CN110875110A - VN particle-containing neodymium iron boron magnetic material and preparation method thereof - Google Patents
VN particle-containing neodymium iron boron magnetic material and preparation method thereof Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/0266—Moulding; Pressing
Abstract
The invention relates to a neodymium iron boron magnetic material and a preparation method thereof, and belongs to the technical field of neodymium iron boron magnetic materials. The preparation method of the VN particle-containing neodymium iron boron magnetic material comprises the following steps of a, smelting neodymium iron boron alloy, wherein 0.15-0.30 wt% of vanadium is added in the smelting process, and 0.10-0.20 wt% of nitrogen is introduced by adopting a high-pressure nitrogen smelting process. The neodymium iron boron magnetic material containing VN particles prepared by the method has small crystal grains, high magnetism, better temperature performance and smaller high-temperature use magnetic loss.
Description
Technical Field
The invention relates to a neodymium iron boron magnetic material and a preparation method thereof, and belongs to the technical field of neodymium iron boron magnetic materials.
Background
The Nd-Fe-B magnetic material is one of magnetic materials and has a chemical formula of Nd2Fe14B is the magnet which is found to have the best commercialization performance at present, has extremely high magnetic performance, and the maximum energy product (BH) max of the magnet is more than 10 times higher than that of ferrite. The Nd-Fe-B magnet has the advantages of high cost performance, small size, light weight, good mechanical property and strong magnetism, etc., is widely applied to modern industry and electronic technology, and is known as the King magnet in the magnetics world. Therefore, the preparation method of the neodymium iron boron magnet is always the focus of continuous attention in the industry.
With the deterioration of the environment and the shortage of resources, especially the introduction of PM2.5 in recent years, the attention on the environment and resources has been greatly increased, and green manufacturing and energy saving have become two major topics for the development of the current era. Just as the application requirements of industrial robots in national defense military industry, chemical industry, light industry and the like, service robots in home service, education and entertainment and the like, and the vigorous advocation and rapid development of new energy automobiles are mentioned in the text of '2025 made by China', the support of permanent magnet materials cannot be avoided. Especially, the neodymium iron boron magnetic material called permanent magnet king has been widely applied to the fields of electronics, electric power, machinery, medical appliances and the like due to its excellent magnetic performance and good cost performance.
At present, the industry commonly adopts a sintering method to manufacture the neodymium iron boron permanent magnet material, and the manufacturing process mainly comprises the following procedures:
smelting, milling, pressing, sintering and tempering. In recent years, demands for miniaturization, weight reduction, energy saving, environmental protection, and the like of computers, communication equipment, and motors for automobiles have been increasing. In order to improve the performance of the magnet, some elements need to be added, at present, the elements are mostly directly added into the neodymium iron boron alloy by adopting the traditional powder metallurgy method, the alloy elements partially enter the main phase, and the saturation magnetization (M) of the main phase is reduced due to most elementss) Thereby reducing the remanence of the magnet; the other part enters an intergranular region to change the structure and the grain boundary structure, so that the coercive force is improved. The added alloy elements mainly comprise heavy rare earth elements such as Dy and Tb, the content of the heavy rare earth element Dy is more and more, the Dy is a scarce heavy rare earth resource, the world reserves are rare, the Nd-Fe-B magnet can only be produced in ion ores in south China at present, the manufacturing cost is increased, and most importantly, when the heavy rare earth elements, particularly various heavy rare earth elements are added at the same time, the magnetic performance of the prepared Nd-Fe-B magnet cannot be improved to the maximum extent. The uniform and fine main phase particles of the magnet are beneficial to improving the magnetic performance, and the alloy sheet of the magnetic material with the average grain diameter of 3 mu m can be prepared by the alloy preparation process of the rapid-hardening casting belt, but the magnetic material is easy to generate abnormal grain growth in the sintering process, so the magnetic performance of the magnetic material cannot be improved to the maximum extent.
Chinese patent application No. 201410763226.7 discloses a heat-resistant sintered nd-fe-b permanent magnet material and a preparation method thereof, which is nd-fe-b powder: nd18.6-23.1%, B0.73-0.81%, Cu0.44-0.53%, Co0.95-1.03%, Ga0.41-0.46%, Nb0.67-0.73%, Dy2.6-3.1%, Al0.23-0.29%, and the balance of Fe; adding nano iron powder, nano strontium titanate and nano vanadium nitride, mixing uniformly and sintering to obtain the product. The invention is a heat-resistant sintered Nd-Fe-B permanent magnetic material; an optimized component formula is adopted, appropriate nano elements are added, and a neodymium iron boron magnet with high performance and high thermal stability is manufactured through a special mixed manufacturing process; the neodymium iron boron magnet not only has small size of a grain boundary angle pair, but also has more regular shape, and crystal grains are homogenized, refined and regulated, so that the magnet has higher corrosion resistance and heat resistance. However, its magnetic properties are nevertheless low.
Disclosure of Invention
The first technical problem to be solved by the invention is to provide a preparation method of a neodymium iron boron magnetic material containing VN particles, and the neodymium iron boron magnetic material containing VN particles prepared by the method is high in magnetism.
In order to solve the first technical problem, the preparation method of the Nd-Fe-B magnetic material containing VN particles comprises the steps of a, smelting the Nd-Fe-B alloy, wherein 0.15-0.30 wt% of vanadium is added in the smelting process, and 0.10-0.20 wt% of nitrogen is introduced by adopting a high-pressure nitrogen smelting process.
Preferably, the nitrogen pressure of the high-pressure nitrogen smelting process is 15-20 MPa, and refining is carried out for 60-120 min at 1400-1500 ℃.
More preferably, the smelting method of the neodymium iron boron alloy comprises the following steps: under the condition that the vacuum degree is 0.05-0.5 Pa, pure iron, ferroboron, cobalt, copper, aluminum and vanadium in the neodymium iron boron raw materials are smelted for 180-240 min at 1200-1400 ℃, then other neodymium iron boron raw materials are added and nitrogen is filled, and a high-pressure nitrogen smelting process is adopted to obtain a molten alloy containing 0.1-0.2 wt% of N.
Preferably, the neodymium iron boron raw material comprises: 28 percent to 33 percent of Pr-Nd, 0 percent to 3 percent of Dy, 0 percent to 3 percent of Tb, 0 percent to 5 percent of Nb, 0 percent to 1 percent of Al, 0.5 percent to 2.0 percent of B, 0 percent to 1 percent of Cu, 0 percent to 3 percent of Co, 0 percent to 1 percent of Ga, 0 percent to 2 percent of Ho, 0 percent to 2 percent of Zr and the balance of Fe.
Preferably, the method further comprises the steps of: b. preparing an alloy sheet; c. crushing the alloy sheet into powder; d. isostatic pressing; e. sintering; f. aging treatment;
and c, the process for crushing the alloy sheet into powder comprises the following steps: absorbing hydrogen at 100-300 ℃ by the alloy sheet, and then dehydrogenating at 550-650 ℃ for 7-10 h to form hydrogen explosion powder; then, carrying out airflow milling on the hydrogen explosion powder to obtain powder with the average particle size of 1.5-2.7 microns; wherein the gas flow is formed by adding 0.5-1.0% by volume of hydrogen into nitrogen.
Preferably, the d. isostatic pressing process comprises: and performing magnetic field orientation molding on the powder in a reducing atmosphere, performing isostatic pressing under the pressure of 150-300 MPa, and then filling the powder into a vacuum sintering material container under the reducing atmosphere or vacuum protection.
Preferably, the e. sintering process comprises: raising the temperature of the vacuum sintering material container in the step d to 750-850 ℃ for primary aging treatment for 120-180 min; then raising the temperature to 1000-1050 ℃ for presintering for 60-120 min; then, the temperature is increased to 1050-1100 ℃ for sintering for 30-60 min.
Preferably, the f. aging treatment process comprises: high-temperature aging and low-temperature aging, wherein the temperature of the high-temperature aging is 750-900 ℃, the temperature of the low-temperature aging is 450-550 ℃, and the inert gas is adopted for cooling to be below 80 ℃ after the low-temperature aging.
Preferably, the b. alloy sheet preparation process comprises the following steps: and c, preparing the alloy prepared in the step a into an alloy sheet with the average grain diameter of 1.5-2.7 microns.
The second technical problem to be solved by the invention is to provide a neodymium iron boron magnetic material containing VN particles, wherein the content of V element in the material is 0.15-0.30 wt%, the content of N element is 0.10-0.20 wt%, Pr-Nd is more than or equal to 28 wt% and less than or equal to 33 wt%, Dy is more than or equal to 0 and less than or equal to 3 wt%, Tb is more than or equal to 0 and less than or equal to 3 wt%, Nb is more than or equal to 0 and less than or equal to 5 wt%, Al is more than or equal to 0 and less than or equal to 1 wt%, B is more than or equal to 0.5 wt% and less than or equal to 2.0 wt% and less than or equal to 1 wt%, Cu is more than or equal to 0 and less than or equal to 3; preferably, the average diameter of main phase particles of the VN-particle-containing neodymium iron boron magnetic material is less than 3 μm, the average grain diameter of VN particles is 5-10 nm, the VN particles are uniformly distributed in the main phase grains and in grain boundaries, and the average diameter of precipitated particles in the grains is smaller than that of precipitated particles in the grain boundaries; preferably, the material is prepared by the method.
Has the advantages that:
(1) the invention utilizes a high-pressure nitrogen adding process, controls the content of nitrogen in the alloy by adjusting the pressure of nitrogen, and can uniformly distribute the added nitrogen atoms in the alloy without introducing other impurities.
(2) The reducing atmosphere is adopted in the powder preparation process of the jet mill, and V with stronger bonding capacity with N is added into the alloy, so that the reaction of nitrogen and rare earth elements in the magnetic material to generate rare earth nitride is effectively prevented, and the effect of rare earth is lost.
(3) The whole isostatic pressing process is carried out in a reducing protective atmosphere, so that powder oxidation is reduced.
(4) Researches show that NdFeB with uniform and fine main phase particles has excellent magnetic performance, before the magnetic material is sintered, primary aging treatment is carried out to separate fine and uniformly distributed VN particles in main phase crystal and at crystal boundary, the average diameter of the VN particles is 5-10 nm, and in the subsequent pre-sintering and sintering processes, abnormal grain growth cannot occur in the sintering process because the VN particles block the movement of the main phase crystal boundary; in the high-temperature and low-temperature aging process after sintering, fine and uniformly distributed VN particles continue to be precipitated in main phase grain boundaries and at grain boundaries, and abnormal grain growth does not occur in the high-temperature and low-temperature aging process because the VN particles hinder the movement of the main phase grain boundaries, so that the neodymium iron boron magnetic material containing the VN particles with the main phase average particle diameter of less than 3 mu m is prepared, and the magnetic material has good temperature performance and small high-temperature use magnetic loss.
(5) The maximum working temperature Tw (DEG C) of the Nd-Fe-B magnetic material containing VN particles prepared by the method can reach more than 82 ℃, and the remanence Br (KG)14.4 or more, coercive force Hcb (KOe)9.9 or more, intrinsic coercive force Hcj (KOe) > 11, maximum energy product (BH) max (KJ/m)3)408 or more.
Detailed Description
The neodymium iron boron magnetic material containing VN particles has the average grain diameter of a main phase smaller than 3 mu m, the average grain diameter of the VN particles is 5-10 nm, and the VN particles are uniformly distributed in the main phase grains and in grain boundaries, wherein the average diameter of precipitated particles in the grains is smaller than that of the precipitated particles in the grain boundaries. The content of V element in the neodymium iron boron magnetic material is 0.15-0.30 wt%, the content of N element is 0.10-0.20 wt%, and the content of the other elements is as follows: 28 percent to 33 percent of Pr-Nd, 0 percent to 3 percent of Dy, 0 percent to 3 percent of Tb, 0 percent to 5 percent of Nb, 0 percent to 1 percent of Al, 0.5 percent to 2.0 percent of B, 0 percent to 1 percent of Cu, 0 percent to 3 percent of Co, 0 percent to 1 percent of Ga, 0 percent to 2 percent of Ho, 0 percent to 2 percent of Zr and the balance of Fe.
The preparation method of the VN particle-containing neodymium iron boron magnetic material mainly comprises alloy smelting, crushing and powder making, isostatic pressing, sintering and aging treatment.
Step 1, smelting neodymium iron boron alloy
Smelting pure iron, ferroboron, cobalt, copper, aluminum and vanadium in the neodymium iron boron raw materials for 180-240 min at 1200-1400 ℃ under the condition that the vacuum degree is 0.05-0.5 Pa, then adding other neodymium iron boron raw materials, filling nitrogen, pressurizing to enable the nitrogen pressure to be 15-20 MPa, refining for 60-120 min at 1400-1500 ℃, and adjusting the nitrogen pressure to obtain the molten alloy containing 0.1-0.2 wt% of N.
Step 2. preparation of alloy sheet
The preparation method comprises the steps of preparing an alloy sheet by adopting a double-sided cooling rapid-hardening casting strip process, casting an alloy liquid onto a first rotating roller with water cooling at the rotating speed of 2-6 m/s to form the alloy sheet, rotating along with the first rotating roller, leaving the rotating roller, falling onto a second rotating roller with water cooling at the rotating speed of 2-6 m/s, leaving the rotating roller, falling along with the rotation to form the alloy sheet with the thickness of 0.1-0.4 mm and the temperature of lower than 650 ℃, entering a crushing device, crushing into the alloy sheet with the length of less than 15mm, entering a guide cylinder with water cooling, and cooling to below 300 ℃ to obtain the alloy sheet with the average grain diameter of 1.5-2.7 mu m.
Step 3, crushing and pulverizing
And (3) feeding the alloy sheet into a vacuum hydrogen crushing furnace, absorbing hydrogen at 100-300 ℃, and then dehydrogenating at 550-650 ℃ for 7-10 h to finally form hydrogen explosion powder. And feeding the hydrogen explosion powder into a nitrogen gas jet mill for jet milling to prepare powder, wherein in order to prevent oxidation in the powder preparation process, 0.5-1.0% by volume of hydrogen is introduced into nitrogen gas to ensure that the powder is prepared in a reducing atmosphere, and the average particle size of the powder is about 1.5-2.7 microns.
Step 4, isostatic compaction
And performing magnetic field orientation molding and packaging on the powder in a reducing atmosphere, performing isostatic pressing under the pressure of 150-300 MPa, conveying the magnetic block into a protective feeding box with the package after isostatic pressing, removing the package, and filling the magnetic block into a vacuum sintering material box.
Step 5, sintering
The vacuum sintering material box is sent into a vacuum sintering furnace, heating is carried out after the vacuum degree is higher than 5Pa, the temperature is raised to 750-850 ℃ for carrying out primary aging treatment, and meanwhile, the process of dehydrogenation, decarburization and deoxidation is carried out, and the time is 120-180 min; then, raising the temperature to 1000-1050 ℃ for pre-sintering for 60-120 min; and then, raising the temperature to 1050-1100 ℃ for sintering for 30-60 min.
Step 6, aging treatment
And respectively carrying out high-temperature aging and low-temperature aging, wherein the high-temperature aging temperature is 750-900 ℃, the low-temperature aging temperature is 450-550 ℃, after the heat preservation is finished, the inert gas is adopted to cool the temperature to be below 80 ℃, and the average diameter of the main phase of the prepared neodymium iron boron magnetic material containing VN particles is less than 3 mu m.
The following examples are provided to further illustrate the embodiments of the present invention and are not intended to limit the scope of the present invention.
Example 1
According to the content of the V element of 0.15wt percent and the content of the other elements: Pr-Nd 31.0 wt%, Dy 3.0 wt%, Tb3.0 wt%, Nb 5.0 wt%, Al1.0 wt%, B2.0 wt%, Cu 1.0 wt%, Co 3.0 wt%, Ga 1.0 wt%, Ho2.0 wt%, Zr 2.0 wt%, and the balance Fe.
Step 1, smelting neodymium iron boron alloy
Smelting pure iron, ferroboron, cobalt, copper, aluminum and vanadium in the neodymium iron boron raw material at 1350 ℃ for 180min under the condition that the vacuum degree is 0.1Pa, then adding other neodymium iron boron raw materials and charging nitrogen, pressurizing to enable the nitrogen pressure to be 18MPa, and refining at 1450 ℃ for 90min to obtain the molten alloy with the nitrogen content of 0.15wt percent.
Step 2. preparation of alloy sheet
The preparation method comprises the steps of preparing an alloy sheet by adopting a double-sided cooling rapid-hardening casting strip process, casting an alloy liquid onto a first rotating roller with water cooling at the rotating speed of 5m/s to form the alloy sheet, rotating along with the first rotating roller, enabling the alloy liquid to leave the rotating roller to fall onto a second rotating roller with water cooling at the rotating speed of 5m/s, enabling the alloy liquid to leave the rotating roller to fall along with the rotation to form the alloy sheet with the thickness of 0.3-0.4 mm and the temperature of lower than 650 ℃, enabling the alloy sheet to enter a crushing device, crushing the alloy sheet into alloy sheets with the length of less than 15mm, enabling the alloy sheets to enter a guide cylinder with water cooling to be cooled to be below 300 ℃, and obtaining the alloy sheet with the average grain diameter of 2.0.
Step 3, crushing and pulverizing
And (3) conveying the alloy sheet into a vacuum hydrogen crushing furnace, absorbing hydrogen at 150 ℃, and then dehydrogenating at 600 ℃ for 8h to finally form hydrogen explosion powder. And feeding the hydrogen explosion powder into a nitrogen gas jet mill for jet milling to prepare powder, wherein in order to prevent oxidation in the powder preparation process, 0.8% of hydrogen is introduced into the nitrogen gas to ensure that the powder is prepared in a reducing atmosphere, and the average particle size of the powder is about 2.0-2.7 microns.
Step 4, isostatic compaction
And performing magnetic field orientation molding and packaging on the powder in a reducing atmosphere, performing isostatic pressing under the pressure of 200MPa, conveying the magnetic block into a protective feeding box with the package after isostatic pressing, removing the package, and filling the magnetic block into a vacuum sintering material box.
Step 5, sintering
The vacuum sintering material box is sent into a vacuum sintering furnace, heating is started after the vacuum degree is higher than 5Pa, the temperature is raised to 800 ℃, and one-time aging treatment is carried out for 150min, and meanwhile, the processes of dehydrogenation, decarburization and deoxidation are also carried out; then raising the temperature to 1050 ℃ for 90min for presintering; the temperature was then raised to 1100 ℃ for 50min sintering.
Step 6, aging treatment
And respectively carrying out 850 ℃/120min high-temperature aging and 500 ℃/60min low-temperature aging, cooling to below 80 ℃ by adopting inert gas after heat preservation is finished, wherein the average diameter of the main phase of the prepared neodymium iron boron magnetic material containing VN particles is 2.2-2.9 mu m, and the average diameter of the VN particles is 5-10 nm. The magnetic performance test of the obtained neodymium iron boron magnetic material is shown in table 1:
TABLE 1
Example 2
According to the content of the V element of 0.25wt percent and the content of the other elements: Pr-Nd 31.0 wt%, Dy 3.0 wt%, Tb3.0 wt%, Nb 5.0 wt%, Al1.0 wt%, B2.0 wt%, Cu 1.0 wt%, Co 3.0 wt%, Ga 1.0 wt%, Ho2.0 wt%, Zr 2.0 wt%, and the balance Fe.
Step 1, smelting neodymium iron boron alloy
Smelting pure iron, ferroboron, cobalt, copper, aluminum and vanadium in the neodymium iron boron raw material at 1300 ℃ for 220min under the condition that the vacuum degree is 0.1Pa, then adding other neodymium iron boron raw materials, filling nitrogen, pressurizing to enable the nitrogen pressure to be 18MPa, and refining at 1400 ℃ for 120min to obtain the molten alloy with the nitrogen content of 0.15 wt%.
Step 2. preparation of alloy sheet
The preparation method comprises the steps of preparing an alloy sheet by adopting a double-sided cooling rapid-hardening casting strip process, casting an alloy liquid onto a first rotating roller with water cooling at the rotating speed of 5.5m/s to form the alloy sheet, rotating along with the first rotating roller, enabling the alloy liquid to leave the rotating roller to fall onto a second rotating roller with water cooling at the rotating speed of 5.5m/s, enabling the alloy liquid to leave the rotating roller to fall along with the rotation to form the alloy sheet with the thickness of 0.3-0.35 mm and the temperature of lower than 650 ℃, enabling the alloy sheet to enter a crushing device, crushing the alloy sheet into the alloy sheet with the length of less than 15mm, enabling the alloy sheet to enter a guide cylinder with water cooling to be cooled to be below 300 ℃ and obtaining the alloy sheet with the average grain diameter of 2..
Step 3, crushing and pulverizing
And (3) conveying the alloy sheet into a vacuum hydrogen crushing furnace, absorbing hydrogen at 200 ℃, and then dehydrogenating at 600 ℃ for 9 hours to finally form hydrogen explosion powder. And feeding the hydrogen explosion powder into a nitrogen gas jet mill for jet milling to prepare powder, wherein 1.0% of hydrogen is introduced into the nitrogen gas to ensure that the powder is prepared under a reducing atmosphere in order to prevent oxidation in the powder preparation process, and the average particle size of the powder is about 2.0-2.5 microns.
Step 4, isostatic compaction
And performing magnetic field orientation molding and packaging on the powder in a reducing atmosphere, performing isostatic pressing under the pressure of 250MPa, conveying the magnetic block into a protective feeding box with the package after isostatic pressing, removing the package, and filling the magnetic block into a vacuum sintering material box.
Step 5, sintering
The vacuum sintering material box is sent into a vacuum sintering furnace, heating is started after the vacuum degree is higher than 5Pa, the temperature is raised to 830 ℃, one-time 120-min aging treatment is carried out, and meanwhile, the processes of dehydrogenation, decarburization and deoxidation are also carried out; then raising the temperature to 1030 ℃ for 120min for presintering; then the temperature is raised to 1080 ℃ for 60min for sintering.
Step 6, aging treatment
Performing 870 ℃/120min high-temperature aging and 550 ℃/60min low-temperature aging respectively, cooling to below 80 ℃ by using inert gas after heat preservation is finished, wherein the average diameter of the main phase of the prepared VN-particle-containing neodymium iron boron magnetic material is 2.1-2.8 mu m, and the average diameter of VN particles is 5-10 nm. The magnetic performance test of the obtained neodymium iron boron magnetic material is shown in table 2:
TABLE 2
Comparative example
According to the element content: Pr-Nd 31.0 wt%, Dy 3.0 wt%, Tb3.0 wt%, Nb 5.0 wt%, Al1.0 wt%, B2.0 wt%, Cu 1.0 wt%, Co 3.0 wt%, Ga 1.0 wt%, Ho2.0 wt%, Zr 2.0 wt%, and the balance Fe.
Step 1, smelting neodymium iron boron alloy
Smelting pure iron, ferroboron, cobalt, copper, aluminum and vanadium in the neodymium iron boron raw material at 1350 ℃ for 180min under the condition that the vacuum degree is 0.1Pa, then adding other neodymium iron boron raw materials and charging nitrogen, and refining at 1450 ℃ for 90min to obtain the molten alloy.
Step 2. preparation of alloy sheet
The preparation method comprises the steps of preparing an alloy sheet by adopting a double-sided cooling rapid-hardening casting strip process, casting an alloy liquid onto a first rotating roller with water cooling at the rotating speed of 5m/s to form the alloy sheet, rotating along with the first rotating roller, enabling the alloy liquid to leave the rotating roller to fall onto a second rotating roller with water cooling at the rotating speed of 5m/s, enabling the alloy liquid to leave the rotating roller to fall along with the rotation to form the alloy sheet with the thickness of 0.3-0.4 mm and the temperature of lower than 650 ℃, enabling the alloy sheet to enter a crushing device, crushing the alloy sheet into alloy sheets with the length of less than 15mm, enabling the alloy sheets to enter a guide cylinder with water cooling to be cooled to be below 300 ℃, and obtaining the alloy sheet with the average grain diameter of 2.1.
Step 3, crushing and pulverizing
And (3) conveying the alloy sheet into a vacuum hydrogen crushing furnace, absorbing hydrogen at 150 ℃, and then dehydrogenating at 600 ℃ for 8h to finally form hydrogen explosion powder. And feeding the hydrogen explosion powder into a nitrogen gas jet mill for jet milling to prepare powder, wherein in order to prevent oxidation in the powder preparation process, 0.8% of hydrogen is introduced into the nitrogen gas to ensure that the powder is prepared under a reducing atmosphere, and the average particle size of the powder is about 2.1-2.8 microns.
Step 4, isostatic compaction
And performing magnetic field orientation molding and packaging on the powder in a reducing atmosphere, performing isostatic pressing under the pressure of 200MPa, conveying the magnetic block into a protective feeding box with the package after isostatic pressing, removing the package, and filling the magnetic block into a vacuum sintering material box.
Step 5, sintering
The vacuum sintering material box is sent into a vacuum sintering furnace, heating is started after the vacuum degree is higher than 5Pa, and the temperature is raised to 800 ℃ for dehydrogenation, decarburization and deoxidation treatment for 150 min; then raising the temperature to 1050 ℃ for 90min for presintering; the temperature was then raised to 1100 ℃ for 50min sintering.
Step 6, tempering treatment
Respectively carrying out high-temperature tempering at 850 ℃/120min and low-temperature tempering at 500 ℃/60min, cooling to below 80 ℃ by adopting inert gas after heat preservation is finished, and the average particle diameter of the main phase of the prepared neodymium iron boron magnetic material is 7-9 mu m. The magnetic performance test of the obtained neodymium iron boron magnetic material is shown in table 3:
TABLE 3
The results of examples 1 and 2 and the comparative example further illustrate that the precipitation of fine and uniformly distributed VN particles during aging of the VN-containing neodymium iron boron magnetic material of the present invention has an obvious effect on preventing abnormal grain growth during sintering and aging (tempering) after sintering.
Claims (10)
1. The preparation method of the VN particle-containing neodymium iron boron magnetic material is characterized by comprising the steps of a, smelting neodymium iron boron alloy, wherein 0.15-0.30 wt% of vanadium is added in the smelting process, and 0.10-0.20 wt% of nitrogen is introduced by adopting a high-pressure nitrogen smelting process.
2. The method of preparing a VN particle-containing neodymium iron boron magnetic material according to claim 1, wherein the nitrogen pressure of the high-pressure nitrogen smelting process is 15-20 MPa, and refining is performed at 1400-1500 ℃ for 60-120 min.
3. The method of producing a VN particle containing neodymium iron boron magnetic material according to claim 1 or 2, wherein the method of melting the neodymium iron boron alloy is: under the condition that the vacuum degree is 0.05-0.5 Pa, pure iron, ferroboron, cobalt, copper, aluminum and vanadium in the neodymium iron boron raw materials are smelted for 180-240 min at 1200-1400 ℃, then other neodymium iron boron raw materials are added and nitrogen is filled, and a high-pressure nitrogen smelting process is adopted to obtain a molten alloy containing 0.1-0.2 wt% of N.
4. The method of making a VN particle containing neodymium iron boron magnetic material of claim 3, wherein the neodymium iron boron raw materials include: 28 percent to 33 percent of Pr-Nd, 0 percent to 3 percent of Dy, 0 percent to 3 percent of Tb, 0 percent to 5 percent of Nb, 0 percent to 1 percent of Al, 0.5 percent to 2.0 percent of B, 0 percent to 1 percent of Cu, 0 percent to 3 percent of Co, 0 percent to 1 percent of Ga, 0 percent to 2 percent of Ho, 0 percent to 2 percent of Zr and the balance of Fe.
5. A method of making a VN particle-containing NdFeB magnetic material according to any one of claims 1 to 4, wherein the method further comprises the steps of: b. preparing an alloy sheet; c. crushing the alloy sheet into powder; d. isostatic pressing; e. sintering; f. aging treatment;
and c, the process for crushing the alloy sheet into powder comprises the following steps: absorbing hydrogen at 100-300 ℃ by the alloy sheet, and then dehydrogenating at 550-650 ℃ for 7-10 h to form hydrogen explosion powder; then, carrying out airflow milling on the hydrogen explosion powder to obtain powder with the average particle size of 1.5-2.7 microns; wherein the gas flow is formed by adding 0.5-1.0% by volume of hydrogen into nitrogen.
6. The method of making a VN particle containing neodymium iron boron magnetic material of claim 5, wherein the d. And performing magnetic field orientation molding on the powder in a reducing atmosphere, performing isostatic pressing under the pressure of 150-300 MPa, and filling the powder into a vacuum sintering material container under the protection of the reducing atmosphere.
7. The method of preparing a VN particle containing neodymium iron boron magnetic material of claim 5 or 6, wherein the process of e. Raising the temperature of the vacuum sintering material container in the step d to 750-850 ℃ for primary aging treatment for 120-180 min; then raising the temperature to 1000-1050 ℃ for presintering for 60-120 min; then, the temperature is increased to 1050-1100 ℃ for sintering for 30-60 min.
8. The method of preparing a neodymium iron boron magnetic material containing VN particles according to any one of claims 5 to 7, wherein the f. aging treatment process comprises: high-temperature aging and low-temperature aging, wherein the temperature of the high-temperature aging is 750-900 ℃, the temperature of the low-temperature aging is 450-550 ℃, and the inert gas is adopted for cooling to be below 80 ℃ after the low-temperature aging.
9. The method of preparing a VN particle containing neodymium iron boron magnetic material according to any one of claims 5 to 8, wherein the b. And c, preparing the alloy prepared in the step a into an alloy sheet with the average grain diameter of 1.5-2.7 microns.
10. The Nd-Fe-B magnetic material containing VN particles is characterized in that the content of V element in the material is 0.15-0.30 wt%, the content of N element is 0.10-0.20 wt%, Pr-Nd is more than or equal to 28 wt% and less than or equal to 33 wt%, Dy is more than or equal to 0 and less than or equal to 3 wt%, Tb is more than or equal to 0 and less than or equal to 3 wt%, Nb is more than or equal to 0 and less than or equal to 5 wt%, Al is more than or equal to 0 and less than or equal to 1 wt%, B is more than or equal to 0.5 wt% and less than or equal to 2.0 wt%, Cu is more than or equal to 0 and less than or equal to 1 wt%, Co is more than or equal to; preferably, the average diameter of main phase particles of the VN-particle-containing neodymium iron boron magnetic material is less than 3 μm, the average grain diameter of VN particles is 5-10 nm, the VN particles are uniformly distributed in the main phase grains and in grain boundaries, and the average diameter of precipitated particles in the grains is smaller than that of precipitated particles in the grain boundaries; preferably, the material is prepared by the method of any one of claims 1 to 9.
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