Determination of transformation plasticity coefficient of steel by horizontal quenching of shaft

Shape accuracy of steel gears and shafts depends on the heat treatment distortion in the oil quenching condition of those parts. The distortion is mainly caused by the inhomogeneous cooling in oil quenching. The deformation by heat treatment can be estimated by the numerical simulation considering transformation plasticity. The key material property for the simulation is the transformation plasticity coefficient. The coefficient is conventionally measured by tensile or bending test under controlled temperature and stress, however the determination of the coefficient is not easy. In this study, the authors propose a simple method to determine the coefficient using horizontal quenching of a steel shaft. Horizontal quenching tests of chrome steel shafts were conducted to demonstrate inhomogeneous deformation by experiments and numerical simulations. The specimen was uniformly heated at 850 degrees C, and then quenched into oil with 100 degrees C. The direction of deflection has changed depending on the diameter of the specimen. Through the comparison between the predicted deformation by simulation and the experimental results, the transformation plasticity coefficients were determined as 3.0 x 10(-5) MPa-1 (austenite -> martensite) and 4.0 x 10(-5) MPa-1 (austenite -> bainite). (C) 2020 The Authors. Published by Elsevier B.V.