Modelling of quenching process and residual stresses in rail wheels

Low carbon bainitic-martensitic steels for rail wheels have been shown to provide favourable properties with superior hardness and strength compared to pearlitic steels. However, there is a concern that conventional quenching of low carbon bainitic-martensitic steel rail wheels may induce undesirable tensile residual stresses and distortions in the tread region of the rail wheels. These stresses may lead to the initiation and propagation of cracks during service. Computational analysis using a finite element method (FEM) has been used to model and accurately predict distortions and residual stresses during the quenching of pearlitic steels and to compare the results with those of low carbon bainitic-martensitic rail wheels. Experiments were undertaken to determine dilatometry data for low carbon bainitic-martensitic steels to characterise the volumetric changes associated with martensite transformation for varying quenching conditions which were then incorporated into the finite element analysis. The result showed that quenching conditions can be designed to promote the development of compressive residual stresses in the tread of low carbon bainitic-martensitic rail wheels, thereby, mitigating the risk of crack initiation and propagation during service.