HR grain boundary diffusion treatment method for R-Fe-B sintered magnets

Abstract

The present invention discloses an R-Fe-B based sintered magnet obtained by subjecting an R-Fe-B based sintered compact to an HR grain boundary diffusion treatment, the R-Fe-B based sintered compact containing at least 28 wt% to 33 wt% R (the R is at least one rare earth element including Nd), 0.83 wt% to 0.96 wt% B, and 0.3 wt% to 1.2 wt% M, the grain boundary diffusion direction being perpendicular to the magnetization direction, and the ratio of the HR contents at any two points along the diffusion direction within 500 μm from the diffusion plane being 0.1 to 1.0. The present invention also discloses a grain boundary diffusion treatment method in which grain boundary diffusion of a diffusion source along a direction perpendicular to the c-axis direction effectively controls partial demagnetization, improves the diffusion effect, simplifies the manufacturing process, eliminates deformation factors, and significantly improves material yield.

Description

[Technical field]

[0001] The present invention relates to the technical field of rare earth permanent magnet materials, and in particular to an R-Fe-B based sintered magnet and a grain boundary diffusion treatment method thereof. [Background technology]

[0002] Since being discovered by American and Japanese scientists in the 1980s, Nd-Fe-B sintered magnets have been widely used in motors, electroacoustic components, computer hard disk drives (HDDs), military equipment, magnetic resonance imaging (MRI), microwave communication technology, controllers, instruments, etc. due to their advantages such as high magnetic energy product and high residual magnetic flux density.

[0003] In recent years, with the increasing demand for high-performance Nd-Fe-B magnets, grain boundary diffusion processing technology has been attracting attention and attention from related researchers. Grain boundary diffusion processing technology is a technique in which heavy rare earth elements are attached to the surface of Nd-Fe-B magnets and then diffused and penetrated into the interior of the magnet through a high-temperature treatment process. Compared to conventional technologies, this technology can significantly improve the coercive force of magnets while maintaining a nearly constant residual magnetic flux density with a smaller amount of heavy rare earth elements.

[0004] Grain boundary diffusion treatment has a large effect on improving the final magnetic properties, but it also has its own limitations. H. Nakamura et al. ("Coercivity distributions in Nd-Fe-B sintered magnets produced by the grain boundary diffusion process" J. Phys, D: Appl. Phys. 2011, 44(6): 540) applied different amounts of TbF3 mixed liquid to the surface of a 14.5 mm thick magnet, cut out samples at different depths, and measured the magnetic properties. They found that at a depth of about 4 mm, the coercivity of the magnet after diffusion treatment had decreased to the same level as before diffusion treatment, meaning that there is a limit to the diffusion distance of heavy rare earth elements into the magnet.

[0005] Niu E et al. (Anisotropy of grain boundary diffusion in sintered Nd-Fe-B magnet, Applied Physics Letters, 2014, 104(26)) found that the penetration effect of grain boundary diffusion is anisotropic in the oriented and non-oriented directions. In this study, they applied dysprosium alloy powder to the entire surface of a sample, the end surface of a sample in the oriented direction, and the end surface of the sample side in the oriented direction, and compared the results. They found that the magnet squareness after diffusion differed depending on the diffusion direction, and that the diffusion effect in the oriented direction was significantly better than that in the non-oriented direction.

[0006] In Patent CN101939804A, the characteristics of grain boundary diffusion anisotropy are ignored, and the grain boundary diffusion depth in the non-oriented direction perpendicular to the magnetization direction and the formation of the core-shell structure are poor, which has no practical effect on most materials. Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above circumstances, the present invention provides an R-Fe-B sintered magnet that has been subjected to HR grain boundary diffusion, which is obtained by performing HR grain boundary diffusion in a direction perpendicular to the magnetization direction, and which is easy to process, does not cause deformation, allows accurate dimensional control, and has a significantly improved material yield. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention employs the following technical means.

[0009] The R-Fe-B sintered magnet is obtained by subjecting an R-Fe-B sintered compact to an HR grain boundary diffusion treatment, and the R-Fe-B sintered compact is R2Fe 14 Contains B-type main phase, 28 wt% to 33 wt% R, where R is at least one rare earth element including Nd; 0.83wt%~0.96wt% B, 0.3 wt% to 1.2 wt% of M (wherein M is at least one selected from Al, Cu, Ga, Bi, Sn, Pb, and In); At least 65.2wt% to 70.5wt% Fe, or Fe and Co (specifically, the Fe content may be 65.2wt% to 70.5wt%, or the two elements Fe and Co may be substituted for each other and the total content thereof may be 65.2wt% to 70.5wt%), The HR is at least one selected from Dy, Tb, Ho, Er, Tm, Y, Yb, Lu, and Gd; the R-Fe-B based sintered compact has a magnetization direction and a plurality of surfaces, a surface perpendicular to the magnetization direction is an oriented surface, and surfaces other than the oriented surface are non-oriented surfaces; a diffusion source including HR is provided to at least one non-oriented surface of the R-Fe-B based sintered compact, and the HR is diffused along the R-Fe-B based sintered compact perpendicular to the magnetization direction, and the non-oriented surface to which the diffusion source is provided is a diffusion surface; Along the diffusion direction, the closer the point is from the diffusion surface, the higher the HR content, and the ratio of the HR contents at any two points within 500 μm from the diffusion surface is 0.1 to 1.0. When calculating the ratio of the HR contents at any two points, the HR content at the point that is the closest from the diffusion surface is used as the denominator of the ratio.

[0010] In the above embodiment, furthermore, the ratio of the HR content at any two points within a distance of 500 μm from the diffusion surface along the diffusion direction is 0.2 to 1.0.

[0011] In the above embodiment, further, the ratio of the HR contents at any two points along the magnetization direction is 0.7 to 1.0, and preferably the ratio is 1.0 or close to 1.0.

[0012] In the above embodiment, the sintered compact further contains 0.05 wt% to 2.5 wt% of T, where T is at least one element selected from Zn, Si, Ti, V, Cr, Mn, Ni, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sb, Hf, Ta, W, O, C, N, S, F, and P.

[0013] In the above embodiment, the M is at least one selected from Ga, Al, and Cu, and the total content of the Ga, Al, and Cu is 0.3 wt % to 0.8 wt %.

[0014] In the above-described embodiment, the diffusion source of the HR grain boundary diffusion is at least one of HR metal, HR oxide, HR hydrofluoric acid, HR fluoride, HR hydrogen, HR oxyfluoride, and HR-M alloy.

[0015] In the above embodiment, the diffusion source is an HR-M alloy, in which the content of M is 2 wt% or more and 30 wt% or less, and the content of HR is 70 wt% or more and 98 wt% or less, where M is at least one selected from Al, Cu, Ga, Bi, Sn, Pb, and In.

[0016] In the above embodiment, the R-Fe-B based sintered compact is preferably a rectangular compact.

[0017] The present invention further discloses an HR grain boundary diffusion treatment method for an R-Fe-B based sintered magnet, in which the R-Fe-B based sintered compact has a magnetization direction and a plurality of surfaces, a surface perpendicular to the magnetization direction is an oriented surface, and surfaces other than the oriented surface are non-oriented surfaces, a diffusion source containing HR is applied to at least one non-oriented surface of the R-Fe-B based sintered compact, and the HR is diffused into the grain boundaries perpendicular to the magnetization direction along the R-Fe-B based sintered compact, followed by heat treatment.

[0018] In the above embodiment, the R-Fe-B based sintered compact is a rectangular compact, and a diffusion source including HR is provided on four non-oriented faces of the R-Fe-B based sintered compact.

[0019] In the above-mentioned embodiment, the production method of the R-Fe-B based sintered compact further includes the steps of melting raw material components of the R-Fe-B based sintered compact to obtain a quenched alloy, hydrogen-pulverizing and finely pulverizing the quenched alloy to obtain a fine powder, and sintering the fine powder by a magnetic field compaction method to obtain the R-Fe-B based sintered compact, wherein the R-Fe-B based sintered compact is a rectangular magnet, and providing a diffusion source including HR to four orientation faces of the R-Fe-B based sintered compact.

[0020] The wt% referred to in the present invention is % by weight.

[0021] The numerical ranges disclosed herein include all point values ​​within the range. [Brief description of the drawings]

[0022] In order to more clearly describe the technical means in the embodiments of the present invention or the prior art, the drawings required in the description of the embodiments or the prior art will be briefly described below. The drawings in the following description are merely the embodiments of the present invention, and it is obvious that a person skilled in the art can derive other drawings from the drawings provided without creative efforts. [Figure 1] FIG. 1 is a schematic plan view of the surface of a rectangular molded body perpendicular to the magnetization direction, with the arrows indicating the diffusion direction. [Diagram 2] FIG. 2 is a schematic plan view of an R—Fe—B sintered magnet. [Diagram 3] FIG. 3 is another schematic plan view of the R—Fe—B based sintered magnet. [Figure 4] FIG. 4 is a schematic plan view of the diffusion surface. [Diagram 5] Fig. 5 is a schematic diagram showing the distribution of H(Tb) elements near the surface of a sintered magnet diffused perpendicular to the magnetization direction, in which (a) is a conventional sintered magnet, and (b) is the sintered magnet of Example 1 of the present invention. [Figure 6] FIG. 6 shows the results of EPMA evaluation of the HR distribution of the sintered magnet of Example 1.1 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In order to make the above-mentioned objectives, features and advantages of the present invention clearer and more obvious, the present invention will be described in more detail below with reference to specific embodiments. However, the scope of protection of the present invention is not limited to the following examples, and the experimental methods in the following examples, which do not specify specific conditions, are in accordance with normal conditions.

[0024] The diffusion direction referred to here is the direction perpendicular to a surface toward the center of the sintered magnet when a diffusion source is applied to one surface of the R-Fe-B sintered magnet by coating, deposition, etc. As shown in Fig. 1, the R-Fe-B sintered compact is a rectangular compact, and diffusion sources including HR are applied to four non-oriented surfaces of the R-Fe-B sintered compact, with the direction indicated by the arrows being the diffusion direction.

[0025] The magnetic property evaluation process, component measurement, and measurement of the temperature coefficient of coercivity mentioned in this specification are defined as follows. Magnetic property evaluation process: The magnetic properties of the sintered magnets were detected using the NIM-200C measurement system from the China Academy of Metrology. Component measurement: Each component was measured using inductively coupled plasma optical emission spectrometry (ICP-OES). The oxygen content was measured using a gas analyzer based on the gas fusion-infrared absorption method. Temperature coefficient of coercivity (20℃~60℃): β=ΔH / ΔT×100% Unit: % / ℃. The detection limit by FE-EPMA (field emission electron probe microanalyzer) was about 100 ppm, and the maximum resolution of the FE-EPMA device reached 3 nm. Measurement of HR content at "points" in sintered magnets: Using FE-EPMA, a specific area on the surface or cut surface where the "points" exist was acted upon to analyze and measure the HR content at the "points," which is the HR content within the area. The surface or cut surface where the "points" exist is a plane or cut surface perpendicular to the diffusion direction, and the specific area is a square area 50 μm long, with the "points" being the midpoints of the square areas. The selection of the measurement points is as follows: the sintered compact is a rectangular parallelepiped with six surfaces, and as shown in FIG. 2, A3 and A4 are oriented surfaces perpendicular to the magnetization direction, and A1 and A2 are non-oriented surfaces parallel to the magnetization direction. A diffusion source is applied to surface A1, and heat treatment is performed to diffuse HR along a direction parallel to A3. Point a is an arbitrary point on surface A1, point d is a point 500 μm away from surface A1, the line connecting point a and point d is parallel to the diffusion direction, and points b and c are 1 / 3 and 2 / 3 of the line connecting point a and point d. FIG. 3 shows a surface parallel to the diffusion surface, point e is 100 μm away from diffusion surface A1 and is located at the middle position in the magnetization direction, point g is 100 μm away from orientation surface A3 in the magnetization direction, and point f is located at the midpoint between points e and g. As shown in Fig. 4, the shaded area in the figure is a square with a length of 50 μm, the midpoint of the square is point a, and the HR content within the square area is HR a was measured as.

[0026] The R-Fe-B sintered magnet is obtained by subjecting an R-Fe-B sintered compact to an HR grain boundary diffusion treatment, and the R-Fe-B sintered compact is R2Fe 14 Contains B-type main phase, 28wt% to 33wt% of R (wherein R is at least one rare earth element including Nd, and may be specifically 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, or 33wt%); 0.83wt% to 0.96wt% B (specifically, it may be 0.83wt%, 0.88wt%, 0.90wt%, 0.92wt%, 0.94wt%, or 0.96wt%); 0.3 wt% to 1.2 wt% M (specifically, it may be 0.3 wt%, 0.5 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, or 1.2 wt%, and the M is at least one selected from Al, Cu, Ga, Bi, Sn, Pb, and In); At least 65.2wt% to 70.5wt% Fe, or Fe and Co (specifically, the Fe content may be 65.2wt% to 70.5wt%, or the two elements Fe and Co may be substituted for each other and the total content thereof may be 65.2wt% to 70.5wt%), The HR is at least one selected from Dy, Tb, Ho, Er, Tm, Y, Yb, Lu, and Gd; the R-Fe-B based sintered compact has a magnetization direction and a plurality of surfaces, a surface perpendicular to the magnetization direction is an oriented surface, and surfaces other than the oriented surface are non-oriented surfaces; a diffusion source including HR is provided to at least one non-oriented surface of the R-Fe-B based sintered compact, and the HR is diffused along the R-Fe-B based sintered compact in a direction perpendicular to the magnetization direction, and the non-oriented surface to which the diffusion source is provided is a diffusion surface; Along the diffusion direction, the closer the point is from the diffusion surface, the higher the HR content is, and the ratio of the HR content at any two points within 500 μm of the diffusion surface is 0.1 to 1.0, specifically, it may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0, and when the distances of both points almost overlap, the ratio is 1.0. Here, when calculating the ratio of the HR content at any two points, the HR content of the point that is the shortest distance from the diffusion surface among the two points is used as the denominator of the ratio. The line connecting the two points is required to be parallel to the diffusion direction.

[0027] In the above embodiment, the ratio of the HR content at any two points along the magnetization direction is 0.7 to 1.0, and the ratio is 1.0 or close to 1.0. This is because there is diffusion competition along the magnetization direction and the perpendicular magnetization direction inside the magnet, and the HR content shows a small fluctuation distribution.

[0028] In the above embodiment, the sintered magnet further contains 0.05 wt% to 2.5 wt% of T, where T is at least one element selected from Zn, Si, Ti, V, Cr, Mn, Ni, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sb, Hf, Ta, W, O, C, N, S, F, and P.

[0029] In the above-mentioned embodiment, the diffusion source of the HR grain boundary diffusion is at least one of HR metal, HR oxide, HR hydrofluoric acid, HR fluoride, HR hydrogen, HR oxyfluoride, and HR-M alloy, and the diffusion source may be in a powder form, or may be manufactured as a target material and deposited on the surface of the molded body by a deposition method, or may be in another form.

[0030] In the above aspect, further, the diffusion source is an HR-M alloy, in which the M content is 2 wt% or more and 30 wt% or less, and the HR content is 70 wt% or more and 98 wt% or less.

[0031] In the above embodiment, the R-Fe-B based sintered compact is preferably a rectangular compact.

[0032] The present invention further discloses an HR grain boundary diffusion treatment method for an R-Fe-B based sintered magnet, the R-Fe-B based sintered magnet having an oriented surface perpendicular to the magnetization direction and a non-oriented surface other than the oriented surface, a diffusion source containing HR is applied to at least one non-oriented surface of the R-Fe-B based sintered magnet, the HR is diffused through grain boundaries along a direction perpendicular to the magnetization direction in the R-Fe-B based sintered magnet, and then a heat treatment is performed.

[0033] In the above embodiment, the R-Fe-B based sintered compact is a rectangular compact, and a diffusion source including HR is provided on four non-oriented faces of the R-Fe-B based sintered compact.

[0034] In the above embodiment, the production of the R-Fe-B based sintered magnet further includes at least the steps of melting raw material components of the R-Fe-B based sintered compact to obtain a quenched alloy, hydrogen-pulverizing and finely pulverizing the quenched alloy to obtain a fine powder, and sintering the fine powder by a magnetic field compaction method to obtain the R-Fe-B based sintered compact.

[0035] In the present invention, the melting process in the manufacturing method is not particularly limited and can be appropriately selected according to the purpose of a person skilled in the art. For example, the mixed raw materials are placed in an alumina crucible and melted in a high-frequency vacuum induction furnace for 10-2 Pa~10 -3 The material is melted in a vacuum of 1 Pa at a temperature of 1500°C or less.

[0036] The casting process in the manufacturing method is not particularly limited and can be appropriately selected according to the purpose of a person skilled in the art. For example, after vacuum melting, Ar gas is introduced into the melting furnace to set the gas pressure at 30,000 to 50,000 Pa, and then the single roll quenching method is used for casting. 2 ℃ / sec~10 4 A quenched alloy is obtained at a cooling rate of 100° C. / sec, and the quenched alloy is subjected to heat treatment at 500° C. to 600° C. for 60 to 120 minutes, and then cooled to room temperature.

[0037] The hydrogen pulverization process in the manufacturing method is not particularly limited and can be appropriately selected according to the purpose of a person skilled in the art. For example, a hydrogen pulverization furnace containing a quenched alloy is evacuated at room temperature, and then hydrogen gas with a purity of 99.5% is introduced into the hydrogen pulverization furnace until the pressure becomes 0.08 MPa to 0.1 MPa, and after sufficient hydrogen is absorbed, the temperature is raised while evacuating, and the furnace is evacuated at a temperature of 500°C to 650°C, and then cooled, and the powder after hydrogen pulverization is taken out.

[0038] The fine pulverization process in the manufacturing method is not particularly limited and can be appropriately selected according to the purpose of a person skilled in the art. For example, the powder after hydrogen pulverization is jet milled for 100 to 200 minutes under a nitrogen gas atmosphere with an oxidizing gas content of 100 ppm or less, with a pressure of 0.38 MPa to 0.42 MPa in the pulverization chamber, to obtain fine powder, and the fine powder is classified using a classifier as necessary. The oxidizing gas means oxygen or moisture.

[0039] The magnetic field compaction process in the manufacturing method is not particularly limited and can be appropriately selected according to the purpose of a person skilled in the art. For example, an organic additive is added to the pulverized fine powder, and the powder is compacted in a magnetic field of 0.4 ton / cm at an aligning magnetic field of 1.8 T using a right-angle aligning magnetic field compaction machine. 2The powder containing the methyl caprylate is molded into a cube with a side length of 50 mm at a molding pressure of 1.4 ton / cm. After the primary molding, the cube is demagnetized in a magnetic field of 0.2 T. The molded body after the primary molding is sealed to prevent it from coming into contact with air, and then it is demagnetized using a secondary molding machine (hydrostatic press molding machine) at a pressure of 1.4 ton / cm. 2 The secondary molding was carried out at a pressure of 1000 MPa.

[0040] The sintering process in the manufacturing method is not particularly limited and can be appropriately selected according to the purpose of a person skilled in the art. For example, each molded body is transported to a sintering furnace and sintered. -3 Under a vacuum of 10 Pa, the material is held at temperatures of 200°C to 300°C and 500°C to 800°C for 2 hours each, and then sintered at a temperature of 920°C to 1050°C for 2 hours. Ar gas is then introduced to set the gas pressure to 0.1 MPa, and the material is then cooled to room temperature.

[0041] The heat treatment process in the manufacturing method is not particularly limited and can be appropriately selected according to the purpose of a person skilled in the art. For example, the heat treatment is performed at a temperature of 460° C. to 600° C. for 1 to 2 hours, and then the product is cooled to room temperature and taken out.

[0042] The method of providing the diffusion source in the manufacturing method is not particularly limited, and can be appropriately selected according to the purpose of a person skilled in the art. For example, a deposition method or a method of applying a slurry obtained by mixing a powder with an organic solvent to the surface can be adopted.

[0043] Incidentally, grain boundary diffusion is generally carried out at a temperature of 700° C. to 1050° C., but since this temperature range is a common choice in the industry, no test verification was performed within the above temperature range in the examples. EXAMPLES

[0044] Raw material blending process: Nd with a purity of 99.5%, industrial grade Fe-B, industrial pure Fe, Co and Zr with a purity of 99.9%, Al, Cu, Ga, and Ti with a purity of 99.5% were prepared and blended by weight percent. Melting process: The mixed raw materials are placed in an alumina crucible and melted in a high-frequency vacuum induction furnace for 10 minutes.-2 The material is melted in a vacuum of 1,500 Pa at a temperature of 1,500°C. Casting process: After vacuum melting, Ar gas is introduced into the melting furnace to set the gas pressure at 50,000 Pa, and then the single-roll quenching method is used for casting. 2 A quenched alloy is obtained at a cooling rate of 100° C. / sec, and the quenched alloy is heat-treated at 600° C. for 60 minutes, and then cooled to room temperature. Hydrogen crushing process: The hydrogen crushing furnace containing the quenched alloy is evacuated at room temperature, then 99.5% pure hydrogen gas is introduced into the hydrogen crushing furnace until the pressure reaches 0.1 MPa. After leaving it for 2 hours, the temperature is increased while evacuating, and the furnace is evacuated to a temperature of 500°C, after which it is cooled and the powder after hydrogen crushing is removed. Fine pulverization step: The powder after hydrogen pulverization is pulverized in a jet mill for 2 hours at a pressure of 0.4 MPa in a nitrogen gas atmosphere with an oxidizing gas content of 100 ppm or less to obtain a fine powder. The oxidizing gas means oxygen or moisture. Using a classifier, a portion of the fine powder after fine grinding (accounting for 30% of the total weight of the fine powder) was classified to remove powder particles with a particle size of 1.0 μm or less, and the classified fine powder was mixed with the remaining unclassified fine powder. After mixing, the volume of the fine powder with a particle size of 1.0 μm or less was reduced to 10% or less of the total powder volume. Methyl caprylate was added to the jet mill-pulverized powder so that the amount was 0.2% based on the weight of the mixed powder, and the mixture was thoroughly mixed in a V-type blender. Magnetic field molding process: Using a right-angle magnetic field molding machine, the magnetic field is oriented at 1.8 T and the pressure is 0.4 ton / cm. 2 The powder to which the methyl caprylate has been added is molded into a cube having a side length of 50 mm at a molding pressure of 1000 MPa, and after the molding, the cube is demagnetized in a magnetic field of 0.2 T. After the primary molding, the molded body is sealed to prevent it from coming into contact with air, and then a secondary molding machine (hydrostatic press molding machine) is used to press the molded body at 1.4 ton / cm. 2 The secondary molding was carried out at a pressure of 1000 MPa. Sintering process: Each compact is transported to a sintering furnace and sintered for 10 minutes. -3The mixture is then held at 200°C and 800°C for 2 hours under a vacuum of 100 Pa, and then sintered at 1030°C for 2 hours. Ar gas is then introduced to adjust the gas pressure to 0.1 MPa, and the mixture is then cooled to room temperature to obtain a sintered compact. Processing step: The sintered compact was processed by inner diameter blade cutting or wire cut electric discharge machining so that the device had a rectangular parallelepiped with dimensions of 18 mm x 39 mm x 50 mm (50 mm is the length in the magnetization direction). Grain boundary diffusion treatment: A Tb hydride diffusion source powder is applied to the four non-oriented faces of the processed sintered compact, and the compact is held at 850°C for 10 hours in a vacuum atmosphere to cause Tb to diffuse into the grain boundaries perpendicular to the magnetization direction along the processed sintered compact. Heat treatment process: After grain boundary diffusion, the sintered compact is heat treated in high-purity Ar gas at 500°C for 1 hour, then cooled to room temperature and removed to obtain a Tb grain boundary diffusion treated R-Fe-B sintered magnet. Post-processing process: The diffusion-treated R-Fe-B sintered magnets are cut into multiple rectangular parallelepipeds along the magnetization direction, and the final processed product dimensions are 18 mm x 39 mm x 1.8 mm (1.8 mm is the length in the magnetization direction).

[0045] In Examples 1.1 to 1.16 and Comparative Examples 1.1 to 1.7 in Table 1, sintered compacts were all produced by the method of Example 1, and the subsequent grain boundary diffusion treatment, heat treatment process, and amount of diffusion source used were the same, and only the raw material components used were different, so the compositions of the sintered compacts were different, and the magnetic properties of the resulting sintered magnets were directly detected and evaluated. The compositions of the sintered compacts of each Example and Comparative Example are shown in Table 1, and the evaluation results of the sintered magnets of each Example and Comparative Example are shown in Table 2.

[0046] [Table 1] [Table 2]

[0047] As is clear from Tables 1-2, in Comparative Example 1.1, the content of B element in Comparative Example 1.1 is more than 0.96wt%, so that sufficient metastable phase cannot be formed, and the diffusion of HR in the perpendicular magnetization direction is suppressed, so that the magnetic properties are significantly deteriorated and the thermal demagnetization resistance is significantly insufficient. On the other hand, in Comparative Example 1.2, the content of B element is lower than that in Examples 1.1-1.4, and although the diffusion effect of HR is improved, the precipitation phenomenon of 2-17 soft magnetic phases exists, so that the thermal demagnetization resistance is reduced. Therefore, in order to improve the diffusion of HR in the perpendicular magnetization direction and improve the thermal demagnetization resistance, it is necessary to control the content of B element within an appropriate range.

[0048] In Comparative Examples 1.3, 1.5, 1.6, and 1.7, the total content of M, which is the three elements Al, Ga, and Cu, is less than 0.3 wt%, which is too small to promote the diffusion of the conventional grain boundary rare earth rich phase to the non-oriented surfaces of HR. In Comparative Example 1.4, the total content of M, which is the three elements Al, Ga, and Cu, is more than 1.2 wt%, which causes an excessive amount of M to penetrate into the 2-14-1 main phase, resulting in deterioration of the magnetic properties. Therefore, by setting the content of M element to 0.3 wt% to 1.2 wt%, the diffusion effect to the non-oriented surfaces can be increased and the thermal demagnetization resistance of the sintered magnet can be significantly improved. EXAMPLES

[0049] Raw material blending process: Nd with a purity of 99.5%, industrial grade Fe-B, industrial pure Fe, Co and Zr with a purity of 99.9%, Al, Cu, Ga, and Ti with a purity of 99.5% were prepared and blended by weight percent. Melting process: The mixed raw materials are placed in an alumina crucible and melted in a high-frequency vacuum induction furnace for 10 minutes. -3 The alloy is melted in vacuum at 1,450°C in a vacuum of 10 Pa. Casting process: After vacuum melting, Ar gas is introduced into the melting furnace to set the gas pressure at 30,000 Pa, and then the single-roll quenching method is used for casting. 4 A quenched alloy is obtained at a cooling rate of 500°C / sec, and the quenched alloy is heat-treated at 500°C for 120 minutes, and then cooled to room temperature. Hydrogen crushing process: The hydrogen crushing furnace containing the quenched alloy is evacuated at room temperature, then 99.5% pure hydrogen gas is introduced into the hydrogen crushing furnace until the pressure reaches 0.08 MPa. After leaving it for 2 hours, the temperature is increased while evacuating, and the furnace is evacuated to a temperature of 650°C, after which it is cooled and the powder after hydrogen crushing is removed. Fine pulverization step: The powder after hydrogen pulverization is pulverized in a jet mill for 100 minutes in a nitrogen gas atmosphere with an oxidizing gas content of 100 ppm or less, with the pressure in the pulverization chamber being 0.42 MPa, to obtain a fine powder. Zinc stearate was added to the jet mill-pulverized powder in an amount of 0.2% based on the weight of the mixed powder, and the mixture was thoroughly mixed in a V-type blender. Magnetic field molding process: Using a right-angle magnetic field molding machine, the magnetic field is oriented at 1.8 T and the pressure is 0.4 ton / cm. 2 The powder to which the zinc stearate has been added is subjected to primary molding at a molding pressure of 1000 g / cm2 to form a cube having a side length of 50 mm. After primary molding, the cube is demagnetized in a magnetic field of 0.2 T. After the primary molding, the molded body is sealed to prevent it from coming into contact with air, and then a secondary molding machine (hydrostatic press molding machine) is used to press the molded body at 1.4 ton / cm. 2 The secondary molding was carried out at a pressure of 1000 MPa. Sintering process: Each compact is transported to a sintering furnace and sintered for 10 minutes. -3 The mixture is then held under a vacuum of 100 Pa at temperatures of 300°C and 600°C for 2 hours, respectively, and then sintered at a temperature of 920°C for 2 hours. Ar gas is then introduced to adjust the gas pressure to 0.1 MPa, and the mixture is then cooled to room temperature to obtain a sintered compact. Processing step: The sintered compact was processed by inner diameter blade cutting or wire cut electric discharge machining so that the device had dimensions of a rectangular parallelepiped of 18 mm x 39 mm x 50 mm (50 mm is the thickness in the orientation direction). Grain boundary diffusion treatment: A diffusion source containing Tb was applied to the four non-oriented surfaces of the processed sintered compact, and the compact was held at 880°C for 8 hours in a vacuum or Ar gas atmosphere, allowing Tb to diffuse into the grain boundaries perpendicular to the magnetization direction along the processed sintered compact. Method of applying the diffusion source: The diffusion source containing Tb was an alloy target, and a thin film containing Tb was deposited on the non-oriented surfaces by physical vapor deposition. Heat treatment process: After grain boundary diffusion, the sintered compact is heat treated in high-purity Ar gas at 600°C for 1 hour, then cooled to room temperature and removed to obtain a Tb grain boundary diffusion treated R-Fe-B sintered magnet. Post-processing: The diffusion-treated R-Fe-B sintered magnets are cut into multiple rectangular parallelepipeds along the magnetization direction, and the final processed product dimensions are 18 mm x 39 mm x 1.8 mm (1.8 mm is the thickness in the orientation direction).

[0050] In each example in Table 3, the diffusion source used for grain boundary diffusion is different, but the total content of Tb element in each diffusion source is the same, and the sintered compacts are manufactured using the method of Example 2, and the components are all the same. In Example 2.4, the content of M is 25wt%, and the content of HR is 75wt%. The components of the sintered compacts of each example are shown in Table 3, and the evaluation results of the sintered magnets of Examples 2.1 to 2.4 are shown in Table 4. [Table 3] [Table 4]

[0051] In the sintered magnet of Example 2.4, it was observed that the diffusion effect perpendicular to the magnetization direction in the HR sintered magnet was significantly increased, and the heat demagnetization resistance of the magnet was greatly improved. This is because the M element in the HR-M alloy effectively helps the HR element to diffuse perpendicular to the magnetization direction from the magnet surface to the inside, effectively solving the problem of heavy rare earth grain boundary diffusion anisotropy. EXAMPLES

[0052] The manufacturing method of the sintered compact in this example was the same as in Example 2.4, that is, an HR-M alloy was used as a diffusion source when performing grain boundary diffusion. The difference between each of the following examples is that the HR content and M content in the HR-M alloy are different, and a diffusion source is provided only on one of the non-oriented faces A1, but the total content of Tb element in each diffusion is the same. The components of the diffusion source in each example are shown in Table 5, and the evaluation results of the sintered magnets of Examples 3.1 to 3.6 are shown in Table 6. [Table 5] [Table 6]

[0053] From Example 2, it can be seen that M effectively assists the diffusion of HR element from the surface to the inside along the direction perpendicular to the magnetization direction. In addition, in Tables 5 and 6, it can be seen that only a small amount of M element is added to the diffusion source of Example 3.1, so that the diffusion effect perpendicular to the magnetization direction of HR in the sintered magnet is slightly improved compared to Example 2.1. In Examples 3.2 to 3.5, the M content is appropriate, and the improvement of the diffusion effect perpendicular to the magnetization direction in Tb is more significant. However, in Example 3.6, the M content is too high, so the HR concentration is greatly diluted, and a large amount of M element is incorporated into the main phase crystal grains, which deteriorates the intrinsic magnetic properties of the main phase crystal grains and also deteriorates the thermal demagnetization resistance.

[0054] The above examples are intended to explain the technical means of the present invention, and are not intended to limit the present invention. Simple modifications, equivalent modifications, and modifications of the above examples based on the technical ideas of the present invention are within the scope of the technical means of the present invention.

Claims

1. An HR grain boundary diffusion treatment method for an R-Fe-B system sintered magnet obtained by subjecting an R-Fe-B system sintered compact to HR grain boundary diffusion treatment, the R-Fe-B system sintered compact containing an R 2 Fe 14 B type main phase, 28 wt % to 33 wt % R, where R is at least one rare earth element including Nd; 0.83 wt% to 0.96 wt% B; 0.3 wt % to 1.2 wt % M (wherein M includes Al, Cu, and Ga); At least 65.2 wt% to 70.5 wt% Fe, or Fe and Co; The HR is at least one selected from Dy, Tb, Ho, Er, Tm, Y, Yb, Lu, and Gd; the R—Fe—B based sintered compact has a magnetization direction and a plurality of surfaces, a surface perpendicular to the magnetization direction is an oriented surface, and a surface other than the oriented surface is a non-oriented surface; a diffusion source including HR is applied to at least one non-oriented surface of the R-Fe-B system sintered compact, the HR is diffused along the R-Fe-B system sintered compact in a grain boundary direction perpendicular to the magnetization direction, the non-oriented surface to which the diffusion source is applied is used as a diffusion surface, and then heat treatment is performed, the diffusion source for the HR grain boundary diffusion is an HR-M alloy, the content of M is 2 wt % or more and 30 wt % or less, and the HR content is 70 wt % or more and 98 wt % or less, The HR content of a point closer to the diffusion surface along the diffusion direction is higher, and the ratio of the HR content at any two points within 500 μm from the diffusion surface is 0.1 to 1.

0.

2. The HR grain boundary diffusion treatment method for an R-Fe-B based sintered magnet according to claim 1, characterized in that the R-Fe-B based sintered compact is a rectangular compact, and a diffusion source including HR is provided on four non-oriented faces of the R-Fe-B based sintered compact.

3. 2. The method for HR grain boundary diffusion treatment of an R-Fe-B based sintered magnet according to claim 1, characterized in that the ratio of the HR content at any two points along the diffusion direction and within a distance of 500 μm from the diffusion surface is 0.2 to 1.

0.

4. The HR grain boundary diffusion treatment method for an R-Fe-B sintered magnet as described in claim 1, characterized in that the ratio of the HR content at any two points along the magnetization direction is 0.7 to 1.

0.

5. The HR grain boundary diffusion treatment method for an R-Fe-B based sintered magnet according to claim 1, characterized in that the sintered compact further contains 0.05 wt % to 2.5 wt % of T, wherein the T is at least one element selected from the group consisting of Zn, Si, Ti, V, Cr, Mn, Ni, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sb, Hf, Ta, W, O, C, N, S, F and P.

6. 2. The HR grain boundary diffusion treatment method for an R—Fe—B based sintered magnet according to claim 1, wherein the M is composed of Ga, Al, and Cu, and the total content of the Ga, Al, and Cu is 0.3 wt % to 0.8 wt %.

7. 7. The HR grain boundary diffusion treatment method for an R—Fe—B sintered magnet according to claim 1, wherein the R—Fe—B sintered compact is a rectangular compact.

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