Permanent magnet powder, preparation method thereof and permanent magnet

Abstract

The invention discloses permanent magnet powder, a preparation method thereof and a permanent magnet, and relates to the technical field of permanent magnet materials. The magnetic powder contains the following alloy composition components: (La < 1-m > Ce < m >) -Feba-Tn-Bd, wherein b, d, m and n are atomic ratios, 12 < = b < = 14, 6.1 < = d < = 8.1, 0.65 < = m < = 1.0, 0.25 < = n < = 3.0; t is at least one of Cr, V, Si and Ti elements; specific elements are added into the permanent magnetic powder to form a specific structure, so that the magnetic performance of the lanthanum-cerium permanent magnetic powder cannot be remarkably reduced under the condition that the lanthanum-cerium permanent magnetic powder has excellent oxidation resistance, and the lanthanum-cerium permanent magnetic powder subjected to oxidation resistance modification can still meet the requirement of the market for the magnetic performance; the method has a positive effect on industrialization and application of the lanthanum cerium / cerium iron boron bonded magnetic powder.

Description

Technical Field

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

[0002] With the sharp rise in the prices of rare earth metals such as neodymium and praseodymium, the price of bonded magnetic powders has also risen sharply. To further expand and seize market share, companies are adopting a highly cost-effective business strategy of replacing neodymium and praseodymium in magnetic powders with low-cost lanthanum and cerium metals to produce more cost-effective magnetic powders to meet market demand. Currently, commercially available lanthanum and cerium can replace up to 98% of praseodymium and neodymium in bonded magnetic powders, significantly reducing the raw material cost of low-performance bonded magnetic powders. Unfortunately, in commercial applications, existing bonded magnetic powders still have not completely broken away from their dependence on high-value rare earth metals such as neodymium and praseodymium, and pure lanthanum / cerium-based magnetic powders are not yet commercially viable. However, compared with traditional NdFeB permanent magnets, lanthanum / cerium permanent magnets exhibit excellent magnetic properties and a high cost-performance ratio, and have broad application prospects in electronics, machinery, energy, and other fields. For example, they have potential application value in the manufacture of small motors, sensors, and magnetic components. Therefore, the development of industrially viable pure lanthanum / cerium-based magnetic powders is of great significance.

[0003] Lanthanum-Ce / Cerium-Iron-Boron bonded magnetic powder is a new type of pure lanthanum / cerium-based magnetic powder. Due to its unique performance and cost advantages, it has attracted extensive attention and research in recent years. Compared with traditional neodymium iron boron (NdFeB) bonded magnetic powder, Lanthanum-Ce / Cerium-Iron-Boron bonded magnetic powder avoids dependence on scarce and expensive rare earth elements such as praseodymium (Pr) and neodymium (Nd), offering a higher cost-performance ratio.

[0004] During storage, transportation, and processing, magnetic powders easily react with oxygen in the air, leading to oxidation and deterioration. This oxidation and deterioration can seriously affect the magnetic properties of the magnetic powder, such as a decrease in magnetic induction intensity and coercivity, thereby affecting the performance and service life of the final product. Therefore, the oxidation resistance of magnetic powders is also one of the key factors affecting the industrialization and application of magnetic powders. In lanthanum-cerium / cerium-iron-boron bonded magnetic powders, the lanthanum and cerium metals contained are very active and easily oxidized in air, resulting in a significant reduction in their magnetic properties. At the same time, in lanthanum-cerium / cerium-iron-boron bonded magnetic powders, in order to obtain higher coercivity to meet the application requirements, the lanthanum and cerium content is often significantly higher than that of the positive part. The excess lanthanum and cerium metal phases will be enriched in large quantities at the grain boundaries. Although this can increase the intrinsic coercivity, it is also more susceptible to oxidation, deteriorating the magnetic properties of the magnetic powder. Therefore, the oxidation resistance modification of lanthanum-cerium / cerium-iron-boron bonded magnetic powders is even more important.

[0005] However, the current development of lanthanum-cerium / cerium-iron-boron bonded magnetic powders focuses more on the research of the magnetic properties of lanthanum-cerium / cerium-iron-boron magnetic powders (mostly focusing on improving the coercive force of the material by optimizing the lanthanum / cerium content and preparation process to enhance the practicality of lanthanum-cerium / cerium-iron-boron bonded magnetic powders); therefore, the oxidation resistance modification treatment of lanthanum-cerium / cerium-iron-boron bonded magnetic powders is of great significance to ensure the industrialization of lanthanum-cerium / cerium-iron-boron bonded magnetic powders.

[0006] Existing methods for improving the oxidation resistance of magnetic powders primarily include the use of antioxidants, surface coating, chemical conversion coating, and composite modification methods. Surface coating involves coating the surface of magnetic powder with a layer of antioxidant (such as a metal, alloy, oxide, or polymer), effectively isolating the powder from air and thereby improving its oxidation resistance. For example, coating the surface of magnetic powder with a layer of metals such as nickel, copper, aluminum, or their alloys using methods such as chemical plating, electroplating, and sol-gel can significantly improve the powder's oxidation resistance and corrosion resistance. Surface coating forms a dense protective film on the surface of the magnetic powder, preventing oxygen intrusion and thereby slowing its oxidation process.

[0007] The chemical conversion film method is a method of forming a dense chemical conversion film (such as phosphate film, silane film, etc.) on the surface of magnetic powder through chemical reaction, which can also improve the oxidation resistance of magnetic powder. For example, the magnetic powder is immersed in a phosphate solution, and a phosphate film is formed on the surface of the magnetic powder through chemical reaction. This film can effectively prevent the intrusion of oxygen, thereby improving the oxidation resistance of the magnetic powder.

[0008] Composite modification is a method that combines multiple modification methods, such as surface coating combined with chemical conversion film, surface coating combined with the addition of antioxidants, etc. It can combine the advantages of multiple methods to further improve the oxidation resistance of magnetic powder. For example, first coating a layer of polymer on the surface of magnetic powder, and then performing chemical conversion film treatment, can form a denser and more stable protective film, effectively improving the oxidation resistance of magnetic powder.

[0009] However, although the above-mentioned oxidation resistance modification method can effectively improve the oxidation resistance of permanent magnetic materials, the introduction of more non-magnetic materials (antioxidant substances, protective films) leads to a decrease in the content of magnetic materials in the magnet, and the introduced non-magnetic materials cannot form a synergistic effect with the magnetic phase to promote the improvement of the magnetic properties of the magnetic powder, resulting in a significant decrease in the magnetic properties of the lanthanum-cerium / cerium-iron-boron bonded magnetic powder. The magnetic properties of the modified lanthanum-cerium / cerium-iron-boron bonded magnetic powder (the cost-effectiveness is greatly reduced) cannot meet the market demand, which is obviously not conducive to the industrialization and application of the lanthanum-cerium / cerium-iron-boron bonded magnetic powder. Summary of the Invention

[0010] The purpose of the present invention is to overcome the problems of poor magnetic properties and antioxidant effects of lanthanum-cerium / cerium-iron-boron bonded magnetic powder treated by existing magnetic powder antioxidant modification methods, and provide a permanent magnetic powder, a preparation method thereof, and a permanent magnet.

[0011] In order to achieve the above-mentioned purpose of the invention, the present invention provides a permanent magnetic powder, comprising the following alloy composition components: (La 1-m Ce m ) b -Fe bal -T n -B d ; Wherein, b, d, m and n are atomic ratios, and 12≤b≤14, 6.1≤d≤8.1, 0.65≤m≤1.0, 0.25≤n≤3.0; T is at least one of Cr, V, Si, Ti elements.

[0012] Among them, "bal" stands for "balanced atomic number", which is the abbreviation of Balance, indicating that the number of atoms of the iron Fe element in the permanent magnetic powder is calculated based on charge balance or chemical balance.

[0013] The permanent magnetic powder of the present invention is characterized by the targeted addition of a specific amount of T element and a corresponding amount of B element, so that the T element and the B element are evenly distributed in the magnetic powder particles, and a non-ferromagnetic phase is formed covering the surface of the main phase grains (main phase grain boundaries) of the magnetic powder. As a result, when the magnetic powder particles come into contact with oxygen, the T element in the non-ferromagnetic phase on the surface of the magnetic powder particles is preferentially oxidized to form a dense oxide film on the surface of the magnetic powder particles, thereby hindering the diffusion of oxygen molecules into the interior of the magnetic powder particles and significantly improving the oxidation resistance of the material. In addition, the non-ferromagnetic phase hinders the expansion of magnetic domain walls and the reversal of magnetic domains, and can effectively hinder the magnetic domain reversal caused by thermal disturbance at high temperature after the magnetization of part of the magnetic powder, thereby significantly reducing the oxidation resistance of the magnetic powder particles. The magnetic performance loss rate of magnetic powder in high temperature environment; at the same time, the non-ferromagnetic phase is similar to "pinning", which can effectively hinder the growth of main phase grains, thereby significantly refining the grain size of the main phase of magnetic powder, and the uniformity of grain size is significantly improved, avoiding the problem of a significant reduction in magnetic performance of magnetic powder due to the introduction of non-ferromagnetic phase; the lanthanum-cerium permanent magnetic powder is formed by adding specific elements and forming a specific structure, so that the magnetic performance of the lanthanum-cerium permanent magnetic powder will not be significantly reduced while having excellent oxidation resistance, so that the lanthanum-cerium permanent magnetic powder after oxidation resistance modification can still meet the market demand for magnetic performance, which has a positive effect on the industrialization and application of lanthanum-cerium / cerium-iron-boron bonded magnetic powder.

[0014] Wherein, the main phase in the permanent magnet powder of the present invention is (Re) 2Fe 14B is a tetragonal compound magnetic phase, where Re is La and / or Ce, and is the main factor determining the magnetic properties of magnetic powder; the non-ferromagnetic phase refers to a material phase in which ferromagnetism does not exist, and the non-ferromagnetic phase can be transformed into a ferromagnetic phase under specific conditions, and its constituent elements include Re, Fe, B, and T.

[0015] Studies have found that whether a non-ferromagnetic phase can be formed on the surface of the main phase is the key to whether the oxidation resistance of the permanent magnetic powder of the present invention can be significantly improved. By specifically adding a specific amount of T element and a corresponding amount of B element, a non-ferromagnetic phase can be formed on the surface of the main phase; preferably, the surface of the main phase grains of the permanent magnetic powder is covered with a non-ferromagnetic phase.

[0016] The study found that the addition amount of T and / or B elements has a significant effect on the oxidation resistance and magnetic properties of the lanthanum-cerium permanent magnetic powder of the present invention. This may be because the addition amount of T and B elements is too small, and the non-ferromagnetic phase may have too small a coverage area on the surface of the main phase grains, making it difficult to form a relatively complete oxide film after contact with oxygen, and it cannot effectively hinder the expansion of the magnetic domain wall or the turning of the magnetic domain, let alone the growth of the main phase grains, thereby resulting in a significant decrease in the oxidation resistance and magnetic properties of the magnetic powder; if the addition amount of T and B elements is too large, although the non-ferromagnetic phase achieves complete coverage of the main phase grain surface, the proportion of the non-ferromagnetic phase in the magnetic powder is too large, and the proportion of the ferromagnetic phase will be greatly reduced, thereby resulting in a significant decrease in the magnetic properties of the magnetic powder; therefore, reasonably controlling the addition amount of T and B elements so that the main phase grain surface of the permanent magnetic powder is covered with an appropriate amount of non-ferromagnetic phase can ensure that the magnetic powder has excellent oxidation resistance and magnetic properties at the same time.

[0017] Preferably, the content of B atoms in the alloy composition is 10-40% higher than the number of atoms required for the main phase, and the 10-40% ratio of B atoms is mainly present in the non-ferromagnetic phase on the grain boundary of the main phase; for example, the content of B atoms in the alloy composition can be 10%, 15%, 20%, 25%, 30%, 35% or 40% higher than the number of atoms required for the main phase; the specific content can be appropriately adjusted according to actual application needs.

[0018] Among them, the main phase is required to form all the main phase ((Re)2Fe 14 B) In the case of , the required amount of element B.

[0019] Among them, the study found that the effect of the addition amount of T element in the permanent magnetic powder of the present invention on the performance of the magnetic powder is also related to the type of T element. Different T elements correspond to different optimal dosages. Optimizing the dosage according to the type of T element is beneficial to improving the oxidation resistance and magnetic properties of the magnetic powder; preferably, when T is a Cr element, 0.25≤n≤1.6, such as n can be 0.25, 0.5, 0.75, 1.0, 1.25 or 1.6; preferably, when T is a Si element, 0.60≤n≤3.0, such as n can be 0.6, 1.0, 1.5, 2.0, 2.5 or 3.0; preferably, when T is a V or Ti element, 0.25≤n≤1.3, such as: n can be 0.25, 0.35, 0.5, 0.85, 1.0, 1.15 or 1.3.

[0020] Among them, the study found that the content ratio of La and Ce in the permanent magnetic powder of the present invention also has a significant effect on the magnetic properties of the magnetic powder; when 0.65≤m≤0.85 (such as m can be 0.65, 0.70, 0.75, 0.80, 0.85), the magnetic flux loss of the magnetic powder at high temperature is significantly reduced, which is more conducive to the application of the magnetic powder under high temperature conditions.

[0021] Among them, the study found that the grain size of the permanent magnetic powder of the present invention has a great influence on the magnetic properties of the magnetic powder. If the grain size is too large, the overall magnetic properties of the magnetic powder will be greatly reduced. Preferably, the grain size of the lanthanum-cerium permanent magnetic powder of the present invention should be no more than 100nm; and the smaller the grain size, the higher the production difficulty, which is not conducive to industrialization. Further preferably, the grain size is better in the range of 10-100nm, and the magnetic properties of the magnetic powder are better.

[0022] Among them, the study found that the grain size distribution of the permanent magnetic powder of the present invention has a significant effect on the oxidation resistance of the permanent magnetic powder. The more uniform the grain size distribution, the better the oxidation resistance of the magnetic powder. This may be related to the degree of damage to the main phase grains during the pulverization of the alloy ribbon. Because after the main phase grains are destroyed, the non-ferromagnetic phase is missing on the grain crushing surface, and the oxide layer cannot be formed, thereby reducing the integrity of the oxide layer formed on the surface of the magnetic powder and reducing the oxidation resistance. Therefore, the more uniform the grain size distribution, the less likely it is to damage the grains during the pulverization process, and the more damaged the grains are. The smaller the number, the more complete the oxide layer can be formed on the surface of the magnetic powder particles, and the magnetic powder has better oxidation resistance; the more uneven the grain distribution is, the easier it is to damage the grains when the alloy ribbon is broken, and the greater the number of damaged grains, so that a better complete oxide layer cannot be formed on the surface of the magnetic powder particles, and the oxidation resistance of the magnetic powder is significantly reduced; preferably, in the permanent magnetic powder, the coefficient of variation of the main phase grain size is not greater than 40%; the preferred coefficient of variation, the more uniform the particle size distribution, the significantly improved oxidation resistance and magnetic properties of the magnetic powder. In addition, the smaller the grain size of the main phase of the magnetic powder, the less likely the grains are to be damaged during the crushing process of the alloy ribbon; more preferably, the average particle size of the permanent magnetic powder grains is better in the range of 20-40nm, and the oxidation resistance of the magnetic powder is better.

[0023] Among them, the experiment found that the permanent magnetic powder of the present invention has excellent antioxidant performance, which is mainly reflected in the burning speed of its standard spline is not more than 25 mm / min (tested according to the GB / T 21618-2008 standard method); the faster the speed of the standard spline during the combustion process, the worse its antioxidant performance; the burning speed of the standard spline is not more than 25 mm / min here, which also includes the case where the standard spline does not burn or the standard spline is partially burned; preferably, the burning speed of the lanthanum-cerium permanent magnetic powder of the present invention is not more than 15 mm / min; the standard spline here refers to: the permanent magnetic powder is piled up by standard to form an equilateral triangle with a length of 250 mm, a cross-section of 10 mm high and a base width of 20 mm (see the preparation of standard splines in GB / T 21618-2008 "Test method for burning rate of flammable solids of dangerous goods").

[0024] Among them, the study found that the permanent magnetic powder of the present invention has excellent antioxidant properties, which is mainly reflected in that after being heated in an atmospheric environment at 175°C for 24 hours, the weight gain per unit specific surface area is no more than 700 mg / (m 2 / g); the greater the weight gain per unit specific surface area, the more oxygen atoms are combined by oxidation during the heating process, and the worse the oxidation resistance of the magnetic powder is. The magnetic powder with better oxidation resistance has an oxidation weight gain per unit specific surface area of no more than 800 mg / (m2) after being heated in an atmosphere of 175°C for 48 hours. 2The unit specific surface area weight gain here refers to the weight gain of the magnetic powder due to oxidation in the same period of time under the condition of a fixed specific surface area. Since the oxidation of magnetic powder starts from the surface of the particles, under the condition of the same surface area of the particles, the greater the weight gain in the same period of time, the more oxygen atoms are absorbed and bound to the surface, the easier it is to oxidize, and the worse the oxidation resistance.

[0025] Among them, research has found that if the alloy composition of the permanent magnetic powder of the present invention also contains the element M, the high temperature resistance of the magnetic powder can be greatly improved, so that the magnetic powder can be used for a long time under higher temperature conditions; wherein the element M is at least one of Zr, Nb, Mo, Hf, Mn, Ta and W, and the atomic percentage is not more than 2.2%; if the addition amount of the element M is too large, the content of the magnetic phase will be reduced, thereby reducing the magnetic properties of the magnetic powder. The specific addition amount of M can be appropriately adjusted according to actual needs.

[0026] In order to achieve the above object of the invention, the present invention further provides a method for preparing permanent magnetic powder, comprising the following steps: (1) Alloying the raw materials according to the alloy composition in the permanent magnetic powder to obtain the raw material alloy; (2) After the raw material alloy is melted, the raw material alloy melt is rapidly cooled into alloy strips by rotating the primary cooling heat conducting medium; (3) Crushing the alloy strips to obtain the permanent magnetic powder.

[0027] Preferably, in step (1), the morphology of the raw material alloy may be a sheet, plate, column or other shaped structure with the minimum dimension in any direction being greater than 0.2 mm.

[0028] Among them, preferably, in step (2), the rotational linear velocity of the initial cooling heat-conducting medium is 20-28 m / s, and the mass flow rate of the raw material alloy melt is 70-90 kg / h; the control of the rotational linear velocity and the mass flow rate is actually the control of the cooling rate of the raw material alloy melt, and the cooling rate directly affects the formation of the crystalline phase and the amorphous phase in the alloy strip and the size of the grains, thereby affecting the various properties of the magnetic powder. In the present invention, due to the influence of the composition of the raw materials, it is very easy to form a lumpy amorphous structure due to overcooling (too fast cooling rate). The magnetic properties of the lumpy amorphous structure strips are low. Even after subsequent structural adjustment, it is difficult to obtain a crystal structure with uniform size, which is often accompanied by some abnormally grown coarse crystals, making it difficult for the magnetic powder to achieve optimal performance; and if the cooling rate is too slow, although the proportion of the amorphous phase is reduced, it will also cause abnormal growth of the grains in the alloy strips, thereby resulting in significant deterioration of the magnetic properties; therefore, choosing a reasonable cooling rate has a more significant impact on the performance of the lanthanum-cerium permanent magnet powder of the present invention; experiments have found that compared with the average cooling rate of the existing bonded magnetic powder, the optimal cooling rate of the present invention is significantly smaller, only 50-80% of the average cooling rate of the existing bonded magnetic powder.

[0029] Among them, preferably, in step (2), the initial cooling heat-conducting medium is a ring structure made of metal molybdenum, titanium-zirconium-molybdenum alloy or molybdenum-lanthanum alloy; the thermal conductivity of the initial cooling heat-conducting medium will affect the crystallization effect on the initial cooling surface of the alloy strip, thereby affecting the magnetic powder performance; the preferred initial cooling heat-conducting medium is conducive to the formation of more uniform main phase grains on the initial cooling surface of the alloy strip.

[0030] Preferably, in step (2), the alloy strip has a thickness of 25-50 microns and a width of 2-5 mm; the preferred strip size is conducive to forming a grain size and particle size distribution with better magnetic properties, thereby obtaining magnetic powder with better performance.

[0031] Preferably, in step (2), on the alloy strip, in an area less than 5 microns on the initial cooling surface along the thickness direction of the alloy strip, the grain size of the main phase is less than 20 nanometers; the preferred alloy strip grain structure has better magnetic properties of the magnetic powder.

[0032] Among them, preferably, step (3) also includes subjecting the crushed alloy powder to crystal control treatment at a temperature of 150-700°C; the crystal control treatment is a high-temperature heat treatment, through which the amorphous phase in the magnetic powder can be transformed into a crystalline phase, and the grains with smaller particle size can be grown, thereby making the grain size in the magnetic powder more uniform, thereby improving the magnetic properties of the magnetic powder; during the high-temperature heat treatment process, it is also necessary to reasonably control the heating and cooling rates to avoid abnormal growth of some grain sizes and deterioration of the magnetic powder performance.

[0033] In order to achieve the above object of the invention, the present invention further provides a permanent magnet containing the above permanent magnet powder.

[0034] Preferably, the permanent magnet is prepared by bonding the above-mentioned permanent magnetic powder through molding, injection or calendering processes; during the preparation process, auxiliary agents such as suitable binders can be added as needed.

[0035] Compared with the prior art, the present invention has the following beneficial effects: 1. The permanent magnetic powder of the present invention adds a specific amount of T element and a corresponding amount of B element so that the T element is evenly distributed in the magnetic powder particles and forms a non-ferromagnetic phase covering the grain boundaries of the main phase grains of the magnetic powder. As a result, when the magnetic powder particles come into contact with oxygen, the T element in the non-ferromagnetic phase on the surface of the magnetic powder particles is preferentially oxidized and forms a dense oxide film on the surface of the magnetic powder particles, thereby hindering the diffusion of oxygen molecules into the interior of the magnetic powder particles and significantly improving the material's oxidation resistance.

[0036] 2. The permanent magnetic powder of the present invention adds a specific amount of T element and a corresponding amount of B element so that the element is evenly distributed in the magnetic powder particles and forms a non-ferromagnetic phase covering the grain boundaries of the main phase of the magnetic powder. The non-ferromagnetic phase will hinder the expansion of the magnetic domain wall and the rotation of the magnetic domain, and can effectively hinder the magnetic domain reversal caused by thermal disturbance at high temperature after magnetization of part of the magnetic powder, thereby significantly reducing the magnetic performance loss rate of the magnetic powder in a high temperature environment.

[0037] 3. The permanent magnetic powder of the present invention adds a specific amount of T element and a corresponding amount of B element so that the element is evenly distributed in the magnetic powder particles and forms a non-ferromagnetic phase covering the grain boundaries of the main phase grains of the magnetic powder. The non-ferromagnetic phase is similar to "pinning" and can significantly refine the grain size of the main phase of the magnetic powder. The uniformity of the grain size is significantly improved, avoiding the problem of a significant reduction in the magnetic properties of the magnetic powder due to the introduction of the non-ferromagnetic phase.

[0038] 4. The permanent magnetic powder of the present invention forms a specific structure by adding specific elements, so that the magnetic properties of the lanthanum-cerium permanent magnetic powder will not be significantly reduced while having excellent oxidation resistance. Therefore, the lanthanum-cerium permanent magnetic powder after oxidation resistance modification can still meet the market demand for magnetic properties, which has a positive effect on the industrialization and application of lanthanum-cerium / cerium-iron-boron bonded magnetic powder.

[0039] 5. The preparation method of the permanent magnetic powder of the present invention is based on the existing rapid quenching method, and the process parameters are targetedly optimized according to the composition of the raw materials. The process technology is mature and the product quality is controllable, which greatly reduces the difficulty of industrializing lanthanum-cerium permanent magnetic powder and is suitable for large-scale production of lanthanum-cerium permanent magnetic powder.

[0040] 6. The permanent magnet of the present invention is prepared using lanthanum-cerium permanent magnet powder as a base material, and thus has the excellent oxidation resistance and magnetic properties of lanthanum-cerium permanent magnet powder. It can meet market demand at a lower cost, and the cost performance is significantly improved, making it suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a magnified microscopic image of the magnetic powder in Example 1 of the present invention. DETAILED DESCRIPTION

[0042] In order to more clearly describe the invention purpose, technical solutions and technical effect advantages in the specific implementation cases of the present invention, the solutions in the specific embodiments will be described in detail in conjunction with the drawings of the specification of the present invention. The specific technical solutions involved in the following specific embodiments are only for the purpose of clearly and completely describing the innovative technical solutions of the present invention. They themselves are only part of the specific implementation plans that can be adopted by the present invention, not all embodiments, and should not be understood as limiting the innovative solutions of the present invention. Any solution that adopts the same inventive concept of the present invention should be included in the scope of protection of the present invention.

[0043] For those skilled in the art, when understanding the solutions described in the specific embodiments of the present invention, they can refer to conventional technical manuals in the field. At the same time, for the places where the above-mentioned terms appear, they can make appropriate understanding or adjustments for reference, and deduce the implementation of the same or similar technical solutions without paying any creative work.

[0044] The "quenching" mentioned in the present invention generally refers to cooling the molten metal to a temperature of 10 3 ~10 6 K / s cooling rate for rapid solidification; for example, using a high-speed rotating molybdenum roller (line speed 20-50m / s) to spin the molten alloy into a 20-50μm alloy strip to achieve rapid quenching, the cooling rate of this process can reach 10 5 ~10 6 K / s; wherein, a cooling medium (such as water) can also be passed through the inside of the molybdenum roller to reduce the temperature of the molybdenum roller, improve the cooling efficiency, and achieve a higher cooling rate.

[0045] Examples 1-42 and Comparative Examples 1-20 A lanthanum-cerium permanent magnet powder is prepared by configuring raw materials according to the alloy composition shown in Table 1-7 and then using the following steps: (1) Alloying the raw materials according to the alloy composition in the lanthanum-cerium permanent magnet powder to obtain a raw material alloy; (2) After the raw material alloy is melted, the raw material alloy melt is rapidly cooled into an alloy strip by rotating a primary cooling heat conducting medium (titanium-zirconium-molybdenum alloy); the rotation linear speed of the primary cooling heat conducting medium is 25 m / s, and the mass flow rate of the raw material alloy melt is 80 kg / h; the thickness of the alloy strip is 40 μm and the width is 3.5 mm; (3) The alloy strips were crushed (the particle size was less than 480 μm), and the crushed alloy powder was subjected to crystal control treatment at a temperature of 500° C. to obtain the corresponding lanthanum-cerium permanent magnetic powder (the microscopic magnification of the magnetic powder in Example 1 is shown in FIG. Figure 1 shown).

[0046] Table 1 Alloy composition in Examples 1-12 and Comparative Examples 1-9

[0047] Table 2 Alloy composition in Examples 13-17 and Comparative Examples 10-11

[0048] Table 3 Alloy composition in Examples 18-22 and Comparative Examples 12-13

[0049] Table 4 Alloy composition in Examples 23-27 and Comparative Examples 14-15

[0050] Table 5 Alloy composition in Examples 28-32 and Comparative Examples 16-17

[0051] Table 6 Alloy composition in Examples 33-37 and Comparative Examples 18-19

[0052] Table 7 Alloy composition in Examples 38-42 and Comparative Examples 20-21

[0053] Examples 43-50 A lanthanum-cerium permanent magnet powder was prepared by adjusting the preparation parameters of the alloy strip and the control treatment conditions in Example 1 to obtain lanthanum-cerium permanent magnet powders with average grain size and coefficient of variation, as shown in Table 8. Table 8 Average grain size and coefficient of variation of magnetic powders prepared in Examples 43-50

[0054] Example 51 A lanthanum-cerium permanent magnet powder is prepared by configuring raw materials according to the alloy composition of Example 1 and then using the following steps: (1) Alloying the raw materials according to the alloy composition in the lanthanum-cerium permanent magnet powder to obtain a raw material alloy; (2) After the raw material alloy is melted, the raw material alloy melt is rapidly cooled into an alloy strip by rotating a primary cooling heat conducting medium (titanium-zirconium-molybdenum alloy); the rotation linear speed of the primary cooling heat conducting medium is 28 m / s, and the mass flow rate of the raw material alloy melt is 70 kg / h; the thickness of the alloy strip is 30 μm and the width is 2 mm; (3) The alloy strips are crushed, and the crushed alloy powder is subjected to crystal control treatment at a temperature of 150° C. to obtain the corresponding lanthanum-cerium permanent magnet powder.

[0055] Example 52 A lanthanum-cerium permanent magnet powder is prepared by configuring raw materials according to the alloy composition of Example 1 and then using the following steps: (1) Alloying the raw materials according to the alloy composition in the lanthanum-cerium permanent magnet powder to obtain a raw material alloy; (2) After the raw material alloy is melted, the raw material alloy melt is rapidly cooled into an alloy strip by rotating a primary cooling heat conducting medium (titanium-zirconium-molybdenum alloy); the rotation linear speed of the primary cooling heat conducting medium is 20 m / s, and the mass flow rate of the raw material alloy melt is 90 kg / h; the thickness of the alloy strip is 60 μm and the width is 5 mm; (3) The alloy strips are crushed, and the crushed alloy powder is subjected to crystal control treatment at a temperature of 700° C. to obtain the corresponding lanthanum-cerium permanent magnet powder.

[0056] Comparative Example 22 A permanent magnetic powder is prepared by configuring raw materials using the alloy composition in Example 1 and using the same preparation method, except that: in the preparation method, the cooling rate of the alloy strip is controlled (the rotational linear speed of the initial cooling heat conducting medium is 30 m / s, and the mass flow rate of the raw material alloy melt is 60 kg / h).

[0057] Comparative Example 23 A permanent magnetic powder is prepared by configuring raw materials using the alloy composition in Example 1 and using the same preparation method, except that: in the preparation method, the cooling rate of the alloy strip is controlled (the rotational linear speed of the initial cooling heat conducting medium is 18 m / s, and the mass flow rate of the raw material alloy melt is 100 kg / h).

[0058] Comparative Example 24 A permanent magnetic powder, prepared by the method of Comparative Example 22, except that its alloy composition is (La 0.15 Ce0.85 ) 14 B6Fe bal .

[0059] Comparative Example 25 A permanent magnetic powder, prepared by the method of Comparative Example 23, except that its alloy composition is (La 0.15 Ce 0.85 ) 14 B6Fe bal .

[0060] Experimental Example 1: The permanent magnetic powders in Examples 1-52 and Comparative Examples 1-24 were subjected to a flame retardancy test (GB / T 21618-2008).

[0061] The specific test method is as follows: 1. The permanent magnetic powders in Example 1-52 and Comparative Example 1-24 are made into standard specimens; 2. Ignite the standard sample (perform at least three tests for each sample and record the average value), observe whether it burns and the burning speed, and record the results as shown in Table 9-17.

[0062] Experimental Example 2 The permanent magnetic powders in Example 1-52 and Comparative Example 1-24 were tested for their antioxidant properties.

[0063] The specific test method is: take the specific surface area of 1m 2 The permanent magnetic powder was weighed and kept at 175℃ in air environment for 24h (Group A) and 48h (Group B). After cooling, the weight change data of the permanent magnetic powder was obtained (three tests were conducted in parallel for each sample). The results are recorded as shown in Table 9-17.

[0064] Experimental Example 3 The permanent magnetic powders in Examples 1-52 and Comparative Examples 1-24 were subjected to room temperature and high temperature magnetic property test (GB / T3217-2013 "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"). φ10*10 standard specimens were made of the permanent magnetic powders and subjected to remanence B at room temperature of 25°C and high temperature of 125°C. 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 compared. The results are shown in Table 9-17. 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℃).

[0065] Table 9 Test results of different magnetic powders in Examples 1-12 and Comparative Examples 1-9

[0066] Analysis of the experimental results in Table 9 shows that in the lanthanum-cerium permanent magnetic powder of the present invention, by specifically adding a specific amount of T element and a corresponding amount of B element and uniformly distributing them in the magnetic powder particles, a non-ferromagnetic phase covering the main phase grain surface (main phase grain boundary) of the magnetic powder can be formed, thereby not only significantly improving the oxidation resistance of the magnetic powder; but also significantly increasing the magnetic performance loss rate of some magnetic powders in a high temperature environment; while changing the type of added elements or not adding the T element, the oxidation resistance of the prepared magnetic powder is significantly reduced, and the magnetic performance loss rate of some magnetic powders is significantly increased.

[0067] Table 10 Test results of different magnetic powders in Examples 13-17 and Comparative Examples 10-11

[0068] Analysis of the experimental results in Table 10 shows that in the lanthanum-cerium permanent magnetic powder of the present invention, the addition amount of Cr element has a significant effect on the oxidation resistance and magnetic properties of the magnetic powder. Among them, when the ratio of Cr atoms is 0.2, an effective oxide layer may not be formed in the magnetic powder, resulting in a significant decrease in the oxidation resistance of the magnetic powder. When the ratio of Cr atoms is 3.25, although the oxidation resistance of the permanent magnetic powder is further improved, an excessively high ratio of Cr in the magnetic powder will also lead to a significant increase in the magnetic flux loss rate of the magnetic powder at high temperatures, and a significant decrease in the remanence and coercive force at room temperature. Therefore, a reasonable ratio of Cr atoms can ensure that the magnetic powder has both excellent oxidation resistance and magnetic properties, thereby facilitating its promotion and use. Further analysis also found that when the ratio of Cr atoms is between 0.25 and 1.6, the permanent magnetic powder has better comprehensive performance in oxidation resistance and magnetic properties.

[0069] Table 11 Test results of different magnetic powders in Examples 18-22 and Comparative Examples 12-13

[0070] Analysis of the experimental results in Table 11 shows that in the lanthanum-cerium permanent magnetic powder of the present invention, the amount of V element added has a significant effect on the oxidation resistance and magnetic properties of the magnetic powder. When the ratio of V atoms is 0.2, an effective oxide layer may not be formed in the magnetic powder, resulting in a significant decrease in the oxidation resistance of the magnetic powder. When the ratio of V atoms is 3.25, although the oxidation resistance of the permanent magnetic powder is further improved, an excessively high ratio of V in the magnetic powder will also lead to a significant increase in the magnetic flux loss rate of the magnetic powder at high temperatures, and a significant decrease in the remanence and coercive force at room temperature. Therefore, a reasonable ratio of V atoms can ensure that the magnetic powder has both excellent oxidation resistance and magnetic properties, thereby facilitating its promotion and use. Further analysis also found that when the ratio of V atoms is between 0.25 and 1.3, the permanent magnetic powder has better comprehensive performance in oxidation resistance and magnetic properties.

[0071] Table 12 Test results of different magnetic powders in Examples 23-27 and Comparative Examples 14-15

[0072] Analysis of the experimental results in Table 12 shows that in the lanthanum-cerium permanent magnetic powder of the present invention, the amount of Si element added has a significant effect on the oxidation resistance and magnetic properties of the magnetic powder. When the Si atom ratio is 0.2, an effective oxide layer may not be formed in the magnetic powder, resulting in a significant decrease in the oxidation resistance of the magnetic powder. When the Si atom ratio is 3.25, although the oxidation resistance of the permanent magnetic powder is further improved, an excessively high Si ratio in the magnetic powder will also lead to a significant decrease in the remanence and coercive force of the magnetic powder at room temperature. Therefore, a reasonable Si atom ratio can ensure that the magnetic powder has both excellent oxidation resistance and magnetic properties, thereby facilitating its promotion and use. Further analysis also found that when the Si atom ratio is between 0.6 and 3.0, the permanent magnetic powder has better comprehensive performance in oxidation resistance and magnetic properties.

[0073] Table 13 Test results of different magnetic powders in Examples 28-32 and Comparative Examples 16-17

[0074] Analysis of the experimental results in Table 13 shows that in the lanthanum-cerium permanent magnetic powder of the present invention, the amount of Ti element added has a significant effect on the oxidation resistance and magnetic properties of the magnetic powder. When the Ti atom ratio is 0.2, an effective oxide layer may not be formed in the magnetic powder, resulting in a significant decrease in the oxidation resistance of the magnetic powder. When the Ti atom ratio is 3.25, although the oxidation resistance of the permanent magnetic powder is further improved, an excessively high Ti ratio in the magnetic powder will also lead to a significant decrease in the remanence and coercive force of the magnetic powder at room temperature. Therefore, a reasonable Ti atom ratio can ensure that the magnetic powder has both excellent oxidation resistance and magnetic properties, thereby facilitating its promotion and use. Further analysis also found that when the Ti atom ratio is between 0.25 and 1.3, the permanent magnetic powder has better comprehensive performance in oxidation resistance and magnetic properties.

[0075] Table 14 Test results of different magnetic powders in Examples 33-37 and Comparative Examples 18-19

[0076] Analysis of the experimental results in Table 14 shows that in the lanthanum-cerium permanent magnetic powder of the present invention, the atomic ratio of La and Ce elements has a great influence on the oxidation resistance and magnetic properties of the magnetic powder, especially on the magnetic flux loss and high-temperature coercivity loss of the magnetic powder at high temperatures. If the atomic ratio of La is too large or too small, the magnetic flux loss and high-temperature coercivity loss of the magnetic powder at high temperatures will increase significantly, which is not conducive to the application of the magnetic powder of the present invention in high-temperature environments. Therefore, a reasonable atomic ratio of La and Ce elements must be selected to ensure that the magnetic powder has excellent oxidation resistance and magnetic properties under high-temperature conditions. Further analysis also found that when the atomic ratio of La and Ce elements is between 0.35:0.65 and 0.15:0.85, the permanent magnetic powder has better comprehensive performance in oxidation resistance and magnetic properties under high-temperature conditions.

[0077] Table 15 Test results of different magnetic powders in Examples 38-42 and Comparative Examples 20-21

[0078] Analysis of the experimental results in Table 15 shows that in the lanthanum-cerium permanent magnetic powder of the present invention, the amount of B added has a significant effect on the oxidation resistance and magnetic properties of the magnetic powder. When the proportion of B atoms is 6.0, there is no B in the magnetic powder that is used to form an effective oxide layer with the T element, which leads to a significant decrease in the oxidation resistance of the magnetic powder. As the proportion of B atoms increases, the oxide layer formed by B and T elements in the magnetic powder increases, thereby significantly increasing the oxidation resistance of the magnetic powder. However, when the proportion of B atoms is 8.3, due to the fixed content of T element, a large amount of B can no longer form an oxide layer with the T element in the magnetic powder, resulting in the oxidation resistance of the magnetic powder being unable to continue to increase. At the same time, excessive B will also reduce the proportion of magnetic phase in the magnetic powder, resulting in a significant decrease in the remanence and coercive force of the magnetic powder at room temperature.

[0079] Table 16 Test results of different magnetic powders in Examples 43-50

[0080] From the analysis of the experimental results of Examples 43-46 in Table 16, it can be seen that in the lanthanum-cerium permanent magnetic powder of the present invention, the coefficient of variation of the grain size and the average grain size of the magnetic powder also have a more significant effect on the oxidation resistance of the magnetic powder. When the average grain size is the same, the smaller the coefficient of variation of the grain size, the better the oxidation resistance of the magnetic powder. This may be related to the degree of damage to the main phase grains during the crushing process of the alloy strip. Because the main phase grains are destroyed, the non-ferromagnetic phase is missing on the crushing surface of the grains, and the oxide layer cannot be formed, thereby reducing the integrity of the oxide layer formed on the surface of the magnetic powder and reducing the oxidation resistance. Therefore, the more uniform the grain distribution is, the less likely it is to damage the grains during the crushing process, and the smaller the number of damaged grains is, so that a better integrity oxide layer can be formed on the surface of the magnetic powder particles, and the magnetic powder has better oxidation resistance. The more uneven the grain distribution is, the easier it is to damage the grains when the alloy strip is crushed, and the smaller the number of damaged grains is, so that a better integrity oxide layer can be formed on the surface of the magnetic powder particles, and the magnetic powder has better oxidation resistance. The larger the number of particles that are destroyed, the less complete the oxide layer can be formed on the surface of the magnetic powder particles, and the oxidation resistance of the magnetic powder is significantly reduced. Further analysis of the experimental results of Examples 43-46 shows that when the coefficient of variation of the grain size is not greater than 40%, the oxidation resistance of the magnetic powder is significantly improved. At the same time, when the coefficient of variation of the grain size is the same, the smaller the average grain size, the better the oxidation resistance of the magnetic powder. This may be because the smaller the grain size of the main phase of the magnetic powder, the more grain interfaces there are, and the more anti-oxidation interfaces of the magnetic powder. At the same time, during the crushing process of the alloy strip, the grains are less likely to be destroyed. Therefore, when the average grain size is 20-40nm, the magnetic powder has better oxidation resistance and magnetic properties.

[0081] Table 17 Test results of magnetic powders prepared in Examples 51-52 and Comparative Examples 22-25

[0082] Analysis of the experimental results for Examples 51-52 and Comparative Examples 22-25 in Table 17 reveals that the cooling rate of the alloy strips during the preparation of the magnetic powders of the present invention also significantly affects the oxidation resistance of the magnetic powder products. In the present invention, due to the influence of the raw material composition (the addition of T elements and excess B elements), a lumpy amorphous structure is easily formed due to overcooling (as in Comparative Example 22). The magnetic properties of the strips with lumpy amorphous structures are relatively low, and even after subsequent structural adjustments, it is difficult to obtain a uniformly sized crystal structure (lumpy amorphous structures often grow abnormally during heat treatment, forming coarse grains), making it difficult for the magnetic powder to achieve optimal performance. On the other hand, an excessively slow cooling rate (as in Comparative Example 23) reduces the amorphous phase ratio but also causes abnormal grain growth in the alloy strips, resulting in significant degradation of magnetic properties. Analysis of the experimental data of Comparative Examples 22-25 shows that when no T element and no excess B element are added to the magnetic powder, a higher cooling rate is required during preparation to make the prepared magnetic powder have better magnetic properties (such as Comparative Example 24). It can be seen that a reasonable selection of the cooling rate of the alloy strip has a significant impact on the performance of the magnetic powder of the present invention. Through analysis and comparison, it can be seen that the cooling rate of the gold strip of the magnetic powder of the present invention is significantly lower than that of conventional magnetic powder.

[0083] Example 53 A lanthanum-cerium permanent magnet is prepared by using the permanent magnet powder in Example 1 as a raw material and mixing it with 4 wt % of a thermosetting epoxy resin through a molding process.

[0084] Example 54 A lanthanum-cerium permanent magnet is prepared by an injection process using the permanent magnet powder of Example 1 as a raw material and mixing it with 10 wt % of a thermoplastic resin (polyphenylene sulfide).

[0085] The above embodiments describe only the basic principles, main features and / or advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and the invention content of the specification only describe the principles or specific cases of the present invention. Without departing from the essence of the innovative ideas of the present invention, the innovative solutions of the present invention may be subject to various changes and improvements, and these changes and improvements all fall within the scope of protection claimed by the present invention.

Claims

1. A permanent magnetic powder, characterized in that: Contains the following alloy composition: (La 1-m Ce m ) b -Fe bal -T n -B d ; Wherein, b, d, m and n are atomic ratios, and 12≤b≤14, 6.1≤d≤8.1, 0.65≤m≤1.0, 0.25≤n≤3.0; bal is the equilibrium atomic number, which is calculated based on charge balance or chemical equilibrium; T is at least one of Cr, V, Si, and Ti.

2. The permanent magnetic powder according to claim 1, characterized in that: The surface of the main phase grains of the permanent magnetic powder is covered with a non-ferromagnetic phase.

3. The permanent magnetic powder according to claim 2, characterized in that: In the alloy composition, the content of B atoms is 10-40% higher than the atomic number required for the main phase, and the 10-40% ratio of B atoms mainly exists in the non-ferromagnetic phase on the grain boundary of the main phase.

4. The permanent magnetic powder according to claim 1, characterized in that: When T is a Cr element, 0.25≤n≤1.

6.

5. The permanent magnetic powder according to claim 1, characterized in that: When T is Si element, 0.60≤n≤3.

0.

6. The permanent magnetic powder according to claim 1, characterized in that: When T is V or Ti element, 0.25≤n≤1.

3.

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

8. The permanent magnetic powder according to claim 1, characterized in that: 0.65≤m≤0.85。 9. The permanent magnetic powder according to claim 1, characterized in that: The grain size of the main phase of the permanent magnetic powder is not greater than 100 nm.

10. The permanent magnetic powder according to claim 9, characterized in that: The grain size of the main phase of the permanent magnetic powder is 10-100 nm.

11. The permanent magnetic powder according to claim 10, characterized in that: In the permanent magnetic powder, the coefficient of variation of the main phase grain size is no more than 40%.

12. The permanent magnetic powder according to any one of claims 1 to 11, characterized in that: The alloy composition further includes an M element, wherein the M element is at least one of Zr, Nb, Mo, Hf, Ta and W, and the atomic percentage of the M element is not greater than 2.2%.

13. The permanent magnetic powder according to any one of claims 1 to 11, characterized in that: The burning speed of the standard stacked specimen of the permanent magnetic powder is no more than 25 mm / min.

14. The permanent magnetic powder according to any one of claims 1 to 11, characterized in that: The permanent magnetic powder is heated at 175°C in an atmospheric environment for 24 hours, and the oxidation weight gain per unit specific surface area is less than 700 mg / (m 2 / g).

15. The permanent magnetic powder according to claim 14, characterized in that: The permanent magnetic powder is heated at 175°C in an atmospheric environment for 48 hours, and the oxidation weight gain per unit specific surface area is less than 800 mg / (m 2 / g).

16. A method for preparing the permanent magnetic powder according to any one of claims 1 to 15, characterized in that: The following steps are involved: (1) Alloying the raw materials according to the alloy composition in the permanent magnet powder to obtain a raw material alloy; (2) After the raw material alloy is melted, the raw material alloy melt is rapidly cooled into alloy strips by rotating the primary cooling heat conducting medium; (3) Crushing the alloy strip to obtain the permanent magnetic powder.

17. The method for preparing permanent magnetic powder according to claim 16, characterized in that: In step (1), the raw material alloy has a morphology of flakes, plates or columns with a minimum dimension greater than 0.2 mm in any direction.

18. The method for preparing permanent magnetic powder according to claim 16, characterized in that: In step (2), during the rapid cooling of the raw material alloy melt, the rotational linear velocity of the initial cooling heat transfer medium is 20-28 m / s, and the mass flow rate of the raw material alloy melt is 70-90 kg / h.

19. The method for preparing permanent magnetic powder according to claim 16, characterized in that: In step (2), the initial cooling heat conducting medium is a ring structure made of metal molybdenum, titanium-zirconium-molybdenum alloy or molybdenum-lanthanum alloy.

20. The method for preparing permanent magnetic powder according to claim 16, characterized in that: In step (2), the alloy strip has a thickness of 25-50 μm and a width of 2-5 mm.

21. The method for preparing permanent magnetic powder according to claim 16, characterized in that: In step (2), on the alloy strip, 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.

22. The method for preparing permanent magnetic powder according to any one of claims 16 to 21, characterized in that: Step (3) further includes subjecting the crushed alloy powder to a crystal structure control treatment at a temperature of 150-700°C.

23. A permanent magnet, characterized in that: Contains the permanent magnetic powder according to any one of claims 1 to 15.

24. The permanent magnet according to claim 23, characterized in that The permanent magnetic powder is prepared by bonding and molding through molding, injection or calendering.

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