SOFT REDUCTION METHOD OF CAST SLAB IN CONTINUOUS CASTING

PROBLEM TO BE SOLVED: To alleviate center segregation by surely performing rolling-reduction of a molten cast slab at the end of solidification by the rolling-reduction amount equivalent to its solidification shrinkage amount without lessening the life of a segment constituting a soft reduction zone in a soft reduction method which carries out rolling-reduction of a molten cast slab at the end of solidification by the rolling-reduction amount equivalent to its solidification shrinkage amount for the purpose of alleviation of center segregation generated in a central part in thickness direction of a cast slab in continuous casting.SOLUTION: In this soft reduction method of a cast slab in continuous casting, at least one or more roll segments where two or more soft reduction rolls are incorporated constitute the soft reduction zone 14 which is used for performing the rolling-reduction of a molten cast slab at the end of solidification 10 by the rolling-reduction amount equivalent to its solidification shrinkage amount, and during the rolling-reduction, a casting speed or a secondary cooling water rate is adjusted so that a solid phase rate in the central part of the cast slab at the soft reduction roll position on the most downstream side in the casting direction of the soft reduction zone is in a range of 0.7 to 0.8.