Process for recycling and regenerating neodymium-iron-boron magnet from waste neodymium-iron-boron

Abstract

The invention relates to the field of regenerated magnetic materials, in particular to a process for recycling a regenerated neodymium iron boron magnet from waste neodymium iron boron. The invention discloses a process for recycling and regenerating a neodymium iron boron magnet from waste neodymium iron boron. The process comprises the following steps: preparing Tb-HoBiO3 powder; pretreating the waste neodymium iron boron; pretreating the waste neodymium iron boron to prepare a blank body; and carrying out low-temperature supergravity sintering impurity removal and tempering treatment on the blank. According to the method, the Tb-HoBiO3 powder is prepared, and the Tb-HoBiO3 powder can better promote the uniform transformation of a blocky grain boundary phase into a strip shape and wrap the periphery of a grain main phase in the blank sintering process, so that local stray fields in the main phase grains and the magnet can be isolated, the demagnetization resistance of the regenerated neodymium-iron-boron magnet is remarkably improved, and the service life of the regenerated neodymium-iron-boron magnet is prolonged. Therefore, the magnetic performance of the regenerated neodymium-iron-boron magnet is improved, main phase crystal grains can be effectively prevented from falling off, the density of the regenerated neodymium-iron-boron magnet is improved, microdefects are reduced, the corrosion resistance of the regenerated neodymium-iron-boron magnet is remarkably improved, and the service life of the regenerated neodymium-iron-boron magnet can be prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of regenerating magnetic materials, in particular to a process for recycling waste neodymium-iron-boron to regenerate neodymium-iron-boron magnets. BACKGROUND

[0002] Neodymium-iron-boron magnets are a kind of rare earth permanent magnet materials, and the main composition is Nd2Fe 14 B main phase, Nd-rich phase, a small amount of boron-rich phase, and trace amounts of neodymium oxide and other oxide phases, which have excellent energy conversion efficiency, power-to-weight ratio, magnetic flux density, and torque density, and the preparation method is mainly sintering preparation, which has low industrial production difficulty and industrialization cost, and is the permanent magnet material with the highest market share at present.

[0003] A large amount of waste neodymium-iron-boron is also produced during the production process and after reaching the service life of the high-usage neodymium-iron-boron magnets. These waste neodymium-iron-boron can be regenerated into neodymium-iron-boron magnets through recycling. The current recycling method for waste neodymium-iron-boron is mainly hydrogenation. After the waste neodymium-iron-boron is degreased and derusted, new materials are added, and then the conventional hydrogen crushing, jet milling, orientation molding, and sintering process are directly used to regenerate neodymium-iron-boron magnets. The process is simple, green, and efficient, but due to the presence of a large amount of impurities in the waste neodymium-iron-boron, the main phase is contacted during the subsequent sintering process, and a large number of defects are generated inside, which can cause the magnetic properties of the regenerated neodymium-iron-boron magnets to decrease, the corrosion resistance to decrease, and the use effect and service life to be unsatisfactory. SUMMARY

[0004] In order to solve the above technical defects, the present application has developed a process for recycling waste neodymium-iron-boron to regenerate neodymium-iron-boron magnets, which is simple and efficient, and can significantly improve the magnetic properties and corrosion resistance of the regenerated neodymium-iron-boron magnets.

[0005] A process for recycling waste neodymium-iron-boron to regenerate neodymium-iron-boron magnets, comprising the following steps:

[0006] S1: Preparation of Tb-HoBiO3 powder

[0007] Bismuth and holmium hydroxide are immersed in an ethylamine solution, while being subjected to magnetic stirring, sodium hydroxide solution is added, then cyclohexylamine and oleic acid are added, after heating and reaction, cooling is performed, then TbCl3 and ethanol solution are added, heating and reaction are continued, then centrifugal separation is performed, and the suspension is obtained by suction filtration, the suspension is subjected to freeze-drying and crushing and grinding, and Tb-HoBiO3 powder is obtained;

[0008] S2: Pretreatment of waste neodymium-iron-boron

[0009] After mixing sodium polyacrylate and phosphoric acid solution uniformly, silicon carbide powder is added, and stirring is performed to obtain phosphoric acid abrasive, the waste neodymium-iron-boron is preheated, then alkali washing is performed, and then the waste neodymium-iron-boron is subjected to all-around washing and polishing with the phosphoric acid abrasive, and pretreated waste neodymium-iron-boron is obtained;

[0010] S3: Preparation of embryo from pretreated waste Nd-Fe-B

[0011] After the pretreated waste Nd-Fe-B is crushed, the content of the components is measured, rare earth elements and Fe are added, and then the alloy cast piece is obtained by melting and strip casting. After the alloy cast piece is crushed, hydrogen crushing and air jet milling are performed to obtain magnetic powder. The magnetic powder, Tb-HoBiO3 powder, lubricant and antioxidant are mixed uniformly in a nitrogen atmosphere, and then orientation molding and isostatic pressing are performed to obtain the embryo.

[0012] S4: Low-temperature supergravity sintering and tempering treatment of the embryo

[0013] The embryo is placed in a specially designed high-temperature supergravity centrifuge for low-temperature supergravity sintering and impurity removal, and then secondary temperature sintering is performed to obtain a sintered magnet. The temperature of the vacuum sintering furnace is adjusted for secondary tempering treatment to obtain a regenerated Nd-Fe-B magnet.

[0014] Further, the preparation of the Tb-HoBiO3 powder in step S1 includes the following steps:

[0015] S1.1: 2-3 parts by weight of bismuth and 2-3 parts by weight of holmium hydroxide are immersed in an ethylamine solution, the speed of the magnetic stirrer is adjusted to 180-200 rpm, and magnetic stirring is continuously performed. Then 5-5.5 mol / L of sodium hydroxide solution is added until the concentration of sodium hydroxide is 1-1.5 mol / L to obtain a mixed solution;

[0016] S1.2: The mixed solution is placed in a reaction kettle, 8-10 parts by weight of cyclohexylamine and 10-12 parts by weight of oleic acid are added, and then the reaction kettle is heated to a temperature of 200-220℃. After holding for 10-12 hours, it is cooled to room temperature to obtain a mixture;

[0017] S1.3: 1-2 parts by weight of TbCl3 and 2-3 parts by weight of ethanol solution are added to the mixture prepared in step S1.2, stirred for 20-25 minutes, heated to a temperature of 200-220℃ for 16-18 hours, and then centrifuged in a high-speed centrifuge. The lowermost suspension is obtained by suction filtration, and then freeze-dried and crushed and ground to obtain the Tb-HoBiO3 powder.

[0018] Further, the pretreatment of the waste Nd-Fe-B in step S2 includes the following steps:

[0019] S2.1: Put the sodium polyacrylate and phosphoric acid solution in a container with a mass ratio of 1: (18-20), stir uniformly, then add silicon carbide powder, make the particle concentration of silicon carbide powder in the phosphoric acid solution 8-10%, then adjust the stirring speed of the high-speed stirrer to 1200-1500 rpm, stir for 12-15 minutes, get the phosphoric acid abrasive;

[0020] S2.2: Put 8-10 parts by weight of waste Nd-Fe-B in a temperature of 310-350℃ for 1-1.5 hours, cool to room temperature, then soak in deionized water at 50-60℃, soak for 25-30 minutes, then put it into alkaline cleaning solution, heat to 60-80℃, stir for 20-30 minutes, then rinse with clean water until the rinse water PH approaches neutral, get the alkali washed waste Nd-Fe-B, heat the phosphoric acid abrasive to 40-50℃, then use a ceramic high-pressure water gun to spray the phosphoric acid abrasive in a sealed glove box, adjust the spraying speed to 80-100 m / s, fully wash and polish the alkali washed waste Nd-Fe-B, the polishing time is 8-10 minutes, get the pretreated waste Nd-Fe-B.

[0021] Further, step S3 pretreatment of waste Nd-Fe-B to prepare the blank, comprising the following steps:

[0022] S3.1: Put the pretreated waste Nd-Fe-B prepared in step S2.2 into a crusher to crush to a particle size less than 2 cm, get the coarse material, put the coarse material into a spectral analysis instrument, measure the content of each component in the coarse material, add ingredients according to the mass fraction PrNd 25-35wt%, erbium 2-6wt%, boron 0.8-1.2wt%, zirconium 0.5-1.0wt%, cobalt 0.3-1.2wt%, the rest is Fe, then use vacuum induction melting method for melting and refining, then use water-cooled roller for tape casting, get alloy cast sheet;

[0023] S3.2: Put the alloy cast sheet into a hydrogen crushing furnace for hydrogen crushing, so that the particle size reaches 50-200μm, then put it into a nitrogen gas stream mill for crushing to a particle size of 5-10μm, get the magnetic powder, put the magnetic powder, Tb-HoBiO3 powder prepared in step S1.3, lubricant and antioxidant into a mixing tank in a mass ratio of 100: (0.8-1.2): (0.06-0.08): (1-1.2), mix for 10-15 minutes, then put it into a press, adjust the pressing density to 5-6g / cm 2 , carry out orientation forming under the protection of nitrogen atmosphere and 2T magnetic field, then carry out secondary pressing through an isostatic press with a pressure of 300-350Mpa, get the blank.

[0024] Further, step S4 low-temperature supergravity sintering and tempering treatment of the blank, comprising the following steps:

[0025] S4.1: Put the embryo prepared in step S3.2 into a special high-temperature-resistant supergravity centrifugal device, heat to 200-220℃ at a heating rate of 10-15℃ / min, then keep the temperature for 8-10 minutes, then start the rotating device, adjust the rotating speed to 1200-1500rpm / min and heat to 400-450℃, and rotate for 45-50 minutes to obtain a degassed embryo;

[0026] S4.2: Take out the degassed embryo and quickly put it into a vacuum sintering furnace, adjust the temperature of the vacuum sintering furnace to 600-800℃, the vacuum degree to 10 -3 -5×10 -3 Pa, keep the temperature for 1-1.5 hours, then heat to 1050-1100℃ for vacuum sintering for 4-5 hours to obtain a sintered magnet;

[0027] S4.3: Adjust the temperature of the vacuum sintering furnace to perform secondary tempering treatment on the sintered magnet, the first tempering treatment parameters are 915-930℃ for 2-2.5 hours, and the second tempering parameters are 450-460℃ for 3-4 hours to obtain a regenerated neodymium-iron-boron magnet.

[0028] Further, the concentrations of the ethylamine solution and the ethanol solution in steps S1.1 and S1.3 are 0.5-0.6mol / L and 0.06-0.08mol / L, respectively.

[0029] Further, the mass fraction of the phosphoric acid solution in step S2.1 is 6-8%.

[0030] Further, the alkaline cleaning solution in step S2.2 is sodium hydroxide, sodium carbonate or sodium bicarbonate with a concentration of 5-10%.

[0031] Further, the lubricant in step S3.2 is an oxidized polyethylene wax, and the antioxidant is prepared by mixing dibutylhydroxytoluene and vitamin E at a mass ratio of 1: (1-1.2).

[0032] Further, the special high-temperature-resistant supergravity centrifugal device in step S4.1 is connected to the rotating shaft in the middle through a support arm by a heating tank and a counterweight tank, and the heating tank is installed with a resistance heating coil and a thermocouple, which can adjust the temperature in the heating tank through an external temperature control box.

[0033] The beneficial effects are: 1, the application prepares the Tb-HoBiO3 powder with nanometer cubic structure, and is blended with the magnetic powder to be pressed into the embryo, and the Tb-HoBiO3 powder can better promote the uniform conversion of the block crystal boundary phase to the strip shape and is wrapped around the main phase of the crystal grain in the sintering process of the embryo, can isolate the main phase crystal grain from the local stray field in the magnet, significantly improves the anti-demagnetization ability of the recycled neodymium-iron-boron magnet, thereby improving the magnetic performance of the recycled neodymium-iron-boron magnet, and can effectively avoid the main phase crystal grain from falling off, so that the density of the recycled neodymium-iron-boron magnet is improved, the micro defects are reduced, the corrosion resistance is significantly improved, and the service life of the recycled neodymium-iron-boron magnet can be prolonged.

[0034] 2, the application carries out low-temperature supergravity sintering on the embryo, in a low-temperature environment, the residual lubricant and antioxidant organic solvents in the embryo are first decomposed, then the rotating device is started to generate centrifugal force, and an ultra-gravity environment is created, the decomposed organic solvents are removed from the embryo in the ultra-gravity environment, the removal efficiency of the organic solvents is effectively improved, the influence of the organic solvents on the density of the embryo in the subsequent high-temperature sintering is better prevented, thereby affecting the magnetic performance of the recycled neodymium-iron-boron magnet, and the magnetic performance of the recycled neodymium-iron-boron magnet is improved.

[0035] 3, the application mixes polyacrylic acid sodium and a phosphoric acid solution, then adds silicon carbide powder, the polyacrylic acid sodium is coated on the surface of the silicon carbide powder, the dispersibility of the silicon carbide powder in the phosphoric acid solution is improved, the phosphoric acid abrasive is obtained, the phosphoric acid abrasive is washed and polished under the action of the ceramic high-pressure water gun, small particle silicon carbide powder finely polishes the surface of the waste neodymium-iron-boron, the polishing efficiency of the waste neodymium-iron-boron is improved, impurities on the surface of the waste neodymium-iron-boron are effectively removed, the influence on the magnetic performance of the recycled neodymium-iron-boron magnet prepared subsequently is prevented, and the magnetic performance of the recycled neodymium-iron-boron magnet is improved. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 A process flow chart for recycling waste neodymium-iron-boron to regenerate a neodymium-iron-boron magnet is adopted for the embodiments of the application. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0038] Embodiment 1

[0039] A process for recycling waste neodymium-iron-boron to regenerate a neodymium-iron-boron magnet is as follows, Figure 1As shown, comprising the following steps:

[0040] S1: Preparation of Tb-HoBiO3 powder

[0041] S1.1: 2 parts by weight of bismuth and 2 parts by weight of holmium hydroxide are immersed in an ethylamine solution with a concentration of 0.5 mol / L, the rotation speed of the magnetic stirrer is adjusted to 180 rpm, the magnetic stirring is continuously carried out, then 5 mol / L of sodium hydroxide solution is added until the concentration of sodium hydroxide is 1 mol / L, and a mixed solution is obtained;

[0042] S1.2: The mixed solution is placed in a reaction kettle, 8 parts by weight of cyclohexylamine and 10 parts by weight of oleic acid are added, then the reaction kettle is heated to a temperature of 200℃, and after being kept for 10 hours, it is cooled to room temperature to obtain a mixture;

[0043] S1.3: 1 part by weight of TbCl3 and 2 parts by weight of ethanol solution with a concentration of 0.06 mol / L are added to the mixture prepared in step S1.2, stirred for 20 minutes, heated at a temperature of 200℃ for 16 hours, then centrifuged in a high-speed centrifuge, and the lowermost suspension is obtained by suction filtration, then the suspension is sequentially freeze-dried and crushed and ground to obtain Tb-HoBiO3 powder.

[0044] S2: Pretreatment of waste neodymium-iron-boron

[0045] S2.1: Sodium polyacrylate and a phosphoric acid solution with a mass fraction of 6% are mixed in a container at a mass ratio of 1:18, the sodium polyacrylate can improve the dispersibility of silicon carbide powder in the phosphoric acid solution, after uniform stirring, silicon carbide powder is added, so that the particle concentration of the silicon carbide powder in the phosphoric acid solution is 8%, and the small particle silicon carbide powder can finely polish the surface of the waste neodymium-iron-boron, then the stirring speed of the high-speed stirrer is adjusted to 1200 rpm, and stirring is carried out for 12 minutes to obtain a phosphoric acid abrasive;

[0046] S2.2: 8 parts by weight of waste neodymium-iron-boron is kept at a temperature of 310℃ for 1 hour, cooled to room temperature, then soaked in deionized water at 50℃ for 25 minutes, taken out and placed in a 5% sodium hydroxide solution, heated to 60℃, stirred for 20 minutes, then washed with clean water until the washing liquid PH approaches neutral to obtain alkali-washed waste neodymium-iron-boron, the phosphoric acid abrasive is heated to 40℃, then a ceramic high-pressure water gun is used to spray the phosphoric acid abrasive in a sealed glove box, the spraying speed is adjusted to 80 m / s, and the alkali-washed waste neodymium-iron-boron is washed and polished in all directions, the polishing time is 8 minutes, the polishing efficiency of the waste neodymium-iron-boron is improved, the impurities on the surface of the waste neodymium-iron-boron are effectively removed, the performance of the regenerated neodymium-iron-boron magnet prepared subsequently is prevented from being affected, and pretreated waste neodymium-iron-boron is obtained.

[0047] S3: Preparation of embryo from pre-processed waste Nd-Fe-B

[0048] S3.1: The pre-processed waste Nd-Fe-B prepared in step S2.2 is crushed to a particle size of less than 2 cm in a crusher to obtain a coarse material. The content of each component in the coarse material is measured in a spectral analysis instrument. In the coarse material, PrNd is 30wt%, erbium is 2wt%, boron is 0.8wt%, zirconium is 0.5wt%, cobalt is 0.3wt%, and the rest is Fe. Then vacuum induction melting method is used for melting and refining, and then water-cooled roller is used for tape casting to obtain alloy cast sheet;

[0049] S3.2: The alloy cast sheet is crushed and placed in a hydrogen crushing furnace for hydrogen crushing to a particle size of 50μm, and then placed in a nitrogen gas stream mill for crushing to a particle size of 5μm to obtain magnetic powder. In a nitrogen-filled glove box, the magnetic powder, the Tb-HoBiO3 powder prepared in step S1.3, the oxidized polyethylene wax, and the antioxidant are loaded into a mixing tank at a mass ratio of 100:0.8:0.06:1, wherein the antioxidant is prepared from dibutylhydroxytoluene and vitamin E at a mass ratio of 1:1. After mixing for 10 minutes, it is added to the press, and the pressing density is adjusted to 5g / cm 2 Under the protection of nitrogen atmosphere, the orientation forming of 2T magnetic field is carried out, and then the secondary pressing is carried out through the isostatic press with a pressure of 300Mpa to obtain the embryo. In the sintering process of the embryo, the Tb-HoBiO3 powder can better promote the uniform transformation of the block grain boundary phase to a strip shape and wrap around the main phase of the crystal grain. It can not only isolate the main phase crystal grain from the local stray field in the magnet, but also significantly improve the demagnetization resistance of the regenerated Nd-Fe-B magnet and the coercive force. Moreover, it can effectively prevent the main phase crystal grain from falling off, improve the density of the regenerated Nd-Fe-B magnet, reduce micro defects, and significantly improve its corrosion resistance.

[0050] S4: Low-temperature supergravity sintering and tempering treatment of the embryo

[0051] S4.1: The embryo prepared in step S3.2 is placed in a specially designed high-temperature supergravity centrifugal device. After heating to 200℃ at a heating rate of 10℃ / min and holding for 8 minutes, the residual lubricant and antioxidant organic solvents in the embryo are decomposed in a low-temperature environment. Then the rotating device is started, the rotating speed is adjusted to 1200rpm / min, and the temperature is raised to 400℃. The rotating and holding treatment is carried out for 45 minutes. The centrifugal force created by the rotating and holding treatment creates a supergravity environment, and the decomposed organic solvents are removed from the embryo in the supergravity environment, effectively improving the removal efficiency of the organic solvents and preventing the organic solvents from affecting the density of the embryo in the subsequent high-temperature sintering, thereby affecting the performance of the regenerated Nd-Fe-B magnet. A decontaminated embryo is obtained.

[0052] S4.2: The decompounded embryo is taken out and quickly placed in a vacuum sintering furnace, the temperature in the vacuum sintering furnace is adjusted to 600℃, the vacuum degree is 10 -3 Pa, and then heated to 1050℃ for vacuum sintering for 4 hours, to obtain a sintered magnet;

[0053] S4.3: The temperature of the vacuum sintering furnace is adjusted, and the sintered magnet is subjected to secondary tempering treatment, the first tempering treatment parameter is 915℃ for 2 hours, and the second tempering parameter is 450℃ for 3 hours, to obtain a regenerated neodymium-iron-boron magnet.

[0054] Example 2

[0055] A process for recycling a waste neodymium-iron-boron to regenerate a neodymium-iron-boron magnet, as shown in the figure, comprises the following steps: Figure 1

[0056] S1: Preparation of Tb-HoBiO3 powder

[0057] S1.1: 3 parts by weight of bismuth and 3 parts by weight of holmium hydroxide are immersed in an ethylamine solution with a concentration of 0.6 mol / L, the rotating speed of the magnetic stirrer is adjusted to 180 rpm, the magnetic stirring is continuously carried out, then 5.5 mol / L of sodium hydroxide solution is added until the concentration of sodium hydroxide is 1.5 mol / L, to obtain a mixed solution;

[0058] S1.2: The mixed solution is placed in a reaction kettle, 10 parts by weight of cyclohexylamine and 12 parts by weight of oleic acid are added, then the reaction kettle is heated to a temperature of 200℃, and after being kept at this temperature for 10 hours, it is cooled to room temperature to obtain a mixture;

[0059] S1.3: 2 parts by weight of TbCl3 and 3 parts by weight of ethanol solution with a concentration of 0.08 mol / L are added to the mixture prepared in step S1.2, after stirring for 20 minutes, it is heated at a temperature of 200℃ for 16 hours, then it is subjected to centrifugal separation in a high-speed centrifuge, and suction filtration is carried out to obtain the lowermost suspension, which is subjected to freeze-drying and crushing and grinding in sequence, to obtain Tb-HoBiO3 powder.

[0060] S2: Pretreatment of waste neodymium-iron-boron

[0061] S2.1: Sodium polyacrylate and a phosphoric acid solution with a mass fraction of 8% are mixed in a container at a mass ratio of 1:20, the sodium polyacrylate can improve the dispersibility of silicon carbide powder in the phosphoric acid solution, after being stirred uniformly, silicon carbide powder is added, so that the particle concentration of the silicon carbide powder in the phosphoric acid solution is 10%, the small particle silicon carbide powder can finely polish the surface of the waste neodymium-iron-boron, then the stirring speed of the high-speed stirrer is adjusted to 1200 rpm, and stirring is carried out for 12 minutes, to obtain a phosphoric acid abrasive;

[0062] ​S2.2: 10 parts by weight of waste Nd-Fe-B is kept at a temperature of 310°C for 1 hour, cooled to room temperature, and then soaked in deionized water at 50°C. After soaking for 25 minutes, it is taken out and placed in a 10% concentration sodium carbonate solution, heated to 60°C, stirred for 20 minutes, then rinsed with clean water until the rinse water PH is close to neutral, obtaining the alkali washed waste Nd-Fe-B. The phosphoric acid abrasive is heated to 40°C, and then sprayed in a sealed glove box using a ceramic high-pressure water gun. The spraying speed is adjusted to 80 m / s, and the alkali washed waste Nd-Fe-B is washed and polished all around. The polishing time is 8 minutes, which improves the polishing efficiency of the waste Nd-Fe-B, effectively removes impurities on the surface of the waste Nd-Fe-B, prevents affecting the performance of the regenerated Nd-Fe-B magnet prepared subsequently, and obtains the pretreated waste Nd-Fe-B.

[0063] S3: Preparation of the embryo from the pretreated waste Nd-Fe-B

[0064] S3.1: The pretreated waste Nd-Fe-B obtained in step S2.2 is crushed in a crusher to a particle size of less than 2 cm, obtaining a coarse material. The content of each component in the coarse material is measured in a spectral analysis instrument. In the coarse material, the mass fraction of PrNd is 35wt%, erbium is 6wt%, boron is 1.2wt%, zirconium is 1.0wt%, cobalt is 1.2wt%, and the remainder is Fe. Then vacuum induction melting method is used for melting and refining, and then water-cooled roller is used for tape casting, obtaining alloy cast sheet;

[0065] S3.2: The alloy cast sheet is crushed and placed in a hydrogen crushing furnace for hydrogen crushing, so that the particle size reaches 50μm. Then it is placed in a nitrogen gas flow mill for crushing to a particle size of 5μm, obtaining magnetic powder. In a glove box filled with nitrogen, the magnetic powder, the Tb-HoBiO3 powder obtained in step S1.3, oxidized polyethylene wax, and antioxidant are loaded into a mixing tank at a mass ratio of 100:1.2:0.08:1.2. The antioxidant is prepared from dibutylhydroxytoluene and vitamin E at a mass ratio of 1:1.2. Mix for 10 minutes, then add to the press, and adjust the pressing density to 5g / cm 2 Under the protection of nitrogen atmosphere, the orientation forming of 2T magnetic field is carried out, and then the secondary pressing is carried out through the isostatic press with a pressure of 300Mpa, obtaining the embryo. During the sintering process of the embryo, the Tb-HoBiO3 powder can better promote the uniform transformation of the blocky grain boundary phase to strip shape and wrap around the main phase of the grain, which can isolate the main phase grain from the local stray field in the magnet, significantly improve the demagnetization resistance of the regenerated Nd-Fe-B magnet, improve the coercive force, and effectively avoid the main phase grain from falling off, so that the density of the regenerated Nd-Fe-B magnet is improved, the micro defects are reduced, and the corrosion resistance is significantly improved.

[0066] S4: Low-temperature supergravity sintering and tempering treatment of the embryo

[0067] S4.1: The preform prepared in step S3.2 is placed in a specially designed high-temperature resistant centrifugal centrifuge and heated to 200°C at a heating rate of 10°C / min, and then held at that temperature for 8 minutes. Under the low-temperature environment, the residual lubricant and antioxidants and other organic solvents in the preform decompose first. Then, the rotating device is started, the speed is adjusted to 1200 rpm / min and the temperature is raised to 400°C. The rotating and holding treatment is carried out for 45 minutes. The centrifugal force generated creates a supergravity environment. The decomposed organic solvents are removed from the preform under the supergravity environment, which effectively improves the removal efficiency of organic solvents and prevents organic solvents from affecting the compactness of the preform in the subsequent high-temperature sintering, thereby affecting the performance of the regenerated NdFeB magnets, and thus obtaining a de-impurified preform.

[0068] S4.2: Remove the impurity-free preform and quickly place it in a vacuum sintering furnace. Adjust the temperature in the vacuum sintering furnace to 600℃ and the vacuum degree to 10. -3 Pa, hold at that temperature for 1 hour, and then raise the temperature to 1050℃ for vacuum sintering for 4 hours to obtain the sintered magnet;

[0069] S4.3: Adjust the temperature of the vacuum sintering furnace and perform a second tempering treatment on the sintered magnet. The first tempering treatment parameters are 915℃ and held for 2 hours, and the second tempering parameters are 450℃ and held for 3 hours to obtain a regenerated NdFeB magnet.

[0070] Example 3

[0071] A process for recycling and regenerating NdFeB magnets from waste NdFeB magnets, such as... Figure 1 As shown, it includes the following steps:

[0072] S1: Preparation of Tb-HoBiO3 powder

[0073] S1.1: Immerse 2 parts by weight of bismuth and 2 parts by weight of holmium hydroxide in a 0.5 mol / L ethylamine solution, adjust the speed of the magnetic stirrer to 200 rpm, and continue to stir magnetically. Then add 5 mol / L sodium hydroxide solution until the sodium hydroxide concentration is 1 mol / L to obtain a mixed solution.

[0074] S1.2: Place the mixed solution in a reaction vessel, add 8 parts by weight of cyclohexylamine and 10 parts by weight of oleic acid, then heat the reaction vessel to 220°C, keep it at that temperature for 12 hours, and then cool it to room temperature to obtain the mixture;

[0075] S1.3: 1 part by weight of TbCl3 and 2 parts by weight of an ethanol solution with a concentration of 0.06 mol / L were added to the mixture prepared in step S1.2, and after stirring for 25 minutes, the mixture was heated at a temperature of 220°C for 18 hours, and then centrifuged in a high-speed centrifuge, and the lowermost suspension was obtained by suction filtration, and the suspension was subjected to freeze-drying and crushing and grinding in sequence to obtain Tb-HoBiO3 powder.

[0076] S2: Pretreatment of waste neodymium-iron-boron

[0077] S2.1: Sodium polyacrylate and a phosphoric acid solution with a mass fraction of 6% were mixed in a container at a mass ratio of 1:18, the sodium polyacrylate could improve the dispersibility of the silicon carbide powder in the phosphoric acid solution, and after uniform stirring, silicon carbide powder was added, so that the particle concentration of the silicon carbide powder in the phosphoric acid solution was 8%, and the fine silicon carbide powder could finely polish the surface of the waste neodymium-iron-boron, and then the stirring speed of the high-speed stirrer was adjusted to 1500 rpm, and stirring was performed for 15 minutes to obtain a phosphoric acid abrasive;

[0078] S2.2: 8 parts by weight of waste neodymium-iron-boron were placed at a temperature of 310°C for 1.5 hours, cooled to room temperature, and then soaked in deionized water at 60°C for 30 minutes, taken out, and placed in a 5% sodium bicarbonate solution, heated to 80°C, stirred for 30 minutes, and then washed with clean water until the washing liquid was close to neutral, to obtain alkali-washed waste neodymium-iron-boron, the phosphoric acid abrasive was heated to 50°C, and then a ceramic high-pressure water gun was used to spray the phosphoric acid abrasive in a sealed glove box, the spraying speed was adjusted to 100 m / s, the alkali-washed waste neodymium-iron-boron was washed and polished in all directions, and the polishing time was 10 minutes, which improved the polishing efficiency of the waste neodymium-iron-boron, effectively removed impurities on the surface of the waste neodymium-iron-boron, and prevented the performance of the regenerated neodymium-iron-boron magnet prepared subsequently from being affected, to obtain pretreated waste neodymium-iron-boron.

[0079] S3: Preparation of a blank body from the pretreated waste neodymium-iron-boron

[0080] S3.1: The pretreated waste neodymium-iron-boron prepared in step S2.2 was crushed to a particle size of less than 2 cm in a crusher to obtain coarse material, the coarse material was placed in a spectral analysis instrument, and the content of each component in the coarse material was measured, PrNd was added to the coarse material at a mass fraction of 30 wt%, erbium was added at a mass fraction of 2 wt%, boron was added at a mass fraction of 0.8 wt%, zirconium was added at a mass fraction of 0.5 wt%, cobalt was added at a mass fraction of 0.3 wt%, and the balance was Fe, then vacuum induction melting was performed for melting and refining, and then the alloy strip was obtained by tape casting with a water-cooled roller;

[0081] S3.2: The alloy ingot is broken and put into a hydrogen breaking furnace for hydrogen breaking to make the particle size reach 200 μm, and then put into a nitrogen gas stream grinder for breaking to a particle size of 10 μm to obtain magnetic powder. The magnetic powder, the Tb-HoBiO3 powder prepared in step S1.3, oxidized polyethylene wax and antioxidant prepared in a mass ratio of 100:0.8:0.06:1 are put into a mixing tank in a nitrogen-filled glove box, wherein the antioxidant is prepared from dibutylhydroxytoluene and vitamin E in a mass ratio of 1:1, mixed for 15 minutes, and then added into a press to adjust the pressing density to 6 g / cm 2 , and the Tb-HoBiO3 powder can better promote the uniform transformation of the block grain boundary phase to a strip shape and wrapping around the main phase of the crystal grain in the sintering process of the blank, which can isolate the main phase crystal grain from the local stray field in the magnet, significantly improve the demagnetization resistance of the recycled neodymium-iron-boron magnet, improve the coercive force, and effectively avoid the main phase crystal grain from falling off, so that the density of the recycled neodymium-iron-boron magnet is improved, the micro defects are reduced, and the corrosion resistance is significantly improved.

[0082] S4: Low-temperature supergravity sintering and tempering treatment of the blank

[0083] S4.1: The blank prepared in step S3.2 is put into a specially-made high-temperature supergravity centrifugal device, heated to 220℃ at a heating rate of 15℃ / min and kept for 10 minutes. In a low-temperature environment, the residual lubricant and antioxidant organic solvents in the blank are first decomposed, then the rotating device is started, the rotating speed is adjusted to 1500 rpm / min, and the temperature is raised to 450℃, and the rotating and keeping treatment is performed for 50 minutes. The centrifugal force generated creates a supergravity environment, and the decomposed organic solvents are removed from the blank in the supergravity environment, effectively improving the removal efficiency of the organic solvents and preventing the organic solvents from affecting the density of the blank and the performance of the recycled neodymium-iron-boron magnet in the subsequent high-temperature sintering, to obtain a decontaminated blank.

[0084] S4.2: The decontaminated blank is taken out and quickly placed in a vacuum sintering furnace, the temperature of the vacuum sintering furnace is adjusted to 800℃, the vacuum degree is adjusted to 5×10 -3 Pa, and kept for 1.5 hours, and then the temperature is raised to 1100℃ for vacuum sintering for 5 hours to obtain a sintered magnet.

[0085] S4.3: The temperature of the vacuum sintering furnace is adjusted for the second tempering treatment of the sintered magnet, the first tempering treatment parameters are 930℃ for 2.5 hours, and the second tempering parameters are 460℃ for 4 hours to obtain a recycled neodymium-iron-boron magnet.

[0086] Comparative Example 1

[0087] Compared with Example 1, the difference of Comparative Example 1 is that Comparative Example 1 removes step S1, and does not load the Tb-HoBiO3 powder into the mixing tank in step S3.2, and the remaining steps are the same as Example 1, and the prepared recycled neodymium-iron-boron magnet is denoted as Comparative Example 1.

[0088] Comparative Example 2

[0089] Compared with Example 1, the difference of Comparative Example 2 is that the rotating device is not started in S4.1 in Comparative Example 2, and the remaining steps are the same as Example 1, and the prepared recycled neodymium-iron-boron magnet is denoted as Comparative Example 2.

[0090] Comparative Example 3

[0091] Compared with Example 1, the difference of Comparative Example 3 is that Comparative Example 3 removes the process of washing and polishing the alkali-washed waste neodymium-iron-boron with phosphoric acid abrasive in step S2.2, and the alkali-washed waste neodymium-iron-boron is pickled by conventional operation, specifically, the alkali-washed waste neodymium-iron-boron is soaked in a phosphoric acid solution with a concentration of 6% for 55-60 minutes, and the remaining steps are the same as Example 1, and the prepared recycled neodymium-iron-boron magnet is denoted as Comparative Example 3.

[0092] The recycled neodymium-iron-boron magnets prepared in the examples, Comparative Example 1, Comparative Example 2 and Comparative Example 3 are respectively taken, and the NIM-62000 permanent magnet material magnetic property precision measuring instrument system is used to record the coercive force of the magnet by magnetizing the recycled neodymium-iron-boron magnet at the same time of static magnetic field scanning, and the higher the coercive force, the higher the comprehensive magnetic performance of the magnet. The test is carried out three times, the data is recorded and a table is made, as shown in Table 1, it can be seen that the coercive force of the recycled neodymium-iron-boron magnet prepared in the examples > the coercive force of Comparative Example 3 > the coercive force of Comparative Example 2 > the coercive force of Comparative Example 1, which can prove that adding Tb-HoBiO3 powder in the magnetic powder can significantly improve the magnetic performance of the recycled neodymium-iron-boron magnet, at the same time, it can prove that sintering the blank in the hypergravity environment can better prevent the influence of organic solvents on the magnetic performance of the recycled neodymium-iron-boron magnet, so that the magnetic performance is improved, and it can also prove that washing and polishing the alkali-washed waste neodymium-iron-boron with phosphoric acid abrasive can effectively remove the impurities on the surface of the waste neodymium-iron-boron, so as to improve the magnetic performance of the recycled neodymium-iron-boron magnet.

[0093] Coercivity / kOe First time Second time Third time Example 1 23.56 23.91 24.21 Example 2 24.72 24.63 24.52 Example 3 23.89 24.31 24.48 Comparative Example 1 17.34 17.11 17.46 Comparative Example 2 22.68 22.81 23.87 Comparative Example 3 23.31 23.17 23.56

[0094] Table 1

[0095] Take 100g of the recycled Nd-Fe-B magnets prepared in Example 1 and the comparative example 1 respectively, which have the same shape, and put them in a NaCl aqueous solution with a mass fraction of 3.5wt%. Take them out and weigh them at 1 day, 7 days and 14 days respectively, record the data and make a table as shown in Table 2. Analysis shows that the corrosion resistance of the recycled Nd-Fe-B magnets prepared in the example is much higher than that of the comparative example 1, which can prove that the addition of Tb-HoBiO3 powder in the magnetic powder can significantly improve the corrosion resistance of the recycled Nd-Fe-B magnets.

[0096] Mass / g 1 day 7 days 14 days Example 1 99.7 94.3 89.6 Comparative Example 1 99.1 91.5 80.2

[0097] Table 2

[0098] The above examples are only illustrative of the principles and effects of the present application, and are not intended to limit the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed by the present application should be covered by the claims of the present application.

Claims

1. A process for recycling and regenerating NdFeB magnets from waste NdFeB magnets, characterized in that, Includes the following steps: S1: Preparation of Tb-HoBiO3 powder Bismuth and holmium hydroxide were immersed in ethylamine solution. Sodium hydroxide solution was added while magnetic stirring. Then cyclohexylamine and oleic acid were added. After heating and reacting, the mixture was cooled. Then TbCl3 and ethanol solution were added. After heating and reacting again, the mixture was centrifuged and filtered to obtain a suspension. The suspension was freeze-dried and crushed and ground to obtain Tb-HoBiO3 powder. S2: Pretreatment of waste NdFeB Sodium polyacrylate and phosphoric acid solution are mixed evenly and then silicon carbide powder is added and stirred to obtain phosphoric acid abrasive. Waste NdFeB is preheated and then alkaline washed, and then washed and polished in all directions with phosphoric acid abrasive to obtain pretreated waste NdFeB. S3: Pretreatment of waste NdFeB to prepare preforms After pre-treated waste NdFeB is crushed, its composition is measured. Rare earth elements and Fe are added, and then it is melted and spun to obtain alloy castings. The alloy castings are crushed and then subjected to hydrogen crushing and air jet milling to obtain magnetic powder. The magnetic powder, Tb-HoBiO3 powder, lubricant and antioxidant are mixed evenly in a nitrogen atmosphere, and then oriented and isostatically pressed to obtain a preform. S4: Low-temperature ultragravity sintering for impurity removal and tempering of the preform The preform is placed in a specially designed high-temperature resistant centrifugal centrifuge for low-temperature high-gravity sintering and impurity removal, and then subjected to a second heating sintering to obtain a sintered magnet. The temperature of the vacuum sintering furnace is then adjusted for a second tempering treatment to obtain a regenerated NdFeB magnet.

2. The process for recycling and regenerating NdFeB magnets from waste NdFeB magnets according to claim 1, characterized in that, The preparation of step S1Tb-HoBiO3 powder includes the following steps: S1.1: Immerse 2-3 parts by weight of bismuth and 2-3 parts by weight of holmium hydroxide in ethylamine solution, adjust the speed of magnetic stirrer to 180-200 rpm, and continue magnetic stirring. Then add 5-5.5 mol / L sodium hydroxide solution until the sodium hydroxide concentration is 1-1.5 mol / L to obtain a mixed solution. S1.2: Place the mixed solution in a reaction vessel, add 8-10 parts by weight of cyclohexylamine and 10-12 parts by weight of oleic acid, then heat the reaction vessel to a temperature of 200-220℃, keep it at that temperature for 10-12 hours, and then cool it to room temperature to obtain the mixture; S1.3: Add 1-2 parts by weight of TbCl3 and 2-3 parts by weight of ethanol solution to the mixture obtained in step S1.2, stir for 20-25 minutes, heat at 200-220℃ for 16-18 hours, then centrifuge in a high-speed centrifuge, filter to obtain the bottom suspension, freeze-dry and grind the suspension to obtain Tb-HoBiO3 powder.

3. The process for recycling and regenerating NdFeB magnets from waste NdFeB magnets according to claim 1, characterized in that, Step S2, the pretreatment of waste NdFeB, includes the following steps: S2.1: Mix sodium polyacrylate and phosphoric acid solution in a mass ratio of 1:(18-20) in a container, stir evenly, add silicon carbide powder, so that the particle concentration of silicon carbide powder in phosphoric acid solution is 8-10%, then adjust the stirring speed of the high-speed stirrer to 1200-1500 rpm, stir for 12-15 minutes to obtain phosphoric acid abrasive. S2.2: Place 8-10 parts by weight of waste NdFeB at 310-350℃ for 1-1.5 hours, cool to room temperature, and then soak in deionized water at 50-60℃ for 25-30 minutes. After soaking, remove and place in an alkaline cleaning solution, heat to 60-80℃, stir for 20-30 minutes, and then rinse with clean water until the pH of the rinsing solution is close to neutral to obtain alkaline-washed waste NdFeB. Heat the phosphoric acid abrasive to 40-50℃, and then spray the phosphoric acid abrasive with a ceramic high-pressure water gun in a sealed glove box. Adjust the spraying speed to 80-100m / s to thoroughly rinse and grind the alkaline-washed waste NdFeB for 8-10 minutes to obtain pretreated waste NdFeB.

4. The process for recycling and regenerating NdFeB magnets from waste NdFeB magnets according to claim 1, characterized in that, Step S3 involves pre-treating waste NdFeB to prepare the preform, including the following steps: S3.1: The pretreated waste NdFeB obtained in step S2.2 is crushed in a crusher until the particle size is less than 2cm to obtain coarse material. The coarse material is placed in a spectrometer to measure the content of each component in the coarse material. The mass fraction of PrNd is 25-35wt%, Erbium 2-6wt%, Boron 0.8-1.2wt%, Zirconium 0.5-1.0wt%, Cobalt 0.3-1.2wt%, and the balance is Fe additive. Then, the coarse material is melted and refined by vacuum induction melting. Finally, it is spun through a water-cooled roller to obtain alloy castings. S3.2: After crushing the alloy casting, place it in a hydrogen crushing furnace for hydrogen crushing to achieve a particle size of 50-200 μm. Then, place it in a nitrogen-filled air jet mill for further crushing to a particle size of 5-10 μm to obtain magnetic powder. In a nitrogen-filled glove box, add the magnetic powder, Tb-HoBiO3 powder obtained in step S1.3, lubricant, and antioxidant to a mixing tank at a mass ratio of 100:(0.8-1.2):(0.06-0.08):(1-1.2). Mix for 10-15 minutes, then add to a press and adjust the pressing density to 5-6 g / cm³. 2 Orientation is carried out under a nitrogen protective atmosphere using a 2T magnetic field, followed by secondary pressing using an isostatic press at a pressure of 300-350 MPa to obtain the preform.

5. The process for recycling and regenerating NdFeB magnets from waste NdFeB magnets according to claim 1, characterized in that, Step S4, the low-temperature ultragravity sintering, impurity removal, and tempering treatment of the preform, includes the following steps: S4.1: Place the embryo prepared in step S3.2 into a specially designed high-temperature resistant centrifuge and heat it to 200-220℃ at a heating rate of 10-15℃ / min. Then keep it at that temperature for 8-10 minutes. Then start the rotating device, adjust the rotation speed to 1200-1500 rpm / min and heat it to 400-450℃. Rotate and keep it at that temperature for 45-50 minutes to obtain the impurity-free embryo. S4.2: Remove the impurity-free preform and quickly place it in a vacuum sintering furnace. Adjust the temperature in the vacuum sintering furnace to 600-800℃ and the vacuum degree to 10. -3 -5×10 -3 Pa, hold at that temperature for 1-1.5 hours, then raise the temperature to 1050-1100℃ and vacuum sinter for 4-5 hours to obtain the sintered magnet; S4.3: Adjust the temperature of the vacuum sintering furnace and perform a second tempering treatment on the sintered magnet. The first tempering treatment parameters are 915-930℃ and held for 2-2.5 hours. The second tempering parameters are 450-460℃ and held for 3-4 hours to obtain regenerated NdFeB magnets.

6. The process for recycling and regenerating NdFeB magnets from waste NdFeB magnets according to claim 2, characterized in that, The concentrations of the ethylamine solution and the ethanol solution in steps S1.1 and S1.3 are 0.5-0.6 mol / L and 0.06-0.08 mol / L, respectively.

7. The process for recycling and regenerating NdFeB magnets from waste NdFeB magnets according to claim 3, characterized in that, The phosphoric acid solution in step S2.1 has a mass fraction of 6-8%.

8. The process for recycling and regenerating NdFeB magnets from waste NdFeB magnets according to claim 3, characterized in that, The alkaline cleaning solution in step S2.2 is sodium hydroxide, sodium carbonate, or sodium bicarbonate with a concentration of 5-10%.

9. The process for recycling and regenerating NdFeB magnets from waste NdFeB magnets according to claim 4, characterized in that, The lubricant in step S3.2 is oxidized polyethylene wax, and the antioxidant is prepared by mixing butylated hydroxytoluene and vitamin E in a mass ratio of 1:(1-1.2).

10. The process for recycling and regenerating NdFeB magnets from waste NdFeB magnets according to claim 5, characterized in that, In step S4.1, the specially designed high-temperature resistant centrifugal device consists of a heating tank and a counterweight tank connected to the central rotating shaft via a support arm. The heating tank is equipped with a resistance heating coil and a thermocouple, and the temperature inside the heating tank can be adjusted by an external temperature control box.

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