High-boron neodymium-iron-boron permanent magnet material and preparation method thereof

Abstract

The application provides a preparation method of sintered neodymium-iron-boron permanent magnet material of a high-boron-content system, and belongs to the field of rare earth permanent magnet materials, and the steps are as follows: 1) preparing high-boron main phase and auxiliary phase rapid solidification alloy castings according to the element ratio; 2) preparing the main phase and auxiliary phase alloy rapid solidification castings into powder respectively; 3) pressing the mixed main phase alloy and auxiliary phase alloy powder into shape in a magnetic field; and 4) sintering and tempering heat treatment of the pressed magnet in a vacuum environment. The application makes the double alloying reaction occur in the auxiliary phase and the boron-rich phase at the grain boundary, and a new main phase shell layer is regenerated, the surface layer local anisotropy field is enhanced, and the main phase proportion is not reduced, so that the reduction of the residual magnetism is avoided, the sintered neodymium-iron-boron magnet with high residual magnetism and high coercivity can be prepared, the method is easy to control, and is suitable for batch production. The application also provides a high-boron neodymium-iron-boron permanent magnet material.

Description

Technical Field

[0001] This invention belongs to the field of rare earth permanent magnet materials technology, and particularly relates to a high boron neodymium iron boron permanent magnet material and its preparation method. Background Technology

[0002] Since their emergence in the 1960s, rare earth permanent magnet materials have experienced rapid development in research, production, and application, and have now reached the third generation: neodymium iron boron (NdFeB). Compared to the previous two generations of rare earth permanent magnet materials, NdFeB permanent magnets are characterized by high remanence, high energy product, and high intrinsic coercivity, making them the most magnetically powerful permanent magnet materials discovered in the world to date. NdFeB is widely used in emerging fields such as new energy vehicles, high-speed and maglev trains, wind power generation, and energy-saving home appliances. The rapid development of these fields is constantly increasing the demand for rare earth permanent magnet materials, while also placing higher requirements on their performance and stability.

[0003] Nd2Fe 14 The theoretical value of the anisotropic field, i.e., the coercivity, of compound B is 73 kOe. However, the actual coercivity of sintered NdFeB alloys differs significantly from the theoretical value, indicating considerable room for improvement. To meet the practical requirements of high-temperature applications in electric vehicles, motors, and other similar environments, it is necessary to increase the room-temperature coercivity of the magnets and improve their temperature resistance.

[0004] Numerous experiments have shown that coercivity is a structure-sensitive parameter, and the ideal microstructure of sintered NdFeB materials should be: uniform thin-area grain boundaries encapsulating Nd2Fe. 14 B-type grains are fine and uniformly distributed. Currently, the coercivity of magnets is commonly improved using a dual-alloy method. Auxiliary phase elements form a shell on the original grain surface, enhancing the local anisotropy field and increasing coercivity. However, because the auxiliary phase elements replace the main phase elements at the grain boundaries, the proportion of the main phase decreases, reducing remanence. Adding elements such as Ga and Cu to form antiferromagnetic Nd6Fe at the grain boundaries... 13 Introducing the M (M = Ga, Cu, Al, Sn, Bi) phase to weaken the exchange coupling between the main phase grains and thus improve coercivity is another technical approach. All of the above methods introduce a second phase (non-magnetic phase), leading to a decrease in remanence. While improving the magnet's coercivity at the expense of remanence, they fail to achieve a dual optimization effect, which is detrimental to the overall improvement of product performance. Therefore, the introduction of a second phase (non-magnetic phase) poses a challenge to the preparation of "dual-high magnets" with high coercivity and high remanence. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a high-boron neodymium iron boron permanent magnet material and its preparation method. The high-boron neodymium iron boron permanent magnet material provided by this invention has the comprehensive properties of high coercivity and high remanence.

[0006] The application provides a high-boron neodymium-iron-boron permanent magnet material, comprising:

[0007] a main phase, a phase component of the main phase being Re12Fe 14 B;

[0008] a shell layer arranged on a surface layer of the main phase, a phase component of the shell layer being Re22Fe 14 B;

[0009] the Re1 and the Re2 are independently selected from rare earth elements.

[0010] The application provides a preparation method of a high-boron neodymium-iron-boron permanent magnet material, comprising:

[0011] mixing a main phase alloy powder and an auxiliary phase alloy powder, and then sequentially performing orientation compression, sintering and tempering treatment to obtain the high-boron neodymium-iron-boron permanent magnet material;

[0012] a component of the main phase alloy powder is shown in formula I:

[0013] Re x B y Al a Cu b M c Co d Fe 100-x-y-a-b-c-d Formula I,

[0014] in formula I, the Re is selected from at least one of Pr, Nd, La, Ce, Y and Ho,

[0015] the M is selected from at least one of Co, Ga, Si, Sn, Ge, Ti, Zn and Al,

[0016] 29≤x≤34, 1.1<y≤2.0, 0≤a≤0.6, 0≤b≤0.6, 0.1≤c≤0.9, 0≤d≤2; a component of the auxiliary phase alloy powder is shown in formula II:

[0017] Re e B f M g Fe 100-e-f-g Formula II,

[0018] in formula II, the Re is selected from at least one of Dy, Tb, Pr, Nd, La, Ce, Y and Ho,

[0019] the M is selected from at least one of Co, Ga, Si, Sn, Ge, Ti, Zn and Al,

[0020] 30≤e≤70, 0≤f≤2, 30≤g≤70.

[0021] Preferably, the mass of the auxiliary phase alloy powder is 0.5-30% of the total mass of the main phase alloy powder and the auxiliary phase alloy powder.

[0022] Preferably, the particle size of the main phase alloy powder and the auxiliary phase alloy powder is independently selected from 2-5 microns.

[0023] Preferably, the preparation method of the main phase alloy powder and the auxiliary phase alloy powder comprises:

[0024] The main phase alloy cast sheet and the auxiliary phase alloy cast sheet are subjected to hydrogen crushing and then air jet milling.

[0025] Preferably, the hydrogen pressure in the hydrogen crushing process is independently selected from 0.1-0.4 MPa, the hydrogen absorption time is independently selected from 2-5 hours, the dehydrogenation temperature is independently selected from 320-500 DEG C, and the dehydrogenation time is independently selected from 4-8 hours.

[0026] Preferably, the hydrogen content in the powder obtained after hydrogen crushing is independently less than 1500 ppm, and the average particle size of the powder is independently selected from 100-250 microns.

[0027] Preferably, the magnetic field strength in the orientation compression process is 1.5-2.0 T.

[0028] Preferably, the sintering temperature is 900-1100 DEG C.

[0029] Preferably, the tempering temperature is 450-600 DEG C.

[0030] The present application obtains a high-boron magnet containing a boron-rich phase by increasing the content of boron, utilizes the reaction of the boron-rich phase and the auxiliary phase introduced by the double alloy to form a shell layer on the surface layer of the original grain, forms a "core-shell" structure, and makes the rare earth elements with high anisotropy field gather in the surface layer of the main phase grain of the magnet in large amounts, improves the magnetic crystal anisotropy field of the surface layer of the main phase grain, thereby improving the magnetic hardness of the surface layer, increases the resistance of the demagnetization nucleus formed in the surface layer of the grain during the demagnetization process, and thereby improves the coercive force of the magnet. At the same time, since the shell layer is grown on the outer layer of the original grain, unlike the shell layer formed by element replacement in the grain boundary addition and diffusion, the shell layer does not reduce the proportion of the main phase, and thus does not lose the remanence. Therefore, the method provided by the present application can simultaneously improve the remanence and the coercive force of the magnet, and prepare a "double-high" magnet.

[0031] The present application can control the microstructure of the rapidly solidified alloy cast sheet obtained by selecting reasonable element components and performing proportioning design, obtain fine columnar crystals without using special casting equipment, the process flow is easy to control, and is suitable for large-scale production. The remanence and coercive force of the Nd-Fe-B permanent magnet material prepared by the method provided by the present application are simultaneously improved, and the comprehensive performance is excellent. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A structure diagram of the high-boron neodymium-iron-boron permanent magnet material provided by the application is shown in the figure.

[0033] Figure 2 An element distribution diagram of the high-boron neodymium-iron-boron permanent magnet material prepared in the embodiment 1 of the application is shown in the figure. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the application, but not all the embodiments of the application. Based on the embodiments in the application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application.

[0035] The application provides a high-boron neodymium-iron-boron permanent magnet material, comprising:

[0036] a main phase, a phase component of the main phase being: Re12Fe 14 B;

[0037] a shell layer arranged on a surface layer of the main phase, a phase component of the shell layer being: Re22Fe 14 B;

[0038] The Re1 and Re2 are independently selected from rare earth elements.

[0039] The application provides a high-boron content system sintered neodymium-iron-boron magnet, in which a boron-rich phase and a double alloy introduced auxiliary phase react to generate a new main phase shell layer on a surface layer of an original 2:14:1 main phase, and a structure diagram is as shown in Figure 1 .

[0040] The application provides a preparation method of the high-boron neodymium-iron-boron permanent magnet material, comprising:

[0041] mixing the main phase alloy powder and the auxiliary phase alloy powder, and then sequentially performing orientation compression molding, sintering and tempering treatment to obtain the high-boron neodymium-iron-boron permanent magnet material;

[0042] a component of the main phase alloy powder is shown in formula I:

[0043] Re x B y Al a Cu b M c Co d Fe 100-x-y-a-b-c-d Formula I,

[0044] In formula I, Re is selected from at least one of Pr, Nd, La, Ce, Y and Ho,

[0045] M is at least one selected from the group consisting of Co, Ga, Si, Sn, Ge, Ti, Zn, Al,

[0046] 29≤x≤34, 1.1

[0047] The composition of the auxiliary phase alloy powder is shown in Formula II:

[0048] Re e B f M g Fe 100-e-f-g Formula II,

[0049] In Formula II, Re is at least one selected from the group consisting of Dy, Tb, Pr, Nd, La, Ce, Y and Ho,

[0050] M is at least one selected from the group consisting of Co, Ga, Si, Sn, Ge, Ti, Zn, Al,

[0051] 30≤e≤70, 0≤f≤2, 30≤g≤70.

[0052] In the present application, in Formula I, x is preferably 30-33, more preferably 31-32; y is preferably 1.2-1.8, more preferably 1.4-1.6, most preferably 1.5; a is preferably 0.1-0.5, more preferably 0.2-0.4, most preferably 0.3; b is preferably 0.1-0.5, more preferably 0.2-0.4, most preferably 0.3; c is preferably 0.2-0.8, more preferably 0.3-0.6, most preferably 0.4-0.5; and d is preferably 0.2-1.8, more preferably 0.5-1.5, most preferably 1.

[0053] In the present application, in Formula II, e is preferably 40-60, more preferably 45-55, most preferably 50; f is preferably 0.2-1.8, more preferably 0.5-1.5, most preferably 1; and g is preferably 40-60, more preferably 45-55, most preferably 50.

[0054] In the present application, the average particle diameter of the main phase alloy powder and the auxiliary phase alloy powder is independently preferably 2-5 microns, more preferably 3-4 microns.

[0055] In the present application, the preparation method of the main phase alloy powder preferably comprises:

[0056] The main phase alloy cast sheet is hydrogen broken and then air-jet milled.

[0057] In the present application, the preparation method of the main phase alloy cast sheet preferably comprises:

[0058] The alloy raw material is melted and then rapidly solidified to obtain the main phase alloy cast sheet.

[0059] The melting method is not particularly limited in the present application, and the alloy raw material is melted after being proportioned according to the desired composition by using a melting method well known to those skilled in the art. In the present application, the vacuum degree during the rapid solidification is preferably less than 10 -2 Pa, the rotating speed is preferably 1.8-3.0 m / s, more preferably 2.0-2.5 m / s, and the pouring temperature is preferably 1200-1500℃, more preferably 1300-1400℃, and most preferably 1350℃.

[0060] In the present application, the hydrogen pressure during the hydrogen decrepitation is preferably 0.1-0.4 MPa, more preferably 0.2-0.3 MPa; the hydrogen absorption time is preferably 2-5 hours, more preferably 3-4 hours; the dehydrogenation temperature is preferably 320-500℃, more preferably 350-450℃, and most preferably 400℃; the dehydrogenation is preferably vacuum dehydrogenation; and the dehydrogenation time is preferably 4-8 hours, more preferably 5-7 hours, and most preferably 6 hours.

[0061] In the present application, the hydrogen content of the powder obtained after the hydrogen decrepitation is preferably less than 1500 ppm, and the average particle size of the powder is preferably 100-250 microns, more preferably 150-200 microns, and most preferably 160-180 microns.

[0062] In the present application, the method for preparing the auxiliary phase alloy powder preferably comprises:

[0063] The auxiliary phase alloy cast sheet is hydrogen decrepitated and then broken by airflow milling.

[0064] In the present application, the method for preparing the auxiliary phase alloy cast sheet preferably comprises:

[0065] The alloy raw material is melted and then rapidly solidified to obtain the main phase alloy cast sheet.

[0066] The melting method is not particularly limited in the present application, and the alloy raw material is melted after being proportioned according to the desired composition by using a melting method well known to those skilled in the art. In the present application, the vacuum degree during the rapid solidification is preferably less than 10 -2 Pa, the rotating speed is preferably 1.8-3.0 m / s, more preferably 2.0-2.5 m / s, and the pouring temperature is preferably 1200-1500℃, more preferably 1300-1400℃, and most preferably 1350℃.

[0067] In the application, the process parameter selection range of the hydrogen crushing is consistent with the above technical solution, which will not be repeated here; the hydrogen content of the powder obtained after the hydrogen crushing is preferably lower than 1500 ppm, and the average particle size of the powder is preferably 100-250 microns, more preferably 150-200 microns, and most preferably 160-180 microns.

[0068] In the application, the thickness of the main phase alloy casting sheet and the auxiliary phase alloy casting sheet is independently preferably 0.1-0.5 mm, more preferably 0.2-0.4 mm, and most preferably 0.3 mm.

[0069] In the application, the mass of the auxiliary phase alloy powder is preferably 0.5-30% of the total mass of the main phase alloy powder and the auxiliary phase alloy powder, more preferably 1-25%, more preferably 5-20%, and most preferably 10-15%.

[0070] In the application, the orientation pressing is preferably isostatic pressing in a magnetic field.

[0071] In the application, the strength of the magnetic field is preferably 1.5-2.0 T, more preferably 1.6-1.9 T, and most preferably 1.7-1.8 T; and the pressure of the isostatic pressing is preferably 150-200 MPa, more preferably 160-190 MPa, and most preferably 170-180 MPa.

[0072] In the application, the sintering is preferably vacuum sintering. In the application, the temperature of the sintering is preferably 900-1100℃, more preferably 950-1050℃, and most preferably 1000℃; and the time of the sintering is preferably 2-5 hours, more preferably 3-4 hours.

[0073] In the application, the temperature of the tempering is preferably 450-600℃, more preferably 500-550℃, and most preferably 520-530℃; and the time of the tempering is preferably 0.5-2 hours, more preferably 1-1.5 hours.

[0074] The application obtains a high-boron magnet containing a boron-rich phase by increasing the content of boron, utilizes the reaction of the boron-rich phase and the auxiliary phase introduced by the double alloy to form a shell layer on the surface layer of the original crystal grain, forms a "core-shell" structure, makes a large amount of rare earth elements with a high anisotropy field gather in the surface layer of the main phase crystal grain of the magnet, improves the magnetic crystal anisotropy field of the surface layer of the main phase crystal grain, thereby improving the magnetic hardness of the surface layer, increases the resistance of the demagnetization nucleus formed in the surface layer of the crystal grain in the demagnetization process, and thereby improves the coercive force of the magnet. At the same time, since the shell layer is grown on the outer layer of the original crystal grain, unlike the shell layer formed by element replacement in the grain boundary addition and diffusion, the shell layer will not reduce the proportion of the main phase, and thus will not lose the remanence. Therefore, the method provided by the application can simultaneously improve the remanence and the coercive force of the magnet, and prepare a "double-high" magnet.

[0075] Example 1

[0076] The main phase rapid solidification alloy castings and auxiliary phase rapid solidification alloy castings were prepared by melting according to the element ratios. The vacuum degree during the preparation of the main phase rapid solidification alloy castings was 3 x 10⁻⁶. -2 Pa, rotation speed 2.0 m / s, casting temperature 1350℃, vacuum degree 3x10 during preparation of the auxiliary phase rapid solidification alloy casting sheet. -2 Pa, rotation speed 2.0 m / s, casting temperature 1000℃, main phase chemical formula mass percentage Nd 29.5 B 1.2 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.1 Fe 68.8 The auxiliary phase chemical formula has a mass percentage of Pr. 70 Fe 30 .

[0077] The main phase alloy casting and the auxiliary phase alloy casting were separately powdered. The rapidly solidified alloy casting was subjected to hydrogen absorption at room temperature and a hydrogen pressure of 0.2 MPa for 3 hours, and then dehydrogenated under vacuum at 450℃ for 9 hours to obtain hydrogen-crushed powder. The hydrogen-crushed powder was then further crushed using an air jet mill to obtain main phase alloy powder and auxiliary phase alloy powder respectively.

[0078] The main phase alloy powder and the auxiliary phase alloy powder were mixed, with the auxiliary phase alloy powder accounting for 9% of the total weight (main phase alloy powder + auxiliary phase alloy powder). The mixed powder was then oriented and pressed in a 1.8T magnetic field and isostatically pressed under a pressure of 180MPa to obtain a magnet. Afterwards, the magnet was sintered in a vacuum sintering furnace under atmospheric isolation conditions at a sintering temperature of 1080℃ for 4 hours. Finally, it was heat-treated at 900℃ and 500℃ for 2 hours each to obtain a NdFeB permanent magnet.

[0079] The distribution of rare earth elements in the grains of the iron-neodymium-boron permanent magnet prepared in Example 1 of this invention was analyzed using energy dispersive spectroscopy (EDS). The detection results are as follows: Figure 2 As shown, the neodymium iron boron permanent magnet prepared in Example 1 has a core-shell structure, with the core phase composition being Nd2Fe. 14 B, the phase composition of the outer shell is Pr2Fe 14 B.

[0080] Comparative Example 1

[0081] The neodymium iron boron permanent magnet was prepared according to the method of Example 1, except that the mass percentage of the main phase chemical formula was Nd. 29.5 B1Al 0.1 Cu 0.2 Ga 0.1 Zr0.1 Fe 69 The auxiliary phase chemical formula has a mass percentage of Pr. 70 Fe 30 .

[0082] The remanence and coercivity of the products prepared in Example 1 and Comparative Example 1 of this invention were measured using a high coercivity permanent magnet measuring instrument (model PFM14.CN) provided by HIRST. The test results are as follows:

[0083] Remanence (kGs) Coercivity (kOe) Example 1 14.5 16.6 Comparative Example 1 13.4 16.4

[0084] Example 2

[0085] The main phase rapid solidification alloy castings and auxiliary phase rapid solidification alloy castings were prepared by melting according to the element ratios. The vacuum degree during the preparation of the main phase rapid solidification alloy castings was 3 x 10⁻⁶. -2 Pa, rotation speed 2.0 m / s, casting temperature 1340℃, vacuum degree 3x10 during preparation of the auxiliary phase rapid solidification alloy casting sheet. -2 Pa, rotation speed 2.0 m / s, casting temperature 950℃, main phase chemical formula mass percentage Nd 23.6 Ce 2.95 La 0.59 Y 2.36 B 1.2 Al 0.25 Cu 0.2 Ga 0.15 Zr 0.1 Fe 68.6 The auxiliary phase chemical formula has a mass percentage of Pr. 60 Fe 30 Al 10 .

[0086] The main phase alloy casting and the auxiliary phase alloy casting were separately powdered. The rapidly solidified alloy casting was subjected to hydrogen absorption at room temperature and a hydrogen pressure of 0.2 MPa for 3 hours, and then dehydrogenated under vacuum at 450℃ for 9 hours to obtain hydrogen-crushed powder. After that, the hydrogen-crushed powder was further crushed by air jet mill to obtain main phase alloy powder and auxiliary phase alloy powder.

[0087] The main phase alloy powder and the auxiliary phase alloy powder were mixed, with the auxiliary phase alloy powder accounting for 5% of the total weight (main phase alloy powder and auxiliary phase alloy powder). The mixed powder was then oriented and pressed in a 1.8T magnetic field and isostatically pressed under a pressure of 180MPa to obtain a magnet. Afterwards, the magnet was sintered in a vacuum sintering furnace under atmospheric isolation conditions at a sintering temperature of 1060℃ for 4 hours. Finally, it was heat-treated at 900℃ and 500℃ for 2 hours each to obtain a NdFeB permanent magnet.

[0088] The Nd-Fe-B permanent magnet prepared in Example 2 was detected according to the method of Example 1, and the detection result was that the Nd-Fe-B permanent magnet prepared in Example 2 had a core-shell structure, the inner core phase composition was (Nd, Ce, Y)2Fe 14 B, and the shell phase composition was Pr2Fe 14 B.

[0089] Comparative Example 2

[0090] The Nd-Fe-B permanent magnet was prepared according to the method of Example 2, and the difference from Example 2 was that the main phase chemical formula mass percentage was Nd 23.6 Ce 2.95 La 0.59 Y 2.36 B1Al 0.25 Cu 0.2 Ga 0.15 Zr 0.1 Fe 68.8 , and the auxiliary phase chemical formula mass percentage was Pr 60 Fe 30 Al 10 .

[0091] The remanence and coercivity of the Nd-Fe-B permanent magnets prepared in Example 2 and Comparative Example 2 were detected according to the methods of Example 1 and Comparative Example 1, and the detection results were:

[0092] Remanence (kGs) Coercivity (kOe) Example 2 13.6 13.5 Comparative Example 2 13.1 12.8

[0093] Example 3

[0094] The main phase rapid solidification alloy cast sheet and the auxiliary phase rapid solidification alloy cast sheet were prepared according to the element ratio, the vacuum degree during preparation of the main phase rapid solidification alloy cast sheet was 3x10 -2 Pa, the rotating speed was 2.0 m / s, and the pouring temperature was 1380℃, the vacuum degree during preparation of the auxiliary phase rapid solidification alloy cast sheet was 3x10 -2 Pa, the rotating speed was 2.0 m / s, and the pouring temperature was 1050℃, the main phase chemical formula mass percentage was Nd 24.8 Ce 4.03 La 1.24 Y 0.93 B 1.1 Cu 0.04 Fe 67.86 , and the auxiliary phase chemical formula mass percentage was Pr 70 Fe 20 Cu 10 .

[0095] The main phase alloy cast piece and the auxiliary phase alloy cast piece are respectively powdered, the alloy rapid solidification cast piece is hydrogenated for 3 hours at room temperature under the condition of hydrogen pressure of 0.2 MPa, and vacuum dehydrogenation is carried out at 450 DEG C for 9 hours to obtain hydrogen broken powder; then, the hydrogen broken powder is further broken by using an air flow mill to obtain the main phase alloy powder and the auxiliary phase alloy powder.

[0096] The main phase alloy powder and the auxiliary phase alloy powder are mixed, the auxiliary phase alloy powder accounts for 9% of the total weight (the main phase alloy powder + the auxiliary phase alloy powder), then the mixed powder is subjected to orientation compression in a 1.8T magnetic field, and is subjected to isostatic pressing under a pressure of 180 MPa to obtain a magnet. Then, the magnet is sent into a vacuum sintering furnace for sintering under the condition of being isolated from the atmosphere, the sintering temperature is 1020 DEG C, the sintering time is 4 hours, and finally, heat treatment is carried out at temperatures of 900 DEG C and 500 DEG C respectively for 2 hours to obtain a neodymium-iron-boron permanent magnet.

[0097] The neodymium-iron-boron permanent magnet prepared in Example 3 is detected according to the method of Example 1, and the detection result is that the neodymium-iron-boron permanent magnet prepared in Example 3 has a core-shell structure, the inner core phase composition is (Nd, Ce, Y)2Fe 14 B, and the shell phase composition is Pr2Fe 14 B.

[0098] Comparative Example 3

[0099] The neodymium-iron-boron permanent magnet is prepared according to the method of Example 3, and the difference from Example 3 is that the mass percentage of the main phase chemical formula is Nd 24.8 Ce 4.03 La 1.24 Y 0.93 B1Cu 0.04 Fe 67.96 , and the mass percentage of the auxiliary phase chemical formula is Pr 70 Fe 20 Cu 10 .

[0100] The remanence and coercivity of the neodymium-iron-boron permanent magnets prepared in Example 3 and Comparative Example 3 are detected according to the methods of Example 1 and Comparative Example 1, and the detection results are as follows:

[0101]

[0102]

[0103] The application obtains high-boron magnet containing boron-rich phase by increasing the content of boron, and utilizes the reaction of boron-rich phase and double alloy introduced auxiliary phase to form shell layer on the surface layer of original grain, form "core-shell" structure, make rare earth elements with high anisotropy field gather in the surface layer of main phase grain of magnet, improve the magnetic crystal anisotropy field of surface layer of main phase grain, thereby improve the magnetic hardness of surface layer, increase the resistance of demagnetization nucleus formed in the surface layer of grain in the demagnetization process, thereby improve the coercivity of magnet. Meanwhile, the shell layer is grown out of the outer layer of original grain, which is different from the shell layer formed by element replacement in grain boundary addition and diffusion, and will not reduce the proportion of main phase, so as not to lose residual magnetism. Therefore, the method provided by the application can simultaneously improve the residual magnetism and coercivity of magnet, and prepare "double high" magnet.

[0104] While the application has been described and illustrated with reference to specific embodiments thereof, these descriptions and illustrations are not intended to limit the application. Those skilled in the art can readily devise numerous changes, substitutions and equivalents that do not depart from the true spirit and scope of the application as defined by the following claims. All such modifications are intended to be within the scope of the claims. Although the methods disclosed herein have been described with reference to particular sequences for performing certain operations, it will be understood that these operations can be combined, sub-divided, or re-ordered to form equivalent methods without departing from the teachings of the present application. Accordingly, unless specifically indicated herein, the order and grouping of operations are not a limitation of the present application.

Claims

1. A high-boron neodymium-iron-boron permanent magnet material, comprising: a main phase, a phase component of the main phase being: Re12Fe 14 B; a shell layer grown on the main phase surface layer, the phase composition of the shell layer being: Re22Fe 14 B; said Re1 and Re2 are independently selected from rare earth elements; a preparation method of the high-boron neodymium-iron-boron permanent magnet material, comprising: mixing the main phase alloy powder and the auxiliary phase alloy powder, and then sequentially performing orientation compression molding, sintering and tempering treatment to obtain the high-boron neodymium-iron-boron permanent magnet material; a composition of the main phase alloy powder is shown in formula I: Re x B y Al a Cu b M c Co d Fe 100-x-y-a-b-c-d formula I, in formula I, Re is selected from at least one of Pr, Nd, La, Ce, Y and Ho, M is selected from at least one of Co, Ga, Si, Sn, Ge, Ti, Zn and Al, 29≤x≤34, 1.1<y≤2.0, 0≤a≤0.6, 0≤b≤0.6, 0.1≤c≤0.9, 0≤d≤2; a composition of the auxiliary phase alloy powder is shown in formula II: Re e M g Fe 100-e-f-g formula II, in formula II, Re is selected from at least one of Dy, Tb, Pr, Nd, La, Ce, Y and Ho, M is selected from at least one of Co, Ga, Si, Sn, Ge, Ti, Zn and Al, 30≤e≤70, 30≤g≤70.

2. The high-boron Nd-Fe-B permanent magnetic material according to claim 1, characterized in that, a mass of the auxiliary phase alloy powder is 0.5-30% of a total mass of the main phase alloy powder and the auxiliary phase alloy powder.

3. The high-boron Nd-Fe-B permanent magnetic material of claim 1, wherein, a particle size of the main phase alloy powder is selected from 2-5 microns.

4. The high-boron Nd-Fe-B permanent magnetic material of claim 1, wherein, a particle size of the auxiliary phase alloy powder is selected from 2-5 microns.

5. The high-boron Nd-Fe-B permanent magnetic material of claim 1, wherein, a preparation method of the main phase alloy powder and the auxiliary phase alloy powder comprises: hydrogen crushing the main phase alloy cast sheet and the auxiliary phase alloy cast sheet respectively, and then performing air flow grinding.

6. The high-boron Nd-Fe-B permanent magnetic material of claim 5, wherein, in the hydrogen crushing process, a hydrogen pressure is independently selected from 0.1-0.4 MPa, a hydrogen absorption time is independently selected from 2-5 hours, a dehydrogenation temperature is independently selected from 320-500℃, and a dehydrogenation time is independently selected from 4-8 hours.

7. The high-boron Nd-Fe-B permanent magnetic material of claim 5, wherein, a hydrogen content in the powder obtained after the hydrogen crushing is independently less than 1500 ppm, and an average particle size of the powder is independently selected from 100-250 microns.

8. The high-boron Nd-Fe-B permanent magnetic material of claim 1, wherein, a magnetic field strength in the orientation compression molding process is 1.5-2.0 T.

9. The high-boron Nd-Fe-B permanent magnetic material of claim 1, wherein, a sintering temperature is 900-1100℃.

10. The high-boron Nd-Fe-B permanent magnetic material of claim 1, wherein, a tempering temperature is 450-600℃.

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