Rare earth magnet and manufacturing method thereof

Abstract

The present disclosure provides a rare earth magnet and manufacturing method thereof, which belongs to the field of rare earth magnet technology. The diffusion source is coated on the NdFeB base material, which is diffused and aged to obtain NdFeB magnet. The diffusion source alloy is R.sub.αM.sub.βB.sub.γFe.sub.100-α-β-γ, wherein R refers to at least one of Nd and Pr, and M Refers to at least one of Al, Cu, Ga. The Br reduction range is lower than 0.03 T, and Hcj growth is more than 318 kA/m.

Claims

1. A rare earth magnet, wherein the rare earth magnet is a NdFeB magnet, and the NdFeB magnet comprises a main phase, a grain boundary phase and a rare earth-rich phase, wherein the grain boundary phase comprises a μ phase and a δ phase, the μ phase is R.sub.36.5Fe.sub.63.5-xM.sub.x, 1≤x≤4; the δ phase is R.sub.32.5Fe.sub.67.5-yM.sub.y, 2≤y≤20, wherein R refers to at least two elements selected from Nd, Pr, Ce and La, and M refers to at least two elements selected from Al, Cu and Ga; wherein the proportions are given in atomic percentages.

2. A method for preparing a rare earth magnet according to claim 1, wherein it comprises the following steps, (S1) the preparation of a diffusion source: providing a diffusion source alloy of chemical formula R.sub.aM.sub.βB.sub.γFe.sub.100-α-β-γ, wherein 10≤α≤80, 15≤β≤90, 0.1≤γ≤3, R is at least one of Nd and Pr, and M is at least one of Al, Cu and Ga; the diffusion source alloy is treated by aging to form the diffusion source, then is treated by hydrogen absorption and dehydrogenation; wherein the proportions are given in mass percentage; (S2) the preparation of NdFeB base material: preparing main alloy and auxiliary alloy of NdFeB magnet base material, the chemical formula of the mixed alloy of the main alloy and the auxiliary alloy is R.sub.αM.sub.bB.sub.cFe.sub.100-a-b-c, wherein 27≤a≤33, 1≤b≤4, 0.8≤c≤1.2, R refers to one or more of Nd, Pr, Ce and La, and M refers to one or more of Al, Cu, Ga, Ti, Zr, Co, Mg, Zn, Nb, Mo and Sn, the remaining component is Fe; wherein the proportions are given in mass percentage; (S3) a diffusion source film layer is coated on the NdFeB base material, which is diffused and aged to obtain NdFeB magnet.

3. The method for preparing a rare earth magnet according to claim 2, wherein in step (S2), the NdFeB base material flakes are mixed with lubricants under hydrogen treatment, and grounded by airflow grinding to prepare mixed powders; then, the mixed powders are pressed, formed and sintered to obtain the NdFeB magnet base material.

4. The method for preparing a rare earth magnet according to claim 2, wherein in step (S1), the diffusion source is powder form and the preparation method of the diffusion source is atomized comminuting process, amorphous throwing belt milling process or ingot milling process.

5. The method for preparing a rare earth magnet according to claim 2, wherein in step (S1), the hydrogen absorption temperature is 50-200° C., and the dehydrogenation temperature is 450-550° C.

6. The method for preparing a rare earth magnet according to claim 3, wherein powder particle size of the airflow grinding is 2-5 μm.

7. The method for preparing a rare earth magnet according to claim 4, wherein powder particle size of the diffusion source is 3-60 μm.

8. The method for preparing a rare earth magnet according to claim 2, wherein in step (S3) the method of coating is one of magnetron sputtering coating, evaporation coating and silk screening coating.

9. The method for preparing a rare earth magnet according to claim 3, wherein the temperature of sintering process for preparing the NdFeB magnet base material is 980-1060° C., sintering time is 6-15 h.

10. The method for preparing a rare earth magnet according to claim 2, wherein in step (S3), diffusion temperature is 800-910° C., diffusion time is 6-30 h, and first-stage aging temperature is 700-850° C., first-level aging time is 2-10 h, second-level aging temperature is 450-600° C., and second-level aging time is 3-10 h.

11. A rare earth magnet prepared by the method according to claim 2.

12. The rare earth magnet according to claim 11, wherein the rare earth magnet is a NdFeB magnet, and the NdFeB magnet comprises a main phase, a grain boundary phase and a rare earth-rich phase, wherein the grain boundary phase comprises a μ phase and a δ phase, the μ phase is R.sub.36.5Fe.sub.63.5M.sub.x, 1≤x≤4; the 6 phase is R.sub.32.5Fe.sub.67.5-yM.sub.y, 2≤y≤20, wherein R refers to at least two elements selected from Nd, Pr, Ce and La, and M refers to at least two elements selected from Al, Cu and Ga; wherein the proportions are given in atomic percentages.

Description

DETAILED DESCRIPTION

[0029] The principles and features are described in the present disclosure, and the examples given are only used to explain the present disclosure and are not intended to limit the scope of the present disclosure.

[0030] General Concept There is provided a method of preparing NdFeB rare earth magnet, including the following steps: [0031] (S1) Diffusion source production: diffusion source alloy composition was made up, which is as shown in Table 1; put into a vacuum melting furnace for melting, pouring to form an alloy sheet, and after cooling to 50° C., it was discharged; the average thickness of the alloy sheet is within the range of 0.25-1 mm, the content of C and O elements in the alloy sheet is ≤200 ppm, and the N content is ≤50 ppm. The alloy sheet was treated with hydrogen absorption and dehydrogenation, in which the hydrogen absorption temperature was 50-200° C. and the dehydrogenation temperature was 450-550° C. [0032] (S2) NdFeB base alloy composition was made up, as shown in Table 2, which is put into vacuum melting furnace for melting, pouring to form a thin sheet, and after cooled to 50° C., it was discharged; the average thickness of the sheet is 0.25 mm, The C, O content is ≤200 ppm, the N content ≤50 ppm. The NdFeB base material flakes and lubricants are mixed for hydrogen treatment and then grinded to powders with size of 2-5 μm by argon gas. The NdFeB powder is put into an automatic press, pressed into blanks under a magnetic field, and packaged into blocks. The rough steak is put into the sintering furnace to get NdFeB base alloy, the sintering temperature is 980-1060° C., and the sintering time is 6-15 h. Finally, NdFeB base alloy is cut into strips. [0033] (S3) The diffusion source prepared in step (S1) is prepared into slurry, and the diffusion source slurry is coated with a film on the NdFeB base metal, and then diffusion and aging treatment are carried out to obtain the NdFeB magnet. Diffusion and aging treatment are carried out to obtain NdFeB magnet, specific process conditions and the performance of NdFeB magnet is shown in Table 1.

[0034] In order to verify the present scheme, sixteen pairs of examples and comparative examples are designed and the difference between the proportion and the embodiment is as follows: The diffusion source of the comparative examples have no the components of B and Fe which are removed from the examples and placed in a vacuum melting furnace melting, pouring to form a thin sheet, and after cooling to 50° C., it was discharged; the thickness of the sheet is 0.25-1 mm, content of C and O≤200 ppm, content of N≤50 ppm. The composition and process conditions of the comparative examples are shown in Table 3.

[0035] Based on the above data, the light rare earth magnet is obtained by diffusion source alloy R.sub.αM.sub.βB.sub.γFe.sub.100-α-β-γ. Light rare earth magnets of all examples have ΔHcj of more than 318 kA/m significantly after diffusion. Residual magnetic reduction of light rare earth magnets of examples is significantly lower than that of comparative examples.

[0036] Therefore, the examples and comparative examples are specifically analyzed as follows:

[0037] Example 1 and Comparative example 1: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc.

[0038] Example 1 shows Br=1.400 T, Hcj=1711.4 kA/m, containing μ phase and δ phase and Comparative example 1 shows Br=1.360 T, Hcj=1592 kA/m, only containing δ phase. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0039] Example 2 and Comparative example 2: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 2 shows Br=1.400 T, Hcj=1830.8 kA/m, containing μ phase and δ phase and Comparative example 2 shows Br=1.350 T, Hcj=1671.6 kA/m, only containing δ phase. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0040] Example 3 and Comparative example 3: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 3 shows Br=1.320 T, Hcj=1950.2 kA/m, containing μ phase and δ phase and Comparative example 3 shows Br=1.290 T, Hcj=1791.00 kA/m, only containing δ phase. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0041] Example 4 and Comparative example 4: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 4 shows Br=1.330 T, Hcj=1990 k/m, containing μ phase and δ phase and Comparative example 4 shows Br=1.280 T, Hcj=1751.2 kA/m, only containing δ phase. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0042] Example 5 and Comparative example 5: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 5 shows Br=1.325 T, Hcj=1910.4 kA/m, containing μ phase and δ phase and Comparative example 5 shows Br=1.270 T, Hcj=1751.2 kA/m. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0043] Example 6 and Comparative example 6: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 6 shows Br=1.335 T, Hcj=1990 k/m, containing μ phase and δ phase and Comparative example 6 shows Br=1.30 T, Hcj=1671.6 kA/m. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0044] Example 7 and Comparative example 7: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 7 shows Br=1.347 T, Hcj=1950.2 kA/m, containing μ phase and δ phase and Comparative example 7 shows Br=1.31 T, Hcj=1711.4 kA/m, only containing δ phase. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example. Example 8 and Comparative example 8: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 8 shows Br=1.35 T, Hcj=1910.4 kA/m, containing μ phase and δ phase and Comparative example 8 shows Br=1.3 T, Hcj=1631.8 kA/m, only containing δ phase. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0045] Example 9 and Comparative example 9: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 9 shows Br=1.29 T, Hcj=2029.8 kA/m, containing μ phase and δ phase and Comparative example 9 shows Br=1.25 T, Hcj=1870.6 kA/m, only containing δ phase. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0046] Example 10 and Comparative example 10: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 10 shows Br=1.345 T, Hcj=2029.8 kA/m, containing μ phase and δ phase and Comparative example 10 shows Br=1.3 T, Hcj=1870.6 kA/m, only containing δ phase. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0047] Example 11 and Comparative example 11: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 11 shows Br=1.38 T, Hcj=1830.8 kA/m, containing μ phase and δ phase and Comparative example 11 shows Br=1.34 T, Hcj=1671.6 kA/m, only containing δ phase. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0048] Example 12 and Comparative example 12: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 12 shows Br=1.37 T, Hcj=1910.40 kA/m, containing μ phase and δ phase and Comparative example 12 shows Br=1.32 T, Hcj=1751.0 kA/m. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0049] Example 13 and Comparative example 13: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 13 shows Br=1.23 T, Hcj=1990 kA/m, containing μ phase and δ phase and Comparative example 13 shows Br=1.2 T, Hcj=1830.8 kA/m, only containing δ phase. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0050] Example 14 and Comparative example 14: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 14 shows Br=1.25 T, Hcj=1910.4 kA/m, containing μ phase and δ phase and Comparative example 14 shows Br=1.23 T, Hcj=1751.2 kA/m. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0051] Example 15 and Comparative example 15: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 15 shows Br=1.335 T, Hcj=1830.8 kA/m, containing μ phase and δ phase and Comparative example 15 shows Br=1.29 T, Hcj=1631.8 kA/m. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0052] Example 16 and Comparative example 16: The NdFeB magnet base alloy are diffused at the same composition and size, the same diffusion and aging temperature etc. Example 16 shows Br=1.325 T, Hcj=2029.8 kA/m, containing μ phase and δ phase and Comparative example 16 shows Br=1.28 T, Hcj=1870.6 kA/m, only containing δ phase. Br (residual magnetism) and Hcj (coercivity) advantages of the Example is significantly improved compared to the Comparative Example.

[0053] The foregoing is only a better embodiment of the present disclosure and is not intended to limit the present disclosure, where any modification, equivalent substitution, improvement, etc. made within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.

TABLE-US-00001 TABLE 1 Diffusion sources, process conditions and characteristics of the NdFeB magnet base alloy after diffusion about Examples. 2.sup.nd Performance after Whether Whether Diff. 1.sup.st Aging Diffusion contains contains Example Diffussion Size Temp. time Aging time Temp. time Hk/ μ δ No. source mm ° C. h Temp. h ° C. h Br Hcj Hcj phase phase 1 Nd: 70%, Al: 15%, 10*10*3 850 15 700 2 450 10 1.400 1711.40 0.95 yes yes B: 3%, Fe: Margin 2 Pr: 65%, Cu: 25%, 10*10*5 800 25 700 3 480 7 1.400 1830.80 0.94 yes yes B: 2%, Fe: Margin 3 Nd: 60%, Al: 15%, 10*10*4 850 10 700 5 480 5 1.320 1950.20 0.94 yes yes Cu: 15%, B: 3%, Fe: Margin 4 Pr: 30%, Al: 50%, 10*10*6 900 25 750 8 500 10 1.330 1990.00 0.95 yes yes Ga: 10%, B: 2%, Fe: Margin 5 Pr: 50%, Ga: 15%, 10*10*4 860 15 750 10 520 3 1.325 1910.40 0.96 yes yes Cu: 30%, B: 1%, Fe: Margin 6 Nd: 80%, Cu: 15%, 10*10*3 850 10 750 2 600 4 1.335 1990.00 0.95 yes yes B: 0.5%, Fe: Margin 7 Pr: 80%, Ga: 15%, 10*10*4 880 10 750 3 540 3 1.347 1950.20 0.94 yes yes B: 0.1%, Fe: Margin 8 Pr: 70%, Ga: 10%, 10*10*3 900 10 750 5 500 8 1.350 1910.40 0.95 yes yes Cu: 15%, B: 0.8%, Fe: Margin 9 Pr: 50%, Cu: 40%, 10*10*5 900 15 800 8 490 6 1.290 2029.80 0.94 yes yes B: 2%, Fe: Margin 10 Pr: 60%, Al: 20%, 10*10*5 910 15 800 10 450 5 1.345 2029.80 0.95 yes yes Cu: 15%, B: 0.5%, Fe: Margin 11 Pr: 65%, Al: 15%, 10*10*7 900 30 800 2 500 10 1.380 1830.80 0.95 yes yes Cu: 15%, B: 1%, Fe: Margin 12 Nd: 30%, Pr: 40%, 10*10*8 910 30 800 3 480 8 1.370 1910.40 0.95 yes yes Cu: 20%, B: 1%, Fe: Margin 13 Nd: 50%, Cu: 20%, 10*10*4 900 15 850 5 450 8 1.230 1990.00 0.95 yes yes Al: 20%, B: 2%, Fe: Margin 14 Nd: 45%, Cu: 30%, 10*10*5 900 7 850 8 500 6 1.250 1910.40 0.94 yes yes Al: 10%, B: 1%, Fe: Margin 15 Nd: 60%, Cu: 15%, 10*10*4 900 8 850 10 530 4 1.335 1830.80 0.95 yes yes Ga: 15%, B: 4%, Fe: Margin 16 Pr: 70%, Cu: 10%, 10*10*6 910 20 850 3 470 10 1.325 2029.80 0.94 yes yes Al: 15%, B: 0.5%, Fe: Margin

TABLE-US-00002 TABLE 2 Composition of NdFeB base alloy and its performance Composition of NdFeB base alloy wt % Performance R M Br Hcj Hk/ Number Pr Nd Cu AI Ga Co Ti Zr Fe B T kA/m Hcj 1 8.58 21.71 0.16 0.17 0.27 0.85 0.02 0.00 Margin 0.90 1.430 1384.24 0.99 2 3.99 26.55 0.13 0.14 0.32 0.46 0.02 0.07 Margin 0.88 1.430 1424.84 0.99 3 4.08 26.55 0.16 0.19 0.26 0.81 0.12 0.00 Margin 0.89 1.358 1592.80 0.98 4 7.60 23.62 0.38 0.28 0.37 0.76 0.09 0.00 Margin 0.87 1.360 1604.74 0.99 5 6.09 25.44 0.14 0.34 0.52 0.93 0.18 0.00 Margin 0.91 1.355 1576.08 0.98 6 6.98 24.00 0.19 0.33 0.42 0.86 0.10 0.00 Margin 0.90 1.366 1502.05 0.99 7 6.70 24.10 0.23 0.25 0.28 0.94 0.07 0.00 Margin 0.87 1.376 1472.60 0.98 8 7.45 24.03 0.23 0.34 0.29 0.91 0.08 0.00 Margin 0.89 1.380 1488.52 0.99 9 4.50 26.55 0.16 0.50 0.39 0.81 0.04 0.09 Margin 0.89 1.320 1671.60 0.98 10 8.34 22.87 0.16 0.35 0.44 1.58 0.08 0.00 Margin 0.87 1.365 1576.08 0.99 11 8.84 21.47 0.21 0.20 0.30 1.45 0.04 0.00 Margin 0.90 1.420 1393.00 0.98 12 6.56 23.48 0.14 0.20 0.37 0.43 0.06 0.00 Margin 0.90 1.398 1498.07 0.99 13 0.00 32.80 0.25 0.95 0.20 1.50 0.00 0.00 Margin 1.10 1.260 1393.00 0.99 14 0.00 32.80 0.15 0.95 0.20 1.50 0.00 0.00 Margin 1.00 1.270 1353.20 0.99 15 6.30 25.20 0.15 0.60 0.20 0.50 0.10 0.00 Margin 0.91 1.360 1353.20 0.98 16 8.21 23.60 0.16 0.35 0.35 0.74 0.15 0.00 Margin 0.86 1.342 1694.68 0.99

TABLE-US-00003 TABLE 3 Diffusion sources, process conditions and characteristics of the NdFeB magnet base alloy after diffusion about Comparative Examples. Performance after Whether Whether Comparative Diffusion Holding Aging Holding Diffusion contains contains Example Diffussion Size Temp. time Temp. time Br Hcj Hk/ μ δ No. source mm ° C. h ° C. h T kA/m Hcj phase phase 1 Nd: 85%, Al: 15% 10*10*3 850 15 450 10 1.360 1592.00 0.95 No yes 2 Pr: 75%, Cu: 25% 10*10*5 800 25 480 7 1.3 1671.60 0.95 No yes 3 Nd: 70%, Al: 15%, 10*10*4 850 10 480 5 1.290 1791.00 0.94 No yes Cu: 15% 4 Pr: 40%, Al: 50%, 10*10*6 900 25 500 10 1.280 1751.20 0.95 No yes Ga: 10% 5 Pr: 55%, Ga: 15%, 10*10*4 860 15 520 3 1.270 1751.20 0.95 No No Cu: 30% 6 Nd: 85%, Cu: 15% 10*10*3 850 10 600 4 1.300 1671.60 0.96 No No 7 Pr: 85%, Ga: 15% 10*10*4 880 10 540 3 1.310 1711.40 0.94 No yes 8 Pr: 75%, Ga: 10%, 10*10*3 900 10 500 8 1.300 1631.80 0.96 No yes Cu: 15% 9 Pr: 60%, Cu: 40% 10*10*5 900 15 490 6 1.250 1870.60 0.94 No yes 10 Pr: 65%, Al: 20%, 10*10*5 910 15 450 5 1.300 1870.60 0.94 No yes Cu: 15% 11 Pr: 70%, Al: 15%, 10*10*7 900 30 500 10 1.340 1671.60 0.95 No yes Cu: 15% 12 Nd: 40%, Pr: 40%, 10*10*8 910 30 480 8 1.320 1751.20 0.94 No No Cu: 20% 13 Nd: 60%, Cu: 20%, 10*10*4 850 15 450 8 1.200 1830.80 0.95 No yes Al: 20% 14 Nd: 60%, Cu: 30%, 10*10*5 900 7 500 6 1.230 1751.20 0.94 No No Al: 10% 15 Nd: 70%, Cu: 15%, 10*10*4 850 8 530 4 1.290 1631.80 0.95 No No Ga: 15% 16 Pr: 75%, Cu: 10%, 10*10*6 910 20 470 10 1.280 1870.60 0.94 No yes Al: 15%