A Sm—Fe—N-based rare earth magnet more resistant to demagnetization than ever before in an environment where an external magnetic field is applied, particularly at high temperatures, and a production method thereof are provided.

The present disclosure presents a production method of a rare earth magnet, including preparing a coated magnetic powder, compression-molding the coated magnetic powder in a magnetic field to obtain a magnetic-field molded body, pressure-sintering the magnetic-field molded body to obtain a sintered body, and heat-treating the sintered body, and a rare earth magnet obtained by the method. D.sub.50 of the magnetic powder in the coated magnetic powder is 1.50 μm or more and 3.00 μm or less, the content ratio of the zinc component in the coated magnetic powder is 3 mass % or more and 15 mass % or less, and the heat treatment temperature is 350° C. or more and 410° C. or less.

The production method for a rare-earth sintered magnet according to the present disclosure comprises: a step for producing a molded article by compression-molding a slurry containing a rare-earth element-containing alloy powder and a dispersion medium using a wet-molding device; and a step for sintering the molded article. When the slurry is being poured into the inside of a space forming a cavity of the wet-molding device, a magnetic field is not applied. By pressing of the slurry, the dispersion medium contained in the slurry starts to be removed from the inside of the space.

A method for manufacturing a magnet includes (1) a step of preparing three or more unmagnetized magnet materials of which magnetization easy axes are oriented in predetermined directions, and adhering the unmagnetized magnet materials with each other to make an assembly, and (2) a step of applying a curved pulse magnetic field to the assembly to magnetize the assembly, wherein in the step (2), the unmagnetized magnet materials are magnetized into magnet blocks, and an angle θ (where 0≤θ≤180 degrees holds) formed by magnetization directions of at least a pair of magnet blocks adjacent to each other is in a range of 30 degrees to 120 degrees.

The present invention involves a graphene-containing rare earth permanent magnet material and preparation method thereof. The graphene-containing rare earth permanent magnet material, comprising: 20.6 to 23.4 weight percent of neodymium, 6.6 to 7.5 weight percent of praseodymium, 0.95 to 1.20 weight percent of boron, 0.4 to 0.6 weight percent of cobalt, 0.11 to 0.15 weight percent of copper, 2.0 to 2.4 weight percent of lanthanum, 1.7 to 2.1 weight percent of cerium, 1 to 5 weight percent of graphene, a remainder being iron. The graphene-containing rare earth permanent magnet material exhibits excellent temperature resistance, good conductivity and magnet properties even without any heavy rare earth elements like terbium or dysprosium, which dramatically reduces the cost, promotes the efficient utilization of rare earth resources and improves product quality. The preparation method within this invention is simple to realize, easy to control, cost-effective and has high production efficiency and stable product performances.

Improved manufacturing processes and resulting anisotropic permanent magnets, such as for example alnico permanent magnets, having highly controlled and aligned microstructure in the solid state are provided. A certain process embodiment involves applying a particular orientation and strength of magnetic field to loose, binder-coated magnet alloy powder particles in a compact-forming device as they are being formed into a compact in order to preferentially align the magnet alloy powder particles in the compact. The preferential alignment of the magnet alloy powder particle is locked in place in the compact by the binder after compact forming is complete. After removal from the device, the compact can be subjected to a subsequent sintering or other heat treating operation.

An anisotropic rare earth sintered magnet represented by the formula (R.sub.1-aZr.sub.a).sub.x(Fe.sub.1-b CO.sub.b).sub.100-x-y(M.sup.1.sub.1-cM.sup.2.sub.c).sub.y where R is at least one element selected from rare earth elements and Sm is essential; M.sup.1 is at least one of V, Cr, Mn, Ni, Cu, Zn, Ga, Al, and Si; M.sup.2 is at least one of Ti, Nb, Mo, Hf, Ta, and W; and x, y, a, b, and c each satisfy certain conditions. The anisotropic rare earth sintered magnet includes 80% by volume or more of a main phase composed of a compound of a ThMn.sub.12 type crystal, the main phase having an average crystal grain size of 1 μm or more, and containing an R-rich phase and an R(Fe,Co).sub.2 phase in a grain boundary portion. A method for producing the anisotropic rare earth sintered magnet is also described.

A molding device for molding a magnet roll with a profiled cross-section comprises a heating and kneading unit that supplies, to a cylindrical metal mold, a kneaded material obtained by heating and kneading a raw mixture including ferromagnetic particles and thermoplastic resin, an extrusion molding unit that molds the supplied kneaded material by the metal mold, and a magnetic field generating unit disposed at an end portion of the metal mold in a lengthwise direction that generates a magnetic field inside the metal mold, and the metal mold has a profiled C-shaped cross-section at an inlet for the kneaded material and a profiled cross-section at an outlet for the kneaded material more complex than the inlet.

An R—Fe—B base sintered magnet is provided consisting essentially of R (which is at least two rare earth elements and essentially contains Nd and Pr), M.sub.1 which is at least two of Si, Al, Mn, Ni, Cu, Zn, Ga, Ge, Pd, Ag, Cd, In, Sn, Sb, Pt, Au, Hg, Pb, and Bi, M.sub.2 which is at least one of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W, boron, and the balance of Fe, and containing an intermetallic compound R.sub.2(Fe,(Co)).sub.14B as a main phase. The magnet contains an R—Fe(Co)-M.sub.1 phase as a grain boundary phase, the R—Fe(Co)-M.sub.1 phase contains A phase which is crystalline with crystallites of at least 10 nm formed at grain boundary triple junctions, and B phase which is amorphous and/or nanocrystalline with crystallites of less than 10 nm formed at intergranular grain boundaries and optionally grain boundary triple junctions.

A dual-rotor machine comprising a dual rotor support structure rotatably connected to a frame. A stationary stator is disposed between the rotors and is fixed to the frame. An inner rotor and outer rotor, each comprising a permanent magnet Halbach array, are coaxially disposed with the stator and are rotable about the stator. In this configuration, the inner rotor channels its magnetic flux to its outside, while the outer rotor channels its magnetic flux to its inside. The magnetic flux density at the stator for the dual-rotor machine can be as high as 2 Tesla or higher for high-grade neodymium-iron-boron permanent magnet material, and the stored magnetic energy for conversion to mechanical or electrical energy available to the stator may be at least 0.5 kJ/m. The rotor Halbach arrays may comprise monolithic permanent magnets with continuously variable magnetic field direction.

A mold which is inexpensive and easy to process and does not embrittle. Also provided is a process by which a sintered NdFeB magnet can be produced using the mold without suffering bending or deformation. At least part (e.g., a bottom plate) of the mold is made of a carbon material. Carbon materials have lower friction with a sinter during sintering than metals. The mold hence enables a sintered NdFeB magnet to be produced without suffering the bending or deformation caused by friction due to sintering shrinkage. Carbon materials are inexpensive and easy to process. The mold does not embrittle even when repeatedly used. Such effects can be significantly produced when a carbon material is used as the bottom plate, on which the load of the sinter is imposed during sintering.