| 简介 |
A sintered permanent magnet comprises rare earth element(s) including yttrium (27-33.5 mass%), boron (0.5-2 mass%), nitrogen (0.002-0.15 mass%), oxygen (=0.25 mass%), carbon (=0.15 mass%), phosphorus (0.001-0.05 mass%), and iron (balance). The magnet has a coercivity of >=1 MA/m. An independent claim is also included for production of sintered permanent magnet by : (i) pulverizing rare earth magnet material, and recovering fine powder directly in mineral oil and/or synthetic oil to form a slurry; (ii) injecting the slurry under pressure into a die cavity in which the slurry is wet-molded in a magnetic field; (iii) heating the resultant green body under reduced pressure to remove the mineral oil and/or synthetic oil from the green body; and (iv) sintering the green body in vacuum. An axial direction of an aperture open in cavity of the die for injecting the slurry under pressure is deviated from a center of a center core in the die. The mineral oil and/or synthetic oil can be mixed with sodium hypophosphite (as fluidity-improving agent) in the form of a solution in glycerin or ethanol. The oxygen content of fine powder is 0.25-0.6 mass%. |
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