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Full text of "Metallurgy Of Cast Iron"

COMPARATIVK  FUSIBILITV  OF FOUNDRY  MKTALS.   339
know that a chilled iron body would give a casting slightly softer than if the chilled part had been rejected and only the gray body utilized. While this knowledge would always have been of much value to the founder, there lias been no time that it could be turned to more profitable account than at the present. It may be asked what evidence there is aside from the drilling tests to prove that the chill roll remelt was softer than that of the gray. This is answered by referring to the columns I>2, I>2, I?2, and J2, Table 74, and noting the greater silicon and graphitic carbon existing in the chill remelt than is found in the gray, as seen at As, C2, B2, and 12. The author's attention was first drawn to the fact that the chill remelt was softer than that of the gray, by drilling to obtain material to make the analyses. The drill worked so much easier in the chill remelt than in the gray as to be a matter of much surprise. The drill press used is shown at Pig. 53, page 239. After a well sharpened twist drill was attached and all ready, the drill was started and allowed to run exactly half a minute. By drilling several holes in the manner describee! on page .r^4, alternately in each of the respective blocks, we could then, by measuring their depth, intelligently tell which of the two was the softer. It is to be said that the drillings of the whole four heats, Nos. 10, 16, 18, and 20, showed the chill remelt to be softer than those of the gray iron.* It will be noticed also that these four remelts are distinct in testing different grades of iron, s<> as to cover a wide range; of metals, from those that would take but a slight chill on the surface of pig metal or a east ing up to those that would chill its whole body as displayed in Pig. 62. Attention is again called to the specific gravity'tests make rolls that were used for heat No. 18,No. 10 and melted down in heat No. 11 is also shown at A2 and 132, Table 74, page 336.Hard.	Hard.	Hard.	Hard.	Hard.	Hard.	Hard.