Patent ID: 9734947
Date: 2017-08-15
CPC Classifications: C22C,H01F

Claim:
1. A method for preparing a R—Fe—B rare earth sintered magnet comprising Nd 2 Fe 14 B crystal phase as major phase, wherein R is an element or a combination of two or more elements selected from rare earth elements inclusive of Sc and Y and contains Nd and/or Pr, said method consisting of: step (A) of preparing a microcrystalline alloy powder, said step (A) consisting of sub-step (a) of strip casting an alloy having the composition R sub-step (b) of hydrogenation-disproportionation-desorption-recombination (HDDR) treatment of heating the strip cast alloy in hydrogen atmosphere at 700 to 1,000° C. to induce disproportionation reaction to disproportionate the Nd sub-step (c) of diffusion treatment of heating the HDDR-treated alloy in vacuum or in an inert gas atmosphere at a temperature of 600 to 1,000° C. for a time of 1 to 50 hours, for thereby preparing a microcrystalline alloy intermediate product consisting essentially of submicron crystal grains of Nd sub-step (d) of pulverizing the microcrystalline alloy intermediate product into a microcrystalline alloy powder, step (B) of pulverizing the microcrystalline alloy powder into a fine powder, and magnetizing the fine powder, step (C) of compacting the magnetized fine powder in a magnetic field into a green compact, and step (D) of heating the green compact in vacuum or in an inert gas atmosphere at 900 to 1,100° C. for sintering, thereby yielding a R—Fe—B rare earth sintered magnet having an average grain size of 0.2 to 2 μm.