JP4402815B2

JP4402815B2 - Nb3Al superconducting multi-core wire and manufacturing method thereof

Info

Publication number: JP4402815B2
Application number: JP2000216950A
Authority: JP
Inventors: 孝夫竹内; 信哉伴野; 仁和田; 浩平田川; 英純森合; 和彦中川
Original assignee: Hitachi Cable Ltd; National Institute for Materials Science
Current assignee: Hitachi Cable Ltd; National Institute for Materials Science
Priority date: 2000-07-18
Filing date: 2000-07-18
Publication date: 2010-01-20
Anticipated expiration: 2020-07-18
Also published as: JP2002033025A

Description

【０００１】
【発明の属する技術分野】
本発明はＮｂ₃Ａｌ超電導多芯線およびその製造方法に関し、特に、高磁界特性およびコイル等の成形加工性に優れるＮｂ₃Ａｌ超電導多芯線およびその製造方法に関する。
【０００２】
【従来の技術】
Ｎｂ₃Ａｌ化合物系超電導線は、超電導線として一般的なＮｂ₃ＳｎおよびＮｂＴｉに比較して、高磁界における臨界電流密度特性に優れているため、核融合炉や高エネルギ−加速器などの超電導線自身に大きな電磁力が加わる大型・応用超電導機器への利用が期待されている。
【０００３】
従来のＮｂ₃Ａｌ化合物系超電導線の製造方法として、急熱急冷・変態（ＲＨＱＴ）法がある。このＲＨＱＴ法では、例えば、ジェリ−ロ−ル（Jelly−Roll；以下、ＪＲとする）法に基づいて形成されたＮｂ／Ａｌ多芯複合線を１ｍ／ｓｅｃの速度で移動させつつ通電加熱することにより０．１秒で２０００℃まで加熱し、冷媒と電極を兼ねた液体Ｇａに浸漬することによって体心立方（ｂｃｃ）相のＮｂに２５ａｔ％Ａｌが過飽和に固溶したＮｂ（Ａｌ）ｓｓを形成する。そして、このＮｂ（Ａｌ）ｓｓに７００℃から８００℃の変態熱処理を施すことによってｂｃｃ相からＡ１５型化合物ヘマッシブ変態させることにより化学量論組成のＮｂ₃Ａｌ化合物系超電導線を形成する。
【０００４】
上記したＲＨＱＴ法に基づくＮｂ（Ａｌ）ｓｓは、冷間加工性に優れることからコイル状に巻いた状態で変態熱処理を施すワインド・アンド・リアクト（Wind and React）法を適用できる。このため、巻き径が小なる高磁界用内層コイルの成形に有効であるが、変態熱処理による積層欠陥の生成が不可避であり臨界温度Ｔｃは１７．９Ｋ、また臨界磁場Ｂｃ２（４．２Ｋ）は２７Ｔと超電導特性に限界がある。
【０００５】
このような超電導特性を改善するものとして、急熱急冷における到達最大温度を下げる、あるいはＣｕ、Ｇｅ、Ｓｉ等の第３元素を添加することによってＡ１５型化合物が直接生成され、化学量論組成のＮｂ₃Ａｌ化合物が形成されることが確認されている。このＡ１５型化合物は長範囲規則性が低下した不規則性の特徴を有し、規則化のために７００℃から８００℃の熱処理を施すことによって臨界温度Ｔｃは１８．５Ｋ、またＢｃ２（４．２Ｋ）は２９Ｔまで向上し、高磁界での臨界電流密度Ｊｃが改善される。
【０００６】
【発明が解決しようとする課題】
しかし、従来のＡ１５型化合物が直接生成するＮｂ₃Ａｌ化合物系超電導線では、熱処理によって不規則Ａ１５型化合物を規則化すると高磁界での臨界電流密度Ｊｃが向上する反面、低磁界での臨界電流密度Ｊｃが低下する。また、脆くなってコイル成形時の巻き込み性や撚り線導体化等の成形加工性が低下する。機械的強度は超電導部に対するＮｂマトリックスの割合を大にすることにより補強できるが、この場合にはoverallＪｃが大幅に低下するという問題がある。
【０００７】
従って、本発明の目的は、高磁界特性に優れ、かつ、コイル成形等の成形加工を阻害しない機械的強度を有するＮｂ₃Ａｌ超電導多芯線およびその製造方法を提供することにある。
【０００８】
【課題を解決するための手段】
本発明は、上記目的を達成するため、過飽和固溶体からＡ１５相に変態したＮｂ₃Ａｌフィラメントおよび不規則Ａ１５相を規則化させたＮｂ₃Ａｌフィラメントを同一の断面内に有するＮｂ₃Ａｌ超電導多芯線を提供する。
【０００９】
また、本発明は、上記目的を達成するため、過飽和固溶体から変態したＮｂ₃Ａｌが体積比で５０％以上のＮｂ₃Ａｌフィラメントと、
該Ｎｂ₃Ａｌフィラメントに不規則Ａ１５相から規則化したＮｂ₃Ａｌフィラメントを分散・混合した構成を有するＮｂ₃Ａｌ超電導多芯線を提供する。
【００１０】
また、本発明は、上記目的を達成するため、Ｎｂのマトリックスで被覆した複数本のサブマルチ線を内周部と外周部に積層して積層体を形成し、
前記積層体をＮｂのマトリックスで被覆してマルチ線を形成し、
前記マルチ線を所定の温度で１次加熱し、
１次加熱された前記マルチ線を冷却用金属材で冷却処理して前記外周部に過飽和固溶体フィラメント、前記内周部に不規則Ａ１５相を生成させ、
冷却後に所定の温度で２次加熱して前記外周部に過飽和固溶体からＡ１５相に変態したＮｂ₃Ａｌフィラメント、前記内周部に不規則Ａ１５相を規則化させたＮｂ₃Ａｌフィラメントを生成させるＮｂ₃Ａｌ超電導多芯線の製造方法を提供する。
【００１１】
上記したＮｂ₃Ａｌ超電導多芯線およびその製造方法によると、延性に富む過飽和固溶体からＡ１５相に変態したＮｂ₃Ａｌフィラメントと超電導特性の良好な不規則Ａ１５相を規則化させたＮｂ₃Ａｌフィラメントとを同一の断面内に配置することによって、曲げ等の機械的歪みによる不規則Ａ１５相Ｎｂ₃Ａｌフィラメントの破断を防ぐとともに超電導特性、特に、overallＪｃを大にできる。
【００１２】
過飽和固溶体Ｎｂ（Ａｌ）ｓｓを生成させるには高温で固溶体を形成する必要がある。外周部のフィラメントがそのような条件を満たすとき、線材・横断面の中心部で不規則Ａ１５相フィラメントを生成させるにはＮｂとＡｌ間の拡散反応が終了していないことが必須で、そのためには、外周部に配されるものと比較してシングル線材のＡｌあるいはＡｌ合金の厚さ（太さ）を２倍以上大きくする必要がある。一方、その比が１００を越えると未反応Ｎｂが大量に残ってＮｂ₃Ａｌの体積比が低くなりoverallＪｃが小になる。また、Ｎｂ（Ａｌ）ｓｓの固溶限は温度の上昇とともに増加するので、中心部に配置されるサブマルチ線の公称Ａｌ濃度を外周部に配されるものと比較して１ａｔ％以上高くすることにより、過飽和固溶体フィラメントと不規則Ａ１５相フィラメントが共存する加熱温度域が存在する。公称Ａｌ濃度が５ａｔ％以上高くなるとＮｂ₂Ａｌ相が大量に生成し、結局、不規則Ａ１５相の体積比が低くなりoverallＪｃは小さくなってしまう。
【００１３】
Ｎｂ（Ａｌ）ｓｓの固溶限は、Ｃｕ、Ｇｅ、Ｓｉの第３元素を添加することにより減少する。中心部に配置されるサブマルチ線にＡｌ合金、また外周部に純Ａｌを用いると不規則Ａ１５相フィラメントと過飽和固溶体フィラメントを同時に生成することができる。そのためにはＣｕを０．５ａｔ％、Ｇｅを５ａｔ％、またＳｉを５ａｔ％以上それぞれＡｌに添加して過飽和固溶体を不安定化させる必要がある。しかし、添加量がそれぞれ２ａｔ％、２０ａｔ％、１５ａｔ％を越えるとＡｌ合金が脆くなり、Ｎｂ／Ａｌ複合体の加工性が低下する。過飽和固溶体と不規則Ａ１５相を混合してフィラメントを形成する場合は、過飽和固溶体の体積率を５０％以上とすることでフィラメントの最低限の加工性を確保できる。
【００１４】
【発明の実施の形態】
表１は、後述する実施例１〜４で形成されるＮｂ₃Ａｌ超電導多芯線の構成、機械的特性、および超電導特性を示す。
【表１】

本発明のＮｂ₃Ａｌ超電導多芯線は、サブマルチ線を複数本組み込んでマルチ構造線とすることにより形成される。サブマルチ線の製造方法には多くの方法が存在するが、本発明ではＪＲ法とロッドインチュ−ブ（ＲＩＴ）法で作製したサブマルチ線について説明する。
【００１５】
〔実施例１〕
図１は、Ｎｂ₃Ａｌ超電導多芯線の断面を示し、（ａ）は本発明の実施の形態にかかるマルチ線、（ｂ）は比較例としての標準試料であるマルチ線である。
（ａ）のマルチ線は、中心部にＮｂジャケットで被覆したＡｇ安定化材１を７本配置し、その周囲に内周部としてＡｌ−２ａｔ％Ｃｕ合金のフィラメント数が７９９９（４２１×１９）本のＮｂ／Ａｌ−２ａｔ％Ｃｕ・ＲＩＴ法サブマルチ線２を１層（計１２本）配置し、また、その外側に外周部としてＮｂ−２５ａｔ％Ａｌの組成を有し、Ａｌの層厚が１００ｎｍのＪＲＮｂ／Ａｌサブマルチ線３を３層（計６６本）配置してマルチ線４を形成し、このマルチ線４に急熱急冷（ＲＨＱ）処理を施した。
【００１６】
（ｂ）のマルチ線は、中心部にＮｂジャケットで被覆したＡｇ安定化材１を７本配置し、その周囲に内周部としてフィラメント状のＮｂ５を配置し、また、その外側に外周部としてＮｂ−２５ａｔ％Ａｌの組成を有し、Ａｌの層厚が１００ｎｍのＪＲＮｂ／Ａｌサブマルチ線３を３層（計６６本）配置しており、急熱急冷条件の異なる標準試料１および２としている。このマルチ線についても同様に急熱急冷処理を施した。
【００１７】
図２は、急熱急冷処理のときの通電電流に対する変態熱処理後の臨界温度Ｔｃを示し、（ａ）は実施例１のマルチ線の臨界温度Ｔｃの変化、（ｂ）は標準試料のマルチ線の臨界温度Ｔｃの変化である。ＲＨＱ処理後、定電流電源から供給される電流値による急熱急冷処理条件に基づいて、８００℃で１０時間の変態熱処理を施したところ、本発明のマルチ線では、外周部に配置されたＪＲサブマルチ（フィラメント）だけが過飽和固溶体になっており、内周部に配置されたＲＩＴサブマルチ（フィラメント）では不規則Ａ１５相が生じる。臨界温度Ｔｃも１８．２Ｋを越える値が得られている。表１に示すように、低磁界の臨界電流密度Ｊｃが若干小さくなるが、高磁界での臨界電流密度Ｊｃは改善され、良好な曲げ加工性を保持している。また、高い臨界温度Ｔｃを示すＲＨＱ条件の選択範囲が広い。
【００１８】
比較例のマルチ線では、標準試料１について、不規則Ａ１５相が生成するＲＨＱ条件では臨界温度Ｔｃが高く、表１に示すように高磁界での臨界電流密度Ｊｃが大きい。しかし、低磁界になっても臨界電流密度Ｊｃは向上せず、急冷後の曲げ加工性が低下する。標準試料２について、過飽和固溶体が生成するＲＨＱ条件では臨界温度Ｔｃが低いが、急冷後は表１に示すように極めて良好な曲げ加工性を有する。磁界が減少すると臨界電流密度Ｊｃは向上するが、高磁界側で臨界電流密度Ｊｃは急速に劣化する。このようにＲＨＱ条件により特性が大きく異なる。
【００１９】
〔実施例２〕
中心部にＮｂジャケットで被覆したＡｇ安定化材を７本配置し、その周囲に内周部としてＮｂ−２５ａｔ％Ａｌの組成を有し、Ａｌの層厚が１μｍのＪＲＮｂ／Ａｌサブマルチ線を配置し、また、その外側に外周部としてＮｂ−２５ａｔ％Ａｌの組成を有し、Ａｌの層厚が１００ｎｍのＪＲＮｂ／Ａｌサブマルチ線を配置してマルチ線を形成した。内周部に配置したＪＲＮｂ／Ａｌサブマルチ線のＡｌの層厚は外周部の層厚より１０倍厚く形成されている。
【００２０】
このマルチ線に急熱急冷処理を施したところ、外周部に配置されたＪＲＮｂ／Ａｌサブマルチ（フィラメント）は過飽和固溶体になっており、内周部に配置されたＪＲＮｂ／Ａｌサブマルチ（フィラメント）では不規則Ａ１５相が生じた。このマルチ線に８００℃で１０時間の変態熱処理を施したところ、表１に示すように、低磁界の臨界電流密度Ｊｃが若干小さくなるものの高磁界での臨界電流密度Ｊｃは改善され、良好な曲げ加工性が得られた。
【００２１】
〔実施例３〕
Ｎｂジャケットで被覆したＡｇ安定化材を中心部に７本配置し、その周囲に内周部としてＮｂ−２７．５ａｔ％Ａｌの組成を有し、Ａｌの層厚が１００ｎｍのＪＲＮｂ／Ａ１サブマルチ線を配置し、また、その外側に外周部としてＮｂ−２５ａｔ％Ａｌの組成を有し、Ａｌの層厚が１００ｎｍのＪＲＮｂ／Ａｌサブマルチ線を配置してマルチ線を形成した。内周部に配置したサブマルチ線の公称Ａｌ濃度は外周部の公称Ａｌ濃度より２．５ａｔ％高くした。
【００２２】
このマルチ線に急熱急冷処理を施したところ、外周部に配置されたＪＲＮｂ／Ａｌサブマルチ（フィラメント）は過飽和固溶体になっており、内周部に配置されたＪＲＮｂ／Ａｌサブマルチ（フィラメント）では不規則Ａ１５相が生じた。このマルチ線に８００℃で１０時間の変態熱処理を施したところ、表１に示すように、低磁界の臨界電流密度Ｊｃが若干小さくなるものの高磁界での臨界電流密度Ｊｃは改善され、良好な曲げ加工性が得られた。
【００２３】
〔実施例４〕
Ｎｂジャケットで被覆したＡｇ安定化材を中心部に７本配置し、その周囲に内周部としてＮｂ／Ａｌ−２ａｔ％ＣｕのＲＩＴ法７芯線４０本とＮｂ／Ａｌ−５ａｔ％ＭｇのＲＩＴ法７芯線８１本を混合して作成したサブマルチ線を配置し、また、その外側に外周部と同一のサブマルチ線を配置してマルチ線を形成した。
【００２４】
このマルチ線に急熱急冷処理を施したところ、各フィラメントには過飽和固溶体と不規則Ａ１５相が約７：３の割合で混合して生じた。このマルチ線を８００℃で１０時間の変態熱処理を施したところ、表１に示すように、低磁界の臨界電流密度Ｊｃが若干小さくなるものの高磁界での臨界電流密度Ｊｃは改善される。この場合でも、コイル成形に必要な曲げ加工性は確保されている。
【００２５】
上記したＮｂ₃Ａｌ超電導多芯線によると、断面内での配置あるいは混合比を制御して、不規則Ａ１５相と過飽和固溶体を同時に生じさせるようにしたので、過飽和固溶体が不規則Ａ１５相を機械的に支持する。このことによって余分なＮｂマトリックスを増大させることなしに良好な成形加工性を保持しながら高磁界特性が改善される。例えば、Wind and React法に基づく巻き径の小なる１ＧＨｚクラスＮＭＲ超電導マグネットの最内層コイル等の形成が可能になる。また、撚り線による大電流容量化も可能となり、最大経験磁場が高くなる次世代核融合炉超電導マグネット導体に適する。超電導特性では、実用線材として使用されているＮｂ₃Ｓｎの２倍以上の臨界電流密度Ｊｃを示し、優れた耐歪み特性を有するので、核融合炉や高エネルギ−加速器などの大型超電導システムの強磁場化を実現するとともにシステム全体のコンパクト化を図ることができ、装置コストを低減することができる。
【００２６】
なお、上記した実施の形態で適用した公称Ａｌ濃度、ＮｂとＡｌ間の拡散距離、合金添加の有無等の製造パラメ−タは、ＪＲ法、ＲＩＴ法以外の他の製造方法であるクラッドチップ押出し法、粉末押出し法においても同様に適用することができる。
【００２７】
【発明の効果】
以上説明した通り、本発明のＮｂ₃Ａｌ超電導多芯線およびその製造方法によると、延性に富む過飽和固溶体からＡ１５相に変態したＮｂ₃Ａｌフィラメントと超電導特性の良好な不規則Ａ１５相を規則化させたＮｂ₃Ａｌフィラメントを同一の断面内に配置したため、高磁界特性に優れ、かつ、コイル成形等の成形加工を阻害しない機械的強度を付与することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係るＮｂ₃Ａｌ超電導多芯線を示し、
（ａ）は、本発明のマルチ線の断面図
（ｂ）は、比較例としての標準試料であるマルチ線の断面図
【図２】急熱急冷処理のときの通電電流に対する変態熱処理後の臨界温度Ｔｃを示す説明図
【符号の説明】
１Ａｇ安定化材
２Ｎｂ／Ａｌ−２ａｔ％Ｃｕ・ＲＩＴ法サブマルチ線
３ＪＲＮｂ／Ａｌサブマルチ線
４マルチ線
５Ｎｂ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an Nb ₃ Al superconducting multicore wire and a method for manufacturing the same, and more particularly to an Nb ₃ Al superconducting multicore wire excellent in high magnetic field characteristics and moldability such as a coil and a method for manufacturing the same.
[0002]
[Prior art]
Nb ₃ Al compound-based superconducting wires are superior to Nb ₃ Sn and NbTi, which are common as superconducting wires, and have superior critical current density characteristics in a high magnetic field. Therefore, superconducting wires such as fusion reactors and high energy accelerators are used. It is expected to be used for large and applied superconducting equipment where large electromagnetic force is applied to itself.
[0003]
As a conventional method for producing a Nb ₃ Al compound-based superconducting wire, there is a rapid thermal quenching / transformation (RHQT) method. In this RHQT method, for example, the Nb / Al multi-core composite wire formed based on the Jelly-Roll method (hereinafter referred to as JR) is heated while being moved at a speed of 1 m / sec. Nb (Al) ss in which 25 at% Al is dissolved in supersaturation in Nb of the body-centered cubic (bcc) phase by heating to 2000 ° C. in 0.1 seconds and immersing in liquid Ga that also serves as a refrigerant and an electrode. Form. Then, a Nb ₃ Al compound superconducting wire having a stoichiometric composition is formed by subjecting this Nb (Al) ss to a transformation heat treatment from 700 ° C. to 800 ° C. to cause a massive transformation from the bcc phase to the A15 type compound.
[0004]
Since Nb (Al) ss based on the above RHQT method is excellent in cold workability, a Wind and React method in which transformation heat treatment is performed in a coiled state can be applied. Therefore, it is effective for forming a high magnetic field inner layer coil with a small winding diameter, but it is inevitable that a stacking fault is generated by transformation heat treatment, the critical temperature Tc is 17.9K, and the critical magnetic field Bc2 (4.2K) is There is a limit to 27T and superconducting properties.
[0005]
In order to improve such superconducting characteristics, an A15 type compound is directly generated by lowering the maximum temperature reached in rapid thermal quenching or by adding a third element such as Cu, Ge, Si, etc. It has been confirmed that an Nb ₃ Al compound is formed. This A15 type compound has the characteristic of irregularity in which long-range regularity is lowered, and the critical temperature Tc is 18.5K and Bc2 (4. 2K) is improved to 29T, and the critical current density Jc in a high magnetic field is improved.
[0006]
[Problems to be solved by the invention]
However, in the conventional Nb ₃ Al compound-based superconducting wire directly produced by the A15 type compound, the critical current density Jc in a high magnetic field is improved when the irregular A15 type compound is ordered by heat treatment, but the critical current in a low magnetic field is improved. The density Jc decreases. Moreover, it becomes brittle and the winding workability at the time of coil forming and forming workability such as making a stranded wire conductor are reduced. The mechanical strength can be reinforced by increasing the ratio of the Nb matrix to the superconducting part, but in this case, there is a problem that the overall Jc is greatly reduced.
[0007]
Accordingly, an object of the present invention is to provide an Nb ₃ Al superconducting multi-core wire having excellent high magnetic field characteristics and having mechanical strength that does not hinder forming processing such as coil forming, and a method for manufacturing the same.
[0008]
[Means for Solving the Problems]
The present invention, in order to achieve the above object, Nb ₃ Al superconducting multifilamentary wire having a Nb ₃ Al filaments obtained by ordering the Nb ₃ Al filaments and irregular A15 phase was transformed to A15 phase from a supersaturated solid solution within the same section I will provide a.
[0009]
In order to achieve the above object, the present invention provides an Nb ₃ Al filament whose Nb ₃ Al transformed from a supersaturated solid solution has a volume ratio of 50% or more,
Providing Nb ₃ Al superconducting multifilamentary wire having a configuration in which the Nb ₃ Al filaments dispersed and mixed Nb ₃ Al filaments ordered from a disordered A15 phase.
[0010]
Further, in order to achieve the above object, the present invention forms a laminate by laminating a plurality of sub-multi wires covered with a Nb matrix on the inner peripheral portion and the outer peripheral portion,
The laminated body is covered with a Nb matrix to form a multi-line,
The multi-wire is primarily heated at a predetermined temperature,
The first heated multi-wire is cooled with a cooling metal material to generate a supersaturated solid solution filament on the outer periphery, and an irregular A15 phase on the inner periphery,
After cooling, secondary heating is performed at a predetermined temperature to generate Nb ₃ Al filaments transformed from a supersaturated solid solution into an A15 phase in the outer peripheral part, and Nb ₃ Al filaments in which irregular A15 phase is ordered in the inner peripheral part. _{3 A} method for producing an Al superconducting multi-core wire is provided.
[0011]
According to Nb ₃ Al superconducting multifilamentary wire and a manufacturing method thereof described above, the Nb ₃ Al filaments obtained by ordering a good irregular A15 phase of Nb ₃ Al filaments and superconducting properties were transformed into A15 phase from a supersaturated solid solution rich in ductility Are disposed in the same cross section, the breakage of the irregular A15 phase Nb ₃ Al filament due to mechanical strain such as bending can be prevented, and the superconducting properties, particularly overall Jc, can be increased.
[0012]
In order to generate the supersaturated solid solution Nb (Al) ss, it is necessary to form the solid solution at a high temperature. When the outer peripheral filament satisfies such a condition, it is essential that the diffusion reaction between Nb and Al is not completed in order to generate an irregular A15 phase filament at the center of the wire / cross section. The thickness (thickness) of the Al or Al alloy of the single wire needs to be increased by at least twice as compared with that disposed on the outer peripheral portion. On the other hand, when the ratio exceeds 100, a large amount of unreacted Nb remains, the volume ratio of Nb ₃ Al becomes low, and overallJc becomes small. In addition, since the solid solubility limit of Nb (Al) ss increases as the temperature rises, the nominal Al concentration of the sub-multi line arranged in the center is increased by 1 at% or more compared to that arranged in the outer periphery. Therefore, there exists a heating temperature region where the supersaturated solid solution filament and the irregular A15 phase filament coexist. When the nominal Al concentration is increased by 5 at% or more, a large amount of Nb ₂ Al phase is generated, and eventually the volume ratio of the irregular A15 phase is lowered and overallJc becomes small.
[0013]
The solid solubility limit of Nb (Al) ss is reduced by adding the third element of Cu, Ge, and Si. When an Al alloy is used for the sub-multi-wire arranged at the center and pure Al is used for the outer periphery, irregular A15 phase filaments and supersaturated solid solution filaments can be generated simultaneously. For this purpose, it is necessary to destabilize the supersaturated solid solution by adding Cu at 0.5 at%, Ge at 5 at%, and Si at 5 at% or more to Al. However, if the addition amount exceeds 2 at%, 20 at%, and 15 at%, respectively, the Al alloy becomes brittle and the workability of the Nb / Al composite is lowered. When the supersaturated solid solution and the irregular A15 phase are mixed to form a filament, the minimum workability of the filament can be ensured by setting the volume ratio of the supersaturated solid solution to 50% or more.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Table 1 shows the configuration, mechanical characteristics, and superconducting characteristics of Nb ₃ Al superconducting multicore wires formed in Examples 1 to 4 described later.
[Table 1]

The Nb ₃ Al superconducting multi-core wire of the present invention is formed by incorporating a plurality of sub-multi wires into a multi-structure wire. There are many methods for manufacturing a sub-multi wire. In the present invention, a sub-multi wire produced by a JR method and a rod-in-tube (RIT) method will be described.
[0015]
[Example 1]
FIG. 1 shows a cross section of an Nb ₃ Al superconducting multi-core wire, where (a) is a multi-wire according to an embodiment of the present invention, and (b) is a multi-wire that is a standard sample as a comparative example.
In the multi-wire of (a), seven Ag stabilizing materials 1 covered with an Nb jacket are arranged in the center, and the number of filaments of Al-2 at% Cu alloy is 7999 (421 × 19) as the inner periphery. One Nb / Al-2 at% Cu · RIT method sub-multi-wire 2 is arranged (total of 12 lines), and the outer periphery has a composition of Nb-25 at% Al, and the Al layer thickness is Three layers (total 66 lines) of 100 nm JRNb / Al sub-multi wires 3 were arranged to form multi wires 4, and the multi wires 4 were subjected to rapid thermal quenching (RHQ) treatment.
[0016]
In the multi-line of (b), seven Ag stabilizing materials 1 covered with an Nb jacket are arranged at the center, a filamentous Nb5 is arranged as an inner periphery around the Ag stabilizing material 1, and an outer periphery as an outer periphery. Three layers (total 66 lines) of JRNb / Al sub-multi wires 3 having a composition of Nb-25 at% Al and an Al layer thickness of 100 nm are arranged as

standard samples

1 and 2 having different rapid heating and quenching conditions. . The multi-wire was also subjected to a rapid heating / cooling treatment.
[0017]
FIG. 2 shows the critical temperature Tc after transformation heat treatment with respect to the energized current during the rapid heating and quenching treatment, (a) shows the change in the critical temperature Tc of the multi-wire of Example 1, and (b) shows the multi-wire of the standard sample. This is a change in the critical temperature Tc. After the RHQ treatment, transformation heat treatment was performed at 800 ° C. for 10 hours based on the rapid heating and quenching treatment conditions based on the current value supplied from the constant current power source. Only the sub-multi (filament) is a supersaturated solid solution, and an irregular A15 phase is generated in the RIT sub-multi (filament) arranged on the inner periphery. The critical temperature Tc is also greater than 18.2K. As shown in Table 1, the critical current density Jc in the low magnetic field is slightly reduced, but the critical current density Jc in the high magnetic field is improved, and good bending workability is maintained. In addition, the selection range of the RHQ condition showing a high critical temperature Tc is wide.
[0018]
In the multi-wire of the comparative example, the critical temperature Tc is high for the standard sample 1 under the RHQ conditions in which the irregular A15 phase is generated, and the critical current density Jc in a high magnetic field is large as shown in Table 1. However, the critical current density Jc does not improve even at a low magnetic field, and the bending workability after rapid cooling is reduced. Regarding the standard sample 2, the critical temperature Tc is low under the RHQ conditions in which a supersaturated solid solution is generated, but after quenching, it has very good bending workability as shown in Table 1. When the magnetic field decreases, the critical current density Jc increases, but the critical current density Jc rapidly deteriorates on the high magnetic field side. In this way, the characteristics vary greatly depending on the RHQ conditions.
[0019]
[Example 2]
Seven Ag stabilizers coated with Nb jacket are arranged at the center, and JRNb / Al sub-multi wires with Nb-25at% Al composition as the inner periphery and Al layer thickness of 1μm are arranged around it. In addition, a JRNb / Al sub-multi line having a composition of Nb-25 at% Al as the outer peripheral portion and an Al layer thickness of 100 nm was disposed on the outer side to form a multi-line. The Al layer thickness of the JRNb / Al sub-multi line arranged in the inner peripheral part is 10 times thicker than the outer peripheral part.
[0020]
When this multi-wire was subjected to rapid heating and quenching treatment, the JRNb / Al sub-multi (filament) disposed on the outer peripheral portion became a supersaturated solid solution, and the JRNb / Al sub-multi (filament) disposed on the inner peripheral portion was not. Rule A15 phase occurred. When this multi-line was subjected to transformation heat treatment at 800 ° C. for 10 hours, as shown in Table 1, although the critical current density Jc in the low magnetic field was slightly reduced, the critical current density Jc in the high magnetic field was improved and improved. Bending workability was obtained.
[0021]
Example 3
7 Ag stabilizers coated with Nb jacket at the center, JRNb / A1 sub-multi wire with a composition of Nb-27.5at% Al as the inner periphery and an Al layer thickness of 100nm Further, a JRNb / Al sub-multi line having a composition of Nb-25 at% Al as the outer peripheral portion and an Al layer thickness of 100 nm was arranged on the outer side to form a multi-line. The nominal Al concentration of the sub-multi wire arranged in the inner peripheral portion was 2.5 at% higher than the nominal Al concentration in the outer peripheral portion.
[0022]
When this multi-wire was subjected to rapid heating and quenching treatment, the JRNb / Al sub-multi (filament) disposed on the outer peripheral portion became a supersaturated solid solution, and the JRNb / Al sub-multi (filament) disposed on the inner peripheral portion was not. Rule A15 phase occurred. When this multi-line was subjected to transformation heat treatment at 800 ° C. for 10 hours, as shown in Table 1, although the critical current density Jc in the low magnetic field was slightly reduced, the critical current density Jc in the high magnetic field was improved and improved. Bending workability was obtained.
[0023]
Example 4
Seven Ag stabilizers coated with an Nb jacket are arranged in the center, and the inner periphery is surrounded by an Nb / Al-2 at% Cu RIT method 7 core wires 40 and an Nb / Al-5 at% Mg RIT method. Sub-multi lines created by mixing 81 seven-core wires were arranged, and the same sub-multi lines as the outer peripheral part were arranged on the outer side to form multi-lines.
[0024]
When this multi-wire was subjected to rapid heating and quenching treatment, supersaturated solid solution and irregular A15 phase were mixed in each filament at a ratio of about 7: 3. When this multi-line was subjected to transformation heat treatment at 800 ° C. for 10 hours, as shown in Table 1, the critical current density Jc in the high magnetic field was improved although the critical current density Jc in the low magnetic field was slightly reduced. Even in this case, the bending workability required for coil forming is ensured.
[0025]
According to the above-described Nb ₃ Al superconducting multifilamentary wire, the arrangement or mixing ratio in the cross section is controlled so that an irregular A15 phase and a supersaturated solid solution are generated at the same time. To support. This improves the high magnetic field characteristics while maintaining good moldability without increasing the extra Nb matrix. For example, it becomes possible to form an innermost layer coil of a 1 GHz class NMR superconducting magnet having a small winding diameter based on the Wind and React method. In addition, a large current capacity can be achieved by using a stranded wire, which is suitable for a next-generation nuclear fusion reactor superconducting magnet conductor that increases the maximum empirical magnetic field. The superconducting properties show a critical current density Jc that is more than twice that of Nb ₃ Sn used as a practical wire, and have excellent strain resistance, so that the strength of large superconducting systems such as fusion reactors and high energy accelerators is strong. A magnetic field can be realized and the entire system can be made compact, and the apparatus cost can be reduced.
[0026]
The production parameters such as the nominal Al concentration, the diffusion distance between Nb and Al, and the presence or absence of alloy addition applied in the above-described embodiment are clad chip extrusion which is a production method other than the JR method and the RIT method. The same applies to the method and the powder extrusion method.
[0027]
【The invention's effect】
As described above, according to the Nb ₃ Al superconducting multifilamentary wire of the present invention and the manufacturing method thereof, the Nb ₃ Al filament transformed from the supersaturated solid solution rich in ductility to the A15 phase and the irregular A15 phase having good superconducting properties are ordered. In addition, since the Nb ₃ Al filaments are arranged in the same cross section, it is possible to impart mechanical strength that is excellent in high magnetic field characteristics and does not hinder molding processing such as coil molding.
[Brief description of the drawings]
FIG. 1 shows a Nb ₃ Al superconducting multicore wire according to an embodiment of the present invention;
(A) is a cross-sectional view of the multi-wire of the present invention (b) is a cross-sectional view of a multi-wire which is a standard sample as a comparative example. FIG. 2 shows the criticality after transformation heat treatment for the energized current during rapid heating and quenching treatment. Explanatory drawing showing temperature Tc 【Explanation of symbols】
1 Ag Stabilizing Material 2 Nb / Al-2 at% Cu · RIT Sub-Multi Line 3 JRNb / Al Sub-Multi Line 4 Multi-Line 5 Nb

Claims

Nb ₃ Al superconducting multifilamentary wire, characterized in that it comprises a Nb ₃ Al filaments transformation was Nb ₃ Al filaments and irregular A15 phases were ordered to A15 phase from a supersaturated solid solution within the same section.

2. The Nb ₃ Al superconducting multi-core wire according to claim 1, wherein the Nb ₃ Al filament transformed from the supersaturated solid solution into the A15 phase is disposed on an outer peripheral portion of the cross section.

2. The Nb ₃ Al superconducting multi-core wire according to claim 1, wherein the Nb ₃ Al filament in which the irregular A15 phase is regularized is disposed on an inner peripheral portion of the cross section.

2. The Nb ₃ Al superconducting multi-core wire according to claim 1, wherein the Nb ₃ Al filament transformed from the supersaturated solid solution into the A15 phase has a nominal Al concentration of 22 at% to 25 at%.

The Nb ₃ Al filament in which the irregular A15 phase is ordered has a nominal Al concentration that is 1 at% to 5 at% higher than the nominal Al concentration of the Nb ₃ Al filament transformed from the supersaturated solid solution into the A15 phase. The Nb ₃ Al superconducting multicore wire according to item 1.

When the composition of the Nb ₃ Al filament in which the irregular A15 phase is ordered is expressed as Nb _y (Al _1−x M _x ) _1−y based on the addition of the element M, the element M is an element When the element M is any one of Cu, element Ge, and element Si and the element M is the element Cu , the addition amount x is 0.005-0.02 , and when the element M is element Ge , the addition amount x is it is 0.05-0.2, if the elements Si, the addition amount x of claim first term of construction is 0.05-0.15 _Nb 3 Al superconducting multifilamentary wire.

_Nb 3 Al filaments transformed into A15 phase from the supersaturated solid solution, Al, when the composition based on the addition of pure Al, or the element M is denoted by _{_{_{Nb y (Al 1-x M}}} x) 1-y, wherein element M is an element Mg, _Nb 3 Al superconducting multifilamentary wire amount x is described first of claims configurations are 0-0.1 of the elements Mg.

An Nb ₃ Al filament in which Nb ₃ Al transformed from the supersaturated solid solution has a volume ratio of 50% or more;
Nb ₃ Al superconducting multifilamentary wire characterized by having a structure obtained by dispersing and mixing a Nb ₃ Al filaments ordered from a disordered A15 phase in the Nb ₃ Al filaments.

The Nb ₃ Al superconducting multi-core wire according to claim 1 or 8, wherein Ag coated with an Nb diffusion barrier is disposed as an internal stabilizer at an arbitrary position in the cross section.

A plurality of sub-multi wires covered with a matrix of Nb are laminated on the inner periphery and the outer periphery to form a laminate,
The laminated body is covered with a Nb matrix to form a multi-line,
The multi-wire is primarily heated at a predetermined temperature,
The first heated multi-wire is cooled with a cooling metal material to generate a supersaturated solid solution filament on the outer periphery, and an irregular A15 phase on the inner periphery,
After cooling, secondary heating is performed at a predetermined temperature to generate Nb ₃ Al filaments transformed from a supersaturated solid solution into an A15 phase in the outer peripheral portion, and Nb ₃ Al filaments in which irregular A15 phases are ordered in the inner peripheral portion. Nb ₃ Al superconducting multifilamentary wire manufacturing method according to claim.

The method for producing a Nb ₃ Al superconducting multi-core wire according to claim 10, wherein an Al layer thickness of the sub-multi wire in the inner peripheral portion is 2 to 100 times larger than an Al layer thickness in the outer peripheral portion.

The nominal Al concentration excluding the Nb sheath of the sub-multi line is in a range of 22 at% to 25 at% at the outer peripheral portion and 1 at% to 5 at% larger than the outer peripheral portion at the inner peripheral portion. Nb ₃ Al superconducting multifilamentary wire method according paragraph 10.

When the element M is added to the Nb ₃ Al filament part in the inner peripheral part and the composition is expressed as Nb _y (Al _1-x M _x ) _1-y , the element M is the element Cu, element Ge, element When the element M is the element Cu , the addition amount x is 0.005-0.02 , and when the element M is Ge , the addition amount x is 0.05-0. 2, when the elements Si, the addition amount x _Nb 3 Al superconducting multifilamentary wire manufacturing method of a is claim 10 claims 0.05-0.15.

The composite composed of Nb and Al constituting the sub multi-line is a mixture of different Al layer thickness , nominal Al concentration, and presence or absence of element addition, and the Al layer thickness is 2 to 100 times smaller, the nominal Al concentration 11. The Nb _{3 according} to claim 10, wherein the Nb ₃ is 1 at% to 5 at% smaller, or the volume ratio of the element not added is 50% or more, and the inner peripheral portion and the outer peripheral portion are bound without being distinguished from each other. Manufacturing method of Al superconducting multi-core wire.

The method for producing a Nb ₃ Al superconducting multi-core wire according to claim 10, wherein Ag coated with a diffusion barrier of Nb is disposed as an internal stabilizer at an arbitrary position in the laminate.