高钨合金微小孔电火花加工工艺及穿透检测技术研究

发布时间：2019-06-10 01:14

【摘要】：高钨合金凭借高强度、耐高温等性质被广泛应用于航空航天等领域中,其中许多零件中包含散热、通气等作用的微小孔,这些微小孔的加工若利用传统方式则存在着很多困难,而电火花加工借助自身的诸多优点提供了一种有效的加工方法。但是在电加工中也存在着电极损耗大、加工效率低、加工效果差等问题,为此针对钨含量高达90%的铜钨合金(CuW90)进行了加工工艺及穿透检测等方面的研究。采用单因素实验和正交试验相结合的方案,使用直径为0.5 mm的管电极对CuW90微小孔电火花加工进行了一系列的基础实验研究。首先对电源电容、电流、伺服参考电压、伺服速度、占空比等实验参数进行了单因素实验研究,分析了使用电火花油和去离子水作为工作液时电极损耗和加工时间不同的原因;之后选用L16(45)正交表对所研究的5个参数进行了正交试验,最终以电极损耗和加工时间为目标得到了微小孔加工的最优参数组合,综合优化幅度达73%。针对CuW90的特殊结构,对其物理模型进行了分析比较,并计算了密度、比热容、热导率和热膨胀系数等性能参数的理论值,从理论上分析了在电火花加工中电极损耗大的原因。对旋转内冲液加工间隙流场进行了仿真分析,利用不同工作液流场结构特点对不同加工阶段流速和压力的分布进行了分析比较,探讨了柱状残留的成因,从理论方面研究了不同深度时的加工特点,解释了使用不同工作液时电极形状发生变化的原因。为实现难加工材料的盲孔加工,利用神经网络法对不同参数下的加工速率进行预测,分析了微小孔加工时有效放电次数和工件材料蚀除量的对应关系,搭建了基于平均电压检测法的检测电路,利用STM32F103ZET6芯片对所采集电压进行了比较判断,通过对数码管的直接驱动实现了加工深度的实时显示,最终所加工盲孔的平均误差为3.9%。以管电极加工时穿透前后电压波形的独特变化趋势为依据,实现了最小出口距离为0.7 mm的通孔加工。对穿透前后柱状残留的影响进行了理论分析与验证,最终证实了穿透检测判据的可靠性。
[Abstract]:High tungsten alloy has been widely used in aerospace and other fields because of its high strength, high temperature resistance and other properties. Many of the parts contain micropores such as heat dissipation, ventilation and so on. There are many difficulties in the processing of these micropores by using the traditional method. With the help of many advantages of EDM, EDM provides an effective machining method. However, there are also some problems in electrical machining, such as large electrode loss, low machining efficiency and poor processing effect. Therefore, the processing technology and penetration detection of copper-tungsten alloy (CuW90) with tungsten content of up to 90% have been studied. A series of basic experiments on CuW90 microhole EDM were carried out by using a tube electrode with diameter of 0.5 mm. Firstly, the single factor experimental study on the experimental parameters such as power capacitance, current, servo reference voltage, servo speed and duty cycle is carried out, and the reasons for the different electrode loss and processing time when EDM oil and deionized water are used as working liquid are analyzed. Then the L16 (45) orthogonal table was selected to carry out orthogonal experiments on the five parameters studied. Finally, the optimal parameter combination of micro hole machining was obtained with the goal of electrode loss and processing time, and the comprehensive optimization range was 73%. According to the special structure of CuW90, the physical models are analyzed and compared, and the theoretical values of performance parameters such as density, specific heat capacity, thermal conductivity and thermal expansion coefficient are calculated, and the reasons for the high electrode loss in EDM are analyzed theoretically. The flow field in the clearance of rotating internal flushing fluid is simulated and analyzed, and the distribution of velocity and pressure in different processing stages is analyzed and compared by using the structural characteristics of different working fluid flow fields, and the causes of cylindrical residue are discussed. The machining characteristics of different depths are studied theoretically, and the reasons for the change of electrode shape when different working fluids are used are explained. In order to realize the blind hole machining of refractory materials, the processing rate under different parameters is predicted by neural network method, and the corresponding relationship between the number of effective discharge and the amount of material erosion in micro hole machining is analyzed. The detection circuit based on average voltage detection method is built, the collected voltage is compared and judged by STM32F103ZET6 chip, and the real-time display of machining depth is realized by driving the digital tube directly. The average error of the blind hole is 3.9%. Based on the unique change trend of voltage waveform before and after penetration of tube electrode, the through hole machining with minimum outlet distance of 0.7 mm is realized. The influence of cylindrical residue before and after penetration is analyzed and verified theoretically, and the reliability of penetration detection criterion is finally verified.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG661

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