Microsegregation and solidification characteristics of an advanced high strength steel - Part I: modelling and prediction on hot cracking susceptibility

Microsegregation is an inherent phenomenon that occurs during the solidification of steel and can result in multiple casting defects. To explain and predict the microsegregation phenomenon, the analytical microsegregation model has been extensively used. However, equilibrium partition coefficients always play a critical role, and the deviations of microsegregation prediction caused by the discrepancy of equilibrium partition coefficients have been recently reported. In this study, the deviations of element redistribution and evolution of solid fraction on an advanced high-strength steel (AHSS) have been demonstrated by introducing two sets of the equilibrium partition coefficients. Based on predicted solidification paths, the hot cracking susceptibility of the steel was evaluated by using Rappaz-Drezet-Gremaud and Kou criteria, respectively. Furthermore, according to modelling results, the solidification path predicted with variable equilibrium partition coefficients is more prone to hot cracking, indicating that a higher degree of solute partition results in higher cracking susceptibility.