Study On Preparation And Magnetic Properties Of Fe-Si-Ni Magnetic Powder Cores

As the rapid development of electronic information technology, magnetic powder cores are widely used in line filter, output inductor, switching power supply and so on. Magnetic powder cores are one of soft magnetic materials which are molded with passivated and insulated powders. Magnetic powder cores can be divided into follow types:iron magnetic powder cores, Fe-Si magnetic powder cores, Fe-Ni magnetic powder cores, Fe-Si-Al magnetic powder cores, Fe-Si-Ni magnetic powder cores, Fe-Ni-Mo magnetic powder cores and amorphous-nanocrystalline magnetic powder cores. Among them the Fe-Si-Ni magnetic powder cores are widely used as one of new products. However, the preparation technology and properties of Fe-Si-Ni magnetic powder cores are few reported.In this study, Fe-Si-Ni magnetic powder cores were prepared with ball milled powders followed by molding. The magnetic properties and passivation of powders were investigated. And the influence of particle size, passivator content, molding pressure, and heat treatment process to density (p), saturation flux density (Bs), coercivity (Hc), effective permeability (ue), quality factor (Q), DC-bias, and core loss (P) of Fe-Si-Ni magnetic powder cores had been researched.The results show that the p decreases while the Q increases with the raise of powder mesh. With the passivator content increasing, the p, Bs, and μe decrease while the Hc, Q, DC-bias, and P increase. The Hc, DC-bias, and P decrease while the p, Bs, μe, and Q increase with increased the molding pressure. When the cores heat treated at650℃for0-5h, the Bs, Hc, and P firstly decrease then increase. With the temperature raising from550℃to750℃, the p and μe increase while the DC-bias and P decrease.Through the research, the optimum technological parameters were achieved. Fe-Si-Ni powders were distributed as particle size after annealed at600℃for1h. Then they were passivated with0.4wt.%acetone phosphate solution and insulated with0.5wt.%epoxy resin and0.04wt.%kaolin. After that,0.25wt.%zinc stearate and0.25wt.%barium stearate were added into powders as lubrication. Then they were molded into toroidal samples under the pressure of1.86GPa. Finally the samples were annealed in argon atmosphere at750℃for1h. The Fe-Si-Ni magnetic powder cores prepared with this process achieved the best soft magnetic properties. The Bs was1.23T, the μe was60.96, the Q was83.72at100kHz, the DC-bias was 48.07%when the DC magnetic field strength was100Oe, and the core loss was only312mW/cm3at50kHz for Bm=50mT.