FREE-CUTTING HIGH-TEMPERATURE LOW-THERMAL EXPANSION CASTING ALLOY AND ITS PRODUCTION

摘要

PURPOSE:To develop a casting alloy which has a small coefft. of thermal expansion, is less dimensionally changed in spite of using the same at a high temp. and has excellent machinability by casting the melt of a high-alloy steel prepd. by adding specific ratios of Ni and Co to a high-carbon steel and subjecting the melt to a heat treatment under specific conditions. CONSTITUTION:The high-alloy steel prepd. by adding 28.0-32.0% Ni and 8.0-18.0% Co to the high-carbon steel contg., by weight %, 0.6-1.0% C, 0.3-1.0% Si, 0.3-1.0% Mn, 0.3% Mg, 0.3% Ca, and 0.1% Ti in such a manner that the total content of Ni and Co attains a 40.0-46.0% range is smelted as the high alloy material which has intricate shapes, is less dimensionally changed in spite of using the same at a high temp. of about 500 deg.C and has the excellent machinability. The molten metal of this material is cast into a casting mold having a desired shape and after the casting is heated to 700-800 deg.C, the casting is subjected to a quick cooling treatment. The free-cutting high-temp. low thermal expansion casting alloy having the average coefft. of thermal expansion between 50-500 deg.C as small as 7.5X10-6/ deg.C and the excellent machinability is thus obtd.