| FeSiAl soft magnetic powder core is a new type of soft magnetic composite material with magnetoelectric conversion effect,which is made by mixing powder containing iron,silicon,aluminum and other alloy elements and insulating medium,and pressed by powder metallurgy process.It has the advantages of high saturation magnetic induction intensity,small magnetostriction coefficient,low loss,and good frequency stability.It is widely used in power factor correction circuits,pulse flyback transformers,and energy storage filter inductors.As a new technology for preparing high-density and high-performance powder metallurgy parts at low cost,the warm compaction process is beneficial to reduce costs and improve its soft magnetic properties when preparing FeSiAl soft magnetic powder cores,and has certain economic value.In this paper,the FeSiAl alloy powder produced by the atomization method is used.At the same time,polyamide powder and polytetrafluoroethylene powder are used as a composite lubricant,and"warm compaction"is introduced to prepare FeSiAl alloy powder composite coated with phosphoric acid and silica at a certain temperature and pressure into a magnetic powder core.After heat treatment,the surface morphology and performance of the magnetic powder core are observed and tested by X-ray diffractometer,scanning electron microscope,soft magnetic material AC testing device and precision magnetic component analyzer.The effects of powder particle size,insulation coating,warm compaction process and annealing heat treatment on the structure and properties of FeSiAl soft magnetic powder core were studied,and the best process parameters of FeSiAl soft magnetic powder core and ways to improve the soft magnetic performance were also explored.Through experimental research and analysis,this article draws the following conclusions:1.The properties of FeSiAl soft magnetic powder cores made by warm compaction with different particle sizes powders are quite different.In this paper,FeSiAl original powder is sieved into three groups:A(-250?+325 mesh),B(-325?+400 mesh),and C(-400 mesh).The study found that the thicker the particle size of the powder(the smaller the mesh size),the greater the density and permeability of the corresponding magnetic powder core and the smaller the magnetic loss.When the powder of group A(-250?+325 mesh)is used,the magnetic powder core has the best comprehensive performance.2.The surface of the powder after insulation coating is covered with an insulating protective film,which increases the resistivity of the magnetic powder core and isolates the powder particles,thereby reducing magnetic loss.First,after passivation with phosphoric acid,the magnetic loss is significantly reduced compared to the unpassivated magnetic powder core.In the concentration range of 0.3%wt to 3wt%,with the increase of the concentration of phosphoric acid solution,the magnetic loss,density and permeability of the FeSiAl soft magnetic powder core with temperature and pressure are gradually reduced,but the quality factor does not change significantly.Secondly,in the concentration range of 1%wt to 3wt%,as the concentration of the binder increases,the magnetic loss,density and permeability of the FeSiAl soft magnetic powder core with temperature and pressure gradually decrease.When the concentration of phosphoric acid solution is 0.7 wt%and the binder concentration is 1.5wt%,the overall performance of the magnetic powder core is the best.3.The comprehensive performance of FeSiAl soft magnetic powder core prepared by the warm compaction process has been greatly improved.First of all,this article uses polyamide powder and polytetrafluoroethylene powder as a composite lubricant.As the lubricant content increases from 0.6wt%to 2.2wt%,the density and permeability of the magnetic powder core first increase and then decrease,and the magnetic loss decreases first.After rising.Secondly,in the temperature range of 90?to 140?,with the increase of temperature and pressure,the density and permeability of the magnetic powder core first increase and then decrease,and the magnetic loss first decreases and then increases.Finally,in the pressure range of 600 MPa to 1100 MPa,with the increase of temperature and pressure,the density and permeability of the FeSiAl soft magnetic powder core first increase and then decrease,and the magnetic loss first decreases and then increases.The conclusion is:when the addition ratio of polytetrafluoroethylene powder and polyamide powder composite lubricant with a mass ratio of 1:1 is 1.5wt%,the warm compaction temperature is 120?,and the warm compaction pressure is 900MPa,the FeSiAl soft magnetic powder core have the best overall performance.4.The soft magnetic properties of warm compaction FeSiAl soft magnetic powder core is greatly improved after heat treatment.First,after annealing for 1h in the temperature range of 550°C to 750°C,the density,permeability and quality factor of the FeSiAl soft magnetic powder core increase first and then decrease with increasing temperature,and the magnetic loss first decreases and then increases with increasing temperature.Secondly,when heat-treated at 600?for 0.5h to 2.0h,with the extension of heat-treatment time,the permeability and quality factor of FeSiAl soft magnetic powder core increase first and then decrease,and the change of magnetic loss is not obvious.The best heat treatment temperature is 600?to 650?,and the best heat treatment time is 1h to 1.5h.5.Adopt the optimized process:the particle size of powder is-250?+325 mesh,the concentration of phosphoric acid solution is 0.7 wt%,the concentration of binder is1.5wt%,the amount of compound lubricant added is 1.5%wt,and the temperature of warm compaction is 120?,pressure of warm compaction is 900MPa,heat treatment at 600?for 1h,the comprehensive performance of the prepared FeSiAl soft magnetic powder core:the density is 6.65 g/cm~3,the magnetic permeability is 154.2(100kHz),and the magnetic loss is 4.24W/kg(50kHz/50mT). |
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