Shin-etsu Chemical Co., Ltd.

Masanobu Shimao

Takehisa Minowa

Hajime Nakamura

Koichi Hirota

Masaaki Nishino

Ken Ohashi

Kazuaki Sakaki

Harukazu Maegawa

Takaharu Yamaguchi

Yoshifumi Nagasaki

Ryuji Hamada

Kazuo Tamura

A production method for a rare earth permanent magnet, wherein: a sintered magnet body comprising an R&#x2014;Fe&#x2014;B composition (Rrepresents one or more elements selected from among rare earth elements, including Y and Sc) is immersed in an electrodeposition liquid comprising a slurry obtained by dispersing a powder containing an Rfluoride (Rrepresents one or more elements selected from among rare earth elements, including Y and Sc) in water; an electrodeposition process is used to coat the powder onto the surface of the sintered magnet body; and, in the state in which the powder is present on the surface of the magnet body, the magnet body and the powder are subjected to a heat treatment in a vacuum or an inert gas at a temperature equal to or less than the sintering temperature of the magnet.

Production method for rare earth permanent magnet

A production method for a rare earth permanent magnet, wherein: a sintered magnet body comprising an R&#x2014;Fe&#x2014;B composition (Rrepresents one or more elements selected from among rare earth elements, including Y and Sc) is immersed in an electrodeposition liquid obtained by dispersing a powder containing an Roxyfluoride and/or an Rhydride (Rand Rrepresent one or more elements selected from among rare earth elements, including Y and Sc) in a solvent; an electrodeposition process is used to coat the powder onto the surface of the sintered magnet body; and, in the state in which the powder is present on the surface of the magnet body, the magnet body and the powder are subjected to a heat treatment in a vacuum or an inert gas at a temperature equal to or less than the sintering temperature of the magnet.

A production method for a rare earth permanent magnet, wherein: a sintered magnet body comprising an R&#x2014;Fe&#x2014;B composition (Rrepresents one or more elements selected from rare earth elements including Y and Sc) is immersed in an electrodeposition liquid obtained by dispersing a powder containing an Roxide (Rrepresents one or more elements selected from rare earth elements including Y and Sc) in a solvent; an electrodeposition process is used to coat the powder to the surface of the sintered magnet body; and, in the state in which the powder is present on the surface of the magnet body, the magnet body and the powder are subjected to heat treatment in a vacuum or an inert gas at a temperature equal to or less than the sintering temperature of the magnet.

A functionally graded rare earth permanent magnet is in the form of a sintered magnet body having a composition RRTAFOMwherein the concentration of R/(R+R) contained in grain boundaries surrounding primary phase grains of (R,R)TA tetragonal system within the sintered magnet body is on the average higher than the concentration of R/(R+R) contained in the primary phase grains, Ris distributed such that its concentration increases on the average from the center toward the surface of the magnet body, the oxyfluoride of (R,R) is present at grain boundaries in a grain boundary region that extends from the magnet body surface to a depth of at least 20 &#x3bc;m, and the magnet body includes a surface layer having a higher coercive force than in the interior. The invention provides permanent magnets having improved heat resistance.

Functionally graded rare earth permanent magnet

A functionally graded rare earth permanent magnet having a reduced eddy current loss in the form of a sintered magnet body having a composition RETAFOMis obtained by causing E and fluorine atoms to be absorbed in a R&#x2014;Fe&#x2014;B sintered magnet body from its surface. F is distributed such that its concentration increases on the average from the center toward the surface of the magnet body, the concentration of E/(R+E) contained in grain boundaries surrounding primary phase grains of (R,E)TA tetragonal system is on the average higher than the concentration of E/(R+E) contained in the primary phase grains, the oxyfluoride of (R,E) is present at grain boundaries in a grain boundary region that extends from the magnet body surface to a depth of at least 20 &#x3bc;m, particles of the oxyfluoride having an equivalent circle diameter of at least 1 &#x3bc;m are distributed in the grain boundary region at a population of at least 2,000 particles/mm, the oxyfluoride is present in an area fraction of at least 1%. The magnet body includes a surface layer having a higher electric resistance than in the interior. In the permanent magnet, the generation of eddy current within a magnetic circuit is restrained.

A rare earth permanent magnet is in the form of a sintered magnet body having a composition RRTAFOMwherein F and Rare distributed such that their concentration increases on the average from the center toward the surface of the magnet body, the concentration of R/(R+R) contained in grain boundaries surrounding primary phase grains of (R,R)TA tetragonal system within the sintered magnet body is on the average higher than the concentration of R/(R+R) contained in the primary phase grains, and the oxyfluoride of (R,R) is present at grain boundaries in a grain boundary region that extends from the magnet body surface to a depth of at least 20 &#x3bc;m. The invention provides R&#x2014;Fe&#x2014;B sintered magnets which exhibit high magnet performance despite minimal amounts of Tb and Dy used.

Rare earth permanent magnet

A rare earth permanent magnet is in the form of a sintered magnet body having a composition RRTAFOMwherein F and Rare distributed such that their concentration increases on the average from the center toward the surface of the magnet body, and grain boundaries having a concentration of R/(R+R) which is on the average higher than the concentration of R/(R+R) contained in primary phase grains of (R,R)TA tetragonal system form a three-dimensional network structure which is continuous from the magnet body surface to a depth of at least 10 &#x3bc;m. The invention provides R&#x2014;Fe&#x2014;B sintered magnets which exhibit a high coercive force.

An iron alloy strip having a gage of 0.1 to 5 mm and a magnetic field strength variation within the strip of 0 to 10 Hz, made of an iron alloy consisting essentially of, in % by weight, 0.0001-0.02% of C, 0.0001-5% of Si, 0.001-0.2% of Mn, 0.0001-0.05% of P, 0.0001-0.05% of S, 0.0001-5% of Al, 0.001-0.1% of O, 0.0001-0.03% of N, 0-10% of Co, 0-10% of Cr, 0.01-5% in total of Ti, Zr, Nb, Mo, V, Ni, W, Ta and/or B, and the balance of Fe, and having a saturation magnetic flux density of 1.7-2.3 Tesla, a maximum relative permeability of 1,200-22,000 and a coercive force of 20-380 A/m is suited for use as yokes in voice coil motor magnetic circuits. The iron alloy strip is highly resistant to corrosion and eliminates a need for a corrosion resistant coating.

Iron alloy strip for voice coil motor magnetic circuits

An R&mdash;Fe&mdash;B permanent magnet wherein R is Nd or a combination of Nd with a rare earth element is prepared by casting an R&mdash;Fe&mdash;B alloy, crushing the alloy in an oxygen-free atmosphere of argon, nitrogen or vacuum, effecting comminution, compaction, sintering, aging, and cutting and/or polishing the magnet to give a finished surface. The magnet is then heat treated in an argon, nitrogen or low-pressure vacuum atmosphere having a limited oxygen partial pressure, obtaining a highly oil resistant sintered permanent magnet having corrosion resistance and hydrogen barrier property even in a high pressure hot environment of refrigerant and/or lubricant as encountered in compressors.

Preparation of rare earth permanent magnets

A sintered rare earth magnet consisting essentially of 20-30% by weight of R (wherein R is Sm or a mixture of Sm and another rare earth element), 10-45% by weight of Fe, 1-10% by weight of Cu, 0.5-5% by weight of Zr, and the balance of Co has on its surface a composite layer containing Sm O and/or CoFe O in Co or Co and Fe. The magnet is resistant to hydrogen embrittlement.

Sintered rare earth magnet and making method

The invention discloses an iron-based alloy sheet as a material for preparing a magnetic yoke member to build up a magnetic circuit in a hard-disk voice-coil motor as well as a magnetic yoke member made from such a sheet material. With an object to improve the magnetic circuit in respect of compactness and flatness, the iron-based alloy forming the sheet material contains inherent side elements including C, Si, Mn, P, S, Al, O and N each in a specified amount and is characterized by specified values of saturated magnetic flux density, maximum magnetic permeability and coercive force. The iron-based alloy may further contain up to 10% by weight of cobalt and/or one or a combination of adjuvant elements selected from Ti, Zr, Nb, Mo, Cr, V, Ni, W, Ta and B.

Iron-based alloy sheet for magnetic yokes in hard-disk voice-coil motor

An improved method is proposed for the preparation of a sintered permanent magnet of a rare earth-iron-boron alloy having remarkably improved magnetic properties and stability by the powder metallurgical process. The scope of the inventive method consists in the particle size classification of the alloy powder for compression molding into a powder compact to be sintered, by which particles having a finer particle diameter and, preferably, a coarser particle diameter than the respective critical values are removed so as to effectively prevent oxidation of the too fine particles and improving the magnetic orientation of the particles as well as the sintering behavior of the particles.

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Echizen, Japan

Masanobu Shimao