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As a core component in the industrial sector， the efficient and high-precision forming of hollow shafts is crucial for ensuring product performance and improving production efficiency. However， traditional open die forging and closed die forging methods face significant challenges， such as low material utilization， insufficient forming precision， and limited production efficiency. These issues severely restrict the development and application of hollow shafts. This paper reviews the latest research advancements in hollow shaft manufacturing， analyzes the current technical challenges， and explores the prospects of emerging forming technologies as well as the application of digital and intelligent technologies in this field. The paper summarizes the applications and advantages of various technologies， including rotary forging， squeeze casting， wedge cross rolling， and three-roll skew rolling， in enhancing the manufacturing efficiency and forming precision of hollow shafts. Rotary forging， by rotating and forging the material， effectively improves material utilization and product performance. Squeeze casting achieves high precision and consistency by pressing liquid metal into molds under high pressure. Wedge cross rolling drives the billet through the mold for reverse rotation， causing radial compression and axial elongation deformation of the metal， ultimately forming the desired stepped shaft parts， thereby improving dimensional accuracy and production efficiency. Three-roll skew rolling technology optimizes the loading mechanism to achieve efficient and continuous axial plastic forming through localized loading. With the manufacturing industry moving towards digitalization and intelligence， hollow shaft manufacturing technology is expected to achieve significant advancements and breakthroughs in the future.

The increasing demand for high-strength lightweight hollow shafts in transportation highlights the need for advanced fabrication techniques. Al–Zn–Mg–Cu alloys, noted for their superior properties, are selected for three-roll skew rolling (TRSR). In TRSR, the material undergoes combined axial tensile and radial compressive stresses. This study evaluates the feasibility of TRSR for producing high-strength lightweight hollow stepped shafts from Al–Zn–Mg–Cu alloy. An integrated approach, including constitutive modeling, hot processing map development, and TRSR numerical simulations/experiments, is employed to optimize the TRSR forming process. The constitutive model was established based on 300°C–450 °C & 0.01–10 s−1 hot compression and 350°C–430 °C & 0.1–5 s−1 high-temperature tensile test data. The established Johnson-Cook optimization by genetic algorithms (GA-JC) model and unified viscoplastic constitutive model, accurately capture the alloy's hot deformation behavior, exhibiting minimal average absolute relative errors (AARE) of 5.431% and 5.808%, respectively. Microstructure evolution analyses shed light on the predominant softening mechanisms, emphasizing dynamic recovery (DRV) at elevated strain rates and diminishing texture intensity with escalating deformation temperatures. The composite hot processing map delineates optimal process parameters (400°C–450 °C & 0.1s−1-1s−1), facilitating informed decision-making in manufacturing practices. The validation of numerical simulations through TRSR forming experiments with initial temperature of 450 °C for the billet and axial moving speed of 10 mm/s for the chuck in affirms the feasibility of producing hollow stepped shafts from high-strength Al–Zn–Mg–Cu alloy. Close agreement was found between simulated and experimental wall thickness variations. This study enhances understanding and optimization of TRSR forming for high-strength lightweight alloys, advancing industrial manufacturing methodologies.

To solve the problem of the long forming process for hollow shafts with constant wall thickness (HSCWT), a new process for forming HSCWT, namely three-roll skew rolling, has been proposed. First, the working principle of the three-roll skew rolling process is presented. Then, the finite element model (FEM) of the three-roll skew rolling HSCWT is established. The strain-stress field and temperature field distribution rules of the three-roll skew rolling HSCWT are analyzed with FEM. The stress-strain field of the rolled piece is distributed uniformly along the axial direction but not uniformly along the radial direction. The variation of the temperature field is related to the axial traction velocity. The greater the axial traction velocity, the smaller the variation of the temperature field. The temperature of rolled pieces varies within 100 °C during rolling. Finally, the three-roll skew rolling experiment of the HSCWT is carried out. The results show that the three-roll skew rolling process can form HSCWT. The temperature field of the three-roll skew rolling HSCWT is evenly distributed. The selection of larger axial traction velocity is conducive to the forming of rolled pieces. The three-roll skew rolling technology has achieved near constant temperature forming of HSCWT. [ABSTRACT FROM AUTHOR]

To solve the problem of the long forming process for hollow shafts with constant wall thickness (HSCWT), a new process for forming HSCWT, namely three-roll skew rolling, has been proposed. First, the working principle of the three-roll skew rolling process is presented. Then, the finite element model (FEM) of the three-roll skew rolling HSCWT is established. The strain-stress field and temperature field distribution rules of the three-roll skew rolling HSCWT are analyzed with FEM. The stress-strain field of the rolled piece is distributed uniformly along the axial direction but not uniformly along the radial direction. The variation of the temperature field is related to the axial traction velocity. The greater the axial traction velocity, the smaller the variation of the temperature field. The temperature of rolled pieces varies within 100 °C during rolling. Finally, the three-roll skew rolling experiment of the HSCWT is carried out. The results show that the three-roll skew rolling process can form HSCWT. The temperature field of the three-roll skew rolling HSCWT is evenly distributed. The selection of larger axial traction velocity is conducive to the forming of rolled pieces. The three-roll skew rolling technology has achieved near constant temperature forming of HSCWT.

The paper introduces a new technology of the integrated forming of shape and inner hole of hollow axle. Firstly, the design of the process is described. Secondly, the range of feed angle of two sets of rolls and the principle to be followed are explained. Finally, the rolling process of hollow axle is simulated by Finite Element Method (FEM), and the variation law of load parameters and the distribution law of temperature and effective plastic strain in the rolling process are analyzed.The numerical results verify the feasibility of rolling hollow axle with this process.

With the rapid development of high-end equipment in aviation, high-speed rail, and other fields, the requirements for the necessary shaft foundation parts on the equipment are more stringent. This has resulted in rapid development of the new generation of three-roll skew rolling (TRSR) flexible forming shaft part technology. It is an important issue to explore the theory and technology of TRSR flexible forming of hollow shaft and systematically expounding the flexible forming theory of TRSR of hollow axle. Therefore, this paper explores the feasibility of TRSR through the combination of theory and experiment and analyzes the formation mechanism as well as develop macro and micro uniformity law in order to clarify the quality control measures. In order to realize the low-cost forming of hollow axle with short process, the piercing-rolling compound forming (integrated forming of shape and inner hole of hollow axle) and the multi-roll skew tandem rolling technology for large section shrinkage shafts are innovated. The forming mechanism is verified through the simulation research. Based on the abovementioned research, it is concluded that skew-rolling composite integrated forming of large hollow shafts, multi-roll skew tandem rolling technology for large section shrinkage shafts, and the flexible forming process and equipment of digital TRSR is the future development direction of the TRSR flexible forming technology of hollow shaft. The results provide a theoretical basis and development direction for improving the precision short process, high efficiency, and high-quality manufacturing of high-end equipment shaft foundation. [ABSTRACT FROM AUTHOR]

The hollow axle is the key component of the high-speed train, and the realization of high-quality forming is the key to ensure the safety of train operation. In this paper, the specimen of the variable-diameter section of the hollow axle is taken as the research object, and the generation mechanism of surface spiral mark defects and the formula of spiral mark depth of variable-diameter section in the TRSR (three-roll skew rolling) process with variable roll spacing are explored. The external roundness error and the function C to measure the wall thickness uniformity of the cross-section were taken as the evaluation indexes and the single-factor simulation experiment was established and simulated in the software Simufact.forming16.0 to obtain the influence law of each process parameter on the external roundness error and wall thickness uniformity of the rolled piece. Orthogonal tests were designed and the order and optimal combination of process parameters on the forming quality were obtained by range analysis and ANOVA analysis. The research results provide theoretical guidance for improving the forming quality of the variable-diameter section of the hollow axle in three-roll skew rolling, and promote the transformation of the TRSR process to high performance and accurate forming. [ABSTRACT FROM AUTHOR]

This paper takes the simplified high-speed train hollow axle variable diameter section sample as the research object, uses Simufact.Forming simulation software for simulation, analyze the rolling piece inner variable diameter section, equal diameter section, outer variable diameter section three stages in the forming process of temperature field distribution characteristics and variation, and discusses the causes of temperature field variation.

This paper adopts a three-roll skew rolling technology with rolls that can either converge or move apart to form shafts with variable cross-section dimensions. Based on the rolling pitch, the effect of rollers’ rotation speed, radial speed, axial speed of chuck on the forming accuracy of the hollow shaft surface is analyzed. Increasing the rotation speed of rollers, reducing the radial speed of rollers and the axial speed of chuck can obtain higher surface forming accuracy. The finite element simulation results verified the correctness of the conclusion.

The spiral marks is one of the main surface quality defects of the three-roll skew rolled hollow axles. In order to eliminate the spiral marks, it is necessary to clarify the cause of the spiral marks on the surface of the rolled piece. Based on the analysis of the kinematics of the three-roll skew rolled hollow axles, the spiral marks is caused by the spiral pitch of the rolled piece being larger than the width of the finishing section of the roller. Increasing the rotation speed of the roller can reduce the spiral pitch of the rolled piece, thereby avoiding the appearance of spiral marks. The correctness of the proposed condition for preventing the defect of spiral marks is verified by simulation.

The paper introduces a new technology of the integrated forming of shape and inner hole of hollow axle. Firstly, the design of the process is described. Secondly, the range of feed angle of two sets of rolls and the principle to be followed are explained. Finally, the rolling process of hollow axle is simulated by Finite Element Method (FEM), and the variation law of load parameters and the distribution law of temperature and effective plastic strain in the rolling process are analyzed. The numerical results verify the feasibility of rolling hollow axle with this process. [ABSTRACT FROM AUTHOR]

The average grain size and microstructure uniformity are the key factors determining the mechanical properties of the hollow shaft. In order to obtain a fine and uniform microstructure, a finite element model of threeroll skew rolling hollow shaft for the coupling of heat, force and microstructure was established. The influence of process parameters on the average grain size and microstructure uniformity of the rolled product was analyzed by using the single factor research method. The results show that the grain size is remarkably refined and the distribution is relatively uniform. The optimum rolling temperature is 1 050 °C; the optimum feed angle is 9 °; the optimum roll rotate speed is 90 rad/min.

This paper adopts a three-roll skew rolling technology with rolls that can either converge or move apart to form shafts with variable cross-section dimensions. Based on the rolling pitch, the effect of rollers’ rotation speed, radial speed, axial speed of chuck on the forming accuracy of the hollow shaft surface is analyzed. Increasing the rotation speed of rollers, reducing the radial speed of rollers and the axial speed of chuck can obtain higher surface forming accuracy. The finite element simulation results verified the correctness of the conclusion. [ABSTRACT FROM AUTHOR]

This paper takes the simplified high-speed train hollow axle variable diameter section sample as the research object, uses Simufact. Forming simulation software for simulation, analyze the rolling piece inner variable diameter section, equal diameter section, outer variable diameter section three stages in the forming process of temperature field distribution characteristics and variation, and discusses the causes of temperature field variation. [ABSTRACT FROM AUTHOR]

The hollow axle is the key component of the high-speed train, and the realization of high-quality forming is the key to ensure the safety of train operation. In this paper, the specimen of the variable-diameter section of the hollow axle is taken as the research object, and the generation mechanism of surface spiral mark defects and the formula of spiral mark depth of variable-diameter section in the TRSR (three-roll skew rolling) process with variable roll spacing are explored. The external roundness error and the function C to measure the wall thickness uniformity of the cross-section were taken as the evaluation indexes and the single-factor simulation experiment was established and simulated in the software Simufact.forming16.0 to obtain the influence law of each process parameter on the external roundness error and wall thickness uniformity of the rolled piece. Orthogonal tests were designed and the order and optimal combination of process parameters on the forming quality were obtained by range analysis and ANOVA analysis. The research results provide theoretical guidance for improving the forming quality of the variable-diameter section of the hollow axle in three-roll skew rolling, and promote the transformation of the TRSR process to high performance and accurate forming.

The spiral marks is one of the main surface quality defects of the three-roll skew rolled hollow axles. In order to eliminate the spiral marks, it is necessary to clarify the cause of the spiral marks on the surface of the rolled piece. Based on the analysis of the kinematics of the three-roll skew rolled hollow axles, the spiral marks is caused by the spiral pitch of the rolled piece being larger than the width of the finishing section of the roller. Increasing the rotation speed of the roller can reduce the spiral pitch of the rolled piece, thereby avoiding the appearance of spiral marks. The correctness of the proposed condition for preventing the defect of spiral marks is verified by simulation. [ABSTRACT FROM AUTHOR]

This paper presents the new technology applied in a three-roll skew rolling railway hollow shaft. The three-roll skew rolling forming simulation is conducted in railway hollow shaft with 1 : 5. The rotation condition of the three-roll skew rolling is deduced and the rolling force and rolling torque are calculated and validated. The influence of process parameters on mechanics parameter is analyzed, from which it concludes that the mechanics parameters of the skew rolling are obviously smaller than those acquired by the cross-wedge rolling when rolling the same size of the railway hollow shaft. The results of this study lay a theoretical foundation for the realization of accurately forming the three-roll skew rolling railway hollow shaft with short process and low cost.

The average grain size and microstructure uniformity are the key factors determining the mechanical properties of the hollow shaft. In order to obtain a fine and uniform microstructure, a finite element model of threeroll skew rolling hollow shaft for the coupling of heat, force and microstructure was established. The influence of process parameters on the average grain size and microstructure uniformity of the rolled product was analyzed by using the single factor research method. The results show that the grain size is remarkably refined and the distribution is relatively uniform. The optimum rolling temperature is 1 050 °C; the optimum feed angle is 9 °; the optimum roll rotate speed is 90 rad/min. [ABSTRACT FROM AUTHOR]

This paper presents the new technology applied in a three-roll skew rolling railway hollow shaft. The three-roll skew rolling forming simulation is conducted in railway hollow shaft with 1: 5. The rotation condition of the three-roll skew rolling is deduced and the rolling force and rolling torque are calculated and validated. The influence of process parameters on mechanics parameter is analyzed, from which it concludes that the mechanics parameters of the skew rolling are obviously smaller than those acquired by the cross-wedge rolling when rolling the same size of the railway hollow shaft. The results of this study lay a theoretical foundation for the realization of accurately forming the three-roll skew rolling railway hollow shaft with short process and low cost. [ABSTRACT FROM AUTHOR]