ThMn12 type rare earth permanent magnet and preparation method thereof

Abstract

The invention discloses a ThMn12 type rare earth permanent magnet and a preparation method thereof. The preparation method comprises the following steps: uniformly mixing raw materials containing Sm, Fe, Ti, V, Al and Cu, smelting to obtain an alloy ingot, and then sequentially carrying out homogenizing annealing heat treatment, hydrogen demolishing and jet milling on the alloy ingot to obtain alloy powder; the alloy powder is subjected to orientation forming and presintering, and a permanent magnet blank is obtained; performing hot pressing treatment on the permanent magnet blank in an inert atmosphere to obtain a compact magnet; and performing high-temperature tempering on the compact magnet to obtain the ThMn12 type rare earth permanent magnet. According to the preparation method, through a pre-sintering-hot pressing-tempering synergistic process, the prepared ThMn12 type rare earth permanent magnet has high density, a stable 1: 12 phase structure and excellent magnetic performance.

Description

Technical Field

[0001] This invention belongs to the field of rare earth permanent magnet materials technology, specifically relating to a ThMn... 12 Rare earth permanent magnets and their preparation methods. Background Technology

[0002] In the field of rare-earth permanent magnet materials, third-generation rare-earth permanent magnets, represented by neodymium iron boron (NdFeB), possess extremely high theoretical maximum energy product and exhibit excellent magnetic properties at room temperature. However, their coercivity significantly decreases under high-temperature service conditions. To maintain their high-temperature magnetic properties, expensive and scarce heavy rare-earth elements, such as dysprosium (Dy) and terbium (Tb), are typically added to the material, significantly increasing material costs. Furthermore, after decades of development and optimization, the performance of NdFeB permanent magnets has gradually approached its theoretical limit, and further breakthroughs face technological bottlenecks. Therefore, developing a new type of permanent magnet material that combines high coercivity and high maximum energy product while reducing dependence on heavy rare-earth elements has become a pursuit goal for the permanent magnet industry towards high performance, low cost, and high stability. This is of great significance for meeting the application needs of electric vehicles, wind power generation, and high-end industrial motors under complex high-temperature conditions.

[0003] ThMn 12 Rare earth permanent magnets have attracted widespread attention due to their excellent theoretical magnetic properties and significantly lower rare earth content compared to neodymium iron boron. However, they face many challenges in the preparation of bulk magnets for practical applications: (1) During alloying and solidification, a large amount of impurity phases such as α-Fe are easily precipitated, leading to ThMn 12 The purity of the main phase decreases, causing ThMn 12 (1) The high theoretical anisotropy of the main phase has not been fully utilized, resulting in a fundamental bottleneck in improving actual coercivity; (2) It is difficult to obtain a block magnet with high density and ideal grain boundary structure by using traditional sintering process, resulting in the actual maximum magnetic energy product being far lower than the theoretical value, which limits its application as a high-performance permanent magnet material.

[0004] Currently, existing technologies such as CN112103022A have been developed to enhance the coercivity of magnets by inducing nonmagnetic grain boundary phases through composition design, suppressing α-Fe phase precipitation by obtaining amorphous precursors through melt quenching technology, obtaining isotropic bulk magnets through hot pressing technology, and inducing magnet anisotropy through hot deformation processes, ultimately obtaining anisotropic ThMn magnets. 12 Rare earth permanent magnets. However, the core technology lies in relying on rapid quenching to achieve microstructure refinement and phase control. In the ingot casting stage, there are still impurities such as α-Fe. Overall, it belongs to the typical technical route of "rapid quenching strip + hot pressing + hot deformation". However, it has many problems such as being unable to achieve large-scale stable production in industry, having stringent requirements for equipment and molds, and poor uniformity. Ultimately, the magnetic performance level is also limited. Summary of the Invention

[0005] The main object of the present invention is to provide a ThMn 12 type rare earth permanent magnet and its preparation method to overcome the defects of the prior art.

[0006] To achieve the foregoing invention object, the technical solutions adopted by the present invention include:

[0007] The first aspect of the present invention provides a preparation method for a ThMn 12 type rare earth permanent magnet, which includes:

[0008] Mixing the raw materials containing Sm, Fe, Ti, V, Al and Cu evenly, melting to obtain an alloy ingot, and then successively performing homogenization annealing heat treatment, hydrogen breaking, and airflow milling on the alloy ingot to obtain alloy powder;

[0009] Performing orientation forming and pre-sintering on the alloy powder to obtain a permanent magnet blank;

[0010] Performing hot pressing treatment on the permanent magnet blank in an inert atmosphere to obtain a dense magnet;

[0011] Performing high-temperature tempering on the dense magnet to obtain a ThMn 12 type rare earth permanent magnet.

[0012] The second aspect of the present invention provides a ThMn 12 type rare earth permanent magnet prepared by the above preparation method, whose composition is Sm x Fe bal Ti8V8Al2Cu 0.5 , where, in atomic percentage, 7% < x < 13%, Ti 8%, V 8%, Al 2%, Cu 0.5%, and the balance is Fe.

[0013] Compared with the prior art, the present invention has at least the following beneficial effects:

[0014] (1) The present invention prepares a highly densified magnet through precise composition design and a multi-step collaborative process including homogenization heat treatment, hot pressing densification, and grain boundary phase regulation tempering, significantly improving the remanence, constructing a non-magnetic grain boundary phase with good magnetic isolation effect, effectively enhancing the coercivity, and finally obtaining a permanent magnet with excellent comprehensive performance of both high coercivity and high maximum magnetic energy product.

[0015] (2) This invention adopts a powder metallurgy technology route, employing a process route of smelting-homogenization heat treatment (precursor design)-hydrogenation-airflow milling-orientation forming-isostatic pressing-pre-sintering-hot pressing-tempering. Anisotropic bulk magnets are obtained through the synergistic process of pre-sintering-hot pressing-tempering. Pre-sintering is used to construct a stable 1:12 main phase and microstructure. The hot pressing stage achieves high densification and texture strengthening. Furthermore, the pre-sintering stage provides initial construction of phase composition and grain boundary states, while tempering further optimizes the grain boundary structure and magnetic exchange coupling, making it more suitable for mass production and industrial applications. Simultaneously, this process route can form a more uniform and continuous microstructure and optimized grain boundary distribution, achieving effective control of unfavorable phases such as α-Fe during the ingot casting stage, resulting in a superior microstructure and ultimately, anisotropic magnets with excellent magnetic properties. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is Sm in Embodiment 1 of the present invention. 8.8 Fe bal Ti8V8Al2Cu 0.5 Backscatter scanning electron microscope image of the ingot;

[0018] Figure 2 This is Sm in Embodiment 7 of the present invention. 11.2 Fe bal Ti8V8Al2Cu 0.5 Backscatter scanning electron microscope image of the ingot;

[0019] Figure 3 This is Sm in Embodiment 1 of the present invention. 8.8 Fe bal Ti8V8Al2Cu 0.5 Backscatter scanning electron microscope image after heat treatment at 1140℃ for 20 hours;

[0020] Figure 4 This is Sm in Embodiment 1 of the present invention. 8.8 Fe bal Ti8V8Al2Cu 0.5 Elemental distribution diagram after heat treatment at 1140℃ for 20 hours;

[0021] Figure 5 This is Sm in Embodiment 7 of the present invention. 11.2 Fe balTi8V8Al2Cu 0.5 Backscatter scanning electron microscope image after heat treatment at 1140℃ for 20 hours;

[0022] Figure 6 This is Sm in Embodiment 7 of the present invention. 11.2 Fe bal Ti8V8Al2Cu 0.5 Elemental distribution diagram after heat treatment at 1140℃ for 20 hours;

[0023] Figure 7 This is Sm in Embodiment 1 of the present invention. 8.8 Fe bal Ti8V8Al2Cu 0.5 Backscattering scanning electron microscope image of a tempered magnet;

[0024] Figure 8 This is Sm in Embodiment 7 of the present invention. 11.2 Fe bal Ti8V8Al2Cu 0.5 Backscatter scanning electron microscope image of a tempered magnet. Detailed Implementation

[0025] In view of the problems existing in the prior art, the inventors of this invention have conducted extensive and in-depth research and have provided a ThMn 12 A rare-earth permanent magnet and its preparation method are disclosed. The permanent magnet possesses both high coercivity and high maximum energy product. The technical solution of this invention will be further explained below.

[0026] The first aspect of the present invention provides a ThMn 12 The preparation methods of rare earth permanent magnets include:

[0027] Raw materials containing Sm, Fe, Ti, V, Al and Cu are mixed evenly and smelted to obtain an alloy ingot. The alloy ingot is then subjected to homogenization annealing heat treatment, hydrogen annealing and air jet milling in sequence to obtain alloy powder.

[0028] The alloy powder is oriented and pre-sintered to obtain a permanent magnet blank.

[0029] The permanent magnet blank is hot-pressed under an inert atmosphere to obtain a dense magnet;

[0030] The dense magnet was subjected to high-temperature tempering to obtain ThMn. 12 Rare earth permanent magnets.

[0031] In some embodiments, the proportions of the raw materials, expressed as atomic percentages, are: Sm 7~13 at.%, Ti 8 at.%, V 8 at.%, Al 2 at.%, Cu 0.5 at.%, with the balance being Fe.

[0032] In some embodiments, the preparation method specifically includes: subjecting the alloy ingot to homogenization annealing heat treatment at 900~1300℃ for 10~30h under an inert atmosphere.

[0033] Furthermore, the homogenization annealing heat treatment is carried out at a temperature of 1000~1200℃ for 15~25h.

[0034] Furthermore, the inert atmosphere includes, but is not limited to, argon.

[0035] In some embodiments, the hydrogen rupture is performed at room temperature and the hydrogen pressure is 0.1~0.2 MPa.

[0036] In some embodiments, the airflow velocity in the nozzle of the air mill is 300~500m / s, the pressure in the grinding chamber is 0.4~0.8MPa, and the speed of the classifying wheel is 80~120m / s.

[0037] In some embodiments, the average grain size of the alloy powder is 2.5 to 4 μm.

[0038] In some embodiments, the preparation method specifically includes: first, magnetically oriented molding of the alloy powder to obtain an oriented low-density blank, then cold isostatic pressing, and then pre-sintering at 1000~1200℃ for 1~5h to obtain the permanent magnet blank.

[0039] Furthermore, the magnetic field for the magnetic orientation shaping is 2~4T, and the time is 20~40s.

[0040] Furthermore, the density of the low-density embryo is 3.5~4.5 g / cm³. 3 .

[0041] Furthermore, the pressure of the cold isostatic pressing is 150~200MPa, and the time is 30~90s.

[0042] In some embodiments, the hot pressing treatment is performed at a temperature of 1000~1200℃, a pressing pressure of 50~150kN, and a time of 2~4min.

[0043] In some embodiments, the preparation method specifically includes: subjecting the dense magnet to high-temperature tempering at 1000~1200℃ for 1~5 hours to obtain ThMn magnets possessing both high coercivity and high maximum energy product. 12 Rare earth permanent magnets.

[0044] In some embodiments, the preparation method further includes: placing coarse Sm metal powder with a thickness of 0.01~1mm during the high-temperature tempering in a sealed environment, and then isolating the dense magnet with molybdenum foil.

[0045] In some more specific embodiments, the preparation method specifically includes the following steps:

[0046] (1) The raw materials are mixed according to the atomic percentage composition of Sm 7~13 at.%, Ti 8 at.%, V 8 at.%, Al 2 at.%, Cu 0.5 at.%, with the balance being Fe. The mixture is smelted under inert gas protection. After the raw materials are completely melted, the alloy ingot is cast.

[0047] (2) The alloy ingot is subjected to homogenization annealing heat treatment at 900~1300℃ for 10~30h under inert atmosphere protection and then cooled in the furnace. The annealed ingot is coarsely crushed into small pieces, and then hydrogen-crushed at room temperature and hydrogen pressure of 0.1~0.2MPa. Alloy powder is obtained by air jet milling process; wherein, the nozzle airflow velocity in air jet milling process is 300~500m / s, the crushing chamber pressure is 0.4~0.8MPa, and the speed of the classifying wheel is 80~120m / s.

[0048] (3) The above alloy powder is subjected to a two-step pressing process. First, it is oriented and pressed under a magnetic field strength of 2~4T for 20~40s to obtain 3.5~4.5 g / cm³. 3 The low-density blank with orientation is then subjected to cold isostatic pressing at 150~200MPa for 30~90s to further increase the density, and then pre-sintered at 1000~1200℃ for 1~5h to obtain the permanent magnet blank.

[0049] (4) Place the above permanent magnet blank into a hot press furnace, press it at a high temperature of 50~150kN and 1000~1200℃ for 2~4 minutes under an inert atmosphere to obtain a dense magnet.

[0050] (5) Place the above-mentioned dense magnet in a vacuum sintering furnace and temper it at 1000~1200℃ for 1~5 hours. During tempering, place a layer of coarse Sm powder with a thickness of 0.01-1mm in a sealed alumina crucible, and then isolate the magnet with molybdenum foil to reduce the volatilization of Sm during the tempering process, thereby obtaining ThMn magnets with excellent coercivity and maximum energy product. 12 Rare earth permanent magnets.

[0051] In the present invention, a powder metallurgy technical route is adopted to directly obtain an anisotropic bulk magnet through a synergistic process of presintering - hot pressing - tempering. Among them, presintering is used to construct a stable 1:12 main phase and tissue basis, the hot pressing stage realizes high densification and texture strengthening, through precursor design and the preliminary construction of phase composition and grain boundary state in the presintering stage, as well as the tempering treatment of grain boundary structure and magnetic exchange coupling, the synergistic optimization of magnetic properties is achieved, which is more suitable for mass production and industrial application. At the same time, this process route can form a more uniform and continuous microstructure and optimized grain boundary distribution, effectively control adverse phases such as α-Fe at the ingot stage, obtain a better organizational structure, and finally the anisotropic magnet has excellent magnetic properties.

[0052] Moreover, in the present invention, during the ingot heat treatment stage, the formation of the 1:12 main phase is promoted and the content of adverse phases is reduced by controlling the diffusion behavior and phase stability. A better grain boundary structure is obtained in the presintering stage, the densification of the magnet is achieved in a short time in the hot pressing stage, and the tempering treatment further optimizes the grain boundary structure. There is a significant synergistic effect between the above steps.

[0053] The second aspect of the present invention provides a ThMn 12 -type rare earth permanent magnet prepared by the described preparation method, whose composition is Sm x Fe bal Ti8V8Al2Cu 0.5 , where, in atomic percentage, 7% < x < 13%, Ti is 8%, V is 8%, Al is 2%, Cu is 0.5%, and the balance is Fe.

[0054] In some embodiments, the coercivity of the ThMn 12 -type rare earth permanent magnet is above 7 kOe, and the maximum magnetic energy product is above 5 MGOe.

[0055] The technical solution, its implementation process, principle, etc. will be further explained as follows.

[0056] For those not specifying specific experimental steps or conditions in the examples, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For those reagents or instruments not specifying the manufacturer, they can all be obtained through commercial purchase. The remaining raw materials not mentioned and the commercial purchase selection of instruments are all conventional selections and do not involve the core technical means of the present invention.

[0057] Example 1

[0058] The composition of the ThMn 12 -type rare earth permanent magnet material is: Sm 8.8 Fe bal Ti8V8Al2Cu 0.5 , and the preparation method is:

[0059] (1) Smelting: The surface of the raw materials is mechanically polished to remove the oxide layer and unnecessary impurities, and then mixed according to the atomic percentage ratio. The prepared raw materials are placed in a crucible and smelted in a vacuum melting furnace under the protection of argon atmosphere. The resulting ingot is then cast and cooled to obtain a casting.

[0060] (2) Heat treatment: The ingot is placed in a vacuum sintering furnace and homogenized annealing heat treatment is carried out under the protection of argon atmosphere. The annealing process parameters are 1140℃ and held for 20h, and then cooled to room temperature to obtain annealed ingot.

[0061] (3) Powder making: The annealed ingot is subjected to hydrogen crushing and air jet milling processes. The hydrogen crushing temperature is room temperature and the hydrogen pressure is 160 MPa. The air jet milling nozzle air velocity is 400 m / s, the crushing chamber pressure is 0.65 MPa, and the classifying wheel speed is 100 m / s to obtain alloy powder with an average grain size of 2.5-4 μm.

[0062] (4) Sintering, hot pressing, and tempering process: The alloy powder is pressed into a compact under a magnetic field, and then isostatic pressing is used to further increase the compact density. The magnetic field for magnetic orientation forming is 2T, and the time is 30s. The density of the low-density compact is 4.2g / cm³. 3 The magnet was subjected to cold isostatic pressing at 160 MPa for 60 seconds, followed by sintering at 1100℃ for 2 hours under argon protection in a vacuum sintering furnace. The sintered magnet was then placed in a hot press furnace and subjected to high-temperature pressing at 1100℃ and 90 kN for 3 minutes to obtain a fully dense magnet. The fully dense magnet was then placed in a vacuum sintering furnace and tempered at 1100℃ for 2 hours under argon protection to obtain ThMn. 12 Rare earth permanent magnets.

[0063] Example 2

[0064] ThMn 12 The composition of rare earth permanent magnet materials is: Sm 9.2 Fe bal Ti8V8Al2Cu 0.5 The preparation method is as follows:

[0065] (1) Smelting: The surface of the raw materials is mechanically polished to remove the oxide layer and unnecessary impurities, and then mixed according to the atomic percentage ratio. The prepared raw materials are placed in a crucible and smelted in a vacuum melting furnace under the protection of argon atmosphere. The resulting ingot is then cast and cooled to obtain a casting.

[0066] (2) Heat treatment: The ingot is placed in a vacuum sintering furnace and homogenized annealing heat treatment is carried out under the protection of argon atmosphere. The annealing process parameters are 1140℃ and held for 20h, and then cooled to room temperature to obtain annealed ingot.

[0067] (3) Powdering: The annealed ingot is subjected to hydrogen crushing and air jet milling processes. The hydrogen crushing temperature is room temperature and the hydrogen pressure is 160 MPa. The air jet milling nozzle air velocity is 400 m / s, the crushing chamber pressure is 0.65 MPa, and the classifying wheel speed is 100 m / s to obtain alloy powder with an average grain size of 2.5-4 μm.

[0068] (4) Sintering, hot pressing, and tempering process: The alloy powder is pressed into a compact under a magnetic field, and then isostatic pressing is used to further increase the compact density. The magnetic field for magnetic orientation forming is 2T, and the time is 30s. The density of the low-density compact is 4.2g / cm³. 3 The magnet was subjected to cold isostatic pressing at 160 MPa for 60 seconds, followed by sintering at 1100℃ for 2 hours under argon protection in a vacuum sintering furnace. The sintered magnet was then placed in a hot press furnace and subjected to high-temperature pressing at 1100℃ and 90 kN for 3 minutes to obtain a fully dense magnet. The fully dense magnet was then placed in a vacuum sintering furnace and tempered at 1100℃ for 2 hours under argon protection to obtain ThMn. 12 Rare earth permanent magnets.

[0069] Example 3

[0070] ThMn 12 The composition of rare earth permanent magnet materials is: Sm 9.6 Fe bal Ti8V8Al2Cu 0.5 The preparation method is as follows:

[0071] (1) Smelting: The surface of the raw materials is mechanically polished to remove the oxide layer and unnecessary impurities, and then mixed according to the atomic percentage ratio. The prepared raw materials are placed in a crucible and smelted in a vacuum melting furnace under the protection of argon atmosphere. The resulting ingot is then cast and cooled to obtain a casting.

[0072] (2) Heat treatment: The ingot is placed in a vacuum sintering furnace and homogenized annealing heat treatment is carried out under the protection of argon atmosphere. The annealing process parameters are 1140℃ and held for 20h, and then cooled to room temperature to obtain annealed ingot.

[0073] (3) Powdering: The annealed ingot is subjected to hydrogen crushing and air jet milling processes. The hydrogen crushing temperature is room temperature and the hydrogen pressure is 160 MPa. The air jet milling nozzle air velocity is 400 m / s, the crushing chamber pressure is 0.65 MPa, and the classifying wheel speed is 100 m / s to obtain alloy powder with an average grain size of 2.5-4 μm.

[0074] (4) Sintering, hot pressing, and tempering process: The alloy powder is pressed into a compact under a magnetic field, and then isostatic pressing is used to further increase the compact density. The magnetic field for magnetic orientation forming is 2T, and the time is 30s. The density of the low-density compact is 4.2g / cm³. 3 The magnet was subjected to cold isostatic pressing at 160 MPa for 60 seconds, followed by sintering at 1100℃ for 2 hours under argon protection in a vacuum sintering furnace. The sintered magnet was then placed in a hot press furnace and subjected to high-temperature pressing at 1100℃ and 90 kN for 3 minutes to obtain a fully dense magnet. The fully dense magnet was then placed in a vacuum sintering furnace and tempered at 1100℃ for 2 hours under argon protection to obtain ThMn. 12 Rare earth permanent magnets.

[0075] Example 4

[0076] ThMn 12 The composition of rare earth permanent magnet materials is: Sm 10 Fe bal Ti8V8Al2Cu 0.5 The preparation method is as follows:

[0077] (1) Smelting: The surface of the raw materials is mechanically polished to remove the oxide layer and unnecessary impurities, and then mixed according to the atomic percentage ratio. The prepared raw materials are placed in a crucible and smelted in a vacuum melting furnace under the protection of argon atmosphere. The resulting ingot is then cast and cooled to obtain a casting.

[0078] (2) Heat treatment: The ingot is placed in a vacuum sintering furnace and homogenized annealing heat treatment is carried out under the protection of argon atmosphere. The annealing process parameters are 1140℃ and held for 20h, and then cooled to room temperature to obtain annealed ingot.

[0079] (3) Powder making: The annealed ingot is subjected to hydrogen crushing and air jet milling processes. The hydrogen crushing temperature is room temperature and the hydrogen pressure is 160 MPa. The air jet milling nozzle air velocity is 400 m / s, the crushing chamber pressure is 0.65 MPa, and the classifying wheel speed is 100 m / s to obtain alloy powder with an average grain size of 2.5-4 μm.

[0080] (4) Sintering, hot pressing, and tempering process: The alloy powder is pressed into a compact under a magnetic field, and then isostatic pressing is used to further increase the compact density. The magnetic field for magnetic orientation forming is 2T, and the time is 30s. The density of the low-density compact is 4.2g / cm³. 3The magnet was subjected to cold isostatic pressing at 160 MPa for 60 seconds, followed by sintering at 1100℃ for 2 hours under argon protection in a vacuum sintering furnace. The sintered magnet was then placed in a hot press furnace and subjected to high-temperature pressing at 1100℃ and 90 kN for 3 minutes to obtain a fully dense magnet. The fully dense magnet was then placed in a vacuum sintering furnace and tempered at 1100℃ for 2 hours under argon protection to obtain ThMn. 12 Rare earth permanent magnets.

[0081] Example 5

[0082] ThMn 12 The composition of rare earth permanent magnet materials is: Sm 10.4 Fe bal Ti8V8Al2Cu 0.5 The preparation method is as follows:

[0083] (1) Smelting: The surface of the raw materials is mechanically polished to remove the oxide layer and unnecessary impurities, and then mixed according to the atomic percentage ratio. The prepared raw materials are placed in a crucible and smelted in a vacuum melting furnace under the protection of argon atmosphere. The resulting ingot is then cast and cooled to obtain a casting.

[0084] (2) Heat treatment: The ingot is placed in a vacuum sintering furnace and homogenized annealing heat treatment is carried out under the protection of argon atmosphere. The annealing process parameters are 1140℃ and held for 20h, and then cooled to room temperature to obtain annealed ingot.

[0085] (3) Powdering: The annealed ingot is subjected to hydrogen crushing and air jet milling processes. The hydrogen crushing temperature is room temperature and the hydrogen pressure is 160 MPa. The air jet milling nozzle air velocity is 400 m / s, the crushing chamber pressure is 0.65 MPa, and the classifying wheel speed is 100 m / s to obtain alloy powder with an average grain size of 2.5-4 μm.

[0086] (4) Sintering, hot pressing, and tempering process: The alloy powder is pressed into a compact under a magnetic field, and then isostatic pressing is used to further increase the compact density. The magnetic field for magnetic orientation forming is 2T, and the time is 30s. The density of the low-density compact is 4.2g / cm³. 3 The magnet was subjected to cold isostatic pressing at 160 MPa for 60 seconds, followed by sintering at 1100℃ for 2 hours under argon protection in a vacuum sintering furnace. The sintered magnet was then placed in a hot press furnace and subjected to high-temperature pressing at 1100℃ and 90 kN for 3 minutes to obtain a fully dense magnet. The fully dense magnet was then placed in a vacuum sintering furnace and tempered at 1100℃ for 2 hours under argon protection to obtain ThMn. 12 Rare earth permanent magnets.

[0087] Example 6

[0088] ThMn12 The composition of rare earth permanent magnet materials is: Sm 10.8 Fe bal Ti8V8Al2Cu 0.5 The preparation method is as follows:

[0089] (1) Smelting: The surface of the raw materials is mechanically polished to remove the oxide layer and unnecessary impurities, and then mixed according to the atomic percentage ratio. The prepared raw materials are placed in a crucible and smelted in a vacuum melting furnace under the protection of argon atmosphere. The resulting ingot is then cast and cooled to obtain a casting.

[0090] (2) Heat treatment: The ingot is placed in a vacuum sintering furnace and homogenized annealing heat treatment is carried out under the protection of argon atmosphere. The annealing process parameters are 1140℃ and held for 20h, and then cooled to room temperature to obtain annealed ingot.

[0091] (3) Powdering: The annealed ingot is subjected to hydrogen crushing and air jet milling processes. The hydrogen crushing temperature is room temperature and the hydrogen pressure is 160 MPa. The air jet milling nozzle air velocity is 400 m / s, the crushing chamber pressure is 0.65 MPa, and the classifying wheel speed is 100 m / s to obtain alloy powder with an average grain size of 2.5-4 μm.

[0092] (4) Sintering, hot pressing, and tempering process: The alloy powder is pressed into a compact under a magnetic field, and then isostatic pressing is used to further increase the compact density. The magnetic field for magnetic orientation forming is 2T, and the time is 30s. The density of the low-density compact is 4.2g / cm³. 3 The magnet was subjected to cold isostatic pressing at 160 MPa for 60 seconds, followed by sintering at 1100℃ for 2 hours under argon protection in a vacuum sintering furnace. The sintered magnet was then placed in a hot press furnace and subjected to high-temperature pressing at 1100℃ and 90 kN for 3 minutes to obtain a fully dense magnet. The fully dense magnet was then placed in a vacuum sintering furnace and tempered at 1100℃ for 2 hours under argon protection to obtain ThMn. 12 Rare earth permanent magnets.

[0093] Example 7

[0094] ThMn 12 The composition of rare earth permanent magnet materials is: Sm 11.2 Fe bal Ti8V8Al2Cu 0.5 The preparation method is as follows:

[0095] (1) Smelting: The surface of the raw materials is mechanically polished to remove the oxide layer and unnecessary impurities, and then mixed according to the atomic percentage ratio. The prepared raw materials are placed in a crucible and smelted in a vacuum melting furnace under the protection of argon atmosphere. The resulting ingot is then cast and cooled to obtain a casting.

[0096] (2) Heat treatment: The ingot is placed in a vacuum sintering furnace and homogenized annealing heat treatment is carried out under the protection of argon atmosphere. The annealing process parameters are 1140℃ and held for 20h, and then cooled to room temperature to obtain annealed ingot.

[0097] (3) Powdering: The annealed ingot is subjected to hydrogen crushing and air jet milling processes. The hydrogen crushing temperature is room temperature and the hydrogen pressure is 160 MPa. The air jet milling nozzle air velocity is 400 m / s, the crushing chamber pressure is 0.65 MPa, and the classifying wheel speed is 100 m / s to obtain alloy powder with an average grain size of 2.5-4 μm.

[0098] (4) Sintering, hot pressing, and tempering process: The alloy powder is pressed into a compact under a magnetic field, and then isostatic pressing is used to further increase the compact density. The magnetic field for magnetic orientation forming is 2T, and the time is 30s. The density of the low-density compact is 4.2g / cm³. 3 The magnet was subjected to cold isostatic pressing at 160 MPa for 60 seconds, followed by sintering at 1100℃ for 2 hours under argon protection in a vacuum sintering furnace. The sintered magnet was then placed in a hot press furnace and subjected to high-temperature pressing at 1100℃ and 90 kN for 3 minutes to obtain a fully dense magnet. The fully dense magnet was then placed in a vacuum sintering furnace and tempered at 1100℃ for 2 hours under argon protection to obtain ThMn. 12 Rare earth permanent magnets.

[0099] Comparative Example 1

[0100] ThMn 12 The composition of rare earth permanent magnet materials is: Sm 8.8 Fe bal Ti8V8Al2Cu 0.5 The preparation method is as follows:

[0101] (1) Smelting: The surface of the raw materials is mechanically polished to remove the oxide layer and unnecessary impurities, and then mixed according to the atomic percentage ratio. The prepared raw materials are placed in a crucible and smelted in a vacuum melting furnace under the protection of argon atmosphere. The resulting ingot is then cast and cooled to obtain a casting.

[0102] (2) Heat treatment: The ingot is placed in a vacuum sintering furnace and homogenized annealing heat treatment is carried out under the protection of argon atmosphere. The annealing process parameters are 1140℃ and held for 20h, and then cooled to room temperature to obtain annealed ingot.

[0103] (3) Powdering: The annealed ingot is subjected to hydrogen crushing and air jet milling processes. The hydrogen crushing temperature is room temperature and the hydrogen pressure is 160 MPa. The air jet milling nozzle air velocity is 400 m / s, the crushing chamber pressure is 0.65 MPa, and the classifying wheel speed is 100 m / s to obtain alloy powder with an average grain size of 2.5-4 μm.

[0104] (4) Sintering and tempering process: The alloy powder is pressed into a compact under a magnetic field, and then isostatic pressing is used to further increase the density of the compact. The magnetic field for magnetic orientation forming is 2T, and the time is 30s. The density of the low-density compact is 4.2g / cm³. 3 The magnet was subjected to cold isostatic pressing at 160 MPa for 60 seconds, followed by sintering at 1100°C for 2 hours under argon protection in a vacuum sintering furnace. The sintered magnet was then further tempered at 1100°C for 2 hours under argon protection in a vacuum sintering furnace to obtain ThMn. 12 Rare earth permanent magnets.

[0105] Comparative Example 2

[0106] ThMn 12 The composition of rare earth permanent magnet materials is: Sm 11.2 Fe bal Ti8V8Al2Cu 0.5 The preparation method is as follows:

[0107] (1) Smelting: The surface of the raw materials is mechanically polished to remove the oxide layer and unnecessary impurities, and then mixed according to the atomic percentage ratio. The prepared raw materials are placed in a crucible and smelted in a vacuum melting furnace under the protection of argon atmosphere. The resulting ingot is then cast and cooled to obtain a casting.

[0108] (2) Heat treatment: The ingot is placed in a vacuum sintering furnace and homogenized annealing heat treatment is carried out under the protection of argon atmosphere. The annealing process parameters are 1140℃ and held for 20h, and then cooled to room temperature to obtain annealed ingot.

[0109] (3) Powdering: The annealed ingot is subjected to hydrogen crushing and air jet milling processes. The hydrogen crushing temperature is room temperature and the hydrogen pressure is 160 MPa. The air jet milling nozzle air velocity is 400 m / s, the crushing chamber pressure is 0.65 MPa, and the classifying wheel speed is 100 m / s to obtain alloy powder with an average grain size of 2.5-4 μm.

[0110] (4) Sintering and tempering process: The alloy powder is pressed into a compact under a magnetic field, and then isostatic pressing is used to further increase the density of the compact. The magnetic field for magnetic orientation forming is 2T, and the time is 30s. The density of the low-density compact is 4.2g / cm³. 3The magnet was subjected to cold isostatic pressing at 160 MPa for 60 seconds, followed by sintering at 1100°C for 2 hours under argon protection in a vacuum sintering furnace. The sintered magnet was then further tempered at 1100°C for 2 hours under argon protection in a vacuum sintering furnace to obtain ThMn. 12 Rare earth permanent magnets.

[0111] Performance testing

[0112] For each embodiment and comparative example ThMn 12 The magnetic properties of the rare earth permanent magnet materials were tested, and the results are shown in Table 1.

[0113] Table 1 ThMn 12 Performance data sheet of rare earth permanent magnet materials

[0114] <![CDATA[H cj (no)]]> <![CDATA[B r (kGs)]]> <![CDATA[BH (max) (MGOe)]]> <![CDATA[ρ(g / cm 3 )]]> Example 1 8.98 6.63 10.11 7.32 Example 2 8.50 6.44 8.49 7.30 Example 3 8.24 6.36 7.85 7.29 Example 4 7.92 6.34 7.80 7.30 Example 5 7.70 6.19 7.11 7.28 Example 6 7.58 6.08 6.84 7.24 Example 7 7.34 6.01 6.57 7.27 Comparative Example 1 9.78 4.80 5.57 5.15 Comparative Example 2 9.02 4.75 5.28 5.56

[0115] Table 1 clearly shows that ThMn 12 The magnetic properties of rare-earth permanent magnets tend to decrease with increasing Sm content, where the composition is Sm. 8.8 Fe bal Ti8V8Al2Cu 0.5 The magnetic properties reach their maximum, and the coercivity (H) is at its highest. cj The remanence (B) is 8.98 kOe. r The maximum energy product (BH) is 6.63 kGs. (max) The content of MgO is 10.11 MGOe, and the density (ρ) is 7.32 g / cm³. 3 The component is Sm 11.2 Fe bal Ti8V8Al2Cu 0.5 The magnetic properties are reduced to a minimum, with a coercivity of 7.34 kOe, remanence of 6.01 kGs, a maximum energy product of 6.57 MGOe, and a density of 7.27 g / cm³. 3 Among them, the magnets in Comparative Examples 1 and 2 that were not treated by hot pressing had insufficient density and many pores inside, resulting in significantly low remanence. Although they exhibited high coercivity, their overall magnetic energy product could not reach the ideal level due to the low remanence.

[0116] observe Figure 1 and Figure 2 It can be seen that as the rare earth content increases, the α-Fe content decreases, while the content of grain boundary phases such as SmFe2 increases. Fe2Ti is distributed in the grain boundary phase, resulting in a highly uneven microstructure. Figure 3 and Figure 4 It was learned that the component is Sm 8.8 Fe bal Ti8V8Al2Cu 0.5After annealing, V enters the main phase, α-Fe is completely eliminated, Fe is evenly distributed, and the microstructure is significantly improved. (Observation) Figure 5 and Figure 6 Therefore, Sm 11.2 Fe bal Ti8V8Al2Cu 0.5 After annealing, the ingot formed a grain boundary phase composed of SmFe2, V element entered the main phase, and α-Fe was completely eliminated, resulting in an improved microstructure. Figure 7 and Figure 8 It can be seen that Sm 8.8 Fe bal Ti8V8Al2Cu 0.5 The compositional magnet forms a Fe-poor grain boundary phase, which is more continuous and achieves effective magnetic isolation. Sm 11.2 Fe bal Ti8V8Al2Cu 0.5 In a composite magnet, SmFe2 consumes excess Sm, resulting in poor magnetic isolation and further reduction in coercivity.

[0117] In summary, this invention controls the Sm content in ingots, performs heat treatment to completely eliminate the precursor α-Fe, and then prepares a highly dense magnet through sintering, hot pressing, and tempering processes. This improves remanence and constructs a non-magnetic grain boundary phase to effectively enhance the magnet's coercivity, thereby obtaining a magnet with excellent comprehensive magnetic properties.

[0118] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0119] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. A ThMn 12 The method for preparing rare earth permanent magnets is characterized by, include: Raw materials containing Sm, Fe, Ti, V, Al and Cu are mixed evenly and smelted to obtain an alloy ingot. The alloy ingot is then subjected to homogenization annealing heat treatment, hydrogen annealing and air jet milling in sequence to obtain alloy powder. The alloy powder is oriented, pre-sintered, and then made into a permanent magnet blank. The permanent magnet blank is hot-pressed under an inert atmosphere to obtain a dense magnet; The dense magnet was subjected to high-temperature tempering to obtain ThMn. 12 Rare earth permanent magnets.

2. The preparation method according to claim 1, characterized in that: The proportions of the raw materials, expressed as atomic percentages, are: Sm 7~13 at.%, Ti 8 at.%, V 8 at.%, Al 2 at.%, Cu 0.5 at.%, with the balance being Fe; And / or, the preparation method specifically includes: subjecting the alloy ingot to homogenization annealing heat treatment at 900~1300 ℃ for 10~30 h under an inert atmosphere; And / or, the hydrogen breakdown temperature is room temperature, and the hydrogen pressure is 0.1~0.2 MPa; And / or, the airflow velocity in the nozzle of the airflow mill is 300~500m / s, the pressure in the grinding chamber is 0.4~0.8MPa, and the speed of the classifying wheel is 80~120m / s; And / or, the average grain size of the alloy powder is 2.5~4 μm.

3. The preparation method according to claim 2, characterized in that: The homogenization annealing heat treatment is performed at a temperature of 1000~1200℃ for 15~25 hours. And / or, the inert atmosphere includes argon.

4. The preparation method according to claim 1, characterized in that, Specifically, it includes: First, the alloy powder is oriented by magnetic field to obtain a low-density blank with orientation. Then, it is cold isostatically pressed and pre-sintered at 1000~1200℃ for 1~5h to obtain the permanent magnet blank.

5. The preparation method according to claim 4, characterized in that: The magnetic field for the magnetic orientation shaping is 2~4T, and the time is 20~40s; And / or, the density of the low-density blank is 3.5~4.5 g / cm³. 3 ; And / or, the pressure of the cold isostatic pressing is 150~200MPa, and the time is 30~90s.

6. The preparation method according to claim 1, characterized in that: The hot pressing process is carried out at a temperature of 1000~1200℃, a pressing pressure of 50~150kN, and a time of 2~4min.

7. The preparation method according to claim 1, characterized in that, Specifically, it includes: The dense magnet is subjected to high-temperature tempering at 1000~1200℃ for 1~5 hours to obtain ThMn magnets that possess both high coercivity and high maximum energy product. 12 Rare earth permanent magnets.

8. The preparation method according to claim 7, characterized in that, Also includes: When performing the high-temperature tempering in a sealed environment, a layer of coarse Sm metal powder with a thickness of 0.01~1mm is placed, and then the dense magnet is isolated with molybdenum foil.

9. ThMn prepared by any one of claims 1-8 12 Rare earth permanent magnet, characterized in that, The ThMn 12 -type rare earth permanent magnet has a composition of Sm x Fe bal Ti8V8Al2Cu 0.5 , where, in atomic percentage, 7% < x < 13%, Ti is 8%, V is 8%, Al is 2%, Cu is 0.5%, and the balance is Fe.

10. The ThMn according to claim 9 12 Rare earth permanent magnet, characterized in that, The ThMn 12 The coercivity of rare earth permanent magnets is above 7 kOe, and the maximum energy product is above 5 MGOe.

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