Constitutive description of a low C-Mn steel deformed under hot-working conditions

The present investigation has been conducted in order to develop a constitutive description for a low C-Mn steel employed in structural applications, when this material is deformed under hot-working conditions. The set of equations that encompass the constitutive description of the steel are based on a simplified form of the Mechanical Threshold Stress Model. Accordingly, it has been shown that the flow stress of the material can be considered to arise from two different contributions: solid solution and precipitation hardening, which do not evolve in the course of plastic deformation and work-hardening, the only evolving component of the flow stress. The evolution of work-hardening has been introduced in the model by means of the work-hardening law proposed by Estrin and Mecking, in differential form. Also, the temperature and strain rate dependence of the contributions of solid solution and precipitation hardening to the flow stress, as well as that of the saturation stress in the work-hardening law, are described by means of the model earlier advanced by Kocks. The constitutive formulation encompasses seven material parameters which have been determined employing the experimental data corresponding to the strain interval where the material only exhibits positive work-hardening. It is able to predict accurately both work-hardening and work-softening transients when changes in deformation conditions occur. Furthermore, it can be easily implemented in any advanced computational tool employed for the analysis of hot-working processes of this material.