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Full text of "Metallurgy Of Cast Iron"

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iron contains. Then again, it may be that nine-tenths of all casts would possess true fractures of hardness. Even if this latter were so, are we not justified in condemning the practice of being guided by the appearance of fractures or hardness, especially when there exists another method (chemical analysis) which is known to be positively correct in defining the grade of any brand of iron every time.it is employed? At the best, what sense is there of any foundryman taking chances of having one out of ten heats result in wrong grades of iron in his castings when, by following chemical analyses, he can have not only all his heats acceptable but also have them far nearer the grade he desires than is ever possible by being guided by fractures or hardness?
From careful observation in contrasting appearances of fractures with chemical analysis, with heats melting from 70 to 100 tons, the author can say that fully one-half of the furnace casts of pig which he used would have given him grades of iron different than what he desired in his castings, and some of the heats would have been practically worthless and caused a loss of much money and trade, had he been guided by the old-school method of judging by fracture or hardness. From the author's observation and experience, he believes it safe to say that from a third to half of the iron made will not, at the present day, agree in the appearance of fracture or hardness with the analysis. The margin that some founders possess in having their castings accepted when the grade of iron is not what it should be, causes them to often be indifferent in exacting the best obtainable. However, the day is coming when such practice will not be tolerated and all founders will, as a rule, be forced by competition to is deceptive to the eye, or hardness test.    It may               >-V be that three-fourths  of all the  iron  cast at  some furnaces may possess a true fracture of hardness or accord with the amount of silicon, sulphur, etc., an     "