| ZHOU Liang,WEI Ying,YIN Jun,FANG Xiaolong.Tool Design and Experimental Study of Electromechanical Polishing with Composite Non-submerged Flow Field[J],53(18):156-166 |
| Tool Design and Experimental Study of Electromechanical Polishing with Composite Non-submerged Flow Field |
| Received:December 07, 2023 Revised:May 14, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.18.013 |
| KeyWord:electromechanical polishing flow field surface quality tool design titanium alloy |
| Author | Institution |
| ZHOU Liang |
Shanghai Institute of Mechanical and Electrical Engineering, Shanghai , China |
| WEI Ying |
Nanjing University of Aeronautics and Astronautics, Nanjing , China |
| YIN Jun |
Nanjing University of Aeronautics and Astronautics, Nanjing , China |
| FANG Xiaolong |
Nanjing University of Aeronautics and Astronautics, Nanjing , China |
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| Abstract: |
| TB2 titanium alloy is a β-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 0.158 μm, but there were serious corrosion pits on the surface. When the tool lifting distance was set to +100 μm, 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. |
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