The Production Management Improvement Model of Small and Medium-sized Permanent Magnetic Materials Manufacturing Companies

An integrated production planning and control model based on MRPⅡand JIT is put forward through analyzing the characteristics of magnetic materials manufacturing companies. Master Production Schedule with limited capacity and operational plan in workshop level based on the basic data of flow chart are formulated by this model which applied JIT idea and based on customer order demand. Push production is adapted during execution phase combined with process flow cards. The model is helpful to reduce inventory,keep certain flexbility of production and improve continuity and equilibrium of manufacturing process.

Mn-based permanent magnets

Mn-based intermetallic compounds have attracted much attention due to their fascinating structural and physical properties,especially their interesting hard magnetic properties.In this paper,we have summarized the magnetic and structural properties of Mn-based intermetallic compounds(Mn X,where X=Al,Bi,and Ga).Various methods for synthesizing single phases of MnAl,MnBi,and Mnx Ga were developed in our lab.A very high saturation magnetization of 125 emu/g,coercivity of 5 kOe,and maximum energy product(BH)_(max)of 3.1 MG·Oe were achieved at room temperature for the pureτ-Mn–Al magnetic phase without carbon doping and the extrusion process.Low temperature phase(LTP)MnBi with a purity above 95 wt.%can be synthesized.An abnormal temperature coefficient of the coercivity was observed for the LTP MnBi magnet.Its coercivity increased with temperature from 100 K to 540 K,reached a maximum of 2.5 T at about540 K,and then decreased slowly to 1.8 T at 610 K.The positive temperature coefficient of the coercivity is related to the evolution of the structure and magnetocrystalline anisotropy field of the LTP MnBi phase with temperature.The LTP MnBi bonded magnets show maximum energy products(BH)_(max)of 8.9 MG·Oe(70 kJ/m^(3))and 5.0 MG·Oe(40 k J/m^(3))at room temperature and 400 K,respectively.Ferrimagnetic Mn_(x)Ga phases with L10 structures(x〈2.0)and D0_(22)structures(x〉2.0)were obtained.All of the above structures can be described by a D0_(22)supercell model in which 2 a-Ga and 2 b-Mn are simultaneously substituted.The tetragonal D0_(22)phases of the Mn_(x)Ga show high coercivities ranging from 7.2 kOe for low Mn content x=1.8 to 18.2 kOe for high Mn content x=3 at room temperature.The Mn_(1.2)Ga sample exhibits a room temperature magnetization value of 80 emu/g.The hard magnetic properties of coercivityiH_(c)=3.5 kOe,remanence M_(r)=43.6 emu/g,and(BH)_(max)=2.5 MG·Oe were obtained at room temperature.Based on the above studies,we believe that Mn-based magnetic materials could be promising candidates for rare earth free permanent magnets exhibiting a high Curie temperature,high magnetocrystalline anisotropy,and very high coercivity.

Development of Strip Casting Technology in Rare Earth Permanent Magnet Alloys and Hydrogen Storage Alloys in China

The SC technique is now being applied widely in material preparation, especially in rare earth functional materials in virtue of its advanced process and high performance product. The applications of SC technique in rare earth permanent magnet alloys and hydrogen storage alloys were analyzed integrative, on the basis of summary of SC technique development in this paper. The paper mainly includes development history of SC technology, effect of SC technology on alloy microstructure, application of SC technology in RE storage hydrogen alloy and sintered Nd-Fe-B alloy, development of SC equipment and SC product industry. At the same time, the paper points out the existing problem of SC products.

An Empirical Study of CAPM’s Applicability to Rare Earth Permanent Magnet Material Stocks

China has the world’s largest reserves of rare earth elements.Rare earth permanent magnet material has always been one of the popular industries in the investment market.CAPM is the basic asset-pricing model in financial economics.There are a number of studies conducted to examine the applicability of CAPM to stock markets in different industries and to investigate the modification method to improve the model’s prediction accuracy.In this study,seven leading enterprises in China’s rare earth permanent magnet material industry listed on the A-share market were selected as the research subjects.Based on CAPM,regression analysis was conducted on the monthly data from March 2016 to February 2022.The results demonstrated that using the β coefficient to explain the risk of China’s rare earth permanent magnet industry is ineffective.The ultimate benefit was less affected by market indexes but mainly by non-systematic risks.CAPM has low applicability to China’s rare earth permanent magnet material industry and requires further improvement.Nevertheless,CAPM still has some guiding significance in making enterprise comparisons and investment decisions.

Preparation of Sm_2Fe_(17)Alloys in Ca-Sm_2O_3-Fe System

Thermodynamics and kinetics for the preparation of Sm2Fe17 alloys by reduction-diffusion （R-D） method in CaSm2O3-Fe System were investigated. With increasing reaction temperature, it is found that the reaction rate of R-D and the amount of Sm in the Sm2Fe17 alloy increase, and the increased amount at lower temperature is higher than that at higher temperature. Moreover, results from contracting core modal show that the peritectic reaction between Sm and Fe is a ratedetermined step in the whole R-D process. The apparent activation energy and the pre-exponential factor for this reaction are 73.74 kJ· mol^ -1 and 7.79 × 10^- 3 respectively.

Achievement of high performance of sintered R-Fe-B magnets based on misch metal doped with PrNd nanoparticles

The magnetic properties and microstructure of sintered R-Fe-B（R, rare earth） magnets with nominal composition of（（PrNd）（1-x）MMx）（30）Fe（bal）B1（x = 0, 0.1.0.2,0.3, 0.4, 0.5 and 0.7; MM, misch metal） prepared using dual-alloy method were investigated. For x = 0.3, the maximum energy product（（BH）（max）） of the sintered magnet is higher than 318.4 kJ·m^-3,but intrinsic coercivity（H（cj）） is lower than 351.8 kA·m^-1. The La and Ce contents are obviously different in some matrix-phase grains, which proves that the multi-hard magnetic phases（La, Ce-rich and La, Ce-lean） exist in the magnets. The coercivity is improved by the method of doping PrNd nanoparticles without sacrificing other magnetic properties. An enhancement in coercivity from 517.2 to 872.9 kA·m^-1 is achieved by doping 5 wt% PrNd nanoparticles. Meanwhile, it could exhibit better magnetic properties（remanence Br = 1.332 T.intrinsic coercivity H（cj）= 872.9 kA·m^-1 maximum energy product（BH）（max）=318.6 kJ·m^-3） and make the distribution of the intergranular phase become more homogeneous.

STRUCTURE AND MAGNETISM OF RTiFe_(11) COMPOUNDS (R=Nd,Sm,Gd,Tb,Dy,Ho,Er and Y)

The crystallographic structure and intrinsic magnetic properties have been investigated in the RTiFe_(11) compounds, where Rrepresents Nd, Sin, Gd, Tb, Dy, Ho, Er and Y. The magnetic structure and the exchange interaction between various magnetic ions in RT Fe_(11) have been analysed. It is found that the intensity of R-Fe exchange interaction is proportional to((?)—1)~2J(J—1) for the heavy-rare-earth ions. while for the light rare earth, the effect caused by 5d-4f electron exchange interaction varying with rare-earth atoms must be taken into account. In RTiFe_(11) compounds the interatomic distance dependence on the exchange interaction between Fe-Fe atoms has been observed, and the result of enhancing the Curie temperature has been obtained. The Fe atomic magnetic moment in RTiFe_(11) is discussed in terms of the band theory, and the approach has been investigated on enhancement of saturation magnetization by means of substitution of atoms. RTiFe_(11) compoumds reveal a variety of magnetocrystalline anisotropy behaviors. For Fe sublattice the easy magnetization direction and the variation of the anisotropy constants with temperature have been measured with X-ray and magnetic techniques. On the basis of the crystalline field theory, by using a single-ion model, the anisotropy conatants and their temperature dependence of the R ions have been calculated, which helps explain the spin reorientations observed in RTiFe_(11).

Density Functional Theory Study on the Complete Substitutions of Nd and Fe by Other Rare-earth and Transition-metal Elements in Nd_(2)Fe_(14)B Compound

To search for proper alternatives to improve the magnetic properties of Nd_(2)Fe_(14)B,using first-principles density functional theory calculations we have systematically studied the R_(2)M_(14)B(R=lanthanides from La to Lu;M=Mn,Fe,Co,and Ni)compounds with the isomorphic structure of Nd_(2)Fe_(14)B.The results show that for rare-earth elements,Pr is the most suitable choice for considering as an alternative of Nd.As for the substitution of Fe in Nd_(2)Fe_(14) B by other transition-metal elements,Co is much more suitable than Mn and Ni because the latter two result in too significant reduction of the magnetic moment.