JP2017055072A - Samarium-iron-nitrogen based sintered magnet, and manufacturing method of samarium-iron-nitrogen based sintered magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a samarium-iron-nitrogen based sintered magnet which includes crystal grains pulverized to a size close to a grain size of a single magnetic domain, and is superior in coercive force.SOLUTION: A samarium-iron-nitrogen based sintered magnet is provided, which comprises a samarium-iron-nitrogen based alloy, where crystal grains included therein are larger than 0.04 μm and 5 μm or less in average grain diameter, and which has an oxygen content of 0.7 wt% or less. Also, a samarium-iron-nitrogen based sintered magnet is provided, which comprises a samarium-iron-nitrogen based alloy, where crystal grains included therein are larger than 0.04 μm and 5 μm or less in average grain diameter, and an oxygen content (wt%) and the average grain diameter (μm) of the crystal grains satisfy the relation given by the following formula (1): (Oxygen content)×(Average grain diameter of crystal grains)<2.2 (1).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a samarium-iron-nitrogen based sintered magnet and a method for producing a samarium-iron-nitrogen based sintered magnet.

  A samarium-iron-nitrogen-based magnet (Sm-Fe-N-based magnet) is a representative of a rare earth-transition metal-nitrogen-based magnet and has a high anisotropic magnetic field and saturation magnetization. And one of the excellent magnet materials along with Sm—Co magnets.

  At present, Nd—Fe—B type magnets often used industrially have a remarkably reduced coercive force at high temperatures, and thus exhibit the required magnetic properties by adding expensive Dy. Sm—Co magnets have a high Curie temperature and are excellent in heat resistance, but have not been widely used because they use a large amount of expensive Co.

  On the other hand, Sm—Fe—N magnets have a high Curie temperature and exhibit excellent magnetic properties without using expensive raw materials. Therefore, it can be said that the Sm—Fe—N magnet is a magnet material having excellent magnetic properties and high heat resistance.

Sm—Fe—N magnets currently in practical use include Sm ₂ Fe ₁₇ N ₃ having a crystal structure of Th ₂ Zn ₁₇ type and Sm ₁ Fe ₉ N _1.5 having a Tb ₁ Cu ₇ type. It is done. Both are used as bonded magnets formed by compression molding or injection molding of raw materials obtained by mixing magnet powder and a resin (epoxy, nylon, etc.) as a binder.

  However, since a bond magnet uses a resin as a binder for magnet powder, its heat resistance and strength depend on the properties of the resin, and is not suitable for use in parts that require high heat resistance or high strength. . In particular, as described above, the Sm—Fe—N magnet is excellent in heat resistance, but when used as a bonded magnet, its superiority cannot be used effectively. Furthermore, since a normal bonded magnet contains a binder, it is difficult to make the volume ratio of the magnet powder 83% or more. Since the binder does not contribute to the development of the magnet characteristics, the magnetic characteristics of the bonded magnet are lower than that of the sintered magnet.

  As a method for solving such a problem, a method of sintering a Sm—Fe—N magnet powder to obtain a sintered magnet containing no binder can be considered. However, the Sm—Fe—N compound undergoes thermal decomposition at about 600 ° C. or more, and the magnet performance is attenuated. For this reason, it is necessary to sinter with respect to Sm-Fe-N type magnet powder below the decomposition temperature of a Sm-Fe-N type compound. However, if an iron-based magnet alloy is to be densified by a sintering technique such as atmospheric pressure sintering, generally, it must be heated to near 1000 ° C., and this temperature is set to Sm—Fe—N magnet powder. If applied to, thermal decomposition is inevitable.

As a technique for producing such a sintered magnet of Sm—Fe—N with low thermal stability, high pressure sintering, hot press method, plasma sintering, etc. as shown in the following (1) to (4) Low temperature sintering has been studied conventionally.
(1) A method of obtaining a dense sintered magnet by sintering Sm—Fe—N fine powder produced through a melting alloying method or a vibration mill pulverization method at 550 ° C. while applying a pressure of 3 GPa (non-patent document) 1).
(2) A method of obtaining a dense sintered magnet by explosive impact compaction of Sm—Fe—N fine powder produced through a melting alloying method or a ball mill pulverization method (see Non-Patent Document 2).
(3) A method of obtaining a rare earth magnet by plasma-sintering a powder of an Sm—Fe—N alloy produced through a melting alloying method or a ball milling method under pressure (Patent Document 1, Non-Patent Document 3, etc.) reference).
(4) A method for producing an isotropic magnet by hot pressing an isotropic Sm—Fe—N-based magnet powder produced through a rapid quenching method under high pressure (Patent Documents 2 and 3) ).

  According to the methods (1) to (4) described above, since sintering can be performed at a low temperature, it is possible to obtain a high-density sintered magnet without causing thermal decomposition.

  As described above, when a sintered magnet is manufactured by the methods (1) to (3), since it can be sintered at a low temperature, it is possible to obtain a high-density sintered magnet without thermal decomposition. However, in the method (1), although no sign of thermal decomposition is observed, the coercive force of the sintered body is significantly lower than that of the raw material powder (8.8 kOe → 2.2 kOe). Even in the methods (2) and (3), the coercive force is reduced by at least 30 to 40% after sintering despite no signs of thermal decomposition.

  Further, according to the method (4), the coercive force is not lowered by sintering, but high magnetic characteristics cannot be expected because the magnets that can be produced are limited to isotropic magnets.

  In any of the methods (1) to (3), the raw material powder is pulverized to near the single domain particle diameter, specifically, to about several μm in order to generate a high coercive force. However, as described above, in the methods (1) to (3), the coercive force of the sintered body is lowered, and if the raw material powder is made into a fine powder in order to impart high magnetic properties to the sintered magnet, On the contrary, a decrease in magnetic properties, particularly coercive force, was unavoidable.

  In Patent Document 4, as a magnet forming method for increasing the coercive force, a temperature at which a magnetic material is pulverized with a metal such as zinc, aluminum or copper, etc., magnetically oriented by applying a magnetic field, and then not decomposed. A method of heating up to is disclosed. However, according to the magnet forming method disclosed in Patent Document 4, the magnetic material reacts with zinc or the like to reduce the volume of the magnetic material, so that there is a problem that the residual magnetization is greatly reduced. .

JP-A-4-323803 JP 2004-319602 A JP2013-89813A JP-A-6-349612

K. Machida et al., Appl. Phys. Lett. 62 (1993) 2874 H. Oda et al., Jpn. J. Appl. Phys. 34 (1995) L35 D.T.Zhang et al., Powder Metall. 50 (2007) 215

  In view of the above-described problems of the prior art, in one aspect of the present invention, a samarium-iron-nitrogen based sintered magnet containing crystal particles pulverized to the vicinity of a single magnetic domain particle diameter and excellent in coercive force is provided. With the goal.

In order to solve the above problems, in one aspect of the present invention,
Contains samarium-iron-nitrogen alloy,
The average particle size of the contained crystal particles is larger than 0.04 μm and 5 μm or less,
A samarium-iron-nitrogen based sintered magnet having an oxygen content of 0.7% by weight or less is provided.

  According to one aspect of the present invention, it is possible to provide a samarium-iron-nitrogen based sintered magnet containing crystal particles pulverized to the vicinity of a single magnetic domain particle diameter and excellent in coercive force.

The schematic diagram of the crystal grain contained in the sintered magnet in embodiment of this invention, and a grain boundary.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described. However, the present invention is not limited to the following embodiments, and various modifications and changes can be made to the following embodiments without departing from the scope of the present invention. Substitutions can be added.
[Samarium-iron-nitrogen based sintered magnet]
(First configuration example)
A first configuration example of the samarium-iron-nitrogen based sintered magnet of the present embodiment will be described below.

  The samarium-iron-nitrogen based sintered magnet of the first configuration example of the present embodiment contains a samarium-iron-nitrogen based alloy, and the average grain size of the contained crystal particles is larger than 0.04 μm and not larger than 5 μm. The oxygen content can be 0.7% by weight or less.

  In order to develop a sintered magnet having a coercive force equal to or higher than that of the raw material powder in the samarium-iron-nitrogen based sintered magnet (hereinafter also simply referred to as “sintered magnet”), the inventors of the present invention We conducted intensive research. As a result, it was found that a small amount of oxygen contained in the sintered magnet was the cause of the decrease in coercive force. For this reason, by suppressing the oxygen content contained in the sintered magnet, it has been found that a sintered magnet having a coercive force equal to or higher than that of the raw material powder and excellent in coercive force can be obtained, and the present invention is completed. I let you. Hereinafter, the sintered magnet of the first configuration example of the present embodiment will be specifically described.

  Note that a sintered magnet having a coercive force equal to or greater than that of the raw material powder means that the coercive force of the sintered magnet is equal to the coercive force of the raw material powder when the coercive force of the raw material powder is compared with that of the sintered magnet. That means that.

Although the specific composition of the samarium-iron-nitrogen-based alloy contained in the sintered magnet of the present embodiment is not particularly limited, the sintered magnet of the present embodiment is a Th ₂ Zn ₁₇ type having practically excellent magnetic properties. It preferably contains a samarium-iron-nitrogen alloy having a crystal structure or a TbCu _7- type crystal structure.

  Further, the elemental composition of the samarium-iron-nitrogen based alloy contained in the sintered magnet of the present embodiment is not limited to the Sm—Fe—N alloy composed of Sm, Fe, and N, and magnet performance In order to improve heat resistance, it may contain several percent of additives.

For example, samarium - iron - formula nitrogen based alloy may be represented by _{R x T 100-x-y} -z A y G z. In the above composition formula, R is one or more elements selected from rare earth elements such as Sm, Nd, and La, and includes at least Sm. T is one or more transition metal elements selected from Fe, Co, and Ni, and includes at least Fe. A represents one or more metal elements selected from Ti, Al, Si, V, Cr, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Hf, and Ta. G is one or more elements selected from nitrogen, hydrogen, carbon, and fluorine, and includes at least nitrogen. In the above composition formula, x, y, and z are not particularly limited, but can be 0 <x, 0 ≦ y, and 0 <z. Further, x + y + z <100 can be satisfied. In particular, x, y, and z preferably satisfy 8.5 <x <14, 0 ≦ y <5, 9.5 <z <17.5, and 8.5 <x <9.5, 0 ≦ y. It is more preferable to satisfy <2, 11.5 <z <15.5.

  And it is preferable that the average particle diameter of the crystal grain contained in the sintered magnet of this embodiment is larger than 0.04 micrometer and 5 micrometers or less.

  In addition, the crystal particle here means the crystal particle of a samarium-iron-nitrogen alloy.

  This is because when the average particle size of the crystal particles included in the sintered magnet of this embodiment exceeds 5 μm, most of the crystal particles have a multi-domain structure, and thus the coercive force is essentially low. It is because the effect which suppresses the coercive force fall from the raw material powder in a magnet is hardly exhibited. Further, if the average particle size of the crystal particles contained in the sintered magnet of the present embodiment is 0.04 μm or less, the crystal particles become superparamagnetic and have no magnet properties.

  The average particle diameter of the crystal particles can be measured from the cross-sectional structure image of the sintered magnet by using a section method or an area measuring method.

  In addition, the average particle diameter of the crystal particle of a sintered magnet can be made equivalent to the average particle diameter of the magnet powder which is a raw material powder. This is because, as will be described later, when a sintered magnet is manufactured, the magnet powder is heated and sintered at a temperature equal to or lower than the thermal decomposition temperature, so that grain growth due to heating does not occur. That is, the sintered magnet of the present embodiment can contain a magnet powder having an average particle size larger than 0.04 μm and 5 μm or less, and the sintered magnet of the present embodiment has a structure in which the magnet powder is combined. be able to.

  The above-mentioned magnet powder is preferably a single crystal powder mainly composed of particles whose crystal axis directions do not change, that is, single crystal particles whose crystal axes are aligned in the same direction. Apart from this, there is also known a polycrystalline powder mainly composed of particles which are produced by an ultra-quenching method or the like and are formed by a collection of a large number of crystals having various crystal axis directions. However, it is preferable that the magnet powder used in the sintered magnet of the present embodiment is not a polycrystalline powder mainly composed of particles having various crystal axis directions.

  And as described above, according to the study of the inventors of the present invention, by suppressing the oxygen content contained in the sintered magnet, the coercive force is equal to or higher than that of the raw material powder, and the coercive force is excellent. It can be a sintered magnet. For this reason, in the sintered magnet demonstrated in the 1st structural example of this embodiment, it is preferable that oxygen content rate is 0.7 weight% or less.

The oxygen content of the sintered magnet can be measured, for example, by an inert gas melting-non-dispersive infrared absorption method (NDIR method), and can be directly obtained as an oxygen weight (% by weight) per unit weight.
(Second configuration example)
Moreover, the sintered magnet of the present embodiment is not limited to the above-described configuration, and may have other configurations. Below, the 2nd structural example of the sintered magnet of this embodiment is demonstrated.

  Here, first, FIG. 1 shows a schematic diagram of the crystal grains of the sintered magnet of this embodiment and the state of the grain boundaries.

  FIG. 1 schematically shows an enlarged view when the cross section of the sintered magnet 10 of the present embodiment is enlarged to such an extent that the crystal particles can be recognized. A region surrounded by a dotted line shows the crystal particles 11, and a dotted line is shown. A grain boundary 12 between crystal grains 11 (hereinafter also referred to as “crystal grain boundary”) 12 is shown. As described in the first configuration example, the sintered magnet of the present embodiment can have a structure in which magnet powder is bonded, and the crystal particles and the magnet powder can be equivalent. For this reason, it can be said that the crystal particles 11 in FIG. 1 are single crystal particles included in the magnet powder, and can have a structure in which the crystal particles 11 are bonded to each other as shown in FIG.

  The inventors of the present invention investigated in detail the effect of reducing the coercive force reduction by reducing the oxygen concentration in the sintered magnet, and most of the oxygen contained in the sintered magnet 10 is shaded in FIG. It became clear that it exists in the oxygen high concentration area | region 13 shown by (5). According to the study of the inventors of the present invention, as shown in FIG. 1, the oxygen high concentration region 13 exists so as to surround the grain boundary 12 of the crystal grain 11, and oxygen is further present in the grain boundary. It was found that the degree of concentration strongly affects the coercive force.

  For example, when observing the microstructure of a samarium-iron-nitrogen based sintered magnet produced by a conventional technique, in all the sintered magnets, there is a region where the oxygen concentration is higher than that of the main phase so as to surround the grain boundaries of crystal grains. Existed. And the coercive force of the sintered magnet was greatly reduced as the region where the oxygen concentration was higher than the main phase was thicker.

  Further, when the inventors of the present invention have studied, the degree of concentration of oxygen at the grain boundary, that is, the oxygen content per unit area of the grain boundary is equal to or less than a certain value, it is equivalent to the coercive force of the raw material powder. It discovered that it could be set as the above sintered magnet.

  Therefore, the samarium-iron-nitrogen based sintered magnet of the second configuration example of the present embodiment contains a samarium-iron-nitrogen based alloy, and the average grain size of the contained crystal particles is larger than 0.04 μm and not larger than 5 μm. It can be. And it can comprise so that the oxygen content rate (weight%) of a sintered magnet and the average particle diameter (micrometer) of a crystal grain may satisfy | fill the relationship of the following formula | equation (1).

(Oxygen content) × (average particle diameter of crystal grains) <2.2 (1)
Here, the above equation (1) will be described.

First, the oxygen content C contained in the grain boundary per unit area is expressed by the following formula (a) using the oxygen content M of the sintered magnet and the grain interface area _AT per unit volume. The
C = M / A _T (a)
Further, the grain interface area _AT per unit volume is expressed by the following formula (b) using the average grain interface area _AG per particle and the average number of crystal grains N per unit volume.
A _T = (A _G / 2) × N (b)
The reason why _AG is divided by 2 in the above formula (b) is that the grain boundary is formed by combining two crystals.

Further, assuming that the crystal grains are spheres, the average grain interface area _AG per grain is expressed by the following formula (c) using the average grain diameter d of the crystal grains.
A _G = 4π (d / 2) ² (c)
Further, the average number of crystal grains N per unit volume is represented by the reciprocal of the average volume per particle,
It is expressed as the following formula (d).
N = 1 / [4π / 3 (d / 2) ³ ] (d)
From the above formulas (b) to (d), the grain interface area _AT per unit volume is expressed by the following formula (e).
A _T = 4π (d / 2) ² × 1 / [4π / 3 (d / 2) ³ ] = 3 / (d / 2) ... (e)
Therefore, from the above formulas (a) and (e), the oxygen content C contained in the grain boundary per unit area is expressed by the following formula (f).
C = M / [3 / (d / 2)] = 1/6 × M × d (f)
From the above formula (f), it was confirmed that the oxygen content normalized by the grain boundary area was proportional to the product of the oxygen content M of the sintered magnet and the average particle diameter d of the crystal particles.

  The inventors of the present invention further provide a sintered magnet in which the product of the oxygen content (% by weight) of this sintered magnet and the average particle size (μm) of the crystal particles is smaller than 2.2. It was found that the coercive force was equal to or greater than that of the powder, and the above formula (1) was completed.

  Thus, when the product of the oxygen content and the average particle size of crystal grains, that is, the oxygen content per unit area of the grain boundary is smaller than a certain value, the coercive force of the raw material powder is maintained in the sintered magnet. The following mechanisms are promising.

  The raw material powder used in the manufacture of conventional sintered magnets has a layer (oxide film) containing a large amount of oxygen on the particle surface. When particles having such a layer containing a large amount of oxygen on the surface are heated for sintering, the metal Sm constituting the samarium-iron-nitrogen-based alloy is converted into iron oxide inside the oxide film due to its extremely strong reducing action. To reduce. As a result of the oxidation-reduction reaction, a minute metal Fe phase is formed in the vicinity of the oxide film.

  In the case of a sintered magnet, since the sintered interface can be regarded as a grain boundary, the formation of the metal Fe phase at the above-described sintered interface causes a significant decrease in coercive force. In particular, when a coercive force generation mechanism such as a samarium-iron-nitrogen based sintered magnet is a nucleation type polycrystalline magnet material, when a soft magnetic phase such as metallic Fe is formed at the grain boundary of crystal grains, It becomes the bud of the reverse magnetic domain and becomes a magnet with a low coercive force.

  In contrast, when the oxygen content normalized by the grain interface area is reduced as in the sintered magnet of this embodiment, that is, when the thickness of the oxide layer at the grain boundary is reduced, it is proportional to it. Therefore, the metal Fe phase is reduced. And since a small amount of metal Fe phase below a certain value no longer works as a bud of the reverse magnetic domain, it is considered that the decrease in coercive force can be suppressed as a result.

  For this reason, the sintered magnet described as the second configuration example satisfies the above-described formula (1), so that the sintered magnet has a coercive force equal to or higher than that of the raw material powder, that is, a sintered having excellent coercive force. It can be a magnet.

  For the preferred composition of the samarium-iron-nitrogen based alloy contained in the sintered magnet of the second configuration example of the present embodiment and the preferred average particle size of the contained crystal particles, the present embodiment described above is used. Since it can be made to be the same as that of the case of the sintered magnet of the 1st structural example of this, description is abbreviate | omitted here.

  Further, in the sintered magnet described as the second configuration example, the oxygen content of the sintered magnet is not particularly limited, and it is sufficient if the above expression (1) including the oxygen content of the sintered magnet is satisfied. However, the oxygen content of the sintered magnet is particularly preferably 0.7% by weight or less.

According to the sintered magnet of the present embodiment described above, it contains crystal particles pulverized to the vicinity of the single domain particle diameter, and has a coercive force equal to or higher than that of the raw material powder, that is, excellent in coercive force, A samarium-iron-nitrogen based sintered magnet can be used.
[Method for producing samarium-iron-nitrogen based sintered magnet]
Next, one structural example of the manufacturing method of the samarium-iron-nitrogen based sintered magnet of the present embodiment will be described.

  The manufacturing method of the samarium-iron-nitrogen based sintered magnet of this embodiment can have the following steps.

  A magnet material containing a samarium-iron-nitrogen alloy is pulverized in an atmosphere having an oxygen concentration of 0.5 volume ppm or less so that the average particle size is greater than 0.04 μm and 5 μm or less to prepare a magnet powder. Crushing process.

  A sintering step of sintering the magnet powder in an atmosphere having an oxygen concentration of 0.5 volume ppm or less at a temperature higher than 300 ° C. and lower than 600 ° C. and a pressure of 1000 MPa to 1500 MPa.

  During the pulverization process and the sintering process, the magnet powder is stored in an atmosphere having an oxygen concentration of higher than 0.5 volume ppm and lower than 50 volume ppm, and the storage period is 6 days or less. It can be stored in an atmosphere of 0.5 volume ppm or less.

  In addition, the samarium-iron-nitrogen based sintered magnet described above can be manufactured by the method for manufacturing a samarium-iron-nitrogen based sintered magnet of the present embodiment. For this reason, in the samarium-iron-nitrogen based sintered magnet, a part of the above-described matters is partially omitted.

The manufacturing method of the samarium-iron-nitrogen based sintered magnet of the present embodiment includes a pulverization step as described above,
A sintering step. Below, each process is demonstrated.

  In the pulverization step, as described above, the magnet material containing the samarium-iron-nitrogen alloy is pulverized so that the average particle size is larger than 0.04 μm and not larger than 5 μm to prepare the magnetic powder as the raw material powder. it can. A magnet powder can be prepared by pulverizing a magnet material containing a samarium-iron-nitrogen alloy, and the magnet powder is a single crystal powder mainly composed of single crystal particles as described above. Is preferred. For this reason, the magnet material is also preferably a coarse powder containing a single crystal, and specifically, a coarse powder containing single crystal particles of a samarium-iron-nitrogen alloy is preferred.

  As described above, if a sintered magnet having a reduced grain boundary oxide layer thickness is obtained, the coercive force can be suppressed from lowering than that of the raw material powder, and equivalent to or higher than the magnet powder. It is possible to obtain a sintered magnet having a coercive force of, that is, an excellent coercive force.

  Here, one of the sources of oxygen contained in the sintered magnet is a surface oxide film on the particle surface of the magnet powder that is the raw material powder. For this reason, in order to obtain a sintered magnet in which the thickness of the oxide layer at the grain boundary is reduced, a magnet powder with a small surface oxide film is required.

  Usually, the raw material powder of the samarium-iron-nitrogen-based magnet is obtained by finely pulverizing a coarse powder, which is a magnetic material of several tens of μm to several mm prepared through a melting alloying method or a reduction diffusion method, to several μm. can get. Even at the production level, the oxygen concentration of the coarse powder is low and both are 0.5 wt% or less. However, when fine powder is obtained through a normal pulverization process, oxygen is adsorbed on the significantly increased surface, so that the oxygen concentration also increases remarkably.

  Therefore, in order to obtain a magnet powder with a small surface oxide film, it is preferable to obtain a magnet powder by carrying out a pulverization step in an atmosphere with a very low oxygen, particularly an oxygen concentration atmosphere of 0.5 volume ppm or less. In addition, although the atmosphere at the time of grind | pulverizing the coarse powder which is a magnet material in a grinding | pulverization process and preparing magnet powder is not specifically limited, For example, in inert gas atmosphere, such as argon, nitrogen, helium, or a vacuum atmosphere Preferably there is.

  In the pulverization step, the means for pulverizing the magnet material containing the samarium-iron-nitrogen alloy is not particularly limited, but the magnet material containing the samarium-iron-nitrogen alloy may be pulverized by a dry jet mill method. preferable.

  Examples of means for pulverizing a magnet material containing a samarium-iron-nitrogen alloy include wet and dry ball mill methods, bead mill methods, and jet mill methods.

  However, as in the ball mill method and the bead mill method, when the collision energy of the ball, which is a grinding medium, is used, the oxygen in the oxide film present on the surface of the ball is converted into a magnet material containing a samarium-iron-nitrogen alloy. Therefore, it is difficult to reduce the oxygen concentration in the obtained magnet powder. On the other hand, the pulverizing medium is not used in the jet mill method, and the powder particles are pulverized by colliding with each other by a high-speed air stream. For this reason, since the frequency of taking in new oxygen is low and it is easy to obtain a magnet powder having a low oxygen concentration, the magnet material containing the samarium-iron-nitrogen alloy is pulverized by the dry jet mill method as described above. It is preferable.

  In the pulverization step, when using a dry jet mill method, a pressurized gas is supplied to the pulverization chamber of the jet mill, a high-speed air stream is formed by the pressurized gas, and powder particles collide with each other by the high-speed air stream. It will be crushed. The gas used at this time is not particularly limited, but it is preferable that the oxygen concentration is low because it comes into contact with the pulverized magnet powder or the like. The gas supplied to the pulverizing chamber of the jet mill is preferably a gas having an oxygen concentration of 0.5 volume ppm or less, and more preferably a gas having an oxygen concentration of 0.1 volume ppm or less. The gas species is not particularly limited, but is preferably an inert gas, for example, nitrogen, argon, or helium.

  In addition, as described above, the magnet powder obtained after the pulverization step preferably has an average particle size of more than 0.04 μm and not more than 5 μm. The average particle size here means the particle size at an integrated value of 50% in the particle size distribution determined by the laser diffraction / scattering method.

  It is preferable to perform a preliminary test or the like and select the grinding conditions so that the magnet powder obtained after the grinding process has a desired average particle diameter. For example, when the dry jet mill method is used, a magnet powder having a desired average particle diameter can be obtained by selecting the pressure of the gas supplied to the pulverization chamber of the jet mill.

  Since the temperature of the magnet powder after the pulverization process is lower than that during pulverization, the oxidation reaction of the magnet powder by oxygen contained in the surrounding atmosphere does not proceed as much as during the pulverization process.

  However, depending on the oxygen concentration in the atmosphere in which the magnet powder is stored, a surface oxide film may be formed on the surface of the magnet powder. For this reason, it is preferable to store the magnet powder after the pulverization step in an atmosphere having an oxygen concentration of 50 ppm by volume or less.

  However, according to the study by the inventors of the present invention, even in an atmosphere having an oxygen concentration of 50 ppm by volume or less, oxidation of the magnet powder is gradually performed in an atmosphere having an oxygen concentration higher than 0.5 ppm by volume. The reaction may proceed. For this reason, when the oxygen concentration of the atmosphere in which the magnet powder is stored is stored in an atmosphere higher than 0.5 ppm by volume and 50 ppm by volume or less, the storage period may be 6 days or less after the end of the pulverization step. preferable. This is because even when the oxygen concentration is stored in an atmosphere higher than 5 volume ppm and lower than 50 volume ppm, the surface oxide film formed on the surface of the magnet powder becomes thicker after 6 days. This is because when the sintered magnet is formed, the coercive force may be lower than that of the magnet powder.

  If the oxygen concentration of the atmosphere in which the magnet powder is stored is 0.5 ppm by volume or less, the oxidation reaction of the magnet powder hardly proceeds, so the storage period is not particularly limited. However, even when the oxygen concentration of the atmosphere in which the magnet powder is stored is an atmosphere having a volume of 0.5 ppm or less, the storage period is preferably short, for example, the storage period is preferably one month or less.

  After the pulverization step is completed, the storage period is preferably short from the viewpoint of suppressing the oxidation of the obtained magnet powder, and it is particularly preferable to perform the sintering step continuously after the pulverization step.

  The gas species in the atmosphere in which the magnet powder is stored is not particularly limited, but is preferably an inert gas, and more preferably, for example, nitrogen, argon, or helium.

  Next, the sintering process will be described.

  In the sintering process, a sintered magnet can be prepared by sintering and solidifying the magnet powder prepared in the pulverization process.

  Also in the sintering step, sintering is performed in a low oxygen atmosphere of 0.5 volume ppm or less from the viewpoint of suppressing the formation of a surface oxide film on the surface of the magnet powder and reducing the oxygen concentration in the sintered magnet. It is preferable.

  The atmosphere in the sintering step is not particularly limited, but is preferably an inert gas atmosphere such as argon, nitrogen, helium, or a vacuum atmosphere. However, if a vacuum atmosphere is used in the sintering process, it is easy to create a low-oxygen atmosphere, but if heated for a long time in a vacuum, denitrification may occur in the samarium-iron-nitrogen alloy. is necessary.

  And in a sintering process, it is preferable to sinter at the temperature higher than 300 degreeC and less than 600 degreeC as mentioned above. When the sintering temperature is low at 300 ° C. or less, the magnetic powder does not cause a sintering bond between the particles, and a sintered body cannot be obtained. For this reason, it is because the intensity | strength of the sintered body obtained after the sintering process becomes remarkably low. On the other hand, if the sintering temperature is 600 ° C. or higher, the decomposition of the samarium-iron-nitrogen alloy proceeds, a large amount of Fe phase precipitates between the magnet powders, and the sintered magnet obtained after the sintering process is retained. This is because the magnetic force is greatly reduced.

  From the viewpoint of further increasing the strength and coercive force of the sintered magnet, the sintering temperature is more preferably 350 ° C. or higher and 550 ° C. or lower, and in particular, a sintered magnet having a high coercive force exceeding the magnet powder as the raw material powder, From this viewpoint, the sintering temperature is more preferably 400 ° C. or more and 500 ° C. or less.

  However, when densification is performed by normal pressure sintering as in the conventional case, the sintering temperature described above, that is, a sintering temperature higher than 300 ° C. and lower than 600 ° C. is too low. For this reason, it is preferable to perform the sintering at a temperature within the temperature range while applying pressure. Specifically, it is preferable to sinter under a pressure of 1000 MPa to 1500 MPa.

  This is because a sintered magnet having a high relative density can be obtained by sintering while applying a pressure of 1000 MPa or more. Moreover, since samarium-iron-nitrogen based alloys are brittle materials, if sintering is performed while applying a pressure higher than 1500 MPa, there is a risk of causing layered cracks and the like.

  In the sintering step, the means for sintering the magnet powder is not particularly limited. For example, it is preferable to use an electric current sintering method.

  In the sintering step, the most common sintering method for satisfying the sintering conditions of heating while applying pressure in the predetermined atmosphere described above is a hot press sintering method. However, in the hot press sintering method, since an external heater is used for heating, the time during which the magnet powder is exposed to a high temperature becomes long. In the sintering process, although the atmosphere during sintering has a low oxygen concentration, oxygen is not completely absent. Therefore, the oxygen concentration in the magnet is inevitably increased as it is exposed to a high temperature for a long time.

  On the other hand, the electric current sintering that heats and sinters by passing an electric current through the sintering mold can make the heating and cooling speed much faster than the hot press method. Easy to achieve. For this reason, in the sintering step, the magnet powder is preferably sintered using an electric current sintering method.

  According to the manufacturing method of the samarium-iron-nitrogen based sintered magnet of the present embodiment described above, the pulverization step of pulverizing the magnet material to make the magnet powder, and the sintering step of producing the sintered magnet from the magnet powder , The amount of oxygen entering can be suppressed. Moreover, it can suppress that a magnet powder is oxidized after a grinding | pulverization process until it implements a sintering process.

  For this reason, a sintered magnet having a small oxygen content can be obtained. Further, it is possible to reduce the surface oxide film on the particle surface of the magnet powder that is the raw material powder, and to reduce the thickness of the oxide layer at the grain boundary of the obtained sintered magnet.

  As a result, a sintered magnet having a coercive force equal to or higher than that of the magnet powder as the raw material powder, that is, a sintered magnet having a high coercive force can be obtained.

  In the sintering process, the magnet powder is heated and sintered at a temperature equal to or lower than the thermal decomposition temperature, so that grain growth due to heating does not occur. For this reason, a samarium-iron-nitrogen-based sintered magnet containing crystal particles pulverized to the vicinity of a single domain particle size can be obtained by using a magnet powder having an average particle size of 5 μm or less as the magnet powder.

  Specific examples will be described below, but the present invention is not limited to these examples.

As Example 1 to Example 5 and Comparative Example 1 to Comparative Example 8, sintered magnets having different conditions until the pulverization process conditions or the sintering process after the pulverization process were carried out were evaluated.
[Example 1]
A samarium-iron-nitrogen sintered magnet was prepared and evaluated by the following procedure.
(Crushing process)
A commercially available coarse powder having a composition of Sm ₂ Fe ₁₇ N ₃ and an average particle diameter of about 25 μm was prepared as a magnet material as a raw material. The coarse powder is a coarse powder containing single crystal particles of a samarium-iron-nitrogen alloy having the above composition. The crude powder had an oxygen content of 0.20% by weight and a coercive force of 0.07 kOe.

  The magnet material was pulverized by the following procedure so as to have the average particle diameter of the magnet powder shown in Table 1.

  As a means for finely pulverizing the magnet material in the pulverization step, pulverization was performed by a dry jet mill method using a pulverization system in which an airflow swirling jet mill (hereinafter simply referred to as a jet mill) was installed in a glove box. A gas circulation type oxygen moisture purifier and an oxygen concentration meter capable of measuring up to 0.01 ppm by volume are connected to the glove box. The jet mill is connected to a high-pressure gas generator that supplies pulverized gas.

After sealing the glove box to put the magnetic material described above in a milling system, the gas inside the glove box by a high-purity _{N 2} gas (purity> 99.99995%, _{O 2} concentration <0.1 vol ppm) The flow was replaced. In the gas flow replacement, a gas having a capacity 5 times the glove box internal volume was flowed as a guide. Further, oxygen was removed using a gas circulation oxygen moisture purifier until the oxygen concentration inside the glove box reached 0.5 ppm by volume. The water concentration was 1 volume ppm or less.

After substituting the atmosphere in the glove box and sufficiently reducing the oxygen concentration and the water concentration, the magnet material was put into a pulverization chamber of a jet mill supplied with high-pressure N ₂ gas little by little and pulverized.

Note that the oxygen concentration of the high-pressure N ₂ gas supplied to the jet mill was 0.1 ppm by volume or less. Further, by controlling the pressure of the gas supplied to the jet mill to 0.95 MPa, a magnet powder that was a fine powder having an average particle size of 2.8 μm was produced.

  A part of the magnet powder produced in the pulverization step was subjected to the sintering step of the present example described later to produce a sintered magnet. The remainder of the magnet powder was also used in Example 2, Comparative Example 1, and Comparative Example 3 described later.

A part of the obtained magnet powder was slowly oxidized for several hours in a mixed gas atmosphere of Ar-0.5% O _{2 in} a glove box and then taken out into the atmosphere. The magnetic properties of the magnet powder taken out into the atmosphere are measured using a vibrating sample magnetometer (VSM) (manufactured by Quantum Design, USA).
As shown in Table 1, it was confirmed that the measured value was 7.8 kOe.

Further, when a mean particle size of a part of the magnet powder taken out from the glove box into the atmosphere as described above was measured by a laser diffraction type particle size distribution measuring method, it was confirmed to be 2.8 μm.
(Sintering process)
Next, the obtained magnet powder was sintered by the following procedure, and a sintering process for producing a sintered magnet was performed.

  Immediately after pulverization in the pulverization step, 0.5 g of the magnet powder was weighed in a glove box maintained in the same atmosphere as in the pulverization step, and filled into a cemented carbide cylindrical die set having an inner diameter of 6 mm. . And it transferred to the pulse electric sintering machine provided with the pressurization mechanism by a servo control type press apparatus, without exposing to air | atmosphere.

  Next, after the sintering chamber was set to a vacuum atmosphere of 2 Pa or less, the magnet powder was loaded with a compression pressure of 1200 MPa and immediately unloaded. A compression pressure of 1200 MPa was again applied to the magnet powder, and current sintering was performed for 1 minute at a sintering temperature of 400 ° C. while maintaining this pressure. The inside of the sintering chamber is a vacuum atmosphere of 2 Pa or less, and the oxygen concentration is 0.5 volume ppm or less.

  When the obtained sintered magnet was magnetically measured using VSM, as shown in Table 1, the coercive force of the sintered magnet exhibited a value exceeding that of the magnet powder.

  When the average particle diameter of the crystal particles contained in the obtained sintered magnet was measured by the area measurement method of the cross-sectional structure image, it was confirmed that it was the same average particle diameter as the magnet powder subjected to the sintering process.

The average particle size of the crystal particles was measured and calculated according to the following procedure. First, a cross-sectional image of the obtained sintered magnet was taken with an FE-SEM (field emission scanning electron microscope). Then, draw a rectangle to include at least 50 or more crystal grains on the cross-sectional image of the sintered magnet obtained, determined the number N _A of the total area A and the crystal grains of the crystal grains existing in the rectangle It was.

The total area A of the obtained crystal particles by dividing the number N _A of the crystal grains (A / N _A), and calculate the average cross-sectional area a of the crystal grains. Then, the square root (a ^1/2 ) of the average cross-sectional area a of the crystal particles was calculated as the average particle size of the crystal particles. In the following examples and comparative examples, the average particle diameter of crystal grains is measured in the same manner using the area measurement method.

  The obtained sintered magnet was sintered by an inert gas melting-non-dispersive infrared absorption method (NDIR method) using an oxygen / nitrogen analyzer (Model: EMGA-620W manufactured by Horiba, Ltd.). The oxygen content in was measured. And the product of the oxygen content rate of a sintered magnet and the average particle diameter of the crystal grain contained in a sintered magnet was computed.

The evaluation results are shown in Table 1.
[Example 2]
Part of the magnet powder obtained in the pulverization step of Example 1 was pulverized in a glove box maintained in an atmosphere of nitrogen atmosphere with an oxygen concentration higher than 0.5 ppm by volume and 50 ppm by volume or less. After standing for 2 days, a sintered magnet was prepared and evaluated in the same manner as in Example 1 except that the cemented carbide cylindrical die set was filled with magnet powder and the sintering process was performed.

  In addition, when the average particle diameter of the crystal particles contained in the obtained sintered magnet was measured by the area measurement method of the cross-sectional structure image, it was confirmed that it was the same average particle diameter as the magnet powder subjected to the sintering process .

The evaluation results for the obtained sintered magnet are shown in Table 1.
[Example 3]
In the pulverization step, a sintered magnet was produced and evaluated in the same manner as in Example 1 except that the pressure of the high-pressure N ₂ gas supplied to the jet mill was 0.85 MPa.

  In addition, as described above, a part of the magnet powder produced in the pulverization process of this example was subjected to the same procedure and conditions as in Example 1, but the rest of the magnet powder was performed later. Also used in Example 4, Example 5, Comparative Example 2, and Comparative Example 4.

A part of the magnet powder obtained in the pulverization step was gradually oxidized in a mixed gas atmosphere of Ar-0.5% O _{2 in} a glove box for several hours and then taken out into the atmosphere. When the magnetic properties of the magnet powder taken out into the atmosphere were measured with a vibrating sample magnetometer (VSM), it was confirmed to be 5.6 kOe as shown in Table 1. Furthermore, when a part of the magnet powder taken out from the glove box into the atmosphere as described above was measured for the average particle size by the laser diffraction particle size distribution measurement method, it was confirmed that it was 4.0 μm.

  Then, the magnet powder pulverized in the pulverization step is filled into a sintered die cemented cylindrical die set in a glove box maintained in the same atmosphere as in the pulverization step, and baked in the same manner as in Example 1. The ligation process was carried out.

  After the sintering process, when the crystal particles contained in the obtained sintered magnet were measured by the area measurement method of the cross-sectional structure image, it was confirmed that the average particle diameter was the same as the magnet powder subjected to the sintering process.

The evaluation results for the obtained sintered magnet are shown in Table 1.
[Examples 4 and 5]
Part of the magnet powder obtained in the pulverization step of Example 3 was pulverized in a glove box maintained in an atmosphere of nitrogen atmosphere with an oxygen concentration higher than 0.5 ppm by volume and 50 ppm by volume or less. Example 3 except that after 2 days (Example 4) or 6 days (Example 5), the magnet powder was filled in a cemented carbide cylindrical die set and the sintering step was performed. In the same manner, sintered magnets were produced and evaluated.

  In all of Examples 4 and 5, when the average particle diameter of the crystal particles contained in the obtained sintered magnet was measured by the area measurement method of the cross-sectional structure image, it was the same as the magnet powder subjected to the sintering step The average particle size was confirmed.

The evaluation results for the obtained sintered magnet are shown in Table 1.
[Comparative Example 1]
A part of the magnet powder obtained in the pulverization step of Example 1 was gradually oxidized in a mixed gas atmosphere of Ar-0.5% O ₂ for several hours in a glove box and then taken out into the atmosphere. A sintered magnet was produced and evaluated in the same manner as in Example 1 except that the gradually oxidized magnet powder was subjected to a sintering process.

  The magnet powder was filled into the cemented carbide cylindrical die set in an air atmosphere outside the glove box.

The evaluation results for the obtained sintered magnet are shown in Table 1.
[Comparative Example 2]
A part of the magnet powder obtained in the pulverization step of Example 3 was gradually oxidized in a mixed gas atmosphere of Ar-0.5% O _{2 in} a glove box for several hours and then taken out into the atmosphere. A sintered magnet was produced and evaluated in the same manner as in Example 3 except that the gradually oxidized magnet powder was subjected to a sintering process.

  The magnet powder was filled into the cemented carbide cylindrical die set in an air atmosphere outside the glove box.

The evaluation results for the obtained sintered magnet are shown in Table 1.
[Comparative Example 3]
Part of the magnet powder obtained in the pulverization step of Example 1 was pulverized in a glove box maintained in an atmosphere of nitrogen atmosphere with an oxygen concentration higher than 0.5 ppm by volume and 50 ppm by volume or less. After standing for 10 days, a sintered magnet was prepared and evaluated in the same manner as in Example 1 except that a cemented carbide cylindrical die set was filled with magnet powder and the sintering step was performed.

The evaluation results for the obtained sintered magnet are shown in Table 1.
[Comparative Example 4]
Part of the magnet powder obtained in the pulverization step of Example 3 was pulverized in a glove box maintained in an atmosphere of nitrogen atmosphere with an oxygen concentration higher than 0.5 ppm by volume and 50 ppm by volume or less. After standing for 10 days, a sintered magnet was prepared and evaluated in the same manner as in Example 3 except that a cemented carbide cylindrical die set was filled with magnet powder and the sintering step was performed.

The evaluation results for the obtained sintered magnet are shown in Table 1.
[Comparative Example 5 and Comparative Example 6]
In the pulverization step, the pulverization step was performed in the same manner as in Example 1 except that the pressure of the high-pressure N ₂ gas supplied to the jet mill was 0.70 MPa (Comparative Example 5) and 0.45 MPa (Comparative Example 6). A magnet powder was prepared.

Part of the magnet powder obtained in the pulverization step was slowly oxidized for several hours in a mixed gas atmosphere of Ar-0.5% O _{2 in} a glove box, and then taken out into the atmosphere. When the magnetic properties of the magnet powder taken out into the atmosphere were measured with a vibrating sample magnetometer (VSM), as shown in Table 1, the magnetic powder of Comparative Example 5 was 3.2 kOe, and the magnetic powder of Comparative Example 6 was 1. It was confirmed that it was 1 kOe. Further, when a mean particle size of a part of the magnet powder taken out from the glove box as described above was measured by a laser diffraction particle size distribution measuring method, it was 6.4 μm in Comparative Example 5 and 10.3 μm in Comparative Example 6. It was confirmed that there was.

  The coercive force of the magnet powder thus obtained was as low as 5 kOe or less, and it was confirmed that the magnet powder had no practical coercive force at the stage of the magnet powder. This is because when the average particle size of the magnet powder is large, the inside of the particles constituting the magnet powder has a multi-domain structure.

As described above, since the coercive force of the magnet powder was low, the obtained magnet powder was not subjected to the sintering step, and production of the sintered magnet was stopped.
[Comparative Example 7]
In the pulverization step, the oxygen concentration in the glove box provided with the jet mill was not lowered to 0.5 ppm by volume, except that the pulverization by the jet mill was started at the stage of 1 ppm by volume, as in Example 3, A pulverization process and a sintering process were carried out to produce and evaluate a sintered magnet.

Part of the magnet powder obtained in the pulverization step was slowly oxidized for several hours in a mixed gas atmosphere of Ar-0.5% O _{2 in} a glove box, and then taken out into the atmosphere. When the magnetic properties of the magnet powder taken out into the atmosphere were measured with a vibrating sample magnetometer (VSM), it was confirmed that it was 5.4 kOe as shown in Table 1. Further, when a part of the magnet powder taken out from the glove box as described above was measured for an average particle size by a laser diffraction particle size distribution measuring method, it was confirmed to be 4.1 μm. Since the gas pressure of the high-pressure N ₂ gas supplied to the jet mill was the same as in Example 3, the average particle size of the magnet powder obtained after the pulverization step was almost the same as in Example 3. It could be confirmed.

The evaluation results for the obtained sintered magnet are shown in Table 1.
[Comparative Example 8]
A pulverization process was not performed, and a commercially available Sm ₂ Fe ₁₇ N ₃ powder (average particle diameter of 3.2 μm) was used as a magnet powder. A sintered magnet was produced and evaluated in the same manner as in Example 1 except for the points implemented. The oxygen content of this commercially available powder was measured by NDIR method using an oxygen / nitrogen analyzer and found to be 1.191% by weight.

  The magnet powder was filled into the cemented carbide cylindrical die set in an air atmosphere outside the glove box.

  The evaluation results for the obtained sintered magnet are shown in Table 1.

  According to Table 1, immediately after the pulverization step, magnet powder was filled into a cemented carbide cylindrical die set in a glove box, transferred to a sintering machine without exposure to the atmosphere, and sintered in Examples 1 and 3. It was confirmed that the coercive force of the sintered magnet exceeded the coercive force of the magnet powder regardless of the powder particle size. That is, it was confirmed that the obtained sintered magnet had a high coercive force.

  However, oxidation proceeds little by little in the glove box. For this reason, about Examples 2, 4, and 5 in which the period of leaving the obtained magnetic powder in a glove box in an atmosphere having an oxygen concentration of higher than 5 volume ppm and lower than or equal to 50 volume ppm is within 6 days after the pulverization step. The coercive force may be slightly lower than that of Example 1 or Example 3. However, in Examples 2, 4, and 5, it was confirmed that a sintered magnet having a coercive force equal to or greater than the coercive force of the magnet powder was obtained. That is, it was confirmed that the obtained sintered magnet had a high coercive force.

  On the other hand, in Comparative Examples 3 and 4 in which the oxygen concentration is higher than 5 volume ppm and left in a glove box having an atmosphere of 50 volume ppm or less, the coercive force is greatly reduced, It was confirmed that the coercive force was lower than.

In Comparative Examples 1 and 2 in which the gradual oxidation of the magnet powder was performed before the sintering process, the increase / decrease rate of the coercivity from the magnet powder in the sintered magnet was -46% and -32%, and the coercivity was greatly reduced. I was able to confirm. As described above, once the magnetic powder exposed to the atmosphere is sintered, the phenomenon that the coercive force decreases drastically has been reported, and the results of Comparative Examples 1 and 2 also reproduce the phenomenon that has been conventionally reported. It was also confirmed that the coercive force was drastically reduced by about 70% in Comparative Example 8 in which commercially available Sm ₂ Fe ₁₇ N ₃ powder was sintered.

  In Comparative Example 7 in which the oxygen concentration in the atmosphere in the glove box when performing the pulverization step was 1.0 volume ppm, it was confirmed that the coercivity of the sintered magnet was lower than the coercivity of the magnet powder. Therefore, in the sintered magnet, in order to maintain the coercive force of the magnet powder and achieve a sintered body having a low oxygen content, the pulverization step may be performed in an atmosphere having an oxygen concentration of 0.5 volume ppm or less. It was confirmed that it was preferable.

  And according to the evaluation results shown in Table 1, when comparing by focusing on the relationship between the oxygen content and the increase / decrease rate of the coercive force from the magnet powder in the sintered magnet, the oxygen content is 0.7% by weight or less. It can be confirmed that the coercive force of the sintered magnet is higher than the coercive force of the magnet powder. That is, it was confirmed that the sintered magnet has a high coercive force.

  Also, from the standpoint that oxygen concentrated at the grain boundary reduces the coercive force, the experimental results are examined focusing on the coercive force of the sintered magnet and the oxygen content contained in the grain boundary per unit area. I do. As described above, the oxygen content contained in the grain boundary per unit area can be expressed by the product of the oxygen content of the sintered magnet and the average particle size of the crystal grains. And when (oxygen content of sintered magnet) × (average particle diameter of crystal particles) <2.2, it is possible to obtain a sintered magnet having a coercive force higher than the coercive force of the magnet powder as the raw material powder. It could be confirmed. That is, it was confirmed that the sintered magnet has a high coercive force.

Claims (5)

Contains samarium-iron-nitrogen alloy,
The average particle size of the contained crystal particles is larger than 0.04 μm and 5 μm or less,
A samarium-iron-nitrogen based sintered magnet having an oxygen content of 0.7% by weight or less. Contains samarium-iron-nitrogen alloy,
The average particle size of the contained crystal particles is larger than 0.04 μm and 5 μm or less,
A samarium-iron-nitrogen based sintered magnet in which the oxygen content (% by weight) and the average particle size (μm) of the crystal particles satisfy the relationship of the following formula (1).
(Oxygen content) × (average particle diameter of crystal grains) <2.2 (1) A magnet material containing a samarium-iron-nitrogen alloy is pulverized in an atmosphere having an oxygen concentration of 0.5 volume ppm or less so that the average particle size is greater than 0.04 μm and 5 μm or less to prepare a magnet powder. Crushing process to
A sintering step of sintering the magnet powder in an atmosphere having an oxygen concentration of 0.5 volume ppm or less and a temperature higher than 300 ° C. and lower than 600 ° C. and a pressure of 1000 MPa to 1500 MPa.
Between the pulverization step and the sintering step, the magnet powder is stored in an atmosphere having an oxygen concentration of higher than 0.5 volume ppm and lower than or equal to 50 volume ppm, and the storage period is 6 days or less. Is a method for producing a samarium-iron-nitrogen based sintered magnet stored in an atmosphere of 0.5 ppm by volume or less.   The method for producing a samarium-iron-nitrogen based sintered magnet according to claim 3, wherein in the pulverizing step, the magnet material containing the samarium-iron-nitrogen based alloy is pulverized by a dry jet mill method. The method for producing a samarium-iron-nitrogen based sintered magnet according to claim 3 or 4, wherein, in the sintering step, the magnet powder is sintered using an electric current sintering method.

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