Relationship analysis between micro-scale phase transformation and macro-hardness of 48MnV steel crankshaft induction hardening

The influence of crankshaft induction hardening on the phase transformation of the structure is a highly nonlinear process, and it is a significant problem in the actual processing to correctly select the processing parameters according to the process deformation mechanism. In this paper, through the comparison of the quasi-coupling analysis model, material nonlinear phase transition, and longitudinal morphology, the internal relationship between microscale phase transition and microhardness of 48MnV steel crankshaft induction hardening is systematically studied, which is an essential basis for selecting processing parameters. The results show that the hardness of the crankshaft journal decreases gradually from the surface to the core after induction hardening, and the microstructure is divided into a hardened zone, transition zone, and matrix. The main reason for material partitioning is the influence of temperature step distribution, the highest surface temperature meets the martensitic transformation, and the axial core temperature after hardening and cooling is 257 ℃ , which does not meet the conditions for microstructure transformation. In addition, the hardened layer depth prediction results are in good agreement with the experimental data, and the absolute value of the error of the hardened layer depth between the simulated value and the practical value is 0 %-2.73 %. The difference between the average hardness of the simulation and the experimental measurement is slight, which ensures the reliability of the simulation model.