Modelling the Austenite to Ferrite Transformation in Low Carbon Steel Strip

A model was developed in order to predict the ferritic grain size obtained during cooling of low carbon steel strip. The model is based in nucleation and growth mechanisms, and assumes that the nuclei are generated on the grain boundaries of austenite. Once a grain of ferrite is formed, it will grow with the speed required for the carbon to migrate into the austenite. Results of the model were compared with previously published results and with grain size measurements conducted on laboratory samples and on strips obtained from an industrial mill. It was found that the ferritic grain size depends on the chemical composition of the steel and on the original grain size of the austenite. It was also found that the model was able to predict the grain sizes measured in strips coiled at temperatures below 710°C.