R-T-B neodymium iron boron permanent magnet with high Ce content and preparation method thereof

Abstract

The invention discloses an R-T-B neodymium-iron-boron permanent magnet with high Ce content and a preparation method thereof, a double-alloy process is adopted, the contents of Cu and Ga in a main alloy A component are limited, and a heat treatment process is performed on a main alloy rapid hardening sheet A, so that Pr and Nd atoms in a rare-earth-rich phase coating main phase grains and Ce atoms in the surfaces of the main phase grains are mutually diffused, and the high-Ce-content R-T-B neodymium-iron-boron permanent magnet is obtained. A (Pr, Nd) 2Fe14B phase with higher saturation magnetization Ms is formed on the surface of main phase crystal grains, and after the main alloy rapid hardening sheet A is subjected to heat treatment, the magnet has higher Br; and the auxiliary alloy B is designed to contain more Pr, Nd, Cu and Ga elements, so that more liquid phases are provided in the sintering process of the magnet, main phase grains of the magnet are more easily isolated by a rare earth-rich phase, meanwhile, sufficient Cu and Ga elements are provided for formation of an RE6 (Fe, M) 14 phase in the aging treatment process, and the coercive force of the magnet is improved. The magnet has the characteristics of high Ce, high Br and high Hcj.

Description

Technical Field

[0001] This invention belongs to the field of rare earth permanent magnets, specifically relating to a high Ce content RTB neodymium iron boron permanent magnet and its preparation method. Background Technology

[0002] With the development of the NdFeB rare earth permanent magnet material industry, the usage of Pr and Nd, the main rare earth raw materials for sintered NdFeB, is gradually increasing. However, Ce, which has the largest proven rare earth reserves, is used in a relatively small amount in the NdFeB magnet industry. If Ce can be effectively used to replace some Pr and Nd and magnets with better magnetic properties can be obtained, the utilization of rare earth resources can be effectively improved.

[0003] The saturation magnetization Ms of Ce is significantly lower than that of Pr and Nd. Adding Ce to sintered NdFeB magnets reduces the remanent magnetic induction Br. Furthermore, with increasing Ce content, the proportion of the CeFe2 phase in the magnet's grain boundaries gradually increases. The CeFe2 phase is a paramagnetic material with a melting point of 925℃. It tends to agglomerate at the magnet's grain boundaries and cannot effectively separate the main phase, significantly weakening the magnet's decoupling magnetization and decreasing its intrinsic coercivity Hcj. Therefore, the higher the Ce content, the greater the decrease in Br and Hcj.

[0004] Compared to single-alloy processes, dual-alloy processes can design the composition of auxiliary alloys according to the materials required for grain boundaries, thereby adjusting the structure of the grain boundary phases in the magnet, optimizing the distribution of grain boundaries, and enabling the magnet to obtain better Hcj.

[0005] Based on the addition of high Ce content, how to increase the Br and Hcj of the magnet to obtain a Ce-containing NdFeB magnet with high Br and Hcj is a development problem that urgently needs to be solved. Summary of the Invention

[0006] To address the issue of low Br and Hcj in high-Ce-content NdFeB magnets, the present invention aims to provide a high-Ce-content RTB NdFeB magnet with Br ≥ 12.6 kGs and Hcj ≥ 12 kOe. This invention optimizes the composition of the main alloy A and auxiliary alloy B, and simultaneously heat-treats the rapidly solidified sheet A of the main alloy. Combining the advantages of a dual-alloy process, a high-Ce-content RTB NdFeB permanent magnet with both high Br and Hcj is obtained.

[0007] The technical solution adopted in this invention is as follows: A high Ce content RTB neodymium iron boron permanent magnet comprises the following components by mass fraction: R: 30.4~31.2 wt.%, R includes at least two of Pr, Nd, and Ce, and must include Ce, with Ce content accounting for ≥12 wt.% of the magnet's mass; preferably, the mass fraction of Ce in the magnet is 12~13.2%; To ensure that the high Ce content RTB NdFeB permanent magnet has high remanence, the rare earth content of the magnet needs to be controlled to not exceed 31.2 wt.% of the magnet's mass in this invention. M1: 0.1~0.5 wt.%, M1 is at least one of Zr, Ti, and Nb; M2: 0.35~1wt.%, M2 is at least two of Al, Cu and Ga, and must include Cu and Ga; M3: 0.5~2.0wt.%, M3 is Co; B: 0.88~0.92 wt.%, B is boron; The balance consists of Fe and other unavoidable impurities; Al, Cu, and Ga elements play a crucial role in improving the coercivity of magnets; therefore, this invention necessitates the addition of certain amounts of Cu and Ga elements. Compared to Cu and Ga, Al has higher solubility in the main phase, directly influencing its intrinsic properties. Al preferentially substitutes for Fe(8j2) crystal sites, improving the intrinsic magnetocrystalline anisotropy of the magnet. However, adding large amounts of Al can also deteriorate the magnet's energy product and high-temperature performance. When the Al content of the magnet is ≥0.05 wt.%, a corresponding amount of Co needs to be added, with a Co content ≥0.5 wt.%.

[0008] The high Ce content RTB NdFeB permanent magnet has a remanence Br ≥ 12.6 and a coercivity Hcj ≥ 12kOe.

[0009] In the high Ce content RTB NdFeB permanent magnet, the Ce content is ≥12wt.%.

[0010] The high Ce content RTB neodymium iron boron permanent magnet has no added heavy rare earth components such as Dy, Tb, Gd and Ho in the blank magnet.

[0011] The high Ce content RTB neodymium iron boron permanent magnet has an oxygen content of ≤580ppm and a carbon content of ≤800ppm in the blank magnet.

[0012] Increased oxygen content leads to an increase in the amount of rare earth oxides in the grain boundary phase. Rare earth oxides have high melting points and are difficult to form a liquid phase during sintering and tempering, easily accumulating at triangular grain boundaries. For high-Ce magnets, which already have a large amount of CeFe2 phase that readily agglomerates at triangular grain boundaries, the increased amount of rare earth oxides results in fewer rare earth-rich grain boundary phases available to coat the main phase grains, weakening the demagnetizing coupling effect of the magnet. Although C atoms can replace Nd2Fe... 14 B atoms in the B-phase structure form Nd2Fe 14 The (B,C) phase can appropriately improve the coercivity of the magnet, but excessive addition of C will lead to a decrease in the Br content of the magnet. Therefore, the carbon content needs to be controlled during the magnet preparation process.

[0013] The high Ce content RTB NdFeB permanent magnet of the present invention can be prepared by the following method: S1: The raw materials of the main alloy and auxiliary alloy, which are prepared according to the weight ratio, are melted separately and cast to obtain the main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B. The composition of main alloy A, by mass percentage, is: (RL1) (1-x) RL2 x ) a N1 b N2 c N3 e T1 (100%-a-b-c-e-f) B f ,in: RL1 is at least one of Pr and Nd, RL2 is Ce, 30wt.%≤a≤30.2wt.%, 0.41≤x≤0.435; N1 is at least two of Al, Cu, and Ga, and must include Cu and Ga, with 0.22wt.%≤b≤0.47wt.%; preferably, in N1, the mass percentage of Ga to the mass percentage of the main alloy A is 0.12~0.15wt.%, with the balance being Cu, or Cu and Al; N2 is at least one of Zr, Ti, and Nb, and by mass percentage, 0.1 wt.% ≤ c ≤ 0.45 wt.%; N3 is Co, 0.5wt.%≤e≤1.5wt.%; When the Ga content in the main alloy A is less than 0.12 wt.%, RE6(Fe,M) grain boundaries cannot form. 14 In this phase, the coercivity of the magnet cannot be effectively increased, while when the Ga content in the main alloy is 0.12~0.15wt.%, RE6(Fe,M) 14The number of phases is significantly increased, the coercivity of the magnet increases, and the Br content of the magnet decreases. For a main alloy with high Ce content, even if the Ga content in the magnet is greater than 0.15 wt.%, the coercivity of the magnet does not increase significantly; instead, the Br content decreases with increasing Ga content. Therefore, to ensure that main alloy A has sufficient remanence Br, the Ga content in main alloy A needs to be limited so that main alloy A can just form RE6(Fe,M). 14 The phase shows a slight increase in magnet coercivity.

[0014] B represents boron, with a concentration of 0.9 wt.% ≤ f ≤ 0.925 wt.%. The balance is T1, which consists of Fe and other unavoidable impurities.

[0015] The composition of auxiliary alloy B, by mass percentage, is RL3. y K1 m K2 n Al a1 B a2 Ti a3 T2 (100%-y-m-n-a1-a2-a3) ,in: RL3 is at least one of Pr and Nd, and 65 wt.% ≤ y ≤ 85 wt.%; K1 is Cu, 1 wt.% ≤ m ≤ 3 wt.%; K2 is Ga, 8 wt.% ≤ n ≤ 10 wt.%; The masses of Al, B, and Ti satisfy the following formulas ① and ②: ①(3*a1+2*a2) / 2*a3≥1.88; ②1.5wt.%≤a1+a2+a3≤2wt.%; The balance is T2, where T2 is Fe or Fe and Co, and the mass percentage of Co to auxiliary alloy B is ≤4 wt.%.

[0016] Adding Al, Ti, and B elements can form TiAl3 and TiB2 intermediates with high melting point characteristics during the formation of rapidly solidified auxiliary alloy flakes. These intermediates provide additional nucleation sites for the solidification of the auxiliary alloy, making it easier to form plate-like rapidly solidified auxiliary alloy flakes. At the same time, the toughness of the rapidly solidified flakes is reduced, which facilitates subsequent crushing.

[0017] The balance is T2, which is Fe or Fe and Co, and the Co content is ≤4 wt.%.

[0018] The content of Pr, Nd, and Ga in auxiliary alloy B must be high. Firstly, Pr and Nd elements are used in the grain boundary phase to provide sufficient liquid phase for the sintering process. Secondly, Ga can be RE6(Fe,M). 14 The formation of the phase continues to provide Ga elements.

[0019] In step S1, after the raw materials are completely melted, the molten steel is refined for 1 to 3 minutes before being poured to ensure that the composition of the main alloy A and auxiliary alloy B quick-setting flakes is uniform.

[0020] The casting temperature of the main alloy A is 1380~1420℃, the casting temperature of the auxiliary alloy B is 1380~1400℃, and the rotation speed of the copper rollers is 70r / min.

[0021] For the main alloy A, the molten steel contains a large amount of Ce, Ce2Fe 14 B has a lower melting point than (PrNd)2Fe 14 With a lower B, the casting temperature can be lowered to 1380℃. When the casting temperature is higher than 1420℃, the molten steel is not easily cooled into quick-solidifying flakes on the surface of the copper roller. This can easily cause some of the molten steel to roll on the quick-solidifying flakes, forming additional agglomerated or strip-shaped quick-solidifying flakes or slag in the water-cooling pan or water-cooling tank, which do not have a clear columnar crystal structure and affect the performance of the magnet.

[0022] S2: Perform high-temperature heat treatment on the main alloy rapid solidification sheet A separately. The temperature of the high-temperature heat treatment is 600~1000℃ and the time is 2~4h. Furthermore, the preferred heat treatment temperature is 700~800℃, the time is 2.5~3h, and the furnace cooling time is 4~8h; For magnets with high Ce content, high-temperature heat treatment is performed during the rapid solidification stage, allowing Pr and Nd atoms from the rare-earth-rich phase to penetrate into the surface layer of the main phase grains, repairing or replacing Ce atoms on the main phase grain surface. For main phase grains with high Ce content, the replacement of Pr and Nd atoms can slightly increase the saturation magnetization Ms of the main phase grain.

[0023] Furthermore, in step S2, the high-temperature heat treatment is performed under a vacuum degree of less than 2.5 × 10⁻⁶. -2 Under Pa conditions, the rapidly solidified sheets must be cooled to below 50°C before being removed from the furnace. This cooling process prevents significant blackening of the surface of the rapidly solidified sheets and reduces their oxygen content. After high-temperature heat treatment, the oxygen content of the main alloy rapidly solidified sheet A is below 350 ppm.

[0024] S3: The main alloy rapid solidification sheet A and the auxiliary alloy rapid solidification sheet B after high temperature heat treatment are mixed to prepare NdFeB fine powder. The NdFeB fine powder is oriented and pressed into a compact. The compact is vacuum sintered and tempered to obtain a high Ce content RTB NdFeB permanent magnet. In the NdFeB fine powder, the mass fraction of the main alloy quick-setting sheet A is 97.5-99%, and the mass fraction of the auxiliary alloy quick-setting sheet B is 1-2.5%. Furthermore, the preparation of NdFeB fine powder by mixing the main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B can be carried out in one of the following two ways: ① Mix the main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B in a certain proportion, and then perform hydrogen crushing and air jet milling to obtain NdFeB fine powder; ② The main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B are subjected to hydrogen pulverization and air jet milling respectively to obtain fine powder A and fine powder B. Fine powder A and fine powder B are mixed in proportion to obtain NdFeB fine powder.

[0025] The average surface area particle size of the neodymium iron boron fine powder is 2.8~3.1μm, preferably 2.9~3.0μm.

[0026] The vacuum sintering temperature is 1000~1040℃, and the time is 3~6h.

[0027] The tempering heat treatment is either single-stage or double-stage tempering. The single-stage tempering process involves treating at 600~680℃ for 2~4 hours; the double-stage tempering process involves treating at 880-950℃ for 2~4 hours, followed by treatment at 600~680℃ for 2~4 hours.

[0028] Furthermore, the preferred cooling method for tempering heat treatment is a combination of vacuum furnace cooling and argon-filled air cooling. Vacuum furnace cooling is used when the heat treatment temperature drops to the range of 320~400℃, and argon-filled air cooling is used when the temperature drops from 320~400℃ to room temperature.

[0029] This invention also provides a method for preparing the high Ce content RTB NdFeB permanent magnet, the method comprising the following steps: S1: The raw materials of the main alloy and auxiliary alloy, which are prepared according to the weight ratio, are melted separately and cast to obtain the main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B. The composition of main alloy A, by mass percentage, is: (RL1) (1-x) RL2 x ) a N1 b N2 c N3 e T1 (100%-a-b-c-e-f) B f ,in: RL1 is at least one of Pr and Nd, RL2 is Ce, 30wt.%≤a≤30.2wt.%, 0.41≤x≤0.435; N1 is at least two of Al, Cu, and Ga, and must include Cu and Ga, with a content of 0.22 wt.% ≤ b ≤ 0.47 wt.%; the mass percentage of Ga relative to the main alloy A is 0.12~0.15 wt.%. N2 is at least one of Zr, Ti, and Nb, and by mass percentage, 0.1 wt.% ≤ c ≤ 0.45 wt.%; N3 is Co, 0.5wt.%≤e≤1.5wt.%; B represents boron, with a concentration of 0.9 wt.% ≤ f ≤ 0.925 wt.%. The balance is T1, which consists of Fe and other unavoidable impurities.

[0030] The composition of auxiliary alloy B, by mass percentage, is RL3. y K1 m K2 n Al a1 B a2 Ti a3 T2 (100%-y-m-n-a1-a2-a3) ,in: RL3 is at least one of Pr and Nd, and 65 wt.% ≤ y ≤ 85 wt.%; K1 is Cu, 1 wt.% ≤ m ≤ 3 wt.%; K2 is Ga, 8 wt.% ≤ n ≤ 10 wt.%; The mass fractions of Al, B, and Ti satisfy the following formulas ① and ②: ①(3*a1+2*a2) / 2*a3≥1.88; ②1.5wt.%≤a1+a2+a3≤2wt.%; The balance is T2, where T2 is Fe or Fe and Co, and the mass percentage of Co to auxiliary alloy B is ≤4 wt.%. S2: Perform high-temperature heat treatment on the main alloy rapid solidification sheet A separately. The temperature of the high-temperature heat treatment is 600~1000℃ and the time is 2~4h. S3: The main alloy rapid solidification sheet A and the auxiliary alloy rapid solidification sheet B after high-temperature heat treatment are mixed to prepare NdFeB fine powder. The NdFeB fine powder is oriented and pressed into a compact. The compact is then vacuum sintered and tempered to obtain a high Ce content RTB NdFeB permanent magnet.

[0031] The high Ce content RTB NdFeB permanent magnet prepared by this invention has excellent magnetic properties, with Ce content ≥12wt.%, Br ≥12.6kGs, and Hcj ≥12kOe.

[0032] The beneficial effects of this invention are as follows: a high-Ce magnet is prepared using a dual-alloy process, and by limiting the Cu and Ga content in the main alloy A, the main alloy A is just able to form RE6(Fe,M). 14The phase imparts a higher Hcj to the magnet, and the heat treatment process on the rapidly solidified main alloy A allows Pr and Nd atoms in the rare earth-rich phase coating the main phase grains to interdiffused with Ce atoms on the surface of the main phase grains, resulting in a (Pr,Nd)2Fe phase with a higher saturation magnetization Ms on the surface of the main phase grains. 14 The B phase, after heat treatment of the main alloy rapid-solidifying sheet A, results in a magnet with a high Br content. Utilizing the auxiliary alloy B's ability to provide additional Pr, Nd, Cu, and Ga elements, more liquid phase is supplied during magnet sintering, making it easier for the main phase grains to be isolated by the rare-earth-rich phase. Simultaneously, during the aging process, it transforms into RE6(Fe,M). 14 The formation of the phase provides sufficient Cu and Ga elements, improving the coercivity of the magnet. The magnet of this invention features high Ce content, high remanence, and high coercivity. It improves magnet performance and saves production costs without the addition of additional rare earth heavy elements, thus possessing significant market value. Attached Figure Description

[0033] Figure 1 This is a photograph of the appearance of the main alloy A rapid solidification sheet SC before heat treatment.

[0034] Figure 2 This is a photograph of the appearance of the heat-treated main alloy A rapid solidification sheet SC.

[0035] Figure 3 This is a SEM image of the AB-2.5 magnet in Example 1. Detailed Implementation

[0036] The technical solution of the present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0037] The raw materials of the main alloy and auxiliary alloy, which are prepared in proportion by weight, are melted separately and cast to obtain main alloy quick-setting sheet A and auxiliary alloy quick-setting sheet B. The composition of main alloy A, by mass percentage, is: (RL1) (1-x) RL2 x ) a N1 b N2 c N3 e T1 (100%-a-b-c-e-f) B f ,in: RL1 is at least one of Pr and Nd, RL2 is Ce, 30wt.%≤a≤30.2wt.%, 0.41≤x≤0.435; N1 is at least two of Al, Cu, and Ga, and Cu and Ga are definitely present. The content of Ga is 0.12~0.15 wt.%, and 0.22 wt.% ≤ b ≤ 0.47 wt.%. N2 is at least one of Zr, Ti, and Nb, and by mass percentage, 0.1 wt.% ≤ c ≤ 0.45 wt.%; N3 is Co, 0.5wt.%≤e≤1.5wt.%; B represents boron, with a concentration of 0.9 wt.% ≤ f ≤ 0.925 wt.%. The balance is T1, which consists of Fe and other unavoidable impurities.

[0038] The composition of auxiliary alloy B, by mass percentage, is RL3. y K1 m K2 n Al a1 B a2 Ti a3 T2 (100%-y-m-n-a1-a2-a3) ,in: RL3 is at least one of Pr and Nd, and 65 wt.% ≤ y ≤ 85 wt.%; K1 is Cu, 1 wt.% ≤ m ≤ 3 wt.%; K2 is Ga, 8 wt.% ≤ n ≤ 10 wt.%; The masses of Al, B, and C satisfy the following formulas ① and ②: ①(3*a1+2*a2) / 2*a3≥1.88; ②1.5wt.%≤a1+a2+a3≤2wt.%; The balance is T2, where T2 is Fe or Fe and Co, and the mass percentage of Co to auxiliary alloy B is ≤4 wt.%.

[0039] In the smelting process of the main alloy A and auxiliary alloy B, after the raw materials are completely melted, the molten steel is refined for 1 to 3 minutes before casting to ensure that the composition of the quick-setting flakes of the main alloy A and auxiliary alloy B is uniform.

[0040] The casting temperature of the main alloy A is 1380~1420℃, the casting temperature of the auxiliary alloy B is 1380~1400℃, and the rotation speed of the copper rollers is 70r / min.

[0041] The main alloy rapid solidification sheet A was subjected to high-temperature heat treatment alone. The temperature of the high-temperature heat treatment was 600~1000℃ and the time was 2~4h. Furthermore, the preferred heat treatment temperature is 700~800℃, the time is 2.5~3h, and the furnace cooling time is 4~8h; High-temperature heat treatment at a vacuum degree less than 2.5 × 10⁻⁶ -2Under Pa conditions, the rapidly solidified sheets must be cooled to below 50°C before being removed from the furnace. This cooling process prevents significant blackening of the surface of the rapidly solidified sheets and reduces their oxygen content. After high-temperature heat treatment, the oxygen content of the main alloy rapidly solidified sheet A is below 350 ppm.

[0042] Neodymium iron boron fine powder was prepared by mixing the main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B after high-temperature heat treatment. The mixing ratio of main alloy quick-setting sheet A and auxiliary alloy quick-setting sheet B is A:B = (99~97.5%):(1~2.5%). Furthermore, the preparation of NdFeB fine powder by mixing the main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B can be carried out in one of the following two ways: ① Mix the main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B in a certain proportion, and then perform hydrogen crushing and air jet milling to obtain NdFeB fine powder; ② The main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B are subjected to hydrogen pulverization and air jet milling respectively to obtain fine powder A and fine powder B. Fine powder A and fine powder B are mixed in proportion to obtain NdFeB fine powder.

[0043] The neodymium iron boron powders described in the embodiments of this invention are all obtained using the method described above①.

[0044] The surface area average particle size (SMD) of NdFeB fine powder is 2.8~3.1μm, preferably 2.9~3.0μm.

[0045] Under inert gas protection, fine powder is pressed into NdFeB green blanks of a certain shape, and then isostatic pressing is performed. The green body after isostatic pressing is then sintered and tempered.

[0046] The vacuum sintering temperature is 1000~1040℃, and the time is 3~6h.

[0047] The tempering heat treatment is either single-stage or double-stage tempering. The single-stage tempering process involves treating at 600~680℃ for 2~4 hours; the double-stage tempering process involves treating at 880-950℃ for 2~4 hours, followed by treatment at 600~680℃ for 2~4 hours.

[0048] Furthermore, the preferred cooling method for tempering heat treatment is a combination of vacuum furnace cooling and argon-filled air cooling. Vacuum furnace cooling is used in the heat treatment temperature range of 320~400℃, and argon-filled air cooling is used from 320~400℃ to 25℃.

[0049] The magnet composition was tested using an ICP analyzer, the oxygen content of the quick-setting sheet was tested using an oxygen-carbon analyzer, and the magnet performance was tested using an NIM-62000 instrument.

[0050] Comparative Example 1: The magnets were smelted, hydrogen-blasted, air-jet milled, oriented, sintered, and tempered according to the main alloy A1, A2, A3, A4, A5, and A6 magnet composition ratios in Table 1. The casting temperature for smelting was 1410℃, the average particle size of the NdFeB fine powder was 3.0 μm, and the sintering and tempering heat treatments were performed at 1040℃*3h + 880℃*3h + 620℃*3h. The magnet composition was tested using ICP, and the magnet performance was tested using an NIM-62000 instrument. The results are shown in Table 2.

[0051] For magnets with high Ce content, comparing the performance of A1 to A3 magnets, when the Ga content is ≤0.1wt.%, the changes in Br and Hcj are minimal. However, when the Ga content is ≥0.12wt.%, the Hcj of A3 magnets increases significantly while Br begins to decrease. Comparing A4 and A5 magnets, when the Ga content exceeds 0.35wt.%, the increase in Hcj is small, while Br decreases significantly. Comparing A4 and A6 magnets, when the PrNd content is increased by 1wt.%, the Hcj increases by only 0.48 kOe, while Br decreases by 0.18 kGs. Using a single-alloy process, increasing the Ga or Pr and Nd elements in the magnet cannot produce magnets with Br ≥12.6 kGs and Hcj ≥12 kOe.

[0052] RE6(Fe,M) 14 In addition to Ga and Cu, the formation of rare earth-rich phases also requires the participation of Fe. The Fe atoms in rare earth-rich phases are relatively fewer than those in the main phase grains, and therefore cannot be entirely RE6(Fe,M). 14 The formation of the phase provides Fe atoms, requiring additional Fe atoms to precipitate from the surface of the main phase grains to participate in RE6(Fe,M). 14 The formation of the phase and the precipitation of Fe atoms lead to (Pr,Nd,Ce)2Fe 14 A decrease in the amount of B phase leads to a decrease in the Br content of the magnet. RE6(Fe,M) 14 The phase has the function of isolating the main phase grains and improving the Hcj of the magnet, but excessive RE6(Fe,M) can lead to problems. 14 Relative increases do not have a beneficial effect on magnet Hcj; on the contrary, they will reduce the number of main phases in the magnet, leading to a decrease in magnet Br.

[0053] The magnet compositions of the main alloys A1, A2, A3, A4, A5, and A6 in Comparative Example 1 are shown in Table 1: Table 1: PrNd Ce B Al Co Cu Ga Fe Zr Ti A1 17.5 12.5 0.92 0.1 0.5 0.2 0 Bal 0.1 0.1 A2 17.5 12.5 0.92 0.1 0.5 0.2 0.1 Bal 0.1 0.1 A3 17.5 12.5 0.92 0.1 0.5 0.2 0.12 Bal 0.1 0.1 A4 17.5 12.5 0.92 0.1 0.5 0.2 0.35 Bal 0.1 0.1 A5 17.5 12.5 0.92 0.1 0.5 0.2 0.5 Bal 0.1 0.1 A6 18.5 12.5 0.92 0.1 0.5 0.2 0.35 Bal 0.1 0.1 The magnetic properties of the main alloys A1, A2, A3, A4, A5 and A6 in the comparative examples are shown in Table 2: Table 2: Main alloy Br / kGs Hcj / kOe A1 12.88 10.33 A2 12.86 10.47 A3 12.81 11.12 A4 12.62 11.87 A5 12.50 12.09 A6 12.44 12.35 Comparative Example 2: The main alloy rapid-solidification sheet was prepared according to the A3 magnet formula in Comparative Example 1. Then, the main alloy rapid-solidification sheet was subjected to high-temperature heat treatment at temperatures of 580℃, 600℃, 800℃, and 1000℃, for 3 hours each time, with a vacuum degree of 1.2 × 10⁻⁶. -2 The material was cooled using argon air cooling for 3 hours. The magnets were designated A3SC-580, A3SC-600, A3SC-800, and A3SC-1000, respectively, while the untreated quick-setting sheet was designated A3SC-0. Except for the heat treatment process, the process parameters for the remaining steps were the same as in Comparative Example 1. The oxygen and carbon content of the quick-setting sheet and magnets were tested using an oxygen and carbon analyzer, with each type of quick-setting sheet tested three times and the average value calculated. The magnet performance was tested using an NIM-62000 instrument.

[0054] The average oxygen and carbon content of the accelerator sheets before and after heat treatment are shown in Table 3. After heat treatment, the oxygen content of the accelerator sheets increased because the sintering furnace was not completely under vacuum; a very small amount of oxygen remained inside, and the accelerator sheets absorbed oxygen during the heat treatment process. The morphologies of the accelerator sheets before and after heat treatment are shown in Table 3. Figure 1 and Figure 2 As shown, the quick-setting sheets that come out of the furnace after being cooled by argon gas are still silvery-white in appearance, rather than severely oxidized and blackened, indicating that the quick-setting sheets are only slightly oxidized.

[0055] The performance of the magnets corresponding to the rapidly solidified sheets after heat treatment is shown in Table 4. According to the magnet performance data in Table 4, compared to the untreated A3SC-0 (i.e., A3 in Table 2), the Br and Hcj values ​​of A3SC-580 remain essentially unchanged. However, starting with A3SC-600, the Br of the rapidly solidified sheets treated at temperatures above 600℃ increased by more than 0.05 kGs, while Hcj showed a slight decrease, less than 0.4 kOe. The decrease in Hcj is attributed to rare earth volatilization; during heat treatment, the higher the temperature, the greater the volatilization of rare earth elements, and the faster the Hcj decreases. At 600℃, the saturated vapor pressure of Ce is 10... -1 The Pa level is higher than that of Pr and Nd, which have much lower saturated vapor pressures, around 10 Pa. -3 ~10 -2 Pa level; at 1000℃, the saturated vapor pressure of Ce is 10. 5 At the Pa level, the saturated vapor pressure of Pr and Nd is around 10. 2 ~10 3 At the Pa level, at 600~800℃, on the one hand, the amount of Ce rare earth volatilization is greater than that of rare earth Pr and Nd, reducing the amount of rare earth-rich phase that isolates the main phase grains and decreasing the magnet Hcj. On the other hand, some Pr and Nd atoms in the rare earth-rich phase replace Ce on the surface of the main phase grains, thus increasing the magnet Br.

[0056] The average oxygen and carbon content of the quick-setting tablets before and after heat treatment are shown in Table 3: Table 3: (Oxygen and carbon content in ppm) A3SC-0 A3SC-580 A3SC-600 A3SC-800 A3SC-1000 Quick-setting tablets O 186 312 324 318 304 Quick-setting tablets C 96 102 111 107 103 Magnet O 465 554 561 576 563 Magnet C 786 795 793 781 788 The properties of the magnets corresponding to the quick-setting sheet after heat treatment are shown in Table 4: Table 4: Br / kGs Hcj / kOe A3SC-580 12.81 11.01 A3SC-600 12.86 10.96 A3SC-800 12.87 10.85 A3SC-1000 12.87 10.62 Example 1: According to the proportions of the main alloy and auxiliary alloy quick-settling sheet composition in Table 5, the raw materials were smelted. The casting temperature of the main alloy was 1420℃ and the casting temperature of the auxiliary alloy was 1400℃, resulting in main alloy quick-settling sheet ASC-1 and auxiliary alloy quick-settling sheet BSC-1, respectively.

[0057] The main alloy rapid-solidification sheet ASC-1 was subjected to high-temperature heat treatment at 750℃ for 3 hours, with a vacuum degree of 1.2×10⁻⁶. -2 Pa was cooled by argon air cooling for 4 hours.

[0058] In this embodiment, the mixing weight ratios of the main alloy A and the auxiliary alloy B are A:B = (99%:1%), (97.5%:2.5%), and (97%:3%), respectively. The corresponding magnets are labeled AB-0, AB-1, AB-2.5, and AB-3 according to the mixing ratio.

[0059] The main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B were weighed and mixed in the above proportion, and then subjected to hydrogen crushing and air jet milling to finally obtain NdFeB fine powder with an average surface area particle size of 3.0 μm. Under inert gas protection, fine powder is pressed into NdFeB green blanks of a certain shape, and then isostatic pressing is performed. The green body after isostatic pressing is then sintered and tempered.

[0060] The sintering process is 1040℃*6h; the two-stage tempering process is 880℃*3h+620℃*3h.

[0061] The oxygen and carbon content of the quick-setting sheet and magnet was tested using an oxygen and carbon analyzer. Each type of quick-setting sheet was tested three times and the average value was calculated. The performance of the magnet was tested using an NIM-62000 instrument.

[0062] The composition of the main alloy and auxiliary alloy quick-setting sheet described in Example 1 is shown in Table 5.

[0063] Table 5: PrNd Ce B Al Co Cu Ga Fe Zr Ti ASC-1 17 13 0.92 0.2 0.5 0.15 0.12 Bal 0.1 0.1 BSC-1 70 / 0.2 1 4 2 9 Bal / 0.5 Example 2: Unlike Example 1, this example uses the ASC-1 quick-setting sheet from Example 1 for blank preparation. The blanks of quick-setting sheets without heat treatment and the blanks of quick-setting sheets after heat treatment are denoted as A6SC-0 and AB-0, respectively. The heat treatment process is the same as that in Example 1.

[0064] The composition of the blanks in Examples 1 and 2 is shown in Table 6. The oxygen and carbon content of the quick-setting sheets and blanks in Examples 1 and 2 is shown in Table 7. The properties of the blanks in Examples 1 and 2 are shown in Table 8.

[0065] As shown in Table 8, the AB-1 and AB-2.5 magnets have Br > 12.6 kGs and Hcj > 12 kOe. Compared with the A6 magnet in Comparative Example 1, the AB-2.5 magnet, through the addition of auxiliary alloys, has similar Ce, Ga, and PrNd contents to the A6 magnet, but the AB-2.5 magnet exhibits superior performance. High Ce magnets with higher Br and Hcj can be obtained through a dual alloying process and high-temperature heat treatment of rapidly solidified sheets. RE6(Fe,M) in the magnet... 14 The substances required for phase formation can be preferentially obtained from Pr, Nd, Fe, Cu and Ga elements in the auxiliary alloy, thereby avoiding a significant reduction in the amount of the main phase and thus affecting the decrease of Br in the magnet. At the same time, the low melting point elements in the auxiliary alloy can improve the wettability of the magnet grain boundary phase, so that the grain boundary phase can better coat the main phase grains, reduce the magnetic coupling between grains, and improve the magnet Hcj.

[0066] Microscopic analysis of the AB-2.5 magnet was performed using a scanning electron microscope. The magnet's grain boundary phase contained gray-white regions of varying brightness, and most of the gray grain boundary phases effectively enveloped the main phase grains.

[0067] Table 6: Composition of Raw Magnets PrNd Ce B Al Co Cu Ga Fe Zr Ti A6SC-0 17 13 0.92 0.2 0.5 0.15 0.12 Bal 0.1 0.1 AB-0 17 13 0.92 0.2 0.5 0.15 0.12 Bal 0.1 0.1 AB-1 17.53 12.87 0.91 0.21 0.54 0.17 0.21 0.10 0.10 0.21 AB-2.5 18.33 12.68 0.90 0.22 0.59 0.20 0.34 0.10 0.11 0.22 AB-3 18.59 12.61 0.90 0.22 0.61 0.21 0.39 0.10 0.11 0.22 Table 7: O and C content of quick-setting tablets and magnets A6SC-0 AB-0 AB-1 AB-2.5 AB-3 Quick-setting tablets O / ppm 173 305 341 310 332 Quick-setting tablets C / ppm 90 109 104 96 93 Magnet O / ppm 489 571 546 539 558 Magnet C / ppm 765 745 785 747 778 Table 8: Magnet Performance Br / kGs Hcj / kOe ASC-0 12.71 11.54 AB-0 12.76 11.50 AB-1 12.70 12.11 AB-2.5 12.63 12.51 AB-3 12.55 12.53

Claims

1. A high Ce content RTB neodymium iron boron permanent magnet, characterized in that, It contains the following components by mass fraction: R: 30.4~31.2 wt.%, R includes at least two of Pr, Nd, and Ce, and must include Ce, with Ce content accounting for ≥12 wt.% of the magnet's mass; M1: 0.1~0.5 wt.%, M1 is at least one of Zr, Ti, and Nb; M2: 0.35~1wt.%, M2 is at least two of Al, Cu and Ga, and the magnet must contain Cu and Ga; M3: 0.5~2.0wt.%, M3 is Co; B: 0.88~0.92 wt.%, B is boron; The balance consists of Fe and other unavoidable impurities; The high Ce content RTB NdFeB permanent magnet has a remanence Br ≥ 12.6 and a coercivity Hcj ≥ 12kOe.

2. The high Ce content RTB NdFeB permanent magnet as described in claim 1, characterized in that... It is prepared by the following method: S1: The raw materials of the main alloy and auxiliary alloy, which are prepared according to the weight ratio, are melted separately and cast to obtain the main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B. The composition of main alloy A, by mass percentage, is: (RL1) (1-x) RL2 x ) a N1 b N2 c N3 e T1 (100%-a-b-c-e-f) B f ,in: RL1 is at least one of Pr and Nd, RL2 is Ce, 30wt.%≤a≤30.2wt.%, 0.41≤x≤0.435; N1 is at least two of Al, Cu, and Ga, and must include Cu and Ga, with a content of 0.22 wt.% ≤ b ≤ 0.47 wt.%; the mass percentage of Ga relative to the main alloy A is 0.12~0.15 wt.%. N2 is at least one of Zr, Ti, and Nb, and by mass percentage, 0.1 wt.% ≤ c ≤ 0.45 wt.%; N3 is Co, 0.5wt.%≤e≤1.5wt.%; B represents boron, with a concentration of 0.9 wt.% ≤ f ≤ 0.925 wt.%. The balance is T1, where T1 is Fe and other unavoidable impurities; The composition of auxiliary alloy B, by mass percentage, is RL3. y K1 m K2 n Al a1 B a2 Ti a3 T2 (100%-y-m-n-a1-a2-a3) ,in: RL3 is at least one of Pr and Nd, and 65 wt.% ≤ y ≤ 85 wt.%; K1 is Cu, 1 wt.% ≤ m ≤ 3 wt.%; K2 is Ga, 8 wt.% ≤ n ≤ 10 wt.%; The mass fractions of Al, B, and Ti satisfy the following formulas ① and ②: ①(3*a1+2*a2) / 2*a3≥1.88; ②1.5wt.%≤a1+a2+a3≤2wt.%; The balance is T2, where T2 is Fe or Fe and Co, and the mass percentage of Co to auxiliary alloy B is ≤4 wt.%. S2: Perform high-temperature heat treatment on the main alloy rapid solidification sheet A separately. The temperature of the high-temperature heat treatment is 600~1000℃ and the time is 2~4h. S3: The main alloy rapid solidification sheet A and the auxiliary alloy rapid solidification sheet B after high-temperature heat treatment are mixed to prepare NdFeB fine powder. The NdFeB fine powder is oriented and pressed into a compact. The compact is then vacuum sintered and tempered to obtain a high Ce content RTB NdFeB permanent magnet.

3. The high Ce content RTB NdFeB permanent magnet according to claim 1 or 2, characterized in that, The blank magnets of the high Ce content RTB NdFeB permanent magnets are free of Dy, Tb, Gd and Ho heavy rare earth elements.

4. The high Ce content RTB NdFeB permanent magnet according to claim 1 or 2, characterized in that, The blank magnets for high Ce content RTB NdFeB permanent magnets have an oxygen content of ≤580ppm and a carbon content of ≤800ppm.

5. The high Ce content RTB NdFeB permanent magnet according to claim 2, characterized in that, In step S3, the mass fraction of the main alloy quick-setting sheet A in the neodymium iron boron fine powder is 97.5-99%, and the mass fraction of the auxiliary alloy quick-setting sheet B is 1-2.5%.

6. The high Ce content RTB NdFeB permanent magnet according to claim 2, characterized in that, In step S2, the oxygen content of the main alloy rapid solidification sheet A after high-temperature heat treatment is less than 350 ppm.

7. The high Ce content RTB NdFeB permanent magnet according to claim 2, characterized in that, In step S3, the main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B are mixed to prepare NdFeB fine powder, which is carried out by one of the following two methods: ① Mix the main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B in a certain proportion, and then perform hydrogen crushing and air jet milling to obtain NdFeB fine powder; ② The main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B are subjected to hydrogen rupture and air jet milling respectively to obtain fine powder A and fine powder B. Fine powder A and fine powder B are mixed in proportion to obtain NdFeB fine powder. The surface area average particle size (SMD) of NdFeB fine powder is 2.8~3.1 μm.

8. The high Ce content RTB NdFeB permanent magnet according to claim 2, characterized in that, In step S3, the vacuum sintering temperature is 1000~1040℃, and the time is 3~6 hours. The tempering heat treatment is either single-stage or double-stage tempering. The single-stage tempering process involves treating at 600~680℃ for 2~4 hours; the double-stage tempering process involves treating at 880-950℃ for 2~4 hours, followed by treatment at 600~680℃ for 2~4 hours.

9. The high Ce content RTB NdFeB permanent magnet according to claim 8, characterized in that, In step S3, after tempering heat treatment, the cooling method is a combination of vacuum furnace cooling and argon-filled air cooling. Vacuum furnace cooling is used when the heat treatment temperature drops to the range of 320~400℃, and argon-filled air cooling is used when the temperature drops from 320~400℃ to room temperature.

10. The method for preparing a high Ce content RTB NdFeB permanent magnet as described in claim 1, characterized in that... The method includes the following steps: S1: The raw materials of the main alloy and auxiliary alloy, which are prepared according to the weight ratio, are melted separately and cast to obtain the main alloy quick-setting sheet A and the auxiliary alloy quick-setting sheet B. The composition of main alloy A, by mass percentage, is: (RL1) (1-x) RL2 x ) a N1 b N2 c N3 e T1 (100%-a-b-c-e-f) B f ,in: RL1 is at least one of Pr and Nd, RL2 is Ce, 30wt.%≤a≤30.2wt.%, 0.41≤x≤0.435; N1 is at least two of Al, Cu, and Ga, and must include Cu and Ga, with a content of 0.22 wt.% ≤ b ≤ 0.47 wt.%; the mass percentage of Ga relative to the main alloy A is 0.12~0.15 wt.%. N2 is at least one of Zr, Ti, and Nb, and by mass percentage, 0.1 wt.% ≤ c ≤ 0.45 wt.%; N3 is Co, 0.5wt.%≤e≤1.5wt.%; B represents boron, with a concentration of 0.9 wt.% ≤ f ≤ 0.925 wt.%. The balance is T1, where T1 is Fe and other unavoidable impurities; The composition of auxiliary alloy B, by mass percentage, is RL3. y K1 m K2 n Al a1 B a2 Ti a3 T2 (100%-y-m-n-a1-a2-a3) ,in: RL3 is at least one of Pr and Nd, and 65 wt.% ≤ y ≤ 85 wt.%; K1 is Cu, 1 wt.% ≤ m ≤ 3 wt.%; K2 is Ga, 8 wt.% ≤ n ≤ 10 wt.%; The mass fractions of Al, B, and Ti satisfy the following formulas ① and ②: ①(3*a1+2*a2) / 2*a3≥1.88; ②1.5wt.%≤a1+a2+a3≤2wt.%; The balance is T2, where T2 is Fe or Fe and Co, and the mass percentage of Co to auxiliary alloy B is ≤4 wt.%. S2: Perform high-temperature heat treatment on the main alloy rapid solidification sheet A separately. The temperature of the high-temperature heat treatment is 600~1000℃ and the time is 2~4h. S3: The main alloy rapid solidification sheet A and the auxiliary alloy rapid solidification sheet B after high-temperature heat treatment are mixed to prepare NdFeB fine powder. The NdFeB fine powder is oriented and pressed into a compact. The compact is then vacuum sintered and tempered to obtain a high Ce content RTB NdFeB permanent magnet.

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