| 主权项 |
1. A method for preparing an R—Fe—B based sintered magnet, the method comprising:
1) preparing a R1—Fe—B-M sintered magnet, wherein the R1—Fe—B-M sintered magnet comprises: between 26 and 33 wt. % of R1 being selected from the group consisting of Nd, Pr, Dy, Tb, Ho, Gd, or a combination thereof; between 0 and 5 wt. % of M being selected from the group consisting of Ti, V, Cr, Mn, Co, Ni, Ga, Ca, Cu, Zn, Si, Al, Mg, Zr, Nb, Hf, Ta, W, Mo, or a combination thereof; between 0.5 and 2 wt. % of B; and the rest Fe; 2) degreasing, acid washing, activating, and washing by deionized water the R1—Fe—B-M sintered magnet obtained from step 1); 3) placing the sintered magnet obtained from step 2) in a sealed box under a circulating Ar 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; 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 10−2 and 10−5 Pa or controlling an Ar pressure in the vacuum sintering furnace of between 5 and 20 kPa to allow Tb or Dy to enter an inner part of the sintered magnet via grain boundary diffusion; and 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. |
