Effect of heating rate on ferrite recrystallization and austenite formation of cold-roll dual phase steel

An investigation was made to determine the effect of heating rate on ferrite recrystallization and austenite formation of cold rolled dual-phase (DP) steel (0.1C-0.4Si-1.6Mn). Three heating rates, 5, 50 and 500 °C/s, and different annealing temperatures ranged from 650 °C to 950 °C were applied to study their effects on the progress of recrystallliztion and austenitization. It has been found that faster heating strongly influences the overlapping extent of the ferrite recrystallization and austenite formation process, the morphology of martensite is observed to shift from network structure to a chain shape under lower temperatures. Higher annealing temperatures minimize the transformation and microstructure difference caused by a difference in heating rate. Rapid heating with high temperature could improve the strength. The microstructural evolution mechanism under rapid heating conditions was also tentatively discussed.