Study On Preparing Process And Soft Magnetic Properties Of Ferrite/ FeSi6.5 Magnetic Powder Cores

As the rapid development of the electronics industry, electronic components gradually transfer to be smaller, lighter, with higher power and higher density. FeSi magnetic powder cores have been widely used in the electronics industry for excellent inductance, anti- drift characteristics and low loss.In this paper, the traditional insulation rubber was replaced by Mn-Zn ferrite to mix with FeSi powders to prepare magnetic powder cores. To integrate the advantages of the both materials, the composite powder cores with a brilliant antidrop performance and good overall soft magnetic properties were obtained. It was the first time to achieve the insulating coated with Mn Zn ferrite for FeSi powders through rapid prefired process. The preparation process of the series of mangetic powder cores were explored and the frequency characteristics, DC bias characteristics and static magnetic properties of the magnetic powder cores were studied in detail.An new rapid prefired process was developed in this paper, and FeSi powders were successfully coated with the Mn-Zn ferrite instead of the organic insulating agent. The coating would be effective by using rapid prefired process when the mass fraction of ferrite was 2wt%. The preparation process of ferrite/FeSi6.5 magnetic powder cores was optimized. Firstly, the presintering material-300 mesh MnZn ferrite were obtained through being calcined at 850℃ for 60 minutes, crushed, milled and sieved. Then the presintering materials were mixed with spherical FeSi6.5 powder size of 200 mesh evenly. And the magnetic powder cores were fabricated after granulated, calcined with a medium frequency induction furnace, and annealed. The research showed that the optimized preparation process of ferrite/FeSi6.5 magnetic powder cores had much advantage such as high rate of finished products, no air pollution during heating process, good anti-drop performance and excellent frequency characteristics.Through the adjustment of particle size gradation and the optimized process, magnetic powder cores in proportion of "FeSi powder(5wt%) of 200 mesh, ferrite powders of 300 mesh " were successfully designed and prepared, the density of product was 6.01 g/cm3, it had a good anti-drop performance. The effective permeability of magnetic powder core was 35.07 before prefired, it significantly improved and maintained a good frequency stability after rapid calcined which reached up to 59.57 and 57.99(decline of 2.65%) on the frequency of 1 k Hz and 200 kHz respectively. The quality factor of magnetic powder cores increased with the increasing of frequency, the value was about 15 to 50. The direct-current bias characteristics of the magnetic core was good, when the applied direct-current magnetic field H was less than 3000 A/m, the effective permeability of magnetic powder cores decreased slowly with the increasing of applied magnetic field. When the value of H was 8520 A/m, μe reduced to 29.03 which was more than the FeSi6.5 powder cores(less than 15) that widely used at present. So it shows that the new magnetic powder cores have a broad application prospect in switching power supplies and power systems.