JP4057563B2 - Granule, sintered body - Google Patents
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- JP4057563B2 JP4057563B2 JP2004193727A JP2004193727A JP4057563B2 JP 4057563 B2 JP4057563 B2 JP 4057563B2 JP 2004193727 A JP2004193727 A JP 2004193727A JP 2004193727 A JP2004193727 A JP 2004193727A JP 4057563 B2 JP4057563 B2 JP 4057563B2
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- Hard Magnetic Materials (AREA)
Description
本発明は、例えばＮｄ−Ｆｅ−Ｂ系に代表される希土類焼結磁石等の製造に際し、原料粉体等の流動性を向上させることのできる顆粒等に関するものである。 The present invention relates to granules and the like that can improve the fluidity of raw material powders and the like, for example, in the production of rare earth sintered magnets typified by Nd-Fe-B.
例えば、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。
For example, when manufacturing rare earth sintered magnets, magnetic properties such as saturation magnetic flux density and coercive force are ensured by refining raw material powder to be sintered. 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、顆粒の状態を維持しようとするため、各一次合金粒子を配向させることは容易ではない。また、焼成後も、顆粒間に間隙が残ることもある。その結果、得られる希土類焼結磁石の配向度が低く、磁気特性、特に残留磁束密度（Ｂｒ）の低下や、物理特性の低下を招くことになる。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、特性を大きく低下させることなく、優れた流動性を有し、成形体の寸法精度の向上及び生産性の向上を図ることができる顆粒等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 has excellent fluidity without greatly reducing the characteristics, and can improve the dimensional accuracy of the molded body and the productivity. It aims at providing the granule etc. which can be performed.
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。このような顆粒は、所定組成の一次合金粒子に対して有機液体を添加して混合物を得た後、この混合物を用いて一次合金粒子を有機液体で結着させることで作製できる。 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. Such a granule can be produced by adding an organic liquid to primary alloy particles of a predetermined composition to obtain a mixture, and then binding the primary alloy particles with the organic liquid using the mixture.
さて、これに基づいてなされた本発明の磁場中成形用の顆粒は、複数の粒子が、有機液体で結着されることで形成され、有機液体が、トルエン、キシレン、ターピネオール、エタノール、ブチルセロソルブ、セロソルブ、カルビトール、ブチルカルビトール、酢酸エチル、アセトン（ジメチルケトン）、メチルイソブチルケトン、メチルエチルケトン、エチレングリコール、ジエチレングリコール及びグリセリンの１種又は２種以上から選択されることを特徴とする。このような顆粒、および顆粒を形成する粒子は、特に、希土類焼結磁石の製造工程において、希土類焼結磁石の原料となる所定組成を有した合金粒子を、有機液体で結着させ、顆粒化するのが有効である。さらに、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である合金粒子に適用することが望ましい。
このような顆粒において、有機液体は、複数の粒子の接点部分に少なくとも介在している。つまり、顆粒の状態において、有機液体は蒸発しておらず、液体の状態のまま存在し、顆粒が濡れたままの状態を維持しているのである。このとき、この顆粒を構成する粒子は、有機液体のみによって結着され、他の結着力を有するバインダ等の固体成分等によって結着されていない。
顆粒の状態において、有機液体が液体の状態のまま存在し、作製された顆粒の形態を維持するには、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／ｃｍ2以上、２０℃における粘度が２０ｃｐ以上、室温では気化しないよう沸点が５０℃以上である、等の特性を備えることが望ましい。
また、粒子の微粉砕粉末の酸化を防止するため、有機液体は、酸素濃度が低く、また水への溶解度（水溶性）が低いものを用いるのが好ましい。
Now, the granule for molding in the magnetic field of the present invention based on this is formed by binding a plurality of particles with an organic liquid, and the organic liquid is toluene, xylene, terpineol, ethanol, butyl cellosolve, cellosolve, carbitol, butyl carbitol, ethyl acetate, acetone (dimethyl ketone), methyl isobutyl ketone, methyl ethyl ketone, ethylene glycol, wherein Rukoto selected from one or more of diethylene glycol and glycerine. Such granules and particles that form the granules, especially in the manufacturing process of the rare earth sintered magnet, the alloy particles having a predetermined composition which is a raw material of the rare earth sintered magnet, is sintered wearing the organic liquid, granular It is effective to make it. Furthermore, the present invention relates to an R 2 T 14 B phase (R is one or more elements selected from rare earth elements, T is one or two elements selected from transition metal elements including Fe or Fe and Co) It is desirable to apply it to alloy particles having a composition containing an element of at least seeds and having an average particle size of 2.5 to 6 μm.
In such a granule, the organic liquid is present at least at the contact portions of the plurality of particles. That is, in the state of granules, the organic liquid is not evaporated, exists in the liquid state, and maintains the state where the granules remain wet. At this time, the particles constituting the granules are bound only by the organic liquid and are not bound by a solid component such as a binder having another binding force.
In the state of granules, the organic liquid exists in a liquid state, and in order to maintain the shape of the prepared granules, the organic liquid has a saturated vapor pressure at 20 ° C. of 75 mmHg (10.0 kPa) or less and at 20 ° C. Desirably, the surface tension is 20 dyn / cm 2 or more, the viscosity at 20 ° C. is 20 cp or more, and the boiling point is 50 ° C. or more so as not to vaporize at room temperature.
In order to prevent oxidation of the finely pulverized powder of particles, it is preferable to use an organic liquid having a low oxygen concentration and a low solubility in water (water solubility).
本発明は、上記のような顆粒を用いて形成される焼結体として捉えることもできる。
すなわち、この焼結体は、複数の粒子を有機液体で結着することによって形成された顆粒を、金型中で磁場を印加しつつ加圧成形し、さらに焼結することによって得られたものであり、前記有機液体がトルエン、キシレン、ターピネオール、エタノール、ブチルセロソルブ、セロソルブ、カルビトール、ブチルカルビトール、酢酸エチル、アセトン（ジメチルケトン）、メチルイソブチルケトン、メチルエチルケトン、エチレングリコール、ジエチレングリコール及びグリセリンの１種又は２種以上から選択されることを特徴とすることができる。
The present invention can also be understood as a sintered body formed using the above granules.
That is, this sintered body was obtained by press-molding granules formed by binding a plurality of particles with an organic liquid while applying a magnetic field in a mold, and further sintering the granules. der is, the organic liquid is toluene, xylene, terpineol, ethanol, butyl cellosolve, cellosolve, carbitol, butyl carbitol, ethyl acetate, acetone (dimethyl ketone), methyl isobutyl ketone, methyl ethyl ketone, ethylene glycol, 1 of diethylene glycol and glycerine it can be characterized by Rukoto selected from species or two or more.
本発明によれば、有機液体により粒子が結着された顆粒により、特性を大きく低下させることなく流動性を向上させることができ、成形体の寸法精度の向上及び生産性の向上を図ることができる。 According to the present invention, the granules in which the particles are bound by the organic liquid can improve the fluidity without greatly reducing the characteristics, and can improve the dimensional accuracy of the molded body and the productivity. it can.
以下、本発明を実施の形態に基づいて詳細に説明する。
本発明では、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。本実施の形態では、粉末の一例として、希土類焼結磁石用の一次合金粒子を挙げる。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、ＰＶＡ等の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。加えて、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。しかも、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. In the present embodiment, primary alloy particles for rare earth sintered magnets are listed as an example of powder. 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, a high degree of orientation can be obtained. Until now, using a binder such as PVA has been considered as a premise for producing granules, but even when an organic liquid is used as in the present invention, it is highly valuable to find that highly fluid granules can be obtained. . In addition, since this granule collapses when a magnetic field is applied, it is suitable for a rare earth sintered magnet that performs molding in a magnetic field. In addition, the organic liquid is extremely easy to remove from the molded body compared to the conventional binder such as PVA, and omits the binder removal step that is essential when using the conventional granule technology. 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 an R 2 T 14 B crystal grain (low R alloy) and an alloy containing more R than the 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うことが効果的である。この水素放出処理は、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. This hydrogen release 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 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. Fatty acids or fatty acid derivatives and hydrocarbons for the purpose of improving 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。すなわち、本発明では、微粉砕粉末（一次合金粒子）を、有機液体による結着力で結着させ、顆粒を形成する。このような液体(本発明では有機液体)による結着力は、液体架橋力と称されている。なおここで、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. That is, in the present invention, finely pulverized powder (primary alloy particles) is bound with a binding force of an organic liquid to form granules. The binding force by such a liquid (in the present invention, an organic liquid) is referred to as a liquid crosslinking force. Here, 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.
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（グリコールエステル系を含む）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種から選択することができる。このような有機液体の具体例を挙げると、炭化水素系化合物としては、トルエン、キシレン、アルコール系化合物としては、ターピネオール、エタノール、エーテル系化合物としては、ブチルセロソルブ、セロソルブ、カルビトール、ブチルカルビトール、エステル系化合物としては、酢酸エチル、ケトン系化合物としては、アセトン（ジメチルケトン）、メチルイソブチルケトン、メチルエチルケトン等がある。
もちろん、ここに挙げた有機液体に限るものではなく、これ以外にも、例えばエチレングリコール、ジエチレングリコール等や、グリセリン等、他の有機液体を用いることも可能である。
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 ester compounds), ketone compounds, fatty acid compounds, and terpene compounds. One or two of the compounds can be selected. Specific examples of such organic liquids include hydrocarbon compounds such as toluene, xylene, alcohol compounds such as terpineol, ethanol, and ether compounds such as butyl cellosolve, cellosolve, carbitol, butyl carbitol, Examples of ester compounds include ethyl acetate, and examples of ketone compounds include acetone (dimethyl ketone), methyl isobutyl ketone, and methyl ethyl ketone.
Of course, the organic liquid is not limited to the organic liquids listed here, and other organic liquids such as ethylene glycol, diethylene glycol, and glycerin can be used.
有機液体を用いて作製された顆粒は、有機液体が、少なくとも微粉砕粉末同士の接点に存在し、その液体架橋力によって微粉砕粉末同士が結着されている。このとき、微粉砕粉末同士の接点には、液体中に、微粉砕粉末同士を結着させるためのバインダ等の固体成分を実質的に含まない。ただし、粉砕性の向上並びに成形時の配向性の向上のために潤滑剤を添加した場合、この潤滑剤の固体成分が液体中に存在することは許容するものとする。 In the granules produced using an organic liquid, the organic liquid is present at least at the contact point between the finely pulverized powders, and the finely pulverized powders are bound together by the liquid crosslinking force. At this time, the contact between the finely pulverized powders does not substantially contain a solid component such as a binder for binding the finely pulverized powders in the liquid. However, when a lubricant is added in order to improve the grindability and the orientation during molding, the solid component of the lubricant is allowed to be present in the liquid.
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。
また、本発明に用いる有機液体は、室温では気化しないよう、沸点が５０℃以上、より好ましくは１００℃以上であるのが好ましい。
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.
In addition, the organic liquid used in the present invention preferably has a boiling point of 50 ° C. or higher, more preferably 100 ° C. or higher so as not to vaporize at room temperature.
本発明に用いる有機液体はまた、顆粒を維持するために十分な結着力を一次合金粒子間に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／ｃｍ2以上である。より望ましい２０℃における表面張力は２５ｄｙｎ／ｃｍ2以上、さらに望ましい２０℃における表面張力は３０ｄｙｎ／ｃｍ2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 impart sufficient binding force between the primary alloy particles to maintain the granules. Therefore, it is desirable in the present invention to specify the surface tension and viscosity of the organic liquid. A desirable surface tension of the organic liquid is 20 dyn / cm 2 or more at 20 ° C. The surface tension at a more desirable 20 ℃ 25dyn / cm 2 or more, the surface tension at further desirable 20 ° C. is 30 dyn / cm 2 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.
さらに、微粉砕粉末の酸化を防止するため、本発明に用いる有機液体は、酸素濃度が低く、また水への溶解度（水溶性）が低いものであるのが好ましい。
表１に、上記に例示した有機液体の物性等を示した。
Furthermore, in order to prevent oxidation of the finely pulverized powder, the organic liquid used in the present invention preferably has a low oxygen concentration and low solubility in water (water solubility).
Table 1 shows the physical properties of the organic liquids exemplified above.
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（一次合金粒子）に対する有機液体の添加量は１．５〜１２．０ｗｔ％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、磁場中成形までに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。なお、添加量の望ましい範囲は、有機液体の種類によって変わり、例えばターピネオールなら２．０〜６．０ｗｔ％、エタノールなら２．０〜１２．０ｗｔ％である。 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, if the amount of the organic liquid added is too large, when the obtained granule is molded as it is in a magnetic field, the liquid may be excessively present to inhibit molding. From the above, it is recommended that the amount of organic liquid added to the finely pulverized powder (primary alloy particles) is 1.5 to 12.0 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 is only necessary to remove part of the organic liquid before molding in a magnetic field. Therefore, it is not an essential problem as compared with the case where the addition amount is small. Note that the desirable range of the addition amount varies depending on the type of the organic liquid. For example, terpineol is 2.0 to 6.0 wt%, and ethanol is 2.0 to 12.0 wt%.
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. Examples of applicable granulation methods include rolling granulation method, vibration granulation method, mixed granulation method, fluidized granulation method, pulverization granulation method, compression molding granulation method, and extrusion granulation method. 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.
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 start to the end of molding, may increase or decrease gradually, 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.
ここで、上記のようにして磁場中成形するに際し、成形体が形成された状態での有機液体の残留量は、４５ｖｏｌ％以下（１０ｗｔ％以下）であるのが好ましい。希土類焼結磁石の製造工程における成形体密度は、５５〜６０％であり、残留する有機液体は成形体の空隙部分にのみ実質的に存在し得るからである。有機液体の残留量が４５ｖｏｌ％程度より多くなると、成形時に、有機液体は金型キャビティ内で成形圧力によって圧縮され、これによって成形体がうまく成形できなくなる。より具体的には、成形圧力から解放された液体が元の容積に戻ろうとするため、成形体の割れが生じることがある。ここで、残留量は、顆粒を形成する粉の重量に対し、顆粒中に存在する有機液体の重量濃度（ｗｔ％）で規定される。残留量を正確に計測するには、顆粒から有機液体のみを揮発させ、その重量変化を測定する。このとき、顆粒の酸化による重量変動の影響を避けるため、容器内に顆粒を入れ、これを高真空にする、あるいは真空や不活性雰囲気下で加熱し、有機液体を揮発させて、そのときの重量変化を計測するのが好ましい。 Here, when forming in the magnetic field as described above, the residual amount of the organic liquid in a state where the formed body is formed is preferably 45 vol% or less (10 wt% or less). This is because the density of the compact in the manufacturing process of the rare earth sintered magnet is 55 to 60%, and the remaining organic liquid can exist substantially only in the void portion of the compact. When the residual amount of the organic liquid is more than about 45 vol%, the organic liquid is compressed by the molding pressure in the mold cavity at the time of molding, so that the molded body cannot be molded well. More specifically, since the liquid released from the molding pressure attempts to return to the original volume, the molded body may be cracked. Here, the residual amount is defined by the weight concentration (wt%) of the organic liquid present in the granules with respect to the weight of the powder forming the granules. To accurately measure the residual amount, only the organic liquid is volatilized from the granule, and its weight change is measured. At this time, in order to avoid the influence of the weight fluctuation due to the oxidation of the granule, the granule is put in a container, and this is put into a high vacuum or heated in a vacuum or an inert atmosphere to volatilize the organic liquid. It is preferable to measure the change in weight.
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。
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.
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, it is effective to hold for a predetermined time in the vicinity of 800 ° C. and 600 ° C. When the heat treatment in the vicinity of 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 heat treatment at around 600 ° C., when the aging treatment is performed in one stage, the aging treatment at around 600 ° C. is preferably performed.
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 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時間の脱水素を行う水素粉砕処理を行った。
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、実施例１〜７の有機液体として、ターピネオール、エタノール、メチルイソブチルケトン、ブチルセロソルブ、セロソルブ、カルビトール、酢酸エチルを、それぞれ添加した後に、乳鉢で十分に混錬した。各有機液体は、微粉砕粉末８０ｇに対し５ｇを添加した。
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。
To the above finely pulverized powder, terpineol, ethanol, methyl isobutyl ketone, butyl cellosolve, cellosolve, carbitol, and ethyl acetate were added as the organic liquids of Examples 1 to 7, and then kneaded sufficiently in a mortar. . Each organic liquid was added in an amount of 5 g to 80 g of finely pulverized powder.
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.
顆粒化がなされたものについて、以下の方法に基づいて顆粒の安息角を測定した。その結果を表２に合わせて示す。なお、表２には、比較例１として、顆粒化する前の微粉砕粉末の安息角を、また比較例２として、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た顆粒の安息角を、それぞれ示した。また、図１は、実施例１〜７の顆粒、および比較例１の微粉砕粉末（生材）の外観のＳＥＭ写真を示す。
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。
About the granulated thing, the angle of repose of the granule was measured based on the following method. The results are also shown in Table 2. In Table 2, the angle of repose of the finely pulverized powder before granulation as Comparative Example 1, and the angle of repose of granules obtained by spray-drying a slurry containing polystyrene as a binder as Comparative Example 2, Shown respectively. Moreover, FIG. 1 shows the SEM photograph of the external appearance of the granule of Examples 1-7 and the finely pulverized powder (raw material) of the comparative example 1. 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.
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。図２は、このようにして得た成形体のＳＥＭ写真であり、（ａ）は実施例１の成形体のＳＥＭ写真、（ｂ）は比較例１の成形体のＳＥＭ写真である。
図２（ａ）に示すように、有機液体を用いて顆粒化された顆粒から形成された成形体は、微粉砕粉末を顆粒化することなく形成した成形体（図２（ｂ）参照）と比較して、空孔が少なく、緻密なものとなっている。
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. 2A and 2B are SEM photographs of the molded body thus obtained. FIG. 2A is an SEM photograph of the molded body of Example 1, and FIG. 2B is an SEM photograph of the molded body of Comparative Example 1.
As shown in FIG. 2 (a), a compact formed from granules granulated using an organic liquid is a compact formed without granulating finely pulverized powder (see FIG. 2 (b)). In comparison, the number of pores is small and it is dense.
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 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２に示す。なお、表２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。なお、比較例２は脱バインダ処理を行っていない。 Table 2 shows the results of measuring the magnetic properties of the obtained sintered magnet. Table 2 shows a sintered magnet (Comparative Example 1) obtained by subjecting a 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, sintering and aging treatment in the same manner as above are also shown. In Comparative Example 2, the binder removal process is not performed.
表２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（比較例１）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。 As shown in Table 2, while the angle of repose of the finely pulverized powder is 60 °, the repose angle can be reduced to 50 ° or less by granulating with an organic liquid, and the fluidity can be improved. 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 (comparative example 1) 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 properties are significantly reduced, and the manufacturing process is simplified and high. The effect of the present invention capable of obtaining magnetic characteristics is remarkable.
次に、有機液体としてターピネオールを用いて、その残留量が及ぼす影響を確認した。その結果を表３および図３に示す。ここで図３の（ａ）は残留量０．５ｗｔ％、（ｂ）は残留量１．０ｗｔ％、（ｃ）は残留量２．５ｗｔ％の顆粒の断面のＳＥＭ写真である。
なお、顆粒の残留量の調整はターピネオールを８．５ｗｔ％添加した後、１０-3Ｔｏｒｒの減圧雰囲気に顆粒を晒す時間を調整することで制御した。
Next, terpineol was used as the organic liquid, and the effect of the residual amount was confirmed. The results are shown in Table 3 and FIG. Here, (a) in FIG. 3 is a SEM photograph of a cross section of a granule with a residual amount of 0.5 wt%, (b) with a residual amount of 1.0 wt%, and (c) with a residual amount of 2.5 wt%.
The residual amount of granules was controlled by adding 8.5 wt% of terpineol and adjusting the time for exposing the granules to a reduced pressure atmosphere of 10 −3 Torr.
表３および図３に示すように、有機液体であるターピネオールの残留量が多くなるほど、安息角が小さくなり、流動性が向上することがわかる。しかし、有機液体としてのターピネオールの残留量が多すぎると、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。以上の結果より、有機液体の残留量は、０〜８．０ｗｔ％とすることが望ましく、より望ましくは０〜５．０ｗｔ％、さらに望ましくは０〜２．５ｗｔ％とする（０を含まず）。 As shown in Table 3 and FIG. 3, it can be seen that as the residual amount of terpineol, which is an organic liquid, increases, the angle of repose decreases and the fluidity improves. However, when the residual amount of terpineol as the organic liquid is too large, there is a problem that moisture is too much and cracks occur after molding. From the above results, the residual amount of the organic liquid is preferably 0 to 8.0 wt%, more preferably 0 to 5.0 wt%, and still more preferably 0 to 2.5 wt% (excluding 0). ).
また、表３に示すように、焼結磁石における有機液体の残留量が多くなると、磁気特性が低下する傾向があった。これは液体による架橋効果が増え、磁場配向しにくくなったためと考えられる。
さらに、有機液体の残留量が減ると安息角が増加する傾向も確認できる。これは、有機液体の残留量が少なくなると微粉砕粉末の接合力が弱くなり、その結果微粉の付着が発生したためと考えられる。
Further, as shown in Table 3, when the residual amount of the organic liquid in the sintered magnet is increased, the magnetic characteristics tend to be deteriorated. This is considered to be because the cross-linking effect by the liquid is increased and the magnetic field orientation becomes difficult.
Furthermore, it can be confirmed that the angle of repose increases as the residual amount of the organic liquid decreases. This is presumably because the bonding force of the finely pulverized powder was weakened as the residual amount of the organic liquid was reduced, and as a result, the fine powder adhered.
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、実施例１のターピネオールを用いて形成した顆粒、実施例２のエタノールを用いて形成した顆粒、比較例１の微粉砕粉末、をそれぞれ往復運動させた。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。測定結果を図４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。また、実施例１と実施例２の顆粒のデータの比較から、安息角が小さいほど、金型キャビティへの充填性が向上することも確認された。 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 is provided in the mold cavity, and on this, granules formed using the terpineol of Example 1, granules formed using the ethanol of Example 2, fine pulverization of Comparative Example 1 The powder was reciprocated. 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 measurement results are shown in FIG. 4, and it was confirmed that the filling ability into the mold cavity can be improved by using the granules. Moreover, it was confirmed from the comparison of the data of the granule of Example 1 and Example 2 that the filling property to a mold cavity improves, so that an angle of repose is small.
Claims (5)
前記有機液体が、トルエン、キシレン、ターピネオール、エタノール、ブチルセロソルブ、セロソルブ、カルビトール、ブチルカルビトール、酢酸エチル、アセトン（ジメチルケトン）、メチルイソブチルケトン、メチルエチルケトン、エチレングリコール、ジエチレングリコール及びグリセリンの１種又は２種以上から選択されることを特徴とする磁場中成形用の顆粒。 A plurality of particles are formed by binding with an organic liquid ,
The organic liquid is one or two of toluene, xylene, terpineol, ethanol, butyl cellosolve, cellosolve, carbitol, butyl carbitol, ethyl acetate, acetone (dimethyl ketone), methyl isobutyl ketone, methyl ethyl ketone, ethylene glycol, diethylene glycol and glycerin. granules for compacting in a magnetic field, characterized in Rukoto selected from the species above.
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| JP2004193727A JP4057563B2 (en) | 2004-06-30 | 2004-06-30 | Granule, sintered body |
| 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 |
| 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 |
| EP05755236.6A EP1762316B1 (en) | 2004-06-30 | 2005-06-28 | Method for producing a rare earth sintered magnet and its raw material and granules |
| EP12181702.7A EP2527062B1 (en) | 2004-06-30 | 2005-06-28 | Method for producing a rare earth sintered magnet |
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