Sintered neodymium-iron-boron magnet and preparation method thereof

Abstract

The invention discloses a sintered neodymium-iron-boron magnet and a preparation method thereof. The sintered neodymium-iron-boron magnet is prepared by adopting a Dy / Tb heavy rare earth diffusion technology. The sintered neodymium-iron-boron magnet is prepared from the following magnet components in percentage by weight: 29 to 33 percent of R, 0.84 to 0.94 percent of B, 0.5 to 3.0 percent of Co, 0 to 0.3 percent of Ga, 0.1 to 0.6 percent of Cu, 0 to 0.3 percent of Al, 0 to 0.2 percent of A and the balance of Fe, wherein R is a rare earth element and comprises Gd, and the content of Gd is 10-20 wt%; a is selected from at least one of Ti, Zr and Nb. The coercive force of the magnet can reach 20.0 kOe, the highest use temperature reaches 150 DEG C, and the requirements of magnets in the field of motors can be met.

Description

Technical Field

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

[0002] As a new type of rare earth permanent magnet material with the highest magnetic properties, NdFeB rare earth permanent magnet material has been widely used in household appliances, electronic communications, medical equipment, new energy vehicles, aerospace and other fields, which has effectively promoted the development of modern scientific and technological products towards miniaturization, integration and intelligence. Entering the 21st century, the output of sintered NdFeB magnets in my country has leapt to the forefront of the world, and has become an important production base of sintered NdFeB magnetic materials in the world.

[0003] In recent years, with the rapid growth of the market for new rare earth materials such as neodymium iron boron permanent magnet materials, the rare earth industry has developed rapidly, resulting in the scale and capacity of rare earth production far exceeding the consumption capacity of rare earths. In particular, the price of PrNd rare earth metal is relatively high, so it is necessary to develop low-cost sintered NdFeB magnets. However, the existing low-cost sintered NdFeB magnets have low operating temperatures and low room temperature coercive force. Therefore, the low-cost magnets prepared by the existing technology cannot meet the requirements of magnets in the motor field. Summary of the invention

[0004] In order to solve the above-mentioned deficiencies in the art, the present application aims to provide a sintered NdFeB magnet and a preparation method thereof, which has lower raw material cost and higher room temperature coercivity.

[0005] According to one aspect of the present application, there is provided a sintered NdFeB magnet, which is produced by using Dy and / or Tb heavy rare earth diffusion technology;

[0006] The magnet components of the sintered NdFeB magnet include: R 29-33wt%, B 0.84-0.94wt%, Co 0.5-3.0wt%, Ga 0-0.3wt%, Cu 0.1-0.6wt%, Al 0-0.3wt%, A 0-0.2wt%, and the balance is Fe;

[0007] Wherein, R is a rare earth element, including Gd, and the content of Gd is 10-20wt% of the total weight of the magnet;

[0008] A is selected from at least one of Ti, Zr and Nb.

[0009] According to some embodiments of the present application, the content of Cu is 0.3-0.6 wt %.

[0010] According to some embodiments of the present application, the depth of the sintered NdFeB magnet along the diffusion direction is in the range of 0-100 μm, and there is R at the grain boundary of the triangular region. 1 -T1 -M 1 Phase, R 2 -T 2 -M 2 Xianghefu R 3 Mutually;

[0011] Among them, R 1 is a rare earth element, T 1 Fe and / or Co, M 1 At least one of Ga, Cu and Al;

[0012] R 2 is a rare earth element, T 2 Fe and / or Co, M 2 At least one of Ga, Cu and Al;

[0013] R 3 For rare earth elements.

[0014] According to some embodiments of the present application, R 1 '=28-31%, M 1 '=8-11%;R 2 '=40-50%, M 2 '=8-11%;R 3 %≥50;

[0015] R' 1 =R 1 % / (R 1 %+T 1 %+M 1 %), M 1 '=M 1 % / (R 1 %+T 1 %+M 1 %);

[0016] R 2 '=R 2 % / (R 2 %+T 2 %+M 2 %), M 2 '=M 2 % / (R 2 %+T 2 %+M 2 %);

[0017] Among them, R 1 % is R 1 -T 1 -M 1 The total atomic percentage of rare earth elements in the phase, T 1 % is R 1 -T1 -M 1 The sum of the atomic percentages of Fe and Co in the phase, M 1 % is R 1 -T 1 -M 1 The sum of the atomic percentages of Ga, Cu, and Al in the phase;

[0018] R 2 % is R 2 -T 2 -M 2 The total atomic percentage of rare earth elements in the phase, T 2 % is R 2 -T 2 -M 2 The sum of the atomic percentages of Fe and Co in the phase, M 2 % is R 2 -T 2 -M 2 The sum of the atomic percentages of Ga, Cu, and Al in the phase;

[0019] R 3 %R 3 The sum of the atomic percentages of rare earth elements in the phase;

[0020] R 1 Contains Gd, Gd in R 1 -T 1 -M 1 The atomic percentage of the phase is X 1 %,X 1 % / R 1 % = 19-25%;

[0021] R 2 Contains Gd, Gd in R 2 -T 2 -M 2 The atomic percentage of the phase is X 2 %,X 2 % / R 2 % = 15-18%;

[0022] R 3 Contains Gd, Gd in R-rich 3 The atomic percentage of the phase is X 3 %.

[0023] According to some embodiments of the present application, X 4 % / R 4 %>X 1 % / R 1 %>X 2 % / R 2 %>X 3 % / R3 %;

[0024] Among them, X 4 % is the atomic percentage of Gd in the main phase grains, R 4 % is the total percentage of rare earth elements in the main phase grains.

[0025] According to another aspect of the present application, a method for preparing a sintered NdFeB magnet is provided, comprising:

[0026] The raw materials are prepared according to the magnet components, and then smelted and cast, air flow milled, oriented pressed and sintered to obtain a rough magnet;

[0027] After the blank magnet is cut, a 5-15 μm film layer having Dy and / or Tb elements is coated on the surface, and a diffusion heat treatment is performed to obtain the sintered NdFeB magnet;

[0028] The magnet components include: R 29-33wt%, B 0.84-0.94wt%, Co0.5-3.0wt%, Ga 0-0.3wt%, Cu 0.1-0.6wt%, Al 0-0.3wt%, A0-0.2wt%, and the balance is Fe;

[0029] Wherein, R is a rare earth element, including Gd, and the content of Gd is 10-20wt% of the total weight of the magnet;

[0030] A is selected from at least one of Ti, Zr and Nb.

[0031] According to some embodiments of the present application, the average thickness of the strip-spun alloy sheet is 0.1-0.5 mm.

[0032] According to some embodiments of the present application, the particle size X of the magnetic powder produced by airflow milling is 50 3-5μm;

[0033] According to some embodiments of the present application, the orientation magnetic field of the orientation pressure molding is 1.6-2.1T.

[0034] According to some embodiments of the present application, the sintering temperature is 1030-1120° C., and the sintering time is 1-10 h.

[0035] According to some embodiments of the present application, the diffusion heat treatment includes: first heating to 850-950° C. and keeping the temperature for 2-30 hours, cooling, and then heating again to 420-670° C. and keeping the temperature for 1-10 hours.

[0036] Compared with the prior art, this application has at least the following beneficial effects:

[0037] The present application provides a sintered NdFeB magnet and a preparation method thereof, wherein the magnet contains more than 10wt% of a low-cost rare earth element, gadolinium. While reducing the cost of raw materials, the present application also solves the problem of low coercivity of the magnet due to excessive gadolinium content by regulating the content of B, Ga, Cu, Al, and A elements and combining Dy and / or Tb heavy rare earth diffusion technology. The sintered NdFeB magnet using the component ratio and preparation method of the present application has a coercivity of more than 1592kA / m and a maximum operating temperature of 150°C, which can meet the requirements of magnets in the motor field. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a microstructure photograph of a magnet cross section parallel to the diffusion direction and 0-50 μm away from the magnet surface according to Example 1 of the present application.

[0039] Figure 2 This is a microstructure photograph of a magnet cross section parallel to the diffusion direction and 50-100 μm away from the magnet surface according to Example 1 of the present application.

[0040] Figure 3 This is a microstructure photograph of a magnet cross section parallel to the orientation direction of Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0041] The technical solution of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0042] It is particularly important to point out that similar substitutions and modifications made to the present application are obvious to those skilled in the art, and they are all deemed to be included in the present application. Relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present application to implement and apply the technology of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments.

[0043] The application is described in detail below.

[0044] Sintered NdFeB magnet is a high-performance magnetic material. Due to its excellent magnetic properties and stability, it is widely used in various high-tech fields, such as motors, wind power generation, and maglev trains. With the rise in the price of PrNd rare earth metal, based on this, the existing technology has developed a low-cost sintered NdFeB magnet. By adding the relatively low-priced gadolinium element and trace amounts of cobalt, aluminum, and copper elements, the mass percentage of gadolinium metal is 7-9%, but the maximum operating temperature of the magnet is only 80°C, which cannot meet the requirements of magnets in the motor field. Current studies have shown that as the gadolinium content increases, the room temperature coercivity of the magnet gradually decreases. However, for magnets used in the motor field, it is usually required that the room temperature coercivity of the magnet reach above 1592kA / m, and the maximum operating temperature is 150°C.

[0045] Based on the above problems, the present application provides a sintered NdFeB magnet, the components of which are: R 29-33wt%, B 0.84-0.94wt%, Co 0.5-3.0wt%, Ga 0-0.3wt%, Cu0.1-0.6wt%, Al 0-0.3wt%, A0-0.2wt%, and the balance is Fe;

[0046] Wherein, R is a rare earth element, including Gd, and the content of Gd is 10-20wt% of the total weight of the magnet;

[0047] A is selected from at least one of Ti, Zr and Nb.

[0048] The present application also provides a method for preparing a sintered NdFeB magnet, comprising:

[0049] Raw materials are prepared according to the magnet component composition, and then smelted and cast in a rapid-setting strip-spinning furnace to obtain strip-spinning alloy sheets;

[0050] The strip-spinning alloy flakes are powdered by air flow grinding, and then oriented and pressed to obtain compacts;

[0051] The green compact is sintered to obtain a green magnet;

[0052] After the blank magnet is cut, a film layer having Dy and / or Tb elements is coated on the surface, and a diffusion heat treatment is performed to obtain a sintered NdFeB magnet;

[0053] Among them, the average thickness of the strip-spinning alloy sheet is 0.1-0.5mm.

[0054] Magnetic powder particle size X 50 (median particle size) is 3-5 μm;

[0055] The orientation magnetic field of the orientation pressing is 1.6-2.1T.

[0056] The sintering temperature is 1030-1120°C and the sintering time is 1-10h.

[0057] The diffusion heat treatment includes: first heating to 850-950°C and keeping it for 2-30 hours, cooling, and then heating again to 420-670°C and keeping it for 1-10 hours.

[0058] The present application has found that when the Gd content exceeds 10wt%, the B content can be reduced and the Ga, Cu, Al, and A element contents can be controlled. Combined with Dy and / or Tb heavy rare earth diffusion technology, the HcJ of the magnet can reach above 1592kA / m and the maximum operating temperature can reach 150°C.

[0059] At the same time, according to the preparation method and magnet formula of the present application, the sintered NdFeB magnet prepared by observing the magnet cross-section microstructure parallel to the diffusion direction shows that the magnet has R at the grain boundary of the triangular region in the range of 0-100 μm along the diffusion direction. 1 -T 1 -M 1 Phase, R 2 -T 2 -M 2 Xianghefu R 3 Mutually;

[0060] Among them, R 1 is a rare earth element, T 1 Fe and / or Co, M 1 At least one of Ga, Cu and Al;

[0061] R 2 is a rare earth element, T 2 Fe and / or Co, M 2 At least one of Ga, Cu and Al;

[0062] R 3 For rare earth elements.

[0063] R' 1 =28-31%, M 1 '=8-11%;R 2 '=40-50%,M 2 '=8-11%;R 3 %≥50;

[0064] R' 1 =R 1 % / (R 1 %+T 1 %+M 1 %), M 1 '=M 1 % / (R 1 %+T 1 %+M 1 %);

[0065] R 2 '=R 2 % / (R 2 %+T 2 %+M 2 %), M 2 '=M 2 % / (R 2 %+T 2 %+M 2 %);

[0066] Among them, R 1 % is R 1 -T 1 -M 1 The total atomic percentage of rare earth elements in the phase, T 1 % is R 1 -T 1 -M 1 The sum of the atomic percentages of Fe and Co in the phase, M 1 % is R 1 -T 1 -M 1 The sum of the atomic percentages of Ga, Cu, and Al in the phase;

[0067] R 2 % is R 2 -T 2 -M 2 The total atomic percentage of rare earth elements in the phase, T 2 % is R 2 -T 2 -M 2 The sum of the atomic percentages of Fe and Co in the phase, M 2 % is R 2 -T 2 -M 2 The sum of the atomic percentages of Ga, Cu, and Al in the phase;

[0068] R 3 %R 3 The sum of the atomic percentages of rare earth elements in the phase;

[0069] R 1 Contains Gd, Gd in R 1 -T 1 -M 1 The atomic percentage of the phase is X 1 %,X 1 % / R 1 % = 19-25%;

[0070] R 2 Contains Gd, Gd in R 2 -T 2 -M2 The atomic percentage of the phase is X 2 %,X 2 % / R 2 % = 15-18%;

[0071] R 3 %≥50;

[0072] R 3 Contains Gd, Gd in R-rich 3 The atomic percentage of the phase is X 3 %.

[0073] X 4 % / R 4 %>X 1 % / R 1 %>X 2 % / R 2 %>X 3 % / R 3 %;

[0074] Among them, X 4 % is the atomic percentage of Gd in the main phase grains, R 4 % is the total percentage of rare earth elements in the main phase grains.

[0075] The technical solution of the present application is further introduced below in conjunction with specific embodiments.

[0076] Example 1

[0077] Magnet formula:

[0078]

[0079] Preparation of sintered NdFeB magnets in this application:

[0080] The raw materials of the magnet formula are placed in a rapid-setting belt-spinning furnace for smelting and casting. The casting temperature is controlled at 1400° C. The average thickness of the obtained belt-spinning alloy sheet is 0.3 mm.

[0081] The belt alloy flakes are air-milled to control the magnetic powder X 50 (Median particle size) is 4 μm.

[0082] The magnetic powder is placed in a mold and oriented and pressed under a 1.8T magnetic field to obtain a pressed embryo.

[0083] The pressed green body was placed in a sintering furnace and the sintering temperature was controlled to be 1060° C. for 5 hours to obtain a green body magnet.

[0084] The blank magnet is machined and cut into the required 30*20*8mm (orientation direction) workpieces, and the two surfaces of the workpiece perpendicular to the orientation direction are coated with DyH2 The film layer of the powder has a thickness of 15 μm.

[0085] The workpiece coated with the film layer is placed in a diffusion heat treatment furnace, the temperature is controlled to be 900°C and kept for 10 hours, then the temperature is lowered to room temperature and then raised to 500°C and kept for 4 hours to obtain a sintered NdFeB magnet.

[0086] Analysis of the sintered NdFeB magnet after diffusion heat treatment shows that the Dy content diffused into the magnet is 0.4wt%.

[0087] Example 2

[0088] Magnet formula:

[0089]

[0090] Preparation of sintered NdFeB magnets in this application:

[0091] The raw materials of the magnet formula are placed in a rapid-setting belt-spinning furnace for melting and casting. The casting temperature is controlled at 1300° C. The average thickness of the obtained belt-spinning alloy sheet is 0.2 mm.

[0092] The belt alloy flakes are air-milled to control the magnetic powder X 50 is 3μm.

[0093] The powder after milling is placed in a mold and oriented and pressed under a 2.0T magnetic field to obtain a compact.

[0094] The compact was placed in a sintering furnace and the sintering temperature was controlled to be 1030° C. for 10 hours to obtain a green magnet.

[0095] The blank magnet is machined and cut into the required 30*20*8mm (orientation direction) workpieces, and a film layer with DyH2 powder is coated on the two surfaces of the workpiece perpendicular to the orientation direction, and the thickness of the film layer is 15μm.

[0096] The workpiece coated with the film layer was placed in a diffusion heat treatment furnace, the temperature was controlled to be 850°C and kept for 28 hours, then the temperature was lowered to room temperature and then raised to 420°C and kept for 10 hours to obtain a sintered NdFeB magnet.

[0097] Analysis of the sintered NdFeB magnet after diffusion heat treatment shows that the Dy content diffused into the magnet is 0.4wt%.

[0098] Example 3

[0099] Magnet formula:

[0100]

[0101] Preparation of sintered NdFeB magnets in this application:

[0102] The raw materials of the magnet formula are placed in a rapid-setting belt-spinning furnace for melting and casting. The casting temperature is controlled at 1500° C. The average thickness of the obtained belt-spinning alloy sheet is 0.5 mm.

[0103] The belt alloy flakes are air-milled to control the magnetic powder X 50 5μm.

[0104] The magnetic powder is placed in a mold and oriented and pressed in a 1.6 T magnetic field to obtain a compact.

[0105] The green compact was placed in a sintering furnace and the sintering temperature was controlled to be 1120° C. for 1 hour to obtain a green magnet.

[0106] The blank magnet is machined and cut into the required 30*20*8mm (orientation direction) workpieces, and the two surfaces of the workpiece perpendicular to the orientation direction are coated with DyH 2 The film layer of the powder has a thickness of 15 μm.

[0107] The workpiece coated with the film layer was placed in a diffusion heat treatment furnace, the temperature was controlled to be 950°C for 5 hours, then cooled to room temperature and then raised to 490°C for 2 hours to obtain a sintered NdFeB magnet.

[0108] Analysis of the sintered NdFeB magnet after diffusion heat treatment shows that the Dy content diffused into the magnet is 0.4wt%.

[0109] Example 4

[0110] Magnet formula:

[0111]

[0112] Preparation of sintered NdFeB magnets in this application:

[0113] The raw materials of the magnet formula are placed in a rapid-setting belt-spinning furnace for melting and casting. The casting temperature is controlled at 1350° C. The average thickness of the obtained belt-spinning alloy sheet is 0.4 mm.

[0114] The belt alloy flakes are air-milled to control the magnetic powder X 50 is 3μm.

[0115] The magnetic powder is placed in a mold and oriented pressed in a 2.1T magnetic field to obtain a compact.

[0116] The green compact was placed in a sintering furnace and the sintering temperature was controlled to be 1110° C. for 1 hour to obtain a green magnet.

[0117] The blank magnet is machined and cut into the required 30*20*8mm (orientation direction) workpieces, and the two surfaces of the workpiece perpendicular to the orientation direction are coated with DyH2 The film layer of the powder has a thickness of 15 μm.

[0118] The workpiece coated with the film layer was placed in a diffusion heat treatment furnace, the temperature was controlled to be 940°C and kept for 4 hours, then cooled to room temperature and then raised to 510°C and kept for 1 hour to obtain a sintered NdFeB magnet.

[0119] Analysis of the sintered NdFeB magnet after diffusion heat treatment shows that the Dy content diffused into the magnet is 0.4wt%.

[0120] Comparative Example 1

[0121] NdFeB magnets were prepared according to the magnet formula and preparation method in Example 1, except that after obtaining the blank magnets, part of the blank magnets were machined and cut into required 30*20*8mm workpieces, and the workpieces were tempered and heat treated.

[0122] The tempering process is as follows: keeping the temperature at 900°C for 4 hours, cooling to room temperature and then heating to 500°C and keeping the temperature for 4 hours to obtain a NdFeB magnet.

[0123] Comparative Example 2

[0124] Magnet formula:

[0125]

[0126] A neodymium iron boron magnet was prepared according to the preparation method in Comparative Example 1.

[0127] Comparative Example 3

[0128] Magnet formula:

[0129]

[0130] A neodymium iron boron magnet was prepared according to the preparation method in Comparative Example 1.

[0131] Comparative Example 4

[0132] Magnet formula:

[0133]

[0134] A neodymium iron boron magnet was prepared according to the preparation method in Comparative Example 1.

[0135] Experimental example

[0136] 1. The magnetic properties of the magnets of the above embodiments and comparative examples were measured, as shown in Table 1.

[0137] Table 1

[0138]

[0139] According to the data in the above table, it can be seen that, by comparing Examples 1-4 with Comparative Examples 1-4, the magnets of the Examples have higher HcJ and still have higher coercive force and better squareness (Hk / HcJ) at 150°C.

[0140] 2. Use SEM to observe the microstructure of the magnet cross section parallel to the diffusion direction of the magnet in Example 1, and analyze the main phase and triangular grain boundary phase composition. Figure 1 As shown, it is a microstructure photograph of the magnet cross section parallel to the diffusion direction and 0-50 μm away from the magnet surface; Figure 2 Shown is a microstructure photograph of a magnet cross section parallel to the diffusion direction and 50-100 μm away from the magnet surface.

[0141] The magnet microstructure of Comparative Example 1 was observed by SEM, and the observed section was parallel to the orientation direction. Figure 3 .

[0142] in, Figure 1-3 The grain boundary phase in the triangle area marked by △ is R 1 -T 1 -M 1 phase; the grain boundary phase in the triangle area marked by * is R 2 -T 2 -M 2 phase; the grain boundary phase in the triangle area marked by ○ is R-rich 3 Phase; The grain boundary phase in the triangular area marked with ◇ is a rare earth-rich Zr phase, with a rare earth content of ≥70at%, and a Zr content of =15-20at%.

[0143] According to Figure 1 and Figure 2 The results of the composition analysis of the main phase and the grain boundary phase in each triangle area are shown in Tables 2 and 3. Figure 3 The composition analysis of the main phase and the grain boundary phase in each triangular area is shown in Table 4:

[0144] Table 2

[0145]

[0146] Table 3

[0147]

[0148] Table 4

[0149]

[0150] R' in the above table 1 =R 1 % / (R 1 %+T 1 %+M 1 %), M 1'=M 1 % / (R 1 %+T 1 %+M 1 %);

[0151] R 2 '=R 2 % / (R 2 %+T 2 %+M 2 %), M 2 '=M 2 % / (R 2 %+T 2 %+M 2 %);

[0152] R 1 % is R 1 -T 1 -M 1 The total atomic percentage of rare earth elements in the phase; R 2 % is R 2 -T 2 -M 2 The total atomic percentage of rare earth elements in the phase; R 3 %R 3 The total atomic percentage of rare earth elements in the phase; R 4 % is the total percentage of rare earth elements in the main phase grains;

[0153] M 1 % is R 1 -T 1 -M 1 The sum of Ga, Cu, and Al atomic percentages in the phase; M 2 % is R 2 -T 2 -M 2 The sum of the atomic percentages of Ga, Cu, and Al in the phase;

[0154] R 1 Contains Gd, Gd in R 1 -T 1 -M 1 The atomic percentage of the phase is X 1 %;

[0155] R 2 Contains Gd, Gd in R 2 -T 2 -M 2 The atomic percentage of the phase is X 2 %;

[0156] R 3 Contains Gd, Gd in R-rich 3 The atomic percentage of the phase is X3 %;

[0157] The atomic percentage of Gd in the main phase grains is X 4 %;

[0158] The above data are the average values ​​after analysis of each phase component in the cross section. It can be seen from the data in the table that X 4 % / R 4 %>X 1 % / R 1 %>X 2 % / R 2 %>X 3 % / R 3 %.

[0159] The microstructure observation and comparison analysis of Example 1 and Comparative Example 1 show that the grain boundary phase in the triangular region of Example 1 is larger and the grain boundary is clearer. The microstructure cross-section analysis of Example 1 in the range of 0-100 μm from the magnet surface along the diffusion depth direction shows that the R 1 -T 1 -M 1 Phase and R 2 -T 2 -M 2 The number of phases is larger, and the ratio of the sum of the grain boundary phase area to the cross-sectional area is larger, which may be the reason why the HcJ of the magnet in Example 1 is higher. In addition, the Gd of the magnet in Example 1 is 1 -T 1 -M 1 Phase, R 2 -T 2 -M 2 and Rich R 3 The content of the phases decreases successively, which is beneficial to improving the temperature resistance.

[0160] The triangular grain boundary of the rare earth-rich Zr phase in Example 1 is beneficial to the improvement of HcJ.

[0161] The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. It should be noted that, for ordinary technicians in this technical field, several improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A sintered NdFeB magnet, characterized in that: The sintered NdFeB magnet is made by using Dy and / or Tb heavy rare earth diffusion technology; The sintered NdFeB magnet comprises: R 29-33wt%, B 0.84-0.94wt%, Co 0.5-3.0wt%, Ga 0-0.3wt%, Cu 0.1-0.6wt%, Al 0-0.3wt%, A 0-0.2wt%, and the balance is Fe; Wherein, R is a rare earth element, including Gd, and the content of Gd is 10-20wt% of the total weight of the magnet; A is selected from at least one of Ti, Zr and Nb.

2. The sintered NdFeB magnet according to claim 1, characterized in that: The content of Cu is 0.3-0.6wt%.

3. The sintered NdFeB magnet according to claim 1, characterized in that: The sintered NdFeB magnet includes main phase grains and R1-T1-M1 phase, R2-T2-M2 phase and R3-rich phase at the grain boundary of the triangular region in the range of 0-100 μm in the diffusion direction; Wherein, R1 is a rare earth element, T1 is Fe and / or Co, and M1 is at least one of Ga, Cu, and Al; R2 is a rare earth element, T2 is Fe and / or Co, and M2 is at least one of Ga, Cu, and Al; R3 is a rare earth element.

4. The sintered NdFeB magnet according to claim 3, characterized in that: R1'=28-31%, M1'=8-11%; R2'=40-50%, M2'=8-11%; R3%≥50; R'1=R1% / (R1%+T1%+M1%), M1'=M1% / (R1%+T1%+M1%); R2'=R2% / (R2%+T2%+M2%), M2'=M2% / (R2%+T2%+M2%); Wherein, R1% is the sum of the atomic percentages of rare earth elements in the R1-T1-M1 phase, T1% is the sum of the atomic percentages of Fe and Co in the R1-T1-M1 phase, and M1% is the sum of the atomic percentages of Ga, Cu, and Al in the R1-T1-M1 phase; R2% is the sum of the atomic percentages of rare earth elements in the R2-T2-M2 phase, T2% is the sum of the atomic percentages of Fe and Co in the R2-T2-M2 phase, and M2% is the sum of the atomic percentages of Ga, Cu, and Al in the R2-T2-M2 phase; R3% is the sum of the atomic percentages of rare earth elements in the R3-rich phase; R1 contains Gd, and the atomic percentage of Gd in the R1-T1-M1 phase is X1%, X1% / R1%=19-25%; R2 contains Gd, and the atomic percentage of Gd in the R2-T2-M2 phase is X2%, X2% / R2%=15-18%.

5. The sintered NdFeB magnet according to claim 4, characterized in that: X4% / R4%>X1% / R1%>X2% / R2%>X3% / R3%; Among them, R3 contains Gd, and the atomic percentage of Gd in the R3-rich phase is X3%; X4% is the atomic percentage of Gd in the main phase grains, and R4% is the total percentage of rare earth elements in the main phase grains.

6. A method for preparing a sintered NdFeB magnet, characterized in that: include: According to the composition of the magnet, the raw materials are prepared for smelting and casting, air flow grinding, oriented pressing and sintering to obtain a rough magnet; After cutting the blank magnet, coating the surface with a 5-15 μm film layer having Dy and / or Tb elements, and performing diffusion heat treatment, thus obtaining the sintered NdFeB magnet; The magnet components include: R 29-33wt%, B 0.84-0.94wt%, Co0.5-3.0wt%, Ga 0-0.3wt%, Cu 0.1-0.6wt%, Al 0-0.3wt%, A 0-0.2wt%, and the balance is Fe; Wherein, R is a rare earth element, including Gd, and the content of Gd is 10-20wt% of the total weight of the magnet; A is selected from at least one of Ti, Zr and Nb.

7. The preparation method according to claim 6, characterized in that: The average thickness of the strip-spinning alloy sheet obtained by the smelting and casting is 0.1-0.5 mm.

8. The preparation method according to claim 6, characterized in that: The magnetic powder particle size X obtained by air flow grinding 50 3-5μm; Optionally, the orientation magnetic field of the orientation pressing is 1.6-2.1T.

9. The preparation method according to claim 6, characterized in that: The sintering temperature is 1030-1120° C., and the sintering time is 1-10 hours.

10. The preparation method according to claim 6, characterized in that: The diffusion heat treatment comprises: firstly heating to 850-950° C. and keeping the temperature for 2-30 hours, cooling, and then heating again to 420-670° C. and keeping the temperature for 1-10 hours.

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