Characterization of Hot Deformation Behavior and Processing Map of As-Cast H13 Hot Work Die Steel

The hot-working behavior of as-cast H13 hot work die steel was investigated in the method of isothermal compression test involving the wide deformation temperatures of 900–1150 °C and strain rates of 0.01–10 s⁻¹, with the true strain to 0.8, on the MMS-200 thermo-mechanical simulator. Two characteristic parameters involving the critical strain for DRX initiation (\(\varepsilon_{c}\)) and the strain for peak stress (\(\varepsilon_{p}\)) were identified. The ratio of critical strain to peak strain ranged from 0.26 to 0.6, which decreased with the increase in temperature and decrease in strain rate. Processing maps were established using dynamic material model at strains of 0.2, 0.4, 0.6, 0.8. The power dissipation maps were not significantly affected by the strain, while the instability maps were sensitivity with the strain when it was over 0.4. The area of instability domain at strain of 0.8 was the largest. The instable characteristics contained the mixed grain structure, adiabatic shear band, intense deformation in serious deformation area and brittle elemental segregation area. The chief effect on the power dissipation was the strain rate, the optimum hot working parameters at strain of 0.8 (910–985 °C, 1010–1150 °C and 0.01–0.05 s⁻¹) were determined. In this filed, the original coarse as-cast grains were gradually refined by dynamic recrystallization mechanism and the DRX grain numbers had a significant increase with the increase of power dissipation efficiency.