Study On Crack Analysis And Life Improvement Of X2 External Tooth Punch

With the rapid development of fine-blanking technology,it is widely used in modern manufacturing industry.The production efficiency and cost of the enterprise will be influenced greatly by the fine-blanking tool life.Therefore,the research of fine-blanking tool life has become a hot topic and focus in the field of fine-blanking.The general crack phenomenon of the X2 external tooth punch has been researched in order to solve the practical problem of the enterprise.Firstly,the failure phenomenon of die was analyzed.It was found that all cracks appeared in punch tooth face chamfered by Electrical Discharge Machining(EDM)after marking the location and counting number of cracks.It was found that the hardness of bevel chamfered by EDM and core are quite different after the mechanical test.The micro-hardness of the bevel edge to core within 40 ?m was measured by the nano indenter and it was found that the hardness showed a single peak with increasing distance.According to this trend of hardness change,it was inferred that there is a white layer at the edge of the bevel and then it was verified whether the prediction is true by means of light and electron microscopy.At the same time,the crack propagation path was observed with an ultra-deep-depth microscope and the initial germination position of the crack was sought.In addition,the morphology of the fractured specimen was analyzed by electron microscopy and finally judged as fatigue fracture.Secondly,the way how to remove white layer has been researched.It was found that the thickness of white layer was indeed reduced and the surface roughness was improved after polishing the white layer caused by WEDM with an electrolytic polishing system made by ourselves.Based on the experimental verification of its feasibility,a set of three-factor and three-level orthogonal tests were designed to explore the effect of electrolytic parameters on polishing quality.Finally,the best polishing effect can be obtained with perchloric alcohol solubility of 10%,electrolysis voltage of 20 V,and electrolysis time of 10 minutes.Furthermore,a preliminary exploration of the white layer caused by WEDM applied in the die industry revealed that the white layer can be removed as well.Finally,the forming process was simulated by a finite element software called DEFORM to analyze the stress distribution of the teeth and chamfered areas.It was found that the stress is not high enough to damage the die and the stress of chamfered area provides the power to expand the internal cracks.A set of punches with chamfers at different angles was designed to improve the flow of material to redistribute the stress and transfer the stress in the chamfered area to the tooth area.Based on the simulation results,it is suggested to increase the chamfer angle,but no more than 60°,which can reduce the stress in the chamfered area and delay the growth of crack to increase the tool life.