Skip to main content

Full text of "Metallurgy Of Cast Iron"

See other formats

396                       METALLURGY   OF   CAST   IRON.
silicon contents of an iron can be defined from the
final contraction of a casting or test bar.    In all the
bars of each   cast  in  Fig  74   the   silicon   percentage
was  nearly  constant.    The   variation in contraction,
therefore,   certainly justifies  the assertion   that   the
amount of silicon cannot be thus determined.    In fact,
the contraction will simply indicate the '' grade "of            *
an iron, and no more.     The metalloids producing this
" grade " can only be determined by analysis.
The " grade " of a cast iron, as I use the term, is a practical name, familiar to heavy founders, though perhaps not capable of precise scientific definition. It is characterized by the degree of hardness, and incidentally by accompanying properties of contraction and of strength. This question of '4 grade '' is further discussed in Chapter XX.
It has been maintained that it is difficult to make cast iron absorb sulphur and that the founder has no              ;
need to fear sulphur in general founding. *   In the tests           ^
shown in Fig. 74,  the amount of sulphur in the iron              I
was  easily  increased  by  the   method   described,   as              I
is proved by the subsequent analysis. At all events, I am sure that up to 0.3 per cent, sulphur can be easily present in cast iron containing about 2.00 per cent, of silicon, which is a percentage of silicon often             *
permissible and  practicable as a maximum in light             j
castings, where the sulphur can be kept below 0.06 in the castings produced.    As o. 2 per cent, of sulphur             [
is sufficient to injure or ruin almost any casting made            f
for other purposes than sash-weights, the ability of          ^
cast iron to absorb as high as o. 3 per cent, of sulphur            I
forcibly illustrates the great reason why the founder has to fear sulphur in fuel, high-sulphur iron, and to            j
* This was advanced by reason of results derived from >-inch               \
test bars, in a lengthy paper seen in Volume XXIII. of the              .*
Transactions of the American Institute of Mining Engineers,                     < side xvei rotated as d.:st.:t ihed on pa^es ,u  ,i j and ;i,nds pe!' (on of iron, or a ratio of 7.7 iron to i coke, in onler to deliver the melted iron in the same condition as on an ordinary day. In other words, an additional fuel consumption <>!' a little over 3,h per cent, is needed under the above conditions......................    3,658 units