Research On Electrochemical Machining Technology Of U71Mn Material's Stretched Complex Surface

In order to meet the extreme reliability requirements of high-end manufacturing equipment for parts,more and more complex surface of various difficult-to-process materials are used in advanced manufacturing,which are widely used in transportation,molds,aerospace and other fields.The use of traditional machining to process complex surface of difficult-to-process materials will result in residual stress or burns during the machining,which makes it difficult to ensure the machining accuracy and machining quality.Machining using EDM technology will affect the forming efficiency and forming accuracy due to the slow machining speed and electrode loss.Electrochemical machining(ECM)of the cathode has no loss,and the machining efficiency and surface quality is relatively high.Therefore,ECM has become one of the main machining methods for difficult-to-machine materials and complex-shaped parts.The thesis takes the U71Mn material as the research object and the ECM process plan is proposed.By studying the key technology researches,including the design of new process equipment,the development of new electrolyte,the optimization of process parameters through simulation and experiments.The problem of low processing efficiency and poor surface quality of U71Mn stretched compound surface is solved.The main research contents are as follows:(1)This thesis proposes a new electrochemical machining process in view of the existing grinding technology for processing U 71 Mn material with complex stretched profiles,which have residual stress,low processing efficiency,insufficient surface quality,and high cost.The ECM process uses the electrochemical dissolution of U71Mn material in the electrolyte to process the workpiece.Compared with the grinding technology,the new scheme has the advantages of no mechanical cutting force,high machining efficiency and good surface quality.(2)New process devices for ECM of complex surface is designed.Using COMSOL simulation software,based on the k-? model in Navier-Stokes equations,the flow field simulation of the gap flow channel model is carried out,and the cathode profile is optimized according to the uniformity of the flow field.The process device,which consists of four parts,including the front-end flow channel system,machining fixture system,the back-end back pressure system and the sealing system is designed.The process experiment is carried out using the new process device,and the experiment shows that the design of the process device is reasonable and reliable.(3)The electrochemical characteristics of U71Mn material are studied,and a new electrolyte formulation is developed.According to the polarization curves of U71Mn material in different electrolytes,the electrochemical characteristics are studied,and the concentration ratio of the electrolyte is initially selected.The electrolyte solution formula is improved by the ECM of small holes.The experiment shows that after adding the complexing agent Na2SO4,the hole machining accuracy and efficiency of the electrolyte machining are better.The final compound electrolyte formula is:5%NaCl+15%NaNO3+2%Na2SO4.(4)The process parameters is optimized and qualified samples are processed.The inlet pressure,outlet pressure,and voltage of the electrolyte are analyzed and optimized through physical field coupling simulation.By studying the ECM forming law of the stretched complex surface,the influence of different parameters on the material removal rate and roughness is analyzed.Through orthogonal experiments,the surface response method is used to conduct multi-objective optimization analysis on the experimental results,and the optimized complex surface machining process parameters are as follows:pulse voltage 25 V,duty cycle 70%,pulse frequency 800Hz,electrolyte inlet pressure 0.6MPa,after optimization qualified samples are processed by the process parameters,the material removal rate is 43.5g/min,the size deviation is 0.58mm,and the roughness is 0.44?m.It is feasible to realize the machining of U71Mn material's stretched complex surface through ECM technology.It can achieve the requirements of no residual stress,higher machining efficiency,better surface quality and lower cost.Compared with the traditional grinding technology,the material removal rate increases by 14%,and the machining efficiency is improved.The surface roughness increases by 78%,and the surface quality is significantly improved.