R-T-B based permanent magnet
The present invention provides an R-T-B based permanent magnet having excellent magnetic properties and corrosion resistance even when Co content is small. The R-T-B based permanent magnet in which R is a rare earth element including one or more selected from Nd and Pr and one or more selected from Dy and Tb, T is a combination of Fe and Co, and B is boron. The R-T-B based permanent magnet further includes Zr. A total content of Nd, Pr, Dy, and Tb is 30.00 mass % to 32.20 mass %, Co content is 0.30 mass % to 1.30 mass %, Zr content is 0.21 mass % to 0.85 mass %, and B content is 0.90 mass % to 1.02 mass % with respect to 100 mass % of the R-T-B based permanent magnet.
1. An R-T-B based permanent magnet in which R is a rare earth element including one or more selected from Nd and Pr and one or more selected from Dy and Tb, T is a combination of Fe and Co, and B is boron, wherein
the R-T-B based permanent magnet further includes Zr,
a total content of Nd, Pr, Dy, and Tb is 30.00 mass % to 32.20 mass %,
Co content is 0.30 mass % to 1.30 mass %,
Zr content is 0.21 mass % to 0.85 mass %, and
B content is 0.90 mass % to 1.02 mass % with respect to 100 mass % of the R-T-B based permanent magnet, and
Zr/Co ratio is 0.48 or more and 1.40 or less.
2. The R-T-B based permanent magnet according to claim 1 further including Cu and Cu content is 0.10 mass % to 0.55 mass %.
3. The R-T-B based permanent magnet according to claim 1 further including Mn and Mn content is 0.02 mass % to 0.10 mass %.
4. The R-T-B based permanent magnet according to claim 1 further including Al and Al content is 0.07 mass % to 0.35 mass %.
5. The R-T-B based permanent magnet according to claim 1 further including Ga and Ga content is 0.02 mass % to 0.15 mass %.
6. The R-T-B based permanent magnet according to claim 1 , wherein a content of a heavy rare earth element is 2.0 mass % or less.
7. The R-T-B based permanent magnet according to claim 1 having a concentration gradient of a heavy rare earth element decreasing from a surface towards an inside of the magnet.
8. The R-T-B based permanent magnet according to claim 1 , wherein the Zr/Co ratio is 0.73 or more and 1.40 or less.
9. The R-T-B based permanent magnet according to claim 1 , wherein the Zr content is 0.25 mass % or more and 0.65 mass % or less.
10. The R-T-B based permanent magnet according to claim 1 , wherein the Zr content is 0.31 mass % or more and 0.60 mass % or less.
11. The R-T-B based permanent magnet according to claim 1 , wherein the Co content is 0.30 mass % or more and 0.43 mass % or less.