粉末粒度分布对烧结钕铁硼微观结构形成的影响

烧结钕铁硼永磁材料是用粉末冶金方法制造的,其生产环节中的每道工序对磁体的最终性能都有相当大的影响。从微观结构上看,磁性能的高低主要是由于具体的微观结构不同造成的。而其中制粉环节粉末的粒度分布对最终产品微观结构的形成具有非常大的影响。采取一组实验,以探讨不同的粉末粒度分布对产品微观结构形成的影响。     

一模32腔圆隙浇口粉末注射成型模具的设计及应用

对于大批量、小规格的永磁粘接磁环大多采用注射成型工艺,其模具设计是产品制造的重要环节之一,模具设计的合理与否直接关系到制品的生产效率、成品质量和经济性等.文章分析了多种注射成型模的方案后,结合小规格钕铁硼稀土永磁粘接薄壁磁环的材料特性,设计了一种32型腔圆隙浇口的薄壁磁环注射成型模.该模具具有自动化程度高、尺寸一致性好、能大批量生产等特点,有较佳的经济效益和进一步行业推广的价值.     

成形工艺对粘结NdFeB磁体结构和磁性能的影响

在粘结NdFeB磁体模压成形过程中存在较大的压力损失，引起磁体密度分布不均匀，致使磁体密度减小。本文研究了压制压强、预压成形和压制方式等对粘结NdFeB磁体结构和磁性能的影响及机理。研究表明：随着压制压强提高，粘结NdFeB磁体的密度和磁性能显著增大；粒度配合、预压成形和双向压制等办法均可增大粘结NdFeB磁体的密度和磁性能；在适当的压制压强下，将粒度配合、预压成形及双向压制工艺结合，制备出密度达到6．5g／cm^3、磁能积达到104kJ／m^3的粘结NdFeB磁体。     

注射成形粘结钕铁硼磁体复合粉研究

磁体的注射成形是一种高效生产的近净成形技术。为了制备出具有较好综合性能的注射成形粘结钕铁硼永磁材料,研究了粘结剂对注射成形磁体的磁性能、加工性能及力学性能的影响;分析了硅烷系列的偶联剂、复合润滑剂和抗氧剂等添加剂对注射成形磁体性能的影响。结果表明,用MQP-B快淬钕铁硼磁粉和尼龙12粘结剂制备出了剩余磁感应强度为0.539 T,磁感矫顽力为345.37 k A/m,内禀矫顽力为681.02 k A/m,最大磁能积为47.37 k J/m3的注射成形钕铁硼磁体。     

Transient Analysis for Magnetic Circuit of a Novel Synchronous Motor Basing on Controllable Flux

The paper refers to a novel permanent magnet motor with composite-rotor, to solve the difficulties of extend speed by “flux weakening”. The rotor is composed of two rotor segments: one is made of AINiCo magnet and the other of NdFeB. Relying on high coercive force and high remnant magnetic flux density quality of NdFeB, permanent magnet motor could get enough air gap magnetic fields. On the other way, by making using of low coercive force characteristics of AINiCo magnet, die permanent motor could be changed the orientation and strength of magnetization when applying a pulse of magnetizing (demagnetizing) current, thus magnetic flux in air gap could be varied over wide range. To achieve the aim, the paper analyzes magnetization process of permanent magnet and transient magnetic circuit in the motor, and then computes the distribution of air gap magnetic field in different magnetization by using finite element method. The numeral results show the validity of the scheme.     

Anisotropic NdFeB/SmCoCuFeZr composite bonded magnet prepared by warm compaction process

Anisotropic NdFeB/SmCoCuFeZr composite bonded magnets were prepared by warm compaction process. The effects of adding SmCoCuFeZr magnetic powder on the properties of anisotropic bonded NdFeB magnet were investigated in this work. The results show that, both magnetic properties and temperature stability of the bonded magnet can be improved by adding fine SmCoCuFeZr magnetic powder. In the present study, the optimal content of SmCoCuFeZr magnetic powder was about 20 wt.%, in this case, the Br, Hcj, and(BH)maxof the NdFeB/SmCoCuFeZr composite magnet achieved 0.943 T, 1250 kA/m, and168 kJ/m~3, respectively.     

注射成形制备NdFeB粘结磁体

为了制备出高性价比的粘结NdFeB注射磁体，本文系统的研究了粘结剂、添加剂的含罱以及磁粉装载量对注射磁体的加工性能、磁性能等的影响规律，并从微观上揭示了其机理。本文采用低成本的陶广：快淬钕铁硼磁粉和国产尼龙6粘结剂制备出了磁性能Br为0．5158T、Heb为321kA／m、Hcj为730kA／m和（BH）max为40kl／m^3的注射磁体，其性能与日本Mate公司的RNI-50产品性能相当，而价格却低得多.     

Characterization of Microstructure and Magnetic Properties of NdFeB Magnet with Dy, Al and Cu Additions

A new alloy of Nd33.5Dy0.99Febal.Al0.52Cu0.1B1.15 (%, mass fraction) was fabricated by powder metallurgy. The effects of Dy, Al and Cu additions on the microstructure and magnetic properties of sintered NdFeB magnet were investigated. The additions of Dy, Al and Cu are effective to refine grains and improve coercivity. Moreover, suitable amounts of Dy, Al and Cu lead to a demagnetization curve with good rectangularity. It is found that the sintered NdFeB magnet has relatively high magnetic performance of Br=12.17kGs, jHc=13.52kOe and (BH)max=34.71MGOe. The sintered NdFeB sample was examined by magnetic force microscope which revealed the domain structures at the surface. It is revealed that the mean Nd2Fe14B grain size is significantly larger than the average scale of the magnetic contrast. An explanation about this is that most Nd2Fe14B grains in sintered NdFeB alloy are dominated with the muhidomain structures when the magnet is in thermally demagnetization state.     

模压成形各向异性NdFeB粘结磁体性能研究

采用模压成形方法制备各向异性粘结NdFeB磁体,主要研究了粉末粒度以及取向磁场强度对粘结磁体磁性能和力学性能的影响.试验结果表明,随着磁粉粒度的减小,粘结磁体的剩磁有所增加,但矫顽力下降明显.随着取向磁场强度的增大,粘结磁体剩磁进一步提高,各向异性明显;粘结磁体密度及抗压强度随磁粉粒度的减小略有提高.经粒度配比后制备的粘结磁体获得了较高的磁性能和抗压强度,其B_r、H_(ci)及σ_(bc)分别为0.81T、828kA/m及204MPa.     

Investigation on the Moldability of HDDR NdFeB Bonded Magnet Prepared by Compression Molding Method

The phenomenon of uneven density distribution is inevitable in the process of preparing bonded magnets with complicated shape or with large geometric size by compression molding due to the friction among magnetic powder grains and between magnetic powder and the die wall, which reduces the pressure along the compression direction. In order to improve the density distribution homogeneity, the thin-wall rings with composition of HDDR NdFeB prepared by compression molding were selected as the investigated object in this study. It was systematically investigated on the effect of addition level of lubricants and the addition methods of lubricants and strengthener on magnet density, density distribution and on magnet strength. By means of joint addition of lubricants and strengthener, which increases the magnet density and improves the magnet density distribution under the precondition of keeping the magnet strength unreduced. Thus the moldability of the bonded magnets is improved.     

Manufacturing of Injection-Molded NdFeB Magnet with (BH)max111 kJ · m-3

The bonded NdFeB magnets prepared by injection molding meet with the development tendency of the magnet in small volume, light weight and high performance ,and have a good prospect.In this paper, a modified nylonbased binder was developed for powder injection molding of NdFeB bonded magnets.The effects of pretreatment of NdFeB anisotropic magnetic powder produced with HDDR processing on the anti-oxidation behaviors of powder and the final magnetic properties of the molded bonded magnets were studied.The optimal powder loading of 65 vol% was achieved with the modified binder.It was found that the properties of the bonded magnets were mainly affected by the powder surface pretreatment and the intensity of the applied alignment magnetic field during injection molding for a certain powder.Bonded magnets with remanence of 0.820 T, intrinsic coercivity of 1140.3 kA· m-1 and maximum energy product of 111 kJ · m-3 were produced with the optimal processing.     

Improved Electrical Insulation of Rare Earth Permanent Magnetic Materials With High Magnetic Properties

 Rare earth permanent magnetic materials are typical electrical conductor, and their magnetic properties will decrease because of the eddy current effect, so it is difficult to keep them stable for a long enough time under a high frequency AC field. In the present study, as far as rare earth permanent magnets are concerned, for the first time, rare earth permanent magnets with strong electrical insulation and high magnetic performance have been obtained through experiments, and their properties are as follows: (1) Sm2TM17: Br=062 T, jHc=8037 kA/m, (BH)m=5897 kJ/m3, ρ=7 Ω·m; (2) NdFeB: Br=0485 T, jHc=76633 kA/m, (BH)m=3796 kJ/m3, ρ=9 Ω·m. The magnetic properties of Sm2TM17 and NdFeB are obviously higher than those of ferrite permanent magnet, and the electric insulating characteristics of Sm2TM17 and NdFeB applied have in fact been approximately the same as those of ferrite. Therefore, Sm2TM17 and NdFeB will possess the ability to take the place of ferrite under a certain high frequency AC electric field.     

NdFeB稀土永磁材料研究进展

本文综述了NdFeB稀土永磁材料的研究进展,主要包括结构、矫顽力机制、添加元素、磁性能、腐蚀行为及其防护等方面,并就国内NdFeB产业的发展进行了讨论。     

Design of Polar Anisotropic Sintered NdFeB Ring-Type Permanent-Magnet for Brushless DC Motor

A Four polar anisotropic sintered NdFeB PM with high surface flux density was developed using dry pressing process with pulse magnetizing fields. In this paper, effects of filling density, magnetic field intensity, distribution of the cavity, and of the way of pre-magnetized powder for the high performance polar anisotropic sintered NdFeB PMs were studied. It can be seen that magnets produced by pre-magnetized powder process shows magnetic surface flux's maximum value that is 6,300 G due to pre-magnetized effects and that the back e.m.f. of Brushless motor, is 5.4 Vp/p per 1000 rpm, an increase about 35% above the conventional segment magnet.     

Microstructure and magnetic properties of(SmCo+FeCo)/NdFeB multicomponent nanocomposite magnets fabricated by HPTC with change in heating temperature and composition

We report the fabrication of bulk anisotropic(SmCo+FeCo)/NdFeB multicomponent nanocomposite magnets using high-pressure thermal compression(HPTC).The correlations among microstructure,magnetic properties,heating temperature and composition of the HPTC nanocomposite magnets were studied.The HPTC magnet made under variable temperatures(VT),with 19 wt% of FeCo phase,exhibits a maximum energy product of 32 MGOe,which is much higher than that(14 MGOe) for the HPTC magnet made under a constant temperature(CT).When the FeCo content increases to～23 wt%,the HPTC magnet made under VT still remains a high energy product of about 25 MGOe.With increasing NdFeB content,the(SmCo+FeCo)/NdFeB multicomponent nanocomposite magnets exhibit an enhanced magnetic anisotropy and coercivity.This work is beneficial to fabricating high-performance and low-cost permanent magnets for practical applications.     

Systematic study of the dependence of magnetic and structural properties of Nd_2Fe_(14)B powders on the average particle size

A systematic study of the magnetic and structural properties dependence on the particle size was realized.For this,commercial NdFeB powder was separated into five different mean particle sizes using sieves.Besides,from the original powder,eleven samples were also produced by mechanical milling assisted by surfactant,using various milling times.A total of sixteen samples were studied by scanning electron microscopy(SEM),X-ray diffraction(XRD),vibrating sample magnetometry(VSM),and Mdssbauer spectrometry(MS).The particle sizes of the samples vary from the micrometer to the nanometer scale.The crystallite size decreases with decreasing particle size.XRD result indicates that the Nd_2Fe_(14)B phase is found in all the samples,and the presence of this phase is also corroborated by MS using six sextets for fitting their spectra,with an additional singlet corresponding to the Nd_(1.1)Fe_4B_4 phase.The mean hyperfine magnetic field increases with increasing particle size because the magnetic dipolar interaction between the magnetic moment of the particles increases with particle size.From the VSM measurements the magnetic energy density(BH)_(max) values were calculated for different particle sizes,and their maximum value of 34.45 MGOe is obtained for the sample with the particle size of 60 μm.     

Preparation Technology and Performances of Zn-Cr Coating on Sintered NdFeB Permanent Magnet

Since appearing in1983,sintered NdFeB perma-nent magnet has been applied widely and become ani mportant basic material in high technology fields be-cause of its excellent magnet property,wide sources ofraw material and low price[1].Active phase such asNd-rich phase and B-rich phase in NdFeB permanentmagnet facilitated easy corrosion in corrosion medium,which weakenedits magnet property,andturnedit intopowder-like,non-usable product.So surface treatingfor anticorrosion was veryi mportant for…     

2种NdFeB粉末的混炼研究

采用快淬法和雾化法制得的2种不同形貌的NdFeB磁粉,以尼龙12作粘结剂,研究了注射成形粘结磁体的混炼过程。分析了2种磁粉的形貌与粉末粒度及其分布,对混合料的粉末临界充填率、均匀度、流变特性的影响,以及混炼温度对磁性能的影响。     

Permanent Magnets Design and Magnetic Field Analysis of Multi-disc Coreless Permanent Magnet Synchronous Motor

This paper presents a new multi-disc coreless permanent magnet synchronous motor whose permanent magnets are arranged in the “Halbach array”. Unit motor combined structure is adopted to simplify processing technology of the motor. Airgap magnetic flux density is increased taking advantage of high remanence and coercive force of NdFeB permanent magnet material and high gathering magnetism function of Halbach array. This also makes coreless motor possible. The structure and the characteristics of the motor using Halbach array are also introduced. The FEM analysis has been done to build the mathematical model and study the magnetic field characteristics of the motor. And finally the interrelated design parameters of permanent magnet and arrangement between unit motors are determined according to the results of die FEM analysis.     

气雾化NdFeB粉末的磁性能与热处理工艺的关系

对气雾化ＮｄＦｅＢ粉末的磁性能与回火温度，保温时间，回火气氛，冷却方式等热处理工艺参数和粉末粒度的关系进行了初步研究，优化了工艺条件，回火态的粉末磁性能优良，接近实用水平，气雾化ＮｄＢｅＢ粉末有望成为粘结磁体的原料。