Permanent magnet powder, method for producing the same, and permanent magnet

Abstract

The application discloses a permanent magnetic powder and a preparation method and a permanent magnet thereof, and relates to the technical field of permanent magnetic materials. 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, and 0.25<=n<=3.0; T is at least one of Cr, V, Si and Ti elements; the permanent magnetic powder is formed by adding specific elements and forming a specific structure, so that the lanthanum-cerium permanent magnetic powder does not significantly reduce the magnetic property under the condition of excellent oxidation resistance, and the lanthanum-cerium permanent magnetic powder after oxidation resistance modification can still meet the market demand for the magnetic property, and has a positive effect on the industrialization and application of the lanthanum-cerium / cerium-iron-boron bonded magnetic powder.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of permanent magnet materials, in particular to a rare earth permanent magnet material, and more particularly to a permanent magnet powder, a preparation method thereof and a permanent magnet. BACKGROUND

[0002] With the substantial rise in the price of rare earth neodymium and praseodymium metals, the price of bonded magnetic powder has also risen substantially. In order to further develop and seize the market, enterprises use low-cost lanthanum and cerium metals to replace neodymium and praseodymium metals in the magnetic powder to produce more cost-effective magnetic powder to meet market demand. This is extremely economically beneficial. Today, commercial lanthanum and cerium can replace up to 98% of praseodymium and neodymium in bonded magnetic powder, substantially reducing the raw material cost of low-performance bonded magnetic powder. Unfortunately, in commercial applications, existing bonded magnetic powder still relies on high-value rare earth neodymium and praseodymium metals, and pure lanthanum / cerium-based magnetic powder has not yet been industrialized. However, compared with traditional neodymium-iron-boron permanent magnet materials, lanthanum-cerium permanent magnet materials exhibit good magnetic properties and high cost-effectiveness, and have broad application prospects in the fields of electronics, machinery, energy, etc., such as potential applications in manufacturing small motors, sensors, and magnetic components. Therefore, it is of great significance to develop industrialized pure lanthanum / cerium-based magnetic powder.

[0003] Lanthanum-cerium / cerium-iron-boron bonded magnetic powder is a new type of pure lanthanum / cerium-based magnetic powder. Due to its unique performance and cost advantage, it has received widespread attention and research in recent years. Compared with traditional neodymium-iron-boron (NdFeB) bonded magnetic powder, lanthanum-cerium / cerium-iron-boron bonded magnetic powder avoids the dependence on rare and expensive praseodymium (Pr) and neodymium (Nd) rare earth elements, and has higher cost-effectiveness.

[0004] During storage, transportation, and processing, magnetic powder is prone to react with oxygen in the air, leading to oxidation and deterioration. This oxidation and deterioration can severely affect the magnetic properties of the magnetic powder, such as reducing the magnetic induction strength and coercive force, thereby affecting the performance and service life of the final product. Therefore, the oxidation resistance of the magnetic powder is one of the key factors affecting the industrialization and application of the magnetic powder. In lanthanum-cerium / cerium-iron-boron bonded magnetic powder, the lanthanum and cerium metals are very active and easily oxidize in the air, leading to a significant reduction in magnetic properties. Additionally, in lanthanum-cerium / cerium-iron-boron bonded magnetic powder, the content of lanthanum and cerium elements is often much higher than the stoichiometric amount in order to achieve higher coercive force for use. The excess lanthanum and cerium metal phases tend to accumulate at the grain boundaries, which can improve the intrinsic coercive force but also make the magnetic powder more susceptible to oxidation, thereby deteriorating the magnetic properties of the magnetic powder. Therefore, the modification of the oxidation resistance of lanthanum-cerium / cerium-iron-boron bonded magnetic powder is more important.

[0005] However, the existing development of lanthanum cerium / cerium iron boron bonded magnetic powder is more focused on the magnetic properties of lanthanum cerium / cerium iron boron bonded magnetic powder (mostly concentrated on improving the coercivity of the material by optimizing the content of lanthanum / cerium and the preparation process to enhance the practicability of lanthanum cerium / cerium iron boron bonded magnetic powder); therefore, the modification treatment of the oxidation resistance of lanthanum cerium / cerium iron boron bonded magnetic powder has important significance for ensuring the industrialization of lanthanum cerium / cerium iron boron bonded magnetic powder.

[0006] The existing magnetic powder oxidation resistance modification methods mainly include antioxidant additive method, surface coating method, chemical conversion film method and composite modification method, etc. Among them, the surface coating method is a method of coating a layer of antioxidant substance (such as metal, alloy, oxide, polymer, etc.) on the surface of the magnetic powder, which can effectively isolate the contact between the magnetic powder and the air, thereby improving its oxidation resistance; for example, a layer of nickel, copper, aluminum or its alloy can be coated on the surface of the magnetic powder by chemical plating, electroplating, sol-gel method, etc., which can significantly improve the oxidation resistance and corrosion resistance of the magnetic powder; the surface coating method can form a dense protective film on the surface of the magnetic powder, preventing the intrusion of oxygen and thus delaying the oxidation process of the magnetic powder.

[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 the magnetic powder through chemical reaction, which can also improve the oxidation resistance of the magnetic powder; for example, by immersing the magnetic powder in a phosphate solution, a layer of phosphate film is formed on the surface of the magnetic powder through chemical reaction, which can effectively prevent the intrusion of oxygen and thus improve the oxidation resistance of the magnetic powder.

[0008] Composite modification is a method of combining multiple modification methods, such as the combination of surface coating and chemical conversion film, the combination of surface coating and the addition of antioxidants, etc., which can integrate the advantages of multiple methods and further improve the oxidation resistance of the magnetic powder; for example, a layer of polymer is first coated on the surface of the magnetic powder, and then chemical conversion film treatment is performed, which can form a more dense and stable protective film, effectively improving the oxidation resistance of the magnetic powder.

[0009] However, although the above oxidation resistance modification methods can better improve the oxidation resistance of permanent magnet materials, the introduction of a large amount of 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 reduction in the magnetic properties of lanthanum cerium / cerium iron boron bonded magnetic powder (the cost performance is greatly reduced), which cannot meet the market demand, obviously not conducive to the industrialization and application of lanthanum cerium / cerium iron boron bonded magnetic powder. SUMMARY

[0010] The present application aims to overcome the problem of poor magnetic performance and poor oxidation resistance of lanthanum-cerium / cerium-iron-boron bonded magnetic powder treated by the existing magnetic powder oxidation resistance modification method, and provides a permanent magnetic powder, a preparation method thereof and a permanent magnet.

[0011] To achieve the above-mentioned application purposes, the present application provides a permanent magnetic powder containing 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 and Ti elements.

[0012] Wherein, "bal" represents "balance atomic number", which is the abbreviation of Balance, indicating that the number of Fe atoms in the permanent magnetic powder is calculated according to charge balance or chemical balance.

[0013] The permanent magnetic powder of the present application can make the T element and the corresponding amount of B element uniformly distributed in the magnetic powder particles and form a non-ferromagnetic phase covering the surface of the main phase grain (main phase grain boundary) of the magnetic powder, so that when the magnetic powder particles contact with oxygen, the T element in the non-ferromagnetic phase on the surface of the magnetic powder particles is preferentially oxidized and a dense oxide film is formed on the surface of the magnetic powder particles, thereby hindering the diffusion of oxygen molecules into the interior of the magnetic powder particles, significantly improving the oxidation resistance of the material; moreover, the non-ferromagnetic phase hinders the expansion of the magnetic domain wall and the turning of the magnetic domain, effectively hinders the magnetic domain reversal caused by thermal disturbance of part of the magnetized magnetic powder at high temperature, significantly reduces the magnetic performance loss rate of the magnetic powder in a high temperature environment; at the same time, the non-ferromagnetic phase is similar to "pinning", which can effectively hinder the growth of the main phase grain, thereby significantly refining the grain size of the main phase of the magnetic powder, and the grain size uniformity is significantly improved, avoiding the problem of significant reduction of the magnetic performance of the magnetic powder caused by the introduction of the non-ferromagnetic phase; the lanthanum-cerium permanent magnetic powder adds specific elements and forms a specific structure, so that the lanthanum-cerium permanent magnetic powder has excellent oxidation resistance without significantly reducing the magnetic performance, so that the lanthanum-cerium permanent magnetic powder after oxidation resistance modification can still meet the market demand for magnetic performance, and 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 magnetic powder of the present application is (Re)2Fe 14B tetragonal compound magnetic phase, Re is La and / or Ce, is the main factor determining the magnetic properties of the magnetic powder; the non-ferromagnetic phase refers to a substance phase without ferromagnetism, and the non-ferromagnetic phase can be converted into a ferromagnetic phase under certain conditions, and the constituent elements include Re, Fe, B and T.

[0015] It is found that whether the 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 can be significantly improved, and the non-ferromagnetic phase can be formed on the surface of the main phase by adding a specific amount of T element and a corresponding amount of B element; preferably, the surface of the main phase crystal grain of the permanent magnetic powder is covered with a non-ferromagnetic phase.

[0016] It is found that the addition amount of T and / or B elements has a significant influence on the oxidation resistance and magnetic properties of the lanthanum-cerium permanent magnetic powder, which may be because the coverage area of the non-ferromagnetic phase on the surface of the main phase crystal grain is too small when the addition amount of T and B elements is too small, so that it is difficult to form a relatively complete oxidation film after contacting oxygen, and it cannot effectively hinder the expansion of the magnetic domain wall or the turning of the magnetic domain, and it cannot effectively hinder the growth of the main phase crystal grain, thereby causing the oxidation resistance and magnetic properties of the magnetic powder to be significantly reduced; when the addition amount of T and B elements is too large, although the non-ferromagnetic phase realizes complete coverage of the surface of the main phase crystal grain, the proportion of the non-ferromagnetic phase in the magnetic powder is too large, so that the proportion of the ferromagnetic phase is greatly reduced, thereby causing the magnetic properties of the magnetic powder to be significantly reduced; therefore, the addition amount of T and B elements is reasonably controlled, so that the surface of the main phase crystal grain of the permanent magnetic powder is covered with an appropriate amount of non-ferromagnetic phase, which can ensure that the magnetic powder has excellent oxidation resistance and magnetic properties.

[0017] Preferably, in the alloy composition, the content of B atoms is 10-40% higher than the number of atoms required by the main phase, and the 10-40% of B atoms mainly exist in the non-ferromagnetic phase on the main phase grain boundary; 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 by the main phase; the specific content can be appropriately adjusted according to the actual application needs.

[0018] Among them, the main phase required is the case where the main phase ((Re)2Fe 14 B) is formed in the magnetic powder.

[0019] In the formula, it is found that the influence of the added amount of the element T on the performance of the magnetic powder is related to the type of the element T, different types of the element T correspond to different optimal amounts, the amount is preferably selected according to the type of the element T, which is beneficial to improve the oxidation resistance and magnetic performance of the magnetic powder; preferably, in the case where T is Cr, 0.25≤n≤1.6, for example, n can be 0.25, 0.5, 0.75, 1.0, 1.25 or 1.6; preferably, in the case where T is Si, 0.60≤n≤3.0, for example, n can be 0.6, 1.0, 1.5, 2.0, 2.5 or 3.0; preferably, in the case where T is V or Ti, 0.25≤n≤1.3, for example, n can be 0.25, 0.35, 0.5, 0.85, 1.0, 1.15 or 1.3.

[0020] In the formula, it is found that the content ratio of La and Ce in the permanent magnetic powder also has a significant influence on the magnetic performance of the magnetic powder; in the case where 0.65≤m≤0.85 (for example, 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 beneficial to the application of the magnetic powder under high temperature conditions.

[0021] In the formula, it is found that the grain size of the permanent magnetic powder has a great influence on the magnetic performance of the magnetic powder, the magnetic performance of the magnetic powder will be greatly reduced as the grain size is too large, preferably, the grain size of the lanthanum-cerium permanent magnetic powder should be not greater than 100 nm; the smaller the grain size, the higher the production difficulty, which is not conducive to industrialization, and further preferably, the grain size is in the range of 10-100 nm, which is better for the magnetic performance of the magnetic powder.

[0022] The research finds that the grain size distribution of the permanent magnetic powder has a significant influence 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, which may be related to the damage degree of the main phase grain in the crushing process of the alloy thin strip, because the main phase grain is damaged, the non-ferromagnetic phase on the grain fracture surface is lack, and thus the oxidation layer cannot be formed, so that the completeness of the oxidation layer formed on the surface of the magnetic powder is reduced, and the oxidation resistance is reduced, therefore, the more uniform the grain distribution, the less likely the grain is damaged in the crushing process, and the smaller the number of damaged grains, so that a better oxidation layer with better completeness can be formed on the surface of the magnetic powder particles, and the magnetic powder has better oxidation resistance, and the more uneven the grain distribution, the more likely the grain is damaged in the crushing process of the alloy thin strip, and the greater the number of damaged grains, so that the oxidation layer with better completeness cannot be formed on the surface of the magnetic powder particles, and the oxidation resistance of the magnetic powder is significantly reduced, preferably, the variation coefficient of the main phase grain size in the permanent magnetic powder is not greater than 40%, preferably, the variation coefficient of the grain size distribution is more uniform, and the oxidation resistance and magnetic properties of the magnetic powder are obviously improved, in addition, the smaller the grain size of the main phase of the magnetic powder, the less likely the grain is damaged in the crushing process of the alloy thin strip, more preferably, the average grain size of the permanent magnetic powder is in the range of 20-40nm, and the oxidation resistance of the magnetic powder is better.

[0023] The experiment finds that the oxidation resistance of the permanent magnetic powder is excellent, mainly manifested in that the burning speed of the standard sample is not greater than 25mm / min (tested according to the standard method of GB / T 21618-2008), the faster the speed of the standard sample in the burning process, the worse the oxidation resistance, here, the burning speed of the standard sample not greater than 25mm / min also includes the cases that the standard sample does not burn or the standard sample partially burns, preferably, the burning speed of the lanthanum-cerium permanent magnetic powder is not greater than 15mm / min, here, the standard sample refers to that the permanent magnetic powder is stacked into a equilateral triangle-shaped stacking body with a length of 250mm, a cross section of 10mm high and 20mm wide (see the preparation of the standard sample in GB / T 21618-2008 “Dangerous Goods Flammable Solids Burning Rate Test Method”).

[0024] The experiment finds that the oxidation resistance of the permanent magnetic powder is excellent, mainly manifested in that the burning speed of the standard sample is not greater than 25mm / min (tested according to the standard method of GB / T 21618-2008), the faster the speed of the standard sample in the burning process, the worse the oxidation resistance, here, the burning speed of the standard sample not greater than 25mm / min also includes the cases that the standard sample does not burn or the standard sample partially burns, preferably, the burning speed of the lanthanum-cerium permanent magnetic powder is not greater than 15mm / min, here, the standard sample refers to that the permanent magnetic powder is stacked into a equilateral triangle-shaped stacking body with a length of 250mm, a cross section of 10mm high and 20mm wide (see the preparation of the standard sample in GB / T 21618-2008 “Dangerous Goods Flammable Solids Burning Rate Test Method”). 2 / g); the greater the unit specific surface area weight gain, the more oxygen atoms combined in the heating process, and the worse the oxidation resistance, the better the oxidation resistance of the magnetic powder, the oxidation weight gain of the unit specific surface area is not greater than 800mg / (m 2 / g). The unit specific surface area weight gain herein refers to: under the condition of fixed specific surface area, the weight gain of the magnetic powder oxidation in the same time; since the oxidation of the 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 time, the more oxygen atoms are absorbed and combined on the surface, the easier the oxidation is, and the poorer the oxidation resistance is.

[0025] In the alloy composition of the permanent magnetic powder, if the M element is further contained, the high-temperature resistance of the magnetic powder can be greatly improved, so that the magnetic powder can be used for a long time at a higher temperature; the M element 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 M element is too large, the content of the magnetic phase will be reduced, thereby reducing the magnetic performance of the magnetic powder; the specific addition amount of the M element can be appropriately adjusted according to actual needs.

[0026] In order to achieve the above-mentioned purposes, further, the application also provides a preparation method of the permanent magnetic powder, comprising the following steps:

[0027] (1) according to the alloy composition of the permanent magnetic powder, the raw material alloy is alloyed to obtain a raw material alloy;

[0028] (2) after the raw material alloy is melted, the raw material alloy melt is rapidly cooled into an alloy strip by rotating the primary cooling heat-conducting medium;

[0029] (3) the alloy strip is broken to obtain the permanent magnetic powder.

[0030] Preferably, in step (1), the morphology of the raw material alloy can be a flaky, plate-like, columnar or other shape structure with a minimum size greater than 0.2mm in any direction.

[0031] Preferably, in step (2), the linear velocity of the primary 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 linear velocity and the mass flow rate is essentially the control of the cooling speed of the raw material alloy melt, and the cooling speed directly affects the formation of the crystal phase and the amorphous phase in the alloy strip and the size of the crystal grains, thereby affecting the various properties of the magnetic powder. In the present application, due to the influence of the composition of the raw material, it is extremely easy to form a massive amorphous structure due to supercooling (too fast cooling speed), and the magnetic properties of the strip with a massive amorphous structure are relatively low. Even if the structure is adjusted later, it is difficult to obtain a crystal structure with uniform size, and often accompanied by partial abnormal growth of coarse grains, making it difficult for the magnetic powder to achieve optimal performance. If the cooling speed is too slow, although the proportion of the amorphous phase is reduced, it will also lead to abnormal growth of the crystal grains in the alloy strip, thereby significantly degrading the magnetic properties. Therefore, selecting a reasonable cooling speed has a relatively significant impact on the performance of the lanthanum-cerium permanent magnetic powder of the present application. It has been found that, compared with the average cooling speed of the existing bonded magnetic powder, the optimal cooling speed of the present application is significantly smaller, only 50-80% of the average cooling speed of the existing bonded magnetic powder.

[0032] Preferably, in step (2), the primary cooling heat-conducting medium is a ring-shaped structure made of metal molybdenum, titanium-zirconium-molybdenum alloy or molybdenum-lanthanum alloy. The heat-conducting performance of the primary cooling heat-conducting medium will affect the crystallization effect on the primary cooling surface of the alloy strip, thereby affecting the performance of the magnetic powder. The preferred primary cooling heat-conducting medium is conducive to the formation of more uniform main phase crystal grains on the primary cooling surface of the alloy strip.

[0033] Preferably, in step (2), the thickness of the alloy strip is 25-50 microns, and the width is 2-5 mm. The preferred strip size is conducive to the formation of better grain size and particle size distribution, thereby obtaining a magnetic powder with better performance.

[0034] Preferably, in step (2), the grain size of the main phase in the region of the primary cooling surface of the alloy strip along the thickness direction of the alloy strip is less than 5 microns, and the grain size of the main phase is less than 20 nanometers. The preferred grain structure of the alloy strip makes the magnetic powder have better magnetic properties.

[0035] Preferably, in step (3), the broken alloy powder is further subjected to crystal regulation treatment at a temperature of 150-700°C. The crystal regulation treatment is high-temperature heat treatment. Through high-temperature heat treatment, the amorphous phase in the magnetic powder can be converted into a crystal phase, and the smaller crystal grains can grow, thereby making the grain size of the magnetic powder more uniform, and thereby improving the magnetic properties of the magnetic powder. During the high-temperature heat treatment, the heating and cooling rates need to be reasonably controlled to avoid abnormal growth of part of the crystal grains and degradation of the performance of the magnetic powder.

[0036] In order to achieve the above-mentioned purposes, the present application further provides a permanent magnet containing the permanent magnetic powder.

[0037] Preferably, the permanent magnet is prepared by using the permanent magnetic powder through a molding, injection or calendering process.

[0038] Compared with the prior art, the present application has the following advantages:

[0039] 1. The permanent magnetic powder of the present application can be uniformly distributed in the magnetic powder particles and form a non-ferromagnetic phase covering the grain boundaries of the main phase of the magnetic powder by adding a specific amount of T element and a corresponding amount of B element, so that when the magnetic powder particles 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 oxidation resistance of the material.

[0040] 2. The permanent magnetic powder of the present application can be uniformly distributed in the magnetic powder particles and form a non-ferromagnetic phase covering the grain boundaries of the main phase of the magnetic powder by adding a specific amount of T element and a corresponding amount of B element, which hinders the expansion of magnetic domain walls and the turning of magnetic domains, effectively hinders the magnetic domain reversal caused by thermal disturbance at high temperature after the magnetization of part of the magnetic powder, and significantly reduces the speed of magnetic performance loss of the magnetic powder in a high temperature environment.

[0041] 3. The permanent magnetic powder of the present application can be uniformly distributed in the magnetic powder particles and form a non-ferromagnetic phase covering the grain boundaries of the main phase of the magnetic powder by adding a specific amount of T element and a corresponding amount of B element, which is similar to "pinning" and can significantly refine the grain size of the main phase of the magnetic powder, significantly improve the uniformity of the grain size, and avoid the problem of significant reduction of the magnetic performance of the magnetic powder caused by the introduction of the non-ferromagnetic phase.

[0042] 4. The permanent magnetic powder of the present application is added with specific elements and forms a specific structure, so that the lanthanum-cerium permanent magnetic powder has excellent oxidation resistance without significant reduction of the magnetic performance, so that the lanthanum-cerium permanent magnetic powder after oxidation resistance modification can still meet the market demand for magnetic performance, and has a positive effect on the industrialization and application of lanthanum-cerium / cerium-iron-boron bonded magnetic powder.

[0043] 5. The preparation method of the permanent magnetic powder of the present application is based on the existing rapid quenching method, and the process parameters are optimized according to the composition of the raw materials, the process technology is mature, the product quality is controllable, and the difficulty of industrialization of the lanthanum-cerium permanent magnetic powder is greatly reduced, which is suitable for large-scale production of lanthanum-cerium permanent magnetic powder.

[0044] 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

[0045] Figure 1 This is a magnified microscopic image of the magnetic powder in Example 1 of the present invention. DETAILED DESCRIPTION

[0046] In order to more clearly describe the purpose of the invention, 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.

[0047] 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.

[0048] 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.

[0049] Examples 1-42 and Comparative Examples 1-20

[0050] 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:

[0051] (1) Alloying the raw materials according to the alloy composition in the lanthanum-cerium permanent magnet powder to obtain a raw material alloy;

[0052] (2) After the raw material alloy is melted, the raw material alloy melt is rapidly cooled into an alloy strip by using rotation of a primary cooling heat transfer medium (titanium-zirconium-molybdenum alloy); the linear speed of rotation of the primary cooling heat transfer 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 microns, and the width of the alloy strip is 3.5 mm;

[0053] (3) The alloy strip is crushed (the particle size is less than 480 μm), and the crushed alloy powder is subjected to crystal regulation treatment at a temperature of 500°C to obtain a corresponding lanthanum-cerium permanent magnet powder (the microscopic magnified image of the magnetic powder in Example 1 is shown in FIG. 1). Figure 1

[0054] Table 1 Alloy composition components in Examples 1-12 and Comparative Examples 1-9

[0055]

[0056] Table 2 Alloy composition components in Examples 13-17 and Comparative Examples 10-11

[0057]

[0058] Table 3 Alloy composition components in Examples 18-22 and Comparative Examples 12-13

[0059]

[0060] Table 4 Alloy composition components in Examples 23-27 and Comparative Examples 14-15

[0061]

[0062] Table 5 Alloy composition components in Examples 28-32 and Comparative Examples 16-17

[0063]

[0064] Table 6 Alloy composition components in Examples 33-37 and Comparative Examples 18-19

[0065]

[0066] Table 7 Alloy composition components in Examples 38-42 and Comparative Examples 20-21

[0067]

[0068] Examples 43-50

[0069] ​A lanthanum-cerium permanent magnetic powder, the preparation parameters of the alloy strip in Example 1 are adjusted and the conditions of the regulation treatment are adjusted, and the average grain size and the variation coefficient of the lanthanum-cerium permanent magnetic powder are obtained, which are shown in Table 8:

[0070] Table 8 Average grain size and variation coefficient of the magnetic powder prepared in Examples 43-50

[0071]

[0072] Example 51

[0073] A lanthanum-cerium permanent magnetic powder, raw materials are configured according to the alloy composition of Example 1, and the following steps are used for preparation:

[0074] (1) Alloy the raw materials according to the composition of the alloy composition in the lanthanum-cerium permanent magnetic powder to obtain a raw material alloy;

[0075] (2) After the raw material alloy is melted, the raw material alloy melt is rapidly cooled into an alloy strip by rotating the primary cooling heat medium (titanium-zirconium-molybdenum alloy); the linear speed of the rotation of the primary cooling heat 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 microns, and the width is 2 mm;

[0076] (3) The alloy strip is crushed, and the crushed alloy powder is treated at a temperature of 150 DEG C for crystal regulation to obtain the corresponding lanthanum-cerium permanent magnetic powder.

[0077] Example 52

[0078] A lanthanum-cerium permanent magnetic powder, raw materials are configured according to the alloy composition of Example 1, and the following steps are used for preparation:

[0079] (1) Alloy the raw materials according to the composition of the alloy composition in the lanthanum-cerium permanent magnetic powder to obtain a raw material alloy;

[0080] (2) After the raw material alloy is melted, the raw material alloy melt is rapidly cooled into an alloy strip by rotating the primary cooling heat medium (titanium-zirconium-molybdenum alloy); the linear speed of the rotation of the primary cooling heat 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 microns, and the width is 2 mm;

[0081] (3) The alloy strip is crushed, and the crushed alloy powder is treated at a temperature of 150 DEG C for crystal regulation to obtain the corresponding lanthanum-cerium permanent magnetic powder.

[0082] Comparative Example 22

[0083] A permanent magnet magnetic powder was prepared by using the raw material prepared by using the alloy composition of Example 1 and by using the same preparation method, except that the cooling speed of the alloy strip was controlled (the linear speed of the rotating heat conduction medium for initial cooling was 30 m / s, and the mass flow rate of the raw material alloy melt was 60 kg / h).

[0084] Comparative Example 23

[0085] A permanent magnet magnetic powder was prepared by using the raw material prepared by using the alloy composition of Example 1 and by using the same preparation method, except that the cooling speed of the alloy strip was controlled (the linear speed of the rotating heat conduction medium for initial cooling was 18 m / s, and the mass flow rate of the raw material alloy melt was 100 kg / h).

[0086] Comparative Example 24

[0087] A permanent magnet magnetic powder was prepared by using the preparation method of Comparative Example 22, except that the alloy composition was (La 0.15 Ce 0.85 ) 14 B6Fe bal .

[0088] Comparative Example 25

[0089] A permanent magnet magnetic powder was prepared by using the preparation method of Comparative Example 23, except that the alloy composition was (La 0.15 Ce 0.85 ) 14 B6Fe bal .

[0090] Experimental Example 1

[0091] The permanent magnet magnetic powders in Examples 1-52 and Comparative Examples 1-24 were subjected to a flame retardant performance test (GB / T 21618-2008).

[0092] The specific test method was as follows: 1. The permanent magnet magnetic powders in Examples 1-52 and Comparative Examples 1-24 were prepared into standard samples;

[0093] 2. The standard samples were ignited (at least 3 tests were performed for each sample, and the average value was recorded), and whether combustion occurred and the speed of combustion were observed, and the results are shown in Tables 9-17.

[0094] Experimental Example 2

[0095] The permanent magnet magnetic powders in Examples 1-52 and Comparative Examples 1-24 were subjected to an oxidation resistance performance test.

[0096] The specific test method was as follows: 1. 1 m 2The permanent magnetic powders were weighed and placed in an air environment at 175°C for 24 hours (Group A) and 48 hours (Group B) respectively. After cooling, the weight change data of the permanent magnetic powders were obtained (three parallel tests were performed for each sample), and the results are shown in Tables 9-17.

[0097] Experimental Example 3

[0098] The permanent magnetic powders in Examples 1-52 and Comparative Examples 1-24 were subjected to normal temperature and high temperature magnetic property test experiments (GB / T3217-2013 "Permanent Magnet (Hard Magnet) Material Magnetic Property Test Method" and GB / T 24270-2009 "Permanent Magnet Material Magnetic Property Temperature Coefficient Measurement Method"). The permanent magnetic powders were made into φ10*10 standard samples, and the magnetic flux loss of the standard samples after being stored in a high-temperature environment of 120°C for 2h and 100h was compared, and the results are shown in Tables 9-17. Among them, "α(B r )(-125°C)" is the remanence temperature coefficient of the sample during the process of increasing the temperature of the sample from 25°C to 125°C (i.e., the percentage change of the remanence of the sample per 1°C increase); "β(H cJ )(-125°C)" is the coercive force temperature coefficient of the sample during the process of increasing the temperature of the sample from 25°C to 125°C (i.e., the percentage change of the coercive force of the sample per 1°C increase). r cJ

[0099] Table 9 Test results of different magnetic powders in Examples 1-12 and Comparative Examples 1-9

[0100]

[0101] Analyzing the experimental result data in Table 9, it can be seen that in the lanthanum-cerium permanent magnetic powders of the application, by 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 surface of the main phase crystal grains (main phase grain boundaries) of the magnetic powder is formed, thereby not only significantly improving the oxidation resistance of the magnetic powder, but also significantly increasing the magnetic property loss rate of part of the magnetic powder in a high-temperature environment. Changing the type of added elements or not adding T elements significantly reduces the oxidation resistance of the prepared magnetic powder and significantly increases the magnetic property loss rate of part of the magnetic powder.

[0102] Table 10 Test results of different magnetic powders in Examples 13-17 and Comparative Examples 10-11

[0103]

[0104] ​​The analysis of the experimental result data in Table 10 shows that: in the lanthanum-cerium permanent magnetic powder, the adding amount of Cr element has a significant influence on the oxidation resistance and magnetic properties of the magnetic powder; when the proportion of Cr atoms is 0.2, the effective oxidation layer in the magnetic powder may not be formed, which leads to a significant decrease in the oxidation resistance of the magnetic powder; when the proportion of Cr atoms is 3.25, although the oxidation resistance of the permanent magnetic powder is further improved, the high proportion of Cr in the magnetic powder also leads to a significant increase in the magnetic flux loss rate of the magnetic powder at high temperature, and the remanence and coercive force at room temperature are also significantly reduced, therefore, a reasonable proportion of Cr atoms can ensure that the magnetic powder has excellent oxidation resistance and magnetic properties at the same time, thereby facilitating popularization and use; further analysis shows that when the proportion of Cr atoms is between 0.25 and 1.6, the comprehensive performance of the permanent magnetic powder in oxidation resistance and magnetic properties will be better.

[0105] Table 11 Test results of different magnetic powders in Examples 18-22 and Comparative Examples 12-13

[0106]

[0107] The analysis of the experimental result data in Table 10 shows that: in the lanthanum-cerium permanent magnetic powder, the adding amount of Cr element has a significant influence on the oxidation resistance and magnetic properties of the magnetic powder; when the proportion of Cr atoms is 0.2, the effective oxidation layer in the magnetic powder may not be formed, which leads to a significant decrease in the oxidation resistance of the magnetic powder; when the proportion of Cr atoms is 3.25, although the oxidation resistance of the permanent magnetic powder is further improved, the high proportion of Cr in the magnetic powder also leads to a significant increase in the magnetic flux loss rate of the magnetic powder at high temperature, and the remanence and coercive force at room temperature are also significantly reduced, therefore, a reasonable proportion of Cr atoms can ensure that the magnetic powder has excellent oxidation resistance and magnetic properties at the same time, thereby facilitating popularization and use; further analysis shows that when the proportion of Cr atoms is between 0.25 and 1.6, the comprehensive performance of the permanent magnetic powder in oxidation resistance and magnetic properties will be better.

[0108] Table 12 Test results of different magnetic powders in Examples 23-27 and Comparative Examples 14-15

[0109]

[0110] The analysis of the experimental result data in Table 12 shows that: in the lanthanum-cerium permanent magnetic powder, the addition amount of Si element has a significant influence on the oxidation resistance and magnetic properties of the magnetic powder; when the proportion of Si atoms is 0.2, the effective oxidation layer in the magnetic powder may not be formed, resulting in a significant decrease in the oxidation resistance of the magnetic powder; when the proportion of Si atoms is 3.25, although the oxidation resistance of the permanent magnetic powder is further improved, the too high proportion of Si in the magnetic powder also causes the remanence and coercive force of the magnetic powder at room temperature to be significantly reduced, therefore, a reasonable proportion of Si atoms can ensure that the magnetic powder has excellent oxidation resistance and magnetic properties at the same time, thereby facilitating popularization and use; further analysis shows that when the proportion of Si atoms is between 0.6 and 3.0, the comprehensive performance of the permanent magnetic powder in oxidation resistance and magnetic properties will be better.

[0111] Table 13 Test results of different magnetic powders in Examples 28-32 and Comparative Examples 16-17

[0112]

[0113] The analysis of the experimental result data in Table 13 shows that: in the lanthanum-cerium permanent magnetic powder, the addition amount of Si element has a significant influence on the oxidation resistance and magnetic properties of the magnetic powder; when the proportion of Si atoms is 0.2, the effective oxidation layer in the magnetic powder may not be formed, resulting in a significant decrease in the oxidation resistance of the magnetic powder; when the proportion of Si atoms is 3.25, although the oxidation resistance of the permanent magnetic powder is further improved, the too high proportion of Si in the magnetic powder also causes the remanence and coercive force of the magnetic powder at room temperature to be significantly reduced, therefore, a reasonable proportion of Si atoms can ensure that the magnetic powder has excellent oxidation resistance and magnetic properties at the same time, thereby facilitating popularization and use; further analysis shows that when the proportion of Si atoms is between 0.6 and 3.0, the comprehensive performance of the permanent magnetic powder in oxidation resistance and magnetic properties will be better.

[0114] Table 14 Test results of different magnetic powders in Examples 33-37 and Comparative Examples 18-19

[0115]

[0116] The analysis of the experimental result data in Table 14 shows that in the lanthanum-cerium permanent magnetic powder, 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 coercive force loss of the magnetic powder at high temperature; wherein, when the atomic ratio of La element is too large or too small, the magnetic flux loss and high-temperature coercive force loss of the magnetic powder at high temperature will be significantly increased, thereby being not conducive to the application of the magnetic powder in the high-temperature environment; therefore, the reasonable atomic ratio of La and Ce elements can ensure that the magnetic powder has excellent oxidation resistance and magnetic properties at high temperature; further analysis shows that when the atomic ratio of La and Ce elements is between 0.35:0.65 and 0.15:0.85, the comprehensive performance of the oxidation resistance and magnetic properties of the permanent magnetic powder at high temperature is better.

[0117] Table 15 Test results of different magnetic powders in Examples 38-42 and Comparative Examples 20-21

[0118]

[0119] The analysis of the experimental result data in Table 15 shows that in the lanthanum-cerium permanent magnetic powder, 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 coercive force loss of the magnetic powder at high temperature; wherein, when the atomic ratio of La element is too large or too small, the magnetic flux loss and high-temperature coercive force loss of the magnetic powder at high temperature will be significantly increased, thereby being not conducive to the application of the magnetic powder in the high-temperature environment; therefore, the reasonable atomic ratio of La and Ce elements can ensure that the magnetic powder has excellent oxidation resistance and magnetic properties at high temperature; further analysis shows that when the atomic ratio of La and Ce elements is between 0.35:0.65 and 0.15:0.85, the comprehensive performance of the oxidation resistance and magnetic properties of the permanent magnetic powder at high temperature is better.

[0120] Table 16 Test results of different magnetic powders in Examples 43-50

[0121]

[0122] From the analysis of the experimental data of Examples 43-46 in Table 16, it can be seen that in the lanthanum-cerium permanent magnetic powders of the present application, the variation coefficient of the grain size and the average grain size of the grains also have a relatively significant influence on the oxidation resistance of the magnetic powders. In the case of the same average grain size, the smaller the variation coefficient of the grain size, the better the oxidation resistance of the magnetic powders, which may be related to the degree of damage to the main phase grains in the crushing process of the alloy thin strip. After the main phase grains are damaged, the non-ferromagnetic phase is absent on the grain broken surface, so that the oxidation layer cannot be formed, and thus the completeness of the oxidation layer formed on the surface of the magnetic powder particles is reduced, and the oxidation resistance is reduced. Therefore, the more uniform the grain distribution, the less likely the grains are damaged in the crushing process, and the smaller the number of damaged grains, so that a better complete oxidation 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, the more likely the grains are damaged in the crushing process of the alloy thin strip, and the greater the number of damaged grains, so that a better complete oxidation layer cannot 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 data of Examples 43-46 shows that when the variation coefficient of the grain size is not greater than 40%, the oxidation resistance of the magnetic powder is significantly improved. Meanwhile, in the case of the same variation coefficient of the grain size, the smaller the average grain size, the better the oxidation resistance of the magnetic powder, which may be because the smaller the grain size of the main phase of the magnetic powder, the more the grain boundaries, and the more the oxidation resistance interfaces of the magnetic powder. At the same time, in the crushing process of the alloy thin strip, the grains are less likely to be damaged. Therefore, when the average grain size is 20-40 nm, the magnetic powder has better oxidation resistance and magnetic properties.

[0123] Table 17 Test results of the magnetic powders prepared in Examples 51-52 and Comparative Examples 22-25

[0124]

[0125] From the analysis of the experimental data of Examples 51-52 and Comparative Examples 22-25 in Table 17, it can be seen that the cooling speed of the alloy strip has a significant influence on the oxidation resistance of the magnetic powder product in the preparation of the magnetic powder of the present application. In the present application, due to the composition of the raw material (addition of T element and excess B element), it is very easy to form a massive amorphous structure due to undercooling (such as Comparative Example 22), and the magnetic properties of the massive amorphous structure strip are low. Even after the late structure adjustment, it is also difficult to obtain a uniform crystal structure (the massive amorphous structure often abnormally grows during heat treatment, thereby forming coarse crystals), so that the magnetic powder is difficult to achieve optimal performance; and if the cooling speed is too slow (such as Comparative Example 23), although the proportion of amorphous phase is reduced, but it will also lead to abnormal growth of the grains in the alloy strip, thereby causing significant degradation of the magnetic properties. And from the analysis of the experimental data of Comparative Examples 22-25, it can be seen that without the addition of T element and excess B element in the magnetic powder, a higher cooling speed needs to be used during preparation, so that the prepared magnetic powder has more excellent magnetic properties (such as Comparative Example 24); it can be seen that the reasonable selection of the cooling speed of the alloy strip has a significant influence on the performance of the magnetic powder of the present application, and through analysis and comparison, it can be seen that the cooling speed of the alloy strip of the magnetic powder of the present application is significantly lower than that of the conventional magnetic powder.

[0126] Example 53

[0127] A lanthanum-cerium permanent magnet, the permanent magnetic powder in Example 1 is used as raw material, and mixed with 4wt% of thermosetting epoxy resin, prepared by a molding process.

[0128] Example 54

[0129] A lanthanum-cerium permanent magnet, the permanent magnetic powder in Example 1 is used as raw material, and mixed with 10wt% of thermoplastic resin (polyphenylene sulfide), prepared by an injection process.

[0130] The above examples only describe the basic principles, main features and / or advantages of the present application, and those skilled in the art should understand that the present application is not limited to the above examples. The above examples and the description of the inventive content part of the specification only describe the principles or specific cases of the present application. Without departing from the essence of the innovative idea of the present application, the innovative scheme of the present application has various changes and improvements, and these changes and improvements all fall within the scope of the present application.

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; The surface of the main phase grains of the permanent magnetic powder is covered with a non-ferromagnetic phase; 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.

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

6.

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

0.

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

3.

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

6. The permanent magnetic powder according to claim 1, characterized in that: 0.65≤m≤0.85。 7. 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.

8. The permanent magnetic powder according to claim 7, characterized in that: The grain size of the main phase of the permanent magnetic powder is 10-100 nm.

9. The permanent magnetic powder according to claim 8, characterized in that: In the permanent magnetic powder, the coefficient of variation of the main phase grain size is no more than 40%.

10. The permanent magnetic powder according to any one of claims 1 to 9, 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%.

11. The permanent magnetic powder according to any one of claims 1 to 9, characterized in that: The burning speed of the standard stacked specimen of the permanent magnetic powder is no more than 25 mm / min.

12. The permanent magnetic powder according to any one of claims 1 to 9, 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).

13. The permanent magnetic powder according to claim 12, 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).

14. A method for preparing the permanent magnetic powder according to any one of claims 1 to 13, 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.

15. The method for preparing permanent magnetic powder according to claim 14, 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.

16. The method for preparing permanent magnetic powder according to claim 15, 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.

17. The method for preparing permanent magnetic powder according to claim 15, 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.

18. The method for preparing permanent magnetic powder according to claim 15, characterized in that: In step (2), the alloy strip has a thickness of 25-50 μm and a width of 2-5 mm.

19. The method for preparing permanent magnetic powder according to claim 15, 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.

20. The method for preparing permanent magnetic powder according to any one of claims 15 to 19, 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.

21. A permanent magnet, characterized in that: Contains the permanent magnetic powder according to any one of claims 1 to 13.

22. The permanent magnet according to claim 21, characterized in that The permanent magnetic powder is prepared by bonding and molding through molding, injection or calendering.

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