Improvement of Center Segregation in Continuously Cast Blooms by Convex Roll Soft Reduction

Abstract

A two-dimensional finite element model has been established based on thermal–mechanical coupled calculation for the determination of soft reduction amount by convex roll during bloom continuous casting. The shrinkage of the mushy zone is then calculated based on mass conservation during solidification. The total shrinkage area is about 75 mm2 for the 180 × 240 mm2 bloom with a casting speed of about 1.25 m min−1. The reduction efficiency of the convex roll is calculated on basis of the visco-elastic-plastic deformation behavior of mushy zone. It decreases linearly from 31.7 to 4.7% when the center solid fraction of the reduction location increases from 0.3 to 0.6. The maximum stress is observed on the bloom surface where the strand contacts to the chamfer of the convex roll, while the maximum plastic strain appears in the inner-arc mushy zone. The total soft reduction amount suggested by the present model is 6.06 mm. It is noticed that the center segregation and “V” segregation have been improved remarkably by soft reduction with convex rolls.