JP3877071B2 - Superconducting wire manufacturing method - Google Patents

Superconducting wire manufacturing method Download PDF

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JP3877071B2
JP3877071B2 JP2003285579A JP2003285579A JP3877071B2 JP 3877071 B2 JP3877071 B2 JP 3877071B2 JP 2003285579 A JP2003285579 A JP 2003285579A JP 2003285579 A JP2003285579 A JP 2003285579A JP 3877071 B2 JP3877071 B2 JP 3877071B2
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metal pipe
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material powder
wire
pipe
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JP2004087488A (en
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直樹 綾井
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Sumitomo Electric Industries Ltd
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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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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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    • Y02E40/60—Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment

Description

本発明は、超電導線材の製造方法に関するものである。特に、長尺な線材であっても、焼結時の膨張や結合性の低下などを抑制して、臨界電流密度(Jc)を向上することが可能な超電導線材の製造方法に関する。   The present invention relates to a method for manufacturing a superconducting wire. In particular, the present invention relates to a method for producing a superconducting wire capable of improving the critical current density (Jc) by suppressing expansion and lowering of bondability during sintering even for a long wire.

従来、パウダーインチューブ法によりBi2223相などの酸化物超電導体を長尺なテープ状線材に形成する技術が知られている。この方法は、まず超電導相の原料粉末を銀などの金属パイプに充填する。次に、原料粉末を充填した金属パイプを伸線加工してクラッド線材とする。複数のクラッド線材を束ねて銀などの金属パイプに挿入し、伸線加工して多芯線材とする。この多芯線材を圧延加工してテープ状線材とする。テープ状線材に一次熱処理を施して目的の超電導相を生成させる。続いて、このテープ状線材を再度圧延してから二次熱処理を施して、超電導相の結晶粒同士を接合させる。これら2回の塑性加工と熱処理は、1回しか行わない場合もあるが、一般に7〜21体積％の酸素を含む雰囲気下にて行われる。そして、金属シース中に多数の超電導フィラメントが含まれるテープ状線材を得る。   Conventionally, a technique for forming an oxide superconductor such as a Bi2223 phase on a long tape-shaped wire by a powder-in-tube method is known. In this method, a raw material powder of a superconducting phase is first filled in a metal pipe such as silver. Next, the metal pipe filled with the raw material powder is drawn into a clad wire. A plurality of clad wires are bundled, inserted into a metal pipe such as silver, and drawn to form a multi-core wire. This multi-core wire is rolled to obtain a tape-like wire. The tape-shaped wire is subjected to a primary heat treatment to produce a desired superconducting phase. Subsequently, the tape-shaped wire is rolled again and then subjected to a secondary heat treatment to join the crystal grains of the superconducting phase. These two plastic workings and heat treatments may be performed only once, but are generally performed in an atmosphere containing 7 to 21% by volume of oxygen. And the tape-shaped wire material in which many superconducting filaments are contained in a metal sheath is obtained.

このようなテープ状線材を製造する技術として、特許文献1〜3に記載された技術がある。   As a technique for manufacturing such a tape-shaped wire, there are techniques described in Patent Documents 1 to 3.

特開平6-342607号公報JP-A-6-342607 特開平6-176635号公報Japanese Patent Laid-Open No. 6-17635 特開平6-309967号公報JP-A-6-309967

しかし、従来の技術では、原料粉末の内部に残留するガスが上記一次熱処理、二次熱処理段階で発生して、超電導体の結晶間に空隙を生じたり、ガスと原料粉末とが結合してアモルファス相が偏析されて、超電導体の結晶間の結合を阻害して臨界電流密度が低下するという問題がある。また、局所的にガスが集まることで膨れなどの欠陥を生じるという問題もある。   However, in the conventional technology, the gas remaining in the raw material powder is generated in the primary heat treatment and secondary heat treatment steps to form voids between the crystals of the superconductor, or the gas and the raw material powder are combined to form an amorphous material. There is a problem in that the phases are segregated and the bonding between the crystals of the superconductor is hindered to reduce the critical current density. In addition, there is a problem that defects such as swelling occur due to the local collection of gas.

そこで、特許文献1では、伸線加工後、減圧雰囲気下で550℃〜760℃の熱処理を施して、原料粉末の吸着ガスを取り除くことを開示している。しかし、この技術では、伸線加工を行ってから熱処理を施しており、伸線加工により金属パイプ内の原料粉末の密度が大きくなって通気性が悪くなることで、ガスが抜けにくく、脱ガス処理を十分に行うことが困難である。また、減圧下で金属パイプ端部を封止していないため、熱処理後に金属パイプの末端から空気などがパイプ内に侵入する恐れがある。   Therefore, Patent Document 1 discloses that after wire drawing, heat treatment at 550 ° C. to 760 ° C. is performed in a reduced pressure atmosphere to remove the adsorbed gas of the raw material powder. However, in this technology, heat treatment is performed after wire drawing, and the density of the raw material powder in the metal pipe is increased due to the wire drawing, resulting in poor air permeability. It is difficult to perform processing sufficiently. Further, since the end of the metal pipe is not sealed under reduced pressure, air or the like may enter the pipe from the end of the metal pipe after the heat treatment.

特許文献2では、真空中または湿度30％以下の雰囲気中で酸化物粉末を金属パイプに充填することを開示している。しかし、この技術では、金属パイプ中に空気が残留することがある。残留した空気は、上記一次熱処理、二次熱処理段階で発生することで、膨れを生じたり、結晶間の結合の阻害して臨界電流密度を低下させたりすることになる。   Patent Document 2 discloses that a metal pipe is filled with oxide powder in a vacuum or in an atmosphere with a humidity of 30% or less. However, with this technique, air may remain in the metal pipe. Residual air is generated in the primary heat treatment and secondary heat treatment steps, thereby causing blistering, and inhibiting the bonding between crystals to lower the critical current density.

更に、特許文献3では、200℃〜800℃に加熱しながら1/103Torr(0.13Pa)以下に減圧した状態にて、酸化物超電導体の粉末からなる棒状成形体を金属パイプに真空封入することを開示している。しかし、この技術では、金属パイプに充填させるのが、粉末ではなく棒状成形体であるため、通気性が悪く、金属パイプの中央部まで脱ガスを十分に行うことができないという問題がある。また、棒状成形体では、伸線加工工程において不均一に変形することがあり、金属パイプ内に空隙などが生じて臨界電流密度が低くなる。更に、加熱温度が高いほどガスをより排出できるが、1/103Torr以下の減圧雰囲気では、800℃まで加熱すると粉末が分解することがあり、実際には、高々700〜750℃程度しか加熱することができず、十分な脱ガスが行うことができない。 Furthermore, in Patent Document 3, a rod-shaped formed body made of oxide superconductor powder is vacuum-sealed in a metal pipe in a state where the pressure is reduced to 1/10 3 Torr (0.13 Pa) or less while heating at 200 ° C. to 800 ° C. Is disclosed. However, this technique has a problem that since the metal pipe is filled with a rod-shaped molded body rather than powder, the air permeability is poor and the degassing cannot be sufficiently performed to the center of the metal pipe. In addition, the rod-shaped molded body may be deformed non-uniformly in the wire drawing process, causing voids in the metal pipe and lowering the critical current density. Furthermore, the higher the heating temperature, the more gas can be discharged, but in a reduced-pressure atmosphere of 1/10 3 Torr or less, the powder may decompose when heated to 800 ° C. In practice, only 700 to 750 ° C is heated at most. Cannot be performed and sufficient degassing cannot be performed.

そこで、本発明の主目的は、金属パイプ内の脱ガスを十分に行うことで臨界電流密度を向上することができる超電導線材の製造方法を提供することにある。   Then, the main objective of this invention is to provide the manufacturing method of the superconducting wire which can improve a critical current density by fully degassing in a metal pipe.

本発明は、酸化物超電導体の原料粉末を10％以上40％以下の充填密度で金属パイプに充填して、その後、減圧した状態でパイプ端部を封止し、前記原料粉末が封入された金属パイプを伸線加工することを特徴とする。   In the present invention, the raw material powder of the oxide superconductor is filled into a metal pipe at a filling density of 10% or more and 40% or less, and then the pipe end is sealed in a decompressed state, and the raw material powder is sealed. It is characterized by drawing a metal pipe.

また、酸化物超電導体の原料粉末を金属パイプに充填後、このパイプを加熱してから減圧してもよい。即ち、本発明超電導線材の製造方法は、酸化物超電導体からなる原料粉末、又は熱処理にて酸化物超電導体となる前駆体からなる原料粉末を金属パイプに充填する工程と、前記原料粉末を充填した金属パイプを400℃以上800℃以下に加熱する工程と、前記加熱した金属パイプ内を100Pa以下に減圧する工程と、前記減圧した状態にて金属パイプ端部の開口部を封止する工程と、前記原料粉末が封入された金属パイプを伸線加工する工程とを具える。そして、前記原料粉末の充填密度を10％以上40％以下とする。   Further, after filling the raw material powder of the oxide superconductor into the metal pipe, the pressure may be reduced after the pipe is heated. That is, the method for producing a superconducting wire of the present invention includes a step of filling a metal pipe with a raw material powder made of an oxide superconductor or a raw material powder made of a precursor that becomes an oxide superconductor by heat treatment, and filling the raw material powder. Heating the metal pipe to 400 ° C. or higher and 800 ° C. or lower, reducing the pressure inside the heated metal pipe to 100 Pa or lower, and sealing the opening at the end of the metal pipe in the reduced pressure state. And a step of drawing a metal pipe in which the raw material powder is encapsulated. And the filling density of the said raw material powder shall be 10% or more and 40% or less.

更に、金属パイプへの充填前において、酸化物超電導体の原料粉末を加熱してもよい。即ち、酸化物超電導体からなる原料粉末、又は熱処理にて酸化物超電導体となる前駆体からなる原料粉末を、金属パイプに充填する工程の前に、400℃以上800℃以下で熱処理する工程を具えてもよい。   Furthermore, the raw material powder of the oxide superconductor may be heated before filling the metal pipe. That is, a step of heat-treating a raw material powder made of an oxide superconductor or a raw material powder made of a precursor that becomes an oxide superconductor by heat treatment at a temperature of 400 ° C. or higher and 800 ° C. or lower before the step of filling the metal pipe. It may be provided.

超電導体の原料粉末の内部には、空気や、後述する原料粉末の作製工程(通常、混合から焼結までの工程)で原料粉末に吸着される吸着ガス(水蒸気、炭素、炭化水素など)、過剰な酸素などのガスが含まれる。これらのガスは、従来、線材化した後の最終熱処理工程(第一熱処理、第二熱処理)にて原料粉末の外に放出される際、超電導体の結晶間に空隙を生じさせたり、原料粉末と結合してアモルファス相を偏析させたりしていた。そして、これら空隙やアモルファス相が結晶間の結合を阻害することで臨界電流密度を低下させていた。また、原料粉末から放出されるガスが金属パイプから排出されずにパイプ内に留まることで、線材が膨れるなどの欠陥を生じさせていた。   Inside the raw material powder of the superconductor, air or an adsorbed gas (water vapor, carbon, hydrocarbon, etc.) adsorbed on the raw material powder in the raw material powder production process (usually the process from mixing to sintering), which will be described later, Excess oxygen and other gases are included. Conventionally, when these gases are released out of the raw material powder in the final heat treatment step (first heat treatment, second heat treatment) after forming the wire, voids are formed between the crystals of the superconductor, or the raw material powder To segregate the amorphous phase. These voids and amorphous phase hinder the bonding between crystals, thereby reducing the critical current density. Further, the gas released from the raw material powder is not discharged from the metal pipe but remains in the pipe, thereby causing defects such as expansion of the wire.

そこで、本発明は、まず、超電導体の原料粉末を金属パイプに充填した後、原料粉末に含有されるガスやガスの元となる水分などを気化して金属パイプ内から排気する脱ガス処理(減圧)を行う。このとき、原料粉末が金属パイプ外へのガスの放出を阻害しにくいように良好な通気性を実現するべく、原料粉末の充填密度を規定する。   Therefore, the present invention is a degassing process in which first, after superconducting raw material powder is filled in a metal pipe, the gas contained in the raw material powder, the moisture that is the source of the gas is vaporized and exhausted from the inside of the metal pipe ( Pressure reduction). At this time, the packing density of the raw material powder is defined so as to realize good air permeability so that the raw material powder does not easily inhibit the release of gas to the outside of the metal pipe.

また、超電導体の原料粉末を金属パイプに前記の充填率(充填密度)で充填し、減圧による脱ガス処理を行った後、金属パイプ内を減圧した状態で金属パイプ端部を封止することで、脱ガス処理を施したパイプ内に新たに空気中の水分や炭酸ガスなどが侵入することを防止することができる。特に、上記原料粉末を充填し、加熱した後、金属パイプ内を減圧した状態で上記封止を行うと、脱ガスをより効果的に行うことができると共に、新たなガスの侵入を防止することができる。   Also, after filling the metal pipe with the superconducting raw material powder at the above-mentioned filling rate (packing density) and performing degassing treatment under reduced pressure, the end of the metal pipe is sealed in a state where the inside of the metal pipe is decompressed Thus, it is possible to prevent moisture in the air, carbon dioxide gas, or the like from entering the pipe that has been subjected to the degassing process. In particular, when the sealing is performed in a state where the inside of the metal pipe is decompressed after being filled with the raw material powder and heated, degassing can be performed more effectively and intrusion of new gas can be prevented. Can do.

さらに、酸化物超電導体からなる原料粉末、又は熱処理にて酸化物超電導体となる前駆体からなる原料粉末を、金属パイプに充填する工程の前に、400℃以上800℃以下で熱処理する工程を具えることにより、原料粉末に含有されるガスやガスの元となる水分などをより効果的に除去することができる。   Furthermore, a step of heat-treating the raw material powder made of an oxide superconductor or the raw material powder made of a precursor that becomes an oxide superconductor by heat treatment at a temperature of 400 ° C. or higher and 800 ° C. or lower before the step of filling the metal pipe. By providing, it is possible to more effectively remove the gas contained in the raw material powder and the moisture that is the source of the gas.

以上説明したように本発明超電導線材の製造方法によれば、原料粉末を充填した金属パイプに減圧による脱ガス処理や加熱及び減圧による脱ガス処理を施すことで、長尺な超電導線材であっても、焼結の際の膨れや結合性の低下などを抑制して、高い臨界電流密度が得られるという優れた効果を奏し得る。特に、充填する原料粉末の充填密度を規定することで、金属パイプ内に原料粉末を均一に充填させて超電導線材の長手方向に亘って臨界電流密度のばらつきを低減することができる。また、十分に脱ガス処理を施すことで、アモルファス相の発生や伸線加工において不均一な変形を抑制して、臨界電流密度を向上することができる。   As described above, according to the method for manufacturing a superconducting wire of the present invention, a metal pipe filled with a raw material powder is subjected to degassing treatment by depressurization or degassing treatment by heating and depressurization. However, it is possible to obtain an excellent effect that a high critical current density can be obtained by suppressing swelling and bonding deterioration during sintering. In particular, by defining the packing density of the raw material powder to be filled, it is possible to uniformly fill the raw material powder in the metal pipe and reduce the variation in critical current density along the longitudinal direction of the superconducting wire. In addition, by performing sufficient degassing treatment, it is possible to improve the critical current density by suppressing generation of an amorphous phase and non-uniform deformation in wire drawing.

以下、本発明をより詳しく説明する。   Hereinafter, the present invention will be described in more detail.

(製造工程の概要)
超電導線材の製造工程は、通常、「原料粉末の調整→クラッド線材の作製→多芯線材の作製→圧延してテープ状線材の作製→熱処理」により行われる。必要に応じて、圧延と熱処理を複数回繰り返す。例えば、「多芯線材の作製」に続いて「一次圧延してテープ状線材の作製→一次熱処理→テープ状線材の二次圧延→二次熱処理」を行う。本発明超電導線材の製造方法は、特に、クラッド線材の作製条件を規定するものであり、「調整した原料粉末を金属パイプに充填→脱ガス処理(減圧)→脱ガスした状態で金属パイプの封止→伸線加工」工程を具える。また、原料粉末を金属パイプに充填した後加熱する場合は、「調整した原料粉末を金属パイプに充填→脱ガス処理(加熱)→脱ガス処理(減圧)→脱ガスした状態で金属パイプの封止→伸線加工」工程を具える。その他の工程は、従来と同様に行うとよい。 (Outline of manufacturing process)
The manufacturing process of the superconducting wire is usually performed by “adjustment of raw material powder → manufacture of clad wire → manufacture of multi-core wire → rolling to form tape-like wire → heat treatment”. Repeat rolling and heat treatment multiple times if necessary. For example, “manufacture of multi-core wire” is followed by “primary rolling to produce tape-like wire → primary heat treatment → secondary rolling of tape-like wire → secondary heat treatment”. The method for producing a superconducting wire of the present invention particularly defines the conditions for producing a clad wire, and “fills the adjusted raw material powder into the metal pipe → degas treatment (reduced pressure) → degass the metal pipe in a sealed state. It includes a “stop-to-draw wire” process. In addition, when heating after filling the raw material powder in the metal pipe, `` filling the adjusted raw material powder into the metal pipe → degassing treatment (heating) → degassing treatment (decompression) → degassing and sealing the metal pipe It includes a “stop-to-draw wire” process. Other steps may be performed in the same manner as in the past.

(原料粉末)
本発明において金属パイプに充填する原料粉末は、酸化物超電導体からなる原料粉末、又は熱処理にて酸化物超電導体となる前駆体からなる原料粉末とする。具体的には、複合酸化物を所定の組成比となるように混合した粉末(前駆体からなる粉末)、その混合粉末を焼結して粉砕した粉末(酸化物超電導体からなる粉末)が挙げられる。具体的には、例えば、Bi2212、Bi2223などが挙げられる。Bi2223の場合、原料粉末として前駆体を用いると、焼結によってより一体化し易く、臨界電流密度をより向上させることができて好ましい。Bi2212の場合、酸化物超電導体からなる粉末を用いると、臨界電流密度を向上させることができて好ましい。 (Raw material powder)
In the present invention, the raw material powder filled in the metal pipe is a raw material powder made of an oxide superconductor or a raw material powder made of a precursor that becomes an oxide superconductor by heat treatment. Specifically, a powder (a powder made of a precursor) mixed with a composite oxide so as to have a predetermined composition ratio, a powder (a powder made of an oxide superconductor) obtained by sintering and pulverizing the mixed powder. It is done. Specific examples include Bi2212, Bi2223, and the like. In the case of Bi2223, it is preferable to use a precursor as the raw material powder because it is easier to integrate by sintering and the critical current density can be further improved. In the case of Bi2212, it is preferable to use a powder made of an oxide superconductor because the critical current density can be improved.

最終的にBi2223系超電導線材を得る方法として、例えば、出発原料にBi、Pb、Sr、Ca、Cuを用いて、これら粉末を700〜870℃、10〜40時間、大気雰囲気又は減圧雰囲気下にて少なくとも1回焼結することが挙げられる。その他、公知の硝酸塩水溶液噴霧熱分解法、ゾルゲル法などが挙げられる。これらの方法により、Bi2223相よりもBi2212相が主体となった原料粉末(Bi2212、Ca2CuO3、Ca2PbO4などの混合物)を得ることができる。 As a method for finally obtaining a Bi2223 superconducting wire, for example, using Bi, Pb, Sr, Ca, Cu as a starting material, these powders are kept at 700 to 870 ° C. for 10 to 40 hours in an air atmosphere or a reduced pressure atmosphere. Sintering at least once. In addition, a known nitrate aqueous solution spray pyrolysis method, sol-gel method, and the like can be given. By these methods, a raw material powder (a mixture of Bi2212, Ca 2 CuO 3 , Ca 2 PbO 4, etc.) mainly composed of the Bi2212 phase rather than the Bi2223 phase can be obtained.

具体的な組成比は、BiaPbbSrcCadCueでa＋b：c：d：e＝1.7〜2.8：1.7〜2.5：1.7〜2.8：3を満たすものが好ましい。中でもBiまたはBi＋Pb：Sr：Ca：Cu＝2：2：2：3を中心とする組成が好適である。特に、Biは1.8付近、Pbは0.3〜0.4、Srは2付近、Caは2.2付近、Cuは3.0付近が望ましい。 Specific composition ratio, Bi a Pb b Sr c Ca d Cu e with a + b: c: d: e = 1.7~2.8: 1.7~2.5: 1.7~2.8: preferably satisfy the 3. Among them, a composition centering on Bi or Bi + Pb: Sr: Ca: Cu = 2: 2: 2: 3 is preferable. In particular, Bi is preferably near 1.8, Pb is 0.3 to 0.4, Sr is near 2, Ca is around 2.2, and Cu is around 3.0.

さらに、必要に応じて、原料粉末を、金属パイプに充填する工程の前に、400℃以上800℃以下で熱処理することにより、原料粉末に含有されるガスやガスの元となる水分などをより効果的に除去することができる。   Furthermore, if necessary, heat treatment is performed at 400 ° C. or higher and 800 ° C. or lower before the step of filling the raw material powder into the metal pipe, so that the gas contained in the raw material powder and the moisture that is the source of the gas are further increased. It can be effectively removed.

(金属パイプ)
金属パイプの原料としては、Ag、Cu、Fe、Ni、Cr、Ti、Mo、W、Pt、Pd、Rh、Ir、Ru、Osより選択される金属またはこれらの金属をベースとする合金が好ましい。特に、酸化物超電導体との反応性や加工性からAgまたはAg合金が好ましい。 (Metal pipe)
As a raw material of the metal pipe, a metal selected from Ag, Cu, Fe, Ni, Cr, Ti, Mo, W, Pt, Pd, Rh, Ir, Ru, Os or an alloy based on these metals is preferable. . In particular, Ag or an Ag alloy is preferable from the viewpoint of reactivity with an oxide superconductor and workability.

(充填密度)
本発明において原料粉末を金属パイプに充填する際の充填密度は、10％以上40％以下が適する。充填密度が10％未満であると、原料粉末が少なすぎて金属パイプ内に均一に充填することが困難である。一方、充填密度が40％超であると、原料粉末が多すぎることで、以下の不具合が生じる。
(1) 金属パイプの通気性が悪くなるため、パイプ端部の開口部付近は脱ガスを行うことができても、パイプの中央部にまで均一な脱ガスを行うことが難しい。
(2) 焼結して固くなる部分が生じるため、金属パイプの加工性が悪くなる。
(3) 伸線加工の際、ソーセージング(金属パイプの断面においてフィラメントがばらついて存在すること)などの不均一な変形が起こる。 (Packing density)
In the present invention, the filling density when filling the raw material powder into the metal pipe is suitably 10% or more and 40% or less. When the packing density is less than 10%, the raw material powder is too small to uniformly fill the metal pipe. On the other hand, when the packing density is more than 40%, the following problems occur because the raw material powder is too much.
(1) Since the air permeability of the metal pipe is deteriorated, it is difficult to perform uniform degassing up to the center of the pipe even though the vicinity of the opening at the end of the pipe can be degassed.
(2) Since a portion hardened by sintering is generated, the workability of the metal pipe is deteriorated.
(3) During wire drawing, non-uniform deformation such as sausaging (the presence of scattered filaments in the cross section of the metal pipe) occurs.

本発明において充填密度は、充填する原料粉末の理論密度を100％とし、この理論密度に対する割合(％)とする。充填する原料粉末の理論密度は、材料粉末の全構成相において各構成相の理論密度とその含有率との積の総和、即ち、Σρi×fｉ(ρi：原料粉末の構成相iの理論密度、fｉ：原料粉末の構成相iの含有比率)で表される。 In the present invention, the packing density is defined as 100% of the theoretical density of the raw material powder to be filled and a ratio (%) to the theoretical density. The theoretical density of the raw material powder to be filled is the sum of the products of the theoretical density of each constituent phase and its content in all constituent phases of the material powder, that is, Σρ i × f i (ρ i : constituent phase i of the raw material powder. The theoretical density, f i : the content ratio of the constituent phase i of the raw material powder).

(脱ガス処理(減圧))
本発明において脱ガス処理(減圧)は、到達圧力を100Pa以下とする。到達圧力が100Pa超であると、残留ガスが多く、脱ガス効果が少ない。常圧から到達圧力への減圧速度は、2kPa/min以下が好ましい。2kPa/min超では、金属パイプ内の原料粉末が圧力の変化に追従できず、パイプから舞い上がって噴出する恐れがある。 (Degassing (decompression))
In the present invention, the degassing process (reduced pressure) is performed so that the ultimate pressure is 100 Pa or less. When the ultimate pressure exceeds 100 Pa, the residual gas is large and the degassing effect is small. The pressure reduction rate from the normal pressure to the ultimate pressure is preferably 2 kPa / min or less. If it exceeds 2 kPa / min, the raw material powder in the metal pipe cannot follow the pressure change, and may rise from the pipe and be ejected.

(脱ガス処理(加熱))
脱ガス処理(加熱)は、金属パイプをある程度加熱してから徐々に排気をして行う。脱ガス処理(加熱)は、原料粉末を充填した金属パイプを400℃以上800℃以下に加熱して行うことが好適である。400℃以上であると、脱ガス効果をより効果的に得られる。また、より高温であるほどガスをより確実に排出できるが、800℃超では、原料粉末が分解する恐れがあるため、本発明では、800℃以下とする。脱ガス処理(加熱)は大気圧で行ってもよいが、400℃までの昇温は大気圧にて行い、400℃超から徐々に排気していって400℃以上800℃以下の熱処理を減圧下、より好ましくは真空中にて行うと脱ガス効果が高く好ましい。少なくとも400℃まで大気圧(常圧)で昇温した後減圧するのは、昇温と同時に減圧すると、ガスの放出に伴って原料粉末が金属パイプから噴出する恐れがあるためである。400℃以上800℃以下の温度を保持する時間は、金属パイプの径、長さなどによって適宜変更するとよい。例えば、金属パイプの内径20〜30mm、長さ500〜1500mmの場合、2〜10時間が好ましく、充填した原料粉末の状態や真空ポンプの能力などによっても適宜変化させるとよい。 (Degassing treatment (heating))
The degassing process (heating) is performed by heating the metal pipe to some extent and then gradually exhausting it. The degassing treatment (heating) is preferably performed by heating a metal pipe filled with the raw material powder to 400 ° C. or higher and 800 ° C. or lower. When the temperature is 400 ° C. or higher, the degassing effect can be obtained more effectively. Further, the higher the temperature, the more reliably the gas can be discharged. However, if it exceeds 800 ° C., the raw material powder may be decomposed. The degassing treatment (heating) may be performed at atmospheric pressure, but the temperature rise to 400 ° C is performed at atmospheric pressure, and the heat treatment from 400 ° C to 800 ° C is reduced by gradually exhausting from over 400 ° C. Lower, more preferably in a vacuum, it is preferable because the degassing effect is high. The reason for reducing the pressure after raising the temperature to at least 400 ° C. at atmospheric pressure (normal pressure) is that if the pressure is reduced at the same time as raising the temperature, the raw material powder may be ejected from the metal pipe as the gas is released. The time for maintaining the temperature of 400 ° C. or higher and 800 ° C. or lower may be appropriately changed depending on the diameter and length of the metal pipe. For example, when the inner diameter of the metal pipe is 20 to 30 mm and the length is 500 to 1500 mm, 2 to 10 hours are preferable, and it may be appropriately changed depending on the state of the filled raw material powder and the capacity of the vacuum pump.

(金属パイプの封止)
本発明では、上記のように減圧した状態、特に100Pa以下に減圧した状態にて金属パイプ端部の開口部を封止する。即ち、金属パイプ内を減圧することで、新たなガスの侵入を抑制することに加えて、金属パイプ端部の開口部を封止することで、パイプ内に新たなガスが侵入することをより確実に防止する。封止方法は、金属パイプを封止した状態で伸線加工を行うことから、伸線加工に耐え得る接合方法で、かつ真空封入に適用可能なものが適する。具体的には、例えば、電子ビーム溶接、ロウ付け、金属パイプに溶接した排気ノズルの圧着などの方法が挙げられる。 (Metal pipe sealing)
In the present invention, the opening at the end of the metal pipe is sealed in a state where the pressure is reduced as described above, particularly in a state where the pressure is reduced to 100 Pa or less. In other words, in addition to suppressing the entry of new gas by reducing the pressure inside the metal pipe, sealing the opening at the end of the metal pipe prevents the new gas from entering the pipe. Make sure to prevent it. Since the wire drawing process is performed with the metal pipe sealed, a sealing method that can withstand the wire drawing process and applicable to vacuum sealing is suitable. Specific examples include methods such as electron beam welding, brazing, and pressure bonding of an exhaust nozzle welded to a metal pipe.

(伸線加工)
本発明において伸線加工は、上記のように原料粉末が充填された金属パイプ端部を封止した状態で行う。 (Wire drawing)
In the present invention, the wire drawing is performed in a state where the end portion of the metal pipe filled with the raw material powder is sealed as described above.

以下、本発明の実施の形態を説明する。
(試験例1)
クラッド線材の製造工程において、原料粉末の充填密度を種々変更してパイプ内を減圧する工程と、減圧した状態にて金属パイプ端部を封止する工程を行った超電導線材を作製し、膨れなどの欠陥の有無、臨界電流密度を調べてみた。 Embodiments of the present invention will be described below.
(Test Example 1)
In the manufacturing process of the clad wire, a superconducting wire is produced by performing various processes such as reducing the filling density of the raw material powder to depressurize the inside of the pipe and sealing the end of the metal pipe in a depressurized state. I examined the presence or absence of defects and the critical current density.

I. 従来と同様の方法で、Bi、Pb、Sr、Ca、Cuを各元素が1.8：0.3：1.9：2：3の割合となるように、Bi2O3、PbO、SrCO3、CaCO3、CuOの各粉末を混合して混合粉末を作製し、大気中にて800℃以上の熱処理を数回行い、各熱処理後にそれぞれ粉砕を行う。このようにして、Bi2212、Ca2CuO3、Ca2PbO4などの混合物からなる酸化物超電導体の原料粉末を得る。 I. In conventional manner, Bi, Pb, Sr, Ca , each of the Cu element is 1.8: 0.3: 1.9: 2: so that the ratio of 3, Bi 2 O 3, PbO , SrCO 3, CaCO 3 Then, each powder of CuO is mixed to prepare a mixed powder, and heat treatment at 800 ° C. or more is performed several times in the atmosphere, and pulverization is performed after each heat treatment. In this way, a raw material powder of an oxide superconductor made of a mixture of Bi2212, Ca 2 CuO 3 , Ca 2 PbO 4 and the like is obtained.

充填密度は、充填する原料粉末の理論密度を100％とし、この理論密度に対する割合を示す。充填密度は、以下のようにして変化させた。30％以上40％以下の充填密度は、原料粉末を湿式造粒機で造粒した粉末を充填することで得られた。40％超の充填密度は、原料粉末をCIP（静水圧プレス）にて棒状体に成型した成型体を充填することで得られた。   The packing density indicates the ratio of the theoretical density of the raw material powder to be filled to 100% and the theoretical density. The packing density was changed as follows. A packing density of 30% or more and 40% or less was obtained by filling a powder obtained by granulating a raw material powder with a wet granulator. A filling density of more than 40% was obtained by filling a molded body obtained by forming the raw material powder into a rod-shaped body by CIP (hydrostatic pressure press).

II. 原料粉末又はその成型体は、銀パイプに充填する直前に、更に約100Paに真空排気しながら、場合によっては、700℃×10時間の熱処理を施して、予め吸着ガス成分を取り除いて、乾燥空気ガスを流して浄化したグローブボックス内で銀パイプに充填した。ここで、充填前の熱処理は、真空排気の他に、窒素やアルゴンなどの不活性ガス中、または、水分を取り除いた乾燥空気中で行っても良い。また、銀パイプへの充填も同様に不活性ガス中、あるいは、真空中で行っても同様の効果が得られる。本例において銀パイプは、一端の開口部に銀製の蓋を溶接した肉厚2mm、内径φ30mmのものを用いた。   II. The raw material powder or its molded body is subjected to heat treatment at 700 ° C. for 10 hours in some cases while evacuating to about 100 Pa immediately before filling into the silver pipe, to remove the adsorbed gas component in advance, The silver pipe was filled in a glove box purified by flowing dry air gas. Here, the heat treatment before filling may be performed in an inert gas such as nitrogen or argon, or in dry air from which moisture has been removed, in addition to vacuum evacuation. The same effect can be obtained by filling the silver pipe in an inert gas or in a vacuum. In this example, a silver pipe having a wall thickness of 2 mm and an inner diameter of 30 mm with a silver lid welded to an opening at one end was used.

III. 原料粉末を充填した銀パイプ内部を2kPa/minの速度で100Pa以下に減圧した。ここで2kPa/min以上の速度で減圧を行ったときには、銀パイプ内部の圧力差が大きくなり粉末が外部に押し出されることがあった。   III. The inside of the silver pipe filled with the raw material powder was depressurized to 100 Pa or less at a rate of 2 kPa / min. Here, when the pressure was reduced at a rate of 2 kPa / min or more, the pressure difference inside the silver pipe was increased, and the powder was sometimes pushed out.

IV. 銀パイプ内に存在する空隙部を真空(100Pa以下)に維持した状態で、銀パイプ他端の開口部に銀製の蓋をロウ付けして封止する。本例では、脱ガス処理からロウ付けまでを図1に示す真空封止装置にて行った。装置の詳細は後述する。   IV. With the void existing in the silver pipe maintained in a vacuum (100 Pa or less), a silver lid is brazed to the opening at the other end of the silver pipe and sealed. In this example, the process from degassing to brazing was performed by the vacuum sealing apparatus shown in FIG. Details of the apparatus will be described later.

V. 銀パイプ内に空気などが侵入しないように銀製の蓋をしたままの状態で伸線加工を施し、線材化してクラッド線材を得る。以降の手順は従来の製造方法と同様である。   V. Perform wire drawing with the silver lid on to prevent air from entering the silver pipe, and turn it into a wire to obtain a clad wire. The subsequent procedure is the same as the conventional manufacturing method.

VI. クラッド線材を複数本束ねて銀パイプ(外径36mm、内径30mm)に挿入して、このパイプ端部の開口部を銀製の蓋にて真空中で封止する。本例では、55本のクラッド線材を用いた。   VI. A plurality of clad wires are bundled and inserted into a silver pipe (outer diameter 36 mm, inner diameter 30 mm), and the opening at the end of the pipe is sealed in a vacuum with a silver lid. In this example, 55 clad wires were used.

VII. 銀パイプ内に空気などが侵入しないように、銀製の蓋をしたままの状態で伸線加工を施し、線材化して多芯線材を得る。本例では、直径φ1.6mmまで伸線した。   VII. To prevent air from entering the silver pipe, the wire is drawn with the silver lid on, and the wire is turned into a multi-core wire. In this example, the wire was drawn to a diameter of φ1.6 mm.

VIII. 多芯線材を幅4mm、厚さ0.2mmのテープ状に圧延してテープ状線材を得る。   VIII. A multifilament wire is rolled into a tape with a width of 4 mm and a thickness of 0.2 mm to obtain a tape-like wire.

IX. 長さ500mのテープ状線材において、フィラメント内にBi2223相の超電導体を生成させるための一次熱処理を行う。更に、中間圧延と、Bi2223相の結晶粒同士を接合させて超電導体を一体化するための追加熱処理を行う。   IX. Primary heat treatment is performed to form a Bi2223 phase superconductor in the filament of a tape-like wire having a length of 500 m. Furthermore, intermediate rolling and additional heat treatment are performed to join the Bi2223 phase crystal grains to integrate the superconductor.

上記のようにして得られた超電導線材において、一次熱処理後の線材に発生した膨れなどの欠陥の個数を調べた。また、追加熱処理後の線材に対して、77K、自己磁場中における臨界電流密度(Jc)を測定した。その結果を図2に示す。   In the superconducting wire obtained as described above, the number of defects such as blisters generated in the wire after the primary heat treatment was examined. In addition, the critical current density (Jc) in a self magnetic field was measured at 77 K for the wire after the additional heat treatment. The result is shown in FIG.

図2に示すように充填密度40％超では、膨れが発生し、臨界電流密度が低くなった。充填密度10％未満では、膨れなどの欠陥は発生していないが、超電導線材の長さ方向において臨界電流密度にばらつきが大きく、全長に亘る臨界電流密度が低くなった。これは、充填密度が10％未満であると、金属パイプに原料粉末が均一に充填されにくく、伸線加工後のフィラメントが長さ方向に不均一になったためと考えられる。なお、充填密度50％超では伸線加工途中で欠陥が発生して長尺線が得られなかった。   As shown in FIG. 2, when the packing density exceeds 40%, swelling occurs and the critical current density decreases. When the packing density was less than 10%, defects such as blistering did not occur, but the critical current density varied greatly in the length direction of the superconducting wire, and the critical current density over the entire length was low. This is considered to be because when the filling density is less than 10%, it is difficult to uniformly fill the metal pipe with the raw material powder, and the filament after the wire drawing process becomes non-uniform in the length direction. When the filling density exceeds 50%, defects occurred during the wire drawing process, and long wires could not be obtained.

これに対し、充填密度10％以上40％以下の場合、膨れなどの欠陥が少なく、かつ超電導線材の全長に亘って高い臨界電流密度が得られた。   On the other hand, when the packing density was 10% or more and 40% or less, there were few defects such as blistering, and a high critical current density was obtained over the entire length of the superconducting wire.

(試験例2)
クラッド線材の製造工程において、加熱温度を種々変更して脱ガス処理を行った超導電線材を作製し、膨れなどの欠陥の有無、臨界電流密度を調べてみた。 (Test Example 2)
In the manufacturing process of the clad wire, a superconducting wire that was degassed by changing the heating temperature was prepared, and the presence or absence of defects such as blistering and the critical current density were examined.

超電導線材は、以下のようにして得た。
I. 従来と同様の方法で、Bi、Pb、Sr、Ca、Cuの各粉末を1.8：0.3：1.9：2：3の割合で混合して混合粉末を作製し、大気中にて800℃以上の熱処理を数回行う。各熱処理後にそれぞれ粉砕を行う。得られた粉末を更に800℃×2時間の熱処理を施して原料粉末を調整する。このように予め熱処理によって吸着ガス成分の含有量を低減させた酸化物超電導体の原料粉末(Bi2212、Ca2CuO3、Ca2PbO4などの混合物)を銀パイプに充填する。原料粉末の充填は、乾燥エアを流して浄化したグローブボックス内で行う。本例において銀パイプは、一端の開口部に銀製の蓋を溶接した肉厚2mm、内径φ30mmのものを用いた。また、本例では、いずれの試料も、原料粉末を銀パイプに充填する際の充填密度を25％とした。 A superconducting wire was obtained as follows.
I. Using the same method as before, Bi, Pb, Sr, Ca, Cu powders were mixed at a ratio of 1.8: 0.3: 1.9: 2: 3 to produce a mixed powder, and 800 ° C or higher in the atmosphere The heat treatment is performed several times. Grinding is performed after each heat treatment. The obtained powder is further subjected to a heat treatment at 800 ° C. for 2 hours to prepare a raw material powder. In this way, the raw material powder (mixture of Bi2212, Ca 2 CuO 3 , Ca 2 PbO 4, etc.) of the oxide superconductor in which the content of the adsorbed gas component is previously reduced by heat treatment is filled into the silver pipe. Filling the raw material powder is performed in a glove box purified by flowing dry air. In this example, a silver pipe having a wall thickness of 2 mm and an inner diameter of 30 mm with a silver lid welded to an opening at one end was used. Moreover, in this example, the filling density at the time of filling a raw material powder into a silver pipe was 25% in this example.

II. 原料粉末を充填した銀パイプを所定の温度(本例では0℃〜650℃、後述する図3参照)まで加熱して脱ガス処理を行う。本例では、400℃まで大気圧にて昇温し、400℃以上から徐々に排気を行って減圧しながら加熱を行う。   II. The silver pipe filled with the raw material powder is heated to a predetermined temperature (in this example, 0 ° C. to 650 ° C., see FIG. 3 described later) to perform degassing treatment. In this example, the temperature is raised to 400 ° C. at atmospheric pressure, the exhaust is gradually exhausted from 400 ° C. or higher, and heating is performed while reducing the pressure.

III. 上記昇温後、適宜加熱を続けながら銀パイプ内を10Pa以下に減圧する。大気圧から10Pa以下に減圧する際の減圧速度を2kPa/minとした。そして、10Pa以下で10時間保持した。   III. After the above temperature rise, the inside of the silver pipe is depressurized to 10 Pa or less while continuing to heat appropriately. The depressurization rate when depressurizing from atmospheric pressure to 10 Pa or less was 2 kPa / min. And it hold | maintained at 10 Pa or less for 10 hours.

IV. 銀パイプ内に存在する空隙部を真空(10Pa以下)に維持した状態で、銀パイプ他端の開口部に銀製の蓋をロウ付けして封止する。本例では、脱ガス処理からロウ付け封止工程までを図1に示す真空封止装置にて行った。   IV. With the void existing in the silver pipe maintained in a vacuum (10 Pa or less), a silver lid is brazed to the opening at the other end of the silver pipe and sealed. In this example, the process from the degassing process to the brazing sealing process was performed by the vacuum sealing apparatus shown in FIG.

図1(A)は、金属パイプの加熱及びロウ付けによる封止を行う真空封止装置の概略図、(B)は、蓋の拡大断面図である。なお、図面の説明においては同一要素には同一符号を付し、重複する説明を省略する。また、図面の寸法比率は、説明のものと必ずしも一致していない。この真空封止装置10は、真空容器11内に金属パイプ1を保持するリフトシリンダ12と、シリンダ12に支持されたパイプ1の外周を覆うように配置されるヒータ13と、一端にパイプ1の蓋3bを支持すると共にシリンダ12と対向するように配置される昇降式操作棒14とを具える。また、加熱により発生したガス及び減圧の際の空気などを排気する排気口15を具える。   FIG. 1A is a schematic view of a vacuum sealing device that seals a metal pipe by heating and brazing, and FIG. 1B is an enlarged cross-sectional view of a lid. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings do not necessarily match those described. The vacuum sealing device 10 includes a lift cylinder 12 that holds a metal pipe 1 in a vacuum vessel 11, a heater 13 that is arranged to cover the outer periphery of the pipe 1 supported by the cylinder 12, and the pipe 1 at one end. An elevating operation rod 14 is provided to support the lid 3b and to be opposed to the cylinder 12. In addition, an exhaust port 15 is provided for exhausting gas generated by heating and air during decompression.

この真空封止装置10による脱ガス処理から金属パイプ1を封止する手順を説明する。まず、真空容器11を開けて、一端に蓋3aが溶接されると共に原料粉末2を充填した金属パイプ1をリフトシリンダ12に配置し、蓋3bを昇降式操作棒14の先端に配置して真空容器11を閉じる。リフトシリンダ12を適当な位置に上下させて金属パイプ1をヒータ13の内周側に配置させて、ヒータ13にてパイプ1を加熱する。加熱後、排気バルブ16を開け、真空容器11内の大気を真空ポンプ17にて排気して減圧する。本例では、排気配管18に流量調整メータ19を具えており、メータ19にて排気する流量を制御して減圧速度を調整することができる。所定の圧力に減圧したら排気バルブ16、メータバルブ20を閉める。昇降式操作棒14を下方に下ろして、ヒータ13の上方に具える高周波加熱コイル21の内周側に蓋3bを配置させて、コイル21にて蓋3bに配置したリング状のロウ3c(図1(B)参照)を溶融する。ヒータ13と高周波加熱コイル21との間には断熱性のシャッタ22を具えており、それぞれの熱が互いに影響しない構成である。蓋3bのロウ3cが溶融されたら、リフトシリンダ12を上方に移動させ、昇降式操作棒14を下方に下げて金属パイプ1他端の開口部1aを封止する。このとき、のぞき窓23から金属パイプ1の開口部1aの位置を確認しながら昇降式操作棒14を下げる。本例では、昇降式操作棒を手動式としたが、自動式でもよい。上記の手順にて、金属パイプが封止される。なお、試験例1の場合は、ヒータ13による加熱を行わず、減圧を行った。   A procedure for sealing the metal pipe 1 from the degassing process by the vacuum sealing device 10 will be described. First, the vacuum vessel 11 is opened, the lid 3a is welded to one end and the metal pipe 1 filled with the raw material powder 2 is placed on the lift cylinder 12, and the lid 3b is placed on the tip of the lifting operation rod 14 to create a vacuum. Close container 11. The lift cylinder 12 is moved up and down to an appropriate position so that the metal pipe 1 is disposed on the inner peripheral side of the heater 13 and the pipe 1 is heated by the heater 13. After the heating, the exhaust valve 16 is opened, and the atmosphere in the vacuum vessel 11 is exhausted by the vacuum pump 17 to reduce the pressure. In this example, the exhaust pipe 18 is provided with a flow rate adjustment meter 19, and the pressure reduction rate can be adjusted by controlling the flow rate exhausted by the meter 19. When the pressure is reduced to a predetermined pressure, the exhaust valve 16 and the meter valve 20 are closed. The elevating operation rod 14 is lowered, a lid 3b is disposed on the inner peripheral side of the high-frequency heating coil 21 provided above the heater 13, and the ring-shaped brace 3c disposed on the lid 3b by the coil 21 (FIG. Melt 1). A heat insulating shutter 22 is provided between the heater 13 and the high frequency heating coil 21, and each heat does not affect each other. When the wax 3c of the lid 3b is melted, the lift cylinder 12 is moved upward and the elevating operation rod 14 is lowered downward to seal the opening 1a at the other end of the metal pipe 1. At this time, the elevating operation rod 14 is lowered while checking the position of the opening 1a of the metal pipe 1 from the observation window 23. In this example, the lifting operation rod is a manual type, but an automatic type may be used. The metal pipe is sealed by the above procedure. In the case of Test Example 1, pressure reduction was performed without heating by the heater 13.

V. 銀パイプ内に空気などが侵入しないように銀製の蓋をしたままの状態で伸線加工を施し、線材化してクラッド線材を得る。以降の手順は従来の製造方法と同様である。   V. Perform wire drawing with the silver lid on to prevent air from entering the silver pipe, and turn it into a wire to obtain a clad wire. The subsequent procedure is the same as the conventional manufacturing method.

VI. クラッド線材を複数本束ねて銀パイプ(外径36mm、内径30mm)に挿入して、このパイプ端部の開口部を銀製の蓋にて真空中で封止する。本例では、55本のクラッド線材を用いた。   VI. A plurality of clad wires are bundled and inserted into a silver pipe (outer diameter 36 mm, inner diameter 30 mm), and the opening at the end of the pipe is sealed in a vacuum with a silver lid. In this example, 55 clad wires were used.

VII. 銀パイプ内に空気などが侵入しないように、銀製の蓋をしたままの状態で伸線加工を施し、線材化して多芯線材を得る。本例では、直径φ1.6mmまで伸線した。   VII. To prevent air from entering the silver pipe, the wire is drawn with the silver lid on, and the wire is turned into a multi-core wire. In this example, the wire was drawn to a diameter of φ1.6 mm.

VIII. 多芯線材を幅4mm、厚さ0.2mmのテープ状に圧延してテープ状線材を得る。   VIII. A multifilament wire is rolled into a tape with a width of 4 mm and a thickness of 0.2 mm to obtain a tape-like wire.

IX. 長さ500mのテープ状線材において、フィラメント内にBi2223相の超電導体を生成させるための一次熱処理を行う。更に、中間圧延と、Bi2223相の結晶粒同士を接合させて超電導体を一体化するための追加熱処理を行う。   IX. Primary heat treatment is performed to form a Bi2223 phase superconductor in the filament of a tape-like wire having a length of 500 m. Furthermore, intermediate rolling and additional heat treatment are performed to join the Bi2223 phase crystal grains to integrate the superconductor.

上記のようにして得られた超電導線材において、一次熱処理後の線材に発生した膨れなどの欠陥の個数を調べた。また、追加熱処理後の線材に対して、77k、自己磁場中における臨界電流密度(Jc)を測定した。その結果を図3に示す。   In the superconducting wire obtained as described above, the number of defects such as blisters generated in the wire after the primary heat treatment was examined. In addition, the critical current density (Jc) in a self-magnetic field was measured at 77 k for the wire after the additional heat treatment. The results are shown in FIG.

図3に示すように脱ガス処理の加熱温度が400℃以上である場合、500mという長尺な超電導線材であっても、膨れなどの欠陥がほとんど見られなかった。一方、400℃未満の場合では、水分や炭素などの残留不純物量が多く、膨れが発生していた。また、脱ガス処理の加熱温度が400℃以上である場合、400℃未満の場合と比較して臨界電流密度(Jc)が全長に亘って非常に高い値を示した。臨界電流密度の最高値も、脱ガス処理の加熱温度が400℃以上の場合の方が400℃未満の場合よりも大きかった。   As shown in FIG. 3, when the degassing heating temperature was 400 ° C. or higher, defects such as blisters were hardly observed even with a superconducting wire as long as 500 m. On the other hand, when the temperature was lower than 400 ° C., the amount of residual impurities such as moisture and carbon was large, and swelling occurred. In addition, when the heating temperature of the degassing treatment was 400 ° C. or higher, the critical current density (Jc) showed a very high value over the entire length as compared with the case of less than 400 ° C. The maximum critical current density was also greater when the degassing heating temperature was 400 ° C or higher than when it was less than 400 ° C.

なお、本例では、ロウ付けによる真空封止装置を用いたが、電子ビームにより、蓋を溶接することで金属パイプを封止してもよいし、図4及び5に示すような排気ノズルを圧着することで金属パイプを封止してもよい。図4及び5に示す装置は、排気ノズルの圧着による真空封止装置であり、いずれも基本的構成がほぼ同様であり、図4は、金属パイプを垂直方向に支持するタイプ、図5は、金属パイプを水平方向に支持するタイプのものである。これら装置による金属パイプの封止手順を図4にて説明する。この装置30は、金属パイプ1の外周を覆うように配置されるヒータ31と、パイプ1端部の開口部1aに取り付けられる排気ノズル32と、ノズル32に連結される真空ポンプ33とを具える。この装置30では、まず、原料粉末を充填した金属パイプ1を枠体34に配置して、パイプ1端部の開口部1aに排気ノズル32を溶接する。この状態で金属パイプ1をヒータ31で加熱し、加熱後、排気ノズル32を介して真空ポンプ33にて金属パイプ1内に存在するガスを排気して減圧する。減圧の際は、流量調整バルブ35にて排気する流量を制御することで、減圧速度を調整可能である。真空度は、真空計36にて確認できる。所定の圧力に減圧したらバルブ37を閉めて真空ポンプ33との接続を解除する。そして、圧着器(図示せず)にて、排気ノズル32を圧着することで金属パイプ端部の開口部を封止する。圧着した後、金属パイプ1を装置30から取り外す。   In this example, a brazing vacuum sealing device was used. However, the metal pipe may be sealed by welding a lid with an electron beam, or an exhaust nozzle as shown in FIGS. The metal pipe may be sealed by pressure bonding. The devices shown in FIGS. 4 and 5 are vacuum sealing devices by pressure bonding of the exhaust nozzle, and the basic configuration is almost the same, FIG. 4 is a type that supports a metal pipe in the vertical direction, and FIG. It is the type that supports the metal pipe in the horizontal direction. The procedure for sealing the metal pipe by these devices will be described with reference to FIG. The device 30 includes a heater 31 disposed so as to cover the outer periphery of the metal pipe 1, an exhaust nozzle 32 attached to the opening 1a at the end of the pipe 1, and a vacuum pump 33 connected to the nozzle 32. . In this apparatus 30, first, the metal pipe 1 filled with the raw material powder is disposed on the frame body 34, and the exhaust nozzle 32 is welded to the opening 1a at the end of the pipe 1. In this state, the metal pipe 1 is heated by the heater 31, and after the heating, the gas existing in the metal pipe 1 is exhausted by the vacuum pump 33 through the exhaust nozzle 32 and decompressed. At the time of depressurization, the depressurization speed can be adjusted by controlling the flow rate exhausted by the flow rate adjusting valve 35. The degree of vacuum can be confirmed with a vacuum gauge 36. When the pressure is reduced to a predetermined pressure, the valve 37 is closed and the connection with the vacuum pump 33 is released. And the opening part of a metal pipe end part is sealed by crimping | bonding the exhaust nozzle 32 with a crimping machine (not shown). After the crimping, the metal pipe 1 is removed from the apparatus 30.

(試験例3)
次に、クラッド線材の製造工程において、原料粉末の充填密度を種々変更して超電導線材を作製して膨れなどの欠陥の有無、臨界電流密度を調べてみた。 (Test Example 3)
Next, in the manufacturing process of the clad wire, the superconducting wire was produced by changing the packing density of the raw material powders, and the presence or absence of defects such as blistering and the critical current density were examined.

超電導線材は、試験例2と同様にして得た。充填密度は、充填する原料粉末の理論密度を100％とし、この理論密度に対する割合を示す。充填密度は、以下のようにして変化させた。30％以上40％以下の充填密度は、原料粉末を湿式造粒機で造粒した粉末を充填することで得られた。40％超の充填密度は、原料粉末をCIP(静水圧プレス)にて棒状体に成形した成形体を充填することで得られた。なお、脱ガス処理の加熱温度は、640℃とし、400℃まで大気圧で昇温して400℃以上から徐々に排気して減圧しながら加熱した。   A superconducting wire was obtained in the same manner as in Test Example 2. The packing density indicates the ratio of the theoretical density of the raw material powder to be filled to 100% and the theoretical density. The packing density was changed as follows. A packing density of 30% or more and 40% or less was obtained by filling a powder obtained by granulating a raw material powder with a wet granulator. A filling density of more than 40% was obtained by filling a molded body obtained by forming the raw material powder into a rod-shaped body by CIP (hydrostatic pressure press). The heating temperature for the degassing treatment was 640 ° C., the temperature was raised to 400 ° C. at atmospheric pressure, the exhaust gas was gradually exhausted from 400 ° C. or higher, and the pressure was reduced.

試験例2と同様にして得られた超電導線材において、試験例2と同様に一次熱処理後の線材に発生した膨れなどの欠陥の個数を調べた。また、追加熱処理後の線材に対して、77k、自己磁場中における臨界電流密度(Jc)を測定した。その結果を図6に示す。   In the superconducting wire obtained in the same manner as in Test Example 2, the number of defects such as blisters generated in the wire after the primary heat treatment was examined in the same manner as in Test Example 2. In addition, the critical current density (Jc) in a self-magnetic field was measured at 77 k for the wire after the additional heat treatment. The results are shown in FIG.

図6に示すように充填密度が10％以上40％以下の場合、膨れなどの欠陥が少なく、かつ超電導線材の全長に亘って高い臨界電流密度(Jc)が得られた。また、この範囲では、臨界電流密度(Jc)の最高値も高かった。特に、充填密度が10％以上30％以下であると、膨れなどの欠陥がほとんどなく、より好ましいことが分かる。なお、充填密度が30％〜40％の超電導線材は、10％以上30％以下の超電導線材と比較して加工性が低下する傾向にあった。また、この傾向は、充填密度が大きくなるほど顕著であった。   As shown in FIG. 6, when the packing density was 10% or more and 40% or less, defects such as blistering were few and a high critical current density (Jc) was obtained over the entire length of the superconducting wire. In this range, the maximum critical current density (Jc) was also high. In particular, it can be seen that when the packing density is 10% or more and 30% or less, there is almost no defect such as blistering, which is more preferable. In addition, the superconducting wire having a filling density of 30% to 40% tended to have lower workability than the superconducting wire having a density of 10% to 30%. Moreover, this tendency became more remarkable as the packing density increased.

一方、充填密度が10％未満では、膨れなどの欠陥は発生していないが、超電導線材の長さ方向において臨界電流密度にばらつきが大きく、全長に亘る臨界電流密度が低くなった。これは、充填密度が10％未満であると、金属パイプに原料粉末が均一に充填されにくく、伸線加工後のフィラメントが長さ方向に不均一になったためと考えられる。   On the other hand, when the packing density was less than 10%, defects such as blistering did not occur, but the critical current density varied greatly in the length direction of the superconducting wire, and the critical current density over the entire length was low. This is considered to be because when the filling density is less than 10%, it is difficult to uniformly fill the metal pipe with the raw material powder, and the filament after the wire drawing process becomes non-uniform in the length direction.

他方、充填密度が40％超では、膨れなどの欠陥が非常に多く発生し、かつ超電導線材の長さ方向において臨界電流密度にばらつきが大きく、全長に亘る臨界電流密度が低くなった。充填密度が40％超であると、金属パイプの通気性が悪くなり、パイプの中央部まで均一な脱ガスを行うことができず、炭素や水分などの残留不純物量が多くなることで、膨れなどの欠陥が発生すると考えられる。また、残留不純物が超電導相の結晶間にアモルファス相となって析出し、このアモルファス相が電流のパスを遮断し易いこと、及び残留不純物により脱ガス処理の際に焼結作用が顕著となって、その後の伸線加工においてソーセージングなどの不均一な変形を起こすことなどから、臨界電流密度が低下すると考えられる。   On the other hand, when the packing density is more than 40%, defects such as blisters occur very often, the critical current density varies greatly in the length direction of the superconducting wire, and the critical current density over the entire length decreases. If the packing density exceeds 40%, the air permeability of the metal pipe will deteriorate, and uniform degassing will not be possible up to the center of the pipe, and the amount of residual impurities such as carbon and moisture will increase, resulting in swelling. Such defects are considered to occur. In addition, residual impurities are precipitated as an amorphous phase between the crystals of the superconducting phase, and this amorphous phase easily interrupts the current path, and the residual impurities make the sintering action remarkable during the degassing process. It is considered that the critical current density is lowered due to non-uniform deformation such as sausaging in the subsequent wire drawing.

本発明は、膨れなどの欠陥が少なく、優れた臨界電流密度を有する超電導線材の製造に適用することが好ましい。   The present invention is preferably applied to the production of a superconducting wire having few defects such as blistering and having an excellent critical current density.

(A)は、金属パイプの加熱及びロウ付けによる封止を行う真空封止装置の概略図、(B)は、蓋の拡大断面図である。(A) is a schematic view of a vacuum sealing device that seals a metal pipe by heating and brazing, and (B) is an enlarged cross-sectional view of a lid. 試験例1における充填密度に対する膨れなどの欠陥の発生個数及び臨界電流密度を示すグラフである。4 is a graph showing the number of defects such as blisters and the critical current density with respect to the packing density in Test Example 1. 試験例2における脱ガス処理の加熱温度に対する膨れなどの欠陥の発生個数及び臨界電流密度を示すグラフである。5 is a graph showing the number of defects such as blistering and the critical current density with respect to the heating temperature of the degassing process in Test Example 2. 金属パイプの加熱及び排気ノズルの圧着による封止を行う真空封止装置の概略図であって、金属パイプを垂直方向に支持するタイプである。It is the schematic of the vacuum sealing apparatus which seals by heating of a metal pipe and crimping | compression-bonding of an exhaust nozzle, Comprising: It is a type which supports a metal pipe in a perpendicular direction. 金属パイプの加熱及び排気ノズルの圧着による封止を行う真空封止装置の概略図であって、金属パイプを水平方向に支持するタイプである。It is the schematic of the vacuum sealing apparatus which seals by heating of a metal pipe and crimping | compression-bonding of an exhaust nozzle, Comprising: It is a type which supports a metal pipe in a horizontal direction. 試験例3における充填密度に対する膨れなどの欠陥の発生個数及び臨界電流密度を示すグラフである。6 is a graph showing the number of defects such as blistering and the critical current density with respect to the packing density in Test Example 3.

符号の説明Explanation of symbols

1 金属パイプ 1a 開口部 2 原料粉末 3a、3b 蓋 3c ロウ
10 真空封止装置 11 真空容器 12 リフトシリンダ 13 ヒータ
14 昇降式操作棒 15 排気口 16 排気バルブ 17 真空ポンプ
18 排気配管 19 流量メータ 20 メータバルブ 21 高周波加熱コイル
22 シャッタ 23 のぞき窓
30 真空封止装置 31 ヒータ 32 排気ノズル 33 真空ポンプ 34 枠体
35 流量調整バルブ 36 真空計 37 バルブ 1 Metal pipe 1a Opening 2 Raw material powder 3a, 3b Lid 3c Wax
10 Vacuum sealing device 11 Vacuum container 12 Lift cylinder 13 Heater
14 Lifting operation rod 15 Exhaust port 16 Exhaust valve 17 Vacuum pump
18 Exhaust piping 19 Flow meter 20 Meter valve 21 High frequency heating coil
22 Shutter 23 Peep window
30 Vacuum sealing device 31 Heater 32 Exhaust nozzle 33 Vacuum pump 34 Frame
35 Flow adjustment valve 36 Vacuum gauge 37 Valve

Claims (5)

酸化物超電導体からなる原料粉末、又は熱処理にて酸化物超電導体となる前駆体からなる原料粉末を金属パイプに充填する工程と、
前記原料粉末を充填した金属パイプを400℃以上800℃以下に加熱する工程と、
前記加熱した金属パイプ内を100Pa以下に減圧する工程と、
前記減圧した状態にて金属パイプ端部の開口部を封止する工程と、
前記原料粉末が封入された金属パイプを伸線加工する工程とを具え、
前記原料粉末の充填密度が10％以上40％以下であり、
前記加熱工程による昇温を開始した後、前記減圧工程における排気を開始することを特徴とする超電導線材の製造方法。 Filling a metal pipe with a raw material powder made of an oxide superconductor or a raw material powder made of a precursor that becomes an oxide superconductor by heat treatment; and
Heating the metal pipe filled with the raw material powder to 400 ° C. or higher and 800 ° C. or lower;
Reducing the pressure in the heated metal pipe to 100 Pa or less;
Sealing the opening at the end of the metal pipe in the decompressed state;
A step of drawing a metal pipe enclosing the raw material powder,
Ri packing density der 10% to 40% of the raw material powder,
After starting the temperature rising by the said heating process, the exhaust_gas | exhaustion in the said pressure reduction process is started , The manufacturing method of the superconducting wire characterized by the above-mentioned . 酸化物超電導体からなる原料粉末、又は熱処理にて酸化物超電導体となる前駆体からなる原料粉末を、金属パイプに充填する工程の前に、400℃以上800℃以下で熱処理する工程を具えることを特徴とする請求項1に記載の超電導線材の製造方法。 It includes a step of heat-treating a raw material powder made of an oxide superconductor or a raw material powder made of a precursor that becomes an oxide superconductor by heat treatment at a temperature of 400 ° C. or higher and 800 ° C. or lower before the step of filling the metal pipe. 2. The method for producing a superconducting wire according to claim 1 , wherein: 減圧工程において、減圧速度を2kPa/min以下とすることを特徴とする請求項1または2に記載の超電導線材の製造方法。 3. The method of manufacturing a superconducting wire according to claim 1, wherein the pressure reduction rate is 2 kPa / min or less in the pressure reduction step. 金属パイプの封止は、電子ビーム溶接、ロウ付け、及び金属パイプに溶接した排気ノズルの圧着のいずれかにて行うことを特徴とする請求項1〜3のいずれかに記載の超電導線材の製造方法。 The superconducting wire according to any one of claims 1 to 3 , wherein the metal pipe is sealed by any one of electron beam welding, brazing, and pressure bonding of an exhaust nozzle welded to the metal pipe. Method. 前記加熱工程、減圧工程および封止工程を同一の真空容器内にて行う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の製造方法。  5. The method of manufacturing a superconducting wire according to claim 1, wherein the heating step, the pressure reduction step, and the sealing step are performed in the same vacuum vessel.
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