Finite Element Simulation of Residual Stress of Large-Scale Gears after Induction Hardening

Temperature change curves and microstructures of G35CrNiMo steel large-scale gears under three induction hardening processes were analyzed. The residual stresses in different regions of gears were measured by blind-hole method combined with dissection method. The finite element model and coupling model of electromagnetic induction and thermal conduction were established. The residual stress distribution of gears was simulated and compared with the experiment results. The results show that high thermal stress appeared in the quenching layer at high quenching temperature, which led to cracking during quenching. The temperature gradient of the quenching layer decreased after gas quenching and followed by water quenching, and the thermal stress decreased; the quenching cracking could be avoided effectively. The maximum transient stress on the surface of gears appeared near the 325℃ isotherm line. The stress in the rack direction and perpendicular to the rack direction were close, and the calculated results were consistent with the experimental results.