MATHEMATICAL-MODEL COUPLING PHASE-TRANSFORMATIONS AND TEMPERATURE EVOLUTIONS IN STEELS

A mathematical model for calculating phase transformations in steels during rapid heating and cooling is presented. It is based on a rule of additivity. The isothermal kinetics are modelled by Johnson-Mehl-Avrami law. The model describes the kinetics of austenitization during heating, the state of austenite at the end of heating (carbon content, grain size), the kinetics of transformations during cooling, the final microstructure and hardness. The model is worked out firstly on dilatometric specimens without thermal gradients in order to validate the modelling and the input data. Then the application of the model to massive cylinders heated up and cooled down with high thermal gradients is presented.