JP3904061B2 - Manufacturing method of rare earth sintered magnet - Google Patents
Manufacturing method of rare earth sintered magnet Download PDFInfo
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- JP3904061B2 JP3904061B2 JP2001399174A JP2001399174A JP3904061B2 JP 3904061 B2 JP3904061 B2 JP 3904061B2 JP 2001399174 A JP2001399174 A JP 2001399174A JP 2001399174 A JP2001399174 A JP 2001399174A JP 3904061 B2 JP3904061 B2 JP 3904061B2
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Description
【0001】
【発明の属する技術分野】
本発明は、水素雰囲気に長時間晒されるモーター等に用いられるSm2Co17系磁石の製造方法に関する。
【0002】
【従来の技術】
希土類元素と遷移金属の金属間化合物においては、水素が結晶格子間に侵入する、即ち、合金中に水素を吸蔵、放出する特性を持っており、その特性はいろいろな分野で利用されている。その例としては、LaNi5に代表される水素吸蔵合金による水素電池が挙げられ、また、希土類焼結磁石においても、R2Fe14B系合金の粉砕方法として、更にR2Fe14B系ボンド磁石の製造方法(HDDR 特開平3−129702号公報)として利用されている。
【0003】
しかしながら、合金中又は磁石中に水素を吸蔵、放出させた場合、水素脆性を引き起こしてしまう。そのため、水素雰囲気中において、希土類焼結磁石を用いたモーター等を使用した場合、希土類焼結磁石が水素脆化を引き起こし、素材にワレ、クラックもしくは粉化がおこるという問題が生じている。
【0004】
現在、希土類焼結磁石には、R2Fe14B系、SmCo5系、Sm2Co17系等の種類がある。一般に、水素に対しては、2−17型結晶構造よりも1−5型結晶構造、1−5型結晶構造よりも2−7型結晶構造の方がプラトー圧は低い、即ち、レアアースリッチ(以下、Rリッチと称す)な合金のほうが水素吸蔵されやすい傾向にあり、水素脆化しやすい。
【0005】
R2Fe14B系磁石は、磁石中にRリッチ相を有するため、0.1MPa以下の圧力の水素雰囲気下で、容易に水素脆性を引き起こし、磁石素材にワレ、クラックもしくは粉化が生じる。通常、R2Fe14B系磁石は、耐食性向上のためメッキ、樹脂コーティングなどの表面処理がなされているが、水素脆化を防止する手段とはなっていない。この問題を解決する方法として、R2Fe14B系磁石の表面処理膜に水素吸蔵合金を含有させる方法を提案した(特開2000−285415号公報)。この方法により作製されたR2Fe14B系磁石は、0.1MPa以下の圧力の水素雰囲気下においては、水素脆性を引き起こさないものの、それを超える圧力の水素雰囲気下においては、水素脆性を引き起こし、磁石素材にワレ、クラックもしくは粉化が生じる場合がある。
【0006】
SmCo5系磁石も、R2Fe14B系磁石と同様に、Rリッチ相を有すると共に、主相であるSmCo5相のプラトー圧が約0.3MPaである。このことから、0.3MPaを超える圧力の水素雰囲気中では、水素脆性を引き起こし、磁石素材にワレ、クラックもしくは粉化が生じる。
【0007】
Sm2Co17系磁石は、主相が2−17相であり、R2Fe14B系、SmCo5系に比べRリッチではないことと、Rリッチ相を含有しないため、水素脆性を引き起こしにくい。しかしながら、1MPaを超える圧力の水素雰囲気中では、他の希土類焼結磁石と同様に、水素脆性を引き起こし、磁石素材にワレ、クラックもしくは粉化が生じることがわかっている。
【0008】
耐水素脆性を向上させるためには、Sm2Co17系磁石を焼結磁石とし、切断及び/又は研磨して表面を加工後、酸素分圧10-6〜152torrの雰囲気において熱処理すればよいことが分かっている(特開2002−118009号公報)。そうすることにより、磁石表面にCo及び/又はCo、Fe中にSm2O3が微細に分散している層を存在させていれば、3MPaを超える高圧水素雰囲気下においても水素脆性は起こさない。しかし、Sm2Co17系磁石及びCo及び/又はCo、Fe中にSm2O3が微細に分散している層は、硬く、欠け易いため、製品組み立て等、取扱いの際、チッピング等を引き起こす場合がある。チッピング等を引き起こした希土類焼結磁石は、磁気特性には影響はないものの、耐水素脆性は大きく低下し、表面層のない場合と同等になってしまう。従って、1MPaを超える圧力の水素雰囲気中では、水素脆性を引き起こし、磁石素材にワレ、クラックもしくは粉化が起こるため、そのような雰囲気中では、使用することができない。
【0009】
【発明が解決しようとする課題】
本発明は、このような問題を解決したSm2Co17系焼結磁石の製造方法を提供するものである。即ち、従来の希土類焼結磁石の様に、水素雰囲気下で、水素脆性を引き起こし、磁石素材にワレ、クラックもしくは粉化が生じるという問題を解決したSm2Co17系焼結磁石の製造方法を提供することを目的とする。
【0010】
【課題を解決するための手段及び発明の実施の形態】
本発明者は、上記目的を達成するため鋭意検討を行った結果、焼結、時効後の焼結磁石を表面加工後、金属メッキを施し、更に最適な熱処理をすることで、磁石体表面に耐水素性に優れた層を形成するという、高圧の水素雰囲気中でも水素脆性を引き起こさない希土類焼結磁石の製造方法を見い出した。このことから、水素雰囲気に長時間晒されるモーター等に好適に用いられるSm2Co17系焼結磁石が得られることを知見し、本発明をなすに至った。
【0011】
即ち、本発明は、前記問題を解決する方法として下記(1)〜(3)の希土類永久磁石の製造方法を提供するものである。
(1)R(但し、RはSm又はSmを50重量%以上含む2種以上の希土類元素)20〜30重量%、Fe10〜45重量%、Cu1〜10重量%、Zr0.5〜5重量%、残部Co及び不可避的不純物からなる合金を溶解、鋳造し、粉砕、微粉砕、磁場中成形、焼結、時効を順次行って焼結磁石とし、更に該焼結磁石を切断及び/又は研磨して表面を加工後、Cu、Ni及びそれらの合金の少なくとも1種からなる金属メッキを施し、その後、酸素分圧が10 -4 Pa〜50kPaである、アルゴン、窒素、空気又は低圧真空雰囲気下において、400〜850℃で10分〜50時間熱処理することを特徴とする耐水素脆性を有する希土類焼結磁石の製造方法、
(2)金属メッキが、多層メッキであることを特徴とする(1)記載の希土類焼結磁石の製造方法、
(3)希土類焼結磁石が水素雰囲気に晒されるモーター用である(1)又は(2)記載の希土類焼結磁石の製造方法。
【0012】
以下に、本発明の詳細を説明する。
本発明におけるSm2Co17系焼結磁石合金組成の主成分は、Sm又はSmを50重量%以上含む2種以上の希土類元素20〜30重量%、Fe10〜45重量%、Cu1〜10重量%、Zr0.5〜5重量%、残部Co及び不可避的不純物からなる。前記Sm以外の希土類金属としては、特に限定されるものではなく、Nd、Ce、Pr、Gdなどを挙げることができる。希土類元素中のSmの含有量が50重量%未満の場合や、希土類元素量が20重量%未満、30重量%を超える場合は、有効な磁気特性をもつことはできない。
【0013】
本発明のSm2Co17系磁石合金は、上記組成範囲の原料をアルゴン等の非酸化性雰囲気中において、高周波溶解により溶解、鋳造する。
【0014】
次に、前記Sm2Co17系磁石合金を粗粉砕し、次いで平均粒径1〜10μm、好ましくは約5μmに微粉砕する。この粗粉砕は、例えば、不活性ガス雰囲気中で、ジョークラッシャー、ブラウンミル、ピンミル及び水素吸蔵等により行うことができる。また、前記微粉砕は、アルコール、ヘキサン等を溶媒に用いた湿式ボールミル、不活性ガス雰囲気中による乾式ボールミル、不活性ガス気流によるジェットミル等により行うことができる。
【0015】
次に、前記微粉砕粉を、好ましくは10kOe以上の磁場を印可することが可能な磁場中プレス機等により、好ましくは500kg/cm2以上2000kg/cm2未満の圧力により圧縮成形する。続いて、得られた圧縮成形体を、熱処理炉により、アルゴンなどの非酸化性雰囲気ガス中で、1100〜1300℃、好ましくは1150〜1250℃において、0.5〜5時間、焼結、溶体化し、終了後、急冷を行う。
【0016】
続いて、アルゴン雰囲気中、700〜900℃、好ましくは750〜850℃の温度で、5〜40時間保持し、−1.0℃/分の降温速度で400℃以下まで徐冷する時効処理を施し、切断及び/又は研磨して表面の加工仕上げを行う。この際、特に限定されるものではないが、希土類焼結磁石体に面取りがなされていることが望ましい。
【0017】
この表面加工仕上げ後、前記希土類焼結磁石体に金属メッキを施す。前記金属メッキの金属は、Cu、Ni、Co、Sn及びそれらの合金の少なくとも1種からなり、メッキ厚さは、1〜100μm、特に1〜50μmが好ましい。また多層メッキを施してもよい。この金属メッキを施す前処理として、特に限定されるものではないが、前記希土類焼結磁石体をアルカリ脱脂、酸洗浄、水洗することが望ましい。メッキの成膜方法としては、特に限定されるものではないが、電解メッキ法が好ましい。また、前記希土類焼結磁石体をメッキ液に浸漬する方法は、バレル法又は引っ掛け治具法のいずれでもよく、希土類焼結磁石体の寸法及び形状によって適当に選択される。
【0018】
なお、電解メッキ液としては、公知の組成のメッキ液を使用し、そのメッキ液に応じた公知の条件でメッキすることができるが、特にpH2〜12のメッキ液が好適である。
【0019】
上記方法により金属メッキを施した後、酸素分圧が10-4Pa〜50kPa、好ましくは10-4Pa〜30kPaである、アルゴン、窒素、空気又は低圧真空雰囲気下において、10分〜50時間、400〜850℃、好ましくは400〜600℃で熱処理する。前記熱処理時間は、10分未満では、耐水素性に優れた層の形成が十分でない、或いは、ばらつきが多くなるため適当ではなく、また、50時間を超える熱処理は、効率的ではないことと、耐水素性に優れた層が厚くなることにより磁気特性を劣化させる原因となることがあるため適当ではない。前記熱処理温度は、80℃未満では、耐水素性に優れた希土類焼結磁石を得るために長時間の処理が必要となり、効率的ではなく、また、850℃を超える温度では、耐水素性に優れた層の形成は成されるものの、希土類焼結磁石と金属メッキが反応する、及び磁石が相変態を起こし磁気特性の劣化が生じる。ちなみに、上記耐水素性に優れた層は、メッキ金属の酸化物層であり、0.1〜100μmの厚さがあることが好ましく、更に好ましくは0.1〜20μmである。
【0020】
次いで、希土類焼結磁石体表面に樹脂塗装(吹き付け塗装、電着塗装、粉体塗装或いはディッピング塗装等のいわゆる樹脂塗装)を施すこともできる。樹脂塗装による皮膜は、耐水素性を有していないが、希土類焼結磁石が用いられたモーターなどが使用される雰囲気により耐酸性を有する必要があることや、モーターなどに希土類焼結磁石が組み込まれる際、表面層に傷をつけないため成されることとなる。なお、樹脂塗装の樹脂は、特に限定されるものではないが、アクリル系、エポキシ系、フェノール系、シリコーン系、ポリエステル系及びポリウレタン系樹脂等が望ましい。
【0021】
【実施例】
次に本発明の実施例を挙げて具体的に説明するが、本発明はこれらに限定されるものではない。
【0022】
[実施例1]
Sm2Co17系磁石合金は、Sm:25.0重量%、Fe:17.0重量%、Cu:4.5重量%、Zr:2.5重量%、残部Coの組成になるように配合し、アルゴンガス雰囲気中で、アルミナルツボを使用して高周波溶解炉で溶解し、鋳型鋳造することにより作製した。
【0023】
次に、前記Sm2Co17系磁石合金を、ジョークラッシャー、ブラウンミルで約500μm以下に粗粉砕後、窒素気流によるジェットミルにより平均粒径約5μmに微粉砕を行った。得られた微粉砕粉を、磁場中プレス機により15kOeの磁場中にて1.5t/cm2の圧力で成形した。得られた成形体は熱処理炉を用い、アルゴン雰囲気中で、1190℃、2時間焼結した後、アルゴン雰囲気中、1175℃、1時間溶体化処理を行った。溶体化処理終了後、急冷し、得られたそれぞれの焼結体を、アルゴン雰囲気中、800℃、10時間保持し、400℃まで−1.0℃/分の降温速度で徐冷を行い、焼結磁石を作製した。得られた焼結磁石から、5×5×5mmに磁石を切り出した。
【0024】
次に、前記焼結磁石に、ピロリン酸Cu60g/L、ピロリン酸K240g/L、シュウ酸K30g/Lで調整したメッキ浴を用い、浴温度40℃、電流密度1.5A/dm2の条件で電解Cuメッキを20μm施し、その後、550℃、12時間、空気中(酸素分圧20kPa)の熱処理を施し、室温まで徐冷し、更にエポキシ系樹脂を吹き付けにより塗装し、水素ガス試験用試料を得、Vibrating Sample Magnetometer(以下、VSMと称す)により磁気特性の測定を行った。
【0025】
前記水素ガス試験用試料を耐圧容器に入れ、水素、10MPa、25℃の条件で封入し、1日放置するという水素ガス試験を施し、その後取り出した。取り出した磁石は、外観を目視で観察し、更にVSMにより磁気特性の測定を行った。
【0026】
[実施例2]
実施例1と同様な組成、方法で焼結磁石を作製した。次に、得られた焼結磁石から実施例1と同様に5×5×5mmに磁石を切り出した。前記磁石に対し、実施例1と同様な条件で電解Cuメッキを20μm施し、その後、550℃、12時間、真空中(酸素分圧10-2Pa)の熱処理を施し、室温まで徐冷し、更にエポキシ系樹脂を吹き付けにより塗装し、水素ガス試験用試料を得、VSMにより磁気特性の測定を行った。前記水素ガス試験用試料に対し、実施例1と同様な条件で水素ガス試験を施し、その後取り出した。取り出した磁石は、外観を目視で観察し、更にVSMにより磁気特性の測定を行った。
【0027】
[比較例1]
実施例1と同様な組成、方法で焼結磁石を作製した。次に、得られた焼結磁石から実施例1と同様に5×5×5mmに磁石を切り出し、更にエポキシ系樹脂を吹き付けにより塗装し、水素ガス試験用試料を得、VSMにより磁気特性の測定を行った。前記水素ガス試験用試料に対し、実施例1と同様な条件で水素ガス試験を施し、その後取り出した。取り出した磁石は、外観を目視で観察した。
【0028】
[比較例2]
実施例1と同様な組成、方法で焼結磁石を作製した。次に、得られた焼結磁石から実施例1と同様に5×5×5mmに磁石を切り出した。前記磁石に対し、実施例1と同様な条件で電解Cuメッキを20μm施し、更にエポキシ系樹脂を吹き付けにより塗装し、水素ガス試験用試料を得、VSMにより磁気特性の測定を行った。前記水素ガス試験用試料に対し、実施例1と同様な条件で水素ガス試験を施し、その後取り出した。取り出した磁石は、外観を目視で観察した。
【0029】
[比較例3、4]
実施例1と同様な組成、方法で焼結磁石を作製した。次に、得られた焼結磁石から実施例1と同様に5×5×5mmに磁石を切り出した。前記磁石に対し、実施例1と同様な条件で電解Cuメッキを20μm施し、その後、50℃、12時間、空気中(酸素分圧20kPa)[比較例3]、及び、900℃、12時間、空気中(酸素分圧20kPa)[比較例4]の熱処理を施し、室温まで徐冷し、更にエポキシ系樹脂を吹き付けにより塗装し、水素ガス試験用試料を得、VSMにより磁気特性の測定を行った。前記水素ガス試験用試料に対し、実施例1と同様な条件で水素ガス試験を施し、その後取り出した。取り出した磁石は、外観を目視で観察し、更にVSMにより磁気特性の測定を行った。
【0030】
【表1】
【0031】
表1に、熱処理条件、水素ガス試験条件、水素ガス試験後の外観を示した。実施例1、2及び比較例4は、水素ガス試験において変化がなかったことに対し、比較例1、2及び3は、粉々に粉砕されていた。このことから、実施例1、2及び比較例4は、水素脆性を引き起こさなかったことは明らかである。
【0032】
【表2】
【0033】
表2に、表面処理前、及び水素ガス試験前後の磁石の磁気特性を示した。表面処理前、及び水素ガス試験前後で、実施例1、2は、ほとんど磁気特性の変化はなかったことに対し、比較例4は、表面処理前と水素ガス試験前で大きく磁気特性が変化していることが分かる。このことは、実施例1、2において、表面処理による磁気特性の劣化、及び、水素脆性がなかったことと、比較例4が表面処理において磁気特性の劣化を招いてしまったことを示している。比較例1、2及び3は、水素処理により粉砕されてしまったため、水素処理後の磁気特性は、測定不能であった。
【0034】
以上、表1、2は、比較例1〜4では、表面処理により磁気特性が明らかに劣化した又は耐水素性の向上が見られなかったのに対し、実施例1、2では、表面処理により磁気特性が劣化することなく、耐水素性が向上したことを示している。
【0035】
【発明の効果】
本発明のSm2Co17系焼結磁石の製造方法により、水素雰囲気中においても、水素脆性を引き起こさない、モーター等に使用できる希土類焼結磁石を得ることが可能となる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an Sm 2 Co 17- based magnet used for a motor or the like that is exposed to a hydrogen atmosphere for a long time.
[0002]
[Prior art]
An intermetallic compound of a rare earth element and a transition metal has a characteristic that hydrogen penetrates between crystal lattices, that is, has a characteristic of occluding and releasing hydrogen in an alloy, and the characteristic is used in various fields. Examples thereof include a hydrogen battery using a hydrogen storage alloy typified by LaNi 5 , and also in a rare earth sintered magnet, as a method for pulverizing an R 2 Fe 14 B alloy, an R 2 Fe 14 B bond is further used. It is used as a magnet manufacturing method (HDDR Japanese Patent Laid-Open No. 3-129702).
[0003]
However, when hydrogen is occluded and released in the alloy or magnet, hydrogen embrittlement is caused. Therefore, when a motor or the like using a rare earth sintered magnet is used in a hydrogen atmosphere, the rare earth sintered magnet causes hydrogen embrittlement, causing a problem that cracking, cracking, or powdering occurs in the material.
[0004]
Currently, there are various types of rare earth sintered magnets such as R 2 Fe 14 B, SmCo 5 and Sm 2 Co 17 systems. In general, for hydrogen, the plateau pressure is lower in the 1-5 type crystal structure than in the 2-17 type crystal structure, and in the 2-7 type crystal structure than in the 1-5 type crystal structure, that is, rare earth rich ( Hereinafter, R-rich alloys tend to be more likely to occlude hydrogen and are more likely to become hydrogen embrittled.
[0005]
Since the R 2 Fe 14 B-based magnet has an R-rich phase in the magnet, it easily causes hydrogen embrittlement in a hydrogen atmosphere at a pressure of 0.1 MPa or less, and cracks, cracks, or powdering occurs in the magnet material. Usually, R 2 Fe 14 B-based magnets are subjected to surface treatment such as plating and resin coating in order to improve corrosion resistance, but they are not means for preventing hydrogen embrittlement. As a method for solving this problem, a method of incorporating a hydrogen storage alloy in the surface treatment film of the R 2 Fe 14 B magnet has been proposed (Japanese Patent Laid-Open No. 2000-285415). An R 2 Fe 14 B magnet produced by this method does not cause hydrogen embrittlement in a hydrogen atmosphere at a pressure of 0.1 MPa or less, but does cause hydrogen embrittlement in a hydrogen atmosphere at a pressure higher than that. In some cases, cracking, cracking or powdering may occur in the magnet material.
[0006]
Similar to the R 2 Fe 14 B magnet, the SmCo 5 magnet also has an R-rich phase, and the plateau pressure of the SmCo 5 phase that is the main phase is about 0.3 MPa. For this reason, in a hydrogen atmosphere at a pressure exceeding 0.3 MPa, hydrogen embrittlement is caused, and cracking, cracking or powdering occurs in the magnet material.
[0007]
The Sm 2 Co 17- based magnet has a 2-17 phase main phase, is not R-rich compared to the R 2 Fe 14 B-based and SmCo 5 -based magnets, and does not contain an R-rich phase, and thus hardly causes hydrogen embrittlement. . However, it has been found that in a hydrogen atmosphere at a pressure exceeding 1 MPa, as with other rare earth sintered magnets, hydrogen embrittlement is caused, and cracking, cracking or powdering occurs in the magnet material.
[0008]
In order to improve hydrogen embrittlement resistance, an Sm 2 Co 17- based magnet should be a sintered magnet, cut and / or polished to process the surface, and then heat treated in an oxygen partial pressure of 10 −6 to 152 torr. Is known (Japanese Patent Laid-Open No. 2002-118209). By doing so, hydrogen brittleness does not occur even in a high-pressure hydrogen atmosphere exceeding 3 MPa if a layer in which Sm 2 O 3 is finely dispersed in Co and / or Co and Fe is present on the magnet surface. . However, the Sm 2 Co 17- based magnet and the layer in which Sm 2 O 3 is finely dispersed in Co and / or Co and Fe are hard and easily chipped, which causes chipping during product assembly and handling. There is a case. The rare earth sintered magnet that causes chipping or the like does not affect the magnetic properties, but the hydrogen embrittlement resistance is greatly reduced, and becomes equivalent to the case without the surface layer. Therefore, in a hydrogen atmosphere at a pressure exceeding 1 MPa, hydrogen embrittlement is caused, and cracks, cracks, or powdering occurs in the magnet material. Therefore, it cannot be used in such an atmosphere.
[0009]
[Problems to be solved by the invention]
The present invention provides a method for producing an Sm 2 Co 17- based sintered magnet that solves such problems. That is, a method for producing an Sm 2 Co 17- based sintered magnet that solves the problem of causing hydrogen embrittlement in a hydrogen atmosphere and causing cracking, cracking or powdering in the magnet material as in the case of a conventional rare earth sintered magnet. The purpose is to provide.
[0010]
Means for Solving the Problem and Embodiment of the Invention
As a result of intensive studies to achieve the above object, the present inventor conducted surface treatment on sintered and aged sintered magnets, then applied metal plating, and further subjected to optimal heat treatment, so that the surface of the magnet body was subjected to heat treatment. The present inventors have found a method for producing a rare earth sintered magnet that does not cause hydrogen embrittlement even in a high-pressure hydrogen atmosphere by forming a layer having excellent hydrogen resistance. From this, it was found that an Sm 2 Co 17- based sintered magnet suitable for use in a motor or the like exposed to a hydrogen atmosphere for a long time was obtained, and the present invention was made.
[0011]
That is, the present invention provides the following methods (1) to ( 3 ) for producing a rare earth permanent magnet as a method for solving the above problems.
(1) R (where R is Sm or two or more rare earth elements containing 50% by weight or more of Sm) 20 to 30% by weight, Fe 10 to 45% by weight, Cu 1 to 10% by weight, Zr 0.5 to 5% by weight The remaining Co and the inevitable impurities alloy are melted, cast, pulverized, finely pulverized, molded in a magnetic field, sintered, and aged sequentially to obtain a sintered magnet, which is further cut and / or polished. After the surface is processed, metal plating made of at least one of Cu, Ni, and alloys thereof is applied, and thereafter, in an argon, nitrogen, air, or low-pressure vacuum atmosphere having an oxygen partial pressure of 10 −4 Pa to 50 kPa. A method for producing a rare earth sintered magnet having hydrogen embrittlement resistance, characterized by heat treatment at 400 to 850 ° C. for 10 minutes to 50 hours,
(2) The method for producing a rare earth sintered magnet according to (1), wherein the metal plating is multilayer plating ,
( 3 ) The method for producing a rare earth sintered magnet according to (1) or (2) , wherein the rare earth sintered magnet is used for a motor exposed to a hydrogen atmosphere.
[0012]
Details of the present invention will be described below.
The main component of the Sm 2 Co 17- based sintered magnet alloy composition in the present invention is Sm or 20 to 30% by weight of rare earth elements containing 50% by weight or more of Sm, 10 to 45% by weight of Fe, and 1 to 10% by weight of Cu. , Zr 0.5 to 5 wt%, balance Co and inevitable impurities. The rare earth metal other than Sm is not particularly limited, and examples thereof include Nd, Ce, Pr, and Gd. When the content of Sm in the rare earth element is less than 50% by weight, or when the rare earth element content is less than 20% by weight or more than 30% by weight, effective magnetic properties cannot be obtained.
[0013]
The Sm 2 Co 17- based magnet alloy of the present invention melts and casts the raw material having the above composition range in a non-oxidizing atmosphere such as argon by high frequency melting.
[0014]
Next, the Sm 2 Co 17- based magnet alloy is coarsely pulverized and then finely pulverized to an average particle size of 1 to 10 μm, preferably about 5 μm. This rough pulverization can be performed by, for example, a jaw crusher, a brown mill, a pin mill, and hydrogen storage in an inert gas atmosphere. The fine pulverization can be performed by a wet ball mill using alcohol, hexane or the like as a solvent, a dry ball mill in an inert gas atmosphere, a jet mill using an inert gas stream, or the like.
[0015]
Next, the finely pulverized powder is preferably compression-molded by a press in a magnetic field capable of applying a magnetic field of 10 kOe or more, preferably at a pressure of 500 kg / cm 2 or more and less than 2000 kg / cm 2 . Subsequently, the obtained compression-molded body was sintered and melted in a non-oxidizing atmosphere gas such as argon in a heat treatment furnace at 1100 to 1300 ° C., preferably 1150 to 1250 ° C., for 0.5 to 5 hours. And after completion, it is cooled rapidly.
[0016]
Subsequently, an aging treatment is performed in an argon atmosphere at 700 to 900 ° C., preferably 750 to 850 ° C., for 5 to 40 hours, and gradually cooled to 400 ° C. or less at a temperature decrease rate of −1.0 ° C./min. Apply, cut and / or polish to finish the surface. At this time, although not particularly limited, it is desirable that the rare earth sintered magnet body is chamfered.
[0017]
After this surface finishing, metal plating is applied to the rare earth sintered magnet body. The metal of the metal plating is made of at least one of Cu, Ni, Co, Sn, and alloys thereof, and the plating thickness is preferably 1 to 100 μm, particularly preferably 1 to 50 μm. Moreover, you may give multilayer plating. Although it does not specifically limit as pre-processing which performs this metal plating, It is desirable to carry out alkaline degreasing | defatting, acid washing, and water washing | cleaning of the said rare earth sintered magnet body. The plating film forming method is not particularly limited, but the electrolytic plating method is preferable. The method of immersing the rare earth sintered magnet body in the plating solution may be either a barrel method or a hooking jig method, and is appropriately selected depending on the size and shape of the rare earth sintered magnet body.
[0018]
As the electrolytic plating solution, a plating solution having a known composition can be used and plating can be performed under known conditions according to the plating solution, but a plating solution having a pH of 2 to 12 is particularly suitable.
[0019]
After performing metal plating by the above method, oxygen partial pressure is 10 −4 Pa to 50 kPa, preferably 10 −4 Pa to 30 kPa, in an argon, nitrogen, air or low pressure vacuum atmosphere for 10 minutes to 50 hours, It heat-processes at 400-850 degreeC, Preferably it is 400-600 degreeC. If the heat treatment time is less than 10 minutes, formation of a layer excellent in hydrogen resistance is not sufficient, or variation is increased, so that heat treatment exceeding 50 hours is not efficient, and water resistance This is not appropriate because a layer having an excellent feature may become thicker and cause deterioration of magnetic properties. When the heat treatment temperature is less than 80 ° C., a long-time treatment is required to obtain a rare earth sintered magnet having excellent hydrogen resistance, which is not efficient, and when the temperature exceeds 850 ° C., the hydrogen resistance is excellent. Although the layer is formed, the rare earth sintered magnet reacts with the metal plating, and the magnet undergoes a phase transformation to cause deterioration of magnetic properties. Incidentally, the layer excellent in hydrogen resistance is an oxide layer of a plated metal, and preferably has a thickness of 0.1 to 100 μm, more preferably 0.1 to 20 μm.
[0020]
Next, resin coating (so-called resin coating such as spray coating, electrodeposition coating, powder coating or dipping coating) can be applied to the surface of the rare earth sintered magnet body. The coating by resin coating does not have hydrogen resistance, but it must have acid resistance depending on the atmosphere in which the motor using the rare earth sintered magnet is used, or the rare earth sintered magnet is incorporated in the motor etc. This is done because the surface layer is not damaged. The resin for resin coating is not particularly limited, but acrylic, epoxy, phenolic, silicone, polyester, and polyurethane resins are desirable.
[0021]
【Example】
Next, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
[0022]
[Example 1]
Sm 2 Co 17- based magnet alloy is compounded to have a composition of Sm: 25.0 wt%, Fe: 17.0 wt%, Cu: 4.5 wt%, Zr: 2.5 wt%, and the balance Co. Then, in an argon gas atmosphere, an alumina crucible was used for melting in a high-frequency melting furnace and casting was performed.
[0023]
Next, the Sm 2 Co 17- based magnet alloy was coarsely pulverized to about 500 μm or less with a jaw crusher and a brown mill, and then finely pulverized to a mean particle size of about 5 μm with a jet mill using a nitrogen stream. The obtained finely pulverized powder was molded at a pressure of 1.5 t / cm 2 in a magnetic field of 15 kOe using a magnetic field press. The obtained molded body was sintered in an argon atmosphere at 1190 ° C. for 2 hours using a heat treatment furnace, and then subjected to a solution treatment in an argon atmosphere at 1175 ° C. for 1 hour. After completion of the solution treatment, it was rapidly cooled, and each of the obtained sintered bodies was held in an argon atmosphere at 800 ° C. for 10 hours, and gradually cooled to 400 ° C. at a temperature-decreasing rate of −1.0 ° C./min. A sintered magnet was produced. A magnet was cut out to 5 × 5 × 5 mm from the obtained sintered magnet.
[0024]
Next, a plating bath adjusted with 60 g / L pyrophosphate, 240 g / L pyrophosphate, and 30 g / L oxalic acid was used as the sintered magnet, and the bath temperature was 40 ° C. and the current density was 1.5 A / dm 2 . Electrolytic Cu plating is applied to 20 μm, and then heat treatment in air (oxygen partial pressure 20 kPa) is performed at 550 ° C. for 12 hours, gradually cooled to room temperature, and further coated by spraying an epoxy resin, and a hydrogen gas test sample is prepared. The magnetic properties were measured using a Vibrating Sample Magnetometer (hereinafter referred to as VSM).
[0025]
The hydrogen gas test sample was placed in a pressure vessel, sealed under conditions of hydrogen, 10 MPa, and 25 ° C., and subjected to a hydrogen gas test that was allowed to stand for 1 day, and then taken out. The magnet taken out was visually observed for appearance, and the magnetic properties were measured by VSM.
[0026]
[Example 2]
A sintered magnet was produced by the same composition and method as in Example 1. Next, a magnet was cut out to 5 × 5 × 5 mm in the same manner as in Example 1 from the obtained sintered magnet. The magnet was subjected to 20 μm electrolytic Cu plating under the same conditions as in Example 1, and then subjected to heat treatment in vacuum (oxygen partial pressure 10 −2 Pa) at 550 ° C. for 12 hours, and gradually cooled to room temperature. Further, an epoxy resin was applied by spraying to obtain a hydrogen gas test sample, and the magnetic properties were measured by VSM. The hydrogen gas test sample was subjected to a hydrogen gas test under the same conditions as in Example 1 and then taken out. The magnet taken out was visually observed for appearance, and the magnetic properties were measured by VSM.
[0027]
[Comparative Example 1]
A sintered magnet was produced by the same composition and method as in Example 1. Next, a magnet is cut out to 5 × 5 × 5 mm from the obtained sintered magnet in the same manner as in Example 1, and further coated with an epoxy resin by spraying to obtain a sample for hydrogen gas test, and measurement of magnetic properties by VSM Went. The hydrogen gas test sample was subjected to a hydrogen gas test under the same conditions as in Example 1 and then taken out. The removed magnet was visually observed for appearance.
[0028]
[Comparative Example 2]
A sintered magnet was produced by the same composition and method as in Example 1. Next, a magnet was cut out to 5 × 5 × 5 mm in the same manner as in Example 1 from the obtained sintered magnet. The magnet was plated with 20 μm of electrolytic Cu under the same conditions as in Example 1, and further coated with an epoxy resin by spraying to obtain a hydrogen gas test sample, and the magnetic properties were measured by VSM. The hydrogen gas test sample was subjected to a hydrogen gas test under the same conditions as in Example 1 and then taken out. The removed magnet was visually observed for appearance.
[0029]
[Comparative Examples 3 and 4]
A sintered magnet was produced by the same composition and method as in Example 1. Next, a magnet was cut out to 5 × 5 × 5 mm in the same manner as in Example 1 from the obtained sintered magnet. The magnet was subjected to electrolytic Cu plating under the same conditions as in Example 1 for 20 μm, and then in air (oxygen partial pressure 20 kPa) [Comparative Example 3] at 50 ° C. for 12 hours, and 900 ° C. for 12 hours. Heat treatment in air (oxygen partial pressure 20 kPa) [Comparative Example 4], gradually cool to room temperature, and further paint by spraying epoxy resin, obtain a sample for hydrogen gas test, and measure the magnetic properties by VSM It was. The hydrogen gas test sample was subjected to a hydrogen gas test under the same conditions as in Example 1 and then taken out. The magnet taken out was visually observed for appearance, and the magnetic properties were measured by VSM.
[0030]
[Table 1]
[0031]
Table 1 shows the heat treatment conditions, hydrogen gas test conditions, and appearance after the hydrogen gas test. Examples 1 and 2 and Comparative Example 4 did not change in the hydrogen gas test, whereas Comparative Examples 1, 2 and 3 were crushed into pieces. From this, it is clear that Examples 1 and 2 and Comparative Example 4 did not cause hydrogen embrittlement.
[0032]
[Table 2]
[0033]
Table 2 shows the magnetic properties of the magnet before the surface treatment and before and after the hydrogen gas test. Before and after the surface treatment and before and after the hydrogen gas test, Examples 1 and 2 showed almost no change in magnetic properties, whereas in Comparative Example 4, the magnetic properties changed greatly before the surface treatment and before the hydrogen gas test. I understand that This indicates that in Examples 1 and 2, there was no deterioration in magnetic properties due to surface treatment and no hydrogen embrittlement, and Comparative Example 4 caused deterioration in magnetic properties in the surface treatment. . Since Comparative Examples 1, 2, and 3 were crushed by the hydrogen treatment, the magnetic properties after the hydrogen treatment were not measurable.
[0034]
As described above, Tables 1 and 2 show that in Comparative Examples 1 to 4, the magnetic properties were clearly deteriorated by the surface treatment or no improvement in hydrogen resistance was observed, whereas in Examples 1 and 2, the magnetic properties were obtained by surface treatment. It shows that the hydrogen resistance has been improved without deterioration of the characteristics.
[0035]
【The invention's effect】
The method for producing a Sm 2 Co 17- based sintered magnet of the present invention makes it possible to obtain a rare-earth sintered magnet that can be used for a motor or the like that does not cause hydrogen embrittlement even in a hydrogen atmosphere.
Claims (3)
Priority Applications (9)
Application Number | Priority Date | Filing Date | Title |
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JP2001399174A JP3904061B2 (en) | 2001-12-28 | 2001-12-28 | Manufacturing method of rare earth sintered magnet |
US10/500,074 US7438768B2 (en) | 2001-12-28 | 2002-12-24 | Rare earth element sintered magnet and method for producing rare earth element sintered magnet |
KR1020047010039A KR100746897B1 (en) | 2001-12-28 | 2002-12-24 | Rare earth element sintered magnet and method for producing rare earth element sintered magnet |
PCT/JP2002/013430 WO2003058648A1 (en) | 2001-12-28 | 2002-12-24 | Rare earth element sintered magnet and method for producing rare earth element sintered magnet |
KR1020077008306A KR100788330B1 (en) | 2001-12-28 | 2002-12-24 | Rare earth element sintered magnet and method for producing rare earth element sintered magnet |
CNB028276272A CN1299300C (en) | 2001-12-28 | 2002-12-24 | Rare earth element sintered magnet and method for producing rare earth element sintered magnet |
EP02806069A EP1467385B1 (en) | 2001-12-28 | 2002-12-24 | Rare earth element sintered magnet and method for producing rare earth element sintered magnet |
DE60237114T DE60237114D1 (en) | 2001-12-28 | 2002-12-24 | SINTERED RARE ELEMENT MAGNET AND METHOD FOR PRODUCING A SINTERED RARE ELEMENT MAGNET |
TW091137527A TWI282101B (en) | 2001-12-28 | 2002-12-26 | Rare earth element sintered magnet and method for producing rare earth element sintered magnet |
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