PROCESS FOR PRODUCING SINTERED NdFeB MAGNET

摘要

A process for producing a sintered NdFeB magnet which has high coercivity and which can be used in applications without lowering its residual magnetic flux density or maximum energy product and without necessitating reprocessing. The process for producing a sintered NdFeB magnet comprises adhering a substance comprising dysprosium and/or terbium to the surface of a sintered NdFeB magnet and heating it to diffuse the dysprosium or terbium into inner parts of the sintered NdFeB magnet via grain boundaries thereof and thereby heighten the coercivity. The process is characterized in that (1) the substance comprising dysprosium or terbium which is to be adhered to the surface of the sintered NdFeB magnet is substantially a metallic powder, (2) the metallic powder comprises a rare earth element (R) and an iron-family transition element (T) or comprises the elements (R) and (T) and an element (X) forming an alloy or intermetallic compound with the element (R) or (T), and (3) the oxygen content in the sintered NdFeB magnet is 5,000 ppm or lower. The element (T) may include nickel or cobalt so as to impart an anticorrosive effect.