Research On Optimization Of Cold-hot Composite Forming Process Of CVT Pulley Shaft

With the continuous implementation of energy conservation and emission reduction policies in the automotive industry,green manufacturing and intelligent production of key automotive components have become the mainstream of development.CVT pulley shaft is an important core part of transmission.How to achieve high-efficiency precision forming is an urgent problem to be solved.In the existing hot die forging process,when forming a forged billet with a large volume,a large number of teeth,and a relatively large diameter,there are problems such as incomplete tooth filling,surface folding,and severe mold cavity wear.In order to improve the forming quality of the forged blank of the pulley shaft,this paper studies the influence of forging process,die design,process parameters on the forming results,and die wear law.Based on the orthogonal experiment method and response surface method,the optimal combination of process parameters is obtained.It provides a certain reference for the forming process of the same type of disk-type solid shaft forgings.The main research contents and conclusions of this article are as follows:(1)According to the structural characteristics of CVT pulley shafts with multiple teeth,flanges,and long shafts,forging drawing designs were proposed.Three hot die forging process routes were proposed,and numerical simulation was used to compare the forming effects.The forward extrusion,pre-forging,The best forming process route plan for final forging,and completed the blank drawing and die structure drawing design of each step of the forming process.(2)Based on the theory of thermo-mechanical coupling finite element analysis,Deform-3D software is used to obtain the metal flow regularity and stress-strain field distribution of the CVT pulley shaft forging process.The final forging process obtained through technical analysis is to ensure the forming quality of the pulley shaft forging blank.The key process,the stress distribution of the punch and the wear distribution of the punch after the final forging process are also obtained.(3)In order to improve the forging quality of the final forging process,the multi-objective optimization design of the final forging process parameters is performed.First,the starting forging temperature,die temperature,friction coefficient,and punch speed were determined as design variables.The equivalent strain,die wear,and overall quality during the final forging process were the optimization goals.Then the orthogonal test method and response surface method were used to optimize the process parameters of the final forging process.It was found that the response surface method was better than the orthogonal experiment method.The optimal parameter combination was: initial forging temperature of 1025 °C and friction coefficient of 0.16.3.The punch speed is 37mm/s and the mold temperature is 280°C.Under this optimized parameter combination,the metal deformation effect is increased by 22%,die wear is reduced by 3%,and the overall quality of final forging is improved by 9%.(4)The optimized process scheme was verified by experiments.The quality of the forgings obtained from the experiments was excellent.After testing,the size error of the forgings was concentrated at 0.05 mm,the metal grain size reached level 8,the surface hardness was between 150 and 170 HB,and the metal did not exist.Bubbles,cracks and other defects,all indicators meet the requirements of parts.The results show that Deform software can accurately predict the metal flow and stress-strain field during the forming process.The finite element analysis technology can effectively save the development time of the forging process and improve the accuracy of the process development.