JP7248017B2 - Method for producing RTB based sintered magnet - Google Patents

Description

The present invention relates to a method for producing an RTB based sintered magnet.

RTB based sintered magnets (R is at least one rare earth element and always contains Nd, T is Fe or Fe and Co, and B is boron) have the highest Known as a high-performance magnet, it is used in various motors such as voice coil motors (VCM) for hard disk drives, motors for electric vehicles (EV, HV, PHV, etc.), motors for industrial equipment, and home appliances.

An RTB system sintered magnet is composed of a main phase mainly composed of an R ₂ T ₁₄ B compound and a grain boundary phase located at the grain boundary portion of the main phase. The main phase R ₂ T ₁₄ B compound is a ferromagnetic material with high saturation magnetization and anisotropic magnetic field, and forms the basis of the properties of the RTB system sintered magnet.

At high temperatures, irreversible thermal demagnetization occurs because the coercive force H _cJ (hereinafter sometimes simply referred to as “H _cJ ”) of the sintered RTB magnet decreases. Therefore, RTB sintered magnets used in motors for electric vehicles are particularly required to have a high _HcJ .

In RTB based sintered magnets, part of the light rare earth element RL (eg Nd and Pr) contained in R in the R ₂ T ₁₄ B compound is replaced with a heavy rare earth element RH (eg Dy and Tb). Substitution is known to improve H _cJ . H _cJ improves as the substitution amount of RH increases.

However, when RH is substituted for RL in the R ₂ T ₁₄ B compound, the H _cJ of the RTB system sintered magnet is improved, while the residual magnetic flux density B _r (hereinafter sometimes simply referred to as “B _r ”) existing) will decrease. In addition, heavy rare earth elements such as Dy and Tb in particular have problems such as unstable supply and large fluctuations in price due to the fact that the abundance of resources is small and the places of production are limited. ing. Therefore, in recent years, there has been a demand for improving H _cJ without using heavy rare earth elements such as Dy and Tb as much as possible.

In Patent Document 1, in order to reduce the amount of heavy rare earth elements used, a unit magnet with a relatively large content of heavy rare earth elements such as Dy is arranged in a portion where _HcJ needs to be increased, and discloses a technique of arranging unit magnets having a relatively low heavy rare earth element content and joining a plurality of these unit magnets. The joint surfaces of the unit magnets are heated while being in contact with each other through a paste obtained by mixing a metal powder containing a heavy rare earth element and an organic substance.

Patent Document 2 discloses a technique of joining an RTB rare earth sintered magnet and a member of different material such as a silicon steel plate via an alloy powder of a rare earth element and another metal element.

JP 2015-73045 A JP-A-8-116633

According to the joining technique disclosed in Patent Document 1, unit magnets containing a relatively large amount of heavy rare earth elements such as Dy and unit magnets containing a relatively small amount of heavy rare earth elements are arranged. Therefore, the amount of heavy rare earth elements used can be reduced. However, the joint surfaces of the unit magnets are joined by heating in a state of contact via a paste in which a metal powder containing a heavy rare earth element and an organic substance are mixed (that is, joining is performed by diffusion of the heavy rare earth element). ing).

In recent years, for applications such as motors for electric vehicles, RTB based sintered magnets having high H _cJ without using Dy and Tb have been desired. In addition, the joining techniques disclosed in Patent Documents 1 and 2 are capable of joining RTB rare earth sintered magnets together or joining an RTB rare earth sintered magnet and an iron-based material. become. However, as a result of studies by the present inventors, it has been found that a new bonding technique capable of achieving higher bonding strength is necessary when used in motors that need to rotate at high speed.

Various embodiments of the present invention provide a method for producing a RTB based sintered magnet having high _Br and high _HcJ without using Dy and Tb while achieving high bonding strength. .

In an exemplary embodiment of the method for producing a RTB based sintered magnet of the present disclosure, an R1-TB based sintered magnet material (R1 is a rare earth element containing at least one of Nd and Pr) is a step of preparing an iron-based metal member; R2: 65% by mass or more and 97% by mass or less (R2 is a rare earth element containing at least one of Nd and Pr, and total content is 50% by mass or less), and M: 3% by mass or more and 35% by mass or less (M is at least one selected from the group consisting of Ga, Cu, In, Al, Sn and Co) a step of preparing an R2-M alloy powder containing and produced by an atomizing method; and arranging the R2-M alloy powder between the R1-T-B based sintered magnet material and the iron-based metal member. and joining the R1-T-B sintered magnet material and the iron-based metal member at a temperature of 450° C. or higher and 1000° C. or lower.

In one embodiment, the total content of Dy and Tb with respect to the entire R2 is 15% by mass or less.

In certain embodiments, R2 must consist of Pr and M must consist of Ga.

In one embodiment, the iron-based metal member contains 50% by mass or more of Fe and more than 0% by mass and 35% by mass or less of a rare earth element.

In one embodiment, the R1-TB based sintered magnet material has a thickness of 2 mm or less.

In one embodiment, the R1-TB based sintered magnet material has a thickness of 1 mm or less.

According to the embodiment of the present disclosure, since the R2-M alloy powder produced by the atomization method is used for bonding, high bonding strength is achieved, and high _Br is achieved without using Dy and Tb. and H _cJ can be produced.

1 is a cross-sectional view schematically showing an enlarged part of an RTB based sintered magnet. FIG. FIG. 1B is a schematic cross-sectional view further enlarging the inside of the broken-line rectangular region of FIG. 1A. FIG. 2 is a schematic cross-sectional view of alloy powder formed by conventional pulverization; 1 is a schematic cross-sectional view of alloy powder formed by an atomizing method according to an embodiment of the present disclosure; FIG. 1 is a perspective view schematically showing a state before joining R1-TB based sintered magnet materials according to an embodiment of the present disclosure; FIG. 1 is a perspective view schematically showing a state in which R1-TB based sintered magnet materials are being joined according to an embodiment of the present disclosure; FIG. 4 is a flow chart showing an example of steps in a method for manufacturing a RTB based sintered magnet according to an embodiment of the present disclosure;

FIG. 1A is a schematic cross-sectional view enlarging a part of an RTB based sintered magnet, and FIG. 1B is a cross-sectional view schematically showing a further enlarged broken-line rectangular area in FIG. 1A. is. In FIG. 1A, as an example, an arrow with a length of 5 μm is shown for reference as a reference length indicating the size. As shown in FIGS. 1A and 1B, the RTB system sintered magnet comprises a main phase 12 mainly composed of an R ₂ T ₁₄ B compound and a grain boundary phase 14 located at the grain boundary portion of the main phase 12. It consists of As shown in FIG. 1B, the grain boundary phase 14 consists of a two-grain grain boundary phase 14a in which two R ₂ T ₁₄ B compound grains (grains) are adjacent to each other, and a grain boundary phase 14a in which three R ₂ T ₁₄ B compound grains are adjacent to each other. field triple point 14b.

The R ₂ T ₁₄ B compound, which is the main phase 12, is a ferromagnetic material with high saturation magnetization and anisotropic magnetic field. Therefore, in the RTB system sintered magnet, _Br can be improved by increasing the abundance ratio of the R ₂ T ₁₄ B compound, which is the main phase 12 . In order to increase the abundance ratio of the R ₂ T ₁₄ B compound, the amount of R, T, and B in the raw material alloy is adjusted to the stoichiometric ratio of the R ₂ T ₁₄ B compound (R amount: T amount: B amount = 2:14:1).

The present inventors discovered that by diffusing at least one selected from the group consisting of Ga, Cu, In, Al, Sn and Co into grain boundaries, it is possible to modify the grain boundary phase and increase _HcJ . turned out to be For such grain boundary phase modification, an R1-T-B system sintered magnet material (R1 is a rare earth element containing at least one of Nd and Pr) is prepared and R1-T-B system sintered It is preferable to supply the metal element M (at least one selected from the group consisting of Ga, Cu, In, Al, Sn and Co) from the surface of the magnet material to the grain boundaries and diffuse the grain boundaries. Such diffusion of the metal element M is an alloy of 65% by mass or more and 97% by mass or less of R2 (a rare earth element containing at least one of Nd and Pr) and 3% by mass or more and 35% by mass or less of M, that is, R2 -M alloy powder can be used. As a result, an RTB based sintered magnet having high B _r and high H _cJ can be obtained without using Dy and Tb.

As a result of further investigation, the inventors of the present invention applied the R2-M alloy powder (atomized powder of R2-M alloy) produced by the atomization method to the surface of the R1-T-B based sintered magnet material for diffusion. It was found that when heat treatment is performed, it can be used as an excellent fusing agent for joining an iron-based metal member to an R1-T-B based sintered magnet material. That is, the atomized powder of the R2-M alloy functions as a diffusion source for introduction into the grain boundaries of the two particles of the R1-T-B based sintered magnet material, and the R1-T-B based sintered magnet material is mixed with iron. It has been found that it can also function as a powder that adheres and uniformly bonds to a base metal member. This is because the atomized powder has a more uniform shape and size distribution than the powder particles formed by pulverizing the R2-M alloy. As a result, voids are less likely to be formed on the joint surfaces, and the joint strength is improved.

When the R1-T-B based sintered magnet material is joined to an iron-based metal member, the strength of the R1-T-B based sintered magnet material itself is supplemented by the iron-based metal member to increase the overall strength and rigidity. becomes possible. This is particularly effective when the thickness of the R1-TB based sintered magnet material is thin. By joining the R1-T-B sintered magnet material to an iron-based metal member, even if it has a sheet-like or rod-like shape with a thickness of 3 mm or less, R1-T-B is less likely to crack or chip. A system sintered magnet is realized.

In general, the thinner the magnet, the lower the operating point, making it difficult to magnetize. According to embodiments of the present disclosure, magnetization characteristics can also be improved by integrating with ferrous metal members.

FIG. 2 is a schematic cross-sectional view of alloy powder 50 formed by conventional pulverization (for example, pulverization after producing a raw material alloy by the ingot method or strip casteing method). The alloy powder is placed between two solid members 20 and is located in the gap created by the facing surfaces (surfaces to be joined) 20S of the members 20 . As can be seen from FIG. 2, the shape and size of the individual powder particles 50P are random. Since the alloy powder 50 is produced by pulverizing an alloy, the particles 50P have flat portions, sharp convex portions, complicated fractured surfaces, and the like.

On the other hand, FIG. 3 is a schematic cross-sectional view of R2-M alloy powder 30 formed by atomization according to an embodiment of the present disclosure. As shown in FIG. 3, individual particles 30P forming the R2-M alloy powder 30 formed by the atomization method are spherical. Such spherical powder particles 30P are arranged between the surfaces (surfaces to be joined) 20S of the solid members 20 facing each other, and when the surfaces 20S of the solid members 20 are brought close to each other, the gaps formed by the surfaces 20S facing each other are uniformly filled. can be rearranged to fill the Therefore, it is possible to increase the degree of adhesion of the joint surfaces 20S without forming unnecessary cavities at the time of joining.

FIG. 4 is a perspective view schematically showing a state before joining an R1-TB based sintered magnet material and an iron-based metal member according to an embodiment of the present disclosure. In the illustrated example, an iron-based metal member 24 and an R1-TB-based sintered magnet material 26 are laminated. A layer of R2-M alloy powder 30 formed by atomization is formed between the iron-based metal member 24 and the R1-TB-based sintered magnet material 26 . In the example of FIG. 4, R2-M alloy powder 30 is applied to the upper surface of ferrous metal member 24 . However, the R2-M alloy powder 30 formed by the atomizing method may be applied to the bottom surface of the R1-T-B system sintered magnet material 26, and the iron-based metal member 24 and the R1-T-B system sintered magnet material 24 may be applied. It may be applied to the entire surface of at least one of the magnetizing materials 26 . The positional relationship between the R1-TB based sintered magnet material 26 and the iron based metal member 24 is not limited to the illustrated example, and may be upside down.

FIG. 5 is a perspective view schematically showing a state in which the iron-based metal member 24 and the R1-TB-based sintered magnet material 26 are being joined. In the state shown in FIG. 5, the iron-based metal member 24 and the R1-TB-based sintered magnet material 26 are close to each other with the R2-M alloy powder 30 interposed therebetween.

In some embodiments, pressure may be applied in the stacking direction. By performing heat treatment in the state shown in FIG. 5, the R2-M alloy powder was melted, and the iron-based metal member 24 and the R1-T-B based sintered magnet material 26 were joined and integrated. An RTB based sintered magnet 200 is produced.

In this joining step, the rare earth element R2 and the metal element M contained in the R2-M alloy powder 30 are removed from the joining surface between the iron-based metal member 24 and the R1-T-B based sintered magnet material 26 by the R1- It diffuses inside the R1-TB based sintered magnet material 26 via the grain boundaries of the TB based sintered magnet material 26 . The R2-M alloy powder 30 produced by the atomization method functions not only as a diffusion source but also as an excellent bonding aid, contributing to improvement in bonding strength.

R2-M alloys such as Pr--Ga alloys have high ductility and generally poor pulverizability. Therefore, pulverization takes a long time, which poses a problem in mass production. In the embodiment of the present disclosure, the use of the R2-M alloy atomized powder makes it possible to obtain powder particles (for example, particles having a particle size of 200 μm or less) without pulverization.

As illustrated in FIG. 6, the method for producing an RTB based sintered magnet according to the present disclosure comprises a step S10 of preparing an R1-TB based sintered magnet material and an iron-based metal member, and an atomizing method. and step S20 of providing an R2-M alloy powder made by. The order of the step S10 of preparing the R1-T-B based sintered magnet material and the iron-based metal member and the step S20 of preparing the R2-M alloy powder produced by the atomization method is arbitrary, and they are performed at different places. The manufactured R1-TB based sintered magnet material and R2-M alloy atomized powder may be used.

Further, the method for producing an RTB based sintered magnet according to the present disclosure includes a step S30 of placing R2-M alloy powder between an R1-TB based sintered magnet material and an iron-based metal member; and a step S40 of joining the R1-TB based sintered magnet materials.

Hereinafter, embodiments of the method for producing a RTB based sintered magnet of the present disclosure will be described in more detail.

1. Step of Preparing R1-TB Based Sintered Magnet Material First, an R1-TB based sintered magnet material is prepared. The R1-T-B system sintered magnet material may be any known RTB system sintered magnet. A typical example of the R1-TB based sintered magnet material that can be used in this embodiment has the following composition.
Rare earth element R1: 27.5 to 35.0% by mass
B (part of B (boron) may be substituted with C (carbon)): 0.80 to 0.99% by mass
Ga: 0 to 0.8% by mass
Additive metal element M (at least one selected from the group consisting of Al, Cu, Zr, and Nb): 0 to 2% by mass
T (a transition metal element mainly composed of Fe, which may contain Co) and inevitable impurities: balance

Moreover, preferably, the following inequality (1) is satisfied.
[T]/55.85>14[B]/10.8 (1)
Here, [T] is the content of T expressed in mass%, and [B] is the content of B expressed in mass%.

Satisfying this inequality means that the content of B is less than the stoichiometric composition ratio of the R ₂ T ₁₄ B compound, that is, the amount of T used to form the main phase (R ₂ T ₁₄ B compound) is This means that the amount of B is relatively small.

To obtain higher B _r and H _cJ without using Dy and Tb by diffusing R2-M alloy powder in an R1-T-B based sintered magnet material satisfying formula (1). can be done.

The rare earth element R1 is mainly a light rare earth element RL (at least one element selected from Nd and Pr), but may contain heavy rare earth elements such as Dy and Tb. However, the amount of heavy rare earth elements such as Dy and Tb used is preferably 2% or less of the total R1-T-B based sintered magnet material, and most preferably, the R1-T-B based sintered magnet material contains Dy and heavy rare earth elements such as Tb (including unavoidable impurities).

The R1-TB based sintered magnet material having the above composition can be produced by any known production method. The R1-T-B based sintered magnet material may be sintered, or may be cut or polished.

In the example shown in FIG. 4, the sizes of the iron-based metal member 24 and the R1-TB-based sintered magnet material 26 are arbitrary. If the thickness of the R1-T-B system sintered magnet material 26 is 2 mm or less, the strength of the R1-T-B system sintered magnet material 26 itself will be low, and handling will generally be difficult. Even in such a case, according to the embodiment of the present disclosure, the iron-based metal member 24 supports the R1-TB-based sintered magnet material 26 to improve the overall strength, making handling easier. . From this point of view, the size of the R1-TB based sintered magnet material 26 is, for example, 0.5 mm or more and 2 mm or less, and can be, for example, 0.5 mm or more and 1 mm or less.

2. Step of Preparing Ferrous Metal Member The ferrous metal member can be made of pure iron, silicon steel, stainless steel, ordinary steel, special steel, cast iron, and the like. The iron-based metal member contains 50% by mass or more of iron (Fe), and may contain various elements other than iron. For example, known ferrous metal members such as SS400, SM400, SK90, SCM514, SUS304, SUS316, and SU310. Examples of elements other than iron are rare earth elements. The content of the rare earth element in the iron-based metal member is preferably 35% by mass or less in order to reduce the influence on the magnetic properties of the R1-T-B based sintered magnet material.

The size of the iron-based metal member can be appropriately determined according to the joint surface of the R1-TB-based sintered magnet material to be joined. When the iron-based metal member has a sheet shape, its thickness can be, for example, in the range of 0.1 mm or more and 10 mm or less. Also, the iron-based metal member may be a laminated member.

3. Step of preparing R2-M alloy powder produced by atomization (R2) R2 is a rare earth element containing at least one of Nd and Pr, and the total content of Dy and Tb with respect to the entire R2 is 50% by mass or less. be. For example, when R2 is 80% by mass of the entire R2-M alloy, the total content of Dy and Tb is 40% by mass or less. Preferably, the total content of Dy and Tb with respect to the entire R2 is 15% by mass or less. Most preferably, the R2-M alloy powder does not contain heavy rare earth elements such as Dy and Tb (including unavoidable impurities). R2 is 65 mass % or more and 97 mass % or less of the entire R2-M alloy. R2 preferably always contains Pr, and the amount of Pr in R2 is preferably 40% by mass or more, more preferably 70% by mass or more.
(M) M is at least one selected from the group consisting of Ga, Cu, In, Al, Sn and Co. M is 3 mass % or more and 35 mass % or less of the entire R2-M alloy. M preferably always contains Ga, and the amount of Ga in M is 50% by mass or more. The R2-M alloy may contain unavoidable impurities. Most preferably, an R2-M alloy powder in which the amount of Pr in R2 is 70% by mass or more and the amount of Ga in M is 50% by mass or more is used. As a result, almost no Ga can be introduced into the interior of the main phase crystal grains, and Ga can be introduced into the two grain boundaries. A high H _cJ can be obtained without using Dy or Tb by introducing a Ga-containing liquid phase at the grain boundaries of two grains.

In embodiments of the present disclosure, the R2-M alloy powder is made by atomization. The atomization method, which is also called a molten metal atomization method, is one type of powder production method, and includes known atomization methods such as a gas atomization method and a plasma atomization method. For example, according to the gas atomization method, a metal or alloy is melted in a melting furnace to form a molten metal, which is sprayed into an inert gas atmosphere such as nitrogen or argon to solidify. Since the sprayed molten metal scatters as fine droplets, it is cooled at a high speed and solidified. Since the powder particles produced each have a spherical shape, no pulverization is necessary. The size of powder particles produced by the atomization method is distributed, for example, in the range of 10 μm to 200 μm.

According to the atomization method, since the droplets of the molten alloy to be sprayed are small and the surface area of each droplet is relatively large relative to its weight, the cooling rate is high. As such, the powder particles formed are amorphous or microcrystalline. These powder particles may additionally be heat-treated before the bonding process to crystallize the amorphous particles.

The particle size of the R2-M alloy powder can be adjusted by sieving. Further, if the amount of powder excluded by sieving is within 10% by mass, the effect is small, so the powder may be used without sieving.

4. Step of disposing R2-M alloy powder between R1-TB based sintered magnet material and iron-based metal member R2-M between R1-TB based sintered magnet material and iron-based metal member The alloy powder is placed (in other words, the R2-M alloy powder is sandwiched between the R1-TB sintered magnet material and the iron-based metal member). As for the arrangement method, the R2-M alloy powder may be applied to both surfaces of the R1-T-B based sintered magnet material and the iron-based metal member, or either one (R1-T-B Only the surface of the sintered magnet material and the surface of the iron-based metal member) may be coated with the R2-M alloy powder. Also, the R2-M alloy powder may be applied to the entire surface of at least one of the R1-TB sintered magnet material and the iron-based metal member, or may be applied only to the joint surface as shown in FIG. Also, two or more types of R2-M alloy powders having different compositions may be used. The method of applying the R2-M alloy powder 30 to the surface of the iron-based metal member and/or the R1-T-B based sintered magnet material is not limited to a specific application method. An application step of applying an adhesive to the surface of the object to be applied and a step of adhering the R2-M alloy powder to the area to which the adhesive is applied may be performed. Examples of adhesives include PVA (polyvinyl alcohol), PVB (polyvinyl butyral), PVP (polyvinylpyrrolidone), and the like. When the adhesive is a water-based adhesive, the RTB-based sintered magnet material may be preliminarily heated before application. The purpose of preheating is to remove the excess solvent, control the adhesive force, and evenly adhere the adhesive. The heating temperature is preferably 60-100°C. This step may be omitted in the case of highly volatile organic solvent-based pressure-sensitive adhesives.

Any method may be used to apply the adhesive to the surface of the RTB based sintered magnet material. Specific examples of application include a spray method, an immersion method, and application using a dispenser. The coating amount of the adhesive can be, for example, 1.02×10 ⁻⁵ to 5.10×10 ⁻⁵ g/mm ² .

5. Step of Joining R1-T-B Based Sintered Magnet Material and Iron-Based Material According to the present disclosure, the R1-T-B based sintered magnet material and R2-M alloy powder (atomized powder) are in contact with each other. start the heat treatment for bonding. As a result, the grain boundary phase of the R1-TB system sintered magnet is reformed throughout the interior of the magnet while achieving high bonding strength, thereby realizing high B _r and H _cJ .

The heat treatment for bonding can be performed at a temperature of 450° C. or more and 1000° C. or less for a time of 5 minutes or more and 720 minutes or less. The heat treatment may be performed at a relatively high temperature (700° C. or higher and 1000° C. or lower) and then at a relatively low temperature (450° C. or higher and 600° C. or lower) (two-step heat treatment). Preferred conditions are heat treatment at 730° C. or higher and 980° C. or lower for about 5 minutes to 500 minutes, cooling (after cooling to room temperature or cooling to 440° C. or higher and 550° C. or lower), and further heating at 440° C. or higher and 550° C. or lower for 5 minutes. For example, the heat treatment may be performed for about 500 minutes. The atmosphere gas for heat treatment can be nitrogen or an inert gas. The atmospheric gas may be decompressed.

The present disclosure will be described in more detail by examples, but the disclosure is not limited thereto.

Experimental example 1
The R1-T-B based sintered magnet material is about No. 1 in Table 1. Each element was weighed so that the composition shown in 1-A was obtained, and the alloy was cast by a strip casting method to obtain an alloy in the form of flakes. After hydrogen embrittlement was applied to the resulting flake-shaped alloy in a pressurized hydrogen atmosphere, dehydrogenation treatment was performed by heating to 550° C. in vacuum and cooling to obtain a coarsely pulverized powder. Next, 0.04% by mass of zinc stearate as a lubricant is added to the coarsely ground powder with respect to 100% by mass of the coarsely ground powder. , dry pulverized in a nitrogen atmosphere to obtain an alloy powder having a particle size D ₅₀ of 4.3 μm. To the alloy powder, 0.3% by mass of a liquid lubricant was added to 100% by mass of the finely pulverized powder, mixed, and then compacted in a magnetic field to obtain a compact. As the forming apparatus, a so-called orthogonal magnetic field forming apparatus (transverse magnetic field forming apparatus) in which the magnetic field application direction and the pressing method direction are orthogonal was used. The compact thus obtained was sintered in vacuum at 1020° C. for 4 hours to prepare a plurality of R1-TB based sintered magnet materials (No. 1-A). The density of the sintered magnet was 7.5 Mg/m ³ or more. Further, the obtained R1-TB based sintered magnet material was machined into a length of 10 mm, a width of 5 mm, and a thickness of 3 mm (the thickness is the direction of magnetization). Table 1 shows the results of the components of the obtained R1-TB sintered magnet material. Each component in Table 1 was measured using high frequency inductively coupled plasma optical emission spectrometry (ICP-OES). In addition, all of the R1-TB based sintered magnet materials satisfied the inequality (1). Also, SS400 (JIS G 3101) was prepared as an iron-based metal member. The dimensions of the iron-based metal member were machined in the same manner as the R1-T-B sintered magnet material, and were 10 mm long, 5 mm wide, and 3 mm thick.

Next, No. in Table 2. An R1-M alloy powder was prepared by atomizing an alloy powder having the composition shown in 1-a. The particle size of the obtained R2-M alloy powder was 106 μm or less. Furthermore, No. in Table 2. Each element was weighed so as to obtain an alloy having the composition shown in 1-b, and cast by a strip casting method to obtain an alloy in the form of flakes. After hydrogen embrittlement was applied to the resulting flake-shaped alloy in a pressurized hydrogen atmosphere, dehydrogenation treatment was performed by heating to 550° C. in vacuum and cooling to obtain a coarsely pulverized powder. After adding 0.04% by mass of zinc stearate as a lubricant to 100% by mass of the coarsely ground powder to the obtained coarsely ground powder and mixing, using an air stream type grinder (jet mill device), a nitrogen atmosphere An alloy powder having a particle size D ₅₀ of 4.3 μm was obtained by dry-grinding in a medium.

Next, No. in Table 1. An adhesive was applied to the entire surface of the R1-TB based sintered magnet material of 1-A. As for the coating method, after heating the R1-TB based sintered magnet material on a hot plate to 60° C., the adhesive was applied to the R1-TB based sintered magnet material by a spray method. PVP (polyvinylpyrrolidone) was used as the adhesive.

Next, No. 1 in Table 2 was applied to the R1-T-B based sintered magnet material (No. 1-A) to which the adhesive was applied. The diffusion source of 1-a (R2-M alloy powder) was deposited. The adhesion method spreads the diffusion source in a container, cools the R1-T-B system sintered magnet material coated with the adhesive to room temperature, and then spreads the diffusion source into the R1-T-B system sintered magnet material in the container. It was made to adhere so as to be sprinkled over the entire surface.

Next, in a state in which the R1-T-B based sintered magnet material (No. 1-A) and the R2-M alloy powder (No. 1-a) are in contact with each other, the R1-T-B based sintered magnet material is No. 1-A and an iron-based metal member are stacked in the thickness (3 mm) direction (the surfaces of 10 mm in length × 5 mm in width are brought into contact) and joined by performing heat treatment to obtain an RTB-based sintered magnet. (No. 1-1) was obtained. The heat treatment was carried out at 900° C. for 8 hours, cooled to room temperature, and further heat treated at 500° C. for 6 hours (two-step heat treatment). In the same manner, the R1-T-B based sintered magnet material (No. 1-A) was subjected to No. 2 in Table 2. The diffusion source of 1-b was adhered and joined by heat treatment in the same manner to obtain an RTB system sintered magnet (No. 1-2).

The generation of cavities on the joint surface of the obtained RTB sintered magnet was confirmed. If many cavities occur, the bonding strength may decrease and peeling may occur starting from the cavities. If so, it is necessary to suppress the occurrence of nests.

RTB system sintered magnets (No. 1-1 and 1-2) were each cut and polished by machining, and the cross section of an arbitrary bonded magnet including the bonded surface (magnet cross section at width 5 mm × thickness 6 mm) was measured. It was observed with a scanning electron microscope (SEM: JCM-7001F manufactured by JEOL Ltd.). The observation area was 500 μm×500 μm, and the occurrence of cavities on the joint surface was visually confirmed. The occurrence of cavities in 10% or less of the joint surface (100×area of cavities/area of joint) is defined as the present invention. Table 3 shows the results. When the occurrence of nests is 10% or less, it is indicated by ◯, and when it exceeds 10%, it is indicated by ×. Furthermore, Table 3 shows the results of the magnetic properties of the RTB system sintered magnets. The magnetic properties were measured using a BH tracer by cutting out only the R1-T-B based sintered magnet material from the bonded RTB-based sintered magnet by cutting.

As shown in Table 3, the invention example suppresses the generation of cavities, whereas the comparative example (in the case of using the diffusion source produced by the strip casting method) does not suppress the generation of cavities.

Experimental example 2
About No. 4 in Table 4. R1-TB based sintered magnet materials were prepared in the same manner as in Experimental Example 1 so as to have the compositions shown in 2-A and 2-B. The obtained R1-TB based sintered magnet material was machined into a size of 10 mm long×5 mm wide×3 mm thick (the thickness is in the direction of magnetization). Table 4 shows the results of the components of the obtained R1-TB sintered magnet material. Each component in Table 4 was measured using high frequency inductively coupled plasma optical emission spectroscopy (ICP-OES). SS400 (JIS G 3101), SM400 (JIS G 3106), and SUS304 (JIS G 4304) were prepared as iron-based metal members. The dimensions of the iron-based metal member were machined in the same manner as the R1-T-B sintered magnet material, and were 10 mm long, 5 mm wide, and 3 mm thick.

Next, No. in Table 5. An R2-M alloy powder was prepared by atomizing alloy powders having the compositions shown in 2-a to 2-e. The particle size of the obtained R2-M alloy powder was 106 μm or less.

Next, under the conditions shown in Table 6, the R1-T-B system sintered magnet material and the iron-based metal member were joined in the same manner as in Experimental Example 1 to obtain an RTB system sintered magnet. No. in Table 6. 2-1 is No. An adhesive was applied to the entire surface of the R1-T-B based sintered magnet material of 2-A in the same manner as in Experimental Example 1, and the R1-T-B based sintered magnet material coated with the adhesive (No. 2- A), No. The R-2M alloy powder of 2-a was deposited in the same manner as in Experimental Example 1. Next, while the R1-TB sintered magnet material (No. 2-A) and the R2-M alloy powder (No. 2-a) are in contact with each other, the R1-T-B sintered magnet material is No. 2-A and an iron-based metal member (SS400) were overlapped in the thickness direction (3 mm) and joined by heat treatment in the same manner as in Experimental Example 1, and an RTB-based sintered magnet (No. 2 -1) is obtained. No. 2-2 to 2-5 are similarly described. In the same manner as in Experimental Example 1, the occurrence of cavities on the joint surfaces of the obtained RTB-based sintered magnet was visually confirmed.

As shown in Table 6, the occurrence of cavities is suppressed in all the examples of the present invention.

According to the present invention, RTB based sintered magnets having high B _r and high H _cJ can be produced. The sintered magnet of the present invention is suitable for various motors such as hybrid vehicle mounted motors exposed to high temperatures, home electric appliances, and the like.

12 Main phase composed of R ₂ T ₁₄ B compound 14 Grain boundary phase 14 a Two grain boundary phase 14 b Grain boundary triple point 20 Solid member 24 Iron-based metal member 30 R2-M alloy powder 26 R1-TB system sintered magnet Material 50 alloy powder

Claims (6)

A step of preparing an R1-T-B based sintered magnet material (R1 is a rare earth element containing at least one of Nd and Pr, T is a transition metal element mainly composed of Fe, and may contain Co). and,
A step of preparing a ferrous metal member;
R2: 65% by mass or more and 97% by mass or less (R2 is a rare earth element containing Pr , the content of Pr in the entirety of R2 is 40% by mass or more, and the total content of Dy and Tb in the entirety of R2 is 50% by mass % or less), and M: 3% by mass or more and 35% by mass or less (M is at least one selected from the group consisting of Ga, Cu, In, Al, Sn and Co)
and preparing an R2-M alloy powder produced by an atomizing method;
a step of applying an adhesive to the surface of the R1-T-B based sintered magnet material in an amount of 1.02×10 ⁻⁵ to 5.10×10 ⁻⁵ g/mm ² ;
a step of adhering the R2-M alloy powder to the adhesive of the R1-T-B based sintered magnet material;
With the R2-M alloy powder arranged between the R1-T-B based sintered magnet material and the iron-based metal member, the R1-T-B based sintered magnet material and the iron-based metal A step of overlapping the members in the thickness direction ;
a step of joining the R1-T-B based sintered magnet material and the iron-based metal member at a temperature of 450° C. or higher and 1000° C. or lower;
A method for producing an RTB-based sintered magnet, comprising: 2. The method for producing an RTB based sintered magnet according to claim 1, wherein the total content of Dy and Tb with respect to the entire R2 is 15% by mass or less. 3. The method for producing an RTB based sintered magnet according to claim 1, wherein M always contains Ga. The RTB system sintering according to any one of claims 1 to 3, wherein the iron-based metal member contains 50% by mass or more of Fe and more than 0% by mass and 35% by mass or less of a rare earth element. Method of manufacturing magnets. 5. The method for producing a RTB sintered magnet according to claim 1, wherein said R1-T-B sintered magnet material has a thickness of 2 mm or less. 6. The method for producing a RTB based sintered magnet according to claim 1, wherein said R1-TB based sintered magnet material has a thickness of 1 mm or less.

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