Study On The Influence Of Process Parameters And Optimization Of Connecting Rod Die-forging

Connecting rod is the core component of internal combustion engine,its main role is to transmit power so that the internal combustion engine can work properly.Due to the harsh working environment of connecting rod,there are high requirements for its mechanical properties and dimensional tolerances,so there are high requirements for its forming process.Therefore,it is very important to study the law of forging and forming of connecting rod and optimize the parameters of forging process to improve the forming quality of connecting rod and reduce the wear of die,and it can provide reference for the optimization of process parameters of forging and forming and the actual production of connecting rod.Taking 42Cr Mo connecting rod as the research object,we analyze its die forging process and design its die forging tool,and establish the simulation model of connecting rod die forging and forming.The billet structure is improved according to the shape and size of the connecting rod forgings to improve the material utilization rate.The influence of different process parameters and structural parameters on the forming characteristics of forgings and die wear is investigated,and the influence of the interaction of different process parameters on the pre-forging forming load,final forging damage value and final forging die wear depth is studied based on the response surface method.Based on the optimization results,a microstructure simulation model was established to simulate the microstructure evolution of the forging process of the connecting rod.The main results of the study are as follows:（1）According to the shape and size of the connecting rod forgings,the billet structure is improved,the material utilization rate is increased by 23.5%,and the forming quality of the improved forgings is good.The effect of different process parameters and structure parameters on forging forming characteristics and die wear is studied by the single parameter sweep method,which shows that the forming load decreases with the increase of billet temperature,die temperature and flying edge height,increases with the increase of friction coefficient,and decreases then increases with the increase of upper die speed;the maximum value of equivalent force decreases with the increase of billet temperature,die temperature and flying edge height,increases with the increase of friction coefficient,and decreases then increases with the increase of upper die speed.The maximum equivalent force decreases with the increase of blank temperature,mold temperature and flying edge height,increases with the increase of friction coefficient,and decreases and then increases with the increase of upper mold speed,in which the effect of flying edge height and friction coefficient on equivalent force is smaller;the depth of mold wear tends to decrease with the increase of blank temperature and flying edge height,increases with the increase of mold temperature and friction coefficient,and decreases and then increases with the increase of upper mold speed.（2）The billet temperature,die temperature,upper die speed and friction coefficient were selected as design variables,and the response surface models of forming load,forging damage value and die wear depth were established by using Box-Behnken experimental design and response surface method,and the model determination coefficients R² were 0.981,0.978 and 0.965,respectively.based on the response surface model,the multi-objective optimization was carried out by combining Multi-The optimal combination of process parameters was obtained by combining multi-objective optimization with Multi-island genetic algorithm.The optimized forming load was reduced from 0.664×10⁷N to 0.321×10⁷N,which was 51.7%;the forging damage value was reduced from 0.624 to 0.547,which was 12.3%;the die wear depth was reduced from 0.501×10^-4mm to 0.389×10^-4mm,which was 22.4%.（3）Simulation analysis of the evolution of the microstructure of the connecting rod die forging process shows that the dynamic recrystallization of the pre-forging process occurs in the order of the big head,small head,rod body,flying edge of the connecting rod;the average dynamic recrystallization volume fraction of the pre-forged parts as a whole is 0.902,the average grain size is 8.28μm,the overall grain refinement phenomenon is more obvious;only a small part of the final forging process occurs completely dynamic recrystallization The maximum average grain size of the final forgings was reduced by 5.1μm compared with the pre-forged parts,and compared with the original grains,all got different degrees of refinement,and the refinement phenomenon is obvious,the grain size order is:rod body,small head,large head.Simulation analysis of the change of microstructure in the large head position shows that the grains basically undergo complete dynamic recrystallization,the grain size distribution is more uniform,and the refinement is obvious compared with the original grains,and the overall performance of the connecting rod is improved.