JP4282013B2 - Manufacturing method of rare earth sintered magnet - Google Patents
Manufacturing method of rare earth sintered magnet Download PDFInfo
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- JP4282013B2 JP4282013B2 JP2004193725A JP2004193725A JP4282013B2 JP 4282013 B2 JP4282013 B2 JP 4282013B2 JP 2004193725 A JP2004193725 A JP 2004193725A JP 2004193725 A JP2004193725 A JP 2004193725A JP 4282013 B2 JP4282013 B2 JP 4282013B2
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- Hard Magnetic Materials (AREA)
- Manufacturing Cores, Coils, And Magnets (AREA)
Description
本発明は、Ｎｄ−Ｆｅ−Ｂ系に代表される希土類焼結磁石を製造する際に用いられる原料粉体に関し、特に原料粉体を顆粒化することにより、磁場中成形時の金型への充填性を向上することにより高い生産性を得るとともに、希土類焼結磁石の小型化への対応を容易にすることのできる手法に関するものである。 The present invention relates to a raw material powder used when producing a rare earth sintered magnet typified by an Nd-Fe-B system, and in particular, by granulating the raw material powder, it can be applied to a mold during molding in a magnetic field. The present invention relates to a technique capable of obtaining high productivity by improving the filling property and facilitating the correspondence to downsizing of rare earth sintered magnets.
希土類焼結磁石を製造する際、焼結に供する原料粉末を微細化することにより飽和磁束密度及び保磁力等の磁気特性を確保している。ところが、原料粉末の微細化は、成形体の寸法精度、生産性を阻害する要因となる。
原料粉末は磁場中での加圧成形により成形体を構成する。この磁場中成形において、静磁場又はパルス磁場を印加して原料粉末の粒子を配向させる。この磁場中成形時、原料粉末が微細であるほどその流動性が悪く、金型への充填性が問題となる。粉末の金型への充填性が劣ると、金型へ粉末を十分に充填することができないために成形体の寸法精度が得られない、あるいは金型への充填自体に時間がかかって生産性を阻害するという問題がある。特に薄肉形状や複雑形状の成形体を精度よくかつ効率的に作製することは困難である。
When manufacturing rare earth sintered magnets, magnetic properties such as saturation magnetic flux density and coercive force are ensured by refining the raw material powder used for sintering. However, the refinement of the raw material powder becomes a factor that hinders the dimensional accuracy and productivity of the compact.
The raw material powder forms a compact by pressure molding in a magnetic field. In the molding in the magnetic field, the raw powder particles are oriented by applying a static magnetic field or a pulse magnetic field. At the time of molding in this magnetic field, the finer the raw material powder, the worse the fluidity and the problem of filling into the mold. If the powder filling property is inferior, the powder cannot be sufficiently filled into the die, so the dimensional accuracy of the molded product cannot be obtained, or the filling of the die itself takes time and productivity. There is a problem of inhibiting. In particular, it is difficult to accurately and efficiently produce a molded body having a thin shape or a complicated shape.
原料粉末の流動性向上の手段の一つとして原料粉末の顆粒化が試みられている。例えば、特開平８−１０７０３４号公報（特許文献１）および特開平８−８８１１１号公報（特許文献２）は希土類金属粉末にバインダを添加したスラリをスプレードライすることにより顆粒化する提案を行っている。
また、特公平７−６０２５号公報（特許文献３）は、希土類金属粉末に磁界を印加して顆粒化する提案を行っている。
Attempts have been made to granulate the raw material powder as one means for improving the fluidity of the raw material powder. For example, JP-A-8-107034 (Patent Document 1) and JP-A-8-88111 (Patent Document 2) propose to granulate by spray-drying a slurry in which a binder is added to a rare earth metal powder. Yes.
Japanese Patent Publication No. 7-6025 (Patent Document 3) proposes granulating a rare earth metal powder by applying a magnetic field.
特許文献１及び２によれば、顆粒を作製することにより流動性を向上することができる。しかし、一次合金粒子同士を例えばＰＶＡ（ポリビニルアルコール）といったバインダで結着しているため、一次合金粒子同士の結着力が比較的強い。このように結着力の強い顆粒を磁場中成形に供しても、各一次合金粒子を配向させることは容易ではない。したがって、得られる希土類焼結磁石は配向度が低く磁気特性、特に残留磁束密度（Ｂｒ）が低いものとなる。また、バインダに含まれる炭素が磁気特性低下の要因となることから、このバインダを除去する工程が必要となる。
特許文献３によれば、加圧体作製時の磁界印加工程および顆粒を金型に充填後、磁気特性を向上させるための交流磁界印加工程を要する。また、磁界を印加した顆粒であるため残留磁化による流動性の低下が懸念される。
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、優れた流動性を有する顆粒を用い、成形体の寸法精度の向上及び生産性の向上を図るとともに、特性を大きく低下させることなく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。
According to
According to
The present invention has been made on the basis of such a technical problem, and uses granules having excellent fluidity to improve the dimensional accuracy and productivity of the molded body and to greatly reduce the characteristics. An object of the present invention is to provide a method for producing a rare earth sintered magnet.
上述したように、従来のバインダを用いる顆粒化技術では、バインダを溶解する溶媒として、また、一次合金粒子を分散する分散媒として、所謂有機溶媒を所定量含むスラリを作製していた。本発明者らは、この有機溶媒に着目した。その結果、有機溶媒のみで顆粒を作製することができ、この顆粒は金型充填時の流動性に優れること、さらに有機溶媒のみで作製されたこの顆粒は一次合金粒子同士の結着力が比較的弱いため、磁場中成形時に印加される磁場により一次合金粒子に分離して、良好な配向状態を実現できることを確認した。したがって本発明は、所定組成の一次合金粒子同士が有機液体により結着された顆粒を作製する工程と、顆粒から有機液体の一部を除去する工程と、有機液体の一部が除去された顆粒を金型キャビティに投入する工程と、金型キャビティに投入された顆粒に磁場を印加し、かつ加圧成形することにより成形体を得る工程と、成形体を焼結する工程と、を備え、有機液体は、エタノール、トルエン、カルビトール、テルペン系化合物、ブチルカルビトール、酢酸ブチルカルビトール、酢酸ｎ−ブチル、ブチルセロソルブ、シクロヘキサノール、ターピネオール、及びピネンの１種又は２種以上であることを特徴とする希土類焼結磁石の製造方法を提供する。
本発明において、有機液体の一部を除去する工程は、顆粒を減圧雰囲気に晒すことによって実行することができるし、さらに、所定の温度に加熱された雰囲気（減圧であってもよい）に顆粒を晒すことによって実行することができる。
As described above, in the granulation technique using a conventional binder, a slurry containing a predetermined amount of a so-called organic solvent is produced as a solvent for dissolving the binder and as a dispersion medium for dispersing the primary alloy particles. The present inventors paid attention to this organic solvent. As a result, it is possible to produce granules only with an organic solvent, the granules are excellent in fluidity when filled with a mold, and the granules produced only with an organic solvent have a relatively high binding force between primary alloy particles. Since it was weak, it was confirmed that it could be separated into primary alloy particles by a magnetic field applied during molding in a magnetic field and a good orientation state could be realized. Accordingly, the present invention provides a step of producing a granule in which primary alloy particles of a predetermined composition are bound together by an organic liquid, a step of removing a portion of the organic liquid from the granule, and a granule from which a portion of the organic liquid has been removed. And a step of applying a magnetic field to the granules put in the mold cavity and obtaining a molded body by pressure molding, and a step of sintering the molded body , the organic liquid is ethanol, toluene, carbitol, terpene compounds, butyl carbitol, butyl carbitol acetate, acetate n- butyl, butyl cellosolve, cyclohexanol, terpineol, and der Rukoto one or more pinene A rare earth sintered magnet manufacturing method is provided.
In the present invention, the step of removing a part of the organic liquid can be performed by exposing the granule to a reduced-pressure atmosphere, and further, the granule can be placed in an atmosphere heated to a predetermined temperature (which may be a reduced pressure). Can be done by exposing.
本発明において、一次合金粒子に対して、有機液体を１．５〜１５．０ｗｔ％添加することが望ましい。１．５ｗｔ％以下では、顆粒を効率よく作製することが困難な場合があるためであり、１５．０ｗｔ％を超えると湿分が多すぎて、適切な磁場中成形を行うために不必要な湿分を除去する作業に手間取るからである。
本発明における有機液体は、２０℃における飽和蒸気圧が７５ｍｍＨｇ(１０．０ｋＰａ)以下、２０℃における表面張力が２０ｄｙｎ／ｃｍ以上、２０℃における粘度が０．３５ｃｐ以上の特性を備えることが望ましい。作製された顆粒の形態を維持するために、これら物性を具備することがのぞまれる。本発明における有機液体としては、エタノール、トルエン、カルビトール、テルペン系化合物、ブチルカルビトール、酢酸ブチルカルビトール、酢酸ｎ−ブチル、ブチルセロソルブ、シクロヘキサノール、ターピネオール、及びピネンの１種又は２種以上を用いる。好ましくは、ブチルセロソルブ、ブチルカルビトール、ターピネオール、ピネンである。
In the present invention, it is desirable to add 1.5 to 15.0 wt% of the organic liquid with respect to the primary alloy particles. If it is 1.5 wt% or less, it may be difficult to produce granules efficiently, and if it exceeds 15.0 wt%, the moisture is too much and is not necessary to perform molding in an appropriate magnetic field. This is because it takes time to remove the moisture.
The organic liquid in the present invention desirably has characteristics such that a saturated vapor pressure at 20 ° C. is 75 mmHg (10.0 kPa) or less, a surface tension at 20 ° C. is 20 dyn / cm or more, and a viscosity at 20 ° C. is 0.35 cp or more. In order to maintain the shape of the produced granules, it is desirable to have these physical properties. As the organic liquid in the present invention, one or more of ethanol, toluene, carbitol, terpene compounds, butyl carbitol, butyl carbitol acetate, n-butyl acetate, butyl cellosolve, cyclohexanol , terpineol, and pinene are used. Use. Preferably, butyl cellosolve, butyl carbitol, terpineol, a-pinene.
本発明による顆粒は、金型キャビティへの迅速な投入を実現するために、有機液体の１部が除去された後に安息角が５０°以下であることが望ましい。
また本発明は、Ｒ2Ｔ14Ｂ相（Ｒは希土類元素から選択される１種又は２種以上の元素、ＴはＦｅ又はＦｅ及びＣｏを含む遷移金属元素から選択される１種又は２種以上の元素）を含む組成を有し、平均粒径が２．５〜６μｍである一次合金粒子に適用することが望ましい。
The granule according to the present invention preferably has an angle of repose of 50 ° or less after a part of the organic liquid is removed, in order to realize rapid injection into the mold cavity.
The present invention also provides an R 2 T 14 B phase (where R is one or more elements selected from rare earth elements, and T is one or two elements selected from transition metal elements including Fe, Fe, and Co). It is desirable to apply to primary alloy particles having a composition containing the above elements) and having an average particle diameter of 2.5 to 6 μm.
本発明によれば、有機液体により一次合金粒子が結着された顆粒を用いるために脱バインダ処理を行う必要がなく、成形体の寸法精度を向上しつつ希土類焼結磁石の生産性を向上することが可能となる。また、顆粒を一旦作製した後に、有機液体の一部を除去することにより、磁気特性の向上に寄与する。 According to the present invention, it is not necessary to perform a binder removal process because a granule in which primary alloy particles are bound with an organic liquid is used, and the productivity of the rare earth sintered magnet is improved while improving the dimensional accuracy of the compact. It becomes possible. Moreover, once a granule is produced, a part of the organic liquid is removed, which contributes to improvement of magnetic properties.
以下、本発明を実施の形態に基づいて詳細に説明する。
本発明は、有機液体により粉末同士を結着させることにより顆粒を構成する。有機液体が粒子間に存在することにより液体架橋が生じて一次合金粒子同士を結着させている。有機液体による結着力は、従来のＰＶＡ等のバインダによる結着力に比べて極めて弱い。したがって、本発明により得られた顆粒は、磁場中成形時に印加される磁場によって容易に崩壊し一次合金粒子に分離する。そのため、高い配向度を得ることができる。これまで、バインダを用いることが顆粒作製の前提として考えられてきたが、本発明のように有機液体を用いた場合でも、流動性の高い顆粒が得られることを見出した価値は大きい。しかも、この顆粒は、磁場印加により崩壊するため、磁場中成形を行う希土類焼結磁石にとって好適である。加えて、有機液体は、従来のバインダであるＰＶＡ等の樹脂に比べて、成形体からの除去が極めて容易であり、従来の顆粒技術を用いた場合には必須とされていた脱バインダ工程を省くことが可能であり、工程的な利点をも含んでいる。
Hereinafter, the present invention will be described in detail based on embodiments.
In the present invention, granules are formed by binding powders with an organic liquid. The presence of the organic liquid between the particles causes liquid crosslinking to bind the primary alloy particles. The binding force by the organic liquid is extremely weak compared to the binding force by a conventional binder such as PVA. Therefore, the granules obtained by the present invention are easily disintegrated and separated into primary alloy particles by a magnetic field applied during molding in a magnetic field. Therefore, it is possible to obtain a high Oriented degree. Up to now, the use of a binder has been considered as a premise for the production of granules. However, even when an organic liquid is used as in the present invention, it is highly valuable to find that granules with high fluidity can be obtained. Moreover, since the granules are collapsed by applying a magnetic field, they are suitable for rare earth sintered magnets that are molded in a magnetic field. In addition, the organic liquid is much easier to remove from the molded body than the conventional binder resin such as PVA, and the debinding process, which is essential when using the conventional granule technology, is performed. It can be omitted and includes process advantages.
以上の有機液体を用いた顆粒化技術を適用した希土類焼結磁石の製造方法について以下説明する。
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。なお、溶解後の偏析を防止するため、例えば水冷銅板に傾注して凝固させることができる。また、還元拡散法によって得られた合金を原料合金として用いることもできる。
Ｒ−Ｔ−Ｂ系焼結磁石を得る場合、Ｒ2Ｔ14Ｂ結晶粒を主体とする合金（低Ｒ合金）と、低Ｒ合金よりＲを多く含む合金（高Ｒ合金）とを用いる所謂混合法を本発明に適用することもできる。
A method for producing a rare earth sintered magnet to which the above granulation technique using an organic liquid is applied will be described below.
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 in the form of a thin plate or flakes (scales). 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. In order to prevent segregation after dissolution, for example, it can be solidified by pouring into a water-cooled copper plate. An alloy obtained by the reduction diffusion method can also be used as a raw material alloy.
When obtaining an RTB-based sintered magnet, a so-called alloy using a R 2 T 14 B crystal grain (low R alloy) and an alloy containing more R than a low R alloy (high R alloy) is used. A mixing method can also be applied to the present invention.
原料合金は粉砕工程に供される。混合法による場合には、低Ｒ合金及び高Ｒ合金は別々に又は一緒に粉砕される。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。水素放出処理は、希土類焼結磁石として不純物となる水素を減少させることを目的として行われる。水素放出のための加熱保持の温度は、２００℃以上、望ましくは３５０℃以上とする。保持時間は、保持温度との関係、原料合金の厚さ等によって変わるが、少なくとも３０分以上、望ましくは１時間以上とする。水素放出処理は、真空中又はＡｒガスフローにて行う。なお、水素吸蔵処理、水素放出処理は必須の処理ではない。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. In the case of the mixing method, the low R alloy and the high R alloy are pulverized separately or together. 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. The hydrogen releasing treatment is performed for the purpose of reducing hydrogen as an impurity as a rare earth sintered magnet. The temperature of heating and holding for releasing hydrogen is 200 ° C. or higher, desirably 350 ° C. or higher. The holding time varies depending on the relationship with the holding temperature, the thickness of the raw material alloy, etc., but is at least 30 minutes or longer, preferably 1 hour or longer. The hydrogen release treatment is performed in a vacuum or Ar gas flow. The hydrogen storage process and the hydrogen release process are not essential processes. 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、望ましくは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。 After the coarse pulverization process, the process proceeds to the fine pulverization process. A jet mill is mainly used for fine pulverization, and a 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.
混合法による場合、２種の合金の混合のタイミングは限定されるものではないが、微粉砕工程において低Ｒ合金及び高Ｒ合金を別々に粉砕した場合には、微粉砕された低Ｒ合金粉末及び高Ｒ合金粉末を窒素雰囲気中で混合する。低Ｒ合金粉末及び高Ｒ合金粉末の混合比率は、重量比で８０：２０〜９７：３程度とすればよい。低Ｒ合金及び高Ｒ合金を一緒に粉砕する場合の混合比率も同様である。なお、成形時の潤滑及び配向性の向上を目的とした脂肪酸又は脂肪酸の誘導体や炭化水素、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、ステアリン酸アルミニウム、ステアリン酸アミド、オレイン酸アミド、エチレンビスイソステアリン酸アミド、炭化水素であるパラフィン、ナフタレン等を微粉砕時に０．０１〜０．３ｗｔ％程度添加することができる。 In the case of the mixing method, the timing of mixing the two kinds of alloys is not limited. However, when the low R alloy and the high R alloy are separately pulverized in the pulverization step, the pulverized low R alloy powder is used. And high R alloy powder in a nitrogen atmosphere. The mixing ratio of the low R alloy powder and the high R alloy powder may be about 80:20 to 97: 3 by weight. The mixing ratio when the low R alloy and the high R alloy are pulverized together is the same. In addition, fatty acids or fatty acid derivatives and hydrocarbons for the purpose of improving the lubrication and orientation during molding, such as zinc stearate, calcium stearate, aluminum stearate, stearamide, olein, which are stearic acid and oleic acid Acid amide, ethylenebisisostearic acid amide, hydrocarbon paraffin, naphthalene and the like can be added in an amount of about 0.01 to 0.3 wt% during pulverization.
以上で得られた微粉砕粉末を造粒して顆粒を作製する。
本発明は有機液体を用いて顆粒を作製する。本発明で用いる有機液体としては、炭化水素系化合物、アルコール系化合物、エーテル系（グリコールエーテル系を含む）化合物、エステル系（グリコールエーテル系を含む）化合物、ケトン系化合物、脂肪酸系化合物、テルペン系化合物の１種又は２種以上から選択することができる。なお、有機液体は、一般に有機溶媒と呼ばれている物質を包含するが、本発明では溶媒として機能しないことから有機液体と呼んでいる。
Granules are produced by granulating the finely pulverized powder obtained above.
In the present invention, granules are prepared using an organic liquid. Examples of the organic liquid used in the present invention include hydrocarbon compounds, alcohol compounds, ether compounds (including glycol ether compounds), ester compounds (including glycol ether compounds), ketone compounds, fatty acid compounds, and terpene compounds. It can be selected from one or more compounds. The organic liquid includes a substance generally called an organic solvent, but is called an organic liquid because it does not function as a solvent in the present invention.
有機液体を用いて作製された顆粒は、所定の工程までその形状を維持している必要がある。一旦作製された顆粒がその形状を維持できなくなると、顆粒から脱落した微細な一次合金粒子が顆粒の周囲に付着した形態を成し、この形態の顆粒は流動性を低下させる。したがって、本発明に用いる有機液体としては、容易に揮発しないことが望ましい。そこで本発明では、２０℃における飽和蒸気圧が７５ｍｍＨｇ(１０．０ｋＰａ)以下の有機液体を用いることが望ましい。より望ましい２０℃における飽和蒸気圧は２０ｍｍＨｇ以下、さらに望ましい２０℃における飽和蒸気圧は５ｍｍＨｇ以下である。 Granules produced using an organic liquid need to maintain their shape until a predetermined step. Once the formed granule cannot maintain its shape, fine primary alloy particles dropped from the granule form a form attached to the periphery of the granule, and this form of the granule reduces fluidity. Therefore, it is desirable that the organic liquid used in the present invention does not volatilize easily. Therefore, in the present invention, it is desirable to use an organic liquid having a saturated vapor pressure at 20 ° C. of 75 mmHg (10.0 kPa) or less. The saturated vapor pressure at 20 ° C. is more preferably 20 mmHg or less, and the more desirable saturated vapor pressure at 20 ° C. is 5 mmHg or less.
本発明に用いる有機液体はまた、一次合金粒子間に顆粒を維持するための十分な結着力を付与する必要がある。そのために、有機液体の表面張力、粘度を特定することが本発明では望ましい。望ましい有機液体の表面張力は、２０℃において２０ｄｙｎ／ｃｍ以上である。より望ましい２０℃における表面張力は２５ｄｙｎ／ｃｍ以上、さらに望ましい２０℃における表面張力は３０ｄｙｎ／ｃｍ以上である。また、望ましい有機液体の粘度は、２０℃において０．３５ｃｐ以上である。より望ましい２０℃における粘度は１ｃｐ以上、さらに望ましい２０℃における粘度は２ｃｐ以上である。 The organic liquid used in the present invention must also provide a sufficient binding force to maintain the granules between the primary alloy particles. Therefore, it is desirable in the present invention to specify the surface tension and viscosity of the organic liquid. The surface tension of the desired organic liquid is 20 dyn / cm or more at 20 ° C. The more desirable surface tension at 20 ° C. is 25 dyn / cm or more, and the more desirable surface tension at 20 ° C. is 30 dyn / cm or more. The desirable viscosity of the organic liquid is 0.35 cp or more at 20 ° C. A more desirable viscosity at 20 ° C. is 1 cp or more, and a further desirable viscosity at 20 ° C. is 2 cp or more.
微粉砕粉末に対する有機液体の添加量は特に制限されないが、有機液体の添加量が少なすぎると、一次合金粒子同士に液体架橋を生じさせるに足る液量を確保することができないために、顆粒化が困難である。一方、有機液体の添加量が多すぎると、得られた顆粒をそのまま磁場中成形する場合に液体が過剰に存在して成形を阻害するおそれがある。以上より、微粉砕粉末に対する有機液体の添加量は１．５〜１５．０ｗｔ％とすることを推奨する。より望ましい有機液体の添加量は１．５〜８．０ｗｔ％、さらに望ましい有機液体の添加量は２．０〜６．０ｗｔ％である。なお、有機液体の添加量が多い場合は、その一部を除去すればよいので、添加量が少ない場合に比べると本質的な問題とは言えない。 The amount of the organic liquid added to the finely pulverized powder is not particularly limited, but if the amount of the organic liquid added is too small, the amount of liquid sufficient to cause liquid crosslinking between primary alloy particles cannot be secured. Is difficult. On the other hand, when the amount of the organic liquid added is too large, when the obtained granule is molded as it is in a magnetic field, an excessive amount of liquid may be present to inhibit the molding. From the above, it is recommended that the amount of organic liquid added to the finely pulverized powder is 1.5 to 15.0 wt%. A more desirable addition amount of the organic liquid is 1.5 to 8.0 wt%, and a more desirable addition amount of the organic liquid is 2.0 to 6.0 wt%. In addition, when the addition amount of the organic liquid is large, it suffices to remove a part thereof, so that it is not an essential problem as compared with the case where the addition amount is small.
微粉砕粉末と有機液体とを用いて顆粒を作製する方法は、従来公知の造粒法を適用すればよい。適用できる造粒方法としては、転動造粒法、振動造粒法、混合造粒法、流動造粒法、解砕造粒法、圧縮成形造粒法、押出し造粒法、噴霧造粒法が掲げられる。微粉砕粉末と有機液体は、造粒法に応じて当該造粒法適用の前に混合、混錬される場合と、造粒法適用時に混合、混錬される場合がある。 A conventionally known granulation method may be applied as a method for producing granules using finely pulverized powder and an organic liquid. Applicable granulation methods include rolling granulation method, vibration granulation method, mixed granulation method, fluidized granulation method, disintegration granulation method, compression molding granulation method, extrusion granulation method, spray granulation method Are listed. Depending on the granulation method, the finely pulverized powder and the organic liquid may be mixed and kneaded before application of the granulation method, or may be mixed and kneaded when the granulation method is applied.
本発明では、以上のようにして得られた顆粒を構成する有機液体の一部を除去する。有機液体は、従来のＰＶＡ等のバインダに比べると磁気特性に与える影響は極めて小さく、かつ後述する焼結工程において容易に除去される。しかし、添加された全てを除去することが困難である一方、顆粒作製のために添加される量は、実際に顆粒を形成するために最小限必要な量よりも多い。つまり、顆粒作製時には有機液体が一次合金粒子全体に湿分を与える必要があり、このために添加される有機液体の量は、顆粒を構成、維持するために最低限必要な有機液体の量よりも多い。そこで本発明では、顆粒作製に必要な湿分を与える量を当初添加して顆粒を作製した後に、有機液体の一部を除去して有機液体の顆粒における残量を制御しようというものである。 In the present invention, a part of the organic liquid constituting the granule obtained as described above is removed. The organic liquid has an extremely small influence on the magnetic properties as compared with a conventional binder such as PVA, and is easily removed in a sintering process described later. However, while it is difficult to remove all added, the amount added to make the granule is higher than the minimum required to actually form the granule. In other words, it is necessary for the organic liquid to moisten the entire primary alloy particles during granule production, and the amount of organic liquid added for this purpose is less than the minimum amount of organic liquid necessary to constitute and maintain the granule. There are also many. Therefore, in the present invention, the amount of moisture necessary for granule preparation is initially added to produce granules, and then a part of the organic liquid is removed to control the remaining amount of the organic liquid in the granules.
有機液体の一部の除去を行う具体的な手段は特に限定されないが、減圧雰囲気に顆粒を晒して揮発させることが簡易かつ効果的である。減圧雰囲気は室温であってもよいが、加熱された減圧雰囲気とすることもできるし、減圧していない加熱雰囲気とすることもできる。減圧雰囲気の圧力が低すぎると有機液体の揮発が十分に進まないために顆粒に残留する有機液体の量を所定量に制御することができない。一方、圧力が高すぎると有機液体の揮発が急激であるため顆粒に残留する有機液体の制御するのが難しくなる。そこで本発明は、減圧雰囲気の圧力を１０-1〜１０-5Ｔｏｒｒの範囲とすることが望ましい。ただし、加熱された減圧雰囲気の場合は、１０0〜１０-2Ｔｏｒｒの範囲で足りる。このときの加熱温度が低すぎると有機液体の揮発が十分進まず、逆に加熱温度が高すぎると顆粒を構成する一次合金粒子に酸化が生じ磁気特性の劣化を招くおそれがある。したがって本発明では、加熱温度を４０〜８０℃とすることが望ましい。 A specific means for removing a part of the organic liquid is not particularly limited, but it is simple and effective to volatilize the granules by exposing them to a reduced pressure atmosphere. The reduced-pressure atmosphere may be room temperature, but may be a heated reduced-pressure atmosphere or a heated atmosphere that is not reduced in pressure. If the pressure in the reduced-pressure atmosphere is too low, volatilization of the organic liquid does not proceed sufficiently, so that the amount of the organic liquid remaining in the granules cannot be controlled to a predetermined amount. On the other hand, if the pressure is too high, volatilization of the organic liquid is rapid and it becomes difficult to control the organic liquid remaining in the granules. Therefore, in the present invention, it is desirable that the pressure of the decompressed atmosphere is in the range of 10 −1 to 10 −5 Torr. However, in the case of a heated reduced-pressure atmosphere, the range of 10 0 to 10 −2 Torr is sufficient. If the heating temperature at this time is too low, the volatilization of the organic liquid does not proceed sufficiently. On the other hand, if the heating temperature is too high, the primary alloy particles constituting the granules may be oxidized and the magnetic properties may be deteriorated. Therefore, in the present invention, the heating temperature is desirably 40 to 80 ° C.
以上のようにして有機液体の一部が除去された顆粒に有機液体がある程度残留してないと顆粒の形態を維持することができない。一方、顆粒に残留する有機液体の量が多すぎると磁気特性向上の効果を享受することができない。そこで本発明では、有機液体の一部が除去された顆粒に残留する有機液体の量は０〜６．０ｗｔ％以下（ただし、０を含まず）の範囲とすることが望ましい。より望ましい顆粒に残留する有機液体の量は０．１〜４．０ｗｔ％、さらに望ましい顆粒に残留する有機液体の量は０．２〜３．０ｗｔ％である。 If the organic liquid does not remain to some extent in the granule from which a part of the organic liquid has been removed as described above, the form of the granule cannot be maintained. On the other hand, if the amount of the organic liquid remaining in the granules is too large, the effect of improving the magnetic properties cannot be enjoyed. Therefore, in the present invention, the amount of the organic liquid remaining in the granule from which part of the organic liquid has been removed is desirably in the range of 0 to 6.0 wt% or less (excluding 0). The amount of the organic liquid remaining in the more desirable granule is 0.1 to 4.0 wt%, and the amount of the organic liquid remaining in the more desirable granule is 0.2 to 3.0 wt%.
以上のようにして得られた顆粒状の造粒粉は磁場中成形に供される。
磁場中成形における成形圧力は０．３〜３ｔｏｎ／ｃｍ2（３０〜３００ＭＰａ）の範囲とすればよい。成形圧力は成形開始から終了まで一定であってもよく、漸増または漸減してもよく、あるいは不規則変化してもよい。成形圧力が低いほど配向性は良好となるが、成形圧力が低すぎると成形体の強度が不足してハンドリングに問題が生じるので、この点を考慮して上記範囲から成形圧力を選択する。磁場中成形で得られる成形体の最終的な相対密度は、通常、５０〜６０％である。
印加する磁場は、１２〜２０ｋＯｅ（９６０〜１６００ｋＡ／ｍ）程度とすればよい。この程度の磁場を印加することにより、顆粒は崩壊して一次合金粒子に分解される。印加する磁場は静磁場に限定されず、パルス状の磁場とすることもできる。また、静磁場とパルス状磁場を併用することもできる。
The granular granulated powder obtained as described above is subjected to molding in a magnetic field.
The molding pressure in the magnetic field molding may be in the range of 0.3 to 3 ton / cm 2 (30 to 300 MPa). The molding pressure may be constant from the beginning to the end of molding, may be gradually increased or gradually decreased, or may vary irregularly. The lower the molding pressure is, the better the orientation is. However, if the molding pressure is too low, the strength of the molded body is insufficient and handling problems occur. Therefore, the molding pressure is selected from the above range in consideration of this point. The final relative density of the molded body obtained by molding in a magnetic field is usually 50 to 60%.
The applied magnetic field may be about 12 to 20 kOe (960 to 1600 kA / m). By applying a magnetic field of this level, the granules are broken down and decomposed into primary alloy particles. The applied magnetic field is not limited to a static magnetic field, and may be a pulsed magnetic field. A static magnetic field and a pulsed magnetic field can also be used in combination.
次いで、成形体を真空又は不活性ガス雰囲気中で焼結する。焼結温度は、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、１０００〜１２００℃で１〜１０時間程度焼結すればよい。なお、脱バインダと焼結を別個の工程として取り扱うこともできるが、焼結の昇温過程を脱バインダに利用することもできる。例えば、焼結における昇温過程の３００〜７００℃の温度範囲を水素雰囲気として０．２５〜３時間保持することによって脱バインダを行うことができる。
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。８００℃近傍での熱処理を焼結後に行なうと、保磁力が増大するため、混合法においては特に有効である。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。
Next, the molded body is sintered in a vacuum or an inert gas atmosphere. Although it is necessary to adjust sintering temperature by various conditions, such as a composition, a grinding | pulverization method, the difference of an average particle diameter, and a particle size distribution, what is necessary is just to sinter at 1000-1200 degreeC for about 1 to 10 hours. In addition, although a binder removal and sintering can also be handled as a separate process, the temperature rising process of sintering can also be utilized for a binder removal. For example, the binder removal can be performed by maintaining the temperature range of 300 to 700 ° C. in the temperature rising process in sintering as a hydrogen atmosphere for 0.25 to 3 hours.
After sintering, the obtained sintered body can be subjected to an aging treatment. This process is an important process 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. When the heat treatment at around 800 ° C. is performed after sintering, the coercive force increases, which is particularly effective in the mixing method. In addition, since the coercive force is greatly increased by the heat treatment at around 600 ° C., the aging treatment at around 600 ° C. is preferably performed when the aging treatment is performed in one stage.
次に本発明が適用される希土類焼結磁石について説明する。
本発明は、特にＲ−Ｔ−Ｂ系焼結磁石に適用することが望ましい。この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、本発明における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Ｒ2Ｔ14Ｂ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Ｒ2Ｔ14Ｂ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％、さらに望ましいＲの量は２９〜３３ｗｔ％である。
Next, a rare earth sintered magnet to which the present invention is applied will be described.
The present invention is particularly preferably applied to an RTB-based sintered magnet. This RTB-based sintered magnet contains 25 to 37 wt% of a rare earth element (R). Here, R in the present invention has a concept including Y, and therefore 1 of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. It is selected from species or two or more 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%, and a more desirable amount of R is 29 to 33 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２．０ｗｔ％以下（０を含まず）、望ましくは０．１〜１．０ｗｔ％、さらに望ましくは０．３〜０．７ｗｔ％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 has a Co content of 2.0 wt% or less (not including 0), preferably 0.1 to 1.0 wt%, more preferably 0.3 to 0. .7 wt% can be contained. Co forms the same phase as Fe, but is effective in improving the Curie temperature and improving the corrosion resistance of the grain boundary phase.
また、本発明が適用されるＲ−Ｔ−Ｂ系焼結磁石は、Ａｌ及びＣｕの１種又は２種を０．０２〜０．５ｗｔ％の範囲で含有することができる。この範囲でＡｌ及びＣｕの１種又は２種を含有させることにより、得られる焼結磁石の高保磁力化、高耐食性化、温度特性の改善が可能となる。Ａｌを添加する場合において、望ましいＡｌの量は０．０３〜０．３ｗｔ％、さらに望ましいＡｌの量は、０．０５〜０．２５ｗｔ％である。また、Ｃｕを添加する場合において、望ましいＣｕの量は０．１５ｗｔ％以下（０を含まず）、さらに望ましいＣｕの量は０．０３〜０．１２ｗｔ％である。
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、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５０００ｐｐｍ以下、さらには３０００ｐｐｍ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。
Moreover, the RTB-based sintered magnet to which the present invention is applied can contain one or two of Al and Cu in a range of 0.02 to 0.5 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 sintered magnet. In the case of adding Al, the desirable amount of Al is 0.03 to 0.3 wt%, and the more desirable amount of Al is 0.05 to 0.25 wt%. Further, in the case of adding Cu, the desirable amount of Cu is 0.15 wt% or less (not including 0), and the more desirable amount of Cu is 0.03 to 0.12 wt%.
The RTB-based sintered magnet to which the present invention is applied allows the inclusion of other elements. For example, elements such as 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 preferably 5000 ppm or less, more preferably 3000 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.
Ｒ−Ｔ−Ｂ系焼結磁石に本発明を適用することが望ましいが、他の希土類焼結磁石に本発明を適用することも可能である。例えば、Ｒ−Ｃｏ系焼結磁石に本発明を適用することもできる。
Ｒ−Ｃｏ系焼結磁石は、Ｒと、Ｆｅ、Ｎｉ、ＭｎおよびＣｒから選ばれる１種以上の元素と、Ｃｏとを含有する。この場合、望ましくはさらにＣｕまたは、Ｎｂ、Ｚｒ、Ｔａ、Ｈｆ、ＴｉおよびＶから選ばれる１種以上の元素を含有し、特に望ましくはＣｕと、Ｎｂ、Ｚｒ、Ｔａ、Ｈｆ、ＴｉおよびＶから選ばれる１種以上の元素とを含有する。これらのうち特に、ＳｍとＣｏとの金属間化合物、望ましくはＳｍ2Ｃｏ17金属間化合物を主相とし、粒界にはＳｍＣｏ5系を主体とする副相が存在する。具体的組成は、製造方法や要求される磁気特性等に応じて適宜選択すればよいが、例えば、Ｒ：２０〜３０ｗｔ％、特に２２〜２８ｗｔ％程度、Ｆｅ、Ｎｉ、ＭｎおよびＣｒの１種以上：１〜３５ｗｔ％程度、Ｎｂ、Ｚｒ、Ｔａ、Ｈｆ、ＴｉおよびＶの１種以上：０〜６ｗｔ％、特に０．５〜４ｗｔ％程度、Ｃｕ：０〜１０ｗｔ％、特に１〜１０ｗｔ％程度、Ｃｏ：残部の組成が望ましい。
以上、Ｒ−Ｔ−Ｂ系焼結磁石、Ｒ−Ｃｏ系焼結磁石について言及したが、本発明は他の希土類焼結磁石への適用を妨げるものではない。
Although it is desirable to apply the present invention to an RTB-based sintered magnet, the present invention can also be applied to other rare earth sintered magnets. For example, the present invention can be applied to an R—Co based sintered magnet.
The R—Co based sintered magnet contains R, one or more elements selected from Fe, Ni, Mn, and Cr, and Co. In this case, it preferably further contains Cu or one or more elements selected from Nb, Zr, Ta, Hf, Ti and V, and particularly preferably from Cu and Nb, Zr, Ta, Hf, Ti and V. Containing one or more selected elements. Among these, in particular, an intermetallic compound of Sm and Co, preferably an Sm 2 Co 17 intermetallic compound, is the main phase, and a subphase mainly composed of SmCo 5 exists at the grain boundary. The specific composition may be appropriately selected according to the production method, required magnetic characteristics, and the like. For example, R: 20 to 30 wt%, particularly about 22 to 28 wt%, Fe, Ni, Mn, and Cr Above: about 1 to 35 wt%, one or more of Nb, Zr, Ta, Hf, Ti and V: 0 to 6 wt%, especially about 0.5 to 4 wt%, Cu: 0 to 10 wt%, especially 1 to 10 wt% To the extent, Co: the balance composition is desirable.
The R-T-B sintered magnet and the R-Co sintered magnet have been described above, but the present invention does not prevent application to other rare earth sintered magnets.
ストリップキャスト法により、２６．５ｗｔ％Ｎｄ−５．９ｗｔ％Ｄｙ−０．２５ｗｔ％Ａｌ−０．５ｗｔ％Ｃｏ−０．０７ｗｔ％Ｃｕ−１．０ｗｔ％Ｂ−Ｆｅの組成を有する原料合金を作製した。
次いで、室温にて原料合金に水素を吸蔵させた後、Ａｒ雰囲気中で６００℃×１時間の脱水素を行なう水素粉砕処理を行なった。
水素粉砕処理が施された合金に、粉砕性の向上並びに成形時の配向性の向上に寄与する潤滑剤を０.０５〜０.１％混合した。潤滑剤の混合は、例えばナウターミキサー等により５〜３０分間ほど行なう程度でよい。その後、ジェットミルを用いて平均粒径が５．０μｍの微粉砕粉末を得た。
A raw material alloy having a composition of 26.5 wt% Nd-5.9 wt% Dy-0.25 wt% Al-0.5 wt% Co-0.07 wt% Cu-1.0 wt% B-Fe is produced by strip casting. did.
Next, after hydrogen was occluded in the raw material alloy at room temperature, hydrogen pulverization treatment was performed in which dehydrogenation was performed at 600 ° C. for 1 hour in an Ar atmosphere.
The alloy that has been subjected to the hydrogen pulverization treatment was mixed with 0.05 to 0.1% of a lubricant that contributes to improvement of pulverization and orientation during molding. The lubricant may be mixed for about 5 to 30 minutes using, for example, a Nauter mixer. Thereafter, a finely pulverized powder having an average particle size of 5.0 μm was obtained using a jet mill.
以上の微粉砕粉末に対して、表１に示す各種有機液体を６ｗｔ％添加した後に、乳鉢で十分に混錬した。この混練物から以下のようにして顆粒を作製した。所定の間隔を隔てて、５０メッシュの篩（第１篩）と８３メッシュの篩（第２篩）を上下方向に配置した。なお、第１篩が上側に位置している。第１篩の上に、得られた混錬物を載せた後に、第１篩及び第２篩をともに所定時間振動させた。振動終了後に、第２篩上に残存した顆粒を採取した。この顆粒は、第１篩及び第２篩の目開き寸法より、１８０〜３００μｍの粒径を有していることになる。得られた顆粒について以下の方法に基づいて安息角を測定した。その結果を表１に合わせて示す。なお、表１には顆粒化する前の微粉砕粉末の安息角も合わせて示している。なお、図１に作製された顆粒の外観ＳＥＭ像を示す。
安息角測定方法：６０ｍｍφの円のテーブルの上に、一定高さからふるいを通して少しずつ顆粒を落下させた。顆粒の山が崩壊する直前で顆粒の供給を停止した。円テーブルの上にできた顆粒の山の底角を測定した。円テーブルを１２０°ずつ回転し、計３箇所について角度を測定し、その平均を安息角とした。
以上で得られた顆粒を表１に示す真空度の減圧雰囲気（室温）に２０〜３００分だけ晒した。
After adding 6 wt% of various organic liquids shown in Table 1 to the finely pulverized powder, the powder was sufficiently kneaded in a mortar. Granules were produced from the kneaded product as follows. A 50-mesh sieve (first sieve) and an 83-mesh sieve (second sieve) were arranged in the vertical direction at a predetermined interval. In addition, the 1st sieve is located on the upper side. After placing the obtained kneaded material on the first sieve, both the first sieve and the second sieve were vibrated for a predetermined time. After completion of the vibration, the granules remaining on the second sieve were collected. This granule has a particle size of 180 to 300 μm from the opening size of the first sieve and the second sieve. The angle of repose of the obtained granule was measured based on the following method. The results are also shown in Table 1. Table 1 also shows the angle of repose of the finely pulverized powder before granulation. In addition, the external appearance SEM image of the produced granule is shown in FIG.
Angle of repose measurement: Granules were dropped little by little through a sieve from a certain height on a 60 mmφ circular table. The granule supply was stopped just before the granule pile collapsed. The bottom angle of the pile of granules formed on the round table was measured. The circular table was rotated by 120 °, the angles were measured at a total of three locations, and the average was taken as the angle of repose.
The granules obtained above were exposed to a vacuum atmosphere (room temperature) shown in Table 1 for 20 to 300 minutes.
得られた顆粒を磁場中成形した。具体的には、１５ｋＯｅの磁場中で１．４ｔ／ｃｍ2の圧力で成形を行い、成形体を得た。抗折強度は２０ｍｍ×１８ｍｍ×６ｍｍの成形体を用い３点曲げ試験により測定した。
得られた成形体を真空中およびＡｒ雰囲気中で１０８０℃まで昇温し４時間保持して焼結を行った。次いで得られた焼結体に８００℃×１時間と５６０℃×１時間（ともにＡｒ雰囲気中）の２段時効処理を施した。
The obtained granules were molded in a magnetic field. Specifically, molding was performed at a pressure of 1.4 t / cm 2 in a magnetic field of 15 kOe to obtain a molded body. The bending strength was measured by a three-point bending test using a 20 mm × 18 mm × 6 mm molded body.
The obtained molded body was heated to 1080 ° C. in vacuum and Ar atmosphere and held for 4 hours for sintering. Next, the obtained sintered body was subjected to a two-stage aging treatment of 800 ° C. × 1 hour and 560 ° C. × 1 hour (both in an Ar atmosphere).
得られた焼結磁石の磁気特性を測定した結果を表１に示す。なお、表１には微粉砕粉末を顆粒化することなく上記と同様にして磁場中成形、焼結及び時効処理を施して得られた焼結磁石（比較例１）、バインダとしてポリスチレンを含むスラリをスプレードライして得られた顆粒を上記と同様にして磁場中成形、焼結及び時効処理を施して得られた焼結磁石（比較例２）の磁気特性も合わせて示している。 The results of measuring the magnetic properties of the obtained sintered magnet are shown in Table 1. Table 1 shows a sintered magnet (Comparative Example 1) obtained by subjecting the finely pulverized powder to granulation, sintering and aging treatment in the same manner as above without granulating the finely divided powder, and a slurry containing polystyrene as a binder. The magnetic properties of the sintered magnet (Comparative Example 2) obtained by subjecting the granules obtained by spray-drying to a magnetic field to be molded, sintered and aged in the same manner as above are also shown.
表１に示すように、微粉砕粉末の安息角が６０°であるのに対して、有機液体を用いて顆粒化することにより安息角を５０°以下とし流動性を向上することができる。また、有機液体を用いた顆粒から作製された焼結磁石は、微粉砕粉末を磁場中成形して得られた焼結磁石と同等の磁気特性を備えることがわかる。特に、ＰＶＡ等のバインダを用いた顆粒から焼結磁石を作製する場合、比較例２を見ればわかるように、脱バインダ処理を行なわなければ磁気特性の低下が著しく、製造工程を簡略化しつつ高い磁気特性を得ることができる本発明の効果は顕著である。
また、表１に示すように、顆粒を一度作製した後に減圧雰囲気に晒すことで、残留する有機液体の量を制御することができるとともに、磁気特性を向上することができる。ただし、有機液体の残留量が０（ゼロ）になると顆粒を維持することが困難になり、安息角が５０°を超えてしまう。
As shown in Table 1, the angle of repose of the finely pulverized powder is 60 °, while granulation using an organic liquid can reduce the angle of repose to 50 ° or less and improve the fluidity. Moreover, it turns out that the sintered magnet produced from the granule using an organic liquid is equipped with a magnetic characteristic equivalent to the sintered magnet obtained by shape | molding finely pulverized powder in a magnetic field. In particular, when producing a sintered magnet from granules using a binder such as PVA, as can be seen from Comparative Example 2, if the binder removal treatment is not performed, the magnetic characteristics are significantly lowered, and the manufacturing process is simplified and high. The effect of the present invention capable of obtaining magnetic characteristics is remarkable.
Moreover, as shown in Table 1, by producing granules once and exposing them to a reduced-pressure atmosphere, the amount of remaining organic liquid can be controlled and the magnetic properties can be improved. However, when the residual amount of the organic liquid becomes 0 (zero), it becomes difficult to maintain the granules, and the angle of repose exceeds 50 °.
次に、有機液体としてターピネオールを２ｗｔ％添加した点、５５℃、１０-1Ｔｏｒｒの減圧雰囲気に顆粒を晒す点を除いて上記と同様にして焼結磁石を作製し、磁気特性を測定した。その結果を表２に示した。なお、減圧雰囲気に晒す時間を変動することにより、有機液体の残留量を調整した。
表２に示すように、加熱することにより、１０-1Ｔｏｒｒ程度の低真空雰囲気であっても有機液体の残留量を制御することができる。また、ターピネオールの残留量が０．１５ｗｔ％程度であっても、顆粒の形態が維持され、安息角を５０°以下にすることができる。
Next, a sintered magnet was prepared in the same manner as described above except that 2 wt% of terpineol was added as an organic liquid and the granules were exposed to a reduced pressure atmosphere at 55 ° C. and 10 −1 Torr, and the magnetic properties were measured. The results are shown in Table 2. The residual amount of the organic liquid was adjusted by changing the time of exposure to the reduced pressure atmosphere.
As shown in Table 2, by heating, the residual amount of the organic liquid can be controlled even in a low vacuum atmosphere of about 10 −1 Torr. Moreover, even if the residual amount of terpineol is about 0.15 wt%, the form of the granules is maintained, and the angle of repose can be made 50 ° or less.
次に、有機液体としてエタノールを用いて、その添加量が及ぼす影響を確認した。その結果を表３に示す。表３に示すように、有機液体としてのエタノールの添加量が少なすぎると、顆粒作製のための湿分が不足して、顆粒を構成しない微粉砕粉末が相当量残存してしまい、有機液体の添加量が少ないと顆粒作製効率が劣ることになる。また、有機液体としてのエタノールの添加量が多すぎると、湿分が多すぎてエタノール除去の時間を長くする、あるいは減圧の圧力を低くしなければ、湿分が多すぎて成形後にクラックが生じてしまう不具合が起こる。また、有機液体であるエタノールの添加量が多くなるほど、安息角が小さくなり流動性が向上すること、成形体の強度が向上することが表３２よりわかる。以上の結果より、有機液体の添加量は、１．５〜１５．０ｗｔ％とすることが望ましく、より望ましくは２．５〜１０．０ｗｔ％、さらに望ましくは２.５〜８．０ｗｔ％とする。 Next, using ethanol as the organic liquid, the effect of the amount added was confirmed. The results are shown in Table 3. As shown in Table 3, if the amount of ethanol added as the organic liquid is too small, the moisture for granule preparation is insufficient, and a considerable amount of finely pulverized powder that does not constitute granules remains. If the amount added is small, the granule production efficiency is poor. Also, if the amount of ethanol added as an organic liquid is too large, the amount of moisture will be too much and the time for ethanol removal will be lengthened, or if the pressure under reduced pressure is not lowered, the amount of moisture will be too much and cracks will occur after molding. A malfunction occurs. Further, it can be seen from Table 32 that the angle of repose becomes smaller and the fluidity is improved and the strength of the molded body is improved as the amount of the organic liquid ethanol added is increased. From the above results, the addition amount of the organic liquid is desirably 1.5 to 15.0 wt%, more desirably 2.5 to 10.0 wt%, and further desirably 2.5 to 8.0 wt%. To do.
流動性の良い顆粒を用いるメリットとして、狭間口の金型への粉体充填性の容易さが挙げられる。それを確認するためにフィーダテストを行った。通常の量産工程において金型へ粉体を供給するためにフィーダという装置が使用される。このフィーダは、金型の上で水平方向に往復運動をする箱であり、箱の下部には供給孔が空けられている。箱の中には一定量の粉がためられており、この箱が往復運動すると、箱下部の供給孔から金型内部に粉が落ちる仕組みになっている。流動性の良い粉ほど、一定回数の往復運動で多くの粉が落ちることになる。そこで、金型キャビティに見立てた３ｍｍ×２０ｍｍの空隙を設け、この上で有機液体を用いた顆粒を往復運動させた。往復運動のスピードは０．４ｍ／ｓとし、５往復で上記隙間に落下した粉の重量を測定した。この５往復を１回の測定対象とし、１５回の測定を繰り返した。使用した粉は顆粒化されていない上記微粉砕粉末（比較例１）及び有機液体（実施例１）を用いた顆粒である。測定結果を図２に示すが、顆粒を用いることにより、金型キャビティへの充填性を向上できることが確認された。 An advantage of using granules with good fluidity is the ease of powder filling into a narrow-mouth mold. A feeder test was conducted to confirm this. An apparatus called a feeder is used to supply powder to a mold in a normal mass production process. This feeder is a box that reciprocates horizontally on a mold, and a supply hole is formed in the lower part of the box. A certain amount of powder is stored in the box, and when this box reciprocates, the powder falls from the supply hole at the bottom of the box into the mold. The more fluid the powder, the more powder falls with a certain number of reciprocating motions. Therefore, a 3 mm × 20 mm gap was provided in the mold cavity, and the granules using the organic liquid were reciprocated on this. The speed of reciprocating motion was 0.4 m / s, and the weight of the powder dropped into the gap after 5 reciprocations was measured. This five reciprocations were set as one measurement object, and 15 measurements were repeated. The used powder is a granule using the above finely pulverized powder (Comparative Example 1) and an organic liquid (Example 1) which are not granulated. The measurement results are shown in FIG. 2, and it was confirmed that the filling properties into the mold cavity can be improved by using the granules.
Claims (7)
前記顆粒から前記有機液体の一部を除去する工程と、
前記有機液体の一部が除去された前記顆粒を金型キャビティに投入する工程と、
前記金型キャビティに投入された前記顆粒に磁場を印加し、かつ加圧成形することにより成形体を得る工程と、
前記成形体を焼結する工程と、
を備え、
前記有機液体は、エタノール、トルエン、カルビトール、テルペン系化合物、ブチルカルビトール、酢酸ブチルカルビトール、酢酸ｎ−ブチル、ブチルセロソルブ、シクロヘキサノール、ターピネオール、及びピネンの１種又は２種以上であることを特徴とする希土類焼結磁石の製造方法。 Producing granules in which primary alloy particles having a predetermined composition are bound together by an organic liquid ;
Removing a portion of the organic liquid from the granules ;
Placing the granules from which a portion of the organic liquid has been removed into a mold cavity;
Applying a magnetic field to the granules put into the mold cavity , and obtaining a molded body by pressure molding; and
Sintering the molded body;
Equipped with a,
The organic liquid is ethanol, toluene, carbitol, terpene compounds, butyl carbitol, butyl carbitol acetate, acetate n- butyl, butyl cellosolve, cyclohexanol, terpineol, and one or more der Rukoto pinene A method for producing a rare earth sintered magnet.
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| JP2004193725A JP4282013B2 (en) | 2004-06-30 | 2004-06-30 | Manufacturing method of rare earth sintered magnet |
| CN2005800102381A CN1938115B (en) | 2004-06-30 | 2005-06-28 | Method for producing raw material powder for rare earth sintered magnet, method for producing rare earth sintered magnet, granule and sintered article |
| EP12181702.7A EP2527062B1 (en) | 2004-06-30 | 2005-06-28 | Method for producing a rare earth sintered magnet |
| EP05755236.6A EP1762316B1 (en) | 2004-06-30 | 2005-06-28 | Method for producing a rare earth sintered magnet and its raw material and granules |
| PCT/JP2005/011787 WO2006003872A1 (en) | 2004-06-30 | 2005-06-28 | Method for producing raw material powder for rare earth sintered magnet, method for producing rare earth sintered magnet, granule and sintered article |
| US11/569,767 US7858023B2 (en) | 2004-06-30 | 2005-06-28 | Method for producing raw material powder for rare earth sintered magnet, method for producing rare earth sintered magnet, granule and sintered body |
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