Metallurgy Of Cast Iron

342 METALLURGY OF CAST IRON.
affinity for it. The reverse is true of silicon, as the longer the iron is exposed to the effects of high heat and blast, the more silicon is lost.
SEMI-STEEL CASTINGS.
Remelting steel requires longer time to fuse than cast iron, as will be seen by Table No. 75, page 340, in which heats Nos. 21, 22, and 23 are continuous rernelts of the same metals. The steel was a " riser-head '' piece of scrap that was moulded to make a single piece of cast iron of the same form, so that conditions as to form and weight could, be the same for both metals in making the comparative fusing test shown. Heats 24, 25, 26, and 27 are two remelts of different quantities of cast iron and steel metals, having similar composition, as will be noted by referring to columns T and U, Table 76, page 341.
Heats 24 and 26 had the metals in scrap form as nearly alike in size and bulk as they could be roughly made, and when melting they ran into moulds to give blocks 2^/2, X4x6 inches, so as to insure a uniform size of stock for making the comparative heats 25 and 27. Heat 28 was a remelt of the blocks obtained from heats 25 and 27. In this heat, it will be noticed, the iron and steel came down closely together. The reason the closing time is not shown is on account of stopping up the tap holes after the iron had started to run, with a view to catching metal in a hand ladle to pour shrinkage and contraction tests (see page 410), which left the matter too indefinite to record the time of actually finishing first, although, as near as we could see or judge, they ended closely together. Table 75ulphur added than shown by the four continuous remelts in heats Nos. 9, 10, n, and 12, Table 73. The author accounts for this in that the metal was held in the cupola but a short time, compared to that generally occupied in ordinary shop practice. The longer heated or semi-molten iron remains in contact with incandescent fuel or is exposed to gases, the more sulphur will be absorbed — up to the limit of the iron'sding its mate.. 2111 3Os i m. mi 3os 3OS. 3111. im ^os Jill l^S i in.