阅读说明：本技术 一种稀土异方性粘结磁粉及其制备方法以及磁体 (Rare earth anisotropic bonded magnetic powder, preparation method thereof and magnet ) 是由 罗阳 王子龙 杨远飞 胡州 于敦波 王仲凯 廖一帆 谢佳君 于 2019-11-06 设计创作，主要内容包括：一种稀土异方性粘结磁粉及其制备方法及磁体,稀土异方性粘结磁粉成分为RYFeMB；其中,R为Nd或PrNd,M为Nb、Ti、Zr、Ga、Si中的一种或多种,R所占总质量的质量分数为28.5％-30.5％；B所占总质量的质量分数为0.97％-1.05％；所述Y占总质量的质量分数为0.1％-5％；所述M为Y质量的质量分数的10％～50％；余量为Te。所述稀土异方性粘结磁粉在120℃以内的矫顽力温度系数大于-0.5％/℃。本发明通过添加一定比例的钇Y元素,改善了异方性磁粉的温度系数,提升了其耐热性；同时M元素的针对性添加有效降低了晶粒尺寸偏差,提高了磁粉的方形度,使得在添加Y元素之后,最大磁能积不明显降低。(A rare earth anisotropic bonded magnetic powder, its preparation method and magnet are provided, wherein the rare earth anisotropic bonded magnetic powder is RYFeMB; wherein R is Nd or PrNd, M is one or more of Nb, Ti, Zr, Ga and Si, and the mass fraction of R in the total mass is 28.5-30.5%; the mass fraction of the B in the total mass is 0.97-1.05%; the mass fraction of Y in the total mass is 0.1-5%; the M accounts for 10-50% of the mass fraction of the Y; the rest is Te. The coercive force temperature coefficient of the rare earth anisotropic bonded magnetic powder within 120 ℃ is larger than-0.5%/DEG C. According to the invention, by adding a certain proportion of yttrium Y element, the temperature coefficient of anisotropic magnetic powder is improved, and the heat resistance of the anisotropic magnetic powder is improved; meanwhile, the targeted addition of the M element effectively reduces the grain size deviation and improves the squareness of magnetic powder, so that the maximum magnetic energy product is not obviously reduced after the Y element is added.)

1. The rare earth anisotropic bonded magnetic powder is characterized in that the rare earth anisotropic bonded magnetic powder is RYFeMB;

wherein R is Nd or PrNd, M is one or more of Nb, Ti, Zr, Ga and Si, R accounts for 28.5 to 30.5 percent of the total mass, and B accounts for 0.97 to 1.05 percent of the total mass;

the mass fraction of Y in the total mass is 0.1-5%;

the M accounts for 10-50% of the mass fraction of the Y;

the balance being Fe;

the coercive force temperature coefficient of the rare earth anisotropic bonded magnetic powder within 120 ℃ is larger than-0.5%/DEG C.

2. The rare earth anisotropically bonded magnetic powder according to claim 1, wherein the anisotropically bonded magnetic powder particles comprise a magnetic powder comprising a magnetic powder of a magnetic powder: 14:1 is a main phase of a grain boundary structure and a grain boundary phase surrounding the main phase.

3. A rare earth anisotropically bonded magnetic powder according to claim 2, wherein the ratio of the content of M in the grain boundary phase to the content in the main phase is between 2 and 5.

4. The rare earth anisotropic bonded magnetic powder according to any one of claims 1 to 3, wherein the grain size σ of the main phase is 200-400nm, and the standard deviation of the grains is 0.5 σ or less.

5. A rare earth anisotropically bonded magnetic powder according to any one of claims 1 to 3, wherein Y accounts for 0.5 to 2% by mass of the total mass.

6. A rare earth anisotropically bonded magnetic powder according to any one of claims 1 to 3, wherein M is 30% by mass of the mass fraction of Y.

7. A method of producing a rare earth anisotropically bonded magnetic powder according to any one of claims 1 to 6, comprising the steps of:

hydrogen absorption disproportionation stage: placing the R-T-B series alloy in the rare earth anisotropic bonded magnetic powder into a rotary gas-solid reaction furnace, heating to a first temperature T1 under the hydrogen pressure of 0-0.1MPa, wherein the range of T1 is 760-860 ℃, then keeping the hydrogen pressure at a first pressure P1 and the range of P1 is 20-100kPa, and preserving the heat for 1-4 h to finish the treatment of the hydrogen absorption disproportionation stage;

slow dehydrogenation repolymerization stage: after the hydrogen absorption disproportionation stage is finished, keeping the temperature in the furnace to 800-;

a complete dehydrogenation stage: after the slow dehydrogenation repolymerization stage is finished, quickly vacuumizing to the hydrogen pressure below 1Pa to finish the complete dehydrogenation stage;

and (3) a cooling stage: and after the complete dehydrogenation stage is finished, cooling to room temperature to obtain the rare earth anisotropic bonded magnetic powder.

8. The method according to claim 7, further comprising, between the hydrogen uptake disproportionation stage and the slow dehydrogenation repolymerization stage, the step of a tissue stabilization stage: after the hydrogen absorption disproportionation stage is finished, raising the temperature in the furnace to T2, simultaneously increasing the hydrogen pressure to P2, ensuring that T2 is more than or equal to T1 and P2 is more than or equal to P1, and finishing the treatment in the tissue stabilization stage.

9. The method of claim 7, wherein the cooling stage comprises a step cooling: after the complete dehydrogenation stage is completed, starting cooling, wherein the cooling speed is 30-50 ℃/min at the temperature of above 650 ℃; cooling at a temperature below 650 deg.C at a rate of 10-35 deg.C/min.

10. A rare earth anisotropically bonded magnet comprising the rare earth anisotropically bonded magnetic powder according to any one of claims 1 to 6.

Technical Field

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

Background

The magnetic powder for bonding the neodymium iron boron permanent magnet material is mainly divided into two main categories of isotropy and anisotropy. At present, the isotropic neodymium iron boron magnetic powder is prepared by a melt rapid quenching method, the maximum magnetic energy product is 12-16MGOe, and the maximum magnetic energy product of the prepared isotropic neodymium iron boron bonded magnet is not more than 12 MGOe. The anisotropic neodymium-iron-boron bonded magnetic powder is usually prepared by an HDDR method, and due to the particularity of the microstructure, namely the parallel arrangement of fine grains (200 plus 500nm) in the direction of an easy magnetization axis, the maximum magnetic energy product of the anisotropic bonded magnetic powder can reach 2-3 times of that of the isotropic bonded magnetic powder, and a high-performance anisotropic bonded magnet can be prepared by a die pressing or injection molding process and accords with the development trend of miniaturization, light weight and precision of motor devices, so that the market demands for the high-performance anisotropic magnetic powder are more and more urgent.

However, the bonded neodymium iron boron magnet prepared by the HDDR magnetic powder has the problem of insufficient heat resistance. For example, in applications such as automobiles where the magnet is exposed to high temperatures, if the heat resistance of the magnet is low, irreversible demagnetization is likely to occur. Therefore, as for the HDDR magnetic powder, the heat resistance is fully improved, and the HDDR magnetic powder can be applied to the fields of automobiles and the like to expand the application range.

There are two main ways to improve the heat resistance of anisotropic magnetic powder, i.e. to reduce the possibility of demagnetization at high temperature, i.e. to increase the coercive force of the magnetic powder at high temperature. The first is to improve the coercivity (room temperature coercivity) of anisotropic magnetic powder, so that the high temperature coercivity is correspondingly improved under the condition that the temperature coefficient is not changed. The second is to increase the temperature coefficient of anisotropic magnetic powder, so that the high-temperature coercive force is correspondingly increased under the condition that the room-temperature coercive force is not changed.

At present, the first approach is mainly focused on improving the coercivity of anisotropic magnetic powder, and the first approach is mainly two approaches, one is to directly add heavy rare earth elements such as Tb and Dy, and the other is to add heavy rare earth elements or low-melting-point alloy elements through grain boundary diffusion. The former undoubtedly brings about great cost increase due to the addition of heavy rare earth; in the latter, due to the increase of the grain boundary diffusion process, the steps of diffusion source preparation, powder mixing, diffusion heat treatment and the like need to be added, so that the production process is more complicated, and the processing cost is increased.

Disclosure of Invention

In order to solve the problems, the invention provides the rare earth anisotropic bonded magnetic powder and the preparation method thereof, which improve the temperature coefficient of the anisotropic magnetic powder by adding yttrium Y element, and can effectively improve the heat resistance of the anisotropic magnetic powder on the premise of not increasing the production process, so that the anisotropic magnetic powder has excellent heat resistance. Meanwhile, the targeted addition of the M element effectively reduces the grain size deviation and improves the squareness of magnetic powder, so that the maximum magnetic energy product is not obviously reduced after the Y element is added.

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

the first aspect of the invention provides a rare earth anisotropic bonded magnetic powder, the rare earth anisotropic bonded magnetic powder is RYFeMB;

wherein R is Nd or PrNd, M is one or more of Nb, Ti, Zr, Ga and Si, R accounts for 28.5-30.5% of the total mass, and B accounts for 0.97-1.05% of the total mass; the mass fraction of Y in the total mass is 0.1-5%; (ii) a

The M accounts for 10-50% of the mass fraction of the Y;

the balance being Fe; the coercive force temperature coefficient of the rare earth anisotropic bonded magnetic powder within 120 ℃ is larger than-0.5%/DEG C.

Further, the anisotropic bonded magnetic powder particles comprise a magnetic powder particle with a ratio of 2:14:1 is a main phase of a grain boundary structure and a grain boundary phase surrounding the main phase.

Further, the ratio of the content of M in the grain boundary phase to the content in the main phase is between 2 and 5.

Further, the grain size sigma of the main phase is 200-400nm, and the standard deviation of the grains is below 0.5 sigma.

Further, the mass fraction of Y in the total mass is 0.5-2%.

Further, the M accounts for 30% of the mass fraction of the mass of the Y.

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

hydrogen absorption disproportionation stage: placing the R-T-B series alloy in the rare earth anisotropic bonded magnetic powder into a rotary gas-solid reaction furnace, heating to a first temperature T1 under the hydrogen pressure of 0-0.1MPa, wherein the range of T1 is 760-860 ℃, then keeping the hydrogen pressure at a first pressure P1 and the range of P1 is 20-100kPa, and preserving the heat for 1-4 h to finish the treatment of the hydrogen absorption disproportionation stage;

slow dehydrogenation repolymerization stage: after the hydrogen absorption disproportionation stage is finished, keeping the temperature in the furnace to 800-;

a complete dehydrogenation stage: after the slow dehydrogenation repolymerization stage is finished, quickly vacuumizing to the hydrogen pressure below 1Pa to finish the complete dehydrogenation stage;

and (3) a cooling stage: and after the complete dehydrogenation stage is finished, cooling to room temperature to obtain the rare earth anisotropic bonded magnetic powder.

Further, between the hydrogen absorption disproportionation stage and the slow dehydrogenation repolymerization stage, the method also comprises the following steps: after the hydrogen absorption disproportionation stage is finished, raising the temperature in the furnace to T2, increasing the hydrogen pressure to P2 at the same time, ensuring that T2 is more than or equal to T1 and P2 is more than or equal to P1, and finishing the treatment in the tissue stabilization stage.

Further, the cooling stage comprises a step cooling: after the complete dehydrogenation stage is completed, starting cooling, wherein the cooling speed is 30-50 ℃/min at the temperature of above 650 ℃; cooling at a temperature below 650 deg.C at a rate of 10-35 deg.C/min.

A third aspect of the invention provides a rare earth anisotropically bonded magnet comprising the rare earth anisotropically bonded magnetic powder as described above.

In summary, the present invention provides a rare earth anisotropic bonded magnetic powder, a method for preparing the same, and a magnet, wherein the rare earth anisotropic bonded magnetic powder is RYFeMB; wherein R is Nd or PrNd, and M is one or more of Nb, Ti, Zr, Ga and Si; the mass fraction of Y in the total mass is 0.1-5%; the coercive force temperature coefficient of the rare earth anisotropic bonded magnetic powder within 120 ℃ is larger than-0.5%/DEG C. The preparation method comprises the steps of hydrogen absorption disproportionation, slow dehydrogenation and repolymerization, complete dehydrogenation and cooling, and finally the rare earth anisotropic bonded magnetic powder is obtained. According to the invention, by adding a certain proportion of yttrium Y element, the temperature coefficient of the anisotropic magnetic powder is improved, and the heat resistance of the anisotropic magnetic powder is improved. Meanwhile, the targeted addition of the M element effectively reduces the grain size deviation and improves the squareness of magnetic powder, so that the maximum magnetic energy product is not obviously reduced after the Y element is added.

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 should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present 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 first aspect of the invention provides a rare earth anisotropic bonded magnetic powder, the rare earth anisotropic bonded magnetic powder is RYFeMB; wherein R is Nd or PrNd, M is one or more of Nb, Ti, Zr, Ga and Si, R accounts for 28.5-30.5% of the total mass, and B accounts for 0.97-1.05% of the total mass; the mass fraction of Y in the total mass is 0.1-5%; the balance being iron; the M accounts for 10 to 50 percent of the mass fraction of the Y; the coercive force temperature coefficient of the rare earth anisotropic bonded magnetic powder within 120 ℃ is larger than-0.5%/DEG C.

Preferably, the mass fraction of M in the total mass is 0.5-2%.

Preferably, M is 30% by mass of Y. The main phase of Nd-Fe-B₂Fe₁₄B, the main phase of the analogous yttrium iron boron is Y₂Fe₁₄B. Y does not contain 4f electrons due to yttrium element₂Fe₁₄The B magnetic crystal anisotropy field is lower, the coercive force of the yttrium iron boron is lower than that of neodymium iron boron, but Y₂Fe₁₄The temperature coefficient of the coercive force of B is positive within a certain temperature range (room temperature to 100 ℃), so that the yttrium element can enter a main phase by adding a certain proportion of yttrium element into anisotropic neodymium-iron-boron magnetic powder, and the temperature coefficient of the coercive force of the B can be effectively reduced and the heat resistance of the B can be improved by partially replacing neodymium element on a specific crystal position. The addition proportion of the yttrium element is 0.1-5%, and if the yttrium element is added too much, the comprehensive magnetic performance of the magnetic powder is inevitably greatly reduced, and if the yttrium element is added too little, the effects of reducing the temperature coefficient of the coercive force and improving the heat resistance cannot be achieved.

Meanwhile, the addition of the M element can achieve the effects of enabling the grain size of the crystal grains to be uniform and reducing the size deviation of the crystal grains, the squareness of the magnetic powder is improved, and the maximum magnetic energy product is not obviously reduced after the Y element is added. The adding proportion of the M element is calculated according to the adding amount of Y, the adding amount is 10% -50% of the mass of Y, too much adding inevitably causes the great reduction of the comprehensive magnetic performance of the magnetic powder, too little adding inevitably does not improve the squareness of the magnetic powder, and the effect of not obviously reducing the maximum magnetic energy product is kept.

Wherein the calculation formula of the coercivity temperature coefficient within 120 ℃ is as follows:

(coercivity-1 at 120 ℃ C./20 ℃ C. (room temperature defined in general) and (120-20) at present, the temperature coefficient of coercivity of an anisotropic bonded magnetic powder is about-0.56%/° C. The temperature coefficient of coercive force of the bonded magnetic powder prepared by the invention can be larger than-0.5%/DEG C.

Further, the anisotropic bonded magnetic powder particles comprise a magnetic powder particle with a ratio of 2:14:1 is a main phase of a crystal structure and a grain boundary phase surrounding the main phase. The anisotropic bonded magnetic powder particles are mainly made of a compound with a stoichiometric ratio of chemical elements of 2:14:1, and are called as a main phase; a layer of rare earth-rich phase with the thickness of 1-5nm exists between the crystal grains of the main phase of the 2:14:1 type compound, and the phase is called a grain boundary phase

Further, the ratio of the content of M in the grain boundary phase to the content in the main phase is greater than 2. The element M is enriched in the crystal boundary phase, so that the pinning effect on the crystal boundary is favorably realized, the appearance of abnormally grown crystal grains is inhibited, and the crystal grain size of the anisotropic bonded magnetic powder is uniform.

Further, the grain size sigma of the main phase is 200-400nm, and the standard deviation of the grains is below 0.5 sigma. The rare earth anisotropic bonded magnetic powder has a recrystallization aggregate structure peculiar to an R-T-B magnet obtained by HDDR treatment, that is, a structure having an average crystal grain diameter of 200 to 400 nm. The crystal grains constituting the recrystallized texture are a 2:14:1 type compound phase. Each powder particle of the HDDR magnetic powder contains a large number of fine crystal grains. The average particle diameter and standard deviation of these crystal grains were measured by observing a cross section of the magnetic powder with a Transmission Electron Microscope (TEM). Specifically, the average grain size and standard deviation of crystal grains can be determined by image analysis of each crystal grain of a TEM image obtained from a sample of magnetic powder processed into a thin slice by Focused Ion Beam (FIB) or the like. Wherein the particle size of the individual crystal grains is calculated as a projected area equivalent diameter in a TEM image of the individual crystal grains, and the average particle size can be obtained by simply averaging the equivalent diameters of the individual crystal grains. Further, the standard deviation is obtained by statistical calculation from the average particle diameter and the particle diameter of each crystal grain. For rare earth anisotropic magnetic powder, the more uniform the grain size, the higher the squareness of the corresponding demagnetization curve, and the higher the maximum magnetic energy product. Therefore, the smaller the standard deviation of the crystal grain size, the more uniform the crystal grain size, and the higher the maximum magnetic energy product of the magnetic powder. The standard deviation of the grain size of the rare earth anisotropic magnetic powder is below 0.5 times of the average grain diameter of the grains. Other documents are silent as to this.

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

hydrogen absorption disproportionation stage: the rare earth anisotropic bonded magnetic powder RYFeMB alloy is characterized in that R accounts for 28.5 to 30.5 percent of the total mass, and B accounts for 0.97 to 1.05 percent of the total mass; the mass fraction of Y in the total mass is 0.1-5%; the M accounts for 10-50% of the mass fraction of the Y; placing the alloy in a rotary gas-solid reaction furnace, heating to a first temperature T1 under the hydrogen pressure of 0-0.1MPa, wherein the range of T1 is 760-860 ℃, then keeping the hydrogen pressure at a first pressure P1 and the range of P1 is 20-100kPa, and preserving heat for 1-4 h to finish the treatment of a hydrogen absorption disproportionation stage;

slow dehydrogenation repolymerization stage: after the hydrogen absorption disproportionation stage is finished, keeping the temperature in the furnace to 800-;

a complete dehydrogenation stage: after the slow dehydrogenation repolymerization stage is finished, quickly vacuumizing to the hydrogen pressure below 1Pa to finish the complete dehydrogenation stage;

and (3) a cooling stage: and after the complete dehydrogenation stage is finished, cooling to room temperature to obtain the rare earth anisotropic bonded magnetic powder.

Further, between the hydrogen absorption disproportionation stage and the slow dehydrogenation repolymerization stage, the method also comprises the following steps: after the hydrogen absorption disproportionation stage is finished, raising the temperature in the furnace to T2, increasing the hydrogen pressure to P2 at the same time, ensuring that T2 is more than or equal to T1 and P2 is more than or equal to P1, and finishing the treatment in the tissue stabilization stage.

Further, the cooling stage comprises a step cooling: after the complete dehydrogenation stage is completed, starting cooling, wherein the cooling speed is 30-50 ℃/min at the temperature of above 650 ℃; cooling at a temperature below 650 deg.C at a rate of 10-35 deg.C/min.

A third aspect of the invention provides a rare earth anisotropically bonded magnet comprising the rare earth anisotropically bonded magnetic powder as described above.

The present invention will be further described with reference to the following specific examples.