CN111180190A - Method for improving magnetic property of sintered neodymium-iron-boron magnet - Google Patents
Method for improving magnetic property of sintered neodymium-iron-boron magnet Download PDFInfo
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- CN111180190A CN111180190A CN202010035542.8A CN202010035542A CN111180190A CN 111180190 A CN111180190 A CN 111180190A CN 202010035542 A CN202010035542 A CN 202010035542A CN 111180190 A CN111180190 A CN 111180190A
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- H01F41/0293—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 diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets
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- 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
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- 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
- H01F1/0576—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 pressed, e.g. hot working
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- 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
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- 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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- 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
- H01F1/06—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 in the form of particles, e.g. powder
- H01F1/08—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 in the form of particles, e.g. powder pressed, sintered, or bound together
- H01F1/086—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 in the form of particles, e.g. powder pressed, sintered, or bound together sintered
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- 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
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Abstract
The invention discloses a method for improving the magnetic performance of a sintered neodymium-iron-boron magnet, which is characterized in that low-melting-point nano metal powder is added by adopting a crystal boundary adding method, so that the crystal boundary is optimized, the continuity and wettability of the crystal boundary are improved, and the magnetic performance of the magnet is improved within a certain range. Secondly, by combining the crystal boundary diffusion process, the crystal boundary expansion of the low-melting point metal provides a continuous diffusion channel for the subsequent crystal boundary diffusion, the diffusion depth and concentration of the low-melting point metal are increased, the coercive force of the magnet is effectively improved, the diffusion time is greatly shortened, and the manufacturing cost is reduced.
Description
Technical Field
The invention belongs to the technical field of rare earth permanent magnet materials, and particularly relates to a method for improving the magnetic property of a sintered neodymium-iron-boron magnet.
Background
The neodymium iron boron permanent magnet is called as 'maga' by virtue of excellent magnetic performance, and is widely applied to the fields of aerospace, wind power generation, energy-saving household appliances, electronic appliances, new energy automobiles and the like. With the continuous progress of the manufacturing technology and the improvement of the environmental protection consciousness of people, the automobile material has market attention in three fields of energy conservation and environmental protection, new energy and new energy automobiles, becomes a key material for realizing the development planning of 'Chinese manufacturing 2025', rapidly increases the consumption at the speed of 10-20% per year, and shows good application prospect.
For a magnet, the coercive force is an important index for evaluating the magnetic performance of the Nd-Fe-B permanent magnet material. The heavy rare earth elements Dy and Tb are important elements for improving the coercive force, so that the anisotropy constant of 2:14:1 phase magnetocrystalline can be effectively improved, but the price is high. Therefore, the coercive force is generally improved by the surface deposition and diffusion mode of the heavy rare earth elements Dy and Tb, and the manufacturing cost of the magnet is reduced. At present, the coercive force of a grain boundary diffusion magnet is improved mainly by means of diffusion of heavy rare earth elements along the crystal, the formation of a nuclear shell layer around a main phase crystal grain can effectively avoid main phase exchange coupling, the nucleation of a reverse magnetization domain is avoided by the grain boundary pinning effect, and the comprehensive effect of the grain boundary pinning effect and the reverse magnetization domain can greatly improve the coercive force of the magnet.
The influence of the number and the micro-morphology of the grain boundary and the grain boundary phase inside the neodymium iron boron magnet on the grain boundary diffusion process is large, but the number of the grain boundary and the grain boundary phase in the magnet is limited, and the continuity of a diffusion channel is poor, so that the diffusion depth of heavy rare earth elements inside the magnet is shallow, and the performance improvement amplitude is limited. At present, related processes are explored, and the number of crystal boundaries and crystal boundary phases is increased and the continuity of the crystal boundaries is improved by modifying the crystal boundaries inside the magnet, so that the efficiency of a crystal boundary diffusion process is improved, and the coercive force of the magnet is further improved.
Disclosure of Invention
The invention aims to provide a method for improving the magnetic property of a sintered neodymium-iron-boron magnet, which comprises the steps of firstly utilizing a conventional sintering process, improving the microscopic appearance in the sintering process by adding low-melting metal nano powder, thereby achieving the purposes of improving the number and the size of a grain boundary Nd-rich phase and improving the wettability of the grain boundary phase, taking the grain boundary Nd-rich phase as a heavy rare earth diffusion channel, promoting the diffusion depth and the diffusion efficiency of elements, greatly shortening the diffusion time, improving the coercive force of the magnet, realizing the stable and batch production of the magnet and reducing the manufacturing cost.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for improving the magnetic property of a sintered neodymium-iron-boron magnet is characterized by comprising the steps of vacuum rapid solidification, hydrogen breaking and powder mixing after jet milling, wherein M powder with the particle size of 200-1000 nm is added during powder mixing, and the M powder is powder of low-melting metal or low-melting alloy. The design of the low-melting metal powder to be added is adjusted in accordance with the alloy phase diagram, considering the wettability of the low-melting metal with the grain boundary Nd-rich phase.
Further, the low-melting metal is one of Cu, Al, Zn, Sn, Mg or Ga.
Further, the low-melting alloy is an alloy formed of a plurality of metals among the low-melting metals.
Further, in the present invention,
1) the vacuum rapid solidification step comprises the steps of carrying out smelting proportioning according to the initial alloy components of the magnet, firstly vacuumizing, filling argon or high-purity nitrogen when the vacuum degree is not more than 5 Pa, controlling the air pressure between 50 and 60 kPa, and rapidly cooling the molten alloy liquid by a water-cooling copper roller to obtain a rapid solidification sheet with the thickness of about 0.2 to 0.5 mm;
2) the hydrogen crushing powder is as follows: respectively placing the quick-setting slices into a hydrogen furnace, and heating at 550-650 deg.C for 6-10h in hydrogen atmosphere to obtain coarse powder with particle size of 200-500 μm;
3) the jet mill comprises the following steps: adding antioxidant and lubricant into the hydrogen-broken coarse powder, and making the oxygen content in the air flow milling process be not more than 500 ppm to obtain magnetic powder with particle size of 3-5 μm;
4) the powder mixing step comprises: fully mixing the prepared magnetic powder with low-melting metal nano powder M with the particle size of 200-1000 nm;
further comprising:
5) orientation compression molding: under the protection of inert gas, pressing the superfine alloy powder, wherein the oxygen content is controlled to be 400ppm or less in the process;
6) and (3) vacuum sintering: putting the pressed blocks into a sintering furnace, and putting the blocks into the sintering furnace under the vacuum degree of less than 2x10-3Sintering at 220, 330, 450, 600, 720 and 900 deg.C in different temperature rangesAfter the temperature is kept for 20 min, the temperature is raised to 1080 ℃ for sintering, and then the sintered sample is cooled to the room temperature by argon; the sintering process is liquid phase sintering, and the added nano powder M effectively promotes the liquid phase to flow by reasonably controlling the sintering process, so that the quantity and the size of a grain boundary phase are improved.
7) Tempering treatment: carrying out multistage tempering treatment on the sintered magnet, wherein the first-stage tempering comprises the following steps: keeping the temperature at 880-920 ℃ for 2-4 h, and performing secondary tempering: keeping the temperature at 480-520 ℃ for 3-6 h;
8) surface deposition: after grinding and polishing, acid washing, alkali washing and oil removing, ultrasonic alcohol oscillation cleaning are carried out on the surface of the magnet, and then the magnet is placed into a vacuum drying oven for drying; then, performing heavy rare earth surface deposition by adopting methods such as spraying or coating, magnetron sputtering, pasting, electrophoresis and the like, wherein the thickness of the heavy rare earth film layer is 30-50 mu m;
9) and (3) diffusion treatment: placing the treated magnet into a high vacuum heat treatment furnace under vacuum degree of less than 1 × 10-3And Pa, performing diffusion treatment for 7 hours.
Further, the average particle size of the magnetic powder prepared in the step 3) is 4 μm.
Further, the diffusion treatment process in the step 9) adopts a heating mode of sectional heating for diffusion, the temperature is increased to 880-920 ℃, the heat preservation time is 7 hours, the secondary annealing time is 480-520 ℃, and the heat preservation time is 3-5 hours.
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the method for improving the magnetic property of the sintered neodymium-iron-boron magnet, the low-melting-point metal or alloy powder is added by adopting a crystal boundary adding method, the low-melting-point metal or alloy powder is dispersed and distributed at the crystal boundary by utilizing the characteristics of the low-melting-point metal or alloy powder, and the number of the crystal boundary and the crystal boundary phase is obviously improved. The magnetic material is used as a diffusion channel of heavy rare earth and oxides thereof, the diffusion depth and the diffusion rate of elements are promoted, the diffusion time is greatly shortened, and the magnetic effect is more remarkable than that of a magnet without grain boundary expansion.
(2) The low-melting-point nano metal powder is added by a crystal boundary adding method, so that the crystal boundary is optimized, the continuity and wettability of the crystal boundary are improved, and the magnetic performance of the magnet is improved within a certain range. Secondly, by combining the crystal boundary diffusion process, the crystal boundary expansion of the low-melting point metal provides a continuous diffusion channel for the subsequent crystal boundary diffusion, the diffusion depth and concentration of the low-melting point metal are increased, the coercive force of the magnet is effectively improved, the diffusion time is greatly shortened, and the manufacturing cost is reduced.
Detailed Description
The present invention will now be more fully described with reference to the following examples. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein.
Example 1
(1) And (3) vacuum rapid solidification, namely designing to obtain Nd11.6Fe83.3B5.1 alloy rapid solidification sheets with nominal components close to 2:14:1, smelting in a vacuum smelting furnace, and rapidly cooling molten alloy liquid through a water-cooled copper roller to obtain the rapid solidification sheets with the thickness of 0.3-0.5 mm.
(2) Hydrogen crushing to obtain powder: the rapidly solidified sheet was put into a hydrogen cracker to absorb hydrogen for 2 hours, followed by holding at 580 ℃ for 6 hours, and then cooled to room temperature to give a coarse powder having a particle size of about 300. mu.m.
(3) And (3) jet milling: adding conventional antioxidant and lubricant into the hydrogen-broken coarse powder according to the proportion of 2mL/kg, and refining the hydrogen-broken coarse powder to fine magnetic powder with the granularity of 4 mu m by an air flow mill, wherein the oxygen content is strictly controlled to be below 400ppm in the air flow mill process, and the rotating speed of a sorting wheel is controlled to be 3600-4000 r/min;
(4) mixing powder: adding 0.2% of Cu powder with the particle size of 700 nm into the magnetic powder prepared by the process, and mixing for 2 h; if the alloy powder is other low-melting metal or low-melting alloy powder, the wettability of the alloy powder and the grain boundary Nd-rich phase needs to be considered, and the proportion meeting the conditions is selected according to an alloy phase diagram.
(5) Orientation compression molding: under the protection of inert gas (oxygen content < 400 ppm), a magnetic field of 2T is applied to the magnetic powder and the powder is pressed into blocks. Followed by cold isostatic pressing at a pressure of 200 MPa for 0.5 h.
(6) And (3) vacuum sintering: putting the pressed blocks into a sintering furnace, and putting the blocks into a high vacuum environment (the vacuum degree is less than or equal to 2x 10)-3Pa) is respectively insulated for 20 min at 220 ℃, 330 ℃, 450, 600, 720 and 900 ℃, and then is sintered for 5h by gradually increasing the temperature to 1080 ℃.
Heat treatment is carried out for 2 hours at 900 ℃; the sample was then incubated at 510 ℃ for 4 h, after which the sintered sample was argon cooled to room temperature.
TABLE 1 magnetic property Change of magnet before and after expansion by Using Low-melting Metal grain boundary
The magnet obtained by the above process was processed into a 7X 3 mm block magnet, which was then subjected to heavy rare earth TbF3Spray deposition, diffusion at 910 deg.C for 7 h, and tempering at 510 deg.C for 4 h. The magnetic property detection is carried out by adopting an NIM-2000HF rare earth permanent magnet measuring device, and the magnetic property of the magnet is shown in Table 1.
Comparative example 1:
the rapid diffusion of the heavy rare earth elements along the crystal is realized by utilizing the grain boundary dilatation effect of the low-melting-point nano metal on the magnet; and sintering, depositing and diffusing to obtain a magnet sample. Comparative example 1 is essentially the same procedure as example 1, except that: the low melting point nano metal or alloy powder in the step (4) is not mixed, but the initial sintered magnet is directly prepared by the conventional sintering process, and then the heavy rare earth Tb or the fluoride TbF thereof is added3The magnet is manufactured by deposition and diffusion. The magnetic properties of the magnet samples produced without the expansion of the low-melting nano-metal grain boundaries are shown in table 2.
TABLE 2 magnetic Properties of magnet after expansion without using low-melting metal grain boundary
As can be seen from the comparison result of the magnetic properties between example 1 and comparative example 1, the remanence and the maximum magnetic energy product of the magnet without grain boundary expansion by the nano powder tend to be stable compared with the magnet with grain boundary expansion, while the coercive force increase is lower than that of the magnet with grain boundary expansion under the same diffusion process.
Comparative example 2:
the rapid diffusion of heavy rare earth elements along the crystal is realized by utilizing the grain boundary expansion effect of low-melting-point nano metal on the magnet(ii) a And sintering, depositing and diffusing to obtain a magnet sample. Comparative example 2 is essentially the same procedure as example 1, except that: the nano metal powder in the step (4) is not adopted, but low-melting metal Cu powder with the particle size of 2 mu m is adopted, then the sintered magnet is prepared by pressing forming and conventional sintering processes, and then heavy rare earth Tb or fluoride TbF thereof is added3The magnet is manufactured by deposition and diffusion. The magnetic properties of the magnet samples produced without the expansion of the low-melting nano-metal grain boundaries are shown in table 3.
TABLE 3 magnetic property variation of magnet after expansion of low-melting metal grain boundary with different grain sizes
As can be seen from the comparison of the magnetic properties of example 1 and comparative example 2, the grain size of the added low-melting metal powder has a significant effect on the grain boundary dilatation effect, and is most suitable when the grain size is 700 nm. When the powder granularity is larger, sintering is difficult to compact in the sintering process, hole defects are generated, and the coercive force is not obviously improved; when the powder granularity is smaller, segregation is easy to occur in the sintering process, the grain boundary phase is unevenly distributed, the ideal expansion effect is difficult to achieve, and the coercive force improvement effect is general.
Comparative example 3:
the rapid diffusion of the heavy rare earth elements along the crystal is realized by utilizing the grain boundary dilatation effect of the low-melting-point nano metal on the magnet; and sintering, depositing and diffusing to obtain a magnet sample. Comparative example 3 is essentially the same procedure as example 1, except that: adding the nano metal powder in the step (4) is not adopted, then directly preparing the sintered magnet through compression molding and conventional sintering process, and then adding the heavy rare earth Tb or the fluoride TbF thereof3The magnet is manufactured by deposition and diffusion, and the diffusion time is prolonged to 20 h. The magnetic properties of the magnet samples produced without the expansion of the low-melting nano-metal grain boundaries are shown in table 4.
TABLE 4 magnetic property variation of magnet before and after expansion using low melting metal grain boundary
As can be seen from the comparison result of the magnetic properties between example 1 and comparative example 3, the grain size of the added low-melting metal powder has a significant effect on the grain boundary dilatation effect, and the magnet without grain boundary dilatation can extend the diffusion time to 20 hours to be close to the coercive force of the dilatation magnet, so that the grain boundary dilatation can actually improve the diffusion efficiency of the magnet greatly.
The method of the embodiment has obvious effect corresponding to other neodymium iron boron magnets.
The above examples are only for illustrating the present invention, and besides, there are many different embodiments, which can be conceived by those skilled in the art after understanding the idea of the present invention, and therefore, they are not listed here.
Claims (6)
1. A method for improving the magnetic property of a sintered neodymium-iron-boron magnet is characterized by comprising the steps of vacuum rapid solidification, hydrogen breaking and powder mixing after jet milling, wherein M powder with the particle size of 200-1000 nm is added during powder mixing, and the M powder is powder of low-melting metal or low-melting alloy.
2. The method for improving the magnetic property of the sintered NdFeB magnet as claimed in claim 1, wherein the low melting metal is one of Cu, Al, Zn, Sn, Mg or Ga.
3. The method for improving the magnetic performance of the sintered NdFeB magnet as claimed in claim 2, wherein the low-melting alloy is an alloy formed by a plurality of metals in the low-melting metal.
4. The method for improving the magnetic performance of the sintered NdFeB magnet according to claim 3,
1) the vacuum rapid solidification step comprises the steps of carrying out smelting proportioning according to the initial alloy components of the magnet, firstly vacuumizing, filling argon or high-purity nitrogen when the vacuum degree is not more than 5 Pa, controlling the air pressure between 50 and 60 kPa, and rapidly cooling the molten alloy liquid by a water-cooling copper roller to obtain a rapid solidification sheet with the thickness of about 0.2 to 0.5 mm;
2) the hydrogen crushing powder is as follows: respectively placing the quick-setting slices into a hydrogen furnace, and heating at 550-650 deg.C for 6-10h in hydrogen atmosphere to obtain coarse powder with particle size of 200-500 μm;
3) the jet mill comprises the following steps: adding antioxidant and lubricant into the hydrogen-broken coarse powder, and making the oxygen content in the air flow milling process be not more than 500 ppm to obtain magnetic powder with particle size of 3-5 μm;
4) the powder mixing step comprises: fully mixing the prepared magnetic powder with low-melting metal nano powder M with the particle size of 200-1000 nm;
further comprising:
5) orientation compression molding: under the protection of inert gas, pressing the superfine alloy powder, wherein the oxygen content is controlled to be 400ppm or less in the process;
6) and (3) vacuum sintering: putting the pressed blocks into a sintering furnace, and putting the blocks into the sintering furnace under the vacuum degree of less than 2x10-3Carrying out fractional heating sintering in the environment, respectively keeping the temperature at 220, 330, 450, 600, 720 and 900 ℃ for 20 min, heating to 1080 ℃ for sintering, and then cooling the sintered sample to the room temperature by using argon;
7) tempering treatment: carrying out multistage tempering treatment on the sintered magnet, wherein the first-stage tempering comprises the following steps: keeping the temperature at 880-920 ℃ for 2-4 h, and performing secondary tempering: keeping the temperature at 480-520 ℃ for 3-6 h;
8) surface deposition: after grinding and polishing, acid washing, alkali washing and oil removing, ultrasonic alcohol oscillation cleaning are carried out on the surface of the magnet, and then the magnet is placed into a vacuum drying oven for drying; then, performing heavy rare earth surface deposition by adopting methods such as spraying or coating, magnetron sputtering, pasting, electrophoresis and the like, wherein the thickness of the heavy rare earth film layer is 30-50 mu m;
9) and (3) diffusion treatment: placing the treated magnet into a high vacuum heat treatment furnace under vacuum degree of less than 1 × 10-3And Pa, performing diffusion treatment for 7 hours.
5. The method for improving the magnetic performance of the sintered neodymium-iron-boron magnet according to claim 4, wherein the average grain diameter of the magnetic powder prepared in the step 3) is 4 μm.
6. The method for improving the magnetic property of the sintered neodymium-iron-boron magnet according to claim 4, wherein the diffusion treatment process in the step 9) adopts a heating mode of sectional temperature rise for diffusion, the temperature is raised to 880-920 ℃, the temperature is kept for 7 hours, and the secondary annealing is 480-520 ℃, and the temperature is kept for 3-5 hours.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112712955A (en) * | 2020-12-23 | 2021-04-27 | 安徽大地熊新材料股份有限公司 | Sintered neodymium-iron-boron magnet and preparation method thereof |
| CN112735718A (en) * | 2020-12-28 | 2021-04-30 | 安徽大地熊新材料股份有限公司 | Preparation method of high-corrosion-resistance high-coercivity sintered neodymium-iron-boron magnet |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112712955A (en) * | 2020-12-23 | 2021-04-27 | 安徽大地熊新材料股份有限公司 | Sintered neodymium-iron-boron magnet and preparation method thereof |
| CN112712955B (en) * | 2020-12-23 | 2023-02-17 | 安徽大地熊新材料股份有限公司 | Sintered neodymium-iron-boron magnet and preparation method thereof |
| CN112735718A (en) * | 2020-12-28 | 2021-04-30 | 安徽大地熊新材料股份有限公司 | Preparation method of high-corrosion-resistance high-coercivity sintered neodymium-iron-boron magnet |
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Application publication date: 20200519 |