PURPOSE: To improve the workability of a hollow casting and to reduce the cost thereof by preheating a metallic mold core having the coefft. of thermal expansion larger than the coefft. of thermal expansion of a casting material to a prescribed temp., casting a molten metal into the mold and allowing the mold core to shrink more largely than the casting, then removing the core.
CONSTITUTION: The casting mold consisting of master mold 1 and the metallic mold core 2 is provided on a mold stool 4 and the melt of a ductile cast iron is cast from a sprue 3 into the mold. SUS304 having the coefft. of thermal expansion larger than the coefft. of thermal expansion of the molten metal material is used for the core 2 and the core 2 is preheated to the prescribed temp. satisfying the equation T1α1>T2α2, where α1, α2 are respectively the coeffts. of thermal expansion of the casting and the metallic mold core, and T1, T2 are respectively the average temps. of the casting and the metallic mold core when the solidification is completed. The mold is cooled down to an ordinary temp. after casting to allow the core 2 to shrink more largely than the casting, then the core is removed. The workability of the hollow casting is thereby improved and the cost is reduced.
YOKOTE HIROMI
YAMANE TAKASHI
