RTB-TYPE SINTERMAGNET AND METHOD FOR MAKING THE SAME

Abstract

Sintered magnet of type RTB, wherein the sintered magnet has a grain boundary region T1, a shell region T2 and an R2Fe 14 B crystal grain area T3 includes; where, at 10 µm to 60 µm from the surface of the sintered magnet to the center, the area ratio of the shell region T2 to the R2Fe 14 B-crystal region T3 is 0.1 to 0.3, where the thickness of the shell region T2 is between 0.5 and 1.2 µm and the coverage of the shell region T2 to R2Fe 14 B Crystal grain area T3 is on average 80% or more; the ratio (HRE+M+Al) / (LRE+T) in the shell region T2 is 0.02-0.4, where (HRE+M+Al) / (LRE+T) is the ratio of the sum of the masses of the heavy rare earths HRE, M and Al to the sum of the masses of the light rare earths LRE and T; The ratio HRE / (LRE+T) in the shell region T2 is higher than the ratio HRE / (LRE+T) in the R2Fe. 14B crystal grain area T3 is, where HRE / (LRE+T) is the ratio of the mass of the heavy rare earth HRE to the sum of the masses of the light rare earths LRE and T; The ratio Al / (LRE+T) in the shell region T2 is higher than the ratio Al / (LRE+T) in the R2Fe. 14 B crystal grain area T3 is, where Al / (LRE+T) is the ratio of the mass of Al to the sum of the masses of the light rare earths LRE and T; R comprises light rare earth elements (LRE) and heavy rare earth elements (HRE), with the proportion of HRE in the sintered magnet being 0.05 to 1.5 wt.%; where T contains one or more transition metals containing Fe and / or FeCo, Al is contained in T, with the proportion of Al in the sintered magnet being 0.22 to 0.35 wt.%, M is contained in T, where M is at least one of Ga, Cu, Zn and where the M / Al mass ratio is 2-3.

Description

TECHNICAL FIELD

[0001] The present invention relates to the technical field of rare earth permanent magnet materials, and more particularly to an RTB type sintered magnet and a method for producing the same. STATE OF THE ART

[0002] Sintered neodymium-iron-boron permanent magnets are widely used in new energy vehicles and other applications due to their excellent combined magnetic properties. With the continuous advancement of manufacturing technology and the improvement of people's awareness of environmental protection, they have attracted market attention in the three fields of energy conservation and environmental protection, new energy, and new energy vehicles. They have become a key material for the implementation of the "Made in China 2025" development plan. Their application volume is growing rapidly at a rate of 10 to 20% per year, showing strong application prospects.

[0003] Coercivity is an important indicator for evaluating the quality of the magnetic properties of a Nd-Fe-B permanent magnet material. The heavy rare earth elements Dy and Tb are important elements for increasing coercivity, and they can effectively increase the magnetocrystalline anisotropy constant in a 2:14:1 phase, but they are expensive. Therefore, the coercivity is generally increased by depositing and diffusing the heavy rare earth elements Dy and Tb on the surfaces to reduce the manufacturing cost of the magnet. However, the concentration of the heavy rare earth elements decreases too much from the surface, and the diffusion depth is small, and the magnitude of the performance improvement is limited.

[0004] Some prior art documents include CN110323053A and DE 102016219533A1. REPRESENTATION OF THE UTILITY MODEL

[0005] In order to improve the coercive force of magnets and achieve a substitute for heavy rare earth elements, the present invention provides an RTB type sintered magnet and a method for producing the same, wherein the diffusion efficiency of heavy rare earth elements inside a magnet is increased by optimizing the conventional method for producing rare earth permanent magnets and the microstructures, thereby greatly increasing the coercive force of the magnet and saving the manufacturing cost.

[0006] To achieve the above object, the invention provides a sintered magnet according to claim 1, and a method for producing a sintered magnet according to claim 3.

[0007] Advantageous embodiments are set out in the subclaims.

[0008] The invention provides a sintered magnet of type RTB having a grain boundary region T1, a shell region T2 and a R2Fe14 B-crystal grain region T3 includes; at 10 µm to 60 µm from the surface of the sintered magnet to the center, the area ratio of the shell region T2 to the R2Fe 14 B-crystal grain area T3 0.1 to 0.3, with the thickness of the shell area T2 being between 0.5 and 1.2 µm; the coverage of the shell area T2 to the R2Fe 14 B -crystal grain region T3 is on average 80% or more; the ratio (HRE+M+Al) / (LRE+T) in the shell region T2 is 0.02-0.4, where (HRE+M+Al) / (LRE+T) is the ratio of the sum of the masses of the heavy rare earths HRE, M and Al to the sum of the masses of the light rare earths LRE and T; the ratio HRE / (LRE+T) in the shell region T2 is higher than the ratio HRE / (LRE+T) in R2Fe 14B crystal grain area T3, where HRE / (LRE+T) is the ratio of the mass of the heavy rare earth HRE to the sum of the masses of the light rare earths LRE and T; the ratio Al / (LRE+T) in the shell area T2 is higher than the ratio Al / (LRE+T) in R2Fe 14 B is crystal grain area T3, where Al / (LRE+T) is the ratio of the mass of Al to the sum of the masses of the light rare earths LRE and T; R comprises light rare earths LRE and heavy rare earths HRE, wherein the proportion of HRE in the sintered magnet is 0.05 to 1.5 wt.%; where T contains one or more transition metals containing Fe and / or FeCo, Al is contained in T, wherein the proportion of Al in the sintered magnet is 0.22 to 0.35 wt.%, M is contained in T, where M is at least one of Ga, Cu, Zn and where the M / Al mass ratio is 2-3.

[0009] In a further development, it is provided that Tb and Dy are contained in HRE, the proportion of R being 29-33 wt.%, the proportion of HRE being 0.05-1.5 wt.%; wherein the proportion of B in the sintered magnet is 0.82 to 0.95 wt.%.

[0010] Another aspect of the present invention provides a method for producing a sintered magnet, which comprises: Preparing a sintered blank; depositing an alloy film on a surface of the sintered blank; Performing heat treatment on the sintered blank after depositing the alloy film to obtain the sintered magnet. In a further training course, the preparation of the sintered blank is planned to include: Melting the raw materials to obtain an alloy, and the alloy is used to prepare a rapidly solidified flake with a thickness of 0.25 to 0.35 μm for the sintered body; the raw material composition is 24.6 wt% Nd, 5.8 wt% Pr, 1.1 wt% Co, 0.15 wt% Al, 0.10 wt% Cu, 0.15 wt% Zr, 0.83 wt% B, and the balance is Fe; Breaking the rapidly solidified flake into alloy powder; Shaping the alloy powder in a magnetic field to obtain a green body; The green body is sintered and tempered to obtain a sintered blank.

[0011] In a further development, it is provided that the breaking of the rapidly solidified flake into alloy powder comprises: the rapidly solidified flake is first absorbed hydrogen at room temperature, and a dehydrogenation treatment is carried out at 620 °C for 1.5 hours, and the flake is then ground in a nitrogen atmosphere to 3.5-4.5 µm fine powder.

[0012] According to the invention, depositing an alloy film on a surface of the sintered blank comprises: Removing an oxide coating on the surface of the sintered blank and drying it; Placing the diffusion source containing the heavy rare earth HRE, Al, and M components on the surface of the blank magnet; M is at least one of Ga, Cu, and Zn, and the M / Al mass ratio is 2-3.

[0013] In a further development, it is planned that the HRE, Al and M films are deposited in any order.

[0014] In a further development, it is provided that the state of the diffusion source in use is: a molten alloy solution of the diffusion source alloy, a rapidly quenched ribbon of the diffusion source alloy, a rapidly solidified flake of the diffusion source alloy, a flake of the diffusion source alloy, the powder of the diffusion source alloy, a diffusion source alloy slurry obtained by mixing alloy powder of the diffusion source alloy and solvent, or a film layer obtained by physical vapor deposition.

[0015] In a further development, the step of heat treating the sintered blank after deposition of the alloy film to obtain the sintered magnet comprises: a diffusion treatment at 650°C to 1000°C for 1-24 hours, followed by an annealing treatment at 400-700°C for 0.5-10 hours. Preferably, the heat treatment is carried out under vacuum or under inert gas protection.

[0016] The above-described technical solutions of the present invention have the following advantageous technical effects: (1) In the present invention, the conventional method for producing rare earth permanent magnets and the microstructure are optimized to increase the diffusion efficiency of heavy rare earths in an interior of a magnet, thereby greatly increasing the coercive force of the magnet and saving the manufacturing cost. (2) The present invention provides an RTB type sintered magnet. Even in the RTB type sintered magnet, Al and M are used to replace part of the heavy rare earth elements, thereby reducing the heavy rare earth elements. In the case of a low content of heavy rare earth elements, it also exhibits high coercive force and residual magnetic flux density at room temperature, and it also exhibits high coercive force at high temperature. SHORT DESCRIPTION OF THE CHARACTERS Fig. Figure 1 is a scanning electron microscope image of a near-surface layer of a type RTB sintered magnet. Fig. Figure 2 is a schematic representation of the near-surface layer of a type RTB sintered magnet. Fig. 3 is a manufacturing process of a sintered magnet. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] To further clarify the objectives, technical solutions, and advantages of the present invention, the present invention will be described in more detail below in conjunction with a detailed description of embodiments with reference to the accompanying drawings. It should be understood that this description is only exemplary and is not intended to limit the scope of the invention. Furthermore, in the following description, descriptions of known structures and techniques are omitted to avoid unnecessarily obscuring the concepts of the present invention.

[0018] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Furthermore, directional designations such as "top", "bottom", "left", "right" or the like in the following embodiments are only the directions with respect to the figures and are therefore used to illustrate and not to limit the invention. All features or steps disclosed in this description in all disclosed methods or processes can be combined in any way with the exception of features and / or steps that are mutually exclusive.

[0019] The present invention mainly optimizes the existence form and content of each element in the magnet and can reduce the amount of heavy rare earths under the condition of obtaining the same coercive force. I. Component

[0020] The sintered magnet provided by the present invention is mainly composed of RTB, wherein R is at least one rare earth element, wherein R comprises light rare earths LRE and heavy rare earths HRE, wherein Pr and Nd are contained in LRE, wherein Tb and Dy are contained in HRE, wherein the content of R is 29-33 wt%, wherein the content of HRE is 0.05-1.5 wt%; wherein T contains one or more transition metals containing Fe and / or FeCo, wherein Al and M are contained in T, and M is at least one of Ga, Cu and Zn, wherein the content of Al is 0.22-0.35 wt%, wherein the M / Al mass ratio is 2-3; wherein the content of B is 0.82 to 0.95 wt%.

[0021] With the composition described above, the amount of B is less than in the general RTB type sintered magnet, and the amount of Al is less than in the general RTB type sintered magnet, and at least one of Ga, Cu and Zn is contained in M. Therefore, M generates the RM phase in the grain boundary region, which contains the R2Fe 14 B - surrounds crystal grains. Here, the representative of the RM phase is the RM2 compound. Due to the large amount of Al, the R(M1-xAlx)2 compound is formed, and a high HcJ can be obtained.

[0022] The individual compositions are described in detail as follows: R is at least one rare earth element, with the proportion of R being 29 to 33 wt% (wt% represents the mass ratio in the element). If R is less than 29 wt%, it is difficult to control the presence of impurity phases such as α-Fe, and it may be difficult to increase the density during sintering. If R exceeds 33 wt%, the proportion of the main phase is reduced, which may not provide high residual magnetism. The proportion of R is preferably 29.6-32.2 wt%, in this range, ensuring better magnetic performance is a top priority.

[0023] In the present invention, R comprises light rare earths LRE and heavy rare earths HRE, where LRE contains Pr and Nd. More preferably, LRE is Nd or PrNd or PrNdCe or PrNdLaCe. More preferably, when LRE contains La and / or Ce, its content is less than 10 wt%.

[0024] R contains a heavy rare earth, HRE, which is essential in the present invention, in a proportion of 0.05 to 1.5 wt.%. In the present invention, the heavy rare earths are necessary to improve the coercive force and to improve the overall magnetic properties. However, by controlling the content of B, M, Al, or the like, it is possible to obtain a sintered magnet of RTB type with a high H cJ to obtain, while reducing the HRE content. The HRE content of 0.05 to 1.5 wt.%, less than 0.05 wt.% does not significantly increase the coercive force, while a content of more than 1.5 wt.% affects the remanence and impairs the improvement of the overall magnetic properties.

[0025] In the present invention, T contains one or more transition metals containing Fe and / or FeCo, with Al and M contained in T, and M is at least one of Ga, Cu, and Zn, with the proportion of Al being 0.22-0.35 wt%, with the M / Al mass ratio being 2-3; by containing Al, HCJ can be increased. Al generally has 0.05 wt% or more as an unavoidable impurity in the manufacturing process, and the total amount of the unavoidable impurity and the amount of active addition of Al can be 0.22 wt% or more and 0.35 wt% or less. The M content is 2-3 times that of Al. If M is less than this factor, high overall magnetic performance cannot be achieved. If M exceeds this factor, the Fe and FeCo content that provides remanence decreases, which adversely affects the increase of remanence.

[0026] T must contain Fe or FeCo, and if Co is included in the material, the amount of Co is less than 5 wt%. Although corrosion resistance and remanence can be improved by the inclusion of Co, if the substitution amount of Co exceeds 5 wt%, the properties may deteriorate.

[0027] In the rare earth magnet of the present invention, rare earths, T, and B may contain all unavoidable impurities, and may also contain Cr, Mn, Si, Sm, Ca, Mg, and the like. Examples of impurities that are unavoidable in the manufacturing process include O (oxygen), N (nitrogen), and C (carbon).

[0028] In addition, the RTB type sintered magnet according to the present invention may also contain one or more elements (elements actively added except for unavoidable impurities). For example, as such an element, a small amount (about 0.1 wt.%) of Sn, Ti, Ge, Y, H, F, V, Ni, Hf, Ta, W, Nb, Zr, or the like may be included. In addition, elements listed as the above-mentioned unavoidable impurities may be actively added, and the sum of these elements does not exceed 1 wt.

[0029] The proportion of B is 0.82 to 0.95 wt%. In the present invention, B is an unavoidable element that forms the main phase of R2T14B. To obtain the R2T 17 - Phase not to be produced as a soft magnetic phase and other foreign phases such as the boron-rich phase, the proportion of B is 0.82 to 0.95 wt.%, more preferably 0.82 to 0.93 wt.%. II. Microstructure

[0030] According to the present invention, the RTB type sintered magnet consists of a region T2, and T1 is a grain boundary region, T2 is a shell region and T3 is a R2Fe 14 B-crystal grain area, as in Fig. 2; regions T1 and T3 are the grain boundary phase and the main phase of the sintered magnet, respectively, and their content, ratio, and distribution are crucial for improving the combined magnetic properties of the sintered magnet. Rather, T2 is key to enhancing the magnetocrystalline anisotropy field of the crystal grains to increase the coercive force. The sintered magnet provided by the present invention has the following microstructure characteristics.

[0031] At 10 µm to 60 µm from the surface of the sintered magnet to the center, preferably at about 15 µm to 40 µm, T2 / T3 area ratio is 0.1 to 0.3, the thickness T2 is 0.5-1.2 µm, the coverage of T2 to T3 is on average 80% or more.

[0032] The mass ratio (HRE+M+Al) / (LRE+T) in the T2 range is 0.02-0.4; the mass ratio HRE / (LRE+T) in T2 is larger than the mass ratio HRE / (LRE+T) in T3; the mass ratio Al / (LRE+T) in T2 is on average higher than the mass ratio Al / (LRE+T) in T3.

[0033] The scanning electron microscope image of the near-surface layer of the RTB series sintered magnet is shown in Fig. 1 shown. III. Manufacturing process

[0034] The manufacturing process of the present invention comprises the following steps in connection with Fig.3: A step of preparing a sintered blank; a step of depositing an alloy film on a surface of the sintered blank; a step of performing heat treatment on the sintered blank after depositing the alloy film to obtain the sintered magnet. 1. The step of preparing a sintered blank;

[0035] The sintered blank according to the present invention is mainly manufactured by a powder metallurgy process, and the manufacturing process includes a process of preparing a rapidly solidified flake, a process of dividing the rapidly solidified flake into an alloy powder, a forming process, and a sintering and tempering process. The individual processes are specifically as follows: (1) Preparing the process of fast solidified flake A raw material containing 24.6 wt% Nd, 5.8 wt% Pr, 1.1 wt% Co, 0.15 wt% Al, 0.10 wt% Cu, 0.15 wt% Zr, 0.83 wt% B, with the balance being Fe, is melted to obtain an alloy, and the alloy is used to obtain a rapidly solidified flake with a thickness of 0.25 to 0.35 µm. The prepared alloy is produced into a rapidly solidified flake for the sintered body by the thin strip continuous casting (SC) process. (2) Process for breaking the rapidly solidified flake into alloy powder The rapidly solidified flake is first subjected to hydrogen absorption at room temperature and then subjected to a dehydrogenation treatment at 620 °C for 1.5 hours to coarsely fracture the rapidly solidified flake. This flake is then ground into a fine powder of 3.5-4.5 µm using conventional jet mill technology under a nitrogen atmosphere. (3) Forming process This step is performed by molding the obtained alloy powder in a magnetic field to obtain a green body. Molding in a magnetic field can use methods known to those skilled in the art, such as a dry molding method in which dry alloy powder is introduced into the cavity of a mold, and molding is performed while applying a magnetic field; a wet molding method in which a slurry in which the powder for sintering is dispersed is injected into a cavity of a mold, and molding is performed while withdrawing a slurry dispersion medium. (4) Sintering and tempering process In this process, the green body obtained through the molding process is primarily sintered to obtain a dense magnet. Sintering of the green body can be performed by a method known to those skilled in the art. Furthermore, the sintering atmosphere in the present invention is preferably carried out in a vacuum or an inert atmosphere. After sintering, tempering is performed, and methods known to those skilled in the art can be used for the tempering temperature and time. 2. Step for deposition of a thin film (1) Removing an oxide coating on the surface of the blank magnet and drying it; (2) Placing the diffusion source of the HRE-Al-M component on the surface of the blank magnet; Preferably, the state of the diffusion source in use is: a molten alloy solution of the diffusion source alloy, a rapidly quenched ribbon of the diffusion source alloy, a rapidly solidified flake of the diffusion source alloy, a flake of the diffusion source alloy, the powder of the diffusion source alloy, a diffusion source alloy slurry obtained by mixing alloy powder of the diffusion source alloy and solvent, or a film obtained by physical vapor deposition.

[0036] Preferably, the state of the diffusion source in use is: film obtained by physical vapor deposition.

[0037] The diffusion source film is preferably obtained by the magnetron sputtering technique in a physical vapor deposition process; Preferably, the diffusion source film is applied to a surface perpendicular to the orientation axis of the blank magnet; the manner in which the diffusion source thin film is deposited is preferably: M film, Al film and HRE film are deposited sequentially in any order, binary Al-M alloy film and HRE film are deposited sequentially in any order, and ternary HRE-Al-M alloy film is deposited; The manner in which the diffusion source thin film is deposited is preferably: ternary HRE-Al-M alloy film is deposited. 3. Step of heat treatment after film deposition

[0038] The heat treatment in the present invention is preferably carried out under vacuum or inert gas protection; the heat treatment process comprises a diffusion treatment at 650 °C to 1000 °C for 1-24 hours.

[0039] In the present invention, the heat treatment is preferably carried out under a certain vacuum condition; the heat treatment process includes a diffusion treatment at 650 °C to 1000 °C for 1-24 hours.

[0040] More preferably, the heat treatment is carried out under specific vacuum conditions, including a diffusion treatment at 650 °C to 1000 °C for 1 to 24 hours and an annealing treatment at 400 °C to 700 °C for 0.5 to 10 hours. Examples of implementation (1) Sintered magnet blanks of one size are provided, the height of which is the orientation direction, the height data of which are given in Table 1; the surface of the blank magnet is cleaned, and it is ensured that an upper surface and a lower surface of the blank magnet are smooth and flat. (2) The surface of the blank magnet is cleaned, and it is ensured that the upper and lower surfaces of the blank magnet are smooth and flat. A certain thickness of the ternary HRE-Al-M alloy film is sputtered onto the upper and lower surfaces perpendicular to the orientation axis of the blank magnet. Table 1 shows the coating amount of HRE, diffusion temperature, and diffusion time. (3) Diffusion and annealing processes are carried out under certain vacuum conditions to obtain sintered magnets with high coercive force. The annealing temperature and annealing time are shown in Table 1.

[0041] After the annealing treatment, the magnet necessary for the invention is obtained, wherein a residual diffusion source and an oxide film are present on the surface of the sintered magnet, and after removing the diffusion source and the oxide film using methods well known to ours, the magnet thickness decreases by less than 10 µm.

[0042] The magnet is then sectioned in the height direction and subjected to microstructure scanning. The scanning mode can be a field emission scanning electron microscope (SEM). The observation method is from the magnet's perforation surface to the center. An observation area of ​​80 μm (long) × 40 μm (wide) or more is set. The T1, T2, and T3 ranges are calibrated. The area, coverage, thickness, atomic mass ratio, etc., are calculated for the T2 range from approximately 15 μm to approximately 40 μm away from the magnet's perforation surface. The correlation data are listed in Table 2.

[0043] The area is calculated as follows: the backscattered electron image is binarized at a predetermined level, the T2 and T3 regions are specified, the T2 and T3 areas from approximately 15 µm to 40 µm away from the magnet's weep surface within an observation range of 80 µm (length) × 40 µm (width) or more are calculated, and the T2 / T3 ratio is obtained. The method for specifying the main phase section and the grain boundary section by binarization at a predetermined level is arbitrary as long as a generally applicable method is used.

[0044] The coverage ratio is calculated as follows: The total sum of the lengths of the outer peripheral parts of T2 and the total sum of the lengths of the uncovered T3 from about 15 µm to about 40 µm away from the seepage surface of the magnet are determined in an observation range of 80 µm (length) × 40 µm (width) or more. The coverage ratio is calculated as the ratio of the total length of the outer peripheral part of T2 to the total length of the outer peripheral part of T2 and the length of T3 that is not covered.

[0045] The thickness is calculated as follows: a T2 thickness at each R2Fe 14 B away from about 15 µm to about 40 µm from the seepage surface of the magnet is measured in an observation range of 80 µm (length) × 40 µm (width) or more, and measured three times at different positions, all measured thicknesses and numbers of measurements are counted, and finally an average value is calculated.

[0046] The atomic mass ratio calculation method is as follows: Using a WDS equipped with EPMA, element surface scanning is performed within an observation area of ​​80 µm (length) × 40 µm (width) or more, scanning the microscopic region from approximately 15 µm to approximately 40 µm away from the magnetic percolation surface. Only the mass concentrations of HRE, LRE, M, Al, and Fe elements are calibrated, and then the mass ratio of (HRE+M+Al) / (LRE+T) is calculated.

[0047] The composition and properties of the magnet are finally listed in Table 3. Note that the measurement of the components is performed using radio-frequency inductively coupled plasma emission spectrometry (ICP-OES). A NIM-500C high-temperature permanent magnet measuring instrument is used to measure the residual magnetic flux density Br and coercive force HcJ. Comparison example 1 (1) Preparing a sintered magnet blank; (2) The blank magnet is cut into pieces of specific size (length * width * height (orientation)). (3) The surface of the blank magnet is cleaned and it is ensured that an upper surface and a lower surface of the blank magnet are smooth and flat. (4) A certain thickness of the ternary HRE film is deposited by sputtering on a top and a bottom surface perpendicular to the orientation axis of the blank magnet. (5) Diffusion and annealing processes are carried out under certain vacuum conditions to obtain sintered magnets with high coercive force.

[0048] The detection method is the same as in the embodiment, and the data are given in Comparative Examples 1-1 and 1-2. Comparison example 2 (1) The blank magnet is cut into pieces of specific size (length * width * height (orientation)). (2) The surface of the blank magnet is cleaned and it is ensured that an upper surface and a lower surface of the blank magnet are smooth and flat. (3) Diffusion and annealing processes are carried out under certain vacuum conditions to obtain sintered magnets with high coercive force.

[0049] The detection method is the same as in the embodiment, and the data are given in Comparative Examples 2-1 and 2-2.

[0050] Working examples 1-1 to 1-8 for producing the sintered magnet according to the method of the present invention and Comparative examples 1-1, 1-2, 2-1, 2-2 for producing the sintered magnet according to the existing method are shown in Table 1, Table 2, Table 3: Table 1 The height of the blank magnet for diffusion (mm) HRE coating amount (wt.%) Diffusion temperature (°C) Diffusion time (hours) Tempered temperature (°C) Tempering time (hours) Example 1-1 5 0,20 880 8 500 5 Implementation example 1-2 5 0,20 920 8 500 5 Implementation example 1-3 5 0,25 880 8 500 5 Implementation example 1-4 5 0,25 920 8 500 5 Implementation example 1-5 5 0,30 880 8 500 5 Example 1-6 5 0,30 920 8 500 5 Implementation example 1-7 5 0,35 880 8 500 5 Implementation example 1-8 5 0,35 920 8 500 5 Comparison example 1-1 5 0,20 880 8 500 5 Comparison example 1-2 5 0,25 880 8 500 5 Comparison example 2-1 5 0 920 8 500 5 Comparison example 2-2 5 0 920 8 500 5 Table 2 at approximately 15 µm to approximately 40 µm from the surface of the sintered magnet to the center T2 / T3 area ratio T2 thickness (µm) T2 to T3 coverage rate (%) Mass ratio of (HRE+M+Al) / (LRE+T) Example 1-1 0,11 0,51 81,5 0,11 Example 1-2 0,14 0,56 83,5 0,15 Example 1-3 0,16 0,62 85,4 0,19 Example 1-4 0,18 0,71 86,8 0,22 Example 1-5 0,20 0,78 87,6 0,26 Example 1-6 0,23 0,83 88,3 0,29 Example 1-7 0,26 0,95 89,6 0,33 Example 1-8 0,28 1,1 90,8 0,38 Comparison example 1-1 0,08 0,32 55 0,07 Comparison example 1-2 0,11 0,40 60 0,11 Comparison example 2-1 0 0 0 0,02 Comparison example 2-2 0 0 0 0,04 Table 3 Share of M B Al B r H CJ (wt%) (wt%) (wt%) (MT) (came) Example 1-1 0,65 0,83 0,26 1432 1751 Example 1-2 0,63 0,83 0,25 1435 1768 Example 1-3 0,70 0,84 0,28 1424 1912 Example 1-4 0,68 0,84 0,27 1420 1956 Example 1-5 0,75 0,85 0,30 1418 2070 Example 1-6 0,73 0,85 0,29 1415 2085 Example 1-7 0,80 0,86 0,32 1405 2155 Example 1-8 0,85 0,86 0,34 1400 2194 Comparison example 1-1 0,32 0,83 0,06 1439 1615 Comparison example 1-2 0,29 0,84 0,08 1438 1823 Comparison example 2-1 0,28 0,85 0,07 1449 1456 Comparison example 2-2 0,33 0,86 0,09 1446 1464

[0051] From Working Examples 1-1 to 1-8, it can be seen that Hcj gradually increases and Br hardly decreases as the diffusion temperature and the HRE content increase. Al, M, and B fluctuate reasonably within the preferred range. Comparing the comparative examples, it can be seen that the coercive force of the HRE-Al-M diffusion magnet is significantly increased.

[0052] The present invention relates to a sintered magnet of RTB type and a method for producing the same, wherein R in sintered magnets is at least one rare earth element, wherein T contains one or more transition metals containing Fe and / or FeCo; wherein R comprises light rare earths LRE and heavy rare earths HRE; wherein Pr and Nd are contained in LRE, wherein Tb and Dy are contained in HRE, wherein the proportion of R is 29-33 wt.%, wherein the proportion of HRE is 0.05-1.5 wt.%; wherein Al and M are contained in T, wherein the proportion of Al is 0.22-0.35 wt.%, M is at least one of Ga, Cu and Zn, and wherein the M / Al mass ratio is 2-3; wherein the proportion of B is 0.82 to 0.95 wt.%; wherein the sintered magnet consists of a T2 region, where T1 is the grain boundary region, T2 is the shell region and T3 is the R2T 14B crystal grain area is; an area ratio of T2 / T3 is 0.1 to 0.3 at about 15 μm to about 40 μm from the surface of the sintered magnet to the center, the thickness T2 is 0.5-1.2 μm, and the coverage ratio of T2 to T3 is 80% or more on average; In the present invention, the conventional method for producing rare earth permanent magnets and the microstructure are optimized to increase the diffusion efficiency of heavy rare earths in an interior of a magnet, thereby greatly increasing the coercive force of the magnet and saving the manufacturing cost. The sintered magnet provided by the present invention has a reduced amount of heavy rare earths while achieving the same coercive force, which is suitable for industrial production.

[0053] It is to be understood that the above-described embodiments of the invention are for illustrative purposes only and explain the principles of the invention and do not limit them.

Claims

[1] Sintered magnet of type RTB, wherein the sintered magnet has a grain boundary region T1, a shell region T2 and a R2Fe 14 B comprises crystal grain region T3; where at 10 µm to 60 µm from the surface of the sintered magnet to the center, the area ratio of the shell region T2 to the R2Fe 14 B-crystal grain area T3 is 0.1 to 0.3, the thickness of the shell area T2 is between 0.5 and 1.2 µm and the coverage of the shell area T2 to the R2Fe 14 B Crystal grain area T3 is on average 80% or more; the ratio (HRE+M+Al) / (LRE+T) in the shell region T2 is 0.02-0.4, where (HRE+M+Al) / (LRE+T) is the ratio of the sum of the masses of the heavy rare earths HRE, M and Al to the sum of the masses of the light rare earths LRE and T; the ratio HRE / (LRE+T) in the shell region T2 is higher than the ratio HRE / (LRE+T) in R2Fe 14B crystal grain area is T3, where HRE / (LRE+T) is the ratio of the mass of the heavy rare earth HRE to the sum of the masses of the light rare earths LRE and T; the ratio Al / (LRE+T) in the shell region T2 is higher than the ratio Al / (LRE+T) in R2Fe 14 B is crystal grain area T3, where Al / (LRE+T) is the ratio of the mass of Al to the sum of the masses of the light rare earths LRE and T; R comprises light rare earths LRE and heavy rare earths HRE, wherein the proportion of HRE in the sintered magnet is 0.05 to 1.5 wt.%; where T contains one or more transition metals containing Fe and / or FeCo, Al is contained in T, the proportion of Al in the sintered magnet being 0.22 to 0.35 wt.%, M is contained in T, where M is at least one of Ga, Cu, Zn and where the M / Al mass ratio is 2-3. [2] Sintered magnet of type RTB according to claim 1, characterized bythat Tb and Dy are contained in HRE, the proportion of R being 29 to 33 wt.%; the proportion of B in the sintered magnet being 0.82 to 0.95 wt.%. [3] A method for producing a sintered magnet according to any one of claims 1 to 2, characterized by that the procedure includes: Preparing a sintered blank; Depositing an alloy film on a surface of the sintered blank, comprising removing an oxide coating on the surface of the sintered blank and drying it; placing the diffusion source containing the heavy rare earth HRE, Al, and M components on the surface of the blank magnet; where M is at least one of Ga, Cu, and Zn, and the M / Al mass ratio is 2-3; Performing a heat treatment on the sintered blank after depositing the alloy film to obtain the sintered magnet. [4] Method according to claim 3, characterized by that the preparation of the sintered blank includes: Melting the raw materials to obtain an alloy, and the alloy is used to produce a rapidly solidified flake with a thickness of 0.25 to 0.35 μm for the sintered body; the raw material composition is 24.6 wt% Nd, 5.8 wt% Pr, 1.1 wt% Co, 0.15 wt% Al, 0.10 wt% Cu, 0.15 wt% Zr, 0.83 wt% B, and the balance is Fe; crushing the rapidly solidified flake into alloy powder; Shaping the alloy powder in a magnetic field to obtain a green body; The green body is sintered and tempered to obtain a sintered blank. [5] Method according to claim 4, characterized bythat involves breaking the rapidly solidified flake into alloy powder: the rapidly solidified flake is first absorbed hydrogen at room temperature, and a dehydrogenation treatment is carried out at 620 °C for 1.5 hours, and the flake is then ground to 3.5-4.5 µm fine powder in a nitrogen atmosphere. [6] Method according to claim 5, characterized by that the state of the diffusion source in use is: a molten alloy solution of the diffusion source alloy, a rapidly quenched ribbon of the diffusion source alloy, a rapidly solidified flake of the diffusion source alloy, a flake of the diffusion source alloy, the powder of the diffusion source alloy, a diffusion source alloy slurry obtained by mixing alloy powder of the diffusion source alloy and solvent, or a film layer obtained by physical vapor deposition. [7] Method according to claim 3 or 4, characterized by that the step of carrying out the heat treatment on the sintered blank after the deposition of the alloy film in order to obtain the sintered magnet comprises: a diffusion treatment at 650 °C to 1000 °C for 1-24 hours, followed by tempering treatment at 400-700 °C for 0.5-10 hours, preferably the heat treatment is carried out under vacuum or under inert gas protection.

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