Effect of reheating processes on grain boundary heritance for 2.25Cr–1Mo–0.25V steel

The effects of reheating processes on the grain boundary heritance for 2.25Cr–1Mo–0.25V steels were investigated. The results show that at higher heating rate (150 °C/min), the coarse characters of prior austenite grains are easily inherited in the reheating temperature range from 920 to 1025 °C. However, at lower heating rate (15 °C/min), the coarse grain boundaries are inherited only at the temperature of 920 °C. The grain boundary heritance is mainly related to the residual austenite located in the bainitic ferrite laths, which can act as the nucleation of the acicular austenite. Because of the combination and growth of the acicular austenite follow in the coherent mode, the prior coarse grain boundaries are preserved during higher reheating processes. On the contrary, the decomposition of the residual austenite during lower reheating processes restricts the forming of acicular austenite, and improves the forming of the granular austenite on the grain boundary, which grows in the non-coherent mode and remove the coarse characters of prior austenitic grain.