JP3845461B2

JP3845461B2 - Method and apparatus for producing permanent magnet alloy powder for bonded magnet

Info

Publication number: JP3845461B2
Application number: JP10799895A
Authority: JP
Inventors: 裕和金清; 哲広沢
Original assignee: Neomax Co Ltd
Current assignee: Proterial Ltd
Priority date: 1995-04-06
Filing date: 1995-04-06
Publication date: 2006-11-15
Anticipated expiration: 2021-11-15
Also published as: JPH08277403A

Description

【０００１】
【産業上の利用分野】
この発明は、各種モーター、スピーカー用ならびにメーターやセンサーなどに最適なボンド磁石用永久磁石合金粉末の製造方法及びその製造装置に係り、非晶質合金粉末もしくは平均結晶粒径が１０ｎｍ以下の超微細結晶組織をもつ合金粉末を連続的に製造できる超急冷合金薄帯の製造方法と前記粉末を特定の熱処理にてボンド磁石用永久磁石合金粉末とする熱処理とを組み合わせることにより、配合原料から平均結晶粒径３００ｎｍ以下である微細結晶型ボンド磁石用磁石合金粉末を連続的に生産するボンド磁石用永久磁石合金粉末の製造方法及びその装置に関する。
【０００２】
【従来の技術】
Ｒ−Ｆｅ−Ｂ系ボンド磁石用磁石合金粉末は、主に銅および鉄からなる回転ロール上に溶融金属を出湯し、急冷・凝固して非晶質合金薄帯を製造する方法が、これまで数多く検討されてきた。
例えば、特開昭５７−２１０９３４号公報や特開昭６０−９８５２号公報等で、Ｎｄ−Ｆｅ−Ｂ系永久磁石を回転ロールによる急冷・凝固法によって製造する方法が紹介されている。また、同様な方法が磁性材料を研究する大学、研究機関において多数研究され、報告されているが、いずれも数１０ｇ〜数１００ｇの合金を底部にオリフィスを有するノズル内で融解し出湯する実験室規模のものである。
【０００３】
処理量を増した例としては、特願昭６３−３３３８２９号公報で溶解炉を傾転させ底部に出湯ノズルを有する容器内へ溶湯を注ぎ、ノズル下方にある回転ロール上に出湯する方法が紹介されている。
しかしながら、工業的量産に対応できるよう処理量を５０ｋｇ以上まで増すためには、当該溶解炉および溶解槽を大きくする必要があるだけでなく、嵩比重が０．０１ｇ／ｃｍ³程度の合金薄帯を収容するために巨大な急冷槽が必要となり、装置が非常に大型となるため、装置の製造コストが巨額になる他、真空排気およびガス置換に多大の時間と膨大な不活性ガスが必要となる。
【０００４】
【発明が解決しようとする課題】
ボンド磁石用磁石合金粉末としてα−鉄および鉄を主成分とする強磁性合金からなる軟磁性相とＮｄ₂Ｆｅ₁₄Ｂ型結晶構造を有する硬磁性相とが共存し、各構成相の平均結晶粒径が１ｎｍ〜５０ｎｍである永久磁石合金粉末、また、Ｎｄ₂Ｆｅ₁₄Ｂ型結晶構造を有する硬磁性相を主相とする平均結晶粒径が３００ｎｍ以下である永久磁石合金粉末は酸化しやすい希土類金属を含むことから、配合原料の溶解、急冷・凝固は、真空中もしくは不活性ガス中で行う必要があるため、装置の大型化に伴い、真空排気時間が長くなると共に、不活性ガス量が膨大になるなど、生産効率および生産コストの上昇の点から、工業生産上実用的でない。
【０００５】
また、前記磁石合金粉末の製造において、回転ロールを用いた急冷・凝固法の処理量向上のためには溶解量を増す必要があるが、溶解量を増すには溶解坩堝、高周波電源の大型化等が必要となり、結果として装置の製造コストの高騰を招き、同時に前述したように設備の大型化は真空排気時間が長くなる、不活性ガス量が膨大になるなどの問題を引き起こす。
【０００６】
一方、回転ロールを用いた急冷・凝固法により得られる合金薄帯の嵩比重は０．０１ｇ／ｃｍ³程度であるため、合金薄帯を回収する容器は同様の組成をもつ比重７．５ｇ／ｃｍ³の鋳造合金の７００倍以上の容積を必要する。
従って、工業生産上溶解量を増し、急冷・凝固の処理量を増した場合、非常に大きな回収容器が必要となる。
【０００７】
ボンド磁石用磁石合金粉末において均一な磁気特性を得るためには、回転ロール上へ出湯される溶湯のヘッド圧の変化に対応して溶解槽と急冷槽の槽間差圧を調整することで、出湯量を一定に保ち、均質な急冷組織をもつ合金薄帯を作製する必要があるが、合金薄帯の生産量を増すために溶解量を増やすと溶湯ヘッド圧の変化が大きくなり、槽間差圧の調整が溶湯ヘッド圧の変化に対応しきれなくなるため、出湯量が変動し均質な急冷組織をもつ合金薄帯が得られない問題がある。
【０００８】
また、貯湯容器内の湯高を測定し、槽間差圧を調整する方法が提案（特開平５−７５８０１号公報）されているが、５０ｋｇ以上の溶解量の大型炉では槽内容積が大きくなり、圧力制御が十分早く達成できず、無理にこれを達成しようとすると、差圧制御のための排気装置およびガス注入機構が著しく大型化、巨大な建設費が必要となる問題がある。
【０００９】
いずれにしてもボンド磁石用磁石合金粉末の製造において、従来からある回転ロールを用いた急冷・凝固装置では処理量を量産規模まで増すためには、装置の大型化が必要となるが、作業効率の低下、装置の製造コストおよび運転コストの上昇、ならびに磁気特性のバラツキを引き起こすため、ボンド磁石用磁石合金粉末のコストアップにつながる。
【００１０】
この発明は、等方性ボンド磁石原料となる３μｍ〜５００μｍの粉末粒径をもつα−鉄および鉄を主成分とする強磁性合金からなる軟磁性相とＮｄ₂Ｆｅ₁₄Ｂ型結晶構造を有する硬磁性相とが共存し、各構成相の平均結晶粒径が１ｎｍ〜５０ｎｍであるボンド磁石用永久磁石合金粉末、また、Ｎｄ₂Ｆｅ₁₄Ｂ型結晶構造を有する硬磁性相を主相とする平均結晶粒径が３００ｎｍ以下である安定した磁気特性を有するボンド磁石用永久磁石合金粉末を連続的に製造して安価に提供できるボンド磁石用永久磁石合金粉末の製造方法及びその装置の提供を目的としている。
【００１１】
【課題を解決するための手段】
発明者は、ボンド磁石用磁石粉末を量産化する上において、溶解槽及び溶解炉等設備の大型化の防止、製造コストの低減と共に真空排気及びガス供給に長時間を要することなく、安価に品質良好なるボンド磁石用永久磁石合金粉末を製造する方法について、種々検討した結果、溶解炉の能力と溶湯を急冷薄帯化する急冷ロール等急冷装置の能力をほぼ等しくし、溶解炉にて溶解した溶湯を急冷装置にて急冷薄帯化する前に、溶湯温度に保温された貯湯容器に溶湯を貯湯し、貯湯容器内の溶湯を急冷装置にて急冷薄帯にする時、溶解炉にて磁石組成の配合原料を連続的に溶解し、貯湯容器内の減少した溶湯に追加補充し、追加補充した溶湯を連続して急冷薄帯化すると共に貯湯容器内の溶湯レベルの低下に伴う出湯ノズルでの溶湯圧の変動により、急冷薄帯の品質、寸法の変動を防止するために、貯湯容器内の溶湯レベルを検出器にて検出し、前記検出信号により貯湯容器内の溶湯のヘッド圧の変化に対応して、急冷槽の圧力を変動させることにより、溶解槽と急冷槽の槽間圧力差と貯湯容器内の溶湯のヘッド圧からなる出湯圧力に依存する出湯量を一定に保持して、急冷薄帯の品質を均一に保持し、急冷薄帯を急冷槽内にて切断圧縮することにより、後続工程での設備の大型化の防止及びガス供給及び排気時間の増大化を防止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、
Ｒ−Ｆｅ−Ｂ系磁石合金（但しＲはＰｒ、Ｎｄ、Ｄｙの一種または二種以上）組成になる如く配合した原料を真空もしくは不活性ガス雰囲気の溶解槽内で、配合原料を追加供給できる機構を有する溶解炉にて溶解後、この溶湯を底部に出湯ノズルを有し出湯温度を保持できる貯湯容器へ傾注後、貯湯容器内の溶湯を出湯ノズル直下に配置した水冷ロール上へ出湯して急冷・凝固により非晶質もしくは平均結晶粒径が１ｎｍ以下の超微細結晶組織をもつ合金薄帯を作製するに際し、出湯ノズルからの出湯時、貯湯容器内の溶湯レベルに応じて水冷ロールを配置する急冷槽内の圧力を制御して一定の出湯量を保持し、又水冷ロールにより溶湯の急冷凝固中に溶解炉へ配合原料を追加供給し、溶解後、再び溶湯容器へ溶湯を供給する作業を繰り返して、連続的に合金薄帯を作製し、作製した前記薄帯を急冷槽内に設けた破断機により薄片となし、さらに、圧縮機により薄片を２ｇ／ｃｍ³〜３ｇ／ｃｍ³に圧縮した後、急冷槽外へと排出し、圧縮薄片を粉砕機により平均粉末粒径が３μｍ〜５００μｍになるよう粉砕した後、不活性ガス中にて６００℃〜８００℃の熱処理を行い、平均結晶粒径３００ｎｍ以下である微細結晶型永久磁石合金粉末を連続的に製造することを特徴とするボンド磁石用永久磁石合金粉末の製造方法である。
【００１３】
また、この発明は、上記の構成において、
組成式をFe_100-x-yR_xB_y(但しRはPr、Nd、Dyの一種または二種以上)と表し、組成範囲を限定する記号x、yが下記値を満足する 90%以上非晶質である合金薄片を粉砕機により平均粉末粒径が3μm〜500μmになるよう粉砕した後、 90%以上非晶質である粉砕粉を不活性ガス中にて結晶化が開始する温度から600℃〜750℃の処理温度までの昇温速度が10℃/分〜50℃/秒になる結晶化熱処理を施し、α-鉄および鉄を主成分とする強磁性合金からなる軟磁性相とNd₂Fe₁₄B型結晶構造を有する硬磁性相とが共存し、各構成相の平均結晶粒径が1nm〜50nmであるボンド磁石用永久磁石合金粉末の製造方法を提案する。
3≦x≦6at%
10≦y≦30at%
【００１４】
また、この発明は、上記の構成において、
組成式をＦｅ_100-x-yＲ_xＢ_y（但しＲはＰｒ、Ｎｄ、Ｄｙの一種または二種以上）と表し、組成範囲を限定する記号ｘ、ｙが下記値を満足する結晶粒径が１０ｎｍ以下の超微細結晶組織を有する合金薄片を粉砕機により平均粉末粒径が３μｍ〜５００μｍになるよう粉砕した後、結晶粒径が１０ｎｍ以下である粉砕粉を不活性ガス中にて５５０℃〜８００℃の温度で平均結晶粒径が３００ｎｍ〜５０ｎｍに粒成長する金属組織制御のための熱処理を施し、Ｎｄ₂Ｆｅ₁₄Ｂ型結晶構造を有する硬磁性相を主相とする平均結晶粒径３００ｎｍ以下であるボンド磁石用永久磁石合金粉末の製造方法を提案する。
８≦ｘ≦２０ａｔ％
４≦ｙ≦１０ａｔ％
【００１５】
また、この発明は、
溶解槽と急冷槽とから構成され、
前記溶解槽は、R-Fe-B(但しRはPr、Nd、Dyの一種または二種以上)磁石合金組成になる如く配合原料を溶解する溶解炉と、底部に出湯ノズルを有しかつ出湯温度に保持する加熱装置を有する貯湯容器と、大気の浸入を防止しつつ配合原料を溶解炉に供給する配合原料供給機構とを配設し、
前記急冷槽は、出湯ノズルから出湯された溶湯を急冷凝固して急冷薄帯とするための水冷可能な回転ロールと、得られた嵩比重0.01g/cm³〜0.05g/cm³の急冷薄帯を破断するための破断機と、破断片を更に嵩比重2g/cm³〜3g/cm³に圧縮する水冷可能な圧縮機と、大気の浸入を防止して合金薄片を槽外に排出可能な合金薄帯回収機構とを有し、
前記出湯ノズルからの出湯量を一定に保持するため、ガスを供給して前記溶解槽と急冷槽の槽内圧力を制御しかつ真空又は不活性ガス雰囲気を保持するためのガス供給口と排気口が、前記溶解槽と急冷槽にそれぞれ配設され、
雰囲気を破ることなく溶解、出湯、急冷凝固、破断、圧縮、排出を並行連続して行うことを特徴とするボンド磁石用永久磁石合金粉末の製造装置である。
【００１６】
また、この発明は、上記の構成において、
溶解槽内の圧力を一定に保持しながら溶解炉から貯湯容器へ傾注された溶湯の溶湯レベル検出装置と、前記検出装置の検出信号により貯湯容器内の出湯ノズルオリフィス部に働く溶湯のヘッド圧の変化に対応して急冷槽内の圧力を制御するガス供給口と排気口とを有し、溶解槽と急冷槽の槽間差圧と貯湯容器内の溶湯のヘッド圧の和からなる出湯圧力に依存する出湯量を一定に保持し、均質な急冷・凝固組織をもつ合金薄帯を連続的に製造するボンド磁石用永久磁石合金粉末の製造装置を併せて提案する。
【００１７】
【作用】
この発明によるボンド磁石用永久磁石合金粉末の製造方法を図１に示す製造装置に基づいて詳述する。
装置は溶解炉３を有する溶解槽１とその下部に接続された急冷槽２を基本とし、いずれも槽内は真空又は不活性ガス雰囲気を保持かつ槽内圧力を調整可能なように排気口１ａ，２ａとガス供給口１ｂ，２ｂを有する。
側壁に排気口１ａ、ガス供給口１ｂを有する溶解槽１上部には、同様に排気口８ａ、ガス供給口８ｂを有する配合原料供給装置８を載置してあり、前記溶解槽１内には傾動可能の溶解炉３と、外周部に図示しない加熱装置を有しかつ下部に出湯ノズル５を有する貯湯容器４を配置してある。
貯湯容器４の出湯ノズル５は溶解槽１と急冷槽２との隔壁に配置され、急冷槽２内にはこの出湯ノズル５下方位置に急冷薄帯を生成する水冷ロール７を設けてある。
【００１８】
急冷槽２には前記水冷ロール７により得られた急冷薄帯２２を回収するための上下方向に配置された合金回収機構部９が接続され、同機構部９には水冷ロール７より送り出される急冷薄帯２２を破断する破断機１０、ホッパー部、ボールバルブ１２を経て、破断された急冷薄片２３を圧縮する圧縮機１１を内蔵し、ボールバルブ１２下方の側壁に排気口９ａ、ガス供給口９ｂを有する。
圧縮機１１は、シリンダー内に落下した急冷薄片２３をピストンで圧縮し、圧縮時に外気を同機構部９内に浸入させることなく、ヘッド側から圧縮した急冷薄片２３を排出できる構成からなる。
【００１９】
貯湯容器４には溶湯レベルを検出するため耐火物製浮き１５を配置し、前記浮き１５の上下動を検出するＣＣＤカメラ１４を溶解槽１上部に設けた覗き窓１３上部に配置し、ＣＣＤカメラ１４にて検知された浮き１５の上下動の変位は、図１に示すごとく演算器にて、溶解槽１内の圧力を検出した信号Ｐ₁と急冷槽２内の圧力を検出した信号Ｐ₂ とともに演算され、出湯ノズル５の出湯圧力を算出し、予め設定された出湯圧力との偏差信号が急冷槽２のガス供給口２ｂに送られて出湯圧力が一定になるように制御されると共に前記偏差信号は溶解槽１のガス供給口１ｂに送られ、溶解槽１内の圧力が一定なる如く、排気量に応じて各々ガス供給口１ｂ，２ｂよりガスが供給される。
この発明において、溶湯レベルの検出装置としてここでは耐火物製浮きとＣＣＤカメラを挙げたが、レーザービームの反射光をＣＣＤカメラにて測定する方法や熱電対法、接触子を入れる方法、γ線法等公知の方法を用いることができる。
【００２０】
真空又は不活性ガスにて保持された溶解槽１内に大気の浸入を防止しながら、Ｒ−Ｆｅ−Ｂ系磁石の所要組成になる如く配合された配合原料２０は、原料供給装置８より溶解炉３に供給されて所要温度にて溶解され、得られた溶湯２１は溶解炉３を傾注して、所要温度に保温された貯湯容器４に貯湯される。図中、６は傾注時に溶湯を貯湯容器４へ集めるロートである。
貯湯容器４の溶湯２１は、容器４底部の出湯ノズル５の直下に配置されて高速回転する水冷ロール７上に落下し、急冷凝固により非晶質又は平均結晶粒径が１０ｎｍ以下の微細結晶組織を有する急冷薄帯２２が得られる。
【００２１】
出湯ノズル５から水冷ロール７へ溶湯２１が出湯する際、上述のごとく、貯湯容器４内の溶湯レベルに応じて、急冷槽２及び溶解槽１の槽内圧力を調整することにより、出湯量は一定に保持され、また、水冷ロール７による溶湯２１の急冷凝固中、溶解炉３へ配合原料２０を配合原料供給装置８より供給し、前記溶解炉３にて溶解後、再度溶湯２１を貯湯容器４内に傾注する作業を繰返し、連続的に水冷ロール７により急冷薄帯２２を製造することができる。
【００２２】
得られたみかけ密度（嵩比重）０．０１ｇ／ｃｍ³〜０．０５ｇ／ｃｍ³の急冷薄帯２２は、直ちに破断機１０により、５０ｃｍ以下のみかけ密度０．１ｇ／ｃｍ³〜１ｇ／ｃｍ³の急冷薄片２３に破断後、前記薄片２３を圧縮機１１により、みかけ密度２ｇ／ｃｍ³〜３ｇ／ｃｍ³に圧縮する。
圧縮機１１より排出され圧縮された圧縮合金薄片は、別途粉砕機により平均粉末粒径が３μｍ〜５００μｍになるように粉砕した後、熱処理炉で不活性ガス中にて６００℃〜８００℃に熱処理して、平均結晶粒径が１ｎｍ〜３００ｎｍの微細結晶のボンド磁石用永久磁石合金粉末を連続的に製造することができる。
【００２３】
この発明において、出湯ノズル５から溶湯２１を出湯する際、出湯ノズル５のオリフィスの直径が０．５ｍｍ〜２ｍｍと小さいため、溶湯２１の粘性が１．７Ｐａ・Ｓ以上と高い場合、溶解炉３から貯湯容器４へ傾注するだけでは、溶湯２３と出湯ノズル５の内部壁面の摩擦力により出湯できないため、溶解槽１内の圧力より急冷槽２内の圧力を下げることで、溶解槽１と急冷層２に圧力差を付け、この圧力差により出湯ノズル５から溶湯２１を出湯することができる。
また、溶解温度が高いために溶湯２１の粘性が１．７Ｐａ・Ｓ未満の場合、溶解炉３から貯湯容器４へ傾注後、直ちに出湯が開始するため、下部に開閉自在の機構を有した出湯ノズル５を設けることにより、出湯操作を行うことができる。
【００２４】
この発明において、急冷ロールにＣｕ製ロールを用いる場合は、付設する水冷装置の冷却能力にも左右されるが、そのロール表面周速度は１０〜５０ｍｍ／秒の範囲が好適の急冷組織が得られるので好ましい。すなわち周速度が１０ｍｍ／秒未満ではアモルファス組織とならず、また、ロール表面周速度が５０ｍｍ／秒を超えると結晶化の際、良好な硬磁気特性の得られる微細結晶集合体とならず好ましくない。
尚、付設する水冷装置は、定常的に凝固熱を抜熱する必要を満たすものでなければならず、単位時間当たりの凝固潜熱と出湯量に応じて算出し、これとバランスしてこれを越えるものでなくてはならず、２０ｋｃａｌ／ｈｒ程度が少なくとも必要となる。
【００２５】
この発明の製造方法により、実質的に９０％以上の非晶質の急冷薄片が得られるが、その磁石組成は組成式Ｆｅ_100-x-yＲ_xＢ_yと表し、組成範囲を限定する記号ｘ、ｙは下記値を満足し、
３≦ｘ≦６ａｔ％１０≦ｙ≦３０ａｔ％
前記急冷薄片は粉砕機により平均粉末粒径が３μｍ〜５００μｍになるように粉砕した後、実質的に９０％以上の非晶質である粉砕粉に、不活性ガス中で結晶化が開始する温度付近から６００℃〜７５０℃の処理温度までの昇温速度が１０℃／分〜５０℃／秒の結晶化熱処理を施すことにより、α−鉄および鉄を主成分とする強磁性化合物からなる軟磁性相とＮｄ₂Ｆｅ₁₄Ｂ型結晶構造を有する硬磁性相が共存し、各構成相の平均結晶粒径が１ｎｍ〜５０ｎｍの微細結晶の磁石粉末が得られる。
【００２６】
この発明において、組成式のｘ、ｙの値を限定した理由はＲは３ａｔ％未満では３．０ｋＯｅ以上のｉＨｃが得られず、また６ａｔ％を超えると６ｋＧ以上のＢｒが得られないため、３ａｔ％〜６ａｔ％の範囲とする。好ましいＲの範囲は４〜５．５ａｔ％である。
又、Ｂは１０ａｔ％未満では超急冷法を用いても非晶質組織が得られず、熱処理を施しても２．０ｋＯｅ未満のｉＨｃしか得られず、又３０ａｔ％を超えると３．０ｋＯｅ以上のｉＨｃが得られないため、１０ａｔ％〜３０ａｔ％の範囲とする。好ましいＢの範囲は１５ａｔ％〜２０ａｔ％である。
【００２７】
この発明において、結晶化熱処理温度を６００〜７５０℃に限定した理由は、６００℃未満ではＮｄ₂Ｆｅ₁₄Ｂ相が析出しないためｉＨｃが発現せず、また、７５０℃を超えると粒成長が著しく、ｉＨｃ、Ｂｒ及び減磁曲線の角型性を劣化するので好ましくない。
また、この発明において、熱処理を結晶化が開始する温度付近からの昇温速度が、１０℃／分未満では昇温中に粒成長が起こり良好な硬磁気特性が得られる微細結晶集合体とならず、３ｋＯｅ以上のｉＨｃが得られず、また、５０℃／秒を超えると６００℃を通過してから生成するＮｄ₂Ｆｅ₁₄Ｂ相の析出が十分に行はれず、ｉＨｃが低下するだけでなく、磁化曲線の第２象限にＢｒ点近傍に磁化の低下のある減磁曲線となり、（ＢＨ）ｍａｘが劣化するので好ましくない。
【００２８】
この発明において、Ｆｅの一部をＡｌ、Ｓｉ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ｇａ、Ｚｒ、Ｎｂ、Ｍｏ、Ａｇ、Ｐｔ、Ａｕ、Ｐｂの一種または数種を組み合せて置換することにより、平均結晶粒径が１ｎｍ〜３０ｎｍに微細化されるために、残留磁束密度が向上し、さらに保磁力を発現するＮｄ₂Ｆｅ₁₄Ｂ型結晶構造を有する硬磁性相の金属組織中における体積比率が増すため、保磁力が向上し、同時に耐熱性および耐食性も向上する。ただし、Ｆｅに対する置換量が０．１％以下の場合はかかる効果を得られず、５０％以上の場合は、飽和磁化が大きく低下するため良好な磁気特性が得られないため、Ｆｅに対する置換量を０．１％〜５０％の範囲とする。好ましいＦｅに対する置換量は２％〜２０％である。
【００２９】
この発明において、各構成相の平均結晶粒径を１ｎｍ〜５０ｎｍに限定した理由は１ｎｍ未満の平均結晶粒径を得ることは工業生産上困難であり、また、５０ｎｍを超えると減磁曲線の角型性が著しく劣化し所要の磁気特性を得ることができない。
また、この発明の実質的に非晶質組織の急冷薄帯を粉砕機にて３μｍ〜５００μｍに粉砕する理由は、３μｍ未満では粉砕粉の表面積が増大するため、ボンド磁石の成形体密度が低下して好ましくなく、５００μｍを超えるとボンド磁石内部の空隙が大きくなり成形体密度が低下するため好ましくない。
【００３０】
また、この発明により結晶粒径が１０ｎｍ以下の超微細結晶組織を有する急冷薄帯の得られる磁石組成は、組成式Ｆｅ_100-x-yＲ_xＢ_y（但しＲはＰｒ、Ｎｄ、Ｄｙの一種または二種以上）と表し、組成範囲を限定する記号ｘ、ｙは下記値を満足し、
８≦ｘ≦２０ａｔ％、４≦ｙ≦１０ａｔ％
前記薄片を粉砕機にて、平均粉末粒径が３μｍ〜５００μｍになるよう粉砕した後、結晶粒径が１０ｎｍ以下である粉砕粉を不活性ガス中にて、５５０℃〜８００℃の温度に平均結晶粒系が３００ｎｍ〜５０ｎｍに粒成長する金属組織制御の熱処理を施し、Ｎｄ₂Ｆｅ₁₄Ｂ型結晶構造を有する硬磁性相を主相とする平均結晶粒径が３００ｎｍ以下のボンド磁石用磁石合金粉末が得られる。
【００３１】
この発明において、組成式のｘ、ｙの値を限定した理由は、Ｒは８ａｔ％未満ではα−Ｆｅと同一構造の立方晶組織が存在するため、８０ｋＯｅ以上のｉＨｃ、ならびに７ｋＧ以上のＢｒが得られず、また、２０ａｔ％を超えるとＲリッチの非磁性相が多くなるため飽和磁化が低下して好ましくないため、８ａｔ％〜２０ａｔ％の範囲とする。好ましいＲの範囲は１０ａｔ％〜１６ａｔ％である。
Ｂは、４ａｔ％未満では菱面体組織となるため、８ｋＯｅ以上のｉＨｃならびに７ｋＧ以上のＢｒが得られず、また、１０ａｔ％を超えると飽和磁化が低下して好ましくないため、４ａｔ％〜１０ａｔ％の範囲とする。好ましいＢの範囲は６ａｔ％〜８ａｔ％である。
【００３２】
Ｆｅは一部又は全量をＣｏと置換しても良く、さらにＦｅ＋Ｃｏの量に対し、０．１％〜２０％の範囲であれば、Ａｌ、Ｓｉ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｎｉ、Ｃｕ、Ｇａ、Ｚｒ、Ｎｂ、Ｍｏ、Ａｇ、Ｐｔ、Ａｕ、Ｐｂを含有しても磁気特性をそれほど劣化させるものでなく許容される。
【００３３】
急冷薄帯の結晶粒径を１０ｎｍ以下に限定した理由は、１０ｎｍを超えると粗大なα−Ｆｅ粒子を含む組織となり好ましくない。
この発明の急冷薄帯を粉砕機にて３μｍ〜５００μｍに粉砕した理由は、３μｍ未満では粉砕粉の表面積が増大するためボンド磁石成形密度が低下して好ましくなく、５００μｍを超えるとボンド磁石内部の空隙が大きくなり、成形体密度が低下するため好ましくない。
本発明における金属組織制御熱処理温度を５５０℃〜８００℃に限定した理由は５５０℃未満では８ＫＯｅ以上のｉＨｃを得るために必要な結晶粒に成長せず、８００℃を超えると平均結晶粒径が３００ｎｍ以上となり、Ｂｒが著しく低下するため、好ましくない。
【００３４】
【実施例】
実施例１
製造装置として、図１に示すこの発明による連続製造装置を用い、Ｎｄ_4.5Ｆｅ₇₇Ｂ_18.5ａｔ％磁石組成になる如く、配合原料２０ｋｇを原料供給装置より溶解炉に装入し、溶解時間２０分後、温度１３５０℃の溶湯を外周部に高周波加熱装置を配設して溶湯を１３００℃に保持可能な容量３．２ｌの貯湯容器内に装入後、前記貯湯容器底部に開閉自在の出湯ノズルより、回転数１２００ｒｐｍの外径３５０ｍｍの水冷Ｃｕロール外周面に出湯して、非晶質組織よりなる厚み４０μｍ、幅３．０ｍｍの急冷薄帯２０ｋｇを２２分にて急冷凝固させた。
この際、前記急冷薄帯を製造中に溶解炉内では連続に装入された配合原料を溶解し、前記貯湯容器内の減少した溶湯に再度溶解した溶湯を追加補充する、溶解、貯湯、急冷凝固工程を連続５回繰返し行って、みかけ密度（嵩比重）０．０２ｇ／ｃｍ³の急冷薄帯を連続して９６ｋｇ製造した。
【００３５】
得られた急冷薄帯は、急冷槽内で続いて破断機により５０ｃｍ以下のみかけ密度０．８ｇ／ｃｍ³の薄片にした後、圧縮機に圧力６．４ｋｇ／ｃｍ³にて前記薄片を圧縮して、みかけ密度２．４ｇ／ｃｍ³に圧縮後、圧縮機外に排出した。
その後、前記圧縮合金薄片を粉砕機にて平均粉末粒径１５０μｍに粉砕後、不活性ガス中で結晶化が開始する温度５８０℃から６４０℃の処理温度までの昇温速度３０℃／分にて結晶化熱処理を施し、この後粉砕してα−鉄および鉄を主成分とする強磁性合金からなる軟磁性相とＮｄ₂Ｆｅ₁₄Ｂ型結晶構造を有する硬磁性相が共存し、各構成相の平均結晶粒径が５０ｎｍのボンド磁石用磁石合金粉末を得た。
【００３６】
得られた合金粉末にエポキシ樹脂からなるバインダーを３ａｔ％の割合で混合したのち、１２ｎｍ×１２ｎｍ×８ｎｍ寸法のボンド磁石を作成した。
得られたボンド磁石は密度６ｇ／ｃｍ³、その磁気特性は、ｉＨｃ＝３．５ｋＯｅ、Ｂｒ＝８．４ｋＧ、ＢＨｍａｘ＝５．５ＭＧＯｅであった。
【００３７】
実施例２
実施例１と同一の製造装置を用い、Ｎｄ₁₃Ｆｅ₈₀Ｂ₇ａｔ％磁石組成になる如く、実施例１と同一条件にて溶製、急冷凝固して、結晶粒径が１０ｎｍ以下の超微細結晶組織を有する急冷薄片を作製し、その後粉砕機にて平均粉末粒径が１５０μｍになるよう粉砕した後、結晶粒径が１０ｎｍ以下の粉砕粉を不活性ガス中で６５０℃に１０分間、金属組織制御の熱処理を行い、平均結晶粒径が２００ｎｍに粒成長させ、Ｎｄ₂Ｆｅ₁₄Ｂ型結晶構造を有する硬磁性相を主相とする平均結晶粒径２００ｎｍ以下のボンド磁石用磁性合金粉末を得た。
得られた合金粉末を実施例１と同一条件にてボンド磁石を作成し、得られたボンド磁石は密度６ｇ／ｃｍ³、その磁気特性は、ｉＨｃ＝９．２ｋＯｅ、Ｂｒ＝６．５ｋＧ、ＢＨｍａｘ＝９ＭＧＯｅであった。
【００３８】
【発明の効果】
この発明は、実施例に明らかなように、溶解炉の能力と溶湯を急冷薄帯化する急冷ロール装置の能力をほぼ等しくして連続化可能にし、かつ装置内のガス供給及び排気時間の増大化を防止したもので、溶解炉にて溶解した溶湯を急冷装置にて急冷薄帯化する前に、出湯温度に保温された貯湯装置に溶湯を貯湯し、貯湯装置内の溶湯を急冷装置にて急冷薄帯にする時、溶解炉にて磁石組成の配合原料を連続的に溶解し、貯湯装置内の減少した溶湯に追加補充し、追加補充した溶湯を連続して急冷薄帯化すると共に、貯湯容器内の溶湯レベルを検出器にて検出し、前記検出信号により貯湯容器内の出湯ノズルのオリフィス部に働く溶湯のヘッド圧の変化に対応して、急冷槽の圧力を調整することにより、溶解槽と急冷槽の槽間圧力差と貯湯容器内の溶湯のヘッド圧からなる出湯圧力に依存する出湯量を一定に保持して、急冷薄帯の品質を均一に保持することができ、さらに、急冷薄帯を急冷槽内にて切断圧縮することにより、後続工程での設備を大型化することなく、安定した磁気特性をもつボンド磁石用磁粉を量産規模で安価に製造できる。
【図面の簡単な説明】
【図１】この発明によるボンド磁石用永久磁石合金粉末の製造するための製造装置の概略を示す説明図である。
【符号の説明】
１溶解槽
１ａ，２ａ，８ａ，９ａ排気口
１ｂ，２ｂ，８ｂ，９ｂガス供給口
２急冷槽
３溶解炉
４貯湯容器
５出湯ノズル
６ロート
７水冷ロール
８配合原料供給装置
９合金回収機構部
１０破断機
１１圧縮機
１２ボールバルブ
１３覗き窓
１４ＣＣＤカメラ
１５浮き
２０配合原料
２１溶湯
２２急冷薄帯
２３急冷薄片[0001]
[Industrial application fields]
The present invention relates to a method and apparatus for producing permanent magnet alloy powder for bonded magnets suitable for various motors, speakers, meters, sensors, etc., and an amorphous alloy powder or an ultrafine particle having an average crystal grain size of 10 nm or less. By combining a method for producing a rapidly quenched alloy ribbon capable of continuously producing an alloy powder having a crystal structure and a heat treatment for converting the powder into a permanent magnet alloy powder for a bond magnet by a specific heat treatment, an average crystal is obtained from a blended raw material. The present invention relates to a method for manufacturing a permanent magnet alloy powder for bonded magnets and a device therefor, which continuously produce magnetic alloy powders for fine crystal bonded magnets having a particle size of 300 nm or less.
[0002]
[Prior art]
The magnet alloy powder for R-Fe-B bond magnets has hitherto been a method of producing an amorphous alloy ribbon by pouring molten metal onto a rotating roll mainly made of copper and iron, and quenching and solidifying it. Many have been studied.
For example, Japanese Patent Application Laid-Open No. 57-210934 and Japanese Patent Application Laid-Open No. 60-9852 introduce a method for producing an Nd—Fe—B permanent magnet by a rapid cooling / solidification method using a rotating roll. A number of similar methods have been studied and reported at universities and research institutes that study magnetic materials, and all of them are laboratories in which several tens to hundreds of grams of alloy are melted and discharged in a nozzle having an orifice at the bottom. Of scale.
[0003]
As an example of increasing the processing amount, Japanese Patent Application No. 63-333829 introduces a method of tilting the melting furnace, pouring the molten metal into a container having a hot water nozzle at the bottom, and pouring the hot water on a rotating roll below the nozzle. Has been.
However, in order to increase the throughput to 50 kg or more so as to be able to cope with industrial mass production, it is not only necessary to enlarge the melting furnace and the melting tank, but also the bulk specific gravity is 0.01 g / cm.^ThreeA huge quenching tank is required to accommodate the alloy ribbon of a certain size, and the apparatus becomes very large. This increases the manufacturing cost of the apparatus, and also requires a lot of time and huge amount of time for evacuation and gas replacement. An active gas is required.
[0004]
[Problems to be solved by the invention]
Soft magnetic phase consisting of α-iron and a ferromagnetic alloy mainly composed of iron as a magnetic alloy powder for bonded magnets and Nd₂Fe₁₄A permanent magnet alloy powder in which a hard magnetic phase having a B-type crystal structure coexists, and an average crystal grain size of each constituent phase is 1 nm to 50 nm;₂Fe₁₄Permanent magnet alloy powders having an average crystal grain size of 300 nm or less with a hard magnetic phase having a B-type crystal structure as the main phase contain oxidizable rare earth metals. Or, since it is necessary to carry out in an inert gas, industrial production from the point of increase in production efficiency and production cost, such as the evacuation time becomes longer and the amount of inert gas becomes enormous with the enlargement of the equipment. Not practical.
[0005]
In addition, in the production of the magnet alloy powder, it is necessary to increase the amount of dissolution in order to improve the throughput of the rapid cooling / solidification method using a rotating roll, but in order to increase the amount of dissolution, the size of the melting crucible and the high-frequency power source must be increased. As a result, the manufacturing cost of the apparatus increases, and as described above, the enlargement of the equipment causes problems such as a longer evacuation time and an increased amount of inert gas.
[0006]
On the other hand, the bulk specific gravity of the alloy ribbon obtained by the rapid cooling / solidification method using a rotating roll is 0.01 g / cm.^ThreeTherefore, the container for recovering the alloy ribbon has a specific gravity of 7.5 g / cm having the same composition.^ThreeThe volume is more than 700 times that of the cast alloy.
Therefore, if the amount of dissolution is increased due to industrial production and the amount of rapid cooling / coagulation is increased, a very large collection container is required.
[0007]
In order to obtain uniform magnetic properties in the magnet alloy powder for bonded magnets, by adjusting the tank differential pressure between the melting tank and the quenching tank in response to the change in the head pressure of the molten metal discharged onto the rotating roll, Although it is necessary to produce an alloy ribbon with a uniform quenching structure while maintaining a constant amount of tapping, increasing the amount of melt to increase the production of alloy ribbon will increase the change in the melt head pressure, and Since the adjustment of the differential pressure cannot fully cope with the change in the molten metal head pressure, there is a problem that the amount of molten metal varies and an alloy ribbon having a homogeneous quenching structure cannot be obtained.
[0008]
In addition, a method of measuring the hot water height in the hot water storage container and adjusting the differential pressure between the tanks has been proposed (Japanese Patent Laid-Open No. 5-75801). However, a large furnace having a melting amount of 50 kg or more has a large tank volume. Thus, pressure control cannot be achieved sufficiently quickly, and if this is to be achieved forcibly, there is a problem that the exhaust device and gas injection mechanism for differential pressure control are significantly increased in size and require huge construction costs.
[0009]
In any case, in the production of magnetic alloy powder for bonded magnets, the conventional quenching and solidification equipment using a rotating roll requires an increase in the size of the equipment in order to increase the throughput to the mass production scale. , Increase in manufacturing cost and operating cost of the apparatus, and variation in magnetic characteristics, leading to an increase in the cost of the magnet alloy powder for bonded magnets.
[0010]
The present invention relates to a soft magnetic phase composed of α-iron having a powder particle diameter of 3 μm to 500 μm and an iron-based ferromagnetic alloy as an isotropic bonded magnet raw material, and Nd₂Fe₁₄A permanent magnet alloy powder for a bond magnet in which a hard magnetic phase having a B-type crystal structure coexists and an average crystal grain size of each constituent phase is 1 nm to 50 nm;₂Fe₁₄For bonded magnets capable of continuously producing permanent magnet alloy powders for bonded magnets having a stable magnetic property having an average crystal grain size of 300 nm or less with a hard magnetic phase having a B-type crystal structure as the main phase and providing them at low cost An object of the present invention is to provide a method of manufacturing permanent magnet alloy powder and an apparatus therefor.
[0011]
[Means for Solving the Problems]
The inventor, in mass production of magnet powder for bonded magnets, prevents the enlargement of facilities such as melting tanks and melting furnaces, reduces manufacturing costs, and does not require a long time for evacuation and gas supply. As a result of various investigations on the method of producing a good permanent magnet alloy powder for bonded magnets, the melting furnace and the quenching apparatus such as a quenching roll for quenching and thinning the molten metal were almost equalized and melted in the melting furnace. Before the molten metal is quenched and thinned with a quenching device, the molten metal is stored in a hot water storage container kept at the molten metal temperature, and when the molten metal in the hot water storage container is quenched with a quenching device, a magnet is used in the melting furnace. A raw material nozzle with a composition that continuously melts and replenishes the reduced molten metal in the hot water storage container, continuously quenches and thins the molten steel in the hot water storage container, and lowers the molten metal level in the hot water storage container. Due to fluctuations in molten metal pressure In order to prevent fluctuations in the quality and dimensions of the quenching ribbon, the level of the molten metal in the hot water storage container is detected by a detector, and the detected signal is used for rapid cooling in response to a change in the head pressure of the molten metal in the hot water storage container. By varying the tank pressure, the amount of hot water depending on the hot water pressure, which is composed of the pressure difference between the tanks of the melting tank and the quenching tank and the head pressure of the molten metal in the hot water storage container, is kept constant, thereby improving the quality of the quenching ribbon. The present invention was completed by discovering that holding the film uniformly and cutting and compressing the quenched ribbon in the quenching tank can prevent the equipment from becoming larger in the subsequent process and prevent the gas supply and exhaust time from increasing. did.
[0012]
That is, this invention
R-Fe-B-based magnet alloy (where R is one or more of Pr, Nd, Dy) A raw material formulated to have a composition can be additionally supplied in a melting tank in a vacuum or an inert gas atmosphere. After melting in a melting furnace with a mechanism, this molten metal is poured into a hot water storage container that has a discharge nozzle at the bottom and can maintain the temperature of the hot water, and then the molten metal in the hot water storage container is discharged onto a water-cooled roll arranged directly under the discharge hot water nozzle. When producing an amorphous ribbon with an amorphous or ultrafine crystal structure with an average grain size of 1 nm or less by rapid cooling and solidification, water cooling rolls are arranged according to the molten metal level in the hot water storage container when pouring from the hot water nozzle. Control the pressure in the quenching tank to maintain a constant amount of hot water, and supply water to the melting furnace during the rapid solidification of the molten metal with a water cooling roll, and then supply the molten metal to the molten metal container again after melting. Repeat , To prepare a thin alloy strip continuously, the produced flakes and without the breaking machine the ribbon provided in the quench tank, further, the flakes by the compressor 2 g / cm^Three~ 3g / cm^ThreeAfter being compressed into a quenching bath, the compressed flakes are pulverized by a pulverizer so that the average powder particle size is 3 μm to 500 μm, and then heat treated at 600 ° C. to 800 ° C. in an inert gas, A method for producing a permanent magnet alloy powder for bonded magnets, comprising continuously producing fine crystal permanent magnet alloy powder having an average crystal grain size of 300 nm or less.
[0013]
  Further, the present invention provides the above-described configuration,
The composition formula is Fe_100-xyR_xB_y(Where R is one or more of Pr, Nd, and Dy), and the symbols x and y that limit the composition range satisfy the following values:Ru 9After pulverizing the alloy flakes that are amorphous more than 0% with a pulverizer so that the average powder particle size becomes 3 μm to 500 μm, 9The temperature at which crystallization of pulverized powder that is more than 0% amorphous in inert gas beginsDegreeSoft magnetic phase consisting of α-iron and a ferromagnetic alloy mainly composed of iron, subjected to crystallization heat treatment at a heating rate of 10 ° C / min to 50 ° C / sec. And Nd₂Fe₁₄A method for producing a permanent magnet alloy powder for a bond magnet in which a hard magnetic phase having a B-type crystal structure coexists and an average crystal grain size of each constituent phase is 1 nm to 50 nm is proposed.
      3 ≦ x ≦ 6at%
      10 ≦ y ≦ 30at%
[0014]
Further, the present invention provides the above-described configuration,
The composition formula is Fe_100-xyR_xB_y(Wherein R is one or more of Pr, Nd and Dy), and the alloy flakes having an ultrafine crystal structure with a crystal grain size of 10 nm or less satisfying the following values: After pulverization with a pulverizer so that the average powder particle size is 3 μm to 500 μm, the pulverized powder having a crystal particle size of 10 nm or less is in an inert gas at a temperature of 550 ° C. to 800 ° C. and the average crystal particle size is 300 nm to A heat treatment for controlling the metal structure that grows grains to 50 nm is applied, and Nd₂Fe₁₄A method for producing a permanent magnet alloy powder for a bond magnet having an average crystal grain size of 300 nm or less having a hard magnetic phase having a B-type crystal structure as a main phase is proposed.
8 ≦ x ≦ 20at%
4 ≦ y ≦ 10at%
[0015]
  In addition, this invention
MeltingIt consists of a demolition tank and a quenching tank,
SaidDissolution tank,R-Fe-B (where R is one or more of Pr, Nd, and Dy) A melting furnace that melts the compounding raw material so as to have a magnet alloy composition, and a heating that has a tapping nozzle at the bottom and maintains the tapping temperature A hot water storage container having a device, and a blended raw material supply mechanism that supplies the blended raw material to the melting furnace while preventing air from entering,
SaidQuenching tank,A water-coolable rotating roll for rapidly solidifying the molten metal discharged from the hot water nozzle to form a rapidly cooled ribbon, and the resulting bulk specific gravity is 0.01 g / cm^Three~ 0.05g / cm^ThreeBreaker for breaking the rapidly cooled ribbon, and further breakage piece to bulk specific gravity 2g / cm^Three~ 3g / cm^ThreeA water-coolable compressor that compresses the alloy, and an alloy ribbon recovery mechanism that can prevent the intrusion of the atmosphere and discharge the alloy flakes outside the tank,
A gas supply port and an exhaust port for supplying gas to control the internal pressure of the melting tank and the quenching tank and maintaining a vacuum or an inert gas atmosphere in order to maintain a constant amount of hot water from the hot water nozzle Are respectively disposed in the dissolution tank and the quenching tank,
An apparatus for producing permanent magnet alloy powder for a bond magnet, wherein melting, hot water, rapid solidification, rupture, compression, and discharge are performed in parallel and continuously without breaking the atmosphere.
[0016]
  Further, the present invention provides the above-described configuration,
While keeping the pressure in the dissolution tank constantDissolvedFocused from the furnace to the hot water storage containerOf the molten metalMolten metal levelWith detection deviceThe aboveOf detection deviceThe pressure in the quenching tank is adjusted according to the change in the head pressure of the molten metal acting on the outlet nozzle orifice in the hot water storage vessel by the detection signalcontrolDoIt has a gas supply port and an exhaust portThe molten steel strip with a homogeneous quenching and solidification structure is continuously maintained by maintaining a constant amount of tapping depending on the tapping pressure consisting of the sum of the differential pressure between the melting tank and the quenching tank and the head pressure of the molten metal in the hot water storage container. An apparatus for producing permanent magnet alloy powders for bonded magnets that are manufactured in an automated manner is also proposed.
[0017]
[Action]
The manufacturing method of the permanent magnet alloy powder for bonded magnets according to the present invention will be described in detail based on the manufacturing apparatus shown in FIG.
The apparatus is basically composed of a melting tank 1 having a melting furnace 3 and a quenching tank 2 connected to the lower part thereof, and both of them have an exhaust port 1a so as to maintain a vacuum or an inert gas atmosphere and to adjust the pressure in the tank. , 2a and gas supply ports 1b, 2b.
Similarly, a mixing raw material supply device 8 having an exhaust port 8a and a gas supply port 8b is placed on the upper side of the dissolution tank 1 having an exhaust port 1a and a gas supply port 1b on the side wall. A tiltable melting furnace 3 and a hot water storage container 4 having a heating device (not shown) on the outer periphery and a hot water discharge nozzle 5 on the lower part are arranged.
A hot water discharge nozzle 5 of the hot water storage container 4 is disposed in a partition wall between the melting tank 1 and the quenching tank 2, and a water cooling roll 7 for generating a quenching ribbon is provided in the quenching tank 2 at a position below the hot water nozzle 5.
[0018]
The quenching tank 2 is connected with an alloy recovery mechanism unit 9 arranged in the vertical direction for recovering the quenching ribbon 22 obtained by the water-cooling roll 7, and the mechanism unit 9 is quenched by the water-cooling roll 7. A breaker 10 that breaks the ribbon 22, a hopper, and a ball valve 12, and a compressor 11 that compresses the rapidly cooled thin piece 23 are built in, and an exhaust port 9 a and a gas supply port 9 b are formed on the side wall below the ball valve 12. Have
The compressor 11 is configured to compress the quenched thin piece 23 dropped into the cylinder with a piston and discharge the compressed quenched thin piece 23 from the head side without allowing outside air to enter the mechanism portion 9 at the time of compression.
[0019]
In hot water storage container 4Is meltedRefractory float 15 to detect hot water levelPlaceThe upper part of the viewing window 13 provided with the CCD camera 14 for detecting the vertical movement of the float 15 in the upper part of the dissolution tank 1InThe up-and-down movement of the float 15 that is placed and detected by the CCD cameraDisplacementIsAs shown in FIG.At the calculator,Signal P that detects the pressure in dissolution tank 1₁And a signal P for detecting the pressure in the quenching tank 2₂ Is computed withThen, the hot water pressure of the hot water nozzle 5 is calculated, and a deviation signal from a preset hot water pressure is sent to the gas supply port 2b of the quenching tank 2 so that the hot water pressure becomes constant and the deviation signal is Gas is supplied from the gas supply ports 1b and 2b in accordance with the displacement so that the pressure in the dissolution tank 1 is sent to the gas supply port 1b of the dissolution tank 1 and the pressure in the dissolution tank 1 becomes constant.
In this invention, the refractory float and the CCD camera are mentioned here as the molten metal level detection device, but the method of measuring the reflected light of the laser beam with the CCD camera, the thermocouple method, the method of inserting a contact, A known method such as a method can be used.
[0020]
The blended raw material 20 blended to have the required composition of the R—Fe—B magnet is dissolved from the raw material supply device 8 while preventing air from entering the melting tank 1 held in a vacuum or an inert gas. The molten metal 21 supplied to the furnace 3 and melted at the required temperature is poured into the hot water storage container 4 kept at the required temperature by pouring the melting furnace 3. In the figure, 6 is a funnel for collecting the molten metal into the hot water storage container 4 at the time of pouring.
The molten metal 21 of the hot water storage container 4 falls on a water-cooled roll 7 that is disposed immediately below the hot water nozzle 5 at the bottom of the container 4 and rotates at high speed, and is amorphous or a fine crystal structure having an average crystal grain size of 10 nm or less by rapid solidification. A quenched ribbon 22 having the following is obtained.
[0021]
When the molten metal 21 is discharged from the hot water nozzle 5 to the water cooling roll 7, it is stored as described above.Hot waterBy adjusting the internal pressures of the quenching tank 2 and the melting tank 1 according to the molten metal level in the container 4, the amount of discharged hot water is kept constant, and during the rapid solidification of the molten metal 21 by the water cooling roll 7, the melting furnace 3 is fed from the blended raw material supply device 8 and melted in the melting furnace 3, and after that, the work of decanting the molten metal 21 again into the hot water storage container 4 is repeated, and the rapidly cooled ribbon 22 is continuously cooled by the water-cooled roll 7. Can be manufactured.
[0022]
Obtained apparent density (bulk specific gravity) 0.01 g / cm^Three~ 0.05g / cm^ThreeThe quenching ribbon 22 is immediately broken by the breaking machine 10 to an apparent density of 50 g or less and 0.1 g / cm.^Three~ 1g / cm^ThreeAfter breaking into the rapidly cooled flakes 23, the flakes 23 were subjected to an apparent density of 2 g / cm by the compressor 11.^Three~ 3g / cm^ThreeCompress to
The compressed alloy flakes discharged and compressed from the compressor 11 are pulverized by a separate pulverizer so that the average powder particle size becomes 3 μm to 500 μm, and then heat-treated at 600 ° C. to 800 ° C. in an inert gas in a heat treatment furnace. Thus, it is possible to continuously produce fine crystal permanent magnet alloy powders for bond magnets having an average crystal grain size of 1 nm to 300 nm.
[0023]
In this invention, when the molten metal 21 is discharged from the hot water nozzle 5, the diameter of the orifice of the hot water nozzle 5 is as small as 0.5 mm to 2 mm. Therefore, when the viscosity of the molten metal 21 is as high as 1.7 Pa · S or more, the melting furnace 3 Just pouring from the hot water storage container 4 to the molten metal23Since the hot water cannot be discharged due to the frictional force of the inner wall of the hot water nozzle 5, the pressure in the quenching tank 2 is lowered from the pressure in the melting tank 1, thereby creating a pressure difference between the melting tank 1 and the quenching layer 2. The molten metal 21 can be discharged from the hot water nozzle 5.
In addition, when the viscosity of the molten metal 21 is less than 1.7 Pa · S due to the high melting temperature, the hot water starts immediately after pouring from the melting furnace 3 to the hot water storage container 4, and therefore the hot water having a mechanism that can be opened and closed at the bottom. By providing the nozzle 5operationIt can be performed.
[0024]
In the present invention, when a Cu roll is used as the quenching roll, although depending on the cooling capacity of the attached water cooling device, a rapid quenching structure having a roll surface peripheral speed in the range of 10 to 50 mm / sec is obtained. Therefore, it is preferable. That is, when the peripheral speed is less than 10 mm / second, an amorphous structure is not obtained, and when the roll surface peripheral speed exceeds 50 mm / second, a fine crystal aggregate capable of obtaining good hard magnetic properties is not obtained during crystallization. .
The attached water cooling device must satisfy the need to steadily remove the heat of solidification, and it is calculated according to the latent heat of solidification per unit time and the amount of tapping water. It must be about 20 kcal / hr.
[0025]
According to the manufacturing method of the present invention, a substantially 90% or more amorphous quenched flake can be obtained._100-xyR_xB_yAnd the symbols x and y that limit the composition range satisfy the following values:
3 ≦ x ≦ 6 at% 10 ≦ y ≦ 30 at%
The quenching flakes are pulverized by a pulverizer so that the average powder particle size becomes 3 μm to 500 μm, and then the temperature at which crystallization starts in an inert gas into pulverized powder that is substantially 90% or more amorphous. By applying a crystallization heat treatment at a rate of temperature increase from near to a processing temperature of 600 ° C. to 750 ° C. at a rate of 10 ° C./min to 50 ° C./sec, a soft compound comprising a ferromagnetic compound mainly composed of α-iron and iron Magnetic phase and Nd₂Fe₁₄A hard magnetic phase having a B-type crystal structure coexists, and a fine crystal magnet powder having an average crystal grain size of 1 nm to 50 nm in each constituent phase is obtained.
[0026]
In the present invention, the reason for limiting the values of x and y in the composition formula is that if R is less than 3 at%, iHc of 3.0 kOe or more cannot be obtained, and if it exceeds 6 at%, Br of 6 kG or more cannot be obtained. The range is 3 at% to 6 at%. A preferable range of R is 4 to 5.5 at%.
In addition, when B is less than 10 at%, an amorphous structure cannot be obtained even when the ultra-quenching method is used, and only iHc less than 2.0 kOe can be obtained even when heat treatment is performed, and when it exceeds 30 at%, 3.0 kOe or more is obtained. IHc cannot be obtained, so the range is 10 at% to 30 at%. A preferable range of B is 15 at% to 20 at%.
[0027]
In the present invention, the reason for limiting the crystallization heat treatment temperature to 600 to 750 ° C. is that Nd is less than 600 ° C.₂Fe₁₄Since the B phase does not precipitate, iHc does not appear, and when it exceeds 750 ° C., grain growth is remarkable, and the squareness of iHc, Br, and demagnetization curve is deteriorated.
In the present invention, if the rate of temperature rise from the vicinity of the temperature at which crystallization starts heat treatment is less than 10 ° C./minute, grain growth will occur during temperature rise and a fine crystal aggregate capable of obtaining good hard magnetic properties will be obtained. In addition, iHc of 3 kOe or more cannot be obtained, and Nd produced after passing 600 ° C. when it exceeds 50 ° C./sec.₂Fe₁₄Precipitation of the B phase is not sufficiently performed, iHc is not only lowered, but also in the second quadrant of the magnetization curve, a demagnetization curve having a decrease in magnetization near the Br point and (BH) max deteriorates, which is not preferable. .
[0028]
In the present invention, a part or part of Fe may be one or several of Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Pt, Au, and Pb. When combined and replaced, the average crystal grain size is refined to 1 nm to 30 nm, so that the residual magnetic flux density is improved and the coercive force is expressed.₂Fe₁₄Since the volume ratio of the hard magnetic phase having the B-type crystal structure in the metal structure is increased, the coercive force is improved, and at the same time, the heat resistance and the corrosion resistance are improved. However, when the substitution amount for Fe is 0.1% or less, such an effect cannot be obtained. When the substitution amount is 50% or more, the saturation magnetization is greatly reduced and good magnetic properties cannot be obtained. Is in the range of 0.1% to 50%. A preferable substitution amount for Fe is 2% to 20%.
[0029]
In this invention, the reason why the average crystal grain size of each constituent phase is limited to 1 nm to 50 nm is that it is difficult for industrial production to obtain an average crystal grain size of less than 1 nm, and if it exceeds 50 nm, the angle of the demagnetization curve The moldability is significantly deteriorated and the required magnetic properties cannot be obtained.
Also, the reason for pulverizing the quenched ribbon of substantially amorphous structure of this invention to 3 μm to 500 μm with a pulverizer is that the surface area of the pulverized powder is increased below 3 μm, so the density of the bonded magnet compact decreases. When the thickness exceeds 500 μm, the gap inside the bonded magnet becomes large and the density of the molded body is lowered.
[0030]
Further, according to the present invention, a magnet composition obtained from a quenched ribbon having an ultrafine crystal structure having a crystal grain size of 10 nm or less has a composition formula of Fe_100-xyR_xB_y(Where R is one or more of Pr, Nd, and Dy), and the symbols x and y that limit the composition range satisfy the following values:
8 ≦ x ≦ 20 at%, 4 ≦ y ≦ 10 at%
After pulverizing the flakes with a pulverizer so that the average powder particle size is 3 μm to 500 μm, the pulverized powder having a crystal particle size of 10 nm or less is averaged at a temperature of 550 ° C. to 800 ° C. in an inert gas. A heat treatment for controlling the metal structure in which the crystal grain system grows to a grain size of 300 nm to 50 nm is performed.₂Fe₁₄A magnet alloy powder for a bonded magnet having an average crystal grain size of 300 nm or less having a hard magnetic phase having a B-type crystal structure as a main phase is obtained.
[0031]
In this invention, the reason for limiting the values of x and y in the composition formula is that when R is less than 8 at%, a cubic structure having the same structure as α-Fe exists, so that iHc of 80 kOe or more and Br of 7 kG or more are present. Further, if it exceeds 20 at%, the R-rich nonmagnetic phase increases and the saturation magnetization is lowered, which is not preferable. Therefore, the range is 8 at% to 20 at%. A preferable range of R is 10 at% to 16 at%.
If B is less than 4 at%, a rhombohedral structure is formed, so iHc of 8 kOe or more and Br of 7 kG or more cannot be obtained, and if it exceeds 10 at%, the saturation magnetization is lowered, which is not preferable. The range. A preferable range of B is 6 at% to 8 at%.
[0032]
Fe may be partially or wholly substituted with Co, and if it is in the range of 0.1% to 20% with respect to the amount of Fe + Co, Al, Si, Ti, V, Cr, Mn, Ni, Cu , Ga, Zr, Nb, Mo, Ag, Pt, Au, and Pb are acceptable because they do not deteriorate the magnetic characteristics so much.
[0033]
The reason why the crystal grain size of the quenched ribbon is limited to 10 nm or less is that if it exceeds 10 nm, a structure containing coarse α-Fe particles is undesirable.
The reason why the quenched ribbon of this invention was pulverized to 3 μm to 500 μm by a pulverizer is less than 3 μm, because the surface area of the pulverized powder increases, which is not preferable because the bond magnet molding density is lowered. This is not preferable because the voids are increased and the density of the molded body is decreased.
The reason for limiting the metal structure control heat treatment temperature in the present invention to 550 ° C. to 800 ° C. is that if it is less than 550 ° C., it does not grow into crystal grains necessary for obtaining iKO of 8 KOe or more. Since it becomes 300 nm or more and Br falls remarkably, it is not preferable.
[0034]
【Example】
Example 1
As the manufacturing apparatus, the continuous manufacturing apparatus according to the present invention shown in FIG._4.5Fe₇₇B_18.5In order to obtain an at% magnet composition, 20 kg of the blended raw material was charged into the melting furnace from the raw material supply device, and after 20 minutes of melting time, the molten metal with a temperature of 1350 ° C. was disposed on the outer peripheral portion and a high-frequency heating device was disposed at 1300 ° C. After charging into a hot water storage container having a capacity of 3.2 liters, a hot water discharge nozzle that can be opened and closed at the bottom of the hot water storage container discharges water to the outer peripheral surface of a water-cooled Cu roll having an outer diameter of 350 rpm and is amorphous. 20 kg of a quenched ribbon having a thickness of 40 μm and a width of 3.0 mm made of a tissue was rapidly solidified in 22 minutes.
At this time, the raw material continuously charged in the melting furnace during the production of the quenching ribbon is melted, and the molten metal reduced in the hot water storage container is replenished with the melt again, melting, hot water storage, rapid cooling The solidification process is repeated 5 times continuously, and the apparent density (bulk specific gravity) is 0.02 g / cm.^Three96 kg of the quenched ribbon was continuously produced.
[0035]
The obtained quenching ribbon is an apparent density of 0.8 g / cm or less in a quenching tank followed by a breaker at 50 cm or less.^ThreeThe pressure is 6.4 kg / cm in the compressor^ThreeThe flakes are compressed with an apparent density of 2.4 g / cm.^ThreeAnd then discharged outside the compressor.
Thereafter, the compressed alloy flakes are pulverized to an average powder particle size of 150 μm by a pulverizer, and then heated at a temperature increase rate of 30 ° C./min from a temperature of 580 ° C. to a treatment temperature of 640 ° C. in an inert gas. A soft magnetic phase composed of a ferromagnetic alloy containing α-iron and iron as a main component, and Nd₂Fe₁₄A magnetic alloy powder for a bonded magnet having a hard magnetic phase having a B-type crystal structure and having an average crystal grain size of each constituent phase of 50 nm was obtained.
[0036]
After a binder made of an epoxy resin was mixed with the obtained alloy powder at a ratio of 3 at%, a bond magnet having a size of 12 nm × 12 nm × 8 nm was prepared.
The obtained bonded magnet has a density of 6 g / cm.^ThreeThe magnetic properties were iHc = 3.5 kOe, Br = 8.4 kG, BHmax = 5.5 MGOe.
[0037]
Example 2
Using the same manufacturing apparatus as in Example 1, Nd₁₃Fe₈₀B₇In order to obtain an at% magnet composition, melting and rapid solidification were performed under the same conditions as in Example 1 to produce a quenched thin piece having an ultrafine crystal structure with a crystal grain size of 10 nm or less, and thereafter average powder was obtained with a pulverizer. After pulverizing to a particle size of 150 μm, the pulverized powder having a crystal grain size of 10 nm or less is subjected to a heat treatment for controlling the metal structure at 650 ° C. for 10 minutes in an inert gas to grow an average crystal grain size to 200 nm. , Nd₂Fe₁₄A magnetic alloy powder for a bond magnet having a hard magnetic phase having a B-type crystal structure as a main phase and an average crystal grain size of 200 nm or less was obtained.
A bonded magnet was prepared from the obtained alloy powder under the same conditions as in Example 1, and the obtained bonded magnet had a density of 6 g / cm.^ThreeThe magnetic properties were iHc = 9.2 kOe, Br = 6.5 kG, BHmax = 9 MGOe.
[0038]
【The invention's effect】
As is apparent from the embodiments, the present invention makes it possible to make the capacity of the melting furnace and the speed of the quenching roll apparatus for quenching and stripping the molten metal substantially equal to each other, and to increase the gas supply and exhaust time in the apparatus. Before the molten metal melted in the melting furnace is quenched and thinned with a quenching device, the molten metal is stored in a hot water storage device kept at the tapping temperature, and the molten metal in the hot water storage device is used as a quenching device. When making a quenching ribbon, melt the blended raw material of the magnet composition continuously in the melting furnace, replenish the reduced molten metal in the hot water storage device, and continuously quench and strip the newly refilled molten metal By detecting the molten metal level in the hot water storage container with a detector and adjusting the pressure of the quenching tank in response to the change in the head pressure of the molten metal acting on the orifice part of the hot water discharge nozzle in the hot water storage container by the detection signal , The pressure difference between the melting tank and the quenching tank and the hot water storage container By maintaining a constant amount of hot water depending on the pressure of the hot water, which is composed of the head pressure of the molten metal, the quality of the quenching ribbon can be kept uniform, and further, by cutting and compressing the quenching ribbon in the quenching tank Thus, magnetic powder for bonded magnets having stable magnetic characteristics can be manufactured at a low cost on a mass production scale without increasing the size of equipment in subsequent processes.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an outline of a production apparatus for producing a permanent magnet alloy powder for a bonded magnet according to the present invention.
[Explanation of symbols]
1 Dissolution tank
1a, 2a, 8a, 9a Exhaust port
1b, 2b, 8b, 9b Gas supply port
2 quenching tank
3 Melting furnace
4 Hot water storage container
5 Hot water nozzle
6 funnel
7 Water-cooled roll
8 Compound raw material supply equipment
9 Alloy recovery mechanism
10 Breaking machine
11 Compressor
12 Ball valve
13 Viewing window
14 CCD camera
15 Float
20 ingredients
21 Molten metal
22 Quenching ribbon
23 Quenching flakes

Claims

R-Fe-B-based magnet alloy (where R is one or more of Pr, Nd, Dy) can be added in the vacuum or inert gas atmosphere dissolution tank. After melting in a melting furnace with a mechanism, this molten metal is poured into a hot water storage container that has a discharge nozzle at the bottom and can maintain the temperature of the hot water, and then the molten metal in the hot water storage container is discharged onto a water-cooled roll arranged directly under the discharge hot water nozzle. When producing an alloy ribbon with an amorphous or ultrafine crystal structure with an average grain size of 1 nm or less by rapid cooling and solidification, water cooling rolls are arranged according to the molten metal level in the hot water storage container when pouring from the hot water nozzle. Control the pressure in the quenching tank to maintain a constant amount of hot water, and supply water to the melting furnace during the rapid solidification of the molten metal with a water cooling roll, and then supply the molten metal to the molten metal container again after melting. Repeatedly produce alloy ribbon continuously , Flakes and without the breaking machine provided with the ribbon produced in the quench tank, further, after compressing the flakes 2g / cm ^³ ~3g / cm ³ by a compressor, and discharged to the quench tank outside compression After pulverizing the flakes with a pulverizer so that the average powder particle size is 3 μm to 500 μm, heat treatment is performed at 600 ° C. to 800 ° C. in an inert gas, and the fine crystal permanent magnet alloy has an average crystal particle size of 300 nm or less. A method for producing a permanent magnet alloy powder for bonded magnets, characterized in that the powder is produced continuously.

Composition formula _{_{_{Fe 100-xy R x B y}}} ( where R is Pr, Nd, one or two or more Dy) represents the symbol x to limit the composition range, y is 90% or more you satisfy the following values after grinding to an average powder particle diameter alloy sheets is amorphous by a pulverizer is 3Myuemu～500myuemu, temperature crystallization starts pulverized powder is 90% or more amorphous in an inert gas soft made of a ferromagnetic alloy heating rate up to the treatment temperature in degrees or et 600 ° C. to 750 ° C. is 10 ° C. / min becomes to 50 ° C. / sec subjected to a crystallization heat treatment, mainly of α- iron and iron _2. The production of a permanent magnet alloy powder for a bond magnet according to claim 1, wherein a magnetic phase and a hard magnetic phase having an Nd ₂ Fe ₁₄ B type crystal structure coexist, and an average crystal grain size of each constituent phase is 1 nm to 50 nm. Method.
3 ≦ x ≦ 6at%
10 ≦ y ≦ 30at%

The composition formula is expressed as Fe _100-xy R _x B _y (where R is one or more of Pr, Nd, and Dy), and the symbols x and y for limiting the composition range satisfy the following values: After pulverizing the alloy flakes having the following ultrafine crystal structure with a pulverizer so that the average powder particle size is 3 μm to 500 μm, the pulverized powder having a crystal particle size of 10 nm or less is 550 ° C. to 800 ° C. in an inert gas. An average crystal grain size of 300 nm or less with a hard magnetic phase having an Nd ₂ Fe ₁₄ B type crystal structure as the main phase, subjected to heat treatment for controlling the metal structure that grows to an average grain size of 300 nm to 50 nm at a temperature of ℃ 2. The method for producing a permanent magnet alloy powder for a bonded magnet according to claim 1, wherein:
8 ≦ x ≦ 20at%
4 ≦ y ≦ 10at%

Is composed of a dissolve tank with quench tank, the melting tank, melting furnace R-Fe-B (where R is Pr, Nd, one or two or more Dy) dissolving the blend material as made to the magnet alloy composition When having a teeming nozzle at the bottom and a hot water storage vessel with a heating device to keep the hot water temperature, arranged and mixed material supply mechanism for supplying mixed material to the melting furnace while preventing the ingress of air, the quench The tank is a water-coolable rotary roll for rapidly solidifying the molten metal discharged from the hot water nozzle to form a quenched ribbon, a breaker for breaking the obtained quenched ribbon, and a bulk specific gravity. and water cooling can be a compressor for compressing the ^{^{2g / cm 3 ~3g / cm 3}} , a and prevent the entry of air alloy flake and a possible alloy ribbon recovery mechanism discharged Sogai, from the teeming nozzle In order to keep the amount of tapping water constant, gas is supplied to control the pressure in the melting tank and the quenching tank and A gas supply port and an exhaust port for maintaining an inert gas atmosphere are provided in the dissolution tank and the quenching tank, respectively , and melting, hot water, rapid solidification, rupture, compression, and discharge are performed in parallel without breaking the atmosphere. An apparatus for producing permanent magnet alloy powder for bonded magnets, which is performed continuously.

The pressure in the dissolution tank from the holding accessories et dissolve furnace constant and molten metal level detector of the molten metal that has been devoted to the hot water storage vessel, the detection signal of the detection device of the molten metal acting on the teeming nozzle orifice in the hot water storage vessel It has a gas supply port and an exhaust port that control the pressure in the quenching tank in response to changes in the head pressure, and consists of the sum of the differential pressure between the melting tank and the quenching tank and the head pressure of the molten metal in the hot water storage container. 5. The apparatus for producing permanent magnet alloy powder for bonded magnet according to claim 4, wherein the amount of tapping depending on the tapping pressure is kept constant, and an alloy ribbon having a homogeneous quenching and solidification structure is continuously produced. .