Influence of Magnetic Field on Friction and Wear of Metal Tools in UHV Transmission Lines

By analyzing the influence of the power-frequency magnetic field environment of UHVDC transmission lines on the wear behavior of the electric power fittings materials, the wear mechanism of the electric power fittings materials in the power-frequency magnetic field environment was explored to provide a theoretical basis for the wear failure prediction of the connected hardware in service. According to the actual operating parameters of UHVDC transmission lines, the power frequency magnetic induction intensity was analyzed and calculated. The self-made electromagnetic coil connected with external voltage and current stabilized power supply was combined with an M-2000 friction and wear testing machine. The magnetic field intensity generated by the coil was measured with a Gaussian meter, and the sample wear test was designed by using the group control variable method. Before the test, a hand-held degaussing device was used to degauss the pin-ring sample and the rotating shaft of the wear machine. Group A: In the range of 0-800 A/m magnetic field intensity, five gradients of 0, 240, 400, 640 and 800 A/m were selected for wear tests to study the wear behavior of goldware materials in different magnetic induction environments. Group B: The power frequency magnetic field intensity of the transmission line under rated working conditions was selected to study the wear process variation of the goldware material in a specific magnetic induction environment. An electronic balance was used to weigh the sample mass before and after the test and calculate the wear rate. A micro-Vickers hardness tester was used to measure the hardness value of the specimen before and after the test. An industrial microscope was used to observe the macro morphology of the wear contact surface of the sample. A FEG scanning electron microscope (SEM) and an energy dispersive spectrometer (EDS) were used to observe the microstructure of the specimen wear contact surface and wear debris, and to analyze the distribution and content of elements. The results showed that the intensity of wear was much less than that without a magnetic field. With the increase of magnetic induction, the weight loss and wear rate of the worn sample decreased, and the friction coefficient decreased slightly with little fluctuation. The higher the microhardness of the worn samples in different magnetic induction intensities, the closer they were to the wear contact surface, and decreased with the depth. In the absence of the magnetic field, there were deep furrows on the worn contact surface, and there were pits on the irregular jagged edges and micro-convex peaks on the ridge. In the condition of the magnetic field, the worn contact surface and the chip surface were smoother, and the oxygen content was significantly higher than that in the absence of the magnetic field. The analysis shows that: The wear samples in the magnetic field environment accelerate from the initial run-in stage and the wear intensification stage to the stable wear stage in a short time, which accelerate the serious wear and adhesive wear to the slight wear. The main wear mechanism in the stable stage is oxidative wear, accompanied by slight wear and adhesive wear as well as three-body wear between the two friction pairs and the wear debris "barrier layer". The power frequency magnetic field environment plays a certain role in reducing friction and reducing wear. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.