Numerical Simulation of Multistep Warm Extrusion Forming for the Outer Race of Universal Joint

Abstract

Hot forging and machining by forging press is the traditional processing method of automotive universal joint outer race. The method has several disadvantages, such as high energy consumption, over-burning and oxidation tendency of the workpiece, large machining allowance, low surface quality, and poor mechanical properties. To solve the problem of low forming quality caused by the traditional processing method of outer race, a multistep warm extrusion forming process was proposed. The optimization of forming process parameters and the quality of this method was discussed in this study. The warm extrusion process was selected through process comparison and analysis. The initial billet size model was designed by applying the principle of constant volume, and four types of solutions were designed with the multistep combination of forward extrusion, upsetting, and backward extrusion. On the basis of finite element analysis method and metal forming flow theory, the numerical simulation was conducted by using the computer aided engineering (CAE) software Deform. The influence of billet diameter, initial extrusion temperature, number of working procedures, and die structure on the material flow, damage, temperature, and stress state in the forming process of outer race was analyzed. The optimal forming solution was obtained after optimization. Results demonstrate that the diameter of the outer race billet with this size is too small and tends to cause folding defects. The optimized billet is φ60 mm × 100 mm. When the initial extrusion temperature is high, the forming load is small and the forming quality is poor. Under the premise that the forming quality is guaranteed, the temperature is reduced as much as possible, and the optimized initial extrusion temperature is 800 o C. The increase in working procedure can reduce the maximum forming force, yet with slight effect. High quality can be obtained by the technology of first forward extrusion to the rod and then backward extrusion to the head. This study provides reference values for the warm extrusion forming of cup/rod-shaped parts.