JP3703903B2

JP3703903B2 - Anisotropic bonded magnet

Info

Publication number: JP3703903B2
Application number: JP07818896A
Authority: JP
Inventors: 秀治辻本; 修嗣三野; 正宏浅野
Original assignee: Neomax Co Ltd
Current assignee: Hitachi Metals Ltd
Priority date: 1996-03-05
Filing date: 1996-03-05
Publication date: 2005-10-05
Anticipated expiration: 2016-03-05
Also published as: JPH09246029A

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Ｈ₂処理法により、特定の平均再結晶粒径を有する正方晶のＲ₂Ｆｅ₁₄Ｂ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系磁石粉末とハードフェライト磁石粉末、並びにバインダーの樹脂を配合混合後、成形、硬化処理して得られた耐熱性、耐候性並びに磁気特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などにより、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Ｈ₂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、Ｒ₂Ｆｅ₁₄Ｂ相が粒内破壊して粉砕されるので、Ｒ₂Ｆｅ₁₄Ｂ相がＲリッチ相で囲まれた組織にならず、Ｒ₂Ｆｅ₁₄Ｂ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Ｒ₂Ｆｅ₁₄Ｂ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、成形圧の増加に伴って、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Ｒ₂Ｆｅ₁₄Ｂ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】
【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粒を特定の熱処理条件のＨ₂処理法により、Ｒ₂Ｆｅ₁₄Ｂ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号公報）。
【０００７】
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知られている。
【０００８】
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上、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、成形時に磁石粉末に割れを発生し、活性な金属面が露出して酸化され易くなり、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Ｏ₂、Ｈ₂Ｏが容易に侵入してボンド磁石が酸化し、磁気特性の劣化を生ずる問題があった。
【０００９】
発明者等は、耐食性のすぐれた高性能ボンド磁石を得るために、前記異方性ボンド磁石にハードフェライト磁石粉末を添加配合した高性能ボンド磁石を提案（特願平７−２７３４７１号）したが、耐食性はすぐれているものの、ハードフェライト磁石粉末は磁気特性が低いために、ボンド磁石の磁気特性の向上効果は十分でなかった。
【００１０】
また、発明者等は、耐食性のすぐれた高性能ボンド磁石を得るために、前記異方性ボンド磁石に液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末を添加配合した高性能ボンド磁石を提案（特願平７−３５３３１２号）したが、ボンド磁石の磁気特性の向上効果は大きいが、液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末自体の酸化により、磁気特性の劣化が起こり、耐食性の改善効果は小さかった。
【００１１】
この発明は、上述の異方性ボンド磁石の問題点を解消し、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及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。
【００１２】
【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系永久磁石粉末およびハードフェライト磁石粉末を配合混合することにより、
（１）液体急冷Ｒ−Ｆｅ−Ｂ系磁石微粉末及びハードフェライト磁石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し、この空隙部からボンド磁石内部にＯ₂、Ｈ₂Ｏが侵入することを防止し、ボンド磁石の耐熱性、耐候性が向上すること、
（２）ボンド磁石内部の空隙部に充填される添加粉末である液体急冷Ｒ−Ｆｅ−Ｂ系磁石微粉末及びハードフェライト磁石粉末は硬質強磁性体であることから、ボンド磁石の単位体積当たりの硬質強磁性体（Ｒ−Ｆｅ−Ｂ系磁石粉末＋液体急冷Ｒ−Ｆｅ−Ｂ系磁石微粉末＋ハードフェライト磁石粉末）の総量は増加し、これによりボンド磁石の磁気特性、特にＢｒの低下を防止し、向上させること、
（３）ボンド磁石内部の空隙部に充填されるハードフェライト磁石粉末は酸化物であり、Ｏ₂、Ｈ₂Ｏによる磁気特性の酸化、水酸化劣化がなく、ボンド磁石の耐熱性、耐候性が向上すること、
（４）ボンド磁石成形時において、液体急冷Ｒ−Ｆｅ−Ｂ系磁石微粉末とハードフェライト磁石粉末の混合粉末は成形時に起こる磁石粉末局部への応力集中を緩和し、磁石粉末の割れによる活性な金属面の発生を抑制するので、耐熱性、耐候性は一段と向上すること、
（５）また、前記応力集中の緩和により、磁石粉末に発生の歪を抑制するため磁気特性が向上すること、
（６）前記の各作用効果の相乗により、ボンド磁石の耐熱性、耐候性の向上及び磁気特性の改善向上に有効であること、
の種々の作用効果を知見して、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Ｒ₂Ｆｅ₁₄Ｂ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系磁石粉末が４５ｗｔ％〜９８．５ｗｔ％、樹脂が１ｗｔ％〜１０ｗｔ％、液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末及びハードフェライト磁石粉末の総量が０．５ｗｔ％〜４５ｗｔ％の組成からなり、
前記液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末とハードフェライト磁石粉末の配合比率が重量比にて２．０／９８．０〜９８．５／１．５である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、Ｒ₂Ｆｅ₁₄Ｂ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Ｈ₂ガス雰囲気中で昇温し、温度７５０℃〜９５０℃に３０分〜８時間のＨ₂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もできる。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。
【００１８】
また、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。さらに好ましい液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末の粒度は１．０μｍ〜１０μｍである。
【００１９】
この発明において、配合添加するハードフェライト磁石粉末は化学式ＭＯ・６Ｆｅ₂Ｏ（Ｍ：Ｂａ，Ｓｒ，Ｐｂ）で表されるＭ型及び化学式２ＭＯ・ＢａＯ・８Ｆｅ₂Ｏ₃（Ｍ：Ｂａ，Ｓｒ，Ｐｂ）で表されるＷ型等のいずれでもよい。
前記ハードフェライト磁石粉末の平均粒度は、０．５μｍ以下では製造的に困難であり、ハードフェライト磁石粉末同士が凝集して均一に分散し難いため好ましくなく、また、１０μｍを越えるとボンド磁石内部の空隙部に十分に充填され難いばかりでなく、ハードフェライト磁石粉末の磁気特性の低下が大きいため、ボンド磁石の耐熱性、耐候性及び磁気特性向上の効果が少ないので好ましくなく、ハードフェライト磁石粉末の平均粒度は０．５μｍ〜１０μｍとする。さらに好ましい平均粒度は０．５μｍ〜５μｍである。
【００２０】
また、異方性Ｒ−Ｆｅ−Ｂ系磁石粉末に配合する液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末とハードフェライト磁石粉末の総量が、０．５ｗｔ％未満では耐熱性、耐候性及び磁気特性の改善効果が得られず、また、４５ｗｔ％を越えるとボンド磁石の磁気特性が劣化するので、０．５ｗｔ％〜４５ｗｔ％とする。さらに好ましい添加配合量は３ｗｔ％〜３０ｗｔ％である。
【００２１】
また、前記磁石粉末に添加配合する液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末とハードフェライト磁石粉末の配合比率を、重量比で２．０／９８．０〜９８．５／１．５に限定する理由は、液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末の配合量が２．０未満、ハードフェライト磁石粉末が９８．０を越えると、異方性ボンド磁石の耐熱性、耐候性の改善向上の効果が充分に得られず、また、液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末の配合量が９８．５を越え、ハードフェライト磁石粉末が１．５未満ではボンド磁石の磁気特性の改善効果が少ないので好ましくない。好ましい液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末とハードフェライト磁石粉末の配合比率は重量比にて３０．０／７０．０〜７０．０／３０．０である。
【００２２】
なお、前記液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末及びハードフェライト磁石粉末の添加は（１）異方性磁石粉末に直接混合したり、（２）磁石粉末と樹脂との混合物に添加混合したり、（３）磁石粉末と樹脂の混合時に同時に混合する等、いずれの方法でも採用でき、また、液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末とハードフェライト粉末は予め所定の量を配合後、前記方法により、異方性磁石粉末に添加してもよく、さらに、液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末とハードフェライト磁石粉末をそれぞれ単独に順次異方性磁石粉末に添加してもよい。
【００２３】
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。
【００２４】
この発明の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。
【００２５】
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。
【００２６】
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。
【００２７】
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。
【００２８】
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。
【００２９】
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、異方性ボンド磁石の（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。
【００３０】
また、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（米国ゼネラルモーターズ製）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。
【００３１】
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、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％を超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たため、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。
【００３２】
【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１１２５℃、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Ｈ₂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Ｈ₂を行って、真空度１×１０^-5Ｔｏｒｒになるまで排気冷却した。
【００３３】
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Ｒ₂Ｆｅ₁₄Ｂ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。
液体急冷Ｒ−Ｆｅ−Ｂ系永久磁石微粉末には、組成がＲ１２ａｔ％−Ｂ５．４ａｔ％−Ｃｏ５ａｔ％・残部Ｆｅからなる平均粒径約１５０μｍの商品名ＭＱＰ−Ｂ磁粉（米国ゼネラルモーターズ社製）を用い、該磁粉をボールミルにより微粉砕して平均粒径３．０μｍの液体急冷Ｎｄ−Ｆｅ−Ｂ系磁石粉末を得た。
【００３４】
得られた平均粒径１５０μｍの前記異方性磁石粉末に、上記方法により得られた平均粒度３．０μｍの液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末と平均粒度２．０μｍのＳｒ−フェライト粉末を前記磁石粉末に対してそれぞれ５ｗｔ％配合後、さらに、バインダーとして３．５ｗｔ％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８ｔｏｎ／ｃｍ²で成形後、温度１４０℃に２時間保持して硬化し、異方性ボンド磁石を得た。
【００３５】
得られた異方性ボンド磁石の磁気特性、角型性および耐候性試験結果を表２に表す。
また、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、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、放置前の磁束からの低下率を算出した。
【００３６】
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系磁石粉末及びハードフェライト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および耐候性試験結果を表２に表す。
【００３７】
【表１】

【００３８】
比較例２
実施例１にて得られた磁石粉末に実施例１と同一の液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末を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および耐候性試験結果を表２に表す。
【００３９】
比較例３
実施例１にて得られた磁石粉末に実施例１と同一のＳｒフェライト粉末を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および耐候性試験結果を表２に表す。
【００４０】
比較例４
実施例１にて得られた磁石粉末に実施例１と同一の液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末３０ｗｔ％とＳｒ−フェライト粉末３０ｗｔ％を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および耐候性試験結果を表２に表す。
【００４１】
【表２】

【００４２】
【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Ｈ₂処理法により、特定の平均再結晶粒径を有する正方晶のＲ₂Ｆｅ₁₄Ｂ相の再結晶粒集合組織を有する異方性磁石粉末となし、微細な液体急冷Ｒ−Ｆｅ−Ｂ系磁石粉末とハードフェライト粉末及びバインダーの樹脂を所定量配合混合して、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。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an anisotropic bonded magnet having excellent heat resistance, weather resistance and magnetic properties, and a specific heat treatment of an R-Fe-B alloy ingot or coarsely pulverized powder obtained by pulverizing the ingot. An anisotropic magnet powder having a recrystallized grain texture of a tetragonal R ₂ Fe ₁₄ B phase having a specific average recrystallized grain size is formed by the H ₂ treatment method under conditions, and a specific amount of fine liquid is added to this. The present invention relates to an anisotropic bonded magnet having excellent heat resistance, weather resistance, and magnetic properties obtained by blending, mixing, and curing and curing a R-Fe-B magnet powder, a hard ferrite magnet powder, and a binder resin. .
[0002]
[Prior art]
In general, bonded magnets have been rapidly expanded in use in recent years due to their superior mechanical strength and high degree of freedom in shape, despite their inferior magnetic properties compared 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 bonded magnets, (1) magnet powder obtained by mechanical pulverization of R—Fe—B ingots or H ₂ occlusion / disintegration method, or (2) liquid quenching method or atomizing method Thus, magnet powder obtained by quenching from a molten alloy is used.
[0004]
In the former (1) magnet powder, since the R ₂ Fe ₁₄ B phase is broken in the grains and pulverized, 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 if the magnet powder is an aggregate powder that forms an R-rich phase at the R ₂ Fe ₁₄ B phase grain boundary, when it is 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]
[Problems to be solved by the invention]
Therefore, recently, as an anisotropic bond magnet powder, an R—Fe—B alloy ingot or crushed coarse particles are made of 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 has been proposed (Japanese Patent Laid-Open No. 1-132106).
[0007]
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 curing the binder is known.
[0008]
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 surface of the powder by a coupling process or the like in advance, the magnetic powder cracks during molding, and the active metal surface The exposed bonded bond is easily oxidized, and the molded bond magnet has a low density and has a large number of holes. O ₂ and H ₂ O easily penetrate into the holes to oxidize the bond magnet. There was a problem that caused deterioration.
[0009]
The inventors have proposed a high-performance bonded magnet in which a hard ferrite magnet powder is added to the anisotropic bonded magnet in order to obtain a high-performance bonded magnet with excellent corrosion resistance (Japanese Patent Application No. 7-273471). Although the corrosion resistance is excellent, since the hard ferrite magnet powder has low magnetic properties, the effect of improving the magnetic properties of the bonded magnet is not sufficient.
[0010]
The inventors also proposed a high-performance bonded magnet in which a liquid quenched R-Fe-B magnet powder was added to the anisotropic bonded magnet in order to obtain a high-performance bonded magnet with excellent corrosion resistance (Japanese Patent Application). However, although the effect of improving the magnetic properties of the bond magnet is large , the oxidation of the liquid quenching R—Fe—B magnet powder itself causes deterioration of the magnetic properties and the effect of improving the corrosion resistance is small. .
[0011]
This invention eliminates the problems of the above-mentioned anisotropic bonded magnet, and without causing cracks in the magnet powder during molding, it has magnetic properties, particularly Br, (BH) max and squareness, as well as heat resistance and weather resistance. The purpose is to provide an excellent anisotropic bonded magnet.
[0012]
[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 blending and mixing a specific amount of fine liquid quenched R-Fe-B permanent magnet powder and hard ferrite magnet powder before blending, simultaneously with blending or after blending,
(1) Liquid quenched R-Fe-B magnet fine powder and hard ferrite magnet powder are preferentially filled into the gap between the magnet powders or the magnet powder thinly covered with resin at the time of molding, and this phenomenon causes bond magnets The porosity of the inside is reduced, and O ₂ and H ₂ O are prevented from entering the bonded magnet from this gap, and the heat resistance and weather resistance of the bonded magnet are improved.
(2) Since the liquid quenched R-Fe-B magnet fine powder and hard ferrite magnet powder, which are additive powders filled in the voids inside the bond magnet, are hard ferromagnetic materials, The total amount of hard ferromagnets (R-Fe-B magnet powder + liquid quenched R-Fe-B magnet powder + hard ferrite magnet powder) increases, which reduces the magnetic properties of bonded magnets, especially Br. Prevent and improve,
(3) The hard ferrite magnet powder filled in the voids inside the bonded magnet is an oxide, and there is no oxidation or hydroxylation deterioration of the magnetic properties due to O ₂ or H ₂ O, and the heat resistance and weather resistance of the bonded magnet are reduced. To improve,
(4) At the time of bonded magnet molding, the mixed powder of liquid quenching R-Fe-B magnet fine powder and hard ferrite magnet powder alleviates stress concentration on the local part of the magnet powder that occurs during molding, and is active due to cracking of the magnet powder. Since the generation of metal surfaces is suppressed, heat resistance and weather resistance are further improved.
(5) Further, the relaxation of the stress concentration improves the magnetic characteristics in order to suppress the distortion generated in the magnet powder.
(6) It is effective in improving the heat resistance, weather resistance, and magnetic properties of the bonded magnet by synergy of the above-mentioned functions and effects.
The present invention was completed by knowing various effects of the above.
[0013]
That is, this invention
Average anisotropy R-Fe-B magnet powder recrystallized grain size has a recrystallized grain texture consisting of R ₂ Fe ₁₄ B tetragonal phase of 0.05μm~50μm is 45wt% ~98.5wt%, The resin has a composition of 1 wt% to 10 wt%, and the total amount of liquid quenched R—Fe—B magnet powder and hard ferrite magnet powder is 0.5 wt% to 45 wt%.
Anisotropic bond, wherein the liquid quenching R-Fe-B magnet powder and the hard ferrite magnet powder are mixed in a weight ratio of 2.0 / 98.0 to 98.5 / 1.5. It is a magnet.
[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 in a vacuum atmosphere at 950 ° C. for 5 minutes to 4 hours, it is cooled and pulverized.
[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, liquid quenching R-Fe-B magnet powder blended and mixed with a specific anisotropic R-Fe-B magnet powder is amorphous or amorphous and ultrafine crystal by super quenching. It is also possible to use magnetically isotropic R—Fe—B based magnet powder obtained by recrystallizing a tape or ribbon having a mixed structure. 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.
[0018]
Moreover, if the average particle size of the liquid quenched R—Fe—B magnet powder is less than 1.0 μm, it is difficult to actually manufacture and the magnetic properties of the powder are deteriorated. In addition, since the stress relaxation effect, that is, the effect of suppressing cracking of the magnet powder is small and the effect of improving heat resistance, weather resistance and magnetic properties is small, the liquid quenching R-Fe-B magnet powder has a particle size of 1.0 μm to 50 μm. The particle size of the liquid quenching R—Fe—B magnet powder is more preferably 1.0 μm to 10 μm.
[0019]
In this invention, the hard ferrite magnet powder to be added is M type represented by the chemical formula MO · 6Fe ₂ O (M: Ba, Sr, Pb) and chemical formula 2MO · BaO · 8Fe ₂ O ₃ (M: Ba, Sr, Any of the W type represented by Pb) may be used.
If the average particle size of the hard ferrite magnet powder is 0.5 μm or less, it is difficult to produce, and it is not preferable because the hard ferrite magnet powders are difficult to aggregate and disperse uniformly. Not only is it difficult to sufficiently fill the voids, but the magnetic properties of the hard ferrite magnet powder are greatly reduced, so the effects of improving the heat resistance, weather resistance, and magnetic properties of the bonded magnet are small. The average particle size is 0.5 μm to 10 μm. A more preferable average particle size is 0.5 μm to 5 μm.
[0020]
In addition, when the total amount of the liquid quenching R-Fe-B magnet powder and the hard ferrite magnet powder blended in the anisotropic R-Fe-B magnet powder is less than 0.5 wt%, the heat resistance, weather resistance and magnetic properties are reduced. The improvement effect cannot be obtained, and if it exceeds 45 wt%, the magnetic properties of the bonded magnet deteriorate, so 0.5 wt% to 45 wt% is set. A more preferable addition amount is 3 wt% to 30 wt%.
[0021]
Further, the mixing ratio of the liquid quenched R—Fe—B magnet powder added to the magnet powder and the hard ferrite magnet powder is limited to 2.0 / 98.0 to 98.5 / 1.5 by weight. The reason is that if the amount of the liquid quenched R—Fe—B magnet powder is less than 2.0 and the hard ferrite magnet powder exceeds 98.0, the effect of improving the heat resistance and weather resistance of the anisotropic bonded magnet is improved. If the blending amount of the liquid quenched R—Fe—B magnet powder exceeds 98.5 and the hard ferrite magnet powder is less than 1.5, the effect of improving the magnetic properties of the bonded magnet is small. It is not preferable. The mixing ratio of the preferred liquid quenching R—Fe—B magnet powder and hard ferrite magnet powder is 30.0 / 70.0 to 70.0 / 30.0 by weight.
[0022]
The liquid quenching R-Fe-B magnet powder and the hard ferrite magnet powder can be added (1) directly to the anisotropic magnet powder, or (2) added to and mixed with the mixture of the magnet powder and the resin. (3) Any method such as mixing at the time of mixing the magnetic powder and the resin can be adopted, and the liquid quenching R-Fe-B magnet powder and the hard ferrite powder are mixed in a predetermined amount in advance, Thus, the liquid quenching R-Fe-B magnet powder and the hard ferrite magnet powder may be added individually and sequentially to the anisotropic magnet powder.
[0023]
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.
[0024]
The rare earth element R used in the 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 La, Ce, Sm, Gd. , Er, Eu, Tm, Yb, Lu, and Y are preferred. 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.
[0025]
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%.
[0026]
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%.
[0027]
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.
[0028]
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.
[0029]
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 in order to make (BH) max of the anisotropic bonded magnet 14 MGOe or more.
[0030]
In addition, the liquid rapidly cooled R—Fe—B magnet powder used for blending is obtained by finely pulverizing a magnet powder (average particle size of about 150 μm) with a trade name of MQP (manufactured by General Motors, USA) to several to several tens of μm. obtain.
[0031]
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 Permanent magnets with 90 atomic% as the main component and excellent magnetic properties when R is less than 8 atomic%, particularly high coercive force, and residual magnetic flux density (Br) decreases when it exceeds 30 atomic%. Since the material was obtained, the range was 8 atomic% to 30 atomic%. When B is less than 2 atomic%, a high coercive force (iHc) cannot be obtained, and when it exceeds 28 atomic%, many B-rich non-magnetic phases exist. Therefore, since the residual magnetic flux density (Br) is reduced, the range of 2 atomic% to 28 atomic% is set, and when Fe is less than 42 atomic%, the residual magnetic flux density (Br) is reduced. Since magnetic force cannot be obtained, the content of 42 atomic% to 90 atomic% , Or by replacing part of Fe with Co, it can be added various additive elements.
[0032]
【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 1125 ° C. for 10 hours.
The ingot is inserted into a heating furnace, and the temperature in the heating furnace is increased from room temperature to 850 ° C. as H ₂ gas of 760 Torr. Subsequently, the temperature is maintained at 850 ° C. for 3 hours, and then maintained at 850 ° C. for 1 hour. Then, the H ₂ was removed and the exhaust was cooled until the degree of vacuum became 1 × 10 ⁻⁵ Torr.
[0033]
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.
The liquid quenching R-Fe-B permanent magnet fine powder has a product name MQP-B magnetic powder (made by General Motors, USA) having an average particle size of about 150 μm composed of R12 at% -B 5.4 at% -Co 5 at% and the balance Fe. The magnetic powder was finely pulverized by a ball mill to obtain a liquid quenched Nd—Fe—B magnet powder having an average particle size of 3.0 μm.
[0034]
To the obtained anisotropic magnet powder having an average particle size of 150 μm, liquid quenched R—Fe—B magnet powder having an average particle size of 3.0 μm obtained by the above method and Sr-ferrite powder having an average particle size of 2.0 μm were added. After blending 5 wt% of each of the magnet powders, and further blending and mixing 3.5 wt% of an epoxy resin as a binder, vacuum drying, molding at a molding pressure of 8 ton / cm ² in a magnetic field of 12 kOe, and a temperature of 140 ° C. And cured for 2 hours to obtain an anisotropic bonded magnet.
[0035]
Table 2 shows the magnetic properties, squareness, and weather resistance test results of the obtained anisotropic bonded magnet.
Moreover, the test conditions of the weather resistance test were the conditions of 100 degreeC x 1000 hours in air | atmosphere, and measured the time-dependent change of the magnetic flux in a test. The magnetic flux aging test method is to magnetize the test piece, measure the magnetic flux, leave it in the atmosphere at 100 ° C. for 1000 hours, magnetize the test piece again, measure the magnetic flux, The reduction rate from was calculated.
[0036]
Comparative Example 1
An anisotropic bonded magnet was prepared under the same manufacturing conditions as in Example 1 except that the liquid quenching R-Fe-B magnet powder and the hard ferrite magnet powder were not mixed and mixed with the magnet powder obtained in Example 1. Table 2 shows the magnetic characteristics and the weather resistance test results of the obtained anisotropic bonded magnet.
[0037]
[Table 1]

[0038]
Comparative Example 2
An anisotropic bonded magnet under the same production conditions as in Example 1 except that the magnet powder obtained in Example 1 is mixed and mixed with 10 wt% of the same liquid quenched R—Fe—B magnet powder as in Example 1. Table 2 shows the magnetic properties and weather resistance test results of the anisotropic bonded magnets obtained.
[0039]
Comparative Example 3
An anisotropic bonded magnet was produced under the same production conditions as in Example 1 except that 10 wt% of the same Sr ferrite powder as in Example 1 was blended and mixed with the magnet powder obtained in Example 1. Table 2 shows the magnetic properties and weather resistance test results of the anisotropic bonded magnet.
[0040]
Comparative Example 4
The same production conditions as in Example 1 except that the magnet powder obtained in Example 1 was mixed and mixed with 30 wt% of the same liquid quenched R—Fe—B magnet powder and 30 wt% of Sr-ferrite powder as in Example 1. Table 2 shows the magnetic properties and the weather resistance test results of the anisotropic bonded magnet obtained.
[0041]
[Table 2]

[0042]
【The invention's effect】
The anisotropic bonded magnet according to the present invention is obtained by subjecting an R—Fe—B alloy ingot or coarsely pulverized powder obtained by pulverizing the ingot to a specific average re-treatment by H ₂ treatment method 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, fine liquid quenched R—Fe—B magnet powder, hard ferrite powder and binder resin As shown in the examples, it is excellent in heat resistance, weather resistance and magnetic properties.

Claims

Average anisotropy R-Fe-B magnet powder recrystallized grain size has a recrystallized grain texture consisting of R ₂ Fe ₁₄ B tetragonal phase of 0.05μm~50μm is 45wt% ~98.5wt%, The resin has a composition of 1 wt% to 10 wt%, and the total amount of liquid quenched R—Fe—B magnet powder and hard ferrite magnet powder is 0.5 wt% to 45 wt%. An anisotropic bonded magnet, wherein the blending ratio of the hard ferrite magnet powder is 2.0 / 98.0 to 98.5 / 1.5 by weight.