Influence of Deformation on Transformation of Low Carbon and High Nb-containing Steel during Continuous Cooling

The effect of deformation in the nonrecrystallized region on the phase transformation for a low carbon and high Nb-containing steel with coarse austenite grain size was investigated by means of dilatometry measurement and microstructure observation. The results show that with the cooling rate increased, both the transformation start and finish temperatures measured by dilatometer are decreased, and the corresponding microstructure is changed from ferrite and pearlite to full granular bainite gradually. The dynamic CCT diagram is plotted according to the dilatometry measurements and microstructure observations. Dilatometry measurements also show that the transformation start and finish temperatures of the tested steel are raised with increasing strain, strain rate and deformation temperature, and the reasons for this are discussed.