LaCe-rich neodymium iron boron permanent magnet having low cost and high coercive force and method for manufacturing the same

Abstract

The present invention discloses a low-cost, high-coercivity LaCe-rich NdFeB permanent magnet and its manufacturing method and application, which is manufactured by mixing and sintering a LaCe-free, HRE-free NdFeB main phase alloy and a LaCe-M alloy. The present invention first smelts a LaCe-free main phase alloy and a LaCe-M auxiliary phase alloy, respectively, and then mills, mixes, presses and sinters them, effectively avoiding the performance defect of the magnet performance degradation caused by LaCe intrusion into the main phase crystal grains, while reducing the manufacturing cost of the magnet and realizing the balanced and sustainable use of rare earth resources. In addition, the present invention utilizes the characteristics of the low melting point and high fluidity of the LaCe-rich grain boundary phase to effectively improve the depth and concentration of HRE diffusion into the magnet, thereby contributing to improving the uniformity of the composition and structure distribution in the magnet.

Description

Technical Field

[0001] This application claims the priority of a prior application filed with the China National Intellectual Property Administration on June 11, 2021, with a patent application number of 202110656406.5 and an invention title of "LaCe-rich neodymium iron boron permanent magnet with low cost and high coercivity, its manufacturing method and application". The above prior application is incorporated herein by reference in its entirety.

[0002] The present invention belongs to the field of rare earth permanent magnets, and specifically relates to a LaCe-rich neodymium iron boron permanent magnet with low cost and high coercivity, its manufacturing method and application.

Background Art

[0003] Sintered neodymium iron boron is mainly composed of elements such as rare earth PrNd, iron, and boron as the third-generation rare earth permanent magnet material. Due to its excellent magnetic performance and high cost performance, it is widely applied in various fields such as rare earth permanent magnet motors, smart consumer electronics products, and medical devices. With the rapid development of the low-carbon environmental protection economy and high technology, the demand for neodymium iron boron-based sintered magnets is increasing, the consumption of rare earth PrNd resources is significantly increasing, and the price of PrNd is gradually rising. La and Ce have similar chemical properties to PrNd and are the rare earth elements with the richest reserves. However, due to their relatively low inherent magnetic performance, their application in the field of rare earth permanent magnet materials is limited.

[0004] La and Ce in the Bayan Obo ore district in China account for more than 70% of the total rare earth content. However, the market demand for La and Ce is limited, and they coexist with Pr, Nd, Dy, and Tb in rare earth ores, resulting in large-scale mining and accumulation at the same time, so the market is in a situation of oversupply. Therefore, applying La and Ce instead of Pr and Nd to sintered neodymium iron boron can not only reduce the raw material cost but also contribute to the balanced utilization of rare earth resources. However, La2Fe 14 B and Ce2Fe 14Since B has lower saturation magnetization intensity and crystalline magnetic anisotropy field compared to R-Fe-B, using La and Ce instead of Pr and Nd will lead to deterioration of the magnetic properties of the magnet.

[0005] In the prior art, there are mainly the following several methods for adding La and Ce to the magnet: The first is to add them in the form of alloying, that is, adding metal La and Ce raw materials in the smelting process. The second is to add them in the form of double alloys, that is, first smelting and manufacturing (R, LaCe)-Fe-B and R-Fe-B alloy flakes (R is one or more selected from Nd, Pr, Dy, Tb, Ho, Gd), and then mixing the above alloy flakes in a certain ratio and then pressing and sintering. The third is to deposit a compound or alloy of La and Ce on the magnet surface and then perform an appropriate heat treatment process to diffuse La and Ce into the magnet interior.

[0006] In the above methods, due to the addition in the form of alloying, La and Ce enter the main phase crystal grains, and the performance such as the saturation magnetization intensity, Curie temperature, and crystalline magnetic anisotropy field of the main phase crystal grains decreases. Furthermore, the initial performance of the magnet decreases, and its application and development are restricted. However, when La and Ce are made to enter the magnet interior by the diffusion addition method, there are technical defects such as the process being complex and cumbersome, the addition amount of La and Ce being insufficient, and it being difficult to improve the coercivity of the magnet. Therefore, the cost performance is low, which is disadvantageous to its application and development. The addition method using double alloys can prevent La and Ce from entering the main phase crystal grains to a certain extent, so it has become the main manufacturing process of La and Ce-containing neodymium iron boron magnets.

[0007] However, in order to compensate for the decrease in magnetic performance caused by the addition of La and Ce and realize the production of high-performance La- and Ce-containing neodymium iron boron magnets, a certain amount of heavy rare earth elements such as Dy and Tb are usually added during the production of La- and Ce-rich magnets to improve the magnetic performance of the magnets. This method not only significantly increases the production cost of the magnets but also exacerbates the crisis of heavy rare earth resources, which is disadvantageous for the sustainable utilization of rare earth resources. Therefore, how to manufacture La- and Ce-rich high-performance neodymium iron boron magnets to reduce the production cost of the magnets and contribute to the sustainable utilization of rare earth resources has become a technical problem to be solved.

Summary of the Invention

Means for Solving the Problems

[0008] In order to improve the above technical problems, the present invention provides a neodymium iron boron permanent magnet composed of components with mass percentages of 24.2 - 38 wt% of Re0+Re1+Re2, 0.1 - 1.5 wt% of Al, 0.1 - 1 wt% of Ga, 0.9 - 1 wt% of B, and the balance of transition metal elements.

[0009] Among them, The above Re0 element is one or two selected from La and Ce, preferably two of La and Ce, and preferably, the percentage of the above Re0 in the total mass of the magnet may be 0.1 - 9 wt%.

[0010] The above Re1 element is one or two selected from Pr and Nd and contains at least Nd, and preferably, the percentage of the above Re1 in the total mass of the magnet may be 24 - 28 wt%.

[0011] The above Re2 element is at least one selected from Dy, Tb, and Ho, and preferably, the percentage of the above Re2 in the total mass of the magnet may be 0.1 - 1 wt%.

[0012] Preferably, the transition metal element contains at least Fe and Co elements. For example, the transition element is selected from Co, Cu, Zr, Ti, and Fe.

[0013] Preferably, the transition metal element contains each composition with a mass percentage such as 0.1 to 3 wt% of Co, 0.1 to 1.5 wt% of Cu, 0 to 1 wt% of Zr, 0.1 to 2 wt% of Ti, and the balance of Fe.

[0014] According to an exemplary embodiment of the present invention, the neodymium iron boron permanent magnet consists of components with mass percentages such as 0.1 to 9 wt% of Re0, 24 to 28 wt% of Re1, 0.1 to 1 wt% of Re2, 0.1 to 3 wt% of Co, 0.1 to 1.5 wt% of Al, 0.1 to 1 wt% of Cu, 0.1 to 1 wt% of Ga, 0 to 1 wt% of Zr, 0.1 to 2 wt% of Ti, 0.9 to 1 wt% of B, and the balance of Fe.

[0015] According to an embodiment of the present invention, the neodymium iron boron permanent magnet has a microstructure feature consisting of a main phase, a grain boundary phase, and a composite phase between the main phase and the grain boundary phase.

[0016] Preferably, the average crystal grain size of the main phase crystal grains is 2 to 7 μm, and exemplarily, it is 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm.

[0017] Preferably, the main phase crystal grains contain the Re1 element but do not contain the Re0 and Re2 elements, and the main phase crystal grains have an R2T 14 B-type phase structure, where T represents a transition metal element, and the T contains at least Fe and Co elements.

[0018] Preferably, the grain boundary phase is continuously distributed in a straight strip along the main phase crystal grain boundaries. Preferably, the grain boundary phase contains at least one of the Re0, Re1, Re2 elements and the Co, Al, Cu, Ga, Zr, Ti, B, Fe elements.

[0019] Preferably, the composite phase exists between the main phase and the grain boundary phase.

[0020] Preferably, the neodymium iron boron permanent magnet basically has the microstructure shown in FIG. 1.

[0021] Preferably, the composite phase contains Re0, Re1, and Re2 elements and has an R2T 14 B-type phase structure, where T represents a transition metal element, and the above T contains at least Fe and Co.

[0022] According to an embodiment of the present invention, the permanent magnet is manufactured by mixing a neodymium iron boron main phase alloy without LaCe and without HRE and a LaCe-M alloy, followed by powdering, pressing, and vacuum sintering. Among them, HRE refers to a heavy rare earth element, for example, at least one selected from Dy, Tb, and Ho, and M represents at least one of Al, Cu, and Fe.

[0023] According to an embodiment of the present invention, in the manufacturing process of the permanent magnet, an antioxidant lubricant may be optionally added. Preferably, the usage amount of the antioxidant lubricant may be 0.01 to 2 wt% of the total weight of the powder, and illustratively, it is 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%.

[0024] The present invention further provides a method for manufacturing the neodymium iron boron permanent magnet, which includes mixing raw materials of a neodymium iron boron main phase alloy without LaCe and without HRE and a LaCe-M alloy, and passing through vacuum liquid phase sintering to obtain the La, Ce-rich neodymium iron boron permanent magnet.

[0025] According to an embodiment of the present invention, the neodymium iron boron main phase alloy without LaCe and without HRE and the LaCe-M alloy have the definitions and selections described above.

[0026] Since rare earth metals contain impurities of La, Ce or HRE in the smelting and metallurgical process, those skilled in the art can understand that when La < 0.1 wt%, Ce < 0.1 wt%, and HRE < 0.1 wt% in the neodymium iron boron main phase alloy, it is considered to be a neodymium iron boron main phase alloy without LaCe and without HRE.

[0027] According to an embodiment of the present invention, the neodymium iron boron main phase alloy without LaCe and without HRE is an alloy flake. Preferably, the thickness of the alloy flake is 0.1 to 0.4 mm, and illustratively, it is 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm.

[0028] According to an embodiment of the present invention, the neodymium iron boron main phase alloy without LaCe and without HRE is obtained by casting after vacuum smelting from raw materials including a Re1 source, a transition metal source, a Ga source, an Al source, and a B source.

[0029] Preferably, the Re1 source is provided by a single substance (pure metal) or an alloy containing the Re1 element, preferably provided by an alloy containing the Re1 element, for example, provided by a PrNd alloy. Preferably, the transition metal source, Ga source, and Al source are provided by a single substance or an alloy containing a transition metal element, Ga element, and Al element, preferably provided by a single substance containing a transition metal element, Ga element, and Al element.

[0030] Preferably, the B source is provided by a compound containing the B element, for example, provided by B-Fe sand.

[0031] According to an embodiment of the present invention, the auxiliary phase alloy is an alloy flake. Preferably, the thickness of the alloy flake is 0.1 to 0.4 mm, and illustratively, it is 0.1 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.4 mm.

[0032] According to an embodiment of the present invention, the auxiliary phase alloy is obtained by casting after vacuum smelting from raw materials including a Re0 source and an M source.

[0033] Preferably, the above Re0 source and M source are provided by a simple substance (pure metal) or alloy containing Re0 element and M element, and preferably provided by a simple substance containing Re0 element and M element.

[0034] Preferably, the above smelting is carried out in an inert gas atmosphere such as a nitrogen gas or argon gas atmosphere, and preferably in an argon gas atmosphere.

[0035] Preferably, the casting temperatures in the smelting processes of the above main phase alloy and auxiliary phase alloy are the same or different. For example, they may be independently 1300 - 1500 °C, and illustratively are 1300 °C, 1400 °C, 1500 °C.

[0036] Preferably, the casting processes of the above main phase alloy and auxiliary phase alloy are the same or different. For example, the molten liquid may be independently cast into a rotating water-cooled copper roller. Further, the rotation speed of the above rotating water-cooled copper roller is 15 - 45 rpm, and illustratively are 15 rpm, 20 rpm, 25 rpm, 30 rpm, 40 rpm, 45 rpm.

[0037] According to an embodiment of the present invention, the smelting of the above main phase alloy / or auxiliary phase alloy is carried out in a vacuum induction furnace.

[0038] According to an embodiment of the present invention, before the above vacuum liquid phase sintering, it further includes mixing the above main phase alloy and auxiliary phase alloy.

[0039] Preferably, further, hydrogen crushing, dehydrogenation, and jet milling treatment are respectively performed on the main phase alloy and the auxiliary phase alloy to produce main phase alloy powder and auxiliary phase alloy powder.

[0040] Preferably, the above main phase alloy and auxiliary phase alloy may be mixed in the form of smelting flakes, or may be mixed at any stage of hydrogen crushing, dehydrogenation or jet milling treatment.

[0041] Preferably, the average particle size of the above main-phase alloy powder is 3 to 6 μm, and illustratively, it is 3 μm, 4 μm, 5 μm, or 6 μm.

[0042] Preferably, the average particle size of the above auxiliary-phase alloy powder is 1 to 3 μm, and illustratively, it is 1 μm, 2 μm, or 3 μm.

[0043] According to an embodiment of the present invention, the above manufacturing method further includes press-forming after mixing the above main-phase alloy powder and the auxiliary-phase alloy powder.

[0044] Preferably, in the above permanent magnet, the mass percentage of the main-phase alloy powder is 75 to 99.5 wt%, for example, 85 to 95 wt%, and the mass percentage of the auxiliary-phase alloy powder is 0.5 to 25 wt%, for example, 5 to 15 wt%.

[0045] According to an embodiment of the present invention, the above mixing is performed under stirring conditions.

[0046] According to an embodiment of the present invention, the above press-forming includes oriented press-forming and isostatic pressing. Preferably, first, an oriented press-forming is performed to obtain a green compact, and then an isostatic pressing is performed to manufacture the green compact, thereby further improving the density of the green compact. Further, the above oriented press is performed in a magnetic field, and the above isostatic pressing is performed with an isostatic press.

[0047] Preferably, the above mixed powder is subjected to oriented press-forming under the protection of an inert gas atmosphere such as a nitrogen gas or argon gas atmosphere, preferably a nitrogen gas atmosphere.

[0048] Preferably, the magnetic field strength of the above oriented magnetic field is 2 to 5 T, and illustratively, it is 2 T, 3 T, 4 T, or 5 T.

[0049] Preferably, the pressure of the above isostatic pressing is 150 to 260 MPa, and illustratively, it is 150 MPa, 180 MPa, 200 MPa, 220 MPa, 240 MPa, or 260 MPa.

[0050] Preferably, the density of the above-mentioned compacted powder is 4 to 6 g / cm 3 and, by way of example, 4 g / cm 3 , 4.6 g / cm 3 , 5 g / cm 3 , 6 g / cm 3 .

[0051] According to an embodiment of the present invention, the above-mentioned vacuum liquid-phase sintering is obtained by manufacturing a neodymium iron boron permanent magnet without HRE rich in LaCe using a secondary sintering process. Preferably, the temperatures of the secondary sintering are the same or different, for example, both are 900 to 1100 °C, preferably 950 to 1100 °C, and by way of example, 900 °C, 950 °C, 1000 °C, 1015 °C, 1030 °C, 1100 °C. For example, the times of the secondary sintering are the same or different, for example, both are 4 to 8 h, preferably 4 to 6 h, and by way of example, 4 h, 5 h, 6 h, 8 h.

[0052] Preferably, the heating rate of the above-mentioned secondary sintering is 5 to 15 °C / min for each, and by way of example, 5 °C / min, 8 °C / min, 10 °C / min, 12 °C / min, 15 °C / min.

[0053] Preferably, the degree of vacuum of the primary sintering process of the above-mentioned vacuum liquid-phase sintering is 1×10 -2 Pa or less.

[0054] Preferably, the secondary sintering process of the above-mentioned vacuum liquid-phase sintering is carried out in an inert gas atmosphere such as a nitrogen or argon gas atmosphere, preferably an argon gas atmosphere.

[0055] According to an embodiment of the present invention, after the primary sintering process of the above-mentioned vacuum liquid-phase sintering is completed, Ar gas is injected and cooled to 100 °C or less. Preferably, the cooling rate ≧ 20 °C / min, and by way of example, 20 °C / min, 25 °C / min, 30 °C / min, 40 °C / min.

[0056] According to an embodiment of the present invention, the above-mentioned manufacturing method further includes cooling the magnet without HRE rich in LaCe obtained after the vacuum liquid-phase sintering to 65 °C or less.

[0057] According to an embodiment of the present invention, the manufacturing method further includes performing an aging treatment on a LaCe-rich HRE-free magnet obtained after vacuum liquid phase sintering to produce a low-HRE La, Ce-rich neodymium iron boron permanent magnet.

[0058] Preferably, the aging treatment uses a two-stage firing treatment. The primary firing temperature is 800 to 1000 °C, illustratively 800 °C, 900 °C, 1000 °C, and the primary firing time is 0.5 to 36 h, illustratively 0.5 h, 1 h, 2 h, 5 h, 12 h, 15 h, 20 h, 24 h, 30 h, 36 h.

[0059] The secondary firing temperature is 400 to 600 °C, preferably 450 to 550 °C, illustratively 400 °C, 450 °C, 500 °C, 510 °C, 550 °C, 600 °C, and the secondary firing time is 1 to 6 h, preferably 2 to 5 h, illustratively 1 h, 2 h, 3 h, 4 h, 5 h, 6 h.

[0060] Preferably, after the primary firing treatment, the reaction product is cooled to 80 °C or lower, for example, cooled to 70 °C, 60 °C, 50 °C, 40 °C, 30 °C or room temperature.

[0061] Preferably, the diffusion source for the aging treatment is a diffusion source containing the Re2 element, where the Re2 element is at least one of Dy, Tb, and Ho. Further, the diffusion source containing the above Re2 element is a pure metal, alloy or compound containing the Re2 element, preferably a compound containing the Re2 element, illustratively a fluorine compound containing Re2.

[0062] Preferably, the method of the aging treatment is to attach a diffusion source containing the Re2 element to the surface of the magnet and perform the aging treatment in a vacuum heat treatment furnace to produce a low-HRE La, Ce-rich neodymium iron boron magnet.

[0063] For example, the diffusion source can be deposited on the surface of the magnet by means such as coating, dipping, magnetron sputtering, spraying, etc., preferably by spraying.

[0064] According to an embodiment of the present invention, the method for manufacturing the neodymium iron boron permanent magnet includes the following steps: Step 1: According to the requirements of component design, weigh and mix the Re1 source, transition metal source, Ga source, Al source, and B source in the above weight percentages, and smelt them using a vacuum induction furnace under the protection of an Ar gas atmosphere. Cast the molten liquid after melting into a rotating water-cooled copper roller to produce the primary phase alloy flakes.

[0065] Step 2: According to the requirements of component design, weigh and mix the Re0 source and M source, which are raw materials, and smelt them using a vacuum induction smelting furnace under the protection of an Ar gas atmosphere. Cast the molten liquid after melting into a rotating water-cooled copper roller to produce the auxiliary phase alloy flakes.

[0066] Step 3: After subjecting the primary phase alloy flakes and the auxiliary phase alloy flakes to hydrogen crushing, dehydrogenation, and jet mill treatment respectively, produce the primary phase alloy powder and the auxiliary phase alloy powder.

[0067] Step 4: After mixing the primary phase alloy powder and the auxiliary phase alloy powder, perform orientation pressing in a magnetic field to obtain a green compact, and then press it with an isostatic press to further improve the density of the green compact.

[0068] Step 5: Sinter the green compact in a vacuum sintering furnace to obtain a magnet without LaCe-rich HRE.

[0069] Step 6: Deposit a diffusion source containing the Re2 element on the surface of the magnet, and perform aging treatment in a vacuum heat treatment furnace to obtain a neodymium iron boron magnet rich in La and Ce with low HRE.

[0070] The present invention further provides the application of the neodymium iron boron permanent magnet in fields such as rare earth permanent magnet motors, smart consumer electrical products, and medical devices.

Advantages of the Invention

[0071] (1) First, the present invention smelts a main phase alloy without LaCe and a LaCe-M auxiliary phase alloy respectively, and then through powder making, mixing, pressing, and sintering, effectively avoids the performance defect of the reduction of magnet performance due to the entry of LaCe into the main phase crystal grains, reduces the manufacturing cost of the magnet at the same time, and realizes the balance and sustainable utilization of rare earth resources.

[0072] (2) The present invention utilizes the excellent characteristics of the low melting point, high fluidity, and wettability of the LaCe-rich grain boundary phase to effectively improve the depth and concentration of HRE diffusion into the magnet, thus contributing to the improvement of the uniformity of the component and tissue distribution in the magnet.

[0073] (3) By performing a diffusion treatment on the LaCe-rich neodymium iron boron, the present invention realizes the manufacture of a LaCe-rich neodymium iron boron permanent magnet with low HRE and high coercivity, effectively reduces the usage amount of HRE, and promotes the balanced utilization and sustainable development of rare earth resources.

[0074] (4) The manufacturing method of the La, Ce-rich neodymium iron boron permanent magnet without HRE of the present invention reduces the usage amount of PrNd in the neodymium iron boron magnet by mixing LaCe-M with the neodymium iron boron alloy flakes without La and Ce, or by respectively performing powder making, mixing, pressing, and sintering to manufacture the magnet, which helps the uniform distribution of the rare earth-rich phase in the magnet, and avoids the deterioration of magnetic parameters such as the crystal magnetic anisotropy and saturation magnetic polarization intensity of the main phase crystal grains due to the entry of La and Ce into the interior of the main phase crystal grains by alloying, thus contributing to the improvement of the magnetic performance of the magnet. On the other hand, the enrichment of La and Ce at the grain boundaries reduces the melting point and sintering temperature of the grain boundary phase, and improves the fluidity and continuity of the grain boundary phase, so that the rare earth-rich phase is distributed along the grain boundaries to form a continuous and smooth grain boundary phase (see Figure 1), thereby suppressing the nucleation of reverse magnetization domains, effectively blocking the magnetic exchange and coupling action between the main phase crystal grains, and further contributing to endowing the La, Ce-rich neodymium iron boron permanent magnet with relatively high magnetic performance.

[0075] (5) In the manufacturing process of the low-HRE La, Ce-rich neodymium iron boron permanent magnet of the present invention, by concentrating La and Ce in the grain boundary phase (see FIGS. 2 to 4), in order to improve the wettability and fluidity of the grain boundary phase, the depth and concentration of HRE diffusion into the magnet core part are promoted, a composite phase with a high crystalline magnetic anisotropy field is formed between the main phase crystal grains and the grain boundary phase inside the magnet, the nucleation magnetic field of the reverse magnetization domain on the surface of the main phase crystal grains is improved, thereby contributing significantly to improving the coercivity of the magnet. Further, due to the fine structure of the composite phase with the same components and structure formed between the main phase crystal grains and the grain boundary phase throughout the magnet, the magnet can be formed so that the reverse magnetization domains are uniformly aligned during reverse magnetization, thus significantly improving the squareness of the magnet.

Brief Description of the Drawings

[0076]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0077] Hereinafter, in accordance with specific embodiments, the technical solution of the present invention will be described in more detail. It should be understood that the following embodiments are merely illustrative explanations of the present invention and should not be construed as limiting the scope of the claims of the present invention. Any technology realized based on the above content of the present invention is included within the scope of the claims of the present invention.

[0078] Unless otherwise specified, all raw materials and reagents used in the following embodiments are commercially available products or can be manufactured by known methods.

[0079] In the following examples of the present invention, PrNd is added in the form of an alloy, the remaining metals are all added in the form of a single substance, and B is provided by B-Fe sand.

Example

[0080] (1) The raw materials of the main-phase alloy were weighed at a mixing ratio of 29.2 wt% PrNd, 1 wt% Co, 0.3 wt% Ga, 0.1 wt% Al, 0.1 wt% Cu, 0.2 wt% Zr, 0.2 wt% Ti, 1.04 wt% B, and the balance Fe, and smelted using a vacuum induction melting furnace under the protection of an Ar gas atmosphere. The molten liquid was cast into a water-cooled copper roller with a rotational speed of 30 rpm, and the liquid casting temperature was set at 1400 °C to produce main-phase alloy flakes with an average thickness of 0.3 mm.

[0081] (2) The raw materials of the auxiliary-phase alloy were weighed at a mixing ratio of 10 wt% La, 50 wt% Ce, 5 wt% Al, 5 wt% Cu, and the balance Fe, and smelted using a vacuum induction melting furnace under the protection of an Ar gas atmosphere. The molten liquid was cast into a water-cooled copper roller with a rotational speed of 35 rpm, and the liquid casting temperature was set at 1400 °C to produce auxiliary-phase alloy flakes with an average thickness of 0.25 mm.

[0082] (3) The main-phase alloy flakes and the auxiliary-phase alloy flakes were respectively subjected to hydrogen crushing, dehydrogenation, and jet milling to produce alloy powders with average particle sizes of 4 μm and 2 μm. 95 wt% of the main-phase alloy powder and 5 wt% of the auxiliary-phase alloy powder were respectively weighed, mixed under the protection of an N2 gas atmosphere, and an antioxidant lubricant (a common antioxidant lubricant known in the art) with a ratio of 0.05 wt% was added and uniformly mixed while stirring.

[0083] (4) The mixed powder was filled into the mold cavity of the pressing equipment under the protection of an N2 gas atmosphere, orientation forming and pressing were performed at an orientation magnetic field strength of 3 T, and then isostatic pressing treatment was carried out at a pressure of 180 MPa in an isostatic press to obtain a green compact with a density of 4.6 g / cm 3 (The green compact was obtained by weighing and measuring the size and then calculating).

[0084] (5) Under the protection of an N2 gas atmosphere, the pressed powder is fed into a vacuum sintering furnace, the temperature is maintained at 1015 °C, and the sintering vacuum degree is set to 1×10 -2 Pa or less, and sintering is carried out for 5 h. After the temperature holding is completed, Ar gas is injected to cool to 80 °C or less, the temperature is raised again to 1030 °C, the temperature is held and sintered for 6 h, and then Ar gas is injected to cool to 65 °C or less and then taken out of the furnace. A sintered pressed powder with a density of 7.55 g / cm 3 is obtained.

[0085] (6) After mechanical processing and grinding treatment are performed on the sintered pressed powder, dysprosium fluoride is sprayed and adhered to the surface of the magnet. Before and after the spraying and adhesion operation of dysprosium fluoride, the weight of the magnet is weighed so that the weight of the sprayed dysprosium fluoride becomes 0.6 wt% of the total weight of the magnet. A diffusion treatment of 900 °C × 20 h is carried out in a vacuum heat treatment furnace, and then Ar gas is injected to cool to 80 °C or less, the temperature is raised again to 510 °C, the temperature is maintained for 5 h for aging treatment, and then Ar gas is injected to cool to 60 °C or less and taken out of the furnace to obtain a low-Dy, La, Ce-rich neodymium iron boron permanent magnet.

Example

[0086] Compared with Example 1, Example 2 is only different in that in step (3), the mass percentage of the main phase alloy powder is 88 wt% and the mass percentage of the auxiliary phase alloy powder is 12 wt%.

Example

[0087] Compared with Example 1, Example 3 is only different in that in step (6), after the sintered pressed powder undergoes surface treatment, a Tb pure metal film layer is adhered, and before and after the adhesion operation, the weight of the magnet is weighed so that the Tb film layer becomes 0.6 wt% of the total weight of the magnet.

Example

[0088] Example 4 is different from Example 1 only in that in step (2), the mixing ratio of the auxiliary alloy components is 60 wt% Ce, 5 wt% Al, 5 wt% Cu, and the balance Fe.

Example

[0089] Example 5 is different from Example 1 only in that in step (1), the mixing ratio of the main alloy components is 28 wt% PrNd, 2.5 wt% Co, 0.3 wt% Ga, 0.3 wt% Al, 0.1 wt% Cu, 0.2 wt% Zr, 0.2 wt% Ti, 1 wt% B, and the balance Fe. Comparative Example 1

[0090] A method for manufacturing a neodymium-iron-boron-based sintered permanent magnet including the following steps was provided.

[0091] (1) Raw materials were weighed at a mixing ratio of 27.74 wt% PrNd, 0.5 wt% La, 2.5 wt% Ce, 0.95 wt% Co, 0.35 wt% Al, 0.35 wt% Cu, 0.29 wt% Ga, 0.19 wt% Zr, 0.19 wt% Ti, 0.99 wt% B, and the balance Fe, melted using a vacuum induction melting furnace under the protection of an Ar gas atmosphere, and the molten liquid was cast into a water-cooled copper roller with a rotational speed of 30 rpm, with the liquid casting temperature set at 1400 °C to produce alloy flakes with an average thickness of 0.3 mm.

[0092] (2) The alloy flakes were subjected to hydrogen crushing, dehydrogenation, and jet milling to produce alloy powder with a particle size of 4 μm. An antioxidant lubricant with a ratio of 0.05 wt% was added under the protection of an N2 gas atmosphere and uniformly mixed while stirring.

[0093] (3) Under the protection of an N2 gas atmosphere, the alloy powder was filled into the mold cavity of a pressing facility, orientation forming and pressing were performed at an orientation magnetic field strength of 3 T, and then isostatic pressing was performed at a pressure of 180 MPa in an isostatic press to obtain a green compact with a density of 4.6 g / cm 3 3.

[0094] (4)Under the protection of an N₂ gas atmosphere, the pressed powder was fed into a vacuum sintering furnace, maintained at a temperature of 1015 °C, and sintered for 5 h while reducing the sintering vacuum degree to 1×10 -2 Pa or less. After the temperature holding was completed, Ar gas was injected to cool it to 80 °C or less, then the temperature was raised again to 1030 °C and held for 6 h of sintering. Subsequently, after injecting Ar gas and cooling to 65 °C or less, it was taken out of the furnace, and a sintered pressed powder with a density of 7.55 g / cm 3 was obtained.

[0095] (5)After subjecting the sintered pressed powder to mechanical processing and grinding treatment, dysprosium fluoride was sprayed and adhered to the surface of the magnet. And before and after the spraying and adhesion operation of dysprosium fluoride so that the content of dysprosium fluoride became 0.6 wt% of the total weight of the magnet, the weight of the magnet was weighed. A diffusion treatment at 900 °C for 20 h was carried out in a vacuum heat treatment furnace. Subsequently, Ar gas was injected to cool it to 80 °C or less, then the temperature was raised again to 510 °C and held for 5 h for aging treatment. After that, Ar gas was injected to cool it to 60 °C or less and taken out of the furnace. Comparative Example 2

[0096] Other steps were the same as those in Comparative Example 1. In step (1), it was only different in that the mixing ratio of the component design was 27.74 wt% of PrNd, 0.95 wt% of Co, 0.1 wt% of Al, 0.1 wt% of Cu, 0.29 wt% of Ga, 0.19 wt% of Zr, 0.19 wt% of Ti, 0.99 wt% of B, and the balance of Fe. Comparative Example 3

[0097] Other steps were the same as those in Example 1. In step (2), it was only different in that the mixing ratio of the auxiliary phase alloy components was 5 wt% of Al, 5 wt% of Cu, and the balance of Fe.

[0098] Using the precision measurement system for NIM-62000 permanent magnet materials, the magnetic properties of the magnets manufactured according to the above Examples 1 to 5 and Comparative Examples 1 to 3 were measured respectively, and the results are shown in Table 1 below.

[0099]

Table 1

[0100] Comparing the results of Examples 1 to 5 in Table 1 and Comparative Example 1, it was found that the magnets produced according to the present invention are superior in Hcj characteristics to the magnets produced by adding LaCe by smelting alloying. Furthermore, comparing the results of Examples 1 to 5 and Comparative Example 2, it was found that the addition of the auxiliary phase alloy of the present invention can reduce the decrease in the Hcj magnetic performance of the magnet due to the addition of LaCe. Comparing the results of Examples 1 to 5 and Comparative Example 3, it was found that the present invention contributes to the production of a low-cost, high coercivity LaCe-rich neodymium iron boron permanent magnet having excellent performance by adding LaCe to the auxiliary alloy.

[0101] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments. Modifications, equivalent substitutions, improvements, etc. made without departing from the gist and principles of the present invention are all included within the scope of the claims of the present invention.

Claims

1. It consists of components with mass percentages of 0.1 to 9 wt% of Re0, 24 to 28 wt% of Re1, 0.1 to 1 wt% of Re2, 0.1 to 3 wt% of Co, 0.1 to 1.5 wt% of Al, 0.1 to 1 wt% of Cu, 0.1 to 1 wt% of Ga, 0 to 1 wt% of Zr, 0.1 to 2 wt% of Ti, 0.9 to 1 wt% of B, and the balance of Fe. Among them, The Re0 element is one or two selected from La and Ce. The Re1 element is one or two selected from Pr and Nd and contains at least Nd. The Re2 element is at least one selected from Dy, Tb, and Ho. The permanent magnet has a microstructure feature composed of a main phase, a grain boundary phase, and a composite phase between the main phase and the grain boundary phase. The main phase crystal grains contain the Re1 element but do not contain the Re0 and Re2 elements. The main phase crystal grains have an R2T14B-type phase structure, where T represents a transition metal element, and the T contains at least Fe and Co elements. The grain boundary phase contains at least one or more of the Re0, Re1, Re2 elements and Co, Al, Cu, Ga, Zr, Ti, B, and Fe elements. The composite phase contains the Re0, Re1, Re2 elements and has an R2T14B-type phase structure, where T represents a transition metal element, and the T contains at least Fe and Co A neodymium iron boron permanent magnet, characterized in that.

2. The aforementioned Re 0 element is two of La and Ce, The permanent magnet according to claim 1, characterized in that.

3. The average crystal grain size of the main phase crystal grains is 2 to 7 μm. The permanent magnet according to claim 1, characterized in that.

4. The grain boundary phase is continuously distributed in a straight strip along the main phase crystal grain boundaries. The permanent magnet according to claim 1, characterized in that.

5. A method for manufacturing a permanent magnet. The manufacturing method mixes raw materials of a neodymium iron boron main phase alloy without Re0 and without heavy rare earth elements and a Re0-M auxiliary phase alloy, and through vacuum sintering, the La, Ce-rich neodymium iron boron permanent magnet is manufactured and obtained, where M represents at least one of Al, Cu, and Fe. The method for manufacturing a permanent magnet according to claim 1, characterized in that.

6. The neodymium iron boron main phase alloy without Re0 and without heavy rare earth elements is obtained by casting after vacuum smelting from raw materials containing a Re1 source, a transition metal source, a Ga source, an Al source, and a B source. The manufacturing method according to claim 5, characterized in that.

7. The auxiliary phase alloy is an alloy flake and has a thickness of 0.1 to 0.4 mm. The manufacturing method according to claim 5, characterized in that...

8. The manufacturing method further includes press-forming after mixing the main-phase alloy powder and the auxiliary-phase alloy powder. In the permanent magnet, the mass percentage of the main-phase alloy powder is 75 - 99.5 wt%, and the mass percentage of the auxiliary-phase alloy powder is 0.5 - 25 wt%. The manufacturing method according to claim 5, characterized in that...

9. Step 1 of manufacturing the main-phase alloy flakes: weighing and mixing a Re1 source, a transition metal source, a Ga source, an Al source, and a B source according to the requirements of component design, smelting using a vacuum induction furnace under the protection of an Ar gas atmosphere, and casting the molten liquid after melting into a rotating water-cooled copper roller. Step 2 of manufacturing the auxiliary-phase alloy flakes: weighing and mixing a Re0 source and an M source, which are raw materials, according to the requirements of component design, smelting using a vacuum induction smelting furnace under the protection of an Ar gas atmosphere, and casting the molten liquid after melting into a rotating water-cooled copper roller. Step 3 of manufacturing the main-phase alloy powder and the auxiliary-phase alloy powder: respectively performing hydrogen crushing, dehydrogenation, and jet milling treatment on the main-phase alloy flakes and the auxiliary-phase alloy flakes. Step 4: After mixing the main-phase alloy powder and the auxiliary-phase alloy powder, performing orientation pressing in a magnetic field to obtain a green compact, and then pressing with an isostatic press to further improve the density of the green compact. Step 5: Sintering the green compact in a vacuum sintering furnace to obtain a magnet without Re0-rich heavy rare earth elements. Step 6: Attaching a diffusion source containing Re2 element to the surface of the magnet, performing aging treatment in a vacuum heat treatment furnace to obtain a Re0-rich and low-Re2 neodymium iron boron magnet. The manufacturing method according to claim 5, characterized in that...

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