Provided is an R—Fe—B-based sintered magnet which has a composition comprising R (wherein R represents at least one element selected from rare earth elements, and essentially contains Nd), B, M (wherein M represents at least one element selected from Si, Al, Mn, Ni, Co, Cu, Zn, Ga, Ge, Pd, Ag, Cd, In, Sn, Sb, Pt, Au, Hg, Pb and Bi), X (wherein X represents at least one element selected from Ti, Zr, Hf, Nb, V and Ta) and C, with a remainder comprising Fe, O and unavoidable impurities, and has a main phase comprising R.sub.2Fe.sub.14B and a grain boundary phase comprising an R—C phase having a higher R concentration and a higher C concentration than those in the main phase, the R—Fe—B-based sintered magnet being characterized in that the area ratio of the R—C phase in a cross section of the magnet is more than 0% and 0.5% or less.

The purpose of the present invention is to achieve both high residual flux density and high coercivity, which are conventionally mutually exclusive characteristics, in an R—Fe—B sintered magnet. The present invention provides an R—Fe—B sintered magnet characterized by having a composition which contains R (R is one or more elements selected from among the rare-earth elements but must be Nd), B. X (X is one or more elements selected from among Ti, Zr, Hf, Nb, V, and Ta), and C, with the remainder comprising Fe, O, other arbitrary elements, and unavoidable impurities. The R—Fe—B sintered magnet is also characterized by satisfying relational expression (1), where [B], [C], [X], and [O] are the atomic percentages of B, C, X, and O, respectively.

0.86×([B]+[C]−2×[X])−4.9<[O]<0.86×([B]+[C]−2×[X])−4.6   (1).

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.

This invention is directed to a corrosion-resistant permanent magnet, to a method for producing a corrosion-resistant permanent magnet, and to an intravascular blood pump comprising the magnet. The magnet is surrounded by a composite coating, the composite coating comprising, in the order recited, a first metal oxide layer, a metal layer, a second metal oxide layer, a linker layer, and a layer formed from poly(2-chloro-p-xylylene). In an alternative embodiment, a further metal layer and, optionally, a further metal oxide layer may be provided between the second metal oxide layer and the linker layer. In a further alternative embodiment, the metal layer may be omitted, and a further layer structure comprising at least one metal oxide layer, a linker layer, and a layer formed from poly(2-chloro-p-xylylene) may be provided instead.

A neodymium-iron-boron permanent magnet, a preparation method and use thereof are disclosed. The neodymium-iron-boron permanent magnet has a composition represented by formula I: [mHR(1-m) (Pr.sub.25Nd.sub.75)].sub.x(Fe.sub.100-a-b-c-dM.sub.aGa.sub.bIn.sub.cSn.sub.d).sub.100-x-yB.sub.y formula I; where a is 0.995-3.493, b is 0.114-0.375, c is 0.028-0.125, d is 0.022-0.100; x is 29.05-30.94, y is 0.866-1.000; m is 0.02-0.05; HR is Dy and/or Tb; M is at least one selected from the group consisting of Co, Cu, Ti, Al, Nb, Zr, Ni, W and Mo.

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.