Investigation on the plastic deformation behavior of ultra-high-strength steel thin-walled conical components formed by counter-roller active flexible power spinning

Aerospace technology reflects a country’s manufacturing capability and international standing and is therefore of great strategic significance. Conical cylindrical parts are widely used in critical aerospace components such as rocket engine nozzles and aircraft turboshaft engines. However, existing manufacturing processes for thin-walled conical parts still suffer from several shortcomings. For example, weld seams introduced by plate rolling and welding can impair the load-bearing capacity of cylindrical shells; precision CNC machining is characterized by low efficiency and size limitations; and mandrel spinning has poor processing flexibility, while mandrel manufacturing and tooling costs are high. To address the above problems, D406A ultra-high-strength steel for aerospace applications was selected as the research material in this study. Its stress–strain curve in the annealed state was obtained through compression tests. On this basis, a novel process for forming thin-walled conical parts by counter-roller active flexible power spinning was proposed, and the corresponding process route was designed. To verify the feasibility of the proposed process, a finite element model for counter-roller active spinning of D406A ultra-high-strength steel thin-walled conical parts was established in ABAQUS. The forming process mainly consisted of two stages: thinning plastic deformation of the initial cylindrical blank by counter-roller active power spinning, and conical-surface forming by counter-roller active spinning. Based on the numerical simulation results, the forming behavior in these two stages was analyzed in terms of the equivalent stress distribution, equivalent strain distribution, wall-thickness distribution of the blank, and the three-directional spinning forces acting on the inner and outer rollers. The results showed that after the first-stage cylindrical thinning process, the average wall thickness in the stable forming zone of the cylinder was 6.23 mm, with an error of 3.83%. After the second-stage conical-surface forming process, the average wall thickness in the stable zone was 3.25 mm and the average cone angle was 14.12°, corresponding to a wall-thickness error of 8.33% and a cone-angle error of 0.86%, respectively. Moreover, compared with traditional counter-roller passive spinning, counter-roller active spinning exhibited smaller torque fluctuations and smoother torque variation of the rollers, required lower fixture torque, and showed improved forming stability. An experimental platform was then established using a vertical dual-counter-roller spinning machine. The experimental scheme was completed and experimentally validated. The final experiments yielded a wall-thickness error of 13.67% and a cone-angle error of 17% for the formed thin-walled conical part. Although certain deviations existed between the experimental results and the numerical simulation results due to factors such as equipment rigidity and material springback, the sources of these deviations can be explained by clear physical mechanisms, and the overall trends remained consistent with the numerical simulation results and mechanism analysis. These results verify the feasibility of the proposed process route for the flexible forming of large-diameter, multi-specification, high-strength thin-walled conical parts, and provide a new process concept for the efficient mandrel-free forming of such components.