JP2020102586A - Rare earth magnet manufacturing method and rare earth magnet - Google Patents

Abstract

To provide a rare earth magnet manufacturing method and a rare earth magnet with excellent heat resistance and strength.SOLUTION: A rare earth magnet manufacturing method includes a step of preparing a magnet composition containing magnetic material particles containing a rare earth element and copper alloy particles having a specific surface area of 0.2 m2/g or more, a step of molding the magnet composition to form a molded body, and a step of heat-treating the molded body in an atmosphere containing oxygen at a temperature of less than 450°C.SELECTED DRAWING: None

Description

The present invention relates to a method for manufacturing a rare earth magnet and a rare earth magnet.

Rare earth magnets using magnetic materials containing rare earth elements include rare earth sintered magnets obtained by sintering magnetic materials at high temperatures, and rare earth bonded magnets obtained by molding a mixture of magnetic materials and binders. It has been known.
Since the rare earth sintered magnet has a large shrinkage due to sintering, it has low dimensional accuracy and requires post-processing after sintering. On the other hand, since the rare earth bonded magnet is obtained by molding, it has a higher degree of freedom in shape than the rare earth sintered magnet. Furthermore, since the rare earth bonded magnet is superior in dimensional accuracy to the rare earth sintered magnet, it does not require post-processing and can be manufactured at low cost. Therefore, rare earth bonded magnets are widely used in automobiles, general household appliances, communication devices, audio devices, medical devices, general industrial devices, and the like.

A resin material or a metal material is mainly used as a binder for the rare earth bonded magnet. As a resin material as a binder in a rare earth bonded magnet, a thermosetting resin is known as disclosed in, for example, Patent Document 1 and Patent Document 2 below. Further, as a metal material as a binder in a rare earth bonded magnet, for example, a metal material such as Zn is known as disclosed in Patent Document 3 and Patent Document 4 below.

JP-A-08-273916 JP, 10-275718, A JP, 2009-076631, A JP, 2017-010960, A

Rare earth bonded magnets are also used in applications where heat resistance is required. In applications requiring heat resistance, rare-earth bonded magnets are required to have improved mechanical strength (hereinafter also referred to as heat resistance and strength) that can withstand use in high temperature environments while ensuring good magnetic properties. It is rising. Rare earth bond magnets that use a metal material as a binder (rare earth metal bond magnets) tend to have better heat resistance than rare earth bond magnets that use a resin material as a binder, but with even higher heat resistance and strength. Improvement is desired.

The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a method for manufacturing a rare earth magnet having excellent heat resistance and strength, and a rare earth magnet.

Means for solving the above problems include the following aspects.
<1> A step of preparing a composition for a magnet, which contains magnetic material particles containing a rare earth element and copper alloy particles having a specific surface area of 0.2 m ² /g or more,
A step of molding the magnet composition to form a molded body,
Heat treating the shaped body at a temperature of less than 450° C. in an atmosphere containing oxygen;
A method for manufacturing a rare earth magnet having:
<2> The method for producing a rare earth magnet according to <1>, wherein the heat treatment is performed in an atmosphere containing water vapor.
<3> The method for producing a rare earth magnet according to <1> or <2>, wherein the magnetic material particles contain samarium (Sm) as a rare earth element.
<4> The method for producing a rare earth magnet according to any one of <1> to <3>, wherein the magnetic material particles contain iron (Fe).
<5> The copper alloy particles according to any one of <1> to <4>, containing at least one selected from the group consisting of phosphorus (P), cobalt (Co), and manganese (Mn). Manufacturing method of rare earth magnet.
<6> The rare earth magnet according to any one of <1> to <5>, wherein the magnet composition does not contain a resin, or the resin content is 10% by mass or less of the entire magnet composition. Manufacturing method.
<7> A heat-treated product of a molded body containing magnetic material particles containing a rare earth element and copper alloy particles having a specific surface area of 0.2 m ² /g or more, and oxides and water of the components contained in the magnetic material particles. A rare earth magnet containing at least one of oxides.
<8> The rare earth magnet according to <7>, wherein the magnetic material particles contain samarium (Sm) as a rare earth element.
<9> The rare earth magnet according to <7> or <8>, wherein at least one of the oxide and hydroxide is at least one of iron (Fe) oxide and hydroxide.
<10> The copper alloy particles according to any one of <7> to <9>, wherein the copper alloy particles include at least one selected from the group consisting of phosphorus (P), cobalt (Co), and manganese (Mn). Rare earth magnets.

According to the present disclosure, a method for manufacturing a rare earth magnet having excellent heat resistance and strength, and a rare earth magnet are provided.

Hereinafter, an embodiment of the present invention will be described in detail.

However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and ranges thereof, and does not limit the present invention.
In the present disclosure, the term “process” refers to a process independent from other processes, and even if the process cannot be clearly distinguished from other processes, as long as the purpose of the process is achieved, the process concerned Is also included.
In the present disclosure, the numerical range indicated by using "to" includes the numerical values before and after "to" as the minimum value and the maximum value, respectively.
In the numerical ranges described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other stages. .. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
In the present disclosure, each component may include a plurality of types of corresponding substances. When there are multiple types of substances corresponding to each component in the composition, the content rate or content of each component is the total content rate or content of the multiple types of substances present in the composition unless otherwise specified. Means quantity.
In the present disclosure, a plurality of types of particles corresponding to each component may be included. When a plurality of types of particles corresponding to each component are present in the composition, the particle size of each component means a value for a mixture of the plurality of types of particles present in the composition unless otherwise specified.

<Rare earth magnet manufacturing method>
One embodiment of a method for producing a rare earth magnet of the present disclosure is to provide magnetic material particles containing rare earth elements (hereinafter also referred to as magnetic material particles) and copper alloy particles having a specific surface area of 0.2 m ² /g or more (hereinafter, A step of preparing a magnet composition containing (also referred to as specific metal particles), a step of molding the magnet composition into a molded body, and a temperature of less than 450° C. in an atmosphere containing the molded body of oxygen. And a step of heat-treating.

Hereinafter, the step of preparing a magnet composition containing magnetic material particles and specific metal particles will be referred to as a magnet composition preparation step. The step of molding the magnet composition to form a molded body is referred to as a molding step. The step of heat-treating the molded body in the presence of oxygen is referred to as a heat treatment step.
In the present disclosure, a treatment performed so that the highest temperature reached by the molded body of the magnet composition is 80° C. or higher is referred to as “heat treatment”.

According to the method of the present disclosure, a rare earth magnet having excellent heat resistance and strength can be obtained. The reason is not clear, but it can be considered as follows.

In the method for manufacturing a rare earth magnet according to the present disclosure, heat treatment is performed in an atmosphere containing oxygen. As a result, the amounts of oxides and hydroxides of the components (for example, Fe contained in the Sm-Fe-N-based magnetic material particles) contained in the magnetic material particles at the boundary between the magnetic material particles and the specific metal particles are There is a tendency to increase relatively. Such a tendency is not seen in the conventional heat treatment in an inert gas. It is presumed that the relatively increased oxide and hydroxide contribute to the improvement of the strength of the rare earth magnet.

Further, in the method of the present disclosure, the heat treatment is performed at a temperature lower than 450°C. Thereby, the decomposition of the magnetic material particles (for example, Sm-Fe-N magnetic material particles) is suppressed, and good magnetic properties tend to be maintained. In addition, it is possible to prevent the magnet composition from being sintered and shrinking in volume, and to obtain good dimensional stability.

(1) Magnet Composition Preparation Step In the magnet composition preparation step, a magnet composition containing magnetic material particles and specific metal particles is prepared. The method for preparing the magnet composition is not particularly limited. For example, the magnet composition may be prepared by mixing magnetic material particles and specific metal particles.
When a magnet composition is prepared by mixing magnetic material particles and specific metal particles, the magnet composition is prepared, for example, by a mixing shaker, a tumbler mixer, a V type mixer, a double cone type mixer, or a ribbon type. It may be carried out using a known mixing device such as a mixer, a Nauta mixer, a Henschel mixer, a super mixer or the like.

-Magnetic material particles-
The type of magnetic material particles is not particularly limited. Examples thereof include magnetic material particles containing Sm (samarium) as a rare earth element and magnetic material particles containing Nd (neodymium) as a rare earth element. The magnetic material particles contained in the magnet composition may be only one kind or a combination of two or more kinds.

As the magnetic material particles containing Sm, SmFe-N magnetic material particles _{(Sm 2 Fe 17 N 3,} SmFe 7 N x and the like), SmFe-B magnetic material particles _{(Sm 2 Fe 14 B, Sm} 15 Fe ₇₇ B ₅ etc.), Sm-Co magnetic material particles (SmCo ₅ , Sm ₂ Co ₁₇ etc.), Sm-Co-N magnetic material particles (Sm ₂ Co ₁₇ N _x etc.), Sm-Co-B magnetic material particles ( Sm ₁₅ Co ₇₇ B ₅ ) and the like.
As the magnetic material particles containing Nd, Nd-Fe-B magnetic material particles _(Nd 2 _{Fe 14} B, etc.) and the like.

From the viewpoint of strength, magnetic material particles containing Fe are preferable as the magnetic material particles. By using the magnetic material particles containing Fe, an oxide and a hydroxide of Fe are generated by heat treatment of the molded body of the magnet composition, and the strength of the rare earth magnet tends to be improved.

Among the magnetic material particles containing Sm, Sm-Fe-N magnetic material particles are more preferable from the viewpoint of excellent balance of coercive force and magnetic flux density. Here, the Sm-Fe-N magnetic material particles mean magnetic material particles containing Sm (samarium), Fe (iron) and N (nitrogen).

The Sm-Fe-N magnetic material particles may contain other elements in addition to Sm, Fe and N. Other elements include Ga, Nd, Zr, Ti, Cr, Co, Zn, Mn, V, Mo, W, Si, Re, Cu, Al, Ca, B, Ni, C, La, Ce, Pr, Examples thereof include Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y and Th. These other elements may be used alone or in combination of two or more. Other elements may be introduced by substituting a part of the phase structure of the magnet phase containing Sm, Fe and N at 50 mass% or more, or may be inserted and introduced. When the Sm-Fe-N magnetic material particles contain an element other than Sm, Fe and N, the total amount of Sm, Fe and N is preferably 50% by mass or more of the whole.

The volume average particle diameter (D50) of the magnetic material particles is not particularly limited and is preferably 1 μm to 100 μm, more preferably 1 μm to 50 μm, and further preferably 1 μm to 20 μm.
The volume average particle diameter (D50) of the magnetic material particles is the particle diameter (D50) when the accumulation from the small diameter side is 50% in the volume-based particle size distribution measured by the laser diffraction/scattering particle size distribution measuring device. Can be measured.

The shape of the magnetic material particles is not particularly limited, and examples thereof include irregular shapes. When the shape of the magnetic material particles is irregular, a void is reduced and a rare earth magnet having improved mechanical strength tends to be obtained in the case of a molded body described later. The ratio of the major axis to the minor axis of the magnetic material particles having an irregular shape (major axis/minor axis) is not particularly limited. From the viewpoint of more easily improving the mechanical strength, the lower limit of the ratio of major axis/minor axis is preferably 1 or more, more preferably 1.5 or more, and further preferably 2 or more. From the viewpoint of dispersibility in the magnet composition, the upper limit of the ratio of major axis/minor axis is preferably 3.5 or less, more preferably 3 or less.

The shape, major axis, and minor axis of the magnetic material particles can be measured by observation with a scanning electron microscope (SEM), a transmission electron microscope (TEM), or the like. The major axis of the magnetic material particles has the longest distance from an arbitrary point a on the surface of the magnetic material particles to an arbitrary point b on the surface of the magnetic material particles different from the point a when the photographed image of the magnetic material particles is observed. The length of the line segment. The minor axis of the magnetic material particles is perpendicular to the major axis and is the length of the longest line segment among the line segments connecting two points on the surface of the magnetic material particles. Then, the ratio of major axis/minor axis is obtained by extracting 100 particles from the image photographed above, calculating the arithmetic mean value of the major axis and the minor axis of each particle, and calculating the ratio of the arithmetic mean values. To be

The content ratio of the magnetic material particles in the magnet composition is not particularly limited. From the viewpoint of a balance between ensuring sufficient magnetic properties and improving heat resistance and strength, it is preferably 40% by mass to 99% by mass of the entire magnet composition. From the viewpoint of strength, the content of the magnetic material particles is more preferably 90% by mass or less, further preferably 85% by mass or less, and further preferably 80% by mass or less based on the entire magnet composition. Particularly preferred. Further, from the viewpoint of ensuring the magnetic characteristics of the rare earth magnet, the content ratio of the magnetic material particles is more preferably 50% by mass or more, and further preferably 60% by mass or more, of the entire magnet composition. It is particularly preferably 70% by mass or more.

-Specific metal particles-
The specific metal particles are not particularly limited as long as they are copper alloy particles having a specific surface area of 0.2 m ² /g or more. The specific metal particles contained in the magnet composition serve as a binder for the magnetic material particles. When the specific surface area of the specific metal particles is 0.2 m ² /g or more, a sufficient contact area with the magnetic material particles can be obtained, and the bonding of the magnetic material particles tends to be stronger. The upper limit of the specific surface area of the specific metal particles is not particularly limited, but may be, for example, 2.0 m ² /g or less.

The specific surface area of the specific metal particles is measured by the BET method (nitrogen gas adsorption method).

The type of copper alloy forming the specific metal particles is not particularly limited. For example, copper and at least one selected from the group consisting of phosphorus (P), cobalt (Co), manganese (Mn), nickel (Ni), zinc (Zn), tin (Sn), and iron (Fe). , Or a copper alloy containing copper and at least one selected from the group consisting of phosphorus (P), cobalt (Co), and manganese (Mn).

The use of copper alloy particles as the metal particles used in combination with the magnetic material particles is more advantageous than the particles of copper alone in terms of controlling the physical properties such as volume change rate and toughness of the rare earth magnet.

The proportion of copper in the copper alloy forming the specific metal particles is not particularly limited. For example, it may be 50% by mass or more, 70% by mass or more, and 80% by mass or more.

The melting point of the specific metal particles is not particularly limited. For example, it may be in the range of 450°C to 1500°C.

The volume average particle diameter (D50) of the specific metal particles is not particularly limited. For example, it is preferably 1 μm to 100 μm, more preferably 1 μm to 50 μm, and further preferably 1 μm to 20 μm.
The volume average particle diameter (D50) of the specific metal particles can be measured in the same manner as the volume average particle diameter (D50) of the magnetic material particles.

-Other metal particles-
The magnet composition may include metal particles other than the specific metal particles. That is, it may contain copper alloy particles having a specific surface area of less than 0.2 m ² /g, or may contain metal particles that are not a copper alloy.
In the present disclosure, “metal particles” means particles of a metal or alloy containing no rare earth element.

The type of metal particles other than the specific metal particles is not particularly limited. For example, particles of at least one metal selected from the group consisting of copper (Cu), aluminum (Al), iron (Fe), titanium (Ti), tin (Sn), and indium (In); Examples include particles of alloys of these metals. These metal particles may be used alone or in combination of two or more. Among these, the metal particles preferably include at least one metal selected from the group consisting of copper (Cu) and aluminum (Al).

When the composition for magnets contains specific metal particles and metal particles other than the specific metal particles, the proportion of the specific metal particles in the entire metal particles is not particularly limited. For example, it may be 50% by mass or more, 70% by mass or more, or 80% by mass or more based on the entire metal particles.

The volume average particle diameter (D50) of the metal particles other than the specific metal particles is not particularly limited. For example, it is preferably 1 μm to 100 μm, more preferably 1 μm to 50 μm, and further preferably 1 μm to 20 μm.
The volume average particle diameter (D50) of the metal particles other than the specific metal particles can be measured in the same manner as the volume average particle diameter (D50) of the magnetic material particles.

The metal particles (meaning both the specific metal particles and the metal particles other than the specific metal particles are the same, and the same shall apply hereinafter) are, from the viewpoint of serving as a binder for the magnetic material particles, a soft metal particle. It is preferably a particle. Specifically, metal particles having a Vickers hardness Hv of 200 or less are preferable. From the viewpoint of the binding property with the magnetic material particles, the Vickers hardness Hv of the metal particles is preferably 150 or less, and more preferably 100 or less. The lower limit value of the Vickers hardness Hv of the metal particles is not particularly limited. For example, it may be 10 or more, or 30 or more.

The method for measuring the Vickers hardness Hv is as follows. According to JIS Z 2244 (2009), a micro Vickers hardness tester (HM-200B manufactured by Mitutoyo Co., Ltd.) is used to press against the surface of the test body with a predetermined test force, and formed at that time. The hardness of the test piece is calculated from the diagonal length of the recess. The Vickers hardness Hv of the metal particles may be specified from the analysis result of the metal component contained in the rare earth magnet. For example, for the rare earth magnet to be measured, elemental analysis is performed by EDS analysis using a scanning electron microscope (JSM-IT100 manufactured by JEOL Ltd.) to specify the type of metal contained in the rare earth magnet. Then, the Vickers hardness Hv of the metal particles contained in the raw material magnet composition may be estimated.

The shape of the metal particles is not particularly limited, and examples thereof include irregular shapes. When the shape of the metal particles is irregular, the voids are reduced and a rare earth magnet having excellent strength tends to be obtained in the case of a molded body described later. The ratio of the major axis to the minor axis of the metal particles having an irregular shape (major axis/minor axis) is not particularly limited. From the viewpoint of more easily improving the mechanical strength, the lower limit of the ratio of major axis/minor axis is preferably 1 or more, more preferably 1.5 or more, and further preferably 2 or more. From the viewpoint of dispersibility in the magnet composition, the upper limit of the ratio of major axis/minor axis is preferably 3.5 or less, more preferably 3 or less. The shape, major axis, minor axis, and major axis/minor axis ratio of the metal particles can be measured by the same method as the measurement of the shape, major axis, minor axis, and major axis/minor axis ratio of the magnetic material particles described above.

The content of the metal particles in the magnet composition is not particularly limited. From the viewpoint of a balance between ensuring magnetic properties and improving heat resistance and strength, the content of metal particles is preferably 1% by mass to 60% by mass of the entire magnet composition. From the viewpoint of obtaining a rare earth magnet having excellent strength, the content of the metal particles is more preferably 10% by mass or more, further preferably 15% by mass or more, and more preferably 20% by mass or more based on the entire magnet composition. Is particularly preferable. From the viewpoint of ensuring the magnetic properties of the rare earth magnet, the content of the metal particles is more preferably 50% by mass or less, further preferably 45% by mass or less, and more preferably 40% by mass with respect to the entire magnet composition. % Or less is particularly preferable.

(Resin component)
The magnet composition may include a resin. Examples of the resin include thermosetting resins such as epoxy resin and phenol resin. From the viewpoint of heat resistance and oil resistance of the obtained rare earth magnet, the magnet composition preferably contains no resin, or the resin content is 10% by mass or less of the entire magnet composition.

(2) Molding Process The molding process is not particularly limited as long as a desired molded product can be obtained. The molding method is preferably a compression molding method from the viewpoint of moldability. The pressure for compression molding is not particularly limited, and the higher the pressure, the higher the magnetic flux density and the strength of the rare earth magnet tend to be obtained. On the other hand, from the viewpoint of productivity, it is preferable that the pressure during compression molding is low. Therefore, the pressure for compression molding may be, for example, 500 MPa to 2500 MPa. From the viewpoint of mass productivity and die life, the pressure for compression molding is more preferably 700 MPa to 1500 MPa.

The density of the molded body (the density of the entire molded body) obtained in the molding step is not particularly limited. For example, it is preferably 75% to 90%, and more preferably 80% to 90% with respect to the true density of the magnet composition as a raw material. When the density of the molded body is in the range of 75% to 90% with respect to the true density of the magnet composition, a rare earth magnet having good magnetic properties and excellent mechanical strength tends to be obtained.

When a mold is used in the molding step, the mold may be heated for molding, or the mold may be molded without heating. When the mold is heated for molding, the heating temperature of the mold is not particularly limited. For example, the heating temperature of the mold is preferably 100°C to 300°C, more preferably 150°C to 250°C. The heating of the mold is different from the "heat treatment" performed on the molded body obtained in the molding step.

(3) Heat Treatment Step In the heat treatment step, the compact obtained in the molding step is heat treated at a temperature of less than 450° C. in an atmosphere containing oxygen. The method of heat treatment is not particularly limited. For example, it can be performed using a known device such as a heating furnace.
By heat-treating the molded body in an atmosphere containing oxygen, it is possible to obtain a rare earth magnet having excellent strength. The "atmosphere containing oxygen" in which the heat treatment is performed is not particularly limited as long as it is an atmosphere in which oxygen exists. For example, it may be performed by supplying oxygen gas, or may be performed in the atmosphere. From an economical point of view, it is preferable to carry out in the atmosphere (generally, the oxygen concentration in the components excluding water is approximately 23% by mass).

The oxygen concentration in the atmosphere containing oxygen (concentration in components excluding water, the same applies hereinafter) is not particularly limited. From the viewpoint of promoting generation of oxides and hydroxides by heat treatment, the oxygen concentration may be, for example, 10% by mass or more. From the viewpoint of suppressing excessive production of oxides and hydroxides, the oxygen concentration may be, for example, 40 mass% or less.

The heat treatment step is preferably performed in an atmosphere containing water vapor (that is, in an atmosphere containing oxygen and water vapor).
As described above, when heat treatment is performed in an atmosphere containing oxygen, it is considered that the water contained in the magnet composition reacts with the components of the magnetic material particles to form hydroxides and oxides. Here, when heat treatment is performed in an atmosphere further containing water vapor in addition to oxygen, water contained in the magnet composition reacts with water vapor and the components of the magnetic material particles to form hydroxides and oxides. Will be promoted more. As a result, it is considered that the strength of the rare earth magnet obtained by increasing the bonding strength of the magnetic material particles is further improved.

The concentration of water vapor in the atmosphere containing water vapor is not particularly limited. From the viewpoint of promoting the production of hydroxides and oxides in the rare earth magnet, the relative humidity is preferably 10% or more. On the other hand, from the viewpoint of suppressing the decrease in strength due to excessive formation of hydroxides and oxides in the rare earth magnet, the concentration of water vapor is preferably 80% or less as relative humidity, and 70% or less, for example. More preferably.

The heat treatment may be performed under reduced pressure or pressure, or at atmospheric pressure. From an economical point of view, it is preferable to carry out under atmospheric pressure.

The temperature of the heat treatment is not particularly limited as long as it is lower than 450°C, and may be 350°C or lower, 300°C or lower, or 250°C or lower. The lower limit of the temperature of the heat treatment is not particularly limited, but from the viewpoint of promoting the formation of oxides and hydroxides in the rare earth magnet, it is preferably 100°C or higher, and more preferably 150°C or higher. In addition, the temperature of the heat treatment in the present disclosure indicates the highest temperature.

The heat treatment time (holding time at the highest reached temperature) is not particularly limited. From the viewpoint of obtaining a sufficient heat treatment effect, the heat treatment time is preferably 10 minutes or longer, more preferably 30 minutes or longer, and further preferably 1 hour or longer. From the viewpoint of mass productivity, the heat treatment time is preferably 100 hours or less.

In the heat treatment step, the rate of temperature increase until the maximum temperature is reached is not particularly limited. The lower limit value of the temperature rising rate may be, for example, 2° C./minute or more, or 5° C./minute or more. The upper limit of the temperature rising rate may be, for example, 20° C./minute or less, or 15° C./minute or less.

After completion of the heat treatment, the molded body is cooled until the temperature of the molded body reaches room temperature (for example, 25° C.). The cooling rate is not particularly limited. The lower limit of the cooling rate may be, for example, 2° C./minute or more, or 5° C./minute or more. Further, the upper limit value of the cooling rate may be, for example, 20° C./minute or less, or 15° C./minute or less.

Through the above steps, a rare earth magnet having excellent strength can be obtained.

The content of the metal contained in the rare earth magnet obtained by the above method is not particularly limited. From the viewpoint of a balance between securing magnetic properties and improving heat resistance and strength, it is preferably 1% by mass to 60% by mass of the whole rare earth magnet. From the viewpoint of obtaining a rare earth magnet having excellent strength, the metal content is more preferably 10% by mass or more, further preferably 15% by mass or more, and more preferably 20% by mass or more based on the entire rare earth magnet. Is particularly preferable. Further, from the viewpoint of ensuring the magnetic characteristics of the rare earth magnet, the metal content is more preferably 50% by mass or less based on the entire rare earth magnet, further preferably 45% by mass or less, and 40% by mass or less. Is particularly preferable.

<Rare earth magnet>
One embodiment of the rare earth magnet of the present disclosure is a heat-treated product of a molded body containing magnetic material particles containing a rare earth element and copper alloy particles having a specific surface area of 0.2 m ² /g or more. The rare earth magnet contains at least one of an oxide and a hydroxide of a component contained in the particles (for example, Fe contained in the Sm-Fe-N-based magnetic material particles).

The rare earth magnet having the above structure has excellent heat resistance and strength. Although the reason for this is not clear, it is considered that the bonding strength of the magnetic material particles is improved by at least one of the oxide and the hydroxide formed in the rare earth magnet. Furthermore, it is conceivable that the copper alloy particles having a specific surface area of 0.2 m ² /g or more act as a binder to improve the bonding strength of the magnetic material particles.

The details and preferable embodiments of the magnetic material particles, the metal particles and the molded body containing these, and the heat treatment conditions in the rare earth magnet of the present disclosure can be applied to those described in the above-mentioned method for producing a rare earth magnet.

As described above, the rare earth magnet of the present disclosure is excellent in heat resistance and strength while ensuring magnetic properties, and thus can be preferably applied to applications where high levels of heat resistance and strength are required. In addition, the rare earth magnet of the present disclosure uses metal particles as a binder, and thus is superior in heat resistance and oil resistance to a rare earth bonded magnet that mainly uses a resin material as a binder. Therefore, the rare earth magnet of the present disclosure can be preferably applied to applications where heat resistance and oil resistance are required.

Hereinafter, the embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In addition, "part" means "part by mass" and "%" means "% by mass" unless otherwise specified.

(Preparation of magnet composition)
A magnetic composition was prepared by preparing magnetic material particles and copper alloy particles shown in Table 1 and mixing them in the compounding amounts (unit: parts by mass) shown in Table 1. The mixing of the magnetic material particles and the copper alloy particles was performed for 30 minutes at about 50 revolutions/minute using a stirrer.

Abbreviations in Table 1 are as follows.
"Sm-Fe-N": Sm-Fe-N magnetic material particles (Sumitomo Metal Mining Co., Ltd., volume average particle diameter 14 μm)
"Cu-P": Copper phosphorus alloy particles (manufactured by Fukuda Metal Foil & Powder Co., Ltd., volume average particle diameter 38 µm, specific surface area 0.13 m ² /g, copper content 95% by mass).
"Cu-Co": Copper cobalt alloy particles (manufactured by Fukuda Metal Foil & Powder Co., Ltd., volume average particle diameter 66 µm, specific surface area 0.09 m ² /g, copper content 97% by mass).
"Cu-Mn": Copper-manganese alloy particles (manufactured by Epson Atomix Co., Ltd., volume average particle diameter 17 μm, specific surface area 1.08 m ² /g, copper content 65% by mass).

(Production of molded body)
The obtained magnet composition was compression-molded using a hydraulic press machine at a pressure of 2000 MPa to prepare a columnar compression-molded body having an outer diameter of 11.3 mm and a height of 10 mm.

(Heat treatment)
The compression molded bodies of Comparative Examples 2 to 4 and Example 1 were heat-treated in the atmosphere (oxygen concentration 23% by mass, relative humidity 60%) at the temperature (maximum temperature reached) and time shown in Table 1, A test piece of rare earth magnet was obtained. The heat treatment shown in Table 1 does not cause the magnet composition to sinter.
In addition, the compression molded body in a state where heat treatment was not performed was used as a test piece of Comparative Example 1.

(Strength evaluation)
As strength evaluation, crush strength was measured as follows.
Using a universal compression tester (manufactured by Shimadzu Corporation, AG-10TBR), compression pressure was applied from the height direction to the test piece produced above under a room temperature environment. Then, the crush strength (MPa) was calculated from the maximum value of the compression pressure when the test piece was broken by the compression pressure, and the strength was evaluated. The results are shown in Table 1.

As shown in Table 1, a molded body of a magnet composition containing magnetic material particles containing a rare earth element and copper alloy particles having a specific surface area of 0.2 m ² /g or more was prepared in an atmosphere containing oxygen. The rare earth magnet of Example 1 obtained by heat treatment at a temperature of less than 450° C. contains the rare earth magnets of Comparative Examples 1 and 2 containing no copper alloy particles and the copper alloy particles having a specific surface area of less than 0.2 m ² /g. Compared with the rare earth magnets of Comparative Examples 3 and 4, which include the same, the crush strength is large and the heat resistance and strength are excellent.

Claims (10)

A step of preparing a magnet composition containing magnetic material particles containing a rare earth element and copper alloy particles having a specific surface area of 0.2 m ² /g or more;
A step of molding the magnet composition to form a molded body,
Heat treating the shaped body at a temperature of less than 450° C. in an atmosphere containing oxygen;
A method for manufacturing a rare earth magnet having: The method for manufacturing a rare earth magnet according to claim 1, wherein the heat treatment is performed in an atmosphere containing water vapor. The method for manufacturing a rare earth magnet according to claim 1, wherein the magnetic material particles contain samarium (Sm) as a rare earth element. The method for manufacturing a rare earth magnet according to claim 1, wherein the magnetic material particles contain iron (Fe). The rare earth magnet according to any one of claims 1 to 4, wherein the copper alloy particles contain at least one selected from the group consisting of phosphorus (P), cobalt (Co), and manganese (Mn). Production method. The method for producing a rare earth magnet according to any one of claims 1 to 5, wherein the magnet composition does not contain a resin, or the resin content is 10% by mass or less based on the entire magnet composition. .. A heat-treated product of a molded body containing magnetic material particles containing a rare earth element and copper alloy particles having a specific surface area of 0.2 m ² /g or more, and oxides and hydroxides of the components contained in the magnetic material particles. A rare earth magnet containing at least one of them. The rare earth magnet according to claim 7, wherein the magnetic material particles contain samarium (Sm) as a rare earth element. The rare earth magnet according to claim 7 or 8, wherein at least one of the oxide and the hydroxide is at least one of an oxide (Fe) and a hydroxide. The rare earth magnet according to any one of claims 7 to 9, wherein the copper alloy particles include at least one selected from the group consisting of phosphorus (P), cobalt (Co), and manganese (Mn).