High intrinsic coercive force corrosion-resistant neodymium iron boron magnet and preparation method thereof

Abstract

The invention relates to the field of neodymium-iron-boron magnet preparation, in particular to a high intrinsic coercive force corrosion-resistant neodymium-iron-boron magnet and a preparation method thereof. Comprising the following steps of melt-spinning, hydrogen demolishing and grinding, compression molding, sintering processing and phosphating treatment, wherein corrosion-resistant components comprise methyl vinyl silazane and polysilazane resin; the phosphating solution comprises the following components in concentration: 30-100 g / L of monopotassium phosphate, 100-200 g / L of phosphoric acid and 5-10 g / L of manganous nitrate; the temperature range of the high-temperature phosphating treatment is 85-98 DEG C. The silicon nitride ceramic is generated by sintering the corrosion-resistant components, so that the corrosion resistance of the neodymium-iron-boron magnet added with Tb and Dy is improved; meanwhile, the sintered neodymium-iron-boron magnet is subjected to phosphating treatment, a phosphating film with high adhesive force is generated through potassium ions in a phosphating solution and silicon nitride ceramic at a high temperature, the corrosion resistance of the neodymium-iron-boron magnet is further improved, and therefore the high intrinsic coercive force corrosion-resistant neodymium-iron-boron magnet is prepared.

Description

Technical Field

[0001] This application relates to the field of neodymium iron boron magnet preparation, and specifically relates to a high intrinsic coercivity and corrosion-resistant neodymium iron boron magnet and a preparation method thereof. Background Art

[0002] Neodymium iron boron magnet (NdFeB) is an alloy composed of elements such as neodymium (Nd), iron (Fe), and boron (B). Neodymium iron boron magnet is the third-generation rare earth permanent magnet material developed and successfully applied in production in the 1980s. Due to its advantages such as high remanence, high coercivity, high magnetic energy product, and good dynamic recovery characteristics, it is currently the magnetic material with the best cost performance. Because of its excellent magnetic properties, it is known as the "magnetic king" and plays an important role in fields such as medical treatment, automobiles, household appliances, aerospace, and communication, and has broad application prospects.

[0003] Intrinsic coercivity is the core index for measuring the demagnetization resistance of magnetic materials. In the application process of neodymium iron boron magnets, high-temperature environments are often encountered. Only magnetic materials with high intrinsic coercivity can effectively resist thermally activated demagnetization and ensure that the equipment maintains a stable magnetic field strength at high temperatures. To improve the intrinsic coercivity of neodymium iron boron magnets, adding heavy rare earth elements is a conventional method. However, for neodymium iron boron magnets added with heavy rare earth elements, their corrosion resistance will decrease, which limits the application of high intrinsic coercivity neodymium iron boron magnets. Summary of the Invention

[0004] To solve the problem that the corrosion resistance of neodymium iron boron magnets added with heavy rare earth elements will decrease, this application provides a preparation method for a high intrinsic coercivity and corrosion-resistant neodymium iron boron magnet. Through the cooperation of the corrosion-resistant component and potassium dihydrogen phosphate in the phosphating solution at high temperature, while ensuring the high intrinsic coercivity of the neodymium iron boron magnet, high corrosion resistance is maintained.

[0005] In the first aspect, this application provides a preparation method for a high intrinsic coercivity and corrosion-resistant neodymium iron boron magnet, adopting the following technical scheme: A preparation method for a high intrinsic coercivity and corrosion-resistant neodymium iron boron magnet, comprising the following steps: Melting and strip casting: Mix the metal raw materials according to the formula amount, melt the mixture to obtain a molten liquid, and pour and strip cast the molten liquid to obtain strip cast sheets; Hydrogen decrepitation and grinding: Hydrogen decrepitate the strip cast sheets into coarse powder, and obtain alloy powder after passing the coarse powder through a jet mill; Pressing and forming: Place the obtained alloy powder and the corrosion-resistant component in a mold, and press and form to obtain a sintered green compact; Sintering and processing: Sinter the sintered green compact under the protection of nitrogen, rapidly cool it to room temperature in stages after sintering, and perform tempering treatment to obtain a neodymium iron boron magnet; Phosphating treatment: After the surface of the neodymium iron boron magnet is treated, it is placed in a phosphating solution for high-temperature phosphating treatment, and then taken out and rinsed to obtain a phosphated neodymium iron boron magnet; The metal raw materials include the following components in parts by weight: Pr 6.5 - 7 parts, Nd 19.5 - 21 parts, B 0.90 - 1.03 parts, Tb 4 - 6 parts, Dy 0 - 1 part, Co 1 - 2 parts, Fe 64 - 68 parts; The corrosion-resistant component includes at least one of methylvinylsilazane and polysilazane resin; The phosphating solution includes the following components in concentration: potassium dihydrogen phosphate 30 - 100 g / L, phosphoric acid 100 - 200 g / L, manganese nitrate 5 - 10 g / L; The temperature range of the high-temperature phosphating treatment is 85 - 98 °C.

[0006] In this application, silicon nitride ceramics are sintered by the corrosion-resistant component to improve the corrosion resistance and intrinsic coercivity of the neodymium iron boron magnet added with Tb and Dy; at the same time, the sintered neodymium iron boron magnet is subjected to phosphating treatment. Through the potassium ions in the phosphating solution, a phosphating film with high adhesion is generated with the silicon nitride ceramics at high temperature, further improving the corrosion resistance of the neodymium iron boron magnet, thereby preparing a neodymium iron boron magnet with high intrinsic coercivity and corrosion resistance.

[0007] By adopting the above technical solution, heavy rare earth metals such as Tb and Dy are added to the neodymium iron boron magnet, mainly to enhance the intrinsic coercivity of the magnet, thereby improving its performance stability in high-temperature environments. However, the addition of these heavy rare earth metals does reduce the corrosion resistance of the neodymium iron boron magnet.

[0008] Methylvinylsilazane and polysilazane resin can form a temporary bonding network at low temperatures. This network structure provides additional support during the green body stage of the magnet, enhancing the mechanical strength of the green body. By reducing the generation of cracks, these resins help improve the density and forming accuracy of the compacted blank, thereby ensuring the structural integrity and performance consistency of the final magnet. During the sintering process, methylvinylsilazane and polysilazane resin crack under high-temperature conditions to produce silicon nitride ceramics. The silicon nitride ceramics can cover the grain boundaries and surfaces of the neodymium iron boron magnet, forming a dense physical barrier. This barrier effectively inhibits the penetration of oxygen and corrosive media, thereby improving the corrosion resistance of the magnet.

[0009] Phosphating treatment can form a dense phosphating film on the surface of the magnet. This phosphating film can well cover the micropores and defects on the surface of the magnet, reducing the direct contact between the corrosive medium and the magnet substrate, thereby preventing these defects from becoming the starting point of corrosion. The formation of the phosphating film can also make the surface of the magnet smoother, reducing the surface roughness, which helps reduce the friction and wear between the magnet and the surrounding environment during use, and extends the service life of the magnet.

[0010] Potassium dihydrogen phosphate is one of the key components in the phosphating solution. The corrosion-resistant component produces silicon nitride ceramics after sintering. Among them, potassium ions form coordination bonds with nitrogen atoms on the silicon nitride ceramics at 85 - 98 °C, thereby generating a stable complex. The phosphating film formed in this way has stronger adhesion, further protecting the magnet substrate from being eroded by the corrosive medium and improving the corrosion resistance of the neodymium iron boron magnet.

[0011] In this application, the corrosion-resistant component is sintered to produce silicon nitride ceramics, improving the corrosion resistance of the neodymium iron boron magnet doped with Tb and Dy. At the same time, the sintered neodymium iron boron magnet is subjected to phosphating treatment. Through the potassium ions in the phosphating solution, a phosphating film with high adhesion is generated with the silicon nitride ceramics at high temperature, further improving the corrosion resistance of the neodymium iron boron magnet, thereby preparing a neodymium iron boron magnet with high intrinsic coercivity and corrosion resistance.

[0012] Preferably, the corrosion-resistant component is polysilazane resin.

[0013] By adopting the above technical solution, during the high-temperature sintering process of methylvinylsilazane and polysilazane resin, gases such as ammonia and carbon dioxide may be released, which will instead increase the porosity of the neodymium iron boron magnet. When the porosity is too high, defects such as micropores and rough surfaces are likely to appear inside and on the surface of the magnet. These defects are likely to become the starting points of corrosion in high-temperature and high-humidity environments, accelerating the corrosion process. In comparison, the corrosion resistance of the neodymium iron boron magnet added with polysilazane resin is better than that of the neodymium iron boron magnet added with methylvinylsilazane, probably because the gas release of polysilazane resin is less.

[0014] Preferably, the weight part of the corrosion-resistant component is 0.2 - 0.5 parts.

[0015] Preferably, the weight part of the corrosion-resistant component is 0.4 parts.

[0016] By adopting the above technical solution, when the content of the corrosion-resistant component is too low, the improvement effect on the corrosion resistance of the neodymium iron boron magnet is not obvious; when the content of the corrosion-resistant component is too high, the corrosion-resistant component will generate more gases during high-temperature sintering, and defects such as micropores and rough surfaces are likely to appear inside and on the surface of the magnet, instead reducing the corrosion resistance of the neodymium iron boron magnet. Therefore, after a large amount of research and experimental verification by the applicant, it is finally determined that the weight part of the corrosion-resistant component in this application is preferably as above.

[0017] Preferably, the concentration of potassium dihydrogen phosphate is 50 - 90 g / L.

[0018] Preferably, the concentration of potassium dihydrogen phosphate is 75 g / L.

[0019] By adopting the above technical solution, when the content of potassium dihydrogen phosphate is low, the number of potassium ions may not be sufficient to fully form a complex with the silicon-nitrogen bonds on the silicon nitride ceramic, resulting in a low adhesion of the phosphating film, and thus the corrosion resistance improvement of the neodymium iron boron magnet is not obvious. When the content of potassium dihydrogen phosphate in the phosphating solution is too high, it will lead to too high a concentration of potassium ions in the solution. Excessive potassium ions may form excessive intermetallic compounds or potassium-rich phases in the phosphating film, and these phases may reduce the hardness and wear resistance of the phosphating film, and instead reduce the corrosion resistance of the neodymium iron boron magnet.

[0020] Preferably, the time of the high-temperature phosphating treatment is 8-15 min.

[0021] By adopting the above technical solution, when the phosphating treatment time is too short, the phosphating reaction is insufficient, and the concentration of film-forming ions does not reach the solubility product, resulting in an overly thin phosphating film and it is difficult to form a dense protective layer; when the phosphating treatment time is too long, the phosphating reaction continues, resulting in an overly thick phosphating film and an increase in roughness, affecting the adhesion; therefore, after a large amount of research and experimental verification by the applicant, it is finally determined that the time of the high-temperature phosphating treatment in this application is preferably the above-mentioned time.

[0022] In a second aspect, this application provides a neodymium iron boron magnet with high intrinsic coercivity and corrosion resistance, adopting the following technical solution: A neodymium iron boron magnet with high intrinsic coercivity and corrosion resistance is prepared by the preparation method of the neodymium iron boron magnet with high intrinsic coercivity and corrosion resistance described above.

[0023] In summary, this application has the following beneficial effects: In this application, a silicon nitride ceramic is generated by sintering corrosion-resistant components, improving the corrosion resistance of the neodymium iron boron magnet doped with Tb and Dy; at the same time, the sintered neodymium iron boron magnet is subjected to a phosphating treatment, and through the potassium ions in the phosphating solution, a phosphating film with high adhesion is generated with the silicon nitride ceramic at high temperature, further improving the corrosion resistance of the neodymium iron boron magnet, thereby preparing a neodymium iron boron magnet with high intrinsic coercivity and corrosion resistance. Detailed Embodiments

[0024] The raw materials in this application include the following parts: Methylvinylsilazane: 1,1,3,3-tetramethyl-1,3-divinyldisilazane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasilazane, etc. can be selected. In this application, 1,1,3,3-tetramethyl-1,3-divinyldisilazane with a CAS number of 7691-02-3 (hereinafter referred to as tetramethyldivinyldisilazane) is used as an example for illustration;

[0025] Polysilazane resin: A commercially available product with a CAS number of 475645-84-2;

[0026] The present application will be further described in detail below with reference to examples and comparative examples.

[0027] Example 1 A method for preparing a neodymium-iron-boron magnet, comprising the following steps: Melting and strip casting: 68 g of Pr, 205 g of Nd, 9.5 g of B, 50 g of Tb, 5 g of Dy, 15 g of Co, and 660 g of Fe are mixed, and the mixture is put into a vacuum melting furnace for melting to obtain a molten liquid. The molten liquid is cast and strip-cast to obtain strip-cast sheets; Hydrogen decrepitation and grinding: The strip-cast sheets are hydrogen-decrepitated into coarse powder, and the coarse powder is ground by a jet mill to obtain alloy powder; Compression molding: The obtained alloy powder and 4 g of polysilazane resin are placed in a mold and compression-molded to obtain a green compact for sintering; Sintering process: The green compact for sintering is sintered under the protection of nitrogen. The sintering temperature is 1100 °C, and the holding time is 3 h. After sintering, it is rapidly cooled to room temperature in stages and subjected to tempering treatment to obtain a neodymium-iron-boron magnet; Phosphating treatment: After the surface of the neodymium-iron-boron magnet is treated, it is heated to 93 °C in 10 L of phosphating solution, and then the neodymium-iron-boron magnet is put into the phosphating solution for phosphating treatment for 12 min, and then taken out and rinsed to obtain a phosphated neodymium-iron-boron magnet.

[0028] Among them, the cooling after sintering of the green compact for sintering includes three stages. In the first stage, the sintering temperature is reduced from 1100 °C to 800 °C, the cooling rate is 7 °C / min, and the holding time is 3 h. In the second stage, the sintering temperature is further decreased from 800 °C to room temperature at a rate of 4 °C / min. The tempering treatment includes two stages. In the first stage, the tempering temperature is 800 °C, and the tempering time is 2 h. After completion, the magnetic material is cooled to room temperature using argon, and then the second stage of tempering treatment is started. The second tempering temperature is 500 °C, and the tempering time is 3 h. After completion, the magnetic material is cooled to room temperature using argon.

[0029] The above surface treatment is to clean the neodymium-iron-boron magnet using an alkaline cleaning solution (a mixture of 100 g / L potassium hydroxide solution and 50 g / L sodium silicate solution, and the mixing volume ratio is potassium hydroxide solution:sodium silicate solution = 1:3), clean it using alcohol and non-woven fabric, and finally air-dry it for later use. Then, the cleaned neodymium-iron-boron magnet is soaked in a potassium nitrate molten solution for 4 min, taken out, dissolved in 35 °C water, rinsed, and dried.

[0030] The above phosphating solution includes components with the following concentrations: potassium dihydrogen phosphate 75 g / L, phosphoric acid 150 g / L, and manganese nitrate 8 g / L.

[0031] Examples 2 - 3 Example 2-3 Based on the preparation method of Example 1, the component ratio of the neodymium iron boron magnet was adjusted, and the specific adjustment is shown in Table 1.

[0032] Comparative Examples 1-4 Comparative Example 1 Based on the preparation method of Example 1, 4 g of polysilazane resin was not added, and phosphating treatment was not carried out, and the other conditions remained unchanged.

[0033] Comparative Example 2 Based on the preparation method of Comparative Example 1, Tb and Dy were not added, and the other conditions remained unchanged.

[0034] Comparative Example 3 Based on the preparation method of Example 1, 4 g of polysilazane resin was not added, and the other conditions remained unchanged.

[0035] Comparative Example 4 Based on the preparation method of Example 1, potassium dihydrogen phosphate in the phosphating solution was replaced with zinc dihydrogen phosphate, and the other conditions remained unchanged.

[0036] Performance detection test The neodymium iron boron magnets of the above Examples 1-3 and Comparative Examples 1-4 were analyzed, and the specific detection methods are as follows: Magnetic properties According to GB / T3217-2013 "Magnetic Test Methods for Permanent Magnet (Hard Magnetic) Materials", its comprehensive magnetic properties were detected.

[0037] Corrosion resistance A neutral salt spray test was carried out. An aqueous sodium chloride solution with a concentration of 5 wt% was used to spray the magnetic material sample, and the test temperature was 35 °C. Since the corrosion reaction of the neodymium iron boron magnet in neutral salt spray is mainly oxidation and exfoliation, the weight loss rate was used as the detection basis for the corrosion resistance of the magnetic material sample, and the weight loss rate = (mass before impregnation - mass after impregnation) / mass before impregnation.

[0038] According to the above detection methods, the test results of Examples 1-3 and Comparative Examples 1-4 were obtained, as shown in Table 1 below: Table 1 Component ratio and performance detection table of neodymium iron boron magnets of Examples 1-3 and Comparative Examples 1-4 (unit: g)

[0039] Referring to Table 1, comparing Examples 1-3 and Comparative Examples 1-4, it can be seen that compared with Example 1 and Comparative Examples 1-2, when heavy rare earth elements such as Tb and Dy are added to the formula of the neodymium iron boron magnet, the intrinsic coercivity of the neodymium iron boron magnet can be greatly improved. It may be because Tb and Dy, as heavy rare earth elements, have special magnetic properties in the magnet, which can effectively enhance the intrinsic coercivity of the magnet.

[0040] It can also be found that when more heavy rare earth elements (Tb and Dy) are added to the NdFeB magnet formula, the corrosion resistance of the NdFeB magnet will be reduced. This may be because when Tb and Dy replace part of neodymium, the main phase Nd2Fe 14 There is an electrochemical potential difference between B and the neodymium-rich phase Nd-rich, which makes the magnet more susceptible to corrosion in an electrochemical environment.

[0041] Compared with Example 1 and Comparative Examples 3-4, only phosphating treatment is performed, and the corrosion resistance of the NdFeB magnet is limited. In addition, replacing potassium dihydrogen phosphate with zinc dihydrogen phosphate in the phosphating solution will also affect the corrosion resistance of the NdFeB magnet. It may be because the polysilazane resin produces silicon nitride ceramics after sintering, and the silicon nitride ceramics can cover the grain boundaries and surfaces of the NdFeB magnets to form a dense physical barrier. This barrier effectively inhibits the penetration of oxygen and corrosive media, thereby improving the corrosion resistance of the magnet. In addition, potassium ions form coordination bonds with nitrogen atoms on silicon nitride ceramics at 85-98°C, thereby generating stable complexes. The phosphating film generated in this way has stronger adhesion, further protects the magnet substrate from erosion by corrosive media, and improves the corrosion resistance of the NdFeB magnet.

[0042] Therefore, it is necessary to add heavy rare earth elements such as Tb and Dy to improve the intrinsic coercivity of NdFeB magnets. At the same time, it is necessary to add corrosion-resistant components such as polysilazane resin and perform phosphating treatment. The phosphating solution includes potassium dihydrogen phosphate, which can greatly improve the corrosion resistance of NdFeB magnets.

[0043] Comparing the intrinsic coercivity of Examples 1-3, Example 1 has the highest intrinsic coercivity, and its corrosion resistance is substantially equivalent to that of Example 2, so it is preferred.

[0044] Embodiment 4-7 In Example 4-6, based on the preparation method of Example 1, the amount of polysilazane resin added was adjusted, and the specific adjustment is shown in Table 2.

[0045] Example 7 Based on the preparation method of Example 1, in the pressing step, the obtained alloy powder and 4 g of tetramethyldivinyldisilazane are placed in a mold and pressed to obtain a sintered green body.

[0046] According to the above detection method, the test results of Examples 4-7 were obtained, as shown in Table 2 below.

[0047] Table 2 Performance test data table of Example 1 and Examples 4-7

[0048] Referring to Table 2, by comparing Example 1 with Examples 4 - 7, it can be seen that adding tetramethyldivinyldisilazane or polysilazane resin can increase the corrosion resistance of NdFeB magnets. This may be because during the sintering process, methylvinylsilazane and polysilazane resin crack under high-temperature conditions to produce silicon nitride ceramics. At the same time, the silicon nitride ceramics can cover the grain boundaries and surfaces of the NdFeB magnets, forming a dense physical barrier. This barrier effectively inhibits the penetration of oxygen and corrosive media, thus significantly improving the corrosion resistance of the magnets.

[0049] Comparatively speaking, the corrosion resistance of NdFeB magnets added with polysilazane resin is better than that of NdFeB magnets added with tetramethyldivinyldisilazane. This may be because the polysilazane resin releases less gas, and there are fewer defects such as micropores and rough surfaces inside and on the surface of the magnets, thus having higher corrosion resistance.

[0050] Examples 8 - 11 Based on the preparation method of Example 1, for Examples 8 - 11, the concentrations of each component of the phosphating solution were adjusted, and the specific adjustments are shown in Table 3.

[0051] Comparative Example 5 Based on the preparation method of Example 1, for Comparative Example 5, the concentrations of each component of the phosphating solution were adjusted to potassium dihydrogen phosphate 10 g / L, phosphoric acid 350 g / L, and potassium nitrate 10 g / L.

[0052] The NdFeB magnets of Examples 8 - 11 and Comparative Example 5 were subjected to the above performance tests, and the test results are shown in Table 3.

[0053] Table 3 Data table of the component ratios and performance test of the phosphating solutions of Example 1, Examples 8 - 11, and Comparative Example 5

[0054] Referring to Table 3, by comparing Example 1, Examples 8 - 11, and Comparative Example 5, it can be seen that as the concentration of potassium dihydrogen phosphate increases, the 96 - h weight loss rate of the NdFeB magnets shows a trend of first decreasing and then increasing. This may be because as the concentration of potassium dihydrogen phosphate increases, the potassium ion content increases, and gradually forms complexes with the silicon - nitrogen bonds on the silicon nitride ceramics sufficiently, making the adhesion of the phosphating film gradually increase, thus continuously improving the corrosion resistance of the NdFeB magnets. When exceeding a certain range, excessive potassium ions may form excessive intermetallic compounds or potassium - rich phases in the phosphating film, and these phases may reduce the hardness and wear resistance of the phosphating film, instead reducing the corrosion resistance of the NdFeB magnets.

[0055] Examples 12 - 13 Based on the preparation method of Example 1, for Examples 12 - 13, the heating temperature in the phosphating treatment step was adjusted, and the specific adjustments are shown in Table 4.

[0056] Comparative Examples 6-7 Based on the preparation method of Example 1, the heating temperature in the phosphating treatment step was adjusted for Comparative Examples 6-7. The specific adjustments are shown in Table 4.

[0057] The NdFeB magnets of Examples 12-13 were subjected to the above performance tests, and the test results are shown in Table 4.

[0058] Table 4 Data Table of Heating Temperature and Performance Tests for Example 1, Examples 12-13, and Comparative Examples 6-7

[0059] Referring to Table 4, by comparing Example 1, Examples 12-13, and Comparative Examples 6-7, it can be seen that as the heating temperature during phosphating treatment continuously increases, the 96h weight loss rate of the NdFeB magnets shows a trend of first decreasing and then increasing. This may be because as the heating temperature during phosphating treatment continuously increases, the silicon nitride ceramics formed by potassium ions and polysilazane resin continuously form coordination bonds, enhancing the adhesion of the phosphating film, thereby enhancing the corrosion resistance of the NdFeB magnets; when exceeding a certain range, the excessive temperature may cause the structure of the phosphating film to be loose, thereby reducing the corrosion resistance of the NdFeB magnets.

[0060] Examples 14-17 Based on the preparation method of Example 1, the phosphating treatment time in the phosphating treatment step was adjusted for Examples 14-17. The specific adjustments are shown in Table 5.

[0061] The NdFeB magnets of Examples 14-17 were subjected to the above performance tests, and the test results are shown in Table 5.

[0062] Table 5 Data Table of Phosphating Treatment Time and Performance Tests for Example 1 and Examples 14-17

[0063] Referring to Table 5, by comparing Example 1 and Examples 14-17, it can be seen that as the phosphating treatment time during phosphating treatment continuously increases, the 96h weight loss rate of the NdFeB magnets shows a trend of first decreasing and then increasing. This may be because as the phosphating treatment time during phosphating treatment continuously increases, the phosphating reaction gradually becomes sufficient, forming a dense protective layer, thereby enhancing the corrosion resistance of the NdFeB magnets; when exceeding a certain range, the phosphating reaction continues, resulting in an overly thick phosphating film with increased roughness, affecting the adhesion, and thereby reducing the corrosion resistance of the NdFeB magnets.

[0064] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment that do not contribute creatively as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A preparation method of a neodymium-iron-boron magnet with high intrinsic coercivity and corrosion resistance, characterized in that, It includes the following steps: Melt spinning: Mix metal raw materials according to the formula amount, melt the mixture to obtain a molten liquid, and cast and spin the molten liquid to obtain a spun strip; Hydrogen decrepitation and grinding: Hydrogen decrepitate the spun strip into coarse powder, and obtain alloy powder after passing the coarse powder through a jet mill; Press molding: Place the obtained alloy powder and corrosion-resistant components in a mold, and press and mold to obtain a green compact for sintering; Sintering process: Sinter the green compact for sintering under the protection of nitrogen, rapidly cool it to room temperature in stages after sintering is completed, and perform tempering treatment to obtain a neodymium iron boron magnet; Phosphating treatment: After surface treatment of the neodymium iron boron magnet, put it into a phosphating solution for high-temperature phosphating treatment, and then take it out and rinse to obtain a phosphated neodymium iron boron magnet; The metal raw materials include the following components in parts by weight: Pr 6.5 - 7 parts, Nd 19.5 - 21 parts, B 0.90 - 1.03 parts, Tb 4 - 6 parts, Dy 0 - 1 part, Co 1 - 2 parts, Fe 64 - 68 parts; The corrosion-resistant component includes at least one of methylvinylsilazane and polysilazane resin; The phosphating solution includes the following components in concentration: potassium dihydrogen phosphate 30 - 100 g / L, phosphoric acid 100 - 200 g / L, manganese nitrate 5 - 10 g / L; The temperature range of the high-temperature phosphating treatment is 85 - 98 °C.

2. The preparation method of the high-intrinsic coercivity corrosion-resistant NdFeB magnet according to claim 1, characterized in that: The corrosion-resistant component is polysilazane resin.

3. The preparation method of the high-intrinsic coercivity corrosion-resistant NdFeB magnet according to claim 1, characterized in that: The parts by weight of the corrosion-resistant component are 0.2 - 0.5 parts.

4. The preparation method of the high-intrinsic coercivity corrosion-resistant NdFeB magnet according to claim 3, characterized in that: The parts by weight of the corrosion-resistant component are 0.4 parts.

5. The preparation method of the high-intrinsic coercivity corrosion-resistant NdFeB magnet according to claim 1, characterized in that: The concentration of the potassium dihydrogen phosphate is 50 - 90 g / L.

6. The preparation method of the high-intrinsic coercivity corrosion-resistant NdFeB magnet according to claim 5, characterized in that: The concentration of the potassium dihydrogen phosphate is 75 g / L.

7. The preparation method of the high-intrinsic coercivity corrosion-resistant NdFeB magnet according to claim 1, characterized in that: The time of the high-temperature phosphating treatment is 8 - 15 min.

8. A neodymium iron boron magnet with high intrinsic coercivity and corrosion resistance, characterized in that: Prepared by the preparation method of the high-intrinsic coercivity corrosion-resistant neodymium iron boron magnet according to any one of claims 1 - 7.

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