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 degrees C for 90min were reheated to four equalization temperatures (1100, 1150, 1200 and 1250 degrees 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 degrees 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. (C) 2009 Elsevier B.V. All rights reserved.