Effect of P addition on texture evolution of Ti+V-bearing ultra-low carbon bake hardening steel

The grain boundary segregation of phosphorous, precipitate behavior, and texture evolution were investigated in a P-added ultra-low carbon bake hardening (ULC-BH) steel and in an ordinary ultra-low carbon bake hardening steel annealed at various times at 750 °C and 810 °C. No observable difference was found in terms of precipitate behavior of the P-added ULC-BH steel and the ordinary ULC-BH steel. The grain boundary segregation of phosphorous has a profound effect on the recrystallization texture of the ULC-BH steel during the annealing process. Phosphorous addition could delay recrystallization and could refine the grain of the P-added ULC-BH steels after annealing. Furthermore, the {111}//ND texture of the P-added ULC-BH steel was stronger compared with ordinary ULC-BH steel annealed at 750 °C. However, the opposite results were observed after annealing at 810 °C, thereby indicating that the grain boundary segregation of phosphorous can be both beneficial and deleterious for {111}//ND texture development of the ULC-BH steel, mainly depending on the annealing temperature. The complexity of the various effects could have been primarily caused by the relative distribution of phosphorous at the differently oriented grain boundary in the P-added ULC-BH steels annealing at certain temperatures.