Rare earth permanent magnet material and preparation method thereof

Abstract

The invention provides a rare earth permanent magnet material and a preparation method thereof. The rare earth permanent magnet material comprises rare earth alloy grains and metal particles distributed at the grain boundary of the rare earth alloy grains, the rare earth alloy grains have a component shown as a formula (I): Re1xRe2aFe100-x-y-a-zMyBz (I), Re1 is selected from one or more of the group consisting of La, Ce, Pr and Nd, Re2 is selected from Dy and / or Tb, M is selected from one or more of the group consisting of Cu, Al, Ga and Co, 20 < = x < = 40, 0 < = a < = 5, 1 < = y < = 5, 0.9 < = z < = 1.1; the metal particles are simple substance particles formed by Mc elements, and the melting point of the metal particles is larger than or equal to 1200 DEG C. The existence of the metal particles can improve the distribution of a rare earth-rich phase among crystal grains, inhibit the abnormal growth of rare earth alloy crystal grains, reduce the size of coarse grains and the width of a coarse grain aggregation region, and improve the magnetic performance of the rare earth permanent magnet material.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth permanent magnet materials, and in particular to a rare earth permanent magnet material and a preparation method thereof. Background Art

[0002] Rare earth permanent magnet materials are a type of alloy materials composed of rare earth metals (such as neodymium, praseodymium, samarium, etc.) and transition metals (such as iron, cobalt, etc.). They have high magnetic energy product, coercive force and remanence, and are widely used in motors, wind turbines, hybrid vehicles and high-end electronic products. As the third generation of rare earth permanent magnet materials, neodymium iron boron (Nd-Fe-B) has been widely used for its excellent magnetic properties. Among them, hot pressing-hot deformation technology is an important method for obtaining high-density and high-anisotropy neodymium iron boron magnets. It is expected to be widely used because of its simple process and high rare earth utilization rate.

[0003] However, the microstructure of NdFeB magnets prepared by hot pressing and hot deformation process is not uniform. There are mainly two types of microstructures. One is the lamellar crystal region inside the particles. The magnetization direction of such grains is consistent with the direction of the external pressure applied during processing. The other is the coarse grain region on one side of the particle boundary. The internal grains are coarse, and the grain size can reach several microns to tens of microns, and there is no orientation. Such grains are multi-domain structures, and the magnetic domain structure inside the grains is relatively complex, which will promote magnetization reversal and cause the coercive force of NdFeB magnets to decrease.

[0004] At present, the methods to improve the magnetic properties of hot pressed and hot deformed magnets mainly include two aspects: one is the optimization of process parameters, and the other is the introduction of foreign elements. The optimization of process parameters mainly covers the adjustment of temperature, solidification rate and alloy composition, while the introduction of foreign elements mainly improves the microstructure inside the magnet by grain boundary diffusion or directly adding specific elements. However, no matter which of the above methods is used to improve the microstructure, the ultimate goal is to refine the grains of hot pressed and hot deformed magnets and optimize the composition and distribution of the rare earth-rich phase inside the magnet. However, since the sensitivity of magnetic powder particle size to the performance of hot pressed and hot deformed magnets varies depending on the composition of the magnetic powder, how to effectively inhibit the growth of coarse grains of NdFeB magnets and how to control the grain size of the magnets are still topics that need to be explored.

[0005] In summary, researching and developing a rare earth permanent magnet material with adjustable rare earth-rich phase distribution and grain size, uniform grain size and narrow strip width in the coarse grain region and its preparation method are of great significance to improving the magnetic properties such as remanence and magnetic energy product of rare earth permanent magnet materials. Summary of the invention

[0006] The main purpose of the present invention is to provide a rare earth permanent magnet material and a preparation method thereof, so as to solve the problems of uncontrollable rare earth rich phase distribution, grain size uniformity and coarse grain zone width of rare earth permanent magnet materials in the prior art, as well as the problems of reduced remanence and magnetic energy product of hot pressed and hot deformed magnets caused thereby.

[0007] In order to achieve the above object, the present invention provides a rare earth permanent magnet material, which includes rare earth alloy grains and metal particles distributed at the grain boundaries of the rare earth alloy grains; the rare earth alloy grains have a composition shown in formula (I): 1 x Re 2 a Fe 100-x-y-a-z M y B z (I), where Re 1 One or more selected from the group consisting of La, Ce, Pr and Nd, Re 2 Selected from Dy and / or Tb, M is selected from one or more of the group consisting of Cu, Al, Ga and Co, 20≤x≤40, 0≤a≤5, 1≤y≤5, 0.9≤z≤1.1; the metal particles are single particles formed by Mc element, and their melting point is ≥1200℃.

[0008] Furthermore, the average particle size of the metal particles is 0.5 to 3 μm.

[0009] Furthermore, the weight ratio of the rare earth alloy grains to the metal particles is 1:(0.001-0.03).

[0010] Furthermore, the rare earth alloy grains with a grain size of 100 to 500 nm are coarse grains, and the width of the aggregation region of the coarse grains is 100 to 1350 nm, preferably 600 to 850 nm.

[0011] Furthermore, the Mc element is selected from one or more of the group consisting of Co, Cr, Ni, Mn, Ta, Hf, Sc and Zr.

[0012] In order to achieve the above-mentioned purpose, another aspect of the present invention also provides a method for preparing the above-mentioned rare earth permanent magnet material provided by the present application, and the preparation method comprises: step S1, crushing the rare earth alloy strip to obtain rare earth magnetic powder, wherein the rare earth alloy strip comprises the components shown in formula (I); step S2, using a single substance formed by the Mc element to perform surface coating treatment on the rare earth magnetic powder to obtain a composite rare earth magnetic powder with a coating layer coated on the surface, wherein the material of the coating layer is a single substance formed by the Mc element; step S3, sequentially performing hot pressing treatment and hot deformation treatment on the composite rare earth magnetic powder to obtain a rare earth permanent magnet material.

[0013] Furthermore, in step S1, the average particle size of the rare earth magnetic powder is 80-170 meshes; preferably, in the rare earth magnetic powder, the weight percentage of the rare earth magnetic powder with an average particle size of 80-120 meshes is 60-80wt%.

[0014] Furthermore, in step S1, the thickness of the rare earth alloy strip is 20-40 μm.

[0015] Further, in step S2, the surface coating treatment method includes: mixing rare earth magnetic powder and a single substance formed by Mc element to obtain a mixture; performing heat treatment and cooling treatment on the mixture in sequence to obtain composite rare earth magnetic powder; or, performing surface coating treatment by chemical plating, chemical vapor deposition or physical vapor deposition, more preferably, physical vapor deposition is magnetron sputtering; preferably, the weight ratio of rare earth magnetic powder to the single substance formed by Mc element is 1:(0.001~0.03); preferably, the average particle size of the single substance formed by Mc element is 0.3~2μm.

[0016] Furthermore, the heat treatment temperature is 500-700°C, and the time is 10-30 min. Preferably, the heat treatment is performed by a rotary heat treatment method, and the feed rate of the mixture is 1-3 kg / min.

[0017] Furthermore, the cooling rate of the cooling treatment is 10-20°C / s.

[0018] Furthermore, the heat treatment and the cooling treatment are performed under a vacuum condition or in an inert gas atmosphere.

[0019] Furthermore, the coating layer of the composite rare earth magnetic powder has a thickness of 2 to 10 nm.

[0020] Furthermore, in the composite rare earth magnetic powder, the weight percentage of the amorphous composite rare earth magnetic powder is 20-50wt%, and the oxygen content of the composite rare earth magnetic powder is ≤0.9wt%.

[0021] Furthermore, in step S3, the temperature of the hot pressing treatment is 600-800° C., the pressure is 300-600 MPa, and the time is 3-10 min.

[0022] Furthermore, in step S3, the temperature of the thermal deformation treatment is 700-900° C., the pressure is 100-300 MPa, and the time is 1-5 min.

[0023] Furthermore, in step S1, a rapid spinning method is used to prepare rare earth alloy strips.

[0024] Applying the technical solution of the present invention, the rare earth permanent magnet material in the present application includes rare earth alloy grains having the composition shown in formula (I) and metal particles distributed at the grain boundaries of the rare earth alloy grains, wherein the melting point of the metal particles is ≥1200°C. The rare earth alloy grains having the composition shown in formula (I) can improve the microstructure of the magnet of the rare earth permanent magnet material, improve the uniformity of the rare earth alloy grain size, and improve the orientation degree of the rare earth alloy grains, thereby improving the magnetic properties and stability of the remanence and magnetic energy product of the rare earth permanent magnet material. The presence of high melting point metal particles (melting point ≥1200°C) can improve the distribution of rare earth-rich phases between grains, inhibit the abnormal growth of rare earth alloy grains, improve the uniformity of the rare earth alloy grain size, reduce the grain size of coarse crystals and the strip width of the coarse crystal aggregation area, and improve the stability of the internal microstructure of the rare earth permanent magnet material magnet, thereby improving the remanence and magnetic energy product of the rare earth permanent magnet material. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 The scanning electron microscope image of the rare earth permanent magnet material prepared in Example 1 of the present application is shown;

[0027] Figure 2 The scanning electron microscope image of the rare earth permanent magnet material prepared in Example 1 of the present application is shown;

[0028] Figure 3 The scanning electron microscope image of the rare earth permanent magnet material prepared in Comparative Example 1 of the present application is shown. DETAILED DESCRIPTION

[0029] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0030] As described in the background technology, the existing rare earth permanent magnet materials have problems of uncontrollable rare earth phase distribution, grain size uniformity and coarse grain width, and the resulting problems of reduced remanence and magnetic energy product of hot pressed and hot deformed magnets. In order to solve the above technical problems, the first aspect of the present application provides a rare earth permanent magnet material, which includes rare earth alloy grains and metal particles distributed at the grain boundaries of the rare earth alloy grains; the rare earth alloy grains have a composition shown in formula (I): Re 1 x Re 2 a Fe 100-x-y-a-z M y B z(I), where Re 1 One or more selected from the group consisting of La, Ce, Pr and Nd, Re 2 Selected from Dy and / or Tb, M is selected from one or more of the group consisting of Cu, Al, Ga and Co, 20≤x≤40, 0≤a≤5, 1≤y≤5, 0.9≤z≤1.1; the metal particles are single particles formed by Mc element, and their melting point is ≥1200℃.

[0031] The rare earth permanent magnet material in the present application includes rare earth alloy grains having the composition shown in formula (I) and metal particles distributed at the grain boundaries of the rare earth alloy grains, wherein the melting point of the metal particles is ≥1200°C. The rare earth alloy grains having the composition shown in formula (I) can improve the microstructure of the rare earth permanent magnet material magnet, improve the uniformity of the rare earth alloy grain size, and improve the orientation of the rare earth alloy grains, thereby improving the magnetic properties and stability such as the remanence and magnetic energy product of the rare earth permanent magnet material. The presence of high melting point metal particles (melting point ≥1200°C) can improve the distribution of rare earth-rich phases between grains, inhibit the abnormal growth of rare earth alloy grains, improve the uniformity of the rare earth alloy grain size, reduce the grain size of coarse crystals and the strip width of the coarse crystal aggregation area, and improve the stability of the internal microstructure of the rare earth permanent magnet material magnet, thereby improving the remanence and magnetic energy product of the rare earth permanent magnet material.

[0032] In a preferred embodiment, the average particle size of the metal particles is 0.5 to 3 nm. The average particle size of the metal particles includes but is not limited to the above range, and limiting it within the above range is conducive to improving the distribution of the rare earth-rich phase between grains, and is conducive to improving the stability of the internal microstructure of the rare earth permanent magnet material, thereby helping to improve the magnetic properties of the rare earth permanent magnet material, such as the remanence and magnetic energy product.

[0033] In order to improve the uniformity of the distribution of metal particles at the grain boundaries of rare earth alloy grains and further improve the magnetic properties such as the remanence and magnetic energy product of rare earth permanent magnet materials, in a preferred embodiment, the weight ratio of rare earth alloy grains to metal particles is 1:(0.001-0.03).

[0034] In a preferred embodiment, the rare earth alloy grains with a grain size of 100 to 500 nm are coarse crystals, and the width of the coarse crystal aggregation area is 100 to 1350 nm. In the present application, the rare earth alloy grains with a grain size of 100 to 500 nm are defined as coarse crystals. The width of the coarse crystal aggregation area includes but is not limited to the above range. Limiting it within the above range is conducive to improving the microstructure of the rare earth permanent magnet material magnet, and is conducive to improving the distribution of the rare earth-rich phase, thereby helping to improve the magnetic properties such as the remanence and magnetic energy product of the rare earth permanent magnet material. Preferably, the width of the coarse crystal aggregation area is 400 to 1200 nm, 500 to 1000 nm, 600 to 900 nm, or 700 to 850 nm. Specifically, the width of the coarse crystal aggregation region can be 650nm, 700nm, 720nm, 750nm, 780nm, 800nm, 810nm, 820nm, 850nm, 900nm, 930nm, 980nm, 1200nm, or 1350nm.

[0035] In order to further improve the microstructure of the rare earth permanent magnet material, further improve the distribution of the rare earth rich phase, and thus further improve the magnetic properties such as the remanence and magnetic energy product of the rare earth permanent magnet material, preferably, the average grain size of the coarse crystals is 100 to 500 nm; more preferably, within the aggregation area of ​​the coarse crystals, the ratio of the maximum grain size to the minimum grain size of the coarse crystals is (4 to 5):(1 to 2).

[0036] It should be noted that in the coarse crystal aggregation area, the ratio of the maximum grain size to the minimum grain size of the coarse crystals reflects the uniformity of the grain size distribution of the coarse crystals in the coarse crystal aggregation area. When the ratio is close to 1, it indicates that the more uniform the grain size distribution is, the smaller the difference in grain size is, which is beneficial to further improve the magnetic properties such as remanence and magnetic energy product of rare earth permanent magnet materials.

[0037] In a preferred embodiment, the Mc element includes, but is not limited to, one or more of the group consisting of Co, Cr, Ni, Mn, Ta, Hf, Sc and Zr. Compared with other types, the use of the above-mentioned types of Mc elements is conducive to improving the stability of the internal microstructure of the magnet of the rare earth permanent magnet material, is conducive to inhibiting the grain boundary migration of the rare earth alloy grains, and is conducive to improving the uniformity of the rare earth alloy grain size, thereby helping to improve the magnetic properties such as the remanence and magnetic energy product of the rare earth permanent magnet material.

[0038] The second aspect of the present application also provides a method for preparing the above-mentioned rare earth permanent magnet material provided by the present application, and the preparation method comprises: step S1, crushing the rare earth alloy strip to obtain rare earth magnetic powder, wherein the rare earth alloy strip comprises the components shown in formula (I); step S2, using a single substance formed by the Mc element to perform surface coating treatment on the rare earth magnetic powder to obtain a composite rare earth magnetic powder with a coating layer coated on the surface, wherein the material of the coating layer is a single substance formed by the Mc element; step S3, sequentially performing hot pressing treatment and hot deformation treatment on the composite rare earth magnetic powder to obtain a rare earth permanent magnet material.

[0039] In the preparation method of the above-mentioned rare earth permanent magnetic material provided by the present application, step S1 crushes the rare earth alloy strip having the composition shown in formula (I) to obtain rare earth magnetic powder; step S2 uses a single substance formed by Mc element to perform surface coating treatment on the rare earth magnetic powder to obtain composite rare earth magnetic powder, and the introduction of a single substance with a high melting point (melting point ≥ 1200°C) can improve the distribution of rare earth-rich phases between grains, and can inhibit the excessive growth of rare earth alloy grains in the subsequent thermal deformation treatment, thereby improving the uniformity of the rare earth alloy grain size, reducing the grain size of coarse crystals and the strip width of the coarse crystal aggregation area, improving the microstructure inside the magnet of the rare earth permanent magnetic material, and improving the magnetic properties such as the remanence and magnetic energy product of the rare earth permanent magnetic material. Step S3 performs hot pressing treatment and hot deformation treatment on the composite rare earth magnetic powder in sequence to obtain a rare earth permanent magnetic material.

[0040] Compared with other methods, the above method of the present application can improve the microstructure inside the magnet of the rare earth permanent magnet material, and obtain a rare earth permanent magnet material with better magnetic properties such as remanence and magnetic energy product.

[0041] In a preferred embodiment, in step S1, the average particle size of the rare earth magnetic powder is 80 to 170 meshes. The average particle size of the rare earth magnetic powder includes but is not limited to the above range. Limiting it within the above range is beneficial to improving the uniformity of the grain size of the rare earth alloy, and is beneficial to reducing the grain size of the coarse crystals and the strip width of the coarse crystal aggregation area, thereby facilitating the improvement of the magnetic properties such as the remanence and magnetic energy product of the rare earth permanent magnet material. Specifically, the average particle size of the rare earth magnetic powder can be 80 mesh, 90 mesh, 100 mesh, 110 mesh, 120 mesh, 140 mesh, 150 mesh or 170 mesh.

[0042] In order to further improve the uniformity of the grain size of the rare earth alloy, further reduce the grain size of the coarse crystal and the strip width of the coarse crystal aggregation area, further improve the microstructure inside the magnet of the rare earth permanent magnet material, and thus further improve the magnetic properties such as the remanence and magnetic energy product of the rare earth permanent magnet material, in a preferred embodiment, in step S1, the weight percentage of the rare earth magnetic powder with an average particle size of 80 to 120 meshes is 60 to 80wt%, preferably 70 to 80wt%. Specifically, the weight percentage of the rare earth magnetic powder with an average particle size of 80 to 120 meshes can be 60wt%, 65wt%, 70wt%, 75wt% or 80wt%.

[0043] In a preferred embodiment, in step S1, the thickness of the rare earth alloy strip is 20-40 μm. The thickness of the rare earth alloy strip includes but is not limited to the above range, and limiting it within the above range facilitates the crushing of the rare earth alloy strip, thereby facilitating the obtaining of rare earth magnetic powder with a particle size of 80-170 mesh, thereby facilitating the improvement of the magnetic properties of the rare earth permanent magnet material.

[0044] Rapid spinning quenching refers to the process of cooling the molten metal or alloy at an extremely high rate (cooling rate ≥ 1×10 5 ℃ / s), forming a thin strip or powder to obtain an amorphous or microcrystalline material preparation method, which can significantly refine the grains of the material and enhance its magnetic properties and mechanical properties. In a preferred embodiment, a rapid spinning method is used to prepare rare earth alloy strips. Compared with other methods, the preparation of rare earth alloy strips by the above method is beneficial to refining the particle size of the rare earth alloy and promoting the formation of rare earth magnetic powder with an amorphous phase, which is beneficial to inhibiting the excessive growth of rare earth alloy grains in subsequent hot pressing and hot deformation treatments, and further beneficial to obtaining rare earth permanent magnet materials with better magnetic properties (such as remanence and magnetic energy product).

[0045] In a preferred embodiment, in step S2, the surface coating treatment method includes: mixing rare earth magnetic powder with a single substance formed by Mc element to obtain a mixture; heat treating and cooling the mixture in sequence to obtain composite rare earth magnetic powder; or, using chemical plating, chemical vapor deposition or physical vapor deposition for surface coating treatment, and more preferably physical vapor deposition is magnetron sputtering. Compared with other methods, the above method is conducive to forming a uniform coating layer on the surface of rare earth magnetic powder, and is also conducive to enhancing the bonding force between rare earth magnetic powders, and is conducive to improving the structure and composition of the grain boundaries of rare earth alloy grains (i.e., rare earth-rich phases), thereby facilitating the improvement of magnetic properties such as remanence and magnetic energy product of rare earth permanent magnet materials.

[0046] In a preferred embodiment, the weight ratio of the rare earth magnetic powder to the single substance formed by the Mc element is 1:(0.001-0.03), preferably 1:(0.005-0.03), and more preferably 1:(0.015-0.02). The weight ratio of the rare earth magnetic powder to the single substance formed by the Mc element includes but is not limited to the above range. Limiting it within the above range is beneficial to improving the uniformity of the grain size of the rare earth alloy, and is beneficial to suppressing the decrease in the magnetic properties of the rare earth permanent magnet material caused by the excess of the single substance formed by the Mc element, thereby helping to improve the magnetic properties of the rare earth permanent magnet material such as coercive force, remanence and magnetic energy product. Specifically, the weight ratio of the rare earth magnetic powder to the metal particles can be 1:0.005, 1:0.01, 1:0.015, 1:0.02, 1:0.025 or 1:0.03.

[0047] In a preferred embodiment, the single substance formed by the Mc element includes but is not limited to one or more of the group consisting of Co single substance, Cr single substance, Ni single substance, Mn single substance, Ta single substance, Hf single substance, Sc single substance and Zr single substance. Compared with other types, the single substance formed by the Mc element of the above type is conducive to improving the distribution of the rare earth-rich phase between grains, and is conducive to inhibiting the excessive growth of rare earth alloy grains in the subsequent thermal deformation treatment, thereby helping to reduce the grain size of the coarse crystal and the strip width of the coarse crystal aggregation area, and further helping to improve the magnetic properties such as the remanence and magnetic energy product of the rare earth permanent magnet material.

[0048] In order to further improve the distribution of rare earth-rich phases between grains, further inhibit excessive growth of rare earth alloy grains in subsequent thermal deformation treatment, thereby further reducing the grain size of coarse crystals and the strip width of the coarse crystal aggregation area, and further improving the magnetic properties of rare earth permanent magnet materials, preferably, the single substance formed by Mc element includes but is not limited to a combination of Co single substance and Ni single substance, a combination of Co single substance and Cr single substance, or a combination of Mn single substance and Cr single substance.

[0049] In a preferred embodiment, the average particle size of the single substance formed by the Mc element is 0.3 to 2 μm. The average particle size of the single substance formed by the Mc element includes but is not limited to the above range. Limiting it within the above range is beneficial to suppress the excessive growth of rare earth alloy grains in the subsequent thermal deformation treatment, thereby improving the uniformity of the rare earth alloy grain size, reducing the grain size of coarse crystals and the strip width of the coarse crystal aggregation area, improving the microstructure inside the magnet of the rare earth permanent magnet material, and further improving the magnetic properties such as the remanence and magnetic energy product of the rare earth permanent magnet material.

[0050] In order to further inhibit the excessive growth of rare earth alloy grains, thereby further improving the uniformity of rare earth alloy grain size, further reducing the grain size of coarse crystals and the strip width of the coarse crystal aggregation area, and further improving the magnetic properties of rare earth permanent magnet materials, preferably, the thickness of the coating layer is 2 to 10 nm.

[0051] In a preferred embodiment, the temperature of the heat treatment is 500-700°C, and the time is 10-30 minutes; preferably, the temperature of the heat treatment is 500-600°C, and the time is 10-20 minutes. The temperature and time of the heat treatment include but are not limited to the above ranges. Limiting it within the above range is beneficial to improving the effect of the surface coating treatment, improving the microstructure inside the magnet of the rare earth permanent magnet material, and inhibiting the excessive growth of the rare earth alloy grains, thereby reducing the grain size of the coarse crystals and the strip width of the coarse crystal aggregation area. Specifically, the temperature of the heat treatment can be 500°C, 550°C, 600°C, 650°C, 680°C or 700°C, and the time of the heat treatment can be 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes.

[0052] In order to further improve the effect of surface coating treatment, further improve the microstructure inside the magnet of rare earth permanent magnet material, further inhibit the excessive growth of rare earth alloy grains, and further reduce the grain size of coarse crystals and the strip width of the coarse crystal aggregation area, preferably, rotary heat treatment is adopted for heat treatment, and the feed rate of the mixture is 1 to 3 kg / min.

[0053] In a preferred embodiment, the cooling rate of the cooling treatment is 10 to 20°C / s, preferably 12 to 20°C / s, and more preferably 15 to 18°C / s. The cooling rate of the cooling treatment includes but is not limited to the above range. Limiting it within the above range is beneficial to inhibiting the abnormal growth of rare earth alloy grains during the cooling treatment, and is beneficial to improving the uniformity of the rare earth alloy grain size. It is also beneficial to improve the stability of the grain boundaries of the rare earth alloy grains, thereby facilitating the improvement of the magnetic properties of the rare earth permanent magnet material, such as the remanence and magnetic energy product. Specifically, the cooling rate of the cooling treatment can be 10°C / s, 12°C / s, 13°C / s, 14°C / s, 15°C / s, 16°C / s, 18°C / s or 20°C / s.

[0054] In order to inhibit the reaction of rare earth magnetic powder with active gases such as oxygen in the environment, thereby further improving the purity of rare earth permanent magnet materials and further improving the magnetic properties and stability of rare earth permanent magnet materials, preferably, the heat treatment and cooling treatment are carried out under vacuum conditions or inert gas atmosphere.

[0055] In order to inhibit the excessive growth of rare earth alloy grains during subsequent hot pressing and hot deformation treatments, and at the same time to reduce the formation of oxides (such as iron oxide), further improve the microstructure inside the rare earth permanent magnet material magnet, thereby further improving its magnetic properties, in a preferred embodiment, in the composite rare earth magnetic powder, the weight percentage of the amorphous composite rare earth magnetic powder is 20-50wt%, and the oxygen content of the composite rare earth magnetic powder is ≤0.9wt%.

[0056] In a preferred embodiment, in step S3, the temperature of the hot pressing treatment is 600-800°C, the pressure is 300-600MPa, and the time is 3-10min; preferably, the temperature of the hot pressing treatment is 600-700°C, the pressure is 400-500MPa, and the time is 5-8min. The temperature, pressure and time of the hot pressing treatment include but are not limited to the above ranges. Limiting them to the above ranges is conducive to improving the efficiency of the hot pressing treatment, improving the density of the rare earth permanent magnet material, and improving the microstructure of the rare earth permanent magnet material, thereby improving the magnetic properties and stability of the rare earth permanent magnet material.

[0057] In a preferred embodiment, in step S3, the temperature of the thermal deformation treatment is 700-900°C, the pressure is 100-300 MPa, and the time is 1-5 min; preferably, the temperature of the thermal deformation treatment is 750-850°C, the pressure is 150-250 MPa, and the time is 2-4 min. The temperature, pressure and time of the thermal deformation treatment include but are not limited to the above ranges. Limiting them to the above ranges is conducive to improving the efficiency of the thermal deformation treatment, inhibiting the excessive growth of rare earth alloy grains, and improving the uniformity of their size, thereby improving the magnetic properties and stability of rare earth permanent magnet materials.

[0058] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0059] It should be noted that a scanning electron microscope was used to characterize the microstructure of the rare earth permanent magnet materials prepared in all the embodiments and comparative examples of the present application, including the average grain size of the coarse crystals (in nm) and the width of the aggregation area of ​​the coarse crystals (in nm); X-ray diffraction (XRD) was used to measure the content of the composite rare earth magnetic powder with an amorphous structure in the composite rare earth magnetic powder in Examples 1 to 24; and an infrared oxygen and nitrogen analyzer was used to measure the oxygen content of the composite rare earth magnetic powder in Examples 1 to 24.

[0060] Example 1

[0061] A method for preparing a rare earth permanent magnetic material comprises the following steps:

[0062] (1) PrNd alloy, Co element, Ga element, iron boride and Fe element are smelted at 1500°C for 1 hour to obtain a material having a composition of (PrNd) 29.9 Fe 65.42 Co 3.2 Ga 0.5 B 0.98 A rare earth alloy ingot is cast, and then the rare earth alloy ingot is used to prepare a rare earth alloy strip with the same composition and a thickness of 30 μm by a rapid spinning method;

[0063] (2) mechanically crushing the rare earth alloy strip obtained in step (1), and sieving the crushed rare earth alloy strip to obtain rare earth magnetic powder with a particle size of 80 to 170 mesh, wherein the weight percentage of the rare earth magnetic powder with a particle size of 80 to 120 mesh is 70wt%;

[0064] (3) mixing the rare earth magnetic powder obtained in step (2) with a single substance of Co having an average particle size of 500 nm to obtain a mixture, wherein the weight ratio of the rare earth magnetic powder to the single substance of Co is 1:0.02; and -2 Pa), heat-treating the mixture in a rotary heat treatment furnace (XG-200T, Chengdu Jinya Industrial Co., Ltd.), and cooling the mixture after completion to obtain a composite rare earth magnetic powder coated with a Co single substance coating layer on the surface, wherein the heat treatment temperature is 580°C, the time is 20min, the feed rate of the mixture is 1kg / min, and the cooling rate of the cooling treatment is 15°C / s; the coating layer thickness is 3nm, wherein the weight percentage of the composite rare earth magnetic powder with an amorphous structure is 40wt%, and the oxygen content of the composite rare earth magnetic powder is 0.85wt%;

[0065] (4) The composite rare earth magnetic powder obtained in step (3) is subjected to hot pressing treatment and heat deformation treatment in sequence to obtain a rare earth permanent magnetic material, wherein the temperature of the hot pressing treatment is 700°C, the pressure is 400 MPa, and the time is 5 min, and the temperature of the heat deformation treatment is 800°C, the pressure is 200 MPa, and the time is 2 min.

[0066] The scanning electron microscope image of the rare earth permanent magnet material prepared in this embodiment is as follows: Figure 1 and Figure 2 shown; according to Figure 1 It can be seen that the coarse crystal aggregation area is composed of 1 to 3 layers of coarse crystal grains. In the rare earth permanent magnet material prepared in Example 1, the average grain size of the coarse crystal is 500nm, and the width of the coarse crystal aggregation area is 700nm. Figure 2 It can be seen that the metal particles are dispersed in the rare earth permanent magnet material.

[0067] Examples 2 to 8

[0068] The differences between Examples 2 to 8 and Example 1 are shown in Table 1, and the remaining steps are the same as those of Example 1.

[0069] Table 1

[0070]

[0071] In Examples 2 to 8, the coating thickness of the composite rare earth magnetic powder obtained in step (3), the weight percentage of the composite rare earth magnetic powder having an amorphous structure in the composite rare earth magnetic powder, and the oxygen content of the composite rare earth magnetic powder are shown in Table 2.

[0072] Table 2

[0073]

[0074] Example 9

[0075] The difference from Example 1 is that in step (3), the weight ratio of rare earth magnetic powder to Co single substance is 1:0.0005, and the remaining steps are the same as Example 1. The coating thickness of the composite rare earth magnetic powder prepared in this example is 1 nm, the weight percentage of the composite rare earth magnetic powder with an amorphous structure is 35wt%, and the oxygen content of the composite rare earth magnetic powder is 0.88wt%.

[0076] Example 10

[0077] The difference from Example 1 is that in step (1), PrNd alloy, Co element, Ga element, DyFe alloy, iron boride and Fe element are smelted at 1500° C. for 1 h to obtain a product having a composition of (PrNd) 28 oeLh 66.7 Co3Ga 0.4 B 0.9 The rare earth alloy ingot obtained from this is composed of (PrNd) 28 oeLh 66.7 Co3Ga 0.4 B 0.9 , the remaining steps are the same as those in Example 1.

[0078] Embodiment 11

[0079] The difference from Example 1 is that in step (1), PrNd alloy, Co element, iron boride and Fe element are smelted at 1500° C. for 1 h to obtain a product having a composition of (PrNd) 30.3 Fe 68.32 Co 0.45 B 0.93 The rare earth alloy ingot obtained from this is composed of (PrNd) 30.3 Fe 68.32 Co 0.45 B0.93 , the remaining steps are the same as those in Example 1.

[0080] Example 12

[0081] The difference from Example 1 is that in the rare earth magnetic powder screened in step (1), the weight percentage of the rare earth magnetic powder with a particle size of 80 to 120 mesh is 60wt%, and the remaining steps are the same as Example 1.

[0082] Example 13

[0083] The difference from Example 1 is that in the rare earth magnetic powder screened in step (1), the weight percentage of the rare earth magnetic powder with a particle size of 80 to 120 mesh is 80wt%, and the remaining steps are the same as Example 1.

[0084] Embodiment 14

[0085] The difference from Example 1 is that in the rare earth magnetic powder screened in step (1), the weight percentage of the rare earth magnetic powder with a particle size of 80 to 120 mesh is 50wt%, and the remaining steps are the same as Example 1.

[0086] Embodiment 15

[0087] The difference from Example 1 is that in step (3), the heat treatment temperature is 500°C, the time is 30 min, the feed rate of the mixture is 3 kg / min, and the remaining steps are the same as in Example 1; in the composite rare earth magnetic powder prepared in this embodiment, the weight percentage of the composite rare earth magnetic powder with an amorphous structure is 50wt%, and the oxygen content of the composite rare earth magnetic powder is 0.85wt%.

[0088] Example 16

[0089] The difference from Example 1 is that: in step (3), the heat treatment temperature is 700°C, the time is 10 min, the feed rate of the mixture is 1 kg / min, and the remaining steps are the same as those in Example 1; in the composite rare earth magnetic powder prepared in this embodiment, the weight percentage of the composite rare earth magnetic powder with an amorphous structure is 45wt%, and the oxygen content of the composite rare earth magnetic powder is 0.8wt%.

[0090] Embodiment 17

[0091] The difference from Example 1 is that: in step (3), the heat treatment temperature is 750°C, the time is 5 min, the feed rate of the mixture is 0.6 kg / min, and the remaining steps are the same as those in Example 1; in the composite rare earth magnetic powder prepared in this embodiment, the weight percentage of the composite rare earth magnetic powder with an amorphous structure is 20wt%, and the oxygen content of the composite rare earth magnetic powder is 0.9wt%.

[0092] Embodiment 18

[0093] The difference from Example 1 is that in step (3), the cooling rate of the cooling treatment is 10°C / s, and the remaining steps are the same as those in Example 1; in the composite rare earth magnetic powder prepared in this embodiment, the weight percentage of the composite rare earth magnetic powder with an amorphous structure is 50wt%, and the oxygen content of the composite rare earth magnetic powder is 0.7wt%.

[0094] Embodiment 19

[0095] The difference from Example 1 is that in step (3), the cooling rate of the cooling treatment is 20°C / s, and the remaining steps are the same as those in Example 1; in the composite rare earth magnetic powder prepared in this embodiment, the weight percentage of the composite rare earth magnetic powder with an amorphous structure is 45wt%, and the oxygen content of the composite rare earth magnetic powder is 0.75wt%.

[0096] Embodiment 20

[0097] The difference from Example 1 is that in step (3), the cooling rate of the cooling treatment is 25°C / s, and the remaining steps are the same as Example 1; in the composite rare earth magnetic powder prepared in this embodiment, the weight percentage of the composite rare earth magnetic powder with an amorphous structure is 50wt%, and the oxygen content of the composite rare earth magnetic powder is 0.9wt%.

[0098] Embodiment 21

[0099] The difference from Example 1 is that in step (4), the temperature of the hot pressing treatment is 800°C, the pressure is 300 MPa, and the time is 8 minutes. The remaining steps are the same as in Example 1.

[0100] Embodiment 22

[0101] The difference from Example 1 is that in step (4), the temperature of the hot pressing treatment is 500°C, the pressure is 250 MPa, and the time is 11 minutes. The remaining steps are the same as in Example 1.

[0102] Embodiment 23

[0103] The difference from Example 1 is that in step (4), the temperature of the thermal deformation treatment is 700° C., the pressure is 100 MPa, and the time is 3 min. The remaining steps are the same as those in Example 1.

[0104] Embodiment 24

[0105] The difference from Example 1 is that in step (4), the temperature of the thermal deformation treatment is 600° C., the pressure is 70 MPa, and the time is 7 min. The remaining steps are the same as those in Example 1.

[0106] Comparative Example 1

[0107] The difference from Example 1 is that in step (2), the weight percentage of the rare earth magnetic powder with a particle size of 80 to 120 mesh is 50wt%, and step (3) is omitted, and the rare earth magnetic powder obtained in step (2) is directly subjected to hot pressing and heat deformation treatment, and the remaining steps are the same as in Example 1.

[0108] The scanning electron microscope image of the rare earth permanent magnet material prepared in this embodiment is as follows Figure 3 As shown, according to Figure 3 It can be seen that the coarse crystal aggregation area of ​​the rare earth permanent magnet material magnet is formed by the accumulation of multiple layers (more than 3 layers) of coarse grains, wherein the average grain size of the coarse crystals is 900nm, and the width of the coarse crystal aggregation area is 5000nm.

[0109] Comparative Example 2

[0110] The difference from Example 1 is that in step (2), the weight percentage of the rare earth magnetic powder with a particle size of 80 to 120 mesh is 40wt%, and step (3) is omitted, and the rare earth magnetic powder obtained in step (2) is directly subjected to hot pressing and heat deformation treatment, and the remaining steps are the same as in Example 1.

[0111] Comparative Example 3

[0112] The difference from Example 1 is that step (3) is omitted, and the rare earth magnetic powder obtained in step (2) is directly subjected to hot pressing and hot deformation treatment, and the remaining steps are the same as those in Example 1.

[0113] The magnetic properties (remanence, coercive force and magnetic energy product) of the rare earth permanent magnetic materials prepared in all the embodiments and comparative examples of the present application were tested using a vibrating sample magnetometer (VSM, VersaLab, Quantum Design, USA).

[0114] The data of the rare earth alloy grain composition, the width of the coarse grain aggregation area, the remanence, the coercive force and the magnetic energy product of the rare earth permanent magnet materials prepared in all the embodiments and comparative examples of the present application are shown in Table 3.

[0115] Table 3

[0116]

[0117]

[0118] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0119] Comparing Examples 1 to 8 and Comparative Examples 1 to 3, it can be seen that the width of the coarse crystal aggregation area in the rare earth permanent magnetic material obtained in Examples 1 to 8 is significantly smaller than that in Comparative Examples 1 to 3; due to the small grain size, the coercivity of the rare earth permanent magnetic material obtained in Examples 1 to 8 is reduced, but its remanence and maximum magnetic energy product are significantly better than those in Comparative Examples 1 to 3, indicating that its overall magnetic properties are better. It can be seen that the introduction of a single substance with a high melting point (melting point ≥ 1200°C) can improve the distribution of the rare earth-rich phase between grains, and can inhibit the excessive growth of rare earth alloy grains in subsequent thermal deformation treatment, thereby improving the uniformity of the rare earth alloy grain size, reducing the grain size of the coarse crystal and the strip width of the coarse crystal aggregation area, improving the microstructure inside the magnet of the rare earth permanent magnetic material, and improving the magnetic properties such as the remanence and maximum magnetic energy product of the rare earth permanent magnetic material.

[0120] By comparing Examples 1 and 9, it can be seen that, compared with other ranges, limiting the weight ratio of the single substance formed by the rare earth magnetic powder and the Mc element within the above-mentioned range of the present application is beneficial to improving the distribution of the rare earth-rich phase between the grains, improving the uniformity of the grain size of the rare earth alloy, and improving the magnetic properties of the rare earth permanent magnet material, such as coercive force, remanence and maximum magnetic energy product.

[0121] Comparing Examples 1 and 12 to 14, it can be seen that due to the larger grain size of the rare earth permanent magnet material obtained in Example 14, its coercive force is relatively larger, but its remanence and maximum magnetic energy product are lower, and the overall magnetic properties are poor. Therefore, compared with other ranges, limiting the content of the rare earth magnetic powder with an average particle size of 80 to 120 meshes to the above range of the present application is conducive to improving the uniformity of the rare earth alloy grain size, reducing the grain size of the coarse crystals and the strip width of the coarse crystal aggregation area, and improving the microstructure inside the magnet of the rare earth permanent magnet material, thereby facilitating the improvement of the remanence and maximum magnetic energy product of the rare earth permanent magnet material.

[0122] Comparing Examples 1 and 15 to 17, it can be seen that since the grain size of the rare earth permanent magnet material obtained in Example 17 is larger than that in Example 16, its coercive force is relatively larger, but its remanence and maximum magnetic energy product are lower, and the overall magnetic properties are poor. Compared with other ranges, limiting the temperature and time of the heat treatment within the above range of the present application is conducive to improving the effect of the surface coating treatment, improving the microstructure inside the magnet of the rare earth permanent magnet material, and inhibiting the excessive growth of rare earth alloy grains, thereby reducing the grain size of the coarse crystals and the strip width of the coarse crystal aggregation area, and further improving the remanence and maximum magnetic energy product of the rare earth permanent magnet material.

[0123] By comparing Examples 1 and 18 to 20, it can be seen that, compared with other ranges, limiting the cooling rate of the cooling treatment within the above-mentioned range of the present application is beneficial to suppressing the abnormal growth of rare earth alloy grains during the cooling treatment, and is beneficial to improving the uniformity of the rare earth alloy grain size. It is also beneficial to improve the stability of the grain boundaries of the rare earth alloy grains, thereby helping to improve the remanence and maximum magnetic energy product of the rare earth permanent magnet material.

[0124] Comparing Examples 1, 21 and 22, it can be seen that since the grain size of the rare earth permanent magnet material obtained in Example 22 is larger than that in Example 21, its coercive force is relatively larger, but its remanence and maximum magnetic energy product are lower, and the overall magnetic properties are poor. Compared with other ranges, limiting the temperature, pressure and time of the hot pressing treatment within the above range of the present application is conducive to improving the efficiency of the hot pressing treatment, improving the density of the rare earth permanent magnet material, and improving the microstructure of the rare earth permanent magnet material, and reducing the size of the coarse crystal and the width of its aggregation area, thereby facilitating the improvement of the remanence and maximum magnetic energy product of the rare earth permanent magnet material.

[0125] By comparing Examples 1, 23 and 24, it can be seen that, compared with other ranges, limiting the temperature, pressure and time of the thermal deformation treatment within the above-mentioned range of the present application is beneficial to improving the efficiency of the thermal deformation treatment, inhibiting the excessive growth of rare earth alloy grains, reducing the size of coarse grains and the width of their aggregation areas, thereby facilitating improving the remanence and maximum magnetic energy product of rare earth permanent magnet materials.

[0126] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0127] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A rare earth permanent magnet material, characterized in that: The rare earth permanent magnet material comprises rare earth alloy grains and metal particles distributed at the grain boundaries of the rare earth alloy grains; the rare earth alloy grains have a composition shown in formula (I): Re 1 x Re 2 a Fe 100-x-y-a-z M y B z (I), where Re 1 One or more selected from the group consisting of La, Ce, Pr and Nd, Re 2 Selected from Dy and / or Tb, M is selected from one or more of the group consisting of Cu, Al, Ga and Co, 20≤x≤40, 0≤a≤5, 1≤y≤5, 0.9≤z≤1.1; the metal particles are single-substance particles formed by Mc element, and the melting point thereof is ≥1200°C.

2. The rare earth permanent magnet material according to claim 1, characterized in that: The average particle size of the metal particles is 0.5 to 3 μm; Preferably, the weight ratio of the rare earth alloy grains to the metal particles is 1:(0.001-0.03).

3. The rare earth permanent magnet material according to claim 1 or 2, characterized in that: The rare earth alloy grains with a grain size of 100 to 500 nm are coarse grains, and the width of the aggregation region of the coarse grains is 100 to 1350 nm, preferably 600 to 900 nm.

4. The rare earth permanent magnet material according to claim 1 or 2, characterized in that: The Mc element is selected from one or more of the group consisting of Co, Cr, Ni, Mn, Ta, Hf, Sc and Zr.

5. A method for preparing the rare earth permanent magnetic material according to any one of claims 1 to 4, characterized in that: The preparation method comprises: Step S1, crushing the rare earth alloy strip to obtain rare earth magnetic powder, wherein the rare earth alloy strip comprises a component represented by formula (I); Step S2, using a single substance formed by the Mc element to perform surface coating treatment on the rare earth magnetic powder to obtain a composite rare earth magnetic powder with a coating layer coated on the surface, wherein the material of the coating layer is the single substance formed by the Mc element; Step S3, performing hot pressing treatment and hot deformation treatment on the composite rare earth magnetic powder in sequence to obtain the rare earth permanent magnetic material.

6. The method for preparing the rare earth permanent magnetic material according to claim 5, characterized in that: In the step S1, the average particle size of the rare earth magnetic powder is 80-170 mesh; Preferably, in the rare earth magnetic powder, the weight percentage of the rare earth magnetic powder with an average particle size of 80 to 120 mesh is 60 to 80 wt%; Preferably, in step S1, the rare earth alloy strip has a thickness of 20 to 40 μm.

7. The method for preparing the rare earth permanent magnetic material according to claim 5 or 6, characterized in that: In the step S2, the surface coating treatment method includes: mixing the rare earth magnetic powder with the single substance formed by the Mc element to obtain a mixture; performing heat treatment and cooling treatment on the mixture in sequence to obtain the composite rare earth magnetic powder; or, performing the surface coating treatment by chemical plating, chemical vapor deposition or physical vapor deposition, and more preferably, the physical vapor deposition is magnetron sputtering; Preferably, the weight ratio of the rare earth magnetic powder to the single substance formed by the Mc element is 1:(0.001-0.03); Preferably, the average particle size of the single substance formed by the Mc element is 0.3-2 μm.

8. The method for preparing rare earth permanent magnetic material according to claim 7, characterized in that: The heat treatment temperature is 500-700°C and the time is 10-30 minutes; Preferably, the heat treatment is carried out by a rotary heat treatment method, and the feed rate of the mixture is 1 to 3 kg / min; Preferably, the cooling rate of the cooling treatment is 10-20°C / s; Preferably, the heat treatment and the cooling treatment are performed under vacuum conditions or in an inert gas atmosphere.

9. The method for preparing rare earth permanent magnetic material according to claim 8, characterized in that: The coating layer of the composite rare earth magnetic powder has a thickness of 2 to 10 nm; Preferably, in the composite rare earth magnetic powder, the weight percentage of amorphous composite rare earth magnetic powder is 20-50wt%, and the oxygen content of the composite rare earth magnetic powder is ≤0.9wt%.

10. The method for preparing rare earth permanent magnetic material according to claim 5, characterized in that: In step S3, the temperature of the hot pressing treatment is 600-800°C, the pressure is 300-600MPa, and the time is 3-10min; Preferably, in step S3, the temperature of the thermal deformation treatment is 700-900°C, the pressure is 100-300 MPa, and the time is 1-5 min; Preferably, in step S1, the rare earth alloy strip is prepared by a rapid spinning method.

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