Influence of the Ti Content on the Grain Stability and the Recrystallization Behavior of Nb-Alloyed High-Strength Low-Alloyed Steels

To achieve higher strength and good hardenability and at the same time use the positive effects of thermomechanical controlled processing, the concept of Nb and Ti microalloyed steels is increasingly used for high-strength low-alloy (HSLA) steels with higher C contents. Herein, how the addition of Ti affects the grain growth and static recrystallization behavior of a Nb microalloyed HSLA steel with a C content of 0.23 wt% is investigated. For this reason, alloys with varying Ti and constant Nb content are produced and investigated by means of annealing and double-hit deformation experiments. Atom probe tomography measurements reveal that the Nb concentration in the matrix decreases with increasing Ti content. Therefore, the static recrystallization behavior is steadily inhibited with decreasing Ti content, as more dissolved Nb is available for the formation of strain-induced NbC precipitates. The annealing experiments show that the combined addition of Ti and Nb is most effective against grain coarsening, regardless of whether the Ti content is 90 or 180 ppm. To use the positive properties of Ti against grain coarsening and Nb to inhibit recrystallization, a middle content must be chosen when alloying Ti to HSLA steels with higher C content.