Method for manufacturing r-fe-b-based permanent magnet by grain boundary diffusion of refractory metal alloys and rare earth alloys, and r-fe-b-based permanent magnet manufactured thereby

Abstract

The present invention relates to a method for manufacturing an R-Fe-B-based permanent magnet by grain boundary diffusion of refractory metal alloys and rare earth alloys and an R-Fe-B-based permanent magnet manufactured thereby, wherein the grain boundary diffusion of a light rare earth alloy containing light rare earth elements that are less expensive than costly heavy rare earth elements can lead to a low manufacturing cost, effective suppression of crystal grain growth (coarsening) inside the permanent magnet, a reduction in the Pr-shell thickness, and an increase in the Pr concentration around the crystal grains, and thus can produce a permanent magnet having enhanced magnetic properties, such as coercivity.

Description

Method for manufacturing an R-Fe-B permanent magnet in which a refractory metal alloy and a rare earth alloy are grain boundary diffused, and an R-Fe-B permanent magnet manufactured thereby

[0001] The present invention relates to a method for manufacturing an R-Fe-B permanent magnet in which a refractory metal alloy and a rare earth alloy are grain boundary-diffused, and to an R-Fe-B permanent magnet manufactured therefrom. The present invention claims the benefit of Korean Patent Application No. 10-2024-0002045, filed with the Korean Intellectual Property Office on January 5, 2024, the entire contents of which are incorporated herein by reference.

[0002] R-Fe-B permanent magnets, like Nd-Fe-B permanent magnets, are used in a variety of fields, including electronics, automotive, medical devices, energy, and transportation. In particular, in line with recent trends toward lighter weight and miniaturization, they are being used in a variety of products, including machine tools, electronic information devices, home appliances, mobile phones, robot motors, wind turbines, small automotive motors, and drive motors.

[0003] For these permanent magnets, a grain boundary diffusion process has been proposed as a post-processing method to improve their magnetic performance. The grain boundary diffusion process utilizes the highly chemically reactive nature of the interface between the permanent magnet and the magnet, coating the surface of the magnet with heavy rare earth elements and then heat-treating them. This grain boundary diffusion process concentrates the heavy rare earth elements around the grain boundaries, i.e., only on the surface of the ferromagnetic grains, forming a core-shell structure in which the grains are surrounded by a layer of high magnetic anisotropy, thereby achieving high coercivity.

[0004] However, the heavy rare earth elements used in the existing interface diffusion method have the problem of being very expensive, and when using inexpensive light rare earth elements, there is the problem of lower coercivity than when using heavy rare earth elements.

[0005] The problem to be solved by the present invention is to provide a method for manufacturing an R-Fe-B permanent magnet having excellent coercivity by intergranular diffusion of inexpensive rare earth elements.

[0006] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

[0007] According to one aspect of the present invention, a method for manufacturing a grain-boundary-diffused R-Fe-B permanent magnet is provided, comprising: a step of applying and drying a refractory metal alloy and a rare earth alloy to an R-Fe-B permanent magnet; and a step of heat-treating the R-Fe-B permanent magnet on which the refractory metal alloy and the rare earth alloy have been applied and dried to cause grain-boundary diffusion; wherein R is Nd, Pr, Dy, Ce, La, Gd, Tb, or Y.

[0008] According to another aspect of the present invention, there is provided an R-Fe-B permanent magnet manufactured by the above manufacturing method and having a coercive force of 15 kOe to 35 kOe.

[0009] A method for manufacturing a grain boundary-diffused R-Fe-B permanent magnet according to one embodiment of the present invention can effectively limit grain growth (coarsening) inside a permanent magnet, reduce the thickness of a Pr shell, and increase the Pr concentration around the grains, thereby manufacturing a permanent magnet with improved magnetic properties such as coercivity.

[0010] A method for manufacturing a grain boundary-diffused R-Fe-B permanent magnet according to one embodiment of the present invention can reduce manufacturing costs by using inexpensive light rare earth elements instead of expensive heavy rare earth elements as a rare earth alloy.

[0011] An R-Fe-B permanent magnet manufactured by a manufacturing method according to one embodiment of the present invention, in which a refractory metal alloy and a rare earth alloy are grain boundary diffused, may have excellent magnetic properties such as coercivity.

[0012] The effects of the present invention are not limited to the effects described above, and effects not mentioned will be clearly understood by those skilled in the art from the specification herein.

[0013] Fig. 1 is Pr 70 Cu 15 Al 10 This shows the results of measuring the melting point of Ga5 alloy.

[0014] Figure 2 is a refractory metal alloy (Zr 25 Fe 75 ) and the results of measuring the coercivity and magnetic flux density of a permanent magnet in which a rare-earth alloy is grain-boundary diffused (Example 1-1 and Example 1-2), a permanent magnet in which a rare-earth alloy is grain-boundary diffused (Comparative Example 1), and a base magnet without a grain-boundary diffusion process are shown.

[0015] Figure 3 is a refractory metal alloy (Ti 74 Ni 26 ) and the results of measuring the coercivity and magnetic flux density of a permanent magnet in which a rare-earth alloy is grain-boundary diffused (Example 2-1 and Example 2-2), a permanent magnet in which a rare-earth alloy is grain-boundary diffused (Comparative Example 1), and a base magnet without a grain-boundary diffusion process are shown.

[0016] When a part in this specification is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0017] Throughout this specification, the unit “parts by weight” means the weight ratio of each component.

[0018] Throughout this specification, the unit “at%” means the ratio of elements between each component.

[0019] Throughout this specification, "rare earth alloy" means an alloy containing one or more rare earth metals. Furthermore, "light rare earth alloy" means an alloy containing one or more light rare earth metals, and "heavy rare earth alloy" means an alloy containing one or more heavy rare earth metals.

[0020] Throughout this specification, “refractory metal alloy” means an alloy containing one or more refractory metals.

[0021] Hereinafter, the present invention will be described in more detail.

[0022]

[0023] One embodiment of the present invention provides a method for manufacturing a grain-boundary diffused R-Fe-B permanent magnet, comprising the steps of: applying and drying a refractory metal alloy and a rare earth alloy to an R-Fe-B permanent magnet; and heat-treating the R-Fe-B permanent magnet on which the refractory metal alloy and the rare earth alloy have been applied and dried to cause grain boundary diffusion; wherein R is Nd, Pr, Dy, Ce, La, Gd, Tb, or Y. By subjecting the refractory metal alloy to grain boundary diffusion, grain growth (coarsening) within the R-Fe-B permanent magnet can be effectively restricted, the thickness of the Pr shell can be reduced, and the concentration of Pr around the grains can be increased, thereby manufacturing an R-Fe-B permanent magnet having improved magnetic properties such as coercivity. Therefore, the R-Fe-B permanent magnet manufactured by the above manufacturing method, in which the refractory metal alloy and the rare earth alloy are grain-diffused, may have superior magnetic properties, such as coercivity, compared to the R-Fe-B permanent magnet manufactured by the above manufacturing method, in which only the rare earth alloy is grain-diffused, and the R-Fe-B permanent magnet (basic magnet) in which the grain-diffusion is not performed.

[0024] According to one embodiment of the present invention, the steps of applying and drying a refractory metal alloy and a rare earth alloy to an R-Fe-B permanent magnet may be performed simultaneously or sequentially, regardless of the order. Specifically, the refractory metal alloy and the rare earth alloy may be applied and dried simultaneously, the refractory metal alloy may be applied and dried and then the rare earth alloy may be applied and dried, or the rare earth alloy may be applied and dried and then the refractory metal alloy may be applied and dried. In addition, when the refractory metal alloy (or rare earth alloy) is applied and dried first, a mixture including polyvinyl alcohol, which will be described later, may be additionally applied and then the rare earth alloy (or refractory metal alloy) may be applied and dried.

[0025] According to one embodiment of the present invention, the refractory metal alloy may include at least one selected from Zr, Fe, Ti, Ni, Ta, W, Nb, V, Mo, Cu, Al, Ga, Mn, Zn and Co. Specifically, the refractory metal alloy may include at least one selected from Zr, Fe, Ti and Ni. In addition, the refractory metal alloy may include two or more of the above-mentioned metals and form a eutectic alloy. Since the refractory metal alloy has eutectic properties, the melting temperature of the refractory metal alloy including the refractory metal having a high melting temperature can be lowered, thereby improving the grain boundary diffusion efficiency of the refractory metal alloy. More specifically, the refractory metal alloy may include Zr having eutectic properties. 25 Fe 75 or Ti 74 Ni 26 It can be done. By performing grain boundary diffusion with the aforementioned refractory metal alloy, it is possible to effectively limit grain growth (coarsening) inside the permanent magnet, reduce the thickness of the Pr shell, and increase the Pr concentration around the grains, thereby manufacturing an R-Fe-B permanent magnet with improved magnetic properties such as coercivity.

[0026] According to one embodiment of the present invention, the amount of the refractory metal alloy applied may be 0.1 parts by weight to 5 parts by weight based on 100 parts by weight of the R-Fe-B permanent magnet. Specifically, the amount of the refractory metal alloy applied may be 0.1 parts by weight to 5 parts by weight, 0.1 parts by weight to 3 parts by weight, 0.1 parts by weight to 2 parts by weight, 0.1 parts by weight to 1.5 parts by weight, 0.1 parts by weight to 1 part by weight, 0.5 parts by weight to 5 parts by weight, 0.5 parts by weight to 4 parts by weight, 0.5 parts by weight to 2 parts by weight, 0.5 parts by weight to 1.5 parts by weight, or 0.5 parts by weight to 1 part by weight. By applying a refractory metal alloy in the aforementioned amount and performing grain boundary diffusion, grain growth (coarsening) inside the permanent magnet can be effectively restricted, the thickness of the Pr shell can be reduced, and the Pr concentration around the grains can be increased, thereby manufacturing an R-Fe-B permanent magnet having improved magnetic properties such as coercivity. On the other hand, if the amount of the refractory metal alloy applied is less than the aforementioned range, the effect of grain boundary diffusion with the refractory metal alloy may be minimal, and if the amount of the refractory metal alloy applied is more than the aforementioned range, grain boundary diffusion of the rare earth alloy may be hindered, thereby deteriorating the magnetic properties of the grain boundary-diffused permanent magnet.

[0027] According to one embodiment of the present invention, the rare earth alloy may include at least one selected from Dy (dysprosium), Tb (terbium), La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), and Sm (samarium). A permanent magnet in which the rare earth alloy including the above-mentioned rare earth element is grain-diffused may have superior coercivity than a basic magnet in which the grain-diffusion is not performed. Furthermore, the rare earth alloy may be at least one selected from La, Ce, Pr, Nd, and Sm, which are light rare earth alloys. By using the light rare earth alloy including the above-mentioned light rare earth element (metal), which is cheaper than the heavy rare earth element (metal), the manufacturing cost may be low.

[0028] According to one embodiment of the present invention, the rare earth alloy may include Pr (praseodymium), Al (aluminum), Cu (copper), and Ga (gallium). Specifically, it may include at least one selected from Dy, Tb, La, Ce, Pr, Nd, and Sm, and may further include Al, Cu, and Ga. The rare earth alloy may include Pr of 60 at% to 80 at%, 65 at% to 80 at%, 70 at% to 80 at%, 75 at% to 80 at%, 60 at% to 75 at%, 65 at% to 75 at%, 67.5 at% to 72.5 at% or 70 at% with respect to the total elements, and may include Cu of 5 at% to 25 at%, 10 at% to 25 at%, 15 at% to 25 at%, 20 at% to 25 at%, 5 at% to 20 at%, 10 at% to 20 at%, 15 at% to 20 at%, 12.5 at% to 17.5 at% or 15 at% with respect to the total elements of the rare earth alloy, and may include Cu of 5 at% to It may include Al of 15 at%, 7.5 at% to 15 at%, 10 at% to 15 at%, 12.5 at% to 15 at%, 5 at% to 12.5 at%, 7.5 at% to 12.5 at%, 10 at% to 12.5 at% or 10 at%, and may include Ga of 0.1 at% to 10 at%, 0.5 at% to 10 at%, 1 at% to 10 at%, 3 at% to 10 at%, 5 at% to 10 at%, 7 at% to 10 at%, 0.1 at% to 8 at%, 0.5 at% to 8 at%, 1 at% to 8 at%, 2 at% to 8 at%, 4 at% to 6 at% or 5 at% based on the total rare earth alloy elements.When the rare earth alloy contains the contents of Pr, Cu, Al and Ga in the aforementioned range, the melting point can be lowered compared to pure Pr, thereby improving the grain boundary diffusion efficiency of the rare earth alloy.

[0029] Specifically, Fig. 1 shows Pr 70 Cu 15 Al 10 This shows the results of measuring the melting point of Ga5 alloy. The melting point of pure Pr is 930 ℃, but Pr 70 Cu 15 Al 10 It was confirmed that the melting point of the Ga5 alloy was 711 ℃, which was lower than that of pure Pr.

[0030] According to one embodiment of the present invention, the coating amount of the rare earth alloy may be 1 part by weight to 20 parts by weight based on 100 parts by weight of the R-Fe-B permanent magnet. Specifically, the coating amount of the rare earth alloy may be 1 part by weight to 20 parts by weight, 1 part by weight to 15 parts by weight, 1 part by weight to 10 parts by weight, 5 parts by weight to 15 parts by weight, 5 parts by weight to 13 parts by weight, 5 parts by weight to 10 parts by weight, 7 parts by weight to 15 parts by weight, 7 parts by weight to 12 parts by weight, or 7 parts by weight to 9 parts by weight. By coating the rare earth alloy in the above-described coating amount and performing grain boundary diffusion, an R-Fe-B permanent magnet having superior magnetic properties such as coercivity compared to an R-Fe-B permanent magnet (basic magnet) that is not subjected to grain boundary diffusion can be manufactured.

[0031] According to one embodiment of the present invention, the drying may be performed at a temperature of 30°C to 500°C for 1 to 60 minutes. Specifically, the drying temperature may be 30°C to 500°C, 30°C to 250°C, 30°C to 150°C, 30°C to 100°C, 50°C to 500°C, 50°C to 300°C, 50°C to 150°C, 50°C to 100°C, 60°C to 100°C or 70°C to 90°C, and the drying temperature may be 1 minute to 60 minutes, 1 minute to 40 minutes, 1 minute to 20 minutes, 1 minute to 10 minutes, 5 minutes to 60 minutes, 5 minutes to 30 minutes, 5 minutes to 20 minutes or 5 minutes to 15 minutes. By drying within the temperature and time ranges described above, a mixture containing polyvinyl alcohol described below can be effectively dried, and the grain boundary diffusion efficiency of a refractory metal alloy and a rare earth alloy can be improved.

[0032] According to one embodiment of the present invention, the grain boundary diffusion step may be a first heat treatment at a temperature of 700°C to 1100°C for 1 to 30 hours, and a second heat treatment at a temperature of 400°C to 700°C for 1 to 10 hours. Specifically, the first heat treatment temperature may be 700 ℃ to 1100 ℃, 700 ℃ to 1050 ℃, 700 ℃ to 1000 ℃, 800 ℃ to 1100 ℃, 800 ℃ to 1050 ℃, 800 ℃ to 1000 ℃, 900 ℃ to 1100 ℃, 900 ℃ to 1050 ℃, 900 ℃ to 1000 ℃, 950 ℃ to 1100 ℃, 950 ℃ to 1050 ℃ or 950 ℃ to 1000 ℃, and the first heat treatment time may be 1 hour to 30 hours, 1 hour to 25 hours, 1 hour to 15 hours, 5 hours to 30 hours, 5 hours to 25 The time may be from 5 hours to 20 hours, from 10 hours to 30 hours, from 10 hours to 25 hours, from 10 hours to 20 hours or from 12 hours to 18 hours. In addition, the secondary heat treatment temperature may be 400°C to 700°C, 400°C to 650°C, 400°C to 600°C, 450°C to 700°C, 450°C to 650°C, 450°C to 600°C, 500°C to 700°C, 500°C to 650°C, or 500°C to 600°C, and the secondary heat treatment time may be 1 hour to 10 hours, 1 hour to 8 hours, 1 hour to 5 hours, 1 hour to 3 hours, 1 hour to 2 hours, 2 hours to 10 hours, 2 hours to 6 hours, or 2 hours to 4 hours. By performing primary heat treatment within the temperature and time ranges described above, the refractory metal alloy and rare earth metal can be melted and grain boundary diffusion can smoothly occur inside the R-Fe-B permanent magnet.In addition, by performing secondary heat treatment within the temperature and time ranges described above, the R-rich phase can be increased inside the R-Fe-B permanent magnet by elements such as rare earth elements, Cu, Al, Ga, etc. diffused into the grain boundaries, and an R-Fe-B permanent magnet with improved magnetic properties such as coercivity can be manufactured.

[0033] According to one embodiment of the present invention, before the step of applying and drying the refractory metal alloy and the rare earth alloy to the R-Fe-B permanent magnet, the method may further include a step of applying a solution containing polyvinyl alcohol to the R-Fe-B permanent magnet. The mixture containing polyvinyl alcohol may further include a solvent, and the solvent may be a C1-C4 alcohol such as methanol, ethanol, or propanol. The mixture containing polyvinyl alcohol acts as an adhesive, allowing the refractory metal alloy and the rare earth metal to be better attached to the R-Fe-B permanent magnet, thereby improving the grain boundary diffusion efficiency of the refractory metal alloy and the rare earth alloy.

[0034] One embodiment of the present invention provides an R-Fe-B permanent magnet manufactured by the above manufacturing method and having a coercive force of 15 kOe to 35 kOe. Specifically, the R-Fe-B permanent magnet may be a grain boundary-diffused R-Fe-B permanent magnet, and more specifically, may be a grain boundary-diffused R-Fe-B permanent magnet of a refractory metal alloy and a rare earth alloy. In addition, the crystal grains of the R-Fe-B permanent magnet of the grain boundary-diffused refractory metal alloy and a rare earth alloy may have a core-shell structure, and specifically, R2Fe 14 Core and R on B 2-x R 1 x Fe 14 It may have a shell on B. Here, the R 1 It may be a rare earth element of a grain boundary diffused rare earth alloy.

[0035] The coercive force of the R-Fe-B permanent magnet in which the above-mentioned refractory metal alloy and rare earth alloy are grain boundary diffused may be 15 kOe to 35 kOe, 15 kOe to 30 kOe, 15 kOe to 28 kOe, 20 kOe to 35 kOe, 20 kOe to 30 kOe, 20 kOe to 28 kOe, 22 kOe to 35 kOe, 22 kOe to 30 kOe, 22 kOe to 28 kOe or 22 kOe to 26 kOe, and the coercive force may be measured by applying a 5 T magnetic field. Since the above-mentioned R-Fe-B permanent magnet in which the refractory metal alloy and rare earth metal are grain-diffused has the aforementioned coercivity, it can exhibit magnetic properties such as coercivity that are superior to those of the R-Fe-B permanent magnet in which only the rare earth alloy is grain-diffused or the basic R-Fe-B permanent magnet.

[0036] Hereinafter, the present invention will be described in detail with examples and experimental examples to specifically explain the present invention. However, the examples and experimental examples according to the present invention may be modified in various different forms, and the scope of the present invention is not construed as being limited to the examples and experimental examples described below. The examples and experimental examples in this specification are provided to more fully explain the present invention to those of average skill in the art.

[0037] Manufacturing Example 1. Manufacturing of rare earth alloys

[0038] Pr 34.504 g, Al 0.944 g, Cu 3.336 g and liquid Ga 1.22 g were melted by applying 3.5 kW of electricity, and then poured onto a high-speed rotating wheel to rapidly cool (melt spinning process), thereby obtaining a ribbon-shaped rare earth alloy. The composition of the rare earth alloy was Pr 70 at%, Cu 15 at%, Al 10 at% and Ga 5 at% (Pr 70 Cu 15 Al 10 Ga5).

[0039] Example 1-1. Manufacturing of permanent magnets with grain boundary diffusion of refractory metal alloys and rare earth alloys.

[0040] The above Nd-Fe-B permanent magnet (base magnet, 12.6 mm wide, 13.5 mm long, 3.7 mm thick) was polished with sandpaper, and then a mixture (adhesive material) of polyvinyl alcohol (PVA) and ethanol was applied.

[0041] A refractory metal alloy (Zr) is applied to the permanent magnet coated with the above polyvinyl alcohol. 25 Fe 75 ) was applied and dried at a temperature of 80 ℃ for 10 minutes. After that, the rare earth alloy (Pr of Manufacturing Example 1) was applied to the dried permanent magnet. 70 Cu 15 Al 10 Ga5) was applied and dried at 80 ℃ for 10 minutes. At this time, the refractory metal alloy (Zr 25 Fe 75 ) was applied at 0.5 parts by weight per 100 parts by weight of the permanent magnet, and the rare earth alloy (Pr 70 Cu 15 Al 10 Ga5) was applied in an amount of 8 parts by weight per 100 parts by weight of the above permanent magnet.

[0042] The above refractory metal alloy (Zr 25 Fe 75 ) and rare earth alloys (Pr 70 Cu 15 Al 10 The dried permanent magnet (Ga5) was first heat-treated at a temperature of 970 ℃ for 15 hours, and then second heat-treated at a temperature of 550 ℃ for 2 hours to obtain a refractory metal alloy (Zr 25 Fe 75 ) and rare earth alloys (Pr 70 Cu 15 Al 10 A permanent magnet with Ga5) grain boundary diffusion was manufactured.

[0043] Example 1-2, Example 2-1 and Example 2-2

[0044] Except that the type and application amount of the refractory metal alloy were adjusted as shown in Table 1 below, the same method as Example 1-1 was used for the refractory metal alloy (Zr 25 Fe 75 or Ti 74 Ni 26 ) and rare earth alloys (Pr 70 Cu 15 Al 10 A permanent magnet with grain boundary diffusion of Ga5) was manufactured. The coating amounts of the refractory metal alloy and rare earth alloy in Table 1 below represent weight parts based on 100 weight parts of the permanent magnet (base magnet). In addition, the numbers in the types of refractory metal alloy and rare earth alloy represent at %.

[0045] Types of refractory metal alloys, amount of refractory metal alloy applied, types of rare earth alloys, amount of rare earth alloy applied, Example 1-1Zr 25 Fe 75 0.5Pr 70 Cu 15 Al 10 Ga58Example 1-2Zr 25 Fe 75 1Pr 70 Cu 15 Al 10 Ga58Example 2-1Ti 74 Ni 26 0.5Pr 70 Cu 15 Al 10 Ga58Example 2-2Ti 74 Ni 26 1Pr 70 Cu 15 Al 10 Ga58 Comparative Example 1--Pr 70 Cu 15 Al 10 Ga58

[0046] Comparative Example 1. Manufacturing of a permanent magnet with grain boundary diffusion of rare earth alloy.

[0047] Except that the process of applying and drying a refractory metal alloy was performed, a rare earth alloy (Pr) was prepared in the same manner as in Example 1-1. 70 Cu 15 Al 10 A permanent magnet with Ga5) grain boundary diffusion was manufactured.

[0048] Experimental Example 1. Evaluation of Magnetic Properties

[0049] The grain boundary-diffusion permanent magnets of Examples 1-1, 1-2, 2-1, 2-2 and Comparative Example 1 and the base magnet (Nd-Fe-B permanent magnet) without the grain boundary diffusion process were magnetized by applying a pulsed magnetic field in a magnetic field of 5 T. Then, the demagnetization curves (coercivity and magnetic flux density) of the magnetized magnets were measured by changing the applied magnetic field from 0 kOe to -30 kOe at room temperature using a BH hysteresis loop tracer. At this time, the magnetic field was applied in the opposite direction to the magnetization direction, and the results are shown in FIGS. 2 and 3.

[0050] Referring to Figure 2, the refractory metal alloy (Zr) of the present invention 25 F 75 ) and the permanent magnets in which the rare-earth alloy was grain-boundary diffused (Examples 1-1 and 1-2) were confirmed to have superior coercivity than the permanent magnets in which only the rare-earth alloy was grain-boundary diffused (Comparative Example 1) and the base magnets in which the grain-boundary diffusion process was not performed.

[0051] Referring to Figure 3, the refractory metal alloy (Ti) of the present invention 74 Ni 26 ) and the permanent magnets in which the rare-earth alloy was grain-boundary diffused (Examples 1-1 and 1-2) were confirmed to have superior coercivity than the permanent magnets in which only the rare-earth alloy was grain-boundary diffused (Comparative Example 1) and the base magnets in which the grain-boundary diffusion process was not performed.

[0052] Although the present invention has been described above through limited embodiments, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

Claims

1. A step of applying and drying a refractory metal alloy and a rare earth alloy to an R-Fe-B permanent magnet; and A step of heat-treating an R-Fe-B permanent magnet coated and dried with the above refractory metal alloy and rare earth alloy to cause grain boundary diffusion; A method for manufacturing a grain boundary-diffused R-Fe-B permanent magnet, wherein the above R is Nd, Pr, Dy, Ce, La, Gd, Tb or Y.

2. In paragraph 1, A method for manufacturing a grain boundary-diffused R-Fe-B permanent magnet, wherein the above-mentioned refractory metal alloy includes at least one selected from Zr, Fe, Ti, Ni, Ta, W, Nb, V, Mo, Cu, Al, Ga, Mn, Zn and Co.

3. In paragraph 1, A method for manufacturing a grain boundary-diffused R-Fe-B permanent magnet, wherein the amount of the refractory metal alloy applied is 0.1 to 5 parts by weight based on 100 parts by weight of the R-Fe-B permanent magnet.

4. In paragraph 1, A method for manufacturing a grain boundary-diffused R-Fe-B permanent magnet, wherein the rare earth alloy includes at least one selected from Dy, Tb, La, Ce, Pr, Nd and Sm.

5. In paragraph 1, A method for manufacturing a grain boundary-diffused R-Fe-B permanent magnet, wherein the rare earth alloy contains Pr, Al, Cu and Ga.

6. In paragraph 1, A method for manufacturing a grain boundary-diffused R-Fe-B permanent magnet, wherein the amount of the rare earth alloy applied is 1 to 20 parts by weight based on 100 parts by weight of the R-Fe-B permanent magnet.

7. In paragraph 1, A method for manufacturing a grain boundary-diffused R-Fe-B permanent magnet, wherein the drying is performed at a temperature of 30°C to 500°C for 1 to 60 minutes.

8. In paragraph 1, A method for manufacturing a grain boundary-diffused R-Fe-B permanent magnet, wherein the above-mentioned grain boundary diffusion step comprises a first heat treatment at a temperature of 700°C to 1,100°C for 1 to 30 hours, and a second heat treatment at a temperature of 400°C to 700°C for 1 to 10 hours.

9. In paragraph 1, Before the step of applying and drying the refractory metal alloy and rare earth alloy to the above R-Fe-B permanent magnet, A method for manufacturing a grain boundary-diffused R-Fe-B permanent magnet, further comprising the step of applying a mixture containing polyvinyl alcohol to the R-Fe-B permanent magnet.

10. An R-Fe-B permanent magnet manufactured by the manufacturing method of paragraph 1 and having a coercive force of 15 kOe to 35 kOe.

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