A Model and Experimental Validation to Predict Heating Rates for Overlap Between Ferrite Recrystallization and Austenite Transformation in Dual Phase Steel Manufacture

A systematic theoretical and experimental study has been conducted to predict the heating rates required to obtain a pre-defined percentage of overlap between the ferrite recrystallization process and the austenite formation process in dual phase steel manufacture. Isothermal recrystallization kinetics for three different cold-reduced low-carbon micro-alloyed steels (50%, 60%, and 75%) with ferrite-pearlite-bainite initial microstructures was evaluated. Using various experimentally determined rate kinetic constants and critical temperatures, a continuous heating rate model which predicts the heating rate required for a predefined amount of overlap was successfully developed. The model predicted the heating rates required for a predefined 1%, 15%, 34%, 67%, 88% and 99% of overlap to be 0.2 degrees C/s, 0.9 degrees C/s, 1.8 degrees C/s, 7 degrees C/s, 50.5 degrees C/s and 511 degrees C/s, respectively. The experimentally determined recrystallization percentage values validated the predicted heating rates.