JP3623583B2

JP3623583B2 - Anisotropic bonded magnet

Info

Publication number: JP3623583B2
Application number: JP35331295A
Authority: JP
Inventors: 修嗣三野; 正宏浅野; 秀治辻本
Original assignee: Neomax Co Ltd
Current assignee: Proterial Ltd
Priority date: 1995-12-27
Filing date: 1995-12-27
Publication date: 2005-02-23
Anticipated expiration: 2015-12-27
Also published as: JPH09186011A

Description

【０００１】
【発明の属する技術分野】
この発明は、耐熱性、耐候性と共に磁気特性、特に残留磁束密度（以下Ｂｒという）、最大磁気エネルギー積（以下（ＢＨ）ｍａｘという）および角型性のすぐれた異方性ボンド磁石に係り、Ｒ−Ｆｅ−Ｂ系合金鋳塊あるいは前記鋳塊を粉砕して得られた粗粉砕粉を特定の熱処理条件のＨ_２処理法により、特定の平均再結晶粒径を有する正方晶のＲ_２Ｆｅ_１４Ｂ相の再結晶粒集合組織を有する異方性磁石粉末となし、これに特定量の微細な液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末およびバインダーの樹脂を配合混合後、成形して得られた耐熱性、耐候性並びにＢｒ、（ＢＨ）ｍａｘ、角型性のすぐれた異方性ボンド磁石に関する。
【０００２】
【従来の技術】
一般にボンド磁石は焼結磁石に比して、磁気特性では劣るにもかかわらず、機械的強度にすぐれ、且つ形状の自由度が高いこと等より、近年、その利用範囲が急速に拡大している。かかるボンド磁石は、磁石粉末と有機バインダー、金属バインダー等により結合して成形されるが、ボンド磁石の磁気特性は使用する磁石粉末の磁気特性に左右される。
【０００３】
ボンド磁石用磁石粉末としては、（１）Ｒ−Ｆｅ−Ｂ系鋳塊を機械的粉砕法、あるいはＨ_２吸蔵崩壊法により得られた磁石粉末や、あるいは、（２）液体急冷法やアトマイズ法によって、溶融合金から超急冷して得られた磁石粉末が利用されている。
【０００４】
前者の（１）磁石粉末では、Ｒ_２Ｆｅ_１４Ｂ相が粒内破壊して粉砕されるので、Ｒ_２Ｆｅ_１４Ｂ相がＲリッチ相で囲まれた組織にならず、Ｒ_２Ｆｅ_１４Ｂ相の一部にＲリッチ相が一部付着した組織となり、また、粉砕時に磁石粉末に歪が残留するため、粉砕のままでは保磁力ｉＨｃは３ｋＯｅ以下に低下し、歪取り熱処理した磁石粉末やＲ_２Ｆｅ_１４Ｂ相粒界部にＲリッチ相を形成させる集合粉末とした磁石粉末でも、ボンド磁石用粉末として使用した場合、成型圧力の増加に伴って、ボンド磁石のｉＨｃは大幅に低下し、また、バインダーの硬化時にも磁気特性が低下する欠点がある。
【０００５】
一方、後者の（２）磁石粉末の場合は、個々のＲ_２Ｆｅ_１４Ｂ相の結晶粒の結晶方向が任意で粉末の磁気特性が等方性であるため、ボンド磁石自体も等方性であるため、高磁気特性が望めず、実用的には用途が制限される問題がある。
【０００６】
また、低価格かつ、高性能なボンド磁石を得るためにフェライト磁石粉末に高性能のＲ−Ｆｅ−Ｂ系磁石粉末を添加配合した高性能ボンド磁石が提案されているが、前記Ｒ−Ｆｅ−Ｂ系磁石粉末は超急冷粉、あるいは鋳塊粉砕粉の等方性の磁石粉末であり、磁気特性の改善向上は小さかった（特開昭６１−２８４９０６号、特開昭６３−２８７００３号、特開平２−７８２０４号、特開平３−１８１１０４号、特開平３−２２２３０３号）。
【０００７】
【発明が解決しようとする課題】
そこで、最近、異方性ボンド用磁石粉末として、Ｒ−Ｆｅ−Ｂ系合金鋳塊あるいは粉砕後の粗粉砕粉を特定の熱処理条件のＨ_２処理法により、Ｒ_２Ｆｅ_１４Ｂ正方晶相からなる再結晶集合組織となした異方性Ｒ−Ｆｅ−Ｂ系磁石粉末が提案されている（特開平１−１３２１０６号）。
【０００８】
前記異方性磁石粉末を用いて異方性ボンド磁石を製造する方法としては、前記磁石粉末にバインダーとして溶剤にて液状化した樹脂を添加配合後、溶剤を蒸発させて前記粉末を乾燥後、圧縮成形し、さらにバインダー硬化のためのキュア熱処理する工程などが一般に知られている。
【０００９】
しかし、原料粉末の異方性磁石粉末は非常に酸化され易いうえ、予め磁石粉末をカップリング処理等で粉末表面を被覆しても、成形時の応力によって磁石粉末には割れが発生し、活性な金属面が露出してより酸化され易くなり、また、成形したボンド磁石は密度が低くて空孔部が多く、前記空孔部にＯ_２、Ｈ_２Ｏが容易に侵入してボンド磁石が酸化し、磁気特性が時間とともに劣化する問題があった。さらに成形時に磁石粉末が割れることは、磁石粉末へ多量の歪を導入することを意味し、保磁力および角型性の劣化を生じる観点からも好ましくなかった。
【００１０】
この発明は、上述の異方性ボンド磁石の問題を解消し、成形時に磁石粉末に割れを生ずることなく、耐熱性、耐候性と共に磁気特性、特にＢｒ、（ＢＨ）ｍａｘおよび角型性のすぐれた異方性ボンド磁石の提供を目的としている。
【００１１】
【課題を解決するための手段】
従来の異方性ボンド磁石の問題点を解決すべく、発明者らは、成形したボンド磁石中の空孔部を減少させる方法について、種々検討を加えた結果、前記磁石粉末にバインダーとして樹脂を配合混合する前、もしくは配合混合と同時に、あるいは配合混合した後に、特定量の微細な液体急冷Ｒ−Ｆｅ−Ｂ系永久磁石粉末を配合混合することにより、液体急冷Ｒ−Ｆｅ−Ｂ系磁石微粉末は成形時に磁石粉末間隙、あるいは薄く樹脂にて被覆された磁石粉末間隙に優先的に充填され、かかる現象により、ボンド磁石中の空孔率が減少すること、また、磁石粉末間隙を占める液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末は成形時に生じる磁石粉末局部への応力集中を緩和し、磁石粉末の割れを抑制することを知見した。
【００１２】
また、発明者らは、１）空孔部の減少によって、磁石内部へのＯ_２、Ｈ_２Ｏの侵入が防止され、耐熱性、耐候性が顕著に向上すること、２）従来空孔部であった部分が液体急冷Ｒ−Ｆｅ−Ｂ系永久磁石粉末によって、置換されるため、そのため磁気特性、とくにＢｒ、（ＢＨ）ｍａｘが向上すること、３）さらに磁石粉末の割れ抑制によって、ボンド磁石中の非常に活性な金属破面が減少するので、耐熱性、耐候性は一段と向上し、４）また、歪の導入も抑制されるので、磁気特性、特に角型性が向上すること、５）かかる作用効果が相乗され、ボンド磁石の耐熱性、耐候性の向上、および磁気特性の改善向上に有効なることを知見し、この発明を完成した。
【００１３】
すなわち、この発明は、
平均再結晶粒径が０．０５μｍ〜５０μｍのＲ_２Ｆｅ_１４Ｂ正方晶相からなる再結晶粒の集合組織を有する異方性Ｒ−Ｆｅ−Ｂ系磁石粉末と、前記磁石粉末との合計に対して０．９〜４９ｗｔ％の液体急冷Ｒ−Ｆｅ−Ｂ系磁石微粉末と１〜１０ｗｔ％の樹脂とからなり、従来ボンド磁石の空隙部であった前記磁石粉末間隙に液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末を充填させたことを特徴とする異方性ボンド磁石である。
【００１４】
【発明の実施の形態】
この発明において、Ｒ_２Ｆｅ_１４Ｂ正方晶相からなる再結晶集合組織の磁石粉末は、Ｒ−Ｆｅ−Ｂ系合金鋳塊あるいは前記鋳塊を粗粉砕して得られた粗粒を均質化処理するか、または、均質化処理せずにＨ_２ガス雰囲気中で昇温し、温度７５０℃〜９５０℃に３０分〜８時間のＨ_２ガス雰囲気中に保持した後、引き続いて温度７５０℃〜９５０℃に５分〜４時間の真空雰囲気中に保持した後、冷却し、粉砕して得られるものである。
【００１５】
かかる異方性Ｒ−Ｆｅ−Ｂ系磁石粉末の平均粒度を５μｍ〜５００μｍに限定した理由は、５μｍ未満では酸化し易く作業中に燃える恐れがあり、また、５００μｍを超えると磁石粉末として実用的ではないので好ましくないことにあり、好ましい平均粒度は１０μｍ〜３００μｍである。
【００１６】
また、異方性Ｒ−Ｆｅ−Ｂ系磁石粉末の平均再結晶粒径は、０．０５μｍ未満では着磁が困難となり、５０μｍを超えるとｉＨｃ（保磁力）が５ｋＯｅ以下となり、磁気特性が低下するため、０．０５μｍ〜５０μｍの範囲とし、好ましい平均再結晶粒径は０．１μｍ〜１０μｍである。
【００１７】
この発明において、特定の異方性Ｒ−Ｆｅ−Ｂ系磁石粉末に配合混合する液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末の平均粒度は、１．０μｍ未満では実際の製造上困難かつ粉末の磁気特性の低下を生じ、また、５０μｍを超えると成形時の空孔低減効果や、応力緩和効果、すなわち磁石粉末の割れ抑制効果が少なく、耐熱性、耐候性並びに磁気特性向上の効果が少ないので好ましくなく、液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末の粒度は１．０μｍ〜５０μｍとする。好ましい液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末の粒度は１．０μｍ〜１０μｍである。
【００１８】
また、液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末の配合量は、磁石粉末との合計に対して、０．９ｗｔ％未満では空孔率低減効果、すなわち耐熱性、耐候性ならびに磁気特性の改善効果が得られず、また４９ｗｔ％を超えるとボンド磁石の磁気特性を劣化するので、０．９ｗｔ％〜４９ｗｔ％とする。好ましい液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末の配合量は１ｗｔ％〜３０ｗｔ％である。
【００１９】
また、バインダーとしての樹脂の配合量は、１ｗｔ％未満ではボンド磁石の強度が十分に得られず、また１０ｗｔ％を超えると磁気特性の劣化を招来するので好ましくないため、樹脂の配合量は１ｗｔ％〜１０ｗｔ％とする。
樹脂としては、熱硬化性あるいは熱可塑性の公知の樹脂で良く、固状の樹脂は溶媒にて液状化バインダーとして使用してもよく、溶媒はボンド磁石の成形前に加熱揮発してもよい。また、ボンド磁石の成形は圧縮成形の他、射出成形や押し出し成形など公知の方法いずれでも良い。
【００２０】
この発明の異方性Ｒ−Ｆｅ−Ｂ系磁石粉末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、シジム等）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し支えない。
【００２１】
Ｒは、上記系磁石粉末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、Ｒは、１０原子％〜３０原子％の範囲が望ましい。
【００２２】
Ｂは、上記系磁石粉末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。
【００２３】
Ｆｅは、上記系磁石粉末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なうことなく、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。
【００２４】
また、Ｒ，Ｂ，Ｆｅのほか、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。
【００２５】
さらに、Ａｌ，Ｔｉ，Ｖ，Ｃｒ，Ｍｎ，Ｂｉ，Ｎｂ，Ｔａ，Ｍｏ，Ｗ，Ｓｂ，Ｇｅ，Ｇａ，Ｓｎ，Ｚｒ，Ｎｉ，Ｓｉ，Ｚｎ，Ｈｆのうち少なくとも１種は、磁石粉末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、ボンド磁石の（ＢＨ）ｍａｘを１４ＭＧＯｅ以上とするには、（Ｂｒ）が少なくとも８ｋＧ以上必要となるため、該条件を満たす範囲が望ましい。
【００２６】
配合混合に用いる液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末は、商品名ＭＱＰで称される磁石粉末（平均粒径約１５０μｍ）を数〜数１０μｍまで微粉砕して得る。
液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末の組成は、Ｒ（但しＲはＹを含む希土類元素のうち少なくとも１種）８原子％〜３０原子％、Ｂ２原子％〜２８原子％、Ｆｅ４２原子％〜９０原子％を主成分とし、合金溶湯急冷のままで５μｍ以下の微細な結晶質からなる磁気異方性を有する複合組織より構成され、主相が正方晶化合物であることが望ましい。
【００２７】
また、液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末には、超急冷により非晶質あるいは非晶質と超微細結晶との混合組織からなるテープやリボンを再結晶化処理した磁気的に等方性である等方性Ｒ−Ｆｅ−Ｂ系磁石粉末を用いることができる。また、同様に超急冷により非晶質と軟磁性結晶材料との中間状態で磁気的に等方性である等方性Ｒ−Ｆｅ−Ｂ系磁石粉末を用いることができる。
【００２８】
液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末の組成は、Ｒは、８原子％未満では高磁気特性、特に高保磁力が得られず、３０原子％を越えると残留磁束密度（Ｂｒ）が低下してすぐれた特性の永久磁石材料が得られないため、８原子％〜３０原子％の範囲とし、Ｂは、２原子％未満では高い保磁力（ｉＨｃ）は得られず、２８原子％を越えると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、２原子％〜２８原子％の範囲とし、Ｆｅは、４２原子％未満では残留磁束密度（Ｂｒ）が低下し、９０原子％を越えると高い保磁力が得られないので、４２原子％〜９０原子％の含有とし、Ｆｅの一部をＣｏで置換したり、種々の添加元素を添加できる。
【００２９】
なお、この発明においては、前記液体急冷Ｒ−Ｆｅ−Ｂ系磁石微粉末の他に、フェライト磁石粉末、Ｒ−Ｆｅ−Ｂ系ナノコンポジット磁石微粉末、Ｒ−Ｃｏ系磁石微粉末、Ｒ−Ｆｅ−Ｎ系磁石微粉末を複合混合してもよい。
【００３０】
【実施例】
実施例１
原料として真空溶解炉にて溶解鋳造し、表１に組成を表すＲ−Ｆｅ−Ｂ系磁石用合金鋳塊を得た。これらの合金鋳塊を温度１１２０℃、時間１０時間でＡｒ雰囲気中にて均質化処理を行った。
前記鋳塊を加熱炉に挿入し、７６０ＴｏｒｒのＨ_２ガスとして、加熱炉内の温度を室温から温度８５０℃に上昇し、引き続いて温度８５０℃に３時間保持した後、８５０℃に１時間保持して脱Ｈ_２を行って、真空度１×１０^−５Ｔｏｒｒになるまで排気冷却した。
その後、鋳塊をＡｒ雰囲気中で３００μｍ以下になるまで粉砕して、Ｒ−Ｆｅ−Ｂ系磁石粉末を得た。得られた磁石粉末は平均結晶粒径０．５μｍのＲ_２Ｆｅ_１４Ｂ正方晶相からなる再結晶粒の集合組織を有する異方性磁石粉末であった。
【００３１】
液体急冷Ｒ−Ｆｅ−Ｂ系永久磁石微粉末には、組成がＮｄ１２ａｔ％−Ｂ５．４ａｔ％−Ｃｏ５ａｔ％−残部Ｆｅからなる平均粒径約１５０μｍのＭＱＰ−Ｂ磁粉（商品名、米国ゼネラルモーターズ社製）を用いた。
該磁粉をボールミルにより微粉砕して得た平均粒度２．７μｍの液体急冷Ｎｄ−Ｆｅ−Ｂ系磁石微粉末を、前述の工程で得られた平均粒径１５０μｍの前記異方性磁石粉末との合計に対して１０ｗｔ％配合後、Ｖ型混合器にて３０分間混合し、さらに、バインダーとして３ｗｔ％のエポキシ樹脂を配合混合後、真空乾燥し、１２ｋＯｅの磁場中で成形圧７ｔｏｎ／ｃｍ^２で成形後、温度１７０℃に１時間保持して硬化し、異方性ボンド磁石を得た。
【００３２】
得られた異方性ボンド磁石の磁気特性、角型性および空孔率と耐候性試験結果を表２に表す。ここで、空孔率は、異方性Ｒ−Ｆｅ−Ｂ系磁石粉末、液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末ならびに樹脂の密度と配合比、および成形したボンド磁石の実測密度から計算によって求めた。
【００３３】
また、耐熱性、耐候性試験の試験条件は大気中で１００℃×１０００時間の条件で、試験中の磁束の経時変化を測定した。なお、磁束の経時変化試験方法は試験片を着磁した後、磁束を測定し、ついで大気中にて１００℃に１０００時間放置後、再び試験片を着磁し磁束を測定し、再着磁によっても復元しない減磁率、すなわち永久的な減磁率を算出した。この永久的な減磁は磁石の腐食等による変質に起因するものであり、耐熱性、耐候性向上の判定指標となり得る。
【００３４】
実施例２
実施例１にて得られた磁石粉末にバインダーとして３ｗｔ％のエポキシ樹脂を配合混合後、真空乾燥し、次いで、実施例１に記載の液体急冷Ｎｄ−Ｆｅ−Ｂ系磁石微粉末を前記磁石粉末との合計に対して１０ｗｔ％配合混合する以外は、実施例１と同一の製造条件にて異方性ボンド磁石を作製し、得られた異方性ボンド磁石の磁気特性、空孔率および耐候性試験結果を表２に表す。
【００３５】
実施例３
実施例１にて得られた組成Ｎｏ．２の磁石粉末に、実施例１に記載の液体急冷Ｎｄ−Ｆｅ−Ｂ系磁石微粉末を、前記磁石粉末との合計に対して０〜５０ｗｔ％の範囲で配合量を変えて混合する以外は実施例１と同一の製造条件にて異方性ボンド磁石を作成し、得られた異方性ボンド磁石の磁気特性を図１に、空孔率および耐候性試験結果を図２に表す。
【００３６】
実施例４
実施例１にて得られた組成Ｎｏ．２の磁石粉末に、ボールミル粉砕時間を変えて作成した１．２μｍ、２．７μｍ、３．５μｍ、４．９μｍ、６．５μｍ、９．７μｍの各平均粒径の液体急冷Ｎｄ−Ｆｅ−Ｂ系磁石微粉末をそれぞれ、前記磁石粉末との合計に対して１０ｗｔ％配合混合する以外は実施例１と同一の製造条件にて異方性ボンド磁石を作成し、得られた異方性ボンド磁石の磁気特性を図３に、空孔率と耐候性試験結果を図４に示す。
【００３７】
比較例１
実施例１にて得られた磁石粉末に液体急冷Ｒ−Ｆｅ−Ｂ系永久磁石粉末を配合混合しない以外は実施例１と同一の製造条件にて異方性ボンド磁石を作成し、得られた異方性ボンド磁石の磁気特性、角型性および空孔率と耐候性試験結果を表２に表す。
【００３８】
【表１】

【００３９】
【表２】

【００４０】
【発明の効果】
この発明による異方性ボンド磁石は、Ｒ−Ｆｅ−Ｂ系合金鋳塊あるいは前記鋳塊を粉砕して得られた粗粉砕粉を、特定の熱処理条件のＨ_２処理法により、特定の平均再結晶粒径を有する正方晶のＲ_２Ｆｅ_１４Ｂ相の再結晶粒集合組織を有する異方性磁石粉末となし、所定量の微細な液体急冷Ｒ−Ｆｅ−Ｂ系永久磁石粉末とバインダーの樹脂を配合混合後、成形して得られたもので、実施例に明らかなように、耐熱性、耐候性並びに磁気特性にすぐれている。
【図面の簡単な説明】
【図１】混合した液体急冷Ｎｄ−Ｆｅ−Ｂ系永久磁石粉末（平均粒度２．７μｍ）の量（ｗｔ％）と得られたボンド磁石の磁気特性との関係を示すグラフである。
【図２】混合した液体急冷Ｎｄ−Ｆｅ−Ｂ系永久磁石粉末（平均粒度２．７μｍ）の量（ｗｔ％）と得られたボンド磁石の空孔率（％）及び耐候性試験後の永久減磁率（％）との関係を示すグラフである。
【図３】１０ｗｔ％混合した液体急冷Ｎｄ−Ｆｅ−Ｂ系永久磁石粉末の平均粒径（μｍ）と得られたボンド磁石の磁気特性との関係を示すグラフである。
【図４】１０ｗｔ％混合した液体急冷Ｎｄ−Ｆｅ−Ｂ系永久磁石粉末の平均粒径（μｍ）と得られたボンド磁石の空孔率（％）及び耐候性試験後の永久減磁率（％）との関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an anisotropic bonded magnet having excellent heat resistance, weather resistance and magnetic properties, in particular, residual magnetic flux density (hereinafter referred to as Br), maximum magnetic energy product (hereinafter referred to as (BH) max), and squareness. R-Fe-B alloy ingot or coarsely pulverized powder obtained by pulverizing the ingot is tetragonal R ₂ Fe having a specific average recrystallized grain size by H ₂ treatment method under specific heat treatment conditions. ₁₄ An anisotropic magnet powder having a recrystallized grain texture of the B phase is obtained, and a specific amount of fine liquid quenched R—Fe—B magnet powder and a binder resin are blended and mixed and then molded. The present invention relates to an anisotropic bonded magnet having excellent heat resistance, weather resistance, Br, (BH) max, and squareness.
[0002]
[Prior art]
In general, bonded magnets have rapidly expanded their use range in recent years due to their superior mechanical strength and high degree of freedom in shape, although they are inferior in magnetic properties to sintered magnets. . Such bonded magnets are formed by combining magnet powder with an organic binder, a metal binder, or the like, but the magnetic properties of the bonded magnet depend on the magnetic properties of the magnet powder used.
[0003]
As magnet powder for bond magnets, (1) magnet powder obtained by mechanical pulverization of R—Fe—B ingots or H ₂ storage / decay method, or (2) liquid quenching method or atomizing method Thus, magnet powder obtained by ultra-rapid cooling from a molten alloy is used.
[0004]
In the former (1) magnet powder, the R ₂ Fe ₁₄ B phase breaks in the grains and is pulverized. Therefore, the R ₂ Fe ₁₄ B phase does not become a structure surrounded by the R rich phase, and R ₂ Fe ₁₄ B Since the R-rich phase is partly adhered to a part of the phase, and strain remains in the magnet powder during pulverization, the coercive force iHc decreases to 3 kOe or less when pulverized, Even when the magnet powder is an aggregate powder that forms an R-rich phase at the R ₂ Fe ₁₄ B phase grain boundary, when used as a bond magnet powder, the iHc of the bond magnet significantly decreases as the molding pressure increases. In addition, there is a drawback that the magnetic properties are lowered when the binder is cured.
[0005]
On the other hand, in the case of the latter (2) magnet powder, since the crystal direction of each R ₂ Fe ₁₄ B phase crystal grain is arbitrary and the magnetic properties of the powder are isotropic, the bond magnet itself is also isotropic. For this reason, high magnetic properties cannot be expected, and there is a problem that practical use is limited.
[0006]
Further, in order to obtain a low-cost and high-performance bonded magnet, a high-performance bonded magnet in which a high-performance R-Fe-B magnet powder is added to a ferrite magnet powder has been proposed. The B-based magnet powder is an isotropic magnet powder such as a super-quenched powder or an ingot pulverized powder, and the improvement in magnetic properties was small (Japanese Patent Laid-Open Nos. 61-284906 and 63-287003, and (Kaihei 2-78204, JP-A-3-181104, JP-A-3-222303).
[0007]
[Problems to be solved by the invention]
Therefore, recently, as an anisotropic bond magnet powder, an R—Fe—B alloy ingot or a coarsely pulverized coarsely pulverized powder is obtained from an R ₂ Fe ₁₄ B tetragonal phase by an H ₂ treatment method under specific heat treatment conditions. An anisotropic R-Fe-B magnet powder having a recrystallized texture is proposed (Japanese Patent Laid-Open No. 1-132106).
[0008]
As a method for producing an anisotropic bonded magnet using the anisotropic magnet powder, after adding and blending a resin liquefied with a solvent as a binder to the magnet powder, the solvent is evaporated and the powder is dried, A process of compression molding and a curing heat treatment for binder curing is generally known.
[0009]
However, the anisotropic magnetic powder of the raw material powder is very easy to oxidize, and even if the magnetic powder is coated on the powder surface in advance by a coupling treatment, the magnetic powder is cracked by the stress at the time of molding and active. The exposed bonded metal surface is more susceptible to oxidation, and the molded bonded magnet has a low density and has a large number of holes, and O ₂ and H ₂ O can easily enter the holes to form a bonded magnet. There was a problem that the magnetic properties deteriorated with time due to oxidation. Further, cracking of the magnet powder during molding means that a large amount of strain is introduced into the magnet powder, which is not preferable from the viewpoint of deteriorating coercive force and squareness.
[0010]
The present invention solves the above-mentioned problems of anisotropic bonded magnets, and does not cause cracks in the magnet powder during molding, and has excellent heat characteristics, weather resistance, and magnetic properties, particularly Br, (BH) max and squareness. The purpose is to provide an anisotropic bonded magnet.
[0011]
[Means for Solving the Problems]
In order to solve the problems of the conventional anisotropic bonded magnet, the inventors have made various studies on the method of reducing the voids in the molded bonded magnet. By mixing and mixing a specific amount of fine liquid quenched R—Fe—B permanent magnet powder before or after compounding, or after compounding and mixing, the liquid quenched R—Fe—B magnet fine particles are mixed and mixed. The powder is preferentially filled in the gap between the magnet powder during molding or the magnet powder gap thinly coated with resin, and this phenomenon reduces the porosity in the bonded magnet, and the liquid occupying the gap in the magnet powder. It has been found that the rapidly cooled R—Fe—B based magnet powder relieves stress concentration on the local portion of the magnet powder generated during molding and suppresses cracking of the magnet powder.
[0012]
In addition, the inventors have 1) the reduction of the pores to prevent O ₂ and H ₂ O from entering the magnet, and the heat resistance and weather resistance are significantly improved. Therefore, the magnetic properties, particularly Br and (BH) max are improved, and 3) the cracking of the magnet powder is further suppressed. Since the extremely active metal fracture surface in the magnet is reduced, the heat resistance and weather resistance are further improved. 4) In addition, since the introduction of strain is also suppressed, the magnetic properties, particularly the squareness, are improved. 5) The present invention has been completed by discovering that such effects are synergistic and effective for improving the heat resistance and weather resistance of the bonded magnet and improving the magnetic properties.
[0013]
That is, this invention
An anisotropic R—Fe—B based magnet powder having a texture of recrystallized grains composed of an R ₂ Fe ₁₄ B tetragonal phase having an average recrystallized grain size of 0.05 μm to 50 μm, and the magnet powder On the other hand, liquid quenching R-Fe-B magnet fine powder of 0.9 to 49 wt% and resin of 1 to 10 wt%, and liquid quenching R-Fe is provided in the gap of the magnet powder, which is a void portion of the conventional bonded magnet. -An anisotropic bonded magnet filled with B-based magnet powder.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the magnet powder of the recrystallized texture composed of the R ₂ Fe ₁₄ B tetragonal phase is homogenized with the R—Fe—B alloy ingot or the coarse particles obtained by coarsely pulverizing the ingot. Or after raising the temperature in the H ₂ gas atmosphere without homogenization and maintaining the temperature in the H ₂ gas atmosphere for 30 minutes to 8 hours at a temperature of 750 ° C. to 950 ° C. After being kept at 950 ° C. in a vacuum atmosphere for 5 minutes to 4 hours, it is obtained by cooling and pulverizing.
[0015]
The reason why the average particle size of the anisotropic R—Fe—B magnet powder is limited to 5 μm to 500 μm is that if it is less than 5 μm, it tends to oxidize and may burn during operation, and if it exceeds 500 μm, it is practical as a magnet powder. Therefore, the average particle size is preferably 10 μm to 300 μm.
[0016]
Also, if the average recrystallized grain size of anisotropic R-Fe-B magnet powder is less than 0.05 μm, it becomes difficult to magnetize, and if it exceeds 50 μm, iHc (coercive force) becomes 5 kOe or less, and the magnetic properties deteriorate. Therefore, a range of 0.05 μm to 50 μm is set, and a preferable average recrystallized grain size is 0.1 μm to 10 μm.
[0017]
In this invention, the average particle size of the liquid quenched R-Fe-B magnet powder blended with the specific anisotropic R-Fe-B magnet powder is less than 1.0 μm, which is difficult in actual production and is magnetic in the powder. Deterioration of the characteristics is caused, and if it exceeds 50 μm, it is preferable because there is little effect of reducing pores and stress relaxation during molding, that is, cracking suppression effect of the magnet powder, and little effect of improving heat resistance, weather resistance and magnetic properties. The particle size of the liquid quenched R—Fe—B magnet powder is 1.0 μm to 50 μm. The particle size of the preferred liquid quenched R—Fe—B magnet powder is 1.0 μm to 10 μm.
[0018]
Also, if the blending amount of the liquid quenching R—Fe—B magnet powder is less than 0.9 wt% with respect to the total amount with the magnet powder, the porosity reduction effect, that is, the heat resistance, weather resistance and magnetic property improvement effect Is not obtained, and if it exceeds 49 wt%, the magnetic properties of the bonded magnet are deteriorated, so 0.9 wt% to 49 wt% is set. The blending amount of the liquid quenching R—Fe—B magnet powder is preferably 1 wt% to 30 wt%.
[0019]
Further, if the amount of the resin as the binder is less than 1 wt%, the strength of the bonded magnet cannot be sufficiently obtained, and if it exceeds 10 wt%, the magnetic properties are deteriorated, which is not preferable. % To 10 wt%.
The resin may be a known thermosetting or thermoplastic resin, the solid resin may be used as a liquefied binder in a solvent, and the solvent may be volatilized by heating before forming the bonded magnet. In addition to the compression molding, the bond magnet may be molded by any known method such as injection molding or extrusion molding.
[0020]
The rare earth element R used in the anisotropic R—Fe—B magnet powder 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, those containing at least one of 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, shidim, etc.) can be used for reasons of convenience. The R may not be a pure rare earth element, and may contain impurities that are inevitable in production within a commercially available range.
[0021]
R is an essential element in the above system magnet powder, and if it is less than 10 atomic%, the crystal structure has a cubic structure having the same structure as 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, R is preferably in the range of 10 atomic% to 30 atomic%.
[0022]
B is an essential element in the above-mentioned system magnet powder, and if it is less than 2 atomic%, the rhombohedral structure becomes the main phase, and a high coercive force (iHc) cannot be obtained, and if it exceeds 28 atomic%, a 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%.
[0023]
Fe is an essential element in the above system magnet powder, 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 impairing the magnetic characteristics of the obtained magnet. However, if the amount of Co substitution exceeds 20% of Fe, the magnetic characteristics are reversed. Since the 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.
[0024]
In addition to R, B, and Fe, the presence of impurities inevitable in 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.
[0025]
Furthermore, at least one of Al, Ti, V, Cr, Mn, Bi, Nb, Ta, Mo, W, Sb, Ge, Ga, Sn, Zr, Ni, Si, Zn, and Hf is based on the magnet powder. It can be added because it is effective in improving the squareness of the coercive force and demagnetization curve, improving the manufacturability, and reducing the price. The upper limit of the amount added is preferably a range that satisfies this condition because (Br) is required to be at least 8 kG or more in order to set (BH) max of the bonded magnet to 14 MGOe or more.
[0026]
The liquid quenching R—Fe—B magnet powder used for blending and mixing is obtained by finely pulverizing a magnet powder (average particle diameter of about 150 μm) with a trade name of MQP to several to several tens of μm.
The composition of the liquid quenched R—Fe—B magnet powder is R (provided that R is at least one of rare earth elements including Y) 8 atomic% to 30 atomic%, B2 atomic% to 28 atomic%, Fe 42 atomic% to It is preferably composed of a composite structure having a magnetic anisotropy composed of fine crystallites of 5 μm or less with 90 atomic% as a main component, with the alloy melt rapidly cooled, and the main phase is a tetragonal compound.
[0027]
In addition, liquid quenching R-Fe-B magnet powder is magnetically isotropic by recrystallizing a tape or ribbon consisting of amorphous or mixed structure of amorphous and ultrafine crystals by ultra-quenching. Isotropic R-Fe-B magnet powder can be used. Similarly, an isotropic R-Fe-B magnet powder that is magnetically isotropic in an intermediate state between an amorphous material and a soft magnetic crystal material can be used by super rapid cooling.
[0028]
The composition of the liquid quenching R—Fe—B magnet powder is such that when R is less than 8 atomic%, high magnetic properties, particularly high coercive force cannot be obtained, and when it exceeds 30 atomic%, the residual magnetic flux density (Br) decreases. Since a permanent magnet material having excellent characteristics cannot be obtained, the range is 8 to 30 atomic%, and if B is less than 2 atomic%, a high coercive force (iHc) cannot be obtained, and if it exceeds 28 atomic%, B Since the rich non-magnetic phase increases and the residual magnetic flux density (Br) decreases, the range of 2 atomic% to 28 atomic% is set. When Fe is less than 42 atomic%, the residual magnetic flux density (Br) decreases, and 90 When the atomic percentage is exceeded, a high coercive force cannot be obtained. Therefore, the content is set to 42 atomic% to 90 atomic%, and a part of Fe can be substituted with Co or various additive elements can be added.
[0029]
In the present invention, in addition to the liquid quenched R—Fe—B magnet fine powder, ferrite magnet powder, R—Fe—B nanocomposite magnet fine powder, R—Co magnet fine powder, R—Fe. -N-based magnet fine powder may be mixed and mixed.
[0030]
【Example】
Example 1
As a raw material, it was melt cast in a vacuum melting furnace, and an alloy ingot for an R—Fe—B magnet whose compositions are shown in Table 1 was obtained. These alloy ingots were homogenized in an Ar atmosphere at a temperature of 1120 ° C. for 10 hours.
The ingot is inserted into a heating furnace, and the temperature inside the heating furnace is increased from room temperature to 850 ° C. as 760 Torr of H ₂ gas. Subsequently, the temperature is maintained at 850 ° C. for 3 hours, and then maintained at 850 ° C. for 1 hour. Then, H ₂ was removed, and the exhaust was cooled until the degree of vacuum became 1 × 10 ⁻⁵ Torr.
Thereafter, the ingot was pulverized in an Ar atmosphere to 300 μm or less to obtain an R—Fe—B magnet powder. The obtained magnet powder was an anisotropic magnet powder having a recrystallized grain texture composed of an R ₂ Fe ₁₄ B tetragonal phase having an average crystal grain size of 0.5 μm.
[0031]
The liquid quenching R-Fe-B permanent magnet fine powder includes an MQP-B magnetic powder having a composition of Nd12at% -B5.4at% -Co5at% -balance Fe with an average particle size of about 150 μm (trade name, General Motors, USA). Made).
The liquid rapidly cooled Nd—Fe—B magnet fine powder having an average particle size of 2.7 μm obtained by finely pulverizing the magnetic powder with a ball mill is combined with the anisotropic magnet powder having an average particle size of 150 μm obtained in the above step. After blending 10 wt% with respect to the total, mix in a V-type mixer for 30 minutes, and further blend and mix 3 wt% epoxy resin as a binder, then vacuum dry, in a magnetic field of 12 kOe at a molding pressure of 7 ton / cm ² . After molding, the material was cured by holding at a temperature of 170 ° C. for 1 hour to obtain an anisotropic bonded magnet.
[0032]
Table 2 shows the magnetic properties, squareness, porosity, and weather resistance test results of the obtained anisotropic bonded magnet. Here, the porosity is obtained by calculation from the anisotropic R-Fe-B magnet powder, the liquid quenched R-Fe-B magnet powder, the density and blending ratio of the resin, and the actually measured density of the molded bond magnet. It was.
[0033]
Moreover, the test conditions of the heat resistance and weather resistance test were the conditions of 100 ° C. × 1000 hours in the air, and the change over time of the magnetic flux during the test was measured. The magnetic flux aging test method is to magnetize the test piece, measure the magnetic flux, and then leave it in the atmosphere at 100 ° C. for 1000 hours, magnetize the test piece again, measure the magnetic flux, and re-magnetize. The demagnetization factor that is not restored by the calculation, that is, the permanent demagnetization factor was calculated. This permanent demagnetization is caused by alteration due to corrosion of the magnet, and can be a determination index for improving heat resistance and weather resistance.
[0034]
Example 2
The magnet powder obtained in Example 1 was mixed and mixed with 3 wt% of an epoxy resin as a binder, followed by vacuum drying, and then the liquid quenched Nd—Fe—B magnet fine powder described in Example 1 was used as the magnet powder. An anisotropic bonded magnet was produced under the same production conditions as in Example 1 except that 10 wt% was mixed with respect to the total of the magnetic properties, porosity, and weather resistance of the obtained anisotropic bonded magnet. The test results are shown in Table 2.
[0035]
Example 3
Composition No. obtained in Example 1 The liquid quenched Nd-Fe-B magnet fine powder described in Example 1 is mixed with the magnet powder of Example 2 except that the blending amount is changed within a range of 0 to 50 wt% with respect to the total with the magnet powder. An anisotropic bonded magnet was prepared under the same manufacturing conditions as in Example 1. The magnetic properties of the obtained anisotropic bonded magnet are shown in FIG. 1, and the porosity and weather resistance test results are shown in FIG.
[0036]
Example 4
Composition No. obtained in Example 1 Liquid quenching Nd—Fe—B having average particle diameters of 1.2 μm, 2.7 μm, 3.5 μm, 4.9 μm, 6.5 μm, and 9.7 μm prepared by changing the ball mill grinding time to the magnet powder of No. 2 An anisotropic bonded magnet was prepared under the same manufacturing conditions as in Example 1 except that 10 wt% of each of the magnet magnet powders was mixed and mixed with the total amount of the magnet powder. FIG. 3 shows the magnetic characteristics of the film and FIG. 4 shows the porosity and the weather resistance test results.
[0037]
Comparative Example 1
An anisotropic bonded magnet was prepared and obtained under the same production conditions as in Example 1 except that the liquid quenched R-Fe-B permanent magnet powder was not mixed and mixed with the magnet powder obtained in Example 1. Table 2 shows the magnetic properties, squareness, porosity, and weather resistance test results of the anisotropic bonded magnet.
[0038]
[Table 1]

[0039]
[Table 2]

[0040]
【The invention's effect】
The anisotropic bonded magnet according to the present invention is obtained by subjecting an R—Fe—B alloy ingot or a coarsely pulverized powder obtained by pulverizing the ingot to a specific average re-treatment by H ₂ treatment under specific heat treatment conditions. An anisotropic magnet powder having a recrystallized grain texture of a tetragonal R ₂ Fe ₁₄ B phase having a crystal grain size, and a predetermined amount of fine liquid quenched R—Fe—B permanent magnet powder and a binder resin As shown in the examples, it is excellent in heat resistance, weather resistance and magnetic properties.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the amount (wt%) of mixed liquid quenched Nd—Fe—B permanent magnet powder (average particle size of 2.7 μm) and the magnetic properties of the obtained bonded magnet.
FIG. 2 shows the amount (wt%) of mixed liquid quenched Nd—Fe—B permanent magnet powder (average particle size 2.7 μm), the porosity (%) of the obtained bonded magnet, and the permanent after weather resistance test. It is a graph which shows the relationship with a demagnetizing factor (%).
FIG. 3 is a graph showing the relationship between the average particle size (μm) of liquid quenched Nd—Fe—B permanent magnet powder mixed with 10 wt% and the magnetic properties of the obtained bonded magnet.
FIG. 4 shows an average particle diameter (μm) of liquid quenched Nd—Fe—B permanent magnet powder mixed with 10 wt%, porosity (%) of the obtained bonded magnet, and permanent demagnetization rate after weathering test (%). ).

Claims

An anisotropic R—Fe—B based magnet powder having a texture of recrystallized grains composed of an R ₂ Fe ₁₄ B tetragonal phase having an average recrystallized grain size of 0.05 μm to 50 μm, and the magnet powder On the other hand, an anisotropic bonded magnet comprising 0.9 to 49 wt% of liquid quenched R—Fe—B magnet powder and 1 to 10 wt% of resin.