Wear Analysis And Optimization Of Hot Extrusion Die For Automotive Bearing Ring

Hot extrusion die is one of the main equipment for automotive bearing ring production all over the world.The die life directly affects the production cost,production efficiency and forging quality.At present,the average life of hot forging die in China is only 1/3-1/5 of the world's advanced level.Wear is the main failure mode of hot extrusion dies,so it is of great engineering significance to improve the wear property of dies.In this paper,the wear state of a hot extrusion die for a certain automobile bearing ring in the original working condition is systematically studied,the wear process and wear type are defined,the characteristics of three common used wear models are analyzed,and Archard temper softening model is selected as the wear model,besides exploring general rule of die surface softening.Based on the model,the effects of loading speed,workpiece temperature and die preheating temperature on the wear of hot extrusion process parameters are studied by finite element method.According to the analysis results,the parameters are adjusted to be more suitable for the hot extrusion process,and the differences of wear amount before and after adjustment are compared and analysed,the average wear amount has been reduced about 12.2% in the end.The simulation results under different process parameters show that the adjustment of process parameters can not solve the problem of heating die surface,which results in surface softening,so the die structure is optimized.Taguchi method is used to optimize the main parameters of the die structure.The influence of different structural parameters on the wear and surface stress distribution of the die is analyzed through the finite element software Deform.The results show that the order of influence of each parameter on wear is: cooling slot width > cooling water temperature > cooling slot location > inner ring thickness > interference fit quantity;the order of influence on effective stress is: interference fit quantity > inner ring wall thickness = cooling slot location > cooling water temperature > cooling slot width.And then the optimal combination of structural parameters is determined by range analysis and variance analysis.Comparing the wear and effective stress of the die under the three conditions of original process,adjusting process,adjusting process and optimizing structure,the results show that the wear rate and effective stress of die are both improved after optimizing structure.Based on the optimization results,the manufacturing process and heat treatment process of the optimized die were determined,and the cooling system of the die is designed and assembled for field test.The optimized die and the original die after service are compared from four aspects: surface temperature during service,wear amount after service,surface roughness and wear morphology.The results show that after process adjustment and structure optimization,the service surface temperature of hot extrusion die decreases,wear amount decreases,surface roughness decreases,wear morphology improves,the wear condition is better than the original die.Aiming at the wear problem of hot extrusion die for automobile bearing ring in actual production,this paper puts forward two methods about adjusting process parameters and optimizing die structure,which have achieved certain results.The research methods adopted in this paper have reference significance for the improvement of other hot forging dies.