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

Abstract

The invention belongs to the technical field of permanent magnet materials, and relates to a high-coercivity sintered neodymium-iron-boron permanent magnet material and a preparation method thereof.The preparation method comprises the following steps that under the protective atmosphere condition, a ReM rare earth alloy sheet and a neodymium-iron-boron green body are placed in an isolated mode through an isolation net; then, first diffusion treatment, second diffusion treatment and sintering treatment are sequentially carried out under the vacuumizing condition; and carrying out tempering treatment, and separating from the separation net to obtain the high-coercivity sintered neodymium-iron-boron permanent magnet material. The preparation method provided by the invention is simple to operate, slicing after traditional sintering does not need to be repeatedly carried out, the requirement of a neodymium iron boron green body with a large orientation thickness can be met, the process cost of grain boundary diffusion is reduced while the coercive force of the neodymium iron boron magnet is effectively improved, and the preparation method has a wide-range popularization and application prospect.

Description

Technical Field

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

[0002] Sintered NdFeB materials have become important basic functional materials due to their high remanence Br and maximum magnetic energy product (BHmax). They are widely used in new energy vehicles, wind power generation, high-speed rail, consumer electronics, household appliances, aerospace and other fields. With the rapid consumption of fossil energy and the increasingly serious environmental problems caused by fossil energy, green energy, especially renewable energy, has become a core issue of global concern. This shift has significantly accelerated the development of high-tech industries such as new energy vehicles, wind power generation and industrial permanent magnet motors, and the demand for NdFeB permanent magnet materials has grown rapidly.

[0003] In order to meet the high coercive force requirements of NdFeB magnets, the grain boundary diffusion process is usually used to make heavy rare earth elements or alloys penetrate into the interior of the magnet along the grain boundaries, strengthen the surface area of ​​the hard magnetic grains, thereby significantly improving the coercive force while reducing the amount of heavy rare earth and reducing its adverse effects on remanence and magnetic energy product. In addition, the grain boundary diffusion process can also achieve the precise distribution of rare earth elements at the grain boundaries of the magnet, which not only improves the coercive force, but also enhances the thermal stability of the magnet. However, as the requirements for NdFeB magnets continue to increase, higher air gap magnetic fields are required, and high-performance, thick magnets can provide greater magnetic field strength, which can improve the strong air gap magnetic field to meet the application scenarios of high-performance motors. However, due to the dense microstructure of the magnet, insufficient diffusion driving force, and limited grain boundary diffusion depth, the coercive force increase of magnets with a thickness of more than 10 mm is limited; the existing technology can only diffuse magnets with a thickness of less than 8 mm using grain boundary diffusion technology, and it is also necessary to process and slice grain boundary diffusion and grinder processing after sintering, which is complicated and increases costs.

[0004] Therefore, it is necessary to provide a high coercive force sintered NdFeB permanent magnet material and a preparation method thereof that further improves the coercive force, so that it is suitable for magnets with a thickness of more than 10 mm and simplifies the process. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a high coercive force sintered NdFeB permanent magnet material and a preparation method thereof. The preparation method does not require repeated traditional sintering and slicing grain boundary diffusion, and can meet the needs of large thickness magnets. It effectively improves the coercive force of NdFeB magnets while greatly reducing the process cost of grain boundary diffusion.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a high coercive force sintered NdFeB permanent magnet material, the preparation method comprising the following steps:

[0008] Under protective atmosphere conditions, the ReM rare earth alloy sheet and the NdFeB green body are isolated and placed through an isolation net; then, a first diffusion treatment, a second diffusion treatment and a sintering treatment are sequentially performed under vacuum conditions; and then, the high coercive force sintered NdFeB permanent magnet material is obtained after a tempering treatment.

[0009] The Re element in the ReM rare earth alloy sheet includes a heavy rare earth element, and the M element includes any one or a combination of at least two of Al, Zn, Ga or Cu;

[0010] The temperature of the first diffusion treatment is 750°C-850°C;

[0011] The temperature of the second diffusion treatment is 850°C-920°C;

[0012] The sintering temperature is 1020°C-1075°C.

[0013] The ReM rare earth alloy sheet of the present invention is placed on one side of the lower end of the orientation direction of the NdFeB green sheet, that is, the thickness direction of the ReM rare earth alloy sheet is parallel to the orientation direction of the NdFeB green sheet.

[0014] The preparation method provided by the present invention performs the first diffusion treatment, the second diffusion treatment and the sintering treatment on the NdFeB green body and the ReM rare earth alloy sheet, and does not need to perform the diffusion in the traditional sintered magnet slice diffusion mode, and effectively opens the diffusion channel of the grain boundary at the same time, so that the rare earth element diffuses deeper in the undensified state, and optimizes the grain boundary phase structure of the NdFeB magnet, thereby solving the problems of insufficient diffusion depth and low coercive force of thick magnets; moreover, the first diffusion treatment, the second diffusion treatment and the sintering treatment process are adopted, so that the rare earth element diffuses deeper, the rare earth element enters the main phase, the decline of the residual magnetization after diffusion is reduced, the microstructure of the NdFeB magnet is optimized, the anisotropy field of the grain epitaxial layer is effectively improved, the nucleation of the reverse magnetization domain is suppressed, and thus the coercive force of the NdFeB permanent magnet material is improved; the preparation method provided by the present invention can also greatly reduce the process cost of grain boundary diffusion while improving the coercive force of the NdFeB magnet.

[0015] Preferably, the heavy rare earth element includes Tb.

[0016] Preferably, the Re element also includes a light rare earth element; the light rare earth element includes Pr.

[0017] Preferably, based on the mass percentage of the ReM rare earth alloy sheet as 100wt%, the mass percentage of Tb is 35wt%-85wt%, the mass percentage of Pr is 7wt%-20wt%, the mass percentage of Al is 2wt%-10wt%, the mass percentage of Zn is 2wt%-10wt%, the mass percentage of Ga is 0wt%-10wt%, and the mass percentage of Cu is 0wt%-15wt%.

[0018] Preferably, based on the mass percentage of the ReM rare earth alloy sheet as 100wt%, the mass percentage of Tb is 70wt%-75wt%, the mass percentage of Pr is 7wt%-12wt%, the mass percentage of Al is 3wt%-7wt%, the mass percentage of Zn is 4wt%-8wt%, and the mass percentage of Cu is 5wt%-10wt%.

[0019] Preferably, the thickness of the ReM rare earth alloy sheet is 2 mm-5 mm.

[0020] Preferably, the composition of the NdFeB green body is 100wt% by mass: 29.4%≤Pr+Nd≤31%, 0.9%≤B≤0.98%, Cu+Ga+Al≤0.5%, 0.1%≤Zr+Ti≤0.25%, Co≤2%, and the balance is iron.

[0021] Preferably, the NdFeB green compact is prepared by a one-step molding method; the pressing magnetic field of the one-step molding is 2T-2.5T, and the pressing pressure is 22t-35t.

[0022] Preferably, the green density of the NdFeB green body is 4.2 g / cm 3 -4.5g / cm 3 .

[0023] Preferably, the NdFeB green body has a thickness in the orientation direction of 8 mm to 15 mm, preferably 10 mm to 15 mm.

[0024] Preferably, the pore size of the isolation net is 40-80 mesh.

[0025] Preferably, the first diffusion treatment takes 2 hours to 5 hours.

[0026] Preferably, the vacuum degree of the first diffusion treatment is 1×10 -3 Pa-1×10 -2 Pa.

[0027] Preferably, the second diffusion treatment lasts for 4 hours to 8 hours.

[0028] Preferably, the vacuum degree of the second diffusion treatment is 1×10-3 Pa-1×10 -2 Pa.

[0029] Preferably, the sintering treatment time is 3h-6h.

[0030] Preferably, the vacuum degree of the sintering process is 1×10 -3 Pa-1×10 -2 Pa.

[0031] Preferably, the tempering treatment comprises: -3 Pa-1×10 -2 The first tempering treatment and the second tempering treatment were carried out sequentially under the conditions of Pa.

[0032] Preferably, the temperature of the first tempering treatment is 860°C-910°C.

[0033] Preferably, the first tempering treatment time is 3h-5h.

[0034] Preferably, the temperature of the second tempering treatment is 410°C-520°C.

[0035] Preferably, the second tempering treatment time is 3h-5h.

[0036] In a second aspect, the present invention provides a high coercive force sintered NdFeB permanent magnet material, wherein the high coercive force sintered NdFeB permanent magnet material is prepared by the preparation method described in the first aspect.

[0037] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The preparation method provided by the present invention performs a first diffusion treatment, a second diffusion treatment and a sintering treatment on the NdFeB green body and the ReM rare earth alloy sheet, which can make the rare earth elements diffuse deeper in the undensified state and optimize the grain boundary phase structure of the NdFeB magnet, thereby solving the problems of insufficient diffusion depth and low coercivity of the NdFeB green body with large orientation thickness; the second diffusion treatment reduces the entry of rare earth elements into the main phase while making the rare earth elements diffuse deeper, reduces the reduction of remanence after diffusion, optimizes the microstructure of the NdFeB magnet, can effectively improve the anisotropy field of the grain epitaxial layer, inhibits the nucleation of the reverse magnetization domain, and improves the coercivity of the magnet;

[0040] (2) The preparation method provided by the present invention performs diffusion treatment and sintering treatment on the NdFeB green body, eliminating the need for diffusion in the traditional sintered magnet slice diffusion method, thereby simplifying the grain boundary diffusion process. While effectively improving the coercive force of the NdFeB magnet, it also greatly reduces the process cost of grain boundary diffusion. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the placement of the ReM rare earth alloy sheet and the NdFeB green body in the present invention. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0043] A certain embodiment of the present invention provides a method for preparing a high coercive force sintered NdFeB permanent magnet material, the preparation method comprising the following steps:

[0044] Under protective atmosphere conditions, the ReM rare earth alloy sheet and the NdFeB green body are isolated and placed through an isolation net; then, a first diffusion treatment, a second diffusion treatment and a sintering treatment are sequentially performed under vacuum conditions; and then, the high coercive force sintered NdFeB permanent magnet material is obtained after a tempering treatment.

[0045] The Re element in the ReM rare earth alloy sheet includes a heavy rare earth element, and the M element includes any one or a combination of at least two of Al, Zn, Ga or Cu;

[0046] The temperature of the first diffusion treatment is 750°C-850°C;

[0047] The temperature of the second diffusion treatment is 850°C-920°C;

[0048] The sintering temperature is 1020°C-1075°C.

[0049] The ReM rare earth alloy sheet of the present invention is placed on one side of the lower end of the orientation direction of the NdFeB green sheet, that is, the thickness direction of the ReM rare earth alloy sheet is parallel to the orientation direction of the NdFeB green sheet.

[0050] The preparation method provided by the present invention performs the first diffusion treatment, the second diffusion treatment and the sintering treatment on the NdFeB green body and the ReM rare earth alloy sheet, and does not need to perform the diffusion in the traditional sintered magnet slice diffusion mode, and effectively opens the diffusion channel of the grain boundary at the same time, so that the rare earth element diffuses deeper in the undensified state, and optimizes the grain boundary phase structure of the NdFeB magnet, thereby solving the problems of insufficient diffusion depth and low coercive force of thick magnets; moreover, the first diffusion treatment, the second diffusion treatment and the sintering treatment process are adopted, so that the rare earth element diffuses deeper, the rare earth element enters the main phase, the decline of the residual magnetization after diffusion is reduced, the microstructure of the NdFeB magnet is optimized, the anisotropy field of the grain epitaxial layer is effectively improved, the nucleation of the reverse magnetization domain is suppressed, and thus the coercive force of the NdFeB permanent magnet material is improved; the preparation method provided by the present invention can also greatly reduce the process cost of grain boundary diffusion while improving the coercive force of the NdFeB magnet.

[0051] The preparation method provided by the present invention controls the temperature of the first diffusion treatment, the second diffusion treatment and the sintering treatment, thereby reducing the entry of rare earth elements into the main phase while making the rare earth elements diffuse deeper, reducing the crystallization of residual magnetism after diffusion, optimizing the microstructure of the NdFeB magnet, and being able to effectively improve the anisotropy field of the grain epitaxial layer, inhibit the nucleation of the reverse magnetization domain, and improve the coercive force of the NdFeB permanent magnet material.

[0052] In the present invention, if the temperature of the first diffusion treatment is too low, the rare earth elements will not be able to smoothly enter the interior of the NdFeB magnet; if the temperature of the second diffusion treatment is too high, the rare earth elements will enter the main phase, the rare earth diffusion amount along the grain boundary will be reduced, resulting in a decrease in magnetic properties.

[0053] Therefore, the temperature of the first diffusion treatment is 750°C-850°C, for example, it can be 750°C, 780°C, 800°C, 820°C, 840°C or 850°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] The temperature of the second diffusion treatment is 850°C-920°C, for example, 850°C, 860°C, 880°C, 900°C or 920°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0055] The sintering temperature is 1020°C-1075°C, for example, 1020°C, 1040°C, 1050°C, 1060°C or 1075°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0056] In some embodiments, the isolation mesh includes any one of a molybdenum mesh, a nickel-chromium alloy mesh, or a 310s stainless steel mesh.

[0057] In certain embodiments, the isolation is performed in a sintering tank.

[0058] In certain embodiments, the heavy rare earth element includes Tb.

[0059] In some embodiments, the Re element further includes a light rare earth element; and the light rare earth element includes Pr.

[0060] In certain embodiments, based on the mass percentage of the ReM rare earth alloy sheet as 100wt%, the mass percentage of Tb is 35wt%-85wt%, the mass percentage of Pr is 7wt%-20wt%, the mass percentage of Al is 2wt%-10wt%, the mass percentage of Zn is 2wt%-10wt%, the mass percentage of Ga is 0wt%-10wt%, and the mass percentage of Cu is 0wt%-15wt%.

[0061] In some embodiments, based on the mass percentage of the ReM rare earth alloy sheet as 100wt%, the mass percentage of Tb is 70wt%-75wt%, for example, it can be 70wt%, 71wt%, 72wt%, 73wt%, 74wt% or 75wt%; the mass percentage of Pr is 7wt%-12wt%, for example, it can be 7wt%, 8wt%, 10wt%, 11wt% or 12wt%; the mass percentage of Al is 3wt%-7wt%, for example, it can be 3wt%, 4wt%, 5wt%, 6wt% or 7wt%; the mass percentage of Zn is 4wt%-8wt%, for example, it can be 4wt%, 5wt%, 6wt%, 7wt% or 8wt%; the mass percentage of Cu is 5wt%-10wt%, for example, it can be 5wt%, 6wt%, 8wt%, 9wt% or 10wt%.

[0062] In some embodiments, the thickness of the ReM rare earth alloy sheet is 2 mm-5 mm, for example, 2 mm, 3 mm, 4 mm or 5 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0063] Optionally, the ReM rare earth alloy sheet is first prepared by induction melting method to prepare ReM rare earth alloy, and then sliced.

[0064] In some embodiments, the composition of the NdFeB green body is 100wt% by mass: 29.4%≤Pr+Nd≤31%, 0.9%≤B≤0.98%, Cu+Ga+Al≤0.5%, 0.1%≤Zr+Ti≤0.25%, Co≤2%, and the balance is iron.

[0065] In the present invention, if the green density of the NdFeB green body is too low, the NdFeB green body will crack during sintering and the magnet will not be sintered densely; if the green density of the NdFeB green body is too high, the orientation of the magnet will be destroyed, resulting in a decrease in remanence.

[0066] Optionally, the NdFeB green billet is prepared by conventional rapid solidification casting, hydrogen crushing, air flow grinding and one-step molding in the art. The present invention does not make specific settings for the selection of specific parameters. As long as the green billet density of the NdFeB green billet is 4.2 g / cm 3 -4.5g / cm 3 That's it.

[0067] Exemplarily, the pressing magnetic field of the one-time molding is 2T-2.5T, for example, it can be 2, 2.1, 2.2, 2.4 or 2.5, etc.; the pressing pressure of the one-time molding is 22t-35t, for example, it can be 22t, 25t, 28t, 30t, 32t or 35t, etc.

[0068] In some embodiments, the green density of the NdFeB green body is 4.2 g / cm 3 -4.5g / cm 3 , for example, it can be 4.2 g / cm 3 , 4.3g / cm 3 4.4g / cm 3 or 4.5g / cm 3 , but not limited to the listed values, the remaining values ​​not listed in the numerical range are also applicable.

[0069] In some embodiments, the thickness of the NdFeB green body in the orientation direction is 8mm-15mm, for example, 8mm, 10mm, 12mm, 14mm or 15mm, but is not limited to the listed values. Other values ​​not listed in the numerical range are also applicable, preferably 10mm-15mm.

[0070] In some embodiments, the pore size of the isolation net is 40 mesh-80 mesh, for example, it can be 40 mesh, 50 mesh, 60 mesh, 70 mesh or 80 mesh, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0071] In some embodiments, the time of the first diffusion treatment is 2 hours to 5 hours, for example, 2 hours, 3 hours, 4 hours or 5 hours, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0072] In some embodiments, the vacuum degree of the first diffusion process is 1×10 -3 Pa-1×10 -2 Pa, for example, can be 1×10 -3Pa, 3×10 -3 Pa, 5×10 -3 Pa, 6×10 -3 Pa, 8×10 -3 Pa or 1×10 -2 Pa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0073] In some embodiments, the time of the second diffusion treatment is 4 hours to 8 hours, for example, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0074] In some embodiments, the vacuum degree of the second diffusion process is 1×10 -3 Pa-1×10 -2 Pa, for example, can be 1×10 -3 Pa, 3×10 -3 Pa, 5×10 -3 Pa, 6×10 -3 Pa, 8×10 -3 Pa or 1×10 -2 Pa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0075] In some embodiments, the sintering treatment time is 3h-6h, for example, 3h, 4h, 5h or 6h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0076] In some embodiments, the vacuum degree of the sintering process is 1×10 -3 Pa-1×10 -2 Pa, for example, can be 1×10 -3 Pa, 3×10 -3 Pa, 5×10 -3 Pa, 6×10 -3 Pa, 8×10 -3 Pa or 1×10 -2 Pa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0077] In some embodiments, the tempering treatment includes a vacuum of 1×10 -3 Pa-1×10 -2 The first tempering treatment and the second tempering treatment were carried out sequentially under the conditions of Pa.

[0078] In some embodiments, the temperature of the first tempering treatment is 860°C-910°C, for example, it can be 860°C, 870°C, 880°C, 890°C, 900°C or 910°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0079] In some embodiments, the time of the first tempering treatment is 3h-5h, for example, 3h, 3.5h, 4h, 4.5h or 5h, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0080] In some embodiments, the temperature of the second tempering treatment is 410°C-520°C, for example, it can be 410°C, 430°C, 450°C, 480°C, 500°C or 520°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0081] In some embodiments, the second tempering treatment time is 3h-5h, for example, 3h, 3.5h, 4h, 4.5h or 5h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0082] A certain embodiment of the present invention provides a high coercive force sintered NdFeB permanent magnet material, and the high coercive force sintered NdFeB permanent magnet material is prepared by the preparation method described in any embodiment.

[0083] Example 1

[0084] This embodiment provides a method for preparing a high coercive force sintered NdFeB permanent magnet material, the preparation method comprising the following steps:

[0085] In an argon atmosphere, a ReM rare earth alloy with a thickness of 3 mm and a green density of 4.3 g / cm 3 , the NdFeB green body with a thickness of 11 mm in the orientation direction is placed in a sintered glass jar, and the ReM rare earth alloy sheet and the NdFeB green body are separated by a 40-mesh molybdenum mesh and placed in a sintered glass jar (see Figure 1 ); then sequentially performing a first diffusion treatment, a second diffusion treatment and a sintering treatment, and separating from the molybdenum mesh after a tempering treatment to obtain the high coercive force sintered NdFeB permanent magnet material;

[0086] The ReM rare earth alloy sheet has a mass percentage of 100wt%, a mass percentage of Tb of 75wt%, a mass percentage of Pr of 7wt%, a mass percentage of Al of 5wt%, a mass percentage of Zn of 5wt%, and a mass percentage of Cu of 8wt%.

[0087] The NdFeB green body has the following components, calculated by mass percentage as 100wt%, 22.88% Nd, 7.63% Pr, 0.94% B, 0.15% Cu, 0.15% Ga, 0.2% Al, 0.15% Ti, 0.5% Co, and the balance is iron; it is prepared by a one-step molding method, the pressing magnetic field of the one-step molding is 2.3T, and the pressing pressure is 26t;

[0088] The first diffusion treatment was performed at a temperature of 760°C, a time of 3 hours, and a vacuum degree of 6×10 -3 Pa;

[0089] The second diffusion treatment was performed at a temperature of 900°C, a time of 7 hours, and a vacuum degree of 4×10 -3 Pa;

[0090] The sintering temperature is 1070°C, the time is 4 hours and the vacuum degree is 6×10 -3 Pa;

[0091] The tempering treatment includes a vacuum degree of 6×10 -3 The first tempering treatment and the second tempering treatment were carried out sequentially under the conditions of Pa. The temperature of the first tempering treatment was 900°C and the time was 3h, and the temperature of the second tempering treatment was 510°C and the time was 3.5h.

[0092] Example 2

[0093] This embodiment provides a method for preparing a high coercive force sintered NdFeB permanent magnet material, the preparation method comprising the following steps:

[0094] In an argon atmosphere, a ReM rare earth alloy with a thickness of 2 mm and a green density of 4.2 g / cm 3 , the NdFeB green body with a thickness of 10 mm in the orientation direction is placed in a sintered glass jar, and the ReM rare earth alloy sheet and the NdFeB green body are separated by a 40-mesh molybdenum mesh and placed in a sintered glass jar (see Figure 1 ); then sequentially performing a first diffusion treatment, a second diffusion treatment and a sintering treatment, and separating from the molybdenum mesh after a tempering treatment to obtain the high coercive force sintered NdFeB permanent magnet material;

[0095] The ReM rare earth alloy sheet has a mass percentage of 100wt%, a mass percentage of Tb of 70wt%, a mass percentage of Pr of 12wt%, a mass percentage of Al of 3wt%, a mass percentage of Zn of 5wt%, and a mass percentage of Cu of 10wt%.

[0096] The NdFeB green body has the following components, calculated by mass percentage as 100wt%, 22.88% Nd, 7.63% Pr, 0.94% B, 0.15% Cu, 0.15% Ga, 0.2% Al, 0.15% Ti, 0.5% Co, and the balance is iron; it is prepared by a one-step molding method, and the pressing magnetic field and pressing pressure of the one-step molding are 2.3T and 26t.

[0097] The first diffusion treatment was performed at a temperature of 750°C, a time of 2 hours, and a vacuum degree of 1×10 -3 Pa;

[0098] The second diffusion treatment was performed at a temperature of 850°C, a time of 4 hours, and a vacuum degree of 1×10 -3 Pa;

[0099] The sintering temperature is 1020°C, the time is 3 hours and the vacuum degree is 1×10 -3 Pa;

[0100] The tempering treatment includes a vacuum degree of 1×10 -3 The first tempering treatment and the second tempering treatment were carried out sequentially under the conditions of Pa. The temperature of the first tempering treatment was 860°C and the time was 3h, and the temperature of the second tempering treatment was 410°C and the time was 3h.

[0101] Example 3

[0102] This embodiment provides a method for preparing a high coercive force sintered NdFeB permanent magnet material, the preparation method comprising the following steps:

[0103] In an argon atmosphere, a ReM rare earth alloy with a thickness of 5 mm and a green density of 4.5 g / cm 3 , the NdFeB green body with a thickness of 15 mm in the orientation direction is placed in a sintered glass jar, and the ReM rare earth alloy sheet and the NdFeB green body are separated by a 80-mesh molybdenum mesh and placed in a sintered glass jar (see Figure 1 ); then sequentially performing a first diffusion treatment, a second diffusion treatment and a sintering treatment, and separating from the molybdenum mesh after a tempering treatment to obtain the high coercive force sintered NdFeB permanent magnet material;

[0104] The ReM rare earth alloy sheet has a mass percentage of 100wt%, a mass percentage of Tb of 72wt%, a mass percentage of Pr of 10wt%, a mass percentage of Al of 3wt%, a mass percentage of Zn of 6wt%, and a mass percentage of Cu of 9wt%;

[0105] The NdFeB green body has the following components, calculated by mass percentage as 100wt%, 22.88% Nd, 7.63% Pr, 0.94% B, 0.15% Cu, 0.15% Ga, 0.2% Al, 0.15% Ti, 0.5% Co, and the balance is iron; it is prepared by a one-step molding method, and the pressing magnetic field and pressing pressure of the one-step molding are 2.3T and 26t.

[0106] The first diffusion treatment was performed at a temperature of 850°C, a time of 5 hours, and a vacuum degree of 1×10 -2 Pa;

[0107] The second diffusion treatment was performed at a temperature of 920°C, a time of 8 hours, and a vacuum degree of 1×10 -2 Pa;

[0108] The sintering temperature is 1075°C, the time is 6 hours and the vacuum degree is 1×10 -2 Pa;

[0109] The tempering treatment includes a vacuum degree of 1×10 -2 The first tempering treatment and the second tempering treatment were carried out sequentially under the conditions of Pa. The temperature of the first tempering treatment was 910°C and the time was 5h, and the temperature of the second tempering treatment was 520°C and the time was 5h.

[0110] Example 4

[0111] This embodiment provides a method for preparing a high coercive force sintered NdFeB permanent magnet material, which is the same as that of Embodiment 1 except that 7wt% Pr in the ReM rare earth alloy sheet component is replaced by Tb element.

[0112] Example 5

[0113] This embodiment provides a method for preparing a high coercive force sintered NdFeB permanent magnet material, which is the same as that of Embodiment 1 except that 5wt% of Zn in the ReM rare earth alloy sheet component is replaced by Tb element.

[0114] Example 6

[0115] This embodiment provides a method for preparing a high coercive force sintered NdFeB permanent magnet material. In addition to changing the size of the primary molding press to make the green density of the NdFeB green billet 4g / cm 3 Except for this, the rest are the same as in Example 1.

[0116] Example 7

[0117] This embodiment provides a method for preparing a high coercive force sintered NdFeB permanent magnet material. In addition to changing the size of the primary molding press to make the green density of the NdFeB green billet 4.8 g / cm 3Except for this, the rest are the same as in Example 1.

[0118] Example 8

[0119] This embodiment provides a method for preparing a high coercive force sintered NdFeB permanent magnet material, the preparation method comprising the following steps:

[0120] In an argon atmosphere, a ReM rare earth alloy with a thickness of 3 mm and a green density of 4.3 g / cm 3 , the NdFeB green body with a thickness of 11 mm in the orientation direction is placed in a sintered glass jar, and the ReM rare earth alloy sheet and the NdFeB green body are separated by a 40-mesh molybdenum mesh and placed in a sintered glass jar (see Figure 1 ); then sequentially performing a first diffusion treatment, a second diffusion treatment and a sintering treatment, and then performing a tempering treatment to obtain the high coercive force sintered NdFeB permanent magnet material;

[0121] The ReM rare earth alloy sheet has a mass percentage of 100wt%, a mass percentage of Tb of 75wt%, a mass percentage of Pr of 7wt%, a mass percentage of Al of 5wt%, a mass percentage of Zn of 5wt%, and a mass percentage of Cu of 8wt%.

[0122] The NdFeB green body has the following components, calculated by mass percentage as 100wt%, 22.88% Nd, 7.63% Pr, 0.94% B, 0.15% Cu, 0.15% Ga, 0.2% Al, 0.15% Ti, 0.5% Co, and the balance is iron; it is prepared by a one-step molding method, the pressing magnetic field of the one-step molding is 2.3T, and the pressing pressure is 26t;

[0123] The first diffusion treatment was performed at a temperature of 760°C, a time of 3 hours, and a vacuum degree of 6×10 -3 Pa;

[0124] The second diffusion treatment was performed at a temperature of 900°C, a time of 7 hours, and a vacuum degree of 4×10 -3 Pa;

[0125] The sintering temperature is 1070°C, the time is 4 hours and the vacuum degree is 6×10 -3 Pa;

[0126] The tempering treatment includes a vacuum degree of 6×10 -3 The first tempering treatment was carried out under the conditions of Pa, and the temperature of the first tempering treatment was 900°C and the time was 3h.

[0127] Comparative Example 1

[0128] This comparative example provides a method for preparing a sintered NdFeB permanent magnet material, which is the same as Example 1 except that the temperature of the first diffusion treatment is 720°C.

[0129] Comparative Example 2

[0130] This comparative example provides a method for preparing a sintered NdFeB permanent magnet material, which is the same as Example 1 except that the temperature of the second diffusion treatment is 950°C.

[0131] Comparative Example 3

[0132] This comparative example provides a method for preparing a sintered NdFeB permanent magnet material, the preparation method comprising the following steps:

[0133] In an argon atmosphere, a ReM rare earth alloy with a thickness of 3 mm and a green density of 4.3 g / cm 3 , the NdFeB green body with a thickness of 11 mm in the orientation direction is placed in a sintered glass jar, and the ReM rare earth alloy sheet and the NdFeB green body are separated by a 40-mesh molybdenum mesh and placed in a sintered glass jar (see Figure 1 ); then sequentially perform a second diffusion treatment and a sintering treatment, and then perform a tempering treatment and separate it from the molybdenum mesh to obtain the sintered NdFeB permanent magnet material;

[0134] The ReM rare earth alloy sheet has a mass percentage of 100wt%, a mass percentage of Tb of 75wt%, a mass percentage of Pr of 7wt%, a mass percentage of Al of 5wt%, a mass percentage of Zn of 5wt%, and a mass percentage of Cu of 8wt%.

[0135] The NdFeB green body has the following components, calculated by mass percentage as 100wt%, 22.88% Nd, 7.63% Pr, 0.94% B, 0.15% Cu, 0.15% Ga, 0.2% Al, 0.15% Ti, 0.5% Co, and the balance is iron; it is prepared by a one-step molding method, the pressing magnetic field of the one-step molding is 2.3T, and the pressing pressure is 26t;

[0136] The second diffusion treatment was performed at a temperature of 900°C, a time of 7 hours, and a vacuum degree of 4×10 -3 Pa;

[0137] The sintering temperature is 1070°C, the time is 4 hours and the vacuum degree is 6×10 -3 Pa;

[0138] The tempering treatment includes a vacuum of 6×10 -3The first tempering treatment and the second tempering treatment were carried out sequentially under the conditions of Pa. The temperature of the first tempering treatment was 900°C and the time was 3h, and the temperature of the second tempering treatment was 510°C and the time was 3.5h.

[0139] Comparative Example 4

[0140] This comparative example provides a method for preparing a sintered NdFeB permanent magnet material, the preparation method comprising the following steps:

[0141] In an argon atmosphere, a ReM rare earth alloy with a thickness of 3 mm and a green density of 4.3 g / cm 3 , the NdFeB green body with a thickness of 11 mm in the orientation direction is placed in a sintered glass jar, and the ReM rare earth alloy sheet and the NdFeB green body are separated by a 40-mesh molybdenum mesh and placed in a sintered glass jar (see Figure 1 ); then sequentially perform a first diffusion treatment and a sintering treatment, and then perform a tempering treatment and separate it from the molybdenum mesh to obtain the sintered NdFeB permanent magnet material;

[0142] The ReM rare earth alloy sheet has a mass percentage of 100wt%, a mass percentage of Tb of 75wt%, a mass percentage of Pr of 7wt%, a mass percentage of Al of 5wt%, a mass percentage of Zn of 5wt%, and a mass percentage of Cu of 8wt%.

[0143] The NdFeB green body has the following components, calculated by mass percentage as 100wt%, 22.88% Nd, 7.63% Pr, 0.94% B, 0.15% Cu, 0.15% Ga, 0.2% Al, 0.15% Ti, 0.5% Co, and the balance is iron; it is prepared by a one-step molding method, the pressing magnetic field of the one-step molding is 2.3T, and the pressing pressure is 26t;

[0144] The first diffusion treatment was performed at a temperature of 760°C, a time of 3 hours, and a vacuum degree of 6×10 -3 Pa;

[0145] The sintering temperature is 1070°C, the time is 4 hours and the vacuum degree is 6×10 -3 Pa;

[0146] The tempering treatment includes a vacuum degree of 6×10 -3 The first tempering treatment and the second tempering treatment were carried out sequentially under the conditions of Pa. The temperature of the first tempering treatment was 900°C and the time was 3h, and the temperature of the second tempering treatment was 510°C and the time was 3.5h.

[0147] Performance Characterization

[0148] The coercive force and remanence of the permanent magnetic materials obtained in the above embodiments and comparative examples were tested using a hysteresis loop instrument NIM-62000 in accordance with GB / T 3217-2013 "Magnetic Test Methods for Permanent Magnet (Hard Magnetic) Materials", and the results are shown in Table 1. The original magnet is the final product prepared by using only NdFeB green billets according to the method of Example 1 without using ReM rare earth alloy.

[0149] Table 1

[0150]

[0151]

[0152] It can be seen from Table 1 that the permanent magnet material obtained by the preparation method provided by the present invention has a coercive force of more than 23.45 kOe and a remanence of more than 13.97 kGs, thereby obtaining the high coercive force sintered NdFeB permanent magnet material of the present invention.

[0153] From the comparison between Example 4 and Example 1, it can be seen that when the composition of the ReM alloy sheet does not contain the Pr element, the remanence decreases from 14.05kGs to 14.02kGs, and the coercive force decreases significantly, directly from 24.01kOe to 23.01kOe, which indicates that the synergistic use of heavy rare earth doping element Tb and light rare earth doping element Pr can improve the coercive force of NdFeB permanent magnet materials.

[0154] From the comparison between Example 5 and Example 1, it can be seen that when the composition of the ReM alloy sheet does not contain the Zn element, the remanence decreases from 14.05 kGs to 13.95 kGs, and the coercive force decreases significantly, directly decreasing from 24.01 kOe to 22.95 kOe, which shows that in order to obtain high coercive force sintered NdFeB permanent magnet material, the addition of Zn element is essential.

[0155] From the comparison between Example 6 and Example 1, it can be seen that when the green body density of the NdFeB green body is low, the green body will crack during the sintering process, resulting in loose sintering, so the remanence is 12.98 kGs and the coercive force is 22.03 kOe.

[0156] From the comparison between Example 7 and Example 1, it can be seen that when the green density of the NdFeB green body is high, the magnet orientation will be destroyed, resulting in a decrease in remanence, so the remanence is 13.52 kGs and the coercive force is 23.04 kOe.

[0157] From the comparison between Example 8 and Example 1, it can be seen that when only the first tempering treatment is performed, the remanence and coercive force decrease slightly, but the remanence can still reach 14.04 kGs, and the coercive force can still reach 21.95 kOe.

[0158] From the comparison between Comparative Example 1 and Example 1, it can be seen that when the temperature of the first diffusion treatment is too low, the heavy rare earth cannot smoothly enter the magnet to form a uniform core-shell structure, and the coercive force is only 22.89 kOe.

[0159] From the comparison between Comparative Example 2 and Example 1, it can be seen that when the temperature of the second diffusion treatment is too high, heavy rare earth elements will enter the main phase, and the diffusion amount of heavy rare earth along the grain boundary will be reduced, resulting in a significant decrease in magnetic properties, with remanence of only 13.75 kGs and coercive force of only 23.02 kOe.

[0160] From the comparison between Comparative Example 3 and Example 1, it can be seen that when the first diffusion treatment is not performed, the coercive force is only 22.75 kOe.

[0161] From the comparison between Comparative Example 4 and Example 1, it can be seen that when the second diffusion treatment is not performed, the coercive force is only 18.92 kOe.

[0162] In summary, the preparation method provided by the present invention performs the first diffusion treatment, the second diffusion treatment and the sintering treatment on the NdFeB green body and the ReM rare earth alloy sheet, which can make the rare earth elements diffuse deeper in the non-densified state, and solve the problem of insufficient diffusion depth of the NdFeB green body with large orientation thickness; the second diffusion treatment reduces the entry of rare earth elements into the main phase while making the rare earth elements diffuse deeper, reduces the reduction of residual magnetism after diffusion, optimizes the microstructure of the NdFeB magnet, and can effectively improve the anisotropy field of the grain epitaxial layer, inhibit the nucleation of the reverse magnetization domain, and improve the coercive force of the magnet; the preparation method provided by the present invention performs diffusion treatment and sintering treatment on the NdFeB green body, and does not need to diffuse in the traditional sintered magnet slice diffusion method, which simplifies the grain boundary diffusion process, and effectively improves the coercive force of the NdFeB magnet while greatly reducing the process cost of grain boundary diffusion.

[0163] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a high coercive force sintered NdFeB permanent magnet material, characterized in that: The preparation method comprises the following steps: Under protective atmosphere conditions, the ReM rare earth alloy sheet and the NdFeB green body are isolated and placed through an isolation net; then, a first diffusion treatment, a second diffusion treatment and a sintering treatment are sequentially performed under vacuum conditions; and then, the high coercive force sintered NdFeB permanent magnet material is obtained after a tempering treatment. The Re element in the ReM rare earth alloy sheet includes a heavy rare earth element, and the M element includes any one or a combination of at least two of Al, Zn, Ga or Cu; The temperature of the first diffusion treatment is 750°C-850°C; The temperature of the second diffusion treatment is 850°C-920°C; The sintering temperature is 1020°C-1075°C.

2. The preparation method according to claim 1, characterized in that: The heavy rare earth element includes Tb; Preferably, the Re element also includes a light rare earth element; the light rare earth element includes Pr.

3. The preparation method according to claim 2, characterized in that: Taking the mass percentage of the ReM rare earth alloy sheet as 100wt%, the mass percentage of Tb is 35wt%-85wt%, the mass percentage of Pr is 7wt%-20wt%, the mass percentage of Al is 2wt%-10wt%, the mass percentage of Zn is 2wt%-10wt%, the mass percentage of Ga is 0wt%-10wt%, and the mass percentage of Cu is 0wt%-15wt%; Preferably, based on the mass percentage of the ReM rare earth alloy sheet as 100wt%, the mass percentage of Tb is 70wt%-75wt%, the mass percentage of Pr is 7wt%-12wt%, the mass percentage of Al is 3wt%-7wt%, the mass percentage of Zn is 4wt%-8wt%, and the mass percentage of Cu is 5wt%-10wt%.

4. The preparation method according to claim 1, characterized in that: The thickness of the ReM rare earth alloy sheet is 2 mm to 5 mm.

5. The preparation method according to claim 1, characterized in that: The composition of the NdFeB green body is calculated based on the mass percentage of 100wt%, which is: 29.4%≤Pr+Nd≤31%, 0.9%≤B≤0.98%, Cu+Ga+Al≤0.5%, 0.1%≤Zr+Ti≤0.25%, Co≤2%, and the balance is iron; Preferably, the NdFeB green compact is prepared by a one-step molding method; the pressing magnetic field of the one-step molding is 2T-2.5T, and the pressing pressure is 22t-35t; Preferably, the green density of the NdFeB green body is 4.2 g / cm 3 -4.5g / cm 3 ; Preferably, the NdFeB green body has a thickness in the orientation direction of 8 mm to 15 mm, preferably 10 mm to 15 mm.

6. The preparation method according to claim 1, characterized in that: The aperture size of the isolation net is 40-80 meshes.

7. The preparation method according to claim 1, characterized in that: The time of the first diffusion treatment is 2h-5h; Preferably, the vacuum degree of the first diffusion treatment is 1×10 -3 Pa-1×10 -2 Pa; Preferably, the second diffusion treatment time is 4h-8h; Preferably, the vacuum degree of the second diffusion treatment is 1×10 -3 Pa-1×10 -2 Pa.

8. The preparation method according to claim 1, characterized in that: The sintering time is 3h-6h; Preferably, the vacuum degree of the sintering process is 1×10 -3 Pa-1×10 -2 Pa.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The tempering treatment includes a vacuum degree of 1×10 -3 Pa-1×10 -2 The first tempering treatment and the second tempering treatment were carried out successively under the conditions of Pa; Preferably, the temperature of the first tempering treatment is 860°C-910°C; Preferably, the first tempering treatment time is 3h-5h; Preferably, the temperature of the second tempering treatment is 410°C-520°C; Preferably, the second tempering treatment time is 3h-5h.

10. A high coercivity sintered NdFeB permanent magnet material, characterized in that: The high coercive force sintered NdFeB permanent magnet material is prepared by the preparation method described in any one of claims 1-9.

Images