Research On The Large Size Ball Pin With Special Structure Cold Extrusion Technology

With the gradual severe crisis of energy resource and aggravation of the market competition, the product production develops to be more high efficiency, high quality, refinement, energy, and material saving. Cold extrusion, as the advanced manufacturing technology for the material near net forming, hold the advantages of high forming precision, high material utilization, high production efficiency and good performance. So it can be broadly used in key parts product. However, cold extrusion, as its disadvantages of large forming load and high die requirement, is unconformity to high strength material processing.Bin pin is ordinarily used in the connection of steering mechanism, as if auto ball pin. There are so many disadvantages such as low production efficiency and severe materials wasting for machining production because of its complicated shape and requirements of surface abrasion resistance and enduring certain intension and toughness in inner part. Relatively speaking, The problems of die design and life for high material intensity and special structure will be solved by using cold extrusion forming. Thus, research on the large size ball pin with special structure and material of 40Cr cold extrusion forming, hopes to deal with the cold extrusion production problem for this kind of parts and develop the range of extrusion technics.According to the theory of cold extrusion forming, we analyze the cold extrusion forming for the ball pin from the aspects of material performance(40Cr) and shape structure(large ball top size and bar with reverse cone structure), make the pre-process included material softening treatment, surface lubricating treatment and blank preparation, study out two set of cold extrusion forming technics projects. Through the contrast and analysis, we determine the equal forming project, design the occlusion cold extrusion die by the type of separate and bisect to fit with the reverse cone structure of ball pin, and complete the design of die drawing by CAD software.Base on the rigid-plastic finite element model (fern) technology, we establish the fem model and simulate forming process by DEFORM fem software. Through changing the technics project and parameters, we research on the effect of the forming parameters in cold extrusion forming, optimize the technics parameter as friction coefficient, length of blank guide area, blank diameter and so on. Finally, we make the logical technics project.Base on the elastic-plastic fem technology, we analyze the die force by MSC.MARC software. In the structure of concave monoblock die, we optimize the die material and confirm the place of stress concentration. In combined die, we construe the displacement field and equivalent stress field of the stress concentration place. So we can infer the appropriate bottom die structure and shrink range and analyze the effect of clamp force to the combined die.Through the cold extrusion forming technics analysis of large size ball pin with special structure and material of 40Cr, die design and simulation of forming process, we solved the problem about cold extrusion of this kind of parts. There is important guiding role for the technics making and design of die structure of this kind of parts.