Neodymium iron boron magnet with XRD (X-Ray Diffraction) characteristic peak and preparation method thereof

Abstract

The invention discloses a neodymium-iron-boron magnet with XRD (X-Ray Diffraction) characteristic peaks and a preparation method thereof. By using Cu-K alpha radiation, the neodymium iron boron magnet has at least one characteristic peak at 39.0-39.5 degrees in X-ray diffraction represented by a 2 theta angle. By adjusting the crystal structure of the neodymium-iron-boron magnet, the saturation magnetostrictive property of the magnet is reduced, and meanwhile good coercive force is kept.

Description

Technical Field

[0001] The invention belongs to the field of NdFeB magnets, and in particular relates to a NdFeB magnet with XRD characteristic peaks and a preparation method thereof. Background Art

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

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

[0004] With the development of sintering NdFeB technology, its magnetic properties are constantly improving, which puts higher requirements on the microstructure of NdFeB. The emergence of rapid solidification casting technology can optimize the microstructure of NdFeB ingots, which has an important impact on the subsequent powder making, orientation, sintering process, powder properties and the organizational structure of the final sintered magnet, and will also affect its magnetostrictive properties. Early studies have shown that the rapid solidification casting technology can avoid the appearance of α-Fe in the rapid solidification casting, reduce the size of the 2:14:1 phase lamellar crystals, and make the Nd-rich phase evenly distributed, which plays 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 through a suitable crystal growth rate, which affects the microstructure of the final NdFeB magnet and reduces the magnetostrictive properties of the magnet. Summary of the invention

[0005] In order to improve the above technical problems, the present invention provides a Re-Fe-BM system NdFeB magnet, which is calculated by 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, Mn, Sn, V and Se, and its mass percentage is: 0-3wt%; The balance is Fe and unavoidable impurity elements; The X-ray diffraction of the Re-Fe-BM system NdFeB magnet using Cu-Kα radiation has at least one characteristic peak at 39.0° to 39.5° in terms of 2θ angle.

[0006] According to an embodiment of the present invention, the Re element in the Re-Fe-MB NdFeB magnet preferably includes Nd and Pr elements, and the M element preferably includes 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.

[0007] According to an embodiment of the present invention, the mass percentage of the M element in the NdFeB magnet is 0-3wt%, for example, greater than 0 and not more than 1.5wt%.

[0008] According to an embodiment of the present invention, the mass percentages (wt%) of Nd, Pr, Cu and Ga elements in the Re-Fe-BM system NdFeB magnet are W Nd , W Pr , W Cu , W Ga , the interplanar spacing corresponding to the characteristic peak is d (Å), which satisfies 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.

[0009] According to an embodiment of the present invention, 18wt%≤W Nd ≤25wt%, exemplified by 18wt%, 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, and 25wt%.

[0010] According to an embodiment of the present invention, 7wt%≤W Pr ≤10wt%, exemplified by 7wt%, 8wt%, 9wt%, and 10wt%.

[0011] According to an embodiment of the present invention, 0.1wt%≤W Cu ≤0.5wt%, e.g. 0.15wt%≤WCu ≤0.4wt%, exemplified by 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%.

[0012] According to an embodiment of the present invention, 0.15wt% <W Ga ≤0.8wt%, e.g. 0.2wt%≤W Ga ≤0.6wt%, exemplified by 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, and 0.55wt%.

[0013] According to an embodiment of the present invention, 0<d≤3, for example, 0.5<d≤2.5, exemplified by 1, 1.5, 2, 2.1, 2.2, 2.3, 2.4.

[0014] According to an embodiment of the present invention, y is 0.91, 0.95, 0.97, 0.98, 1.0 or 1.1.

[0015] According to an embodiment of the present invention, 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, preferably greater than 25 ppm and less than 30 ppm, for example, 28.0-29.5 ppm.

[0016] According to an embodiment of the present invention, the Re-Fe-BM system NdFeB magnet is prepared by a method including a smelting process of raw materials, wherein 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: Relation ② 0.08 <L / (0.3R×H×ω) 2 <0.12.

[0017] According to an embodiment of the present invention, the coercive force of the Re-Fe-BM series NdFeB magnet is not less than 1360 kA / m, for example, 1375-1400 kA / m.

[0018] The present invention also provides a method for preparing Re-Fe-BM series NdFeB magnets, comprising a raw material smelting process, wherein 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: Relation ② 0.08 <L / (0.3R×H×ω) 2 <0.12.

[0019] According to an embodiment of the present invention, the smelting process comprises: the raw materials are firstly vacuum smelted, then poured on the surface of a quenching roller, and then dropped into a water-cooled disc to obtain alloy flakes.

[0020] According to an embodiment of the present invention, the radius R of the chill roll is 0.4m≤R≤0.6m, for example, 0.4m, 0.5m.

[0021] According to an embodiment of the present invention, the width H of the chill roll is 0.4m≤H≤0.6m, such as 0.4m, 0.5m.

[0022] According to an embodiment of the present invention, the speed of rotation of the chill roller ω is 0.5r / s≤ω≤1.5r / s, for example, 0.7r / s, 0.75r / s, 1.4r / s.

[0023] According to the embodiment of the present invention, the molten steel flow rate L, 1.5E-04 (m 3 / s)≤L≤8.0 E-04(m 3 / s), for example 1.5E-04 (m 3 / s)、2.00E-04(m 3 / s)、8.00E-04(m 3 / s).

[0024] According to an embodiment of the present invention, the raw material includes Nd, Pr, Cu, and Ga elements, and the Nd, Pr, Cu, and Ga elements meet the above-mentioned definitions.

[0025] According to an embodiment of the present invention, the raw material further includes B, Fe and / or M elements, which also meet the above definition.

[0026] According to an embodiment of the present invention, the preparation method further comprises: a powder making process, a pressing process, a heat treatment process, and / or a diffusion process.

[0027] According to an embodiment of the present invention, the Re-Fe-BM series NdFeB magnet has the above-mentioned definitions.

[0028] The term "at least one" means one or more than two.

[0029] Beneficial effects: The invention adjusts the crystal structure of the NdFeB magnet to reduce the saturation magnetostriction performance of the magnet while maintaining good coercive force.

[0030] In addition, the present invention controls the relationship between the quench roller radius, the quench roller width, the quench roller rotation speed and the molten steel flow rate during the smelting process to make the crystal growth rate appropriate, thereby obtaining a NdFeB magnet with a desired crystal structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The XRD diffraction spectra of Examples 1-3 and Comparative Examples 1-4 are shown. DETAILED DESCRIPTION

[0032] [Preparation of NdFeB magnets] According to an embodiment of the present invention, the smelting process comprises: the raw material is first vacuum smelted, then poured on the surface of a quenching roller, and then falls into a water-cooled disc to obtain alloy flakes; For example, the temperature of the vacuum melting is 1400-1600° C. (exemplarily 1500° C.).

[0033] According to an embodiment of the present invention, the powder making process comprises: subjecting the alloy flakes to hydrogen explosion treatment with a hydrogen absorption pressure of 20 MPa, followed by ball milling and air flow milling to obtain air flow milled powder with a D50 of 1.5 to 5 μm.

[0034] According to an embodiment of the present invention, the pressing process comprises: filling the air flow milled powder into a vacuum press module, performing orientation pressing in a magnetic field with a field strength of 2T, and then obtaining a green body after cold isostatic pressing.

[0035] According to an embodiment of the present invention, the heat treatment process comprises: vacuum sintering and aging treatment of the green body to obtain the NdFeB magnet; For example, the temperature is raised to 1000-1150°C at a rate of 2-10°C / min for vacuum sintering, and the sintering time is 3-10 hours.

[0036] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0037] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0038] Test method: The sintered NdFeB magnets prepared in the following examples and comparative examples of the present invention were tested for XRD and magnetostrictive properties, and the testing equipment and methods used were as follows: X-ray diffraction (XRD) test: Japan Rigaku XRD X-ray polycrystal diffractometer SmartLab, 2θ scanning angle 10-90°, Cu target Kα ray, voltage 40kV, current 40mA.

[0039] d (Å) is the interplanar spacing corresponding to the characteristic peak within 39.0° to 39.5°, which is obtained based on the peak position of the XRD spectrum.

[0040] Magnetostriction coefficient: CZS-3600 material magnetostriction measuring instrument, the saturation magnetostriction coefficient in the orientation direction is measured under 2T magnetic field.

[0041] Example 1 The raw materials are configured according to the partial composition table of the Re-Fe-BM system NdFeB magnet of Example 1 in Table 1 (all in wt%), wherein the contents of Nd, Pr, Cu and Ga satisfy the relationship ①, and the raw materials also include M element, B element and Fe element. The M element is composed of Co 1.0wt%, Al 0.5wt%, Ti 0.1wt% and Zr 0.05wt%, the B element is 1.0wt%, and the balance is Fe. The sintered NdFeB magnet is prepared by the following preparation method: The above raw materials were first vacuum melted at 1500°C, then poured on the surface of a quenching roller, and finally dropped into a water-cooled disc to obtain alloy flakes; wherein, the quenching roller radius R, the quenching roller width H, the quenching roller speed ω and the molten steel flow rate L are shown in Table 2.

[0042] The quick-setting flakes obtained above were subjected to hydrogen explosion treatment with a hydrogen absorption pressure of 20 MPa, followed by ball milling and then jet milling to obtain jet milled powder with a target particle size of D50 = 2.9 μm.

[0043] The jet milled powder is filled into a vacuum press mold, oriented and pressed in a magnetic field with a magnetic field strength of 2T, and then isostatically pressed at 170MPa to obtain a green compact. The green compact is placed in a vacuum sintering furnace, heated to 1070°C at a rate of 5°C / min, sintered at a controlled sintering temperature of 1070°C, sintered for 5h, and subjected to aging treatment to obtain the rare earth permanent magnet of this embodiment.

[0044] The crystal structure and magnetostrictive properties of the NdFeB magnet of this embodiment were tested using the test method described above. Figure 1 It shows that the NdFeB magnet of Example 1 has a characteristic peak at 39.28°, and the interplanar spacing d corresponding to the characteristic peak is 2.291 Å; Table 3 shows that the NdFeB magnet of Example 1 has a low saturation magnetostriction coefficient and a high coercive force.

[0045] Example 2 The raw materials are configured according to the composition table of the Re-Fe-BM system NdFeB magnet of Example 2 in Table 1 (all in wt%), and the raw materials also include M element, B element and Fe element, M element is composed of Co 1.0wt%, Al 0.5wt%, Ti 0.1wt%, Zr0.05wt%, B element is 1.0wt%, and the balance is Fe. The sintered NdFeB magnet is prepared by the following preparation method: The above raw materials are first vacuum melted at 1500°C, then poured on the surface of a quenching roller, and finally dropped into a water-cooled disc to obtain alloy flakes; wherein the quenching roller radius R, the quenching roller width H, the quenching roller speed ω, and the molten steel flow rate L are shown in Table 2.

[0046] The quick-setting flakes obtained above were subjected to hydrogen explosion treatment with a hydrogen absorption pressure of 20 MPa, followed by ball milling and then jet milling to obtain jet milled powder with a target particle size of D50 = 2.9 μm.

[0047] The jet milled powder is filled into a vacuum press mold, oriented and pressed in a magnetic field with a magnetic field strength of 2T, and then isostatically pressed at 170MPa to obtain a green compact. The green compact is placed in a vacuum sintering furnace, heated to 1070°C at a rate of 5°C / min, sintered at a controlled sintering temperature of 1070°C, sintered for 5h, and subjected to aging treatment to obtain the rare earth permanent magnet of this embodiment.

[0048] The crystal structure and magnetostrictive properties of the NdFeB magnet of this embodiment were tested using the test method described above. Figure 1 It shows that the NdFeB magnet of Example 2 has a characteristic peak at 39.27°, and the interplanar spacing d corresponding to the characteristic peak is 2.292 Å; Table 3 shows that the NdFeB magnet of Example 2 has a low saturation magnetostriction coefficient and a high coercive force.

[0049] Example 3 The raw materials are configured according to the composition table of the Re-Fe-BM system NdFeB magnet of Example 3 in Table 1 (all in wt%), and the raw materials also include M element, B element and Fe element, M element is composed of Co 1.0wt%, Al 0.5wt%, Ti 0.1wt% and Zr 0.05wt%, B element is 1.0wt%, and the balance is Fe. The sintered NdFeB magnet is prepared by the following preparation method: The above raw materials are first vacuum melted at 1500°C, then poured on the surface of a quenching roller, and finally dropped into a water-cooled disc to obtain alloy flakes, wherein the quenching roller radius R, the quenching roller width H, the quenching roller speed ω, and the molten steel flow rate L are shown in Table 2.

[0050] The quick-setting flakes obtained above were subjected to hydrogen explosion treatment with a hydrogen absorption pressure of 20 MPa, followed by ball milling and then jet milling to obtain jet milled powder with a target particle size of D50 = 2.9 μm.

[0051] The jet milled powder is filled into a vacuum press mold, oriented and pressed in a magnetic field with a magnetic field strength of 2T, and then isostatically pressed at 170MPa to obtain a green compact. The green compact is placed in a vacuum sintering furnace, heated to 1070°C at a rate of 5°C / min, sintered at a controlled sintering temperature of 1070°C, sintered for 5h, and subjected to aging treatment to obtain the rare earth permanent magnet of this embodiment.

[0052] The crystal structure and magnetostrictive properties of the NdFeB magnet of this embodiment were tested using the test method described above. Figure 1 It shows that the NdFeB magnet of this embodiment 3 has a characteristic peak at 39.32°, and the interplanar spacing d corresponding to the characteristic peak is 2.289 Å; Table 3 shows that the NdFeB magnet of this embodiment 3 has a low saturation magnetostriction coefficient and a high coercive force.

[0053] Comparative Example 1 The raw material composition of this comparative example is the same as that of Example 1. The manufacturing method is different from that of Example 1 in that the radius R of the quenching roller, the width H of the quenching roller, the rotation speed ω of the quenching roller, and the flow rate L of the molten steel are adjusted. The parameters do not satisfy the relationship ②. See Table 2 for details.

[0054] The crystal structure and magnetostrictive properties of the NdFeB magnet of this comparative example were tested using the test method described above. Figure 1 It shows that the NdFeB magnet of Comparative Example 1 has no characteristic peak in the range of 39.0° to 39.5° expressed by the X-ray diffraction of 2θ angle. Table 3 shows that the NdFeB magnet of Comparative Example 1 has a higher saturation magnetostriction coefficient and a lower coercive force.

[0055] Comparative Example 2 The difference from Example 1 is that the ratio of Nd, Pr, Cu, and Ga elements in the raw material composition is adjusted, the Fe element is adaptively adjusted, and the ratio of other elements remains 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 the relationship ②. By changing the element ratio, it still satisfies the relationship ① when there is no characteristic peak.

[0056] The crystal structure and magnetostrictive properties of the NdFeB magnet of this comparative example were tested using the test method described above. Figure 1 It shows that the NdFeB magnet of Comparative Example 2 has no characteristic peak within the range of 39.0° to 39.5° in X-ray diffraction expressed as 2θ angle. Table 3 shows that the NdFeB magnet of Comparative Example 2 has a higher saturation magnetostriction coefficient and a lower coercive force.

[0057] Comparative Example 3 The difference from Example 1 is that the ratio of the raw material components Pr, Cu, and Ga elements is adjusted, the Fe element is adaptively adjusted, and the ratio of other elements remains unchanged, see Table 1 for details. The change in composition ultimately causes this example to not satisfy the relationship ①.

[0058] The crystal structure and magnetostrictive properties of the NdFeB magnet of this comparative example were tested using the test method described above. Figure 1 It shows that the NdFeB magnet of Comparative Example 3 has no characteristic peak in the range of 39.0° to 39.5° expressed by the X-ray diffraction of 2θ angle. Table 3 shows that the NdFeB magnet of Comparative Example 3 has a higher saturation magnetostriction coefficient and a lower coercive force.

[0059] Comparative Example 4 The difference from Example 1 is that only the ratio of Pr, Cu, and Ga elements in the raw material composition is adjusted, the Fe element is adaptively adjusted, and the ratio of other elements remains unchanged (see Table 1 for details), and the radius R of the quenching roller, the width H of the quenching roller, the speed ω of the quenching roller, and the flow rate L of the molten steel are also adjusted (see Table 2 for details). This comparative example does not satisfy the relationship ①, nor does it satisfy the relationship ②.

[0060] The crystal structure and magnetostrictive properties of the NdFeB magnet of this comparative example were tested using the test method described above. Figure 1 The X-ray diffraction of the NdFeB magnet of Comparative Example 4 expressed at 2θ angles shows no characteristic peak within the range of 39.0° to 39.5°; Table 3 shows that the NdFeB magnet of Comparative Example 4 has a higher saturation magnetostriction coefficient and a lower coercive force.

[0061] Table 1 Some raw materials and proportions of NdFeB magnets (wt%)

[0062] Table 2 Parameters of quenching roller and molten steel flow rate

[0063] Table 3 Saturation magnetostriction coefficient

[0064] Through appropriate ingredients and appropriate process parameters, the magnet forms a specific crystal structure, which also makes the XRD test spectrum of the magnet have a characteristic peak between 39.0° and 39.5°. The inventors found that this specific crystal structure can reduce the saturation magnetostriction performance while maintaining good coercive force.

[0065] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in 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 formula 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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