Austenite Grain Growth Behavior of 40CrNiMoA Alloy Structural Steel

The austenite grain size is an important factor affecting the strength and toughness of 40CrNiMoA alloy structural steel. To fully explore the performance potential of 40CrNiMoA steel， it is necessary to investigate its grain evolution behavior during the austenitization process. Using a high-temperature laser confocal microscope， the effects of heating temperature and holding time on the austenite grain growth behavior of 40CrNiMoA steel were investigated， and the grain growth models were subsequently established. The results show that the average austenite grain size of 40CrNiMoA steel increases continuously with increasing heating temperature or prolonged holding time. Beck， Hillert and Sellars models were established to describe the austenite grain growth behavior of 40CrNiMoA steel. The fitting results indicate that the Beck model underestimates the measured values at lower heating temperatures but overestimates them at higher temperatures， while the Hillert model consistently predicts significantly higher values than the measured values. In contrast， the Sellars model exhibits an excellent agreement with the experimental results， providing a reliable basis for optimizing the heating process of 40CrNiMoA steel in practical production.