Influence of ferrite rolling temperature on microstructure and texture in deformed low C and IF steels

Abstract

Single pass rolling experiments were carried out on two low carbon steels and an IF grade at temperatures between ambient and 700°C. The main aim was to investigate the transition from the well known behavior observed under cold rolling conditions to the less understood warm rolling behavior. Three aspects of the deformed state were examined: the occurrence of in-grain shear banding at angles of 30°-35° (and 17°-20°) to the rolling plane; the stored energy of deformation; and the final texture. These were chosen because of their effect on recrystallization. In-grain shear bands were evident, to one degree or another, in all samples. Their sensitivity to deformation temperature, however, was markedly different in the two low C grades compared to the IF grade. In the low C material, the frequency of banding was high at low temperatures but virtually nil at high temperatures. The degree of banding remained constant with temperature in the IF steel. These observations are explained in terms of strain rate sensitivity differences. The stored energy measurements were consistent with results in the dynamic strain aging literature. The deformation textures obtained were also in line with typical ferrite rolling textures. The overall sharpness of the rolling textures of the low C grades, however, increased markedly with temperature. This is ascribed to a drop in the texture weakening caused by in-grain shear banding.