JP5288276B2 - Manufacturing method of RTB-based permanent magnet - Google Patents

Description

  The present invention relates to a method for producing an R-T-B system permanent magnet, and more particularly to a method for producing a HDDR magnet having improved magnetic properties by mixing Zn powder with a R-T-B system alloy powder and subjecting it to HDDR treatment.

R-T-B permanent magnets typical as high-performance permanent magnets (R is a rare earth element containing Nd and / or Pr, T is Fe or a part of Fe substituted with Co and / or Ni, B is Boron) has a structure including an R ₂ T ₁₄ B phase, which is a ternary tetragonal compound, as a main phase, and exhibits excellent magnetic properties.

An HDDR (Hydrogenation-Deposition-Decomposition-Recombination) processing method is known as one of the methods for producing an R-T-B permanent magnet. The HDDR treatment method means a process of sequentially performing hydrogenation and disproportionation, dehydrogenation and recombination, and is a magnetic powder for anisotropic bonded magnets. It is adopted as a manufacturing method. According to the known HDDR treatment, an R-T-B alloy ingot or powder is maintained at a temperature of 500 ° C. to 1000 ° C. in an H ₂ gas atmosphere or a mixed atmosphere of an H ₂ gas and an inert gas. It said after ingot or powder in a hydrogen is occluded, such as H ₂ pressure is 13Pa or less of vacuum atmosphere, or H ₂ partial pressure is dehydrogenated at a temperature 500 ° C. to 1000 ° C. until the following inactive atmosphere 13Pa by Then, it is cooled.

In the above treatment, typically, the following reaction proceeds. That is, hydrogenation and disproportionation reactions (both are collectively referred to as “HD reaction” by heat treatment for occluding hydrogen). Examples of reaction formulas: Nd ₂ Fe ₁₄ B + 2H ₂ → 2NdH ₂ + 12Fe + Fe ₂ B) It progresses and a fine structure is formed. Next, by performing heat treatment for dehydrogenation, dehydrogenation and recombination reaction (both are referred to as “DR reaction”. Example of reaction formula: 2NdH ₂ + 12Fe + Fe ₂ B → Nd ₂ Fe ₁₄ B + 2H ₂ ) occur. An alloy containing a fine R ₂ T ₁₄ B crystal phase is obtained. The HD reaction and the DR reaction are collectively referred to as an HDDR reaction, the heat treatment for causing the HD reaction is called “HD treatment”, and the heat treatment for causing the DR reaction is called “DR treatment”.

The R-T-B magnet powder produced by the HDDR process has a large coercive force and exhibits magnetic anisotropy. The reason for having such a property is that the metallographic structure is substantially as fine as 0.1 μm to 1 μm, and a crystal with easy magnetization axes aligned in one direction by appropriately selecting reaction conditions and composition. It is because it becomes the aggregate of. More specifically, since the grain size of the ultrafine crystal obtained by the HDDR treatment is close to the single domain critical grain size of the tetragonal R ₂ T ₁₄ B-based compound, it exhibits a high coercive force. An aggregate of very fine crystals of this tetragonal R ₂ T ₁₄ B-based compound is called a “recrystallized texture”.

  Magnet powder (hereinafter referred to as “HDDR magnetic powder”) produced by the HDDR process is usually mixed with a binder resin (binder) to form a mixture (compound), and then compression molding or injection molding in a magnetic field. Thus, an anisotropic bonded magnet is formed. Further, it has been studied and reported that HDDR magnetic powder is densified by hot compression molding and used as a bulk magnet.

However, R-T-B permanent magnets containing HDDR magnetic powder are not sufficiently high in heat resistance and are difficult to use because they are likely to cause irreversible demagnetization in applications exposed to high temperatures such as automobile applications. . In order to improve the heat resistance, it is necessary to improve the coercive force, and several methods for improving the coercive force have been proposed so far.
In Patent Document 1, the HDDR treatment is performed on a mixed powder obtained by blending a rare earth hydride powder, a ferroboron powder, and an iron powder, thereby simultaneously generating the R ₂ Fe ₁₄ B phase and the fine crystal structure. And the effect of improving the coercive force by adding Dy, Tb, Pr to the rare earth hydride powder and adding Co, C, Al, Ga, Si, Cr, Ti, V, Nb to the iron powder. It is disclosed that there is.
Patent Document 2 discloses HDDR as a method for adding Dy, Tb, etc., in which the composition is difficult to control due to the large vapor pressure when added during the production of an alloy ingot, and as a result, the coercive force is hardly improved. Having a coating layer of Nd, Dy, Tb, Pr or an alloy containing them on the surface of the magnetic powder, specifically, HDDR magnetic powder and a hydride or alloy powder of these elements are mixed and heat-treated, It is disclosed that the coercive force is improved by diffusing the magnetic powder.
Patent Document 3 discloses a method of performing a dehydrogenation step after diffusion heat treatment by mixing RFeB-based material hydride powder, simple substance such as Dy, Tb, Nd, and Pr, alloy, compound, or hydride powder thereof. In addition, the RFeB-based material contains at least one of Ti, V, Zr, Ni, Cu, Al, Si, Cr, Mn, Zn, Mo, Hf, W, Ta, and Sn. It is disclosed that coercive force and squareness can be improved. Further, Patent Document 4 discloses Dy, Tb, Ho, Er, Tm, Gd, Nd, Sm, Pr, Ce, La, Y, Zr, Cr, Mo, V, High magnetic properties, corrosion resistance, and weather resistance are improved by attaching at least one metal vapor selected from Ga, Zn, Cu, Mg, Li, Al, Mn, Nb, and Ti to the magnetic powder and heat-treating and diffusing. To be disclosed It is, in particular Dy, discloses that Tb or the like is a magnet of high magnetic properties by diffusing at the grain boundaries of the magnetic powder.
Moreover, in patent document 5, Zn powder is mixed with HDDR magnetic powder, it heats to 300-500 degreeC in a vacuum, Zn which became metal vapor adheres to a magnetic powder, is diffused, a magnetic grain surface, and the grain boundary inside a magnetic powder. Although the coercive force immediately after the treatment is slightly reduced by forming a rust preventive layer in the region along the magnetic field, the corrosion resistance of the magnetic powder is improved, and the residual magnetic flux density B _{r at} 120 ° C. of the bond magnet produced using the magnetic powder is increased. It is disclosed that the temperature coefficient is improved.

  Among the elements used disclosed in these patent documents, Ga, Dy, and Tb are particularly known to have a high coercive force improving effect. However, Ga, Dy, and Tb are expensive, and Dy and Tb are particularly scarce in resources. Therefore, a method for improving the coercive force of HDDR magnetic powder while minimizing the amount of these elements to be used is desired.

JP-A-2-217406 JP 2000-96102 A JP 2002-93610 A JP 2008-69415 A JP 2002-105503 A

  The present invention solves the above-mentioned problems, suppresses the use of expensive or resource-rare elements such as Ga, Dy, Tb, etc. for HDDR magnetic powder, and makes use of elements that do not contain these HD reactions, It aims at improving the coercive force of HDDR magnetic powder by controlling DR reaction.

  As described above, it has been conventionally studied to improve the coercive force by adding various additive elements to the HDDR magnetic powder at various timings. However, as an additive element at that time, Zn has a boiling point as low as 907 ° C. and has a high vapor pressure, so that it is easy to evaporate or sublimate, and it is difficult to adjust the composition by dissolution. Also, there is a problem that Zn is sublimated during HDDR treatment, and addition before HDDR treatment is difficult.

  In Patent Document 4 and Patent Document 5, a study of diffusion heat treatment by attaching a metal vapor of Zn to HDDR magnetic powder is also being conducted. However, in Patent Document 4, Dy and Tb can be expected to greatly improve the coercive force. The coercive force is improved by the mixed metal vapor and the like, and in Patent Document 5, the treatment with the metal vapor of Zn alone is carried out, but the coercive force immediately after the treatment is decreased. In the study by the inventors, the HDDR magnetic powder having the same composition as that of the HDDR magnetic powder used in the prior art (although alloy powder having a rare earth content of 13 atomic% (29 mass%) or less is used) is used. On the other hand, the coercive force did not improve at all even when diffusion vapor heat treatment was performed by attaching metal vapor alone with Zn.

  Therefore, the inventors examined how to add Zn to improve the coercive force. As a result, the powdered Zn was added to the R—T—B alloy powder having a larger amount of rare earth than the conventional one. -By mixing with TB alloy powder and HDDR treatment, the HDDR reaction is controlled, and even if Zn eventually evaporates and sublimates, the coercive force of the HDDR magnetic powder obtained can be improved. I found out.

The manufacturing method of the R-T-B system permanent magnet of the present invention formed as described above is such that the rare earth amount in the composition is more than 29 mass% and not more than 40 mass%, and the B amount is not less than 0.3 mass% and not more than 2 mass%. A step of preparing an RTB-based alloy powder, a step of preparing a Zn-containing powder which is a powder of any metal or alloy containing at least 30 mass% of Zn and not containing Ga, Dy, and Tb; The step of mixing the RTB alloy powder and the Zn-containing powder so that Zn is 0.50 mass% or more and 1.5 mass% or less of the whole to obtain a mixed powder; And obtaining a RTB-based permanent magnet powder.
In a preferred embodiment, the RTB-based permanent magnet powder is hot compression molded to produce a bulk magnet.
In a preferred embodiment, the method includes a step of subjecting the RTB-based permanent magnet powder or the bulk magnet to an aging heat treatment at a temperature of 450 ° C. or higher and 700 ° C. or lower in a vacuum or an inert gas.
In a preferred embodiment, before performing the hot compression molding, the RTB-based permanent magnet powder is molded in a magnetic field to temporarily form a green compact, and the green compact is subjected to hot compression molding. A bulk magnet having magnetic anisotropy is produced.

  According to the present invention, it is possible to provide a high-performance RTB-based permanent magnet with improved coercive force while suppressing the use of expensive and scarce resources such as Ga, Dy, and Tb as much as possible.

It is a flowchart which shows the manufacturing process of the RTB type permanent magnet by this invention. It is a figure which shows the structural example of the apparatus for carrying out hot compression molding of mixed powder.

The method for producing an RTB-based permanent magnet according to the present invention includes an RTB-based alloy powder in which the amount of rare earth in the composition is more than 29 mass% and not more than 40 mass% and the amount of B is not less than 0.3 mass% and not more than 2 mass%. A step of preparing a Zn-containing powder which is a powder of any metal or alloy containing at least 30 mass% of Zn and not containing Ga and heavy rare earth metal, and the RTB-based alloy powder and A step of mixing Zn-containing powder so that Zn is 0.50 mass% or more and 1.5 mass% or less of the whole to obtain a mixed powder, and HDDR treatment of the mixed powder to obtain an R-T-B permanent magnet Obtaining a powder.

  According to the study by the inventors, in the present invention, the amount of Zn in the R-T-B system permanent magnet powder after the HDDR treatment is much smaller than the amount mixed before the HDDR treatment, and is about 1/20. It becomes as follows. Nevertheless, the coercive force of the R-T-B system permanent magnet of the present invention is remarkably improved compared to that in which the mixing amount of Zn powder is not appropriate, the structure of Zn during the HDDR reaction. It is presumed that the coercive force is improved due to the change. Furthermore, the improvement of the coercive force by mixing Zn powder is the same as that of the HDDR magnetic powder used in Patent Documents 1 to 5 (all rare earth content is 13). It has been found that this does not occur unless the amount of rare earth is greater than 29 mass%, which is larger than the amount of rare earth in the composition of an atomic percent (29 mass%) or less alloy powder is used. From this, the rare earth R is also involved in the reaction involving Zn in the HDDR reaction, and when the rare earth amount is 29 mass% or less, R is consumed in the reaction, and the R of the grain boundary It is presumed that the R amount constituting the rich phase is insufficient.

  FIG. 1 is a flowchart showing a manufacturing process of an RTB permanent magnet according to the present invention. Hereinafter, description will be given with reference to FIG.

<RTB alloy powder (raw material powder)>
The RTB-based alloy powder is produced by pulverizing a raw material alloy (starting alloy) by a known method. Hereinafter, each process will be described in detail.

<Starting alloy>
First, an RTB-based alloy (starting alloy) having an R ₂ T ₁₄ B phase (Nd ₂ Fe ₁₄ B type compound phase, hereinafter abbreviated as “R ₂ T ₁₄ B”) as a hard magnetic phase. Prepare an ingot. Here, “R” is a rare earth element and contains Nd and / or Pr at 50 mass% or more. The rare earth element R in this specification may contain yttrium (Y). “T” is a transition metal element in which Fe or a part of Fe is substituted with Co and / or Ni and contains 50 mass% or more of Fe. “B” may be partially substituted with C.
This R-T-B system alloy (starting alloy) contains R ₂ T ₁₄ B phase in a volume ratio of 50% or more. In order to obtain a high residual magnetic flux density _Br , it is preferable that 80% or more of the R ₂ T ₁₄ B phase is included by volume ratio.

Most of the rare earth element R contained in the starting alloy constitutes the R ₂ T ₁₄ B phase, but a part constitutes the R rich phase, R ₂ O ₃ , and other phases. According to the study by the inventors, in the prior art, Zn powder was mixed with HDDR magnetic powder, and the coercive force was not improved even after heat treatment. It was found that a part of R in the starting alloy was consumed for forming the Zn compound, and the amount of R constituting the R-rich phase at the grain boundary was insufficient.
According to the study by the inventors, the amount of the rare earth element R needs to be contained in excess of 29 mass%. When the Zn content is 0.5 mass% or more, the amount of R is preferably 30 mass% or more, and when the Zn content is 1 mass% or more, the amount of R is more preferably 31 mass% or more. The upper limit of R is not particularly limited, considering the decrease in corrosion resistance and residual magnetic flux density _{B r,} is preferably not more than 40 mass%, more preferably at most 35 mass%. By setting a part of R of the starting alloy (about 5 mass% of the whole) to Dy and / or Tb, it is possible to improve the coercive force. Further, from the viewpoint of minimizing the amount of rare resources Dy and Tb used, the amount is preferably 2 mass% or less, and more preferably 1 mass% or less. Substitution of Dy and Tb is possible by Zn mixed later.

If the amount of B in the R-T-B system permanent magnet is too small, a phase that lowers the magnetic properties such as the R ₂ T ₁₇ phase will precipitate, and if it is too large, a nonmagnetic phase such as the B-rich phase will precipitate and residual magnetic flux density B _{Since r} decreases, the total alloy content is preferably 0.5 mass% or more and 2 mass% or less, more preferably 0.7 mass% or more and 1.5 mass% or less, and further preferably 0.9 mass% or more and 1.2 mass% or less. .

T occupies the remainder. As described above, T is a transition metal element in which Fe or a part of Fe is substituted with Co and / or Ni and contains 50% or more of Fe. A part of T may be Co and / or Ni for the purpose of increasing the Curie point and enhancing the corrosion resistance. From the viewpoint of increasing the saturation magnetization of the R ₂ T ₁₄ B phase, it is desirable to select Co rather than Ni. Further, the total amount of Co with respect to the entire alloy is preferably 20% by mass or less, and more preferably 8% by mass or less from the viewpoint of cost and the like. High magnetic properties can be obtained even when no Co is contained, but more stable magnetic properties can be obtained when containing 1 mass% or more of Co.

  In order to obtain effects such as improvement of magnetic properties, elements such as Al, Ti, V, Cr, Ga, Nb, Mo, In, Sn, Hf, Ta, W, Cu, Si, and Zr are appropriately added to the raw material alloy. Also good. However, since an increase in the amount of addition causes a decrease in saturation magnetization in particular, the total amount is preferably 10 mass% or less. In addition, since V, Ga, In, Hf, and Ta are expensive, 1 mass% or less is preferable from the viewpoint of cost.

The starting alloy is produced by a known method such as a book mold method, a centrifugal casting method, or a strip casting method. However, the HDDR magnetic powder needs to have an easy magnetization axis in one direction in each particle of the raw material powder in order that each particle of the magnet powder exhibits excellent magnetic anisotropy after the HDDR treatment. For this reason, the starting alloy has a structure in which the average size of the region in which the crystal orientations of the Nd ₂ Fe ₁₄ B type crystal phase are aligned in the same direction before the pulverization is larger than the average particle size of the pulverized powder particles It is necessary to select a manufacturing method as appropriate. When using a raw material alloy obtained by coarsening an Nd ₂ Fe ₁₄ B type compound by a book mold method or a centrifugal casting method, it is difficult to completely remove α-Fe, which is the primary crystal of casting, and the structure of the raw material alloy is homogeneous. Heat treatment may be applied to the raw material alloy before pulverization for the purpose of making it easier. Such heat treatment can be performed in a vacuum or inert atmosphere, typically at a temperature of 1000 ° C. or higher.

<Crushing>
Next, a raw material powder is produced by pulverizing the raw material alloy (starting alloy) by a known method. In the present embodiment, first, the starting alloy is pulverized using a mechanical pulverization method such as a jaw crusher or a known hydrogen pulverization method to produce pulverized powder having a size of about 50 μm to 1000 μm.

<Zn-containing powder>
The Zn-containing powder is a powder of any metal or alloy that contains at least 30 mass% of Zn and does not contain Ga, Dy, and Tb. Further, oxides and the like may be partially contained due to handling problems. However, from the viewpoint of lowering the magnetic properties due to the inclusion of impurities and lowering the diffusion efficiency due to the increase in melting point when alloyed, powders other than impurities are preferably composed of Zn. The particle size of the Zn-containing powder is preferably 100 μm or less, and more preferably 10 μm or less from the viewpoint of dispersibility. Moreover, since such fine Zn powder is active, it is preferable to handle it in an inert gas.

<Mixed>
R-T-B alloy powder and Zn-containing powder are mixed using a known technique such as a mixer, so that Zn is 0.50 mass% to 1.5 mass% of the whole, and the mixed powder is mixed. Make it. By mixing Zn in an amount of 0.50 mass% or more, the effect of improving the coercive force is exhibited. If the amount of Zn mixed exceeds 1.5 mass%, the coercive force decreases. In order to suppress oxidation of the alloy powder or the Zn-containing powder, the mixing is preferably performed in an inert gas.

<HDDR processing>
Next, the HDDR process is performed with respect to the mixed powder obtained by the said grinding | pulverization process. The temperature raising step for the HD reaction is performed in a hydrogen gas atmosphere with a hydrogen partial pressure of 10 kPa or more and 500 kPa or less, or a mixed atmosphere of hydrogen gas and an inert gas (such as Ar or He), an inert gas atmosphere, or in a vacuum. . When the temperature raising step is performed in an inert gas atmosphere or in a vacuum, it is possible to suppress a decrease in magnetic characteristics due to difficulty in controlling the reaction rate at the time of temperature raising.

  The HD treatment is performed at 650 ° C. or more and less than 1000 ° C. in a hydrogen gas atmosphere having a hydrogen partial pressure of 10 kPa or more and 500 kPa or less or in a mixed atmosphere of hydrogen gas and inert gas (Ar, He, etc.). The hydrogen partial pressure during HD processing is more preferably 20 kPa or more and 200 kPa or less. The treatment temperature is more preferably 700 ° C. or higher and 900 ° C. or lower. The time required for HD processing is 15 minutes or more and 10 hours or less, and is typically set in a range of 30 minutes or more and 5 hours or less. When T in the R-T-B alloy is 3 mass% or less with respect to the composition of the entire alloy, the hydrogen partial pressure during temperature rise and / or HD treatment is 5 kPa or more and 100 kPa or less. Preferably, a decrease in anisotropy in the HDDR process can be suppressed by setting the pressure to 10 kPa or more and 50 kPa or less.

DR processing is performed after HD processing. The HD process and the DR process can be performed continuously in the same apparatus, but can also be performed discontinuously using separate apparatuses.
The DR treatment is performed at 650 ° C. or higher and lower than 1000 ° C. in a vacuum or an inert gas atmosphere. The treatment time is usually 15 minutes or more and 10 hours or less, and is typically set in a range of 30 minutes or more and 2 hours or less. Needless to say, the atmosphere can be controlled stepwise (for example, the hydrogen partial pressure can be lowered stepwise or the reduced pressure can be lowered stepwise). In this way, an R-T-B permanent magnet powder is obtained.

  The R-T-B permanent magnet powder after the HDDR treatment is subjected to an aging heat treatment at a temperature of 450 ° C. to 700 ° C. in vacuum or in an inert gas for the purpose of further improving the magnetic properties. May be.

<Hot compression molding>
The RTB-based permanent magnet powder can be used as a magnetic powder for a bonded magnet by performing an aging heat treatment as necessary as described above, but by using hot compression molding such as a hot press method. Then, it can be densified to obtain a bulk magnet.

  An example of a specific embodiment will be shown below for full condensation by hot compression molding. Heat compression for the mixed powder can be performed using a known heat compression technique. For example, it is possible to perform heat compression treatment such as hot pressing, SPS (spark plasma sintering) method, HIP, hot rolling. Especially, the hot press and SPS method which are easy to obtain a desired shape can be used suitably. In this embodiment, hot pressing is performed according to the following procedure.

First, a green compact is temporarily formed using the above R-T-B system permanent magnet powder. The step of temporarily forming the green compact is preferably performed in a magnetic field (such as a static magnetic field or a pulsed magnetic field) of 0.4 MA / m to 16 MA / m by applying a pressure of 10 MPa to 200 MPa. The temporary molding can be performed by a known powder press apparatus. Compact density when taken out from the powder press machine (preformed body density) ^is 3.5g / cm ³ ~5.2g / cm 3 order.

  The temporary forming step may be performed without applying a magnetic field. Moreover, it is not necessary to perform a temporary forming process. When the magnetic field orientation is not performed, or when the heat compression treatment is performed while the powder is used without performing the provisional molding step, an isotropic fluence magnet is finally obtained. However, in order to obtain higher magnetic characteristics, it is preferable to perform a temporary forming step while performing magnetic field orientation, and finally obtain an anisotropic fluence magnet.

  In this embodiment, a hot press apparatus having the configuration shown in FIG. 2 is used. This apparatus includes a die (die) 27 having an opening in the center, an upper punch 28a and a lower punch 28b for pressurizing HDDR magnetic powder or green compact, and a drive unit 30a for raising and lowering these punches 28a and 28b. , 30b.

The HDDR magnetic powder or green compact produced by the method described above is loaded into the mold 27 shown in FIG. At this time, it is preferable to perform loading so that the magnetic field direction (orientation direction) and the pressing direction coincide. The mold 27 and the punches 28a and 28b are formed of a material that can withstand the heating temperature and the applied pressure in the atmosphere gas to be used. As such a material, carbon and cemented carbide are preferable. In the case of a green compact, anisotropy can be increased by setting the outer dimension to be smaller than the opening dimension of the mold 27. Next, the mold 27 loaded with HDDR magnetic powder or green compact is set in a hot press apparatus. The hot press apparatus preferably includes a chamber 26 that can be controlled to an inert gas atmosphere or a vacuum of 10 ⁻¹ Torr or more. In the chamber 26, for example, a heating device such as a carbon heater by resistance heating or a coil for high-frequency heating, and a cylinder for pressurizing and compressing the sample are provided.

  After filling the chamber 26 with a vacuum or an inert gas atmosphere, the mold 27 is heated by a heating device (not shown), and the temperature of the HDDR magnetic powder or green compact loaded in the mold 27 is set to 600 ° C to 900 ° C. Increase. At this time, the HDDR magnetic powder or green compact is pressurized with a pressure P of 20 MPa to 1000 MPa. The pressurization of the HDDR magnetic powder or the green compact is preferably started after the temperature of the mold 27 reaches a set level. While maintaining pressure at a temperature of 450 ° C. or higher and lower than 900 ° C. for 1 minute or longer, cool. After the magnet fully condensed by heat compression is cooled to a low temperature (about 100 ° C. or less) that does not oxidize due to contact with the atmosphere, the magnet of this embodiment is taken out from the chamber. Thus, the bulk magnet of this embodiment can be obtained from the HDDR magnetic powder.

  The above-described aging heat treatment for the purpose of improving the magnetic properties is preferably performed at the end of all the heat treatment in the magnet manufacturing process. When a bulk magnet is formed, it is preferable to perform aging heat treatment on the bulk magnet. .

  The density of the magnet thus obtained reaches 95% or more of the true density. In addition, according to the present embodiment, in the final crystal phase texture, the crystal grains in which the ratio b / a of the shortest grain size a to the longest grain size b of each crystal grain is less than 2 are 50 of the total crystal grains. It exists by volume% or more. In this respect, the magnet of the present embodiment is greatly different from the conventional anisotropic bulk magnet by hot plastic working described in, for example, Japanese Patent Laid-Open No. 02-39503. In the crystal structure of the magnet by hot plastic working, flat crystal grains in which the ratio b / a between the shortest particle diameter a and the longest particle diameter b exceeds 2 are dominant.

  The present invention relates to a method for producing an R—Fe—B based porous magnet by HDDR treatment described in WO2007 / 135981 and an R—Fe—B fine crystal height by HDDR treatment described in WO2008 / 065903. It is applicable also to the manufacturing method of a density magnet.

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples according to the present invention.
Cast alloys having the compositions shown in Table 1 below were produced by the known production method described above.

  These alloys were pulverized into a powder having a particle size of 300 μm or less by a hydrogen pulverization method. After the Zn powder having a particle diameter of about 7 μm was manually mixed in the glass bottle with the mixing amount shown in Table 2, it was subjected to HDDR treatment. Specifically, after the powder obtained by mixing Zn powder with the pulverized alloy is heated to 820 ° C. in an argon flow of 100 kPa (atmospheric pressure), and then the atmosphere is switched to a hydrogen flow of 100 kPa (atmospheric pressure). The hydrogenation / disproportionation reaction was carried out at 820 ° C. for 300 minutes. Next, the dehydrogenation and recombination treatment was performed by maintaining for 60 minutes in an argon flow reduced to 5.3 kPa while maintaining the temperature at 820 ° C. Further, the HDDR-treated powder was subjected to an aging heat treatment at 500 ° C. or 550 ° C. for 15 minutes in a vacuum of 10 Pa or less. The magnetic properties of the obtained sample were measured with a vibrating sample magnetometer (VSM: device name VSM5 (manufactured by Toei Kogyo Co., Ltd.)). Further, the residual amount of Zn in the obtained sample was measured by ICP emission spectroscopic analysis. The results are shown in Table 2.

In Table 2, J _max is the maximum measured value of the magnetization J (T) of the sample when an external magnetic field H is applied up to 1.6 MA / m in the magnetization direction of the magnetized sample.

Compared with Comparative Example 1, Comparative Example 3, and Comparative Example 5 in which Zn was not added, Examples 1 to 6 in which 0.5 mass% of Zn was mixed remained in the magnetic powder only in a small amount of 0.04 mass% or less after heat treatment. It can be seen that the coercive force _HcJ is improved. Moreover, Comparative Example 2, Comparative Example 4, and Comparative Example 6 in which Zn was mixed in excess of 1.5 mass% remained in the magnetic powder of 0.02 to 0.06 mass% after the heat treatment, but Zn was mixed. It can be seen that the coercive force H _cJ is lower than those of Comparative Example 1, Comparative Example 3, and Comparative Example 5 that are not present. Further, in Comparative Examples 7 to 10 using the alloy D having a rare earth amount of 29 mass% or less, the coercive force _HcJ was not improved even when Zn was mixed.

  According to the present invention, a high-performance permanent magnet can be manufactured while reducing the amount of expensive additive elements such as Ga and rare resources such as Dy and Tb.

26 Chamber 27 Mold 28a Upper punch 28b Lower punch

Claims (4)

A step of preparing an RTB-based alloy powder having a rare earth content in the composition of more than 29 mass% and not more than 40 mass% and a B content of not less than 0.3 mass% and not more than 2 mass%;
Preparing a Zn-containing powder which is a powder of any metal or alloy containing at least Zn of 30 mass% or more and not containing Ga, Dy, and Tb;
Mixing the RTB-based alloy powder and the Zn-containing powder so that Zn is 0.50 mass% or more and 1.5 mass% or less of the whole to obtain a mixed powder;
A step of subjecting the mixed powder to HDDR to obtain an R-T-B permanent magnet powder;
The manufacturing method of the RTB type | system | group permanent magnet characterized by including these.   2. The method for producing an RTB-based permanent magnet according to claim 1, wherein the RTB-based permanent magnet powder is hot compression molded to produce a bulk magnet.   The aging heat treatment is performed at a temperature of 450 ° C. or higher and 700 ° C. or lower in vacuum or in an inert gas with respect to the RTB-based permanent magnet powder or bulk magnet. The manufacturing method of the RTB type | system | group permanent magnet of 2 description. Before performing the hot compression molding, the RTB-based permanent magnet powder is molded in a magnetic field to temporarily form a green compact, and the green compact is hot compression molded to be magnetically anisotropic. The manufacturing method of the RTB type | system | group permanent magnet of Claim 2 characterized by producing the bulk magnet which has property.

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