Patent ID: 8317941
Filing Date: 2012-11-27
Classification: B22F,C22C,H01F

Abstract:
1. An R-T-B based sintered magnet having a composition comprising: 27.3 mass % to 29.5 mass % of R, which is at least one of the rare-earth elements that include Y and of which at least 50 mass % is Pr and/or Nd; 0.92 mass % to 1 mass % of B; 0.05 mass % to 0.3 mass % of Cu; at most 0.5 mass % (including 0 mass %) of M, which is one, two, or more elements that are selected from the group consisting of Al, Ti, V, Cr, Mn, Ni, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Au, Pb and Bi; and T as the balance, which is Fe with or without Co and of which at least 50 mass % is Fe, and having an oxygen content of 0.02 mass % to 0.2 mass %, wherein the main phase of the sintered magnet is an R wherein the crystal grain size of the main phase is represented by an equivalent circle diameter of 8 μm or less and wherein crystal grains with equivalent circle diameters of 4 μm or less account for at least 80% of the overall area of the main phase.