Research On Key Technologies For Electrochemical Machining Of Shaped Hot Forging Model Cavities

Hot forging die is used to manufacture forging processing of metal at high temperatures,is an important basic equipment in modern industry,in machinery manufacturing,weapons and equipment,aerospace,automobile manufacturing and other fields have a very wide range of applications.With the rapid development of new industries,the large number of applications of difficult-to-process materials and complex-shaped structures brings many challenges to the processing and manufacturing of hot forging cavities.The electrochemical machining technology is a special processing and manufacturing method for material removal at the ionic level,which has the advantages of forming in one process,good processing quality,no residual stress on the surface and no loss at the cathode,and significant advantages in the processing of hot forging cavities.This paper adopts the method of electrochemical machining and researches key technologies such as electrolyte formulation,the law of shaped cavity electrochemical machining forming,cathode structure optimization and processing device design,and process parameter optimization,as follows:（1）The polarization characteristic curves of 40Cr Ni Mo V material in different concentrations of Na Cl electrolyte,Na NO₃ electrolyte and Na Cl and Na NO₃ composite electrolyte were measured by an electrochemical workstation and three-electrode system,and the principle of electrolytic reaction and mechanism of action of the material in different electrolytes were explored and analyzed.Combining the experimental and theoretical analysis results,a composite electrolyte formulation with 8%Na Cl+11%Na NO₃ concentration was finally obtained.（2）To obtain the electrolytic forming rules for shaped hot forging model cavities,this paper takes a large size and unconventional structure of"T"shaped cavities as the object of research,and carries out multi-physical field simulation analysis based on electric field,gas-liquid two-phase flow field,temperature field and structural field,and obtains the influence of different process parameters as well as the flow rate,temperature and bubble rate of electrolyte on the anode The results show that the effects of different process parameters as well as the flow rate,temperature and bubble rate of the electrolyte on the accuracy of the anode surface were obtained.Combined with the process experiments,it is shown that the results of the multi-physics field simulation are close to the measured values,achieving a realistic prediction of the surface shape of the workpiece anode.（3）To obtain the cathode structure of the hot forging cavity of the shaped end cap part,the optimum flow of electrolyte was selected as the counter-flow type and the cathode through-flow structure was optimised as a"cross"shaped through-flow tank through multi-physics simulation,based on the influence of the flow rate,temperature and bubble rate of the interstitial electrolyte on the accuracy of the cavity forming.At the same time,a reverse flow electrochemical machining device including a cathode fixture,sealing device and workpiece fixture is designed.（4）To optimise the process parameters,a range of process parameters was defined based on the influence of inlet pressure,processing voltage and cathode feed rate on the accuracy of cavity forming.The Box-Behnken experimental design method was used to design an orthogonal experimental,to propose a measurement and evaluation scheme for the process target,and to optimise the experimental results using the response surface method to obtain the optimal combination of process parameters of 1.2 MPa inlet pressure,9 V machining voltage and 0.7mm/min feed rate.Based on the optimal combination of process parameters,the error rate between the predicted and experimental values of the process target is about 10%,and the accuracy and quality of the cavity processing are good and meet the requirements.