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Full text of "Metallurgy Of Cast Iron"

CHAPTER XLIV.
CHEMICAL  CONSTRUCTION
AND  STRENGTH   OF TYPICAL FOUNDRY
IRON MIXTURES.
The chemical construction and highest strength of
all the prominent mixtures now being used in general founding, as obtained by the author for this work to illustrate in a concise and accurate manner true analyses of mixtures actually used by our leading founders, are shown in Tables 60 and 61. The specimens analyzed are taken from the respective tests described in Chapter LX. The determinations were made by the able and careful chemist, Mr. W. A. Barrows, Jr., of Sharps-ville, Pa.:
Analyses Nos. i and 2 are obtained from " air furnace " iron and those of Nos. 3, 4, 5, 6 and 7 from cupola iron. A peculiarity which will attract the attention of those making a study of the following Table is that of the combined carbon being so high, with low sulphur and the silicon not far from i.oo per cent, in analyses Nos. i and 2. This illustrates the benefit derived 'from melting iron in an *' air furnace,'' where it is not brought in contact with the fuel to so radically chn.r~.ge the character of iron, and clearly demonstrates the superiority of the " air furnace " over the cupola to refine or obtain the best strength possible in cast iron.s claimed that high cupolas may have a reducing action on oxide of iron, so as to obtain more metal from rusty scrap, etc., than low cupolas. High cupolas should at least cause a greater loosening than low cupolas of the scale from iron, and often permit more of it being blown out of the stack to remove some of its evils. However, in striving to obtain very soft or clean castings, rusty or burnt scrap of all kinds is best avoided where practical.stings as they are poured. Where there is any apprehension of such difficulty, it is often well to addo break, he can, by " siz-