Residual stress during heat treatment of steel grinding balls

This work aimed to model the temperature distribution, phase transformation and residual stress induced during the heat treatment of grinding balls of 3 and 5 in. diameter. The temperature model considered factors such as the heating of the water and the formation of a steam layer that surrounds the balls at the start of the quenching. The model of the residual stress field considered: the temperature distribution, the force equilibrium equations and the constitutive thermo-elastic relationships, including the expansion due to the austenite–martensite transformation. A good agreement between the experimental and theoretical values for the temperature distribution was obtained with the differences at the end of the quenching being no higher than 0.5%. The experimental behavior of the balls in a mill simulator, as well as the residual stress measured by X-ray diffraction, agreed satisfactorily with the theoretical predictions.