Samarium-iron-nitrogen magnetic powder and preparation method thereof

Abstract

The invention relates to the technical field of rare earth permanent magnet materials, in particular to samarium-iron-nitrogen magnetic powder and a preparation method thereof.The preparation method comprises the steps that 1, a samarium elementary substance and an iron elementary substance are smelted, then cast to a cooling roller and fall to a water cooling disc, and a samarium-iron alloy sheet is obtained; (2) the samarium-iron alloy sheet is subjected to homogenization treatment and then hydrogenated, and samarium-iron coarse powder is obtained; and (3) nitriding the samarium-iron coarse powder to obtain samarium-iron-nitrogen coarse powder, and then adding the samarium-iron-nitrogen coarse powder into an airflow classifier for screening and ball milling. According to the preparation method of the samarium-iron-nitrogen magnetic powder, oxidation of the samarium-iron-nitrogen magnetic powder can be effectively prevented before nitriding, the samarium-iron-nitrogen magnetic powder uniform in particle size and excellent in performance can be obtained, and the requirement of magnetic components for high-performance magnetic powder is met; meanwhile, the preparation method also has the advantages of high production efficiency, low energy consumption and environmental friendliness, and can meet the requirements of large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth permanent magnetic materials, and in particular to samarium iron nitrogen magnetic powder and a preparation method thereof. Background Art

[0002] As an important functional material, SmFeN magnetic powder is widely used in various magnetic components. Currently, the main methods for preparing SmFeN magnetic powder include the HDDR method, melt quenching method, and reduction diffusion method. While the HDDR method can produce SmFeN magnetic powder with high magnetocrystalline anisotropy, it is complex, energy-intensive, and has low production efficiency, making it unsuitable for large-scale production. The reduction diffusion method has attracted attention due to its advantages, such as simple equipment, low raw material costs, and easy-to-implement process conditions. However, it has the disadvantage that SmN is prone to excessive volatilization, which is not conducive to the thorough diffusion reaction.

[0003] Other issues exist in existing technologies. For example, the method of crushing samarium-iron alloy flakes using hydrogen pulverization and airflow milling can easily oxidize the samarium-iron magnetic powder during the transfer process, resulting in reduced performance after subsequent nitriding. While utilizing the principle of hydrogen absorption and disproportionation to crush the samarium-iron alloy flakes into powder through hydrogenation and dehydrogenation, while this avoids oxidation, the powder particle size after hydrogen pulverization is uneven, making the coarse powder incapable of saturated nitriding and resulting in lower performance.

[0004] Patent CN114012096A discloses a method for preparing anisotropic Sm-Fe-N magnetic powder. This method uses a rapid solidification process to produce uniformly sized sheets with a Sm-rich phase distributed in a network at the grain boundaries. Hydrogen fracturing prior to nitriding causes volume expansion of the main phase alloy, creating microcracks and pores in the particles, which aids the nitriding and regrinding processes. However, in practice, this method still requires further optimization of hydrogen fracturing conditions, such as increasing hydrogen pressure and temperature and extending hydrogen treatment time, to achieve finer magnetic powder particles and higher coercivity.

[0005] CN 118969491 B discloses a method for preparing isotropic samarium iron nitrogen magnetic powder, comprising the following steps: weighing metal Sm and Fe according to the ratio of Sm2Fe17, with an excess of 5% to 10% of Sm, and smelting and rapidly solidifying to form samarium iron alloy flakes; crushing the samarium iron alloy flakes to prepare powdered samarium iron alloy; subjecting the powdered samarium iron alloy to HDDR treatment to obtain isotropic alloy blocks; crushing the isotropic alloy blocks and subjecting them to aging treatment to obtain isotropic alloy powder; subjecting the aged isotropic alloy powder to high temperature nitriding treatment to obtain Sm2Fe 17N3 isotropic magnetic powder. Sm-Fe alloy flakes are prepared using a combination of hydrogen crushing and jet milling. However, during this process, the samarium-iron powder easily reacts with oxygen in the air during transfer and oxidizes. Once oxidized, subsequent nitriding treatment significantly reduces the final performance of the powder.

[0006] CN 117912795 A discloses an in-situ multi-stage preparation method of SmFeN magnetic powder. In a protective atmosphere, samarium iron alloy flakes are obtained by induction melting and rapid solidification. The samarium iron alloy flakes are added to a reactor and crushed into powder by hydrogenation and dehydrogenation based on the principle of hydrogen absorption and disproportionation decomposition. High-pressure nitrogen is filled into the reactor to perform in-situ nitriding on the samarium iron alloy powder to obtain Sm2Fe 17 N3 magnetic powder. While this method effectively avoids oxidation during the crushing process, it introduces new challenges. The resulting powder particle size after hydrogen crushing is uneven, with a high concentration of coarse powder. This coarse powder cannot achieve saturated nitriding during the subsequent nitriding process. The larger particle size of the coarse powder limits the diffusion and reaction of nitrogen atoms, resulting in insufficient nitriding and ultimately lower overall performance of the magnetic powder. This uneven particle size and insufficient nitriding also limit the use of samarium iron nitrogen magnetic powder in applications that require high performance consistency and stability.

[0007] Therefore, there is an urgent need for a method for preparing samarium iron nitrogen magnetic powder to overcome the above technical problems. Summary of the Invention

[0008] The present invention aims to address the problem that, while the hydrogen crushing method used in the prior art to prepare samarium-iron magnetic powder overcomes the oxidation problem of the samarium-iron coarse powder, the powder particle size of the samarium-iron coarse powder is uneven, the nitriding effect is poor, and the magnetic properties of the samarium-iron-nitrogen magnetic powder are relatively low. The existing hydrogen crushing process conditions, such as hydrogen pressure, temperature, and time, need to be further optimized to obtain samarium-iron-nitrogen magnetic powder with finer magnetic particles and higher coercivity. Thus, a samarium-iron-nitrogen magnetic powder and a preparation method thereof are provided. This preparation method not only effectively prevents oxidation of the samarium-iron magnetic powder before nitriding, but also produces samarium-iron-nitrogen magnetic powder with uniform particle size and excellent performance, meeting the demand for high-performance magnetic powder for magnetic components. Furthermore, this preparation method should have the advantages of high production efficiency, low energy consumption, and environmental friendliness, making it suitable for large-scale production.

[0009] In order to achieve the above object, in a first aspect, the present invention provides a method for preparing samarium iron nitrogen magnetic powder, characterized in that the preparation method comprises: 1) Smearing samarium and iron, then casting them onto a cooling roller and dropping them onto a water-cooled plate to obtain samarium-iron alloy flakes; 2) homogenizing the samarium iron alloy flakes and then hydrogenating them to obtain samarium iron coarse powder; 3) Nitriding the samarium iron coarse powder to obtain samarium iron nitrogen coarse powder, and then adding the samarium iron nitrogen coarse powder to an air flow classifier for screening and ball milling.

[0010] Preferably, in step 1), the molar ratio of the samarium element to the iron element is 2.2-3.0:17.

[0011] Preferably, in step 1), the smelting conditions include: pressure <1 Pa, temperature 1400-1600° C., and time 20-40 min.

[0012] Preferably, the smelting further comprises first smelting the iron element and 50% of the samarium element, and then adding the remaining samarium element for smelting after melting.

[0013] Preferably, in step 1), the casting conditions include: the rotation speed of the cooling roller is 3-5 rpm.

[0014] Preferably, in step 2), the homogenization treatment conditions include: a pressure of 1×10 -2 Pa, temperature is 900-1100℃, time is 6-10h.

[0015] Preferably, in step 2), the hydrogenation conditions include: a pressure of 1×10 -2 Pa, temperature is 250-350℃, absolute pressure of hydrogen is 0.10-0.20MPa, and time is 1.5-3h.

[0016] Preferably, in step 3), the conditions of the nitriding treatment include: first raising the temperature to 350-450°C at a heating rate of 5-15°C / min, charging nitrogen to a nitrogen pressure of 0.2-0.8 MPa, and keeping warm for 0.5-1.5 hours, then raising the temperature to 500-600°C at a heating rate of 5-15°C / min, keeping warm for 8-12 hours, and then cooling to 15-30°C.

[0017] Preferably, in step 3), the screening conditions include: particle size <10 μm is H grade samarium iron nitrogen coarse powder, 10 μm≤particle size≤30 μm is M grade samarium iron nitrogen coarse powder, and particle size >30 μm is L grade samarium iron nitrogen coarse powder.

[0018] Preferably, in step 3), the D50 of the ball-milled samarium iron nitrogen magnetic powder is ≤2.0 μm.

[0019] Preferably, the preparation method further comprises: after adding the powder to an air flow classifier for screening, the obtained L-grade samarium iron nitrogen coarse powder with a nitrogen content of ≤2.8% and a particle size of >30 μm can be subjected to a secondary nitriding treatment by repeating steps 2) and 3).

[0020] In a second aspect, the present invention provides a samarium iron nitrogen magnetic powder, which is prepared by the preparation method described in the first aspect.

[0021] In the above technical scheme, the preparation method of samarium iron nitrogen magnetic powder of the present invention adopts the method of air flow classification after nitriding, and the samarium iron nitrogen magnetic powder after nitriding is classified into samarium iron nitrogen coarse powder with particle size <10μm, 10μm≤particle size≤30μm and particle size>30μm, and they are ball-milled to D50≤2.0μm respectively, so as to obtain samarium iron nitrogen magnetic powder with different performances of three grades of H grade, M grade and L grade at one time, which not only reduces the production cost but also can be used separately or compounded according to the required proportion to meet the needs of different application scenarios.

[0022] At the same time, the samarium iron nitrogen magnetic powder prepared by this preparation method has uniform particle size and excellent performance. It also has the advantages of simple process, low raw material cost, high production efficiency, low energy consumption, and environmental friendliness. It has broad application prospects and is suitable for large-scale industrial production.

[0023] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 This is the particle size distribution diagram of the H-grade samarium iron nitrogen magnetic powder after ball milling in Example 1. DETAILED DESCRIPTION

[0025] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0026] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0027] In a first aspect, the present invention provides a method for preparing samarium iron nitrogen magnetic powder, characterized in that the preparation method comprises: 1) Smearing samarium and iron, then casting them onto a cooling roller and dropping them onto a water-cooled plate to obtain samarium-iron alloy flakes; 2) homogenizing the samarium iron alloy flakes and then hydrogenating them to obtain samarium iron coarse powder; 3) Nitriding the samarium iron coarse powder to obtain samarium iron nitrogen coarse powder, and then adding the samarium iron nitrogen coarse powder to an air flow classifier for screening and ball milling.

[0028] The preparation method of the samarium iron nitride magnetic powder of the present invention adopts a method of air flow classification after nitriding, and the magnetic powder after nitriding is classified into samarium iron nitride coarse powder with particle size less than 10 μm, particle size 10 μm≤particle size≤30 μm and particle size>30 μm, and they are respectively ball-milled to D50≤2.0 μm, so that samarium iron nitride magnetic powder with different performance of three grades of H grade, M grade and L grade can be obtained at one time. Not only does it reduce the production cost, but it can also be used separately or compounded according to the required proportion to meet the needs of different application scenarios.

[0029] At the same time, the samarium iron nitrogen magnetic powder prepared by this preparation method has uniform particle size and excellent performance. It also has the advantages of simple process, low raw material cost, high production efficiency, low energy consumption, and environmental friendliness. It has broad application prospects and is suitable for large-scale industrial production.

[0030] In a preferred embodiment of the present invention, in order to ensure the magnetic properties of the prepared samarium iron nitrogen magnetic powder, in step 1), the molar ratio of the samarium element to the iron element is 2.2-3.0:17.

[0031] In a preferred embodiment of the present invention, the samarium element is provided by samarium particles with a purity of 99.9% and a particle size of 1 to 10 mm.

[0032] In a preferred embodiment of the present invention, in order to ensure the magnetic properties of the prepared SmFeN magnetic powder, in step 1), the smelting conditions include: pressure <1 Pa, temperature 1400-1600° C., and time 20-40 min.

[0033] In a preferred embodiment of the present invention, in order to ensure the magnetic properties of the prepared samarium iron nitrogen magnetic powder, the smelting further includes first smelting the iron element and 50% of the samarium element, and then adding the remaining samarium element for smelting after melting.

[0034] In a preferred embodiment of the present invention, in step 1), the casting conditions include: the rotation speed of the cooling roller is 3-5 rpm.

[0035] In a preferred embodiment of the present invention, since the alloy flakes obtained after casting include Sm2Fe 17 Phase, samarium-rich phase and α-Fe phase. The homogenization treatment is to eliminate the samarium-rich phase and α-Fe phase to obtain purer Sm2Fe 17phase, thereby having higher performance. In step 2), the conditions of the homogenization treatment include: pressure of 1×10-2Pa, temperature of 900-1100℃, and time of 6-10h.

[0036] In a preferred embodiment of the present invention, in order to prevent the alloy sheet from being too coarse and too thick to be directly nitrided, the alloy sheet can be crushed into a particle size of 10-100 μm during hydrogenation treatment to facilitate nitriding. In step 2), the hydrogenation conditions include: a pressure of 1×10 -2 Pa, temperature is 250-350℃, absolute pressure of hydrogen is 0.10-0.20MPa, and time is 1.5-3h.

[0037] In a preferred embodiment of the present invention, in order to ensure the magnetic properties of the prepared samarium iron nitrogen magnetic powder, in step 3), the conditions of the nitriding treatment include: first raising the temperature to 350-450°C at a heating rate of 5-15°C / min, filling with nitrogen to a nitrogen pressure of 0.2-0.8 MPa, and keeping warm for 0.5-1.5h, then raising the temperature to 500-600°C at a heating rate of 5-15°C / min, keeping warm for 8-12h, and cooling to 15-30°C.

[0038] In a preferred embodiment of the present invention, in order to obtain uniform SmFeN magnetic powder, in step 3), the sieving conditions include: particle size <10 μm is H-grade SmFeN coarse powder, 10 μm≤particle size≤30 μm is M-grade SmFeN coarse powder, and particle size >30 μm is L-grade SmFeN coarse powder.

[0039] In a preferred embodiment of the present invention, in order to obtain uniform SmFeN magnetic powder, in step 3), the D50 of the ball-milled SmFeN magnetic powder is ≤2.0 μm.

[0040] In a preferred embodiment of the present invention, for the case where the samarium iron coarse powder cannot be fully nitrided after the hydrogenation reaction, after airflow classification, the L-grade samarium iron nitrogen magnetic powder with a nitrogen content of ≤2.8% is subjected to secondary nitriding to increase the nitrogen content and magnetic properties of the samarium iron nitrogen magnetic powder from L grade to M grade or even H grade, thereby improving its use value. The preparation method further includes: adding an airflow classifier for screening, and the preparation method further includes: adding an airflow classifier for screening, and for the L-grade samarium iron nitrogen coarse powder with a nitrogen content of ≤2.8% and a particle size of >30 μm, repeating steps 2) and 3) for secondary nitriding treatment.

[0041] In a second aspect, the present invention provides a samarium iron nitrogen magnetic powder, which is prepared by the preparation method described in the first aspect.

[0042] In the present invention, the room temperature is 15-30°C.

[0043] The present invention will be described in detail below by way of examples. In the following examples, the drugs and pharmaceuticals are all conventional commercial products.

[0044] Example 1 (1) According to Sm2Fe 17 Prepare raw materials in a stoichiometric ratio, in which samarium is in excess of 30%, to prepare 100 kg of samarium-iron alloy, weigh 75.95 kg of iron rods with a purity of 99%, and 31.26 kg of samarium particles with a purity of 99.9% and a particle size of 1-10 mm, put the weighed iron rods and 50% of the samarium particles into a crucible, and put the remaining 50% of the samarium particles into a secondary feeding silo, evacuate to below 1 Pa, melt the raw materials in the crucible at 1500 ° C, add the samarium particles in the secondary feeding silo, continue smelting for 30 minutes after the raw materials are completely melted, and pass the molten samarium-iron alloy steel liquid through the tundish and runner and cast it onto a cooling roller with a rotation speed of 3 r / min, so that the samarium-iron alloy forms Sm2Fe 17 Phase, and falls onto the water-cooled plate below to obtain samarium iron alloy flakes; (2) After the samarium iron alloy sheet in step (1) is cooled to room temperature, it is placed in a vacuum heat treatment furnace and vacuumed to 1×10 -2 Pa, and heat to 1000℃ and stop heating. After keeping the temperature for 8 hours, cool to 300℃ and keep the temperature. In a vacuum environment, introduce hydrogen into the furnace. The absolute pressure of hydrogen is controlled at 0.15MPa. The hydrogenation time is 2 hours. (3) The temperature was raised to 400°C at a heating rate of 10°C / min, nitrogen was introduced to a nitrogen pressure of 0.5 MPa, and the mixture was kept at this temperature for 1 hour. The temperature was then raised to 530°C at a heating rate of 10°C / min, and the mixture was kept at this temperature for 10 hours. The furnace temperature was then lowered to room temperature to obtain the nitrided samarium iron nitrogen coarse powder. (4) Adding the samarium iron nitrogen coarse powder in step (3) to the feed port of an air flow classifier, and classifying the samarium iron nitrogen coarse powder into H-grade samarium iron nitrogen coarse powder with a particle size of less than 10 μm, M-grade samarium iron nitrogen coarse powder with a particle size of 10 μm ≤ ≤ 30 μm, and L-grade samarium iron nitrogen coarse powder with a particle size of more than 30 μm through the rotating classifying disk of the air flow classifier; (5) The three grades of samarium iron nitrogen coarse powder obtained in step (4) were added to a ball mill respectively and ball-milled until D50 ≤ 2 μm to obtain the corresponding three grades of samarium iron nitrogen magnetic powder, namely H grade, M grade, and L grade, which were recorded as B1H, B1M, and B1L, respectively.

[0045] Example 2 The method described in Example 1 was followed, except that the "samarium excess of 30%" in step (1) was changed to "samarium excess of 50%". Other conditions remained unchanged, and three grades of samarium iron nitrogen magnetic powder, namely H grade, M grade, and L grade, were obtained, which were recorded as B2H, B2M, and B2L, respectively.

[0046] Example 3 The method described in Example 1 was followed, except that the "samarium excess of 30%" in step (1) was changed to "samarium excess of 10%". Other conditions remained unchanged, and three grades of samarium iron nitrogen magnetic powder, namely H grade, M grade, and L grade, were obtained, which were recorded as B3H, B3M, and B3L, respectively.

[0047] Example 4 The samarium iron nitrogen magnetic powders of three grades, H, M and L, obtained in Example 1 were compounded in a weight ratio of 2:2:1 to prepare samarium iron nitrogen magnetic powder, which was recorded as B4.

[0048] Example 5 The samarium iron nitrogen magnetic powder of the L grade in Example 3 was subjected to the hydrogenation treatment of step (2) and the nitridation reaction of step (3) in Example 1, and ball-milled to D50≤2μm to obtain samarium iron nitrogen magnetic powder, which was recorded as B5.

[0049] Comparative Example 1 The method described in Example 1 was followed, except that the airflow classification in step (4) was not performed, and the coarse SmFeN powder was directly ball-milled to obtain SmFeN magnetic powder, which was recorded as D1.

[0050] Test Example 1 The magnetic properties and nitrogen content of the samarium iron nitrogen magnetic powders prepared in Examples 1-4 and Comparative Example 1 were tested using VSM. The results are shown in Table 1.

[0051] Table 1

[0052] From the data in Table 1, it can be seen that the smaller the particle size of the magnetic powder after air flow classification in Examples 1-3, the higher the magnetic properties after ball milling. This is because for the samarium iron coarse powder after hydrogenation, the smaller the particle size of the magnetic powder, such as the samarium iron coarse powder with a particle size of ≤10μm, the easier it is to nitride, and the nitrogen content can be nitrided to saturation, and relatively pure Sm2Fe 17 N3 phase, Sm2Fe 17 The impurity phases such as α-Fe are relatively small, so the performance is relatively high; however, since nitrogen is difficult to diffuse into the interior of the samarium iron coarse powder with a particle size greater than 30μm, the surface of the magnetic powder can be nitrided, while the nitrogen content in the core of the magnetic powder is lower than that on the surface, and there may even be residual Sm2Fe 17 phase, while Sm2Fe 17 The phase is a non-magnetic phase, which leads to a decrease in remanence and coercivity and lower magnetic properties.

[0053] At the same time, combined with the data of Examples 1-3, it can be seen that the higher the samarium content, the higher the coercive force of the samarium-iron-nitrogen magnetic powder, and the lower the samarium content, the higher the remanence of the samarium-iron-nitrogen magnetic powder. This is because when the samarium content increases, there will be more samarium-rich phases in the quick-setting sheet. The samarium-rich phase is a non-magnetic phase and does not contribute to the remanence. However, when the samarium-rich phase is evenly distributed around the samarium-iron phase, it plays a magnetic isolation role and can increase the coercive force.

[0054] Furthermore, by comparing the data of Example 1 and Comparative Example 1, it is found that the magnetic properties of the samarium iron nitrogen magnetic powder obtained in Comparative Example 1 are lower than those of the M-grade samarium iron nitrogen magnetic powder obtained in Example 1. Not only can the high-performance H-grade samarium iron nitrogen magnetic powder in Example 1 not be provided, but it is also less economical.

[0055] Furthermore, it can be seen from the data of Example 4 that for the air-classified samarium iron nitrogen magnetic powder, after compounding according to a specific ratio, a samarium iron nitrogen magnetic powder with performance far higher than that of the original samarium iron nitrogen coarse powder can be obtained, and compared with pure H-grade samarium iron nitrogen magnetic powder, the cost can be greatly reduced while the performance is similar.

[0056] Finally, the nitrogen content of generally qualified samarium iron nitrogen magnetic powder in this field should be higher than 3.0%. The samarium iron nitrogen magnetic powder with a nitrogen content lower than 3.0% has too low use value due to its too low coercive force. Even if high remanent magnetic materials such as the H-grade samarium iron nitrogen magnetic powder in Example 3 are required in certain specific scenarios, the L-grade samarium iron nitrogen magnetic powder in Example 3 has basically no use value due to its too low nitrogen content and coercive force. However, from the performance of the samarium iron nitrogen magnetic powder prepared in Example 5, it can be seen that the preparation method of the present invention can perform secondary nitriding on the samarium iron nitrogen magnetic powder that is not fully nitrided, thereby increasing the nitrogen content and magnetic properties of the samarium iron nitrogen magnetic powder, and can upgrade the unusable low-performance material to high performance for use to reduce costs.

[0057] In summary, the preparation method of the samarium iron nitrogen magnetic powder of the present invention is classified after nitriding to avoid oxidation of the samarium iron magnetic powder before nitriding, and through the airflow classification method after nitriding, three grades of magnetic powder with different performance can be obtained at the same time, which is lower cost and higher efficiency; not only that, the samarium iron nitrogen magnetic powder of different grades obtained by the present invention can not only be used separately and independently, but also can be compounded according to different proportions, providing a flexible solution for more complex and diversified applications to meet the specific requirements of magnetic powder performance in different application scenarios, thereby realizing adjustable performance of samarium iron nitrogen magnetic powder and efficient utilization of resources. Through this innovative preparation method, not only the problems existing in the prior art are solved, but also the performance level of samarium iron nitrogen magnetic powder is enriched, making the performance of samarium iron nitrogen magnetic powder more abundant and diverse, greatly expanding the application range of samarium iron nitrogen magnetic powder, and having broad application prospects.

[0058] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0059] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0060] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing samarium iron nitrogen magnetic powder, characterized in that: The preparation method comprises: 1) Smearing samarium and iron, then casting them onto a cooling roller and dropping them onto a water-cooled plate to obtain samarium-iron alloy flakes; 2) homogenizing the samarium iron alloy flakes and then hydrogenating them to obtain samarium iron coarse powder; 3) nitriding the samarium iron coarse powder to obtain samarium iron nitrogen coarse powder, and then adding the samarium iron nitrogen coarse powder to an air classifier for screening and ball milling; In step 1), the molar ratio of samarium elemental substance to iron elemental substance is 2.2-3.0:17; In step 1), the smelting conditions include: pressure <1 Pa, temperature 1400-1600° C., time 20-40 min; and / or, The smelting further comprises first smelting the iron element and 50% of the samarium element, and then adding the remaining samarium element to smelt after the melting; In step 2), the hydrogenation conditions include: a pressure of 1×10 -2 Pa, temperature is 250-350℃, absolute pressure of hydrogen is 0.10-0.20MPa, time is 1.5-3h; In step 3), the sieving conditions include: particle size <10 μm is H grade samarium iron nitrogen coarse powder, particle size 10 μm≤≤30 μm is M grade samarium iron nitrogen coarse powder, particle size >30 μm is L grade samarium iron nitrogen coarse powder; and / or, The D50 of the ball-milled samarium iron nitrogen magnetic powder is less than or equal to 2.0 μm; The preparation method further comprises: after adding the powder to an air flow classifier for screening, the obtained L-grade samarium iron nitrogen coarse powder with a nitrogen content of ≤2.8% and a particle size of >30 μm can be subjected to a secondary nitriding treatment by repeating steps 2) and 3).

2. The preparation method according to claim 1, characterized in that In step 1), the casting conditions include: the rotation speed of the cooling roller is 3-5 rpm.

3. The preparation method according to claim 1, characterized in that In step 2), the homogenization treatment conditions include: a pressure of 1×10 -2 Pa, temperature is 900-1100℃, time is 6-10h.

4. The preparation method according to claim 1, characterized in that In step 3), the conditions of the nitriding treatment include: first raising the temperature to 350-450°C at a heating rate of 5-15°C / min, charging nitrogen to a nitrogen pressure of 0.2-0.8 MPa, and keeping the temperature for 0.5-1.5 hours, then raising the temperature to 500-600°C at a heating rate of 5-15°C / min, keeping the temperature for 8-12 hours, and then cooling to 15-30°C.

5. A samarium iron nitrogen magnetic powder, characterized in that: The samarium iron nitrogen magnetic powder is prepared by the preparation method according to any one of claims 1 to 4.

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