Austenite Grain Size Evolution in Railway Wheel During Multi-Stage Forging Processes

The knowledge of microstructure evolution of railway wheel during hot forming process is the prerequisite of improving mechanical properties of the final product. In order to investigate the austenite grain size evolution of railway wheel during multi-stage forging process, mathematical models of recrystallization and austenite grain growth were derived firstly by hot compression tests for railway wheel steel CL50D, which then were integrated with a thermal-mechanical finite element model by the developed subroutines. The information about kinetics of recrystallization and grain size distribution during the forging process was obtained by simulation. The predicted results were validated by experiments in an industrial scale, and the average error between the predicted grain sizes and the measured ones is about 5%. The result shows that, under the current railway wheel forging process, the grain size distribution after final forging is inhomogeneous extremely. There is a narrow coarse grain zone between the external part and center of the hub caused by static recrystallization after final forging. With cooling of 60 s after final forging, the grain size is about 85 μm for the areas near the web surface and 175 μm for center areas of the hub and rim.

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