WO2022006973A1 - Ndfeb magnetic powder, ndfeb sintered magnet and preparation method therefor - Google Patents

Abstract

The present disclosure relates to the technical field of magnetic material, and in particular to an NdFeB magnetic powder, an NdFeB sintered magnet and a preparation method therefor. The NdFeB magnetic powder and the preparation method therefor improve the composition of the NdFeB magnetic powder, and does not carry out a dehydrogenation treatment after a hydrogen decrepitation process. The resulting NdFeB magnetic powder has a rare earth-rich grain boundary phase and low oxygen content, helping to reduce the loss of rare earth elements in the sintered magnet and inhibit grain growth during the sintering process. The structure of the sintered magnet is improved, and the magnetic performance and mechanical performance of the sintered magnet is enhanced. The resulting NdFeB magnetic powder has low average particle size, helping to further improve the mechanical performance of the sintered magnet.

Description

NdFeB-based magnetic powder, NdFeB-based sintered magnet and preparation method technical field

The present application relates to the technical field of magnet materials, in particular to a NdFeB-based magnetic powder, an NdFeB-based sintered magnet and a preparation method.

Background technique

NdFeB magnets are permanent magnets with the strongest magnetic force so far. The maximum magnetic energy product (BH)max is more than 10 times higher than that of ferrite. In the state of bare magnetism, its magnetic force can reach about 3500 Gauss. . The advantages of NdFeB magnets are high cost performance, small size, light weight, good mechanical properties and strong magnetic properties, and have been widely used in modern industry and electronic technology.

In the prior art, in the process of sintering NdFeB magnets to form NdFeB magnets, micro-cracks are easily generated due to the precipitation of hydrogen gas. To solve this problem will increase the sintering time and difficulty. At present, it is difficult to stably mass-produce rare earth magnets with a median diameter D50 of 3 microns. The main reason is that the smaller the particle size of the magnetic powder, the easier it is to oxidize, and it is difficult to orientate, and the coercive force increases with the decrease of the particle size.

In order to solve the above problems, a new preparation method of high-performance NdFeB magnetic powder, the high-performance NdFeB magnetic powder obtained therefrom, and the high-performance NdFeB magnet obtained based on the NdFeB magnetic powder are required.

technical problem

The purpose of this application is to provide a preparation method of NdFeB series magnetic powder, NdFeB series magnetic powder, NdFeB series sintered magnet and NdFeB series sintered magnet preparation method, to solve the problems in the prior art that are not conducive to improving the coercive force and mechanical properties of sintered magnets technical problem. The problem that the oxidation of NdFeB magnets in the preparation process leads to the decline of magnet performance is effectively controlled; the high-temperature dehydrogenation process is cancelled, and the production cost is reduced; on this basis, the fine-grain technology is used to improve the coercivity and mechanical properties; The problem of easy cracking of magnets with high hydrogen content during sintering is solved.

technical solutions

The technical solution of the present application is as follows: a preparation method of NdFeB-based magnetic powder is provided, including:

In the alloy melting process, the NdFeB-based alloy raw material is heated to melt, and the molten NdFeB-based alloy raw material is shaken to form an alloy thin strip;

Hydrogen crushing process, in which the alloy thin strip is subjected to hydrogen absorption under the first hydrogen pressure to carry out hydrogen crushing of the alloy thin strip to obtain alloy hydrogen crushed powder;

In the jet pulverization step, the alloy hydrogen pulverized powder is subjected to jet pulverization to obtain NdFeB-based magnetic powder.

Preferably, the NdFeB-based alloy raw materials include 30-31.2 wt% Pr-Nd alloy, 0.008-0.012 wt% Dy-Tb alloy, 0.8-1.00 wt% Co, 0.90-1.10 wt% B, 0.19-19 wt% 0.23 wt% Al, 0.08-0.12 wt% Cu, and the balance Fe.

Preferably, the NdFeB-based alloy raw materials include 30-31.2 wt% Pr-Nd alloy, 0.01wt% Dy-Tb alloy, 0.90wt% Co, 1.00wt% B, 0.21wt% Al, 0.10wt% % Cu and balance Fe.

Preferably, the thickness of the alloy thin strip is 0.15-0.3 mm.

Preferably, in the hydrogen crushing process, the first hydrogen pressure is greater than or equal to one atmospheric pressure and less than or equal to two atmospheric pressures, and the hydrogen absorption temperature is 5-35°C; When the value is less than the preset pressure value, it is judged that the hydrogen absorption of the alloy thin strip is completed, and it is maintained for 30 to 60 minutes.

Preferably, in the jet pulverization process, the hydrogen pulverized powder and the first auxiliary agent are uniformly mixed to form a first mixture, and then the first mixture is subjected to jet pulverization to obtain the NdFeB-based magnetic powder, wherein the first The adjuvants include one or more of methyl stearate, monochlorobenzene, tributyl borate, methyl laurate or n-hexane.

Another technical solution of the present application is as follows: to provide a NdFeB-based magnetic powder obtained by sampling the above preparation method, the NdFeB-based magnetic powder includes a main phase of a NdFeB crystal phase and a grain boundary phase of a rare-earth-rich phase, and a group of the NdFeB-based magnetic powder Divided into R _a M _b Co _c B _d Al _e Cu _f Fe _balance , where,

R is selected from one or both of Nd and Pr;

M is selected from one or both of Dy and Tb;

The oxygen content of the NdFeB-based magnetic powder is less than 800 mass ppm, and the average particle size of the NdFeB-based magnetic powder is 1.8-2.3 μm.

Preferably, the ratio of D90/D10 of the NdFeB-based magnetic powder is less than or equal to 4.5.

Another technical solution of the present application is as follows: to provide an NdFeB-based sintered magnet, the NdFeB-based sintered magnet is obtained by sequentially orienting and sintering NdFeB-based magnetic powder, and the intrinsic coercivity of the sintered magnet is greater than 14.0KOe, The bending strength of the sintered magnet is greater than 400 MPa, and the NdFeB-based magnetic powder is NdFeB-based magnetic powder prepared according to the above-mentioned preparation method.

Another technical solution of the present application is as follows: a preparation method of an NdFeB based sintered magnet is provided, comprising:

Orientation forming process, the NdFeB magnetic powder is oriented and formed to obtain a green body;

In the sintering process, after the green body is heated and degassed, the temperature is raised to the sintering temperature at a heating rate of 0.5-2.5°C/min, and the green body is sintered to obtain a sintered magnet;

Wherein, the NdFeB-based magnetic powder is NdFeB-based magnetic powder prepared according to the above-mentioned preparation method.

Preferably, the heating and degassing adopts a gradient heating method, and the sintering process specifically includes:

The green body is placed in a sintering furnace, heated from room temperature to 250-350°C at a heating rate of 0.5-2.5°C/min, and kept for 60-120min;

Continue to heat up to 450-550°C at a heating rate of 0.5-2.5°C/min, and keep the temperature for 60-120min;

Continue to heat up to the sintering temperature at a heating rate of 0.5-2.5°C/min, and keep the temperature for 1-3 hours, wherein the sintering temperature is 800-1200°C.

Preferably, the green body having a density of ^{3.2g / cm3 ~ 4.0g / cm 3} ;

In the orientation molding process, the NdFeB-based magnetic powder and the second auxiliary agent are uniformly mixed to form a second mixture, and then the second mixture is oriented and shaped to obtain the green body, wherein the second auxiliary agent The agent includes one or more of methyl stearate, monochlorobenzene, tributyl borate, methyl laurate or n-hexane.

beneficial effect

The beneficial effects of the present application are: in the preparation method of NdFeB-based magnetic powder of the present application, dehydrogenation treatment is not performed after the hydrogen crushing process, and the grain boundary phase of the obtained NdFeB-based magnetic powder is a rare earth-rich phase and has a low oxygen content, which is beneficial to reduce sintering. The loss of rare earth elements in the magnet and the inhibition of grain growth during the sintering process can improve the structure of the sintered magnet, and improve the magnetic and mechanical properties of the sintered magnet. Mechanical properties of magnets.

Description of drawings

FIG. 1 is a scanning electron microscope image of the alloy thin strip in the preparation method of NdFeB-based magnetic powder in Example 1 of the application (where Pa2=4.742 μm, Pa3=2.256 μm);

FIG. 2 is a scanning electron microscope image of another magnification of the alloy ribbon in the preparation method of NdFeB-based magnetic powder of Example 1 of the application (where Pa1=2.426 μm);

3 is a scanning electron microscope image of the NdFeB-based magnetic powder prepared in Example 1 of the application;

4 is a scanning electron microscope image of another magnification of the NdFeB-based magnetic powder prepared in Example 1 of the application;

5 is a scanning electron microscope image of the NdFeB-based sintered magnet of Example 1 of the application (where Pa1=3.568 μm, Pa2=2.929 μm, Pa3=6.463 μm).

Embodiments of the present invention

In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application.

In order to make the description of the present disclosure more detailed and complete, the following provides an illustrative description of the implementation manners and specific embodiments of the present application; but this is not the only form of implementing or using the specific embodiments of the present application. The features of various specific embodiments as well as method steps and sequences for constructing and operating these specific embodiments are encompassed in the detailed description. However, other embodiments may also be utilized to achieve the same or equivalent function and sequence of steps.

The "remanence" mentioned in this specification refers to the value of the magnetic flux density corresponding to the zero magnetic field strength on the saturation hysteresis loop, usually denoted as Br, and the unit is Tesla (T) or Gauss (Gs). ), where 1Gs=0.0001T.

The "coercive force" mentioned in this specification, also known as the intrinsic coercive force, refers to the state of magnetization from the saturation magnetization of the magnet, the magnetic field is monotonically reduced to zero and increased in the opposite direction, so that the magnetization is along the saturation magnetization state. The magnetic field strength when the hysteresis loop decreases to zero is usually recorded as Hcj or MHc, and the unit is Oersted (Oe) or KOe or Ampere/meter (A/m), where 1Oe=79.6A/m.

The "maximum magnetic energy product" mentioned in this specification refers to the maximum value of the product of Br and Hcj on the demagnetization curve, usually denoted as (BH)max, which is one of the important parameters to measure the energy stored by the magnet, and the unit is megaheight. Austria (MGOe).

The "squareness" mentioned in this specification is expressed by Hk/Hcj, the magnetic field Hk at the bending point is the magnetic field corresponding to J=0.9Br on the demagnetization curve, also called the knee point coercivity; Hcj is the room temperature Intrinsic coercivity.

The "orientation degree" mentioned in this specification is represented by Br/Bs, and the unit is %.

The "high-performance magnet" mentioned in this specification is a sintered magnet whose sum of the magnetic energy product (unit: MGsOe) and the intrinsic coercive force (unit: KOe) is greater than or equal to 65.

The "average particle size D10" mentioned in this specification refers to the equivalent diameter of the largest particle when the cumulative distribution in the particle size distribution curve is 10%, and its physical meaning is that particles with a particle size smaller than D10 account for 10%.

The "average particle size D50" mentioned in this specification refers to the equivalent diameter of the largest particle when the cumulative distribution in the particle size distribution curve is 50%. Its physical meaning is that particles with a particle size smaller than D50 account for 50%, and particles with a particle size larger than D50. Also accounting for 50%, D50 is also known as the median particle size.

The "average particle size D90" mentioned in this specification represents the equivalent diameter of the largest particle in the particle size distribution curve when the cumulative distribution is 90%, and its physical meaning is that particles with a particle size smaller than D90 account for 90%.

The "D90/D10" mentioned in this specification represents the concentration of particle distribution. In the magnetic material industry, the smaller the value of D90/D10, the better the concentration of particle size distribution.

The rare earth elements mentioned in this specification include but are not limited to praseodymium (Pr), neodymium (Nd) or heavy rare earth element RH. Among them, the heavy rare earth element RH, also known as the yttrium group element, includes yttrium (Y), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), Nine elements including ytterbium (Yb) and lutetium (Lu).

In this specification, the description of "a1-a2" means "greater than or equal to a1" and "less than or equal to a2", for example, x is 0-1, that is: 0≤x≤1.

In order to facilitate understanding of the present application, in the examples of the present application, the preparation method is first described, and then the product is described. 

Magnetic powder and magnetic powder preparation example

The preparation method of NdFeB magnetic powder comprises the following steps:

S101, smelting NdFeB-based alloy raw materials to obtain alloy flakes;

S102, the alloy flakes are made into NdFeB-based magnetic powder.

Among them, the NdFeB alloy raw materials include 30-31.2wt% Pr-Nd alloy, 0.008-0.012wt% Dy-Tb alloy, 0.8-01.00wt% Co, 0.90-1.10wt% B, 0.19-0.23wt% Al, 0.08-0.12wt% of Cu and the balance of Fe. Further, in an optional embodiment, the NdFeB-based alloy raw materials include 30-31.2wt% Pr-Nd alloy, 0.01wt% Dy-Tb alloy, 0.90wt% Co, 1.00wt% B, 0.21 wt% wt% Al, 0.10 wt% Cu and balance Fe.

It should be noted that, in the preparation process of the magnetic powder and the subsequent process of further preparation of the sintered magnet, a small amount of oxygen will inevitably be introduced.

In step S101, the smelting process adopts the rapid-setting casting process, and the NdFeB alloy raw material is heated to melting for smelting, and the smelted raw material is rapidly cooled and solidified, and is thrown into an alloy thin strip. In order to prevent the NdFeB alloy raw materials and the prepared alloy flakes from being oxidized, the smelting process is carried out in a vacuum or an inert atmosphere. In step S101, the thickness of the alloy thin strip is 0.15-0.3 mm, preferably 0.20-0.25 mm. Please refer to FIG. 1 and FIG. 2 , the columnar crystal width of the alloy flake prepared in step S101 is uniform and runs through the roller surface and the free surface, and the columnar crystal width is about 2.3 μm.

In step S102, a hydrogen crushing process and an airflow crushing process are sequentially included. In the hydrogen crushing process, the alloy ribbon is crushed into hydrogen crushed powder with relatively large particle size, and the hydrogen crushed powder is further crushed into magnetic powder with smaller particle size in the airflow crushing process. In order to prevent the alloy flakes and the hydrogen powder and magnetic powder formed by their crushing from being oxidized, the whole pulverizing process is carried out in a vacuum or an inert atmosphere.

In the hydrogen crushing process, the alloy ribbon is made to absorb hydrogen, and the alloy ribbon reacts with hydrogen to cause the volume expansion of the alloy ribbon lattice, and then the alloy ribbon is crushed along the crystal boundary to form alloy hydrogen powder.

In the hydrogen crushing process, the hydrogen pressure is greater than or equal to one atmospheric pressure and less than or equal to two atmospheric pressures, and the hydrogen absorption temperature is room temperature, such as 5-35°C. After the hydrogen absorption is completed, continue to maintain for 30min-60min. In this embodiment, the pressure in the hydrogen crushing furnace is detected to determine whether the hydrogen absorption is completed. Further, the first time is 5min, and the preset pressure value is 1Kpa.

The hydrogen content of the alloy hydrogen pulverized powder prepared by the hydrogen crushing process is greater than 3500ppm, while the hydrogen content of the dehydrogenated hydrogen pulverized powder in the prior art is generally 700-1200 ppm. Carry out dehydrogenation, directly enter the airflow pulverization process, and use the airflow to accelerate the alloy hydrogen pulverized powder to collide with each other and further crush. The gas stream can be an inert gas stream, preferably a nitrogen gas stream, and the pressure of the gas stream can be 0.1-2.0 MPa, for example, 0.8-1.0 MPa. In an optional embodiment, the hydrogen pulverized powder and a first auxiliary agent are uniformly mixed to form a first mixture, and then the first mixture is subjected to jet pulverization, and the first auxiliary agent includes methyl stearate, monochlorobenzene , one or more of tributyl borate, methyl laurate or n-hexane.

The average particle size of the NdFeB-based magnetic powder prepared by jet milling is 1.8-2.3 μm, which is close to the width of the alloy ribbon columnar crystal. The ratio of D90/D10 of the NdFeB-based magnetic powder is less than or equal to 4.5, and the particle size distribution concentration is good.

Please refer to Figures 3 and 4. Figures 3 and 4 are taken in the scanning electron microscope backscattering mode. The dark part is the NdFeB crystal phase, and the white part is the rare-earth-rich phase. When the particle size of the pulverized magnetic powder is similar, the alloy flakes will be fractured intergranularly to the greatest extent, and the NdFeB crystal phase in the magnetic powder is the main phase, and the rare earth-rich phase is the grain boundary phase.

In step S102, the hydrogen content of the hydrogen pulverized alloy prepared by the hydrogen pulverization process is greater than 3500 ppm, the hydrogen pulverized alloy is not dehydrogenated, and the hydrogen pulverized alloy is directly subjected to airflow pulverization. If the content is high, the alloy hydrogen pulverized powder has strong oxidation resistance, and the oxygen content of the NdFeB series magnetic powder formed after jet pulverization is less than 800ppm.

The NdFeB-based magnetic powder prepared in this embodiment has the following characteristics: (1) The average particle size of the NdFeB-based magnetic powder is 1.8-2.3 μm, and the relatively small average particle size can greatly improve the coercive force of the sintered magnet prepared from the magnetic powder. It is beneficial to improve the mechanical properties of sintered magnets; (2) The oxygen content of the NdFeB magnetic powder is less than 800ppm, and the magnetic powder with low oxygen content can reduce the loss of rare earth elements during the sintering process; (3) The grain boundary phase on the surface of the NdFeB magnetic powder is Rare earth-rich phase, the increase of rare earth element content on the surface of NdFeB magnetic powder is beneficial to the subsequent sintering of the magnet, which can improve the structure of the sintered magnet, thereby improving the magnetic properties and mechanical properties of the sintered magnet; (4) NdFeB magnetic powder is not desorbed during the preparation process. Hydrogen, the hydrogen content of NdFeB-based magnetic powder is relatively high, and hydrogen will be slowly released in the process of sintering to form a sintered magnet, which can inhibit the problem of easy oxidation caused by the small average particle size of NdFeB-based magnetic powder to a certain extent, which is beneficial to reduce the problem of easy oxidation. Oxygen content of the prepared sintered magnets.

The NdFeB-based magnetic powder prepared according to the above preparation method includes the main phase of the NdFeB crystal phase and the grain boundary phase of the rare-earth-rich phase. Further, the composition of the NdFeB-based magnetic powder is the remainder of RaMbCocBdAleCufFe, wherein, R is selected from one or both of Nd and Pr, and M is selected from one or both of Dy and Tb; a% is R in The mass percentage of all elements of NdFeB-based magnetic powder, a is 30-31.2; b% is the mass percentage of M in all elements of NdFeB-based magnetic powder, b is 0.008-0.012; c% is the mass of Co in all elements of NdFeB-based magnetic powder Percentage, c is 0.8～01.00; d% is the mass percentage of B in all elements of NdFeB magnetic powder, d is 0.90～1.10; e% is the mass percentage of Al in all elements of NdFeB magnetic powder, e is 0.19～0.23; f% is the mass percentage of Cu in all elements of the NdFeB-based magnetic powder, and f is 0.08 to 0.12. Further, a% is 30-31.2%, b% is 0.01%, c% is 0.90%, d% is 1.00%, e% is 0.21%, and f% is 0.10%.

Sintered magnet and preparation example of sintered magnet

The embodiment of the present application also provides a method for preparing a NdFeB-based sintered magnet, comprising the following steps:

S201, NdFeB-based magnetic powder is prepared.

For the preparation method of the NdFeB-based magnetic powder, refer to the above-mentioned embodiments for details, and will not be repeated here.

S202, orienting the NdFeB-based magnetic powder to obtain a green body.

S203 , after the heating and degassing of the green body is completed, the temperature is raised to a sintering temperature at a heating rate of 0.5-2.5° C./min, and the green body is sintered to obtain a sintered magnet.

In step S202, the NdFeB-based magnetic powder is placed in an orientation magnetic field to perform a molding process. In order to prevent the NdFeB-based magnetic powder from being oxidized, the molding process is performed in a vacuum or an inert atmosphere. In an optional embodiment, the forming process is compression forming followed by isostatic pressing to obtain a green body. In another optional embodiment, the forming process is vibration forming without isostatic pressing. The strength of the orientation magnetic field can be selected according to actual needs, for example, the strength of the magnetic field is 1-5T, preferably 1-3T or 3-5T.

In step S202, in an optional embodiment, the NdFeB-based magnetic powder and the second auxiliary agent are uniformly mixed to form a second mixture, and then the second mixture is subjected to orientation molding, and the second auxiliary agent includes methyl stearate , one or more of monochlorobenzene, tributyl borate, methyl laurate or n-hexane.

The orientation degree (Br/Bs) of the sintered magnet prepared in this example can reach more than 90%.

Since the NdFeB-based magnetic powder used in this embodiment has not undergone dehydrogenation operation during the preparation process, the hydrogen content of the NdFeB-based magnetic powder is relatively high. In order to suppress the formation of cracks inside the magnet in the subsequent sintering process, the density of the green body and/or the density of the green body can be appropriately reduced. The size of the green body is controlled. In an optional embodiment, the density of the green body is 3.2g/cm3 to 4.0g/cm3; in another optional embodiment, the size of the green body is less than or equal to 26*22 *9.7cm, that is, the length of the green body is less than or equal to 26cm, the width is less than or equal to 22cm, and the height is less than or equal to 9.7cm.

In step S203, in order to suppress the formation of cracks inside the magnet during the sintering process, the time of heating and degassing can be appropriately extended, and the heating and degassing is performed by a gradient heating method. Step S203 specifically includes:

The green body is placed in a sintering furnace, heated from room temperature to 250-350°C at a heating rate of 0.5-2.5°C/min, and kept for 60-120min;

Continue to heat up to 450-550°C at a heating rate of 0.5-2.5°C/min, and keep the temperature for 60-120min;

Continue to heat up to the sintering temperature at a heating rate of 0.5-2.5°C/min, and keep the temperature for 1-3 hours, wherein the sintering temperature is 800-1200°C.

In an optional embodiment, the heating rate in step S203 is 1°C/min, the temperature of the first gradient is 300°C, and the temperature of the second gradient is 800°C.

Please refer to 5. Compared with the particle size of the NdFeB-based magnetic powder prepared in the previous example, the grain size of the sintered magnet prepared in this example does not grow significantly, indicating that the surface of the NdFeB-based magnetic powder is covered with rare earth-rich phase. , has a certain inhibitory effect on the grain growth during the sintering process, and the boundaries between the grains of the sintered magnet are clear, which is beneficial to improve Hcj and mechanical properties.

Example 1

The present embodiment provides a method for preparing a NdFeB based sintered magnet, comprising the following steps:

1. Prepare NdFeB alloy raw materials according to the formula in Table 1. After melting, they are spun into alloy thin strips with a thickness of 0.15~0.3 mm. The microstructure of the alloy thin strips is shown in Figures 1 and 2.

Table 1 NdFeB alloy raw material formula

alloy composition	Nd+Pr	Dy+Tb	Co	B	Al	Cu	Fe
wt%	30~31.2	0.01	0.90	1.00	0.21	0.10	margin

2. The alloy thin strip absorbs hydrogen at room temperature under normal pressure or 2 atmospheres to form hydrogen powder. The standard for determining the completion of hydrogen absorption is that the pressure change in the hydrogen crushing furnace is less than 1KPa in 5 minutes, and it is maintained for 30min~60min.

3. After the hydrogen pulverized powder is mixed with the first auxiliary agent, it is air pulverized into magnetic powder with an average particle size of 1.8~2.3um. The powder morphology is shown in Figure 3 and Figure 4, and the particle size distribution is shown in Table 2.

Table 2 Results of particle size distribution of NdFeB-based magnetic powder

	D10	D50	D90	The average particle size	D90/D10
Particle size (μm)	1.16	3.00	5.17	2.07	4.46

4. After the magnetic powder after jet pulverization is mixed with the second auxiliary agent, it is oriented and formed into ^{a green body with a density of 3.2~4g/cm 3} and a size of about 26*22*9.7cm.

5. Put the green body into the sintering furnace, heat it at a heating rate of 1 °C/min to about 300 °C in stages, then heat it up to 500 °C for insulation, and finally heat it up to about 1000 °C for sintering. The microstructure of the sintered magnet is shown in Figure 5, the magnetic properties of the sintered magnet are shown in Table 3, and the mechanical properties of the magnet are shown in Table 4.

Table 3 Magnet performance results of sintered magnets

Comparative ratio

Comparative Example 1 is a magnet of N52 grade produced by a Japanese manufacturer, and the mechanical properties of the magnet are shown in Table 4.

Comparative example 2 is a magnet of N52 grade produced by domestic supplier 1, and the mechanical properties of the magnet are shown in Table 4.

Comparative example 3 is a magnet of N52 grade produced by domestic supplier 2, and the mechanical properties of the magnet are shown in Table 4.

Table 4 Results of mechanical properties of sintered magnets

The above-mentioned is only the embodiment of the present application, it should be pointed out that for those of ordinary skill in the art, without departing from the premise of the present application's creative concept, improvements can also be made, but these are all It belongs to the protection scope of this application.

Claims (12)

1. A preparation method of NdFeB-based magnetic powder, characterized in that, comprising:

In the alloy melting process, the NdFeB-based alloy raw material is heated to melt, and the molten NdFeB-based alloy raw material is shaken to form an alloy thin strip;

Hydrogen crushing process, in which the alloy thin strip is subjected to hydrogen absorption under the first hydrogen pressure to carry out hydrogen crushing of the alloy thin strip to obtain alloy hydrogen crushed powder;

In the jet pulverization step, the alloy hydrogen pulverized powder is jet pulverized to obtain NdFeB-based magnetic powder.

2. The method for preparing NdFeB-based magnetic powder according to claim 1, wherein the NdFeB-based alloy raw material comprises 30-31.2 wt% Pr-Nd alloy, 0.008-0.012 wt% Dy-Tb alloy, 0.8 ∼1.00 wt% Co, 0.90∼1.10 wt% B, 0.19∼0.23 wt% Al, 0.08∼0.12 wt% Cu, and balance Fe.

3. The method for preparing NdFeB-based magnetic powder according to claim 2, wherein the NdFeB-based alloy raw material comprises 30-31.2 wt% Pr-Nd alloy, 0.01 wt% Dy-Tb alloy, 0.90 wt% Co, 1.00wt% B, 0.21wt% Al, 0.10wt% Cu and balance Fe.

4. The method for preparing NdFeB-based magnetic powder according to claim 1, wherein the thickness of the alloy thin strip is 0.15-0.3 mm.

5. The method for preparing NdFeB-based magnetic powder according to claim 1, wherein in the hydrogen crushing process, the first hydrogen pressure is greater than or equal to one atmospheric pressure and less than or equal to two atmospheric pressures, and the hydrogen absorption temperature is 5 to 35°C; when the change value of the pressure in the hydrogen crushing furnace in the first time is less than the preset pressure value, it is judged that the hydrogen absorption of the alloy thin strip is completed, and the temperature is continued for 30 to 60 minutes.

6. The method for preparing NdFeB-based magnetic powder according to claim 1, wherein in the jet pulverization process, the hydrogen pulverized powder and the first auxiliary agent are uniformly mixed to form a first mixture, and then the first mixture is mixed Air-jet pulverization is performed to obtain the NdFeB-based magnetic powder, wherein the first auxiliary agent includes one or more of methyl stearate, monochlorobenzene, tributyl borate, methyl laurate or n-hexane .

7. A NdFeB-based magnetic powder obtained by the preparation method according to any one of claims 1 to 6, wherein the NdFeB-based magnetic powder comprises the main phase of the NdFeB crystal phase and the grain boundary phase of the rare-earth-rich phase, and the The composition of the NdFeB-based magnetic powder is the _{balance of R a} M _b Co _c B _d Al _e Cu _f Fe, wherein,

R is selected from one or both of Nd and Pr;

M is selected from one or both of Dy and Tb;

The oxygen content of the NdFeB-based magnetic powder is less than 800 mass ppm, and the average particle size of the NdFeB-based magnetic powder is 1.8-2.3 μm.

8. The NdFeB-based magnetic powder according to claim 7, wherein the ratio of D90/D10 of the NdFeB-based magnetic powder is less than or equal to 4.5.

9. An NdFeB-based sintered magnet, characterized in that the NdFeB-based sintered magnet is obtained by sequentially orienting and sintering NdFeB-based magnetic powder, the intrinsic coercivity of the sintered magnet is greater than 14.0 KOe, and the sintered magnet The bending strength is greater than 400MPa, and the NdFeB-based magnetic powder is a NdFeB-based magnetic powder prepared according to the preparation method described in any one of claims 1 to 6.

10. A method for preparing a NdFeB-based sintered magnet, comprising:

Orientation forming process, the NdFeB magnetic powder is oriented and formed to obtain a green body;

In the sintering process, after the heating and degassing of the green body is completed, the temperature is raised to the sintering temperature at a heating rate of 0.5-2.5° C./min, and the green body is sintered to obtain a sintered magnet;

Wherein, the NdFeB-based magnetic powder is NdFeB-based magnetic powder prepared according to the preparation method of any one of claims 1 to 6.

11. The method for preparing a NdFeB based sintered magnet according to claim 10, wherein the heating and degassing adopts a gradient heating method, and the sintering process specifically comprises:

The green body is placed in a sintering furnace, heated from room temperature to 250-350°C at a heating rate of 0.5-2.5°C/min, and kept for 60-120min;

Continue to heat up to 450-550°C at a heating rate of 0.5-2.5°C/min, and keep the temperature for 60-120min;

Continue to heat up to the sintering temperature at a heating rate of 0.5-2.5°C/min, and keep the temperature for 1-3 hours, wherein the sintering temperature is 800-1200°C.

12, the NdFeB system as claimed in claim 10, preparation of a sintered magnet, wherein the green body has a density of ^{3.2g / cm3 ~ 4.0g / cm 3} ;

In the orientation molding process, the NdFeB-based magnetic powder and the second auxiliary agent are uniformly mixed to form a second mixture, and then the second mixture is oriented and shaped to obtain the green body, wherein the second auxiliary agent The agent includes one or more of methyl stearate, monochlorobenzene, tributyl borate, methyl laurate or n-hexane.