A high-performance ultra-thin rare-earth permanent magnet magnetic sheet and its preparation method

Abstract

The present invention discloses a high-performance ultra-thin rare-earth permanent magnet magnetic sheet and a preparation method thereof, belonging to the technical field of rare-earth permanent magnet material preparation. The preparation method includes the following steps: iron raw materials and part of samarium raw materials are melted under vacuum conditions, and then the remaining samarium is added, and melting is continued. The obtained molten alloy is poured onto a cooling roller to obtain a samarium-iron alloy sheet; the samarium-iron alloy sheet is sequentially subjected to homogenization treatment, hydrogenation treatment and nitridation treatment to obtain nitrided magnetic powder; phosphoric acid and a corrosion inhibitor are added to the magnetic powder, and after wet ball milling and drying, surface-treated magnetic powder is obtained; a binder is added to the surface-treated magnetic powder, and magnetic particles are obtained by internal mixer; the magnetic particles are pressed by a flat vulcanizing machine. The prepared rare-earth permanent magnet magnetic sheet has a thickness of only 0.2 mm - 0.4 mm, the magnetic sheet has strong corrosion resistance, sufficient surface magnetism, strong magnetic properties, and low preparation cost, and can meet the application requirements of specific scenarios.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth permanent magnet material preparation, and in particular relates to a high-performance ultra-thin rare earth permanent magnet sheet and a preparation method thereof. Background Art

[0002] Rare earth permanent magnet materials are widely used in various fields due to their excellent magnetic properties. Among them, samarium iron nitrogen permanent magnet materials are regarded as a new generation of permanent magnet materials after neodymium iron boron due to their high Curie temperature, high coercive force and excellent anti-oxidation performance. However, since samarium iron nitrogen compounds are easily decomposed at high temperatures, they cannot be prepared by traditional sintering processes and can only be made into bonded magnets. In the prior art, samarium iron nitrogen magnetic powder is usually prepared by powder metallurgy process, and then mixed with organic binder and pressed into shape. However, since the magnetic properties of bonded magnets are relatively low and it is difficult to further process them after pressing and forming, its promotion in practical applications is limited.

[0003] The calendering process can produce thin SmFeN permanent magnet materials, but due to the high hardness of SmFeN magnetic powder, calendering processing has certain difficulties, especially when the calendering thickness is less than 0.4mm, the calender is difficult to process. At the same time, the surface magnetism of the thin magnets prepared by calendering is low, which cannot meet the needs of practical applications. Moreover, the magnets have poor corrosion resistance and are prone to rust, which cannot meet the needs of specific usage scenarios. Patent document CN118213147A discloses an ultra-thin flexible magnetic composite material and a preparation method thereof, which belongs to the technical field of rubber magnetic materials. The magnetic strip includes the following raw materials by weight: 5-10 parts of SmFeN magnetic powder, 90-95 parts of ferrite magnetic powder, 8-9 parts of binder, 0.5-1 parts of lubricant, 0.1-0.3 parts of thermal stabilizer, 0.5-0.6 parts of silane coupling agent, and 0.5-1.5 parts of ethanol. Ferrite is used as the main raw material, and after mixing with SmFeN rare earth magnetic powder, an ultra-thin flexible magnetic composite material is prepared by calendering process. Although the thickness of the flexible magnetic composite material prepared by this method reaches 0.3mm-0.9mm, there are still some application scenarios such as magnetic eyelashes that require the thickness of the magnetic sheet to be as thin as about 0.2mm, the surface magnetism is higher than 500Gs and corrosion resistance, and the existing technology is still difficult to meet the requirements. Therefore, it is urgent to develop a new type of samarium iron nitrogen permanent magnetic material and its preparation method to improve the magnetic properties of the material and solve the difficulties of calendering processing, so as to promote the practical application of samarium iron nitrogen permanent magnetic materials. Summary of the invention

[0004] One of the purposes of the present invention is to provide a method for preparing a high-performance ultra-thin rare earth permanent magnet sheet to solve the problems of severe magnetic loss, poor corrosion resistance and large thickness of the rare earth permanent magnet sheet during the preparation process.

[0005] The second object of the present invention is to provide a rare earth permanent magnet sheet prepared by the method for preparing a high-performance ultra-thin rare earth permanent magnet sheet.

[0006] In a first aspect, a method for preparing a high-performance ultra-thin rare earth permanent magnet magnetic sheet includes the following steps:

[0007] S1. Melt all the iron raw materials and 45 wt% - 55 wt% of the samarium raw materials under vacuum conditions, then add the remaining samarium, and continue smelting. Pour the obtained molten alloy onto a cooling roller to obtain a samarium-iron alloy sheet;

[0008] S2. Perform homogenization treatment, hydrogenation treatment, and nitridation treatment on the samarium-iron alloy sheet in sequence to obtain nitrided magnetic powder;

[0009] S3. Add phosphoric acid and a corrosion inhibitor to the magnetic powder, perform wet ball milling, and dry it to obtain surface-treated magnetic powder;

[0010] S4. Add a binder to the surface-treated magnetic powder and perform internal mixing to obtain magnetic particles;

[0011] S5. Press the magnetic particles using a flat vulcanizer to obtain a rare earth permanent magnet magnetic sheet.

[0012] As a further scheme of the present invention, in S1, the samarium raw material and the iron raw material are weighed according to a molar ratio of 2:17, and then 1 wt% - 10 wt% of the samarium raw material is added;

[0013] According to the chemical formula Sm 2 Fe 17 of samarium iron alloy, calculated based on 2 mol of Sm and 17 mol of Fe, theoretically, m(Sm) = 2 mol × 150.36 g / mol = 300.72 g and m(Fe) = 17 mol × 55.86 g / mol = 949.45 g need to be weighed; on this basis of weighing, Sm is additionally weighed (i.e., in excess) by 1 wt% - 10 wt%, and the converted mass is m(Sm) = 300.72 g + 3.0072 g - 300.72 g + 30.072 g = 303.7272 g - 330.792 g.

[0014] As a further scheme of the present invention, in S1, all the iron raw materials and 50 wt% of the samarium raw materials are melted under vacuum conditions.

[0015] As a further scheme of the present invention, in S1, the vacuum degree is < 10 Pa, the smelting temperature is 1510 °C - 1580 °C, and the smelting time is 30 min - 50 min.

[0016] As a further scheme of the present invention, in S1, the molten alloy is poured onto the cooling roller through a tundish and a runner to form a continuous samarium-iron alloy strip, and then falls onto the lower water-cooled plate to obtain a samarium-iron alloy sheet.

[0017] As a further solution of the present invention, the rotation speed of the cooling roller is 1 r / min - 3 r / min.

[0018] As a further solution of the present invention, in S2, the homogenization treatment specifically is to put the samarium-iron alloy sheet into a heat treatment furnace, evacuate the air, and then conduct heat treatment at a temperature of 900 °C - 1100 °C for 7.5 h - 8.5 h.

[0019] As a further solution of the present invention, the vacuum degree is 1×10 -2 Pa.

[0020] As a further solution of the present invention, in S2, the hydrogenation treatment specifically is to cool the homogenized samarium-iron alloy sheet to 250 °C - 300 °C and keep it warm. In a vacuum environment, introduce hydrogen into the furnace, control the absolute pressure of hydrogen at 0.05 MPa - 0.15 MPa, and the hydrogenation time is 2 h.

[0021] As a further solution of the present invention, in S2, the nitridation treatment specifically is to uniformly heat the temperature at a rate of 10 °C / min to 350 °C - 450 °C, fill nitrogen to 0.5 MPa, and keep the reaction for 1 h; then uniformly heat the temperature at a rate of 0.2 °C / min to 500 °C - 550 °C, and keep the reaction for 10 h; cool it to room temperature (25 °C - 30 °C) with the furnace to obtain the nitrided magnetic powder.

[0022] As a further solution of the present invention, in S2, the average particle size of the nitrided magnetic powder is 20 ± 2 μm.

[0023] As a further solution of the present invention, in S3, calculated by the weight of the magnetic powder, the addition amount of phosphoric acid is 1 wt%;

[0024] The corrosion inhibitor is benzotriazole, and the addition amount of benzotriazole is 0.1 wt% - 3 wt%.

[0025] As a further solution of the present invention, in S3, the average particle size of the surface-treated magnetic powder is 2.0 ± 0.3 μm.

[0026] Utilize phosphoric acid to react with the surface of the samarium-iron-nitrogen magnetic powder to generate phosphate and iron phosphate salts. These compounds form a dense passivation film on the surface of the magnetic powder, which can effectively prevent the magnetic powder from further oxidation; on the other hand, benzotriazole has good antioxidant properties and can form a protective layer on the surface of the magnetic powder to reduce the contact between the magnetic powder and oxygen, thereby reducing the oxidation rate; in addition, through the wet ball milling process, phosphoric acid and benzotriazole can continuously undergo surface chemical reactions with the metal during the friction process to generate metal salt compounds, playing a role in lubrication and anti-wear, thereby improving the mechanical properties of the magnetic powder. The two work together to improve the corrosion resistance, antioxidant property and mechanical properties of the magnetic powder.

[0027] As a further solution of the present invention, in S4, the binder is composed of CPE (chlorinated polyethylene), calcium stearate, KH570 (coupling agent) and PE wax;

[0028] Calculated by the weight of magnetic powder, the addition amount of CPE is 8wt%, the addition amount of calcium stearate is 0.5wt%, the addition amount of KH570 is 0.5wt%, and the addition amount of PE (polyethylene) wax is 1wt%.

[0029] As a further solution of the present invention, in S4, the mixing temperature is 100°C - 120°C, and the mixing time is 1h.

[0030] As a further solution of the present invention, in S4, the size of the magnetic particles is 1mm - 5mm.

[0031] As a further solution of the present invention, in S5, the temperature for molding by a flat vulcanizing machine is 80°C - 100°C, and the pressure is 10MPa - 15MPa.

[0032] In a second aspect, a high-performance ultra-thin rare earth permanent magnet magnetic sheet is prepared by the above preparation method. The base material of the rare earth permanent magnet magnetic sheet is samarium iron nitride (Sm 2 Fe 17 N x ) material, the thickness is 0.2mm - 0.4mm, and the surface magnetic field > 500 Gs.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. The present invention provides a preparation method of a high-performance ultra-thin rare earth permanent magnet magnetic sheet. During its preparation process, the secondary feeding method is adopted for rapid solidification melting. By optimizing the process settings, while improving the surface magnetic field of the magnetic sheet, the magnetic loss is effectively reduced. The thickness of the rare earth permanent magnet magnetic sheet obtained by flat vulcanization pressing is only 0.2mm - 0.4mm, effectively solving the problem that the calender in the prior art cannot process to less than 0.4mm. The magnetic sheet has strong corrosion resistance, is not easy to rust, has sufficient surface magnetic field, and strong magnetic properties; and the preparation cost is relatively low, which can meet the application requirements of specific scenarios.

[0035] 2. In the raw material ratio of the present invention, by compensating for the excessive samarium, the loss of metallic samarium during the melting process can be made up, so as to ensure that the finally melted alloy is Sm 2 Fe 17 with uniform phase composition; by optimizing the subsequent process, the volatilization amount of samarium is reduced, so that the addition amount of excessive samarium is only excessive by 1wt% - 10wt%. While ensuring the avoidance of the appearance of impurity phases, the dosage of compensating samarium is effectively reduced, and the cost of raw materials is reduced.

[0036] 3. During the smelting process, due to the relatively high melting point of iron, adding a part of samarium to the crucible can form a low-melting alloy with iron during the melting process, thus effectively accelerating the melting of iron raw materials. By homogenizing the samarium-iron alloy sheet, it further forms a uniform Sm 2 Fe 17 phase. After hydrogen decrepitation and nitriding, Sm 2 Fe 17 N x magnetic powder can be obtained, which can effectively improve the magnetic properties of the magnetic powder, thereby improving the magnetic properties of the final magnetic sheet. The surface magnetic field of the magnetic sheet is higher than 500 Gs, solving the problem of the relatively low surface magnetism of the thin magnets prepared by rolling in the prior art and meeting the actual application requirements.

[0037] 4. The mechanism of adding phosphoric acid and benzotriazole to the samarium-iron-nitrogen magnetic powder for ball milling surface treatment mainly includes that phosphoric acid forms a passivation film through chemical reactions, benzotriazole provides antioxidant and lubricating protection, and the ball milling process accelerates chemical reactions and homogenization effects. These factors act together to significantly improve the antioxidant property, corrosion resistance and mechanical properties of the magnetic powder. Calcium stearate in the binder can significantly improve the fluidity of the magnetic powder particles, reduce the resistance during molding, improve the remanence and consistency of the magnetic sheet, and at the same time act as a lubricant to reduce the friction between the magnetic powder, making the magnetic powder more uniform during the mixing process and avoiding agglomeration; Using CPE and PE wax can significantly improve the bonding property of the magnetic powder. As a thermoplastic elastomer, CPE has good flexibility and heat resistance and can maintain a stable bonding effect at high temperatures. At the same time, PE wax, as a lubricant and binder, can further improve the fluidity and mixing uniformity of the magnetic powder, thereby improving the mechanical properties of the final product; Using the coupling agent KH570 can form chemical bonding with the surface of the magnetic powder, enhancing the surface denseness and bonding force of the magnetic powder, thereby improving its antioxidant property.

[0038] 5. Using a relatively low internal mixer temperature and flat vulcanization rolling temperature can effectively improve the pressing and forming ability of the magnetic powder, thereby further reducing the heavy magnetic loss during the processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention will be further described below with reference to the accompanying drawings.

[0040] Figure 1 is a process flow chart of the preparation of a high-performance ultra-thin rare earth permanent magnet magnetic sheet of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0042] Embodiment 1

[0043] Please refer to Figure 1 , a preparation method of a high-performance ultra-thin rare-earth permanent magnet magnetic sheet, comprising the following steps:

[0044] The samarium raw material and the iron raw material are proportioned and weighed according to a molar ratio of 2:17, and then the input amount of the samarium raw material is increased, and the samarium raw material is in excess by 5wt%; the iron raw material is a steel rod with a purity of 99%, and the samarium raw material in the pre-storage bin is metallic samarium particles with a purity of 99.9%, and the particle size is 1mm - 10mm; taking 100 kg of samarium-iron alloy to weigh the raw materials, wherein 75.95 kg of the steel rod is weighed, and 25.25 kg of the samarium particles is weighed, and 25.25 kg includes 5wt% excess samarium raw material;

[0045] S1. Put the weighed steel rod and 50wt% of the samarium particles in the crucible of the melting furnace, and put the remaining samarium particles in the secondary feeding bin; evacuate to a vacuum degree < 10Pa, heat at a temperature of 1550°C to melt the raw materials in the crucible, then add the raw materials in the secondary feeding bin, continue to heat until completely melted and then continue to smelt for 40 min to obtain molten samarium-iron alloy steel liquid; the molten alloy passes through the tundish and the runner, and is poured onto a cooling roller rotating at 2 r / min to form a continuous samarium-iron alloy strip, and falls onto the water-cooled disk below to obtain samarium-iron alloy sheets;

[0046] S2. After the samarium-iron alloy sheet is naturally cooled to room temperature, put it into a vacuum heat treatment furnace, evacuate to 1×10 - 2 Pa, raise the temperature to 1000°C, keep the temperature for heat treatment for 5 h, and then stop heating;

[0047] Cool to 260°C and keep the temperature. In a vacuum environment, introduce hydrogen into the furnace, control the absolute pressure of hydrogen at 0.08 MPa, and the hydrogenation time is 2 h;

[0048] After the hydrogen breaking is completed, raise the temperature at a uniform speed of 10°C / min to 400°C, fill nitrogen to 0.5 MPa, and keep the temperature for reaction for 1 h; then raise the temperature at a uniform speed of 0.2°C / min to 530°C, and keep the temperature for reaction for 10 h; cool with the furnace to room temperature to obtain nitrided magnetic powder with an average particle size of 20±2μm;

[0049] S3. Based on the weight of the magnetic powder, add 1 wt% of phosphoric acid and 1 wt% of benzotriazole to the magnetic powder, and after wet ball milling and drying, obtain surface-treated magnetic powder with an average particle size of 2.0 ± 0.3 μm;

[0050] S4. Add a binder to the surface-treated magnetic powder and knead to obtain magnetic particles;

[0051] Based on the weight of the surface-treated magnetic powder, add 8 wt% of CPE, 0.5 wt% of calcium stearate, 0.5 wt% of KH570, and 1 wt% of PE wax, and knead at 110 °C for 1 h to obtain magnetic particles with a size of 1 - 5 mm;

[0052] S5. Press the magnetic particles using a flat vulcanizing machine at a temperature of 90 °C and a pressure of 13 MPa to form a rare earth permanent magnet magnetic sheet with a thickness of 0.3 mm.

[0053] After magnetizing the magnetic sheet, measure the surface magnetic field; expose the magnetic sheet in an environment with a temperature of 85 °C and a humidity of 85% for 10 h, and observe the number of rust spots on the surface of the magnetic sheet within an area of 1 cm 2 The test results are shown in Table 1.

[0054] Example 2

[0055] A method for preparing a high-performance ultra-thin rare earth permanent magnet magnetic sheet, which is different from Example 1 in that the samarium raw material and the iron raw material are weighed according to a molar ratio of 2:17, and then the input amount of the samarium raw material is increased, with the samarium raw material being in excess by 1 wt%; the remaining steps and parameters are the same as those in Example 1.

[0056] After magnetizing the magnetic sheet, measure the surface magnetic field; expose the magnetic sheet in an environment with a temperature of 85 °C and a humidity of 85% for 10 h, and observe the number of rust spots on the surface of the magnetic sheet within an area of 1 cm 2 The test results are shown in Table 1.

[0057] Example 3

[0058] A method for preparing a high-performance ultra-thin rare earth permanent magnet magnetic sheet, which is different from Example 1 in that the samarium raw material and the iron raw material are weighed according to a molar ratio of 2:17, and then the input amount of the samarium raw material is increased, with the samarium raw material being in excess by 10 wt%; the remaining steps and parameters are the same as those in Example 1.

[0059] After magnetizing the magnetic sheet, measure the surface magnetic field; expose the magnetic sheet in an environment with a temperature of 85 °C and a humidity of 85% for 10 h, and observe the number of rust spots on the surface of the magnetic sheet within an area of 1 cm 2 The test results are shown in Table 1.

[0060] Example 4

[0061] A preparation method of a high-performance ultra-thin rare earth permanent magnet magnetic sheet, which is different from Example 1 in that in S3, the addition amount of benzotriazole is 3 wt%; the remaining steps and parameters are the same as those in Example 1.

[0062] After magnetizing the magnetic sheet, the surface magnetic field is measured; the magnetic sheet is exposed to an environment with a temperature of 85 °C and a humidity of 85% for 10 h, and the number of rust spots on the surface of the magnetic sheet within an area of 1 cm 2 is observed, and the test results are shown in Table 1.

[0063] Example 5

[0064] A preparation method of a high-performance ultra-thin rare earth permanent magnet magnetic sheet, which is different from Example 1 in that in S3, the addition amount of benzotriazole is 0.1 wt%; the remaining steps and parameters are the same as those in Example 1.

[0065] After magnetizing the magnetic sheet, the surface magnetic field is measured; the magnetic sheet is exposed to an environment with a temperature of 85 °C and a humidity of 85% for 10 h, and the number of rust spots on the surface of the magnetic sheet within an area of 1 cm 2 is observed, and the test results are shown in Table 1.

[0066] Example 6

[0067] A preparation method of a high-performance ultra-thin rare earth permanent magnet magnetic sheet, which is different from Example 1 in that in S5, the pressing and forming temperature of the flat vulcanizer is 80 °C and the pressure is 15 MPa, and the remaining steps and parameters are the same as those in Example 1, and a rare earth permanent magnet magnetic sheet with a thickness of 0.4 mm is obtained by pressing.

[0068] After magnetizing the magnetic sheet, the surface magnetic field is measured; the magnetic sheet is exposed to an environment with a temperature of 85 °C and a humidity of 85% for 10 h, and the number of rust spots on the surface of the magnetic sheet within an area of 1 cm 2 is observed, and the test results are shown in Table 1.

[0069] Example 7

[0070] A preparation method of a high-performance ultra-thin rare earth permanent magnet magnetic sheet, which is different from Example 1 in that in S5, the pressing and forming temperature of the flat vulcanizer is 100 °C and the pressure is 11 MPa, and the remaining steps and parameters are the same as those in Example 1, and a rare earth permanent magnet magnetic sheet with a thickness of 0.2 mm is obtained by pressing.

[0071] After magnetizing the magnetic sheet, the surface magnetic field is measured; the magnetic sheet is exposed to an environment with a temperature of 85 °C and a humidity of 85% for 10 h, and the number of rust spots on the surface of the magnetic sheet within an area of 1 cm 2 is observed, and the test results are shown in Table 1.

[0072] Comparative Example 1

[0073] A preparation method of a rare earth permanent magnet magnetic sheet, which is different from that of Example 1 in that the samarium raw material and the iron raw material are proportioned and weighed according to a molar ratio of 2:17, and then the input amount of the samarium raw material is increased, and the samarium raw material is in an excess of 20 wt%; the remaining steps and parameters are the same as those of Example 1.

[0074] After magnetizing the magnetic sheet, the surface magnetic field is measured; the magnetic sheet is exposed to an environment with a temperature of 85 °C and a humidity of 85% for 10 h, and the number of rust spots on the surface of the magnetic sheet within an area of 1 cm 2 is observed, and the test results are shown in Table 1.

[0075] Comparative Example 2

[0076] A preparation method of a rare earth permanent magnet magnetic sheet, which is different from that of Example 1 in that in S3, the addition amount of benzotriazole is 0 wt%; the remaining steps and parameters are the same as those of Example 1.

[0077] After magnetizing the magnetic sheet, the surface magnetic field is measured; the magnetic sheet is exposed to an environment with a temperature of 85 °C and a humidity of 85% for 10 h, and the number of rust spots on the surface of the magnetic sheet within an area of 1 cm 2 is observed, and the test results are shown in Table 1.

[0078] Comparative Example 3

[0079] A preparation method of a rare earth permanent magnet magnetic sheet, which is different from that of Example 1 in that in S3, the addition amount of benzotriazole is 5 wt%; the remaining steps and parameters are the same as those of Example 1.

[0080] After magnetizing the magnetic sheet, the surface magnetic field is measured; the magnetic sheet is exposed to an environment with a temperature of 85 °C and a humidity of 85% for 10 h, and the number of rust spots on the surface of the magnetic sheet within an area of 1 cm 2 is observed, and the test results are shown in Table 1.

[0081] Comparative Example 4

[0082] A preparation method of a rare earth permanent magnet magnetic sheet, which is different from that of Example 1 in that in S5, the pressing and forming temperature of the flat vulcanizer is 110 °C and the pressure is 16 MPa, and the remaining steps and parameters are the same as those of Example 1, and a rare earth permanent magnet magnetic sheet with a thickness of 0.15 mm is pressed.

[0083] After magnetizing the magnetic sheet, the surface magnetic field is measured; the magnetic sheet is exposed to an environment with a temperature of 85 °C and a humidity of 85% for 10 h, and the number of rust spots on the surface of the magnetic sheet within an area of 1 cm 2 is observed, and the test results are shown in Table 1.

[0084] Comparative Example 5

[0085] A preparation method of a rare earth permanent magnet magnetic sheet, which is different from Example 1 in that in S1, the iron raw material and the samarium raw material are put into the crucible together without secondary feeding. Specifically, S1 is to put the weighed iron rod and samarium particles into the crucible of the melting furnace, evacuate to a vacuum degree < 10 Pa, heat to 1550 °C to melt the raw materials in the crucible, and then continue melting for 40 min to obtain molten samarium-iron alloy steel liquid; the molten alloy passes through the tundish and the runner, and is poured onto a cooling roll rotating at 2 r / min to form a continuous samarium-iron alloy strip, and then falls onto the water-cooled plate below to obtain samarium-iron alloy sheets; the remaining steps and parameters are the same as those in Example 1.

[0086] After magnetizing the magnetic sheet, the surface magnetic field is measured; the magnetic sheet is exposed to an environment with a temperature of 85 °C and a humidity of 85% for 10 h, and the number of rust spots on the surface of the magnetic sheet within an area of 1 cm 2 is observed, and the test results are shown in Table 1.

[0087] Comparative Example 6

[0088] A preparation method of a rare earth permanent magnet magnetic sheet, which is different from Example 1 in that in S2, the nitriding treatment is carried out by directly raising the temperature. Specifically, after the hydrogen desorption is completed, the temperature is uniformly raised to 530 °C at a rate of 10 °C / min, nitrogen is filled to 0.5 MPa, after holding for reaction for 10 h, it is cooled to room temperature with the furnace to obtain nitrided magnetic powder; the remaining steps and parameters are the same as those in Example 1.

[0089] After magnetizing the magnetic sheet, the surface magnetic field is measured; the magnetic sheet is exposed to an environment with a temperature of 85 °C and a humidity of 85% for 10 h, and the number of rust spots on the surface of the magnetic sheet within an area of 1 cm 2 is observed, and the test results are shown in Table 1.

[0090] The relevant process parameters and performance test results of Example 1 - Example 7 and Comparative Example 1 - Comparative Example 6 are shown in Table 1.

[0091] Table 1

[0092]

[0093] As can be seen from Table 1, comparing Example 1 - Example 3 and Comparative Example 1, when additional samarium is added to the samarium raw material weighed according to the stoichiometric ratio of Sm:Fe = 2:17, the less the samarium is in excess, the lower the rare earth content in the magnetic powder. After forming the Sm 2 Fe 17 phase, there are fewer non-magnetic phases, so it has a higher remanence. After making it into a magnetic sheet, it has a higher surface magnetic field.

[0094] Comparing Comparative Example 1, Example 4, Example 5 with Comparative Example 2 and Comparative Example 3, within a certain range, the more the addition amount of the corrosion inhibitor benzotriazole, the fewer the rust spots on the magnetic sheet during the corrosion resistance test, and the better the corrosion resistance. When the addition amount of benzotriazole is excessive, it may react with phosphoric acid, further affecting the formation and distribution of phosphates, accelerating the chemical reaction on the surface of the magnetic powder, changing the chemical properties of the magnetic powder surface, and resulting in irreversible loss of magnetic properties. Therefore, it is necessary to strictly control the addition amount of benzotriazole to ensure the performance stability and reliability of the magnetic powder.

[0095] Comparing Comparative Example 1, Example 6, Example 7 with Comparative Example 4, by adjusting the temperature and pressure of the flat vulcanizing machine during molding, the thickness of the magnetic sheet can be adjusted. When the thickness of the magnetic sheet is larger, the amount of magnetic phase contained is relatively more, and the surface magnetic naturally is relatively higher.

[0096] Comparing Comparative Example 1 with Comparative Example 5, under the condition of the same amount of raw materials, when the samarium raw material is not added for the second time and is melted and refined simultaneously with the iron raw material, the volatilization amount of samarium increases during this process; while the second addition can effectively reduce the volatilization of Sm, and the Sm content is greatly increased, and the Sm 2 Fe 17 phase is more uniform and the surface magnetic is larger.

[0097] Comparing Comparative Example 1 with Comparative Example 6, adopting a segmented heating method during the nitriding process can effectively control the rate and degree of the nitriding reaction, avoiding problems such as grain growth or uneven nitriding caused by too high temperature. By cooling to room temperature with the furnace, the stress concentration during the cooling process can be reduced, and the overall quality of the nitrided magnetic powder can be improved.

[0098] In summary, it can be seen that in the present invention, the magnetic particles are pressed to 0.2 mm - 0.4 mm by flat vulcanization, which can solve the problem that the rolling mill in the prior art cannot process below 0.4 mm; by having 1 wt% - 10 wt% excess samarium in the formula and after homogenization treatment, Sm 2 Fe 17 alloy sheets are obtained. After hydrogen decrepitation and nitriding, Sm 2 Fe 17 N xMagnetic powder can effectively improve the magnetic properties of the magnetic powder, thereby enhancing the magnetic properties of the final magnetic sheet. The surface magnetic field of the magnetic sheet is higher than 500 Gs, solving the problem of low surface magnetism of the thin magnets prepared by rolling in the prior art and meeting the actual application requirements. Through surface treatment after ball milling, adding 1 wt% phosphoric acid + 1 wt% corrosion inhibitor, the corrosion resistance of the magnetic powder is improved, thus enhancing the corrosion resistance of the final magnetic sheet. By adding organic binders such as 8 wt% CPE, 0.5 wt% calcium stearate, 0.5 wt% coupling agent, and 1 wt% PE wax, the temperature of internal mixer and the temperature of compression molding by flat vulcanization are low, which can effectively improve the compression molding performance of the magnetic powder, thereby enhancing the compression molding performance of the final magnetic sheet.

[0099] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0100] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-performance ultra-thin rare earth permanent magnet sheet, characterized in that: The following steps are involved: S1, melting all the iron raw materials and 45wt%-55wt% of the samarium raw materials under vacuum conditions, adding the remaining samarium, continuing to smelt, and pouring the obtained molten alloy onto a cooling roller to obtain a samarium-iron alloy sheet; S2, sequentially performing homogenization treatment, hydrogenation treatment and nitridation treatment on the samarium-iron alloy sheet to obtain nitrided magnetic powder; S3, adding phosphoric acid and corrosion inhibitor to the magnetic powder, wet ball milling, and drying to obtain surface treated magnetic powder; According to the weight of magnetic powder, the amount of phosphoric acid added is 1wt%; The corrosion inhibitor is benzotriazole, and the amount of benzotriazole added is 0.1wt%-3wt%; S4, adding a binder to the surface treated magnetic powder, and kneading to obtain magnetic particles; S5. The magnetic particles are pressed by a flat vulcanizing machine to obtain rare earth permanent magnet sheets.

2. The method for preparing a high-performance ultra-thin rare earth permanent magnet sheet according to claim 1, characterized in that: In S1, samarium raw material and iron raw material are weighed according to a molar ratio of 2:17, and 1wt%-10wt% of samarium raw material is added.

3. The method for preparing a high-performance ultra-thin rare earth permanent magnet sheet according to claim 1, characterized in that: In S1, all the iron raw materials and 50 wt% of the samarium raw materials are melted under vacuum conditions.

4. The method for preparing a high-performance ultra-thin rare earth permanent magnet sheet according to claim 1, characterized in that: In S1, the vacuum degree is <10Pa, the melting temperature is 1510°C-1580°C, and the melting time is 30min-50min.

5. The method for preparing a high-performance ultra-thin rare earth permanent magnet sheet according to claim 1, characterized in that: In S2, the homogenization treatment is to place the samarium iron alloy sheet into a heat treatment furnace, evacuate the vacuum and heat treat it at a temperature of 900°C-1100°C for 7.5h-8.5h; The hydrogenation treatment is to cool the homogenized samarium iron alloy sheet to 250°C-300°C and keep it warm, and then introduce hydrogen into the furnace under vacuum, with the absolute pressure of hydrogen controlled at 0.05MPa-0.15MPa, and the hydrogenation time is 2h; The nitriding treatment is to uniformly increase the temperature to 350°C-450°C at a rate of 10°C / min, fill with nitrogen to 0.5MPa, and keep the temperature for 1 hour; then uniformly increase the temperature to 500°C-550°C at a rate of 0.2°C / min, keep the temperature for 10 hours; and cool to room temperature with the furnace.

6. The method for preparing a high-performance ultra-thin rare earth permanent magnet sheet according to claim 1, characterized in that: In S4, the binder consists of CPE, calcium stearate, KH570, and PE wax; Calculated based on the weight of magnetic powder, the added amount of CPE is 8wt%, the added amount of calcium stearate is 0.5wt%, the added amount of KH570 is 0.5wt%, and the added amount of PE wax is 1wt%.

7. The method for preparing a high-performance ultra-thin rare earth permanent magnet sheet according to claim 1, characterized in that: In S4, the mixing temperature is 100°C-120°C, and the mixing time is 1 hour.

8. The method for preparing a high-performance ultra-thin rare earth permanent magnet sheet according to claim 1, characterized in that: In S5, the temperature of the flat vulcanizing press for pressing is 80°C-100°C and the pressure is 10MPa-15MPa.

9. A high-performance ultra-thin rare earth permanent magnet sheet, characterized in that: The rare earth permanent magnet sheet is prepared by the preparation method described in any one of claims 1 to 8, wherein the substrate of the rare earth permanent magnet sheet is samarium iron nitrogen material, the thickness is 0.2mm-0.4mm, and the surface magnetism is greater than 500Gs.

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