A comparative study on the evolutions of thermal and mechanical parameters and microstructure of 30Si2MnCrMoVE steel during hot ACDR and upsetting deformation

Axial closed-die rolling (ACDR), as a new type of local loading and labor-saving forming method, has a broad application prospect in the production of large-scale rotary parts, compared with traditional upsetting forming. However, the different evolutions of thermal and mechanical parameters and microstructure between the two forming modes are still ambiguous. In this study, the thermal and mechanical parameters and microstructure evolutions of 30Si2MnCrMoVE UHSS after ACDR and upsetting deformation were studied by means of numerical simulation, metallographic observation, and scanning electron microscope (SEM). The temperature and effective strain evolution of the upper surface, central axis, and middle height (1/2h) of the workpiece were analyzed by numerical simulation. Combined with the evolution of temperature and equivalent strain, the mechanisms of original austenite microstructure evolution of the two deformation modes were analyzed. The results show that there is only one deformation dead zone at the lower end of the workpiece after ACDR deformation which is different from upsetting. The deformation temperature is the primary reason for the difference of microstructure evolution at 1/2h between ACDR and upsetting deformation. The microhardness at 1/2h of the sample after ACDR deformation and direct quenching is lower than that of upsetting.