Constitutive analysis of high-temperature workability of a high-nitrogen bearing steel

In this paper, the hot working behaviour of X30 CrMoN 15 1 high N steel was investigated by torsion testing. A new constitutive model based on the Garofalo equation was used to describe the flow stress dependence on temperature, strain and strain rate. Adiabatic heating was accounted for in the modelling of the flow curves. An excellent description of the experimental data was obtained by the model, which suggests that in isothermal condition the flow curves are characterised by a peak, followed by a moderate softening to a steady state. The high values of the activation energy for hot working were rationalised by considering the strengthening effect of undissolved particles hindering dislocation motion.