Method for producing sintered NdFeB magnet

摘要

The present invention provides a method for producing a sintered NdFeB magnet having high coercivity and capable of being brought into applications without lowering its residual magnetic flux density or maximum energy product and without reprocessing. The method for producing a sintered NdFeB magnet according to the present invention includes applying a substance containing dysprosium (Dy) and/or terbium (Tb) to the surface of the sintered NdFeB magnet forming a base body and then heating the magnet to diffuse Dy and/or Tb through the grain boundary and thereby increase the coercivity of the magnet. This method is characterized in that: (1) the substance containing Dy or Tb to be applied to the surface of the sintered NdFeB magnet is substantially a metal powder; (2) the metal powder is composed of a rare-earth element R and an iron-group transition element T, or composed of R, T and another element X, the element X capable of forming an alloy or intermetallic compound with R and/or T; and (3) the oxygen content of the sintered NdFeB magnet forming the base body is 5000 ppm or lower. The element T may contain nickel (Ni) or cobalt (Co) to produce an anticorrosion effect.