JP3639417B2

JP3639417B2 - Liquid rapid solidification method and apparatus that does not use molten metal blowing nozzle

Info

Publication number: JP3639417B2
Application number: JP27526897A
Authority: JP
Inventors: 泰文古屋
Original assignee: Japan Science and Technology Agency; National Institute of Japan Science and Technology Agency
Current assignee: Japan Science and Technology Agency; National Institute of Japan Science and Technology Agency
Priority date: 1997-09-22
Filing date: 1997-09-22
Publication date: 2005-04-20
Anticipated expiration: 2017-09-22
Also published as: JPH1190584A

Description

【０００１】
【産業上の利用分野】
本発明は、金属、特に高融点金属、活性金属およびこれらの合金、セラミックス等の電導性を有する各種原料素材の溶湯を急冷凝固することによって薄帯または細線状の高性能の材料、機能性新素材等を製造する方法および装置およびこれによって得られた材料に関する。
【０００２】
【従来の技術】
金属、半金属、セラミックス系材料の材料特性、機能特性等は、それらの材料自体の内部組織形態、例えば、結晶粒度、結晶方位、微細析出物等とその分布形態に大きく依存している。例えば、従来から多く試みられてきた単ロール法での液体急冷凝固法（メルトスパン法）では、冷却速度によって金属結晶組織が大きく異なる。このような液体急冷凝固法を用いて、冷却速度を１０ ⁶ ℃／秒以上（＞１０ ⁶ ℃／秒）にすると、ある種の過冷度の大きな合金系では溶解液体状態のままで急速に凝固するために、原子配列がランダムな非晶質（アモルファス）が形成されて、磁性や強度等に特異な性能が得られることは周知のことである。また、アモルファス形成条件よりもやや低速冷却域（１０ ³ ℃／秒＜Ｔ＜１０ ⁶ ℃／秒）では、ＦｅやＡｌのある種の合金系で、微細なナノ〜メゾ結晶形成により、同様に磁性や強度の性能の大幅な向上が得られることが分かって来ている。
【０００３】
このように、溶解金属を直接的に冷却媒体で急冷し、その際に非平衡相組織や極微細結晶組織を形成することが、材料機能性向上や新素材開発に極めて有効な手段であることは多くの研究成果として発表されているが、その主な手段である液体急冷凝固法においては、多くの場合、以下に示す溶解、溶湯吹き出し、急速冷却方式を採用して来た。
【０００４】
従来から多く試みられてきた単ロール法での液体急冷凝固法（メルトスパン法）では、先ず、高周波電磁誘導コイル内に設置された石英ガラス製ノズル内に溶解用素材（原料）を封入して、素材自体の電磁誘導（渦電流）・抵抗加熱効果により原料を石英管の中で溶解する。このとき、封入された素材は、溶解用電磁コイルが発生する電磁浮遊力（ローレンツ力）により、ノズル下部の吹き出し部よりも上方で溶解されるので、溶湯をノズル下部の回転冷却用ロール上に落とすために、石英ノズルの上部からＡｒ等の不活性ガス圧を加えて溶湯と一緒に回転ロール上に吹き出し、溶湯を急冷凝固する方式を採用している。
【０００５】
なお、液体急冷凝固法で一般に用いられてきた、原料の電磁浮遊溶解（レビテーション）に関する研究と技術開発に関しては、溶湯浮遊作用力と高周波電磁コイル形状の関係、その電磁場解析、坩堝を使わない非接触溶解による材料（製品）の高純度化、電磁場中溶解凝固組織の特徴等に関する報告が、１９８０年代からフランス、日本等を中心としてなされてきた。しかし、そこでは、電磁場中浮遊溶解での溶解メカニズムや溶湯安定保持技術等が中心であり、液体急冷凝固方式を考えた装置開発・材料高性能化研究例は、ほとんどなされていない。なお、前述のように、石英ノズル方式での液体急冷凝固装置と急冷材料組織変化による高性能化の研究例は、非晶質（アモルファス）〜ナノ結晶材料開発方面で多くなされている。
【０００６】
【発明が解決しようとする課題】
石英ガラス製のノズルを用い、その内部の溶湯をガスで吹き出し急冷する方式からなる液体急冷凝固法（以下、「ノズル吹き出し液体急冷凝固法」という）では、次のような問題点が材料製造プロセス上の技術的課題となっていた。すなわち、第一には、（１）ＴｉやＮｉ合金等非常に活性でかつ酸化されやすい金属や非常に高融点の金属、金属間化合物（Ｎｉ−Ａｌ、Ｍｏ−Ｓｉ系等）では、石英ノズルの主成分である酸化珪素（ＳｉＯ ₂ ）と溶湯金属（Ｔｉ、Ｎｉ）がすぐに反応して、溶湯が酸化され変質してしまったり、不純物の巻き込み等が起きて、多くの場合は材質が脆弱化されて、ボロボロの断片状になってしまい、連続的な薄帯や細線製品を得ることが出来なかった。それは、今まで、研究開発されて来た非晶質（アモルファス）やナノ結晶材料の多くが、比較的低融点で弱酸化性の鉄系やＡｌ系合金であることからも分かる。
【０００７】
特に、Ｔｉ−Ｎｉ、Ｎｉ−Ａｌ系を代表とする形状記憶合金（ＳＭＡ）は、高融点で活性な金属であり、難加工性の金属間化合物に属しており、薄い板や繊維（ファイバ）等の製造が困難なため、高価格であり、家電、生体医療、電気機器、柔軟型ロボット、さらには知的複合材料開発等へこれらの材料を応用する障害になっている。ＳＭＡの組織（結晶、ドメイン）を電磁場中で制御して大きな変態ひずみや機械的強度と耐久性の高い、かつ高速で加工熱処理等も可能な急冷凝固ＳＭＡ合金を製造出来れば、ＳＭＡの高機能化と著しい用途拡大が可能である。
【０００８】
第二には、（２）ノズル吹き出し液体急冷凝固法においては、予め石英ガラス製ノズル内に溶解用原料を一定量置いて、その後に、ノズル内で高周波電磁浮遊溶解を行う。それゆえに、溶解金属（溶湯）量から決まる急冷凝固材料の生産量は、一回のチャージごとに石英ノズル内部に導入した原料素材の重量で決まってしまい、一回のチャージ分をすべて溶解吹き出ししなければ、次の生産プロセス（チャージ）に移れなかった。すなわち、一回のチャ−ジを電磁浮遊溶解した後での生産量の増加もしくは減少の調整は不可能であり、これは液体急冷凝固法を工業化、連続生産技術化させる場合に不適切な点であった。
【０００９】
さらに、第三には、（３）従来のノズル吹き出し液体急冷凝固法においては、溶湯吹き出し用の石英ガラス（セラミックス系）製ノズルを使用しなければならず、それも一回ごとに取り替えなければならず、その労力、消耗品費用等を考えると、より、連続生産ができ、省力化できる新規プロセスの開発が望まれていた。
【００１０】
【課題を解決するための手段】
本発明者は、上記技術的課題の解決に対して鋭意調査研究した結果、溶湯吹き出し量制御（コントロール）法として、ノズルの代わりに溶解以降の溶湯滴下部分への電磁場制御を行えば、従来技術では最大のネックとなっていた、溶湯吹き出しノズルを除去・削除して、高温活性型素材も含む広範囲な材料に適用可能な液体急冷凝固法を更に発展させることが可能となることを見出した。さらに、高周波誘導加熱コイル内の溶湯溜まりの上方から溶解用原料素材を連続的に供給する手段や中断する手段を組み込むことで、生産量を増減さらには中断することを可能ならしめることにより、液体急冷凝固法における工業的生産上の問題である連続急冷凝固材料の連続生産プロセスを可能とした。これにより、石英ノズル消耗品を使う従来法よりも生産コストをかなり押さえられることになる。
【００１１】
本発明の方法および装置は、素材を高周波電磁浮遊溶解するための第一の電磁誘導コイルと、該第一の電磁誘導コイルの下部に位置し溶湯溜まりからの滴下溶湯流を電磁場制御に伴う電磁力でさらに絞り込み、連続滴下流を形成するための第二の電磁誘導コイルを急冷用ロ−ルの上方に設けたことを特徴とする。第一の電磁誘導コイルの上方からは素材（原料）を定常的に供給出来るとともに、第二の電磁誘導コイルの電磁力で滴下溶湯の流れを絞り込み、溶湯滴下量を調整して、定常流、すなわち液の流動状態が時間によって変化しない流れとする。
【００１２】
【発明の実施の形態】
本発明の溶湯吹き出しノズルを使用しない体急冷凝固法は、図１の左側に模式図として示されるように、単ロール、双ロール等の急冷凝固用の高速回転ロール６の上方に配置した第一の高周波電磁コイル３の上方より連続的に供給されるランダム方位の多結晶体である原料素材１を、該高周波電磁コイル３内で電磁浮遊溶解させて、そこに電磁浮遊力により浮遊した溶湯溜まり２を作る。該電磁コイル３は、らせん状に巻かれ、上方の内径寸が大きく、下方の内径寸が小さい逆円錐状の構造となっている。該電磁コイル３の下部に位置して、さらに内径寸が小さい溶湯流絞り込み用の第二の高周波電磁コイル４を配置する。
【００１３】
電磁コイル３に電流を流し、原料（固体）１として、例えば金属を上方より電磁コイル３内に供給すると、図２に示すように、電磁コイル３に流れる電流が作るローレンツ力Ｆ（磁束方向Ｂ）により、電磁コイル３の内側の金属原料１に上方への電磁浮遊力Ｗが作用し、かつ高周波電磁誘導加熱（うず電流）効果により、金属原料１は加熱溶解されたままで電磁コイル３の中央部に浮遊した溶湯溜まり２として保持され、さらにうず電流により攪拌されて均質・高純度化される。原料１の溶解量を次第に増量させると電磁浮遊力Ｗよりも浮遊した溶湯溜まり２の重さが勝り、また、溶湯自身の表面張力や粘性との関連性で溶湯は、電磁コイル３の下方に滴下していくが、電磁コイル３の下部に更に設けた第二の高周波電磁コイル４で滴下する溶湯は細く絞り込まれ、長い定常流５として回転急冷ロール６の所定箇所に流下する。急冷凝固された薄帯または細線７は、材料送り板８に受け取られて横方向に進行する。
【００１４】
この際に重要な制御パラメー夕は、第３図に示すように、（１）第一の高周波電磁コイル３の形状、特に逆三角錐型に巻かれた電磁コイル３の底部の開き角度（θ）と、（２）電磁コイル３への通電電流（ｉ１）である。開き角度θを増加させると、浮遊した溶湯溜まり２は、大きな電磁力Ｆ（ローレンツ力）を受けてコイル３の内部（中心部）から浮き上がり不安定になり、溶湯が電磁コイル３に接触したり、電磁コイル３上方からはずれてしまうことが起き、不適切となる。また、通電電流ｉ１も電磁浮遊力に関連し、余り大きすぎると電磁コイル３の上部で溶解が始まり，溶湯溜まり２は、その後電磁コイル３内で不安定な挙動をとるようになる。さらに、過大電流は、溶湯溜まり２の融点以上での過度の温度上昇をもたらすので、液体急冷凝固組織制御を適切に行うためにも、通電電流ｉ１の調整も重要となる。
【００１５】
また、溶解用コイルである第一の高周波電磁コイル３の下側に位置する第二の高周波電磁コイル４の設置・設定条件も電磁力による絞込みによって溶湯滴下量を適切に制御して出来るだけ長い定常細流を作るために重要である。すなわち、電磁コイル４の形状としては、例えば同心円形高周波コイルを用いるが、重要な制御パラメータとしては、（１）第一の高周波電磁コイル３の下部と第二の高周波電磁コイル４の上部との間隔、（２）第二の高周波電磁コイル４内への通電方向（電磁力作用方向）、（３）電流量ｉ２（電磁力による滴下流絞り込み力）である。例えば、第一の電磁コイル３（反時計回り）と第二の電磁コイル４に同方向（反時計回り）の電流を負荷した場合、第一の電磁コイル３と第二の電磁コイル４とが余りにも近接し過ぎると、第一の電磁コイル３内の溶湯溜まり２から滴下する溶湯が第二の電磁コイル４側からも浮遊力を受けて下方の第二の電磁コイル４の内側に滴下しにくくなり、第一の電磁コイル３と溶湯が接触等を起こして材料作成は出来なくなる例も起こることになる。そこで、第一の電磁コイル３と第二の電磁コイル４との間の間隔をいろいろ調整設定して、最適な距離を決める必要がある。
【００１６】
第二の電磁コイル４側の通電方向を第一の電磁コイル３側と逆方向にすると、第二の電磁コイル４の内部では滴下溶湯に更に下側に押し出す電磁力（ローレンツ力）が働き、溶湯滴下流の速度の上昇を図ることが出来る。また、第二の電磁コイル４側への電流を増すと、滴下溶湯はさらに強い電磁力で下方に押され、かつ、その表面では渦電流効果に伴う電磁コイル４の中心方向への溶湯押し込み効果が相乗されてさらに長い滴下細束流の形成が可能になる。第二の電磁コイル内部から急冷用回転ロール直上までの溶湯滴下量を出来るだけ長く細く絞ること（定常細流化）が出来れば、溶湯表面からロール表面への熱放散が促進されて、溶湯急冷効果が一段と増し、試料内部表面での均質組織や板厚方向に結晶方位の揃った微細柱状結晶の形成が容易になり、材料機能の高性能化とともに、それらの線材や帯板を長く連続的に製造出来るメリットが出てくるので有意義である。
【００１７】
第二の電磁コイル４の巻き数は、効果的な長い細い滴下流を得るためには大きい方が望ましい。さらに、第二の電磁コイル４による溶湯の絞り込み、連続流下の制御は、溶融金属の粘性、表面張力、比重等の影響を強く受けるのでこれらの要因を考慮して最適に制御する必要がある。溶解素材の比重、粘性、表面張力等の要因を考慮して上部からの原料供給量と下部の滴下量を等しくすれば理想的な連続滴下流となる。さらに、必要に応じて、高速回転冷却用ロール直上での滴下溶湯の流れを電磁力でさらに精密に制御することも出来る。また、滴下溶湯流の絞り込み最終部分にカルシア（ＣａＯ）等の不活性セラミックスノズルを使用することによって、滴下溶湯を双ロ−ルの間隙や単ロールの所定の位置にさらに正確に供給するための位置決めが可能になる。
【００１８】
流下した溶湯は急冷用回転ロール上で急冷凝固させて組織制御を行い、材料の高性能、高機能化を図る。図１の右側の模式図は、ランダム方位の他結晶である原料が本発明による急冷凝固により異方性の組織制御合金となる様子を示している。図のＨは、磁場、熱量、Ｌは元の長さ、ΔＬは、変態のび、歪（磁歪、形状記憶変化）を示している。図１は、冷却ロールとして双ロールを用いた例を示しているが、上方に位置する原料の回転軸およびコイルを片側ロール上に移動可能とする等により、単ロールを用いてもよい。本発明の方法および装置を使用すれば４０〜３００ミクロン厚さの薄帯を製造出来る。また、双ロール法で、ロール中央部に溝を設けるか先端部の尖ったそろばん玉状の回転ロールを用いた単ロール法で流下する溶湯の先端を直接ロール表面に接触させれば、直径３０〜２００ミクロン程度の細線を製造することが出来る。
【００１９】
なお、Ｔｉ合金やＮｉ高融点材料等は、高温雰囲気では極めて活性で酸化されやすく、そのため空気中では材質が変質して脆化して連続的な板材や線材にはならないので、これらの材料を製造する際には、本発明の装置を収容した容器をいったん真空に引いた後、高純度Ａｒで置換して電磁浮遊溶解と急冷凝固を行う。ただし、真空のままでの材料の製造も可能であるが、溶解中の金属蒸気、ガス等の容器壁への飛散を少なくするためには、Ａｒ置換が望ましい。本発明によれば、Ｔｉ−Ｎｉ系金属間化合物のみならず従来の石英製ノズルでは不可能であったＮｉ−Ａｌ系金属間化合物等、さらには、Ｔａ−Ｒｕ（タンタル−ルテニウム）合金系等の高融点、高温変態温度（約１０００℃）を有するＳＭＡを製造することが出来る。また、本発明はＰＺＴ系やＰＬＺＴ系の圧電セラミックス材の製造にも適する。
【００２０】
例えば、双ロール方式でＡｒ置換雰囲気中で厚さ１００ミクロン、幅１０〜１６ｍｍのＴｉの薄い板材料を作成した。作成した材料の表面性状は、酸化はほとんど見られずＴｉ特有の金属光沢をしており、高延性、高強度の薄板が得られた。従来の石英製ノズルを使用した液体急冷法の場合は、高温下で石英と非常に活性な溶解Ｔｉが酸化反応を起こしてしまい、試料は黒く酸化され、脆化が起って、長い薄板として作成出来なかった。
【００２１】
本発明の製造方法で得られた素材は、高融点・活性金属系での強度、延性が向上し、高純度化による耐蝕性の大幅な向上も実現できるので、形状記憶合金として、感熱ブレーカ（火災報知器）、マイクロロボット・マイクロマシン用小型アクチュエータ、生体医療用材料（耐食性利用）・・・能動内視鏡用カテーテル駆動素子、歯科矯正ワイヤ、超弾性ガイドワイヤとして適する。また、急冷微細・高純度化組織（結晶方位）制御で現状の超磁歪素子を越える新素材、特に磁性を有する形状記憶合金、ホイスラ−型Ｆｅ−Ｐｄ、Ｎｉ−Ｍｎ−Ｇａ系合金等、の開発が可能であり、高性能超磁歪素子として、高速応答磁気アクチュエータ、耐腐食環境内での磁気アクチュエータ、高周波発信素子、振動制御素子として適する。さらに、高強度、センサ・アクチュエ−タ機能を有する高温金属間化合物の薄帯や細線を製造可能であり、複合材料（金属、ポリマー、セラミックス）強化用の埋め込み用繊維、薄帯として使用出来、特に、高温型Ｔｉ、Ｎｉ系金属間化合物系複合材料や、環境応答型知的（スマート）材料・構造へ適用出来る。また、薄帯や細線の積層圧着、細線束の融合加工によりバルク材料にすることが出来、構造材として使用出来る。その他に、（１）結晶性（熱電変換、水素吸蔵機能）材料、（２）活性・超高温（１０００℃以上で作動）特殊形状記憶合金、（３）複合材料埋め込み素子（フィラー）等の用途にも適する。
【００２２】
【実施例】
以下に本発明の実施例につき説明する。本発明の溶湯吹き出しノズルを使用しない液体急冷凝固法の実施例としては、第一の電磁コイルのらせん型高周波コイル内での逆三角形の溶湯溜まりをまず作り、溶湯内を滴下規定温度に達成させた後、下方の第二の円筒型の電磁コイルに溶湯を送り込む。この際に第一の電磁コイル側での重要な制御パラメータは、（１）第一の電磁コイル（らせん型）の形状、特に逆三角錐型コイル底部の開き角度（θ）と、（２）通電量（ｉ）であるが、特に溶湯溜まりの形成に重要な開き角度（θ）の最適値を検証した実験結果を表１に示す。開き角度（θ）を増加させると、浮遊溶湯溜まりは大きな電磁力（ロ−レンツ力）を受けてコイル内部（中心部）から浮き上がり不安定になり、溶湯がコイルに接触したり、コイル上方からはずれてしまうことが起きる。実験は、素材に、Ｔｉ−Ｎｉ50.2原子％形状記憶合金の丸棒（直径１０ｍｍ）を用い、第一の電磁コイルのみの通電電流ｉ１＝３６Ａ（一定）、Ｖ１＝Ｖ２＝２００Ｖ、電流周波数１８３ｋＨｚで、θ＝３６、４０、４４度の三種類で行った。図３中に示される溶湯溜まりの幅（Ｗ１）、垂直長さ（Ｌ１）の比より、逆三角形に近いθ＝４０度（Ｗ１／Ｌ１＝０．８８）が最適であった。
【００２３】
【表１】

【００２４】
次に、第一の電磁コイルの通電最適量ｉ１＝３６Ａに決定し、両方のコイルへの通電量をｉ１＝ｉ２＝３６Ａ（同一）、Ｖ１＝Ｖ２＝２００Ｖ（同一）とした場合、両コイル間隔（Ｓ）を１０ｍｍとした場合が滴下流は最も長かった。更に両コイルの長さ（Ｃ１＝Ｃ２＝２１ｍｍ、３ターン、開き角度θ＝４０度）を同一条件とした場合に、第二の電磁コイルの通電方向の変化（正、逆）が滴下流の長さに与える影響を検討した。表２には、第二の電磁コイル側への通電量を逆（ｉ１＝＋３６Ａ、ｉ２＝−３６Ａ）とした場合の滴下連続流の長さの変化を示す。第一の電磁コイル内での溶湯溜まりの長さ（Ｌ１）、第二の電磁コイル側での滴下流の長さ（Ｌ２）の比を示すが、第二の電磁コイル側に逆電流を流した場合の方が明確な滴下溶湯長さの増加が認められた。
【００２５】
【表２】

【００２６】
本発明の方法および装置を用いて、以下の仕様の試料を作成し、（１）金属組織観察（走査電子顕微鏡での結晶粒成長状況観察、Ｔｉ−Ｎｉ40原子％−Ｃｕ10原子％形状記憶合金）（図４、図５、図６）、（２）Ｘ線回折による結晶構造解析（図７）、（３）形状記憶変態ひずみ〜温度ヒステリシス曲線の変化の測定（形状記憶効果の向上確認）（図８）、（４）腐食テスト（強酸、食塩水中の腐食抵抗曲線、アノ一ド分極曲線（自然電極電位〜電流密度曲線）（図９）、および（５）Ｘ線表面元素分析（図１０）を行った。Ｘ線表面元素分析の比較例として、同じ原料からなる溶解・加工材料を用いた（図１１）。
【００２７】
本発明の実証確認のために供した材料は、感温センサ（検知）およびアクチュエータ（駆動素子）の両方の機能を併せ持つ代表的なチタン系の形状記憶合金２種である、Ｔｉ−Ｎｉ50.2原子％合金およびＴｉ−Ｎｉ40−Ｃｕ10（原子％）合金で、前者は、広い形状記憶温度ヒステリシスを有する最も広く使用されている合金系で、後者は、狭い形状記憶温度ヒステリシスを有するマイクロロボット駆動用等のアクチュエータ素子として注目されている合金系であるので、それらの形状記憶現象に対する「完全非接触電磁浮遊溶解」と「液体急冷凝固」とを組み合わせた効果を実証・確認するために選定した。
【００２８】
電磁浮遊溶解用容器（チャンバー）内部を真空（１．３３×１０ ^−１Ｐａ）に引いた後、不活性Ａｒガス置換した。チャンバー上方から連続的に供給される原料素材を電磁浮遊溶解して、その後、滴下溶湯を下方の回転銅製双ロール上でロール回転速度の変化とともに急冷凝固した。原料供給量、第二の電磁コイルによる滴下溶湯の制御は下記のとおりとした。原料は、Ｔｉ−Ｎｉ50.2原子％、Ｔｉ−Ｎｉ40−Ｃｕ10原子％の形状記憶合金であり、予めアーク溶解で作成した丸棒状素材（直径１０ｍｍ、長さ１０ｃｍ〜１５ｃｍ）をチャンバー上部に設定された試料供給回転冶具に把持して、下方の第二の電磁コイル中央部に送り速度＝０．０４ｍｍ／ｓｅｃ（２．４ｍｍ／ｍｉｎ、約０．２ｃｍ ³ ／ｍｉｎ）で供給した。ロール回転数は１００〜５０００ｒｐｍ、双ロール法での片側銅ロール径を１５０ｍｍとした場合、ロール表面速度は０．８〜４０ｍ／秒であり、双ロール中央部でのロールギャップは３０ミクロンで、冷却速度は１０ ² 〜１０ ⁶ ℃／秒に達している。この場合の通電量は、第一、第二のコイルで、ｉｌ＝３６Ａ、ｉ２＝−３６Ａ（逆方向）、Ｖ１＝Ｖ２＝２００Ｖ（同一）、コイル電流周波数１８３ｋＨであった。加熱電力（Ｗ）は、電圧（Ｖ）と電流（ｉ）の積から求まり、７．２ｋＷで、両コイルの間隔（Ｓ）は１０ｍｍ、両コイルの長さＣ１＝Ｃ２は２１ｍｍ（３ターン、開き角度θ＝４０度）であった。
【００２９】
Ｔｉ−Ｎｉ40−Ｃｕ10（原子％）合金の断面組織写真（下部に急冷ロール速度を記述した）を図４〜６に示す。図４は、ロール速度１ｍ／秒（冷却速度１０ ²℃／秒）、図５は、ロール速度５ｍ／秒（冷却速度１０ ³ ℃／秒）、図６は、ロール速度１０ｍ／秒（冷却速度１０ ⁴ 〜１０ ⁵ ℃／秒）である。溶湯冷却用ロールの回転速度を次第に上げていくと、デンドライト型平衡拡散結晶から板厚方向にそろった微細柱状結晶に遷移して行くのが観察された。
【００３０】
急冷凝固したＴｉ−Ｎｉ50.2原子％合金（ロール速度２８ｍ／秒、３６００ｒｐｍ、冷却速度１０ ⁵ ℃／秒）と溶解加工材料（８００℃、６０％熱間加工繰り返し丸棒切り出し原料）の表面のＸ線回折による結晶構造解析結果を図７に示す。溶解加工材に比べて、急冷材では(100) 、(200) 系基本面でのＸ線相対強度（Ｘ線カウント数）が著しく大きく、大きな結晶異方性が生じていることがわかった。これは、Ｔｉ−Ｎｉ−Ｃｕ系合金でも一般にみられた急冷に伴う、一方向に揃った柱状結晶形成現象と関連付けられる。
【００３１】
感温センサとアクチュエータ機能を併せ持つ形状記憶合金の実用化には、大きな形状記憶変態ひずみを得ること、早い応答性、繰り返し応答の耐久性、医用材料としての生体内部や低温度差熱エンジンへの適用等の腐食環境中での耐食性等が要求されている。本発明装置で製造された、急冷Ｔｉ−Ｎｉ50.2原子％合金薄帯試料での、形状記憶変態ひずみ変化幅〜温度ヒステリシス曲線の変化を図８に示す。一定負荷応力＝６０ＭＰａ下での熱弾性型形状記憶相変態ひずみ幅（縦軸）は、ランダム結晶の溶解加工材料の場合よりも２〜３倍増加し、また、加熱〜冷却一サイクルでのヒステリシス幅で示される変態温度輻も減少していることが確認出来る。すなわち、曲線屈曲部での接線法で定義される、高温側の逆変態終了温度Ａｆと低温側マルテンサイト変態終了温度Ｍｆとの差（Ａｆ−Ｍｆ）で定義される変態温度幅（ΔＴ＝Ａｆ−Ｍｆ）は、溶解加工材ではΔＴ＝Ａｆ（３４３Ｋ）−Ｍｆ（２９８Ｋ）＝４５Ｋ、一方、急冷材料ではΔＴ＝Ａｆ（３２７Ｋ）一Ｍｆ（２９０Ｋ）＝３７Ｋで減少し、ヒステリシス曲線の立ち上がりで表される形状記憶回復速度（形状記憶応答性）が向上した。
【００３２】
図９には、化学的腐食テストとして、Ｔｉ・Ｎｉ40−Ｃｕ10（原子％）合金での強酸（塩酸ＨＣｌ）および食塩水（ＮａＣｌ）中での一般的なアノ一ド分極曲線、すなわち、自然電極電位〜電流密度曲線の測定結果を示す。電磁浮遊急冷試料は、いずれの場合もアノ一ド電位差が溶解加工試料よりも高くならなければ電流が流れず腐食抵抗が大きく向上していることが分かる。
【００３３】
腐食テスト後に、電磁浮遊急冷材料（Ｔｉ−Ｎｉ40−Ｃｕ10原子％合金、ロール速度＝１０ｍ／秒）（図１０）と溶解加工材（Ｔｉ−Ｎｉ40−Ｃｕ10原子％合金、６５０℃、１時間焼鈍）（図１１）との表面腐食性生成物を調べる目的で、Ｘ線表面元素分析（ＥＤＡＸ）試験を行った。急冷材料では、場所によるばらつきは小さく、その表層は均一な緻密な材質になっていることがわかるが、溶解加工材料では、Ｎｉ、Ｔｉ、Ｃｕ成分の強度分布が場所によりばらついている。この分析結果によれば、急冷材料は腐食されにくく、大きな耐食性が得られたものと推定される。
【００３４】
【発明の効果】
本発明によれば、従来の石英製ノズルを使用する方法では困難であった滴下流量の調整が、本発明では、第二の電磁誘導コイルの形状の工夫と通電量の調整により可能となり、原料の連続供給や停止が出来るので、連続的または反連続的に均一で高性能な特性を有する急冷凝固による薄帯や細線の製造が可能となった。さらに、本発明の方法によれば、石英製ノズルを使用する必要がないので、材料の高純度化、高性能化（強度、延性）が低コストで実現し、Ｔｉ−Ｎｉ系金属間化合物等の従来は急冷凝固法での製造が困難であった材料の薄帯や細線での大きな結晶異方性の出現による形状記憶効果、延性等の材料機能の大幅な向上が実現出来た。さらに、溶湯絞り込みと双ロ−ル法による凝固・圧延加工過程を組み合わせて、急冷凝固速度（回転ロール速度）を変えることで材料の微視組織制御、特に結晶方位配向性制御による材料の高性能化を実現出来た。
【図面の簡単な説明】
【図１】本発明の溶湯吹き出しノズルを使用しない液体急冷凝固装置と金属凝固組織の模式図。
【図２】第一の高周波電磁コイル内での電磁浮遊溶解と作用電磁力と溶解金属表面渦電流発生の模式図。
【図３】第二の高周波電磁コイルの通電方向と電磁力の関係を示す模式図。
【図４】本発明の方法を用いて（冷却速度１０ ² ℃／秒）製造したＴｉ−Ｎｉ40−Ｃｕ10（原子％）合金の断面の走査電子顕微鏡組織写真。
【図５】本発明の方法を用いて（冷却速度１０ ³ ℃／秒）製造したＴｉ−Ｎｉ40−Ｃｕ10（原子％）合金の断面の走査電子顕微鏡組織写真。
【図６】本発明の方法を用いて（冷却速度１０ ⁴ 〜１０ ⁵ ℃／秒）製造したＴｉ−Ｎｉ40−Ｃｕ10（原子％）合金の断面の走査電子顕微鏡組織写真。
【図７】本発明の方法により製造したＴｉ−Ｎｉ50.2原子％合金表面の結晶構造解析結果を示すＸ線回折図。
【図８】本発明の方法により製造した急冷Ｔｉ−Ｎｉ50.2原子％合金薄帯試料での、形状記憶変態ひずみ〜温度ヒステリシス曲線を示す図。
【図９】本発明の方法により製造したＴｉ−Ｎｉ40−Ｃｕ10（原子％）合金の強酸（塩酸ＨＣｌ）および食塩水（ＮａＣｌ）中でのアノ一ド分極曲線図。
【図１０】本発明の方法により製造したＴｉ−Ｎｉ40−Ｃｕ10（原子％）合金の表面腐食性生成物を調べるＸ線表面元素分析図。
【図１１】比較例の溶解加工したＴｉ−Ｎｉ40−Ｃｕ10（原子％）合金の表面腐食性生成物を調べるＸ線表面元素分析図。[0001]
[Industrial application fields]
  The present invention provides a new high-performance material such as a thin ribbon or a thin wire by rapidly solidifying a molten metal of various raw materials having conductivity, such as metals, particularly high melting point metals, active metals and alloys thereof, and ceramics. The present invention relates to a method and apparatus for manufacturing a raw material and the like, and a material obtained thereby.
[0002]
[Prior art]
  The material characteristics, functional characteristics, and the like of metals, metalloids, and ceramic materials greatly depend on the internal structure of the materials themselves, such as crystal grain size, crystal orientation, fine precipitates, and the distribution form thereof. For example, in the liquid rapid solidification method (melt span method) in the single roll method that has been tried many times in the past, the metal crystal structure varies greatly depending on the cooling rate. Using such a liquid rapid solidification method,10 ⁶ ℃ / second or more (>10 ⁶ (° C./sec), some alloy systems with a large degree of supercooling rapidly solidify in a dissolved liquid state, so that an amorphous structure with a random atomic arrangement is formed. It is well known that performance unique to the above can be obtained. In addition, the cooling zone is slightly slower than the amorphous formation conditions (10 ^Three ° C / sec <T <10 ⁶ (° C./sec), it has been found that, in a certain alloy system of Fe and Al, the formation of fine nano to mesocrystals can provide significant improvements in magnetic and strength performance as well.
[0003]
  Thus, quenching the molten metal directly with a cooling medium and forming a non-equilibrium phase structure or ultrafine crystal structure at that time is an extremely effective means for improving material functionality and developing new materials. Has been published as a number of research results, but in the liquid rapid solidification method, which is the main means, the following melting, molten metal blowing, and rapid cooling methods have been adopted in many cases.
[0004]
  In the liquid rapid solidification method (melt span method) in the single roll method, which has been tried many times in the past, first, a melting material (raw material) is sealed in a quartz glass nozzle installed in a high frequency electromagnetic induction coil, The raw material is melted in the quartz tube by the electromagnetic induction (eddy current) and resistance heating effect of the material itself. At this time, the encapsulated material is melted above the blowout part below the nozzle by the electromagnetic levitation force (Lorentz force) generated by the melting electromagnetic coil, so the molten metal is placed on the rotating cooling roll below the nozzle. In order to drop, a method is adopted in which an inert gas pressure such as Ar is applied from the upper part of the quartz nozzle and blown onto the rotating roll together with the molten metal to rapidly cool and solidify the molten metal.
[0005]
  Regarding research and technology development related to electromagnetic levitation melting (levitation) of raw materials commonly used in liquid rapid solidification methods, the relationship between molten metal floating action force and high-frequency electromagnetic coil shape, its electromagnetic field analysis, crucible not used Reports on the purification of materials (products) by non-contact melting and the characteristics of dissolved and solidified structures in an electromagnetic field have been made mainly in France and Japan since the 1980s. However, there is a focus on the melting mechanism in floating dissolution in an electromagnetic field, the molten metal stable retention technology, etc., and there have been almost no examples of research on device development and material performance improvement considering the liquid rapid solidification method. In addition, as described above, there are many examples of research on improving the performance by the rapid cooling and solidification apparatus using the quartz nozzle method and the rapid change of the material structure in the development of amorphous to nanocrystalline materials.
[0006]
[Problems to be solved by the invention]
  The liquid rapid solidification method (hereinafter referred to as “nozzle blown liquid rapid solidification method”), which uses a quartz glass nozzle and blows and quenches the molten metal with gas, has the following problems. It was a technical issue above. That is, first, for (1) a very active and easily oxidized metal such as Ti or Ni alloy, a metal having a very high melting point, or an intermetallic compound (Ni-Al, Mo-Si, etc.), a quartz nozzle Silicon oxide (SiO ₂ ) And the molten metal (Ti, Ni) react immediately, and the molten metal is oxidized and denatured, or impurities are involved, and in many cases, the material becomes brittle and breaks into fragments. As a result, it was not possible to obtain a continuous ribbon or thin wire product. This can also be seen from the fact that many amorphous and nanocrystalline materials that have been researched and developed so far are relatively low melting and weakly oxidizable iron-based and Al-based alloys.
[0007]
  In particular, shape memory alloys (SMA) typified by Ti—Ni and Ni—Al are high melting point and active metals, belonging to difficult-to-work intermetallic compounds, and are thin plates and fibers (fibers). Are difficult to manufacture, and are expensive, which is an obstacle to the application of these materials to home appliances, biomedical, electrical equipment, flexible robots, and intelligent composite material development. If the SMA structure (crystal, domain) is controlled in an electromagnetic field to produce a rapidly solidified SMA alloy with high transformation strain, high mechanical strength and durability, and capable of high-speed heat treatment, etc. And remarkable expansion of applications.
[0008]
  Secondly, (2) in the nozzle blown liquid rapid solidification method, a predetermined amount of a melting raw material is previously placed in a quartz glass nozzle, and then high-frequency electromagnetic floating melting is performed in the nozzle. Therefore, the production volume of rapidly solidified material determined by the amount of molten metal (molten metal) is determined by the weight of the raw material introduced into the quartz nozzle for each charge, and all the charge for one charge is melted and blown out. Without it, we could not move on to the next production process (charge). In other words, it is impossible to adjust the increase or decrease in production after electromagnetic fusing of a single charge, which is inappropriate when the liquid rapid solidification method is industrialized or put into continuous production technology. Met.
[0009]
  Third, (3) in the conventional nozzle blowing liquid rapid solidification method, a quartz glass (ceramics) nozzle for blowing molten metal must be used, and it must be replaced every time. However, in view of the labor, consumables costs, etc., it was desired to develop a new process capable of continuous production and labor saving.
[0010]
[Means for Solving the Problems]
  As a result of earnest investigation and research on the solution of the above technical problem, the present inventor, as a molten metal blowing amount control (control) method, if the electromagnetic field control to the molten metal dropping portion after melting is performed instead of the nozzle, the prior art Then, it was found that the liquid quenching and solidification method applicable to a wide range of materials including high temperature active materials can be further developed by removing and deleting the melt blowing nozzle, which was the biggest bottleneck. Furthermore, by incorporating means for continuously supplying the raw material for melting from the upper part of the molten metal pool in the high frequency induction heating coil and means for interrupting it, it is possible to increase or decrease the production volume and to interrupt it. The continuous production process of continuous rapid solidification material, which is a problem in industrial production in rapid solidification method, was made possible. As a result, the production cost can be considerably reduced as compared with the conventional method using a quartz nozzle consumable.
[0011]
  The method and apparatus of the present invention includes a first electromagnetic induction coil for dissolving a material by high-frequency electromagnetic levitation and, Located below the first electromagnetic induction coil from the molten metal poolThe second molten metal flow is further narrowed down by the electromagnetic force accompanying the electromagnetic field control, and a second electromagnetic induction coil for forming a continuous dropped flow is provided above the quenching roll. The material (raw material) can be constantly supplied from above the first electromagnetic induction coil, the flow of the molten metal is narrowed down by the electromagnetic force of the second electromagnetic induction coil, the amount of molten metal dropped is adjusted, the steady flow, That is, the flow state of the liquid does not change with time.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
  Of the present inventionDo not use molten metal blowing nozzleAs shown in the schematic diagram on the left side of FIG. 1, the body rapid cooling and solidification method is continuous from above the first high-frequency electromagnetic coil 3 disposed above the high-speed rotating roll 6 for rapid solidification such as a single roll or a twin roll. The raw material 1, which is a randomly oriented polycrystalline material, is electromagnetically floated and melted in the high frequency electromagnetic coil 3,Floating due to electromagnetic buoyancyMake the molten metal pool 2. The electromagnetic coil 3 is wound in a spiral shape, and has an inverted conical structure in which the upper inner diameter is large and the lower inner diameter is small. The electromagnetic coil 3Located at the bottom ofIn addition, molten metal with a smaller inner diameterFlowA second high-frequency electromagnetic coil 4 for narrowing down is arranged.
[0013]
  When a current is passed through the electromagnetic coil 3 and, for example, metal is supplied into the electromagnetic coil 3 from above as the raw material (solid) 1, as shown in FIG. 2, the Lorentz force F (flux direction B) generated by the current flowing through the electromagnetic coil 3 ) Causes an upward electromagnetic buoyancy W to act on the metal raw material 1 inside the electromagnetic coil 3, and the metal raw material 1 remains heated and melted due to the high-frequency electromagnetic induction heating (eddy current) effect. It is held as a molten metal pool 2 floating in the part, and further stirred and agitated by eddy current to be homogeneous and highly purified. If the melting amount of the raw material 1 is gradually increased, the weight of the molten metal pool 2 that has floated will be greater than the electromagnetic buoyancy W, and the molten metal will be located below the electromagnetic coil 3 due to the surface tension and viscosity of the molten metal itself. The molten metal dropped by the second high-frequency electromagnetic coil 4 further provided below the electromagnetic coil 3 is narrowed down and flows down to a predetermined location on the rotary quenching roll 6 as a long steady flow 5. The rapidly solidified ribbon or thin wire 7 is received by the material feed plate 8 and travels in the lateral direction.
[0014]
  At this time, as shown in FIG. 3, the important control parameters are as follows: (1) The shape of the first high-frequency electromagnetic coil 3, particularly the opening angle (θ of the bottom of the electromagnetic coil 3 wound in an inverted triangular pyramid shape) ) And (2) current (i1) applied to the electromagnetic coil 3. When the opening angle θ is increased, the floated molten metal reservoir 2 receives a large electromagnetic force F (Lorentz force) and rises from the inside (center) of the coil 3 to become unstable, and the molten metal comes into contact with the electromagnetic coil 3. The electromagnetic coil 3 may be detached from above, making it inappropriate. The energizing current i1 is also related to the electromagnetic levitation force, and if it is too large, melting starts at the upper part of the electromagnetic coil 3, and the molten metal pool 2 then becomes unstable in the electromagnetic coil 3. Furthermore, since the excessive current causes an excessive temperature rise above the melting point of the molten metal pool 2, the adjustment of the energization current i1 is also important in order to appropriately control the liquid rapid solidification structure.
[0015]
  In addition, the installation and setting conditions of the second high-frequency electromagnetic coil 4 located below the first high-frequency electromagnetic coil 3 that is a melting coilBy narrowing down by electromagnetic forceIt is important for making a steady trickle as long as possible by appropriately controlling the amount of molten metal dripping. That is, as the shape of the electromagnetic coil 4, for example, a concentric circular high-frequency coil is used, but important control parameters are (1) the lower part of the first high-frequency electromagnetic coil 3 and the upper part of the second high-frequency electromagnetic coil 4. The interval, (2) the energization direction into the second high-frequency electromagnetic coil 4 (electromagnetic force acting direction), and (3) the current amount i2 (the dropping flow constricting force due to the electromagnetic force). For example, when a current in the same direction (counterclockwise) is applied to the first electromagnetic coil 3 (counterclockwise) and the second electromagnetic coil 4, the first electromagnetic coil 3 and the second electromagnetic coil 4 are If it is too close, the molten metal dripping from the molten metal pool 2 in the first electromagnetic coil 3 also receives floating force from the second electromagnetic coil 4 side and drops inside the second electromagnetic coil 4 below. In some cases, the first electromagnetic coil 3 and the molten metal come into contact with each other and the material cannot be produced. Therefore, it is necessary to adjust and set various intervals between the first electromagnetic coil 3 and the second electromagnetic coil 4 to determine the optimum distance.
[0016]
  When the energizing direction on the second electromagnetic coil 4 side is opposite to the first electromagnetic coil 3 side, an electromagnetic force (Lorentz force) that pushes the molten metal further downward acts inside the second electromagnetic coil 4, The speed of the molten metal dropping flow can be increased. Further, when the current to the second electromagnetic coil 4 side is increased, the molten molten metal is pushed downward by a stronger electromagnetic force, and on the surface thereof, the molten metal is pushed toward the center of the electromagnetic coil 4 due to the eddy current effect. Synergize with each other to form a longer drop bundle flow. If the amount of molten metal dripping from the inside of the second electromagnetic coil to just above the rotating roll for quenching can be narrowed down as long as possible (steady trickling), heat dissipation from the molten metal surface to the roll surface is promoted, and the molten metal quenching effect This makes it easier to form a homogeneous structure on the inner surface of the sample and a fine columnar crystal with a uniform crystal orientation in the plate thickness direction. This is significant because it provides merit that can be manufactured.
[0017]
  The larger number of turns of the second electromagnetic coil 4 is desirable in order to obtain an effective long thin dripping flow. Further, the control of the molten metal squeezing and the continuous flow by the second electromagnetic coil 4 is strongly influenced by the viscosity, surface tension, specific gravity and the like of the molten metal, so it is necessary to optimally control in consideration of these factors. Considering factors such as specific gravity, viscosity, surface tension, etc. of the melted material, an ideal continuous dripping flow can be obtained by equalizing the amount of raw material supplied from the top and the amount of dripping at the bottom. Furthermore, if necessary, the flow of the molten metal just above the high-speed rotating cooling roll can be controlled more precisely by electromagnetic force. In addition, calcia (CaO By using an inert ceramic nozzle such as), it is possible to position the molten metal more accurately in the gap between the twin rolls or in a predetermined position of the single roll.
[0018]
  The molten metal is rapidly cooled and solidified on a rotating roll for rapid cooling to control the structure, thereby improving the performance and functionality of the material. The schematic diagram on the right side of FIG. 1 shows that a raw material that is another crystal of random orientation becomes an anisotropic structure control alloy by rapid solidification according to the present invention. In the figure, H represents the magnetic field, the amount of heat, L represents the original length, and ΔL represents transformation and distortion (magnetostriction, shape memory change). FIG. 1 shows an example in which a twin roll is used as a cooling roll. However, a single roll may be used, for example, by allowing the rotating shaft and coil of the raw material located above to be movable on one side roll. Using the method and apparatus of the present invention, 40-300 micron thick ribbons can be produced. Further, if the tip of the molten metal flowing down by the single roll method using a double roll method with a groove in the center of the roll or a abacus-shaped rotating roll with a sharp tip is brought into contact with the roll surface directly, the diameter 30 Fine wires of about ~ 200 microns can be manufactured.
[0019]
  Ti alloys, Ni refractory materials, etc. are extremely active and easily oxidized in high-temperature atmospheres. Therefore, the materials change in air and become brittle and do not become continuous plates or wires. In this case, the container containing the apparatus of the present invention is once evacuated and then replaced with high-purity Ar to carry out electromagnetic floating dissolution and rapid solidification. However, although it is possible to manufacture the material in a vacuum, Ar substitution is desirable in order to reduce scattering of metal vapor, gas, etc. during melting to the container wall. According to the present invention, not only a Ti—Ni-based intermetallic compound but also a Ni—Al-based intermetallic compound that has been impossible with a conventional quartz nozzle, and a Ta—Ru (tantalum-ruthenium) alloy system, etc. SMA having a high melting point and a high temperature transformation temperature (about 1000 ° C.) can be produced. The present invention is also suitable for manufacturing PZT and PLZT piezoelectric ceramic materials.
[0020]
  For example, a thin Ti plate material having a thickness of 100 microns and a width of 10 to 16 mm was prepared in an Ar substitution atmosphere by a twin roll method. As for the surface property of the prepared material, oxidation was hardly observed, and Ti had a metallic luster, and a thin plate having high ductility and high strength was obtained. In the case of a liquid quenching method using a conventional quartz nozzle, quartz and a very active dissolved Ti cause an oxidation reaction at a high temperature, the sample is oxidized black, embrittled, and becomes a long thin plate. Could not create.
[0021]
  The material obtained by the production method of the present invention has improved strength and ductility in a high melting point / active metal system, and can also realize a significant improvement in corrosion resistance due to high purity. Therefore, as a shape memory alloy, a thermal breaker ( Fire alarms), micro-robots / micro-machine actuators, biomedical materials (use of corrosion resistance) ... catheter drive elements for active endoscopes, orthodontic wires, super-elastic guide wires. In addition, new materials that exceed the present giant magnetostrictive element by controlling the quenching fine and highly purified structure (crystal orientation), especially shape memory alloys having magnetism, whistler type Fe-Pd, Ni-Mn-Ga based alloys, etc. It can be developed and is suitable as a high-performance giant magnetostrictive element, a high-speed response magnetic actuator, a magnetic actuator in a corrosion-resistant environment, a high-frequency transmission element, and a vibration control element. Furthermore, it is possible to manufacture high-strength intermetallic compound ribbons and thin wires with high strength and sensor / actuator function, and can be used as embedding fibers and ribbons for reinforcing composite materials (metals, polymers, ceramics). In particular, it can be applied to high-temperature Ti, Ni-based intermetallic compound-based composite materials and environmentally responsive intelligent (smart) materials and structures. In addition, it can be made into a bulk material by laminating and bonding thin ribbons and thin wires, and by fusing thin wire bundles, and can be used as a structural material. Other uses such as (1) crystalline (thermoelectric conversion, hydrogen storage function) materials, (2) active / ultra-high temperature (operating above 1000 ° C) special shape memory alloy, (3) composite material embedded element (filler), etc. Also suitable for.
[0022]
【Example】
  Examples of the present invention will be described below. Of the present inventionDo not use molten metal blowing nozzleAs an example of the liquid rapid solidification method, first, an inverted triangular molten metal pool in the helical high frequency coil of the first electromagnetic coil is formed, and after the molten metal is achieved at a prescribed drop temperature, the lower second cylinder is formed. Feed the molten metal into the electromagnetic coil of the mold. At this time, important control parameters on the first electromagnetic coil side are (1) the shape of the first electromagnetic coil (spiral type), in particular, the opening angle (θ) of the bottom of the inverted triangular pyramid coil, and (2) Table 1 shows the experimental results of verifying the optimum value of the opening angle (θ) which is the energization amount (i), which is particularly important for the formation of the molten metal pool. When the opening angle (θ) is increased, the floating molten metal pool receives a large electromagnetic force (Lorentz force) and rises from the inside (center) of the coil and becomes unstable, so that the molten metal contacts the coil or from above the coil. It comes off. In the experiment, a Ti—Ni 50.2 atomic% shape memory alloy round bar (diameter 10 mm) was used as the material, and the conduction current i1 = 36 A (constant) of only the first electromagnetic coil, V1 = V2 = 200 V, current frequency The test was performed at 183 kHz and θ = 36, 40, and 44 degrees. From the ratio of the molten metal pool width (W1) and the vertical length (L1) shown in FIG. 3, θ = 40 degrees (W1 / L1 = 0.88) close to an inverted triangle was optimal.
[0023]
[Table 1]

[0024]
Next, when the optimum energization amount i1 = 36A of the first electromagnetic coil is determined and the energization amounts to both coils are i1 = i2 = 36A (identical) and V1 = V2 = 200V (identical), both coils The drop flow was the longest when the interval (S) was 10 mm. Furthermore, when the lengths of both coils (C1 = C2 = 21 mm, 3 turns, opening angle θ = 40 degrees) are set to the same condition, the change in the energization direction of the second electromagnetic coil (forward and reverse) The effect on length was examined. Table 2 shows changes in the length of the continuous dripping flow when the energization amount to the second electromagnetic coil side is reversed (i1 = + 36A, i2 = −36A). The ratio of the length of the molten metal pool (L1) in the first electromagnetic coil and the length of the dripping flow (L2) on the second electromagnetic coil side is shown, but a reverse current flows to the second electromagnetic coil side. In this case, a clear increase in the length of the molten metal was observed.
[0025]
[Table 2]

[0026]
  Samples having the following specifications were prepared using the method and apparatus of the present invention, and (1) metal structure observation (observation of crystal grain growth with a scanning electron microscope, Ti—Ni 40 atomic% —Cu 10 atomic% shape memory alloy) (FIG. 4, FIG. 5, FIG. 6), (2) Crystal structure analysis by X-ray diffraction (FIG. 7), (3) Measurement of change in shape memory transformation strain to temperature hysteresis curve (confirmation of improvement in shape memory effect) ( 8), (4) Corrosion test (corrosion resistance curve in strong acid, saline solution, anodic polarization curve (natural electrode potential to current density curve) (FIG. 9), and (5) X-ray surface elemental analysis (FIG. 10). As a comparative example of the X-ray surface elemental analysis, a dissolved / processed material made of the same raw material was used (FIG. 11).
[0027]
  The material provided for verification of the present invention is Ti-Ni50.2, which is two typical titanium-based shape memory alloys having both functions of a temperature sensor (detection) and an actuator (drive element). Atomic% alloy and Ti-Ni40-Cu10 (atomic%) alloy, the former being the most widely used alloy system with wide shape memory temperature hysteresis, the latter for micro robot drive with narrow shape memory temperature hysteresis Therefore, it was selected in order to demonstrate and confirm the combined effect of “complete non-contact electromagnetic floating dissolution” and “liquid rapid solidification” on the shape memory phenomenon.
[0028]
  Vacuum the inside of the electromagnetic floating dissolution vessel (chamber)1.33 × 10 ^-1 Pa) And then replaced with inert Ar gas. The raw material continuously supplied from the upper part of the chamber was electromagnetically floated and melted, and then the dripped molten metal was rapidly cooled and solidified on the lower rotating copper twin roll along with the change of the roll rotation speed. Control of the amount of raw material supplied and the molten molten metal by the second electromagnetic coil was as follows. The raw material is a shape memory alloy of Ti—Ni 50.2 atomic% and Ti—Ni 40 —Cu 10 atomic%, and a round bar-shaped material (diameter 10 mm, length 10 cm to 15 cm) previously prepared by arc melting is set in the upper part of the chamber. The sample feeding rotary jig is held, and the feed rate = 0.04 mm / sec (2.4 mm / min, about 0.2 mm) at the center of the lower second electromagnetic coil.cm ^Three / Min). When the roll rotation speed is 100 to 5000 rpm and the one-side copper roll diameter in the twin roll method is 150 mm, the roll surface speed is 0.8 to 40 m / second, and the roll gap at the center of the twin roll is 30 microns. Cooling rate is10 ² ~10 ⁶ C./second has been reached. In this case, the energization amounts were il = 36A, i2 = −36A (reverse direction), V1 = V2 = 200V (same), and the coil current frequency 183 kH for the first and second coils. The heating power (W) is obtained from the product of voltage (V) and current (i), is 7.2 kW, the distance (S) between the coils is 10 mm, and the length C1 = C2 of both coils is 21 mm (3 turns, The opening angle was θ = 40 degrees.
[0029]
  4 to 6 show cross-sectional structure photographs of the Ti-Ni40-Cu10 (atomic%) alloy (the quenching roll speed is described in the lower part). 4 shows a roll speed of 1 m / second (cooling speed).10 ²FIG. 5 shows a roll speed of 5 m / sec (cooling speed).10 ^Three FIG. 6 shows a roll speed of 10 m / second (cooling speed).10 ^Four ~10 ^Five ° C / second). As the rotational speed of the molten metal cooling roll was gradually increased, it was observed that the dendrite-type equilibrium diffusion crystal transitioned to fine columnar crystals aligned in the plate thickness direction.
[0030]
  Rapidly solidified Ti-Ni50.2 atomic% alloy (roll speed 28m / sec, 3600rpm, cooling speed10 ^Five FIG. 7 shows the results of crystal structure analysis by X-ray diffraction of the surfaces of the melt processed material (800 ° C., 60% hot-work repeated round bar cutting raw material). Compared to the melt-processed material, it was found that the quenching material has a remarkably large X-ray relative intensity (X-ray count number) on the (100) and (200) system basic surfaces, and a large crystal anisotropy occurs. This is associated with the columnar crystal formation phenomenon aligned in one direction, which is generally observed in Ti—Ni—Cu alloys.
[0031]
  For the practical application of shape memory alloys that have both a temperature sensor and an actuator function, a large shape memory transformation strain is obtained, quick response, durability of repeated response, internal living organisms as medical materials and low temperature difference heat engine Corrosion resistance in a corrosive environment such as application is required. FIG. 8 shows the change in the shape memory transformation strain variation to the temperature hysteresis curve in the quenched Ti—Ni 50.2 atomic% alloy ribbon sample produced by the apparatus of the present invention. The thermoelastic shape memory phase transformation strain width (vertical axis) under a constant load stress = 60 MPa is increased by 2 to 3 times compared to the case of a melt-processed material of random crystals, and the hysteresis in one cycle of heating to cooling It can be confirmed that the transformation temperature radiation indicated by the width also decreases. That is, the transformation temperature range (ΔT = Af) defined by the difference (Af−Mf) between the high temperature side reverse transformation end temperature Af and the low temperature side martensitic transformation end temperature Mf, which is defined by the tangent method at the curved bend. -Mf) decreases with ΔT = Af (343K) -Mf (298K) = 45K for the melt-processed material, while ΔT = Af (327K) -Mf (290K) = 37K for the quenched material, and at the rise of the hysteresis curve The expressed shape memory recovery speed (shape memory responsiveness) was improved.
[0032]
  FIG. 9 shows a general anodic polarization curve in a strong acid (HCl HCl) and saline (NaCl) in a Ti · Ni40—Cu10 (atomic%) alloy as a chemical corrosion test, that is, a natural electrode. The measurement result of a potential-current density curve is shown. It can be seen that the electromagnetic floating quench sample in any case has a significantly improved corrosion resistance because no current flows unless the anodic potential difference is higher than that of the melt processed sample.
[0033]
  After corrosion test, electromagnetic floating quenching material (Ti-Ni40-Cu10 atomic% alloy, roll speed = 10 m / sec) (Fig. 10) and melt processed material (Ti-Ni40-Cu10 atomic% alloy, 650 ° C, 1 hour annealing) An X-ray surface elemental analysis (EDAX) test was conducted for the purpose of investigating surface corrosive products with (FIG. 11). It can be seen that the quenching material has little variation depending on the location, and the surface layer is a uniform and dense material, but in the melt processed material, the strength distribution of the Ni, Ti, and Cu components varies depending on the location. According to this analysis result, it is presumed that the quenched material is hardly corroded and has a high corrosion resistance.
[0034]
【The invention's effect】
  According to the present invention, adjustment of the dropping flow rate, which was difficult with the conventional method using a quartz nozzle, is made possible by adjusting the shape of the second electromagnetic induction coil and adjusting the energization amount in the present invention. Therefore, it is possible to manufacture ribbons and thin wires by rapid solidification with uniform and high performance characteristics continuously or anti-continuously. Further, according to the method of the present invention, since it is not necessary to use a quartz nozzle, high purity and high performance (strength and ductility) of the material can be realized at a low cost, and a Ti—Ni intermetallic compound, etc. In the past, material functions, such as shape memory effect and ductility, were realized due to the appearance of large crystal anisotropy in thin ribbons and thin wires of materials that were difficult to manufacture by rapid solidification. In addition, by combining the process of narrowing the molten metal and the solidification / rolling process by the twin-roll method, the microstructure of the material is controlled by changing the rapid solidification speed (rotary roll speed), especially by controlling the crystal orientation. Could be realized.
[Brief description of the drawings]
FIG. 1 of the present inventionDo not use molten metal blowing nozzleThe schematic diagram of a liquid rapid solidification apparatus and a metal solidification structure | tissue.
FIG. 2 is a schematic diagram of electromagnetic floating melting, acting electromagnetic force, and molten metal surface eddy current generation in the first high-frequency electromagnetic coil.
FIG. 3 is a schematic diagram showing a relationship between an energization direction of a second high-frequency electromagnetic coil and electromagnetic force.
FIG. 4 (cooling rate using the method of the present invention)10 ² (° C./second) Scanning electron micrograph of the cross section of the manufactured Ti—Ni 40 —Cu 10 (atomic%) alloy.
FIG. 5: Using the method of the present invention (cooling rate10 ^Three (° C./second) Scanning electron micrograph of the cross section of the manufactured Ti—Ni 40 —Cu 10 (atomic%) alloy.
FIG. 6 shows the method of the present invention (cooling rate).10 ^Four ~10 ^Five (° C./second) Scanning electron micrograph of the cross section of the manufactured Ti—Ni 40 —Cu 10 (atomic%) alloy.
FIG. 7 is an X-ray diffraction diagram showing the results of crystal structure analysis of the surface of a Ti—Ni 50.2 atomic% alloy produced by the method of the present invention.
FIG. 8 is a diagram showing a shape memory transformation strain-temperature hysteresis curve in a quenched Ti—Ni 50.2 atomic% alloy ribbon sample produced by the method of the present invention.
FIG. 9 is an anodic polarization curve diagram of Ti—Ni 40 —Cu 10 (atomic%) alloy produced by the method of the present invention in strong acid (HCl HCl) and saline (NaCl).
FIG. 10 is an X-ray surface elemental analysis diagram for examining surface corrosive products of a Ti—Ni 40 —Cu 10 (atomic%) alloy produced by the method of the present invention.
FIG. 11 is an X-ray surface elemental analysis diagram for examining surface corrosive products of a melt-processed Ti—Ni 40 —Cu 10 (atomic%) alloy of a comparative example.

Claims

In a method for producing a ribbon or fine wire by continuously supplying a molten metal of a conductive material such as metal or ceramic to a quenching roll and rapidly solidifying it,
The material is floated and melted using the first electromagnetic induction coil for melting the material provided above the roll, and held as a molten metal pool floated by electromagnetic buoyancy in the center of the first electromagnetic induction coil.
The amount of melt of the material is gradually increased, and the molten metal flow dripping from the molten metal pool is overcome by the weight of the molten metal pool surpassing the electromagnetic buoyancy.
A thin continuous flow to the electromagnetic force caused by the second electromagnetic induction coil located below the first electromagnetic induction coil for the material dissolved in the electromagnetic field control thus narrowing down,
A liquid rapid solidification method that does not use a molten metal blowing nozzle, wherein the steady flow is continuously supplied to a rapid cooling roll.

The electromagnetic field control parameters by the second electromagnetic induction coil are (1) the interval between the lower part of the first electromagnetic induction coil and the upper part of the second electromagnetic induction coil, and (2) the direction of energization in the second electromagnetic induction coil. 2. The liquid rapid solidification method according to claim 1, which is (electromagnetic force acting direction) and (3) a current amount (a dripping flow narrowing force by an electromagnetic force).

The liquid rapid solidification method according to claim 1 or 2, wherein the dropping flow velocity is reduced by setting the current directions of the first electromagnetic induction coil and the second electromagnetic induction coil to be the same.

The liquid rapid solidification method according to claim 1 or 2, wherein the drip flow rate is accelerated with the current directions of the first electromagnetic induction coil and the second electromagnetic induction coil as opposite directions.

In a device that manufactures ribbons or fine wires by continuously supplying molten metal of conductive materials such as metals and ceramics to a quenching roll and rapidly solidifying it, the material is subjected to high-frequency electromagnetic floating melting and electromagnetic floating force is formed in the center. A first electromagnetic induction coil to be held as a molten metal pool floating by the first electromagnetic induction coil, and a continuous drop by further narrowing down the molten metal flow from the molten metal pool located at the lower part of the first electromagnetic induction coil with an electromagnetic force associated with electromagnetic field control. The liquid rapid solidification apparatus used for the method according to any one of claims 1 to 4, wherein a second electromagnetic induction coil for forming the downstream is provided above the quenching roll.