JP4016570B2

JP4016570B2 - Oxide superconducting wire and method for producing the same

Info

Publication number: JP4016570B2
Application number: JP2000115854A
Authority: JP
Inventors: 高明笹岡; 岳海室賀
Original assignee: Hitachi Cable Ltd
Current assignee: Hitachi Cable Ltd
Priority date: 2000-04-12
Filing date: 2000-04-12
Publication date: 2007-12-05
Anticipated expiration: 2020-04-12
Also published as: JP2001297638A

Description

【０００１】
【発明の属する技術分野】
本発明はセグメント間に電気絶縁性のバリア材を介在させた酸化物超電導線材及びその製造方法に関するものである。
【０００２】
【従来の技術】
超電導体を複数に分割してフィラメントとし、それらを金属でマトリックス状に被覆した金属被覆超電導線材が知られており、高温で超電導特性を有する酸化物超電導線材も同様の構造が提案され、銀または銀合金をマトリックス状に被覆した、いわゆる銀シース多芯超電導線材の開発が進められている。この場合、酸化物超電導体としては、例えばＢｉ−２２１２、Ｂｉ−２２２３、Ｔｌ−１２２３、Ｔｌ−２２２３、Ｙ−１２３、Ｎｄ−１２３等の酸化物超電導前駆体粉末を出発原料とし、銀または銀合金の被覆材と複合させ、さらに超電導化熱処理を施して超電導線材が得られる。
【０００３】
このような酸化物超電導線材の一つとして、例えば図５に示すように、撚線を断面丸型に成型した超電導線材５２がある。この線材は超電導フィラメント２ｂと銀又は銀合金マトリックス３ａからなる断面丸型の素線の複数を撚り合せ加工した後、その撚線に縮径加工を施し、その縮径加工された撚線に超電導化熱処理を施して酸化物超電導線材とされる。尚、縮径加工においては油性潤滑材を用いるのが通常の手法である。
【０００４】
また、交流損失の低減を配慮する場合は、図２に示すように、超電導フィラメント２ｂ間の電気的結合を抑制するため、電気絶縁性のバリア材４ｂを介在させたバリア付きの成型丸線５１とすることもある。このバリア材４ｂとしてはＢｉ_２Ｓｒ_２Ｃｕ_１Ｏ_Ｘ、ＢａＺｒＯ_３、ＳｒＺｒＯ_３、ＭｇＯ、ＭｎＯ、ＳｒＴｉＯ_３、Ｓｒ−Ｖ−Ｏなどの酸化物が提案されている。
【０００５】
一方、バリア材としては次のような事項が要求される。
【０００６】
（１）超電導化熱処理を経ても気化せずに残留すること。
【０００７】
（２）残留後はその素材がマトリックス材より電気抵抗率がはるかに大きい絶縁バリアとなること。
【０００８】
（３）超電導化熱処理により超電導フィラメントと拡散反応が起きて線材の臨界電流密度（Ｊｃ）の特性を低下させないこと。
【０００９】
（４）縮径加工が可能であること。
【００１０】
【発明が解決しようとする課題】
上記した４つの事項に対し、前記した従来材は（１）〜（３）を満足するが、（４）の加工性については十分でない。特に、形態として酸化物となるバリア材が介在することで縮径加工が困難となる場合が多く、加工可能な範囲が制約されたり、断面が長手方向で不均一に変動したり、超電導特性がバラついたり、加工中に断線が発生したりする等の問題が発生する。原因は前記材料自身が塑性加工の不可能な脆性材料であるためと考えられる。
【００１１】
本発明の目的は、上記したバリア材に要求される４つの事項をほぼ満足させることのできる方法を提供することにある。
【００１２】
【課題を解決するための手段】
上記課題を解決するため、本発明では、遅くとも撚線の縮径加工の際にセグメントの表面に酸化チタンの粉末を適用し、超電導化熱処理を経た線材におけるセグメント間に前記酸化チタンの層を介在させる方策を採用する。
【００１３】
この酸化チタン粉末は潤滑材の機能を有しており、線材の縮径加工性を損なうことがなく、超電導化熱処理後は、その酸化チタンがセグメント間に介在し、交流損失低減に寄与する電気絶縁性のバリア材となる。
【００１４】
この酸化チタン粉末としては、ルチル型やアナターゼ型の結晶構造のもの、アモルファス状態のもの等があるが、それらは当該型の単独、当該型を主体としたもの、他の型のものと混合したもの等何れであっても差し支えなく、素線への適用に際しては粉末のままであったり、溶媒や有機物質の塗料等と混合したりして用いられるが、その適用の時期としては素線の状態のとき、撚り合せ加工する際、撚線を縮径加工する際等が考えられ、それらの時期に少なくとも1 回適用される。撚り合せ加工に先だって素線に塗布しておく場合には、乾燥後に酸化チタン粉末が脱落しないよう有機物質の塗料等と混合した状態で適用することが好ましい。
【００１５】
なお、本発明による酸化物超電導線材は、それ自体導体として、或いはその複数本を集合化した導体として用いる場合のほか、それらを他の部材と複合化した構成にしてもよい。その応用例としてはマグネット、コイル、ケーブル、ブスバー、電流リード、磁気シールド、永久電流スイッチ等の超電導デバイスがあげられる。さらに、前記の応用として使用する場合、その製作法はＲ＆Ｗ（React &mp; Wind）法又はその逆のＲ＆Ｗ法何れであってもよい。
【００１６】
【発明の実施の形態】
以下、図面を参照して本発明の実施の形態を説明する。
【００１７】
Ａ．単芯素材の作製
まず、１本の超電導フィラメントと金属被覆からなる単芯素材を作製する。フィラメントを構成する物質は公知の酸化物超電導材料、例えば、Ｂｉ−２２１２、Ｂｉ−２２２３、Ｔｌ−１２２３、Ｔｌ−２２２３、Ｙ−１２３、Ｎｄ−１２３などからなる。一方、金属被覆は特に限定するものではないが、フィラメントとなる酸化物超電導材料と反応して超電導特性を低下させることのない材料が好ましく、例えば、Ｂｉ−２２１２，Ｂｉ−２２２３の材料のときは、銀又は銀合金（Ａｇを主成分としてＡｕ、Ｐｄ、Ｍｇ、Ｔｉ、Ｎｉ，Ｎｂ、Ｓｂ、Ａｌ、Ｍｎ、Ｚｒ、より選ばれた少なくとも１種を添加したもの）であることが好ましい。
【００１８】
単芯素材の製造の例として、超電導材料は超電導化熱処理を施していない粉末又は一旦熱処理した後に粉砕した粉末、所謂前駆体粉末を所定長さの被覆用金属管内に充填し、次いで減面加工することにより横断面が略円形の単芯線材とする。この工程で得られた線材の金属被覆をフィラメント被覆と称することがある。
【００１９】
なお、超電導フィラメントの中心に芯材として金属素材を配置する場合もある。この金属芯材はフィラメント被覆より柔らかい材質のものが好ましい。中心を柔らかくすることによって後工程での超電導フィラメントの変形がスムーズに起こるようになる。
【００２０】
Ｂ．多芯素材の作製
次に、前記単芯素材の複数本を所定長さの金属管内に組み込み、多芯ビレット化する。金属管は、好ましくは銀または銀合金（Ａｇを主成分としてＡｕ、Ｐｄ、Ｔｉ、Ｍｇ、Ｎｉ、Ｎｂ、Ｓｂ、Ａｌ、Ｍｎ、Ｚｒ、Ｍｏより選ばれた少なくとも１種を添加したもの）からなり、前記フィラメント被覆材や後述する金属芯材と同じか、それらより硬い材料を用いることが好ましい。多芯ビレット化の際は、中心に金属被覆と同様の材料からなる超電導フィラメントを含まない金属芯材を配置してもよい。
【００２１】
次いで、多芯ビレット化された複合体を押出し、スウエージャー又は伸線により減面加工し、横断面が略円形で多数の超電導フィラメント２ａを有する多芯素材１ａを作製する。この工程で得られた多芯素材１ａにおける金属被覆３ａをセグメント被覆と称することがある。後述の説明の便宜上、得られた素材の外径をｄ_０、長さをＬ_０とする。
【００２２】
Ｃ．ツイストと撚線加工
次に、得られた素材１ａの複数本に夫々ツイスト加工（ツイスト加工後の素線ピッチをＰ_０とする）を施した後、それらの表面に、例えばルチル型、アナターゼ型の結晶構造、又はアモルファス状態の酸化チタン粉末をポリエステル系樹脂塗料、ポリエステルイミド系樹脂塗料、ポリアミド系樹脂塗料等と混合したものを塗布し、その皮膜４ａを乾燥させた後、その複数本の素材１ａを所定のピッチＰ_１で撚り合せ加工する。
【００２３】
撚りピッチＰ_１は、素材１ａが図３に示すように２本の場合はＰ_１／ｄ_０＝１．５〜３０、図１に示すように３本の場合はＰ_１／ｄ_０＝４〜４０、５本の場合はＰ_１／ｄ_０＝４〜４０を満足する範囲とすることが好ましい。通常の撚り合せで形状を維持するためにはＰ_１／ｄ_０の上限としては約１００までは可能である。しかし、撚線５、６に縮径加工が施される場合、Ｐ_１／ｄ_０が１００程度まで大きいと縮径加工の際に素材１ａがばらけてしまい縮径加工が困難になる恐れがある。一方、Ｐ_１／ｄ_０が小さすぎると、撚り合せ加工時に素材１ａが過度の加工歪を受け、金属被覆３ａ中のフィラメント２ａの組織に乱れや破壊が生じ、そのために最終的に得られた超電導線材において超電導特性の低下を招く恐れがあるが、撚り合せ加工前の素材１ａにツイスト加工を施すことにより撚り合せ加工によるフィラメント２ｂの乱れを結果として防止することができる。発明者らの実験によれば、撚り合せ加工で線材のＪｃ特性に劣化の生じないＰ_１／ｄ_０の下限は１．５、素材が２本の場合は３、３本の場合は４であった。
【００２４】
Ｄ．撚線の縮径加工
次に、得られた撚線５、６にダイスを用いた伸線装置またはスウエージャー等の公知の手段により縮径加工を施す。この縮径加工は１回でも複数回の繰り返しでもよいが、１回の縮径加工による外径の減少率が２〜２０％となるようにダイス口径を選定することが好ましい。縮径加工を複数回繰り返すときは、縮径加工の途中で焼鈍処理や超電導化のための中間熱処理、あるいは前駆体粉末組織の脱ガス処理を施してもよい。中間熱処理を行うときは、その後の縮径加工は１回のパスによる外径の減少率は２〜５％とすることが好ましい。
【００２５】
縮径加工によって得られる線材の外径をｄとすると、素材１ａが２本の場合はｄ＜１．３ｄ_０、３本の場合はｄ＜１．８ｄ_０に達すると、素材１ａの横断面が半円形（図４）又は中心角が１２０度（図２）、７２度等の略扇形に変形し、これら半円形又は扇形のセグメント１ｂ、１ｃを長手方向に所定のピッチで螺旋状に集合した集合体の線材５１、６１が形成される。また、各々の超電導フィラメント２ｂは個々のセグメント１ｂ、１ｃ内で螺旋状に配置されているので、結果として各超電導フィラメント２ｂは２次螺旋状に集合された構成となっている。
【００２６】
撚線５、６を構成する素材１ａの表面には酸化チタンの粉末の皮膜４ａが形成されているので、この縮径加工の際、その皮膜４ａの酸化チタン粉末が潤滑材として作用し、撚線５、６の縮径加工を容易にし、線材のより小径化を可能にする。場合によっては、この縮径加工の際、酸化チタンの粉末を追加的に適用してもよく、この縮径加工のときだけ酸化チタン粉末を適用してもよい。勿論、縮径加工が複数回にわたる場合、各回毎に酸化チタンの粉末を追加的に適用しなくてもよい。
【００２７】
Ｅ．縮径加工途中のツイスト加工
工程Ｄの縮径加工において、外径ｄと撚線ピッチＰがＰ／ｄ＞Ｐ_２／ｄ、すなわち繰り返しの縮径加工が困難なとき、または所定のピッチＰｓを縮径加工以外の方法でより短く調整しようとするときは、縮径加工の途中で撚線にねじり（ツイスト）加工を施すことによりＰ／ｄを小さくすることができる。この加工は、通常、撚線の撚りが締まる方向に回転させることで行なわれる。このツイスト加工後のピッチをＰ_３、ツイスト加工時の撚線外径をｄとすると、ツイスト加工に必要な単位長さあたりの回転数ｄｎは次式で与えられる。
【００２８】
ｄｎ＝１／Ｐ_３ −１／Ｐ_２
このツイスト加工に先立ち、ツイストをやり易くするために金属被覆３ａに焼鈍処理を施してもよい。
【００２９】
また、ツイスト加工の加工度が大きすぎると超電導フィラメント２ａの組織に乱れが生じたり、破壊に至ることがあるので、ツイスト加工といってもその加工度には限度がある。発明者の実験によれば、素材２ａが２本の場合はＰ_３／ｄ＞３であり、３本及び５本の場合はＰ_３／ｄ＞５である。
【００３０】
Ｆ．超電導化熱処理
超電導化熱処理は、超電導フィラメント２ｂの超電導特性を発現させるために必要な処理である。この熱処理の条件は、一般に酸化物超電導材料の種類に依存するが、超電導フィラメント２ｂの厚さ（断面積）、アスペクト比、金属被覆マトリックス３ａ、３１ａの組成等によっても若干左右される。この熱処理によってフィラメント２ｂを構成している前駆体粉末は酸化物超伝導体に転化される。この場合、図２及び図４に示すように、少なくともセグメント１ｂ、１ｃ間に酸化チタンの層４ｂ、４ｃが残存・介在するが、この酸化チタンは金属被覆３ａ、３ｃや酸化物超電導体と多少反応してもその特性に影響することがなく、セグメント１ｂ、１ｃ間に密着し、電気絶縁物として有効に作用する。
【００３１】
なお、酸化チタン粉末の層４ｂ、４ｃを形成する際使用された樹脂エナメル塗料は、この超電導化熱処理の熱によって分解・消失し、酸化チタンだけが残存することになる。
【００３２】
［実施例１］
組成としてＢｉ_２Ｓｒ_２Ｃａ_１Ｃｕ_２Ｏ_Ｘ（以後Ｂｉ−２２１２と称す）が得られるようにＢｉ_２Ｏ_３、ＳｒＣＯ_３、ＣａＣＯ_３、ＣｕＯの各粉末を混合し、これに大気中で８２０℃−２０ｈの熱処理を施した後、それを粉砕してＢｉ−２２１２相の前駆体粉末を用意し、その前駆体粉末を外径１５mm、内径１３．５mm、長さ５００mmの銀合金パイプ中に充填して複合体とした。この複合体を対辺寸法７．６４mmの６角棒形状に伸線加工して素材Ａを得た。この素材Ａの５５本を外径７１．１mm、内径６４mm、長さ５００mmの銀合金パイプ中に組込み、銀合金被覆酸化物ビレットＸを得、このビレットＸに押出し加工、スエジャー加工、伸線加工を施して外径１．７mm、長さ７０５ｍの銀合金被覆酸化物の丸線（素材Ｂ）を得た。
【００３３】
次に、得られた素材Ｂの３本に夫々ピッチＰ_０＝７．５mmにてｚ方向のツイスト加工を施し、さらに、それらの素材Ｂの表面に、ルチル型結晶構造の酸化チタン粉末（平均１μｍメッシュ）をポリエステルイミド系エナメル塗料に重量比１対１の割合で混合したものを１０μｍの厚さに塗布して酸化チタンの皮膜を形成した後、２５０℃で３０分熱処理して乾燥させた。その後、その皮膜を有する素材Ｂを３本束ね、ｚ方向の撚り合せ加工を施してピッチ３６mmの３本撚りの線材を作製した。
【００３４】
次に、この撚線に対し、ダイス引き伸線による縮径加工を施した。ここでダイス引きの際、ルチル型構造構造の酸化チタンの粉末（平均１μｍメッシュ）を潤滑材として追加的に使用した。この縮径加工を経ることで、３本の丸線は徐々に潰され、最外径が２．４mmまで縮径されると、中心角が略１２０度の扇形セグメントが互いに合わさった丸型集合体（素材Ｃ）として成型された。素材Ｃの少なくともセグメント間には酸化チタンが層として介在し、外径０．７mmまで断線することなく縮径加工を実施することができた。
【００３５】
この後、得られた素材Ｃに１ａｔｍ、大気中で８８０℃、１０分間保持後、５℃／時間の冷却速度で８３０℃まで徐冷し、さらに１時間保持して炉冷する熱処理を施すことで、バリア付３本撚りの成型超電導線材を得た。
【００３６】
［実施例２］
撚り合せ加工前の丸線（素材Ｂ）にルチル型結晶構造の酸化チタン粉末を塗布しないこと以外は、実施例１と同様にしてバリア付３本撚りの成型超電導線材を得た。
【００３７】
［実施例３］
撚線のダイス引き伸線による縮径加工の際、ルチル型結晶構造の酸化チタン粉末を追加的に適用しないこと以外は、実施例１と同様にしてバリア付３本撚りの成型超電導線材を得た。
【００３８】
［比較例１］
バリア素材を適用せず、撚線のダイス引き伸線の際、油性潤滑材を使用した以外は実施例１と同様にして３本撚りの成型超電導線材を得た。
【００３９】
［比較例２］
撚り合せ加工前はバリア素材を適用せず、撚線のダイス引き伸線の際、バリア素材としてＭｇＯ粉末を使用した以外は、実施例１と同様にして３本撚りの成型超電導線材を得た。
【００４０】
［比較例３］
撚り合せ加工前の丸線（素材Ｂ）にバリア素材としてＭｇＯ粉末を塗布し、撚線のダイス引き伸線の際、バリア素材を使用せず、実施例１と同様に加工し、３本撚りの成型超電導線材を得た。
【００４１】
［比較例４］
撚り合せ加工前はバリア素材を適用せず、撚線のダイス引き伸線の際、バリア素材としてＳｒＴｉＯ_３粉末を使用した以外は、実施例１と同様にして３本撚りの成型超電導線材を得た。
【００４２】
［比較例５］
撚り合せ加工前の丸線（素材Ｂ）にバリア素材としてＳｒＴｉＯ _３粉末を塗布し、撚線のダイス引き伸線の際、バリア素材を使用せず、実施例１と同様にして３本撚りの成型超電導線材を得た。
【００４３】
［比較例６］
撚り合せ加工前はバリア素材を使用せず、撚線のダイス引き伸線の際、バリア素材としてＺｒＯ粉末を使用した以外は実施例１と同様にして３本撚りの成型超電導線材を得た。
【００４４】
［比較例７］
撚り合せ加工前の丸線（素材Ｂ）にバリア素材としてＺｒＯ粉末を塗布し、撚線のダイス引き伸線の際、バリア素材を使用せず、実施例１と同様に加工し、３本撚りの成型超電導線材を得た。
【００４５】
以上の各例で得られた３本撚りの成型超電導線材の加工結果と超電導特性及び交流損失特性を評価した。その結果を表１に示す。尚、表中の「手法採否」におけるＸは撚り合せ加工前にバリア素材を塗布、Ｙは縮経加工にバリア素材使用を表す。また超電導特性の評価は液体ヘリウム温度（４．２Ｋ）、外部磁場ゼロにおける線材としての臨界電流密度Ｊｅ（Ａ／mm^２）の測定値、交流損失Ｐは温度液体ヘリウム温度、磁場１Ｔ、周波数５０Ｈｚ下における磁化損失（Ｗ／ｍ^３）の測定値とした。
【００４６】
【表１】

【００４７】
表１に示すように、酸化チタンを用いた場合のみ加工性、超電導特性、交流損失も全て良好の線材が得られた。また、バリア材として酸化チタン以外のものを使った場合は、加工度が大きくとれず、そのためＪｅ値がバリア無しに比べ低下したと考えられる。
【００４８】
［実施例４］
実施例１で用いたと同じ丸線（素材Ｂ、長さ７０５ｍ、外径１．７mm）を２本用意し、それに夫々ピッチ７．５mmにてｚ方向のツイスト加工を施し、さらに、その表面に実施例１と同様の酸化チタン粉末の皮膜を形成し、ピッチ１５mmにて撚り合せ、２本撚りの線材を作製した。この２本撚りの線材に対し、実施例１と同様の縮径加工を施した。この縮径加工を経ることで、２本撚りの線材は徐々に潰され、最外径が１．６mmまで縮径されると、２個の半円形のセグメントが互いに合わさった丸型集合体に成型され、セグメント間には酸化チタンが層として介在し、外径０．４mmまで断線なく縮径加工を実施することができた。
【００４９】
この素材に実施例１と同様の超電導化熱処理を施すことで２本撚りの成型超電導線材４ｂを得た。
【００５０】
［実施例５］
撚り合せ加工前の丸線にルチル型結晶構造の酸化チタン粉末を塗布しないこと以外は実施例４と同様にしてバリア付２本撚りの成型超電導線材を得た。
【００５１】
［実施例６］
撚線のダイス引き伸線による縮径加工の際、ルチル型結晶構造の酸化チタン粉末を適用しないこと以外は実施例４と同様にしてバリア付２本撚りの成型超電導線材を得た。
【００５２】
［比較例８］
バリア素材を適用せず、撚線のダイス引き伸線の際、油性潤滑材を使用した以外は実施例４と同様にして２本撚りの成型超電導線材を得た。
【００５３】
［比較例９］
撚り合せ加工前はバリア素材を適用せず、撚線のダイス引き伸線の際、バリア素材としてＭｇＯ粉末を使用した以外は、実施例４と同様にして２本撚りの成型超電導線材を得た。
【００５４】
［比較例１０］
撚り合せ加工前の丸線（素材Ｂ）にバリア素材としてＭｇＯ粉末を塗布し、撚線のダイス引き伸線の際、バリア素材を使用せず実施例４と同様に加工し、２本撚りの成型超電導線材を得た。
【００５５】
［比較例１１］
撚り合せ加工前はバリア素材を適用せず、撚線のダイス引き伸線の際、バリア素材としてＳｒＴｉＯ_３粉末を使用した以外は、実施例４と同様にして２本撚りの成型超電導線材を得た。
【００５６】
［比較例１２］
撚り合せ加工前の丸線（素材Ｂ）にバリア素材としてＳｒＴｉＯ _３粉末を塗布し、撚線のダイス引き伸線の際、バリア素材を使用せず実施例４と同様に加工し、２本撚りの成型超電導線材を得た。
【００５７】
［比較例１３］
撚り合せ加工前はバリア素材を使用せず、撚線のダイス引き伸線の際、バリア素材としてＺｒＯ粉末を使用した以外は実施例４と同様にして２本撚りの成型超電導線材を得た。
【００５８】
［比較例１４］
撚り合せ加工前の丸線（素材Ｂ）にバリア素材としてＺｒＯ粉末を塗布し、撚線のダイス引き伸線の際、バリア素材を使用せず実施例４と同様に加工し、２本撚りの成型超電導線材を得た。
【００５９】
以上の各例で得られた２本撚りの成型超電導線材の加工結果と超電導特性及び交流損失特性を評価した。その結果を表２に示す。尚、表中の評価等は表１の場合と同様である。
【００６０】
【表２】

【００６１】
表２に示すように、酸化チタンを用いた場合のみ加工性、超電導特性、交流損失も全て良好の線材が得られた。
【００６２】
［実施例７］
酸化チタン粉末としてアナターゼ型結晶構造のもの（平均１μｍメッシュ）を用いた以外は、実施例１と同様の素材、工程を採用して３本撚りの成型超電導線材を得、実施例１と同様に評価した。その結果は表１に示した結果とほぼ同じであった。
【００６３】
［実施例８］
酸化チタン粉末としてアナターゼ型結晶構造のもの（平均１μｍメッシュ）を用いた以外は、実施例４と同様の素材、工程を採用して２本撚りの成型超電導線材を得、実施例１と同様に評価した結果、表２に示した結果とほぼ同じであった。
【００６４】
［実施例９］
酸化チタン粉末としてアモルファス状態のもの（平均０．０２μｍメッシュ）を用いた以外は、実施例１と同様の素材、工程を採用して３本撚りの成型超電導線材を得、実施例１と同様に評価した結果、表１に示した実施例１の結果とほぼ同じであった。
【００６５】
［実施例１０］
酸化チタン粉末としてアモルファス状態のもの（平均０．０２μｍメッシュ）
を用いた以外は、実施例４と同様の素材、工程を採用して２本撚りの成型超電導線材を得、実施例４と同様に評価した結果、表２に示した実施例４の結果とほぼ同じであった。
【００６６】
【発明の効果】
以上説明したように、本発明によれば、横断面が略円形の外径を有する酸化物超電導線材であって、超電導線材の断面内に電気絶縁分割層付きの線材が得られ、それにより交流損失の少ない線材が得られる。また、同時に、電気絶縁層となる酸化チタン自身に潤滑効果があるので、縮径加工における加工度も大きく確保できる。また、同じ加工度で比較すると、加工による断線確率も低減できる効果も期待できる。
【図面の簡単な説明】
【図１】本発明に係る超電導線材の製造工程における撚り合せ加工の状態を示す説明図である。
【図２】本発明に係る超電導線材の製造工程における縮径加工後の状態を示す説明図である。
【図３】本発明に係る超電導線材の製造工程における撚り合せ加工の状態を示す説明図である。
【図４】本発明に係る超電導線材の製造工程における縮径加工後の状態を示す説明図である。
【図５】従来型の超電導線材の例を示す横断面図である。
【符号の説明】
１ａ素材
１ｂ、１ｃセグメント
２ａ、２ｂ超電導フィラメント
３ａ金属被覆
４ａ酸化チタンの皮膜
４ｂ酸化チタンの層
５、６撚線
５１、６１超電導線材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oxide superconducting wire in which an electrically insulating barrier material is interposed between segments, and a method for manufacturing the same.
[0002]
[Prior art]
A metal-coated superconducting wire is known in which a superconductor is divided into a plurality of filaments and these are coated in a matrix with a metal, and a similar structure is proposed for an oxide superconducting wire having superconducting properties at high temperatures. Development of a so-called silver sheath multi-core superconducting wire in which a silver alloy is coated in a matrix is underway. In this case, as the oxide superconductor, for example, an oxide superconducting precursor powder such as Bi-2212, Bi-2223, Tl-1223, Tl-2223, Y-123, and Nd-123 is used as a starting material, and silver or silver A superconducting wire is obtained by being combined with an alloy coating and further subjected to a superconducting heat treatment.
[0003]
As one of such oxide superconducting wires, for example, as shown in FIG. 5, there is a superconducting wire 52 in which a stranded wire is molded into a round cross section. In this wire, after twisting a plurality of strands having a round cross section made of superconducting filament 2b and silver or silver alloy matrix 3a, the stranded wire is subjected to diameter reduction processing, and the reduced diameter stranded wire is superconductive. An oxide superconducting wire is obtained by performing a heat treatment. In the diameter reduction processing, it is a normal method to use an oil-based lubricant.
[0004]
When considering reduction of AC loss, as shown in FIG. 2, in order to suppress electrical coupling between the superconducting filaments 2b, a molded round wire 51 with a barrier with an electrically insulating barrier material 4b interposed therebetween. Sometimes. As the barrier material 4b, oxides such as Bi ₂ Sr ₂ Cu ₁ O _X , BaZrO ₃ , SrZrO ₃ , MgO, MnO, SrTiO ₃ and Sr—V—O have been proposed.
[0005]
On the other hand, the following items are required for the barrier material.
[0006]
(1) It remains without being vaporized even after a superconducting heat treatment.
[0007]
(2) After the residue, the material becomes an insulating barrier having a much higher electrical resistivity than the matrix material.
[0008]
(3) The superconducting heat treatment does not cause a diffusion reaction with the superconducting filament to deteriorate the critical current density (Jc) characteristics of the wire.
[0009]
(4) Diameter reduction processing is possible.
[0010]
[Problems to be solved by the invention]
With respect to the above four items, the above-described conventional material satisfies (1) to (3), but the processability of (4) is not sufficient. In particular, it is often difficult to reduce the diameter due to the presence of a barrier material that is an oxide as a form, the range that can be processed is restricted, the cross section varies unevenly in the longitudinal direction, and the superconducting characteristics are Problems such as variations and breakage during processing occur. The cause is thought to be that the material itself is a brittle material that cannot be plastically processed.
[0011]
An object of the present invention is to provide a method capable of substantially satisfying the four items required for the barrier material.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, in the present invention, at the latest, the titanium oxide powder is applied to the surface of the segment during the diameter reduction processing of the stranded wire, and the titanium oxide layer is interposed between the segments in the wire material that has undergone superconducting heat treatment. Adopt a strategy that
[0013]
This titanium oxide powder has the function of a lubricant and does not impair the diameter reduction workability of the wire, and after superconducting heat treatment, the titanium oxide is interposed between the segments and contributes to reducing AC loss. It becomes an insulating barrier material.
[0014]
As this titanium oxide powder, there are rutile type and anatase type crystal structures, amorphous ones, etc., but these are mixed with other types of single type, mainly of the type. Any of these can be used, and when applied to a strand, it is used as a powder or mixed with a solvent or organic paint, etc. In the state, it may be applied when twisting, when reducing the diameter of the stranded wire, and is applied at least once in those periods. When it is applied to the strands prior to the twisting process, it is preferably applied in a state of being mixed with an organic material paint or the like so that the titanium oxide powder does not fall off after drying.
[0015]
Note that the oxide superconducting wire according to the present invention may be used as a conductor per se or as a conductor in which a plurality of the conductors are assembled, or may be combined with other members. Examples of such applications include superconducting devices such as magnets, coils, cables, bus bars, current leads, magnetic shields, and permanent current switches. Furthermore, when used as the above-mentioned application, the manufacturing method may be either the R & W (React &mp; Wind) method or the reverse R & W method.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0017]
A. Production of single-core material First, a single-core material consisting of one superconducting filament and metal coating is produced. The substance constituting the filament is made of a known oxide superconducting material such as Bi-2212, Bi-2223, Tl-1223, Tl-2223, Y-123, Nd-123, and the like. On the other hand, the metal coating is not particularly limited, but a material that does not deteriorate the superconducting properties by reacting with the oxide superconducting material to be a filament is preferable. For example, when the material is Bi-2212 or Bi-2223 Silver or a silver alloy (added with at least one selected from Au, Pd, Mg, Ti, Ni, Nb, Sb, Al, Mn, and Zr with Ag as a main component) is preferable.
[0018]
As an example of the production of a single core material, a superconducting material is a powder that has not been subjected to a superconducting heat treatment, or a powder that has been heat-treated and then pulverized, so-called precursor powder, is filled into a coating metal tube of a predetermined length, and then surface-reduced By doing so, a single core wire having a substantially circular cross section is obtained. The metal coating of the wire obtained in this step may be referred to as filament coating.
[0019]
In some cases, a metal material is disposed as a core material in the center of the superconducting filament. This metal core is preferably made of a material softer than the filament coating. By making the center soft, the deformation of the superconducting filament in the subsequent process occurs smoothly.
[0020]
B. Production of multi-core material Next, a plurality of single-core materials are incorporated into a metal tube having a predetermined length to form a multi-core billet. The metal tube is preferably made of silver or a silver alloy (added with at least one selected from Au, Pd, Ti, Mg, Ni, Nb, Sb, Al, Mn, Zr, and Mo with Ag as a main component). Therefore, it is preferable to use a material that is the same as or harder than the filament coating material and the metal core material described later. In the multi-core billet formation, a metal core material that does not include a superconducting filament made of the same material as the metal coating may be disposed at the center.
[0021]
Next, the multi-core billeted composite is extruded and surface-reduced by a swager or wire drawing to produce a multi-core material 1a having a substantially circular cross section and a large number of superconducting filaments 2a. The metal coating 3a in the multi-core material 1a obtained in this process may be referred to as segment coating. For the convenience of the following description, the outer diameter of the obtained material is d ₀ and the length is L ₀ .
[0022]
C. Twist stranded wire processing Next, after performing respectively twisted to a plurality of the resulting material 1a (the wire pitch after twisting and P _0), on their surface, for example rutile, anatase After applying a mixture of a titanium oxide powder in a crystalline structure or an amorphous state with a polyester resin paint, a polyesterimide resin paint, a polyamide resin paint, etc., and drying the film 4a, the plurality of materials 1a to combined machining twisted at a predetermined pitch _{P 1.}
[0023]
The twist pitch P ₁ is P ₁ / d ₀ = 1.5 to 30 when the material 1 a is two as shown in FIG. 3, and P ₁ / d ₀ = 4 when there are three materials 1 a as shown in FIG. In the case of ˜40 and 5 pieces, it is preferable that P ₁ / d ₀ = 4 to 40 is satisfied. In order to maintain the shape by normal twisting, the upper limit of P ₁ / d ₀ can be up to about 100. However, when diameter reduction processing is performed on the stranded

wires

5 and 6, if P ₁ / d ₀ is as large as about 100, the material 1 a may be scattered during the diameter reduction processing, and the diameter reduction processing may be difficult. is there. On the other hand, if P ₁ / d ₀ is too small, the material 1a is subjected to excessive processing strain at the time of twisting, and the structure of the filament 2a in the metal coating 3a is disturbed and broken, and thus finally obtained. Although the superconducting wire may be deteriorated in superconducting characteristics, the twist of the raw material 1a before twisting can prevent the filament 2b from being disturbed by twisting. According to the experiments by the inventors, the lower limit of P ₁ / d ₀ which does not cause deterioration in the Jc characteristics of the wire by twisting processing is 1.5, 3 when there are 2 materials, and 4 when 3 materials. there were.
[0024]
D. Next, the obtained stranded

wires

5 and 6 are reduced in diameter by a known means such as a wire drawing device using a die or a swager. The diameter reduction process may be repeated once or a plurality of times, but it is preferable to select the die diameter so that the reduction rate of the outer diameter by one diameter reduction process is 2 to 20%. When the diameter reduction process is repeated a plurality of times, an annealing process, an intermediate heat treatment for superconductivity, or a degassing process of the precursor powder structure may be performed during the diameter reduction process. When performing intermediate heat treatment, the reduction rate of the outer diameter is preferably a 2-5% and to Turkey by subsequent diameter reduction is one pass.
[0025]
Assuming that the outer diameter of the wire obtained by the diameter reduction processing is d, the cross section of the material 1a is reached when d <1.3d ₀ in the case of two materials 1a and d <1.8d ₀ in the case of three materials 1a. Is semicircular (Fig. 4) or deformed into a substantially sector shape with a central angle of 120 degrees (Fig. 2), 72 degrees, etc., and these semicircular or

sector segments

1b, 1c are spirally assembled at a predetermined pitch in the longitudinal direction. Wire rods 51 and 61 of the assembled body are formed. Further, since each superconducting filament 2b is spirally arranged in each

segment

1b, 1c, as a result, each superconducting filament 2b is assembled in a secondary spiral.
[0026]
Since the titanium oxide powder film 4a is formed on the surface of the material 1a constituting the stranded

wires

5 and 6, the titanium oxide powder of the film 4a acts as a lubricant during the diameter reduction processing, The diameter reduction processing of the

wires

5 and 6 is facilitated, and the wire diameter can be further reduced. In some cases, a titanium oxide powder may be additionally applied during the diameter reduction processing, or the titanium oxide powder may be applied only during the diameter reduction processing. Of course, when the diameter reduction processing is performed a plurality of times, it is not necessary to additionally apply the titanium oxide powder each time.
[0027]
E. Twist processing during diameter reduction In the diameter reduction processing in step D, the outer diameter d and the stranded wire pitch P are P / d> P ₂ / d, that is, when repeated diameter reduction processing is difficult, or a predetermined pitch Ps is set. When trying to make the adjustment shorter by a method other than the diameter reduction processing, P / d can be reduced by twisting the twisted wire during the diameter reduction processing. This processing is usually performed by rotating in a direction in which the twist of the stranded wire is tightened. When the twisted pitch is P ₃ and the twisted wire outer diameter during twisting is d, the rotational speed dn per unit length necessary for twisting is given by the following equation.
[0028]
dn = 1 / P ₃ -1 / P ₂
Prior to this twisting process, the metal coating 3a may be annealed to facilitate twisting.
[0029]
In addition, if the degree of processing of the twist processing is too large, the structure of the superconducting filament 2a may be disturbed or may be broken, so that there is a limit to the degree of processing even with twist processing. According to the inventor's experiment, P ₃ / d> 3 when the number of raw materials 2a is two, and P ₃ / d> 5 when the number of raw materials 2 and 3 is five.
[0030]
F. Superconducting heat treatment The superconducting heat treatment is a treatment necessary to develop the superconducting properties of the superconducting filament 2b. The conditions for this heat treatment generally depend on the type of the oxide superconducting material, but are slightly influenced by the thickness (cross-sectional area) of the superconducting filament 2b, the aspect ratio, the composition of the metal coating matrices 3a and 31a, and the like. By this heat treatment, the precursor powder constituting the filament 2b is converted into an oxide superconductor. In this case, as shown in FIG. 2 and FIG. 4, at least the

segments

1b and 1c have the titanium oxide layers 4b and 4c remaining and interposed, but this titanium oxide is somewhat different from the metal coatings 3a and 3c and the oxide superconductor. Even if it reacts, the characteristic is not affected, it adheres between

segments

1b and 1c, and acts effectively as an electrical insulator.
[0031]
The resin enamel paint used for forming the titanium oxide powder layers 4b and 4c is decomposed and disappeared by the heat of this superconducting heat treatment, and only titanium oxide remains.
[0032]
[Example 1]
Each powder of Bi ₂ O ₃ , SrCO ₃ , CaCO ₃ , and CuO is mixed so as to obtain Bi ₂ Sr ₂ Ca ₁ Cu ₂ O _X (hereinafter referred to as Bi-2212) as a composition, and this is mixed with 820 in the atmosphere. After heat treatment at -20 ° C., it is pulverized to prepare a Bi-2212 phase precursor powder. The precursor powder is placed in a silver alloy pipe having an outer diameter of 15 mm, an inner diameter of 13.5 mm, and a length of 500 mm. Filled into a composite. This composite was drawn into a hexagonal bar shape having an opposite side dimension of 7.64 mm to obtain a material A. 55 pieces of this material A were incorporated into a silver alloy pipe having an outer diameter of 71.1 mm, an inner diameter of 64 mm, and a length of 500 mm to obtain a silver alloy-coated oxide billet X, which was extruded, swaged, and drawn. As a result, a silver alloy coated oxide round wire (material B) having an outer diameter of 1.7 mm and a length of 705 m was obtained.
[0033]
Next, three of the obtained materials B were twisted in the z direction at a pitch P ₀ = 7.5 mm, respectively, and further, the surface of the material B was subjected to rutile crystal structure titanium oxide powder (average 1 μm mesh) is mixed with a polyesterimide enamel paint at a weight ratio of 1: 1 to form a titanium oxide film, and then heat treated at 250 ° C. for 30 minutes and dried. . Thereafter, three materials B having the coating were bundled and twisted in the z direction to produce a three-strand wire with a pitch of 36 mm.
[0034]
Next, diameter reduction processing by die drawing was performed on the stranded wire. Here, when dicing, titanium oxide powder having an rutile structure (average 1 μm mesh) was additionally used as a lubricant. Through this diameter reduction processing, the three round wires are gradually crushed, and when the outermost diameter is reduced to 2.4 mm, a circular assembly in which fan segments with a central angle of approximately 120 degrees are combined with each other. Molded as a body (material C). Titanium oxide was present as a layer between at least the segments of the material C, and the diameter reduction processing could be carried out without breaking the outer diameter to 0.7 mm.
[0035]
Thereafter, the obtained material C is subjected to a heat treatment of 1 atm, held at 880 ° C. in the atmosphere for 10 minutes, gradually cooled to 830 ° C. at a cooling rate of 5 ° C./hour, and further held for 1 hour to cool the furnace. Thus, a three-strand molded superconducting wire with a barrier was obtained.
[0036]
[Example 2]
Except that no titanium oxide powder of rutile type crystal structure is applied on the stranding process before the round wire (Material B) was obtained a molded superconducting wire twisted three - Disability in the same manner as in Example 1.
[0037]
[Example 3]
A three-strand molded superconducting wire with a barrier is obtained in the same manner as in Example 1 except that a titanium oxide powder having a rutile-type crystal structure is not additionally applied during diameter reduction processing by die drawing of a stranded wire. It was.
[0038]
[Comparative Example 1]
A three-strand molded superconducting wire was obtained in the same manner as in Example 1 except that the barrier material was not applied and the oil-based lubricant was used when the stranded wire was drawn.
[0039]
[Comparative Example 2]
Before twisting, a barrier material was not applied, and a three-strand molded superconducting wire was obtained in the same manner as in Example 1 except that MgO powder was used as the barrier material when the stranded wire was drawn. .
[0040]
[Comparative Example 3]
The MgO powder was applied to stranding unprocessed round wire (Material B) as the barrier material, when the die pull drawing of stranded wire, without using a barrier Material was processed in the same manner as in Example 1, three A twisted superconducting wire was obtained.
[0041]
[Comparative Example 4]
Before combined machining twist without applying the barrier material, when the die pull drawing of stranded wire, except using SrTiO ₃ powder as a barrier material, a molded superconducting wire twisted three in the same manner as in Example 1 Obtained.
[0042]
[Comparative Example 5]
SrTiO ₃ as a barrier material on the round wire (material B) before twisting Powder was applied, when the die pull drawing of stranded wire, without using a barrier material, to obtain a molded superconducting wire twisted three in the same manner as in Example 1.
[0043]
[Comparative Example 6]
Before combined machining twist without using a barrier material, when the die pull drawing of twisted wires, except for using ZrO powder as barrier Material was obtained a molded superconducting wire twisted three in the same manner as in Example 1 .
[0044]
[Comparative Example 7]
Twisted ZrO powder coating as a barrier material in combined before processing round wire (material B), when the die pull drawing of stranded wire, without using a barrier material, and processed in the same manner as in Example 1, 3-ply A molded superconducting wire was obtained.
[0045]
The processing results, superconducting characteristics, and AC loss characteristics of the three-strand molded superconducting wire obtained in each of the above examples were evaluated. The results are shown in Table 1. In the table, “X” in the “appropriate method” indicates that the barrier material is applied before the twisting process, and Y indicates that the barrier material is used for the warping process. Evaluation of superconducting properties is liquid helium temperature (4.2K), measured value of critical current density Je (A / mm ² ) as a wire at zero external magnetic field, AC loss P is temperature liquid helium temperature, magnetic field 1T, frequency 50Hz. The measured value of the magnetization loss (W / m ³ ) below was used.
[0046]
[Table 1]

[0047]
As shown in Table 1, only when titanium oxide was used, a wire with good workability, superconducting properties, and AC loss was obtained. In addition, when a material other than titanium oxide is used as the barrier material, the degree of processing cannot be increased, and therefore the Je value is considered to be lower than that without the barrier.
[0048]
[Example 4]
Two round wires (material B, length 705 m, outer diameter 1.7 mm) same as those used in Example 1 were prepared, and twisted in the z direction at a pitch of 7.5 mm, respectively. A film of titanium oxide powder similar to that in Example 1 was formed and twisted at a pitch of 15 mm to produce a two-stranded wire. The diameter reduction process similar to Example 1 was performed with respect to this 2 strand wire. Through this diameter reduction processing, the two-stranded wire is gradually crushed, and when the outermost diameter is reduced to 1.6 mm, the two semicircular segments are combined into a round aggregate. The titanium oxide was interposed between the segments as a layer, and the diameter could be reduced without disconnection to an outer diameter of 0.4 mm.
[0049]
This material was subjected to the same superconducting heat treatment as in Example 1 to obtain a two-strand molded superconducting wire 4b.
[0050]
[Example 5]
Except that no coating titanium oxide powder of rutile type crystal structure combined before processing round wire twisting to obtain a molded superconducting wire Similarly twisted two - Disability Example 4.
[0051]
[Example 6]
A two-strand molded superconducting wire with a barrier was obtained in the same manner as in Example 4 except that the titanium oxide powder having the rutile crystal structure was not applied during the diameter reduction processing by die drawing of the stranded wire .
[0052]
[Comparative Example 8 ]
A double-stranded molded superconducting wire was obtained in the same manner as in Example 4 except that the barrier material was not applied and an oil-based lubricant was used when the stranded wire was drawn.
[0053]
[Comparative Example 9 ]
Before twisting, a barrier material was not applied, and a twisted superconducting wire was obtained in the same manner as in Example 4 except that MgO powder was used as the barrier material when the stranded wire was drawn. .
[0054]
[Comparative Example 10 ]
Twisted MgO powder was applied as a barrier material in combined before processing round wire (material B), when the die pull drawing of the stranded wire was processed as in Example 4 without using a barrier Material, 2-ply A molded superconducting wire was obtained.
[0055]
[Comparative Example 1 1 ]
Before combined machining twist does not apply a barrier material, when the die pull drawing of stranded wire, except using SrTiO ₃ powder as a barrier material, a molded superconducting wire 2-ply in the same manner as in Example 4 Obtained.
[0056]
[Comparative Example 1 2 ]
SrTiO ₃ as a barrier material on the round wire (material B) before twisting Powder was applied, when the die pull drawing of the stranded wire was processed as in Example 4 without using a barrier material, to obtain a molded superconducting wire 2-ply.
[0057]
[Comparative Example 1 3 ]
Before combined machining twist without using a barrier material, when the die pull drawing of twisted wires, except for using ZrO powder as barrier Material was obtained a molded superconducting wire twisted two in the same manner as in Example 4 .
[0058]
[Comparative Example 1 4 ]
Twisted ZrO powder coating combined before processing round wire in (Material B) as the barrier material, when the die pull drawing of the stranded wire was processed as in Example 4 without using a barrier material, two twist A molded superconducting wire was obtained.
[0059]
The processing results, superconducting characteristics, and AC loss characteristics of the two-stranded molded superconducting wires obtained in the above examples were evaluated. The results are shown in Table 2. The evaluations in the table are the same as in Table 1.
[0060]
[Table 2]

[0061]
As shown in Table 2, a wire with good workability, superconducting properties, and AC loss was obtained only when titanium oxide was used.
[0062]
[Example 7]
Except for using anatase crystal structure (average 1 μm mesh) as the titanium oxide powder, the same material and process as in Example 1 were used to obtain a three-strand molded superconducting wire, as in Example 1. evaluated. The result was almost the same as the result shown in Table 1.
[0063]
[Example 8]
Except for using anatase crystal structure (average 1 μm mesh) as the titanium oxide powder, the same material and process as in Example 4 were used to obtain a two-strand molded superconducting wire, as in Example 1. As a result of the evaluation, it was almost the same as the result shown in Table 2.
[0064]
[Example 9]
Except for using titanium oxide powder in an amorphous state (average 0.02 μm mesh), the same material and process as in Example 1 were used to obtain a three-strand molded superconducting wire, as in Example 1. As a result of the evaluation, it was almost the same as the result of Example 1 shown in Table 1.
[0065]
[Example 10]
Amorphous titanium oxide powder (average 0.02 μm mesh)
Except that was used, the same material and process as in Example 4 were adopted to obtain a two-strand molded superconducting wire and evaluated in the same manner as in Example 4. As a result, the results of Example 4 shown in Table 2 were obtained. It was almost the same.
[0066]
【The invention's effect】
As described above, according to the present invention, an oxide superconducting wire having a substantially circular outer diameter in a cross section is obtained, and a wire with an electrically insulating dividing layer is obtained in the cross section of the superconducting wire. A wire with less loss can be obtained. At the same time, since the titanium oxide itself serving as the electrical insulating layer has a lubricating effect, it is possible to ensure a high degree of processing in the diameter reduction processing. In addition, when compared at the same degree of machining, an effect of reducing the disconnection probability due to machining can also be expected.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a state of twisting in a manufacturing process of a superconducting wire according to the present invention.
FIG. 2 is an explanatory view showing a state after diameter reduction processing in the manufacturing process of the superconducting wire according to the present invention.
FIG. 3 is an explanatory view showing a state of twisting in the manufacturing process of the superconducting wire according to the present invention.
FIG. 4 is an explanatory view showing a state after diameter reduction processing in the manufacturing process of the superconducting wire according to the present invention.
FIG. 5 is a cross-sectional view showing an example of a conventional superconducting wire.
[Explanation of symbols]

1a Material

1b, 1c

Segment

2a, 2b Superconducting filament 3a Metal coating 4a Titanium oxide film 4b

Titanium oxide layer

5, 6 Stranded wire 51, 61 Superconducting wire

Claims

An oxide superconducting wire having an outer shape with a substantially circular cross section, the superconducting wire spiraling in the longitudinal direction through a plurality of titanium semi-circular or fan-shaped segments with a titanium oxide layer interposed therebetween. An oxide superconducting wire characterized in that the oxide superconducting wire comprises an aggregate assembled in a shape, and the segment is composed of at least one superconducting filament and a metal coating covering the superconducting filament.

The oxide superconducting wire according to claim 1, wherein the titanium oxide layer is obtained by heat-treating a powder having a rutile crystal structure.

2. The oxide superconducting wire according to claim 1, wherein the titanium oxide layer is obtained by heat-treating a powder having an anatase crystal structure.

The oxide superconducting wire according to claim 1, wherein the titanium oxide layer is obtained by heat-treating powder in an amorphous state.

After twisting a plurality of segments having a substantially circular cross section covered with metal at least one of the superconducting filaments at a predetermined pitch to form a stranded wire, the cross section having a predetermined outer diameter is substantially circular. A method of manufacturing an oxide superconducting wire in which the cross section of the segment is formed into a substantially semicircular shape or a sector shape, and then the wire is subjected to a superconducting heat treatment. when, by attaching titanium oxide powder between the segments, oxide characterized that you form aggregates that set spirally in the longitudinal direction through the layer of titanium oxide between a plurality of said segments Manufacturing method of superconducting wire.

6. The method for producing an oxide superconducting wire according to claim 5, wherein titanium oxide powder is adhered to the surface of each segment before twisting.

6. The oxide superconducting wire according to claim 5, wherein titanium oxide powder is attached to the surface of each segment before twisting, and titanium oxide powder is supplied to the twisted wire during diameter reduction processing. Manufacturing method.

Method of manufacturing an oxide superconducting wire according to any one of claims 5-7, characterized in applying those titanium oxide powder was mixed with a resin coating on the surface of the segment.

Method of manufacturing an oxide than conductive wire material according to any one of claims 5-8, wherein the titanium oxide is a powder of rutile type crystal structure.

Method of manufacturing an oxide than conductive wire material according to any one of claims 5-8, wherein the titanium oxide is a powder of anatase type crystal structure.

Method of manufacturing an oxide than conductive wire material according to any one of claims 5-8, wherein the titanium oxide is a powder in an amorphous state.