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 evolut...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.展开更多
Five forging experiments were designed and conducted to investigate the effect of process parameters on microstructure evolution during hot deformation for X12CrMoWVNbN10-1-1 steel.The experimental results indicated t...Five forging experiments were designed and conducted to investigate the effect of process parameters on microstructure evolution during hot deformation for X12CrMoWVNbN10-1-1 steel.The experimental results indicated that average grain size became finer with the increasing number of upsetting and stretching.Especially,the size of stretching three times with upsetting twice had the most remarkable effect on refinement,and the size was only 27.36%of the original one.Moreover,the stress model was integrated into the software and finite element models were established.Simulation results demonstrated that the strain at center point of workpiece was far larger than critical strain value in each process,so that dynamic recrystallization(DRX) occurred in each workpiece,which implied DRX could occur for several times with the increasing number of upsetting and stretching,and uniform finer microstructure would be obtained.However,the results also showed that higher temperature was an unfavorable factor for grain refinement,so the times of heating should be limited for workpiece,and as many forging processes as possible should be finished in once heating.展开更多
基金Item Sponsored by High-Tech Research and Development Program (863Program) of China(2008AA030703)
文摘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.
基金the National Science and Technology Major Project of China(No.2012ZX04012-011-02)the National Basic Research Program(973)of China(No.2011CB012903)
文摘Five forging experiments were designed and conducted to investigate the effect of process parameters on microstructure evolution during hot deformation for X12CrMoWVNbN10-1-1 steel.The experimental results indicated that average grain size became finer with the increasing number of upsetting and stretching.Especially,the size of stretching three times with upsetting twice had the most remarkable effect on refinement,and the size was only 27.36%of the original one.Moreover,the stress model was integrated into the software and finite element models were established.Simulation results demonstrated that the strain at center point of workpiece was far larger than critical strain value in each process,so that dynamic recrystallization(DRX) occurred in each workpiece,which implied DRX could occur for several times with the increasing number of upsetting and stretching,and uniform finer microstructure would be obtained.However,the results also showed that higher temperature was an unfavorable factor for grain refinement,so the times of heating should be limited for workpiece,and as many forging processes as possible should be finished in once heating.
