Sintered neodymium-iron-boron magnet and method for producing the same

Abstract

This invention provides a method as shown in formula R x T 100‑x‑y1‑y2‑ z M y1 A y2 B z The sintered NdFeB magnet shown is characterized by the following composition: 28.5 wt% ≤ x ≤ 32.0 wt%, 0.2 wt% ≤ y1 ≤ 0.8 wt%, 0.60 wt% ≤ y2 ≤ 1.5 wt%, and 0.88 wt% ≤ z ≤ 0.94 wt%; R is selected from one or more rare earth elements and must include Nd; M is selected from one or more of Ti, Zr, and Nb; and A is Cu, Ga, and Al. This application also provides a method for preparing the sintered NdFeB magnet. This invention adds and optimizes the specific amounts of M and A elements, and specially designs the remaining components, thereby improving the remanence, coercivity, and energy product of the magnet alloy, resulting in higher performance, reduced production costs, and a simple process with wide applicability, making it suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of magnetic materials technology, and in particular to a sintered NdFeB magnet and its preparation method. Background Technology

[0002] Sintered NdFeB magnets are the highest energy density permanent magnets discovered by mankind to date, and large-scale commercial production has been achieved. Since their discovery, sintered NdFeB magnets have been widely used in many fields such as computer hard drives, hybrid vehicles, medical devices, and wind power generation, and their application scope and production are increasing year by year, especially in the field of new energy vehicles.

[0003] Many applications of NdFeB sintered magnets are in high-temperature environments, thus requiring not only high remanence but also high coercivity. Coercivity is a key parameter of permanent magnet materials; higher coercivity indicates stronger resistance to demagnetization. In applications, higher coercivity is desirable for NdFeB sintered magnets to ensure good temperature stability and allow operation at higher temperatures.

[0004] In existing technologies, the method to improve the coercivity of NdFeB sintered magnets is to partially replace Nd with Dy and Tb. However, heavy rare earth elements Dy and Tb reduce remanence; and there is a risk of price instability or large fluctuations for Dy and Tb.

[0005] Therefore, how to further improve the overall performance of magnets, so that the coercivity, remanence and energy product of magnets can be improved, while at the same time using little or no heavy rare earth elements, has become the focus and hot topic of research for technicians in this field. Summary of the Invention

[0006] The technical problem solved by this invention is to provide a sintered NdFeB magnet with good remanence, energy product and coercivity.

[0007] In view of this, this application provides a sintered NdFeB magnet as shown in Formula (I);

[0008] R x T 100-x-y1-y2-z M y1 A y2 B z (I);

[0009] Where x, y1, y2, and z are the mass percentages of the corresponding elements, 28.5wt%≤x≤32.0wt%, 0.2wt%≤y1≤0.8wt%, 0.60wt%≤y2≤1.5wt%, and 0.88wt%≤z≤0.94wt%.

[0010] R is selected from one or more rare earth elements and must contain Nd;

[0011] A is selected from Cu, Ga, and Al, with Cu content ranging from 0.30 to 0.55 wt%, Ga content ranging from 0.25 to 0.45 wt%, and Al content ranging from 0.02 to 0.5 wt%.

[0012] M is selected from one or more of Ti, Zr and Nb, and 1.5 < A / M < 6;

[0013] T is selected from Fe and Co, with Co content ranging from 0 to 1.0 wt% and the balance being Fe.

[0014] Preferably, when M is selected solely from Ti, the Ti content is 0.2wt%~0.35wt%; and 3

[0015] When M is selected solely from Zr, the Zr content is 0.35 wt%~0.75%; and 1.5

[0016] When M is selected solely from Nb, the Nb content is 0.35 wt% to 0.75 wt%; and 1.5

[0017] When M is selected from two or three of Ti, Zr, and Nb, M' = Ti*2 + Zr + Nb, M' is 0.4wt%~0.8wt%, and Ti + Zr + Nb > 0.2wt%; and 1.5

[0018] Preferably, the rare earth element is selected from one or more of Pr, Dy, Tb, Gd, La and Ce, wherein the content of Pr is 0~14.5wt%, the content of Nd is 10wt%~32wt%, the content of Dy+Tb is 0~4.5wt%, the content of Gd is 0~4.5wt%, and the content of La+Ce is 0~15wt%.

[0019] Preferably, the content of Pr is 7wt%~9wt%, the content of Nd is 20wt%~25.5wt%, and the content of Dy is 0~3wt%.

[0020] Preferably, the Cu content is 0.35wt%~0.5wt%, the Ga content is 0.30wt%~0.45wt%, and the Al content is 0.02wt%~0.3wt%.

[0021] Preferably, the content of Co is 0~0.8wt%, and the content of B is 0.90wt%~0.94wt%.

[0022] ​​​​This application also provides a method for preparing the sintered NdFeB magnet, comprising the following steps:

[0023] A) The raw materials for NdFeB sintered magnets are mixed according to the specified ratio and then subjected to rapid solidification sheet treatment to obtain NdFeB rapid solidification sheets;

[0024] B) The NdFeB rapid solidification flakes were sequentially subjected to hydrogen crushing and air jet milling to obtain NdFeB powder;

[0025] C) The neodymium iron boron powder is sequentially oriented and sintered to obtain a sintered neodymium iron boron magnet.

[0026] Preferably, the temperature for processing the rapidly solidifying sheet is 1400~1500℃, and the thickness of the neodymium iron boron rapidly solidifying sheet is 0.10~0.60mm;

[0027] During the hydrogen crushing process, the hydrogen absorption time is 1-3 hours, the hydrogen absorption temperature is 20-300℃, the hydrogen dehydrogenation time is 3-7 hours, and the hydrogen dehydrogenation temperature is 550-600℃.

[0028] During the air jet milling process, a lubricant is added for grinding. The lubricant is 0.02~0.1% of the mass of the mixed fine powder obtained by hydrogen crushing. The average particle size of the powder after air jet milling is 2~6μm.

[0029] Preferably, the orientation forming includes sequential orientation pressing and isostatic pressing; the magnetic field strength of the orientation forming is 1.2~3T.

[0030] Preferably, the sintering temperature is 1000~1200℃, the time is 5~15h, and the vacuum degree is less than or equal to 0.02Pa;

[0031] The sintering process further includes an aging treatment, which includes a first aging treatment and a second aging treatment.

[0032] The temperature of the first aging treatment is 800~980℃, and the time of the first aging treatment is 1~10 hours;

[0033] The temperature of the second aging treatment is 420~580℃, and the time of the second aging treatment is 1~8 hours.

[0034] This invention provides a sintered NdFeB magnet, which increases the amount of high-melting-point element M among many alloying elements, and rationally designs the remaining components to include the addition of low-melting-point element A, so that the A / M ratio is within a certain range, allowing M and A to combine and form an alloy phase. Increasing the high-melting-point element M can refine the grains and improve coercivity, while the composite addition of low-melting-point element A can cause M to form an alloy phase and accumulate at the grain boundaries, improving the grain boundary structure and increasing coercivity.

[0035] The neodymium iron boron magnet and its preparation method provided by this invention can not only produce neodymium iron boron magnetic materials with high performance, but also improve the remanence, coercivity and magnetic energy product of the magnet alloy without increasing heavy rare earth elements, thereby reducing production costs. Moreover, the process is simple, widely applicable, and suitable for large-scale industrial production.

[0036] Experimental results show that, compared with the same type of neodymium iron boron magnet, the coercivity of the neodymium iron boron magnet provided by this invention is increased by more than 1.3 kOe without reducing the remanence. Detailed Implementation

[0037] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0038] To address the issue of unbalanced cost and performance in existing sintered NdFeB magnets, this application provides a sintered NdFeB magnet that achieves element matching by adding alloying elements and defining their proportions, ultimately resulting in a sintered NdFeB magnet with better remanence, energy product, and coercivity. Specifically, this invention discloses a sintered NdFeB magnet as shown in formula (I);

[0039] R x T 100-x-y1-y2-z M y1 A y2 B z (I);

[0040] Where x, y1, y2, and z are the mass percentages of the corresponding elements, 28.5wt%≤x≤32.0wt%, 0.2wt%≤y1≤0.8wt%, 0.60wt%≤y2≤1.5wt%, and 0.88wt%≤z≤0.94wt%.

[0041] R is selected from one or more rare earth elements and must contain Nd;

[0042] A is selected from Cu, Ga, and Al, with Cu content ranging from 0.30 to 0.55 wt%, Ga content ranging from 0.25 to 0.45 wt%, and Al content ranging from 0.02 to 0.5 wt%.

[0043] M is selected from one or more of Ti, Zr and Nb, and 1.5 < A / M < 6;

[0044] T is selected from Fe and Co, with Co content ranging from 0 to 1.0 wt% and the balance being Fe.

[0045] The present invention does not impose any particular limitation on the specific definition of Formula I shown, and any expression familiar to those skilled in the art can be used. Here it can be understood as the mass percentage of the corresponding element.

[0046] In this application, R is selected from one or more rare earth elements and must include Nd, specifically selected from one or more of Pr, Dy, Tb, Gd, La, and Ce and Nd; the content of R is 28.5~32.0 wt%; more specifically, the content of Pr is 0~14.5 wt%, the content of Nd is 10 wt%~32 wt%, the content of Dy+Tb is 0~4.5 wt%, the content of Gd is 0~4.5 wt%, and the content of La+Ce is 0~15 wt%; more specifically, the content of Pr is 3~12 wt%, the content of Nd is 15~30 wt%, and the content of Dy is 0~3 wt%; more specifically, the content of Pr is 3.2 wt%. , 3.6wt%, 3.9wt%, 4.5wt%, 4.8wt%, 5.0wt%, 5.3wt%, 5.5wt%, 5.7wt%, 5 .9wt%, 6.3wt%, 6.5wt%, 6.8wt%, 7.0wt%, 7.3wt%, 7.5wt%, 7.6wt%, 7.8 wt%, 7.9wt%, 8.0wt%, 8.2wt%, 8.5wt%, 8.8wt%, 8.9wt%, 9.1wt%, 9.2wt %, 9.5wt%, 9.6wt%, 9.8wt%, 10.0wt%, 10.3wt%, 10.5wt%, 10.8wt%, 10.9 The Nd content was 15.2wt%, 15.8wt%, 15.9wt%, 16.0wt%, 16.2wt%, 16.3wt%, 16.5wt%, 16.7wt%, 16.6wt%, 16.9wt%, 17.0wt%, 17.6wt%, 18.1wt%, 18.5wt%, 19.2wt%, 19.5wt%, 19.8wt%, 20.1wt%, 20.3wt%, 20.6wt%, 20.9wt%, 21.1wt%, 21.3wt%, and 21.8wt%, respectively. %, 22wt%, 22.3wt%, 22.6wt%, 22.8wt%, 23.2wt%, 23.5wt%, 23.7wt%, 23.8%, 24.0wt%, 24.3wt%, 24.5wt%, 24.6wt%, 24.8wt%, 25.2wt%, 25.3wt%, 25.6wt%, 25.7wt%, 25.9wt%, 26.2wt%, 26.8wt%, 27.4wt%, 27.6wt%, 27.8wt%, 28.2wt%, 28.6wt%, 29.1wt%, 29.6wt% or 29.9wt%, with a Dy content of 3.0%.

[0047] In this application, A is selected from Cu, Ga, and Al, and the content of Cu is 0.30~0.55wt%, the content of Ga is 0.25~0.45wt%, and the content of Al is 0.02~0.5wt%; specifically, the content of Cu is 0.35wt%~0.5wt%, the content of Ga is 0.30wt%~0.45wt%, and the content of Al is 0.02wt%~0.3wt%; more specifically, the content of Cu is 0.35wt%, 0.36wt%, 0.37wt%, 0.38wt%, 0.39wt%, 0.40wt%, 0.41wt%, 0.42wt%, 0.44wt%, or 0.45wt%; and the content of Ga is 0.26wt%, 0.28wt%, or 0.28wt%. The content of Al is 0.03wt%, 0.30wt%, 0.31wt%, 0.32wt%, 0.35wt%, 0.36wt%, 0.38wt%, 0.39wt%, 0.40wt%, 0.41wt%, 0.42wt%, 0.43wt%, 0.44wt%, or 0.45wt%; the content of Al is 0.03wt%, 0.05wt%, 0.08wt%, 0.10wt%, 0.12wt%, 0.13wt%, 0.14wt%, 0.16wt%, 0.17wt%, 0.19wt%, 0.20wt%, 0.21wt%, 0.24wt%, 0.25wt%, 0.26wt%, 0.28wt%, 0.29wt%, or 0.30wt%. Elements in Al can form MA alloy phases, optimize grain boundaries, wet grain boundaries, and significantly improve coercivity Hcj while keeping remanence Br constant.

[0048] In this application, the content of M is 0.2~0.8 wt%, specifically selected from one or more of Ti, Zr, and Nb, and 1.5 < A / M < 6; more specifically, when M is selected only from Ti, the content of Ti is 0.2 wt%~0.35 wt%; and 3

[0049] ​When M is selected solely from Zr, the Zr content is 0.35 wt%~0.75%; and 1.5

[0050] When M is selected solely from Nb, the Nb content is 0.35 wt% to 0.75 wt%; and 1.5

[0051] ​​When M is selected from two or three of Ti, Zr, and Nb, M' = Ti*2 + Zr + Nb, and M' is 0.4wt%~0.8wt%; and 1.5

[0052] T is selected from Fe and Co, wherein the content of Co is 0 to 1.0 wt%, more specifically, the content of Co is 0 to 0.8 wt%.

[0053] Furthermore, this application also provides a method for preparing sintered NdFeB magnets, including the following steps:

[0054] A) The raw materials for NdFeB sintered magnets are mixed according to the specified ratio and then subjected to rapid solidification sheet treatment to obtain NdFeB rapid solidification sheets;

[0055] B) The NdFeB rapid solidification flakes were sequentially subjected to hydrogen crushing and air jet milling to obtain NdFeB powder;

[0056] C) The neodymium iron boron powder is sequentially oriented and sintered to obtain a sintered neodymium iron boron magnet.

[0057] In the above steps of this invention, the selection principles and preferred ranges of NdFeB raw materials, unless otherwise specified, correspond to the selection principles and preferred ranges of NdFeB raw materials, and will not be repeated here.

[0058] This invention first processes neodymium iron boron raw materials through a rapid solidification thin-film process to obtain neodymium iron boron rapid solidification thin films.

[0059] The present invention does not impose any particular restrictions on the source of the neodymium iron boron raw material. Any conventional magnet raw material source known to those skilled in the art is acceptable. Those skilled in the art can select and adjust the source based on actual production conditions, product requirements, and quality control factors.​

[0060] This invention does not impose any particular limitation on the specific steps of the rapid solidification sheet process. The rapid solidification sheet process of sintered NdFeB magnets, which is well-known to those skilled in the art, can be used. Those skilled in the art can select and adjust the steps according to actual production conditions, product requirements, and quality control factors. The preferred temperature for the rapid solidification sheet process is 1450~1490℃, more preferably 1455~1485℃, even more preferably 1460~1480℃, and even more preferably 1465~1475℃. The preferred thickness of the NdFeB rapid solidification sheet is 0.10~0.60 mm, more preferably 0.20~0.50 mm, and even more preferably 0.25~0.35 mm.

[0061] The present invention then sequentially subjects the NdFeB rapid solidification flakes obtained in the above steps to hydrogen crushing and air jet milling to obtain NdFeB powder. The present invention does not particularly limit the specific steps of the hydrogen crushing process; any steps of the hydrogen crushing process in the preparation of sintered NdFeB magnets well known to those skilled in the art are acceptable. In the hydrogen crushing process of the present invention, the hydrogen absorption time is preferably 1-3 h, more preferably 1.2-2.8 h, and even more preferably 1.5-2.5 h; the hydrogen absorption temperature is preferably 20-300 °C, more preferably 70-250 °C, and even more preferably 120-200 °C; the hydrogen removal time is preferably 3-7 h, more preferably 3.5-6.5 h, and even more preferably 4-5 h; the hydrogen removal temperature is preferably 550-600 °C, more preferably 560-590 °C, and even more preferably 570-580 °C.

[0062] The hydrogen crushing process described in this invention preferably includes a water cooling step. The water cooling time is preferably 1~3 hours, more preferably 1.2~2.8 hours, and even more preferably 1.5~2.5 hours.

[0063] To further improve the grinding effect of the air jet mill, it is more preferable to add a lubricant during the air jet milling process. The present invention does not impose any particular limitation on the lubricant; any magnetic air jet mill lubricant well-known to those skilled in the art is acceptable. The lubricant in the present invention preferably accounts for 0.02% to 0.1% of the mass of the mixed fine powder, more preferably 0.03% to 0.09%, and even more preferably 0.05% to 0.08%.

[0064] The average particle size after grinding, i.e. the average particle size of the mixed fine powder, is preferably 2~5μm, more preferably 2.5~4.5μm, and even more preferably 3~4μm.

[0065] Finally, the neodymium iron boron powder obtained in the above steps is sequentially oriented and sintered to obtain a neodymium iron boron magnet. The present invention does not particularly limit the specific steps of the orientation forming; any specific steps of magnet orientation forming well-known to those skilled in the art can be used. Those skilled in the art can select and adjust the steps according to actual production conditions, product requirements, and quality requirements. The orientation forming described in the present invention preferably includes orientation pressing and isostatic pressing steps, and more preferably, magnetic field orientation forming is carried out in a sealed oxygen-free or low-oxygen glove box, ensuring that the product is oxygen-free or low-oxygen throughout the entire operation and isostatic pressing process.

[0066] The magnetic field strength for orientation pressing in this invention is preferably 1.2~3T, more preferably 1.7~2.5T, and even more preferably 1.6~2.4T; the orientation pressing time is preferably 2~10s, more preferably 3~9s, and even more preferably 5~7s. The isostatic pressing pressure is preferably 120~240MPa, more preferably 150~210MPa, and even more preferably 160~200MPa; the isostatic pressing holding time is preferably 30~120s, more preferably 50~100s, and even more preferably 70~80s. To further ensure and improve the performance of the final magnet product, the density of the magnet blank after orientation pressing is preferably 3.8~4.3g / cm³. 3 More preferably, it is 3.9~4.2 g / cm³. 3 More preferably, it is 4.0~4.1 g / cm³. 3 The density of the magnet blank after isostatic pressing is preferably 4.5~5.0 g / cm³. 3 More preferably, it is 4.6~4.9 g / cm³. 3 More preferably, it is 4.7~4.8 g / cm³. 3 .

[0067] Finally, the magnet blank obtained by the above steps is sintered. The present invention does not have any particular limitation on the specific steps of sintering, and any specific steps of magnet sintering known to those skilled in the art can be used. The sintering of the present invention is preferably vacuum sintering. The sintering process preferably includes an aging treatment step. The aging treatment more preferably includes a first aging treatment and a second aging treatment.

[0068] The sintering temperature of this invention is preferably 1000~1200℃, more preferably 1025~1175℃, even more preferably 1040~1150℃, and even more preferably 1050~1080℃; the sintering time is preferably 5~15h, more preferably 7~13h, and even more preferably 8~10h. The vacuum bag used for sintering in this invention is preferably less than or equal to 0.02Pa, more preferably less than or equal to 0.015Pa, and even more preferably less than or equal to 0.01Pa. To further ensure and improve the performance of the final magnet product, the density of the sintered magnet blank is preferably 7.4~7.7 g / cm³. 3 More preferably, it is 7.45~7.65 g / cm³. 3 More preferably, it is 7.5~7.6 g / cm³. 3 .

[0069] The present invention does not particularly limit the specific steps of the aging treatment; any specific steps of magnet aging treatment known to those skilled in the art will suffice. The preferred temperature for the first aging treatment is 800-980℃, more preferably 820-960℃; the preferred duration of the first aging treatment is 1-10 hours, more preferably 2-8 hours. The preferred temperature for the second aging treatment is 420-580℃, more preferably 440-560℃; the preferred duration of the second aging treatment is 1-8 hours, more preferably 2-7 hours.

[0070] The present invention does not impose any particular limitation on the overall preparation process of the above-mentioned magnets. The sintered NdFeB magnet preparation process known to those skilled in the art can be used. That is, the blank after the raw materials have gone through the steps of batching, rapid solidification thin sheet process (melting), hydrogen crushing and powdering, powder orientation pressing and molding, and vacuum sintering, and then after surface treatment and processing, it can be used as a finished NdFeB magnet.

[0071] The neodymium iron boron magnet and its preparation method provided by this invention can not only produce neodymium iron boron magnetic materials with high performance, but also improve the remanence, coercivity and magnetic energy product of the magnet alloy without increasing heavy rare earth elements, thereby reducing production costs. Moreover, the process is simple, widely applicable, and suitable for large-scale industrial production.

[0072] Experimental results show that, compared with the same type of neodymium iron boron magnet, the coercivity of the neodymium iron boron magnet provided by this invention is increased by more than 1.3 kOe without reducing the remanence.

[0073] To further understand the present invention, the sintered NdFeB magnet and its preparation method provided by the present invention will be described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0074] Table 1. Raw material formulation data (wt%) for the embodiments.

[0075]

[0076] Note: When M in the table is selected from two or three of Ti, Zr and Nb, A / M represents A / M'.

[0077] Example 1

[0078] The raw materials were prepared according to Example 1 shown in Table 1, and then melted in a vacuum induction melting furnace. The resulting melt was cast at 1460°C and cooled on a copper roller at a speed of 40 rpm to obtain a NdFeB alloy casting with an average thickness of 0.30 mm. The casting was then subjected to hydrogen crushing, with a hydrogen absorption time of 1 hour, a dehydrogenation time of 5 hours, a dehydrogenation temperature of 600°C, and a cooling time of 2 hours. The resulting powder was then subjected to air jet milling to obtain a powder with a particle size of 3.4 μm. The powder was then subjected to magnetic orientation forming in a sealed oxygen-free glove box under a magnetic field of 17320 Gauss, and then subjected to isostatic pressing at 200 MPa to obtain a magnet blank. The magnet blank was sintered at 1070°C for 6 hours, then aged at 910°C for 2 hours, and finally aged at 525°C for 5 hours to obtain a NdFeB magnet.

[0079] Comparative Example 1a and Comparative Example 1b were prepared using the same steps.

[0080] Parallel tests were conducted to compare the neodymium iron boron magnets prepared by the above method of the present invention with the neodymium iron boron magnets prepared in Comparative Example 1. The comparison results are shown in Table 2, which is a performance data table of the magnets prepared in the examples and the comparative examples.

[0081] Table 2 Performance data of magnets prepared in the examples and comparative examples

[0082]

[0083] As shown in Tables 1 and 2, in Example 1 and Comparative Example 1a, Ti is the same, but A / M is less than the range, and the coercivity differs by 1.6 kOe; compared with Example 1b, A / M is within the range, but Ti is less than the range, and the coercivity differs by 2.20 kOe.

[0084] Example 2

[0085] The raw materials were prepared according to Example 2 shown in Table 1. The raw materials were melted in a vacuum induction melting furnace. The resulting melt was cast at 1465°C and cooled on a copper roller at a speed of 40 rpm to obtain a NdFeB alloy casting with an average thickness of 0.28 mm. The casting was subjected to hydrogen crushing, with a hydrogen absorption time of 1 hour, a dehydrogenation time of 5 hours, a dehydrogenation temperature of 600°C, and a cooling time of 2 hours. The resulting powder was subjected to air jet milling to obtain a powder with a particle size of 3.4 micrometers. The powder was subjected to magnetic orientation forming treatment in a sealed oxygen-free glove box under a magnetic field of 17500 Gauss, and then subjected to isostatic pressing at 200 MPa to obtain a magnet blank. The magnet blank was sintered at 1070°C for 6 hours, then aged at 910°C for 2 hours, and finally aged at 525°C for 5 hours to obtain a NdFeB magnet.

[0086] Comparative Example 2 was prepared using the same steps.

[0087] Parallel tests were conducted to compare the neodymium iron boron magnets prepared by the above method of the present invention with ordinary neodymium iron boron magnets. The comparison results are shown in Table 3. Table 3 is a data table of magnet performance prepared in the examples and comparative examples.

[0088] Table 3. Performance data of magnets prepared in the examples and comparative examples.

[0089]

[0090] As shown in Tables 1 and 3, in Example 2 and Comparative Example 2a, A / M is greater than the range and M is not within the range, with a difference of 2.6 kOe in coercivity.

[0091] Example 3

[0092] The raw materials were prepared according to Example 3 shown in Table 1, and then melted in a vacuum induction melting furnace. The resulting melt was cast at 1468°C and cooled on a copper roller at a speed of 40 rpm to obtain a NdFeB alloy casting with an average thickness of 0.32 mm. The casting was then subjected to hydrogen crushing, with a hydrogen absorption time of 1 hour, a dehydrogenation time of 5 hours, a dehydrogenation temperature of 600°C, and a cooling time of 2 hours. The resulting powder was then subjected to air jet milling to obtain a powder with a particle size of 3.4 micrometers. The powder was then subjected to magnetic orientation forming in a sealed oxygen-free glove box under a magnetic field of 17560 Gauss, followed by isostatic pressing at 200 MPa to obtain a magnet blank. The magnet blank was then sintered at 1070°C for 6 hours, followed by aging treatment at 910°C for 2 hours, and finally aging treatment at 525°C for 5 hours to obtain a NdFeB magnet.

[0093] Comparative Example 3 was prepared using the same steps.

[0094] Parallel tests were conducted to compare the neodymium iron boron magnets prepared by the above method of the present invention with ordinary neodymium iron boron magnets. The comparison results are shown in Table 4. Table 4 is a data table of magnet performance of the examples and comparative examples.

[0095] Table 4. Performance data of magnets prepared in the examples and comparative examples.

[0096]

[0097] As shown in Tables 1 and 4, M is within the range in Example 3 and Comparative Example 3, but A / M is out of range, and the coercivity differs by 0.8 kOe.

[0098] Example 4

[0099] The raw materials were prepared according to Example 4 shown in Table 1. The raw materials were melted in a vacuum induction melting furnace, and the resulting melt was cast at 1458°C and cooled on a copper roller at 40 rpm to obtain a NdFeB alloy casting with an average thickness of 0.29 mm. The casting was then subjected to hydrogen breakage, with a hydrogen absorption time of 1 hour, a dehydrogenation time of 5 hours, a dehydrogenation temperature of 600°C, and a cooling time of 2 hours. The resulting powder was then subjected to air jet milling to obtain a powder with a particle size of 3.4 micrometers. The powder was then subjected to magnetic orientation forming in a sealed, oxygen-free glove box under a magnetic field of 17700 Gauss, followed by isostatic pressing at 200 MPa to obtain a magnet blank. The magnet blank was sintered at 1070°C for 6 hours, then aged at 910°C for 2 hours, and finally aged at 525°C for 5 hours to obtain a NdFeB magnet. Comparative Example 4 was prepared using the same steps.

[0100] Parallel tests were conducted to compare the neodymium iron boron magnets prepared by the above method of the present invention with ordinary neodymium iron boron magnets. The comparison results are shown in Table 5. Table 5 is a table of magnet performance data prepared by the examples and comparative examples.

[0101] Table 5. Performance data of magnets prepared in the examples and comparative examples.

[0102]

[0103] As shown in Tables 1 and 5, in Example 4 and Comparative Example 4, M is out of range, A / M is within range, the remanence differs by 0.11 kGs, and the coercivity differs by 0.6 kOe.

[0104] Example 5

[0105] The raw materials were prepared according to Example 5 shown in Table 6, and then melted in a vacuum induction melting furnace. The resulting melt was cast at 1458°C and cooled on a copper roller at a speed of 40 rpm to obtain a NdFeB alloy casting with an average thickness of 0.29 mm. The casting was then subjected to hydrogen crushing, with a hydrogen absorption time of 1 hour, a dehydrogenation time of 5 hours, a dehydrogenation temperature of 600°C, and a cooling time of 2 hours. The resulting powder was then subjected to air jet milling to obtain a powder with a particle size of 3.4 micrometers. The powder was then subjected to magnetic orientation forming in a sealed oxygen-free glove box under a magnetic field of 17700 Gauss, followed by isostatic pressing at 200 MPa to obtain a magnet blank. The magnet blank was then sintered at 1070°C for 6 hours, followed by aging treatment at 910°C for 2 hours, and finally aging treatment at 525°C for 5 hours to obtain a NdFeB magnet.

[0106] Comparative Example 5 was prepared using the same steps.

[0107] Parallel tests were conducted to compare the neodymium iron boron magnets prepared by the above method of the present invention with ordinary neodymium iron boron magnets. The comparison results are shown in Table 6. Table 6 is a data table of magnet performance of the examples and comparative examples.

[0108] Table 6. Performance data of magnets prepared in the examples and comparative examples.

[0109]

[0110] As shown in Tables 1 and 6, in Example 5 and Comparative Example 5, A / M' is within the range, but M' is not within the range. The remanence differs by 0.31 kGs, and the coercivity differs by 0.4 kOe.

[0111] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0112] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sintered NdFeB magnet as shown in Formula (I); R x T 100-x-y1-y2-z M y1 A y2 B z (I); in, x, y1, y2, and z represent the mass percentages of the corresponding elements, with 28.5wt%≤x≤32.0wt%, 0.2wt%≤y1≤0.8wt%, 0.60wt%≤y2≤1.5wt%, and 0.88wt%≤z≤0.94wt%. R is selected from one or more rare earth elements and must contain Nd; A is selected from Cu, Ga, and Al, with Cu content ranging from 0.30 to 0.55 wt%, Ga content ranging from 0.25 to 0.45 wt%, and Al content ranging from 0.02 to 0.5 wt%. T is selected from Fe and Co, with Co content ranging from 0 to 1.0 wt% and the balance being Fe; M is selected from two or three of Ti, Zr and Nb, M = Ti*2 + Zr + Nb, M is 0.4wt%~0.8wt%, and Ti + Zr + Nb > 0.2wt%; and the rare earth element mentioned in 1.5 is selected from one or more of Pr, Dy, Tb, Gd, La and Ce, wherein the content of Pr is 0~14.5wt%, the content of Nd is 10wt%~32wt%, the content of Dy + Tb is 0~4.5wt%, the content of Gd is 0~4.5wt%, and the content of La + Ce is 0~15wt%.

2. The sintered NdFeB magnet according to claim 1, characterized in that, The content of Pr is 7wt%~9wt%, the content of Nd is 20wt%~25.5wt%, and the content of Dy is 0~3wt%.

3. The sintered NdFeB magnet according to claim 2, characterized in that, The Cu content is 0.35wt%~0.5wt%, the Ga content is 0.30wt%~0.45wt%, and the Al content is 0.02wt%~0.3wt%.

4. The sintered NdFeB magnet according to claim 1, characterized in that, The content of Co is 0~0.8wt%, and the content of B is 0.90wt%~0.94wt%.

5. The sintered NdFeB magnet according to claim 1, characterized in that, 6. A method for preparing the sintered NdFeB magnet according to any one of claims 1 to 5, comprising the following steps: A) The raw materials for NdFeB sintered magnets are mixed according to the specified ratio and then subjected to rapid solidification sheet treatment to obtain NdFeB rapid solidification sheets; B) The NdFeB rapid solidification flakes were sequentially subjected to hydrogen crushing and air jet milling to obtain NdFeB powder; C) The neodymium iron boron powder is sequentially oriented and sintered to obtain a sintered neodymium iron boron magnet. The temperature for processing the rapidly solidifying sheet is 1400~1500℃, and the thickness of the neodymium iron boron rapidly solidifying sheet is 0.10~0.60mm; 7. The preparation method according to claim 6, characterized in that, During the hydrogen crushing process, the hydrogen absorption time is 1-3 hours, the hydrogen absorption temperature is 20-300℃, the hydrogen dehydrogenation time is 3-7 hours, and the hydrogen dehydrogenation temperature is 550-600℃. During the air jet milling process, a lubricant is added for grinding. The lubricant is 0.02~0.1% of the mass of the mixed fine powder obtained by hydrogen crushing. The average particle size of the powder after air jet milling is 2~6μm. The orientation forming includes sequential orientation pressing and isostatic pressing; the magnetic field strength of the orientation forming is 1.2~3T.

8. The preparation method according to claim 6, characterized in that, The sintering temperature is 1000~1200℃, the time is 5~15h, and the vacuum degree is less than or equal to 0.02Pa; 9. The preparation method according to claim 6, characterized in that, ​ The sintering process further includes an aging treatment, which includes a first aging treatment and a second aging treatment. The temperature of the first aging treatment is 800~980℃, and the time of the first aging treatment is 1~10 hours; The temperature of the second aging treatment is 420~580℃, and the time of the second aging treatment is 1~8 hours.

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