Sintered NdFeB magnet and method for manufacturing the same

摘要

Disclosed is a sintered NdFeB magnet having high coercivity (HcJ) a high maximum energy product ((BH)max) and a high squareness ratio (SQ) even when the sintered magnet has a thickness of 5 mm or more. The sintered NdFeB magnet is produced by diffusing Dy and/or Tb in grain boundaries in a base material of the sintered NdFeB magnet by a grain boundary diffusion process. The sintered NdFeB magnet is characterized in that the amount of rare earth in a metallic state in the base material is between 12.7 and 16.0% in atomic ratio, a rare earth-rich phase continues from the surface of the base material to a depth of 2.5 mm from the surface at the grain boundaries of the base material, and the grain boundaries in which RH has been diffused by the grain boundary diffusion process reach a depth of 2.5 mm from the surface.

主权项

1. A method for manufacturing a sintered NdFeB magnet, comprising:
making a starting alloy ingot by a strip-cast method in which an amount of rare-earth in a metallic state is between 12.7% and 16.0% in atomic ratio and lamellas of rare-earth rich phases are formed at an average interval controlled to be substantially the same as a target average particle size; making a powder containing particles in which fragments of the rare-earth rich phases are attached to main phase particles by grinding the starting alloy ingot so that an average particle size becomes the target average particle size; sintering the powder to make a base material of the NdFeB magnet; and performing a grain boundary diffusion process of RH, where RH is Dy and/or Tb, to the base material, wherein, in the powder, a rate of main phase particles to which the fragments of the rare earth rich phases are attached is equal to or higher than 80%.