GRAIN-GROWTH DURING THE THERMOMECHANICAL PROCESSING OF AUSTENITIC STAINLESS-STEELS

When modelling the microstructural evolution during multipass hot rolling of stainless, one of the largest ambiguities between different research groups exists when describing grain growth after recrystallisation is complete. Experiments have, therefore, been carried out to investigate the grain growth behaviour after recrystallisation of grade 316L stainless steel under conditions relevant to industrial thermomechanical processing. Annealing experiments involving the reheating of recrystallised material over relatively long times showed that the material exhibited classical parabolic growth. However, comparison with literature data revealed large discrepancies between authors for values of k in the grain growth equation d(2) = d(0)(2) + kt (see below for definition of symbols). Plane strain compression tests enabled growth to be studied immediately after the completion of recrystallisation at short times relevant to interstand times in hot rolling. Results from these showed that growth followed a parabolic law, but of two distinct stages with differing growth rates. Initial growth after recrystallisation is relatively fast, but after a certain 'break point' growth reverts to the same relatively low rate as experienced in annealing experiments. It is important then that the correct growth equation is applied when modelling the microstructural processes during metal rolling. The significance of different values of k on grain growth during multipass rolling has been demonstrated in this work and can, therefore, improve the agreement between microstructural models and actual microstructural evolution. (C) Institute of Materials.