Improvement of Semi-macro Segregation in Continuously Cast Slabs by Controlled Plane Reduction

Abstract

To improve center segregation in continuously cast slabs, a new technology, named 'controlled plane reduction', was developed. By this technology, the movement of molten steel in the final stage of solidification was restrained by both the support and the reduction of unsolidified slabs with two walking-bar blocks to prevent bulging and compensate for the solidification shrinkage. As a result, it was found that the center segregation in continuously cast slabs can be improved by the controlled plane reduction to a level comparable to that of interdendritic microsegregation. To thoroughly alleviate the center segregation by the controlled plane reduction, it is important to apply an optimum reduction taper to the unsolidified slab and to minimize the reduction taper difference between the two walking-bar blocks. The resulting optimum reduction taper by the controlled plane reduction experiments agreed with that estimated by a theoretical study based on the analysis of a molten steel flow.