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Full text of "Metallurgy Of Cast Iron"

CHAPTER XVIII.
SEGREGATION   OF   IRON   AT   FURNACE AND FOUNDRY.
We often find a segregation of metalloids in pig iron,
but rarely, if ever, in re-melted iron or castings. One peculiarity in this respect lies in the difference often found in the upper cast body or face of pig iron containing the highest sulphur, as shown by the following four samples, Table 18:
TABLE  18. SEGREGATION OF SULPHUR IN PIG IRON.
	No. i.	No. 2.	No. 3.	No. 4.
Top ................................	117	11%	084	QCC
Bottom ....................................	.08^	094	070	047
				
The above analysis shows that '' direct metal,'' or iron coming from a blast furnace, tends to favor the escape of sulphur, but that owing to the top surface of the pig chilling so as to form a crust at an early stage of the solidification of the metal in the pig beds, the sulphur in rising to escape was caught and hence the higher sulphur found in the top body of the pig, as shown.
Silicon also segregates in pig metal. Wherever pig iron shows soft gray spots, analysis will generally show these to be higher in silicon than the surrounding metal. Then again, it has been found that the first metal from a furnace is generally lower in silicon than that which flows afterward, in a manner often so uniform as to show that there is a graduald XLV., pages 78 and 306. Furnacemen are finding that if they are not called upon to increase temperatures of             j