High intrinsic coercive force neodymium iron boron magnetic material and preparation method thereof

Abstract

The invention relates to the field of neodymium iron boron magnetic materials, in particular to a high intrinsic coercive force neodymium iron boron magnetic material and a preparation method thereof, and the high intrinsic coercive force neodymium iron boron magnetic material comprises the following raw materials in parts by weight: 52.5-57.2 parts of PrNd, 105-115.3 parts of Nd, 9.0-10.3 parts of B, 15-35 parts of Tb, 70-80 parts of Dy, 10-25 parts of Co and 650-680 parts of Fe. The two rare earth elements Tb and Dy are added into the neodymium-iron-boron magnetic material, so that the magnetocrystalline anisotropy field of the crystal is remarkably enhanced, and the intrinsic coercive force of the neodymium-iron-boron magnetic material is greatly improved.

Description

Technical Field

[0001] The present application relates to the field of NdFeB magnetic materials, and in particular to a high intrinsic coercivity NdFeB magnetic material and a preparation method thereof. Background Art

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

[0003] Intrinsic coercivity is a core indicator used to measure the ability of magnetic materials to resist demagnetization. In the application process of NdFeB magnetic materials, high temperature environments are often encountered. 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. However, as the application scope of NdFeB magnetic materials continues to expand, people's demand for optimizing the magnetic properties of NdFeB magnetic materials is also increasing. Therefore, a NdFeB magnetic material with high intrinsic coercivity is urgently needed. Summary of the invention

[0004] In order to improve the intrinsic coercivity of NdFeB magnetic materials, the present application provides a high intrinsic coercivity NdFeB magnetic material and a preparation method thereof.

[0005] In the first aspect, the present application provides a high intrinsic coercivity NdFeB magnetic material, which adopts the following technical solution: A high intrinsic coercivity NdFeB magnetic material comprises raw materials of the following components in parts by weight: 52.5-57.2 parts of PrNd, 105-115.3 parts of Nd, 9.0-10.3 parts of B, 15-35 parts of Tb, 70-80 parts of Dy, 10-25 parts of Co and 650-680 parts of Fe.

[0006] By adopting the above technical solution, the present invention adds two rare earth elements, Tb and Dy, at a high content, which can diffuse along the grain boundary at high temperature to form (Nd, Tb) 2 Fe 14 B shell and (Nd, Dy) 2 Fe 14B shell and wrap the main phase grains, significantly enhancing the magnetocrystalline anisotropy field of the crystal, thereby greatly improving the intrinsic coercivity of the NdFeB magnetic material. By adding an appropriate amount of Pr, the coarsening of the grains can be suppressed, and the intrinsic coercivity of the NdFeB magnetic material can be indirectly improved. The addition of Co can replace part of Fe, which can not only increase the Curie temperature of the magnetic material and enhance the high-temperature stability of the magnet, but also inhibit the formation of Fe-Tb / Dy soft magnetic phase, delay the attenuation of the intrinsic coercivity of the magnetic material at high temperature, and improve the intrinsic coercivity of the NdFeB magnetic material through the coordination of various elements.

[0007] Preferably, the high intrinsic coercivity NdFeB magnetic material further includes a first additive, wherein the first additive is at least one of calcium and magnesium, and the amount of the first additive accounts for 0.1-0.4wt% of the total amount of the raw material.

[0008] By adopting the above technical solution, since adding more Tb and Dy to the NdFeB magnetic material will lead to higher brittleness of the NdFeB magnetic material, in order to weaken this effect, the first additive is added to the alloy. Calcium and magnesium have strong reducing properties and can reduce brittle oxides such as FeO at the grain boundary to generate more stable CaO and MgO, thereby reducing the brittle oxide phase. Moreover, CaO and MgO are high melting point oxides with high stability, which can be used as grain boundary strengthening phases to improve the grain boundary bonding force and enhance the toughness of the NdFeB magnetic material.

[0009] Since calcium and magnesium are active metals, when the amount of the first additive is too high, violent volatilization will occur during the melting process, causing the melt to splash, which will increase the porosity of the magnetic material. During the sintering process, excessive first additives may replace Nd in the lattice, disrupt the crystal structure, reduce magnetocrystalline anisotropy, and cause a decrease in coercive force and remanence. When the amount of the first additive is too low, the brittle oxide cannot be fully reduced, causing the magnetic properties of the NdFeB magnet to decrease while the brittleness increases.

[0010] Preferably, the high intrinsic coercivity NdFeB magnetic material further includes a second additive, wherein the second additive is at least one of hafnium and titanium, and the amount of the second additive accounts for 0.1-0.4wt% of the total amount of the raw materials.

[0011] Preferably, the second additive is hafnium.

[0012] By adopting the above technical solution, hafnium and titanium are transition metal elements with strong affinity to oxygen. They can preferentially combine with oxygen to form HfO under aerobic conditions. 2 and TiO 2 This type of high melting point oxide, HfO 2 and TiO 2 It is evenly distributed at the grain boundaries, replacing the brittle oxides that are easily formed, thereby reducing the formation of brittle phases at the grain boundaries, enhancing the bonding force of the grain boundaries, inhibiting the initiation of cracks, and effectively improving the toughness of NdFeB magnets.

[0013] Among them, hafnium preferentially combines with oxygen to form HfO 2 , HfO 2 It can form a stable strengthening phase at the grain boundary and enhance the bonding force of the grain boundary. 2 It can also form a dense protective layer at the grain boundary, effectively blocking the diffusion of oxygen into the magnetic material, delaying high-temperature oxidation, and improving the anti-oxidation performance of NdFeB magnetic materials. At the same time, the strong reducing property of hafnium can reduce the formation of brittle oxides, thereby reducing the brittleness of grain boundaries. Hafnium can also act as a grain growth inhibitor to inhibit the abnormal growth of grains, significantly refine the grain size of the main phase, and improve the intrinsic coercivity of NdFeB magnetic materials.

[0014] When the amount of the second additive added is too low, the degree of grain refinement is insufficient, resulting in a decrease in intrinsic coercivity. When the amount of the second additive added is too high, excess hafnium or titanium may occupy the lattice position of the main phase, replacing iron or rare earth elements, destroying the integrity of the crystal structure, reducing the magnetocrystalline anisotropy field, and resulting in a decrease in the magnetic properties of the NdFeB magnet.

[0015] Preferably, a third additive is further included, wherein the third additive is at least one of methylvinylsilazane and polysilazane resin, and the amount of the third additive accounts for 1-1.5wt% of the total amount of the raw materials.

[0016] Preferably, the third additive is methylvinylsilazane.

[0017] By adopting the above technical scheme, methylvinylsilazane and polysilazane resins have strong adhesion to metals. Methylvinylsilazane and polysilazane resins also have low-temperature adhesion and high-temperature ceramic properties. At low temperatures, methylvinylsilazane and polysilazane resins can form a temporary bonding network, enhance the strength of the sintered green body, reduce the generation of cracks, and improve the density and molding accuracy of the pressed green body; during the sintering process, methylvinylsilazane and polysilazane resins are decomposed under high temperature conditions to produce silicon nitride ceramics. Silicon nitride itself has lubricity and can fill the gaps in the powder, thereby improving the intrinsic coercive force of the NdFeB magnetic material. At the same time, silicon nitride ceramics can cover the grain boundaries and surfaces of the NdFeB magnetic material and form a dense physical barrier to inhibit the penetration of oxygen and corrosive media, thereby improving the oxidation resistance and corrosion resistance of the NdFeB magnetic material.

[0018] Since methylvinylsilazane has the characteristics of low viscosity, high activity and high ceramic yield, methylvinylsilazane is preferred in this application. However, methylvinylsilazane decomposes and produces gas during pyrolysis, resulting in an increase in the porosity of the NdFeB magnetic material. The introduction of hafnium can serve as a nucleating agent to promote the uniform decomposition of methylvinylsilazane, and the surface of hafnium is highly active, capable of adsorbing the gas produced by the decomposition of methylvinylsilazane and forming high-melting-point compounds, which can be used as nanoscale filling phases during sintering, occupying the position of grain boundaries or voids, thereby reducing the porosity of the NdFeB magnetic material. At the same time, the introduction of hafnium can also enhance the interface bonding strength between the silicon nitride ceramic layer formed after high-temperature ceramicization of methylvinylsilazane and the NdFeB magnetic material.

[0019] When the amount of the third additive added is too small, the bonding force between the magnetic powder particles is weak, resulting in low strength of the pressed embryo, affecting the forming efficiency, and reducing the corrosion resistance of the resulting NdFeB magnetic material; when the amount of the third additive added is too high, it will decompose during the sintering process to produce excessive gas, destroying the uniformity of the sintering of the magnetic material, and causing the brittleness of the magnetic material to increase.

[0020] In a second aspect, the present application provides a method for preparing a high intrinsic coercivity NdFeB magnetic material, using the following technical solution: A method for preparing a high intrinsic coercivity NdFeB magnetic material, used for preparing the above-mentioned high intrinsic coercivity NdFeB magnetic material, comprises the following steps: S1. Melting strip: PrNd, Nd, B, Tb, Dy, Co, Fe and other raw materials are mixed according to the formula, and the mixture is melted to obtain a molten liquid, and the molten liquid is cast and stripped to obtain a strip sheet; S2, hydrogen crushing and grinding: the strips are hydrogen crushed into coarse powder, and the coarse powder is jet milled to obtain alloy powder; S3, pressing and molding: placing the obtained alloy powder in a mold, and pressing and molding to obtain a sintered green body; S4. Sintering process: The green compact is sintered under the protection of nitrogen. After sintering, it is rapidly cooled to room temperature in stages and tempered to obtain NdFeB magnetic material.

[0021] By adopting the above technical scheme, through the steps of melt spinning, hydrogen grinding, pressing and sintering, efficient utilization of raw materials and uniform distribution of components are achieved, the formation of fine grains and the construction of ordered magnetic domain structure are promoted, thereby significantly optimizing the magnetic properties of NdFeB magnets, including improving key indicators such as intrinsic coercive force and magnetic energy product, while improving production efficiency and quality stability, and reducing production costs, providing an efficient and reliable way to prepare high-performance, high-quality NdFeB magnets.

[0022] Preferably, it comprises a first alloy and a second alloy, wherein the components of the first alloy are 26.25-28.60 parts of PrNd, 52.50-57.65 parts of Nd, 4.50-5.15 parts of B, 7.5-17.5 parts of Tb, 60-65 parts of Dy, 5-12.5 parts of Co, and 325-340 parts of Fe, and the components of the second alloy are 26.25-28.60 parts of PrNd, 52.50-57.65 parts of Nd, 4.50-5.15 parts of B, 7.5-17.5 parts of Tb, 10-15 parts of Dy, 5-12.5 parts of Co, and 325-340 parts of Fe; In S1, a first stripping sheet is manufactured according to the composition of a first alloy, and a second stripping sheet is manufactured according to the composition of a second alloy; In S2, the first belt-spinning pieces and the second belt-spinning pieces are hydrogen-crushed into coarse powder, and the coarse powder is jet-milled to form alloy powder.

[0023] By adopting the above technical solution, the first alloy contains 3.00-3.25 parts of Dy, and the second alloy contains 0.50-0.75 parts of Dy. By preparing NdFeB magnetic materials by the dual-main phase method of mixing the first alloy with high Dy content and the second alloy with low Dy content, a composite structure of "hard magnetic phase + soft magnetic phase" can be formed to improve the magnetic properties of NdFeB magnetic materials. In the first alloy with high Dy content, Dy atoms replace Nd atoms, which increases the magnetocrystalline anisotropy field and forms a hard magnetic phase with high coercivity. The second alloy with low Dy content retains the high remanence characteristics of the Nd-Fe-B system. Due to the low Dy content, the proportion of Nd-rich phase in the second alloy is relatively high, which helps to form a continuous Nd-rich phase network and promotes the uniform orientation of magnetic domains, thereby maintaining the high remanence level of NdFeB magnetic materials. Through the synergistic effect of the hard magnetic phase and the soft magnetic phase, the hard magnetic phase, as a strengthening phase at the grain boundary, can effectively isolate the soft magnetic phase grains, inhibit the magnetic coupling between grains, and reduce the disordered reversal of magnetic domains, thereby significantly improving the intrinsic coercive force while maintaining high remanence.

[0024] Preferably, in S1, the first additive or the second additive is mixed with PrNd, Nd, B, Tb, Dy, Co, and Fe and then melt-spinned.

[0025] By adopting the above technical scheme, the first additive or the second additive is mixed with PrNd, Nd, B, Tb, Dy, Co, and Fe in S1 and then melt-spinned, which can promote the uniform distribution of alloy components. The first additive can reduce the brittle oxides in the NdFeB magnetic material and form more stable compounds. The second additive can preferentially combine with oxygen to reduce the formation of brittle oxides. Both of them can enhance the bonding strength of the grain boundaries, thereby improving the toughness of the NdFeB magnetic material.

[0026] Preferably, in S3, the third additive is mixed with the alloy powder and then placed in a mold for compression molding.

[0027] By adopting the above technical solution, the third additive is mixed with the alloy powder in S3 and then placed in a mold for pressing and forming. The third additive is liquid at room temperature and can fill the pores between the alloy powders to act as a binder. The addition of the third additive can reduce the friction between the magnetic powder particles, improve the fluidity of the powder in the mold, make the pressing more uniform, and help to improve the strength of the sintered green body.

[0028] In summary, the present application includes at least one of the following beneficial technical effects: 1. This application adds rare earth elements Tb and Dy to NdFeB magnetic materials. Tb and Dy can diffuse along the grain boundaries at high temperatures to form (Nd, Tb) 2 Fe 14 B shell and (Nd, Dy) 2 Fe 14 B shell and wrap the main phase grains, significantly enhancing the magnetocrystalline anisotropy field of the crystal, thereby greatly improving the intrinsic coercivity of the NdFeB magnetic material, and by adding Co to replace part of Fe, it can enhance the high temperature stability of the NdFeB magnetic material while inhibiting the formation of Fe-Tb / Dy soft magnetic phase, thereby improving the magnetic properties of the NdFeB magnetic material; 2. In this application, hafnium is added to the NdFeB magnetic material. Hafnium can preferentially combine with oxygen to form HfO in the presence of oxygen. 2 , HfO 2 It is a high melting point oxide that can replace the brittle oxide that is easy to form, reduce the formation of brittle phase at the grain boundary, enhance the bonding force of the grain boundary, inhibit the initiation of cracks, and effectively improve the toughness of NdFeB magnetic materials. In addition, the generated HfO 2 It can also form a dense protective layer at the grain boundary, effectively blocking the diffusion of oxygen into the magnetic material and delaying the high-temperature oxidation of NdFeB magnetic materials; 3. The present application adds methylvinylsilazane to the NdFeB magnet. Methylvinylsilazane has strong adhesion to metals and has the properties of low-temperature adhesion and high-temperature ceramicization. It can form a temporary bonding network at low temperatures to enhance the strength of the sintered green body. At high temperatures, methylvinylsilazane undergoes pyrolysis to produce silicon nitride ceramics. The silicon nitride ceramics can cover the grain boundaries and surfaces of the NdFeB magnets and form a dense physical barrier to inhibit the penetration of oxygen and corrosive media, thereby improving the oxidation resistance and corrosion resistance of the NdFeB magnets. The combination of hafnium and methylvinylsilazane can effectively reduce the effect of increased porosity of the NdFeB magnets caused by methylvinylsilazane. DETAILED DESCRIPTION

[0029] 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 and tetramethyldivinyldisilazane can be selected. The present application takes tetramethyldivinyldisilazane with CAS No. 7691-02-3 as an example.

[0030] Polysilazane resin: a commercially available product with CAS number 475645-84-2.

[0031] The present application is further described in detail below with reference to examples and comparative examples. Example 1

[0032] A high intrinsic coercivity NdFeB magnetic material comprises the following components in parts by weight: 54.85 g of PrNd, 110.15 g of Nd, 9.65 g of B, 25 g of Tb, 75 g of Dy, 17.5 g of Co and 665 g of Fe.

[0033] A method for preparing a high intrinsic coercivity NdFeB magnetic material, used for preparing the above-mentioned high intrinsic coercivity NdFeB magnetic material, comprises the following steps: S1, melt stripping: PrNd, Nd, B, Tb, Dy, Co, and Fe are mixed according to the formula, and the mixture is put into a vacuum melting furnace for melting to obtain a molten liquid, and the molten liquid is cast into a strip to obtain a strip-spinning sheet; S2, hydrogen crushing and grinding: the strips are hydrogen crushed into coarse powder, and the coarse powder is jet milled to obtain alloy powder; S3, pressing and molding: placing the obtained alloy powder in a mold, and pressing and molding to obtain a sintered green body; S4. Sintering process: The green compact is sintered under the protection of nitrogen at a sintering temperature of 1100°C for 3 hours. After sintering, it is rapidly cooled to room temperature in stages and tempered to obtain NdFeB magnetic material.

[0034] Among them, the cooling of the sintered green body after sintering includes three stages. In the first stage, the sintering temperature is reduced from 1100℃ to 800℃, the cooling rate is 7℃ / min, and the temperature is kept for 3h. In the second stage, the sintering temperature is reduced from 800℃ to room temperature at 4℃ / min. The tempering treatment includes two stages. The tempering temperature of the first stage is 800℃, the tempering time is 2h, and the magnetic material is cooled to room temperature with argon gas after the end. Then the second stage of tempering treatment begins. The second tempering temperature is 500℃, the tempering time is 3h, and the magnetic material is cooled to room temperature with argon gas after the end.

[0035] Example 2-3 Example 2-3 Based on the preparation method of Example 1, the component ratio of the NdFeB magnetic material is adjusted, and the specific adjustment is shown in Table 1.

[0036] Comparative Examples 1-3 Comparative Examples 1-3 Based on the preparation method of Example 1, the component ratio of the NdFeB magnetic material is adjusted, and the specific adjustment is shown in Table 1.

[0037] Performance testing The NdFeB magnetic materials of the above-mentioned Examples 1-3 and Comparative Examples 1-3 were analyzed, and the specific detection method is as follows: Magnetic properties The comprehensive magnetic properties are tested according to GB / T3217-2013 "Magnetic Test Methods for Permanent Magnetic (Hard Magnetic) Materials".

[0038] According to the above detection method, the test results of Examples 1-3 and Comparative Examples 1-3 were obtained, as shown in Table 1 below.

[0039] Table 1 Component ratios and performance test data of NdFeB magnetic materials of Examples 1-3 and Comparative Examples 1-3 (unit: g)

[0040] Referring to Table 1, by comparing the remanence of the NdFeB magnetic materials obtained in Examples 1-3 and Comparative Examples 1-3, it can be found that the remanence of Examples 1-3 is lower than that of the NdFeB magnetic materials obtained in Comparative Examples 1-3, indicating that the addition of Tb and Dy during the preparation of the NdFeB magnetic materials will reduce the remanence of the NdFeB magnetic materials. The intrinsic remanence of the NdFeB magnetic materials obtained in Examples 1-3 and Comparative Examples 1-3 is lower than that of the NdFeB magnetic materials obtained in Comparative Examples 1-3. It can be found that the intrinsic coercive force of the NdFeB magnetic materials obtained in Examples 1-3 is significantly improved compared with the intrinsic coercive force of the NdFeB magnetic materials obtained in Comparative Examples 1-3, especially when the added amount of Tb is 25g and the added amount of Dy is 75g, the intrinsic coercive force of the NdFeB magnetic materials is the highest, indicating that the addition of Tb and Dy can slightly reduce the remanence of the NdFeB magnetic materials while greatly improving the intrinsic coercive force of the NdFeB magnetic materials. Example 4

[0041] Example 4 Based on the preparation method of Example 1, calcium in an amount of 0.3 wt% of the total raw material is added to S1 and melted together with the raw material. Example 5

[0042] Example 5 Based on the preparation method of Example 1, magnesium in an amount accounting for 0.3 wt% of the total amount of raw materials is added to S1 and melted together with the raw materials. Example 6

[0043] Example 6 Based on the preparation method of Example 1, titanium in an amount accounting for 0.3 wt% of the total raw material is added to S1 and melted together with the raw material. Example 7

[0044] Example 7 Based on the preparation method of Example 1, hafnium in an amount of 0.3 wt % of the total raw material is added to S1 and melted together with the raw material.

[0045] Performance testing The NdFeB magnetic materials of the above-mentioned Examples 4-7 were analyzed, and the specific detection method is as follows: toughness The magnet samples were processed into standard size impact specimens with a length of 55mm and a cross section of 10*10mm in accordance with GB / T229-2007 Charpy Pendulum Impact Test Method for Metallic Materials. There was a V-notch in the middle of the specimen length, the V-notch angle was 45°, and the depth was 2mm. The impact toughness test was carried out using a JBS300 digital pendulum impact testing machine with a 150J pendulum to obtain the absorbed work of the magnet samples.

[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 NdFeB magnetic material composition and performance test data of Example 1 and Examples 4-7

[0048] Referring to Table 2, by comparing Example 1 and Examples 4-7, it can be seen that the toughness of the NdFeB magnet obtained in Example 4-7 by adding calcium, magnesium, titanium and hafnium to S1 is improved compared with the NdFeB magnet obtained in Example 1, but the difference in toughness of the NdFeB magnets obtained between Examples 4-7 is not significant. By comparing the intrinsic coercive force of the NdFeB magnetic material obtained in Example 1 with the intrinsic coercive force of the NdFeB magnetic material obtained in Examples 4-7, it can be found that compared with Example 1, the intrinsic coercive force of the NdFeB magnetic material obtained in Examples 4-6 is not significantly improved, while the intrinsic coercive force of the NdFeB magnetic material obtained in Example 7 is improved to a certain extent, which shows that the introduction of hafnium can not only improve the toughness of the NdFeB magnetic material, but also improve the intrinsic coercive force of the NdFeB magnetic material. This is because hafnium can act as a grain growth inhibitor, inhibiting the abnormal growth of grains, significantly refining the grain size of the main phase, thereby improving the intrinsic coercive force of the NdFeB magnetic material.

[0049] Embodiment 8-9 In Example 8-9, based on the preparation method of Example 4, the amount of calcium added was adjusted, and the specific adjustment is shown in Table 3.

[0050] Comparative Examples 4-5 Comparative Example 4-5 Based on the preparation method of Example 4, the amount of calcium added was adjusted, and the specific adjustment is shown in Table 3.

[0051] The NdFeB magnetic materials of Examples 8-9 and Comparative Examples 4-5 were subjected to the above performance tests, and the test results are shown in Table 3.

[0052] Table 3 The percentage of calcium usage and performance test data of Example 4, Examples 8-9 and Comparative Examples 4-5

[0053] Referring to Table 3, by comparing Example 4, Examples 8-9 and Comparative Examples 4-5, it can be seen that when the amount of calcium accounts for 0.1-0.3wt% of the total amount of raw materials, the toughness of the obtained NdFeB magnetic material is in an ideal state. When the amount of calcium accounts for too high a proportion, the toughness of the obtained NdFeB magnetic material decreases. This may be because calcium will increase the porosity of the NdFeB magnetic material during the melting process, reduce the density of the NdFeB magnetic material, and thus reduce the toughness of the NdFeB magnetic material. When the amount of calcium accounts for too low a proportion, many brittle oxide phases in the grain boundaries are not reduced, resulting in a decrease in the toughness of the NdFeB magnetic material.

[0054] Embodiment 10-11 In Examples 10-11, based on the preparation method of Example 5, the amount of magnesium added was adjusted, and the specific adjustments are shown in Table 4.

[0055] Comparative Examples 6-7 Comparative Example 6-7 is based on the preparation method of Example 5, and the amount of magnesium added is adjusted. The specific adjustment is shown in Table 4.

[0056] The NdFeB magnetic materials of Examples 10-11 and Comparative Examples 6-7 were subjected to the above performance tests, and the test results are shown in Table 4.

[0057] Table 4 Performance test data table of magnesium dosage ratio in Example 5, Examples 10-11 and Comparative Examples 6-7

[0058] Referring to Table 4, it can be seen from Example 5, Example 10-11 and Comparative Example 6-7 that when the amount of magnesium accounts for 0.1-0.3wt% of the total amount of raw materials, the toughness of the obtained NdFeB magnetic material is in an ideal state, especially when the amount of magnesium accounts for 0.3wt% of the total amount of raw materials, the toughness of the obtained NdFeB magnetic material is optimal. When the amount of magnesium accounts for too high a proportion, the toughness of the obtained NdFeB magnetic material decreases. This may be because magnesium will volatilize at high temperatures to increase the porosity of the NdFeB magnetic material, affecting the density of the NdFeB magnetic material and causing the toughness of the NdFeB magnetic material to decrease. When the amount of magnesium accounts for too low a proportion, many brittle oxide phases in the grain boundaries are not reduced, resulting in a decrease in the toughness of the NdFeB magnetic material. Example 12

[0059] Example 12 Based on the preparation method of Example 7, 12 g of tetramethyldivinyldisilazane was added to S3, and the tetramethyldivinyldisilazane and alloy powder were placed in a mold for pressing. Example 13

[0060] Example 13 Based on the preparation method of Example 7, 12 g of polysilazane resin was added to S3, and the polysilazane resin and alloy powder were placed in a mold for pressing.

[0061] Comparative Example 8 Comparative Example 8: Based on the preparation method of Example 1, 12 g of tetramethyldivinyldisilazane was added to S3, and the tetramethyldivinyldisilazane and the alloy powder were placed in a mold for pressing.

[0062] Performance testing The NdFeB magnetic materials of Examples 12-13 and Comparative Example 8 were analyzed, and the specific detection method is as follows: Corrosion resistance A neutral salt spray test was conducted using a 5wt% sodium chloride aqueous solution to spray the magnetic material samples at a test temperature of 35°C. Since the corrosion reaction of NdFeB magnetic materials in neutral salt spray is mainly oxidation and peeling, the weight loss rate after 144h is used as the basis for testing the corrosion resistance of the magnetic material samples, and the weight loss rate after 144h = (mass before immersion - mass after immersion) / mass before immersion.

[0063] The NdFeB magnetic materials of Examples 12-13 and Comparative Example 8 were subjected to the above performance tests, and the test results are shown in Table 5.

[0064] Table 5 Performance test data table of Example 7, Examples 12-13 and Comparative Example 8

[0065] Referring to Table 5, it can be seen from the comparison of Example 7, Example 12-13 and Comparative Example 8 that Example 12-13 respectively adds tetramethyl divinyl disilazane and polysilazane resin on the basis of Example 7, which significantly reduces the weight loss rate of the NdFeB magnetic material in the salt corrosion reaction, indicating that the corrosion resistance of the NdFeB magnetic material has been significantly improved. Among them, the weight loss rate of the NdFeB magnetic material of Example 12 is less than the weight loss rate of the NdFeB magnetic material of Example 13, indicating that the addition of tetramethyl divinyl disilazane on the basis of the preparation method of Example 7 makes the corrosion resistance of the NdFeB magnetic material better, because tetramethyl divinyl disilazane has higher fluidity at low temperatures, can more evenly wrap the magnetic powder particles, and the vinyl of tetramethyl divinyl disilazane can participate in cross-linking at high temperatures, and the ceramic yield is higher than that of polysilazane resin, so the corrosion resistance of the obtained NdFeB magnetic material is stronger.

[0066] By comparing Example 7, Example 12 and Comparative Example 8, it can be found that the absorption work of the NdFeB magnet obtained in Comparative Example 8 is the lowest. Because hafnium is not introduced into the NdFeB magnet of Comparative Example 8, the brittle oxide phase at the grain boundary cannot be reduced, resulting in increased brittleness and decreased toughness of the NdFeB magnet. However, the weight loss rate of the NdFeB magnet obtained in Comparative Example 8 is between that of Example 7 and Example 12, indicating that by combining hafnium and tetramethyldivinyldisilazane, the toughness of the NdFeB magnet can be improved while further improving the corrosion resistance of the NdFeB magnet. Embodiment 14

[0067] Example 14 Based on the preparation method of Example 1, 1.5 g of calcium and 1.5 g of hafnium were added to S1 and melted together with the raw materials. Embodiment 15

[0068] Example 15 Based on the preparation method of Example 1, 1.5 g of magnesium and 1.5 g of hafnium are added to S1 and melted together with the raw materials.

[0069] The NdFeB magnetic materials of Examples 14-15 were subjected to the above performance tests, and the test results are shown in Table 6.

[0070] Table 6 Performance test data table of Example 7 and Examples 14-15

[0071] Referring to Table 6, by comparing Example 7 with Examples 14-15, it can be seen that the absorption work of the NdFeB magnetic material obtained in Examples 14-15 is greater than that of the NdFeB magnetic material obtained in Example 7, indicating that adding composite calcium and hafnium or magnesium and hafnium in the preparation process of NdFeB magnetic material can improve the toughness of NdFeB magnetic material. This is because calcium and magnesium have strong reducing properties and can reduce the brittle oxides at the grain boundaries to generate more stable CaO and MgO, while hafnium can preferentially combine with oxygen to generate HfO 2 It can replace the brittle oxides that are easily formed. Through the synergistic effect of the two, the toughness of NdFeB magnets is further improved. Example 16

[0072] Example 16 Based on the preparation method of Example 1, the NdFeB magnet is divided into a first alloy and a second alloy, the components of the first alloy are PrNd 27.425g, Nd 55.075g, B 4.825g, Tb 12.5g, Dy 62.5g, Co8.75g, Fe 332.5g, and the components of the second alloy are PrNd 27.425g, Nd 55.075g, B 4.825g, Tb 12.5g, Dy12.5g, Co 8.75g, Fe 332.5g. In S1, a first stripping sheet is made according to the components of the first alloy, and a second stripping sheet is made according to the components of the second alloy. In S2, the first stripping sheet and the second stripping sheet are hydrogen-broken to form coarse powder, and the coarse powder is formed into alloy powder by air flow grinding.

[0073] The NdFeB magnetic material of Example 16 was subjected to the above performance tests, and the test results are shown in Table 7.

[0074] Table 7 Performance test data table of Example 1 and Example 16

[0075] Referring to Table 7, by comparing Example 1 and Example 16, it can be seen that compared with the single-main phase method in Example 1, Example 16 prepares NdFeB magnetic materials by a dual-main phase method in which a first alloy with a high Dy content and a second alloy with a low Dy content are mixed, thereby forming a composite structure of "hard magnetic phase + soft magnetic phase", which significantly improves the magnetic properties of NdFeB magnetic materials. The first alloy with a high Dy content can provide a hard magnetic phase with high coercivity, and the second alloy with a low Dy content can maintain a high remanence level of the NdFeB magnetic material, so that the NdFeB magnetic material can significantly improve the intrinsic coercivity while maintaining a high remanence.

[0076] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A high intrinsic coercivity NdFeB magnetic material, characterized in that: A raw material comprising the following components in parts by weight: 52.5-57.2 parts of PrNd, 105-115.3 parts of Nd, 9.0-10.3 parts of B, 15-35 parts of Tb, 70-80 parts of Dy, 10-25 parts of Co, and 650-680 parts of Fe; The second additive is at least one of hafnium and titanium, and the amount of the second additive is 0.1-0.4wt% of the total amount of the raw material; The third additive is at least one of methylvinylsilazane and polysilazane resin, and the amount of the third additive accounts for 1-1.5wt% of the total amount of raw materials.

2. The high intrinsic coercivity NdFeB magnetic material according to claim 1, characterized in that: The invention also includes a first additive, which is at least one of calcium and magnesium. The amount of the first additive is 0.1-0.4wt% of the total amount of the raw material.

3. The high intrinsic coercivity NdFeB magnetic material according to claim 1, characterized in that: The second additive is hafnium.

4. The high intrinsic coercivity NdFeB magnetic material according to claim 1, characterized in that: The third additive is methylvinylsilazane.

5. A method for preparing a high intrinsic coercivity NdFeB magnetic material according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Melting strip: PrNd, Nd, B, Tb, Dy, Co, Fe and other raw materials are mixed according to the formula, and the mixture is melted to obtain a molten liquid, and the molten liquid is cast and stripped to obtain a strip sheet; S2, hydrogen crushing and grinding: the stripping pieces are hydrogen crushed into coarse powder, and the coarse powder is jet milled to obtain alloy powder; S3, pressing and molding: placing the obtained alloy powder in a mold, and pressing and molding to obtain a sintered green body; S4. Sintering process: The green compact is sintered under the protection of nitrogen. After sintering, it is rapidly cooled to room temperature in stages and tempered to obtain NdFeB magnetic material.

6. The method for preparing a high intrinsic coercivity NdFeB magnetic material according to claim 5, characterized in that: Comprising a first alloy and a second alloy, wherein the components of the first alloy are 26.25-28.60 parts of PrNd, 52.50-57.65 parts of Nd, 4.50-5.15 parts of B, 7.5-17.5 parts of Tb, 60-65 parts of Dy, 5-12.5 parts of Co, and 325-340 parts of Fe, and the components of the second alloy are 26.25-28.60 parts of PrNd, 52.50-57.65 parts of Nd, 4.50-5.15 parts of B, 7.5-17.5 parts of Tb, 10-15 parts of Dy, 5-12.5 parts of Co, and 325-340 parts of Fe; In S1, a first stripping sheet is manufactured according to the composition of a first alloy, and a second stripping sheet is manufactured according to the composition of a second alloy; In S2, the first belt-spinning pieces and the second belt-spinning pieces are hydrogen-crushed into coarse powder, and the coarse powder is jet-milled to form alloy powder.

7. The method for preparing a high intrinsic coercivity NdFeB magnetic material according to claim 5, characterized in that: In S1, the first additive or the second additive is mixed with PrNd, Nd, B, Tb, Dy, Co, and Fe and then melt-spinned.

8. The method for preparing a high intrinsic coercivity NdFeB magnetic material according to claim 5, characterized in that: In S3, the third additive is mixed with the alloy powder and then placed in a mold for compression molding.

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