High-performance sintered neodymium-iron-boron magnet and preparation method thereof

Abstract

The invention discloses a high-performance sintered neodymium-iron-boron magnet and a preparation method thereof.The high-performance sintered neodymium-iron-boron magnet is characterized in that raw materials for preparing the neodymium-iron-boron magnet comprise a main alloy and an auxiliary alloy, and the auxiliary alloy does not contain Fe and Co elements; the microstructure of the neodymium-iron-boron magnet comprises a matrix phase and a rare earth-rich grain boundary phase, the matrix phase is (RE / RE ') 2 (F) 14B, F is Fe and Co, the content of Co is 0-3, the mass percent of Fe to RE / RE' in the rare earth-rich grain boundary phase is 1: (1.4-7), RE is Nd or PrNd, and RE 'is one or more of Pr, Ho, Dy and Tb. The neodymium-iron-boron magnet has relatively high magnet magnetic performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of rare earth permanent magnet materials, and particularly relates to a high-performance sintered NdFeB magnet and a preparation method thereof. Background Art

[0002] Sintered NdFeB magnets are widely used in industries such as new energy vehicles, wind power generation, white household appliances, consumer electronics, and industrial motors due to their excellent magnetic properties and cost performance. With the continuous growth of the demand for high-performance magnets, the price of rare earths has been rising continuously, especially the prices of the heavy rare earth elements Tb and Dy, which are used more in sintered NdFeB, have increased even more. Therefore, how to reduce or not use heavy rare earths to manufacture high-performance magnets has been one of the main directions of the industry's technological development in recent years.

[0003] Currently, the main technology for reducing the content of heavy rare earths is the grain boundary diffusion technology. The principle is to prepare powders of heavy rare earth metals or alloys of a certain size, and through printing, sputtering, coating, evaporation plating and other methods, attach the powders containing heavy rare earths to the surface of the magnet. Under a reasonable heat treatment process, the heavy rare earth elements diffuse into the magnet interior along the grain boundary channels of the magnet. The heavy rare earth elements are mainly distributed in the outermost extension region of the main phase grains, optimizing the demagnetization exchange coupling effect of the main phase grains and significantly improving the coercivity of the magnet. Under the condition of the same performance, compared with the conventional process, the usage amount of heavy rare earths is greatly reduced.

[0004] The grain boundary diffusion technology has a very significant effect on the utilization of heavy rare earths. However, limited by the product specifications, currently, the effect on large-size products (orientation thickness greater than 1 cm) is poor, and there are disadvantages such as poor consistency and poor diffusion operability for ultra-small-size products.

[0005] The double alloy process is also one of the current process routes for reducing heavy rare earths. The principle is to design two different alloys. The main phase has a mass ratio close to the volume fraction of the Nd 2 Fe 14 B phase without heavy rare earths, and the auxiliary phase is mainly composed of a high anisotropy field rare earth-rich phase (HR2Fe14B). Coating the high anisotropy field phase around the main phase to achieve the purpose of improving the coercivity of the magnet.

[0006] The invention patent application with the publication number CN 106601407 A discloses a method for improving the coercivity of Nd-Fe-B magnets. Using the R1-Fe-B-M1 type powder as the main phase alloy powder and the R1-R2-Fe-B-M1 type powder as the auxiliary phase alloy powder, mixing the main phase alloy powder with the auxiliary phase alloy powder, so that the auxiliary phase alloy powder is evenly distributed on the surface of the main phase alloy powder; wherein, R1 includes Nd and Pr; M1 is selected from one or more of Co, Cu, Zr, Al, Ga, Si, Mn, Ni, Zn, Ge, Pd, Ag, Cd, In, Sn, Sb, Pt, Au, Hg, Pb and Bi; R2 is selected from one or more of Gd, Dy, Tb, Ho, Er, Tm, Yb, Lu, Y. This invention patent application adopts the main phase alloy powder and the auxiliary phase alloy powder with good compatibility, which can significantly improve the coercivity of Nd-Fe-B magnets and reduce the usage amount of heavy rare earths. However, the above invention patent application has relatively high contents of Fe and Co elements in the grain boundary phase, which has a certain influence on the coercivity of Nd-Fe-B magnets.

[0007] The double alloy process method is simple and convenient, not restricted by product specifications, with uniform element distribution inside the magnet and good performance consistency. However, the conventional double alloy design mainly forms the REFe(Co)B phase, which not only reduces the proportion of the Nd 2 Fe 14 B phase, but also the promotion effect on H cj (intrinsic coercivity) is much smaller than that of the grain boundary diffusion process, which has a certain limiting effect on the preparation of high-performance magnets.

[0008] Therefore, it is of great significance to develop a new double alloy process to reduce the usage amount of heavy rare earths while improving the magnet performance. Summary of the Invention

[0009] The present invention provides a high-performance sintered Nd-Fe-B magnet, which has high magnetic properties.

[0010] The present invention provides a high-performance sintered Nd-Fe-B magnet. The raw materials for preparing the Nd-Fe-B magnet include a main alloy and an auxiliary alloy, and the auxiliary alloy does not contain Fe and Co elements; The main alloy, by mass percentage, includes the following chemical components: RE x B y M z T w F 1-x-y-z-w , RE is rare earth Nd or PrNd, B is boron element, M is at least one of Nb, Zr, Ti, T is Cu and Ga, F contains Fe and Co, wherein the Co content is 0 - 3 wt.%, and the Fe content is not 0; Among them, the content of each element is as follows: x: 27 - 30 wt.%, y: 0.9 - 1.1 wt.%, z: 0.05 - 0.25 wt.%, w: 0.1 - 0.5 wt.%.

[0011] The microstructure of the NdFeB magnet includes a matrix phase and a rare-earth-rich grain boundary phase. The matrix phase is (RE / RE') 2 (F) 14 B, where F is Fe and Co, the content of Co is 0 - 3, and the mass percentage of Fe and RE / RE' in the rare-earth-rich grain boundary phase is 1:(1.4 - 8), where RE is Nd or PrNd, and RE' is one or more of Pr, Ho, Dy, and Tb.

[0012] Compared with the conventional double-alloy technical solution, in the double-alloy process of the present invention, Fe and Co elements are not added to the auxiliary alloy. During the mixing and sintering phase transformation process with the main alloy, there is only a very small amount or no new (RE / RE') 2 Fe(Co) in the matrix phase. Thus, the volume fraction of (RE / RE') 2 Fe 14 B in the matrix phase of the obtained NdFeB magnet is extremely high, and the magnet has a high remanence.

[0013] On the other hand, since the auxiliary alloy is a rare-earth B alloy without Fe and Co elements, an antiferromagnetic-dominated auxiliary phase structure, that is, a rare-earth-rich grain boundary phase, is obtained. The rare-earth-rich grain boundary phase is coated around the main phase, and the uniform distribution of the antiferromagnetic auxiliary phase around the main phase effectively blocks the exchange coupling effect between the main phases, thereby improving the demagnetization resistance of the magnet. While maintaining a high remanence, the coercivity can also be greatly improved.

[0014] Preferably, the NdFeB magnet is prepared by a double-alloy process.

[0015] Preferably, the grain boundary rare-earth-rich phase is Pr 3 Fe, Nd 3 (PrNd) 3 Fe or one or more of them.

[0016] Preferably, in the microstructure of the NdFeB magnet, the mass ratio of the main alloy to the auxiliary alloy is (94 - 98):(2 - 6).

[0017] The present invention controls the content of the rare-earth-rich grain boundary phase, while achieving excellent magnetic properties of the magnet, improving the coercivity of the magnet.

[0018] Preferably, the D50 particle size of the main alloy is 3.5 - 4.5 μm, and the D50 particle size of the auxiliary alloy is 2.5 - 3.5 μm.

[0019] By controlling the particle size of the main alloy and the auxiliary alloy, the magnet has better magnetic properties, while avoiding a decrease in antioxidant performance due to an overly large surface area. By further refining the auxiliary alloy particles, they are effectively dispersed into the grain boundaries between the main phase grains, enhancing the demagnetization coupling effect between the main phases, and significantly improving the coercivity of the magnet. Therefore, a high-performance permanent magnet with high remanence and high coercivity can be prepared.

[0020] Preferably, in the element T, the mass percentages of Cu and Ga are 1:(1.2 - 1.5).

[0021] By controlling the content of element T in the present invention, the stability of the magnet is improved, the distribution of the RE / RE' phase is promoted, and the coercivity of the magnet can be enhanced in cooperation with the RE / RE' phase. Since the price of Ga is 30 - 40 times that of Cu, by providing an appropriate amount of Cu to replace Ga in the present invention, the cost is appropriate while achieving similar effects.

[0022] The appropriate amount of Co provided by the present invention can increase the Curie temperature of the magnet and improve the thermal stability of the magnet. The addition of Co is related to the actual application of the magnet, while avoiding a sharp deterioration of the magnet performance. At the same time, Co is a strategic material, and its content is restricted in some terminal applications.

[0023] Since the auxiliary alloy in the present invention does not contain Co and Fe, and the content of Co in the main alloy is low, the proportion of the matrix phase in the magnet provided by the present invention is very high, while the proportion of the soft magnetic Fe - Co phase is extremely low, which is beneficial to improving the magnetic properties.

[0024] Preferably, the auxiliary alloy, by mass percentage, includes the following chemical components: RE' 1-a-b-c B a M b c , RE' is one or more of Pr, Ho, Dy, Tb, B is the boron element, M is at least one of Nb, Zr, Ti, is Cu and Ga, where the mass percentages of Cu and Ga are 1:(1.2 - 1.5); Among them, the contents of each element are a: 0.5 - 5 wt.%; b: 0 - 2 wt.%, c: 4 - 10 wt.%.

[0025] The auxiliary alloy provided by the present invention does not contain Fe and Co elements. The surplus Fe element in the main elements forms a rare-earth-rich grain boundary phase that is beneficial to improving the coercivity with the rare-earth elements, M and T elements in the auxiliary alloy, avoiding or reducing the formation of the Fe - Co soft magnetic phase and destroying the coercivity.

[0026] Preferably, the mass percentage of the main alloy in the raw materials is 94% - 98%, and the mass percentage of the auxiliary alloy in the raw materials is 2% - 6%.

[0027] By controlling the proportion of the auxiliary alloy, the present invention avoids the influence on the remanence intensity (Br), and can also form sufficient rare-earth-rich grain boundary phases to enhance the coercivity of the magnet.

[0028] Preferably, the coercivity of the NdFeB magnet is 17 - 19 kOe, the remanence is 14.25 - 14.5 kGs, and the squareness is above 98%.

[0029] On the other hand, the present invention also provides a method for preparing the high-performance sintered NdFeB magnet, including: Preparing the master alloy RE x B y M z T w F 1-x-y-z-w powder and the auxiliary alloy RE' 1-a-b-c B a M b T c powder, where RE is rare earth Nd or PrNd, B is boron element, M is at least one of Nb, Zr, and Ti, T is Cu and Ga, F contains Fe and Co, the Co content is 0 - 3 wt.%, the Fe content is not 0, RE' is one or several of Pr, Ho, Dy, and Tb, and the contents of each element are x: 27 - 30 wt.%, y: 0.9 - 1.1 wt.%, z: 0.05 - 0.25 wt.%, w: 0.1 - 0.5 wt.%, a: 0.5 - 5 wt.%; b: 0 - 2 wt.%, c: 4 - 10 wt.%; Mixing the master alloy RE x B y M z T w F 1-x-y-z-w powder and the auxiliary alloy RE' 1-a-b-c B a M b T c powder evenly to obtain a mixed powder, and pressing the mixed powder into a green compact by a magnetic field forming method or a hot pressing and hot deformation method; Sintering the green compact into a blank in a vacuum or an inert gas; Performing multi-stage aging treatment on the blank to obtain a high-performance sintered NdFeB magnet.

[0030] Preferably, the multi-stage aging treatment includes three-stage aging treatment; Among them, the temperature of the first-stage aging treatment is 890 - 930 °C; The temperature of the second-stage aging treatment is 580 - 680 °C; The temperature of the third-stage aging treatment is 420 - 520 °C.

[0031] By controlling the temperatures of the first-stage and second-stage aging treatments, the present invention enables the diffusion of rare-earth elements in the magnet towards the grain boundaries to eliminate stress. By controlling the temperature of the third-stage aging treatment, the distribution of rare-earth elements becomes more uniform.

[0032] Preferably, the master alloy RE x B y M z T w F 1-x-y-z-w The preparation method of the powder includes: S11. Weigh the elemental raw materials for vacuum melting, and then cast at a temperature of 1350 - 1450 °C to obtain a master-phase cast sheet with a thickness of 0.2 - 0.35 mm. The grain spacing of the master-phase cast sheet is 3.5 - 4.5 μm, and the contents of oxygen and nitrogen passing through are oxygen content < 120 ppm and nitrogen content < 30 ppm; x B y M z T w F 1-x-y-z-w S12. Treat the master-phase cast sheet by the conventional hydrogen crushing process to obtain master-phase hydrogen crushed powder: the hydrogen absorption pressure for hydrogen crushing is 1.5 - 2 kg / cm S12. Treat the master-phase cast sheet by the conventional hydrogen crushing process to obtain master-phase hydrogen crushed powder: the hydrogen absorption pressure for hydrogen crushing is 1.5 - 2 kg / cm 2 , the dehydrogenation temperature is 500 °C - 600 °C, and the oxygen content of the hydrogen crushed powder < 1000 ppm and the hydrogen content < 1000 ppm; S13. Carry out jet milling on the master-phase hydrogen crushed powder to obtain a master alloy with a D50 particle size of 3.5 - 4.5 μm.

[0033] Preferably, the preparation method of the auxiliary alloy RE' 1-a-b-c B a M b T c The preparation method of the powder includes: S21. Weigh the elemental raw materials for vacuum melting, and then cast at a temperature of 1480 - 1520 °C to obtain an auxiliary-phase cast sheet with a thickness of 0.05 - 0.25 mm. The grain spacing of the auxiliary-phase cast sheet is 0.5 - 2 μm, the oxygen content < 120 ppm, and the nitrogen content < 30 ppm; 1-a-b-c B a M b T c S22. Carry out hydrogen crushing on the auxiliary-phase cast sheet: First, heat the auxiliary-phase cast sheet to 300 - 350 °C and introduce hydrogen for primary hydrogen absorption, with a hydrogen absorption pressure of 3 - 4 kg / cm S22. Carry out hydrogen crushing on the auxiliary-phase cast sheet: First, heat the auxiliary-phase cast sheet to 300 - 350 °C and introduce hydrogen for primary hydrogen absorption, with a hydrogen absorption pressure of 3 - 4 kg / cm 2 , and then evacuate and heat to 800 - 900 °C for secondary heat preservation hydrogen absorption, with a hydrogen absorption pressure of 3 - 4 kg / cm 2, finally, heat preservation and dehydrogenation are carried out at 400 - 500 °C to obtain a secondary-phase hydrogenated crushed powder with an oxygen content < 1000 ppm and a hydrogen content in the range of 3000 - 5000 ppm; S23. Carry out jet milling on the secondary-phase hydrogenated crushed powder, control the oxygen content of the jet milling system < 10 ppm, and obtain a secondary alloy with a D50 particle size of 2.5 - 3.5 μm.

[0034] Further preferably, the carbon content of the rare earth element in the elemental raw material < 200 ppm, the carbon content of pure iron < 30 ppm, and the carbon content of the remaining elements < 500 ppm. By controlling the carbon content, the present invention avoids the influence of the carbon content in the elemental raw materials on the magnet performance.

[0035] Preferably, before mixing the master alloy RE x B y M z T w F 1-x-y-z-w powder and the secondary alloy RE' 1-a-b-c B a M b T c powder evenly to obtain a mixed powder, zinc stearate or borate ester with a mass of 0.05 - 0.2 wt.% of the total mass of the master alloy and the secondary alloy is added as a lubricant, and the oxygen content during the powder mixing process < 100 ppm.

[0036] Preferably, a magnetic field forming method is used to prepare a green compact, wherein the magnetic field strength is not less than 1.5 T, the forming pressure is greater than 160 MPa, the atmosphere is controlled with an oxygen content < 100 ppm, and the green compact density is not less than 4.4 g / cm 3 .

[0037] Preferably, in step S4, the sintering temperature is 1050 - 1075 °C, the sintering vacuum degree is better than 0.1 Pa, and the sintering time > 6 hours.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses a secondary alloy not containing Fe and Co elements as a raw material, tries to reduce the content of Co in the rare earth-rich grain boundary phase, so as to minimize the formation of the Fe-Co soft magnetic phase that can significantly reduce the coercivity of the magnet, and at the same time increase the proportion of the matrix phase. At the same time, by using the surplus Fe and RE / RE', without reducing the proportion of the matrix phase, a rare earth-rich grain boundary phase is formed at the grain boundary, thereby improving the coercivity and magnetic properties. Description of the Drawings

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0040] Figure 1 It is the metallographic structure diagram of the master alloy rapid solidification casting sheet obtained in Example 1; Figure 2 It is the scanning electron microscope diagram of the magnet obtained in Example 1; Figure 3 It is the metallographic structure diagram of the magnet prepared by the existing double alloy process technology. Detailed implementation manners

[0041] The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. Unless otherwise clearly indicated to the contrary in the context, the singular forms used herein are also intended to include the plural forms. It should also be understood that the term "comprising" does not specifically refer to a certain characteristic, field, integer, step, action, element and / or component, but excludes the existence or addition of other characteristics, fields, integers, steps, actions, elements, components and / or groups.

[0042] If a part is described as being above another part, it can be directly above the other part or there are other parts in between. When a part is described as being directly above another part, there will be no other parts in between. Although not otherwise defined, the meanings of all terms (including technical terms and scientific terms) used herein are the same as those generally understood by those skilled in the art. For terms defined in the dictionary, they should be interpreted as having the same meaning as the relevant technical literature and the content disclosed herein, and should not be interpreted in an idealized or overly formal sense.

[0043] The following further elaborates on the concept of the present invention.

[0044] In a preferred embodiment of the present invention, a high-performance sintered neodymium iron boron magnet is made of a master alloy and a secondary alloy, and the mass ratio of the master alloy to the secondary alloy is (94~98):(2~6).

[0045] The element ratio of the master alloy is: RE x B y M z T w F 1-x-y-z-w, wherein RE is rare earth Nd or PrNd, B is boron; M is at least one of Nb, Zr, and Ti; T is a combination of Cu and Ga, wherein the ratio of Cu:Ga is 1:(1.2~1.5); F comprises Fe and Co, wherein the Co content is 0~3wt.%, and the Fe content is not 0; the components are matched according to the following mass percentages: x: 27~30wt.%; y: 0.9~1.1wt.%, z: 0.05~0.25wt.%, and w: 0.1~0.5wt.%.

[0046] The auxiliary alloy element ratio is: RE' 1-a-b-c B a M b T c , wherein RE' is one or more of Pr, Ho, Dy, Tb, B is boron, M is at least one of Nb, Zr, Ti; T is a combination of Cu and Ga, wherein the ratio of Cu:Ga is 1:(1.2~1.5); the auxiliary alloy is matched according to the following mass percentages: a: 0.5~5wt.%; b: 0~2wt.%, c: 4~10wt.%. The coercive force of the high-performance sintered NdFeB magnet exceeds 17kOe, while the remanence is above 14.25kGs and the squareness is above 98%.

[0047] Furthermore, the D50 particle size of the main alloy is 3.5-4.5 μm, and / or the D50 particle size of the auxiliary alloy is 2.5-3.5 μm.

[0048] The auxiliary alloy is pulverized by HDDR+air flow grinding and then coated around the main phase. The uniform distribution of the antiferromagnetic auxiliary phase around the main phase effectively isolates the exchange coupling between the main phases, thereby improving the anti-demagnetization ability of the magnet. While maintaining a high remanence, the coercive force can also be greatly improved, and the final squareness of the magnet is excellent.

[0049] According to a preferred embodiment of the present invention, a method for preparing a low (no) heavy rare earth high performance sintered NdFeB magnet comprises the following steps: A. The main phase alloy and the auxiliary phase alloy are prepared according to the above rules.

[0050] B. The configured main phase alloy and auxiliary phase alloy are respectively subjected to vacuum melting to prepare rapid solidification casting sheets.

[0051] C. The main phase and auxiliary phase rapid solidification casting sheets are respectively subjected to hydrogen crushing and air flow grinding crushing to produce micron-sized fine powder.

[0052] D. Prepare the main phase and auxiliary phase fine powders in a certain proportion, add lubricant and antioxidant, and mix.

[0053] E. In a low-oxygen nitrogen atmosphere, the mixed powder is oriented under a high magnetic field and pressed into a shape, and then an isostatic pressing with an ultra-high pressure is carried out to obtain a green compact.

[0054] F. The green compact is subjected to vacuum sintering under vacuum, and then a high-performance neodymium-iron-boron magnet is obtained through multi-stage aging treatment.

[0055] In step A, raw materials with a relatively low carbon content are preferably selected. The carbon content of the rare earth element is controlled at <200 ppm, the carbon content of pure iron is <30 ppm, and the carbon content of the remaining components is <500 ppm.

[0056] In step B, for the main-phase alloy, the casting temperature is preferably 1350 °C to 1450 °C, the thickness of the cast sheet is 0.2 mm to 0.35 mm, and the grain spacing is controlled at 3.5 to 4.5 μm; for the auxiliary-phase alloy, the casting temperature is preferably 1480 °C to 1520 °C, the thickness of the cast sheet is 0.05 mm to 0.25 mm, and the grain spacing is controlled at 0.5 to 2 μm. The oxygen content in each cast sheet is <120 ppm, and the nitrogen content is <30 ppm.

[0057] In step C, the main-phase cast sheet adopts a conventional hydrogenation-crushing process. The hydrogenation-crushing hydrogen absorption pressure is 1.5 to 2 kg / cm 2 , and the dehydrogenation temperature is 500 °C to 600 °C. The obtained hydrogenation-crushed powder has O <1000 ppm and H <1000 ppm. The hydrogen absorption pressure of the auxiliary-phase cast sheet is 3 to 4 kg / cm 2 . When absorbing hydrogen, first heat to 300 °C to 350 °C and introduce hydrogen, then evacuate and heat to 800 °C to 900 °C for secondary heat preservation and hydrogen absorption, and finally carry out dehydrogenation at 400 °C - 500 °C. Finally, the auxiliary-phase hydrogenation-crushed powder retains a relatively high H content to prevent oxidation, and the H content is controlled at 3000 ppm to 5000 ppm, and the oxygen content is <1000 ppm preferably. For grinding into powder by a jet mill, the particle size distribution D50 control range of the main-phase alloy is: 3.5 to 4.5 μm, and the particle size distribution of the auxiliary-phase alloy is 2.5 to 3.5 μm. When grinding the powder, the oxygen content of the jet mill system is controlled at <10 ppm.

[0058] In step D, the fine powders of the main and auxiliary-phase alloys that meet the particle size requirements are mixed in a certain proportion. The addition ratio of the auxiliary phase is 2% - 6%. In addition, 0.05% - 0.2% of the total weight of the two alloy powders of lubricant (preferably zinc stearate or borate ester) is added and stirred in a mixer for about 2 to 5 hours. After mixing, it is placed in a sealed steel cylinder with an oxygen content <100 ppm, and the standing time should be greater than 12 hours.

[0059] In step E, the mixed powder is magnetically oriented and formed in an atmosphere with an oxygen content lower than 100 ppm. The magnetic field strength is not less than 1.5 T. After pressing by a press, it is vacuum packaged, and then further pressed by an isostatic pressing with a pressure greater than 160 MPa to obtain a density not less than 4.4 g / cm 3The green compact.

[0060] In step F, the isostatically pressed green compact is placed in a vacuum sintering furnace for vacuum sintering and aging treatment. The sintering temperature is 1050°C to 1075°C, the sintering vacuum degree is better than 0.1 Pa, and the sintering time is > 6 hours. The multi-stage aging is a three-stage process, and the temperature of each stage process is 890 - 930°C, 580 - 680°C, 420 - 520°C respectively. The aging time of each stage should be > 3 hours. The second and third stage aging coolings adopt filling N 2 Air cooling, and the cooling rate should be greater than 10°C / min preferably. By rapid cooling, the generation of impurity phases is prevented, which is beneficial to improving the product H cj and obtaining a higher demagnetization squareness.

[0061] The following further describes the present invention in detail with specific embodiments for better understanding and implementation.

[0062] Embodiment 1: This embodiment provides a method for preparing low heavy rare earth high-performance sintered NdFeB, and its operation steps are as follows: Step 1: Prepare the low heavy rare earth master alloy A and the auxiliary alloy B. The prepared raw materials of the master alloy A and the auxiliary alloy B are respectively melted into alloys through vacuum melting, and then cast into the master alloy A cast sheet and the auxiliary alloy B cast sheet at high temperature.

[0063] To obtain an excellent microstructure, the master alloy A and the auxiliary alloy B are respectively prepared with different process parameters. In this embodiment, the casting temperature of the master alloy A is 1420°C to 1450°C, the linear speed of the casting copper roller is 0.9 - 1.5 m / s, and the cooling water temperature is 10°C to 30°C, so as to obtain a master alloy rapid solidification cast sheet with a thickness of 0.2 mm to 0.4 mm and a grain spacing of 3.5 - 4.5 μm, having an excellent columnar-like microstructure, as shown in the appendix Figure 1 shown, the gray is (RE / RE') 2 Fe 14 B phase, and the white is the rare earth-rich phase.

[0064] The casting temperature of the auxiliary alloy B is 1500°C to 1520°C, the linear speed of the casting copper roller is 5 - 10 m / s, and the cooling water temperature is 2°C to 8°C to obtain a fine and uniform microstructure with a thickness of 0.05 mm to 0.15 mm and a grain spacing of 0.5 - 2 μm.

[0065] In this embodiment, the weight percentages of the master alloy A are: 29% PrNd, 0.93% B, 0.2% Zr, 0.1% Cu, 0.15% Ga, 1.2% Co, 68.42% Fe, and the weight percentages of the auxiliary alloy B are: 40% Dy, 47.5% Pr, 1% B, 4% Zr, 3% Cu, 4.5% Ga. The specific components are shown in Table 1.

[0066] Step 2: Prepare hydrogenated powder. The master alloy A ingot is hydrogenated, and the hydrogen absorption pressure is 1.8 kg / cm 2 until saturation, and then dehydrogenated. The dehydrogenation temperature is 550 °C. The obtained hydrogenated powder has an O content of 852 ppm and an H content of 780 ppm. The hydrogen absorption pressure of the auxiliary alloy B ingot is 3.5 kg / cm 2 . During hydrogen absorption, it is first heated to 300 °C and held for 0.5 hours, then hydrogen is introduced, and then evacuated and heated to 880 °C for secondary hydrogen absorption until saturation. Finally, it is held at 450 °C for dehydrogenation, and a reasonable dehydrogenation time is controlled. Finally, the measured H content of the secondary phase hydrogenated powder is 4236 ppm, and the O content is 912 ppm.

[0067] Step 3: Grind the powder by air jet mill and mix the master and auxiliary fine powders. The hydrogenated powder of the master alloy A is ground by air jet mill to a particle size D50 of 3.89 μm, and the hydrogenated powder of the auxiliary alloy B is ground by air jet mill to a particle size D50 of 2.73 μm. The main phase powder A and the secondary phase powder B are mixed according to a weight ratio of 98:2, and 0.06% of liquid lubricant is added respectively and stirred for 3 hours.

[0068] Step 4: Orient the mixed powder magnetically in an atmosphere with an oxygen content lower than 100 ppm. The magnetic field strength is 1.8 T. After pressing by a press, it is vacuum packaged, and then an isostatic pressing blank with a density of 4.4 g / cm 3 is obtained under a pressure of 180 MPa.

[0069] Step 5: Place the isostatic pressing blank in a vacuum sintering furnace for vacuum sintering and aging treatment. The sintering process is 1072 °C for 8 h, and the sintering vacuum degree is better than 0.1 Pa. The aging process is aging at 900 °C for 3 h + aging at 650 °C for 3 h + aging at 495 °C for 5 h. During the second and third stages of aging, cooling is carried out by filling N 2 and air cooling, and the cooling rate is 12 °C / min.

[0070] Example 2: The difference between this example and Example 1 is that in Step 3, the master alloy A and the master alloy B are mixed according to a weight ratio of 96:4. The process parameters of other steps are the same as those in Example 1.

[0071] Example 3: This example provides a method for preparing a heavy-rare-earth-free high-performance sintered NdFeB, and its operation steps are as follows: Step 1: Prepare a heavy-rare-earth-free master alloy A and an auxiliary alloy B. The prepared raw materials of the master alloy A and the auxiliary alloy B are respectively melted into alloys by vacuum melting, and then high-temperature cast into master alloy A ingots and auxiliary alloy B ingots.

[0072] To obtain an excellent microstructure, different process parameters are selected for the main alloy A and the auxiliary alloy B. In this embodiment, the casting temperature of the main alloy A is 1420°C to 1450°C, the linear speed of the casting copper roller is 0.9 to 1.5 m / s, and the cooling water temperature is 10°C to 30°C, so as to obtain a columnar-like microstructure with excellent properties, having a thickness of 0.2 mm to 0.4 mm and a grain spacing of 3.5 to 4.5 μm.

[0073] The casting temperature of the auxiliary alloy B is 1500°C to 1520°C, the linear speed of the casting copper roller is 5 to 10 m / s, and the cooling water temperature is 2°C to 8°C, so as to obtain a fine and uniform microstructure with a thickness of 0.05 mm to 0.15 mm and a grain spacing of 0.5 to 2 μm.

[0074] In this embodiment, the main alloy A by weight percentage is: 29% PrNd, 0.91% B, 0.2% Zr, 0.2% Cu, 0.3% Ga, 0.8% Co, 68.59% Fe, and the auxiliary alloy B by weight percentage is: 87.7% Pr, 0.8% B, 4% Zr, 3% Cu, 4.5% Ga. The specific composition is shown in Table 1.

[0075] Step two: Prepare hydrogenated and crushed powder. The main alloy A cast sheet is hydrogenated and crushed, and the hydrogen absorption pressure is 1.8 kg / cm 2 until saturation, and then dehydrogenated. The dehydrogenation temperature is 550°C. The obtained hydrogenated and crushed powder has an O content of 780 ppm and an H content of 769 ppm; the hydrogen absorption pressure of the auxiliary alloy B cast sheet is 3.5 kg / cm 2 . When hydrogen absorption is carried out, it is first heated to 300°C and held for 0.5 hours, then hydrogen is introduced, and then evacuated and heated to 880°C for secondary hydrogen absorption until saturation. Finally, dehydrogenation is carried out at 450°C while controlling a reasonable dehydrogenation time. The measured H content of the auxiliary alloy hydrogenated and crushed powder is 3800 ppm, and the O content is 890 ppm.

[0076] Step three: Grind the powder by air classifier and mix the main and auxiliary fine powders. The hydrogenated and crushed powder of the main alloy A is ground by air classifier to a particle size D50 of 3.92 μm, and the auxiliary alloy B is ground by air classifier to a particle size D50 of 2.85 μm. The main alloy A and the auxiliary alloy B are mixed according to a weight ratio of 98:2 respectively, and 0.06% of liquid lubricant is added and stirred for 3 hours.

[0077] Step four: Orient and form the mixed powder in an atmosphere with an oxygen content lower than 100 ppm under a magnetic field. The magnetic field strength is 1.8 T. After being pressed by a press, it is vacuum packaged, and then an isostatic pressing blank with a density of 4.4 g / cm 3 is obtained under an isostatic pressure of 180 MPa.

[0078] Step 5: Place the isostatic pressed green compact into a vacuum sintering furnace for vacuum sintering and aging treatment. The sintering process is sintering at 1072 °C for 8 h, and the sintering vacuum degree is better than 0.1 Pa. The aging process is aging at 900 °C for 3 h + aging at 650 °C for 3 h + aging at 495 °C for 5 h. The cooling in the second and third stages of aging adopts nitrogen 2 air cooling, and the cooling rate is 12 °C / min.

[0079] Example 4: The difference between this example and Example 3 is that in Step 3, the master alloy A and the master alloy B are compounded according to a weight ratio of 96:4. The process parameters of other steps are the same as those in Example 1.

[0080] Example 5: Step 1: Prepare the low heavy rare earth master alloy A and the auxiliary alloy B. The prepared raw materials of the master alloy A and the auxiliary alloy B are respectively melted into alloys through vacuum melting, and then high-temperature cast into the master alloy A cast sheet and the auxiliary alloy B cast sheet.

[0081] To obtain an excellent microstructure, different process parameters are selected for the master alloy A and the auxiliary alloy B respectively. In this example, the casting temperature of the master alloy A is 1420 °C to 1450 °C, the linear speed of the casting copper roller is 0.9 to 1.5 m / s, and the cooling water temperature is 10 °C to 30 °C, so as to obtain a master alloy rapid solidification cast sheet with a thickness of 0.2 mm to 0.4 mm and a grain spacing of 3.5 to 4.5 μm, having an excellent columnar-like microstructure, as shown in the appendix Figure 1 shown, the gray is (RE / RE') 2 Fe 14 B phase, and the white is the rare earth-rich phase.

[0082] The casting temperature of the auxiliary alloy B is 1500 °C to 1520 °C, the linear speed of the casting copper roller is 5 to 10 m / s, and the cooling water temperature is 2 °C to 8 °C to obtain a fine and uniform microstructure with a thickness of 0.05 mm to 0.15 mm and a grain spacing of 0.5 to 2 μm.

[0083] In this example, the weight percentages of the master alloy A are: 29% Nd, 0.93% B, 0.2% Zr, 0.1% Cu, 0.15% Ga, 1.2% Co, 68.42% Fe, and the weight percentages of the auxiliary alloy B are: 40% Dy, 47.5% Pr, 1% B, 4% Zr, 3% Cu, 4.5% Ga. The specific components are shown in Table 1.

[0084] Step 2: Prepare hydrogenated powder. The master alloy A cast sheet is hydrogenated until saturated at a hydrogen absorption pressure of 1.8 kg / cm 2 and then dehydrogenated at a dehydrogenation temperature of 550 °C. The obtained hydrogenated powder has an O content of 852 ppm and an H content of 780 ppm; the hydrogen absorption pressure of the auxiliary alloy B cast sheet is 3.5 kg / cm 2, during hydrogen absorption, first heat to 300 °C and hold for 0.5 hours, then introduce hydrogen, then evacuate to vacuum and heat to 880 °C for secondary hydrogen absorption until saturation, and finally hold at 450 °C for dehydrogenation. Control the reasonable dehydrogenation time. Finally, the measured H content of the secondary phase hydrogen crushed powder is 4236 ppm, and the O content is 912 ppm.

[0085] Step 3: Jet milling and mixing of main and secondary fine powders. The hydrogen crushed powder of main alloy A is milled by jet mill to a particle size D50 of 3.89 μm, and the hydrogen crushed powder of auxiliary alloy B is milled by jet mill to a particle size D50 of 2.73 μm. Mix the main phase powder A and the secondary phase powder B according to a weight ratio of 98:2, and add 0.06% of liquid lubricant and stir for 3 hours respectively.

[0086] Step 4: Orient the mixed powder magnetically in an atmosphere with an oxygen content lower than 100 ppm, with a magnetic field strength of 1.8 T. After pressing by a press, perform vacuum packaging, and then perform isostatic pressing with a pressure of 180 MPa to obtain a green compact with a density of 4.4 g / cm 3 .

[0087] Step 5: Place the isostatic pressed green compact in a vacuum sintering furnace for vacuum sintering and aging treatment. The sintering process is 1072 °C for 8 h, and the sintering vacuum degree is better than 0.1 Pa. The aging process is aging at 900 °C for 3 h + aging at 650 °C for 3 h + aging at 495 °C for 5 h. During the second and third stages of aging, cooling is carried out by filling N 2 and air cooling, with a cooling rate of 12 °C / min.

[0088] Example 6: Step 1: Prepare low heavy rare earth main alloy A and auxiliary alloy B. The prepared raw materials of main alloy A and auxiliary alloy B are respectively melted into alloys through vacuum melting, and then cast at high temperature to form main alloy A cast sheets and auxiliary alloy B cast sheets.

[0089] To obtain excellent microstructures, different process parameters are selected for main alloy A and auxiliary alloy B respectively. In this example, the casting temperature of main alloy A is 1420 °C - 1450 °C, the linear speed of the casting copper roller is 0.9 - 1.5 m / s, and the cooling water temperature is 10 °C - 30 °C, so as to obtain main alloy rapid solidification cast sheets with a thickness of 0.2 mm - 0.4 mm and a grain spacing of 3.5 - 4.5 μm, having excellent columnar-like microstructures, as shown in the appendix Figure 1 , where the gray is (RE / RE') 2 Fe 14 B phase, and the white is the rare earth-rich phase.

[0090] The casting temperature of auxiliary alloy B is 1500 °C - 1520 °C, the linear speed of the casting copper roller is 5 - 10 m / s, and the cooling water temperature is 2 °C - 8 °C to obtain a fine and uniform microstructure with a thickness of 0.05 mm - 0.15 mm and a grain spacing of 0.5 - 2 μm.

[0091] In this embodiment, the weight percentages of the master alloy A are: 29% PrNd, 0.93% B, 0.2% Zr, 0.1% Cu, 0.15% Ga, 1.2% Co, 68.42% Fe, and the weight percentages of the auxiliary alloy B are: 40% Tb, 47.5% Pr, 1% B, 4% Zr, 3% Cu, 4.5% Ga. The specific components are shown in Table 1.

[0092] Step 2: Prepare hydrogenated and crushed powder. The master alloy A cast sheet is hydrogenated and crushed, and the hydrogen absorption pressure is 1.8 kg / cm 2 until saturation, and then dehydrogenated. The dehydrogenation temperature is 550 °C. The obtained hydrogenated and crushed powder has an O content of 852 ppm and an H content of 780 ppm; the hydrogen absorption pressure of the auxiliary alloy B cast sheet is 3.5 kg / cm 2 , and during hydrogen absorption, it is first heated to 300 °C and held for 0.5 hours, then hydrogen is introduced, and then it is evacuated and heated to 880 °C for secondary hydrogen absorption until saturation. Finally, it is held at 450 °C for dehydrogenation, and a reasonable dehydrogenation time is controlled. The measured H content of the secondary phase hydrogenated and crushed powder is 4236 ppm, and the O content is 912 ppm.

[0093] Step 3: Grind the powder by jet milling and mix the main and auxiliary fine powders. The hydrogenated and crushed powder of the master alloy A is ground by jet milling to a particle size D50 of 3.89 μm, and the hydrogenated and crushed powder of the auxiliary alloy B is ground by jet milling to a particle size D50 of 2.73 μm. The main phase powder A and the secondary phase powder B are mixed according to a weight ratio of 98:2, and 0.06% of a liquid lubricant is added and stirred for 3 hours.

[0094] Step 4: Orient the mixed powder magnetically in an atmosphere with an oxygen content lower than 100 ppm. The magnetic field strength is 1.8 T. After pressing by a press, it is vacuum packaged, and then an isostatic pressing with a pressure of 180 MPa is carried out to obtain a green compact with a density of 4.4 g / cm 3 of the green compact.

[0095] Step 5: Place the isostatically pressed green compact in a vacuum sintering furnace for vacuum sintering and aging treatment. The sintering process is 1072 °C for 8 h, and the sintering vacuum degree is better than 0.1 Pa. The aging process is aging at 900 °C for 3 h + aging at 650 °C for 3 h + aging at 495 °C for 5 h. During the second and third stages of aging, the cooling is carried out by filling N 2 and air cooling, and the cooling rate is 12 °C / min.

[0096] Example 7: Step 1: Prepare a low-heavy rare earth master alloy A and an auxiliary alloy B. The prepared raw materials of the master alloy A and the auxiliary alloy B are respectively melted into alloys by vacuum melting, and then high-temperature cast to form a master alloy A cast sheet and an auxiliary alloy B cast sheet.

[0097] To obtain excellent microstructures, master alloy A and auxiliary alloy B are prepared with different process parameters respectively. In this embodiment, the casting temperature of master alloy A is 1420 °C to 1450 °C, the linear speed of the casting copper roller is 0.9 to 1.5 m / s, and the cooling water temperature is 10 °C to 30 °C, so as to obtain a master alloy rapid solidification cast sheet with a thickness of 0.2 mm to 0.4 mm and a grain spacing of 3.5 to 4.5 μm, having an excellent columnar-like microstructure, as shown in Figure 1 shown, the gray color is (RE / RE') 2 Fe 14 phase B, and the white color is the rare earth-rich phase.

[0098] The casting temperature of auxiliary alloy B is 1500 °C to 1520 °C, the linear speed of the casting copper roller is 5 to 10 m / s, and the cooling water temperature is 2 °C to 8 °C to obtain a fine and uniform microstructure with a thickness of 0.05 mm to 0.15 mm and a grain spacing of 0.5 to 2 μm.

[0099] In this embodiment, the weight percentages of master alloy A are: 29% PrNd, 0.93% B, 0.2% Zr, 0.1% Cu, 0.15% Ga, 1.2% Co, 68.42% Fe, and the weight percentages of auxiliary alloy B are: 40% Dy, 47.5% Pr, 1% B, 4% Ti, 3% Cu, 4.5% Ga. The specific components are shown in Table 1.

[0100] Step 2: Prepare hydrogenated crushed powder. The master alloy A cast sheet is hydrogenated and crushed, and the hydrogen absorption pressure is 1.8 kg / cm 2 until saturation, and then dehydrogenated. The dehydrogenation temperature is 550 °C. The obtained hydrogenated crushed powder has an O content of 852 ppm and an H content of 780 ppm; the hydrogen absorption pressure of the auxiliary alloy B cast sheet is 3.5 kg / cm 2 , when hydrogen absorption is carried out, it is first heated to 300 °C and held for 0.5 hours, then hydrogen is introduced, and then it is evacuated and heated to 880 °C for secondary hydrogen absorption until saturation. Finally, it is held at 450 °C for dehydrogenation, and the reasonable dehydrogenation time is controlled. Finally, the H content of the auxiliary phase hydrogenated crushed powder is measured to be 4236 ppm and the O content is 912 ppm.

[0101] Step 3: Jet mill pulverization and mixing of master and auxiliary fine powders. The hydrogenated crushed powder of master alloy A is pulverized by a jet mill to a particle size D50 of 3.89 μm, and the hydrogenated crushed powder of auxiliary alloy B is pulverized by a jet mill to a particle size D50 of 2.73 μm. The master phase powder A and the auxiliary phase powder B are mixed according to a weight ratio of 98:2, and 0.06% of a liquid lubricant is added and stirred for 3 hours.

[0102] Step 4: Magnetically orient and form the mixed powder in an atmosphere with an oxygen content lower than 100 ppm. The magnetic field strength is 1.8 T. After pressing by a press, it is vacuum packaged, and then isostatically pressed at a pressure of 180 MPa to a density of 4.4 g / cm3 The green compact.

[0103] Step Five: Place the isostatically pressed green compact in a vacuum sintering furnace for vacuum sintering and aging treatment. The sintering process is at 1072 °C for 8 h, and the sintering vacuum degree is better than 0.1 Pa. The aging process is aging at 900 °C for 3 h + aging at 650 °C for 3 h + aging at 495 °C for 5 h. During the second and third stages of aging, cooling is carried out by filling with N 2 Air cooling, and the cooling rate is 12 °C / min.

[0104] Comparative Example 1: Prepare a single alloy according to the mixed theoretical composition of the main alloy A and the auxiliary alloy B with a mixing ratio of 98:2 in Example 1 above. Then, prepare fine powder from the single alloy according to the melting, hydrogen crushing, and air jet milling process parameters of the main alloy A in Example 1. Then, mix the single fine powder, and the pressing and sintering processes remain unchanged according to the process in Example 1; the specific composition is shown in Table 1.

[0105] Comparative Example 2: Prepare a single alloy according to the mixed theoretical composition of the main alloy A and the auxiliary alloy B with a mixing ratio of 96:4 in Example 2 above. Then, prepare fine powder from the single alloy according to the melting, hydrogen crushing, and air jet milling process parameters of the main alloy A in Example 2. Then, mix the single fine powder, and the pressing and sintering processes remain unchanged according to the process in Example 2; the specific composition is shown in Table 1.

[0106] Comparative Example 3: Prepare a single alloy according to the mixed theoretical composition of the main alloy A and the auxiliary alloy B with a mixing ratio of 98:2 in Example 3 above. Then, prepare fine powder from the single alloy according to the melting, hydrogen crushing, and air jet milling process parameters of the main alloy A in Example 3. Then, mix the single powder, and the pressing and sintering processes remain unchanged according to the process in Example 3; the specific composition is shown in Table 1.

[0107] Comparative Example 4: Prepare a single alloy according to the mixed theoretical composition of the main alloy A and the auxiliary alloy B with a mixing ratio of 96:4 in Example 4 above. Then, prepare fine powder from the single alloy according to the melting, hydrogen crushing, and air jet milling process parameters of the main alloy A in Example 4. Then, mix the single powder, and the pressing and sintering processes remain unchanged according to the process in Example 4; the specific composition is shown in Table 1.

[0108] Magnetic property test provided by the specific embodiments of the present invention: The main magnetic property test methods for materials of varieties N, M, H, SH, and UH are carried out according to the provisions of GB / T 3217, and the main magnetic property test methods for materials of EH and TH are carried out according to the provisions of GB / T 29628; the neodymium iron boron magnetic property standard is in accordance with GB / T 13560-2017.

[0109] The magnetic performance test and comparison data of the magnets with the formulations of Examples 1-4 were respectively compared with the magnets of the same composition in Comparative Examples 1-4, and the results are shown in Table 2.

[0110] Table 1 Mass percentage table of each element in Examples and Comparative Examples:

[0111] Table 2 Magnetic performance table of Examples and Comparative Examples

[0112] Combined with Tables 1 and 2, it can be seen that the magnetic performance Br, H cj and the squareness value of the demagnetization curve of the magnets prepared by the preparation method of the present invention are all higher than those of the magnets made by the existing methods under the condition of the same ingredient composition. On the premise of the same magnetic performance, using the method of the present invention can reduce or even eliminate the use of heavy rare earths to meet the requirements of high magnetic performance.

[0113] At the same time, it can be seen from Figure 2 that the microstructure of the NdFeB magnet in Example 1 includes a matrix ((RE / RE') 2 Fe 14 B) phase and a rare earth-rich grain boundary phase. In addition, it can be seen from the microstructure of the magnet obtained by the existing double alloy process technology shown in Figure 3 that the grain boundary phase of the existing magnet is unevenly distributed around the matrix phase and there are breaks, while the grain boundary phase in the magnet prepared by the present invention is more evenly distributed around the matrix phase.

[0114] Among them, in the present invention, the matrix phase accounts for 97.5% - 98% of the total volume fraction, and the grain boundary phase accounts for 2% - 2.5% of the total volume fraction. The grain size of the main matrix phase ((RE / RE') 2 Fe 14 B) is about 8 - 12 μm, and the width of the grain boundary phase is about 5 - 10 nm.

[0115] The grain boundary phase is composed of a rare earth-rich phase. After statistics, the mass ratio of Fe to RE / RE' in the rare earth-rich phase in Example 1 is w(Fe):w(RE / RE') = 1:2, and the chemical formula of the rare earth-rich phase is (RE / RE')Fe 1.3 , and the specific chemical formula is Pr Fe 1.3 , NdFe 1.3 , Dy Fe 1.3 , PrDyFe 1.3 , NdDyFe 1.3 , PrNdDy Fe 1.3 one or more of them.

[0116] In Example 2, the mass ratio of Fe to RE / RE' in the rare-earth-rich phase is w(Fe):w(RE / RE') = 1:2.5, and the chemical formula of the rare-earth-rich phase is (RE / RE')Fe; the specific chemical formula may be one or more of PrFe, NdFe, DyFe, PrDyFe, NdDyFe, PrNdDyFe.

[0117] In Example 3, the mass ratio of Fe to RE / RE' in the rare-earth-rich phase is w(Fe):w(RE / RE') = 1:6.0, and the chemical formula of the rare-earth-rich phase is (RE / RE') 2 Fe; the specific chemical formula may be Pr 2 Fe, Nd 2 Fe, (PrNd) 2 Fe, one or more of them; In Example 4, the mass ratio of Fe to RE / RE' in the rare-earth-rich phase is w(Fe):w(RE / RE') = 1:7.5, and the chemical formula of the rare-earth-rich phase is (RE / RE') 3 Fe; the specific chemical formula may be Pr 3 Fe, Nd 3 Fe, (PrNd) 3 Fe, one or more of them.

[0118] The present invention can be implemented in various different ways and is not limited to the above embodiments and / or examples. Those of ordinary skill in the art can understand that the present invention can be implemented by other specific means without changing the technical idea or essential features of the present invention. Therefore, it should be understood that the above embodiments and / or examples are exemplary and not used to limit the present invention.

Claims

1. A high performance sintered NdFeB magnet, characterized in that: The raw materials for preparing the NdFeB magnet include a main alloy and an auxiliary alloy, and the auxiliary alloy does not contain Fe and Co elements; The main alloy, in terms of mass percentage, comprises the following chemical components: RE x B y M z T w F 1-x-y-z-w , RE is rare earth Nd or PrNd, B is boron, M is at least one of Nb, Zr, and Ti, T is Cu and Ga, and F contains Fe and Co, wherein the content of Co is 0-3wt.%, and the content of Fe is not 0, wherein the content of each element is x: 27-30wt.%, y: 0.9-1.1wt.%, z: 0.05-0.25wt.%, and w: 0.1-0.5wt.%; The microstructure of the NdFeB magnet includes a matrix phase and a rare earth-rich grain boundary phase, wherein the matrix phase is (RE / RE')2 (F) 14 B, wherein F is Fe and Co, the mass percentage of Co is 0-3, the mass percentage of Fe and RE / RE' in the rare earth-rich grain boundary phase is 1: (1.4~8), wherein RE is Nd or PrNd, and RE' is one or more of Pr, Ho, Dy, and Tb.

2. The high performance sintered NdFeB magnet according to claim 1, characterized in that: The NdFeB magnet is prepared by a double alloy process.

3. The high performance sintered NdFeB magnet according to claim 1, characterized in that: In the microstructure of the NdFeB magnet, the matrix phase accounts for 97.5% to 98%, and the mass percentage of the rare earth-rich grain boundary phase is 2% to 2.5%.

4. The high performance sintered NdFeB magnet according to claim 1, characterized in that: The D50 particle size of the main alloy is 3.5-4.5 μm, and the D50 particle size of the auxiliary alloy is 2.5-3.5 μm.

5. The high performance sintered NdFeB magnet according to claim 1, characterized in that: In element T, the mass percentage of Cu and Ga is 1:(1.2~1.5).

6. The high performance sintered NdFeB magnet according to claim 1, characterized in that: The auxiliary alloy, in terms of mass percentage, includes the following chemical components: RE' 1-a-b-c B a M b c , RE' is one or more of Pr, Ho, Dy, Tb, B is boron, M is at least one of Nb, Zr, Ti, Cu and Ga, wherein the mass percentage of Cu and Ga is 1:(1.2~1.5), wherein the content of each element is a: 0.5~5wt.%; b: 0~2wt.%, c: 4~10wt.%.

7. The high performance sintered NdFeB magnet according to claim 1, characterized in that: The mass ratio of the main alloy to the auxiliary alloy is (94-98): (2-6).

8. A method for preparing a high performance sintered NdFeB magnet according to any one of claims 1 to 7, characterized in that: include: S1. Prepare powders of the main alloy and auxiliary alloy according to any one of claims 1 to 7; S2, mixing the main alloy powder and the auxiliary alloy powder uniformly to obtain a mixed powder, and pressing the mixed powder into a compact by a magnetic field forming method or a hot pressing and hot deformation method; S4, sintering the compact into a blank in vacuum or inert gas; S5. Perform multi-stage aging treatment on the blank to obtain a high-performance sintered NdFeB magnet.

9. The method for preparing a high performance sintered NdFeB magnet according to claim 8, characterized in that: The multi-stage aging treatment includes three stages of aging treatment; Among them, the temperature of the first stage of aging treatment is 890~930℃; The temperature of the second stage aging treatment is 580~680℃; The temperature of the third aging treatment is 420~520℃.

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