Study On The Magnetic And Mechanical Properties Of Gas-atomized Fe-Si-Al Soft Magnetic Powder Core

Metallic soft magnetic powder core has been widely used in various power electronic devices because of its distributed air gap structure,high resistivity insulation layer,good DC-bias performance and low loss.However,the current insulation coating method cannot meet the requirements of effectively improving the strength of the powder core while maintaining good magnetic properties.Thus,it is urgent to develop a novel insulation coating method to improve the comprehensive properties of the metallic soft magnetic powder core.In this research,the gas-atomized Fe-Si-Al magnetic powder was coated by the composite of epoxy resin,MgO and aluminum dihydrogen phosphate.The addition sequence of MgO is found to have a significant effect on the magnetic properties and mechanical properties of the Fe-Si-Al magnetic powder core.Treating the magnetic powder with aluminum dihydrogen phosphate solution after the basic insulation with epoxy resin and MgO would be helpful for improving the strength of the magnetic powder core.Hereinto,the amount of MgO,the amount of water in the solution of aluminum dihydrogen phosphate,the size of MgO particle,the amount and the type of release agent and the molding pressure all have major impacts on the magnetic and mechanical properties of the Fe-Si-Al powder core.The detailed results are as follows:(1)The effective permeability of the powder core decreases with increasing the dosage of MgO and aluminum dihydrogen phosphate in equal proportion,while the loss of the powder core increases and the DC-bias property becomes better.As to the core's strength,the strength of the green core decreases with the increase of the dosage of MgO after an initial increase,while the strength of the annealed core exhibits a decline tendency.(2)Increasing the water content in aluminum dihydrogen phosphate solution is beneficial to increasing the tensile strength and the effective permeability of the powder core,but unfavorable for improving DC-bias property.(3)The powder core prepared with 100 nm MgO particles has the lowest effective permeability,the best DC-bias performance,the largest loss and the strongest green strength.For the annealed cores,their strength increases with MgO particle size,which may be due to larger MgO particle served as structure support point within annealed cores.(4)Among the three release agents,zinc stearate is conducive to achieving high green strength and low loss under the same content.(5)With the increase of molding pressure,the effective permeability and the hysteresis loss are improved,but the eddy-current loss and the DC-bias performance deteriorate.And the tensile strength exhibits a trend of first increasing and then decreasing.The results show that when the amount of MgO is 1.5 wt.%,the particle size of MgO is 100 nm,the water content is 16.7 wt.%,the zinc stearate content is 0.3 wt.%,and the pressing pressure is 1860 MPa,the green strength of the core can reach 51.66 N and the strength after annealing is 26.28 N.Meanwhile,the effective permeability of the core is 30.71 at 100 kHz,the DC bias performance is 74.49%at 100 Oe and the core loss is 414.76 mW/cm3 at 50 kHz/1000 Gs.This paper would shed new light on the design of metallic soft magnetic powder core with good magnetic and mechanical properties.