Strain summation in finite element modelling of multipass hot rolling

The shear strain distributions in two pass forward-forward (FF) and forward-reverse (FR) rolling have been modelled using plane strain finite element models of individual passes and then summing the results from the individual passes. This method gives excellent agreement with the average shear strain, defined by the net shear angle, and with the distribution of shear strain through the thickness, measured from the distortion of mild steel pins inserted through the thickness of experimentally rolled type 316L stainless steel slabs. The spread in breadth of the experimental slabs has little effect on the shear strain distribution or on the net equivalent strain at any position in the rolled slabs. For a given total reduction, the shear strain for FF two pass rolling is less than that for a single pass and is reduced when a smaller first pass and larger second pass reduction is applied. For FIR two pass rolling, the shear strain of the first pass is essentially removed for 30%+30% reductions, but not for 50%+50% reductions. For the experimental conditions studied, the recrystallisation kinetics and recrystallised grain size produced by annealing after FF and FR two pass rolling are satisfactorily correlated by the net equivalent strain, with no evidence of any effect of the different strain paths to achieve the same value of equivalent strain.