JP4353430B2 - Method for removing lubricant and method for producing rare earth sintered magnet - Google Patents
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- 238000004519 manufacturing process Methods 0.000 title claims description 11
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- CJZGTCYPCWQAJB-UHFFFAOYSA-L calcium stearate Chemical compound [Ca+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O CJZGTCYPCWQAJB-UHFFFAOYSA-L 0.000 description 1
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- FATBGEAMYMYZAF-UHFFFAOYSA-N oleicacidamide-heptaglycolether Natural products CCCCCCCCC=CCCCCCCCC(N)=O FATBGEAMYMYZAF-UHFFFAOYSA-N 0.000 description 1
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Description
本発明は、希土類焼結磁石の製造方法に関し、特に磁場中成形時の成形性、配向性を確保するために添加される潤滑剤を効率よく除去することのできる潤滑剤の除去方法及び希土類焼結磁石の製造方法に関するものである。 The present invention relates to a method for producing a rare earth sintered magnet, and more particularly to a method for removing a lubricant capable of efficiently removing a lubricant added to ensure formability and orientation during molding in a magnetic field, and rare earth sintering. The present invention relates to a method for manufacturing a magnetized magnet.
希土類元素(R)、Fe又はFe及びCoを必須とする少なくとも1種以上の遷移金属元素(T)及びホウ素(B)を主成分とするR−T−B系焼結磁石は、所定粒度を有する合金粉末を磁場中成形した後に、焼結して製造される。磁気特性の高いR−T−B系焼結磁石を得るために、磁場中成形により得られる成形体の配向性を向上することが求められる。また、磁場中成形に供される合金粉末は、例えばジェットミルによって平均粒径2〜6μm程度まで微粉砕して得られるが、このときの粉砕性が高いことが求められる。これらの要望に応えるために、従来、微粉砕の前にオレイン酸アミド等の有機物を構成要素とする潤滑剤を添加することが知られている(例えば、特許文献1、特許文献2参照)。添加された潤滑剤は、真空あるいは不活性ガス雰囲気中において、100〜500℃で成形体を加熱することにより除去する(以下、潤滑剤除去処理と称す)ことが知られている(例えば、特許文献1)。 R-T-B system sintered magnet mainly composed of at least one kind of transition metal element (T) and boron (B), which essentially contains rare earth elements (R), Fe or Fe and Co, has a predetermined particle size. The alloy powder is formed in a magnetic field and then sintered. In order to obtain an RTB-based sintered magnet having high magnetic properties, it is required to improve the orientation of a molded body obtained by molding in a magnetic field. The alloy powder used for forming in a magnetic field is obtained by finely pulverizing to an average particle size of about 2 to 6 μm by, for example, a jet mill, and is required to have high pulverizability at this time. In order to meet these demands, it is conventionally known to add a lubricant containing an organic substance such as oleic acid amide before pulverization (see, for example, Patent Document 1 and Patent Document 2). It is known that the added lubricant is removed by heating the molded body at 100 to 500 ° C. in a vacuum or an inert gas atmosphere (hereinafter referred to as a lubricant removal treatment) (for example, patents). Reference 1).
しかし、真空あるいは不活性ガス雰囲気中の加熱処理を行っても、潤滑剤を十分に除去することができないか、除去するための加熱処理を長時間行わなければならない。潤滑剤が成形体に多量に残留していると、焼結時に希土類元素と反応して希土類炭化物を形成することにより、磁気特性を低下させる。あるいは、成形体の収縮率が不均一になり、成形体、ひいては焼結体に変形が生ずることがある。このような問題を解決するためには、水素を含む雰囲気にて潤滑剤除去処理を行うことが有効である(例えば、特許文献3)。 However, even if heat treatment is performed in a vacuum or an inert gas atmosphere, the lubricant cannot be sufficiently removed, or heat treatment for removal must be performed for a long time. If a large amount of lubricant remains in the molded body, it reacts with rare earth elements during sintering to form rare earth carbides, thereby reducing the magnetic properties. Or the shrinkage | contraction rate of a molded object becomes non-uniform | heterogenous, and a deformation | transformation may arise in a molded object and by extension, a sintered compact. In order to solve such a problem, it is effective to perform the lubricant removal treatment in an atmosphere containing hydrogen (for example, Patent Document 3).
本発明者等は、水素を含む雰囲気にて潤滑剤除去処理を行ったところ、希土類焼結磁石にクラックが発生することを経験した。そこで本発明は、成形体から効率よく潤滑剤を除去し、かつ焼結後の変形及びクラックの発生を抑制することのできる潤滑剤の除去方法及び希土類焼結磁石の製造方法を提供することを目的とする。 The present inventors experienced that a crack was generated in the rare earth sintered magnet when the lubricant removal treatment was performed in an atmosphere containing hydrogen. Therefore, the present invention provides a method for removing a lubricant and a method for producing a rare earth sintered magnet that can efficiently remove a lubricant from a molded body and suppress deformation and cracking after sintering. Objective.
本発明者等は希土類焼結磁石に発生するクラックの原因を究明するべく種々の実験を行ったところ、潤滑剤除去処理時に成形体(R−T−B系合金)が水素を吸蔵することによる膨張がクラック発生の原因であることが判明した。より具体的には、後述する実施例の欄で示すように、水素を含む雰囲気で潤滑剤除去処理を行うと、R2T14B相の格子体積が膨張している。そこで、本発明は、水素を含む雰囲気における潤滑剤除去処理において、潤滑剤除去処理の対象である成形体が水素を吸蔵しない条件を採用することを提案する。ここで、水素の吸蔵量は温度に依存し、低温ほど多くなる。一般的な傾向として、成形体は不可避的に又は意図的に水素が吸蔵されており、この成形体は低温度領域で水素を吸蔵し、高温度領域では水素を排出する。潤滑剤除去処理時における水素の吸蔵又は排出の境界は、潤滑剤除去処理に供される成形体に吸蔵されている水素量に依存する。すなわち、潤滑剤除去処理に供される成形体の水素吸蔵量が、潤滑剤除去処理を行う条件における水素吸蔵量以上の量であれば、潤滑剤除去処理時に新たに水素を吸蔵することがないため格子は膨張せずクラックが発生しない。以上の知見に基づく本発明の潤滑剤の除去方法は、有機物を構成要素とする潤滑剤と、原料合金に対して水素吸蔵を施して得られるものであり、Rを25〜37wt%、Bを0.5〜4.5wt%含有するR−T−B(Rは希土類元素の1種又は2種以上、TはFe又はFe及びCo)系の合金粉末とを含む組成物を磁場中で加圧成形して成形体を得る工程と、成形体の水素量を把握する工程と、成形体を、水素(H2)を含む雰囲気ガスの下、かつ100〜550℃の温度範囲で、成形体の水素量を維持又は減少しつつ加熱処理することにより潤滑剤を除去する工程と、を含むことを特徴とする。 The present inventors conducted various experiments in order to investigate the cause of cracks generated in the rare earth sintered magnet. As a result, the compact (RTB-based alloy) occludes hydrogen during the lubricant removal treatment. It was found that expansion was the cause of cracking. More specifically, as shown in the column of Examples described later, when the lubricant removal treatment is performed in an atmosphere containing hydrogen, the lattice volume of the R 2 T 14 B phase is expanded. In view of this, the present invention proposes to adopt a condition in which the molded body that is the object of the lubricant removal treatment does not occlude hydrogen in the lubricant removal treatment in an atmosphere containing hydrogen. Here, the occlusion amount of hydrogen depends on the temperature, and increases as the temperature decreases. As a general tendency, the molded body inevitably or intentionally occludes hydrogen, and this molded body occludes hydrogen in a low temperature region and discharges hydrogen in a high temperature region. The boundary between the occlusion and discharge of hydrogen during the lubricant removal process depends on the amount of hydrogen occluded in the molded body subjected to the lubricant removal process. That is, if the hydrogen occlusion amount of the molded body subjected to the lubricant removal treatment is equal to or greater than the hydrogen occlusion amount in the condition for performing the lubricant removal treatment, hydrogen is not newly occluded during the lubricant removal treatment. Therefore, the lattice does not expand and cracks do not occur. The method for removing a lubricant of the present invention based on the above knowledge is obtained by performing hydrogen storage on a lubricant containing an organic substance and a raw material alloy, wherein R is 25 to 37 wt%, B is A composition containing 0.5 to 4.5 wt% of R-T-B (R is one or more of rare earth elements, T is Fe or Fe and Co) based alloy powder is added in a magnetic field. A step of obtaining a molded body by pressure molding, a step of grasping the amount of hydrogen in the molded body, and a molded body in an atmosphere gas containing hydrogen (H 2 ) and in a temperature range of 100 to 550 ° C. And a step of removing the lubricant by heat treatment while maintaining or reducing the amount of hydrogen.
本発明において、合金粉末が、原料合金に対して水素吸蔵を施して得られるものとすることができる。水素を吸蔵することにより粉砕(水素粉砕)されて合金粉末を得ることができるが、このような水素粉砕された合金粉末に対して本発明を適用することができる。水素粉砕された合金粉末は、所定量の水素を含んでおり、この水素が最終的に得たい特性を得るための弊害となる場合がある。その場合には、水素吸蔵後に水素排出処理を施すことが行われており、その場合も本発明を適用することができる。水素吸蔵のままの状態では合金粉末が多量の水素を含んでいるため、潤滑剤除去処理の過程で水素を吸蔵する例はほとんどない。これに対して水素排出処理を行った場合には、水素量が低減されているために、潤滑剤除去処理において水素を吸蔵して水素量が増加する場合がある。この水素量増加を本発明は回避するのである。 In the present invention, the alloy powder can be obtained by subjecting the raw material alloy to hydrogen storage. Although alloy powder can be obtained by pulverizing (hydrogen pulverizing) by storing hydrogen, the present invention can be applied to such hydrogen-pulverized alloy powder. The hydrogen-pulverized alloy powder contains a predetermined amount of hydrogen, and this hydrogen may be an adverse effect for obtaining the desired properties. In that case, a hydrogen discharge process is performed after storing the hydrogen, and the present invention can be applied also in that case. Since the alloy powder contains a large amount of hydrogen in the state where the hydrogen is occluded, there are almost no examples of occlusion of hydrogen during the process of removing the lubricant. On the other hand, when the hydrogen discharge process is performed, the amount of hydrogen is reduced, and therefore, the amount of hydrogen may increase due to occlusion of hydrogen in the lubricant removal process. The present invention avoids this increase in the amount of hydrogen.
本発明において、潤滑剤除去処理における加熱処理の雰囲気ガスは、不活性ガスを含むことが好ましい。 In the present invention, atmosphere gas heating in the lubricant removal treatment preferably contains an inert gas.
本発明は、希土類焼結磁石に適用することが好ましく、したがってRを25〜37wt%、Bを0.5〜4.5wt%含有するR−T−B(Rは希土類元素の1種又は2種以上、TはFe又はFe及びCo)系の原料合金に水素を吸蔵させた後に所定温度に加熱して水素を排出させる水素処理工程と、水素処理工程で得られた合金粉末を、有機物を構成要素とする潤滑剤が添加された状態でさらに微細に粉砕する微粉砕工程と、微粉砕工程で得られた粉砕粉末を磁場中成形する工程と、成形体の水素量を把握する工程と、磁場中成形で得られた成形体を、水素(H2)を含む雰囲気ガスの下で、100〜550℃の温度範囲に加熱保持して成形体の水素量を維持又は減少しつつ潤滑剤を除去する工程と、潤滑剤が除去された成形体を焼結する工程と、を備えることを特徴とする希土類焼結磁石の製造方法が提供される。 The present invention is preferably applied to a rare earth sintered magnet. Therefore, R-T-B containing R of 25 to 37 wt% and B of 0.5 to 4.5 wt% (R is one or two of rare earth elements). More than seeds, T is Fe or Fe and Co). Oxygen is occluded by hydrogen treatment process in which hydrogen is occluded in a raw material alloy and heated to a predetermined temperature to discharge hydrogen. A fine pulverization step for further finely pulverizing the lubricant as a constituent element, a step of forming the pulverized powder obtained in the fine pulverization step in a magnetic field, a step of grasping the hydrogen content of the molded body, The molded body obtained by molding in a magnetic field is heated and held in a temperature range of 100 to 550 ° C. under an atmosphere gas containing hydrogen (H 2 ) to maintain or reduce the amount of hydrogen in the molded body while maintaining the lubricant. The step of removing and the molded body from which the lubricant has been removed are sintered. Method for producing a rare earth sintered magnet characterized by comprising the steps, is provided.
以上説明したように、本発明によれば、水素を含む雰囲気ガスの下で潤滑剤除去処理を行う場合でも、希土類焼結磁石等の焼結体のクラック発生を抑制することができる。しかも本発明によれば、水素を含む雰囲気ガスの下で潤滑剤除去処理を行うので、効率よく潤滑剤を除去することができるとともに、焼結体の変形を低減することができる。 As described above, according to the present invention, the occurrence of cracks in a sintered body such as a rare earth sintered magnet can be suppressed even when the lubricant removal treatment is performed under an atmosphere gas containing hydrogen. In addition, according to the present invention, since the lubricant removal treatment is performed under an atmosphere gas containing hydrogen, the lubricant can be efficiently removed and deformation of the sintered body can be reduced.
以下、本発明を実施の形態を希土類焼結磁石の製造方法を例にして詳細に説明する。
希土類焼結磁石は、通常、原料合金作製、原料合金の粉砕、粉砕された粉末の磁場中成形、成形体の焼結という基本的な工程を経て作製される。以下、本発明の特徴部分である潤滑剤除去処理工程を含め、工程順にその製造方法を説明する。
Hereinafter, embodiments of the present invention will be described in detail by taking a method for producing a rare earth sintered magnet as an example.
Rare earth sintered magnets are usually produced through the basic steps of producing a raw material alloy, grinding the raw material alloy, forming the pulverized powder in a magnetic field, and sintering the compact. Hereinafter, the manufacturing method will be described in the order of steps including the lubricant removal treatment step which is a characteristic part of the present invention.
原料合金は、真空又は不活性ガス、好ましくはAr雰囲気中でストリップキャスト法、その他公知の溶解法により作製することができる。ストリップキャスト法は、原料金属をArガス雰囲気などの非酸化性雰囲気中で溶解して得た溶湯を回転するロールの表面に噴出させる。ロールで急冷された溶湯は、薄板または薄片(鱗片)状に急冷凝固される。この急冷凝固された合金は、結晶粒径が1〜50μmの均質な組織を有している。原料合金は、ストリップキャスト法に限らず、高周波誘導溶解等の溶解法によって得ることができる。 The raw material alloy can be produced by a strip casting method or other known melting methods in a vacuum or an inert gas, preferably in an Ar atmosphere. In the strip casting method, a molten metal obtained by melting a raw metal in a non-oxidizing atmosphere such as an Ar gas atmosphere is ejected onto the surface of a rotating roll. The melt rapidly cooled by the roll is rapidly solidified 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.
原料合金は粉砕工程に供される。粉砕工程には、粗粉砕工程と微粉砕工程とがある。まず、原料合金を、粒径数百μm程度になるまで粗粉砕する。粗粉砕は、スタンプミル、ジョークラッシャー、ブラウンミル等を用い、不活性ガス雰囲気中にて行なうことが好ましい。粗粉砕に先立って、原料合金に水素を吸蔵させた後に排出させることにより粉砕を行なうことが効果的である。この水素粉砕を粗粉砕と位置付けて、機械的な粗粉砕を省略することもできる。この場合、例えばストリップキャスト法で得られた原料合金は、数mm〜数十mmのサイズに切断された状態で水素粉砕に供される。 The raw material alloy is subjected to a grinding process. The pulverization process includes a coarse pulverization process and a fine pulverization process. First, the raw material alloy is coarsely pulverized until the particle size becomes about several hundred μm. The coarse pulverization is preferably 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 storing the hydrogen in the raw material alloy and then discharging it. This hydrogen pulverization can be regarded as coarse pulverization, and mechanical coarse pulverization can be omitted. In this case, for example, the raw material alloy obtained by the strip casting method is subjected to hydrogen pulverization in a state of being cut into a size of several mm to several tens mm.
原料合金には水素が不純物として不可避的に含まれる。したがって、粗粉砕として機械的な粉砕手法を採用したとしても粗粉砕粉末には10〜30ppm程度の水素が含まれる。一方、粗粉砕として水素粉砕を適用すると、粗粉砕粉末には3500〜5000ppm程度の水素が含まれる。粉砕だけを目的とする場合水素吸蔵のみを行えば足りる。しかし、このように大量に水素を吸蔵した状態の粗粉砕粉末は、Nd−Fe−B系合金の磁気特性を悪化させる酸素との親和力が大きい状態となっているため、従来、水素吸蔵の後に、水素排出を行っていた。ただし、後の微粉砕における粉砕性を考慮すると粗粉砕粉末に水素が含まれていることが好ましいため、水素排出を行ったとしても、1000〜2000ppm程度の水素を残存させることが好ましい。また、この程度の水素量であれば、後の潤滑剤除去処理工程、あるいは焼結工程で希土類焼結磁石にとって問題のない程度まで低減することができる。 The raw material alloy inevitably contains hydrogen as an impurity. Therefore, even if a mechanical pulverization method is employed as the coarse pulverization, the coarsely pulverized powder contains about 10 to 30 ppm of hydrogen. On the other hand, when hydrogen pulverization is applied as the coarse pulverization, the coarsely pulverized powder contains about 3500 to 5000 ppm of hydrogen. If the purpose is only crushing, it is sufficient to store only hydrogen. However, the coarsely pulverized powder in a state in which a large amount of hydrogen is occluded in this manner has a large affinity with oxygen that deteriorates the magnetic properties of the Nd—Fe—B alloy, and thus, conventionally, after hydrogen occlusion The hydrogen was discharged. However, considering the pulverization property in the subsequent fine pulverization, it is preferable that the coarsely pulverized powder contains hydrogen. Therefore, even if hydrogen is discharged, it is preferable to leave about 1000 to 2000 ppm of hydrogen. In addition, if the amount of hydrogen is about this level, it can be reduced to a level that does not cause a problem for the rare earth sintered magnet in the subsequent lubricant removal processing step or sintering step.
以後の微粉砕工程、磁場中成形工程においてR−T−B系合金の水素量は基本的に増加することはない。前述したように、水素を含む雰囲気で潤滑剤除去処理工程を行う本発明において、潤滑剤除去処理の対象である成形体の水素量が少なければ、水素を吸蔵することにより希土類焼結磁石にクラックが発生する。したがって、この粗粉砕工程後の粗粉砕粉末の状態の水素量をある程度確保しておくことが本発明にとって好ましい。粗粉砕として水素粉砕を適用する場合には、水素排出を行わないという選択肢がある。また、水素排出を行う場合でも、排出量を制限するという選択肢がある。一方、粗粉砕として機械的な粉砕を適用する場合には、水素を含む雰囲気で粉砕を行う、あるいは水素を含む雰囲気に粗粉砕粉末を晒す等により水素量を増加させることができる。具体的な水素量は、潤滑剤除去処理工程における温度によって適宜変動させることになる。 In the subsequent pulverization process and forming process in a magnetic field, the amount of hydrogen in the RTB-based alloy does not basically increase. As described above, in the present invention in which the lubricant removal treatment process is performed in an atmosphere containing hydrogen, if the amount of hydrogen in the molded object that is the subject of the lubricant removal treatment is small, the rare earth sintered magnet is cracked by occlusion of hydrogen. Occurs. Therefore, it is preferable for the present invention to secure a certain amount of hydrogen in the state of the coarsely pulverized powder after the coarsely pulverized step. When hydrogen pulverization is applied as coarse pulverization, there is an option not to discharge hydrogen. Even when hydrogen is discharged, there is an option to limit the discharge amount. On the other hand, when mechanical pulverization is applied as coarse pulverization, the amount of hydrogen can be increased by performing pulverization in an atmosphere containing hydrogen or exposing the coarsely pulverized powder to an atmosphere containing hydrogen. The specific amount of hydrogen is appropriately changed depending on the temperature in the lubricant removal treatment process.
粗粉砕工程後、微粉砕工程に移る。微粉砕には主にジェットミルが用いられ、粒径数百μm程度の粗粉砕粉末を、平均粒径2.5〜6μm、好ましくは3〜5μmとする。ジェットミルは、高圧の不活性ガスを狭いノズルより開放して高速のガス流を発生させ、この高速のガス流により粗粉砕粉末を加速し、粗粉砕粉末同士の衝突やターゲットあるいは容器壁との衝突を発生させて粉砕する方法である。
微粉砕前後又はその両方にて、有機物を構成要素とする潤滑剤を0.01〜0.5wt%程度添加することにより、次の磁場中成形時に配向性の高い微粉を得ることができる。また、微粉砕前に潤滑剤を添加した場合には、微粉砕工程において所望の粒径の微粉末を効率よく製造することができる。この潤滑剤としては、脂肪酸又は脂肪酸の誘導体、例えばステアリン酸系やオレイン酸系であるステアリン酸亜鉛、ステアリン酸カルシウム、ステアリン酸アミド、オレイン酸アミド等を用いることができる。
After the coarse pulverization process, the process proceeds to the fine pulverization process. A jet mill is mainly used for the fine pulverization, and the coarsely pulverized powder having a particle size of about several hundreds of μm has an average particle size of 2.5 to 6 μm, preferably 3 to 5 μm. The jet mill releases a high-pressure inert gas from a narrow nozzle to generate a high-speed gas flow, accelerates the coarsely pulverized powder with this high-speed gas flow, collides with the coarsely pulverized powder, and collides with the target or the container wall. It is a method of generating a collision and crushing.
By adding about 0.01 to 0.5 wt% of a lubricant containing an organic substance before and after pulverization or both, fine powder with high orientation can be obtained at the time of molding in the next magnetic field. In addition, when a lubricant is added before fine pulverization, fine powder having a desired particle diameter can be efficiently produced in the fine pulverization step. As this lubricant, fatty acid or a derivative of fatty acid, for example, stearic acid-based or oleic acid-based zinc stearate, calcium stearate, stearamide, oleamide, or the like can be used.
以上のようにして得られた微粉末は磁場中成形に供される。この磁場中成形は、800〜1360kA/m(10〜17kOe)の磁場中で、50〜200MPa(0.5〜2ton/cm2)前後の圧力で行なえばよい。また、印加する磁場は、静磁場に限らずパルス状の磁場を用いることができる。さらに、印加する磁場の方向は、加圧方向と平行な方向、加圧方向と直交する方向のいずれであってもよい。 The fine powder obtained as described above is subjected to molding in a magnetic field. The forming in the magnetic field may be performed at a pressure of about 50 to 200 MPa (0.5 to 2 ton / cm 2 ) in a magnetic field of 800 to 1360 kA / m (10 to 17 kOe). The applied magnetic field is not limited to a static magnetic field, and a pulsed magnetic field can be used. Furthermore, the direction of the magnetic field to be applied may be either a direction parallel to the pressing direction or a direction orthogonal to the pressing direction.
以上で得られた成形体は、前述した潤滑剤を含んでいる。この潤滑剤は、前述したように、希土類元素であるNdと反応するために、R−Fe−B系焼結磁石として希土類元素の量が不足することにより磁気特性の劣化を招く。また、潤滑剤を多く含んでいると焼結時の収縮が焼結体中で不均一となり焼結後に変形するおそれがある。
そこで、本発明では、水素(H2)を含む雰囲気ガスの下で潤滑剤の除去のための潤滑剤除去処理を行う。水素を含む雰囲気ガスの下で潤滑剤除去処理を成形体に施すと、真空下又は不活性ガス雰囲気下における潤滑剤除去処理に比べて成形体に残留する炭素の量を迅速に低減することができる。
The molded body obtained as described above contains the lubricant described above. As described above, since this lubricant reacts with Nd, which is a rare earth element, the amount of the rare earth element is insufficient as an R—Fe—B based sintered magnet, thereby deteriorating magnetic properties. In addition, when a large amount of lubricant is contained, shrinkage during sintering becomes non-uniform in the sintered body and there is a risk of deformation after sintering.
Therefore, in the present invention, a lubricant removal process for removing the lubricant is performed under an atmosphere gas containing hydrogen (H 2 ). When the lubricant removal treatment is performed on the molded body under an atmosphere gas containing hydrogen, the amount of carbon remaining in the molded body can be rapidly reduced compared to the lubricant removal treatment in a vacuum or an inert gas atmosphere. it can.
本発明は、潤滑剤除去のための加熱処理である潤滑剤除去処理を、水素を含む雰囲気ガス下で行うが、その分圧P(H2)が低くなると潤滑剤除去の効果が小さくなる。逆に、水素分圧P(H2)が高くなりすぎると、成形体の水素量によっては、潤滑剤除去の温度が高くなければ、成形体が水素を吸蔵してしまう。したがって、P(H2)は3〜100kPaの範囲とすることが好ましい。さらに好ましいP(H2)は10〜95kPaであり、より好ましいP(H2)は25〜90kPaである。
この雰囲気ガスは、水素(H2)のほかに不活性ガスを含むことが好ましい。この不活性ガスは、H2のキャリアガスとして機能する。不活性ガスとしては、Arガス、N2ガスを用いることができる。
In the present invention, the lubricant removal treatment, which is a heat treatment for removing the lubricant, is performed in an atmosphere gas containing hydrogen. However, when the partial pressure P (H 2 ) is lowered, the effect of removing the lubricant is reduced. Conversely, if the hydrogen partial pressure P (H 2 ) becomes too high, depending on the amount of hydrogen in the molded body, the molded body occludes hydrogen unless the lubricant removal temperature is high. Accordingly, P (H 2 ) is preferably in the range of 3 to 100 kPa. Further preferred P (H 2 ) is 10 to 95 kPa, and more preferred P (H 2 ) is 25 to 90 kPa.
This atmospheric gas preferably contains an inert gas in addition to hydrogen (H 2 ). This inert gas functions as a carrier gas for H 2 . Ar gas or N 2 gas can be used as the inert gas.
潤滑剤除去処理のための加熱処理は、100〜550℃の温度範囲に保持する。100℃未満では潤滑剤除去の効果を十分得ることができないためであり、一方、550℃を超えると効果が飽和するためである。ここで、100〜550℃の温度範囲に保持する、とは当該温度範囲の一定温度に成形体を保持する場合に限らず、所定時間だけ当該温度範囲のいずれかの温度に成形体が加熱されていればよい。したがって、100〜550℃にかけて連続的に昇温する形態、100〜550℃の範囲において段階的に温度を上昇させる形態等、種々の形態を包含する。好ましい加熱処理の温度は、150〜450℃、さらに好ましい加熱処理の温度は200〜400℃である。 Heat treatment for the lubricant removal treatment, that holds the temperature range of 100 to 550 ° C.. This is because the effect of removing the lubricant cannot be sufficiently obtained when the temperature is lower than 100 ° C., and the effect is saturated when the temperature exceeds 550 ° C. Here, holding in the temperature range of 100 to 550 ° C. is not limited to holding the molded body at a constant temperature in the temperature range, and the molded body is heated to any temperature in the temperature range for a predetermined time. It only has to be. Therefore, various forms, such as a form in which the temperature is continuously increased over 100 to 550 ° C. and a form in which the temperature is raised stepwise in the range of 100 to 550 ° C., are included. A preferable heat treatment temperature is 150 to 450 ° C., and a more preferable heat treatment temperature is 200 to 400 ° C.
ここで、潤滑剤除去処理における加熱温度で注意を要するのは、成形体(又は成形体を構成する微粉砕粉末)に含まれる水素の量を考慮して加熱温度を定める必要があるということである。潤滑剤除去処理工程において成形体が水素を吸蔵すると希土類焼結磁石にクラックが発生するおそれがあるからである。成形体が水素を吸蔵するか否かは、当該雰囲気の温度、水素分圧が影響を及ぼす。すなわち、当該条件における水素量吸蔵量未満の量しか成形体が水素を含んでいない場合には、成形体は水素を吸蔵する。逆に、当該条件における水素吸蔵量を超える量の水素を成形体が含んでいる場合には、成形体は水素を吸蔵しない。したがって、成形体が含む水素量を把握しておき、潤滑除去処理の条件における水素吸蔵量が、成形体が含む水素量未満となる温度で潤滑剤除去処理を行うべきである。
なお、クラックは、成形体の段階でその外観を目視することにより観察されるものがあるが、成形体の段階では外観から観察できない場合がある。この場合、焼結を経ることにより焼結体の表面にクラックを観察できることがある。
Here, it is necessary to pay attention to the heating temperature in the lubricant removal treatment because it is necessary to determine the heating temperature in consideration of the amount of hydrogen contained in the molded body (or finely pulverized powder constituting the molded body). is there. This is because if the molded body occludes hydrogen in the lubricant removing process, cracks may occur in the rare earth sintered magnet. Whether or not the molded body occludes hydrogen is affected by the temperature of the atmosphere and the hydrogen partial pressure. That is, when the molded body contains hydrogen only in an amount less than the hydrogen storage amount under the conditions, the molded body occludes hydrogen. On the contrary, when the molded body contains an amount of hydrogen that exceeds the hydrogen storage amount under the above conditions, the molded body does not occlude hydrogen. Therefore, the amount of hydrogen contained in the molded body should be grasped, and the lubricant removal process should be performed at a temperature at which the hydrogen occlusion amount under the condition of the lubrication removal process is less than the amount of hydrogen contained in the molded body.
Some cracks are observed by visually observing the appearance at the stage of the molded body, but may not be observed from the appearance at the stage of the molded body. In this case, cracks may be observed on the surface of the sintered body through sintering.
加熱処理の保持時間が短いと潤滑剤除去の効果が不十分であり、一方保持時間が長すぎても潤滑剤除去の効果が飽和してしまう。したがって、加熱処理の保持時間は、0.5〜10時間とすることが好ましく、さらには1〜3時間とすることが好ましい。 If the holding time of the heat treatment is short, the effect of removing the lubricant is insufficient, while if the holding time is too long, the effect of removing the lubricant is saturated. Therefore, the heat treatment holding time is preferably 0.5 to 10 hours, and more preferably 1 to 3 hours.
以上の潤滑剤除去処理が施された成形体は、焼結に供される。焼結は、真空又は不活性ガス雰囲気中、好ましくは真空中で行われる。焼結条件は、組成、粉砕方法、平均粒径と粒度分布の違い等、諸条件により調整する必要があるが、1000〜1100℃の温度で1〜10時間程度保持すれば緻密な焼結体を得ることができる。
焼結後、得られた焼結体に時効処理を施すことができる。この工程は、保磁力を制御する重要な工程である。時効処理を2段に分けて行なう場合には、750〜950℃、500〜700℃での所定時間の保持が有効である。また、500〜700℃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500〜700℃の時効処理を施すとよい。
The molded body that has been subjected to the above lubricant removal treatment is subjected to sintering. Sintering is performed in a vacuum or an inert gas atmosphere, preferably in a vacuum. Sintering conditions need to be adjusted according to various conditions such as composition, pulverization method, difference in average particle size and particle size distribution, etc., but a dense sintered body can be maintained at a temperature of 1000 to 1100 ° C. for about 1 to 10 hours. Can be obtained.
After sintering, the obtained sintered body can be subjected to an aging treatment. This process is an important process for controlling the coercive force. When the aging treatment is performed in two stages, holding for a predetermined time at 750 to 950 ° C. and 500 to 700 ° C. is effective. Further, since the coercive force is greatly increased by heat treatment at 500 to 700 ° C., the aging treatment at 500 to 700 ° C. is preferably performed when the aging treatment is performed in one stage.
本発明を適用した希土類焼結磁石の製造方法において、潤滑剤除去処理を焼結と独立して行うことができる。また、本発明において、潤滑剤除去処理を焼結の昇温過程で行うこともできる。後者の形態を図1に示す。図1に示すように、潤滑剤除去のために焼結の昇温過程の所定の温度域(100〜500℃)で焼結炉内の雰囲気を、H2を含む雰囲気ガスとすればよい。所定時間経過した後に、焼結炉から雰囲気ガスを排出し、かつ焼結炉内を減圧して所定の真空度にする。この真空度を維持しながら焼結温度まで昇温し、かつ所定時間保持する。なお、図1は潤滑剤除去を一定の温度に保持する例を示しているが、前述したように、図2に示すように連続的に昇温してもよいし、図3に示すように段階的に昇温してもよい。 In the method for producing a rare earth sintered magnet to which the present invention is applied, the lubricant removal treatment can be performed independently of the sintering. In the present invention, the lubricant removal treatment can also be performed in the temperature rising process of sintering. The latter form is shown in FIG. As shown in FIG. 1, the atmosphere in the sintering furnace may be an atmosphere gas containing H 2 in a predetermined temperature range (100 to 500 ° C.) in the temperature raising process of sintering in order to remove the lubricant. After a predetermined time has elapsed, the atmospheric gas is discharged from the sintering furnace, and the inside of the sintering furnace is depressurized to a predetermined degree of vacuum. While maintaining this degree of vacuum, the temperature is raised to the sintering temperature and held for a predetermined time. FIG. 1 shows an example in which the lubricant removal is maintained at a constant temperature. However, as described above, the temperature may be continuously increased as shown in FIG. 2, or as shown in FIG. The temperature may be raised stepwise.
図4は、製造過程における水素量の変遷を示す図である。図4において、本発明Iは水
素吸蔵後に水素排出を行わない形態を示し、本発明IIは水素吸蔵後に水素排出を行う形態
を示している。また図4において、比較例は水素吸蔵後に水素排出を行う形態を示している。本発明IIと比較例は水素排出後の水素量が相違しており、本発明IIに比べて比較例は
水素をより多く排出しており水素排出後の水素量が少ない。
図4において、本発明Iは水素吸蔵後の水素量が潤滑剤除去前まで維持される。前述し
たように、水素を含む雰囲気ガス中で潤滑剤除去処理を行うが、成形体(微粉砕粉末)の水素量が高いため、潤滑剤除去処理の過程で水素を排出する。
図4において、本発明IIは水素吸蔵後に水素排出を行うため、水素量が所定量まで低減
される。本発明IIは、水素排出後の水素量によって2つの形態に区分することができる。
1つは潤滑剤除去処理工程で水素量が低減する形態(本発明II−a)である。他の1つは
、潤滑剤除去処理工程で水素量が維持される形態(本発明II−b)である。いずれの形態
であっても、その後に水素を含む雰囲気ガス中で潤滑剤除去処理を行っても水素を吸蔵しないため、水素排出後の水素量が焼結前まで維持される。
図4において、比較例は水素吸蔵後に水素排出を行う。このときの水素量は、前述したように、本発明(I、II)よりも低い。この水素量は微粉砕、磁場中成形の過程では維持
されるが、潤滑剤除去工程において成形体(微粉砕粉末)が水素を吸蔵するために、水素量が増加する。そのために、成形体にクラックが発生する。
FIG. 4 is a diagram showing changes in the amount of hydrogen in the production process. In FIG. 4, the present invention I shows a mode in which hydrogen is not discharged after storing hydrogen, and the present invention II shows a mode in which hydrogen is discharged after storing hydrogen. Moreover, in FIG. 4, the comparative example has shown the form which discharges | emits hydrogen after hydrogen storage. The amount of hydrogen after hydrogen discharge is different between the present invention II and the comparative example. Compared to the present invention II, the comparative example discharges more hydrogen and the amount of hydrogen after hydrogen discharge is small.
In FIG. 4, the present invention I maintains the amount of hydrogen after hydrogen storage until the lubricant is removed. As described above, the lubricant removal treatment is performed in an atmosphere gas containing hydrogen. However, since the amount of hydrogen in the compact (finely pulverized powder) is high, hydrogen is discharged during the lubricant removal treatment.
In FIG. 4, the present invention II discharges hydrogen after occlusion of hydrogen, so that the amount of hydrogen is reduced to a predetermined amount. Invention II can be divided into two forms according to the amount of hydrogen after hydrogen discharge.
One is a form (invention II-a) in which the amount of hydrogen is reduced in the lubricant removal treatment step. The other is a form in which the amount of hydrogen is maintained in the lubricant removal treatment process (present invention II-b). In any form, hydrogen is not occluded even if the lubricant removal treatment is performed in an atmosphere gas containing hydrogen thereafter, so that the amount of hydrogen after hydrogen discharge is maintained before sintering.
In FIG. 4, the comparative example discharges hydrogen after storing hydrogen. The amount of hydrogen at this time is lower than that of the present invention (I, II) as described above. This amount of hydrogen is maintained in the process of fine pulverization and molding in a magnetic field, but the amount of hydrogen increases because the compact (fine pulverized powder) occludes hydrogen in the lubricant removal step. Therefore, a crack occurs in the molded body.
本発明はR−T−B(Rは希土類元素の1種又は2種以上、TはFe又はFe及びCo)で示されるR−T−B系焼結磁石について適用する。
R−T−B系焼結磁石は、希土類元素(R)を25〜37wt%含有する。ここで、RはYを含む概念を有しており、したがってY、La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb及びLuの1種又は2種以上から選択される。Rの量が25wt%未満であると、R−T−B系焼結磁石の主相となる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。好ましいRの量は28〜35wt%である。
The present invention is R-T-B (R is one or more rare earth elements, T is Fe or Fe and Co) that apply for R-T-B based sintered magnets represented by.
The RTB-based sintered magnet contains 25 to 37 wt% of rare earth element (R). Here, R has a concept including Y. Therefore, one or two of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Selected from more than species. If the amount of R is less than 25 wt%, the R 2 T 14 B phase, which is the main phase of the RTB-based 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 preferable amount of R is 28 to 35 wt%.
また、本発明が適用されるR−T−B系焼結磁石は、ホウ素(B)を0.5〜4.5wt%含有する。Bが0.5wt%未満の場合には高い保磁力を得ることができない。一方で、Bが4.5wt%を超えると残留磁束密度が低下する傾向がある。したがって、Bの上限を4.5wt%とする。好ましいBの量は0.5〜1.5wt%、さらに好ましいBの量は0.8〜1.2wt%である。
本発明が適用されるR−T−B系焼結磁石は、Coを5.0wt%以下(0を含まず)、好ましくは0.1〜3.0wt%含有することができる。CoはFeと同様の相を形成するが、キュリー温度の向上、粒界相の耐食性向上などに効果がある。
Further, the RTB-based sintered magnet to which the present invention is applied contains 0.5 to 4.5 wt% of boron (B). When B is less than 0.5 wt%, a high coercive force cannot be obtained. On the other hand, when B exceeds 4.5 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit of B is set to 4.5 wt%. A preferable amount of B is 0.5 to 1.5 wt%, and a more preferable amount of B is 0.8 to 1.2 wt%.
The RTB-based sintered magnet to which the present invention is applied can contain Co of 5.0 wt% or less (excluding 0), preferably 0.1 to 3.0 wt%. Co forms the same phase as Fe, but is effective in improving the Curie temperature and the corrosion resistance of the grain boundary phase.
本発明が適用されるR−T−B系焼結磁石は、他の元素の含有を許容する。例えば、Al、Cu、Zr、Ti、Bi、Sn、Ga、Nb、Ta、Si、V、Ag、Ge等の元素を適宜含有させることができる。一方で、酸素、窒素、炭素等の不純物元素を極力低減することが好ましい。特に磁気特性を害する酸素は、その量を8000ppm以下、さらには5000ppm以下とすることが好ましい。酸素量が多いと非磁性成分である希土類酸化物相が増大して、磁気特性を低下させるからである。 The RTB-based sintered magnet to which the present invention is applied allows the inclusion of other elements. For example, elements such as Al, Cu, Zr, Ti, Bi, Sn, Ga, Nb, Ta, Si, V, Ag, and Ge can be appropriately contained. On the other hand, it is preferable 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 8000 ppm or less, more preferably 5000 ppm or less. This is because when the amount of oxygen is large, the rare-earth oxide phase, which is a nonmagnetic component, increases and the magnetic properties are deteriorated.
ストリップキャスト法により30wt%Nd−2wt%Dy−0.2wt%Al−0.5wt%Co−0.1wt%Cu−1wt%B−bal.Feの組成を有する合金を作製した。得られたストリップキャスト合金に室温で水素を吸蔵させた後に200℃又は600℃の温度で水素排出する水素処理による粗粉砕粉末を得た。なお、水素吸蔵後に水素排出を行わない粗粉砕粉末も用意した。以上の粗粉砕粉末をジェットミルにより微粉砕を行って平均粒径4.5μmの微粉砕粉末を得た。なお、ジェットミルによる微粉砕を行う際に、オレイン酸アミドを0.1wt%添加した。 An alloy having a composition of 30 wt% Nd-2 wt% Dy-0.2 wt% Al-0.5 wt% Co-0.1 wt% Cu-1 wt% B-bal.Fe was produced by strip casting. The obtained strip cast alloy was occluded with hydrogen at room temperature, and then coarsely pulverized powder was obtained by hydrogen treatment in which hydrogen was discharged at a temperature of 200 ° C or 600 ° C. A coarsely pulverized powder that does not discharge hydrogen after occlusion of hydrogen was also prepared. The above coarsely pulverized powder was finely pulverized by a jet mill to obtain a finely pulverized powder having an average particle size of 4.5 μm. When finely pulverizing with a jet mill, 0.1 wt% of oleic acid amide was added.
得られた微粉砕粉末を印加磁場:1200kA/m、成形圧力:100MPaの条件で磁場中成形して、70×10×50mmの寸法の成形体を得た。なお、この成形体の配向方向(磁場印加方向)は、70mmの方向である。以上の成形体を、180mm×180mm×180mmのサイズのトレーに18個載置した状態で潤滑剤除去処理を行った。なお、成形体は、10mm×50mmの面が底面になるようにトレーに載置された。 The obtained finely pulverized powder was molded in a magnetic field under the conditions of an applied magnetic field of 1200 kA / m and a molding pressure of 100 MPa to obtain a molded body having a size of 70 × 10 × 50 mm. In addition, the orientation direction (magnetic field application direction) of this molded body is a direction of 70 mm. Lubricant removal treatment was performed in a state where 18 of the above molded bodies were placed on a tray having a size of 180 mm × 180 mm × 180 mm. In addition, the molded object was mounted in the tray so that the surface of 10 mm x 50 mm might become a bottom face.
潤滑剤除去処理の条件は、120℃、280℃、320℃で及び500℃の各温度で1時間、水素を含む雰囲気ガス中に保持するというものである。この雰囲気ガスは水素(H2)とArの混合ガスで、水素の分圧P(H2)が50kPa、アルゴンの分圧P(Ar)が50kPaである。
潤滑剤除去処理を行った成形体について、水素量、炭素量を測定するとともにXRD(X Ray Diffraction)によりR2Fe14B相の格子体積を測定した。その結果を表1〜表3、図5〜図7に示した。
The condition for the lubricant removal treatment is to hold in an atmosphere gas containing hydrogen at 120 ° C., 280 ° C., 320 ° C. and 500 ° C. for 1 hour. This atmosphere gas is a mixed gas of hydrogen (H 2 ) and Ar, and the hydrogen partial pressure P (H 2 ) is 50 kPa, and the argon partial pressure P (Ar) is 50 kPa.
For molded body subjected to lubricant removal treatment, the amount of hydrogen was measured lattice volume of the R 2 Fe 14 B phase by XRD (X Ray Diffraction) with measuring the carbon amount. The results are shown in Tables 1 to 3 and FIGS.
表1及び図5に示すように、水素吸蔵をした状態(潤滑剤除去前)の成形体の水素量は4200ppm程度であるが、水素排出を200℃で行うことにより成形体の水素量は3400ppm程度に低減され、さらに水素排出を600℃で行うことにより成形体の水素量は1600ppm程度に低減される。このように、水素排出の温度が高いほど、成形体が含有することのできる水素量が少なくなる。このことは、潤滑剤除去温度が高くなれば成形体に含まれる水素量が少なくなることを示唆している。ただし、この示唆は、表1及び図5から明らかなように、水素排出を行っていない場合に当てはまるものの、水素排出を600℃で行っている場合には、120℃での潤滑剤除去により水素量が相当増加している。これは、600℃で水素排出を行った成形体の1600ppmという水素量は、P(H2):50kPa及びP(Ar):50kPaの雰囲気ガス、120℃の条件下における水素吸蔵量よりも低いためと解される。200℃で水素排出を行っている場合は、水素排出後の成形体の水素量が、P(H2):50kPa及びP(Ar):50kPaの雰囲気ガス、120℃の条件下における水素吸蔵量とほぼ同等である。 As shown in Table 1 and FIG. 5, the hydrogen content of the molded product in the hydrogen occluded state (before removing the lubricant) is about 4200 ppm, but the hydrogen content of the molded product is 3400 ppm by discharging hydrogen at 200 ° C. Further, by performing hydrogen discharge at 600 ° C., the hydrogen content of the compact is reduced to about 1600 ppm. Thus, the higher the hydrogen discharge temperature, the smaller the amount of hydrogen that the molded body can contain. This suggests that the amount of hydrogen contained in the molded body decreases as the lubricant removal temperature increases. However, as is apparent from Table 1 and FIG. 5, this suggestion applies when hydrogen is not discharged, but when hydrogen is discharged at 600 ° C., hydrogen removal is performed by removing the lubricant at 120 ° C. The amount has increased considerably. This is because the hydrogen amount of 1600 ppm of the molded body that had been discharged with hydrogen at 600 ° C. was lower than the hydrogen occlusion amount under the conditions of P (H 2 ): 50 kPa and P (Ar): 50 kPa, 120 ° C. It is understood that. When hydrogen is discharged at 200 ° C., the hydrogen content of the molded body after hydrogen discharge is P (H 2 ): 50 kPa and P (Ar): 50 kPa atmosphere gas, hydrogen storage amount under the conditions of 120 ° C. Is almost equivalent.
図5より、成形体の水素量が3500ppm以上であれば、潤滑剤除去処理の温度を問わず、成形体の水素量が増加することはないといえる。 From FIG. 5, it can be said that if the hydrogen content of the compact is 3500 ppm or more, the hydrogen content of the compact does not increase regardless of the temperature of the lubricant removal treatment.
次に、表2及び図6のR2Fe14B相の格子体積についてみると、表1及び図5の水素量の挙動と同様の傾向を示していることがわかる。水素排出を600℃で行った場合には、潤滑剤除去処理を120℃で行うことにより格子体積が増大することがわかる。この格子体積の増大が、希土類焼結磁石のクラック発生の原因とみなすことができる。
また、図5及び図6より、水素排出を行わない場合には、潤滑剤除去温度を規制しなくても、潤滑剤除去処理過程における水素吸蔵によるクラック発生のおそれはない。
Next, regarding the lattice volume of the R 2 Fe 14 B phase in Table 2 and FIG. 6, it can be seen that the same tendency as the hydrogen amount behavior in Table 1 and FIG. 5 is shown. It can be seen that when the hydrogen discharge is performed at 600 ° C., the lattice volume is increased by performing the lubricant removing process at 120 ° C. This increase in the lattice volume can be regarded as a cause of the occurrence of cracks in the rare earth sintered magnet.
Further, as shown in FIGS. 5 and 6, when hydrogen is not discharged, there is no possibility of cracking due to hydrogen occlusion in the lubricant removal process even if the lubricant removal temperature is not regulated.
水素排出を行った場合には、水素排出後の水素量を考慮して水素排出の温度を定める必要がある。具体的には、図5に示すような潤滑剤除去温度−水素量曲線を予め求めておき、水素量が増大しない条件、換言すれば水素量が維持又は減少する条件で潤滑剤除去処理を行えばよい。例えば、200℃で水素排出を行った場合には、120℃以上のいずれの温度で潤滑剤除去処理を行っても水素量の増大を回避することができる。しかし、200℃を超える温度で水素排出を行った場合には、120℃での潤滑剤除去処理では水素量が増大して、クラック発生の可能性が大きくなる。相対的には、水素排出の温度が高ければ潤滑剤除去処理の温度を高くしなければならず、水素排出の温度が低ければ潤滑剤除去処理の温度を低くすることができる。図5からすれば、600℃で水素排出を行った場合でも、潤滑剤除去処理を400℃以上で行えば水素量の増大を防ぐことができる。最大公約数的には、水素排出の温度で潤滑剤除去処理を行えば、潤滑剤除去の過程で水素を吸蔵することはない。 When hydrogen is discharged, it is necessary to determine the temperature of hydrogen discharge in consideration of the amount of hydrogen after hydrogen discharge. Specifically, a lubricant removal temperature-hydrogen amount curve as shown in FIG. 5 is obtained in advance, and the lubricant removal process is performed under conditions where the hydrogen amount does not increase, in other words, under conditions where the hydrogen amount is maintained or decreased. Just do it. For example, when hydrogen is discharged at 200 ° C., an increase in the amount of hydrogen can be avoided even if the lubricant removal treatment is performed at any temperature of 120 ° C. or higher. However, when hydrogen is discharged at a temperature exceeding 200 ° C., the amount of hydrogen is increased in the lubricant removal treatment at 120 ° C., and the possibility of occurrence of cracks increases. In comparison, if the temperature of hydrogen discharge is high, the temperature of the lubricant removal process must be increased, and if the temperature of hydrogen discharge is low, the temperature of the lubricant removal process can be decreased. According to FIG. 5, even when hydrogen is discharged at 600 ° C., an increase in the amount of hydrogen can be prevented by performing the lubricant removal treatment at 400 ° C. or higher. In terms of the greatest common divisor, if the lubricant removal treatment is performed at the temperature of hydrogen discharge, hydrogen is not occluded during the lubricant removal process.
次に、表3及び図7に示すように、潤滑剤除去温度が高くなるほど成形体の炭素量が低減され、潤滑剤が除去されていることがわかる。ただし、潤滑剤除去温度が500℃と高くなると成形体の炭素量低減効果が小さくなる。これは、炭素が希土類と反応して除去されない形態となるためと考えられる。炭素量が多いと磁気特性に悪影響を及ぼすとともに、焼結時の変形のおそれが大きくなる。したがって、潤滑剤除去の効果の観点から、潤滑剤除去温度は500℃以下にすることが好ましい。 Next, as shown in Table 3 and FIG. 7, it can be seen that the higher the lubricant removal temperature, the lower the carbon content of the molded body and the more the lubricant is removed. However, when the lubricant removal temperature is as high as 500 ° C., the effect of reducing the carbon content of the compact is reduced. This is presumably because carbon is in a form that is not removed by reaction with rare earth. A large amount of carbon adversely affects magnetic properties and increases the risk of deformation during sintering. Therefore, from the viewpoint of the effect of removing the lubricant, the lubricant removal temperature is preferably 500 ° C. or lower.
また潤滑剤除去後の成形体を焼結及び時効処理を行って焼結体を得た。焼結は真空中で1030℃で4時間保持する条件とし、時効処理はAr雰囲気中で900℃で1時間保持後、530℃で1時間保持する2段時効処理とした。得られた焼結体のクラック発生状況と変形量の測定を行った。その結果を表4及び表5に示す。なお、クラックは目視により確認した。変形量は、得られた焼結体の40mmの幅における中間部のふくらみ値を図8に示すように測定し、18ケの焼結体の中の最大値を変形量とした。ただし、クラックの発生した焼結体については変形量の測定を行っていない(表5に測定不能と表示)。 Further, the molded body after removing the lubricant was subjected to sintering and aging treatment to obtain a sintered body. Sintering was performed under the condition of holding at 1030 ° C. for 4 hours in vacuum, and the aging treatment was a two-stage aging treatment of holding at 900 ° C. for 1 hour in an Ar atmosphere and then holding at 530 ° C. for 1 hour. The resulting sintered body was measured for the occurrence of cracks and the amount of deformation. The results are shown in Tables 4 and 5. In addition, the crack was confirmed visually. As for the amount of deformation, the bulging value of the intermediate part in the width of 40 mm of the obtained sintered body was measured as shown in FIG. 8, and the maximum value among the 18 sintered bodies was defined as the amount of deformation. However, the amount of deformation was not measured for the sintered body in which the crack occurred (indicated as “unmeasureable” in Table 5).
表4に示すように、水素排出を行わないで得られた焼結体及び水素排出を200℃で行った得られた焼結体は、クラックの発生が確認されなかった。これに対して、600℃で水素排出を行って得られた焼結体は、潤滑剤除去温度が120℃及び280℃の場合に、全ての焼結体にクラックが発生した。しかし、潤滑剤除去温度が320℃ではクラック発生頻度が低くなり、潤滑剤除去温度が500℃の場合にはクラックは発生しなかった。
以上の結果と表1及び図5を参酌すると、水素量が増加する条件で潤滑剤除去処理を行うと、焼結後にクラックが発生する可能性が増大することがわかる。
As shown in Table 4, generation of cracks was not confirmed in the sintered body obtained without discharging hydrogen and the sintered body obtained after discharging hydrogen at 200 ° C. In contrast, in the sintered body obtained by discharging hydrogen at 600 ° C., cracks occurred in all the sintered bodies when the lubricant removal temperatures were 120 ° C. and 280 ° C. However, when the lubricant removal temperature was 320 ° C., the frequency of occurrence of cracks was low, and when the lubricant removal temperature was 500 ° C., no cracks were generated.
Considering the above results and Table 1 and FIG. 5, it can be seen that if the lubricant removal treatment is performed under the condition that the amount of hydrogen is increased, the possibility of occurrence of cracks after sintering increases.
表5に示すように、潤滑剤除去処理を行うことにより、焼結体の変形を抑制できることがわかる。ただし、成形体における炭素量の高い500℃の潤滑剤除去では、それ以下の温度における潤滑剤除去処理よりも変形量が大きくなった。これは、成形体に残留する炭素量に比例しており、成形体に残留する炭素が焼結体の変形の原因と推察される。 As shown in Table 5, it can be seen that the deformation of the sintered body can be suppressed by performing the lubricant removal treatment. However, the removal amount of the lubricant at 500 ° C. with a high carbon content in the molded body was larger than that in the lubricant removal treatment at a temperature lower than that. This is proportional to the amount of carbon remaining in the molded body, and it is assumed that the carbon remaining in the molded body is the cause of deformation of the sintered body.
得られた焼結体のいくつかについて磁気特性を測定した。その結果を表6に示すが、潤滑剤除去処理を行うことにより、保磁力(HcJ)を向上できることが確認された。 Magnetic properties of some of the obtained sintered bodies were measured. The results are shown in Table 6. It was confirmed that the coercive force (HcJ) can be improved by performing the lubricant removal treatment.
水素排出を300℃で行った以外は実施例1と同様にして磁場中成形まで行って成形体を得た。得られた成形体に対して、表7に示す水素及びArからなる雰囲気ガス中にて400℃で1時間潤滑剤除去処理を行った。潤滑剤除去処理後の水素量、炭素量を測定した。その結果を表7に示した。 Except that hydrogen was discharged at 300 ° C., a compact was obtained in the same manner as in Example 1 until forming in a magnetic field. The resulting molded body was subjected to a lubricant removal treatment at 400 ° C. for 1 hour in an atmosphere gas composed of hydrogen and Ar shown in Table 7. The amount of hydrogen and carbon after the lubricant removal treatment were measured. The results are shown in Table 7.
潤滑剤除去処理後の成形体に、実施例1と同様にして焼結、時効処理を施して焼結体を得た。得られた焼結体について、実施例1と同様にクラック発生状況と変形量の測定を行うとともに、磁気特性も測定した。その結果を表7に併せて示す。 The molded body after the lubricant removal treatment was sintered and aged in the same manner as in Example 1 to obtain a sintered body. About the obtained sintered compact, the crack generation situation and the amount of deformation were measured similarly to Example 1, and the magnetic characteristics were also measured. The results are also shown in Table 7.
Claims (4)
前記成形体の水素量を把握する工程と、
前記成形体を、水素(H2)を含む雰囲気ガスの下、かつ100〜550℃の温度範囲で、前記成形体の前記水素量を維持又は減少しつつ加熱処理することにより前記潤滑剤を除去する工程と、を含み、
前記合金粉末は、原料合金に対して水素吸蔵を施して得られるものであり、Rを25〜37wt%、Bを0.5〜4.5wt%含有するR−T−B(Rは希土類元素の1種又は2種以上、TはFe又はFe及びCo)系の合金粉末であることを特徴とする潤滑剤の除去方法。 A step of pressure-molding a composition containing a lubricant containing an organic substance and an alloy powder having a predetermined composition in a magnetic field to obtain a molded body;
Grasping the amount of hydrogen in the molded body;
Removing said lubricant said molded body under the atmospheric gas containing hydrogen (H 2), and in the temperature range of 100 to 550 ° C., by heating maintained or reduced, while the hydrogen content of the green body Including the steps of:
The alloy powder is obtained by subjecting a raw material alloy to hydrogen storage, and R-T-B (R is a rare earth element) containing 25 to 37 wt% R and 0.5 to 4.5 wt% B. 1 or 2 or more, T is Fe or Fe and Co) based alloy powder.
前記水素処理工程で得られた合金粉末を、有機物を構成要素とする潤滑剤が添加された状態でさらに微細に粉砕する微粉砕工程と、
前記微粉砕工程で得られた粉砕粉末を磁場中成形する工程と、
前記成形体の水素量を把握する工程と、
前記磁場中成形で得られた成形体を、水素(H2)を含む雰囲気ガスの下で、100〜550℃の温度範囲に加熱保持して、前記成形体の前記水素量を維持又は減少しつつ前記潤滑剤を除去する工程と、
前記潤滑剤が除去された前記成形体を焼結する工程と、
を備えることを特徴とする希土類焼結磁石の製造方法。 R-T-B (R is one or more of rare earth elements, T is Fe or Fe and Co) based material alloy containing 25 to 37 wt% R and 0.5 to 4.5 wt% B A hydrogen treatment process in which hydrogen is exhausted by heating to a predetermined temperature after occluding hydrogen;
A finely pulverizing step of further finely pulverizing the alloy powder obtained in the hydrogen treatment step with a lubricant containing an organic substance as a component;
Forming the pulverized powder obtained in the fine pulverization step in a magnetic field;
Grasping the amount of hydrogen in the molded body;
The molded body obtained in the magnetic field molding under an atmosphere gas containing hydrogen (H 2), and heated and maintained at a temperature range of 100 to 550 ° C., maintaining or reducing the hydrogen content of the forming body Removing the lubricant while
Sintering the molded body from which the lubricant has been removed;
A method for producing a rare earth sintered magnet.
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