Three-dimensional simulation of quenching process of plain carbon steel gears incorporating phase transformations

In the present work, a numerical model was developed for the simulation of the quenching process of plain carbon steel gears in water and oil using finite element method. For diffusional transformations, the Johnson–Mehl–Avrami equation was coupled with the additivity rule, while for non-diffusional transformation, the empirical model of Koistinen–Marburger was employed. In addition, the model of Maynier et al. was used to compute the hardness distribution throughout the parts. To evaluate the cooling power of quenching media, the heat transfer coefficients of quenching media were calculated by solving an inverse problem using a stainless steel probe. In addition, a novel approach was applied for computing the actual phase fractions in the multiphase steel. The effects of the latent heat releases during phase transformations along with the effect of temperature and phase fractions on the variation of thermophysical properties were considered. Experimental tests including cooling curve analysis, metallographic investigations and hardness measurements were performed to evaluate the validity of the model. The comparisons indicated that the simulation results were consistent with the experimental results. The multiphase transformation model presented here is capable to predict the distribution of temperature, microstructures and hardness during continuous cooling of steel.