Study On Electrochemical Machining Technology Of Small Inner-Walled Structure Of Hard-to-Cut Materials

With the rapid development of science and technology,the demand for high-performance new materials and complex structure or parts is increasing day by day,and higher requirements are placed on its processing technology and machining quality.As a new type of alloy material,corrosion resistant material 1J116 is widely used in these important fields such as aviation,aerospace and national defense due to its excellent characteristics.With the increasing use of 1J116,it is particularly urgent to achieve precise and efficient machining.At present,the precision forming of the inner wall structure of 1J116 is mainly realized by electric discharge machining(EDM)technology,but there are defects such as low machining efficiency,residual stress,surface metamorphic layer and micro cracks,which would seriously affect the work performance and service life of the work-piece.Electrochemical machining(ECM)technology has unique advantages for the small-sized inner wall structure because of its ionic state,non-contact,no cutting force,no loss of tools and low processing cost.In view of the problems existing in the existing EDM process,this topic uses ECM instead of EDM to improve the machining quality and efficiency of the small-size inner-wall structure.In this paper,the small-size inner-wall structure of 1J116 is taken as research object,and the research on tool cathode structure design and optimization,multi-physics simulation,cathode structure modification,forming law and optimization of ECM parameters is carried out.The main contents are as follows:(1)In order to optimize tool electrode that can ensure the ECM stability,the liquid supply method of ECM inner-wall ring groove is firstly determined,and the flow field is theoretically calculated.Four kinds of tool electrodes with basic structure are proposed according to the equal gap method,and the flow field simulations of the four tool electrodes are analyzed respectively based on the k-? model in the Navier-Stokes equation.The research shows that the structure-IV is a tool electrode with uniform distribution,which can ensure the ECM stability.(2)To predict the machinability of different radial depths of the inner-wall ring groove,a mathematical model based on electric field is established,and the electrical characteristics of the inner-wall ring groove under different width-depth ratio are simulated.In addition,the structure of the tool electrode was further modified for the drum-shaped state of the inner wall ring groove processed by the structure-IV,and the different curvatures were analyzed by COMSOL software.The multi-physics simulations of the modified tool cathodes were conducted,and the simulation results were used to summarize the reasons that affect the drum shape.At the same time,the contour of the modified cathode under different machining time was simulated and predicted.The prediction results show when the machining time is about 3 minutes,an inner-wall ring groove with a radial depth of 0.4 mm can be machined.(3)In order to study the forming law of the ECM inner-wall ring groove,according to the ECM basic theory,the mathematical model of the forming law of the inner wall structure was established by the integral method.A single factor experiment on the pulse voltage,duty cycle,pulse frequency and electrolyte inlet pressure was performed on the corrosion resistant material 1J116 work-piece with a positive flow copper cathode to study the formation of the inner-wall structure and the forming law was obtained.(4)Through orthogonal experiment and variance analysis,the optimal machining parameters were determined.That is,the pulse voltage is 12 V,the pulse frequency is 800 Hz,the duty ratio is 70%,and the inlet pressure of the electrolyte is 240 MPa.It can be seen from comprehensive experiment that the drum shape of the inner-wall ring groove is significantly improved,and the inner-wall ring groove has a width of 3.01 mm and a depth of 0.4 mm.The surface roughness Ra measured by the white light interferometer can reach 0.45 ?m.It is feasible to realize ECM of inner-wall ring groove without metamorphic layer,residual stress and micro crack,and avoid the defects caused by EDM;At the same time,it laid a certain foundation for the further study of the inner wall structure.