Research On Key Technologies Of Joint Pin Cold Forming Based On Radial Extrusion

In order to solve the problems of low material utilization rate and too muchfabrication procedures, the cold working process of radial extrusion was studiedaccording to the features of the part. Feasibility of single step forming process ofuniversal joint pin, flow of metal, load and stress distribution and structure of themold were studied.3D model of universal joint pin and its CAE model were built and thecharacteristics of cold forming process based on radial extrusion with doublepunches and the requirements of mold structure were analyzed.The pre-treatment of extrusion billet was introduced briefly. In order to get alow friction coefficient between the metal and the extrusion mold, the billet mustbe saponified and parkerized. Forming processes with single and double puncheswere compared and the advantage of double punches was described: the quality ofshaft shoulder of universal joint pin is better with double punches. Thus, processwith two punches was adopted.With DEFORM3D, the extrusion pressure, the properties of metal flow, thedistribution of equivalent stress and changes of temperature were studied. Thewhole process of extrusion was divided into3stages: upsetting stage, shoulderforming stage, end stage of extrusion. In the end stage of extrusion, the load ofpunch grows rapidly. In order to solve this problem and protect the die surface,mold shaft shoulder of universal joint pin was added by0.5mm according to thestructure and usage of universal joint pin.For further study of the influence of radial extrusion on the extrusion mold,the process of forming of universal joint pin was investigated by studying the keyparameters such as friction coefficient, radius of die fillet corner and structure ofdie.The main conclusions were: the inhomogeneous ofplastic formation and the load ofpunch and die increased with the rise of friction coefficient. Additionally,theequivalentstress, temperature and wear of mold also increased with therise offriction coefficient. Thegrowth of transition radius of die decreased the load of mold and improved the surfacequality of the extrusion part. When taper angle of the punch α=30°, the radical flow speedof the metal was fast and the extrusion process was more steady, the equivalent stressdecreased in a certain degree.At last, by analysis of the load applied on the punch, the structure of die wasoptimized and a double layer combined die was introduced. With orthogonalexperiment and ABAQUS software, the optimized combination was obtained. Inthis situation, the mechanical properties of die material were fully utilized and theamount of material was saved.The research results can help to plan forming process and to design the diestructure of universal joint pin.