Hot workability in process modeling of a bearing steel by using combined constitutive equations and dynamic material model

The high temperature workability of a 1%C–1.5%Cr steel was investigated by means of torsion experi- ments carried out between 1125 and 1000 C. The main task of the study was the quantification of the effect of processing conditions (temperature and strain rate) on the flow stress, by means of constitutive models capable of providing the entire shape of the stress vs strain curves. An excellent description was indeed obtained by the Hensel and Spittel relationship, provided that the portions of each curve before and after the peak stress were described separately. The same model curves were then used to estimate the peak and steady state stress for each of the investigated conditions, again obtaining an excellent cor- relation with the experimental data. To further facilitate the identification of the optimum processing window for this material, dissipation efficiency maps were obtained using as input the stress vs strain rate values computed by a constitutive model, in this case based on the Garofalo sinh equation.