Dowa Electronics Materials Co., Ltd.

Dowa F-tec Co., Ltd.

Dowa Mining Co., Ltd.

Nippon Bengara Kogyo Co., Ltd.

Keisuke Ayabe

Masayasu Senda

Satoru Tsuboi

Shinichi Suenaga

Yasunobu Mishima

Toshiyuki Sakai

Shuichi Kohayashi

Hiroya Ikeda

Hideki Katayama

Kouji Hirata

Kazuyosi Horii

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.

To provide ferrite magnetic powders for bond magnet capable of surely suppressing residual hexavalent chrome, being an environmental load substance, having no adverse influence on the magnetic characteristics, which is an obstacle in use, and without damaging productivity and at a low cost. The method includes the steps of obtaining sintered powders by sintering raw material powders; wet-pulverizing the sintered powders; wet-cleaning the sintered powders; and annealing the cleaned sintered powders, wherein in the step of the wet-pulverization and in the step of wet-cleaning, generation of the hexavalent chrome, being an environmental load substance, is suppressed by performing the pulverization and cleaning while maintaining pH of a dispersion solvent at 8.5 or less, at the time of pulverization and cleaning.

Ferrite magnetic powder for bond magnet and manufacturing method of the same, and bond magnet

A bonded magnet is required to have a large energy product, which is the product of magnetization Br and coercive force Hc. However, in a ferrite powder for a bonded magnet, when the particle diameter is reduced to improve the coercive force, the packing properties are impaired, and the Br is lowered. When the particle diameter is increased to improve the magnetization, the coercive force is lowered. Therefore, to increase the energy product, both the Br and Hc must be increased. A ferrite powder that has a large particle size, is composed of smooth crystals, and suffers only a small reduction in coercive force even after pressurization is obtained by mixing a fine ferrite powder having a small particle size with a ferrite powder calcined at a temperature of 1050&#xb0; C. to 1300&#xb0; C. in the presence of a chloride at its saturated vapor pressure and then annealing the mixture at 800&#xb0; C. to 1100&#xb0; C. A bonded magnet produced using the powder has an energy product of 2.0 MGOe or more.

Ferrite powder for bonded magnet, method for manufacturing ferrite powder, and bonded magnet using ferrite powder

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 %.

Growing community of inventors

Okayama, Japan

Keisuke Ayabe