RTB permanent magnet materials, their manufacturing methods and applications

Abstract

To provide a permanent magnet material that improves corrosion resistance without changing magnetic characteristics, improves moldability in press molding, and also improves the applicability and yield of a product.SOLUTION: An R-T-B-based permanent magnet material can precisely control the oxygen content in a magnet by forming oxide of M at grain boundary triple points and concentrating oxygen at the grain boundary triple points. In the permanent material and a manufacturing method according to the present invention, a product with high corrosion resistance can be manufactured without changing magnetic characteristics, the moldability in press molding can be improved, and the yield of the product can be improved.SELECTED DRAWING: None

Description

Detailed Description of the Invention

[0001] This application claims priority to a prior patent application filed by the applicant with the State Intellectual Property Office of the People's Republic of China on December 13, 2022, bearing application number 202211600047.2 and entitled "RTB-based permanent magnet material and its manufacturing method and application," which is hereby incorporated by reference in its entirety.

[0002] The present invention relates to an RTB permanent magnet material, its manufacturing method, and applications, and belongs to the field of magnetic materials.

[0003] [Background technology] Permanent magnet materials, also known as hard magnetic materials, have the characteristics of high anisotropy magnetic field, high coercive force, large hysteresis loop area, large magnetization magnetic field required for saturation, and the ability to maintain strong magnetic properties for a long time even after the external magnetic field is removed. Among permanent magnet materials, neodymium iron boron (NdFeB) sintered permanent magnets have better magnetic properties than other permanent magnet materials. For example, neodymium iron boron sintered permanent magnets have high magnetic energy product, coercive force and energy density, and their mechanical performance is good and easy to process. Due to these excellent properties, neodymium iron boron sintered permanent magnets are widely used in modern industry and electronic technology, such as motors, speakers, magnetic separators, computer disk drives, and magnetic resonance imaging devices.

[0004] Rare earth elements, which are the main components of NdFeB magnets, are easily oxidized, and the magnetic properties of the magnets are reduced if a large amount of oxygen is introduced during the manufacturing process. Therefore, it is possible to improve the effect on the properties of the magnets by controlling the oxygen content, which is one of the important directions in the prior art. In the manufacturing process of NdFeB sintered permanent magnet materials, oxygen is inevitably mixed into the NdFeB sintered magnets from the atmosphere, but there is a large difference in the method of controlling the oxygen content in the prior art. For example, patent document CN111554499A discloses that if the oxygen content of a sintered magnet is too high, on the one hand, the non-magnetic phase oxygen is incorporated, which reduces the overall magnetic properties, and on the other hand, these oxygen atoms are highly likely to form crack initiation points after being incorporated into the magnet, which has a serious impact on the use under harsh operating conditions. Therefore, this document discloses that the pre-sintered body is subjected to a hot press densification process after orientation molding, thereby increasing the density of the pre-sintered body, greatly reducing the porosity in the body, and discharging most of the impurity gas during the sintering process, thereby reducing the oxygen content of the NdFeB-based sintered permanent magnet. For example, patent document CN112614685A discloses that the oxygen content of the NdFeB magnet can be controlled by adding an antioxidant to the coarse powder without adding oxygen during the jet milling process, adding water to replenish oxygen after producing fine powder, uniformly mixing the fine powder and water, and then uniformly combining the oxygen decomposed during the sintering process with the NdFeB.

[0005] The above method only considers controlling the oxygen content of the atmosphere during the process, and the control method is complicated, so there is a need to further develop NdFeB-based sintered permanent magnets and their manufacturing methods to improve the above technical problems.

[0006] Summary of the Invention In order to improve the above problems, the present invention provides an RTB type permanent magnet material, in which R is one, two or more elements selected from neodymium (Nd), praseodymium (Pr), gadolinium (Gd), holmium (Ho), dysprosium (Dy) and terbium (Tb), T contains at least iron (Fe), and B is boron; The permanent magnet material further includes M selected from one or more of a transition metal element, a low melting point metal element, a nonmetal element, and a light rare earth element; and The permanent magnet material has an oxide of M in the grain boundary phase. The present invention provides an RTB type permanent magnet material characterized by:

[0007] According to an embodiment of the present invention, R is preferably selected from Nd or NdPr.

[0008] According to an embodiment of the present invention, T is preferably selected from iron (Fe) or a mixture thereof with other metal elements, which may be selected from one or more transition metal elements other than iron.

[0009] Transition metal elements in the context of the present invention have the meaning well known in the art and refer to metal elements in the d and ds blocks of the periodic table of elements, where the d block elements include elements of groups IIIB to VIIB and VIII, but do not include lanthanides and actinides, and the ds block elements include elements of groups IB to IIB. In general, transition metal elements include elements of groups 3 to 12, totaling 10, but do not include inner transition elements of the f block (elements 58 to 71 of the periodic table are called 4f inner transition elements, and elements 90 to 103 are called 5f inner transition elements, both of which belong to the f block).

[0010] According to an embodiment of the present invention, the low melting point metal may be selected from metals having a melting point of 1300° C. or less, and examples thereof may include one or more of copper (Cu), gallium (Ga), aluminum (Al), zirconium (Zr), titanium (Ti), tin (Sn) and manganese (Mn).

[0011] According to an embodiment of the present invention, the light rare earth element may be one or more elements selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), and europium (Eu).

[0012] According to an embodiment of the present invention, M may be selected from one or more of Cu, Ga, Al, Zr, Ti, Sn, Mn, B, V, Se, for example, one or more of Cu, Ga, Al, Zr, Ti, Sn, Mn, Se, preferably one or more of B, Cu, Ga, Al, Sn, Mn.

[0013] According to an embodiment of the present invention, the mass percentage content of R is 28.5% or more and 32.5% or less, for example, 29.0%, 29.5%, 30.0%, 30.5%, 31.0%, 31.5%, 32.0%, 32.5%, based on the mass of the permanent magnet material.

[0014] According to an embodiment of the present invention, the mass percentage content of B is 0.88% or more and 1.05% or less, for example, 0.90%, 0.95%, 0.98%, 1.00% or 1.05%, based on the mass of the permanent magnet material.

[0015] According to an embodiment of the present invention, the total mass percentage content of M is ≧0.1% and ≦4.0%, preferably ≧0.15% and ≦2.5%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5% or 4.0%, based on the mass of said permanent magnet material.

[0016] According to an embodiment of the present invention, the permanent magnet material may include Co. For example, the mass percentage content of Co is 0% or more and 0.7% or less, more preferably 0.1% or more and 0.5% or less, based on the mass of the permanent magnet material. For example, the mass percentage content of Co may be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0017] According to an embodiment of the present invention, the balance of the permanent magnet material is Fe, O, and inevitable impurities, and the inevitable impurities are at least one of C, N, and the like.

[0018] According to an embodiment of the present invention, the mass percentage content of O is 700 to 4000 ppm (mass percent) based on the mass of the permanent magnet material, for example, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 200 ppm, 350 ppm, 40 ... The mass percentage content of O is preferably 700 to 2000 ppm.

[0019] According to an embodiment of the present invention, an RMO-rich phase is present in the grain boundary phase, preferably at the grain boundary triple junctions, of the permanent magnet material.

[0020] According to an embodiment of the present invention, in the grain boundary phase of the permanent magnet material, the sum of the mass percentage of M and the mass percentage of oxygen at the grain boundary triple junction is 20% or more, preferably ≧40%. For example, at the grain boundary triple junction, the mass percentage of M is 15-45%, preferably 20-40%, for example 30-35%, an example of which may be 32%, and for example, at the grain boundary triple junction, the mass percentage of oxygen is 5-15%, preferably 6-12%, for example 7-10%, an example of which may be 8%.

[0021] According to an embodiment of the present invention, the ratio of the mass percentage content of O at the grain boundary triple junction of the permanent magnet material to the mass percentage content of O at the two grain boundaries is >1, preferably 1.5 or more, for example 1.5, 2, 2.5, 3.

[0022] According to an embodiment of the present invention, the mass percentage content of C, if present, is 400-800 ppm based on the mass of said permanent magnet material.

[0023] According to an embodiment of the present invention, the grain boundaries of the permanent magnet material may further include a compound of M, for example, one or more selected from the compounds MC and MB.

[0024] According to an embodiment of the present invention, the permanent magnet material further comprises a heavy rare earth element (HRE), where the heavy rare earth element has a meaning well known in the art and may be selected from gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y).

[0025] According to an embodiment of the present invention, the grain size of the crystal grains of the permanent magnet material is ≦6 μm, for example, 0.1 to 6 μm, for example, 0.1 μm, 0.5 μm, 1.0 μm, 1.5 μm, 3.0 μm, 4.5 μm, or 6.0 μm.

[0026] In the context of the present invention, when a numerical range is described as "greater than or equal to" or "less than or equal to" a certain numerical value, it is understood that the numerical range includes the numerical value. In other words, the expression "greater than or equal to" a certain numerical value means a numerical range of "≧the numerical value", i.e., the numerical range includes a range equal to the numerical value and a range greater than the numerical value, and the expression "less than or equal to" a certain numerical value means a numerical range of "≦the numerical value", i.e., the numerical range includes a range equal to the numerical value and a range less than the numerical value.

[0027] The present invention further provides a metal composition comprising a metal R, T, B as a substrate, and an oxide of M present in said substrate.

[0028] According to an embodiment of the present invention, the composition is in the form of a powder, the particle size of the powder is 500 μm or less, for example, 1 to 300 μm, preferably 1 to 50 μm, more preferably 3 to 40 μm, and for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm.

[0029] According to an embodiment of the present invention, the mass percentage content of the oxide of M is 0.05% or more and 5.00% or less, preferably 0.10% or more and 3.00% or less, based on the mass percentage content of the substrate in the composition, and examples thereof may be 0.05%, 0.10%, 0.20%, 0.30%, 0.40%, 0.50%, 0.60%, 0.70%, 0.80%, 0.90%, 1.00%, 1.50%, 2.00%, 2.50%, 3.00%, 3.50%, 4.00%, 4.50% or 5.00%.

[0030] According to an embodiment of the present invention, the substrate may further include inevitable impurities, and the inevitable impurities are, for example, at least one of C, N, and the like.

[0031] The present invention further provides a sintered material comprising the sintered metal composition described above.

[0032] The present invention further provides a permanent magnet comprising the heat-treated sintered material and a heavy rare earth element adhered to the sintered material and heat-treated.

[0033] The present invention further provides a permanent magnet comprising a sintered material obtained by sintering and heat treating the above metal composition, and a heavy rare earth element adhered to the sintered material and heat treated.

[0034] According to an embodiment of the present invention, a method for producing the sintered material includes molding the metal composition to obtain a molded body, and sintering the molded body to obtain the sintered material.

[0035] According to embodiments of the present invention, the compacting or sintering steps may be carried out using conditions known in the art.

[0036] According to an embodiment of the present invention, the molding step can dry mold the mixture of the metal composition. For example, the mixture of the metal composition can be filled in a mold placed in a magnetic field, and the mixture of the metal composition can be molded to obtain a molded body by applying pressure. In this case, by molding while applying a magnetic field, the mixture of the metal composition can be molded in a state in which the crystal axes of the mixture of the metal composition are oriented in a specific direction. In the molding step, a molding assistant known in the art can be added as necessary. Preferably, the pressure during pressing can be, for example, 30 MPa or more and 300 MPa or less, and the magnetic field applied can be a static magnetic field and / or a pulsed magnetic field, and the magnetic field strength can be, for example, 1000 kA / m or more and 1600 kA / m or less. Alternatively, wet molding can be adopted in which a mixture of the metal composition is molded using a slurry dispersed in a solvent such as oil.

[0037] Those skilled in the art should understand that the specific shape of the molded body is not particularly limited and can be adjusted according to the application conditions of the RTB permanent magnet material. For example, the molded body may be in the shape of a rectangular parallelepiped, a flat plate, a column, a ring, a C-shape, etc.

[0038] According to an embodiment of the present invention, in the sintering step, the obtained molded body is sintered in a vacuum or in an inert gas atmosphere. As an example, the sintering temperature may be 1000°C or more and 1150°C or less, or 1050°C or more and 1130°C or less. The sintering time is not particularly limited, and may be, for example, 2 hours or more and 10 hours or less, or 2 hours or more and 8 hours or less. The atmosphere during sintering is not particularly limited. For example, it may be an inert atmosphere, a vacuum atmosphere of less than 100 Pa, or a vacuum atmosphere of less than 10 Pa. After sintering the molded body to obtain a sintered body, it can be cooled. The cooling rate is not particularly limited, but the sintered body may be cooled rapidly, for example, at a rate of 20°C / min or more, in order to increase production efficiency.

[0039] According to an embodiment of the present invention, the surface of the sintered material is coated with a heat-treated heavy rare earth element to form a coating layer.

[0040] According to an embodiment of the present invention, the heat treatment includes a thermal diffusion treatment and a tempering treatment.

[0041] According to an embodiment of the present invention, the thermal diffusion treatment is a grain boundary diffusion treatment, and the treatment method is a process known in the art. Here, the temperature of the thermal diffusion treatment may be 800°C or more, for example, 850-950°C, and examples thereof may be 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, or 900°C. The time of the thermal diffusion treatment may be 5h or more, for example, 10-50h, for example, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, or 50h.

[0042] According to an embodiment of the present invention, the tempering temperature may be 700° C. or less, for example, 450 to 650° C., and examples thereof may be 450° C., 460° C., 470° C., 480° C., 490° C., 500° C., 510° C., 520° C., 530° C., 540° C., 550° C., 560° C., 570° C., 580° C., 590° C., 600° C., 610° C., 620° C., 630° C., 640° C., or 650° C. The tempering time may be 1 h or more, for example, 1 to 10 h, and examples thereof may be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, or 10 h.

[0043] The present invention relates to a method for producing the RTB permanent magnet material, the method comprising the steps of: forming the metal composition to obtain a formed body of the metal composition; sintering the compact to obtain a substrate comprising the sintered metal composition; contacting a heavy rare earth element with a substrate comprising the sintered metal composition; The present invention further provides a method of manufacturing the present invention, comprising the steps of:

[0044] Preferably, a heavy rare earth element is contacted with a substrate comprising the sintered metal composition to form a coating layer of the heavy rare earth element on the surface of the substrate.

[0045] The present invention further provides a method for preparing the above metal composition, comprising contacting the above metal composition with one or more of the oxides of M.

[0046] According to an embodiment of the present invention, the powder or powders selected from the metal composition, M or compound of M may be produced by a powdering process known in the art, which may be selected from a powder metallurgy process or a hydroblast jet milling process.

[0047] According to an exemplary embodiment of the present invention, the powder metallurgy process can include rapid solidification or arc melting, hydrofractionation, and high energy ball milling of the raw material. The hydrofractionation jet milling process can include rapid solidification or arc melting, hydrofractionation, and jet milling of the raw material.

[0048] According to an exemplary embodiment of the present invention, in the step of preparing the metal composition, the oxide of M is mixed with the metals R, T, B as substrates before hydro-shredding.

[0049] The present invention further provides an application of the above-mentioned Re-Fe-B based permanent magnet material in the fields of motors, speakers, magnetic separators, computer disk drives, magnetic resonance imaging devices, etc., preferably as magnetic steel for motor rotors in motors.

[0050] [Beneficial Effects] The inventor unexpectedly discovered that increasing the oxygen content in a permanent magnet material can improve thermal weight loss and corrosion resistance, but that if the oxygen content is too high, the magnetic properties are significantly reduced. The RTB permanent magnet material of the present invention can precisely control the oxygen content inside the magnet by forming an oxide of M at the grain boundary triple junction to concentrate oxygen at the grain boundary triple junction. The permanent magnet material of the present invention can improve corrosion resistance without changing the magnetic properties, and can improve formability during press molding, thereby improving the applicability and yield of the product.

[0051] BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an EMPA analysis diagram of the permanent magnet material sample F13 produced in Example 3, in which oxides of M are present at the grain boundary triple junctions.

[0052] FIG. 2 is an EMPA analysis diagram of the permanent magnet material sample F0 produced in Comparative Example 1.

[0053] FIG. 3 is an EPMA image of the permanent magnet material sample F13 produced in Example 3, showing a line scan analysis of the O content.

[0054] FIG. 4 is an EPMA image of the permanent magnet material sample F0 produced in Comparative Example 1, showing a line scan analysis of the O content.

[0055] [Mode for carrying out the invention] The technical solution of the present invention will be described in more detail below with reference to specific examples. It should be understood that the following examples are merely illustrative and interpretive of the present invention and should not be interpreted 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 in the scope of the claims of the present invention.

[0056] Unless otherwise specified, all materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0057] [Apparatus and Method] [EMPA analysis] Equipment: Shimadzu EPMA-1720 electron probe microscope, Japan. Inspection conditions: accelerating voltage is 10 kV, beam current is 20 nA, the inspection time for elements B and O is 30 s, background inspection is 10 s, and other elements are 10 s by default.

[0058] [Magnetic property inspection] Equipment: NIM-62000 rare earth permanent magnet measuring system from the Institute of Metrology. Test conditions: 20~200℃ closed circuit test.

[0059] [Weight loss performance test] Equipment: D10-10 column, German HAST high temperature and humidity test instrument. Test conditions: 130℃, 0.26atm, 100%RH, 480h.

[0060] [Production Example 1: Production of Nd-Fe-B flakes] Through vacuum smelting and stripping, NdFeB flake samples A1, A2, A3, A4 and A5 were obtained.

[0061] After testing, the mass percentage content of each element is shown in the table below. [Table 1]

[0062] [Production Example 2: Production of Nd-Fe-B coarse powder] The Nd-Fe-B flakes of Production Example 1 were subjected to hydrogen crushing to obtain Nd-Fe-B coarse powder samples B1, B2, B3, B4, and B5.

[0063] [Preparation Example 3: Production of M oxide powder] The M compounds shown in the table below were each taken and subjected to liquid phase precipitation to generate oxide precipitates, which were then filtered, washed, dried, roasted and pyrolyzed to obtain the following powder samples. [Table 2]

[0064] [Example 1: Production of Nd-Fe-B alloy powder mixture] The sample obtained in Production Example 1 and the sample obtained in Production Example 3 were mixed and homogenized, and then pulverized by hydrogen crushing and jet milling, and the surface of the neodymium iron boron-based powder was completely coated with M oxide to form a coating layer of M oxygen compound. Alternatively, the sample obtained in Production Example 2 and the sample obtained in Production Example 3 were uniformly mixed, and after mixing, the surface of the neodymium iron boron-based powder was completely coated with M oxide to form a coating layer of M oxygen compound. Specific samples are shown in the table below. [Table 3] [Table 4] [Table 5] [Table 6] [Table 7]

[0065] [Example 2: Production of sintered body of Nd-Fe-B alloy powder mixture] Samples D1 to D23 in Example 1 were treated in the following steps to produce sintered body samples E1 to E23 of the Nd—Fe—B based alloy powder mixture, respectively.

[0066] (1) Molding The samples D1 to D23 in Example 1 were press-molded in an aligning magnetic field, the magnetic field strength of the aligning magnetic field was in the range of 2 to 8 T, and the density of the samples after press molding was 3.6 to 4.2 g / cm 3 After isostatic pressing, the density of the green compacts D1 to D23 was further improved and green compacts without fine cracks were formed.

[0067] (2) Sintering The sample compacts D1 to D23 of step (1) were each sintered in a vacuum atmosphere at a sintering temperature in the range of 1080 to 1100°C, with the sintering time controlled within 2 to 10 hours. The sintered magnets were then cooled to obtain sintered samples E1 to E23.

[0068] [Example 3: Production of Nd-Fe-B based permanent magnet material] The sintered body samples E1 to E23 produced in Example 2 were treated as follows to obtain Nd—Fe—B based permanent magnet material samples F1 to F23.

[0069] (1) Coating with heavy rare earth elements A certain mass of Dy-Fe alloy or Tb-Fe alloy powder was uniformly mixed in a specific solvent, and after uniform mixing, a heavy rare earth coating slurry was obtained, and the heavy rare earth slurry was uniformly applied on the surface of the sintered sample, and a uniform and flat heavy rare earth alloy powder coating was obtained after drying.

[0070] (2) Thermal diffusion treatment The Nd-Fe-B sintered body samples with the heavy rare earth alloy attached to the surface were placed in a vacuum sintering furnace and subjected to thermal diffusion treatment at a diffusion temperature of 910°C or 890°C for a diffusion time of 20 to 35 hours.

[0071] (3) Tempering After tempering at temperatures of 480 to 550° C. for 4 hours, Nd—Fe—B based permanent magnet material samples F1 to F23 were obtained.

[0072] Comparative Example The manufacturing method of the Nd-Fe-B based permanent magnet material sample F1 is different from that of the Nd-Fe-B based permanent magnet material sample F0, in that the molding, sintering, diffusion and tempering steps were carried out without adding the M oxide powder.

[0073] [Test example 1: EMPA analysis of permanent magnet material] EPMA inspection was performed on the Nd-Fe-B permanent magnet material sample F13 produced in Example 3 above and the sample F0 produced in the comparative example, and as a result, Cu was found to be concentrated in the grain boundaries of the sample to which the M oxide powder was added, indicating that the oxide content of M(Cu) was high, as shown in Figures 1 and 2. Here, the M(Cu) content of sample F1 at the grain boundary triple junction was 32%, and the O content was 8%.

[0074] The O content of the F13 and F0 samples was analyzed by line scan using EPMA. As shown in Figures 3 and 4, the O content at the grain boundary triple junction in the sample with M oxide powder added was more than 1.5 times that of the two-particle grain boundary, whereas no obvious change trend was observed in the O content at different positions in the sample without M oxide powder added.

[0075] [Test example 2: Testing magnetic properties and weight loss properties of permanent magnet materials] The magnetic properties, oxygen content and weight loss characteristics of the Nd-Fe-B permanent magnet material samples F1 to F23 produced in Example 3 above, and sample F0 obtained in the comparative example were measured, and the results are as follows. [Table 8]

[0076] The conclusions are as follows:

[0077] Comparing samples F1 to F4, it can be seen that increasing the amount of M oxide powder added significantly increases the oxygen content inside the magnet, but the relatively high oxygen content reduces the magnetic properties of the magnet and also affects the corrosion resistance of the magnet. When the amount added is small, the content of the M oxide structure formed at the grain boundary triple junction is insufficient, the distribution of the oxygen content within the magnet becomes uneven, and the effect of improving the corrosion resistance of low Co products is not clear.

[0078] Comparing samples F5 to F9, it can be seen that the Co content clearly improves the corrosion resistance of the magnet, but an increase in the Co content has the effect of weakening the magnet Hcj. At the same time, considering that Co is a strategic material, it can be seen that the corrosion resistance of the magnet can also be improved by adding M oxide powder.

[0079] A comparison of samples F1 with F10 to F14 shows that the oxygen content that can be supplied differs depending on the mass fraction of the oxides of different M, and the effect differs significantly depending on the thickness of the coating layer, of which BO, CuO, and MgO have better effects.

[0080] A comparison of samples F1 with F15 to F18 shows that M oxide powders of different particle sizes also result in differences in properties and corrosion resistance. If the powder particles are too small, the powder itself is prone to agglomeration, which affects the mixing effect of the magnetic powder and oxide powder, resulting in uneven mixing and the formation of oxygen-enriched regions at the grain boundaries, which affects the magnetic properties. If the powder particles are too large, if there is a relatively large amount of M oxide during heat treatment, the liquid phase flow of the neodymium-rich phase is hindered, the grain boundaries become discontinuous, and this also affects the magnetic properties and corrosion resistance.

[0081] A comparison of samples F1-F5 with F19-F23 shows that adding M oxide powder before HD (hydrogen depletion) is more effective than adding it after HD. It is possible that rare earth elements and M oxide react in the high temperature environment during the process, leaving oxygen as a compound at the grain boundaries, whereas there is a possibility of aggregation and non-uniformity even after mixing the magnet powder and oxide powder after HD, and the oxygen content at the grain boundary triple junction is reduced.

[0082] A comparison between samples F1 and F0 shows that the permanent magnet material samples of the present invention form MO compounds at the grain boundary triple junctions, concentrating oxygen at the grain boundary triple junctions, thereby making it possible to control the oxygen content inside the magnet.

[0083] The above is an illustrative description of the embodiments of the present invention. However, the scope of the claims of the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art without departing from the spirit and principles of the present invention are also included in the scope of the claims of the present invention. [Brief description of the drawings]

[0084] [Figure 1] 1 is an EMPA analysis diagram of the permanent magnet material sample F13 produced in Example 3, in which an oxide of M is present at the grain boundary triple junction. [Diagram 2] FIG. 1 is an EMPA analysis diagram of the permanent magnet material sample F0 produced in Comparative Example 1. [Diagram 3]FIG. 1 is an EPMA image of the permanent magnet material sample F13 produced in Example 3, showing a line scan analysis of the O content. [Figure 4] 1 is an EPMA image of the permanent magnet material sample F0 produced in Comparative Example 1, showing a line scan analysis of the O content.

Claims

1. An R-T-B system permanent magnet material, in which R is selected from Nd or NdPr, T contains at least iron (Fe), and B is boron; The permanent magnet material further includes M selected from one or more of a transition metal element, a low melting point metal element, a nonmetal element, and a light rare earth element; and an oxide of M is present in the grain boundary phase of the permanent magnet material; an R-M-O rich phase is present at the grain boundary triple junction of the permanent magnet material; At the grain boundary triple junction, the sum of the mass percentage of M and the mass percentage of oxygen is 20% or more; the ratio of the mass percentage content of O at the grain boundary triple junction to the mass percentage content of O at the two-particle grain boundary is 1.5 or more; The balance of the permanent magnet material is Fe, O, and unavoidable impurities. The R-T-B system permanent magnet material is characterized by the above.

2. The low melting point metal may be selected from metals having a melting point of 1300° C. or less, and examples thereof may include one or more of copper (Cu), gallium (Ga), aluminum (Al), zirconium (Zr), titanium (Ti), tin (Sn), and manganese (Mn); The light rare earth element may be one or more elements selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), and europium (Eu); 2. The R-T-B system permanent magnet material according to claim 1 .

3. M is selected from one or more of Cu, Ga, Al, Zr, Ti, Sn, Mn, B, V, and Se; 3. The R-T-B system permanent magnet material according to claim 2.

4. The mass percentage content of R is 28.5% or more and 32.5% or less based on the mass of the permanent magnet material; The mass percentage content of B is 0.88% or more and 1.05% or less, based on the mass of the permanent magnet material; The total mass percentage content of M is 0.1% or more and 4.0% or less, based on the mass of the permanent magnet material; 2. The R-T-B system permanent magnet material according to claim 1 .

5. The permanent magnet material contains Co, and the mass percentage content of Co is 0.1% or more and 0.7% or less based on the mass of the permanent magnet material.

2. The R-T-B system permanent magnet material according to claim 1 .

6. The mass percentage content of O is 700 to 2000 ppm based on the mass of the permanent magnet material; 2. The R-T-B system permanent magnet material according to claim 1 .

7. At the grain boundary triple point of the permanent magnet material, the sum of the mass percentage of M and the mass percentage of oxygen is ≧40%.

2. The R-T-B system permanent magnet material according to claim 1 .

8. A method for producing an R-T-B system permanent magnet material according to claim 1, comprising the steps of: a step of preparing a metal composition, the composition comprising metals R, T, B as substrates and an oxide of M present in the substrate, the composition being in powder form, the particle size of the powder being 500 μm or less, and the mass percentage content of the oxide of M being 0.05% or more and 5.00% or less based on the mass percentage of the substrate in the composition, the oxide of M being mixed with the metals R, T, B as substrates before hydro-shredding; forming the metal composition to obtain a formed body of the metal composition; sintering the compact to obtain a substrate comprising the sintered metal composition; contacting a heavy rare earth element with a substrate comprising the sintered metal composition; A manufacturing method comprising:

9. Contacting the heavy rare earth element with a substrate containing the sintered metal composition to form a coating layer of the heavy rare earth element on a surface of the substrate. The method according to claim 8 .

10. 2. The RTB system permanent magnet material according to claim 1, wherein the RTB system permanent magnet material is used as magnetic steel for motor rollers in a motor.

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