COMPARATIVE FUSIBILITY OF FOUNDRY METALS. 333
from the same ladle of iron. The fractures of the gray and chilled iron are shown in Figs. 61 and 62, this page and 337. The gray and sand rolls which were used in these
FIG. 6l.óGRAY ROLL. Combined Carbon, 1.20. Graphitic Carbon, 2.90.
comparative tests were all tumbled, so as to get the sand off them thoroughly before they were charged. Before explaining the results and tests shown by Tables 72 and 73, next page, we will describe the plan followed in conducting the heats shown:
For heat No. 9, Table 7 2, charcoal pig iron was charged in both chambers of the cupola and run out of one tapving been poured from the same ladles or cast of iron, and that steel proper requires higher heat than cast iron to fuse it; also that remelting of steel in contact with incandescent fuel wholly destroys its original character. Making comparisons of the fusibility of gray and chilled bodies, both of the same composition excepting the combined carbon, was accomplished by the following plan. A heat of chilling or low charcoal iron, designated as heat No. 9, Tables 72 and 73, was caught in hand ladles and then poured into sand and chill moulds, placed side by side. A view of the chill mould and chill roll cast in it is seen at Figs. 58 and 59, page 312. This gives a wholly gray body of iron in the casting coming from the sand mould, and a wholly chilled or white crystallized body of iron from the chill or all-iron mould; both, it is to be remembered, being pouredn the soft pig, and only .68 per cent, in the hard white one. In melting these two pigs under exactly the same conditions, the hard one went first. It held its form well, but in melting ran like water, and was melted beforeiron used as a comparative constant to the hard irons throughout the eight heats. It may be stated that drillings for45 s. i m. 10 s. 45 s. i m. 15 s. nil 3os nn 458