Rare earth permanent magnet material composition design for extreme environment

Abstract

The invention discloses component design of a rare earth permanent magnet material for an extreme environment, and belongs to the field of rare earth permanent magnet materials. According to the invention, Sm, Co and Cu elementary substances are used as raw materials, and samarium cobalt-based rare earth permanent magnet material powder with Cu-doped chemical components is prepared through electric arc melting and physical crushing processes. The samarium-cobalt-based permanent magnet material has good hydrogen resistance, and the problem that the SmCo5 alloy has high hydrogen absorption capacity in a hydrogen environment is solved. According to the method, the hydrogen resistance of the SmCo5-based permanent magnet can be effectively improved, the comprehensive magnetic performance of the SmCo5-based permanent magnet is also improved, and meanwhile, the cost is reduced by replacing part of Co with Cu. The preparation can be completed by using conventional equipment, the process is simple, and a new feasible method is provided for the development of the hydrogen-resistant SmCo5 magnet.

Description

Technical Field

[0001] The present invention relates to the field of rare earth permanent magnet materials, and particularly to a composition design of rare earth permanent magnet materials for extreme environments. Background Art

[0002] As an important functional material, rare earth permanent magnet materials have been widely used in new energy, aerospace, electronic communication and other fields. As the first generation of rare earth permanent magnets, SmCo5 exhibits excellent magnetic properties, such as high temperature stability, oxidation resistance and corrosion resistance, making it widely used in high-tech and high-temperature fields. Rare earth permanent magnet alloys are highly sensitive to hydrogen. In a hydrogen environment at a certain temperature and pressure, the magnets are prone to hydrogenation, resulting in magnetic failure, expansion and breakage. The application in the hydrogen energy field requires the development of rare earth permanent magnets with good hydrogen resistance. This demand urgently requires the development of rare earth magnetic alloys with excellent hydrogen resistance to meet the operating requirements of hydrogen-containing environments.

[0003] The SmCo5 material is prone to react with hydrogen, and the hydrogen decrepitation (HD) process is used to produce SmCo powder. This technology proves the strong destructive effect of hydrogen on the magnet in reverse. Usually, a coating / plating layer is prepared on the material surface to protect the material from hydrogen damage. This can effectively shield most of the hydrogen, while a small amount of hydrogen will still enter the magnet. Therefore, it is crucial to conduct in-depth research on the material itself to enhance its hydrogen resistance.

[0004] SmCo5 absorbs hydrogen to form the hydride SmCo5H x . The mechanism of the hydrogen absorption process can be explained as follows: First, hydrogen dissolves in the alloy to form a solid solution phase; as the hydrogen absorption increases, part of the solid solution phase transforms into a hydride phase, and at this stage, the two phases coexist; finally, when the hydrogen absorption reaches a certain level, SmCo5 is completely transformed into the hydride phase SmCo5H x , and the crystal structure changes. Therefore, if the hydrogen absorption reaction can be inhibited, the hydrogen resistance of the SmCo5 rare earth permanent magnet material can be improved. To solve the performance problems of rare earth permanent magnet materials in a hydrogen environment, researchers have conducted certain explorations. The existing methods mainly reduce the intrusion of hydrogen atoms through physical barriers (surface film layers) and grain boundary densification (composition / heat treatment). For example, the Chinese invention patent with the publication number CN111243804B provides a rare earth permanent magnet with hydrogen resistance and its preparation method, which forms Sm2(CoCuFeZr) by adding elements such as Zr and Fe 17Magnets are designed with a composition where the sum of Co / Fe content exceeds three times that of Sm. Combined with three-stage heat treatment, it promotes grain boundary densification to block the diffusion of hydrogen atoms. And surface sealing treatment is adopted to form a composite film with self-healing ability, filling surface micropores and inhibiting hydrogen atom adsorption. However, these methods have insufficient regulation of the intrinsic hydrogen absorption thermodynamic behavior of the alloy and fail to fundamentally inhibit the transformation from the solid solution phase to the hydride phase. But during the melting process of the multi-alloy system, there is a high risk of generating heterogeneous phases. For example, the grain boundary interface energy of the Sm2Co7 phase is relatively high, and hydrogen atoms are likely to accumulate here and induce microcracks, resulting in deterioration of the hydrogen resistance performance; the Zr element is prone to react with hydrogen to form ZrH2, causing volume expansion and damaging the microstructure, forming new hydrogen diffusion channels. And the relatively complex process requires high control requirements, and batch performance fluctuations are likely to occur in industrial production.

[0005] Therefore, there is an urgent need for a preparation method of rare earth permanent magnet materials with simple composition design and process optimization to solve the problems of complex multi-element systems and insufficient intrinsic hydrogen resistance performance in the existing technology, and to achieve the long-term stable service of rare earth permanent magnets in a hydrogen environment. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a composition design of rare earth permanent magnet materials for extreme environments.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] <First aspect>

[0009] The present invention provides a samarium-cobalt-based rare earth permanent magnet material, which is composed of Sm, Co, and Cu elements. In terms of atomic ratio, Sm:Co:Cu = 1:(5 - x):x, where x ∈ (0,1].

[0010] As an implementation scheme, the atomic ratio of each element in the samarium-cobalt-based rare earth permanent magnet material is Sm:Co:Cu = 1:(5 - x):x, where x = 0.5 - 1.

[0011] In some embodiments, the atomic ratio of each element in the samarium-cobalt-based rare earth permanent magnet material is Sm:Co:Cu = 1:4:1.

[0012] As an implementation scheme, the samarium-cobalt-based rare earth permanent magnet material is the SmCo5 phase and the Sm2Co7 phase.

[0013] As an implementation scheme, the Sm2Co7 phase in the samarium-cobalt-based rare earth permanent magnet material is less than 37 wt.%.

[0014] As an implementation scheme, the Sm2Co7 phase in the samarium-cobalt-based rare earth permanent magnet material is less than 22 wt.%.

[0015] In some embodiments, the content of the Sm2Co7 phase in the samarium-cobalt-based rare earth permanent magnet material is 15 wt.%.

[0016] As an embodiment, the particle size of the samarium-cobalt-based rare earth permanent magnet material is 300 μm fine.

[0017] In some embodiments, the particle size of the samarium-cobalt-based rare earth permanent magnet material is 300 μm fine.

[0018] <Second aspect>

[0019] A method for preparing a samarium-cobalt-based rare earth permanent magnet material, comprising the following steps:

[0020] Vacuum arc melting of pure Sm, pure Co and pure Cu metal elements to obtain a master alloy ingot;

[0021] Removing the outer oxide skin of the master alloy ingot, and then pulverizing it under a protective atmosphere to obtain the samarium-cobalt-based rare earth permanent magnet material.

[0022] As an embodiment, the vacuum arc melting parameters are: the pre-pumping vacuum is not less than 3×10 -3 Pa, and then the chamber is filled with 4 - 6×10 4 Pa of protective gas for melting.

[0023] In some embodiments, the protective atmosphere is argon.

[0024] In some embodiments, during the melting process, the protective gas in the chamber is 5×10 4 Pa.

[0025] As an embodiment, during the melting process: perform two pre-pumping vacuums, flush with the protective gas at least three times, the distance between the electrode tip and the sample is less than 1 cm, and the arc starting current shall not exceed 350 A.

[0026] In some embodiments, during the melting process: perform two pre-pumping vacuums, flush with the protective gas four times, the distance between the electrode tip and the sample is about 0.5 cm, and the arc starting current is about 210 A.

[0027] As an embodiment, during the melting process, perform 3 - 4 times of melting, and turn over the sample after each melting to obtain a master alloy ingot with uniform composition.

[0028] In some embodiments, during the melting process, perform 3 times of melting.

[0029] As an embodiment, the pulverized samarium-cobalt-based rare earth permanent magnet material is sieved through a 50-mesh sieve to obtain a samarium-cobalt-based rare earth permanent magnet material with a particle size of 300 μm.

[0030] <Third aspect>

[0031] Application of a samarium-cobalt-based rare earth permanent magnet material in a high-temperature and high-pressure hydrogen environment.

[0032] As an embodiment, the application of the samarium-cobalt-based rare earth permanent magnet material in a high-temperature and hydrogen-resistant permanent magnet motor.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The preparation method of the samarium-cobalt-based rare earth permanent magnet material with enhanced hydrogen resistance provided by the present invention obtains a Sm-Co-Cu ingot by melting different contents of Cu with pure Sm and pure Co, and performs physical crushing and grinding and sieving on it to obtain the final product. It is simple and easy to operate, has low requirements for equipment, and has the advantages of simple operation and short preparation time. Compared with the existing complex preparation processes of multi-element alloy systems, it does not require precise control of the ratios of multiple elements and complex heat treatment processes, and also avoids the risk of formation of impurity phases caused by excessive elements, reduces the requirements for operators and production equipment, is conducive to large-scale industrial production, and can quickly convert technology into actual productivity.

[0035] (2) The samarium-cobalt-based rare earth permanent magnet material prepared by the present invention replaces part of the Co metal with Cu metal, saving costs. Its hydrogen absorption amount at 150 °C and 0.3 MPa is significantly reduced by more than 50% (Example 2: reduced by 70%, Example 3: reduced by 90%). This shows that the doping of Cu elements can effectively inhibit the hydrogen absorption of SmCo5 alloy, greatly reducing the possibility of hydrogen atoms entering the magnet interior, fundamentally alleviating the problems of magnetic property degradation and material structure damage caused by hydrogen absorption, and significantly improving the stability of the magnet in a hydrogen environment, laying a solid foundation for its long-term stable service in a hydrogen-containing working environment.

[0036] (3) While enhancing the hydrogen resistance performance, the present invention significantly improves the comprehensive magnetic properties of the magnet. The coercivity at room temperature and a 50 kOe magnetic field is increased by more than 3 times (Example 2: about 3.25 times, Example 3: about 3.32 times). While effectively enhancing the hydrogen resistance performance, it has good magnetic properties. The significant increase in coercivity means that the ability of the magnet to resist external magnetic field interference and maintain its own magnetism is enhanced, which is crucial for application scenarios that require stable magnetism, such as motors and sensors, and can effectively improve the performance and reliability of related equipment.

[0037] (4) By replacing part of the Co metal with Cu metal, the present invention effectively reduces the production cost while ensuring the magnet performance. Description of the Drawings

[0038] Other features, objectives, and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0039] Figure 1 X-ray diffraction patterns of the SmCo 5-x Cu x (x = 0 to 1) materials prepared in Examples 1 to 3 of the present invention;

[0040] Figure 2 Hydrogen absorption kinetics test graphs at 150 °C of the SmCo 5-x Cu x (x = 0 to 1) materials prepared in Examples 1 to 3 of the present invention;

[0041] Figure 3 First derivative curves of the hydrogen absorption kinetics at 150 °C of the SmCo 5-x Cu x (x = 0 to 1) materials prepared in Examples 1 to 3 of the present invention;

[0042] Figure 4 Room temperature demagnetization curves of the SmCo 5-x Cu x (x = 0 to 1) materials prepared in Examples 1 to 3 of the present invention;

[0043] Figure 5 Scanning electron microscope images of the SmCo 5-x Cu x (x = 0, 0.5) master alloy ingots prepared in Examples 1 and 2, where (a) is Example 1 and (b) is Example 2. Detailed Embodiments

[0044] The present invention will be described in detail below with reference to the embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several adjustments and improvements can be made. These all fall within the protection scope of the present invention.

[0045] Sm: purity ≥ 99.5%, purchased from Hebei Jiuyue New Materials;

[0046] Co: purity ≥ 99.5%, purchased from Benyu Metal Materials;

[0047] Cu: purity ≥ 99.5%, purchased from Hebei Jiuyue New Materials;

[0048] 1:5 phase: SmCo5 phase;

[0049] 2:7 phase: Sm2Co7 phase.

[0050] Example 1

[0051] This embodiment provides a method for preparing a samarium-cobalt-based rare earth permanent magnet material with enhanced hydrogen resistance, comprising the following steps:

[0052] Raw material preparation:

[0053] Pure Sm and pure Co metal elements were weighed and prepared according to the atomic ratio of Sm:Co=1:5. When weighing pure Sm, an additional 5wt.% was added on the basis of the required mass to compensate for the mass loss caused by Sm burning during the smelting process.

[0054] The three raw materials were put into a vacuum arc melting furnace with a total mass of 25 g, and the vacuum in the furnace was evacuated to 3×10 -3 Pa or less, filled with 5×10 4 Pa protective gas Ar gas, the electrode head was 0.5cm away from the sample during smelting, the arc current was slowly increased to about 210A, smelting was performed 3 times, each smelting was about 1 minute, cooling was about 1 minute, and the ingot was turned over after each melting, and finally the Sm-5Co master alloy ingot was obtained;

[0055] The outer oxide scale of the master alloy ingot was polished, and then placed in an argon glove box and crushed using a mortar and pestle. After grinding and passing through a 50-mesh sieve, 300 μm fine Sm-5Co alloy powder was obtained.

[0056] Example 2

[0057] This embodiment provides a method for preparing a samarium-cobalt-based rare earth permanent magnet material with enhanced hydrogen resistance, comprising the following steps:

[0058] Raw material preparation:

[0059] Pure Sm, pure Co and pure Cu metal elements were weighed and prepared according to the atomic ratio of Sm:Co:Cu=1:4.5:0.5. When weighing pure Sm, an additional 5wt.% was added on the basis of the required mass to compensate for the mass loss caused by Sm burning during the smelting process.

[0060] The three raw materials were put into a vacuum arc melting furnace with a total mass of 25 g, and the vacuum in the furnace was evacuated to 3×10 -3 Pa or less, filled with 5×10 4 Pa protective gas Ar gas, the electrode head was 0.5 cm away from the sample during smelting, the arc current was slowly increased to about 210A, smelting was performed 3 times, each smelting was about 1 minute, cooling was about 1 minute, and the ingot was turned over after each melting, and finally the Sm-4.5Co-0.5Cu master alloy ingot was obtained;

[0061] The outer oxide scale of the master alloy ingot was polished, and then placed in an argon glove box and crushed using a mortar and pestle. After grinding and passing through a 50-mesh sieve, 300 μm fine Sm-4.5Co-0.5Cu alloy powder was obtained.

[0062] Example 3

[0063] This embodiment provides a method for preparing a samarium-cobalt-based rare earth permanent magnet material with enhanced hydrogen resistance, comprising the following steps:

[0064] Raw material preparation:

[0065] Pure Sm, pure Co and pure Cu metal elements were weighed and prepared according to the atomic ratio of Sm:Co:Cu=1:5:1. When weighing pure Sm, an additional 5wt.% was added on the basis of the required mass to compensate for the mass loss caused by Sm burning during the smelting process.

[0066] The three raw materials were put into a vacuum arc melting furnace with a total mass of 25 g, and the vacuum in the furnace was evacuated to 3×10 -3 Pa or less, filled with 5×10 4 Pa protective gas Ar gas, the electrode head was 0.5 cm away from the sample during smelting, the arc current was slowly increased to about 210A, smelting was performed 3 times, each smelting was about 1 minute, cooling was about 1 minute, and the ingot was turned over after each melting, and finally the Sm-4Co-1Cu master alloy ingot was obtained;

[0067] The outer oxide scale of the master alloy ingot was polished, and then placed in an argon glove box and crushed using a mortar and pestle. After grinding and passing through a 50-mesh sieve, 300 μm fine Sm-4Co-1Cu alloy powder was obtained.

[0068] Test analysis

[0069] (1)XRD

[0070] Figure 1 The X-ray diffraction patterns of samarium cobalt-based rare earth permanent magnet materials prepared in Examples 1 to 3 are shown. In the figure, all three materials are composed of SmCo5 phase (PDF#97-062-5195) and Sm2Co7 phase (PDF#00-058-0293). The diffraction peak intensity of the Sm2Co7 phase of the Sm-4.5Co-0.5Cu material of Example 2 is significantly lower than that of the Sm-5Co material of Example 1, and the content of the Sm2Co7 phase is reduced from 37wt.% in Example 1 to 21.4wt.%. The diffraction peak intensity of the Sm2Co7 phase of the Sm-4Co-1Cu material of Example 3 is extremely weak, and its phase content is further reduced to 15wt.%. The addition of Cu can effectively inhibit the formation of the Sm2Co7 phase and enhance the structural stability.

[0071] (2) Hydrogen absorption kinetics

[0072] Put the materials into a high-pressure hydrogen storage adsorption device, and test 1.0 g of the samarium-cobalt-based rare earth permanent magnet materials prepared in each example at 150 °C and 0.3 MPa of hydrogen. The change in hydrogen absorption amount with time is as Figure 2 shown, and the first derivative of the hydrogen absorption amount (used to evaluate the hydrogen absorption rate) is as Figure 3 shown. The maximum hydrogen absorption amount and the maximum hydrogen absorption rate are shown in Table 1.

[0073] Table 1

[0074] Maximum hydrogen absorption capacity wt.% Maximum hydrogen absorption rate wt.% / min Example 1 0.1790 0.1878 Example 2 0.0894 0.0562 Example 3 0.0782 0.0198

[0075] The Sm-5Co material of Example 1 has a relatively large maximum hydrogen absorption amount and a relatively fast hydrogen absorption rate; the maximum hydrogen absorption amount of Example 2 is reduced by 50% compared with Example 1, and the hydrogen absorption rate is reduced compared with Example 1; the maximum hydrogen absorption amount and the hydrogen absorption rate of Example 3 are further reduced. It can be seen that the doping of Cu effectively enhances the hydrogen resistance of the samarium-cobalt-based permanent magnet material, and with the increase of the Cu content, its hydrogen resistance is stronger.

[0076] Figure 3 Among them, obvious peaks are shown in the first derivative curves of Example 1 and Example 2, but the maximum hydrogen absorption rate of Example 2 is reduced by 70% compared with that of Example 1; the first derivative of Example 3 is relatively smooth, indicating that the hydrogen absorption process is slow and stable, and its maximum hydrogen absorption rate is only 0.0198 wt.%, which is reduced by 90% compared with Example 1, indicating that the addition of Cu significantly enhances the hydrogen resistance of the samarium-cobalt-based permanent magnet material.

[0077] (3) Room temperature demagnetization curve

[0078] Figure 4 The room temperature demagnetization curves of the materials prepared in the examples are shown. After magnetization with a 50 kOe pulsed magnetic field at room temperature, the properties of each material are shown in Table 2. It can be seen that the introduction of the Cu element improves the comprehensive magnetic properties of the samarium-cobalt-based permanent magnet material, and the coercivity is increased by about 3.3 times at most.

[0079] Table 2

[0080] Intrinsic coercivity kOe Remanence emu / g Maximum magnetic energy product MGOe Example 1 0.98 60.76 2.76 Example 2 3.19 66.38 9.13 Example 3 3.25 53.43 5.87

[0081] (4) SEM

[0082] Figure 5Scanning electron microscope images of the master alloy ingots prepared in Example 1 and Example 2, where (a) corresponds to Example 1 and (b) corresponds to Example 2. It can be seen that both Example 1 and Example 2 are composed of two phases, namely SmCo5 phase and Sm2Co7 phase; the inset shows the elemental spectrum within the corresponding red region. It can be seen from the inset that the Cu element is distributed in both the matrix SmCo5 phase and Sm2Co7 phase in Example 2, and is enriched more in the Sm2Co7 phase.

[0083] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. A samarium-cobalt-based rare earth permanent magnet material, characterized in that, It is composed of Sm, Co and Cu elements. In terms of atomic ratio, Sm:Co:Cu = 1:(5 - x):x, where x ∈ (0,1].

2. The material according to claim 1, characterized in that The atomic ratio of Sm:Co:Cu is 1:(5 - x):x, where x = 0.5 - 1.

3. The material according to claim 1, wherein It contains two phases of SmCo5 phase and Sm2Co7 phase, and the Sm2Co7 phase is less than 37 wt.%.

4. The material according to claim 1, characterized in that, The particle size of the samarium-cobalt-based rare earth permanent magnet material is as fine as 300 μm.

5. The preparation method of the samarium-cobalt-based rare earth permanent magnet material according to any one of claims 1 to 4, characterized in that, Vacuum arc melting is carried out on pure Sm, pure Co and pure Cu metal elements to obtain a master alloy ingot; The outer layer of oxide scale of the master alloy ingot is removed, and then it is crushed under a protective atmosphere to obtain the samarium-cobalt-based rare earth permanent magnet material.

6. The preparation method according to claim 5, wherein The vacuum arc melting parameters are as follows: the pre-pumping vacuum is not less than 3×10 -3 Pa, and then the chamber is filled with 4-6×10 4 Pa of protective gas for melting.

7. The preparation method according to claim 6, characterized in that, During the melting process: pre-vacuum pumping is carried out twice, the protective gas is flushed at least three times, the distance between the electrode head and the sample is less than 1 cm, and the arc starting current shall not exceed 350 A.

8. The preparation method according to claim 6, characterized in that, During the melting process, melting is carried out 3 - 4 times, and the sample is turned over after each melting to obtain a master alloy ingot with uniform composition.

9. The preparation method according to claim 6, wherein The crushed samarium-cobalt-based rare earth permanent magnet material is sieved through a 50-mesh sieve.

10. Application of the samarium-cobalt-based rare earth permanent magnet material according to any one of claims 1 to 4 in a high-temperature and high-pressure hydrogen environment.

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