Regular Article

Mean field model of phase transformations in steels during cooling, which predicts evolution of carbon concentration in the austenite

¹ AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland
² Łukasiewicz Research Network, Institute for Ferrous Metallurgy, ul. K. Miarki 12, 44-100 Gliwice, Poland

^* e-mail: bachniak@agh.edu.pl

Received: 26 February 2021
Accepted: 21 May 2021

Abstract

The objectives of the paper were twofold. The first was exploring possibility of fast and reliable modelling of phase transformations during cooling of steels, accounting for the evolution of the carbon concentration in the austenite. Existing discrete models require long computing times and their application to optimization of industrial processes is limited. Therefore, a model based on the modified JMAK equation was proposed. Control of the carbon concentration in the austenite during ferritic and bainitic transformations allowed to predict incomplete austenite transformation and occurrence of the retained austenite. Moreover, prediction of the onset of pearlitic transformation after the bainitic was possible. The model was validated by comparison the predictions with the results of physical simulations. Numerical simulations for various industrial processes were performed. Problem of the difference in the incubation time between isothermal and constant cooling rate tests was raised.