Experimental and numerical prediction of austenite grain size distribution in round-oval shape rolling

Abstract

To determine austenite grain size (AGS) distribution during round-oval shape rolling of mild carbon steel (0.2 wt% C), three-dimensional non-isothermal finite element analysis in couple with an AGS evolution model available in the literature was carried out in the present investigation. A hot rolling test was conducted at the laboratory to verify the numerical data obtained from the analysis. For more accurate prediction of the temperature history during the process, interface heat transfer coefficient between the billet and rolls was determined by comparing the numerical temperature history with the measured data at three locations in the billet. Metallographic investigation of the rolled specimen after quenching showed that recrystallization behavior could be classified into two regions: interior zone with refined grain dominated by metadynamic recrystallization, and exterior zone with less refined grain due to static recrystallization. It was found that the numerically predicted AGS distribution was in good agreement with the experimentally measured one. In addition, the conventional additivity rule generally used for the prediction of recrystallization behavior for non-isothermal rolling conditions was modified in order to bear a better comparison with the experimentally measured AGS values.