In this work, a 3D thermo-microstructural model was developed to simulate the continuous cooling of steel. The model was employed for simulation of cooling process of the gears made from a plain carbon steel (AISI 1045) and a low alloy steel (AISI 4140). Temperature-dependent heat transfer coefficients for two different quenching media were evaluated by experimental and computational methods. The effects of latent heat releases during phase transformations, temperature and phase fractions on the variation of thermo-physical properties were investigated. The present model was validated against cooling curve measurements, metallographic analysis, and hardness tests, and good agreement was found between the experimental and simulation results. This model was used to simulate the continuous cooling process and to predict the final distribution of microstructures and hardness in steel gears.

Keywords: Steel, Quenching, Numerical simulation, Phase transformation.

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