Patent ID: 7438768

Claim:
A method of manufacturing rare-earth sintered magnets, characterized by subjecting an alloy composed of 20 to 30 wt % of a constituent R (R being samarium alone or at least 50 wt % samarium in combination with one or more other rare-earth element), 10 to 45 wt % iron, 1 to 10 wt % copper and 0.5 to 5 wt % zirconium, with the balance being cobalt and inadvertent impurities, to the steps of, in order, melting, casting, coarse size reduction, milling, molding in a magnetic field, sintering and aging so as to form a sintered magnet, surface machining the sintered magnet by cutting and/or grinding, metal plating the surface-machined magnet with a metal-plating metal, then heat treating the metal-plated magnet at 80 to 850° C. for a period of from 10 minutes to 50 hours in an argon, nitrogen, air or low-pressure vacuum atmosphere having an oxygen partial pressure of 10 −4 Pa to 50 kPa to form an oxide layer of the metal-plating metal as a hydrogen resistance layer, the metal-plating metal being one or more selected from among copper, nickel, cobalt, tin, and alloys thereof.