Study On The Preparation And Magnetic And Electrical Properties Of High-performance Fe-Si Soft Magnetic Powder Cores

Soft magnetic powder cores with distributed air gaps meet the requirements of futural electrical and electric devices because they possess both high saturation flux density of soft magnetic alloys and large resistance of soft magnetic ferrites. With the continuous development of the devices with high power and low iron loss, Fe-Si soft magnetic powder cores with good DC-bias performance have attracted much attention.Fe-6.5wt%Si soft magnetic powder cores were prepared by using the phosphating technique. The influences of the contents of the insulation solution and the binder and the compaction pressure on the magnetic and electrical properties were studied in detail. It was found that large additions of the insulation solution and the binder can decrease the core's effective permeability and eddy-current loss and improve the DC-bias performance. The proper increase of the compaction pressure can raise the core's effective permeability and reduce the high-frequency loss. All these changes in the core's performance were determined by the pinned degree of the domain's shift, which was affected by the thickness of the unferromagnetic layer between the magnetic powders and the amounts of the decomposed residues of the insulation additives and the air gap influenced by changing the preparation parameters. Good performances, namely the iron loss at 50kHz/100mT lower than 600 mW/cm3 and the percent permeability at 100 Oe higher than 81%, were achieved in the 60? Fe-Si magnetic powder cores.Based on the study of the Fe-Si powder core, the Fe-Si/Sendust composite cores were prepared through adding the low-cost Fe-9.6wt%Si-5.4wt%Al insulated powders into the Fe-Si powder core. The dependence of the composite's performance on the addition content of the Sendust powder and the parameters of the heating treatment was investigated systematically. It was found that the addition of the Sendust powders, the proper increase of the heating temperature and the suitable elongation of the heating time can improve the core's iron loss and deteriorate the DC-bias performance as well. The changes of the magnetic performance were believed to be determined by two factors. One is the near-zero magnetostriction constant and magnetic anisotropic constant. The other is the reduction of the sites pinning the shift of the domain which was caused by the relaxation of the inner stress and the decomposition of the insulation additives. Good performances, namely the iron loss at 50kHz/100mT of 457 mW/cm3 and the percent permeability at 100 Oe of 62.68%, were achieved in the 60? Fe-Si/Sendust composite powder cores.