Mathematical description of the strain-rate sensitivity index at hot forming of steel

Abstract

The methodology of determination of strain-rate sensitivity index was developed, based on hot rolling of a set of samples with the same draft but different speed at defined temperature levels. It was proved that initial grain size had nearly negligible influence on the investigated variable, in contrast to phase composition whose influence was remarkable. Combined influence of strain rate and temperature on deformation resistance of various types of steel was studied. For a selected group of steels an universal equation was set up, which described with a good accuracy impact of reciprocal temperature and chemical composition, expressed simply by nickel equivalent, on strain-rate sensitivity in hot state.