PURPOSE: To prevent generation of center porosity and to favorably improve the internal quality of a continuously cast slab by applying larger rolling reduction than unsolidified thickness in this cast slab in the range, which solid phase ratio in the center part of thickness in the cast slab becomes the specific value or higher.
CONSTITUTION: In the range, where the solid phase ratio in the center part of thickness in the continuously cast slab is ≥0.9, the larger rolling reduction than the unsolidified thickness in this cast slab, is applied. By mutually approaching/separating dies 2a, 2b with rotation of a crank shaft 5, squeezing work is applied to the cast slab strand 1. It is suitable to use the dies having inclined surface O at tip part thereof from where the cast slab strand 1 is received so as not to develop crack on solidified interface in the cast slab strand 1 at the time of applying the squeezing work. As the center porosity exists in almost center part in the cast slab, in the case of continuously casting a bloom, the apparatus having such construction that the prescribed range of the bloom width in center range in width direction can be locally applied with the rolling reduction is favorable.
MIZOTA HISAKAZU
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