Rare earth permanent magnet powder, bonded magnet and device using the bonded magnet

Abstract

A rare-earth permanent magnet powder, wherein the rare-earth permanent magnet powder comprises 4 to 12 atomic% Nd, 0.1 to 2 atomic% C, 10 to 25 atomic% N and 62.2 to 85.9 atomic% T, wherein the T is Fe or FeCo and the main phase of the rare-earth permanent magnet powder is a hard magnetic phase with a TbCu7 structure; wherein the rare-earth permanent magnet powder further comprises 1 to 5 atomic% of element A and 0.1 to 2 atomic% of element boron; where the element A is Zr and / or Hf, the ratio of the content of the element boron to the content of the element A is 0.1 to 0.5; where the content of the element Nd and the element A in the rare-earth permanent magnet powder is 4 to 12 atomic % of the total content of the rare-earth permanent magnet powder, and the ratio of the content of the element C to the sum of the content of the element Nd and the element A in the rare-earth permanent magnet powder is 0.05 to 0.12.

Description

Technical field

[0001] This application relates to the field of rare-earth permanent magnet materials and relates in particular to a rare-earth permanent magnet powder, a bonded magnet and a device that uses the bonded magnet. background

[0002] Due to advantages such as good formability, high dimensional accuracy, and good magnetic properties, bonded rare-earth permanent magnets are widely used in fields encompassing various electronic accessories, office automation, automobiles, and especially in micro-specialized motors. To meet the demands of miniaturization and microminiaturization of accessories in scientific and technological development, it is necessary to further optimize the properties of bonded magnetic powder.

[0003] The key to manufacturing a bonded rare-earth permanent magnet lies in the production of rare-earth permanent magnet powder. The properties of the magnetic powder directly determine the quality and market price of the bonded magnet. Mature bonded rare-earth permanent magnets on the early market are essentially isotropic bonded NdFeB magnets. This type of widely used NdFeB magnetic powder is generally produced using a rapid quenching process. Such NdFeB magnets exhibit good properties. However, as patented products, NdFeB magnets have been, and continue to be, controlled by a few companies. In recent years, efforts have focused on developing more innovative bonded permanent magnet powder products to further expand the applications of these products.Bound permanent magnet powder, including an isotropic HDDR powder (HDDR = hydrogenation disproportionation desorption recombination), an isotropic powder of the Th2Zn type. 17 , an isotropic powder of type TbCu7 and an isotropic powder of type ThMn 12 etc., attracts a great deal of attention.

[0004] Currently, rare-earth permanent magnet powder of the samarium-iron-nitrogen series is attracting considerable attention due to its outstanding properties. During the manufacturing process of the SmFe series alloy, a rapidly quenched magnetic powder with a hard magnetic phase of a TbCu7 structure is produced using a strip casting technique. However, the manufacturing process, especially an industrial process, exhibits the following problems: (1) Samarium is extremely volatile at low vapor pressure during the manufacturing process and therefore leads to fluctuating alloy production costs; the volatile samarium, which oxidizes very easily, can easily catch fire and cause safety-related accidents; the volatile samarium can block a pipeline, causing great damage in a vacuum system; (2) The high viscosity of the samarium alloy, which has poor wettability with a copper wheel during the rapid quenching process, can easily cause splashing of alloy fluid, fluctuating fluid flows on the surface of a strip casting, and surface unevenness, further resulting in an uneven alloy phase structure and microstructure. This reduces the magnetic properties of the produced rare-earth permanent magnet powder of the samarium-iron-nitrogen series. This is also a major reason currently affecting the large-scale industrial use of the material.

[0005] To solve these problems that arise during the manufacturing process of the samarium-iron alloy, a new topic in the field of rare-earth permanent magnet powder development is to find a type of new rare-earth permanent magnet powder with better magnetic properties. Summary

[0006] A rare-earth permanent magnet powder, a bonded magnet, and a device that uses the bonded magnet are provided to improve the magnetic properties of the rare-earth permanent magnet powder.

[0007] Therefore, the application provides a rare-earth permanent magnet powder comprising 4 to 12 atomic percent Nd, 0.1 to 2 atomic percent C, 10 to 25 atomic percent N, and 62.2 to 85.9 atomic percent T. T is Fe or FeCo, and the main phase of the rare-earth permanent magnet powder is a hard magnetic phase with a TbCu7 structure.

[0008] Furthermore, the rare-earth permanent magnet powder has the structure in the general formula (I), and the general formula (I) is shown as follows: Nd x T 100-x-y-a C y N a (I), where 4 ≦ x ≦ 12, 0,1 ≦ y ≦ 2 and 10 ≦ a ≦ 25.

[0009] Furthermore, the rare-earth permanent magnet powder contains 1 to 5 atomic percent of element A and 0.1 to 2 atomic percent of element B. Element A is Zr and / or Hf; the ratio of element B to element A is 0.1 to 0.5.

[0010] Furthermore, the B content of the rare earth permanent magnet powder is between 0.3 and 2 atomic percent.

[0011] Furthermore, the content of the elements Nd and A in the rare-earth permanent magnet powder is 4 to 12 atomic percent of the total content of the rare-earth permanent magnet powder, and the ratio of the content of element C to the sum of the content of element Nd and element A in the rare-earth permanent magnet powder is 0.03 to 0.15.

[0012] Furthermore, the ratio of the content of element C to the sum of the content of element Nd and element A in the rare-earth permanent magnet powder is 0.05 to 0.12.

[0013] Furthermore, the rare-earth permanent magnet powder has the structure in General Formula (II), and General Formula (II) is shown as follows: Nd x A w T 100-x-y-z-a C y B z N a (II) where T is Fe or FeCo; A is Zr and / or Hf; 4 ≤ x + w ≤ 12, 1 ≤ w ≤ 5, 0.1 ≤ z ≤, 10 ≤ a ≤ 25, 0.1 ≤ z / w ≤ 0.5 and 0.1

[0014] Furthermore, the rare-earth permanent magnet powder also contains 0.3 to 10 atomic percent M, and M is at least one of Ti, V, Cr, Ni, Cu, Nb, Mo, Ta, W, Al, Ga and Si.

[0015] Furthermore, the M content of the rare-earth permanent magnet powder is 0.5 to 8 atomic percent.

[0016] Furthermore, the M content of the rare-earth permanent magnet powder is 0.5 to 5 atomic percent, and M is at least one of Nb, Ga, Al and Si.

[0017] Furthermore, the roller contact surface roughness Ra of the rare-earth permanent magnet powder is below 2.8 μm. Preferably, the roller contact surface roughness Ra is below 1.6 μm.

[0018] Preferably, the average grain size of the rare-earth permanent magnet powder is 3 to 100 nm.

[0019] Furthermore, the element Nd in the rare-earth permanent magnet powder is partially replaced by Sm and / or Ce. The Sm and / or Ce content in the rare-earth permanent magnet powder is 0.5 to 4.0 atomic percent.

[0020] Furthermore, a bonded magnet is provided upon registration. The bonded magnet is obtained by binding the rare-earth permanent magnet powder with a binder.

[0021] Furthermore, a device that uses the bound magnet is provided during registration.

[0022] The application has the following advantageous effect: In the rare-earth permanent magnet powder, the bonded magnet and the device that uses the bonded magnet of the application, volatilization of material can be effectively avoided during the manufacturing process of the rare-earth permanent magnet powder, thereby improving the wettability with a water cooling roller during the manufacturing process and providing the final manufactured materials with good magnetic properties. Detailed description

[0023] It should be noted that, where no conflict exists, embodiments in the application and characteristics in the embodiments can be combined. The application is described in detail below with reference to the specific embodiments.

[0024] A rare-earth nitrogen-series permanent magnet powder is essentially manufactured using samarium and iron. This is because, of all rare-earth compounds, only nitrides of samarium-series alloys are anisotropic in the preferred direction, enabling the formation of a material with specific permanent magnetic properties. Other rare-earth iron alloys, which are all anisotropic in the base plane, do not exhibit permanent magnetic properties even when nitrided (nitrogenized). Therefore, adding other rare-earth elements can significantly reduce the magnetic properties of samarium-iron-nitrogen magnet powder, rather than providing the permanent magnetic properties of rare-earth permanent magnet powder.

[0025] Based on the principles of the above theory, the inventor tried many processes with rare-earth permanent magnet powder of the N series, based on samarium and iron, to overcome the disadvantage that the magnetic properties of the produced rare-earth permanent magnet powder of the samarium-iron-nitrogen series were reduced due to poor wettability of the rare-earth permanent magnet powder of the samarium-iron-nitrogen series with a water-cooling roller; however, no improvement was achieved. Therefore, research regarding such inventions stagnated for a long time.

[0026] The inventor randomly mixed elements Nd, C, N, and Fe to produce a rare-earth permanent magnet powder, which exhibits a hard magnetic phase with a TbCu7 structure as its main phase, using a rapid quenching process. Surprisingly, the wettability between the resulting rare-earth permanent magnet powder and the water-cooling roller was improved, thus enhancing the magnetic properties of the produced rare-earth permanent magnet powder of the samarium-iron-nitrogen series. This change can be attributed to the NdFe alloy possessing a hard magnetic phase of a metastable TbCu7 structure, formed during the manufacturing process through non-equilibrium solidification. Such an NdFe alloy, exhibiting a metastable TbCu7 hard magnetic phase, is uniaxially anisotropic.After crystallization, the rapidly quenched alloy is imparted with specific hard magnetic properties. Furthermore, after nitriding, the coercivity of the rapidly quenched alloy was improved to obtain a practical rare-earth permanent magnet material.

[0027] In an exemplary embodiment of the application, a rare-earth permanent magnet powder comprises 4 to 12 atomic % Nd, 0.1 to 2 atomic % C, 10 to 25 atomic % N and 62.2 to 85.9 atomic % T, wherein T is Fe or FeCo and the main phase of the rare-earth permanent magnet powder is a hard magnetic phase with a TbCu7 structure.

[0028] The rare-earth permanent magnet powder incorporates a neodymium series iron alloy as its primary component, with a certain amount of carbon. The synergistic addition of Nd and carbon effectively reduces material volatilization during alloy melting, further improving the wettability of the rare-earth permanent magnet powder with a water-cooled roller during rapid quenching. This results in a final rapidly quenched alloy with stable alloy components, a stable structure, and a stable surface condition.

[0029] The rare-earth (Nd) content of the rare-earth permanent magnet powder ranges from 4 to 12 atomic percent. In rare-earth permanent magnet powder, more α-Fe phases are formed when the Nd content is less than 4 atomic percent, which significantly reduces the coercivity. However, more re-rich phases are formed when the Nd content is higher than 12 atomic percent, which is detrimental to improving magnetic properties. Preferably, the rare-earth (Nd) content is between 4 and 10 atomic percent.

[0030] The rare-earth permanent magnet powder contains 0.1 to 2 atomic percent carbon (C), preferably 0.3 to 1.5 atomic percent. C is added to improve the coercivity of the rare-earth permanent magnet powder and is mixed with Nd to improve the surface condition of the material and ultimately to obtain stable alloy components and a stable structure.

[0031] In rare-earth permanent magnet powder, Tn is Fe or Fen and Co. A specific amount of Co is added to improve the remanence and temperature stability of the nitrogen-containing magnetic powder. Simultaneously, a metastable TbCu7 phase structure can be stabilized to enhance effects such as wettability during the manufacturing process. Considering factors including cost, the amount of Co added is preferably not more than 20 atomic percent of the Tn content.

[0032] The rare-earth permanent magnet powder is nitrided to obtain rare-earth permanent magnet powder. The addition of nitrogen (N) increases the distance between iron-iron atoms, significantly improving the iron-iron exchange interaction and thereby increasing the Curie temperature and coercivity. The nitrogen content of the rare-earth permanent magnet powder is 10 to 25 atomic percent.

[0033] Too little nitrogen added does not increase the atomic distance and does not improve the magnetic properties, whereas too much nitrogen added instead occupies unfavorable crystal sites, negatively affecting the final magnetic properties.

[0034] The main phase of the rare-earth permanent magnet powder is the hard magnetic phase with the TbCu7 structure. The main phase refers to the phase with the highest volume ratio in the material. Due to reasons including mixing variations and oxidation, other impurity phases may be introduced during the material manufacturing process. Powder component phases are verified by X-ray diffraction (XRD) upon registration, and any impurity phases that cannot be distinguished by X-rays are identified.

[0035] In one embodiment of the application, the rare-earth permanent magnet powder has the structure of general formula (I). General formula (I) is as follows: Nd x T 100-x-y-a C y N a (I) where 4 ≦ x ≦ 12, 0.1 ≦ y ≦ 2 and 10 ≦ a ≦ 25. The rare-earth permanent magnet powder with the general formula (I) exhibits good wettability with the water cooling roller, and the final produced rare-earth permanent magnet powder has the advantage of good magnetic properties.

[0036] In an exemplary embodiment of the application, the rare-earth permanent magnet powder further contains 1 to 5 atomic percent of element A and 0.1 to 2 atomic percent of element B. Element A is Zr and / or Hf. The ratio of the content of B to the content of element A is 0.1 to 0.5.

[0037] In this rare-earth permanent magnet powder, the element A, i.e., the element Zr and / or Hf, is added. This is advantageous for increasing the proportion of rare-earth elements in the alloy, thereby stabilizing the hard magnetic phase with the TbCu7 structure and achieving higher remanence. Preferably, the A content is controlled to range from 1 to 5 atomic percent. The phase structure-stabilizing effect is not significant if the A content is too low, whereas an excessively high A content increases costs and is detrimental to improving the magnetic properties.

[0038] Simultaneously, the addition of boron (B) to the rare-earth permanent magnet powder is advantageous for improving the glass-forming capacity of the alloy, which can accelerate the formation of a material with relatively good properties at a relatively low copper content. A specific amount of boron is also added, which is advantageous for refining the grain size and improving parameters of the magnetic properties, including remanence, of the material. The application requires that the range of boron content be 0.1 to 2 atomic percent, preferably 0.3 to 2 atomic percent, and more preferably 0.5 to 1.5 atomic percent. Too much boron leads to Nd₂Fe₂ formation. 14 B-phase in the material, which is unfavorable for improving the overall magnetic properties.

[0039] Furthermore, the ratio of the content of added element A to the content of added element B in the rare-earth permanent magnet powder of the application is 0.1 to 0.5. The content of A and the content of B in the rare-earth permanent magnet powder lies within the above ratio range, which is advantageous for synergistically improving the material properties of the rare-earth permanent magnet powder, with an effect that is more pronounced than that achieved by using the two separately. This is because, as mentioned above, too much B readily leads to the Nd₂Fe 14The presence of a B phase in the material leads to deterioration, although the addition of B can effectively improve the material's ability to form fast-quenched glass. Therefore, the improvement of the overall magnetic properties is hindered. If the A and B components are added in a specific ratio in a mixed manner, the B content can be relatively increased to avoid a poor phase, thus further improving the material's manufacturability and final magnetic properties. Preferably, the B content is 0.3 to 2 atomic percent.

[0040] In a preferred embodiment of the application, the content of elements Nd and A in the rare-earth permanent magnet powder is 4 to 12 atomic percent of the total content of the rare-earth permanent magnet powder, and the ratio of the content of element C to the sum of the content of elements Nd and A in the rare-earth permanent magnet powder is 0.03 to 0.15. The content of elements Nd and A in the rare-earth permanent magnet powder is controlled to be 4 to 12 atomic percent of the total content of the rare-earth permanent magnet powder, which is advantageous for obtaining a permanent magnet material with a single TbCu7 phase structure. At the same time, the ratio of the content of element C to the sum of the content of element Nd and element A in the rare-earth permanent magnet powder is controlled to be between 0.03 and 0.15, and the ratio range of the two is regulated, which is advantageous in this respect, Nd2Fe.14 The aim is to reduce the carbon phases formed by the addition of element carbon, resulting in a more stable alloy phase structure and improved overall material properties. Preferably, the ratio is between 0.05 and 0.12.

[0041] In an exemplary embodiment of the application, the rare-earth permanent magnet powder has the structure in General Formula (II), and General Formula (II) is shown as follows: Nd x A w T 100-x-v-z-a C y B z N a (II) where T is Fe or FeCo; A is Zr and / or Hf; 4 ≤ x + w ≤ 12, 1 ≤ w ≤ 5, 0.1 ≤ z ≤ 2, 10 ≤ a ≤ 25, 0.1 ≤ z / w ≤ 0.5 and 0.1 ≤ y ≤ 2. This rare-earth permanent magnet powder exhibits the advantages of good wettability with the water-cooling roller and good magnetic properties of the final produced rare-earth permanent magnet powder.

[0042] In an exemplary embodiment of the application, the rare-earth permanent magnet powder further contains 0.3 to 10 atomic percent of M, and M is at least one of Ti, V, Cr, Ni, Cu, Nb, Mo, Ta, W, Al, Ga, and Si. In this rare-earth permanent magnet powder, the addition of element M can refine the particle size and improve magnetic properties, including the final coercivity and remanence, etc. Preferably, the content of element M is 0.5 to 8 atomic percent. More preferably, the content of M in the rare-earth permanent magnet powder is 0.5 to 5 atomic percent, and M is at least one of Nb, Ga, Al, and Si.

[0043] By selecting different raw materials, different phase structures, e.g., a ThMn, can be achieved. 12 -structure and a Th2Zn 17The presence of a hard magnetic phase with the TbCu7 structure alongside the hard magnetic phase in the material is almost unavoidable during the manufacturing process of the rare-earth permanent magnet powder. In a preferred embodiment, the hard magnetic phase with the TbCu7 structure of the rare-earth permanent magnet powder exhibits a maximum diffraction angle between 2θ = 40° and 45° under a Cu target X-ray image. Preferably, when the accuracy of the X-ray diffraction is 0.02° and the standard deviation of the rare-earth permanent magnet powder is less than 0.8°, the rare-earth permanent magnet powder that meets the above requirements exhibits a single and stable phase structure and good magnetic properties.

[0044] In the production of the rapidly quenched rare-earth permanent magnet powder alloy, the wettability between the alloying liquid and the water cooling roller directly influences the surface roughness of the resulting alloy. The higher the roughness value (Ra), the more uneven the surface. This is because flakes of varying thicknesses exhibit different cooling rates. Under extreme conditions, some parts of the same flake are rapidly over-quenched, while the cooling rates of other parts are insufficient. Consequently, the phase structures and microstructures of the final alloy are inevitably affected. Furthermore, a non-uniform flake leads to varying dynamic conditions during the nitriding process, resulting in inconsistent nitriding. The final magnetic properties of the material are influenced by all of the above factors.

[0045] To further improve the magnetic properties of the rare-earth permanent magnet powder provided by the application, the roller contact surface roughness Ra of the rare-earth permanent magnet powder is less than 2.8 μm in an exemplary embodiment of the application. In the application, the roller contact surface roughness Ra is the arithmetic mean deviation of the contour that indicates the surface condition of the flake. The arithmetic mean deviation of the contour Ra ​​is the arithmetic mean of the absolute values ​​of the contour offset distance within the sample length L, and the calculation formula is as follows:

[0046] In the formulas above, y is the contour offset distance, which refers to the distance between a contour point and a reference line in the measurement direction. The reference line is the center line of the contour. The contour is divided by this line, and the sum of the squares of the contour offset distance from the line within the sample length is minimal.

[0047] The roller contact surface roughness Ra of the rare-earth permanent magnet powder is controlled to be below 2.8 μm, which is advantageous for controlling the material wettability of the rare-earth permanent magnet powder and thus obtaining a rare-earth permanent magnet powder with relatively good magnetic properties. Preferably, the roller contact surface roughness Ra of the rare-earth permanent magnet powder is controlled to be below 2.8 μm; more preferably, the roller contact surface roughness Ra of the rare-earth permanent magnet powder is 2.2 μm; and further preferably, the roller contact surface roughness Ra of the rare-earth permanent magnet powder is below 1.6 μm.

[0048] In an exemplary embodiment of the application, the average grain size of the rare-earth permanent magnet powder is 3 to 100 nm. If the average grain size of the hard magnetic phase in the rare-earth permanent magnet powder is less than 3 nm, a coercive force of more than 5 kOe can hardly be obtained, while it is difficult to produce the rare-earth permanent magnet powder, thus reducing the yield. If the average grain size is greater than 100 nm, the resulting remanence is relatively low. The grain size of the hard magnetic phase is preferably in the range of 5 to 80 nm, more preferably in the range of 5 to 50 nm.

[0049] In a preferred embodiment of the application, the element Nd in the rare-earth permanent magnet powder is partially replaced by Sm and / or Ce. The content of Sm and / or Ce in the rare-earth permanent magnet powder is 0.5 to 4.0 atomic percent. Sm and / or Ce are added to the rare-earth permanent magnet powder to improve the material properties and reduce costs, and to improve the phase formation conditions and the surface condition of the flake.

[0050] The application also provides a manufacturing process for the rare-earth permanent magnet powder, which uses the following steps: (1) First, proportioning materials for an alloy with specific components, melting the materials using processes that include medium-frequency processing and arc processing, etc., to obtain alloy ingots; (2) performing induction melting on coarsely crushed alloy blocks to form an alloying liquid, and quenching the alloying liquid to obtain flaky alloy powder; (3) performing a crystallization treatment on the obtained alloy powder at a specific temperature over a specific period of time, and subsequently performing a nitriding treatment and / or carbonization treatment at approximately 350 to 550°C, the nitrogen source being a mixed gas of pure industrial nitrogen, hydrogen, and ammonia, etc.; Step 4: Obtaining the rare-earth permanent magnet powder.

[0051] For the material components disclosed above, all processes, including rapid quenching, comminution, crystallization, and nitriding, etc., must be controlled in a stable and uniform manner throughout the entire manufacturing process. At the rapid quenching stage, factors that must be strictly controlled include the melting temperature, the nozzle diameter, and the rotational speed of the rapid quenching wheel, with the jet pressure being controlled synergistically.

[0052] The jet pressure in the application has two main functions: one is to ensure a stable and uniform discharge of the alloying molten metal, and the other is to inhibit the volatilization of elements, particularly rare earth elements, during the melting process, thus ensuring the uniformity of the material components. Simultaneously, the jet pressure is continuously regulated according to the amount of alloying molten metal and the rapid quenching conditions to prevent inconsistencies in materials produced at different stages of the manufacturing process. During the initial rapid quenching stage, a relatively low jet pressure can be applied, as the pressure exerted by the molten metal steel is sufficient to ensure a uniform discharge.In the middle and later stages of rapid quenching, the jet pressure is momentarily increased to ensure uniform rapid quenching due to slow liquid flows or even a difficulty in ejecting the molten steel caused by a drop in the level.

[0053] The melting point is also an important reference index. The melting point of an NdFe-based alloy is relatively low. Simultaneously, a specific amount of M is added to effectively lower the melting point, ensuring the overall process is stable and minimizing volatilization. During the initial application, the melting point is between 1,200°C and 1,600°C and is fine-tuned depending on the specific components.

[0054] In the crystallization and nitriding stages, the treatment temperature and time must be controlled to prevent grain growth of soft and hard magnetic phases. Simultaneously, improving crystallization and nitriding efficiency is a key factor in avoiding abnormal grain growth. The application utilizes a treatment process with a relatively low temperature and long duration to obtain a magnetic powder with good properties while maintaining favorable microstructures.

[0055] The application provides rare-earth permanent magnet powder with the TbCu7 structure as the main phase. An isotropic bonded magnet can be produced by mixing the rare-earth permanent magnet powder with a fabricating resin. The manufacturing process can include compression molding, injection molding, calendering, and extrusion, etc., and the fabricated bonded magnet can be in various forms, including block and ring shapes, etc.

[0056] The bonded magnet obtained through the application can be used to manufacture a corresponding device. The rare-earth permanent magnet powder with good properties and the magnet produced using the above methods are advantageous for miniaturizing the device.

[0057] The advantageous effect of the rare-earth permanent magnet powder provided by the application is described in more detail below in combination with specific embodiments S1 to S71.

[0058] X-ray diffraction demonstrates that the main phases of the hard magnetic phases in the rare-earth permanent magnet powder produced according to the following embodiments S1 to S71 are TbCu7 structures. The components, grain sizes, grain distribution, and magnetic powder properties of the rare-earth permanent magnet powder are described in more detail below. (1) Components of the rare-earth permanent magnet powder

[0059] Rare earth alloy powder components are produced by nitriding molten alloy powder, and magnetic powder components are nitrided magnetic powder components, expressed in atomic percent. (2) Grain size σ

[0060] Method for expressing an average grain size: an electron microscope must be used to acquire a microstructure image of a material and to observe grains of a TbCu7 structure in the hard magnetic phase and grains of an α-Fe phase in the soft magnetic phase within the image. The specific procedure involves: calculating the total cross-sectional area S of n grains of the same type, then making the cross-sectional area S equivalent to the area of ​​a circle, calculating the diameter of the circle to obtain the average grain size σ, whose unit is nm, and the calculation formula is as follows: (3) Behavior of magnetic powder

[0061] The behavior of magnetic powder is recorded using a vibrating sample magnetometer (VSM – Vibrating Sample Magnetometer). where Br is the remanence with kGs as the unit; Hcj is the internal coercive force with kOe as the unit; (BH)m is the product of the magnetic energy with MGOe as the unit. (4) Roughness Ra

[0062] The roughness is measured using a roughness meter. I. Rare-earth permanent magnet powder Nd x T 100-x-y-a C y N a

[0063] The rare-earth permanent magnet powders of Examples 1–16 are produced by mixing the crude metals according to the proportions listed in Table 1 and by placing the metals in an induction melting furnace. Under the protection of gaseous argon, alloy ingots are obtained by molten metals, and subsequently, after coarse grinding, the alloy ingots are placed in a rapid quenching furnace for rapid quenching. The protective gas is gaseous argon, the jet pressure is 55 kPa, the number of nozzles is 2, and the cross-sectional area is 0.85 mm².2 The linear speed of the water cooling roller is 50 m / s, and the copper roller diameter is 300 mm; after rapid quenching, flaky alloy powder is obtained.

[0064] After the alloy has been processed for 1.5 minutes under the protection of gaseous Ar at 730°C, it is nitrided for 6 hours at 430°C by gaseous N2 of an atmosphere to obtain nitride magnetic powder, and an X-ray diffraction detection is carried out on the obtained nitride magnetic powder.

[0065] The components, magnetic properties, and particle size distribution of the resulting flaky nitride magnetic powder are recorded. The components and properties of the materials are as shown in Table 1. S represents an exemplary embodiment. Comparative examples are obtained from different components using the same process. D represents a comparative example. Table 1 Component, structure and properties of the material sample Components (bal represents the remaining parts) Ra σ Characteristics Br Hcj (BH)m S1 Nd 10,3 Fe bal Co 4,5 C 0,8 N 13,5 0,83 43 9,6 7,3 16,9 S2 Nd 8,3 Fe bal Co 4,5 C 0,8 N 12,5 0,8 56 9,1 7,6 16,6 S3 Nd 9,5 Fe bal Co 4,5 C 0,1 N 13,5 2,2 71 8,2 6,8 15,5 S4 Nd 8,9 Fe bal Co 15,5 C 0,7 N 15 1,3 45 9,5 7,4 16,7 S5 Nd 8,5 Fe bal Co 4,5 C 0,9 N 15,5 1,2 47 9,3 8,0 17,2 S6 Nd 5,1 Fe bal Co 4,5 C 2,0 N 13,5 1,4 59 8,4 7,3 16,4 S7 Nd 8,9 Fe bal C 0,3 N 13,5 2,2 26 8,1 6,5 14,7 S8 Nd 8,3 Fe bal Co 4,5 C 0,6 N 13,5 0,9 31 9,5 7,5 16,7 S9 Nd 12,0 Fe bal Co 11,5 C 0,8 N 20,0 2,8 38 8,1 6,8 15,1 S10 Nd 8,5 Fe bal Co 4,5 C 0,9 N 13,5 0,9 31 9,2 7,4 17,5 S11 Nd 8,3 Fe bal Co 4,5 C 1,5 N 13,5 1,8 61 8,4 7,0 16,1 S12 Nd 4,0 Fe bal Co 20,0 C 0,5 N 10,0 1,9 49 8,5 7,3 16,7 S13 Nd 8,3 Fe bal Co 6,5 C 0,8 N 13,5 0,5 43 9,4 7,5 17,6 S14 Nd 8,3 Fe bal Co 4,5 C 0,8 N 15 0,8 45 9,3 7,7 17,4 S15 Nd 9,3 Fe bal Co 4,5 C 0,3 N 13,5 1,7 52 8,3 6,9 14,4 S16 Nd 8,1 Fe bal C 0,2 N 14,5 2,1 33 8,5 6,9 15,2 D1 Sm 9,0 Feb bal Co 4,5 N 15 4,5 41 7,3 5,9 12,7 D2 Nd 9,0 Fe bal Co 4,5 C 3,5 N 15 3,1 46 7,9 6,4 13,9 D3 Nd 9,0 Fe bal N 15 3,7 40 7,1 6,1 11,6

[0066] The results from Examples 1 to 16 and Comparative Examples 1 to 3 show that the ratios of the raw materials can be controlled to obtain relatively good properties when the rare-earth permanent magnet powder is produced using the elements Nd, C, N, and T (T being Fe or FeCo). The surface roughness and magnetic properties are reduced to varying degrees, particularly when the C content of the produced rare-earth permanent magnet powder is not within the ranges required by the applications. II. Rare-earth permanent magnet powder to which the elements A (Zr and / or Hf) and B are added.

[0067] The rare-earth permanent magnet powders of Example 17–36 are produced by mixing the crude metals according to the proportions listed in Table 2 and by placing the metals in an induction melting furnace. Under the protection of gaseous argon, alloy ingots are obtained by molten metals, and subsequently, after coarse grinding, the alloy ingots are placed in a rapid quenching furnace for rapid quenching. The protective gas is gaseous argon, the jet pressure is 20 kPa, the number of nozzles is 2, and the cross-sectional area is 0.75 mm². 2 The linear speed of the water cooling roller is 55 m / s, and the copper roller diameter is 300 mm; after rapid quenching, flaky alloy powder is obtained.

[0068] After the alloy has been processed for 10 minutes under the protection of gaseous Ar at 730°C, it is nitrided for 7 hours at 420°C by gaseous N2 of an atmosphere to obtain nitride magnet powder.

[0069] The components, magnetic properties, and particle size distribution of the resulting flaky nitride magnetic powder are recorded. The components and properties of the materials are as shown in Table 2. S represents an exemplary embodiment. Comparative examples are obtained from different components using the same process. D represents a comparative example. Table 2 Components, structures and properties of the material sample Components (bal represents the remaining parts) Ra Characteristics Br Hcj (BH)m S17 Nd 8,5 Zr 11 Fe bal Yes 4,5 C 0,5 B 0,5 N 13,5 2,5 37 9,3 7,8 16,7 S18 Nd 8,5 Zr 1,6 Fe bal Yes 4,5 C 0,5 B 0,8 N 13,5 2,9 39 7,6 7,7 15,5 S19 Nd 7,9 Zr 2,1 Fe bal Yes 4,5 C 0,8 B 0,8 N 15,5 1,5 32 9,2 7,3 17,2 S20 Nd 7,3 Zr 1,7 Fe bal Yes 4,5 C 0,3 B 0,3 N 13,5 2,4 49 7,9 5,3 15,8 S21 Nd 7,8 Zr 1,6 Fe bal Yes 4,5 C 0,7 B 0,8 N 13,5 0,9 29 9,3 6,0 17,2 S22 Nd 8,5 Zr 1,4 Fe bal Yes 15,5 C 0,8 B 0,3 N 15,5 1,1 38 9,1 6,2 16,9 S23 Nd 8,5 Zr 2,5 Hf 1,0 Fe bal Co 4,5 C 0,5 B 0,8 N 15,5 2,5 41 8,1 6,6 15,7 S24 Nd 8,5 Zr 1,7 Fe bal Yes 4,5 C 1,1 B 0,8 N 13,5 1,2 47 7,9 7,3 17,4 S25 Nd 8,5 Zr 1,7 Fe bal Yes 4,5 C 0,9 B 0,8 N 13,5 1,3 48 7,2 7,6 16,9 S26 Nd 7,5 Hf 2,3 Fe bal Co 4,5 C 1,4 B 0,8 N 13,5 2,3 41 8,3 7,7 16,3 S27 Nd 8,5 Zr 1,5 Fe bal Yes 4,5 C 0,7 B 0,8 N 15,5 1,2 51 9,3 7,7 17,2 S28 Nd 6,5 Zr 5,0 Fe bal Yes 3,5 C 1,4 B 2,0 N 13,5 2,3 87 8,4 8,0 16,4 S29 Nd 6,9 Zr 1,5 Fe bal Yes 4,5 C 0,7 B 0,3 N 15,5 0,8 59 9,5 7,3 17,5 S30 Nd 6,3 Zr 1,1 Fe bal Yes 10,3 C 0,8 B 0,3 N 15,5 0,9 61 9,3 7,1 17,2 S31 Nd 7,5 Zr 1,6 Fe bal Yes 4,5 C 0,7 B 0,8 N 13,5 0,7 47 9,6 6,8 17,7 S32 Nd 3,0 Zr 1,0 Hf 0,2 Fe bal Co 11,5 C 0,6 B 0,1 N 13,5 2,8 67 7,9 5,3 15,4 S33 Nd 8,5 Zr 1,7 Fe bal Yes 4,5 C 1,1 B 0,8 N 17,5 1,6 64 6,8 6,5 15,9 S34 Nd 6,9 Zr 1,5 Fe bal Yes 4,5 C 0,7 B 0,3 N 25 0,9 71 6,5 5,9 15,3 S35 Nd 9,1 Zr 1,3 Fe bal Yes 4,5 C 1,1 B 0,6 N 13,5 1,4 43 9,2 7,5 17,0 S36 Nd 8,4 Hf 1,6 Fe bal Co 4,5 C 1,5 B 0,8 N 13,5 2,2 79 8,4 7,8 16,2 D4 Nd 6,3 Zr 1,1 Fe bal Yes 10,3 C 0,8 B 0,3 N 15,5 3,2 83 6,8 5,7 8,6 D5 Nd 6,0 Zr 1,5 Fe bal Yes 11,5 C 0,6 B 0,1 N 13,5 4,7 76 6,9 6,4 9,0 D6 Nd 6,3 Zr 0,3 Fe bal Yes 10,3 C 0,8 B 0,3 N 15,5 3,1 91 7,1 6,1 9,8

[0070] Table 2 shows that the rare-earth permanent magnet powder of the applications can acquire relatively good properties after the addition of element A and element B by controlling the ranges of ratios of the raw materials. Optimal surface conditions and magnetic properties can be obtained, in particular, when the ratio of element B to element A is controlled between 0.1 and 0.5, while the ratio of C to the sum of A and Nd is controlled in the range of 0.05 to 0.12. At the same time, the exemplary embodiments show that the magnetic properties decrease beyond the ranges of these ratios. III. Rare-earth permanent magnet powder to which the element M is added.

[0071] The rare-earth permanent magnet powder is produced using the elements Nd, C, N, T (T is Fe or FeCo) and M, where M is at least one of Ti, V, Cr, Ni, Cu, Nb, Mo, Ta, W, Al, Ga and Si.

[0072] The rare-earth permanent magnet powders of example s37–s53 are produced by mixing the crude metals according to the proportions listed in Table 3 and by placing the metals in an induction melting furnace. Under the protection of gaseous argon, alloy ingots are obtained by molten metals. These alloy ingots are then placed in a rapid quenching furnace for rapid quenching after coarse grinding. The protective gas is gaseous argon, the jet pressure is 35 kPa, the number of nozzles is 1, and the cross-sectional area is 0.9 mm². 2The linear speed of the water cooling roller is 65 m / s, and the copper roller diameter is 300 mm; after rapid quenching, flaky alloy powder is obtained.

[0073] After the alloy has been processed for 10 minutes under the protection of gaseous Ar at 750°C, it is nitrided for 6 hours at 430°C by gaseous N2 of an atmosphere to obtain nitride magnet powder.

[0074] X-ray diffraction analysis is performed on the resulting nitride magnetic powder. The components, magnetic properties, and particle size distribution of the resulting flaky nitride magnetic powder are determined. The components and properties of the materials are as shown in Table 3. S represents an exemplary embodiment. Comparative examples are obtained from different components using the same process. D represents a comparative example. Table 3 Components, structures and properties of the material sample Components (bal represents the remaining parts) Ra σ Characteristics Br Hcj (BH)m S37 Nd 8,5 Fe bal Yes 4,5 My soul 2,4 C 0,8 N 13,5 1,5 23 8,8 6,2 15,4 S38 Nd 8,5 Feb bal Co 3,5 Dad 2,4 C 0,8 N 13,5 1,4 31 8,6 5,5 15,4 S39 Nd 8,5 Fe bal Co 4,5 Nb 2,4 C 0,8 N 12,5 1,5 29 8,8 6,9 15,6 S40 Nd 8,5 Fe bal Co 4,5 Won't 2,4 C 0,8 N 13,6 0,9 23 8,9 6,1 15,5 S41 Nd 8,5 Feb bal Co 5,0 Si 2,4 C 0,8 N 12,5 0,8 31 9,0 6,5 15,4 S42 Nd 8,5 Fe bal Co 4,5 Al 10,0 C 0,8 N 12,5 1,3 65 8,1 7,1 14,1 S43 Nd 8,5 Fe bal Won't 5,0 C 0,8 N 12,2 1,3 31 8,6 7,3 15,7 S44 Nd 8,5 Feb bal Co 4,5 Si 0,5 C 0,8 N 13,2 1,2 41 8,5 5,7 15,0 S45 Nd 8,5 Fe bal Co 4,5 Zr 0,4 Won't 2,4 C 0,8 N 14,0 0,75 35 8,6 6,0 15,2 S46 Nd 8,5 Fe bal Co 1,5 Al 2,4 C 1,3 N 13,5 0,5 19 8,7 6,7 15,3 S47 Nd 9,2 Fe bal Co 4,5 Nb 3,4 C 0,8 N 12,5 1,2 45 8,5 7,1 15,0 S48 Nd 6,2 Fe bal Yes 6,9 Tea 4,3 V 2,2 N 12,3 1,6 54 8,2 7,3 14,9 S49 Nd 7,3 Feb bal Co 21,0 Al 1,3 Dad 0,2 Mo 4,2 N 12,5 1,9 71 8,5 6,2 14,9 S50 Nd 6,2 Feb bal Co 11,9 Si 3,3 W 1,5 Ni 5,2 N 12,3 2,5 100 8,3 6,7 13,1 S51 Nd 7,3 Feb bal Co 21,0 Al 1,3 Cr 0,2 Si 0,2 N 12,5 1,5 56 8,6 6,0 15,2 S52 Nd 6,2 Feb bal Co 11,9 Al 0,5 Cu 1,5 Ni 0,2 N 12,3 1,5 47 8,5 5,6 15,1 S53 Nd 6,2 Fe bal Yes 11,9 Al 0,3 N 13,8 2,3 62 8,2 6,4 14,2 D7 Sm 9,0 Fe bal What 4,5 Al 0,4 Ga 2,4 N 15 3,5 89 6,9 5,1 9,2 D8 Nd 9,0 Fe bal Yes 4,5 C 3,5 From 0,4 Go 2,4 N 15 3,1 55 7,1 5,7 10,9 D9 Nd 9,0 Fe bal Nb 0,4 Won't 2,4 N 15 4,2 63 7,3 5,5 11,2

[0075] Table 3 shows that adding a certain amount of M can also result in a relatively low surface roughness. However, the magnetic properties are somewhat reduced compared to rare-earth permanent magnet powder without M, and the surface roughness and magnetic properties will be reduced to varying degrees, especially if the components deviate from the ranges required by the application. IV. Rare-earth permanent magnet powder to which element M is added.

[0076] The rare-earth permanent magnet powder is produced using the elements Nd, C, N, T (T is Fe or FeCo), A, B and M, where M is at least one of Ti, V, Cr, Ni, Cu, Nb, Mo, Ta, W, Al, Ga and Si.

[0077] The rare-earth permanent magnet powders of example s54–s63 are produced by mixing the crude metals according to the proportions listed in Table 4 and by placing the rare-earth and transition metals in an induction melting furnace. Under the protection of gaseous argon, alloy ingots are obtained by molten metal. These alloy ingots are then rapidly quenched in a rapid quenching furnace after coarse grinding. The protective gas is gaseous argon, the jet pressure is 30 kPa, the number of nozzles is 3, and the cross-sectional area is 0.83 mm². 2 The linear speed of the water cooling roller is 61 m / s, and the copper roller diameter is 300 mm; after rapid quenching, flaky alloy powder is obtained.

[0078] After the alloy has been processed for 10 minutes under the protection of gaseous Ar at 700°C, it is nitrided for 5.5 hours at 420°C by gaseous N2 of an atmosphere to obtain nitride magnet powder.

[0079] X-ray diffraction analysis is performed on the resulting nitride magnetic powder. The components, magnetic properties, and particle size distribution of the resulting flaky nitride magnetic powder are determined. The components and properties of the materials are as shown in Table 4. Figure S represents an exemplary embodiment. Table 4 Components, structures and properties of the material sample Components (bal represents the remaining parts) Ra σ Characteristics Br Hcj (BH)m S54 Nd 7,8 Zr 1,6 Fe bal Co 4,5 Nb 2,5 C 0,7 B 0,8 N 13,5 1,6 47 8,7 5,7 15,9 S55 Nd 8,5 Zr 1,4 Fe bal Co 15,5 Won't 2,5 C 0,8 B 0,3 N 15,5 1,8 42 8,1 4,9 15,6 S56 Nd 6,9 Hf 1,5 Feb bal Co 4,5 Si 2,5 C 0,7 B 0,3 N 15,5 1,6 53 8,4 6,0 15,5 S57 Nd 6,3 Zr 1,1 Fe bal Co 10,3 Al 12,5 C 0,8 B 0,3 N 15,5 2,0 59 8,3 6,4 16,3 S58 Nd 7,5 Zr 1,6 Fe bal Co 4,5 Won't 1,9 If 3,1 C 0,7 B 0,8 N 13,5 1,9 37 8,1 7,5 15,6 S59 Nd 7,8 Zr 1,5 Fe bal Yes 4,5 Al 1,5 From 0,3 C 0,7 B 0,75 N 13,5 2,2 29 8,2 5,5 15,3 S60 Nd 8,5 Hf 1,4 Feb bal Co 15,5 Ga 1,3 Si 0,8 C 0,8 B 0,3 N 15,5 2,5 76 8,9 6,2 16,2 S61 Nd 6,9 Zr 1,0 Hf 0,5 Fe bal Co 4,5 C 0,7 W 0,1 Cr 1,5 B 0,3 N 15,5 2,4 59 8,5 5,9 16,1 S62 Nd 6,3 Zr 1,1 Fe bal Even though 9,3 The 2,1 Mo 0,4 C 0,8 B 0,3 N 15,5 2,3 43 8,1 4,7 15,9 S63 Nd 7,5 Zr 0,8 Hf 0,7 Feb bal Co 4,5 Dad 2,3 C 0,7 B 0,75 N 13,5 2,5 61 8,7 5,6 16,1

[0080] Table 4 shows that adding a certain amount of M can also result in a relatively low surface roughness. However, the magnetic properties are somewhat reduced compared to rare-earth permanent magnet powder without M, and the surface roughness and magnetic properties will be reduced to varying degrees, especially if the components deviate from the ranges required by the application. V. Influence of other rare earth elements on the magnetic properties of the rare earth permanent magnet powder provided by the application

[0081] The rare-earth permanent magnet powders of examples s64–s71 are produced by mixing the rare-earth and transition metals according to the proportions listed in Table 5 and by placing the rare-earth and transition metals in an induction melting furnace. Under the protection of gaseous argon, alloy ingots are obtained by molten metal. These alloy ingots are then placed in a rapid quenching furnace for rapid quenching after coarse grinding. The protective gas is gaseous argon, the jet pressure is 45 kPa, the number of nozzles is 4, and the cross-sectional area is 0.75 mm². 2 The linear speed of the water cooling roller is 60 m / s, and the copper roller diameter is 300 mm; after rapid quenching, flaky alloy powder is obtained.

[0082] After the alloy has been processed for 10 minutes under the protection of gaseous Ar at 700°C, it is nitrided for 6 hours at 430°C by gaseous N2 of an atmosphere to obtain nitride magnet powder.

[0083] X-ray diffraction analysis is performed on the resulting nitride magnetic powder. The components, magnetic properties, and particle size distribution of the resulting flaky nitride magnetic powder are determined. The components and properties of the materials are as shown in Table 5. Figure S represents an example. Table 5 Components, structures and properties of the material sample Components (bal represents the remaining parts) Ra σ Characteristics Br Hcj (BH)m S64 Nd 7,3 Sm 1,2 Fe bal Co 4,5 C 0,8 N 13,5 2,4 61 7,5 6,8 12,8 S65 when 8,3 What 1,5 Fe bal Co. 4,5 C 0,8 N 12,5 2,3 57 6,9 6,6 9,6 S66 Nd 6,5 Sm 4,0 Fe bal Co 4,5 C 0,9 N 15,5 2,5 43 7,2 6,8 12,5 S67 Nd 6,3 Ce 0,5 Zr 1,1 Fe bal Co 10,3 C 0,8 B 0,3 N 15,5 2,6 47 6,1 6,4 10,6 S68 Nd 5,5 Sm 3,7 Zr 1,5 Fe bal Co 4,5 C 0,7 B 0,8 N 13,5 2,7 49 6,8 6,2 10,2 S69 Nd 7,8 Ce 1,3 Zr 1,5 Fe bal Co 4,5 C 0,7 B 0,8 N 13,5 2,6 39 5,7 6,0 10,9 S70 Nd 7,8 Ce 0,9 Zr 1,6 Fe bal Co 4,5 Nb 2,5 C 0,7 B 0,8 N 13,5 1,6 47 8,7 1,6 11,3 S71 Nd 8,5 Sm 1,3 Zr 1,4 Fe bal Co 15,5 Ga 2,5 C 0,3 B 0,3 N 15,5 1,8 42 8,1 1,8 11,1

[0084] According to the above description, the TbCu7 structure rare earth nitride magnetic powder provided by the application is equipped with optimized components and can effectively avoid problems in the manufacturing process, including rare earth volatilization and poor wettability, etc., in order to obtain a material with uniform phase structures and a uniform microstructure as well as good magnetic properties.

[0085] Furthermore, according to the application, the magnetic powder can be mixed and bonded with a binder to produce a bonded magnet for use in applications including motors, stereo systems, measuring instruments, etc.

[0086] The above are merely preferred embodiments of the application and should not be used to limit the application. To those skilled in the art, the application may exhibit various modifications and amendments. Any modifications, equivalent substitutions, improvements, and the like within the spirit and principle of the application shall be subject to the scope of protection of the application.

Claims

[1] A rare-earth permanent magnet powder, wherein the rare-earth permanent magnet powder comprises 4 to 12 atomic% Nd, 0.1 to 2 atomic% C, 10 to 25 atomic% N and 62.2 to 85.9 atomic% T, wherein the T is Fe or FeCo and the main phase of the rare-earth permanent magnet powder is a hard magnetic phase with a TbCu7 structure. [2] The rare-earth permanent magnet powder according to claim 1, wherein the rare-earth permanent magnet powder has the structure in general formula (I) and general formula (I) is shown as follows: Nd x T 100-x-y-a C y N a (I), where 4 ≦ x ≦ 12, 0,1 ≦ y ≦ 2 and 10 ≦ a ≦ 25. [3] The rare-earth permanent magnet powder according to claim 1, wherein the rare-earth permanent magnet powder further comprises 1 to 5 atomic % of element A and 0.1 to 2 atomic % of element B; element A is Zr and / or Hf, and the ratio of the content of element B to the content of element A is 0.1 to 0.

5. [4] The rare earth permanent magnet powder according to claim 3, wherein the B content of the rare earth permanent magnet powder is between 0.3 and 2 atomic %. [5] The rare-earth permanent magnet powder according to claim 3, wherein the content of element Nd and element A in the rare-earth permanent magnet powder is 4 to 12 atomic % of the total content of the rare-earth permanent magnet powder and the ratio of the content of element C to the sum of the content of element Nd and element A in the rare-earth permanent magnet powder is 0.03 to 0.

15. [6] The rare-earth permanent magnet powder according to claim 5, wherein the ratio of the content of element C to the sum of the content of element Nd and element A in the rare-earth permanent magnet powder is 0.05 to 0.

12. [7] The rare-earth permanent magnet powder according to claim 5, wherein the rare-earth permanent magnet powder has the structure in general formula (II) and general formula (II) is shown as follows: Nd x A w T 100-x-y-z-a C y B z N a (II) where T is Fe or FeCo; A is Zr and / or Hf; 4 ≦ x + w ≦ 12, 1 ≦ w ≦ 5, 0.1 ≦ z ≦ 2, 10 ≦ a ≦ 25, 0.1 ≦ z / w ≦ 0.5 and 0.1 ≦ y ≦ 2. [8] The rare-earth permanent magnet powder according to one of claims 1, 3 or 6, wherein the rare-earth permanent magnet powder further comprises 0.3 to 10 atomic % M and M is at least one of Ti, V, Cr, Ni, Cu, Nb, Mo, Ta, W, Al, Ga and Si. [9] The rare earth permanent magnet powder according to claim 8, wherein the M content of the rare earth permanent magnet powder is 0.5 to 8 atomic %. [10] The rare-earth permanent magnet powder according to claim 9, wherein the content of M in the rare-earth permanent magnet powder is 0.5 to 5 atomic % and M is at least one of Nb, Ga, Al and Si. [11] The rare-earth permanent magnet powder according to any one of claims 1 to 10, wherein the roller contact surface roughness Ra of the rare-earth permanent magnet powder is less than 2.8 μm; preferably the roller contact surface roughness Ra is less than 1.6 μm. [12] The rare earth permanent magnet powder according to any one of claims 1 to 11, wherein the average grain size of the rare earth permanent magnet powder is 3 to 100 nm. [13] The rare-earth permanent magnet powder according to any one of claims 1 to 11, wherein the element Nd in the rare-earth permanent magnet powder is partially replaced by Sm and / or Ce; the content of Sm and / or Ce in the rare-earth permanent magnet powder is 0.5 to 4.0 atomic %. [14] A bonded magnet, wherein the bonded magnet is obtained by binding the rare-earth permanent magnet powder according to any one of claims 1 to 11 with a binder. [15] A device wherein the device uses the bound magnet according to claim 14.