PURPOSE: To obtain a hollow steel ingot having fine undirectionally solidified structure by forming a casting mold and core installed on a molding board into heat insulating structure and the molding board into water cooling structure and covering the surface of the molten steel in the casting mold with a heat retaining material.
CONSTITUTION: A heat insulating material 3 is fixed to the inside of the casting mold 2 installed on the water cooled molding board 1 and the molten steel 4 is poured by a bottom pouring method through a core consisting of a pouring pipe 5 externally clad with the heat insulating material 3. The heat retaining material 6 is thrown onto the surface of the molten steel. The hollow steel ingot which has the fine undirectionally solidified structure from the bottom toward the top and is free from segregation and shrunk hole is thus obtd.
KODAMA HIDEYO
KAJIWARA HIDEFUMI
WATANABE YASUO
