Rare earth magnet and method for producing the same

Abstract

The present invention relates to a rare earth magnet and a method for manufacturing the same. A method for manufacturing a rare earth magnet and a rare earth magnet obtained by the method, the method comprising: preparing a magnetic powder of the Sm-Fe-N system; preparing a modified material powder containing metallic zinc; mixing the magnetic powder and the modified material powder to obtain a mixed powder; compression molding the mixed powder in a magnetic field to obtain a magnetic field formed body; pressure sintering the magnetic field formed body to obtain a sintered body; and heat treating the sintered body, wherein the content ratio of the metallic zinc in the modified material powder is 10 to 30% by mass relative to the mixed powder, and, regarding the conditions of the heat treatment, when the temperature and time are set to x°C and y hours, respectively, y≧-0.32x+136 and 350≦x≦410 are satisfied.

Description

Technical Field

[0001] The present disclosure relates to a rare earth magnet and a method for manufacturing the same. The present disclosure particularly relates to a rare earth magnet having Sm, Fe and N and having at least a portion of Th2Zn 17 Type and Th2Ni 17 A rare earth magnet having a magnetic phase of a crystal structure of any type and a method for producing the same. Background Art

[0002] As high-performance rare earth magnets, Sm-Co rare earth magnets and Nd-Fe-B rare earth magnets have been put to practical use, and in recent years, research has been conducted on rare earth magnets other than these.

[0003] For example, rare earth magnets containing Sm, Fe, and N (hereinafter sometimes referred to as "Sm-Fe-N rare earth magnets") are being studied. Sm-Fe-N rare earth magnets are manufactured, for example, using magnetic powder containing Sm, Fe, and N (hereinafter sometimes referred to as "SmFeN powder").

[0004] SmFeN powder has Th2Zn 17 Type and Th2Ni 17 It is believed that in this magnetic phase, N is solid-dissolved in the Sm-Fe crystal in an intrusive manner. Therefore, in the case of SmFeN powder, N is detached due to heat and is easily decomposed. Therefore, Sm-Fe-N based rare earth magnets are mostly manufactured by molding SmFeN powder using resin and / or rubber.

[0005] As another method for producing Sm-Fe-N rare earth magnets, for example, there is the method disclosed in International Publication No. 2015 / 199096. In this method, SmFeN powder and powder containing metal zinc (hereinafter sometimes referred to as "metal zinc powder") are mixed, the mixed powder is molded in a magnetic field, and the magnetic field molded body is sintered (including liquid phase sintering).

[0006] In addition, for example, Japanese Patent Application Laid-Open Nos. 2017-117937 and 2020-102606 disclose methods for producing SmFeN powder. Summary of the invention

[0007] The sintering methods of magnetic field formed bodies are roughly divided into pressureless sintering method and pressure sintering method. In any sintering method, by sintering the magnetic field formed body, a high-density rare earth magnet (sintered body) can be obtained. In the pressureless sintering method, no pressure is applied to the magnetic field formed body during sintering, so in order to obtain a high-density sintered body, the magnetic field formed body is generally sintered at a high temperature of more than 900°C for a long time of more than 6 hours. On the other hand, in the pressure sintering method, pressure is applied to the magnetic field formed body during sintering, so even if the magnetic field formed body is sintered at a low temperature of 600 to 800°C for a short time of 0.1 to 5 hours, a high-density sintered body can generally be obtained.

[0008] When sintering the magnetic field forming body of the mixed powder of SmFeN powder and metal zinc powder, in order to avoid the decomposition of SmFeN powder due to heat, pressure sintering is adopted, but the sintering is carried out at a temperature lower than the sintering temperature of the usual pressure sintering and in a short time. The reason why sintering can be carried out even at such a low temperature and in a short time is that the zinc component in the metal zinc powder diffuses on the surface of the magnetic powder during sintering and is sintered (solidified). In this way, the metal zinc powder in the magnetic field forming body has the function of a binder. In addition, the metal zinc powder in the magnetic field forming body also has the function of a modifying material, which modifies the αFe phase in the SmFeN powder and absorbs oxygen in the SmFeN powder to increase the coercive force. Hereinafter, the powder having both the function of a binder and the function of a modifying material used in the manufacture of Sm-Fe-N rare earth magnets is sometimes referred to as "modifying material powder".

[0009] When permanent magnets such as Sm-Fe-N rare earth magnets are used in motors, they are placed in an external magnetic field environment that changes periodically. Therefore, the permanent magnets are demagnetized by the increase in the external magnetic field. This is explained using the accompanying drawings.

[0010] Figure 1 1 is an explanatory diagram schematically showing a magnetization-magnetic field curve (MH curve) of a permanent magnet. The solid line represents the magnetization-magnetic field curve of a permanent magnet with a high degree of orientation, and the dotted line represents the magnetization-magnetic field curve of a permanent magnet with a reduced degree of orientation.

[0011] exist Figure 1 The permanent magnets in the motor are used in an external magnetic field environment within the range shown in the "Motor Operating Range" in FIG. Figure 1 When the magnetization changes greatly in the working area of ​​the motor, as in the case of the permanent magnet shown by the middle dotted line, the current control on the stator side of the motor becomes complicated, and the load on the inverter connected to the motor increases. In this case, a large-capacity inverter is required, which impairs economic efficiency.

[0012] In addition, when the orientation degree decreases, the coil (recoil) magnetic permeability decreases, and the magnetization on the side with a larger absolute value of the external magnetic field in the working area of ​​the motor decreases, so the output (torque) of the motor decreases. 17 Type and / or Th2Ni 17 The magnetic phase of the crystal structure of this type is difficult to orient due to the large anisotropic magnetic field.

[0013] In order to increase the magnetization of the permanent magnet, it is effective to increase the volume ratio of the magnetic phase that exhibits magnetization. Therefore, it is effective to increase the density of the permanent magnet. In the case where the permanent magnet is obtained by molding a magnetic powder, it is effective to sinter the magnetic powder in order to increase the density of the permanent magnet. However, in order to obtain a sintered body of SmFeN powder, in order to avoid decomposition of the SmFeN powder due to heat, pressure sintering is performed at a low temperature and in a short time compared to conventional pressure sintering. In order to achieve low-temperature and short-time pressure sintering, as described above, a modifying material powder such as metal zinc powder having both the function of a binder and the function of a modifying material is used. When such a modifying material powder is used, the magnetization is reduced accordingly. Therefore, when the orientation degree of the sintered body (Sm-Fe-N based rare earth magnet) is reduced, Figure 1 In the "motor operating area", the side with the larger absolute value of the external magnetic field ( Figure 1 The magnetization decrease is more serious on the left side of the image.

[0014] Therefore, the present inventors have conceived of producing a Sm—Fe—N based rare earth magnet having an improved degree of orientation while suppressing a decrease in magnetization due to the use of a modifying material powder.

[0015] The present disclosure provides a Sm-Fe-N based rare earth magnet which suppresses the reduction of magnetization due to the use of a modifying material powder and improves the degree of orientation, and a method for producing the same.

[0016] The inventors of the present invention have conducted intensive research and have completed the rare earth magnet and the method for producing the same disclosed in the present invention. The rare earth magnet and the method for producing the same disclosed in the present invention include the following aspects.

[0017] <1> A first embodiment of the present invention relates to a method for manufacturing a rare earth magnet, characterized by comprising:

[0018] A magnetic powder is prepared, wherein the magnetic powder contains Sm, Fe and N, and at least a part of the magnetic powder contains Th2Zn 17 Type and Th2Ni 17 The magnetic phase of any crystal structure of the type,

[0019] Preparing a modified material powder containing metallic zinc,

[0020] The magnetic powder and the modified material powder are mixed to obtain a mixed powder,

[0021] The mixed powder is compressed and molded in a magnetic field to obtain a magnetic field molded body,

[0022] The magnetic field formed body is pressure-sintered to obtain a sintered body, and

[0023] heat treating the sintered body;

[0024] The content of the metal zinc in the modified material powder is 10 to 30% by mass relative to the mixed powder.

[0025] For the heat treatment conditions, when the temperature and time are set to x°C and y hours respectively, the following conditions are satisfied:

[0026] y≧-0.32x+136, and

[0027] 350≦x≦410.

[0028] <2> The x may satisfy 350≦x≦400.

[0029] <3> The y may satisfy y≦40.

[0030] <4> The magnetic field formed body may be pressure-sintered at a pressure of 1000 to 1500 MPa and a temperature of 300 to 400° C. for 1 to 30 minutes.

[0031] <5> In the magnetic powder, the ratio of magnetic particles having a particle size of 1.0 μm or less may be 1 to 20% relative to the total number of magnetic particles of the magnetic powder.

[0032] <6> A second aspect of the present invention relates to a rare earth magnet comprising Sm, Fe and N, at least a portion of which has Th2Zn 17 Type and Th2Ni 17 A magnetic phase having a crystal structure of any one of the types; containing 10 to 30 mass % of a zinc component, wherein the magnetic phase and the zinc component form crystalline phase particles; and relative to the total number of the crystalline phase particles, the proportion of the crystalline phase particles having a particle size of less than 1.0 μm is less than 10.00%.

[0033] According to the present disclosure, by making the zinc content from the modified material within a specified range and making the presence of a microcrystalline phase below a specified ratio, it is possible to provide a Sm-Fe-N rare earth magnet that suppresses the reduction in magnetization caused by the use of modified material powder and improves the degree of orientation. In addition, by mixing modified material powder within a specified range and heat-treating the sintered body obtained by pressure sintering at a low temperature and for a short time, it is possible to provide a method for manufacturing a Sm-Fe-N rare earth magnet that suppresses the reduction in magnetization caused by the use of modified material powder and improves the degree of orientation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like symbols represent like elements, and wherein:

[0035] Figure 1 This is an explanatory diagram schematically showing a magnetization-magnetic field curve (MH curve) of a permanent magnet.

[0036] Figure 2 It is an explanatory diagram showing a scanning electron microscope image of SmFeN powder.

[0037] Figure 3 This is an explanatory diagram showing a scanning electron microscope image of a sintered body of a mixed powder of SmFeN powder and a modifying material powder obtained by the method for producing a rare earth magnet disclosed in the present invention.

[0038] Figure 4 It is an explanatory diagram showing an optical microscope image of a sample of the resin-embedded SmFeN powder.

[0039] Figure 5 It is an explanatory diagram showing an optical microscope image of a cross section of a sintered body after heat treatment.

[0040] Figure 6 This is a graph showing the particle size distribution of the SmFeN powder used to prepare the samples of Examples 1 to 6 and Comparative Examples 1 to 6.

[0041] Figure 7 This is a graph showing the results of investigating the particle size distribution of crystal phase particles for the sample of Example 1 (sintered body after heat treatment).

[0042] Figure 8 This is a graph showing the results of investigating the particle size distribution of crystal phase particles for the sample of Comparative Example 1 (sintered body after heat treatment).

[0043] Fig. 9 This is a graph showing the relationship between the heat treatment temperature and the heat treatment time for a sample containing 10% by mass of the modifying material powder.

[0044] Fig.10 It is a graph showing a part of the magnetization-magnetic field curve (MH curve) of the sample of Example 6.

[0045] Fig.11 This is a graph showing the relationship between the amount of the modifying material powder blended and the magnetization when the external magnetic field is -1600 kA / m.

[0046] Fig.12 It is a graph showing the relationship between the blending amount of the modifying material powder and the orientation degree. DETAILED DESCRIPTION

[0047] Hereinafter, embodiments of the rare earth magnet and the method for producing the same according to the present disclosure will be described in detail. In addition, the embodiments described below do not limit the rare earth magnet and the method for producing the same according to the present disclosure.

[0048] In order to give orientation to the sintered body of the mixed powder of SmFeN powder and the modified material powder, the magnetic field molded body obtained by compression molding the mixed powder in a magnetic field is pressure sintered. At this time, the reason why the orientation degree of the sintered body is improved according to the manufacturing method of the rare earth magnet disclosed in the present invention is explained using the drawings.

[0049] Figure 2 It is an explanatory diagram showing a scanning electron microscope image of SmFeN powder. Figure 3 This is an explanatory diagram showing a scanning electron microscope image of a sintered body of a mixed powder of SmFeN powder and a modifying material powder obtained by the method for producing a rare earth magnet disclosed in the present invention.

[0050] Figure 2 The scanning electron microscope image shown is a rough and unclear image overall. It can be understood from this that the SmFeN powder contains fine powder particles. On the other hand, Figure 3 The scanning electron microscope image shown is clear and distinct as a whole, and there is very little microstructure (micro crystalline phase) from the fine powder particles in the SmFeN powder. Figure 3 The sintered body (the rare earth magnet of the present disclosure) having the structure shown above suppresses the decrease in magnetization caused by the use of the modified material powder and improves the degree of orientation. The present inventors believe that the reason for obtaining such a rare earth magnet is as follows, without being bound by theory.

[0051] As for micropowder particles, it is generally difficult to orient them even by compression molding in a magnetic field. In addition, the anisotropic magnetic field of the magnetic phase in the SmFeN powder is very high, so a strong magnetic field is required to orient it. Therefore, even if compression molding is performed in a strong magnetic field, particles with relatively large particle sizes (particles other than micropowder particles) are oriented, but micropowder particles are difficult to orient. It should be noted that in this specification, unless otherwise specified, the degree of orientation indicating the degree of orientation is defined as (magnetization under an external magnetic field of 1000kA / m) / (magnetization under an external magnetic field of 6000kA / m).

[0052] When the magnetic field molded body obtained by compression molding a mixed powder of a modified material powder and a SmFeN powder containing fine powder particles is pressure-sintered, if the magnetic phase from the fine powder particles remains as it is, the orientation degree of the obtained sintered body is significantly reduced. This is because when the sintered body is magnetized (magnetized, "magnetized"), the magnetic phase from the fine powder particles exists in the direction of magnetic irregularities, and therefore, the magnetic phase from the fine powder particles will offset part of the strong magnetization generated by the magnetic orientation of particles with relatively large particle sizes. In other words, this means that when the magnetic phase is oriented, strong magnetization is generated by magnetization, but when the magnetic phase from the fine powder particles exists in the direction of magnetic irregularities, not only does the magnetization decrease by a corresponding amount, but also a part of the strong magnetization generated by the oriented magnetic phase is offset.

[0053] In order to avoid the above-mentioned disadvantages of fine powder particles, a method of pressure sintering the mixed powder after removing the fine powder particles in the SmFeN powder may be considered. However, fine powder particles are often electrostatically charged, and the removal of fine powder particles often requires a lot of work.

[0054] The inventors have found that by reacting the micropowder particles with the modified material powder in the mixed powder appropriately, the magnetic phase in the micropowder particles can be made into a non-magnetic phase, thereby suppressing the disadvantages of the micropowder particles. In addition, the inventors have found that, for this purpose, it is sufficient to heat-treat the sintered body obtained by pressure sintering at a low temperature and in a short time by combining the modified material powder in a prescribed range. Moreover, it is believed that in the sintered body (the rare earth magnet disclosed in the present invention) obtained after the heat treatment, most of the crystalline phase (non-magnetic phase) from the micropowder particles is integrated with the modified phase (non-magnetic phase) coated on the surface of the particles with a relatively large particle size (particles other than the micropowder particles). Therefore, the inventors have found that the tiny crystalline phase (non-magnetic phase) from the micropowder particles in the rare earth magnet disclosed in the present invention with improved orientation is very small. It should be noted that the modified phase will be described in detail later.

[0055] The following describes the components of the rare earth magnet and the method for producing the same according to the present disclosure, which have been completed based on the findings described so far.

[0056] 《Method for producing rare earth magnets》

[0057] The method for producing a rare earth magnet disclosed in the present invention (hereinafter sometimes referred to as the "production method disclosed in the present invention") includes a magnetic powder preparation step, a modified material powder preparation step, a mixing step, a magnetic field forming step, a pressure sintering step, and a heat treatment step. Each step is described below.

[0058] <Magnetic powder preparation process>

[0059] Prepare magnetic powder (SmFeN powder). The magnetic powder (SmFeN powder) used in the manufacturing method of the present disclosure is a powder containing Sm, Fe and N, and at least a part of which has Th2Zn 17 Type and Th2Ni 17 The crystal structure of the magnetic phase may be any one of the crystal structures of the TbCu7 type. In addition to the above-mentioned structure, the crystal structure of the magnetic phase may also be a phase having a crystal structure of the TbCu7 type. For example, Sm is samarium, Fe is iron, and N is nitrogen. In addition, Th is holmium, Zn is zinc, Ni is nickel, Tb is terbium, and Cu is copper.

[0060] The SmFeN powder may contain, for example, (1-i) R i )2(Fe (1-j) Co j ) 17 N h The rare earth magnet obtained by the production method of the present disclosure (hereinafter sometimes referred to as a "product") exhibits magnetization due to the magnetic phase in the SmFeN powder. In addition, i, j and h are molar ratios.

[0061] In the magnetic phase in the SmFeN powder, R may also be contained within a range that does not hinder the effect of the manufacturing method disclosed herein and the magnetic properties of the product. Such a range is represented by i in the above composition formula. For example, i may be greater than 0, greater than 0.10, or greater than 0.20, and may be less than 0.50, less than 0.40, or less than 0.30. R is one or more rare earth elements selected from Y, Zr, and Sm. In this specification, rare earth elements refer to Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. For illustration, Y is yttrium, Zr is zirconium, Sc is scandium, La is lanthanum, Ce is cerium, Pr is praseodymium, Nd is neodymium, Pm is promethium, Sm is samarium, Eu is europium, Gd is gadolinium, Tb is terbium, Dy is dysprosium, Ho is holmium, Er is erbium, Tm is thulium, Yb is ytterbium, and Lu is lutetium.

[0062] About (Sm (1-i) R i )2(Fe (1-j)Co j ) 17 N h Typically, R in Sm2(Fe (1-j) Co j ) 17 N h For example, a portion of R may be placed in Sm2 (Fe (1-j) Co j ) 17 N h .

[0063] The magnetic phase in the SmFeN powder may contain Co within a range that does not hinder the effect of the production method disclosed herein and the magnetic properties of the product. Such a range is represented by j in the above composition formula. j may be greater than or equal to 0, greater than or equal to 0.10, or greater than or equal to 0.20, and may be less than or equal to 0.52, less than or equal to 0.40, or less than or equal to 0.30.

[0064] About (Sm (1-i) R i )2(Fe (1-j) Co j ) 17 N h Typically, Co in (Sm (1-i) R i )2Fe 17 N h For example, part of Co may be arranged in an intrusive manner in (Sm (1-i) R i )2Fe 17 N h .

[0065] As for the magnetic phase in SmFeN powder, N exists in the form of intrusion. (1-i) R i )2(Fe (1-j) Co j ) 17 In the crystal grains shown, this helps to manifest and improve the magnetic properties.

[0066] About (Sm (1-i) R i )2(Fe (1-j) Co j ) 17 N h , h can be 1.5 to 4.5, typically (Sm (1-i) R i )2(Fe (1-j) Co j )17 N3. h can be 1.8 or more, 2.0 or more, or 2.5 or less, 4.2 or less, 4.0 or less, or 3.5 or less. (1-i) R i )2(Fe (1-j) Co j ) 17 N h Overall, (Sm (1-i) R i )2(Fe (1-j) Co j ) 17 The content of N3 is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass. (1-i) R i )2(Fe (1-j) Co j ) 17 N h It may not be all (Sm (1-i) R i )2(Fe (1-j) Co j ) 17 N3. Relative to (Sm (1-i) R i )2(Fe (1-j) Co j ) 17 N h Overall, (Sm (1-i) R i )2(Fe (1-j) Co j ) 17 The content of N3 may be 98 mass % or less, 95 mass % or less, or 92 mass % or less.

[0067] SmFeN powder consists of (Sm (1-i) R i )2(Fe (1-j) Co j ) 17 N h In addition to the magnetic phases shown, oxygen, M 1 From the perspective of ensuring the magnetic properties of the product, relative to the entire SmFeN powder, (Sm (1-i) R i )2(Fe (1-j) Co j ) 17 N hThe content of the magnetic phase represented by (SmFeN) may be 80 mass % or more, 85 mass % or more, or 90 mass % or more. On the other hand, even if the content of the magnetic phase represented by (SmFeN) is not excessively increased relative to the whole SmFeN powder, (1-i) R i )2(Fe (1-j) Co j ) 17 N h The content of the magnetic phase represented by (Sm) is not a problem in practical use. Therefore, its content can be 97 mass % or less, 95 mass % or less, or 93 mass % or less. (1-i) R i )2(Fe (1-j) Co j ) 17 N h The remainder of the magnetic phase represented by is oxygen and M 1 In addition, oxygen and M 1 A portion of the ions may exist in the magnetic phase in an intrusive and / or substitutional manner.

[0068] As the above M 1 , and one or more selected from Ga, Ti, Cr, Zn, Mn, V, Mo, W, Si, Re, Cu, Al, Ca, B, Ni and C can be listed. The inevitable impurity elements refer to the impurity elements that are inevitably contained in the raw materials and / or the production of magnetic powder, etc., or that cause a significant increase in manufacturing costs in order to avoid them. These elements may exist in the above-mentioned magnetic phases in a substitutional and / or intrusive form, or in phases other than the above-mentioned magnetic phases. Alternatively, they may also exist in the grain boundaries of these phases. For explanation, Ga is gallium, Ti is titanium, Cr is chromium, Zn is zinc, Mn is manganese, V is vanadium, Mo is molybdenum, W is tungsten, Si is silicon, Re is rhenium, Cu is copper, Al is aluminum, Ca is calcium, B is boron, Ni is nickel, and C is carbon.

[0069] The particle size D of SmFeN powder 50 As long as the product has the desired magnetic properties, there is no particular limitation. 50 It may be 1.00 μm or more, 2.00 μm or more, 3.00 μm or more, 3.08 μm or more, 4.00 μm or more, 5.00 μm or more, 6.00 μm or more, 7.00 μm or more, 8.00 μm or more, or 9.00 μm or less, 19.00 μm or less, 18.00 μm or less, 17.00 μm or less, 16.00 μm or less, 15.00 μm or less, 14.00 μm or less, 13.00 μm or less, 12.00 μm or less, 11.00 μm or less, or 10.00 μm or less. 50 Refers to the median particle size.

[0070] D of SmFeN powder 50 The particle size distribution of the SmFeN powder was calculated and measured (investigated) by the following method: In this specification, unless otherwise specified, the size (particle diameter) of the particles of the SmFeN powder is described based on the following measurement method (investigation method).

[0071] A sample of SmFeN powder filled with resin was prepared, and the surface of the sample was polished and observed with an optical microscope. Figure 4 This is an explanatory diagram showing an optical microscope image of a sample of resin-embedded SmFeN powder. Figure 4 In the figure, the bright field represents the particles of the SmFeN powder, and the dark field represents the resin.

[0072] like Figure 4 As shown, a straight line is drawn on the optical microscope image, and the length of the line segment divided by the SmFeN particles (bright field) is measured. The particle size distribution of the SmFeN powder is obtained based on the frequency distribution of the line segment length. The particle size distribution obtained by this method is basically equal to the particle size distribution obtained by the intersection method.

[0073] Due to manufacturing reasons, etc., there are fine powder particles in the SmFeN powder, but the manufacturing method disclosed in the present invention can suppress the disadvantages of fine powder particles, so there is no particular restriction on the proportion of magnetic particles (fine powder particles) with a particle size of 1.0 μm or less in the SmFeN powder. The proportion of magnetic particles (fine powder particles) with a particle size of 1.0 μm or less in the SmFeN powder can be 1.0% or more, 3.0% or more, 5.0% or more, 7.0% or more, or 10.0% or more, and can be 20.0% or less, 18.0% or less, 16.0% or less, 14.0% or less, 13.4% or less, or 12.0% or less, relative to the total number of magnetic particles in the SmFeN powder.

[0074] In the manufacturing method disclosed in the present invention, the modified material powder described later is mixed in the SmFeN powder. The oxygen in the SmFeN powder is absorbed by the metal zinc or zinc alloy powder in the modified material powder, thereby improving the magnetic properties of the product, especially the coercive force. The oxygen content in the SmFeN powder can be determined by considering the amount of oxygen in the SmFeN powder absorbed by the modified material powder in the manufacturing process. Preferably, the oxygen content of the SmFeN powder is low relative to the overall SmFeN powder. Relative to the overall SmFeN powder, the oxygen content of the SmFeN powder is preferably 2.0 mass% or less, more preferably 1.5 mass% or less, and further preferably 1.0 mass% or less. On the other hand, extremely reducing the oxygen content in the SmFeN powder will lead to an increase in manufacturing costs. Therefore, relative to the overall SmFeN powder, the oxygen content of the SmFeN powder can be 0.1 mass% or more, 0.2 mass% or more, or 0.3 mass% or more.

[0075] As for SmFeN powder, as long as the description so far is met, there is no particular restriction on its manufacturing method, and commercial products can be used. As a method for manufacturing SmFeN powder, for example, a method for manufacturing Sm-Fe powder from samarium oxide and iron powder by reduction diffusion method, a method for obtaining Sm-Fe-N powder by heating at 600°C or less in an atmosphere of a mixed gas of nitrogen and hydrogen, nitrogen and ammonia, etc. can be cited. Alternatively, for example, a method for manufacturing Sm-Fe alloy by dissolution method, nitriding the coarsely pulverized particles obtained by coarsely pulverizing the alloy, and further pulverizing it to a desired particle size can be cited. For example, a dry jet mill, a dry ball mill, a wet ball mill, or a wet bead mill can be used for pulverization. They can also be used in combination.

[0076] In addition to the above-mentioned production method, for example, SmFeN powder can be obtained by a production method including the following steps: a pretreatment step of heat-treating an oxide containing Sm and Fe in an atmosphere containing a reducing gas to obtain a partial oxide; a step of heat-treating the partial oxide in the presence of a reducing agent to obtain alloy particles; and a step of heat-treating the alloy particles at a first temperature of 400° C. to 470° C. in an atmosphere containing nitrogen or ammonia, and then heat-treating the alloy particles at a second temperature of 480° C. to 610° C. to obtain a nitride. In particular, in alloy particles with a large particle size, such as alloy particles containing La, nitridation may not be sufficiently performed inside the oxide particles. When nitridation is performed at a two-stage temperature, the inside of the oxide particles is also sufficiently nitrided, and an anisotropic SmFeN powder with a narrow particle size distribution and high residual magnetization can be obtained.

[0077] 〈Pre-treatment process〉

[0078] The oxide containing Sm and Fe used in the pretreatment step can be produced, for example, by mixing Sm oxide and Fe oxide, preferably by a step of mixing a solution containing Sm and Fe and a precipitant to obtain a precipitate containing Sm and Fe (precipitation step), and by calcining the precipitate to obtain an oxide containing Sm and Fe (oxidation step).

[0079] 〈Precipitation process〉

[0080] In the precipitation process, the Sm raw material and the Fe raw material are dissolved in a strong acid solution to prepare a solution containing Sm and Fe. 17 When N3 is the main phase, the molar ratio of Sm to Fe (Sm:Fe) is preferably 1.5:17 to 3.0:17, and more preferably 2.0:17 to 2.5:17. Raw materials such as La, W, Co, Ti, Sc, Y, Pr, Nd, Pm, Gd, Tb, Dy, Ho, Er, Tm, and Lu may also be added to the above solution. From the viewpoint of residual magnetic flux density, La is preferably included. From the viewpoint of coercive force and squareness ratio, W is preferably included. From the viewpoint of temperature characteristics, Co and Ti are preferably included.

[0081] The Sm raw material and the Fe raw material are not limited as long as they can be dissolved in a strongly acidic solution. For example, from the viewpoint of easy availability, samarium oxide can be cited as the Sm raw material, and FeSO4 can be cited as the Fe raw material. The concentration of the solution containing Sm and Fe can be appropriately adjusted within the range in which the Sm raw material and the Fe raw material are substantially dissolved in the acidic solution. As the acidic solution, sulfuric acid and the like can be cited from the viewpoint of solubility.

[0082] By reacting a solution containing Sm and Fe with a precipitant, an insoluble precipitate containing Sm and Fe is obtained. Here, the solution containing Sm and Fe can be converted into a solution containing Sm and Fe when reacting with the precipitant. For example, raw materials containing Sm and Fe can be prepared as solutions respectively, and each solution can be added dropwise to react with the precipitant. When preparing the solutions separately, each raw material can be appropriately adjusted within the range that is substantially dissolved in an acidic solution. The precipitant is not limited as long as it is a substance that reacts with a solution containing Sm and Fe in an alkaline solution to obtain a precipitate, and examples thereof include ammonia water, caustic soda, etc., preferably caustic soda.

[0083] From the viewpoint of being able to easily adjust the properties of the precipitate particles, the precipitation reaction preferably comprises a method in which a solution containing Sm and Fe and a precipitant are respectively added dropwise to a solvent such as water. By appropriately controlling the supply rate of the solution containing Sm and Fe and the precipitant, the reaction temperature, the concentration of the reaction solution, the pH during the reaction, etc., a precipitate having a uniform distribution of constituent elements, a narrow particle size distribution, and a neat powder shape can be obtained. By using such a precipitate, the magnetic properties of the SmFeN powder as the final product are improved. The reaction temperature may be above 0°C and below 50°C, preferably above 35°C and below 45°C. In terms of the concentration of the reaction solution, the total concentration of metal ions is preferably above 0.65 mol / L and below 0.85 mol / L, more preferably above 0.7 mol / L and below 0.85 mol / L. The reaction pH is preferably above 5 and below 9, more preferably above 6.5 and below 8.

[0084] From the viewpoint of magnetic properties, the solution containing Sm and Fe preferably further contains one or more metals selected from La, W, Co and Ti. For example, from the viewpoint of residual magnetic flux density, it is preferred to contain La, from the viewpoint of coercive force, it is preferred to contain W, and from the viewpoint of temperature characteristics, it is preferred to contain Co and Ti. As a La raw material, there is no limitation as long as it can be dissolved in a strongly acidic solution. For example, from the viewpoint of easy availability, La2O3, LaCl3, etc. can be listed. Similar to the Sm raw material and the Fe raw material, the La raw material, the W raw material, the Co raw material, and the Ti raw material are appropriately adjusted within the range that is substantially soluble in the acidic solution. From the viewpoint of solubility, sulfuric acid can be listed as an acidic solution. As a W raw material, ammonium tungstate can be listed, as a Co raw material, cobalt sulfate can be listed, and as a titanium raw material, sulfated titanium dioxide (sulfated titania) can be listed.

[0085] When the solution containing Sm and Fe further contains one or more metals selected from La, W, Co and Ti, an insoluble precipitate containing Sm, Fe and one or more metals selected from La, W, Co and Ti is obtained. Here, when the solution reacts with the precipitant, it may contain one or more metals selected from La, W, Co and Ti. For example, each raw material may be prepared as a solution, and each solution may be added dropwise to react with the precipitant, or the solution containing Sm and Fe may be prepared together.

[0086] The powder particle size, powder shape, and particle size distribution of the SmFeN powder finally obtained are roughly determined based on the powder obtained by the precipitation step. When the particle size of the powder obtained is measured using a laser diffraction wet particle size distribution meter, it is preferred that the size and distribution of the entire powder fall within a range of 0.05 μm to 20 μm, preferably a range of 0.1 μm to 10 μm.

[0087] After the precipitate is separated, in order to prevent the precipitate from re-dissolving in the solvent remaining in the subsequent heat treatment of the oxidation step, the precipitate from aggregating when the solvent evaporates, or the particle size distribution, powder particle size, etc., changes, it is preferred to separate the separated product from the solvent (separate from the solvent). As a method for separating the solvent, specifically, for example, the following method can be cited: when water is used as the solvent, drying in an oven at 70° C. or higher and 200° C. or lower for a time of 5 hours or higher and 12 hours or lower.

[0088] After the precipitation step, a step of separating and washing the obtained precipitate may be included. The washing step is appropriately performed until the conductivity of the supernatant reaches 5 mS / m 2 As the step of isolating the precipitate, for example, a solvent (preferably water) is added to the obtained precipitate, the mixture is mixed, and then the mixture is separated by filtration or decantation.

[0089] 〈Oxidation process〉

[0090] The oxidation step is a step of obtaining an oxide containing Sm and Fe by calcining the precipitate formed in the precipitation step. For example, the precipitate can be converted into an oxide by heat treatment. When the precipitate is heat treated, it is necessary to perform the heat treatment in the presence of oxygen, for example, it can be performed in an atmospheric atmosphere. In addition, since it is necessary to perform the heat treatment in the presence of oxygen, it is preferred that the non-metallic part in the precipitate contains oxygen atoms.

[0091] The heat treatment temperature (hereinafter, oxidation temperature) in the oxidation step is not particularly limited, but is preferably 700° C. or higher and 1300° C. or lower, and more preferably 900° C. or higher and 1200° C. or lower. When the temperature is lower than 700° C., oxidation is insufficient, and when the temperature exceeds 1300° C., the shape, average particle size, and particle size distribution of the target SmFeN powder tend not to be obtained. The heat treatment time is also not particularly limited, but is preferably 1 hour or higher and 3 hours or lower.

[0092] The obtained oxide is an oxide particle in which Sm and iron are sufficiently microscopically mixed in the oxide particle, and the shape, particle size distribution, etc. of the precipitate are reflected.

[0093] 〈Pre-treatment process〉

[0094] The pretreatment step is a step of obtaining a partial oxide in which a part of the oxide is reduced by heat-treating the oxide containing Sm and Fe in an atmosphere containing a reducing gas.

[0095] Here, partial oxide refers to an oxide in which a part of the oxide is reduced. The oxygen concentration of the partial oxide is not particularly limited, but is preferably 10% by mass or less, and more preferably 8% by mass or less. When it exceeds 10% by mass, the reduction heat with Ca becomes larger in the reduction process, and the sintering temperature becomes higher, so there is a tendency to produce particles with abnormal particle growth. Here, the oxygen concentration of the partial oxide can be measured by non-dispersive infrared absorption method (ND-IR).

[0096] The reducing gas can be appropriately selected from hydrocarbon gases such as hydrogen (H2), carbon monoxide (CO), and methane (CH4). From the perspective of cost, hydrogen is preferred, and the flow rate of the gas is appropriately adjusted within the range in which the oxide does not scatter. The heat treatment temperature (hereinafter, pretreatment temperature) in the pretreatment process is preferably above 300°C and below 950°C, and the lower limit is more preferably above 400°C, and further preferably above 750°C. The upper limit is more preferably less than 900°C. When the pretreatment temperature is above 300°C, the reduction of oxides containing Sm and Fe is effectively carried out. In addition, when it is below 950°C, the particle growth and segregation of the oxide particles are suppressed, and the desired particle size can be maintained. The heat treatment time is not particularly limited and can be above 1 hour and below 50 hours. In addition, when hydrogen is used as a reducing gas, it is preferred to adjust the thickness of the oxide layer used to less than 20 mm, and then adjust the dew point in the reactor to less than -10°C.

[0097] 〈Reduction process〉

[0098] The reduction step is a step of obtaining alloy particles by heat treating the partial oxide in the presence of a reducing agent, for example, by contacting the partial oxide with a calcium melt or calcium vapor. From the viewpoint of magnetic properties, the heat treatment temperature is preferably 920°C to 1200°C, more preferably 950°C to 1150°C, and further preferably 980°C to 1100°C.

[0099] The metallic calcium as a reducing agent is used in the form of granules or powders, and its particle size is preferably less than 10 mm. Therefore, it is possible to more effectively suppress aggregation during the reduction reaction. In addition, the metallic calcium is preferably added in a ratio of 1.1 to 3.0 times the reaction equivalent (the stoichiometric amount required to reduce the rare earth oxide, including the amount required to reduce the Fe component in the form of an oxide), and more preferably 1.5 to 2.5 times.

[0100] In the reduction process, together with the metal calcium as a reducing agent, a disintegration promoter can be used as needed. The disintegration promoter is a reagent used to promote the disintegration and granulation of the product during the water washing process described later, and for example, alkaline earth metal salts such as calcium chloride and alkaline earth metal oxides such as calcium oxide can be listed. Relative to samarium oxide, these disintegration promoters are used in a ratio of more than 1 mass % and less than 30 mass %, preferably more than 5 mass % and less than 30 mass %.

[0101] 〈Nitriding process〉

[0102] The nitriding process refers to a process in which the alloy particles obtained in the reduction process are heat-treated at a first temperature of 400°C to 470°C in an atmosphere containing nitrogen or ammonia, and then heat-treated at a second temperature of 480°C to 610°C to perform nitriding treatment, thereby obtaining anisotropic magnetic particles. Since the granular precipitate obtained in the above-mentioned precipitation process is used, porous block-shaped alloy particles are obtained through the reduction process. As a result, nitriding can be performed directly in a nitrogen atmosphere without performing a pulverization process, so that nitriding can be performed uniformly. When heat treatment is performed at a high temperature of the second temperature without nitriding at the first temperature, nitriding may proceed rapidly, resulting in abnormal heat generation, SmFeN decomposition, and the magnetic properties may be greatly reduced. In addition, the atmosphere in the nitriding process is preferably substantially a nitrogen-containing atmosphere, because the progress of nitriding can be further slowed down. The term “substantially” used here takes into consideration that elements other than nitrogen are inevitably contained due to mixing of impurities, etc. For example, the proportion of nitrogen in the atmosphere is 95% or more, preferably 97% or more, and more preferably 99% or more.

[0103] The first temperature in the nitriding step is 400°C to 470°C, preferably 410°C to 450°C. When the temperature is lower than 400°C, the nitriding progresses very slowly, and when the temperature exceeds 470°C, excessive nitriding or decomposition is likely to occur due to heat generation. The heat treatment time at the first temperature is not particularly limited, but is preferably 1 hour to 40 hours, more preferably 20 hours or less. When the temperature is less than 1 hour, the nitriding may not proceed sufficiently, and when the temperature exceeds 40 hours, the productivity deteriorates.

[0104] The second temperature is 480°C to 610°C, preferably 500°C to 550°C. When the temperature is lower than 480°C, if the particles are large, nitridation may not be sufficiently performed, and when the temperature is higher than 610°C, excessive nitridation or decomposition may occur. The heat treatment time at the second temperature is preferably 15 minutes to 5 hours, more preferably 30 minutes to 2 hours. When the temperature is less than 15 minutes, nitridation may not be sufficiently performed, and when the temperature is higher than 5 hours, productivity may deteriorate.

[0105] The heat treatment at the first temperature and the heat treatment at the second temperature may be performed continuously, or a heat treatment at a temperature lower than the second temperature may be included between these heat treatments. However, from the viewpoint of productivity, they are preferably performed continuously.

[0106] 〈Post-processing process〉

[0107] The product obtained after the nitriding process contains, in addition to magnetic particles, by-produced CaO, unreacted metallic calcium, etc., which sometimes become a composite sintered mass state. The product obtained after the nitriding process is put into cooling water, and CaO and metallic calcium can be separated as a suspended calcium hydroxide (Ca(OH)2). Furthermore, the magnetic powder can also be washed with acetic acid or the like to fully remove the residual calcium hydroxide. When the product is put into water, the composite sintered mass-like reaction product is disintegrated, that is, micronized, by the oxidation reaction of metallic calcium with water and the hydration reaction of the by-product CaO.

[0108] <Alkali treatment process>

[0109] The product obtained after the nitriding step can be put into an alkaline solution. As the alkaline solution used in the alkaline treatment step, for example, calcium hydroxide aqueous solution, sodium hydroxide aqueous solution, ammonia solution, etc. can be listed. Among them, calcium hydroxide aqueous solution and sodium hydroxide aqueous solution are preferred from the viewpoint of drainage treatment and high pH. By the alkaline treatment of the product, a Sm-rich layer containing a certain degree of oxygen remains and functions as a protective layer, because the increase in oxygen concentration caused by the alkaline treatment is suppressed.

[0110] The pH of the alkaline solution used in the alkaline treatment step is not particularly limited, but is preferably 9 or more, more preferably 10 or more. When the pH is less than 9, the reaction rate when calcium hydroxide is generated is fast and heat generation increases, so the oxygen concentration of the finally obtained SmFeN powder tends to be high.

[0111] In the alkali treatment step, the SmFeN powder obtained after the treatment with the alkali solution may be dehydrated by decantation or the like as needed.

[0112] 〈Acid treatment process〉

[0113] After the alkali treatment step, an acid treatment step may be further included. In the acid treatment step, at least a portion of the Sm-rich layer is removed to reduce the oxygen concentration in the entire SmFeN powder. In addition, in the manufacturing method of the embodiment of the present invention, since pulverization is not performed, the average particle size of the SmFeN powder is small, the particle size distribution is narrow, and fine powder generated by pulverization is not contained, so the increase in oxygen concentration can be suppressed.

[0114] The acid used in the acid treatment step is not particularly limited, and examples thereof include hydrogen chloride (hydrochloric acid), nitric acid, sulfuric acid, acetic acid, etc. Among them, hydrogen chloride and nitric acid are preferred from the viewpoint of preventing impurities from remaining.

[0115] As for the amount of acid used in the acid treatment process, it is preferably 3.5 parts by mass or more and 13.5 parts by mass or less, and more preferably 4 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of SmFeN powder. When it is less than 3.5 parts by mass, the oxide on the surface of the SmFeN powder remains and the oxygen concentration becomes high. When it exceeds 13.5 parts by mass, it is easy to be reoxidized when exposed to the atmosphere. In addition, in order to dissolve the SmFeN powder, the cost also tends to be higher. By setting the amount of acid to 3.5 parts by mass or more and 13.5 parts by mass or less relative to 100 parts by mass of SmFeN powder, it is possible to cover the surface of the SmFeN powder with an Sm-rich layer that is oxidized to the extent that it is difficult to be reoxidized when exposed to the atmosphere after acid treatment, so that a SmFeN powder with a low oxygen concentration, a small average particle size, and a narrow particle size distribution can be obtained.

[0116] In the acid treatment step, the SmFeN powder obtained after the acid treatment may be reduced in water content by a method such as decantation as necessary.

[0117] 〈Dehydration process〉

[0118] After the acid treatment step, it is preferred to include a dehydration step. By reducing the water content in the solid component before vacuum drying through dehydration, oxidation during drying (deepening of oxidation) caused by the solid component before vacuum drying containing more water can be suppressed. Here, dehydration refers to a process of reducing the water content in the solid component after dehydration by applying pressure or centrifugal force to the solid component before dehydration, and does not include simple decantation, filtration, and drying. The dehydration method is not particularly limited, and examples thereof include pressing, centrifugal separation, and the like.

[0119] The amount of water contained in the SmFeN powder after the dehydration treatment is not particularly limited, but is preferably 13% by mass or less, and more preferably 10% by mass or less, from the viewpoint of suppressing the progress of oxidation.

[0120] The SmFeN powder obtained by acid treatment or the SmFeN powder obtained by dehydration treatment after acid treatment is preferably vacuum dried. The drying temperature is not particularly limited, but is preferably 70° C. or higher, more preferably 75° C. or higher. The drying time is also not particularly limited, but is preferably 1 hour or more, more preferably 3 hours or more.

[0121] 〈Modified material powder preparation process〉

[0122] Prepare modified material powder. The modified material powder used in the manufacturing method disclosed herein contains metallic zinc. Metallic zinc refers to unalloyed zinc. The metallic zinc in the modified material powder is used not only to combine and modify the particles of the SmFeN powder, but also to suppress the disadvantages of the fine powder particles in the SmFeN powder in terms of magnetic orientation. Without being bound by theory, in the heat treatment process described later, the Fe and metallic zinc of the SmFeN powder mainly form a Fe-Zn alloy phase. Ideally, the purity of the metallic zinc is 100% by mass, but in practice, it can be, for example, 95.0% by mass or more, 96% by mass or more, or 97.0% by mass or more, and can be 99.9% by mass or less, 99.5% by mass or less, 99.0% by mass or less, 98.5% by mass or less, or 98.0% by mass or less.

[0123] Regarding the particles of SmFeN powder, in the particles with relatively large particle size (particles other than fine powder particles), Fe-Zn alloy phase is formed on the surface. 17 Type and / or Th2Ni 17 The part where the crystal structure of the SmFeN powder is incomplete (imperfect), such as the SmFeN type, has an α-Fe phase in the part, which causes the coercive force to decrease. The α-Fe phase forms a Fe-Zn alloy phase with metal zinc, which suppresses the decrease in coercive force. That is, the Fe-Zn alloy phase acts as a modified phase. Between the particles of the SmFeN powder and the particles of the modified material powder, Fe and Zn diffuse with each other to form a Fe-Zn alloy phase. Therefore, the particles of the SmFeN powder and the particles of the modified material powder can be firmly combined. That is, the modified material powder functions as a binder.

[0124] On the other hand, regarding the particles of SmFeN powder, it is believed that the Fe-Zn alloy phase is formed in almost all particles of the fine powder particles. This is because it is believed that the Th2Zn 17 Type and / or Th2Ni 17 Moreover, most of the Fe-Zn alloy phases from the fine powder particles are integrated with the Fe-Zn alloy phases formed on the particles with relatively large particle sizes (particles other than the fine powder particles). Therefore, it is believed that there are Figure 2 The powder particles shown in the figure are Figure 3 As shown, the fine Fe-Zn alloy phase derived from the fine powder particles is hardly visible.

[0125] When the content ratio of the metal zinc in the modified material powder is 10% or more by mass relative to the mixed powder, the surface of the particles with a relatively large particle size (particles other than the micropowder particles) is almost completely covered with metal zinc, forming a homogeneous Fe-Zn alloy phase, so the coercive force is improved. That is, on the surface of the particles with a relatively large particle size (particles other than the micropowder particles), a homogeneous film-like Fe-Zn alloy phase as a modified phase is formed. In addition, when the content ratio of the metal zinc in the modified material powder is 10% or more by mass relative to the mixed powder, the metal zinc is also spread over the surface of the micropowder particles, promoting the suppression of the disadvantages of the micropowder particles. From this viewpoint, the content ratio of the metal zinc in the modified material powder can be 12% or more by mass, 14% or more by mass, 16% or more by mass, 18% or more by mass, or 20% or more by mass relative to the mixed powder.

[0126] On the other hand, when the content ratio of metal zinc in the modified material powder is 30 mass % or less relative to the mixed powder, the reduction of magnetization caused by the use of the modified material powder can be suppressed. From this viewpoint, the content ratio of metal zinc in the modified material powder can be 28 mass % or less, 26 mass % or less, 24 mass % or less, or 22 mass % or less relative to the mixed powder.

[0127] The modified material powder may contain, in addition to metallic zinc, metals and / or alloys having a binder function and / or a modifying function and other functions as long as the effects of the present invention are not impaired. Other functions include, for example, a function to improve corrosion resistance.

[0128] As metals and / or alloys other than metallic zinc, typically zinc alloys can be mentioned. 2 When it refers to zinc alloy, M 2 Elements and inevitable impurity elements that can be alloyed with Zn (zinc) to lower the melting start temperature of the zinc alloy to below the melting point of Zn can be selected. As a result, the sinterability is improved in the pressure sintering step described later. 2 , Zn and M 2 Elements that form eutectic alloys, etc. 2 Typically, Sn, Mg, Al, and combinations thereof can be cited. Sn is tin, Mg is magnesium, and Al is aluminum. 2 , and elements that do not hinder the melting point lowering effect of these elements and the characteristics of the product can also be selected. In addition, the inevitable impurity elements refer to impurities contained in the raw materials of the modified material powder, etc., which are inevitable or cause a significant increase in manufacturing costs in order to avoid them.

[0129] In the Zn-M 2In the zinc alloy represented by 2 The ratio (molar ratio) of M is to make the sintering temperature appropriate. 2 The ratio (molar ratio) to the entire zinc alloy may be, for example, 0.05 or more, 0.10 or more, or 0.20 or less, or 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.30 or less.

[0130] The particle size of the modified material powder is not particularly limited, but is preferably finer than that of the SmFeN powder. As a result, the particles of the modified material powder are easily distributed among the particles of the SmFeN powder. 50 (median particle size), for example, it can be 0.1 μm or more, 0.5 μm or more, 1 μm or more, or 12 μm or less, 11 μm or less, 10 μm or less, 9 μm or less, 8 μm or less, 7 μm or less, 6 μm or less, 5 μm or less, or 4 μm or less. In addition, the particle size D of the modified material powder is 50 (Median diameter) is measured by, for example, a dry laser diffraction / scattering method.

[0131] When the oxygen content of the modified material powder is low, it is possible to absorb a large amount of oxygen in the SmFeN powder, so it is preferred. From this point of view, the oxygen content of the modified material powder is preferably 5.0% by mass or less, more preferably 3.0% by mass, and further preferably 1.0% by mass or less relative to the entire modified material powder. On the other hand, extremely reducing the oxygen content of the modified material powder will lead to an increase in manufacturing costs. Therefore, the oxygen content of the modified material powder can be 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more relative to the entire modified material powder.

[0132] 〈Mixing process〉

[0133] SmFeN powder and modified material powder are mixed to obtain a mixed powder. The mixing method is not particularly limited. As the mixing method, a method of mixing using a mortar, a wheel mixer, a stirring mixer, a mechanical fusion machine, a V-type mixer, and a ball mill can be cited. These methods can also be combined. In addition, a V-type mixer is a device that has two cylindrical containers connected in a V-shaped container, and by rotating the container, the powder in the container is repeatedly collected and separated due to gravity and centrifugal force, thereby mixing.

[0134] <Magnetic field forming process>

[0135] The mixed powder is compressed and molded in a magnetic field to obtain a magnetic field molded body. This can impart orientation to the magnetic field molded body and impart anisotropy to the product (rare earth magnet) to increase residual magnetization.

[0136] The magnetic field forming method can be a known method such as a method in which a forming die with a magnetic field generating device is used to compress and form the mixed powder. The forming pressure can be more than 10MPa, more than 20MPa, more than 30MPa, more than 50MPa, more than 100MPa, or more than 150MPa, and can be less than 1500MPa, less than 1000MPa, or less than 500MPa. The size of the applied magnetic field can be more than 500kA / m, more than 1000kA / m, more than 1500kA / m, or more than 1600kA / m, and can be less than 20000kA / m, less than 15000kA / m, less than 10000kA / m, less than 5000kA / m, less than 3000kA / m, or less than 2000kA / m. As the method for applying the magnetic field, a method for applying a static magnetic field using an electromagnet and a method for applying a pulsed magnetic field using an alternating current can be listed.

[0137] 〈Pressure sintering process〉

[0138] The magnetic field forming body is pressure-sintered to obtain a sintered body. The pressure sintering method is not particularly limited, and a known method can be applied. As a pressure sintering method, for example, the following method can be cited: a mold having a cavity and a punch that can slide inside the cavity are prepared, the magnetic field forming body is inserted into the cavity, and pressure is applied to the magnetic field forming body by the punch, and the magnetic field forming body is sintered at the same time.

[0139] The pressure sintering conditions may be appropriately selected so that the magnetic field forming body can be sintered while applying pressure to the magnetic field forming body (hereinafter, sometimes referred to as “pressure sintering”).

[0140] When the sintering temperature is above 300°C, in the magnetic field formed body, the Fe on the particle surface of the SmFeN powder and the metal zinc of the modified material powder slightly diffuse with each other, which helps sintering. From this point of view, the sintering temperature can be, for example, above 310°C, above 320°C, above 340°C or above 350°C. On the other hand, when the sintering temperature is below 400°C, the Fe on the particle surface of the SmFeN powder and the metal zinc of the modified material powder will not excessively diffuse with each other, and will not hinder the subsequent heat treatment process or adversely affect the magnetic properties of the obtained sintered body. From these viewpoints, the sintering temperature can be below 390°C, below 380°C, below 370°C or below 360°C.

[0141] Regarding the sintering pressure, a sintering pressure that can increase the density of the sintered body can be appropriately selected. The sintering pressure can typically be 100 MPa or more, 200 MPa or more, 400 MPa or more, 600 MPa or more, 800 MPa or more, or 1000 MPa or less, 2000 MPa or less, 1800 MPa or less, 1600 MPa or less, 1500 MPa or less, 1300 MPa or less, or 1200 MPa or less.

[0142] The sintering time can be appropriately determined so that the Fe on the particle surface of the SmFeN powder and the metal zinc of the modified material powder can diffuse slightly with each other. The sintering time does not include the heating time until the heat treatment temperature is reached. The sintering time can be, for example, more than 1 minute, more than 2 minutes, or more than 3 minutes, and can be less than 30 minutes, less than 20 minutes, less than 10 minutes, or less than 5 minutes.

[0143] After the sintering time has passed, the sintered body is cooled to terminate the sintering. The faster the cooling rate, the more oxidation of the sintered body can be suppressed. The cooling rate may be, for example, 0.5 to 200° C. / sec.

[0144] As for the sintering atmosphere, inert gas atmosphere is preferred in order to suppress oxidation of the magnetic field molded body and the sintered body. The inert gas atmosphere includes a nitrogen atmosphere.

[0145] 〈Heat treatment process〉

[0146] The sintered body is heat-treated. As a result, regarding the particles of SmFeN powder, a Fe-Zn alloy phase is formed on the surface of particles with a relatively large particle size (particles other than the fine powder particles), and the particles of SmFeN powder and the particles of the modified material powder are more firmly combined (hereinafter, sometimes referred to as "solidification" or "solidification"), while promoting modification. In addition, regarding the particles of SmFeN powder, in the fine powder particles, a Fe-Zn alloy phase is formed on almost all particles, and most of them are integrated with the Fe-Zn alloy phase formed on the particles with a relatively large particle size (particles other than the fine powder particles). As a result, the disadvantages of the fine powder particles of SmFeN powder present in the magnetic field forming body on the orientation degree of the sintered body (Sm-Fe-N rare earth magnet disclosed in the present invention) after heat treatment can be suppressed.

[0147] Regarding the conditions of the heat treatment, when the temperature and time are set to x° C. and y hours, respectively, if the following formulas (1) and (2) are satisfied, curing and modification can be performed while suppressing the adverse effects of fine powder particles.

[0148] y≧-0.32x+136···Formula (1)

[0149] 350≦x≦410···Formula (2)

[0150] When the heat treatment temperature x°C is above 350°C, Fe-Zn alloy phases are appropriately formed on the surface of particles with relatively large particle sizes (particles other than fine powder particles) and on almost all fine powder particles, which can solidify, modify and suppress the disadvantages of fine powder particles. From this point of view, the heat treatment temperature x°C can be above 360°C, above 370°C, or above 380°C.

[0151] On the other hand, when the heat treatment temperature x (°C) is below 410°C, Fe and Zn do not diffuse excessively with each other on the surface of particles with relatively large particle sizes (particles other than fine powder particles) and in fine powder particles. However, although the heat treatment temperature x (°C) of 410°C can solidify, modify and suppress the disadvantages of fine powder particles, a sharp break occurs, so the heat treatment temperature x (°C) is preferably below 400°C or below 390°C. It should be noted that the so-called sharp break refers to a sharp decrease in magnetization relative to a slight decrease in the magnetic field in an area other than the area showing the coercive force of the magnetization-magnetic field curve (MH curve).

[0152] When the heat treatment temperature x (°C) is within the range of 350 to 410°C (the range of formula (2)), the heat treatment temperature x (°C) and the heat treatment time y (time) satisfy formula (1). Formula (1) is a formula confirmed by experiments, which specifically shows that in order to solidify, modify and suppress the disadvantages of fine powder particles, the higher the heat treatment temperature, the shorter the heat treatment time.

[0153] The magnetic phase in SmFeN powder has Th2Zn 17 Type and / or Th2Ni 17 type crystal structure, which is basically stable. However, on the surface of particles with relatively large particle sizes (particles other than micropowder particles), the above crystal structure is sometimes slightly disordered, and there is a single Fe (α-Fe phase). In addition, micropowder particles are mostly particles obtained by crushing particles with relatively large particle sizes. Therefore, most of the above crystal structures in the micropowder particles are disordered, and a large amount of single Fe (α-Fe phase) is sometimes present in the micropowder particles. In either case, the amount of single Fe (α-Fe phase) is limited, and when the heat treatment time y (time) is 40 hours, the formation of the Fe-Zn alloy phase is saturated. From an economic point of view, the heat treatment time y (time) is preferably less than 40 hours, less than 35 hours, less than 30 hours, less than 25 hours, or less than 24 hours.

[0154] In order to suppress oxidation of the sintered body, it is preferred to heat treat the sintered body in a vacuum or in an inert gas atmosphere, wherein the inert gas atmosphere includes a nitrogen atmosphere. The heat treatment of the sintered body may be performed in a mold for pressure sintering, but no pressure is applied to the sintered body during the heat treatment. Therefore, when the above-mentioned heat treatment conditions are met, the normal magnetic phase decomposes to generate an α-Fe phase, and as a result of the generation, Fe and Zn do not diffuse excessively with each other.

[0155] The rare earth magnet obtained by the production method of the present disclosure described above will be described below.

[0156] Rare Earth Magnets

[0157] The rare earth magnet disclosed in the present invention has a material containing Sm, Fe and N and at least a part of Th2Zn 17 Type and Th2Ni 17 The composition of the magnetic phase is as described in "Method for producing rare earth magnet".

[0158] The rare earth magnet disclosed in the present invention is obtained by using a mixed powder of SmFeN powder and a modifying material powder containing metallic zinc. Therefore, it contains a zinc component of metallic zinc from the modifying material powder. As described above, a part of the particles of the SmFeN powder and a part of the metallic zinc of the modifying material powder diffuse with each other to form a Fe-Zn alloy phase. Therefore, in the rare earth magnet disclosed in the present invention, there is zinc present as metallic zinc and zinc present as a constituent element of the Fe-Zn alloy phase. Therefore, in this specification, unless otherwise specified, the sum of these zincs is referred to as "zinc component". The content ratio (content) of "zinc component" is the content ratio (content) of Zn (zinc element). The zinc component of the rare earth magnet disclosed in the present invention comes from the metallic zinc in the modifying material powder. Therefore, the reason why the content ratio of the zinc component is in the range of 10 to 30% by mass is the same as the reason why the content ratio of metallic zinc in the modifying material powder is 10 to 30% by mass relative to the mixed powder, as described in "The Manufacturing Method of Rare Earth Magnet".

[0159] The rare earth magnet disclosed in the present invention is obtained by further heat treating the sintered body obtained by pressure sintering the magnetic field molded body of the mixed powder under prescribed conditions. In the magnetic field molded body, the surface of the particles of the SmFeN powder with a relatively large particle size (particles other than the fine powder particles) is coated with a modified phase (Fe-Zn phase) alloyed with metal zinc to form crystalline phase particles. In addition, the fine powder particles of the SmFeN powder are also alloyed with metal zinc to form a Fe-Zn phase, and most of the Fe-Zn phase from the fine powder particles is integrated with the modified phase covering the surface of the particles with a relatively large particle size (particles other than the fine powder particles). Therefore, the Fe-Zn phase from the fine powder particles, that is, the crystal particles with a particle size of less than 1.0μm are very few. From this point of view, the proportion of crystalline phase particles with a particle size of less than 1.0μm relative to the total number of crystalline phase particles is less than 10.00%, less than 9.08%, less than 9.00%, or less than 8.95%. The total number of so-called crystal phase particles refers to the total of the number of crystal phase particles with the magnetic phase covered with modified phase and the number of crystal phase particles with Fe-Zn phase from fine powder particles. In addition, crystal phase particles can be observed as particles by optical microscope, containing more than one crystal phase (crystalline phase) in a crystal phase particle. Crystal phase is magnetic phase and / or Fe-Zn phase. Therefore, as crystal phase particles, there are crystal phase particles covered with modified phase (Fe-Zn phase) of the particles (particles other than fine powder particles) with a relatively large particle size from SmFeN powder and Fe-Zn phase from fine powder particles and crystal phase particles not integrated with modified phase. That is, in the rare earth magnet disclosed in the present invention, the magnetic phase of the SmFeN particles and the zinc component of the modified material powder form crystalline phase particles, and there are crystalline phase particles with relatively large particle sizes (particles other than fine powder particles) from the SmFeN powder and covered with a modified phase (Fe-Zn phase), and crystalline phase particles with Fe-Zn phase from the fine powder particles that are not integrated with the modified phase.

[0160] The particle size of the crystal phase particles is measured (investigated) by the following method. In this specification, unless otherwise specified, the description of the particle size of the crystal phase particles is based on the following measurement method (investigation method).

[0161] The cross section of the sintered body after the heat treatment was ground and observed with an optical microscope. Figure 5 This is an explanatory diagram showing an optical microscope image of a cross section of a sintered body after heat treatment. Figure 5 In the figure, the bright field is the crystalline phase particles. Figure 5 The optical microscope image shown is subjected to image analysis to determine the frequency distribution of the major axes of the crystal phase particles, thereby measuring (investigating) the particle sizes of the crystal phase particles.

[0162] Metamorphosis

[0163] In addition to the above-described contents, the rare earth magnet and the method for producing the same according to the present disclosure can be modified in various ways within the scope of the contents described in the claims.

[0164] For example, a part of the fine powder particles in the SmFeN powder can be removed in advance before magnetic field molding. Most of the fine powder particles cannot be completely removed. After the fine powder removal operation, the disadvantages of the fine powder particles remaining in the SmFeN powder can be suppressed by the manufacturing method disclosed in the present invention. The fine powder removal operation (fine powder removal method) is not particularly limited. As the fine powder removal operation (fine powder removal method), a method using a Sicron (registered trademark) classifier, a method using a sieve, a method using a magnetic field, and a method using static electricity can be listed. It can also be a combination of them.

[0165] The rare earth magnet and the method for producing the same according to the present disclosure are further described in detail below by way of examples and comparative examples. It should be noted that the rare earth magnet and the method for producing the same according to the present disclosure are not limited to the conditions used in the following examples.

[0166] 《Sample Preparation》

[0167] The rare earth magnet sample was prepared as follows.

[0168] <Example 1>

[0169] 5.0 kg of FeSO4·7H2O was mixed and dissolved in 2.0 kg of pure water. 0.49 kg of Sm2O3, 0.74 kg of 70% sulfuric acid, and 0.035 kg of La2O3 were added and stirred thoroughly to completely dissolve. Then, pure water was added to the obtained solution to adjust the final Fe concentration to 0.726 mol / L and the Sm concentration to 0.112 mol / L, thereby preparing a SmFeLa sulfuric acid solution.

[0170] 〈Precipitation process〉

[0171] In 20 kg of pure water maintained at 40° C., the prepared SmFe sulfuric acid solution was dripped in full while stirring within 70 minutes from the start of the reaction, and 15% ammonia water was dripped to adjust the pH to 7-8. Thus, a slurry containing SmFeLa hydroxide was obtained. The obtained slurry was washed with pure water by decantation, and the hydroxide was separated into solid and liquid. The separated hydroxide was dried in an oven at 100° C. for 10 hours.

[0172] 〈Oxidation process〉

[0173] The hydroxide obtained in the precipitation step was calcined in air at 1000° C. for 1 hour and then cooled to obtain a red SmFeLa oxide as a raw material powder.

[0174] 〈Pre-treatment process〉

[0175] 100 g of SmFeLa oxide was placed in a steel container so that the deposition thickness (loft) of the SmFeLa oxide was 10 mm. The container was placed in a furnace, and after the pressure was reduced to 100 Pa, hydrogen was introduced while the temperature was raised to 850°C, which was the pretreatment temperature, and the mixture was kept for 15 hours. The oxygen concentration was measured by non-dispersive infrared absorption method (ND-IR) (EMGA-820 manufactured by Horiba, Ltd.), and it was 5% by mass. It can be seen from this that a black partial oxide was obtained in which the oxygen bonded to Sm was not reduced and 95% of the oxygen bonded to Fe was reduced.

[0176] 〈Reduction process〉

[0177] 60g of the partial oxide obtained in the pretreatment step and 19.2g of metal calcium with an average particle size of about 6mm were mixed and placed in a furnace. After the furnace was evacuated, argon gas (Ar gas) was introduced. The temperature was raised to the first temperature of 1090°C, maintained for 45 minutes, and then cooled to obtain SmFe alloy particles.

[0178] 〈Nitriding process〉

[0179] Next, the furnace temperature was cooled to 100°C, evacuated, and while introducing nitrogen, the temperature was raised to the first temperature of 430°C and maintained for 3 hours. Next, the temperature was raised to the second temperature of 500°C and maintained for 1 hour, and then cooled to obtain a bulk product containing magnetic particles.

[0180] 〈Post-processing process〉

[0181] The blocky product obtained in the nitriding step is added to 3 kg of pure water and stirred for 30 minutes. After standing, the supernatant is discharged by decantation. The addition of pure water, stirring and decantation are repeated 10 times. Next, 2.5 g of 99.9% acetic acid is added and stirred for 15 minutes. After standing, the supernatant is discharged by decantation. The addition of pure water, stirring and decantation are repeated 2 times.

[0182] 〈Acid treatment process〉

[0183] A 6% aqueous hydrochloric acid solution was added to 100 parts by mass of the powder obtained in the water washing step so that the hydrogen chloride was 4.3 parts by mass, and the mixture was stirred for 1 minute. After standing, the supernatant was discharged by decantation. The addition of pure water, stirring and decantation were repeated twice. After solid-liquid separation, the mixture was vacuum dried at 80°C for 3 hours to obtain a composition of Sm 9.2 Fe 77.1 N 13.59 La 0.11 of SmFeN powder.

[0184] The obtained SmFeN powder was placed in a sample container together with paraffin wax, and the paraffin wax was melted in a dryer, and then the easy magnetization domains were aligned using an orientation magnetic field of 16 kA / m. The sample with magnetic field orientation was pulse magnetized (pulse magnetization) in a magnetizing magnetic field (magnetizing magnetic field) of 32 kA / m, and the magnetic properties were measured at room temperature using a VSM (vibrating sample magnetometer) with a maximum magnetic field of 16 kA / m. As a result, the residual magnetization was 1.44 T and the coercive force was 750 kA / m.

[0185] The particle size distribution of the SmFeN powder obtained by the above method was investigated, and the results were as follows: Figure 6 In addition, the D 50 The ratio of particles with a particle size of 1.0 μm or less is shown in Table 1. It should be noted that the ratio of particles with a particle size of 1.0 μm or less is the ratio (%) relative to the total number of particles of SmFeN powder. In addition, in Table 1, the ratio of particles with a particle size of 1.0 μm or less is simply referred to as "ratio (%) of 1.0 μm or less".

[0186] As a modified material powder, metal zinc powder was prepared. 50 The metal zinc powder had a purity of 99.9% by mass.

[0187] The SmFeN powder and the modifying material powder were mixed to obtain a mixed powder. The mixing amount of metal zinc relative to the entire mixed powder is shown in Table 1.

[0188] The mixed powder was compressed in a magnetic field to obtain a magnetic field molded body. The compression molding pressure was 50 MPa and the applied magnetic field was 1600 kA / m.

[0189] The magnetic field formed body was pressure-sintered under the conditions shown in Table 1 to obtain a sintered body. Then, the sintered body was heat-treated under the conditions shown in Table 1. The sintered body after the heat treatment was used as a sample of Example 1.

[0190] <Examples 2 to 6 and Comparative Examples 1 to 6>

[0191] A sample was prepared in the same manner as in Example 1 except that the blending amount of the modifying material powder and the heat treatment conditions were as shown in Table 1.

[0192] "evaluate"

[0193] The magnetic properties of each sample (sintered body after heat treatment) were measured to investigate the particle size distribution of the magnetic phase. The magnetic properties were measured at room temperature using a vibrating sample magnetometer (VSM). The particle size distribution of the magnetic phase was investigated by the above method.

[0194] The evaluation results are shown in Table 1. In Table 1, "magnetization at -1600 kA / m" in the column of magnetic properties means "magnetization when the external magnetic field is -1600 kA / m", and "ratio (%) of less than 1.0 μm" in the column of sintered body after heat treatment means "ratio (%) of magnetic phase having a grain size of less than 1.0 μm".

[0195] In Table 1, the magnetic properties of the green compact of the mixed powder are also recorded as Reference Example 1. As shown in Table 1, in Reference Example 1, the D 50 , the amount of modified material powder, and the magnetic field molding conditions are different from those in Example 1. Furthermore, as shown in Table 1, since the pressure sintering temperature is 23°C, sintering is not actually performed, and no heat treatment is performed, so it is still a green compact. That is, the magnetic properties of the green compact of Reference Example 1 can be considered to be the magnetic properties of the mixed powder. It should be noted that the reason why the magnetic property "magnetization at -1600kA / m" is a negative value is that the green compact is not heated, so it is not modified at all and has a small coercive force. Therefore, when the external magnetic field is -1600kA / m, the magnetization is a negative value.

[0196] in addition, Figure 6 It is a graph showing the particle size distribution of the SmFeN powder used for preparing the samples of Examples 1 to 6 and Comparative Examples 1 to 6. Figure 7 This is a graph showing the results of investigating the particle size distribution of crystal phase particles for the sample of Example 1 (sintered body after heat treatment). Figure 8 This is a graph showing the results of investigating the particle size distribution of crystal phase particles for the sample of Comparative Example 1 (sintered body after heat treatment). Fig. 9 This is a graph showing the relationship between temperature and time for a sample containing 10% by mass of the modifying material powder. Fig.10 It is a graph showing a part of the magnetization-magnetic field curve (MH curve) of the sample of Example 6. Fig.11 This is a graph showing the relationship between the amount of the modifying material powder blended and the magnetization when the external magnetic field is -1600 kA / m. Fig.12 This is a graph showing the relationship between the amount of modified material powder and the degree of orientation. Figure 6 to Figure 8 In the “data interval”, “0” means “greater than 0 μm and less than 0.5 μm”, “0.5” means “greater than 0.5 μm and less than 1.0 μm”, and “1” means “greater than 1.0 μm and less than 1.5 μm” (the same below).

[0197] [Table 1]

[0198]

[0199] As can be understood from Table 1, the proportion of microcrystalline phases with a particle size of 1.0 μm or less in the samples of Examples 1 to 6 is reduced, and the degree of orientation is increased. Fig.12 It is understood that in order to increase the degree of orientation, it is necessary to add metallic zinc at a predetermined content ratio or higher.

[0200] In the preparation of the samples of Examples 1 to 6 and Comparative Examples 1 to 6, it can be seen from Table 1 that the same SmFeN powder was used in all of them, as shown in Table 1 and Figure 6 As shown in Table 1, the SmFeN powder contains a relatively large amount of fine powder particles (particles having a particle size of 1.0 μm or less). Figure 7 As shown in Table 1 and Table 6, it can be understood that the proportion of the microcrystalline phase having a particle size of 1.0 μm or less derived from the fine powder particles is reduced. Figure 8 As shown, it can be understood that in Comparative Examples 1 to 5, a large amount of minute crystal phases having a particle size of 1.0 μm or less derived from fine powder particles remain.

[0201] From Table 1 and Fig.11 It can be seen that when the amount of metal zinc is excessive (Comparative Example 6), although the orientation degree is good, the magnetization at an external magnetic field of -1600 kA / m is reduced. This shows that in order to suppress the reduction in magnetization caused by the use of the modified material powder, the amount of metal zinc must be kept below a specified ratio.

[0202] From Table 1 and Fig. 9 It can be seen that when the temperature x and time y during heat treatment satisfy the above-mentioned formulas (1) and (2), the presence of tiny crystalline phases is below the specified proportion, and a rare earth magnet can be obtained that suppresses the reduction in magnetization caused by the use of modified material powder and improves the degree of orientation.

[0203] From Table 1 and Fig.10 It can be seen that when the temperature x (°C) during the heat treatment is near the upper limit (Example 6), a sharp break occurs, and the magnetization is locally reduced in the region where the absolute value of the external magnetic field is small in the demagnetization curve (the third quadrant of the magnetization-magnetic field curve). Fig. 9 It is understood that when the temperature x (° C.) during the heat treatment is 400° C. or less, the effect of the present invention can be more significantly achieved.

[0204] From the above results, the effects of the rare earth magnet and the method for producing the same according to the present disclosure can be confirmed.

Claims

1. A method for producing a rare earth magnet, characterized in that: include: A magnetic powder is prepared, wherein the magnetic powder contains Sm, Fe and N, and at least a part of the magnetic powder contains Th2Zn 17 Type and Th2Ni 17 The magnetic phase of any crystal structure of the type, Preparing a modified material powder containing metallic zinc, The magnetic powder and the modified material powder are mixed to obtain a mixed powder, The mixed powder is compressed and molded in a magnetic field to obtain a magnetic field molded body, The magnetic field formed body is pressure-sintered to obtain a sintered body, and heat treating the sintered body; The content of the metal zinc in the modified material powder is 10 to 30% by mass relative to the mixed powder. For the heat treatment conditions, when the temperature and time are set to x°C and y hours respectively, the following conditions are satisfied: -0.32x+136≤y≤40, and 350≤x≤400， In the magnetic powder, the proportion of fine powder particles having a particle size of 1.0 μm or less is 10 to 20% relative to the total number of magnetic particles in the magnetic powder. Through the heat treatment, a coated Fe-Zn alloy phase is formed on the surface of particles other than the fine powder particles in the magnetic powder, and a Fe-Zn alloy phase is formed in the fine powder particles in the magnetic powder. The Fe-Zn alloy phase formed in the fine powder particles is integrated with the coated Fe-Zn alloy phase formed on the surface of particles other than the fine powder particles.

2. The method for manufacturing a rare earth magnet according to claim 1, characterized in that: The magnetic field formed body is pressure-sintered at a pressure of 1000 to 1500 MPa and a temperature of 300 to 400° C. for 1 to 30 minutes.

3. A rare earth magnet obtained by the method for producing a rare earth magnet according to claim 1, characterized in that: Containing Sm, Fe and N, at least part of which contains Th2Zn 17 Type and Th2Ni 17 A magnetic phase of a crystal structure of any type; Containing 10 to 30 mass % of a zinc component, the magnetic phase and the zinc component form crystalline phase particles; and The ratio of the crystal phase particles having a particle size of 1.0 μm or less is 10.00% or less relative to the total number of the crystal phase particles.

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