Permanent magnet alloy powder, preparation method thereof, prepared permanent magnet and method

Abstract

The invention relates to the technical field of rare earth permanent magnet materials, in particular to permanent magnet alloy powder, a preparation method thereof, a prepared permanent magnet and a method. Wherein the permanent magnet alloy powder and the permanent magnet alloy comprise the following components: REa (La1-mCems) b-Feba-Mc-Tn-Bd, and RE is at least one of Pr, Nd, Sm, Y, Gd, Tb, Dy, Ho and Yb; m is at least one of Zr, Nb, Mo, Hf, Mn, Ta and W; t is at least one of Cr, V, Si and Ti; wherein 0 < a < = 2.0, 11 < = b < = 13.5, 0 < = c < = 1.5, 6 < = d < = 8.1, 0 < = m < = 1, and 0 < n < = 3.0. According to the permanent magnet alloy powder, lanthanum and cerium are adopted to replace part of precious rare earth elements to prepare the permanent magnet alloy powder, the cost can be greatly reduced, the oxidation resistance is improved and the flammability is reduced through a small amount of refractory metal M and antioxidant reinforced metal T matched elements, and the problem that a pure praseodymium neodymium-lanthanum cerium / cerium-based iron boron material is poor in temperature resistance and oxidation resistance is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth permanent magnetic materials, in particular to a permanent magnetic alloy powder and a preparation method thereof, and a permanent magnetic body and a preparation method thereof.

[0002] In particular, the invention relates to a rapid-quenching rare earth permanent magnetic powder containing a relatively high proportion of high-abundance rare earth, a magnet made from the magnetic powder and related production technology, which are applicable to the fields of information technology, automobiles and the like. Background Art

[0003] Using high-abundance, low-cost rare earth metals such as lanthanum and cerium to replace neodymium, praseodymium, and neodymium in magnetic powder production can reduce the cost of magnet raw materials and better meet the needs of the magnet market. At the same time, it can also promote the balanced utilization of rare earth resources and alleviate the over-consumption of praseodymium and neodymium rare earth resources.

[0004] However, the use of large amounts of lanthanum, cerium or other high-abundance, low-cost rare earth metals as substitutes in rapid quenching magnetic powders has two major problems: poor oxidation resistance and poor temperature resistance. This not only reduces the performance of rare earth magnets, but also affects the large-scale production and application of such rare earth magnets.

[0005] First, poor oxidation resistance. Lanthanum and cerium metals are very active and easily oxidized in air. The rapid oxidation of lanthanum cerium / cerium in praseodymium-neodymium-lanthanum-cerium / cerium-based permanent magnet materials will significantly reduce the magnetic properties of the material. At the same time, in order to obtain a higher coercive force to meet the needs of use, the total rare earth content of praseodymium-neodymium-lanthanum-cerium / cerium-based permanent magnet materials is often significantly higher than that of the positive part. The excess lanthanum cerium / cerium metal phase will be enriched in large quantities at the grain boundaries. Although this can increase the intrinsic coercive force, it also makes it more likely that the material will be oxidized along the grain boundaries, deteriorating the material performance. At the same time, the oxidation of a large amount of rare earth elements releases heat, which further promotes the rapid oxidation of the material, resulting in a significant increase in the risk of oxidation and combustion of the material, which can easily lead to serious safety accidents.

[0006] Second, the temperature resistance is poor. Theoretically, pure Ce2Fe 14 The Curie temperature of the B phase is about 424 K, La2Fe 14 B has a slightly higher Curie temperature, which can reach 530 K, but is still lower than Nd2Fe 14 The Curie temperature of B is 585 K, and its heat resistance is directly affected by its Curie temperature. The introduction of large amounts of lanthanum-cerium or cerium inevitably lowers the material's Curie temperature, resulting in poorer heat resistance. Although lanthanum offers better heat resistance than cerium, the lanthanum ion itself has a large radius, making the lanthanum-iron-boron phase unstable and difficult to form as a primary phase. The limited addition ratio of lanthanum has limited effect on improving heat resistance. When rare earth permanent magnets are used in harsh environments, performance limitations arise.

[0007] Existing technologies for treating magnetic powder oxidation resistance primarily utilize methods such as antioxidant additives, surface coating, and chemical conversion coating. These methods enhance the oxidation resistance of magnetic powders by coating the surface with an antioxidant layer to isolate the powder from air. However, these antioxidant modification methods require the introduction of a significant amount of non-magnetic phase, which reduces the proportion of the magnetic phase. Furthermore, the non-magnetic phase interacts with the magnetic powder, leading to ineffectiveness of the antioxidant coating and reduced magnetic powder performance. These methods fail to effectively address the poor oxidation resistance and temperature resistance associated with the substitution of lanthanum / cerium for rare earth magnetic powders. Summary of the Invention

[0008] The purpose of the present invention is to overcome the problems of rising prices of existing rare earth materials, poor oxidation resistance and temperature resistance of lanthanum and cerium-doped magnetic powders, and reduced magnetic properties and poor antioxidant effects of conventional anti-oxidation technologies. A permanent magnet alloy powder and a preparation method thereof, as well as a permanent magnet and a method for preparing the same are provided.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is: A first object of the present invention is to provide a permanent magnet alloy powder.

[0010] A permanent magnet alloy powder, the composition of the permanent magnet alloy is as follows: RE a (La 1-m Ce m ) b -Fe bal -M c -T n -B d , RE is at least two of Pr, Nd, Sm, Y, Gd, Tb, Dy, Ho and Yb; M is at least one of Zr, Nb, Mo, Hf, Mn, Ta and W; T is at least one of Cr, V, Si, and Ti; Among them, 0<a≤2.0, 11≤b≤13.5, 0≤c≤1.5 and 6≤d≤8.1, 0≤m≤1, 0<n≤3.0; the subscripts of each element are atomic ratios.

[0011] Among them, "bal" stands for "balanced atomic number", which is the abbreviation of Balance, indicating that the number of iron Fe atoms in the permanent magnet alloy molecule is calculated based on charge balance or chemical balance.

[0012] The present invention is based on RE2Fe 14B designs the permanent magnet alloy composition. Lanthanum and cerium are used in the permanent magnet alloy powder to partially replace precious rare earth elements, significantly reducing the cost of rare earth permanent magnet alloy powder. To address the poor temperature and oxidation resistance of pure praseodymium-neodymium-lanthanum-cerium / cerium-based iron-boron materials, small amounts of refractory metals (M) and antioxidant-enhancing metals (T) (such as Cr, V, Ti, and Si) are incorporated into the permanent magnet alloy powder. During the alloying process, the refractory metals (M) and antioxidant-enhancing metals (T) are uniformly distributed throughout the permanent magnet material. The doping of these metal elements refines the grain size, optimizes the grain boundary structure, and inhibits grain growth in the rare earth permanent magnet alloy. The high-melting-point non-magnetic phase hinders the expansion of magnetic domain walls or the reorientation of magnetic domains. This in turn hinders domain reversal caused by thermal disturbances at high temperatures after magnetization, reducing the rate of magnetic performance loss. On the other hand, doped metals enhance the pinning effect of magnetic domains, and the high-melting-point non-magnetic phase also "pins" and hinders the growth of grains, refining the grain size of the main phase inside the material. Uniform and fine nano-grains are a prerequisite for obtaining high-performance magnetic properties. Therefore, the addition of high-melting-point elements also further optimizes the magnetic properties of the material and improves the magnetic properties.

[0013] Then, when the surface of the permanent magnet alloy powder material encounters oxygen, these elements preferentially oxidize, forming a dense and uniform oxide film on the material's surface. This hinders the diffusion of oxygen molecules into the material, improving the material's oxidation resistance and significantly reducing the risk of performance failure during use. These modifications make lanthanum-cerium / cerium-iron-boron permanent magnet materials promising for commercial application. At the same time, the doping elements form a high-melting-point non-magnetic phase at the grain boundaries of the primary phase.

[0014] Therefore, the rare earth permanent magnet alloy powder of the present invention combines the grain boundary diffusion characteristics of the permanent magnet alloy powder during oxidation, and the added refractory metal M and antioxidant strengthening metal T improve the oxidation resistance of the material, effectively controlling the oxidation of the material at higher temperatures, so that the material has a smaller magnetic property loss at high temperatures, ensuring that the material can be used at higher temperatures and meeting the requirements of high temperature use environments.

[0015] In summary, the present invention realizes the preparation of rare earth permanent magnet alloys with cheap rare earth elements, obtains high oxidation resistance, and at the same time has good magnetic performance. Rare earth permanent magnet alloy products with good magnetic properties can be obtained at a relatively low cost, and the products can maintain magnetic properties under relatively harsh high-temperature working conditions, meeting the application requirements of industries such as information technology.

[0016] Further, among them, .

[0017] Furthermore, 0.1≤a≤2.0, preferably, 0.1≤a≤0.9, preferably 0.2≤a≤0.9. Further, 11.6≤b≤13.1.

[0018] Furthermore, 0.7≤c≤1.5, preferably, 1≤c≤1.5, preferably, 0.7≤c≤1.1. Preferably, 1≤c≤1.1.

[0019] Furthermore, 6.5≤d≤8.1. Preferably, 6.5≤d≤7.

[0020] Further, 0.65≤m≤1.

[0021] Furthermore, 0.25≤n≤3.0 is preferred, and 0.64≤n≤2.7.

[0022] Furthermore, RE is a rare earth metal composed of Pr and Nd.

[0023] Furthermore, when T is Cr, 0.25≤n≤2.5.

[0024] Furthermore, when T is Si, 0.60≤n≤2.7. Preferably, 0.9≤n≤3.0.

[0025] Furthermore, when T is V or Ti, 0.60≤n≤1.3.

[0026] Furthermore, T is at least one of Si and Ti. T can be a combination of one or more metals and / or non-metals.

[0027] Furthermore, M is at least one of Zr and Nb. M may be a combination of one or more metals.

[0028] Furthermore, the B content is higher than that of RE2Fe 14 The number of B atoms required for the positive part is 10-40%; among them, 1-40% of the B atoms are wrapped in RE2Fe 14 M is formed in the grain boundaries of the B main phase y B and T z B non-magnetic phase.

[0029] In addition, doping refractory metal M and antioxidant strengthening metal T will also generate boride with boron B. If a large amount of doping metal elements are added, a large amount of B atoms will be consumed, resulting in RE2Fe 14 Therefore, the rare earth permanent magnet alloy powder of the present invention also optimizes the element ratio of the rare earth permanent magnet alloy powder, designs the component with more than the positive B content, and ensures the improvement of the oxidation resistance while ensuring the RE2Fe 14 The proportion of the B main phase is not significantly reduced, and the performance is not significantly weakened.

[0030] Furthermore, the particle size of the permanent magnet alloy powder is no greater than 100 nm.

[0031] Furthermore, the permanent magnet alloy powder has a grain size of 10-100 nm.

[0032] Furthermore, in the permanent magnet alloy powder, the main phase grains with a particle size of 20-50nm account for more than 80%.

[0033] Further, wrap RE2Fe 14 Phases within the grain boundaries of the B-major phase include rare earth-rich phase, B-rich phase, MB phase, and TB phase. A rare earth-rich phase refers to a phase in which the concentration of rare earth elements (such as Nd, Pr, La, and Ce) is significantly higher than in other regions of the material. The B-rich phase is a phase with a high boron (B) content, existing as a boride. The MB phase is a compound phase formed by metal (M) and boron (B). The TB phase is a compound phase formed by metal (T) and boron (B).

[0034] Furthermore, the element T and oxygen on the surface of the permanent magnet alloy powder form an oxygen barrier film. This oxide film gives the magnetic powder a high degree of oxidation resistance. The oxygen barrier film formed on the surface of the permanent magnet alloy prevents oxygen in the air from reaching the permanent magnet alloy, thereby improving the material's oxidation resistance.

[0035] Furthermore, for a powder sample of the permanent magnet alloy powder under a 100-mesh standard sieve and on a 280-mesh standard sieve, its standard stacked sample oxidation combustion rate is less than 22 mm / minute, or it cannot be completely burned or cannot be burned (tested in accordance with the standard method of GB / T 21618-2008 "Test Method for Burning Rate of Dangerous Flammable Solids"); the standard stacked sample is 250 mm long and has a triangular cross-section with an inner height of 10 mm and a width of 20 mm.

[0036] Furthermore, after the permanent magnet alloy powder is baked in an atmosphere at 175°C for 24 hours, the oxidation weight gain per unit specific surface area is less than 313 mg / (m 2 / g).

[0037] Furthermore, after the permanent magnet alloy powder is baked in an atmosphere at 175°C for 48 hours, the oxidation weight gain per unit specific surface area is less than 332 mg / (m 2 / g).

[0038] Furthermore, the grain size of the microcrystalline or amorphous regions less than 5 microns along the thickness of the alloy strip on the initial cooling surface is less than 20 nm. The resulting permanent magnet alloy powder has a moderate grain size, and the magnetic properties of the alloy powder obtained by subsequent crushing are superior to those of magnetic powder with larger coarse grains.

[0039] Furthermore, the primary cooling surface has airbag-like holes arranged in the same direction. The airbag-like holes form a primary cooling surface for the alloy liquid to quickly cool, which enhances the magnetization performance of the permanent magnet alloy powder. Because the holes increase the primary cooling area of the alloy strip, its cooling rate is increased, and the corresponding magnetic powder performance is better.

[0040] The second aspect of the present invention is to provide a method for preparing the above-mentioned permanent magnet alloy powder.

[0041] A method for preparing permanent magnet alloy powder comprises the following steps: Step 1: Prepare the raw materials required for the alloy compound according to the element ratio in the permanent magnet alloy powder, and smelt it into a permanent magnet alloy; Step 2: quenching the permanent magnet alloy at a temperature above its melting point into an alloy strip having a partially microcrystalline size or an amorphous state; Step 3: performing a crystal structure control treatment on the alloy strip or not performing a crystal structure control treatment; Step 4: Crushing the alloy strips that have been regulated or not regulated into a desired size to obtain permanent magnet alloy powder.

[0042] Furthermore, in step 1, the morphology of the smelted permanent magnet alloy is a sheet, plate, or column with a minimum dimension greater than 0.2 mm. The smelted permanent magnet alloy can also have other shapes and structures, as long as the same intermediate alloy can be obtained, and can be used as the raw material for the subsequent rapid quenching to prepare alloy powder.

[0043] The materials are alloyed by smelting to obtain a permanent magnet alloy, which is used as an intermediate material for rapid quenching to prepare alloy strips. Its morphology can be various, which is convenient for subsequent rapid quenching into alloy thin strips.

[0044] Preferably, the method of rapidly cooling the alloyed compound at a temperature above its melting point includes water cooling, air cooling, etc.

[0045] Furthermore, in step 2, the alloy strip has a thickness dimension of 30-60 microns and a width dimension of 2-5 mm.

[0046] Furthermore, in step 2, the grain size in the alloy strip is 0-100 nm.

[0047] Furthermore, when the rapid cooling treatment is performed, the cooling mass flow rate is 60-120 kg / h.

[0048] Furthermore, during the rapid cooling treatment, the primary cooling heat conducting medium used is a ring structure made of metal molybdenum, titanium-zirconium-molybdenum alloy or molybdenum-lanthanum alloy.

[0049] Furthermore, during the rapid cooling treatment, the rotational linear speed of the primary cooling heat transfer medium used is 10-35 m / s.

[0050] Furthermore, during the rapid cooling treatment, the strip in contact with the heat transfer medium has a main phase RE2Fe with a thickness of less than 5 microns from the initial cooling surface to the center of the alloy. 14 B is a microcrystalline region or amorphous region with a grain size of less than 20 nanometers.

[0051] The quenching process involves rapidly rotating a heat-conducting ring, ejecting the molten alloy to form alloy strips, rapidly cooling the strips. During the cooling process, the desired strip structure is a uniform microcrystalline structure to achieve optimal performance. Controlling the quenching process parameters improves consistency, reduces grain differences between the initial cold surface and the free surface, and minimizes grain differences between the left and right ends and the center of the strip, resulting in a more ideal, uniform microstructure. Cooling is performed at an appropriate linear speed while controlling the thickness of the thin strips to ensure consistent cooling rates across the strip and consistent grain size.

[0052] Because the alloying raw materials contain a large number of high-melting-point elements, the alloy liquid is easily overcooled into an amorphous structure when it cools. The magnetic properties of the amorphous structure strip are relatively low. Even after subsequent structural adjustments, it is difficult to obtain a uniformly sized crystal structure, which is often accompanied by some abnormally grown coarse grains, making it difficult for the magnetic powder to achieve optimal performance. Therefore, the above-mentioned linear speed and cooling mass flow rate are adopted to obtain a suitable crystal structure on the initial cooling surface and free surface of the rapidly quenched strip to achieve optimal performance. In contrast, the traditional understanding of accelerating the rapid cooling process and increasing the linear speed of the heat transfer medium rotation does not optimize the performance of this permanent magnet alloy.

[0053] Furthermore, in step 4, the alloy strips that have been regulated or not regulated are crushed to a desired size by any one or a combination of methods such as rolling and cutting.

[0054] Furthermore, the alloy strip is subjected to a crystal structure control treatment by high temperature treatment at a temperature of 300-800° C. Preferably, the treatment temperature is 400-800° C.

[0055] Through high-temperature treatment within the above-mentioned temperature range, the microcrystals on the initial cooling surface are appropriately grown, or the amorphous structure is transformed into a crystalline structure; at the same time, the grain size of the free surface is prevented from growing abnormally, and the grain size is controlled within a certain range, so that the difference in grain size between the initial cooling surface and the free surface is small, and the structure is close to uniform, thereby obtaining higher magnetic properties.

[0056] Furthermore, the above preparation method obtains permanent magnet alloy powder with a grain size of 10-100 nm.

[0057] The third aspect of the present invention is to provide a permanent magnet prepared using the above-mentioned permanent magnet alloy powder.

[0058] A permanent magnet contains the above-mentioned permanent magnet alloy powder as raw material.

[0059] A fourth aspect of the present invention is to provide a method for preparing the above-mentioned permanent magnet.

[0060] A method for preparing a permanent magnet comprises the following steps: using the above-mentioned permanent magnet alloy powder and a polymer binder to prepare the permanent magnet through compression molding, injection molding or calendering molding.

[0061] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention utilizes lanthanum-cerium to replace some of the precious rare earth elements in its permanent magnet alloy powder, significantly reducing costs. Furthermore, the inclusion of a small amount of refractory metal M and antioxidant-enhancing metal T (such as Cr, V, Ti, and Si) as additives to the permanent magnet alloy powder enhances the powder's oxidation resistance and reduces its flammability, thus addressing the poor heat resistance and oxidation resistance of pure PrNd-LanCe / Ce-based FeB materials. This addresses the issue of conventional LaCeFeB alloys, which are prone to ignition and rapid spread when subjected to friction or heat during the production process.

[0062] 2. The refractory metal M and the antioxidant strengthening metal T in the permanent magnetic alloy material of the present invention are evenly distributed in the permanent magnetic material. On the one hand, the doped metal elements play a role in refining the grains, optimizing the grain boundary structure, and inhibiting grain growth in the rare earth permanent magnetic alloy. The high-melting-point non-magnetic phase will hinder the expansion of the magnetic domain wall or the turning of the magnetic domain, and will also hinder the magnetic domain reversal caused by thermal disturbance at high temperature after the material is magnetized, thereby reducing the rate of magnetic performance loss. On the other hand, the doped metal enhances the magnetic domain pinning effect. The high-melting-point non-magnetic phase also "pins" and hinders the growth of grains, refining the grain size of the main phase inside the material. Uniform and fine nano-grains are a prerequisite for obtaining high-performance magnetic properties. Therefore, the addition of high-melting-point elements further optimizes the magnetic properties of the material and improves the magnetic properties.

[0063] 3. The element ratio of rare earth permanent magnet alloy powder is optimized in the permanent magnet alloy material of the present invention, and the component with more than positive B content is designed, so as to ensure the improvement of oxidation resistance and the RE2Fe 14 The proportion of the B main phase is not significantly reduced, and the performance is not significantly weakened. This ensures that the magnets made of permanent magnet alloy materials have low magnetic performance loss during long-term use and meet performance requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is a magnified microscopic image of the magnetic powder in Example 1 of the present invention. DETAILED DESCRIPTION

[0065] The "quenching" mentioned in the present invention refers to the quenching of molten metal at 10 3 ~10 6 K / s cooling rate for rapid solidification, such as speed 10 5 -106 K / s cooling. For example, using a high-speed rotating molybdenum roller (line speed 20-50m / s) to throw the molten alloy liquid into a 20-50μm alloy thin strip to achieve rapid quenching. The cooling rate of this process is 10 5 ~10 6 A cooling medium (such as water) is passed through the interior of the molybdenum roller to reduce the temperature of the molybdenum roller, improve the cooling efficiency, and achieve a higher cooling rate.

[0066] Preferably, in step 2 of the method for preparing the permanent magnet alloy powder, the alloyed material is quenched at a temperature above its melting point to form an alloy strip having a partially crystallite size or amorphous state. The linear speed of the rotating roller is controlled within the range of 10-35 m / s. If the linear speed of the roller is too high, a large amount of amorphous state will be formed, and the performance of the rare earth permanent magnet alloy after heat treatment will be poor, with a maximum performance loss of up to 50%.

[0067] The present invention is RE a (La 1-m Ce m ) b -Fe bal -M c -T n -B d Rare earth alloy magnets, RE is PrNd; Nd is neodymium metal; Pr is praseodymium metal. The ratio of Nd to Pr is not limited. For example, in some embodiments of the present invention, the ratio of Pr to Nd is 75:25. La is lanthanum metal; Ce is cerium metal, with LaCe replacing a portion of the neodymium or praseodymium-neodymium metal. This creates an NdFeB magnet in which lanthanum-cerium replaces a portion of the praseodymium-neodymium metal, resulting in a lower cost compared to praseodymium-neodymium rare earth magnets.

[0068] A method for preparing a permanent magnet alloy comprises the following steps: Step 1: Prepare raw materials according to the permanent magnet alloy formula and melt the raw materials into alloy ingots; Step 2, melting the alloy ingot and rapidly quenching it into an alloy strip; Step 3, heat treating the alloy strip; During smelting, a certain amount of doping elements (such as Cr / Si / V / Ti) is added to form an alloy ingot, which is then rapidly quenched into alloy magnetic powder. When this modified magnetic powder oxidizes, a dense and continuous oxide passivation film forms on its surface, hindering the further diffusion of oxygen into the alloy matrix. This makes the magnetic powder less flammable and exhibits excellent flame retardancy and antioxidant properties.

[0069] The present invention will be further described in detail below with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments, as all technologies implemented based on the present invention fall within the scope of the present invention.

[0070] Example 1 A method for preparing a permanent magnet alloy comprises the following steps: 1. Material configuration The material configuration is carried out according to the following permanent magnet alloy element composition ratio.

[0071] (Pr 0.75 Nd 0.25 ) 0.2 (La 0.2 Ce 0.8 ) 12.5 Zr 1.06 Si 1.7 B 6.5 Fe bal 2. Material alloying The prepared raw materials for the permanent magnet alloy are alloyed at high temperature. After alloying, the molten material is rapidly cooled to form a permanent magnet alloy ingot with a minimum dimension greater than 0.2 mm in the form of a sheet, plate, column, or other structure. Rapid cooling methods include water cooling and air cooling. In this embodiment, water cooling is used to rapidly cool the ingot.

[0072] 3. Alloy belt The permanent magnet alloy ingot is remelted and rapidly cooled to form alloy strips with a thickness dimension of 30-60 microns and a width dimension of 2-5 mm. In this embodiment, the target alloy strip thickness is controlled to be 50 microns (within ±10% of the actual error) and a width of 4 mm (within ±10% of the actual error). The mass flow rate of the rapid cooling process is 70-120 kg / h. In this embodiment, the target mass flow rate of the rapid cooling process is controlled to be 100 kg / h. During the rapid cooling process, the first heat transfer medium used for cooling is a ring-shaped metal material made of metal molybdenum, titanium-zirconium-molybdenum alloy, or molybdenum-lanthanum alloy. The second heat transfer medium is a flowing liquid, which performs secondary heat transfer with the aforementioned ring-shaped metal material.

[0073] When the molten alloy is rapidly cooled, the first heat transfer medium is rotated at a linear speed of 20-40 m / s; when the alloy strip is cooled, the strip from the initial cold surface in contact with the heat transfer medium to the center of the alloy has a main phase RE2Fe with a thickness of less than 5 microns. 14 B is a microcrystalline region or amorphous region with a grain size of less than 20 nanometers.

[0074] This embodiment uses a roller made of metal molybdenum for cooling, and cooling water is passed through the inside of the metal molybdenum roller; the molten permanent magnet alloy liquid is sprayed onto the surface of the high-speed rotating metal molybdenum roller, and the linear speed of the roller surface is 15m / s. The alloy strip obtained by cooling is 40-50 microns thick and 3-4mm wide.

[0075] During rapid cooling, the strip structure is expected to be a uniform microcrystalline structure to achieve optimal performance. In order to obtain the ideal uniform microstructure, especially to reduce the grain difference between the initial cooling surface and the free surface, as well as the grain difference between the left and right end surfaces and the center of the strip, a higher rotational linear speed is usually used for cooling to reduce the thickness of the strip, so that the cooling rate of each part of the strip is as consistent as possible and the grain size is guaranteed to be consistent.

[0076] 4. Strip breakage The strips are crushed by rolling, cutting, etc. In this embodiment, the strips are crushed by cutting.

[0077] 5. Stripe structure regulation The crushed magnetic powder needs to be subjected to structural control treatment at a temperature range of 400-800°C. In this embodiment, heat treatment at 550°C for 30 minutes is performed to complete the structural control of the permanent magnet alloy powder. Due to the matching of the linear speed of the aforementioned rapid cooling to form the alloy strips, the magnetic properties of the permanent magnet alloy powder after heat treatment are optimized. Compared with alloy strips obtained by other faster rapid cooling methods, the magnetic properties of the permanent magnet alloy powder formed by the alloy strips obtained by rapid cooling at a linear speed of 10-35m / s after crushing are optimized.

[0078] The microcrystals on the initial cooling surface are properly grown, or the amorphous structure is transformed into a crystalline structure; at the same time, the heating and cooling rates are controlled so that the grain size of the free surface does not grow abnormally, and its grain size is controlled within a certain range, so that the difference in grain size between the initial cooling surface and the free surface is small, and the structure is close to uniform, so that higher magnetic properties can be obtained.

[0079] 6. Magnetic Powder Characteristics The permanent magnet alloy powder material prepared by the above method, when the surface of the powder comes into contact with oxygen, the doped elements such as Cr, V, Ti, Si are preferentially oxidized, and a dense and uniform oxide film can be formed on the surface of the material, which hinders the oxygen molecules from continuing to diffuse into the interior of the material, thereby improving the material's oxidation resistance and greatly reducing the risk of performance failure during the use of the material.

[0080] At the same time, the substantial addition of B content compensates for the consumption of B element due to the large addition of Cr, V, Ti, Si and other elements, ensuring RE2Fe 14 The proportion of B main phase is not significantly reduced, and the magnetic properties are not significantly weakened. At the same time, the proportion of 1-40% B atoms in the RE2Fe 14 M is formed in the grain boundaries of the B main phase y B and T z B is a non-magnetic phase that hinders the reversal of magnetic domains and increases the coercivity of the material.

[0081] 7. Magnet Preparation The rare earth permanent magnet alloy powder material prepared by the above method is combined with a polymer binder and prepared by compression molding, injection molding or calendering molding. This embodiment adopts compression molding process for preparation.

[0082] Test the flame retardancy of permanent magnet alloy powder (tested in accordance with GB / T 21618-2008 "Test method for burning rate of flammable solids of dangerous goods"): First, permanent magnet alloy powders prepared with varying atomic ratios were sieved. Powder samples that fell below a 100-mesh standard sieve and above a 280-mesh standard sieve were taken to create standard stacking samples. These samples were 250 mm long, with a triangular cross-section measuring 10 mm in height and 20 mm in width. The standard stacking samples were placed in air, and their oxidation and combustion behavior was observed to measure their combustion rate.

[0083] Results The permanent magnet alloy powder prepared in this example had good flame retardancy and a burning speed of 10.8 mm / min.

[0084] Test the magnetic properties of permanent magnet alloy powder: GB / T 3217-2013 "Magnetic Test Methods for Permanent Magnetic (Hard Magnetic) Materials" and GB / T 24270-2009 "Measurement Method for Temperature Coefficient of Magnetic Properties of Permanent Magnetic Materials" were used for testing. Permanent magnetic powder was used to make φ10*10 standard specimens and the remanence B r and coercivity H cJ The magnetic flux loss of the standard sample after being stored in a high temperature environment of 120℃ for 2h and 100h was tested and compared. The magnetic properties of the permanent magnet alloy powder were obtained by testing: the permanent magnet alloy powder α(B r ) (-125℃) = - 0.25% / ℃, β(H cJ )(-125℃) = - 0.28% / ℃. Among them, “α(B r )(-125℃)” is the remanent magnetism temperature coefficient of the sample when the temperature is raised from 25℃ to 125℃ (i.e., the percentage change of the remanent magnetism of the sample when the temperature rises by 1℃); “β(H cJ )(-125℃)” is the coercive force temperature coefficient of the sample when the temperature is increased from 25℃ to 125℃ (i.e., the percentage change in the coercive force of the sample when the temperature increases by 1℃).

[0085] Permanent magnet alloy powders were aged at 120°C for 2 and 100 hours. The powders were then tested for magnetic properties at room temperature (25°C) according to GB / T 3217-2013, "Test Methods for Magnetic Properties of Permanent (Hard) Magnetic Materials," to compare the extent of performance loss at high temperatures. The results showed that the magnetic property losses of the powders after aging were 1.55% and 3.41%, respectively.

[0086] Example 2 Permanent magnet alloy powders were produced and processed using the same method as in Example 1 to obtain permanent magnet alloy powders with different atomic ratios. These powders were then tested to compare the flame retardancy of the different permanent magnet alloy powders. Specifically, permanent magnet alloy powders with different element ratios were prepared and tested for flame retardancy using the same testing method as in Example 1.

[0087] The addition of doping elements imparts excellent oxidation resistance and flame retardancy to the alloyed magnetic powder, alleviating the flammability issues associated with lanthanum-cerium or cerium-quenched magnetic powders. Furthermore, the resulting bonded magnets exhibit enhanced oxidation resistance due to the powder's superior oxidation resistance, resulting in less magnetic loss due to oxidation and improved stability.

[0088] The specific ratio of permanent magnet alloy elements and combustion test results are shown in the following table.

[0089] 1. Flame retardant data Table 1: Effect of different Cr contents on PrNdCe matrix

[0090] Table 2: Effect of different Cr contents on PrNdLaCe matrix

[0091] Table 3: Effect of different Si contents on PrNdLaCe matrix

[0092] Table 4: Effect of different V contents on PrNdLaCe matrix

[0093] Table 5: Effect of different Si contents on PrNdLaCe matrix

[0094] Table 6: Effect of different Cr contents on PrNdLaCe matrix

[0095] Table 7: Effect of different LaCe ratios on PrNdLaCe matrix

[0096] Table 8: Effect of different B contents on PrNdLaCe matrix

[0097] Table 9: Effect of different element contents on PrNdLaCe matrix

[0098] The experimental results in the table above demonstrate that doping Cr, Si, V, and Zr into a LaCePrNd rare earth permanent magnet alloy can achieve improved flame retardancy. When the Cr, Si, V, and Zr doping ratios reach a certain level, the rare earth permanent magnet alloy powder exhibits flame-proof properties, preventing it from spreading or burning. This demonstrates excellent flame retardancy, meeting production safety requirements for permanent magnet alloy powders, while also making the powder less susceptible to oxidation damage from air.

[0099] Example 3 Permanent magnet alloy powder was prepared using the method of Example 1. The composition of the alloy powder is shown in the following table. Based on the raw material ratios of the permanent magnet alloy powder prepared in the previous example, the raw material ratios of the permanent magnet alloy were adjusted to produce permanent magnet alloys with various ratios. The room temperature and high temperature magnetic properties of the permanent magnet alloy powders were tested.

[0100] As in Example 1, the permanent magnetic powder was made into a φ10*10 standard sample, and then the test was carried out using GB / T 3217-2013 "Magnetic Test Methods for Permanent Magnet (Hard Magnetic) Materials". The permanent magnetic alloy powder was subjected to remanence B at room temperature 25°C and high temperature 125°C. r and coercivity H cJ Test. And compare the magnetic properties loss of permanent magnet alloy powder after being stored in a high temperature environment of 120℃ for 2h. r )(-125℃)” is the remanent magnetism temperature coefficient of the sample when the temperature is raised from 25℃ to 125℃ (i.e., the percentage change of the remanent magnetism of the sample when the temperature rises by 1℃); “β(H cJ )(-125℃)” is the coercive force temperature coefficient of the sample when the temperature is increased from 25℃ to 125℃ (i.e., the percentage change in the coercive force of the sample when the temperature increases by 1℃).

[0101] The test results were compared with the test results at room temperature (25°C), and the high-temperature magnetic loss, remanence, and coercive force temperature coefficient data were used to prove that the improved magnetic powder of the present invention, due to its excellent oxidation resistance, effectively controls the oxidation of the magnetic powder at higher temperatures, so that the magnetic powder has less magnetic property loss at high temperatures, ensuring that the magnetic powder can be used at higher temperatures and improving the stability of high-temperature use.

[0102] Table 10: Effect of different elements on magnetic property loss of permanent magnet alloy powder

[0103] Table 11: Effect of different elements on magnetic property loss of permanent magnet alloy powder

[0104] Table 12: Effect of different B contents on magnetic property loss of permanent magnet alloy powders

[0105] Table 13: Effect of different LaCe ratios on magnetic property loss of permanent magnet alloy powders

[0106] On the basis of Example 2, the element ratio of the permanent magnet alloy powder of Example 3 was further designed. The performance of the permanent magnet alloy powder made by the component ratio of each embodiment and the comparative example shows that after adding the elements in the proportion of the present invention, the ratio of each element is controlled to meet the design requirements, and a better effect of resisting magnetic property loss can be obtained.

[0107] The permanent magnet alloy powder prepared in the above embodiment was subjected to a grain size test. The test results showed that with the addition of a large amount of high melting point elements, the growth of the main phase grains was suppressed, and fine and uniform nanocrystalline magnetic powder with a size of 20-50nm was obtained. The ultrafine nanocrystalline structure also ensured that the magnetic powder achieved higher performance.

[0108] Example 4 An oxidation weight gain test of the permanent magnet alloy powder was conducted, and the oxidation weight gain data was used to prove that the improved magnetic powder of the present invention has a lower weight gain ratio after oxidation, indicating that the magnetic powder has strong oxidation resistance.

[0109] Specifically, referring to the permanent magnet alloy powder prepared by the method of Example 3, further testing was conducted on the baking oxidation weight gain of each alloy powder under specific conditions. In particular, the two extreme alloy component ratios shown in Tables 10 and 11 of Example 3 were used as a basis for further optimizing the oxidation weight gain data at these selected levels.

[0110] Table 14: Impact of different elements

[0111] Table 15: Impact of different elements

[0112] Table 16: Effect of different B contents

[0113] Table 17: Effects of different LaCe ratios

[0114] Comparative Example 1 Permanent magnet alloy powder was prepared using the same process and raw material ratios as in Example 1, with the only difference being that the roller speeds were adjusted to achieve rapid cooling of the molten alloy at linear speeds of 8 m / s, 10 m / s, 20 m / s, 30 m / s, 35 m / s, and 40 m / s, respectively. The alloy was rapidly cooled to obtain ribbons at different linear speeds, which were then crushed to obtain alloy powders. The magnetic properties of the different alloy powders after heat treatment were then analyzed and tested.

[0115] Table 18: Effects of different linear speeds on the properties of permanent magnet alloy powders

[0116] *Heat treatment: The prepared alloy was heat treated at 550°C for 30 minutes.

[0117] However, since the alloy of the present invention contains a large number of high-melting-point elements, it is very easy to overcool into an amorphous structure when the alloy liquid is cooled. The magnetic properties of the amorphous structure strip are relatively low. Even after subsequent structural adjustments, it is difficult to obtain a crystal structure with uniform size. It is often accompanied by some abnormally grown coarse crystals, making it difficult for the magnetic powder to achieve optimal performance. Therefore, for the alloy of this scheme, it is not appropriate to use a high rotational linear speed for cooling. If a lower linear speed is used, the strip thickness will be thicker, resulting in a large difference in grain size between the initial cold surface and the free surface in the thickness direction of the strip, which will also reduce the magnetic properties. Therefore, it is necessary to reasonably control the rapid quenching cooling rate to obtain a suitable crystal structure on the initial cold surface and the free surface of the rapid quenching strip, in the hope of correcting the strip crystal structure through subsequent heat treatment to achieve optimal performance.

[0118] After many experiments, the inventors found that the magnetic properties of the permanent magnet alloy are maximized when the linear speed of the rotating roller is controlled in the range of 10-35m / s.

[0119] Comparative Example 2 The effects of different permanent magnet alloy element ratios on the properties of the permanent magnet alloy powder were compared. The permanent magnet alloy powder was prepared using the method of Example 1. All preparation process parameters remained unchanged, and only the ratio of ingredients in the permanent magnet alloy smelting was changed. This resulted in a change in the element ratios in the smelted permanent magnet alloy. The specific target ratios of the permanent magnet alloy elements were as follows.

[0120] RE a (La 1-m Ce m ) b -Fe bal -M c -T n -B d , Adjust the raw material ratio so that the subscripts of each element in the target permanent magnet alloy are as follows: Table 19: Element ratios of multiple permanent magnet alloys prepared in Comparative Example 2

[0121] The two columns on the far left of the table are conditional statements. The first column lists the element or element combination corresponding to the subscript. The second column, or corresponding subscript, corresponds to the element subscript value in the target permanent magnet alloy corresponding to each value in the table. The last row is the value obtained by calculating the corresponding formula based on the subscript value.

[0122] Table 20: Performance test results of permanent magnet alloys with different element ratios

[0123] The experimental results of Comparative Example 2 show that the performance of permanent magnet alloys varies greatly when different element ratios are selected. Combined with the aforementioned single factor analysis experiment, it can be seen that the flame retardant properties of permanent magnet alloys can be improved by adding M elements or T elements, making them less likely to burn. Then, combined with the empirical formula:

[0124] Adjust and optimize the ratio of permanent magnet alloy elements, use the rare earth element RE as the reference point and compare it with the boron B of the NdFeB permanent magnet, and adjust the ratio of the applied T element so that the product of the above empirical formula is between 0-67.5, ensuring that the added doping elements maximize the antioxidant and flame retardant effects, while maintaining the best magnetic performance of the rare earth permanent magnet alloy after it is made into powder.

[0125] In summary, the present invention solves the problem of poor temperature resistance and oxidation resistance of pure lanthanum cerium / cerium-based iron boron materials. By adding a small amount of elements such as Cr, V, Ti, and Si during the alloying process, they are evenly distributed in the permanent magnetic material. When the surface of the material encounters oxygen, these elements are preferentially oxidized, forming a dense and uniform oxide film on the surface of the material, hindering the diffusion of oxygen molecules into the interior of the material, improving the oxidation resistance of the material, and significantly reducing the risk of performance failure during the use of the material. Through these modifications, lanthanum cerium / cerium iron boron permanent magnetic materials have commercial application prospects.

[0126] By adding small amounts of elements such as Cr, V, Ti, and Si, the material's oxidation resistance is improved, effectively controlling oxidation at higher temperatures. This minimizes magnetic property loss at high temperatures, ensuring the material can be used at higher temperatures and improving its stability during high-temperature operation. With a small increase in cost, the temperature resistance of pure lanthanum-cerium / cerium-iron-boron permanent magnets is significantly improved, significantly reducing their high-temperature magnetic property loss, enabling them to meet the requirements of higher-temperature operating environments and resolving the issue of poor high-temperature performance and inability to use pure lanthanum-cerium / cerium-iron-boron permanent magnets at higher temperatures.

[0127] At the same time, by adding a small amount of high-melting-point elements such as Cr, V, Ti, and Si, a high-melting-point non-magnetic phase will be formed at the grain interface of the main phase of the material. These high-melting-point non-magnetic phases have two advantages. First, these high-melting-point non-magnetic phases will hinder the expansion of the magnetic domain wall or the turning of the magnetic domain, which will also hinder the magnetic domain reversal caused by thermal disturbance at high temperature after the material is magnetized, thereby reducing the rate of magnetic property loss. Secondly, these high-melting-point non-magnetic phases also "pin" and hinder the growth of grains, refining the grain size of the main phase inside the material. Uniform and fine nano-grains are a prerequisite for obtaining high-performance magnetic properties. Therefore, the addition of high-melting-point elements also further optimizes the magnetic properties of the material.

[0128] However, the addition of large amounts of elements such as Cr, V, Ti, and Si will generate borides with B, consuming a large number of B atoms and causing RE2Fe 14 The proportion of B main phase is greatly reduced, resulting in a significant decrease in performance. In order to improve the performance, we designed a composition with a content of more than the positive B content, while ensuring the improvement of antioxidant properties and at the same time ensuring RE2Fe 14 The proportion of the B main phase is not significantly reduced, and the performance is not significantly weakened.

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A permanent magnet alloy powder, characterized in that: The composition of the permanent magnet alloy powder is as follows: RE a (La 1-m Ce m ) b -Fe bal -M c -T n -B d , RE is at least one of Pr, Nd, Sm, Y, Gd, Tb, Dy, Ho and Yb; M is at least one of Zr, Nb, Mo, Hf, Mn, Ta and W; T is at least one of Cr, V, Si, and Ti; Where 0<a≤2.0, 11≤b≤13.5, 0≤c≤1.5 and 6≤d≤8.1, 0≤m≤1, 0<n≤3.0; bal indicates that the number of Fe atoms is calculated based on chemical equilibrium.

2. The permanent magnet alloy powder according to claim 1, characterized in that in, 。 3. The permanent magnet alloy powder according to claim 1, characterized in that 0.1≤a≤0.9, 11.6≤b≤13.1, 0.7≤c≤1.1, 6.5≤d≤8.1, 0.65≤m≤1, 0.64≤n≤2.

7.

4. The permanent magnet alloy powder according to claim 1, characterized in that RE is a rare earth metal composed of Pr and / or Nd.

5. The permanent magnet alloy powder according to claim 1, characterized in that When T is Cr, 0.25≤n≤2.

5.

6. The permanent magnet alloy powder according to claim 1, characterized in that: When T is Si, 0.60≤n≤2.

7.

7. The permanent magnet alloy powder according to claim 1, characterized in that: When T is V or Ti, 0.60≤n≤1.

3.

8. The permanent magnet alloy powder according to claim 1, characterized in that: T is at least one of Si and Ti.

9. The permanent magnet alloy powder according to claim 1, characterized in that: M is at least one of Zr and Nb.

10. The permanent magnet alloy powder according to claim 1, characterized in that: B content is higher than RE2Fe 14 The number of atoms required for the positive portion of B is 10-40%; Among them, 1-40% of the B atoms are wrapped in RE2Fe 14 M is formed in the grain boundaries of the B main phase y B and T z B non-magnetic phase.

11. The permanent magnet alloy powder according to claim 1, characterized in that: The particle size of the permanent magnet alloy powder is not greater than 100 nm.

12. The permanent magnet alloy powder according to claim 10, characterized in that: The particle size of permanent magnet alloy powder is 10-100nm.

13. The permanent magnet alloy powder according to claim 1, characterized in that: In the permanent magnet alloy powder, the main phase grains with a particle size of 20-50nm account for more than 80%.

14. The permanent magnet alloy powder according to claim 1, characterized in that: Package RE2Fe 14 Phases in the grain boundaries of the B major phase include a rare earth-rich phase, a B-rich phase, an MB phase, and a TB phase.

15. The permanent magnet alloy powder according to claim 1, characterized in that: For the powder sample of permanent magnet alloy powder under the 100 mesh standard sieve and on the 280 mesh standard sieve, the standard stacking specimen oxidation combustion rate is less than 22mm / minute or cannot be completely burned or cannot be burned; the standard stacking specimen is 250mm long and the cross section is a triangle with an inner height of 10mm and a width of 20mm.

16. The permanent magnet alloy powder according to claim 1, characterized in that: The permanent magnet alloy powder is baked in an atmosphere at 175°C for 24 hours, and its oxidation weight gain per unit specific surface area is less than 313 mg / (m 2 / g).

17. The permanent magnet alloy powder according to claim 1, characterized in that: The permanent magnet alloy powder is baked in an atmosphere at 175°C for 48 hours, and its oxidation weight gain per unit specific surface area is less than 332 mg / (m 2 / g).

18. The permanent magnet alloy powder according to claim 1, characterized in that: In the microcrystalline region or amorphous region less than 5 microns along the thickness direction of the alloy strip on the initial cooling surface, the grain size is less than 20 nm.

19. The permanent magnet alloy powder according to claim 1, characterized in that: The primary cooling surface has air bag-shaped holes arranged in the same direction.

20. A method for preparing permanent magnet alloy powder, characterized in that: The following steps are involved: Step 1: Prepare the raw materials required for the alloy compound according to the element ratio in the permanent magnet alloy powder according to any one of claims 1 to 8, and smelt them into a permanent magnet alloy; Step 2, quenching the permanent magnet alloy at a temperature above its melting point into an alloy strip having a partially microcrystalline size or an amorphous state; Step 3: performing a crystal structure control treatment on the alloy strip or not performing a crystal structure control treatment; Step 4: Crushing the alloy strips that have been regulated or not regulated into a desired size to obtain permanent magnet alloy powder.

21. The method for preparing permanent magnet alloy powder according to claim 20, characterized in that: In step 1, the morphology of the melted permanent magnet alloy is a sheet, plate or column with a minimum dimension greater than 0.2 mm.

22. The method for preparing permanent magnet alloy powder according to claim 20, characterized in that: In step 2, the alloy strip has a thickness dimension of 30-60 microns and a width dimension of 2-5 mm.

23. The method for preparing permanent magnet alloy powder according to claim 20, characterized in that: In step 2, the grain size in the alloy ribbon is 0-100 nm.

24. The method for preparing permanent magnet alloy powder according to claim 20, characterized in that: In step 2, when the rapid cooling treatment is performed, the cooling mass flow rate is 60-120 kg / h.

25. The method for preparing permanent magnet alloy powder according to claim 20, characterized in that: In step 2, when the rapid cooling treatment is performed, the primary cooling heat conducting medium used is a ring structure made of metal molybdenum, titanium-zirconium-molybdenum alloy or molybdenum-lanthanum alloy.

26. The method for preparing permanent magnet alloy powder according to claim 20, characterized in that: In step 2, when the rapid cooling treatment is performed, the rotation linear speed of the primary cooling heat transfer medium used is 10-35 m / s.

27. The method for preparing permanent magnet alloy powder according to claim 20, characterized in that: In step 3, the alloy strip is subjected to a crystal structure control treatment method, wherein the crystal structure is controlled by heat treatment at a treatment temperature of 300-800°C.

28. The method for preparing permanent magnet alloy powder according to claim 20, characterized in that: The obtained permanent magnet alloy powder has a grain size of 10-100 nm.

29. A permanent magnet, characterized in that: The permanent magnet alloy powder according to any one of claims 1 to 19 is used as a raw material.

30. A method for preparing the permanent magnet according to claim 29, characterized in that: The following steps are involved: The permanent magnet is prepared by using the permanent magnet alloy powder according to any one of claims 1 to 19 and a polymer binder through compression molding, injection molding or calendering molding.

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