The Investigation on Multi-stage Cold Forming Process for Manufacturing of SCM435 Alloy Steel Spherical Joints

Abstract

Multi-stage cold forming is commonly used for forging fasteners and parts. This study numerically simulates the five-stage cold forming process of SCM435 alloy steel spherical joints. The five-stage cold forming process includes preparation along with centering, upsetting, twice backward extrusions over a moving punch along with upsetting to spherical shape, and piercing. The numerical simulations of cold forming are carried out using the finite element code of DEFORM-3D. The formability of the workpiece is studied, such as the forming force response, maximum forming forces, effective stress and strain distributions, and metal flow pattern. In the five-stage forming process, the effective stress and effective strain of the workpiece are significantly increased due to the large deformation in the two forming stages of backward extrusion along with upsetting to a spherical shape, and in the forming stage of piercing. The flow line distributions are also very complex, especially the flow lines in the piercing region around the inner wall of the hole are severely bent and highly compacted, eventually leading to fracture. In the fourth stage, the workpiece is secondly backward extruded along with upset, and the maximum axial forming force is the largest of the five stages. In the third stage of the firstly backward extrusion along with upset, the forming energy is the highest of the five stages due to the longer acted axial forming stroke. From the first stage to the last stage, the total maximum axial forming forces are 2,209.5 kN and the total forming energies are approximately 4.60 kJ.