Method for preparing high-performance neodymium-iron-boron magnet from neodymium-iron-boron waste

Abstract

The invention provides a method for preparing a high-performance neodymium-iron-boron magnet from neodymium-iron-boron waste, and belongs to the technical field of neodymium-iron-boron magnet preparation. The preparation process comprises the following steps: pretreating the waste neodymium iron boron material; preparing waste neodymium iron boron powder; carrying out sputtering treatment; performing surface treatment on the mixture; preparing a neodymium-iron-boron magnet; and preparing composite diffusion source slurry and carrying out grain boundary diffusion on the neodymium-iron-boron magnet. The rare earth alloy sputtering target material is prepared by optimizing alloy components, the rare earth alloy is sputtered on the surface of the powder, and then the rare earth elements are uniformly distributed at the neodymium iron boron grain boundary by utilizing a sintered grain boundary diffusion form, so that the defect that the grain boundary rare earth is insufficient when a new magnet is remanufactured by waste neodymium iron boron magnetic steel is overcome; the coercive force of the regenerated magnet can be greatly improved, the use amount of rare earth is reduced, and the regenerated neodymium-iron-boron magnet with excellent performance is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of NdFeB magnet preparation, and in particular to a method for preparing high-performance NdFeB magnets by utilizing NdFeB waste. Background Art

[0002] NdFeB magnets are widely used in various high-tech products due to their excellent magnetic properties. With the replacement or scrapping of these products, a large amount of waste containing NdFeB materials will be generated, and NdFeB products will inevitably produce about 20%-30% of scraps and defective products during the production and processing. At the same time, as time goes by, some mechanical equipment and motors using NdFeB permanent magnets will produce a lot of waste containing NdFeB materials due to failures, expiration of service life, etc., and rare earth elements such as neodymium and dysprosium are important components of NdFeB materials. At present, rare earth resources are relatively scarce and the mining cost is high. If a large amount of waste containing NdFeB materials is discarded at will, it will not only cause a waste of resources, but also pose a potential threat to the environment. Through recycling and reuse, environmental pollution can be effectively reduced, which is in line with the concept of sustainable development.

[0003] The existing recycling of waste NdFeB materials mostly adopts chemical refining, extraction and separation of elements and the method of adding new raw materials to NdFeB waste to recycle. The chemical method inevitably uses chemical reagents and acids, which are not conducive to environmental protection. The mixed use of NdFeB waste and new raw materials to prepare new magnets requires re-testing the waste composition and adjusting the composition of the strips according to the waste composition. The proportion of waste added is about 40-50%, and the smelting and stripping process is complicated and costly. In addition, the effects of various elements in the waste NdFeB materials cannot be brought into play, the recycling rate is not high, the magnetic properties of NdFeB are not good, and the practical value is limited.

[0004] Therefore, we proposed a preparation method that can improve the coercivity of regenerated NdFeB and obtain high-performance NdFeB magnets with excellent performance. Summary of the invention

[0005] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for preparing high-performance NdFeB magnets using NdFeB waste.

[0006] A method for preparing high-performance NdFeB magnets using NdFeB waste materials comprises the following steps:

[0007] S1: pre-treating the waste NdFeB materials, demagnetizing, grinding, cleaning and mechanically crushing the waste NdFeB materials to obtain pre-treated waste NdFeB materials;

[0008] S2: preparing waste NdFeB powder, performing hydrogen crushing and air flow grinding on the pretreated waste NdFeB material to obtain NdFeB waste powder;

[0009] S3: Sputtering treatment, using vacuum induction melting furnace to prepare Dy 65 Y 10 Fe8Ga 10 Cu5Ti2 ingot, Dy 65 Y 10 Fe8Ga 10 Cu5Ti2 alloy is sputtered on the surface of NdFeB waste powder to obtain a sputtered mixture;

[0010] S4: performing surface treatment on the mixture, treating the sputtered mixture with phosphoric acid to obtain phosphating magnetic powder, then mixing the phosphating magnetic powder with an acetone solution of a silane coupling agent KH792 in equal amounts, then adding deionized water, and soaking to obtain a surface-treated mixture;

[0011] S5: Preparation of NdFeB magnets, pre-orienting the surface treated mixture, sintering at high temperature and performing two-stage tempering treatment, and then cooling to obtain sintered NdFeB magnets;

[0012] S6: Prepare composite diffusion source slurry and perform grain boundary diffusion on NdFeB magnets to prepare Pr 80 Al 20 Composite powder coated with TbF3 to prepare Pr 80 Al 20 High performance NdFeB magnets are prepared by diffusion using composite powder coated with TbF3 as a diffusion source.

[0013] Furthermore, step S1 pre-treats the waste NdFeB material, specifically comprising the following steps:

[0014] S1.1: Demagnetize the waste NdFeB materials at 400-420℃ so that the waste NdFeB materials no longer have magnetic properties;

[0015] S1.2: Grind the surface of the demagnetized waste NdFeB material to remove the oxide scale, oil stains and rust on the surface, then boil the polished waste NdFeB material in boiling water for 10-20 minutes, then use ultrasonic cleaning to remove the dirt remaining on the waste NdFeB material, use a heater to dry the surface of the cleaned waste NdFeB material at 100-150℃, and control the oxygen content of the waste NdFeB material to 2000-3000ppm;

[0016] S1.3: The dried waste NdFeB material is mechanically coarsely crushed to less than 1000 μm to obtain pretreated waste NdFeB material.

[0017] Furthermore, step S2 prepares waste NdFeB powder, specifically comprising the following steps:

[0018] S2.1: The pretreated waste NdFeB material is placed in a hydrogen explosion furnace, evacuated and preheated to 80-100°C, and then 0-1Mpa high-purity hydrogen is introduced to fully absorb hydrogen, so that the main phase and the neodymium-rich phase are separated, and finally heated to 500-550°C for dehydrogenation, and the intergranular fracture and transgranular fracture of the NdFeB alloy itself during the process of hydrogen absorption and dehydrogenation are used to cause the alloy to be pulverized, thereby obtaining coarse NdFeB waste powder;

[0019] S2.2: The NdFeB waste coarse powder is put into a jet mill under nitrogen circulation protection with a system oxygen content of less than 5 ppm to obtain NdFeB waste powder for later use.

[0020] Furthermore, step S3 sputtering treatment specifically includes the following steps:

[0021] S3.1: Preparation of Dy using vacuum induction melting furnace 65 Y 10 Fe8Ga 10 Cu5Ti2 ingots are cast, and then the ingots are subjected to homogenization heat treatment at 1000-1100°C for 3-4 hours under vacuum protection. After the heat treatment, argon gas is filled in for air cooling, and then the heat-treated ingots are surface-polished and processed into sputtering targets;

[0022] S3.2: Use magnetron sputtering to deposit Dy 65 Y 10 Fe8Ga 10 Cu5Ti2 alloy is sputtered on the surface of NdFeB waste powder to obtain a sputtered mixture.

[0023] Furthermore, step S4 performs surface treatment on the mixed material, which specifically includes the following steps:

[0024] S4.1: 0.2-0.3 parts by weight of phosphoric acid and 20-30 parts by weight of acetone are uniformly mixed, and then 10-12 parts by weight of the sputtered mixture is added, and the mixture is stirred for 10-12 hours, and then dried at 60-65° C. to obtain phosphating magnetic powder;

[0025] S4.2: Weigh the silane coupling agent KH792 liquid and acetone reagent to prepare a silane coupling agent KH792 acetone solution with a concentration of 0.5%-2%;

[0026] S4.3: Mix equal amounts of phosphating magnetic powder and silane coupling agent KH792 acetone solution, then add 10-20wt% deionized water and stir thoroughly, then soak for 30-35h, filter, and dry the filtered mixture at 50-60°C to obtain a surface-treated mixture.

[0027] Furthermore, step S5 of preparing the NdFeB magnet specifically comprises the following steps:

[0028] S5.1: Place the surface treated mixture into a mold, and then place it into a fully sealed magnetic field molding press under nitrogen circulation protection with an oxygen content of less than 50ppm for pre-orientation molding. The orientation magnetic field intensity is 2.0T, and the compact density is controlled at 4.3g / cm 3 , obtaining a magnet embryo;

[0029] S5.2: placing the magnet embryo into a microwave vacuum sintering furnace for high-temperature sintering at a temperature of 1000-1020°C for 30-40 minutes at a microwave frequency of 4-4.2Kw. After sintering, argon gas is filled in for air cooling to obtain a pre-sintered NdFeB magnet;

[0030] S5.3: The pre-sintered NdFeB magnet is subjected to two-stage tempering treatment, and then cooled to obtain a sintered NdFeB magnet.

[0031] Furthermore, step S6 prepares a composite diffusion source slurry and performs grain boundary diffusion on the NdFeB magnet, specifically comprising the following steps:

[0032] S6.1: Pr with a particle size of 200-300 μm is prepared by batching, smelting, flaking and coarse grinding. 80 Al 20 Coarse particles, Pr 80 Al 20 The coarse particles and TbF3 coarse powder with a particle size of 50-60 μm are uniformly mixed in a ratio of 7:2-3, and then ball-milled for 3-4 hours under the protection of anhydrous ethanol to prepare a composite powder required for diffusion;

[0033] S6.2: The composite powder and anhydrous ethanol are uniformly mixed in proportion under ultrasonic vibration to prepare a composite diffusion source slurry;

[0034] S6.3: Coat the composite diffusion source slurry on the surface of the NdFeB magnet, place the coated NdFeB magnet in a tubular sintering furnace, and evacuate to 1×10 -3 Pa, diffusion treatment at 840-960℃ for 10-12h, and then tempering treatment at 490-500℃ for 3-4h to obtain high performance NdFeB magnets.

[0035] Furthermore, in step S3.1, the Dy 65 Y 10 Fe8Ga 10 The content of Cu5Ti2 alloy is such that its weight accounts for 0.5-1% of the total weight.

[0036] Furthermore, in step S5.3, the two-stage tempering treatment is specifically as follows: the primary treatment temperature is 850-930°C, and the tempering time is 1.5-2h; the secondary treatment temperature is 500-650°C, and the tempering time is 2-3h.

[0037] Furthermore, in step S6.2, the mixing ratio of the composite powder and anhydrous ethanol is 1-2:1-2.

[0038] Compared with the prior art, the present invention has at least the following beneficial effects:

[0039] The beneficial effects are as follows: 1. The present invention sputters Dy on the powder surface. 65 Y 10 Fe8Ga 10 Cu5Ti2 rare earth alloy, rare earth elements Dy and Y will preferentially concentrate at the grain boundaries. These rare earth elements have large atomic magnetic moments and strong magnetocrystalline anisotropy. The phases they form at the grain boundaries have high magnetocrystalline anisotropy fields, which is equivalent to setting up a series of "barriers" on the path of movement of the magnetic domain wall. The magnetic domain wall needs to overcome a greater energy barrier when crossing the grain boundary, because the magnetocrystalline anisotropy at the grain boundary is different from that inside the grain. This difference makes it difficult for the magnetic domain wall to move easily, thereby effectively hindering the displacement of the magnetic domain wall and thereby increasing the coercive force. At the same time, Ga can improve the wettability of the grain boundary and promote the element Diffusion uniformity; Cu can form a metastable phase at the grain boundary, interact with the rare earth elements, and synergistically improve the stability and magnetic properties of the grain boundary. Ti can refine the grains and increase the grain boundary area, thereby providing more places for the pinning of rare earth elements and the play of magnetocrystalline anisotropy. Therefore, the mutual diffusion and coupling between these elements jointly promote the optimization of grain boundary characteristics, further improve the coercive force of the regenerated magnet, reduce the use of rare earths, and obtain regenerated NdFeB magnets with excellent performance. In addition, there is no need to mix NdFeB waste and new raw material stripping sheets to prepare new magnets, which reduces the melting and stripping steps and reduces production costs.

[0040] 2. The present invention performs surface coating treatment after phosphating the mixture, and then performs surface coating modification after phosphating to prevent oxidation of the mixture and increase its fluidity, thereby improving its magnetic properties. A phosphating film is formed on the surface of the mixture through phosphating. This phosphating film itself has a certain density and can act as a physical barrier to prevent oxygen from contacting the mixture. After that, the silane coupling agent is hydrolyzed to generate silanol groups. When the silane coupling agent contacts the phosphating film, the silanol groups will undergo condensation reaction with the hydroxyl groups on the surface of the phosphating film to form stable silicon-oxygen bonds. , so that the silane coupling agent can be firmly attached to the surface of the phosphating film to form a tight bonding layer, which can isolate the mixture from external oxygen, achieve efficient anti-oxidation effect, and avoid oxidation reaction of the mixture during placement, ensuring the crystal structure integrity of the magnetic material during the preparation process. The intact grain boundaries and internal structure of the grains can make the magnetic domain wall more difficult to be driven to move when subjected to the reverse magnetic field, thereby improving the coercive force, and the silane coupling agent decomposes under the high temperature in the subsequent sintering process, so it will not affect the magnetic properties of the subsequently prepared magnet.

[0041] 3. In the process of ball milling, the present invention 80 Al 20 The surface of the alloy powder is activated purposefully, so that the TbF3 powder is adsorbed on its surface. On the other hand, due to the difference in particle size, the TbF3 powder with smaller particle size is easily adsorbed on the Pr 80 Al 20 The surface of the alloy powder, so that TbF3 powder is coated on Pr 80 Al 20 The surface of the alloy powder, the Pr 80 Al 20 The composite powder coated with TbF3 on the surface is used as a diffusion source. During grain boundary diffusion, the solid TbF3 powder will be immersed in the Pr-Al alloy liquid and undergo liquid-liquid diffusion with the liquid grain boundary phase, thereby repairing the discontinuous grain boundary phase on the magnet surface in advance. After the repair, the continuity of the grain boundary phase is improved, reducing the possibility of irregular movement of the magnetic domain wall at the grain boundary and pinning failure, making the overall performance of the magnet more stable, and providing a basic guarantee for the improvement of coercive force. The magnetic isolation effect of the continuous Pr-rich and Al grain boundary phases can effectively prevent the direct phase separation of magnetic domains between grains. The interaction between the two elements prevents the domain wall from moving freely between the grains, thereby improving the coercivity. The magnetic hardening effect of the Tb- and Pr-rich shells formed during the grain boundary diffusion process further increases the coercivity. The Tb element has a strong magnetocrystalline anisotropy, and its enrichment in the shell significantly enhances the magnetocrystalline anisotropy of this region. The high magnetocrystalline anisotropy will limit the direction and difficulty of the movement of the domain wall. When the domain wall moves to the Tb- and Pr-rich shell region, it is difficult for the domain wall to continue moving due to the resistance caused by the strong magnetocrystalline anisotropy, thereby greatly improving the coercivity of the magnet. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, further serve to explain the principles of the invention and to enable those skilled in the relevant art to make and use the invention.

[0043] Figure 1 The present invention is a flowchart of a method for preparing high-performance NdFeB magnets using NdFeB waste materials. DETAILED DESCRIPTION

[0044] The following is a detailed description of a method for preparing high-performance NdFeB magnets using NdFeB waste provided by the present invention in conjunction with the accompanying drawings and specific embodiments. At the same time, it is explained here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art may also adopt other alternatives to implement some known technologies; and the accompanying drawings are only for a more specific description of the embodiments, and are not intended to specifically limit the present invention.

[0045] Example 1

[0046] A method for preparing high-performance NdFeB magnets using NdFeB waste, such as Figure 1 As shown, the following steps are included:

[0047] S1: Pretreatment of waste NdFeB materials

[0048] S1.1: Demagnetize the waste NdFeB materials at 400°C so that the waste NdFeB materials no longer have magnetic properties;

[0049] S1.2: Grind the surface of the demagnetized waste NdFeB material to remove the oxide scale, oil stains and rust on the surface, then boil the polished waste NdFeB material in boiling water for 10 minutes, then use ultrasonic cleaning to remove the dirt remaining on the waste NdFeB material, use a heater to dry the surface of the cleaned waste NdFeB material at 100°C, and control the oxygen content of the waste NdFeB material to 2000ppm;

[0050] S1.3: Mechanically crushing the dried waste NdFeB material to less than 1000 μm to obtain pretreated waste NdFeB material;

[0051] S2: Preparation of waste NdFeB powder

[0052] S2.1: The pretreated waste NdFeB material is placed in a hydrogen explosion furnace, evacuated and preheated to 80°C, and then 1Mpa of high-purity hydrogen is introduced to fully absorb hydrogen, thereby separating the main phase from the neodymium-rich phase, and finally heated to 500°C for dehydrogenation. The intergranular fracture and transgranular fracture of the NdFeB alloy itself during the process of hydrogen absorption and dehydrogenation are used to cause the alloy to be pulverized, thereby obtaining coarse NdFeB waste powder;

[0053] S2.2: The NdFeB waste coarse powder is put into a jet mill under nitrogen circulation protection with a system oxygen content of less than 5 ppm to obtain NdFeB waste powder for standby use;

[0054] S3: Sputtering treatment

[0055] S3.1: Preparation of Dy using vacuum induction melting furnace 65 Y 10 Fe8Ga 10 Cu5Ti2 ingots are cast, and then the ingots are homogenized and heat treated at 1000°C for 3 hours under vacuum protection. After the heat treatment, argon gas is filled in for air cooling. Then, the ingots after the heat treatment are surface polished and processed into sputtering targets;

[0056] S3.2: Use magnetron sputtering to deposit Dy 65 Y 10 Fe8Ga 10 Cu5Ti2 alloy was sputtered on the surface of NdFeB scrap powder, and the Dy 65 Y 10 Fe8Ga 10 The content of Cu5Ti2 alloy is such that its weight accounts for 0.5% of the total weight to obtain a mixed material after sputtering;

[0057] S4: Surface treatment of the mixture

[0058] S4.1: 0.2 parts by weight of phosphoric acid and 20 parts by weight of acetone are uniformly mixed, and then 10 parts by weight of the sputtered mixture is added, and the mixture is stirred for 10 hours, and then dried at 60° C. to obtain phosphating magnetic powder;

[0059] S4.2: Weigh the silane coupling agent KH792 liquid and acetone reagent to prepare a silane coupling agent KH792 acetone solution with a concentration of 0.5%;

[0060] S4.3: Mix the phosphating magnetic powder and the silane coupling agent KH792 acetone solution in equal amounts, then add 10wt% deionized water and stir thoroughly, then soak for 30h, filter, and dry the filtered mixture at 50°C to obtain a surface treated mixture;

[0061] S5: Preparation of NdFeB magnets

[0062] S5.1: Place the surface treated mixture into a mold, and then place it into a fully sealed magnetic field molding press under nitrogen circulation protection with an oxygen content of less than 50ppm for pre-orientation molding. The orientation magnetic field intensity is 2.0T, and the compact density is controlled at 4.3g / cm 3 , obtaining a magnet embryo;

[0063] S5.2: placing the magnet embryo into a microwave vacuum sintering furnace for high-temperature sintering at a temperature of 1000°C for 30 minutes at a microwave frequency of 4Kw. After sintering, argon gas is filled in for air cooling to obtain a pre-sintered NdFeB magnet;

[0064] S5.3: The pre-sintered NdFeB magnet is subjected to two-stage tempering treatment, wherein the primary treatment temperature is 850°C and the tempering time is 1.5h; the secondary treatment temperature is 500°C and the tempering time is 2h, and then cooled to obtain a sintered NdFeB magnet;

[0065] S6: Preparation of composite diffusion source slurry and grain boundary diffusion of NdFeB magnets

[0066] S6.1: 200 μm Pr was prepared by batching, smelting, slicing and coarse grinding. 80 Al 20 Coarse particles, Pr 80 Al 20 The coarse particles and TbF3 coarse powder with a particle size of 50 μm were uniformly mixed in a ratio of 7:2 and then ball-milled for 3 h under the protection of anhydrous ethanol to prepare the composite powder required for diffusion;

[0067] S6.2: The composite powder and anhydrous ethanol are uniformly mixed in a ratio of 1:1 under ultrasonic vibration to prepare a composite diffusion source slurry;

[0068] S6.3: Coat the composite diffusion source slurry on the surface of the NdFeB magnet, place the coated NdFeB magnet in a tubular sintering furnace, and evacuate to 1×10 -3 Pa, diffusion treatment was performed at 840℃ for 10h, and then tempering treatment was performed at 490℃ for 3h to obtain high performance NdFeB magnets.

[0069] Example 2

[0070] A method for preparing high-performance NdFeB magnets using NdFeB waste, such as Figure 1 As shown, the following steps are included:

[0071] S1: Pretreatment of waste NdFeB materials

[0072] S1.1: Demagnetize the waste NdFeB materials at 420°C so that the waste NdFeB materials no longer have magnetic properties;

[0073] S1.2: Grind the surface of the demagnetized waste NdFeB material to remove the oxide scale, oil stains and rust on the surface, then boil the polished waste NdFeB material in boiling water for 20 minutes, then use ultrasonic cleaning to remove the dirt remaining on the waste NdFeB material, use a heater to dry the surface of the cleaned waste NdFeB material at 150°C, and control the oxygen content of the waste NdFeB material to 2000ppm;

[0074] S1.3: Mechanically crushing the dried waste NdFeB material to less than 1000 μm to obtain pretreated waste NdFeB material;

[0075] S2: Preparation of waste NdFeB powder

[0076] S2.1: The pretreated waste NdFeB material is placed in a hydrogen explosion furnace, evacuated and preheated to 100°C, and then 1Mpa of high-purity hydrogen is introduced to fully absorb hydrogen, thereby separating the main phase from the neodymium-rich phase, and finally heated to 550°C for dehydrogenation. The intergranular fracture and transgranular fracture of the NdFeB alloy itself during the process of hydrogen absorption and dehydrogenation are used to cause the alloy to be pulverized, thereby obtaining coarse NdFeB waste powder;

[0077] S2.2: The NdFeB waste coarse powder is put into a jet mill under nitrogen circulation protection with a system oxygen content of less than 5 ppm to obtain NdFeB waste powder for standby use;

[0078] S3: Sputtering treatment

[0079] S3.1: Preparation of Dy using vacuum induction melting furnace 65 Y 10 Fe8Ga 10 Cu5Ti2 ingots are cast, and then the ingots are homogenized and heat treated at 1100°C for 4 hours under vacuum protection. After the heat treatment, argon gas is filled in for air cooling. Then, the heat-treated ingots are surface-polished and processed into sputtering targets.

[0080] S3.2: Use magnetron sputtering to deposit Dy 65 Y 10 Fe8Ga 10 Cu5Ti2 alloy was sputtered on the surface of NdFeB scrap powder, and the Dy 65 Y 10 Fe8Ga 10 The content of Cu5Ti2 alloy is such that its weight accounts for 0.5% of the total weight to obtain a mixed material after sputtering;

[0081] S4: Surface treatment of the mixture

[0082] S4.1: 0.2 parts by weight of phosphoric acid and 20 parts by weight of acetone are uniformly mixed, and then 10 parts by weight of the sputtered mixture is added, and the mixture is stirred for 12 hours, and then dried at 65° C. to obtain phosphating magnetic powder;

[0083] S4.2: Weigh the silane coupling agent KH792 liquid and acetone reagent to prepare a silane coupling agent KH792 acetone solution with a concentration of 0.5%;

[0084] S4.3: Mix the phosphating magnetic powder and the silane coupling agent KH792 acetone solution in equal amounts, then add 10wt% deionized water and stir thoroughly, then soak for 35h, filter, and dry the filtered mixture at 60°C to obtain a surface-treated mixture;

[0085] S5: Preparation of NdFeB magnets

[0086] S5.1: Place the surface treated mixture into a mold, and then place it into a fully sealed magnetic field molding press under nitrogen circulation protection with an oxygen content of less than 50ppm for pre-orientation molding. The orientation magnetic field intensity is 2.0T, and the compact density is controlled at 4.3g / cm 3 , obtaining a magnet embryo;

[0087] S5.2: placing the magnet embryo into a microwave vacuum sintering furnace for high temperature sintering at a temperature of 1020°C for 40 minutes at a microwave frequency of 4.2Kw. After sintering, argon gas is filled in for air cooling to obtain a pre-sintered NdFeB magnet;

[0088] S5.3: The pre-sintered NdFeB magnet is subjected to two-stage tempering treatment, wherein the primary treatment temperature is 930°C and the tempering time is 2h; the secondary treatment temperature is 650°C and the tempering time is 3h, and then cooled to obtain a sintered NdFeB magnet;

[0089] S6: Preparation of composite diffusion source slurry and grain boundary diffusion of NdFeB magnets

[0090] S6.1: 300 μm Pr was prepared by batching, smelting, flaking and coarse grinding. 80 Al 20 Coarse particles, Pr 80 Al 20 The coarse particles and TbF3 coarse powder with a particle size of 60 μm were uniformly mixed in a ratio of 7:2 and then ball-milled for 4 h under the protection of anhydrous ethanol to prepare the composite powder required for diffusion;

[0091] S6.2: The composite powder and anhydrous ethanol are uniformly mixed in a ratio of 1:1 under ultrasonic vibration to prepare a composite diffusion source slurry;

[0092] S6.3: Coat the composite diffusion source slurry on the surface of the NdFeB magnet, place the coated NdFeB magnet in a tubular sintering furnace, and evacuate to 1×10 -3 Pa, diffusion treatment was performed at 960℃ for 12h, and then tempering treatment was performed at 500℃ for 4h to obtain high performance NdFeB magnets.

[0093] Example 3

[0094] A method for preparing high-performance NdFeB magnets using NdFeB waste, such as Figure 1 As shown, the following steps are included:

[0095] S1: Pretreatment of waste NdFeB materials

[0096] S1.1: Demagnetize the waste NdFeB materials at 400°C so that the waste NdFeB materials no longer have magnetic properties;

[0097] S1.2: Grind the surface of the demagnetized waste NdFeB material to remove the oxide scale, oil stains and rust on the surface, then boil the polished waste NdFeB material in boiling water for 10 minutes, then use ultrasonic cleaning to remove the dirt remaining on the waste NdFeB material, use a heater to dry the surface of the cleaned waste NdFeB material at 100°C, and control the oxygen content of the waste NdFeB material to 3000ppm;

[0098] S1.3: Mechanically crushing the dried waste NdFeB material to less than 1000 μm to obtain pretreated waste NdFeB material;

[0099] S2: Preparation of waste NdFeB powder

[0100] S2.1: The pretreated waste NdFeB material is placed in a hydrogen explosion furnace, evacuated and preheated to 80°C, and then 1Mpa of high-purity hydrogen is introduced to fully absorb hydrogen, thereby separating the main phase from the neodymium-rich phase, and finally heated to 500°C for dehydrogenation. The intergranular fracture and transgranular fracture of the NdFeB alloy itself during the process of hydrogen absorption and dehydrogenation lead to alloy pulverization, thereby obtaining coarse NdFeB waste powder;

[0101] S2.2: The NdFeB waste coarse powder is put into a jet mill under nitrogen circulation protection with a system oxygen content of less than 5 ppm to obtain NdFeB waste powder for standby use;

[0102] S3: Sputtering treatment

[0103] S3.1: Preparation of Dy using vacuum induction melting furnace 65 Y 10 Fe8Ga 10Cu5Ti2 ingots are cast, and then the ingots are homogenized and heat treated at 1000°C for 3 hours under vacuum protection. After the heat treatment, argon gas is filled in for air cooling. Then, the ingots after the heat treatment are surface polished and processed into sputtering targets;

[0104] S3.2: Use magnetron sputtering to deposit Dy 65 Y 10 Fe8Ga 10 Cu5Ti2 alloy was sputtered on the surface of NdFeB scrap powder, and the Dy 65 Y 10 Fe8Ga 10 The content of Cu5Ti2 alloy is such that its weight accounts for 1% of the total weight to obtain a mixed material after sputtering;

[0105] S4: Surface treatment of the mixture

[0106] S4.1: 0.3 parts by weight of phosphoric acid and 30 parts by weight of acetone are uniformly mixed, and then 12 parts by weight of the sputtered mixture is added, and the mixture is stirred for 10 hours, and then dried at 60° C. to obtain phosphating magnetic powder;

[0107] S4.2: Weigh the silane coupling agent KH792 liquid and acetone reagent to prepare a silane coupling agent KH792 acetone solution with a concentration of 2%;

[0108] S4.3: Mix the phosphating magnetic powder and the silane coupling agent KH792 acetone solution in equal amounts, then add 20wt% deionized water and stir thoroughly, then soak for 30h, filter, and dry the filtered mixture at 50°C to obtain a surface treated mixture;

[0109] S5: Preparation of NdFeB magnets

[0110] S5.1: Place the surface treated mixture into a mold, and then place it into a fully sealed magnetic field molding press under nitrogen circulation protection with an oxygen content of less than 50ppm for pre-orientation molding. The orientation magnetic field intensity is 2.0T, and the compact density is controlled at 4.3g / cm 3 , obtaining a magnet embryo;

[0111] S5.2: placing the magnet embryo into a microwave vacuum sintering furnace for high-temperature sintering at a temperature of 1000°C for 30 minutes at a microwave frequency of 4Kw. After sintering, argon gas is filled in for air cooling to obtain a pre-sintered NdFeB magnet;

[0112] S5.3: The pre-sintered NdFeB magnet is subjected to two-stage tempering treatment, wherein the primary treatment temperature is 850°C and the tempering time is 1.5h; the secondary treatment temperature is 500°C and the tempering time is 2h, and then cooled to obtain a sintered NdFeB magnet;

[0113] S6: Preparation of composite diffusion source slurry and grain boundary diffusion of NdFeB magnets

[0114] S6.1: 300 μm Pr was prepared by batching, smelting, flaking and coarse grinding. 80 Al 20 Coarse particles, Pr 80 Al 20 The coarse particles and TbF3 coarse powder with a particle size of 60 μm were uniformly mixed in a ratio of 7:3 and then ball-milled for 3 h under the protection of anhydrous ethanol to prepare the composite powder required for diffusion;

[0115] S6.2: The composite powder and anhydrous ethanol are uniformly mixed in a ratio of 1:1.5 under ultrasonic vibration to prepare a composite diffusion source slurry;

[0116] S6.3: Coat the composite diffusion source slurry on the surface of the NdFeB magnet, place the coated NdFeB magnet in a tubular sintering furnace, and evacuate to 1×10 -3 Pa, diffusion treatment was performed at 840℃ for 10h, and then tempering treatment was performed at 490℃ for 3h to obtain high performance NdFeB magnets.

[0117] Comparative Example 1

[0118] Compared with Example 1, the difference of Comparative Example 1 is that Comparative Example 1 removes steps S3, S4 and S6, and directly replaces the surface-treated mixture in step S5 with an equal mass of NdFeB waste powder to prepare a NdFeB magnet, which is recorded as Comparative Example 1.

[0119] Comparative Example 2

[0120] Compared with Example 1, the difference of Comparative Example 2 is that Comparative Example 2 removes the sputtering treatment of step S3, replaces the mixed material in step S4.2 with an equal mass of NdFeB waste powder, and prepares a NdFeB magnet by keeping the other steps unchanged, which is recorded as Comparative Example 2.

[0121] Comparative Example 3

[0122] Compared with Example 1, the difference of Comparative Example 3 is that Comparative Example 3 removes the surface treatment of the mixture in step S4, replaces the surface-treated mixture in step S5.1 with an equal mass of sputtered mixture, and prepares a high-performance NdFeB magnet without changing the other steps, which is recorded as Comparative Example 3.

[0123] Comparative Example 4

[0124] Compared with Example 1, the difference of Comparative Example 4 is that Comparative Example 4 removes step S6 of preparing composite diffusion source slurry and performing grain boundary diffusion on NdFeB magnet, and the remaining steps are unchanged to prepare NdFeB magnet, which is recorded as Comparative Example 4.

[0125] Comparative Example 5

[0126] Compared with Example 1, the difference of Comparative Example 5 is that step S6.1 is removed in Comparative Example 5, the composite powder in S6.2 is replaced with an equal weight portion of TbF3 coarse powder with a particle size of 60 μm, and the NdFeB magnet prepared by the other steps remains unchanged, which is recorded as Comparative Example 5.

[0127] Comparative Example 6

[0128] Compared with Example 1, the difference of Comparative Example 6 is that step S6.1 is removed in Comparative Example 6, the composite powder in S6.2 is replaced with an equal weight portion of 300 μm Pr80Al20 coarse particles, and the remaining steps remain unchanged to prepare the NdFeB magnet, which is recorded as Comparative Example 6.

[0129] Comparative Example 7

[0130] Compared with Example 1, the difference of Comparative Example 7 is that Comparative Example 7 removes the step S4.1 and S4.3 in which 10 wt% of deionized water is added afterwards, and the phosphating treated magnetic powder in S4.3 is replaced with an equal weight portion of the sputtered mixture, and the remaining steps remain unchanged to prepare the NdFeB magnet, which is recorded as Comparative Example 7.

[0131] Testing: The remanence and intrinsic coercivity of the NdFeB magnets obtained in Examples 1-3 and Comparative Examples 1-7 were tested according to the provisions of GB / T3217-2013. The test results are shown in Table 1.

[0132] Table 1: Remanence and intrinsic coercivity test results of Examples 1-3 and Comparative Examples 1-7

[0133] Remanence Br(KGs) Intrinsic coercivity Hcj(Koe) Example 1 13.25 20.3 Example 2 13.37 21.5 Example 3 13.29 19.6 Comparative Example 1 13.47 12.4 Comparative Example 2 13.41 15.3 Comparative Example 3 13.46 17.5 Comparative Example 4 13.39 14.7 Comparative Example 5 13.42 15.6 Comparative Example 6 13.4 15.1 Comparative Example 7 13.44 16.3

[0134] It can be seen from Table 1 that the intrinsic coercivity of the embodiments is higher than that of the comparative examples, and the remanence is only slightly reduced. The intrinsic coercivity of the comparative examples 2-7 is higher than that of the comparative example 1. It can be seen from the data of the comparative examples 4-6 that Pr 80 Al 20 The composite powder coated with TbF3 on the surface can be used as a diffusion source to improve the intrinsic coercivity, and Pr 80 Al 20 The composite powder coated with TbF3 is better than that of single Pr 80 Al 20 Or TbF3, the effect of improving the intrinsic coercivity is better, which means that Pr 80 Al20 The elements in the composite powder coated with TbF3 on the surface produce a synergistic effect, which greatly improves the coercive force of the magnet.

[0135] It can be seen from the data of Comparative Examples 3 and 7 that surface coating treatment of the mixture after sputtering is also beneficial to the improvement of intrinsic coercivity, and phosphating first and then surface coating treatment has a better effect on improving intrinsic coercivity, indicating that phosphating first and then surface coating treatment can achieve efficient anti-oxidation effect, thereby effectively ensuring the integrity of the crystal structure of the magnetic material during the preparation process, thereby improving the coercivity.

[0136] From the data of Comparative Example 2, it can be seen that by sputtering Dy 65 Y 10 Fe8Ga 10 Cu5Ti2 rare earth alloy can improve the intrinsic coercivity.

[0137] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing high-performance NdFeB magnets using NdFeB waste, characterized in that: The steps include: S1: pre-treating the waste NdFeB materials, demagnetizing, grinding, cleaning and mechanically crushing the waste NdFeB materials to obtain pre-treated waste NdFeB materials; S2: preparing waste NdFeB powder, performing hydrogen crushing and air flow grinding on the pretreated waste NdFeB material to obtain NdFeB waste powder; S3: Sputtering treatment, using vacuum induction melting furnace to prepare Dy 65 Y 10 Fe8Ga 10 Cu5Ti2 ingot, Dy 65 Y 10 Fe8Ga 10 Cu5Ti2 alloy is sputtered on the surface of NdFeB waste powder to obtain a sputtered mixture; S4: performing surface treatment on the mixture, treating the sputtered mixture with phosphoric acid to obtain phosphating magnetic powder, then mixing the phosphating magnetic powder with an acetone solution of a silane coupling agent KH792 in equal amounts, then adding deionized water, and soaking to obtain a surface-treated mixture; S5: Preparation of NdFeB magnets, pre-orienting the surface treated mixture, sintering at high temperature and performing two-stage tempering treatment, and then cooling to obtain sintered NdFeB magnets; S6: Prepare composite diffusion source slurry and perform grain boundary diffusion on NdFeB magnets to prepare Pr 80 Al 20 Composite powder coated with TbF3 to prepare Pr 80 Al 20 High performance NdFeB magnets are prepared by diffusion using composite powder coated with TbF3 as a diffusion source.

2. A method for preparing high-performance NdFeB magnets using NdFeB waste according to claim 1, It is characterized in that Step S1 pre-treats the waste NdFeB material, specifically comprising the following steps: S1.1: Demagnetize the waste NdFeB materials at 400-420℃ so that the waste NdFeB materials no longer have magnetic properties; S1.2: Grind the surface of the demagnetized waste NdFeB material to remove the oxide scale, oil stains and rust on the surface, then boil the polished waste NdFeB material in boiling water for 10-20 minutes, then use ultrasonic cleaning to remove the dirt remaining on the waste NdFeB material, use a heater to dry the surface of the cleaned waste NdFeB material at 100-150℃, and control the oxygen content of the waste NdFeB material to 2000-3000ppm; S1.3: The dried waste NdFeB material is mechanically coarsely crushed to less than 1000 μm to obtain pretreated waste NdFeB material.

3. The method for preparing high-performance NdFeB magnets using NdFeB waste according to claim 2, characterized in that: Step S2 prepares waste NdFeB powder, specifically comprising the following steps: S2.1: Place the pretreated waste NdFeB material in a hydrogen explosion furnace, evacuate and preheat to 80-100°C, then introduce 0-1Mpa high-purity hydrogen to make it fully absorb hydrogen, thereby separating the main phase from the neodymium-rich phase, and finally heat to 500-550°C for dehydrogenation. The intergranular and transgranular fractures produced by the NdFeB alloy itself during the hydrogen absorption and desorption process lead to alloy pulverization, thereby obtaining NdFeB waste coarse powder; S2.2: Place the NdFeB waste coarse powder in an air flow grinding equipment with a system oxygen content of less than 5ppm under nitrogen circulation protection to obtain NdFeB waste powder for standby use.

4. The method for preparing high-performance NdFeB magnets using NdFeB waste according to claim 3, characterized in that: Step S3: sputtering treatment, specifically comprising the following steps: S3.1: Preparation of Dy using vacuum induction melting furnace 65 Y 10 Fe8Ga 10 Cu5Ti2 ingots are cast, and then the ingots are subjected to homogenization heat treatment at 1000-1100°C for 3-4 hours under vacuum protection. After the heat treatment, argon gas is filled in for air cooling, and then the heat-treated ingots are surface-polished and processed into sputtering targets; S3.2: Use magnetron sputtering to deposit Dy 65 Y 10 Fe8Ga 10 Cu5Ti2 alloy is sputtered on the surface of NdFeB waste powder to obtain a sputtered mixture.

5. The method for preparing high-performance NdFeB magnets using NdFeB waste according to claim 4, characterized in that: Step S4 performs surface treatment on the mixed material, which specifically includes the following steps: S4.1: 0.2-0.3 parts by weight of phosphoric acid and 20-30 parts by weight of acetone are uniformly mixed, and then 10-12 parts by weight of the sputtered mixture is added, and the mixture is stirred for 10-12 hours, and then dried at 60-65° C. to obtain phosphating magnetic powder; S4.2: Weigh the silane coupling agent KH792 liquid and acetone reagent to prepare a silane coupling agent KH792 acetone solution with a concentration of 0.5%-2%; S4.3: Mix equal amounts of phosphating magnetic powder and silane coupling agent KH792 acetone solution, then add 10-20wt% deionized water and stir thoroughly, then soak for 30-35h, filter, and dry the filtered mixture at 50-60°C to obtain a surface-treated mixture.

6. The method for preparing high-performance NdFeB magnets using NdFeB waste according to claim 5, characterized in that: Step S5: Preparation of NdFeB magnets, specifically comprising the following steps: S5.1: Place the surface treated mixture into a mold, and then place it into a fully sealed magnetic field molding press under nitrogen circulation protection with an oxygen content of less than 50ppm for pre-orientation molding. The orientation magnetic field intensity is 2.0T, and the compact density is controlled at 4.3g / cm 3 , obtaining a magnet embryo; S5.2: placing the magnet embryo into a microwave vacuum sintering furnace for high-temperature sintering at a temperature of 1000-1020°C for 30-40 minutes at a microwave frequency of 4-4.2Kw. After sintering, argon gas is filled in for air cooling to obtain a pre-sintered NdFeB magnet; S5.3: The pre-sintered NdFeB magnet is subjected to two-stage tempering treatment, and then cooled to obtain a sintered NdFeB magnet.

7. The method for preparing high-performance NdFeB magnets using NdFeB waste according to claim 6, characterized in that: Step S6 prepares a composite diffusion source slurry and performs grain boundary diffusion on the NdFeB magnet, specifically comprising the following steps: S6.1: Pr with a particle size of 200-300 μm is prepared by batching, smelting, flaking and coarse grinding. 80 Al 20 Coarse particles, Pr 80 Al 20 The coarse particles and TbF3 coarse powder with a particle size of 50-60 μm are uniformly mixed in a ratio of 7:2-3, and then ball-milled for 3-4 hours under the protection of anhydrous ethanol to prepare a composite powder required for diffusion; S6.2: The composite powder and anhydrous ethanol are uniformly mixed in proportion under ultrasonic vibration to prepare a composite diffusion source slurry; S6.3: Coat the composite diffusion source slurry on the surface of the NdFeB magnet, place the coated NdFeB magnet in a tubular sintering furnace, and evacuate to 1×10 -3 Pa, diffusion treatment at 840-960℃ for 10-12h, and then tempering treatment at 490-500℃ for 3-4h to obtain high performance NdFeB magnets.

8. The method for preparing high-performance NdFeB magnets using NdFeB waste according to claim 4, characterized in that: In step S3.1, the Dy 65 Y 10 Fe8Ga 10 The content of Cu5Ti2 alloy is such that its weight accounts for 0.5-1% of the total weight.

9. The method for preparing high-performance NdFeB magnets using NdFeB waste according to claim 65, characterized in that: The two-stage tempering treatment in step S5.3 is specifically as follows: the primary treatment temperature is 850-930°C, and the tempering time is 1.5-2h; the secondary treatment temperature is 500-650°C, and the tempering time is 2-3h.

10. The method for preparing high-performance NdFeB magnets using NdFeB waste according to claim 7, characterized in that: In step S6.2, the mixing ratio of the composite powder and anhydrous ethanol is 1-2:1-2.

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