Kinetic Analysis of the Austenite Grain Growth in GCr15 Steel

The growth behavior of austenite grains in GCr15 steel was investigated through the isothermal annealing tests of the steel under different heating temperatures and holding times. The tests were performed on a Gleeble-3800 thermo-mechanical simulation machine. Austenitizing temperatures 1223, 1323, 1373, and 1423 K were chosen, and holding time varied from 0 to 480 s. Experimental results suggest that austenite grains grow gradually with the increase of heating temperature, and holding time has an important effect on the growth of austenite grains. The time exponent for the growth is bigger at higher temperature, and the growth rate decreases with increasing time. On the basis of previous models and experimental results, a mathematical model that can describe the growth behavior of austenite grains in the tested steel under different heating temperatures and holding times was obtained using regression analysis. The predicted grain sizes by the model are in good agreement with measured ones.