Research On Axle Stress Evolution During Forging And Residual Stress During Heat Treating

Abstract:With the rapid development of railway construction, the requirements of the properties and reliabilities of the axles are higher and higher. As important material processing technologies during the preparation of axles, forging and heat treatment play an important role in the properties of axles. Through numerical simulation analysis of the forging and heat treatment process, the distribution of stress-strain field and temperature field in the axle could be obtained, and the probable defects can be predicted which could then be used to provide scientific basis for designers to conduct process analysis and optimize process design.In this thesis, the chamfering and rounding process of25CrMo axle forging under different anvils such as flat,90V-shaped,120V-shaped and different arc anvils were simulated by rigid viscoplasticity finite element method. During the simulation, the influence of different anvil shapes on the size precision and strain-stress distribution of the forged axles were discussed. And then the optimized anvil shape and its process route were obtained.The FEM model of the35CrMo axle was built in the software DEFORM. The distributions of temperature, microstructure and stress under different quenching processes such as brine, polymer solutions, oil and air were obtained. Then, the influences of heat transfer coefficient on the temperature field, the martensite distribution of axle heart, the instantaneous stress variation law of the axle surface and center and depth of the axle surface residual compressive stress were analyzed. Finally, the finite element model of25CrMo subway train axle under water quenching and polymer solutions was built and the distributions of temperature, microstructure and stress in different cross section were obtained, which provides theory basis for the heat treatment process of axle.The residual stresses of different axles were measured by the X-ray diffraction method and layer stripping. Then the experimental results were compared with simulation results and the reliability of the finite element model of quenching was verified. Besides, the experimental results show that the residual stress of subway axle after quenched and tempered process accord with standard of Europe EN13261.