MODELING OF THE PERITECTIC REACTION AND MACROSEGREGATION IN CASTING OF LOW-CARBON STEEL

Macro-microscopic models have been developed to describe the macrosegr egation behavior associated with the peritectic reaction of low carbon steel. The macrosegregation model has been established on the basis o f previously published work and experimental data. A microscopic model of a three-phase reaction L + delta --> gamma has been modeled by usi ng Fredriksson's approach. Four horizontal and unidirectional solidifi ed experimental groups simulating continuous casting have been perform ed with a low carbon steel containing 0.13 wt pct carbon. The extent o f macrosegregation of carbon was determined by wet chemical analysis o f millings. It is confirmed, by comparing calculated results with expe rimental results, that this model successfully predicts the occurrence of macrosegregation. The results indicate that a peritectic reaction which is associated with a high cooling rate generates high thermal co ntraction and a high tensile strain rate at the peritectic temperature . Therefore, the macrosegregation, particularly at the ingot surface, is very sensitive to the cooling rate, where extremely high positive s egregation was observed in the case of a high cooling rate. However, i n the case of slow cooling rate, negative segregation was noted. The m echanism of macrosegregation with peritectic reaction is discussed in detail.