Optimization of strength and toughness of railway wheel steel by alloy design

For the purpose of developing a railway wheel steel with a good combination of strength and toughness, an improved wheel steel containing high contents of Si and Mn and a low content of Cr was developed. Microstructures and mechanical properties of the improved wheel steel at different depths in the wheel rim were evaluated by optical microscopy, scanning electron microscopy, electron probe microanalysis, tensile, hardness and Charpy impact tests, with a comparison to two traditional wheel steels. The results indicate that the improved wheel steel has a higher strength without impairing its impact toughness. The improved steel is hardened by solid solution strengthening and refinement of pearlite interlamellar spacing, while the impact absorbed energy is raised by increasing the proeutectoid ferrite fraction. The hardness of materials reduces with an increase in the depth in the wheel rim due to the increasing of proeutectoid ferrite fraction and interlamellar spacing. Materials deeper in the wheel rim exhibit a lower impact absorbed energy because of their larger interlamellar spacing and pearlite colony size. The thickness of complex layer is successfully reduced by alloy design in this study.