Phase Transformation Modelling for Different Hot Rolled Dual Phase Steels

Two alloying concepts of hot rolled dual phase steels, Mn-Mo and Mn-Si-Cr, were selected for laboratory rolling simulation and numerical modelling. Almost all the critical transformation temperatures were calculated by thermodynamic approaches. The recrystallised austenite grain size evolved between the deformation steps was calculated according to an empirical equation. The ferrite transformation kinetics on the Run Out Table (ROT) was mapped as a function of temperature and austenite conditioning by Leblond and Devaux's rate law. With the help of a so-called 'modified CCT diagram', the critical cooling rate of the enriched austenite for bainite and martensite is revealed. The martensite transformation was further modelled by the rate law concept with a parameter coupled to the Koistinen-Marburger approach.