Simulation of the Center-Line Segregation Generated by the Formation of Bridging

The macrosegregation model that heat transfer, solidification, liquid flow and solute movement were considered was developed to simulate the generation of the center-line segregation in the casting of steel. The center of cast has negative segregation only under influence of the liquid flow with solidification shrinkage when calculated in a conventional model. It was necessary to consider the bulging of cast slab so that positive segregation was formed in the center of cast. This macrosegregation model considering three driving force of fluid flow; solute concentration, thermal expansion, and solidification shrinkage, calculated that positive segregation was generated in the center of cast by the bridging being formed to a solidifying shell in last stage of solidification. This simulation results show effect of driving force of solidification shrinkage with bridging is larger than the other driving force. And a mechanism of generating center-line segregation with bridging was suggested.