PURPOSE: To improve an internal quality for LH directional solidified ingot by pouring in a range of a specified relation for a super heating degree of molten steel at the time of executing the directional solidification from a bottom surface on a surface plate toward an upper part.
CONSTITUTION: A mold 1, which is covered by a heat insulating material 3 on the inside wall thereof in substance except a bottom part of the mold 1, is used and the casting ingot is produced to directional solidification from the bottom surface on the surface plate 2 toward the upper part, as keeping the hot temp. of the top part for the casting molten steel 4 by a heat insulating material 5. In this case, the over heating degree for the molten steel ΔT is as under-mentioned. 85°C<ΔT<180°C. In this way, a stable internal quality of LH ingot is obtd.
NAKANO NOBURU
KIGUCHI HIROSHI
