It is necessary to establish a constitutive model of 30CrMoA steel to optimize the forming shape and mechanical properties of high-speed train axles. The experimental stress–strain curve of 30CrMoA steel was obtained by an isothermal compression test on a Gleeble-3500 thermal simulation test machine under temperature of 1273~1423 K and strain rate of 0.01~10 s⁻¹. Considering the effect of strain on the material constant, an empirical constitutive model was proposed with strain correction for 30CrMoA steel. In addition, the material constant in the constitutive model is determined by linear regression analysis of the experimental stress–strain curve. Comparing the theoretical value and experimental value of flow stress, the correlation R is 0.9828 and the average relative error (ARRE) is 4.652%. The constitutive model of 30CrMoA steel with strain correction can reasonably predict the flow stress under various conditions. The results provide an effective numerical tool for further study on accurate near-net forming of high-speed train axles.

The hollow axle is the key basic component of high-speed trains. How to realize its production with short process and high-quality precision plastic forming is the frontier of current research and a major problem to be solved. On the basis of analyzing the advantages and disadvantages of the existing forging process of the hollow axle, this paper expounds the principles and characteristics of multi-wedge synchrostep cross-wedge rolling (MSCWR) technology, multi-roll cross-wedge rolling (MCWR) technology, three-roll skew rolling (TRSR) technology, and tandem flexible skew rolling (TFSR) technology in detail, and discusses the feasibility and key technical problems of these technologies to form the hollow axle. It is concluded that tandem flexible skew rolling (TFSR) technology has the advantages of short process, high quality, high efficiency, energy saving, and material saving, and this technology is the development direction of precision plastic forming of the hollow axle. The research results provide technical guidance and research directions for promoting global high-speed rail development.

To improve the production quality and efficiency of the concave ring, a multi-pass stamping technology is used to replace the spinning technology to form the concave ring. First, the multi-pass stamping dies are designed according to the structural characteristics of the concave ring. Then, the process parameters are determined based on the bending conditions and the dimensional requirements of the concave ring. Next, the rationality of the designed stamping dies is verified by analyzing the stress and strain field of the multi-pass stamping concave ring. Finally, the stamping experiments are carried out. Experimental results show that the dimensional error of the concave ring formed by multi-pass stamping is less than 0.5%. The multi-pass stamping technology is feasible to form the concave ring. The reasonable design of the mold is the key factor to prevent defects in the workpiece. The concave ring formed by multi-pass stamping meets the industrial requirements.

At present, hollow axles with constant hole diameter are mainly formed by turning thick-walled hollow tubes. This method of processing has low material utilization and processing efficiency. And heat treatment is required to improve the mechanical properties of hollow axles. In order to improve the material utilization and processing efficiency of a hollow axle with constant hole

The turbine shaft is a crucial core component of aeroengines, made of difficult-to-deform high-temperature alloy materials, characterized as a long hollow stepped shaft with deep internal holes. Achieving efficient, high-performance, and precise manufacturing of turbine shafts is a cutting-edge...

The material constitutive equation of 25CrMo4 steel was established through an isothermal compression experiment. First, a thermal compression experiment was carried out with a Gleeble-3500 thermal simulator to study the thermoplastic deformation behaviour of 25CrMo4 steel at various temperatures (850, 950, 1050, and 1150 °C) and strain rates (0.01, 0.1, 1.0, and 10 s⁻¹). The measured true stress–strain curve showed that when the temperature is constant, the flow stress increases with the strain rate, whereas when the strain rate is constant, the flow stress decreases with the temperature. Then, the constitutive model of peak stress of 25CrMo4 was established after analyzing the stress and strain statistics. The model parameters were optimized. The accuracy of the flow stress constitutive model was verified by comparing the flow stress prediction model with the experimental results. The hot forging process of the inner core wheel was numerically simulated based on DEFORM-3D v11 software, and the parameters of this process were formulated by analyzing the metal flow rate and equivalent stress and strain fields.