PURPOSE: To improve the internal characteristic of a steel ingot owing to accelerated cooling of the molten metal charged into an annular metallic mold on a molding board and to prevent cracking on the inside surface thereof by disposing a coolable core at the center of said mold and forming the hollow steel ingot.
CONSTITUTION: A core 1 to be disposed at the center of an annular metallic mold has a thin walled consumable shell 2 on the outside surface and is embedded with many cooling piping 4 groups within a shapeless refractory 3 layer packed therein in proximity to the inside surface of said shell. The cooling medium supplied into the central inside cylinder 5 of the core 1 is passed through the inside of the individual pipings 4 in the piping 4 group. Cooling on the inside surface side of the molten steel charged into the mold is accelerated by the extraction of the heat by the cooling medium and at the same time the thermal shrinkage of the inside solidified shell of the hollow thick walled steel ingot growing in melt sticking to the shell 2 is released by the compressibility of the layer 3 packed in proximity to the shell 2, by which the internal characteristic of the hollow steel ingot is improved.
KOJIMA SHINJI
NANBA AKIHIKO
