Low-cost high-cerium neodymium-iron-boron diffusion magnet and preparation method and application thereof

Abstract

The invention discloses a low-cost high-cerium neodymium iron boron diffusion magnet and a preparation method and application thereof, and relates to the technical field of rare earth permanent magnet materials. Comprising the steps that a neodymium iron boron alloy casting piece Ce30 with the Ce content being 10 wt% and a neodymium iron boron alloy casting piece Ce50 with the Ce content being 15 wt% are prepared through burdening and smelting, after the Ce30 and Ce50 neodymium iron boron alloy casting pieces are evenly mixed, hydrogen decrepitation, jet milling, oriented pressing, cold isostatic pressing and vacuum sintering are sequentially carried out, and a high-cerium sintered neodymium iron boron matrix is obtained; carrying out grain boundary diffusion on the high-cerium sintered neodymium-iron-boron matrix to obtain a high-cerium neodymium-iron-boron diffused magnet; the performance of the blank prepared through the method is close to the N40 mark, the performance of the magnetic sheet after diffusion reaches the 38MT mark, the magnetic performance is kept at the high level, the Ce content is high, efficient utilization of the high-abundance element cerium is achieved, the production cost of the rare earth permanent magnet material is greatly reduced, industrial batch production can be achieved, and balanced utilization of rare earth resources is promoted.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth permanent magnet materials, and in particular to a low-cost high-cerium neodymium iron boron diffusion magnet and a preparation method and application thereof. Background Art

[0002] Neodymium iron boron (Nd-Fe-B) magnets are currently the type of permanent magnet material with the highest magnetic energy product. Due to their excellent performance, they are widely used in energy, transportation, medical and other fields. They are key materials to support the development of information communication, energy conservation and emission reduction, rail transportation, intelligent manufacturing and other fields. The proportion of rare earth elements in Nd-Fe-B magnets is about 30wt.%. After more than 20 years of rapid development of the NdFeB industry, its production and application have consumed a large amount of rare earth Nd / Pr resources, while the rare earths such as La, Ce, and Y that co-exist in the mining process are more stockpiled but less used. This has led to high prices for rare earth Nd / Pr, accounting for more than 65% of the production cost of NdFeB magnets, and at the same time caused unbalanced utilization of rare earth resources. Therefore, how to promote the large-scale application of high-abundance rare earths such as La, Ce, and Y in NdFeB permanent magnet materials is an urgent problem to reduce the production cost of NdFeB magnets and improve the comprehensive and balanced utilization of rare earth resources.

[0003] Practice shows that due to Ce2Fe 14 The intrinsic performance of B is much lower than that of Nd2Fe 14 B, therefore, Ce replacing Nd in the 2:14:1 lattice will produce a strong magnetic dilution effect, resulting in a significant decrease in the coercive force and Curie temperature of the final magnet, which seriously limits the production and application of high-cerium NdFeB magnets. In order to apply Ce to sintered NdFeB magnets and keep them in relatively good magnetic properties, scientific and technological workers around the world have conducted a lot of research.

[0004] my country's patent application CN201711339217.5 proposes a method for simultaneously improving the magnetic properties and corrosion resistance of Nd:Ce:Fe:B sintered magnets. The method uses a dual-phase alloy process and adds a small amount of Nd:Pr hydride powder to reconstruct the grain boundary structure during powder mixing. This not only changes the distribution of the grain boundary structure, but also changes the phase composition of the grain boundary structure. However, the actual production operation of the dual-phase alloy powder mixing and the addition of Nd:Pr hydride powder to the grain boundary is complicated and not suitable for mass production.

[0005] my country's patent application CN202410497748.0 proposes a N40 NdCeFeB sintered permanent magnet material and its preparation method. By providing a specific formula and process, the production costs of raw materials, energy and labor of N40 sintered NdCeFeB are greatly reduced, effectively solving the defect of increased formula cost caused by the increase in the mass percentage of high-grade raw materials in conventional processes. However, the required specific process adds a secondary vacuum secondary tempering on the basis of conventional secondary tempering, which increases labor and energy costs. Summary of the invention

[0006] The present invention aims to solve the technical problem of how to apply low-cost Ce to sintered NdFeB magnets and maintain good magnetic properties while being suitable for mass production. The present invention aims to provide a low-cost high-cerium NdFeB diffused magnet and a preparation method and application thereof. The performance of the prepared blank is close to that of the N40 grade, and the performance of the magnetic sheet after diffusion reaches the 38MT grade. The magnetic properties are maintained at a high level, and the Ce content is high, thereby achieving efficient utilization of the high-abundance element cerium, greatly reducing the production cost of rare earth permanent magnet materials, realizing industrial mass production, and promoting the balanced utilization of rare earth resources.

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

[0008] The first object of the present invention is to provide a method for preparing a low-cost high-cerium NdFeB diffusion magnet, comprising the following steps:

[0009] Smelting the ingredients to prepare NdFeB alloy casting flakes Ce30 with a Ce content of 8-12wt.% and NdFeB alloy casting flakes Ce50 with a Ce content of 13-17wt.%;

[0010] After Ce30 and Ce50 NdFeB alloy flakes are uniformly mixed, hydrogen crushing, jet milling, orientation pressing, cold isostatic pressing, and vacuum sintering are sequentially performed to obtain a high-cerium sintered NdFeB matrix;

[0011] The high cerium NdFeB diffusion magnet is obtained by grain boundary diffusion of high cerium sintered NdFeB matrix.

[0012] Furthermore, the chemical composition of Ce30 is Ce a RE1 b M1 c B x Fe y , wherein RE1 is selected from at least one element of Pr, Nd, La, Gd, Y, and Ho, M1 is selected from at least one element of Cu, Al, Ga, Co, Zr, and Ti, B is boron, and Fe is iron; a, b, c, x, and y are the mass percentages of the corresponding elements, and at the same time satisfy 8≤a≤12, 18≤b≤22, 28≤a+b≤31, 0≤c≤2, 0.85≤x≤0.95, and y=100-abcx; the chemical composition of Ce50 is Ce d RE2 e M2 f B j Fe q, wherein RE2 is selected from at least one element of Pr, Nd, La, Gd, Y, and Ho, M2 is selected from at least one element of Cu, Al, Ga, Co, Zr, and Ti, B is boron, and Fe is iron; d, e, f, j, and q are the mass percentages of the corresponding elements, and at the same time satisfy 13≤d≤17, 13≤e≤17, 28≤d+e≤31, 0≤f≤2, 0.85≤j≤0.95, and q=100-defj.

[0013] Furthermore, the Ce content in the Ce30 is preferably 10%, and the Ce content in the Ce50 is preferably 15%.

[0014] Furthermore, in the mixture of Ce30 and Ce50 NdFeB alloy casting sheets, the mass proportion of Ce50 NdFeB alloy casting sheets is 20%-40%.

[0015] Furthermore, in the hydrogen crushing process, the alloy casting absorbs hydrogen at room temperature for 1.5 to 2 hours, and then dehydrogenates at 450°C to 500°C for 4 to 5 hours to obtain a coarse alloy powder with a particle size of 1 to 3 mm; the particle size SMD parameter of the alloy fine powder obtained after the air flow milling process is between 2.8 and 3.2 μm; the magnetic field strength used in the orientation pressing is not less than 2.0 T, and the pressure adopted in the cold isostatic pressing process is between 170 and 220 MPa.

[0016] Furthermore, the vacuum sintering process is specifically as follows:

[0017] Heat up to 200-350℃ at 10℃ / min and keep warm for 30-60min;

[0018] Then, the temperature was raised to 600-800°C at 5°C / min and kept at this temperature for 60-120 min;

[0019] Then, the temperature was raised to 900-1100°C at 10°C / min and kept at that temperature for 240-480min;

[0020] Finally, cool quickly to room temperature.

[0021] Furthermore, the step of obtaining a high-cerium NdFeB diffused magnet by grain boundary diffusion of a high-cerium sintered NdFeB matrix comprises the following steps:

[0022] The high-cerium sintered NdFeB substrate is processed into a thin sheet substrate of required thickness, and the magnetic sheet is sandblasted to remove surface impurities;

[0023] The heavy rare earth Dy alloy diffusion source is sprayed onto the surface of the substrate by the spray diffusion method, and a high cerium NdFeB diffusion magnet is obtained after high temperature diffusion and multi-stage tempering.

[0024] The thickness of the magnet sheet substrate is preferably 2 to 4 mm, and the chemical formula of the heavy rare earth Dy alloy powder is Dy x M y , wherein 0≤x≤1, 0≤y≤1, and M is one or more of Al, Cu, Ga, Fe, Co, Sn, Ni, and Zr.

[0025] Preferably, a diffusion auxiliary agent may be added to the heavy rare earth Dy alloy diffusion source, accounting for 20% to 50% of the total mass of the diffusion source, and the particle size SMD parameter of the heavy rare earth Dy alloy powder is between 3 and 5 μm.

[0026] Furthermore, the spraying amount of the heavy rare earth Dy alloy diffusion source is 0.5-1.5wt.% of the weight of the substrate magnetic sheet.

[0027] Furthermore, the high temperature diffusion process is to heat up to 750-900°C at 10°C / min, keep warm for 10-15h, and finally cool quickly to room temperature; the tempering process includes a primary tempering process and a secondary tempering process, wherein the process adopted in the primary tempering process is: heating up to 600-800°C at 10°C / min, keeping warm for 120-240min, and finally cool quickly to room temperature; the process adopted in the secondary tempering process is: heating up to 400-500°C at 10°C / min, keeping warm for 120-240min, and finally cool quickly to room temperature.

[0028] The preparation process of the present invention is carried out under a strictly oxygen-controlled environment, with an oxygen content of <80ppm; the vacuum sintering, high-temperature diffusion and multi-stage tempering processes are all carried out under a high vacuum environment, with a vacuum degree better than 1.0×10 -3 Pa.

[0029] The second object of the present invention is to provide a low-cost high-cerium NdFeB diffused magnet prepared by the above method.

[0030] The third object of the present invention is to provide an application of a neodymium iron boron magnet in electric two-wheeled vehicles, the automotive industry, electronic products, wind power, elevators, industrial robots or aerospace.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] 1. According to two cerium-containing alloy formulas, the present invention prepares ingredients and melts them into casting sheets respectively, and then mixes, hydrogen-crushes, airflow mills, magnetic field forms, isostatic presses, and vacuum-sinters to obtain high-cerium NdFeB sintered blanks, and the blanks have performance close to that of N40 grade; the blanks are processed into magnetic sheets of specific thickness, and high-cerium NdFeB diffusion magnets with excellent performance are obtained after sandblasting, heavy rare earth Dy alloy slurry spraying, high-temperature diffusion, and tempering. After diffusion, the performance of the magnetic sheets reaches 38MT grade, and the Ce content is as high as 11.5wt.%, realizing efficient utilization of high-abundance element cerium, and the magnetic properties are still maintained at a high level, which can meet the basic needs of the application field for permanent magnetic materials, and at the same time greatly reduce the production cost of rare earth permanent magnetic materials, can realize industrial mass production, and promote the balanced utilization of rare earth resources.

[0033] 2. The present invention makes it more convenient and quick to mix the two cerium-containing alloy formula castings in the hydrogen cracking process, and the mixing is more uniform, avoiding the oxidation of fine powders during long-term mixing, which is conducive to obtaining better magnetic properties.

[0034] 3. The present invention adopts two cerium-containing alloy formulas in a certain proportion for dual alloy sintering. Compared with the single alloy sintered magnet with the same composition, the intergranular phase of the present invention is more uniform, and there are fewer CeFe2 phases at the triple grain boundaries, which is conducive to the efficient diffusion of heavy rare earth Dy alloy along the grain boundaries, thereby obtaining higher magnetic properties. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the embodiments. Obviously, the schematic implementation modes of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0036] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range.

[0037] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0038] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0039] Unless otherwise specified, the terms "include" and "comprising" mentioned in this application may be open-ended or closed-ended. For example, the terms "include" and "comprising" may mean that other substances not listed may also be included or only the listed substances may be included.

[0040] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. The technical solution of the present invention is further described in detail below in conjunction with the embodiments.

[0041] It should be noted that the experimental methods used in the examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by those skilled in the art through commercial channels.

[0042] Example 1

[0043] A method for preparing a high-cerium sintered NdFeB matrix comprises the following steps:

[0044] The chemical formula is (PrNd) 19 Ce 10 Ho1Al 0.25 Cu 0.2 Co 0.1 Zr 0.3 B 0.89 Fe bal (wt.%) The ingredients were melted to prepare a Ce30 alloy casting with a Ce content of 10wt.%, according to the chemical formula (PrNd) 13.7 Y 0.8 Ho 0.5 Ce 15 Al 0.2 Cu 0.2 Co 0.1 Zr 0.3 B 0.9 0Fe 68.30 (wt.%) ingredients were melted to prepare Ce50 alloy flakes with a Ce content of 15wt.%.

[0045] Ce30 and Ce50 alloy flakes are mixed in a ratio of 70%:30% and then subjected to hydrogen crushing and airflow grinding. The fine powder particle size SMD after airflow grinding is 2.8μm. The airflow milled fine powder is subjected to oriented pressing under a magnetic field strength of 2.0T, and then cold isostatic pressing is performed under a pressure of 200MPa to form a green body. It is then placed in a high vacuum sintering furnace for high-temperature sintering, wherein the high-temperature sintering process is to heat up to 320℃ at 10℃ / min and keep warm for 60min, then heat up to 640℃ at 5℃ / min and keep warm for 120min, then heat up to 1048℃ at 10℃ / min and keep warm for 300min, and finally quickly cool to room temperature to obtain high-cerium NdFeB sintered blank 1-0#.

[0046] Comparative Example 1

[0047] A method for preparing a high-cerium sintered NdFeB matrix comprises the following steps:

[0048] The chemical formula is (PrNd) 19 Ce 10 Ho1Al 0.25 Cu 0.2 Co 0.1 Zr 0.3 B 0.89 Fe bal (wt.%) The ingredients were melted to prepare a Ce30 alloy casting with a Ce content of 10wt.%, according to the chemical formula (PrNd) 13.7 Y 0.8 Ho 0.5 Ce 15 Al 0.2 Cu 0.2 Co 0.1 Zr 0.3 B 0.9 0Fe 68.30 (wt.%) ingredients were melted to prepare Ce50 alloy flakes with a Ce content of 15wt.%.

[0049] Ce30 and Ce50 alloy flakes are each prepared into fine powder by hydrogen crushing and airflow milling, and the fine powder particle size SMD is controlled to be 2.8μm. Ce30 and Ce50 fine powders are evenly mixed in a mass ratio of 70%:30%, oriented pressing is performed under a magnetic field strength of 2.0T, and then cold isostatic pressing is performed under a pressure of 200MPa to form a green body. Then it is placed in a high vacuum sintering furnace for high-temperature sintering, wherein the high-temperature sintering process is heated to 320℃ at 10℃ / min and kept warm for 60min, then heated to 640℃ at 5℃ / min and kept warm for 120min, then heated to 1048℃ at 10℃ / min and kept warm for 300min, and finally quickly cooled to room temperature to obtain high-cerium NdFeB sintered blank 1-1#.

[0050] Comparative Example 2

[0051] A method for preparing a high-cerium sintered NdFeB matrix comprises the following steps:

[0052] The chemical formula is (PrNd) 17.4 Y 0.24 Ho 0.85 Ce 11.5 Al 0.235 Cu 0.2 Co 0.1 Zr 0.3 B 0.893 Fe 68.27 (wt.%) ingredients are melted to prepare alloy castings, and then the castings are subjected to hydrogen crushing and air flow grinding processes. The fine powder particle size SMD after air flow grinding is 2.8μm. The air flow ground fine powder is subjected to oriented pressing under a magnetic field strength of 2.0T, and then cold isostatic pressing is performed under a pressure of 200MPa to form a green billet. It is then placed in a high vacuum sintering furnace for high-temperature sintering, wherein the high-temperature sintering process is to heat up to 320℃ at 10℃ / min and keep warm for 60min, then heat up to 640℃ at 5℃ / min and keep warm for 120min, then heat up to 1048℃ at 10℃ / min and keep warm for 300min, and finally quickly cool to room temperature to obtain high-cerium NdFeB sintered blanks 1-2#.

[0053] Example 2

[0054] A method for preparing a low-cost high-cerium neodymium iron boron diffusion magnet comprises the following steps:

[0055] The chemical formula is (PrNd) 19 Ce 10 Ho1Al 0.25 Cu 0.2 Co 0.1 Zr 0.3 B 0.89 Fe bal (wt.%) The ingredients were melted to prepare a Ce30 alloy casting with a Ce content of 10wt.%, according to the chemical formula (PrNd) 13.7 Y 0.8 Ho 0.5 Ce 15 Al 0.2 Cu 0.2 Co 0.1 Zr 0.3 B 0.9 0Fe 68.30 (wt.%) ingredients were melted to prepare Ce50 alloy flakes with a Ce content of 15wt.%.

[0056] Ce30 and Ce50 alloy flakes are mixed in a ratio of 70%:30% and then subjected to hydrogen crushing and airflow grinding. The fine powder particle size SMD after airflow grinding is 2.8μm. The airflow-milled fine powder is subjected to oriented pressing under a magnetic field strength of 2.0T, and then cold isostatic pressing is performed under a pressure of 200MPa to form a green body. It is then placed in a high vacuum sintering furnace for high-temperature sintering, wherein the high-temperature sintering process is to heat up to 320℃ at 10℃ / min and keep it for 60min, then heat up to 640℃ at 5℃ / min and keep it for 120min, then heat up to 1048℃ at 10℃ / min and keep it for 300min, and finally quickly cool to room temperature to obtain a high-cerium NdFeB sintered blank.

[0057] After the blank is processed to 2mm, the magnetic sheet is sandblasted and then the heavy rare earth Dy alloy diffusion source is sprayed on the surface of the magnetic sheet through the automatic spraying production line. The increment of the diffusion source is controlled to be 0.75wt.%, and then high-temperature diffusion is performed. Among them, the diffusion process is to heat up to 900℃ at 10℃ / min and keep it for 15h, and finally cool it to room temperature quickly; the first-level tempering process is to heat up to 700℃ at 10℃ / min and keep it for 120min, and then cool it to room temperature quickly; the second-level tempering process is to heat up to 400℃ at 10℃ / min and keep it for 120min, and finally cool it to room temperature quickly. Finally, the high-cerium NdFeB diffusion magnet 2-0# is obtained.

[0058] Comparative Example 3

[0059] A method for preparing a low-cost high-cerium neodymium iron boron diffusion magnet comprises the following steps:

[0060] The chemical formula is (PrNd) 19 Ce 10 Ho1Al 0.25 Cu 0.2 Co 0.1 Zr 0.3 B 0.89 Fe bal (wt.%) The ingredients were melted to prepare a Ce30 alloy casting with a Ce content of 10wt.%, according to the chemical formula (PrNd) 13.7 Y 0.8 Ho 0.5 Ce 15 Al 0.2 Cu 0.2 Co 0.1 Zr 0.3 B 0.9 0Fe 68.30 (wt.%) ingredients were melted to prepare Ce50 alloy flakes with a Ce content of 15wt.%.

[0061] Ce30 and Ce50 alloy flakes are each prepared into fine powder by hydrogen crushing and airflow milling, and the fine powder particle size SMD is controlled to be 2.8μm. Ce30 and Ce50 fine powders are evenly mixed in a mass ratio of 70%:30%, oriented pressing is performed under a magnetic field strength of 2.0T, and then cold isostatic pressing is performed under a pressure of 200MPa to form a green body. Then it is placed in a high vacuum sintering furnace for high-temperature sintering, wherein the high-temperature sintering process is heated to 320℃ at 10℃ / min and kept warm for 60min, then heated to 640℃ at 5℃ / min and kept warm for 120min, then heated to 1048℃ at 10℃ / min and kept warm for 300min, and finally quickly cooled to room temperature to obtain high-cerium NdFeB sintered blank 1-1#.

[0062] The blank is processed to 2mm magnetic sheet, and after sandblasting, the heavy rare earth Dy alloy diffusion source is sprayed on the surface of the magnetic sheet through the automatic spraying production line. The increment of the diffusion source is controlled to be 0.75wt.%, and then high-temperature diffusion is carried out. Among them, the diffusion process is to heat up to 900℃ at 10℃ / min and keep it for 15h, and finally cool it to room temperature; the first-level tempering process is to heat up to 700℃ at 10℃ / min and keep it for 120min, and then cool it to room temperature; the second-level tempering process is to heat up to 400℃ at 10℃ / min and keep it for 120min, and finally cool it to room temperature. Finally, high-cerium NdFeB diffusion magnet 2-1# is obtained.

[0063] Comparative Example 4

[0064] A method for preparing a low-cost high-cerium neodymium iron boron diffusion magnet comprises the following steps:

[0065] The chemical formula is (PrNd) 17.4 Y 0.24 Ho 0.85 Ce 11.5 Al 0.235 Cu 0.2 Co 0.1 Zr 0.3 B 0.893 Fe 68.27 (wt.%) ingredients are melted to prepare alloy castings, and then the castings are subjected to hydrogen crushing and air flow grinding processes. The fine powder particle size SMD after air flow grinding is 2.8μm. The air flow ground fine powder is subjected to oriented pressing under a magnetic field strength of 2.0T, and then cold isostatic pressing is performed under a pressure of 200MPa to form a green body. It is then placed in a high vacuum sintering furnace for high-temperature sintering, wherein the high-temperature sintering process is to heat up to 320℃ at 10℃ / min and keep warm for 60min, then heat up to 640℃ at 5℃ / min and keep warm for 120min, then heat up to 1048℃ at 10℃ / min and keep warm for 300min, and finally quickly cool to room temperature to obtain a high-cerium NdFeB sintered blank.

[0066] The blank is processed to 2mm magnetic sheet, and after sandblasting, the heavy rare earth Dy alloy diffusion source is sprayed on the surface of the magnetic sheet through the automatic spraying production line. The increment of the diffusion source is controlled to be 0.75wt.%, and then high-temperature diffusion is carried out. Among them, the diffusion process is to heat up to 900℃ at 10℃ / min and keep it for 15h, and finally cool it to room temperature; the first-level tempering process is to heat up to 700℃ at 10℃ / min and keep it for 120min, and then cool it to room temperature; the second-level tempering process is to heat up to 400℃ at 10℃ / min and keep it for 120min, and finally cool it to room temperature. Finally, high-cerium NdFeB diffusion magnet 2-2# is obtained.

[0067] Example 3

[0068] The difference between this embodiment and embodiment 1 is that Ce30 and Ce50 alloy flakes are mixed in a ratio of 80%:20%.

[0069] Example 4

[0070] The difference between this embodiment and embodiment 1 is that Ce30 and Ce50 alloy flakes are mixed in a ratio of 60%:40%.

[0071] The magnetic properties of the high-cerium NdFeB magnets prepared in the above examples and comparative examples were tested, and the test results are shown in Table 1.

[0072] Table 1 Performance test data of high cerium NdFeB magnets prepared in Examples and Comparative Examples

[0073]

[0074] It can be seen from the data in Table 1 that only by preparing the magnet according to the method of the present invention can the optimal magnet performance results be obtained, and its comprehensive performance is better than that of the comparative example.

[0075] Comparison of sintered blanks: Compared with Example 1, Example 1 uses two formula castings that are hydrogen-broken and air-flow-milled and then mixed, and the magnetic properties are reduced. Example 2 uses a single alloy with the same composition for sintering, and the magnetic properties are significantly reduced; while Example 1 is a blank in which two formula castings are mixed and sintered in the hydrogen-broken process, which has higher remanence, and the coercive force is increased by 4.4% compared with Example 1 and 9.4% compared with Example 2, the maximum magnetic energy product is increased by 3.8% compared with Example 1 and 9.3% compared with Example 2, the squareness is increased by 1.2% compared with Example 1 and 9.9% compared with Example 2, and the blank performance of Example 1 is close to that of N40 grade.

[0076] Comparative diffused magnets: diffused magnets were prepared based on the blanks. Compared with Example 2, the magnetic properties of Example 3 and Example 2 were significantly reduced, while the diffused magnet prepared in Example 2 had higher remanence, better maximum magnetic energy product and squareness, especially the coercive force was increased by 4.0% compared with Example 3 and 9.5% compared with Example 4. After diffusion, the magnet performance of Example 2 reached 38MT grade, and the Ce content was as high as 11.5wt.%.

[0077] Finally, it should be noted that the above specific embodiments are only used to explain in detail the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific implementation method of the present invention and is not used to limit the protection scope of the present invention. Although the present invention is described in detail with reference to the above specific embodiments, ordinary technicians in this field should understand that it is still possible to modify the technical solutions recorded in the above embodiments, or to replace or improve some or all of the technical features therein. These modifications, equivalent replacements and improvements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for preparing a low-cost high-cerium neodymium iron boron diffusion magnet, characterized in that: The following steps are involved: Smelting the ingredients to prepare NdFeB alloy casting flakes Ce30 with a Ce content of 8-12wt.% and NdFeB alloy casting flakes Ce50 with a Ce content of 13-17wt.%; After Ce30 and Ce50 NdFeB alloy flakes are uniformly mixed, hydrogen crushing, jet milling, orientation pressing, cold isostatic pressing, and vacuum sintering are sequentially performed to obtain a high-cerium sintered NdFeB matrix; The high cerium NdFeB diffusion magnet is obtained by grain boundary diffusion of high cerium sintered NdFeB matrix.

2. The method for preparing a low-cost high-cerium NdFeB diffused magnet according to claim 1, characterized in that: The chemical composition of Ce30 is Ce a RE1 b M1 c B x Fe y , wherein RE1 is selected from at least one element of Pr, Nd, La, Gd, Y, and Ho, M1 is selected from at least one element of Cu, Al, Ga, Co, Zr, and Ti, B is boron, and Fe is iron; a, b, c, x, and y are the mass percentages of the corresponding elements, and at the same time satisfy 8≤a≤12, 18≤b≤22, 28≤a+b≤31, 0≤c≤2, 0.85≤x≤0.95, and y=100-abcx; the chemical composition of Ce50 is Ce d RE2 e M2 f B j Fe q , wherein RE2 is selected from at least one element of Pr, Nd, La, Gd, Y, and Ho, M2 is selected from at least one element of Cu, Al, Ga, Co, Zr, and Ti, B is boron, and Fe is iron; d, e, f, j, and q are the mass percentages of the corresponding elements, and at the same time satisfy 13≤d≤17, 13≤e≤17, 28≤d+e≤31, 0≤f≤2, 0.85≤j≤0.95, and q=100-defj.

3. The method for preparing a low-cost high-cerium NdFeB diffused magnet according to claim 1, characterized in that: The Ce content of the Ce30 is 10%, and the Ce content of the Ce50 is 15%.

4. The method for preparing a low-cost high-cerium NdFeB diffused magnet according to claim 1, characterized in that: In the mixture of Ce30 and Ce50 NdFeB alloy casting sheets, the mass proportion of Ce50 NdFeB alloy casting sheets is 20%-40%.

5. The method for preparing a low-cost high-cerium NdFeB diffused magnet according to claim 1, characterized in that: In the hydrogen crushing process, the alloy casting sheet absorbs hydrogen at room temperature for 1.5 to 2 hours, and then dehydrogenates at 450°C to 500°C for 4 to 5 hours to obtain alloy coarse powder with a particle size of 1 to 3 mm; the particle size SMD parameter of the alloy fine powder obtained after the air flow milling process is between 2.8 and 3.2 μm; the magnetic field strength used in the orientation pressing is not less than 2.0 T; the pressure adopted in the cold isostatic pressing process is between 170 and 220 MPa.

6. The method for preparing a low-cost high-cerium NdFeB diffused magnet according to claim 1, characterized in that: The vacuum sintering process is specifically as follows: Heat up to 200-350℃ at 10℃ / min and keep warm for 30-60min; Then, the temperature was raised to 600-800°C at 5°C / min and kept at this temperature for 60-120 min; Then, the temperature was raised to 900-1100°C at 10°C / min and kept at that temperature for 240-480min; Finally, cool quickly to room temperature.

7. The method for preparing a low-cost high-cerium NdFeB diffused magnet according to claim 1, characterized in that: The method of obtaining a high-cerium NdFeB diffusion magnet by grain boundary diffusion of a high-cerium sintered NdFeB matrix comprises the following steps: The high-cerium sintered NdFeB substrate is processed into a thin sheet substrate of required thickness, and the magnetic sheet is sandblasted to remove surface impurities; The heavy rare earth Dy alloy diffusion source is sprayed onto the surface of the substrate by the spray diffusion method, and a high cerium NdFeB diffusion magnet is obtained after high temperature diffusion and multi-stage tempering.

8. The method for preparing a low-cost high-cerium NdFeB diffused magnet according to claim 7, characterized in that: The spraying amount of the heavy rare earth Dy alloy diffusion source is 0.5-1.5wt.% of the weight of the substrate magnetic sheet.

9. A low-cost high-cerium neodymium iron boron diffusion magnet, characterized in that: The method is prepared by any one of claims 1 to 8.

10. Use of the NdFeB magnet obtained by the preparation method according to any one of claims 1 to 8 and / or the NdFeB magnet according to claim 9 in electric two-wheeled vehicles, automobile industry, electronic products, wind power, elevators, industrial robots or aerospace.

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