A high coercivity Nd-Fe-B magnetic material and its preparation method

Abstract

This application relates to the technical field of magnetic material preparation, and specifically discloses a high coercivity NdFeB magnetic material and a preparation method thereof. The high coercivity NdFeB magnetic material of this application includes the following raw materials: praseodymium-neodymium alloy, copper, boron, cobalt, titanium, cerium, gadolinium, zirconium, and an auxiliary agent, with the balance being iron and other inremovable impurities. The auxiliary agent is composed of Fe3Pt, FePt, and carbon. The preparation method includes the following steps: melting the praseodymium-neodymium alloy, copper, boron, cobalt, titanium, cerium, gadolinium, iron, zirconium, and the auxiliary agent to obtain a molten liquid, and performing strip casting on the obtained molten liquid to obtain strip cast pieces; an inert gas is introduced for protection during the melting of the raw materials; after the strip cast pieces are hydrogenated and crushed and then subjected to jet milling, hydrogenated and crushed powder is obtained; the hydrogenated and crushed powder is pressed to obtain a green compact, and the green compact is further pressed to obtain a green magnet; the green magnet is sintered and tempered, and then cooled to room temperature to obtain the product. The high coercivity NdFeB magnetic material of this application has better magnetic properties.

Description

Technical Field

[0001] This application relates to the technical field of magnetic material preparation. More specifically, it relates to a high coercivity neodymium iron boron magnetic material and a preparation method thereof. Background Art

[0002] Rare earth permanent magnet materials are widely used in various fields of the national economy such as aerospace, aviation, computers, communications, information, energy, transportation, ships, petroleum, chemical industry, textiles, household appliances, etc., and are an essential cornerstone for informatization, automation, intelligence, energy conservation and environmental protection. In particular, neodymium iron boron magnetic materials are used in household appliances, etc.

[0003] Neodymium iron boron magnetic materials, as the latest achievements in the development of rare earth permanent magnet materials, are known as the "magnetic king" due to their excellent magnetic properties. Due to their extremely high magnetic energy product and coercive force, as well as the advantages of high energy density, neodymium iron boron materials have been widely used in modern industry and electronic technology, making it possible to miniaturize, lighten, and thin devices such as instruments, electroacoustic motors, magnetic separation and magnetization.

[0004] Neodymium iron boron magnetic materials are restricted by a relatively low Curie temperature, and their magnetic properties deteriorate rapidly in high-temperature environments. Improving the coercivity of neodymium iron boron magnetic materials may reduce the magnetic property loss of neodymium iron boron magnetic materials at higher temperatures. Summary of the Invention

[0005] In order to facilitate the improvement of the coercivity of neodymium iron boron magnetic materials, this application provides a high coercivity neodymium iron boron magnetic material and a preparation method thereof.

[0006] In the first aspect, this application provides a high coercivity neodymium iron boron magnetic material, adopting the following technical solution: A high coercivity neodymium iron boron magnetic material includes raw materials in the following weight percentages: praseodymium-neodymium alloy 10-20%, copper 0.1-0.3%, boron 0.5-1.5%, cobalt 0.1-0.3%, titanium 0.2-0.5%, cerium 10-15%, gadolinium 0.5-1%, zirconium 0.1-0.2%, auxiliary agent 1-2%, and the balance is iron and other impurities that cannot be removed. The auxiliary agent is composed of Fe3Pt, FePt, and carbon in a mass ratio of (3-5):(1-2):(1-2).

[0007] By adopting the above technical solutions, cerium elements are mainly distributed at grain boundaries, strengthening the grain boundaries and possibly increasing the coercivity; meanwhile, cerium elements may make the grains tend to be uniform and regular, reducing the greatly reduced or even disappearing of grains with sharp edges and corners such as strip-shaped, quadrilateral, and wedge-shaped grains and grains with too large or too small sizes, making the grains closer to each other, increasing the toughness at grain boundaries, and thus increasing the coercivity of the magnet; while making the grains tend to be uniform, cerium elements may refine the grains. When the grain size is too small, the intergranular exchange interaction is strong, and the magnetization directions of each grain are roughly the same. During demagnetization, adjacent grains will be driven to reverse synergistically instead of each grain reversing independently. Therefore, the demagnetization of the grains may reduce the coercivity of the magnet; the addition of the auxiliary agent facilitates reducing the interaction domains between grains. Fe3Pt and FePt form clusters with smaller particle sizes in the magnet and are distributed on the non-magnetic carbon matrix. Due to the small grain size, the soft magnetic phase Fe3Pt and the hard magnetic phase FePt in the cluster can be completely magnetically coupled, and the clusters are isolated by non-magnetic phases, enabling each cluster to be demagnetized independently, thereby increasing the coercivity of the magnetic material.

[0008] Preferably, the mass ratio of the cerium to the auxiliary agent is (11 - 13):(1.5 - 1.8).

[0009] By adopting the above technical solutions, the ratio of cerium to the auxiliary agent is further optimized, making the ratio of the two components reach the best, so as to further improve the synergistic effect between the auxiliary agent and cerium elements, and thus improve the magnetism of the magnet.

[0010] Preferably, the cobalt is modified cobalt, and the modified cobalt has a cobalt core and a CoPt shell layer.

[0011] Preferably, the preparation method of the modified cobalt includes the following steps: mixing cobalt powder with a thermosetting resin, heating and stirring to obtain pretreated cobalt, and then mixing CoPt with the pretreated cobalt to obtain the modified cobalt.

[0012] Preferably, the mass ratio of CoPt to cobalt is (4 - 5):(1 - 2). Further preferably, the μm.

[0013] Preferably, the heating temperature is 110 - 120 °C.

[0014] Preferably, the thermosetting resin is phenolic resin.

[0015] By adopting the above technical solutions, Co is wrapped with CoPt. CoPt is a hard magnetic material and has large magnetocrystalline anisotropy and large shape anisotropy. Wrapping it on the outer layer of Co facilitates increasing the saturation magnetization intensity of Co, increasing the magnetic energy product. At the same time, based on the exchange coupling effect between the soft and hard magnetic materials, the saturation magnetization intensity of the material is increased, and thus the magnetic properties of the prepared neodymium-iron-boron magnetic material are improved.

[0016] Preferably, it further includes 0.2-0.5% of TiC.

[0017] By adopting the above technical solution, the addition of TiC may change the microstructure of the magnet, thereby facilitating the improvement of the magnetic properties of the magnet. The solubility of titanium in the Nd-Fe-B phase is small. During the grain growth process, titanium is extruded from the Nd-Fe-B phase and accumulates at the grain boundaries, which has the effect of inhibiting grain growth. Titanium carbide has the effect of isolating the grains of the hard magnetic phase, which is conducive to improving the coercivity of the magnet.

[0018] In a second aspect, the present application provides a method for preparing a high coercivity Nd-Fe-B magnetic material, adopting the following technical solution:

[0019] A method for preparing a high coercivity Nd-Fe-B magnetic material, including the following steps:

[0020] (1) Melting and strip casting: melting praseodymium-neodymium alloy, copper, boron, cobalt, titanium, cerium, gadolinium, iron, zirconium, and auxiliary agents to obtain a molten liquid, and strip casting the obtained molten liquid to obtain strip-cast sheets; an inert gas is introduced for protection during the melting of the raw materials;

[0021] (2) Hydrogen decrepitation and grinding: subjecting the strip-cast sheets obtained in step (1) to hydrogen decrepitation and jet milling to obtain hydrogen decrepitated powder;

[0022] (3) Compression molding: pressing the hydrogen decrepitated powder obtained in step (2) to obtain a green compact, and further pressing the green compact to obtain a green magnet;

[0023] (4) Sintering: sintering and tempering the green magnet obtained in step (3), and cooling to room temperature to obtain the product.

[0024] Preferably, the sintering temperature in step (4) is 1000-1050 °C.

[0025] Preferably, the hydrogen decrepitation operation in step (2) is as follows: placing the strip-cast sheets in a hydrogen atmosphere, allowing the strip-cast sheets to absorb hydrogen for 2-3 h to obtain a hydrogen decrepitated product, controlling the hydrogen absorption pressure to be 0.7-0.9 MPa, and the hydrogen absorption temperature to be 350-500 °C; then heating the hydrogen decrepitated product to 600-700 °C for dehydrogenation treatment.

[0026] By adopting the above technical solution, the Nd-Fe-B magnetic material of the present application undergoes melting, hydrogen decrepitation, compression molding, sintering, and tempering treatments. The Nd-Fe-B magnetic material thus prepared has better magnetic properties. Moreover, during the melting of the present application, a nitrogen protection method is adopted, which is conducive to reducing the oxidation of the raw materials, so as to further improve the magnetic properties of the Nd-Fe-B magnetic material.

[0027] Preferably, the particle size of the hydrogen decrepitated powder in step (2) is 1-2 μm.

[0028] By adopting the above technical solution, the particle size of the hydrogenated powder is small, which is convenient for improving the coercivity of the magnet under the condition of affecting the remanence. The appropriate fine powder particle size can not only reduce the agglomeration between the fine powders and improve the orientation degree of the fine powders after forming and orientation, but also ensure the compactness of the NdFeB magnetic material after pressing.

[0029] Preferably, in the step (2), the strip casting is mixed with an antioxidant, and then hydrogenation crushing and jet milling are carried out.

[0030] By adopting the above technical solution, during the preparation of the hydrogenated powder, the hydrogenated powder is in sufficient contact with oxygen in the jet mill, making the magnetic powder tend to be oxidized. The antioxidant inhibits the formation of high-melting-point oxides with oxygen elements in the NdFeB magnetic material, thereby limiting the probability of generating pores due to the formation of high-melting-point oxides, making the coercivity of the NdFeB magnetic material meet the standard, improving the corrosion resistance of the NdFeB magnetic material, and thus extending the working life of the NdFeB magnetic material.

[0031] Preferably, the antioxidant is composed of antioxidant 1010, antioxidant 1076, and zinc stearate in a mass ratio of (4 - 5):(1 - 2):(1 - 2).

[0032] Preferably, the antioxidant is composed of antioxidant 1010, antioxidant 1076, and zinc stearate in a mass ratio of 5:2:2.

[0033] By adopting the above technical solution, one of antioxidant 1076 and antioxidant 1010 serves as the main antioxidant and the other as the auxiliary antioxidant. Antioxidant 1010 and antioxidant 1076 cooperate with each other and act synergistically to further improve the antioxidant effect of the hydrogenated powder. Zinc stearate has a lubricating effect, which is convenient for improving the fluidity of the prepared hydrogenated powder, reducing the friction between powder particles, and further reducing the phenomenon of powder particle agglomeration. At the same time, the rotational resistance between the hydrogenated powders is reduced, and the powder orientation degree is improved, which is convenient for improving the magnetic properties of the magnet.

[0034] Preferably, the hydrogenated powder in the step (3) is pretreated. The method for pretreating the hydrogenated powder includes the following steps: immersing the hydrogenated powder in an organic silicone resin solution, mixing evenly, spin-drying and drying to obtain the product.

[0035] Preferably, the spin-drying is carried out by spin coating.

[0036] Preferably, the spin-drying voltage of the spin dryer is 180V.

[0037] Preferably, the mass fraction of the organic solution of the organic silicone resin is 40 - 50%.

[0038] Preferably, the drying process is as follows: first bake in a vacuum drying oven for 20 - 30 minutes at a baking temperature of 55 - 60 °C. After the solvent has evaporated, bake at 110 °C for 50 - 60 minutes to obtain the product.

[0039] Preferably, the organic solution is ethanol.

[0040] Preferably, the silicone resin is commercially available.

[0041] By adopting the above technical solution, an outer layer of silicone resin is wrapped around the hydrogen - cracked powder, which is convenient for improving the particle dispersion degree of the hydrogen - cracked powder, may improve the compactness of the magnet prepared, and at the same time, further improves the oxidation resistance of the hydrogen - cracked powder, contributing to improving the oxidation resistance and corrosion resistance of the magnetic material prepared.

[0042] Preferably, after sintering the green magnet, tempering treatment is carried out at a temperature of 900 - 950 °C and held for 3 - 4 hours; the green magnet is cooled to 600 - 700 °C, held for 2 - 3 hours, then cooled to 300 - 400 °C, held for 2 - 3 hours, and cooled to room temperature for discharging.

[0043] Preferably, after sintering the green magnet, tempering treatment is carried out at a temperature of 900 °C and held for 4 hours; the green magnet is cooled to 700 °C, held for 2 hours, then cooled to 350 °C, held for 2 hours, and cooled to room temperature for discharging.

[0044] By adopting the above technical solution, during heat preservation, tempering can be carried out through the temperature of the material itself, so that multiple temperings can be achieved through one - time heating, greatly saving the energy consumed by heating, thereby reducing the production cost and achieving energy conservation and emission reduction. At the same time, multiple temperings can also improve the coercivity of the Nd - Fe - B magnetic material.

[0045] In summary, the present application has the following beneficial effects:

[0046] 1. The high - coercivity Nd - Fe - B magnetic material of the present application is obtained by adding cerium and an auxiliary agent. The auxiliary agent is compounded from three components: Fe3Pt, FePt, and carbon. Cerium and the auxiliary agent cooperate with each other. Cerium improves the magnetic properties of the Nd - Fe - B magnetic material by refining the grain size, and the auxiliary agent improves the magnetic properties of the Nd - Fe - B magnetic material by reducing the interaction domains between grains.

[0047] 2. The high - coercivity Nd - Fe - B magnetic material of the present application wraps CoPt around the Co. CoPt is a hard magnetic material with large magnetocrystalline anisotropy and large shape anisotropy. Wrapping it around the Co is convenient for improving the saturation magnetization intensity of Co, increasing the magnetic energy product. At the same time, based on the exchange coupling effect between the hard and soft magnetic materials, the saturation magnetization intensity of the material is increased, thereby improving the magnetic properties of the Nd - Fe - B magnetic material prepared.

[0048] 3. The high coercivity NdFeB magnetic material of the present application may change the microstructure of the magnet and thus facilitate the improvement of the magnetic properties of the magnet by adding TiC. Titanium has a low solubility in the NdFeB phase. During the grain growth process, titanium is extruded from the NdFeB phase and accumulates at the grain boundaries, which has the effect of inhibiting grain growth. Titanium carbide has the effect of isolating the hard magnetic phase grains, which is convenient for improving the coercivity of the magnet. Detailed implementation mode

[0049] The present application will be further described in detail below in conjunction with embodiments.

[0050] The praseodymium-neodymium alloy of the present application is commercially available. Further optionally, the praseodymium-neodymium alloy of the present application is purchased from Beijing Xingrongyuan Technology Co., Ltd. and is composed of praseodymium powder and neodymium powder. The purity of both the praseodymium powder and the neodymium powder is 99.99%, and praseodymium accounts for 15.5 wt% of the total amount of the praseodymium-neodymium powder.

[0051] The iron powder of the present application is commercially available. Further optionally, the iron powder of the present application is purchased from Shijiazhuang Hualang Mineral Products Trading Co., Ltd., and it is magnet powder with an iron content of 99.9%.

[0052] The adjuvant of the present application is composed of Fe3Pt, FePt, and carbon in a mass ratio of (3-5):(1-2):(1-2). Further optionally, the adjuvant of the present application is composed of Fe3Pt, FePt, and carbon in a mass ratio of 5:2:2.

[0053] The addition amount of TiC in the present application is 0.2-0.5%, and further optionally, the addition amount of TiC is 0.5%.

[0054] Embodiment

[0055] Embodiment 1: A high coercivity NdFeB magnetic material, comprising the following raw materials in weight percentages: 10% praseodymium-neodymium alloy, 0.1% copper, 0.5% boron, 0.1% cobalt, 0.2% titanium, 10% cerium, 0.5% gadolinium, 0.1% zirconium, 1% adjuvant, and the balance is iron and other impurities that cannot be removed. Among them, the adjuvant is composed of Fe3Pt, FePt, and carbon in a mass ratio of 5:2:2.

[0056] The preparation method of the above high coercivity NdFeB magnetic material comprises the following steps:

[0057] (1) Melting and strip casting: Melting the praseodymium-neodymium alloy, copper, boron, cobalt, titanium, cerium, gadolinium, iron, zirconium, and adjuvant to obtain a molten liquid, and subjecting the obtained molten liquid to strip casting to obtain strip cast sheets; an inert gas is introduced for protection during the melting of the raw materials;

[0058] (2) Hydrogen breaking and grinding: Subjecting the strip cast sheets obtained in step (1) to hydrogen breaking and jet milling to obtain hydrogen broken powder; the hydrogen breaking operation is: placing the strip cast sheets in a hydrogen atmosphere to allow the strip cast sheets to absorb

[0059] Hydrogen is absorbed by hydrogen 2h to obtain a hydrogen-breaking product, and the hydrogen absorption pressure is controlled at 0.8 MPa and the hydrogen absorption temperature is 400 °C; then the hydrogen-breaking product is heated to 650 °C for dehydrogenation treatment; the particle size of the hydrogen-breaking powder is 2 μm;

[0060] (3) Compression molding: The hydrogen-breaking powder obtained in step (2) is pressed to obtain a green body, and the green body is further pressed to obtain a green magnet;

[0061] (4) Sintering: The green magnet obtained in step (3) is sintered and tempered, and then cooled to room temperature to obtain the product; among them, the sintering temperature is 1050 °C; the green magnet is tempered at a temperature of 900 °C after sintering and kept warm for 4 h; the green magnet is cooled to 700 °C, kept warm for 2 h, then cooled to 350 °C, kept warm for 2 h, and then cooled to room temperature and taken out of the furnace.

[0062] Table 1 Raw material component ratios of high coercivity NdFeB magnetic materials in Examples 1-5

[0063]

[0064]

[0065] Examples 2-4: A high coercivity NdFeB magnetic material, the component ratios of each raw material are shown in Table 1, and the difference from Example 1 is that: the component ratios of each raw material are different.

[0066] Example 5: A high coercivity NdFeB magnetic material, the component ratios of each raw material are shown in Table 1, and the difference from Example 4 is that: 0.5% of TiC is also added.

[0067] Example 6: A high coercivity NdFeB magnetic material, the difference from Example 5 is that: the cobalt is modified cobalt, the modified cobalt has a cobalt core and a CoPt shell layer, and the preparation method of the modified cobalt includes the following steps: mixing cobalt powder with a thermosetting resin, heating and stirring to obtain pretreated cobalt, and mixing CoPt with the pretreated cobalt to obtain the product. Among them, the mass ratio of CoPt to cobalt is 5:1, the mass ratio of the thermosetting resin to cobalt powder is 3:1, the particle size of cobalt powder is 30 μm, the particle size of CoPt is 5 μm, the heating temperature is 110 °C, and the thermosetting resin is phenolic resin.

[0068] Example 7: A high coercivity NdFeB magnetic material, the difference from Example 6 is that: the preparation method of the high coercivity NdFeB magnetic material includes the following steps:

[0069] (1) Melt spinning: Praseodymium-neodymium alloy, copper, boron, cobalt, titanium, cerium, gadolinium, iron, zirconium, and auxiliary agent are melted to obtain a molten liquid, and the obtained molten liquid is spun to obtain a spun ribbon; the raw materials are protected by passing an inert gas during melting;

[0070] (2) Hydrogen desorption and grinding: After hydrogen desorption and jet milling of the strip cast sheet obtained in step (1) with an antioxidant, hydrogen desorbed powder is obtained. The hydrogen desorption operation is as follows: Place the strip cast sheet in a hydrogen atmosphere to allow the strip cast sheet to absorb hydrogen for 2 h to obtain a hydrogen desorbed product, control the hydrogen absorption pressure at 0.8 MPa, and the hydrogen absorption temperature at 400 °C; then heat the hydrogen desorbed product to 650 °C for dehydrogenation treatment; the particle size of the hydrogen desorbed powder is 2 μm; wherein, the antioxidant is antioxidant 1010;

[0071] (3) Compression molding: Press the hydrogen desorbed powder obtained in step (2) to obtain a green compact, and further press the green compact to obtain a green magnet;

[0072] (4) Sintering: Sinter and temper the green magnet obtained in step (3), and cool to room temperature to obtain the product; wherein, the sintering temperature is 1050 °C; after sintering, the green magnet is tempered at 900 °C for 4 h; the green magnet is cooled to 700 °C, held for 2 h, then cooled to 350 °C, held for 2 h, and cooled to room temperature and taken out of the furnace.

[0073] Example 8: A high coercivity NdFeB magnetic material, different from Example 7 in that: the antioxidant in step (2) consists of antioxidant 1010, antioxidant 1076, and zinc stearate in a mass ratio of 5:2:2.

[0074] Example 9: A high coercivity NdFeB magnetic material, different from Example 8 in that: the hydrogen desorbed powder in step (3) is pretreated. The method for pretreating the hydrogen desorbed powder includes the following steps: Immerse the hydrogen desorbed powder in an organosilicon resin solution, mix evenly, spin-dry and dry it to obtain the product. Spin-drying is carried out by spin coating. The spin-drying voltage of the spin dryer is 180 V. The mass fraction of the organic solution of the organosilicon resin is 40%, and the drying process is as follows: First bake in a vacuum drying oven for 25 min at a baking temperature of 60 °C. After the solvent volatilizes, bake at 110 °C for 60 min to obtain the product. The organic solution is ethanol; the organosilicon resin is commercially available.

[0075] Comparative example

[0076] Comparative example 1: A high coercivity NdFeB magnetic material, different from Example 1 in that: cerium is not added.

[0077] Comparative example 2: A high coercivity NdFeB magnetic material, different from Example 1 in that: the auxiliary agent is not added.

[0078] Comparative example 3: A high coercivity NdFeB magnetic material, different from Example 1 in that: the auxiliary agent consists of Fe3Pt and FePt in a mass ratio of 3:1.

[0079] Comparative Example 4: A high coercivity NdFeB magnetic material, which is different from Example 1 in that the auxiliary agent is composed of Fe3Pt and carbon in a mass ratio of 3:1.

[0080] Comparative Example 5: A high coercivity NdFeB magnetic material, which is different from Example 1 in that the auxiliary agent is Fe3Pt.

[0081] Detection method

[0082] Magnetic property detection: For the high coercivity NdFeB magnetic materials prepared in Examples 1-9 and Comparative Examples 1-5, according to the detection method in GB / T 3217-2013 "Magnetic Test Methods for Permanent (Hard Magnetic) Materials", the magnetic properties of the high coercivity NdFeB magnetic materials were tested at a temperature of 20 °C in the NIM-10000H rare earth permanent magnet non-destructive detection system. The test results are shown in Table 2.

[0083] Table 2 Detection results of the magnetic properties of the high coercivity NdFeB magnetic materials prepared in Examples 1-9 and Comparative Examples 1-5

[0084]

[0085]

[0086] Combined with Examples 1-4 and the data in Table 2, it can be seen that the coercivity, maximum magnetic energy product, and remanence of the high coercivity NdFeB magnetic materials prepared in Examples 1-4 are relatively large, and the magnetic properties are relatively good. The inventors of the present application speculate that the cerium element, the auxiliary agent, and other materials in the high coercivity NdFeB magnetic material cooperate with each other, and the cerium element and the auxiliary agent act synergistically, which may further improve the magnetic properties of the high coercivity NdFeB magnetic material.

[0087] Combined with Examples 4-5 and the data in Table 2, it can be seen that compared with Example 4, TiC is added to the high coercivity NdFeB magnetic material in Example 5. The coercivity, maximum magnetic energy product, and remanence of the high coercivity NdFeB magnetic material prepared thereby are relatively large, and the magnetic properties are relatively good. The inventors of the present application speculate that the addition of TiC may further inhibit the growth of grains. The solubility of titanium in the NdFeB phase is relatively small. During the grain growth process, it is extruded from the NdFeB phase and accumulates at the grain boundaries, which has the effect of inhibiting grain growth. Titanium carbide has the effect of isolating the grains of the hard magnetic phase, which is convenient for improving the magnetic properties of the magnet.

[0088] Combined with Examples 5-6 and the data in Table 2, it can be seen that compared with Example 5, in Example 6, Co was modified by coating CoPt on the outer layer of cobalt. As a result, the coercivity, maximum magnetic energy product, and remanence of the high coercivity NdFeB magnetic material prepared are larger, and the magnetic properties are better. The inventors of the present application speculate that the modified Co may improve the magnetocrystalline anisotropy and shape anisotropy of Co through the coated CoPt layer, which helps to improve the magnetic properties of the prepared magnet.

[0089] Combined with Examples 6-7 and the data in Table 2, it can be seen that compared with Example 6, in Example 7, during the crushing process of the strip-cast sheet, it was mixed with an antioxidant. As a result, the coercivity, maximum magnetic energy product, and remanence of the high coercivity NdFeB magnetic material prepared are larger, and the magnetic properties are better. The inventors of the present application speculate that the addition of the antioxidant may inhibit the formation of high melting point oxides with oxygen elements in the NdFeB magnetic material, thereby limiting the probability of generating pores due to the formation of high melting point oxides, which helps to improve the corrosion resistance of the NdFeB magnetic material and further improve the magnetic properties of the NdFeB magnetic material.

[0090] Combined with Examples 7-8 and the data in Table 2, it can be seen that compared with Example 7, in Example 8, during the crushing process of the strip-cast sheet, it was mixed with the compounded antioxidant. As a result, the coercivity, maximum magnetic energy product, and remanence of the high coercivity NdFeB magnetic material prepared are larger, and the magnetic properties are better. The inventors of the present application speculate that antioxidant 1010 and antioxidant 1076 cooperate with each other and have a synergistic effect, further improving the antioxidant effect of the hydrogenated powder; zinc stearate may reduce the phenomenon of powder particles agglomerating. At the same time, it reduces the rotational resistance between the hydrogenated powders, improves the powder orientation degree, and is convenient for improving the magnetic properties of the magnet.

[0091] Combined with Examples 8-9 and the data in Table 2, it can be seen that compared with Example 8, the high coercivity NdFeB magnetic material prepared in Example 9 has an antioxidant layer coated on the outer layer of the prepared hydrogenated powder. As a result, the coercivity, maximum magnetic energy product, and remanence of the high coercivity NdFeB magnetic material prepared are larger, and the magnetic properties are better. The inventors of the present application speculate that coating an organosilicon resin layer on the outer layer of the hydrogenated powder is convenient for improving the particle dispersion degree of the hydrogenated powder, may improve the denseness of the prepared magnet, and at the same time, further improves the antioxidant property of the hydrogenated powder, which helps to improve the antioxidant property and corrosion resistance of the prepared magnetic material.

[0092] Combined with Example 1 and Comparative Examples 1-2 and the data in Table 2, it can be seen that the differences between Comparative Examples 1-2 and Example 1 are as follows: in Example 1, cerium and an auxiliary agent were added simultaneously, and the magnetic properties of the high coercivity NdFeB magnetic material prepared are better than those of the high coercivity NdFeB magnetic materials prepared in Comparative Examples 1-2.

[0093] Combined with Example 1, Comparative Examples 3-5, and the data in Table 2, it can be seen that the difference between the high coercivity NdFeB magnetic materials prepared in Comparative Examples 3-5 and those prepared in Example 1 is that the auxiliary agent in Example 1 is composed of three components, namely Fe3Pt, FePt, and carbon, which cooperate synergistically. The magnetic properties of the high coercivity NdFeB magnetic materials prepared are superior to those of the high coercivity NdFeB magnetic materials prepared in Comparative Examples 3-5.

[0094] This specific embodiment is only an interpretation of the present application, and it does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions 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 high coercivity NdFeB magnetic material, characterized in that: It includes raw materials with the following weight percentages: praseodymium-neodymium alloy 10-20%, copper 0.1-0.3%, boron 0.5-1.5%, cobalt 0.1-0.3%, titanium 0.2-0.5%, cerium 10-15%, gadolinium 0.5-1%, zirconium 0.1-0.2%, auxiliary agent 1-2%, and the balance is iron and other non-removable impurities; The auxiliary agent is composed of Fe3Pt, FePt, and carbon in a mass ratio of (3-5):(1-2):(1-2); The mass ratio of the cerium to the auxiliary agent is (11-13):(1.5-1.8); The cobalt is modified cobalt, with cobalt as the core and CoPt as the shell layer.

2. The high coercivity Nd-Fe-B magnetic material according to claim 1, characterized in that: It also includes 0.2-0.5% of TiC.

3. A method for preparing a high coercivity Nd-Fe-B magnetic material according to any one of claims 1-2, characterized in that: It includes the following steps: (1) Melting and strip casting: Melting praseodymium-neodymium alloy, copper, boron, cobalt, titanium, cerium, gadolinium, iron, zirconium, and auxiliary agent to obtain a molten liquid, and subjecting the obtained molten liquid to strip casting to obtain strip-cast sheets; an inert gas is introduced for protection during the melting of the raw materials; (2) Hydrogenation and milling: Subjecting the strip-cast sheets obtained in step (1) to hydrogenation and jet milling to obtain hydrogenated powder; (3) Compression molding: Pressing the hydrogenated powder obtained in step (2) to obtain a green compact, and further pressing the green compact to obtain a green magnet; (4) Sintering: Sintering and tempering the green magnet obtained in step (3), and cooling to room temperature to obtain the product.

4. The preparation method of a high coercivity neodymium iron boron magnetic material according to claim 3, characterized in that: The particle size of the hydrogenated powder in step (2) is 1-2 μm.

5. The preparation method of a high coercivity neodymium iron boron magnetic material according to claim 3, characterized in that: In step (2), the strip-cast sheets are mixed with an antioxidant, and then subjected to hydrogenation and jet milling.

6. The preparation method of a high coercivity neodymium iron boron magnetic material according to claim 5, characterized in that: The antioxidant is composed of antioxidant 1010, antioxidant 1076, and zinc stearate in a mass ratio of (4-5):(1-2):(1-2).

7. The preparation method of a high coercivity NdFeB magnetic material according to claim 3, characterized in that: The hydrogenated powder in step (3) is pretreated, and the method for pretreating the hydrogenated powder includes the following steps: Immersing the hydrogenated powder in an organosilicon resin solution, mixing evenly, spin-drying and drying to obtain the product.

8. The preparation method of a high coercivity NdFeB magnetic material according to claim 3, characterized in that: After sintering, the green magnet in step (4) is subjected to tempering treatment at a temperature of 900-950 °C and held for 3-4 h; the green magnet is cooled to 600-700 °C, held for 2-3 h, then cooled to 300-400 °C, held for 2-3 h, and cooled to room temperature for discharging.

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