Prediction of Austenite Grain Growth During Austenitization of a 0.7%C Pearlitic Rail Steel

The prior austenite grain size of steels greatly influences the phase transformation kinetics during austenitization and the microstructure which determines the mechanical properties. The effect of temperature and time on austenite grain growth of 0.7% carbon rail steel during reheating was studied. The grain growth behaviour of this steel was investigated under different heating temperatures and holding times at a constant heating rate of 4°C/min. Samples were heated in a tube furnace at temperatures of 1150, 1200 and 1250oC and held for 0, 1800, 3600, 5400, 7200 and 9000 seconds before quenching into water. The prior austenite grains were observed using an optical microscope and austenite grain sizes were measured by the linear intercept method. The measured austenite grain sizes were used in determining the grain growth constants Q, A and n which were used in developing the constitutive equation for grain growth prediction. A good agreement was found between the actual and the predicted austenite grain size within the typical industrial soaking temperature range of 1150 and 1200oC.