• In hot rolling, the microstructural evolution is key to making advanced steels. • Laboratory-scale rolling and stress relaxation tests conducted. • A coupled hot rolling model set is upgraded and validated. • Mild-alloyed and niobium steel are compared. • Niobium steel showed slower recrystallization due to precipitation effects. Developing and validating metallurgical models for microstructural evolution during hot rolling was the aim of this work. In earlier studies recrystallization and grain growth have been simulated and combined with the academic version of the Virtual Rolling Mill, and in this study the models are further improved and compared to experimental data. The effect of Nb-C precipitation is also studied by comparing a niobium-containing steel with a mildly alloyed steel. Accurate information is needed for hot rolling in a controlled environment to obtain reliable experimental data. For that, a laboratory-scale hot rolling mill and thermo-mechanical simulator were used. Hot rolling experiments have been conducted in this study, and the model results have been compared to the experimental results. The comparison showed good correspondence, and the model set was validated successfully.
Seppälä et al. (Sun,) studied this question.