitic carbon,
c
3-42
0-82
Combined carbon,
c
0-46
2-83
Silicon,
Si
2-20
0-63
Phosphorus,
Sulphur,
P
s
0-045
0-045
2-75
0-07
Manganese,
Mn
0-47
1-75
Iron, .
Fe
A
A
100-00
100-00
.
It may be noticed at a glance that the basic pig iron is high
in combined carbon, in phosphorus, and in manganese. The
silicon in it is low, and for a good reason, namely — the result
of oxidising silicon is the production of silica, which, being
acid, is undesirable in large amount in the slag. The maker
of basic pig iron, therefore, keeps the silicon in the pig iron as
low as he can. In pig irons which do not contain much
silicon, most of the carbon, as a rule, exists in the combined
state.
There is considerable amount of manganese in good basic
pig iron, because
(a) Presence of much manganese tends to keep the per-
centage of sulphur low.
THE BASIC BESSEMER PROCESS.
(b) Because the manganese, while undergoing oxidation in
the converter, makes good, as far as possible, the heat
which would have been derived from the presence of
silicon. Manganese oxide (MnO) being basic, is not
so objectionable in the slag.
But the chief feature in the comparison is the large amount
of phosphorus in the basic pig iron. The percentage of phos-
phorus is high, because
(a) Puddlers tap (tap cinder), from which it is largely
made, is comparatively cheap, and contains much
phosphorus as well as iron.
(b) A large amount of phosphorus is necessary to maintain
the needed high temperature in the converter during
the continuance of the after-blow, and the heat can be
had by the oxidation, or burning, of a comparatively
large quantity of phosphorus.
. (c) The higher the percentage of phosphorus in the pig iron
the richer, under ordinary conditions, will the slag be
in phosphoric acid, and the higher will be the price
obtainable for the slag. With each increase in per-
centage of phosphoric acid there is a very considerable
increase in market value. The basic pig iron is
purposely enriched in phosphorus by using mineral
phosphate in its production. Under certain circum-
stances, such as a very hot blow, a little of the
phosphorus may escape in the outgoing gases.
APPROXIMATE COMPOSITION OF GOOD QUALITY BASIC BESSEMER SLAG.
Constituents.
Chemical Formulae.
Percentage.
Phosphoric acid,
P20e
20
Silica, .
SiO2
CaO
6
46
Magnesia,
Ferrous oxide,
MgO
FeO
6
13
Ferric oxide, .
Fe203
2
Manganous oxide,
, Alumina, &c.,
MnO
A1A, Ac.
5
2
100
96 IRON AND STEEL MANUFACTURE.
When the slag has cooled down it is broken up, ground to
a very fine powder, placed in bags, and sold as a fertiliser.
Eeduction to powder may be effected by grinding, or by the
action of superheated steam. The lime, and especially the
phosphoric acid, in the slag, make it highly valuable for
certain soils and crops.
The greater the percentage of easily soluble phosphoric acid
in the slag the higher is the price it will fetch. And justly
so, because such soluble slags will yield a quicker and a greater
return to the farmer : a quicker return, because the plants
grown in the field which is enriched with this fertiliser will
more easily assimilate it, and be thereby helped in healthy
growth ; and a greater return, because there will be less of the
precious phosphoric acid left in the ground, with the possibility
of much of it being washed by the winter's rain so deeply into
the soil as to get beyond the reach of the roots of the next
year's crop.
97
CHAPTER X.
PLANT AND APPLIANCES FOR THE SIEMENS-
MARTIN OR OPEN-HEARTH PROCESS.
MILD or medium steels are regularly made in charges of
5 tons and upwards. The smaller furnaces are for making
steel castings. 30-, 40-, and 50-ton charges are now common,
and furnaces for 160 tons, and even for 200 tons, are built
and at work.
The fuel used in this process is either producer gas.
which is specially made in gas producers, or natural gas as
found in certain territories in the United States. The regen-
erative system — a system suggested and practically applied
to an engine by the Eev. Dr. STIRLING — is adopted, so as
to utilise in the furnace as much as possible of the heat
generated.
Gas Producers. — A gas producer is designed to burn solid
fuel in such a manner as to convert as much as practicable
of it into combustible gases,* which can be collected, conveyed,
and used where required.
When coal slack or other suitable fuel is charged into a
producer which has been made hot and is in working order,
the fixed carbon (C) which it contains is converted into carbon
dioxide (C02), and the dioxide is reduced to carbon monoxide
(CO) if a moderate supply of air has access to plenty of glowing
fuel. Hydrocarbons, such as methane or marsh gas (CH4)r
are liberated from the solid fuel, and hydrogen (mostly
from the decomposition in the producer of the steam which
is used to impel the air blast) is also found in the pro-
ducer gas (see analysis on p. 246).
These three components (carbon monoxide, methane, and
hydrogen) are all combustible, and the value of the producer
gas will depend on the quantity of these in its composition.
* Gases which can be burned.
7
98
IRON AND STEEL MANUFACTURE.
The Siemens G-as Producer consists of a rectangular com-
partment built of brick walls, with fire-bars. Four compart-
ments make up a block and several blocks may be built
together. Over each compartment is a hopper by which
the coal slack, or other fuel which is to be gasified, is
charged into the producer. Air may be admitted between
the fire-bars, but the general practice is to close the opening
in front of the ashpit and inject air by the force of one
Fig. 36.— Wilson ,Gas Producer— Section.
or two steam jets. A water trough is provided for the
ashes. The gas which is produced is collected and conveyed
by an overhead main pipe or by culverts (underground
passages) to the furnaces.
The Wilson Gas Producer is an upright cylindrical structure
of mild steel plates lined with fireclay bricks or blocks. It
OPEN-HEARTH PLANT.
is shown in section in fig. 36. The solid fuel, from which
the gas is to be made, is charged in by a hopper — a hollow
tapered iron casting which is bolted to the top of the
producer. A cone closes the passage from the hopper to
Fig. 37.— Wilson Gas Producer with Water Bottom.
100 IRON" AND STEKL MANUFACTURE.
the producer, and a lid covers the hopper. The hopper is
filled with fuel, and, when it is intended to discharge it, the
lid is shut down and the cone is allowed to descend. The
fuel is thus admitted to the producer, the cone causing an
equal distribution of the slack or other fuel used. As the
fuel burns* the charge is in due course decomposed, and
every part of it except the ash is converted into gas. The
gas is drawn off by suitable ports or openings to the downtake,
from whence it is conveyed by culverts or pipes. Air is forced
in by means of an injector consisting of a steam jet and
a pipe with an enlarged entrance. The amount of air and
steam can easily be regulated. They are forced through
the pipe into a horizontal brick passage — the distributor —
above the flooring of the producer and distributed through
openings for that purpose in the brick passage.
The producer has a solid bottom, and, when it is necessary
to clear out ashes, iron bars are inserted at a certain height
so as to keep the unconsumed fuel up while the ashes are
withdrawn through the cleaning door.
" Solid bottom producers are cleaned out at intervals varying
from 12 to 48 hours apart, according to the quality of the
coal and the amount of work they are doing. This does not
by any means involve emptying the producer of fuel. The
bottom doors are opened after stopping the blast, &c., and the
ash and refuse at the bottom are raked out. The doors are
then closed and gas-making resumed ."f
In a later design the producer is set on a long water trough,,
as shown in fig. 37. Near the bottom of the producer the
inner space is contracted so that the unconsumed fuel is held
up, but as it burns away the ash drops into the water in the
trough below. A plate suited to the curvature dips from the
contracted part into the water lute and prevents the escape
of gas. Water-bottom producers are worked continuously,
the clinker and ashes being withdrawn from the trough from
time to time. To make sure that sufficient is being with-
drawn to keep the producer clean and in the best working
order, it is necessary in this arrangement to go on shovelling
ash out until more or less unburnt fuel comes down.
* A fire must be kindled in the producer on starting it to work,
t Power Gas Plant, by Alfred Wilson, p. 25.
OPEN-HEARTH PLANT. 101
The Wilson water-bottom producer with constant ' a\sh-
removing gear is shown in section in fig. 38. As in the
solid-hearth producer, there are no fire-bars. The solid
matter sinks down through water inside the lower part of
the producer and is forced out by an Archimedian screw
arrangement and up an inclined plane to the outside, no gas
Fig. 38. — Wilson Gas Producer with Archimedian Screw for
removing ashes.
being able to escape. The screw is caused to constantly
revolve very slowly, being driven by suitable gearing from a
shaft.
The screws or worms are made tapering, the largest
diameter being at the outlet end; their blades are also of
102 IftCN AND STEEL MANUFACTURE.
increasing pitch -towards the same end, and by this arrange-
ment nothing can stick in the screw. There is a considerable
evaporation from the water at the bottom as the hot ashes
gradually descend into it. The steam is, however, decomposed
higher up, and serves to increase the percentage of hydrogen
Fig. 39.— A. B. Duff Gas Producer.
in the resulting gas. Owing to the constant agitation of the
fuel by the revolving worm the production of gas is uniform,
and good working is secured.
The A. B. Duff Producer, which is so much in favour at
home, on the Continent, and in America, has a thick lining
OPEN-HEARTH PLANT. 103
»f fireclay blocks encased in a sheathing of malleable plates.
It is of the upright cylinder type, and is surmounted by
a hopper through which the fuel is fed in to work its
way steadily downwards. The whole structure is set on
a water bottom. A sketch, partly in section, is shown in
fig. 39.
The necessary air, which is often preheated, is injected by
steam, and enters the producer by a circular central tower
having slotted cast-iron plates for its sides and a roof
arranged to permit the passage of air between its upper and
lower parts. An efficient distribution of air is thus ensured.
The central tower contracts the space and thus causes the
fuel (already somewhat swollen and caked together by heat)
to be held up until the combustible components are converted
into gases by the action of the injected air. The gases
thereby produced ascend and are conveyed by the downtake
to a culvert. The ash drops into the water bottom, from
whence it is raked out without deranging or stopping the
gas-making.
The Gas Valves are of two kinds: mushroom valves for
regulating the amount of gas, and butterfly valves for
determining the direction of the air and the gas. Many
patent gas valves are in use.
Open-hearth furnaces are either stationary or movable, the
latter being known as rolling or tilting furnaces (see p. 255).
The Stationary Open-hearth Furnace is a huge oblong
structure built of silica bricks cemented with suitable mortar
arid braced with buckstaves and tie-rods and set over five
arches. Of these arches the central one is left blank, the
two arches next to the central one are for air regenerators,
and the outer two are for gas regenerators. But the
inner ones may be arranged for gas and the outer ones
for air. These regenerative chambers contain firebricks,
which are packed checkerwise in such a manner as to
expose as much surface of brick as possible while allowing
free passage for gas or for air. The bricks absorb heat
_.
OPEN-HEARTH PLANT. 105
from the outgoing (hot) gases and impart heat to the ingoing
(cold) air and gas.
Fig. 40 shows the front view of furnaces at the Norfolk
Works of Messrs. Thomas Firth & Son, Sheffield.
The chambers communicate with passages both at top and
bottom; the top passage of each ascending from its re-
generator to port, or ports, at its own end of the furnace.
Each end of the furnace includes an outer and an inner wall.
The latter may be straight across or be built with a slight
curvature. The upright passages leading from the re-
generators are built between the two end walls, like an
ordinary domestic chimney, but in this case terminating at
the top of the ports. The ports are openings (constructed
with a slight slant) in the inner wall; they lead from the
upward passages to the inside of the furnace. There may be
one gas and one (larger) air port at each end. or there may be
three air ports and two gas ports, or two gas ports and one
wide air port. The air ports are at a higher level than the
gas ports. At each end of the furnace the ports and passages
correspond in arrangement, number, and size with those at the
other end.
When the furnace is at work, producer gas is conveyed
through one of the gas regenerators * to its port or ports,
and air is conveyed through the neighbouring air regenerator
to its port or ports. Where the gas and air meet in the hot
furnace, ignition immediately takes place — just as when gas is
lit at an ordinary gas burner — and a long sheet of flame
sweeps along and heats the furnace, much heat being, in time,
deflected from the roof. The hot, spent gases (the products
of combustion) pass out at the opposite ports, and, proceeding
by proper channels to the top of the regenerators at what is
then the outgoing end, impart much heat to the checkered
packing of bricks in the regenerators, and are drawn off by
passages left under the checker work of the regenerators, and
under the valve pit, to the chimney. The chimney is usually
a cylindrical brick structure, about 50 feet or so in height,
encased in ri vetted plates. It is set on a firm base and is
stayed by stout wire cables. In the base, arrangements are
* Natural gas, being rich in combustible component?, does not require
to be passed through a regenerative chamber.
106
IRON AND STBEL MANUFACTURE.
OPEN-HEARTH PLANT. 107
made for kindling a fire to create a "draught" sufficient to
" pull " the products of combustion through the furnace and
regenerators when lighting, drying, and starting the furnace
when new or after repairs. The "draught" is moderated,
when required, by the use of a damper.
Beside each of the four checkered chambers is a receptacle
known as a slag pocket or dust catcher. The slag pocket
is intended to retain fine particles of dust — iron ore dust,
lime dust, &c. — and an occasional overflow of slag. The dust
is liable to be carried over in the current from the furnace
and would flux and clog the " checkers " and interfere with
the storing up of heat, causing thereby inconvenience and
expense.
To return to the consideration of the regenerative system :
When the flame has continued to travel in one direction for
about 20 or 30 minutes, the valves are reversed and the gas
and air are caused to pass upwards through the regenerators
which have been heated by the outgoing gases.
The ingoing gas and air are thus preheated and yield
a hotter flame. The outgoing spent gases pass out at the
ports which were formerly inlet ports and descend between
the checkered brickwork in the corresponding regenerators
which are thus heated highly. Again, in due course, the
valves are reversed, and with each reversal the furnace
becomes more highly heated, until a temperature which can
melt steel is attained. Such, in brief outline, is the regenera-
tive system.
The sides of the furnace are strengthened by iron plates
and castings. Buckstaves — which are often made of old
rails — are set upright at intervals and "tied" by tie-rods,
which are screwed at the ends to suit large nuts, to the
buckstaves opposite. These tie-rods extend, above the roof,
from end to end and from side to side. Two tie-rods also
reach, in diagonal directions, from strong supports at the
corners, thus adding strength to the structure.
As the roof of the furnace is built of bricks it would be
impossible in practice to keep it from falling in if it were
108
IRON AND STEEL MANUFACTURE.
A,
B,
C,
D,
K,
F,
O,
H,
I,
J,
K,
L,
built flat. It is, therefore, arched across. And as the bricks
expand very much on being heated, and contract considerably
on cooling, the nuts at the ends of the tie-rods are gradually
loosened when the furnace is being heated up for a campaign
and tightened as the furnace cools down at the close. The
general rise and fall of temperature during ordinary working
J K
K J
Fig. 42. — Siemens Furnace — Cross Section.
Wheel for rotating casting ladle.
Ladle.
Ingot mould.
Casting pit.
Slag ladle.
Launder.
Tapping spout.
Taphole.
Wall.
Air port.
Gas port.
Buckstave.
M, Charging door.
N, Foreplate or sill.
O, Working lining.
P, Firebricks.
Q, Charging platform of iron plates.
R, Butterfly valve for air.
S, Flap for regulating amount of
air.
T, Butterfly valve for gas.
U, Valve for regulating amount of
gas.
V, Culvert for gas from producers.
causes expansion and contraction, and the arching of the roof
allows a slight but sufficient rising or depressing along the
centre and at other parts of the roof as required.
The bottom of the furnace consists of iron plates or castings
which are carried on strong steel girders supported on brick-
110 IRON AND STEEL MANUFACTURE.
work, or, better still, on columns. Cast-iron plates make up
a long deep tray with sloping sides. On the tray good bricks
are set so as to form an outline somewhat resembling an oval
basin. Over the bricks the working lining of sand coated
with slag is laid in the manner described on p. 11 4.
On the front or charging side there are generally three
openings, and on the tapping side two openings. These can be
closed by doors, which consist of silica bricks set in strong iron
frames. The iron frames are made larger than the openings so
that they are not directly exposed to the high temperature of
the furnace. The doors may be raised or lowered mechanically
or by hand. If by the latter they are suspended from the
shorter portion of a lever, on the longer portion of which is a
counterpoise which nearly balances the weight of the door.
In the centre of some doors there is a peep-hole through
which the progress of the process can be observed. A disc
or plate covers the peep-hole between observations. Through
the three doors on the front side the solid materials are
usually charged, and the charge is rabbled when required.
Samples are withdrawn through the central front door. All
doors admit repairing-material and tools. At the bottom of
each door is a thick projecting sill or foreplate of cast iron.
The Shoot or Launder, along which the steel arid slag are
conveyed from the taphole to the ladle, is a half-round gutter
made of steel plates. It is often in two parts — a short one
which slopes sharply, and a longer one which is set with a
slope which is not so steep. The short one is fixed to the
furnace, the long one rests on trunnions. They are well lined
with a thick coating of ganister; the joining of the two is
carefully made, and the whole is thoroughly dried and warm
when the furnace is tapped. Fig. 43 shows a view of the
back or " tapping side " of one of the Siemens furnaces at the
Rutland Works of Messrs. Samuel Osborn & Son, Sheffield.
Movable (rolling or tilting} furnaces are described in the
appendix. — See page 255.
The Casting Pit for the Siemens-Martin process is generally
in a straight line behind the row of open-hearth furnaces.
Rails are laid on the tops of the two long walls of the casting
pit (fig. 44), and on these rails a four-wheeled bogey, carry-
ing the casting ladle, travels when pushed or pulled by a
I
I
OPEN-HEARTH PLANT. Ill
travelling engine running on rails which are parallel to the
pit. The Travelling Engine or Crane Locomotive oi the kind
made by Messrs. Andrew Barclay, Sons & Co., Kilmarnock,
and illustrated on opposite page, is employed for setting the
ingot moulds, stripping and removing the ingots, &c.
The Ladle is of the Bessemer type, is brick-lined, and has
rod, stopper, and nozzle.* It is mounted on a four-wheel
bogey, which can be caused to travel on the rails at the casting
pit. The large ladle, as made by the Lilleshall Company,
Fig. 44. — Siemens Casting Pit, with Ladle in the distance.
shown in fig. 45, has double stopper arrangements, so that,
when teeming, two ingots may be run at the same time.
Preparing the Furnace. — When a furnace has been built or
repaired, a lining of firebricks is placed on the bottom plates,
and additional bricks are laid so as to form an oval hollow.
The furnace is then carefully dried, the gas introduced with
caution, the working lining patiently put in, and the taphole
made up.
* See description of Bessemer ladle on p. 68.
OPEN-HEARTH PLANT. 113
To dry the furnace, a fire is kindled in the temporary fireplace
in the chimney, and fires are also kindled in the regenerative
chambers. In about two days the chimney and chambers may
be partially dried; the fires are then withdrawn from the cham-
bers. Long fireclay bricks are then built (without mortar or
other setting) to form supports on which bricks are piled in
open order to make up the checker work in the regenerators.
A fire is then kindled in the furnace, air being admitted
through the doors, and the hot products of combustion drawn
downwards through the four air and gas regenerators to the
passages leading to the chimney. When the furnace is ready,
gas from the producers is allowed to blow through the culvert
as far as the outlet nearest to the furnace, in order to clear
the air out of the culvert. Quick-burning materials, such as
shavings, splinters of dry wood, &c., are heaped in the furnace
so as to fill it with flame and pass much carbon dioxide into
the regenerators at the outgoing end. The doors are all
closed, and gas from the producers is cautiously admitted;
and, under these conditions, it should ignite gently. Careless-
ness or laziness in preparing to admit gas is unpardonable.
For want of ordinary prudence the furnace and checker work
may be shaken, and the whole campaign carried on under ad-
verse conditions on account of an easily-preventable explosion.
When the gas has become ignited, more air is admitted
to the furnace by opening the doors a little, and, afterwards,
a regulated quantity is supplied through the air regenerator.
After about seven hours the current may be reversed, the gas
being followed a few minutes after by a gentle passage of air
through the neighbouring regenerator. The gas and air valves
are subsequently reversed from time to time at lessening
intervals.
As the temperature of the furnace rises the bricks expand,
and the nuts at the end of the tie-bolts must be turned so as
to allow the buckstaves to give way a little. Otherwise the
roof would become dangerously distorted, and the stability of
the furnace would be impaired.
When the heat in the furnace is sufficient to frit * sand, the
first sprinkling of the working lining is put in. The working
* Frit, from a Latin word signifying to roast, means in metallurgy to
soften by heat, so that the particles stick together.
8
114 IRON AND STEEL MANUFACTURE.
lining consists of white Belgian sand with an admixture of
less pure sand, or of loam, as a binding material.
To make up the required thickness of sand lining a thin
layer of the mixture is spread over the bricks, and, when the
heat of the furnace has caused the sand particles to firmly
stick to each other, another sprinkling of sand is thrown in
which " frits " or melts just enough to cause the sticking of
the grains to each other and to the layer beneath. In that
way, by " shifts " working day and night for about a week, the
Fig. 46. — Tapping a Siemens Furnace.
working bottom (bed and banks) is built up little by little.
When the bricks are covered with a thick enough lining —
which is continued until it rests also on the silica bricks of
which the furnace walls are composed — pieces of Siemens
(acid) slag are scattered over the surface. The slag melts
and sinks a little into the sand lining, forming a glaze over
the surface.
The working lining of the furnace is shaped so as to slope
towards the taphole, at the centre of the tapping side — that
is, the side at which the metal is tapped, or discharged, when
ready. Before charging the furnace the taphole is well
rammed with a mixture of crushed anthracite and sand, firmly
enough to prevent a breaking out of the melted charge, yet
OPEN-HEARTH PLANT. 115
not jammed so tightly as to cause a " hard tap." A hard tap
occasions undue delay when the metal is ready for the ladle.
When required, the taphole is opened by means of a pointed
rod and a sledge hammer. The rod is driven in from the
outside, a ring is slipped on, and a wedge inserted between
the rod and the ring with its thin end towards the ladle. Gn
hammering the wedge the rod is forced out, and the opening
made is widened by means of a rod worked through from the
charging side of the furnace.
After the metal and slag have been tapped out, the sand
bottom is repaired by fritting sand where hollows have formed.
All slag is carefully cleared away from about the taphole.
To make up the taphole for the next charge an iron tool,
consisting of a long rod with a plate or an enlargement at
one end, is used. The larger end of the rod is pressed against
the inner end of the taphole, which is then firmly rammed
with the usual mixture of sand and crushed anthracite.
A Siemens furnace is not usually hurried in the working of
its earlier charges : it generally does its best work in the
second week of its campaign, which, as a rule, lasts about ten
weeks before the furnace requires partial repair.
Parts which wear away quickly are patched up where they
can be got at. Should a part of the roof give way, a " crab "
—that is, a flat iron clamp, or clamps, embracing a number
of silica bricks — is placed over the worn part.
For charging the furnaces machinery has been installed in
several leading works. Indeed, since the decided increase in
the capacity of open-hearth furnaces, machine charging has
become imperative. Large furnaces, mounted on circled
supports, and which can be tilted either to receive a charge
or to be tapped, are in successful operation. Plant has also
been installed for teeming from the ladle to the ingot moulds
in a separate part of the work. Overhead cranes form an
important part of that and some other arrangements.
Modern charging machines are described on page 256.
116
CHAPTER XL
THE ACID OPEN-HEARTH PROCESS.
As already indicated. Siemens, or Siemens-Martin, steel is
made in large reverberatory furnaces with regenerators, and
gas is supplied for fuel.
Working an Acid Open -hearth Charge.* — The furnace
being in good working condition and the taphole having been
made up, the charge of pig iron and scrap is put in either by
hand or by machinery.
To charge by hand a piece of old rail is laid on the sill or
foreplate at one of the charging doors, and the flat part of
a mild steel peel (fig. 47) is set on it. A piece t of hematite
Fig. 47.— Peel, Rail, and Foreplate.
pig iron is placed on the peel, the door is raised, the peel
is pushed into the furnace and turned over or jerked so as to
drop the pig iron into the furnace. The peel is quickly with-
drawn, another piece of pig iron is placed on it (fig. 48), and
is quickly charged in like manner. The parts of the working
* The first charge in a new furnace, or a furnace which has been
"off" for repairs, does not carry as heavy a tonnage as following
charges. The second and third charges are heavier, and at the fourth
the full amount may be charged and worked.
t For convenience of charging, the " pigs" of iron are broken across
into two parts.
THE ACID OPEN-HFARTH PROCESS. 117
bed of the furnace furthest from the doors being thus charged,
and the pig iron well placed at the sides and back of the
working bed, the remainder of the pig iron is thrown in.
Steel scrap is similarly charged over the top of the pig
iron.*
When charging is completed the doors are closed (they are
kept closed as much as possible during charging), the valves
are reversed from time to time, and the charge in the
furnace molts
Fig. 48. —Men Charging Steel Furnace.
Oxidation steadily proceeds. In the first two stages the
oxidation is effected by the excess air which enters the furnace
along with the producer gas. To bring on the " boil," ore
is charged towards the end. The, oxidised products — silica
(Si02), oxide of manganese (MnO), and some oxides of iron
(FeO and Fe203) — go into the slag. In the third stage oxida-
tion is largely due to the oxygen in the ore which is fed in.
When the charge has become sufficiently decarburised, and the
bath of metal is in good position for tapping, the taphole is
* Instead of charging cold pig iron into the furnace, much fluid metal
is now used in some works.
118 IRON AND STEEL MANUFACTURE.
opened — as described on p. 115 — and the metal flows from
the furnace along the spout and launder into the hot ladle
(fig. 49) which is ready to receive it.
On tapping the furnace the " metal " comes first, then metal
and slag, then mostly slag. When nearly all the steel has
gone into the ladle, the launder (see fig. 42) is struck a heavy
blow with a sledge hammer, thus separating the two parts.
The slag, with a little of the metal, is thereby diverted to th«
slag tub beneath. When the ball of slag has solidified it is
Fig. 49. — Steel and Slag being Tapped from Furnace.
emptied out of its tub, and any metal which may have been
with it is collected.
In some works all the slag is run into the ladle, some
of the slag being allowed to overflow into the adjoining slag
tub. In such cases practically the whole of the steel goes into
the ingot moulds. It is a good plan ; more ingot steel is
, and less scrap steel ; besides, the slag left on the top
THE ACID OPEN-HEARTH PROCESS. 119
keeps the steel warm while casting is going on. But this
plan involves the use of very large ladles.
When about one-third of the metal has entered the ladle
a weighed quantity of hot ferro-manganese, in small pieces, is
shovelled into the ladle to act as a deoxidiser and to provide
a small percentage of manganese, which acts beneficially in
the steel. The " addition " is generally completed when the
Fig. 50.— Teeming Steel into Ingot Moulds.
second-third has run into the ladle. It soon melts, and the
churning up, due to the fall of the remainder of the metal into
the ladle, causes the ferro-manganese to become so diffused
that a fairly homogeneous steel, containing a definite per-
centage of carbon and manganese, is produced.
If, instead of mild steel, a medium steel (say a steel with
0-5 per cent, of carbon) is required, a weighed quantity of hot
120 IRON AND STEEL MANUFACTURE.
spiegel-eisen is added, and allowed to melt and mix through
the bath of metal before tapping the furnace. Ferro-manganese
is also added in the ladle. Spiegel-eisen is not used in the
manufacture of mild steel.
The steel in the ladle is discharged through the nozzle into
the moulds in the manner described in connection with the
Bessemer process, and shown in fig. 50. When the ingot has
set, the mould is stripped off (see fig. 51), and the ingot is
Fig. 51.— Stripping Steel Ingot.
removed for reheating or to be stocked. The peculiarities of
a steel ingot and the further treatment to which it is subjected
are dealt with in Chapter xiii.
On the completion of the teeming, the ladle is wheeled to
a convenient part of the casting pit, turned over to get rid of
the remaining slag (fig. 52), and the nozzle is knocked out to
be ready for the fitting in of a new one.
Composition of the Materials used in the Open-hearth
Process. — The pig iron is of the kind known in the trade as
THE ACID OPEN-HEARTH PROCESS.
121
Bessemer pig iron, or hematite pig iron, the composition of
which is noted below. The steel scrap charged has, of course,
Fig. 52.— Empty Steel Ladle.
the composition of the finished steel, which is also noted
below : —
Constituents.
Chemical
Symbols.
Hematite
Pig Iron.
Steel Scrap.
jCarbon (graphitic),
c
3-500
None.
Carbon (combined), .
c
0-250
0-170
Silicon, ....
Si
2-200
0-025
Sulphur, ....
s
0-047
0-049
Phosphorus,
p
0-047
0-050
Manganese,
Mn
0-500
0-500
Iron (by difference), .
Fe
93-464
99-215
100-000
100-000
The finishing materials (ferro-manganese and spiegel-eisen)
are similar to those used for the Bessemer process. Their
composition is noted on p. 237.
Good Campanil Ore, a favourite brown hematite for the
process, approximates in composition to the following : —
122
IRON AND STEEL MANUFACTURE.
Constituents.
Chemical
Formulae.
Percentage.
Ferric oxide, .
Manganic oxide, .
Silica, .
Fe203
Mn304
Si02
CaO
75-0
1-0
6-0
4-50
Magnesia,
Phosphoric acid, .
Carbon dioxide, .
Water (combined),
MgO
PA
CO.,
H26
HO
1-50
0-03
4-8
4-0
3-0
99-83
Metallic iron, ....
Fe
52-5
The carbon dioxide and combined water are soon driven off
at the temperature of the furnace. The ore thus becomes
porous — a good condition for being rapidly reduced.
Chemical Considerations.
During the first stage of the process — the melting down
stage — about one-half of the silicon and about one-third of
the manganese in the charge are oxidised. The oxides,
uniting with oxidised iron, form slag. A little of the carbon
may be oxidised and escape in the outgoing gases.
During the second stage — going on the boil — the remainder
of the silicon and manganese are eliminated, and there is a
noticeable diminution in the amount of carbon left in the
charge.
During the third, or boiling stage, more carbon is oxidised,
and, as the carbon-with-oxygen compounds (carbon monoxide
and carbon dioxide) are gaseous, they cause a commotion,
with appearance of boiling, as they come off. When this
stage is reached good, pure, lumpy hematite ore (preferably
Campanil ore) is cautiously fed into the furnace. The chief
constituent of the ore is ferric oxide (Fe2O3), which, in the
furnace, is decomposed ; its oxygen hastens the burning out
of the carbon, and the iron which is reduced increases the
TUB ACID OPEN-HEARTH PROCESS. 123
weight of ingots produced. A double duty is thus done—
the carbon of the pig iron is oxidised and eliminated, and
iron is produced direct from the ore.
If too much ore is fed in, or if it is fed too quickly, the
steel is apt to be " wild," unmanageable, and unsound.
The chemical reactions are the same as in the acid
Bessemer process, as detailed on pp. 78 and 79, but in the
open-hearth process the oxidation of the carbon is chiefly
effected by oxygen from ferric oxide (in the ore used), as
indicated by the equation —
3C + Fe203 = 2Fe + SCO
Carbon and ferric oxide yield iron and carbon monoxide.
Carbon dioxide (C02) is also produced.
The gases, carbon monoxide or carbon dioxide, as the case
may be, escape with the outgoing gases from the furnace.
The other oxidised materials go into the slag.
Action of the Ferro-Manganese or Spiegel-eisen. — The
deoxidising action of the manganese is the same as in the
Bessemer process (see p. 79); but in the Bessemer process
the metal is completely deearburised before the spiegel-eisen
or ferro-manganese are added. In the open-hearth process the
"metal" which is ready for tapping contains carbon. In
deciding on the material necessary for deoxidising open-hearth
steel, allowance must be made for the carbon contained in the
ferro-manganese or spiegel-eisen. In deoxidising Bessemer
metal, carbon must be added to carbonise the metal : in finish-
ing open-hearth steel, the carbon which is unavoidably present
in the deoxidising materials must be allowed for, and the open-
hearth metal deearburised to the proper percentage before
being tapped. Thus, for a charge of finished steel to contain
a half per cent. ('50) of carbon, the bath of metal in a furnace
will be held to be sufficiently deearburised when -37 per cent.*
of carbon is present. If at this stage the other indications
give assurance that the metal is ready for finishing and
tapping, the right quantity of hot spiegel-eisen will be thrown
in. There are unmistakable signs known to good steel
* The steel melters would call this 37 points.
124 IRON AND STEEL MANUFACTURE.
smelters. If, for instance, the slag which clings to the handle
of a sample spoon or other tool breaks off in a clean, crisp
manner when thrown down, the "first hand" — taking into
account, of course, other considerations— will correctly con-
clude that the charge is in good condition for tapping. The
fracture of the small test button — which is obtained by taking
out a sample, partly cooling it, hammering it flat, breaking it
across, and examining the appearance of the fracture — its
soundness and malleability (or the absence of these qualities)
afford valuable guidance.
Before finishing a charge it is generally good practice to
" pig back " — that is, to place a few half pigs of good rich
grey hematite iron (hematite pig iron containing much carbon
and silicon) just inside the doors of the furnace, and, when the
pig iron is red-hot, to push the pieces into the bath and rabble
vigorously. The result of this is most beneficial, as the silicon
" kills " some of the active oxides which may remain. A quiet
metal may thus be ensured. The unfinished steel may then
receive the addition of spiegel-eisen, if a medium steel is
required, or be tapped and treated with ferro-manganese in
the ladle if mild steel is wanted.
Before tapping, it is essential to success that the metal and
the slag should both be in good condition. The metal should
be hot enough to undergo the natural cooling in the ladle
before and during pouring into the several moulds — with, of
course, a margin of safety. But it is well that the steel
should not be too hot when teemed.
The proportion of pig iron and scrap steel in a charge will
depend on circumstances. As steel cannot be worked without
the production of scrap it is necessary to have a process in
which it can be utilised. Where scrap is plentiful, as much as
80 per cent, may be charged, and with such a proportion the
charge can be worked through quickly. On the other hand,
charges containing 75 per cent, of pig iron are regularly
worked. Scrap steel is not necessary for the process. Some-
times it is convenient to work with about equal quantities of
pig iron and scrap steel, and such a charge might be made up
of the following for each 10 tons: —
THE ACID OPEN-HEARTH PROCESS.
125
6 tons of hematite pig iron (of various brands*),
4 tons of scrap steel.
1£ tons of brown hematite ore will be used for feeding, and
about
2 cwts. of ferro-manganese may be required for deoxidising,
and yielding the required manganese.
The progress of the process may be traced from the following
figures : —
Composi-
tion of the
Pig Iron
and Scrap
Steel as
Charged.
Composi-
tion when
Melted.
Composi-
tion at the
Beginning
of the Boil.
Composi-
tion when
ready for
the Ferro
or Spiegel.
Composi-
tion of the
Finished
Mild
Steel.
Carbon,
Silicon,
Phosphorus,
Sulphur,
Manganese,
Iron, .
2-85
1-41
0-048
0-048
0-75
A
2-63
0-84
0-048
0-048
0-56
A
2-50
0-36
0-049
0-049
0-11
A
0-13
0-02
0-049
0-050
Trace.
A
0-18t
0-02
0-05
0-05
0-54
A
100-000
100-000
100-000
100-000
100-000
1
The increase in the percentage of phosphorus is due to its
being concentrated in less weight of " metal " up to the time
of boiling, for, in addition to the elimination of carbon, silicon,
and manganese, some iron will have become oxidised, and, as
oxide, removed to the slag. As the ore which is fed in
becomes reduced the weight of " metal " increases, but as the
ore contains phosphoric acid (P205), which is reduced to
phosphorus, the percentage in the metal is not diminished
thereby. A slight increase in the percentage takes place on
the addition of ferro-manganese, which is due to phosphorus
in that material.
* Where pig iron is purchased, a variety of brands — each with the
distinctive mark of the maker— is prepared for each charge. Steel-
makers who produce pig iron use their own make.
fThe carbon is purposely varied to suit requirements, the other
elements are fairly constant in percentage.
A By difference.
126
IRON AND STEEL MANUFACTURE.
The same remarks apply, in some measure, to the increase
in the percentage of sulphur. And the melted metal some-
times takes up sulphur from the producer gas which is burnt
in the furnace. By careful boiling of the charge it is possible
to diminish the amount of absorbed sulphur.
The Slag produced may be composed of the following, in
proportions near to the figures given : —
Constituents.
Chemical
Formulae.
Approximate
Percentage.
Silica,
SiO«
56
Alumina,
Ferrous oxide, ....
Manganous oxide, ....
fifr
MnO
CaO
1
27
10
5
MgO, &c.
1
100
Although such slag contains 21 per cent, of iron and 7 '75
per cent, of manganese, no process is at work for utilising more
than a very small amount of the enormous quantity which is
regularly produced.
127
CHAPTER XII.
THE BASIC OPEN-HEARTH PROCESS.
THE production of trustworthy steel from materials which
contain phosphorus in medium amount has been forced on the
trade. The process has assumed large proportions and is
growing in importance. The elimination of phosphorus from
melted pig iron having been successfully carried on in a basic-
lined Bessemer converter, attempts to dephosphorise in an
open-hearth furnace became inevitable. Open-hearth steel is
popular with many purchasers.
The advantages of working in a reverberatory furnace
have already been stated, see p. 14. To the advantages
previously mentioned may be added this important one,
namely : — That as the temperature is maintained by burning
the gas supplied for heat raising, it is not necessary, as in
the basic Bessemer process, to have a large percentage of
phosphorus to keep up the heat by its oxidation.
Many ores yield pig iron containing a medium quantity of
phosphorus — too high to be dealt with in an acid-lined furnace,
or acid-lined converter, and not high enough to yield heat
sufficient for Bessemerising. And even from pig iron obtained
from good ores comparatively low in phosphorus, some of that
deleterious element can be eliminated and a superior quality
of soft steel obtained.
Until the advent of the basic open-hearth process such
ores were almost valueless for steel - making. A famous
American iron-master bought extensive mines of medium
phosphoric ore for a modest sum. By the successful working
of the basic open-hearth process these ores attained a high
commercial value.
The furnace requires a basic lining, for reasons stated on
p. 84, and the basic lining is the only matter in which the
plant differs from the original open-hearth, or, as it is now
called, the acid Siemens process ; except that, as a greater
quantity of slag is produced in the basic than in the acid
128 IRON AND STEEL MANUFACTURE.
process, smaller charges of basic steel must be worked in
furnaces of given capacity.
The same style of valves, cranes, ladles, moulds, &c., are
used as for the acid open-hearth process.
The furnace bottom is of cast-iron plates carried on steel
bearers. Bricks, preferably of a neutral nature, are laid over
the cast-iron plates and the bricks are covered with a thick
basic lining of burnt magnesite or burnt dolomite and hot,
boiled, anhydrous tar. The basic lining may be put in
in one of three ways : —
(a) It may be spread and pressed with hot rammers, in
the manner described when dealing with the lining
of a basic converter.
(5) It may be made up of pressed bricks cemented together
and covered over with rammed basic material.
(c) It may be spread and heated so that the materials fuse
together, one thin layer being run on the top of an-
other in the same manner as a sand lining is put in
an open -hearth furnace.
A good method of lining a basic open-hearth furnace is to
set a course of firebricks on the iron plates and a layer of
magnesia bricks thereon, then " burn in " a coating of burnt
dolomite mixed with 5 per cent, of finely-ground basic slag,
each layer being firmly bound together by heat. When the
"burning in" is finished, ground basic slag is thrown on the
banks, where it melts and is absorbed. This is continued till
a pool of melted slag is found on the bottom.
It is a safe plan to finish the bottom by ramming, and
then heat the furnace with gas for at least a week before
commencing to charge.
A magnesia lining formed of thoroughly calcined magnesite,
cemented with magnesium chloride, is highly recommended.
As chemical action would take place between the acid
bricks, of which the furnace walls are built up, and the basic
lining, it is usual to form a neutral course where the thin part
of the lining rests on the brickwork as shown in fig. 53.
The neutral course may consist of a mixture of crushed
THE BASIC OPEN-HEARTH PROCESS.
129
Fig. 53.— Neutral Rib, B, dividing Silica
Bricks, A, from Dolomite Lining, 0.
chrome iron ore and tar rammed in position, or of neutral bricks
(made of chrome iron ore mixed with tar, pressed and kiln-
fired) carefully built in
the course. It is not
unusual to have mag-
nesia brick walls below
the line of the neutral
rib.
The mixture used for
ramming the taphole is
calcined dolomite, with
tar and anthracite.
The Materials used
in the Process are pig
iron, broken iron cast-
ings, scrap steel, scrap wrought iron, iron cinders which do
not contain too much silica, calcined pottery mine, purple ore,
impure hematite ore, and limestone — both raw and calcined.
The charge is finished with ferro-manganese in the usual way.
The Composition of the Pig Iron used varies considerably,
the process being capable of utilising pig irons, &c., having
a wide range of composition. Suitable pig iron is low in
silicon and in sulphur. The content of phosphorus is not of
so much consequence as in the Bessemer process ; if high, a
richer slag is produced, which sells at a higher price, but the
risks in working are greater, and more time is occupied in
working a charge.
The following may be taken as fairly representative of
average pig iron for use in the process : —
Constituent.
Symbol.
Percentage.
Carbon,
c
About 3 '50
Si
1-00
Phosphorus,
P
2-00
Sulphur, .....
Manganese,
s
Mn
Fe
0-06
„ 1-50
A
100-00
130 IRON AND STEEL MANUFACTURE.
Pig irons containing over 3 per cent, of phosphorus are
regularly worked.
Working a Basic Open-hearth Charge. — When the furnace
has been brought into good working condition, the scrap is
charged, then lime, and perhaps some ore, and, lastly, the pig
iron. In due course the charge melts, and calcined pottery
mine or good cinder is fed into the furnace to hasten
Fig. 54. — Shovelling Lime into a Steel-Melting Furnace.
oxidation, and lime and limestone are also added to keep the
slag in good basic condition. Elimination of silicon, phos-
phorus, sulphur, and carbon proceeds steadily. From time to
time samples of the " metal " are taken, and quickly tested.
When it is found to be pure enough, it is tapped out, received
in a hot Bessemer ladle, deoxidised with ferro-manganese, and
discharged into the ingot moulds.
If the pig iron is high in sulphur, 3J cwts. of limestone and
1^ cwts. of cinder rich in iron oxide are charged per ton of
metal. This yields a very thick slag, which is opened out
with 3 or 4 cwts. of calcium chloride or fluorspar and 5 or 6
cwts. of mill scale containing not more than 8 per cent, of
THE BASIC OPEN-HEARTH PROCESS. 131
silica. If the slag is kept in proper condition, so as not
to eliminate the carbon too quickly, the sulphur may be
diminished in quantity and brought down to a low percentage.
The working of Cleveland pig iron into good steel in basic
open-hearth furnaces was ably pioneered by Mr. E. H. Saniter.
Mr. G. A. Wilson gives details* of a charge containing
1 per cent, of silicon, 0*2 per cent, of sulphur, and V5 per
cent, of phosphorus being so worked as to produce a finished
steel containing carbon 0'16, silicon 0'004, manganese 0'44,
sulphur 0'042, and phosphorus 0'019 per cent.
Chemical Considerations. — The rate at which the elements
are eliminated depends on the composition of the " metal " and
slag and the conditions of working. Speaking generally, silicon
is removed early, and manganese is also rapidly removed. This
is fortunate, as the excess oxide of manganese formed neutral-
ises the acid nature of the silica which is formed by the
oxidation of the silicon. The carbon and the phosphorus are
both steadily oxidised and removed throughout the process.
It is important that all the carbon should not be removed
before the phosphorus, as the commotion caused by the
elimination of carbon (as gas) aids in quickly bringing the
metal into more intimate contact with the slag from which,
especially towards the finish, the oxidation is derived, and
the lime of which takes up the phosphoric acid.
A slag which is too rich in iron oxides or is not of the
right consistency may give rise to trouble in working the
charge. Insufficiency of lime in the slag may cause a charge
to go "off the boil" before enough phosphorus has been
eliminated. In such a case, more lime is added and hot pig
iron is charged in order to renew the "boiling," so that a
steel containing only a small quantity of phosphorus may be
produced.
The composition of the finished steel is much the same as
that of acid open -hearth steel. Basic steel is, however,
frequently lower in phosphorus. The percentage of carbon is
varied as required.
* West of Scotland Iron and Steel Institute Journal, Nov. 1903.
132
IRON AND STEEL MANUFACTURE.
The (basic) slag — which contains much phosphoric acid
when a highly phosphoric pig iron is used — is collected, and,
if rich enough in phosphoric acid, is ground to fine powder,
and sold for manure. If poor, it is tipped on the slag heap.
The slag produced when fluorspar is used is not as soluble
as ordinary basic slag; it therefore has a lower agricultural
value, and does not command such a high price.
The chief points of difference between the acid and the basic
open-hearth processes are : —
ACID.
with
siliceous
Furnace lined
material.
Taphole rammed with anthracite
and sand.
Hematite pig iron used.
Pure scrap used.
Pure quality brown hematite ore
used for feeding.
No elimination of phosphorus.
Valueless slag produced.
BASIC.
Furnace lined with basic material.
Taphole rammed with calcined
dolomite and tar, and some
anthracite.
Phosphoric pig iron used.
Phosphoric scrap may be used.
Iron ores or cinders containing
phosphorus used for feeding.
Lime freely used.
Phosphorus eliminated.
Fertilising slag produced and sold,
COMPOSITION OP STEELS.
133
I
By difference.
1
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OS
H
ID
S
c
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§ g S §
1 8
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CC O5 »d IO id r*H »C
• • •••••
9 9 y ?
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^ IO ^ ^rf*
9999999
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o
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g g 9
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^o o os ec o o
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O H PH O
134
CHAPTER XIII.
i
BESSEMER AND SIEMENS STEEL INGOTS.
As stated in preceding chapters, ingot moulds are suitably
set and fluid steel is poured into them.
If the newly-teemed steel proves to be " fiery " or " wild "
— throwing off sparks very actively and frothing or boiling
in the moulds — quietness may be induced by throwing little
pieces of aluminium into the steel. The effect appears
magical and out of all proportion to the small amount of
aluminium used. Soundness in the ingot may be promoted
by the judicious addition in the furnace of an alloy of iron
containing much silicon. Alloys such as silico-ferro and silico-
spiegel (see analysis on p. 238) may be used in small amount.
A common practice for promoting soundness is that of
stoppering the ingot. The practice is this: — The mould is
not quite filled with steel, and sand is thrown into the
unoccupied space ; on the top of the sand a rigid metal plate
is placed, a bar is thrust through the two lugs of the mould
and a wedge is firmly driven in between the plate and the
bar. Ingots stoppered down in this way are shown in fig. 50,
p. 119.
When the ingots have sufficiently solidified, on the out-
side, so that the crust can safely contain the still fluid
interior portion, the moulds may be stripped off (see fig. 51,
p. 120), the covering (if any) of plate and sand having been
previously removed. If an ingot is stripped too soon a
portion of the crust or shell may give way and steel may ooze
or flow out — a condition known in works as " bleeding."
Such ingots are objectionable. Serious accidents have arisen
through premature stripping of ingots. The shrinking of the
ingot during cooling facilitates stripping.
BESSEMER AND SIEMENS STEEL INGOTS. 135
To remove ingots they are gripped by " dogs " at the end
of a crane chain (see fig. 32, p. 77) and conveyed to be
brought into condition for rolling, or to be stocked till
required.
The moulds are cooled either by natural exposure to air,
or, more quickly, in a vat or by a spray of water. The latter
method is not economical. They are re-set as required for
further use.
An ingot of steel, while cooling, becomes, naturally, solid
on the outside before the inside. Impurities
are concentrated in the portion which re-
mains longest in the fluid state, and the
more slowly an ingot cools the more marked
will be the concentration, or segregation as
it is called, of impurities in the centre.
On subjecting drillings from the longitu-
dinal centre of an ingot to chemical analysis
it is found that there is a perceptibly higher
percentage of carbon, phosphorus, and sul-
phur than in drilling from parts nearer the
sides of the ingot. This is fortunate, for
on rolling out the ingot into plates, bars.
&c., the least pure portion is, and remains,
furthest from the surface. There are thus
malleable surfaces and a harder backbone
in cast and rolled steel. Fig 55> _ sketch
representing
In steel works practice the top part of Vertical Section
an ingot is cut off and treated as scrap, of Partly -cooled
because it is unsound. Why so 1 There Ingot,
are two good reasons.
As the steel ingot cools it contracts, and contraction goes
on smoothly until the mass has become partly solid. So long
as the steel is even feebly fluid the topmost portion settles
down comfortably on the lower parts (fig. 55). But, in course
of cooling, the outside portion of the upper part — the top, and
the parts next the ingot mould — solidities, while the still
136 IRON AND STEEL MANUFACTURE.
liquid centre portion flows downwards and continues to make
good the void arising from the gradual cooling and contraction
of the mid and bottom parts. A hollow, or pipe, is thus
formed in the centre of the top part, as indicated in fig. 55.
This piping is well marked in good crucible steel ingots.
And there is another serious imperfection in the top part.
This arises from the comparatively slow expulsion of gases
from the cooling ingot. The retaining of gases in fluid, and
even solid, steel is remarkable. We speak of occluded gases
and of occlusion — that is, of gases which are naturally retained
in liquid metals, and sometimes for a considerable time in
solid metals. As a steel ingot cools down, and becomes more
solid and dense, some of the gases are, as it were, squeezed
out, and ascend through the still liquid upper parts of the
mass. But the topmost part solidifies before the whole of
the middle and lower parts, and thus a crust is formed which
the ascending gases are unable to get through. The gases
which are thus trapped often gather into globules, and exert
such a pressure as to force a part of the solidified top slightly
upwards. The cavities so formed in the steel are known as
blowholes.* These blowholes naturally accumulate near the
top, and render that portion unreliable (see fig. 55). Hence
the trade practice of cutting off the top part and treating it
as scrap.
The advantages of pressing a newly-teemed ingot with
a layer of sand and firmly covering with a wedged-down steel
plate should be plainly apparent. The top part does not then
solidify as quickly as when exposed to the air ; the ascending
gases are thus allowed more time to escape through the fluid
steel at the top. Without difficulty the gases which rise
clear of the steel find an exit between the sand granules and
past the edges of the plate. Later, the top part cannot be so
easily raised by the gases, and so the ingot is left in a more
solid condition.
A sample of Bessemer steel was found to have occluded
seventy times its own bulk of gases. On withdrawing the
* The escape, or non-escape, of the gases from a cooling ingot have
some resemblance to the " working" of a piece of dough. Sometimes a
bubble bursts through the dough, but the dough being in the plastic
condition, the opening is soon closed. Much of the gas, however,
cannot escape, hence the open structure of bread.
BESSEMER AND SIEMENS STEEL INGOTS.
137
gases the steel was to all appearance quite solid. Occluded
gases are slowly given off from cold steel.
The composition of the gaseous mixture occluded in solid
steel must vary very much. The following may be accepted
as approximately representing average composition : —
Carbon dioxide, ... 2 per cent.
Carbon monoxide, . . .55 „
Hydrogen, &c., . . . 43 ,.
The large percentage (98) of reducing gases is important.
Treatment of Ingots before Rolling. — The ingots produced
by either of the Bessemer or Siemens processes require to be
Fig. 56. — Reheating Furnace— Longitudinal Section.
H, Fire-bridge.
J, Coal-firing door.
K, Iron bearers.
A, Stack.
B, Buckstave.
C, Plates.
D, Tie-rod.
E, Roof (brickwork).
F, Door.
reheated, or have their heat equalised, before being rolled into
useful forms. An ingot, as previously stated, naturally cools
more quickly on its outside than in its interior. As soon as
the outside has solidified sufficiently, or as soon as a thick
enough crust or shell has formed, the mould is stripped off the
ingot and is laid aside. The ingot (which is then red hot on
the outside and white hot and quite fluid within) is conveyed
138 IRON AND STEEL MANUFACTURE.
to a reheating furnace,* or to a soaking pit, or a vertical re-
heating furnace, to be heated uniformly before being rolled
or hammered.
An ordinary reheating furnace is of the reverberatory
type. It is built of refractory fireclay bricks, has suspended
doors, and is very much like a puddling furnace. The chief
differences are that the reheating furnace has no flue-bridge,
and that the neck, or flue, between the furnace and the
chimney is arranged so as to form a slag run for the flue
cinder (fig. 56).
Reheating furnaces are worked by gas or by a coal fire.
One district favours one system, while another district adopts
and retains the other. Doubtless each has found out the one
best adapted to its requirements and suited to its fuel.
The working bottom of the furnace may be of sand, or of
iron ore, or of selected basic slag. The latter was patented
by Messrs. Harbord & Tucker, and has given much satisfaction
in steel works.
The ingots are charged horizontally into a furnace, and
are allowed to remain there until each has attained throughout
its mass a suitable temperature for rolling.
A distinct advance in steel-working was made by the late
Mr. John Gjers' invention of the soaking pit.
Soaking Pits are arranged in sets. They are built in
a mass of brickwork on a concrete foundation. Each pit has
a carefully mitred lining of fireclay lumps 6 inches thick on its
four sides. A good hard working bottom is made of broken
bricks and silver sand. At the top, on the floor level, is
a frame of cast iron, and the working doors or covers consist
of iron frames enclosing firebrick slabs These covers are
lifted and replaced, when required, by cranes, or are moved by
other contrivances. Each pit is about 6 inches deeper and
3 inches wider than the ingots intended to be dealt with.
Soaking pits are worked by the heat remaining in the hot
ingots which are charged into them.
* Occasionally the ingots are allowed to cool down completely, and
are afterwards reheated and rolled.
BESSEMER AND SIEMENS STEEL INGOTS.
139
To begin with, each pit is warmed by a succession of hot
ingots which impart heat to the brickwork : on being taken
out these ingots are reheated in a furnace. The pits, having
been thus heated, are ready for regular working, and are
charged with semi-cooled ingots. The heat of the steel tends
to become equalised through the whole ingot. Little heat
escapes from the pit, and much is absorbed and afterwards
reflected from the brickwork on to the ingot. If a constant
Fig. 57.— Gjers' Soaking Pit.
A, Fireclay cap or cover.
B, Brickwork.
C, Concrete foundation.
D, Ingot.
E, Firebrick lining.
F, Cast-iron plates.
G, Cast-iron plates enclosing F.
H, Cast-iron brick-lined cover.
J, Working bottom.
succession of hot ingots is kept up, the initial heat is sufficient,
by equalising, to bring the whole mass of the metal into a fit
state for rolling.
The advantages of the soaking pit are : —
(a) Saving of fuel,
(b) The ingots are handled and kept in a vertical position,
(c) The four sides of the ingots are heated equally, and
(d) The waste of iron is lessened.
140
IRON AND STEEL MANUFACTURE.
The chief drawbacks are the awkwardness of the preliminary
heating and the uncertainty of maintaining a constant supply
of hot ingots from the casting pits.
It is now usual to have soaking pits coal-fired, or in con-
junction with producers which supply the gas for heating the
pits before starting and when empty. They are therefore
now known by such names as " soaking furnaces," " vertical
furnaces," &c. Fig. 58 represents half of a series of soaking
furnaces which are gas-fired.
Fig. 58. — Gas-fired Soaking Furnace — Longitudinal Vertical Section.
A, Floor of mild-steel plates.
B, Air regenerator.
C, Gas regenerator.
D, Port.
E, Brick arch.
F, Cover of soaking chamber.
G, One of the soaking chambers.
A set of gas-fired soaking furnaces consists of a series of
firebrick-lined cells below the level of the works floor. Deep
archways of firebrick support the covers, and from these a large
amount of heat is reflected. This keeps the top part of the
ingot particularly hot and thus prolongs the fluid and plastic
conditions where most beneficial. A working bottom is made
up as in the original soaking pits, and tha ingots are set and
kept in the vertical position while soaking. At the lowest
point a taphole is provided through which slag is run off.
BESSEMER AND SIEMENS STEEL INGOTS. 141
Producer gas is provided and its combustion supplements
the heat in the recently-stripped ingots. At each end of the
series of pits are regenerators for gas and for air. The pits
are worked on the regenerative system,* and the flame, in
passing from one end to the other (alternately from each end),
heats the ingot with fair uniformity.
From a furnace which is sunk in the ground there is not
much loss of heat, and, as the current passing through soaking
furnaces is not strong, the reducing gases from the ingots are
not rapidly carried off. The " atmosphere " in the soaking
furnace is therefore not so strongly oxidising as that of the
ordinary reverberatory reheating furnace, f and hence the waste
of steel is not so great. The vertical position in which the
ingot is set for soaking is preferable to the horizontal position.
The ingot settles more solidly and all sides are heated alike.
In daily works practice, the ingots are, as soon as per-
missible (with, of course, a working margin of safety), con-
veyed to the hot cells of the furnace and allowed to " soak "
in the heat thereof. When taken out, an ingot is externally
hotter than when charged — its heat has been equalised
throughout its mass.
* See pp. 105 and 107 for an explanation of this system.
f It should be remembered that an ordinary reverberatory furnace
must be worked with an excess of air if a high temperature is to be
maintained.
CHAPTER XIV.
MECHANICAL TESTING OF STEEL AND IRON.
THE fitness of finished steel and iron for certain purposes is
mechanically tested by subjecting prepared test-pieces to a
gradually increasing pull or stress in a testing machine, noting
the tonnage at which it breaks, and measuring the extent to
which it has stretched and the reduction in area of the
fractured surfaces. The capacity of the material to with-
stand cracking or rupture on being bent or flanged is some-
times ascertained, and its welding quality is tried on certain
occasions. Resistance to impact from a falling weight and
other tests are also applied.
Preparation of Test-Pieces. — A selection is made from
Fig. 59a.— Flat Test-piece, before Testing.
Fig. 596.— Flat Test-piece, after Testing.
the plates, bars, or other products to be inspected, and, from
portions systematically selected, test-pieces are shaped and
marked.
Strips from plates, &c., are cut in batches to the shape shown
in fig. 59a, and marks are punched at certain distances —
say 6, cy, or 10 inches apart. If from plates J inch thick, the
strips may be machined so that the narrowest part is 2 inches
broad, thus giving a cross area of 1 inch. In all cases the
rolled surfaces are left untouched, the machine cutting being
MECHANICAL TESTING OP STEEL AND IRON. 143
done on the edges to the extent necessary to bring the
breaking stress within the capacity of the testing machine.
From massive pieces, such as axles, tyres, &c., portions are
cut out and turned to the shape shown in fig. 60a. These
when finished in the lathe often have a diameter of 798 inch
on the narrow part : this gives a cross area of '500224,
or a mere trifle over half an inch. Wrought-iron pieces are
often turned to a diameter equal to 1 square inch. Marks are
punched at certain distances apart. In preparing test-pieces
the ends are left broader than the centre portion: this ensures
a good grip when in the testing machine.
Fig. 60a. — Cylindrical Test-piece, before Testing.
Fig. 607>. — Cylindrical Test-piece, after Testing.
Testing the Tensile'' Strength of a Test-Piece. — The
prepared piece having been securely fixed in the jaws of the
testing machine, power (generally hydraulic) is applied to
pull the piece till the stress fractures it. The amount of
stress is indicated by the position of a jockey weight which
is caused to travel along a graduated scale on a beam. If
the cross area of a test-piece, before being fixed in the
machine, is exactly 1 square inch (1 ID") the indicated tonnage
at which the piece was ruptured shows directly the tensile
strength of the metal. When pieces which were turned to
a diameter equal to J a square inch are ruptured the indicated
tonnage is, of course, doubled so that the tensile strength is
reported in terms of tons per square inch.
In works practice a gauge is used to see if the turned test-
pieces are of the correct diameter. Special scales, slide rules,
and tables are also used to facilitate calculations, for all test-
pieces are not cut or turned to set sizes. But as a student
* Tensile strength means the strength or power to hold together
while subjected to a force tending to stretch or sunder by pulling.
144 IRON AND STEEL MANUFACTURE.
should be able to calculate areas, &c., without such aids the
following explanations and examples may prove useful. The
decimal system is in use in test houses. The cross area of a
flat test-piece is ascertained by measuring the breadth and
the thickness, converting any vulgar fractions into decimal
equivalents, and multiplying one dimension by the other.
To Ascertain the Cross Area of a Cylindrical Piece. — Square
the diameter and multiply the result by '7854-
Example. — What is the cross area of a test-piece which has
been turned to '797 inch diameter?
•797 X '797 x '7854 = -635209 x '7854
•635209 x '7854 = '49889
and -49889 = cross area.
To Compute the Tensile Strength of a Test-piece. — Divide
the indicated tonnage by Us original cross area.
Example. — A test-piece *8 inch diameter broke under a
maximum stress of 1 6 '8 tons. What was its tensile strength 1
•8 X '8 X '7854 = -50265,
16'8 -33-42
^50262- l2'
and 33-42 = tensile strength per square inch.
To Compute the Percentage Elongation of a Test-piece. —
Find the difference in the distance between the punch marks on the
piece before and after rupture. Divide the difference by the original
distance, and, in order to find the percentage elongation, multiply
the result by 100.
Example. — Distance between the marks when
the test-piece broke = 9 '82 inches.
Distance between the marks on the test-
piece before fixing it in the testing
machine = 8'00
Difference = 1'82 „
Then, "» x 100 = 32.75
o
and 22-75 = elongation per cent.
MECHANICAL TESTING OF STEEL AND IRON. 145
To Compute the Percentage Contraction of Area of a Test-
piece. — Find the difference between its cross area before and after
testing. Divide that difference by the original cross area, and, in
order to find percentage, multiply the result by 100.
Example. — Diameter of the piece before testing = '800 inch.
Diameter of the test-piece when broken = '521 „
Then, '8 x '8 x '7854 = -50265 inch.
•521 X -521 x '7854 = '21319
Difference = '28946 „
'28946 x 100
•50265
5 7 '5 8 = percentage contraction of area.
The quality of a certain make of steel will depend chiefly
on (a) its composition, (J) the working of the steel in the
furnace or converter, and (c) the treatment to which it was
subjected after being poured into the ladle.
The percentage of carbon will, to a large extent, influence
its tensile strength and its elongation. Within limits, the
higher the percentage of carbon present the greater will be its
tensile strength and the less its capacity for elongation before
breaking. The other elements present will have a marked
effect on its mechanical properties. Malleable metals are
improved by judicious manipulation, such as rolling at proper
temperature.
Mild steels generally have composition near to the
following : —
Carbon, '17*
Phosphorus, '05
Sulphur, -05
Silicon, -02
Manganese. ...... '50
Iron (by difference), A
100-00
* The percentage of carbon is purposely varied to suit the purpose
for which the steel is intended.
10
146
IRON AND STEEL MANUFACTURE.
The tensile strength of such steel is generally equal to from
27 to 32 tons per square inch, with an elongation of from 16
to 22 per cent, on 8 inches.
SPECIFICATIONS FOE MILD STBKL.
Tensile
Strength in
Tons per
Square Inch.
Percentage Elongation
Ship plates-
Admiralty, . . ~. ' r
Lloyds, . ... V
26 to 30
28 „ 32
20 per cent, on 8 ins.
16 ,, ,, „
Boiler plates —
Admiralty, . .
Board of Trade,
Lloyds, ....
27 , 30
27 , 32
27 , 32
20 ,
18 ,
20 ,
Boilers (other parts) —
Admiralty, . . ' '.'t ..
Board of Trade, . : r >
Lloyds, . . . V « ''
24 , 27
26 , 30
26 , 30
25 ,
20 ,
20 ,
Steel for bridge building, .
27 „ 31
20 per cent, on 8 or 10 ins.
Pieces which have been rolled into thin sections or drawn
into wire yield better results than thicker sections.
Common wrought iron may contain —
Carbon, W C-/ ',! '' X ' . ' v\'" . .. '05
Phosphorus, \- .^'^»' . V •/ "35
Sulphur, v ,- v^;>V» ;" • ? • V . *06
Silicon, '...•.'•.;'->,' '•.vi-v\-v;<-;.?v', .V.'': '23
Slag,. ;V^* i^ ;,.^\wv ', .; . about 3 '3
Best wrought iron may contain —
Carbon, . -.' .' "V
•: -TV '.'-•*••••'.••-% '06
V"' •••;-:-''-ik .' . *04
Silicon,
k '/ •• " ""»••' •'•'•••. '20
:.' ••V-V''^6V; " '. '06
Slag.
, about 2*8
MECHANICAL TESTING OP STEEL AND IRON.
STRENGTH OF WROUGHT IRON.
147
Tensile
Strength
in Tons per
Square Inch.
Percentage
Elongation.
Percentage
Contraction.
Puddled bar, .
18-6
4 to 8
4-5
Common iron,
21-0
8 „ 16
5-3
Treble best, .
23-0
12 ,,25
15 to 35
STRENGTH OF CAST IRON.
For testing the power of iron castings to withstand crushing,
test-pieces 3 inches by 1 inch are prepared, and they show a
resisting power of 25 to 90 tons, with a probable average of
about 45 tons.
For testing the transverse strength of castings, a bar 2 inches
deep by 1 inch in breadth is laid on supports 3 feet apart.
Under these conditions common iron will carry from 23 to 27
cwts., and better iron will carry from 28 to 31 cwts., with a
deflection of *3 inch.
148
CHAPTER XV.
FOUNDRY PRACTICE— IRON AND STEEL CASTINGS.
THE object of the iron-founder is fo " cast " or form pig iron
into shapes required. This he does by pouring melted pig
iron into prepared moulds, so that the " castings " will be of
the desired size, shape, and strength.
For the production of sound and shapely castings the
melted " metal " must be of suitable chemical composition,
and must be cast at proper temperature in reliable moulds
Increasing attention is now being paid to these points.
The moulds must be of material which will withstand,
without softening or fusing, the heat of the molten pig iron;
the material must have coherency — that quality which binds
it together so as to hold against the pressure of the fluid metal
— it must be close enough to contain the liquid metal, while,
at the same time, open, or porous enough to permit the escape
of gases which are liberated from the melted metal during
solidification. The chief constituent of the material for the
mould is silica * (Si02), as shown in the following analyses : —
Constituents.
Chemical
Formulae.
Fire
Sand.
Moulding
Sand.
Core
Sand.
Silica, .
Si02
98-0
86-0
94-3
Alumina,
A^Oo
1-5
8-5
2-0
Iron oxide,
FeoOo
o-i
2-0
0-3
Lime, . " .
CaO
0-2
0-5
o-o
Carbonate of lime,
CaC03
0-3
1-6
Magnesia,
Alkalies,
MgO
Na20 and K2O
b-i
0-8
o-i
0-5
o-i
Combined water,
H20
o-i
1-5
1-0
Organic matter, .
...
0-3
0-2
100-0
100-0
100-0
* White sand is a familiar example of silica ; a still better example of
pure silica is quartz, a hard, glistening substance.
IRON AND STEEL CASTINGS. 149
Fire sand is useful for mixing so as to increase the power
of withstanding a very high temperature, and especially for
steel-casting purposes. It is also useful for correcting a
moulding sand which is too apt to bind.
Moulding sand of the composition stated is suitable for
medium iron work. For lighter iron work moulding material
with 82 per cent, of silica is suitable ; for heavy iron work the
silica may amount to 88 per cent., or over.
In moulding materials silica is the fire-resisting substance.
Alumina is also refractory, but it "bakes together" when heated
with silica — it possesses "bond." When too much alumina
is present there is danger of the mould being spoiled by
excessive shrinkage or by being non-porous. A sand low in
alumina and iron will permit of the rapid escape of gases ;
with high alumina the sand bakes and holds back the gases.
" Organic matter gives bond to sand, but the bond or binding
property is destroyed the moment it comes in contact with the
molten metal, the organic matter being burned out; conse-
quently there is a loss in volume, and this shrinkage causes
the sand to fall or crumble." * The other ingredients men-
tioned in the table tend to cause the material to fuse or melt.
Alkalies (potash and soda) are specially bad. Being thus
objectionable they can only be tolerated in small amount.
The mechanical condition, the intimacy of intermixture, the
pressure to which the substance has been subjected while
in its native bed, and the fineness to which the particles have
been ground — all these have an important bearing on the
quality of moulding material. The proof of its fitness or un-
fitness may best be found by trial. But chemical analysis
may, in a most helpful degree, suggest the proper proportion in
which to mix with some other material to produce a good
moulding compound.
The moulding material must be of the proper grain; its
binding power may be increased by admixture with clay, or
with tar, or with cheap gum. Cores have been made of pure
sand and thick oil. Porosity may be improved by judicious
* C. Scott, see paper by J. E. Stead, F.R.S., Cleveland Institute of
Engineers, Feb. 1905.
150 IRON AND STEEL MANUFACTURE.
admixture with coal dust. Binding power is sometimes im-
proved at the expense of porosity ; improved porosity may
mean corresponding diminution in binding power. Chopped
straw, cow hair, horse dung, &c., are mixed with sand and
loam. They give additional strength, and, as they burn off,
leave passages for the escape of gases.
Green-sand is the term applied to moulds made of sand
in its natural, raw, 'or green state. The composition of the
sand may be correct for light castings, or an addition of 5
or 6 per cent, of fireclay may be necessary for heavy castings.
Green-sand moulds need a facing, about an inch in thickness, of
a mixture of sand and coal dust towards the hot metal. The
coal dust prevents fusion, and the castings have a cleaner
surface. The surface is blacked with graphite (plumbago), or
other suitable substances. For dry-sand castings the moulds
are carefully dried before pouring in the metal. This takes
time, and increases the cost. For large castings loam moulds
are prepared. ,Loam moulding is the most expensive form of
founding, but is practically the only one for certain purposes.
The Melting of " Metal " for Foundry Purposes. — In a few
works the " metal," as it comes from the blast furnace, is run
directly into ironfounders' moulds. But, as a rule, it is cast
into " pigs " (see p. 208), which are allowed to solidify, and
are afterwards graded and remelted in the foundry. Metal
for special purposes is remelted in reverberatory furnaces, as
they are well under control and can discharge at one time
a large quantity of fluid metal of uniform composition.
When melted metal is required in small quantities only, the
pig iron is remelted in crucibles. For general foundry pur-
poses a cupola is employed for remelting. A Bessemer works'
cupola has been described on p. 71, and it differs from the
foundry cupola chiefly in size. A Bessemer cupola is worked
day and night ; as a rule, a foundry cupola is not.
Foundry Cupolas. — A foundry cupola is an upright cylin-
drical structure of firebrick encased in rivetted boiler plates.
Internal rings or angle irons are attached at intervals - to the
plates for supporting the brickwork. An air blast is injected
through tuyeres, which may be in one row or more. For
IRON AND STEEL CASTINGS.
151
Fig. 61.— Foundry Cupola with Solid Bottom.
152
IRON AND STEEL MANUFACTURE.
Fig. 62.— Foundry Cupola with Drop Bottom,
IRON AND STEEL CASTINGS.
153
heavy foundry work the tuyeres are placed higher than for
small foundry work. Pig iron, fuel, and flux are charged into
the hot cupola ; molten metal is tapped out, when required,
and runs from the taphole along a
spout or launder into the casting ladle.
For small foundry work the spout is
placed about 20 inches from the
ground ; for heavier work it is placed
higher. From larger cupolas slag is
tapped off from the slaghole as it
gathers.
Some cupolas have solid bottoms, as
shown in fig. 6 1 ; others are con-
structed with a " drop " iron bottom
plate, as shown in figs. 62 and 63.
On an iron foundation plate four
massive cast-iron columns are set;
these support a substantial base plate
which carries the shell of the cupola.
When the bottom plate is removed,
or unfastened, the materials left in
the cupola — those which have not been
tapped out — are -removed. Fig. 63
shows a section of such a "drop-
bottom" cupola erected to the specifi-
cation of Mr. Robert Buchanan in
the Soho Foundry of Messrs. W. & T.
4very, Limited. Its tuyeres are not
at one uniform level, but are arranged
as points in a spiral. Beneath the
lowest tuyere, in the tuyere belt, is a
ping composed of an alloy which melts
very readily, and in the event of slag
or metal rising accidentally to an in-
convenient extent, the " fusible plug "
melts, and thus an outlet is provided
and damage to the tuyere is prevented.
Fig. 64 shows a view of one of the improved rapid cupolas
erected by Messrs. Thwaites Brothers, Bradford. An im-
/
"*"'"*- ;
'f,
y
y
6 E
I
y
/
t
f^-^
| j
o
^
/ O %
j
0. £-^
i °%
^ ^
c —
IT1
A=^^ -
-IfJ 1
— A
Fig. 63. — Section of
Koundry Cupola
with Drop Bottom.
A, Columns.
C, Drop bottom.
D, Tuyere.
E, Air belt.
F, Iron angle.
G, Charging platform.
H, Charging door.
I, Iron shell.
J, Brickwork.
154
IBON AND STEEL MANUFACTURE.
portant adjunct is the receiver, which is lined with firebrick,
and connected with the cupola by a brick-lined channel. It
has usually about half the hourly melting capacity of the
cupola. The hot-air pipe between the receiver and the cupola
supplies sufficient hot air from the latter to prevent the
chilling of the " metal."
Fig. 64. — Foundry Cupola with Drop Bottom and Receiver.
The blast required for a cupola is usually supplied at
a pressure of about 1 0 ozs. per square inch.* " The quantity of
air needed is about 650 cubic feet per minute for each ton of
* Equal to a 21 -inch column on a water gauge.
IRON AND STEEL CASTINGS.
155
pig iron melted. The amount and pressure vary according
to circumstances. An economical and convenient appliance
for supplying the required air blast is the Boots blower,
Fig. 65. — Roots' Blower with Electric Motor.
which is illustrated in figs. 65 and 6G. As made by Messrs.
Thvvaites Brothers, Bradford, Yorks, the blower consists of
Fig. 66. — Section of Roots' Blower.
a carefully-machined cast-iron case which is elliptical in cross
section. The end plates are bored by a duplex machine for
the journals of the shafts for the revolvers. Each revolver is
156 IRON AND STBEL MANUFACTURE.
cast in one piece, accurately machined all over to gauge,
specially centred, and carefully balanced. Conical adjustable
bearings are used. Geared wheels are introduced to equalise
the power transmitted to the revolvers. Oil baths set for the
lower part of each wheel ensure comparatively silent and
smooth working. Generally there is a wooden cover with
perforated metal panels on the top of the cylinder, but
sometimes the air inlet is placed on one side.
The blower is mounted on a bed plate, and may be driven
by TDelt, by steam engine direct, or by a motor. For a cupola
melting about 4 tons of pig iron per hour the blower may be
worked at 380 revolutipns per minute; for cupolas of greater
capacity the revolutions will be less, but the driving pulleys
will be of greater diameter.
Fans are frequently used for forcing the air required for
cupolas.
Working a Foundry Cupola. — When the cupola has been
brought into working condition a coal fire is kindled and then
covered with a " bed " of coke. When the coke has burned
up to the level of the tuyeres, the door near the bottom of
the cupola, as described in p. 71, is placed in position, and
charging from the charging door is begun.
Mr. Robert Buchanan gives the following particulars*: —
Bed of coke = 5 cwts.
Five charges of 10 cwts. of pig iron, alternating with
1 i cwts. of coke.
Alternate charges of 10 cwts. of pig iron with 1 cwt.
of coke.
Towards the end of the working day the proportion of coke
is further diminished.
The amount of coke consumed varies, 1 Ib. of coke sufficing,
on an average, to melt 10 Ibs. of "metal" for heavy castings,
or 8 Ibs. of " metal " for light castings.
Limestone is also charged into the cupola to supply lime to
combine with the ash of the coke and the sand on the pig iron
to form a fusible slag. The amount of limestone used varies
between a quarter and a half hundredweight per ton of metal.
* Proceedings of the Sta/ordahire Iron and Steel Institute, Nov. 1901.
IRON AND STEEL CASTINGS.
157
Foundry Ladles are of cast iron if small, of wrought iron or
mild steel if larger, and have a capacity. of from half a hundred-
*
so
weight up to several tons. They are lined with refractory
materials and should be heated before using. Figs. 67 and
158
IRON AND STEEL MANUFACTURE.
68 represent hand ladles used for small castings. In Fig. 69
is shown a large-sized geared crane ladle, as manufactured by
to
£
Messrs. Thwaites Brothers, Bradford. A trolley ladle, which
is convenient for conveying and dealing with foundry metal,
IRON AND STEEL CASTINGS
159
160 IRON AND STEEL MANUFACTURE.
is illustrated in Fig. 70. The latter, made by C. M'Neil,
Glasgow, is of stamped steel, without weld or rivets.
The contents of the ladles are generally emptied over a
lip or spout, the ladle being tilted as required and the slag
held back during pouring when necessary.
Pig Iron for Foundry Use. — The pig iron, or mixture of pig
irons, should be of a composition suited to the qualities needed
in the castings which are to be produced. A strong, heavy
casting is best made from pig iron which is not suited for
light ornamental work, and " metal " which is well adapted
for light work does not suit for strong castings. It is a
costly mistake to attempt to improve certain castings by
incorporating high-priced hematite pig iron. The author
has frequently, with most satisfactory results, advised the
introduction of more cheap pig iron in mixtures. There
is in the minds of many foundrymen a notion that in order
to make good castings costly pig iron is necessary, and when-
ever trouble comes and castings are faulty, tests bad, and
rejections numerous, recourse is had to hematite as the cure
for all ills. ' It is equally a mistake — although not by any
means so common — to seek to improve all mixtures by using
cheap, highly-phosphoric pig irons. The purchase and use
of a first-class foundry pig iron, of a good old standard
brand, is often a profitable investment for the foundryman.
Castings which have been proved by long and useful service
to be excellent do not vary in composition to any great
extent.
By selecting grey and white, or grey and mottled pig, irons
in such proportions that the chemical composition will yield
"metal" from the cupola of the composition required, one
of the first conditions for the production of suitable castings
will be complied with. The changes in composition which
pig iron undergoes while passing through the cupola — such
as oxidation of iron, diminution in percentage of silicon and of
manganese, increase in percentage of sulphur, and the slight
increase in percentage of phosphorus — must, of course, be
allowed for in making up the cupola charge. With well-
arranged and well -finished moulds of proper materials,
suitable metal, attention to the best temperature at which
IRON AND STEEL CASTINGS. 161
to pour, and the rate at which the castings are allowed to
cool, waste will be reduced to a minimum.
Silicon is the element in pig iron which has a dominant
effect, either directly or indirectly, in modifying the character
of a casting. It has a marked effect on the condition of
the carbon. When the percentage of silicon is high the
carbon is mostly in the graphitic state,* and the sulphur
is, as a rule, low. Such a pig iron is grey, unless produced
under abnormal blast-furnace conditions. A pig iron, or
a mixture of pig irons, containing a fair proportion of silicon,
is well adapted for casting, because it is very fluid when
melted, fills the mould well, and makes a casting which is
likely to be free from blowholes. A soft grey pig iron is
best suited for castings which are to be tooled.
Professor Turner investigated the relations between chemical
composition and mechanical qualities, and found that —
Castings of maximum tensile strength contained 1 '8 per cent, of silicon.
,, ,, transverse ,, ,, I '4 ,, ,,
,, „ crushing „ „ 0'75 „
Phosphorus in pig iron increases the fluidity but reduces
the strength. Sulphur tends to whiten the iron and may, to
a limited extent, add to its strength. Its presence beyond a
limited amount is objectionable. In experiments conducted
by Mr. Chas. Wood, the presence of 0*16 per cent, of sulphur
did not appear to be harmful.
The effects of carbon in castings are most marked. " Com-
bined carbon is mainly the determining factor of the hardness
and shrinkage of a casting. . . . For general engineering
foundry castings about 0'5 per cent, is a fair amount. . . .
The total carbon should not exceed 3 '2 5 per cent, either in
hard or soft castings."f When pig iron contains a high per-
centage of graphitic carbon the plates of graphite are generally
large, and, as they distinctly break the metallic continuity of
the casting, its strength is lessened. Professor Turner has
investigated the influence of size of graphite plates in castings
with important results.
*See p. 12.
tJ. E. Stead, paper read before the Cleveland Institution of
Engineers, February, 1905.
162 IRON AND STEEL MANUFACTURE.
APPROXIMATE ANALYSIS OF OBEY FOUNDRY PIG IRON.
Chemical
Symbols.
~~l
Per cent.
Graphitic carbon, , v » •
C
c
3-25
0-25
c
3-50
Silicon, ... • •
Si
P
2-50
0-80
s
O'lO
Mn
1-30
Fe
A
100-00
COMPOSITION OF IRON CASTINGS.
Chemical
Symbols.
Heavy,
Strong.
Light,
but Fairly
Strong.
Ornamental.
Carbon, .
Silicon, .
Phosphorus,
Sulphur, .
Manganese,
Iron,
C
Si
P
S
Mn
Fe
3-5
1-9
06
0-09
0-5
A
3-8
2-3
0-8
0-08
0-5
A
4-0
2-8
1-0
0-09
0-5
A
100-00
100-00
100-00
Cast iron can be softened by altering its composition,
especially by enriching with silicon, or by allowing to cool
slowly. And it can be hardened by remelting, so as to
eliminate silicon, or by causing it to cool quickly — as in the
making of chilled castings. Materials which are known in
foundry practice as softeners are regularly produced, and they
are useful in " correcting " irons which are too hard, and for
promoting soundness in castings. Softeners must, of course,
be added " with brains."
For composition of softeners see p. 238.
When melted grey pig iron is allowed to stand for some
time in a ladle? kish? which consists largely of graphite and
IRON AND STEEL CASTINGS. 163
contains notable amounts of manganese and sulphur (all of
which are eliminated from the iron), collects on the surface.
A ladleful of melted pig iron, especially if covered with
ground coke, or any other suitable substance which will
retard cooling, will remain in teeming condition for a long
time.
Remelting of pig iron is, and repeated remeltings may be, up
to a certain point, beneficial. But as some silicon is eliminated
during each remelting, it is clear that when the silicon has
reached the proper percentage for the purpose in view any
further remelting must be a dis-
tinct disadvantage. Manganese
is also lessened in amount during
each remelting, and sulphur (un-
less precautions are taken) is
increased.
Chilled Castings. — Certain
castings have parts of their sur-
faces purposely hardened by
being cast in moulds which are Fig. 71.— Chilled Casting,
partly of iron. Thus a wheel S = Sand mould,
may be hardened on the wearing = ^°4T! "
surface of the rim, and the centre
of the nave may be also hardened. Fig. 71 may convey an
idea of how the superficial hardening is induced. The chill
is not deep, and the comparative pliancy and absence of
brittleness of the portions which have not been chilled are
advantageous.
The crystallisation of cast iron calls for consideration.
Iron, like other metals, crystallises at right angles to the surface
which is cooled.* If a casting is not designed with a due
regard to the formation of crystals its strength may be
insufficient. The earlier cylinders employed at the erection
of the Menai Bridge had sharp corners, as shown in fig. 72,
and they soon broke along the lines of weakness, as represented
* A piece of common spelter (ingot zinc) shows well the lines of
crystallisation in cast metal
164
IRON AND -STEEL MANUFACTURE.
in fig. 73. The form sketched in fig. 74 was an improved
design, which, having no pronounced lines of weakness, with-
stood the heavy pressure. The lines of crystallisation in a
Fig. 72. — Section of Original Fig. 73. —Section of Cast -iron
Cast-iron Cylinder — Sketch Cylinder (broken) — Sketch
Showing Arrangement of Showing Arrangement of
Crystals. Crystals.
circular casting are shown in fig. 75, and figs. 76 and 77
indicate the crystallisation in a square and a long iron casting.
Fig. 74. — Improved Section of Cast-iron Cylinder — Sketch
Showing Arrangement of Crystals.
Fig. 76. — Circular Casting.
Fig. 76. — Square Casting.
IRON AND STEEL CASTINGS. 165
In making castings, the shrinkage which occurs must be
allowed for; they must be cast larger than the finished pro-
ducts are required to be. The amount of shrinkage varies
with the class of pig iron, and also with the size of the casting.
Fig. 77. — Long Casting.
Massive castings do not shrink, relatively, as much as lighter
ones do. As a general indication of the trade practice the
following figures are useful : —
The allowance for
Massive castings is . . i inch in 18 inches.
Medium ., . . £ „ 15 „
. . 12
STEEL CASTINGS.
The chief difficulties in the way of producing good steel
castings arise from the high temperature at which it is
necessary to produce and teem the metal, the unsatisfactory
nature of iron-moulding material for steel castings, the great
skrinkage, and the want of soundness and strength in the
finished material, due in large measure to the great quantity
oi gas which steel is apt to occlude. By occluding is meant
that power by which melted metals can dissolve many times
their own bulk of gases and retain them fw a time. Some of
the occluded gases become liberated during the cooling of
the metal, and, after a crust has formed, they cannot easily
escape. In these circumstances gases gather in one or more
parts of the casting and form cavities or blowholes.
The temperature at which the "metal" for steel castings
melts is said to be from 1,450° C. (= 2,642° F.) to 1,500° C.
(= 2,732 F.),* and a higher temperature must be employed.
*The temperatures expressed here were ascertained by a modem
pyrometer which indicates much lower (but probably more accurate)
degrees for high temperature. The older heat measurements of high
temperatures are not reliable.
166
IRON AND STEEL MANUFACTURE.
A satisfactory moulding material, capable of withstanding the
great heat, and yet porous enough to allow free escape of the
large volume of contained gases, is made by heating quartz,
quenching in water, grinding to powder, and mixing with
clay in proper proportion. The prepared moulds require to
be well faced with graphite. The shrinkage is about double
that of iron castings. It is usual to strip the castings as soon
as permissible, the cores, &c., being removed early.
The troubles incidental to the introduction of a new branch
of manufacture have been overcome, and sound steel castings
are now made with fair regularity. Steel for castings is
produced in crucibles, in converters, and in open -hearth
furnaces. As it is not easy to keep the metal hot during
the long time occupied in casting large quantities, small
furnaces and converters are in general use for steel founding.
Basic steel castings are in some instances preferred to those of
acid steel. The procedure for producing steel for castings in
open-hearth furnaces is much the same as for the production
of ingots. For castings it is essential that the steel should
be finished hot, and in practice ferro-silicon (see p. 238) is
freely but judiciously used.
Steel castings vary widely in chemical composition, each
tap of metal being finished to suit the order in hand. The
following are examples : —
Percentage of
Carbon.
Silicon.
Phos-
phorus.
Sulphur.
Man-
ganese.
Stern frame, .
•17
•50
•055
•048
•56
Railway wheel,
Railway wheel,
•30
•44
•27
•38
•065
•051
039
•043
•63
•51
Crank axle,
•34
•15
•041
•042
•56
Bracket, .
•41
•57
•060
•068
66
167
CHAPTER XVI.
MALLEABLE CASTINGS.
NUMEROUS small articles of intricate shape, and fairly strong,
are in daily demand — such articles as keys, parts of locks,
nozzles, hooks, &c. It would not pay to fashion keys by
hammering wrought iron into shape, and cast-iron keys would
not be strong enough, unless heavy. Hence the desire for a
process by which some of the qualities of wrought iron may be
conferred on castings of complicated shape. The castings can
be more cheaply worked out by a sand pattern than in the
iron itself. By the annealing process to which they are sub-
jected, important changes are effected by which they become
malleable.
The manufacture of malleable castings embraces the
following stages : —
Making the Pattern. — The moulds are of green or of dry
sand.
Melting the Metal. — The metal is melted in graphite
crucibles, or, in some cases where the castings are large, in
cupolas, and cast in the moulds. A special kind of pig iron
is required, and suitable scrap is melted with it.
Cleaning the Castings. — When cold, the castings are
cleaned by being turned over many times in a horizontal
rotating barrel designed with sharp corners. The castings
rub against each other, and the sharp corners hasten the de-
taching of the sand.
Annealing the Castings. — The articles to be annealed are
carefully packed in red hematite iron ore in suitable vessels,
and are carefully heated and allowed to cool down slowly.
The ore, having been crushed as small as peas, is sifted, and
a mixture of two or three parts of old ore with one part of
new ore is used. When new ore is used alone the "annealing"
action is too keen. The containing vessels are crucibles or
"pots," or cast-iron boxes called "saggers," or wrought-iron
boxes.
168
IRON AND STEEL MANUFACTURE.
The pots, or boxes, which may be square or circular in plan,
are cast from a special mixture of white iron and scrap, and
they vary in capacity according to the size of the castings to
be annealed in them. For certain castings the ore and pot
together may weigh 2£ cwts., the castings for annealing f cwt.
When the packing of a pot or box is completed the lid is luted
on. The packed boxes are then placed in the furnace.
The furnaces are coal-fired or gas-fired. Some are rectangular
in plan, with dome-shaped roofs. They are built in rows, each
furnace being connected with a flue leading to a stack. Such
a furnace is shown in fig. 78.* The middle portion of the
bed is raised, thus providing two
passages down the sides for the
fires. The boxes containing the
castings are placed on this raised
floor, three or four in each pile, the
joints between them being sealed
with fireclay or wheelswarf, and the
top box completely covered with
the same substance. Each furnace
holds from 12 to 20 boxes. The
most important articles are placed
in the centre pots.
During Bannister's investigations
from 10 to 20 boxes were placed
» a furnace, and the temperature
maintained was from 1,000 0.
(1,832° F.) to 1,100° C. (2,012° F.) during days, the fires
being damped down for nights, thus giving a bright red heat
during days, and a dull red during nights. The furnace
was fired from five to nine days, and allowed to cool down
for two days.
In Royston's investigations f the pots, 60 in number, were
charged into a black-hot furnace which had just been emptied.
The door was luted and firing commenced. The temperature
of the furnnce on the second day was 750° 0., on the third day
* From paper by C. 0. Bannister, A.B.S.M., Inst. Mech. Engineers,
January, 1904.
t Journal of the Iron and Steel Institute, i., 1897.
MALLEABLE CASTINGS.
169
it was 860° C., while on the fourth, fifth, and sixth days the
furnace heat did not vary more than 40° from 860° C. As
the pots became red hot, copious jets of flame were emitted
and burned with a blue flame, which may be accepted as
evidence of the escape of carbon monoxide (CO) from within
the pots. The coal used amounted to If tons per ton of
metal annealed. When the furnace had cooled sufficiently
the pots were withdrawn. Three days, instead of seven, may
suffice for some kinds of work.
The boxes are in due course unpacked, the castings are
cleaned, and are then ready for the market.
Malleable castings, if in thin sections, can be welded The
castings are not brittle, as they were before annealing, but are
generally tough enough to stand bending into a U shape even
when cold. They are cleaned, and are then ready for the
market.
Consideration of Composition and Changes. — The pig iron
used should be low in silicon, phosphorus, and manganese, as
these remain unaffected during annealing and their presence
in the finished casting is harmful. Manganese and sulphur
retard the annealing. The pig iron used sometimes contains
over *3 per cent, of sulphur, which is not desirable. The
best " metal " for the purpose is refined white hematite pig
iron along with good scrap.
TABLE OF COMPOSITION.
Refined
Constituents.
Chemical
Symbols.
White
Hematite
Pig Iron
White
Hematite
Pig Iron
after
Castings
after being
Annealed.
Melting.
Melting.
Graphitic carbon
Combined carbon
C
C
0-61
3-33
0-19
3-69
1-56
0-74
Total carbon,
C
3-94
3-88
2-30
Silicon,
Si
0-61
0-57
0-57
Sulphur,
Phosphorus,
Manganese,
s
p
Mn
0-03
0-044
0-112
o-io
0-045
0-043
0-057
0-045
0-043
Iron (by difference),
Fe
A
A
A
100-00
100-00
100-00
170 IRON AND STEEL MANUFACTURE.
The metal takes up sulphur during melting, whether in a
crucible* or in a cupola.* Royston found the following
percentages of sulphur: —
Before melting = '031.
After melting in an open crucible = '096.
After melting in a cupola = '161.
The coke used contained 1*60 per cent, of sulphur, which is
a high percentage.
During annealing the changes induced are : —
(a) Change in the condition of some of the carbon ;
(b) Reduction in the amount of carbon ;
(c) Reduction in the amount of sulphur ; and
(d) Reduction of some oxide of iron to the metallic
state.
In Bannister's experiments the sulphur was diminished
•03 per cent. The used ore has been found to contain
pellets of iron, and sulphur has been taken up by the ore
when the castings were not low in sulphur before annealing,
The spent ore also contains carbon derived from the castings.
About half of the carbon is withdrawn from the iron, a change
which is quite the reverse of that resulting from the cementa-
tion process. Most of the remaining carbon is changed from
the combined state to fine-grained graphite.
The combined carbon in the pig iron lowers its melting
point, increases its fluidity, and enables a clean, sharp casting
to be made. The amount of combined carbon which is left in
the finished casting does not impair its malleability too much.
* For description of a crucible see p. 42, and of a cupola see p. 150.
171
CPJAPTEB, XVII.
CASE-HARDENING.
SOMETIMES it is requisite that wrought-iron articles should be
hardened on the surface and a little beneath. The most
convenient known method of hardening is by adding carbon
and then quickly quenching from a suitable temperature.
In case-hardening, the carbon addition is effected by packing
the articles in a box containing a sufficiency of substances
which are rich in carbon and in nitrogen. The most com-
monly-used substances are leather cuttings, horse-hoof pairings,
potassic ferro-cyanide (popularly called prussiate of potash),
and bone charcoal. The articles are embedded in one or
other of the above-named substances. The lid is then closely
luted with fireclay. The box and contents are placed in a
furnace which is raised to a cherry -red heat (about 860° C.)
and maintained at that temperature for 12 or even up to
24 hours, according to the depth of hardening wanted. The
box is allowed to cool down till the contents are cold enough
to bear removal — although still red hot — when they are
plunged into cold water. If cooled too much before removal
from the box, the articles are reheated and suddenly quenched.
Those parts which are not to be case-hardened are carefully
covered with fireclay before placing in the box in which the
carbonisation is carried on.
The smooth wearing parts of axles are covered with a
leather sheath and placed in a furnace. When the part which
is in contact with the leather is judged to have taken up
enough carbon it is withdrawn from the furnace and quenched.
The other end is then similarly treated.
When wrought iron — which does not contain much carbon
— is embedded in charcoal and steadily heated for several
days (see p. 39) to a high temperature, carbon penetrates
172 IRON AND STEEL MANUFACTURE.
right to the heart of the wrought iron and converts it into
steel. In case-hardening, the conversion to steel is superficial,
and as it is practised on articles of finished shape they must
be embedded in a substance which quickly yields carbonaceous
material at such a moderate temperature as will not cause
distortion of the articles.
In distinct contrast to these processes, by which iron is
caused to take up carbon, is the method of treating iron
castings so that the carbon is changed and withdrawn, and
some of the qualities of wrought iron conferred on them.
ITS
Having in the foregoing pages dealt with tho
selection and working of pig irons to achieve
desired ends, we are now in a position to proceed
to the consideration of the composition of iron
ores and their treatment in the production of pig
iron suited to various requirements.
174
CHAPTER XVIIL
IRON ORES: THEIR COMPOSITION, CHARACTERS,
AND DISTRIBUTION. KIND OF PIG IRON PRO-
DUCED FROM EACH.
ANY large quantity of naturally-deposited matter containing
metals — either in the free state or in chemical combination —
may be considered an ore if the metals are present in sufficient
quantity and in such a state as to permit of profitable extrac-
tion. In ores the metals are generally in combination with
oxygen or sulphur, or they exist as carbonates or silicates.
Less frequently, the metal or metals are in combination with
chlorine or some other non-metal. When an ore contains
metal which is not in chemical combination with a non-metal
it is said to be " native." Certain ores are very complex, and
some contain metals which are not easily separated during
extraction. Ores which occur near the surface of the earth
are dug or quarried; those which are found at lower depths
are mined.
Iron Ores. — When iron is exposed to ordinary moist air
it " rusts " — the bright, strong metal is converted into a
voluminous, crumbling mass of earthy-looking matter quite
devoid of the characteristic good qualities which iron possesses.
Some deposits of iron ore may be looked upon as iron rust,
more or less altered in composition by heat, and which have
become naturally mixed with widely- vary ing amounts of other
matter, such as silica, clay, calcic phosphates, &c. The " other
matter" constitutes the gangue of the ore, and the gangue
usually requires some flax to accompany it in the blast fur-
nace. For example, silica (Si02), which forms such a large
percentage of the gangue of many ores, is quite infusible even
at the very high temperature of the blast furnace, but at that
temperature the silica may be caused to enter into chemical
combination with the flux so as to form a fluid compound
and be tapped out as slag.
IRON ORES. 175
The ores of iron which are smelted are all essentially oxides
of iron mixed with gangue, and they all contain phosphorub
They may be conveniently classed thus : —
Ferrous ores —
Blackband ironstone,
Clayband ironstone.
Cleveland ironstone.
Spathic iron ore.
Ferric ores —
Red hematite.
Brown hematite,
Ferrous-ferric ores —
Magnetite.
Franklinite.
Ilmenite.
Ferrous Ores consist essentially of ferrous carbonate
(FeO,C02) with other matters. Clayband ironstone contains
ferrous carbonate and clay. Blackband ironstone contains
coaly matter in addition. Cleveland ironstone contains ferrous
carbonate and clay, and is more highly phosphoric than the
others. Spathic ore, or siderite,* sometimes contains a
notable amount of manganese and much less phosphorus than
the other ferrous ores. It is, as its name indicates, sparry
or crystalline.
Ferric Ores consist essentially of ferric oxide (Fe903) with
other matters. The typical red hematite of Cumberland
and. North Lancashire is remarkably low in phosphorus
and sulphur. Of this class of ore there are several varieties.
Red hematite is largely mined in small fragments, which
are ruddy - coloured, have a greasy feel, and stain the
hands when touched. It also exists in iron-grey masses,
which, where weathered, are red-coloured. This variety is
known as pencil ore, from the facility with which it splits
into long fragments, which are sometimes used for marking
sandstones. Kidney ore occurs in lumps with rounded
surfaces which are dark steel-grey in colour. Another kind
* From a Greek word signifying iron.
176 IRON AND STEEL MANUFACTURE.
is found like flattened grains, and is known as lenticular
(pea-shaped) ore. Specular ore is of a bluish-black colour
and sparkles from many crystals on its surface.
Ferric ores, which contain a notable quantity of alumina,
are shipped from the north of Ireland to the nearest districts
where hematite ores are smelted. They are known in the trade
as Aluminous ores, Antrim ores, Belfast ores, and Irish ores,
Occasionally they are washed before being shipped.
Brown Hematites may be fairly compact or moderately
soft. In colour, ores of this class vary from rich brown to
yellow. They consist essentially of ferric oxide, with about
10 per cent, or so of combined water. Some kinds contain as
little phosphorus as good red hematite does, while others are
highly phosphoric and do not contain a high percentage of iron.
Ores of the Ferrous-ferric Type do not occur in notable
quantities in the British Isles, but ores of this class, which
are found in other countries, are of considerable importance.
Magnetite is found in masses in Sweden. The ore is
frequently rich in iron and is usually low in phosphorus and
sulphur. It is generally dark and hard. A magnet will cling
to a mass of the ore and can lift small fragments of it.
Other Sources of Iron are : —
Burnt Pyrites. — This is the residue from the treatment of
pyrites — an ore containing iron and sulphur, and often a
small quantity of copper. In the first place the ore is broken
into smaller lumps, when necessary, and slowly burned ; the
resulting sulphury gas (sulphur dioxide) is led into huge leaden
chambers where sulphuric acid (commonly called vitriol) is
made. If the "burnt pyrites" contains enough copper to more
than cover the cost of its extraction it is crushed smaller than
peas, mixed with salt, carefully roasted, and then leached
(soaked) in water to dissolve the copper compound. The
residual iron — which was oxidised during the burning of the
sulphur — has a dark purple colour, and is generally known in
iron works as "Purple Ore" or "Blue Billy."
Burnt pyrites and purple ore have recently become of
considerable importance as sources of iron.
Flue Cinder, which is the slag from certain reheating
furnaces, is also used for the production of certain classes
of pig iron.
IRON ORES.
177
Puddlers' Cinder, or Puddlers' Tap (see p. 25), is smelted
along with local ores, in blast furnaces, for the production of
cinder pig. It yields a highly-phosphoric pig iron, which is
well suited for the basic Bessemer process.
Mineral phosphates (apatite, &c.) are occasionally charged
into blast furnaces to increase the percentage of phosphorus
in the pig iron for basic steel-making.
The following figures represent, in round numbers, the
composition of some of the chief iron ores : —
Constituents.
Chemical
[formula?.
FERROUS ORES.
Blackband
Ironstone
(Staffs.)
Clayband
Ironstone
Ayrshire)
Cleveland
ronstone.
Spathic
Ore.
Ferrous oxide, .
FeO
42-0
40-0
38-0
49-33
Ferric oxide,
Fe,03
6-0
...
6-0
0-8
Manganous oxide,
MnO
3-0
1-0
0-5
2-2
Silica,
Si02
1-5
10-5
12-0
4-0
Alumina, .
A LA.,
0-3
5-0
11-0
0-7
Lime,
CaO
4-0
5-0
5'5
3-3
Magnesia. .
MgO
2/0
3-0
3-5
2-6
Phosphoric acid.
Sulphur, .
PA
s
0-7
0-5
1-3
0-2
1-5
03
0-03
0-04
Carbon dioxide,
C02
26-0
3TO
21-0
37-0
Organic matter,
...
'14-0
3-0
0-7
Combined water,
Total,
Metallic iron, .
H,0
...
100-0
100-0
1000
100-00
36-87
31-11
33-75
38-93
Phosphorus,
...
0-31
0-57
0-65
0-013
lli
178
IRON AND STEEL MANUFACTURE.
OVtACTll
FERRIC ORBS.
FERROUS-FERRIC
ORES.
Constituents.
unerni-
cal
For-
English
fied
Spanish
English
Brown
mulae.
Hema-
Brown
Hema-
Magnetite.
Magnetite.
tite.
Hematite.
tite.
Sweden.
Sweden.
Cumber-
Bilbao.
North-
land.
ampton.
Ferrous oxide, .
FeO
1-0
23-00
27-00
Ferric oxide,
Fe203
86<)0
78-00
63-0
52-00
60-00
Manganous oxide,
Silica,
MnO
Si(X>
0-25
9-00
1-00
9-00
0-2
9-0
2-00
8-00
o-io
5-00
Alumina, . ,'.•
AlA
0-50
1-00
6-0
2-00
1:00
'Lime, . . x-.'
CaO
3-00
0-70
3-0
6-00
3-00
Magnesia, .
MgO
1-00
0-20
0-5
5-00
2-00
Phosphoric acid,
P20S
0-03
0-04
1-8
0-02
2-00
Sulphur,
8
0-04
0-03
0-2
0-02
o-oi
Carbon dioxide, .
Organic matter, .
C02
...
2-0
1 2-00
...
Combined water,
H^O
...
10 -00
13-6
if° , "-V v"
Total,
...
99-82
99-97
99-7
100-04
100-11
Metallic iron,
60-20
54-60
44-88
54-29
63-00
Phosphorus,
0-013
0-017
0-79
0-009
0-87
For analyses of other ores, see pp. 242, 243, and 244.
THE SUPPLY OF ORES FOR THE BRITISH IRON TRADE.
As Great Britain has been for a long period the abode of an
active iron-producing people, the working-out or impoverish-
ment of certain mining districts must come as a matter of
course. At present, about twelve million tons of iron ores are
annually raised in Great Britain, and about six million tons
are imported.
Kefl Hematite Ores are mined in that part of the north-
west of England which is known as the hematite district —
Cumberland and North Lancashire.
The purer varieties of Brown Hematite Ores are mined
in the Forest of Dean, on the Severn estuary, near to South
Wales. The less pure (highly phosphoric) Brown Hematite
Ores are extensively worked in Lincolnshire, Leicestershire,
IRON ORES. 179
and Northamptonshire. Some of the ore beds consist largely
of carbonate. Considerable quantities are quarried, calcined,
and sent into Staffordshire.
Spathic Ores. — Ores of this class were mined in Weardale
(County Durham), from the Brendon Hills (Somersetshire),
and from Exmoor (Devonshire). The latter contained a
notable percentage of manganese.
Blackband Ironstone is still mined towards the east of
Scotland and in North Staffordshire.
Cleveland Ironstone exists in large quantities in the hilly
district of Cleveland, in the north-east of Yorkshire.
Clayband Ironstone was formerly a chief source of British
iron : at present it is only mined in a few districts where the
deposits are comparatively thick and rich. It is still worked
to a large extent in Ayrshire, Yorkshire, Derbyshire, Stafford-
shire, and East Worcestershire. In other districts the " coal
balls " met with in coal-mining are often saved for use in
blast furnaces.
Imported Iron Ores. — Large and increasing quantities of
iron ores are brought from abroad at comparatively low
freights. The imported ores comprise: — Manganese ores from
India and elsewhere, chrome-iron ore from Russia and other
countries, specular ore from Elba, in the Mediterranean;
iron ores from Greece and the south of Spain; and, in much
larger quantities, brown hematite and calcined carbonate from
the north of Spain. From Dunderland, in Norway, immense
supplies of concentrated ores may be obtained.
Imported ores are smelted in districts at or near the sea-
board where good fuel is cheap. Of these the most convenient
are South .Wales, Middlesbrough (in the north of Yorkshire),
and the district around Glasgow, which has the advantage of
a waterway — the Clyde — a river which has been persistently
deepened with commendable enterprise. To North Lanca-
shire and Cumberland, where rich deposits of hematite ores
have been found, the purer varieties of hematite ores are also
imported, and smelted along with the local ores. Durham
coke is much used in the blast furnaces in the hematite
district in the north-west of England.
180 IRON ANT) STEEL MANUFACTURE.
The purpose for which a pig iron is best suited is decided,
in large measure at least, by the percentage of phosphorus
it contains. With few exceptions of small importance, nearly
all the phosphorus which is present in the ore, the flux, and the
fuel used in smelting goes into the pig iron* The kind of pig
iron made in any district will depend very much on the
class, or grade, of ore which can be had there at a paying
price.
The Production of Hematite/ Pig Iron — known also as
Bessemer Pig Iron — for use in the acid Bessemer and the acid
Siemens processes is conducted in Cumberland and in North
Lancashire where good hematite ores are mined, and which
are supplemented by hematite ores imported from Spain.
The chief drawback to that district — apart from royalties,
&c. — is the want of a good cheap fuel. The railway charge
for the carriage of coke is a heavy burden. In South Wales,
where good coal is abundant and fair-quality coke is cheap,
brown hematite ores mined in the Forest of Dean are smelted,
as are also hematite ores from the north-west of England and
from Spanish ores. In the district of which Glasgow is the
commercial centre, a mixture of English and Spanish hematite
ores is smelted. The aluminous ores from the North of
Ireland are also used in the blast furnaces producing hematite
pig iron in Scotland and in the English hematite districts,
both of which are convenient to Ireland. At and near
Middlesbrough, adjoining the district where perhaps the
finest coke in the world is made, hematite ores from Spain
and from the north-west of England are smelted together.
It is also well situated for dealing with Swedish ores and the
Dunderland ores, which, as concentrated, are pure enough for
making the best quality of hematite pig iron.
The •Production of Pig Irons for use in Forges and
Foundries is a feature of those districts where clayband or
impure brown hematite ores exist. They are, of course, made
mostly from the local ores.
Basic Pig Iron, being even more highly phosphoric than
the foregoing, is made in or near localities in which puddling
* The phosphorus exists as phosphorus pentoxide (P205), or phosphoric
acid as it is more often called, in all iron ores and solid fuels.
[To face p. 180.
Reduced from a diagram in " Caseier'g Magazine.
IRON ORES. 181
is, or has been, a staple industry, because there puddlers'
cinder may be had cheaply and in abundance.
Ores used for Various Kinds of Pig Iron. — The purest
Swedish pig irons are smelted from pure magnetites, with
charcoal as fuel. Pig iron smelted from such ores, with such
pure fuel as charcoal, is remarkably low in both phosphorus
and sulphur.
Bessemer Pig Iron is made from hematite or other ores,
such as magnetites and Spanish carbonates, which are
low in phosphorus. The fuel and the flux require to be
carefully selected. Bessemer pig iron, or hematite pig iron as
it is also called, is used for the acid Bessemer and the acid
Siemens processes; and sometimes, although not always
judiciously, for superior castings. White hematite pig iron
is used for the manufacture of malleable castings.
Foundry and Forge Pig Irons are made from blackband,
clay band, and Cleveland ironstones. Phosphoric hematite
and other ores are also used.
All-mine Pig Irons are made from ores. Cinder pig irons
are made from a mixture of puddlers' tap (tap cinder) and
local ores.
Basic Pig Iron is made in Lincolnshire from ores obtained
in that county ; in other districts it is made from puddlers'
tap and clayband, Cleveland, or impure brown hematite ores,
and some manganese ore and mineral phosphates from abroad.
The proportion of puddlers' tap used is sometimes considerable ;
the ores used are mined or quarried not far from the works,
with the exception of the manganese ore, which is always
foreign.
182
CHAPTER XIX.
PREPARATION OF ORES FOR SMELTING.
SOME iron ores require preparation before being charged into
the blast furnace. The preliminary treatment may consist of
breaking or crushing lumpy ores to suitable size. Or, on the
oilier hand, the ores which are in pellets, or even in a finer
state of division, are, with advantage, pressed into blocks
or briquettes and "burnt," so that the fine ore will not
be so liable to be forced out of the blast furnace with the
exit gases, or be so likely to " gob " the furnace or derange the
working by hindering the free course of the gases. Many ores
are delivered with such a large proportion of " smalls " as to
cause trouble to managers and workmen.
Some poor ores are subjected to magnetic concentration.
Such ores are crushed to powder, and caused to fall in a fine
stream near to electro-magnets. The magnetic influence draws
aside nearly all the metallic portion, which falls into a truck
apart from the bulk of the gangue. The concentrated iron
oxide is then made into blocks in the manner described above.
Besides the breaking up, or the binding, of iron ores, other
treatment is sometimes called for. Some iron ores are so
firmly united in the mine to layers of shale that separation of
one from the other is difficult. By weathering — that is, by
exposing to atmospheric influences for a time — the shale may
be easily split off. Weathering may, to a slight extent, cause
the removal of sulphur from certain ores.
All ferrous ores are subjected to preliminary heat treatment
with access of plenty of air. This roasting process is known
in the trade as calcination or burning.
The effects of calcination are: —
The lower iron oxide (ferrous oxide) is changed into
the more highly oxidised ferric oxide, and, at the same
time, the oxide of manganese which is present combines
with more oxygen.
PREPARATION OF ORES FOR SMELTING.
183
Carbon dioxide is driven off.
Moisture is driven off.
Organic matter is driven off.
Carbon monoxide is occasionally given off in small
amount.
Sulphur may be driven off in perceptible amount,
especially if calcination is conducted slowly at a proper
temperature and with access of abundance of air.
The chief chemical changes may be represented by the
equations —
4FeCO,
0,
2Fe2Oa
4CO,
6MnC03 + 02
Manqanous \ ,
and ox^en
carbonate
2Mn304 + 6COa
( manganoso- } -, ( carbon
\ manganic oxide } and \ dioxide.
The chemical changes which take place may be further
traced in the following table : —
Chemical
Cleveland
Ironstone.
Constituents.
Formate.
Before
Calcination.
After
Calcination.
Ferrous oxide, . - . . ,v
FeO
35-00
Ferric oxide,
Fe203
5-55
58*43
Manganous oxide, . . /••. '-»'
Manganoso-manganic oxide,
Silica, ....
MnO
Mn304
Si02
0-41
10-97
6-56
14-33
Alumina, ....
A1203
10-22
13-34
Lime, . . . ' .'
CaO
4-84
6-37
Magnesia, .... ; , , ' ,,
MgO
3-50
4-55
Sulphur, .
S
0-25
0-81
Phosphoric acid,
Carbon dioxide,
PA
C02
1-25
18-01
1-67
Combined water, moisture, and
carbonaceous matter, . ' t .
...
10-10
...
Total, .' , v ' V
100-12
100*06
Metallic iron, . . . .
Fe
31-11
40-90
184 IRON AND STEEL MANUFACTURE.
Advantages of Calcination. — Peroxidised iron (ferric oxide)
works better in the furnace ; it does not enter into chemical
union with the silica in the ore and "scour" into the slag.
The driving off — outside the blast furnace — of the carbon
dioxide which is always present in ferrous ores prevents the
overpowering of the reducing gases which require to be in
excess in the blast furnace. The vast volume of gases which
issue from the blast furnace are increased in value, for power
purposes, by containing that lesser quantity of carbon dioxide.
In like manner the preliminary driving away of moisture is an
advantage. Calcined ores, being more porous, permit the
blast-furnace gases to more readily permeate them, and thus
the reducing action is hastened.
The shrinkage which takes place during calcination is a
double advantage. In the first place, a greater weight of ore
can be kept in the furnace, and there is produced an increased
weight of pig iron, per day, in consequence. And, in the
second place, the furnace works more smoothly than with an
ore which would shrink during an early stage of the smelting.
Brown hematite ores, which are ferric ores with combined
water, are sometimes " calcined " to drive off the water they
contain, as well as the carbonic acid which is often present.
Bed hematite ores are not subjected to calcination.
Calcination may be conducted in open heaps, in stalls, or in
kilns. To carry on calcination in open heaps a piece of
suitable ground is selected, a layer of small lumps of ore is laid
down, and some coal is placed over it. Then alternate layers,
or a mixture of ore with about 8 per cent, of coal slack, are
heaped up to a height of about 6 feet, so as to form a mound,
or heap, which may be of considerable length and breadth.
The dimensions differ in different districts, and the amount of
coal is varied to suit the nature of the ore and the conditions
of working. Owing to the heat generated by the further
oxidation of the ferrous and manganous oxides, it is not
necessary to use much fuel. Blackband ores contain more
combustible (bituminous) matter than is needed to compL-te
the calcination, the pieces are well burned, and, in many
instances, show signs of fusion.
The fuel is kindled at one end of the heap, and calcination
is allowed to proceed slowly, the " burning " of a heap occupy-
PREPARATION OP ORES FOR SMELTING. 185
ing a few weeks. Calcination in open heaps is primitive, is
wasteful of fuel, and the costs for handling are high. As
a compensation, much of the sulphur may be eliminated.
At Kilsyth, Scotland, the blackband ore is tipped into
heaps, each about 200 feet long, 68 feet wide, and about
8 feet high. Each heap or " hearth " holds about 3,000 tons
of raw ore. To start the burning, a coal fire along one end is
lighted, and the draught, is regulated to avoid sintering (the
fusing of the masses to each other), and the burning continues
for five or six weeks. The ore, before calcination, contains
34'1 per cent, of iron, and afterwards 55*5 per cent. The
ore shrinks to half its original bulk during calcination. Three
heaps are worked at the same time — one being filled, one
burning, and the other being emptied. Railway lines are laid
at a lower level for the trucks into which the calcined ore —
known in Scotland as " char " — is loaded.
Calcination in stalls is a more modern method. A series of
stalls consists of a long wall from which other walls project at
right angles, so that each compartment, or stall, has three
walls. Each stall is filled with raw ore and fuel, and the
remaining side, or rather front, is temporarily built up with
bricks or with lumps of ore. If of brick, air holes are left in
the front wall. The fuel is kindled, and calcination continues
as in the open heaps.
The raw ore may be conveniently delivered from trucks on
rails which are placed above the level of the tops of the stalls,
and the calcined ore delivered into trucks or barrows at a
lower level.
Calcination in stalls is under better control than in heaps, as
the air can be more easily regulated. The fuel consumed is
slightly less.
Calcination in kilns is a more convenient and economical
method than either of the foregoing. A calcining kiln is an
upright shaft furnace which is open at the top, and up which
a current of air passes when the kiln is at work. There is
neither forced draught nor a chimney.
The Scotch kiln is built of firebricks. The raw ore and the
fuel are charged at the top. A fire having been kindled in
the kiln at the commencement of a campaign, the fuel which
is charged with the ore in due course burns, and calcination
186
IRON AND STEEL MANUFACTURE.
goes on. The calcined ore is withdrawn, through openings
near the bottom, directly into trucks.
The inside dimensions of the kiln represented in fig. 79
are: — Height, 40 feet; diameter at widest part, 15 feet
6 inches, contracted to 8 feet 3 inches diameter at the top of
the cone which is fixed for directing the ore outwards.
The kiln delivers 40 tons of calcined ore per day, and the
fuel required is equal to 3 per cent, of the weight of raw ore.
,-J
Fig. 79.— Scotch Calcining
Kiln.
Fig. 80.— Gjer's Calcining
Kiln.
Gjer's kilns are cylindrical structures of firebrick, sheathed
in metal plates and set on short cast-iron columns. The ore
which is to be calcined is conveyed in trucks to the top, and
tipped, along with the necessary fuel, into the kiln. The air,
for maintaining the combustion of the fuel and peroxidising
the metallic oxides, has access by openings in the tapered part
of the kiln, and also by the openings between the upper and
lower parts of the hollow cone which is set centrally at the
PREPARATION OF ORES FOR SMELTING. 187
bottom. By having the central opening as arranged, dust,
from the crumbling of the ore, is not likely to interrupt the
smooth working of the kiln.
A kiln is about 24 feet in diameter, and is generally about
33 feet high. The consumption of fuel is low, 1 ton of small
coal sufficing for the calcination of 25 tons of raw Cleveland
ore. Other ores have been calcined with a smaller quantity of
fuel. The kiln works continuously.
The calcined ore is withdrawn through openings, into the
barrows in which it is taken to the top of the blast furnace.
188
CHAPTER XX.
THE BLAST FURNACE AND ITS EQUIPMENT.
THE blast furnace is a most compact and efficient erection
for cheaply and quickly treating large quantities of heavy
materials. In it iron ore is dealt with at a high temperature,
and the iron is extracted.
The solid materials charged into the blast furnace are —
(a) The ore from which the iron is to be extracted,
(b) The fuel required to carry on the work, and
(c) The flux, which, on uniting with impurities in the ore
and the fuel, causes the formation of fluid compounds.
These solids are delivered at the top of the furnace and in
due course descend. A strong air blast is injected near the
bottom of the furnace where the fuel is burned.
The products of the blast furnace are —
(a) The pig iron,
(6) Slag, and
(c) Gases,
and all three have a commercial value. They are each dealt
with in the next chapter.
Blast furnaces were formerly small, and were built of heavy
masonry, with a lining of fireclay blocks ; now they are tall
and comparatively slender in appearance. Formerly the
throats were open and gases were allowed to burn at the top.
Structurally, the modern blast furnace is a tall upright
cylinder, -sheathed in iron or mild steel plates, and having a
working lining of good firebricks. The blast furnaces in a
work are built in a row, each being as close to the others -as
convenient. Fig. 8 1 shows one of the ranges of blast furnaces
at Messrs. Bell Brothers' works, Port Clarence, Middlesbrough.
Near to the furnaces are grouped the arrangements for
190 IRON AND STEEL MANUFACTURE.
hoisting the raw materials ; the blowing engines for forcing,
and the stoves for heating,* the air blast ; pipes for conveying
the exit gases ; accommodation for the slag bogies or cars, and
space for casting, or machinery for conveying, the pig iron
which is produced.
Details of Structure. — The foundations for a large erection
for dealing with heavy materials must be good. Firm land
which can be easily drained must be selected, or expense will
be entailed in providing and driving in piles and making
the ground suitable. Extensive concrete foundations may be
put in. The firestones, blocks, or bricks which constitute the
base of the inner part of the furnace must be designed and
laid in such a manner as to resist any tendency to be pushed
directly upwards if the " metal " should unfortunately find a
way underneath. They are generally set so as to form a
shallow cavity, or an inverted arch, and are so placed that
pressure from beneath forces them more tightly together.
The main body of the blast furnace is carried on cast-iron
hollow columns surmounted by a lintel of heavy cast-iron or
steel plates. Not only does the lintel carry the brickwork, but
it also directly supports the casing of rivetted metal plates.
These latter sustain the weight of the platform at the top,
over which the charges for the furnace are wheeled in barrows.
Internally the furnace consists of the hearth, or well, of
brickwork at the bottom, which is built up from the founda-
tion to where it joins the brickwork of the next part — the
bosh, or working part. Above the bosh is the stack, or heat-
intercepting part.
Viewed from the top the stack expands in diameter. The
widening of the diameter makes allowance for the expansion
(due to heat) of the materials which are charged in from
the top of the furnace, and permits the " unpacking " of the
materials as they descend. The bosh contracts in diameter,
so that the materials which have gone down so far may be
held up until the fuel is burned away at or near the top of the
well, and the then melted pig iron and slag gradually drop
into the hearth, or well, where, by reason of difference of
density, the slag and pig iron separate from each other, and
* If the air supplied is heated before it is forced into the furnace a
large saving of fuel is effected.
Fig. 82. — Modern Iron-smelting Blast Furnace.*
A, Cylinder with
plunger.
B, Beam.
C, Cone.
D, Cup.
E, Uptake.
F, Outlet for gases.
G, Downtake or down-
comer.
H, Firebrick lining.
J, Iron plates.
K, Firebrick lining.
L, Dust-catcher.
M, Downtake from
dust-catcher.
N, Iron plates for
shell.
0, Lintel.
P, Iron columns.
Q, Horse-shoe main.
R, Goose neck.
S, Tuyere.
* Details from The Designing and Equipment oj Blast Furnaces, by
John L. Stevenson.
192 IRON AND STEEL MANUFACTURE.
are in due course each tapped out, in the fluid condition, from
the furnace.
The inner lining of the furnace is of good firebricks or
blocks. Bricks are now preferred to the large blocks which
were formerly favoured for furnace-building. True, they need
more setting and cementing, but bricks are more likely to be
thoroughly kiln-fired. Large blocks may be raw in the heart,
and cause trouble when the furnace becomes hot in course of
a campaign. Bricks of secondary quality are used to back the
bricks which constitute the lining. A space of 1 inch or more
is left between the bricks and the metal sheathing, so that the
structure may not be distorted when the brickwork gives way
slightly after starting the working of the furnace. The inter-
space may be partially filled with granulated slag.
The "Cup and Cone" is an arrangement for charging the
solids and distributing the charge in the furnace in the
manner best suited to the working conditions. The arrange-
ment keeps the throat of the furnace closed, except at the
instant* of charging in the materials, thus enabling most of the
blast-furnace gases to be collected. The "cup" consists of
iron castings, which, when bolted together and fixed in posi-
tion, complete a structure which is like the wider part of an
inverted hollow cone. The " cone " is also of iron castings
bolted together and finished to fit the lower edge of the cup.
It is suspended to one arm of a counterpoised beam. The
charge of solid materials is tipped from barrows into the
circular, tapered trough formed by the cup and cone. When
the beam is released the cone * descends, and the materials
slip into the furnace. The cone immediately rises, by the
weight of the counterpoise at the farther end of the beam, and
closes the " mouth " or " throat " of the furnace.
In order to avoid the jerking which would arise from the
sudden lowering and raising of the cone, a water cylinder with
a plunger and a curved connecting pipe is provided. A rod
from the plunger within the cylinder is fastened to the
weighted end of the beam. On being released, the beam end
cannot travel faster than permitted by the flow of water from
the upper- exit of the cylinder through the connecting pipe
(see top left part of fig. 82) to the lower part of the cylinder,
* Generally called the " bell" by blast-furnace men.
THE BLAST FURNACE AND ITS EQUIPMENT. 193
under the plunger. And when the cone begins to rise the
beam cannot move faster than allowed by the checked flow of
water up the connecting pipe to the top part of the cylinder —
above the plunger. The plunger cannot but move slowly and
smoothly. The water acts as a cushion, and a moderated and
steady lowering and raising of the " bell " is insured.
The diameter and the angle of the cone have a marked
effect on the working of the furnace to which it is fitted. It
is most important that it should be correctly designed, so as to
cause the charge to be spread in the furnace without the
lumpy portions of the charge accumulating either in the
centre or towards the lining of the furnace. A blast furnace
will not work smoothly unless the lumps are fairly well mixed
among the " smalls." If the cone is not wide enough, there
will be an accumulation of finer ore in the centre and of lumps
towards the sides of the furnace ; if it is too wide, lumps will
gather in the centre. In either case, the ascending gases,
which carry on much of the furnace work, will find easy
passage between the lumps ; and where the smalls are close
together there will be comparative stagnation and a tendency
to furnace derangement. Hence the great importance of a cup
and cone properly proportioned to the furnace and the ores,
&c., so that the lumps and the smalls will be well mixed
through each other when charged.
The air required to urge the fire within the furnace is forced
in through tuyeres which are, at regular intervals, let into the
furnace at an uniform level above the hearth. The work of
the furnace is carried on by the fuel and the products of com-
bustion. As the latter ascend they meet with, and impart
heat to, the descending solids. At the top, the gases are led
off from the furnace through an outlet, or outlets, into the
downcomer, and from thence into the culverts, which convey
them for further use.
The air supply is forced by powerful blowing engines
through the stoves in which the air is heated.* The hot air
from the hot-blast stoves is conveyed through a large brick-
lined iron pipe known as the hot-blast main. A short brick-
* Hot air is used in all iron-smelting blast furnaces except thoa»
producing cold-blast pig iron.
13
194 IRON AND STEEL MANUFACTURE.
lined pipe connects the hot-blast main with the horse-shoe
main. The horse-shoe main is a large brick-lined iron pipe
which almost entirely encircles the furnace. It is carried
on brackets which are bolted to the cast-iron columns at a
suitable height. Pipes called goose-necks descend at regular
intervals, and conduct the air supply from the horse-shoe main
to the tuyeres through which the air is directly forced into
the furnace.
As the hot-blast tuyeres (which are not brick lined like the
horse-shoe main, nor exposed to the air as are the goose-necks)
are constantly subjected to the heat of the furnace, means
Fig. 83.— Scotch Tuyere.
must be taken to prevent the melting of the iron of which
they are made, and no better method is known and practised
than that devised by Mr. Condie, a West of Scotland blast-
furnace manager, shortly after the hot blast was introduced by
James Beaumont Neilson. Condie's tuyere — known as the
Scotch tuyere — consists of a wrought-iron pipe, generally
about 1 inch diameter, formed into a tapering coil around
Fig. 84. — Staffordshire Tuyere. Fig. 85. — Lloyd's Spray Tuyere.
which melted pig iron has been moulded to the shape shown
in section in fig. 83. When the tuyere is in position a plentiful
supply of water is caused to flow through the coiled pipe. The
water carries off heat so quickly that the iron pipe cannot melt.
Other forms of tuyeres are the Staffordshire tuyere (fig. 84)
and Lloyd's spray tuyere (fig. 85).
THE BLAST FURNACE AND ITS EQUIPMENT. 195
In Foster's Patent Tuyere the water is drawn through the
cooling coil. This new method possesses distinct advantages.
In furnaces designed for a very large output the tuyeres
are made of bronze or of pure copper, and are surrounded
by a larger bronze " block tuyere" or "Jumbo." The water
blocks now so extensively used outside blast-furnace boshes
are often made of bronze.
Dimensions and Output. — An improved blast furnace be-
longing to Dud Dudley (17th century) produced 7 tons of pig
iron in one week. The output was deemed so excessive that
a riot ensued, and the new blowing arrangements were
destroyed ! A fully-equipped American blast furnace working
on easily reduced ores has produced on an average 500 tons
of pig iron per day. The present output is about 430 tons
per day.
A modern blast furnace of average capacity may be of the
following dimensions : —
Height of furnace, .
Diameter at throat,
,, top of bosh,
,, top of hearth,
Number of tuyeres,
Diameter of tuyeres,
Pressure of blast, .
Temperature of blast,
80 feet.
14 „
21 „
12 „
8 to 16.
up to 6 inches.
10 Ibs. per square inch.
1,400° F.
For regular working the angle or slope of the bosh should
be about 75°. Rapid working depends on the design of the
furnace, the blast supply, the nature of the burden, and other
points.
Furnaces of large capacity work economically. A tall
furnace does not require so much coke for the reduction of
ore as a shorter furnace does. But the height of a furnace
is limited by the frailty of the fuel — which is more easily
crushed than the other components of the charge. The
mechanical condition of the ore is also an important factor.
There is at the present time a tendency to abandon furnaces
of 100 feet in height in favour of 90 or 80 feet furnaces.
The diameter of a blast furnace must not be too great, or the
air blast will not be able to get near enough to the centre.
196 IRON AND STEEL MANUFACTURE.
Blowing engines consist essentially of large cylinders with
clack valves which respond to the movement of the piston
within — opening to admit air while the piston moves in one
direction, and closing when it moves in the opposite direction.
The air piston is worked from a steam engine, or, as in
many new installations, a gas engine. Air which enters the
cylinder is forced into the cold-blast main, which conducts
it under pressure either to the hot-blast stove, or directly to
the blast furnace.
The Stoves for preheating the air for use in the blast furnace
were originally like boilers and chests : they were made of
malleable iron plates, and afterwards of cast iron. These
remained in use till the introduction of cast-iron pipe stoves,
which are still employed in some works. By means of pipe
stoves air can be heated to a temperature of 1,000° P.,* and
maintained steadily at a temperature of about 800° F., at
which the limit of endurance of cast iron is reached. There
is also a danger of much leakage at the joints or sockets. A
great saving of fuel and a larger output of pig iron accom-
panied each increase of temperature arising from improvements
in the construction of the stoves.
Firebrick hot-blast stoves worked on the regenerative system
satisfactorily heat the blast to 1,400° F., and even up to 1,500°
F., and enable a still further saving of fuel to be effected, and
the pig iron output to be further increased.
Hot-blast Pipe Stoves are oblong chambers of brickwork
enclosing a range of cast-iron pipes, and they may be heated
either by a coal fire, or by gas from the blast furnaces. Two
pipes, with several sockets cast on at equal distances apart, are
laid horizontally along the chamber. Arched pipes are
arranged, each extending from one of these horizontal pipes to
the other, and having their ends carefully cemented in a socket
of each. Stops are placed at intervals in the horizontal pipes,
so as to cause the air, which is forced in at one end, to travel
successively from the first horizontal pipe to the others many
times. As the air travels through the pipes it becomes highly
heated and expanded.
* Many iron-masters believed that when the air was heated above
600° F. they were on dangerous ground.
THE BLAST FURNACE AND ITS EQUIPMENT.
197
There are several modifications in the design of such stoves.
In the pistol pipe stove the upright pipes are curved over at
the top, and an internal division extends nearly to the end of
the curved part, and causes the air to travel up and down the
same pipe. This arrangement reduces by half the number of
sockets. In the Swedish stove all the pipes are laid horizon-
tally, and the bends which unite them are jointed outside the
stove. Leakage at the joints can thus be detected at once,
and if a pipe is supposed to be cracked the jointings can be
undone, the pipe taken out and examined, and, if necessary,
renewed without much trouble.
A, Chimney.
B, Arched pipe.
C, Brickwork.
D, Socket for pipe.
E, Horizontal pipe.
F, Grate.
Fig. 86. —Cast-iron Hot-blast Stove.
The first firebrick hot-blast stove was designed by the late
Mr. Edward A. Cowper. Such stoves are heated by blast-
furnace, gas, and worked on the regenerative system as applied
in the Siemens furnace. A Cowper stove (like others of
modern design) is externally a tall, upright, cylindrical shell,
with dome-shaped roof, of mild-steel plates. The plates are
firmly rivetted together so as to form a gas-tight structure,
and a lining of firebrick is built within to protect the plates.
A firebrick .flame-flue or combustion chamber of elliptical
section, and approaching to the full height of the stove, is
constructed. Divisions are arranged at the lower part of the
198
IRON AND STEEL MANUFACTURE.
chamber to split the gas into sheets, so that speedy and com-
plete combustion is effected with little excess of air. Cowper's
stove is sketched in figs. 87 and 88 — the latter being on a
scale double that of the former.
A, Culvert for gases from
blast furnaces.
B, Blast-furnace gas
valve.
C, Air inlet.
D, Divisions.
E, Combustion chamber
or flame-flue.
F, Outlet for hot blast.
G, Hot-blast valve.
H, Iron or mild -steel
plates.
I, Firebrick lining.
J, Combustion chamber
or flame-flue.
L, Manhole.
M, Regenerative brick.
N, Grids.
0, Columns.
P, Chimney valve.
R, Culvert to chimney.
Fig. 87.— Cowper's Hot-blast Stove.
The remainder of the interior is filled in with firebricks, so
designed and laid as to form a number of hexagonal (six-sided)
passages, each extending from iron grids near the bottom of
the stove up to the level of the top of the combustion chamber.
The bricks which make up the "honeycomb filling" leave
passages of about 6 or 7 inches wide, separated from each
THE BLAST FURNACE AND ITS EQUIPMENT.
199
other by walls 2 inches thick. To minimise lodgment of dust
carried over in the blast-furnace gas, the inner corners are
slightly rounded and the topmost bricks are tapered. The
grids are carried on girders supported on short iron columns.
There are cleaning doors near the top and manholes near the
bottom, as well as one at the top of the dome. The stove is
Fig. 88.— Plan of Cowper's Hot-blast Stove.
A, Hot-blast pipe.
B, Hot-blast valve.
C, Combustion chamber or flame-
flue.
D, Regenerator (hexagon) bricks.
E, Inner firebrick lining.
F, Cold air inlet.
G, Chimney valve.
H, Iron or mild-steel plates.
J, Firebrick lining.
K, Columns and supports for grids.
L, Opening to regenerators.
N, Grids for supporting regenera-
tor bricks.
0, Brickwork lining for flame-flue
chamber.
set on a substantial foundation, and flues are arranged under-
ground for the conveyance of the blast-furnace gas, and for
taking off the spent gases to the chimney. Gas, air, and
chimney valves are provided, and will be better understood by
an examination of the sketches.
200 IRON AND STEEL MANUFACTURE.
Other forms of firebrick stoves are : —
The Whitwell,
The Massick & Crookes,
The Ford & Moncur, and
The Cowper-Kennedy.
They are all worked on the same principle as the Cowper
stove.
Working the Hot-blast Stoves. — Blast-furnace gas * is
admitted to the combustion chamber through the gas valve.
At the same time air is admitted through the adjoining air
valve. The combustion chamber being hot, ignition takes
place and a long tongue of flame shoots up the combustion
chamber. The hot products of combustion travel up the
flame-flue and down through the hexagonal passages, impart-
ing much heat to the brickwork before being drawn off
through the chimney valve to the tall stack by which they
escape into the atmosphere. When the bricks have thus been
heated sufficiently, the supply of gas and air is turned off and
the chimney valve is closed. Air, forced in by the blowing
engine, is now sent through the cold-blast valve into the
stove, and the air becoming heated by contact with the hot
brickwork while travelling up the passages and down the
combustion chamber, emerges through the hot-blast valve (at
a temperature of 1,500° F. to 1,100° F.) to the blast furnace.
When the stove has cooled down to the lower temperature
the open valves are closed and the closed ones opened for the
entrance of blast-furnace gas and air for reheating. Air is
forced through the neighbouring stove, which has been highly
heated in the interval. The stoves are worked in pairs or
double pairs, or in sets of three.
The current of gas from the blast furnace unavoidably
carries in dust which impairs the efficiency of the stove by
covering the regenerative brickwork with a coating which
does not readily transmit heat. As a consequence each stove
requires to be cleaned at intervals, or arrangements are made
for driving out the dust by the blast at each change of
the stove.
* See composition on p. 221-
THE BLAST FURNACE AND ITS EQUIPMENT. 201
The hoists or lifts by which materials are hoisted to the
top of the blast furnace may he either vertical or sloping, and
they may be worked by means of a winding engine driven
by steam, by pneumatic or by hydraulic pressure, or by a
water balance. The newest and best method is by means of
electricity.
For the vertical hoist with direct winding, a tower is built
with its top higher than the charging platform at the top of
the furnace. A wheel and axle surmounts the tower, and
over the wheel a rope passes, which is fastened at one end to
the movable platform or cage, while the other is attached to a
drum in the engine-house. When the drum is caused to
revolve, the rope is coiled round it, and the movable platform
or lift, with its laden barrows, is raised. On reversing the
direction of the revolving drum, the moving platform, with
the empty barrows, descends. Hoisting plant may be dupli-
cated, and arranged so that as one lift is raised the other
descends. In fig. 81 hoists are shown. In this instance they
are lattice-work structures with wheels at the top.
In the inclined hoist the track from the ground level to
the furnace tops generally slopes at an angle which is largely
determined by the space at disposal. The movable platform
— which, having one pair of wheels larger than the other,
remains level — is pulled up by means of cables.
For working the water-balance lift, water is steadily
pumped to a cistern at the top of the furnace. Two plat-
forms are worked together. Under the sole of each platform
there is a tank. Water is run into the tank of the movable
platform which is at the top, in quantity more than sufficient
to counterbalance the weight of the other platform and its
load. On being released the water-laden platform descends
and the other one is raised. The water is then run out of
the tank of the platform which is at the bottom. At the
same time water is allowed to flow into the tank of the
platform which is then at the top.
Within recent years there have been considerable develop-
ments in the equipment of blast furnaces. Water for cooling
is now plentifully supplied. There has been a liberal aug-
mentation of blowing and heating power. Charging is expe-
202 IRON AND STEEL MANUFACTURE.
ditiously performed by means of electrically-propelled skips
which quickly travel on aerial rails and discharge through
a rotating distributor into the furnace, the whole being
controlled by one man at the bottom. Costly machines for
" casting " the iron into pigs as it comes from the furnace, or
cranes for removing the pig iron from the sand beds and
' breaking and delivering into trucks, have also been provided.
Some modern appliances are described in the appendix
to this volume.
203
CHAPTER XXL
THE WORKING OF A BLAST FURNACE.
THE work done in a blast furnace is the extraction of iron
from ores and the production of pig iron, which is the crude,
impure form in which iron is tapped from the blast furnace.
As delivered at the blast furnace the ore contains —
(a) Iron and manganese.
(b) Oxygen in chemical union with these metals.
(c) Earthy impurities (the gangue) associated with the
metallic oxides.
(d) Moisture, which is soon vaporised in the blast
furnace, and escapes as steam in the exit gases.
It need not be more than mentioned, at this point, that the
ores contain the iron which is wanted, that the fuel supplies
the heat and the chemical energy needed, and that the func-
tion of the flux is to form, by combining with the gangue, a
slag basic enough to absorb most of the sulphur of the fuel and
ore, and fluid enough to flow from the furnace when tapped.
The ore and the flux make up the burden of the furnace;
the ore, flux, and fuel make up the charge. This statement
may be expressed thus : —
Fuel.
A certain number of charges — enough to fill the space at
the cup and cone — make up a round.
The smooth working of a furnace, and the character of the
pig iron produced, depend largely on the relative weight and
quality of the burden to the weight and quality of the fuel.
It is the fuel that " carries " the burden. If the ore and flux
204 IRON AND STEEL MANUFACTURE.
together are heavy, in proportion to the fuel, the furnace is
said to have a heavy burden. But if, on the other hand, the
ore and flux together are light, in proportion to the fuel, the
furnace is said to have a light burden. By increasing the
burden on a furnace the output may be increased, while less
fuel is required per ton of pig iron produced.
Fuel. — The subject of fuel is dealt with in Chapter xxiii.
But it may be noted here that the kind of fuel used in the
blast furnaces of a district depends on the local supplies,
or on the price at which fuel from another district can be
introduced.
Coal and Coke. — Where the coal is suitable for coking it
is coked, but if it is not of a coking nature it is used in the
" raw " state — that is, without being coked before charging.
Coke is preferred to coal for blast-furnace purposes. It yields
a more intense local heat, and is stronger than coal. Blast
furnaces which are to be coke-fed are built of a greater height
than those intended to be coal-fed.
Raw Coal is used in Scotland and in North Staffordshire.
In some South Staffordshire works both coal and coke are
charged ; in other districts in Britain coke is used almost
exclusively.
Other Fuels. — Charcoal, which is the purest of the solid
fuels, is much used in Sweden, because in that country coal
is not plentiful, and wood — which is converted into charcoal
by a process like coking — * can be profitably grown. Lignite,
or brown coal, which is abundant in some parts of Germany,
is used in some blast furnaces there. Anthracite has been
employed in some of the Welsh blast furnaces, is charged in
small quantities into a few English blast furnaces, and is
freely used in some American ones. It requires a strong
blast. In districts in process of being cleared for civilisation
wood has been used as fuel. The use of dried and compressed
peat has been proposed.
For composition of fuels see p. 226.
Flux. — For the purpose of providing lime to act as a flux
* Charcoal was prepared long before coal -was coked. The earliest
methods of making coke were clearly copied from the practice of
charcoal burning.
THE WORKING OF A BLAST FURNACE. 205
for the silica and alumina in the iron ore, &c., and which are
infusible at the blast-furnace temperature, limestone forms
part of most blast-furnace charges. The limestone contains
calcic carbonate (CaO, C02) and is soon calcined : the carbon
dioxide is liberated and escapes in the blast-furnace gases.
The lime (CaO) which is left enters into combination with
silica, forming calcic silicate, a compound the melting point
of which is below the temperature of the blast furnace. Com-
pound silicates melt still more easily, as explained on p. 229.
Some ores are self -going or self - fluxing ; in them the
proportions of silica and lime — which, when highly heated,
mutually combine with each other to form a compound which
becomes fluid at a high temperature — are (naturally) so pro-
portioned that addition of flux is unnecessary.
By judiciously mixing iron ores in proper proportions, a
self-fluxing burden may be charged into the furnace. A good
example of this practice is seen in the Fordingham district,
where the limey iron ores of North Lincolnshire are mixed
with the more siliceous iron ores of Mid-Lincolnshire. These
ores vary very widely in composition, but the following may
be taken as approximately representing the percentage of the
chief components : —
Chief Constituents.
Fordingham
Mid-
Lincolnshire
Ore.
Metallic iron,* .....
33
39
Metallic manganese,*
1-5
1
Silica and alumina, ....
11
22
19
4
It is customary to load up separately the ore from the
various well-marked layers of the quarry or mine, and to
stock each in a separate " drop " at the blast furnaces. From
these the ore is withdrawn in such quantities as will yield a
smooth-working mixture, thus utilising all the Fordingham
ores and guarding against the old erratic results.
* These exist in the ore in a highly-oxidised state.
206 IRON AND STEEL MANUFACTURE.
In making up a blast-furnace burden, as much suitable iron-
bearing material as possible should be used as can be had at
a reasonable price.
The work done in a blast furnace includes —
(a) Reduction of the iron and manganese compounds to the
metallic state, and
(b) Separation of the iron from the gangue.
Incidentally, the iron takes up carbon (C) from the fuel,
and silicon (Si), phosphorus (P), and sulphur (S), which have
been reduced from materials in the charge. The compound
of iron with these (and sometimes other) elements constitutes
pig iron. The term " cast iron," which is sometimes applied,
is confusing : cast iron is pig iron which has been cast into a
finished shape.
In a working blast furnace there are steady movements of
materials in opposite directions. The solid materials — the
ore, the fuel, and the flux — which are charged in at the top
of the furnace, descend gradually. These are met by an
ascending current of hot reducing gases which seek their
upward way between the pieces of descending materials. By
tracing, separately, each of these counter currents, an under-
standing of the working may be arrived at.
The Upward Current. — The air for the blast furnace is
forced by the blowing engines along the cold-blast main to
the hot-blast stoves, where it is heated. From the stoves the
hot air is sent through the hot-blast main, horse-shoe main,
goose-necks, and tuyeres into the furnace. In the furnace
the hot air is brought into contact with fuel which is already
glowing; the oxygen of the air enters into chemical union
with the combustible elements of the fuel and creates a very
high temperature. The chemical action of oxygen on excess
of incandescent fuel produces carbon monoxide, as explained
on p. 209.
Carbon monoxide, being eager for more oxygen, takes it
from those descending oxides which part most easily with it.
This transferring of oxygen is known as reduction, and the
substance which parts with its oxygen is said to be reduced.
THE WORKING OF A BLAST FURNACE. 207
Oxide of iron is readily reduced to metallic iron by the action
of hot carbon monoxide and other reducing gases in the
ascending current. The up-going gases not only perform
the chemical duty of reducing the ore, but they impart much
heat to the solids which are on their way down. On reaching
the top of the furnace the gases are taken off through one
or more openings into the downtake, or "downcomer," or
"bustle pipe," and set to do more useful work. When the
gases are quite spent they are led off by the chimney into
the air.
The Course of the Solid Materials in the Blast Furnace.—
The ore, fuel, and flux are conveyed by barrows to a weighing
machine, and are then hoisted to the platform at the top
of the furnace. The contents of the barrows are tipped
into the circular hollow formed by the cup and cone. The
" fillers," as the men at the top of the furnace are called,
withdraw to a safe distance and lower the cone, thereby
charging and spreading the materials in the furnace. The
cone is then raised into position, and thus the mouth of the
furnace is closed and the further escape of gases — which
occurred during the momentary lowering of the cone — is
prevented.
The solids are soon acted on by the hot reducing gases,
but it is not until the hottest zone of the furnace is reached
that the reduction and separation are completed.
Provision is made in the design of the blast furnace for the
expansion due to the heating of the descending materials.
When a certain point is reached, however, a diminution occurs
— fuel is burned and the pig iron and slag become molten
and drop down into the well of the furnace. There the pig
iron and slag separate from each other because of the differ-
ence of density. Slag, being lighter, floats on the top of the
pig iron and is tapped off as often as required. The pig iron
is tapped from the furnace every twelve, eight, or six hours,
and even more frequently in some instances.
The pig iron as it is tapped from the furnace may be
allowed to flow into the recesses previously moulded in sand
in the slightly sloping terrace in front of the blast furnace,
which is known as the " pig bed." The pig iron flows down
208
IRON AND STEEL MANUFACTURE.
the runner — which is a channel in the sand traversing nearly
the entire length of the pig bed — into the moulded cross
channels which are known as the " sows," and from the sows
into the " pig " moulds which are again at right angles.
Each " pig " is about a yard long and weighs over 1 cwt.
As the molten pig iron comes from the furnace it is
allowed to flow to the end of the runner and along the lowest
sow" into the connected
" pig " moulds.
\AThen these are
Fig. 89. — Pig Beds in front of Blast Furnace.
filled with fluid pig iron the runner is blocked below the next
sow and a way is made for the metal to flow along the sow
into the next row of pigs. Thus, one by one the rows receive
the pig iron until the " cast " is finished ; that is, until all the
iron obtainable at that time from the hearth has run out
(fig. 89), Steps may be taken to hasten the cooling of the
pigs, which, when sufficiently solidified, are broken off from
the sows, and the sows from the runners. These are broken
THE WORKING OF A BLAST FURNACE. 209
into useful sizes. In due course all the pig iron is lifted and
conveyed to trucks.
In some other countries it is customary to " cast " the pig
iron under cover.
From a mechanical point of view, sand is a suitable sub-
stance in which to cast pig iron ; from a chemical standpoint,
it is one of the worst materials known. Various other
substances have been suggested and some have been tried,
such as coke dust and fine ore. In Sweden, heavy cast-iron
troughs or trays are extensively used as moulds for pig iron,
with good results.
In a blast furnace which is making pig iron, all, or nearly
all, the iron is reduced ; the proportion of manganese and of
silicon reduced will depend on the conditions prevailing in the
furnace, and the conditions will decidedly influence the amount
of carbon and sulphur in the pig iron produced. With very
few exceptions nearly all the phosphorus compounds in the ore,
fuel, and flux are decomposed, all but a little of the phosphorus
going into the pig iron.
Of the descending materials m a working blast furnace all that
retain their oxygen go into the slag, and (with the exception of some
sulphur which is collected in the slag) all that are reduced go into
the pig iron.
The chemical work of a blast furnace is effected by a
strongly reducing action.
The chemical reactions which take place are : —
Carbon, when burned in a blast furnace, forms carbon
monoxide (CO). This is believed to be effected in two stages.
Firstly, carbon dioxide (CO,,) is formed —
C + 02 C02
Carbon and oxygen yield carbon dioxide
and then the dioxide is converted by the excess of glowing
carbon into carbon monoxide, thus —
CO2 + C 2CO
Carbon dioxide and carbon yield carbon monoxide.
In the course of his extensive investigations on blast-furnace
eases the author has been unable to find carbon dioxide in the
14
210 IRON AND STEEL MANUFACTUEE.
gases drawn off from the hearth. But whether carbon dioxide
is formed in the first instance, or the monoxide is formed
directly, there can be no difference in the chemical or the
thermal effects.
Although there is reason to believe that the cyanides which
are present in the gases in the lower regions of the blast
furnace exert influence in carrying on reduction, and that
hydrogen must have a notable effect, the chief agent in
carrying on reduction must be either hot carbon or carbon
monoxide, both of which are present in large quantities. The
action of the latter may be represented by the following
chemical equations : —
Reduction of ferric oxide —
+ SCO = 2Fe + 3C02
and -f carbon \ vield iron and I c?rbon
[ monoxide f y ( dioxide.
Reduction of manganese oxide —
Mn3O4 + 4CO = 3Mn + 4C02
Manganese oxide and | J^^l Vidd
Reduction of phosphorus pentoxide (often called phosphoric
acid) —
P205 + SCO 2P + 5C02
Phosphoric acid and h *** P^orus ^ {
Reduction of ferric oxide takes place in the upper region of
the stack, but is not completed till the still unreduced portions
of the ore reach the bosh.
The composition of the gases from charcoal-fed and coke-fed
blast furnaces proves that oxidation of carbon or carbon
monoxide to carbon dioxide takes place.
Carbon Impregnation. — Hot iron can decompose carbon
monoxide, thus —
2CO = C + C02.
The carbon so liberated enters into combination with, or
deposits carbon on, the spongy pig iron.
It has been experimentally proved that, on a small scale,
THE WORKING OF A BLAST FURNACE. 211
carbon monoxide cannot reduce silica. We may therefore
represent it as being directly reduced by carbon, thus —
Si02 + 2C Si + 2CO
Silica and carbon yield silicon and carbon •tuon.n.rlde.
It is not safe, however, to assume that reactions on the
small scale are the same as those which take place on a
large scale.
In the formation of slags chemical union takes place
between the lime of the flux and some of the silica of the
ore or the ash of the fuel, and the reaction may be represented
thus —
2CaO + Si02 = 2CaO . Si02
Lime and silica yield silicate of lime.
Any free alumina which may be present would also combine
with silica, and the reaction may be stated thus —
2A1203 + 3Si02 = 2A1203 . 3Si02
Alumina and silica yield silicate of alumina.
The silicates of lime and alumina unite to form a compound
silicate. Some blast-furnace slags have a composition which
can be summed in the formula —
2A1203, 3Si02 + 6(2CaO, Si02).
Calculation shows such a slag to consist of —
Silica (Si02), . . 3 8" 14 per cent.
Alumina (AlgOj), . . 14-41
Lime (CaO), . . 47'45 „
Other oxides are present in the slags, notably oxide of man-
ganese (MnO) and magnesic oxide or magnesia (MgO). These
replace, as far as they can, the lime : being bases they can
combine with silica. Very rarely blast-furnace slags are
produced which contain no lime.
When a furnace is working on a light burden the slag
produced is generally white or grey; when the burden is
heavy a dark coloured or black slag is usually produced.
Such dark or black slags contain ferrous oxide (FeO) which,
212 IRON AND STEEL MANUFACTURE.
when in combination with silica, forms a very fluid com-
pound at the blast-furnace temperature. These black, ferrous,
scouring slags are very severe on the furnace lining. Slags
containing manganese in notable amount may be brown
or yellow coloured. Portions which contain manganese and
much silica are green coloured. If much lime is present the
slag may have a cold, stony appearance, while presence of
much alumina is usually shown by the opalescent character
of the slag.
Quickly-cooled slags are glassy and present a shell-like
(conchoidal) fracture, but if cooled slowly the same slag may
be dull in appearance.
Disposal of Blast-furnace Slag. — The slag issues from the
furnace in the fluid condition, and is allowed to flow into iron
tubs or ladles which are set on trucks or trolleys. It may be
(a) applied to useful purpose, or (b) be tipped on heaps and
encumber the ground, or (c) be granulated and carried away
by rivers, or (d) be conveyed to sea on barges and tipped into
deep water.
Of late years a considerable quantity of blast-furnace slag
has been granulated in water and made into cement or bricks.
Slag wool is also made, and large quantities of slag are used
for road making and mending and for " ballast " between
railway sleepers. In some iron-making districts the whole of
the slag is utilised.
Slag intended to be tipped on heaps may either be allowed
to solidify in the large ladle in which it is caught and the
" ball " tipped on the slag hill, or as soon as the ladle is full
it may be taken to the top of the slag hill and the contents
poured out there.
On the European continent it is customary in some works
to permit the slag to trickle to the nearest river. Contact
with the water into which it flows has the immediate effect
of breaking it up into grains, and these are carried away by
the current.
213
CHAPTER XXII.
THE PRODUCTS OP THE BLAST FURNACE.
THE chief aim of the blast-furnace manager is the production
of good pig iron at the lowest possible cost. In recent times
the value of the bye-products — gas and slag — have received
a considerable amount of attention.
Pig Iron. — The purpose for which a lot of pig iron is best
suited, and the price it will command, is largely determined
by the percentage of phosphorus which it contains. It has
already been pointed out that, with few exceptions, almost all
the phosphorus in the blast-furnace charge goes into the pig
iron. Hence, it follows, that in order to regulate the amount
of that element in the pig iron which is to be produced, the
charge must be carefully selected. If pig iron with a small
percentage of phosphorus is required, care must be taken to
exclude ore, fuel, and flux which contain more than a little of
that element — for unfortunately none of these are quite free
from phosphorus, and the total amount may irretrievably injure
the quality of the pig iron. On the other hand, some classes
of pig iron, such as that used in the basic Bessemer process,
must contain a decided amount of phosphorus, and, within a
limit which is seldom if ever exceeded, more phosphorus is
desirable. In 'a lesser, but essential, degree phosphorus is
necessary in foundry pig iron.
The following may be taken as representating, in round
numbers, the composition of certain pig irons : —
Constituents.
Swedish.
Bessemer.
Foundry.
Forge.
Cleveland.
Basic.
Graphitic carbon,
2-00
3-30
2-75
2-00
3-20
0-50
Combined carbon,
2-00
0-50
0-75
1-00
0-50
2-80
Silicon,
1 "20
2-20
2-00
1-00
2-60
0-50
Phosphorus, . 0'03
0-05
0'90 1'30
1-60
3-00
Sulphur,
o-oi
0-04
0-09
o-io
0-08
0-07
Manganese,
3-00
0-50
0-60
0-50
0-60
2-00
Iron, .
91-76
93-41
93-41
94-10
91-42
91-13
214 IRON AND STEEL MANUFACTURE.
Analyses of grades of certain classes of pig iron will be
found on p. 241.
By giving attention to the temperature of the blast furnace
and the condition (whether basic or otherwise) of the slag, the
percentage of silicon, of carbon, and of manganese may be
regulated fairly well.
The best system for producing pig iron containing only a
small percentage of sulphur is to carefully select raw materials
which contain a low percentage of sulphur. This, however,
involves a high cost, and recourse must be had to means and
conditions which will cause much of the sulphur either to go
off in the gases or go into the slag. The latter is the less
objectionable method. A furnace which is working hot and
with abundance of lime in the burden is not so likely to yield
a sulphury pig iron, but if the furnace is comparatively cold
and the slag produced is deficient in lime, a pig iron high in
sulphur will result.
Carbon exists in pig iron in two states at least (a) as
combined carbon, and (b) as graphitic carbon. In the latter
condition the carbon is not in chemical union with any other
element : it exists in the free state, and at times in flakes so
large and so loose that they may be detached.
The percentage of carbon in the pig iron produced depends
very much on the quantity and quality of the fuel. Apart
from other conditions, a furnace which is hot and supplied
liberally with fuel is likely to contain much carbon, especially
graphitic carbon ; and the high temperature and the surplus
energy which that implies, having an active reducing effect,
tends to the production of pig iron rich in silicon.
In " finishing materials " such as ferro-silicon, in which
silicon predominates, the carbon is not plentiful, and it exists
chiefly in the graphitic state. Manganese acts differently •
where there is much manganese — unless it is interfered with
by silicon — the percentage of combined carbon is higher than
in ordinary pig irons. A comparison of the analyses on
pp. 237 and 238 shows clearly these differences.
For the production of a pig iron containing a high
percentage of silicon, the proper blast-furnace conditions
are: —
THE PRODUCTS OF THE BLAST FURNACE. 215
(a) Presence of Plenty of Siliceous Matter, especially such
as can be easily reduced. Certain ores are prone to yield
highly siliceous pig iron, even if the percentage of silicon
in the ore is not great.
(b) A High Temperature, which means plenty of spare
energy in the furnace to cause the reduction of much
silica (Si02) to silicon (Si).
(c) The Furnace working slowly. — This condition allows
more time for the reduction to be effected.
(d) Not too much Lime in the Burden. — If there is
plenty of lime present the silica will combine with it
and be carried into the slag, but if lime is comparatively
scarce the free silica will be left more open to reducing
influence.
There is no intention to suggest that all the above condi-
tions will exist at the same time, but each one tends to the
production of siliceous pig iron. Contrary conditions will
result in the production of a pig iron in which the content of
silicon will be comparatively low.
For the production of a pig iron with much manganese in
it, it is necessary to have —
(a) A large amount of manganese in the blast-furnace
charge.
(b) A high temperature : manganese oxide in quantity
is more difficult to reduce than iron oxide.
(c) Presence of abundance of lime in the charge.
Lime, being basic, will combine with the free silica, and
the silica being thus satisfied will not so readily combine
with the (basic) oxide of manganese of the ore.
The blast-furnace conditions may be briefly summarised
thus : —
To produce a pig iron
Fuel should be
Lime should be
High
5?
Low
in carbon, .
silicon, .
manganese, .
in sulphur, .
Abundant.
»>
M
Not too plentiful.
Abundant.
}>
216
IRON AND STEEL MANUFACTURE.
Grey and White Pig Iron. — A blast furnace which is
working on a light burden (see p. 203), or at a high tempera-
ture, produces, as a rule, grey pig iron; that is, pig iron which
contains much carbon and silicon — the silicon, as usual, causing
much of the carbon to pass into the graphitic state.
On the other hand, a blast furnace which is working on a
heavy burden, or at a comparatively low temperature, generally
produces a white pig iron; that is, a pig iron containing less
carbon and silicon, and in which most of the carbon is
chemically combined with the iron.
Mottled pig iron is intermediate in composition, and may
be looked on as an intimate mixture of the two kinds.
Grey pig iron has a higher melting point than white pig
iron ; in other words, it requires a higher temperature to melt
the grey variety. When melted, grey pig iron is more fluid
than white pig iron. Melted grey pig iron expands just
before solidifying. This enables it to take a sharp impression
when cast in a mould, hence it is most suitable for fine
castings. White pig iron does not so expand before be-
ginning to solidify. During melting and cooling, white pig
iron passes through a pasty stage which is favourable for
puddling.
The chief characteristics of grey and white pig iron from an
ordinary blast furnace burden for foundry or forge iron may
be conveniently summarised and compared thus : —
GREY PIG IRON.
Contains much carbon.
Most of the carbon is in the
graphitic state.
Contains a high percentage of
silicon.
Contains much manganese.
Contains little sulphur.
Average specific gravity about
71.
Is large-grained (open-grained),
grey, soft, and tough.
WHITE PIG IRON.
Most of the carbon is combined.
Does not contain so much silicon.
Does not contain so much man-
Contains more sulphur.
Average specific gravity about
7*5.
Is fine-grained (close-grained),
white, hard, and brittle.
THE PRODUCTS OF THE BLAST FURNACE. 217
GREY PIG IRON. WHITE PIG IRON.
Melting point, about 1,400° C.
Is more fluid when melted than
is white iron.
Expands just before solidifying.
Melting point, about 1,300° C.
Is not so fluid when melted as
grey iron is.
Passes into a pasty condition
when below its melting point.
It must be distinctly understood that the above table shows
the characteristics of average pig iron of each kind. There
are exceptions. The physical condition and appearance
(which may not inaptly be called the texture) of a pig iron—
whether grey, mottled, or white — are affected by its chemical
composition, the rate at which it has been cooled, and by
other circumstances. The appearance of the fracture is not a
safe guide in grading pig irons. The grading should be
arranged according to analyses. Sometimes the grey pig iron
from a blast furnace actually contains less silicon than a white
pig iron from the same or a previous cast. A blast furnace
working smoothly on a proper burden is not so likely to
produce such abnormal pig irons, but if a "slip" has occurred
the pig iron may easily show a deceptive fracture. Swedish
pig iron, which is "chilled" by being cast in thick iron
moulds, is white on the under part of the plate (or pig), while
the upper part of the same pig iron is grey. The bottom
part is hard, the upper part is soft. The percentage of silicon
is nearly the same in each part, but in the lower portion the
combined carbon predominates. In the upper part the carbon
is mostly in the form of graphite in fine grains — not in scales,
as one finds it in grey pig iron which has been cast in sand.
Grading of Pig Irons.— It is customary to call the richest
grey pig iron "No. 1." It is the dearest of its class, and
rightly so, since, on account of the greater consumption of
fuel used in its production, it costs more. Pig iron which is
less grey is called No. 2, and so the grading goes on through
the mottled pig iron to the whitest of all.
Staffordshire part mine pig iron — which is made chiefly
from North Staffordshire ore, Northampton ore, and a little
flue cinder — is generally graded as mine foundry No. 1, mine
foundry No. 2. mine foundry No. 3, grey forge, forge, strong
forge, mottled, and white. Cinder foundry pig iron is generally
218
IRON AND STEEL MANUFACTURE.
sold in mixed numbers 1, 2, and 3. Very rarely cinder No. 1
pig iron is ordered,
mottled, and white.
Other cinder pig irons are cinder forge,
Fig. 90.— Fracture of Grey
Pig Iron.
Fig. 91.— Fracture of Mottled
Pig Iron.
Fig. 92.— Fracture of White
Pig Iron.
Fig. 93.— Fracture of Pig Iron,
White at Bottom, Grey at Top.
THE PRODUCTS OP THE BLAST FURNACE. 219
In Scotland it is usual to grade pig irons as No. 1, No. 3,
No. 4, mottled, and white. Some makers quote No. 2, and
all will select it when wanted. Several ironmasters have
their own manner of grading. One grades thus: — No. 1,
No. 3, No. 3 hard, No. 4, mottled, and white. Another
one grades No. 1, No 3 special, No. 3 soft, No. 3 foundry,
No. 3 close, and No. 3 hard. Lots which are sold under the
Scotch pig-iron warrant system as Gr.M.B. are made up in the
proportion of three-fifths of No. 1 and two-fifths of No. 3.
The grading of pig iron in the United States is complicated.
Thirteen grades have been mentioned and nine grades are
well-known, viz. : — Silver grey, No. 1 soft, No. 2 soft, No. 1
foundry, No. 2 foundry, No. 3 foundry, grey forge, mottled,
and white. It has been suggested that the following six
grades should suffice : — Silvery iron, soft iron, foundry iron,
grey forge, mottled, and white. The practice of purchasing
pig iron by analysis has established itself in the States, and is
finding extensive acceptance. Other considerations must,
however, count as well as composition.
SLAGS. — The slag from a blast furnace which is smelting
iron ores is made up of the gangue, the fixed constituents of
the flux, and the ash of the fuel. All the gangue, except the
portion which is reduced, goes into the slag. The fixed con-
stituents of the flux includes all except carbon dioxide, organic
matter, and water.
The quantity of slag will depend chiefly on the amount and
the nature of the gangue. Ores which contain much gangue
requiring plentiful addition of flux will, of course, yield more
slag than ore or ores containing a comparatively small quantity
of self-fluxing gangue. Self-fluxing gangue consists of silica
and bases in such relative proportions that no addition of flux
is necessary to produce a mixture, or slag, which can readily be
melted at the working temperature of the blast furnace. The
amount of slag produced varies widely. It has been stated as
between 10 cwts. and 35 cwts. per ton of pig iron produced.
Slags from blast furnaces which are producing white pig
iron, contain, as a rule, more silica than a neighbouring
furnace which is producing grey pig iron. This is quite
natural. There has not been such an abundant reduction of
220
IRON AND STEEL MANUFACTURE.
silica during the making of white pig iron, therefore more
silica must be left free to go into the slag.
The following are approximate analyses of average slags : —
Constituents.
Chemical
Formulae.
From
Clayband
Ores.
From
Cleveland
Ores.
From
Mixed
Hematite
Ores.
Silica,
Si02
36
28
34
Alumina, ....
Lime, .....
^
16
42
22
40
13
51
Magnesia,
Manganous oxide,
Ferrous oxide,
Sulphur,
MgO
MnO
FeO
s
4
1
) i
7
0-2
0-8
1
1
Alkalies, &c.,
Calcic sulphide, .
CaS
I '
2
...
L __
100
100-0
100
GASES. — A working blast furnace emits an enormous volume
of gases. William Jones stated* that the gases from the
Scotch (coal-fed) blastfurnaces averaged over 230,000 cubic
feet at the temperature (500° F.) at which they left the blast
furnace. James Biley considered f that the volume of gas,
measured at ordinary temperature and pressure, from 1 ton
of coal measured 130,000 cubic feet, while from 1 ton of coke
the gases measured 180,000 cubic feet under like conditions.
The weight of the gases, per ton of pig iron produced, is
about 7 tons.
The gases from the blast furnace were called " waste gases,"
and the term was quite correct at one time. Now that, after
discharging fully their duties in the blast furnace, they perform
much useful work, the term surplus gas would be more
accurate, but the generally accepted name — blast-furnace gas
— is sufficient. Because of the presence of certain constituents,
the surplus gas is strongly reducing. An excess of powerfully
reducing gases must be present in the surplus gas or the work
of the blast furnace could not be carried on. Now, those
* Iron and Steel Institute Journal, 1885, ii., p. 412.
d., 1898, i., p. 33.
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THE PRODUCTS OF THE BLAST FURNACE.
221
constituents which have reducing power are capable of com-
bining rapidly with oxygen and evolving much heat. Blast-
furnace gas is therefore carefully collected and utilised for
heat-raising and steam-raising.
The following may be noted as fairly representative analyses
of blast-furnace gases : —
Constituents.
Chemical
Formulae.
From
Charcoal -
fed
Furnace.
From
Coke-fed
Furnace.
From
Coal-fed
Furnace.
Reducing gases —
Carbon monoxide,
CO
25
28-00
28-0
Hydrogen,
Methane or marsh gas,
H0
CH4
4
1
1-00
0-25
5-5
45
Total combustible gases,
30
29-25
38-0
Inert or neutral gases —
Carbon dioxide,*
COo
12
15-00
8-6
Nitrogen, ....
N2
58
55-75
53-4
100
100-00
100-0
Steam-raising by means of surplus blast-furnace gas may
be carried on by burning the gas with a regulated amount
of air in a "front" or grate and combustion tube of an
ordinary boiler, or by the well-known Babcock & Wilcox
boilers compactly enclosed. RS shown in the opposite
illustration.
But the tendency of the times is to utilise the gas by
generating power direct in a gas engine rather than by
means of steam. Increased power (perhaps three or four
times as much) may be obtained by means of the gas
engine.
The gases from many (indeed nearly all) coal-fed blast
furnaces are condensed and scrubbed so as to recover the
ammonia, tar, and oils from them. The scrubbed gases are
used for heat-raising and other purposes.
* Under certain conditions carbon dioxide acts as an oxidising gas.
222
IRON AND STEEL MANUFACTURE.
At one work the blast-furnace gas
Distils the tar and ammonia liquor,
Heats the hot-blast stoves,
Provides steam for the whole works,
Melts the steel in the steel foundry,
Heats the core stoves for three large foundries,
Burns the ore briquettes in 12 -chamber kilns,
Distils the coal for the gas works supplying the
village,
Supplies fuel for an enamel brickwork a mile
away, &c.
Fig. 94. — Front of Boilers Fired with Blast-furnace Gaa.
THE PRODUCTS OF THE BLAST FURNACE.
223
Fig. 95. — Sketch Showing Section of Arrangement for Utilising
Blast-furnace Gas for Steam Raising.
Fig. 96.— Engine Worked by Blast-furnace Gas.
224
CHAPTER XXIII.
NOTES ON FUELS, FLUXES, REFRACTORY
MATERIALS, &c.
FUEL is "anything that feeds a fire." A substance to be of
service as a fuel must be capable of burning rapidly, and of
giving forth much heat while burning. Cheap fuel is an
important point in connection with manufactures.
Burning results from the kindling of inflammable material
where air* in proper quantity has free access, and combustion
is continued by the chemical combination of oxygen with the
fuel. Slow combustion (breathing, decay, &c.), on the one
hand, and the very rapid combination causing explosion or
conflagration, on the other hand, do not come within the
present scope.
The chief components of solid fuel are : —
Carbon.
Hydrogen.
Compounds of carbon and hydrogen.
Oxygen.
Nitrogen.
Ash.
The three tirst are of service because they can combine with
oxygen and yield much heat : the remaining three are worse
than useless from a heat-raising point of view — they contri-
bute nothing, but are heated by the burning of the other
constituents.
The following simple experiment may help to make clear
how the components of a solid fuel act when heated : — Into a
small crucible put 2 grammes of powdered coal. Cover with
a lid, and apply heat from a Bunsen burner or other smokeless
flame to the bottom part of the crucible. In the course of two
* Air contains about one-fifth of its volume of the active gas called
oxygen.
NOTES ON FUELS, FLUXES, ETC. 225
or three minutes take off the lid and examine its under part.
Globules of water should be seen. If not, the experiment has
been hurried by too hot a flame, or has not been continued
long enough. After a trial or two the correct conditions will
be found. Replace the lid, increase the heat, or set the
crucible further down into the tip of the flame, and allow to
remain for some time. Smoke will issue from the crucible,
and shortly afterwards a flame will appear round the edge of
the lid, showing clearly that an inflammable gas is 'being
driven off from the coal by heat. Continue the heating for
an hour before removing from over the flame. When the
crucible has become cold, examine the contents, which should
consist of a black substance either in powder or caked together
(coke), and which has not been burned away even on the
application of prolonged heat. Weigh the contents and re-
place in the crucible. Then, with the lid off, continue the
heating. The mass in the crucible will glow, and after a time
a white or coloured residue (ash) will be left. Heat and air
do not affect it. When cool, weigh the ash.
The experiment shows that the coal contained —
(a) Water.
(b) Matter which was driven off (volatilised) by
heat, and, on coming into contact with air, could easily
be burned. From other experiments these are known
to be hydrocarbons (which are compounds of carbon and
hydrogen) and other gases.
(c) Matter (fixed carbon) which could only be burned
by heating, with excess of air ; and
(d) A residue (ash) which could not be burned off.
Heat Value. — When 1 Ib. of carbon enters into chemical
union with enough oxygen to form carbon dioxide (C02),
sufficient heat is generated to raise 8,080 Ibs. of water 1° on
the Centigrade thermometer, or 8,080 Centigrade heat units.
But if the 1 Ib. of carbon cannot have more than enough
oxygen to form carbon monoxide (CO), the heat generated
is only equal to 2,400 heat units.* On further oxidation of
the resulting 2J units of carbon monoxide (CO) into carbon
dioxide (C02) another 5,600 heat units are generated.
*"Heat units" are also known by the terms "calorific power"
(Latin, color = heat) or "calorific value."
15
226
IRON AND STEEL MANUFACTURE.
When 1 Ib. of carbon is fully burned, 3f Ibs. of carbon
dioxide are formed and about 11 Ibs. of nitrogen accom-
pany the necessary oxygen, making about 13-j- Ibs. in all.
Beyond the oxygen (and nitrogen) stated, an excess of air is
necessary in practice. All these gases are heated to the
temperature of the furnace, and thus a great deal of heat is
carried away up the chimney. A " draught " is created
thereby.
The heat value, or calorific power, of hydrogen is 34,000
when oxidised under favourable experimental conditions to
form water, the chemical formula of which is H20 — a formula
which indicates that two atoms of hydrogen have entered into
chemical union with one atom of oxygen. But in practice the
water is converted into steam — which is H20 in the gaseous
state. That conversion requires such an expenditure of
energy (or heat) that less than 29,000 heat units are left
over. Every pound of hydrogen when burned combines with
8 Ibs. of oxygen to form 9 Ibs. of steam. Owing to the large
quantity of steam formed and to the capacity of steam for
carrying off heat, the surplus heat derived is not so large as
from the burning of 1 Ib. of carbon.
The composition of solid fuels varies considerably, but an
idea of their composition may be gathered from the following
table : —
NATURAL FUELS.
PREPARED FUELS.
Wood.
Bitu-
minous
Coal.
Anthra-
cite.
Charcoal.
Coke.
Fixed Carbon,
Hydrocarbons, Ac.,
Ash,
Water, .
Sulphur in the ash,
25
52
22
56
33
5
6
82
10
6
2
92
1
4
3
87
2
8
3
,00
100
100
100
100
,
1
...
1
NOTES ON FUELS, FLUXES, ETC. 227
Coals may be classified thus —
1. Bituminous coal.
(a) Caking, or coking.
(b) Non-caking.
2. Anthracite.
Bituminous coals may burn either with a long or a short
flame. The long-flame coal is useful for reverberatory fur-
naces. Anthracite does not produce much flame when burning.
Our coal deposits were formed from plants, and it may be
instructive to briefly consider their formation. To begin
with, plants, when in life, decompose carbon dioxide (C02),
giving back oxygen to the air while retaining the carbon.
They also absorb water (H20). From carbon and water they
build up cellulose or woody fibre, the composition of which is
C6H1005 or C6(H20)5. In a byegone geological period im-
mense forests were covered over, and for long ages the plants
(blub mosses, trees, &c.) were subjected to the influence of the
internal heat of the earth.* This caused decomposition,
The volatile matters were partially driven off and fixed
carbon concentrated. This concentration is strongly marked
in anthracite. Most of the ash is from earthy matter which
intermingled with the covered-over trees, &c.
When coal which is of a coking nature is Tiighly heated for
some time without access of air, or air in very limited amount,
it is converted into coke. During coking, water and the
volatile hydrocarbons are driven off. The result is a further
concentration of carbon and the production of a strong fuel
which is capable of generating an intensely high temperature.
Good coke does not contain much volatile matter and not
more than a moderate amount of ash. It is strong, lustrous,
dense, and at the same time porous. It must be strong so as
to1 withstand well the crushing of materials in a cupola or a
tall blast furnace. When a coking oven is very hot, some of
the liberated hydrocarbons become decomposed ; hydrogen is
* As one descends a mine he can hardly fail to note the rise in
temperature.
228 IRON AND STEEL MANUFACTURE.
set free and finely-divided carbon is deposited on the coke.
The shining silvery lustre is taken as evidence of the coke
having been prepared in a highly-heated coke oven.
When coke is porous its numerous small pores may become
filled with the hot gases in the furnace and the coke will burn
quickly when kindled. Density along with porosity implies
that the material comprising the walls of the cells, or pores,
is compact ; otherwise the coke would crumble.
The favourite coke of many foundry and blast-furnace
managers is made in bee-hive ovens. Much coke is now made
in retort ovens which are arranged in batteries, each coking
chamber being about 33 feet long, 6 feet high, and 1 foot
6 inches wide— the actual width depending on the nature of the
coal. The crushed coal intended for coking is quickly dropped
from two 2-ton overhead hoppers into a hot coking chamber.
In more modern coking plant the crushed coal is compressed in
a mould and the block is charged into the hot coking chamber.
The gases which come off are scrubbed to extract the ammonia
and other valuable " residuals," and then passed along with a
regulated amount of air to be ignited and burned in passages
at the sides and underneath the coking chamber. When the
coking is finished a ram pushes out the block of coke.
Charcoal is prepared by drying and heating wood, under a
covering of non- combustible matter, or in a kiln, till it it
charred as black as coal. The volatile matters (water anc
hydrocarbons) are nearly all driven off. There is less ash ir
charcoal than in coal.
FLUXES. — Substances which are to be used for fluxing4
must be of a chemical nature opposite to that of the substances
which are to be fluxed. The chief idea is to form from th<
gangue a fluid slag. If silica (which is of an acid nature
predominates in the gangue of an ore, the flux must be basi
(see p. 26). Lime (CaO) being cheap is freely used. Mono
silicate of lime (2 CaO, Si02) is a common constituent of blast
furnace slags. But if a furnace temperature is not equal to th
* The words "fluxing" and "fluid" are from the Latin and signif
flowing.
NOTES ON FUELS, FLUXES, ETC. 229
task of melting a compound of such high melting point, a base
which will form a compound, or slag, of lower melting point
must be used in order to work a metallurgical process success-
fully. In such a case ferrous oxide (FeO) will be supplied, so
that the silica may form with it silicate of iron (2FeO, Si02),
which melts at a moderate furnace temperature. Ferrous
silicate is the chief constituent of the slag from a puddling
furnace. The puddling furnace cannot be relied on to melt
silicate of lime, and, besides, lime has been found to interfere
seriously with the quality of wrought iron. It is, however,
used sparingly with success. Lime, being a cheaper flux than
iron oxide, is used where enough heat can be had, as in blast-
furnace practice and in the manufacture of steel.
Silicates with two bases are, as a rule, more fusible than
those containing either of the bases singly. When required,
a second substance is selected to assist in the fluxing of gangue.
Of this a well-known instance is the charging of aluminous ore
along with limestone when smelting English hematite ore. The
result is a slag containing silicate of lime and alumina. This
compound silicate melts at a lower temperature, and so helps
blast-furnace working. In smelting clay-band ironstone it is
not necessary to add more than one fluxing material, because
clay (which constitutes the bulk of the gangue) contains both
silica and alumina. Addition of the necessary lime, therefore,
leads to the formation of the compound silicate of lime and
alumina.
SUMMARY OF COMMON FLUXES.
Silica . . acts as a flux for ferrous oxide.
Ferrous oxide „ „ silica.
Silica . „ „ lime.
Lime „ „ silica.
Lime . „ clay.
Clay . . „ „ lime.
Alumina (A1203) may act as a base when silica predominates,
or may act as an acid when lime is the chief component.
230 IRON AND STEEL MANUFACTURE.
Magnesia (MgO) may, in part at least, be substituted for
lime. Its silicate does not melt quite so readily, but magnesia
tends to form a hard slag which can, when cold, be usefully
applied. Under certain conditions magnesia readily combines
with sulphur.
Manganons oxide (MnO) may also with advantage replace
some of the lime.
Ferrous oxide (FeO) is out of place in blast-furnace slag.
Fluor spar is useful for increasing the fluidity of certain
slags and is very helpful as a desulphuriser. Its use in iron
and steel works is steadily increasing.
REFRACTORY MATERIALS for metallurgical purposes are
such as successfully withstand chemical, mechanical, and
thermal* actions.
They are required to resist combination with oxygen, thus
differing from fuels. They are required to resist chemical
union with gangue or slag, thus differing from fluxes. They
should also be able to withstand continued exposure to in-
tense heat, and also sudden changes of temperature, without
softening, cracking, or changing shape.
Refractory materials are chiefly composed of
I.
Silica, ....
Titanic oxide,
. Si02
. Ti02
II.
Alumina, ....
Chromic oxide, .
Ferric oxide, ,
. A1A
. CrA
. FeA
III.
Lime, ....
Magnesia, .
. CaO
. MgO
IV. Impurities —
Ferrous carbonate, . . . FeC03
Iron pyrites, . . . . FeS
Potash, K20
Soda, Na,0
* From Greek therm6 = heat.
NOTES ON FUELS, FLUXE8, ETC. 231
Class I. = acid substances.
Class II. = neutral „
Class III. = basic „
Class IV. — Lime and magnesia are amongst the most
fatal impurities of fireclays. All the iron compounds are
injurious to firebricks, but the most serious is iron pyrites
(FeS2). When a firebrick is kiln-burnt this loses half its
sulphur and forms the highly-fusible ferrous sulphide, which
gradually combines with silica and fuses. Potash and soda
are alkaline substances, and presence of either or both in
more than minute quantities is highly injurious to acid
refractory materials and in a lesser degree to the others.
A good refractory material is simple in its composition ;
one substance, or substances of a like constitution and chemical
nature, must largely predominate in its composition, with
enough component of an opposite chemical nature to hold
it together, yet not enough to cause it to flow or soften at the
temperature of the furnace or lining for which it is used.
Take as examples the lining and the walls of a Siemens
furnace. The furnace is worked at a very high temperature.
The working lining is made up of silver sand, which, being
very pure, does not even frit with the intense heat of the
furnace. A small quantity of loam or of impure sand (which
can be melted at the furnace temperature) is added as a
binding material. The bricks of which the walls and the
roof are built require a stronger binding, and this is sup-
plied by mixing about 2 per cent, of lime, made into a
thick cream with water, to the crushed siliceous rock of which
the bricks are made. Fireclay, on the other hand, usually
contains more binding material (chiefly alumina) than is
required.
In selecting a refractory material for a furnace one of the
first considerations is the chemical nature of the slag. Will
it be acid or basic ? A refractory substance of the same
nature, or a neutral substance, must be selected. The amount
of binding material must be determined by the temperature
at which the furnace is to be worked.
232 IRON AND STEEL MANUFACTURE.
The chief acid refractory materials used in iron and steel
works are : —
Silver Sand, largely imported from Belgium; ordinary brown
sand, and crushed Dinas (South Wales) rock.
G-anister. — Found abundantly near Sheffield. In its
composition silica largely predominates, but it also has in
itself enough binding material to enable it to hold firmly
together while enduring the commotion and the heat incidental
to a Bessemer blow.
Fireclay which, as already noted, is over-rich in binding
material, and suffers in its heat-resisting qualities in
consequence.
Clays of greater purity than fireclays.
Fire-stones, which are capable of withstanding great heat
and considerable alterations of temperature without cracking.
Silica Bricks. — These are made by mixing siliceous
(quartzose) rock — which has been broken and crushed — with
cream of lime; moulding, drying, and kiln-firing. When
broken, these bricks show a rough fracture — pieces of quartz
showing up distinctly amongst the finer particles and the
binding of lime. Prominent yellowish spots indicate the
presence of iron oxide in very small amount. The bricks are
tender when cold ; they must be handled carefully, and kept
from exposure to damp. When heated they expand, and
they are not so tender as when cold.
G-anister Bricks resemble silica bricks in material, method
of manufacture, and general character.
Firebricks are made by selecting, tempering (or weathering),
grinding, and sifting the fireclay, mixing it with water,
moulding, drying, and then kiln-firing at a temperature almost
approaching to whiteness. The bricks are allowed to cool
down slowly in the kiln after the fire has been withdrawn.
It is usual to incorporate sand, or old, clean bricks, in order
to diminish shrinkage and increase their power of resisting
heat Coke dust is sometimes added.
Firebricks contract during drying and firing; they thus
differ from silica bricks, which expand during burning and
also when in use. When broken across, firebricks show a
much finer grain than silica bricks.
HOTES ON FUELS, FLUXES, ETC.
233
The following table shows, approximately, the composition
of the chief acid refractory materials: —
Constituents.
Chemical
Formulae.
White
Sand
(Dried).
Gan-
ister.
Fire-
clay.
Silica
Brick.
Fire-
Brick.
Silica,
Si02
98-5
94-6
56-7
96-0
65-0
Alumina, .
A1A
1-0
1-5
30-0
1-0
31-0
Ferric oxide,
Ferrous oxide,
Fe20
FeO
}...
1-0
1-5
1-0
2-0
Lime,
CaO
J
0-6
1-0
1-7
1-0
Magnesia, .
MgO
0-5
o-i
0-2
o-i
0-3
Alkalies— (
Potash and soda, \
K20 1
Na^O/
L
0-2
0-6
0'2
0-7
Water,
2-0
10-0
...
100-0
100-0
1000
100-0
100-0
Basic Refractory Materials have been referred to at some
length in Chapters ix. and xii., and a table of analyses appears
on p. 85.
Dolomite is not of a basic nature until its carbon dioxide *
(C02) has been driven off by calcination. Some firms pur-
chase calcined dolomite. This saves a considerable amount
on railway carriage, but there is danger of deterioration by
damp during transit. Dolomite bricks are usually made in steel
works. Magnesia bricks are, as a rule, bought ready made.
Magnesia Bricks, which are very dense, are composed of
burnt, ground magnesite, and may be bound with tar, strongly
pressed, and kiln-fired. These are dark coloured. Other
brands are bound with magnesic chloride, and have a ruddy
colour, due to the presence of a little ferric oxide. These,
when fractured, show a grain resembling firebrick. Some
brands contain more than 90 per cent, of magnesia.
Neutral Refractory Materials include chrome iron ore,
bauxite, and carbon.
Chrome Iron Oref — the chief components of which are an
oxide of chromium (Cr203) and ferrous oxide (FeO) — may be
used in the form of lumps cemented in position with fine
Sometimes spoken of as carbonic acid. t See analysis on p. 24tp»
234 IKON AND STEEL MANUFACTURE.
ore and tar. Bessemer converters thus lined last remarkably
well.
Chrome Bricks are made of crushed chrome iron ore mixed
with tar, pressed, and kiln-fired. They are black or of a deep
purple colour, and show a moderately rough fracture when
broken (see analysis on p. 245).
Bauxite Bricks are made of crushed bauxite, and have clay
for a binding material. In colour they are yellowish-brown.
They are moderately dense and externally firm. Their frac-
ture may perhaps be described as resembling oatmeal of
medium fineness. The fractured parts may be worn away by
rubbing with the finger tips (see analysis on p. 245).
Carbon is a strictly neutral substance. It withstands a
high temperature if oxygen has not access to it. Where the
conditions inside a furnace are non-oxidising, carbon does not
burn.
During the working of an iron-smelting blast furnace, a
"carbonaceous concrete" is formed in the bosh. It is this
concrete which protects the brickwork from the fluxing action
of the slag. According to the late Sir I. Lowthian Bell, " the
solvent power of the slag over the brick was almost as much
as the solvent power of water over sugar."* The carbonaceous
concrete has been found to be several inches thick, and to
contain about 46*6 per cent, of carbon. Bricks of similar
composition have been used for blast-furnace boshes. In
percentage of carbon the blast-furnace "concrete" does not
differ much from ordinary graphite crucibles.
Plumbago or graphite is used in the manufacture of
crucibles and for facing moulds for iron and steel castings.
In composition plumbago varies over a wide range. The
following figures may be accepted as representing fair average
quality : —
Fixed carbon, . . .77 per cent.
Volatile matters, 3 „
Ash, . . . . . 20 „
100
•Iron and Steel Institute Journal, 1887, ii., 117.
NOTES ON FUELS, FLUXES, ETC. 235
DEOXIDISING AND RECARBURISING MATERIALS. — The
following notes are added to supplement the references to
those in preceding chapters : —
Spiegel-eisen is a compound German word signifying
" mirror-iron." It is highly crystalline, and, when fractured,
displays large brilliant plates — hence the name. It is made
in blast furnaces, and cast in pigs or in slabs. It may, with
comparative ease, be broken into fragments (crystals) which
are very hard and difficult to powder, and it is not easily
melted. The trade practice is to charge it into the converter
in the liquid state or into the furnace (not into the ladle) in
a highly-heated condition.
As the percentage of manganese increases, there is a slight
rise in the percentage of carbon. See analyses on p. 237.
Ferro-manganese. — The percentage of manganese is higher
in ferro-manganese than in spiegel-eisen. It was originally
made in crucibles ; afterwards it was manufactured in a
reverberatory furnace. Now it is regularly made in blast
furnaces from ores containing much manganese, and a richer
variety is manufactured in electric furnaces. Ferro-manganese
is grey, finely granular, moderately hard, and is more friable
(that is, more easily broken) than spiegel-eisen.
The percentage of carbon increases slightly as the manganese
increases. See analyses on p. 237.
As stated in previous chapters, ferro-manganese is used for
mild steels, and spiegel-eisen is added for medium (higher
carbon) steels, because the quantity of ferro-manganese
required to give to the steel a low percentage of carbon will
do so without yielding more than the desired percentage of
manganese. On the other hand, the amount of spiegel-eisen
which would give to the steel the required percentage of
manganese would yield a greater amount of carbon.
To make this more clear —
100 Ibs. of 60 per cent, ferro-manganese would contain
60 Ibs. of manganese and about 6J Ibs of carbon.
400 Ibs. of 15 per cent, spiegel-eisen would contain 60
Ibs. of manganese and about 17| Ibs. of carbon.
236 IRON AND STEEL MANUFACTURE.
Spiegel-eisen usually contains from 15 to 25 per cent, of
manganese, ferro-manganese contains over 40 per cent.
Silicon is useful for promoting soundness in steel castings
and in steel ingots. It appears to have the power of increasing
the solubility of carbon monoxide, thus lessening the tendency
to cause blow-holes by keeping the gas in the occluded state
until after the steel has solidified. The beneficial effects of
silicon have been recognised in iron foundries since 1884.
Certain pig irons containing silicon in noted amount (known
as glazed pigs, blazed pigs, and silky pigs) are used as
softeners. Good, sound iron castings may be made by the
judicious mixing of proper quantities of softener with pig irons
which are of themselves too white for foundry purposes. Pig
iron very rich in silicon is now made in blast furnaces, and
is called ferro-silicon : if also rich in manganese it is called
silico-spiegel. Analyses are noted on p. 238.
Very rich silicon alloys are now made in electric furnaces.
Aluminium — a silver- white, soft, and remarkably light
metal, which is prepared in a fair state of purity in electric
furnaces — possesses marvellous powers for inducing soundness
in ingots. Its presence even in small amount lessens segrega-
tion— a fact pointed out by Pourcel some years ago, and
amply confirmed by Benjamin Talbot.
An alloy containing the three valuable components — silicon,
aluminium, and manganese — is made by Messrs. Blackwell, of
Liverpool.
237
APPENDIX.
ANALYSES OF FINISHING MATERIALS,
SOFTENERS, ORES, &c.
SPIEGEL-EISEN.
Constituents.
Chemical
Symbols.
*
Combined carbon,
Manganese, ....
Silicon,
c
Mn
Si
P
4'27
8-11
0-11
0-08
4'76
19-67
•83
•08
s
•01
Iron,
Fe
87-40
A
99-97
100-00
FERRO-MANGANESE.
Constituents.
Chemical
Symbols.
*
*
Combined carbon,?
Manganese,
Silicon,
Sulphur, .
Phosphorus,
Copper,
Iron, .
C
Mn
Si
S
P
Cu
Fe
5-63
41-82
0-42
6-io
si'-9o
5-90
60-58
0-93
0-007
0-19
"A
6-17
71-32
1-12
0-162
0-33
20-65
6-38
81-35
0-88
Trace.
0-23
A
99-87
100-000
99-752
100-00
* Analyses by Mr.
A By difference.
T. E. Holgate.
Including, in some instances, a little finely-divided graphite. Mr. T. W. Hogg,
Newburn, found beautiful crystals of nitro-cyanide of copper in the residue undis-
solved in acid. These are also found in bear, which is an accumulation of iron, <fec.,
in the lowest part of a blast furnace.
238
APPENDIX.
FERRO-SILICON. *
Constituents.
Chemical
Symbols.
Graphitic )
carbon, \
c
2-40
1-70
1-20
0-62
0-55
Combined )
carbon, )
c
0-14
0-11
0-23
0-35
o-ii
Total carbon,
c
2-54
1-81
1-43
0-97
0-66
Manganese, .
Silicon, .
Mn
Si
3-25
8-54
2-16
10-18
1-95
14-00
2-29
1613
1-07
17-80
Sulphur,
S
0-064
0-055
0-078
0-050
0-041
Phosphorus, .
P
0-047
0-104
0-076
0-090
0-115
Iron,
Fe
A
A
A
A
A
100-000
100-000
100-000
100-000
100-000
SILICON-SPIEGEL.
Constituents.
Chemical
Symbols.
Graphitic carbon, .
C
0-33
0-67
1-13
0-90
Combined , ,
C
1-85
0-98
0-29
0-30
Total ,,
C
2-18
1-65
1-42
1-20
Manganese, .
Silicon, .
Mn
Si
19-64
10-74
19-74
12-60
22-98
14-19
24-36
1594
Phosphorus,
Iron,
P
Fe
0-074
67-56
0-080
66-10
0-095
61-60
0-085
58-30
100-194
100-17
100-285
99-885
The above analyses are by Mr. T. E. Holgate, Darwen. Absence of
sulphur may be noted. The author of this book did not find more than
traces of that element in any of the many samples he examined. He
found consignments from various makers to average over 0'2 per cent,
of phosphorus, although samples with 0'08 per cent, of phosphorus
were not wanting.
* Analyses by Mr. T. B. Holgate.
A Iron by difference— not stated in Mr. Holgate's analyses.
APPENDIX.
239
s "
fi
?«
It
111
"o^o
ill
I' I
6|l<
OO ^T
W5 O O S O
<N TH (^ 0 OJ <,
1
*,flf*
CO — ( O O O
8
A
g ?
(N
w ^ 6 6 6
1
o
^
0 CO
« T1 <P 9 » <J
g
*
CO
CO C^ O O O
I
"•2
0 2
p-H CO
O O lO M 1C
^ 0 CO O 0 <j
o
XB
CO
co e* o o o
8
-d
§ c$
sssis.
1
^
CO
CO W O O O
8
0
2;
CO
co co 6 6 6 o
8
8
iO O O f>l
*"*
»O I^H
d
CO
CO CO O O •-<
8
11
g!
O 0
O 02 (^ a? S PR
1 s
*
••81
3 1 * 1
!!
H°lft|i
t30 PL,] QQ S M
240
APPENDIX.
p; p ^H r-C5O(N (N 0>O >p -71 »
APPENDIX.
COMPOSITION OF SCOTCH Pio IRON.
Constituents.
Chemical
Symbols.
No. 1.
No. 3.
No. 3.
Hard.
Verge.
Graphitic carbon,
c
3-46
3-14
2-93
2-66
Combined ,,
c
0-25
0'38
0-47
•55
Total „
c
3-71
3-52
3-40
3-21
Silicon, .
Si
3-39
2-43
1-64
1-39
Phosphorus,
p
0-91
091
0-92
1-27
Sulphur, .
s
0-03
0-03
0-04
0-06
Manganese, .
Mn
1-78
1-62
1-49
1-28
Iron, ....
Fe
A
A
A
A
100-00
100-00
100-00
100-00
CLEVELAND PIG IRON (MUNNOCH).*
Grade
Graphitic
Carbon.
Combined
Carbon.
Silicon.
Phos-
phorus.
Sul-
phur.
Man-
ganese.
Iron.
No. 1,
3-30
0 10
3'50
1-60
•02
0-65
,,2, . .
3-20
0'15
3-30
1-57
•03
0-65
,,3,
,, 4 Foundry, .
3-00
2-85
0'30
0-40
2-75
2-25
1-57
1-55
•05
•08
0-60
0-55
1
,, 4 Forge,
2-50
0-70
1-75
1-57
•13
0-50
£
Mottled, .
1-77
1-30
1-10
1-58
•25
0-30
White,
Nil.
3-05
0-75
1-60
•45
0-20
A By difference.
* Table of ideal analyses, Cleveland Institution of Engineers, February 1005.
16
242
APPENDIX.
ANALYSES or ORES.
Constituents.
Chemical
Formulae.
Stafford-
shire
Pottery
Mine.
Stafford-
shire
Pottery
Mine.
Calcined.
Froding-
ham Iron
Ore.
Mid
Lincoln-
shire
Iron Ore.
Ferrous oxide, .
FeO
42-18
6-43
...
Ferric ,,
Fe203
6-29
80-88
44-66
60-91
Oxide of manganese, .
MnO
2-93
1-85*
2-32
traces
Silica,
SiOa
1-50
3-00
738
13-24
Alumina, .
A120,
0-22
0-16
5-95
8-03
Lime, . .
CaO
4-20
4-10
18-27
1-60
Magnesia, .
MgO
1-80
1-30
3-51
0-06
Phosphoric acid,
PA
0-70
1-15
0-68
1-02
Sulphuric ,,
SOS
1-02
1-15
0-06
0-03
Bituminous matter, .
)
...
Combined water,
Carbon dioxide, .
H20
C02
V39-29
...
13-29
3-82
| 15-35
Loss on ignition,
Metallic iron,
Fe
...
0-31
...
100-13
100-33
99-94
100-24
37*20
61-60
31-26
42-64
* Oxidised to Mn304.
APPENDIX.
243
c
<
pq
I
'oo
8
CD CO O <N ^H O I^H pli : O CO
»0 CO
8
~ :°8
: QO — < o o o oo o o o
ooo oco A-
CD •<* O O U5 O O If5 CO »O
: O5 F^H o '-H o oo o o o • oo
8
n si 'i'lrfl
.2 ®
x^
2." c3 b
H i s
u)^ 5 •§ »£S *5 *»
"
c.2
1!
ss.
11
If
»is
IB
IP
III
Uj
^l*1
J
244
APPENDIX.
IBON ORBS MINED NEAR THE MEDITERRANEAN SEABOARD.
Constituents.
Chemical
Formulae.
Cartagena
Ore.
Garrucha
Ore.
Elba Ore.
Ferric oxide,
Fe203
72-05
79-46
81-14
Ferrous oxide,
FeO
Nil
2-64
Manganese oxide,
Mn804
2-96
2-40
0-20
Silica,.
Si02
4-30
7-25
3-58
Alumina, ,
A1A
0-80
0-27
2-85
Lime, ....
CaO
7-28
2-34
o-io
AJagnesia, .
MgO
1-30
0-54
o-io
Phosphoric acid, .
PA
0-03
0-04
0-04
Sulphuric oxide, .
S03
0-03
0-28
0-13
Carbon dioxide, .
Combined water,
C02
H20
7-10
4-00
| 7-04
6-97
Moisture, ...
Iron in dried ore,
H30
...
1-95
99-85
99-62
99-70
50-75
55-62
59-95
,, ore as received,
47-87
49-62
58-85
Phosphorus in ore,
0-013
0-017
0-017
APPENDIX.
245
COMPOSITION OF BRICKS.
The following are analyses of good quality bricks as supplied to steel
works by British firms : —
Constituents.
Chemical
Formulae.
Magiiesite Bricks.*
Magnesia,
MgO
94-24
91 -32
91-50
CaO
0-64
1-40
2-10
Silica,
Alumina, .
Ferric oxide,
Si02
A1A
Fe203
3-20
}»*
5-30
1-80
0-35
6-05
Alkalies — potash and soda, .
/K20 \ ft.1R
1 Na20 £ C
o-is{
not esti-
mated.
100-00
10000
100-00
Constituents.
Chemical
Formulas. Bauxite Brick.
Chrome
Brick.*
Silica, . .
Si02
3-50
35-80
5-20
Titanic oxide,
TiOo
3-08
3-70
0-50
Alumina, ....
A1203
51-40
55-80
13-90
Chromic oxide,
Cr203
53-66
Ferric oxide,
Ferrous oxide,
Fe203
FeO
38-37
1 3-40
16-20
Lime, .....
CaO
2-46
0-90
0-78
Magnesia, ....
MgO
0-79
Sundries
9-22
Alkalies — potash or soda, .
(K20
\Na20
| 0-40
not esti-
mated.
0-54
100-00
100-00 1 100-00
CHROME IRON ORE. — COMPOSITION OF AVERAGE SAMPLE.
Constituents.
Chemical
Formulae.
Silica,
Titanic oxide, .....
Si02
TiO.,
1 2-00
Al,03
19-25
Chromic oxide, .....
Ferrous oxide,
Lime, .......
Magnesia, ......
Loss on ignition — combined water, &c.,
S5P
CaO
MgO
41-67
14-70
3-75
17-66
097
100-00
• Tarry matter (about 5 per cent.) for binding was burnt off before making analyses.
246
APPENDIX.
ANALYSES OF GASES.
PRODUCER GAS.
Constituents.
Chemical
Formulae.
Scotch
Steel
Work.*
American
Steel Work.
Reducing gases —
Carbon monoxide,
Hydrogen,
Methane or marsh gas,
Total combustible gases,
CO
H.2
CH4
25-7
11-8
2-3
16 5
8-6
2-7
22-3
28-7
1-0
39-8
27-8
52-0
Inert or neutral gases —
Carbon dioxide,
Nitrogen, ....
CO,
N2~
6-3
53-9
9-3
62-9
6-1
41-9
100-0
100-0
100-0
WATER GAS AND NATURAL GAS.
Constituents.
Chemical
Formulae.
Water Gag.
Natural Gas.
Approximate
Approximate
Average.
Average.
Reducing gases —
Hydrogen,
Carbon monoxide,
&
49-00
44-00
22-00
0-60
Methane or marsh gas, .
CH4
0-50
67-00
Ethylene or olefiant gas, .
Ethane or ethyl hydride, .
C2H4
C2H6
...
1-00
5-00
Total combustible gases,
93-50
95-60
Other gases-
Carbon dioxide,
C02
3-25
0-60
Nitrogen, ....
No
3-25
3-00
Oxygen, ....
0,
...
0-80
100-00
100-00
* Steam-urged producer, fed with bituminous coal slack.
APPENDIX.
247
AMERICAN IRON ORES.
The American continent is rich in iron ores, and in the fuels, fluxes,
and refractory materials necessary for extracting iron and for carrying
on the manufacture of iron and steel.
The richness of their virgin fields, the enterprise of the inhabitants,
and the rapid development in many directions of this great continent
have contributed to the enormous expansion of the iron and steel trades.
Analyses of some of the chief iron ores are noted on this and the
following pages. On this page the figures were obtained from dried
samples, those on pages 248 and 249 show the composition of natural
(undried) samples.
IBON ORES (DRIED), LAKE SUPERIOR DISTRICT.
Gogebic
Range.
Mar-
quette
Range.
Meno-
minee
Range.
Mesaba
Range.
Vermilion
Ran«re.
Iron, maximum,.
64-15
66-53
60-28
63-56
65-00
,, minimum, . .
48-16
39-78
37-60
52-00
59-20
Phosphorus, maximum,
0-128
0-415
1-28
0-11
0-166
, , minimum,
0-018
0-012
0-012
0-023
0-038
Manganese, maximum,
6-95
4-70
4-60
3-00
0-25
Silica, maximum, .
23-80
40-60
41-53
15-97
9-28
,, minimum,
2-57
2-76
4-33
2-80
4-77
248
APPENDIX.
CO
<M
UJ^.
05 CO t^ 3! §
S 'S ^ S
£?
§.2
«S
V 3
0 0 0 ** 0*
e^ I-H o oo
<*
II
CO 0 0 CO £i
s s i 2
53
»0 O © 00 -H
O 1-1 O 00
g 1 5 g 8
CO >O O O
g
g 0 0 <0 0
—• o o -*
oT
. $ 8 « CO
«, » § 0
*
•€«
3 «>
s = ° s -
o o o ^
~
i
(M
CO -J OS OS 0
Xi O O CO CO
S 2 8 CO
OS
t— O O >O -*
0 O O OS
o
>o
O CO CO CO CO
^ S i S
o
It
OS O CO CO -H
0 O O OS
CO
.25
is
Is
2S
— . CC CN r^* O
i>* <O O CC ^^
t*.
O C^ £ CO
o b b os
CO
1
*
2
1
c«
• 1 1 1 1
g s 1 J I
1 £ a i 3
"i % u
11*5
3 1 1 ^
Other V
APPENDIX.
249
"2 v
oo
H
ogjcc— ic^c^Tfp
^H o 6 t^ cc •* — b
* "
i.
8 S 2 g ? 8 , 2
.
S ^
t^ 0 O — i ^ 10 O
O
^ c
slisssss
£1
t~*OOOO— t(NCCO>
9
be t^
CO
cooot^to^-^o
^^ co
1O f^
II
t-OOOO-HOOO
lO —
- ft
Sao
1
"-0 2
O Oi
»O !>•
IOOOXTOOOO
10 — .
COOCO-*COOSC5^<
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I|
=OOO»O(NOOO
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O O "^ ^O ^^ to "^ •
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JO 0 0 « 0 - -
oa cc
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1
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§ »"
!£a
"o
• S c • § • -1 tf
•^ 5 S s
i I f 1 1 1 » I
££Sa5^iJ^c»
1 1
i 0
250 APPENDIX.
American Ore Supplies. — As already mentioned, the American
continent is rich in iron ores. The extensive deposits in the Lake
Superior regions contain a high percentage of iron. The ores are, in
many places, easily quarried. Much ingenuity has been displayed in
contriving plant for digging and handling the ores. The chief ore
fields are far from the fuel deposits. The means employed for trans-
porting the ores are ingenious and enterprising. Steam shovels dig
out the ore; buckets mounted on endless bands carry the ores to
vessels or to railway trucks ; capacious steamers which can take in
cargoes of 12,000 tons are quickly loaded, and convey the ore over the
great North American Lakes, where discharging is conducted with the
utmost despatch, the largest vessels being emptied in the course of five
or six hours.
It is not unusual to transport the ore a distance of 700 or 800 miles.
At Gary, on the southern shore of Lake Michigan, immense iron and
steel works have been laid out. The ore for these works is taken
direct from the lake steamers to the storage bins or heaps. For works
in and around Pittsburg and other towns it is necessary to convey the
ore a considerable distance by train. The trucks are lifted bodily and
the contents are tipped into large bins. As the great lakes are frozen
during the winter months, enormous heaps of ore must be accumulated
during the "open" season to keep the furnaces going.
g I
APPENDIX.
251
Modern Hoisting Machinery.— A modern, well-equipped American
blast furnace working on rich ore requires, on an average, about one
ton of solid material at the top every minute. Electrically-driven
hoisting machinery has been set up for dealing with this quantity.
On the opposite page is an illustration of a modern hoisting
plant by the Lilleshall Company, Limited, Engineers, Oakengates,
Shropshire.
The following abridged description of the plant is taken from The
Iron and Coal Trades Review: — The solids — ore, fuel, and flux — are
conveniently tipped from railway trucks into storage bunkers. From
the bunkers the solids are dropped into special buckets carried on
transporter cars. Each bucket has a capacity of 6^ cubic yards, and
can be closed by a gas-tight lid. Through the centre of each there passes
a strong shackle extending upwards from the cone, the lower part of
Fig. 97.— Demag Transport Car with two Charging Buckets.
which closes the bottom opening of the hopper. Each hopper rests on
a turntable on the transporter car. The turntables are revolved by an
electric motor during filling, thus securing uniformity of loading at the
storage bunkers. Each turntable is mounted on a separate weighing
machine which has three steelyards — for ore, fuel, and limestone
weighings — and each steelyard is provided with a poise which can be
locked at any desired position. The weighing apparatus is also
furnished with an automatic weight-recorder which prints the variations
from the required load. Fig. 97 shows the transporter car — which is
driven by a 22 horse-power motor — for conveying the buckets from the
storage bunkers to the foot of the blast furnace incline. The incline
supports a travelling trolly which is moved by means of a winding
252
APPENDIX.
engine. To convey the weighed charge to the furnace top the shackle
of a loaded bucket is connected to the travelling troll}', the winding
engine is set in motion, and the bucket, with its contents, is lifted from
the transporter car and taken evenly up the track until it arrives at
the curved part of the upper rail. The bucket is then brought to rest
on the seat at the furnace mouth. A gas-tight joint is made by means
of an asbestos rope which is carried in a groove in the seat. Fig. 98
shows the hopper at the top, and the illustration on the opposite page
shows a view of the plant. The bucket cover is then lowered and the
Fig. 98.— Charging Bucket being placed in position at top of Blast Furnace.
internal cone at the bottom of the bucket is set free, while at the same
time the bell of the furnace is automatically lowered. The material
drops into the furnace with, it may be mentioned, the minimum
breakage of coke, and the charge is evenly distributed in the furnace.
As the top of the hopper is closed the quantity of gas escaping is
negligible.
When the contents of the bucket have been discharged the bucket is
lifted off the furnace. Simultaneously the cover is lifted, so that all gas
is cleared from the bucket during its descent. The empty bucket is
placed on the transporter car, the next bucket is carried upwards and
its contents are charged into the blast furnace.
LU
APPENDIX 253
Handling Pig Iron at Blast Furnaces.— As previously stated,
the pig iron as it Hows from the blast furnace may be run into moulds
previously prepared in the sand beds in front of the furnace. After
the pig iron has solidified it may be lifted by hand and carried to
trucks. This, however, involves hard labour and is costly.
For more quickly dealing with the pig iron produced, pig-lifting
and pig-breaking plant is employed. When the pig iron has
solidified, each sow is broken off from the runner, and a sow with all
its pigs attached — a lot known as a " comb" — is taken by an overhead
crane to the pig-breaking machine.
The illustration on the opposite page shows a "comb" suspended
from the electric overhead crane at the Ayresome Works, near
Middlesbrough. This handy crane was erected by Messrs. Babcock &
Wilcox, Limited, and has a span of 110 feet. It can carry a load of
5 tons at the rate of 400 feet per minute.
By means of a pig-breaking machine — which consists essentially of a
block and rams, the latter worked by hydraulic pressure — each pig in
turn is held down and broken into two pieces, and the sow and runner
are also broken into pieces of suitable size. All the pieces slide down
a shoot into trucks which are placed in position to receive them.
For another method, the pig iron as it is tapped from the blast
furnace is collected in casting ladles and conveyed to a pig-easting
machine. Such machines consist of long endless metal chains which
carry a continuous series of iron moulds fixed across the chains. As
the chains travel, the moulds are brought in succession under the spout
of the ladle and charged with fluid pig iron. The molten metal is
quickly cooled by water which is sprayed during the continuance of
the travel. By the time a filled mould has reached the sprocket the
pig iron, in the form of cakes about 21 inches long, 10 inches broad,
and only f inch thick, has become solid enough to be fit for dropping.
Each mould is inverted as it rounds the sprocket, and as a consequence
the solidified pig-iron cakes drop into a trough of water, from which it
is delivered by an endless belt into trucks. While the moulds are still
inverted and returning to the pouring or filling point, they are sprayed
with lime-water. The heat of the moulds drives off the water, and a
protecting coating of lime is left on the moulds, which are then ready
to receive another lot of pig iron from the ladle.
In some instances the pig iron is tapped from the blast furnace into
a ladle and taken direct to a converter or to a basic open-hearth
furnace. But, as the composition of the pig iron in a blast furnace is
subject to variation, which, of course, leads to irregularities in subse-
quent working, this system has been abandoned in several works and
mixers have been installed.
254 APPENDIX
MixePS are receptacles in which pig iron is stored. They have
usually a capacity of about 300 tons, but much larger mixers are not
uncommon. All the pig iron from the blast furnaces in a work may be
poured into the mixer, and quantities are withdrawn from time to time
as required. A mixer is a convenient storing receptacle ; in it the
composition of the pig iron tends to become averaged, thereby leading
to more steady working of steel-making processes. Modern mixers
resemble tilting open-hearth furnaces in design. 8ome mixers have gas
producers and regenerators, and in these a considerable amount of
refining is sometimes effected.
APPENDIX. 255
Movable Furnaces.— In the Wellman Rolling Furnace, the
body, which is roughly rectangular in section, is enclosed in a strong
cage constructed of steel plates, channels, and angle bars, with stout
tie-rods. The walls and roof are of silica bricks and a suitable lining
is put in. The furnace is mounted on strong steel ribs supported on
heavy mocks.
Rolling is effected by means of hydraulic rams, the cylinders of which
are mounted on trunnions at their lower ends. The upper ends of the
piston-rods are attached to the body of the furnace. To move the
furnace water is admitted to the top part of the cylinder. In case of
accidental failure of the hydraulic system the furnace returns to its
normal position, or in the event of any hitch or accident occurring
during tapping the pouring can be instantly stopped.
Slag can be poured off at any time during the working of a charge,
and every particle of metal and slag can be removed after each charge.
A movable furnace can be easily brought into position to facilitate
repairs.
As the taphole is kept above the level of the charge during working,
it does not require to be "made up" to resist the pressure of the
molten charge, but is only loosety covered to exclude air. It is, there-
fore, easily opened as soon as the metal is in correct condition for
tapping. This is particularly advantageous when making special steels.
Some furnaces are provided with electric (instead of hydraulic) tilting
gear. A photograph of such a furnace is reproduced on the opposite
page. It is a view of a Wellman rolling furnace built at Dommeldingen,
Luxembourg, by Messrs. Wellman, Seaver & Head, Limited, and shows
the furnace in its ordinary working position with the taphole above
the level of the charge. The electric motor is also shown, as well as
the gearing for working the rack and pinion. These latter are enclosed
in metal casing.
The regenerative chambers are not placed under the furnace as in
the Siemens design, but are arranged side by side in pairs at each end
of the furnace. The ports are mounted on flanged wheels and can be
moved away from the furnace ends to allow the furnace to be tilted.
This is clearly shown in the illustration on the opposite page, and in
the frontispiece. When pouring is finished the ports are again moved
towards the furnace ends. Movable ports permit ready access for
repairs.
The success of movable furnaces paved the way for the introduction
of modified steel-smelting processes, such as the Talbot and the
Bertrand-Thiel.
256 APPENDIX.
Charging* Machines. — Open-hearth furnaces have been increased
so much in capacity that charging machines have become an imperative
necessity for dealing with the heavy tonnage of pig iron and scrap to
be charged.
The materials to be charged are placed in long narrow charging boxes,
each capable of containing about one or two tons, or even more.
Charging boxes are made of steel plates, one end consisting of a steel
casting having a slide and an opening to which an attachment may be
made. These are shown on the right lower part of the illustration on
the opposite page.
The charged boxes are brought within the range of the arm of the
machine. The arm is thrust forward, and by mechanical movements is
locked to one of the full boxes. This is borne to an opened door of the
furnace, is pushed in, and, by a rotary motion of the arm, is turned
over. By these movements the materials in the box are dropped in the
furnace. The box is then withdrawn, turned into its former position,
and deposited on the trolly from which it was taken. Other charged
boxes are similarly dealt with, so that a furnace is quickly charged.
The illustration on the page opposite shows an overhead charging
machine installed by Messrs. Wellman, Seaver & Head, in the Parkhead
Works, Glasgow.
Charging by hand is hot, exhausting work, and occupies much more
time than machine charging.
A 50-ton charge, which would take four men four or five hours to
repair and charge, may be charged in one hour by a charging machine.
Quick charging by a machine, leads to larger output in a given time,
and materially reduces costs for fuel.
Originally, charging machines were worked by hydraulic power, they
are now actuated by electricity. Formerly they were set on broad,
gauge rails laid parallel with the range of furnaces, and the boxes were
brought on a narrow gauge railway directly in front of the furnaces.
But many modern machines are worked on the overhead system, and
as the arm can be rotated to any degree, the trolly rails may be run in
any direction near the furnaces. Large and heavy pieces of metal are
placed on a fork or strong peel, and can then be charged by a machine.
In the illustration facing the next page a Wellman overhead charging
machine is shown in the act of conveying a box.
•
APPENDIX. 257
The applications Of electricity to the various branches of iron
and steel manufacture are of groat importance. Among such applications
mention may be made of the following : —
I. Separation of magnetic (iron-containing) portions of finely-
crushed ore from non-magnetic portions of the ore. Some ores which
are too poor in content of iron may be successfully treated and the
richer portion profitably made into briquettes and smelted.
II. Lifting of iron and steel goods, such as pig iron, plates, rivets,
etc. This is, in many instances, more convenient than attaching by
hooks, etc.
III. Driving of rolling mills and other kinds of machinery, Bucb
as cranes. Electric power is cheaply generated from blast-furnace
gas, and is used for driving blowing engines, mills, etc.
IV. Smelting iron ores. Only in exceptional circumstances — as, for
instance, where ores are cheap or of superior quality and suitable
water power is abundant — can electric smelting be economically
carried on.
V. Producing special alloys, free from or containing only traces of
carbon, producing high-grade ferro-silicon, etc.
VI. Refining iron and steel.
Owing to want of space the first five sections cannot be dealt with in
this volume, and the sixth can only be treated in outline.
Electric refining furnaces are of two classes —
(a) Arc furnaces, including the Girod, Heroult, Keller, Nathusius,
and Stassano furnaces. In these the high temperature is derived from
the electric arc between the electrodes, the heat from which is largely
reflected or reverberated from the furnace roof.
(6) Induction furnaces, including the Grondal-Kjellin, Frick, and
Rochling-Rodenhauser furnaces. In these the high temperature is
induced by the resistance to the current while passing through the
metals in the furnaces.
For refining purposes the advantages of an electric furnace over an
ordinary fuel-fired furnace arises from the rapidity with which a high
temperature can be attained and the ease and constancy with which it
can be kept up. No deleterious element (such as sulphur) is introduced
by the heating agent, and no gases (which are liable to be occluded) are
introduced during the refining. Thus a pure metal, almost free from
occluded gases, can be produced. Overkilling is impossible.
There is another point in favour of electric furnaces : an intense
local heat can be produced— thereby bringing about a rapid reaction
between the metal and the slag which acts as the refining oxygen
carrier — at points far from the walls and roof of the furnace.
In shape the Grondal-Kjellin furnace may be said to be like a
grindstone laid flat. For convenience in working it is mounted for
tilting, and has tapholes at different levels. It is constructed of highly -
refractor}7 bricks and has a \\orking lining of magncsite. An annular
space is grooved in the working lining, and into this the cold or the
molten metal, as the case may be, is charged. In the centre of the
17
258 APPENDIX.
furnace a primary coil is placed : the metal ring in the annular space
constitutes the secondary coil. "An alternating electric current passing
through this primary coil forms an induced current in the rin£ of metal
contained in the hearth. As this ring forms a single circuit round the
core, the current induced in it is approximately equal to the primary
current multiplied by the number of turns in the winding of the coil.
A portion of the charge is left in the furnace after each
tapping, and pig and scrap are added to this in proper proportion, so
as to arrive at the desired carbon content. As soon as the metal is
properly ' killed ' the furnace is tilted and the contents tapped into a
ladle. . . . The upper part of the furnace serves as a charging
platform, and the necessary materials are easily charged by removing
the brick covers."
The photograph reproduced on the opposite page shows a Grondal-
Kjellin furnace at Messrs. Jessops' Steel Works, Brightside, Sheffield.
This furnace is provided with its own generator set and control gear.
It is capable of carrying a charge of 30 cwts., and the maximum current
consumed is 250 kwa.
°H "S
APPENDIX.
CITY AND GUILDS OF LONDON INSTITUTE.
SYLLABUS— IRON AND STEEL MANUFACTURE.
The Examinations will be held in three grades. Candidates will be
permitted to present themselves for the Examination in Grade I. in a
year previous or subsequent to that in which they present themselves
for examination in Grade II., or to enter for both Grade I. and Grade
II. in the same year. No Candidate will, however, receive a Certificate
until he shall have passed the Examinations in both grades. The
successes of Candidates in either grade will be notified to the Secretaries
of the Centres at which they were examined.
Prizes will be awarded on the results of the Examination in Grade
II. to those Candidates only who have passed Grade I. in a previous
year, or who pass both parts in the same year.
Candidates for the Final Examination must hold a Certificate in
Grade II.
In order to encourage Teachers to devote special attention to those
processes of Iron and Steel Manufacture which may be most suitable
for their respective districts, the Syllabus has been divided into two
parts, and in the Examination a number of questions will be given so
as to allow considerable choice in the selection. All Candidates will,
however, be expected to afford evidence of a general knowledge of
the subject as a whole, and in order to pass in the first class a
Candidate will be expected to answer satisfactorily, questions both in
Iron Manufacture and in Steel Manufacture. In the Final Examin-
ation, Candidates will be permitted to select their questions either
from one section only or from both.
f. GRADE L
Manufacture of Iron.
1. Composition and general characters of the chief ores of iron.
2. Construction and mode of working of blast furnaces.
3. Hot and cold blast ; effects of these and of variations in amount
of fuel and flux on the production and character of the iron made.
4. Physical characters of pig irons from various classes of ore.
Grey, mottled, and white irons. Bessemer, mine, and cinder pigs.
Numbering of irons.
5. Physical characters of charcoal, coal, and coke used for iron
smelting.
6. Chemical and physical properties of iron used for foundry
purposes.
7. Chemical and physical properties of forge pigs.
8. Refining, puddling, and the production of finished iron.
XIV APPENDIX.
9. Chemical composition of fettling and of wrought iron.
10. A general knowledge of the construction of furnaces, hammers,
and rolls required for the manufacture of wrought iron.
11. Manufacture of malleable iron castings from crucibles, cupolas,
or the open-hearth furnace. Practice and theory of ore annealing.
Manufacture of Steel.
12. Compositions and properties of the materials used for acid and
basic linings for converters and steel furnaces.
13. Outline of the construction of cupolas, converters, and of the
general arrangement of a Bessemer plant.
14. Outline of the construction of gas producers, melting furnaces
and regenerators, and of the general arrangement of an open-hearth
steel plant.
15. Ingot moulds, nozzles, and stoppers ; making up the taphole,
and repairing the bed of the open-hearth furnace between heats.
16. Outline of the reactions involved in the various processes.
17. A general idea of reheating furnaces, soaking pits, hammers,
and rolls used for converting ingots into the various forms of steel
required for the market.
18. General knowledge of the furnaces used for melting in crucibles
by means of coke or gas.
19. Chemical and physical characteristics of coke suitable for steel
melting.
20. Composition and physical characters of the various materials
used for the manufacture of crucible steel — viz., Swedish, Walloon, and
Lancashire hearth bars, unconverted and cemented, charcoal, Swedish
white iron, the various classes of steel scrap, and ferro-manganese.
21. Hammering, rolling, and reeling of crucible steel.
22. Shear and double shear steel, composition and method of
manufacture.
23. Testing steel in tension, with arithmetical calculations connected
therewith.
GRADE II.
Manufacture of Iron.
1. Preparation of raw ores for smelting ; changes in composition
thereby produced.
2. Mechanical preparation of iron ores. Magnetic concentration.
3. Subsidiary appliances required in the construction and working
of blast furnaces — e.g., hoists, blast heating stoves, and apparatus for
utilisation of surplus gases.
4. Mechanical charging appliances. Pig casting machines, pig
breakers, and similar appliances.
5. Chemical nature of fluxes requisite under various conditions.
Composition of slags.
6. Handling and utilisation of blast-furnace slags.
7. Chemical composition ol charcoal, coal, and coke used for iron
smelting. Composition of gases from the blast furnace.
APPENDIX. XV
8. Chemical and mechanical characteristics of pig irons from various
classes of ore.
9. Iron-founding, including cupolas, moulds, ladles, and foundry
appliances.
10. Machine moulding, core making, foundry sand and compositions.
11. Production of castings of special kinds — e.g., large castings, fine
castings, chilled castings, &c.
12. The theory of puddling. Machine puddling.
13. Mechanical properties of the various qualities of wrought iron.
Composition and tests of wrought iron suitable for various purposes.
14. Direct production of wrought iron.
15. Composition of iron suitable for the production of malleable
castings. Conditions under which carbon separates from white iron.
Other changes during the annealing process.
Manufacture of Steel.
16. Theory of the acid Bessemer blow. Theory of the acid open-
"aearth process. Slags produced.
17. Theory of the basic Bessemer blow. Theory of the basic open-
nearth process. Slags produced.
18. The functions of manganese, silicon, and aluminium. Influence
of varying quantities of silicon and manganese on the temperature of
the acid Bessemer blow.
19. Comparative advantages and disadvantages of blowing metal
direct from the blast furnace, and re-melted in cupolas.
20. Chemical and physical characteristics of coke suitable for
Bessemer cupolas and of coal for gas producers. Composition of
producer gases.
21. Bessemer, open-hearth, and crucible steel castings. Nature and
elimination of blowholes.
22. Low pressure surface blown modifications of the Bessemer
process and their products.
23. Modified open-hearth processes conducted in tilting furnaces,
&c. — e.g., the Talbot process, the "Rertrand-Thiel process, &c.
24. Methods of dealing with emergencies— «,</., hot or cold heats
or blows.
25. Manufacture and compositions of clay and plumbago crucibles.
Annealing clay crucibles. Stands and covers. Sanding.
26. The cementation process. Bar numbers.
27. Impurities eliminated or introduced in crucible melting.
Calculation of mixtures.
28. Causes leading to "runners" in crucibles — e.g., inclusion of
basic granules, frost-crack, &c.
29. Practice of hardening and tempering steel.
FINAL EXAMINATION.
Candidates for this Examination will be expected to answer
questions dealing with subjects included in Grades I. and II., and may
select their questions from one section only, or from both. The
following additional subjects will also be included.
XVI APPENDIX.
Manufacture of Iron.
1. Geographical and geological distribution of iron ores. Relation
of composition to geological distribution.
2. Handling and transportation of iron ores and other materials
employed.
3. Thermal calculations relative to the calorific value of fuel and of
blast-furnace gases, and to the reactions of the blast furnace.
4. The testing of cast iron otherwise than by chemical analysis.
5. Theories of puddling. Calculations relative to the yield of pig
iron of given composition.
6. The micro-structure of pure iron, of wrought iron, and of various
kinds of cast iron.
7. The production of spiegel-eisen, ferro-manganese, ferro-chrome,
and ferro-silicon, in the blast furnace. Properties of these alloys.
8. The applications of electricity in the production of iron and iron
alloys.
Manufacture of Sted.
1. The relative position of the steel trade in the chief steel-making
countries, and the reasons for the adoption of certain methods or
processes in particular countries or districts.
2. The general arrangement of a steel works, and the appliances and
methods used in handling, charging, rolling, pressing, hammering, or
otherwise shaping large masses of steel.
3. Chemical and thermal calculations relative to the various steel
processes, and to producer gas.
4. Liquation and segregation in ingots. Methods of producing sound
and uniform metal.
5. Influence of heat treatment of steels of various kinds. Theory
of hardening, tempering, and annealing.
6. Special materials used in steel manufacture, such as ferro-chrome.
ferro-nickel, tungsten, &c. Properties of the special steels so produced,
7. Influence of carbon and other elements on the tenacity and
ductility of the various qualities of steel. Composition necessary to
fulfil given mechanical specifications.
8. Applications of electricity in the production of steel.
xvii
INDEX.
ACID, 26, 93.
Bessemer process, 58, 75.
materials, 231, 232, 233.
open hearth, 60.
pig iron, 94.
Siemens process, 58, 60, 97.
steel, 61.
„ making, 97-126.
,, ,, appliances,
97-115, 254.
Action on crucible, 48.
Afterblow, 90.
Aired bars, 41.
Air chambers, 103.
ior Bessemer process, 65.
blastfurnace, 196.
cupola, 154.
hot-blast stove, 200
kilns, 185.
Euddling, 17.
iemens process. 113.
ports, 105, 255.
preheated, 103, 107, 193.
regenerators, 103, 106, 25,5.
valves, 103, 107.
Alloy, 4.
Alumina, 26, 229, 230.
Aluminium, 81, 134, 236.
American ores, 63, 247, 248, 249, 250.
Analyses of —
American ores, 248, 249.
Anthracite, 226.
Ayrshire ore, 177.
, , pig iron, 240.
Basic pig iron, 91, 94, 129, 213.
„ slag, 95. .
Bauxite brick, 245.
Bessemer pig iron, 213.
„ slag, 82, 95.
Best tap, 18.
Bilbao ores, 243.
Blackband ironstone, 177.
Analyses of —
Blast-furnace gases,' 221.
,, slags, 220.
Blister steel, 47.
Blown metal, 91.
Boilings, 25.
Bricks, 233, 245.
Bridge-work steel, 133.
British ores, 177.
Brown hematite ore, 178, 243
Bull dog, 18.
Calcined ironstone, 183.
Campanil ore, 122, 243.
Cannon steel, 133.
Cartagena ore, 244.
Castings, iron, 162.
,, malleable, 169.
steel, 166.
Cast steel, 47.
Cemented bars, 47.
Charcoal, 226.
Chrome bricks, 245.
,, iron ore, 245.
Clay band ironstone, 177.
Cleveland ironstone, 177, 183.
,, pig iron, 213, 240, 241,
Coal, 226.
Coke, 226.
Core sand, 148.
Crucible cast steel, 47.
Cumberland ore, 178.
,, pig iron, 240.
Derbyshire pig iron, 240.
Die steel, 133.
Dolomite, 85, 86.
East Coast pig iron, 240.
Elba ore, 244.
Electrical steel, 133.
Ferric ores, 178.
Ferro-manganese, 80, 237.
Ferro-silicon, 238.
Ferrous ores, 177.
Fettling materials, 18.
Finishing materials, 237.
XV111
INDEX.
Analyses of —
Firebrick, 233.
Fireclay, 233.
Fire sand, 148.
Foreign ores, 179.
Forge pig iron, 12, 213, 241.
Foundry pig iron, 162, 213, 241.
Frodingham ores, 205, 242.
Ganister, 66, 233.
Garrucha ore, 244.
Gases, 137, 221, 245, 246.
Glengarnock pig iron, 239.
Graphite, 234.
Grey pig iron, 162.
4Jun steel, 133.
Hammer slag, 25.
Hematite ores, 178, 243.
,, pig iron, 78, 91, 121,
169, 213.
Iron castings, 162.
„ ores, 122, 177, 178, 183, 205,
242.
Ironstones, see Ores.
Lanarkshire pig iron, 240.
Lancashire pig iron, 240.
Lime, 85, 86.
Limestone, 85, 86.
Lincolnshire ore, 205, 242.
,, pig iron, 240.
Magnesia bricks, 245.
,, burnt, 85.
Magnesite, 85, 86.
Magnetic ore, 178.
Malleable castings, 169.
iron, 12, 47, 57, 146.
Mediterranean ores, 244.
Medium steels, 133.
Melted charge, 125.
Mild steel, 57, 78, 91, 125, 133,145.
Monmouthshire pig iron, 240.
Mottled pig iron, 241.
Moulding sands, 148.
Northamptonshire ore, 178.
,, pig iron, 240.
Nottinghamshire pig iron, 240.
Occluded gases, 137.
Open-hearth charge, 125.
Ores, 122, 177, 178, 183, 205,
242, 248, 249.
Pig irons, 12,47,78,91,94,121,
129, 162, 169, 213, 239, 240,
241, 243, 244.
Plumbago, 234.
Analyses of —
Pottery mine, 242
Producer gas, 246.
Projectile steel, 133.
Puddlers' cinders, 25.
,, slags, 25.
Purple ore, 18.
Rail steel, 133.
Red hematite ore, 178.
Rubio ore, 243.
Sands, U8, 233.
Scotch pig iron, 241.
Scrap steel, 121.
Ship's plates, 133.
Siemens charge, 125.
,, slag, 126.
Silica brick, 233.
Silico-ferro, 238.
Silico-spiegel, 238.
Slags, 25, 83, 95, 126, 220.
Softeners, 238.
Spanish ores, 178, 243.
Spathic ore, 177, 243.
Spiegel-eisen, 80, 237.
Staffordshire ores, 177, 242.
,, pig iron, 240.
Steel castings, 166.
Steels, 47, 57, 78, 91, 121, 125, 133.
Stirlingshire pig iron, 240.
Swedish magnetite, 178.
,, pig iron, 47, 213.
,, wrought iron, 47.
Tap cinder, 25.
Tinned plates, 133.
Tool steel, 47, 50.
Tyre steel, 133.
Vena ore, 243.
White pig iron, 241.
„ sand, 233.
Wood, 226.
Wrought iron, 12, 47, 57, 146.
Yorkshire pig iron, 240.
Annealed steel, 52.
Annealing castings, 167.
,, furnace, 168.
Anthracite, 204, 226. 227.
Apatite, 177.
Appliances, see Plant.
Aolf Ac2, Ac3, 52.
Arlt Ar2, Ar3, 52.
Archimedian screw, 101.
Area, Calculation of, 144.
Ash, 224, 225, 227.
INDEX.
XIX
Ash, Removal of, 100, 101, 103.
Ayrshire ore, 177.
,, pig iron, 177.
B
BABCOCK & WILCOX Boiler, 221
Ball. Puddled, 22.
Balling, 22.
Ba r mill, 32, 33.
Bars, Aired, 41.
,, Blister, 40, 41.
„ Cemented, 37, 47-
„ Converted, 40.
,, Finished, 41.
„ Flushed, 41.
,, Glazed, 41.
,, Merchant, 28.
,, Puddled, 28.
„ Steel, 41.
„ Swedish, 35.
„ Tap, 39.
„ Trial, 39.
Bases, 26, 27, 61, 93.
Basic Bessemer process, 89, 90, 91 .
,, bricks, 85, 86.
,, lining, 87, 88,89, 127j 128, 129.
,, machinery, 86, 87, 89, 128.
,, open-hearth process, 127-132.
,, pig iron, 91, 94, 129, 213.
„ plant, 84, 85, 86, 87, 88, 127,
128, 129.
„ plug, 87, 88.
„ press, 86.
,, process, 89, 90, 91, 130, 131.
,, refractory materials, 233.
„ Siemens plant, 127, 128, 129.
,, „ process, 127-132.
„ slag, 61, 95, 96, 131, 132.
„ steel, 61, 166.
,, substances, 231.
,, tuyeres, 88.
Bauxite brick, 234, 245.
Beehive coke oven, 228.
Bell, see Cup and cone.
Bessemer air-blast, 65, 68.
blowing engine, 68.
bottom, Acid, 67.
,, Basic, 87, 88.
„ Renewal, 64.
converter, Acid, 64, 76.
Basic, 84, 85,
86.
crane, 70, 89.
Bessemer cupola, 71, 72, 74.
,, Heat evolved during
blow, 81.
ladle, 68.
lining, Acid, 66, 67.
Basic, 84, 85, 86,
127, 128.
machinery, 68, 69, 70, 85,
pig iron, 213. [89
plant, 14-74, 84, 85.
platform, 68.
plug, 87.
process, 58, 59, 75, 76, 77,
89, 90, 91.
pulpit, 68.
scrap, 49.
slag, Acid, 82, 83.
,, Basic, 95, 96.
steel, 61, 78, 166.
Swedish practice, 81.
tuyeres, Acid, 6(5, 67.
Basic, 88.
Best best iron, 28.
„ tap, 17, 18.
,, Yorkshire iron, 34.
Bilbao ores, 243.
Binding materials, 86, 114.
,, power, 150.
Bituminous coal, 23, 226.
Blackbaud ironstone, 177.
Blast for converter, 65, 68.
,, ,, cupola, 154, 155, 156.
,, ,, furnace, 193.
,, ,, producer, 98.
,, furnace, 188, 191.
,, ,, blowing engine, 196.
,, ,, bosh, 190.
,, ,, dimensions, 195.
,, ,, equipment, 188.
,, ,, foundations, 190.
gases, 188, 210, 220,
221, 222.
,, ,, hearth, 190.
,. ,, hoists, 201,251,252.
lining, 188, 192.
output, 195.
slags, 188, 211, 212,
220.
,, „ stack, 190.
stoves, 196, 197, 198,
199.
tuyeres, 194, 195.
well, 190.
INDEX.
Bleeding, 134.
Blister steel, 40, 47.
Blooms, 28.
Blow, Bessemer acid, 75, 76, 77.
„ ,, basic, 89, 90.
Blower, 68, 69.
„ Roots', 155, 156.
Blowholes, 136, 165.
Blowing engines, 68, 196.
Blown metal, 91.
Blows, Cold, 82.
„ Hot, 82.
Blue Billy, 176.
Boiling, 21, 22, 25, 122.
Boilings, 25.
Bosh, 195.
Bottom, 88, 108, 128.
Boxes, 37, 167, 168, 169, 171.
Breeze fire, 53.
Bricks, Basic, 85, 86.
Bauxite, 234, 245.
,, Chrome, 234, 245.
,, Dolomite, 233.
„ Fire-, 231, 232, 233.
„ Ganister, 232.
,, Magnesia, 233, 245.
Neutral, 129.
„ Silica, 232, 233.
Brinell's formulae, 52.
Briquettes, 182.
British ores, 177.
Brown hematite ore, 176, 178, 243.
Buckstave, 103, 107.
Bulldog, 17, 18.
Burden, 203.
Self-fluxing, 205.
Burning in, 128.
out, 12.
Burnt dolomite, 85.
„ iron, 8.
,, limestone, 85, 89.
,, magnesite, 85.
,, pyrites, 176.
Bustle pipe, 207.
CALCIC phosphate, 93.
Calcination of ores, 182, 183, 184.
Calcined ironstone, 183.
Calorific power, 226.
Campanil ore, 122, 243.
Candles, Puddlers', 22.
Carbon, 5, 6, 145, 146.
addition, 194.
Cement, 52.
Combined, 12.
deposition, 228.
dioxide, 5, 26, 97.
Fixed, 225, 226.
Graphitic, 12.
Hardening, 52.
impregnation, 210.
penetration, 39.
Carbonic acid, 26.
3arburisation, 40.
Cartagena ore, 244.
Case hardening, 171.
Cast ng pit, 69, 110.
^ast ngs, Annealing, 167
Chilled, 163.
Cleaning, 167.
Dry sand, 150.
Green sand, 150.
Iron, 148, 162.
Malleable, 169.
Steel, 148, 165, 166.
Cast iron, 147.
castings, 163, 164, 16&
cylinders, 163, 164.
Hardened, 162, 163.
Shrinkage of, 165.
Softened, 162.
tests, 147.
steel, 35, 42, 47.
Cementation boxes, 35, 38.
,, cover, 39.
,, furnace, 37.
„ pots, 35, 38.
,, process, 35.
Cement carbon, 52.
Cemented bars, 37, 47.
Chamber, Regenerative, 103.
Changes induced in steel, 51.
Charcoal, 204, 226, 228.
Charger, 45.
Charges, 19, 38, 39, 45, 71, 73, 76,
77, 89, 124, 125, 130, 156, 167,203.
Charging, Appliances for, 115, 116,
251, 256. [252.
„ blast furnaces, 207, 251,
boxes, 38, 39, 167.
„ converters, 76, 77.
„ crucibles, 45.
„ cupolas, 71, 73, 156.
„ ingots into furnace, 138,
139.
INDEX.
XXI
Charging kilns, 185, 186.
, , lime into furnace, 89.
,, Machinery for, 11 5, 25 1,256.
„ reheating furnaces, 188.
„ soaking furnaces, 141.
Checkers, 107.
Checker work, 103, 199.
Chemical change, 4.
,, combination, 6.
,, composition, see Analyses,
,, formulae, 5, 6.
„ reactions, 5, 6, 27, 28, 79,
80, 92, 93, 122, 183, 209,
210, 211.
,, residuals, 103.
,, symbols, 3, 5, 7.
Chemical considerations —
Acid Bessemer process, 78, 79.
,, Siemens process, 122, 123.
Basic Bessemer process, 91, 92,
qq
t/O.
,, Siemens process, 131.
Blast-furnace working, 209, 210,
211.
Crucible process, 47, 48, 49.
Malleable castings process, 169.
Puddling process, 25, 26, 27, 28.
Chilled castings, 163.
Chimney, 16, 105.
Chrome bricks, 234, 245.
iron ore, 85, 129, 233, 245.
Chromic oxide, 230.
Cinder, see also Slag.
Elimination of, 23, 26.
Flue, 177.
Functions of, 27.
hole, 17.
notch, 17.
pig iron, 177.
Puddlers', 177.
Tap, 24, 25.
Truck, 23.
Utilisation of, 129.
waggon, 23.
Clay, 4, 229, 232.
Clay band ironstone, 177.
Cleaning castings, 167.
Clearing stage, 20, 21.
Cleveland ironstone, 183.
pig iron, 131, 213, 240,
241.
Clinker, 39.
Coal, 39, 97, 204, 226, 227.
Coarse grained steel, 52, 53.
Coke, 156, 204, 225, 226, 227, 228.
,, ovens, 228.
Coking, 227, 228.
coal, 227.
Cold-shortness, 8, 57, 84.
Composition, see Analyses.
Compounds, 4.
Compound slag, 228.
Cone, 99, 186, 192, 193.
Contraction of area, 145.
, , Calculation of,
145.
Conversion, 40.
Converter, 64, 166.
bottom, 67, 87, 88.
hood, 67, 87.
lining, 66.
nose, 67, 87.
plug, 67, 88.
rack, 65.
ram, 65.
ramming, 67.
renewal, 64.
trunnion, 65.
Cooling, 52.
Cores, 149.
Core sand, 148.
Cotter bolts, 89.
Country heat, 40, 41.
Cowper stove, 197.
Crab, 115.
Cranes, 70, 111, 115.
Critical points, 51.
Crocodile squeezer, 28.
Crucible cast steel, 35, 42, 47, 49,
50, 51, 55.
„ charge, 46.
Crucibles, 42, 45, 49, 150, 166,
167.
,, Action on, 46.
Crushing strength, 161.
Crystallisation, 11, 163.
Cumberland ore, 175, 178.
, , pig iron, 240.
Cup and cone, 192, 203, 204.
Cupola, 71, 72. 150, 153, 155.
,, ' Bessemer works, 71, 72,
73, 74.
,, charge, 156.
Drop bottom, 152, 153.
„ Foundry, 150.
,, Fuel for, 156.
IHDBX.
Cupola receiver, 154.
Solid bottom, 151, 153.
„ Steel works, 71, 72, 73.
Currents in blast furnace, 206, 207.
Cutlery, 49.
Cutting edge, <
Cyanides, 210.
Cylinders, 163, 164, 192.
49.
DAMPER, 16, 107.
Dannemora bar iron, 35.
Decarburising, 117.
Defects produced by hardening, 54.
Deoxidising, 13, 77, 79, 93, 119.
„ materials, 235.
Dephosphorising, 27, 84.
Derbyshire pig iron, 240.
Diminishing weight of charges, 4b.
Direct process, 11.
Distorted roof , 113.
Dogs for lifting ingots, 77, 135.
Dolomite, 85, 86, 128, 233.
bricks, 233.
„ lining, 85, 86, 87, 128
Double shear steel, 41.
Doubling, 23.
Downcorner, 207.
Downtake, 207.
Draught, 45, 107, 226.
Drawing wire, 9.
Drop of flame, 78.
Dry puddling, 11.
,, sand castings, 150.
Ductility, 9.
Duff producer, 102, 103.
Durham coke, 179.
Dust catcher, 191.
„ pocket, 107.
EAST Coast pig iron, 240.
Elasticity, 9.
,, Limit of, 9.
Elba ore, 244.
Electric furnaces, 257, 258.
Elements, 4.
Eliminate, 12.
Elimination, 25, 27, 61, 90, 91,
92.
Elongation, 9, 144.
Engine, Travelling, 111.
Equivalents, 6, 7.
Explosion, 113.
Expulsion of slag, 23.
Extensibility, 9.
Extraction, 3.
FERRIC ores, 178.
,, oxide, 5, 6, 230.
Ferro-manganese, 49, 80, 235, 237.
Use of, 49, 119,
123, 129.
Ferro-silicon, 236, 238.
Ferrous carbonate, 230.
-ferric ores, 177.
ores, 177.
oxide, 4, 6, 26, 229, 230.
silicate, 10.
Fettling, 12, 13, 14, 17, 18.
Functions of, 27.
materials, 18.
Fibrous structure, 11.
Fiery steel, 134.
Fillers, 207.
Fine-grained steel, 52, 53.
Finishing materials, 237.
Fire-bars, 41.
-bridge, 16, 17.
-grate, 17, 38.
-hole, 17.
-sand, 148.
, -stones, 232.
Firebrick, 231, 232, 233.
stoves, 200.
Fireclay, 232, 233.
nozzle, 68.
sleeve, 68.
,, stopper, 68.
Firth's Steel Works, 104.
Flame drops, 78.
„ flue, 197, 207.
Flue, 15, 44.
„ -bridge, 16, 17.
,, cinder, 176.
Fluid metal, 71.
Fluorspar, 130, 132, 230.
INDRX.
xxiii
Flushed bars, 41.
Fluxes, 4, 21, 24, 118, 188, 204,
205, 228.
Fluxing, 11.
,, oxide, 12.
Foreign ores, 179.
Foreplate, 17, 110.
Forge pig iron, 12, 213, 241.
„ plant, 28.
„ train, 31, 32.
Formulae, 4, 5.
Foster's tuyeres, 195.
Foundry cupola, 150, 151, 152, 153.
,, Drop bottom, 153.
,, receiver, 154.
,, Solid bottom, 153.
ladle, 157, 158, 159.
mixtures, 160.
pig iron, 160, 162, 213,
241.
,, practice, 148.
Fracture, 40.
,, of ingot, 46.
Frit, 113.
Frodingham ores, 205, 242.
Fuel, 3, 7, 188, 224.
„ for annealing furnace, 169.
„ ,, Bessemer process, 82, 91,
95.
„ „ blast furnace, 204, 215.
,, calcining kiln, 186, 187.
,, ,, cementation furnace, 39.
,, ,, crucible furnace, 44.
,, ,, cupola, 156.
„ gas producer, 97, 246.
,, ,, open-hearth furnace, 97.
,, ,, puddling furnace, 23.
,, ,, regenerative furnace, 97.
„ ,, reheating furnace, 138.
,, ,, reverberatory furnace, 14,
23.
,, ,, Siemens furnace, 97.
,, ,, soaking furnace, 140.
,, Natural, 226.
,, Prepared, 226.
Funnel, 45.
Furnace, Annealing, 168.
Blast, 188.
Cementation, 37.
Crucible, 42.
Electrical, 257
Movable, 103, 255.
Open-hearth, 103, 255.
Furnace, Puddling, 14.
Regenerative, 103, 255.
Reheating, 138.
Reverberatory, 14.
Rolling, 103, 255.
Siemens, 103, 255.
Soaking, 138.
Tilting, 103.
Vertical, 140.
GANGUE, 4, 174, 219, 228.
Self-fluxing, 219.
Ganister, 66, 232, 233.
brick, 232.
,, lining of Bessemer con-
verter, 67.
Garrucha ore, 244.
Gas engine, 221.
Natural, 9*7, 246.
ports, 105.
producers, 97-103, 141, 246.
A. B. Duff, 102.
,, Siemens, 98.
Wilson's, 98.
,, ,, self clean-
ing, 101.
valve, 103.
Cases from blast furnace, 188, 210,
220, 221.
,, producer, 246.
„ steel, 137.
Occluded, 136, 137, 257.
Reducing, 137, 220.
Surplus, 220, 221.
Utilisation of, 221, 222, 223.
Waste, 220.
German Steel Trade, 63.
Gjers' kiln, 186, 187.
„ soaking pit, 138, 139.
Glazed bars, 41.
Glengarnock pig iron. 239.
Goose-neck, 194.
Grading pig iron, 214, 217.
Graphite, 12, 234.
Graphitic carbon, 12.
Grate-bars, 17.
Green sand, 150.
Grey pig iron, 162, 216, 217.
Guide mill, 32, 33.
XXIV
INDEX.
H
HAMMER scale, 24.
slag, 25.
Hardening carbon, 52.
„ defects, 54.
,, iron, 163.
„ steel, 51, 52, 54.
Hard tap, 115.
Head melter, 45.
Hearth, Blast-furnace, 190.
Heat, Country, 42.
Double shear, 42.
evolved, 81.
Irish, 42.
Melting, 42.
Single shear, 42.
Spring, 41.
Steel-through, 42.
units, 225.
value, 225, 226.
Helve, 29.
Hematite ores, 18, 167, 175, 176,
178, 243.
pig iron, 78, 91, 121,
169, 213.
Hoists, 201, 251. 252.
Hole, Cinder, 17.
„ Firing, 17.
„ Staff, 17.
,, Steel-melting, 42.
,, Stopper, 17.
Holley's improvement on converter,
64.
Homogeneous steel, 42.
Honeycombed steel, 47, 119.
Hopper, 99.
Horse-shoe main, 194.
Hot-blast, 193.
,, main, 193.
„ stove, 196.
„ „ Cast iron, 196.
„ ,, Firebrick, 196.
,, ,, valve, 199.
,, ,, Working of, 200.
,, tuyeres, 194.
House, Steel-melting, 42, 43.
Housings, 31, 32, 34.
Hungry pigs, 13.
Hydrocarbons, 97, 224, 226, 226
227.
Hydrogen, 7, 97.
IMPACT, 142.
Imported ores, 179.
Impurities, 8, 135, 231.
Increased yield, 13, 24, 40.
Inferior steel, 46.
Ingot, Bessemer, 77.
,, Bleeding, 134.
„ Contraction of, 135.
„ Cooling of, 134, 135.
„ Impurities in, 135.
,, iron, 57.
„ moulds, 70, 134.
„ „ Stripping, 70.
„ Objectionable, 134.
,, outer crust, 134.
,, Perfect, 136.
,, Pressing, 136.
,, Removal of, 135.
,, Scorched, 46.
,, Segregation in, 135.
„ Shrinking of, J 34.
,, Solidified, 134, 135.
,, Sound, 134.
,, Stoppering, 134.
„ Stripping, 70, 71, 77, 120,
,, Treatment of, 137.
,, unsound tops, 135, 136.
Injector, 17, 99, 100.
Irish ores, 176.
„ temper, 41.
Iron, Best best, 28.
Best Yorkshire, 34.
Burnt, 8.
castings, 148, 162, 163, 164.
Chemically pure, 4.
Dannemora, 35.
,, Extraction of, 3.
,, Ingot, 57.
„ ,, moulds, 70.
„ ,, ,, Cooling of, 135.
,, Malleable, 11.
„ ores, 122, 177, 178, 183, 205,
242.
„ oxides, 4, 5, 6, 26, 229, 230.
,, Properties of, 8, 11.
„ Pure, 4, 8.
„ pyrites, 230.
„ Reheating, 137.
„ rust, 4.
INDEX.
XXV
Iron, Spongy, 22.
Swedish, 35.
Treble best, 28.
Wrought, 11, 12, 47, 57, 146,
147.
Slag in, 11.
Yorkshire, 34.
JUMBO, 175.
K
KIDNEY ore, 175.
Killing, 46.
Kiln, Calcining, 185.
„ Gjers', 186.
„ Scotch, 185.
Kindling furnace, 113.
,, producer, 100.
,, Siemens furnace, 107.
Kish, 162.
LADLE, Bessemer, 68, 111, 112.
„ Crane, 89.
,, for hot metal, 73.
„ ,, side tapping, 89, 90.
Ladles, Foundry, 157.
Geared, 158.
Mounted, 159, 160,
Lanarkshire pig iron, 240.
Lancashire hearth, 35.
ore, 175, 179.
,, pig iron, 240.
Launder, 110
Lignite, 204.
Lilleshall Company, 111.
Lime, 26, 85, 228, 229, 230.
,, in blast furnace, 215.
Limestone, 85, 86.
Lincolnshire ores, 205, 242.
,, pig iron, 240.
Lining converter, Acid, 67, 86, 87,
88.
„ „ Basic, 86.
„ Siemens furnace, 114, 127,
128.
„ with dolomite, 128.
Lining with ganister, 66, 67.
,, ,, magnesia, 128.
Lloyds' tuyere, 194.
Loam, 114, 231.
Loss of metal, 74.
Lower oxide, 80.
MACHINE charging, 115, 202, 256,
Magnesia, 26, 85, 230.
bricks, 233, 245.
,, limestone, 85, 86.
,, lining, 128.
Magnesite, 85, 86, 128.
,, bricks, see Magnesia
bricks.
Magnetic concentration, 182.
,, ore, 178.
,, oxide, 5.
Making up taphole, 114, 115.
Malleable castings, 167, 168, 169.
,, iron (wrought iron), 11,
12, 47, 57, 146, 147.
Malleability, 9.
Manganese, 7, 9.
Action of, 48, 49, 79,
80,81,93,94,95,119,
120, 121, 129, 214.
ores, 179, 181.
,, silicate, 48.
Manganous oxide, 26, 28.
Manhole, 38.
Marsh gas, 221.
Martin process, 60.
Mechanical testing, 142.
Mediterranean ores, 244.
j Medium steel, 119, 133.
Melted charge, 125.
Melting-down stage, 19, 122.
,, heat, 40.
,, of metal, 150.
,, slag, 228.
,, steel, 42.
Merchant bar, 28.
Mercury, Quenching in, 54.
Metal, Fluid, 71.
,, mixer, 71.
Solidifying, 82.
„ Wild, 82.
Metallic state, 3.
Metalloids, 7.
XXVI
INDEX.
Methane gaa, 97.
Mild steel, 57, 58, 91, 119, 125,
133, 145.
,, specifications, 146.
Mill, 32, 33.
„ Bar, 32, 33.
,, Guide, 32, 33.
„ Merchant, 32, 33.
,, train, 28.
Mixer, 71.
Monmouthshire pig iron, 240.
Mottled pig iron, 216, 241.
Moulding cores, 149.
,, materials, 149, 166.
sands, 148.
Moulds, 45.
,, for castings, 148.
,, for crucibles, 45.
Ingot, 70.
,, Loam, 150.
Reeked, 46.
Movable furnace, 103, 255.
Muffles, 53.
Mushet steel, 40.
N
NATIVE, 174.
Natural gas, 97, 246.
Neutral course, 128.
,, refractory materials, 234.
,, substances, 234.
Non-metal, 4, 7.
Normal steel, 52.
Northamptonshire ore, 178.
,, pig iron, 240.
Nostrums, 49.
Notch, 17.
Nottinghamshire pig iron, 200.
Nozzle of ladle, 68, 70.
OCCLUDED gases, 136, 137, 165, 257.
Occlusion, 136, 165.
Oil-hardened tools, 56.
Open hearth, 166 (see Siemens).
Ores, Aluminous, 176.
,, American, 247, 248, 249, 250.
,, Antrim, 176.
,, Ayrshire, 177.
„ Belfast, 176.
Ores, Bilbao, 243.
Blackband, 175, 177, 179.
Brown hematite, 175, 176,
178, 243.
Campanil, 121, 122, 243.
Cartagena, 244.
Clayband, 177.
Cleveland, 175, 177, 179, 183.
Cumberland, 175, 178.
Dunderland, 179.
Elba, 179.
Ferric, 175.
Ferrous, 175.
Ferrous-ferric, 175, 176.
Foreign, 179.
Franklinite, 175.
Frodingham, 205.
Garrucha, 244.
Greek, 179.
hematite, Brown, 175, 176,
178, 243.
„ Red, 167, 175, 178.
Ilmenite, 175.
Imported, 179.
Indian, 179.
Irish, 176.
Kidney, 175.
Lancashire, 175.
Lenticular, 176.
Lincolnshire, 205, 242.
Magnetite, 175, 176, 178.
Manganese, 179.
Mediterranean, 179.
Northamptonshire, 178.
Norwegian, 179.
Pencil, 175.
Pottery mine, 242.
Purple, 17, 18, 176.
Red hematite, 167, 175, 178.
Rubio, 243.
Russian, 179.
Self -fluxing, 205.
„ -going, 205.
Siderite, 175.
Spanish, 178, 179, 243.
Spathic, 175, 177, 243.
Specular, 176.
Staffordshire, 177, 242.
,, Swedish, 178.
Osborn's Works, 109.
Ovens, Coke, 228.
Oxidation, 12, 74, 78, 79, 117, 130.
„ tints, 56.
INDFX.
XXV11
Oxygen, 3.
,, carrier, 25.
PACK INC. pots, 39.
Pattern, lt>7.
Peat, 204.
Peel, 116.
Pencil ore, 175.
Penetration of carbon, 39.
Permanent set, 10.
Phenomenon of hardening, 51.
Phosphoric acid '26.
anhydride, 26.
Phosphorus, Elimination of, 26, 27,
90, 127.
„ in pig iron, 8, 161, 177,
1 80.
,, in steel, 8.
Physic, 45, 49, 80.
Pig bed, 207.
,, boiling, 1 1.
Pigging back, 124.
Pig iron, 188, 213.
,, Abnormal, 217.
,, Acid Bessemer, 94, 181,
213.
,, ,, Siemens, 181.
„ All-mine, 181.
,, Basic Bessemer, 94, 181.
213.
,, Carbon in, 214.
„ Chilled, 217.
„ Cinder, 117,217,218.
„ Cleveland, 213.
„ Forge, 12, 213.
„ Foundry, 160, 161, 180.
„ fractures, 118, 216, 217.
„ Grading of, 217.
„ Grey, 216, 217.
„ Malleable castings, 169.
„ Manganese in, 94, 95, 2 1 5.
„ Mottled, 216, 217, 219.
,, Phosphoric, 132.
,, Phosphorus in, 214.
„ Production of, 180, 181.
„ Puddling, 12.
„ Silicon in, 214, 215.
„ Silvery, 219.
„ Soft, 219.
„ Sulphur in, 214.
Pig iron, Swedish, 35, 48, 181, 213.
White, 216, 217, 219.
Piles for reheating, 28, 42.
Pipe, 136.
,, stove, 196.
Piping, 136.
Pistol pipe stove, 197.
Plant for blast furnace, 188.
Bessemer, 64-74, 84-89.
,, open hearth, 97 - 115,
127-129.
,, Siemens, 97.
Platform, 68, 69.
Plating, 41.
Plumbago, 234.
,, crucible, 49.
Plug, 87, 88.
Plunger, 192.
Points, Arrestment, 51.
Critical, 51.
Pon sity of moulds, 150, 166.
Potash, 200.
Pots, 42, 105, 167, 168.
,, Cementation, 38.
Pottery mine, 18, 129, 242.
Pouring metals, 76.
Preheated air, 103, 107, 196.
Problem of elimination of phos-
phorus, 61, 63.
Producer gas, 97, 103, 141, 246.
Producers, Gas, 97-103, 140.
Properties of iron, 8.
Protection of piles, 42.
Puddled ball, 22, 28.
„ bars, 23, 28.
,, steel, 49.
Puddlers' candles, 22.
,, cinders, 25, 177.
„ slags, 25, 177.
tap, 177.
Puddling, Dry, 11.
,, furnace, 14-17.
,, ,, Preparation of,
18.
„ process, 19.
balling, 22.
boiling, 21.
charging, 19.
clearing, 20.
coming to
nature, 23.
melting down,
19, 20.
18
XXV111
INDEX.
Puddling process, rabbling, 12,21.
,, ,, shingling, 23.
Wet, 11.
"Puller out, "45.
Pulpit, 68.
Pulpit man, 68.
Purifying melted pig iron, 64.
Purple ore, 17, 18, 129, 17G.
Pyrites, 230.
Pyrometer, 53.
QUARTZ, 7.
Quenching in brine, 54.
,, mercury, 54.
oil, 54.
„ water, 51, 53 54.
Quick -cutting tool steel, 50.
RABBLING, 12, 21.
Ramming, 67, 87, 128.
Rapid-cutting tool steel, 49, 50.
Reactions, 5, 6, 27, 28, 48, 79, 80,
Ji2, 93, 123, 209, 210.
Recarburising, 81, 93.
,, materials, 235.
Receiver, 154.
Red hematite ore, 167, 175, 176,
178.
Red-shortness, 8. 57.
Reducing gases, 137, 221.
Reduction, 3, 13, 209, 210.
Reeking, 46.
Reeling, 47.
Refining, 7.
Refractory materials, 230, 231.
Acid, 232.
Basic, 233.
Neutral, 233,
234.
Regenerative chambers. 103, 105,
141, 255.
,, system, 103, 107.
Regenerators, 103, 105.
Reheating ingots, 47, 77, 137.
piles, 28, 42.
Remelting pig iron, 1 63.
Repairing sand bottom, 1 15.
Kephosphorising, 91.
Residuals, 103.
Retardation, 51, 52.
Retort ovens, 228.
Rcverberatory furnace, i4, 138, 150
Rolling furnace, 103, 265.
Rolls, Forge, 23.
Roots' blower, In5.
Rubio ore, 243.
Rust, 4.
SAND, 7.
„ Belgian, 114, 232.
Core, 148.
Dry, 150.
Fire, 148, 149.
for pig moulds, 209.
Fritting, 113.
Green, 150.
Lining, 114.
Moulding, 148, 149.
Silver, 114, 232.
White Be' gian, 114, 233.
Saggers, 167.
Sap, 40, 41.
Scotch kilns, 185, 186.
„ pig iron, 241.
,, tuyeres, 194.
Scrap steel, 121.
Segregation, 135.
Selective action, 12, 78.
Self-fluxing ore, 205.
,, -going ore, 203.
Separation of slag, 13, 23, 45, 57,
77, 91, 118, 207.
Shingling, 23, 29.
Shoot, 110.
Shrinkage, Allowance for, 165.
of castings, 165, 166
,, ,, ingots, 134.
Siemens appliances, 97.
charge, 125.
furnace, 59, 103-110, 255.
plant, 97.
process, 58, 59, CO, 97.
producer, 98.
regenerator, 103, 105, 141.
slag, 126.
steel, 5«, 60, 61, 116.
valves, 103.
Silica, 7, 13, 26, 228, 229, 2.JO.
XXIX
Silica bricks, 232, 233.
Silicate of iron, 10.
,, ,, manganese, 48.
Silicates, 229.
,, Compound, 229.
Silico-ferro, see Ferro-silicon.
„ -spiegel, 236, 238.
Silicon, 7, 8, 13, 48, 81, 134, 161, 236.
,, Increase in, 48.
Sill, 17, 110.
Silver sand, 232.
Skull, 82.
Slag, 126.
„ ball, 212.
„ Basic, 61, 95, 96.
,, Bessemer, 82, 83.
basic, 95, 96.
„ Blast-furnace, 18S, 211, 212,
219, 220.
,, cement, 212.
„ Disposal of, 212.
,, Expulsion of, 23.
,, for furnace lining, 114.
,, Grinding of, 51, 96.
„ heaps, 212.
,, indication, 124.
,, in wrought iron, 11.
„ pocket, 107.
„ Puddlers', 25, 177.
„ Purifying, 131.
„ Separation of, 13, 23, 45, 57,
77, 91, 118, 207.
,, Siemens, 126.
„ Spoon for testing, 124.
,, tub, 118.
„ Utilisation of, 212.
„ wool, 212.
Sleeve, 68.
Smoked moulds, 46.
Soaking furnace, 140.
pits, 138.
Soda, 230.
Softeners, 162, 238.
Solid bottom cupola, 100.
,, producer, 100.
Sow, 207.
Spanish ores, 178, 179.
Spathic ores, 177, 243.
Specifications, 146.
Spiegel-eisen, 49, 80, 235, 236, 237.
Use of, 119, 123.
Spongy iron, 22.
Spray tuyere, 194.
Spring heat, 40.
Squeezer, 28.
Stack, 16, 37.
Blast-furnace, 207.
Steel cased, 16.
Staff hole, 17.
Staffordshire ores, 177, 179, 242,
,, pig iron, 240.
,, tuyeres, 194.
Steam hammer, 30.
,, jet, 17, 98, 100.
Steel, 35.
„ Acid, 58, 61.
,, Annealed, 52.
„ Basic, 58, 61.
,, Bessemer, 58, 59, 91.
,, Blister, 40, 47.
,, castings, 148, 165, 166.
,, Changes induced in, 51.
,, ,, observable in, 51.
,, Coarse-grained, 52, 53.
,, Crucible cast, 35, 42, 47.
ingot, 49.
,, Double shear, 41.
,, Fiery, 134.
,, Fine, 52, 53.
,, Hardened, 52.
,, Hardening defects, 55.
of, 51, 53.
Homogeneous, 42, 119.
Honey-combed, 47.
Inferior, 46.
ingot, Solid, 49.
makers, 50.
Martin, 58, 60.
Medium, 119.
melting furnace, 42.
„ holes, 42.
,, house, 42.
Mild, 57, 78, 119, 125.
Mushet's, 29.
Normal, 52.
Open-hearth, see Siemen*.
Puddled, 49.
Scorched ingot, 46.
Scrap, 121.
Self hardening, 49.
Shear, 41.
„ heat, 40.
,, Double, 40.
,, ,, „ Single, 40.
,, Shrinkage of castings, 186,
166.
XXX
INDEX,
Steel, Shrinkage of ingot, 134.
„ Siemens, 58, 59," 125.
„ „ -Martin, 58, 60, 61.
125.
„ Single shear, 41.
,, Special, 50.
,, Spongy, 46.
,, -through heat, 40.
„ Tool, 35.
,, Treatment of, 51.
,, user, 50.
,, Weldable, 49.
,, Wild, 134.
Stirlingshire pig it on, 240.
Stopper, 68.
hole, 17.
,, notch, 17.
Stoppering ingot, 134.
Stoves, 19ti.
Cast-iron, 196.
Cowper, 197, 19S. 190.
Firebrick, 196, 197, 2<,0.
Hot-blast, 196.
Swedish, 19i>.
Strength, Crushing, 161.
,, of cast iron, 147.
,, ,, malleable iron, 146.
„ ,, mild steel, 146.
„ ,, moulding materials,
149.
„ Tensile, 161.
,, Transverse, 161.
Stretching force, 10.
Stripper, Hydraulic, 71.
Stripping, 70, 71, 77, 1'20, 134.
Sudden cooling, 52.
Sulphur, 8, 48.
,, beneficial, 8.
,, taken up, 170.
Swedish bars, 35, 47.
„ pig iron, 35, 47, 48, 213.
TAP bars, 39.
,, cinder, 24, 25.
Taphole, 114, 115, 118, 129, 132.
,, Making up, 115.
„ Opening, 115, 118.
Tapping furnace, 118, 207.
side, 109, 110.
Tar, Anhydrous, 86.
Teeming, 70, 120.
Teeming, Chilled steel. 46.
"Dead, "46.
holes, 46.
Temperature, Regulation of, 44.
Tempering, 55, 56.
Tenacity, 10.
Tensile strength, 10, 143, 144, 146,
161.
,, ,, Calculation of,
144.
Test pieces, 142.
„ sample, 90, 124. 130.
Testing cast iron, 147.
,, machine, 142.
steel. 142.
Tetra-calcic phosphate, 93.
Thomas-Gilchrist process, 63.
Tie-rods, 103, 107.
Tilting Furnace. 103.
Tinned plates, 133.
Titanic oxide, 2t>, 230.
Tool steel, see Crucihle. cant steel.
Tools, Treatment of, 51.
,, Quenching, in mercury, 54.
,, in oil, 56.
,, ,. in water, 53.
Toughness, 10.
Transverse strength, 161.
Travelling crane, 111.
,, engine, 111.
Trays, 209.
Treble best iron, 28.
Tr.al bars, 38, 39.
,, holes, 3S.
Triple compounds, 80.
Trolley, 22, 23.
Troughs. 209.
Truck, Cinder, 23
Trunnions, 65, 110.
Tungsten, 9.
Tuyere block, 195.
Tuyeres, Bessemer acid, 65, 66.
basic, 87, 88.
,, Blast furnace, 194, 195.
Cupola, 72, 73, 74, 150,
153.
Tyre steel, 133.
U
UNPACKING, 190.
Utilisation of gases, 220 221, 222.
„ of slags, 212.
INDEX.
XXXI
VALUE of elements, 6, 7.
Valves, Butterfly, 103.
Gas, 103, 107.
,, Mushroom, 103.
,, Reversing, 107.
Vena ore, '243.
Vertical furnace, 140.
hoist, 201.
Vessel, see Converter.
W
WALLOON method, 35.
Water-balance lift, 201.
blocks, 195.
bottom, 99, 100.
cracks, 54.
,, Prevention of, 54.
in fuel, 225.
trough, 99.
Welding, 10.
Well of blast furnace, 190.
Wet puddling, 11.
W heels warf, 39.
White pig iron, 216, 217, 241.
„ (Belgian) sand, 233.
Wild metal, 82, i34.
Wilson producer, 98.
Wire-drawing, 9.
Wood, 204, 226.
Wool, Slag, 212.
Working Bessemer acid process 7$,
76, 77.
,, ,, basic process,
8i), 90, 91.
blast furnace, 203, 206.
,, cementation process, 38,
39, 40.
crucible process, 44-47.
cupolas, 71, 72, 73.
door, 17.
,, foundry cupola, 156.
hot- blast stove, 200.
kilns, 185, 186, 187.
,, puddling furnace, 18-23.
,, Reheating, furnace, 138,
139, 140, 141.
,, Siemens furnace, acid,
103-110.
,, Siemens furnace, basic,
127-129.
Wrought iron, 11, 12, 47, 57, 146,
147.
YIELD of metal, 13, 24, 40.
Yorkshire best iron, 34.
„ pig iron, 240.
XXX11
NAMES MENTIONED.
Avery, Messrs., 188, 189.
Bannister, C. O., 168, 170.
Bell Bros., 188, 189.
Bessemer, 58, 59.
Blackwell, George, 236.
Brinnel, 52.
Buchanan, Robert, vi, 153.
Burnie, K. W., 62.
Cowper, E. A., 197.
Dolomieu, 85.
Dutl, A. B., 102.
Firth & Sons, 36, 37, 104, 105.
Foster, William J., 195.
Gilchrist, P. C., 62.
Gjers, John, 138, U6, 187.
Ball, John W., 138.
Haibord, F. W., 13S.
Harrison, Joseph H., vi.
Harvey, Alfred, vi.
Hogg, T. W., 237.
Holgate, T. E., 238.
Holley, Alex. L., 64.
Huntsman, 35.
Jones, Wm., 220.
LilleshallCo., 111.
Lloyd, F. H., 194.
Martin, E. P., 62.
M'Neil, Charles, 160.
Metcalfe, William, 50.
Munnoch, Peter, 240, 241.
Mushet, Robt. F.,49.
Osborn & Company, 42, 43, 100,
110.
Pourcel, Alexandre, 236.
Pretty, W. H., 239.
Richards, E Windsor, 62.
Ridsdale, C. H., 93.
Riley, James, 220.
Royston, G. P., 168, 170.
Saniter, E. H., 220.
Seebohm, Henry, 42.
Sexton, Prof , vi.
Scott, C., 149.
Siemens, Frederick, 59.
Sir Wm., 58.
Snelus, George J., 62.
Stead, J. E.. 149, 101.
Stevenson, John L., 191.
Stirling, Rev. Dr., 97.
Talbot, Benjamin, 236.
Taylor & White. 49.
Thomas, S. Gilchrist, 62.
Thwaites Bros. , 153, 155, 158,
Tucker, A. E., 13S.
Turner, Prof., 56, 161.
Waldron, H. W., 51.
Wilson, Alfred, 100.
Wilson, G. A., 131.
Wood, Charles, 161.
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