Grain growth behavior of coarse-grained austenite in a Nb–V–Ti microalloyed steel

Grain growth of coarse-grained austenite during equalization in a simulated thin slab casting and direct rolling process (TSDR) has been studied on a Nb–V–Ti microalloyed steel. Coarse-grained austenite produced by reheating at 1350 °C for 90 min were reheated to four equalization temperatures (1100, 1150, 1200 and 1250 °C) for 30 min, then the austenite grain sizes and precipitates were examined. The experimental results show that coarse-grained austenite keep its wide range of grain sizes at elevated equalization temperatures. Ti-rich carbonitrides retain its strong pinning effect on grain boundary of coarse-grained austenite at temperatures below 1250 °C. The occurrence of abnormal grain growth in coarse-grained austenite may be difficult when particle coarsening occurs as it is hard for the smaller grains which has the larger driving forces to grow into neighboring larger grain matrix.