RARE EARTH SINTERED MAGNET AND PROCESS FOR PRODUCING THE SAME

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PROBLEM TO BE SOLVED : To provide a process for producing a rare earth sintered magnet causing a heavy rare earth element RH to diffuse into an outer shell portion of main phase crystal grains over the whole of a magnet. SOLUTION : In the process for producing an R-Fe-B rare earth sintered magnet, first, there is prepared an R-Fe-B sintered magnet whose main phase consists of R2Fe14B compound crystal grains containing light rare earth element RL (at least one of Nd and Pr) as main rare earth element R. Subsequently, the sintered magnet body on its surface is coated with an RHM alloy layer composed of the RH (wherein RH is one or two or more rare earth elements selected from among Dy, Ho and Tb) and metal M (wherein M is one or two or more metal elements selected from among Al, Cu, Co, Fe and Ag), the metal M forming RHM so as to induce a melting point lowering. Thereafter, heat treatment is carried out at 800 to 1, 000°C in vacuum or Ar atmosphere so as to cause the metal element M to diffuse from the surface into the internal portion of the sintered magnet and to cause the heavy rare earth element RH to diffuse from the surface into the internal portion of the rare earth sintered magnet body. COPYRIGHT : (C)2011, JPO&INPIT