Prediction of hot deformation resistance during processing of microalloyed steels in plate rolling process

Mean flow stress of microalloyed high-strength steels during plate rolling has been thoroughly studied. It has been found out by both thermomechanical tests and measurements taken in the industrial plate mill. For this purpose, log data obtained from the plate rolling mills have been converted to mean flow stress using the Sims approach. The agreement between thermomechanical tests and mill data has been tested in order to confirm that thermomechanical testing can provide an easy, convenient and very effective simulation of industrial hot rolling process. The results are analysed and compared to the predictions of some mathematical models developed in literature. Subsequently, the best performing formula, namely the Poliak's equation, has been optimised by means of genetic algorithms and the standard Gauss-Newton method. This latter has allowed a finer tuning of the models' parameters in order to fit at best the available data. The Poliak's formula optimised by genetic algorithms is shown to accurately predict the mean flow stress and therefore it provides a useful tool for the determination of the milling settings before the incoming strip enters the mill.