JP4798357B2 - Manufacturing method of rare earth sintered magnet - Google Patents
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- JP4798357B2 JP4798357B2 JP2006056221A JP2006056221A JP4798357B2 JP 4798357 B2 JP4798357 B2 JP 4798357B2 JP 2006056221 A JP2006056221 A JP 2006056221A JP 2006056221 A JP2006056221 A JP 2006056221A JP 4798357 B2 JP4798357 B2 JP 4798357B2
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- 238000010438 heat treatment Methods 0.000 claims description 64
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- 239000002994 raw material Substances 0.000 claims description 11
- 150000002431 hydrogen Chemical class 0.000 claims description 9
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- 239000000126 substance Substances 0.000 claims description 7
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- 229910052782 aluminium Inorganic materials 0.000 description 1
- 229940053200 antiepileptics fatty acid derivative Drugs 0.000 description 1
- CJZGTCYPCWQAJB-UHFFFAOYSA-L calcium stearate Chemical compound [Ca+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O CJZGTCYPCWQAJB-UHFFFAOYSA-L 0.000 description 1
- 239000008116 calcium stearate Substances 0.000 description 1
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- 239000013078 crystal Substances 0.000 description 1
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- 238000007599 discharging Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- 150000004678 hydrides Chemical class 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
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- QXJSBBXBKPUZAA-UHFFFAOYSA-N isooleic acid Natural products CCCCCCCC=CCCCCCCCCC(O)=O QXJSBBXBKPUZAA-UHFFFAOYSA-N 0.000 description 1
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- 230000005389 magnetism Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 229910001172 neodymium magnet Inorganic materials 0.000 description 1
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- LYRFLYHAGKPMFH-UHFFFAOYSA-N octadecanamide Chemical compound CCCCCCCCCCCCCCCCCC(N)=O LYRFLYHAGKPMFH-UHFFFAOYSA-N 0.000 description 1
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- ZQPPMHVWECSIRJ-KTKRTIGZSA-N oleic acid Chemical compound CCCCCCCC\C=C/CCCCCCCC(O)=O ZQPPMHVWECSIRJ-KTKRTIGZSA-N 0.000 description 1
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- IZUPBVBPLAPZRR-UHFFFAOYSA-N pentachlorophenol Chemical compound OC1=C(Cl)C(Cl)=C(Cl)C(Cl)=C1Cl IZUPBVBPLAPZRR-UHFFFAOYSA-N 0.000 description 1
- -1 rare earth carbides Chemical class 0.000 description 1
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- Hard Magnetic Materials (AREA)
- Manufacturing Cores, Coils, And Magnets (AREA)
Description
本発明は、希土類焼結磁石の製造方法に関し、特に磁場中成形時の成形性、配向性を確保するために添加される潤滑剤を効率よく除去することのできる希土類焼結磁石の製造方法に関するものである。 The present invention relates to a method for producing a rare earth sintered magnet, and more particularly to a method for producing a rare earth sintered magnet capable of efficiently removing a lubricant added to ensure formability and orientation during molding in a magnetic field. Is.
希土類元素(R)、Fe又はFe及びCoを必須とする少なくとも1種以上の遷移金属元素(T)及びホウ素(B)を主成分とするR−T−B系焼結磁石は、所定粒度を有する合金粉末を磁場中成形した後に、焼結して製造される。磁気特性の高いR−T−B系焼結磁石を得るために、磁場中成形により得られる成形体の配向性を向上することが求められる。また、磁場中成形に供される合金粉末は、例えばジェットミルによって平均粒径2〜6μm程度まで微粉砕して得られるが、このときの粉砕性が高いことが求められる。これらの要望に応えるために、従来、微粉砕の前に脂肪酸や炭化水素系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、この処理を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1参照。)。 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 organic substances such as fatty acids and hydrocarbons 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, this treatment is referred to as a lubricant removal treatment) ( For example, see Patent Document 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ず、十分に除去するためには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3参照。)。 However, even if heat treatment is performed in a vacuum or an inert gas atmosphere, the lubricant cannot be sufficiently removed, and heat treatment must be performed for a long time in order to sufficiently remove the lubricant. 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, see 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しつつ、高い磁気特性を得ることのできる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. Accordingly, the present invention provides a method for producing a rare earth sintered magnet capable of obtaining a high magnetic property while efficiently removing a lubricant from a molded body and suppressing deformation and cracking after sintering. With the goal.
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う場合、希土類焼結磁石に発生するクラックを防止するには、なるべく高い温度で加熱処理を行うのが好ましいことを見出した。しかしながら、高温で加熱処理を行うと、潤滑剤に含まれる有機物が成形体中に残留し、最終的な焼結体における残留炭素濃度が高くなってしまうことも判明した。
そこで、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)系焼結磁石の製造方法であって、所定組成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、磁場中成形により得られた成形体を、潤滑剤の沸点または分解温度よりも低い温度領域にて、少なくともその一部の過程において水素(H 2 )を含む雰囲気ガス下で加熱処理することにより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。
このようにすることで、加熱処理において潤滑剤が熱分解するのを防ぐことができ、潤滑剤を構成する有機物の残留を抑えることができる。
この場合、成形体へのクラックの発生を抑えるため、潤滑剤に、沸点または分解温度が300℃以上のものを用い、加熱処理をなるべく高い温度で行う。
また、潤滑剤の除去効果を高めるため、潤滑剤を除去する工程において、雰囲気ガスに含まれる水素濃度および加熱処理温度のうち、少なくとも加熱処理温度を変動させる。加熱処理温度を変動させる場合、加熱処理の少なくとも一部の過程で前記の温度領域内に温度を維持するようにすれば良い。
潤滑剤を除去する工程の後、前記の温度領域よりも高い温度で成形体を加熱処理することにより、潤滑剤をさらに除去する工程をさらに含むこともできる。
The present inventors have found that when the lubricant removal treatment is performed in an atmosphere containing hydrogen, it is preferable to perform the heat treatment at a temperature as high as possible in order to prevent cracks generated in the rare earth sintered magnet. However, it has also been found that when heat treatment is performed at a high temperature, organic substances contained in the lubricant remain in the molded body, and the residual carbon concentration in the final sintered body increases.
Accordingly, the present invention provides a method for producing a RTB (where R is one or more rare earth elements, T is Fe, Fe and Co) based sintered magnets, wherein The hydrogen treatment process in which hydrogen is exhausted by heating to a predetermined temperature after the occlusion is performed, and the alloy powder obtained in the hydrogen treatment process is further finely pulverized in a state where a lubricant containing an organic substance is added. A pulverizing step, a step of molding the pulverized powder obtained in the pulverizing step in a magnetic field, and a molded body obtained by molding in the magnetic field at least in a temperature range lower than the boiling point or decomposition temperature of the lubricant. Characterized in that it comprises a step of removing the lubricant by heat treatment under an atmosphere gas containing hydrogen (H 2 ) in a part of the process, and a step of sintering the molded body from which the lubricant has been removed. To do.
By doing in this way, it can prevent that a lubricant decomposes | disassembles in heat processing, and can suppress the residue of the organic substance which comprises a lubricant.
In this case, in order to suppress the occurrence of cracks in the molded body, a lubricant having a boiling point or a decomposition temperature of 300 ° C. or higher is used, and the heat treatment is performed at a temperature as high as possible.
In order to enhance the effect of removing the lubricant , at least the heat treatment temperature is varied among the hydrogen concentration contained in the atmospheric gas and the heat treatment temperature in the step of removing the lubricant. In the case where the heat treatment temperature is changed, the temperature may be maintained in the temperature range in at least a part of the heat treatment.
After the step of removing the lubricant, it may further include a step of further removing the lubricant by heat-treating the molded body at a temperature higher than the above temperature range.
以上説明したように、本発明によれば、効率よく潤滑剤を除去することができ、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、残留炭素量を抑えて磁気特性を向上させることができ、しか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可能となる。 As described above, according to the present invention, the lubricant can be efficiently removed, and even when the lubricant removal treatment is performed under an atmosphere gas containing hydrogen, the residual carbon amount is suppressed and the magnetic characteristics are improved. In addition, it is possible to suppress the occurrence of cracks in a sintered body such as a rare earth sintered magnet.
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 way has a large affinity with oxygen that deteriorates the magnetic properties of the Nd—Fe—B alloy, so that 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.
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、エチレンビスステアリン酸アミド、ヘキサデカン、オクタデカン、エイコサン、テトラコサン、オクタコサン、ドトリアコンタン、ヘキサトリアコンタン、テトラコンタン、テトラテトラコンタン、ペンタコンタン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. Examples of the lubricant include fatty acids or fatty acid derivatives such as stearic acid-based and oleic acid-based zinc stearate, calcium stearate, stearic acid amide, oleic acid amide, ethylenebisstearic acid amide, hexadecane, octadecane, eicosane, tetracosane. , Octacosane, dotriacontane, hexatriacontane, tetracontane, tetratetracontane, pentacontane and 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、加熱処理によって行う。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, the lubricant removal treatment for removing the lubricant is performed by heat treatment 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.
潤滑剤除去処理のための加熱処理の上限温度は、潤滑剤の沸点または分解温度よりも低くなるように設定するのが好ましい。加熱処理温度が、潤滑剤の沸点、分解温度より高くなりすぎると、潤滑剤を構成する有機物が除去されずに成形体中に残存してしまうからである。そこで、加熱処理の上限温度は、潤滑剤の沸点または分解温度のいずれか低い方の温度に対し、5℃低い温度とするのが好ましい。好ましい加熱処理の上限温度は、潤滑剤の沸点または分解温度のいずれか低い方の温度に対し10℃低い温度、さらに好ましい加熱処理の下限温度は、潤滑剤の沸点または分解温度のいずれか低い方の温度に対し20℃低い温度である。このようにすることで、有機物の成形体中への残存を抑え、残留炭素量を抑えることが可能となる。
加熱処理は、下限を少なくとも100℃とした温度範囲に保持することが好ましい。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る。好ましい加熱処理の下限温度は、150℃、さらに好ましい加熱処理の下限温度は200℃である。
また、加熱処理の温度を、上記の温度範囲内で、なるべく高めに設定するのが好ましい。加熱温度が高温であるほど、成形体に含まれる水素量を低い状態に保つことができ、焼結体にクラックが発生しにくくなるからである。したがって、加熱処理の下限温度は、潤滑剤の沸点または分解温度のいずれか低い方の温度に対し、50℃以内、より好ましくは30℃以内に設定するのが好ましい。さらに、同様の理由から、潤滑剤には、沸点または分解温度が高いものを用いるのが好ましく、前記した中では、ヘキサデカン(沸点または分解温度:287℃)、オクタデカン(同:317℃)、エイコサン(同:344℃)、テトラコサン(同:392℃)、オクタコサン(同:430℃)、ドトリアコンタン(同:468℃)、ヘキサトリアコンタン(同:497℃)、テトラコンタン(同:523℃)、テトラテトラコンタン(同:548℃)、ペンタコンタン(同:568℃)等が好ましい。
ここで、前記したような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、設定した温度範囲の下限から上限にかけて連続的に昇温する形態、設定した温度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。
The upper limit temperature of the heat treatment for the lubricant removing treatment is preferably set so as to be lower than the boiling point or decomposition temperature of the lubricant. This is because if the heat treatment temperature is too higher than the boiling point and decomposition temperature of the lubricant, the organic matter constituting the lubricant remains in the molded body without being removed. Therefore, the upper limit temperature of the heat treatment is preferably 5 ° C. lower than the lower of the boiling point or the decomposition temperature of the lubricant. The upper limit temperature of the preferred heat treatment is a temperature 10 ° C. lower than the lower temperature of the boiling point or decomposition temperature of the lubricant, and the more preferred lower limit temperature of the heat treatment is the lower of the boiling point or decomposition temperature of the lubricant. The temperature is 20 ° C. lower than By doing in this way, it becomes possible to suppress the residual organic substance in the molded body and to suppress the amount of residual carbon.
The heat treatment is preferably held in a temperature range where the lower limit is at least 100 ° C. This is because if it is less than 100 ° C., the effect of removing the lubricant cannot be obtained sufficiently. A preferable lower limit temperature of the heat treatment is 150 ° C., and a more preferable lower limit temperature of the heat treatment is 200 ° C.
Moreover, it is preferable to set the temperature of the heat treatment as high as possible within the above temperature range. This is because the higher the heating temperature, the lower the amount of hydrogen contained in the molded body, and the less likely the cracks are generated in the sintered body. Therefore, the lower limit temperature of the heat treatment is preferably set within 50 ° C., more preferably within 30 ° C., whichever is lower of the boiling point or the decomposition temperature of the lubricant. Further, for the same reason, it is preferable to use a lubricant having a high boiling point or decomposition temperature. Among them, hexadecane (boiling point or decomposition temperature: 287 ° C.), octadecane (same: 317 ° C.), eicosane are used. (Same as 344 ° C), tetracosane (same as 392 ° C), octacosane (same as 430 ° C), dotriacontane (same as 468 ° C), hexatriacontane (same as 497 ° C), tetracontane (same as 523 ° C) ), Tetratetracontane (same: 548 ° C.), pentacontane (same: 568 ° C.) and the like are preferable.
Here, holding in the temperature range as described above 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. Just do it. Therefore, various forms are included, such as a form in which the temperature is continuously raised from the lower limit to the upper limit of the set temperature range, and a form in which the temperature is raised stepwise in the set temperature range.
潤滑剤除去処理の間、水素濃度は、95%以上を維持するのが好ましいが、水素濃度を変動させることも有効である。例えば、水素濃度を1%未満にした後、95%以上にしたり、その逆に、水素濃度を95%以上とした後、1%未満としたりすることができる。さらに、このような水素濃度の変動操作を複数回繰り返しても良い。なお、水素濃度を1%未満とする場合には、前記したような不活性ガスに置換したり、真空引きすればよい。このような操作を行うことで、水素とともに潤滑剤を除去することができ、その除去効率を高めることができる。 During the lubricant removal process, the hydrogen concentration is preferably maintained at 95% or more, but it is also effective to vary the hydrogen concentration. For example, the hydrogen concentration can be made less than 1% and then 95% or more, and conversely, the hydrogen concentration can be made 95% or more and then less than 1%. Further, such a hydrogen concentration fluctuation operation may be repeated a plurality of times. When the hydrogen concentration is less than 1%, it may be replaced with an inert gas as described above or evacuated. By performing such an operation, the lubricant can be removed together with hydrogen, and the removal efficiency can be increased.
また、潤滑剤除去処理の間、温度を、上記の温度範囲内で変動させる。さらに、このような温度の変動操作を複数回繰り返しても良い。このような操作を行うことでも、水素とともに潤滑剤を除去することができ、その除去効率を高めることができる。 Also, during the lubricant removal process, the temperature is varied within the above temperature range . Further, such temperature fluctuation operation may be repeated a plurality of times. By performing such an operation, the lubricant can be removed together with hydrogen, and the removal efficiency can be increased.
潤滑剤除去処理のための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1〜7時間とすることが好ましい。 If the holding time of the heat treatment for the lubricant removing process 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 7 hours.
さらにこの後、図1に示すように、潤滑剤除去処理の効果をさらに高めるため、第二の加熱処理を行うのが好ましい。この第二の加熱処理では、雰囲気ガスを、主に不活性ガスとするか、もしくは真空引きした状態とし、600〜650℃の温度範囲に保持することが好ましい。これにより、成形体中の潤滑剤の更なる除去およびR成分(希土類成分)の水素化物を有効に除去することができる。ここで、第二の加熱処理の好ましい温度は、610〜640℃、さらに好ましい加熱処理の温度は620〜630℃である。 Thereafter, as shown in FIG. 1, it is preferable to perform the second heat treatment in order to further enhance the effect of the lubricant removal treatment. In the second heat treatment, it is preferable that the atmospheric gas is mainly an inert gas or is evacuated and maintained in a temperature range of 600 to 650 ° C. Thereby, further removal of the lubricant in the molded body and hydride of the R component (rare earth component) can be effectively removed. Here, the preferable temperature of the second heat treatment is 610 to 640 ° C, and the more preferable temperature of the heat treatment is 620 to 630 ° C.
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2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3に示すように連続的に昇温してもよいし、図4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 of the sintering temperature rising process for removing 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. 2 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. 3, or as shown in FIG. The temperature may be raised stepwise.
本発明はR−T−B(Rは希土類元素の1種又は2種以上、TはFe又はFe及びCo)で示される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 applied to an RTB-based sintered magnet represented by RTB (R is one or more rare earth elements, and T is Fe or Fe and Co) .
The RTB-based sintered magnet contains 25 to 37 wt% of rare earth element (R). Here, R has a concept including Y. Therefore, one or two of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Selected from more than species. If the amount of R is less than 25 wt%, the R 2 T 14 B phase, which is the main phase of the 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.
以上、R−T−B系焼結磁石について説明したが、本発明は他の希土類焼結磁石、さらには磁石以外の他の焼結体に適用することができることは、当業者であれば、以上の説明あるいは以下の実施例の説明から明らかである。 The R-T-B system sintered magnet has been described above. However, those skilled in the art can apply the present invention to other rare earth sintered magnets, and other sintered bodies other than magnets. It is clear from the above description or the description of the following examples.
ストリップキャスト法により、次に示す2種類の原料合金を作製した。
合金(1)28.0wt%Nd−0.2wt%Al−1.0wt%B−0.2wt%Zr−bal.Fe
合金(2)32.0wt%Nd−10.0wt%Co−1.0wt%Cu−0.2wt%Al−bal.Fe
The following two types of raw material alloys were produced by strip casting.
Alloy (1) 28.0 wt% Nd-0.2 wt% Al-1.0 wt% B-0.2 wt% Zr-bal. Fe
Alloy (2) 32.0 wt% Nd-10.0 wt% Co-1.0 wt% Cu-0.2 wt% Al-bal. Fe
ついで、得られた合金(1)、(2)のそれぞれに室温で水素を吸蔵させた後にAr雰囲気中で600℃×1時間の脱水素処理を行い、粗粉砕粉末を得た。 Next, after each of the obtained alloys (1) and (2) was occluded with hydrogen at room temperature, a dehydrogenation treatment was performed in an Ar atmosphere at 600 ° C. for 1 hour to obtain a coarsely pulverized powder.
以上の粗粉砕粉末を、高圧窒素ガスを用いた気流式のジェットミルにより微粉砕を行って平均粒径3〜6μm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、潤滑剤として、オレイン酸アミド、エチレンビスステアリン酸アミド、ヘキサデカン、エイコサン、テトラコサン、オクタコサン、ドトリアコンタン、ヘキサトリアコンタン、テトラコンタン、テトラテトラコンタン、ペンタコンタンを、0.15wt%添加した。 The above coarsely pulverized powder was finely pulverized by an airflow type jet mill using high-pressure nitrogen gas to obtain finely pulverized powder having an average particle size of 3 to 6 μm. When finely pulverizing with a jet mill, oleic acid amide, ethylenebisstearic acid amide, hexadecane, eicosane, tetracosane, octacosane, dotriacontane, hexatriacontane, tetracontane, tetratetracontane, pentacon Tan was added at 0.15 wt%.
得られた合金(1)、(2)の微粉末を、所望の最終組成:28.4wt%Nd−1.0wt%Co−0.1wt%Cu−0.2wt%Al−1.0wt%B−0.2wt%Zr−bal.Feとなるように配合、混合した。 The fine powders of the obtained alloys (1) and (2) were mixed with the desired final composition: 28.4 wt% Nd-1.0 wt% Co-0.1 wt% Cu-0.2 wt% Al-1.0 wt% B -0.2 wt% Zr-bal. It mix | blended and mixed so that it might become Fe.
得られた微粉砕粉末を印加磁場:1200kA/m、成形圧力:120MPa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 120 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、表1に示す所定温度に到達した後、6時間、水素を95%以上含む雰囲気ガス中に保持するというものである。なお、所定温度に到達するまでは、真空とした。
続いて、真空中で600〜650℃で3時間加熱処理した。
また、潤滑剤としてオレイン酸アミドを用いたものについては、比較のため、この真空中、600〜650℃で3時間の加熱処理(第2の加熱処理)を行わないものも用意した(実施例1−3、1−4)。
The condition for the lubricant removal treatment is to hold in an atmospheric gas containing 95% or more of hydrogen for 6 hours after reaching the predetermined temperature shown in Table 1. A vacuum was applied until a predetermined temperature was reached.
Then, it heat-processed at 600-650 degreeC in the vacuum for 3 hours.
In addition, for those using oleic acid amide as a lubricant, for comparison purposes, a material that was not subjected to heat treatment (second heat treatment) at 600 to 650 ° C. for 3 hours in this vacuum was also prepared (Examples). 1-3, 1-4).
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1030〜1090℃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。
また、比較のため、潤滑剤除去処理を行わず、成形体を焼結および時効処理することで得た焼結体を用意した。
Further, the molded body after removing the lubricant was subjected to sintering and aging treatment to obtain a sintered body. Sintering was carried out in vacuum at 1030 to 1090 ° C. for 4 hours, and the aging treatment was a two-stage aging treatment in which Ar was held at 900 ° C. for 1 hour and then held at 530 ° C. for 1 hour.
For comparison, a sintered body obtained by sintering and aging the molded body without preparing the lubricant was prepared.
得られた焼結体について、残留炭素量と、残留磁束密度Brを測定した。また、得られた焼結体のクラック発生状況を、目視により確認した。
その結果を表1に示す。
About the obtained sintered compact, the amount of residual carbon and the residual magnetic flux density Br were measured. Moreover, the crack generation state of the obtained sintered compact was confirmed visually.
The results are shown in Table 1.
表1に示すように、いずれの潤滑剤においても、潤滑剤除去処理における加熱処理温度が低いほど、残留炭素量の低減、残留磁束密度Brの向上が図れることがわかる。特に、用いた潤滑剤の沸点または分解温度よりも低い温度で加熱処理を行った場合、特に残留炭素量が顕著に低減している。
一方、クラック発生率は、加熱処理温度が低すぎると、クラック発生率が増加する傾向にある。
したがって、潤滑剤除去のための加熱処理は、用いる潤滑剤の沸点または分解温度よりも低く、かつなるべく高い温度で行うのが好ましいと言える。
As shown in Table 1, it can be seen that in any lubricant, the lower the heat treatment temperature in the lubricant removal treatment, the lower the residual carbon amount and the higher the residual magnetic flux density Br. In particular, when the heat treatment is performed at a temperature lower than the boiling point or decomposition temperature of the lubricant used, the amount of residual carbon is particularly reduced.
On the other hand, the crack generation rate tends to increase if the heat treatment temperature is too low.
Accordingly, it can be said that the heat treatment for removing the lubricant is preferably performed at a temperature lower than the boiling point or decomposition temperature of the lubricant to be used and as high as possible.
また、潤滑剤の種類ごとに比較すると、沸点または分解温度が高い潤滑剤ほど、上記の加熱処理の条件、すなわち潤滑剤の沸点または分解温度よりも低く、かつなるべく高い温度を高くできるので、クラック発生率も低く、特に沸点または分解温度が300℃を超える潤滑剤であるエイコサンを用いた場合の実施例4−1(加熱温度300℃)、テトラコンサンを用いた場合の実施例5−1、5−2(加熱温度375℃、300℃)、オクタコサンを用いた場合の実施例6−1(加熱温度400℃)、ドトリアコンタンを用いた場合の実施例7−1(加熱温度450℃)、ヘキサトリアコンタンを用いた場合の実施例8−1(加熱温度450℃)においては、残留炭素量も550ppm以下、残留磁束密度Brも15kG以上となる。同様に、沸点または分解温度が500℃を超えるテトラコンタン、テトラテトラコンタン、ペンタコンタンの場合も、低いクラック発生率、高い残留磁束密度Brを得ることができるが、残留炭素量が若干増加する傾向がわかる。 In addition, when compared with each type of lubricant, the higher the boiling point or decomposition temperature, the lower the temperature of the above-mentioned heat treatment conditions, that is, the boiling point or decomposition temperature of the lubricant, and the higher the temperature possible. Example 4-1 (heating temperature 300 ° C.) in the case of using eicosane, which is a lubricant having a low occurrence rate, particularly a boiling point or decomposition temperature exceeding 300 ° C., and Example 5-1 in the case of using tetraconsane. 5-2 (heating temperature 375 ° C., 300 ° C.), Example 6-1 using octacosan (heating temperature 400 ° C.), Example 7-1 using dotriacontane (heating temperature 450 ° C.) In Example 8-1 (heating temperature 450 ° C.) when hexatriacontane is used, the residual carbon amount is 550 ppm or less and the residual magnetic flux density Br is 15 kG or more. Similarly, in the case of tetracontane, tetratetracontane or pentacontane whose boiling point or decomposition temperature exceeds 500 ° C., a low crack generation rate and a high residual magnetic flux density Br can be obtained, but the residual carbon amount tends to increase slightly. I understand.
さらに、オレイン酸アミドを用いた場合の実施例1−1、1−3、1−4、比較例1−1を比較すると、潤滑剤処理のための加熱処理を行うことで残留炭素量の低減、残留磁束密度Brの向上を図ることができ、さらに潤滑剤処理のための加熱処理と第2の加熱処理の双方を行うことで残留炭素量が一層低減されることがわかる。 Furthermore, when Examples 1-1, 1-3, 1-4, and Comparative Example 1-1 in the case of using oleic acid amide are compared, the amount of residual carbon is reduced by performing heat treatment for lubricant treatment. It can be seen that the residual magnetic flux density Br can be improved and the residual carbon amount is further reduced by performing both the heat treatment for the lubricant treatment and the second heat treatment.
続いて、潤滑剤除去のための加熱処理において、水素濃度を変化させることの効果を検討した。
このため、上記と同様の工程で成形体を形成した。このとき、微粉砕工程で用いる潤滑剤は、オレイン酸アミド、オクタデカンとし、それぞれ0.15wt%を混合した。
そして、この後の潤滑剤除去のための加熱処理においては、表2に示す所定温度に到達した後、水素ガスの濃度を表2のような条件とし、トータルで6時間の加熱を行った。このとき、比較のため、水素ガスを用いず、真空中での加熱処理も行った。
Subsequently, the effect of changing the hydrogen concentration in the heat treatment for removing the lubricant was examined.
For this reason, the molded object was formed in the process similar to the above. At this time, the lubricant used in the pulverizing step was oleic acid amide and octadecane, and 0.15 wt% was mixed respectively.
In the subsequent heat treatment for removing the lubricant, after reaching the predetermined temperature shown in Table 2, the concentration of hydrogen gas was set as shown in Table 2 and heating was performed for a total of 6 hours. At this time, for comparison, heat treatment was also performed in vacuum without using hydrogen gas.
その結果、表2に示すように、潤滑剤としてオレイン酸アミドを用いた場合、加熱処理中の雰囲気に水素ガスを存在させることで、残留炭素量の低減、残留磁束密度Brの向上が図れることがわかる(実施例20−1、20−2、比較例20−1、20−2)。また、実施例20−1と実施例1−1との比較から、水素濃度が高いほど、特に残留炭素量が大幅に低減することが確認できる。
さらに、実施例20−3〜実施例20−10のように、水素濃度を変動させることで、残留炭素量の低減、残留磁束密度Brの向上が図れる。このとき、実施例20−3と実施例20−5、実施例20−4と実施例20−6との比較から、水素ガス濃度の低い状態から高い状態に移行させるよりも、水素ガス濃度の高い状態から低い状態に移行させる方が、残留炭素量の低減、残留磁束密度Brの向上効果は顕著なものとなる。これは、水素ガス濃度が高い状態から低い状態に移行するときに成形体から抜け出る水素ガスとともに、潤滑剤成分が抜け出ていくためだと思われる。
この傾向は、水素ガス濃度の変動を複数回行った実施例20−7〜実施例20−10においても同様であり、複数回の変動により、その効果はさらに顕著となっている。
また、潤滑剤としてオクタデカンを用いた実施例21−1〜21−10においても、オレイン酸アミドを用いた場合と同様の傾向が確認でき、さらに、オレイン酸アミドよりもオクタデカンを用いた場合の方が、残留炭素量、残留磁束密度Br、クラック発生率とも、より優れた特性を得ることができるのがわかる。特に残留炭素量は、オレイン酸アミドを用いた場合に比較して大幅に低減されており、潤滑剤除去のための加熱処理温度をなるべく高めるのが好ましいことが確認できる。
As a result, as shown in Table 2, when oleic acid amide is used as the lubricant, the residual carbon amount can be reduced and the residual magnetic flux density Br can be improved by allowing hydrogen gas to exist in the atmosphere during the heat treatment. (Examples 20-1, 20-2, Comparative examples 20-1, 20-2). Moreover, from the comparison between Example 20-1 and Example 1-1, it can be confirmed that, as the hydrogen concentration is higher, the residual carbon amount is significantly reduced.
Further, as in Example 20-3 to Example 20-10, the residual carbon amount can be reduced and the residual magnetic flux density Br can be improved by changing the hydrogen concentration. At this time, from the comparison between Example 20-3 and Example 20-5, Example 20-4 and Example 20-6, the hydrogen gas concentration was changed from the low hydrogen gas concentration state to the high state state. The effect of reducing the residual carbon amount and improving the residual magnetic flux density Br becomes more remarkable when the state is shifted from the high state to the low state. This seems to be because the lubricant component escapes together with the hydrogen gas that escapes from the compact when the hydrogen gas concentration shifts from a high state to a low state.
This tendency is the same also in Example 20-7 to Example 20-10 in which the change of the hydrogen gas concentration was performed a plurality of times, and the effect becomes more remarkable due to the plurality of variations.
Moreover, also in Examples 21-1 to 21-10 using octadecane as a lubricant, the same tendency as in the case of using oleic amide can be confirmed, and furthermore, the case of using octadecane rather than oleic amide. However, it can be seen that more excellent characteristics can be obtained with respect to the residual carbon amount, the residual magnetic flux density Br, and the crack generation rate. In particular, the amount of residual carbon is greatly reduced as compared with the case of using oleic amide, and it can be confirmed that it is preferable to increase the heat treatment temperature for removing the lubricant as much as possible.
次に、潤滑剤除去のための加熱処理において、温度を変化させることの効果を検討した。
このため、上記と同様の工程で成形体を形成した。このとき、微粉砕工程で用いる潤滑剤は、オレイン酸アミド、オクタデカンとし、それぞれ0.15wt%を混合した。
そして、この後の潤滑剤除去のための加熱処理においては、表3に示す温度条件となるようにした。なお、このとき、水素ガスの濃度は表3の通りとし、トータルで6時間の加熱を行った。
Next, the effect of changing the temperature in the heat treatment for removing the lubricant was examined.
For this reason, the molded object was formed in the process similar to the above. At this time, the lubricant used in the pulverizing step was oleic acid amide and octadecane, and 0.15 wt% was mixed respectively.
In the subsequent heat treatment for removing the lubricant, the temperature conditions shown in Table 3 were satisfied. At this time, the concentration of hydrogen gas was as shown in Table 3, and heating was performed for a total of 6 hours.
その結果、表3に示すように、加熱処理中に温度を変動させることでも、水素ガス濃度を変動させた場合と同様、クラック発生率、残留炭素量、残留磁束密度Brが変化することがわかる。
これは、加熱処理温度を変動させることで成形体から抜け出る水素ガスとともに、潤滑剤成分が抜け出ていくためだと思われる。
そして、加熱処理の初期の段階で、上記したような、使用する潤滑剤の沸点または分解温度以下に温度を維持した後、温度を変動させた場合(実施例30−1〜実施例30−3、実施例30−7〜10)、特に残留炭素量の低減効果が確認できる。また、実施例30−3〜実施例30−10のように、加熱処理の間に、潤滑剤の沸点または分解温度以上としても、加熱処理の少なくとも一部の過程で潤滑剤の沸点または分解温度以下に温度を維持することで、残留炭素量の低減効果は確保できる。しかしながら、その場合も、加熱処理中の平均温度がなるべく低くなるようにするのが好ましく、それによって残留炭素量の低減効果を確実なものとできることがわかる。
また、潤滑剤としてオクタデカンを用いた実施例31−1〜31−13においても、オレイン酸アミドを用いた場合と同様の傾向が確認でき、さらに、オレイン酸アミドよりもオクタデカンを用いた場合の方が、残留炭素量、残留磁束密度Br、クラック発生率とも、より優れた特性を得ることができるのがわかる。特に残留炭素量は、オレイン酸アミドを用いた場合に比較して大幅に低減されており、潤滑剤除去のための加熱処理温度をなるべく高めるのが好ましいことが確認できる。
As a result, as shown in Table 3, it can be seen that even when the temperature is changed during the heat treatment, the crack generation rate, the residual carbon amount, and the residual magnetic flux density Br change as in the case where the hydrogen gas concentration is changed. .
This seems to be because the lubricant component escapes together with the hydrogen gas that escapes from the molded body by changing the heat treatment temperature.
Then, in the initial stage of the heat treatment, after maintaining the temperature below the boiling point or decomposition temperature of the lubricant to be used, the temperature is changed (Example 30-1 to Example 30-3). Examples 30-7 to 10), in particular, the effect of reducing the amount of residual carbon can be confirmed. In addition, as in Example 30-3 to Example 30-10, the boiling point or decomposition temperature of the lubricant during at least a part of the heat treatment even when the temperature is equal to or higher than the boiling point or decomposition temperature of the lubricant during the heat treatment. By maintaining the temperature below, the effect of reducing the amount of residual carbon can be secured. However, in that case as well, it is preferable to make the average temperature during the heat treatment as low as possible, and it can be seen that the effect of reducing the amount of residual carbon can be ensured.
Moreover, also in Examples 31-1 to 31-13 using octadecane as a lubricant, the same tendency as in the case of using oleic amide can be confirmed, and further, the case of using octadecane rather than oleic amide. However, it can be seen that more excellent characteristics can be obtained with respect to the residual carbon amount, the residual magnetic flux density Br, and the crack generation rate. In particular, the amount of residual carbon is greatly reduced as compared with the case of using oleic amide, and it can be confirmed that it is preferable to increase the heat treatment temperature for removing the lubricant as much as possible.
Claims (2)
所定組成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、
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し、沸点または分解温度が300℃以上の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、
磁場中成形により得られた成形体を、前記潤滑剤の沸点または分解温度よりも低い温度領域にて、少なくともその一部の過程において水素(H 2 )を含む雰囲気ガス下で加熱処理することにより前記潤滑剤を除去する工程と、
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、
前記潤滑剤を除去する工程において、前記雰囲気ガスに含まれる水素濃度および加熱処理温度のうち、少なくとも加熱処理温度を変動させ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), a method for producing a sintered magnet,
A hydrogen treatment process in which hydrogen is stored in a raw material alloy having a predetermined composition and then heated to a predetermined temperature and discharged;
A fine pulverization step in which the alloy powder obtained in the hydrogen treatment step is further finely pulverized in a state where a lubricant having a boiling point or a decomposition temperature of 300 ° C. or more is added with an organic substance as a component;
Forming the pulverized powder obtained in the fine pulverization step in a magnetic field;
By heat-treating a molded body obtained by molding in a magnetic field in an atmosphere gas containing hydrogen (H 2 ) in at least a part of the process in a temperature range lower than the boiling point or decomposition temperature of the lubricant. Removing the lubricant;
Sintering the molded body from which the lubricant has been removed, and
The method for producing a rare earth sintered magnet , wherein in the step of removing the lubricant , at least the heat treatment temperature is varied among the hydrogen concentration contained in the atmospheric gas and the heat treatment temperature.
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