JP2002164238A5 - - Google Patents

Description

【００１５】
本発明に好適な潤滑剤の極性基はＣＯＯ（エステル結合）に限られ、親油基の炭素数は５個以上20個以下の潤滑剤が好ましい。ここでCOO基は潤滑剤の1分子中に1個ないし2個以上含んでいてもよい。また親油基の炭化水素鎖（C_nH_m）も2個以上含んでいてもよい（ｍ，ｎは正の整数である）が、一つの親油基中の炭素数は５個以上20個以下が好ましい。親油基中の炭素量が５個未満では十分な潤滑性が得られず、磁気特性を改善することが困難である。又親油基中の炭素量が20個超では潤滑剤の分子量が過大となり沸点が上昇し、揮発性が低下して残留炭素量が0.1重量％超になり、iHcの低下を招く。あるいは潤滑が過剰になり成形体強度を低下させてしまう。親油基の炭化水素は飽和、不飽和のいずれでもよい。具体的には、本発明に用いる潤滑剤は脂肪酸の1価アルコールエステル，多塩基酸の1価アルコールエステル，多価アルコールの脂肪酸エステル及びそれらの誘導体のうちから選択される少なくとも1種である。潤滑剤の添加量は、R-Fe-B系合金微粉との比率で表わされる。配合比率は、（R-Fe-B系合金微粉）：（潤滑剤）＝99.99〜99.5重量部：0.01〜0.5重量部とすることが好ましく、99.99〜99.7重量部：0.01〜0.3重量部がより好ましい。潤滑剤の添加量が前記範囲未満では添加効果が得られず、前記範囲を超えると成形体強度及びiHcが顕著に低下する。なお、R-Fe-B系合金微粉と潤滑剤に対する前記油の配合重量比率は特に限定されず、R-Fe-B系合金微粉表面をくまなく被覆できるとともにスラリー中にR-Fe-B系合金微粉と潤滑剤とが良好に分散し、スラリーの磁場配向性が向上するので好ましい。潤滑剤の添加時期は微粉砕前のR-Fe-B系合金粗粉に添加してもよいし、スラリー作製時点で添加してもよい。
【００１６】
潤滑剤として適用可能なものを下記する。例えば脂肪酸の一価アルコールエステルではカプリン酸メチル、ミリスチン酸メチル、ラウリン酸メチル、ステアリン酸メチル、オイレン酸メチル、あるいはこれらエステルのメチル基の代わりにブチル基、プロピル基、エチルヘキシル基がついているものがある。また、多塩基酸の一価アルコールエステルでは、アジピン酸ジオレイル、アジピン酸ジイソデシル、アジピン酸ジイソブチル、フタル酸ジトリデシル、フタル酸２−エチルヘキシル、フタル酸ジイソノニル、フタル酸ジデシル、フタル酸ジアルキル等がある。また、多価アルコールの脂肪酸およびその誘導体では、ソルビタントリオレエート等がある。多価アルコールの脂肪酸およびその誘導体のものよりは脂肪酸の一価アルコールエステル、または多塩基酸の一価アルコールエステルの方が若干ではあるが磁石の配向性を向上させやすい。
【００１７】
本発明による希土類焼結磁石がR₂Fe₁₄B金属間化合物（ＲはＹを含む希土類元素の少なくとも１種であり、Ｒに占めるＮｄが50原子％以上である）を主相とする場合、主要成分組成を、重量％で、Ｒ：28〜33％、Ｂ：0.8〜1.5％、Ｍ_１：０〜0.6％（Ｍ_１はＮｂ，Ｍｏ，Ｗ，Ｖ，Ｔａ，Ｃｒ，Ｔｉ，Ｚｒ及びＨｆからなる群から選ばれた少なくとも１種である）， Ｍ_２：０〜0.6％（Ｍ_２はＡｌ，Ｇａ及びＣｕからなる群から選ばれた少なくとも１種である。）及び残部Ｆｅ（但し、Ｒ＋Ｂ＋Ｆｅ＋Ｍ_１＋Ｍ_２＝100重量％とした場合）とするのが好ましい。以下、単に％と記すのは重量％を意味するものとする。
【００１８】
Ｒ量は28〜33％が好ましい。良好な耐食性を具備するために、Ｒ量は28〜32％がより好ましく、28〜31％が特に好ましい。Ｒ量が28％未満では所定のiHcを得られず、33％超ではＢｒが著しく減少する。所定のＢｒ及び配向度を得るために、ＲはＮｄ又はＮｄとＤｙ、又はＮｄとＤｙとＰｒ及び不可避的Ｒ成分からなることが好ましい。即ち、Ｒに占めるＮｄを50原子％以上とし、Ｄｙ含有量を0.3〜10％にするのが好ましい。又Ｒに占めるＮｄを90原子％以上とし、Ｄｙ含有量を0.5〜８％にするのがより好ましい。Ｒに占めるＮｄが50原子％未満では資源上豊富なＮｄの使用が制限されて、実用性が低下する。Ｄｙ含有量が0.3％未満ではＤｙの含有効果が得られず、10％超ではBrが低下し所定の配向度を得られない。
【００１９】
Ｂ量は0.8〜1.5％が好ましく、0.85〜1.2％がより好ましい。Ｂ量が0.8％未満では1.1MA/m（14kOe）以上のiHcを得ることが困難であり、Ｂ量が1.5％超ではＢｒが著しく低下する。
【００２０】
Ｎｂ，Ｍｏ，Ｗ，Ｖ，Ｔａ，Ｃｒ，Ｔｉ，Ｚｒ及びＨｆの少なくとも１種からなる高融点金属元素Ｍ_１を0.01〜0.6％含有することが磁気特性を高めるために好ましい。Ｍ_１を0.01〜0.6％含有することにより、焼結過程での主相結晶粒の過度の粒成長が抑制され、1.1MA/m（14kOe）以上のiHcを安定して得ることができる。しかし、Ｍ_１を0.6％超含有すると逆に主相結晶粒の正常な粒成長が阻害され、Brの低下を招く。又Ｍ_１含有量が0.01％未満では磁気特性を改良する効果が得られない。
【００２１】
Ｍ_２元素（Ａｌ，Ｇａ及びＣｕの少なくとも１種）の含有量は0.01〜0.6％が好ましい。Ａｌの含有によりiHcが向上し、耐食性が改善されるが、Ａｌ含有量が0.6％超ではBrが大きく低下し、0.01％未満ではiHc及び耐食性を高める効果が得られない。より好ましいＡｌ含有量は0.05〜0.3％である。Ｇａの含有によりiHcが顕著に向上するが、Ｇａ含有量が0.6％超ではBrが大きく低下し、0.01％未満ではiHcを高める効果が得られない。より好ましいＧａ含有量は0.05〜0.2％である。Ｃｕの微量添加は耐食性の改善及びiHcの向上に寄与するが、Ｃｕ含有量が0.3％超ではBrが大きく低下し、0.01％未満では耐食性及びiHcを高める効果が得られない。より好ましいＣｕ含有量は0.05〜0.3％である。
【００２２】
Ｃｏの含有により耐食性が改善され、キュリー点が上昇し、希土類焼結磁石の耐熱性が向上するが、Ｃｏ含有量が５％超では磁気特性に有害なＦｅ−Ｃｏ相が形成されあるいはＲ_２（Ｆｅ，Ｃｏ）_１４Ｂ相が形成されて、Br及びiHcが大きく低下する。従って、Ｃｏ含有量は５％以下が好ましい。一方、Ｃｏ含有量が0.5％未満では耐食性及び耐熱性の向上効果が得られない。よって、Ｃｏ含有量は0.5〜５％が好ましい。
Ｃｏを0.5〜５％及びＣｕを0.01〜0.3％含有するときに1.1MA/m（14kOe）以上の室温のiHcを得られる第２次熱処理の許容温度が広がる効果を得られ、特に好ましい。
【００２３】
Ａｌを0.01〜0.3％含有させると保磁力向上に寄与するとともに、熱処理温度のばらつきによる保磁力の変動を低減することが可能である。またNbを0.01〜0.08％含有させると焼結過程での結晶粒成長を抑制し、粗大粒の形成を抑制することができる。
【００２４】
不可避に含有される酸素量は0.3％以下が好ましく、0.2％以下がより好ましく、0.18％以下が特に好ましい。酸素含有量を0.3％以下に低減することにより焼結体密度を略理論密度まで高めることができる。R₂Fe₁₄B型金属間化合物を主相とするR-Fe-B系極異方性焼結リング磁石の場合7.56Mg/m^３（g/cm^３）以上の焼結体密度を安定して得られ、さらに主要成分組成、微粉砕平均粒径及び焼結温度等を適宜選択すれば7.58Mg/m^３（g/cm^３）以上、さらには7.59Mg/m^３（g/cm^３）以上のものを得ることができる。
【００２５】
又不可避に含有される炭素量は0.1％以下が好ましく、0.07％以下がより好ましい。炭素含有量の低減により希土類炭化物の生成が抑えられ、有効希土類量が増大し、iHc及び(BH)max等を高めることができる。
【００２６】
又不可避に含有される窒素量は0.15％以下が好ましい。窒素量が0.15％を超えるとBrが大きく低下する。本発明の磁石には公知の表面処理被膜（Ｎｉめっき等）が被覆され、実用に供されるが、Ｒ量が28〜32％でかつ窒素量が0.002〜0.15％のときに良好な耐食性が付与されるのでより好ましい。
【００２７】
又、原料合金としてＣａを還元剤とする還元拡散法により作製したものを用いて本発明の磁石を作製した場合、所定のiHc及び配向度を得るために、前記磁石の全重量を100重量％としてＣａ含有量を0.1重量％以下（０を含まず）に抑えることが好ましく、0.03重量％以下（０を含まず）に抑えることがより好ましい。
【００２８】
本発明の希土類焼結磁石の製造方法における原料合金の微粉砕は不活性ガスを粉砕媒体とするジェットミル等による乾式粉砕装置または酸化を阻止できる条件に設定された湿式ボールミル等の湿式粉砕装置を用いて行うことができる。
【００２９】
例えば、酸素濃度が0.1体積％未満、より好ましくは0.01体積％以下の不活性ガス雰囲気中でジェットミル微粉砕後、大気に触れないように前記不活性ガス雰囲気中から直接微粉を所定配合比率の鉱油、合成油及び植物油から選択される少なくとも１種の油と潤滑剤とからなる非酸化性液中に回収し、スラリー化する。前記微粉の平均粒径は１〜10μmが好ましく、３〜６μmがより好ましい。平均粒径が１μm未満では微粉の粉砕効率が大きく低下し、10μm超ではiHc及び配向度が大きく低下する。
【００３０】
回収したスラリーを成形原料として、所定の成形装置により磁場中成形する。成形体の酸化による磁気特性の劣化を阻止するために、成形直後から脱油までの間前記液中で保存することが望ましい。
【００３１】
成形体を常温から焼結温度まで急激に昇温すると成形体の内部温度が急激に上昇し、成形体に残留する油と成形体を構成する希土類元素とが反応して希土類炭化物を生成し磁気特性が劣化する。この対策として、温度100〜500℃、真空度13.3Pa（10^−１Torr）以下で30分間以上加熱する脱油処理を施すことが望ましい。脱油処理により成形体に残留する油が十分に除去される。なお、脱油処理の加熱温度は100〜500℃であれば一点である必要はなく二点以上であってもよい。また13.3Pa（10^−１Torr）以下で室温から500℃までの昇温速度を10℃/分以下、より好ましくは５℃/分以下とする脱油処理を施すことによっても脱油が効率よく行われる。
【００３２】
鉱油、合成油又は植物油として、脱油及び成形性の点から、分留点が350℃以下のものがよい。又室温の動粘度が10cSt以下のものがよく、５cSt以下のものがさらに好ましい。
【００３３】
【実施例】
以下、実施例により本発明を説明するが、本発明はそれらにより限定されるものではない。
（実施例１）
重量％で、Ｎｄ：23.1％，Ｐｒ：6.4％，Ｄｙ：1.0％，Ｂ：0.9％，Ｃｏ：2.0％，Ｇａ：0.1%，Ｃｕ：0.1％及び残部：ＦｅからなるR-Fe-B系合金粗粉を、酸素濃度が体積比で10ppm以下に調整した窒素ガス雰囲気中でジェットミル微粉砕し、得られた平均粒径4.0μmの微粉をこの窒素ガス雰囲気中で大気に触れることなく鉱油（出光興産（株）製、商品名：出光スーパーゾルPA-30）中に回収しスラリー化した。なお、平均粒径はSympatec社製レーザー回折型粒径分布測定装置（商品名：ヘロス・ロードス）により測定した。次いで得られたスラリーに所定量のオレイン酸メチルを添加し、攪拌機により混合した。スラリーの配合内訳を前記微粉：70重量部、鉱油：29.9重量部、オレイン酸メチル：0.10重量部とした。このスラリーを所定の金型キャビティに注入し、配向磁場強度：1.0MA/m（13kOe），成形圧力： 98MPa（1.0ton/cm²）の条件で横磁場の圧縮成形を行い、15mm×25mm×10mmの直方体状の成形体を得た。また、配向方向は10mm辺方向とした。
この成形体の室温強度を3点曲げ試験により測定した。なお、成形体の15mm×25mmの面が上下面になるように曲げ試験機の治具にセットし、10mmの辺に平行に加圧し３点曲げ強度を測定した。結果を表1に示す。
【００３４】
また同様にして成形した別の成形体を真空度約66.5Pa（5×10^−１Torr），200℃の条件で3時間加熱して脱油し、次いで同雰囲気中で1050℃まで昇温し、次いで1050℃で2時間保持して焼結し、その後室温まで冷却した。得られた焼結体をアルゴン雰囲気中で900℃で2時間加熱し、次いで室温まで急冷する第１次熱処理を行い、続いてアルゴン雰囲気中で480℃で1時間加熱し、次いで室温まで冷却する第２次熱処理を行い、約10mm角のR-Fe-B系焼結磁石を得た。得られた焼結磁石を7mm角に加工し、磁気特性測定用試料とした。次に、室温（20℃）において11.9MA/m（150kOe）のパルス磁場を前記試料の異方性付与方向に沿って印加し、磁気特性を測定した。磁気特性は11.9MA/mのパルス磁場を印加したときの磁化の強さの最大値（4πI_max）を求め、配向度を（Br/4πI_max ）で定義し、評価した。結果を表１に示す。
又得られた焼結磁石の含有炭素量の分析値を表１に示す。
【００３５】
（実施例２〜４）
オレイン酸メチルの代わりにステアリン酸メチル、アジピン酸ジイソデシル、ステアリン酸２−エチルヘキシルを各々添加した以外は、実施例１と同様にして各３種のスラリーを作製した。以降このスラリーを用いた以外は実施例１と同様にして各R-Fe-B系焼結磁石を作製し評価した。結果を表１に示す。
【００３６】
（比較例１）
オレイン酸メチルを添加せずに、実施例１のR-Fe-B系微粉と鉱油とからなるスラリーを作製し、以降このスラリーを用いた以外は実施例１と同様にしてR-Fe-B系焼結磁石を作製し評価した。結果を表１に示す。
【００３７】
（比較例２）
オレイン酸メチルに替えて、実施例１のスラリーにオレイルアルコールを0.1重量部添加した以外は実施例１と同様の手順でR-Fe-B系焼結磁石を作製し評価した。結果を表１に示す。
【００３８】
（比較例３）
オレイン酸メチルに替えて、実施例１のスラリーにオレイルアミンを0.1重量部添加した以外は実施例１と同様の手順でR-Fe-B系焼結磁石を作製し評価した。結果を表１に示す。
【００３９】
（比較例４）
オレイン酸メチルに替えて、実施例１のスラリーに酢酸メチルを0.1重量部添加した以外は実施例１と同様の手順でR-Fe-B系焼結磁石を作製し評価した。結果を表１に示す。
【００４０】
（比較例５）
オレイン酸メチルに替えて、実施例１のスラリーにベヘニン酸メチルを0.1重量部添加した以外は実施例１と同様の手順でR-Fe-B系焼結磁石を作製し評価した。結果を表１に示す。
【００４１】
実施例１の成形体強度は比較例１（潤滑剤無添加）に比べてやや低いが工業生産上なんら問題を発生しないレベルであることが実証された。
【００４２】
実施例１のオレイン酸メチル、比較例２のオレイルアルコール、比較例３のオレイルアミンは各々親油基が同一（炭素数17個）であり、極性基だけが異なる（順に−ＣＯＯ−、−ＯＨ、＞ＮＨ_２）。実施例１及び比較例２，３から明らかなように成形体強度は潤滑剤の極性基の種類に依存することがわかる。又磁気特性は、実施例１及び比較例２，３ではいずれも配向度（Br/4πI_max）は同程度であるが、実施例１に比べて比較例２，３のiHcが低下している。比較例１を基準にすると、添加した潤滑剤の残留により焼結体炭素量が増加し、iHcが低下する程度が異なることから焼結体炭素量も極性基の種類に依存していると判断される。
【００４３】
又、比較例４，５は潤滑剤の極性基を−ＣＯＯ−とし、親油基中の炭化水素鎖の炭素数を変えたものである。比較例４の結果から、炭化水素鎖が短い場合には配向度（Br/4πI_max ）の改善が認められないので、前記微粉間の潤滑性向上には寄与していないと判断される。一方、比較例５から、炭化水素鎖が長い場合には配向度（Br/4πI_max）がみられるものの、焼結体炭素量が増加してしまいiHcの低下が大きいことがわかる。
【００４４】
【表１】

【００４５】
以下に極異方性を有する、R-Fe-B系焼結リング磁石を作製し、評価した実施例を説明する。
（実施例５）
重量％で、主要成分組成がＮｄ：23.1％，Ｐｒ：6.4％，Ｄｙ：1.0％，Ｂ：1.05％、Ｇａ：0.08％、Ｎｂ：0.2％，Ａｌ：0.05％，Ｃｕ：0.13％，Ｃｏ：2.0％及び残部ＦｅからなるR-Fe-B系原料合金粗粉（320メッシュアンタ゛ー）を酸素濃度が１ppm未満（体積比）の窒素雰囲気中でジェットミル粉砕し、得られた平均粒径3.8μmの微粉を用いた以外は実施例１と同様にしてスラリーを作製した。得られたスラリーを、図４に示す成形機のキャビティ59に充填後、成形圧力：78.4MPa(0.8ton/cm^２)及び１００Ｖのパルス磁場で極異方性が付与されるよう磁場中成形し、成形体を得た。成形体を真空度が約66.5Pa(5×10^−１Torr)、200℃の条件で１時間加熱し脱油後、続いて約4.0×10^−３Pa(3×10^−５Torr)、1060℃の条件で２時間焼結後室温まで冷却し焼結体を得た。次に、アルゴン雰囲気中で900℃で１時間加熱後550℃まで冷却し、次いで550℃で2時間加熱後さらに室温まで冷却する熱処理を行った。次に所定寸法に加工後、電着により平均膜厚12μmのエポキシ樹脂膜をコーティングし、外径48mm、内径30mm及び高さ11mmの８極の極異方性を有する極異方性リングを得た。
【００４６】
次に上記の極異方性リングの外径面での磁極間中央部が測定できるようＸ線回折用の試料を切り出し、その試料を理学電気(株)製のＸ線回折装置(RU-200BH)にセットし、２θ−θ走査法によりＸ線回折した。Ｘ線源にはＣｕＫα１線（λ＝0.15405nm）を用い、ノイズ（バックグラウンド）は装置に内蔵されたソフトにより除去した。主な回折ピークは主相であるR₂ Fe ₁₄B型金属間化合物の、２θ＝29.08°の(004)面、38.06°の(105)面、44.34°の(006)面であり、(006)面からのＸ線回折ピーク強度：I(006)を100％として、I(004)/I(006)＝0.33，I(105)/I(006)＝0.63であった。結果を表２に示す。
【００４７】
（比較例６）
実施例５のスラリーに替えて、比較例１のスラリーにより極異方性が付与されるように磁場中成形した以外は実施例５と同様にして比較例の極異方性リングを作製した。以後は実施例５と同様に比較例６の極異方性リングのＸ線回折を行なった。結果を表２に示す。主な回折ピークは実施例５と同様であったが、I(004)/I(006)＝0.32，I(105)/I(006)＝0.96であった。又前記極異方性リングの酸素量は0.13重量％であり、炭素量は0.05重量％であり、窒素量は0.003重量％であった。
【００４８】
【表２】

【００４９】
表２の実施例５及び比較例６の結果より、本発明によれば、極異方性を有し、密度が7.56 Mg/m^３（g/cm^３）以上であり、リング外径面での磁極間中心部表面位置で測定した（105）面からのＸ線回折ピーク強度：Ｉ（105）と（006）面からのＸ線回折ピーク強度：Ｉ（006）との比率が、Ｉ（105）/Ｉ（006）＝0.5〜0.8である極異方性リングを提供できることがわかる。
【００５０】
以下に全体が軸垂直方向へ一方向に配向した（以後、平行異方性という）、R-Fe-B系焼結リング磁石を作製し、評価した実施例を説明する。
（実施例６）
実施例１と同様にしてスラリーを作製した。得られたスラリーを、図４に示す成形機のキャビティ59(ダイス51及び52の内径：60mm、コア53の外径：45mm、ダイス強磁性部51の長さ：34mm、充填深さ：34mm)に充填後、成形圧力：78.4MPa(0.8ton/cm^２)及び軸垂直方向へ一方向に磁場強度：約238.7kA/m(3kOe)をかけた条件で磁場中成形し、成形体を得た。以後は実施例５と同様にして平行異方性を有する平行異方性リングを得た。
【００５１】
次に、図５に示すように、作製した前記平行異方性リング70の配向方向に沿って切り出し、接線方向５mm×長さ方向6.5mm×径方向2.8mmの直方体を得た。直方体の切り出し要領については図5(b)により説明する。平行異方性リング70の中心点Ｏから半径方向に配向方向に垂直に直線OPQを引く。点Ｐは内周面との接点であり、点Ｑは外周面との接点である。次に、接点Ｐにおける接線RPSを引き、接線RPSの長さが接点Ｐを中心にして５mmになるようにする。次に、接線RPSに垂直に直線RT（長さ2.8mm）及び直線SU（長さ2.8mm）を引く。次に、接線RPSに平行に直線TU（長さ５mm）を引く。長方形RSUTにおけるRPS方向及びTU方向が平行異方性リング70の接線方向であり、RT方向およびSU方向を平行異方性リング70の配向方向と定義する。又、長方形RSUTの厚み方向が平行異方性リング70の長さ方向であり6.5mmの長さに切り出した。この切り出し要領により合計４個の直方体を切り出した後、それらの各方向を一致させて貼りあわせた直方体を得た。この直方体により下記の磁気特性を測定した。なお、測定対象の平行異方性リングから前記寸法の直方体が切り出せない場合は、寸法が異なる以外は前記の切り出し要領に従い複数の直方体を切り出した後、それらの各方向を一致させて貼りあわせて寸法を調整すればよい。前記直方体の室温（20℃）における配向方向の残留磁束密度（Br//）、保磁力iHc、最大エネルギー積(BH)max及び角形比(Hk/iHc)を測定した。Hkは４πＩ（磁化の強さ）−Ｈ（磁界の強さ）曲線の第２象限において、0.9Brに相当するＨの値であり、HkをiHcで除した角形比(Hk/iHc)は４πＩ−Ｈ減磁曲線の矩形性を示している。次に、前記直方体の室温（20℃）における長さ方向の残留磁束密度（Br⊥）を測定後、［(Br//)/(Br//+ Br⊥)×100(％)］により定義する平行異方性リングの配向度を求めた。又平行異方性リングの密度を測定した。それらの測定結果を表３に示す。又前記平行異方性リングの酸素量は0.13重量％であり、炭素量は0.05重量％であり、窒素量は0.003重量％であった。
【００５２】
（比較例７）
実施例５のスラリーに替えて、比較例１のスラリーにより配向方向へ磁場中成形した以外は実施例５と同様にして比較例の平行異方性リングを作製し、評価した。結果を表３に示す。
【００５３】
【表３】

【００５４】
表３の実施例６及び比較例７の結果より、本発明によれば、従来にない高い磁気特性を有する平行異方性リングを提供できることがわかる。
【００５５】
以下に他の実施例として平行異方性を有する、R-Fe-B系焼結アークセグメント磁石を作製し、評価した実施例を説明する。
【００５６】
（実施例７）
実施例１で作製したスラリーを図１のスラリー供給装置15の原料タンク13に充填した。次に、スラリー供給管６をシリンダー（図示省略）で下降させ、アークセグメント形状のキャビティ３の底面近傍位置（下パンチ２の上面近傍位置）で停止させた。次に、ポンプ10を作動させて原料タンク13からスラリーを配管11を通してスラリー供給管６からキャビティ３に吐出しながらスラリー供給管６をシリンダー（図示省略）でキャビティ３の上端部位置まで上昇し、キャビティ３に所定量のスラリーを充填した。次いでスラリー供給管６をシリンダー（図示省略）で上昇させてキャビティ３から引き抜いた後、供給ヘッド９をシリンダー４により左方向に移動し、次いで水平方向に1.0MA/m(13kOe)の配向磁場を印加しながら上パンチ（図示省略）及び下パンチ２により98MPa（１ton/cm^２）の圧力を加えて横磁場圧縮成形を行い、アークセグメント成形体を得た。以降は実施例１と同様にして成形体を脱油後、焼結し、熱処理した。次いで得られた焼結磁石素材表面の焼結肌が無くなるまで加工し、次いで平均膜圧１５μmのエポキシ樹脂膜をコーティングしてなる。図２に示す厚みＴ_１＝2.8mm、長さＬ_１＝80.0mm、中心角θ_１＝45°の薄肉、長尺形状のR-Fe-B系焼結アークセグメント磁石30を得た。加工前の前記素材のＬ_１方向の反りは１mm未満であり小さく、異方性付与方向の配向度（Br/4πI_max）が良好であった。アークセグメント焼結磁石30の異方性は↑方向（紙面にほぼ垂直方向）に付与されている。前記アークセグメント磁石30から試料を切り出し、磁気異方性付与方向の磁気特性を室温(20℃)で測定した結果、配向度（Br/4πI_max）＝96.8％、iHc＝1.24MA/m(15.6kOe)及び(BH)max＝394.8kJ/m^３(49.6MGOe)という高い値が得られた。又、密度は7.60 Mg/m^３（g/cm^３）であり、酸素量は0.14重量％、炭素量は0.05重量％及び窒素量は0.02重量％であった。又、試料を理学電気(株)製のＸ線回折装置(RU-200BH)にセットし、２θ−θ走査法によりＸ線回折（ＣｕＫα１線；λ＝0.15405nmを使用）した結果、主な回折ピークは主相であるR₂ Fe ₁₄B型金属間化合物の、２θ＝29.08°の(004)面，38.06°の(105)面、及び44.34°の(006)面であり、(006)面からのＸ線回折ピーク強度：I(006)を100％として、I（105）/Ｉ（006）＝0.66であった。
【００５７】
（実施例８）
キャビティ３の厚み及びスラリーの充填量を変えた以外は実施例７と同様にして、表２の長さＬ_１，厚みＴ_１及びθ_１の寸法を有する薄肉、長尺形状の焼結アークセグメント磁石を作製した。これらの磁石は、磁気異方性付与方向の配向度（Br/４πＩmax）＝96.4〜96.7％、iHc＝1.23〜1.25MA/m(15.4〜15.7kOe)、(BH)max＝393.2〜395.6kJ/m^３(49.4〜49.7MGOe)という高い磁気特性を有し、密度は7.60 Mg/m^３（g/cm^３）であり、酸素量は0.13〜0.14重量％、炭素量は0.06重量％及び窒素量は0.02〜0.03重量％であった。又、実施例７の場合と同様にしてＸ線回折した結果、Ｉ（105）/Ｉ（006）＝0.67〜0.68であった。
【００５８】
（比較例８）
比較例１のスラリーを成形原料とした以外は実施例７と同様に横磁場成形法を適用し、Ｔ＝1.0〜4.0mmのR-Fe-B系焼結アークセグメント磁石用成形体の成形を試みたが、成形体に亀裂が発生し、亀裂の無い健全な成形体を得られなかった。
【００５９】
【表４】

【００６０】
以下にラジアル異方性を有する、R-Fe-B系焼結アークセグメント磁石を作製し、評価した実施例を説明する。
【００６１】
（実施例９）
ラジアル異方性を有するアークセグメント焼結磁石用成形体の内径寸法及びラジアル配向磁場強度(Hap)を変化させて、最終的に長さＬ_２＝65mm、厚みＴ_２＝2.5mm、θ_２＝40°及び表３の内径を有する図３の焼結アークセグメント磁石40を作製し、内径とHap及びラジアル方向の配向度（％）との関係を調査した。調査結果を表３に示す。なお、このアークセグメント焼結磁石の製造は、成形条件及び成形体寸法を変えた以外は実施例７と同様にして順次脱油、焼結、熱処理、加工及び表面処理を行った。表３よりラジアル方向の高い配向度を有することがわかる。又、表３のアークセグメント磁石はいずれも角形比（Hk/iHc）が87.5％超であり、iHcは1.1MA/m(14kOe)超であり、酸素量は0.13〜0.14重量％であり、炭素量は0.05〜0.06重量％であり、窒素量は0.003〜0.004重量％であった。
【００６２】
（比較例９）
比較例１のスラリーを成形原料とした以外は実施例９と同様の形状を有する焼結アークセグメント磁石用成形体の成形を試みたが、成形体亀裂が発生し、焼結アークセグメント磁石を作製することができなかった。
【００６３】
【表５】

【００６４】
次に、ラジアルリングの実施例について説明する。
（実施例10）
重量％で、主要成分組成がＮｄ：21.4％，Ｐｒ：6.0％，Ｄｙ：3.1％，Ｂ：1.05％、Ｇａ：0.08％、Ｎｂ：0.2％，Ａｌ：0.05％，Ｃｕ：0.13％，Ｃｏ：2.0％及び残部ＦｅからなるR-Fe-B系原料合金粗粉（320メッシュアンタ゛ー）を酸素濃度が１ppm未満（体積比）のアルゴン雰囲気中でジェットミル粉砕し、得られた平均粒径3.8μmの微粉を用いた以外は実施例１と同様にしてスラリーを作製した。得られたスラリーを、図４に示す成形機のキャビティ59(ダイス51及び52の内径：60mm、コア53の外径：45mm、ダイス強磁性部51の長さ：34mm、充填深さ：34mm)に充填後、成形圧力：78.4MPa(0.8ton/cm^２)及びラジアル方向の配向磁場強度：約238.7kA/m(3kOe)の条件でラジアル磁場中成形し、成形体を得た。成形体を真空度が約66.5Pa(5×10^−１Torr)、200℃の条件で１時間加熱し脱油後、続いて約4.0×10^−３Pa(3×10^−５Torr)、1060℃の条件で２時間焼結後室温まで冷却し焼結体を得た。次に、アルゴン雰囲気中で900℃で１時間加熱後550℃まで冷却し、次いで550℃で2時間加熱後さらに室温まで冷却する熱処理を行った。次に所定寸法に加工後、電着により平均膜厚12μmのエポキシ樹脂膜をコーティングし、外径48mm、内径39mm及び高さ11mmのラジアル異方性を有するラジアルリングを得た。
【００６５】
次に、図５に示すように、作製した前記ラジアルリング70の任意の位置から接線方向５mm×長さ方向6.5mm×ラジアル方向2.8mmの直方体を切り出した。直方体の切り出し要領について図5(b)により説明する。ラジアルリング70の中心点Ｏから半径方向に直線OPQを引く。点Ｐは内周面との接点であり、点Ｑは外周面との接点である。次に、接点Ｐにおける接線RPSを引き、接線RPSの長さが接点Ｐを中心にして５mmになるようにする。次に、接線RPSに垂直に直線RT（長さ2.8mm）及び直線SU（長さ2.8mm）を引く。次に、接線RPSに平行に直線TU（長さ５mm）を引く。長方形RSUTにおけるRPS方向及びTU方向がラジアルリング70の接線方向であり、RT方向およびSU方向をラジアルリング70のラジアル方向と定義する。又、長方形RSUTの厚み方向がラジアルリング70の長さ方向であり6.5mmの長さに切り出した。この切り出し要領により合計４個の直方体を切り出した後、それらの各方向を一致させて貼りあわせた直方体を得た。この直方体により下記の磁気特性を測定した。なお、測定対象のラジアルリングから前記寸法の直方体が切り出せない場合は、寸法が異なる以外は前記の切り出し要領に従い複数の直方体を切り出した後、それらの各方向を一致させて貼りあわせて寸法を調整すればよい。前記直方体の室温（20℃）におけるラジアル方向の残留磁束密度（Br//）、保磁力iHc、最大エネルギー積(BH)max及び角形比(Hk/iHc)を測定した。Hkは４πＩ（磁化の強さ）−Ｈ（磁界の強さ）曲線の第２象限において、0.9Brに相当するＨの値であり、HkをiHcで除した角形比(Hk/iHc)は４πＩ−Ｈ減磁曲線の矩形性を示している。次に、前記直方体の室温（20℃）における長さ方向の残留磁束密度（Br⊥）を測定後、［(Br//)/(Br//+ Br⊥)×100(％)]により定義するラジアルリングの配向度を求めた。又ラジアルリングの密度を測定した。それらの測定結果を表４に示す。又前記ラジアルリングの酸素量は0.13重量％であり、炭素量は0.05重量％であり、窒素量は0.003重量％であった。
【００６６】
（比較例10）
実施例10のスラリーに替えて、比較例１のスラリーによりラジアル磁場中成形した以外は実施例10と同様にして比較例のラジアルリングを作製し、評価した。結果を表４に示す。
【００６７】
【表６】

【００６８】
表４の実施例10及び比較例10の結果より、本発明によれば、密度が7.56g/cm^３以上、ラジアル方向におけるBr//が1.25Ｔ(12.5kG)以上、iHcが1.1MA/m(14.0kOe)以上、(BH)maxが282.6kJ/m^３(35.5MGOe)以上、(Hk/iHc)が87.5％以上、及びラジアル方向の配向度が85.5％以上という、従来にない高い磁気特性を有するラジアルリングを提供できることがわかる。
【００６９】
（実施例11）
図４の成形機のダイス51,52及びコア53等の寸法を変化させてラジアル異方性を有する成形体リングの内径寸法を変化させ、ラジアル配向磁場強度(Hap)を変えたときのHap、最終的に得られたラジアルリングの内径及びラジアル方向の配向度（％）の関係を調査した。Hapは表７に示すようにラジアル異方性を有する成形体リングすなわちラジアルリングの内径が小さくなるほど低下する。ラジアルリングの内径が100mmのときのHapは磁場発生用電源及びコイルの発熱等により716.2kA/m(９kOe)が上限であった。前記成形体リングの内径、外径（外径＝内径＋(８〜20mm)）及びHapを変えたラジアル磁場成形条件とした以外は実施例10と同様にして順次脱油、焼結、熱処理、加工及び表面処理を行い、表７に示す内径寸法を有するラジアルリングを作製した。表７のいずれのラジアルリングもラジアル方向の配向度が高いことがわかる。又、いずれのラジアルリングも角形比（Hk/iHc）は87.5％超であり、1.1MA/m(14.0kOe)超のiHcを有し、酸素量は0.14〜0.16重量％であり、炭素量は0.04〜0.05重量％であり、窒素量は0.003〜0.004重量％であった。
【００７０】
（比較例11）
比較例１のスラリーを成形原料とした以外は実施例11と同様にして表５のラジアルリングを作製し、ラジアル方向の配向度を求めた。
【００７１】
【表７】

【００７２】
表５より、本発明によれば、内径が100mm以下の従来にない高性能ラジアルリングを提供できることがわかる。
【００７３】
【発明の効果】
以上記述の通り、本発明によれば、低酸素含有量であり、高い焼結体密度を有し、従来に比べて配向度を高めた高性能の希土類焼結磁石が得られる製造方法を提供することができる。
又、低酸素含有量であり、高い焼結体密度を有し、従来に比べて配向度を高めた、極異方性を有する高性能のR-Fe-B系焼結リング磁石を提供することができる。

【図面の簡単な説明】
【図１】 本発明に用いる成形装置の例を示す要部断面図である。
【図２】 本発明に係る平行異方性を有するアークセグメント磁石を示す斜視図である。
【図３】 本発明に係るラジアル異方性を有するアークセグメント磁石を示す斜視図である。
【図４】 本発明に用いる成形装置の一例を示す要部斜視図である。
【図５】 リング磁石の評価用試料の切り出し要領を説明する斜視図(a)、要部断面図(b)である。

【符号の説明】
１ ダイス、２ 下パンチ、３ キャビティ、４ 移動手段、５ 供給ヘッド、６ スラリー供給管、７ プレート、８ 摺動板、９ 供給ヘッド本体、１０ スラリー供給手段、11 配管、12 制御装置、13 タンク、15 スラリー供給装置、30，40 アークセグメント磁石、51 ダイス強磁性部、52 ダイス非磁性部、53 コア、54 上パンチ、55 下パンチ、56 上部コイル、57 下部コイル、58 プレスフレーム、59 キャビティ、70 ラジアルリング。
[Document Name] Statement
Patent application title: Method for producing rare earth sintered magnet and ring magnet
[Claims]
(1)
  R _Two Fe ₁₄ R-Fe-B based on B intermetallic compound (R is at least one rare earth element including Y, and Nd in R is 50 atomic% or more)The alloy coarse powder for a sintered magnet is pulverized in a non-oxidizing atmosphere to an average particle size of 1 to 10 μm, and the obtained fine powder is mixed with at least one oil selected from mineral oil, synthetic oil and vegetable oil, and one of fatty acids. The slurry is recovered in a non-oxidizing liquid comprising a lubricant comprising at least one selected from polyhydric alcohol esters, monohydric alcohol esters of polybasic acids, fatty acid esters of polyhydric alcohols and derivatives thereof. A method for producing a rare earth sintered magnet, which comprises producing, then molding with the slurry, deoiling the obtained molded body, sintering, and heat treating.
(2)
  The method for manufacturing a rare earth sintered magnet according to claim 1,The amount of the lubricant added is in the range of (R-Fe-B based alloy fine powder) :( lubricant) = 99.99-99.5 parts by weight: 0.01-0.5 parts by weight.Characterized byManufacturing method of rare earth sintered magnet.
(3)
  The method for manufacturing a rare earth sintered magnet according to claim 1 or 2,SaidR-Fe-B systemAlloy powder for sintered magnetsBy weight%, R: 28-33%, B: 0.8-1.5%, M ₁ : 0 to 0.6% (M ₁ Is at least one selected from the group consisting of Nb, Mo, W, V, Ta, Cr, Ti, Zr and Hf), M _Two : 0 to 0.6% (M _Two Is at least one selected from the group consisting of Al, Ga and Cu) and the balance Fe (provided that R + B + Fe + M ₁ + M _Two = 100% by weight)Consists of major components and unavoidable impuritiesCharacterized byManufacturing method of rare earth sintered magnet.
(4)
  R _Two Fe ₁₄ A ring magnet consisting of an R-Fe-B sintered magnet whose main phase is a B intermetallic compound (R is at least one kind of rare earth element including Y, and Nd in R is 50 atomic% or more). So,
  The amount of oxygen inevitably contained in the total weight of the ring magnet is 0.3.weight%Less thanHas a carbon content of 0.10% by weight or less and a nitrogen content of 0.15% by weight or less,Polar anisotropy, density 7.56 Mg / m^ThreeThe ring outer diameter surfaceInCenter position between magnetic polesMeasured atThe ratio of the obtained X-ray diffraction peak intensity from the (105) plane: I (105) to the X-ray diffraction peak intensity from the (006) plane: I (006) is I (105) / I (006) = 0.5. A ring magnet characterized by being 0.8.
(5)
  The ring magnet according to claim 4, wherein R: 28-33%, B: 0.8-1.5%, M ₁ : 0 to 0.6% (M ₁ Is at least one selected from the group consisting of Nb, Mo, W, V, Ta, Cr, Ti, Zr and Hf), M _Two : 0 to 0.6% (M _Two Is at least one selected from the group consisting of Al, Ga and Cu) and the balance Fe (provided that R + B + Fe + M ₁ + M _Two = 100% by weight) and a density of 7.58 Mg / m ^Three A ring magnet characterized by the above.
6.
  The ring magnet according to claim 4 or 5, wherein R-Fe-B-based sintered magnet alloy coarse powder (R is at least one rare earth element including Y, and Nd in R is 50 atomic% or more. Is pulverized in a non-oxidizing atmosphere to an average particle size of 1 to 10 μm, and the obtained fine powder is mixed with at least one oil selected from mineral oil, synthetic oil and vegetable oil, monohydric alcohol ester of fatty acid, A lubricant is prepared by recovering in a non-oxidizing oil comprising a monohydric alcohol ester of a basic acid, a fatty acid ester of a polyhydric alcohol and at least one selected from derivatives thereof, and a slurry (provided that The fine powder: the lubricant = 99.99 to 99.5 parts by weight: in the range of 0.01 to 0.5 part by weight), and the obtained slurry is molded in a magnetic field in order to impart polar anisotropy to the obtained molded body. And then sintering, and the obtained sintered body is Ring magnet characterized by heat treatment.
DETAILED DESCRIPTION OF THE INVENTION
     [0001]
   TECHNICAL FIELD OF THE INVENTION
  The present invention has a low oxygen content, a high sintered body density, andPolar anisotropicHigh performance rare earth sintered magnet with higher degree of orientationofIt relates to a manufacturing method.
  Further, the present invention has a low oxygen content, a high sintered body density, and a highly anisotropic or parallel anisotropic orientation degree is increased as compared with the prior art.R-Fe-B polar anisotropyIt relates to a sintered ring magnet.
     [0002]
   [Prior art]
  R-Fe-B based sintered magnets (R is at least one of rare earth elements including Y) are obtained by roughly pulverizing an R-Fe-B based alloy having a predetermined composition,₂And the like, and the resulting fine powder having an average particle size of 1 to 10 μm is molded in a magnetic field, then sintered and heat-treated. In order to increase the residual magnetic flux density Br and the maximum energy product (BH) max, it is extremely important to reduce the oxygen content. For this reason, the present applicant has discovered mineral oil or synthetic oil having a remarkable effect of inhibiting the progress of the oxidation of the fine powder, recovering the fine powder in the oil to form a slurry, molding the slurry, and then obtaining the slurry. Proposed a manufacturing process to obtain a high-performance, high-density R-Fe-B sintered magnet with low oxygen content and high density by deoiling, sintering and heat-treating the compact (Patent No. 2731337, etc.) reference). This manufacturing process has a feature that the progress of oxidation is substantially suppressed by coating the fine powder and the molded body with the oil and shielding the air from the atmosphere, and the R- obtained by deoiling and sintering is obtained. The oxygen content of the Fe-B-based sintered body is kept at a low level corresponding to the R-Fe-B-based alloy coarse powder before fine pulverization. Therefore, the R element in the R-Fe-B-based sintered body is oxidized, and the decrease in the amount of the effective rare earth caused by substantial loss is suppressed small, and the rare earth rich phase forming the grain boundary phase is kept sound. You. Since the R content can be set lower by the amount that the substantial loss of the effective rare earth amount is small, the excess R-rich phase and rare earth oxide can be reduced as compared with the conventional case, and the R_TwoFe₁₄Since the volume ratio of the B-type crystal grains (main phase) can be increased, Br and (BH) max are significantly improved.
    [0003]
   [Problems to be solved by the invention]
  However, there is a strong need for smaller and lighter magnet products such as VCMs, CD pickups, and motors for home appliances, and the demand for smaller size and higher performance of rare earth sintered magnets is becoming more and more severe. I have. In response to this demand, the present inventors also applied the above-described manufacturing process (see Patent No. 2731337 or the like) capable of obtaining a high-performance type R-Fe-B sintered magnet having a low oxygen content and a high density. Br and (BH) max were not as high as expected. As a result of a detailed investigation of this phenomenon by the present inventors, it has been found that the magnetic field orientation of the slurry is not sufficient, leaving room for improvement.
      [0004]
  In view of this problem, the present inventors have already recovered the fine powder in an oil obtained by mixing a non-oxidizing oil such as a mineral oil and a non-ionic or anionic surfactant in a predetermined ratio, and obtained the fine powder. Slurry has good magnetic field orientation, and then it is molded in a magnetic field with this slurry, then successively deoiling, sintering and heat treatment to increase rare earth sintering compared to conventional rare earth sintering We found that a magnet could be obtained, and applied for a manufacturing method (Japanese Patent Application No. 2000-196345).
      [0005]
  The present inventors have conducted intensive studies in search of slurry modifiers other than nonionic or anionic surfactants that can obtain similar effects as those described above. It was discovered that.
  As described above, the problem to be solved by the present invention is a high-performance rare-earth sintered magnet having a low oxygen content, a high sintered body density, and a higher degree of orientation than in the past.ofIt is to provide a manufacturing method.
  Another object of the present invention is to provide a low-oxygen content, high-sintered-body density, and a highly anisotropic or parallel anisotropic orientation degree as compared with the prior art, and high performance.R-Fe-B polar anisotropyIt is to provide a sintered ring magnet.
      [0006]
    [Means for Solving the Problems]
  The method for producing a rare earth sintered magnet of the present invention that has solved the above-mentioned problems,R _Two Fe ₁₄ R-Fe-B based on B intermetallic compound (R is at least one rare earth element including Y, and Nd in R is 50 atomic% or more)The alloy coarse powder for a sintered magnet is pulverized in a non-oxidizing atmosphere to an average particle size of 1 to 10 μm, and the obtained fine powder is mixed with at least one oil selected from mineral oil, synthetic oil and vegetable oil, and one of fatty acids. And the slurry is recovered in a non-oxidizing oil comprising a lubricant comprising at least one selected from polyhydric alcohol esters, monohydric alcohol esters of polybasic acids, fatty acid esters of polyhydric alcohols and derivatives thereof. It is characterized in that it is produced, then molded with the slurry, the obtained molded body is deoiled, then sintered and heat-treated.
      [0007]
  The amount of the lubricant added is preferably in the range of (R-Fe-B-based alloy fine powder) :( lubricant) = 99.99 to 99.5 parts by weight: 0.01 to 0.5 part by weight.
      [0008]
  The alloy coarse powder for the R-Fe-B based sintered magnet is, by weight%, R: 28-33%, B: 0.8-1.5%, M: ₁ : 0 to 0.6% (M ₁ Is at least one selected from the group consisting of Nb, Mo, W, V, Ta, Cr, Ti, Zr and Hf), M _Two : 0 to 0.6% (M _Two Is at least one selected from the group consisting of Al, Ga and Cu) and the balance Fe (provided that R + B + Fe + M ₁ + M _Two = 100% by weight) as well as inevitable impurities.
      [0009]
  The ring magnet of the present invention,R _Two Fe ₁₄ A ring magnet consisting of an R-Fe-B sintered magnet whose main phase is a B intermetallic compound (R is at least one kind of rare earth element including Y, and Nd in R is 50 atomic% or more). So,The amount of oxygen inevitably contained in the total weight of the ring magnet is 0.3.weight%Less thanHas a carbon content of 0.10% by weight or less and a nitrogen content of 0.15% by weight or less,Polar anisotropy, density 7.56 Mg / m^ThreeThe ring outer diameter surfaceInCenter position between magnetic polesMeasured atThe ratio of the obtained X-ray diffraction peak intensity from the (105) plane: I (105) to the X-ray diffraction peak intensity from the (006) plane: I (006) is I (105) / I (006) = 0.5. ~ 0.8. The ring magnet has an X-ray diffraction peak intensity from (105) plane by X-ray diffraction using CuKα1 ray (λ = 0.15405 nm) as an X-ray source: X-ray diffraction from I (105) and (006) planes Peak intensity: The ratio to I (006) is measured, and when I (105) / I (006) = 0.5 to 0.8, a higher Br and (BH) max than before can be obtained.
      [0010]
  The present inventionThe ring magnet isR: 28-33%,B: 0.8-1.5%, M ₁ : 0 to 0.6% (M ₁ Is at least one selected from the group consisting of Nb, Mo, W, V, Ta, Cr, Ti, Zr and Hf), M _Two : 0 to 0.6% (M _Two Is at least one selected from the group consisting of Al, Ga and Cu) and the balance Fe (provided that R + B + Fe + M ₁ + M _Two = 100% by weight) and a density of 7.58 Mg / m ^Three It is preferable that it is above.
      [0011]
  The ring magnet of the present invention does not oxidize R-Fe-B based sintered alloy coarse powder (R is at least one rare earth element including Y, and Nd in R is 50 atomic% or more). Pulverized in a neutral atmosphere to an average particle size of 1 to 10 μm, and the obtained fine powder is at least one oil selected from mineral oil, synthetic oil and vegetable oil, monohydric alcohol ester of fatty acid and monohydric acid of polybasic acid A slurry is prepared by recovering in a non-oxidizing oil consisting of an alcohol ester, a fatty acid ester of a polyhydric alcohol and at least one selected from derivatives thereof, and a slurry (provided that the fine powder: Agent = 99.99 to 99.5 parts by weight: in the range of 0.01 to 0.5 parts by weight), and the resulting slurry is molded in a magnetic field to impart polar anisotropy, and the obtained molded body is deoiled, Then, it is preferable to perform sintering and heat-treat the obtained sintered body. Good.
      [0012]
    BEST MODE FOR CARRYING OUT THE INVENTION
  The present inventors have proposed a hydrocarbon chain (C_nH_m), And -OH, -COOH, -COO-,> NH₂We studied organic chemicals composed of polar groups such as. When R-Fe-B-based alloy fine powder is collected and slurried in a liquid obtained by mixing mineral oil, synthetic oil or vegetable oil and the lubricant in a predetermined weight ratio, the polar groups of the lubricant are adsorbed on the fine powder particles. The lipophilic group of the lubricant serves as a protective film. The source of the adsorptive power is the electric attraction of the polar group, but in some cases, it reacts with the constituent elements of the R-Fe-B-based alloy fine particles to chemically adsorb. For this reason, the strength of adsorption between the lubricant and the fine powder particles and the number of molecules adsorbed on the fine powder particle surface per unit area vary depending on the type of the polar group, and after the deoiling step and the subsequent sintering step. It was found that the amount of residual carbon significantly changed. In addition, even if they have the same polar group, when the number of carbon atoms of the lipophilic group increases, the molecular weight of the lubricant itself increases, the volatility decreases, and a phenomenon in which the residual carbon amount increases is observed.
      [0013]
  Thus, the present inventors first, the relationship between the type of polar group and lipophilic group and the amount of R-Fe-B-based sintered carbon, and second, the relationship between the type of polar group and lipophilic group and magnetic properties. Focusing on the relationship, a lubricant suitable for solving the above-mentioned problem was examined in detail. As a result, a lubricant of the basic structural formula of [Chemical Formula 1] has been discovered, in which an increase in the carbon content of the sintered body can be suppressed to a very small level, a high iHc can be obtained, and a high compact strength suitable for mass production can be obtained. did. In Chemical Formula 1, R₁, R₁'Is a hydrocarbon group.
      [0014]
  Embedded image

      [0015]
  The polar group of the lubricant suitable for the present invention is limited to COO (ester bond), and a lipophilic group having 5 to 20 carbon atoms is preferable. Here, one or more COO groups may be contained in one molecule of the lubricant. The lipophilic hydrocarbon chain (C_nH_m) May be included (m and n are positive integers), but the number of carbon atoms in one lipophilic group is preferably 5 or more and 20 or less. If the carbon content in the lipophilic group is less than 5, sufficient lubricity cannot be obtained, and it is difficult to improve the magnetic properties. On the other hand, if the carbon content in the lipophilic group is more than 20, the molecular weight of the lubricant becomes excessive, the boiling point increases, the volatility decreases, the residual carbon content exceeds 0.1% by weight, and the iHc decreases. Or, the lubrication becomes excessive and the strength of the molded body is reduced. The lipophilic hydrocarbon may be saturated or unsaturated. Specifically, the lubricant used in the present invention is at least one selected from monohydric alcohol esters of fatty acids, monohydric alcohol esters of polybasic acids, fatty acid esters of polyhydric alcohols and derivatives thereof. The amount of the lubricant added is represented by the ratio to the R-Fe-B-based alloy fine powder. The compounding ratio is preferably (R-Fe-B based alloy fine powder) :( lubricant) = 99.99 to 99.5 parts by weight: 0.01 to 0.5 parts by weight, more preferably 99.99 to 99.7 parts by weight: 0.01 to 0.3 parts by weight. preferable. If the amount of the lubricant added is less than the above range, the effect of addition cannot be obtained, and if it exceeds the above range, the strength of the molded article and iHc are significantly reduced. The mixing weight ratio of the oil to the R-Fe-B-based alloy fine powder and the lubricant is not particularly limited, and can cover the entire surface of the R-Fe-B-based alloy fine powder, and the R-Fe-B-based This is preferable because the alloy fine powder and the lubricant are well dispersed and the magnetic field orientation of the slurry is improved. The lubricant may be added to the R-Fe-B-based alloy coarse powder before pulverization or may be added at the time of slurry preparation.
      [0016]
  The following can be applied as a lubricant. For example, monohydric alcohol esters of fatty acids include methyl caprate, methyl myristate, methyl laurate, methyl stearate, and methyl oleate, or those with a butyl, propyl, or ethylhexyl group in place of the methyl group of these esters. is there. Examples of monohydric alcohol esters of polybasic acids include dioleyl adipate, diisodecyl adipate, diisobutyl adipate, ditridecyl phthalate, 2-ethylhexyl phthalate, diisononyl phthalate, didecyl phthalate, and dialkyl phthalate. In addition, fatty acids of polyhydric alcohols and derivatives thereof include sorbitan trioleate and the like. A monohydric alcohol ester of a fatty acid or a monohydric alcohol ester of a polybasic acid is more likely to improve the orientation of the magnet, albeit slightly, than those of a fatty acid and a derivative thereof of a polyhydric alcohol.
      [0017]
  Rare earth sintered magnet according to the present invention is R_TwoFe₁₄When a B intermetallic compound (R is at least one rare earth element containing Y and Nd in R is 50 atomic% or more) is used as a main phase, the main component composition is represented by R: 28% by weight. ~ 33%,B: 0.8-1.5%, M₁: 0 to 0.6% (M₁Is from Nb, Mo, W, V, Ta, Cr, Ti, Zr and HfSelected from the groupAt least one), M₂: 0 to 0.6% (M₂Is from Al, Ga and CuSelected from the groupAt least oneIt is.) And the balance Fe (R + B + Fe + M₁+ M₂= 100% by weight). Hereinafter, simply writing% means weight%.
      [0018]
  The amount of R is preferably 28 to 33%. In order to provide good corrosion resistance, the R amount is more preferably from 28 to 32%, particularly preferably from 28 to 31%. When the amount of R is less than 28%, a predetermined iHc cannot be obtained, and when it exceeds 33%, Br is remarkably reduced. In order to obtain a predetermined Br and degree of orientation, it is preferable that R comprises Nd or Nd and Dy, or Nd, Dy and Pr, and an unavoidable R component. That is, it is preferable that the Nd occupying R is 50 atomic% or more and the Dy content is 0.3 to 10%. Further, it is more preferable that Nd occupying R is 90 atomic% or more and Dy content is 0.5 to 8%. When Nd in R is less than 50 atomic%, use of Nd which is abundant in resources is restricted, and practicality is reduced. If the Dy content is less than 0.3%, the effect of containing Dy cannot be obtained, and if it exceeds 10%, Br decreases and the predetermined degree of orientation cannot be obtained.
      [0019]
  The B content is preferably from 0.8 to 1.5%, more preferably from 0.85 to 1.2%. If the amount of B is less than 0.8%, it is difficult to obtain iHc of 1.1 MA / m (14 kOe) or more, and if the amount of B exceeds 1.5%, Br is significantly reduced.
      [0020]
  Refractory metal element M comprising at least one of Nb, Mo, W, V, Ta, Cr, Ti, Zr and Hf₁Is preferably contained in an amount of 0.01 to 0.6% in order to enhance magnetic properties. M₁By containing 0.01 to 0.6%, excessive grain growth of the main phase crystal grains during the sintering process is suppressed, and iHc of 1.1 MA / m (14 kOe) or more can be stably obtained. But M₁If more than 0.6% is contained, the normal grain growth of the main phase crystal grains is hindered, leading to a decrease in Br. And M₁If the content is less than 0.01%, the effect of improving the magnetic properties cannot be obtained.
      [0021]
  M₂The content of the element (at least one of Al, Ga and Cu) is preferably 0.01 to 0.6%. The content of Al improves iHc and improves corrosion resistance. However, when the Al content exceeds 0.6%, Br is greatly reduced, and when the Al content is less than 0.01%, the effect of increasing iHc and corrosion resistance cannot be obtained. A more preferred Al content is 0.05 to 0.3%. The content of Ga significantly improves iHc, but when the content of Ga exceeds 0.6%, Br is greatly reduced, and when the content of Ga is less than 0.01%, the effect of increasing iHc cannot be obtained. A more preferable Ga content is 0.05 to 0.2%. The addition of a small amount of Cu contributes to the improvement of corrosion resistance and iHc, but when the Cu content exceeds 0.3%, Br is greatly reduced, and when the Cu content is less than 0.01%, the effect of increasing corrosion resistance and iHc cannot be obtained. A more preferred Cu content is 0.05 to 0.3%.
      [0022]
  The content of Co improves the corrosion resistance, raises the Curie point, and improves the heat resistance of the rare earth sintered magnet. However, if the Co content exceeds 5%, a Fe—Co phase harmful to magnetic properties is formed or R₂(Fe, Co)₁₄A phase B is formed, and Br and iHc are greatly reduced. Therefore, the Co content is preferably 5% or less. On the other hand, if the Co content is less than 0.5%, the effect of improving corrosion resistance and heat resistance cannot be obtained. Therefore, the Co content is preferably 0.5 to 5%.
When 0.5 to 5% of Co and 0.01 to 0.3% of Cu are contained, the allowable temperature of the second heat treatment for obtaining iHc at room temperature of 1.1 MA / m (14 kOe) or more is obtained, which is particularly preferable.
      [0023]
  When Al is contained in an amount of 0.01 to 0.3%, it contributes to the improvement of the coercive force, and it is possible to reduce the variation of the coercive force due to the variation of the heat treatment temperature. When Nb is contained in an amount of 0.01 to 0.08%, crystal grain growth during the sintering process is suppressed, and formation of coarse grains can be suppressed.
      [0024]
  The amount of oxygen inevitably contained is preferably 0.3% or less, more preferably 0.2% or less, and particularly preferably 0.18% or less. By reducing the oxygen content to 0.3% or less, the density of the sintered body can be increased to approximately the theoretical density. R_TwoFe₁₄R-Fe-B system with B-type intermetallic compound as main phasePolar anisotropySinteringring7.56Mg / m for magnet³(G / cm³) The above sintered body density can be obtained stably and 7.58Mg / m if the main component composition, finely pulverized average particle size and sintering temperature are appropriately selected.³(G / cm³) Above and even 7.59Mg / m³(G / cm³The above can be obtained.
      [0025]
  The unavoidable carbon content is preferably 0.1% or less, more preferably 0.07% or less. The reduction of the carbon content suppresses the formation of rare earth carbides, increases the effective rare earth amount, and can increase iHc and (BH) max.
      [0026]
  In addition, the amount of unavoidable nitrogen is 0.15%Less thanIs preferred. When the amount of nitrogen exceeds 0.15%, Br is greatly reduced. The magnet of the present invention is coated with a known surface treatment film (Ni plating or the like) and put to practical use. However, when the R amount is 28 to 32% and the nitrogen amount is 0.002 to 0.15%, good corrosion resistance is obtained. It is more preferable because it is provided.
      [0027]
When the magnet of the present invention was manufactured using a material alloy manufactured by a reduction diffusion method using Ca as a reducing agent, the total weight of the magnet was reduced to 100% by weight in order to obtain a predetermined iHc and orientation degree. The Ca content is preferably suppressed to 0.1% by weight or less (excluding 0), and more preferably 0.03% by weight or less (excluding 0).
      [0028]
  The fine pulverization of the raw material alloy in the method for producing a rare earth sintered magnet of the present invention is performed by a dry pulverizer such as a jet mill using an inert gas as a pulverizing medium or a wet pulverizer such as a wet ball mill set to a condition capable of preventing oxidation. It can be performed using:
      [0029]
  For example, after finely pulverizing a jet mill in an inert gas atmosphere having an oxygen concentration of less than 0.1% by volume, more preferably 0.01% by volume or less, fine powders are mixed at a predetermined mixing ratio directly from the inert gas atmosphere so as not to be exposed to the air. It is recovered in a non-oxidizing liquid composed of at least one oil selected from mineral oil, synthetic oil and vegetable oil and a lubricant, and slurried. The average particle size of the fine powder is preferably 1 to 10 μm, more preferably 3 to 6 μm. If the average particle size is less than 1 μm, the pulverization efficiency of the fine powder is significantly reduced, and if it is more than 10 μm, iHc and the degree of orientation are significantly reduced.
      [0030]
  The recovered slurry is used as a forming raw material and is formed in a magnetic field by a predetermined forming apparatus. In order to prevent deterioration of the magnetic properties due to oxidation of the molded body, it is desirable to store the molded body in the liquid immediately after molding until deoiling.
      [0031]
  When the temperature of the compact rapidly rises from room temperature to the sintering temperature, the internal temperature of the compact rapidly rises, and the oil remaining in the compact and the rare earth elements constituting the compact react with each other to generate rare-earth carbides and magnetic properties. The characteristics deteriorate. As a countermeasure, the temperature is 100 to 500 ° C and the degree of vacuum is 13.3Pa (10^-1It is preferable to perform a deoiling treatment in which heating is performed at Torr or less for 30 minutes or more. Oil remaining on the compact is sufficiently removed by the deoiling treatment. The heating temperature in the deoiling treatment is not required to be one point as long as it is 100 to 500 ° C., and may be two or more points. 13.3Pa (10^-1Deoiling can also be carried out efficiently by performing a deoiling treatment at a temperature rising rate from room temperature to 500 ° C. at 10 ° C./min or less, more preferably 5 ° C./min or less.
      [0032]
  As a mineral oil, a synthetic oil or a vegetable oil, those having a fractionation point of 350 ° C. or lower are preferred from the viewpoint of deoiling and moldability. The kinematic viscosity at room temperature is preferably 10 cSt or less, more preferably 5 cSt or less.
      [0033]
    【Example】
Hereinafter, the present invention will be described by way of examples,The present invention providesIt is not limited.
(Example 1)
  R-Fe-B system consisting of 23.1% by weight, Nd: 23.1%, Pr: 6.4%, Dy: 1.0%, B: 0.9%, Co: 2.0%, Ga: 0.1%, Cu: 0.1% and the balance: Fe The alloy coarse powder is finely pulverized by a jet mill in a nitrogen gas atmosphere in which the oxygen concentration is adjusted to 10 ppm or less by volume ratio, and the obtained fine powder having an average particle size of 4.0 μm is exposed to mineral oil in this nitrogen gas atmosphere without contacting the atmosphere. (Made by Idemitsu Kosan Co., Ltd., trade name: Idemitsu Super Sol PA-30) and slurried. The average particle size was measured with a laser diffraction type particle size distribution measuring device (trade name: Heros Rhodes) manufactured by Sympatec. Next, a predetermined amount of methyl oleate was added to the obtained slurry and mixed with a stirrer. The composition of the slurry was 70 parts by weight of the fine powder, 29.9 parts by weight of mineral oil, and 0.10 parts by weight of methyl oleate. This slurry is injected into a predetermined mold cavity, and the orientation magnetic field strength: 1.0 MA / m (13 kOe), molding pressure: 98 MPa (1.0 ton / cm)^TwoThe compression molding of the transverse magnetic field was performed under the conditions of (1) to obtain a rectangular parallelepiped compact of 15 mm × 25 mm × 10 mm. In addition, the orientation direction was a 10 mm side direction.
The room temperature strength of this molded body was measured by a three-point bending test. The molded body was set on a jig of a bending tester such that the 15 mm × 25 mm surface was the upper and lower surfaces, and was pressed in parallel to the 10 mm side to measure the three-point bending strength. Table 1 shows the results.
      [0034]
In addition, another molded body molded in the same manner was vacuumed to about 66.5 Pa (5 × 10^-1Torr) at 200 ° C. for 3 hours to remove oil, and then heated to 1050 ° C. in the same atmosphere, then kept at 1050 ° C. for 2 hours for sintering, and then cooled to room temperature. The obtained sintered body is heated in an argon atmosphere at 900 ° C. for 2 hours, and then subjected to a first heat treatment of rapidly cooling to room temperature, followed by heating in an argon atmosphere at 480 ° C. for 1 hour and then cooling to room temperature. A second heat treatment was performed to obtain an R-Fe-B sintered magnet of about 10 mm square. The obtained sintered magnet was processed into a 7 mm square to obtain a magnetic property measurement sample. Next, a pulse magnetic field of 11.9 MA / m (150 kOe) was applied at room temperature (20 ° C.) along the anisotropy imparting direction of the sample, and the magnetic properties were measured. The magnetic property is the maximum value of the magnetization intensity when a pulse magnetic field of 11.9 MA / m is applied (4πI_max) And determine the degree of orientation as (Br / 4πI_max ) And evaluated. Table 1 shows the results.
Table 1 shows the analysis values of the carbon content of the obtained sintered magnet.
      [0035]
(Examples 2 to 4)
  Three kinds of slurries were prepared in the same manner as in Example 1 except that methyl stearate, diisodecyl adipate, and 2-ethylhexyl stearate were added instead of methyl oleate. Thereafter, each R-Fe-B based sintered magnet was prepared and evaluated in the same manner as in Example 1 except that this slurry was used. Table 1 shows the results.
      [0036]
(Comparative Example 1)
  Without adding methyl oleate, a slurry composed of the R-Fe-B-based fine powder of Example 1 and mineral oil was prepared, and the same procedure was followed as in Example 1 except that this slurry was used. A sintered magnet was produced and evaluated. Table 1 shows the results.
      [0037]
(Comparative Example 2)
  R-Fe-B sintered magnets were prepared and evaluated in the same procedure as in Example 1 except that 0.1 parts by weight of oleyl alcohol was added to the slurry of Example 1 instead of methyl oleate. Table 1 shows the results.
      [0038]
(Comparative Example 3)
  R-Fe-B sintered magnets were prepared and evaluated in the same procedure as in Example 1 except that 0.1 parts by weight of oleylamine was added to the slurry of Example 1 instead of methyl oleate. Table 1 shows the results.
      [0039]
(Comparative Example 4)
  R-Fe-B based sintered magnets were prepared and evaluated in the same procedure as in Example 1 except that 0.1 parts by weight of methyl acetate was added to the slurry of Example 1 instead of methyl oleate. Table 1 shows the results.
      [0040]
(Comparative Example 5)
R-Fe-B sintered magnets were prepared and evaluated in the same procedure as in Example 1 except that 0.1 parts by weight of methyl behenate was added to the slurry of Example 1 instead of methyl oleate. Table 1 shows the results.
      [0041]
  The strength of the molded article of Example 1 was slightly lower than that of Comparative Example 1 (without adding a lubricant), but it was proved that the strength was at a level that would not cause any problem in industrial production.
      [0042]
  The methyl oleate of Example 1, the oleyl alcohol of Comparative Example 2, and the oleylamine of Comparative Example 3 each have the same lipophilic group (17 carbon atoms) and differ only in the polar group (in order of -COO-, -OH, > NH₂). As is clear from Example 1 and Comparative Examples 2 and 3, it can be seen that the strength of the compact depends on the type of polar group of the lubricant. The magnetic characteristics of Example 1 and Comparative Examples 2 and 3 were all the degree of orientation (Br / 4πI_max) Are similar, but the iHc of Comparative Examples 2 and 3 is lower than that of Example 1. Based on Comparative Example 1, the amount of sintered carbon increases due to the residual lubricant added, and the degree of decrease in iHc is different. Therefore, it is determined that the amount of carbon in the sintered compact also depends on the type of the polar group. Is done.
      [0043]
    In Comparative Examples 4 and 5, the polar group of the lubricant was -COO-, and the carbon number of the hydrocarbon chain in the lipophilic group was changed. From the results of Comparative Example 4, when the hydrocarbon chain is short, the degree of orientation (Br / 4πI_max ) Is not recognized, so that it is judged that it does not contribute to the improvement of the lubricity between the fine powders. On the other hand, from Comparative Example 5, when the hydrocarbon chain is long, the degree of orientation (Br / 4πI_max) Can be seen, but the amount of carbon in the sintered body increases and the decrease in iHc is large.
      [0044]
[Table 1]

      [0045]
  R- which has polar anisotropy belowFeAn example in which a -B sintered ring magnet was manufactured and evaluated will be described.
(Example 5)
  In weight%, the main component composition was 23.1% Nd, 6.4% Pr, 1.0% Dy, 1.05% B, 0.08% Ga, 0.2% Nb, 0.05% Al, 0.13% Cu, and 0.13% Co. R-Fe-B-based raw material alloy coarse powder (320 mesh antenna) composed of 2.0% and balance Fe is jet-milled in a nitrogen atmosphere having an oxygen concentration of less than 1 ppm (volume ratio), and the obtained average particle size is 3.8 μm. A slurry was prepared in the same manner as in Example 1 except that the fine powder was used. The obtained slurry is4After filling into the cavity 59 of the molding machine shown in, molding pressure: 78.4MPa (0.8ton / cm²) And extremely anisotropic with 100V pulse magnetic fieldIs givenIn a magnetic field, a compact was obtained. Vacuum degree of molded product is about 66.5Pa (5 × 10^-1(Torr), heated at 200 ° C for 1 hour and deoiled, then about 4.0 × 10^-3Pa (3 × 10^-5After sintering at 1060 ° C for 2 hours, the mixture was cooled to room temperature to obtain a sintered body. Next, heat treatment was performed in an argon atmosphere at 900 ° C. for 1 hour, followed by cooling to 550 ° C., followed by heating at 550 ° C. for 2 hours and further cooling to room temperature. Next, after processing to a predetermined size, an epoxy resin film with an average film thickness of 12 μm is coated by electrodeposition, and a polar anisotropic material having eight poles with an outer diameter of 48 mm, an inner diameter of 30 mm, and a height of 11 mmsexGot a ring.
      [0046]
  Next, the above extreme anisotropicsexA sample for X-ray diffraction was cut out so that the center between magnetic poles on the outer diameter surface of the ring could be measured, and the sample was set on an X-ray diffractometer (RU-200BH) manufactured by Rigaku Denki Co., Ltd. X-ray diffraction was performed by a scanning method. A CuKα1 ray (λ = 0.15405 nm) was used as an X-ray source, and noise (background) was removed by software built in the apparatus. The main diffraction peak is the main phase R_Two Fe ₁₄The (004) plane at 2θ = 29.08 °, the (105) plane at 38.06 °, and the (006) plane at 44.34 ° of the B-type intermetallic compound. X-ray diffraction peak intensity from the (006) plane: I (006) ) As 100%, I (004) / I (006) = 0.33 and I (105) / I (006) = 0.63. Table 2 shows the results.
      [0047]
(Comparative Example 6)
  Extremely anisotropic by the slurry of Comparative Example 1 instead of the slurry of Example 5To be givenExcept for molding in a magnetic field, the same procedure as in Example 5 was carried out to obtain a very anisotropic comparative example.sexA ring was made. Thereafter, similarly to Example 5, the extremely anisotropic material of Comparative Example 6 was used.sexX-ray diffraction of the ring was performed. Table 2 shows the results. The main diffraction peaks were the same as in Example 5, but I (004) / I (006) = 0.32 and I (105) / I (006) = 0.96. Also the extreme anisotropicsexThe ring had an oxygen content of 0.13 wt%, a carbon content of 0.05 wt% and a nitrogen content of 0.003 wt%.
      [0048]
  [Table 2]

      [0049]
  table2According to the results of Example 5 and Comparative Example 6, the present invention has polar anisotropy and a density of 7.56 Mg / m³(G / cm³) Or more at the surface position of the center between the magnetic poles on the ring outer diameter surface.MeasurementThe ratio of the obtained X-ray diffraction peak intensity from the (105) plane: I (105) to the X-ray diffraction peak intensity from the (006) plane: I (006) is I (105) / I (006) = 0.5. Extremely anisotropic which is ~ 0.8sexIt can be seen that a ring can be provided.
      [0050]
  Below, the whole was oriented in one direction perpendicular to the axis (hereinafter referred to as parallel anisotropy).FeAn example in which a -B sintered ring magnet was manufactured and evaluated will be described.
(Example 6)
  A slurry was prepared in the same manner as in Example 1. The obtained slurry is4After filling into the cavity 59 (inner diameter of the dies 51 and 52: 60 mm, outer diameter of the core 53: 45 mm, length of the ferromagnetic part 51: 34 mm, filling depth: 34 mm) of the molding machine shown in (1), molding pressure: 78.4 MPa (0.8ton / cm²) And a magnetic field intensity of about 238.7 kA / m (3 kOe) in one direction perpendicular to the axis, and molded in a magnetic field to obtain a molded article. Thereafter, a parallel anisotropic ring having parallel anisotropy was obtained in the same manner as in Example 5.
      [0051]
  Then figure5As shown in the figure, a rectangular parallelepiped of 5 mm in the tangential direction, 6.5 mm in the length direction, and 2.8 mm in the radial direction was obtained by cutting out the produced parallel anisotropic ring 70 along the orientation direction. See the figure for how to cut a rectangular parallelepiped.5 (b)This will be described below. From the center point O of the parallel anisotropic ring 70, a straight line OPQ is drawn radially perpendicular to the orientation direction. Point P is a contact point with the inner peripheral surface, and point Q is a contact point with the outer peripheral surface. Next, a tangent line RPS at the contact point P is drawn so that the length of the tangent line RPS becomes 5 mm around the contact point P. Next, a straight line RT (length 2.8 mm) and a straight line SU (length 2.8 mm) are drawn perpendicular to the tangent line RPS. Next, a straight line TU (length 5 mm) is drawn parallel to the tangent line RPS. The RPS direction and the TU direction in the rectangular RSUT are tangential directions of the parallel anisotropic ring 70, and the RT direction and the SU direction are defined as the orientation directions of the parallel anisotropic ring 70. The thickness direction of the rectangular RSUT is the length direction of the parallel anisotropic ring 70, and was cut into a length of 6.5 mm. After a total of four rectangular parallelepipeds were cut out according to the cutout procedure, a rectangular parallelepiped was obtained in which the directions of the rectangular parallelepipeds were matched and bonded. The following magnetic properties were measured using this rectangular parallelepiped. If a rectangular parallelepiped having the above dimensions cannot be cut out from the parallel anisotropic ring to be measured, a plurality of rectangular parallelepipeds are cut out in accordance with the above-described cutout procedure except that the dimensions are different, and then their respective directions are matched and bonded. The dimensions may be adjusted. The residual magnetic flux density (Br //), coercive force iHc, maximum energy product (BH) max, and squareness ratio (Hk / iHc) of the rectangular parallelepiped at room temperature (20 ° C.) were measured. Hk is the value of H corresponding to 0.9Br in the second quadrant of the 4πI (magnetization intensity) -H (magnetic field intensity) curve, and the squareness ratio (Hk / iHc) obtained by dividing Hk by iHc is 4πI This shows the rectangularity of the -H demagnetization curve. Next, after measuring the residual magnetic flux density (Br⊥) in the length direction of the rectangular parallelepiped at room temperature (20 ° C), it is defined by [(Br //) / (Br // + Br⊥) × 100 (%)]. The degree of orientation of the parallel anisotropic ring was determined. The density of the parallel anisotropic ring was measured. Table 3 shows the measurement results. The amount of oxygen in the parallel anisotropic ring was 0.13% by weight, the amount of carbon was 0.05% by weight, and the amount of nitrogen was 0.003% by weight.
      [0052]
(Comparative Example 7)
  A parallel anisotropic ring of a comparative example was produced and evaluated in the same manner as in Example 5 except that the slurry of Comparative Example 1 was molded in a magnetic field in the orientation direction instead of the slurry of Example 5. Table 3 shows the results.
      [0053]
  [Table 3]

      [0054]
  From the results of Example 6 and Comparative Example 7 in Table 3, it is understood that the present invention can provide a parallel anisotropic ring having unprecedented high magnetic properties.
      [0055]
  R- having parallel anisotropy as another example below,FeAn example in which a -B-based sintered arc segment magnet was manufactured and evaluated will be described.
      [0056]
(Example 7)
  Figure shows the slurry produced in Example 1.1The raw material tank 13 of the slurry supply device 15 was filled. Next, the slurry supply pipe 6 was lowered by a cylinder (not shown), and stopped at a position near the bottom surface of the cavity 3 having the arc segment shape (a position near the upper surface of the lower punch 2). Next, the pump 10 is operated to discharge the slurry from the raw material tank 13 through the pipe 11 to the cavity 3 from the slurry supply pipe 6 and raise the slurry supply pipe 6 to the upper end position of the cavity 3 by a cylinder (not shown). The cavity 3 was filled with a predetermined amount of slurry. Next, after raising the slurry supply pipe 6 with a cylinder (not shown) and pulling it out of the cavity 3, the supply head 9 is moved leftward by the cylinder 4, and then an orientation magnetic field of 1.0 MA / m (13 kOe) is horizontally applied. 98MPa (1 ton / cm) by upper punch (not shown) and lower punch 2 while applying voltage.²) Was applied to perform transverse magnetic field compression molding to obtain an arc segment molded body. Thereafter, the molded body was deoiled, sintered, and heat-treated in the same manner as in Example 1. Next, the obtained sintered magnet material is processed until the surface of the sintered magnet disappears, and then coated with an epoxy resin film having an average film pressure of 15 μm. Figure2Thickness T shown in₁= 2.8mm, length L₁= 80.0mm, central angle θ₁A thin, long, R-Fe-B based sintered arc segment magnet 30 of 45 ° was obtained. L of the material before processing₁The warpage in the direction is less than 1 mm, which is small, and the degree of orientation in the anisotropic direction (Br / 4πI_max) Was good. The anisotropy of the arc segment sintered magnet 30 is given in the ↑ direction (almost perpendicular to the paper surface). A sample was cut out from the arc segment magnet 30 and the magnetic properties in the direction in which magnetic anisotropy was imparted were measured at room temperature (20 ° C.). As a result, the degree of orientation (Br / 4πI_max) = 96.8%, iHc = 1.24 MA / m (15.6 kOe) and (BH) max = 394.8 kJ / m³(49.6MGOe). The density is 7.60 Mg / m³(G / cm³), The amount of oxygen was 0.14% by weight, the amount of carbon was 0.05% by weight, and the amount of nitrogen was 0.02% by weight. The sample was set on an X-ray diffractometer (RU-200BH) manufactured by Rigaku Denki Co., Ltd., and subjected to X-ray diffraction (using CuKα1 ray; λ = 0.15405 nm) by 2θ-θ scanning method. Peak is main phase R_Two Fe ₁₄The (004) plane at 2θ = 29.08 °, the (105) plane at 38.06 °, and the (006) plane at 44.34 ° of the B-type intermetallic compound. X-ray diffraction peak intensity from the (006) plane: I ( 006) as 100%, I (105) / I (006) = 0.66.
      [0057]
(Example 8)
  In the same manner as in Example 7 except that the thickness of the cavity 3 and the filling amount of the slurry were changed, the length L of Table 2 was changed.₁, Thickness T₁And θ₁A thin, long-sized sintered arc segment magnet having the following dimensions was produced. These magnets have a degree of orientation in the direction of imparting magnetic anisotropy (Br / 4πImax) = 96.4 to 96.7%, iHc = 1.23 to 1.25 MA / m (15.4 to 15.7 kOe), (BH) max = 393.2 to 395.6 kJ / m³(49.4 ~ 49.7MGOe) with high magnetic properties, density 7.60 Mg / m³(G / cm³), The amount of oxygen was 0.13 to 0.14% by weight, the amount of carbon was 0.06% by weight, and the amount of nitrogen was 0.02 to 0.03% by weight. Further, as a result of X-ray diffraction in the same manner as in Example 7, I (105) / I (006) = 0.67 to 0.68.
      [0058]
(Comparative Example 8)
  A transverse magnetic field forming method was applied in the same manner as in Example 7 except that the slurry of Comparative Example 1 was used as a forming raw material, to form a R-Fe-B based sintered arc segment magnet having a T = 1.0 to 4.0 mm. An attempt was made, but cracks occurred in the molded body, and a sound molded body without cracks could not be obtained.
      [0059]
  [Table 4]

      [0060]
  R- having the following radial anisotropyFeAn example in which a -B-based sintered arc segment magnet was manufactured and evaluated will be described.
      [0061]
(Example 9)
  By changing the inner diameter and radial orientation magnetic field strength (Hap) of the arc segment sintered magnet compact having radial anisotropy, finally the length L₂= 65mm, thickness T₂= 2.5mm, θ₂Figure with = 40 ° and inner diameter of Table 33Was manufactured, and the relationship between the inner diameter, Hap, and the degree of orientation (%) in the radial direction was investigated. Table 3 shows the survey results. The production of this arc segment sintered magnet was performed in the same manner as in Example 7, except that the molding conditions and the size of the molded body were changed, and then the deoiling, sintering, heat treatment, processing, and surface treatment were sequentially performed. Table 3 shows that the film has a high degree of orientation in the radial direction. The arc segment magnets in Table 3 all have a squareness ratio (Hk / iHc) of more than 87.5%, iHc of more than 1.1 MA / m (14 kOe), an oxygen content of 0.13 to 0.14% by weight, The amount was 0.05-0.06% by weight and the nitrogen amount was 0.003-0.004% by weight.
      [0062]
(Comparative Example 9)
  An attempt was made to form a molded body for a sintered arc segment magnet having the same shape as in Example 9 except that the slurry of Comparative Example 1 was used as a raw material for forming the sintered arc segment magnet. I couldn't.
      [0063]
[Table 5]

      [0064]
  Next, an embodiment of the radial ring will be described.
(Example 10)
  By weight, the main component composition is 21.4% for Nd, 6.0% for Pr, 3.1% for Dy, 1.05% for B, 0.08% for Ga, 0.2% for Nb, 0.05% for Al, 0.13% for Cu, and 0.1% for Co. R-Fe-B-based raw alloy coarse powder (320 mesh antenna) composed of 2.0% and the balance Fe is jet-milled in an argon atmosphere having an oxygen concentration of less than 1 ppm (volume ratio), and the obtained average particle size is 3.8 μm. A slurry was prepared in the same manner as in Example 1 except that the fine powder was used. The obtained slurry is4After filling into the cavity 59 (inner diameter of the dies 51 and 52: 60 mm, outer diameter of the core 53: 45 mm, length of the ferromagnetic part 51: 34 mm, filling depth: 34 mm) of the molding machine shown in (1), molding pressure: 78.4 MPa (0.8ton / cm²) And radial magnetic field strength: about 238.7 kA / m (3 kOe), and molded in a radial magnetic field to obtain a molded article. Vacuum degree of molded product is about 66.5Pa (5 × 10^-1(Torr), heated at 200 ° C for 1 hour and deoiled, then about 4.0 × 10^-3Pa (3 × 10^-5After sintering at 1060 ° C for 2 hours, the mixture was cooled to room temperature to obtain a sintered body. Next, heat treatment was performed in an argon atmosphere at 900 ° C. for 1 hour, followed by cooling to 550 ° C., followed by heating at 550 ° C. for 2 hours and further cooling to room temperature. Next, after processing to a predetermined size, an epoxy resin film having an average film thickness of 12 μm was coated by electrodeposition to obtain a radial ring having an outer diameter of 48 mm, an inner diameter of 39 mm, and a height of 11 mm having radial anisotropy.
      [0065]
  Then figure5As shown in the figure, a rectangular parallelepiped of 5 mm in the tangential direction, 6.5 mm in the length direction, and 2.8 mm in the radial direction was cut out from an arbitrary position of the manufactured radial ring 70. Illustration of how to cut a rectangular parallelepiped5 (b)This will be described below. A straight line OPQ is drawn from the center point O of the radial ring 70 in the radial direction. Point P is a contact point with the inner peripheral surface, and point Q is a contact point with the outer peripheral surface. Next, a tangent line RPS at the contact point P is drawn so that the length of the tangent line RPS becomes 5 mm around the contact point P. Next, a straight line RT (length 2.8 mm) and a straight line SU (length 2.8 mm) are drawn perpendicular to the tangent line RPS. Next, a straight line TU (length 5 mm) is drawn parallel to the tangent line RPS. The RPS direction and the TU direction in the rectangular RSUT are tangential directions of the radial ring 70, and the RT direction and the SU direction are defined as the radial directions of the radial ring 70. The thickness direction of the rectangular RSUT is the length direction of the radial ring 70, and was cut into a length of 6.5 mm. After a total of four rectangular parallelepipeds were cut out according to the cutout procedure, a rectangular parallelepiped was obtained in which the directions of the rectangular parallelepipeds were matched and bonded. The following magnetic properties were measured using this rectangular parallelepiped. If a rectangular parallelepiped of the above dimensions cannot be cut out from the radial ring to be measured, cut out a plurality of rectangular parallelepipeds according to the above cutout procedure except that the dimensions are different, and adjust the dimensions by matching their directions and bonding them. do it. The residual magnetic flux density (Br //), coercive force iHc, maximum energy product (BH) max, and squareness ratio (Hk / iHc) of the rectangular parallelepiped at room temperature (20 ° C.) were measured. Hk is the value of H corresponding to 0.9Br in the second quadrant of the 4πI (magnetization intensity) -H (magnetic field intensity) curve, and the squareness ratio (Hk / iHc) obtained by dividing Hk by iHc is 4πI This shows the rectangularity of the -H demagnetization curve. Next, after measuring the residual magnetic flux density (Br⊥) in the length direction of the rectangular parallelepiped at room temperature (20 ° C), it is defined by [(Br //) / (Br // + Br⊥) × 100 (%)]. The degree of orientation of the radial ring was determined. The radial ring density was also measured. Table 4 shows the measurement results. The radial ring had an oxygen content of 0.13% by weight, a carbon content of 0.05% by weight, and a nitrogen content of 0.003% by weight.
      [0066]
(Comparative Example 10)
  A radial ring of a comparative example was prepared and evaluated in the same manner as in Example 10 except that the slurry of Comparative Example 1 was molded in a radial magnetic field instead of the slurry of Example 10. Table 4 shows the results.
      [0067]
  [Table 6]

      [0068]
  From the results of Example 10 and Comparative Example 10 in Table 4, according to the present invention, the density was 7.56 g / cm.³Above, Br // in the radial direction is 1.25 T (12.5 kG) or more, iHc is 1.1 MA / m (14.0 kOe) or more, (BH) max is 282.6 kJ / m³It can be seen that a radial ring having an unprecedented high magnetic property of (35.5 MGOe) or more, (Hk / iHc) of 87.5% or more, and a degree of radial orientation of 85.5% or more can be provided.
      [0069]
(Example 11)
  Figure4Hap when changing the radial orientation magnetic field strength (Hap) by changing the inner diameter of the molded body ring having radial anisotropy by changing the dimensions of the dies 51, 52 and the core 53 of the molding machine of The relationship between the inner diameter of the obtained radial ring and the degree of orientation (%) in the radial direction was examined. Hap table7As shown in (1), the lower the inner diameter of the molded body ring having radial anisotropy, that is, the radial ring, the lower. When the inner diameter of the radial ring was 100 mm, the upper limit of Hap was 716.2 kA / m (9 kOe) due to heat generation of a magnetic field generating power supply and a coil. Deoiling, sintering, heat treatment, and the like were performed in the same manner as in Example 10 except that the inner diameter, outer diameter (outer diameter = inner diameter + (8 to 20 mm)) of the molded body ring and radial magnetic field molding conditions in which Hap was changed were used. After processing and surface treatment,7A radial ring having an inner diameter dimension shown in FIG. table7It can be seen that all the radial rings have a high degree of orientation in the radial direction. Each radial ring has a squareness ratio (Hk / iHc) of more than 87.5%, an iHc of more than 1.1 MA / m (14.0 kOe), an oxygen content of 0.14 to 0.16% by weight, and a carbon content of The content was 0.04 to 0.05% by weight, and the amount of nitrogen was 0.003 to 0.004% by weight.
      [0070]
(Comparative Example 11)
  Radial rings shown in Table 5 were prepared in the same manner as in Example 11 except that the slurry of Comparative Example 1 was used as a forming raw material, and the degree of orientation in the radial direction was determined.
      [0071]
  [Table 7]

      [0072]
  Table 5 shows that the present invention can provide an unprecedented high-performance radial ring having an inner diameter of 100 mm or less.
      [0073]
    【The invention's effect】
    As described above, the present inventionToAccording to the high-performance rare earth sintered magnet, which has a low oxygen content, a high sintered body density, and a higher degree of orientation than beforeButCan provide the manufacturing method obtainedTo.
    In addition, it has low oxygen content, high sintered body density, andOrientation degreeEnhanced polar anisotropyToHigh performance R-Fe-Can provide sintered ring magnets based on BTo.
    
[Brief description of the drawings]
FIG. 1 is a sectional view of a main part showing an example of a molding apparatus used in the present invention.
FIG. 2 The present inventionPerspective view showing an arc segment magnet having parallel anisotropy according to FIG.It is.
FIG. 3 shows the present invention.A perspective view showing an arc segment magnet having such radial anisotropy.It is.
FIG. 4 Perspective view of an essential part showing an example of a molding apparatus used in the present invention.It is.
FIG. 5 A perspective view (a) illustrating a procedure for cutting out a sample for evaluation of a ring magnet, and a cross-sectional view of a main part (b).It is.

    [Explanation of symbols]
  Reference Signs List 1 die, 2 lower punches, 3 cavities, 4 moving means, 5 supply head, 6 slurry supply pipe, 7 plate, 8 sliding plate, 9 supply head body, 10 slurry supply means, 11 piping, 12 control device, 13 tank , 15 Slurry feeder, 30, 40 arc segment magnet, 51 dice ferromagnetic part, 52 dice non-magnetic part, 53 core, 54 upper punch, 55 lower punch, 56 upper coil, 57 lower coil, 58 press frame, 59 cavity , 70 radial rings.