A preparation method of high-temperature resistant NdFeB magnetic material

Abstract

The present application relates to the technical field of magnetic materials, and discloses a preparation method of a high-temperature resistant neodymium iron boron magnetic material, comprising the following steps: S1 melting, S2 pulverizing, S3 orientation and pressing, S4 sintering, S5 vacuum coating; the neodymium iron boron magnetic material comprises the following components in fractions: 13-18 wt% praseodymium-neodymium, 0.5-1 wt% boron, 18-30 wt% samarium and yttrium, 3-8 wt% auxiliary metal, 0.08-0.12 wt% iridium, 8-10 wt% niobium, 3-5 wt% dysprosium, 10-15 wt% cerium, and the balance being iron and inremovable impurities, and the mass ratio of yttrium to samarium is 5-14:1. The present application can improve the magnetic properties and high-temperature resistance of the neodymium iron boron magnetic material.

Description

Technical Field

[0001] This application relates to the technical field of magnetic materials, and particularly to a preparation method of high-temperature resistant neodymium iron boron magnetic materials. Background Art

[0002] Sintered neodymium iron boron magnetic materials are the most powerful permanent magnetic materials at present. They have excellent properties such as high magnetic energy product and high cost performance, and have now been applied in fields such as aviation, aerospace, microwave communication technology, electronics, electroacoustics, and electromechanics. However, with the continuous expansion of the application scope of permanent magnetic materials, the demand for them has also increased accordingly. While meeting the equipment models of permanent magnetic materials, challenges have also been posed to the applicable temperature of permanent magnetic materials.

[0003] Although neodymium iron boron magnetic materials have high magnetic properties, their Curie temperature (about 310 °C) is relatively low, and the temperature coefficient is relatively high (in the temperature range of 20 - 100 °C, the reversible temperature coefficient of remanence is about -0.13% / °C).

[0004] When the ambient temperature rises, the magnetic properties of neodymium iron boron magnetic materials will significantly decline, greatly restricting the use range of neodymium iron boron magnetic materials, and improvement is needed. Summary of the Invention

[0005] In order to improve the magnetic properties and high-temperature resistance of neodymium iron boron magnetic materials, this application provides a preparation method of high-temperature resistant neodymium iron boron magnetic materials.

[0006] This application provides a preparation method of high-temperature resistant neodymium iron boron magnetic materials using the following technical solutions:

[0007] A preparation method of neodymium iron boron magnetic materials includes the following steps:

[0008] S1 Melting: Put niobium iron blocks, boron iron blocks, praseodymium neodymium blocks, dysprosium iron blocks, pure iron blocks, cerium blocks, iridium blocks and auxiliary metals into a melting furnace for melting according to a certain weight ratio; the obtained molten liquid is poured onto a water-cooled roller for strip casting to obtain strip cast sheets.

[0009] S2 Crushing: Put the thin strips obtained in S1 into a hydrogen breaking furnace for hydrogen breaking treatment, and after the obtained hydrogenated powder is crushed by a jet mill, magnetic powder is obtained.

[0010] S3 Orientation and Compression: Weigh a certain weight of the magnetic powder obtained in S2, put it into a molding die under a nitrogen atmosphere, press, magnetize, and demagnetize to obtain a green magnet.

[0011] S4 Sintering: The green magnet obtained in S3 is evacuated for 1 - 1.5 hours in each of the three temperature ranges of 280 - 320 °C, 690 - 710 °C, and above 880 - 920 °C, and then heated to 800 - 1000 °C in a nitrogen atmosphere for sintering for 3 - 6 hours, and cooled in the furnace to obtain a sintered magnet.

[0012] S5 Vacuum Coating: Place the raw magnet prepared in S3 into a vacuum coating machine. Then, put the samarium block and yttrium block into a crucible and place the crucible into the vacuum coating machine. Under vacuum conditions, vaporize the samarium block and yttrium block onto the surface of the raw magnet to obtain a coated magnet;

[0013] The neodymium-iron-boron magnetic material comprises the following components in fractions: 13 - 18 wt% praseodymium-neodymium, 0.5 - 1 wt% boron, 18 - 30 wt% samarium and yttrium, 3 - 8 wt% auxiliary metal, 0.08 - 0.12 wt% iridium, 8 - 10 wt% niobium, 3 - 5 wt% dysprosium, 10 - 15 wt% cerium, with the balance being iron and inremovable impurities. The mass ratio of yttrium to samarium is 5 - 14:1.

[0014] By adopting the above technical solution, samarium and yttrium are light rare earth elements with relatively low costs, and yttrium has a relatively high content in nature. Adding samarium and yttrium to the magnetic material has the advantages of low production cost and high stability.

[0015] Neodymium-iron-boron includes a main phase and a neodymium-rich phase. Samarium can lower the melting point of the neodymium-rich phase, improve the fluidity of the neodymium-rich phase, make the distribution of the neodymium-rich phase more uniform, so that the grain boundaries between the neodymium-rich phase and the main phase are more obvious, in order to improve the anisotropy of the magnetic material and thus improve the coercivity of the magnetic material.

[0016] Adding samarium and yttrium to the magnetic material, the combined action of the two can reduce the remanence temperature coefficient and coercivity temperature coefficient of the neodymium-iron-boron magnet, reduce the adverse effects of temperature rise on the remanence and coercivity of the magnetic material, and thus improve the high-temperature resistance of the magnetic material.

[0017] Although the addition of samarium can improve the high-temperature resistance of the magnetic material, the addition of samarium will also increase the ability of the magnetic material to combine with oxygen, thus destroying the magnetic properties of the magnetic material. Since metallic iridium has strong antioxidant ability, adding a small amount of iridium to the magnetic material can effectively reduce the defects caused by samarium doping, making the coercivity, remanence and magnetic energy product of the magnet all significantly improved.

[0018] Deposit samarium and iridium on the surface of neodymium-iron-boron by means of vacuum coating, so that a dense and uniformly distributed coating is formed on the surface of the neodymium-iron-boron magnetic material. And under vacuum conditions, oxygen atoms are not easily introduced into the coating, thus reducing the combination of oxygen atoms with the magnetic material, and thus ensuring the excellent magnetic properties of the magnetic material. During the vacuum coating process, the samarium and yttrium layers on the surface of the magnetic material will diffuse into the magnet along the grain boundaries. Samarium and yttrium located at the grain boundaries can undergo a displacement reaction with neodymium at the grain boundaries, so that SmFeB and YFeB compound structures are formed at the grain boundaries of the main phase, improving the anisotropy at the grain boundaries, and thus effectively improving the coercivity of neodymium-iron-boron.

[0019] The NdFeB magnetic materials prepared by the above process have higher consistency, more stable properties, and better processability. The NdFeB material products prepared by the above formula process are applicable to small-sized NdFeB magnets with a diameter between 4 and 10 mm, and the shapes of the NdFeB magnets include, but are not limited to, cylinders, cuboids, etc.

[0020] Optionally, the mass ratio of yttrium to samarium is 7-11:1.

[0021] By adopting the above technical solution, since the content of yttrium in rare earth metals is relatively high and it is relatively easy to obtain, the content of yttrium can be appropriately increased to reduce the production cost of magnetic materials. When the mass ratio of yttrium to samarium is 8-10:1, the magnetic properties of the magnetic materials are better.

[0022] Optionally, in the S5 vacuum coating, the absolute pressure during coating is 2.5-9*10^ -3 Pa.

[0023] By adopting the above technical solution, in a lower absolute pressure environment, the oxygen content can be ignored, and the oxygen content in the prepared coated magnetic materials is very small, so as to minimize the influence of oxygen on the magnetic materials. After testing, when the absolute pressure is 2.5-9*10^ -3 Pa, the coercivity, remanence, and magnetic energy product of the prepared magnetic materials are the largest.

[0024] Optionally, in the S5 vacuum coating, the thickness of the samarium and yttrium metal films in the prepared coated magnets is 3-5 μm.

[0025] By adopting the above technical solution, when the rare earth metal film is too thick, there is more rare earth metal on the surface of the magnetic material, and more rare earth metal raw materials are required in the preparation process, resulting in waste of rare earth metals. When the rare earth metal film is less, the improvement of the performance of NdFeB magnetic materials is not obvious. When the thickness of the rare earth metal film is 1-2 μm, the coercivity, remanence, and magnetic energy product of the prepared NdFeB magnetic materials are larger.

[0026] Optionally, the auxiliary metal includes a mixture of cobalt, copper, gallium, and gadolinium, and the mass ratio of gadolinium, copper, gallium, and cobalt is 4.5-4.8:0-0.3:0-1.2:1-2.

[0027] By adopting the above technical solution, the reserves of rare earth gadolinium are the highest among rare earth elements. Adding gadolinium to auxiliary metals can effectively reduce the production cost of NdFeB magnetic materials, and GdFeB formed by gadolinium and magnetic materials has a relatively high Curie temperature, which can effectively improve the high-temperature resistance performance of NdFeB magnetic materials. The addition of copper can make up for the deficiency of the reduction of magnetic properties of magnetic materials caused by gadolinium. The addition of gallium can increase the Curie temperature and coercivity of NdFeB magnetic materials, but the content range in which gallium can play a role is very small. Cobalt has a relatively high Curie temperature and a large atomic magnetic moment, which can improve the magnetic properties and high-temperature resistance performance of magnetic materials. At the same time, it can also increase the amount of gallium that can be added to magnetic materials and ensure the high-temperature resistance performance of magnetic materials. When the mass ratio of gadolinium, copper, gallium and cobalt meets the above ratio, the magnetic properties and high-temperature resistance performance of the prepared NdFeB magnetic materials are both maintained at a good level.

[0028] Optionally, the density of the green magnet prepared by S3 orientation and pressing is 3.8 - 4.0 g / cm 3 .

[0029] By adopting the above technical solution, the density of the green magnet is related to the tightness of the atomic arrangement inside the magnet. When the atomic arrangement is tighter, it is more difficult for rare earth metals to diffuse into the magnet along the grain boundaries. When the atomic arrangement is looser, the contact between rare earth metal atoms and neodymium at the grain boundaries is not tight enough, which is not conducive to the occurrence of displacement reactions.

[0030] Optionally, it further includes the following steps: S6 heat treatment: heating the coated magnet prepared in S5 to 900 - 1000 °C in a nitrogen atmosphere and holding for 2 - 3 h, and then cooling to obtain the NdFeB magnet.

[0031] By adopting the above technical solution, after another high-temperature treatment, the diffusion effect of the samarium and yttrium metal coatings on the surface of the magnetic material becomes more thorough. Samarium and yttrium metals will gather in the combined area of the main phase and the grain boundary phase, improving the anisotropy of the magnetic material, thereby increasing the coercivity of the magnet.

[0032] Optionally, the NdFeB magnet prepared in S6 is subjected to the following surface treatment: plating an aluminum coating on the surface of the NdFeB magnet, and the thickness of the aluminum coating is 200 - 500 nm.

[0033] By adopting the above technical solution, aluminum has good corrosion resistance. Plating aluminum on the surface of the NdFeB magnet can improve the bonding strength and corrosion resistance of the coating, and at the same time can increase the coercivity of the magnet.

[0034] In summary, the present application has the following beneficial effects:

[0035] 1. NdFeB includes a main phase and a neodymium-rich phase. Samarium can reduce the melting point of the neodymium-rich phase, improve the fluidity of the neodymium-rich phase, make the distribution of the neodymium-rich phase more uniform, and thus make the grain boundaries between the neodymium-rich phase and the main phase more obvious, so as to improve the anisotropy of the magnetic material and thereby increase the coercivity of the magnetic material;

[0036] 2. Adding samarium and yttrium to the magnetic material, the combined action of the two can significantly improve the high-temperature resistance of the neodymium iron boron magnet;

[0037] 3. Due to the strong antioxidant ability of iridium metal, adding a small amount of iridium to the magnetic material can effectively reduce the defects caused by samarium doping, resulting in obvious improvement in the coercivity, remanence and magnetic energy product of the magnet;

[0038] 4. Depositing samarium and iridium on the surface of neodymium iron boron by vacuum coating, so that a dense and evenly distributed coating is formed on the surface of the neodymium iron boron magnetic material. And under vacuum conditions, oxygen atoms are not easily introduced into the coating, thereby reducing the combination of oxygen atoms and the magnetic material, thus ensuring the excellent magnetic properties of the magnetic material;

[0039] 5. The reserves of rare earth gadolinium are the highest among rare earth elements. Adding gadolinium to the auxiliary metal can effectively reduce the production cost of neodymium iron boron magnetic materials, and GdFeB formed by gadolinium and the magnetic material has a relatively high Curie temperature, which can effectively improve the high-temperature resistance of neodymium iron boron magnetic materials. The addition of copper can make up for the deficiency of gadolinium in reducing the magnetic properties of the magnetic material. The addition of gallium can increase the Curie temperature and coercivity of neodymium iron boron magnetic materials, but the content range in which gallium can play a role is very small; cobalt has a relatively high Curie temperature and a large atomic magnetic moment, which can improve the magnetic properties and high-temperature resistance of the magnetic material, and at the same time can also increase the amount of gallium that can be added to the magnetic material and ensure the high-temperature resistance of the magnetic material. Specific embodiments

[0040] The following further elaborates on this application in combination with examples and comparative examples.

[0041] Examples

[0042] Example 1:

[0043] A high-temperature resistant neodymium iron boron magnetic material, including the following components in fractions: 13wt% praseodymium neodymium, 0.5wt% boron, 15wt% yttrium, 3wt% samarium, 2.5wt% gadolinium, 0.5wt% cobalt, 0.08wt% iridium, 8wt% niobium, 3wt% dysprosium, 10wt% cerium, and the balance is iron and unavoidable impurities.

[0044] The preparation method of the above-mentioned neodymium iron boron magnetic material includes the following steps:

[0045] S1 Melting: Put niobium iron blocks, boron iron blocks, praseodymium neodymium blocks, dysprosium iron blocks, pure iron blocks, cerium blocks, iridium blocks, yttrium blocks and samarium blocks into a melting furnace for melting according to a certain weight ratio; the obtained molten liquid is poured onto a water-cooled roller for strip casting to obtain strip castings;

[0046] S2 Crushing: The ribbon obtained in S1 is put into a hydrogen decrepitation furnace with an absolute pressure of 2 Pa inside. Hydrogen is introduced at room temperature, and hydrogen decrepitation treatment is carried out for 10 h. The obtained hydrogen decrepitated powder is added to a jet mill device, and after jet milling treatment under a nitrogen atmosphere, magnetic powder is obtained. The particle size of the obtained powder is about 3 μm;

[0047] S3 Orientation and Compression: Weigh a certain weight portion of the magnetic powder obtained in S2, put it into a molding die under a nitrogen atmosphere and a pulsed magnetic field of 5 T, press, magnetize, and demagnetize it to obtain a green magnet with a density of 3.8 g / cm 3 ;

[0048] S4 Sintering: First, put the green magnet obtained in S3 into a sintering furnace, evacuate it for 1 hour at three temperatures of 280 °C, 690 °C, and 880 °C respectively, and then heat it up to 800 °C under a nitrogen atmosphere and sinter for 3 hours. After the furnace cools down, a sintered magnet is obtained.

[0049] S5 Vacuum Coating: Put the sintered magnet obtained in S4 into a vacuum coating machine. Then put yttrium blocks and samarium blocks into a crucible and put them into the vacuum coating machine. Under the conditions of an absolute pressure of 2.5×10^ -3 Pa and a temperature of 500 °C, evaporate samarium and yttrium onto the surface of the sintered magnet. The evaporation time is 20 min to obtain a coated magnet. The thickness of the samarium and yttrium metal films on the surface of the magnetic material is 2 μm. The specifications of the obtained magnetic material products include but are not limited to a diameter between 4 - 10 mm, and the shapes of neodymium iron boron magnets include but are not limited to cylinders, cuboids, etc.

[0050] Example 2:

[0051] A high-temperature resistant neodymium iron boron magnetic material, comprising the following components in fractions: 15 wt% praseodymium-neodymium, 0.75 wt% boron, 21.5 wt% yttrium, 2.5 wt% samarium, 4 wt% gadolinium, 1 wt% cobalt, 0.10 wt% iridium, 9 wt% niobium, 4 wt% dysprosium, 12 wt% cerium, and the balance being iron and unavoidable impurities.

[0052] The preparation method of the above neodymium iron boron magnetic material comprises the following steps:

[0053] S1 Melting: Put niobium iron blocks, boron iron blocks, praseodymium-neodymium blocks, dysprosium iron blocks, pure iron blocks, cerium blocks, iridium blocks, yttrium blocks, and samarium block powders into a melting furnace according to a certain weight ratio for melting; the obtained molten liquid is poured onto a water-cooled roller for strip casting to obtain strip casting sheets;

[0054] S2 Crushing: The ribbon obtained in S1 is put into a hydrogen decrepitation furnace with a vacuum degree of 2 Pa inside. Hydrogen is introduced at room temperature, and hydrogen decrepitation treatment is carried out for 10 h. The obtained hydrogen decrepitated powder is added to a jet mill device, and after jet milling treatment under a nitrogen atmosphere, magnetic powder is obtained. The particle size of the obtained powder is about 3 μm;

[0055] S3 Orientation and Compression: Weigh a certain weight portion of the magnetic powder obtained in S2, place it in a forming mold under a nitrogen atmosphere and a pulsed magnetic field of 5T, press, magnetize, and demagnetize it to obtain a green magnet with a density of 3.9 g / cm 3 ;

[0056] S4 Sintering: First, place the green magnet obtained in S3 in a sintering furnace, evacuate it for 1.2 hours at three temperatures of 300 °C, 700 °C, and 900 °C respectively, and then heat it to 900 °C in a nitrogen atmosphere and sinter for 4.5 hours. After the furnace cools down, a sintered magnet is obtained.

[0057] S5 Vacuum Coating: Place the sintered magnet obtained in S4 in a vacuum coating machine. Then, put yttrium blocks and samarium blocks into a crucible and place it in the vacuum coating machine. Under the conditions of an absolute pressure of 6×10^ -3 Pa and a temperature of 550 °C, evaporate samarium and yttrium onto the surface of the sintered magnet for 40 minutes to obtain a coated magnet. The thickness of the rare earth metal film on the surface of the magnetic material is 4 μm. The specifications of the obtained magnetic material products include but are not limited to a diameter between 4 - 10 mm, and the shapes of neodymium iron boron magnets include but are not limited to cylinders, cuboids, etc.

[0058] Example 3:

[0059] A high-temperature resistant neodymium iron boron magnetic material, comprising the following components in fractions: 18 wt% praseodymium-neodymium, 1 wt% boron, 28 wt% samarium, 6.5 wt% gadolinium, 1.5 wt% cobalt, 0.12 wt% iridium, 10 wt% niobium, 5 wt% dysprosium, 15 wt% cerium, and the balance being iron and inremovable impurities.

[0060] The preparation method of the above neodymium iron boron magnetic material comprises the following steps:

[0061] S1 Melting: Charge niobium iron blocks, boron iron blocks, praseodymium-neodymium blocks, dysprosium iron blocks, pure iron blocks, cerium blocks, iridium blocks, yttrium blocks, and samarium blocks into a melting furnace according to a certain weight ratio for melting; pour the obtained molten liquid onto a water-cooled roller for strip casting to obtain strip castings;

[0062] S2 Crushing: Put the strip casting obtained in S1 into a hydrogen breaking furnace. The absolute pressure in the hydrogen breaking furnace is 2 Pa. Introduce hydrogen at room temperature and conduct hydrogen breaking treatment for 10 h. Add the obtained hydrogenated powder to a jet mill device and conduct jet milling treatment in a nitrogen atmosphere to obtain magnetic powder. The size of the obtained powder is about 3 μm;

[0063] S3 Orientation and Compression: Weigh a certain weight portion of the magnetic powder obtained in S2, place it in a forming mold under a nitrogen atmosphere and a pulsed magnetic field of 5T, press, magnetize, and demagnetize it to obtain a green magnet with a density of 4.0 g / cm 3 ;

[0064] S4 Sintering: First, put the green magnets obtained in S3 into a sintering furnace, evacuate the air for 1.5 hours at three temperatures of 320 °C, 710 °C, and 920 °C respectively, then heat up to 1000 °C in a nitrogen atmosphere and sinter for 6 hours. After the furnace cools down, sintered magnets are obtained.

[0065] S5 Vacuum Coating: Put the sintered magnets obtained in S3 into a vacuum coating machine. Then put yttrium blocks and samarium blocks into a crucible and place them in the vacuum coating machine. Under the conditions of an absolute pressure of 2.5 * 10^ -3 Pa and a temperature of 500 °C, evaporate samarium and yttrium onto the surface of the sintered magnets. The evaporation time is 60 min to obtain coated magnets. The thickness of the samarium and yttrium metal films on the surface of the magnetic materials is 6 μm. The specifications of the obtained magnetic material products include, but are not limited to, a diameter between 4 - 10 mm, and the shapes of neodymium iron boron magnets include, but are not limited to, cylinders, cuboids, etc.

[0066] Example 4:

[0067] Based on the method of Example 2, the raw material components were adjusted. The neodymium iron boron magnetic material includes the following components by weight: 15wt% praseodymium-neodymium, 0.75wt% boron, 21wt% yttrium, 3wt% samarium, 4wt% gadolinium, 1wt% cobalt, 0.10wt% iridium, 9wt% niobium, 4wt% dysprosium, 12wt% cerium, and the balance is iron and inremovable impurities.

[0068] Example 5:

[0069] Based on the method of Example 2, the raw material components were adjusted. The neodymium iron boron magnetic material includes the following components by weight: 15wt% praseodymium-neodymium, 0.75wt% boron, 22wt% yttrium, 2wt% samarium, 4wt% gadolinium, 1wt% cobalt, 0.10wt% iridium, 9wt% niobium, 4wt% dysprosium, 12wt% cerium, and the balance is iron and inremovable impurities.

[0070] Example 6:

[0071] The difference from Example 1 is that in S5 vacuum coating, the evaporation time is 30 min to obtain coated magnets, and the thickness of the samarium and yttrium metal films is 3 μm.

[0072] Example 7:

[0073] The difference from Example 1 is that in S5 vacuum coating, the evaporation time is 50 min to obtain coated magnets, and the thickness of the samarium and yttrium metal films is 5 μm.

[0074] Example 8:

[0075] Based on the method of Example 2, the raw material components were adjusted. The neodymium-iron-boron magnetic material comprises the following components in fractions: 15 wt% praseodymium-neodymium, 0.75 wt% boron, 21.5 wt% yttrium, 2.5 wt% samarium, 3.4 wt% gadolinium, 0.11 wt% copper, 0.43 wt% gallium, and 1.1 wt% cobalt, 9 wt% niobium, 4 wt% dysprosium, 12 wt% cerium, and the balance is iron and inremovable impurities.

[0076] Example 9:

[0077] The difference from Example 8 is that the preparation method of the neodymium-iron-boron further comprises the following step: S6 Heat treatment: The coated magnet obtained in S5 is heated to 950 °C in a nitrogen atmosphere and held for 2.5 h, and the neodymium-iron-boron magnet is obtained after cooling.

[0078] Example 10:

[0079] The difference from Example 9 is that the preparation method of the neodymium-iron-boron further comprises the following step: The neodymium-iron-boron magnet obtained in S6 is subjected to the following surface treatment: A layer of aluminum coating with a thickness of 200-500 nm is deposited on the surface of the neodymium-iron-boron magnet by atomic layer deposition.

[0080] Comparative example

[0081] Comparative example 1:

[0082] Based on the method of Example 1, samarium, yttrium and iridium elements are not added to the neodymium-iron-boron magnetic material.

[0083] Comparative example 2:

[0084] Based on the method of Example 1, yttrium and iridium elements are not added to the neodymium-iron-boron magnetic material.

[0085] Comparative example 3:

[0086] Based on the method of Example 1, iridium element is not added to the neodymium-iron-boron magnetic material.

[0087] Comparative example 4:

[0088] The difference from Example 1 is that in the preparation method of the high-temperature resistant neodymium-iron-boron magnetic material, the S4 vacuum coating step is not carried out, and samarium and yttrium are put into the melting furnace together with other raw materials in the S1 melting step for melting.

[0089] Performance test

[0090] The neodymium-iron-boron magnets prepared by Examples 1-10 and Comparative examples 1-4: The specifications are 4-10 mm, and the shapes are cylinders or cuboids, which are used as test samples. The magnetic properties and Curie temperature of the magnets are measured according to the detection standard of GB / T 13560 2017, and the detection results are as follows:

[0091] Table 1 Record Table of Performance Test Results of Magnetic Materials

[0092]

[0093]

[0094] It can be seen from Table 1 that:

[0095] 1. By comparing the test data of Comparative Example 1 and Comparative Example 2, it can be obtained that adding samarium element to the raw material system of the magnetic material significantly improves the coercivity of the magnetic material.

[0096] 2. By comparing the test data of Comparative Example 2 and Comparative Example 3, it can be obtained that compared with only adding samarium element to the raw material system, the magnetic material prepared by adding samarium and yttrium simultaneously to the raw material system has good high-temperature resistance performance.

[0097] 3. By comparing the test data of Examples 1-3 and Comparative Example 3, it can be obtained that compared with only adding samarium and yttrium elements to the raw material system, when adding samarium, yttrium and iridium elements simultaneously to the raw material system, the coercivity, remanence and magnetic energy product of the prepared magnetic material are all significantly improved.

[0098] 4. By comparing the test data of Examples 1-3 and Comparative Example 4, it can be obtained that compared with the process of directly mixing samarium and yttrium metals with the raw material system for smelting, the coercivity, remanence and magnetic energy product of the magnetic material prepared by the process of evaporating samarium and yttrium on the surface of the green magnet under vacuum conditions are all significantly improved.

[0099] 5. By comparing the test data of Examples 1-5, it can be obtained that as the total amount of samarium and yttrium added increases, the increase amounts of the coercivity, remanence and maximum magnetic energy product of the prepared magnetic material also increase. However, when the addition amounts of samarium and yttrium reach a certain value, the coercivity, remanence and maximum magnetic energy product of the magnetic material basically remain unchanged. When the mass ratio of samarium to yttrium is 1:7-11, the coercivity, remanence and maximum magnetic energy product of the prepared magnetic material are all relatively high.

[0100] 6. By comparing the test data of Examples 4, 5 and Example 2, it can be obtained that when the mass ratio of samarium to iridium is about 9:1, the coercivity, remanence and maximum magnetic energy product of the prepared magnetic material are all relatively high.

[0101] 7. By comparing the test data of Examples 1-3 and Examples 6-7, it can be obtained that when the thickness of the rare earth metal film in the magnetic material is 3 μm, compared with the case where the thickness of the rare earth metal film in the magnetic material is 1 μm, the coercivity, remanence, and maximum magnetic energy product of the prepared magnetic material are all significantly improved. When the thickness of the rare earth metal film is 5 μm, the coercivity, remanence, and maximum magnetic energy product of the magnetic material also increase, indicating that as the thickness of the rare earth metal film increases, the coercivity, remanence, and maximum magnetic energy product of the magnetic material increase accordingly. When the thickness of the rare earth metal film increases from 5 μm to 6 μm, the coercivity, remanence, and maximum magnetic energy product of the magnetic material basically do not change, indicating that when the thickness of the rare earth metal film is in the range of 3-5 μm, the improvement effect of samarium and iridium on the performance of the magnetic material is the best.

[0102] 8. By comparing the test data of Example 7 and Example 8, it can be obtained that after adding gallium and copper elements to the magnetic material, the coercivity, remanence, maximum magnetic energy product, and Curie temperature of the prepared magnetic material are all significantly improved.

[0103] 9. By comparing the test data of Example 9 and Example 8, it can be obtained that after the magnetic material is heat-treated, its coercivity, remanence, maximum magnetic energy product, and Curie temperature are all significantly improved.

[0104] 10. By comparing the test data of Example 10 and Example 9, it can be obtained that after the surface of the magnetic material is aluminized by atomic deposition, the Curie temperature of the magnetic material is significantly improved.

[0105] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A preparation method of a high-temperature resistant NdFeB magnetic material, characterized in that: It includes the following steps: S1 Melting: Put niobium iron blocks, boron iron blocks, praseodymium-neodymium blocks, dysprosium iron blocks, pure iron blocks, cerium blocks, iridium blocks and auxiliary metals into a melting furnace for melting according to a certain weight ratio; the obtained molten liquid is poured onto a water-cooled roller for strip casting to obtain strip-cast sheets. S2 Crushing: Put the thin strips obtained in S1 into a hydrogen breaking furnace for hydrogen breaking treatment, and after the obtained hydrogenated powder is crushed by a jet mill, magnetic powder is obtained. S3 Orientation and Compression Molding: Weigh a certain weight portion of the magnetic powder obtained in S2, put it into a molding die under a nitrogen atmosphere, press, magnetize and demagnetize it to obtain a green magnet. S4 Sintering: The green magnet obtained in S3 is evacuated for 1 - 1.5 hours in each of the three temperature ranges of 280 - 320 °C, 690 - 710 °C and above 880 - 920 °C, then heated to 800 - 1000 °C in a nitrogen atmosphere and sintered for 3 - 6 hours, and cooled in the furnace to obtain a sintered magnet. S5 Vacuum Coating: Put the sintered magnet obtained in S4 into a vacuum coating machine, and then put samarium blocks and yttrium blocks into a crucible and put it into the vacuum coating machine. Under vacuum conditions, the samarium blocks and yttrium blocks are evaporated and deposited on the surface of the sintered magnet to obtain a coated magnet. The neodymium iron boron magnetic material includes the following components in fractions: 13 - 18 wt% praseodymium-neodymium, 0.5 - 1 wt% boron, 18 - 30 wt% yttrium and samarium, 3 - 8 wt% auxiliary metals, 0.08 - 0.12 wt% iridium, 8 - 10 wt% niobium, 3 - 5 wt% dysprosium, 10 - 15 wt% cerium, and the balance is iron and non-removable impurities. The mass ratio of yttrium to samarium is 5 - 14:

1. The auxiliary metal is a mixture of gadolinium, copper, gallium and cobalt, and the mass ratio of gadolinium, copper, gallium and cobalt is 4.5 - 4.8:0 - 0.3:0 - 1.2:1 - 2.

2. The preparation method of a high-temperature resistant NdFeB magnetic material according to claim 1, characterized in that: The mass ratio of yttrium to samarium is 7 - 11:

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3. The preparation method of a high-temperature resistant NdFeB magnetic material according to claim 1, characterized in that: The absolute pressure during coating in S5 vacuum coating is 2.5*10 -3 Pa - 9*10 -3 Pa.

4. The preparation method of a high-temperature resistant NdFeB magnetic material according to claim 1, characterized in that: In S5 vacuum coating, the thickness of the samarium and yttrium metal films in the obtained coated magnet is 3 - 5 μm.

5. The preparation method of a high-temperature resistant NdFeB magnetic material according to claim 1, characterized in that: The density of the green magnet prepared by S3 orientation and pressing is 3.8 - 4.0 g / cm 3 .

6. The preparation method of a high-temperature resistant NdFeB magnetic material according to claim 1, characterized in that: It further includes the following step: S6 Heat Treatment: Heat the coated magnet obtained in S5 to 900 - 1000 °C in a nitrogen atmosphere and hold for 2 - 3 h, and then cool it to obtain a neodymium iron boron magnetic material.

7. The preparation method of a high-temperature resistant NdFeB magnetic material according to claim 1, characterized in that: The neodymium iron boron magnetic material obtained in S6 is subjected to the following surface treatment: Coat a layer of aluminum coating on the surface of the neodymium iron boron magnetic material, and the thickness of the aluminum coating is 200 - 500 nm.

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