CN113223801A - High-boron neodymium-iron-boron permanent magnet and preparation method thereof - Google Patents
High-boron neodymium-iron-boron permanent magnet and preparation method thereof Download PDFInfo
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- CN113223801A CN113223801A CN202110556006.7A CN202110556006A CN113223801A CN 113223801 A CN113223801 A CN 113223801A CN 202110556006 A CN202110556006 A CN 202110556006A CN 113223801 A CN113223801 A CN 113223801A
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Abstract
The application relates to the field of magnetic materials, and particularly discloses a high-boron neodymium-iron-boron permanent magnet and a preparation method thereof. The high-boron neodymium-iron-boron permanent magnet comprises the following raw materials in parts by weight: 145 parts of praseodymium-neodymium 130-doped material, 18-23 parts of holmium-iron, 38-45 parts of cerium, 28-33 parts of boron, 0.7-1.5 parts of copper, 2-4 parts of aluminum, 2-4 parts of zirconium, 3-5 parts of cobalt and 380 parts of iron 370-doped material; the preparation method comprises the following steps: weighing the raw materials according to a proportion, sequentially carrying out vacuum melting, hydrogen explosion treatment, grinding, press forming, vacuum sintering and secondary tempering treatment, and cooling to obtain the neodymium iron boron permanent magnet. The high-boron neodymium iron boron permanent magnet has the advantage that the production cost of the neodymium iron boron permanent magnet is reduced while the magnetic performance of the neodymium iron boron permanent magnet is kept basically unchanged.
Description
Technical Field
The application relates to the field of magnetic materials, in particular to a high-boron neodymium-iron-boron permanent magnet and a preparation method thereof.
Background
In recent years, the price of rare earth metal is continuously increased, which leads to the increase of the production cost of the ndfeb permanent magnet, cerium is usually adopted to replace expensive rare earth elements such as praseodymium and neodymium so as to reduce the production cost, but a large amount of cerium replaces praseodymium and neodymium to cause the magnetic performance of the ndfeb permanent magnet to be reduced, and the use requirement is not met.
Therefore, a method for reducing the production cost and keeping the magnetic performance of the neodymium iron boron permanent magnet basically unchanged is required to be searched.
Disclosure of Invention
In order to reduce the production cost of the neodymium iron boron permanent magnet while keeping the magnetic performance of the neodymium iron boron permanent magnet unchanged basically, the application provides a high-boron neodymium iron boron permanent magnet and a preparation method thereof.
In a first aspect, the present application provides a high-boron neodymium-iron-boron permanent magnet, which adopts the following technical scheme:
the high-boron neodymium-iron-boron permanent magnet comprises the following raw materials in parts by weight: 145 parts of praseodymium and neodymium, 18-23 parts of holmium iron, 38-45 parts of cerium, 28-33 parts of boron, 0.7-1.5 parts of copper, 2-4 parts of aluminum, 2-4 parts of zirconium, 3-5 parts of cobalt and 385 parts of iron 370.
By adopting the technical scheme, because cerium is adopted to replace part of praseodymium and neodymium and higher boron content is adopted, the prepared neodymium iron boron permanent magnet has high coercivity, and the remanence does not decline or even rises.
Preferably, the holmium accounts for 2.5-2.7% of the total mass of the raw materials.
By adopting the technical scheme, a certain amount of holmium elements are added, so that the distribution of neodymium-rich phases in the neodymium iron boron ingot is uniform, and the distribution state of a neodymium-rich liquid phase in the sintering process of the magnet is favorably improved, thereby promoting the sintering densification process of the magnet, improving the densification degree of the magnet, and enabling the neodymium-rich phases in the magnet to form a uniform distribution state.
Meanwhile, the addition of the holmium element can reduce or even eliminate alpha-Fe phase in the neodymium iron boron ingot and promote the directional growth of main phase grains, so that the crushing performance of the neodymium iron boron ingot is improved, and neodymium iron boron powder with uniform particle size distribution is conveniently prepared in the subsequent powder making process, thereby improving the oxidation resistance of the neodymium iron boron powder and simultaneously reducing the magnetic agglomeration effect among powder particles.
The magnetic agglomeration effect is reduced, the magnetic field orientation process of the powder is favorably and smoothly carried out, and the phenomenon of abnormal growth of crystal grains in the sintering process of the magnet is reduced or even avoided to a certain extent, so that the crystal grain size distribution of the magnet is uniform, and the average crystal grain size is reduced to a certain extent.
A certain amount of holmium element is added, although the anisotropy field of the main phase is not improved, the intrinsic coercive force of the sintered magnet is still greatly improved due to the improvement of the microstructures of the neodymium iron boron alloy ingot and the sintered magnet.
The addition of a large amount of holmium elements can have adverse effects on the squareness of the J-H demagnetization curve of the magnet, even cause the J-H demagnetization curve to have obvious step shape defects, thereby reducing the maximum magnetic energy product of the sintered magnet.
Preferably, the mass of the cerium accounts for 6.6-6.8% of the total mass of the raw materials.
By adopting the technical scheme, the magnetic performance of the neodymium iron boron is basically unchanged while the cost is reduced by adding a certain amount of cerium.
If the content of cerium is low, the production cost cannot be greatly reduced. If the content of cerium is too high, the magnetic properties of neodymium iron boron are reduced.
Preferably, the mass of the boron accounts for 4.8-5.0% of the total mass of the raw materials.
By adopting the technical scheme, the high boron content is beneficial to obtaining high coercive force but not beneficial to obtaining high remanence, the boron content is controlled within the range of 4.8-5.0%, the remanence is not obviously reduced while the high boron content is ensured, and the total remanence is not reduced or even increased by matching with other elements.
If the boron content is less than 4.8%, the coercivity of the prepared neodymium iron boron permanent magnet is low, and the best magnetic performance cannot be obtained. If the boron content is more than 4.8%, the prepared neodymium iron boron permanent magnet has high coercive force, but the remanence is obviously reduced, so that the excellent comprehensive magnetic performance is not obtained.
Preferably, the mass of the praseodymium-neodymium accounts for 22.0-22.5% of the total mass of the raw materials.
By adopting the technical scheme, the coercive force and the cost of the neodymium-iron-boron permanent magnet are increased along with the increase of the praseodymium-neodymium content, the remanence tends to be reduced, and when the rare earth content is 22.0-22.5%, the neodymium-iron-boron permanent magnet can obtain the best comprehensive magnetic performance.
If the praseodymium-neodymium content is less than 22.0%, the prepared neodymium-iron-boron permanent magnet cannot have excellent magnetic performance. If the content of praseodymium and neodymium is more than 22.5%, the cost for preparing the neodymium-iron-boron permanent magnet is greatly improved, and the magnetic performance is improved to some extent, but the method is not helpful to practical use.
Preferably, the mass ratio of the praseodymium-neodymium to the cerium is (3.2-3.3): 1.
by adopting the technical scheme, the mass ratio of the praseodymium-neodymium to the cerium is (3.2-3.3): 1, the prepared neodymium iron boron permanent magnet has excellent comprehensive magnetic performance and is low in production cost.
If the mass ratio of praseodymium-neodymium to cerium is less than 3.2: 1, namely the content of cerium is increased, the production cost is reduced, but the magnetic performance of the neodymium iron boron permanent magnet is also reduced.
If the mass ratio of praseodymium-neodymium to cerium is more than 3.2: 1, the proportion of praseodymium and neodymium is larger, and the magnetic performance of the neodymium-iron-boron permanent magnet is improved, but the production cost is increased.
In a second aspect, the application provides a preparation method of a high-boron neodymium-iron-boron permanent magnet, which adopts the following technical scheme:
a preparation method of a high-boron neodymium-iron-boron permanent magnet comprises the following preparation steps:
s1, pretreatment
Weighing the raw materials according to a proportion, and carrying out vacuum melting to obtain a neodymium iron boron ingot;
s2, hydrogen fragmentation
Performing hydrogen explosion treatment on the neodymium iron boron cast ingot to obtain neodymium iron boron particles;
s3, preparing powder
Grinding the neodymium iron boron particles to obtain neodymium iron boron powder;
s4, molding
Pressing and molding neodymium iron boron powder to obtain a neodymium iron boron green body;
s5, sintering
And carrying out vacuum sintering and secondary tempering treatment on the neodymium iron boron green body, and cooling to obtain the neodymium iron boron permanent magnet.
By adopting the technical scheme, the neodymium iron boron permanent magnet with good comprehensive magnetic performance is obtained through a series of preparation steps of hydrogen crushing, grinding, pressing, sintering and the like.
Preferably, in S3, the oxygen content is controlled to be less than 500 ppm.
By adopting the technical scheme, in the powder preparation process, the oxygen content has a large influence on the performance of the neodymium iron boron permanent magnet, and the lower the oxygen content is, the better the corrosion resistance of the sintered neodymium iron boron magnetic material is. If the oxygen content in the magnet is very high, rare earth oxide formed in the subsequent sintering process exists in the grain boundary in the form of solid particles, so that the infiltration effect of the neodymium-rich phase relative to the main phase grains is reduced, the neodymium-rich phase is easily enriched at the corner of the grain boundary, the oxygen content of the local area of the neodymium-iron-boron permanent magnet is improved, the surface corrosion of the neodymium-iron-boron permanent magnet is promoted to be expanded inwards, the main phase grains are separated, the weight loss rate is improved, and the corrosion resistance of the neodymium-iron-boron permanent magnet is reduced.
Preferably, the carbon content of the neodymium iron boron permanent magnet is in the range of 0.4-0.5 ppm.
By adopting the technical scheme, the antioxidant and the lubricant are added before compression molding, carbon is introduced by the addition of the antioxidant and the lubricant, and part of carbon is not removed in the sintering process and remains in the neodymium iron boron permanent magnet. If the carbon content is too high, the corrosion resistance of the neodymium iron boron permanent magnet is affected, and the service life of the neodymium iron boron permanent magnet is further affected.
In summary, the present application has the following beneficial effects:
1. because the method adopts the cheap rare earth elements to replace expensive rare earth elements and has higher boron content, the production cost of the neodymium iron boron permanent magnet is reduced, and the comprehensive magnetic performance of the neodymium iron boron permanent magnet is ensured not to be reduced;
2. according to the method, a certain amount of holmium element is preferably added into the raw materials, and the holmium element can promote the directional growth of main phase grains, so that the crushing performance of the neodymium-iron-boron cast ingot is improved, and the subsequent obtaining of neodymium-iron-boron powder with uniform particle size distribution is facilitated;
3. in the application, the mass of boron is preferably 4.8-5.0% of the total mass of the raw materials, and in the range, the neodymium iron boron permanent magnet can obtain high coercive force and the remanence is basically unchanged;
4. according to the method, the neodymium iron boron permanent magnet with good comprehensive magnetic performance is obtained through a series of preparation steps of hydrogen crushing, grinding, pressing, sintering and the like.
Detailed Description
The present application will be described in further detail with reference to examples.
Examples
The high-boron neodymium-iron-boron permanent magnet comprises the following raw materials in parts by weight: 145 parts of praseodymium and neodymium, 18-23 parts of holmium iron, 38-45 parts of cerium, 28-33 parts of boron, 0.7-1.5 parts of copper, 2-4 parts of aluminum, 2-4 parts of zirconium, 3-5 parts of cobalt and 385 parts of iron 370.
Wherein, the mass of holmium accounts for 2.5-2.7% of the total mass of the raw materials, the mass of cerium accounts for 6.6-6.8% of the total mass of the raw materials, the mass of boron accounts for 4.8-5.0% of the total mass of the raw materials, and the mass of praseodymium and neodymium accounts for 22.0-22.5% of the total mass of the raw materials.
The mass ratio of praseodymium-neodymium to cerium is preferably (3.2-3.3): 1.
a preparation method of a high-boron neodymium-iron-boron permanent magnet comprises the following preparation steps:
s1, pretreatment
Weighing the raw materials according to a proportion, putting the weighed raw materials into a vacuum sintering furnace for vacuum smelting to obtain neodymium iron boron cast ingots;
s2, hydrogen fragmentation
Performing hydrogen explosion treatment on the neodymium iron boron cast ingot to obtain neodymium iron boron particles;
s3, preparing powder
Grinding the neodymium iron boron particles, and adding a lubricant and an antioxidant according to needs before grinding to obtain neodymium iron boron powder with the particle size of 3-4 mu m;
s4, molding
Performing compression molding on the neodymium iron boron powder under the conditions of an oriented compression magnetic field of 2T, isostatic pressure of 240-260MPa and compression time of 80-100s to obtain a neodymium iron boron green body;
s5, sintering
Carrying out vacuum sintering and secondary tempering treatment on the neodymium iron boron green body, wherein the vacuum sintering comprises two stages: the first stage, heating to 740-; and in the second stage, the temperature is raised to 1020-1060 ℃, the temperature is kept for 1.5-2.5h, the temperature raising rate is 5-6 ℃/min, and the neodymium iron boron permanent magnet is obtained through natural cooling.
Example 1
A preparation method of a high-boron neodymium-iron-boron permanent magnet comprises the following preparation steps:
s1, pretreatment
Weighing the raw materials according to a proportion, wherein the components and the using amount of the raw materials are shown in table 1, and putting the weighed raw materials into a vacuum sintering furnace for vacuum smelting to obtain a neodymium iron boron ingot;
s2, hydrogen fragmentation
Performing hydrogen explosion treatment on the neodymium iron boron cast ingot to obtain neodymium iron boron particles;
s3, preparing powder
Grinding the neodymium iron boron particles to obtain neodymium iron boron powder with the particle size of 3-4 mu m;
s4, molding
Pressing and molding the neodymium iron boron powder under the condition of an orientation pressing magnetic field of 2T, isostatic pressing of 260MPa and pressing time of 80s to obtain a neodymium iron boron green body;
s5, sintering
Carrying out vacuum sintering and secondary tempering treatment on the neodymium iron boron green body, wherein the vacuum sintering comprises two stages: in the first stage, the mixture is firstly heated to 740 ℃ at normal temperature, and the temperature is kept for 1.5h, wherein the heating rate is 8 ℃/min; and in the second stage, raising the temperature to 1020 ℃, preserving the heat for 2h, raising the temperature at the rate of 5 ℃/min, and naturally cooling to obtain the neodymium iron boron permanent magnet.
Example 2
A preparation method of a high-boron neodymium-iron-boron permanent magnet comprises the following preparation steps:
s1, pretreatment
Weighing the raw materials according to a proportion, wherein the components and the using amount of the raw materials are shown in table 1, and putting the weighed raw materials into a vacuum sintering furnace for vacuum smelting to obtain a neodymium iron boron ingot;
s2, hydrogen fragmentation
Performing hydrogen explosion treatment on the neodymium iron boron cast ingot to obtain neodymium iron boron particles;
s3, preparing powder
Grinding the neodymium iron boron particles to obtain neodymium iron boron powder with the particle size of 3-4 mu m;
s4, molding
Pressing and molding the neodymium iron boron powder under the condition of an orientation pressing magnetic field of 2T, isostatic pressing of 240MPa and pressing time of 100s to obtain a neodymium iron boron green body;
s5, sintering
Carrying out vacuum sintering and secondary tempering treatment on the neodymium iron boron green body, wherein the vacuum sintering comprises two stages: in the first stage, the mixture is firstly heated to 740 ℃ at normal temperature, and the temperature is kept for 1.5h, wherein the heating rate is 8 ℃/min; and in the second stage, raising the temperature to 1020 ℃, preserving the heat for 2h, raising the temperature at the rate of 5 ℃/min, and naturally cooling to obtain the neodymium iron boron permanent magnet.
Example 3
A preparation method of a high-boron neodymium-iron-boron permanent magnet comprises the following preparation steps:
s1, pretreatment
Weighing the raw materials according to a proportion, wherein the components and the using amount of the raw materials are shown in table 1, and putting the weighed raw materials into a vacuum sintering furnace for vacuum smelting to obtain a neodymium iron boron ingot;
s2, hydrogen fragmentation
Performing hydrogen explosion treatment on the neodymium iron boron cast ingot to obtain neodymium iron boron particles;
s3, preparing powder
Grinding the neodymium iron boron particles to obtain neodymium iron boron powder with the particle size of 3-4 mu m;
s4, molding
Pressing and molding the neodymium iron boron powder under the condition of an orientation pressing magnetic field of 2T, isostatic pressing of 260MPa and pressing time of 80s to obtain a neodymium iron boron green body;
s5, sintering
Carrying out vacuum sintering and secondary tempering treatment on the neodymium iron boron green body, wherein the vacuum sintering comprises two stages: in the first stage, the mixture is firstly heated to 760 ℃ at normal temperature, and the temperature is kept for 1h, wherein the heating rate is 8 ℃/min; and in the second stage, raising the temperature to 1060 ℃, preserving the heat for 1.5h, raising the temperature at the rate of 5 ℃/min, and naturally cooling to obtain the neodymium iron boron permanent magnet.
Table 1 the raw material components and their amounts in examples 1-3
| Raw material dosage/g | Example 1 | Example 2 | Example 3 |
| Praseodymium neodymium | 136.5 | 130 | 145 |
| Holmium iron | 21 | 18 | 23 |
| Cerium (Ce) | 42 | 38 | 45 |
| Boron | 30 | 28 | 33 |
| Copper (Cu) | 1.2 | 0.7 | 1.5 |
| Aluminium | 2.5 | 2 | 4 |
| Zirconium | 2.6 | 2 | 4 |
| Cobalt | 4 | 3 | 5 |
| Iron | 380.2 | 370 | 385 |
Example 4
The preparation method of the high-boron neodymium-iron-boron permanent magnet in the embodiment is the same as that in the embodiment 1, except that the dosage of boron is 28g, the dosage of iron is 382.2g, and other raw materials are kept unchanged.
Example 5
The preparation method of the high-boron neodymium-iron-boron permanent magnet in the embodiment is the same as that in the embodiment 1, except that the dosage of boron is 33g, the dosage of iron is 377.2g, and other raw materials are kept unchanged.
Comparative example
Comparative example 1
The preparation method of the high-boron neodymium-iron-boron permanent magnet in the comparative example is the same as that in example 1, except that the amount of boron is 25g, the amount of iron is 385.2g, and other raw materials are kept unchanged.
Comparative example 2
The preparation method of the high-boron neodymium-iron-boron permanent magnet in the comparative example is the same as that of the example 1, and the difference is that the dosage of boron is 36g, the dosage of iron is 374.2g, and other raw materials are kept unchanged.
Comparative example 3
The preparation method of the high-boron neodymium-iron-boron permanent magnet in the comparative example is the same as that in example 1, except that the mass of holmium accounts for 2% of the total mass of the raw materials, the mass fraction of praseodymium and neodymium in the raw materials is correspondingly changed, and other raw materials are kept unchanged.
Comparative example 4
The preparation method of the high-boron neodymium-iron-boron permanent magnet in the comparative example is the same as that in example 1, except that the mass of holmium accounts for 3% of the total mass of the raw materials, the mass fraction of praseodymium and neodymium in the raw materials is correspondingly changed, and other raw materials are kept unchanged.
Comparative example 5
The preparation method of the high-boron neodymium-iron-boron permanent magnet in the comparative example is the same as that in example 1, and the difference is only that the mass ratio of praseodymium-neodymium to cerium is 2: 1.
comparative example 6
The preparation method of the high-boron neodymium-iron-boron permanent magnet in the comparative example is the same as that in example 1, and only the difference is that the mass ratio of praseodymium-neodymium to cerium is 4: 1.
performance test
Residual magnetism Br: detecting by using an AMT-4 magnetization characteristic automatic measuring instrument;
intrinsic coercive force Hcj: the AMT-4 magnetization characteristic automatic measuring instrument is used for detection.
TABLE 2 test results of examples 1 to 5 and comparative examples 1 to 4
| Br（kGs） | Hcj（kOe） | |
| Example 1 | 11.7 | 16.16 |
| Example 2 | 11.3 | 15.53 |
| Example 3 | 11.5 | 15.81 |
| Example 4 | 11.4 | 15.73 |
| Example 5 | 11.2 | 16.38 |
| Comparative example 1 | 11.6 | 14.97 |
| Comparative example 2 | 10.8 | 16.64 |
| Comparative example 3 | 11.6 | 15.49 |
| Comparative example 4 | 11.3 | 16.31 |
| 38m | About 11.8 | 14-17 |
As can be seen by combining examples 1-3 with Table 2, the NdFeB permanent magnets prepared in examples 1-3 have good comprehensive magnetic performance which is similar to that of the magnet with the model number of 38 m.
This shows that the magnetic performance of the ndfeb permanent magnet is kept basically unchanged while the production cost is reduced by adopting the ndfeb permanent magnet prepared in the application.
Combining example 1, examples 4-5 and comparative examples 1-2 with table 2, it can be seen that the remanence of the ndfeb permanent magnet in example 1 is greater than that of examples 4-5, but the remanence measured in examples 4-5 is similar to that of 38 m.
The coercive force of the neodymium iron boron permanent magnet in the comparative example 2 is larger than that of the neodymium iron boron permanent magnet in the embodiment 5, the coercive force of the neodymium iron boron permanent magnet in the embodiment 5 is larger than that of the embodiment 1, but the difference between the remanence measured by the neodymium iron boron permanent magnet in the comparative example 2 and the remanence of 38m is larger.
The reason for this may be: the high boron content is beneficial to obtaining high coercive force, but is not beneficial to obtaining high remanence, the boron content is controlled within the range of 4.8-5.0%, the remanence is not obviously reduced while the high coercive force is ensured, and the total remanence is not reduced or even increased through the matching of other elements.
If the boron content is less than 4.8%, the coercivity of the prepared neodymium iron boron permanent magnet is low, and the best magnetic performance cannot be obtained. If the boron content is more than 4.8%, the prepared neodymium iron boron permanent magnet has high coercive force, but the remanence is obviously reduced, so that the excellent comprehensive magnetic performance is not obtained.
Combining example 1 and comparative examples 3-4 and table 2, it can be seen that the coercivity of the ndfeb permanent magnet in comparative example 4 is greater than the coercivity of the ndfeb permanent magnet in example 1, but the rise is limited, and the remanence of the ndfeb permanent magnet in comparative example 4 is similar to the remanence of the ndfeb permanent magnet in example 1.
The coercive force of the neodymium iron boron permanent magnet in the comparative example 3 is smaller than that of the neodymium iron boron permanent magnet in the example 1, and the remanence of the neodymium iron boron permanent magnet in the comparative example 4 is smaller than that of the neodymium iron boron permanent magnet in the example 1.
The reason for this may be: in a certain range, the limit structure of the neodymium iron boron permanent magnet can be improved by adding holmium element, so that the coercive force of the neodymium iron boron permanent magnet is improved, but if the adding amount is too small, the influence is not obvious. After the range is exceeded, the coercive force of the neodymium iron boron permanent magnet does not rise obviously with the increase of the addition amount of the holmium element, gradually tends to balance, and the remanence decreases.
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 (9)
1. The high-boron neodymium-iron-boron permanent magnet is characterized by comprising the following raw materials in parts by mass: 145 parts of praseodymium and neodymium, 18-23 parts of holmium iron, 38-45 parts of cerium, 28-33 parts of boron, 0.7-1.5 parts of copper, 2-4 parts of aluminum, 2-4 parts of zirconium, 3-5 parts of cobalt and 385 parts of iron 370.
2. The high-boron neodymium-iron-boron permanent magnet according to claim 1, characterized in that: the holmium accounts for 2.5-2.7% of the total mass of the raw materials.
3. The high-boron neodymium-iron-boron permanent magnet according to claim 1, characterized in that: the mass of the cerium accounts for 6.6-6.8% of the total mass of the raw materials.
4. The high-boron neodymium-iron-boron permanent magnet according to claim 1, characterized in that: the mass of the boron accounts for 4.8-5.0% of the total mass of the raw materials.
5. The high-boron neodymium-iron-boron permanent magnet according to claim 1, characterized in that: the mass of the praseodymium-neodymium accounts for 22.0-22.5% of the total mass of the raw materials.
6. The high-boron neodymium-iron-boron permanent magnet according to claim 1, characterized in that: the mass ratio of the praseodymium-neodymium to the cerium is (3.2-3.3): 1.
7. the method for preparing the high-boron neodymium-iron-boron permanent magnet according to any one of claims 1 to 6, characterized by comprising the following preparation steps:
s1, pretreatment
Weighing the raw materials according to a proportion, and carrying out vacuum melting to obtain a neodymium iron boron ingot;
s2, hydrogen fragmentation
Performing hydrogen explosion treatment on the neodymium iron boron cast ingot to obtain neodymium iron boron particles;
s3, preparing powder
Grinding the neodymium iron boron particles to obtain neodymium iron boron powder;
s4, molding
Performing compression molding on the neodymium iron boron powder under the conditions of an oriented compression magnetic field of 2T, isostatic pressure of 240-260MPa and compression time of 80-100s to obtain a neodymium iron boron green body;
s5, sintering
Carrying out vacuum sintering and secondary tempering treatment on the neodymium iron boron green body, wherein the vacuum sintering comprises two stages: the first stage, heating to 740-; and in the second stage, the temperature is raised to 1020-1060 ℃, the temperature is kept for 1.5-2.5h, the temperature raising rate is 5-6 ℃/min, and the neodymium iron boron permanent magnet is obtained through natural cooling.
8. The method for preparing the high-boron neodymium-iron-boron permanent magnet according to claim 7, characterized by comprising the following steps: in S3, the oxygen content is controlled to be less than 500 ppm.
9. The method for preparing the high-boron neodymium-iron-boron permanent magnet according to claim 7, characterized by comprising the following steps: the carbon content of the neodymium iron boron permanent magnet is within the range of 0.4-0.5 ppm.
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