# The Study of Multi-Stage Cold Forming Process for the Manufacture of Relief Valve Regulating Nuts
###### Abstract
[PERSON] and [PERSON] [12] conducted numerical and experimental studies on two forming modes for the two-stage extrusion forming of AISI 1010 carbon steel. The numerical results for the effective strain distribution were consistent with the hardness distribution tested in the experiment. In order to meet the needs for higher quality, lower fabricating cost, and fast delivery in automotive fastener production, [PERSON] et al. [13] studied injection forging as a possibility for industrial production of automotive fasteners, owing to its potential to shorten the process chains to cold form complex shape parts. With a focus on reducing the cold-forming forces and improving the dimensional accuracy of the parts, they proposed to improve the process and tool design. For the outer race of a constant velocity joint with six inner ball grooves, [PERSON] and [PERSON] [14] conducted a series of experimental studies on the multi-stage cold-forming process. Spheroidized SCr420H billets were used in the experimental study. While with the proposed multi-stage cold forging process, it was verified that the outer race was well formed and the dimensional accuracy of the cold-formed outer race met the demands. [PERSON] and [PERSON] [15] proposed a new metal-forming process to produce two-step outer flanges on the hollow parts extruded by a movable sleeve. They applied the new method to bring the end flange of the 6060 aluminum alloy tubular blank. They designed this cold-forming process based on numerical simulations and experiments. The experimental results verified the feasibility of cold forging a two-step flange with a diameter approximately twice the outer diameter of the tubular blank. A two-stage cold-forging process was proposed by [PERSON] [16] for the fabrication of AISI 1035 steel drive shafts with internal spline and spur gear geometry. The process mainly included a forward extrusion of preform and forward and backward extrusion of the drive shaft. The results illustrated that the proposed two-stage cold-forming process may well be applied to fabricate drive shafts with internal spline and spur gear structures. [PERSON] et al. [17] constructed a six-stage cold-forming process design for the AISI 1010 steel shell of the spark plug fabrication using a 3D geometric model. Numerical analyses were carried out on the product part dimensions, forging loads, effective stresses, contact pressure, and velocity fields. The actual dimensions and forging loads of the product parts at six stages were compared by using the finite element simulation results to verify whether the analysis results were acceptable. [PERSON] et al. [18] conducted a numerical study on the automatic multi-stagecold-forging of SUS304 stainless steel ball studs. They investigated the plastic deformation behavior of SUS304 stainless steel from room temperature to 400 \({}^{\circ}\)C and expressed the flow stress as a closed-form function of the strain, strain rate, and temperature, using a general method. It was optimal at high strains, especially during multi-stage cold forging. [PERSON] et al. [19] applied DEFORM 2D/3D to study, numerically, a six-stage cold forging process on the 42 CrMo4 steel hollow flanged part to determine whether the proposed forging technique could be used to produce flanged hollow parts. A multi-stage cold-forming process applying finite element analysis was developed by [PERSON] et al. [20] to fabricate a high-strength one-body input shaft with a long body without separate parts. This study demonstrated the design and development of a multi-stage cold-forming process to fabricate a one-body input shaft with better mechanical properties and material recovery. [PERSON] et al. [21] introduced the cold forging process of flanged bolts to obtain a consistent, acceptable, and inconsistent grain flow pattern. Then, the FEM simulation results were correlated with the conducted experiments. [PERSON] et al. [22] investigated the hardness behavior and microstructure of 42 CrMo4 steel hollow parts with external flanges.