Numerical Simulation of Macrosegregation in a Continuous Casting Mold with Electromagnetic Stirring

Negative segregation beneath the surface of the slab is generated by the flow of molten steel in continuous casting. Negative segregation of austenite stabilizing elements such as Ni and C results in the formation of delta ferrite, which can cause cracks near the slab surface in austenitic stainless steel. In the current study, we developed a numerical simulation model to predict negative segregation in the continuous casting process. The model used an effective distribution coefficient that is dependent on the solidification rate and the liquid velocity in front of a solidifying shell. A comparison of the numerical simulation and the experimental results for the solidification in a crucible with a rotating and cooling pipe indicated the validity of the proposed numerical simulation model. Additionally, the numerical simulation results of continuous casting for austenitic stainless steel showed that the maximum degree of negative segregation occurred near the slab corners when casting at high speed with electromagnetic stirrer. The degree and location of negative segregation in the numerical simulation were comparable to those obtained from EPMA and Spark-OES analysis of slab samples. These results indicated that the proposed simulation model enables accurate prediction of negative segregation beneath the slab surface in continuous casting and is useful for the optimization of continuous casting process. The negative segregation was caused by the molten steel flow in front of a solidifying shell. Consequently, the results from simulation without EMS or at low casting speeds showed that negative segregation was suppressed.