498 METALLURGY OF CAST IRON.
of work or other. All that is wanted is a knowledge of its chemical and physical properties; and when the furnaceman and founder understand these as they should, pig iron of any " grade " or quality need never be shipped to the wrong customer. It is simply a question of " carding the car " right, to have a furnace-man clean his yards, and have no complaint about his iron, however " bad " he may occasionally make it, if he will but give a correct analysis.
The foundry iron of the analysis in Table 107 is an excellent grade to make a machinable, strong casting for very heavy work, such as should not be under three inches thick in its lightest part, if all pig be used; but if the furnaceman gets the wrong shipping card on such a car of iron, and some unprogressive founder receives the iron, and because it may look " soft " or " open-grained J' tries to mix one-third scrap with it, for light or medium castings, he abuses the furnaceman, because his castings crack and come out " white iron."
The cupola illustrated on page 501 is the smallest I know of now used for practical purposes. Before taking a " heat" out of this small cupola, there was but one point that I felt doubtful about, in practice with such a small size for the work I intended it to perform, and that was, whether it would increase the sulphur, by remelting, more or less than is done on an average in the large cupolas commonly used.
Owing to records of cupola mixtures kept at our foundry since 1892, or of the analyses of the pig metal that go to make exacting work (in which only shop-scrap can be utilized), and of the castings produced, we are enabled to judge fairly of the increase of sulphur by remelting, and found by comparison that thend whether the fault was not their own before entering complaints to the furnacemen.practice, inudi better with round bars than with square »»nis.burs..........................*fi$7 "