复合非浸没流场电解机械复合抛光工具设计及试验研究

Tool Design and Experimental Study of Electromechanical Polishing with Composite Non-submerged Flow Field

目的为了提高电解机械复合抛光时电解液更新交换能力,提高电解机械复合抛光TB2钛合金的表面质量,探究流场对表面质量的影响。方法提出了复合非浸没流场电解机械复合抛光模式,电解液通过送液装置从抛光间隙侧向和内喷液阴极径向供给到抛光区域。设计了径向内喷液工具阴极,借助计算流体力学软件,模拟工具阴极出液口处流场分布,优选工具阴极出液口分布方案;设计溶解特性试验,通过表面形貌分析,优选NaCl^(-)乙二醇电解液浓度;提出通过设置抬刀距离控制黏性层厚度的方法,探究抬刀距离对抛光后表面质量的影响;通过表面形貌、粗糙度分析,探究复合非浸没流场流速对表面质量的影响。结果采用五行两列的出液口分布方案后,流场更加均匀;电解液选择1mol/L NaCl^(-)乙二醇溶液;侧向冲液流速对电解抛光黏性层影响很大,当侧向冲液入口流速为0.8 m/s时,电解预处理表面粗糙度Ra最低为0.158μm,表面质量不均匀;当设置抬刀距离为+100μm、侧向冲液电解机械复合加工时,获得最低表面粗糙度Ra为38nm的平滑表面,表面存在局部缺陷;在此基础上,进一步补充径向内喷液,在径向内喷液入口流速为0.1 m/s时,表面粗糙度Ra降到25.7 nm,表面质量更均匀。结论侧向冲液+径向内喷液的复合流场分布均匀,有助于获得高质量的TB2钛合金电解机械复合抛光表面。

TB2 titanium alloy is aβ-type titanium alloy independently developed in China,which has excellent cold forming and welding properties,and is often used in the manufacturing of aerospace high pressure vessels and satellite and arrow connection devices.The special needs of its service scenario put forward higher requirements for the surface quality of aerospace TB2 titanium alloy parts.Electromechanical polishing is often used to polish titanium alloys,which removes the passivation film through mechanical action,making the electrolytic action of the base material smoother.The state of electrolyte flow profoundly affects the surface quality of electromechanical polishing.In order to improve the electrolyte renewal exchange ability and obtain higher quality polished surface,a composite non-submerged flow field polishing mode was proposed,in which electrolyte was supplied from the polishing gap side and the rotating cathode to the polishing area through the liquid feeding device.The cathode of the radial internal spray tool was designed.In order to obtain a uniform flow field,the outlet distribution of the rotary cathode was optimized by means of flow field simulation.In order to clarify the anodic dissolution behavior of the workpiece in NaCl^(-)glycol solution,the anodic dissolution characteristic tests with different concentrations were carried out by cyclic voltammetry,and the appropriate electrolyte concentrations were selected.In order to inhibit the stray corrosion in the non-machining area,a one-step electrolytic pretreatment was set,namely that the electrode moved quickly along the surface of the workpiece with a gap distance of 5 mm,and the effect of the downwash flow rate on the surface quality of the workpiece was investigated.The electrochemical dissolution was controlled by the viscous layer covered by the workpiece surface.In order to control the thickness of the viscous layer,a method was proposed to control the thickness of the viscous layer by setting the tool lifting distance,and an experiment was designed to optimize the appropriate tool lifting distance.The effect of different radial flow rates on the surface quality of the workpiece was investigated by adding radial internal flushing to the lateral external flushing,and the surface quality of the workpiece without internal flushing was compared.The results showed that 1 mol/L NaCl^(-)glycol solution was suitable for electrolytic polishing of TB2.According to the fluid simulation results,the outlet distribution mode of the rotary cathode was determined to be five rows and two columns,in which the gap between the two adjacent rows was 5 mm and the maximum angle between the two columns was 45°.The anodic dissolution was controlled by the surface TiCl4 viscous layer.The lateral flushing flow rate had great effect on the viscous layer of electrolytic pretreatment.When the flow rate was 0.8 m/s,the lowest surface roughness Ra was 0.158μm,but there were serious corrosion pits on the surface.When the tool lifting distance was set to+100μm,the smooth surface with roughness of Ra 38 nm was obtained,and the surface had local defects.On this basis,the radial internal spray was further added.When the flow rate of the internal spray was 0.1 m/s,the surface roughness was reduced to Ra 25.7 nm,and there was no corrosion micro-pit on the surface.The composite flow field electromechanical polishing can make the flow field more uniform,inhibit stray corrosion,and contribute to better surface quality.