WO2020225909A1

WO2020225909A1 - Rare earth non-sintered magnet

Info

Publication number: WO2020225909A1
Application number: PCT/JP2019/018585
Authority: WO
Inventors: 輝雄伊藤; 千生石原; 大地氏田; 有紗平良
Original assignee: 昭和電工マテリアルズ株式会社
Priority date: 2019-05-09
Filing date: 2019-05-09
Publication date: 2020-11-12
Also published as: JP7294413B2; JPWO2020225909A1

Abstract

A rare earth non-sintered magnet which is a heat-treated molded body comprising magnetic particles containing a rare earth element and which has a rate of mass increase when heat-treated for 504 hours at 200°C in an ambient atmosphere of 1.0% or less.

Description

Rare earth non-sintered magnet

The present invention relates to a rare earth non-sintered magnet.

Permanent magnets (rare earth magnets) that use magnetic materials containing rare earth elements are widely used in household products, automobiles, electrical appliances, communication equipment, audio equipment, medical equipment, general industrial equipment, and the like.

Known rare earth magnets include neodymium magnets, samarium-cobalt magnets, placeozim magnets, and Sm-Fe-N (samarium-iron-nitrogen) magnets. Among these, neodymium magnets and samarium-cobalt magnets, which have excellent heat resistance, are used as so-called sintered magnets manufactured by sintering at a high temperature. On the other hand, the Samarium iron-nitrogen magnet has performance comparable to that of a neodymium magnet, but its magnetism decreases when heated at a high temperature. Therefore, it is generally used as a so-called bond magnet obtained by mixing with a binder such as resin. (See, for example, Patent Document 1 and Patent Document 2).

Japanese Unexamined Patent Publication No. 08-273916 Japanese Unexamined Patent Publication No. 10-275718

Bonded magnets have advantages such as lower manufacturing cost and easier processing than sintered magnets. On the other hand, from the viewpoint of application in applications requiring heat resistance, there is an increasing demand for improvement of mechanical strength (hereinafter, also referred to as strength under high temperature) that can withstand use in a high temperature environment.

The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a rare earth non-sintered magnet having excellent strength at high temperatures.

The means for solving the above problems include the following aspects.
<1> A rare earth non-sintered magnet that is a heat-treated product of a molded product containing magnetic material particles containing rare earth elements, and has a mass increase rate of 1.0% or less when heat-treated at 200 ° C. for 504 hours in an air atmosphere. ..
<2> A heat-treated product of a molded body containing magnetic material particles containing rare earth elements, and the absolute value of the dimensional change rate when heat-treated at 200 ° C. for 504 hours in an air atmosphere is 1.4% or less. Sintered magnet.
<3> The rare earth non-sintered magnet according to <1> or <2>, wherein the magnetic material particles contain samarium (Sm) as the rare earth element.
<4> The rare earth non-sintered magnet according to any one of <1> to <3>, which contains at least one of an oxide and a hydroxide as a component contained in the magnetic material particles.
<5> The rare earth non-sintered magnet according to any one of <1> to <4>, which further contains metal particles other than the magnetic material particles.
<6> The rare earth non-sintered magnet according to any one of <1> to <5>, which does not contain a resin component or has a content of the resin component of 10% by mass or less.

According to the present disclosure, a rare earth non-sintered magnet having excellent strength at high temperature is provided.

Hereinafter, one 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 components (including element steps and the like) are not essential unless otherwise specified. The same applies to the numerical values and their ranges, and does not limit the present invention.
In the present disclosure, the term "process" is used in addition to a process independent of other processes, even if the process cannot be clearly distinguished from other processes, as long as the purpose of the process is achieved. Is also included.
In the present disclosure, the numerical range indicated by using "-" includes the numerical values before and after "-" as the minimum value and the maximum value, respectively.
In the numerical range 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 another numerical range described stepwise. .. 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 contain a plurality of applicable substances. When a plurality of substances corresponding to each component are present in the composition, the content rate or content of each component is the total content rate or content of the plurality 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 contained. When a plurality 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 particles present in the composition unless otherwise specified.
In the present disclosure, a rare earth magnet obtained without sintering magnetic material particles containing a rare earth element is referred to as a "rare earth non-sintered magnet".
In the present disclosure, the treatment performed so that the maximum temperature of the molded product reaches 80 ° C. or higher is referred to as "heat treatment".

<Rare earth non-sintered magnet>
[First Embodiment]
The rare earth non-sintered magnet of the first embodiment according to the present disclosure is a heat-treated product of a molded product containing magnetic material particles containing rare earth elements, and has a mass increase rate when heat-treated at 200 ° C. for 504 hours in an air atmosphere. Is 1.0% or less. Since the rare earth non-sintered magnet of the first embodiment has a small mass increase rate when exposed to high temperature conditions for a long time, oxides, hydroxides, etc. are used as general-purpose magnets at the boundary between magnetic material particles. There are many of them in comparison, and as a result, it is presumed that they are excellent in strength at high temperatures.

From the viewpoint of strength at high temperature, the rare earth non-sintered magnet of the first embodiment preferably has a mass increase rate of 0.95% or less when heat-treated at 200 ° C. for 504 hours in an air atmosphere. , 0.9% or less is more preferable. Further, the above-mentioned mass increase rate may be 0.1% or more.
The above-mentioned mass increase rate can be obtained by the method described in Examples described later.

The rare earth non-sintered magnet of the first embodiment is obtained by heat-treating the molded body at a temperature at which the magnetic material particles in the molded body are not sintered (for example, 500 ° C. or lower). By heat-treating the molded body at a temperature at which the magnetic material particles do not sinter, magnetic material particles that are not suitable for manufacturing sintered magnets (for example, Sm-Fe-N magnetic material particles) are also suitably used as raw materials. can do.

The rare earth non-sintered magnet of the first embodiment preferably contains at least one of an oxide and a hydroxide of the components contained in the magnetic material particles. By containing at least one of the above-mentioned oxides and hydroxides, the strength of the rare earth non-sintered magnet is superior.

-Magnetic material particles-
The type of magnetic material particles contained in the molded product is not particularly limited. For example, magnetic material particles containing Sm (samarium) as a rare earth element and magnetic material particles containing Nd (neodymium) as a rare earth element can be mentioned. The magnetic material particles contained in the molded product may be only one type or a combination of two or more types.

Examples of the magnetic material particles containing Sm include Sm-Fe-N magnetic material particles (Sm ₂ Fe ₁₇ N ₃ , Sm Fe ₇ N _x, etc., x is a positive number) and Sm-Fe-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., x is positive Number), Sm-Co-B magnetic material particles (Sm ₁₅ Co ₇₇ B _5, etc.) and the like.
Examples of the magnetic material particles containing Nd include Nd—Fe—B magnetic material particles (Nd ₂ Fe ₁₄ B and the like).

As the magnetic material particles, magnetic material particles further containing Fe in addition to the rare earth element are preferable. By using magnetic material particles containing Fe, oxides and hydroxides of Fe are generated by heat treatment of the molded product in an atmosphere containing oxygen, and the strength of the rare earth non-sintered magnet tends to be further improved.

Among the magnetic material particles containing Sm, Sm-Fe-N magnetic material particles are preferable from the viewpoint of excellent balance between 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, Th and the like. One of these other elements may be used alone, or two or more of them may be used in combination. Other elements may be introduced by being replaced with a part of the phase structure of the magnet phase containing 50% by mass or more of Sm, Fe and N in total, or may be inserted and introduced. When the Sm-Fe-N magnetic material particles contain elements other than Sm, Fe and N, the total amount of Sm, Fe and N is preferably 50% by mass or more of the total amount.

The volume average particle diameter (D50) of the magnetic material particles is not particularly limited. For example, it may be selected from the range of 0.1 μm to 100 μm.
The smaller the volume average particle diameter of the magnetic material particles, the higher the strength of the obtained rare earth non-sintered magnet tends to be. It is considered that this is because the smaller the volume average particle diameter of the magnetic material particles, the larger the surface area of the particles per volume, and the more the formation of oxides and hydroxides on the surface of the magnetic material particles progresses. From the viewpoint of the strength of the rare earth non-sintered magnet, the volume average particle diameter (D50) of the magnetic material particles is preferably 50 μm or less, more preferably 25 μm or less, still more preferably 15 μm or less. It is particularly preferably 10 μm or less, and extremely preferably 4 μm or less. The volume average particle diameter (D50) of the magnetic material particles may be 1 μm or more.
From the viewpoint of the strength and magnetic properties of the rare earth non-sintered magnet, two or more kinds of magnetic material particles having different volume average particle diameters (D50) may be used in combination.
The volume average particle size (D50) of the magnetic material particles is defined as the particle size (D50) when the accumulation from the small diameter side is 50% in the volume-based particle size distribution measured by the laser diffraction / scattering type particle size distribution measuring device. Can be measured.

The shape of the magnetic material particles is not particularly limited. From the viewpoint of the magnetic properties of the rare earth non-sintered magnet, the shape of the magnetic material particles is preferably spherical or close to spherical.
In the present disclosure, examples of the spherical shape or a shape close to a spherical shape include a shape having a circularity coefficient of 78% or more or a needle-likeness coefficient of 75% or more.
From the viewpoint of the strength of rare earth non-sintered magnets, magnetic material particles having a spherical or near-spherical shape and other shapes, that is, a shape having a circularity coefficient of less than 78% and an needle-likeness coefficient of less than 75%. It may be used in combination with magnetic material particles.

The magnetic material particles may have a circularity coefficient of 78% or more, 80% or more, 85% or more, or 90% or more. It can be said that the larger the circularity coefficient of the magnetic material particles, the closer the shape of the magnetic material particles is to a spherical shape. The circularity coefficient of the magnetic material particles is defined as follows.
Circularity coefficient = (4πS / L ² ) × 100
S = Area of particle image L = Peripheral length of particle image

The magnetic material particles may have an acicularity coefficient of 75% or more, 80% or more, 85% or more, or 90% or more. It can be said that the larger the needle-likeness coefficient of the magnetic material particles, the closer the shape of the magnetic material particles is to a spherical shape. The needle-likeness coefficient of the magnetic material particles is defined as follows.
Needle degree coefficient (%) = (b / a) x 100
a = major axis of particle image b = minor axis of particle image

The area, peripheral length, major axis and minor axis of the particle image of the magnetic material particles can be measured by observation with a scanning electron microscope (SEM), a transmission electron microscope (TEM), or the like. Specifically, 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 different from the point a when observing a photographed image of the magnetic material particles. 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 line segment having the longest length among the line segments connecting the two points on the surface of the magnetic material particles. The area, peripheral length, major axis and minor axis of the particle image of the magnetic material particles may be calculated using image software or the like. The area, circumference length, major axis, and minor axis of the particle image of the magnetic material particles are obtained as arithmetic mean values of the measured values of 100 particles.

The content of magnetic material particles in the molded product before and after the heat-treated product is not particularly limited, and from the viewpoint of ensuring the magnetic properties and improving the strength at high temperatures, the molded product It is preferably 30% by mass to 100% by mass of the whole. From the viewpoint of ensuring the magnetic properties of the rare earth non-sintered magnet, the content of the magnetic material particles described above is more preferably 35% by mass or more, and further preferably 40% by mass or more of the entire molded body. , 45% by mass or more is particularly preferable. From the viewpoint of the strength of the rare earth non-sintered magnet, the content of the magnetic material particles described above is more preferably 90% by mass or less, still more preferably 85% by mass or less, and 80% by mass. It is particularly preferable that it is% or less.

-Metal particles-
The molded product may be composed of only the magnetic material particles, or may further contain metal particles other than the magnetic material particles in addition to the magnetic material particles. When the molded body contains metal particles, the strength of the obtained rare earth non-sintered magnet tends to be further improved.
In the present disclosure, the term "metal particles" means particles of a metal or alloy that does not contain rare earth elements.

The specific surface area of the metal particles is preferably 0.2 m ² / g or more from the viewpoint that a sufficient contact area with the magnetic material particles can be obtained and the bonding of the magnetic material particles becomes stronger. The upper limit of the specific surface area of the metal particles is not particularly limited, and may be, for example, 2.0 m ² / g or less.
The specific surface area of the metal particles can be measured by the BET method (nitrogen gas adsorption method).

The type of metal particles is not particularly limited. Specifically, the metal particles include simple substance particles of metals such as copper (Cu), aluminum (Al), iron (Fe), titanium (Ti), tin (Sn), and indium (In), alloys of these metals, and the like. Particles can be mentioned. One type of these metal particles may be used alone, or two or more types may be used in combination. Among these, the metal particles preferably contain at least one of copper (Cu) and aluminum (Al).

The metal particles more preferably contain Cu for the reasons shown below.
(1) When a magnet of a desired size is produced using metal particles having a large specific gravity without changing the content rate (mass standard) of the metal particles, the ratio (volume ratio) of the magnetic material particles to the entire magnet ) Can be increased. Therefore, when metal particles having a large specific gravity are used without changing the content rate based on the mass, the rare earth metal bond magnet can easily secure the magnetic characteristics.
(2) Since Cu has high ductility, when it is used as metal particles, the magnetic material particles and the metal particles in the molded body are likely to be packed most closely, and the density of the molded body is improved. Further, Cu has excellent slidability, that is, low frictional resistance, which leads to a long life of the mold used for molding.
(3) When Cu is used as the metal particles, the coefficient of thermal expansion of the obtained magnet becomes close to that of iron (Fe). Therefore, when an iron member is used for the portion to which the magnet is applied, the obtained coefficient of thermal expansion is preferable.

The metal particles may be particles of an alloy (copper alloy) containing copper and an element other than copper. Specifically, the copper alloy is selected from the group consisting of copper and phosphorus (P), cobalt (Co), manganese (Mn), nickel (Ni), zinc (Zn), tin (Sn) and iron (Fe). Included are at least one type of copper alloy.

The volume average particle diameter (D50) of the metal particles is not particularly limited. For example, it is preferably 1 μm to 100 μm, more preferably 10 μm to 80 μm, and even more preferably 20 μm to 70 μm.
As the metal particles, two or more kinds of metal particles having different volume average particle diameters (D50) may be used in combination.
The volume average particle diameter (D50) of the metal particles can be measured in the same manner as the volume average particle diameter (D50) of the magnetic material particles.

The metal particles are preferably soft metal particles from the viewpoint of playing a role as a binder for the magnetic material particles. Specifically, it is preferably metal particles having a Vickers hardness Hv of 200 or less. 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 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 Vickers hardness Hv is as follows. According to JIS Z 2244 (2009), using a Micro Vickers hardness tester (manufactured by Mitutoyo Co., Ltd .: HM-200B), the test piece is pressed against the surface of the test piece 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 non-sintered magnet. For example, the rare earth non-sintered magnet to be measured is subjected to elemental analysis by energy dispersive X-ray analysis (EDS) using a scanning electron microscope (manufactured by Nippon Denshi Co., Ltd .: JSM-IT100) to perform element analysis on the rare earth non-sintered magnet. By specifying the type of metal contained in the sintered magnet, the Vickers hardness Hv of the metal particles used as a raw material may be estimated.

The shape of the metal particles is not particularly limited. For example, an irregular shape can be mentioned. Since the shape of the metal particles is irregular, the voids in the molded body can be reduced, and a rare earth non-sintered magnet having excellent strength tends to be obtained. The ratio of the major axis to the minor axis (major axis / minor axis) of the metal particles having an irregular shape is not particularly limited. From the viewpoint that the mechanical strength is more likely to be improved, the value of the major axis / minor axis ratio is preferably larger than 1, more preferably 1.5 or more, and further preferably 2 or more. Further, from the viewpoint of dispersibility in the molded product, the value of the major axis / minor axis ratio is preferably 3.5 or less, and more preferably 3 or less. The major axis and minor axis of the metal particles can be measured by the same method as the major axis and minor axis of the magnetic material particles described above.

When the molded product contains metal particles, the content of the metal particles before the heat-treated product and after the heat-treated product is not particularly limited. From the viewpoint of ensuring the magnetic properties and improving the strength, the content of the metal particles is preferably 5% by mass to 70% by mass of the entire molded product. From the viewpoint of the strength of the rare earth non-sintered magnet, the content of the metal particles described above is more preferably 10% by mass or more, further preferably 15% by mass or more, and 20% by mass of the entire molded product. The above is particularly preferable. From the viewpoint of the magnetic properties of the rare earth non-sintered magnet, the content of the metal particles described above is more preferably 65% by mass or less, still more preferably 60% by mass or less, and 55% by mass. It is particularly preferable that it is% or less.

-Resin component-
The molded product may contain 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 non-sintered magnet, the molded product does not contain resin, or the content of the resin before and after the heat-treated product is the total of the molded product. The content is preferably 10% by mass or less, and the molded product does not contain a resin, or the content of the above-mentioned resin is more preferably 5% by mass or less of the entire molded product.

[Second Embodiment]
The rare earth non-sintered magnet of the second embodiment according to the present disclosure is a heat-treated product of a molded body containing magnetic material particles containing rare earth elements, and has a dimensional change rate when heat-treated at 200 ° C. for 504 hours in an air atmosphere. The absolute value of is 1.4% or less. Since the rare earth non-sintered magnet of the second embodiment has a small absolute value of the dimensional change rate when exposed to a high temperature condition for a long time, oxides, hydroxides, etc. are generated at the boundary between the magnetic material particles. It is abundant in comparison with general-purpose magnets, and as a result, it is presumed that it has excellent strength at high temperatures.

The preferred configuration of the rare earth non-sintered magnet of the second embodiment is the same as that of the rare earth non-sintered magnet of the first embodiment described above. For example, the rare earth non-sintered magnet of the second embodiment has the above-mentioned mass increase. The condition of the rate may be satisfied.

The rare earth non-sintered magnet of the second embodiment has an absolute value of 1.0% or less of the dimensional change rate when heat-treated at 200 ° C. for 504 hours in an air atmosphere from the viewpoint of strength at high temperature. It is preferably 0.5% or less, more preferably 0.3% or less, and particularly preferably 0.2% or less.
Further, the absolute value of the above-mentioned dimensional change rate may be 0.05% or more.
The absolute value of the above-mentioned dimensional change rate can be obtained by the method described in Examples described later.

The above-mentioned dimensional change rate may have a negative value, for example, it may be -0.5% or more and -0.05% or less, or -0.3% or more and -0.05% or less. It may be -0.2% or more and -0.05% or less.

Since the rare earth non-sintered magnet of the present disclosure has excellent strength at high temperatures, it can be preferably applied to applications requiring heat resistance. Further, the rare earth non-sintered magnet of the present disclosure is compared with a rare earth non-sintered magnet that mainly uses a resin material as a binder when the resin is not contained or the amount of the resin is 10% by mass or less. It is also excellent in oil resistance, and the rare earth non-sintered magnet of the present disclosure can be preferably applied to applications requiring oil resistance.

<Manufacturing method of rare earth non-sintered magnet>
An embodiment of the method for producing a rare earth non-sintered magnet of the present disclosure will be described below. The manufacturing method of the present embodiment is a manufacturing method of a rare earth non-sintered magnet having a step of heat-treating a molded body containing magnetic material particles containing a rare earth element in an atmosphere containing oxygen.

According to the method of the present disclosure, a rare earth non-sintered magnet having excellent strength at high temperature can be obtained. The reason is not clear, but it can be thought of as follows.

In the method for producing a rare earth non-sintered magnet disclosed in the present disclosure, a molded product containing magnetic material particles is heat-treated in an atmosphere containing oxygen. As a result, at the boundary between the magnetic material particles, the amounts of oxides and hydroxides of the components contained in the magnetic material particles (for example, Fe contained in the Sm-Fe-N-based magnetic material particles) are relative to each other. There is a tendency to increase. This tendency is not seen in heat treatment under an inert gas atmosphere. It is presumed that the relatively increased oxides and hydroxides contribute to the improvement of the strength of the rare earth non-sintered magnet.

Hereinafter, a specific example of a method for manufacturing the rare earth non-sintered magnet of the present disclosure will be described. In the following specific examples, it is obtained in a step of preparing a material for magnets containing magnetic material particles (material preparation step for magnets), a step of molding a material for magnets into a molded product (molding step), and a molding step. A step of heat-treating the molded product in an atmosphere containing oxygen (heat treatment step) is carried out in this order. However, the method for producing a rare earth non-sintered magnet of the present disclosure is not limited to the following specific examples.

(1) Material preparation process for magnets In the material preparation process for magnets, materials for magnets containing magnetic material particles are prepared. The method of preparing the material for the magnet is not particularly limited. For example, a material for a magnet may be prepared by mixing magnetic material particles and, if necessary, metal particles contained therein.

When preparing a material for magnets by mixing magnetic material particles and other materials (for example, metal particles), the preparation of the material for magnets is, for example, a mixing shaker, a tumbler mixer, a V-type mixer, a double cone type mixing. A known mixing device such as a machine, a ribbon type mixer, a Nauter mixer, a Henschel mixer, or a super mixer may be used.

(2) Molding process In the molding process, a magnet material is molded into a molded product. The molding method is not particularly limited. From the viewpoint of moldability, the compression molding method is preferable. The pressure for compression molding is not particularly limited, and the higher the pressure, the higher the magnetic flux density and the higher the strength of the rare earth non-sintered magnet. On the other hand, from the viewpoint of productivity, it is preferable that the pressure in the case of 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 mold life, the pressure for compression molding is more preferably 700 MPa to 1500 MPa.

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

When a mold is used in the molding process, the mold may be heated and molded, or the mold may be molded without being heated. 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 product obtained in the molding step.

(3) Heat Treatment Step In the heat treatment step, the molded product obtained in the molding step is heat-treated in an atmosphere containing oxygen. The heat treatment method is not particularly limited. For example, it can be carried out using a known device such as a heating furnace. 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 is present. For example, oxygen gas may be supplied or the operation may be performed in the atmosphere. From an economical point of view, it is preferable to carry out the operation in the atmosphere (generally, the oxygen concentration in the components excluding water is about 23% by mass).

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

The heat treatment step is preferably performed in an atmosphere containing oxygen and water vapor.
As described above, when the heat treatment is performed in an atmosphere containing oxygen, it is considered that the water content in the molded body reacts with the components of the magnetic material particles to generate hydroxides and oxides. Here, when the heat treatment is performed in an atmosphere further containing water vapor in addition to oxygen, the water content contained in the molded body reacts with the water vapor and the components of the magnetic material particles to produce more hydroxides and oxides. It is thought to be promoted. As a result, it is considered that the strength of the rare earth non-sintered 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 formation of hydroxides and oxides, the concentration of water vapor is preferably 10% or more as a relative humidity, for example. On the other hand, from the viewpoint of suppressing the decrease in strength due to the excessive formation of hydroxides and oxides, the concentration of water vapor is preferably 80% or less, and more preferably 70% or less, for example, as a relative humidity. preferable.

The heat treatment may be performed under reduced pressure, pressurized pressure, or atmospheric pressure. From an economic 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 the magnetic material particles are not sintered, and can be set in consideration of the heat resistance of the magnetic material particles contained in the molded product.
From the viewpoint of maintaining sufficient magnetic properties, the heat treatment temperature may be, for example, 500 ° C. or lower, 450 ° C. or lower, 350 ° C. or lower, or 300 ° C. or lower. It may be 250 degreeC or less. The lower limit of the heat treatment temperature is not particularly limited, but from the viewpoint of promoting the formation of oxides and hydroxides, it is preferably 100 ° C. or higher, and more preferably 150 ° C. or higher. The heat treatment temperature in the present disclosure represents the maximum temperature reached.

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

In the heat treatment process, the rate of temperature rise until the maximum temperature is reached is not particularly limited. The rate of temperature rise may be, for example, 2 ° C./min or higher, or 5 ° C./min or higher. The heating rate may be, for example, 20 ° C./min or less, or 15 ° C./min or less.

After the heat treatment is completed, the molded product is cooled until the temperature of the molded product reaches room temperature (for example, 25 ° C.). The cooling rate is not particularly limited. The cooling rate value may be, for example, 2 ° C./min or higher, or 5 ° C./min or higher. The cooling rate may be, for example, 20 ° C./min or less, or 15 ° C./min or less.

Hereinafter, 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.

<Examples 1 and 2>
In Example 1, the magnetic material particles shown in Table 3 are used as materials for magnets, and in Example 2, the magnetic material particles and metal particles shown in Table 3 are mixed so as to be 75:25 on a mass basis for magnets. The material was prepared. In Example 2, the magnetic material particles and the metal particles were mixed by stirring at about 50 rpm for 30 minutes using a stirrer.

(Making a molded product)
Using the materials for magnets of Examples 1 and 2, compression molding was performed at a pressure of 980 MPa using a hydraulic press to prepare a cylindrical compression molded body having an outer diameter of 11.3 mm and a total length of 10 mm. The density of the molded product (Mg / m ³ ) is shown in Table 3.

(Heat treatment)
The obtained molded product was heat-treated in the air (oxygen concentration 23% by mass, relative humidity 60% at a temperature of 25 ° C.) at 200 ° C. for 1 hour to obtain a test piece of a rare earth non-sintered magnet. Obtained. This heat treatment does not cause sintering of the magnet material.

<Comparative Examples 1 and 2>
In Comparative Examples 1 and 2, the magnetic material particles shown in Table 3 were used as the magnet material.

(Making a molded product)
Using the materials for magnets of Comparative Examples 1 and 2, compression molding was performed at a pressure of 980 MPa using a hydraulic press to prepare a cylindrical compression molded body having an outer diameter of 11.3 mm and a total length of 10 mm. The density of the molded product (Mg / m ³ ) is shown in Table 3.

(Heat treatment)
The obtained molded product was heat-treated in a nitrogen atmosphere at 200 ° C. for 1 hour to obtain a test piece of a rare earth non-sintered magnet.

The abbreviations in Table 3 are as follows.
Magnetic material particles: Sm-Fe-N magnetic material particles (Sumitomo Metal Mining Co., Ltd., volume average particle diameter: 3 μm)
Metal particles: Copper particles ("CE-15" manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., major axis / minor axis ratio: 2.8.5, Vickers hardness Hv: 50, volume average particle diameter: 45 μm)
Magnetic material particles: Nd-Fe-B magnetic material particles (also referred to as "Nd-Fe-B (1)", manufactured by Hitachi Metals Co., Ltd., volume average particle diameter: 100 μm, scaly particles, heat-resistant epoxy resin 2 Including mass%.)
Magnetic material particles: Nd-Fe-B magnetic material particles (also referred to as "Nd-Fe-B (2)", manufactured by Hitachi Metals Co., Ltd., volume average particle diameter: 100 μm, scaly particles, heat-resistant epoxy resin 1 Including mass%.)

(Calculation of mass change rate)
Mass change when the test piece of the rare earth non-sintered magnet produced above is heat-treated at 200 ° C. for the time shown in Table 1 under an air atmosphere (oxygen concentration 23% by mass, temperature 25 ° C., relative humidity 60%). The rate (mass increase rate if it is a positive value) was calculated based on the following formula. The above heat treatment was performed in a constant temperature bath, and the ventilation holes of the constant temperature bath were open.
Mass change rate (%) = [(AB) / B] x 100
(A means the mass (g) of the test piece of the rare earth non-sintered magnet after the heat treatment, and B means the mass (g) of the test piece of the rare earth non-sintered magnet before the heat treatment.)
The results are shown in Table 1.

(Calculation of dimensional change rate)
Dimensional change when the test piece of the rare earth non-sintered magnet produced above is heat-treated at 200 ° C. for the time shown in Table 2 under an atmospheric atmosphere (oxygen concentration 23% by mass, temperature 25 ° C., relative humidity 60%). The rate was calculated based on the following formula.
Dimensional change rate (%) = [(CD) / D] x 100
(C means the outer diameter dimension (mm) of the test piece of the rare earth non-sintered magnet after the heat treatment, and D means the outer diameter dimension (mm) of the test piece of the rare earth non-sintered magnet before the heat treatment. means.)
The results are shown in Table 2.

(Evaluation of strength at 150 ° C)
Using a universal compression tester (manufactured by Shimadzu Corporation, AG-10TBR), the test piece of the rare earth non-sintered magnet produced above was subjected to compression pressure from the height direction in an atmosphere of 150 ° C. .. Then, the crushing strength (MPa) was calculated from the maximum value of the compressive pressure when the test piece was broken by the compressive pressure, and the high-temperature crushing strength (MPa) was evaluated. The high temperature crushing strength (MPa) was N = 3, and the average value was calculated for each. The results are shown in Table 3.

As shown in Tables 1 to 3, in Examples 1 and 2, the crushing strength of the rare earth non-sintered magnet was higher than that of Comparative Examples 1 and 2 in which the absolute values of the mass change rate and the dimensional change rate were larger, respectively. it was high.

All documents, patent applications, and technical standards described herein are to the same extent as if the individual documents, patent applications, and technical standards were specifically and individually stated to be incorporated by reference. Incorporated and incorporated herein.

Claims

It is a heat-treated product of a molded product containing magnetic material particles containing rare earth elements.
A rare earth non-sintered magnet having a mass increase rate of 1.0% or less when heat-treated at 200 ° C. for 504 hours in an air atmosphere.
It is a heat-treated product of a molded product containing magnetic material particles containing rare earth elements.
A rare earth non-sintered magnet having an absolute dimensional change rate of 1.4% or less when heat-treated at 200 ° C. for 504 hours in an air atmosphere.
The rare earth non-sintered magnet according to claim 1 or 2, wherein the magnetic material particles contain samarium (Sm) as the rare earth element.
The rare earth non-sintered magnet according to any one of claims 1 to 3, which contains at least one of an oxide and a hydroxide as a component contained in the magnetic material particles.
The rare earth non-sintered magnet according to any one of claims 1 to 4, further containing metal particles other than the magnetic material particles.
The rare earth non-sintered magnet according to any one of claims 1 to 5, which does not contain a resin component or has a content of the resin component of 10% by mass or less.