METHOD FOR IMPROVING INNER QUALITY OF CONTINUOUSLY CAST SLAB BY LARGE ROLLING REDUCTION UNDER UNSOLIDIFIED CONDITION

PURPOSE:To prevent the development of center segregation and center porosity at the time of continuously casting a rectangular cast slab. CONSTITUTION:A flatness ratio of the cast slab 1 is made to be >=1.1. Rolling reduction terminals 4 are arranged at the position (y) satisfying the inequality I or the inequality II. Casting velocity is adjusted and the solid phase ratio at the center part in the cross section of the cast slab 1 at the inlet side of the rolling reduction terminals 4 is made to be 0.6-0.95. The rolling reduction terminal 4 having >=200mm radius of curvature in the axial direction of the cast slab at the part executing the rolling reduction to the cast slab 1 is used, and the cast slab is drafted in 5-40% draft in the thickness direction of the cast slab 1 at 80-540mm/min rolling reduction speed. Then, the inquality I and the inquality II are expressed as follows, in the case of 0