Hot deformation characteristics and microstructure evolution of industrial grade AISI M35 high-speed steel produced by ESR

The hot deformation behavior and microstructure evolution of industrial grade American Iron and Steel Institute (AISI) M35 high-speed steel produced by electroslag remelting at different parameters were investigated. The results indicated that grains coarsening and M₂C carbides decomposing appeared in the steel at 1150 °C for 5 min, and the network carbides were broken and deformed radially after the hot deformation. A constitutive equation was determined based on the corrected flow stress–strain curves considering the effects of friction and temperature, and a constitutive model with strain-compensated was established. The dynamic recrystallization (DRX) characteristic values were calculated based on the Cingara–McQueen model, and the grain distribution under different conditions was observed and analyzed. Significantly, the action mechanisms of carbides on the DRX were illuminated. It was found from a functional relation between average grain size and \(Z\) $Z$ parameter that grain size increased with increasing temperature and decreasing strain rate. Optimal parameters for the hot deformation were determined as 980–1005 °C ~ 0.01–0.015 s⁻¹ and 1095–1110 °C ~ 0.01–0.037 s⁻¹ at the strain ranging from 0.05 to 0.8. Increasing the strain rate appropriately during deformation process was suggested to obtain fine and uniformly distributed carbides. Besides, an industrial grade forging deformation had also verified practicability of the above parameters.