Metallurgy Of Cast Iron

MIXING AND MELTING SCRAP IRON. 295
in all white scrap iron as it comes to the foundry.
Burnt iron can be said to be the most undesirable class of scrap for a founder to handle, and there is a doubt in the author's mind that it pays any founder in the end to experiment with it, for making anything' other than castings like sash weights, for, as a general thing, its loss in weight by re-melting will range all the way from 30 to 95 per cent. It is a very indefinite quality to judge of as to its chemical composition. It is safe to say it will greatly injure other irons when mixed with them in raising the sulphur and lowering the silicon so as to produce a '' white iron,'' and can often spoil many castings.
Any intelligent foundry laborer should, with a little training, be able to select and pile scrap according to its grade. As some would prefer an approximation for the silicon and sulphur contents of grey scrap, the au-thor would say that iron ranging from stove plate up to one inch in thickness may be considered as an approximate equivalent to remelted pig metal that has its silicon ranging from 1.50 up to 2.00 per cent., and for bodies above one inch thick up to three inches thick from i.oo up to 1.75 in silicon, sulphur in all cases to be considered as constant at about .07, Above three inches in thickness a grey open fracture can range in silicon all the way from. 75 up to 2.50, and the grading of such heavy bodies generally requires a more skilled eye than with scrap, which might be under three inch-es in thickness; but practice would soon bring one to an approximately close guessing of the grade of heavy, as well as light bodies. Where scrap comes to the. foundry yard in the form of complete castings, which the founder will have to break, he can, by " siz-