MANUFACTURE OF RARE EARTH-COBALT MAGNET POWDER FOR RESIN MAGNET

PURPOSE:To obtain RCo5 magnet powder suitable for a resin magnet by a method wherein the oxide of R element, a reducing agent and cobalt powder are mixed in such a manner that the weight ratio of the R element and cobalt contained in magnet powder will be made as prescribed, the mixed materials are treated under the specific condition, and their particle size is adjusted properly. CONSTITUTION:In the manufacture of RCo5 (R indicates one or more kinds of rare earth elements containing Y) magnet powder, an oxide of R element, a reducing agent and cobalt powder are mixed in such a manner that the weight ratio of the R element contained in magnet powder and cobalt will be brought to 32.5-34.0:67.5-66.0. The mixed material is heated up to 900-1,100 deg.C in an inert gas atmosphere of normal pressure, and after the temperature has been raised to 1,150-1,200 deg.C, it is cooled down to 800 deg.C at the cooling speed of 1-5 deg.C/min and it is cooled from 800 deg.C to 700 deg.C at the cooling speed of 10 deg.C/min or above. After it has been cooled to 400-200 deg.C, it is maintained at that temperature for 1-10hr, it is cooled to the normal temperature, and it is brought into a slurry form by putting the heat-treated material into water. The slurry is treated by the water and an acid aqueous solution, and a particle-size adjustment is performed on the obtained powder so that its average particle diameter will be made to 5-10mum.