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

When modelling the microstructural evolution during multipass hot roll ing of stainless, one of the largest ambiguities between different res earch groups exists when describing grain growth after recrystallisati on is complete. Experiments have, therefore, been carried out to inves tigate the grain growth behaviour after recrystallisation of grade 316 L stainless steel under conditions relevant to industrial thermomechan ical processing. Annealing experiments involving the reheating of recr ystallised material over relatively long times showed that the materia l exhibited classical parabolic growth. However, comparison with liter ature data revealed large discrepancies between authors for values of k in the grain growth equation d(2) = d(0)(2) + kt (see below for defi nition of symbols). Plane strain compression tests enabled growth to b e studied immediately after the completion of recrystallisation at sho rt times relevant to interstand times in hot rolling. Results from the se showed that growth followed a parabolic law, but of two distinct st ages with differing growth rates. Initial growth after recrystallisati on is relatively fast, but after a certain 'break point' growth revert s to the same relatively low rate as experienced in annealing experime nts. 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 multipas s rolling has been demonstrated in this work and can, therefore, impro ve the agreement between microstructural models and actual microstruct ural evolution. (C) Institute of Materials.