A regenerated magnetic powder, a method for preparing the regenerated magnetic powder by using a salinization-reduction diffusion method, and an application thereof

Abstract

The application provides a regenerated magnetic powder and a method and application of preparing the regenerated magnetic powder by a salinization-reduction diffusion method, and the method comprises the following steps: (1) mixing neodymium iron boron sludge and a solid salt agent, and performing selective salinization roasting to obtain a roasting product; (2) mixing the roasting product and a reducing agent, and performing a reduction diffusion reaction to obtain the regenerated magnetic powder; wherein the solid salt agent comprises sulfidation salt and / or nitration salt. The neodymium iron boron sludge is recycled by the salinization-reduction diffusion method, and the regenerated magnetic powder with low oxygen content and low impurity content can be obtained and can be used for preparing high-performance regenerated sintered neodymium iron boron magnets. The method is green and efficient, can effectively improve the calcium removal efficiency and the intrinsic magnetic properties of the regenerated rare earth permanent magnet material, can reduce the cost, and realizes high-value recycling and reuse.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of recycling and reusing rare earth permanent magnet waste, and particularly relates to a regenerated magnetic powder and a method for preparing the regenerated magnetic powder by using salinization-reduction diffusion and application thereof. BACKGROUND

[0002] Currently, the industrialized recycling method of neodymium iron boron sludge waste mainly separates and extracts rare earth elements in the waste through traditional hydrometallurgy process, mainly including steps of oxidation roasting, acid leaching, neutralization and impurity removal, extraction separation, oxalate precipitation and the like. However, if neodymium iron boron magnetic powder is to be prepared, a series of links such as molten salt electrolysis, rapid solidification smelting, hydrogen explosion and jet mill need to be further undergone, and the process is long and the energy consumption is high. The high pollution problem brought by the molten salt electrolysis process is also difficult to avoid. In addition, with the increasingly stringent environmental regulations at home and abroad, the environmental cost of rare earth ore mining is increasing. Therefore, researchers have carried out research on new processes and new methods for green and efficient recycling and reusing of neodymium iron boron sludge waste.

[0003] For example, CN109852809A discloses a method for recycling neodymium iron boron alloy powder from neodymium iron boron sludge waste through a short process, which comprises: a sludge waste drying step: drying the neodymium iron boron sludge waste to obtain neodymium iron boron sludge; a reduction diffusion step: adding FeB, neodymium and / or a neodymium-containing compound, and Ca to the neodymium iron boron sludge, carrying out hydrogen reduction, and then carrying out calcium reduction diffusion reaction to obtain a mixture of neodymium iron boron alloy powder and calcium oxide. CN113652538B discloses a method for separating and recycling rare earth and iron from neodymium iron boron sludge, which adopts a detergent to wash and remove the oil sludge in the neodymium iron boron sludge, and then carries out oxidation roasting on the oil-removed neodymium iron boron after washing to obtain neodymium iron boron calcine, and then leaches the neodymium iron boron calcine. CN103882234B discloses a method for preparing regenerated neodymium iron boron magnetic powder from neodymium iron boron sludge, and the process flow is: neodymium iron boron sludge-distillation separation-common precipitation to recover all valuable elements-mixed oxide-addition of metal calcium and the like according to the proportion-mixed reaction product-high temperature thermal reduction diffusion-removal of calcium oxide in the product-vacuum drying-regenerated neodymium iron boron magnetic powder. CN115961138B discloses a method for preparing regenerated magnetic powder by recycling neodymium iron boron sludge waste through chlorination-reduction diffusion combination, which converts the by-product CaO of the reduction diffusion into CaCl2 by using chlorination roasting technology, thereby improving the impurity removal efficiency of the regenerated magnetic powder. However, in the reaction process, the solid chlorinating agent reacts with the sludge waste to produce NdOCl, FeOCl and other water-insoluble oxychloride by-products, which on the one hand hinders the complete removal of impurities due to the inclusion of the by-products, and on the other hand causes the loss of main components such as rare earth and iron components in the magnetic separation process for washing and removing calcium, thereby reducing the yield of the regenerated magnetic powder. In addition, the decomposition temperature of solid chlorinating agents such as NH4Cl is very low, and the generated HCl gas has a certain negative impact on the equipment and environment.

[0004] The above method has improved to some extent, but still has problems and shortcomings such as large calcium usage, high reaction temperature, high O content in regenerated neodymium-iron-boron magnetic powder, incomplete removal of impurities Ca, further improvement of the recovery rate of regenerated neodymium-iron-boron magnetic powder, and non-environmentally friendly process. In addition, the residual amount of Ca, O and other impurity elements in the regenerated magnetic powder is large, which leads to low remanence of the regenerated sintered magnet, limiting its application in composite regenerated sintered neodymium-iron-boron magnets.

[0005] Therefore, it is a technical problem to be solved to develop a green, efficient and high-value recycling technology to prepare a method for preparing a low-oxygen and low-impurity content regenerated magnetic powder. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a regenerated magnetic powder and a method and application of preparing a regenerated magnetic powder by a salinization-reduction diffusion method. The present application recovers neodymium-iron-boron sludge by a salinization-reduction diffusion method, and obtains a low-oxygen and low-impurity content regenerated magnetic powder which can be used for the preparation of composite regenerated sintered neodymium-iron-boron magnets. This method is green and efficient, can effectively improve the calcium removal efficiency and the intrinsic magnetic properties of regenerated rare earth permanent magnet materials, and can also reduce the cost and realize high-value recycling.

[0007] To achieve the purpose of the present application, the following technical solutions are adopted:

[0008] In a first aspect, the present application provides a method for preparing a regenerated magnetic powder by a salinization-reduction diffusion method, the method comprising the following steps:

[0009] (1) mixing neodymium-iron-boron sludge and a solid salt agent, and performing selective salinization roasting to obtain a roasting product;

[0010] (2) mixing the roasting product and a reducing agent, and performing a reduction diffusion reaction to obtain the regenerated magnetic powder;

[0011] The solid salt agent comprises a sulfated salt and / or a nitrated salt.

[0012] The present application recovers neodymium-iron-boron sludge by a salinization-reduction diffusion method, i.e. by selective salinization roasting to selectively convert rare earth elements in the sludge into rare earth salts, thereby converting the subsequent calcium reduction diffusion by-product from CaO which is difficult to dissolve in water and insoluble in alcohol into CaSO4 which has a larger solubility, or Ca(NO3)2 which is easily soluble in water and alcohol, and thus obtaining a low-oxygen and low-impurity content regenerated magnetic powder which can be used for the preparation of composite regenerated sintered neodymium-iron-boron magnets. This method is green and efficient, can effectively improve the calcium removal efficiency and the intrinsic magnetic properties of regenerated rare earth permanent magnet materials, and can also reduce the cost and realize high-value recycling.

[0013] It should be noted that the sulfated salt or nitrated salt used in the present application can play a fluxing role, and can reduce the reduction diffusion reaction temperature and the amount of reducing agent, thereby reducing the production cost.

[0014] It should be noted that, compared with chloride salt, the sulfated salt or nitrated salt used in the present application can avoid the generation of non-magnetic oxychloride such as FeOCl and NdOCl, thereby greatly avoiding the loss of rare earth and iron and other main components in the magnetic separation step in the washing and impurity removal process, improving the recovery rate of rare earth and other valuable elements in the neodymium iron boron waste, and improving the synthesis rate and recovery rate of the regenerated neodymium iron boron magnetic powder.

[0015] As a preferred technical solution of the present application, the sulfated salt in step (1) includes any one or a combination of at least two of (NH4)2SO4, FeSO4, Fe2(SO4)3, Al2(SO4)3, ZnSO4, CuSO4, NiSO4 or CoSO4.

[0016] Preferably, the nitrated salt includes any one or a combination of at least two of NH4NO3, Fe(NO3)2, Fe(NO3)3, Al(NO3)3, Zn(NO3)2, Cu(NO3)2, Ni(NO3)2 or Co(NO3)2.

[0017] Preferably, the solid salt agent in step (1) includes sulfated salt and nitrated salt, and the mass ratio of the sulfated salt to the nitrated salt is (1-3):(3-1), for example, which can be 3:1, 2:1, 1:1, 1:2 or 1:3, etc.

[0018] Preferably, based on the mass of the rare earth converted into the corresponding rare earth salt in the neodymium iron boron sludge, the neodymium iron boron sludge is mixed with the solid salt agent at 1-3 times the stoichiometric ratio, for example, which can be 1 times, 2 times or 3 times, etc.

[0019] In the present application, if the amount of the solid salt agent is too small, the selective salinization roasting reaction is incomplete, and the rare earth component is not fully converted; if the amount of the solid salt agent is too large, the metal Fe and other components in the neodymium iron boron sludge are easy to participate in the selective salinization roasting reaction, thereby causing part of the non-rare earth components to be salinized.

[0020] As a preferred technical solution of the present application, the selective salinization roasting in step (1) is carried out in a protective atmosphere.

[0021] Preferably, the protective atmosphere is an inert atmosphere or a vacuum atmosphere.

[0022] Preferably, the gas in the inert atmosphere includes nitrogen and / or argon.

[0023] Preferably, the vacuum degree of the vacuum atmosphere is <1.0x10-3 Pa, for example, can be 0.8*10 -3 Pa, 0.5*10 - 3 Pa, 0.3*10 -3 Pa, 1*10 -4 Pa, or 0.5*10 -4 Pa, etc.

[0024] Preferably, the temperature of the selective salting roasting in step (1) is 100-750℃, for example, can be 100℃, 200℃, 300℃, 400℃, 500℃, 600℃, 700℃ or 750℃, etc., and the time is 1-4h, for example, can be 1h, 2h, 3h or 4h, etc.

[0025] In the present application, if the temperature of the selective salting roasting is too low, the reaction rate of the selective salting reaction is slow, and the reaction is not sufficient; if the temperature of the selective salting roasting is too high, the solid salt agent is easy to decompose or volatilize.

[0026] As a preferred technical solution of the present application, the neodymium iron boron sludge is pretreated before being mixed with the solid salt agent in step (1), and the specific steps include:

[0027] The neodymium iron boron sludge is sequentially cleaned and magnetically separated, and after drying, the purified neodymium iron boron sludge is obtained.

[0028] It should be noted that the present application does not make specific limitations on the type of cleaning solution used in the cleaning process. For example, it can be an ethanol solution, a 0.1-0.5mol / L sodium hydroxide-5% OP emulsifier mixed aqueous solution (for example, 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L or 0.5mol / L, etc.), a 0.1-0.5mol / L sodium hydroxide-5% OP emulsifier mixed ethanol solution (for example, 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L or 0.5mol / L, etc.), a 0.1-0.5mol / L hydrochloric acid-5% OP emulsifier mixed aqueous solution (for example, 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L or 0.5mol / L, etc.), or a 0.1-0.5mol / L hydrochloric acid-5% OP emulsifier mixed ethanol solution (for example, 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L or 0.5mol / L, etc.), etc., wherein 5% OP emulsifier is one type of OP series (condensate of alkyl phenol and ethylene oxide).

[0029] As a preferred technical solution of the present application, the reducing agent in step (2) includes elemental calcium and / or calcium hydride.

[0030] Preferably, the mass fraction of the reducing agent is 5-25% based on the mass of the neodymium-iron-boron slurry, for example, it can be 5%, 10%, 15%, 20%, or 25%, etc.

[0031] In the present application, if the mass fraction of the reducing agent is too small, the reaction is insufficient, and the morphology of the magnetic powder is poor; if the mass fraction of the reducing agent is too large, there are many by-products, which is not conducive to impurity removal.

[0032] Preferably, the reducing diffusion reaction in step (2) is carried out in a protective atmosphere, which is an inert atmosphere or a vacuum atmosphere.

[0033] Preferably, the gas in the inert atmosphere includes nitrogen and / or argon.

[0034] Preferably, the vacuum degree of the vacuum atmosphere is <1.0×10 -3 Pa, for example, it can be 0.8×10 -3 Pa, 0.5×10 - 3 Pa, 0.3×10 -3 Pa, 1×10 -4 Pa, or 0.5×10 -4 Pa, etc.

[0035] Preferably, the temperature of the reducing diffusion reaction in step (2) is 700-1000℃, for example, it can be 700℃, 800℃, 900℃, or 1000℃, etc.

[0036] Preferably, the time of the reducing diffusion reaction in step (2) is 1-3h, for example, it can be 1h, 1.5h, 2h, 2.5h, or 3h, etc.

[0037] As a preferred technical solution of the present application, after the reducing diffusion reaction in step (2) is completed, the obtained reaction product is further subjected to the steps of washing, magnetic separation, and drying.

[0038] It should be noted that the present application does not specifically limit the detergent used in the washing process, for example, it can be anhydrous ethanol, ethylene glycol, n-propanol, n-butanol, n-pentanol, methanol, methanol-ammonium chloride solution, methanol-ammonium nitrate, methanol-ammonium acetate, deionized water, ice deionized water, propylene glycol, or glycerol, etc.

[0039] Preferably, the solid-liquid ratio of the reaction product and the detergent used in the washing process is 1g:(10-100)mL, for example, it can be 1g:10mL, 1g:20mL, 1g:30mL, 1g:40mL, 1g:50mL, 1g:60mL, 1g:70mL, 1g:80mL, 1g:90mL or 1g:100mL, etc.

[0040] It should be noted that the solid-liquid ratio refers to the ratio of the mass of the reaction product and the volume of the detergent.

[0041] Preferably, the washing time of the washing is 10-180min, for example, it can be 10min, 30min, 50min, 70min, 90min, 120min, 150min or 180min, etc.

[0042] Preferably, the number of times of washing is 1-3 times, for example, it can be 1 time, 2 times or 3 times, etc.

[0043] As a preferred technical solution of the present application, the method comprises the following steps:

[0044] (I) Pretreatment:

[0045] The neodymium iron boron sludge is mixed with the cleaning liquid for cleaning, and then subjected to magnetic separation and drying to obtain purified neodymium iron boron sludge;

[0046] (II) Selective salinization roasting:

[0047] The purified neodymium iron boron sludge is mixed with a solid salt agent, and after selective salinization roasting at 100-750℃ in a protective atmosphere for 1-4h, a roasting product is obtained;

[0048] Among them, based on the mass of all rare earths in the neodymium iron boron sludge being converted into corresponding rare earth salts, the neodymium iron boron sludge is mixed with the solid salt agent at 1-3 times of the stoichiometric ratio, and the solid salt agent includes sulfidation salt and nitration salt in a mass ratio of (1-3):(3-1);

[0049] (III) Reduction diffusion reaction:

[0050] The roasting product is mixed with a reducing agent, and subjected to reduction diffusion reaction at 700-1000℃ in a protective atmosphere for 1-3h, and after the reaction is completed, the obtained reaction product is sequentially subjected to washing, magnetic separation and drying to obtain the regenerated magnetic powder;

[0051] Among them, based on the mass of the neodymium iron boron sludge, the mass fraction of the reducing agent is 5-25%.

[0052] In a second aspect, the present application provides a regenerated magnetic powder, which is prepared by the method as described in the first aspect.

[0053] Preferably, the oxygen content of the regenerated magnetic powder is 500-2000 ppm, for example, it can be 500 ppm, 700 ppm, 900 ppm, 1100 ppm, 1300 ppm, 1500 ppm, 1700 ppm or 1900 ppm, etc.

[0054] In a third aspect, the present application provides a regenerated sintered NdFeB magnet, which is obtained by mixing and sintering the regenerated magnetic powder and the multi-element rare earth-rich alloy powder as described in the second aspect.

[0055] In the present application, by adding the rare earth-rich alloy, the grain boundary structure can be optimized, the coercivity of the regenerated magnet can be improved, and a regenerated magnet with excellent comprehensive magnetic properties can be prepared.

[0056] The multi-element rare earth-rich alloy powder is any one of RE-M1, RE-M1-M2 or RE-M1-M2-M3, wherein RE is a rare earth element, RE includes any one or a combination of at least two of La, Ce, Pr, Nd, Dy or Tb, M1, M2 or M3 independently includes any one or a combination of at least two of Cu, Al, Ga, Fe or B.

[0057] Preferably, the multi-element rare earth-rich alloy includes any one or a combination of at least two of RE-Cu, RE-Cu-Al, RE-Cu-Al-Ga, (RE)4Fe 14 B or RE6Fe 13 Ga.

[0058] Preferably, the mass fraction of the multi-element rare earth-rich alloy powder is 1-40% based on the mass of the regenerated sintered NdFeB magnet, for example, it can be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35% or 40%, etc.

[0059] Preferably, the sintering temperature is 1020-1080℃, for example, it can be 1020℃, 1030℃, 1040℃, 1050℃, 1060℃, 1070℃ or 1080℃, etc., and the time is 2-3h, for example, it can be 2h, 2.2h, 2.4h, 2.6h, 2.8h or 3h, etc.

[0060] Preferably, before mixing and sintering the regenerated magnetic powder and the multi-element rare earth-rich alloy powder, the obtained mixture is subjected to dehydrogenation treatment.

[0061] Preferably, after mixing and sintering the regenerated magnetic powder and the multi-element rare earth-rich alloy powder, multi-stage annealing treatment is performed.

[0062] Preferably, the multi-stage annealing comprises a first-stage annealing and a second-stage annealing, the temperature of the first-stage annealing is higher than that of the second-stage annealing.

[0063] Preferably, the temperature of the first-stage annealing is 640-900℃, for example, 650℃, 700℃, 750℃, 800℃, 850℃ or 900℃, etc., and the time is 1-3h, for example, 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h or 3h, etc.

[0064] The temperature of the second-stage annealing is 420-500℃, for example, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, etc., and the time is 1-3h, for example, 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h or 3h, etc.

[0065] In a fourth aspect, the present application provides a high-performance recycled sintered Nd-Fe-B magnet, which is prepared by subjecting the recycled sintered Nd-Fe-B magnet and the diffusion source as described in the third aspect to grain boundary diffusion heat treatment.

[0066] In the present application, the grain boundary structure can be optimized by the multi-element rare earth alloy grain boundary diffusion method, the coercivity of the recycled magnet can be improved, and the recycled magnet with excellent comprehensive magnetic properties can be prepared.

[0067] Preferably, the preparation steps of the high-performance recycled sintered Nd-Fe-B magnet comprise: coating the diffusion source on the surface of the recycled sintered Nd-Fe-B magnet, and then subjecting to grain boundary diffusion heat treatment to obtain the high-performance recycled sintered Nd-Fe-B magnet.

[0068] Preferably, the diffusion source is a multi-element rare earth alloy diffusion source.

[0069] Preferably, the composition of the multi-element rare earth alloy diffusion source is HRE-FHRE-M, wherein HRE includes Dy and / or Tb, FHRE includes any one or a combination of at least two of La, Ce, Pr, Nd, Ho, Y or Sm, and M includes any one or a combination of at least two of Cu, Al, Co, Ga, Zn, Ni, Zr or Nb.

[0070] Preferably, the weight gain ratio of the heavy rare earth element HRE of the multi-element rare earth alloy diffusion source in the high-performance recycled sintered Nd-Fe-B magnet is 0.1-5wt%, for example, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 3wt%, 4wt% or 5wt%, etc.

[0071] Preferably, the grain boundary diffusion heat treatment comprises a first heat treatment, a second heat treatment and a third heat treatment in sequence, and the temperature of the third heat treatment < the temperature of the first heat treatment < the temperature of the second heat treatment.

[0072] In the present application, the temperature relationship among the first heat treatment, the second heat treatment and the third heat treatment helps to increase the diffusion depth of the diffusion source and the uniformity of the heavy rare earth element distribution by low-temperature long-time heat treatment, thereby maximizing the coercivity.

[0073] Preferably, the temperature of the first heat treatment is 630-670℃, for example, it can be 630℃, 640℃, 650℃, 660℃ or 670℃, etc., and the time is 8-48h, for example, it can be 8h, 9h, 10h, 11h, 15h, 20h, 25h, 30h, 35h, 40h or 48h, etc.

[0074] Preferably, the temperature of the second heat treatment is 850-950℃, for example, it can be 850℃, 860℃, 880℃, 900℃ or 950℃, etc., and the time is 3-4h, for example, it can be 3h, 3.2h, 3.4h, 3.6h, 3.8h or 4h, etc.

[0075] Preferably, the temperature of the third heat treatment is 400-500℃, for example, it can be 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃ or 500℃, etc., and the time is 3-4h, for example, it can be 3h, 3.2h, 3.4h, 3.6h, 3.8h or 4h, etc.

[0076] The numerical range in the present application not only includes the point values listed above, but also includes any point values between the above numerical ranges that are not listed, and the specific point values included in the range are not listed due to the length and for the sake of simplicity.

[0077] Compared with the prior art, the present application has the following beneficial effects:

[0078] (1) The present application recovers neodymium iron boron sludge by saltization-reduction diffusion method, that is, selectively converts rare earth elements in the sludge into rare earth salt by selective saltization roasting, thereby converting the by-product of subsequent calcium reduction diffusion from CaO which is difficult to dissolve in water and insoluble in alcohol into CaSO4 which has greater solubility or Ca(NO3)2 which is easily soluble in water and alcohol, and further obtaining low-oxygen and low-impurity content regenerated magnetic powder which can be used for the preparation of high-performance regenerated sintered neodymium iron boron magnets.

[0079] (2) The method provided by the application is green and efficient, can effectively improve the calcium removal efficiency and the intrinsic magnetic properties of the regenerated rare earth permanent magnet material, increases the recovery rate of valuable elements in the waste material, improves the yield of the regenerated magnetic powder, reduces the production cost, realizes high-value recycling and reuse.

[0080] (3) The application can optimize the grain boundary structure and improve the coercivity of the regenerated magnet by adding a rare earth-rich alloy or by grain boundary diffusion of a multi-element rare earth alloy, so as to prepare a regenerated magnet with excellent comprehensive magnetic properties. BRIEF DESCRIPTION OF DRAWINGS

[0081] Figure 1 ΔG of the saltization reaction of the main elements in the neodymium iron boron slurry used in the application with solid (NH4)2SO4 θ T -T graph.

[0082] Figure 2 ΔG of the reduction diffusion reaction of the selective saltization roasting product and the oxide provided by the application θ T -T graph.

[0083] Figure 3 XRD pattern of the purified neodymium iron boron slurry and the regenerated magnetic powder in Example 1 of the application.

[0084] Figure 4 Demagnetization curve of the regenerated sintered neodymium iron boron magnet in Example 1 and Example 3 of the application and demagnetization curve of the high-performance regenerated sintered neodymium iron boron magnet in Example 2 of the application. DETAILED DESCRIPTION

[0085] The technical solutions of the application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the application and should not be regarded as specific limitations on the application.

[0086] The following examples all pretreat the neodymium iron boron slurry, and the specific steps include:

[0087] The neodymium iron boron slurry is first ultrasonically cleaned with 0.5 g / L sodium hydroxide-5% OP emulsifier mixed ethanol solution for 30 min, cleaned for 3 times, then cleaned with ethanol for 2 times, and then separated by magnetic separation and vacuum dried to obtain the purified neodymium iron boron slurry.

[0088] It should be noted that the composition table of the neodymium iron boron slurry is shown in Table 1.

[0089] Table 1

[0090]

[0091] Example 1

[0092] The embodiment provides a method for preparing regenerated magnetic powder by using a salting-reduction diffusion method, and the method comprises the following steps:

[0093] (1) selective salting roasting:

[0094] 100 g of purified neodymium iron boron sludge and 82.46 g of (NH4)2SO4 are uniformly mixed, pressed under a pressure of 30 MPa, and then placed into a tube furnace for selective salting roasting in a nitrogen atmosphere at 400 ℃ for 3 h, so that a roasting product is obtained;

[0095] wherein, based on the mass of the rare earths in the neodymium iron boron sludge being completely converted into corresponding rare earth salts, the neodymium iron boron sludge and (NH4)2SO4 are mixed in a stoichiometric ratio of 2.0 times;

[0096] (2) reduction diffusion reaction:

[0097] The roasting product and 25 g of elemental calcium are mixed, pressed into a block under a pressure of 30 MPa, and then subjected to calcium reduction diffusion reaction in an argon atmosphere at 950 ℃ for 3 h; after the reaction is completed, the obtained reaction product is ground to 100 mesh, then placed into a beaker containing ice deionized water in a solid-liquid ratio of 1:100 for ultrasonic cleaning for 2 times, each time for 90 min, and then subjected to magnetic separation and vacuum drying, so that regenerated magnetic powder with Ca and O contents of 40 ppm and 1800 ppm, respectively, is obtained;

[0098] wherein, based on the mass of the neodymium iron boron sludge, the mass fraction of the reducing agent is 25%.

[0099] The embodiment further provides a regenerated sintered neodymium iron boron magnet, which is prepared by the following steps:

[0100] The above regenerated magnetic powder is uniformly mixed with 20 wt.% of Pr4Fe 14 B rich rare earth alloy powder, oriented and compression molded under a magnetic field of 1.8 T and cold isostatic pressed under a pressure of 225 MPa, subjected to dehydrogenation treatment, sintered at 1070 ℃ for 3 h, and then subjected to first-stage annealing and second-stage annealing at 900 ℃ and 500 ℃, respectively, and the annealing time is 3 h, so that a regenerated sintered neodymium iron boron magnet with residual magnetism B r = 12.3 kG, coercivity H cj = 15.5 kOe, and maximum magnetic energy product (BH) max = 36.8 MGOe is finally obtained.

[0101] Figure 3 The XRD patterns of the purified neodymium iron boron sludge and the regenerated magnetic powder in the embodiment are shown.

[0102] Embodiment 2

[0103] The embodiment provides a method for preparing regenerated magnetic powder by using a salting-reduction diffusion method, and the method comprises the following steps:

[0104] (1) selective salting roasting:

[0105] 100g of purified neodymium iron boron sludge and 61.85g of (NH4)2SO4 are uniformly mixed, briquetted under a pressure of 30MPa, and then placed into a tube furnace for selective salting roasting in a nitrogen atmosphere at 400 DEG C for 3h, so that a roasting product is obtained;

[0106] wherein, based on the mass of the rare earths in the neodymium iron boron sludge being completely converted into corresponding rare earth salts, the neodymium iron boron sludge is mixed with (NH4)2SO4 at 1.5 times of the stoichiometric ratio;

[0107] (2) reduction diffusion reaction:

[0108] The roasting product and 20g of elemental calcium are mixed, briquetted under a pressure of 30MPa, and then subjected to calcium reduction diffusion reaction in an argon atmosphere at 950 DEG C for 3h; after the reaction, the obtained reaction product is ground to 100 meshes, then placed into a beaker containing ice deionized water at a solid-liquid ratio of 1:50, and subjected to ultrasonic cleaning for 2 times, each time for 90min; then, the product is separated by magnetic separation and vacuum dried, so that regenerated magnetic powder with Ca and O contents of 20ppm and 1500ppm respectively is obtained;

[0109] wherein, based on the mass of the neodymium iron boron sludge, the mass fraction of the reducing agent is 20%.

[0110] The embodiment further provides a regenerated sintered neodymium iron boron magnet, which is prepared by the following steps:

[0111] The above regenerated magnetic powder is uniformly mixed with 30wt.% of Nd4Fe 14 B rich rare earth alloy powder, oriented and compression molded under a magnetic field of 1.8T and cold isostatic pressed under a pressure of 225MPa, dehydrogenated, sintered at 1050 DEG C for 2.5h, and then subjected to primary annealing and secondary annealing at 850 DEG C and 450 DEG C respectively, each for 3h, so that a regenerated sintered neodymium iron boron magnet with residual magnetism B r =12.7kG, coercivity H cj =15.0kOe, maximum magnetic energy product (BH) max =39.3MGOe is finally obtained.

[0112] The embodiment further provides a high-performance regenerated sintered neodymium iron boron magnet, and the preparation steps of the high-performance regenerated sintered neodymium iron boron magnet comprise:

[0113] A Nd-Dy-Cu alloy diffusion source is coated on the surface of a recycled sintered Nd-Fe-B magnet, and then a grain boundary diffusion heat treatment is sequentially performed at 650℃, 900℃ and 430℃ for 8h, 3h and 3h respectively, and a high-performance recycled sintered Nd-Fe-B magnet with a residual magnetism B r = 12.5kG, a coercivity H cj = 17.8kOe, a maximum magnetic energy product (BH) max = 38.0MGOe is obtained.

[0114] In the high-performance recycled sintered Nd-Fe-B magnet, the weight gain ratio of the heavy rare earth element HRE in the multi-element rare earth alloy diffusion source is 0.3wt%.

[0115] Embodiment 3

[0116] The embodiment provides a method for preparing a recycled magnetic powder by using a salinization-reduction diffusion method, and the method comprises the following steps:

[0117] (1) selective salinization roasting:

[0118] 100g of purified Nd-Fe-B sludge and 61.85g of (NH4)2SO4 are uniformly mixed, briquetted under a pressure of 30MPa, and then placed in a tube furnace to be subjected to selective salinization roasting at 300℃ under a vacuum atmosphere with a vacuum degree of 0.5×10 -3 Pa for 4h, and a roasting product is obtained.

[0119] In the method, the Nd-Fe-B sludge and (NH4)2SO4 are mixed in a stoichiometric ratio of 1.5 times, based on the mass of the rare earths in the Nd-Fe-B sludge being completely converted into corresponding rare earth salts.

[0120] (2) reduction diffusion reaction:

[0121] The roasting product and 15g of CaH2 are mixed and briquetted under a pressure of 30MPa, and then subjected to a calcium reduction diffusion reaction under a vacuum atmosphere with a vacuum degree of 0.5×10 -3 Pa for 3h, and the reaction temperature is 800℃, and after the reaction, the obtained reaction product is ground to 100 mesh, and then placed in a beaker containing ice deionized water in a solid-liquid ratio of 1:75 for ultrasonic cleaning for 2 times, each time for 90min, and then subjected to magnetic separation and vacuum drying, and a recycled magnetic powder with Ca and O contents of 20ppm and 1300ppm respectively is obtained.

[0122] In the method, the mass fraction of the reducing agent is 15%, based on the mass of the Nd-Fe-B sludge.

[0123] The embodiment further provides a recycled sintered Nd-Fe-B magnet, which is prepared by the following steps.

[0124] The regenerated magnetic powder was mixed with 40 wt.% of Nd4Fe 14 After the B-rich rare earth alloy powder was mixed uniformly, it was oriented and compacted under a 1.8T magnetic field and cold isostatic pressed at 225MPa, and after dehydrogenation treatment, it was sintered at 1050°C for 2.5h, and then first annealed and second annealed at 870°C and 470°C respectively, and the annealing time was 2h each time, and finally a regenerated sintered neodymium-iron-boron magnet with residual magnetism B r = 13.3kG, coercivity H cj = 14.7kOe, maximum magnetic energy product (BH) max = 42.9MGOe.

[0125] Figure 4 The demagnetization curves of the regenerated sintered neodymium-iron-boron magnets in Example 1 and Example 3, and the high-performance regenerated sintered neodymium-iron-boron magnet in Example 2 are shown.

[0126] Example 4

[0127] The difference between this example and Example 2 is that (NH4)2SO4 in step (1) is replaced by equal mass of (NH4)2SO4 and NH4NO3, and the mass ratio of the two is 1:1.

[0128] The rest of the preparation method and parameters remain the same as in Example 2.

[0129] The regenerated magnetic powder prepared in this example is a regenerated magnetic powder with Ca and O contents of 10ppm and 1000ppm respectively, and the magnetic performance parameters of the regenerated sintered neodymium-iron-boron magnet are as follows: residual magnetism B r = 13.77kG, coercivity H cj = 13.76kOe, maximum magnetic energy product (BH) max = 45.39MGOe. The magnetic performance parameters of the high-performance regenerated sintered neodymium-iron-boron magnet are as follows: residual magnetism B r = 13.65kG, coercivity H cj = 17.50kOe, maximum magnetic energy product (BH) max = 46.39MGOe

[0130] Example 5

[0131] The difference between this example and Example 1 is that the amount of (NH4)2SO4 in step (1) is adjusted so that (NH4)2SO4 is mixed with neodymium-iron-boron slurry at 0.5 times the stoichiometric ratio.

[0132] The rest of the preparation method and parameters remain the same as in Example 1.

[0133] The magnetic performance parameters of the regenerated sintered neodymium-iron-boron magnet prepared in this example are as follows: residual magnetism Br = 10.83 kG, coercivity H cj = 15.81 kOe, maximum magnetic energy product (BH) max = 26.98 MGOe.

[0134] Example 6

[0135] The difference between this example and Example 1 is that the amount of (NH4)2SO4 in step (1) is adjusted so that (NH4)2SO4 is mixed with the neodymium iron boron slurry at 4 times the stoichiometric ratio.

[0136] The rest of the preparation method and parameters remain the same as Example 1.

[0137] The magnetic performance parameters of the regenerated sintered neodymium iron boron magnet prepared in this example are as follows: remanence B r = 11.66 kG, coercivity H cj = 16.49 kOe, maximum magnetic energy product (BH) max = 31.78 MGOe.

[0138] Comparative Example 1

[0139] The difference between this comparative example and Example 1 is that (NH4)2SO4 is replaced by NH4Cl in step (1).

[0140] The rest of the preparation method and parameters remain the same as Example 1.

[0141] The magnetic performance parameters of the regenerated sintered neodymium iron boron magnet prepared in this example are as follows: remanence B r = 10.27 kG, coercivity H cj = 13.46 kOe, maximum magnetic energy product (BH) max = 24.24 MGOe.

[0142] Analysis:

[0143] Figure 1 The ΔG θ T -T diagram of the main elements in the neodymium iron boron slurry used in the present application and the solid salt agent (NH4)2SO4 undergoing salinization reaction is shown.

[0144] Figure 2 The ΔG θ T -T diagram of the main elements in the neodymium iron boron slurry used in the present application and the solid salt agent (NH4)2SO4 undergoing salinization reaction is shown.

[0145] From Example 2 and Example 4, it can be seen that using a mixture of nitrate and sulfate as solid salt agent can greatly avoid the loss of rare earth and iron and other main components, improve the recovery rate of rare earth and other valuable elements in neodymium iron boron waste, thereby improving the synthesis rate and recovery rate of the final regenerated neodymium iron boron magnetic powder.

[0146] From Example 1 and Examples 9-10, it can be seen that if the amount of solid salt agent is too small, the selective salinization roasting reaction is not complete, and the conversion of rare earth components is not sufficient, which makes the magnetic properties of the regenerated sintered neodymium iron boron magnet worse; if the amount of solid salt agent is too large, the metal Fe and other components in the neodymium iron boron slurry are easy to participate in the selective salinization roasting reaction, thereby causing part of the non-rare earth components to be salinized, which makes the magnetic properties of the regenerated sintered neodymium iron boron magnet worse.

[0147] From Example 1 and Comparative Example 1, it can be seen that compared with chloride salt, using sulfide salt is beneficial to avoid the generation of non-magnetic oxychloride such as FeOCl and NdOCl, thereby greatly reducing the loss of rare earth and iron and other main components in the magnetic separation step in the washing and impurity removal process, improving the recovery rate of rare earth and other valuable elements in neodymium iron boron waste, thereby improving the synthesis rate and recovery rate of the final regenerated neodymium iron boron magnetic powder, and avoiding impurity inclusions, improving the impurity removal efficiency.

[0148] The applicant declares that the process method of the present application is illustrated by the above examples, but the present application is not limited to the above process steps, that is, it does not mean that the present application must rely on the above process steps to be implemented. It should be understood by those skilled in the art that any improvement on the present application, equivalent replacement of the raw materials selected by the present application, addition of auxiliary ingredients, selection of specific methods, etc. fall within the scope of protection and disclosure of the present application.

Claims

1. A method for producing a regenerated magnetic powder by a salting-reduction diffusion method, characterized by, The method comprises the following steps: (1) mixing neodymium iron boron sludge and solid salt agent, and performing selective salinization roasting to obtain a roasting product; The selective salinization roasting in step (1) is performed at a temperature of 100-750 ℃ for 1-4 h; (2) mixing the roasting product and a reducing agent, and performing a reduction diffusion reaction to obtain the regenerated magnetic powder; The solid salt agent comprises any one or a combination of at least two of sulfated salts and / or nitrated salts; the sulfated salts comprise (NH4)2SO4, FeSO4, Fe2(SO4)3, Al2(SO4)3, ZnSO4, CuSO4, NiSO4 or CoSO4; the nitrated salts comprise any one or a combination of at least two of NH4NO3, Fe(NO3)2, Fe(NO3)3, Al(NO3)3, Zn(NO3)2, Cu(NO3)2, Ni(NO3)2 or Co(NO3)2; The reduction diffusion reaction in step (2) is performed at a temperature of 700-1000 ℃ for 1-3 h.

2. The method of claim 1, wherein, The solid salt agent in step (1) comprises sulfated salts and nitrated salts, and the mass ratio of the sulfated salts to the nitrated salts is (1-3):(3-1); And / or, based on the mass of the rare earth in the neodymium iron boron sludge being completely converted into corresponding rare earth salts, the neodymium iron boron sludge is mixed with the solid salt agent at 1-3 times the stoichiometric ratio.

3. The method of claim 1, wherein, The selective salinization roasting in step (1) is performed in a protective atmosphere; The protective atmosphere is an inert atmosphere or a vacuum atmosphere.

4. The method of claim 3, wherein, The gas in the inert atmosphere comprises nitrogen and / or argon; And / or, the vacuum atmosphere has a vacuum degree < 1.0 x 10 -3 Pa.

5. The method of claim 1, wherein, Before the neodymium iron boron sludge is mixed with the solid salt agent in step (1), the neodymium iron boron sludge is pretreated, and the specific steps comprise: The neodymium iron boron sludge is sequentially cleaned and magnetically separated, and then dried to obtain purified neodymium iron boron sludge.

6. The method of claim 1, wherein, The reducing agent in step (2) comprises elemental calcium and / or calcium hydride; And / or, based on the mass of the neodymium iron boron sludge, the mass fraction of the reducing agent is 5-25%; And / or, the reduction diffusion reaction in step (2) is performed in a protective atmosphere, and the protective atmosphere is an inert atmosphere or a vacuum atmosphere.

7. The method of claim 1, wherein, After the reduction diffusion reaction in step (2) is completed, the obtained reaction product is further washed, magnetically separated and dried.

8. The method of claim 1, wherein, The method comprises the following steps: (Ⅰ) pretreatment: The neodymium iron boron sludge is mixed with a cleaning liquid for cleaning, and then magnetically separated and dried to obtain purified neodymium iron boron sludge; (Ⅱ) selective salinization roasting: The purified neodymium iron boron sludge is mixed with a solid salt agent, and then selectively salinized and roasted in a protective atmosphere at 100-750 ℃ for 1-4 h to obtain a roasting product; Based on the mass of the rare earth in the neodymium iron boron sludge being completely converted into corresponding rare earth salts, the neodymium iron boron sludge is mixed with the solid salt agent at 1-3 times the stoichiometric ratio, and the solid salt agent comprises sulfated salts and nitrated salts in a mass ratio of (1-3):(3-1); (Ⅲ) reduction diffusion reaction: mixing the calcined product with a reducing agent, performing a reduction diffusion reaction in a protective atmosphere at 700-1000℃ for 1-3h, and then sequentially washing, magnetically separating and drying the obtained reaction product to obtain the regenerated magnetic powder; wherein the mass fraction of the reducing agent is 5-25% based on the mass of the neodymium-iron-boron oil slurry.

9. A regenerated magnetic powder, characterized by, The regenerated magnetic powder is prepared by the method of any one of claims 1-7. The oxygen content of the regenerated magnetic powder is 500-2000ppm.

10. A recycled sintered neodymium-iron-boron magnet, characterized in that The regenerated sintered neodymium-iron-boron magnet is prepared by mixing and sintering the regenerated magnetic powder of claim 9 and a multi-element rare earth-rich alloy powder.

11. The recycled sintered neodymium-iron-boron magnet according to claim 10, characterized in that The multi-element rare earth-rich alloy powder is any one of RE-M1, RE-M1-M2 or RE-M1-M2-M3, wherein RE is a rare earth element, RE includes any one or a combination of at least two of La, Ce, Pr, Nd, Dy or Tb, M1, M2 or M3 independently includes any one or a combination of at least two of Cu, Al, Ga, Fe or B.

12. The recycled sintered neodymium-iron-boron magnet according to claim 11, characterized in that The multi-principal rare earth alloy includes any one or a combination of at least two of RE-Cu, RE-Cu-Al, RE-Cu-Al-Ga, (RE)4Fe 14 B or RE6Fe 13 Ga. And / or, the mass fraction of the multi-element rare earth-rich alloy powder is 1-40% based on the mass of the regenerated sintered neodymium-iron-boron magnet; And / or, the sintering temperature is 1020-1080℃, and the time is 2-3h; And / or, the obtained mixture is subjected to dehydrogenation treatment before mixing and sintering the regenerated magnetic powder and the multi-element rare earth-rich alloy powder; And / or, the regenerated magnetic powder and the multi-element rare earth-rich alloy powder are subjected to multi-stage annealing treatment after mixing and sintering.

13. The recycled sintered neodymium-iron-boron magnet according to claim 12, characterized in that The multi-stage annealing includes primary annealing and secondary annealing, and the temperature of the primary annealing is higher than that of the secondary annealing; The temperature of the primary annealing is 640-900℃, and the time is 1-3h; The temperature of the secondary annealing is 420-500℃, and the time is 1-3h.

14. A high performance, recycled sintered neodymium-iron-boron magnet, characterized in that, The high-performance regenerated sintered neodymium-iron-boron magnet is prepared by subjecting the regenerated sintered neodymium-iron-boron magnet of claim 10 to grain boundary diffusion heat treatment with a diffusion source; The diffusion source is a multi-element rare earth alloy diffusion source.

15. The high-performance, recycled sintered neodymium-iron-boron magnet of claim 14, wherein, The multi-element rare earth alloy diffusion source has a composition of HRE-FHRE-M, wherein HRE includes Dy and / or Tb, FHRE includes any one or a combination of at least two of La, Ce, Pr, Nd, Ho, Y or Sm, and M includes any one or a combination of at least two of Cu, Al, Co, Ga, Zn, Ni, Zr or Nb; And / or, the weight gain ratio of the heavy rare earth element HRE in the multi-element rare earth alloy diffusion source in the high-performance regenerated sintered neodymium-iron-boron magnet is 0.1-5wt%; And / or, the grain boundary diffusion heat treatment includes first-order heat treatment, second-order heat treatment and third-order heat treatment, and the temperature of the third-order heat treatment is lower than that of the first-order heat treatment, which is lower than that of the second-order heat treatment; The temperature of the first-order heat treatment is 630-670℃, and the time is 8-48h; The temperature of the second-order heat treatment is 850-950℃, and the time is 3-4h; The temperature of the third-order heat treatment is 400-500℃, and the time is 3-4h.

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