The present invention provides a rare earth sintered magnet which contains R (R represents one or more rare earth elements essentially including Nd), T (T represents one or more iron group elements essentially including Fe), B, M.sup.1 (M.sup.1 represents one or more elements selected from among Al, Si, Cr, Mn, Cu, Zn, Ga, Ge, Mo, Sn, W, Pb and Bi) and M.sup.2 (M.sup.2 represents one or more elements selected from among Ti, V, Zr, Nb, Hf and Ta), while comprising an R.sub.2T.sub.14B phase as the main phase. This rare earth sintered magnet is characterized in that: the M.sup.1 is in an amount of from 0.5% by atom to 2% by atom; if (R), (T), (M.sup.2) and (B) are the respective atomic percentages of the above-described R, T, M.sup.2 and B, the relational expression (1) ((T)/14)+(M.sup.2)≤(B)≤((R)/2)+((M.sup.2)/2) is satisfied; and from 0.1% by volume to 10% by volume of all grain boundary phases in the magnet is composed of an R.sub.6T.sub.13M.sup.1 phase. This rare earth sintered magnet is able to achieve excellent magnetic characteristics including a good balance between high Br and high H.sub.cJ.

A method for producing a heavy rare earth grain-boundary-diffused RE-Fe—B-based rare earth magnet and a heavy rare earth grain-boundary-diffused RE-Fe—B-based rare earth magnet produced thereby is disclosed. More particularly, a method for producing a heavy rare earth grain-boundary-diffused RE-Fe—B-based rare earth sintered magnet having a reduced content of a heavy rare earth element is disclosed, in which a hydrogen compound of a heavy rare earth is mainly used as a diffusion material in the production of the grain-boundary-diffused magnet so that a product having uniform and stable quality can be produced. The coercive force of the magnet can be increased while minimizing the amount of heavy rare earth used in the production of the grain-boundary-diffused magnet, by solving the problem that the heavy rare earth is not uniformly diffused into the magnet, and a heavy rare earth grain-boundary-diffused RE-Fe—B-based rare earth magnet produced thereby.

The present invention relates to an RFeB-based sintered magnet having a composition including: 24-31% by mass of at least one element selected from the group consisting of Nd, Pr, La and Ce; 0.1-6.5% by mass of at least one element selected from the group consisting of Dy and Tb; 0.8-1.4% by mass of B; 0.03-0.2% by mass of at least one element selected from the group consisting of Zr, Ti, Hf and Nb; 0.8-5.5% by mass of Co; 0.1-1.0% by mass of Cu; and 0.1-1.0% by mass of Al, with a remainder being Fe and unavoidable impurities, in which the composition has a total content of Cu and Al being higher than 0.5% by mass.

A method of producing a motor core includes preparing a soft magnetic plate containing a transition metal element, preparing a modifying member containing an alloy having a melting point lower than a melting point of the soft magnetic plate, bringing the modifying member into contact with a part of a plate surface of the soft magnetic plate, causing the modifying member to diffuse and penetrate into the soft magnetic plate from a contact surface between the soft magnetic plate and the modifying member and forming a hard magnetic phase-containing part in a part of the soft magnetic plate, and laminating a plurality of soft magnetic plates on each other after the modifying member is brought into contact with the part of the plate surface of the soft magnetic plate.

A rare earth sintered magnet has a C concentration of 800-1,400 ppm, an O concentration of up to 1,000 ppm, and a N concentration of up to 800 ppm, an average crystal grain size D50 of up to 4.5 μm, and a degree of orientation Or (%) which is defined by the formula: Or (Br/4πIs)*100, wherein D50 and Or meet the relationship: Or>0.7*D50+95. The sintered magnet shows both high values of Br and H.sub.cJ.

A method for manufacturing a sintered magnet includes molding a green compact formed by compacting a magnet powder by press-molding the magnet powder, the green compact forming an R—Fe—B based sintered magnet having Nd as the principal component and containing a rare earth element R, sintering the green compact by heating to a sintering temperature, so as to mold a sintered magnet, pressure molding the sintered magnet by heating to a temperature not exceeding the sintering temperature, so as to correct dimensions of the sintered magnet, and adjusting the texture of the sintered magnet by aging heat treatment using heated atmosphere produced when correcting the dimensions of the sintered magnet at a temperature not exceeding the temperature during the pressure molding.

Disclosed are a continuous heat treatment device and method for a sintered Nd—Fe—B magnet workpiece. The device comprises a first heat treatment chamber, a first cooling chamber, a second heat treatment chamber, and a second cooling chamber continuously disposed in sequence, as well as a transfer system disposed among the chambers to transfer the alloy workpiece or the metal workpiece; both the first cooling chamber and the second cooling chamber adopt a air cooling system, wherein a cooling air temperature of the first cooling chamber is 25° C. or above and differs from a heat treatment temperature of the first heat treatment chamber by at least 450° C.; a cooling air temperature of the second cooling chamber is 25° C. or above and differs from a heat treatment temperature of the second heat treatment chamber by at least 300° C. The continuous heat treatment device and method can improve the cooling rate and production efficiency and improve the properties and consistency of the products.

The present invention discloses a grain boundary diffusion method of an R—Fe—B series rare earth sintered magnet, an HRE diffusion source, and a preparation method thereof, comprising the following steps: engineering A of forming a dry layer on a high-temperature-resistant carrier, the dry layer being adhered with HRE compound powder, the HRE being at least one of Dy, Tb, Gd, or Ho; and engineering B of performing heat treatment on the R—Fe—B series rare earth sintered magnet and the high-temperature-resistant carrier treated with the engineering A in a vacuum or inert atmosphere and supplying HRE to a surface of the R—Fe—B series rare earth sintered magnet. The method can reduce the consumption of heavy rare earth element and control the loss of residual magnetism Br while increasing the coercivity.

An R-T-B based permanent magnet, in which R is a rare earth element, T is Fe or a combination of Fe and Co, and B is boron, includes main phase grains made of an R.sub.2T.sub.14B crystal phase and grain boundaries formed between the main phase grains. The grain boundaries include an R—O—C—N concentrated part having higher concentrations of R, O, C, and N than that of the main phase grains. The R—O—C—N concentrated part includes a heavy rare earth element. The R—O—C—N concentrated part has a core part and a shell part covering at least part of the core part. A concentration of the heavy rare earth element in the shell part is higher than a concentration of the heavy element in the core part. A covering ratio of the shell part with respect to the core part of the R—O—C—N concentrated part is 45% or more in average.

The disclosure relates to the technical field of sintered type NdFeB permanent magnets, in particular to a low-cost rare earth magnet and manufacturing method. There is provided a method of preparing a high-coercivity, sintered NdFeB magnet including cerium comprising the following steps:

(S1) Providing alloy flakes composed of R.sub.xT.sub.(1-x-y-z)B.sub.yM.sub.z;

(S2) Mixing the alloy flakes, a low melting point powder, and a lubricant, then subjecting the mixture to a hydrogen embrittlement process followed in this order by pulverizing the process product to an alloy powder by jet milling, magnetic field orientation molding of the alloy powder to obtain a blank, sintering and aging treatment the blank;

(S3) Coating a film composed of a diffusion source of formula R1.sub.xR2.sub.yH.sub.zM.sub.1-x-y-z on the sintered NdFeB magnet; and

(S4) Performing a diffusion heat treatment, followed by aging the sintered NdFeB magnet to obtain the low-cost rare earth magnet.