WO2022126949A1 - Method for nitriding rare-earth magnet, and nitrided rare-earth magnet - Google Patents

Abstract

A method for nitriding a rare-earth magnet, comprising: 1) vacuumizing, adding a nitrogen source into a reactor filled with the rare-earth magnet, and performing three-stage heating treatment to obtain a semi-finished product, the heating temperature of the three-stage heating treatment is increased stage by stage; and 2) raising the temperature of the semi-finished product to a first set temperature, then adjusting the temperature to a second set temperature, vacuumizing, introducing inert gas, and performing heat preservation at the second set temperature to obtain a nitrided rare-earth magnet, the second set temperature being lower than the first set temperature.

Description

Method for nitriding rare earth magnet and nitriding rare earth magnet technical field

The application belongs to the technical field of magnetic materials, and relates to a method for nitriding rare earth magnets and a nitriding rare earth magnet.

Background technique

In recent years, with the progress and development of science and technology, the application of magnetic materials has become more and more extensive, and people's lives are more and more inseparable from magnetic materials. Magnetic materials are divided into permanent magnetic materials and soft magnetic materials, and different properties have different uses. Rare earth magnetic materials are widely used due to their excellent magnetic properties.

The most commonly used rare earth permanent magnet material is NdFeB, which is currently the rare earth permanent magnet material with the highest magnetic energy product of permanent magnet performance. However, due to the low content of rare earth elements in the earth's crust, the mining and purification costs are very high, resulting in the high cost of NdFeB materials with high performance.

Samarium iron nitrogen magnets avoid the disadvantages of low Curie temperature, easy oxidation and high cost of neodymium iron boron magnets, and become a hot spot in the research of a new generation of rare earth permanent magnet materials. The introduction of nitrogen atoms does not change the crystal structure of the samarium iron alloy, but causes the lattice expansion, which enhances the ferromagnetic coupling exchange effect of the alloy, greatly increases the Curie temperature of the alloy, and enhances the anisotropy field. The key to magnetic properties, so the nitriding process plays a crucial role in the preparation of samarium iron nitrogen magnets. At present, the relatively mature nitriding process at home and abroad is to obtain alloy powder by mechanical method first, and then carry out nitriding treatment. Solid powder nitriding has the disadvantages of uneven nitriding, incomplete nitriding, low efficiency and easy oxidation of powder.

Rare earth-iron-nitrogen materials, including SmFeN, NdFeN, CeFeN, etc., some use the permanent magnetic properties of the materials, and some use the soft magnetic properties of the materials, but in the preparation process, the preparation method is to form a rare earth-iron alloy first, and then to the alloy. Nitriding is carried out.

Computers, mobile phones, network equipment, etc. used in modern communication will generate electromagnetic interference and electromagnetic radiation in the process of use. In order to effectively reduce and eliminate electromagnetic interference and radiation, it is necessary to use absorbing materials with high complex magnetic permeability. The currently widely used ferrite materials have shortcomings such as narrow frequency band and low complex magnetic permeability at high frequencies, while metal soft magnetic materials have eddy current losses that lead to low high frequency soft magnetic properties. Materials such as CeFeN can maintain high magnetic permeability and wide resonant frequency at high frequencies, can achieve electromagnetic shielding and reduce signal noise in a wide frequency band, meet modern technical requirements, and are widely used in instruments, meters, communications and other fields.

Rare earth transition metal magnetic materials will show excellent magnetic properties after nitridation, but insufficient nitrogen content and uneven distribution of nitrogen elements during the nitridation process will seriously affect the properties of the materials.

CN101699578A discloses a rare-earth iron-nitrogen high-frequency soft magnetic material and a composite material thereof and a preparation method. First, 10-30% wt of rare earth elements and 70-90% wt of iron are smelted into iron-based alloys, and then pulverized It is ground into small particles and then ground into powder, and then subjected to nitriding treatment. The treatment temperature is 250-550°C, and the chemical formula of the material is R ₂ Fe ₁₇ N _3-δ . However, the nitrogen content and uniformity of the product obtained by this method need to be improved.

CN 107557551A discloses a preparation method of samarium iron-nitrogen permanent magnet material. The metastable samarium iron alloy is subjected to large plastic deformation, and then subjected to nitriding treatment and annealing crystallization treatment, and the defects generated by the large plastic deformation are used to facilitate nitrogen The entry and diffusion of atoms significantly improve the nitriding amount and uniformity of the alloy. However, the process of this solution is too complicated, which leads to an increase in the preparation cost.

SUMMARY OF THE INVENTION

The purpose of the present application is to provide a method for nitriding rare earth magnets and nitriding rare earth magnets. The method provided by the present application solves the problems of insufficient nitrogen content and uneven distribution of nitrogen elements after nitridation of rare earth magnets.

For this purpose, the application adopts the following technical solutions:

In a first aspect, the present application provides a method for nitriding rare earth magnets, the method comprising the following steps:

(1) vacuumize, add nitrogen source to the reactor equipped with rare earth magnet, carry out three-stage heat treatment, obtain semi-finished product; The heating temperature of described three-stage heat treatment is raised section by section;

(2) the semi-finished product described in step (1) is heated to the first set temperature, then the temperature is adjusted to the second set temperature and vacuumized, and an inert gas is introduced, and at the second set temperature, heat preservation is performed to obtain A rare earth nitride magnet; the second set temperature is lower than the first set temperature.

In the method provided by this application, the three-stage heating treatment is the main nitriding process, which can ensure that the nitrogen-containing gas molecules adsorbed on the surface of the alloy diffuse into the alloy (rare earth magnet) to form a nitrogen-containing alloy (ie, a semi-finished product), so that nitrogen elements After being adsorbed to the powder surface, the diffusion kinetics can be reasonably utilized to increase the penetration depth of nitrogen elements, thereby increasing the nitrogen content; heating at the first set temperature is a homogenization treatment step, which can further promote the adsorption and diffusion of nitrogen elements into the alloy, The nitrogen element is distributed more uniformly in the alloy; and the heating at the second set temperature makes the nitrogen element diffuse evenly in the alloy.

In the method provided by the present application, the method of adjusting the temperature to the second set temperature and vacuuming in step (2) may be directly cooling to the second set temperature and then vacuuming, or cooling to room temperature first, vacuuming , and then reheat to the second set temperature.

In the method provided in the present application, three different parts of the obtained rare earth nitride magnet can be selected to measure the mass fraction of nitrogen element with a nitrogen element content detection device to check whether the distribution of nitrogen element is uniform.

In the present application, the rare earth magnet in step (1) may be a block or powder, and powder may be selected for better effect.

The following are optional technical solutions of the present application, but are not intended to limit the technical solutions provided by the present application. Through the following optional technical solutions, the technical purposes and beneficial effects of the present application can be better achieved and realized.

As an optional technical solution of the present application, the general formula of the rare earth magnet in step (1) is ReTm, wherein Re is a rare earth metal, and Tm is a 3d transition group element and/or a 4d transition group element. The 3d transition group elements include at least one of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu or Zn, and the 4d transition group elements refer to Y, Zr, Nb, Mo, Tc, At least one of Ru, Rh, Pd, Ag or Cd.

Optionally, the general formula of the rare earth nitride magnet is ReTmN. In the present application, the specific ratio of Re and Tm is not limited, as long as it can form a phase.

Optionally, the vacuuming in step (1) reduces the pressure of the reactor to below 1000Pa, for example, 900Pa, 500Pa, 100Pa, 50Pa, 10Pa, 5Pa, etc., optionally to below 10Pa.

Optionally, the nitrogen source in step (1) includes a gaseous nitrogen source and/or a solid nitrogen source.

Optionally, the gaseous nitrogen source is a nitrogen-containing gas.

Optionally, the gaseous nitrogen source includes nitrogen and/or ammonia.

Optionally, the gaseous nitrogen source further includes hydrogen.

Optionally, the solid nitrogen source includes ammonium bicarbonate.

Optionally, the nitrogen source in step (1) is a gaseous nitrogen source, and the pressure of the gaseous nitrogen source in the reactor is 0.001-10 MPa, such as 0.001 MPa, 1 MPa, 2 MPa, 5 MPa, 8 MPa or 10 MPa, etc., optional is 0.01-2MPa.

Optionally, the nitrogen source in step (1) is a solid nitrogen source, and before the three-stage heating treatment, a protective gas is introduced into the reactor to a pressure of 0.001-10 MPa, such as 0.001 MPa, 1 MPa, 2 MPa, 5 MPa , 8MPa or 10MPa, etc., optional 0.01-2MPa.

As an optional technical solution of the present application, the temperature of the first stage of the three-stage heating treatment in step (1) is 330-470K, such as 330K, 350K, 380K, 400K, 420K, 450K or 470K, etc., and can be 370-470K. 420K.

Optionally, the holding time of the first stage of the three-stage heating treatment in step (1) is 0-24h and does not include 0, such as 0.1h, 0.5h, 1h, 5h, 10h, 20h or 24, etc., which can be selected as 0.1-5h.

In the present application, the purpose of the first-stage heating in the three-stage heating in step (1) is to discharge the gas adsorbed in the ReTm alloy, especially oxygen, so as to avoid oxidation of the alloy during subsequent nitridation.

As an optional technical solution of the present application, the temperature of the second stage of the three-stage heating treatment in step (1) is 670-730K and does not include 730K, such as 670K, 680K, 690K, 700K, 710K or 720K, etc., which can be selected as 690-710K.

Optionally, the second-stage holding time of the three-stage heat treatment in step (1) is 0-24h and does not include 0, such as 0.1h, 0.5h, 1h, 5h, 10h, 20h or 24, etc., which can be selected as 0.1-5h.

In the present application, the function of the second-stage heating in the three-stage heating in step (1) is to preheat and adsorb the ReTm and N element atmosphere, so that the nitrogen-containing element atmosphere is fully adsorbed on the surface of ReTm.

As an optional technical solution of the present application, the temperature of the third stage of the three-stage heating treatment in step (1) is 730-830K and does not include 830K, such as 730K, 740K, 750K, 760K, 770K, 780K, 790K, 800K, 810K or 820K, etc., optional 750-780K.

Optionally, the holding time of the third stage of the three-stage heating treatment in step (1) is 0-24h and does not include 0, such as 0.1h, 0.5h, 1h, 5h, 10h, 20h or 24, etc., which can be selected as 0.1-5h.

In the present application, the purpose of the third-stage heating in the three-stage heating in step (1) is that the gas molecules adsorbed on the surface of the alloy can enter the interior of the alloy through diffusion to form a ReTmN alloy.

As an optional technical solution of the present application, the first set temperature in step (2) is 830-860K and does not include 860K, such as 830K, 835K, 840K, 845K or 850K, etc., and can be 830-840K. In the present application, if the first set temperature is too high, ReTmN will be decomposed into ReN and Tm phases, and the product will deviate from the desired composition; if the first set temperature is too low, the N content will be low and uneven.

Optionally, in step (2), the temperature rising time to the first set temperature is 0-24h and does not include 0, such as 1h, 5h, 10h, 15h, 20h or 24h, etc., optionally 0.5-24h 5h.

As an optional technical solution of the present application, the vacuuming described in step (2) reduces the pressure of the reactor to below 1000Pa, such as 900Pa, 500Pa, 100Pa, 50Pa, 10Pa, 5Pa, etc., and can be optionally reduced to below 10Pa.

Optionally, in step (2), the pressure of the reactor is adjusted to 0.001-1 MPa, such as 0.001 MPa, 0.01 MPa, 0.1 MPa, 0.5 MPa or 1 MPa, etc., by introducing an inert gas.

Optionally, the second set temperature in step (2) is 600-700K, such as 600K, 610K, 620K, 630K, 640K, 650K, 660K, 670K, 680K, 690K or 700K, etc., and can be 620-670K .

Optionally, the holding time described in step (2) for carrying out heat preservation at the second set temperature is 0-24h and does not include 0, such as 1h, 5h, 10h, 15h, 20h or 24h, etc., optionally 0.5-24h 5h.

As an optional technical solution of the present application, step (2) further includes: cooling to room temperature after heat preservation at the second set temperature.

As a further optional technical solution of the method described in this application, the method comprises the following steps:

(1) Place the rare earth magnet in the reactor, evacuate to below 1000Pa, pass in the gas containing nitrogen element, heat up to 370-420K for 0.1-5h, heat up to 690-710K for 0.1-5h, heat up to 750- 780K heat preservation for 0.1-5h to obtain semi-finished products;

(2) the semi-finished product described in step (1) is heated to 830-840K with 0.5-5h, then the temperature is adjusted to 620-670K and the pressure of the reactor is reduced to below 1000Pa by vacuuming, and the pressure of the inert gas reactor is adjusted It is 0.001-1MPa, and is kept at the second set temperature for 0.5-5h, and cooled to room temperature to obtain a rare earth nitride magnet.

In a second aspect, the present application provides a nitrided rare earth magnet obtained by the method for nitriding a rare earth magnet according to the first aspect.

Compared with the prior art, the present application has the following beneficial effects:

The method for nitriding rare earth magnets provided by the present application can increase the nitrogen content and at the same time make the distribution of nitrogen elements in the magnets more uniform, and solve the problems of insufficient nitrogen content and uneven distribution of nitrogen elements after nitriding rare earth magnets in the prior art .

Detailed ways

In order to better illustrate the present application and facilitate the understanding of the technical solutions of the present application, the present application will be described in further detail below. However, the following embodiments are only simple examples of the present application, and do not represent or limit the protection scope of the present application. The protection scope of the present application is subject to the claims.

The following are typical but non-limiting examples of the application:

Example 1

In this embodiment, the nitridation of rare earth magnets is carried out according to the following method:

(1) get the Sm ₂ Fe ₁₇ alloy block, put it into the nitriding furnace, evacuate until the pressure drops to 95Pa, close the evacuation system, and fill in the ammonia gas of 1.2MPa;

(2) be warmed up to 450K, keep warm for 2 hours;

(3) After the 450K temperature insulation is completed, the temperature is raised to 710K, and the temperature is kept for 1 hour;

(4) After the 710K heat preservation is completed, the temperature is raised to 780K, and the heat preservation is carried out for 5 hours to obtain a semi-finished product;

(5) After the 780K heat preservation is completed, the temperature is raised to 850K after 1 hour;

(6) Cool to 680K after the 850K heat preservation, extract the gas in the nitriding furnace, evacuate until the pressure drops to 90Pa, and then introduce 0.05MPa of argon, and keep the temperature for 3 hours;

(7) After the 680K heat preservation, it was cooled to room temperature, and the nitrided SmFeN alloy was taken out, and three different parts of the material were taken, and the mass fraction of nitrogen was measured with a nitrogen content detection device. The test results are shown in Table 1. .

Example 2

In this embodiment, the nitridation of rare earth magnets is carried out according to the following method:

(1) Take Sm ₂ Fe ₁₇ alloy powder with a particle size of 0.1 μm to 10 mm, put it into a nitriding furnace, vacuumize until the pressure drops to 9Pa, close the vacuuming system, and fill with 1.2MPa ammonia gas;

(2) be warmed up to 420K, keep warm for 2 hours;

(3) After the 420K temperature insulation is completed, the temperature is raised to 680K, and the temperature is kept for 1 hour;

(4) After the 680K heat preservation is completed, the temperature is raised to 750K, and the heat preservation is carried out for 4 hours;

(5) After the 750K heat preservation is completed, the temperature is raised to 830K for 1 hour to obtain a semi-finished product;

(6) Cool down to 670K after the 830K heat preservation, extract the gas in the nitriding furnace, evacuate until the pressure drops to 9Pa, then introduce 0.03MPa of argon, and keep it for 1 hour;

(7) After the 670K heat preservation, it was cooled to room temperature, and the nitrided SmFeN alloy powder was taken out, and three different parts of the material were taken, and the mass fraction of nitrogen was measured with a nitrogen content detection device. The test results are shown in Table 1. Show.

Example 3

Except for step (6) in Example 2, the rest are the same, step (6) in this embodiment is that the 830K insulation is finished and cooled to room temperature, the gas in the nitriding furnace is drawn out, evacuated until the pressure is reduced to below 10Pa, and then fed Argon gas of 0.03MPa was heated to 670K and kept for 1 hour.

Example 4

Except for step (1) in Example 2, the rest are the same. Step (1) in this embodiment is to close the vacuuming system and fill with 1.2MPa ammonia gas and hydrogen gas mixture (mixing molar ratio 1:1).

Example 5

SmFeN alloy was prepared under the same conditions as in Example 2, except that the Sm ₂ Fe ₁₇ alloy powder was replaced by the SmFe ₉ alloy powder.

Example 6

CeFeN alloy was prepared under the same conditions as in Example 2, except that the Sm ₂ Fe ₁₇ alloy powder was replaced with Ce ₂ Fe ₁₇ alloy powder.

Example 7

A NdFeN alloy was prepared under the same conditions as in Example 2, except that the Sm ₂ Fe ₁₇ alloy powder was replaced by the Nd ₂ Fe ₁₇ alloy powder.

Example 8

NdFeN alloy was prepared under the same conditions as in Example 2, except that the Sm ₂ Fe ₁₇ alloy powder was replaced with NdFe ₁₂ alloy powder.

Example 9

In this embodiment, the nitridation of rare earth magnets is carried out according to the following method:

(1) Take Sm ₂ Fe ₁₇ alloy powder with a particle size of 0.1 μm to 10 mm, put it in a nitriding furnace, vacuumize until the pressure drops to 5Pa, close the vacuuming system, and fill with a mixture of 0.01MPa nitrogen and ammonia Gas (mixed molar ratio 1:1);

(2) heat up to 400K, keep warm for 0.1 hour;

(3) After the 400K temperature insulation is completed, the temperature is raised to 700K, and the temperature is kept for 0.1 hour;

(4) After the 700K heat preservation is completed, the temperature is raised to 770K, and the heat preservation is carried out for 0.1 hour;

(5) After the 770K heat preservation is completed, the temperature is raised to 840K after 0.5 hours to obtain a semi-finished product;

(6) Cool to 650K after the 840K heat preservation, extract the gas in the nitriding furnace, evacuate until the pressure drops to 5Pa, then feed argon gas of 0.01MPa, and keep the temperature for 0.5 hours;

(7) After the 650K heat preservation, it was cooled to room temperature, and the nitrided SmFeN alloy powder was taken out, and three different parts of the material were taken, and the mass fraction of nitrogen was measured with a nitrogen content detection device. The test results are shown in Table 1. Show.

Example 10

In this embodiment, the nitridation of rare earth magnets is carried out according to the following method:

(1) Take Sm ₂ Fe ₁₇ alloy powder with a particle size of 0.1 μm to 10 mm, put it into a nitriding furnace, vacuumize until the pressure drops to 5Pa, close the vacuum system, and fill with 2MPa ammonia;

(2) be warmed up to 370K, keep warm for 5 hours;

(3) After the 370K temperature insulation is completed, the temperature is raised to 690K, and the temperature is kept for 5 hours;

(4) After the 690K heat preservation is completed, the temperature is raised to 770K, and the heat preservation is carried out for 5 hours;

(5) After the 770K heat preservation is completed, the temperature is raised to 835K for 5 hours to obtain a semi-finished product;

(6) Cool to 620K after the 835K heat preservation, extract the gas in the nitriding furnace, evacuate until the pressure drops to 5Pa, and then introduce 1MPa of argon, and keep it for 5 hours;

(7) After the 620K heat preservation, it was cooled to room temperature, and the nitrided SmFeN alloy powder was taken out, and three different parts of the material were taken, and the mass fraction of nitrogen was measured with a nitrogen content detection device. The test results are shown in Table 1. Show.

Example 11

Except that the operation in step (1) is to mix Sm ₂ Fe ₁₇ alloy powder (powder particle size between 0.1 μm and 10 mm) and mass ammonium bicarbonate and place it in a nitriding furnace, evacuate until the pressure drops to 9Pa, close the evacuation The SmFeN alloy was prepared under the same conditions as in Example 2 except that the system was filled with 1.2MPa argon.

Comparative Example 1

The difference between this comparative example and the method of Example 2 is only that the operations of step (2) and step (3) are not performed, and the operation of step (3) is to raise the temperature to 750K and keep the temperature for 4 hours.

Comparative Example 2

The difference between this comparative example and Example 2 is only that the operation of step (5) is not performed, and the step (6) is directly cooled from 750K to room temperature.

Comparative Example 3

The difference between this comparative example and the method of Example 2 is only that the operation of step (3) is not carried out, and the operation of step (4) is changed to 420K after the temperature preservation is completed, and then the temperature is raised to 750K for 4 hours.

testing method

For each example and comparative example, three different parts of the obtained rare earth nitride magnet were taken, and the mass fraction of nitrogen was measured with a nitrogen content detection device. The test results are shown in Table 1.

Table 1

Numbering	Nitrogen content/% (Part 1)	Nitrogen content/% (Part 2)	Nitrogen content/% (Part 3)
Example 1	3.61	3.68	3.65
Example 2	3.83	3.81	3.85
Example 3	3.73	3.71	3.70
Example 4	3.21	3.18	3.25
Example 5	3.36	3.40	3.43
Example 6	3.82	3.85	3.80
Example 7	0.95	0.93	0.97
Example 8	0.92	0.95	0.93
Example 9	3.08	3.02	3.05
Example 10	3.90	3.93	3.97

Example 11	3.15	3.12	3.10
Comparative Example 1	2.78	2.75	2.80
Comparative Example 2	2.58	2.70	2.82
Comparative Example 3	2.91	2.95	2.97

Combining the above examples and comparative examples, it can be seen that the nitridation method for rare earth magnets provided in the examples can increase the nitrogen content and at the same time make the nitrogen element more uniformly distributed in the magnet, which solves the problem of the nitrogen content of the rare earth magnets in the prior art after nitridation. Insufficient and uneven distribution of nitrogen elements.

The low nitrogen content in the products of Example 7 and Example 8 is because the types of rare earth elements used are different from those of Example 1, and their nitrogen content is not comparable to Example 1.

In Comparative Example 1, the semi-finished product was prepared without multi-stage heating, and only one stage of heating was carried out, resulting in incomplete exhaust, insufficient nitrogen adsorption, low nitrogen content after nitriding, and poor nitriding effect.

Comparative Example 2 did not perform homogenization treatment (ie, did not perform heating at the first set temperature), resulting in large fluctuations in nitrogen content and very unevenness.

In Comparative Example 3, only two stages of heating were not performed when preparing the semi-finished product, resulting in insufficient nitrogen adsorption and low nitrogen content after nitriding.

The applicant declares that the present application illustrates the detailed method of the present application through the above-mentioned embodiments, but the present application is not limited to the above-mentioned detailed method, which does not mean that the present application must rely on the above-mentioned detailed method for implementation.

Claims (11)

1. A method for nitriding rare earth magnets, wherein the method comprises the following steps:

   (1) vacuumize, add nitrogen source to the reactor that is equipped with rare earth magnet, carry out three-stage heating treatment, obtain semi-finished product; The heating temperature of described three-stage heating treatment is raised section by section;

   (2) the semi-finished product described in step (1) is heated up to the first set temperature, then the temperature is adjusted to the second set temperature and evacuated, and an inert gas is introduced, and at the second set temperature, heat preservation is carried out to obtain A rare earth nitride magnet; the second set temperature is lower than the first set temperature.
2. The method according to claim 1, wherein the first set temperature in step (2) is 830-860K and does not include 860K.
3. The method according to claim 1 or 2, wherein the general formula of the rare earth magnet in step (1) is ReTm, wherein Re is a rare earth metal, and Tm is a 3d transition group element and/or a 4d transition group element.
4. The method of claim 3, wherein the general formula of the rare earth nitride magnet is ReTmN.
5. The method according to any one of claims 1-4, wherein, the vacuuming in step (1) reduces the pressure of the reactor to below 1000Pa, optionally to below 10Pa;

   Optionally, the nitrogen source in step (1) includes a gaseous nitrogen source and/or a solid nitrogen source;

   Optionally, the gaseous nitrogen source is a nitrogen-containing gas;

   Optionally, the gaseous nitrogen source includes nitrogen and/or ammonia;

   Optionally, the gaseous nitrogen source also includes hydrogen;

   Optionally, the solid nitrogen source includes ammonium bicarbonate and/or ammonium chloride;

   Optionally, the nitrogen source in step (1) is a gaseous nitrogen source, and the pressure of the gaseous nitrogen source in the reactor is 0.001-10 MPa, optionally 0.01-2 MPa;

   Optionally, the nitrogen source in step (1) is a solid nitrogen source, and before the three-stage heating treatment, a protective gas is introduced into the reactor to a pressure of 0.001-10 MPa, optionally 0.01-2 MPa.
6. The method according to any one of claims 1-5, wherein the temperature of the first stage of the three-stage heating treatment in step (1) is 330-470K, optionally 370-420K;

   Optionally, the first-stage holding time of the three-stage heat treatment in step (1) is 0-24h and does not include 0, and can be optionally 0.1-5h;

   Optionally, the temperature of the second stage of the three-stage heating treatment in step (1) is 670-730K and does not include 730K, and can be optionally 690-710K;

   Optionally, the second-stage holding time of the three-stage heat treatment in step (1) is 0-24h and does not include 0, and can be optionally 0.1-5h;

   Optionally, the temperature of the third stage of the three-stage heating treatment in step (1) is 730-830K and does not include 830K, and can be optionally 750-780K;

   Optionally, the holding time of the third stage of the three-stage heating treatment in step (1) is 0-24h excluding 0, and can be optionally 0.1-5h.
7. The method according to any one of claims 2-6, wherein the first set temperature of step (2) is 830-840K;

   Optionally, in step (2), the heating time for the temperature rising to the first set temperature is 0-24 h and 0 is not included, and can be optionally 0.5-5 h.
8. The method according to any one of claims 1-7, wherein, the vacuuming in step (2) reduces the pressure of the reactor to below 1000Pa, optionally to below 10Pa;

   Optionally, in step (2), the pressure of the reactor is adjusted to 0.001-1 MPa by introducing an inert gas;

   Optionally, the second set temperature in step (2) is 600-700K, optionally 620-670K;

   Optionally, the holding time of the holding at the second set temperature described in step (2) is 0-24 h excluding 0, and can be optionally 0.5-5 h.
9. The method according to any one of claims 1-8, wherein step (2) further comprises: cooling to room temperature after heat preservation at the second set temperature.
10. The method according to any one of claims 1-9, wherein the method comprises the steps of:

    (1) Place the rare earth magnet in the reactor, evacuate to below 1000Pa, pass in the gas containing nitrogen element, heat up to 370-420K for 0.1-5h, heat up to 690-710K for 0.1-5h, heat up to 750- 780K heat preservation for 0.1-5h to obtain semi-finished products;

    (2) the semi-finished product described in step (1) is heated up to 830-840K with 0.5-5h, then the temperature is adjusted to 620-670K and the pressure of the reactor is reduced to below 1000Pa by vacuuming, and the pressure of the inert gas reactor is adjusted It is 0.001-1MPa, and is kept at the second set temperature for 0.5-5h, and cooled to room temperature to obtain a rare earth nitride magnet.
11. A nitrided rare earth magnet obtained by the nitridation method of the rare earth magnet according to any one of claims 1-10.