Method for producing sintered rare earth magnet and sintered ring magnet

A polar anisotropic ring magnet constituted by an R—Fe—Co—Cu—B-based, sintered magnet comprising 28-33 weight % of R, wherein R is at least one rare earth element including Y, 50 atomic % or more of R being occupied by Nd, 0.8-1.5 weight % of B, 0.5-5 weight % of Co, and 0.01-0.3 weight % of Cu, the balance being substantially Fe and inevitable impurities;

• the amount of oxygen inevitably contained being 0.3 weight % or less based on the total weight of said ring magnet;
• said ring magnet having a density of 7.56 g/cm3 or more;
• and a ratio of I (105)/I (006) being 0.5-0.8, wherein I (105) and I (006) are X-ray diffraction peak intensity measured with respect to (105) and (006) planes, respectively, at a middle position on an outer surface between magnetic poles of said ring magnet.

A thin, sintered arc segment magnet having a thickness of 1-4 mm constituted by an R′—Fe—B-based, sintered magnet comprising 28-33 weight % of R′, wherein R′ is at least one of rare earth elements including Y, 50 atomic % or more of R′ being occupied by Pr, 0.8-1.5 weight % of B, 5 weight % or less of Co, and 0.3 weight % or less of Cu, the balance being substantially Fe and inevitable impurities;

• the amount of oxygen inevitably contained being 0.3 weight % or less based on the total weight of said arc segment magnet;
• said arc segment magnet having a density of 7.50 g/cm3 or more, a coercivity iHc of 1.1 MA/m (14 kOe) or more at room temperature, and orientation (Br/4πI) of 96% or more in an anisotropy direction.

A radially anisotropic, sintered arc segment magnet having an inner diameter of 100 mm or less constituted by an R′—Fe—B-based, sintered magnet comprising 28-33 weight % of R′, wherein R′ is at least one of rare earth elements including Y, 50 atomic % or more of I′ being occupied by Pr, 0.8-1.5 weight % of B, 5 weight % or less of Co, 0.3 weight % or less of Cu, the balance being substantially Fe and inevitable impurities;

• the amount of oxygen inevitably contained being 0.3 weight % or less based on the total weight of said arc segment magnet;
• said arc segment magnet having a density of 7.50 g/cm3 or more and a coercivity iHc of 1.1 MA/m (14 kOe) or more at room temperature;
• and the degree of orientation expressed by [(Br//)/(Br+Br⊥)]×100(%) being 85.5% or more, wherein Br// is a residual magnetic flux density in a radial direction at room temperature, and Br⊥ is a residual magnetic flux density in a longitudinal direction perpendicular to said radial direction.

A radially anisotropic, sintered ring magnet having an inner diameter of 100 mm or less constituted by an R′—Fe—B-based, sintered magnet comprising 28-33 weight % of R′, wherein R′ is at least one of rare earth elements including Y, 50 atomic % or more of R′ being occupied by Pr, 0.8-1.5 weight % of B, 5 weight % or less Co, 0.3 weight % or less of Cu, the balance being substantially Fe and inevitable impurities;

• the amount of oxygen inevitably contained being 0.3 weight % or less based on the total weight of said ring magnet;
• said ring magnet having a density of 7.50 g/cm3 or more and a coercivity iHc of 1.1 MA/m (14 kOe) or more at room temperature;
• and the degree of orientation expressed by [(Br//)/(Br//+Br⊥)]×100(%) being 85.5% or more, wherein Br// is a residual magnetic flux density in a radial direction at room temperature, and Br⊥ is a residual magnetic flux density in a longitudinal direction perpendicular to said radial direction.