R-T-B MAGNET AND PREPARATION METHOD THEREFOR

Abstract

Disclosed are an R-T-B magnet and a preparation method therefor. The R-T-B magnet comprises the following components: R29 wt. %, R being a rare earth element and containing Nd, wherein Nd is 22 wt. %; 0.2-0.75 wt. % of Ti+Nb; 0.05-0.45 wt. % of Cu; 0.955-1.15 wt. % of B; and 58-69 wt. % of Fe, wherein wt. % is the ratio of the mass of each component to the total mass of the components; and the mass ratio of Ti to Nb is (1-5):1. According to the present invention, the matching relationship among the added elements in the R-T-B magnet is further optimized, and an R-T-B magnet with better magnetic properties such as relatively high residual magnetization, coercivity, and squareness can be prepared by using the formula.

Claims

1. A R-T-B magnet, characterized by comprising the following components of: 29 wt % of R, said R is a rare earth element comprising Nd, wherein the content of Nd in all components is 22 wt %; 0.2-0.75 wt % of Ti+Nb; 0.05-0.45 wt % of Cu; 0.955-1.15 wt % of B; and 58-69 wt % of Fe, wherein wt % is a ratio of the mass of respective component to the total mass of all components; and the mass ratio of said Ti to said Nb is (1-5):1.

2. The R-T-B magnet according to claim 1, characterized in that: the content of R is 30-32 wt %, such as 30 wt %, 30.6 wt %, 30.7 wt % or 31.2 wt %; and/or the content of Nd is 25-31 wt %, such as 28.5 wt %, 28.7 wt %, 29.1 wt %, 29.2 wt %, 29.3 wt %, 29.5 wt %, 29.7 wt % or 30.4 wt %; and/or the R comprises Pr and/or RH, wherein the RH is a heavy rare earth element; wherein, the content of the Pr is preferably 0.3 wt % or less, such as 0.2 wt %, wherein wt % is the mass percentage of Pr in the total mass of all components; wherein, the content of RH is preferably 2.5 wt % or less, such as 0.5 wt %, 0.8 wt %, 1 wt %, 1.1 wt %, 1.4 wt %, 2 wt %, 2.2 wt %, wherein wt % is the mass percentage of RH in the total mass of all components; wherein, the RH preferably comprises Tb and/or Dy; when the RH comprises Tb, the content of Tb is preferably 0.5-1.4 wt %, such as 0.5 wt %, 0.6 wt %, 0.8 wt %, 1 wt %, 1.1 wt % or 1.4 wt %, wherein wt % is the mass percentage of Tb in the total mass of all components; when the RH comprises Dy, the content of Dy is preferably 0.5-2 wt %, such as 0.5 wt %, 1 wt %, 1.6 wt % or 2 wt %, wherein wt % is the mass percentage of Dy in the total mass of all components; wherein the ratio of the atomic percentage of the RH to the atomic percentage of the R is 0.1 or less, such as 0.02, 0.04 or 0.06.

3. The R-T-B magnet according to claim 1, characterized in that: the content of Ti+Nb is 0.22-0.7 wt %, such as 0.22 wt %, 0.28 wt %, 0.35 wt %, 0.38 wt %, 0.45 wt %, 0.58 wt %, 0.59 wt % or 0.7 wt %, preferably 0.25-0.55 wt %; and/or the mass ratio of Ti to Nb is (1.2-4.8): 1, such as 1.2:1, 1.8:1, 2.5:1, 3.5:1, 3.8:1, 4:1 or 4.8:1, more preferably Ground is (1.5-3.5): 1; and/or the content of Ti is 0.12-0.56 wt %, such as 0.12 wt %, 0.18 wt %, 0.25 wt %, 0.3 wt %, 0.35 wt %, 0.48 wt % or 0.56 wt %; and/or the content of Nb is 0.08-0.14 wt %, such as 0.08 wt %, 0.1 wt %, 0.11 wt % or 0.14 wt %.

4. The R-T-B magnet according to claim 1, characterized in that: the content of Cu is 0.06-0.39 wt %, such as 0.06 wt %, 0.15 wt %, 0.31 wt %, 0.34 wt %, 0.35 wt %, 0.36 wt %, 0.38 wt % or 0.39 wt %; and/or the content of B is 0.98-1.1 wt %, such as 0.99 wt %; and/or the ratio of the atomic percentage of B to the atomic percentage of R in the R-T-B magnet is 0.38 or more, such as 0.4, 0.41, 0.42, 0.43 or 0.44; and/or the content of Fe is 65-69 wt %, such as 66.64 wt %, 67.14 wt %, 67.25 wt %, 67.33 wt %, 67.42 wt %, 67.47 wt %, 67.55 wt %, 67.62 wt %, 67.64 wt %, 67.68 wt %, 67.7 wt %, 67.74 wt %, 67.88 wt %, 67.97 wt % or 68.34 wt %; and/or the R-T-B magnet further comprises Co; wherein, the content of Co is preferably 1.2 wt % or less, such as 0.5 wt % or 1 wt %, wherein wt % is the mass percentage of Co in the total mass of all components.

5. The R-T-B magnet according to claim 1, characterized in that: the R-T-B magnet comprises a Ti.sub.xNb.sub.1 phase, wherein the X is 3-5; the Ti.sub.xNb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.xNb.sub.1 phase to the total area of the main phase particles is 1-2%; wherein, the ratio of the area of the Ti.sub.xNb.sub.1 phase to the total area of the main phase particles is, for example, 1.3%, 1.4%, 1.5%, 1.6% or 1.7%.

6. The R-T-B magnet according to claim 1, characterized in that: the R-T-B magnet comprises the following components of: 29.3 wt % of Nd, 1.4 wt % of Tb, 0.39 wt % of Cu, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.64 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.40%; or the R-T-B magnet comprises the following components of: 29.3 wt % of Nd, 1.4 wt % of Tb, 0.38 wt % of Cu, 0.3 wt % of Ti, 0.08 wt % of Nb, 0.99 wt % of B and 67.55 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.4Nb.sub.1 phase; the Ti.sub.4Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.4Nb.sub.1 phase to the total area of the main phase particles is 1.40%; or the R-T-B magnet comprises the following components of: 29.3 wt % of Nd, 1.4 wt % of Tb, 0.39 wt % of Cu, 0.48 wt % of Ti, 0.11 wt % of Nb, 0.99 wt % of B and 67.33 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.5Nb.sub.1 phase; the Ti.sub.5Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.5Nb phase to the total area of the main phase particles is 1.70%; or the R-T-B magnet comprises the following components of: 29.3 wt % of Nd, 1.4 wt % of Tb, 0.36 wt % of Cu, 0.56 wt % of Ti, 0.14 wt % of Nb, 0.99 wt % of B and 67.25 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.5Nb.sub.1 phase; the Ti.sub.5Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.5Nb.sub.1 phase to the total area of the main phase particles is 1.80%; or the R-T-B magnet comprises the following components of: 29.3 wt % of Nd, 1.4 wt % of Tb, 0.39 wt % of Cu, 0.12 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.7 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.3%; or the R-T-B magnet comprises the following components of: 29.3 wt % of Nd, 1.4 wt % of Tb, 0.34 wt % of Cu, 0.25 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.62 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.5%; or the R-T-B magnet comprises the following components of: 29.3 wt % of Nd, 1.4 wt % of Tb, 0.39 wt % of Cu, 0.35 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.47 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.4Nb.sub.1 phase; the Ti.sub.4Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.4Nb.sub.1 phase to the total area of the main phase particles is 1.6%; or the R-T-B magnet comprises the following components of: Nd 29.3 wt %, Tb 1.4 wt %, Cu 0.31 wt %, Ti 0.48 wt %, Nb 0.1 wt %, B 0.99 wt % and Fe 67.42 wt %, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.5Nb.sub.1 phase; the Ti.sub.5Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.5Nb.sub.1 phase to the total area of the main phase particles is 1.5%; or the R-T-B magnet comprises the following components of: 29.5 wt % of Nd, 1.1 wt % of Tb, 0.39 wt % of Cu, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.74 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.4%; or the R-T-B magnet comprises the following components of: 30.4 wt % of Nd, 0.8 wt % of Tb, 0.39 wt % of Cu, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.14 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.5%; or the R-T-B magnet comprises the following components of: 29.5 wt % of Nd, 0.5 wt % of Tb, 0.39 wt % of Cu, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 68.34 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.3%; or the R-T-B magnet comprises the following components of: 28.7 wt % of Nd, 2 wt % of Dy, 0.39 wt % of Cu, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.64 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.4%; or the R-T-B magnet comprises the following components of: 28.5 wt % of Nd, 0.6 wt % of Tb, 1.6 wt % of Dy, 0.39 wt % of Cu, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.64 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.5%; or the R-T-B magnet comprises the following components of: 29.7 wt % of Nd, 1 wt % of Dy, 0.39 wt % of Cu, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.64 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.4%; or the R-T-B magnet comprises the following components of: 29.2 wt % of Nd, 1 wt % of Tb, 0.5 wt % of Dy, 0.39 wt % of Cu, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.64 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.4%; or the R-T-B magnet comprises the following components of: 29.3 wt % of Nd, 1.4 wt % of Tb, 0.39 wt % of Cu, 0.5 wt %, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.14 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.5%; or the R-T-B magnet comprises the following components of: 29.3 wt % of Nd, 1.4 wt % of Tb, 0.39 wt % of Cu, 1 wt %, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 66.64 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.5%; or the R-T-B magnet comprises the following components of: 29.3 wt % of Nd, 1.4 wt % of Tb, 0.35 wt % of Cu, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.68 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.5%; or the R-T-B magnet comprises the following components of: 29.3 wt % of Nd, 1.4 wt % of Tb, 0.15 wt % of Cu, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.88 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.5%; or the R-T-B magnet comprises the following components of: 29.3 wt % of Nd, 1.4 wt % of Tb, 0.06 wt % of Cu, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.97 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.3%; or the R-T-B magnet comprises the following components of: 29.1 wt % of Nd, 0.2 wt % of Pr, 1.4 wt % of Tb, 0.39 wt % of Cu, 0.18 wt % of Ti, 0.1 wt % of Nb, 0.99 wt % of B and 67.64 wt % of Fe, wherein wt % is the ratio of the mass of respective component to the total mass of all components; the R-T-B magnet comprises a Ti.sub.3Nb.sub.1 phase; the Ti.sub.3Nb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles is 1.5%.

7. A preparation method of a R-T-B magnet, characterized by comprising the steps of subjecting a raw mixture comprising the respective components for the R-T-B magnet according to claim 1 to an aging treatment and then a cooling treatment, wherein: the aging treatment comprises a primary aging treatment and a secondary aging treatment; and the cooling treatment has a rate of 20 C./min or more.

8. The preparation method of the R-T-B magnet according to claim 7, characterized in that: the temperature for the primary aging treatment is 860-920 C., such as 900 C.; and/or the time for the primary aging treatment is 2.5-4 h, such as 3 h; and/or the temperature for the secondary aging treatment is 460-530 C., such as 510 C.; and/or the time for the secondary aging treatment is 2.5-4 h, such as 3 h; and/or the cooling treatment has a rate of 20-40 C./min.

9. The preparation method of the R-T-B magnet according to claim 7, characterized in that the preparation method further comprises the steps of smelting, casting, hydrogen decrepitation, pulverization, magnetic field shaping and sintering treatment before the aging treatment, wherein, the vacuum degree for the smelting is, for example, 510.sup.2 Pa; wherein, the temperature for the melting is, for example, 1550 C. or less; wherein, the temperature for the casting is preferably 1390-1460 C., such as 1450 C.; wherein, the alloy sheet obtained after the casting has a thickness of preferably 0.25-0.40 mm, such as 0.29 mm; wherein, the process of the hydrogen decrepitation preferably comprises hydrogen absorption, dehydrogenation, and a cooling treatment in turn, wherein the hydrogen absorption is preferably carried out under a condition of a hydrogen pressure of 0.085 MPa; the dehydrogenation is preferably carried out under the condition of raising the temperature while evacuating, and the temperature for the dehydrogenation is preferably 480-520 C., For example, 500 C.; wherein, the pulverization is preferably jet mill pulverization; wherein, the magnetic field shaping is preferably carried out under the protection of a nitrogen atmosphere with a magnetic field strength of 1.8 T or more, such as 1.8-2.5 T; wherein, the temperature for the sintering treatment is preferably 1000-1100 C., such as 1080 C.; wherein, the time for the sintering treatment is preferably 4-8 h, such as 6 h; and/or wherein, when the R-T-B magnet comprises a heavy rare earth element, the preparation method further comprises a grain boundary diffusion treatment after the cooling treatment; wherein, the temperature for the grain boundary diffusion treatment is preferably 800-900 C., such as 850 C.; wherein, the time for the grain boundary diffusion is preferably 5-10 h, such as 8 h; wherein, the method of adding heavy rare earth elements in the R-T-B magnet preferably comprises the steps of adding 0-80% of heavy rare earth elements during the smelting and adding the remaining heavy rare earth elements during the grain boundary diffusion; for example, when the heavy rare earth elements in the R-T-B magnet are Tb with a content of greater than 0.5 wt %, 25-50% of Tb is added during the smelting, and the rest is added during the grain boundary diffusion; or, for example, when the heavy rare earth elements in the R-T-B magnet are Tb and Dy, the Tb is added during smelting, and the Dy is added during the grain boundary diffusion; or for example, when the heavy rare earth elements in the R-T-B magnet are Tb with a content of less than or equal to 0.5 wt %, or when the heavy rare earth elements in the R-T-B magnet are Dy, the heavy rare earth elements in the R-T-B magnet are added during the grain boundary diffusion.

10. A R-T-B magnet prepared by the preparation method of the R-T-B magnet according to claim 7.

11. The R-T-B magnet according to claim 2, characterized in that: the R-T-B magnet comprises a Ti.sub.xNb.sub.1 phase, wherein the X is 3-5; the Ti.sub.xNb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.xNb.sub.1 phase to the total area of the main phase particles is 1-2%; wherein, the ratio of the area of the Ti.sub.xNb.sub.1 phase to the total area of the main phase particles is, for example, 1.3%, 1.4%, 1.5%, 1.6% or 1.7%.

12. The R-T-B magnet according to claim 3, characterized in that: the R-T-B magnet comprises a Ti.sub.xNb.sub.1 phase, wherein the X is 3-5; the Ti.sub.xNb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.xNb.sub.1 phase to the total area of the main phase particles is 1-2%; wherein, the ratio of the area of the Ti.sub.xNb.sub.1 phase to the total area of the main phase particles is, for example, 1.3%, 1.4%, 1.5%, 1.6% or 1.7%.

13. The R-T-B magnet according to claim 4, characterized in that: the R-T-B magnet comprises a Ti.sub.xNb.sub.1 phase, wherein the X is 3-5; the Ti.sub.xNb.sub.1 phase is located between a Nd-rich phase and main phase particles; and the ratio of the area of the Ti.sub.xNb.sub.1 phase to the total area of the main phase particles is 1-2%; wherein, the ratio of the area of the Ti.sub.xNb.sub.1 phase to the total area of the main phase particles is, for example, 1.3%, 1.4%, 1.5%, 1.6% or 1.7%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0098] FIG. 1 shows the result of the FE-EPMA detection of the R-T-B magnet in Example 1.

DETAILED DESCRIPTION OF THE INVENTION

[0099] The present invention is further illustrated below by means of examples, but the present invention is not limited to the scope of the examples. The experimental methods not indicating specific conditions in the following examples were carried out according to conventional methods and conditions, or were selected according to the product instructions.

Example 1

[0100] The raw materials were prepared according to the compositions of the R-T-B magnet of Example 1 shown in Table 1 below to obtain a raw material mixture. The raw material mixture (0.4 wt % of Tb in the formula in Table 1 was added during the smelting) was sequentially subjected to smelting, casting, hydrogen crushing, pulverization, magnetic field forming, sintering, aging treatment, cooling treatment and grain boundary diffusion treatment. The raw material mixture did not comprise a heavy rare earth element.

[0101] Among them, the smelting was carried out in a high-frequency vacuum induction melting furnace with a vacuum degree of 5102 Pa, wherein the smelting temperature was 1550 C. or less.

[0102] The casting was carried out by the strip casting process to obtain an alloy sheet with a thickness of 0.29 mm, wherein the casting temperature was 1450 C.

[0103] The hydrogen decrepitation included hydrogen absorption, dehydrogenation, and cooling treatment in sequence. The hydrogen absorption was carried out under the condition of a hydrogen pressure of 0.085 MPa. The dehydrogenation was carried out under the condition of heating while vacuuming, and the dehydrogenation temperature was 500 C.

[0104] The pulverization Process: The pulverization included jet mill pulverization in an atmosphere having an oxidizing gas content of 100 ppm or less. The oxidizing gas refers to oxygen or moisture content. The pressure in the grinding chamber of the jet mill pulverization was 0.68 MPa. After pulverizing, a lubricant, that is, zinc stearate, was added and the addition amount thereof was 0.12% by weight of the powder after mixing.

[0105] The magnetic field shaping was carried out under the protection of a nitrogen atmosphere with a magnetic field strength of 1.8-2.5 T.

[0106] The sintering treatment included sintering under a vacuum condition of 510.sup.3 Pa and 1080 C. for 6 h, and then cooling. Before cooling, Ar gas can be introduced to make the pressure reach 0.05 MPa.

[0107] Aging treatment: the temperature for the primary aging was 900 C., and the time for the primary aging was 3 h: the temperature for the secondary aging was 510 C., and the time for the secondary aging was 3 h.

[0108] The rate of the cooling treatment was 20 C./min.

[0109] Grain boundary diffusion treatment: the remaining heavy rare earth elements (1 wt % Tb) were melted and attached on the surface of the material, and grain boundary diffusion was carried out at 850 C. for 8 h.

[0110] 2. The raw material formula and the rate of cooling treatment for the R-T-B magnets in Examples 2-21 and Comparative Examples 1-8 are as shown in Table 1, and the rest of the preparation process is the same as in Example 1. In Examples 2-10, 16-21 and Comparative Examples 1-8, 0.4 wt % of Tb was added during smelting, and the remaining Tb was diffused into the R-T-B magnets through grain boundary diffusion. In Example 11, 0.4 wt % of Tb was diffused into the R-T-B magnet only through grain boundary diffusion. In Example 13 and Example 15, Tb was added during smelting, while Dy was diffused into the R-T-B magnet through grain boundary diffusion.

[0111] Table 1 Components and contents (wt %) of the R-T-B magnets Effect Example 1

1. Determination of Components

[0112] The R-T-B magnets in Examples 1-21 and Comparative Examples 1-8 were measured using a high-frequency inductively coupled plasma optical emission spectrometer (ICP-OES). The test results are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Components and contents (wt %) of the R-T-B magnets Rate of Ti + Ti/ Cooling Nd Pr Tb Dy Cu Co Ti Nb B Fe Nb Nb Treatment Example 1 29.3 / 1.4 / 0.39 / 0.18 0.1 0.99 67.64 0.28 1.8 20 C./min Example 2 29.3 / 1.4 / 0.38 / 0.3 0.08 0.99 67.55 0.38 3.8 20 C./min Example 3 29.3 / 1.4 / 0.39 / 0.48 0.11 0.99 67.33 0.59 4.4 20 C./min Example 4 29.3 / 1.4 / 0.36 / 0.56 0.14 0.99 67.25 0.7 4 20 C./min Example 5 29.3 / 1.4 / 0.39 / 0.12 0.1 0.99 67.7 0.22 1.2 20 C./min Example 6 29.3 / 1.4 / 0.34 / 0.25 0.1 0.99 67.62 0.35 2.5 20 C./min Example 7 29.3 / 1.4 / 0.39 / 0.35 0.1 0.99 67.47 0.45 3.5 20 C./min Example 8 29.3 / 1.4 / 0.31 / 0.48 0.1 0.99 67.42 0.58 4.8 20 C./min Example 9 29.5 / 1.1 / 0.39 / 0.18 0.1 0.99 67.74 0.28 1.8 20 C./min Example 10 30.4 / 0.8 / 0.39 / 0.18 0.1 0.99 67.14 0.28 1.8 20 C./min Example 11 29.5 / 0.5 / 0.39 / 0.18 0.1 0.99 68.34 0.28 1.8 20 C./min Example 12 28.7 / 0 2 0.39 / 0.18 0.1 0.99 67.64 0.28 1.8 20 C./min Example 13 28.5 / 0.6 1.6 0.39 / 0.18 0.1 0.99 67.64 0.28 1.8 20 C./min Example 14 29.7 / 0 1 0.39 / 0.18 0.1 0.99 67.64 0.28 1.8 20 C./min Example 15 29.2 / 1 0.5 0.39 / 0.18 0.1 0.99 67.64 0.28 1.8 20 C./min Example 16 29.3 / 1.4 / 0.39 0.5 0.18 0.1 0.99 67.14 0.28 1.8 20 C./min Example 17 29.3 / 1.4 / 0.39 1 0.18 0.1 0.99 66.64 0.28 1.8 20 C./min Example 18 29.3 / 1.4 / 0.35 / 0.18 0.1 0.99 67.68 0.28 1.8 20 C./min Example 19 29.3 / 1.4 / 0.15 / 0.18 0.1 0.99 67.88 0.28 1.8 20 C./min Example 20 29.3 / 1.4 / 0.06 / 0.18 0.1 0.99 67.97 0.28 1.8 20 C./min Example 21 29.1 0.2 1.4 / 0.39 / 0.18 0.1 0.99 67.64 0.28 1.8 20 C./min Comparative 29.3 / 1.4 / 0.39 / 0.12 0.16 0.99 67.64 0.28 0.8 20 C./min Example 1 Comparative 29.3 / 1.4 / 0.39 / 0.6 0.11 0.99 67.21 0.71 5.5 20 C./min Example 2 Comparative 29.3 / 1.4 / 0.39 / 0.03 0.12 0.99 67.77 0.15 0.3 20 C./min Example 3 Comparative 29.3 / 1.4 / 0.39 / 0.6 0.2 0.99 67.12 0.8 3 20 C./min Example 4 Comparative 29.3 / 1.4 / 0.39 / 0.18 0.1 0.99 67.64 0.28 1.8 15 C./min Example 5 Comparative 29.3 / 1.4 / 0.39 / 0.18 0.1 0.99 67.64 0.28 1.8 10 C./min Example 6 Comparative 29.3 / 1.4 / 0 / 0.18 0.1 0.99 68.03 0.28 1.8 20 C./min Example 7 Comparative 29.3 / 1.4 / 0.48 / 0.18 0.1 0.99 67.55 0.28 1.8 20 C./min Example 8 Note: / indicates that this element is not comprised. Ga and Zr were not detected in the R-T-B magnets of the above-mentioned Examples and Comparative Examples. C, O, Mn and Al were inevitably introduced into the R-T-B magnet of the final product during the preparation process. The contents described in the respective Examples and Comparative Examples do not include these impurities.

2. Testing for Magnetic Performance

[0113] The R-T-B magnets in Examples 1-21 and Comparative Examples 1-8 were tested by using a PFM pulsed BH demagnetization curve testing equipment to obtain the data of remanence (Br), intrinsic coercivity (Hcj), maximum energy product (BHmax) and squareness (Hk/Hcj). The testing results are shown in Table 2 below.

TABLE-US-00002 TABLE 2 20 C. Br 20 C. Hcj 20 C. BHmax (kGs) (kOe) (MGOe) 20 C. Hk/Hcj Example 1 14.22 27.8 48.1 0.99 Example 2 14.19 27.9 47.9 0.99 Example 3 14.14 28.0 47.6 0.99 Example 4 14.12 28.1 47.5 0.99 Example 5 14.23 27.3 48.2 0.98 Example 6 14.2 27.9 48 0.99 Example 7 14.18 27.9 47.9 0.98 Example 8 14.15 28.0 47.7 0.99 Example 9 14.31 26.5 48.8 0.99 Example 10 14.5 25.0 50.1 0.99 Example 11 14.69 23.5 51.4 0.99 Example 12 13.99 24.0 46.6 0.98 Example 13 14 28.5 46.7 0.99 Example 14 14.27 21.4 48.5 0.99 Example 15 14.15 26.5 47.7 0.99 Example 16 14.24 27.4 48.3 0.99 Example 17 14.23 27.9 48.2 0.99 Example 18 14.22 28.1 48.1 0.99 Example 19 14.22 27.2 48.1 0.99 Example 20 14.22 27.0 48.1 0.99 Example 21 14.22 27.9 48.1 0.99 Comparative 14.22 25.8 48.1 0.99 Example 1 Comparative 14.22 25.6 48.1 0.99 Example 2 Comparative 14.22 25.7 48.1 0.99 Example 3 Comparative 14.22 25.9 48.1 0.99 Example 4 Comparative 14 26.5 46.7 0.93 Example 5 Comparative 14 26.7 46.7 0.88 Example 6 Comparative 14.22 24.8 48.1 0.96 Example 7 Comparative 14.22 25.3 48.1 0.94 Example 8

3. Testing for Microstructures

FE-EPMA Detection:

[0114] The vertically oriented faces of the R-T-B magnets in Examples 1-21 and Comparative Examples 1-8 were polished, and tested by using a Field Emission Electron Probe Microanalyzer (FE-EPMA) (JEOL, 8530F). Firstly, the distribution of Ti and Nb in the R-T-B magnets was determined by surface scanning using FE-EPMA. Then, the contents of Ti and Nb in the Ti.sub.xNb.sub.1 phase (x is 3-5) were determined by single-point quantitative analysis using FE-EPMA. The test conditions included an accelerating voltage of 15 kv and a probe beam current of 50 nA.

[0115] FIG. 1 shows the element distributions and contents of the R-T-B magnet in Example 1 detected by FE-EPMA. After single-point quantitative analysis, it is clear that a Ti.sub.3Nb.sub.1 phase was formed between the main phase particles and the Nd-rich phase in the R-T-B magnet in Example 1 of the present invention. In addition, the ratio of the area of the Ti.sub.3Nb.sub.1 phase to the total area of the main phase particles was 1.4%. The area of the Ti.sub.3Nb.sub.1 phase and the total area of the main phase particles respectively refer to the area thereof occupied in the cross-section (that is, the vertically oriented face as mentioned above) of the detected R-T-B magnet during FE-EPMA detection. The testing results of FE-EPMA for the R-T-B magnets prepared in Examples 1-21 and Comparative Examples 1-8 are shown in Table 3 below.

TABLE-US-00003 TABLE 3 Area Structure Percentage of Phase of Phase Example 1 Ti.sub.3Nb.sub.1 1.4 Example 2 Ti.sub.4Nb.sub.1 1.4 Example 3 Ti.sub.5Nb.sub.1 1.7 Example 4 Ti.sub.5Nb.sub.1 1.8 Example 5 Ti.sub.3Nb.sub.1 1.3 Example 6 Ti.sub.3Nb.sub.1 1.5 Example 7 Ti.sub.4Nb.sub.1 1.6 Example 8 Ti.sub.5Nb.sub.1 1.5 Example 9 Ti.sub.3Nb.sub.1 1.4 Example 10 Ti.sub.3Nb.sub.1 1.5 Example 11 Ti.sub.3Nb.sub.1 1.3 Example 12 Ti.sub.3Nb.sub.1 1.4 Example 13 Ti.sub.3Nb.sub.1 1.5 Example 14 Ti.sub.3Nb.sub.1 1.4 Example 15 Ti.sub.3Nb.sub.1 1.4 Example 16 Ti.sub.3Nb.sub.1 1.5 Example 17 Ti.sub.3Nb.sub.1 1.5 Example 18 Ti.sub.3Nb.sub.1 1.5 Example 19 Ti.sub.3Nb.sub.1 1.5 Example 20 Ti.sub.3Nb.sub.1 1.3 Example 21 Ti.sub.3Nb.sub.1 1.5 Comparative Example 1 Ti.sub.3Nb.sub.1 1 Comparative Example 2 Ti.sub.5Nb.sub.1 0.9 Comparative Example 3 Ti.sub.4Nb.sub.1 0.8 Comparative Example 4 Ti.sub.3Nb.sub.1 0.9 Comparative Example 5 / / Comparative Example 6 / / Comparative Example 7 Ti.sub.3Nb.sub.1 0.9 Comparative Example 8 Ti.sub.3Nb.sub.1 0.8 Note: / indicates that the phase was not formed.

[0116] From the above experimental data, it can be seen that the remanence, coercivity, and squareness or the like of the magnet materials prepared according to the formula for R-T-B magnet designed by the inventors are all at a relatively high level, and its comprehensive magnetic properties are excellent, which are suitable for applications in areas with high demands. After further analysis of the microstructure, the inventors found that after the R-T-B magnets with the above specific formula as magnet materials were prepared, a Ti.sub.xNb.sub.1 phase (x is 3-5) with a specific area percentage was formed between the main phase particles and the Nd-rich phase, and the existence of this specific phase significantly improves the magnetic properties of the magnet materials, especially the intrinsic coercivity Hcj.