Research On Soft Magnetic Properties Of FeSiAl Magnetic Powder Core During The Preparation Process

FeSiAl soft magnetic alloy,also known as Sendust alloy,has excellent comprehensive soft magnetic properties such as high magnetic permeability,high resistivity,low coercivity and good wear resistance.The magnetic powder core made of FeSiAl alloy has good bias characteristics and temperature stability,can work in a wide temperature range,and has low noise during operation.It is widely used in electronic components such as switching power supplies,inductors,and filters..With the advancement of science and technology,electronic components tend to be miniaturized and high-frequency.However,FeSiAl magnetic powder cores have high losses at high frequencies and are easy to generate heat,which limits their applications in high-frequency broadband.To meet the needs of the development of the power industry,it is necessary to further improve the magnetic properties of FeSiAl magnetic powder cores.This paper starts with the four steps of powder processing,insulation coating,compression molding,and annealing during the preparation of the FeSiAl magnetic powder core.The FeSiAl powder is flattened by the ball milling process.The magnetic powder core samples were prepared by using different coating agents,pressing pressures and stress relief annealing temperatures.The X-ray diffraction technology,scanning electron microscope,B-H AC magnetic characteristic analyzer,and PPMS comprehensive physical property measurement system were used to systematically explore the characterization methods.The influence of powder morphology,type and content of coating agent,forming pressure and annealing temperature on the soft magnetic properties of FeSiAl magnetic powder cores,and the following main research conclusions are obtained:(1)The FeSiAl powder gradually flattened as the ball milling time prolonged,and the density and resistivity of the pressed magnetic powder core gradually increased.However,the ball milling time was too long,and the powder structure was damaged,which affected the density and resistivity of the magnetic powder core.The soft magnetic properties of FeSiAl magnetic powder core are closely related to its own density and resistivity.With the increase of the powder ball milling time,the magnetic powder core's permeability increases first and then decreases,the loss decreases first and then increases,and the quality factor increases first and then decreases.When the powder ball milling time is about 15 hours,a powder with a diameter of about 30 ?m,a thickness of about 0.2 ?m,and a particle aspect ratio(diameter/thickness)of 150 can be obtained.At this time,the prepared magnetic powder core has the best comprehensive magnetic properties.(2)The type of binder has a great influence on the magnetic properties of the FeSiAl magnetic powder core.Selecting a suitable binder is beneficial to obtain a magnetic powder core with the best coating effect.The magnetic powder core obtained by using water glass as a binder has the highest magnetic permeability,the lowest loss,the highest quality factor at high frequencies,and the best comprehensive magnetic performance.Different binder contents have different effects on the magnetic properties of FeSiAl magnetic powder cores.When the content is less,the more the binder,the smaller the loss of the FeSiAl magnetic powder core,and the larger the quality factor as a whole.Generally speaking,when water glass is used as a binder and the content is between 3% and 4%,the obtained magnetic powder core has the best comprehensive magnetic performance.(3)The molding pressure affects the permeability and loss of the FeSiAl magnetic powder core by affecting the density and resistivity of the powder core.Within a certain pressure range,as the pressure increases,the density and resistivity of the magnetic powder core increase,the insulation coating effect is improved,the magnetic permeability is increased,and the loss is reduced;the excessive pressure destroys the insulating layer on the surface of the powder,and the internal stress concentration makes the magnetic powder core smaller in permeability and larger in loss.Decreasing the boosting rate can not only avoid the internal stress concentration of the powder core,improve the magnetic performance of the powder core,but also extend the service life of the mold;the holding time has little effect on the magnetic performance of the FeSiAl magnetic powder core.In terms of the effect of the comprehensive molding process on the magnetic performance of the magnetic powder core,selecting a molding pressure of about 1200 MPa,a holding time of about 90 s,and a slow boost rate can obtain the FeSiAl magnetic powder core with the best comprehensive performance.(4)As a magnetic insulating coating,ferrite itself has excellent magnetic properties that traditional non-magnetic coating materials do not have.Its proper addition improves the comprehensive magnetic properties of the FeSiAl magnetic powder core.However,too much ferrite is added,on the one hand,its own saturation magnetization has the disadvantage that the saturation magnetization of the composite magnetic powder core is reduced;On the other hand,the large amount of small particles aggregates increases the number of internal gaps in the powder core,affects the density and resistivity of the magnetic powder core,reduces the magnetic permeability and increases the loss.The comprehensive influence of ferrite on the magnetic properties of FeSiAl magnetic powder cores.When the MnZn ferrite coating content is 5%,the obtained MnZn / FeSiAl composite magnetic powder cores have the best magnetic properties,and the optimal stress-relief annealing temperature is 650 ?.