Investigation On The Current Efficiency Curve Measured With Constant Interelectrode Gap In Electrochemical Machining

Current efficiency curve is not only the important fundamental data of the calculation of machining gap and electrochemical machining speed,it can also reflect the concentrated corrosion ability during the electrochemical machining(ECM).Accurate measurement of current efficiency curve has an important significance for analysis on process regularity,improvement in machining accuracy and surface quality in ECM.Constant current densities with constant current voltage and interelectrode gap is the key of precise measurement of current efficiency for ECM.Aiming at accurate measurement of current efficiency,this paper includes the following researches:1)Two schemes of constant interelectrode gap and mathematical analysis were introduced.Devices with constant interelectrode gap were designed,and control over quantity of inlet flow and method of anodic electric conduction were optimized.Experiments were carried out,which indicated that the scheme of constant interelectrode gap with forward flow model had a better performance than the scheme with lateral flow model on the basis of machining current,device of constant interelectrode gap with forward flow model was selected to measure the current efficiency curve.2)To address the problem of non-uniform flow field,guiding forward flow model was put forward.Flow models of different structures were simulated and optimized by finite element method(FEM),the uniformity of the flow field was improved.Comparison experiments were carried out with pulse current,the result reveals that fluctuation of machining current was dropped to 4% from 23% and surface quality could be increased to Ra 0.608μm from Ra 1.237μm with guiding forward flow model.3)Effect of the insulated hollow cylinder on the flow field was investigated,results of simulation and experiments indicated that uniformity of the flow field at the inlet of machining area was improved,and better surface quality of the workpiece could be obtained.4)Current efficiency during the electrochemical machining of 2Cr13 stainless steel and alloy GH4169 in 20% NaNO3 electrolyte were measured with direct current and pulse current,and the effect of duty ratio on current efficiency was investigated.Results show that with direct current,current efficiency curve of 2Cr13 was nonlinear,while current efficiency of alloy GH4169 was not affected almost by current density;but the curves of these two materials were nonlinear with pulse current,the nonlinear feature was strengthened with the decrease in duty ratio...