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Full text of "Metallurgy Of Cast Iron"

CHAPTER XXL
GRADING PIG IRON BY  ANALYSES.
Previous to 1890 almost all pig iron was graded by fracture and piled according to the open character of the grain, the most open iron being used for the softest castings and the close, grained for the hard ones, as shown in the last chapter. Furnacemen and founders gradually came to learn, by means of following chemical analysis, that such was not reliable and could often be deceptive. This has been so thoroughly demonstrated that it is now (1901) rare to find a furnacemaii paying any attention to the appearances of fracture, unless a customer asks him to, and instead being wholly guided by a knowledge of the chemical constituents of the iron. While this is now the current practice of most all furnacemen and about 75 per cent, of f otmdrymen, we have the evil of disabusing the general sense of numbering the grades which certain analyses will give. For example, a No. i iron is generally supposed to be such as will give soft castings in those ranging from one inch in thickness down to stove plate. Nevertheless, we have today (1901) furnacemen designating pig iron as No. i that would run white in stove plate and require castings to be a foot thick or more in order to be sufficiently soft to be drilled, etc. An iron to be No. i by analysis should contain at least fromefly used as mill iron in puddling furnaces producing wrought iron, and also for the manufacture of water pipes, etc., often being mixed with higher silicon irons.