Rare earth magnet manufacturing method and rare earth magnet

Abstract

To provide a method for manufacturing a rare earth magnet capable of improving magnetic characteristics by achieving both high densification of a sintered body and suppression of distortion of a magnetic phase.SOLUTION: A method for manufacturing a rare earth magnet includes the steps of: preparing magnetic powder containing Sm, Fe and N; preparing modifier powder containing at least one of metallic zinc and a zinc alloy; obtaining mixed powder by mixing the magnetic powder with the modifier powder; compression-molding the mixed powder in a magnetic field to obtain a magnetic field molded body; and pressure-sintering the magnetic field molded body to obtain a sintered body. In the pressure-sintering, the magnetic field molded body is pressure-sintered at temperature of 360°C or higher and 390°C or lower for a time of one hour or more and 24 hours or less under pressure of 500 MPa or more and 900 MPa or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for producing a rare earth magnet and a rare earth magnet, and more particularly to a method for producing a rare earth magnet in which magnetic powder containing Sm, Fe, and N is sintered, and a rare earth magnet. [Background technology]

[0002] Conventionally, SmCo-based rare earth magnets and NdFeB-based rare earth magnets have been put to practical use as high-performance rare earth magnets, but in recent years, development has been underway of SmFeN-based rare earth magnets containing Sm, Fe, and N. SmFeN-based rare earth magnets are produced using SmFeN-based magnetic powder containing Sm, Fe, and N. Known examples of methods for producing SmFeN-based rare earth magnets and rare earth magnets include a method for producing a rare earth magnet that includes mixing SmFeN-based magnetic powder and a modifier powder containing a zinc component to obtain a mixed powder, compression-molding the mixed powder in a magnetic field to obtain a magnetically compacted body, and pressure-sintering the magnetically compacted body to obtain a sintered body, and the rare earth magnet obtained thereby (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-077289 Summary of the Invention [Problem to be solved by the invention]

[0004] The method for producing a rare earth magnet described in Patent Document 1 involves reacting the SmFeN magnetic powder with the zinc component of the modifier powder during pressure sintering to form a modifier phase on the surface of the magnetic powder and suppress demagnetization. Furthermore, to achieve high density and improve magnetic properties, the magnetically compacted body is pressure-sintered at a pressure of 200 MPa to 1500 MPa and a temperature of 300°C to 400°C for 1 minute to 30 minutes. However, under these conventional pressure sintering conditions, the high pressure can cause distortion to accumulate in the magnetic phase of the sintered body, potentially resulting in poor remanence. Furthermore, the high temperature can cause excessive reaction between the SmFeN magnetic powder and the zinc component of the modifier powder, reducing the proportion of the magnetic phase in the sintered body and potentially reducing remanence.

[0005] The present invention has been made in consideration of these points, and its object is to provide a method for manufacturing a rare earth magnet and a rare earth magnet that can improve magnetic properties by achieving both high density of the sintered body and suppression of distortion of the magnetic phase. [Means for solving the problem]

[0006] In order to solve the above problems, the method for manufacturing a rare earth magnet of the present invention comprises the steps of: preparing a magnetic powder containing Sm, Fe, and N (magnetic powder preparation step); preparing a modifier powder containing at least one of metallic zinc and a zinc alloy (modifier powder preparation step); mixing the magnetic powder and the modifier powder to obtain a mixed powder (mixing step); compressing the mixed powder in a magnetic field to obtain a magnetically molded body (magnetic field molding step); and pressure-sintering the magnetically molded body to obtain a sintered body (pressure sintering step), wherein the pressure sintering step is characterized in that the magnetically molded body is pressure-sintered at a pressure of 500 MPa to 900 MPa and a temperature of 360°C to 390°C for 1 hour to 24 hours.

[0007] In order to solve the above-mentioned problems, the rare earth magnet of the present invention comprises a sintered body of a mixed powder comprising a magnetic powder containing Sm, Fe, and N, and a modifier powder containing at least one of metallic zinc and a zinc alloy, and the sintered body has a half-width of a diffraction peak of the (024) plane measured by X-ray diffraction of 0.2 degrees or less, and a bulk density of 6.2 g / cm. 3 The present invention is characterized in that: [Effects of the Invention]

[0008] According to the present invention, the magnetic properties can be improved by achieving both high density of the sintered body and suppression of distortion of the magnetic phase. [Brief explanation of the drawings]

[0009] [Figure 1] 1(a) to 1(c) are schematic process diagrams showing a method for producing a rare earth magnet according to one embodiment. [Figure 2] 1(a) and 1(b) are schematic process diagrams showing a method for producing a rare earth magnet according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] First, an outline of the method for manufacturing a rare earth magnet and the rare earth magnet according to an embodiment will be described using one embodiment as an example. Figures 1(a) to 2(b) are schematic process diagrams showing the method for manufacturing a rare earth magnet according to one embodiment.

[0011] In one embodiment of the method for producing a rare earth magnet, first, as shown in FIG. 1(a), coated magnetic powder 4 is prepared (magnetic powder preparation step). The coated magnetic powder 4 includes coated magnetic particles 2, each of which has magnetic particles 2a having a magnetic phase and a phosphate coating 2b covering the surface of the magnetic particles 2a. The coated magnetic powder 4 is an anisotropic magnetic powder. The magnetic particles 2a contain Sm, Fe, and N. Next, as shown in FIG. 1(b), metal zinc powder 8 containing metal zinc particles 6 is prepared as modifier powder 8 (modifier powder preparation step). Next, as shown in FIG. 1(c), the coated magnetic powder 4 and the metal zinc powder 8 are mixed to obtain a mixed powder 10A (mixing step).

[0012] Next, as shown in FIG. 1(d), a molding die 40 and an electromagnetic coil 50 are used to compression-mold the mixed powder 10A in a magnetic field (magnetic field molding) to obtain a magnetic field molded body 10B (magnetic field molding process). The molding die 40 includes a die 40A and a punch 40B. The die 40A has a cavity 40C, and the punch 40B slides inside the cavity 40C. The electromagnetic coils 50 are arranged on both sides of the periphery of the die 40A in a direction perpendicular to the sliding direction of the punch 40B (direction of the white arrow). The magnetic field molding is performed in a nitrogen gas atmosphere. First, the mixed powder 10A is placed in the cavity 40C of the die 40A in a nitrogen gas atmosphere. Next, the punch 40B is moved while applying a magnetic field to the mixed powder 10A in the cavity 40C of the die 40A in a direction perpendicular to the sliding direction of the punch 40B (in the direction of the arrow) using the electromagnetic coil 50, thereby compression-molding the mixed powder 10A.

[0013] Next, as shown in FIG. 2(a), the magnetic field compact 10B is pressure-sintered using a sintering mold 60 and a heater 70 to obtain a sintered body 10C (pressure sintering process). The sintering mold 60 includes a die 60A and a punch 60B. The die 60A has a cavity 60C, and the punch 60B slides inside the cavity 60C. The heater 70 includes a high-frequency induction coil 70A that is arranged around the die 60A in a direction perpendicular to the sliding direction of the punch 60B (the direction of the white arrow). Pressure sintering is performed in an argon gas atmosphere. First, the magnetic field compact 10B is transferred from the die 40A of the molding mold 40 into the cavity 60C of the die 60A of the sintering mold 60. Next, the magnetically compacted body 10B in the cavity 60C of the die 60A is heated by the high-frequency induction coil 70A while the punch 60B is moved to pressurize the magnetically compacted body 10B. In this manner, the magnetically compacted body 10B is pressure-sintered at a pressure of 500 MPa to 900 MPa and a temperature of 360°C to 390°C for 1 hour to 24 hours.

[0014] Next, although not shown, the punch 60B of the sintering mold 60 is moved to remove the sintered body 10C from the cavity 60C of the die 60A. As a result, as shown in FIG. 2(b), a rare earth magnet 1 including the sintered body 10C is manufactured as a rare earth magnet according to one embodiment. In the rare earth magnet 1, the magnetic particles 2a in the sintered body 10C are bonded by a modifier phase 5 formed by alloying the α-Fe phase in the surface portion with the zinc component of the modifier powder 8. Furthermore, in an X-ray diffraction pattern measured by X-ray diffraction of the surface of the sintered body 10C, the half-width of the diffraction peak of the (024) plane of the crystalline structure of the magnetic phase of the magnetic particles 2a in the sintered body 10C is 0.2 degrees or less. Furthermore, the bulk density of the sintered body 10C is 6.2 g / cm. 3 That's all.

[0015] In one embodiment of the method for producing a rare earth magnet, the magnetically compacted body is pressure-sintered at a pressure of 500 MPa to 900 MPa and a temperature of 360°C to 390°C for a time of 1 hour to 24 hours. By performing pressure-sintering under conditions of lower pressure and longer time than conventional methods, the bulk density of the sintered body can be increased to 6.2 g / cm. 3 The above can be achieved, and the half-width of the diffraction peak of the (024) plane of the crystal structure of the magnetic phase of the magnetic particles in the sintered body can be reduced to 0.2 degrees or less. In other words, it is possible to achieve both high density in the sintered body of the rare earth magnet according to one embodiment and suppress distortion of the magnetic phase. This makes it possible to improve the magnetic properties of the rare earth magnet according to one embodiment, such as remanent magnetization. Next, details of the manufacturing method of the rare earth magnet according to the embodiment and the rare earth magnet will be described.

[0016] 1. Rare earth magnet manufacturing method The method for manufacturing a rare earth magnet includes a magnetic powder preparation step, a modifier powder preparation step, a mixing step, a magnetic field compaction step, and a pressure sintering step.

[0017] (1)Magnetic powder preparation process In the magnetic powder preparation step, a magnetic powder containing Sm, Fe, and N (hereinafter sometimes abbreviated as "SmFeN-based magnetic powder" or "magnetic powder") is prepared. The SmFeN-based magnetic powder is not particularly limited as long as it has a magnetic phase and contains magnetic particles containing Sm, Fe, and N. A common SmFeN-based magnetic powder may be used, but is usually an anisotropic magnetic powder. The SmFeN-based magnetic powder may be, for example, an uncoated magnetic powder in which the surfaces of the magnetic particles are not covered with a phosphate coating, or a coated magnetic powder containing coated magnetic particles comprising magnetic particles and a phosphate coating covering the surfaces of the magnetic particles. Coated magnetic powder is preferred as the SmFeN-based magnetic powder, as the phosphate coating can suppress deterioration of the magnetic particles due to oxidation during the magnet manufacturing process.

[0018] The magnetic phase of the magnetic particles of the magnetic powder is not particularly limited as long as it contains Sm, Fe, and N, and may be a general one. However, it is preferable that at least a part of the magnetic phase contains Th2Zn. 17Type and Th2Ni 17 It is a phase having at least one of the crystal structures of the TbCu7 type. The magnetic phase is not particularly limited, but examples thereof include a phase having a TbCu7 type crystal structure. Sm is samarium, Fe is iron, and N is nitrogen. Th is thorium, Zn is zinc, Ni is nickel, Tb is terbium, and Cu is copper. Rare earth magnets exhibit magnetization due to the magnetic phase of the magnetic particles in the magnetic powder.

[0019] The magnetic particles of the magnetic powder are not particularly limited as long as they have the magnetic phase described above and contain Sm, Fe, and N, and any magnetic particles having a general composition are sufficient. For example, particles that further contain one or more elements selected from the group consisting of La, W, and R (R is at least one selected from the group consisting of Ti, Ba, Sr, and Co) in addition to Sm, Fe, and N are included, and among these, particles whose composition is represented by the following general formula (1) are preferred.

[0020] Sm v Fe (100-v―w-x-y-z) N w La x W y R z (1) (The subscripts v, w, x, y, and z in the formula satisfy the conditions 3≦v≦30, 3≦w≦15, 0≦x≦0.5, 0≦y≦2.5, and 0≦z≦0.3.)

[0021] In the general formula (1), v is specified to be 3 to 30 because if v is less than 3, the unreacted portion of the iron component (α-Fe phase) may separate, reducing the coercivity of the magnetic powder. If v exceeds 30, Sm elements may precipitate, making the magnetic powder unstable in the air and reducing remanence. w is specified to be 3 to 15 because if w is less than 3, almost no coercivity is exhibited, and if w exceeds 15, nitrides of Sm or iron itself may form. x is specified to be 0 to 0.5, but preferably 0.05 to 0.5. If x is less than 0.05, the effect of addition is insufficient. If x exceeds 0.5, nitrides of Sm or iron itself may form, reducing magnetization. y is specified to be 0 to 2.5, but preferably 0.05 to 2.5. If y is less than 0.05, the effect of the addition is insufficient, and if y exceeds 2.5, nitrides of Sm or iron itself may be formed, which may result in a decrease in magnetization. z is 0 or more and 0.3 or less, and preferably 0.0001 or more and 0.3 or less. If z is less than 0.0001, the effect of the addition is insufficient, which may result in a decrease in magnetization, which may result in a decrease in nitrides of Sm or iron itself.

[0022] The Sm content in the magnetic particles of the magnetic powder is, for example, preferably 3% by mass or more and 30% by mass or less, and more preferably 20% by mass or more and 25% by mass or less. The N content in the magnetic particles of the magnetic powder is, for example, preferably 3% by mass or more and 15% by mass or less, and more preferably 3.3% by mass or more and 3.5% by mass or less. If the N content is too high, over-nitriding occurs, and if the N content is too low, nitriding occurs insufficiently, and the magnetic properties tend to deteriorate. The Fe content in the magnetic particles of the magnetic powder is the amount obtained by subtracting the content of elements other than Fe from the content of all elements contained in the magnetic particles of the magnetic powder.

[0023] When the magnetic particles of the magnetic powder further contain La, the La content is preferably 0.1% by mass to 5% by mass, and more preferably 0.15% by mass to 1% by mass, from the viewpoint of, for example, remanence magnetization. When the magnetic particles of the magnetic powder further contain W, the W content is preferably 0.1% by mass to 5% by mass, and more preferably 0.15% by mass to 1% by mass, from the viewpoint of, for example, coercivity. When the magnetic particles of the magnetic powder further contain R, the R content is preferably 1.0% by mass or less, and more preferably 0.5% by mass or less, from the viewpoint of, for example, temperature characteristics.

[0024] Cumulative 50% particle size D in the volume-based particle size distribution of magnetic powder 50 The (median diameter) is not particularly limited and may be a general one, but when the magnetic powder is a coated magnetic powder, it is preferably, for example, 2 μm or more and 5 μm or less, and more preferably 2.5 μm or more and 4.5 μm or less. 50 If D is too small, the amount of magnetic powder packed into the magnet will be small, which may result in a decrease in magnetization. 50 If the magnetic powder is uncoated, the coercive force of the magnet tends to decrease. 50 Also, when the magnetic powder is a coated magnetic powder, the D 50 The same applies to the magnetic powder D 50 can be determined by measurement using, for example, a laser diffraction particle size distribution measuring device.

[0025] The coated magnetic powder is obtained by phosphate treating a magnetic powder containing magnetic particles having a magnetic phase containing Sm, Fe, and N. By phosphate treating the magnetic powder, a phosphate coating, which is a passive film with P-O bonds, is formed on the surfaces of the magnetic particles of the magnetic powder. In the phosphate treatment, the magnetic powder is reacted with a phosphate treating agent, such as a phosphate salt such as orthophosphoric acid. This can be done by adding the magnetic powder to a phosphoric acid solution in which the phosphate treating agent is dissolved in water or an organic solvent. When phosphate treating the magnetic powder, it is preferable to dry the magnetic powder under atmospheric pressure or in a vacuum after the phosphate treatment. This is because chemically bonding the phosphate coating to the magnetic particles can improve the coercive force of the magnet. The drying temperature is preferably 140°C or higher. The thickness of the phosphate coating is not particularly limited and may be any conventional thickness. The thickness of the phosphate coating is, for example, 1 nm to 50 nm, preferably 5 nm to 30 nm.

[0026] (2) Modifier powder preparation process In the modifier powder preparation step, modifier powder containing at least one of metallic zinc and a zinc alloy is prepared, and the modifier powder modifies and bonds the magnetic particles of the magnetic powder with the zinc component.

[0027] The modifier powder is not particularly limited as long as it is the powder described above, and may be a general modifier powder. The modifier powder may be, for example, a metal zinc powder containing metal zinc particles or a zinc alloy powder containing zinc alloy particles.

[0028] Zinc alloys are made by dissolving Zn in another element (M 2 ) alloyed with (hereinafter referred to as "Zn-M 2 "), where Zn is zinc, M is 2 is another element other than zinc. 2 There are no particular restrictions on the M element, as long as it can be alloyed with Zn, and any common element will do. 2As the element, for example, it is preferable to use one or more elements selected from elements that lower the melting start temperature of the zinc alloy below the melting point of Zn (hereinafter, sometimes abbreviated as "melting point depressing elements"), inevitable impurity elements, etc. This is because it improves the sinterability during pressure sintering. Examples of melting point depressing elements include elements that can form a eutectic alloy with Zn, and specifically, one or more elements such as Sn, Mg, and Al. Sn is tin, Mg is magnesium, and Al is aluminum. Note that M 2 The modifier may further contain one or more elements that do not impair the melting point lowering effect of the melting point lowering element or the properties of the magnet, in addition to the melting point lowering element and inevitable impurity element. The inevitable impurity element means an impurity element that cannot be avoided from being contained in the modifier powder, such as an impurity contained in the raw material of the modifier powder, as well as an impurity element that requires a significant cost to avoid being contained in the modifier powder. Zn-M 2 Zn and M in 2 The molar ratio of Zn-M is not particularly limited, and may be a general molar ratio, which may be appropriately determined so that the sintering temperature during pressure sintering is appropriate. 2 M in 2 The molar ratio of Zn-M is, for example, 0.05 or more, preferably 0.10 or more, and particularly preferably 0.20 or more. 2 M in 2 The molar ratio is, for example, 0.90 or less, and is preferably 0.80 or less, particularly preferably 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.30 or less.

[0029] The total content of metallic zinc and zinc alloy in the modifier powder is not particularly limited and may be a common content, for example, 90% by mass or more and 100% by mass or less, and preferably 95% by mass or more and 100% by mass or less. In addition to metallic zinc and zinc alloy, the modifier powder may optionally contain a substance having at least one of a binder function, a modifier function, and other functions (such as a function to improve corrosion resistance) as long as the effects of the present invention are not impaired. The content of such a substance in the modifier powder is, for example, the content of the portion excluding metallic zinc and zinc alloy from the entire modifier powder.

[0030] Cumulative 50% particle size D in the volumetric particle size distribution of modifier powder 50 The (median diameter) is not particularly limited, but is, for example, 0.1 μm or more, preferably 0.5 μm or more, and particularly preferably 1 μm or more. 50 is, for example, 4 μm or less, more preferably 2 μm or less, and particularly preferably 1 μm or less. 50 can be determined by measurement using, for example, a laser diffraction particle size distribution measuring device.

[0031] (3) Mixing process In the mixing step, the magnetic powder and the modifier powder are mixed to obtain a mixed powder. The content of the modifier powder in the mixed powder is not particularly limited and may be a general content, but from the viewpoint of remanence magnetization, it is preferably 2 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the SmFeN magnetic powder, and more preferably 5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the SmFeN magnetic powder.

[0032] The method for mixing the magnetic powder and modifier powder is not particularly limited and may be a common method, such as a mortar, a Muller wheel mixer, an agitator mixer, a mechanofusion mixer, a V-type mixer, or a ball mill.

[0033] (4) Magnetic field forming process In the magnetic field compaction process, the mixed powder is compressed in a magnetic field (hereinafter sometimes abbreviated as "magnetic field compaction") to obtain a magnetic field compact. The magnetic field compact is given orientation, which gives the rare earth magnet anisotropy and improves remanence.

[0034] The magnetic field compaction method is not particularly limited and may be a conventional method. For example, a method of compressing the mixed powder in a compaction mold while applying a magnetic field to the mixed powder using a magnetic field generator disposed around the compaction mold (e.g., a metal mold) can be used. Examples of magnetic field generators include devices such as electromagnetic coils that apply static magnetic fields and devices that apply pulsed magnetic fields using alternating current. The atmosphere in which the magnetic field compaction is performed is not particularly limited, but an inert gas atmosphere such as an argon gas atmosphere or a nitrogen gas atmosphere is preferred, as this can suppress oxidation of the magnetically compacted body. The compaction pressure in the magnetic field compaction is, for example, 10 MPa or more, preferably 20 MPa or more, and particularly preferably 30 MPa or more, 50 MPa or more, or 100 MPa or more. The compaction pressure is, for example, 1500 MPa or less, preferably 1000 MPa or less, and particularly preferably 500 MPa or less, 200 MPa or less, or 100 MPa or less. The application time of the compaction pressure is, for example, 0.5 minutes or more, preferably 1 minute or more, and particularly preferably 3 minutes or more. The application time of the molding pressure is, for example, 10 minutes or less, preferably 7 minutes or less, and particularly preferably 5 minutes or less. The strength of the magnetic field in the magnetic field molding is, for example, 500 kA / m or more, preferably 1000 kA / m or more, and particularly preferably 1500 kA / m or more or 1600 kA / m or more. The strength of the magnetic field is, for example, 20,000 kA / m or less, preferably 15,000 kA / m or less, and particularly preferably 10,000 kA / m or less, 5,000 kA / m or less, 3,000 kA / m or less, or 2,000 kA / m or less.

[0035] (5) Pressure sintering process In the pressure sintering step, the magnetically compacted body is pressure-sintered (hereinafter sometimes abbreviated as "pressure sintering") to obtain a sintered body. The pressure sintering method is not particularly limited and may be a common method, but examples include a method in which the magnetically compacted body is heated in a heating device while being pressed in a molding die such as a metal mold. Examples of the heating device include a heater equipped with a high-frequency induction coil arranged around the molding die. The atmosphere in which pressure sintering is performed is not particularly limited, but an inert gas atmosphere such as an argon gas atmosphere or a nitrogen gas atmosphere is preferable, as this can suppress oxidation of the sintered body.

[0036] In the pressure sintering, the magnetically compacted body is pressure sintered at a pressure of 500 MPa to 900 MPa and a temperature of 360°C to 390°C for 1 hour to 24 hours, thereby achieving both high density of the sintered rare earth magnet and suppression of distortion of the magnetic phase.

[0037] When the pressure sintering pressure is 500 MPa or more and 900 MPa or less, the sintered body can be densified and the distortion of the magnetic phase can be suppressed. When the pressure sintering temperature is 360°C or more and 390°C or less, a modified phase, which is an Fe-Zn alloy phase formed by alloying the α-Fe phase on the surface of the magnetic particles with the zinc component of the modifier powder on the surface of the magnetic particles, can be formed, suppressing demagnetization. In addition, the sintered body can be densified and the distortion of the magnetic phase can be suppressed. When the temperature is less than 360°C, the modified phase may not be formed. When the temperature is more than 390°C, the magnetic powder and the zinc component of the modifier powder react excessively, reducing the proportion of the magnetic phase in the sintered body and increasing the distortion of the magnetic phase. In addition, various phases, such as alloy phases and α-Fe phases other than the modified phase, can be formed on the surface of the magnetic particles, causing demagnetization. When the pressure sintering time is 1 hour or more and 24 hours or less, the sintered body can be densified and the distortion of the magnetic phase can be suppressed. When the time is less than 1 hour, the sintered body may not be densified.

[0038] (6) Manufacturing method of rare earth magnets The method for producing a rare earth magnet is not particularly limited as long as it includes the above steps, but for example, a preferred method is one in which the magnetic powder is a coated magnetic powder containing coated magnetic particles that have magnetic particles with a magnetic phase containing Sm, Fe, and N and a phosphate coating covering the surfaces of the magnetic particles, the modifier powder is metal zinc powder, and the content of the modifier powder in the mixed powder is 5 to 10 parts by mass per 100 parts by mass of the magnetic powder. The method is also suitable for achieving a sintered body with a (024) plane diffraction peak half-width of 0.2 degrees or less as measured by X-ray diffraction and a bulk density of 6.2 g / cm. 3This is because it is easy to achieve the above. In other words, it is easy to achieve both high density of the sintered body of the rare earth magnet and suppress distortion of the magnetic phase. A method for manufacturing a rare earth magnet is, for example, to obtain a sintered body of the rare earth magnet having a cumulative 50% particle diameter D 50 is 2 μm or more and 5 μm or less, and the cumulative 50% particle size D in the volume-based particle size distribution of the modifier powder 50 A method in which the average particle size is 0.1 μm or more and 4 μm or less is preferred, as this makes it easier to achieve both high density sintered rare earth magnets and suppress distortion of the magnetic phase.

[0039] 2. Rare earth magnets The rare earth magnet comprises a sintered body of a mixed powder comprising a magnetic powder containing Sm, Fe, and N, and a modifier powder containing at least one of metallic zinc and a zinc alloy, and the sintered body has a half-width of a diffraction peak of the (024) plane measured by X-ray diffraction of 0.2 degrees or less, and a bulk density of 6.2 g / cm. 3 The rare earth magnet is not particularly limited as long as it is one of the above rare earth magnets, but it is preferable to use one manufactured by the method for manufacturing a rare earth magnet described above in "1. Manufacturing method of a rare earth magnet."

[0040] The magnetic powder contained in the mixed powder used for the sintered rare earth magnet is the same as the SmFeN magnetic powder described above in "1. Method for producing a rare earth magnet (1) Magnetic powder preparation step." The modifier powder contained in the mixed powder is the same as the modifier powder described above in "1. Method for producing a rare earth magnet (2) Modifier powder preparation step." The mixed powder is the same as the mixed powder described above in "1. Method for producing a rare earth magnet (3) Mixing step." The sintered rare earth magnet is not particularly limited as long as it is the above sintered body, but a sintered body of a magnetic field compact of the mixed powder is preferred, for example. [Example]

[0041] Hereinafter, the method for producing a rare earth magnet and the rare earth magnet according to the embodiment will be described in more detail with reference to examples and comparative examples.

[0042] [Example 1] An example of a method for manufacturing a rare earth magnet according to one embodiment of the present invention was carried out. First, coated magnetic powder was prepared (magnetic powder preparation step). The coated magnetic powder included coated magnetic particles, each of which had a magnetic phase and a phosphate coating covering the surface of the magnetic particles. The magnetic particles contained Sm (22.3 mass%), Fe (71.5 mass%), N (3.3 mass%), La (0.48 mass%), W (0.51 mass%), and Ti (0.17 mass%). The coated magnetic powder was obtained by phosphate treating magnetic powder containing magnetic particles. In this phosphate treatment, the magnetic powder was first added to pure water to obtain a slurry, and then a phosphate solution was added to the slurry so that PO of phosphoric acid (H3PO4) was added at 1 mass% relative to the solid content of the magnetic particles. Next, the slurry was stirred for 5 minutes, solid-liquid separation was performed, and then vacuum drying was carried out at 190°C for 3 hours. This formed a phosphate coating, a passive film having PO bonds, on the surface of the magnetic particles. Coated magnetic powder D 50 was 3.00 μm.

[0043] Next, as the modifier powder, a metal zinc powder containing metal zinc particles (metal zinc purity: 99.9 mass%, D 50 A modifier powder preparation step was performed. Next, the coated magnetic powder and the metal zinc powder were blended so that the metal zinc powder content was 7.5 mass %, and then the coated magnetic powder and the metal zinc powder were mixed using a vibration mill to obtain a mixed powder (mixing step).

[0044] Next, the mixed powder was compression molded in a magnetic field (magnetic field molding) to obtain a magnetically compacted body (magnetic field molding process). Magnetic field molding was performed in a nitrogen gas atmosphere, with the molding pressure of 50 MPa, the application time of the magnetic field molding being 1 minute, and the magnetic field strength of the magnetic field molding being 1600 kA / m. The magnetic field orientation during magnetic field molding aligns the easy axes of magnetization of the magnetic particles in the magnetically compacted body.

[0045] Next, the magnetically compacted body was pressure-sintered to obtain a sintered body (pressure sintering process). Pressure sintering was carried out in an argon gas atmosphere at 97,000 Pa, with a pressure (press pressure) of 900 MPa, a pressure (press temperature) of 390°C, and a pressure sintering time (press time) of 24 hours. In this way, a rare earth magnet comprising a sintered body was produced. The manufacturing conditions, including the composition of the mixed powder and the pressure sintering conditions, are shown in Table 1 below.

[0046] [Examples 2 to 4 and Comparative Examples 1 to 9] The pressure, temperature, and time for pressure sintering were as shown in Table 1 below. Except for this, a rare earth magnet comprising a sintered body was produced in the same manner as in Example 1.

[0047] [Evaluation of the half-width of the diffraction peak of the (024) plane of the sintered body] X-ray diffraction measurements were performed on the surface perpendicular to the easy axis of magnetization of the rare earth magnet sintered compacts of each of Examples 1 to 4 and Comparative Examples 1 to 9, and the X-ray diffraction patterns were obtained. The measurements were performed in an inert atmosphere using CuKα radiation. The half-width [degrees] of the diffraction peak of the (024) plane of the crystalline structure of the magnetic phase of the magnetic particles of the sintered compacts was then determined from the X-ray diffraction patterns. The results are shown in Table 1 below.

[0048] [Bulk density evaluation] The weight and volume of the sintered rare earth magnet of each of Examples 1 to 4 and Comparative Examples 1 to 9 were measured. The bulk density [g / cm 3 ] of the sintered rare earth magnet was calculated from the weight and volume (calculated from the dimensions) of the sintered rare earth magnet. 3 The results are shown in Table 1 below.

[0049] [Evaluation of magnetic properties] The magnetic properties of the rare earth magnets of Examples 1 to 4 and Comparative Examples 1 to 9 were evaluated. Each rare earth magnet was pulse-magnetized at room temperature in a magnetizing field of 6400 kA / m, and the remanence Br [T] was measured using a VSM (vibrating sample magnetometer) with a maximum magnetic field of 1600 kA / m. The results are shown in Table 1 below.

[0050] [Table 1]

[0051] [Consideration] As shown in Table 1 above, in Examples 1 to 4, the manufacturing conditions for the rare earth magnets were a pressure sintering pressure (pressing pressure) of 500 MPa or more and 900 MPa or less, a pressure sintering temperature (pressing temperature) of 360°C or more and 390°C or less, and a pressure sintering time (pressing time) of 1 hour or more and 24 hours or less. As a result, the evaluation results for the rare earth magnets showed that the bulk density of the sintered body was 6.2 g / cm 3 As a result, the half-width of the diffraction peak of the (024) plane of the crystalline structure of the magnetic phase of the sintered body was 0.2 degrees or less, and as a result, the remanent magnetization Br was 0.9 T or more.

[0052] On the other hand, in Comparative Examples 1 and 2, the half-value width exceeded 0.2 degrees. This is thought to be because the pressure exceeded 900 MPa, which caused the magnetic particles to deform significantly and reduced the crystallinity of the magnetic phase. In Comparative Examples 3 and 4, the bulk density was 6.2 g / cm 3 The half-width was less than 0.2 degrees. This is thought to be because the pressure was less than 500 MPa and the sintered body could not be densified. In Comparative Example 5, the half-width exceeded 0.2 degrees. This is thought to be because the temperature exceeded 390°C, which caused significant deformation of the magnetic particles and reduced crystallinity of the magnetic phase. In Comparative Example 6, the half-width exceeded 0.2 degrees. This is thought to be because the temperature was less than 360°C under a pressure of 900 MPa, maintaining the hardness of the magnetic particles and increasing the pressing force between the magnetic particles, resulting in reduced crystallinity of the magnetic phase. In Comparative Example 7, the half-width exceeded 0.2 degrees. This is thought to be because the temperature exceeded 390°C, which caused an excessive reaction between the magnetic powder and the zinc component and increased distortion of the magnetic phase. In Comparative Example 8, the bulk density was 6.2 g / cm 3 The half-width was below 0.2 degrees. This is thought to be because the sintered body could not be densified due to the temperature being less than 360°C under the pressure of 500 MPa. In Comparative Example 9, the half-width exceeded 0.2 degrees. This is thought to be because the time exceeded 24 hours, which increased the deformation of the magnetic particles and reduced the crystallinity of the magnetic phase.

[0053] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the spirit of the present invention as set forth in the claims. [Explanation of symbols]

[0054] 1: Rare earth magnet, 2: Coated magnetic particles, 2a: Magnetic particles, 2b: Phosphate coating, 4: Coated magnetic powder, 5: Modifier phase, 6: Metal zinc particles, 8: Metal zinc powder (modifier powder), 10A: Mixed powder, 10B: Magnetic field compact, 10C: Sintered body

Claims

1. preparing a magnetic powder containing Sm, Fe, and N; preparing a modifier powder containing at least one of metallic zinc and a zinc alloy; a step of mixing the magnetic powder and the modifier powder to obtain a mixed powder; A step of obtaining a magnetically compacted body by compression molding the mixed powder in a magnetic field; and a step of obtaining a sintered body by pressure sintering the magnetic field compact, In the pressure sintering, the magnetically compacted body is pressure sintered at a pressure of 500 MPa or more and 900 MPa or less and at a temperature of 360°C or more and 390°C or less for a time of 1 hour or more and 24 hours or less, the half-value width of the diffraction peak of the (024) plane measured by X-ray diffraction of the sintered body is 0.2 degrees or less; The method for producing a rare earth magnet, wherein the sintered body has a bulk density of 6.2 g / cm 3 or more.

2. The magnetic material has a sintered body of a mixed powder including a magnetic powder containing Sm, Fe, and N, and a modifier powder containing at least one of metal zinc and a zinc alloy, The half-value width of the diffraction peak of the (024) plane measured by X-ray diffraction of the sintered body is 0.2 degrees or less, The bulk density of the sintered body is 6.2 g / cm ３ A rare earth magnet characterized by the above.

Images