| Summary: | 碩士 === 國立臺北科技大學 === 材料科學與工程研究所 === 103 === In this study, using different concentrations phosphoric acid and phosphoric acid zinc passivation solution to insulate Fe-Si-Cr alloy powders at different temperatures and different times, then using uniaxial hydraulic machine to compress into an annular magnetic core at 662.3 MPa at room temperature in order to analyze frequency characteristic and soft magnetic properties. By X-ray diffraction analyzer (XRD) and scanning electron microscope (SEM) to observe the microstructure and surface morphology of the insulating soft magnetic powder, using impedance analyzer (LCR meter) measured the frequency characteristics of the sample, with insulation resistance tester measuring surface insulation resistance value.
According to the results, alloy powders draped a passivation layer and have higher surface insulation resistance after passivation treatment. With passivation concentration, temperature, and time increasing, the surface insulation resistance increased dramatically, but the green density and initial permeability are decreased. Comparison of different passivation process of the powder in the same conditions, zinc phosphate passivation powder has lower surface insulation resistance, higher initial permeability and green density.
For consolidating initial permeability and surface insulation resistance at the same time, phosphoric acid passivation process optimization parameters is 5 minutes, 2 weight percent and 50 °C, initial permeability is 29 and the surface insulation resistance is 8.3 MΩ, and zinc phosphate passivation process optimization parameters is 5 minutes, 3 weight percent and 50 °C, initial permeability is 32.1 and the surface insulation resistance is 3.32 MΩ. Compared with the core in the industry, alloy powders have better green density and insulation resistance after zinc phosphate passivation treatment at optimization parameters, in addition, the initial permeability is in line with industry needs.
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