Abstract: It is an object of the present invention to obtain a highly coercive R-T-B system sintered magnet by making the crystal microstructure of a raw material alloy prepared by strip casting more uniform, thereby making the crushed powder obtained from such raw material alloy more fine and making the size distribution more narrow. The present invention provides a raw material alloy for an R-T-B system sintered magnet containing grains of an R2T14B compound, wherein a P and/or S content is between 100 and 950 ppm. This raw material alloy preferably has a composition comprising 25 to 35% by weight of R, 0.5 to 4% by weight of B, 0.02 to 0.6% of one or both of Al and Cu, 5% by weight or less of Co, and the balance of Fe.

Abstract: The present invention provides a technique to improve an adhesion strength between a magnet main body and a protective film. The rare earth sintered magnet of the present invention comprises a magnet main body of a sintered body containing a rare earth element and a protective film formed on the magnet main body, wherein the ratio of a 10-point average surface roughness Rz of the magnet main body on which the protective film is formed to a mean grain size D50 in the magnet main body (Rz/D50 ratio) is kept in a range from 0.20 to 10.00, inclusive. This gives the rare earth sintered magnet which is coated with the protective film having a high adhesion strength of 100 N/m or more and exhibits high corrosion resistance.

Abstract: It is an object of the present invention to obtain a highly coercive R-T-B system sintered magnet by making the crystal microstructure of a raw material alloy prepared by strip casting more uniform, thereby making the crushed powder obtained from such raw material alloy more fine and making the size distribution more narrow. The present invention provides a raw material alloy for an R-T-B system sintered magnet containing grains of an R2T14B compound, wherein a P and/or S content is between 100 and 950 ppm. This raw material alloy preferably has a composition comprising 25 to 35% by weight of R, 0.5 to 4% by weight of B, 0.02 to 0.6% of one or both of Al and Cu, 5% by weight or less of Co, and the balance of Fe.

Abstract: The present invention provides a technique to improve an adhesion strength between a magnet main body and a protective film. The rare earth sintered magnet of the present invention comprises a magnet main body of a sintered body containing a rare earth element and a protective film formed on the magnet main body, wherein the ratio of a 10-point average surface roughness Rz of the magnet main body on which the protective film is formed to a mean grain size D50 in the magnet main body (Rz/D50 ratio) is kept in a range from 0.20 to 10.00, inclusive. This gives the rare earth sintered magnet which is coated with the protective film having a high adhesion strength of 100 N/m or more and exhibits high corrosion resistance.

Abstract: A method for compacting a magnetic powder in a magnetic field comprising steps of filling a die with a magnetic powder, applying a pulsed magnetic field to the magnetic powder in the die to orientate the powder, and compressing the magnetic powder, wherein the pulsed magnetic field is applied twice or more when density ? of a compacted body of said magnetic powder satisfies the relationship ?=?×H0.5+?(?=0.63 and ?=1 to 2), where H is intensity (T) of the applied magnetic field.

Abstract: A sintered body comprising a main phase consisting of an R2T14B phase (wherein R represents one or more rare earth elements (providing that the rare earth elements include Y), and T represents one or more transition metal elements essentially containing Fe, or Fe and Co), and a grain boundary phase containing a higher amount of R than the main phase, wherein a platy or acicular product exists. This sintered body enables to inhibit the grain growth, while keeping a decrease in magnetic properties to a minimum, and to improve a suitable sintering temperature range.

Abstract: A sintered body with a composition consisting of 25% to 35% by weight of R (wherein R represents one or more rare earth elements, provided that the rare earth elements include Y), 0.5% to 4.5% by weight of B, 0.02% to 0.6% by weight of Al and/or Cu, 0.03% to 0.25% by weight of Zr, 4% or less by weight (excluding 0) of Co, and the balance substantially being Fe. This sintered body has a coefficient of variation (CV value) showing the dispersion degree of Zr of 130 or less. In addition, this sintered body has a grain boundary phase comprising a region that is rich both in at least one element selected from a group consisting of Cu, Co and R, and in Zr. This sintered body enables to inhibit the grain growth, while keeping the decrease of magnetic properties to a minimum, and to improve the suitable sintering temperature range.

Abstract: When an R-T-B system rare earth permanent magnet is obtained by a mixing method to obtain a sintered body with a composition consisting essentially of 25% to 35% by weight of R (wherein R represents one or more rare earth elements, providing that the rare earth elements include Y), 0.5% to 4.5% by weight of B, 0.02% to 0.6% by weight of Al and/or Cu, 0.03% to 0.25% by weight of Zr, 4% or less by weight (excluding 0) of Co, and the balance substantially being Fe, wherein a coefficient of variation (CV) showing the dispersion of Zr is 130 or lower, Zr is contained in a low R alloy. This sintered body enables to inhibit the grain growth, while keeping the decrease of magnetic properties to a minimum, and to improve the suitable sintering temperature range.

Abstract: A method for manufacturing an R-T-B system rare earth permanent magnet that is a sintered body comprising a main phase consisting of an R2T14B phase (wherein R represents one or more rare earth elements (providing that the rare earth elements include Y), and T represents one or more transition metal elements essentially containing Fe, or Fe and Co), and a grain boundary phase containing a higher amount of R than the above main phase, wherein a product that is rich in Zr exists in the above R2T14B phase, the above manufacturing method comprising the steps of: preparing an R-T-B alloy containing as a main component the R2T14B phase and also containing Zr, and an R-T alloy containing R and T as main components, wherein the amount of R is higher than that of the above R-T-B alloy; obtaining a mixture of the R-T-B alloy powder and the R-T alloy powder; preparing a compacted body with a certain form from the above mixture; and sintering the above compacted body, wherein, in the above sintering step, the above produ

Abstract: A sintered body with a composition consisting of 25% to 35% by weight of R (wherein R represents one or more rare earth elements, providing that the rare earth elements include Y), 0.5% to 4.5% by weight of B, 0.02% to 0.6% by weight of Al and/or Cu, 0.03% to 0.25% by weight of Zr, 4% or less by weight (excluding 0) of Co, and the balance substantially being Fe, wherein a coefficient of variation (CV) showing the dispersion of Zr is 130 or lower. This sintered body enables to inhibit the grain growth, while keeping the decrease of magnetic properties to a minimum, and to improve the suitable sintering temperature range.

Abstract: It is an object of the present invention to obtain a highly coercive R-T-B system sintered magnet by making the crystal microstructure of a raw material alloy prepared by strip casting more uniform, thereby making the crushed powder obtained from such raw material alloy more fine and making the size distribution more narrow. The present invention provides a raw material alloy for an R-T-B system sintered magnet containing grains of an R2T14B compound, wherein a P and/or S content is between 100 and 950 ppm. This raw material alloy preferably has a composition comprising 25 to 35% by weight of R, 0.5 to 4% by weight of B, 0.02 to 0.6% of one or both of Al and Cu, 5% by weight or less of Co, and the balance of Fe.

Abstract: A method for compacting a magnetic powder in a magnetic field comprising steps of filling a die with a magnetic powder, applying a pulsed magnetic field to the magnetic powder in the die to orientate the powder, and compressing the magnetic powder, wherein the pulsed magnetic field is applied twice or more when density ? of a compacted body of said magnetic powder satisfies the relationship ?=?×H0.5+? (?=0.63 and ?=1 to 2), where H is intensity (T) of the applied magnetic field.

Abstract: An R—T—B system rare earth permanent magnet, which is a sintered body comprising: a main phase consisting of an R2T14B phase (wherein R represents one or more rare earth elements (providing that the rare earth elements include Y), and T represents one or more transition metal elements essentially containing Fe, or Fe and Co); and a grain boundary phase containing a higher amount of R than the above main phase, wherein a product that is rich in Zr exists in the above R2T14B phase. The product that is rich in Zr has a platy or acicular form. The R—T—B system rare earth permanent magnet containing the product enables to inhibit the grain growth, while keeping a decrease in magnetic properties to a minimum, and to obtain a wide suitable sintering temperature range.

Abstract: A sintered body comprising a main phase consisting of an R2T14B phase (wherein R represents one or more rare earth elements (providing that the rare earth elements include Y), and T represents one or more transition metal elements essentially containing Fe, or Fe and Co), and a grain boundary phase containing a higher amount of R than the main phase, wherein a platy or acicular product exists. This sintered body enables to inhibit the grain growth, while keeping a decrease in magnetic properties to a minimum, and to improve a suitable sintering temperature range.

Abstract: A method for manufacturing an R—T—B system rare earth permanent magnet that is a sintered body comprising a main phase consisting of an R2T14B phase (wherein R represents one or more rare earth elements (providing that the rare earth elements include Y), and T represents one or more transition metal elements essentially containing Fe, or Fe and Co), and a grain boundary phase containing a higher amount of R than the above main phase, wherein a product that is rich in Zr exists in the above R2T14B phase, the above manufacturing method comprising the steps of: preparing an R—T—B alloy containing as a main component the R2T14B phase and also containing Zr, and an R-T alloy containing R and T as main components, wherein the amount of R is higher than that of the above R—T—B alloy; obtaining a mixture of the R—T—B alloy powder and the R-T alloy powder; preparing a compacted body with a certain form from the above mixture; and sintering the above compacted body, where

Abstract: An R-T-B system rare earth permanent magnet, which is a sintered body comprising: a main phase consisting of an R2T14B phase (wherein R represents one or more rare earth elements (providing that the rare earth elements include Y), and T represents one or more transition metal elements essentially containing Fe, or Fe and Co); and a grain boundary phase containing a higher amount of R than the above main phase, wherein a product that is rich in Zr exists in the above R2T14B phase. The product that is rich in Zr has a platy or acicular form. The R-T-B system rare earth permanent magnet containing the product enables to inhibit the grain growth, while keeping a decrease in magnetic properties to a minimum, and to obtain a wide suitable sintering temperature range.

Abstract: A sintered body with a composition consisting of 25% to 35% by weight of R (wherein R represents one or more rare earth elements, provided that the rare earth elements include Y), 0.5% to 4.5% by weight of B, 0.02% to 0.6% by weight of Al and/or Cu, 0.03% to 0.25% by weight of Zr, 4% or less by weight (excluding 0) of Co, and the balance substantially being Fe. This sintered body has a coefficient of variation (CV value) showing the dispersion degree of Zr of 130 or less. In addition, this sintered body has a grain boundary phase comprising a region that is rich both in at least one element selected from a group consisting of Cu, Co and R, and in Zr. This sintered body enables to inhibit the grain growth, while keeping the decrease of magnetic properties to a minimum, and to improve the suitable sintering temperature range.

Abstract: When an R-T-B system rare earth permanent magnet is obtained by a mixing method to obtain a sintered body with a composition consisting essentially of 25% to 35% by weight of R (wherein R represents one or more rare earth elements, providing that the rare earth elements include Y), 0.5% to 4.5% by weight of B, 0.02% to 0.6% by weight of Al and/or Cu, 0.03% to 0.25% by weight of Zr, 4% or less by weight (excluding 0) of Co, and the balance substantially being Fe, wherein a coefficient of variation (CV) showing the dispersion of Zr is 130 or lower, Zr is contained in a low R alloy. This sintered body enables to inhibit the grain growth, while keeping the decrease of magnetic properties to a minimum, and to improve the suitable sintering temperature range.

Abstract: A sintered body with a composition consisting of 25% to 35% by weight of R (wherein R represents one or more rare earth elements, providing that the rare earth elements include Y), 0.5% to 4.5% by weight of B, 0.02% to 0.6% by weight of Al and/or Cu, 0.03% to 0.25% by weight of Zr, 4% or less by weight (excluding 0) of Co, and the balance substantially being Fe, wherein a coefficient of variation (CV) showing the dispersion of Zr is 130 or lower. This sintered body enables to inhibit the grain growth, while keeping the decrease of magnetic properties to a minimum, and to improve the suitable sintering temperature range.

Abstract: In the manufacture of a rare earth sintered magnet of the Nd.sub.2 Fe.sub.14 B system, closed voids are formed in the magnet in a predetermined fraction to minimize shrinkage. Unlike open voids or pores in conventional semi-sintered magnets, the closed voids do not incur magnet corrosion since they do not communicate to the magnet exterior. By minimizing shrinkage during sintering in this way, a ring or plate-shaped thin wall anisotropic magnet can be prepared without machining for shape correction, achieving a cost reduction and a productivity improvement. Since a high density compact has a high deflective strength, it is easy to handle, minimizing cracking and chipping between the compacting and sintering steps.