Hot deformation behavior and hot working map of Mn–Cr–Ni–Co steel for ball mill liner forging process

To explore the thermoformability of Mn-Cr-Ni-Co steel for ball mill liner, isothermal compression tests were performed on Mn-Cr-Ni-Co steel using a Gleeble-3800 thermal compressive testing machine. Flow stress curves at 900°C∼1200°C and 0.01s-1∼10s-1 were obtained. Results show Mn-Cr-Ni-Co steel has obvious positive strain rate sensitivity, with peak stress decreasing with increasing temperature. A constitutive equation for Mn-Cr-Ni-Co steel was established using the Arrhenius model based on strain compensation, and fitted values were compared to experimental values. A hot working map for Mn-Cr-Ni-Co steel was established and analyzed. Hot working process parameters are: deformation temperature of 980∼1200°C, strain rate of 0.04∼1.78s-1, providing a basis for selecting the hot forging process of the ball mill liner. Forging and forming experiments of the ball mill liner were carried out using the optimal parameters of Mn-Cr-Ni-Co steel from the hot working map. The ball mill liner has good forming quality with a relatively uniform martensitic structure inside. Tensile and impact tests were performed on the ball mill liner. Compared to the mechanical properties of traditional cast Mn13 ball mill liners, results show the tensile strength increased by 159.75%, elongation by 18.8%, and impact capacity by about 16.7%.