A method for producing high-performance NdFeB using sintered NdFeB waste

Abstract

This invention discloses a method for producing high-performance NdFeB using sintered NdFeB waste, comprising the following steps: (1) mixing sintered NdFeB waste with a reducing agent and a fluxing agent and then smelting and slag forming; (2) pulverizing the material obtained in step (1) to obtain nano-NdFeB; (3) performing composition analysis on the nano-NdFeB obtained in step (2); (4) adding nano-oxides of Ho, Gd, and Pr elements to the nano-NdFeB according to the analysis results in step (3), mixing evenly to obtain alloy powder, wherein Ho element accounts for 0.6%-0.8% of the total mass of the alloy powder; This invention uses sintered NdFeB waste as the main raw material, and by analyzing the composition and then adding corresponding nano-oxides of Ho, Gd, and Pr elements according to the composition, the sintered NdFeB waste is effectively utilized, eliminating resource waste.

Description

Technical Field

[0001] This invention relates to the field of neodymium iron boron technology, and in particular to a method for producing high-performance neodymium iron boron using sintered neodymium iron boron waste. Background Technology

[0002] Rare earth elements are important strategic resources with wide applications in high-tech fields. The recycling and utilization of rare earth resources is urgently needed. Sintered NdFeB magnets, due to their excellent magnetic properties, have become the most widely used rare earth permanent magnet material. However, in the production and processing of NdFeB billets, defective products or processing scraps are inevitably generated. Currently, these NdFeB wastes are not effectively utilized, leading to resource waste. Therefore, it is necessary to research a method for directly preparing new sintered NdFeB materials by using sintered NdFeB waste as the main raw material for NdFeB production. Summary of the Invention

[0003] In view of this, the present invention addresses the deficiencies of the existing technology, and its main objective is to provide a method for producing high-performance NdFeB using sintered NdFeB waste, which can effectively solve the problem of resource waste caused by the ineffective utilization of existing sintered NdFeB waste.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for producing high-performance NdFeB using sintered NdFeB waste includes the following steps:

[0006] (1) The sintered NdFeB waste is mixed with reducing agent and flux and then smelted to form slag;

[0007] (2) The material obtained in step (1) is pulverized to obtain nano-neodymium iron boron;

[0008] (3) The composition of the nano-neodymium iron boron obtained in step (2) was analyzed;

[0009] (4) Based on the detection results in step (3), add nano-oxides of Ho, Gd and Pr elements to nano-neodymium iron boron and mix them evenly to obtain alloy powder, wherein Ho element accounts for 0.6%-0.8% of the total mass of alloy powder, Gd element accounts for 0.5%-1% of the total mass of alloy powder, and Pr element accounts for 1.5%-2% of the total mass of alloy powder.

[0010] (5) Under vacuum conditions, the alloy powder is pressed to obtain a blank, and a carbon fiber cloth with a thickness of 8-10 mm is coated on the outer surface of the blank to make a first intermediate.

[0011] (6) Under vacuum conditions, the first intermediate is placed in a heating mold and heated to solidify the carbon fiber cloth to form a carbon fiber shell;

[0012] (7) The first intermediate is taken out from the heating mold and graphite powder is wrapped on the outer surface of the carbon fiber shell to form the second intermediate. The particle size of the graphite powder is 10-14μm and the thickness of the graphite powder is 6-7mm.

[0013] (8) Place the second intermediate directly into the sintering furnace, evacuate the vacuum, and start heating. Raise the temperature from room temperature to 500-600℃ and hold for 1-1.5h; then continue to raise the temperature to 950-1000℃ and hold for 1-1.5h.

[0014] (9) After the heat preservation is completed, the temperature is raised to 1300-1400℃ and kept for 5-8 minutes; then the temperature is raised to 1450-1500℃ and kept for 2-3 minutes. After cooling, the third intermediate is obtained.

[0015] (10) Remove the third intermediate from the sintering furnace, mechanically break the outer shell, and remove the high-performance neodymium iron boron in the middle.

[0016] Preferably, the particle size of the nano-oxides of Ho, Gd, and Pr elements in step (4) is less than 50 nanometers.

[0017] Preferably, in step (8), the vacuum is evacuated to a vacuum level of <1 Pa.

[0018] Preferably, the sintering furnace in step (8) is a single-chamber sintering furnace.

[0019] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, as can be seen from the above technical solution:

[0020] This invention uses sintered NdFeB waste as the main raw material. By analyzing the composition, corresponding nano-oxides of Ho, Gd, and Pr elements are added to effectively utilize the sintered NdFeB waste and prevent resource waste. Simultaneously, before sintering, the green body is wrapped with carbon fiber cloth and heated to solidify, forming a carbon fiber shell. This carbon fiber shell acts as a buffer and protective layer, eliminating the need for molds. Fine-grained graphite powder is used as an insulating layer to reduce the chance of contact with air during green body sintering, preventing excessive surface oxidation and ensuring sintering uniformity. Furthermore, multiple sintering temperatures are used in combination during the sintering process to more effectively suppress solid-phase sintering and grain growth, further ensuring finer grains in the magnet, thereby significantly improving coercivity and achieving high performance. Detailed Implementation

[0021] This invention discloses a method for producing high-performance NdFeB using sintered NdFeB waste, comprising the following steps:

[0022] (1) The sintered NdFeB waste is mixed with reducing agent and flux and then smelted to form slag.

[0023] (2) The material obtained in step (1) is crushed to obtain nano-neodymium iron boron.

[0024] (3) The composition of the nano-neodymium iron boron obtained in step (2) is analyzed.

[0025] (4) Based on the detection results in step (3), add the nano-oxides of Ho, Gd, and Pr elements to the nano-neodymium iron boron and mix them evenly to obtain alloy powder, wherein Ho element accounts for 0.6%-0.8% of the total mass of the alloy powder, Gd element accounts for 0.5%-1% of the total mass of the alloy powder, and Pr element accounts for 1.5%-2% of the total mass of the alloy powder. The particle size of the nano-oxides of Ho, Gd, and Pr elements is less than 50 nanometers.

[0026] (5) Under vacuum, the alloy powder is pressed to obtain a blank, and a carbon fiber cloth with a thickness of 8-10 mm is coated on the outer surface of the blank to make a first intermediate.

[0027] (6) Under vacuum, the first intermediate is placed in a heating mold and heated to solidify the carbon fiber cloth to form a carbon fiber shell.

[0028] (7) The first intermediate is taken out from the heating mold and graphite powder is wrapped on the outer surface of the carbon fiber shell to form the second intermediate. The particle size of the graphite powder is 10-14μm and the thickness of the graphite powder is 6-7mm.

[0029] (8) Place the second intermediate directly into the sintering furnace, evacuate the vacuum, and start heating. Raise the temperature from room temperature to 500-600℃ and hold for 1-1.5 hours. Then continue to raise the temperature to 950-1000℃ and hold for 1-1.5 hours. Evacuate the vacuum to a vacuum degree of <1 Pa. The sintering furnace is a single-chamber sintering furnace.

[0030] (9) After the heat preservation is completed, the temperature is raised to 1300-1400℃ and kept for 5-8 minutes; then the temperature is raised to 1450-1500℃ and kept for 2-3 minutes. After cooling, the third intermediate is obtained.

[0031] (10) Remove the third intermediate from the sintering furnace, mechanically break the outer shell, and remove the high-performance neodymium iron boron in the middle.

[0032] The present invention will be further described in detail below with reference to several embodiments:

[0033] Example 1:

[0034] A method for producing high-performance NdFeB using sintered NdFeB waste includes the following steps:

[0035] (1) The sintered NdFeB waste is mixed with reducing agent and flux and then smelted to form slag.

[0036] (2) The material obtained in step (1) is crushed to obtain nano-neodymium iron boron.

[0037] (3) The composition of the nano-neodymium iron boron obtained in step (2) is analyzed.

[0038] (4) Based on the detection results in step (3), add the nano-oxides of Ho, Gd, and Pr elements to the nano-neodymium iron boron and mix them evenly to obtain alloy powder, wherein Ho element accounts for 0.6% of the total mass of the alloy powder, Gd element accounts for 0.5% of the total mass of the alloy powder, and Pr element accounts for 1.5% of the total mass of the alloy powder. The particle size of the nano-oxides of Ho, Gd, and Pr elements is less than 50 nanometers.

[0039] (5) Under vacuum, the alloy powder is pressed to obtain a blank, and a carbon fiber cloth with a thickness of 9 mm is coated on the outer surface of the blank to make a first intermediate.

[0040] (6) Under vacuum, the first intermediate is placed in a heating mold and heated to solidify the carbon fiber cloth to form a carbon fiber shell.

[0041] (7) The first intermediate is taken out from the heating mold and graphite powder is wrapped on the outer surface of the carbon fiber shell to form the second intermediate. The graphite powder has a particle size of 10 μm and a thickness of 6 mm.

[0042] (8) The second intermediate was placed directly into the sintering furnace, and after evacuation, heating was started. The temperature was increased from room temperature to 500℃ and held for 1 hour; then the temperature was increased to 950℃ and held for 1.2 hours. The sintering furnace was a single-chamber sintering furnace, and the vacuum was evacuated to a vacuum degree of 0.5 Pa.

[0043] (9) After the heat preservation is completed, the temperature is raised to 1300℃ and kept for 5 minutes; then the temperature is raised to 1458℃ and kept for 2 minutes. After cooling, the third intermediate is obtained.

[0044] (10) Remove the third intermediate from the sintering furnace, mechanically break the outer shell, and remove the high-performance neodymium iron boron in the middle.

[0045] Example 2:

[0046] A method for producing high-performance NdFeB using sintered NdFeB waste includes the following steps:

[0047] (1) The sintered NdFeB waste is mixed with reducing agent and flux and then smelted to form slag.

[0048] (2) The material obtained in step (1) is crushed to obtain nano-neodymium iron boron.

[0049] (3) The composition of the nano-neodymium iron boron obtained in step (2) is analyzed.

[0050] (4) Based on the detection results in step (3), add the nano-oxides of Ho, Gd, and Pr elements to the nano-neodymium iron boron and mix them evenly to obtain alloy powder, wherein Ho element accounts for 0.8% of the total mass of the alloy powder, Gd element accounts for 1% of the total mass of the alloy powder, and Pr element accounts for 2% of the total mass of the alloy powder. The particle size of the nano-oxides of Ho, Gd, and Pr elements is less than 50 nanometers.

[0051] (5) Under vacuum, the alloy powder is pressed to obtain a blank, and a carbon fiber cloth with a thickness of 8mm is coated on the outer surface of the blank to make a first intermediate.

[0052] (6) Under vacuum, the first intermediate is placed in a heating mold and heated to solidify the carbon fiber cloth to form a carbon fiber shell.

[0053] (7) The first intermediate is taken out from the heating mold and graphite powder is wrapped on the outer surface of the carbon fiber shell to form the second intermediate. The graphite powder has a particle size of 12μm and a thickness of 7mm.

[0054] (8) The second intermediate was placed directly into the sintering furnace, and after evacuation, heating was started. The temperature was increased from room temperature to 600℃ and held for 1.5h; then the temperature was increased to 1000℃ and held for 1h. The sintering furnace was a single-chamber sintering furnace, and the vacuum was evacuated to a vacuum degree of 0.8Pa.

[0055] (9) After the heat preservation is completed, the temperature is raised to 1350℃ and kept for 8 minutes; then the temperature is raised to 1500℃ and kept for 2.5 minutes. After cooling, the third intermediate is obtained.

[0056] (10) Remove the third intermediate from the sintering furnace, mechanically break the outer shell, and remove the high-performance neodymium iron boron in the middle.

[0057] Example 3:

[0058] A method for producing high-performance NdFeB using sintered NdFeB waste includes the following steps:

[0059] (1) The sintered NdFeB waste is mixed with reducing agent and flux and then smelted to form slag.

[0060] (2) The material obtained in step (1) is crushed to obtain nano-neodymium iron boron.

[0061] (3) The composition of the nano-neodymium iron boron obtained in step (2) is analyzed.

[0062] (4) Based on the detection results in step (3), add the nano-oxides of Ho, Gd, and Pr elements to the nano-neodymium iron boron and mix them evenly to obtain alloy powder, wherein Ho element accounts for 0.7% of the total mass of the alloy powder, Gd element accounts for 0.7% of the total mass of the alloy powder, and Pr element accounts for 1.8% of the total mass of the alloy powder. The particle size of the nano-oxides of Ho, Gd, and Pr elements is less than 50 nanometers.

[0063] (5) Under vacuum, the alloy powder is pressed to obtain a blank, and a carbon fiber cloth with a thickness of 10 mm is coated on the outer surface of the blank to make a first intermediate.

[0064] (6) Under vacuum, the first intermediate is placed in a heating mold and heated to solidify the carbon fiber cloth to form a carbon fiber shell.

[0065] (7) The first intermediate is taken out from the heating mold and graphite powder is wrapped on the outer surface of the carbon fiber shell to form the second intermediate. The graphite powder has a particle size of 14μm and a thickness of 6.5mm.

[0066] (8) The second intermediate was placed directly into the sintering furnace, and after evacuation, heating was started. The temperature was increased from room temperature to 550°C and held for 1.2 hours. Then the temperature was increased to 980°C and held for 1.5 hours. The sintering furnace was a single-chamber sintering furnace, and the vacuum was evacuated to a vacuum degree of 0.85 Pa.

[0067] (9) After the heat preservation is completed, the temperature is raised to 1400℃ and kept for 7 minutes; then the temperature is raised to 1450℃ and kept for 3 minutes. After cooling, the third intermediate is obtained.

[0068] (10) Remove the third intermediate from the sintering furnace, mechanically break the outer shell, and remove the high-performance neodymium iron boron in the middle.

[0069] Example 4:

[0070] A method for producing high-performance NdFeB using sintered NdFeB waste includes the following steps:

[0071] (1) The sintered NdFeB waste is mixed with reducing agent and flux and then smelted to form slag.

[0072] (2) The material obtained in step (1) is crushed to obtain nano-neodymium iron boron.

[0073] (3) The composition of the nano-neodymium iron boron obtained in step (2) is analyzed.

[0074] (4) Based on the detection results in step (3), add the nano-oxides of Ho, Gd, and Pr elements to the nano-neodymium iron boron and mix them evenly to obtain alloy powder, wherein Ho element accounts for 0.65% of the total mass of the alloy powder, Gd element accounts for 0.5% of the total mass of the alloy powder, and Pr element accounts for 1.6% of the total mass of the alloy powder. The particle size of the nano-oxides of Ho, Gd, and Pr elements is less than 50 nanometers.

[0075] (5) Under vacuum, the alloy powder is pressed to obtain a blank, and a carbon fiber cloth with a thickness of 8.5 mm is coated on the outer surface of the blank to form a first intermediate.

[0076] (6) Under vacuum, the first intermediate is placed in a heating mold and heated to solidify the carbon fiber cloth to form a carbon fiber shell.

[0077] (7) The first intermediate is taken out from the heating mold and graphite powder is wrapped on the outer surface of the carbon fiber shell to form the second intermediate. The graphite powder has a particle size of 13μm and a thickness of 6.3mm.

[0078] (8) The second intermediate was placed directly into the sintering furnace, and after evacuation, heating was started. The temperature was increased from room temperature to 580°C and held for 1.3 hours. Then the temperature was increased to 960°C and held for 1.4 hours. The sintering furnace was a single-chamber sintering furnace, and the vacuum was evacuated to a vacuum degree of 0.7 Pa.

[0079] (9) After the heat preservation is completed, the temperature is raised to 1360℃ and kept for 6 minutes; then the temperature is raised to 1490℃ and kept for 2.2 minutes. After cooling, the third intermediate is obtained.

[0080] (10) Remove the third intermediate from the sintering furnace, mechanically break the outer shell, and remove the high-performance neodymium iron boron in the middle.

[0081] Example 5:

[0082] A method for producing high-performance NdFeB using sintered NdFeB waste includes the following steps:

[0083] (1) The sintered NdFeB waste is mixed with reducing agent and flux and then smelted to form slag.

[0084] (2) The material obtained in step (1) is crushed to obtain nano-neodymium iron boron.

[0085] (3) The composition of the nano-neodymium iron boron obtained in step (2) is analyzed.

[0086] (4) Based on the detection results in step (3), add the nano-oxides of Ho, Gd, and Pr elements to the nano-neodymium iron boron and mix them evenly to obtain alloy powder, wherein Ho element accounts for 0.8% of the total mass of the alloy powder, Gd element accounts for 0.9% of the total mass of the alloy powder, and Pr element accounts for 1.9% of the total mass of the alloy powder. The particle size of the nano-oxides of Ho, Gd, and Pr elements is less than 50 nanometers.

[0087] (5) Under vacuum, the alloy powder is pressed to obtain a blank, and a carbon fiber cloth with a thickness of 9.5 mm is coated on the outer surface of the blank to form a first intermediate.

[0088] (6) Under vacuum, the first intermediate is placed in a heating mold and heated to solidify the carbon fiber cloth to form a carbon fiber shell.

[0089] (7) The first intermediate is taken out from the heating mold and graphite powder is wrapped on the outer surface of the carbon fiber shell to form the second intermediate. The graphite powder has a particle size of 12μm and a thickness of 6.8mm.

[0090] (8) The second intermediate was placed directly into the sintering furnace, and after evacuation, heating was started. The temperature was increased from room temperature to 560°C and held for 1.1 hours. Then the temperature was increased to 970°C and held for 1.3 hours. The sintering furnace was a single-chamber sintering furnace, and the vacuum was evacuated to a vacuum degree of 0.6 Pa.

[0091] (9) After the heat preservation is completed, the temperature is raised to 1370℃ and kept for 5 minutes; then the temperature is raised to 1470℃ and kept for 2.6 minutes. After cooling, the third intermediate is obtained.

[0092] (10) Remove the third intermediate from the sintering furnace, mechanically break the outer shell, and remove the high-performance neodymium iron boron in the middle.

[0093] Example 6:

[0094] A method for producing high-performance NdFeB using sintered NdFeB waste includes the following steps:

[0095] (1) The sintered NdFeB waste is mixed with reducing agent and flux and then smelted to form slag.

[0096] (2) The material obtained in step (1) is crushed to obtain nano-neodymium iron boron.

[0097] (3) The composition of the nano-neodymium iron boron obtained in step (2) is analyzed.

[0098] (4) Based on the detection results in step (3), nano-oxides of Ho, Gd, and Pr elements are added to nano-neodymium iron boron and mixed evenly to obtain alloy powder, wherein Ho element accounts for 0.75% of the total mass of alloy powder, Gd element accounts for 0.7% of the total mass of alloy powder, and Pr element accounts for 1.6% of the total mass of alloy powder. The particle size of the nano-oxides of Ho, Gd, and Pr elements is less than 50 nanometers.

[0099] (5) Under vacuum, the alloy powder is pressed to obtain a blank, and a carbon fiber cloth with a thickness of 8.2 mm is coated on the outer surface of the blank to form a first intermediate.

[0100] (6) Under vacuum, the first intermediate is placed in a heating mold and heated to solidify the carbon fiber cloth to form a carbon fiber shell.

[0101] (7) The first intermediate is taken out from the heating mold and graphite powder is wrapped on the outer surface of the carbon fiber shell to form the second intermediate. The graphite powder has a particle size of 10 μm and a thickness of 6.4 mm.

[0102] (8) The second intermediate was placed directly into the sintering furnace, and after evacuation, heating was started. The temperature was increased from room temperature to 590°C and held for 1.4 hours. Then the temperature was increased to 990°C and held for 1.1 hours. The sintering furnace was a single-chamber sintering furnace, and the vacuum was evacuated to a vacuum degree of 0.9 Pa.

[0103] (9) After the heat preservation is completed, the temperature is raised to 1390℃ and kept for 7 minutes; then the temperature is raised to 1480℃ and kept for 2.7 minutes. After cooling, the third intermediate is obtained.

[0104] (10) Remove the third intermediate from the sintering furnace, mechanically break the outer shell, and remove the high-performance neodymium iron boron in the middle.

[0105] Comparative example:

[0106] Nano-oxides of Ho, Gd, and Pr elements are added to NdFeB powder, and then the alloy powder is mixed, pressed, vacuum sintered, and aged using conventional methods to produce magnets.

[0107] The magnets prepared in the above embodiments and comparative examples were tested using existing technologies. The testing methods for the magnets will not be described in detail here. The test results are shown in the table below:

[0108]

[0109]

[0110] As can be seen from the table above, the magnets prepared by the method of the present invention have higher coercivity and remanence, and the magnetic energy product is also increased accordingly, resulting in a significant improvement in performance.

[0111] The key design focus of this invention is as follows: This invention uses sintered NdFeB waste as the main raw material. By analyzing the composition, and then adding corresponding Ho, Gd, and Pr nano-oxides based on the composition, the sintered NdFeB waste is effectively utilized, eliminating resource waste. Simultaneously, before sintering, the blank is wrapped with carbon fiber cloth and heated to solidify, forming a carbon fiber shell. This carbon fiber shell serves as a buffer and protective layer, eliminating the need for molds. Fine-grained graphite powder is used as an insulating layer to reduce the probability of contact with air during blank sintering, preventing excessive surface oxidation and ensuring sintering uniformity. Furthermore, multiple sintering temperatures are used in combination during the sintering process to more effectively suppress solid-phase sintering and grain growth, further ensuring finer grains in the magnet, thereby significantly improving coercivity and achieving high performance.

[0112] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A method for producing high-performance NdFeB using sintered NdFeB waste, characterized in that: It includes the following steps: (1) The sintered NdFeB waste is mixed with reducing agent and flux and then smelted to form slag; (2) The material obtained in step (1) is pulverized to obtain nano-neodymium iron boron; (3) The composition of the nano-neodymium iron boron obtained in step (2) was analyzed; (4) Based on the detection results in step (3), add nano-oxides of Ho, Gd and Pr elements to nano-neodymium iron boron and mix them evenly to obtain alloy powder, wherein Ho element accounts for 0.6%-0.8% of the total mass of alloy powder, Gd element accounts for 0.5%-1% of the total mass of alloy powder, and Pr element accounts for 1.5%-2% of the total mass of alloy powder. (5) Under vacuum conditions, the alloy powder is pressed to obtain a blank, and a carbon fiber cloth with a thickness of 8-10 mm is coated on the outer surface of the blank to make a first intermediate. (6) Under vacuum conditions, the first intermediate is placed in a heating mold and heated to solidify the carbon fiber cloth to form a carbon fiber shell; (7) The first intermediate is taken out from the heating mold and graphite powder is wrapped on the outer surface of the carbon fiber shell to form the second intermediate. The particle size of the graphite powder is 10-14μm and the thickness of the graphite powder is 6-7mm. (8) Place the second intermediate directly into the sintering furnace, evacuate the vacuum, and start heating. Raise the temperature from room temperature to 500-600℃ and hold for 1-1.5h; then continue to raise the temperature to 950-1000℃ and hold for 1-1.5h. (9) After the heat preservation is completed, the temperature is raised to 1300-1400℃ and kept for 5-8 minutes; then the temperature is raised to 1450-1500℃ and kept for 2-3 minutes. After cooling, the third intermediate is obtained. (10) Remove the third intermediate from the sintering furnace, mechanically break the outer shell, and remove the high-performance neodymium iron boron in the middle.

2. The method for producing high-performance NdFeB using sintered NdFeB waste as described in claim 1, characterized in that: In step (4), the nano-oxides of Ho, Gd, and Pr elements have a particle size of less than 50 nanometers.

3. The method for producing high-performance NdFeB using sintered NdFeB waste as described in claim 1, characterized in that: In step (8), the vacuum level is reduced to <1 Pa.

4. The method for producing high-performance NdFeB using sintered NdFeB waste as described in claim 1, characterized in that: In step (8), the sintering furnace is a single-chamber sintering furnace.

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