Magnetic property regulation and mechanism analysis of FeSiBC soft magnetic composites by mixing with FeSiCr or carbonyl iron powder

Abstract

FeSiBC, FeSiCr, and CIP (carbonyl iron powder) are the main raw materials for the preparation of molding choke. In this study, water atomized FeSiCr powder with three particle size groups and CIP with a fixed particle size were used as raw materials to explore the influence of fine powder size and type on soft magnetic properties of FeSiBC SMPCs (soft magnetic powder cores). The results show that by adding a certain proportion of FeSiCr fine powder, the pores between large-size FeSiBC amorphous powder could be effectively filled, so that the density and permeability of SMPCs increased monotonically with the increase of FeSiCr content, while the porosity and DC bias performance decreased monotonically. In addition, the smaller the particle size of the FeSiCr, the more beneficial it was to reduce the eddy current loss of SMPCs. In the mixed FeSiCr scheme, adding 10 wt% FeSiCr with an average particle size of 6 μm was the best. In this case, the permeability of SMPCs was 18.01 and the core loss was 239.15 mW·cm−3 (100 kHz, 50 mT). Compared with hard FeSiCr, the deformation of CIP was greater during the pressing process due to its extremely low hardness, which could effectively fill the pores of SMPCs, thus greatly improving the comprehensive performance. The FeSiBC/30 %CIP SMPCs prepared in this study had excellent soft magnetic properties (permeability of 26.26, DC bias performance of 94.58 % at 100 Oe and core loss of 192.10 mW·cm−3 at 100 kHz and 50 mT), highest strength (6.54 ± 0.08 MPa) and lowest cost (13.7 $∙kg−1), and the comprehensive performance was significantly better than that of FeSiBC/FeSiCr SMPCs with different particle sizes. It can be seen that mixing FeSiBC amorphous powder with a small amount of powder that has a significant difference in hardness and particle size and complementary soft magnetic properties is an effective way to improve the magnetic properties of SMPCs.