Hitachi Metals, Ltd.

Kimio Uchida

Masahiro Takahashi

Hisato Tokoro

Fumitake Taniguchi

Shigeho Tanigawa

Kazuo Oda

Tsukasa Mikamoto

Masaaki Tokunaga

Tsunehiro Kawata

Akitoshi Hiraki

Akira Kikuchi

Shuichi Shiina

Masamichi Ozaki

A thin arc segment magnet made ofaan R--rare earth sintered magnet substantially comprising 28-33 weight % of R and 0.8-1.5 weight % of B, the balance being substantiallyFeT, wherein R is at least one rare earth element including Y, and T is Fe or Fe and Co, which has an oxygen content of 0.3 weight % or less, a density of 7.56 g/cmor more, a coercivity iHc of 1.1 MA/m (14 kOe) or more at room temperature, and an orientation Br/4&#x3c0;Iof 96% or more in an anisotropy-providing direction at room temperature can be produced by using a slurry mixture formed by introducing fine alloy powder of the above composition into a mixture liquid comprising 99.7-99.99 parts by weight of a mineral oil, a synthetic oil or a vegetable oil and 0.01-0.3 parts by weight of a nonionic surfactant and/or an anionic surfactant.

Arc segment magnet, ring magnet and method for producing such magnets

A sintered rare earth magnet is produced by finely pulverizing a coarse rare earth magnet alloy powder to an average particle size of 1-10 &mgr;m in a non-oxidizing atmosphere; introducing the resultant fine rare earth magnet alloy powder into a non-oxidizing liquid comprising at least one oil selected from the group consisting of mineral oils, synthetic oils and vegetable oils, and at least one lubricant selected from the group consisting of esters of aliphatic acids and monovalent alcohols, esters of polybasic acids and monovalent alcohols, esters of aliphatic acids and polyvalent alcohols and their derivatives to prepare a slurry; molding the slurry; degreasing the resultant green body; sintering the degreased green body; and then heat-treating the green body.

Method for producing sintered rare earth magnet and sintered ring magnet

An R&mdash;T&mdash;B sintered permanent magnet having a composition including 28-33 weight % of R, and 0.5-2 weight % of B, the balance being substantially T and inevitable impurities, wherein R is at least one rare earth element including Y, at least one heavy rare earth element selected from the group consisting of Dy, Tb and Ho being indispensable, and T is Fe or Fe and Co, the permanent magnet having a crystal structure comprising first R T B-type, main-phase crystal grain particles having a higher heavy rare earth element concentration than that of a crystal grain boundary phase, and second R T B-type, main-phase crystal grain particles having a lower heavy rare earth element concentration than that of the crystal grain boundary phase.

R-T-B sintered permanent magnet

A thin arc segment magnet made of a rare earth sintered magnet substantially comprising 28-33 weight % of R and 0.8-1.5 weight % of B, the balance being substantially Fe, wherein R is at least one rare earth element including Y, and T is Fe or Fe and Co, which has an oxygen content of 0.3 weight % or less, a density of 7.56 g/cm,or more, a coercivity iHc of 1.1 MA/m (14 kOe) or more at room temperature, and an orientation Br/4&pgr;I,of 96% or more in an anisotropy-providing direction at room temperature can be produced by using a slurry mixture formed by introducing fine alloy powder of the above composition into a mixture liquid comprising 99.7-99.99 parts by weight of a mineral oil, a synthetic oil or a vegetable oil and 0.01-0.3 parts by weight of a nonionic surfactant and/or an anionic surfactant.

A method of producing an R--Fe--B-based, sintered permanent magnet, wherein R is at least one rare earth element including Y, having a small oxygen content. A coarse alloy powder prepared by a reductive diffusion method is milled and recovered into a solvent to form a slurry. The slurry is wet-compacted to form a green body which is then sintered after removing the solvent. The milling, recovering, wet-compacting, solvent-removing and sintering steps are carried out while preventing the powder, slurry and green body from being brought into contact with air to minimize the oxygen content in the final sintered permanent magnet. The sintered permanent magnet produced has a high density and a high magnetic properties due to a low oxygen content.

Rare earth permanent magnet and production method thereof

A rare earth permanent magnet consisting essentially, by weight, of 27.0-31.0 % of at least one rare earth element including Y, 0.5-2.0 % of B, 0.02-0.15 % of N, 0.25 % or less of O, 0.15 % or less of C, at least one optional element selected from the group consisting of 0.1-2.0 % of Nb, 0.02-2.0 % of Al, 0.3-5.0 % of Co, 0.01-0.5 % of Ga and 0.01-1.0 % of Cu, and a balance of Fe, and a production method thereof. The contents of rare earth element, oxygen, carbon and oxygen in the magnet are regulated within the specific ranges.

Rare earth permanent magnet and method for producing the same

A rare earth permanent magnet consisting essentially, by weight, of 27.0-31.0% of at least one rare earth element including Y, 0.5-2.0% of B, 0.02-0.15% of N, 0.25% or less of O, 0.15% or less of C, at least one optional element selected from the group consisting of 0.1-2.0% of Nb, 0.02-2.0% of Al, 0.3-5.0% of Co, 0.01-0.5% of Ga and 0.01-1.0% of Cu, and a balance of Fe, and a production method thereof. The contents of rare earth element, oxygen, carbon and oxygen in the magnet are regulated within the specific ranges.

An R-Fe-B-based, sintered magnet, wherein R is one or more of rare earth elements including Y, is produced by the method including the steps of mixing fine R-Fe-B-based magnet powder with a mineral oil and/or a synthetic oil having a fractional distillation temperature range of 150.degree.-400.degree. C. and a kinetic viscosity of 10 cSt or less to prepare a mixture; charging the mixture under pressure into a die cavity equipped with a filter, to which an orientated magnetic field is applied, while removing a mineral oil and/or a synthetic oil from the mixture; compressing the mixture in the die cavity to carry out a wet molding while orientating the powder to prepare a green body; heating the green body to a temperature up to 500.degree. C. at a speed of 10.degree. C./min or less under pressure of 10.sup.-1 Torr or less for 30 minutes or more to remove a mineral oil and/or a synthetic oil from the green body; and then sintering the green body.

Method for producing R-Fe-B-based, sintered magnet

A permanent magnet having superior resistance to radioactive deterioration of magnetic properties. The magnet has a composition represented by the formula R.sub.a Fe.sub.bal. Co.sub.b B.sub.c Ga.sub. M.sub.e, in which the R denotes at least one element selected from the group consisting of Nd, Pr, Dy, Tb, Ho, and Ce, and the M denotes at least one element selected from the group consisting of Al, Si, Nb, Ta, Ti, Zr, Hf, and W, with the proviso that 12.ltoreq.a.ltoreq.18, 0.ltoreq.b.ltoreq.30, 4.ltoreq.c.ltoreq.10, 0.01.ltoreq.d.ltoreq.3 and 0.ltoreq.e.ltoreq.2 in terms of atomic percent. The permanent magnet has fine crystal grains provided with magnetic anisotropy.

Permanent magnet for accelerating corpuscular beam

A method of producing a neodymium-iron-boron permanent magnet alloy having a composition of 25.0-50.0 weight % of neodymium, 0.3-5.0 weight % of boron and balance substantially iron, including the steps of adding metal calcium, calcium hydride or a mixture thereof as a reducing agent to neodymium fluoride, iron and boron (or ferroboron), and further adding thereto at least one of calcium chloride, sodium chloride and potassium chloride as a flux, melting the resulting mixture in an inert gas atmosphere, or in a reducing gas atmosphere or substantially in vacuum at 1,000.degree.-1,300.degree. C., thereby reducing said neodymium fluoride to provide said alloy with as small a calcium content as 0.1 weight % or less. The starting materials may contain dysprosium fluoride and niobium to provide Nd-Dy-Fe-B-Nb alloys containing 0.5-15.0 weight % Dy and 0.05-5.0 weight % Nb. This method makes it possible to produce Nd-Fe-B or Nd-Dy-Fe-B-Nb permanent magnet alloys with as small a calcium content as 0.1 weight % or less directly from starting materials. Accordingly, it is economically advantageous over the conventional reduction method which produces mother alloys.

Method of producing neodymium-iron-boron permanent magnet

A mold for producing an anisotropic magnet from a composition essentially consisting of magnetic powder and a binder, a mold body, a cavity for molding the composition in the presence of an anisotropically oriented magnetic field produced by a plurality of first magnets for providing magnetic fluxes for the magnetic field in the cavity, yokes, each provided between the cavity and the first magnets, and second magnets provided on both circumferential sides of the yokes for preventing the leakage of the magnetic fluxes. The first and second magnets are made of permanent magnets such as rare earth cobalt magnets. The mold may be provided at both ends with third magnets for preventing the axial leakage of the magnetic flux from the axial ends of the yokes. Two or more molds may be combined in a single molding apparatus while sharing the first magnets. This mold is suitable for the injection, extrusion or insert molding of bonded magnet rolls, motor rotors, etc.

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Saitama-ken, Japan

Kimio Uchida