A high-cerium-content sintered magnet and a method for manufacturing the same

Abstract

The application provides a high-Ce-content sintered magnet and a preparation method thereof, and relates to the technical field of rare earth permanent magnet materials. A Ce-rich main phase with a Ce content greater than 22.0wt.% is used as a main alloy, and sintered Nd-Fe-B magnet waste containing heavy rare earth Dy and Tb and having a coercivity greater than 20kOe is used as an auxiliary alloy to provide main phase grains with high magnetic crystal anisotropy field (H A ). By designing the powder particle size of the two main phase alloys and the heat treatment process, the main phase grains with small particle sizes and rich in heavy rare earth Dy and Tb are uniformly dispersed around the Ce-rich main phase grains, and the solid-solid diffusion between the two kinds of main phase grains is utilized in long-time sintering-in-situ diffusion heat treatment to construct a Dy and Tb-rich shell layer with high H A on the surface layer of the Ce-rich main phase grains, while the fine grain size is maintained, so that the sintered magnet with high Ce content and good magnetic properties is prepared by using sintered Nd-Fe-B magnet waste.

Description

Technical Field

[0001] The present invention relates to the field of rare earth permanent magnet material preparation technology, in particular to a high Ce content sintered magnet and a preparation method thereof. Background Art

[0002] Rare earth permanent magnets represent the largest application area for rare earth resources and are a key foundational material supporting the rapid development of strategic emerging and future industries, such as new energy vehicles, advanced rail transit equipment, high-end CNC machine tools, and robotics. Driven by major national strategic needs, such as the "dual carbon" initiative and sustainable development, the rare earth permanent magnet industry has experienced rapid growth in recent years. The production of sintered Nd-Fe-B magnets has increased annually, leading to a sharp increase in demand for rare earth elements such as Nd, Pr, Dy, and Tb. Due to the coexistence of rare earth elements in rare earth ores, excessive consumption of Nd, Pr, Dy, and Tb in the production of Nd-Fe-B permanent magnets has led to a significant decline in the use of less expensive light rare earth elements such as La and Ce, which account for approximately 70% of total rare earth reserves. This has led to a significant imbalance in the utilization of my country's rare earth resources. Furthermore, the production and processing of sintered Nd-Fe-B magnets generates a large amount of scrap. The increase in annual production of sintered Nd-Fe-B magnets has also led to a rapid increase in the amount of secondary rare earth permanent magnet resources, including scrap and discarded magnets. Therefore, utilizing high-abundance, low-cost Ce and sintered Nd-Fe-B magnet waste to prepare sintered magnets with high Ce content is an important approach to promoting the efficient utilization of rare earth resources in my country, and is of great strategic significance in terms of economic efficiency and sustainable development.

[0003] In terms of Ce element utilization, due to Ce2Fe 14 The intrinsic performance of B is much lower than that of Nd2Fe 14 B and Pr2Fe 14 B, Ce replacing Nd and Pr will reduce RE2Fe 14The intrinsic magnetic properties of the tetragonal phase B lead to a strong magnetic dilution effect. In order to weaken the magnetic dilution effect caused by the introduction of Ce elements, a dual-phase alloy process is currently used to design and prepare a Ce-containing main phase magnetic powder and a Ce-free main phase magnetic powder, which are then uniformly mixed in a certain proportion to prepare a multi-phase Ce-based sintered magnet. Compared with single-phase magnets, the rare earth elements in a single main phase grain of a multi-phase magnet are unevenly distributed and exhibit a "core-shell" structure, as well as Ce-rich and Ce-poor grains. The chemical composition heterogeneity caused by the uneven distribution of rare earth elements within the main phase grains and between grains can effectively weaken the magnetic dilution effect caused by the introduction of Ce. For example, the invention patents 201210315684.5 and 201310090328.2 adopt a dual-phase alloy process, by preparing two different compositions of quick-setting sheets, crushing and pulverizing, mixing, sintering and heat treatment to obtain the final multi-phase magnet, wherein at least one quick-setting sheet contains a Nd-rich 2:14:1 main phase, and the high anisotropy field Nd2Fe 14 In the prior art, the dual-phase alloy process for preparing Ce magnets must use Nd-rich quick-solidified sheets and then use hydrogen crushing and air flow milling to prepare magnetic powder as Nd2Fe 14 The source of B grains is obviously not conducive to further reducing the manufacturing cost of Ce magnets and reducing the dependence on Pr and Nd rare earth elements.

[0004] In response to the increasing amount of sintered Nd-Fe-B magnet scrap, in addition to traditional remelting and re-refining techniques, a new green technology, using surface treatment, crushing and pulverizing, orientation pressing, sintering, and heat treatment to re-prepare blanks, is rapidly developing, as described in invention patents 201610455267.9 and 201910862247.7. However, scrap magnets not only have a high oxygen content, but also suffer from severe rare earth loss after re-crushing and pulverizing, resulting in a significant reduction in the magnetic properties of the re-prepared magnets. Therefore, during the preparation of recycled magnets, a certain amount of rare earth-rich alloy is often added to replenish the rare earth content and improve the magnetic properties of the recycled magnets. For example, alloys or single elements of Ce, La, Pr, and Nd are added, as described in invention patents 202310288509.X and 202311435476.3, and nano-TbH3 particles and Nd-Fe-B magnetic powder with high remanence are added, as described in invention patent 202011324051.1. Although the above method can effectively utilize sintered Nd-Fe-B magnet waste, it still requires additional rare earth content or the addition of high-performance sintered Nd-Fe-B magnetic powder. The prepared recycled magnets not only have low magnetic properties, but also have limited effect on reducing production costs.

[0005] Recently, in the invention patent 202010157867.3, a dual-main-phase alloy process was used to prepare cost-effective rare earth permanent magnet materials. The first main phase is sintered Nd-Fe-B magnet recycled material, with an addition amount of 10-70wt.%; the second main phase is a high-abundance rare earth-based permanent magnet phase with a high total rare earth content (33-37wt.%), of which the high-abundance rare earth elements La, Ce, and Y account for 10-80wt.%; in addition, it can also include a third permanent magnet main phase that does not contain high-abundance rare earths, with a total rare earth content (29-33wt.%); then the initially crushed Nd-Fe-B magnet recycled material and the second main phase and the third main phase rapid solidification sheets are mixed in proportion for hydrogen crushing and air flow grinding to prepare regenerated sintered magnets. This invention patent uses sintered Nd-Fe-B magnet recycled material as the main body and uses the second main phase and the third main phase to provide the grain boundary phase. However, when the Ce content in the high-abundance rare earth-based second main phase with a high total rare earth content is high, a large amount of CeFe2 grain boundary phase will be generated. When the CeFe2 phase is used as the grain boundary phase in the recycled magnet, it is harmful to the magnetic properties, especially causing a serious reduction in coercivity. In general, in order to obtain higher magnetic properties (as stated in the claims: remanence: 12-14 kG, coercivity: 11.9-17 kOe, magnetic energy product: 36-48 MGOe) by using this method to prepare recycled sintered magnets, it still requires the use of a large amount of non-high-abundance rare earth elements other than La, Ce, and Y, which is not conducive to the balanced utilization of rare earth resources and the further reduction of production costs.

[0006] In summary, on the one hand, in order to reduce the backlog of Ce elements, promote the balanced utilization of rare earth resources, and give full play to its advantages as a high-abundance rare earth resource, on the other hand, in order to make high-value use of sintered Nd-Fe-B magnet waste, there is an urgent need for a new method to use high-abundance rare earth Ce and sintered Nd-Fe-B magnet waste to prepare sintered magnets with high Ce content and maintain high coercive force, so as to achieve the replacement of medium and low-grade magnets. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the present invention provides a high Ce content sintered magnet and its preparation method, by adding sintered Nd-Fe-B magnet scrap containing heavy rare earth Dy and Tb and having a coercive force greater than 20kOe to the Ce-rich main phase alloy, and using the sintered Nd-Fe-B magnet scrap to provide a high magnetocrystalline anisotropy field (H A ) main phase grains; further control the particle size and sintering process of Ce-rich main phase alloy powder and sintered Nd-Fe-B magnet waste powder, and combine in-situ diffusion technology to construct a high H A shell, thereby realizing the preparation of high Ce content sintered magnets with better magnetic properties using sintered Nd-Fe-B magnet waste.

[0008] To achieve the above object, the present application is implemented by the following technical solutions:

[0009] A high Ce content sintered magnet, which is composed of a main alloy A and an auxiliary alloy B in a mass ratio of 9-6:1-4, and the sum of the mass ratio of the main alloy A and the auxiliary alloy B is 10;

[0010] The main alloy A is a Ce-rich main phase, and the chemical formula is [Re a Ce 1-a ] x Fe 100-x-y-z M y B z , wherein the Ce content is greater than 22.0wt.%, Re is one or several of Pr and Nd, M is one or several of Nb, Ti, V, Zr, Co, Mn, Ni, Ga, Al, Au, and Cu, wherein a, x, y, and z satisfy the following relationships: 0.1≤a≤0.3, 32≤x≤34, 0.5≤y≤3, and 0.8≤z≤1.0; the auxiliary alloy B is sintered Nd-Fe-B magnet waste, and the sintered Nd-Fe-B magnet waste contains rare earths Dy and Tb and has a coercivity greater than 20kOe.

[0011] A preparation method of the high Ce content sintered magnet includes the following steps:

[0012] (1) selecting each metal component and other components according to the chemical formula of the main alloy A and placing them in a crucible, then performing material drying under vacuum, filling argon for smelting, and then pouring onto a rotating water-cooled copper roller to prepare a rapid solidification sheet;

[0013] (2) performing hydrogen crushing treatment on the rapid solidification sheet obtained in step (1), obtaining hydrogen crushing coarse powder A after dehydrogenation, then adding a lubricant and an antioxidant and mixing uniformly to obtain a mixed coarse powder for standby use;

[0014] (3) performing airflow milling on the mixed coarse powder in step (2) to obtain fine powder A with an average particle size of 2.5-4.0μm for standby use;

[0015] (4) removing a surface plating layer and impurities from sintered Nd-Fe-B magnet waste with heavy rare earths Dy and Tb and a coercivity greater than 20kOe, then performing coarse crushing with a jaw crusher, and then performing hydrogen crushing treatment, obtaining hydrogen crushing coarse powder B after dehydrogenation;

[0016] (5) performing first airflow milling on the hydrogen crushing coarse powder B prepared in step (4) to obtain preliminary fine powder with an average particle size of 3.5-5.0μm, then adding a lubricant and an antioxidant and mixing uniformly to obtain mixed preliminary fine powder;

[0017] (6) The preliminary fine powder is subjected to second airflow milling to obtain fine powder B with an average particle size of 1.0-2.5 μm;

[0018] (7) The fine powder A and the fine powder B are mixed to obtain mixed fine powder C, and then a lubricant and an antioxidant are added and uniformly mixed, and the mixture is oriented and formed in a magnetic field with a magnetic field strength of 1.5-2.5 T under protection of inert gas, and then vacuum packaged and subjected to cold isostatic pressing to obtain a green body for standby use;

[0019] (8) The green body is placed in a vacuum sintering furnace for sintering-diffusion synergistic treatment, i.e., first heat preservation at 960-1000 ℃ for 5-8 h, then heat preservation at 800-900 ℃ for 2-6 h, and finally argon gas cooling to room temperature, to obtain a multi-main-phase magnet for standby use;

[0020] (9) The multi-main-phase magnet is placed in a vacuum sintering furnace for two-stage heat treatment, wherein the first-stage heat treatment temperature is 680-780 ℃, and the time is 2-4 h; and the second-stage heat treatment temperature is 390-490 ℃, and the time is 3-6 h.

[0021] Preferably, the rotating speed of the water-cooled copper roller in step (1) is 1-3 m / s, and the thickness of the speeded-coagulation piece is 150-350 μm.

[0022] Preferably, the adding amount of the lubricant in step (2) is 0.05%-0.8% of the total mass of the hydrogen-crushed coarse powder A, and the adding amount of the antioxidant is 0.05%-1.0% of the total mass of the hydrogen-crushed coarse powder A.

[0023] Preferably, the adding amount of the lubricant in step (5) is 0.05%-0.8% of the total mass of the preliminary fine powder, and the adding amount of the antioxidant is 0.05%-1.0% of the total mass of the preliminary fine powder.

[0024] Preferably, the adding amount of the lubricant in step (7) is 0.05%-0.8% of the total mass of the mixed fine powder C, and the adding amount of the antioxidant is 0.05%-1.0% of the total mass of the mixed fine powder C.

[0025] The present application provides a sintered magnet with high Ce content and a preparation method thereof, which has the following advantages compared with the prior art:

[0026] (1) The present application uses high-abundance rare earth element Ce and sintered Nd-Fe-B magnet waste to prepare a sintered magnet with high Ce content, which promotes the balanced utilization of rare earth resources and solves the problem of recycling of sintered Nd-Fe-B magnet waste, and has very important significance in economic benefits and sustainable development;

[0027] (2) The present invention provides a high H magnet by using a dual-phase alloy process and utilizing sintered Nd-Fe-B magnet waste containing heavy rare earths Dy and Tb and having a coercive force greater than 20kOe. A The 2:14:1 phase grains are prepared by designing the particle size of the two main phase alloy powders so that the main phase grains with smaller particle size and rich in heavy rare earths Dy and Tb are evenly dispersed around the Ce-rich main phase grains. During the long sintering-diffusion heat treatment, the two main phase grains undergo solid-solid diffusion, forming a Dy and Tb-rich shell on the surface of the Ce-rich main phase grains while maintaining a small grain size, thereby significantly improving the coercivity of the multi-main-phase Ce-based magnet;

[0028] (3) The high Ce content sintered magnet prepared by the present invention has magnetic properties between those of sintered Nd-Fe-B magnets and permanent ferrites, and has lower production costs than sintered Nd-Fe-B magnets, giving full play to the advantages of high-abundance rare earth resources. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] The following lubricant is Nd-Fe-B special lubricant 6# produced by Tianjin Yuesheng New Materials Research Institute;

[0031] The antioxidant is Nd-Fe-B special antioxidant 5# produced by Tianjin Yuesheng New Materials Research Institute.

[0032] Example 1:

[0033] High Ce content multi-phase magnets are prepared using sintered Nd-Fe-B magnet scrap containing heavy rare earths Dy and Tb and with a coercivity greater than 20kOe:

[0034] According to the nominal composition of the main alloy A (Ce 0.8 Nd 0.2 ) 33.0 Fe bal Al 0.8 Cu 0.5 Co1Ga 0.35 Zr 0.2 B 0.95(wt.%) with a copper roll rotating speed of 1.3 m / s to obtain a rapidly solidified sheet with a thickness of about 220 μm. The rapidly solidified sheet was then hydrogen decrepitated to obtain a coarse decrepitated powder, which was dehydrogenated and then mixed with 0.06% by mass of a lubricant and 0.08% by mass of an oxidation inhibitor to obtain a fine powder A with an average particle size of X 50 = 3.5 μm.

[0035] Sintered Nd-Fe-B magnet scrap of N45UH grade was selected as the auxiliary alloy B, and the total rare earth content was 30.8% by mass as determined by ICP, which contained 1.2% by mass of Tb and 2.0% by mass of Dy. The magnet scrap was first treated in an acidic solution to remove the surface plating and impurities, and then coarsely broken by a jaw crusher. The coarsely broken powder was then hydrogen decrepitated, dehydrogenated, and then first jet-milled to obtain a fine powder A with an average particle size of X 50 = 4.3 μm. The fine powder A was then mixed with 0.08% by mass of a lubricant and 0.10% by mass of an oxidation inhibitor, and then second jet-milled to obtain a fine powder B with an average particle size of X 50 = 1.8 μm.

[0036] The fine jet-milled powders of A and B were mixed in a glove box at a mass ratio of 7.5:2.5, and then mixed with 0.10% by mass of a lubricant and 0.14% by mass of an oxidation inhibitor to obtain a fine jet-milled powder C with a Ce content of 19.8% by mass. The fine jet-milled powder C was oriented and formed in a magnetic field with a magnetic field strength of 2.0 T under an inert gas atmosphere to obtain a green compact. The green compact was vacuum packaged and cold isostatic pressed, and then sintered and diffused in a vacuum sintering furnace. The sintering and diffusion process was first performed at 980°C for 6 hours, and then the temperature was lowered to 880°C for 4 hours, and then the argon gas was blown to cool to room temperature. The sintered and diffused product was then subjected to two-step heat treatment at low temperature. The first step was performed at 740°C for 3 hours, and then the argon gas was blown to cool to room temperature. The second step was performed at 400°C for 4 hours, and then the argon gas was blown to cool to room temperature to obtain a multi-main-phase magnet C. The magnetic properties of the multi-main-phase magnet C were tested in a BH tester, and the results were as follows:

[0037] Magnet C: B r = 11.07 kG, H cj = 10.53 kOe, (BH) max = 29.43 MGOe, H k / H cj = 96.9%.

[0038] Example 2:

[0039] The sintered Nd-Fe-B magnet waste containing heavy rare earth Dy and Tb and having coercivity greater than 20 kOe is used to prepare high Ce content multi-main phase magnet:

[0040] According to the nominal composition (Ce 0.7 Nd 0.3 ) 33.0 Fe bal Al 0.8 Cu 0.5 Co1Ga 0.35 Zr 0.2 B 0.95 (wt.%) and a copper roll rotating speed of 1.3 m / s, a rapidly solidified sheet with a thickness of about 220 μm is prepared. Then the rapidly solidified sheet is subjected to hydrogen crushing, and after dehydrogenation, coarse crushed magnetic powder is obtained. Then, after adding 0.06% of lubricant and 0.08% of antioxidant by mass ratio respectively and mixing uniformly, the gas jet milling is carried out under inert gas protection atmosphere, to obtain gas jet milled fine powder A1 with an average particle size X 50 of 3.5 μm.

[0041] The sintered Nd-Fe-B magnet waste of N45UH brand is selected as the auxiliary alloy B, and the total rare earth content is 30.8 wt.% by ICP detection, containing 1.2 wt.% of Tb and 2.0 wt.% of Dy. After removing the surface plating and impurities of the magnet waste in an acidic solution, the coarse crushing is carried out by using a jaw crusher, and then the coarse crushing powder is subjected to hydrogen crushing treatment. After dehydrogenation, the hydrogen crushed coarse powder is obtained. Then, the hydrogen crushed coarse powder is subjected to first gas jet milling, to obtain fine powder with an average particle size X 50 of 4.3 μm. Then, after adding 0.08% of lubricant and 0.10% of antioxidant by mass ratio respectively and mixing uniformly, the second gas jet milling is carried out, to obtain fine powder B with an average particle size X 50 of 1.8 μm.

[0042] In the glove box, the gas jet milled fine powders of A1 and B are mixed in a mass ratio of 7.0:3.0, and then 0.10% of lubricant and 0.14% of antioxidant by mass ratio are added respectively and mixed uniformly, to obtain gas jet milled fine powder C1 with a Ce content of 16.17 wt.%.

[0043] Under an inert gas protective atmosphere, the jet-milled powder C1 was oriented and formed in a magnetic field with a magnetic field strength of 2.0 T to obtain a compact. The compact was vacuum-sealed and cold isostatically pressed, and then placed in a vacuum sintering furnace for sintering-diffusion process coordinated treatment. The compact was first kept at 980°C for 6 hours, then lowered to 880°C and kept for 4 hours, and then cooled to room temperature with argon gas. Then, a two-step heat treatment was performed at low temperature. The compact was first kept at 740°C for 3 hours, then cooled to room temperature with argon gas, and then kept at 400°C for 4 hours, and then cooled to room temperature with argon gas. The multi-phase magnet C1 was obtained and its magnetic properties were tested in a BH tester. The results are as follows:

[0044] Magnet C1: B r =11.35kG, H cj =12.48kOe, (BH) max =31.08MGOe, H k / H cj =96.7%.

[0045] Example 3:

[0046] High Ce content multi-phase magnets are prepared using sintered Nd-Fe-B magnet scrap containing heavy rare earths Dy and Tb and with a coercivity greater than 20kOe:

[0047] According to the nominal composition of the main alloy A1 (Ce 0.7 Nd 0.3 ) 33.0 Fe bal Al 0.8 Cu 0.5 Co1Ga 0.35 Zr 0.2 B 0.95 (wt.%), using a copper roller speed of 1.3m / s, to prepare a quick-setting sheet with a thickness of about 220μm. Then the quick-setting sheet was hydrogen crushed, and after dehydrogenation, coarse crushed magnetic powder was obtained. Then, 0.06% of lubricant and 0.08% of antioxidant were added, mixed thoroughly, and then jet milled under an inert gas atmosphere to obtain an average particle size of X 50 The jet milled powder A1 is 3.5 μm.

[0048] Sintered Nd-Fe-B magnet scrap of N40EH grade was selected as auxiliary alloy B1. The total rare earth content was 31.5wt.%, including 3.5wt.% Dy and 1.5wt.% Tb according to ICP. The surface coating and impurities of the magnet scrap were removed in an acidic solution, and then the scrap was coarsely crushed by a jaw crusher. The coarsely crushed powder was then subjected to hydrogen crushing treatment. After dehydrogenation, the hydrogen-crushed coarse powder was obtained. The hydrogen-crushed coarse powder was then subjected to the first air flow milling to obtain an average particle size of X 50The fine powder is 4.3 μm, then 0.08% of lubricant and 0.10% of antioxidant are added and mixed well, and then the powder is prepared by second jet milling, to obtain the fine powder A1 with average particle size X 50 The fine powder is 1.8 μm, and is B1.

[0049] In the glove box, the jet-milled fine powder of A1 and B1 is mixed in a mass ratio of 7.0:3.0, then 0.10% of lubricant and 0.14% of antioxidant are added respectively and mixed well, to obtain the jet-milled fine powder C2 with Ce content of 16.17 wt.%.

[0050] Under the protection of inert gas, the jet-milled fine powder C2 is oriented and formed in a magnetic field with a magnetic field strength of 2.0 T, to obtain a compact, which is vacuum packaged and cold isostatic pressed, and then put into a vacuum sintering furnace for sintering-diffusion process, first at 980℃ for 6 hours, then reduced to 880℃ for 4 hours, and then cooled to room temperature by argon gas; then two-step heat treatment at low temperature, first at 740℃ for 3 hours, then cooled to room temperature by argon gas, and then at 400℃ for 4 hours, and then cooled to room temperature by argon gas, to obtain the multi-main-phase magnet C2, which is put into a BH tester to test the magnetic properties, and the results are as follows:

[0051] Magnet C2: B r = 11.22 kG, H cj = 14.07 kOe, (BH) max = 30.24 MGOe, H k / H cj = 96.3%.

[0052] Comparative Example 1:

[0053] A high-Ce-content multi-main-phase magnet is prepared by a traditional double-alloy process:

[0054] According to the nominal composition of the main alloy A (Ce 0.8 Nd 0.2 ) 33.0 Fe bal Al 0.8 Cu 0.5 Co1Ga 0.35 Zr 0.2 B 0.95 (wt.%), according to the nominal composition of the auxiliary alloy B2 (Nd 31 Fe bal Al 0.1 Cu 0.5 Co 0.8 Ga 0.35 Zr 0.2 B 0.95wt.%) with a copper roll rotating speed of 1.3 m / s to obtain two kinds of rapidly solidified ribbons A and B2 with a thickness of about 220 μm.

[0055] The rapidly solidified ribbons A and B2 were hydrogen broken respectively, and the coarse broken magnetic powders were obtained after dehydrogenation. Then, the powders were mixed with 0.06% lubricant and 0.08% antioxidant respectively, and then were jet milled under inert gas protection to obtain the jet milled powders of A and B2. The average particle size X 50 of the jet milled powder of A was 3.5 μm, and the average particle size X 50 of the jet milled powder of B2 was 2.6 μm.

[0056] The jet milled powders of A and B2 were mixed with 0.12% lubricant and 0.16% antioxidant respectively in a glove box, and then were mixed with each other to obtain the jet milled powder C3 with a Ce content of 19.8 wt.%.

[0057] The jet milled powder C3 was oriented and formed in a magnetic field with a magnetic field strength of 2.0 T under inert gas protection to obtain a green compact. The green compact was vacuum packaged, cold isostatic pressed, and then was put into a vacuum sintering furnace for traditional sintering process. After being kept at a sintering temperature of 1010 °C for 5 hours, the green compact was cooled to room temperature by argon gas. Then, the green compact was treated by two-step conventional heat treatment, i.e., first kept at 820 °C for 3 hours, then cooled to room temperature by argon gas, and then kept at 400 °C for 4 hours, and then cooled to room temperature by argon gas. A multi-main-phase magnet C3 was obtained, and the magnetic properties of the magnet were tested in a BH tester. The results are as follows:

[0058] Magnet C3: B r = 11.17 kG, H cj = 6.54 kOe, (BH) max = 28.76 MGOe, H k / H cj = 96.2%.

[0059] Comparative Example 2:

[0060] A high Ce content multi-main-phase magnet was prepared by using a traditional double-alloy process combined with sintering-in-situ diffusion heat treatment:

[0061] According to the nominal composition (Ce 0.8 Nd 0.2 ) 33.0 Fe bal Al 0.8 Cu 0.5 Co1Ga 0.35 Zr 0.2 B 0.95(wt.%), according to the nominal composition of the auxiliary alloy B2 Nd 31 Fe bal Al 0.1 Cu 0.5 Co 0.8 Ga 0.35 Zr 0.2 B 0.95 (wt.%), using a copper roller speed of 1.3 m / s, A and B2 component rapidly solidified ribbons with a thickness of about 220 μm were prepared.

[0062] The A and B2 component rapidly solidified ribbons were separately subjected to hydrogen decrepitation, and after dehydrogenation, coarse broken magnetic powders were obtained. Then, after adding 0.06% of a lubricant and 0.08% of an antioxidant by mass ratio, respectively, and thoroughly mixing and homogenizing, the A and B2 component powders were subjected to jet milling under an inert gas atmosphere, to obtain A and B2 component jet milled fine powders. The average particle size X 50 of the A component jet milled fine powder was 3.5 μm, and the average particle size X 50 of the B2 component jet milled fine powder was 2.6 μm.

[0063] In a glove box, the A and B2 component jet milled fine powders were again separately added with 0.12% of a lubricant and 0.16% of an antioxidant by mass ratio, and then mixed and homogenized. Then, the A and B2 component jet milled fine powders were mixed at a mass ratio of 7.5:2.5, to obtain a jet milled fine powder C3 having a Ce content of 19.8 wt.%.

[0064] Under an inert gas atmosphere, the jet milled fine powder C3 was oriented and formed in a magnetic field with a magnetic field strength of 2.0 T, to obtain a green compact. The green compact was vacuum packaged and subjected to cold isostatic pressing, and then placed in a vacuum sintering furnace for sintering-diffusion process cooperative treatment. First, the temperature was held at 980°C for 6 hours, and then decreased to 880°C for 4 hours, and then cooled to room temperature with argon gas. Then, two-step heat treatment was performed at low temperature. First, the temperature was held at 740°C for 3 hours, and then cooled to room temperature with argon gas, and then the temperature was held at 400°C for 4 hours, and then cooled to room temperature with argon gas, to obtain a multi-main-phase magnet C4. The magnetic properties of the magnet C4 were tested in a BH tester, and the results were as follows:

[0065] Magnet C4: B r = 11.13 kG, H cj = 7.26 kOe, (BH) max = 29.23 MGOe, H k / H cj = 97.3%.

[0066] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A high Ce content sintered magnet, characterized by: The high Ce content sintered magnet is composed of a main alloy A and an auxiliary alloy B in a mass ratio of 9-6:1-4, and the sum of the mass ratios of the main alloy A and the auxiliary alloy B is 10; The main alloy A is a Ce-rich main phase, and the chemical formula is [Re a Ce 1-a ] x Fe 100-x-y-z M y B z , wherein the Ce content is greater than 22.0wt.%, Re is one or more of Pr and Nd, M is one or more of Nb, Ti, V, Zr, Co, Mn, Ni, Ga, Al, Au, and Cu, wherein a, x, y, and z satisfy the following relationship: 0.1≤a≤0.3, 32≤x≤34, 0.5≤y≤3, and 0.8≤z≤1.0; the auxiliary alloy B is sintered Nd-Fe-B magnet scrap, and the sintered Nd-Fe-B magnet scrap contains rare earths Dy and Tb and has a coercive force greater than 20kOe.

2. A method for preparing a high Ce content sintered magnet according to claim 1, characterized in that: The preparation method comprises the following steps: (1) According to the chemical formula of the main alloy A, the metal components and other components are selected and placed in a crucible. After the materials are dried under vacuum, argon gas is filled in for melting, and then poured onto a rotating water-cooled copper roller to prepare a quick-setting sheet; (2) subjecting the quick-setting sheet obtained in step (1) to hydrogen crushing treatment to obtain hydrogen crushing coarse powder A after dehydrogenation, and then adding a lubricant and an antioxidant to mix uniformly to obtain a mixed coarse powder for use; (3) The mixed coarse powder in the above step (2) is subjected to air flow grinding to obtain fine powder A with an average particle size of 2.5 to 4.0 μm for standby use; (4) Sintered Nd-Fe-B magnet scrap containing heavy rare earth elements Dy and Tb and having a coercivity greater than 20 kOe is subjected to coarse crushing using a jaw crusher after removing surface coatings and impurities, followed by hydrogen crushing treatment, and dehydrogenation to obtain hydrogen crushed coarse powder B; (5) The hydrogen-crushed coarse powder B obtained in step (4) is subjected to a first airflow milling to obtain a preliminary fine powder with an average particle size of 3.5-5.0 μm, and then a lubricant and an antioxidant are added and mixed to obtain a mixed preliminary fine powder; (6) subjecting the mixed preliminary fine powder to a second airflow milling to obtain fine powder B with an average particle size of 1.0-2.5 μm; (7) The fine powder A and the fine powder B are mixed to obtain a mixed fine powder C, and a lubricant and an antioxidant are added to mix evenly. Under the protection of an inert gas, the mixture is oriented and formed in a magnetic field with a magnetic field strength of 1.5-2.5T. After vacuum packaging, the mixture is cold isostatically pressed to obtain a green body for use; (8) placing the green compact into a vacuum sintering furnace for sintering-diffusion coordinated treatment, i.e., firstly keeping the temperature at 960-1000°C for 5-8 hours, then cooling the temperature to 800-900°C for 2-6 hours, and finally cooling the green compact to room temperature with argon gas to obtain a multi-phase magnet for standby use; (9) The multi-phase magnet is placed in a vacuum sintering furnace for two-stage heat treatment, wherein the first stage heat treatment temperature is 680-780°C for 2-4 hours; the second stage heat treatment temperature is 390-490°C for 3-6 hours.

3. The preparation method according to claim 2, wherein: In the step (1), the rotation speed of the water-cooled copper roller is 1-3 m / s, and the thickness of the quick-setting sheet is 150-350 μm.

4. The preparation method according to claim 2, wherein: In the step (2), the amount of lubricant added is 0.05%-0.8% of the total mass of the hydrogen-crushed coarse powder A, and the amount of antioxidant added is 0.05%-1.0% of the total mass of the hydrogen-crushed coarse powder A.

5. The preparation method according to claim 2, wherein: In the step (5), the amount of lubricant added is 0.05%-0.8% of the total mass of the preliminary fine powder, and the amount of antioxidant added is 0.05%-1.0% of the total mass of the preliminary fine powder.

6. The preparation method according to claim 2, wherein: In the step (7), the amount of lubricant added is 0.05%-0.8% of the total mass of the mixed fine powder C, and the amount of antioxidant added is 0.05%-1.0% of the total mass of the mixed fine powder C.