Patent ID: 9623482
Date: 2017-04-18
CPC Classifications: B22F,C22C,H01F

Claim:
1. A method for preparing an R—Fe—B based sintered magnet, the method comprising: 1) preparing an R 2) degreasing, acid washing, activating, and washing by deionized water the R 3) placing the sintered magnet obtained from step 2) in a sealed box comprising a hot spray gun under a circulating Ar protective atmosphere; employing Tb or Dy as a coating material, and coating a layer of the coating material having a thickness of between 10 and 200 μm on each surface of the sintered magnet by hot spraying, wherein the hot spraying is performed by feeding a metal wire comprising Tb or Dy into the hot spray gun, turning on the hot spray gun to produce electric arc inside the hot spray gun to heat and melt the metal wire comprising Tb or Dy into melted metal, and then supplying compressed Ar gas into the hot spray gun to atomize the melted metal into droplets and then spraying the droplets out of the hot spray gun toward each surface of the sintered magnet to form a coating layer on each surface of the sintered magnet; 4) placing the sintered magnet obtained from step 3) in a vacuum sintering furnace, heating the sintered magnet at a temperature of between 750 and 1000° C. for between 2 and 72 hrs; and controlling a vacuum degree of the vacuum sintering furnace at between 10 5) aging the sintered magnet obtained from step 4) at a temperature of between 450 and 600° C. for between 1 and 10 hrs to obtain the R—Fe—B based sintered magnet.