Nd-Fe-B rare earth permanent magnet material
A rare earth permanent magnet material is based on an R—Fe—Co—B—Al—Cu system wherein R is at least one element selected from Nd, Pr, Dy, Tb, and Ho, 15 to 33% by weight of Nd being contained. At least two compounds selected from M-B, M-B—Cu and M-C compounds (wherein M is Ti, Zr or Hf) and an R oxide have precipitated within the alloy structure as grains having an average grain size of up to 5 μm which are uniformly distributed in the alloy structure at intervals of up to 50 μm.
1. A rare earth permanent magnet material consists essentially of, in % by weight:
27 to 33% of R, wherein R is at least one element selected from the group consisting of Nd, Pr, Dy, Tb, and Ho, including 15 to 33% by weight of Nd,
0.1 to 10% of Co,
0.8 to 1.5% of B,
0.05 to 1.0% of Al,
0.02 to 1.0% of Cu,
0.02 to 1.0% of an element selected from Ti, Zr and Hf,
0.123 to 0.3% of C,
0.04 to 0.4% of O,
0.002 to 0.1% of N, and
the balance of Fe and incidental impurities,
wherein (i) at least two compounds selected from the group consisting of an M-B based compound, an M-B—Cu based compound, and an M-C based compound, wherein M is at least one metal selected from the group consisting of Ti, Zr, and Hf, and
(ii) an R oxide have precipitated within the alloy, and the precipitated compounds have an average grain size of up to 5 μm and are distributed in the alloy at a maximum interval of up to 50 μm between adjacent precipitated compounds.
2. The permanent magnet material of claim 1 wherein an R 2 Fe 14 B i phase is present as a primary phase component in a volumetric proportion of 89 to 99%, and borides, carbides and oxides of rare earth or rare earth and transition metal are present in a total volumetric proportion of 0.1 to 3%.
3. The permanent magnet material of claim 1 wherein abnormally grown giant grains of R 2 Fe 14 B i phase having a grain size of at least 50 μm are present in a volumetric proportion of up to 3% based on the overall metal structure.
4. The permanent magnet material of claim 1 , exhibiting magnetic properties including a remanence Br of at least 12.5 kG, a coercive force iHc of at least 10 kOe, and a squareness ratio 4×(BH)max/Br 2 of at least 0.95.
5. The permanent magnet material of claim 1 wherein the R—Fe—Co—B—Al—Cu system alloy contains 0.132 to 0.3% by weight of C.
6. The permanent magnet material of claim 1 wherein the R—Fe—Co—B—Al—Cu system alloy contains 0.141 to 0.3% by weight of C.
7. The permanent magnet material of claim 1 wherein the R—Fe—Co—B—Al—Cu system alloy contains 0.132 to 0.3% by weight of C.
8. The permanent magnet material of claim 1 wherein the R—Fe—Co—B—Al—Cu system alloy contains 0.141 to 0.3% by weight of C.
9. The permanent magnet material of claim 1 wherein R is at least one element selected from the group consisting of Nd, Dy, Tb, and Ho.
10. The permanent magnet material of claim 1 wherein R is Pr and at least one element selected from the group consisting of Nd, Dy, Tb and Ho, and the alloy contains 0.123 to 0.3% by weight of C.
11. The permanent magnet material of claim 1 wherein (i) all of the M-B based compound, the M-B based compound, and the M-B—Cu based compound, and the M-C based compound, wherein M is at least one metal selected from the group consisting of Ti, Zr, and Hf and (ii) the R oxide have precipitated within the alloy.