恒间隙法测定电解加工电流效率曲线研究

发布时间：2019-01-26 21:44

【摘要】：电解加工中,电流效率曲线不仅是计算加工间隙和电解加工速度的重要基础数据,还可以反映出电解加工中集中蚀除能力的大小。精确测定电解加工电流效率曲线对于分析与掌握电解加工成形规律、精确设计工具电极具有极为重要的意义。在恒定的加工电压下,保持恒定的加工间隙从而获得恒定的电流密度是精确获得电流效率曲线的关键。为了精确测定电解加工电流效率曲线,本文对以下内容开展相关研究:1)介绍电解液正向流动与侧向流动恒间隙电解加工方案,并对这两种方案实现恒定加工间隙的过程进行数学分析。分别设计了恒间隙电解加工装置,优化了入口流量控制和阳极引电方式。开展了侧向流动和正向流动恒间隙法电解加工试验,结果表明:与侧向流动相比,采用正向流动对于实现恒定的加工间隙具有更好的响应能力,电流波动小,确定正向流动恒间隙方案用以测定电流效率曲线。2)针对开放式正向流动恒间隙法的流场不均匀问题,设计一种背压式正向流动电解液流动方式。建立开放式正向流动和不同出口数量下的背压式正向流动的流场模型,开展了有限元仿真分析研究,仿真结果表明:与开放式正向流动相比,背压式正向流动的流场更加均匀。开展了开放式正向流动和背压式正向流动恒间隙法脉冲电解加工对比试验研究,结果表明:采用背压正流式电解液流动方式可以将加工电流波动量从23%减小到4%,表面质量从Ra=1.237μm提高到Ra=0.608μm,验证有限元仿真分析的准确性和电解液流动方式设计的合理性。3)研究了具有倒圆角结构的阴极内孔绝缘环对加工区域入口流场的影响问题,仿真与试验结果表明:相比较于无绝缘环,采用入口倒圆角的绝缘环可以有效减少加工间隙内电解液入口处流场的空化现象,提高加工区域流场的均匀性,改善加工区电解液入口处的工件表面质量。4)介绍采用恒间隙装置进行电解加工电流效率曲线测定的试验方法。针对不锈钢2Cr13和镍基高温合金GH4169,在20%NaNO3溶液中,开展直流和脉冲电流电解加工电流效率曲线测定与分析研究,并对脉冲占空比对电流效率曲线的影响展开了对比试验分析。结果表明:在20%NaNO3溶液中,直流电解加工不锈钢2Cr13,电流效率曲线具有非线性,但是加工镍基高温合金GH4169,电流效率曲线不具有非线性,ηω值随电流密度的变化波动较小;当采用脉冲电流进行电解加工时,这两种材料的电流效率曲线均具有非线性,而且随着占空比的减小,非线性特性得到强化。
[Abstract]:In ECM, the current efficiency curve is not only the important basic data for calculating machining clearance and ECM speed, but also reflects the magnitude of concentrated erosion ability in ECM. Accurate measurement of current efficiency curve of ECM is very important for analyzing and mastering the forming law of ECM and designing tool electrode accurately. At constant processing voltage, keeping constant machining gap and obtaining constant current density is the key to obtain accurate current efficiency curve. In order to accurately measure the current efficiency curve of ECM, the following research works are carried out in this paper: 1) the electrolytic solution with forward flow and lateral flow with constant gap is introduced. The process of realizing constant machining gap between these two schemes is analyzed mathematically. The constant gap ECM device is designed, and the inlet flow control and anode power generation are optimized. Experiments were carried out on the side flow and forward flow constant gap electrolysis machining. The results show that compared with the lateral flow, the forward flow has better response ability to realize the constant machining gap, and the current fluctuation is small. The forward flow constant gap scheme is determined to measure the current efficiency curve. 2) to solve the problem of non-uniform flow field in open forward flow constant gap method, a back pressure forward flow electrolyte flow mode is designed. The flow field model of the open forward flow and the back pressure forward flow is established. The finite element simulation analysis is carried out. The simulation results show that the flow field of the back pressure forward flow is more uniform than that of the open forward flow. A comparative study on open forward flow and back pressure forward flow constant gap pulse ECM is carried out. The results show that the flow of back pressure positive flow electrolyte can reduce the fluctuation of machining current from 23% to 4%. The surface quality is improved from Ra=1.237 渭 m to Ra=0.608 渭 m. The accuracy of finite element simulation analysis and the rationality of electrolyte flow design are verified. 3) the influence of cathode inner hole insulation ring with inverted circular structure on the flow field at the inlet of the machining area is studied. The simulation and experimental results show that compared with the non-insulated ring, the cavitation phenomenon at the electrolyte inlet of the machining gap can be effectively reduced and the uniformity of the flow field in the machining area can be improved by using the inlet reverse circular ring. Improving the surface quality of the workpiece at the inlet of electrolyte in the processing zone. 4) the test method of measuring the current efficiency curve of ECM with constant gap device is introduced. The measurement and analysis of current efficiency curves of DC and pulse current ECM were carried out in 20%NaNO3 solution for stainless steel 2Cr13 and nickel-base superalloy GH4169,. The effects of pulse duty cycle ratio on current efficiency curves were compared and analyzed. The results show that the current efficiency curve of 2Cr13 stainless steel prepared by DC electrolysis in 20%NaNO3 solution is nonlinear, but the current efficiency curve of GH4169, is not nonlinear, and 畏蠅 value fluctuates little with the change of current density. When the pulse current is used in ECM, the current efficiency curves of both materials are nonlinear, and the nonlinear characteristics are strengthened with the decrease of duty cycle.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG662

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