JP2011014304A - Superconducting wire rod - Google Patents

Superconducting wire rod Download PDF

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JP2011014304A
JP2011014304A JP2009155883A JP2009155883A JP2011014304A JP 2011014304 A JP2011014304 A JP 2011014304A JP 2009155883 A JP2009155883 A JP 2009155883A JP 2009155883 A JP2009155883 A JP 2009155883A JP 2011014304 A JP2011014304 A JP 2011014304A
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mgb
superconducting
superconducting wire
powder
magnesium
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JP5356132B2 (en
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Masaya Takahashi
雅也 高橋
Michiya Okada
道哉 岡田
Hiroaki Kumakura
浩明 熊倉
Hitoshi Kitaguchi
仁 北口
Shigeyuki Nakane
茂行 中根
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Hitachi Ltd
National Institute for Materials Science
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National Institute for Materials Science
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02E40/60—Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment

Abstract

PROBLEM TO BE SOLVED: To provide a MgBsuperconducting wire rod capable of being produced longer and superior in supercoducting performance while suppressing reacting non-uniformity between Mg and B.SOLUTION: The superconducting wire rod includes a superconductive core portion containing magnesium diboride, and a stabilizing layer covering the superconductive core portion. The superconductive core portion has an outer peripheral part as a magnesium diboride powder sintered region, and a central part as a reaction region where magnesium powder and boron powder are mixed to react with each other.

Description

本発明は、超電導線材に関するものである。   The present invention relates to a superconducting wire.

二ホウ化マグネシウム（ＭｇＢ２）超電導線材は、ＭｇＢ２粉末又はマグネシウム（Ｍｇ）粉末とホウ素（Ｂ）粉末との混合粉末、さらには、それらに炭化ケイ素（ＳｉＣ）などの第三元素を添加した混合粉末を金属シース管に充填し、線引き加工することで作製している。そのため、金属シースには加工性の高い金属が選択され、長尺線化しやすいような線材断面設計がされている。一方、この線材を高性能化するためには、ＭｇＢ２の単相化を図ること、ＭｇＢ２に金属粉末を添加して結晶粒同士の接合性を向上すること、ＭｇＢ２を高圧下で合成することなど、ＭｇＢ２同士を高純度で結合させることが重要である。 Magnesium diboride (MgB 2 ) superconducting wire is made of MgB 2 powder or mixed powder of magnesium (Mg) powder and boron (B) powder, and further added with a third element such as silicon carbide (SiC). The mixed powder is filled in a metal sheath tube and drawn. For this reason, a metal having a high workability is selected as the metal sheath, and a wire cross section is designed so as to be easily formed into a long wire. Meanwhile, in order to performance of this wire is possible to single phase of MgB 2, to improve the bonding of the crystal grains by adding a metal powder to MgB 2, synthesized MgB 2 under high pressure For example, it is important to bond MgB 2 with high purity.

これらを両立させるため、ドローベンチなどの線引き加工装置を用いて、加工条件を最適化することで、ＭｇＢ２超電導線材を作製している。これらは特許文献１及び２に記載されている。 To achieve both these, using a wire drawing apparatus such as a drawbench, by optimizing the processing conditions, and to produce a MgB 2 superconducting wire. These are described in Patent Documents 1 and 2.

特許文献１には、ホウ素を含む超電導体を充填又は内包してなる超電導線材において、磁場中においても実用的な臨界電流密度を有する超電導線材とその製造方法、及びそれを用いた超電導マグネットを提供することを目的として、当該超電導体の外周に金、銀、アルミニウム、銅、鉄等から選ばれた単独の金属或いはそれらの複数から成る合金の金属被覆材が配置され、最終加工後の該超電導体の密度が理論密度の８０％以上であり、かつ該超電導線材の臨界温度が３０Ｋ以上であることを特徴とする超電導線材が開示されている。   Patent Document 1 provides a superconducting wire having a practical critical current density even in a magnetic field in a superconducting wire filled or encapsulated with a superconductor containing boron, a manufacturing method thereof, and a superconducting magnet using the same. For this purpose, a metal coating material made of a single metal selected from gold, silver, aluminum, copper, iron, or the like or an alloy thereof is arranged on the outer periphery of the superconductor, and the superconductor after final processing A superconducting wire is disclosed in which the density of the body is 80% or more of the theoretical density and the critical temperature of the superconducting wire is 30K or more.

特許文献２には、高臨界電流密度化、高安定化、高強度化、長尺化を同時に達成できるＭｇＢ２超電導線材とその製造方法を提供することを目的として、室温でのビッカース硬さが５０以上で、かつ、１つあるいは複数の孔を設けた金属母材中に、室温での比電気抵抗が７μΩｃｍ以下の金属で被覆した単芯線又は多芯線を組み込むことを特徴とする複合シースＭｇＢ２超電導線材が開示されている。 Patent Document 2 discloses a Vickers hardness at room temperature for the purpose of providing a MgB 2 superconducting wire that can achieve high critical current density, high stability, high strength, and lengthening at the same time, and a method for producing the same. A composite sheath MgB characterized by incorporating a single-core wire or a multi-core wire coated with a metal having a specific electric resistance of 7 μΩcm or less at room temperature into a metal base material having 50 or more and one or more holes provided Two superconducting wires are disclosed.

一般的に、高い超電導特性を有するＭｇＢ２超電導線材を製造方法の公知技術としては、次のものがある。 In general, the following are known techniques for producing a MgB 2 superconducting wire having high superconducting properties.

（１）減面加工率を向上させる。   (1) Improve the surface reduction rate.

（２）粉末の初期充填率を向上させる。   (2) Improve the initial filling rate of the powder.

（３）第三元素を添加したＭｇＢ２コア部とする。 (3) An MgB 2 core portion to which a third element is added is used.

（４）超電導コア部を大きくする。   (4) Increase the superconducting core.

これらは、線引き加工によって長尺化すると同時に、ＭｇＢ２コア部を大面積・高密度化させることで、高性能で、かつ長尺化したＭｇＢ２超電導線材を得るとしている。 These are intended to obtain a high-performance and elongated MgB 2 superconducting wire by increasing the length and density of the MgB 2 core at the same time as by drawing.

しかしながら、現状、これらの方法では十分な性能を有する高性能なＭｇＢ２超電導線材が得られていない。 However, at present, these methods do not provide a high-performance MgB 2 superconducting wire having sufficient performance.

特開２００２−３７３５３４号公報JP 2002-373534 A 特開２００４−３１９１０７号公報JP 2004-319107 A

Ｍｇ粉末とＢ粉末との混合粉末を用いてＭｇＢ２超電導線材を作製する場合、銅（Ｃｕ）等で形成された金属シース（外側金属管）にＭｇ粉末とＢ粉末との混合粉末を充填し、熱処理を行ってＭｇとＢとを反応させる際、Ｍｇが拡散して金属シースを構成するＣｕ等と結合し、ＭｇとＢとの反応において不均一が生じる。このため、ＭｇＢ２超電導線材の超電導性能が低下してしまうという問題がある。 When producing a MgB 2 superconducting wire using a mixed powder of Mg powder and B powder, a mixed powder of Mg powder and B powder is filled in a metal sheath (outer metal tube) formed of copper (Cu) or the like. When Mg and B are reacted by performing heat treatment, Mg diffuses and bonds with Cu or the like constituting the metal sheath, and non-uniformity occurs in the reaction between Mg and B. Thus, superconductivity of MgB 2 superconducting wire is lowered.

本発明の目的は、ＭｇとＢとの反応における不均一を抑制し、線材の長尺化が可能で、超電導性能が高いＭｇＢ２超電導線材を提供することにある。 An object of the present invention is to provide an MgB 2 superconducting wire that suppresses non-uniformity in the reaction between Mg and B, makes the wire length longer, and has high superconducting performance.

本発明の超電導線材は、二ホウ化マグネシウムを含む超電導コア部と、この超電導コア部を覆う安定化層とを含む超電導線材であって、前記超電導コア部が、二ホウ化マグネシウム粉末の焼結領域である外周部と、マグネシウム粉末及びホウ素粉末を混合して反応させた反応領域である中心部とを有することを特徴とする。   The superconducting wire of the present invention is a superconducting wire comprising a superconducting core part containing magnesium diboride and a stabilizing layer covering the superconducting core part, wherein the superconducting core part is sintered with magnesium diboride powder. It has the outer peripheral part which is an area | region, and the center part which is a reaction area | region which mixed and reacted magnesium powder and the boron powder.

本発明によれば、ＭｇとＢとの反応における不均一を抑制し、線材の長尺化が可能で、超電導性能が高いＭｇＢ２超電導線材を得ることができる。 According to the present invention, it is possible to obtain a MgB 2 superconducting wire that suppresses non-uniformity in the reaction between Mg and B, enables the length of the wire, and has high superconducting performance.

従来のＭｇＢ２超電導線材の断面図である。It is a cross-sectional view of a conventional MgB 2 superconducting wire. 従来のＭｇＢ２超電導線材の断面図である。It is a cross-sectional view of a conventional MgB 2 superconducting wire. 本発明による実施例１を示すＭｇＢ２超電導線材の断面図である。Example 1 according to the present invention is a cross-sectional view of a MgB 2 superconducting wire shown. 本発明による実施例のＭｇＢ２超電導線材の超電導特性を示すグラフである。It is a graph showing the superconducting properties of MgB 2 superconductor material of Example of the present invention. 本発明による実施例のＭｇＢ２超電導線材のＸ線回折装置によって測定した材料特性を示すグラフである。It is a graph showing the material characteristics measured by X-ray diffraction apparatus of MgB 2 superconductor material of Example of the present invention. 本発明による実施例２を示すＭｇＢ２超電導線材の断面図である。EXAMPLE 2 according to the present invention is a cross-sectional view of a MgB 2 superconducting wire shown. 本発明による実施例３を示すＭｇＢ２超電導線材の断面図である。Example 3 according to the present invention is a cross-sectional view of a MgB 2 superconducting wire shown. 本発明のＭｇＢ２超電導線材の断面を示す拡大写真及び模式図である。It is an enlarged photograph and schematic diagram showing a cross-section of MgB 2 superconductor material of the present invention. 本発明のＭｇＢ２超電導線材の製造工程を示す図である。It is a diagram showing a manufacturing process of the MgB 2 superconducting wire of the present invention. 本発明のＭｇＢ２超電導線材の製造工程を示す図である。It is a diagram showing a manufacturing process of the MgB 2 superconducting wire of the present invention. 本発明のＭｇＢ２超電導線材の製造工程を示す図である。It is a diagram showing a manufacturing process of the MgB 2 superconducting wire of the present invention. 本発明のＭｇＢ２超電導線材の製造工程を示す図である。It is a diagram showing a manufacturing process of the MgB 2 superconducting wire of the present invention. 本発明のＭｇＢ２超電導線材の製造工程を示す図である。It is a diagram showing a manufacturing process of the MgB 2 superconducting wire of the present invention. 本発明のＭｇＢ２超電導線材の製造工程を示す図である。It is a diagram showing a manufacturing process of the MgB 2 superconducting wire of the present invention. 本発明のＭｇＢ２超電導線材の製造工程を示す図である。It is a diagram showing a manufacturing process of the MgB 2 superconducting wire of the present invention. 本発明のＭｇＢ２超電導線材の製造工程を示す図である。It is a diagram showing a manufacturing process of the MgB 2 superconducting wire of the present invention. 本発明のＭｇＢ２超電導線材の製造工程を示す図である。It is a diagram showing a manufacturing process of the MgB 2 superconducting wire of the present invention.

本発明は二ホウ化マグネシウム（以下、ＭｇＢ２と略す）超電導線材に関するものである。具体的には、電流リード、送電ケーブル、大型マグネット、核磁気共鳴分析装置、医療用磁気共鳴診断装置、超電導電力貯蔵装置、磁気分離装置、磁場中単結晶引き上げ装置、冷凍機冷却超電導マグネット装置、超電導エネルギー貯蔵、超電導発電機、核融合炉用マグネット等の機器において適用される。 The present invention relates to a magnesium diboride (hereinafter abbreviated as MgB 2 ) superconducting wire. Specifically, current leads, power transmission cables, large magnets, nuclear magnetic resonance analyzers, medical magnetic resonance diagnostic devices, superconducting power storage devices, magnetic separation devices, single crystal pulling devices in magnetic fields, refrigerator-cooled superconducting magnet devices, It is applied in equipment such as superconducting energy storage, superconducting generator, and fusion reactor magnet.

本発明は、超電導コア部を覆う電気伝導度の高い安定化層と二ホウ化マグネシウム超電導体が存在する超電導コア部とを含む二ホウ化マグネシウム超電導線材において、上記超電導コア部が、二ホウ化マグネシウムの外周層と、マグネシウム及びホウ素の混合体の中心部とを有する前駆体を含み、その安定化層に囲まれた前駆体を細線化加工後、熱処理することで、外周層の二ホウ化マグネシウム同士の焼結反応、及び中心部のマグネシウムとホウ素との反応を生じさせ、熱処理後の超電導コア部が半径方向に焼結領域及び反応領域の２層を形成し、そのマグネシウム及び酸化マグネシウムの濃度がそれぞれの領域において異なることを特徴とする。   The present invention relates to a magnesium diboride superconducting wire including a stabilization layer having high electrical conductivity covering a superconducting core and a superconducting core having a magnesium diboride superconductor, wherein the superconducting core is diboride. A precursor having a magnesium outer layer and a central portion of a mixture of magnesium and boron, and the precursor surrounded by the stabilizing layer is thinned and then heat-treated, whereby the outer layer is diborated. A sintering reaction between magnesium and a reaction between magnesium and boron in the central part are caused, and the superconducting core part after the heat treatment forms two layers of a sintered region and a reaction region in the radial direction. The density is different in each region.

また、本発明は、超電導コア部を覆う電気伝導度の高い安定化層と、二ホウ化マグネシウム超電導体が存在する超電導コア部とを含む二ホウ化マグネシウム超電導線材において、上記超電導コア部が、二ホウ化マグネシウムの外周層と、マグネシウム及びホウ素の混合体で、マグネシウムとホウ素との比率の異なる２層以上の中心部とを有する前駆体で構成され、その安定化層に囲まれた前駆体を細線化加工後、熱処理することで、外周層の二ホウ化マグネシウム同士の焼結反応、及び中心部のマグネシウムとホウ素との反応を生じさせ、熱処理後の超電導コア部が半径方向に、焼結領域及び反応領域に分かれ、そのマグネシウム及び酸化マグネシウムの濃度がそれぞれの領域において異なることを特徴とする。   Further, the present invention is a magnesium diboride superconducting wire including a stabilization layer having high electrical conductivity covering the superconducting core part, and a superconducting core part in which a magnesium diboride superconductor is present. A precursor composed of a magnesium diboride outer peripheral layer and a precursor having a mixture of magnesium and boron and having two or more central portions having different ratios of magnesium and boron, and surrounded by the stabilization layer After thinning, heat treatment is performed to cause a sintering reaction between the magnesium diboride in the outer peripheral layer and a reaction between magnesium and boron in the center, and the superconducting core after the heat treatment is sintered in the radial direction. It is divided into a crystallization region and a reaction region, and the concentration of magnesium and magnesium oxide is different in each region.

また、本発明は、超電導コア部を覆う電気伝導度の高い安定化層と、二ホウ化マグネシウム超電導体が存在する超電導コア部とを含む二ホウ化マグネシウム超電導線材において、上記超電導コア部が、二ホウ化マグネシウムの外周層と、マグネシウム、ホウ素及び炭化物の混合体の中心部を有する前駆体とを含み、その安定化層に囲まれた前駆体を細線化加工後、熱処理することで、外周層の二ホウ化マグネシウム同士の焼結反応、及び中心部のマグネシウムとホウ素とを反応を生じさせ、熱処理後の超電導コア部が半径方向、焼結領域及び反応領域に分かれており、そのマグネシウム及び酸化マグネシウムの濃度がそれぞれの領域において異なることを特徴とする。   Further, the present invention is a magnesium diboride superconducting wire including a stabilization layer having high electrical conductivity covering the superconducting core part, and a superconducting core part in which a magnesium diboride superconductor is present. Including the outer peripheral layer of magnesium diboride and a precursor having a central portion of a mixture of magnesium, boron and carbide, the precursor surrounded by the stabilization layer is heat treated after thinning, Sintering reaction between magnesium diboride in the layer and reaction between magnesium and boron in the central part, and the superconducting core part after heat treatment is divided into a radial direction, a sintered region and a reaction region, The concentration of magnesium oxide is different in each region.

また、本発明は、超電導コア部を覆う電気伝導度の高い安定化層と、二ホウ化マグネシウム超電導体が存在する超電導コア部とを含む二ホウ化マグネシウム超電導線材において、上記超電導コア部が、二ホウ化マグネシウムの外周層と、マグネシウム、ホウ素及び炭化物の混合体で、マグネシウムとホウ素との比率の異なる２層以上の中心部とを有する前駆体で構成され、その安定化層に囲まれた前駆体を細線化加工後、熱処理することで、外周層の二ホウ化マグネシウム同士の焼結反応、及び中心部のマグネシウムとホウ素とを反応を生じさせ、熱処理後の超電導コア部が半径方向に、焼結領域及び反応領域に分かれ、そのマグネシウム及び酸化マグネシウムの濃度がそれぞれの領域において異なることを特徴とする。   Further, the present invention is a magnesium diboride superconducting wire including a stabilization layer having high electrical conductivity covering the superconducting core part, and a superconducting core part in which a magnesium diboride superconductor is present. Consists of a precursor having an outer peripheral layer of magnesium diboride and a mixture of magnesium, boron and carbide, and two or more central portions having different ratios of magnesium and boron, and surrounded by the stabilization layer The precursor is thinned and then heat treated to cause a sintering reaction between the magnesium diboride in the outer peripheral layer and a reaction between magnesium and boron in the center, and the superconducting core after heat treatment is in the radial direction. , And is divided into a sintering region and a reaction region, and the concentration of magnesium and magnesium oxide is different in each region.

また、本発明は、超電導コア部を覆う電気伝導度の高い安定化層と二ホウ化マグネシウム超電導体が存在する超電導コア部とを含む二ホウ化マグネシウム超電導線材であって、この二ホウ化マグネシウム超電導線材を複数本束ねて形成したことを特徴とする。   The present invention also relates to a magnesium diboride superconducting wire comprising a stabilization layer having high electrical conductivity covering the superconducting core part and a superconducting core part in which a magnesium diboride superconductor is present. It is characterized by being formed by bundling a plurality of superconducting wires.

また、本発明は、安定化層がＣｕ、Ａｌ、Ａｇ、Ａｕ及びＮｉ並びにそれらの合金を含むことを特徴とする。さらに、安定化層は、Ｃｕ、Ａｌ、Ａｇ、Ａｕ及びＮｉ並びにそれらの合金を主成分として含むことが望ましい。   In addition, the present invention is characterized in that the stabilization layer includes Cu, Al, Ag, Au, and Ni and alloys thereof. Furthermore, it is desirable that the stabilization layer contains Cu, Al, Ag, Au, Ni and alloys thereof as main components.

以下に、図を用いて、従来例と比較しながら、本発明による実施例を説明する。   Hereinafter, embodiments according to the present invention will be described with reference to the drawings, in comparison with a conventional example.

これに先立って、比較例として、従来方法で作製した二ホウ化マグネシウム超電導線材（以下、ＭｇＢ２超電導線材又は単に超電導線材と呼ぶ）について説明する。 Prior to this, a magnesium diboride superconducting wire produced by a conventional method (hereinafter referred to as MgB 2 superconducting wire or simply superconducting wire) will be described as a comparative example.

（比較例１）
まず、Ｃｕ等で形成された外側金属管とＭｇとの反応を防止するためのバリア層として内側金属管を用いる場合を示す。 (Comparative Example 1)
First, the case where an inner metal tube is used as a barrier layer for preventing the reaction between Mg and an outer metal tube formed of Cu or the like will be described.

図１に作製したＭｇＢ２超電導線材の断面構造を示す。ＭｇＢ２超電導線材１は、外側金属管２、内側金属管３及びＭｇＢ２コア部４（超電導コア部）で構成されている。この場合、外側金属管２が銅管（Ｃｕ管）であり、内側金属管３がニオブ管（Ｎｂ管）である。内側金属管３にボールミル混合したＭｇ粉末及びＢ粉末をＡｒガス中で充填し、その外側に外側金属管２を被せ、ドローベンチによる線引き加工を実施した。線材の径はφ０．８ｍｍである。この製造方法は、ドローベンチなどにより金属シース全体を均一に減面加工することで長尺線材化（長尺の線材を形成）しながら、ＭｇＢ２コア部を高密度化する製法である。 FIG. 1 shows a cross-sectional structure of the MgB 2 superconducting wire produced. The MgB 2 superconducting wire 1 is composed of an outer metal tube 2, an inner metal tube 3, and an MgB 2 core portion 4 (superconducting core portion). In this case, the outer metal tube 2 is a copper tube (Cu tube), and the inner metal tube 3 is a niobium tube (Nb tube). The inner metal tube 3 was filled with Mg powder and B powder mixed in a ball mill in Ar gas, the outer metal tube 2 was covered on the outer side, and the drawing process was performed with a draw bench. The diameter of the wire is φ0.8 mm. This manufacturing method is a manufacturing method in which the MgB 2 core portion is densified while forming a long wire (forming a long wire) by uniformly reducing the entire surface of the metal sheath with a draw bench or the like.

しかしながら、この製造方法では、ＭｇＢ２超電導線材の超電導性能が安定せず、長尺方向での均一性を維持することができなかった。また、３本作製したところ、１本は途中で断線し、線引き不可能となった。この状態で、超電導コイルを作製した場合、長尺線材中の最も低い特性をもつ場所でコイル特性が決定されるため、特性が低い超電導コイルとなる。 However, in this manufacturing method, the superconducting performance of the MgB 2 superconducting wire is not stable, and the uniformity in the longitudinal direction cannot be maintained. Moreover, when three were produced, one was disconnected in the middle, and drawing became impossible. When a superconducting coil is manufactured in this state, the coil characteristic is determined at a place having the lowest characteristic in the long wire rod, so that a superconducting coil having low characteristics is obtained.

この要因としては、粉末の充填密度や充填状態の影響で、線引き加工によって減面化（細線化）されたＭｇＢ２コア部の密度が不均一となったことが考えられる。この状態で熱処理をすると、ＭｇとＢとの反応効率にも不均一が生じ、ＭｇＢ２超電導線材の超電導性能も不均一となる。 As this factor, it is considered that the density of the MgB 2 core portion that has been reduced (thinned) by the drawing process becomes non-uniform due to the influence of the powder packing density and packing state. When heat treatment is performed in this state, the reaction efficiency between Mg and B also becomes non-uniform, and the superconducting performance of the MgB 2 superconducting wire becomes non-uniform.

また、この影響をさらに小さくするために線径を細くすることを検討しても、不均一性を出している線材の径がφ０．８ｍｍであり、これ以上の細線化は、線材の作製中の断線率が急激に増大するため適用困難である。さらに、線材を細線化できたとしても、超電導コイルを作製する際、占積率も低下するため、より長尺なＭｇＢ２超電導線材が必要となる。 In addition, even if we consider reducing the wire diameter to further reduce this effect, the diameter of the wire that shows nonuniformity is φ0.8 mm. This is difficult to apply because the disconnection rate of the wire increases rapidly. Furthermore, even if the wire can be made thin, the space factor also decreases when producing a superconducting coil, so a longer MgB 2 superconducting wire is required.

以上のことから、従来方法で作製する場合は、長尺で高性能なＭｇＢ２超電導線材を作製できない。 From the above, when producing by the conventional method, a long and high performance MgB 2 superconducting wire cannot be produced.

他の高性能ＭｇＢ２超電導線材の製造方法としては、以下の方法もある。 Other methods for producing a high-performance MgB 2 superconducting wire include the following methods.

（比較例２）
つぎに、初期の粉末充填量を高める場合について示す。 (Comparative Example 2)
Next, a case where the initial powder filling amount is increased will be described.

ＭｇＢ２超電導線材の断面構造は従来方法１と同様である。この製造方法では、Ａｒフロー中で金属シースに充填するＭｇＢ２粉末、又はＭｇ粉末及びＢ粉末の充填量を増加させることで、ＭｇＢ２コア部を高密度化させる。 The cross-sectional structure of the MgB 2 superconducting wire is the same as that of the conventional method 1. In this manufacturing method, the MgB 2 core portion is densified by increasing the amount of MgB 2 powder or Mg powder and B powder filled in the metal sheath in Ar flow.

この比較例における初期粉末充填率は約５０％である。しかし、これ以上の充填率向上は困難であった。これは充填する粉末が微細であるため、流動性が低下し、充填時にかさ張り、緻密化しにくい。また、ガス成分を同時に巻き込むため、更に充填が困難となる。   The initial powder filling rate in this comparative example is about 50%. However, it was difficult to improve the filling rate beyond this. Since the powder to be filled is fine, the fluidity is lowered, and it is difficult to be bulked and densified during filling. Further, since the gas components are simultaneously entrained, the filling becomes more difficult.

さらに、充填できたと仮定しても、緻密に充填されているため、線引き加工時に必要な粉末の流動性が確保できないため、線引き途中で断線する確率が非常に高い。   Furthermore, even if it is assumed that the filling has been performed, since the powder is densely filled, the fluidity of the powder necessary for the drawing process cannot be ensured, so the probability of disconnection during the drawing is very high.

したがって、この比較例の場合、使用可能なＭｇＢ２超電導線材を作製することが困難である。 Therefore, in the case of this comparative example, it is difficult to produce a usable MgB 2 superconducting wire.

ＭｇＢ２超電導線材の超電導特性を向上させるためには、ＭｇＢ２コア部に緻密で、かつ流動性の高いＭｇＢ２層を形成させる必要がある。また、それらを長手方向に均一化させる必要がある。 In order to improve the superconducting characteristics of the MgB 2 superconducting wire, it is necessary to form a dense and highly fluid MgB 2 layer in the MgB 2 core. Moreover, it is necessary to make them uniform in the longitudinal direction.

（比較例３）
この比較例は、超電導コア部を増加させたＭｇＢ２超電導線材の製造方法である。 (Comparative Example 3)
This comparative example is a method for manufacturing a MgB 2 superconducting wire with an increased number of superconducting cores.

図２に作製したＭｇＢ２超電導線材の断面構造を示す。ＭｇＢ２超電導線材１１は、外側金属管２、ＭｇＢ２コア部４から形成された構造である。この比較例においては、外側金属管２が銅管（Ｃｕ管）である。外側金属管２にＭｇＢ２粉末をＡｒガス中で充填し、ドローベンチによる線引き加工を実施した。線材の径はφ０．８ｍｍである。この製造方法により得られたＭｇＢ２超電導線材１１は、超電導性能が安定し、長尺方向での均一性を有することがわかった。 FIG. 2 shows a cross-sectional structure of the MgB 2 superconducting wire produced. The MgB 2 superconducting wire 11 has a structure formed from the outer metal tube 2 and the MgB 2 core portion 4. In this comparative example, the outer metal tube 2 is a copper tube (Cu tube). The outer metal tube 2 was filled with MgB 2 powder in Ar gas, and was drawn by a draw bench. The diameter of the wire is φ0.8 mm. It was found that the MgB 2 superconducting wire 11 obtained by this manufacturing method has stable superconducting performance and uniformity in the longitudinal direction.

また、Ｍｇを用いないため、バリア層の働きをする内側金属管を用いる必要がなく、外側金属管２が一重であるため、ＭｇＢ２超電導線材１１に占める超電導コア部４の面積は、比較例１と比較して大きくすることができた。 In addition, since Mg is not used, it is not necessary to use an inner metal tube that functions as a barrier layer, and since the outer metal tube 2 is single, the area of the superconducting core portion 4 in the MgB 2 superconducting wire 11 is a comparative example. Compared to 1, it could be increased.

しかし、超電導性能が非常に低く、比較例１の２０％以下という結果となった。これは、充填したＭｇＢ２粉末の表面に酸化物（酸化マグネシウム（ＭｇＯ））が付着していたため、超電導の電流パス（電流流路）が減少したと考える。 However, the superconducting performance was very low, which was 20% or less of Comparative Example 1. This is considered because the oxide (magnesium oxide (MgO)) was adhered to the surface of the filled MgB 2 powder, and thus the superconducting current path (current flow path) was reduced.

比較例１〜３の結果から、高性能なＭｇＢ２超電導線材の作製が困難となる要因として以下の２点が挙げられる。 From the results of Comparative Examples 1 to 3, the following two points can be cited as factors that make it difficult to produce a high-performance MgB 2 superconducting wire.

（１）超電導特性の高いＭｇ粉末及びＢ粉末の混合粉末をＣｕ等の外側金属管に充填すると、Ｍｇ粉末が外側金属管と反応してしまう。そこで、外側金属管とＭｇ粉末及びＢ粉末の混合粉末との間にバリア層として内側金属管を設ける対策が採られるが、この場合、超電導コア部の面積が低減し、ＭｇＢ２超電導線材の特性向上を阻害する。 (1) When a mixed powder of Mg powder and B powder having high superconducting characteristics is filled in an outer metal tube such as Cu, the Mg powder reacts with the outer metal tube. Therefore, measures are taken to provide an inner metal tube as a barrier layer between the outer metal tube and the mixed powder of Mg powder and B powder. In this case, the area of the superconducting core is reduced, and the characteristics of the MgB 2 superconducting wire are reduced. Impedes improvement.

（２）熱処理を必要としないＭｇＢ２粉末を適用すると、コア面積は大きくなる。しかし、粉末表面の初期の酸化層が影響し、ＭｇＢ２線材の特性向上を阻害する。 (2) When an MgB 2 powder that does not require heat treatment is applied, the core area increases. However, the initial oxide layer on the surface of the powder is affected, and the improvement of the properties of the MgB 2 wire is hindered.

以上の要因を検討し、これらの問題を解決するための手段として、本発明を見出した。   The present invention has been found as a means for studying the above factors and solving these problems.

ＭｇとＢとの反応における不均一を抑制し、線材の長尺化が可能で、超電導性能が高いＭｇＢ２超電導線材を提供するためには、超電導コア部を大きくするとともに、超電導コア部の成分が、特に製造工程において外側金属管と反応しないようにする必要がある。 In order to suppress the non-uniformity in the reaction between Mg and B, to increase the length of the wire, and to provide a MgB 2 superconducting wire with high superconducting performance, the superconducting core portion is enlarged and the components of the superconducting core portion are provided. However, it is necessary not to react with the outer metal tube particularly in the manufacturing process.

本発明においては、ＭｇＢ２コア部を外側のＭｇＢ２層と内側のＭｇ及びＢの混合粉末層（混合粉末充填部とも呼ぶ）とで構成することにより、ドローベンチによる減面加工及び生成熱処理を施した後の、ＭｇＢ２コア部の面積を大きくするとともに、充填率を高くすることができる。これにより、高密度かつ高性能のＭｇＢ２超電導線材を製造することができる。 In the present invention, the MgB 2 core portion is composed of an outer MgB 2 layer and an inner Mg and B mixed powder layer (also referred to as a mixed powder filling portion), so that the surface-reduction processing and generation heat treatment by the draw bench are performed. After the application, the area of the MgB 2 core part can be increased and the filling rate can be increased. Thereby, a high-density and high-performance MgB 2 superconducting wire can be manufactured.

図８は、本発明のＭｇＢ２超電導線材の断面を示す拡大写真及び模式図である。図８の右図が拡大写真であり、図８の左図が模式図である。 FIG. 8 is an enlarged photograph and a schematic view showing a cross section of the MgB 2 superconducting wire of the present invention. The right figure of FIG. 8 is an enlarged photograph, and the left figure of FIG. 8 is a schematic diagram.

本図において、ＭｇＢ２超電導線材は、外側からシース材８２、外側コア部８３及び内側コア部８４で構成されている。 In this figure, the MgB 2 superconducting wire is composed of a sheath material 82, an outer core portion 83, and an inner core portion 84 from the outside.

図９Ａ〜９Ｉは、ＭｇＢ２線材の製造工程の例を示す図である。 9A to 9I are diagrams illustrating an example of the manufacturing process of the MgB 2 wire.

各図における工程は次の通りである。   The steps in each figure are as follows.

銅製の管（シース材９２、外径７．４ｍｍ、内径４．２ｍｍ（先端部に直径２．５ｍｍの凹部を有する。））を用意し（図９Ａ：シース材用の銅管（Ｃｕ ｔｕｂｅ ｆｏｒ ｓｈｅａｔｈ ｍａｔｅｒｉａｌ））、銅管の中央部に炭化タングステン（ＷＣ）の棒９６（直径２．５ｍｍ）を差し込んで、銅管との隙間に二ホウ化マグネシウム粉末１０１を入れる（図９Ｂ：外側コア部の充填工程（Ｆｉｌｌｉｎｇ ｐｒｏｃｅｓｓ ｆｏｒ ｏｕｔｅｒ Ｅｘ−ｓｉｔｕ ｃｏｒｅ））。炭化タングステンの棒９６を入れたまま、その周囲に銅管よりも径の小さい炭化タングステンの管９７（外径４．２ｍｍ、内径２．５ｍｍ）を差し込み、０．３ＧＰａで押し込む。この場合、０．１〜２．０ＧＰａでも同様の効果が得られる（図９Ｃ：外側コア部の加圧工程（Ｐｒｅｓｓｉｎｇ ｔｈｅ ｏｕｔｅｒ ｃｏｒｅ））。その後、炭化タングステンの棒９６及び管９７の両方を引き抜き、二ホウ化マグネシウム粉末の外周部９３を作製する（図９Ｄ：棒及び管の除去工程（Ｒｅｍｏｖａｌ ｏｆ ｃｅｎｔｅｒ ｐｏｌｅ））。   A copper tube (sheath material 92, outer diameter 7.4 mm, inner diameter 4.2 mm (having a concave portion with a diameter of 2.5 mm at the tip)) (FIG. 9A: copper tube for sheath material (Cu tube for) sheet material)), and a tungsten carbide (WC) rod 96 (diameter 2.5 mm) is inserted into the center of the copper tube, and the magnesium diboride powder 101 is placed in the gap with the copper tube (FIG. 9B: outer core). (Filling process for outer Ex-situ core). With the tungsten carbide rod 96 inserted, a tungsten carbide tube 97 (outer diameter 4.2 mm, inner diameter 2.5 mm) having a diameter smaller than that of the copper tube is inserted around the rod 96 and pushed in at 0.3 GPa. In this case, the same effect can be obtained even at 0.1 to 2.0 GPa (FIG. 9C: Pressing the outer core pressing process). Thereafter, both the tungsten carbide rod 96 and the tube 97 are pulled out to produce the outer peripheral portion 93 of the magnesium diboride powder (FIG. 9D: Removal of the rod and tube (Removal of center pole)).

さらに、中央の開口部にマグネシウム１０２及びホウ素１０３を１：２の割合で混合した粉末を入れ（図９Ｅ：内側コア部の充填工程（Ｆｉｌｌｉｎｇ ｐｒｏｃｅｓｓ ｆｏｒ ｉｎｎｅｒ ｉｎ−ｓｉｔｕ ｃｏｒｅ））、炭化タングステンの棒を押し込み加圧して（図９Ｆ：内側コア部の加圧工程（Ｐｒｅｓｓｉｎｇ ｔｈｅ ｉｎｎｅｒ ｃｏｒｅ））、マグネシウム１０２及びホウ素１０３の混合粉末９４の周囲に二ホウ化マグネシウム粉末部９３及び銅管９２を配置した構成とし、粉末を充填した金属管を作製する（図９Ｇ：多層コア前駆体（Ｄｏｕｂｌｅ ｃｏｒｅ ｐｒｅｃｕｒｓｏｒ））。この場合、０．１〜２．０ＧＰａでも同様の効果が得られる。また、充填量は、銅管内への充填密度が理論密度の２０〜７０％になるようにする。   Further, a powder in which magnesium 102 and boron 103 are mixed at a ratio of 1: 2 is put into the central opening (FIG. 9E: Filling process for inner in-situ core), and a tungsten carbide rod (FIG. 9F: Pressing the inner core), and a magnesium diboride powder portion 93 and a copper tube 92 were disposed around a mixed powder 94 of magnesium 102 and boron 103. A metal tube filled with powder is prepared (FIG. 9G: Double core precursor). In this case, the same effect can be obtained even at 0.1 to 2.0 GPa. The filling amount is set so that the filling density into the copper tube is 20 to 70% of the theoretical density.

金属管を線引き加工し（図９Ｈ：延伸工程（Ｄｒａｗｉｎｇ））、５００℃〜９００℃で熱処理してＭｇＢ２線材を作製する（図９Ｉ：焼結工程（Ｓｉｎｔｅｒｉｎｇ））。なお、延伸工程及び焼結工程を併せてＰＩＴ工程（ＰＩＴ ｐｒｏｃｅｓｓ）と呼ぶ。 The metal tube is drawn (FIG. 9H: Drawing step (Drawing)) and heat-treated at 500 ° C. to 900 ° C. to produce an MgB 2 wire (FIG. 9I: Sintering step). In addition, a extending process and a sintering process are collectively called a PIT process (PIT process).

以下、実施例に基づいて説明する。   Hereinafter, a description will be given based on examples.

図３は、本発明により作製したＭｇＢ２超電導線材の断面構造を示す。本図において、ＭｇＢ２超電導線材２１は、外側金属管２２（安定化層と呼ぶ）、外側超電導層２３（焼結領域、外周層又は外周部と呼ぶ）及び内側混合粉末充填部２４（反応領域又は中央部と呼ぶ）から形成されている。ここで、外側超電導層２３及び内側混合粉末充填部２４を併せて超電導コア部２５と呼ぶ。 FIG. 3 shows a cross-sectional structure of a MgB 2 superconducting wire produced according to the present invention. In this figure, the MgB 2 superconducting wire 21 includes an outer metal tube 22 (referred to as a stabilization layer), an outer superconducting layer 23 (referred to as a sintered region, outer peripheral layer or outer peripheral portion), and an inner mixed powder filling portion 24 (reactive region). Or a central portion). Here, the outer superconducting layer 23 and the inner mixed powder filling portion 24 are collectively referred to as a superconducting core portion 25.

最初に、市販されているＭｇＢ２粉末を管状に成形し、ＭｇＢ２管を作製した。これが外側超電導層２３となる。つぎに、市販されているＭｇ粉末及びＢ粉末をＡｒガス中又は真空中においてボールミルポットに化学量論組成で充填し、ボールミル混合した。つぎに、ＭｇＢ２管をＣｕ管（外側金属管２２）に挿入した後、ボールミル混合したＭｇ及びＢの混合粉末をＭｇＢ２管に充填し、管全体を封止した。 First, a commercially available MgB 2 powder was formed into a tubular shape to produce an MgB 2 tube. This becomes the outer superconducting layer 23. Next, commercially available Mg powder and B powder were filled in a stoichiometric composition in a ball mill pot in Ar gas or in vacuum, and mixed with the ball mill. Next, after inserting the MgB 2 tube into the Cu tube (outer metal tube 22), the MgB 2 tube was filled with the mixed powder of Mg and B mixed with the ball mill, and the entire tube was sealed.

そして、その封止した管の両端をスゥェジャーで封止・細線化した後、ドローベンチによる線引き加工を行い、最後に、熱処理を施した。   Then, both ends of the sealed tube were sealed and thinned with a swagger, followed by drawing with a draw bench, and finally heat treatment.

本発明は、ＭｇＢ２超電導線材の高性能化を阻害する従来の要因をすべてカバーしている。これは、ＭｇＢ２粉末で作製した成形管を適用することで、この成形管を超電導コア部の一部とし、かつ、Ｍｇと外側金属管との反応を阻害するバリア層として機能させることができる。 The present invention covers all the conventional factors that hinder the high performance of the MgB 2 superconducting wire. By applying a molded tube made of MgB 2 powder, this molded tube can be made a part of the superconducting core and function as a barrier layer that inhibits the reaction between Mg and the outer metal tube. .

また、Ｍｇ及びＢの混合粉末とＭｇＢ２成形管の界面は、Ｍｇ、Ｂおよび反応で生成したＭｇＢ２で構成されるため、従来例と比べて高い超電導特性を得ることができる。 Further, since the interface between the mixed powder of Mg and B and the MgB 2 shaped tube is composed of Mg, B and MgB 2 generated by the reaction, it is possible to obtain higher superconducting characteristics than in the conventional example.

以上をまとめると、本発明のＭｇＢ２超電導線材は、外側金属管内にＭｇＢ２成形管を入れ、その中にＭｇ及びＢの混合粉末を充填し、熱処理することで、高い超電導特性を付加させることができる。 To summarize the above, the MgB 2 superconducting wire of the present invention can be provided with high superconducting properties by placing a MgB 2 molded tube in the outer metal tube, filling it with mixed powder of Mg and B, and heat-treating it. Can do.

以下に、その製造プロセスを示す。   The manufacturing process is shown below.

本実施例におけるＭｇＢ２超電導線材の、それぞれの管の初期寸法は以下の通りである。 The initial dimensions of each tube of the MgB 2 superconducting wire in this example are as follows.

外側金属管（Ｃｕ管）：外径１８ｍｍ、内径１６ｍｍ、長さ１００ｍｍ
ＭｇＢ２成形体（ＭｇＢ２成形管）：外径１５ｍｍ、内径１１ｍｍ、長さ１００ｍｍ
まず、市販されているＭｇＢ２粉末を用いて、上記寸法に成形加圧した。 Outer metal tube (Cu tube): outer diameter 18mm, inner diameter 16mm, length 100mm
MgB 2 molded body (MgB 2 molded tube): outer diameter 15 mm, inner diameter 11 mm, length 100 mm
First, using the commercially available MgB 2 powder, it was molded and pressed to the above dimensions.

つぎに、市販されているＭｇ粉末及びＢ粉末をモル比で１：２の割合になるように混合し、真空混合用ポットに入れた。そして、真空封止した後、ボールミル装置で粉末を混合させた。その際、真空度は、１．０×１０−４ｔｏｒｒであった。 Next, commercially available Mg powder and B powder were mixed at a molar ratio of 1: 2, and placed in a vacuum mixing pot. And after vacuum-sealing, the powder was mixed with the ball mill apparatus. At that time, the degree of vacuum was 1.0 × 10 −4 torr.

つぎに、Ｃｕ管に挿入したＭｇＢ２成形管にＭｇ及びＢの混合粉末を真空グローブボックス内で充填した。 Next, the mixed powder of Mg and B were filled in a vacuum glove box MgB 2 forming tube inserted into Cu tube.

つぎに、Ｃｕ管の両端にＣｕ棒を挿入し、Ｃｕの両端をＡｇろう付け（銀ろう付け）することで、管内部を真空に保持した充填金属管を作製した。   Next, a Cu metal rod was inserted into both ends of the Cu tube, and both ends of Cu were brazed with Ag (silver brazing) to produce a filled metal tube in which the inside of the tube was kept in vacuum.

なお、この際、以下の方法でも同様又はそれ以上の効果が得られる。   In this case, the same or more effect can be obtained by the following method.

１）Ｃｕ棒は入れなくてもよいが、入れた方がより優れた真空封止管を作製できる。   1) Although it is not necessary to put a Cu rod, a better vacuum sealed tube can be produced if it is put.

２）Ｃｕ管側ではなく、ＭｇＢ２成形管側にろう付けをしてもよいが、ろう付け温度が低いＣｕ管の方がＭｇＢ２線材の特性上、優れている。 2) Brazing may be performed not on the Cu tube side but on the MgB 2 formed tube side, but the Cu tube having a lower brazing temperature is superior in terms of the properties of the MgB 2 wire.

３）ＭｇＢ２成形管は加圧成形で作製してもよいが、冷間等方圧加圧法（Ｃｏｌｄ Ｉｓｏｓｔａｔｉｃ Ｐｒｅｓｓｉｎｇ、ＣＩＰ）などで作製してもよい。また、高さの短い成形品を積み上げる方法でもよい（例えば、本実施例では、長さ５０ｍｍ×２個、１０ｍｍ×１０個など）。 3) The MgB 2 shaped tube may be produced by pressure molding, but may also be produced by cold isostatic pressing (CIP) or the like. Alternatively, a method of stacking molded articles having a short height may be used (for example, in this embodiment, length 50 mm × 2, 10 mm × 10, etc.).

４）Ｍｇ及びＢの混合粉末を充填する際、加圧成形した成形品を挿入してもよい。また、成形管と同様に、高さの短い成形品を積み上げる方法でもよい。   4) When filling the mixed powder of Mg and B, a pressure-molded molded article may be inserted. Moreover, the method of piling up the molded product with short height may be sufficient like a shaping | molding pipe | tube.

５）使用したＭｇ粉末は、ＭｇＨ２やＭｇＣｕなどのＭｇ合金でも同様の効果が得られる。 5) The same effect can be obtained even when the Mg powder used is an Mg alloy such as MgH 2 or MgCu.

６）熱処理温度は５００〜９００℃までで、雰囲気はＡｒ、Ｎ２などの不活性ガス中、又は真空中で同様の効果が得られるが、特性上は６００〜６５０℃が最も優れている。 6) The heat treatment temperature is 500 to 900 ° C., and the same effect can be obtained in an inert gas such as Ar or N 2 or in a vacuum, but 600 to 650 ° C. is most excellent in terms of characteristics.

それを真空封止したグローブボックスから取り出し後、その両端をスゥェジャーで加工し、真空封止をより強化させた。そして、ドローベンチにより線引き加工を実施し、全体径がφ１．０ｍｍまで細線化した。この際、スゥェジャー加工を行わずに、線引き加工を実施してもよい。そして、最後に６３０℃×１ｈｒ、Ａｒ中で熱処理を施した。   After removing it from the vacuum-sealed glove box, both ends thereof were processed with a swagger to further strengthen the vacuum sealing. Then, drawing was performed with a draw bench, and the entire diameter was reduced to φ1.0 mm. At this time, the drawing process may be performed without performing the swagger process. Finally, heat treatment was performed in Ar at 630 ° C. × 1 hr.

このＭｇＢ２超電導線材を用いて臨界電流の測定を行った。測定は、一般的な直流四端子法を用いて、試料全体を液体ヘリウム中に浸漬して行った。 The critical current was measured using this MgB 2 superconducting wire. The measurement was performed by immersing the entire sample in liquid helium using a general DC four-terminal method.

図４にその結果を示す。横軸に磁場、縦軸に臨界電流密度をとっている。   FIG. 4 shows the result. The horizontal axis represents the magnetic field, and the vertical axis represents the critical current density.

本図から、本実施例のデータは、従来例のデータの延長線上に、より高い磁場の領域で得られていることがわかる。よって、本実施例のＭｇＢ２超電導線材は、磁場依存性を示す超電導線材であることがわかった。また、従来例のＭｇＢ２超電導線材より優れた特性であることがわかった。また、本実施例のＭｇＢ２超電導線材を金属ボビンに無誘導巻し、長尺線材を用いて臨界電流測定を測定したところ、短尺特性と同様の結果を示した。このことから、この線材が長手方向に均一性を有することがわかった。 From this figure, it can be seen that the data of this example is obtained in the region of higher magnetic field on the extension line of the data of the conventional example. Therefore, MgB 2 superconducting wire of the present example was found to be superconducting wire showing the magnetic field dependence. Further, it was found to be an excellent property from MgB 2 superconducting wire of a conventional example. Further, when the MgB 2 superconducting wire of this example was non-inductively wound around a metal bobbin and the critical current measurement was performed using a long wire, the same result as the short length characteristic was shown. From this, it was found that this wire has uniformity in the longitudinal direction.

以上のことから、ＭｇＢ２超電導線材を上記構造にすることで、超電導特性が向上することがわかった。さらに、長尺に線引きする加工性も向上することがわかった。 From the above, it has been found that superconducting properties are improved by using the MgB 2 superconducting wire with the above structure. Furthermore, it was found that the workability of drawing a long line was improved.

ここで、超電導コア部の内側及び外側のＭｇ残存量についてＸ線回折装置を用いて評価を行った。   Here, the remaining amount of Mg inside and outside the superconducting core portion was evaluated using an X-ray diffractometer.

図５にその評価結果を示す。横軸に回折角度の２倍の値（２θ）、縦軸にＸ線強度をとっている。破線が中心部、実線が外周部のデータを表す。図中、丸印で示した位置は、未反応のＭｇの回折角度を示している。また、菱形印、三角印はそれぞれ、ＭｇＢ２、ＭｇＯの回折角度を示している。 FIG. 5 shows the evaluation results. The horizontal axis represents the value twice the diffraction angle (2θ), and the vertical axis represents the X-ray intensity. A broken line represents data at the center and a solid line represents data at the outer periphery. In the figure, the positions indicated by circles indicate the diffraction angle of unreacted Mg. Moreover, the rhombus mark and the triangle mark indicate the diffraction angles of MgB 2 and MgO, respectively.

本図から、超電導コア部の中心部では少量のＭｇが検出されるが、外周部ではＭｇが検出されないことがわかる。これにより、本実施例のＭｇＢ２超電導線材の超電導コア部におけるＭｇ残量が内側と外側とで異なることがわかる。すなわち、外周部と中心部とでマグネシウム又は酸化マグネシウムの濃度が異なる。内側及び外側の構成の違いは、顕微鏡写真等でも結晶形状の違いから確認することができる。 From this figure, it can be seen that a small amount of Mg is detected in the central portion of the superconducting core portion, but no Mg is detected in the outer peripheral portion. Thus, it can be seen that Mg remaining in the superconducting core part of the MgB 2 superconducting wire of the present embodiment is different between inside and outside. That is, the concentration of magnesium or magnesium oxide differs between the outer peripheral portion and the central portion. The difference between the inner and outer structures can be confirmed from the difference in crystal shape even in a micrograph or the like.

また、超電導特性向上のためには、Ｍｇ及びＢの混合粉末にＳｉＣを代表とする炭化物を添加する方法が有効である。さらに、ＭｇＢ２超電導線材だけでなく、粉末を充填して作製するＮｂ３Ｓｎ超電導線材やＮｂ３Ａｌ超電導線材にも同様に適用が可能である。 In order to improve the superconducting characteristics, a method of adding a carbide represented by SiC to the mixed powder of Mg and B is effective. Further, not only MgB 2 superconducting wire, but also Nb 3 Sn superconducting wire and Nb 3 Al superconducting wire manufactured by filling powder can be similarly applied.

図６は、本発明による他の実施例を示すＭｇＢ２超電導線材の断面図である。ＭｇＢ２超電導線材３１は、外側金属管３２及びＭｇＢ２多層コア部３６で構成され、ＭｇＢ２多層コア部３６は、外側超電導層３３、中間部混合粉末充填部３４及び内側混合粉末充填部３５を含む構造である。ここで、中間部混合粉末充填部３４及び内側混合粉末充填部３５は、Ｍｇ及びＢの混合粉末を反応させてＭｇＢ２を生成させた領域であり、反応領域又は中心部と呼ばれる部位である。 FIG. 6 is a cross-sectional view of an MgB 2 superconducting wire showing another embodiment according to the present invention. The MgB 2 superconducting wire 31 is composed of an outer metal tube 32 and an MgB 2 multilayer core portion 36, and the MgB 2 multilayer core portion 36 includes an outer superconducting layer 33, an intermediate mixed powder filling portion 34 and an inner mixed powder filling portion 35. It is a structure including. Here, the intermediate mixed powder filling portion 34 and the inner mixed powder filling portion 35 are regions where MgB 2 is produced by reacting the mixed powder of Mg and B, and are portions called a reaction region or a central portion.

本実施例のＭｇＢ２超電導線材の製造方法は、以下の通りである。 The manufacturing method of the MgB 2 superconducting wire of this example is as follows.

市販されているＭｇＢ２粉末を用いて成形加圧し、外側超電導層３３として成形管を形成した。 A molded tube was formed as the outer superconducting layer 33 by pressing with a commercially available MgB 2 powder.

つぎに、市販されているＭｇ粉末及びＢ粉末をモル比で１：２及び１：２．５の割合になるように、それぞれ真空混合用ポットに入れ、真空封止した後、ボールミル装置で粉末を混合させた。   Next, commercially available Mg powder and B powder are put into vacuum mixing pots in a molar ratio of 1: 2 and 1: 2.5, respectively, vacuum sealed, and then powdered with a ball mill device. Were mixed.

つぎに、上記のモル比が１：２の混合比率の混合粉末を成形加圧し、中間部混合粉末充填部３４として成形管を形成した。   Next, the mixed powder having a mixing ratio of 1: 2 was molded and pressed to form a molded tube as the intermediate mixed powder filling section 34.

その後、Ｃｕ管（外側金属管３２）の中にＭｇＢ２成形管、中間部混合粉末充填部３４の成形管を挿入した後、ＭｇＢ２成形管の中に、上記のモル比が１：２．５の混合比率のＭｇ及びＢの混合粉末を真空グローブボックス内で充填した。 Thereafter, MgB 2 forming tube into a Cu pipe (outer metal tube 32), after insertion of the forming tube of the intermediate portion mixed powder filling unit 34, in the MgB 2 forming tube, the molar ratio of above 1: 2. A mixed powder of Mg and B at a mixing ratio of 5 was filled in a vacuum glove box.

つぎに、その両端にＣｕ管と同径のＣｕ棒を入れた後、Ｃｕ管の両端をＡｇろう付けすることにより、真空封止を保持した充填金属管を作製した。そして、それを真空封止したグローブボックスから取り出し後、その両端をスゥェジャーで加工し、真空封止をより強化させた。そして、ドローベンチにより線引き加工を実施し、全体の径がφ１．０ｍｍまで細線化し、最後に６３０℃×１ｈｒ、Ａｒ中で生成熱処理した。   Next, after inserting a Cu rod having the same diameter as the Cu tube at both ends thereof, the both ends of the Cu tube were brazed with Ag to prepare a filled metal tube holding a vacuum seal. And after taking it out from the glove box which carried out the vacuum sealing, the both ends were processed with the swagger, and the vacuum sealing was strengthened more. And the drawing process was implemented with the draw bench, the whole diameter was thinned to (phi) 1.0mm, and it finally produced | generated heat-treated in Ar at 630 degreeC x 1 hr.

ここで、上記のモル比が１：２．５の混合比率の混合粉末を充填した部分が内側混合粉末充填部３５となる。   Here, the portion filled with the mixed powder having the molar ratio of 1: 2.5 is the inner mixed powder filling portion 35.

すなわち、本実施例においては、中心部がＭｇとＢとの比率の異なる２層以上を含む構成となっている。   That is, in this embodiment, the central portion includes two or more layers having different ratios of Mg and B.

この作製したＭｇＢ２超電導線材も実施例１と同様に臨界電流特性を評価したところ、磁場依存性を示す超電導線材であることがわかった。 The produced MgB 2 superconducting wire was evaluated for critical current characteristics in the same manner as in Example 1, and was found to be a superconducting wire exhibiting magnetic field dependency.

本実施例では、ＭｇとＢとの比率がモル比で１：２及び１：２．５の割合でＭｇＢ２超電導線材を作製したが、これらの割合に限定されるものではない。ＭｇとＢとの比率は、モル比で１：０．１〜１：１０の範囲で自在に設定することができる。 In this example, the MgB 2 superconducting wire was produced at a molar ratio of 1: 2 and 1: 2.5, but the present invention is not limited to these ratios. The ratio of Mg and B can be freely set in a molar ratio of 1: 0.1 to 1:10.

図７は、本発明による他の実施例を示すＭｇＢ２超電導線材の断面図である。ＭｇＢ２単芯コア部４５は、外側金属管４２、外側超電導層４３及び内側混合粉末充填部４４を含む構成となっている。このＭｇＢ２単芯コア部４５が７芯、すなわち７本束ねてＭｇＢ２超電導線材４１を構成している。 FIG. 7 is a cross-sectional view of an MgB 2 superconducting wire showing another embodiment according to the present invention. The MgB 2 single core core portion 45 includes an outer metal tube 42, an outer superconducting layer 43, and an inner mixed powder filling portion 44. The MgB 2 single-core portion 45 is 7 core, i.e. seven bundled constitutes a MgB 2 superconducting wire 41.

ＭｇＢ２単芯コア部４５を作製する方法は、実施例１と同様である。作製したＭｇＢ２単芯コア部４５を７本の穴の開いたＣｕ管４６に１本ずつ挿入し、Ｃｕ管４６の両端をスゥェジャーで封止・細線化した後、ドローベンチによる線引き加工を実施し、最後に、６３０℃×１ｈｒ、Ａｒ中で生成熱処理した。 The method for producing the MgB 2 single core core 45 is the same as that in the first embodiment. Insert the MgB 2 single core core 45 into the Cu tube 46 with 7 holes one by one, seal and thin the both ends of the Cu tube 46 with a swagger, and then perform drawing with a draw bench Finally, a generation heat treatment was performed in Ar at 630 ° C. × 1 hr.

なお、本実施例においては、７芯のＭｇＢ２超電導線材４１を作製したが、これに限定されるものではなく、１９芯、３７芯、又はそれ以上の多芯構造のＭｇＢ２超電導線材も作製することができる。 In this example, the 7-core MgB 2 superconducting wire 41 was produced, but the present invention is not limited to this, and a 19-core, 37-core, or more multi-core MgB 2 superconducting wire is also produced. can do.

本実施例のＭｇＢ２超電導線材も実施例１と同様に臨界電流特性を評価したところ、磁場依存性を示す超電導線材であることがわかった。 When the critical current characteristics of the MgB 2 superconducting wire of this example were evaluated in the same manner as in Example 1, it was found that the superconducting wire showed magnetic field dependency.

ＭｇＢ２超電導線材を更に高性能化させるためには、Ｍｇ粉末及びＢ粉末を混合する前に、それぞれの粉末をボールミルなどで粉砕した後、所定の割合で混合する。 In order to further improve the performance of the MgB 2 superconducting wire, before mixing the Mg powder and the B powder, each powder is pulverized with a ball mill or the like and then mixed at a predetermined ratio.

また、それぞれの粉末を混合や粉砕の前に、十分乾燥させ、水分を除去しておく。   Moreover, before mixing and grinding | pulverizing each powder, it fully dries and water | moisture content is removed.

これらの粉砕及び／又は乾燥を行うことにより、ＭｇＢ２の生成反応を非常に効果的に促進することができる。 By performing such pulverization and / or drying, the formation reaction of MgB 2 can be promoted very effectively.

また、ＭｇＢ２粉末を用いる場合においても、上記のＭｇＢ２粉砕及び／又は乾燥により、ＭｇＢ２粉末の新鮮面の露出面積が増加し、ＭｇＢ２粉末の表面の水分が除去され、焼結した際の電流パスが増加する。これにより、ＭｇＢ２超電導線材を高性能化することができる。 Further, even in the case of using the MgB 2 powder, by MgB 2 milling and / or drying of the above increases the exposed area of the fresh surface of the MgB 2 powder, water MgB 2 powder surface is removed, when the sintering Current path increases. Thereby, the performance of the MgB 2 superconducting wire can be improved.

以上の実施例においては、ＭｇＢ２超電導線材の断面形状が円形の場合に関して説明したが、断面形状は、これに限定されるものではなく、三角形状、四角形状（矩形状、平板状）等の多角形状でもよい。 In the above embodiments, the case where the cross-sectional shape of the MgB 2 superconducting wire is circular has been described. Polygon shape may be sufficient.

上述のＭｇＢ２超電導線材を用いて、超電導コイル作製することができる。また、この超電導コイルは、核磁気共鳴分析装置（Ｎｕｃｌｅａｒ Ｍａｇｎｅｔｉｃ Ｒｅｓｏｎａｎｃｅ、ＮＭＲ）、磁気共鳴画像分析装置（Ｍａｇｎｅｔｉｃ Ｒｅｓｏｎａｎｃｅ Ｉｍａｇｉｎｇ、ＭＲＩ）等の超電導マグネットシステムに適用することができる。 A superconducting coil can be manufactured using the MgB 2 superconducting wire described above. Moreover, this superconducting coil can be applied to superconducting magnet systems such as a nuclear magnetic resonance analyzer (Nuclear Magnetic Resonance, NMR) and a magnetic resonance image analyzer (Magnetic Resonance Imaging, MRI).

１、１１、２１、３１、４１：ＭｇＢ２超電導線材、２、２２、３２：外側金属管、３：内側金属管、４：ＭｇＢ２コア部、２３、３３：外側超電導層、２４、３５：内側混合粉末充填部、２５：超電導コア部、３４：中間部混合粉末充填部、３６：ＭｇＢ２多層コア部、４５：ＭｇＢ２単芯コア部、４６：Ｃｕ管。 1, 11, 21, 31, 41: MgB 2 superconducting wire, 2 , 22, 32: outer metal tube, 3: inner metal tube, 4: MgB 2 core, 23, 33: outer superconducting layer, 24, 35: Inner mixed powder filling portion, 25: superconducting core portion, 34: intermediate portion mixed powder filling portion, 36: MgB 2 multilayer core portion, 45: MgB 2 single core portion, 46: Cu tube.

Claims (8)

二ホウ化マグネシウムを含む超電導コア部と、この超電導コア部を覆う安定化層とを含む超電導線材であって、前記超電導コア部が、二ホウ化マグネシウム粉末の焼結領域である外周部と、マグネシウム粉末及びホウ素粉末を混合して反応させた反応領域である中心部とを有することを特徴とする超電導線材。   A superconducting wire including a superconducting core portion containing magnesium diboride and a stabilizing layer covering the superconducting core portion, wherein the superconducting core portion is a sintered region of magnesium diboride powder; and A superconducting wire comprising a central portion which is a reaction region in which magnesium powder and boron powder are mixed and reacted. 前記外周部と前記中心部とでマグネシウム又は酸化マグネシウムの濃度が異なることを特徴とする請求項１記載の超電導線材。   The superconducting wire according to claim 1, wherein the concentration of magnesium or magnesium oxide is different between the outer peripheral portion and the central portion. 前記中心部が、マグネシウムとホウ素との比率の異なる２層以上を含むことを特徴とする請求項１又は２に記載の超電導線材。   The superconducting wire according to claim 1 or 2, wherein the central portion includes two or more layers having different ratios of magnesium and boron. 前記中心部が、マグネシウム、ホウ素及び炭化物を含むことを特徴とする請求項１〜３のいずれか１項に記載の超電導線材。   The superconducting wire according to any one of claims 1 to 3, wherein the central portion includes magnesium, boron, and carbide. 前記安定化層がＣｕ、Ａｌ、Ａｇ、Ａｕ及びＮｉ並びにそれらの合金を含むことを特徴とする請求項１〜４のいずれかに記載の超電導線材。   The superconducting wire according to any one of claims 1 to 4, wherein the stabilization layer includes Cu, Al, Ag, Au, and Ni and alloys thereof. 請求項１〜５のいずれか１項に記載の超電導線材を複数本束ねて形成したことを特徴とする多芯材。   A multi-core material formed by bundling a plurality of superconducting wires according to any one of claims 1 to 5. 請求項１〜５のいずれか１項に記載の超電導線材又は請求項６記載の多芯材で形成されたことを特徴とする超電導コイル。   A superconducting coil comprising the superconducting wire according to any one of claims 1 to 5 or the multi-core material according to claim 6. 請求項７記載の超電導コイルを含むことを特徴とする超電導マグネットシステム。   A superconducting magnet system comprising the superconducting coil according to claim 7.
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