Reduction Behavior in Large-Sized Round Bloom During Continuous Casting by Numerical Simulation

Solidification end reduction is an effective approach to control the central porosity during continuous casting of round bloom, although it is not widely reported. In the present work, a three-dimensional finite element model has been developed with coupling heat transfer and mechanical deformation for a φ690 mm continuously cast round bloom, and verified by the surface temperature, shrinkage zone width, reduction crack location, and deformed contour shape. It is found that the contact width between roller and the bloom increases with the increase of reduction amount and approximately in a parabolic relationship. To cover the whole range of the shrinkage zone, the total reduction amount should not be smaller than 25 mm as the width of the shrinkage zone is about 120 mm. The bulge width along the horizontal direction during reduction increases as the total reduction amount increases, and the relationship can be fitted by a parabolic equation. The reduction thickness in the shrinkage zone is larger when the reduction amount is higher, and it also follows parabolic relationship. The deformation in the shrinkage zone is more obvious when the reduction is conducted before crater end. The reduction efficiency for φ690 mm round bloom before solidification is between 20 and 30 pct, while after solidification is roughly between 12 and 20 pct. It increases with the increase of apparent reduction amount, mainly related to the increase of the strain rate. The deformation of the shrinkage zone in φ690 mm round bloom with 30 mm apparent reduction in continuous casting and hot rolling has been compared. The equivalent strain in the shrinkage zone of the round bloom in continuous casting is about 0.047 to 0.052, while that in hot rolling is about 0.031 to 0.036, indicating the reduction efficiency of the former is about 1.5 times higher than the latter.