| 摘要 |
PROBLEM TO BE SOLVED: To provide a continuously cast slab free from central segregation through its entire width and length, its casting method and a manufacturing method of heavy plate by hot rolling it. SOLUTION: The slab contains S of 10 ppm or less, Mn of less than 0.2% in area ratio of 2.0 mass % or more and Ca, within 10 mm thickness in the center of the slab thickness including a final solidification band in its center. In the production process of the slab, the slab being cast is rolling-reduced by more than a pair of rolls after subjected to bulging but before fully solidified in the center of thickness. Rolling-reduction is applied at a position where a central solid phase rate is 0.2 to 0.7 and to its reduction ratio Lf of 0.9 to 1.5 satisfying the equation (A) below. L=D1/D2...(A) D1: Amount of reduction in the center of width of slab (mm), D2: Thickness of un-solidified layer (mm) when reduction is started at solid phase rate of 0.8 or less.
|
