【作者】 王震；

【导师】 刘先松；

【作者基本信息】 安徽大学 ， 材料科学与工程， 2020， 硕士

【摘要】 铁硅铝软磁合金,又称作仙台合金,具有高磁导率、高电阻率、低矫顽力和良好的耐磨性等优异的综合软磁性能。用FeSiAl合金粉末制备的磁粉芯具有良好的偏置特性和温度稳定性,能够在较宽的温度范围内工作,并且工作时噪音低,广泛应用于开关电源、电感器、滤波器等电子元器件中。随着科技的进步,电子元器件越来越趋向于小型化、高频化,然而FeSiAl磁粉芯在高频下损耗高、易发热,限制了其在高频宽频下的应用。要想满足电力行业发展的需要,人们有必要对FeSiAl磁粉芯的磁性能作进一步的提升。本论文从FeSiAl磁粉芯制备过程中的粉末处理、绝缘包覆、压制成型和退火处理等四个环节入手,通过球磨工艺实现FeSiAl粉末的扁平化,选用不同的包覆剂、压制压力和去应力退火温度制得磁粉芯样品,利用X射线衍射技术、扫描电子显微镜、B-H交流磁特性分析仪和PPMS综合物性测量系统等表征手段,系统地探究了粉末形貌、包覆剂的种类和含量、成型压力和退火温度等因素对FeSiAl磁粉芯软磁性能的影响规律,并得出以下主要研究结论:(1)FeSiAl粉末随球磨时间的延长逐渐实现扁平化,压制成的磁粉芯密度和电阻率逐渐增大,但球磨时间过长,粉末结构遭到破坏,反而影响磁粉芯的密度和电阻率。FeSiAl磁粉芯的软磁性能与其自身密度和电阻率密切相关,随粉末球磨时间的延长,磁粉芯的品质因数先升高后降低,当粉末球磨时间为15小时左右时,可以获得直径约为30μm、厚度约为0.2μm、颗粒纵横比(直径/厚度)为150的粉末,此时制得的磁粉芯综合磁性能最佳。(2)粘结剂的种类对FeSiAl磁粉芯磁性能的影响很大,选取合适的粘结剂有利于获得包覆效果最佳的磁粉芯。水玻璃做粘结剂得到的磁粉芯,磁导率最高,损耗最低,高频下品质因数最大,综合磁性能最好。粘结剂的含量不同,对FeSiAl磁粉芯磁性能的影响效果不同。添加含量较少时,粘结剂越多,FeSiAl磁粉芯的损耗越小,品质因数整体上越大,但添加含量过多,会极大影响磁粉芯的磁导率。综合来讲,使用水玻璃作粘结剂且添加含量在3%-4%之间时,得到的磁粉芯综合磁性能最佳。(3)成型压力通过影响粉芯的密度和电阻率,进而影响FeSiAl磁粉芯的磁导率和损耗。在一定的压力范围内,随压力的增加,磁粉芯的密度和电阻率增大,绝缘剂包覆效果得到改善,磁导率升高、损耗降低;压力过大,破坏了粉末表面的绝缘层,且内部应力集中,使得磁粉芯磁导率变小、损耗变大。降低升压速率,不仅可以避免粉芯内部应力集中,改善粉芯磁性能,还可以延长模具使用寿命;保压时间对FeSiAl磁粉芯的磁性能影响不大。综合成型工艺对磁粉芯磁性能的影响效果来看,选择1200 MPa左右的成型压力、90 s左右的保压时间和缓慢的升压速率,可以得到综合性能最佳的FeSiAl磁粉芯。(4)铁氧体作为磁性的绝缘包覆剂,其本身具有传统的非磁性涂覆材料不具备的优良磁性能,它的适当加入改善了FeSiAl磁粉芯的综合磁性能。但铁氧体添加含量过多,一方面其自身饱和磁化强度的劣势,使得复合磁粉芯的饱和磁化强度降低;另一方面,小颗粒物大量聚集增加了粉芯内部间隙的数量,影响了磁粉芯的密度和电阻率,使得磁导率降低、损耗增加。综合铁氧体对FeSiAl磁粉芯磁性能的影响规律,当MnZn铁氧体的包覆含量为5%时,得到的MnZn/FeSiAl复合磁粉芯磁性能最佳,且最佳去应力退火温度为650℃。更多还原

【Abstract】 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 μm,a thickness of about 0.2 μm,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 ℃.更多还原