A neodymium iron boron magnet with XRD characteristic peaks and a preparation method thereof

Abstract

The present invention discloses a neodymium iron boron magnet having XRD characteristic peaks and a preparation method thereof. Using Cu-Kα radiation, the neodymium iron boron magnet has at least one characteristic peak in the range of 39.0° to 39.5° in terms of 2θ angle in X-ray diffraction. By adjusting the crystal structure of the neodymium iron boron magnet, the present invention can reduce the saturation magnetostriction performance of the magnet while maintaining good coercivity.

Description

Technical Field

[0001] The present invention belongs to the field of neodymium iron boron magnets, and particularly relates to a neodymium iron boron magnet with XRD characteristic peaks and a preparation method thereof. Background Art

[0002] As the most widely used rare earth permanent magnet material today, since its advent in the 1980s, the neodymium iron boron permanent magnet material has been widely used in many fields such as the automotive industry, medical equipment, electronic information, and aerospace due to its excellent magnetic properties and extremely high cost performance, and has become a key support for the development of related fields towards intelligence, miniaturization, and lightweight.

[0003] In high-precision fields such as aerospace, the magnetostrictive performance of materials is also an important parameter for measuring material stability. Magnetostriction refers to the elongation or shortening of the length of a material in the magnetization direction as the magnetic field changes when the object is in a magnetic field. Due to the magnetostrictive effect, the neodymium iron boron material will undergo micro-deformation or generate sound energy in an electromagnetic field environment, which will affect its associated equipment. Therefore, it is particularly important to reduce the influence of its magnetostriction. For neodymium iron boron materials, their magnetostrictive performance is affected by various factors, including material composition, structure, preparation process, and temperature, etc.

[0004] With the development of sintered neodymium iron boron technology, its magnetic properties have been continuously improved, which puts higher requirements on the microstructure of neodymium iron boron. The emergence of the rapid solidification casting sheet technology can optimize the microstructure of the neodymium iron boron ingot, which has an important impact on subsequent powder making, orientation, sintering process, powder properties, and the microstructure of the final sintered magnet, and also affects its magnetostrictive performance. Early research showed that through the rapid solidification casting sheet technology, the appearance of α-Fe in the rapid solidification casting sheet can be avoided, the size of the 2:14:1 phase flaky crystal can be reduced, and the Nd-rich phase can be evenly distributed, which has an important role in improving its magnetic properties. However, there is currently a lack of research on the specific crystal growth rate, and it is difficult to control the crystal structure of the rapid solidification casting sheet through a suitable crystal growth rate, which affects the microstructure of the final neodymium iron boron magnet, thereby reducing the magnetostrictive performance of the magnet. Summary of the Invention

[0005] In order to improve the above technical problems, the present invention provides a Re-Fe-B-M series neodymium iron boron magnet. By mass percentage,

[0006] Re is selected from at least one of Nd, Pr, Dy, Tb, Ho, Gd, Ce, La, and Y, and its mass percentage is: 25-35wt%;

[0007] The mass percentage of B is: 0.8-1.5wt%;

[0008] M is selected from at least one of Al, Ti, Cu, Ga, Zr, Co, Nb, Si, Mn, Sn, V and Se, and its mass percentage is: 0 - 3 wt%;

[0009] The balance is Fe and inevitable impurity elements;

[0010] Using Cu-Kα radiation, the X-ray diffraction of the Re-Fe-B-M series neodymium iron boron magnet expressed in 2θ angle has at least one characteristic peak at 39.0° to 39.5°.

[0011] According to an embodiment of the present invention, the Re element in the Re-Fe-M-B neodymium iron boron magnet preferably contains Nd and Pr elements, and the M element preferably contains Cu and Ga elements. In one embodiment, the Re element is composed of Nd and Pr elements, and the M element is composed of Cu and Ga elements.

[0012] According to an embodiment of the present invention, the mass percentage of the M element in the neodymium iron boron magnet is 0 - 3 wt%, for example, greater than 0 and not exceeding 1.5 wt%.

[0013] According to an embodiment of the present invention, the mass percentages (wt%) of Nd, Pr, Cu, and Ga elements in the Re-Fe-B-M series neodymium iron boron magnet are W Nd , W Pr , W Cu , W Ga , and the interplanar spacing corresponding to the characteristic peak is d (Å), satisfying the relational expression ①:

[0014] Relational expression ① 0.5×sin(W Pr / W Nd ) + 0.5×cos(W Cu / W Ga ) + arctan(W Cu / W Ga ) / π×d = y;

[0015] 0.9 < y < 1.2;

[0016] W Nd , W Pr , W Cu , W G and d are not zero.

[0017] According to an embodiment of the present invention, 18 wt% ≤ W Nd ≤ 25 wt%, for example, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%.

[0018] According to an embodiment of the present invention, 7 wt% ≤ W Pr ≤ 10 wt%, and examples are 7 wt%, 8 wt%, 9 wt%, 10 wt%.

[0019] According to an embodiment of the present invention, 0.1 wt% ≤ W Cu ≤ 0.5 wt%, for example 0.15 wt% ≤ W Cu ≤ 0.4 wt%, and examples are 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%.

[0020] According to an embodiment of the present invention, 0.15 wt% < W Ga ≤ 0.8 wt%, for example 0.2 wt% ≤ W Ga ≤ 0.6 wt%, and examples are 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, 0.5 wt%, 0.55 wt%.

[0021] According to an embodiment of the present invention, 0 < d ≤ 3, for example 0.5 < d ≤ 2.5, and examples are 1, 1.5, 2, 2.1, 2.2, 2.3, 2.4.

[0022] According to an embodiment of the present invention, y is 0.91, 0.95, 0.97, 0.98, 1.0 or 1.1.

[0023] According to an embodiment of the present invention, the c-axis / orientation axis saturation magnetostriction coefficient of the Re-Fe-B-M system neodymium iron boron magnet is greater than 10 ppm and less than 40 ppm, preferably greater than 25 ppm and less than 30 ppm, for example 28.0 - 29.5 ppm.

[0024] According to an embodiment of the present invention, the Re-Fe-B-M system neodymium iron boron magnet is prepared by a method including a melting process of raw materials, and in the melting process, the radius R (m) of the quenching roll, the width H (m) of the quenching roll, the rotational speed ω (r / s) of the quenching roll, and the molten steel flow rate L (m 3 / s) satisfy relation ②:

[0025] Relation ② 0.08 < L / (0.3R × H × ω) 2 < 0.12.

[0026] According to an embodiment of the present invention, the coercivity of the Re-Fe-B-M system neodymium iron boron magnet is not less than 1360 kA / m, for example 1375 - 1400 kA / m.

[0027] The present invention also provides a method for preparing a Re-Fe-B-M series neodymium iron boron magnet, including a melting process of raw materials. In the melting process, the radius R (m) of the quenching roll, the width H (m) of the quenching roll, the rotational speed ω (r / s) of the quenching roll, and the molten steel flow rate L (m 3 / s) satisfy the relational expression ②:

[0028] Relational expression ②: 0.08 < L / (0.3R×H×ω) 2 < 0.12.

[0029] According to an embodiment of the present invention, the melting process includes: first subjecting the raw materials to vacuum melting, then pouring them on the surface of the quenching roll, and finally dropping them into a water-cooled disk to obtain alloy scales.

[0030] According to an embodiment of the present invention, for the radius R of the quenching roll, 0.4 m ≤ R ≤ 0.6 m, such as 0.4 m, 0.5 m.

[0031] According to an embodiment of the present invention, for the width H of the quenching roll, 0.4 m ≤ H ≤ 0.6 m, such as 0.4 m, 0.5 m.

[0032] According to an embodiment of the present invention, for the rotational speed ω of the quenching roll, 0.5 r / s ≤ ω ≤ 1.5 r / s, such as 0.7 r / s, 0.75 r / s, 1.4 r / s.

[0033] According to an embodiment of the present invention, for the molten steel flow rate L, 1.5E-04 (m 3 / s) ≤ L ≤ 8.0 E-04 (m 3 / s), such as 1.5E-04 (m 3 / s), 2.00E-04 (m 3 / s), 8.00E-04 (m 3 / s).

[0034] According to an embodiment of the present invention, the raw materials include Nd, Pr, Cu, and Ga elements, and the Nd, Pr, Cu, and Ga elements satisfy the above limitations.

[0035] According to an embodiment of the present invention, the raw materials further include B, Fe, and / or M elements, which also satisfy the above limitations.

[0036] According to an embodiment of the present invention, the preparation method further includes: a powder-making process, a molding process, a heat treatment process, and / or a diffusion process.

[0037] According to an embodiment of the present invention, the Re-Fe-B-M series neodymium iron boron magnet has the limitations as shown above.

[0038] The term "at least one" means one or more than two.

[0039] Beneficial effects:

[0040] By adjusting the crystal structure of the neodymium-iron-boron magnet, the present invention reduces the saturation magnetostriction performance of the magnet while maintaining good coercivity.

[0041] In addition, the present invention also controls the relationship between the radius, width, rotation speed of the quenching roller and the molten steel flow rate during the melting process, so that the crystal growth rate is appropriate to obtain a neodymium-iron-boron magnet with the required crystal structure. Description of the drawings

[0042] Figure 1 XRD diffraction spectra of Examples 1-3 and Comparative Examples 1-4. Detailed implementation manners

[0043] [Preparation of neodymium-iron-boron magnet]

[0044] According to the implementation manner of the present invention, the melting process includes: the raw materials are first subjected to vacuum melting, then poured on the surface of the quenching roller, and then fall into the water-cooled disk to obtain alloy scales;

[0045] For example, the temperature of the vacuum melting is 1400~1600°C (exemplarily 1500°C).

[0046] According to the implementation manner of the present invention, the powder-making process includes: performing hydrogen explosion treatment on the alloy scales, with a hydrogen absorption pressure of 20 MPa, and then performing rough ball milling and jet milling to obtain jet-milled powder with a D50 of 1.5~5μm.

[0047] According to the implementation manner of the present invention, the molding process includes: filling the jet-milled powder into a vacuum press module, performing orientation molding in a magnetic field strength of 2T, and then obtaining a green body after cold isostatic pressing.

[0048] According to the implementation manner of the present invention, the heat treatment process includes: subjecting the green body to vacuum sintering and aging treatment to obtain the neodymium-iron-boron magnet;

[0049] For example, heating is performed at a rate of 2~10°C / min to 1000~1150°C for vacuum sintering, and the sintering time is 3~10h.

[0050] The technical solution of the present invention will be further described in detail below with specific examples. It should be understood that the following examples are only for illustrative explanation of the present invention and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection of the present invention.

[0051] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

[0052] Testing method:

[0053] The sintered Nd-Fe-B magnets prepared in the following examples and comparative examples of the present invention were tested for XRD and magnetostrictive properties. The testing equipment and methods used are as follows:

[0054] X-ray diffraction (XRD) test: Rigaku SmartLab X-ray powder diffractometer, 2θ scanning angle 10 - 90°, Cu target Kα ray, voltage 40 kV, current 40 mA.

[0055] d (Å) is the interplanar spacing corresponding to the characteristic peak within 39.0° to 39.5°, obtained from the XRD spectrum peak position.

[0056] Magnetostriction coefficient: CZS-3600 type material magnetostriction measuring instrument, the saturation magnetostriction coefficient in the orientation direction was measured under a 2T magnetic field.

[0057] Example 1

[0058] The raw materials were configured according to the partial composition table of the Re-Fe-B-M system Nd-Fe-B magnet in Example 1 in Table 1 (unit: wt%). The contents of Nd, Pr, Cu, and Ga satisfy the relationship ①. At the same time, the raw materials also include M element, B element, and Fe element.

[0059] The M element consists of 1.0 wt% Co, 0.5 wt% Al, 0.1 wt% Ti, and 0.05 wt% Zr. The B element is 1.0 wt%, and the balance is Fe. The sintered Nd-Fe-B magnet was prepared by the following preparation method:

[0060] The above raw materials were first vacuum melted at 1500 °C, then poured on the surface of a chill roll, and then fell into a water-cooled disc to obtain alloy flakes. Among them, the radius R of the chill roll, the width H of the chill roll, the rotation speed ω of the chill roll, and the steel liquid flow rate L are shown in Table 2.

[0061] The as-obtained rapidly solidified flakes were subjected to hydrogen explosion treatment, and the hydrogen absorption pressure was 20 MPa. Then, rough grinding was carried out by ball milling, and subsequently, jet milling was carried out to obtain jet mill powder with a target particle size D50 = 2.9 μm.

[0062] The above jet mill powder was filled into a vacuum press mold, and orientation pressing was carried out in a magnetic field with a magnetic field strength of 2T. Then, isostatic pressing at 170 MPa was carried out to obtain a green compact. The above green compact was placed in a vacuum sintering furnace and heated to 1070 °C at a rate of 5 °C / min. The sintering temperature was controlled at 1070 °C, and sintering was carried out for 5 h. After aging treatment, the rare earth permanent magnet of this example was obtained.

[0063] The crystal structure and magnetostrictive properties of the NdFeB magnet of this embodiment were detected by using the above-described test method. Figure 1 It is shown that the NdFeB magnet of Example 1 has a characteristic peak at 39.28°, and the crystal plane spacing corresponding to the characteristic peak is d = 2.291 Å; Table 3 shows that the NdFeB magnet of Example 1 has a low saturation magnetostriction coefficient and a high coercivity.

[0064] Example 2

[0065] The raw materials were configured according to the composition table of the Re-Fe-B-M series NdFeB magnet of Example 2 in Table 1 (the units are all wt%), and the raw materials also included element M, element B, and element Fe. Element M consisted of Co 1.0 wt%, Al 0.5 wt%, Ti 0.1 wt%, and Zr 0.05 wt%. Element B was 1.0 wt%, and the balance was Fe. The sintered NdFeB magnet was prepared by using the following preparation method:

[0066] The above raw materials were first vacuum melted at 1500 °C, then poured on the surface of a chill roll, and then fell into a water-cooled disk to obtain alloy flakes; for the radius R of the chill roll, the width H of the chill roll, the rotational speed ω of the chill roll, and the steel liquid flow rate L, refer to Table 2.

[0067] The above-obtained rapidly solidified flakes were subjected to hydrogen explosion treatment, and the hydrogen absorption pressure was 20 MPa. Then, rough grinding was carried out by ball milling, and subsequently, jet milling was carried out to obtain jet-milled powder with a target particle size D50 = 2.9 μm.

[0068] The above jet-milled powder was filled into a vacuum press mold, and orientation pressing was carried out in a magnetic field with a magnetic field strength of 2 T, and then an isostatic pressing of 170 MPa was carried out to obtain a green compact. The above green compact was placed in a vacuum sintering furnace and heated to 1070 °C at a rate of 5 °C / min, and the sintering temperature was controlled at 1070 °C and sintered for 5 h. After aging treatment, the rare earth permanent magnet of this embodiment was obtained.

[0069] The crystal structure and magnetostrictive properties of the NdFeB magnet of this embodiment were detected by using the above-described test method. Figure 1 It is shown that the NdFeB magnet of Example 2 has a characteristic peak at 39.27°, and the crystal plane spacing corresponding to the characteristic peak is d = 2.292 Å; Table 3 shows that the NdFeB magnet of Example 2 has a low saturation magnetostriction coefficient and a high coercivity.

[0070] Example 3

[0071] Prepare raw materials according to the composition table of the Re-Fe-B-M series neodymium iron boron magnet in Example 3 of Table 1 (the units are all wt%), and the raw materials also include element M, element B and element Fe. Element M consists of 1.0 wt% Co, 0.5 wt% Al, 0.1 wt% Ti and 0.05 wt% Zr. Element B is 1.0 wt%, and the balance is Fe. And prepare a sintered neodymium iron boron magnet by the following preparation method:

[0072] First, vacuum melt the above raw materials at 1500 °C, then pour them on the surface of a chill roll, and then let them fall into a water-cooled disk to obtain alloy flakes. For the radius R of the chill roll, the width H of the chill roll, the rotation speed ω of the chill roll, and the molten steel flow rate L, refer to Table 2.

[0073] Perform hydrogen explosion treatment on the obtained rapidly solidified flakes, and the hydrogen absorption pressure is 20 MPa. Then perform rough ball milling, and then perform jet milling to obtain jet mill powder with a target particle size D50 = 2.9 μm.

[0074] Fill the above jet mill powder into a vacuum press mold, perform orientation pressing in a magnetic field, the magnetic field strength is 2 T, and then obtain a green compact through isostatic pressing at 170 MPa. Place the above green compact in a vacuum sintering furnace, heat it up to 1070 °C at a rate of 5 °C / min, control the sintering temperature at 1070 °C for sintering for 5 h, and perform aging treatment to obtain the rare earth permanent magnet of this example.

[0075] Detect the crystal structure and magnetostrictive properties of the neodymium iron boron magnet of this example by using the test method described above. Figure 1 It shows that the neodymium iron boron magnet of Example 3 has a characteristic peak at 39.32°, and the lattice plane spacing d corresponding to the characteristic peak is 2.289 Å; Table 3 shows that the neodymium iron boron magnet of Example 3 has a low saturation magnetostrictive coefficient and a high coercivity.

[0076] Comparative Example 1

[0077] The raw material composition of this comparative example is the same as that of Example 1. The difference in the manufacturing method from Example 1 is that the radius R of the chill roll, the width H of the chill roll, the rotation speed ω of the chill roll, and the molten steel flow rate L are adjusted, and their parameters do not satisfy the relational expression ②. For details, refer to Table 2.

[0078] Detect the crystal structure and magnetostrictive properties of the neodymium iron boron magnet of this comparative example by using the test method described above. Figure 1 It shows that for the neodymium iron boron magnet of Comparative Example 1, no characteristic peak was found in the X-ray diffraction represented by the 2θ angle within 39.0° to 39.5°; Table 3 shows that the neodymium iron boron magnet of Comparative Example 1 has a relatively high saturation magnetostrictive coefficient and a relatively low coercivity.

[0079] Comparative Example 2

[0080] The difference from Example 1 is that the ratio of Nd, Pr, Cu, and Ga elements in the raw material composition is adjusted, and the Fe element is adjusted accordingly, while the ratios of other elements remain unchanged. See Table 1 for details. The manufacturing method of this comparative example is the same as that of Comparative Example 1, that is, it does not satisfy relationship ②. By changing the element ratios, it still satisfies relationship ① even without characteristic peaks.

[0081] The crystal structure and magnetostrictive properties of the Nd-Fe-B magnet of this comparative example were detected using the testing method described above. Figure 1 It shows that the Nd-Fe-B magnet of Comparative Example 2 did not show characteristic peaks within the range of 39.0° to 39.5° in the X-ray diffraction expressed in 2θ angle; Table 3 shows that the Nd-Fe-B magnet of Comparative Example 2 has a relatively high saturation magnetostriction coefficient and a relatively low coercive force.

[0082] Comparative Example 3

[0083] The difference from Example 1 is that the ratios of Pr, Cu, and Ga elements in the raw material composition are adjusted, and the Fe element is adjusted accordingly, while the ratios of other elements remain unchanged. See Table 1 for details. The change in the composition ultimately results in this example not satisfying relationship ①.

[0084] The crystal structure and magnetostrictive properties of the Nd-Fe-B magnet of this comparative example were detected using the testing method described above. Figure 1 It shows that the Nd-Fe-B magnet of Comparative Example 3 did not show characteristic peaks within the range of 39.0° to 39.5° in the X-ray diffraction expressed in 2θ angle; Table 3 shows that the Nd-Fe-B magnet of Comparative Example 3 has a relatively high saturation magnetostriction coefficient and a relatively low coercive force.

[0085] Comparative Example 4

[0086] The difference from Example 1 is that: only the ratios of Pr, Cu, and Ga elements in the raw material composition are adjusted, the Fe element is adjusted accordingly, and the ratios of other elements remain unchanged (see Table 1 for details), and the radius R of the chill roll, the width H of the chill roll, the rotational speed ω of the chill roll, and the molten steel flow rate L are also adjusted (see Table 2 for details). This comparative example does not satisfy relationship ① and does not satisfy relationship ② either.

[0087] The crystal structure and magnetostrictive properties of the Nd-Fe-B magnet of this comparative example were detected using the testing method described above. Figure 1 It shows that the Nd-Fe-B magnet of Comparative Example 4 did not show characteristic peaks within the range of 39.0° to 39.5° in the X-ray diffraction expressed in 2θ angle; Table 3 shows that the Nd-Fe-B magnet of Comparative Example 4 has a relatively high saturation magnetostriction coefficient and a relatively low coercive force.

[0088] Table 1 Partial raw materials and ratios (wt%) of Nd-Fe-B magnets

[0089]

[0090] Table 2 Quenching roll parameters and molten steel flow rate

[0091]

[0092] Table 3 Saturation magnetostriction coefficient

[0093]

[0094] Through appropriate compositions and appropriate process parameters, a specific crystal structure is formed in the magnet. This specific crystal structure also makes the XRD test spectrum of the magnet have characteristic peaks in the range of 39.0° to 39.5°. The inventor found that this specific crystal structure can maintain good coercivity while reducing the saturation magnetostriction performance.

[0095] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A Re-Fe-BM system NdFeB magnet, characterized in that: In terms of mass percentage, Re is selected from at least one of Nd, Pr, Dy, Tb, Ho, Gd, Ce, La, and Y, and its mass percentage is: 25-35wt%; B mass percentage: 0.8-1.5wt%; M is selected from at least one of Al, Ti, Cu, Ga, Zr, Co, Nb, Si and Mn, and its mass percentage is: 0-3wt%; The balance is Fe and unavoidable impurity elements; The Re-Fe-BM system NdFeB magnet has at least one characteristic peak at 39.0° to 39.5° in X-ray diffraction expressed in 2θ angle using Cu—Kα radiation.

2. The Re-Fe-BM system NdFeB magnet according to claim 1, characterized in that: The Re contains at least Nd and Pr, and the M contains at least Cu and Ga; The mass percentages (wt%) of Nd, Pr, Cu and Ga in the NdFeB magnet are W Nd , W Pr , W Cu , W Ga , of which 18wt% <W Nd ≤25wt%,7wt%≤W Pr <10wt%, 0.1wt%≤W Cu ≤0.5wt%, 0.15wt% <W Ga ≤0.8wt%.

3. A method for preparing a Re-Fe-BM system NdFeB magnet, characterized in that: Using Cu-Kα radiation, the Re-Fe-BM system NdFeB magnet has at least one characteristic peak at 39.0° to 39.5° in X-ray diffraction expressed in 2θ angles; The preparation method comprises a smelting process of Re-Fe-BM series NdFeB magnet raw materials; The raw materials include Nd, Pr, Cu and Ga elements, and the weight percentage (wt%) of Nd, Pr, Cu and Ga elements in the Re-Fe-BM system NdFeB magnet is W Nd , W Pr , W Cu , W Ga The ingredients are prepared, and the interplanar spacing corresponding to the characteristic peak is d (Å), satisfying the relationship ①: Relationship ① 0.5×sin(W Pr / W Nd ) + 0.5×cos(W Cu / W Ga ) + arctan(W Cu / W Ga ) / π×d = y 0.9< y <1.2； W Nd , W Pr , W Cu , W G Both d and d are not 0; The quenching roller radius R (m), the quenching roller width H (m), the quenching roller speed ω (r / s) and the molten steel flow rate L (m 3 / s) satisfies the relationship ②: Relationship ② 0.08 < L / (0.3R×H×ω) 2 < 0.

12.

4. The preparation method according to claim 3, characterized in that: Re also contains at least one of Dy, Tb, Ho, Gd, Ce, La, and Y, and the mass percentage of Re is: 25-35wt%; B mass percentage: 0.8-1.5wt%; M further comprises at least one of Al, Ti, Zr, Co, Nb, Si and Mn, and the mass percentage of M is: 0-3wt%; The balance is Fe and inevitable impurity elements.

5. The preparation method according to claim 3 or 4, characterized in that: 0＜d≤3。 6. The preparation method according to claim 3 or 4, characterized in that: 18wt%≤W Nd ≤25wt%, 7wt%≤W Pr ≤10wt%,0.15wt%≤W Cu ≤0.4wt%, 0.2wt%≤W Ga ≤0.6wt%, and / or, 0<d≤2.

5.

7. The preparation method according to claim 3, characterized in that: The smelting process comprises: the raw materials are firstly smelted in vacuum, then poured on the surface of a quenching roller, and finally fall into a water-cooled disc to obtain alloy flakes.

8. The preparation method according to claim 3, characterized in that: The radius R of the cooling roller is 0.4m≤R≤0.6m; The width H of the chill roll is 0.4m≤H≤0.6m; The speed of the cooling roller ω, 0.5r / s≤ω≤1.5r / s; And / or, the molten steel flow rate L, 1.5E-04 (m 3 / s)≤L≤8.0 E-04(m 3 / s).

9. The preparation method according to claim 3, characterized in that: The preparation method further comprises: a powder making process, a pressing process, a heat treatment process and / or a diffusion treatment process.

10. The preparation method according to claim 3, characterized in that: The coercive force of the Re-Fe-BM system NdFeB magnet is not less than 1360 kA / m, and / or the c-axis / orientation axis saturation magnetostriction coefficient of the Re-Fe-BM system NdFeB magnet is greater than 10 ppm and less than 40 ppm.

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