A rare earth auxiliary alloy powder, a preparation method and application thereof

Abstract

This invention discloses a rare earth auxiliary alloy powder, according to RE x M 100‑x‑y B y The rare earth auxiliary alloy powder is prepared by weight percentage. RE is a mixture of one or more elements selected from Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; M is a mixture of one or more elements selected from Mg, Al, Ca, Ti, V, Fe, Co, Ni, Cu, Zn, Ga, In, Sn, Sb, and Bi, wherein 30% ≤ x ≤ 80% and 0 ≤ y ≤ 0.5%. RE is added in the form of elemental metal or RE-Fe, M is added in the form of powder or alloy powder, and B is added in the form of B-Fe sand. The mixture is then added to a hydrogen crushing furnace for mixing and hydrogen crushing to obtain rare earth auxiliary alloy powder. Its application in the preparation of sintered NdFeB magnets can improve the coercivity, reduce the remanence reduction, and reduce the amount of heavy rare earth elements used.

Description

Technical Field

[0001] This invention relates to the field of neodymium iron boron magnet preparation technology, specifically to a rare earth auxiliary alloy powder, its preparation method, and its application. Background Technology

[0002] Third-generation permanent magnet materials, sintered Nd-Fe-B alloys, possess high coercivity, high remanence, and high energy product, making them indispensable functional materials in modern society. They are widely used in new energy, information technology, and other fields. With the development of clean energy and next-generation information products, the consumption of sintered Nd-Fe-B permanent magnets is also increasing dramatically.

[0003] Nd2Fe 14 The theoretical remanence of alloy B is Br = 16.0 kGs, and its theoretical magnetic energy product (BH) is... m =64 MGOe, theoretical coercivity j Hc = 67 kOe. Currently, Nd₂Fe 14 The remanence of NdFeB alloy (Br) has reached 15.5 kGs, close to 97% of the theoretical value, and the magnetic energy product (BH)m is close to 59.55 MGOe, reaching 93% of the theoretical value. However, its coercivity (Hcj) is currently only 8.2 kOe, only 12% of the theoretical value, indicating significant room for improvement. Adding heavy rare earth elements (Dy and Tb) to NdFeB alloys can significantly improve the coercivity of the magnets. However, the magnetic moments of Dy and Tb interact with the magnetic moment of Fe, resulting in antiferromagnetic coupling and a decrease in the remanence of the rare earth magnets. Furthermore, the reserves of heavy rare earth elements (Dy and Tb) are far lower than those of light rare earth elements (La, Ce, Pr, and Nd), leading to significantly higher market prices. Extensive use of heavy rare earth elements (Dy and Tb) is also detrimental to the rational and balanced utilization of rare earth resources.

[0004] At present, the industry mainly focuses on improving the coercivity of sintered NdFeB magnets while reducing the cost of the products. The mainstream process technology is to optimize the material composition and microstructure to improve the coercivity, and to use mixed rare earth and reduce heavy rare earth to reduce material costs. The main technologies include: (1) grain refinement of sintered magnets, (2) dual alloy technology of sintered magnets, (3) heat treatment optimization technology of sintered magnets, (4) composition optimization of mixed rare earth sintered magnets, and (5) grain boundary diffusion technology.

[0005] In dual-alloy technology, the main process involves using primary and secondary alloy sheets. This involves simultaneously melting a primary alloy with high remanence and low coercivity, and a secondary alloy with a high rare-earth content. These are then mixed in a specific ratio, powdered, shaped, sintered, and heat-treated. The secondary alloy optimizes the grain boundary phase to enhance coercivity. For example, patent application CN103103442A, "Method for Preparing NdFeB Using Primary and Secondary Alloys," uses a secondary alloy ingot or sheet with a high rare-earth content. This provides a richer rare-earth liquid phase during sintering and aging to strengthen the grain boundaries of the primary phase, isolating the magnetic coupling between the primary phase grains and thus improving the magnet's coercivity. Patent application CN111696742A, "A High-Performance NdFeB Permanent Magnet Material Without Heavy Rare Earth and Its Preparation Method," improves coercivity by adding PrNi alloy sheets with high rare-earth content without using heavy rare-earth alloys. Patent application CN111834118A, "A Method for Improving the Coercivity of Sintered NdFeB Magnets," designs RE... x M y M' 14-y The process involves mixing the strip sheet with the main alloy, powdering, forming, sintering, and aging to form a specific RE6M. 13 The M'1 non-magnetic phase isolates the magnetic coupling effect between the main phase grains, improving the coercivity of the magnet. In the aforementioned processes, the auxiliary alloy is manufactured using a combination of main and auxiliary alloy design elements—melting and casting ingots or sheets—proportioning of main and auxiliary alloy sheets—hydrogenation—air jet milling—forming—sintering—aging process. In other words, the auxiliary alloy powder is produced using the melting and casting method. However, the main-auxiliary alloy process requires the simultaneous melting of two alloy sheets with different formulations, increasing the auxiliary alloy melting step. Furthermore, the internal structure forms a dual-main-phase structure. While the auxiliary alloy primarily optimizes the grain boundary phase to improve coercivity, the increase is limited. Additionally, the incorporation of a significant amount of rare earth elements into the main phase leads to a substantial decrease in remanence. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned deficiencies and to disclose to the public a rare earth auxiliary alloy powder, its preparation method and application, which can improve the magnetic properties of sintered NdFeB products without relying on the smelting auxiliary alloy casting process. Compared with conventional alloy addition, the coercivity is increased by 1000-1500 Oe, the remanence is reduced by 100-200 Gs, and the amount of heavy rare earth elements used can be reduced.

[0007] The technical solution of this invention is implemented as follows:

[0008] A rare earth auxiliary alloy powder, according to RE x M 100-x-y B yThe ingredients are formulated by weight percentage, wherein RE is a mixture of one or more elements selected from Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and M is a mixture of one or more elements selected from Mg, Al, Ca, Ti, V, Fe, Co, Ni, Cu, Zn, Ga, In, Sn, Sb, and Bi, wherein 30% ≤ x ≤ 80% and 0 ≤ y ≤ 0.5%.

[0009] As an improvement, the melting point of the added M metal is controlled to be lower than that of RE.

[0010] As an improvement, the mixture can be controlled to form intermetallic compounds at 500-800℃.

[0011] A method for preparing rare earth auxiliary alloy powder includes the following steps: RE is added in the form of metallic element or RE-Fe, M is added in the form of powder or alloy powder, and B is added in the form of B-Fe sand in a specific ratio, and mixed and hydrogenated in a hydrogen crushing furnace; hydrogen is first introduced into the furnace to carry out a hydrogen absorption reaction, and when the pressure inside the furnace reaches the upper limit protection of 0.1 MPa, water cooling is performed, and the hydrogen absorption temperature is controlled at 200-350℃, and the hydrogen absorption time is controlled at 60-120 min; after the hydrogen absorption is completed, dehydrogenation treatment is performed. The first step of dehydrogenation is carried out by heating to 400-600℃ at a heating rate of 10-30℃ / min and holding for 60-120 min; the second step is to heat to 500℃-800℃ at a heating rate of 10-30℃ / min and hold for 60 min, while adjusting the furnace rotation speed to 6-9 r / min so that the added M metal powder can uniformly coat RE or RE-Fe to form an M metal coating layer of a certain thickness, thereby modifying the surface of the rare earth metal and forming rare earth auxiliary alloy powder.

[0012] As an improvement, elemental RE or RE-Fe is first crushed into blocks of 20mm-50mm before being added to the hydrogen crushing furnace. The particle size of M powder or alloy powder is controlled at 0.1-5μm. During the hydrogen crushing process, elemental RE or RE-Fe is first dehydrogenated and crushed into small particles at 400℃-600℃, and then the temperature is increased accordingly to 500℃-800℃ so that the added M powder or alloy powder becomes liquid or solid particles at a relatively high temperature and uniformly coats elemental RE.

[0013] As an improvement, after RE metal elemental or RE-Fe, M powder or its alloy powder, B-Fe sand are loaded into the hydrogen crushing furnace, they are first rotated and stirred for 30-60 minutes to ensure that the metal powder is mixed evenly before hydrogen crushing.

[0014] An application of a rare earth auxiliary alloy powder in the preparation of sintered NdFeB magnets.

[0015] The method for preparing the sintered NdFeB magnet includes:

[0016] Step 1: Build RE x M y B z Fe 100-x-y-z The main alloy is smelted to form a strip casting, wherein RE includes at least two elements selected from Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and M includes at least three elements selected from C, O, Mg, Al, Si, Ca, Ti, V, Co, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Sn, Ta, W, and Bi, and x, y, and z are the weight percentages of their respective elements, and 29%wt≤x≤34%wt, 0.1%wt≤y≤5%wt, and 0.8%wt≤z≤1.4%wt;

[0017] Step 2: Hydrogen crush the strip castings obtained in Step 1 at a temperature of 400℃-600℃ for a time of not less than 3 hours. After hydrogen crushing, rare earth auxiliary alloy powder is added and mixed evenly for 1 hour to obtain coarse material.

[0018] Step 3: The mixed coarse powder is pulverized using an air jet mill at a speed of 2800-3800 r / min to obtain sintered NdFeB fine powder;

[0019] Step 4: The obtained NdFeB fine powder is oriented, pressed, and isostatically pressed to obtain sintered NdFeB green blanks.

[0020] Step 5: Sinter the NdFeB green blank in a vacuum or inert gas atmosphere. The sintering temperature is raised to 800-900℃ and held for 3-4 hours. The sintering temperature is 900℃-1100℃ and held for 6-8 hours to obtain the sintered NdFeB green blank.

[0021] Step 6: The sintered billet is subjected to two-stage aging in a sealed box. The first stage of aging is carried out at a temperature of 650℃-950℃ for 3-5 hours. After argon purging and cooling to 70℃, the second stage of aging begins. The second stage of aging is carried out at a temperature of 450℃-650℃ for 3-8 hours. After argon purging and cooling to room temperature, sintered NdFeB magnets are obtained.

[0022] As an improvement, in step two, the weight percentage of rare earth auxiliary alloy powder is 0.5%-15%.

[0023] As an improvement, in step five, the vacuum degree is ≤10. -2 Pa.

[0024] The advantages of this invention compared to the prior art are:

[0025] (1) After mixing RE or RE-Fe with low-melting-point metal powder M, the temperature is controlled during the hydrogen crushing process to form RE metal powder wrapped by M metal. During the sintering and aging process, the low-melting-point outer layer of M metal melts and diffuses into the grain boundary phase. Finally, the added RE metal melts and diffuses, so that the added RE metal is "slowly released" into the grain boundary phase to increase the thickness of the grain boundary phase, enhance the decoupling effect of the main phase, and achieve the effect of enhancing coercivity.

[0026] (2) Due to the “slow release effect” of RE metal, only a small proportion of RE metal enters the main phase, which has little effect on remanence but increases coercivity by a relatively large margin.

[0027] (3) Optimize grain boundary structure, generate specific non-magnetic phases and increase the thickness of grain boundary phases, thereby improving the demagnetizing coupling effect of grain boundary phases. Under the same addition ratio, the coercivity improvement is 1000-1500 Oe greater than that of conventional addition, and the remanence reduction is 100-200 Gs less.

[0028] (4) This invention employs the direct addition of appropriately proportioned auxiliary alloy raw materials during the hydrogen crushing process. The auxiliary alloy powder is produced by matching the hydrogen crushing temperature and hydrogen pressure. Simultaneously, the hydrogen crushing temperature is controlled to micro-alloy the added elements on their surfaces, preventing element segregation. The main alloy rough is then mixed with the powder during or after the hydrogen crushing process and subjected to air jet milling. By combining the melting points of the added metal elements in the rare earth auxiliary alloy and controlling the sintering temperature, the amount of rare earth metal entering Nd2Fe in the rare earth auxiliary alloy is minimized. 14 B increases the thickness of the grain boundary phase, improves the coercivity of the magnet while reducing the remanence, reduces element loss during the auxiliary alloy smelting process, and reduces the use of heavy rare earth elements. Attached Figure Description

[0029] Figure 1 This is a flowchart of the process for preparing sintered NdFeB magnets using rare earth auxiliary alloy powder according to the present invention;

[0030] Figure 2 These are SEM images and energy dispersive spectroscopy (EDS) analyses of Pr, Nd, and Cu elements in the coarse rare earth auxiliary alloy powder particles after hydrogen crushing. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings:

[0032] A rare earth auxiliary alloy powder, according to RE x M 100-x-y B yThe ingredients are formulated by weight percentage, wherein RE is a mixture of one or more elements selected from Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and M is a mixture of one or more elements selected from Mg, Al, Ca, Ti, V, Fe, Co, Ni, Cu, Zn, Ga, In, Sn, Sb, and Bi, wherein 30% ≤ x ≤ 80% and 0 ≤ y ≤ 0.5%.

[0033] Furthermore, in the selection of M and RE, the melting point of the added M metal is controlled to be lower than that of RE; and the mixture is controlled to form an intermetallic compound at 500-800℃.

[0034] A method for preparing rare earth auxiliary alloy powder includes the following steps: RE is added to a hydrogen crushing furnace in the form of elemental metal or RE-Fe, M is added in the form of powder or alloy powder, and B is added in the form of B-Fe sand. After the powder is added to the hydrogen crushing furnace, it is first stirred by rotation for 30-60 minutes to ensure that the metal powder is mixed evenly. Then, it is added to the hydrogen crushing furnace for mixed hydrogen crushing. Hydrogen is first introduced into the furnace to carry out a hydrogen absorption reaction. When the pressure inside the furnace reaches the upper limit protection of 0.1 MPa, water cooling is performed to control the hydrogen absorption temperature at 200-350℃ and the hydrogen absorption time at 60-120 minutes. After hydrogen absorption, dehydrogenation is performed. The first step involves heating to 400-600℃ at a rate of 10-30℃ / min and holding for 60-120 minutes. The second step involves heating to 500℃-800℃ at a rate of 10-30℃ / min and holding for another 60 minutes, while adjusting the furnace rotation speed to 6-9 r / min. This allows the added M metal powder to uniformly coat RE or RE-Fe, forming an M metal coating layer of a certain thickness, thus performing surface metal modification on the rare earth metal and forming rare earth auxiliary alloy powder (grain boundary phase precursor). The resulting rare earth auxiliary alloy powder allows the added M metal powder to uniformly coat RE or RE-Fe, forming an M metal coating layer of a certain thickness, thus performing surface metal modification on the rare earth metal.

[0035] The above dehydrogenation process adopts a two-step dehydrogenation process. The first step ensures that the RE metal element or RE-Fe can be completely dehydrogenated. The second step ensures that the added metal M can form a certain degree of metal compound with the RE metal or RE-Fe. The dehydrogenation temperature of the second step is determined according to 1-1.2 times the lowest melting point of the metal compound that the added metal mixture can form.

[0036] By mixing RE or RE-Fe with low-melting-point metal powder M, the temperature is controlled during hydrogen sintering to form RE metal powder encapsulated by M metal. During sintering and aging, the low-melting-point outer layer of M metal melts and diffuses into the grain boundary phase. Finally, the added RE metal melts and diffuses, achieving a "slow release" of the added RE metal into the grain boundary phase, increasing the thickness of the grain boundary phase, enhancing the decoupling effect of the main phase, and thus enhancing the coercivity.

[0037] Furthermore, due to the "slow-release effect" of RE metal, only a small proportion of RE metal enters the main phase, having virtually no impact on remanence while significantly increasing coercivity. Experimental calculations show that compared to conventional alloy additions, the increase in coercivity is 1000-1500 Oe, and the decrease in remanence is reduced by 100-200 Gs.

[0038] Furthermore, elemental RE or RE-Fe is first crushed into 20mm-50mm blocks before being added to the hydrogen crushing furnace. The particle size of M powder or alloy powder is controlled at 0.1-5μm. During the hydrogen crushing process, elemental RE or RE-Fe is first dehydrogenated and crushed into small particles at 400℃-600℃, and then the temperature is increased accordingly to 500℃-800℃ so that the added M powder or alloy powder forms liquid or solid particles that uniformly coat the elemental RE at a relatively high temperature. This is beneficial because the rare earth auxiliary alloy powder has less rare earth element entering the main phase during the sintering process, and only forms a specific non-magnetic phase at the grain boundary phase position, increasing the thickness of the grain boundary phase.

[0039] An application of a rare earth auxiliary alloy powder in the preparation of sintered NdFeB magnets.

[0040] The above-mentioned method for preparing sintered NdFeB magnets includes:

[0041] Step 1: Build RE x M y B z Fe 100-x-y-z The main alloy is smelted to form a strip casting, wherein RE includes at least two elements selected from Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and M includes at least three elements selected from C, O, Mg, Al, Si, Ca, Ti, V, Co, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Sn, Ta, W, and Bi, and x, y, and z are the weight percentages of their respective elements, and 29%wt≤x≤34%wt, 0.1%wt≤y≤5%wt, and 0.8%wt≤z≤1.4%wt.

[0042] Step 2: The strip castings obtained in Step 1 are subjected to hydrogen pulverization at a temperature of 400℃-600℃ for at least 3 hours. Rare earth auxiliary alloy powder is then added and mixed uniformly for 1 hour to obtain coarse material. The weight percentage of rare earth auxiliary alloy powder is 0.5%-15%.

[0043] Step 3: The mixed coarse powder is pulverized using an air jet mill at a speed of 2800-3800 r / min to obtain sintered NdFeB fine powder.

[0044] Step 4: The obtained NdFeB fine powder is oriented, pressed, and isostatically pressed to obtain sintered NdFeB green blanks.

[0045] Step 5: Place the NdFeB green blank under a vacuum (vacuum degree ≤ 10). -2 Sintering is carried out under an inert gas atmosphere (Pa) or by heating to 800-900℃ and holding for 3-4 hours, followed by sintering at 900℃-1100℃ and holding for 6-8 hours to obtain sintered NdFeB blanks. The formed NdFeB blanks are composed of Nd2Fe 14 The structure consists of a B main phase, a rare earth-rich phase, and RE metal powder encapsulated by an M metal layer. The sintering process begins with heating from room temperature to the sintering temperature. During this heating process, the outer M metal first diffuses or melts into the grain boundary phase. Finally, the added RE metal undergoes melting and diffusion, achieving a "slow-release" effect where the added RE metal enters the grain boundary phase, increasing its thickness and enhancing the decoupling effect of the main phase. A very small amount of RE metal enters Nd₂Fe. 14 B is the main phase, thereby achieving the purpose of enhancing coercivity.

[0046] Step 6: The sintered billet is subjected to two-stage aging in a sealed box. The first stage of aging is carried out at a temperature of 650℃-950℃ for 3-5 hours. After argon purging and cooling to 70℃, the second stage of aging begins. The second stage of aging is carried out at a temperature of 450℃-650℃ for 3-8 hours. After argon purging and cooling to room temperature, sintered NdFeB magnets are obtained.

[0047] The following specific examples further illustrate this point:

[0048] Example 1:

[0049] According to weight percentage (PrNd) 80 Cu 20 PrNd metal blocks of about 20 mm and nano-Cu powder (~100 nm) were added to the hydrogen crushing furnace in the following proportions. The mixture was first rotated and stirred for 30 minutes to ensure that the metal powders were mixed evenly, and then hydrogen crushing was performed.

[0050] The hydrogen-containing furnace is first charged with hydrogen gas to induce a hydrogen absorption reaction. When the furnace pressure reaches the upper limit protection of 0.1 MPa, water cooling is applied to control the hydrogen absorption temperature at 300℃ and the hydrogen absorption time at 120 min. After hydrogen absorption, a two-step dehydrogenation process is performed. The first step involves heating to 450℃ at a rate of 10℃ / min and holding for 120 min. The second step involves heating to 600℃ at a rate of 15℃ / min and holding for 120 min. The furnace rotation speed is adjusted to a suitable frequency of 6 r / min to ensure that the added M metal powder can uniformly coat RE or RE-Fe, forming an M metal coating layer of a certain thickness, thus obtaining rare earth auxiliary alloy powder A.

[0051] According to the Nd-Cu binary alloy phase diagram, when the alloy Nd 84 Cu 16 When the Nd:Cu atomic ratio is 7:3, the alloy melting point is approximately 520℃. The second dehydrogenation temperature is determined to be 1-1.2 times the lowest melting point at which the added metal mixture can form a metal compound. At this temperature, due to the interdiffusion of elements, the metal mixture can form a certain degree of metal compound. Therefore, the dehydrogenation temperature is determined to be 600℃. At this temperature, due to the interdiffusion between atoms, a Cu metal layer of a certain thickness can be formed on the RE metal surface with a certain degree of bonding force.

[0052] The particles of rare earth auxiliary alloy powder A were characterized by SEM, as detailed in the figure below. Figure 2 It can be seen that nano-Cu metal forms a relatively uniform coating layer on the surface of PrNd metal.

[0053] The weight percentage is (PrNdHo) 30.5 (BAlCuCoGaZr) 2.9 Fe bal The raw materials are batched and alloy sheets are obtained using a rapid solidification thin sheet process, and coarse main alloy powder is obtained using a hydrogen-crushing process.

[0054] The rare earth auxiliary alloy powder A and the main alloy coarse powder were mixed together, with rare earth auxiliary alloy powder A accounting for 1% of the total weight, and the mixing time was 1 hour. The mixed main and auxiliary alloy coarse materials were subjected to an air jet mill with a sorting wheel speed of 3200 rpm to obtain fine powder with a particle size of about 2.8 μm.

[0055] The obtained fine powder was pressed into shape under nitrogen protection to obtain NdFeB green blanks. The NdFeB green blanks were then further processed under vacuum (vacuum degree ≤ 10). -2 The sintering process is carried out in an inert gas atmosphere (Pa) or an inert gas atmosphere. The sintering temperature is 890℃ for 4 hours and 1075℃ for 7 hours to obtain sintered NdFeB blanks.

[0056] The sintered blank was subjected to two-stage aging in a sealed container. The first stage of aging involved holding the blank at 890℃ for 3 hours, followed by argon purging and cooling to 70℃ before starting the second stage of aging. The second stage involved holding the blank at 480℃ for 6 hours, followed by argon purging and cooling to room temperature. This yielded a sintered and aged NdFeB magnet blank, which was then machined into a 10mm × 10mm sample column for magnetic performance testing.

[0057] Comparative Example 1-1 uses (PrNdHo) as the component. 30.5 (BAlCuCoGaZr) 2.9 Fe bal The main alloy powder is supplemented with rare earth auxiliary alloy powder A-(PrNd) according to the method described above. 80 Cu 20 The percentage of the total weight is 0%, and the magnetic properties of the resulting sintered aged magnet are: Br-13.4kGs, Hcj-18.5kOe.

[0058] Comparative Examples 1-2 used components of (PrNdHo) 30.5 (BAlCuCoGaZr) 2.9 Fe bal The main alloy powder is prepared without rare earth auxiliary alloy powder A according to the above method. Before the air jet mill, 0.8% PrNd and 0.2% Cu powder by weight are added and mixed evenly. The magnetic properties of the resulting sintered and aged magnet are: Br-12.95kGs, Hcj-19.5kOe.

[0059] Example 1-1 uses a component of (PrNdHo) 30.5 (BAlCuCoGaZr) 2.9 Fe bal The main alloying powder is supplemented with auxiliary alloying powder A-(PrNd) according to the method described above. 80 Cu 20 The percentage of the total weight is 1%, and the resulting sintered aged magnet properties are: Br-13.1, Hcj-20.54.

[0060] The properties of sintered NdFeB magnets using auxiliary alloy powder A are listed in Table 1:

[0061] Table 1 compares the performance of magnets prepared in Comparative Examples 1-1 to 1-2 with those prepared in Example 1-1:

[0062] Comparative Example 1-1 Rare Earth Auxiliary Alloy Powder A 0 13.40 18.50 Comparative Examples 1-2 Regular addition 0.8% PrNd + 0.2% Cu 12.95 19.50 Example 1-1 Rare Earth Auxiliary Alloy Powder A 1％ 13.10 20.54

[0063] Comparative data of magnet performance prepared by Comparative Examples 1-1, 1-2 and Example 1-1 show that rare earth auxiliary alloy powder A using this technical solution can increase coercivity by 1040 Oe and reduce remanence by 150 Gs compared with conventional mixing and addition. This technical solution can effectively increase the coercivity of sintered NdFeB magnets with less reduction in remanence.

[0064] Example 2:

[0065] According to weight percentage (PrNd) 70 Cu 20 Ga 10 The materials were fed in the following proportions: PrNd metal blocks, Cu powder (~100nm), and metallic Ga were added to the hydrogen crushing furnace. The mixture was first rotated and stirred for 30 minutes to ensure that the metal powders were mixed evenly, and then hydrogen crushing was performed.

[0066] The hydrogen crusher is first charged with hydrogen gas to induce a hydrogen absorption reaction. When the pressure inside the furnace reaches the upper limit protection of 0.1 MPa, water cooling is performed to control the hydrogen absorption temperature at 300℃ and the hydrogen absorption time at 120 min. A two-step dehydrogenation process is adopted. In the first step, the temperature is increased to 480℃ at a heating rate of 10℃ / min and held for 120 min. In the second step, the temperature is increased to 570℃ at a heating rate of 15℃ / min and held for 120 min. The furnace rotation speed is adjusted to a suitable frequency of 6 r / min so that the added metallic Ga and nano-Cu powder can coat RE to form a metal coating of a certain thickness.

[0067] A layer of metal compound containing Pr, Nd, Cu, and Ga elements can be formed on the surface of RE metal in the mixture, resulting in rare earth auxiliary alloy powder B.

[0068] The weight percentage is (PrNdDy) 30.5 (BAlCuCoZr) 2.37 Fe bal The raw materials are batched and alloy sheets are obtained using a rapid solidification thin sheet process, and coarse main alloy powder is obtained using a hydrogen-crushing process.

[0069] The rare earth auxiliary alloy powder B and the main alloy coarse powder are mixed together, with the rare earth auxiliary alloy powder B accounting for 1%-2% of the total weight, and the mixing time is 1 hour. The mixed main and auxiliary alloy coarse materials are subjected to an air jet mill with a sorting wheel speed of 3200 rpm to obtain fine powder with a particle size of about 3.0 μm.

[0070] The obtained fine powder was pressed into shape under nitrogen protection to obtain NdFeB green blanks. The NdFeB green blanks were then further processed under vacuum (vacuum degree ≤ 10). -2 The sintering process is carried out in an inert gas atmosphere (Pa) or an inert gas atmosphere. The temperature is maintained at 890℃ for 3 hours during the sintering process, and the sintering temperature is 1080℃ to obtain sintered NdFeB blanks.

[0071] The sintered blank was subjected to two-stage aging in a sealed container. The first stage of aging involved holding at a predetermined temperature between 80°C and 90°C for 3 hours, followed by argon purging and cooling to 70°C before initiating the second stage of aging. The second stage of aging involved holding at 490°C for 6 hours, followed by argon purging and cooling to room temperature. This yielded a sintered and aged NdFeB magnet blank, which was then machined into a 10mm × 10mm sample column for magnetic performance testing.

[0072] Comparative Example 2-1 uses (PrNdDy) as the component. 30.5 (AlCuCoZr) 1.42 B 0.95 Fe bal Rare earth permanent magnet materials are prepared by adding rare earth auxiliary alloy powder B-(PrNd) according to the above method. 70 Cu 20 Ga 10 The percentage of the total weight is 0%, and the magnetic properties of the resulting sintered aged magnet are: Br-14.3kGs, Hcj-15.5kOe.

[0073] Comparative Example 2-2 uses (PrNdDy) as the component. 30.5 (AlCuCoZr) 1.42 B 0.95 Fe bal The rare earth permanent magnet material was prepared by the above method without adding rare earth auxiliary alloy powder B. Before the air jet mill, 0.7% PrNd, 0.2% Cu powder, and 0.1% Ga by weight were added and mixed evenly. The magnetic properties of the resulting sintered and aged magnet were: Br-14.05kGs, Hcj-16.5kOe.

[0074] Example 2-1: The component is (PrNdDy) 30.5 (AlCuCoZr) 1.42 B 0.95 Fe bal Rare earth permanent magnet materials are made by adding rare earth auxiliary alloy powder (B-PrNd) according to the above method. 70 Cu 20 Ga 10 The percentage of the total weight is 1%, and the resulting sintered aged magnet properties are: Br-14.17, Hcj-17.6.

[0075] Example 2-2 uses a component of (PrNdDy) 30.5 (AlCuCoZr) 1.42 B 0.95 Fe bal Rare earth permanent magnet materials are prepared by adding rare earth auxiliary alloy powder B-(PrNd) according to the above method. 70 Cu 20 Ga 10The percentage of the total weight is 2%, and the resulting sintered aged magnet properties are: Br-14.08, Hcj-18.2.

[0076] The properties of sintered NdFeB magnets using auxiliary alloy powder B are listed in Table 2:

[0077] Table 2 compares the performance of magnets prepared in Comparative Examples 2-1 to 2-2 with those prepared in Examples 2-1 to 2-2:

[0078]

[0079] Comparative data of magnet performance prepared in Examples 2-1 to 2-2 and Examples 2-3 to 2-4 show that rare earth auxiliary alloy powder B using this technical solution can increase coercivity by 1100 Oe and reduce remanence by 120 Gs less than conventional mixing and addition. This technical solution can effectively increase the coercivity of sintered NdFeB magnets with less reduction in remanence.

[0080] The preferred embodiments of the present invention have been described, and various changes or modifications made by those skilled in the art will not depart from the scope of the present invention.

Claims

1. A method for preparing rare earth auxiliary alloy powder, characterized in that: According to RE x M 100-x-y B y The ingredients are weighed in percentage, wherein RE is one or more than one element of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and M is one or more than one element of Mg, Al, Ca, Ti, V, Fe, Co, Ni, Cu, Zn, Ga, In, Sn, Sb, Bi, wherein 30%≤x≤80%, 0≤y≤0.5%, the added M metal is controlled to have a melting point lower than that of RE, and the mixture is controlled to form intermetallic compounds at 500-800℃. The process includes the following steps: RE is added in the form of elemental metal or RE-Fe, M is added in the form of powder or alloy powder, and B is added in the form of B-Fe sand in a specific ratio. These are then mixed and hydrogenated in a hydrogen crushing furnace. Hydrogen is first introduced into the furnace for hydrogen absorption. When the furnace pressure reaches the upper limit protection of 0.1 MPa, water cooling is performed to control the hydrogen absorption temperature at 200-350℃ and the absorption time at 60-120 min. After hydrogen absorption, dehydrogenation is performed. The first step of dehydrogenation involves heating to 400-600℃ at a rate of 10-30℃ / min and holding for 60-120 min. The second step involves heating to 500℃-800℃ at a rate of 10-30℃ / min and holding for 60 min. The furnace rotation speed is adjusted to 6-9 r / min to ensure that the added M metal powder can uniformly coat RE or RE-Fe, forming an M metal coating layer of a certain thickness. This surface metal modification of the rare earth metal results in rare earth auxiliary alloy powder.

2. The method for preparing rare earth auxiliary alloy powder according to claim 1, characterized in that: RE or RE-Fe is first crushed into 20mm-50mm blocks and then added to the hydrogen crushing furnace. The particle size of M powder or alloy powder is controlled at 0.1-5μm. During the hydrogen crushing process, RE or RE-Fe is first dehydrogenated and crushed into small particles at 400℃-600℃, and then the temperature is increased to 500℃-800℃ so that the added M powder or alloy powder becomes liquid or solid particles at a relatively high temperature and uniformly coats the RE.

3. The method for preparing rare earth auxiliary alloy powder according to claim 1, characterized in that: After RE metal elemental or RE-Fe, M powder or its alloy powder, B-Fe sand are loaded into the hydrogen crushing furnace, they are first rotated and stirred for 30-60 minutes to ensure that the metal powder is mixed evenly before hydrogen crushing.

4. The application of the rare earth auxiliary alloy powder prepared by the method for preparing rare earth auxiliary alloy powder according to claim 1, characterized in that: It is used in the preparation of sintered NdFeB magnets.

5. The application of the rare earth auxiliary alloy powder according to claim 4, characterized in that: The method for preparing the sintered NdFeB magnet includes: Step 1: Build RE x M y B z Fe 100-x-y-z The main alloy is smelted to form a strip casting, wherein RE includes at least two elements selected from Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and M includes at least three elements selected from C, O, Mg, Al, Si, Ca, Ti, V, Co, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Sn, Ta, W, and Bi, and x, y, and z are the weight percentages of their respective elements, and 29%wt≤x≤34%wt, 0.1%wt≤y≤5%wt, and 0.8%wt≤z≤1.4%wt; Step 2: Hydrogen crushing is performed on the strip casting sheet obtained in Step 1. The hydrogen crushing temperature is 400℃-600℃ and the hydrogen crushing time is not less than 3 hours. The rare earth auxiliary alloy powder is added to the powder making process after hydrogen crushing and mixed evenly for 1 hour to obtain the coarse material. Step 3: The mixed coarse powder is pulverized using an air jet mill at a speed of 2800-3800 r / min to obtain sintered NdFeB fine powder; Step 4: The obtained NdFeB fine powder is oriented, pressed, and isostatically pressed to obtain sintered NdFeB green blanks. Step 5: Sinter the NdFeB green blank in a vacuum or inert gas atmosphere. The sintering temperature is raised to 800-900℃ and held for 3-4 hours. The sintering temperature is 900℃-1100℃ and held for 6-8 hours to obtain the sintered NdFeB green blank. Step 6: The sintered billet is subjected to two-stage aging in a sealed box. The first stage of aging is carried out at a temperature of 650℃-950℃ for 3-5 hours. After argon purging and cooling to 70℃, the second stage of aging begins. The second stage of aging is carried out at a temperature of 450℃-650℃ for 3-8 hours. After argon purging and cooling to room temperature, sintered NdFeB magnets are obtained.

6. The application of the rare earth auxiliary alloy powder according to claim 5, characterized in that: In step two, the weight percentage of rare earth auxiliary alloy powder is 0.5%-15%.

7. The application of the rare earth auxiliary alloy powder according to claim 5, characterized in that: In step five, the vacuum degree is ≤10. -2 Pa.

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