A high remanence sintered NdFeB permanent magnet material and preparation method thereof

Abstract

The invention discloses a high remanence sintered NdFeB permanent magnet material and a preparation method thereof, and relates to the technical field of permanent magnet materials. The preparation method comprises the following steps: obtaining NdFeB coarse powder by smelting and hydrogen cracking; jet-milling the NdFeB coarse powder, adding auxiliary alloy powder to mix to obtain mixed powder, wherein the auxiliary alloy powder contains any one or more combinations of B, C, and Cu elements, and in terms of mass percentage, B element ≤10%, C element ≤40%, 50%≤Cu element<100%, and the percentage of the auxiliary alloy powder to the total mass of the mixed powder is Z, 0.1%≤Z≤0.4%; pressing the mixed powder into a shape, cold isostatic pressing, and vacuum sintering to obtain a blank; performing grain boundary diffusion on the surface of the blank to obtain the NdFeB permanent magnet material. The invention realizes the effective improvement of the residual magnetic induction intensity of the sintered NdFeB permanent magnet material under the condition that the coercive force remains almost unchanged.

Description

Technical Field

[0001] The invention relates to the technical field of permanent magnet materials, and in particular to a high remanence sintered NdFeB permanent magnet material and a preparation method thereof. Background Art

[0002] Residual magnetic induction (Br) is an important indicator for measuring the performance of magnetic materials. Improving the residual magnetic induction of permanent magnet materials can effectively reduce the no-load speed and no-load current of the motor, and at the same time increase the torque of the motor. Therefore, it is very necessary to develop a new production process for sintered NdFeB permanent magnet materials to improve their residual magnetic induction.

[0003] Existing technical solutions often use methods such as reducing the total amount of rare earth content, using pure neodymium to replace praseodymium and neodymium, reducing the amount of Fe substitution elements, and increasing the orientation magnetic field to increase the degree of orientation to increase the residual magnetic induction intensity of sintered NdFeB permanent magnet materials. However, these methods have major disadvantages: reducing the total amount of rare earth in sintered NdFeB permanent magnet materials, using pure neodymium to replace praseodymium and neodymium, and reducing the amount of Fe substitution elements will significantly reduce the coercivity of sintered NdFeB permanent magnet materials. In addition, there are also problems such as unstable performance of mass-produced products and easy oxidation.

[0004] Based on this, it is very necessary to develop a new production process for sintered NdFeB permanent magnet materials to improve their residual magnetic induction intensity without reducing the coercive force of sintered NdFeB permanent magnet materials. Summary of the invention

[0005] The present invention aims to solve the technical problem of how to improve the residual magnetic strength of sintered NdFeB permanent magnet materials while keeping the coercive force almost unchanged. The present invention aims to provide a high residual magnetic sintered NdFeB permanent magnet material and a preparation method thereof, thereby effectively improving the residual magnetic induction strength of sintered NdFeB permanent magnet materials while keeping the coercive force almost unchanged.

[0006] The present invention is achieved through the following technical solutions:

[0007] The first object of the present invention is to provide a method for preparing a high remanence sintered NdFeB permanent magnet material, comprising the following steps:

[0008] The NdFeB coarse powder is obtained through smelting and hydrogen cracking;

[0009] Grind the NdFeB coarse powder by jet milling, add auxiliary alloy powder and mix to obtain mixed powder, wherein the auxiliary alloy powder contains any one or more combinations of B, C, and Cu elements, and in terms of mass percentage, B element ≤10%, C element ≤40%, 50%≤Cu element<100%, and the percentage of the auxiliary alloy powder to the total mass of the mixed powder is Z, 0.1%≤Z≤0.4%;

[0010] The mixed powder is pressed into shape, cold isostatically pressed, and vacuum sintered to obtain a blank;

[0011] Grain boundary diffusion is carried out on the surface of the blank to obtain NdFeB permanent magnet material.

[0012] Furthermore, the auxiliary alloy powder has a composition of B a Cu c , in terms of mass percentage, 0<a≤10%, 90%≤c<100%.

[0013] Furthermore, 5≤a≤10%, 90%≤c≤95%.

[0014] Furthermore, 0.1%≤Z≤0.2%.

[0015] Furthermore, the auxiliary alloy powder has a composition of B a C b Cu c , calculated in percentage by mass, 0<a≤10%, 0<b≤40%, 50%≤c<100%.

[0016] Furthermore, 5≤a≤10%, 5≤b≤20%, 70%≤c≤90%.

[0017] Furthermore, 0.1%≤Z≤0.2%.

[0018] Furthermore, 5%≤a≤8%, 10≤b≤15%, 80%≤c≤85%.

[0019] Furthermore, the grain boundary diffusion is performed by coating the diffusion source on the surface of the blank through screen printing or spraying process.

[0020] The second object of the present invention is to provide a high remanence sintered NdFeB permanent magnet material prepared by the above method.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] 1. The present invention adds auxiliary alloy powder after the production of NdFeB fine powder is completed. The auxiliary alloy powder can promote the formation of Nd-Fe-C phase with high magnetic polarization intensity in the grain boundary of sintered NdFeB permanent magnet material, and can effectively improve the residual magnetic induction intensity of sintered NdFeB permanent magnet material under the condition that the coercive force remains almost unchanged. The blank prepared by the present invention has a crystal microstructure that is easy to diffuse, and the residual magnetic induction intensity after diffusion is significantly improved compared with the traditional process, which provides a feasible solution for the production of ultra-high performance sintered NdFeB permanent magnet material.

[0023] 2. The present invention adds B a Cu cThe alloy promotes the C in the blank to form Nd-Fe-C phase, which slightly improves the residual magnetic induction intensity and coercive force of the product.

[0024] 3. The present invention adds B a C b Cu c The alloy further increases the C content of the blank, and increases the Nd-Fe-C phase content under the joint promotion of B and Cu. Among them, B promotes the nucleation of the Nd-Fe-C phase, and Cu promotes the growth of the Nd-Fe-C phase. There is a synergistic effect between B, C, and Cu, which promotes the C in the blank to form the Nd-Fe-C phase with high magnetic polarization intensity. Under the condition of almost unchanged coercive force, the residual magnetic induction intensity of the sintered NdFeB permanent magnet material is greatly improved. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the embodiments. Obviously, the schematic implementation modes of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0026] The following is a detailed description of the embodiments of a high remanence sintered NdFeB permanent magnet material and a preparation method thereof. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions and repeated descriptions of well-known matters are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art.

[0027] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range.

[0028] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0029] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0030] Unless otherwise specified, the terms "include" and "comprising" mentioned in this application may be open-ended or closed-ended. For example, the terms "include" and "comprising" may mean that other substances not listed may also be included or only the listed substances may be included.

[0031] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0032] The invention aims to solve the technical problem that the residual magnetic induction of sintered NdFeB permanent magnet material is increased by reducing the total amount of rare earth in sintered NdFeB permanent magnet material, replacing NdPr with pure Nd and reducing the amount of Fe substitution elements in the prior art, but the coercive force of sintered NdFeB permanent magnet material is significantly reduced.

[0033] The present invention develops a method for preparing a high remanence sintered NdFeB permanent magnet material, which can improve the residual magnetic induction intensity of the sintered NdFeB permanent magnet material without reducing the coercive force of the sintered NdFeB permanent magnet material, comprising the following steps:

[0034] (1) subjecting the alloy raw materials to vacuum melting and hydrogen crushing to obtain NdFeB coarse powder;

[0035] (2) jet-milling the NdFeB coarse powder, adding the auxiliary alloy powder and mixing to obtain a mixed powder, wherein the auxiliary alloy powder contains any one or more combinations of B, C, and Cu elements, and in terms of mass percentage, the B element is ≤10%, the C element is ≤40%, and the Cu element is 50%≤100%, and the percentage of the auxiliary alloy powder to the total mass of the mixed powder is Z, and 0.1%≤Z≤0.4%;

[0036] (3) pressing the mixed powder into a shape, cold isostatic pressing, vacuum sintering, and aging treatment to obtain a blank;

[0037] (4) The diffusion source is coated on the surface of the blank by screen printing or spraying process to carry out grain boundary diffusion to obtain NdFeB permanent magnet material.

[0038] The present invention adds auxiliary alloy powder after the production of NdFeB fine powder is completed. The auxiliary alloy powder can be introduced by a single powder mixing method or a composite alloy method. The auxiliary alloy powder can promote the formation of Nd-Fe-C phase with high magnetic polarization intensity in the grain boundary of the sintered NdFeB permanent magnet material, and can effectively improve the residual magnetic induction intensity of the sintered NdFeB permanent magnet material while the coercive force remains almost unchanged. The blank prepared by the present invention has a crystal microstructure that is easy to diffuse, and the residual magnetic induction intensity after diffusion is significantly improved compared with the traditional process.

[0039] As a preferred embodiment, the auxiliary alloy powder has a composition of B a Cu c , in terms of mass percentage, 0<a≤10%, 90%≤c<100%, the percentage of the auxiliary alloy powder to the total mass of the mixed powder is Z, 0.1%≤Z≤0.4%. For example, the value of a can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., the value of c can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc., and the value of z can be 0.1%, 0.15%, 0.2%, 0.5%, 0.3%, 0.4%, etc.

[0040] The present invention adds B a Cu c The alloy promotes the C in the blank to form Nd-Fe-C phase, which slightly improves the residual magnetic induction intensity and coercive force of the product.

[0041] As a preferred embodiment, the values ​​of a, b, and c are: 5≤a≤10%, 90%≤c≤95%, and 0.1%≤Z≤0.2%. a Cu c The content of each component is optimized. When 5≤a≤10%, 90%≤c≤95%, the residual magnetic induction intensity and coercive force of the product are slightly improved. More preferably, when a=5%, c=95%, Z=0.15, the comprehensive performance is the best, the residual magnetism is improved to a certain extent, and the coercive force is significantly improved.

[0042] As a preferred embodiment, the auxiliary alloy powder has a composition of B a C b Cu c , in terms of mass percentage, 0<a≤10%, 0<b≤40%, 50%≤c<100%, the percentage of the auxiliary alloy powder in the total mass of the mixed powder is Z, 0.1%≤Z≤0.4%. For example, the value of a can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., the value of b can be 1%, 3%, 5%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, etc., the value of c can be 50%, 55%, 60%, 65%, 70%, 75%, 78%, 80%, 83%, 85%, 88%, 90%, 93%, 95%, 99%, etc., and the value of z can be 0.1%, 0.15%, 0.2%, 0.5%, 0.3%, 0.4%, etc.

[0043] The present invention adds B a C b Cu cThe alloy further increases the C content of the blank, and the Nd-Fe-C phase is increased under the joint promotion of B and Cu. Among them, B promotes the nucleation of the Nd-Fe-C phase, and Cu promotes the growth of the Nd-Fe-C phase. There is a synergistic effect between B, C, and Cu, which promotes the C in the blank to form the Nd-Fe-C phase with high magnetic polarization intensity. Under the condition of almost unchanged coercive force, the residual magnetic induction intensity of the sintered NdFeB permanent magnet material is greatly improved.

[0044] Preferably, the values ​​of a, b, c, and z are: 5≤a≤10%, 5≤b≤20%, 70%≤c≤90%, and 0.1%≤Z≤0.2%. The inventors found in the research process that when the values ​​of a, b, c, and z are within the aforementioned range, as the carbon content in the alloy increases, the residual magnetic induction intensity of the sintered NdFeB permanent magnet material increases significantly and steadily. However, when the value of b (C content) is 20%, the residual magnetic induction intensity and coercive force of the sintered NdFeB permanent magnet material both show a significant decrease, which may be due to the excessively high C content, which causes Nd-Fe-C to replace the Nd-Fe-B main phase and causes its performance to decrease.

[0045] Therefore, the more preferred ranges of a, b, c, and z are: 5%≤a≤8%, 10≤b≤15%, 80%≤c≤85%, and Z=0.15%. At this time, the residual magnetic induction intensity of the sintered NdFeB permanent magnet material is greatly improved without reducing the coercive force.

[0046] Based on the above preparation method, the present invention obtains a high remanence sintered NdFeB permanent magnet material.

[0047] The technical solution of the present invention is further described in detail below in conjunction with embodiments.

[0048] It should be noted that the experimental methods used in the examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by those skilled in the art through commercial channels.

[0049] In the following examples, the composition of the matrix blank is (PrNd) 30.3 (GaAlCuCoTiZr) 1.5 Fe 67.34 B 0.96 .

[0050] Comparative Example 1

[0051] A method for preparing a high remanence sintered NdFeB permanent magnet material comprises the following steps:

[0052] (1) According to the composition of the matrix blank, the alloy raw material is vacuum melted and cast into a 0.2-0.35 mm thick sheet at a casting temperature of about 1440°C to obtain a NdFeB quick-setting sheet;

[0053] (2) dehydrogenating the NdFeB quick-setting sheet at 560-600°C and coarsely crushing it to obtain NdFeB coarse powder;

[0054] (3) The particle size of NdFeB powder prepared by jet mill is 2-4um;

[0055] (4) A 60*43*39 mm blank is pressed by a forming press, the orientation magnetic field is >1.8T, and cold isostatic pressing is performed at 200MPa;

[0056] (5) Vacuum sintering at 1076°C for 6 hours;

[0057] (6) Aging process 1: 850-950°C, holding time 2-6h, aging process 2: 700-850°C, holding time 3-20h, aging process 3: 450-550°C, holding time 2-6h, to obtain a blank.

[0058] (7) Performing grain boundary diffusion on the above blank to obtain NdFeB permanent magnet material:

[0059] The sintered NdFeB permanent magnet blank is processed into a square magnet with a thickness of 2mm in the magnetization direction (the length and width are arbitrary) by multi-wire cutting. Dy is evenly coated on the surface of the magnet by screen printing, and the Dy coating amount is controlled to be 0.65wt%. Heat treatment is carried out in a vacuum sintering furnace, and the heat treatment includes a primary heat treatment temperature range of 850℃-950℃, a heat treatment time of 5h-40h, a secondary heat treatment temperature range of 400℃-700℃, a heat treatment time of 2.5h-6.5h, and the vacuum degree of the diffusion furnace is controlled to 10 -1 -10 -4 Pa, and obtain the diffused NdFeB permanent magnet material.

[0060] Example 1

[0061] The difference between this embodiment and comparative example 1 is that the component B is added after the jet mill 5 Cu 95 The auxiliary alloy powder is added in an amount of 0.1%.

[0062] Example 2

[0063] The difference between this embodiment and embodiment 1 is that: 5 Cu 95 The addition amount of auxiliary alloy powder was changed to 0.15%.

[0064] Example 3

[0065] The difference between this embodiment and embodiment 1 is that: 5 Cu 95 The addition amount of auxiliary alloy powder was changed to 0.2%.

[0066] Example 4

[0067] The difference between this embodiment and comparative example 1 is that the component B is added after the jet mill 5 C 5 Cu 90 The auxiliary alloy powder is added in an amount of 0.15%.

[0068] Example 5

[0069] The difference between this embodiment and embodiment 4 is that the auxiliary alloy powder composition is changed to B 5 C 10 Cu 85 .

[0070] Example 6

[0071] The difference between this embodiment and embodiment 4 is that the auxiliary alloy powder composition is changed to B 5 C 15 Cu 80 .

[0072] Example 7

[0073] The difference between this embodiment and embodiment 4 is that the auxiliary alloy powder composition is changed to B 8 C 20 Cu 72 .

[0074] Example 8

[0075] The difference between this embodiment and embodiment 4 is that the auxiliary alloy powder composition is changed to C 15 Cu 85 .

[0076] The C content and magnetic properties of the sintered NdFeB permanent magnet materials produced under the processes of each embodiment and test example were detected by using the CS-3000 CS analyzer and the NIM-62000 permanent magnet precision measurement system. The diffused sample was first polished to a light finish by double-sided grinding, and then five diffused samples were stacked and taken. The test results are shown in Table 1.

[0077] Table 1. C content and magnetic properties of sintered NdFeB permanent magnet materials of comparative examples and embodiments

[0078]

[0079] From the data in Table 1, we can see that:

[0080] By comparing the data of Comparative Example 1, Example 1, Example 2 and Example 3, it can be seen that as B 5 Cu 95 With the increase of alloy addition, the residual magnetic induction intensity and coercivity of the product have a slight increase. This is due to the fact that B 5 Cu 95 The addition of promotes the formation of Nd-Fe-C phase by C in the blank, while the addition of Cu slightly improves the coercivity of the sintered NdFeB permanent magnet material.

[0081] By comparing the data of Example 4, Example 5, and Example 6, it can be learned that with the increase of the carbon content in the auxiliary alloy, the carbon content and residual magnetic induction intensity in the blank are steadily increasing, and the residual magnetic induction intensity increases greatly, while the coercive force hardly changes. When the carbon content in the added auxiliary alloy rises to 20% (Example 7), the residual magnetic induction intensity and coercive force of the sample both show a significant decrease. This is because the excessive carbon content causes Nd-Fe-C to replace the main phase of Nd-Fe-B, resulting in a decrease in its performance. It can be seen that when the carbon content in the auxiliary alloy is 10-15%, the comprehensive performance is the best, which can greatly improve the residual magnetic induction intensity of the sintered NdFeB permanent magnet material without causing a decrease in coercive force.

[0082] In Examples 6 and 8, the carbon content of the auxiliary alloy powder is 15%, but B and Cu are added simultaneously in Example 6, while only Cu is added in Example 8. Comparative data show that the coercive force of the sample in Example 6 is almost unchanged compared with that in Comparative Example 1, and the residual magnetic induction intensity is greatly improved, but the residual magnetic induction intensity of the sample in Example 8 is not significantly changed compared with that in Comparative Example 1, and the coercive force is almost unchanged. This indicates that the formation of the Nd-Fe-C phase with high magnetic polarization intensity is jointly promoted by B and Cu.

[0083] Finally, it should be noted that the above specific embodiments are only used to explain in detail the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific implementation method of the present invention and is not used to limit the protection scope of the present invention. Although the present invention is described in detail with reference to the above specific embodiments, ordinary technicians in this field should understand that it is still possible to modify the technical solutions recorded in the above embodiments, or to replace or improve some or all of the technical features therein. These modifications, equivalent replacements and improvements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for preparing a high remanence sintered NdFeB permanent magnet material, characterized in that: The following steps are involved: The NdFeB coarse powder is obtained through smelting and hydrogen cracking; Grinding NdFeB coarse powder by jet milling, adding auxiliary alloy powder and mixing to obtain mixed powder, wherein the auxiliary alloy powder contains B and Cu elements, or contains B, C and Cu elements, and in terms of mass percentage, B element ≤10%, C element ≤40%, 50%≤Cu element<100%, and the percentage of the auxiliary alloy powder to the total mass of the mixed powder is Z, 0.1%≤Z≤0.4%; The mixed powder is pressed into shape, cold isostatically pressed, and vacuum sintered to obtain a blank; Grain boundary diffusion is carried out on the surface of the blank to obtain NdFeB permanent magnet material.

2. The method for preparing a high remanence sintered NdFeB permanent magnet material according to claim 1, characterized in that: The auxiliary alloy powder is composed of B a Cu c , in terms of mass percentage, 0<a≤10%, 90%≤c<100%.

3. The method for preparing a high remanence sintered NdFeB permanent magnet material according to claim 2, characterized in that: 5≤a≤10%, 90%≤c≤95%.

4. The method for preparing a high remanence sintered NdFeB permanent magnet material according to claim 2 or 3, characterized in that: 0.1％≤Z≤0.2％。 5. The method for preparing a high remanence sintered NdFeB permanent magnet material according to claim 1, characterized in that: The auxiliary alloy powder is composed of B a C b Cu c , calculated in percentage by mass, 0<a≤10%, 0<b≤40%, 50%≤c<100%.

6. The method for preparing a high remanence sintered NdFeB permanent magnet material according to claim 5, characterized in that: 5≤a≤10%, 5≤b≤20%, 70%≤c≤90%.

7. The method for preparing a high remanence sintered NdFeB permanent magnet material according to claim 6, characterized in that: 0.1％≤Z≤0.2％。 8. The method for preparing a high remanence sintered NdFeB permanent magnet material according to any one of claims 5 to 7, characterized in that: 5%≤a≤8%, 10≤b≤15%, 80%≤c≤85%.

9. The method for preparing a high remanence sintered NdFeB permanent magnet material according to claim 1, characterized in that: The grain boundary diffusion is carried out by coating the diffusion source on the surface of the blank through screen printing or spraying process.

10. A high remanence sintered NdFeB permanent magnet material, characterized in that: The method is prepared by any one of claims 1 to 9.

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