30CrMnSiA thin-wall cup-shaped part is a key basic component widely used in the flexible gear of harmonic reducer. Aiming at the problem of the low bearing capacity and short service life of harmonic reducer caused by insufficient strength and toughness of 30CrMnSiA thin-wall cup-shaped parts manufactured by traditional turning method, this paper proposed a plastic deformation-heat treatment process which consists of spinning, quenching, tempering, spinning and aging to manufacture 30CrMnSiA thin-wall cup-shaped parts with less or no cutting and excellent mechanical properties. Through the tensile and impact experiment, by comparing the mechanical properties of each process part, the microorganization of each process part was analyzed. The results show that tempered sorbite microstructure with high strength can be obtained by spinning-quenching and tempering process, but the plasticity was reduced significantly. The fibrous microstructure of spun parts can be further refined by aging heat treatment, and the fine carbides precipitated and uniformly distributed on the ferrite matrix. High strength and good plasticity can be obtained by subsequent aging at 300 ℃ for 6 h. As compared with parts obtained by turning forming after quenching and tempering heat treatment, the yield strength and tensile strength of 30CrMnSiA thin-wall cup-shaped parts manufactured by plastic deformation and heat treatment are improved by 93.65% and 47.88%, respectively. The hardness is increased by 26.87%, and the impact strength is increased by 12.01%. Meanwhile, the elongation and percentage reduction of area are 11.60% and 24.64%, respectively. The thin-wall cup-shaped parts with high strength and toughness can be manufactured by the plastic deformation and heat treatment process of spinning-quenching-tempering-spinning-aging, which provides a new method for manufacturing the thin-wall cupshaped parts with high-strength and toughness.

To solve the problems of long forming process, low efficiency, and difficult quality control in the traditional machining methods for thin-walled deep cup-shaped parts, a deep drawing-flow multi-process compound spinning method, which can realize the precise preparation of such parts with high efficiency, was proposed in this paper. Based on software Abaqus, a finite element model of Compound Spinning for the deep cup-shaped part of SPHC steel was established. It was used to study the strain and stress distribution and the flow of the material in the compound spinning process of deep cup shaped parts, and reveal the forming mechanism of compound spinning. Combining with the compound spinning forming experiments, the correctness of the finite element model was verified. The results show that the multi-process compound spinning process can obtain the thin-walled deep cup-shaped parts with good forming quality in single spinning process. According to the deformation of materials, multi process compound spinning can be divided into drawing spinning stage, flow spinning initial stage and compound spinning stable stage. In the initial stage of flow spinning, the maximum equivalent strain rises sharply with the progress of spinning. In the stable spinning stage, the maximum equivalent strain appears in the formed region, and its deformation state is axial and tangential tension and radial compression, while the transition region is axial tension, radial and tangential compression. In the initial stage of flow spinning, the axial flow of the material in the die area to the mouth increases with the increase of the axial offset between the rollers for deep drawing and flow spinning. In the stable stage of compound spinning, the outer area of the blank in contact with the roller for deep drawing spinning is subject to three-dimensional compressive stress, while the inner area is subject to three-dimensional tensile stress,and the contact area between the blank and the roller for flow spinning is subject to three-dimensional compressive stress. To ensure the spinning forming quality, the axial offset between the roller for spinning drawing and the roller for flow spinning should be greater than 5.3 mm.

Exploring the material flow behavior during the closed die forging is the theoretical basis for controlling forming defects such as insufficient filling and obtaining high-precision die forgings. In response to the problem of insufficient filling during hot die forging of gear blanks with deep spoke, this study selected the SCr420H gear blank with deep spoke as the research object and designed a multi-station closed hot die forging process of“cutting—heating—upsetting—preforging Ⅰ—preforging Ⅱ—final forging”based on structure analysis of the gear blank. Based on Deform, it established a finite element simulation model for the entire process of multi-station closed hot die forging. The reliability of the finite element model was verified by the experimental results, and the material flow law during the multistation closed hot die forging process was studied. The results show that a circular cake shaped blank can be obtained when the upsetting ratio is 3.7. The material flow along radial direction is uneven due to the friction effect between the upper and lower surfaces, resulting in a bulge shape at the waist of the billet during upsetting. A concave structure was formed on the bottom surface for positioning during pre-forging station Ⅰ, and it reduced the difficulty of material filling in subsequent stations. The material flow law during pre-forging Ⅱ and final forging are similar. The material mainly flows to the wheel flange part in the early stage of forming. It mainly flows to the wheel hub part in the middle stage, and flows to the rounded corner in the late stage. There is no defect of insufficient material filling during final forging. In the late forming stage, a small amount of metal material flows out of the guide gap of the upper and lower die of the final forging, forming a longitudinal flying edge. Through the production test, the well-filled gear blank with deep spoke was formed. The maximum error between the simulated value and the actual production value is not more than 3.15%, the longitudinal flying edge height is less than 0.5 mm, and the size deviation of each part is less than 0.2 mm, which verifies the rationality of the designed multi-stage closed die forging process.