Improvement of Semi-macro Segregation in Continuous Cast Slabs by Soft Reduction

摘要

The optimum conditions of soft reduction were determined to minimize centerline segregation in the continuously cast slabs using a solidification model and a series of tests at Pohang Works of POSCO. A solidification model reflecting microsegregation model that can precisely predict surface temperature and the crater end, was developed on the basis of surface temperature measured by thermocouple and solid shell thickness measured by pin shooting method. Optimum soft reduction conditions such as reduction zones and casting speeds for various carbon steel grades were determined on the basis of the simulation results. Changing test of casting speed was carried out to validate optimum casting speed predicted by a solidification model. In a series of tests for soft reduction, the center segregation degree of manganese was reduced from 1.08 to 1.04 and the area fraction of phosphorus segregation was reduced from 0.77 to 0.18 percent.