JP2004303909A - Rare earth permanent magnet and manufacturing method thereof - Google Patents

Rare earth permanent magnet and manufacturing method thereof Download PDF

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Publication number
JP2004303909A
JP2004303909A JP2003094313A JP2003094313A JP2004303909A JP 2004303909 A JP2004303909 A JP 2004303909A JP 2003094313 A JP2003094313 A JP 2003094313A JP 2003094313 A JP2003094313 A JP 2003094313A JP 2004303909 A JP2004303909 A JP 2004303909A
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Japan
Prior art keywords
rare earth
coercive force
particle size
less
permanent magnet
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JP2003094313A
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Japanese (ja)
Inventor
Tsutomu Ishizaka
Makoto Iwasaki
Eiji Kato
英治 加藤
信 岩崎
力 石坂
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Tdk Corp
Tdk株式会社
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Abstract

<P>PROBLEM TO BE SOLVED: To provide technology for stably obtaining a rare earth permanent magnet which exhibits coercive force higher than a conventional one without dispersion while degradation of residual magnetic flux density is suppressed. <P>SOLUTION: A manufacturing method of R-T-B (R: one type or two or above types of rare earth elements comprising Y, T: one or two or above types of transition metal elements in which Fe or Fe and Co are made indispensable and B: boron) system rare earth permanent magnet is provided with a step for forming powder whose ratio of D50 (D50: Particle size whose cumulative volume ratio becomes 50%) with respect to D99 (D99: Particle size whose cumulative volume ratio becomes 99%) is below 2.99, and a step for sintering an obtained molding body and obtaining a sintered body. Thus, high coercive force of not less than 15kOe and not less than 16kOe and residual magnetic flux density of not less than 13kG are given even if Dy effective for high coercive force is not contained by setting a particle size ratio "D99/D50" to be below 2.99. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to R (R is one or more rare earth elements including Y), T (T is one or two or more transition metal elements indispensable for Fe or Fe and Co) and B (boron). ) As a main component and a method for producing a rare earth permanent magnet having excellent magnetic properties.
[0002]
[Prior art]
Among the rare earth magnets, R 2 T 14 An RTB-based rare earth permanent magnet (hereinafter simply referred to as a rare earth permanent magnet) having a B-based intermetallic compound as a main phase and an R-rich phase (grain boundary phase) surrounding the B-based intermetallic compound as a main constituent phase has a magnetic property. Demand is increasing year by year because of its superiority and the fact that Nd as the main component is abundant in resources and relatively inexpensive. Rare earth permanent magnets are usually produced by pulverizing an alloy, molding the pulverized alloy powder in a magnetic field, sintering and aging.
Conventionally, various attempts have been made to improve the magnetic properties of rare-earth permanent magnets, particularly the coercive force, which is an important element in the magnetic properties. As a method for improving the coercive force, (1) a part of the rare earth element of the main phase is replaced with Dy, Tb or the like (first method), and (2) a grain boundary is added by adding Cu or the like. Modifying the structure (second method), (3) increasing the rare earth composition to increase the R-rich phase required for coercive force development (third method), and (4) crystal grains of the sintered body Techniques such as reducing the diameter (fourth technique) are known.
[0003]
All of the above four methods are effective in improving the coercive force of the rare earth permanent magnet, but each has the following problems.
First, in the first method, since expensive heavy rare earth elements such as Dy and Tb are used, the manufacturing cost of the magnet increases. Also, by adding Dy, Tb, etc., the saturation magnetization of the main phase decreases, and as a result, the residual magnetic flux density also decreases. That is, when the first method of replacing a part of the rare earth element of the main phase with Dy, Tb or the like is used, the coercive force is improved while the residual magnetic flux density is reduced.
In the second method for modifying the grain boundary structure by adding an element for modifying the grain boundary structure, such as Cu, the coercive force is improved as the amount of the grain boundary structure modifying element is increased, but the effect is smaller. When the addition amount of the field structure modifying element reaches a certain value, it becomes saturated. Therefore, it is not possible to further increase the coercive force of the rare-earth permanent magnet by the second method.
In the third technique for increasing the composition of the rare earth element, the volume ratio of the main phase is reduced, and the coercive force is also improved while the residual magnetic flux density is reduced.
[0004]
Prior arts that disclose a fourth technique for reducing the crystal grain size of a sintered body include JP-A-8-279406 and JP-A-2002-175931.
JP-A-8-279406 discloses that a high (BH) max and a coercive force of 13 kOe or more can be obtained by setting the average crystal grain size to 3 to 8 μm and the standard deviation to 2.5 μm or less. JP-A-8-279406 describes an example in which a coercive force of 16.5 kOe was obtained in Example 1 (see FIG. 1 of JP-A-8-279406).
[0005]
[Problems to be solved by the invention]
However, considering that the composition is obtained by adding 0.4 at% of Dy, JP-A-8-279406 discloses that the composition is not less than 15 kOe, more preferably not less than 16 kOe without using expensive heavy rare earth elements such as Dy and Tb. The technology for obtaining such a high coercive force has not yet been provided. In addition, as a result of the present inventor producing a sample having a sintered body crystal grain size having an average crystal grain size of 3 to 8 μm and a standard deviation of 2.5 μm or less, the coercive force is not always constant, Was large and was not suitable for mass production.
[0006]
[Patent Document 1]
JP-A-8-279406 (Claims)
[Patent Document 2]
JP-A-2002-175931 (Claims)
[0007]
In order to reduce the crystal grain size of the sintered body, there is a method of reducing the particle size of the finely pulverized powder in a fine pulverization step performed before the sintering step. However, when the average particle size of the finely pulverized powder is reduced, the amount of oxygen contained in the finely pulverized powder increases due to an increase in the surface area, and the coercive force appears in the sintered body after being molded, sintered, and aged in a magnetic field. However, there is a problem that the coercive force is reduced because the amount of the R-rich phase required for the above is reduced. In order to solve this problem, the coercive force is restored by increasing the amount of the rare earth element corresponding to the oxidation amount by increasing the rare earth element in the composition. However, when the amount of the rare earth element is relatively increased, the coercive force is restored, but the residual magnetic flux density is reduced.
In addition, by reducing the particle size of the finely pulverized powder, the moment applied to each finely pulverized powder during molding in a magnetic field is reduced, so that the degree of orientation is reduced, and even if such a compact is sintered, the orientation is poor. As a result, the residual magnetic flux density also decreases. In addition, if the particle size of the finely pulverized powder is reduced, the processing capacity of a finely pulverized device such as an airflow pulverizer is greatly reduced, and the production efficiency is poor.
[0008]
On the other hand, in JP-A-2002-175931, particles having a particle size larger than 2.0 μm and smaller than 5.0 μm occupy 45% or more in a volume ratio, and a particle size larger than 10 μm is 1%. It is disclosed that the coercive force of the rare-earth permanent magnet can be improved while the problem of oxidation and ignition due to contact with the atmosphere is avoided by setting the value to less than the above.
However, when the present inventor produced such a sintered magnet having a particle size distribution, it was found that individual variations were large and that a constant high coercive force could not always be obtained. Further, in the examples in JP-A-2002-175931, the Dy and Tb-free composition, the coercive force is 1178.1 kA / m (14.8 kOe), and the residual magnetic flux density is 1.35 T (13.5 kG). ). Therefore, there is a need for a technique for stably obtaining a rare earth permanent magnet having higher magnetic characteristics without variation.
[0009]
Accordingly, an object of the present invention is to provide a technique for stably obtaining a rare earth permanent magnet exhibiting a higher coercive force than before in a stable manner without suppressing a decrease in residual magnetic flux density. Another object of the present invention is to provide a technique for manufacturing a rare earth permanent magnet having high magnetic properties at low cost.
[0010]
[Means for Solving the Problems]
For this purpose, the above-described fourth method of making the sintered body particle size of the main phase portion finer is developed in various ways by a different approach from Japanese Patent Application Laid-Open Nos. 8-279406 and 2002-175931. I tried to. In particular, as a result of intensive studies on the relationship between the particle size distribution of the finely pulverized powder and the structure and properties of the sintered body, D99 (D99: cumulative volume ratio of D50 to D50: cumulative volume ratio becomes 50%) of the powder is It has been found that setting the ratio of (the particle size to 99%) to less than 2.99 is extremely effective in improving the coercive force without variation. That is, the present invention relates to R-T-B (R: one or more rare earth elements including Y, T: one or two or more transition metal elements containing Fe or Fe and Co as essential elements, B: : Boron) -based rare earth permanent magnet, wherein the ratio of D99 (D99: particle size at which the cumulative volume ratio becomes 99%) to D50 (D50: particle size at which the cumulative volume ratio becomes 50%) of the powder is A method for producing a rare earth permanent magnet, comprising: a step of molding a powder having a particle size of less than 2.99; and a step of sintering the obtained molded body to obtain a sintered body. According to this method, it is possible to obtain a rare-earth permanent magnet having a higher coercive force than the conventional one without lowering the residual magnetic flux density, even when a high-cost heavy rare-earth element such as Dy or Tb is not contained. it can.
[0011]
In the method for manufacturing a rare earth permanent magnet according to the present invention, setting D99 to 8.5 μm or less, and more preferably 5.5 to 8.5 μm, is particularly effective for obtaining a coercive force of 16 kOe or more. In this case, D50 described above may be 2 to 5 μm, preferably 2 to 4 μm.
Further, in the method for manufacturing a rare earth permanent magnet according to the present invention, R: 30 to 35 wt% (R: one or more of rare earth elements including Y), B: 0.5 to 2 wt%, Al: 0 to 0 It is possible to obtain an RTB-based rare earth permanent magnet made of a sintered body having a final composition of 0.5 wt%, Co: 0 to 3 wt%, Cu: 0 to 0.2 wt%, and the balance substantially consisting of Fe. It is possible.
Furthermore, the sintered body constituting the rare earth permanent magnet has an oxygen content of 3000 to 8000 ppm, and has a 90% crystal grain size (90% crystal grain size: the cumulative number ratio of the crystal grain size of the sintered body). It is desirable that the particle size (a particle size at which 90% becomes 90%) be 4.5 μm or less in order to obtain a rare-earth permanent magnet having both high coercive force and residual magnetic flux density.
[0012]
Further, according to the present invention, R: 30 to 35 wt% (R: one or more of rare earth elements including Y), B: 0.5 to 2 wt%, Al: 0 to 0.5 wt%, Co: Is a rare earth permanent magnet composed of a sintered body composed of: 0 to 3 wt%, Cu: 0 to 0.2 wt%, and the balance substantially composed of Fe, wherein the sintered body has an average crystal grain size of 2.6 μm or less. And the sintered body has a 90% crystal grain size (90% crystal grain size: a grain size at which the cumulative number ratio of the crystal grain size of the sintered body becomes 90%) is 4.5 μm or less, and the sintered body A rare-earth permanent magnet is provided, wherein the amount of oxygen therein is 3000 to 6000 ppm.
The rare-earth permanent magnet according to the present invention exhibits high magnetic properties such as a coercive force of 16 kOe or more and a residual magnetic flux density of 13 kG or more even when Nd is selected as the rare-earth element and Dy and Tb are not selected. it can.
In the case where Dy or Tb effective for obtaining a high coercive force is selected together with Nd as a rare earth element, it is possible to achieve higher magnetic properties such as a coercive force of 24 kOe or more and a residual magnetic flux density of 12 kG or more.
In the rare earth permanent magnet according to the present invention, R, that is, the amount of the rare earth element is desirably set to 32 to 35 wt%.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the method for producing a rare earth permanent magnet according to the present invention will be described in detail.
<Organization>
First, the structure of the rare earth permanent magnet obtained by the present invention will be described.
As is well known, the rare earth permanent magnet alloy obtained by the present invention has a R 2 T 14 A main phase composed of a B compound phase (R is one or more of rare earth elements including Y, T is substantially Fe) and a grain boundary phase (R-rich phase) containing more R than the main phase. Contains at least.
[0014]
<Chemical composition>
Next, a desirable chemical composition of the rare earth permanent magnet according to the present invention will be described. The chemical composition here means the final composition after sintering.
[0015]
The rare earth permanent magnet of the present invention contains 30 to 35 wt% of a rare earth element (R).
Here, R is one or two or more of rare earth elements containing Y (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu). When the amount of the rare earth element is less than 30 wt%, it is difficult to obtain a high coercive force of 15 kOe or more because the amount of the R-rich phase required for developing the coercive force is small. On the other hand, if the rare earth element exceeds 35 wt%, the main phase of R 2 T 14 The volume ratio of the B phase decreases, and the residual magnetic flux density decreases. Therefore, in the present invention, the amount of the rare earth element is set to 30 to 35 wt%. A desirable amount of the rare earth element is 32-35 wt%, and a more desirable amount of the rare earth element is 32-34 wt%.
Since Nd is abundant in resources and relatively inexpensive, it is preferable that the main component as a rare earth element be Nd.
The present invention can improve the coercive force when Dy and Tb are not contained, but does not exclude the inclusion of Dy and Tb as described below. Dy content is R 2 T 14 This is effective in increasing the anisotropic magnetic field of the B phase and improving the coercive force. Therefore, when Nd and Dy are selected as the rare earth elements, the total of Nd and Dy is desirably 30 to 35 wt%. When selecting Tb, which is effective for improving the coercive force similarly to Dy, together with Nd, it is desirable that the total of Nd and Tb is 30 to 35 wt%. When both Dy and Tb are selected as rare earth elements in addition to Nd, the total of these rare earth elements may be 30 to 35 wt%.
A desirable Dy amount is 0 to 3 wt%, and a more desirable Dy amount is 0 to 1 wt%. A desirable Tb amount is 0 to 1.5 wt%, and a more desirable Tb amount is 0 to 0.5 wt%. It is desirable that the amounts of Dy and Tb are appropriately determined within the above range depending on which of the residual magnetic flux density and the coercive force is important.
[0016]
Moreover, the rare earth permanent magnet of the present invention contains boron (B) in an amount of 0.5 to 2% by weight. If B is less than 0.5 wt%, a high coercive force cannot be obtained. However, when B exceeds 2 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit is set to 2 wt%. A desirable amount of B is 0.8 to 1.2 wt%, and a more desirable amount of B is 0.9 to 1.1 wt%.
[0017]
Further, the rare earth permanent magnet of the present invention contains Co in an amount of 3 wt% or less (excluding 0), preferably 0.1 to 1.0 wt%, and more preferably 0.3 to 0.7 wt%. Co forms a phase similar to that of Fe, but is effective for improving the Curie temperature and improving the corrosion resistance of the grain boundary phase.
[0018]
The rare earth permanent magnet according to the present invention can contain Al in the range of 0 to 0.5 wt%. The rare earth permanent magnet according to the present invention may contain Cu in a range of 0 to 0.2 wt%. By containing one or two of Al and Cu in this range, it is possible to increase the coercive force, increase the corrosion resistance, and improve the temperature characteristics of the obtained rare earth permanent magnet.
When Al is added, a desirable amount of Al is 0.03 to 0.3 wt%, and a more desirable amount of Al is 0.05 to 0.3 wt%. In addition, when Cu is added, a desirable amount of Cu is 0.15 wt% or less (excluding 0), and a more desirable amount of Cu is 0.03 to 0.08 wt%.
[0019]
Further, the rare earth permanent magnet according to the present invention may contain Sn, Bi, and Ga. All of these elements are effective in improving the coercive force. When Sn is contained, a desirable amount of Sn is 0.01 to 0.2 wt%, and a more desirable amount of Sn is 0.01 to 0.05 wt%. When Bi is contained, a desirable amount of Bi is 0.01 to 0.3 wt%, and a more desirable amount of Bi is 0.01 to 0.2 wt%. When Ga is contained, a desirable amount of Ga is 0.01 to 0.3 wt%, and a more desirable amount of Ga is 0.03 to 0.2 wt%.
[0020]
The rare earth permanent magnet of the present invention preferably has an oxygen content of 8000 ppm or less. This is because if the amount of oxygen is large, the oxide phase, which is a nonmagnetic component, increases, thereby deteriorating magnetic properties. Therefore, in the present invention, the amount of oxygen contained in the sintered body is set to 8000 ppm or less. However, when the oxygen content is less than 3000 ppm, the oxide phase having the effect of suppressing grain growth is reduced, and grain growth easily occurs in the process of obtaining a sufficient density increase during sintering. Accordingly, the coercive force is significantly reduced, and the residual magnetic flux density is also reduced. Therefore, in the present invention, the oxygen amount is set to 3000 to 8000 ppm. However, since the residual magnetic flux density tends to decrease as the oxygen amount increases, the desirable oxygen amount in the sintered body is 3000 to 7000 ppm, and the more desirable oxygen amount is 3000 to 6000 ppm.
[0021]
<Production method>
Next, a method for manufacturing a rare earth permanent magnet according to the present invention will be described.
In the method for producing a rare earth permanent magnet according to the present invention, the ratio of D99 (D99: particle size at which the cumulative volume ratio becomes 99%) to D50 (D50: particle size at which the cumulative volume ratio becomes 50%) of the powder is 2.99. The greatest feature is to produce a molded body using a powder having a particle size of less than. Conventionally, it has been practiced to control the average particle size of the powder to make the crystal particle size of the finally obtained sintered magnet finer and to improve the coercive force. However, according to the study of the present inventors, the coercive force should consider not only the average particle size of the powder but also D99 of the powder. By using a powder having a ratio of D99 to D50 of the powder (hereinafter, referred to as a particle size ratio “D99 / D50”) of less than 2.99, it is possible to have both high coercive force and high residual magnetic flux density. The particle size distribution here can be determined by measuring the diffraction of the laser beam by the powder and calculating by the Fraunhofer diffraction theory.
[0022]
Rare earth permanent magnets can be produced by a method using a single alloy having a desired composition as a starting material (hereinafter, referred to as a single method) or a method using a plurality of alloys having different compositions as starting materials (hereinafter, a single method). , A mixing method). The present invention can be applied to both the single method and the mixed method. Here, an embodiment in which the present invention is applied to the single method will be described.
[0023]
First, an alloy having a desired composition is obtained by melting and casting a raw metal in a vacuum or an inert gas, preferably an Ar atmosphere. As the raw material metal, a rare earth metal or a rare earth alloy, pure iron, ferroboron, or an alloy thereof can be used.
Various methods such as arc melting and strip casting can be employed for melting and casting. Above all, strip casting is desirable. When casting is performed by strip casting, an alloy having a fine structure is obtained, so that the pulverizability is improved.
If there is solidification segregation, the ingot obtained after melting and casting is subjected to a solution treatment if necessary. The condition may be that the temperature is maintained at 700 to 1500 ° C. for one hour or more in a vacuum or Ar atmosphere.
[0024]
After an alloy having the desired composition is made, the alloy is ground. The pulverizing step includes a coarse pulverizing step and a fine pulverizing step.
First, the coarse grinding step will be described. In the coarse pulverizing step, the ingot of the alloy is coarsely pulverized until the particle size becomes about 100 μm. Coarse pulverization can be performed in an inert gas atmosphere using a stamp mill, a jaw crusher, a brown mill, or the like.
[0025]
In order to improve the pulverizability in the coarse pulverization, it is effective to perform hydrogen pulverization in advance. Hydrogen pulverization is divided into a hydrogen absorption step and a dehydrogenation step.
In the hydrogen absorbing step, hydrogen is brought into contact with the alloy directly at room temperature to cause a reaction. At this time, by setting the hydrogen partial pressure to 1 atm or less, the pulverizability at the time of fine pulverization described later is improved. However, if the air pressure is too low, it takes time for the alloy to occlude hydrogen sufficiently, so that the hydrogen partial pressure is preferably around 1 atm.
The dehydrogenation step is desirably performed at a temperature of 500 to 600C. The atmosphere may be an inert gas atmosphere such as Ar, but by performing the dehydrogenation step in a vacuum state, the precipitation of α-Fe due to the decomposition of the compound is suppressed, and the pulverizability is improved.
[0026]
After the coarse grinding step, the process proceeds to the fine grinding step. The fine pulverization is mainly performed using an air-flow pulverizer, and the pulverization is performed until the coarsely pulverized powder having a particle diameter of about 100 μm becomes 2 to 5 μm in average particle diameter. The air-flow crusher opens a high-pressure inert gas (for example, nitrogen gas) from a narrow nozzle to generate a high-speed gas flow, accelerates the coarsely crushed powder by the high-speed gas flow, This is a device for crushing by generating collision with a target or a container wall.
[0027]
In addition, it is effective to add about 0.01 to 0.5 wt% of additives such as fatty acid salts, fatty acid esters, and fatty acid amides to the coarse powder before the fine pulverization in order to improve the pulverizability. In particular, zinc stearate and oleic acid amide are effective.
[0028]
The most characteristic feature of the present invention is to prepare a powder having a particle size ratio “D99 / D50” of less than 2.99 prior to the molding step, and to produce a molded body using the powder. A powder having a particle size ratio “D99 / D50” of less than 2.99 can be obtained by controlling the conditions of the pulverization step. In order to control the particle size ratio in such a range, it is desirable to perform fine pulverization using an airflow pulverizer. As the airflow pulverizer, a pulverizer with a classifier is desirable. By using a fine pulverizer with a classifier, coarse powder can be removed or reground to obtain a target particle size distribution. The particle size ratio “D99 / D50” can also be adjusted to less than 2.99 by changing the pulverization rate.
[0029]
Next, the reason for setting the ratio of D99 to D50 of the powder to be less than 2.99 in the present invention will be described. By setting the particle size ratio “D99 / D50” to less than 2.99, a sintered magnet having high magnetic properties can be obtained even in a composition not containing Dy or Tb. Conventionally, it has been known that when Dy or Tb is selected as a rare earth element, a high coercive force is obtained. However, since Dy and Tb are rare elements, the use of these elements makes it difficult to manufacture magnets. Cause a rise. However, as recommended by the present invention, by setting the particle size ratio “D99 / D50” to less than 2.99, even if Dy or Tb effective for increasing coercive force is not contained, Dy or Tb is contained. It is possible to have a coercive force equal to or higher than that of the above-described method, that is, a high coercive force of 15 kOe or more, and more preferably 16 kOe or more, and a residual magnetic flux density of 13 kG or more. A desirable range of the particle size ratio “D99 / D50” is 2.7 or less, more preferably 2 to 2.65. The present invention does not exclude the case where Dy or Tb effective for increasing the coercive force is contained in the final composition. When Dy or Tb is contained, the content is suppressed while the production cost of the magnet is reduced. The rare earth permanent magnet having high magnetic properties can be obtained with almost no increase in the magnetic field.
[0030]
The step of obtaining a powder having a particle size ratio “D99 / D50” of less than 2.99 is not limited to the pulverization step. For example, after the pulverizing step, the particle size ratio “D99 / D50” may be reduced to less than 2.99 by performing an operation such as removing or re-pulverizing the coarse powder on the fine powder obtained in the pulverizing step. . That is, as long as the powder to be subjected to the molding step has a particle size ratio “D99 / D50” of less than 2.99, it is included in the scope of the present invention.
[0031]
Next, the molding step will be described. In the molding step, a powder having a particle size ratio “D99 / D50” of less than 2.99 is molded in a magnetic field. Specifically, the finely pulverized powder is filled in a mold held by an electromagnet and molded in a magnetic field with its crystal axis oriented by applying a magnetic field. This molding in a magnetic field is performed in a magnetic field of 12 to 17 kOe in a range of 1.0 to 1.8 t / cm. 2 Pressure. Molding pressure is 1.0t / cm 2 Below, the shape retention is difficult, while the molding pressure is 1.8 t / cm 2 If it exceeds, the consumption of the mold is severe. When the magnetic field is lower than 12 kOe, the orientation becomes insufficient. On the other hand, when the magnetic field is higher than 17 kOe, the molding apparatus becomes large-sized, and the cost is increased. Further, when 0.01 to 0.5 wt% of a fatty acid salt, a fatty acid ester, a fatty acid amide, or the like is added to the finely pulverized powder before molding, the orientation is improved. Particularly, methyl caprylate, ethyl caprylate, and butyl oleate are effective.
[0032]
After compacting in a magnetic field, the compact is sintered in a vacuum or inert gas atmosphere. The sintering temperature needs to be adjusted according to various conditions such as the composition and the pulverization method, but may be maintained at 950 to 1100 ° C for about 1 to 8 hours. In the present invention, after the sintering step (after aging treatment when aging treatment described later is performed), the 90% crystal grain size (hereinafter referred to as “X90”) of the sintered body is 6 μm or less, further 5 μm or less, A more desirable form is 4.5 μm or less. In particular, by setting X90 to 3.0 to 4.5 μm, a high coercive force can be obtained. Here, the crystal grain size of the sintered body is a value obtained from a result obtained by observing a cross section (a plane including the axis of the magnetic orientation direction) of the sintered body and measuring individual crystal grain sizes by image analysis. . Specifically, after observing the cross-section of the mirror-polished sintered body with a polarizing microscope and recognizing individual particles, the area of each particle is obtained by image processing and calculated as the diameter of a circle with the same area as that value Value. Measurement was performed on 200 to 300 crystal grains per sample. The average crystal grain size is the average value of the crystal grain sizes of all the measured particles. X90 is the crystal grain size of all the measured particles arranged in ascending order, and the value of the crystal grain size when the cumulative number ratio becomes 90%. And
After sintering, the obtained sintered body can be subjected to an aging treatment. This step is an important step for controlling the coercive force. It is desirable to perform the aging process in two stages. In this case, the first stage is maintained at 750 to 900 ° C. for 1 hour or more and cooled once, and then the second stage is maintained at 500 to 600 ° C. for 1 hour or more and then cooled, thereby improving the coercive force. Is effective in
[0033]
In addition, if the heat treatment at 750 to 900 ° C. is performed after sintering, the coercive force increases, which is particularly effective in the mixing method. Further, since the coercive force is greatly increased by the heat treatment at 500 to 600 ° C., when performing the aging treatment in one stage, it is preferable to perform the aging treatment at 500 to 600 ° C.
[0034]
The method for producing a rare earth permanent magnet according to the present invention has been described above in detail. According to the method for manufacturing a rare-earth permanent magnet of the present invention, even when an expensive heavy rare-earth element such as Dy is not contained, a rare-earth permanent magnet having high magnetic properties such as a coercive force of 16 kOe or more and a residual magnetic flux density of 13 kG or more is provided. A magnet can be obtained stably without variation. When a heavy rare earth element such as Dy is contained, a rare earth permanent magnet having high magnetic properties such as a coercive force of 24 kOe or more and a residual magnetic flux density of 12 kG or more can be obtained.
[0035]
Although the process of manufacturing the rare earth permanent magnet according to the present invention by a single method has been described above, it is of course possible to manufacture the rare earth permanent magnet according to the present invention by the mixing method as described above. When the mixing method is adopted, R 2 T 14 An alloy mainly containing a B compound (hereinafter sometimes referred to as a low R alloy) and an alloy containing more R than the low R alloy (hereinafter sometimes referred to as a high R alloy) are mixed. The low R alloy is for forming a main phase of the present magnet, and the high R alloy is for forming a grain boundary phase. The use of a low-R alloy in which the amount of the rare earth element is adjusted to 30 wt% or more improves the pulverizability. This makes it easy to adjust the particle size distribution, that is, to make the particle size ratio “D99 / D50” less than 2.99.
[0036]
【Example】
Next, the present invention will be described in more detail with reference to specific examples.
(Experimental example 1)
<Raw material alloy>
According to the strip casting method, 28.5Nd-5.0Pr-0.25Al-0.5Co-0.07Cu-1B-bal. Fe (wt%) alloy (alloy a) and 27.5Nd-5.0Pr-0.25Al-0.5Co-0.07Cu-1B-bal. An alloy (alloy b) which was Fe (wt%) was produced. Note that the alloy b has a composition in which the Nd content is smaller by 1.0 wt% than the alloy a.
[0037]
<Hydrogen grinding process>
Hydrogen was absorbed in the obtained alloy at room temperature (atmospheric pressure flow of 100% hydrogen at room temperature). After occlusion of hydrogen, a hydrogen pulverization treatment of performing dehydrogenation at 600 ° C. × 1 hour in an Ar atmosphere (atmospheric pressure flow) was performed to obtain a coarse powder.
[0038]
<Pulverizing process>
After adding and mixing 0.05 wt% of oleic acid amide as a grinding aid to the coarse powder obtained in the hydrogen grinding step, the mixture was finely ground by an air current grinder equipped with a classifier. By adjusting the processing amount of the pulverizer and the conditions of the classifier, nine types of fine powders a1 to a3 and fine powders b1 to b6 having different particle size distributions shown in Table 1 were produced. The fine powders a1 to a3 were prepared using the alloy a, and the fine powders b1 to b6 were prepared using the alloy b. The grinding atmosphere was nitrogen containing 3000 ppm of oxygen. The particle size distribution was measured using a dry laser diffraction particle size distribution analyzer HELOS & RODOS manufactured by sympatec.
[0039]
[Table 1]
[0040]
<Molding process>
0.05 wt% of butyl oleate was added to and mixed with the obtained fine powders a1 to a3 and fine powders b1 to b6, respectively, and molded in a magnetic field. Specifically, the fine powder was filled in a mold held by an electromagnet, and was subjected to pressure molding with its crystal axis oriented by applying a magnetic field (transverse magnetic field). In this experiment, 1.4 t / cm in a magnetic field of 14 kOe 2 The molding was performed under the pressure described above to obtain a molded body.
[0041]
<Sintering process>
The obtained molded body was sintered in a vacuum under the following conditions.
Molded product using fine powders a1 to a3: 1010 ° C. × 4 hours
Molded body using fine powders b1 to b6: 1030 ° C. × 4 hours
[0042]
<Aging process>
Next, the obtained sintered body was subjected to two-stage aging treatment at 800 ° C. × 1 hour and 540 ° C. × 1 hour (both in an Ar atmosphere) to obtain nine rare-earth permanent magnets (samples a1 to a3 and samples b1 to b6). ) Got. The sample a1 was manufactured using the fine powder a1. Similarly, the samples a2 and a3 were manufactured using the fine powders a2 and a3, respectively. It was produced using fine powders b1 to b6.
[0043]
The magnetic characteristics of the samples a1 to a3 and the samples b1 to b6 were measured using a BH tracer. Further, for samples a1 to a3 and samples b1 to b6, the average crystal grain size of the sintered body and X90 (the grain size at which the cumulative number ratio of the crystal grain size of the sintered body becomes 90%) were determined. The results are shown in Table 1. Table 1 shows D10 (D10: particle size at which the cumulative volume ratio becomes 10%), D50, D99, and the particle size ratio “D99 / D50” of the powders used in producing the samples a1 to a3 and the samples b1 to b6. Are also shown.
FIG. 1 shows the relationship between D50 and the coercive force HcJ, and FIG. 2 shows the relationship between the average crystal grain size of the sintered body and the coercive force HcJ. As shown in FIG. 1, the coercive force HcJ tends to increase as the value of D50 decreases, and as shown in FIG. 2, the coercive force HcJ tends to increase as the average crystal grain size of the sintered body decreases. Understand. However, it is clear from FIG. 1 that the coercive force HcJ is different while having substantially the same D50. From the above, it can be said that the coercive force HcJ can be controlled by controlling D50, but it can be seen that the values vary.
Here, the particle size ratio “D99 / D50” was determined for each sample, and the value was added to FIG. Then, in each of the samples a1 to a3, b1, b3, b5 and b2, b4, b6 where D50 almost coincides, it is understood that the smaller the value of the particle size ratio “D99 / D50”, the larger the coercive force HcJ. The above results indicate that, since the samples a1 to a3 have the same composition, in order to obtain a higher coercive force HcJ in a magnet having the same composition, the particle size ratio “D99 / D50” may be controlled. Suggests.
Samples a1, b1 and b2 have a particle size ratio “D99 / D50” ≦ 2.3, and samples a2, b3 and b4 have a particle size ratio “D99 / D50” of 2.3 <“D99 / D50” < Since a3, b5 and b6 are in the range of 2.99 and the particle size ratio “D99 / D50” ≧ 2.99, the desirable particle size ratio “D99 / D50” for obtaining a high coercive force HcJ is 2 It is less than .99, more preferably 2.3 or less.
[0044]
Next, FIG. 3 shows the relationship between D50 and residual magnetic flux density Br for samples a1 to a3 and samples b1 to b6.
From FIG. 3, it can be said that when D50 is equal, substantially the same residual magnetic flux density Br can be obtained regardless of the difference in the particle size ratio “D99 / D50”. In other words, even if the particle size ratio “D99 / D50” is set to less than 2.99, or even 2.3 or less in order to obtain a high coercive force HcJ, the residual magnetic flux density Br is not reduced.
From the above results, in order to combine high coercive force HcJ and high residual magnetic flux density Br, the particle size ratio “D99 / D50” is less than 2.99, more preferably 2.3 <particle size ratio “D99 / D50” < It was found that it is effective to set the value to 2.99, more preferably 2.3 or less.
[0045]
Next, FIG. 4 shows the relationship between D99 and the coercive force HcJ, and FIG. 5 shows the relationship between X90 of the sintered body and the coercive force HcJ. As shown in FIG. 4, the coercive force HcJ increases as D99 decreases. Particularly, when the value of D99 is 9 μm or less, a high coercive force HcJ of 16 kOe or more is obtained. Therefore, the value of D99 is desirably 9 μm or less, and further preferably 8.5 μm or less. Further, it can be seen that the relationship between X90 and the coercive force HcJ is similar to the relationship between D99 and the coercive force HcJ. Since a high coercive force HcJ of 16 kOe or more is obtained when X90 is 4.5 μm or less, it can be said that a desirable value of X90 is 4.5 μm or less, further 4.3 μm or less.
FIG. 6 shows the relationship between D10 and the coercive force HcJ. It can be seen that the coercive force HcJ does not depend on D10.
[0046]
Here, the relationship between X90 and D99 is shown in FIG. 7, and the relationship between X90 and D50 is shown in FIG. 8, respectively.
7 and 8 that X90 depends not on D50 but on D99. As described above, X90 is an effective element for improving the coercive force HcJ, but it can be seen from FIGS. 7 and 8 that D99 should be controlled to control X90. As described above, setting the value of X90 to 4.5 μm or less is effective in obtaining a high coercive force HcJ of 16 kOe or more, but for that purpose, D99 may be set to 9.0 μm or less. Understand. Further, in order to make the value of X90 4.3 μm or less, D99 may be controlled to 8.3 μm or less.
[0047]
Next, Table 1 shows a product “Br * HcJ” of the residual magnetic flux density Br and the coercive force HcJ. The value of “Br * HcJ” can be used as an index for comprehensively determining the magnetic characteristics. In the following, description will be made while omitting the unit (kG · kOe) of “Br * HcJ”.
As shown in Table 1, it can be seen that as the particle size ratio “D99 / D50” increases, the value of “Br * HcJ” decreases. When the particle size ratio “D99 / D50” exceeds 3.02 (sample a3) exceeding the value less than 2.99 recommended by the present invention, the value of “Br * HcJ” decreases to 208. . On the other hand, sample a1 (particle size ratio “D99 / D50”: 2.30) and sample a2 (particle size ratio “D99 / D50”: 2.61) having a particle size ratio “D99 / D50” of less than 2.99 are “ As for “Br * HcJ”, a value of 210 or more is obtained.
From the above results, in order to obtain a value of 210 or more for "Br * HcJ" while obtaining a coercive force HcJ of 16 kOe or more, the particle size ratio "D99 / D50" must be less than 2.99, and more preferably 2-2. 0.7 was found to be effective.
[0048]
The same tendency applies to the samples b1 to b6. The coercive force HcJ decreases as the particle size ratio “D99 / D50” increases, and “Br * HcJ” increases as the particle size ratio “D99 / D50” increases. It can be seen that the value of
Here, the samples b1 to b6 manufactured using the alloy b have a sintered body rare earth content of about 1 wt% less than the samples a1 to a3 manufactured using the alloy a. Therefore, the samples b1 to b6 have compositions in which the residual magnetic flux density Br is higher and the coercive force HcJ is lower than those of the samples a1 to a3. However, paying attention to the columns of the particle size ratios “D99 / D50” and “Br * HcJ”, the particle size ratio “D99 / D50” is set to less than 2.99, and further to 2 to 2.7 for the samples b1 to b6. It can be said that this is effective.
[0049]
(Experimental example 2)
A hydrogen pulverizing step and a pulverizing step were performed using the alloy a produced in Experimental Example 1 under the same conditions as in Experimental Example 1 except that the pulverizing atmosphere was nitrogen containing 5 ppm oxygen, and a fine powder was obtained. The particle size distribution of the obtained fine powder was D10 = 1.71 μm, D50 = 3.18 μm, D99 = 7.29 μm, and D99 / D50 = 2.29.
A molding step, a sintering step, and an aging step are performed in the same procedure as in Experimental Example 1 except that the amount of oxygen in the atmosphere in the molding step is controlled. (Samples a4 to a9) were prepared (the sintering conditions were 1010 ° C. × 4 hours, as in the samples a1 to a3). The magnetic characteristics of the samples a4 to a9 were measured using a BH tracer. Table 2 shows the results.
[0050]
[Table 2]
[0051]
Looking at the samples a5 to a9 in Table 2, it can be seen that the coercive force HcJ decreases as the oxygen content of the sintered body increases. Specifically, the sample a5 having an oxygen content of 3122 ppm has a very high coercive force HcJ of 18 kOe or more, whereas the sample a5 having an oxygen content of 7565 ppm (sample a8) has a coercive force of 16.3 kOe. When the oxygen amount exceeds 8000 ppm (sample a9), the coercive force decreases to 15.5 kOe. Therefore, in the composition of Experimental Example 2, that is, in a composition not containing heavy rare earth elements such as Dy and Tb, it is effective to set the oxygen amount to 8000 ppm or less in order to obtain a coercive force HcJ of 16 kOe or more. Was. However, when the oxygen amount is 2562 ppm (sample a4), the coercive force HcJ decreases to 9.8 kOe. This is because when the oxygen content is less than 3000 ppm, the oxide phase having the effect of suppressing grain growth is reduced, and grain growth easily occurs in the process of obtaining a sufficient density increase during sintering. As described above, when grain growth occurs, the coercive force HcJ decreases significantly, and the residual magnetic flux density Br also decreases. Therefore, it can be said that a desirable sintered body oxygen amount is 3000 to 8000 ppm.
[0052]
Next, focusing on the relationship between the sintered body oxygen amount and the residual magnetic flux density Br, when the sintered body oxygen amount is 3000 ppm or more, a high residual magnetic flux density Br of 13 kG or more is obtained. However, in consideration of the balance between the coercive force HcJ and the residual magnetic flux density Br, in order to set “Br * HcJ” to a value of 210 or more, it is desirable that the oxygen amount of the sintered body be 8000 ppm or less. Here, according to the samples a5 to a8 in which the oxygen amount is 3000 to 8000 ppm, “Br * HcJ” can be set to 210 or more, and according to the samples a5 and a6 in which the oxygen amount is 3000 to 6000 ppm, “Br * HcJ” can be set to 230 or more.
[0053]
(Experimental example 3)
According to the strip casting method, 26.5Nd-5.0Pr-0.25Al-0.5Co-0.07Cu-1B-bal. Fe (wt%) alloy (alloy c), 30.5Nd-5.0Pr-0.25Al-0.5Co-0.07Cu-1B-bal. An alloy (alloy d) which was Fe (wt%) was produced. The alloy c has a composition in which the Nd content is 2.0 wt% less than the alloy a produced in Example 1, and the alloy d has a composition in which the Nd content is 2.0 wt% larger than the alloy a produced in Example 1. ing.
[0054]
The hydrogen pulverizing step and the pulverizing step were performed in the same procedure as in Experimental Example 1, and two types of fine powders c and d having different particle size distributions shown in Table 3 were produced. The pulverizing atmosphere is the same as in Experimental Example 1. 0.05 wt% of butyl oleate was added and mixed to the obtained fine powders c and d, and the molding step, the sintering step and the aging step were performed in the same procedure as in Experimental Example 1 to obtain samples c and d. The binding conditions were 1010 ° C. × 4 hours, similarly to the samples a1 to a3). In addition, the sample c was manufactured using the fine powder c, and similarly, the sample d was manufactured using the fine powder d.
[0055]
The magnetic properties of the samples c and d were measured using a BH tracer. Table 3 shows the results. Table 3 also shows the characteristics of the sample a1 manufactured in Experimental Example 1 for convenience of comparison.
[0056]
[Table 3]
[0057]
As shown in Table 3, Samples c and d have substantially the same particle size ratio “D99 / D50” and sintered body oxygen content as Sample a1. However, the sample a1 having a rare earth composition of 33.4 wt% shows a coercive force HcJ of 17.4 kOe or more, whereas the sample c having a rare earth composition of 31.3 wt% has a coercive force HcJ of 14.3 kOe. Stay. As a result, the value of “Br * HcJ” is only 197 for the sample c.
On the other hand, Sample d having a rare earth composition of 36.5 wt% showed insufficient values for both coercive force HcJ and residual magnetic flux density Br. As a result, the value of "Br * HcJ" was only 167 for sample d.
From the above results, it can be said that the desirable value of the rare earth composition is 32 to 35 wt%. In particular, when the rare earth composition exceeds 35 wt% as in sample d, both the residual magnetic flux density Br and the coercive force HcJ decrease.
[0058]
(Experimental example 4)
Using the fine powder a1 obtained in Experimental Example 1, except that butyl oleate was not added, the hydrogen pulverization step, the pulverization step, the molding step, the sintering step, and the aging step were performed in the same procedure as in the sample a1. Then, a sample e was obtained. The magnetic characteristics of the sample e were measured using a BH tracer. Table 4 shows the results. Table 4 also shows the magnetic characteristics of the sample a1 manufactured in Experimental Example 1 for convenience of comparison.
[0059]
[Table 4]
[0060]
Sample e shows the same coercive force HcJ as sample a1. However, the residual magnetic flux density Br of the sample e is 13.1 kG, whereas the residual magnetic flux density Br of the sample a1 to which butyl oleate is added is 13.4 kG. This is because the degree of orientation is improved by adding butyl oleate. Therefore, it was found that butyl oleate is an effective additive in order to combine high coercive force HcJ and high residual magnetic flux density Br.
[0061]
(Experimental example 5)
In each of Experimental Examples 1 to 4, the alloys a to c containing no heavy rare earth element such as Dy in the composition were used. In this experimental example, it is confirmed that it is effective to set the particle size ratio “D99 / D50” to less than 2.99 even in a composition containing Dy.
[0062]
According to a strip casting method, 25.5Nd-5.0Pr-3Dy-0.25Al-0.5Co-0.07Cu-0.1Bi-1B-bal. An alloy (alloy w) which was Fe (wt%) was produced.
The hydrogen pulverizing step and the pulverizing step were performed in the same procedure as in Experimental Example 1, and three types of fine powders w1 to w3 having different particle size distributions shown in Table 5 were produced. The pulverizing atmosphere is the same as in Experimental Example 1.
[0063]
[Table 5]
[0064]
0.05 wt% of butyl oleate was added to and mixed with the obtained fine powders w1 to w3, and a molding step, a sintering step, and an aging step were performed in the same procedure as in Experimental Example 1 to obtain samples w1 to w3. The binding conditions were 1010 ° C. × 4 hours, similarly to the samples a1 to a3). In addition, the sample w1 was produced using the fine powder w1, and similarly, the samples w2 and w3 were produced using the fine powder w2 and w3, respectively.
[0065]
The magnetic properties of the samples w1 to w3 were measured using a BH tracer. The results are also shown in Table 5.
[0066]
As shown in Table 5, the particle size ratio “D99 / D50” of Samples w1 to w3 was higher than that of Sample w3 having the particle size ratio “D99 / D50” of 3.05, despite all having the same D50. Samples w1 and w2, which are less than 2.99, show higher coercive force HcJ. Therefore, it was found that controlling the particle size ratio “D99 / D50” to less than 2.99 is effective even when the composition contains Dy. According to the samples w1 and w2 in which the particle size ratio “D99 / D50” is less than 2.99, the coercive force HcJ of 24 kOe or more and the residual magnetic flux density Br of 12 kG or more can be combined, and “Br * HcJ” It is also possible to obtain a value of 300 or more.
[0067]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the rare earth permanent magnet which shows a coercive force higher than before can be obtained stably with no variation, suppressing the fall of a residual magnetic flux density. Further, a rare earth permanent magnet having high magnetic properties can be manufactured at low cost.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between D50 and coercive force HcJ.
FIG. 2 is a graph showing a relationship between an average crystal grain size of a sintered body and a coercive force HcJ.
FIG. 3 is a graph showing a relationship between D50 and residual magnetic flux density Br.
FIG. 4 is a graph showing a relationship between D99 and coercive force HcJ.
FIG. 5 is a graph showing a relationship between X90 of a sintered body and coercive force HcJ.
FIG. 6 is a graph showing a relationship between D10 and a coercive force HcJ.
FIG. 7 is a graph showing the relationship between X90 and D99.
FIG. 8 is a graph showing the relationship between X90 and D50.

Claims (8)

  1. R-T-B (R: one or more rare earth elements including Y, T: Fe or one or more transition metal elements containing Fe and Co as essential, B: boron) rare earth permanent A method for manufacturing a magnet, comprising:
    Molding a powder having a ratio of D99 (D99: particle size at which the cumulative volume ratio becomes 99%) to D50 (D50: particle size at which the cumulative volume ratio becomes 50%) of the powder is less than 2.99;
    A step of sintering the obtained molded body to obtain a sintered body,
    A method for producing a rare earth permanent magnet, comprising:
  2. The method of claim 1, wherein the D99 is 8.5 μm or less.
  3. The sintered body is
    R: 30 to 35 wt% (R: one or more rare earth elements including Y), B: 0.5 to 2 wt%, Al: 0 to 0.5 wt%, Co: 0 to 3 wt%, Cu: 3. The method for producing a rare-earth permanent magnet according to claim 1, wherein the permanent-earth magnet has a composition of 0 to 0.2 wt% and the balance substantially consisting of Fe.
  4. The sintered body has an oxygen content of 3000 to 8000 ppm and a 90% crystal grain size of the sintered body (90% crystal grain size: a particle size at which the cumulative number ratio of the crystal grain size of the sintered body becomes 90%) ) Is 4.5 μm or less, the method for producing a rare earth permanent magnet according to claim 1, wherein
  5. R: 30 to 35 wt% (R: one or more rare earth elements including Y), B: 0.5 to 2 wt%, Al: 0 to 0.5 wt%, Co: 0 to 3 wt%, Cu: 0 to 0.2 wt%, the balance being a rare earth permanent magnet composed of a sintered body substantially composed of Fe,
    The average crystal grain size of the sintered body is 2.6 μm or less, and the 90% crystal grain size of the sintered body (90% crystal grain size: the cumulative number ratio of the crystal grain size of the sintered body becomes 90%) Is 4.5 μm or less, and
    A rare earth permanent magnet, wherein the amount of oxygen in the sintered body is 3000 to 6000 ppm.
  6. The rare-earth permanent magnet according to claim 5, wherein when Nd is selected as the rare-earth element and Dy and Tb are not selected, the coercive force is 16 kOe or more and the residual magnetic flux density is 13 kG or more.
  7. The rare-earth permanent magnet according to claim 5, wherein when Nd and Dy are essential as the rare-earth element, the coercive force is 24 kOe or more and the residual magnetic flux density is 12 kG or more.
  8. The rare-earth permanent magnet according to claim 5, wherein the R is 32 to 35 wt%.
JP2003094313A 2003-03-31 2003-03-31 Rare earth permanent magnet and manufacturing method thereof Pending JP2004303909A (en)

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WO2008065903A1 (en) * 2006-11-30 2008-06-05 Hitachi Metals, Ltd. R-Fe-B MICROCRYSTALLINE HIGH-DENSITY MAGNET AND PROCESS FOR PRODUCTION THEREOF
JP2009123968A (en) * 2007-11-15 2009-06-04 Hitachi Metals Ltd POROUS MATERIAL FOR R-Fe-B BASED PERMANENT MAGNET, AND MANUFACTURING METHOD THEREOF
WO2009122709A1 (en) 2008-03-31 2009-10-08 日立金属株式会社 R-t-b-type sintered magnet and method for production thereof
WO2009150843A1 (en) * 2008-06-13 2009-12-17 日立金属株式会社 R-t-cu-mn-b type sintered magnet
CN105828983A (en) * 2013-12-23 2016-08-03 通用电器技术有限公司 Gamma prime precipitation strengthened nickel-base superalloy for use in powder based additive manufacturing process
WO2017159576A1 (en) * 2016-03-17 2017-09-21 日立金属株式会社 Method for manufacturing r-t-b based sintered magnet
JP2017183710A (en) * 2016-03-28 2017-10-05 Tdk株式会社 R-t-b based permanent magnet
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JP4924615B2 (en) * 2006-11-30 2012-04-25 日立金属株式会社 R-Fe-B fine crystal high-density magnet and method for producing the same
JPWO2008065903A1 (en) * 2006-11-30 2010-03-04 日立金属株式会社 R-Fe-B fine crystal high-density magnet and method for producing the same
WO2008065903A1 (en) * 2006-11-30 2008-06-05 Hitachi Metals, Ltd. R-Fe-B MICROCRYSTALLINE HIGH-DENSITY MAGNET AND PROCESS FOR PRODUCTION THEREOF
US8128758B2 (en) 2006-11-30 2012-03-06 Hitachi Metals, Ltd. R-Fe-B microcrystalline high-density magnet and process for production thereof
JP2009123968A (en) * 2007-11-15 2009-06-04 Hitachi Metals Ltd POROUS MATERIAL FOR R-Fe-B BASED PERMANENT MAGNET, AND MANUFACTURING METHOD THEREOF
WO2009122709A1 (en) 2008-03-31 2009-10-08 日立金属株式会社 R-t-b-type sintered magnet and method for production thereof
JP5477282B2 (en) * 2008-03-31 2014-04-23 日立金属株式会社 R-T-B system sintered magnet and manufacturing method thereof
US8317941B2 (en) 2008-03-31 2012-11-27 Hitachi Metals, Ltd. R-T-B-type sintered magnet and method for production thereof
US8092619B2 (en) 2008-06-13 2012-01-10 Hitachi Metals, Ltd. R-T-Cu-Mn-B type sintered magnet
WO2009150843A1 (en) * 2008-06-13 2009-12-17 日立金属株式会社 R-t-cu-mn-b type sintered magnet
CN105828983A (en) * 2013-12-23 2016-08-03 通用电器技术有限公司 Gamma prime precipitation strengthened nickel-base superalloy for use in powder based additive manufacturing process
CN105828983B (en) * 2013-12-23 2019-04-12 安萨尔多能源英国知识产权有限公司 γ ' precipitating enhancing nickel based super alloy for the increasing material manufacturing process based on powder
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