Ferrite powder for bonded magnets, method for producing the same and ferrite bonded magnet
AssigneesDowa Electronics Materials Co., Ltd., Dowa F-Tec Co., Ltd.
InventorsSatoru TSUBOI, Yasunobu MISHIMA, Keisuke AYABE, Masayasu SENDA
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Abstract
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 m2/g or more and less than 3.20 m2/g; a compression density is 3.30 g/cm3 or more and less than 3.60 g/cm3, and a compressed molding has a coercive force of 3250 Oe or more and less than 3800 Oe.
Claims15
A ferrite powder for bonded magnets, wherein
- a specific surface area is 2.20 m2/g or more and less than 3.20 m2/g;
- a compression density is 3.30 g/cm3 or more and less than 3.60 g/cm3, and
- a compressed molding has a coercive force of 3250 Oe or more and less than 3800 Oe.
The ferrite powders for bond magnets, wherein when the ferrite powder for bonded magnets and nylon resin powder are kneaded to obtain a compound of F.C. 91.7 mass % and when the compound is molded into a bonded magnet, inj-iHc of the bonded magnet is 3600 Oe or more.
A method for producing a ferrite powder for bonded magnets, comprising:
- granulating a plurality of ferrite raw materials including iron oxide, and obtaining a first granulated material;
- sintering the obtained first granulated material at a first temperature, and obtaining a coarse powder of a sintered product;
- granulating a plurality of ferrite raw materials including iron oxide, and obtaining a second granulated material;
- sintering the obtained second granulated material at a second temperature lower than the first temperature, and obtaining fine powder of the sintered product;
- mixing the obtained coarse powder and fine powder, to obtain a mixed powder;
- and
- adding a mechanical pulverizing force to the obtained mixed powder to obtain a pulverized mixture, and applying annealing to the obtained pulverized mixture, wherein the first temperature is 1180° C. or more and less than 1220° C., and the second temperature is 900° C. or more and 1000° C. or less, and when a mixing ratio of the coarse powder and the fine powder is expressed by [mass of the coarse powder/mass of (coarse powder+fine powder)]×100%, it is 65 mass % or more and less than 75 mass %,
- wherein, the mechanical pulverizing force is the force caused by a pulverization processing in which a vibration ball mill with a capacity of 2 to 4 L and power of 0.3 to 0.5 kW, is loaded with steel balls having a diameter of 8 to 14 mm as media, so that pulverization is performed at a rotation number of 1700 to 1900 rpm and an amplitude of 7 to 9 mm, for 20 to 100 minutes as a processing time, or the force equivalent thereto.
Dependencies are inferred from the claim text.