Experimental and Numerical Investigation of the Thermal Effects on Railway Wheels for Shoe-Braked High-Speed Train Applications

An improved railway wheel steel containing higher contents of C, Mn, Si and V than the traditional ER7 steel was developed by alloy design for shoe braked high speed train applications. The effects of the thermal load on the microstructure and mechanical properties of a wheel made from this steel were investigated using a combined experimental and numerical approach. The wheel braking was studied using finite element (FE) simulations that account for the thermal loading of the wheel in order to find the temperatures reached in the wheel rim. Hardness measurements, tensile tests, toughness tests, fatigue crack growth tests and microstructural observations were carried out on samples extracted from real wheels, with and without heat treatments simulating the modification of the microstructure due to the shoe braking. The results on the un-treated samples showed that the improved steel has a better combination of strength and toughness than ER7 steel. The results on the heat treated samples showed that the improved steel maintains acceptable mechanical properties provided the maximum temperature during braking is below the A3 temperature of the steel (around 790 °C).