Sintered neodymium-iron-boron magnet with high comprehensive performance and preparation method thereof

Abstract

The invention discloses a sintered neodymium-iron-boron magnet with high comprehensive performance and a preparation method of the sintered neodymium-iron-boron magnet, a main alloy A of a high-gallium and low-boron alloy and a low-gallium and high-boron auxiliary alloy B are subjected to rapid hardening, crushing, jet milling, mixing and co-sintering, and the low-gallium and high-boron auxiliary alloy B can well supplement the volume fraction of a main phase of the high-gallium and low-boron main alloy A; under the condition that coercive force is high, it can be guaranteed that the overall residual magnetism is not affected, and the magnet with high comprehensive performance is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of NdFeB preparation, and in particular to a high comprehensive performance sintered NdFeB magnet and a preparation method thereof. Background Art

[0002] Since the advent of sintered NdFeB, it has been widely used in IT, medical, motor, new energy vehicles and other fields due to its excellent magnetic properties. With the development of the market, sintered NdFeB magnets are not only required to have high magnetism but also high heat resistance, that is, not only are magnets required to have a high maximum magnetic energy product, but also high intrinsic coercivity. Therefore, improving the coercivity of magnets while ensuring magnetism has become a hot spot in technology research and development. The mainstream method in the industry is to partially replace Nd and Pr in the original magnets with heavy rare earth metal elements such as Gd, Dy or Tb to increase the coercivity, but as the amount of Dy or Tb replaced increases, while the coercivity is increased, Dy or Tb will enter the main phase and greatly reduce the magnetism of the magnet; on the other hand, the price of heavy rare earth metals such as Dy or Tb is higher than that of Nd, which greatly increases the cost of magnet production and manufacturing. Therefore, in order to reduce or even stop the use of Dy or Tb while ensuring high coercivity, the industry has adopted the method of adding Co, Zr, and Ti to further refine the grains to achieve the effect of high-content Ga doping without heavy rare earths, achieving a coercivity of more than 17KOe, and realizing H-performance grade heavy rare earth-free sintered NdFeB products.

[0003] However, when different trace elements replace the 2:14:1 main phase of Fe, they have different intrinsic magnetic properties. Compared with Fe, Zr or Ti, the saturation magnetic polarization intensity Js and magnetocrystalline anisotropy field HA after replacement are lower, so the addition will inevitably lead to a decrease in the performance of permanent magnet materials. The most important thing is that for high gallium-doped magnets, the non-ferromagnetic Nd6Fe 13 The introduction of Ga phase is considered to be the main reason for the high coercivity of the magnet. During the heat treatment process, the rare earth-rich phase and part of the Nd2Fe 14 The B main phase reacts to produce Nd6Fe at the grain boundary 13 Ga phase, the volume fraction of rare earth-rich phase increased, and the distribution of rare earth-rich phase at grain boundary was optimized, which effectively weakened the Nd2Fe 14 However, too much Ga addition will bring two problems. First, during the heat treatment process, Ga will form Nd6Fe 13 Ga phase will inevitably consume Nd2Fe 14 The B main phase leads to a decrease in the overall Br content. In addition, the high-content doping of Ga is bound to bring about the problem of excessively high costs. Summary of the invention

[0004] The object of the present invention is to provide a sintered NdFeB magnet with high comprehensive performance and a preparation method thereof, by uniformly mixing two kinds of jet milled magnetic powder A and jet milled magnetic powder B with different gallium and boron contents, a high-performance and balanced sintered NdFeB magnet is achieved.

[0005] In order to solve the above technical problems, the present invention adopts the following solutions:

[0006] A method for preparing a sintered NdFeB magnet with high comprehensive performance comprises the following steps:

[0007] Step 1: prepare a main alloy A with high gallium and low boron and an auxiliary alloy B with low gallium and high boron, and obtain jet milled magnetic powder A and jet milled magnetic powder B after jet milling;

[0008] Step 2, after the jet milled magnetic powder A and the jet milled magnetic powder B are mixed evenly, a lubricant is added, the mixture is oriented and formed, and the mixture is pressed into a green billet, and the green billet is dehydrogenated and heat treated to obtain a sintered NdFeB magnet;

[0009] The mass percentage of the jet mill magnetic powder A is 85% to 100%, and the mass percentage of the jet mill magnetic powder B is 0 to 15%.

[0010] The present invention provides a high-performance sintered NdFeB magnet, and the raw materials for its preparation include a high-Ga and low-B matrix main alloy A and a low-Ga and high-B auxiliary alloy B. At present, the Ga addition amount of the same product in the industry is 0.15wt% to 0.30wt%, and the B addition amount is 0.92wt% to 0.94wt%, where wt% is the mass percentage content. In the present application, the Ga addition amount in the high-Ga and low-B is higher than the existing Ga addition amount, and the B addition amount is lower than the existing B addition amount; the Ga addition amount in the low-Ga and high-B is lower than the existing Ga addition amount, and the B addition amount is higher than the existing B addition amount.

[0011] The composition of the main alloy A with high Ga and low B is R a T (1-a-b-c-d) Ga b M c B d , wherein R is one or two of Nd and Pr, T is Fe and Co, the mass ratio of Fe and Co is (60-140):1, M is one or more of Cu and Al and one or two of Ti and Zr, and does not contain heavy rare earths such as Gd, Dy, and Tb. At the same time, the micron-sized powders of A and B are uniformly mixed by a dual alloy process, and the addition ratio of B is 0-15%.

[0012] The main alloy A of high Ga and low B alloy and the auxiliary alloy B of low Ga and high B are mixed and then co-sintered through rapid solidification, crushing, air flow milling, and high B and low Ga auxiliary alloy B can well supplement the volume fraction of the main phase of the main alloy A, so that the coercive force is high while ensuring that the overall remanence is not affected. Figure 1 .

[0013] Furthermore, the main alloy A with high gallium and low boron is composed of R a T (1-a-b-c-d) Ga b M c B d ;

[0014] Wherein, R is one or two of Nd and Pr;

[0015] T is a mixture of Fe and Co;

[0016] M is one or more of Cu and Al and one or two of Ti and Zr;

[0017] The mass ratio of Fe to Co is (60-140):1; the mass percentage of Ga is 0.4wt%-0.7wt%; the mass percentage of B is 0.89wt%-0.91wt%; a is 29wt%-33wt%, b is 0.45wt%-0.7wt%, c is 0-2.0wt%, and d is 0.88wt%-0.91wt%.

[0018] Furthermore, the composition of the auxiliary alloy B with low gallium and high boron is R a T (1-a-b-c-d) Ga b M c B d ;

[0019] Wherein, R is one or two of Nd and Pr;

[0020] T is a mixture of Fe and Co;

[0021] M is one or more of Cu and Al and one or two of Ti and Zr;

[0022] The mass ratio of Fe to Co is (60-140):1; the mass percentage of Ga is 0wt%-0.15wt%; the mass percentage of B is 0.94wt%-0.98wt%; a is 29wt%-33wt%, b is 0-0.15wt%, c is 0-2.0wt%, and d is 0.94wt%-1wt%.

[0023] Furthermore, the jet mill treatment further includes a rapid solidification process, wherein the rapid solidification process includes first smelting and then casting to obtain a casting A or a casting B;

[0024] The smelting temperature is 1450°C to 1500°C, and the casting temperature is 1400°C to 1450°C.

[0025] Furthermore, the rotation speed of the copper roller in the rapid solidification process is 1.5 m / s to 4.0 m / s; and the average thickness of the casting A or the casting B is 0.2 mm to 0.4 mm.

[0026] Furthermore, the casting A or casting B is subjected to hydrogen crushing treatment, and then sieved in an argon protection box to obtain coarse crushed powder A or coarse crushed powder B, and then ground in a jet mill under nitrogen conditions to obtain jet mill magnetic powder A or jet mill magnetic powder B;

[0027] The average particle size of the jet mill magnetic powder A is 3 μm to 4 μm; the average particle size of the jet mill magnetic powder B is 2 to 3 μm.

[0028] Furthermore, the magnetic field intensity of the orientation molding is 1.5T to 2T; the pressing adopts isostatic pressing treatment, and the pressure is 200Mpa to 250Mpa;

[0029] The green material enters the sintering furnace and is kept at 550℃~600℃ for 5h~7h before being dehydrogenated.

[0030] Furthermore, the stirring time after adding the lubricant is 4 to 8 hours.

[0031] Further, the heat treatment includes sintering and tempering heat treatment;

[0032] The sintering temperature is 1050°C to 1100°C, and the sintering time is 6h to 8h;

[0033] The tempering heat treatment includes: a first-level tempering temperature of 800° C. to 920° C., a tempering time of 2 h to 4 h; a second-level tempering temperature of 460° C. to 540° C., a tempering time of 4 h to 6 h.

[0034] A sintered NdFeB magnet with high comprehensive performance is prepared by adopting the above-mentioned method for preparing a sintered NdFeB magnet with high comprehensive performance.

[0035] The beneficial effects of the present invention are:

[0036] (1) The present invention adopts dual alloy components: a main alloy A of high Ga and low B alloy and an auxiliary alloy B of low Ga and high B are mixed through belt spinning, crushing, and air flow milling and then co-sintered. The auxiliary alloy B of low Ga and high B can well supplement the volume fraction of the main phase of the main alloy A, achieving a high coercive force while ensuring that the overall remanence is not affected.

[0037] (2) The present invention makes the auxiliary alloy B obviously different from the main alloy A except for the content of B and Ga, while the types and contents of other elements are not much different, thereby avoiding the impact on process differences and manufacturing costs.

[0038] (3) The present invention can flexibly control the coercive force and remanence of the sintered NdFeB magnet by adjusting the mixing ratio of the main alloy A and the auxiliary alloy B, thereby achieving a magnet with higher comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the microstructure of the main alloy A with high gallium and low boron and the auxiliary alloy B with low gallium and high boron of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Additionally, descriptions of well-known structures, functions, and configurations may be omitted for clarity and conciseness.One of ordinary skill in the art will recognize that various changes and modifications may be made to the examples described herein without departing from the spirit and scope of the present disclosure.

[0042] Technologies, methods, and apparatus known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, such technologies, methods, and apparatus should be considered part of the authorization specification.

[0043] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0044] Where bal refers to the remaining mass percentage.

[0045] Example 1

[0046] 1. Rapid solidification process: According to the main alloy A (PrNd 30.5 Cu 0.4 Ga 0.55 Zr 0.15 Ti 0.15 Co 0.45 B 0.9 Fe bal ) and low gallium and high boron auxiliary alloy B (PrNd 31.5 Cu 0.2 Al 0.2 Ga 0.05 Zr 0.15 Ti 0.15 Co 0.45 B 0.96 Fe bal ) are prepared respectively, the prepared raw materials are put into a crucible and filled with argon for melting, and then poured onto a copper roller with a rotation speed of 3m / s to prepare castings A and B with a thickness of 0.2-0.4mm.

[0047] 2. Hydrogen crushing treatment: The castings A and B were subjected to hydrogen crushing treatment using a rotary hydrogen crushing furnace, and the castings A and B were crushed into coarse crushed powders A and coarse crushed powders B with particles of less than 500 μm, respectively.

[0048] 3. Airflow milling: Use high-pressure nitrogen gas to jet mill at 0.5Mpa~1.0Mpa, and control the speed of the sorting wheel to grind the coarse powder A and coarse powder B into airflow mill magnetic powder A and airflow mill magnetic powder B with an average particle size of 3μm~4μm and 2μm~3μm respectively.

[0049] 4. Powder mixing: Mix the jet mill magnetic powder A and the jet mill magnetic powder B in a mass ratio of 90:10, add lubricant and stir for 4h to 8h, and then mix on a powder mixer for 5h.

[0050] 5. Orientation molding and sintering: The mixed powder is oriented and pressed under a magnetic field of 1.8T, and isostatically pressed under a pressure of 240MPa to obtain a green blank; the green blank after isostatic pressing enters a sintering furnace, and is dehydrogenated at 550℃ for 5h in a vacuum sintering furnace, and then sintered at a sintering temperature of 1070℃ and a sintering time of 5h to obtain a sintered magnet. The first tempering temperature is 915℃ and the tempering time is 3 hours; the second tempering temperature is 540℃ and the tempering time is 4 hours to obtain a sintered NdFeB magnet blank.

[0051] Example 2

[0052] 1. Rapid solidification process: According to the main alloy A (PrNd 30.5 Cu 0.4 Ga 0.7 Zr0.3 Co 0.45 B 0.9 Fe bal ) and low gallium and high boron auxiliary alloy B (PrNd 31.5 Cu 0.2 Al 0.2 Zr 0.15 Ti 0.15 Co 0.45 B 0.98 Fe bal ) are prepared respectively, the prepared raw materials are put into a crucible and filled with argon for melting, and then poured onto a copper roller with a rotation speed of 3m / s to prepare castings A and B with a thickness of 0.2-0.4mm.

[0053] 2. Hydrogen crushing treatment: The castings A and B were subjected to hydrogen crushing treatment using a rotary hydrogen crushing furnace, and the castings A and B were crushed into coarse crushed powders A and coarse crushed powders B with particles of less than 500 μm, respectively.

[0054] 3. Airflow milling: Use high-pressure nitrogen gas to jet mill at 0.5Mpa~1.0Mpa, and control the speed of the sorting wheel to grind the coarse powder A and coarse powder B into airflow mill magnetic powder A and airflow mill magnetic powder B with an average particle size of 3μm~4μm and 2μm~3μm respectively.

[0055] 4. Powder mixing: Mix the jet mill magnetic powder A and the jet mill magnetic powder B in a mass ratio of 90:10, add lubricant and stir for 4h to 8h, and then mix on a powder mixer for 5h.

[0056] 5. Orientation molding and sintering: The mixed powder is oriented and pressed under a 1.8T magnetic field, and isostatically pressed under a pressure of 240MPa to obtain a green blank; the green blank after isostatic pressing enters a sintering furnace, and is dehydrogenated at 600℃ for 7h in a vacuum sintering furnace, and then sintered in a vacuum sintering furnace at a sintering temperature of 1070℃ for 4.5h to obtain a sintered magnet. The first tempering temperature is 915℃ for 2h; the second tempering temperature is 470℃ for 4h to obtain a sintered NdFeB magnet blank.

[0057] Comparative Example 1

[0058] The preparation method is consistent with that of Example 1, except that the powder of composite gold B is not added to obtain the NdFeB magnet material without composite gold B.

[0059] Comparative Example 2

[0060] The preparation method is consistent with that of Example 2, except that the powder of composite gold B is not added to obtain the NdFeB magnet material without composite gold B.

[0061] Comparative Example 3

[0062] The preparation method is consistent with that of Example 2, except that the addition amounts of Ga and B are conventional mass percentages (Ga: 0.15-0.30 wt %; B: 0.92%-0.94% wt %), i.e., PrNd 31.5 Cu 0.2 Al 0.2 Ga 0.25 Zr 0.15 Ti 0.15 Co 0.4 5B 0.93 The prepared NdFeB magnet material.

[0063] The magnetic properties of the magnetic material samples obtained in the embodiment and the comparative example after sintering were tested, and the test results are shown in Table 1:

[0064] Table 1 shows the magnetic properties test results of the samples prepared in the examples and the samples prepared in the comparative examples.

[0065] Project Category Br(kGs) Hcj(kOe) (BH)max(MGOe) Example 1 14.2 18.2 49.1 Example 2 14 18.8 48.9 Comparative Example 1 13.7 18.5 47.8 Comparative Example 2 13.67 19.2 47.5 Comparative Example 3 13.85 16.25 48.0

[0066] According to Table 1, in Example 1 and Example 2, the low-gallium and high-boron auxiliary alloy B supplements the high-gallium and low-boron main alloy A. The mixing ratio between the two can flexibly control the coercive force and remanence of the sintered NdFeB magnet performance, thereby achieving a magnet with higher comprehensive performance. The magnet is superior to the NdFeB magnet material without composite gold B obtained in Comparative Examples 1 and 2, and is also superior to the NdFeB magnet material obtained in Comparative Example 3 using Ga and B in a conventional addition range.

[0067] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a sintered NdFeB magnet with high comprehensive performance, characterized in that: The following steps are involved: Step 1: prepare a main alloy A with high gallium and low boron and an auxiliary alloy B with low gallium and high boron, and obtain jet milled magnetic powder A and jet milled magnetic powder B after jet milling; Step 2, after the jet milled magnetic powder A and the jet milled magnetic powder B are mixed evenly, a lubricant is added, the mixture is oriented and formed, and the mixture is pressed into a green billet, and the green billet is dehydrogenated and heat treated to obtain a sintered NdFeB magnet; The mass percentage of the jet mill magnetic powder A is 85% to 100%, and the mass percentage of the jet mill magnetic powder B is 0 to 15%.

2. The method for preparing a sintered NdFeB magnet with high comprehensive performance according to claim 1, characterized in that: The main alloy A with high gallium and low boron is composed of R a T (1-a-b-c-d) Ga b M c B d ; Wherein, R is one or two of Nd and Pr; T is a mixture of Fe and Co; M is one or more of Cu and Al and one or two of Ti and Zr; The mass ratio of Fe to Co is (60-140):1; the mass percentage of Ga is 0.4wt%-0.7wt%; the mass percentage of B is 0.89wt%-0.91wt%; a is 29wt%-33wt%, b is 0.45wt%-0.7wt%, c is 0-2.0wt%, and d is 0.88wt%-0.91wt%.

3. The method for preparing a sintered NdFeB magnet with high comprehensive performance according to claim 1, characterized in that: The composition of the auxiliary alloy B with low gallium and high boron is R a T (1-a-b-c-d) Ga b M c B d ; Wherein, R is one or two of Nd and Pr; T is a mixture of Fe and Co; M is one or more of Cu and Al and one or two of Ti and Zr; The mass ratio of Fe to Co is (60-140):1; the mass percentage of Ga is 0wt%-0.15wt%; the mass percentage of B is 0.94wt%-0.98wt%; a is 29wt%-33wt%, b is 0-0.15wt%, c is 0-2.0wt%, and d is 0.94wt%-1wt%.

4. The method for preparing a sintered NdFeB magnet with high comprehensive performance according to claim 1, characterized in that: The jet mill treatment also includes a rapid solidification process, wherein the rapid solidification process includes first smelting and then casting to obtain a casting A or a casting B; The smelting temperature is 1450°C to 1500°C, and the casting temperature is 1400°C to 1450°C.

5. The method for preparing a sintered NdFeB magnet with high comprehensive performance according to claim 4, characterized in that: The rotation speed of the copper roller in the rapid solidification process is 1.5 m / s to 4.0 m / s; the average thickness of the casting A or the casting B is 0.2 mm to 0.4 mm.

6. The method for preparing a sintered NdFeB magnet with high comprehensive performance according to claim 4, characterized in that: After the casting sheet A or casting sheet B is subjected to hydrogen cracking treatment, it is sieved in an argon protection box to obtain coarse crushed powder A or coarse crushed powder B, and then ground in a jet mill under nitrogen conditions to obtain jet mill magnetic powder A or jet mill magnetic powder B; The average particle size of the jet mill magnetic powder A is 3 μm to 4 μm; the average particle size of the jet mill magnetic powder B is 2 μm to 3 μm.

7. The method for preparing a sintered NdFeB magnet with high comprehensive performance according to claim 4, characterized in that: The magnetic field intensity of the orientation molding is 1.5T to 2T; the pressing adopts isostatic pressing treatment, and the pressure is 200Mpa to 250Mpa; The green material enters the sintering furnace and is kept at 550℃~600℃ for 5h~7h before being dehydrogenated.

8. The method for preparing a sintered NdFeB magnet with high comprehensive performance according to claim 4, characterized in that: The stirring time after adding the lubricant is 4h to 8h.

9. The method for preparing a sintered NdFeB magnet with high comprehensive performance according to claim 4, characterized in that: The heat treatment includes sintering and tempering heat treatment; The sintering temperature is 1050°C to 1100°C, and the sintering time is 6h to 8h; The tempering heat treatment includes: a first-stage tempering temperature of 800°C to 920°C and a tempering time of 2h to 4h; The secondary tempering temperature is 460℃~540℃, and the tempering time is 4h~6h.

10. A sintered NdFeB magnet with high comprehensive performance, characterized in that: The magnet is prepared according to the method for preparing a sintered NdFeB magnet with high comprehensive performance according to any one of claims 1 to 9.

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