Development of constitutive equations for modelling of hot rolling

Constitutive equations which describe the flow stress behaviour of materials during hot deformation are used to model forming processes. Since the flow stress depends on both temperature and strain rate, the Zener-Hollomon parameter which combines these factors, is frequently used to describe the shape of such curves. For materials which dynamically recover, (only) the flow stress reaches a steady state value at high strains and methodologies which enable such behaviour to be modelled have previously been presented. Beyond the onset of dynamic recrystallisation, the flow stress of materials, such as steels, reach a peak in flow stress before gradual softening. The relative position of the peak in the how stress shifts as a function of the Zener-Hollomon parameter further complicating such analyses. The present paper describes the development and application of a methodology for modelling the flow stress of microalloyed steels: materials which exhibit dynamic recrystallisation behaviour.