. Transactions. Fig. 2.—Eaely type of Doehler machine. come chilled before the inner portion has been filled; this will cause blow-holes that no vacuum will eliminate. A similar effect will be produced ifthe metal was too cold at the time of casting. The writer has producedcastings having only an outer shell, similar to that shown in Fig. 8,by limiting the amount of metal injected into the die to a quantity lessthan that required to make the casting. A similar result may be obtainedby running the metal so cold that it will chill the thinner sections of thecasting before the heavier sections ar
. Transactions. Fig. 2.—Eaely type of Doehler machine. come chilled before the inner portion has been filled; this will cause blow-holes that no vacuum will eliminate. A similar effect will be produced ifthe metal was too cold at the time of casting. The writer has producedcastings having only an outer shell, similar to that shown in Fig. 8,by limiting the amount of metal injected into the die to a quantity lessthan that required to make the casting. A similar result may be obtainedby running the metal so cold that it will chill the thinner sections of thecasting before the heavier sections are completely filled. Lack of pres-sure will produce the same result. 580 DIE CASTINGS AND THEIR APPLICATION TO THE WAR PROGRAM Blow-holes in die castings may also be caused by the phenomenonthat we sometimes call piping. Makers of rolling-mill ingots haveoften been confronted with this problem. In Fig. 9 is shown cross-sec-tion of another casting gatedat A. The metal flowing into the die at A. 1 Fig. 3.—Doehler compressed-air machine. will fill the entire mold cavity, assuming all casting conditions to be ideal,but the metal in the thin section adjoining A will chill before the heaviersection so that, the chilling being from the outside, a shrinkage hole willbe left in the center. Here again no advantage can be gained by theuse of the vacuum system. CHARLES PACK 581 Dies In the manufacture of die castings from zinc, tin, and lead alloys,dies made from low-carbon machine steel last almost indefinitely andanswer every purpose. In the first attempts to die-cast aluminum,the problem of obtaining a suitable die material presented serious diffi-culties, which were described by the writer in a paper read before the
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
