PURPOSE: To make it possible to improve the tensile strength considerably, by mold- casting the molten metal at a prescribed temperature after a coating of a prescribed thickness is applied on the surface of mold having a prescribed mold thickness ratio, and by heating the metal for a prescribed time at a prescribed temperature after it is solidified and taken out from the mold, and then by cooling the metal at a prescribed cooling rate.
CONSTITUTION: The molten metal is poured into the metal mold of 60W250°C temperature, the thickness of which is formed so that the ratio of mold thickness becomes 4W10 and which has a coating of 0.05W0.5mm on the surface. When the molten metal is solidified, the metal is taken out from the mold and heated for 0.5W6hr at 900W930°C temperature in the heat treatment furnace, and then it is cooled at 10W200°C/sec cooling rate and thus the hardening is performed. By this, a spheroidal graphite cast iron casting which is small in grain diameter, uniform in metallic structure, and high in tensile strength, is obtained.
KOMURO HIROO
KAGITANI MASAYUKI
