| Slotted screen tubes are commonly used sand control equipment in the oil extraction industry.EDM/ECM is one of the ways to process slotted screen tubes.In view of the problems of low machining efficiency and poor safety and cleanness in traditional compound working fluid,two kinds of EDM/ECM working fluids were designed in this paper.The effect of working fluid on the machining efficiency,slotting width and surface roughness of EDM/ECM composite machining was studied.The best formula was determined and the working fluid was studied.The influence of the best formula matching process parameters on the composite machining was observed,and the surface topography of the machined surface was also observed.In this paper,using No.20 oil,pure water and span 80 as raw materials,the work liquid is developed.The results show that the HLB value of the compound emulsifier is 8,and the ratio of water,oil and emulsifier is m?water?:m?oil?:m?milk?=3.1:2:1.4 at the temperature of45?,and the stable emulsion can be obtained.Under the condition of constant process parameters,the best formula of water bag oil type working liquid is obtained by adding 14g sucrose,1gNaNO3 and 0.25gNaCl.The machining efficiency is 10.39×10-3mm/s,the slot width is 0.37mm,and the surface roughness is 3.050?m.The optimum formula of oil in water working fluid was used for slotting,and the parameters of EDM process were optimized by orthogonal test.Under the experimental conditions,the optimal parameters are current 60A,pulse gap 10?s,electrode disk speed 400r/min,pulse width 48?s,the machining efficiency is59.57×10-3mm/s,the slot width is 0.35mm,the surface roughness is 3.067?m.Compared with the effect of the machining of electric spark oil,the machining efficiency of the hydraulic working fluid is improved and the surface roughness is reduced,the surface quality is improved,but the slot width is increased.In this paper,water soluble working liquid was prepared with pure water,polyethylene glycol 400 and triethanolamine as raw materials.Under the condition of 30?,the ratio of pure water,polyethylene glycol 400 and triethanolamine was m?water?:m?poly?:m?three?=11:11:3,and the dilute solution of basic working liquid 10%?mass fraction?was the best.On the basis of adding 35g sucrose,the best formula of water soluble working fluid was obtained,such as 1gNaNO3 and 0.25gNaCl.The machining efficiency was 8.57×10-3mm/s,the slot width was 0.39mm,and the surface roughness was 2.970?m.The optimum formula of water soluble working fluid is slotted and optimized by orthogonal test.Under the conditions of orthogonal experiment,the optimum parameters are current 60A,pulse gap 30?s,electrode disc speed 300 r/min,pulse width 44?s,machining efficiency is 31.82×10-3mm/s,slot width is0.34mm,surface roughness is 2.541?m.Compared with the effect of the machining of electric spark oil,the surface roughness of water soluble working fluid is reduced,the safety and cleanness are improved,but the machining efficiency is reduced and the slot width is slightly increased.There are many discharge pits,needle hole shaped holes and tiny holes on the surface of the sample,which is due to the heat gasification and electrolysis of the material,and there are many large convex and spherical bulges,which are due to the solidification of molten metal,or the thermal explosion force and the cooling effect of the material gasification. |
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