Method for efficiently recycling sintered cerium-containing permanent magnet waste

Abstract

The invention relates to the technical field of waste recovery, in particular to a method for efficiently recovering sintered cerium-containing permanent magnet waste, which comprises the following steps: classifying the waste, and carrying out microwave-plasma cooperative treatment; carrying out coarse crushing and composite hydrogen crushing; then preparing multi-element alloyed nano powder containing a special additive; then adding an antioxidant for jet milling, and carrying out molecular self-assembly powder mixing; and finally, performing magnetic field assisted forming and gradient sintering to prepare the high-performance permanent magnet. Rare earth resources can be efficiently utilized, and waste is reduced; environmental protection performance is high, and pollution is reduced; the prepared permanent magnet is excellent in performance and excellent and stable in indexes such as magnetic energy product; and various wastes can be treated, the adaptability is wide, and the enterprise cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of waste recycling, and particularly to a method for efficiently recycling sintered cerium-containing permanent magnet waste. Background Art

[0002] Rare earth permanent magnet materials, especially sintered cerium-containing permanent magnets, play an indispensable role in many key fields of modern industry due to their excellent magnetic properties, such as drive motors for new energy vehicles, core components of wind power generation equipment, and micro-motors of electronic devices. With the booming development of these industries, the demand for sintered cerium-containing permanent magnets continues to climb, which also makes the quantity of waste materials and scrapped products generated during the production process increase day by day. If these waste materials cannot be properly handled, it will not only cause a large amount of waste of rare earth resources, but also lead to serious environmental problems.

[0003] Currently, there are many drawbacks in the methods for treating sintered cerium-containing permanent magnet waste. Traditional pyrometallurgical processes require smelting at high temperatures, which not only consumes a large amount of energy, but also during the smelting process, rare earth elements such as cerium are prone to volatilization loss, resulting in low recovery rates. At the same time, high-temperature treatment may also introduce impurities, affecting the performance of the recycled materials. Although hydrometallurgical processes can avoid the problems caused by high temperatures to a certain extent, the process is complex, requires the use of a large amount of chemical reagents, and is prone to environmental pollution. Moreover, whether it is pyrometallurgy or hydrometallurgy, it is difficult to accurately control the microstructure and magnetic properties of the recycled materials, resulting in unstable quality of the recycled products and difficulty in meeting the requirements of the high-end market.

[0004] In addition, existing waste recycling methods often ignore the diversity of waste materials. The surface states, compositions, and structures of waste materials generated in different production processes vary greatly. For example, waste materials generated during the sintering process may have a severe oxide layer on the surface; machining waste may be contaminated with oil; electroplating waste has a coating. If these differences are not addressed, it will affect the effect of subsequent recycling processes.

[0005] Against the backdrop of the increasingly fierce global competition for rare earth resources and the ever-stricter environmental protection requirements, it is urgent to develop a method for recycling sintered cerium-containing permanent magnet waste that is efficient, environmentally friendly, and capable of precisely regulating the properties of recycled materials. This not only helps to alleviate the shortage of rare earth resources, reduce the production costs of enterprises, but also reduces environmental pollution and promotes the sustainable development of related industries. This patent is precisely based on such a situation, aiming to fill the gaps in the existing technology and provide innovative solutions for the recycling and utilization of sintered cerium-containing permanent magnet waste. Summary of the Invention

[0006] (I) Technical Problems to be Solved

[0007] In view of the deficiencies of the prior art, the present invention provides a method for efficiently recycling sintered cerium-containing permanent magnet waste.

[0008] (II) Technical solution

[0009] A method for efficiently recycling sintered cerium-containing permanent magnet waste, comprising the following key steps:

[0010] Waste classification and pretreatment strengthening: The sintered unqualified magnetic blocks are used as the first type of waste, and the oxide layer is removed by chamfering; the machining waste is the second type, and degreasing at low temperature and chamfering treatment are carried out; the electroplating unqualified products and scrapped products are the third type, and high-temperature roasting and stripping and chamfering treatment are carried out; all three types of waste are subjected to water washing, ultrasonic oscillation, magnetic separation, drying and air cooling treatment;

[0011] Composite hydrogen crushing: First, the pretreated waste is mixed and coarsely crushed to a particle size less than 25 mm, and argon protection is introduced; in the hydrogen crushing stage, a step-by-step hydrogen treatment process is adopted. In the first step, hydrogen is absorbed for 1-3 h under a hydrogen absorption pressure of 0.08-0.12 MPa, and in the second step, the pressure is increased to 0.15-0.2 MPa and hydrogen is absorbed for 1-2 h;

[0012] Preparation of multi-element alloyed nano-powder: Weigh the auxiliary materials and ingredients and place them in a high-temperature and high-pressure alloying nano-furnace. Arc melting is carried out under a hydrogen-argon mixed gas atmosphere, and evaporation condensation is used to prepare the auxiliary alloy MMxT1-x nano-powder, which is passivated in a nitrogen-argon mixed glove box. The particle size D50 of the nano-powder is 30-150 nm;

[0013] Intelligent air flow mill classification: Add a new antioxidant with a proportion of 0.3-0.5‰ to the hydrogen-crushed coarse powder. The structural formula of the new antioxidant is:

[0014]

[0015] Mix for 1.5-2.5 h; Use the intelligent air flow mill system to automatically adjust the rotation speed of the sorting wheel and the pressure in the grinding chamber to make the average particle size D50 be 3.2-4.5 μm, and the ratio of particle size D90 to D10 is less than 4.2;

[0016] Molecular self-assembly powder mixing: Add the multi-element alloyed nano-powder to the waste fine powder according to 3-5% of the total powder mass, and then add a self-assembly lubricant accounting for 0.6-0.8‰ of the total mass of the mixed fine powder; in a three-dimensional mixer, first mix the powder at a low speed of 150-200 r / min; then mix the powder at a high speed of 300-400 r / min;

[0017] Magnetic field-assisted forming and gradient sintering: After powder mixing, in a magnetic field orientation press, apply a 2-3 T pulsed magnetic field to assist in orientation pressing, and then carry out densification treatment by a cold isostatic press; the green body is subjected to gradient sintering in a vacuum sintering furnace.

[0018] Preferably, the time for chamfering and removing oxide scale is more than 30 minutes; the temperature selected for low-temperature degreasing of the second type of waste is 200 °C.

[0019] Preferably, in the auxiliary alloy MMxT1-x, MM is a mixed rare earth alloy containing La, Ce, Pr, and Nd, and T is one or more of non-rare earth metals such as Al, Cu, Ga, and Co. Among them, x is the value obtained by multiplying the mass percentage of the mixed rare earth MM in the auxiliary alloy by 100, and 50.0 ≤ x < 100.0.

[0020] Preferably, when the self-assembled lubricant is mixed with powder at high speed, the bond energy between the end groups of the hyperbranched polymer molecules and the surface active sites of the powder is 20 - 30 kJ / mol.

[0021] Preferably, during magnetic field-assisted forming, the pulse frequency of the pulsed magnetic field is 50 - 100 Hz, and the pulse width is 5 - 10 ms.

[0022] Preferably, during the gradient sintering process, the vacuum degree in the vacuum sintering furnace is maintained at 3 - 5×10-3 Pa throughout the process.

[0023] Preferably, the maximum magnetic energy product of the permanent magnet is 35 MGOe ≤ (BH)max ≤ 55 MGOe, the remanence range is 12 - 15 kGs, and the coercivity range is 13 - 15 kOe.

[0024] Preferably, the internal grain size of the recycled cerium-containing rare earth permanent magnet prepared by this method is uniform, and the average grain size is 5 - 10 μm.

[0025] Preferably, the gradient sintering is carried out in a high-vacuum environment. The temperature of the first vacuum heat treatment is 960 - 1030 °C, and the treatment time is 4 - 6 h; the temperature of the second heat treatment is 780 - 880 °C, and the treatment time is 2 - 3 h; the temperature of the third heat treatment is 460 - 550 °C, and the treatment time is 3 - 6 h.

[0026] (III) Beneficial technical effects

[0027] Compared with the existing technology, the beneficial effects of the present invention are as follows:

[0028] 1. Through precise waste classification and advanced pretreatment technology, rare earth elements in waste can be fully recovered, greatly improving the utilization rate of rare earth resources; compared with traditional methods, the loss of rare earth elements during the recycling process is reduced, effectively alleviating the problem of rare earth resource shortage, and providing strong support for the sustainable development of related industries.

[0029] 2. It abandons the high - energy - consuming and highly polluting links in the traditional process; the microwave - plasma collaborative treatment technology, compared with the traditional surface treatment methods, does not require the use of a large amount of chemical reagents, reducing the generation of wastewater, waste gas and waste residue; moreover, the energy consumption of the entire recycling process is relatively low, meeting the current development concept of green environmental protection.

[0030] 3. The method of this patent can accurately regulate the microstructure and magnetic properties of the recycled permanent magnets; the addition of multi - alloyed nanometer powders, combined with the molecular self - assembly powder mixing and gradient sintering processes, enables the key performance indicators such as the maximum magnetic energy product, remanence and coercivity of the recycled permanent magnets to perform excellently, and the performance stability is high; its maximum magnetic energy product can be stabilized between 35 - 55 MGOe, which can meet the performance requirements of permanent magnets in different fields, especially the strict requirements of high - end manufacturing for high - performance permanent magnets.

[0031] 4. This invention has strong adaptability and can process cerium - containing permanent magnet wastes from different sources and in different states; whether it is the waste generated during sintering, machining or electroplating, it can be processed through targeted processes to achieve efficient recycling and reuse, greatly expanding the application scope of waste recycling, reducing the production cost for enterprises and improving the economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flowchart of a method for efficient recycling of sintered cerium - containing permanent magnet wastes proposed by this invention;

[0033] Figure 2 is a columnar comparison chart of the maximum magnetic energy product of the examples and the comparative examples;

[0034] Figure 3 is a line - graph comparison chart of the remanence and coercivity of the examples and the comparative examples;

[0035] Figure 4 is a columnar comparison chart of the average grain size of the examples and the comparative examples;

[0036] Figure 5 is the nuclear magnetic resonance spectrum of the new antioxidant. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] Example 1

[0038] Raw material preparation: Collect cerium - containing permanent magnet wastes generated during sintering, machining and electroplating, and label them as the first - type, second - type and third - type wastes respectively. Prepare raw materials such as mixed rare - earth alloy MM, non - rare - earth metals (Al, Cu), antioxidant, self - assembly lubricant based on hyperbranched polymer, etc.

[0039] Strengthening of waste classification and pretreatment: Place the three types of waste separately. Chamfer the first type of waste for 45 minutes to remove the oxide layer; degrease the second type of waste at 200 °C for 2 h and chamfer for 40 minutes; roast and strip the third type of waste at 850 °C for 2 h and chamfer for 35 minutes. All the waste is successively subjected to ultrasonic oscillation (40 kHz / 15 min), magnetic separation (magnetic field intensity of 1.2 T), drying at 80 °C and air cooling (airflow at 25 °C).

[0040] Composite hydrogen pulverization: Mix the pretreated waste, and coarsely crush it with a crusher to a particle size less than 20 mm, and carry out composite hydrogen pulverization under argon protection. In the first step, absorb hydrogen for 2 hours at a hydrogen absorption pressure of 0.1 MPa, in the second step, increase the pressure to 0.18 MPa and continue to absorb hydrogen for 1.5 hours, control the dehydrogenation temperature at 500 °C, and the vacuum degree at the end of dehydrogenation is 1.5 Pa to obtain coarse powder.

[0041] Preparation of multi-element alloyed nanopowder: According to the ratio of MM 70 (AlCu) 25 for batching, and put it into a high-temperature and high-pressure alloying nano-furnace. Under the atmosphere of hydrogen-argon mixed gas, carry out arc melting at 1600 °C and 6 MPa for 3 hours. After evaporation and condensation, passivate it in a nitrogen-argon mixed glove box (nitrogen:argon = 1:3) to obtain nanopowder with a D50 particle size of 100 nm.

[0042] Intelligent air classifier: Add 0.4‰ antioxidant to the coarse powder after hydrogen pulverization and mix for 2 hours. Using the intelligent air classifier system, according to the real-time monitoring feedback of laser particle size, adjust the rotation speed of the sorting wheel to 4000 rpm and the pressure in the grinding chamber to 0.6 MPa, so that the average particle size D50 of the magnetic powder is 4 μm, and the ratio of particle size D90 to D10 is 4.

[0043] Molecular self-assembly powder mixing: Add multi-element alloyed nanopowder to the fine waste powder at 4% of the total powder mass, and then add 0.7‰ self-assembly lubricant based on the total mass of the mixed fine powder. In a three-dimensional mixer, first mix the powder at a low speed of 180 r / min for 1.5 hours, and then mix the powder at a high speed of 350 r / min for 2.5 hours.

[0044] Magnetic field-assisted forming and gradient sintering: After powder mixing, in a magnetic field orientation press, apply a 2.5 T pulsed magnetic field to assist in orientation pressing, with a pulse frequency of 80 Hz and a pulse width of 8 ms. Then carry out densification treatment with a cold isostatic press. The green body is subjected to gradient sintering in a vacuum sintering furnace. The first stage is heated to 980 °C for 4 hours; the second stage is cooled to 840 °C for 2.5 hours; the third stage is heated to 500 °C for 5 hours to obtain a recycled cerium-containing rare earth permanent magnet.

[0045] Performance Test: The performance test results of this permanent magnet show that its maximum energy product reaches 45 MGOe, the remanence is 13.5 kGs, the coercivity is 14 kOe, and the average grain size is 8 μm.

[0046] Example 2

[0047] Raw Material Preparation: Similar to Example 1, prepare cerium-containing permanent magnet waste from different sources, as well as raw materials such as MM and non-rare earth metals (Ga, Co), etc.

[0048] Waste Classification and Pretreatment Enhancement: The first type of waste is chamfered for 50 minutes to remove the oxide layer; the second type of waste is degreased at 200 °C for 2 h and chamfered for 50 minutes; the third type of waste is calcined and degalvanized at 850 °C for 2 h and chamfered for 40 minutes. All wastes are successively subjected to ultrasonic oscillation (40 kHz / 15 min), magnetic separation (magnetic field intensity of 1.2 T), drying at 80 °C and air cooling (airflow at 25 °C);

[0049] Composite Hydrogen Crushing: Coarse crush to a particle size less than 22 mm. Under argon protection, in the first step, hydrogen is absorbed at a hydrogen absorption pressure of 0.09 MPa for 2.5 hours, in the second step, the pressure is increased to 0.16 MPa and hydrogen is absorbed for 1.2 hours, the dehydrogenation temperature is 490 °C, and the vacuum degree at the end of dehydrogenation is 1.8 Pa to obtain coarse powder.

[0050] Preparation of Multicomponent Alloyed Nanopowder: According to the ratio of MM 80 (GaCo) 17 for proportioning, melt in a high-temperature and high-pressure alloying nano-furnace under the same atmosphere and conditions for 3.5 hours. After passivation, nano-powder with a D50 particle size of 120 nm is obtained.

[0051] Intelligent Air Jet Mill Classification: Add 0.4‰ antioxidant and mix for 2.2 hours. Adjust the sorting wheel speed of the intelligent air jet mill to 4100 rpm and the grinding chamber pressure to 0.65 MPa to make the average particle size D50 of the magnetic powder 4.2 μm, and the ratio of particle size D90 to D10 is 4.1.

[0052] Molecular Self-Assembly Powder Mixing: The addition amount of nano-powder is 4.5% of the total powder mass, add 0.7‰ self-assembly lubricant, mix at a low speed of 190 r / min for 1.8 hours, and mix at a high speed of 380 r / min for 2.2 hours.

[0053] Magnetic Field-Assisted Molding and Gradient Sintering: Under the assistance of a 2.8 T pulsed magnetic field (pulse frequency 90 Hz, pulse width 9 ms), orientation pressing is carried out, and cold isostatic pressing is used for densification. The green body is placed in a vacuum sintering furnace. In the first stage, it is heated to 990 °C and treated for 4.5 hours; in the second stage, it is cooled to 850 °C and treated for 2.8 hours; in the third stage, it is heated to 510 °C and treated for 5.5 hours to make a permanent magnet.

[0054] Performance Test: The performance test results of this permanent magnet show that its maximum energy product is as high as 48 MGOe, the remanence reaches 14 kGs, the coercivity is 14.2 kOe, and the average grain size is 7 μm.

[0055] Example 3

[0056] Raw Material Preparation: Collect waste materials and prepare raw materials such as MM and non-rare earth metals (Al, Cu, Ti).

[0057] Waste Classification and Pretreatment Enhancement: The first type of waste is chamfered for 50 minutes to remove the oxide layer; the second type of waste is degreased at 200 °C for 2.5 h and chamfered for 45 minutes; the third type of waste is calcined and stripped at 860 °C for 2.2 h and chamfered for 40 minutes. All waste materials are successively subjected to ultrasonic oscillation (45 kHz / 20 min), magnetic separation (magnetic field strength of 1.8 T), drying at 85 °C, and air cooling (airflow at 20 °C).

[0058] Composite Hydrogen Crushing: Coarse crush to a particle size less than 23 mm. Under argon protection, in the first step, hydrogen is absorbed at a hydrogen absorption pressure of 0.11 MPa for 1.8 hours, in the second step, the pressure is increased to 0.17 MPa and hydrogen is absorbed for 1.3 hours, the dehydrogenation temperature is 510 °C, and the vacuum degree at the end of dehydrogenation is 1.6 Pa to obtain coarse powder.

[0059] Preparation of Multicomponent Alloyed Nanopowder: According to the ratio of MM 65 (AlCuTi) 32 for proportioning, melt in a high-temperature and high-pressure alloying nano-furnace for 4 hours to obtain nanopowder with a particle size D50 of 80 nm and passivate it.

[0060] Intelligent Airflow Mill Classification: Add 0.35‰ antioxidant and mix for 2.3 hours. Adjust the sorting wheel speed of the intelligent airflow mill to 3900 rpm and the grinding chamber pressure to 0.55 MPa to make the average particle size D50 of the magnetic powder 3.8 μm, and the ratio of particle size D90 to D10 is 3.9.

[0061] Molecular Self-Assembly Powder Mixing: The addition amount of nanopowder is 3.5% of the total powder mass. Add 0.65‰ self-assembly lubricant and mix the powder at a low speed of 170 r / min for 1.6 hours and at a high speed of 360 r / min for 2.3 hours.

[0062] Magnetic Field-Assisted Molding and Gradient Sintering: Under the assistance of a 2.6 T pulsed magnetic field (pulse frequency 70 Hz, pulse width 7 ms), perform orientation pressing and cold isostatic pressing for densification. The green compact is placed in a vacuum sintering furnace. In the first stage, it is heated to 970 °C and treated for 4.2 hours; in the second stage, it is cooled to 830 °C and treated for 2.3 hours; in the third stage, it is heated to 490 °C and treated for 4.8 hours to obtain the permanent magnet.

[0063] Performance Test: The performance test results of this permanent magnet show that its maximum energy product is 42 MGOe, the remanence reaches 13 kGs, the coercivity is 13.5 kOe, and the average grain size is 9 μm.

[0064] Comparative Example

[0065] Raw Material Preparation: Select the same source and quantity of cerium-containing permanent magnet waste as in Example 1, and prepare conventional additives and lubricants.

[0066] Processing Procedure: Adopt the traditional classification processing method, only perform simple surface cleaning and mechanical grinding. Hydrogen crushing uses conventional single-step hydrogen absorption, with a hydrogen absorption pressure of 0.098 MPa, a hydrogen absorption time of 3 hours, and a dehydrogenation temperature of 550 °C. The jet mill uses ordinary equipment without intelligent control. Powder mixing uses ordinary lubricants and is mixed in an ordinary mixer at a single rotation speed of 200 r / min for 3 hours. The forming and sintering processes are carried out according to the traditional process without magnetic field assistance and gradient sintering.

[0067] Performance Test: The performance test results of this permanent magnet show that its maximum energy product is 30 MGOe, the remanence is 11 kGs, the coercivity is 12 kOe, and the average grain size is 12 μm.

[0068] Key Performance Comparison Table between Example and Comparative Example:

[0069]

[0070]

[0071] Conclusion: This table compares the differences in the key performance indicators of the permanent magnet between the example and the comparative example. The example is significantly superior to the comparative example in terms of maximum energy product, remanence, and coercivity, and the average grain size is smaller, indicating that the recycling method of this patent can effectively improve the performance of the permanent magnet.

[0072] Process Parameter and Cost Comparison Table between Example and Comparative Example:

[0073] Item Example 1 Example 2 Example 3 Comparative Example Microwave power (W) 400 500 450 - Plasma discharge frequency (kHz) 30 35 32 - Hydrogen absorption pressure (MPa) 0.1 / 0.18 0.09 / 0.16 0.11 / 0.17 0.098 Dehydrogenation temperature (°C) 500 490 510 550 Production cost (yuan / kg) 80 82 78 90

[0074] Conclusion: This table shows the differences in process parameters and production costs between the example and the comparative example. The example adopts innovative process parameters, and the production cost is lower than that of the comparative example, reflecting the advantages of the method of this patent in process optimization and cost control.

[0075] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for efficiently recovering sintered cerium-containing permanent magnet waste, characterized in that: The key steps include: Waste classification and pretreatment strengthening: unqualified sintered magnetic blocks are regarded as the first type of waste, and the oxide layer is removed by chamfering; Machining waste is the second category, which is treated by low-temperature degreasing and chamfering; electroplating defective products and scrapped products are the third category, which are treated by high-temperature roasting, deplating and chamfering; all three categories of waste are treated by water washing, ultrasonic oscillation, magnetic separation, drying and air cooling; Composite hydrogen crushing: First, the pre-treated waste is mixed and coarsely crushed to a particle size of less than 25mm, and argon is introduced for protection; in the hydrogen crushing stage, a step-by-step hydrogen treatment process is adopted. The first step is to absorb hydrogen at a hydrogen absorption pressure of 0.08-0.12MPa for 1-3h, and the second step is to increase the pressure to 0.15-0.2MPa to absorb hydrogen for 1-2h; Preparation of multi-element alloyed nanopowder: Weigh the auxiliary materials and place them in a high-temperature and high-pressure alloying nano furnace, perform arc melting in a hydrogen-argon mixed gas atmosphere, evaporate and condense to prepare auxiliary alloy MMxT1-x nanopowder, and passivate in a nitrogen-argon mixed glove box. The nanopowder particle size D50 is 30-150nm; Intelligent air flow mill classification: Add 0.3-0.5‰ of a new antioxidant to the hydrogen crushed coarse powder. The structural formula of the new antioxidant is: Mix for 1.5-2.5h; use the intelligent jet mill system to automatically adjust the speed of the classifying wheel and the grinding chamber pressure to make the average particle size D50 3.2-4.5μm and the ratio of particle size D90 to D10 less than 4.2; Molecular self-assembly powder mixing: add multi-element alloyed nanopowder to waste fine powder according to 3-5% of the total weight of the powder, and then add self-assembly lubricant accounting for 0.6-0.8‰ of the total weight of the mixed fine powder; in a three-dimensional mixer, first mix the powder at a low speed of 150-200r / min; then mix the powder at a high speed of 300-400r / min; Magnetic field-assisted molding and gradient sintering: After mixing the powder, a 2-3T pulsed magnetic field is applied in a magnetic field orientation press to assist orientation pressing, and then densification treatment is carried out by a cold isostatic press; the green body is gradient sintered in a vacuum sintering furnace.

2. The method for efficiently recovering sintered cerium-containing permanent magnet waste according to claim 1, characterized in that: The chamfering and descaling time is more than 30 minutes; the temperature used for low-temperature degreasing of the second type of waste is 200℃.

3. The method for efficiently recovering sintered cerium-containing permanent magnet waste according to claim 1, characterized in that: In the auxiliary alloy MMxT1-x, MM is a mixed rare earth alloy containing La, Ce, Pr, and Nd, and T is one or more non-rare earth metals such as Al, Cu, Ga, and Co, wherein x is the value obtained by multiplying the mass percentage of the mixed rare earth MM in the auxiliary alloy by 100, and 50.0≤x<100.

0.

4. The method for efficiently recovering sintered cerium-containing permanent magnet waste according to claim 1, characterized in that: When the self-assembling lubricant is mixed at high speed, the chemical bond energy formed between the end groups of the hyperbranched polymer molecules and the active sites on the surface of the powder is 20-30 kJ / mol.

5. The method for efficiently recovering sintered cerium-containing permanent magnet waste according to claim 1, characterized in that: During magnetic field-assisted forming, the pulse frequency of the pulse magnetic field is 50-100 Hz and the pulse width is 5-10 ms.

6. The method for efficiently recovering sintered cerium-containing permanent magnet waste according to claim 1, characterized in that: During the gradient sintering process, the vacuum degree in the vacuum sintering furnace is maintained at 3-5×10-3Pa throughout the process.

7. The regenerated cerium-containing rare earth permanent magnet prepared by the method for efficiently recycling sintered cerium-containing permanent magnet waste according to claim 1, characterized in that: The maximum magnetic energy product of the permanent magnet is 35MGOe≤(BH)max≤55MGOe, the remanence range is 12-15kGs, and the coercive force range is 13-15kOe.

8. The method for efficiently recovering sintered cerium-containing permanent magnet waste according to claim 1, characterized in that: The regenerated cerium-containing rare earth permanent magnet prepared by the method has uniform internal grain size, and the average grain size is 5-10 μm.

9. The method for efficiently recovering sintered cerium-containing permanent magnet waste according to claim 1, characterized in that: The gradient sintering is carried out in a high vacuum environment, wherein the first vacuum heat treatment temperature is 960-1030°C and the treatment time is 4-6 hours; the second heat treatment temperature is 780-880°C and the treatment time is 2-3 hours; and the third heat treatment temperature is 460-550°C and the treatment time is 3-6 hours.

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