Jet Quenching Simulation with Consideration for Distribution of Heat Transfer Coefficient and Latent Heat for Martensitic Transformation under Rapid Cooling

摘要

The accurate simulation of jet quenching is required to optimize the dimensions of the cooling jacket, the positional relationship between the cooling jacket and workpiece, and the various cooling parameters (such as the flow rate of the jet and the cooling time) without requiring a trial-and-error empirical approach. In this study, for the purpose of developing an accurate and simple jet quenching simulation technique without using the CFD simulation, heat transfer between surface of a workpiece and jet is summarized using heat transfer coefficients which depend on surface temperature of a workpiece and jet density. Additionally, because a martensitic transformation occurs during the quenching of carbon steels, the latent heat of this transformation was incorporated into the simulation. A means of obtaining the latent heat for martensitic transformation during rapid cooling was also developed and used in the simulation. Providing heat transfer coefficients adequate for practical use improved the prediction accuracy for the overall quenching process, and consideration of the latent heat for martensitic transformations under rapid cooling increased the accuracy, in particular below 473 K, which is the onset temperature for the martensitic transformation. When experimental temperature of workpiece was 339 K, after 1 seconds of cooling time, the error between the experimental and calculation results for tooth bottom of a gear was approximately 4 K. This error is 14 times smaller than that obtained with a conventional calculation without consideration of the heat transfer coefficients which depend on surface temperature and jet density and latent heat of martensitic transformation.