阅读说明：本技术 一种异方性粘结磁粉及其制备方法 (Anisotropic bonded magnetic powder and preparation method thereof ) 是由 罗阳 杨远飞 王子龙 胡州 于敦波 廖一帆 王仲凯 谢佳君 于 2019-11-06 设计创作，主要内容包括：一种异方性粘结磁粉及其制备方法,该异方性粘结磁粉为HDDR方法制备的R-T-B永磁粉末,所述异方性粘结磁粉R-T-B中,R为包含一种以上的稀土元素,R含量为29.1-30.5wt.％；T为Fe或FeCo或FeCoNb,T中Fe含量在50wt.％以上；B为硼,B含量为0.9～1.2wt.％；该制备方法包括扩散源制备、原粉和扩散源混粉、热处理、冷却的步骤,最终得到该异方性粘结磁粉。本发明通过添加不含稀土元素的扩散源制备形成具有高矫顽力的稀土异方性粘结磁粉,有效地降低了成本,同时制备方法中热处理温度较低,提高了制备效率,降低了制备能耗。(An anisotropic bonded magnetic powder and a preparation method thereof, the anisotropic bonded magnetic powder is R-T-B permanent magnetic powder prepared by HDDR method, in the anisotropic bonded magnetic powder R-T-B, R is more than one rare earth element, and the content of R is 29.1-30.5 wt.%; t is Fe or FeCo or FeCoNb, and the content of Fe in T is more than 50 wt%; b is boron, and the content of B is 0.9-1.2 wt.%; the preparation method comprises the steps of diffusion source preparation, raw powder and diffusion source powder mixing, heat treatment and cooling, and the anisotropic bonded magnetic powder is finally obtained. According to the invention, the rare earth anisotropic bonded magnetic powder with high coercivity is prepared by adding the diffusion source without rare earth elements, so that the cost is effectively reduced, meanwhile, the heat treatment temperature in the preparation method is lower, the preparation efficiency is improved, and the preparation energy consumption is reduced.)

1. An anisotropic bonded magnetic powder, characterized in that the anisotropic bonded magnetic powder is an R-T-B permanent magnetic powder prepared by an HDDR method;

in the anisotropic bonded magnetic powder R-T-B, R is more than one rare earth element, and the content of R is 29.1-30.5 wt.%; t is Fe or FeCo or FeCoNb, and the content of Fe in T is more than 50 wt%; b is boron, and the content of B is 0.9-1.2 wt.%.

2. An anisotropically bonded magnetic powder according to claim 1, comprising R₂T₁₄B and a grain boundary phase surrounding the main phase, wherein the volume ratio of the main phase to the grain boundary phase is 30:1-60: 1.

3. The anisotropic bonded magnetic powder according to claim 2, wherein the grain boundary phase contains AlX₁X₂Wherein X is₁Is one or two of Cu and Ni, X₂Is one or more of Zn, Sn and Ga, AlX₁X₂Has a content of R₂T₁₄0.5-2 wt.% of B.

4. An anisotropically bonded magnetic powder according to claim 2 or 3, wherein X is₁The content of the grain boundary phase is 1.5-3 wt.%.

5. Anisotropic bonded magnetic powder according to any one of claims 2 to 4, characterized in that X is X₂The content of the grain boundary phase is 0.15-2 wt.%.

6. Anisotropic bonded magnetic powder according to any of claims 2 to 5, characterized in that the R content is less than 50 wt.% in the grain boundary phase.

7. An anisotropically bonded magnetic powder according to any of claims 1 to 6, wherein R is Nd or PrNd.

8. An anisotropically bonded magnetic powder according to any one of claims 1 to 7, wherein the average particle size of the R-T-B permanent magnetic powder is 200-500 μm, and the content of particles smaller than 200 μm is less than 1 wt.%.

9. A method of producing an anisotropically bonded magnetic powder according to any of claims 1 to 8 comprising the steps of:

preparing raw powder by using an HDDR method:

(1) a low-temperature hydrogenation stage: putting the RFeB rare earth master alloy in an environment with hydrogen pressure of 0.01-0.1 MPa and temperature of 20-650 ℃ for heat preservation for 0.3-4 h;

(2) high-temperature hydrogen absorption disproportionation stage: heating, adjusting and maintaining the hydrogen pressure at 30-80 kPa during heating, and preserving the heat for 1.0-4.5 h when the temperature reaches 780-880 ℃;

(3) slow dehydrogenation recombination stage: keeping the hydrogen pressure within the range of 1-5 kPa, and keeping the temperature for 0.2-0.6 h;

(4) a rapid complete dehydrogenation stage: when the hydrogen pressure is reduced to be not more than 1.0Pa, rapidly cooling to room temperature, then heating to 200-300 ℃, preserving heat for 0.5-2 h, and then cooling to room temperature again;

preparation of diffusion Source AlX₁X₂The grain diameter of the diffusion source is less than 200 mu m, and the content of the diffusion source is the raw powder R₂T₁₄0.5-2 wt.% of B;

mixing the raw powder with a diffusion source to obtain mixed powder;

carrying out heat treatment on the mixed powder at the temperature of 400-600 ℃;

cooling to obtain the anisotropic bonded magnetic powder.

10. The method as claimed in claim 9, wherein the step of heat-treating the mixed powder at a temperature of 400-600 ℃ comprises:

performing first diffusion at 400-500 ℃ in a vacuum atmosphere;

the second diffusion was performed at 450-600 ℃ under an inert gas atmosphere.

Technical Field

The invention relates to the technical field of magnetic materials, in particular to anisotropic bonded magnetic powder and a preparation method thereof.

Background

The rare earth bonded neodymium iron boron permanent magnet material has the advantages of strong magnetism, high shape freedom degree, good consistency and the like, and is widely applied to the fields of hard disks, optical disk drives, office automation, consumer electronics, household appliances, automobiles and the like. At present, the main product of the neodymium iron boron bonded magnet is isotropic, the maximum magnetic energy product of the commercial quick-quenching neodymium iron boron magnetic powder is 12-18MGOe, and the high-end requirement is difficult to meet. Particularly, with the trend toward miniaturization, weight reduction, and precision of devices such as rotating electric machines, the demand for high-performance anisotropic bonded magnets in the market is becoming more and more urgent.

The R-T-B rare earth anisotropic magnetic powder has excellent magnetic characteristics, is positioned in a blank area between a homosquareness bonding permanent magnet material and a sintering permanent magnet material, very meets the development requirements of motor light weight and miniaturization, and has wide application prospects in high and new technical fields of new energy automobiles, intelligent household appliances, wind power generation and the like. But the Curie temperature is low, the thermal stability is poor, and the coercive force is sharply reduced along with the increase of the temperature when the temperature is increased. In particular, in recent years, in some new application fields such as electric vehicles and hybrid vehicles, the neodymium iron boron permanent magnet is required to have good thermal stability, i.e. high coercivity at room temperature can resist the problem of thermal demagnetization of the magnet in a high-temperature working environment. Therefore, it is necessary to manufacture magnetic powder having a large coercive force in advance, and to ensure coercive force even at high temperature.

The grain size of the R-T-B rare earth anisotropic magnetic powder is usually less than 3 mu m, the grain boundary phase is very thin, and the improvement space of the coercive force is larger compared with sintered neodymium iron boron, so that high coercive force is obtained. The common method is to improve the coercive force by a grain boundary diffusion method, so that the coercive force and the thermal stability of the bonded magnet are improved, and finally the magnetic flux loss of the bonded magnet in a high-temperature environment is weakened as much as possible, thereby meeting the requirements of some high-temperature application fields on the thermal stability of the magnet.

Conventionally, studies have been made on improving the coercive force of magnet powder by adding Dy to a raw material alloy, or by diffusing an R — Cu (e.g., NdCu) alloy or the like added during or after an HDDR step. However, rare earth elements and hydrides thereof in alloys such as Dy, hydride and NdCu for enhancing coercive force are expensive rare resources, which increases the cost of magnetic powder, and when Dy is added, Dy is mixed into Nd₂Fe₁₄The main phase B, and hence there is a technical problem that the residual flux density of the R-T-B-based rare earth magnet powder obtained is lowered. In addition, in the conventional technique, additional heat treatment such as adjustment and addition, aging heat treatment, and the like are required in addition to the HDDR step and the diffusion step, and therefore, the steps become complicated, and productivity is lowered.

Disclosure of Invention

In order to solve the above problems, the present invention provides an anisotropic bonded magnetic powder and a method for manufacturing the same, in which a diffusion source not containing rare earth is added to the magnetic powder, thereby increasing the coercive force of an anisotropic magnet and reducing the magnetic energy and the residual magnetic flux loss.

In order to achieve the above purpose, the present invention adopts the following scheme:

the first aspect of the invention provides an anisotropic bonded magnetic powder, which is an R-T-B permanent magnetic powder prepared by an HDDR method;

in the anisotropic bonded magnetic powder R-T-B, R is more than one rare earth element, and the content of R is 29.1-30.5 wt.%; t is Fe or FeCo or FeCoNb, and the content of Fe in T is more than 50 wt%; b is boron, and the content of B is 0.9-1.2 wt.%.

Further, containing R₂T₁₄B and a grain boundary phase surrounding the main phase, wherein the volume ratio of the main phase to the grain boundary phase is 30:1-60: 1.

Further, crystal grainBoundary phase contains AlX₁X₂Wherein X is₁Is one or two of Cu and Ni, X₂Is one or more of Zn, Sn and Ga, AlX₁X₂Has a content of R₂T₁₄0.5-2 wt.% of B.

Further, X₁The content of the grain boundary phase is 1.5-3 wt.%.

Further, X₂The content of the grain boundary phase is 0.15-2 wt.%.

Further, the R content is less than 50 wt.% in the grain boundary phase content.

Further, R is Nd or PrNd. Further, the average particle size of the R-T-B permanent magnetic powder is 200-500 mu m, and the content of particles smaller than 200 mu m is less than 1 wt.%.

The second aspect of the present invention provides a method for preparing an anisotropic bonded magnetic powder, comprising the steps of:

preparing raw powder by using an HDDR method:

(1) a low-temperature hydrogenation stage: putting the RFeB rare earth master alloy in an environment with hydrogen pressure of 0.01-0.1 MPa and temperature of 20-650 ℃ for heat preservation for 0.3-4 h;

(2) high-temperature hydrogen absorption disproportionation stage: heating, adjusting and maintaining the hydrogen pressure at 30-80 kPa during heating, and preserving the heat for 1.0-4.5 h when the temperature reaches 780-880 ℃;

(3) slow dehydrogenation recombination stage: keeping the hydrogen pressure within the range of 1-5 kPa, and keeping the temperature for 0.2-0.6 h;

(4) a rapid complete dehydrogenation stage: when the hydrogen pressure is reduced to be not more than 1.0Pa, rapidly cooling to room temperature, then heating to 200-300 ℃, preserving heat for 0.5-2 h, and then cooling to room temperature again;

preparation of diffusion Source AlX₁X₂The grain diameter of the diffusion source is less than 200 mu m, and the content of the diffusion source is the original powder R₂T₁₄0.5-2 wt.% of B;

mixing the raw powder with a diffusion source to obtain mixed powder;

carrying out heat treatment on the mixed powder at the temperature of 400-600 ℃;

cooling to obtain the anisotropic bonded magnetic powder.

Further, the step of performing heat treatment on the mixed powder at the temperature of 400-600 ℃ comprises the following steps:

performing first diffusion at 400-500 ℃ in a vacuum atmosphere;

the second diffusion was performed at 450-600 ℃ under an inert gas atmosphere.

In summary, the invention provides an anisotropic bonded magnetic powder and a preparation method thereof, the anisotropic bonded magnetic powder is R-T-B permanent magnetic powder prepared by HDDR method, in the anisotropic bonded magnetic powder R-T-B, R is one or more rare earth elements, and the content of R is 29.1-30.5 wt.%; t is Fe or FeCo or FeCoNb, and the content of Fe in T is more than 50 wt%; b is boron, and the content of B is 0.9-1.2 wt.%; the preparation method comprises the steps of diffusion source preparation, raw powder and diffusion source powder mixing, heat treatment and cooling, and finally the anisotropic bonded magnetic powder is obtained. According to the invention, the rare earth anisotropic bonded magnetic powder with high coercivity is prepared by adding the diffusion source without rare earth elements, so that the cost is effectively reduced, and meanwhile, the heat treatment temperature in the preparation method is lower, so that the preparation efficiency is improved, and the preparation energy consumption is reduced.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It is to be understood that this description is made only by way of example and not as a limitation on the scope of the invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.

The invention is realized by the following technical scheme:

the invention provides rare earth anisotropic bonded magnetic powder, which is R-T-B series permanent magnetic powder prepared by an HDDR method; wherein R is more than one rare earth element containing Y, T is Fe or FeCo or FeCoNb, the Fe content in T is more than 50 wt%, and the raw powder is R in the average composition of the powder₂T₁₄A phase B structure, wherein the content of R is 29.1-30.5 wt.%, T is FeCo or Fe, the content of B is 0.9-1.2 wt.%, and the powderComprising a compound containing R₂T₁₄B main phase crystal grains and a grain boundary phase surrounding the main phase crystal grains, the grain boundary phase containing AlX₁X₂Wherein X is₁Is more than one of Cu and Ni, X₂Is one or more of Zn, Sn and Ga; x₁The content is 1.5-3 wt.%, and X₂The content is 0.15-2 wt%, and the content of R in a grain boundary phase is less than 50 wt%. The average particle size D of the original powder in the R-T-B permanent magnet powder₅₀200-500 μm, and less than 1 wt.% of particles smaller than 200 μm.

The rare earth element R constituting the R-T-B-based rare earth magnet powder of the present invention may be selected from Nd and PrNd. R content at average composition 29.1-30.5 wt.%; when the content of R is less than 29.1 wt.%, the R content of the grain boundary phase composition becomes less than 13.5 at.%, and the R content in the grain boundary phase becomes too low to sufficiently obtain the effect of improving the coercive force. At an R amount of the average composition of more than 30.5 wt.%, the residual magnetic flux density of the powder decreases due to an increase in grain boundary phase with low magnetization. Therefore, the R content of the average composition is preferably 29.1 to 30.5 wt.%, more preferably 29.5 wt.% or more and 30.2 wt.% or less.

The element T constituting the R-T-B type rare earth magnet powder of the present invention is Fe, or FeCo or FeCoNb. The T amount of the average composition of the powder is the balance excluding other elements constituting the powder. In addition, since the curie temperature can be increased by adding Co as an element substituting for Fe, too much leads to a decrease in the residual magnetic flux density of the powder, the residual magnetic flux density Br can be increased by adding Nb as an element substituting for Fe, and too much passivates the hydrogenation reaction during HDDR, the content of Fe having an average composition in the powder is 50 wt.% or more, preferably 55 to 70 wt.%

In the average composition of the R-T-B rare earth magnet powder, the content of B is 0.9-1.2 wt.%. When the B content of the average composition is less than 0.9 wt.%, due to R₂Fe₁₇The magnetic properties are degraded due to the equal precipitation. In addition, when the amount of B of the average composition is more than 1.2 wt.%, the residual magnetic flux density of the powder is reduced. The amount of B in the average composition is preferably 0.95 to 1.1 wt.%.

The R-T-B rare earth magnet powder of the inventionThe average composition of the powder comprises₂T₁₄B main phase crystal grains and a grain boundary phase surrounding the main phase crystal grains, the grain boundary phase containing AlX₁X₂Wherein X is₁Is more than one of Cu and Ni, X₂Is one or more of Zn, Sn and Ga, wherein AlX is₁X₂The alloy has a relatively low melting point and is melted with respect to the orthorhombic compound R₂T₁₄The B main phase has relatively high wettability and therefore contains AlX₁X₂The grain boundary phase (2) can be smoothly coated on the surface of the main phase, and generation of reverse magnetic domains in the vicinity of the surface can be suppressed. In addition, each R may be₂T₁₄Isolation of B main phase grains and blocking of adjacent R₂T₁₄The magnetic force generated by the B main phase crystal grains interacts. The volume ratio of the main phase to the grain boundary phase is 30:1-60:1, if the volume ratio is less than 30:1, the grain boundary phase is too much, and because the grain boundary phase is a nonmagnetic phase, the pinning of a magnetic domain wall is weakened when the content is too much, so that the coercive force is reduced, and if the volume ratio is more than 60:1, the grain boundary phase is too small to cover the surface sufficiently to suppress the generation of reverse magnetic domains near the surface, and thus the coercive force is not improved. Wherein X is₁Is more than one of Cu and Ni, if X₁When the content is less than 1.5 wt.%, the melting point of the molten alloy is high, and the process of preparing magnetic powder causes grain growth, if X is₁At a content of more than 3 wt.%, melting AlX₁X₂Alloy and R₂T₁₄The wettability of the B main phase is poor, the covering effect is poor, and the coercive force is not obviously improved. X₂Is one or more of Zn, Sn and Ga, if X₂When the content is less than 0.15 wt.%, the melting point of the molten alloy is high, and the process of preparing the magnetic powder causes the crystal grains to grow, if X is large₂At contents greater than 2 wt.%, the residual magnetic flux density of the powder decreases. The R content is less than 50 wt.%, and the R content in the grain boundary phase is too low to sufficiently obtain the effect of improving the coercive force.

In the specification, the hydrogen pressure in the high-temperature hydrogen absorption-disproportionation stage in the HDDR step in the R-T-B permanent magnet powder preparation process is 30-80 kPa, and if the hydrogen pressure is less than 30kPa, the average particle size D of the powder is₅₀Too large, uneven coverage of the alloy with the molten diffusion source may occurHomogenization, if the hydrogen pressure is greater than 80kPa, the average particle size D of the powder₅₀The surface of the R-T-B permanent magnetic powder is oxidized in a too small preparation process, the magnetic property is reduced, and the large-scale production is not facilitated, so that the average particle size of the R-T-B permanent magnetic powder is 200-500 mu m, and the content of particles smaller than 200 mu m is less than 1%.

In addition, the method for preparing the rare earth anisotropic bonded magnetic powder comprises the following steps:

preparing raw powder by using an HDDR method:

(1) a low-temperature hydrogenation stage: putting the RFeB rare earth master alloy in an environment with hydrogen pressure of 0.01-0.1 MPa and temperature of 20-650 ℃ for heat preservation for 0.3-4 h;

(2) high-temperature hydrogen absorption disproportionation stage: heating, adjusting and maintaining the hydrogen pressure at 30-80 kPa during heating, and preserving the heat for 1.0-4.5 h when the temperature reaches 780-880 ℃;

(3) slow dehydrogenation recombination stage: keeping the hydrogen pressure within the range of 1-5 kPa, and keeping the temperature for 0.2-0.6 h;

(4) a rapid complete dehydrogenation stage: when the hydrogen pressure is reduced to be not more than 1.0Pa, rapidly cooling to room temperature, then heating to 200-300 ℃, preserving heat for 0.5-2 h, and then cooling to room temperature again;

preparing a diffusion source, wherein the particle size of the diffusion source is less than 200 mu m, and if the particle size is more than 200 mu m, the particles are too large to be fully mixed with the raw powder; the proportion of the diffusion source is 0.5-2% of the original powder, if the proportion of the diffusion source is less than 0.5%, the diffusion source covers the main phase insufficiently, and if the proportion of the diffusion source is more than 2%, the residual magnetic flux density of the R-T-B permanent magnetic powder is reduced.

Mixing the raw powder with a diffusion source to obtain mixed powder;

performing heat treatment on the mixed powder at 400-600 ℃;

the heat treatment comprises a first diffusion step at 400-500 ℃ in a vacuum atmosphere;

and a second diffusion step at 450-600 ℃ in an inert gas atmosphere;

when the heating temperature is too low, the fluidity of the diffusion source is not good, and the diffusion is not facilitated, and when the heating temperature is too high, the diffusion source can flow into the diffusion chamberResult in R₂T₁₄The crystal grains of the B main phase grow up, and energy consumption is wasted.

Cooling to obtain the rare earth anisotropic bonded magnetic powder.

The following description is given of specific embodiments of the present invention, but the present invention is by no means limited to the embodiments described.