Hot Deformation Behavior and Numerical Simulation of 40CrNiMo Steel for Wind Turbine Pulley Shafts

The hot deformation behavior (T = 800–1100 °C, $\dot{\epsilon }$ = 0.01–10 s⁻¹) of 40CrNiMo steel for wind turbine pulley shafts was studied by Gleeble-3800 thermomechanical simulator. A constitutive equation and hot processing map are established based on the friction and temperature correction curves. The most available hot processing parameters are determined by combining microstructure analysis. The temperature fields and effective strain fields under different deformation conditions are simulated by Deform-3D software. The results indicate that the effect of friction on the flow curves is greater than that of temperature rise, the activation energy Q of hot deformation for 40CrNiMo steel calculated based on the theoretical calculation is 368.292 kJ mol⁻¹. The constitutive model based on strain compensation has high accuracy, with an average relative error of 6.65% and a correlation coefficient of 0.987. The optimum hot processing interval is at a deformation temperature of 950–1050 °C and a strain rate of 0.03–0.25 s⁻¹, which has a high-power dissipation value and avoids the instability region. Additionally, numerical simulation results show that the temperature field distribution is uniform in this deformation range, and the standard deviation of the effective strain is low, making it suitable for hot processing.