JP4034936B2 - Permanent magnet alloy with excellent heat resistance and manufacturing method thereof - Google Patents

Permanent magnet alloy with excellent heat resistance and manufacturing method thereof Download PDF

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JP4034936B2
JP4034936B2 JP2000562572A JP2000562572A JP4034936B2 JP 4034936 B2 JP4034936 B2 JP 4034936B2 JP 2000562572 A JP2000562572 A JP 2000562572A JP 2000562572 A JP2000562572 A JP 2000562572A JP 4034936 B2 JP4034936 B2 JP 4034936B2
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heat resistance
alloy
magnet alloy
irreversible demagnetization
permanent magnet
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雅美 鎌田
道夫 尾畠
祐一 佐藤
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Dowa Holdings Co Ltd
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Dowa Mining Co Ltd
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    • H—ELECTRICITY
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    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
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    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
    • H—ELECTRICITY
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    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
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    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
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    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
    • H01F41/0266—Moulding; Pressing
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Description

技術分野
本発明は，大気中２００℃で使用されても磁力が殆んど劣化しないという極めて耐熱性に優れたＲ−Ｂ−Ｃ−Ｃｏ−Ｆｅ系永久磁石合金（ＲはＹまたは希土類元素）に関する。
背景技術
耐熱性に優れた希土類磁石としてＳｍ−Ｃｏ磁石が知られている。しかし，この磁石は高価である。ここで言う耐熱性とは特に磁力が熱によって劣化しないことを意味する。より安価で且つ耐熱性を改善した希土類磁石として，同一出願人に係る特開平４−１１６１４４号公報（特許第２７４０９８１号）に記載のＲ−Ｂ−Ｃ−Ｃｏ−Ｆｅ系永久磁石合金がある。この磁石合金は，Ｃ（炭素）を必須の合金元素としたうえ，Ｒとして軽希土類と重希土類を組み合わせて使用したものである。該公報にはＣを含有させると不可逆減磁率が顕著に向上する（マイナスの値が０％の側に近づく）ことが示されており，またＲの一部に重希土類元素を用いると一層不可逆減磁率が向上することを教示している。
発明の目的
発熱源の近くに設置される機器類に永久磁石を取り付ける場合には，温度が上昇しても磁力が低下しないこと，すなわち残留磁束密度（Ｂｒ）が劣化しないことが要求されるが，磁石の使用温度が２００℃近辺となる場合には（例えば自動車用エンジン回りに設置される機器類では２００℃近辺となるものがあり，電気自動車用モータも例にもれない），従来品のなかではＳｍ−Ｃｏ磁石しか適用できない。しかし，これは前述のように高価である。また通常のＮｄ−Ｆｅ（Ｃｏ）−Ｂ系希土類磁石ではこのような高温（例えば２００℃）での使用は不可である。
前記の特開平４−１１６１４４号公報に記載されたようにＣ（炭素）を合金元素とするものでは，Ｃの含有により不可逆減磁率が向上し，またＲの一部に重希土類元素を用いると一層不可逆減磁率が向上するが，該公報には２００℃に昇温されても減磁しないようなものは示されていない。
したがって，本発明の課題は，２００℃でも使用に耐えるような耐熱性に優れると共に安価な永久磁石合金を得ることである。
発明の開示
前記の諸課題を解決するため，特開平４−１１６１４４号公報に提案したようにＣの含有が耐熱性を向上させるという基本的な考え方に立脚したうえ，重希土類元素の個々の耐熱性に及ぼす影響を調査研究したところ，ＮｄやＰｒ等の基本的希土類元素に加えて，適量のＤｙとＴｂを複合添加した場合には，特に，ＤｙとＴｂを互いに関連する量で添加した場合には，顕著に耐熱性が向上することを新たに見い出した。
すなわち本発明は，原子百分率（ａｔ．％）で，
Ｃ：０．１〜１５ａｔ．％，
Ｂ：０．５〜１５ａｔ．％，
Ｃ＋Ｂ：２〜３０ａｔ．％，
Ｃｏ：４０ａｔ．％以下（０％を含まず），
Ｄｙ＋Ｔｂ：０．５〜５ａｔ．％で，
好ましくはＴｂ（ａｔ．％）／Ｄｙ（ａｔ．％）：０．１〜０．８，
Ｒ：８〜２０ａｔ．％，
ただし，ＲはＮｄ，Ｐｒ，Ｃｅ，Ｌａ，Ｙ，Ｇｄ，Ｈｏ，ＥｒおよびＴｍからなる群から選ばれた元素の少なくとも一種を表す，
残部：Ｆｅおよび不可避的不純物，
からなる耐熱性に優れた永久磁石合金を提供するものである。
この永久磁石合金の耐熱性は，下記の（１）式に従う不可逆減磁率（２００℃）が０％〜−２０％の範囲，さらに好ましくは０％〜−１５％の範囲（但しｉＨｃ≧１３ＫＯｅ）を示す点において特徴づけられる。
不可逆減磁率（２００℃）＝１００×（Ａ２００−Ａ２５）／Ａ２５・・（１）
ただし，
Ａ２５ ：パーミアンス係数（Ｐｃ）が１になるように形状を調整した試料を５０ＫＯｅで着磁後，室温（２５℃）で測定したフラックス値
Ａ２００：Ａ２５を測定した試料を２００℃に１２０分間保持したあと室温（２５℃）まで冷却して測定したフラックス値。
とくに，不可逆減磁率が０〜−２０％のものは，ＤｙとＴｂの適正な組合せ，例えばＤｙ＋Ｔｂ：０．５〜５ａｔ．％で且つＤｙが０．３〜４．９ａｔ．％でＴｂが０．１〜４．７ａｔ．％の範囲の組合せ（図１の点Ａ，Ｂ，ＣおよびＤで囲われる範囲）で得ることができ，さらに不可逆減磁率が０〜−１５％のものは，図１に示される点Ｂ，Ｃ，Ｈ，Ｅ，ＦおよびＧで囲われる範囲のＤｙ含有量とＴｂ含有量によって得ることができる。
発明の好ましい形態
磁石の使用温度が場合によっては２００℃になることもあると予定して機器類を設計する場合，その指針となるものは２００℃における不可逆減磁率である。すなわち，前記（１）式の不可逆減磁率（２００℃）の値（マイナス）が出来るだけ０％に近づくものであるのがよい。
Ｒが代表的にはＮｄまたはＮｄ＋ＰｒであるＲ−Ｂ−Ｃｏ−Ｆｅ系焼結磁石合金に適量のＣを含有させると不可逆減磁率（１６０℃）の値（マイナス）が０に近づくようになる。この事実は，特開平４−１１６１４４号公報の実施例に示されている。しかし，この公報に示された不可逆減磁率（１６０℃）は，前記（１）式におけるＡ２００をＡ１６０に置き換えたもので（Ａ１６０は１６０℃に１２０分間保持したあと室温まで冷却して測定したフラックス値），しかもパーミアンス係数（Ｐｃ）が３での測定値である。すなわち，Ｐｃが３になるように形状を調製した試料に対して５０ＫＯｅで着磁後，Ａ２５とＡ１６０おフラックス値を測定して求めた不可逆減磁率（１６０℃）である。この公報に見られるようにＣ含有による耐熱性向上効果（更には耐酸化性効果）が知られているが，２００℃での不可逆減磁率については不明であった。また，従来のあらゆるＲ−（Ｆｅ，Ｃｏ）−Ｂ系焼結磁石合金（Ｃを合金元素としないもの）において不可逆減磁率（２００℃）の値が０％〜−２０％を示すものは知られていなかった。
本発明者らは，前記公報に提案して以来も，Ｒ−Ｆｅ−Ｃｏ−Ｃ−Ｂ系の焼結磁石合金の耐熱性をさらに向上させるべく，その合金組成や製造法について種々の試験研究を続けてきたが，数ある希土類元素のうちでも，ＤｙとＴｂを適量複合添加した場合には，著しく不可逆減磁率の低い磁石合金が得られることを知見した。ＤｙとＴｂを単独添加してもそれほど効果は見られないが、両者を複合添加した場合に耐熱性が良好となるのである。
以下に本発明の磁石合金の各成分含有量の範囲を規制する理由の概略と本発明に従う合金磁石の製造法について説明する。
〔Ｃ：０．１〜１５ａｔ．％〕
Ｃは，特開平４−１１６１４４号公報に記載のとおり，本磁石合金の磁気特性を良好に維持しながら希土類磁石の欠点である酸化し易い性質を改質し，耐酸化性を向上させる作用を供する。また不可逆減磁率の低下にも寄与する。Ｃの耐酸化性および耐熱性向上効果は０．１ａｔ．％未満では十分ではない。しかし１５ａｔ．％を超えるとＢｒが低下するようになる。このため，０．１〜１５ａｔ．％のＣ量を含有させるが，好ましいＣ量は１．０〜１０ａｔ．％の範囲，さらに好ましいＣ量は２．５〜７ａｔ．％の範囲である。
〔Ｂ：０．５〜１５ａｔ．％〕
Ｂは磁性相形成のために必要であり，このためには少なくとも０．５ａｔ．％を必要とする。しかし，過剰の添加はかえって磁気特性を劣化させる。このため，０．５〜１５ａｔ．％のＢ量を含有させるが，好ましいＢ量は１．０〜１０ａｔ．％の範囲，さらに好ましいＢ量は１．５〜７ａｔ．％の範囲である。
〔Ｃ＋Ｂ：２〜３０ａｔ．％〕
磁性相の形成と耐酸化性向上のためにＣ＋Ｂは少なくとも２ａｔ．％を含有させる。しかし，３０ａｔ．％を超えると磁気特性を劣化させるので，Ｃ＋Ｂを２〜３０ａｔ．％とする。
〔Ｃｏ：４０ａｔ．％以下〕
Ｃｏは磁気特性を維持しながらキューリ点を高める作用がある。このためＣｏの含有を必須とするが，４０ａｔ．％を超えると保磁力の低下が顕著となるので４０ａｔ．％以下の量で含有させる。
〔Ｄｙ＋Ｔｂ：０．５〜５ａｔ．％〕
ＤｙとＴｂは本発明磁石の特徴的元素であり，両元素を複合して添加することにより不可逆減磁率を顕著に低下させることができる。このため，Ｄｙ＋Ｔｂの合計量として０．５ａｔ．％以上を必要とするが，この合計量が５ａｔ．％を超えても耐熱性向上効果は飽和し，かえって磁気特性を劣化させることがあるので，この合計量を０．５〜５ａｔ．％とする。なお，Ｄｙ単独またはＴｂ単独の添加では後記の比較例に示すように不可逆減磁率低下にそれほど寄与しない。このことから，両元素の相乗効果により不可逆減磁率が低下するものと考えられる。また，両元素の含有割合Ｔｂ（ａｔ．％）／Ｄｙ（ａｔ．％）は０．１〜０．８の範囲であるのがよく，後記の実施例に示すように，Ｄｙが０．３〜４．９ａｔ．％でＴｂが０．１〜４．７ａｔ．％の範囲であれば，パーミアン係数＝１のもとでの２００℃での不可逆減磁率が０〜−２０％，望ましくは０〜−１５％を示す耐熱性に優れた磁石を得ることができる。
〔Ｒ：８〜２０ａｔ．％〕
ＤｙとＴｂ以外の希土類元素として，Ｎｄ，Ｐｒ，Ｃｅ，Ｌａ，Ｙ，Ｇｄ，Ｈｏ，Ｅｒ，Ｔｍの一種または二種以上を８〜２０ａｔ．％含有することにより，焼結磁石合金において磁性相と粒界相を形成し，高いｉＨｃとＢｒを維持することができる。このＲ元素のうち，特に好ましい元素はＮｄとＰｒであり，Ｎｄ単独またはＮｄとＰｒの複合添加が特に望ましい。Ｒが８ａｔ．％未満では十分なＢｒが得られず，２０ａｔ．％を超えても十分なＢｒが得られない。好ましいＲ元索の含有量は１３〜１８ａｔ．％である。
以上の成分組成からなる本発明の永久磁石合金は，前記の（１）式に従う不可逆減磁率（２００）が０〜−２０％，好ましくは０〜−１５％という低い値，さらには０〜−５％の値を有することができ，希土類磁石としてはＳｍ−Ｃｏ磁石以外では始めて高温用途の永久磁石合金が提供される。これまでのＢ含有希土類磁石では，昇温されたときの減磁を予定して高い保磁力のものを使用するということで対処していたのであるが，本発明磁石では昇温しても減磁が殆んど起きないので，高い磁力のまま永久磁石として機能し続けることができる。特に本発明磁石はｉＨｃが１３ＫＯｅ以上，好ましくは１５ＫＯｅ以上であれば昇温用途に使用しても磁気特性を維持することができる。従来の磁石では昇温用途で磁気特性を維持するためには，相当高いｉＨｃを有するものを使用しなければならなかったのに比べると，有効な永久磁石合金であると言える。
本発明の永久磁石合金を製造するには，溶解，鋳造，粉砕，成形，焼結という一連の工程で焼結磁石とすることができる。溶解鋳造法としては，真空溶解・鋳造法，不活性ガス雰囲気溶解・鋳造法，急冷ロール法，アトマイズ法等が採用できる。磁気特性と耐熱性に優れた焼結磁石とするには，鋳造工程と粉砕工程の間に熱処理工程を挿入し，粉砕前のものを不活性ガス雰囲気中で６００℃以上の温度で熱処理するのが好ましく，これにより一層不可逆減磁率を低下させることができる。また，焼結工程では不活性ガス中で１０００〜１２００℃の温度で焼結し，この焼結温度から６００〜９００℃まで徐冷し，次いでその温度から急冷するのが好ましい。この焼結後の急冷によっても不可逆減磁率を一層低下させることができる。
前記の熱処理と焼結後の急冷処理のほかは，特開平４−１１６１４４号公報に記載の焼結磁石と同様の方法に従って本発明の焼結磁石合金を製造することができる。その概要は次のとおりである。
まず，合金組成となるように秤量した各成分の原料を真空溶解炉で１６００℃以上で溶解し，水冷鋳型に急冷鋳造する。得られた鋳塊を前記のように６００℃以上でＡｒ雰囲気中で熱処理したあと，ジョークラッシャーで粗粉砕する。得られた粗粉を振動ボールミルで微粉砕し，平均粒径２〜１０μｍの粉末にする。これらの粉砕工程もＡｒ雰囲気中で行う。また後者の微粉砕の工程において，Ｃ原料の一部を添加することができる。すなわちＣ原料の一部は真空溶解炉に投入するが，残部はこの微粉砕工程で添加する。このＣ原料としてはカーボンブラックが適切であるが，脂肪族炭化水素，高級脂肪酸系アルコール，高級脂肪酸，脂肪酸アマイド，金属石けん，脂肪酸エステル等のＣを含有する有機物質も使用可能である。
次いで該粉体を外部磁場中で圧粉成形する。成形圧としては１〜５ｔ／ｃｍ２の範囲，外部磁場としては１５ＫＯｅ以上が適切である。この成形工程も望ましくはＡｒ雰囲気中で行う。この成形品をＡｒ雰囲気中１０００〜１２００℃で約２時間の焼結を行う。そして，前記のように焼結温度から６００〜９００℃まで徐冷し，次いでその温度から急冷する。６００〜９００℃から急冷を開始させるには，その温度から低温の不活性ガスを吹付ける方法，水または油またはこれに類する液中に浸漬する方法で行うことができるが，この急冷開始温度６００〜９００℃から４００℃まで，またはそれ以下まで−５０℃／ｍｉｎ以上，好ましくは−１００℃／ｍｉｎ以上の冷却速度で急冷するのがよい。
したがって，本発明によれば，合金成分の各原料を溶解鋳造し，得られた合金を粉砕し，その粉体を圧粉成形し，その成形品を不活性ガス中で１０００〜１２００℃の温度で焼結して，前記の成分組成の焼結磁石合金を製造するさいに，粉砕前の合金を６００℃以上の温度で不活性ガス中で熱処理すること，および／または不活性ガス中で１０００〜１２００℃の温度で焼結したあと，その焼結温度から６００〜９００℃まで徐冷し，その後急冷することを特徴とする耐熱性に優れた永久磁石合金の製造法を提供する。そのさい，Ｃ原料の一部を溶解時に添加し，Ｃ原料の他部を合金の粉砕時に添加することができる。
以下に本発明磁石の代表的な実施例を挙げる。
実施例
〔実施例１〕
下記の成分組成を有する合金を以下に述べる方法で製造した。

Figure 0004034936
「製造法」
前記の合金組成となるように各成分原料を計量し，真空溶解炉で溶解した。そのさい，Ｃ原料の一部は該溶解炉には投入せず保存しておいた。得られた溶湯を銅水冷鋳型に１６００℃から急冷鋳造して鋳塊合金を得た。この鋳塊合金を，表１に示す温度でＡｒ雰囲気中で熱処理するか又はせずして，ジヨークラッシャーで粗粉砕し，この粗粉と保存しておいた前記のＣ原料を振動ボールミルに入れて粉砕し，平均粒径５μｍの粉体を得た。
この粉体を圧力２ｔ／ｃｍ２で外部磁場１５ＫＯｅ中で磁場成形し，この成形体をＡｒ雰囲気中で１１００℃で２時間焼結したあと，この焼結温度から表１に示す急冷開始温度まで徐冷し，その急冷開始温度からＡｒを吹付けて表示の冷却速度で急冷した。得られた焼結品の磁気特性，耐熱性および耐酸化性を評価し，その結果を表１に示した。耐熱性と耐酸化性評価は次のようにして行った。
「耐熱性評価」
（１）２００℃での不可逆減磁率の測定
パーミアンス係数（Ｐｃ）が１になるように試料を形状調整する。具体的には２．５ｍｍ×２．５ｍｍ×１．０５ｍｍの試料を切り出す。
この試料を５０ＫＯｅの外部磁場で着磁し，室温（２５℃）でフラックスを測定する。このフラックスの測定は東洋磁気工業株式会社製のフラックスメーターに鉄心コイルを装着して行った。この時のフラックスの値をＡ２５とする。
次に，この着磁した試料を２００℃に１２０分保持した。この加熱保持はシリコンオイルを充填したオイルバス中で行った。オイルバスの温度は±０．１に精密制御した。オイルバスから取り出した試料は室温で十分に冷却したあと，前記のフラックスメーターで再びフラックスを測定する。この時のフラックスの値をＡ２００とする。測定したＡ２５とＡ２００から次式で不可逆減磁率を算出する。
不可逆減磁率（２００）（％）＝１００×（Ａ２００−Ａ２５）／Ａ２５
（２）１６０℃での不可逆減磁率の測定
特開平４−１１６１４４号公報の実施例のものと同様にパーミアンス係数（Ｐｃ）が３になるように試料を形状調整し，オイルバスでの加熱保持を１６０℃×１２０分とした以外は，前記の２００℃での測定と同様にＡ２５とＡ１６０を測定し，前式により不可逆減磁率を算出する。
（３）磁気特性および保磁力の温度係数
試料を５０ＫＯｅの外部磁場で着磁したあと，振動型磁力測定器で室温（２５℃）での磁気特性を測定する。保磁力の温度係数については，室温での保磁力をＢ０とし，同じく振動型磁力測定器で１６０℃で測定した保磁力をＢ１として次式により算出する。
保磁力の温度係数（％／℃）
＝１００×（Ｂ１−Ｂ０）／Ｂ０／（１６０−２５）
（４）耐酸化性の測定
プレッシャークッカ試験（ＰＣＴ）で錆の進行を測定する。具体的にはタバイエスペック社製の試験器で試料を１２０℃，２気圧，１００％ＲＨ（飽和条件）で１００時間保持したときの錆の発生を目視観察する。
Figure 0004034936
表１の結果に見られるように，不可逆減磁率（２００℃）が−３％の永久磁石合金が得られた（例えば表１のａ）。また不可逆減磁率（１６０℃）はａ合金では−０．７％であり，殆んど０％に近い。したがって，高温用途でも高い磁力を維持できる。
製造条件について見ると．例えばａとｂを比較すると明らかなように，鋳塊の熱処理を行うと不可逆減磁率が低くなる。また，ａとｃとｄを比較すると明らかなように，焼結後に少なくとも７００℃以上の温度から急冷すると保磁力が向上し且つ不可逆減磁率も低くなる。
〔実施例２〜１６〕および〔比較例１〜６〕
合金の成分組成を表２に示すように変えた以外は，実施例１のａと同じ製造条件で焼結品を製造した。得られた焼結磁石の特性を実施例１と同様に測定し，その結果を表２に併記した。
Figure 0004034936
表３に見られるように，ＤｙとＴｂの両者を添加した実施例２〜１６のものはいずれも２００℃での不可逆減磁率が低く，また１６０℃での不可逆減磁率も殆んど０％に近い。また，保磁力の温度係数も低く且つ耐酸化性にも優れている。
これに対し，ＤｙとＴｂが無添加の比較例１，０．５ａｔ．％ＤｙでＴｂ無添加の比較例２，およびＤｙ無添加で０．５ａｔ．％Ｔｂの比較例４のものは，２００℃での不可逆減磁率は−９５％，−９５％および−９１％であり，２００℃に昇温されると磁力をほぼ完全に無くしてしまう。すなわち，ＤｙとＴｂの一方だけを添加しても２００℃での不可逆減磁率に対しては効果を示さない。なお，比較例３のようにＤｙ単独でもその含有量を高めれば不可逆減磁率はある程度低くなるが，それでも十分ではない。また，比較例５はＣ量が本発明で規定する範囲より低いので，耐酸化性に劣っている。比較例６はＤｙ無添加でＴｂを３．０ａｔ．％添加したものであるが，比較例４よりは耐熱性が良好であるものの２００℃での不可逆減磁率は−３０％と低い。
図１は，横軸にＤｙ含有量（ａｔ．％），縦軸にＴｂ含有量（ａｔ．％）をとり，表２の磁石全て（但し点錆が発生した比較例５は除く）について，各々が含有するＤｙとＴｂ量では，２００℃での不可逆減磁率の値がどのようなレベルに分布されるか，を示したものである。図１にプロットした数値はその位置での２００℃での不可逆減磁率の値を示している。
図１の結果からＤｙ：２〜３ａｔ．％で，Ｔｂ：０．３〜１．５ａｔ．％の領域において，２００℃の不可逆減磁率にピーク（不可逆減磁率が０％に近づく点）が存在することが伺い知ることができる。より具体的には，２００℃での不可逆減磁率が０〜−２０％を示す領域は，直線（１）（２）（３）（４）（５）（６）の交点のうち，点Ａ，Ｂ，ＣおよびＤで囲われる範囲であり，２００℃での不可逆減磁率が０〜−１５％を示す領域は，点Ｂ，Ｃ，Ｈ，Ｅ，ＦおよびＧで囲われる範囲であることがわかる。
なお，直線（１）〜（６）は，次の式で表される。
直線（１）：Ｄｙ＝０．３
直線（２）：Ｔｂ＋Ｄｙ＝０．５
直線（３）：Ｔｂ＝０．１
直線（４）：Ｔｂ＝０．１Ｄｙ
直線（５）：Ｔｂ＝０．８Ｄｙ
直線（６）：Ｔｂ＋Ｄｙ＝５．０
また，点Ａ〜Ｈの座標（Ｄｙａｔ．％，Ｔｂａｔ．％）は次のとおりである。
点Ａ（０．３，４．７）
点Ｂ（０．３，０．２）
点Ｃ（０．４，０．１）
点Ｄ（４．９，０．１）
点Ｅ（４．５，０．５）
点Ｆ（２．８，２．２）
点Ｇ（０．３，０．２４）
点Ｈ（１．０，０．１）
図２と図３は，特開平４−１１６１４４号公報に開示された実施例磁石のうち最も耐熱性がよいと見られる実施例２４のものと，本発明に従う実施例２のものとを，パーミアンス係数（Ｐｃ）が３になるように形状を調整した試料を５０ＫＯｅで着磁した場合（図２）と，Ｐｃが１になるように形状を調製した試料を５０ＫＯｅで着磁した場合（図３）について，各々測定温度を変えて不可逆減磁率を測定した結果を示したものである。特開平４−１１６１４４号公報の実施例２４の磁石（公開磁石と呼ぶ）は，９Ｎｄ−９Ｄｙ−５９Ｆｅ−１５Ｃｏ−１Ｂ−７Ｃの組成を有し，Ｐｃ＝３における１６０℃での不可逆減磁率が−１．０％であると該公報に記載されている。
図２のように，Ｐｃ＝３となるように形状を調整した試料では，１６０℃での不可逆減磁率が公開磁石のものは−１．０％，本発明実施例２のものでは−０．７％でありそれほど差は見られない。しかし，Ｐｃ＝３で２００℃での不可逆減磁率は公開磁石は−１２．９％であるのに対し，本発明実施例２のものは−１．９％にまで向上している。このような傾向は，Ｐｃが１になるように形状を調整した試料を用いた図３では一層明確に見られる。すなわち，Ｐｃ＝１においては，１６０℃での不可逆減磁率が公開磁石では−９．４％であるのに対し，本発明実施例２では−１．７％に向上し，２００℃の不可逆減磁率については公開磁石では−２２．３％であるのに対し，本発明実施例２では−４％にまで向上している。
以上説明したように，本発明によれば，Ｒ−Ｆｅ（Ｃｏ）−Ｂ系磁石の分野において，これまで達成されたことのない優れた耐熱性と耐酸化性を具備する永久磁石合金が得られる。したがって，昇温が予測される機器に装着される永久磁石として，安価で且つ磁気特性の優れた材料を提供できる。
【図面の簡単な説明】
図１は，表２の磁石の２００℃での不可逆減磁率の値をＤｙとＴｂの含有量で整理して示した不可逆減磁率の分布図である。
図２は，特開平４−１１６１４４号公報の実施例２４の磁石と，本発明に従う実施例２のものとを，パーミアンス係数（Ｐｃ）が３になるように形状を調整した試料を５０ＫＯｅで着磁した場合について，測定温度を変えて不可逆減磁率を測定した結果を示した図である。
図３は，パーミアンス係数（Ｐｃ）が１となるように形状を調整した試料を用いた以外は，図２と同様の不可逆減磁率測定結果を示した図である。TECHNICAL FIELD The present invention relates to an R—B—C—Co—Fe based permanent magnet alloy (R is Y or a rare earth element) that is extremely excellent in heat resistance so that the magnetic force hardly deteriorates even when used at 200 ° C. in the atmosphere. About.
BACKGROUND ART Sm—Co magnets are known as rare earth magnets having excellent heat resistance. However, this magnet is expensive. The heat resistance mentioned here means that the magnetic force is not particularly deteriorated by heat. As a rare-earth magnet having lower heat resistance and improved heat resistance, there is an R—B—C—Co—Fe based permanent magnet alloy described in Japanese Patent Application Laid-Open No. 4-116144 (Patent No. 2740981) of the same applicant. In this magnet alloy, C (carbon) is an essential alloy element, and R is a combination of light rare earth and heavy rare earth. The gazette shows that the irreversible demagnetization rate is remarkably improved when C is contained (a negative value approaches 0%), and if a heavy rare earth element is used for a part of R, the irreversibility is further increased. It teaches that the demagnetization factor is improved.
When attaching a permanent magnet to equipment installed near a heat source, it is required that the magnetic force does not decrease even if the temperature rises, that is, the residual magnetic flux density (Br) does not deteriorate. , When the operating temperature of the magnet is around 200 ° C. (for example, some devices installed around an automobile engine have a temperature around 200 ° C., and an electric vehicle motor is not an example). Of these, only Sm-Co magnets can be applied. However, this is expensive as described above. Further, ordinary Nd—Fe (Co) —B rare earth magnets cannot be used at such a high temperature (for example, 200 ° C.).
In the case of using C (carbon) as an alloy element as described in the above-mentioned JP-A-4-116144, the irreversible demagnetization rate is improved by the inclusion of C, and if a heavy rare earth element is used as a part of R, Although the irreversible demagnetization rate is further improved, this publication does not show anything that does not demagnetize even when the temperature is raised to 200 ° C.
Accordingly, an object of the present invention is to obtain a permanent magnet alloy that is excellent in heat resistance that can withstand use even at 200 ° C. and that is inexpensive.
DISCLOSURE OF THE INVENTION In order to solve the above-mentioned problems, based on the basic idea that the inclusion of C improves the heat resistance as proposed in JP-A-4-116144, the individual heat resistance of heavy rare earth elements As a result of investigating and studying the effects on the properties, in addition to the basic rare earth elements such as Nd and Pr, when an appropriate amount of Dy and Tb is added in combination, especially when Dy and Tb are added in amounts related to each other. Newly found that the heat resistance is remarkably improved.
That is, the present invention is an atomic percentage (at.%),
C: 0.1 to 15 at. %,
B: 0.5-15 at. %,
C + B: 2 to 30 at. %,
Co: 40 at. % Or less (excluding 0%),
Dy + Tb: 0.5-5 at. %so,
Preferably, Tb (at.%) / Dy (at.%): 0.1 to 0.8,
R: 8-20 at. %,
Where R represents at least one element selected from the group consisting of Nd, Pr, Ce, La, Y, Gd, Ho, Er, and Tm.
Balance: Fe and inevitable impurities,
The present invention provides a permanent magnet alloy having excellent heat resistance.
The heat resistance of this permanent magnet alloy is such that the irreversible demagnetization rate (200 ° C.) according to the following formula (1) is in the range of 0% to −20%, more preferably in the range of 0% to −15% (however, iHc ≧ 13 KOe) It is characterized in the point which shows.
Irreversible demagnetization factor (200 ° C.) = 100 × (A 200 −A 25 ) / A 25 (1)
However,
A 25: permeance coefficient (Pc) is after magnetization of the samples the shape was adjusted to 1 at 50 kOe, room temperature flux values were measured at (25 ℃) A 200: Samples were measured A 25 to 200 ° C. 120 Flux value measured by holding for a minute and then cooling to room temperature (25 ° C).
In particular, when the irreversible demagnetization factor is 0 to -20%, an appropriate combination of Dy and Tb, for example, Dy + Tb: 0.5 to 5 at. % And Dy is 0.3 to 4.9 at. %, And Tb is 0.1 to 4.7 at. % Range (range surrounded by points A, B, C and D in FIG. 1), and those having an irreversible demagnetization factor of 0 to −15% are shown in FIG. It can be obtained by the Dy content and Tb content in the range surrounded by C, H, E, F and G.
The preferred embodiment of the present invention When designing the equipment on the assumption that the operating temperature of the magnet may be 200 ° C. in some cases, the guideline is the irreversible demagnetization factor at 200 ° C. In other words, the value (minus) of the irreversible demagnetizing factor (200 ° C.) in the equation (1) should be as close to 0% as possible.
When an appropriate amount of C is contained in an R—B—Co—Fe sintered magnet alloy in which R is typically Nd or Nd + Pr, the value (minus) of the irreversible demagnetization rate (160 ° C.) approaches zero. . This fact is shown in the example of Japanese Patent Laid-Open No. 4-116144. However, the irreversible demagnetization factor (160 ° C.) shown in this publication is obtained by replacing A 200 in the above equation (1) with A 160 (A 160 is kept at 160 ° C. for 120 minutes and then cooled to room temperature. The measured flux value), and the permeance coefficient (Pc) is 3. That, Pc is after magnetization at 50KOe on a sample of the shape was adjusted to 3, A 25 and A 160 irreversible demagnetization was calculated by measuring the Contact flux values (160 ° C.). As seen in this publication, the effect of improving the heat resistance (and also the oxidation resistance effect) due to the C content is known, but the irreversible demagnetization rate at 200 ° C. was unknown. In addition, all conventional R- (Fe, Co) -B sintered magnet alloys (those that do not use C as an alloy element) have irreversible demagnetization values (200 ° C) of 0% to -20%. It was not done.
Since the present inventors have proposed in the above publication, in order to further improve the heat resistance of the R—Fe—Co—C—B based sintered magnet alloy, various test studies have been conducted on its alloy composition and manufacturing method. However, it has been found that a magnetic alloy having a remarkably low irreversible demagnetization rate can be obtained when a suitable amount of Dy and Tb is added in combination among rare earth elements. Even if Dy and Tb are added alone, the effect is not so much, but when both are added in combination, the heat resistance is improved.
Below, the outline of the reason for regulating the range of each component content of the magnet alloy of the present invention and the method for producing the alloy magnet according to the present invention will be described.
[C: 0.1 to 15 at. %]
C, as described in JP-A-4-116144, has the effect of improving the oxidation resistance by modifying the oxidizable property, which is a defect of the rare earth magnet, while maintaining the magnetic properties of the present magnet alloy well. Provide. It also contributes to a decrease in irreversible demagnetization rate. The effect of improving the oxidation resistance and heat resistance of C is 0.1 at. Less than% is not enough. However, 15 at. If it exceeds%, Br will fall. For this reason, 0.1-15 at. % C is contained, but the preferred C amount is 1.0 to 10 at. %, And more preferable C amount is 2.5 to 7 at. % Range.
[B: 0.5 to 15 at. %]
B is necessary for the formation of the magnetic phase, and for this purpose at least 0.5 at. % Required. However, excessive addition deteriorates the magnetic properties. For this reason, 0.5 to 15 at. % Of B is contained, but a preferable amount of B is 1.0 to 10 at. %, And more preferable B content is 1.5-7 at. % Range.
[C + B: 2 to 30 at. %]
In order to form a magnetic phase and improve oxidation resistance, C + B is at least 2 at. %. However, 30 at. %, The magnetic properties deteriorate, so C + B is set to 2 to 30 at. %.
[Co: 40 at. %Less than〕
Co has the effect of increasing the curie point while maintaining the magnetic characteristics. For this reason, it is essential to contain Co, but 40 at. %, The decrease in coercive force becomes noticeable, so 40 at. It is made to contain in the quantity below%.
[Dy + Tb: 0.5-5 at. %]
Dy and Tb are characteristic elements of the magnet of the present invention, and the irreversible demagnetization rate can be remarkably lowered by adding both elements in combination. Therefore, the total amount of Dy + Tb is 0.5 at. % Or more, but the total amount is 5 at. %, The heat resistance improvement effect is saturated and the magnetic properties may be deteriorated. Therefore, the total amount is 0.5 to 5 at. %. Note that the addition of Dy alone or Tb alone does not contribute much to the loss of irreversible demagnetization as shown in the comparative examples described later. From this, it is considered that the irreversible demagnetization rate decreases due to the synergistic effect of both elements. Further, the content ratio Tb (at.%) / Dy (at.%) Of both elements is preferably in the range of 0.1 to 0.8, and as shown in the examples described later, Dy is 0.3. -4.9 at. %, And Tb is 0.1 to 4.7 at. % In the range of 0% to -20%, preferably 0 to -15% of the irreversible demagnetization rate at 200 ° C. under the permeance coefficient = 1, and can be obtained. .
[R: 8-20 at. %]
As rare earth elements other than Dy and Tb, one or more of Nd, Pr, Ce, La, Y, Gd, Ho, Er, and Tm are used in an amount of 8 to 20 at. In the sintered magnet alloy, a magnetic phase and a grain boundary phase can be formed, and high iHc and Br can be maintained. Among these R elements, particularly preferable elements are Nd and Pr, and Nd alone or a combined addition of Nd and Pr is particularly desirable. R is 8 at. %, Sufficient Br cannot be obtained, and 20 at. Even if it exceeds%, sufficient Br cannot be obtained. The preferred R element cord content is 13 to 18 at. %.
The permanent magnet alloy of the present invention having the above component composition has an irreversible demagnetization factor (200) according to the above formula (1) of 0 to -20%, preferably a low value of 0 to -15%, and further 0 to- A permanent magnet alloy for high temperature applications is provided for the first time as a rare earth magnet other than an Sm-Co magnet. Previous B-containing rare earth magnets have been dealt with by using magnets with a high coercive force that are scheduled to be demagnetized when the temperature is raised. Since almost no magnetism occurs, it can continue to function as a permanent magnet with a high magnetic force. In particular, the magnet of the present invention can maintain the magnetic characteristics even when used for temperature rising purposes if iHc is 13 KOe or more, preferably 15 KOe or more. It can be said that the conventional magnet is an effective permanent magnet alloy as compared with the case where a magnet having a considerably high iHc had to be used in order to maintain the magnetic characteristics in the temperature rising application.
In order to produce the permanent magnet alloy of the present invention, a sintered magnet can be formed by a series of steps of melting, casting, crushing, molding and sintering. As a melting casting method, a vacuum melting / casting method, an inert gas atmosphere melting / casting method, a rapid cooling roll method, an atomizing method, or the like can be adopted. In order to make a sintered magnet with excellent magnetic properties and heat resistance, a heat treatment step is inserted between the casting step and the crushing step, and the pre-crushed one is heat treated at a temperature of 600 ° C. or higher in an inert gas atmosphere. Is preferable, and this can further reduce the irreversible demagnetization factor. In the sintering step, it is preferable to sinter at a temperature of 1000 to 1200 ° C. in an inert gas, gradually cool from the sintering temperature to 600 to 900 ° C., and then rapidly cool from the temperature. The irreversible demagnetization rate can be further reduced by this rapid cooling after sintering.
The sintered magnet alloy of the present invention can be produced according to the same method as the sintered magnet described in JP-A-4-116144, except for the heat treatment and the quenching treatment after sintering. The outline is as follows.
First, raw materials of each component weighed so as to have an alloy composition are melted at 1600 ° C. or higher in a vacuum melting furnace, and then rapidly cast into a water-cooled mold. The obtained ingot is heat-treated in an Ar atmosphere at 600 ° C. or higher as described above, and then coarsely pulverized with a jaw crusher. The obtained coarse powder is finely pulverized with a vibration ball mill to obtain a powder having an average particle diameter of 2 to 10 μm. These pulverization steps are also performed in an Ar atmosphere. In the latter pulverization step, a part of the C raw material can be added. That is, a part of the C raw material is put into a vacuum melting furnace, and the rest is added in this pulverization step. Carbon black is suitable as the C raw material, but organic substances containing C such as aliphatic hydrocarbons, higher fatty acid alcohols, higher fatty acids, fatty acid amides, metal soaps, fatty acid esters and the like can also be used.
The powder is then compacted in an external magnetic field. A molding pressure in the range of 1 to 5 t / cm 2 and an external magnetic field of 15 KOe or more are appropriate. This forming step is also preferably performed in an Ar atmosphere. The molded product is sintered in an Ar atmosphere at 1000 to 1200 ° C. for about 2 hours. Then, as described above, it is gradually cooled from the sintering temperature to 600 to 900 ° C., and then rapidly cooled from that temperature. In order to start the rapid cooling from 600 to 900 ° C., it is possible to carry out by a method of spraying a low-temperature inert gas from that temperature, a method of immersing in water or oil or a similar liquid. It is preferable to quench rapidly from ˜900 ° C. to 400 ° C. or lower at a cooling rate of −50 ° C./min or more, preferably −100 ° C./min or more.
Therefore, according to the present invention, each raw material of the alloy component is melt cast, the obtained alloy is pulverized, the powder is compacted, and the molded product is heated to 1000-1200 ° C. in an inert gas. In order to produce a sintered magnet alloy having the above-mentioned composition by sintering, the alloy before pulverization is heat-treated in an inert gas at a temperature of 600 ° C. or higher, and / or 1000 in an inert gas. Provided is a method for producing a permanent magnet alloy having excellent heat resistance, characterized in that sintering is performed at a temperature of ˜1200 ° C., followed by slow cooling from the sintering temperature to 600 ° C. to 900 ° C., followed by rapid cooling. At that time, a part of the C raw material can be added at the time of melting, and the other part of the C raw material can be added at the time of grinding the alloy.
The following are typical examples of the magnet of the present invention.
Example [Example 1]
An alloy having the following component composition was produced by the method described below.
Figure 0004034936
"Production Method"
Each component raw material was weighed so as to have the above-described alloy composition and melted in a vacuum melting furnace. At that time, a part of the C raw material was stored without being charged into the melting furnace. The obtained molten metal was quenched and cast from 1600 ° C. into a copper water-cooled mold to obtain an ingot alloy. The ingot alloy was heat-treated in an Ar atmosphere at the temperatures shown in Table 1 or not and coarsely pulverized with a diyoke lasher. The coarse powder and the stored C raw material were put into a vibrating ball mill. The mixture was pulverized to obtain a powder having an average particle size of 5 μm.
This powder was magnetically molded in an external magnetic field of 15 KOe at a pressure of 2 t / cm 2 , and this compact was sintered at 1100 ° C. for 2 hours in an Ar atmosphere, and from this sintering temperature to the rapid cooling start temperature shown in Table 1 Slow cooling was performed, and Ar was sprayed from the rapid cooling start temperature to quench at the indicated cooling rate. The obtained sintered product was evaluated for magnetic properties, heat resistance and oxidation resistance, and the results are shown in Table 1. The heat resistance and oxidation resistance were evaluated as follows.
"Heat resistance evaluation"
(1) Adjust the shape of the sample so that the measurement permeance coefficient (Pc) of the irreversible demagnetization factor at 200 ° C. becomes 1. Specifically, a 2.5 mm × 2.5 mm × 1.05 mm sample is cut out.
This sample is magnetized with an external magnetic field of 50 KOe, and the flux is measured at room temperature (25 ° C.). The flux was measured by attaching an iron core coil to a flux meter manufactured by Toyo Magnetic Industry Co., Ltd. The value of the flux at this time is A 25.
Next, this magnetized sample was held at 200 ° C. for 120 minutes. This heating and holding was performed in an oil bath filled with silicon oil. The temperature of the oil bath was precisely controlled to ± 0.1. The sample taken out from the oil bath is sufficiently cooled at room temperature, and the flux is measured again with the flux meter. The value of the flux at this time is A 200. An irreversible demagnetizing factor is calculated from the measured A 25 and A 200 by the following equation.
Irreversible demagnetization factor (200) (%) = 100 × (A 200 −A 25 ) / A 25
(2) Measurement of irreversible demagnetization factor at 160 ° C. The shape of the sample is adjusted so that the permeance coefficient (Pc) is 3 as in the example of Japanese Patent Laid-Open No. 4-116144, and the sample is heated and held in an oil bath. except that was 160 ° C. × 120 minutes, the measurements as well as a 25 and a 160 at 200 ° C. of the measures, calculates the irreversible demagnetization by the previous equation.
(3) Temperature coefficient of magnetic characteristics and coercive force After a sample is magnetized with an external magnetic field of 50 KOe, the magnetic characteristics at room temperature (25 ° C.) are measured with a vibration type magnetometer. The temperature coefficient of the coercive force is calculated by the following equation, where B 0 is the coercive force at room temperature and B 1 is the coercive force measured at 160 ° C. with a vibration type magnetometer.
Coercivity temperature coefficient (% / ℃)
= 100 × (B 1 -B 0 ) / B 0 / (160-25)
(4) Measurement of oxidation resistance The progress of rust is measured by a pressure cooker test (PCT). Specifically, the occurrence of rust is visually observed when the sample is held at 120 ° C., 2 atm, and 100% RH (saturated condition) for 100 hours using a tester manufactured by Tabai Espec.
Figure 0004034936
As can be seen from the results in Table 1, a permanent magnet alloy having an irreversible demagnetization rate (200 ° C.) of −3% was obtained (for example, a in Table 1). The irreversible demagnetization rate (160 ° C.) is −0.7% in the alloy a, and is almost 0%. Therefore, high magnetic force can be maintained even in high temperature applications.
Looking at the manufacturing conditions. For example, as is clear when a and b are compared, the irreversible demagnetization factor decreases when the ingot is heat-treated. Further, as is apparent from a comparison of a, c, and d, when the material is rapidly cooled from a temperature of at least 700 ° C. after sintering, the coercive force is improved and the irreversible demagnetization factor is also lowered.
[Examples 2 to 16] and [Comparative Examples 1 to 6]
A sintered product was produced under the same production conditions as in Example 1 except that the composition of the alloy was changed as shown in Table 2. The characteristics of the obtained sintered magnet were measured in the same manner as in Example 1, and the results are also shown in Table 2.
Figure 0004034936
As can be seen from Table 3, all of Examples 2 to 16 to which both Dy and Tb were added had a low irreversible demagnetization rate at 200 ° C, and the irreversible demagnetization rate at 160 ° C was almost 0%. Close to. In addition, it has a low temperature coefficient of coercive force and excellent oxidation resistance.
On the other hand, Comparative Example 1, 0.5 at. % Dy and Tb-free Comparative Example 2, and Dy-free 0.5 at. In the comparative example 4 of% Tb, the irreversible demagnetization rate at 200 ° C. is −95%, −95% and −91%, and when the temperature is raised to 200 ° C., the magnetic force is almost completely lost. That is, even if only one of Dy and Tb is added, there is no effect on the irreversible demagnetization rate at 200 ° C. Note that, even if Dy alone is increased as in Comparative Example 3, the irreversible demagnetization rate is lowered to some extent, but it is not sufficient. Moreover, since the amount of C is lower than the range prescribed | regulated by this invention in the comparative example 5, it is inferior to oxidation resistance. In Comparative Example 6, Dy was not added and Tb was 3.0 at. Although the heat resistance is better than Comparative Example 4, the irreversible demagnetization rate at 200 ° C. is as low as −30%.
FIG. 1 shows the Dy content (at.%) On the horizontal axis and the Tb content (at.%) On the vertical axis, for all the magnets in Table 2 (except for Comparative Example 5 where spot rust occurred). The amount of Dy and Tb contained in each indicates the level at which the irreversible demagnetization value at 200 ° C. is distributed. The numerical values plotted in FIG. 1 indicate the irreversible demagnetization value at 200 ° C. at that position.
From the results of FIG. 1, Dy: 2 to 3 at. %, Tb: 0.3 to 1.5 at. It can be seen that there is a peak in the irreversible demagnetization factor at 200 ° C. (the point where the irreversible demagnetization factor approaches 0%) in the% region. More specifically, the region where the irreversible demagnetization factor at 0 to −20% at 0 ° C. is the point A among the intersections of the straight lines (1) (2) (3) (4) (5) (6). , B, C, and D, and the region where the irreversible demagnetization factor at 0 ° C to 0 to -15% is a range surrounded by points B, C, H, E, F, and G I understand.
The straight lines (1) to (6) are expressed by the following equations.
Straight line (1): Dy = 0.3
Straight line (2): Tb + Dy = 0.5
Straight line (3): Tb = 0.1
Straight line (4): Tb = 0.1 Dy
Straight line (5): Tb = 0.8 Dy
Straight line (6): Tb + Dy = 5.0
The coordinates (Dyat.%, Tbat.%) Of the points A to H are as follows.
Point A (0.3, 4.7)
Point B (0.3, 0.2)
Point C (0.4, 0.1)
Point D (4.9, 0.1)
Point E (4.5, 0.5)
Point F (2.8, 2.2)
Point G (0.3, 0.24)
Point H (1.0, 0.1)
FIGS. 2 and 3 show the permeance of Example 24, which is considered to have the best heat resistance among the Example magnets disclosed in Japanese Patent Laid-Open No. 4-116144, and Example 2 according to the present invention. When a sample whose shape is adjusted so that the coefficient (Pc) is 3 is magnetized with 50 KOe (FIG. 2), and a sample whose shape is adjusted so that Pc is 1 is magnetized with 50 KOe (FIG. 3). ) Shows the results of measuring the irreversible demagnetization factor at different measurement temperatures. The magnet (referred to as a public magnet) in Example 24 of JP-A-4-116144 has a composition of 9Nd-9Dy-59Fe-15Co-1B-7C, and has an irreversible demagnetization rate at 160 ° C. at Pc = 3. It is described in the publication as being -1.0%.
As shown in FIG. 2, in the sample whose shape is adjusted so that Pc = 3, the irreversible demagnetization rate at 160 ° C. is −1.0% for the open magnet, and −0. It is 7% and there is not much difference. However, the irreversible demagnetization factor at 200 ° C. with Pc = 3 is −12.9% for the public magnet, whereas it is improved to −1.9% for Example 2 of the present invention. Such a tendency is more clearly seen in FIG. 3 using a sample whose shape is adjusted so that Pc becomes 1. That is, at Pc = 1, the irreversible demagnetization rate at 160 ° C. is −9.4% for the disclosed magnet, whereas it is improved to −1.7% in Example 2 of the present invention, and the irreversible decrease at 200 ° C. The magnetic susceptibility is −22.3% for the open magnet, whereas it is improved to −4% in Example 2 of the present invention.
As described above, according to the present invention, in the field of R-Fe (Co) -B magnets, permanent magnet alloys having excellent heat resistance and oxidation resistance that have not been achieved so far can be obtained. It is done. Therefore, an inexpensive and excellent magnetic property material can be provided as a permanent magnet to be mounted on a device whose temperature rise is expected.
[Brief description of the drawings]
FIG. 1 is a distribution diagram of the irreversible demagnetization factor in which the values of the irreversible demagnetization factor at 200 ° C. of the magnets in Table 2 are arranged by the contents of Dy and Tb.
FIG. 2 shows a sample obtained by adjusting the shape of the magnet of Example 24 of JP-A-4-116144 and that of Example 2 according to the present invention so that the permeance coefficient (Pc) is 3 at 50 KOe. It is the figure which showed the result of having measured the irreversible demagnetization factor by changing measurement temperature about the case where it magnetized.
FIG. 3 is a view showing the irreversible demagnetization factor measurement results similar to those of FIG. 2 except that a sample whose shape is adjusted so that the permeance coefficient (Pc) is 1 is used.

Claims (11)

原子百分率（ａｔ．％）で、
Ｃ：０.１〜１５ａｔ．％、
Ｂ：０.５〜１５ａｔ．％、
Ｃ＋Ｂ：２〜３０ａｔ．％、
Ｃｏ：４０ａｔ．％以下（０％を含まず）、
Ｄｙ＋Ｔｂ：０.５〜５ａｔ．％、
Ｒ：８〜２０ａｔ．％、
ただし、ＲはＮｄ、Ｐｒ、Ｃｅ、Ｌａ、Ｙ、Ｇｄ、Ｈｏ、ＥｒおよびＴｍからなる群から選ばれた少なくとも一種の元素を表す、
残部：Ｆｅおよび不可避的不純物、
からなり、Ｔｂ（ａｔ．％）／Ｄｙ（ａｔ．％）：０ . １〜０ . ８である耐熱性に優れた永久磁石合金。Atomic percentage (at.%)
C: 0.1-15 at. %,
B: 0.5 to 15 at. %,
C + B: 2 to 30 at. %,
Co: 40 at. % Or less (excluding 0%),
Dy + Tb: 0.5-5 at. %,
R: 8-20 at. %,
Where R represents at least one element selected from the group consisting of Nd, Pr, Ce, La, Y, Gd, Ho, Er, and Tm.
Balance: Fe and inevitable impurities,
Tona Ri, Tb (at%.) / Dy (at%.):.. 0 1~0 8 der Ru excellent heat resistance permanent magnet alloy. Ｃ：１〜１０ａｔ．％である請求の範囲１に記載の耐熱性に優れた永久磁石合金。C: 1 to 10 at. The permanent magnet alloy having excellent heat resistance according to claim 1 . ＲはＮｄ単独またはＮｄとＰｒである請求の範囲１または２に記載の耐熱性に優れた永久磁石合金。The permanent magnet alloy excellent in heat resistance according to claim 1 or 2, wherein R is Nd alone or Nd and Pr. ｉＨｃが１３ＫＯｅ以上である請求の範囲１、２または３に記載の耐熱性に優れた永久磁石合金。4. The permanent magnet alloy having excellent heat resistance according to claim 1 , wherein iHc is 13 KOe or more. 原子百分率（ａｔ．％）で、
Ｃ：０.１〜１５ａｔ．％、
Ｂ：０.５〜１５ａｔ．％、
Ｃ＋Ｂ：２〜３０ａｔ．％、
Ｃｏ：４０ａｔ．％以下（０％を含まず）、
Ｄｙ＋Ｔｂ：０.５〜５ａｔ．％、
Ｒ：８〜２０ａｔ．％、
ただし、ＲはＮｄ、Ｐｒ、Ｃｅ、Ｌａ、Ｙ、Ｇｄ、Ｈｏ、ＥｒおよびＴｍからなる群から選ばれた少なくとも一種の元素を表す、
残部：Ｆｅおよび不可避的不純物、
からなり、下記の（１）式に従う不可逆減磁率（２００℃）が０％〜−２０％の範囲にある（但しｉＨｃ≧１３ＫＯｅである）耐熱性に優れたＲ−Ｂ−Ｃ−Ｃｏ−Ｆｅ系焼結磁石合金。
不可逆減磁率（２００℃）＝１００×（Ａ200−Ａ25）／Ａ25・・（１）
ただし、
Ａ25：パーミアンス係数（Ｐｃ）が１になるように形状を調整した試料を５０ＫＯｅで着磁後、室温（２５℃）で測定したフラックス値。
Ａ200：Ａ25を測定した試料を２００℃に１２０分間保持したあと室温（２５℃）まで冷却して測定したフラックス値。Atomic percentage (at.%)
C: 0.1-15 at. %,
B: 0.5 to 15 at. %,
C + B: 2 to 30 at. %,
Co: 40 at. % Or less (excluding 0%),
Dy + Tb: 0.5-5 at. %,
R: 8-20 at. %,
Where R represents at least one element selected from the group consisting of Nd, Pr, Ce, La, Y, Gd, Ho, Er, and Tm.
Balance: Fe and inevitable impurities,
From it, the irreversible demagnetization according to the following equation (1) (200 ° C.) is in the range of 0% to -20% (although iHc ≧ 13 kOe is) excellent in heat resistance R-B-C-Co- Fe Sintered magnet alloy.
Irreversible demagnetization factor (200 ° C.) = 100 × (A 200 −A 25 ) / A 25 .. (1)
However,
A 25 : A flux value measured at room temperature (25 ° C.) after magnetizing a sample whose shape is adjusted so that the permeance coefficient (Pc) is 1 at 50 KOe.
A 200 : A flux value measured by holding the sample measured for A 25 at 200 ° C. for 120 minutes and then cooling to room temperature (25 ° C.). Ｄｙ：０.３〜４.９ａｔ．％、Ｔｂ：０.１〜４.７ａｔ．％で２００℃での不可逆減磁率が０〜−２０％である請求の範囲５に記載の耐熱性に優れたＲ−Ｂ−Ｃ−Ｃｏ−Ｆｅ系焼結磁石合金。Dy: 0.3-4.9 at. %, Tb: 0.1 to 4.7 at. The R—B—C—Co—Fe based sintered magnet alloy having excellent heat resistance according to claim 5 , wherein the irreversible demagnetization rate at 200 ° C. is 0 to −20%. ＤｙとＴｂの含有量（ａｔ．％）が図１に示される点Ｂ、Ｃ、Ｈ、Ｅ、ＦおよびＧで囲われる範囲にあり、２００℃での不可逆減磁率が０〜−１５％である請求の範囲５に記載の耐熱性に優れたＲ−Ｂ−Ｃ−Ｃｏ−Ｆｅ系焼結磁石合金。The content of Dy and Tb (at.%) Is in the range surrounded by points B, C, H, E, F and G shown in FIG. 1, and the irreversible demagnetization factor at 200 ° C. is 0 to −15%. The R—B—C—Co—Fe based sintered magnet alloy having excellent heat resistance according to claim 5 . 不可逆減磁率（２００℃）が０％〜−５％の範囲にある請求の範囲５に記載の耐熱性に優れたＲ−Ｂ−Ｃ−Ｃｏ−Ｆｅ系焼結磁石合金。The R—B—C—Co—Fe based sintered magnet alloy having excellent heat resistance according to claim 5, wherein the irreversible demagnetization rate (200 ° C.) is in the range of 0% to −5%. 合金成分の各原料を溶解鋳造し、得られた合金を粉砕し、その粉体を圧粉成形し、その成形品を不活性ガス中で１０００〜１２００℃の温度で焼結して、下記の成分組成の焼結磁石合金を製造する方法において、前記粉砕前の合金を６００℃以上の温度で不活性ガス中で熱処理することを特徴とする耐熱性に優れた永久磁石合金の製造法。
〔焼結磁石合金の成分組成〕
Ｃ：０.１〜１５ａｔ．％、
Ｂ：０.５〜１５ａｔ．％、
Ｃ＋Ｂ：２〜３０ａｔ．％、
Ｃｏ：４０ａｔ．％以下（０％を含まず）、
Ｄｙ＋Ｔｂ：０.５〜５ａｔ．％、
Ｒ：８〜２０ａｔ．％、
ただし、ＲはＮｄ、Ｐｒ、Ｃｅ、Ｌａ、Ｙ、Ｇｄ、Ｈｏ、ＥｒおよびＴｍからなる群から選ばれた少なくとも一種の元素を表す、
残部：Ｆｅおよび不可避的不純物。Each raw material of the alloy component is melt cast, the obtained alloy is pulverized, the powder is compacted, and the molded product is sintered in an inert gas at a temperature of 1000 to 1200 ° C. A method for producing a sintered magnet alloy having a component composition, wherein the pre-ground alloy is heat-treated in an inert gas at a temperature of 600 ° C. or higher.
[Component composition of sintered magnet alloy]
C: 0.1-15 at. %,
B: 0.5 to 15 at. %,
C + B: 2 to 30 at. %,
Co: 40 at. % Or less (excluding 0%),
Dy + Tb: 0.5-5 at. %,
R: 8-20 at. %,
Where R represents at least one element selected from the group consisting of Nd, Pr, Ce, La, Y, Gd, Ho, Er, and Tm.
The balance: Fe and inevitable impurities. 不活性ガス中で１０００〜１２００℃の温度で焼結したあと、その焼結温度から６００〜９００℃まで徐冷し、その後急冷する請求の範囲９に記載の永久磁石合金の製造法。The method for producing a permanent magnet alloy according to claim 9, wherein sintering is performed at a temperature of 1000 to 1200 ° C in an inert gas, and thereafter, it is gradually cooled from the sintering temperature to 600 to 900 ° C and then rapidly cooled. Ｃ原料の一部を溶解時に添加し、Ｃ原料の他部を合金の粉砕時に添加する請求の範囲９または１０に記載の永久磁石合金の製造法。The method for producing a permanent magnet alloy according to claim 9 or 10, wherein a part of the C raw material is added at the time of melting and the other part of the C raw material is added at the time of pulverizing the alloy.
JP2000562572A 1998-07-29 1999-07-28 Permanent magnet alloy with excellent heat resistance and manufacturing method thereof Expired - Fee Related JP4034936B2 (en)

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