R-T-B based sintered magnet
To provide an R-T-B based sintered magnet having high B r and high H cJ while suppressing the content of Dy. Disclosed is an R-T-B based sintered magnet represented by the formula: uRwBxGayCuzAlqM(balance)T, where R is composed of light rare-earth element(s) RL and heavy rare-earth element(s) RH, RL is Nd and/or Pr, RH is Dy and/or Tb, T is Fe, and 10% by mass or less of Fe is capable of being replaced with Co, M is Nb and/or Zr, inevitable impurities being included, and u, w, x, y, z and q are expressed in terms of % by mass; RH accounts for 5% by mass or less of the R-T-B based sintered magnet, 0.4≤x≤1.0, 0.07≤y≤1.0, 0.05≤z≤0.5, 0≤q≤0.1, and 0.100≤y/(x+y)≤0.340; v=u−(6α+10β+8γ), where the amount of oxygen (% by mass) is α, the amount of nitrogen (% by mass) is β, and the amount of carbon (% by mass) is γ; and v and w satisfy the following inequality expressions: v≤32.0, 0.84≤w≤0.93, and −12.5w+38.75≤v≤−62.5w+86.125.
1. An R-T-B based sintered magnet represented by the following formula (1):
u R w B x Ga y Cu z Al q M(100- u - w - x - y - z - q )T (1)
wherein R is composed of light rare-earth element(s) RL and optionally heavy rare-earth element(s) RH, RL is Nd and/or Pr, RH is Dy and/or Tb, T as balance is Fe, and 10% by mass or less of Fe being replaced with Co, M is Nb and/or Zr, and u, w, x, y, z, q and 100-u-w-x-y-z-q are expressed in terms of % by mass;
said RH accounts for 5% by mass or less of the R-T-B based sintered magnet, the following inequality expressions (2) to (6) being satisfied:
0.4≤ x≤ 1.0 (2)
0.07≤ y≤ 1.0 (3)
0.05≤ z≤ 0.5 (4)
0≤ q≤ 0.1 (5)
0.100≤ y /( x+y )≤0.340 (6)
v=u−(6α+10β+8γ), wherein the amount of oxygen (% by mass) of the R-T-B based sintered magnet is α, the amount of nitrogen (% by mass) is β, and the amount of carbon (% by mass) is γ; and
v and w satisfy the following inequality expressions (7) to (9):
v≤ 29.5 (7)
0.89≤ w≤ 0.93 (8)
−12.5 w+ 38.75≤ v≤− 62.5 w+ 86.125 (9).
2. The R-T-B based sintered magnet according to claim 1 , satisfying the following inequality expressions (10) and (11):
0.4≤ x≤ 0.7 (10)
0.1≤ y≤ 0.7 (11).
3. The R-T-B based sintered magnet according to claim 1 , satisfying the following inequality expression (12):
0.4≤ x≤ 0.6 (12).
4. The R-T-B based sintered magnet according to claim 1 , satisfying the following inequality expression (13):
v≤ 28.5 (13).
5. The R-T-B based sintered magnet according to claim 1 , satisfying the following inequality expression (14):
0.90≤ w≤ 0.93 (14).
6. The R-T-B based sintered magnet according to claim 1 , satisfying the following inequality expression (15):
0.1≤ y≤ 0.361 (15).
7. The R-T-B based sintered magnet according to claim 2 , satisfying the following inequality expression (16):
0.1≤ y≤ 0.30 (16).