COMPARATIVE FUSIBILITY OF FOUNDRY METALS. 343
shows that the more we remelt steel scrap the less difference exists in the iron starting- and closing- ahead of the steel. This is clue to the fact that remelting steel raises its total and combined carbon and at the same time we find that steel remelts will be very spongy or filled with gas or blow-holes, which increase more in size and number with each successive heat, ttms causing the steel product to be very porous and thereby permitting the heat to better penetrate its body and bring it quicker to a fluid state.
Table 76 shows the folly of trying to remelt steel and obtain from it the original metal, as can be closely done with cast iron. Nothing has led founders on more wild-goose chases than giving ear to some of the high-sounding claims made for remelts of steel or its mixture with cast iron. It is true that steel scrap mixed with cast iron can strengthen the latter to a limited degree, but the extreme claims some make for its mixture with cast irons are erroneous and unfounded. We have no metal that will deteriorate from its original state by reason of remelting, so much as steel scrap. The action taking place in remelting steel in a cupola increases the carbon in the metal, as shown in Table 76. We find that the first remelt raised the carbon from .60 to 1.48; the second sent it up to 2.74, and the third to 3.05 — an increase in either of these three remelts sufficient to show that we are very far from retaining anything like the original steel in any remelts in a cupola which compels the steel to be in contact with the fuel from which it absorbs the carbon with avidity.
When steel is melted in a reverberatory or air furnace, in mixture with cast iron, we have more favor-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.