Additional grain refinement in recrystallization controlled rolling of Ti-microalloyed steels processed by near-net-shape casting technology

This paper analyzes the recrystallization kinetics in Ti-microalloyed steels processed using “beam blank” casting technology. The faster solidification rates associated with this technology brings a finer precipitation of TiN particles which are very effective in controlling austenite grain growth during hot working. Furthermore, these small precipitates have been shown to delay static and dynamic recrystallization. The finer the precipitates the higher the delay in recrystallization. Nevertheless, beyond particle size and distribution, the level of delay is very dependent on microstructure (above all austenite grain size) and deformation conditions (strain and temperature). This paper studies the effects of this recrystallization delay on the microstructure evolution during hot rolling. Special attention was paid to the study of the occurrence of partial recrystallization during the final stages of rolling, which could lead to the presence of mixed microstructures before transformation. The possibility of achieving an additional austenite grain size refinement prior to transformation was evaluated.