JP3652818B2

JP3652818B2 - Corrosion-resistant permanent magnet and method for manufacturing the same

Info

Publication number: JP3652818B2
Application number: JP27720096A
Authority: JP
Inventors: 文秋菊井; 雅子鈴木; 吉村　　公志
Original assignee: Neomax Co Ltd
Current assignee: Hitachi Metals Ltd
Priority date: 1996-09-26
Filing date: 1996-09-26
Publication date: 2005-05-25
Anticipated expiration: 2016-09-26
Also published as: JPH10106816A

Description

【０００１】
【発明の属する技術分野】
この発明は、高磁気特性を有し、かつ密着性がすぐれ、耐食性、耐酸、耐アルカリ性、耐摩耗性にすぐれた耐食性被膜を設けたＲ−Ｆｅ−Ｂ系永久磁石に係り、耐食性、特に塩水噴霧試験において発錆が少なく、初期磁石特性からの劣化が少なく極めて安定した磁石特性を有する耐食性永久磁石及びその製造方法に関する。
【０００２】
【従来の技術】
先に、ＮｄやＰｒを中心とする資源的に豊富な軽希土類を用いてＢ，Ｆｅを主成分とし、高価なＳｍやＣｏを含有せず、従来の希土類コバルト磁石の最高特性を大幅に超える新しい高性能永久磁石として、Ｒ−Ｆｅ−Ｂ系永久磁石が提案されている（特開昭５９−４６００８号公報、特開昭５９−８９４０１号公報）。
【０００３】
前記磁石合金のキュリー点は、一般に３００℃〜３７０℃であるが、Ｆｅの一部をＣｏにて置換することにより、より高いキュリー点を有するＲ−Ｆｅ−Ｂ系永久磁石（特開昭５９−６４７３３号、特開昭５９−１３２１０４号）を得ており、さらに、前記Ｃｏ含有のＲ−Ｆｅ−Ｂ系希土類永久磁石と同等以上のキュリー点並びにより高い（ＢＨ）ｍａｘを有し、その温度特性、特にｉＨｃを向上させるため、希土類元素（Ｒ）としてＮｄやＰｒ等の軽希土類を中心としたＣｏ含有のＲ−Ｆｅ−Ｂ系希土類永久磁石のＲの一部にＤｙ、Ｔｂ等の重希土類のうち少なくとも１種を含有することにより、２５ＭＧＯｅ以上の極めて高い（ＢＨ）ｍａｘを保有したままで、ｉＨｃをさらに向上させたＣｏ含有のＲ−Ｆｅ−Ｂ系希土類永久磁石が提案（特開昭６０−３４００５号公報）されている。
【０００４】
しかしながら、上記のすぐれた磁気特性を有するＲ−Ｆｅ−Ｂ系磁気異方性焼結体からなる永久磁石は主成分として、希土類元素及び鉄を含有する活性な化合物組織を有するため、磁気回路に組込んだ場合に、磁石表面に生成する酸化物により、磁気回路の出力低下及び磁気回路間のばらつきを惹起し、また、表面酸化物の脱落による周辺機器への汚染の問題があった。
【０００５】
【発明が解決しようとする課題】
そこで、上記のＲ−Ｆｅ−Ｂ系永久磁石の耐食性の改善のため、磁石体表面に無電解めっき法あるいは電解めっき法により耐食性金属めっき層を被覆した永久磁石（特公平３−７４０１２号）が提案されている。
【０００６】
上記めっき法では永久磁石体が焼結体で有孔性のため、この孔内にめっき前処理での酸性溶液またはアルカリ溶液が残留し、経年変化とともに腐食する恐れがあり、また磁石体の耐薬品性が劣るため、めっき時に磁石表面が腐食されて密着性、防蝕性が劣る問題があった。また、耐食性めっきを設けても、温度６０℃、相対湿度９０％の条件下の耐食性試験で１００時間放置にて、磁石特性は初期磁石特性が１０％以上劣化し、非常に不安定であった。
【０００７】
そのため、Ｒ−Ｆｅ−Ｂ系永久磁石の耐食性の改善向上のため、前記磁石表面にイオンプレーティング法、イオンスパッタリング法等により、ＴｉＮ、Ａｌ、Ｔｉ被膜を被着して耐食性の改善向上することが提案（特公平５−１５０４３号）されている。
【０００８】
上記のＴｉＮ被膜はＲ−Ｆｅ−Ｂ系磁石体と結晶構造の他、熱膨張係数、延性等が相違するため密着性が悪く、またＴｉあるいはＡｌ被膜は密着性、耐食性は良好であるが、耐摩耗性が低い等の欠点があり、これを解決するためＲ−Ｆｅ−Ｂ系永久磁石体表面にＴｉとＴｉＮの積層被膜を被着することが提案（特開昭６３−９９１９号公報）されている。ところが、Ｔｉ被膜とＴｉＮ被膜は結晶構造、熱膨張係数及び延性等が異なるため、その密着性が悪く剥離等を生じて、耐食性の低下を招来する問題があった。
【０００９】
この発明は、Ｒ−Ｆｅ−Ｂ系永久磁石下地との密着性にすぐれ、耐摩耗性、耐食性の改善向上を目的に、特に温度３４℃〜３６℃、５％中性ＮａＣｌ溶液による塩水噴霧試験において、長時間の試験でも初期磁石特性からの劣化が極力少なく、安定した高磁石特性、耐磨耗性、耐食性を有するＲ−Ｆｅ−Ｂ系永久磁石並びにその製造方法を提供することを目的にする。
【００１０】
【課題を解決するための手段】
発明者らは、すぐれた耐食性、特に温度３４℃〜３６℃、５％中性ＮａＣｌ溶液の塩水噴霧により発錆するまでの時間を長時間に延長でき、下地との密着性がすぐれ、被着した耐食性被膜の耐食性、耐磨耗性により、その磁石特性が安定したＲ−Ｆｅ−Ｂ系永久磁石を目的に、永久磁石体表面へのＴｉ_1-xＡｌ_xＮ被膜形成法について種々検討した結果、下地被膜が前記の提案されたＴｉ被膜、あるいはＡｌ被膜のみの場合はＲ−Ｆｅ−Ｂ系磁石全体としての電位はＴｉあるいはＡｌよりも「貴」であるが、磁石内のＮｄ部分など局部的に非常に「卑」な部分が存在するため、苛酷な耐食性試験の塩水噴霧試験ではＴｉＮ被膜のわずかなピンホールを通して発錆が起こり易いことを知見した。
【００１１】
そこで、発明者らは、Ｔｉ_1-xＡｌ_xＮ被膜形成法についてさらに検討した結果、Ｔｉ_1-xＡｌ_xＮ被膜の下地として、まず永久磁石体表面にＴｉ被膜層を、次いでＡｌ被膜層を設けることによって、Ｔｉに比べてＡｌの方が電気化学的に若干「卑」であるため、Ａｌ被膜層がＴｉ被膜層に対して犠牲被膜として作用し、表面層のＴｉ_1-xＡｌ_xＮ被膜の僅かなピンホールから腐食が発生しても、素地の磁石体まで下地膜を一気に貫通することなく、下地層のＴｉ被膜と表面層のＴｉ_1-xＡｌ_xＮ被膜の間の中間層としてＡｌ被膜が存在する限り、下地層のＴｉ被膜に被覆されたＲ−Ｆｅ−Ｂ系永久磁石は保護され、さらにＡｌ被膜上にＴｉ_1-xＡｌ_xＮ被膜を形成することにより、界面には
Ｔｉ_1- _■Ａｌ_■Ｎ_■なるＴｉ，Ａｌ，Ｎの複合被膜が生成し、このＴｉ_1- _■Ａｌ_■Ｎ_■の組成、膜厚は、基板温度、バイアス電圧、成膜スピード、Ｔｉ_1-xＡｌ_xＮ組成等によって変化し、Ｔｉ_1-xＡｌ_xＮ界面に向かってＴｉ，Ｎが連続的に増加する組成となっており、これにより、Ａｌ被膜とＴｉ_1-xＡｌ_xＮ被膜との密着性は著しく改善できることを知見し、この発明を完成した。
【００１２】
すなわち、この発明は、
主相が正方晶相からなるＲ−Ｆｅ−Ｂ系永久磁石体表面に形成された膜厚０．１μｍ〜３．０μｍのＴｉ被膜上に、膜厚０．１μｍ〜５μｍのＡｌ被膜を介して膜厚０．５μｍ〜１０μｍのＴｉ_1-xＡｌ_xＮ（但し、０．０３＜ｘ＜０．７０）被膜層を有する耐食性永久磁石である。
【００１３】
【発明の実施の形態】
この発明は、主相が正方晶相からなるＲ−Ｆｅ−Ｂ系永久磁石体の清浄化された表面に、薄膜形成法により、膜厚０．１μｍ〜３．０μｍのＴｉ被膜を形成後、前記Ｔｉ被膜上に膜厚０．１μｍ〜５μｍのＡｌ被膜を形成し、前記Ａｌ被膜上に膜厚０．５μｍ〜１０μｍの
Ｔｉ_1-xＡｌ_xＮ（但し、０．０３＜ｘ＜０．７０）被膜層を形成したことを特徴とする。耐食性永久磁石の製造方法の一例を以下に詳述する。
【００１４】
１）例えば、アークイオンプレーティング装置を用いて、真空容器を到達真空度１×１０^-3ｐａ以下まで真空排気した後、Ａｒガス圧１０ｐａ、−５００ＶでＡｒイオンによる表面スパッターにてＲ−Ｆｅ−Ｂ系磁石体表面を清浄化する。
次に、Ａｒガス圧０．１ｐａ、バイアス電圧−８０Ｖにより、ターゲットのＴｉを蒸発させて、アークイオンプレーティング法にて、磁石体表面に０．１μｍ〜３．０μｍ膜厚のＴｉ被膜層を形成する。
【００１５】
２）次に、Ａｒガス圧０．１ｐａ、バイアス電圧−５０Ｖにより、ターゲットのＡｌを蒸発させて、アークイオンプレーティング法にて、Ｔｉ被膜層上に０．１μｍ〜５μｍ膜厚のＡｌ被膜層を形成する。
【００１６】
３）続いて、ターゲットとして合金Ｔｉ_1-yＡｌ_y（但し、０．０３＜ｙ＜０．８０）を用い、基板の磁石温度を２５０℃に保持し、Ｎ₂ガス圧３ｐａ、バイアス電圧−１２０Ｖの条件にて、Ａｌ被膜層上に特定厚のＴｉ_1-xＡｌ_xＮ（但し、０．０３＜ｘ＜０．７０）被膜層を形成する。
【００１７】
この発明において、Ｒ−Ｆｅ−Ｂ系永久磁石体表面に被着のＴｉ被膜層、Ａｌ被膜層、Ｔｉ_1-xＡｌ_xＮ被膜層の形成方法としては、イオンプレーティング法や蒸着法などの公知の薄膜形成法を適宜選定できるが、被膜の緻密性、均一性、被膜形成速度等の理由から、イオンプレーティング法、イオン反応プレーティング法が好ましい。
【００１８】
被膜生成時の基板磁石の温度は２００℃〜５００℃に設定するのが好ましく、２００℃未満では基板磁石との反応密着が十分でなく、また５００℃を超えると常温（−２５℃）との温度差が大きくなり、処理後の冷却過程で被膜に亀裂が入り、一部基板より剥離を発生するため、基板磁石の温度を２００℃〜５００℃に設定する。
【００１９】
この発明において、磁石体表面のＴｉ被膜厚を０．１μｍ〜３．０μｍに限定した理由は、０．１μｍ未満では磁石表面との密着性が十分でなく、３．０μｍを越えると効果的には問題ないが、下地膜としてはコスト上昇を招来して、実用的でなく好ましくないので、Ｔｉ被膜厚は０．１μｍ〜３．０μｍとする。
【００２０】
また、この発明において、Ｔｉ被膜上に形成されるＡｌ被膜厚を０．１μｍ〜５μｍに限定した理由は、０．１μｍ未満ではＴｉ被膜表面にＡｌが均一に付着しにくく、中間層膜としての効果が十分でなく、また５μｍを越えると効果的には問題ないが、中間層膜としてコスト上昇を招来して好ましくないので、Ａｌ被膜厚は０．１μｍ〜５μｍとする。
【００２１】
また、Ｔｉ_1-xＡｌ_xＮ（但し、０．０３＜ｘ＜０．７０）被膜厚を０．５μｍ〜１０μｍに限定した理由は、０．５μｍ未満ではＴｉ_1-xＡｌ_xＮ被膜としての耐食性、耐摩耗性が十分でなく、１０μｍを超えると効果的には問題ないが、製造コスト上昇を招来するので好ましくない。また、Ｔｉ_1-xＡｌ_xＮ被膜において、ｘの値を限定した理由は、０．０３未満ではＴｉ_1-xＡｌ_xＮ被膜としての性能（耐食性、耐摩耗性）が得られず、また０．７０を超えても性能の向上が得られないためである。
【００２２】
この発明の永久磁石に用いる希土類元素Ｒは、組成の１０原子％〜３０原子％を占めるが、Ｎｄ、Ｐｒ、Ｄｙ、Ｈｏ、Ｔｂのうち少なくとも１種、あるいはさらに、Ｌａ、Ｃｅ、Ｓｍ、Ｇｄ、Ｅｒ、Ｅｕ、Ｔｍ、Ｙｂ、Ｌｕ、Ｙのうち少なくとも１種を含むものが好ましい。また、通常Ｒのうち１種をもって足りるが、実用上は２種以上の混合物（ミッシュメタル、ジジム等）を入手上の便宜等の理由により用いることができる。なお、このＲは純希土類元素でなくてもよく、工業上入手可能な範囲で製造上不可避な不純物を含有するものでも差支えない。
【００２３】
Ｒは、上記系永久磁石における必須元素であって、１０原子％未満では結晶構造がα−鉄と同一構造の立方晶組織となるため、高磁気特性、特に高保磁力が得られず、３０原子％を超えるとＲリッチな非磁性相が多くなり、残留磁束密度（Ｂｒ）が低下してすぐれた特性の永久磁石が得られない。よって、Ｒ１０原子％〜３０原子％の範囲が望ましい。
【００２４】
Ｂは、上記系永久磁石における必須元素であって、２原子％未満では菱面体構造が主相となり、高い保磁力（ｉＨｃ）は得られず、２８原子％を超えるとＢリッチな非磁性相が多くなり、残留磁束密度（Ｂｒ）が低下するため、すぐれた永久磁石が得られない。よって、Ｂは２原子％〜２８原子％の範囲が望ましい。
【００２５】
Ｆｅは、上記系永久磁石において必須元素であり、６５原子％未満では残留磁束密度（Ｂｒ）が低下し、８０原子％を超えると高い保磁力が得られないので、Ｆｅは６５原子％〜８０原子％の含有が望ましい。また、Ｆｅの一部をＣｏで置換することは、得られる磁石の磁気特性を損うことなく、温度特性を改善することができるが、Ｃｏ置換量がＦｅの２０％を超えると、逆に磁気特性が劣化するため、好ましくない。Ｃｏの置換量がＦｅとＣｏの合計量で５原子％〜１５原子％の場合は、（Ｂｒ）は置換しない場合に比較して増加するため、高磁束密度を得るために好ましい。
【００２６】
また、Ｒ、Ｂ、Ｆｅの他、工業的生産上不可避的不純物の存在を許容でき、例えば、Ｂの一部を４．０ｗｔ％以下のＣ、２．０ｗｔ％以下のＰ、２．０ｗｔ％以下のＳ、２．０ｗｔ％以下のＣｕのうち少なくとも１種、合計量で２．０ｗｔ％以下で置換することにより、永久磁石の製造性改善、低価格化が可能である。
【００２７】
さらに、Ａｌ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｂｉ、Ｎｂ、Ｔａ、Ｍｏ、Ｗ、Ｓｂ、Ｇｅ、Ｓｎ、Ｚｒ、Ｎｉ、Ｓｉ、Ｚｎ、Ｈｆ、のうち少なくとも１種は、Ｒ−Ｆｅ−Ｂ系永久磁石材料に対してその保磁力、減磁曲線の角型性を改善あるいは製造性の改善、低価格化に効果があるため添加することができる。なお、添加量の上限は、磁石材料の（ＢＨ）ｍａｘを２０ＭＧＯｅ以上とするには、Ｂｒが少なくとも９ｋＧ以上必要となるため、該条件を満す範囲が望ましい。
【００２８】
また、この発明の永久磁石は平均結晶粒径が１〜８０μｍの範囲にある正方晶系の結晶構造を有する化合物を主相とし、体積比で１％〜５０％の非磁性相（酸化物相を除く）を含むことを特徴とする。
この発明による永久磁石は、保磁力ｉＨｃ≧１ｋＯｅ、残留磁束密度Ｂｒ＞４ｋＧを示し、最大エネルギー積（ＢＨ）ｍａｘは、（ＢＨ）ｍａｘ≧１０ＭＧＯｅを示し、最大値は２５ＭＧＯｅ以上に達する。
【００２９】
【実施例】
実施例１
公知の鋳造インゴットを粉砕し、微粉砕後に成形、焼結、熱処理後に、１５Ｎｄ−１Ｄｙ７６Ｆｅ−８Ｂ組成の径１２ｍｍ×厚み２ｍｍ寸法の磁石体試験片を得た。その磁石特性を表１に示す。
【００３０】
真空容器内を１×１０^-3ｐａ以下に真空排気し、Ａｒガス圧１０ｐａ、−５００Ｖで２０分間、表面スパッターを行って、磁石体表面を清浄化した後、Ａｒガス圧０．１ｐａ、バイアス電圧−８０Ｖ、基板磁石温度を２８０℃にて、ターゲットとして金属Ｔｉをアークイオンプレーティング法にて、磁石体表面に１μｍ厚のＴｉ被膜層を形成する。
【００３１】
その後、Ａｒガス圧０．１ｐａ、バイアス電圧−５０Ｖ、基板磁石温度を２５０℃にして、ターゲットとして金属Ａｌを用いて、アークイオンプレーティング法にて、Ｔｉ被膜表面に２μｍ厚のＡｌ被膜層を形成した。次に、基板磁石温度３２０℃、バイアス電圧−１００Ｖで、Ｎ₂ガス１ｐａにて、ターゲットとして合金Ｔｉ_0.45Ａｌ_0.55をアークイオンプレーティング法にてＡｌ被膜表面に膜厚２μｍのＴｉ_1-xＡｌ_xＮ被膜層を形成した。なお、生成被膜の組成はＴｉ_0.5Ａｌ_0.5Ｎであった。
【００３２】
その後、放冷後、得られたＴｉＮ被膜を表面に有する永久磁石を温度３５℃、５％中性ＮａＣｌ溶液の条件による塩水噴霧試験（ＪＩＳＺ２３７１）を行い、発錆時間を測定して、その結果を磁石特性と共に表２に表す。
【００３３】
比較例１
実施例１と同一組成の磁石体試験片を用いて、実施例１と同一条件にて磁石体試験片にＴｉ被膜層を３μｍ形成後、実施例１と同一条件にて同一膜厚（２μｍ）のＴｉ_0.5Ａｌ_0.5Ｎ被膜層を形成後、実施例１と同一条件の塩水噴霧試験を行い、発錆時間を測定して、その結果を磁石特性と共に表２に表す。
【００３４】
比較例２
実施例１と同一組成の磁石体試験片を用いて、前記磁石体表面に実施例１と同一条件にてＡｌ被膜層を３μｍ形成後、実施例１と同一条件にて、同一膜厚のＴｉ_0.5Ａｌ_0.5Ｎ被膜層を形成後、実施例１と同一条件の塩水噴霧試験を行い、発錆時間を測定して、その結果を磁石特性と共に表２に表す。
【００３５】
【表１】

【００３６】
【表２】

【００３７】
【発明の効果】
この発明は、Ｒ−Ｆｅ−Ｂ系永久磁石体表面をイオンスパッター法等により清浄化した後、前記磁石体表面にイオンプレーティング法等の薄膜形成法によりＴｉ被膜を形成後、更にＡｌ被膜を中間層として形成後、Ｎ₂ガス中にてイオン反応プレーティング等の薄膜形成法により、Ｔｉ_1-xＡｌ_xＮ被膜を形成したことを特徴とし、中間層としてＡｌ被膜層を存在させることにより、永久磁石体と下地層のＴｉ被膜に対して犠牲被膜として作用し、Ｔｉ被膜間の密着性が著しく改善されると共に、苛酷な耐食性試験の塩水噴霧試験においても発錆時間を延長して、すぐれた耐食性、耐磨耗性により、その磁石特性の安定したＲ−Ｆｅ−Ｂ系永久磁石が得られる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an R-Fe-B permanent magnet provided with a corrosion-resistant coating film having high magnetic properties, excellent adhesion, and excellent corrosion resistance, acid resistance, alkali resistance, and wear resistance. The present invention relates to a corrosion-resistant permanent magnet having little rusting in a spray test and having extremely stable magnet characteristics with little deterioration from initial magnet characteristics, and a method for producing the same.
[0002]
[Prior art]
First, B and Fe are used as the main components using lightly abundant rare earths centering on Nd and Pr, they do not contain expensive Sm and Co, and greatly exceed the highest characteristics of conventional rare earth cobalt magnets. R-Fe-B permanent magnets have been proposed as new high performance permanent magnets (Japanese Patent Laid-Open Nos. 59-46008 and 59-89401).
[0003]
The Curie point of the magnet alloy is generally 300 ° C. to 370 ° C., but an R—Fe—B permanent magnet having a higher Curie point can be obtained by substituting part of Fe with Co (Japanese Patent Laid-Open No. Sho 59). -64733, JP-A-59-132104), and has a Curie point equal to or higher than that of the Co-containing R-Fe-B rare earth permanent magnet and a higher (BH) max. In order to improve temperature characteristics, particularly iHc, a part of R of a Co-containing R—Fe—B rare earth permanent magnet mainly including a light rare earth such as Nd or Pr is used as a rare earth element (R) such as Dy and Tb. Proposed Co-containing R-Fe-B rare earth permanent magnet with further improved iHc while retaining extremely high (BH) max of 25 MGOe or more by containing at least one of heavy rare earths JP 60-34005 JP) are.
[0004]
However, a permanent magnet made of an R-Fe-B magnetic anisotropic sintered body having excellent magnetic properties has an active compound structure containing a rare earth element and iron as a main component. When incorporated, the oxide generated on the surface of the magnet causes a decrease in the output of the magnetic circuit and a variation between the magnetic circuits, and there is a problem of contamination of peripheral devices due to the drop of the surface oxide.
[0005]
[Problems to be solved by the invention]
Therefore, in order to improve the corrosion resistance of the R-Fe-B permanent magnet, a permanent magnet (Japanese Patent Publication No. 3-74012) in which a magnet body surface is coated with a corrosion-resistant metal plating layer by an electroless plating method or an electrolytic plating method. Proposed.
[0006]
In the above plating method, since the permanent magnet body is a sintered body and porous, the acidic solution or alkali solution in the plating pretreatment remains in the hole, and there is a risk of corrosion with aging. Due to inferior chemical properties, the magnet surface was corroded during plating, resulting in inferior adhesion and corrosion resistance. Even when corrosion-resistant plating was provided, the magnetic properties of the magnets deteriorated by more than 10% in the corrosion resistance test under the conditions of a temperature of 60 ° C. and a relative humidity of 90%, and the initial magnet properties deteriorated by 10% or more. .
[0007]
Therefore, in order to improve the corrosion resistance of the R—Fe—B permanent magnet, the TiN, Al and Ti coatings are deposited on the magnet surface by ion plating, ion sputtering, etc. to improve the corrosion resistance. Has been proposed (Japanese Patent Publication No. 5-15043).
[0008]
The above TiN coating has a poor adhesion due to differences in thermal expansion coefficient, ductility, etc. in addition to the R-Fe-B magnet body and crystal structure, and the Ti or Al coating has good adhesion and corrosion resistance, There are drawbacks such as low wear resistance, and in order to solve this, it is proposed to apply a laminated film of Ti and TiN on the surface of the R-Fe-B permanent magnet body (Japanese Patent Laid-Open No. 63-9919). Has been. However, since the Ti coating and the TiN coating differ in crystal structure, thermal expansion coefficient, ductility, etc., there is a problem in that the adhesion is poor and peeling occurs, leading to a decrease in corrosion resistance.
[0009]
The present invention is excellent in adhesion to an R—Fe—B permanent magnet base, and is improved in improvement in wear resistance and corrosion resistance, in particular, a salt spray test using a 5% neutral NaCl solution at a temperature of 34 ° C. to 36 ° C. The purpose of the present invention is to provide an R—Fe—B permanent magnet having stable high magnet characteristics, wear resistance, and corrosion resistance, and a method for producing the same, with minimal deterioration from initial magnet characteristics even in a long-term test. To do.
[0010]
[Means for Solving the Problems]
The inventors have excellent corrosion resistance, in particular, a temperature of 34 ° C. to 36 ° C., can extend the time until rusting by spraying with a salt solution of a 5% neutral NaCl solution for a long time, has excellent adhesion to the substrate, and is attached. Various methods for forming Ti _1-x Al _x N coatings on the surface of permanent magnet bodies were investigated for the purpose of R-Fe-B permanent magnets with stable magnet properties due to the corrosion resistance and wear resistance of the corrosion resistant coatings. As a result, when the underlying coating is only the proposed Ti coating or Al coating, the potential of the R-Fe-B magnet as a whole is "noble" rather than Ti or Al, but the Nd portion in the magnet, etc. Since there is a very “base” part locally, it was found that rusting is likely to occur through a slight pinhole in the TiN coating in the salt spray test of the severe corrosion resistance test.
[0011]
Therefore, the inventors have further studied the Ti _1-x Al _x N film forming method, and as a result, first, as a base of the Ti _1-x Al _x N film, a Ti film layer is formed on the surface of the permanent magnet body, and then the Al film layer. Since Al is slightly more “base” electrochemically than Ti, the Al coating layer acts as a sacrificial coating on the Ti coating layer, and the surface layer Ti _1-x Al _x Even if corrosion occurs from a slight pinhole in the N coating, the intermediate layer between the Ti coating on the base layer and the Ti _1-x Al _x N coating on the surface layer does not penetrate the base film all the way to the base magnet body. As long as the Al film exists as a layer, the R—Fe—B permanent magnet coated on the Ti film of the underlayer is protected, and further, a Ti _1-x Al _x N film is formed on the Al film, thereby forming an interface. comprising Ti _1- _{_{_■}} Al _■ N _■ in Ti, Al, a composite target of N There was generated, this Ti _1- _{_{_■}} Al _■ N _■ composition, film thickness, substrate temperature, bias voltage, and varies depending on the film forming speed, Ti _{_1-x} Al x N composition, etc., Ti _{_1-x} Al x N It has a composition in which Ti and N continuously increase toward the interface, and it has been found that the adhesion between the Al coating and the Ti _1-x Al _x N coating can be remarkably improved, thereby completing the present invention. .
[0012]
That is, this invention
A Ti film with a film thickness of 0.1 μm to 3.0 μm formed on the surface of an R—Fe—B permanent magnet body whose main phase is composed of a tetragonal phase via an Al film with a film thickness of 0.1 μm to 5 μm. This is a corrosion-resistant permanent magnet having a coating layer of Ti _1-x Al _x N (where 0.03 <x <0.70) having a film thickness of 0.5 μm to 10 μm.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, after a Ti film having a film thickness of 0.1 μm to 3.0 μm is formed on a cleaned surface of an R—Fe—B permanent magnet body having a main phase of a tetragonal phase by a thin film forming method, An Al film having a film thickness of 0.1 μm to 5 μm is formed on the Ti film, and Ti _1-x Al _x N having a film thickness of 0.5 μm to 10 μm (where 0.03 <x <0. 70) A coating layer is formed. An example of a method for producing a corrosion-resistant permanent magnet will be described in detail below.
[0014]
1) For example, using an arc ion plating apparatus, the vacuum vessel is evacuated to an ultimate vacuum of 1 × 10 ⁻³ pa or less, and then R-Fe is formed by surface sputtering with Ar ions at an Ar gas pressure of 10 pa and −500 V. -Clean the surface of the B-based magnet body.
Next, Ti of the target is evaporated with an Ar gas pressure of 0.1 pa and a bias voltage of −80 V, and a Ti coating layer having a thickness of 0.1 μm to 3.0 μm is formed on the surface of the magnet body by an arc ion plating method. Form.
[0015]
2) Next, the target Al is evaporated at an Ar gas pressure of 0.1 pa and a bias voltage of −50 V, and an Al coating layer having a thickness of 0.1 μm to 5 μm is formed on the Ti coating layer by an arc ion plating method. Form.
[0016]
3) Subsequently, the alloy Ti _{_1-y} Al y (where as a target, 0.03 with <y <0.80), and holds the magnet temperature of the substrate 250 ° C., N ₂ gas pressure 3pa, bias voltage - Under a condition of 120 V, a Ti _1-x Al _x N (where 0.03 <x <0.70) film layer having a specific thickness is formed on the Al film layer.
[0017]
In the present invention, the Ti coating layer, the Al coating layer, and the Ti _1-x Al _x N coating layer deposited on the surface of the R—Fe—B permanent magnet body may be formed by ion plating or vapor deposition. A well-known thin film forming method can be selected as appropriate, but the ion plating method and the ion reaction plating method are preferable because of the denseness, uniformity, and film formation speed of the film.
[0018]
The temperature of the substrate magnet during film formation is preferably set to 200 ° C. to 500 ° C. If the temperature is less than 200 ° C., the reaction adhesion with the substrate magnet is not sufficient, and if it exceeds 500 ° C., it is normal temperature (−25 ° C.). Since the temperature difference becomes large and cracks occur in the coating during the cooling process after the treatment and peeling occurs from a part of the substrate, the temperature of the substrate magnet is set to 200 ° C to 500 ° C.
[0019]
In the present invention, the reason why the Ti film thickness on the surface of the magnet body is limited to 0.1 μm to 3.0 μm is that if it is less than 0.1 μm, the adhesion to the magnet surface is not sufficient, and if it exceeds 3.0 μm, it is effective. Although there is no problem, the cost of the underlying film is increased, which is not practical and not preferable. Therefore, the Ti film thickness is set to 0.1 μm to 3.0 μm.
[0020]
In the present invention, the reason why the Al film thickness formed on the Ti film is limited to 0.1 μm to 5 μm is that if it is less than 0.1 μm, it is difficult for Al to adhere uniformly to the surface of the Ti film, The effect is not sufficient, and if it exceeds 5 μm, there is no problem in effect, but the intermediate layer film is not preferable because it causes an increase in cost, so the Al film thickness is set to 0.1 μm to 5 μm.
[0021]
Further, the reason why the Ti _1-x Al _x N (where 0.03 <x <0.70) film thickness is limited to 0.5 μm to 10 μm is that the Ti _1-x Al _x N coating is less than 0.5 μm. The corrosion resistance and wear resistance of the film are not sufficient, and if it exceeds 10 μm, there is no problem effectively, but it is not preferable because it causes an increase in manufacturing cost. In addition, the reason for limiting the value of x in the Ti _1-x Al _x N coating is that if it is less than 0.03, performance (corrosion resistance, wear resistance) as a Ti _1-x Al _x N coating cannot be obtained. This is because even if it exceeds 0.70, performance cannot be improved.
[0022]
The rare earth element R used in the permanent magnet of the present invention occupies 10 atomic% to 30 atomic% of the composition, but at least one of Nd, Pr, Dy, Ho, and Tb, or further La, Ce, Sm, Gd. , Er, Eu, Tm, Yb, Lu, and Y are preferable. In addition, one type of R is usually sufficient, but in practice, a mixture of two or more types (Misch metal, didymium, etc.) can be used for reasons of convenience in obtaining. The R may not be a pure rare earth element, and may contain impurities that are inevitable in production within a commercially available range.
[0023]
R is an essential element in the above system permanent magnet, and if it is less than 10 atomic%, the crystal structure has the same cubic structure as that of α-iron, so that high magnetic properties, particularly high coercive force cannot be obtained, and 30 atoms. If it exceeds 50%, the R-rich non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, the range of R10 atomic% to 30 atomic% is desirable.
[0024]
B is an essential element in the above system permanent magnet, and if it is less than 2 atomic%, the rhombohedral structure becomes the main phase, and a high coercive force (iHc) cannot be obtained. If it exceeds 28 atomic%, B-rich nonmagnetic phase And the residual magnetic flux density (Br) decreases, so that an excellent permanent magnet cannot be obtained. Therefore, B is preferably in the range of 2 atomic% to 28 atomic%.
[0025]
Fe is an essential element in the above-described permanent magnets, and if it is less than 65 atomic%, the residual magnetic flux density (Br) decreases, and if it exceeds 80 atomic%, a high coercive force cannot be obtained. The content of atomic% is desirable. Substituting a part of Fe with Co can improve the temperature characteristics without deteriorating the magnetic characteristics of the obtained magnet, but conversely, when the amount of Co substitution exceeds 20% of Fe, Since magnetic characteristics deteriorate, it is not preferable. When the substitution amount of Co is 5 atom% to 15 atom% in terms of the total amount of Fe and Co, (Br) is increased as compared with the case where no substitution is performed, and thus it is preferable for obtaining a high magnetic flux density.
[0026]
In addition to R, B, and Fe, the presence of impurities unavoidable for industrial production can be allowed. For example, a part of B is 4.0 wt% or less C, 2.0 wt% or less P, 2.0 wt%. By replacing at least one of the following S and 2.0 wt% or less of Cu with a total amount of 2.0 wt% or less, it is possible to improve the manufacturability of the permanent magnet and reduce the price.
[0027]
Furthermore, at least one of Al, Ti, V, Cr, Mn, Bi, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr, Ni, Si, Zn, and Hf is R-Fe-B. It can be added to the permanent magnet material because it has the effect of improving the coercive force and the squareness of the demagnetization curve, improving the manufacturability, and reducing the price. It should be noted that the upper limit of the addition amount is desirably a range that satisfies the above condition because Br is required to be at least 9 kG or more in order that the (BH) max of the magnet material is 20 MGOe or more.
[0028]
In addition, the permanent magnet of the present invention is mainly composed of a compound having a tetragonal crystal structure with an average crystal grain size in the range of 1 to 80 μm, and a nonmagnetic phase (oxide phase) having a volume ratio of 1% to 50%. Is included).
The permanent magnet according to the present invention exhibits a coercive force iHc ≧ 1 kOe, a residual magnetic flux density Br> 4 kG, a maximum energy product (BH) max indicates (BH) max ≧ 10 MGOe, and the maximum value reaches 25 MGOe or more.
[0029]
【Example】
Example 1
A known cast ingot was pulverized, and after fine pulverization, molding, sintering, and heat treatment, a magnet body test piece having a 15Nd-1Dy76Fe-8B composition with a diameter of 12 mm and a thickness of 2 mm was obtained. The magnet characteristics are shown in Table 1.
[0030]
The inside of the vacuum chamber is evacuated to 1 × 10 ⁻³ pa or less, surface sputtering is performed at an Ar gas pressure of 10 pa and −500 V for 20 minutes to clean the surface of the magnet body, and then an Ar gas pressure of 0.1 pa and a bias are applied. A Ti film layer having a thickness of 1 μm is formed on the surface of the magnet body by arc ion plating with a voltage of −80 V, a substrate magnet temperature of 280 ° C., and metal Ti as a target.
[0031]
Thereafter, an Ar gas pressure of 0.1 pa, a bias voltage of −50 V, a substrate magnet temperature of 250 ° C., and using a metal Al as a target, an Al coating layer having a thickness of 2 μm is formed on the Ti coating surface by arc ion plating. Formed. Next, the substrate magnet temperature 320 ° C., with a bias voltage -100 V, in N ₂ gas 1 Pa, a thickness of 2μm alloy Ti _0.45 Al _0.55 As target Al film surface by an arc ion plating Ti _1-x Al _{An xN} coating layer was formed. The composition of the produced coating was Ti _0.5 Al _0.5 N.
[0032]
Then, after standing to cool, the permanent magnet having the obtained TiN coating on the surface was subjected to a salt spray test (JIS Z2371) under conditions of a temperature of 35 ° C. and a 5% neutral NaCl solution, and the rusting time was measured. The results are shown in Table 2 together with the magnet characteristics.
[0033]
Comparative Example 1
Using a magnet test piece having the same composition as in Example 1 and forming a 3 μm Ti coating layer on the magnet test piece under the same conditions as in Example 1, the same film thickness (2 μm) under the same conditions as in Example 1 After forming the Ti _0.5 Al _0.5 N coating layer, a salt spray test under the same conditions as in Example 1 was performed, the rusting time was measured, and the results are shown in Table 2 together with the magnet characteristics.
[0034]
Comparative Example 2
Using a magnet test piece having the same composition as in Example 1, an Al coating layer was formed on the surface of the magnet body at 3 μm under the same conditions as in Example 1, and then Ti with the same thickness under the same conditions as in Example 1. _{After the 0.5} Al _0.5 N coating layer was formed, a salt spray test under the same conditions as in Example 1 was performed, the rusting time was measured, and the results are shown in Table 2 together with the magnet characteristics.
[0035]
[Table 1]

[0036]
[Table 2]

[0037]
【The invention's effect】
In the present invention, after the surface of the R-Fe-B permanent magnet body is cleaned by an ion sputtering method or the like, a Ti film is formed on the surface of the magnet body by a thin film forming method such as an ion plating method, and then an Al film is further formed. After forming as an intermediate layer, a Ti _1-x Al _x N film is formed by a thin film formation method such as ion reaction plating in N ₂ gas, and by making an Al film layer exist as an intermediate layer , Acting as a sacrificial coating for the Ti film of the permanent magnet body and the underlayer, the adhesion between the Ti coating is remarkably improved, and the rusting time is extended in the salt spray test of severe corrosion resistance test, R-Fe-B permanent magnets having stable magnetic properties can be obtained due to excellent corrosion resistance and wear resistance.

Claims

A Ti film with a film thickness of 0.1 μm to 3.0 μm formed on the surface of an R—Fe—B permanent magnet body whose main phase is composed of a tetragonal phase via an Al film with a film thickness of 0.1 μm to 5 μm. A corrosion-resistant permanent magnet having a coating layer of Ti _1-x Al _x N (where 0.03 <x <0.70) having a thickness of 0.5 μm to 10 μm.

A Ti film having a film thickness of 0.1 μm to 3.0 μm is formed on the cleaned surface of the R—Fe—B permanent magnet body having a main phase of a tetragonal phase by a thin film forming method, and then the Ti film is formed on the Ti film. An Al film having a thickness of 0.1 μm to 5 μm is formed on the film, and a Ti _1-x Al _x N film (0.53 <x <0.70) having a film thickness of 0.5 μm to 10 μm is formed on the Al film. The manufacturing method of the corrosion-resistant permanent magnet which forms.