Simulation of Heat Treatment Response and Distortion of Bearing Steels

The present paper is a review of recent results on simulation of heat treatment response of bearing steels. Two aspects are considered namely firstly the evolution of the microstructure during heat treatment, especially the carbide structure and the corresponding distribution of alloying elements in the austenite around the carbides. This information is important in order to understand the hardening response of the steel. The analysis is based on thermodynamics and kinetics of multi component systems. Both single carbide sizes and realistic size distributions are considered. Secondly the evolution of the residual stresses and the distortion is considered during the full heat treatment cycle including heating and cooling. These latter simulations focus on the behaviour of full components. Special interest is devoted to origins of out of roundness of bearing rings. Factors like original geometrical imperfections, residual stresses from mechanical manufacturing steps, segregation and uneven cooling action during quenching are considered.