Method for preparing high-performance regenerated magnet by recycling neodymium iron boron waste

Abstract

The invention discloses a method for preparing a high-performance regenerated magnet by recycling neodymium-iron-boron waste, which comprises the following steps of: (1) pretreating the neodymium-iron-boron waste, sampling, detecting the components of the waste by ICP, classifying the components of the waste, and converting the components of the waste into the components with the following atomic percentage general formula: Rer0Gag0Bb0Mm0Fef0, wherein r0, g0, b0, m0 and f0 respectively represent the atomic percentage contents of Re, Ga, B, M and Fe elements in the neodymium-iron-boron waste; (2) designing the component of the target neodymium-iron-boron magnet as Rer1Gag1Bb1Mm1Fef1; wherein x1 is equal to b1 / f1, and the range of x1 is 0.062 to 0.072; y1 = r1 / f1, and the range of y1 is 0.17-0.21; z1 is equal to g1, and the range of z1 is 0.05%-0.5%; feeding according to the component difference between the neodymium-iron-boron waste and the target neodymium-iron-boron magnet; and (3) smelting the neodymium iron boron waste and supplemented raw materials, and preparing the high-performance regenerated magnet according to a conventional process. According to the method, the target magnet is designed to be low in boron and high in gallium, so that the Re6Fe13Ga phase exists in the magnet, the adverse effect caused by high carbon is weakened, the high-performance neodymium-iron-boron magnet with the performance close to or even higher than that of an original magnet is obtained, and therefore the production quality of the neodymium-iron-boron magnet is improved.

Description

Technical Field

[0001] The invention belongs to the field of sintered NdFeB magnets, and in particular relates to a method for preparing high-performance regenerated magnets by recycling NdFeB waste. Background Art

[0002] NdFeB magnet is a high-performance magnetic material widely used in various electronic devices, such as electric vehicles, wind turbines, maglev trains, etc. With the development of science and technology and the improvement of environmental protection requirements, the performance requirements of NdFeB magnets are getting higher and higher. At the same time, since a large amount of waste will be generated in the production process of NdFeB magnets, how to effectively recycle these wastes and reduce resource waste and environmental pollution has become a problem that needs to be solved urgently. In the field of magnetic material manufacturing technology, sintered NdFeB waste is usually recycled by smelting and separation method, that is, the waste is crushed, burned and other series of treatments, and then the required rare earth oxides are separated by chemical methods, and then electrolytic reduction is used to obtain rare earth metals; rare earth metals are then smelted, powdered, molded, and sintered to obtain NdFeB magnets. The crushing and adding method can also be used to recycle NdFeB waste, such as CN112331474A, the waste is hydrogen-crushed and powdered, and then blended with normal NdFeB powder to produce NdFeB magnets.

[0003] In the existing technology, although the smelting separation method can obtain high-performance magnets, it needs to go through a complex smelting separation process, which is long and costly, and the recycling rate is low. Elements other than rare earths cannot be recycled, which easily leads to resource waste and environmental pollution. The crushing and adding method has a short process step, but the waste material is easy to bring in impurities, causing magnet defects and affecting the magnet strength; and the magnetic properties of the waste material are uncontrollable, and the magnetic properties of the entire batch of products may be affected by individual waste materials with poor magnetic properties, which cannot meet the market demand for high-performance magnets.

[0004] Therefore, how to develop an efficient, environmentally friendly and economical NdFeB waste recycling technology is an urgent problem to be solved in this field. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing high-performance regenerated magnets by recycling NdFeB waste.

[0006] The technical solution adopted by the present invention is: A method for preparing high-performance regenerated magnets by recycling NdFeB waste, the method comprising the following steps: (1) Waste composition analysis: After pretreatment, the NdFeB waste is sampled and the waste composition is tested by ICP. The waste components are classified and converted into atomic percentages as follows: Re r0 Ga g0 B b0 Mm0 Fe f0 , all rare earth elements are included in Re; Al, Cu, Nb, Zr, Ti, and Mn are included in M; elements other than Re, Ga, B, and M are included in Fe, r0, g0, b0, m0, and f0 represent the atomic percentage contents of Re, Ga, B, M, and Fe elements in NdFeB waste respectively, and f0=100%-r0-g0-b0-m0.

[0007] (2) Composition design: The composition of the design target NdFeB magnet is Re r1 Ga g1 B b1 M m1 Fe f1 r1, g1, b1, m1, and f1 represent the atomic percentage contents of Re, Ga, B, M, and Fe in the target NdFeB magnets, respectively. Where x1=b1 / f1, the range of x1 is limited to 0.062~0.072; y1=r1 / f1, limit the range of y1 to 0.17~0.21; z1=g1, the range of z1 is limited to 0.05%~0.5%; f1=100%-r1-g1-b1-m1 Feeding is carried out according to the difference in composition between NdFeB waste and target NdFeB magnets; (3) Adding NdFeB waste and supplementary raw materials into a vacuum induction furnace for smelting to obtain NdFeB alloy, and then producing high-performance recycled magnets according to conventional processes.

[0008] In the step (3), the NdFeB alloy is subjected to hydrogen crushing and air flow grinding to obtain powder; the obtained powder is subjected to orientation molding, and then vacuum sintering and tempering treatment to obtain a high-performance regenerative magnet.

[0009] The orientation molding is generally carried out in a magnetic field of ≥1.2T; The vacuum sintering is generally carried out in a vacuum sintering furnace at a temperature of 1000-1110° C. for 3-15 hours; The tempering treatment includes a two-stage tempering treatment, wherein the first-stage tempering treatment is tempering at a temperature of 880-920° C. for 1-6 hours, and the second-stage tempering treatment is tempering at a temperature of 420-500° C. for 2-8 hours.

[0010] In the step (1), x0=b0 / f0, y0=r0 / f0, z0=g0.

[0011] In the present invention, all rare earth elements are counted as Re, and the rare earth elements include: Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0012] In the step (1), the pretreatment steps of the NdFeB waste are: high temperature demagnetization, degreasing, cleaning, vibration grinding, and sieving to remove visible impurities. The obtained waste is classified and sampled. The sampling can be a single sample or a mixed sample.

[0013] In the present invention, the design adopts Re6Fe 13 Ga phase is used to weaken the adverse effects caused by high carbon in NdFeB scrap recycled magnets, and in order to generate enough Re6Fe 13 Ga phase, b1:f1 must satisfy ≤0.072, otherwise Re2Fe will be generated first 14 Phase B consumes almost all Fe, and there is not enough Fe, so Re6Fe 13 Ga phase is difficult to generate or the generated amount is very small, so it cannot play the role of Re6Fe 13 Ga phase weakens the adverse effects of carbon. At the same time, considering other magnetic properties, it is more reasonable to take b1 / f1 as 0.062~0.072, that is, the range of x1 is 0.062~0.072. The higher the Hcj requirement of the target magnet or the higher the carbon content in the NdFeB scrap, the value of x1 should be appropriately reduced.

[0014] NdFeB magnets are mainly composed of the main phase Re2Fe 14 The B phase and the grain boundary Re-rich phase are composed of the Re-rich phase. The presence of a sufficient Re-rich phase can decouple the magnet to have high magnetic properties. 14 The B phase requires r1:f1=1:7, which is approximately equal to 0.14. To obtain sufficient grain boundary Re-rich phase, this ratio needs to be ≥0.14. Considering the high comprehensive magnetic properties and high cost performance, this ratio is usually 0.14~0.17 in conventional processes. For the high carbon characteristics of NdFeB waste recycled magnets, the present invention adjusts this ratio to 0.17~0.21, that is, the range of y1 is 0.17~0.21, and the higher the carbon content, the higher the value of y1 should be. Increasing the y1 value is equivalent to increasing the Re element content in the magnet, which is beneficial to improving the magnetic property Hcj, but the higher the y1 value is, the more rare earth elements are added, which will increase the production cost. When y1 reaches a certain value, the beneficial effect on Hcj tends to be flat or even reduced, and the adverse effect on Br is more obvious. Therefore, the design of y1 should comprehensively consider the balance between cost and magnet performance. In addition, there will be a small amount of burnout of the Re element during the production process, so when designing the y1 value, it can be appropriately higher than the actual value.

[0015] 6Fe 13The formation of Ga phase requires Ga element, which generates Re6Fe 13 The Ga phase requires the atomic percentage of Ga to be ≥ 0.05%. The higher the Ga content, the higher the cost. However, if there is enough Re and Fe, the generated Re6Fe 13 The more Ga phase there is, the better the Hcj of the magnet. Considering the comprehensive magnetic properties and cost performance, the Ga content is controlled at 0.05%~0.5%, that is, the range of z1 is 0.05%~0.5%. The value of z1 is related to the x1 value, that is, it is related to the carbon content of the NdFeB scrap and the Hcj of the target magnet. The higher the x1 value, the lower the z1 value should be. If z0<z1 or Ga is not detected in the NdFeB scrap, Ga element needs to be supplemented during smelting, and the amount of Ga supplement needs to be calculated by the difference between z1-z0, otherwise, no Ga supplement is needed.

[0016] In the step (2), the materials need to be added according to the difference in composition between the NdFeB scrap and the target NdFeB magnet. However, since the composition of the NdFeB scrap is diverse and uncontrollable, it is unknown which element is more and which element is less according to the composition design. Generally speaking, when adding materials, it is necessary to first determine which element is more, and supplement other elements based on this element.

[0017] Therefore, the specific feeding calculation steps are generally as follows: The difference of x0-x1 is used to evaluate the boron content in NdFeB scrap. x0=b0 / f0 is the mass ratio of boron to iron in NdFeB scrap, and x1=b1 / f1 is the mass ratio of boron to iron in the target NdFeB magnet. If the difference is positive, it means that the B in the scrap is x0-x1 more than Fe, otherwise it is x1-x0 less. The difference between y0 and y1 is used to evaluate the Re content in NdFeB scrap. y0 = r0 / f0 is the mass ratio of Re element to iron in NdFeB scrap. y1 = r1 / f1 is the mass ratio of Re element to iron in the target NdFeB magnet. If the difference is positive, it means that Re is y0-y1 more than Fe, otherwise it is y1-y0 less. Compare x0-x1, (y0-y1) / 2 and 0, and take the maximum value as k. The maximum value is to determine which of B, Re and Fe is relatively the largest. The largest element will be supplemented with the other two elements according to the relative difference. Because the content of Re in NdFeB magnets is about twice that of B, it is more reasonable to use (y0-y1) / 2 to compare with x0-x1.

[0018] Supplement boron according to the scrap weight × 0.138 × (k + x1 - x0). It should be noted that in actual production, ferroboron is generally used, and the addition amount of ferroboron needs to be calculated according to the boron content in ferroboron; supplement rare earth according to the scrap weight × (4k + 2y1 - 2y0), and different types of rare earth raw materials can be selected according to the target magnetic properties requirements; supplement pure iron according to the scrap weight × 8k; when z0 < z1, supplement Ga metal according to the scrap weight × 1.1 × (z1 - z0).

[0019] It should be noted that there are multiple rare earth elements, and there are molecular weight differences among different rare earth elements. Therefore, when supplementing rare earth by multiplying the scrap weight by (4k + 2y1 - 2y0), if different rare earth elements are selected for feeding, the atomic percentages may vary, but in practice, the impact on the atomic percentages of rare earth elements in the final recycled magnet is not significant and is within the target requirements range.

[0020] The main difficulties in the recovery and preparation of NdFeB by the waste melting method in the prior art are uncontrollable composition and high carbon content. The rare earth carbide deteriorates the grain boundary structure, thereby affecting the magnetic properties. The sintered NdFeB magnet prepared by the present invention can achieve controllable composition to a certain extent; by designing the target magnet to have low boron and high gallium, combined with an appropriate preparation process, there is Re6Fe 13 Ga phase in the magnet. This phase is distributed along the grain boundaries and has the function of repairing the lattice structure and weakening the adverse effects brought by high carbon, enabling the NdFeB magnet to have the high performance of a normal NdFeB magnet, and even the Hcj is higher than that of the original magnet. The technical solution has been verified to be feasible and has been applied to large-scale production to meet the market demand.

[0021] The beneficial effects of the present invention are as follows: 1. Solve the problem that it is difficult to obtain a stable high-performance NdFeB magnet in the prior art. Through waste remelting and reasonable adjustment of the waste composition, the magnet can still obtain high performance although it has a high carbon content. This is because the magnet has a high rare earth content, and there is still enough rare earth phase after combining with impurity elements such as carbon and oxygen; the low boron and high gallium composition design introduces Re6(FeCo) 13 Ga phase to repair the grain boundary structure and weaken the adverse effects of rare earth carbide on the grain boundaries.

[0022] 2. Solve the problems of relatively long recovery process and high cost in the prior art. Compared with the long-range rare earth recovery, the recovery process of the present invention does not require smelting separation, and a high-performance NdFeB magnet can be directly obtained through the remelting process, greatly shortening the recovery process and reducing the recovery cost.

[0023] 3. The problem of low recycling rate, inability to effectively utilize resources, and easy waste of resources and environmental pollution in the prior art is solved. The present invention recycles the NdFeB waste, fully utilizes all elements in the waste, reduces the pollution of the waste to the environment, and is conducive to sustainable development.

[0024] 4. The problem of difficulty in improving the production quality of NdFeB magnets in the prior art is solved. By adjusting the waste composition and the remelting process, the present invention can obtain high-performance NdFeB magnets with performance close to or even higher than that of the original magnets, thereby improving the production quality of NdFeB magnets. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below in conjunction with specific embodiments. The embodiments described below are exemplary and are only used to better understand the present invention, and should not be construed as limiting the present invention.

[0026] Embodiment 1: Take 500kg of N42 material skin, the original blank magnetic properties are Br 13.2kGs, Hcj 12.5kOe, clean it with degreasing spirit and water, grind it with sawdust and corundum, then sieve it to pick out the impurities visible to the naked eye; take a sample for ICP composition analysis to get: Pr 6.9 Nd 21 Ce 2.5 Cu 0.1 Al 0.3 Ga 0.1 Zr 0.2 B 0.95 Co 0.5 Fe bal (mass fraction), converted to atomic percentage general formula Re r0 Ga g0 B b0 M m0 Fe f0, it is obtained that r0 = 13.86%, g0 = 0.09%, b0 = 5.73%, m0 = 0.97%, f0 = 79.35%, and the carbon content is 1200 ppm. The target grade is N42M, and the target magnetic property is above 13 kGs + 14 kOe. Considering the above factors comprehensively, x1 = b1 / f1 takes the value of 0.07, y1 = r1 / f1 takes the value of 0.19, and z1 = g1 takes the value of 0.3%; it is calculated that b0 / f0 - x1 = 0.00226, (r0 / f0 - y1) / 2 = -0.00766. k is the maximum value of b0 / f0 - x1, (r0 / f0 - y1) / 2, and 0, then k = b0 / f0 - x1 = 0.00226. Since 0.138(k + x1 - b0 / f0) = 0, boron supplementation is not required; (4k + 2y1 - 2y0)×500 = 19.84, and 19.84 kg of PrNd metal needs to be supplemented (the PrNd alloy is an alloy with a Pr:Nd mass ratio of 25:75, and other rare earth elements or PrNd alloys with other mass ratios can also be supplemented. Although there are differences in the molecular weights of rare earth elements, the impact on the atomic percentage content results of the total rare earth elements is not significant. The same applies hereinafter); because g0 < z1, 1.1 kg of metal Ga needs to be supplemented (the calculation formula is (0.3% - 0.09%)×1.1×500 = 1.05 ≈ 1.135 kg). The amount of iron supplementation is the weight of the waste multiplied by 8k, and it is calculated that 8×0.00226×500 = 9.04 kg, so 9.04 kg of iron is supplemented. The neodymium iron boron waste and the supplementary raw materials are put into a vacuum melting furnace to melt the neodymium iron boron alloy; the hydrogen crushing + jet milling process is used to make powder, and the average particle size of the powder is 3.2 μm; under the protection of closed nitrogen, a magnetic field of 1.5 T is applied for orientation forming; it is sintered at 1080 °C for 8 hours in a vacuum sintering furnace, and the tempering process is 900 °C×4 hours + 460 °C×6 hours, and air-cooled to room temperature to obtain the neodymium iron boron blank. The composition of the blank is tested and converted into the general formula of atomic percentage, which is Re 14.9 Ga 0.3 B 5.51 M 0.93 Fe 78.36 . During the production process, a small amount of Re element will be burned out. The same applies hereinafter. r / f = 0.190, b / f = 0.070, g1 = 0.294%, and the actual composition is very close to the designed composition. A cylinder with a diameter of 10×10 is taken to test the magnetic properties. The results show that Br is 13 kGs and Hcj is 15.8 kOe. Without adding heavy rare earths, Hcj has a significant increase, greatly improving the high-temperature resistance of the magnet, making it possible for the recycled magnet of neodymium iron boron waste products to be applied to the high-end market.

[0027] Example 2: Take 500 kg of the material skin of N38 material. The original magnetic properties of the blank are Br = 12.4 kGs and Hcj = 12.1 kOe. The pretreatment is the same as that in Example 1. Sampling for ICP composition analysis gives: Pr 5.9 Nd 18 Ce8Cu 0.1 Al 0.5 Ga 0.2 Zr 0.2 B 0.85 Co 0.5 Fe bal (mass fraction). Converting to the general formula of atomic percentage Re r0 Ga g0 B b0 M m0 Fe f0 , it is obtained that r0 = 14.79%, g0 = 0.19%, b0 = 5.2%, m0 = 1.47%, f0 = 78.35%, and the carbon content is 1100 ppm. The target grade is N38M, and the target magnetic properties are above 12.4 kGs + 14 kOe. Considering the above factors comprehensively, x1 = b1 / f1 takes the value of 0.069, y1 = r1 / f1 takes the value of 0.2, and z1 = g1 takes the value of 0.25%; it is calculated that b0 / f0 - x1 = -0.00269, (r0 / f0 - y1) / 2 = -0.00563. k is the maximum value of b0 / f0 - x1, (r0 / f0 - y1) / 2, and 0, then k = 0. Since 0.138(k + x1 - x0)×500 = 0.185, 0.185 kg of boron needs to be added. Note: In the operation, it is necessary to convert according to the purity of ferrosilicon boron into the weight of ferrosilicon boron. The influence of the increased Fe on the composition is very small and can be ignored. The same applies hereinafter. (4k + 2y1 - 2y0)×500 = 11.26, 11.26 kg of PrNd metal needs to be added; since g0 < z1, 0.33 kg of metal Ga needs to be added (the calculation formula is (0.25% - 0.19%)×1.1×500 ≈ 0.33 kg). k = 0, no iron needs to be added. The subsequent process is the same as that in Example 1. Test the composition of the blank and convert it into the general formula of atomic percentage, which is Re 15.5 Ga 0.25 B 5.36 M 1.46 Fe 77.43 . r1 / f1 = 0.20, b1 / f1 = 0.069, g1 = 0.25%, and the actual composition is very close to the designed composition. Take a cylinder with a diameter of 10×10 to test the magnetic properties. The results show that Br = 12.4 kGs and Hcj = 14.5 kOe. Without adding heavy rare earths, Hcj has a significant increase and basically meets the design value.

[0028] Example 3: Take 500 kg of the material skin of N35H material. The original magnetic properties of the blank are Br = 12.1 kGs and Hcj = 17.3 kOe. The pretreatment is the same as in Example 1; samples are taken for ICP composition analysis to obtain: Pr 7.9 Nd 24 Cu 0.1 Ga 0.2 Zr 0.2 B 0.88 Co 0.5 Fe bal (mass fraction). Converted to the general formula of atomic percentage Re r0 Ga g0 B b0 M m0 Fe f0 , and it is obtained that r0 = 14.78%, g0 = 0.19%, b0 = 5.41%, m0 = 0.25%, f0 = 79.37%, and the carbon content is 1000 ppm. The target grade is N35H, and the target magnetic properties are above 12 kGs + 18 kOe. Considering the above factors comprehensively, x1 = b1 / f1 takes the value of 0.069, y1 = r1 / f1 takes the value of 0.175, and z1 = g1 takes the value of 0.33%; it is calculated that b0 / f0 - x1 = -0.00083, (r0 / f0 - y1) / 2 = 0.00566. k is the maximum value of b0 / f0 - x1, (r0 / f0 - y1) / 2, and 0, then k = 0.00566. Because 0.138(k + x1 - x0)×500 = 0.45, 0.45 kg of boron needs to be added. 4k + 2y1 - 2y0 = 0, so no Re needs to be added. Because g0 < z1, 0.766 kg of metallic Ga needs to be added (the calculation formula is (0.33% - 0.19%)×1.1×500 ≈ 0.766 kg). The amount of iron added is the weight of the waste multiplied by 8k, and it is calculated that 8×0.00566×500 = 22.65 kg, so 22.65 kg of iron is added. The subsequent process is the same as in Example 1. The composition of the blank is tested and converted into the general formula of atomic percentage, which is Re 13.82 Ga 0.32 B 5.63 M 0.24 Fe 79.99 . r1 / f1 = 0.173, b1 / f1 = 0.07, g1 = 0.32%, and the actual composition is close to the designed composition. Take a cylinder with a diameter of 10×10 to test the magnetic properties. The results show that Br = 12 kGs and Hcj = 18.4 kOe. In this example of the process, no new rare earth raw materials are put in. Therefore, when the total mass of rare earth elements does not change, the Hcj of the recycled magnet increases by 1.1 kOe, and the magnetic properties are improved. In this example, the value of y1 is relatively low, and the increase range of Hcj is limited, but the magnetic properties of the obtained recycled magnet still meet the design requirements.

Claims

1. A method for preparing high-performance regenerated magnets by recycling NdFeB waste, characterized in that The method includes the following steps: (1) Waste composition analysis: After pretreatment, the NdFeB waste is sampled and the waste composition is tested by ICP. The waste components are classified and converted into atomic percentages as follows: Re r0 Ga g0 B b0 M m0 Fe f0 , all rare earth elements are included in Re; Al, Cu, Nb, Zr, Ti, Mn are included in M; elements other than Re, Ga, B, M are included in Fe, r0, g0, b0, m0, f0 represent the atomic percentage content of Re, Ga, B, M, Fe elements in NdFeB waste, f0=100%-r0-g0-b0-m0; (2) Composition design: The composition of the design target NdFeB magnet is Re r1 Ga g1 B b1 M m1 Fe f1 r1, g1, b1, m1, and f1 respectively represent the atomic percentage contents of Re, Ga, B, M, and Fe elements in the target NdFeB magnet. Where x1 = b1 / f1, and the range of x1 is limited to 0.062 - 0.

072. y1 = r1 / f1, and the range of y1 is limited to 0.17 - 0.

21. z1 = g1, and the range of z1 is limited to 0.05% - 0.5%. f1 = 100% - r1 - g1 - b1 - m1. Charging is carried out according to the compositional differences between the NdFeB waste and the target NdFeB magnet. (3) Adding the NdFeB waste and the supplementary raw materials into a vacuum induction furnace for smelting to obtain an NdFeB alloy, and preparing a high-performance recycled magnet according to the conventional process.

2. The method according to claim 1, characterized in that In the step (1), all rare earth elements are included in Re, and the rare earth elements include: Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu.

3. The method according to claim 1, characterized in that In the step (3), the NdFeB alloy is hydrogenated and crushed, and then ground into powder by a jet mill; the obtained powder is oriented and formed, and then subjected to vacuum sintering and tempering treatment to prepare a high-performance recycled magnet.

4. The method according to claim 3, characterized in that The orientation forming is carried out under a magnetic field ≥ 1.2T; the vacuum sintering is carried out in a vacuum sintering furnace at a temperature of 1000 - 1110°C for 3 - 15 hours; the tempering treatment includes a two-stage tempering treatment, where the first-stage tempering treatment is carried out at a temperature of 880 - 920°C for 1 - 6 hours, and the second-stage tempering treatment is carried out at a temperature of 420 - 500°C for 2 - 8 hours.

5. The method according to claim 1, characterized in that In the step (2), the charging calculation steps are as follows: The difference between x0 and x1 is used to evaluate the boron content in the NdFeB waste. x0 = b0 / f0 is the mass ratio of boron to iron in the NdFeB waste, and x1 = b1 / f1 is the mass ratio of boron to iron in the target NdFeB magnet. If the difference is positive, it means that B in the waste is more than Fe by x0 - x1, and vice versa, it is less by x1 - x0. The difference between y0 and y1 is used to evaluate the Re content in the NdFeB waste. y0 = r0 / f0 is the mass ratio of the Re element to iron in the NdFeB waste, and y1 = r1 / f1 is the mass ratio of the Re element to iron in the target NdFeB magnet. If the difference is positive, it means that Re is more than Fe by y0 - y1, and vice versa, it is less by y1 - y0. Compare x0 - x1, (y0 - y1) / 2, and 0, and take the maximum value as k. Supplement boron according to the waste weight × 0.138 × (k + x1 - x0); supplement rare earth according to the waste weight × (4k + 2y1 - 2y0); supplement pure iron according to the waste weight × 8k; when z0 < z1, supplement Ga metal according to the waste weight × 1.1 × (z1 - z0).

6. The method according to claim 1, characterized in that In the step (1), the pretreatment steps of the NdFeB waste are: high-temperature demagnetization, degreasing, cleaning, vibration milling, sieving to remove visible impurities, and sampling after classifying the obtained waste.