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JP2006063387A - Method for producing rare earth sintered magnet - Google Patents

Method for producing rare earth sintered magnet Download PDF

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JP2006063387A
JP2006063387A JP2004247039A JP2004247039A JP2006063387A JP 2006063387 A JP2006063387 A JP 2006063387A JP 2004247039 A JP2004247039 A JP 2004247039A JP 2004247039 A JP2004247039 A JP 2004247039A JP 2006063387 A JP2006063387 A JP 2006063387A
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rare earth
lubricant
sintered magnet
earth sintered
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JP4215258B2 (en
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Makoto Iwasaki
信 岩崎
Takeshi Nomura
武史 野村
Takeshi Masuda
健 増田
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TDK Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently removing a lubricant, and further, to provide a method for producing a rare earth sintered magnet in which magnetic properties are satisfactory, and also, deformation is suppressed since the content of residual carbon is low. <P>SOLUTION: The method for producing the rare earth sintered magnet includes: a stage where a composition comprising a lubricant using an organic matter as a constituent and alloy powder having a prescribed composition is compacted in a magnetic field so as to obtain a compact; and a stage where the compact is subjected to heat treatment under an atmospheric gas containing H<SB>2</SB>O and H<SB>2</SB>so as to remove the lubricant. Regarding the stage for sintering the compact, it is desirable that the compact is subjected to the heat treatment under the atmospheric gas containing H<SB>2</SB>O and H<SB>2</SB>in the process where its temperature is raised to a prescribed sintering temperature. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、希土類焼結磁石の製造方法に関し、特に磁場中成形時の成形性、配向性を確保するために添加される潤滑剤を効率よく除去することのできる希土類焼結磁石の製造方法に関するものである。   The present invention relates to a method for producing a rare earth sintered magnet, and more particularly to a method for producing a rare earth sintered magnet capable of efficiently removing a lubricant added to ensure formability and orientation during molding in a magnetic field. Is.

希土類元素(R)、Fe又はFe及びCoを必須とする少なくとも1種以上の遷移金属元素(T)及びホウ素(B)を主成分とするR−T−B系焼結磁石は、所定粒度を有する合金粉末を磁場中成形した後に、焼結して製造される。磁気特性の高いR−T−B系焼結磁石を得るために、磁場中成形により得られる成形体の配向性を向上することが求められる。また、磁場中成形に供される合金粉末は、例えばジェットミルによって平均粒径2〜6μm程度まで微粉砕して得られるが、このときの粉砕性が高いことが求められる。この要望に応えるために、従来、微粉砕の前にオレイン酸アミド等の有機物を含む潤滑剤を添加することが知られている(例えば、特許文献1、特許文献2参照)。
添加された潤滑剤は、真空あるいは不活性ガス雰囲気中において、100〜500℃で成形体を加熱することにより除去することが知られている(例えば、特許文献1)。
R-T-B system sintered magnet mainly composed of at least one kind of transition metal element (T) and boron (B), which essentially contains rare earth elements (R), Fe or Fe and Co, has a predetermined particle size. The alloy powder is formed in a magnetic field and then sintered. In order to obtain an RTB-based sintered magnet having high magnetic properties, it is required to improve the orientation of a molded body obtained by molding in a magnetic field. The alloy powder used for forming in a magnetic field is obtained by finely pulverizing to an average particle size of about 2 to 6 μm by, for example, a jet mill, and is required to have high pulverizability at this time. In order to meet this demand, it is conventionally known to add a lubricant containing an organic substance such as oleic acid amide before pulverization (see, for example, Patent Document 1 and Patent Document 2).
It is known that the added lubricant is removed by heating the molded body at 100 to 500 ° C. in a vacuum or an inert gas atmosphere (for example, Patent Document 1).

特開平7−240329号公報(特許請求の範囲)Japanese Patent Laid-Open No. 7-240329 (Claims) 特開平8−111308号公報(特許請求の範囲)JP-A-8-111308 (Claims)

しかし、真空あるいは不活性ガス雰囲気中の加熱処理を行っても、潤滑剤を十分に除去することができないか、除去するための加熱処理を長時間行わなければならない。潤滑剤が成形体に残留していると、焼結時に希土類元素と反応して希土類炭化物を形成することにより、磁気特性を低下させる。あるいは、成形体の収縮率が不均一になり、焼結体に変形が生ずることがある。   However, even if heat treatment is performed in a vacuum or an inert gas atmosphere, the lubricant cannot be sufficiently removed, or heat treatment for removal must be performed for a long time. If the lubricant remains in the molded body, it reacts with a rare earth element during sintering to form a rare earth carbide, thereby reducing the magnetic properties. Or the shrinkage | contraction rate of a molded object becomes non-uniform | heterogenous and a deformation | transformation may arise in a sintered compact.

本発明は、このような技術的課題に基づいてなされたもので、効率よく潤滑剤を除去する方法を提供し、ひいては残留する炭素の量が少ないために磁気特性が良好で、かつ変形が抑制された希土類焼結磁石を製造する方法を提供することを目的とする。   The present invention has been made on the basis of such a technical problem, and provides a method for efficiently removing a lubricant. As a result, since the amount of carbon remaining is small, magnetic characteristics are good and deformation is suppressed. It is an object of the present invention to provide a method for producing a rare earth sintered magnet.

成形体から潤滑剤を効率よく除去するべく、加熱処理の条件について検討を行ったところ、H2O及びH2を含む雰囲気ガスの下で加熱処理を行うと、真空下で同様の加熱処理を行った場合に比べて焼結体の炭素量を低減できること、これに伴って磁気特性が良好な希土類焼結磁石を製造できる。しかも、得られる焼結体の変形も低減される。
本発明は、このような知見に基づいてなされた希土類焼結磁石の製造方法であって、有機物を構成要素とする潤滑剤と所定組成の合金粉末とを含む組成物を磁場中で加圧成形して成形体を得る工程と、
成形体をH2O及びH2を含む雰囲気ガスの下で加熱処理することにより潤滑剤を除去する工程と、を備えることを特徴とする。
In order to efficiently remove the lubricant from the molded body, the heat treatment conditions were examined. When heat treatment was performed under an atmosphere gas containing H 2 O and H 2 , the same heat treatment was performed under vacuum. Compared with the case where it carries out, the carbon amount of a sintered compact can be reduced, and the rare earth sintered magnet with a favorable magnetic characteristic can be manufactured in connection with this. Moreover, deformation of the obtained sintered body is also reduced.
The present invention is a method for producing a rare earth sintered magnet based on such knowledge, and a composition containing a lubricant containing an organic substance and an alloy powder having a predetermined composition is pressed in a magnetic field. And obtaining a molded body,
And a step of removing the lubricant by heat-treating the molded body under an atmosphere gas containing H 2 O and H 2 .

本発明の希土類焼結磁石の製造方法において、雰囲気ガスにおけるH2Oの分圧をP(H2O)、H2の分圧をP(H2)とすると、P(H2O)/P(H2)≧10-10であることが、潤滑剤の除去を効率よく行う上で重要である。また、P(H2)が2〜130kPaであることも同様に潤滑剤の除去を効率よく行う上で重要である。 The method of manufacturing a rare earth sintered magnet of the present invention, the partial pressure of H 2 O in the atmospheric gas P (H 2 O), when the partial pressure of H 2 and P (H 2), P ( H 2 O) / It is important for P (H 2 ) ≧ 10 −10 to efficiently remove the lubricant. Similarly, P (H 2 ) of 2 to 130 kPa is also important for efficiently removing the lubricant.

本発明の希土類焼結磁石の製造方法において、加熱処理は、200〜600℃の温度範囲で所定時間保持することが望ましい。また、雰囲気ガスは、不活性ガスを含むことが望ましい。   In the method for producing a rare earth sintered magnet of the present invention, the heat treatment is desirably held in a temperature range of 200 to 600 ° C. for a predetermined time. Further, it is desirable that the atmospheric gas contains an inert gas.

本発明は、成形体を焼結する工程を備え、成形体を所定の焼結温度まで昇温する過程で成形体をH2O及びH2を含む雰囲気ガスの下で加熱処理することができる。
本発明に用いる潤滑剤は、脂肪酸又は脂肪酸の誘導体の1種又は2種以上から選択することができる。
The present invention includes a step of sintering a molded body, and the molded body can be heat-treated under an atmosphere gas containing H 2 O and H 2 in the process of raising the temperature of the molded body to a predetermined sintering temperature. .
The lubricant used in the present invention can be selected from one or more fatty acids or fatty acid derivatives.

本発明によれば、効率よく潤滑剤を除去するとともに、残留する炭素の量が少ないために磁気特性が良好で、かつ変形が抑制された希土類焼結磁石を製造することができる。   According to the present invention, it is possible to produce a rare earth sintered magnet that efficiently removes the lubricant and has good magnetic properties and suppressed deformation due to the small amount of carbon remaining.

以下、本発明を実施の形態に基づいて詳細に説明する。
希土類焼結磁石は、通常、原料合金作製、原料合金の粉砕、粉砕された粉末の磁場中成形、成形体の焼結という基本的な工程を経て作製される。以下、希土類焼結磁石としてNd−Fe−B系焼結磁石を例にして、上記方策を含め、工程順にその製造方法を説明する。
Hereinafter, the present invention will be described in detail based on embodiments.
Rare earth sintered magnets are usually produced through the basic steps of producing a raw material alloy, pulverizing the raw material alloy, forming the pulverized powder in a magnetic field, and sintering the compact. Hereinafter, an Nd—Fe—B based sintered magnet is taken as an example of the rare earth sintered magnet, and the manufacturing method thereof will be described in the order of steps including the above measures.

原料合金は、真空又は不活性ガス、望ましくはAr雰囲気中でストリップキャスト法、その他公知の溶解法により作製することができる。ストリップキャスト法は、原料金属をArガス雰囲気などの非酸化性雰囲気中で溶解して得た溶湯を回転するロールの表面に噴出させる。ロールで急冷された溶湯は、薄板または薄片(鱗片)状に急冷凝固される。この急冷凝固された合金は、結晶粒径が1〜50μmの均質な組織を有している。原料合金は、ストリップキャスト法に限らず、高周波誘導溶解等の溶解法によって得ることができる。   The raw material alloy can be produced by a strip casting method or other known melting methods in a vacuum or an inert gas, preferably in an Ar atmosphere. In the strip casting method, a molten metal obtained by melting a raw metal in a non-oxidizing atmosphere such as an Ar gas atmosphere is ejected onto the surface of a rotating roll. The melt rapidly cooled by the roll is rapidly solidified into a thin plate or a thin piece (scale). This rapidly solidified alloy has a homogeneous structure with a crystal grain size of 1 to 50 μm. The raw material alloy can be obtained not only by the strip casting method but also by a melting method such as high frequency induction melting.

原料合金は粉砕工程に供される。粉砕工程には、粗粉砕工程と微粉砕工程とがある。まず、原料合金を、粒径数百μm程度になるまで粗粉砕する。粗粉砕は、スタンプミル、ジョークラッシャー、ブラウンミル等を用い、不活性ガス雰囲気中にて行なうことが望ましい。粗粉砕に先立って、原料合金に水素を吸蔵させた後に放出させることにより粉砕を行なうことが効果的である。この水素粉砕を粗粉砕と位置付けて、機械的な粗粉砕を省略することもできる。   The raw material alloy is subjected to a grinding process. The pulverization process includes a coarse pulverization process and a fine pulverization process. First, the raw material alloy is coarsely pulverized until the particle size becomes about several hundred μm. The coarse pulverization is desirably performed in an inert gas atmosphere using a stamp mill, a jaw crusher, a brown mill or the like. Prior to coarse pulverization, it is effective to perform pulverization by allowing hydrogen to be stored in the raw material alloy and then releasing it. This hydrogen pulverization can be regarded as coarse pulverization, and mechanical coarse pulverization can be omitted.

粗粉砕工程後、微粉砕工程に移る。微粉砕には主にジェットミルが用いられ、粒径数百μm程度の粗粉砕粉末を、平均粒径2.5〜6μm、好ましくは3〜5μmとする。ジェットミルは、高圧の不活性ガスを狭いノズルより開放して高速のガス流を発生させ、この高速のガス流により粗粉砕粉末を加速し、粗粉砕粉末同士の衝突やターゲットあるいは容器壁との衝突を発生させて粉砕する方法である。
微粉砕前後又はその両方にて、有機物を構成要素とする潤滑剤を0.01〜0.5wt%程度添加することにより、次の磁場中成形時に配向性の高い微粉を得ることができる。また、微粉砕前に潤滑剤を添加した場合には、微粉砕工程において所望の粒径の微粉末を効率よく製造することができる。この潤滑剤としては、脂肪酸又は脂肪酸の誘導体、例えばステアリン酸系やオレイン酸系であるステアリン酸亜鉛、ステアリン酸カルシウム、ステアリン酸アミド、オレイン酸アミド等を用いることができる。
After the coarse pulverization process, the process proceeds to the fine pulverization process. A jet mill is mainly used for the fine pulverization, and the coarsely pulverized powder having a particle size of about several hundreds of μm has an average particle size of 2.5 to 6 μm, preferably 3 to 5 μm. The jet mill releases a high-pressure inert gas from a narrow nozzle to generate a high-speed gas flow, accelerates the coarsely pulverized powder with this high-speed gas flow, collides with the coarsely pulverized powder, and collides with the target or the container wall. It is a method of generating a collision and crushing.
By adding about 0.01 to 0.5 wt% of a lubricant containing an organic substance before and after pulverization or both, fine powder with high orientation can be obtained at the time of molding in the next magnetic field. In addition, when a lubricant is added before fine pulverization, fine powder having a desired particle diameter can be efficiently produced in the fine pulverization step. As this lubricant, fatty acid or a derivative of fatty acid, for example, stearic acid-based or oleic acid-based zinc stearate, calcium stearate, stearamide, oleamide, or the like can be used.

以上のようにして得られた微粉末は磁場中成形に供される。この磁場中成形は、800〜1360kA/m(10〜17kOe)の磁場中で、50〜200MPa(0.5〜2t/cm2)前後の圧力で行なえばよい。 The fine powder obtained as described above is subjected to molding in a magnetic field. The forming in the magnetic field may be performed at a pressure of about 50 to 200 MPa (0.5 to 2 t / cm 2 ) in a magnetic field of 800 to 1360 kA / m (10 to 17 kOe).

以上で得られた成形体は、前述した潤滑剤を含んでいる。この潤滑剤は、前述したように、希土類元素と反応するために、R−Fe−B系焼結磁石として希土類元素の量が不足することにより磁気特性の劣化を招く。また、焼結時の収縮が焼結体中で不均一となり焼結後に変形するおそれがあった。
そこで、本発明では、潤滑剤の除去のために、特徴的な処理を成形体に施す。この処理は、成形体を、H2O及びH2を含む雰囲気ガスの下で所定時間保持する加熱処理である。この加熱処理を成形体に施すと、真空化における加熱処理に比べて成形体、ひいては最終的に焼結体に残留する炭素の量を低減することができる。
The molded body obtained as described above contains the lubricant described above. As described above, since this lubricant reacts with rare earth elements, the amount of rare earth elements is insufficient as an R—Fe—B based sintered magnet, thereby deteriorating magnetic properties. Further, shrinkage during sintering becomes non-uniform in the sintered body, which may cause deformation after sintering.
Therefore, in the present invention, a characteristic treatment is applied to the molded body in order to remove the lubricant. This treatment is a heat treatment in which the compact is held for a predetermined time under an atmospheric gas containing H 2 O and H 2 . When this heat treatment is applied to the molded body, the amount of carbon remaining in the molded body and eventually the sintered body can be reduced as compared with the heat treatment in vacuum.

この潤滑剤除去のための加熱処理を行う雰囲気ガスにおいて、H2Oの分圧をP(H2O)、H2の分圧をP(H2)とすると、P(H2O)/P(H2)≧10-10とすることにより、潤滑剤の除去効果が顕著となる。さらに望ましくはP(H2O)/P(H2)≧10-5、より望ましくはP(H2O)/P(H2)を10-8〜10-4とする。
また、H2の分圧P(H2)が低くなると潤滑剤除去の効果が小さくなり、逆に高くなると装置の安全性を確保するために装置が高価になる。したがって、P(H2)は2〜130kPaの範囲とすることが望ましい。さらに望ましいP(H2)は27〜110kPaである。
In the atmosphere gas to perform heat treatment for the lubricant removal, the partial pressure of H 2 O P (H 2 O ), when the partial pressure of H 2 and P (H 2), P ( H 2 O) / By setting P (H 2 ) ≧ 10 −10 , the effect of removing the lubricant becomes remarkable. More desirably, P (H 2 O) / P (H 2 ) ≧ 10 −5 , and more desirably, P (H 2 O) / P (H 2 ) is set to 10 −8 to 10 −4 .
Further, if the H 2 partial pressure P (H 2 ) is lowered, the effect of removing the lubricant is reduced, and if it is increased, the apparatus is expensive in order to ensure the safety of the apparatus. Therefore, P (H 2 ) is desirably in the range of 2 to 130 kPa. Further desirable P (H 2 ) is 27 to 110 kPa.

潤滑剤除去のための加熱処理は、200〜600℃の温度範囲に保持することが望ましい。200℃未満では潤滑剤除去の効果を十分得ることができないためであり、一方、600℃を超えると効果が飽和するためである。ここで、200〜600℃の温度範囲に保持する、とは当該温度範囲の一定温度に成形体を保持する場合に限らず、所定時間だけ当該温度範囲のいずれかの温度に成形体が加熱されていればよい。したがって、200〜600℃にかけて連続的に昇温する形態、200〜600℃の範囲において段階的に温度を上昇させる形態等、種々の形態を包含する。望ましい加熱処理の温度は、250〜500℃、さらに望ましい加熱処理の温度は400〜500℃である。   The heat treatment for removing the lubricant is desirably held in a temperature range of 200 to 600 ° C. This is because if the temperature is less than 200 ° C., the effect of removing the lubricant cannot be obtained sufficiently, and if the temperature exceeds 600 ° C., the effect is saturated. Here, holding in the temperature range of 200 to 600 ° C. is not limited to holding the molded body at a constant temperature in the temperature range, and the molded body is heated to any temperature in the temperature range for a predetermined time. It only has to be. Therefore, various forms, such as a form in which the temperature is continuously increased over 200 to 600 ° C. and a form in which the temperature is increased stepwise in the range of 200 to 600 ° C., are included. A desirable heat treatment temperature is 250 to 500 ° C., and a more desirable heat treatment temperature is 400 to 500 ° C.

加熱処理の保持時間が短いと潤滑剤除去の効果が不十分であり、一方保持時間が長すぎても潤滑剤除去の効果が飽和してしまう。したがって、加熱処理の保持時間は、0.5〜10時間とすることが望ましく、さらには1〜3時間とすることが望ましい。   If the holding time of the heat treatment is short, the effect of removing the lubricant is insufficient, while if the holding time is too long, the effect of removing the lubricant is saturated. Therefore, the heat treatment holding time is preferably 0.5 to 10 hours, and more preferably 1 to 3 hours.

潤滑剤除去のための加熱処理を行う雰囲気ガスは、H2O、H2のほかに不活性ガスを含むことが望ましい。この不活性ガスは、H2O、H2のキャリアガスとして機能する。不活性ガスとしては、Arガス、N2ガスを用いることができる。不活性ガスの分圧をP(IG)とすると、雰囲気ガスにおいて不活性ガスは1kPa≦P(IG)≦130kPaの範囲で含むことが望ましい。 The atmosphere gas for performing the heat treatment for removing the lubricant desirably contains an inert gas in addition to H 2 O and H 2 . This inert gas functions as a carrier gas for H 2 O and H 2 . Ar gas or N 2 gas can be used as the inert gas. Assuming that the partial pressure of the inert gas is P (IG), it is desirable that the inert gas is included in the range of 1 kPa ≦ P (IG) ≦ 130 kPa in the atmospheric gas.

以上の潤滑剤除去処理が施された成形体は、焼結に供される。焼結は、真空又は不活性ガス雰囲気中、望ましくは真空中で行われる。焼結条件は、組成、粉砕方法、平均粒径と粒度分布の違い等、諸条件により調整する必要があるが、1000〜1100℃の温度で1〜10時間程度保持すれば緻密な焼結体を得ることができる。
焼結後、得られた焼結体に時効処理を施すことができる。この工程は、保磁力を制御する重要な工程である。時効処理を2段に分けて行なう場合には、800℃近傍、600℃近傍での所定時間の保持が有効である。また、600℃近傍の熱処理で保磁力が大きく増加するため、時効処理を1段で行なう場合には600℃近傍の時効処理を施すとよい。
The molded body that has been subjected to the above lubricant removal treatment is subjected to sintering. Sintering is performed in a vacuum or an inert gas atmosphere, preferably in a vacuum. Sintering conditions need to be adjusted according to various conditions such as composition, pulverization method, difference in average particle size and particle size distribution, etc., but a dense sintered body can be maintained at a temperature of 1000 to 1100 ° C. for about 1 to 10 hours. Can be obtained.
After sintering, the obtained sintered body can be subjected to an aging treatment. This step is an important step for controlling the coercive force. In the case where the aging treatment is performed in two stages, holding for a predetermined time at around 800 ° C. and around 600 ° C. is effective. In addition, since the coercive force is greatly increased by the heat treatment near 600 ° C., the aging treatment near 600 ° C. is preferably performed when the aging treatment is performed in one stage.

本発明を適用した希土類焼結磁石の製造方法において、潤滑剤除去のための加熱処理を独立して行うことができる。また、本発明において、潤滑剤除去のための加熱処理を焼結の昇温過程で行うこともできる。後者の形態を図1に示す。図1に示すように、潤滑剤除去のために焼結の昇温過程の所定の温度域(200〜600℃)で焼結炉内の雰囲気をH2O及びH2を含む雰囲気ガスとすればよい。もちろん、昇温当初から焼結炉内の雰囲気をH2O及びH2を含む雰囲気ガスとすることもできる。所定時間経過した後に、焼結炉から前記雰囲気ガスを排出し、かつ焼結炉内を減圧して所定の真空度にする。この真空度を維持しながら焼結温度まで昇温し、かつ所定時間保持する。なお、図1は潤滑剤除去を一定の温度に保持する例を示しているが、前述したように、図2に示すように連続的に昇温してもよいし、図3に示すように段階的に昇温してもよい。 In the method for producing a rare earth sintered magnet to which the present invention is applied, heat treatment for removing the lubricant can be performed independently. In the present invention, the heat treatment for removing the lubricant can also be performed during the temperature rising process of sintering. The latter form is shown in FIG. As shown in FIG. 1, in order to remove the lubricant, the atmosphere in the sintering furnace is replaced with an atmospheric gas containing H 2 O and H 2 in a predetermined temperature range (200 to 600 ° C.) in the temperature rising process of sintering. That's fine. Of course, the atmosphere in the sintering furnace can be an atmosphere gas containing H 2 O and H 2 from the beginning of the temperature rise. After a predetermined time has elapsed, the atmospheric gas is discharged from the sintering furnace, and the inside of the sintering furnace is depressurized to a predetermined degree of vacuum. While maintaining this degree of vacuum, the temperature is raised to the sintering temperature and held for a predetermined time. Although FIG. 1 shows an example in which the lubricant removal is held at a constant temperature, as described above, the temperature may be continuously increased as shown in FIG. 2, or as shown in FIG. The temperature may be raised stepwise.

本発明はR−T−B(Rは希土類元素の1種又は2種以上、TはFe又はFe及びCo)で示されるネオジム系焼結磁石について適用することが望ましい。
R−T−B系焼結磁石は、希土類元素(R)を25〜37wt%含有する。ここで、RはYを含む概念を有しており、したがってY、La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb及びLuの1種又は2種以上から選択される。Rの量が25wt%未満であると、R−T−B系焼結磁石の主相となるR214B相の生成が十分ではなく軟磁性を持つα−Feなどが析出し、保磁力が著しく低下する。一方、Rが37wt%を超えると主相であるR214B相の体積比率が低下し、残留磁束密度が低下する。またRが酸素と反応し、含有する酸素量が増え、これに伴い保磁力発生に有効なRリッチ相が減少し、保磁力の低下を招く。したがって、Rの量は25〜37wt%とする。望ましいRの量は28〜35wt%である。
The present invention is preferably applied to a neodymium-based sintered magnet represented by R-T-B (R is one or more rare earth elements and T is Fe or Fe and Co).
The RTB-based sintered magnet contains 25 to 37 wt% of rare earth element (R). Here, R has a concept including Y. Therefore, one or two of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Selected from more than species. If the amount of R is less than 25 wt%, the R 2 T 14 B phase, which is the main phase of the R-T-B system sintered magnet, is not sufficiently generated, and α-Fe having soft magnetism is precipitated and retained. The magnetic force is significantly reduced. On the other hand, when R exceeds 37 wt%, the volume ratio of the R 2 T 14 B phase, which is the main phase, decreases, and the residual magnetic flux density decreases. Further, R reacts with oxygen, the amount of oxygen contained increases, and accordingly, the R-rich phase effective for the generation of coercive force decreases, leading to a decrease in coercive force. Therefore, the amount of R is set to 25 to 37 wt%. A desirable amount of R is 28 to 35 wt%.

また、本発明が適用されるR−T−B系焼結磁石は、ホウ素(B)を0.5〜4.5wt%含有する。Bが0.5wt%未満の場合には高い保磁力を得ることができない。一方で、Bが4.5wt%を超えると残留磁束密度が低下する傾向がある。したがって、Bの上限を4.5wt%とする。望ましいBの量は0.5〜1.5wt%、さらに望ましいBの量は0.8〜1.2wt%である。
本発明が適用されるR−T−B系焼結磁石は、Coを5.0wt%以下(0を含まず)、望ましくは0.1〜3.0wt%含有することができる。CoはFeと同様の相を形成するが、キュリー温度の向上、粒界相の耐食性向上などに効果がある。
Further, the RTB-based sintered magnet to which the present invention is applied contains 0.5 to 4.5 wt% of boron (B). When B is less than 0.5 wt%, a high coercive force cannot be obtained. On the other hand, when B exceeds 4.5 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit of B is set to 4.5 wt%. A desirable amount of B is 0.5 to 1.5 wt%, and a more desirable amount of B is 0.8 to 1.2 wt%.
The RTB-based sintered magnet to which the present invention is applied can contain Co in an amount of 5.0 wt% or less (excluding 0), preferably 0.1 to 3.0 wt%. Co forms the same phase as Fe, but is effective in improving the Curie temperature and the corrosion resistance of the grain boundary phase.

本発明が適用されるR−T−B系焼結磁石は、他の元素の含有を許容する。例えば、Al、Cu、Zr、Ti、Bi、Sn、Ga、Nb、Ta、Si、V、Ag、Ge等の元素を適宜含有させることができる。一方で、酸素、窒素、炭素等の不純物元素を極力低減することが望ましい。特に磁気特性を害する酸素は、その量を8000ppm以下、さらには5000ppm以下とすることが望ましい。酸素量が多いと非磁性成分である希土類酸化物相が増大して、磁気特性を低下させるからである。   The RTB-based sintered magnet to which the present invention is applied allows the inclusion of other elements. For example, elements such as Al, Cu, Zr, Ti, Bi, Sn, Ga, Nb, Ta, Si, V, Ag, and Ge can be appropriately contained. On the other hand, it is desirable to reduce impurity elements such as oxygen, nitrogen, and carbon as much as possible. In particular, the amount of oxygen that impairs magnetic properties is desirably 8000 ppm or less, more preferably 5000 ppm or less. This is because when the amount of oxygen is large, the rare-earth oxide phase, which is a nonmagnetic component, increases and the magnetic properties are deteriorated.

31wt%Nd−0.2wt%Al−0.5wt%Co−0.07wt%Cu−1.0wt%B−残部Feからなる合金をストリップキャスト法により作製した。得られたストリップキャスト合金に室温で水素を吸蔵させた後に、500℃の温度下で脱水素する水素吸蔵・脱水素処理による粗粉砕を行った。その後、ジェットミルにより微粉砕を行って平均粒径4.0μmの粒径の微粉末を得た。なお、ジェットミルによる微粉砕を行う際に、オレイン酸アミドを0.1wt%添加した。   An alloy composed of 31 wt% Nd-0.2 wt% Al-0.5 wt% Co-0.07 wt% Cu-1.0 wt% B-remaining Fe was produced by strip casting. The obtained strip cast alloy was occluded with hydrogen at room temperature, and then coarsely pulverized by hydrogen occlusion / dehydrogenation treatment in which dehydrogenation was performed at a temperature of 500 ° C. Thereafter, fine pulverization was performed by a jet mill to obtain a fine powder having an average particle size of 4.0 μm. When finely pulverizing with a jet mill, 0.1 wt% of oleic acid amide was added.

次いでこの微粉末を、1200kA/mの磁場を印加しつつ150MPaの圧力で磁場中成形した。得られた成形体を3列×3列に整列してモリブテン容器に収容して、表1に示す種々の条件で潤滑剤除去のための熱処理を行った。成形体の寸法は、70×30×10mmである。この成形体を、真空中、1050℃で4時間保持することにより焼結体を得た。得られた焼結体について、炭素量、酸素量を測定するとともに、変形量を測定した。なお、変形量は、得られた焼結体の幅方向と長さ方向を含む面の長さ方向40mmの長さにおいて中間部のふくらみを図10に示すように測定し、その値を変形量とした。9個の焼結体のうち変形が最大であったものの変形量を表1に示す。さらに、この焼結体について磁気特性を測定した。その結果を表1に示す。また、炭素量、酸素量及び変形量については、P(H2O)/P(H2)との関係を、図4〜図6に示す。 Next, this fine powder was molded in a magnetic field at a pressure of 150 MPa while applying a magnetic field of 1200 kA / m. The obtained molded bodies were arranged in 3 rows × 3 rows and accommodated in a molybdenum container, and heat treatment for removing the lubricant was performed under various conditions shown in Table 1. The dimension of the molded body is 70 × 30 × 10 mm. The molded body was held in vacuum at 1050 ° C. for 4 hours to obtain a sintered body. About the obtained sintered compact, while measuring the carbon content and the oxygen content, the deformation amount was measured. The amount of deformation is measured by measuring the swelling of the intermediate portion as shown in FIG. 10 in the length direction of 40 mm of the surface including the width direction and the length direction of the obtained sintered body, and the value is the amount of deformation. It was. Table 1 shows the amount of deformation of the nine sintered bodies that had the greatest deformation. Furthermore, the magnetic characteristics of this sintered body were measured. The results are shown in Table 1. Moreover, the carbon amount, the oxygen amount and the deformation amount, the relationship between P (H 2 O) / P (H 2), 4 to 6.

Figure 2006063387
Figure 2006063387

表1に示すように、潤滑剤除去を真空中で加熱する方法に比べて、H2O及びH2を含む雰囲気ガス中で加熱する方が、焼結体の炭素量を低減することができ、焼結体の変形量が少なくなることがわかる。
図4〜図6に示すように、H2O及びH2を含む雰囲気ガス中における加熱において、P(H2O)/P(H2)が大きくなると炭素量が少なくなって変形量も小さくなる一方、酸素量は多くなることがわかる。
また、P(H2O)/P(H2)の値が大きくなる、つまり水の量が多くなると、焼結体の酸素量が増大して磁気特性に劣化が生じる傾向がある。したがって、焼結体の変形抑制のみを考えればP(H2O)/P(H2)は小さいほど良いが、変形と磁気特性の両者を考慮すると、P(H2O)/P(H2)を10-8〜10-4とするのが良い。
As shown in Table 1, the amount of carbon in the sintered body can be reduced by heating in an atmosphere gas containing H 2 O and H 2 as compared with the method of heating the lubricant in vacuum. It can be seen that the amount of deformation of the sintered body is reduced.
As shown in FIGS. 4 to 6, in the heating in the atmospheric gas containing H 2 O and H 2 , when P (H 2 O) / P (H 2 ) increases, the amount of carbon decreases and the amount of deformation decreases. On the other hand, it can be seen that the amount of oxygen increases.
Further, when the value of P (H 2 O) / P (H 2 ) increases, that is, the amount of water increases, the amount of oxygen in the sintered body tends to increase and the magnetic properties tend to deteriorate. Therefore, considering only the deformation suppression of the sintered body, the smaller P (H 2 O) / P (H 2 ) is better, but considering both deformation and magnetic properties, P (H 2 O) / P (H 2 ) should be 10 −8 to 10 −4 .

次に、潤滑剤除去のための加熱温度を変えて、上記と同様の測定を行った、その結果を表2及び図7〜図9に示す。加熱温度が300〜500℃の範囲において、本発明の効果を享受できることが確認できる。   Next, the heating temperature for removing the lubricant was changed and the same measurement as described above was performed. The results are shown in Table 2 and FIGS. It can be confirmed that the effects of the present invention can be enjoyed when the heating temperature is in the range of 300 to 500 ° C.

Figure 2006063387
Figure 2006063387

焼結の昇温過程に本発明の潤滑剤除去処理を行う一形態を示す図である。It is a figure which shows one form which performs the lubricant removal process of this invention in the temperature rising process of sintering. 焼結の昇温過程に本発明の潤滑剤除去処理を行う他の形態を示す図である。It is a figure which shows the other form which performs the lubricant removal process of this invention in the temperature rising process of sintering. 焼結の昇温過程に本発明の潤滑剤除去処理を行う他の形態を示す図である。It is a figure which shows the other form which performs the lubricant removal process of this invention in the temperature rising process of sintering. P(H2O)/P(H2)と焼結体の炭素量の関係を示すグラフである。And P (H 2 O) / P (H 2) is a graph showing the amount of carbon relation sintered body. P(H2O)/P(H2)と焼結体の酸素量の関係を示すグラフである。Is a graph showing the relationship between P (H 2 O) / P (H 2) and oxygen content of the sintered body. P(H2O)/P(H2)と焼結体の変形量の関係を示すグラフである。It is a graph showing the relationship between P (H 2 O) / P (H 2) and the amount of deformation of the sintered body. 加熱温度と焼結体の炭素量の関係を示すグラフである。It is a graph which shows the relationship between heating temperature and the carbon content of a sintered compact. 加熱温度と焼結体の酸素量の関係を示すグラフである。It is a graph which shows the relationship between heating temperature and the oxygen content of a sintered compact. 加熱温度と焼結体の酸素量の関係を示すグラフである。It is a graph which shows the relationship between heating temperature and the oxygen content of a sintered compact. 実施例における焼結体変形量の測定方法を示す図である。It is a figure which shows the measuring method of the sintered compact deformation amount in an Example.

Claims (7)

有機物を構成要素とする潤滑剤と所定組成の合金粉末とを含む組成物を磁場中で加圧成形して成形体を得る工程と、
前記成形体を、H2O及びH2を含む雰囲気ガスの下で加熱処理することにより前記潤滑剤を除去する工程と、
を備えることを特徴とする希土類焼結磁石の製造方法。
A step of pressure-molding a composition containing a lubricant containing an organic substance and an alloy powder having a predetermined composition in a magnetic field to obtain a molded body;
Removing the lubricant by heat-treating the molded body under an atmosphere gas containing H 2 O and H 2 ;
A method for producing a rare earth sintered magnet.
前記雰囲気ガスにおけるH2Oの分圧をP(H2O)、H2の分圧をP(H2)とすると、P(H2O)/P(H2)≧10-10であることを特徴とする請求項1に記載の希土類焼結磁石の製造方法。 The partial pressure of H 2 O in the atmospheric gas P (H 2 O), when the partial pressure of H 2 and P (H 2), is P (H 2 O) / P (H 2) ≧ 10 -10 The method for producing a rare earth sintered magnet according to claim 1. P(H2)が2〜130kPaであることを特徴とする請求項1又は2に記載の希土類焼結磁石の製造方法。 The method for producing a rare earth sintered magnet according to claim 1, wherein P (H 2 ) is 2 to 130 kPa. 前記加熱処理は、200〜600℃の温度範囲で所定時間保持することを特徴とする請求項1〜3のいずれかに記載の希土類焼結磁石の製造方法。   The method for producing a rare earth sintered magnet according to any one of claims 1 to 3, wherein the heat treatment is held for a predetermined time in a temperature range of 200 to 600 ° C. 前記雰囲気ガスは、不活性ガスを含むことを特徴とする請求項1〜4のいずれかに記載の希土類焼結磁石の製造方法。   The method for producing a rare earth sintered magnet according to claim 1, wherein the atmospheric gas includes an inert gas. 前記成形体を焼結する工程を備え、
前記成形体を所定の焼結温度まで昇温する過程で前記成形体をH2O及びH2を含む前記雰囲気ガスの下で加熱処理することを特徴とする請求項1〜5のいずれかに記載の希土類焼結磁石の製造方法。
Comprising the step of sintering the molded body,
The heat treatment is performed under the atmosphere gas containing H 2 O and H 2 in the process of raising the temperature of the formed body to a predetermined sintering temperature. The manufacturing method of the rare earth sintered magnet of description.
前記潤滑剤は、脂肪酸又は脂肪酸の誘導体の1種又は2種以上から選択されることを特徴とする請求項1〜6のいずれかに記載の希土類焼結磁石の製造方法。   The method for producing a rare earth sintered magnet according to any one of claims 1 to 6, wherein the lubricant is selected from one or more of fatty acids or fatty acid derivatives.
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