Application of Magnetic Field in Fabrication Process of Anisotropic Bonded Nd-Fe-B Magnet

This work studied the application of the different magnetic field used in the compaction process for die fabrication of anisotropic Nd-Fe-B bonded magnet. The static field made from Nd-Fe-B permanent magnets was used in the blending process to separate the particles each other. The SEM observation gave intuitionistic results about it. The anisotropic Nd-Fe-B bonded magnets were fabricated with warm-compaction under the electromagnetic field about 2.5 T. It is known that magnetic field is necessary for anisotropic materials fabrication for alignment. And warm compaction was used to decrease the viscousness of binder, to enhance alignment magnetic particle while press, and to get high density materials. For coercivity of Nd-Fe-B magnets decrease largely with the temperature increasing, press in proper temperature and oriented field is benefit to the magnetic characteristics and the mechanical properties of the anisotropic bonded Nd-Fe-B magnets. Finally solidifying process was performed under the pulse field of 4 T. The increment for solidifying in the field was about 15% for maximum energy product of the bonded magnet. The magnetic properties of anisotropic bonded Nd-Fe-B magnets from d-HDDR powders compact at 90 °C in alignment field of 2.5 T were: B_r=8.55 kGs, _iH_c=12.0 kOe, (BH)_max=14.57 MGOe.     

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.     

Study on Fabrication Process of Anisotropic Injection Bonded Nd-Fe-B Magnets

This study is on the injection molding process for the fabricating anisotropic Nd-Fe-B bonded magnets. The effects of powder loading, particle size of the magnetic powder, polymer binder and the fabricating process on the magnetic and the mechanical properties of anisotropic Nd-Fe-B magnets were investigated. The proper powder loading, particle size and binder are 60%(vol%), 75–106 μm and PA 1010, respectively. The optimum condition for good magnetic properties of anisotropic injection bonded Nd-Fe-B magnets is mixing the binder and the chemicals in the temperature between 205–215 °C, injection temperature of 265 °C, the injection pressure of 5–6 MPa, the press time of 5 second, and molding temperature of 80 °C. The magnetic properties of anisotropic bonded Nd-Fe-B magnets made in above conditions from d-HDDR powder were: B_r=0.72 T, _iH_c=983 kA/m, (BH)_max=75 kJ/m^c.     

Ni对热变形Nd-Fe-B磁体磁性能及力学性能的影响

为提高热压结合热变形工艺制备的各向异性Nd-Fe-B磁体的力学性能,向磁体中掺杂高熔点、弱磁性金属元素Ni,研究Ni含量对磁体的磁性能、力学性能以及微观结构的影响。掺杂Ni的质量分数在0~5%之间时,Nd-Fe-B复合磁体的抗弯强度先增大后减小,2%Ni含量的Nd-Fe-B复合磁体具有最高平均抗弯强度212 MPa,其最大磁能积保持在40 MGOe以上。从磁体断口形貌上看,Ni会在孔洞附近富集,强化增韧晶界相,从而提高晶界相的裂纹扩展阻力,使抗弯强度提高。     

加剂方式对烧结钕铁硼磁体磁性能的影响

钕铁硼永磁材料在民用、航空航天等众多领域得到广泛的应用。高档次烧结钕铁硼磁体具有良好的市场前景。商业磁体多是由大块烧结毛坯切割而成,磁性能一致性是市场的基本要求之一,润滑剂等化学试剂和磁粉混合不均匀是影响一致性的一个重要因素。钕铁硼磁粉化学性质活泼、容易氧化,制粉的全过程都在氮气气氛下进行,没有合适的设备,想均匀加入化学试剂困难很大。研究人员因设备条件不足无法开展进一步探索。针对这个问题,项目组自行开发了专利产品"自动雾化加剂设备"。通过改变化学试剂加入方式,改善了磁粉和化学试剂混合均匀性,提高了磁体取向度,生产过程中也更好地保护了磁粉,得到内部一致性更好、磁性能更高的烧结钕铁硼磁体:剩磁(Br)=1.426 T,内禀矫顽力(Hcj)=1373.1 kA·m^-1,最大磁能积((BH)max)=406.99 kJ·m^-3。毛坯内部磁性能一致性的提高对后期加工成小片的商业磁体很有意义。开发的"自动雾化加剂设备"已经在烧结钕铁硼行业中得到广泛应用。     

Preparation and magnetic properties of anisotropic Nd_2Fe_(14)B/Sm_2Co_(17) hybrid-bonded magnets

In the present work, anisotropic Nd_2 Fe_(14) B/Sm_2 Co_(17) hybrid-bonded magnets were prepared with different Nd-Fe-B contents. It is found that the particle distributions and ratios between the two magnetic phases have important roles in the magnetic properties, microstructures and thermal stability of the magnets. With increase of Nd-Fe-B content, the saturation magnetization of the anisotropic hybrid magnet increases significantly, however, coercivity decreases, and the demagnetization curves show magnetically single-phase behavior. The anisotropic Nd_2 Fe_(14) B/Sm_2 Co_(17) hybrid-bonded magnets exhibit a maximum energy product and remanence of 14.15 MGOe and 99.53 A·m~2/kg, respectively, when the NdFe-B content is 70 wt% at room temperature. Furthermore, the hybrid magnets also have better thermal stability at elevated temperatures due to the interaction between the two magnetic particles.     

HDDR NdFeB磁粉两步法伴温磁场取向制备高性能柔性各向异性NdFeB黏结磁体

利用高性能吸氢-歧化-脱氢-再复合(HDDR)NdFeB各向异性磁粉,通过两步法伴温磁场取向工艺制备高性能柔性各向异性NdFeB黏结磁体,重点研究了两步法伴温磁场取向工艺制备出不同成分配比磁体的磁性能和力学性能.结果发现:制备出磁体的取向度有大幅度提高,当成分配比(质量分数)为96.5%磁粉+1%偶联剂+2.5%黏结体系的磁体在120℃加热保温30 min磁场取向后,磁能积达到97 kJ·m-3,而磁体的矫顽力最大降幅只有1.3%,论证了两步法伴温磁场取向工艺制备柔性各向异性NdFeB黏结磁体在实际生产的可行性.环氧树脂润滑剂的加入使得制备出磁体的延伸率和柔性均大幅度下降,并且加入量越多,下降幅度越大,因此环氧树脂润滑剂最大加入量不应超过1%(质量分数).      

生坯密度对烧结 Nd-Fe-B 磁体结构与性能的影响

结合国内烧结Nd-Fe-B磁体工业生产过程，研究了压制成型时生坯密度变化对烧结Nd—Fe—B磁体致密化程度、显微组织、取向度与磁性能的影响。试验结果表明，生坯密度的提高可促进烧结致密化过程，抑制烧结过程晶粒的不均匀长大，提高取向度，改善磁性能。     

Preparation of Rapidly Quenching （ Nd, Pr ） 12 （ FeCoZr ）82 B6 Alloy and Magnetic Properties of Bonded Magnets

TheanisotropyfieldHAofPr2 Fe14 Bisabout 30 %higherthanthatofNd2 Fe14 Bwhichresultsinhighin trinsiccoercivityfornanocrystallineexchangecoupledcompositepermanentmagnets .SothePr basedisotropicbondedmagnetshavecurrentlyattractedmuchattentions[1～ 4 ] .Howeverthistypeofpermanentmagnethasnotbeenusedinpractice .Thereexistmagneticinteractionsbetweenadja centgrainseitherinnanocrystallinecompositemagnetsorinanassemblyofsinglehardmagneticphaseofrareearth transitionmetalintermetalliccompounds[5～ 8] …     

Preparation and characterization of sodium silicate/epoxy resin composite bonded Nd-Fe-B magnets with high performance

As an organic binder for bonded Nd-Fe-B magnets, epoxy resin(EP) has poor heat resistance but good moisture resistance, while sodium silicate(SS) has poor moisture absorption but better heat resistance and corrosion resistance. In order to improve high temperature stability and decrease moisture absorption of bonded Nd-Fe-B magnets, EP/SS composites were applied as the binder to prepare bonded Nd-Fe-B magnets. The magnetic properties, moisture absorption, corrosion resistance, compressive strength and microstructure of composite bonded magnets were investigated. The results show that EP/SS bonded magnets can obtain excellent magnetic properties at room temperature, and even useable magnetic properties a thigh temperature environments at 200°C. EP/SS composite binder effectively improves heat resistance and corrosion resistance of bonded Nd-Fe-B magnets, and reduces the hygroscopic properties. The molecule of sodium silicateis rigid and keeps it original shape at high temperature environments. In addition, SS in composite binder improves the mobility of the magnetic powders during the pre-pressing process, which makes the magnetic powders attain a more regular structure. These two factors will increase the mechanical properties. Moreover, sodium silicate in the composite binder can also cover the surfaces protecting the magnetic powders from oxidation and corrosion. EP in composite binder can cover SS surface to reduce the water absorption of SS as epoxy is a hydrophobic material. The EDX analysis shows that the composite binder has accumulated in the gaps of the magnet powders, which not only improves heat resistance and corrosion resistance, but also increases the mechanical properties. Therefore, EP/SS composite binder endows bonded Nd-Fe-B magnets excellent comprehensive properties.