| Multi-step shaft is one of common shaft parts on automobile and motorcycle. In thetraditional machining, material loss is great and efficiency is low, which can not meet thedemand of mass production. Currently, these parts which are processed with cold extrusionmethod can avoid the defect of machining, keep metal flow lines and improve themechanical properties of parts. But in the process of cold extrusion of multi-step shaftparts, it requires Multiple necking and upsetting, which is easy to bend and deformate innecking, and collapse and not fill in upsetting. So, how to avoid defects is the key of coldextrusion to multi-step shaft parts.In this paper, a micro-car engine shaft is studied. Through analyzing the structuralcharacteristics of multi-step shaft parts, a " necking+gathering material+upsetting "process scheme is developed to forming multi-step shaft parts. With the help of thenumerical simulation software Deform-3D, the forming process is simulated and the flowlaw is studied. Then the reasonable parameters is determined, which can control thedeformation in necking to meet the production requirements. At last, the equation ofpredicting deformation in necking is designed with experiment. The results show that theprocess of "Gathering material+upsetting " can reduce upsetting limit, but not avoidfilling insufficient. So a new approach, which makes a concave in the end face of mouldwhen the billet is gathered, was presented.The new process scheme makes the contact areaand friction between the billet and the mould reduced, which be benefits for the metal toradial flow and avoid filling insufficient.Based on the study results above, the cold extrusion process test on the shaft isfinished under the conditions of existing equipment. The test results showed that both thesize and filling quality of cold extrusion parts meet the design requirements and theforming force is reduced when parameters are optimized, which is consistent well with thesimulation results. |
PDF Full Text Request