Dowa Electronics Materials Co., Ltd.

Dowa Mining Co., Ltd.

Dowa F-tec Co., Ltd.

Nippon Bengara Kogyo Co., Ltd.

Masayasu Senda

Keisuke Ayabe

Shinichi Suenaga

Satoru Tsuboi

Yasunobu Mishima

Yuichi Sato

Seiichi Hisano

Toshio Ueda

Seiji Isoyama

Toshiyuki Sakai

Hideki Katayama

A ferrite powder for bonded magnets capable of producing a ferrite bonded magnet having high BH, and excellent in fluidity when converted to a compound, and having a high p-iHc value, and a method for producing the same, and a ferrite bonded magnet using the ferrite powder for bonded magnets, wherein an average particle size of particles obtained by a dry laser diffraction measurement is 5 &#x3bc;m or less; a specific surface area is 1.90 m/g or more and less than 2.80 m/g; a compression density is 3.50 g/cmor more and less than 3.78 g/cm, and a compressed molding has a coercive force of 2300 Oe or more and less than 2800 Oe.

Ferrite powder for bonded magnets, method for producing the same and ferrite bonded magnet

A ferrite powder for bonded magnets having a high iHc value usable even in a low temperature environment, a method for producing the same, and a bonded magnet using the ferrite powder and having high iHc value which can be used even in a low temperature environment, wherein a specific surface area is 2.20 m/g or more and less than 3.20 m/g; a compression density is 3.30 g/cmor more and less than 3.60 g/cm, and a compressed molding has a coercive force of 3250 Oe or more and less than 3800 Oe.

There is provided a ferrite powder for bonded magnets capable of producing ferrite bonded magnets with high BH, excellent in MFR when converted to a compound, with high p-iHc, wherein an average particle size of particles obtained by a dry laser diffraction measurement is 5 &#x3bc;m or less, a specific surface area is 1.90 m/g or more and less than 3.00 m/g, a compression density is 3.40 g/cmor more and less than 3.73 g/cm, and a compressed molding has a coercive force of 2800 Oe or more and less than 3250 Oe.

A ferrite magnetic powder for bonded magnets bonded using a rubber-base resin as binder, which powder is a ferrite magnetic powder containing an alkaline earth metal and having a chlorine content of 0.05 wt % or less and a powder pH of less than 6. The magnetic powder is produced by pulverizing a calcinated product of ferrite composition containing an alkali earth metal, annealing the pulverized ferrite composition to relieve crystal strain, dispersing the annealed powder in water and adding to it a mineral acid, adding a dispersant thereto, and subjecting the dispersion to solid-liquid separation followed by vacuum drying to obtain a ferrite magnetic powder having a chlorine content of 0.05 wt % or less and a powder pH of less than 6.

Ferrite magnetic powder and method for production thereof

A ferrite magnetic powder for bond magnet that experiences only small decrease in coercivity when molded into a bond magnet is provided, which is a ferrite magnetic powder that includes an alkaline-earth metal constituent and exhibits a decrease in coercivity of not greater than 600 Oe when subjected to a prescribed molding test. The magnetic powder can be obtained by mixing a fine ferrite powder of an average particle diameter of greater than 0.50 to 1.0 &#x3bc;m and a coarse ferrite powder of an average particle diameter of greater than 2.50 to 5.0 &#x3bc;m at ratio to incorporate the fine powder at a content ratio of 15-40 wt %.

Ferrite magnet powder bond magnet

Bond magnet and ferrite magnetic powder for bond magnet

A process for producing a permanent magnet alloy based on a R--Fe--B--C system wherein R is at least one of the rare earth elements including Y, comprising the steps of preparing a molten crude alloy, producing a powder directly therefrom or after casting it into an alloy ingot and then grinding it into the powder, compacting the thus obtained powder and sintering the compacted product, the ingot or powder of the alloy before being sent to the compacting step being subjected to a heat treatment which is carried out at a temperature of 500.degree.-1,100.degree. C. for a period of 0.5 hour or more so as to produce a permanent magnet alloy based on an a R--Fe--B--C system whose individual magnetic crystal grains are covered with an oxidation-resistant protective film which has a C content higher than that of the individual crystal grains.

Process for production of permanent magnet alloy having improved

A permanent magnet made of an R-Fe-B-C or R-Fe-Co-B-C based alloy (where R is at least one rare-earth element) consisting of its individual magnetic crystal grains that are covered with an oxidation-resistant protective film is promising as a practicable next-generation magnet because of its having not only excellent magnetic properties inclusive of magnetic force that surpasses Sm-Co based magnets but also such highly improved oxidation resistance that may withstand use in practical applications for a prolonged time period without being coated on its outermost exposed surface with an oxidation-resistant protective film. Said protective film surrounding the individual magnetic crystal grains contains at least one, preferably substantially all, of the alloying elements of which said magnetic crystal grains are made, with 0.05-16 wt. %, preferably 0.1-16 wt. % of said protective film being composed of C.

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Okayama, Japan

Masayasu Senda