JP2018186200A - Method of producing rare earth magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a rare earth magnet in which an R-T-B system rare earth magnet is used as a precursor and a penetration material is penetrated into the precursor and which therefore has an improved coercive force and a suppressed reduction in magnetization.SOLUTION: The method of producing a rare earth magnet is provided that includes: bringing an R-Cu-Fe-Ga alloy (Ris a rare earth element) into contact with a rare earth magnet precursor comprising an R-T-B system main phase (Ris a rare earth element, and T is one or more types selected from Fe and Co), and an Rrich grain boundary phase present around the main phase to obtain a contact body; and performing heat treatment on the contact body to cause the R-Cu-Fe-Ga alloy to penetrate into the rare earth magnet precursor.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a method of manufacturing a rare earth magnet. The present disclosure relates to an R ¹ -T-B main phase (R ¹ is a rare earth element, T is one or more selected from Fe and Co), and an R ¹ -rich grain boundary existing around the main phase. The present invention relates to a method for producing a rare earth magnet in which a penetrating material is permeated into a rare earth magnet precursor having a phase.

  Rare earth magnets using rare earth elements are widely used as high-performance magnets, in addition to motors constituting hard disks and MRI, as well as drive motors for hybrid vehicles and electric vehicles.

Among the performance indexes of rare earth magnets, there are magnetization and coercive force as typical ones. In a rare earth magnet including a main phase having a crystal structure represented by R ¹ ₂ Fe ₁₄ B and an R ¹ rich grain boundary phase existing around the main phase, magnetization reversal is performed across a plurality of main phases. When propagated, the coercive force decreases.

Conventionally, a rare-earth magnet having a main phase having a crystal structure represented by R ¹ ₂ Fe ₁₄ B and an R ¹ -rich grain boundary phase existing around the main phase is used as a precursor. Attempts have been made to obtain rare earth magnets with improved coercive force by impregnating a penetrating material.

  For example, Patent Document 1 obtains a rare earth magnet having an improved coercive force by using an Nd—Fe—B rare earth magnet as a precursor and infiltrating a penetrating material of an Nd—Cu alloy into the precursor. It is disclosed. However, since the penetrating material is a non-magnetic material, the magnetization of the rare earth magnet infiltrated with the penetrating material is lowered.

Patent Document 2 discloses a rare earth material in which a nanocomposite magnet having both an Nd ₂ Fe ₁₄ B phase and an α-Fe phase is used as a precursor, and an Nd—Cu alloy infiltrant is infiltrated into the precursor. A magnet is disclosed. In the nanocomposite magnet before being penetrated by the penetrating material disclosed in Patent Document 2, the magnetization is sufficiently enhanced by combining the Nd ₂ Fe ₁₄ B phase and the α-Fe phase. For this reason, a rare earth magnet in which a penetrating material is infiltrated into the precursor using this as a precursor has a lower magnetization than the precursor, but the decrease is rarely a problem.

JP 2014-127491 A JP 2012-234985 A

From what has been described so far, an R ¹ -T-B rare earth magnet is used as a precursor, and a penetrating material is infiltrated into the precursor to improve the coercive force and suppress a decrease in magnetization. The present inventors have found that a method for producing a rare earth magnet is desired. In the present specification, unless otherwise specified, R ¹ is a rare earth element, and T is one or more selected from Fe and Co.

The present disclosure has been made in view of the above problems. The present disclosure provides a method for producing a rare earth magnet, which can infiltrate a penetrating material into an R ¹ -T-B rare earth magnet precursor to improve coercive force and suppress a decrease in magnetization. The purpose is to do.

In order to achieve the above object, the present inventors have made extensive studies and completed the method for producing a rare earth magnet of the present disclosure. The summary is as follows.
^<1> R ¹ -T-B based main phase of ^{(R 1} is a rare earth element, T is one or more selected from Fe and Co) and, ^{R 1} rich grain boundaries existing on the periphery of the main phase the rare-earth magnet precursor and a ^phase, R 2 -Cu-Fe-Ga-based alloy ^{(R 2} is a rare earth element) contacting a, obtaining contact body, and,
Heat treating the contact body to infiltrate the R ² —Cu—Fe—Ga alloy into the rare earth magnet precursor;
A method for producing a rare earth magnet, comprising:

According to the method of manufacturing a rare earth magnet of the present disclosure, by adding Fe to the penetrating material, it is possible to suppress the diffusion of Fe from the R ¹ -T-B system main phase to the grain boundary phase. As a result, it is possible to suppress a decrease in the volume fraction of the main phase of the R ¹ -T-B system in the rare earth magnet that has been infiltrated with the infiltrant.

In addition, according to the method of manufacturing a rare earth magnet of the present disclosure, by adding Ga to the permeation material, the Fe concentration decreases in the grain boundary phase of the rare earth magnet after the permeation material is infiltrated, and R ¹ -T-B type main phases can be separated.

Thus, according to the method of manufacturing a rare earth magnet of the present disclosure, an R ¹ -T-B rare earth magnet is used as a precursor, and a penetrant is infiltrated into the precursor to improve the coercive force. It is possible to provide a method for producing a rare earth magnet capable of suppressing a decrease in magnetization.

FIG. 1 is a graph showing the relationship between coercive force and magnetization for the samples of Examples 1 to 3 and Comparative Examples 1 to 3. FIG. 2 is a diagram showing hysteresis curves for the samples of Examples 1 to 3. FIG. 3 is a diagram illustrating a hysteresis curve for the samples of Comparative Examples 1 to 3. FIG. 4 is a diagram showing a cross-sectional structure of the sample of Example 3. FIG. 5 is a diagram showing a cross-sectional structure of the sample of Comparative Example 3.

  Hereinafter, an embodiment of a method for producing a rare earth magnet according to the present disclosure will be described in detail. In addition, embodiment shown below does not limit the manufacturing method of the rare earth magnet of this indication.

R ¹ -T-B based rare earth ^magnet, the main phase having a crystal structure represented by _R 1 2 _{Fe 14} B (hereinafter sometimes referred to as ^"R 1 -T-B based main phase of".) R ¹ rich grain boundary phase present around the main phase. The main phase of R ¹ -T-B ^system, causes the magnetic force of the R 1 -T-B based rare earth magnet.

Improvement of the coercive force of a magnet including a main phase and a grain boundary phase is achieved by magnetically separating the main phases so that magnetization reversal does not propagate across a plurality of main phases. For this purpose, an R ¹ -T-B rare earth magnet is used as a precursor (hereinafter sometimes referred to as “rare earth magnet precursor”), and a non-magnetic penetrating material is infiltrated into the precursor. It is useful. If it does so, a nonmagnetic osmosis | permeation material will osmose | permeate the grain-boundary phase which exists around the main phase, and will isolate | separate main phases magnetically. As a result, the coercive force is improved.

  However, in a rare earth magnet that has been infiltrated with a penetrating material (hereinafter sometimes referred to as “rare earth magnet after permeation”), the ratio of non-magnetic penetrating material has increased, so that the magnetization decreases. It has been known for a long time.

  Under such circumstances, the present inventors have newly found the following.

When the penetrating material penetrates into the rare earth magnet precursor, the penetrating material penetrates through the grain boundary phase of the rare earth magnet precursor. Conventional penetrating materials generally have a rare earth element-rich composition such as Nd ₇₀ Cu ₃₀ . For this reason, when a conventional penetrant is infiltrated into the rare earth magnet precursor, the Fe concentration gradient increases between the main phase of the R ¹ -TB system and the grain boundary phase. This is because T is one or more selected from Fe and Co, and most of T is Fe. When the concentration gradient of Fe increases, Fe is easily diffused from the main phase of the R ¹ -TB system to the grain boundary phase using this concentration gradient as a driving force. As a result, the volume fraction of the main phase of the R ¹ -T-B system decreases in the infiltrated rare earth magnet. Thereby, the magnetization of the rare earth magnet after the penetration further decreases.

Therefore, when Fe is added to the permeation material, even if the permeation material is permeated into the inside of the rare earth magnet precursor, the Fe concentration gradient between the main phase and the grain boundary phase of the R ¹ -T-B system. Can be prevented from becoming large. Thus, Fe can be prevented from diffusing from the main phase of R ¹ -T-B system to the grain boundary phase. As a result, it is possible to suppress a decrease in the volume fraction of the R ¹ -T-B main phase in the infiltrated rare earth magnet. In this way, it is possible to suppress a decrease in magnetization of the rare earth magnet after penetration.

  In addition, the present inventors have newly discovered the following.

  In order to infiltrate the penetrating material into the rare earth magnet precursor, the rare earth magnet precursor and the penetrating material are brought into contact with each other and heat-treated. During the heat treatment, the penetrating material penetrates into the rare earth magnet precursor through the grain boundary phase of the rare earth magnet precursor.

When the penetrant contains Ga in addition to R ² and Fe (R ² is a rare earth element), R ¹ , R ² , Fe, and Ga coexist in the grain boundary phase of the rare earth magnet precursor during the heat treatment. The coexistence of these elements lowers the melting point of the grain boundary phase, so that most of the grain boundary phase becomes a liquid phase during the heat treatment. And in the grain boundary phase which is mostly liquid phase, it is considered that (R ¹ , R ² ) —Fe—Ga phase is generated in the cooling process of heat treatment. On the other hand, in the grain boundary phase, the majority of which is a liquid phase, the concentration of Fe decreases in portions other than the (R ¹ , R ² ) —Fe—Ga phase, and the R ¹ —TB system main phases The breakability is further improved. As a result, the coercive force is further improved.

  The constituent requirements of the method for producing a rare earth magnet according to the present disclosure based on these findings will be described next.

<< contacting the rare-earth magnet precursor and ^R 2 -Cu-Fe-Ga-based alloy >>
First, an R ² —Cu—Fe—Ga based alloy is brought into contact with a rare earth magnet precursor including an R ¹ —T—B based main phase and an R ¹ rich grain boundary phase existing around the main phase. To obtain a contact body.

The rare earth magnet precursor includes an R ¹ -T-B main phase and an R ¹ rich grain boundary phase existing around the main phase. The rare earth magnet precursor may be a powder, a ribbon, an isotropic bulk, an anisotropic bulk, or the like. Hereinafter, the overall composition of the rare earth magnet precursor, the R ¹ -T-B main phase, the grain boundary phase, and the method for producing the rare earth magnet precursor will be described.

(Overall composition of rare earth magnet precursor)
Overall composition of the rare-earth magnet precursor, for ^example, represented by _{R 1 x Fe 100-y-} w-z Co y B w M z. T is divided into Fe and Co.

x, y, w, and z are atomic%. For example, x is preferably 5 to 20, y is 0 to 8, w is 4.0 to 6.5, and z is preferably 0 to 2.0. . By making x, y, w, and z in this way, the rare earth magnet precursor includes a main phase of R ¹ -T-B system and a grain boundary phase rich in R ¹ .

  M is one or more selected from Ga, Al, Cu, Au, Ag, Zn, In, and Mn, and is an unavoidable impurity. M is an element and an unavoidable impurity added in a small amount within a range not impairing the magnetic properties of the rare earth magnet obtained by the production method of the present disclosure. Inevitable impurities refer to impurities such as impurities contained in the raw material that cannot be avoided, or incurring a significant increase in manufacturing cost.

(Main phase of R ¹ -T-B system)
The main phase of the R ¹ -T-B system includes a phase having a crystal structure represented by R ¹ ₂ T ₁₄ B (hereinafter sometimes referred to as “R ¹ ₂ T ₁₄ B phase”). Fe or Co is present at the position T in the R ¹ ₂ T ₁₄ B phase. In _{^{R 1 x Fe 100-y-}} w-z Co y B w M z, since y is 0-8, many of the T is Fe. That is, in the R ¹ ₂ T ₁₄ B phase, a part of Fe is substituted with Co. Fe and Co are both classified as iron group elements, and their properties are common in that they exhibit ferromagnetism at room temperature and normal pressure. In the R ¹ ₂ T ₁₄ B phase, by replacing Fe with Co, the magnetization is improved and the Curie point is raised. Co is not necessarily essential.

In the R ¹ ₂ T ₁₄ B phase, the atoms of R ¹ , T, and B constitute crystals at a ratio of 2: 14: 1.

The main phase of the R ¹ -T-B system may contain a small amount of crystals that are not constituted in such a proportion. The content of R ¹ ₂ T ₁₄ B ^phase, the main phase the entire R 1 -T-B based, preferably at least 90 vol%, more preferably at least 95 vol%, still more preferably not less than 99 vol% .

(Grain boundary phase)
A grain boundary phase exists around the main phase of the R ¹ -TB system. The composition of the grain boundary phase is R ¹ rich. Therefore, the melting point of the grain boundary phase is lower than the melting point of the main phase of the R ¹ -T-B system.

(Method for producing rare earth magnet precursor)
If the rare earth magnet precursor has the main phase and the grain boundary phase described above, the method for producing the rare earth magnet precursor is not particularly limited. For example, the following manufacturing method is mentioned.

  First, a ribbon of rare earth magnet precursor (hereinafter sometimes simply referred to as “strip”) is manufactured. As a method for producing the ribbon, a liquid quenching method may be mentioned. Examples of the liquid quenching method include a roll cooling method in which a molten metal having the above-described overall composition is discharged onto the surface of a rotating cooling roll. Examples of the roll cooling method include a single roll method and a twin roll method. Here, although the conditions in the single roll method when the cooling roll is made of copper or a copper alloy are illustrated, the present invention is not limited to this.

  The nozzle diameter may typically be 0.3 mm or more, 0.4 mm or more, or 0.5 mm or more, and may be 0.9 mm or less, 0.8 mm or less, or 0.7 mm or less.

Discharge pressure of the molten metal is typically, 0.1kg ^/ cm 2 (10kPa) or more, 0.2kg ^/ cm 2 (20kPa) or more, or 0.3 kg ^/ cm may be at 2 (29 kPa) or more. On the other hand, the discharge pressure of the molten metal may typically be 0.9 kg / cm ² (88 kPa) or less, 0.8 kg / cm ² (78 kPa) or less, or 0.7 kg / cm ² (68 kPa) or less. .

  The peripheral speed of the cooling roll may typically be 20 m / s or more, 21 m / s or more, 22 m / s or more, or 23 m / s or more, 50 m / s or less, 30 m / s or less, 29 m / s. Hereinafter, it may be 28 m / s or less, or 27 m / s or less.

  The molten metal discharge temperature is typically 1300 ° C or higher, 1340 ° C or higher, or 1380 ° C or higher, and may be 1600 ° C or lower, 1560 ° C or lower, or 1520 ° C or lower.

  The ribbon thus produced may be used as a rare earth magnet precursor. Alternatively, the ribbon may be pulverized to produce a powder, and this powder may be used as a rare earth magnet precursor. The powder also includes flakes obtained by cutting a ribbon. Alternatively, the powder may be compacted to produce a green compact, and the green compact may be subjected to liquid phase sintering to produce an isotropic bulk, and the isotropic bulk may be used as a rare earth magnet precursor. Good. The isotropic bulk starting material may be a compact produced by direct compression without crushing the ribbon. Such a compact is also included in the green compact. The above-mentioned powder is compacted while being magnetically oriented to produce a green compact, and this is subjected to liquid phase sintering to produce an anisotropic bulk, and this anisotropic bulk is used as a rare earth magnet precursor. Also good. Alternatively, the above-described isotropic bulk may be hot hard processed to produce an anisotropic bulk, and this anisotropic bulk may be used as a rare earth magnet precursor. In addition, the size of the above-mentioned powder may be 0.1 μm or more, 10 μm or more, or 50 μm or more in the maximum length, and may be 1000 μm or less, 500 μm or less, 250 μm or less, or 100 μm or less. The maximum length means that the maximum length of individual particles is within the above-described range for 80% or more of all particles.

  The liquid phase sintering method may be a conventional method, and examples thereof include a spark plasma sintering (SPS) method, a hot press using high frequency heating, and a hot press using condensing heating. These methods are preferable in that the temperature of the green compact can be rapidly increased to a desired temperature, so that the crystal grains can be prevented from becoming coarse before the green compact reaches the desired temperature.

  The sintering temperature may be appropriately selected depending on the composition and size of the powder constituting the green compact, and is preferably 550 to 800 ° C. If the sintering temperature is 550 ° C. or higher, the green compact can be sintered in a relatively short time. The sintering temperature is more preferably 580 ° C. or higher. On the other hand, if the sintering temperature is 800 ° C. or lower, the crystal grains will not be coarsened during sintering. The sintering temperature is more preferably 750 ° C. or lower.

  The sintering time may be appropriately determined according to the mass of the green compact. The sintering time may be 2 minutes or more, 5 minutes or more, or 15 minutes, and may be 120 minutes or less, 60 minutes or less, or 30 minutes or less.

  During sintering, in order to prevent the green compact from being deformed due to expansion, it is preferable to pressurize the lid of the mold containing the green compact at 100 to 500 MPa. If the applied pressure is 100 MPa or more, the expansion force can be countered. From the viewpoint of combating the expansion force, the applied pressure is more preferably 200 MPa or more, and even more preferably 300 MPa or more. On the other hand, if the applied pressure is 500 MPa or less, the compact or the green compact is not excessively plastically deformed during sintering. From the viewpoint of avoiding excessive plastic deformation, the applied pressure is more preferably 450 MPa or less.

  The atmosphere during sintering is preferably an inert gas atmosphere or a vacuum in order to prevent oxidation of the green compact. The inert gas atmosphere includes a nitrogen gas atmosphere.

  Next, hot strong processing will be described.

  Hot hot working is to compress the above-mentioned isotropic bulk at 700 to 1000 ° C. at a working rate of 30% or more. By hot hot processing, the easy axis of magnetization is oriented, and high anisotropy can be imparted to the isotropic bulk. A representative isotropic bulk is a sintered body after liquid phase sintering. In the following, a sintered body will be described as an example, but the present invention is not limited to this.

  If the temperature of the strong hot working is 700 ° C. or higher, the sintered body is softened and the sintered body can be compressed relatively easily. As a result, the easy magnetization axis is oriented, and high anisotropy can be imparted to the sintered body. From this point of view, the temperature of hot hot working is preferably 800 ° C. or higher.

  On the other hand, if the temperature of hot hot working is 1000 ° C. or less, the crystal grains are not coarsened and the magnetic properties are not deteriorated. Further, the sintered body is excessively softened, and the sintered body is not damaged when compressing and deforming the sintered body. From these viewpoints, the temperature of hot hot working is preferably 900 ° C. or lower.

The processing rate at the time of hot strong processing is defined as follows.
Processing rate (%) =
(Compression direction thickness before compression-Compression direction thickness after compression) / (Compression direction thickness before compression) × 100

  About a processing rate, 30 to 90% is preferable. If the processing rate is 30% or more, the orientation effect of the easy axis described above can be obtained. From the viewpoint of the orientation effect, the processing rate is more preferably 50% or more, 70% or more, or 75% or more. On the other hand, when the processing rate is 90% or less, the sintered body is rarely damaged. From the viewpoint of preventing damage to the sintered body, the processing rate is more preferably 85% or less.

  Examples of the hot hot working method include hot upsetting and hot backward extrusion. These methods can be selected as appropriate.

^(R 2 -Cu-Fe-Ga-based alloy)
The R ² —Cu—Fe—Ga alloy is a penetrating material. R ² is a rare earth element, and R ² may be the same as or different from R ¹ . In this specification, unless otherwise specified, rare earth elements are Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. 17 elements.

The composition of the R ² -Cu-Fe-Ga-based alloy ^is represented by _{R 2 100-p-q-} r Cu p Fe q Ga r. Here, the value of p, q, and r is atomic%, for example, it is preferable that p is 1-50, q is 1-50, r is 1-30. Furthermore, it is more preferable that p is 1 to 10, q is 5 to 25, and r is 10 to 30.

If the value of p is 1 or more, that is, if the Cu content is 1 atomic% or more, the R ¹ -TB main phases are easily magnetically separated. From the viewpoint of magnetically separating the main phases of the R ¹ -TB system, the value of p is more preferably 2 or more, and even more preferably 3 or more. On the other hand, if the value of p is 10 or less, that is, if the Cu content is 10 atomic% or less, the non-magnetic elements in the rare earth magnet after permeation are unlikely to be excessive, and as a result, it is easy to suppress a decrease in magnetization. . From the viewpoint of suppressing a decrease in magnetization, the value of p is more preferably 8 or less, and even more preferably 6 or less.

If the value of q is 5 or more, that is, if the Fe content is 5 atomic% or more, it is easy to suppress the diffusion of Fe from the R ¹ -T-B system main phase to the grain boundary phase. From the viewpoint of suppressing the diffusion of Fe from the R ¹ -TB system main phase to the grain boundary phase, the value of q is more preferably 7 or more, and even more preferably 9 or more. On the other hand, if the value of q is 25 or less, that is, if the Fe content is 25 atomic% or less, it is difficult to inhibit magnetic separation between the main phases of the R ¹ -TB system. From the viewpoint of reducing the inhibition of magnetic partitioning between the main phases of the R ¹ -TB system, the value of q is more preferably 20 or less, and even more preferably 18 or less.

If the value of r is 10 or more, that is, if the Ga content is 10 atomic% or more, most of the grain boundary phase is likely to be in the liquid phase during the heat treatment described later. And in the process of cooling the grain boundary phase, most of which is a liquid phase, the (R ¹ , R ² ) —Fe—Ga phase is likely to be generated in the grain boundary phase. And in the grain boundary phase, in the portion other than the (R ¹ , R ² ) —Fe—Ga phase, the Fe concentration is reduced, and the separation between the main phases of the R ¹ —TB system is improved. . From the viewpoint of making most of the grain boundary phases into a liquid phase during the heat treatment, the value of r is more preferably 12 or more, and even more preferably 14 or more. On the other hand, if the value of r is 30 or less, that is, if the Ga content is 30 atomic% or less, the non-magnetic elements in the rare earth magnet after permeation are unlikely to be excessive, and as a result, it is easy to suppress a decrease in magnetization. . From the viewpoint of suppressing the decrease in magnetization, the value of r is more preferably 28 or less, and even more preferably 26 or less.

The content of R ² is the balance of Cu, Fe, and Ga. When the content of R ² is 50 atomic% or ^more, it reduces the melting point of the R 2 -Cu-Fe-Ga-based ^alloy, which makes it easy to penetrate R 2 -Cu-Fe-Ga-based alloy rare earth magnet precursor. From the viewpoint of easy penetration, the content of R ² is more preferably 55 atomic% or more, and even more preferably 60 atomic% or more. On the other hand, if the content of R ² is 84 atom% or less, it is easy to obtain the effects of Cu, Fe, and Ga described above. From this viewpoint, the content of R ² is more preferably 80 atomic percent or less, and even more preferably 70 atomic percent or less.

This alloy may contain a small amount of elements other than R ² , Cu, Fe, and Ga as long as the effectiveness of the R ² —Cu—Fe—Ga alloy is not impaired. R ^2, Cu, Fe, and the allowable amount of elements other than ^Ga, is represented by _{R 2 100-p-q-} r Cu p Fe q Ga r purity (% by mass), the purity, at least 90% Preferably, 95% or more is even more preferable. Elements other than R ² , Cu, Fe, and Ga contain unavoidable impurities. Inevitable impurities refer to impurities such as impurities contained in the raw material that cannot be avoided, or incurring a significant increase in manufacturing cost.

(Method for producing R ² —Cu—Fe—Ga alloy)
As long as the composition of the R ² —Cu—Fe—Ga based alloy satisfies the above range, the method for producing the R ² —Cu—Fe—Ga based alloy is not particularly limited. You may comply with the manufacturing method of a rare earth magnet precursor.

(Mode of contact between rare earth magnet precursor and R ² —Cu—Fe—Ga alloy)
If the R ² —Cu—Fe—Ga based alloy penetrates into the rare earth magnet precursor in the heat treatment described later, the contact aspect between the R ² —Cu—Fe—Ga based alloy and the rare earth magnet precursor is particularly It is not limited. It is not necessary that all surfaces of the rare earth magnet precursor are in contact with all surfaces of the R ² —Cu—Fe—Ga alloy. It suffices that at least a part of the rare earth magnet precursor is in contact with at least a part of the R ² —Cu—Fe—Ga alloy. However, when the contact area between the rare earth magnet precursor and the R ² —Cu—Fe—Ga alloy is larger, the R ² —Cu—Fe—Ga alloy is more likely to penetrate into the rare earth magnet precursor.

As described above, the rare earth magnet precursor may have any form such as powder, ribbon, isotropic bulk, or anisotropic bulk. Depending on the form of the rare earth magnet precursor, the form of the R ² —Cu—Fe—Ga alloy may take any form such as powder, ribbon, green compact, and the like. The powder includes a thin piece obtained by cutting a ribbon.

As an example of the contact mode, as an example, at least a part of the R ² —Cu—Fe—Ga alloy having a ribbon shape is brought into contact with at least a part of the rare earth magnet precursor having an anisotropic bulk form. To obtain a contact body. In this way, the anisotropic bulk rare earth magnet ^precursor, from the contact surface between the ribbons R 2 -Cu-Fe-Ga-based ^alloy, R 2 -Cu-Fe-Ga alloy to penetrate.

As another example, both surfaces of a ribbon of rare earth magnet precursor are sandwiched between two ribbons of R ² —Cu—Fe—Ga alloy, and each is brought into contact with each other to obtain a contact body. It is done. In this way, the R ² —Cu—Fe—Ga alloy penetrates from both surfaces of the ribbon of the rare earth magnet precursor.

As another example, a rare earth magnet precursor powder and an R ² —Cu—Fe—Ga alloy powder are mixed and brought into contact with each other to obtain a contact body. In this way, the R ² —Cu—Fe—Ga alloy penetrates from the outer periphery of the particles of the R ¹ —T—B rare earth magnet.

<Heat treatment process>
By heat-treating the above-described contact body, the R ² —Cu—Fe—Ga-based alloy penetrates into the rare earth magnet precursor. The R ² —Cu—Fe—Ga-based alloy penetrates into the interior of the rare earth magnet precursor mainly through the grain boundary phase of the rare earth magnet precursor.

During the heat treatment, the heat treatment temperature is set so that most of the grain boundary phase of the rare earth magnet precursor infiltrated with the R ² —Cu—Fe—Ga alloy is in the liquid phase. It is preferable that 80% by volume or more of the grain boundary phase of the rare earth magnet precursor infiltrated with the R ² —Cu—Fe—Ga alloy during the heat treatment becomes a liquid phase. In this way, the cooling process of the heat treatment, the grain boundary ^phase, is considered to R 2 -Fe-Ga phase is ^produced, in the portion other than the R 2 -Fe-Ga phase, the concentration of Fe decreases , R ¹ -T-B system main phases are further separated. As a result, the coercive force is further improved. On the other hand, all of the grain boundary phases of the rare earth magnet precursor infiltrated with the R ² —Cu—Fe—Ga alloy during the heat treatment may be in a liquid phase.

Temperature R ² -Cu-Fe-Ga-based alloy to penetrate into the rare-earth magnet precursor ^is not limited to a temperature above the melting point of the R 2 -Cu-Fe-Ga-based alloy. When a part of the R ² —Cu—Fe—Ga based alloy penetrates into the rare earth magnet precursor and the composition of the R ² —Cu—Fe—Ga based alloy varies, R ² —Cu—Fe—Ga The melting point of the alloy decreases. Then, penetration of the R ² —Cu—Fe—Ga alloy into the rare earth magnet precursor proceeds rapidly. Therefore, in the initial stage of the heat treatment, only solid phase diffusion may occur between the rare earth magnet precursor and the R ² —Cu—Fe—Ga alloy.

Temperature solid phase diffusion occurs between the rare-earth magnet precursor and ^R 2 -Cu-Fe-Ga-based alloy, depending on the state of contact between the rare-earth magnet precursor and ^R 2 -Cu-Fe-Ga-based alloy To do. The heat treatment temperature may be a temperature at which solid phase diffusion occurs between the rare earth magnet precursor and the R ² —Cu—Fe—Ga alloy. The heat treatment temperature is preferably 5 ° C. or 10 ° C. lower than the temperature at which all the grain boundary phases during the heat treatment become a liquid phase. This facilitates maintenance of the shape of the contact body during the heat treatment. The heat treatment temperature refers to the holding temperature from the completion of the temperature rise to the start of cooling. The heat treatment temperature (holding temperature) may not be constant. For example, the heat treatment temperature (holding temperature) may be lowered from the middle in anticipation of a decrease in the melting point of the R ² —Cu—Fe—Ga alloy described above.

As heat processing temperature, it may be 500 degreeC or more, 525 degreeC or more, 550 degreeC or more, or 575 degreeC or more, for example, 700 degreeC or less, 675 degreeC or less, 650 degreeC or less, or 625 degreeC. Thereby, the R ² —Cu—Fe—Ga alloy penetrates into the rare earth magnet precursor.

As long as the rare earth magnet precursor and the R ² —Cu—Fe—Ga alloy are not altered, the rate of temperature rise is not particularly limited. The heating rate may be, for example, 20 ° C./min or more, 40 ° C./min or more, 60 ° C./min or more, or 80 ° C./min or more, 180 ° C./min or less, 160 ° C./min or less, 140 ° C. / Min or less, or 120 ° C./min or less.

After the R ² —Cu—Fe—Ga based alloy penetrates into the rare earth magnet precursor, it is preferable to set the cooling rate so that the R ¹ —T—B based main phase does not become coarse. The cooling rate may be, for example, 20 ° C./min or more, 40 ° C./min or more, 60 ° C./min or more, or 80 ° C./min or more, 180 ° C./min or less, 160 ° C./min or less, 140 ° C./min. It may be less than or equal to 120 minutes or 120 ° C./minute.

The heat treatment time may be appropriately determined depending on the amount and form of the rare earth magnet precursor and the R ² —Cu—Fe—Ga alloy. The heat treatment time may be, for example, 30 minutes or more, 40 minutes or more, or 50 minutes or more, and may be 120 minutes or less, 100 minutes or less, or 80 minutes or less. The heat treatment time is the time from the completion of the temperature rise to the start of cooling.

The heat treatment atmosphere is preferably an inert gas atmosphere or a vacuum in order to prevent oxidation of the rare earth magnet precursor and the R ² —Cu—Fe—Ga alloy. The inert gas atmosphere preferably does not include a nitrogen gas atmosphere.

  Hereinafter, the method for producing a rare earth magnet of the present disclosure will be described more specifically with reference to examples and comparative examples. In addition, the manufacturing method of the rare earth magnet of this indication is not limited to the conditions used in the following Examples and Comparative Examples.

(Sample preparation)
Using a liquid quenching apparatus (single roll method), a quenching ribbon used for the rare earth magnet precursor was produced. The composition of the raw material was Nd _13.2 Fe _76.0 Co _5.6 B _4.7 Ga _0.5 . This raw material was melted at high frequency, and the molten metal was discharged from the quartz nozzle toward the outer peripheral surface of the copper cooling roll. The nozzle diameter was 0.6 mm, the discharge pressure was 40 kPa, the molten metal temperature was 1400 ° C., and the peripheral speed of the cooling roll was 25 m / s.

  The ribbon was coarsely pulverized into powder (flakes) having a maximum length of 0.1 to 1000 μm. This maximum length means that the maximum length of individual particles is in the range of 0.1 to 1000 μm for 50% or more of all particles.

  This powder was compacted to obtain a compact. Next, the green compact was sintered to obtain a sintered body. The sintering temperature was 600 ° C., the sintering pressure was 400 MPa, and the sintering time was 5 minutes.

  This sintered body was further subjected to hot strong processing. The hot hot processing temperature was 780 ° C., and the processing rate (rolling rate) was 75%.

The anisotropic bulk thus obtained was processed into a size of 4 mm × 4 mm × 2 mm to obtain a rare earth magnet precursor. Six rare earth magnet precursors were prepared, and the magnetic properties of each were measured. The measurement method was the same as the evaluation method described later. Measurements, the coercive force _{H cj} is 13.9～14.1KOe, remanence _{B r} was 1.502～1.507T.

The composition of the raw _{materials, Nd 62 Fe 14 Ga 20 Cu} 4, and except that the _Nd 80 _Ga 15 Cu _5, in the same way as when preparing a rare earth magnet precursor, to produce a thin strip used in the infiltration material.

The rare-earth magnet _precursor, by contacting the ribbon having a composition of Nd ₆₂ Fe _{14 Ga} 20 Cu ₄ (the infiltrating material), to produce a contact body 1-3. Also, the rare-earth magnet _precursor, by contacting the ribbon having a composition of Nd _{80 Ga} 15 Cu ₅ (the infiltrating material), to produce a contact body 4-6.

  Each of the contact bodies 1 to 6 was wrapped in tantalum foil and subjected to heat treatment. The heat treatment conditions were as follows. The temperature was raised from room temperature to 600 ° C. in 30 minutes, held at 600 for 1 hour, and then cooled to room temperature at a rate of 100 ° C./min.

(Evaluation)
About each of the contact bodies 1-6 which heat-processed, after removing the osmotic material which remained on the surface by grinding | polishing, the mass increase rate and the volume increase rate with respect to the rare earth magnet precursor were measured. And about the heat-treated contact bodies 1-3, the sample whose mass change is 5 mass%, 13 mass%, and 20 mass% was made into the sample of Example 1, 2, and 3, respectively. Moreover, about the heat-treated contact bodies 4-6, the sample whose mass change is 15 mass%, 20 mass%, and 35 mass% was made into the sample of Comparative Examples 1, 2, and 3, respectively.

  About each sample of Examples 1-3 and Comparative Examples 4-6, the magnetic characteristic was measured using SQUID-VSM. Moreover, about each sample of Example 3 and Comparative Example 3, structure | tissue observation was performed using the scanning electron microscope.

  The measurement results are shown in Tables 1 and 2. Further, from the contents shown in Tables 1 and 2, the relationship between the coercive force and the magnetization of the samples of Examples 1 to 3 and Comparative Examples 1 to 3 is summarized in FIG. For reference, FIG. 2 shows a hysteresis curve for the samples of Examples 1 to 3, and FIG. 3 shows a hysteresis curve for the samples of Comparative Examples 1 to 3. FIG. 2 and FIG. 3 also show hysteresis curves of the rare earth magnet precursor before penetrating the penetrating material. Further, FIG. 4 shows a cross-sectional structure of the sample of Example 3, and FIG. 5 shows a cross-sectional structure of the sample of Comparative Example 3.

  As can be seen from FIG. 1 that summarizes Tables 1 and 2, it was confirmed that the sample of the example had higher magnetization than the sample of the comparative example if the coercive force was comparable. For example, although the sample of Example 3 and the sample of Comparative Example 3 both have the same coercive force, the sample of Example 3 is more magnetized than the sample of Comparative Example 3. high.

Furthermore, the following could be confirmed from FIGS. 4 and 5, on the screen, the black structure is the main phase of the R ¹ -T-B system, and the white structure is the grain boundary phase. When the area ratio of the grain boundary phase is calculated from the images shown in FIGS. 4 and 5, the area ratio of the grain boundary phase in the sample of Example 3 shown in FIG. 4 is 18%, and the comparison shown in FIG. The area ratio of the grain boundary phase in the sample of Example 3 was 35%.

From this, it was confirmed that the sample of Example 3 was able to suppress the decrease in the volume fraction of the main phase of the R ¹ -TB system than the sample of Comparative Example 3.

  From the above results, the effect of the method for producing a rare earth magnet of the present disclosure was confirmed.

Claims (1)

A main phase of R ¹ -T-B system (R ¹ is a rare earth element, T is one or more selected from Fe and Co), and an R ¹ rich grain boundary phase present around the main phase. An R ² —Cu—Fe—Ga alloy (R ² is a rare earth element) is contacted with the rare earth magnet precursor provided to obtain a contact body; and
Heat treating the contact body to infiltrate the R ² —Cu—Fe—Ga alloy into the rare earth magnet precursor;
A method for producing a rare earth magnet, comprising: