To prevent the occurrence of macro-segregation and porosity by forcibly cooling molten metal surface after pouring the molten metal into a mold for ingot- making, solidifying, taking out a cast ingot from the mold in the state which the molten metal exists in the inner part of the cast ingot, and successively, applying rolling reduction to a part of the side surfaces of the cast ingot.
The cast ingot 1 is forcibly cooled and the molten metal 2 is closed in the inner part of the cast ingot 1 and the rolling reduction is applied to a part of the side surfaces of the cast ingot 1 in the direction 4 of the rolling reduction with the rolling reduction jigs 3. A metal, such as carbon steel, alloy steel, stainless steel, Ni base superalloy, is made to use as a subject. The application to the steel ingot having ≥ about 10 ton is particularly effective. It is desirable that the timing of starting of the rolling reduction is at the time when solid phase ratio at the center part of the steel ingot is 0.1-0.8. In the case that the whole height of the steel ingot in 100%, the rolling reduction is applied to the position having about 25-75% height from the bottom end part. At the point of time when the surface temp. of the steel ingot becomes ≤900°C, the rolling reduction starts. A hydraulic press is generally used as a rolling reduction apparatus.
ITO YOSHIKI
AMAMOTO MITSUHIRO
YAMAMOTO KATSUYUKI
YAMAGUCHI EIRYO
NISHINO KAZUHISA
MORIYA TORU
