CN113528929B - Sintered neodymium-iron-boron magnet and preparation method thereof - Google Patents
Sintered neodymium-iron-boron magnet and preparation method thereof Download PDFInfo
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- 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
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Abstract
The application relates to the field of magnetic materials, and particularly discloses a sintered neodymium-iron-boron magnet and a preparation method thereof. The sintered neodymium-iron-boron magnet comprises the following raw materials in parts by mass: 0.5-0.7 part of lanthanum, 20-24 parts of cerium, 16-20 parts of praseodymium, 50-54 parts of neodymium, 0.1-0.2 part of samarium, 6-8 parts of dysprosium, 0.2-0.4 part of holmium, 20-22 parts of boron and 255 parts of iron 248-doped iron; the preparation method comprises the following steps: weighing the components in proportion, carrying out vacuum melting, and then sequentially carrying out hydrogen crushing, press forming, sintering and tempering treatment to obtain the sintered neodymium-iron-boron magnet. The sintered neodymium-iron-boron magnet can be used for preparing a generator and has the advantage of improving the magnetic performance of the sintered neodymium-iron-boron magnet.
Description
Technical Field
The application relates to the field of magnetic materials, in particular to a sintered neodymium-iron-boron magnet and a preparation method thereof.
Background
In recent years, in order to protect the environment and save resources, development of new energy vehicles such as electric vehicles has been a trend. In new energy vehicles, including driving motors, generators and the like, neodymium iron boron permanent magnet materials are required to be sintered. The sintered Nd-Fe-B permanent magnet is small in size and high in performance, can well reduce the quality of a motor, improves the efficiency of the motor, and is more suitable for miniaturization and light weight of automobiles.
However, with the development of the technology, the requirement for the magnetic performance of the sintered ndfeb magnet is becoming more and more stringent, and the performance of the sintered ndfeb magnet in the related technology has not met the requirement, so that the magnetic performance of the sintered ndfeb magnet needs to be continuously improved to meet the higher use requirement.
Disclosure of Invention
In order to improve the magnetic performance of the sintered neodymium-iron-boron magnet, the application provides the sintered neodymium-iron-boron magnet and a preparation method thereof.
In a first aspect, the present application provides a sintered nd-fe-b magnet, which adopts the following technical scheme:
a sintered neodymium-iron-boron magnet comprises the following raw materials in parts by mass: 0.5-0.7 part of lanthanum, 20-24 parts of cerium, 16-20 parts of praseodymium, 50-54 parts of neodymium, 0.1-0.2 part of samarium, 6-8 parts of dysprosium, 0.2-0.4 part of holmium, 20-22 parts of boron and 255 parts of iron 248-doped iron.
By adopting the technical scheme and adopting the matching mode of all rare earth elements, the neodymium iron boron magnet has excellent comprehensive magnetic performance. And the addition of the holmium element which is a heavy rare earth element can eliminate or obviously reduce the alpha-Fe phase in the alloy ingot and promote the directional growth of main phase grains, thereby improving the crushing performance of the ingot, ensuring that the alloy powder prepared by the jet mill has more uniform grain size distribution and reducing the number of particles with overlarge or undersize grain sizes in the powder. The addition of a certain amount of holmium elements obviously improves the intrinsic coercive force of the neodymium iron boron magnet, and the remanence of the magnet is basically not changed.
Preferably, the remaining components other than boron and iron account for 26.3 to 27.5wt% of the total mass of the raw materials.
By adopting the technical scheme, the proportion of the rare earth elements in the raw materials is higher, which is beneficial to improving the mechanical property of the neodymium iron boron magnet. And the higher the content of the rare earth element is, the more uniform and continuous the distribution of the rare earth-rich phase can be.
Preferably, the total mass of the praseodymium, the neodymium and the dysprosium accounts for 20-21wt% of the total mass of the raw materials.
By adopting the technical scheme, the total mass of praseodymium, neodymium and dysprosium is higher, the magnetic performance of the neodymium-iron-boron magnet is better, but along with the increase of the total mass of praseodymium, neodymium and dysprosium, the production cost of the neodymium-iron-boron magnet is increased along with the increase of the total mass of praseodymium, neodymium and dysprosium, and the trend of improving the magnetic performance of the magnet tends to be stable, so that the occupation ratio of the neodymium-iron-boron magnet to the neodymium-iron-boron magnet is required to be controlled and cannot be too high while the magnetic performance of the neodymium-iron-boron magnet is ensured, otherwise, the production cost of the neodymium-iron-boron magnet is caused to be too high.
Preferably, the mass of the cerium accounts for 5.6-6.2wt% of the total mass of the raw materials.
Through adopting above-mentioned technical scheme, cerium element is used for replacing partial neodymium element that the price is expensive, and cerium element's addition can reduce the manufacturing cost of neodymium iron boron magnet, but the content of cerium is too much in the neodymium iron boron magnet, can reduce the magnetic property of neodymium iron boron magnet, so need control the content of cerium, reduce cost on the basis of guaranteeing the magnetic property of neodymium iron boron magnet.
Preferably, the ratio of the mass sum of praseodymium and neodymium to the mass of cerium is (3.1-3.3): 1.
by adopting the technical scheme, cerium is used for replacing part of expensive neodymium elements, the magnetic performance of the neodymium-iron-boron magnet can be ensured by controlling the proportion of cerium to cerium, and the phenomenon that the magnetic performance of the neodymium-iron-boron magnet is obviously reduced by adding too much cerium is avoided.
In a second aspect, the application provides a method for preparing a sintered ndfeb magnet, which adopts the following technical scheme:
a preparation method of a sintered neodymium-iron-boron magnet comprises the following preparation steps:
s1, preparing the ingredients
Weighing the components in proportion;
s2, smelting
Vacuum melting is carried out on the components weighed in the S1;
s3, hydrogen cracking
Hydrogen crushing the components subjected to vacuum melting in S2 to obtain coarse particles;
s4, preparing powder
Crushing the coarse particles in the S3 to prepare alloy powder, wherein an antioxidant is added in the crushing process;
s5, molding
Pressing and forming the alloy powder in the S4 to obtain a pressed compact;
s6, sintering
Sintering the pressed compact in the S5;
s7 tempering treatment
And (4) tempering the sintered pressed compact in the step (S6), and cooling by water to obtain the sintered neodymium-iron-boron magnet.
By adopting the technical scheme, the antioxidant is added in the process steps to reduce the oxygen content of the magnet, so that the reduction of the magnetic performance of the magnet caused by the increase of the oxygen content in the magnet is prevented. This is because the magnets of the present invention have a low rare earth content, less than 28.1%, and as the oxygen content of the magnet increases, the net rare earth content of the magnet may decrease to a critical value, resulting in loss of Nd rich solution, and the absence of a liquid phase rich in rare earth may also result in less dense sintering, resulting in reduced magnetic properties of the magnet.
Preferably, in S4, the alloy powder has a particle size of 3-5 μm.
By adopting the technical scheme, when the granularity of the alloy powder is within the range, the powder can be ensured to be fine and uniform, and the phenomenon that grains are not easy to aggregate and grow up can be avoided. If the powder particle size is too fine, the thermodynamic state is unstable, oxidation easily occurs, and the phenomenon of grain growth easily occurs during sintering, thereby causing a decrease in the density and magnetic properties of the magnet.
Preferably, in S5, the press forming is performed by cold isostatic pressing.
By adopting the technical scheme, the pressed blank can be ensured to have enough density by a cold isostatic pressing mode, so that the magnetic performance of the magnet is ensured.
Preferably, in S6, the sintering adopts a cyclic sintering process, which is specifically implemented as: 1100 ℃ X0.5 h, 1060 ℃ X3 h, 1100 ℃ X0.5 h, 1060 ℃ X3 h.
By adopting the technical scheme, compared with the conventional sintering process, the magnet prepared by adopting the cyclic sintering process can improve the coercive force of the magnet, and the remanence and the magnetic energy product of the magnet are basically kept unchanged. Firstly, the formed liquid phase is less when the magnet is sintered at a lower temperature, the growth of the crystal grains of the sintered magnet is inhibited, and the Nd-rich liquid phase can more uniformly coat the fine main phase crystal grains. And secondly, the acting force generated in the high-temperature and low-temperature circulating burning process promotes the Nd-rich liquid phase to flow at the grain boundary of the main phase, the Nd-rich liquid phase is distributed more uniformly, the microstructure is optimized, and the Nd-rich liquid phase can better play a role in demagnetization and exchange coupling. The two advantages together lead to the improvement of the coercive force of the magnet.
The reason for this may be: the cyclic sintering process can improve the grain boundary of the magnet, so that the magnet presents a clear, continuous and clean interface, and the coercive force of the magnet is improved. The neodymium iron boron main phase crystal grains are heated to expand in the process of heating from 1060 ℃ to 1100 ℃, and stress is generated by cooling contraction in the process of cooling from 1100 ℃ to 1060 ℃ and acts on the Nd-rich phase. The thermal expansion stress in the temperature rise process and the cooling shrinkage stress in the temperature reduction process act on the main phase grain boundary and the corner of the triangular grain boundary. The thermal expansion pressure and the capillary force act on the Nd-rich phase, particularly the acting force on the Nd-rich liquid phase at the triangular grain boundary is the largest, so that the liquid phase moves among the main phase grains.
Preferably, in S7, the tempering treatment is specifically: 880-920 ℃ for 2-3h and 500-540 ℃ for 2-3 h.
By adopting the technical scheme, the crystal grain boundary can be clearer by the secondary tempering treatment mode, the main phase crystal grains are better isolated, the exchange coupling effect among the crystal grains is removed, and the coercive force of the magnet is favorably improved.
In summary, the present application has the following beneficial effects:
1. because the method of matching each rare earth element is adopted, the neodymium iron boron magnet has excellent comprehensive magnetic performance;
2. in the application, cerium is preferably used for replacing part of expensive neodymium, and the addition of cerium can reduce the production cost of the neodymium-iron-boron magnet;
3. according to the method, the antioxidant is added in the powder preparation step to reduce the oxygen content of the magnet, so that the reduction of the magnetic performance of the magnet caused by the increase of the oxygen content in the magnet is prevented.
Detailed Description
The present application will be described in further detail with reference to examples.
The antioxidant 1010 is commercially available in this application.
Examples
The sintered ndfeb magnets of examples 1-8 were prepared in the same manner, except for the differences in the raw materials and process parameters (see table 1 for details).
Example 1
The sintered neodymium-iron-boron magnet disclosed in embodiment 1 of the invention is prepared by the following steps:
s1, preparing the ingredients
Weighing the components in proportion, wherein the components and the use amount thereof are shown in a table 1;
s2, smelting
Vacuum melting is carried out on the components weighed in the S1;
s3, hydrogen cracking
Subjecting the components subjected to vacuum melting in S2 to hydrogen breaking to obtain coarse particles, wherein the vacuum degree in the furnace is controlled at 1.0 × 10-2Pa is inside;
s4, preparing powder
Coarse particles in S3 are added in N2Crushing under the protection of atmosphere to obtain alloy powder, wherein an antioxidant 1010 accounting for 0.05wt% of the total mass of the alloy powder is added in the crushing process, and the granularity of the alloy powder is 3-5 mu m;
s5, molding
Carrying out orientation compression on the alloy powder in the S4 in an oxygen-free fully-closed environment, wherein the size of an orientation field is 2T, carrying out cold isostatic pressing after orientation, keeping the pressure at 210MPa for 1min, and obtaining a pressed compact;
s6, sintering
And (3) performing cyclic sintering on the pressed compact in the step S5, and specifically implementing the following steps: 1100 ℃ multiplied by 0.5h, 1060 ℃ multiplied by 3h, 1100 ℃ multiplied by 0.5h, 1060 ℃ multiplied by 3 h;
s7 tempering treatment
And (3) tempering the sintered compact in S6, wherein the tempering treatment specifically comprises the following steps: keeping the temperature at 920 ℃ for 2h and at 540 ℃ for 2h, and cooling by water to obtain the sintered Nd-Fe-B magnet.
Example 2
The sintered neodymium-iron-boron magnet disclosed by the embodiment 2 of the invention is prepared by the following steps:
s1, preparing the ingredients
Weighing the components in proportion, wherein the components and the use amount thereof are shown in a table 1;
s2, smelting
Vacuum melting is carried out on the components weighed in the S1;
s3, hydrogen cracking
Subjecting the components subjected to vacuum melting in S2 to hydrogen breaking to obtain coarse particles, wherein the vacuum degree in the furnace is controlled at 1.0 × 10-2Pa is inside;
s4, preparing powder
Coarse particles in S3 are added in N2Crushing under the protection of atmosphere to obtain alloy powder, wherein an antioxidant 1010 accounting for 0.05wt% of the total mass of the alloy powder is added in the crushing process, and the granularity of the alloy powder is 3-5 mu m;
s5, molding
Carrying out orientation compression on the alloy powder in the S4 in an oxygen-free fully-closed environment, wherein the size of an orientation field is 2T, carrying out cold isostatic pressing after orientation, keeping the pressure at 210MPa for 1min, and obtaining a pressed compact;
s6, sintering
And (3) performing cyclic sintering on the pressed compact in the step S5, and specifically implementing the following steps: 1100 ℃ multiplied by 0.5h, 1060 ℃ multiplied by 3h, 1100 ℃ multiplied by 0.5h, 1060 ℃ multiplied by 3 h;
s7 tempering treatment
And (3) tempering the sintered compact in S6, wherein the tempering treatment specifically comprises the following steps: keeping the temperature at 900 ℃ for 3h, keeping the temperature at 520 ℃ for 3h, and cooling by water to obtain the sintered neodymium-iron-boron magnet.
Example 3
The sintered neodymium-iron-boron magnet disclosed in embodiment 3 of the invention is prepared by the following steps:
s1, preparing the ingredients
Weighing the components in proportion, wherein the components and the use amount thereof are shown in a table 1;
s2, smelting
Vacuum melting is carried out on the components weighed in the S1;
s3, hydrogen cracking
Subjecting the components subjected to vacuum melting in S2 to hydrogen breaking to obtain coarse particles, wherein the vacuum degree in the furnace is controlled at 1.0 × 10-2Pa is inside;
s4, preparing powder
Coarse particles in S3 are added in N2Crushing under the protection of atmosphere to obtain alloy powder, wherein an antioxidant 1010 accounting for 0.05wt% of the total mass of the alloy powder is added in the crushing process, and the granularity of the alloy powder is 3-5 mu m;
s5, molding
Carrying out orientation compression on the alloy powder in the S4 in an oxygen-free fully-closed environment, wherein the size of an orientation field is 2T, carrying out cold isostatic pressing after orientation, keeping the pressure at 210MPa for 1min, and obtaining a pressed compact;
s6, sintering
And (3) performing cyclic sintering on the pressed compact in the step S5, and specifically implementing the following steps: 1100 ℃ multiplied by 0.5h, 1060 ℃ multiplied by 3h, 1100 ℃ multiplied by 0.5h, 1060 ℃ multiplied by 3 h;
s7 tempering treatment
And (3) tempering the sintered compact in S6, wherein the tempering treatment specifically comprises the following steps: keeping the temperature at 880 ℃ for 3h, keeping the temperature at 500 ℃ for 3h, and cooling by water to obtain the sintered neodymium-iron-boron magnet.
TABLE 1
Example 4
This example was based on example 2, with the amounts of the other components except for boron and iron being varied.
Example 4a
The present embodiment is different from embodiment 2 in that: the amounts of the other components except boron and iron are minimized.
Example 4b
The present embodiment is different from embodiment 2 in that: the amounts of the other components except boron and iron were the maximum.
Example 5
In this example, the total mass of praseodymium, neodymium and dysprosium is changed based on example 2.
Example 5a
The present embodiment is different from embodiment 2 in that: the dosage of praseodymium, neodymium and dysprosium is minimum, the dosage of praseodymium is 16kg, the dosage of neodymium is 50kg, and the dosage of dysprosium is 6 kg.
Example 5b
The present embodiment is different from embodiment 2 in that: the dosage of praseodymium, neodymium and dysprosium is the maximum, the dosage of praseodymium is 20kg, the dosage of neodymium is 54kg, and the dosage of dysprosium is 8 kg.
Example 6
The present example was based on example 2, and the ratio of the sum of the mass of praseodymium and neodymium to the mass of cerium was changed.
Example 6a
The present embodiment is different from embodiment 2 in that: the ratio of the mass sum of praseodymium and neodymium to the mass of cerium is 2.75: 1.
Example 6b
The present embodiment is different from embodiment 2 in that: the ratio of the mass sum of praseodymium and neodymium to the mass of cerium is 3.70: 1.
Example 7
The present embodiment is different from embodiment 2 in that: the sintering adopts a conventional process, which specifically comprises the following steps: 1100 ℃ for 2 h.
Example 8
The present embodiment is different from embodiment 2 in that: antioxidant 1010 is not added in the preparation process.
Comparative example
Comparative example 1
This comparative example differs from example 1 in that: holmium is not added into the raw materials, the dosage of iron is changed to 270.2kg, and the dosages of the other components are not changed.
Comparative example 2
This comparative example differs from example 1 in that: the amount of cerium was 28kg, the amount of neodymium was 46kg, and the amounts of the remaining components were unchanged.
Performance test
Residual magnetism Br: the AMT-4 magnetization characteristic automatic measuring instrument is used for detection.
Intrinsic coercive force Hcj: the AMT-4 magnetization characteristic automatic measuring instrument is used for detection.
Maximum magnetic energy product (BH) m: the AMT-4 magnetization characteristic automatic measuring instrument is used for detection.
TABLE 2
It can be seen from the combination of examples 1-3 and table 2 that the sintered ndfeb magnets of examples 1-3 all have good overall magnetic properties, with example 2 being preferred.
Combining example 2 with examples 4a-4b and table 2, it can be seen that the balance of the components other than boron and iron in example 4a is 25.5wt% of the total mass of the raw materials, the balance of the components other than boron and iron in example 4a is lower, resulting in a decrease in the magnetic properties of the sintered ndfeb magnet compared to example 2, the balance of the components other than boron and iron in example 4b is 28.4wt% of the total mass of the raw materials, the balance of the components other than boron and iron in example 4b is higher, and the magnetic properties of the sintered ndfeb magnet are similar to those of example 2.
By combining example 2 with examples 5a-5b and table 2, it can be seen that the total mass of praseodymium, neodymium and dysprosium in example 5a accounts for 19.7wt% of the total mass of the raw materials, the ratio of praseodymium, neodymium and dysprosium in example 5 is low, the performance of the sintered ndfeb magnet in example 5 is inferior to that of example 2, the total mass of praseodymium, neodymium and dysprosium in example 5b accounts for 21.8wt% of the total mass of the raw materials, the ratio of praseodymium, neodymium and dysprosium in example 5 is high, and the performance of the sintered ndfeb magnet in example 5 is slightly superior to that of example 2, but the two are close.
The reason for this may be: the higher the ratio of the total mass of praseodymium, neodymium and dysprosium is, the better the magnetic performance of the neodymium-iron-boron magnet is, but with the increase of the ratio of the praseodymium, the neodymium and the dysprosium, the production cost of the neodymium-iron-boron magnet also increases, and the trend of improving the magnetic performance of the magnet tends to be stable.
It can be seen from the combination of example 2 and examples 6a to 6b and table 2 that the ratio of the sum of the mass of praseodymium and neodymium to the mass of cerium in example 6a is 2.75:1, the ratio of the sum of the mass of praseodymium and neodymium to the mass of cerium in example 6a is low, and the amount of cerium replacing neodymium is too much, resulting in that the magnetic performance of example 6a is lower than that of example 2. The ratio of the sum of the mass of praseodymium and neodymium to the mass of cerium in example 6b was 3.70:1, the ratio of the sum of the mass of praseodymium and neodymium to the mass of cerium was high in example 6b, the amount of cerium substituted for neodymium was not large, and the magnetic performance of example 6b was slightly higher than that of example 2, but was closer.
The reason for this may be: cerium is used for replacing part of expensive neodymium elements, the magnetic performance of the neodymium-iron-boron magnet can be guaranteed by controlling the proportion of the cerium elements and the neodymium elements, and the magnetic performance of the neodymium-iron-boron magnet can be obviously reduced by adding too much cerium elements.
As can be seen by combining example 1 and comparative example 1 and table 2, the magnetic performance of the sintered ndfeb magnet prepared without adding holmium in comparative example 1 is obviously inferior to that of the sintered ndfeb magnet prepared with adding holmium in example 1, which shows that the addition of holmium element can improve the magnetic performance of the sintered ndfeb magnet.
Combining example 1 and comparative example 2 and table 2, it can be seen that the amount of cerium used in comparative example 2 is 28kg, and the content of cerium in the magnet is relatively high, which results in a decrease in the magnetic properties of the sintered ndfeb magnet prepared in comparative example 2.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.
Claims (7)
1. The sintered neodymium-iron-boron magnet is characterized by comprising the following raw materials in parts by mass: 0.5-0.7 part of lanthanum, 20-24 parts of cerium, 16-20 parts of praseodymium, 50-54 parts of neodymium, 0.1-0.2 part of samarium, 6-8 parts of dysprosium, 0.2-0.4 part of holmium, 20-22 parts of boron, 255 parts of iron 248-doped iron, wherein the total mass of praseodymium, neodymium and dysprosium is 20-21wt% of the total mass of the raw materials, the mass of cerium is 5.6-6.2wt% of the total mass of the raw materials, and the mass ratio of the sum of the mass of praseodymium and neodymium to the mass of cerium is (3.1-3.3): 1.
2. the sintered nd-fe-b magnet according to claim 1, wherein: the rest components except boron and iron account for 26.3 to 27.5 weight percent of the total mass of the raw materials.
3. The method for preparing the sintered NdFeB magnet according to any one of claims 1-2, comprising the following steps:
s1, preparing the ingredients
Weighing the components in proportion;
s2, smelting
Vacuum melting is carried out on the components weighed in the S1;
s3, hydrogen cracking
Hydrogen crushing the components subjected to vacuum melting in S2 to obtain coarse particles;
s4, preparing powder
Crushing the coarse particles in the S3 to prepare alloy powder, wherein an antioxidant is added in the crushing process;
s5, molding
Pressing and forming the alloy powder in the S4 to obtain a pressed compact;
s6, sintering
Sintering the pressed compact in the S5;
s7 tempering treatment
And (4) tempering the sintered pressed compact in the step (S6), and cooling by water to obtain the sintered neodymium-iron-boron magnet.
4. The method for preparing the sintered NdFeB magnet according to claim 3, wherein: in S4, the alloy powder has a particle size of 3-5 μm.
5. The method for preparing the sintered NdFeB magnet according to claim 3, wherein: in S5, the press forming is performed by cold isostatic pressing.
6. The method for preparing the sintered NdFeB magnet according to claim 3, wherein: in S6, the sintering adopts a circulating sintering process, which is specifically implemented as follows: 1100 ℃ X0.5 h, 1060 ℃ X3 h, 1100 ℃ X0.5 h, 1060 ℃ X3 h.
7. The method for preparing the sintered NdFeB magnet according to claim 3, wherein: in S7, the tempering treatment specifically includes: 880-920 ℃ for 2-3h and 500-540 ℃ for 2-3 h.
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|---|---|---|---|---|
| CN102280240A (en) * | 2011-08-23 | 2011-12-14 | 南京理工大学 | Method for preparing sintered NdFeB with low dysprosium content and high performance |
| CN104715876A (en) * | 2013-12-11 | 2015-06-17 | 北京中科三环高技术股份有限公司 | Mixed rare earth sintering permanent magnet and preparation method thereof |
| CN109585113A (en) * | 2018-11-30 | 2019-04-05 | 宁波韵升股份有限公司 | A kind of preparation method of Sintered NdFeB magnet |
| CN112562952A (en) * | 2020-11-20 | 2021-03-26 | 宁波合力磁材技术有限公司 | Neodymium-iron-boron permanent magnet material and preparation method thereof |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102280240A (en) * | 2011-08-23 | 2011-12-14 | 南京理工大学 | Method for preparing sintered NdFeB with low dysprosium content and high performance |
| CN104715876A (en) * | 2013-12-11 | 2015-06-17 | 北京中科三环高技术股份有限公司 | Mixed rare earth sintering permanent magnet and preparation method thereof |
| CN109585113A (en) * | 2018-11-30 | 2019-04-05 | 宁波韵升股份有限公司 | A kind of preparation method of Sintered NdFeB magnet |
| CN112562952A (en) * | 2020-11-20 | 2021-03-26 | 宁波合力磁材技术有限公司 | Neodymium-iron-boron permanent magnet material and preparation method thereof |
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