Method and system for recycling and high-value reuse of neodymium-iron-boron permanent magnet material

Abstract

The application discloses a high-value recycling method and system for neodymium-iron-boron permanent magnet material recycling materials. The classification pretreatment unit classifies the waste materials, the surface of the blocky materials is cleaned, and then the hydrogen crushing is performed, the muddy powder is deoiled and degreased, and then dried, and then the oxygen control roasting unit is entered, and the roasting is performed in the 3% to 8% oxygen atmosphere at 650 to 780 DEG C, so that the iron is selectively oxidized into triiron tetroxide, and the rare earth is converted into an oxide. The product is entered into the hydrogen reduction melting separation unit, and the hydrogen gas is reduced into metallic iron at 850 to 950 DEG C, and the inert atmosphere is melted and separated at 1250 to 1350 DEG C to obtain a rare earth slag phase and an iron-based alloy phase. The slag phase is subjected to nitric acid leaching, iron and aluminum are removed by pH segmentation, rare earth is precipitated by oxalic acid, and calcination is performed to obtain mixed rare earth oxides, which are mixed with hydrogen crushing powder, additional heavy rare earth and trace elements are added, and a recycled neodymium-iron-boron alloy is prepared by melting and rapid solidification casting.

Description

Technical Field

[0001] This invention belongs to the field of magnetic material waste recycling technology, specifically relating to a method and system for high-value reuse of recycled neodymium iron boron permanent magnet materials. Background Technology

[0002] Sintered NdFeB permanent magnets, with their excellent magnetic properties, are widely used in new energy vehicles, wind power generation, electronic information, and energy-saving home appliances. During their production and processing, from smelting, powdering, molding, and sintering to machining and surface treatment, a large amount of waste is generated at each stage. This waste mainly includes sintered lumpy defective products, machining scraps, grinding magnetic putty, cutting putty, electroplated substandard products, and ultrafine magnetic powder.

[0003] Existing processes often involve mixing these waste materials or designing process routes specifically for a single type of waste. However, the physicochemical properties of blocky waste and muddy waste differ significantly. Blocky waste retains a relatively complete alloy structure and basic magnetic properties, and can be directly reused after simple treatment; while muddy waste is severely oxidized and has a high impurity content, requiring deep separation and purification. Mixing not only results in the downgrading of high-quality waste but also increases the difficulty and cost of subsequent separation. Summary of the Invention

[0004] The purpose of this invention is to provide a method and system for the high-value reuse of recycled neodymium iron boron permanent magnet materials, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for high-value reuse of recycled neodymium iron boron permanent magnet materials, comprising the following steps:

[0006] Step 1: Classification and pretreatment. The NdFeB waste is classified according to its source and degree of pollution. The blocky sintering waste and electroplating defective products are directly subjected to hydrogen crushing after surface cleaning. The machining magnetic mud and cutting oil mud are degreased and dried to obtain mud-like powder.

[0007] Step 2: Oxygen-controlled roasting. The mud-like powder obtained in Step 1 is roasted in an oxygen-deficient atmosphere with an oxygen volume content of 3% to 8% at 650 to 780°C, so that iron is selectively oxidized to iron(III) oxide and rare earth is converted into rare earth oxides. The roasting time is 1 to 2 hours.

[0008] Step 3: Hydrogen reduction-melting separation. The roasted product obtained in Step 2 is subjected to hydrogen reduction treatment in a hydrogen atmosphere at 850-950℃ to reduce iron tetroxide to metallic iron. Then, the atmosphere is switched to inert and the temperature is raised to 1250-1350℃ for melting and separation to obtain the upper rare earth oxide slag phase and the lower iron-based alloy phase.

[0009] Step 4: Wet leaching and short-range purification. The rare earth oxide slag phase obtained in Step 3 is leached with nitric acid solution. After adjusting the pH value of the leaching solution and removing iron and aluminum impurities by staged precipitation, rare earth is directly precipitated with oxalic acid. The rare earth oxalate is then calcined to obtain mixed rare earth oxides.

[0010] Step 5: Targeted composition reconstruction. The mixed rare earth oxides obtained in Step 4 are mixed with the lumpy powder obtained after hydrogen crushing in Step 1 in a certain proportion. Only the heavy rare earth metals and trace elements required for the target grade are added. After smelting and rapid solidification casting, the recycled NdFeB alloy is obtained.

[0011] Preferably, in step one, the specific operation of the classification preprocessing is as follows:

[0012] After being demagnetized, the blocky sintering waste is subjected to surface reduction treatment at 300-600°C in a hydrogen atmosphere to remove the surface oxide layer.

[0013] The electroplated defective products are treated with an alkaline stripping solution to remove the plating layer;

[0014] The machining putty and cutting putty are washed with a hot alkaline solution at 80-120°C to remove oil and grease, and then vacuum dried until the moisture content is less than 0.5 wt%.

[0015] Preferably, in step two, the oxygen-controlled roasting is carried out in a fluidized bed reactor, where the powder is oxidized in a suspended state in an oxygen-deficient gas flow. The oxygen volume content is controlled to be 3% to 8% by adjusting the ratio of nitrogen to air in the inlet gas. In the obtained roasting product, iron exists as iron(III) oxide phase, and the area of ​​iron oxide diffraction peaks in the XRD pattern is not less than 90%.

[0016] Preferably, in step three, the hydrogen reduction and melting are carried out in stages within the same densification furnace:

[0017] The first stage involves maintaining a temperature of 850–950°C in a hydrogen atmosphere for 1–3 hours.

[0018] The second stage involves switching to an argon atmosphere and heating to 1250–1350°C, holding at that temperature for 0.5–1 hour. After melting, the mixture is cooled and crushed, and then separated from the iron-based alloy phase through density sorting.

[0019] Preferably, step four includes the following specific operations:

[0020] A nitric acid solution with a concentration of 2–4 mol / L was used for leaching for 1–2 hours at a liquid-to-solid ratio of 3:1–5:1 and a temperature of 70–85°C.

[0021] The pH of the leachate was adjusted to 3.5–4.0, and iron and aluminum were removed by precipitation. After filtration, the pH was adjusted to 1.5–2.0, and oxalic acid was added to precipitate rare earth elements at a temperature of 50–70°C.

[0022] The obtained rare earth oxalate is calcined at 800-900℃ for 2-3 hours to obtain mixed rare earth oxides, the total amount of which is not less than 98 wt%.

[0023] Preferably, in step five, the specific operation of the directional component reconstruction is as follows:

[0024] The lumpy powder obtained from hydrogen crushing in step one provides the basic iron-boron framework and some light rare earth elements, while the mixed rare earth oxides obtained in step four provide supplementary light rare earth elements.

[0025] Based on the total mass of raw materials used to prepare the recycled alloy as 100%, the amount of mixed rare earth oxides added is 15-25%, the amount of heavy rare earth metals added is 2-8%, the amount of trace elements added is 0.5-2%, and the remainder is the blocky powder after hydrogen crushing in step one.

[0026] The heavy rare earth metal is dysprosium and / or terbium, and the trace element is one or more of cobalt, aluminum, copper, and gallium.

[0027] Preferably, in step five, the vacuum degree of the melting and rapid solidification casting process is no greater than 5×10⁻²Pa, the casting temperature is 1420~1460℃, the surface linear velocity of the copper roller is 1.2~1.8m / s, and a recycled NdFeB alloy strip with a thickness of 0.2~0.3mm is obtained.

[0028] Preferably, the recycled NdFeB alloy obtained in step five satisfies the following conditions: oxygen content not greater than 500 ppm, carbon content not greater than 1000 ppm, and total content of calcium, silicon, and chlorine not greater than 800 ppm.

[0029] A system for the high-value reuse of recycled neodymium iron boron permanent magnet materials includes, in sequence along the material flow direction:

[0030] The classification pretreatment unit includes a demagnetizing device, a hot alkaline degreasing kettle, an alkaline stripping tank, a hydrogen crushing furnace, and a vacuum dryer;

[0031] The oxygen-controlled roasting unit includes a fluidized bed reactor equipped with a nitrogen-air ratio adjustment system, and an online oxygen content detection and feedback control device.

[0032] The hydrogen reduction-melting unit includes a densification furnace with dual-path atmosphere switching for hydrogen / argon, as well as a cooling crushing and density sorting device;

[0033] The wet purification unit includes a nitric acid dissolution vessel, a pH fractional precipitation vessel, an oxalic acid precipitation vessel, and a calcination rotary kiln;

[0034] The alloy recycling unit includes an automated batching system and a vacuum rapid solidification casting furnace.

[0035] Preferably, in the oxygen-controlled roasting unit, a mixed gas distribution plate is provided at the bottom of the fluidized bed reactor, and the online oxygen content detection and feedback control device monitors the oxygen concentration of the tail gas in real time through a zirconia oxygen analyzer and automatically adjusts the intake ratio of nitrogen and air to maintain the oxygen volume content in the roasting zone within the set range of 3% to 8%.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] Neodymium iron boron (NdFeB) waste was pretreated by classification according to its source and degree of contamination. Blocky sintering waste and electroplating defects were directly subjected to hydrogen crushing after surface cleaning. Machining magnetic mud and cutting sludge were degreased, dried, and then processed into mud-like powder. The mud-like powder was then subjected to controlled-oxygen roasting at 650–780°C in an oxygen-deficient atmosphere (3%–8% by volume) for 1–2 hours, selectively oxidizing iron to magnetite (Fe3O4) and converting rare earth elements into rare earth oxides. The roasted product was then subjected to hydrogen reduction treatment in a hydrogen atmosphere at 850–950°C, reducing magnetite to metallic iron. The atmosphere was then switched to inert, and the temperature was raised to 1250–1350°C for melting and separation, yielding an upper rare earth oxide slag phase and a lower iron-based alloy phase. Rare earth oxide slag is leached with nitric acid solution. After adjusting the pH value, the leachate is precipitated in stages to remove iron and aluminum impurities. Rare earth is then directly precipitated with oxalic acid. The rare earth oxalate is calcined to obtain mixed rare earth oxides. The mixed rare earth oxides are mixed with hydrogen-crushed lumpy powder in a certain proportion, with only the heavy rare earth metals and trace elements required for the target grade added. After smelting and rapid solidification casting, recycled NdFeB alloy is obtained. Attached Figure Description

[0038] Figure 1 This is a structural view of the method of the present invention.

[0039] Figure 2 This is a structural view of the classification preprocessing of the present invention.

[0040] Figure 3 This is a schematic diagram of the oxygen-controlled roasting conditions of the present invention.

[0041] Figure 4 This is a schematic diagram of the segmented hydrogen reduction-melting process of the present invention.

[0042] Figure 5 This is a schematic diagram of the wet purification process of the present invention.

[0043] Figure 6 This is a schematic diagram of the process for the formation of recycled ingredients according to the present invention.

[0044] Figure 7 This is a schematic diagram of the process parameters for the rapid solidification casting sheet of the present invention.

[0045] Figure 8This is a flowchart illustrating the alloy impurity index of the present invention.

[0046] Figure 9 This is a schematic diagram of the system unit of the present invention.

[0047] Figure 10 This is a schematic diagram of the closed-loop control of oxygen content in this invention. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] Example 1:

[0050] A method for high-value reuse of recycled neodymium iron boron permanent magnet materials includes the following steps:

[0051] Step 1: Classification and pretreatment. The NdFeB waste is classified according to its source and degree of pollution. The blocky sintering waste and electroplating defective products are directly subjected to hydrogen crushing after surface cleaning. The machining magnetic mud and cutting oil mud are degreased and dried to obtain mud-like powder.

[0052] Step 2: Oxygen-controlled roasting. The mud-like powder obtained in Step 1 is roasted in an oxygen-deficient atmosphere with an oxygen volume content of 3% to 8% at 650 to 780°C, so that iron is selectively oxidized to iron(III) oxide and rare earth is converted into rare earth oxides. The roasting time is 1 to 2 hours.

[0053] Step 3: Hydrogen reduction-melting separation. The roasted product obtained in Step 2 is subjected to hydrogen reduction treatment in a hydrogen atmosphere at 850-950℃ to reduce iron tetroxide to metallic iron. Then, the atmosphere is switched to inert and the temperature is raised to 1250-1350℃ for melting and separation to obtain the upper rare earth oxide slag phase and the lower iron-based alloy phase.

[0054] Step 4: Wet leaching and short-range purification. The rare earth oxide slag phase obtained in Step 3 is leached with nitric acid solution. After adjusting the pH value of the leaching solution and removing iron and aluminum impurities by staged precipitation, rare earth is directly precipitated with oxalic acid. The rare earth oxalate is then calcined to obtain mixed rare earth oxides.

[0055] Step 5: Targeted composition reconstruction. The mixed rare earth oxides obtained in Step 4 are mixed with the hydrogen-crushed lumpy powder obtained in Step 1 in a specific ratio. Only the heavy rare earth metals and trace elements required for the target grade are added. After smelting and rapid solidification casting, recycled NdFeB alloy is obtained. The specific operations of the classification pretreatment in Step 1 are as follows:

[0056] After demagnetization, the blocky sintering waste is subjected to surface reduction treatment at 300-600℃ in a hydrogen atmosphere to remove the surface oxide layer.

[0057] Electroplated defective products are treated with an alkaline stripping solution to remove the plating layer;

[0058] After being washed and degreased with a hot alkaline solution at 80–120°C, the machining putty and cutting putty are vacuum dried until the moisture content is below 0.5 wt%. In step two, oxygen-controlled roasting is carried out in a fluidized bed reactor, where the powder is oxidized in suspension in an oxygen-deficient gas stream. The oxygen volume content is controlled to be 3%–8% by adjusting the ratio of nitrogen to air in the inlet gas. In the resulting roasted product, iron exists as the iron(III) oxide phase, and the area of ​​the iron oxide diffraction peak in the XRD pattern is not less than 90%. In step three, hydrogen reduction and melting are carried out in stages in the same densification furnace.

[0059] The first stage involves maintaining a temperature of 850–950°C in a hydrogen atmosphere for 1–3 hours.

[0060] The second stage involves switching to an argon atmosphere and heating to 1250–1350℃, holding at that temperature for 0.5–1 hour. After melting, the mixture is cooled and crushed, and density separation is used to separate the rare earth oxide slag phase from the iron-based alloy phase. The specific operations in step four include:

[0061] A nitric acid solution with a concentration of 2–4 mol / L was used for leaching for 1–2 hours at a liquid-to-solid ratio of 3:1–5:1 and a temperature of 70–85°C.

[0062] The pH of the leachate was adjusted to 3.5–4.0, and iron and aluminum were removed by precipitation. After filtration, the pH was adjusted to 1.5–2.0, and oxalic acid was added to precipitate rare earth elements at a temperature of 50–70°C.

[0063] The obtained rare earth oxalate is calcined at 800–900℃ for 2–3 hours to obtain mixed rare earth oxides, the total amount of which is not less than 98 wt%. The specific operation for directional component reconstruction in step five is as follows:

[0064] The lumpy powder obtained from hydrogen crushing in step one provides the basic iron-boron framework and some light rare earth elements, while the mixed rare earth oxides obtained in step four provide supplementary light rare earth elements.

[0065] Based on the total mass of raw materials for preparing recycled alloys as 100%, the amount of mixed rare earth oxides added is 15-25%, the amount of heavy rare earth metals added is 2-8%, the amount of trace elements added is 0.5-2%, and the remainder is the blocky powder after hydrogen crushing in step one.

[0066] The heavy rare earth metals are dysprosium and / or terbium, and the trace elements are one or more of cobalt, aluminum, copper, and gallium. In step five, the vacuum degree of the smelting and rapid solidification casting process is no greater than 5 × 10⁻² Pa, the casting temperature is 1420–1460℃, and the surface linear velocity of the copper roller is 1.2–1.8 m / s, resulting in a recycled NdFeB alloy strip with a thickness of 0.2–0.3 mm. The recycled NdFeB alloy obtained in step five meets the following requirements: oxygen content no greater than 500 ppm, carbon content no greater than 1000 ppm, and total content of calcium, silicon, and chlorine no greater than 800 ppm.

[0067] A system for the high-value reuse of recycled neodymium iron boron permanent magnet materials includes, in sequence along the material flow direction:

[0068] The classification pretreatment unit includes a demagnetizing device, a hot alkaline degreasing kettle, an alkaline stripping tank, a hydrogen crushing furnace, and a vacuum dryer;

[0069] The oxygen-controlled roasting unit includes a fluidized bed reactor equipped with a nitrogen-air ratio adjustment system, and an online oxygen content detection and feedback control device.

[0070] The hydrogen reduction-melting unit includes a densification furnace with dual-path atmosphere switching for hydrogen / argon, as well as a cooling crushing and density sorting device;

[0071] The wet purification unit includes a nitric acid dissolution vessel, a pH fractional precipitation vessel, an oxalic acid precipitation vessel, and a calcination rotary kiln;

[0072] The alloy regeneration unit includes an automatic batching system and a vacuum rapid solidification casting furnace. In the oxygen-controlled roasting unit, a mixed gas distribution plate is installed at the bottom of the fluidized bed reactor. An online oxygen content detection and feedback control device monitors the oxygen concentration of the tail gas in real time through a zirconia oxygen analyzer and automatically adjusts the nitrogen and air intake ratio to maintain the oxygen volume content in the roasting zone within the set range of 3% to 8%.

[0073] The above technical solution involves first classifying and pre-treating NdFeB waste according to its physical form, source, and surface contamination level. The waste is then divided into two processing paths. The first path targets blocky waste, including sintered blocky defective products, machining scraps, and electroplated substandard products. This type of waste retains its complete alloy block structure, with only surface contamination from oil, plating, or oxide layers. After surface cleaning such as sandblasting, washing, or grinding to remove surface contaminants, it undergoes direct hydrogen crushing. The second path targets sludge-like powder, including grinding magnetic putty and cutting oil putty. This type of waste consists of alloy powder mixed with processing coolant and grease to form a slurry, which is heavily oxidized and contains high levels of impurities. It undergoes degreasing and oil separation processes such as pressure filtration, centrifugation, or chemical cleaning to separate oil and water, followed by a drying process to obtain loose, sludge-like powder. The mud-like powder was placed in an oxygen-deficient atmosphere with an oxygen volume content of 3%–8% for controlled oxygen roasting at a temperature of 650–780℃ for 1–2 hours. Iron was selectively oxidized to magnetite (Fe3O4), and rare earth elements were converted into rare earth oxides. The roasted product was then subjected to hydrogen reduction treatment in a hydrogen atmosphere at a temperature of 850–950℃, reducing magnetite to metallic iron. After switching to an argon atmosphere, the temperature was raised to 1250–1350℃ for melting and separation, yielding an upper rare earth oxide slag phase and a lower iron-based alloy phase. The rare earth oxide slag phase was leached with nitric acid solution, and the leachate was subjected to staged precipitation by adjusting the pH value to remove iron and aluminum impurities. Rare earth elements were directly precipitated with oxalic acid to obtain rare earth oxalate. The rare earth oxalate was calcined to obtain mixed rare earth oxides. The mixed rare earth oxides were mixed with hydrogen-crushed lumpy powder in a specific ratio, with only the heavy rare earth metals and trace elements required for the target grade added. The mixture is smelted and rapidly solidified into cast sheets to produce recycled NdFeB alloy.

[0074] The following is the complete text after inserting the keywords in the appropriate locations in the specification as required. All original technical feature names, parameters, and components remain unchanged; only descriptions related to the application field have been added.

[0075] Example 2:

[0076] Step one of this embodiment is classification and pretreatment, in which neodymium iron boron waste is classified according to its source and degree of pollution. Among them, blocky sintering waste and electroplating defective products are directly subjected to hydrogen crushing treatment after surface cleaning; machining magnetic mud and cutting oil mud are degreased and dried to obtain mud-like powder.

[0077] Step two is oxygen-controlled roasting. The mud-like powder obtained in step one is roasted in an oxygen-deficient atmosphere with an oxygen volume content of 3% to 8% at 650 to 780°C, so that iron is selectively oxidized to iron(III) oxide and rare earth elements are converted into rare earth oxides. The roasting time is 1 to 2 hours.

[0078] Step 3 is hydrogen reduction-melting separation. The roasted product obtained in step 2 is subjected to hydrogen reduction treatment in a hydrogen atmosphere at 850-950℃ to reduce iron tetroxide to metallic iron. Then, the atmosphere is switched to inert and the temperature is raised to 1250-1350℃ for melting and separation to obtain an upper rare earth oxide slag phase and a lower iron-based alloy phase.

[0079] Step four involves wet leaching and short-range purification. The rare earth oxide slag phase obtained in step three is leached with nitric acid solution. After adjusting the pH value of the leaching solution and removing iron and aluminum impurities through staged precipitation, rare earth is directly precipitated with oxalic acid. The rare earth oxalate is then calcined to obtain mixed rare earth oxides.

[0080] Step five involves directional composition reconstruction. The mixed rare earth oxides obtained in step four are mixed with the hydrogen-crushed lumpy powder obtained in step one in a specific ratio. Only the heavy rare earth metals and trace elements required for the target grade are added. After smelting and rapid solidification casting, recycled NdFeB alloy is obtained. This recycled NdFeB alloy can be further processed into permanent magnets and applied in the manufacturing of transformers, rectifiers, and inductors, such as intelligent large transformers, DC converter transformers, and intelligent reactors. It can also be used in the manufacturing of power distribution switch control equipment for intelligent power distribution systems and facilities, as well as magnetic components required for cross-linked polyethylene insulated power cables and cable accessories.

[0081] Example 3:

[0082] In step one of this embodiment, the specific operations of the classification and pretreatment are as follows. For blocky sintering waste, it is first demagnetized to eliminate residual magnetism and facilitate subsequent operations. The demagnetized blocky sintering waste is placed in a hydrogen atmosphere at 300-600°C for surface reduction treatment. Through the chemical reaction between hydrogen and the surface oxide layer, the oxide layer is reduced to a metallic state, thereby removing the surface oxide layer.

[0083] For electroplated defective products, an alkaline stripping solution is used for treatment. The alkaline components in the stripping solution react with the plating layer, causing it to peel off and dissolve from the substrate surface, thus removing the plating layer. For machining putty and cutting sludge, they are washed in a hot alkaline solution at 80–120°C. The hot alkaline solution, through saponification or emulsification, separates and dissolves the grease and oil adhering to the surface of the putty and sludge from the solid particles, achieving degreasing.

[0084] The washed material is then vacuum dried by heating in a vacuum environment to evaporate the moisture until the moisture content of the material is less than 0.5 wt%, thus obtaining a dry mud-like powder.

[0085] Example 4:

[0086] In step two of this embodiment, oxygen-controlled roasting is carried out in a fluidized bed reactor. The sludge-like powder obtained in step one is fed into the fluidized bed reactor, where it is oxidized in a suspended state in an oxygen-deficient gas stream. By adjusting the ratio of nitrogen to air in the inlet gas, the oxygen volume content in the reactor is controlled to be 3%–8%.

[0087] The powder is fully contacted with the gas flow in a fluidized bed to achieve uniform oxidation. The calcination temperature is maintained at 650–780℃, and the calcination time is controlled at 1–2 hours. In the obtained calcined product, iron exists as the magnetite phase, and the area of ​​the iron oxide diffraction peak in the XRD pattern is not less than 90%. Rare earth elements are converted into rare earth oxides during the calcination process.

[0088] The suspended oxidation environment within the fluidized bed reactor ensures sufficient contact between the powder particles and the oxygen-deficient flow, preventing localized over-oxidation and guaranteeing the selective oxidation of iron to magnetite (Fe3O4) rather than ferric oxide (Fe2O3). The nitrogen-to-air ratio is adjusted using a mass flow controller, maintaining the oxygen volume content consistently within the range of 3%–8%. The calcined product is discharged from the bottom of the fluidized bed reactor, cooled, and then proceeds to step three for hydrogen reduction and melting.

[0089] Example 5:

[0090] In step three of this embodiment, hydrogen reduction and melting are carried out in stages within the same densification furnace. In the first stage, the atmosphere inside the furnace is switched to a hydrogen atmosphere, the temperature is raised to 850-950°C and held for 1-3 hours, so that the iron(III) oxide in the calcined product obtained in step two undergoes a reduction reaction with hydrogen, and the iron(III) oxide is reduced to metallic iron, while the rare earth oxides remain stable.

[0091] In the second stage, the furnace atmosphere is switched to argon, and the temperature is raised to 1250–1350℃ and held for 0.5–1 hour. This allows the reduced material to completely melt in the inert atmosphere. Due to the density difference, the metallic iron and rare earth oxide slag phases separate into layers: the upper layer is the rare earth oxide slag phase, and the lower layer is the iron-based alloy phase. After melting, the melt is cooled to room temperature to obtain solidified lumpy material. The lumpy material is then crushed to a particle size of less than 5 mm.

[0092] The crushed particles are separated into rare earth oxide slag phase and iron-based alloy phase by density separation. Density separation employs either heavy medium separation or airflow separation. The rare earth oxide slag phase has a lower density, while the iron-based alloy phase has a higher density; the two separate due to the difference in settling velocity in the separation medium. The separated rare earth oxide slag phase is collected for subsequent wet leaching steps, while the iron-based alloy phase is recovered as a byproduct.

[0093] Example 6:

[0094] In step four of this embodiment, the rare earth oxide slag phase obtained in step three is placed in a reaction vessel, and a nitric acid solution with a concentration of 2-4 mol / L is added. The liquid-solid ratio is controlled at 3:1-5:1. The mixture is heated to 70-85°C and continuously stirred for 1-2 hours to leach, allowing the rare earth elements and impurities in the rare earth oxide slag phase to enter the solution. After leaching, the leachate is filtered to remove undissolved residues. Alkali solution is added to the filtrate to adjust the pH to 3.5-4.0. Within this pH range, iron and aluminum ions hydrolyze to form hydroxide precipitates. The precipitates are separated by filtration to remove iron and aluminum impurities.

[0095] After removing iron and aluminum, the filtrate is added to an alkaline solution to adjust the pH to 1.5–2.0. Then, oxalic acid solution is added, and the precipitation temperature is controlled at 50–70°C. Oxalic acid reacts with rare earth ions to form rare earth oxalate precipitate. The precipitation process is continuously stirred to ensure complete reaction. After precipitation, the rare earth oxalate precipitate is collected by filtration and washed with deionized water to remove residual nitrate and impurity ions. The washed rare earth oxalate is placed in a calcining furnace and calcined at 800–900°C for 2–3 hours. The rare earth oxalate decomposes upon heating, transforming into mixed rare earth oxides. After cooling, the calcined product yields a mixed rare earth oxide product with a total rare earth oxide content of not less than 98 wt%.

[0096] Example 7:

[0097] In this embodiment, the lumpy powder obtained from hydrogen crushing in step one provides the basic iron-boron framework and a portion of light rare earth elements, while the mixed rare earth oxides obtained in step four provide supplementary light rare earth elements. Based on 100% of the total mass of raw materials used to prepare the recycled alloy, the amount of mixed rare earth oxides added is 15-25%, the amount of heavy rare earth metals added is 2-8%, the amount of trace elements added is 0.5-2%, and the remainder is the lumpy powder obtained from hydrogen crushing in step one. The heavy rare earth metals are dysprosium and / or terbium, and the trace elements are one or more of cobalt, aluminum, copper, and gallium.

[0098] The bulk powder obtained from hydrogen crushing in step one is mixed with the mixed rare earth oxides obtained in step four in the above proportions. The light rare earth elements in the mixed rare earth oxides enter the alloy matrix during subsequent smelting, supplementing the insufficient light rare earth content caused by oxidation loss or compositional deviation. The iron-boron framework structure retained in the bulk powder serves as the matrix framework of the alloy, maintaining the basic phase composition of the magnet. Heavy rare earth metals dysprosium and / or terbium are added; their atoms diffuse into the shell region of the main phase grains during smelting, forming a highly anisotropic field region and enhancing the intrinsic coercivity of the regenerated alloy. One or more trace elements, cobalt, aluminum, copper, and gallium, are added. Cobalt partially replaces iron atoms, increasing the Curie temperature and improving temperature stability; aluminum and copper are enriched in the grain boundary phase, optimizing grain boundary wettability and reducing intergranular exchange coupling; gallium promotes uniform distribution of the grain boundary phase and inhibits the nucleation of antimagnetic domains.

[0099] The mixture is smelted under vacuum or inert atmosphere protection at a temperature controlled between 1350 and 1450°C to ensure complete melting of the lumpy powder and full alloying with the mixed rare earth oxides, heavy rare earth metals, and trace elements. The melt is then processed using a rapid solidification casting process, pouring the melt onto the surface of a rotating cooling copper roller at a cooling rate of 10³–10⁻⁶. 5 At ℃ / second, thin flakes with a thickness of 0.2–0.5 mm are formed. During the rapid solidification casting process, the alloy melt solidifies rapidly, inhibiting the precipitation of the α-Fe phase and promoting the precipitation of the main Nd2Fe phase. 14 B-columnar crystals grow perpendicular to the surface of the cast sheet, with a grain size controlled between 3 and 10 micrometers. The cast sheet undergoes subsequent powder preparation, molding, sintering, and heat treatment processes to produce recycled NdFeB alloy. The resulting permanent magnets can be used to manufacture intelligent large transformers, DC converter transformers, intelligent reactors, and other transformers, rectifiers, and inductors, as well as magnetic components in intelligent power distribution systems and facilities. They can also meet the demand for high-performance permanent magnet materials in cross-linked polyethylene insulated power cables and cable accessories.

[0100] Example 8:

[0101] In step five of this embodiment, the mixed rare earth oxides are mixed with the hydrogen-crushed lumpy powder in a certain proportion, and the heavy rare earth metals and trace elements required for the target grade are added. The mixture is then sent to a melting furnace for melting. The melting process is carried out under vacuum conditions, with a vacuum degree not exceeding 5×10⁻² Pa, to eliminate the oxidation effect of residual gas in the furnace on the alloy composition.

[0102] The melting temperature is controlled within the range of 1420–1460℃ to ensure complete melting and alloying of the mixture, forming a homogeneous alloy melt. Once the melt reaches the casting temperature, it is poured onto the surface of a high-speed rotating copper roller for rapid solidification casting. The linear velocity of the copper roller surface is set to 1.2–1.8 m / s, and rapid cooling solidifies the melt into a recycled NdFeB alloy strip with a thickness of 0.2–0.3 mm. During the rapid solidification casting process, the melt cools rapidly upon contact with the copper roller, inhibiting the precipitation of the α-Fe phase and promoting the formation of columnar crystal structures, thereby obtaining an alloy strip with a good microstructure.

[0103] The resulting recycled NdFeB alloy strips can be directly used in subsequent powdering, molding, and sintering processes to produce high-performance recycled NdFeB permanent magnet materials. These permanent magnet materials are particularly suitable for manufacturing transformers, rectifiers, and inductors, such as intelligent large transformers, DC converter transformers, and intelligent reactors. They can also be used in the manufacture of intelligent power distribution systems, facilities, and other power distribution switch control equipment, as well as for use with cross-linked polyethylene insulated power cables and cable accessories.

[0104] Example 9:

[0105] In this embodiment, the recycled NdFeB alloy obtained in step five has an oxygen content of no more than 500 ppm, a carbon content of no more than 1000 ppm, and a total content of calcium, silicon, and chlorine of no more than 800 ppm. In step five, the mixed rare earth oxides obtained in step four are mixed with the hydrogen-crushed lumpy powder obtained in step one in a certain proportion, with only the heavy rare earth metals and trace elements required for the target grade added. After smelting and rapid solidification casting, the recycled NdFeB alloy is obtained. The mixed rare earth oxides are obtained by calcining the rare earth oxalate from step four, and their purity directly affects the impurity level of the final alloy.

[0106] The lumpy powder obtained after hydrogen crushing comes from the surface cleaning of lumpy sintering waste and electroplating defects in step one. This powder retains a relatively complete alloy structure and has relatively low carbon and oxygen content. The added heavy rare earth metals and trace elements are precisely added according to the target grade requirements, without introducing additional impurities. The smelting process is carried out in a vacuum or inert atmosphere, with the temperature controlled between 1350℃ and 1450℃, so that the mixed rare earth oxides and lumpy powder can be fully melted and undergo a reduction reaction, and the rare earth oxides are reduced to a metallic state and enter the alloy melt.

[0107] Rapidly solidified flakes are formed by rapidly cooling the molten material by pouring it onto a rotating copper roller, creating flakes with a thickness of 0.3 mm to 0.5 mm, thus suppressing grain growth and compositional segregation. The final oxygen content of the alloy is achieved by controlling the melting atmosphere and the oxygen content of the raw materials. The carbon content is affected by residual carbon on the surface of the blocky powder and carbon diffusion from the graphite crucible during melting. The total content of calcium, silicon, and chlorine depends on the purity of the mixed rare earth oxides and the impurity level of the added raw materials. The high-purity recycled NdFeB alloy obtained in this embodiment can be processed into permanent magnets and applied in the manufacture of transformers, rectifiers, and inductors, such as intelligent large transformers, DC converter transformers, and intelligent reactors. It provides reliable magnetic properties in the manufacture of power distribution switch control equipment for intelligent power distribution systems and facilities, and can meet the stringent requirements for magnetic materials in cross-linked polyethylene insulated power cables and cable accessories.

[0108] Example 10:

[0109] In this embodiment, the system for high-value reuse of recycled NdFeB permanent magnet materials operates sequentially along the material flow direction. The sorting and pretreatment unit first receives the waste material, the demagnetizing device demagnetizes the waste material to eliminate residual magnetism, the hot alkaline degreasing kettle degreases the waste material with hot alkaline to remove oily contaminants, the alkaline stripping tank strips the waste material with alkaline to remove the surface coating, the hydrogen crushing furnace hydrogenates the blocky waste material to crack along the grain boundaries to form powder, and the vacuum dryer vacuum dries the muddy powder to remove moisture.

[0110] The oxygen-controlled roasting unit receives sludge-like powder from the classification and pretreatment unit. The fluidized bed reactor is equipped with a nitrogen-air ratio adjustment system, which controls the oxygen volume content in the reactor to be between 3% and 8% by adjusting the ratio of nitrogen to air. An online oxygen content detection and feedback control device monitors the oxygen content in the reactor in real time and adjusts the nitrogen-air ratio accordingly. The sludge-like powder is roasted in an oxygen-deficient atmosphere at 650 to 780 degrees Celsius for 1 to 2 hours. Iron is selectively oxidized to iron(III) oxide, and rare earth elements are converted into rare earth oxides.

[0111] The hydrogen reduction-melting unit receives the roasting products from the oxygen-controlled roasting unit. The densification furnace has a dual-atmosphere switching function of hydrogen / argon. First, hydrogen is introduced to reduce the roasting products in a hydrogen atmosphere of 850 to 950 degrees Celsius, reducing iron(III) oxide to metallic iron. Then, the atmosphere is switched to argon and the temperature is raised to 1250 to 1350 degrees Celsius for melting and separation. The upper rare earth oxide slag phase and the lower iron-based alloy phase naturally separate due to the density difference. The cooling and crushing device cools and crushes the solidified slag phase, and the density separation device separates the rare earth oxide slag phase according to the density difference.

[0112] The wet purification unit receives the rare earth oxide slag phase separated by the hydrogen reduction-melting unit. The nitric acid leaching kettle uses nitric acid solution to leach the rare earth oxide slag phase to obtain a leachate. The pH segmented precipitation kettle adjusts the pH value of the leachate to perform segmented precipitation to remove iron and aluminum impurities. The oxalic acid precipitation kettle adds oxalic acid to the leachate after impurity removal to precipitate rare earth to obtain rare earth oxalate. The calcination rotary kiln calcines the rare earth oxalate to obtain mixed rare earth oxides.

[0113] The alloy recycling unit receives mixed rare earth oxides from the wet purification unit and hydrogen-crushed powder from the sorting and pretreatment unit. An automatic batching system calculates the ratio of mixed rare earth oxides to hydrogen-crushed powder based on the target grade formula and adds heavy rare earth metals and trace elements. A vacuum rapid solidification casting furnace melts and rapidly solidifies the batched mixture into recycled NdFeB alloy. The permanent magnets made from this recycled alloy through subsequent processes can be specifically supplied for the manufacture of transformers, rectifiers, and inductors, such as intelligent large transformers, DC converter transformers, and intelligent reactors. They can also be used in the manufacture of power distribution switch control equipment for intelligent power distribution systems and facilities, as well as in the production of permanent magnet components in cross-linked polyethylene insulated power cables and cable accessories.

[0114] Example 11:

[0115] In this embodiment, a mixed gas distribution plate is installed at the bottom of the fluidized bed reactor in the oxygen-controlled roasting unit. This distribution plate evenly distributes the nitrogen-air mixture to the bottom of the reactor, allowing the gas to pass through the roasting zone at a stable flow rate. An online oxygen content detection and feedback control device monitors the oxygen concentration of the exhaust gas in real time using a zirconia oxygen analyzer.

[0116] The zirconia oxygen analyzer is installed on the exhaust gas outlet pipe of the fluidized bed reactor. Its sensor directly contacts the exhaust gas and outputs an electrical signal corresponding to the oxygen partial pressure. This electrical signal is fed back to the proportional control controller, which automatically calculates the nitrogen to air intake ratio based on a preset oxygen volume content range (3% to 8%).

[0117] When the oxygen concentration in the exhaust gas is higher than 8%, the controller increases the opening of the nitrogen intake valve and decreases the opening of the air intake valve to reduce the oxygen content in the mixture. When the oxygen concentration in the exhaust gas is lower than 3%, the controller decreases the opening of the nitrogen intake valve and increases the opening of the air intake valve to increase the oxygen content in the mixture.

[0118] The adjustment process is continuous, ensuring that the oxygen volume content in the calcination zone remains within the set range of 3% to 8%. The mixed gas distribution plate is made of porous ceramic or sintered metal, with its porosity and pore size designed according to the diameter of the fluidized bed reactor and the particle size of the material, ensuring uniform gas distribution and preventing channeling. Within the fluidized bed reactor, the material is fluidized under the influence of the gas, ensuring full contact between the material particles and the gas.

[0119] The oxygen content control accuracy is ±0.5%, and the response time is no more than 5 seconds. This control mechanism keeps the oxygen volume content in the roasting zone stable within the set range, avoiding incomplete selective oxidation of iron or excessive oxidation of rare earth elements due to fluctuations in oxygen content.

[0120] Example 12:

[0121] The calcined product obtained in step two is loaded into a densification furnace. The phase composition of the calcined product is iron(III) oxide and rare earth oxides, with iron(III) oxide accounting for 65% to 75% by mass and rare earth oxides accounting for 25% to 35% by mass. After closing the furnace door, a vacuum is drawn to below 10 Pa, and then hydrogen gas is introduced until the pressure inside the furnace reaches 0.11 MPa, with a hydrogen purity of not less than 99.99%. The temperature is increased to 900℃ at a rate of 5℃ / min. During the heating process, hydrogen gas undergoes a reduction reaction with iron(III) oxide, with the reaction formula being Fe3O4 + 4H2 → 3Fe + 4H2O. The generated water vapor is discharged with the tail gas.

[0122] The mixture was kept at 900℃ for 2 hours, during which hydrogen was continuously introduced and the hydrogen flow rate was maintained at 2L / min. This caused the iron oxide particles to be gradually reduced to metallic iron from the surface to the inside. The size of the metallic iron particles ranged from 0.5μm to 5μm. At this temperature, the rare earth oxides did not react with hydrogen and maintained their oxide form.

[0123] After the heat preservation is completed, the hydrogen inlet valve is closed, and argon gas is switched to it with a purity of not less than 99.999%. The temperature is increased to 1300℃ at a rate of 10℃ / min. During the heating process, the metallic iron particles begin to sinter and form a continuous iron matrix, while the rare earth oxide particles migrate and aggregate due to their high surface energy.

[0124] When the temperature reaches 1300℃, metallic iron completely melts to form a molten iron pool. Rare earth oxides remain solid because their melting point is higher than 1600℃. They float in the molten iron due to the density difference. The density of the molten iron is 7.8 g / cm³, while the density of the rare earth oxides is 6.5 g / cm³ to 7.0 g / cm³. The density difference drives the rare earth oxide particles to migrate to the surface of the melt.

[0125] The furnace is held at this temperature for 0.5 hours to allow the rare earth oxides to fully float to the surface and form a continuous slag layer on the surface of the molten iron. The slag layer is 5 mm to 15 mm thick, with the molten iron layer located below it. After holding at this temperature, heating is stopped, and the furnace is allowed to cool naturally to room temperature while maintaining an argon atmosphere. The cooling rate is 5°C to 10°C / min.

[0126] During the cooling process, the molten iron solidifies into an iron-based alloy ingot, and the rare earth oxide slag layer solidifies into a dense slag block. The interface between the two is clear, with no interpenetrating layer. After the solidified material is removed, mechanical knocking is applied, and the slag block and iron ingot naturally separate along the interface.

[0127] The separated rare earth oxide slag is crushed to a particle size of less than 2 mm by a jaw crusher, and then ground to a particle size of less than 0.1 mm by a ball mill to obtain rare earth oxide powder. Iron-based alloy ingots are collected as by-products, with an iron content of not less than 95 wt%.

[0128] Example 13:

[0129] Weigh the lumpy powder obtained from hydrogen crushing in step one and the mixed rare earth oxides obtained in step four at a mass ratio of 75:25. The particle size of the lumpy powder is 0.1 mm to 1 mm, and the particle size of the mixed rare earth oxides is 1 μm to 10 μm. Mix the two powders in a V-type mixer for 30 minutes. After uniform mixing, add dysprosium metal particles and cobalt metal particles. The amount of dysprosium metal added accounts for 5% of the total mass of the mixture, and the amount of cobalt metal added accounts for 1.5% of the total mass of the mixture. The particle size of both dysprosium metal particles and cobalt metal particles is 0.5 mm to 2 mm.

[0130] The mixture was loaded into a magnesium oxide crucible, which was placed in a vacuum induction melting furnace. After evacuating to 5 × 10⁻² Pa, heating began. The temperature was increased to 800 °C at a rate of 15 °C / min and held at 800 °C for 30 minutes. During this stage, the NdFeB main phase in the block powder began to soften. The NdO and praseodymium oxide in the mixed rare earth oxides reacted with the metallic NdO in the block powder in a reduction reaction, with the reaction formula being Nd₂O₃ + 2Nd → 3NdO. NdO further decomposed into metallic NdO and oxygen at high temperature. The oxygen reacted with the metallic iron in the block powder to form ferrous oxide. The ferrous oxide volatilized under vacuum conditions and was removed by the vacuum system.

[0131] Continue heating to 1400℃ at a rate of 10℃ / min, and hold at 1400℃ for 20 minutes to completely melt all materials. Dysprosium and cobalt metals dissolve into the melt. The melt is then homogenized by electromagnetic stirring at a frequency of 50Hz and a power of 5kW.

[0132] After the heat preservation period, the molten metal is poured onto the surface of a rotating copper roller. The copper roller has a diameter of 600 mm and a surface linear velocity of 1.5 m / s. Cooling water flows inside the copper roller at a temperature of 25°C and a flow rate of 50 L / min. After the molten metal contacts the copper roller, it rotates at a speed of 10... 4 Solidification occurred at a cooling rate of ℃ / s, forming a thin ribbon with a thickness of 0.25 mm and a width of 50 mm. The microstructure of the ribbon consisted of columnar crystals, which grew perpendicular to the surface of the ribbon and had a width of 5 μm to 8 μm. The main phase was Nd₂Fe. 14 The volume fraction of B is not less than 90%, and the grain boundary phase is uniformly distributed around the main phase grains. After collection, the thin strip can be directly used in subsequent powder preparation processes. The final permanent magnet can be used in the manufacture of transformers, rectifiers, and inductors such as intelligent large transformers, DC converter transformers, and intelligent reactors. It can also be used in the manufacture of power distribution switch control equipment such as intelligent power distribution systems and facilities, as well as high-performance permanent magnet components required for cross-linked polyethylene insulated power cables and cable accessories.

[0133] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0134] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the spirit and scope of the technical solution of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A method for high-value reuse of recycled neodymium iron boron permanent magnet materials, characterized in that, Includes the following steps: Step 1: Classification and pretreatment. The NdFeB waste is classified according to its source and degree of pollution. The blocky sintering waste and electroplating defective products are directly subjected to hydrogen crushing treatment after surface cleaning. After degreasing and drying, machining putty and cutting putty are used to obtain mud-like powder. Step 2: Oxygen-controlled roasting. The mud-like powder obtained in Step 1 is roasted in an oxygen-deficient atmosphere with an oxygen volume content of 3% to 8% at 650 to 780°C, so that iron is selectively oxidized to iron(III) oxide and rare earth is converted into rare earth oxides. The roasting time is 1 to 2 hours. Step 3: Hydrogen reduction-melting separation. The roasted product obtained in Step 2 is subjected to hydrogen reduction treatment in a hydrogen atmosphere at 850-950℃ to reduce iron tetroxide to metallic iron. Then, the atmosphere is switched to inert and the temperature is raised to 1250-1350℃ for melting and separation to obtain the upper rare earth oxide slag phase and the lower iron-based alloy phase. Step 4: Wet leaching and short-range purification. The rare earth oxide slag phase obtained in Step 3 is leached with nitric acid solution. After adjusting the pH value of the leaching solution and removing iron and aluminum impurities by staged precipitation, rare earth is directly precipitated with oxalic acid. The rare earth oxalate is then calcined to obtain mixed rare earth oxides. Step 5: Targeted composition reconstruction. The mixed rare earth oxides obtained in Step 4 are mixed with the lumpy powder obtained after hydrogen crushing in Step 1 in a certain proportion. Only the heavy rare earth metals and trace elements required for the target grade are added. After smelting and rapid solidification casting, the recycled NdFeB alloy is obtained.

2. The method for high-value reuse of recycled NdFeB permanent magnet materials according to claim 1, characterized in that, In step one, the specific operations of the classification preprocessing are as follows: After being demagnetized, the blocky sintering waste is subjected to surface reduction treatment at 300-600°C in a hydrogen atmosphere to remove the surface oxide layer. The electroplated defective products are treated with an alkaline stripping solution to remove the plating layer; The machining putty and cutting putty are washed with a hot alkaline solution at 80-120°C to remove oil and grease, and then vacuum dried until the moisture content is less than 0.5 wt%.

3. The method for high-value reuse of recycled neodymium iron boron permanent magnet materials according to claim 1, characterized in that, In step two, the oxygen-controlled roasting is carried out in a fluidized bed reactor. The powder is oxidized in a suspended state in an oxygen-deficient gas flow. The oxygen volume content is controlled to be 3% to 8% by adjusting the ratio of nitrogen to air in the inlet gas. In the obtained roasting product, iron exists as iron(III) oxide phase, and the area of ​​iron oxide diffraction peaks in the XRD pattern is not less than 90%.

4. The method for high-value reuse of recycled neodymium iron boron permanent magnet materials according to claim 1, characterized in that, In step three, the hydrogen reduction and melting process is carried out in stages within the same densification furnace: The first stage involves maintaining a temperature of 850–950°C in a hydrogen atmosphere for 1–3 hours. The second stage involves switching to an argon atmosphere and heating to 1250–1350°C, holding at that temperature for 0.5–1 hour. After melting, the mixture is cooled and crushed, and then separated from the iron-based alloy phase through density sorting.

5. The method for high-value reuse of recycled NdFeB permanent magnet materials according to claim 1, characterized in that, Step four includes the following specific operations: A nitric acid solution with a concentration of 2–4 mol / L was used for leaching for 1–2 hours at a liquid-to-solid ratio of 3:1–5:1 and a temperature of 70–85°C. The pH of the leachate was adjusted to 3.5–4.0, and iron and aluminum were removed by precipitation. After filtration, the pH was adjusted to 1.5–2.0, and oxalic acid was added to precipitate rare earth elements at a temperature of 50–70°C. The obtained rare earth oxalate is calcined at 800-900℃ for 2-3 hours to obtain mixed rare earth oxides, the total amount of which is not less than 98 wt%.

6. The method for high-value reuse of recycled NdFeB permanent magnet materials according to claim 1, characterized in that, In step five, the specific operation of the directional component reconstruction is as follows: The lumpy powder obtained from hydrogen crushing in step one provides the basic iron-boron framework and some light rare earth elements, while the mixed rare earth oxides obtained in step four provide supplementary light rare earth elements. Based on the total mass of raw materials used to prepare the recycled alloy as 100%, the amount of mixed rare earth oxides added is 15-25%, the amount of heavy rare earth metals added is 2-8%, the amount of trace elements added is 0.5-2%, and the remainder is the blocky powder after hydrogen crushing in step one. The heavy rare earth metal is dysprosium and / or terbium, and the trace element is one or more of cobalt, aluminum, copper, and gallium.

7. A method for high-value reuse of recycled neodymium iron boron permanent magnet materials according to claim 1 or 6, characterized in that, In step five, the vacuum degree of the melting and rapid solidification casting process is no greater than 5×10⁻²Pa, the casting temperature is 1420~1460℃, the surface linear velocity of the copper roller is 1.2~1.8m / s, and a recycled NdFeB alloy strip with a thickness of 0.2~0.3mm is obtained.

8. The method for high-value reuse of recycled neodymium iron boron permanent magnet materials according to claim 1, characterized in that, The recycled NdFeB alloy obtained in step five meets the following requirements: oxygen content not greater than 500 ppm, carbon content not greater than 1000 ppm, and total content of calcium, silicon, and chlorine not greater than 800 ppm.

9. A system for the high-value reuse of recycled neodymium iron boron permanent magnet materials, characterized in that, Along the material flow direction, the following are included in sequence: The classification pretreatment unit includes a demagnetizing device, a hot alkaline degreasing kettle, an alkaline stripping tank, a hydrogen crushing furnace, and a vacuum dryer; The oxygen-controlled roasting unit includes a fluidized bed reactor equipped with a nitrogen-air ratio adjustment system, and an online oxygen content detection and feedback control device. The hydrogen reduction-melting unit includes a densification furnace with dual-path atmosphere switching for hydrogen / argon, as well as a cooling crushing and density sorting device; The wet purification unit includes a nitric acid dissolution vessel, a pH fractional precipitation vessel, an oxalic acid precipitation vessel, and a calcination rotary kiln; The alloy recycling unit includes an automated batching system and a vacuum rapid solidification casting furnace.

10. A system for high-value reuse of recycled neodymium iron boron permanent magnet materials according to claim 9, characterized in that, In the oxygen-controlled roasting unit, a mixed gas distribution plate is provided at the bottom of the fluidized bed reactor. The online oxygen content detection and feedback control device monitors the oxygen concentration of the tail gas in real time through a zirconia oxygen analyzer and automatically adjusts the intake ratio of nitrogen and air to maintain the oxygen volume content in the roasting zone within the set range of 3% to 8%.

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