JP5330725B2 - Superconducting wire substrate and manufacturing method thereof - Google Patents
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Description
本発明は、超電導線材用基板およびその製造方法に係り、特に、基板表面の金属結晶の方位が揃い、かつ、該結晶のほとんどが長手方向に1を超えるアスペクト比を有することにより、優れた超電導特性を示す超電導線を可能にする超電導線材用基板およびその製造方法に関する。 The present invention relates to a substrate for a superconducting wire and a method for manufacturing the same, and in particular, excellent superconductivity because the orientation of metal crystals on the substrate surface is uniform and most of the crystals have an aspect ratio exceeding 1 in the longitudinal direction. The present invention relates to a substrate for a superconducting wire that enables a superconducting wire exhibiting characteristics and a method for manufacturing the same.
金属基板を用いた高温超電導線は、一般に、2軸配向多結晶金属基板上に、中間層として、下層側から例えばCeO2/YSZ/CeO2の3層構造を形成し、この中間層の上にさらに超電導層を成膜したものが知られている(例えば、特許文献1、2参照)。
A high-temperature superconducting wire using a metal substrate generally forms, for example, a CeO 2 / YSZ / CeO 2 three-layer structure as an intermediate layer on a biaxially oriented polycrystalline metal substrate from the lower layer side. Further, a superconducting layer is further formed (see, for example,
このような高温超電導線では、超電導層は酸化物高温超電導体であって、その組成はRE−Ba−Cu−O(RE:希土類金属)である。超電導層の上には安定化金属として銀などの金属が成膜されている。 In such a high-temperature superconducting wire, the superconducting layer is an oxide high-temperature superconductor, and its composition is RE-Ba-Cu-O (RE: rare earth metal). A metal such as silver is formed as a stabilizing metal on the superconducting layer.
高温超電導線の実用化のためには、線材幅あたりの超電導電流(臨界電流密度)は少なくとも100A/cm以上、望ましくは200A/cm以上が要求されている。しかしながら、配向金属基板を用いた超電導線では、その超電導層の臨界電流密度は、その超電導体の単結晶から得られる本来の臨界電流密度よりも低く、このため応用機器の開発や製作において、小型化や低コスト化の観点から問題となっていた。 In order to put a high-temperature superconducting wire into practical use, a superconducting current (critical current density) per wire width is required to be at least 100 A / cm, preferably 200 A / cm. However, in a superconducting wire using an oriented metal substrate, the critical current density of the superconducting layer is lower than the original critical current density obtained from the single crystal of the superconductor. It has become a problem from the viewpoint of cost reduction and cost reduction.
一般に、配向金属基板を用いた酸化物高温超電導線の製造においては、金属を強圧延加工してテープ状とし、それに配向熱処理を施して、少なくとも基板の表面層の結晶を2軸配向させた配向金属基板上に、中間層をエピタキシャル成長させ、さらにその中間層上に超電導層をエピタキシャル成長させる。 In general, in the production of oxide high-temperature superconducting wires using an oriented metal substrate, the metal is strongly rolled into a tape shape, and orientation heat treatment is applied thereto, so that at least the crystal of the surface layer of the substrate is biaxially oriented. An intermediate layer is epitaxially grown on the metal substrate, and a superconducting layer is epitaxially grown on the intermediate layer.
この超電導層の臨界電流特性は、超電導層内の各結晶粒の2軸配向性(超電導体結晶軸のa軸とb軸が面内にあり、そのa軸とb軸の方向が各結晶粒で揃っている状態)が高い(結晶方位が揃っている)ときに高い特性を示し、逆に一部の結晶粒の方位が大きくずれて(大傾角粒界が存在する状態)配向性が低いと、臨界電流特性が低いことが知られている。これは、結晶粒内の問題ではなく、大傾角結晶粒界では、粒界をまたいで流れる電流が大きく制限されるためである。結晶粒界では、傾角が4°以下のときは、比較的大きな超電導電流を流すことができるが、10°以上ではほとんど超電導電流を流すことはできない。 The critical current characteristic of this superconducting layer is the biaxial orientation of each crystal grain in the superconducting layer (the a-axis and b-axis of the superconductor crystal axis are in the plane, and the direction of the a-axis and b-axis is the direction of each crystal grain. Shows a high characteristic when the crystal orientation is uniform (the crystal orientation is uniform), and conversely, the orientation of some crystal grains is greatly shifted (a state where a large tilt grain boundary exists) and the orientation is low. It is known that the critical current characteristic is low. This is not a problem within the crystal grains, but the current flowing across the grain boundaries is greatly limited at the large tilt grain boundaries. At the crystal grain boundary, when the tilt angle is 4 ° or less, a relatively large superconducting current can flow, but when it is 10 ° or more, almost no superconducting current can flow.
超電導層は中間層上にエピタキシャルに成長するため、中間層の配向性が大きく超電導層の配向性に影響するのであるが、配向金属基板上に最初の中間層(シード層)を成膜した時点で、ほぼ中間層の配向性状は決定される。配向金属基板の基板表面における2軸配向組織({001}<100>方向を有する結晶)の面積率(%)と超電導層の臨界電流については、これまでに概ね図1に示すような結果が得られている。 Since the superconducting layer grows epitaxially on the intermediate layer, the orientation of the intermediate layer is large and affects the orientation of the superconducting layer, but when the first intermediate layer (seed layer) is formed on the oriented metal substrate Thus, the orientation property of the intermediate layer is almost determined. Regarding the area ratio (%) of the biaxially oriented structure (crystal having {001} <100> direction) and the critical current of the superconducting layer on the substrate surface of the oriented metal substrate, the results as shown in FIG. Has been obtained.
即ち、配向金属基板における2軸配向組織の面積率(%)が向上するにつれ、シード層の配向性も向上し、それにより超電導層の配向性も向上し、超電導層での結晶流界の傾角は小さくなり臨界電流が大きく向上する。これまでの研究から、配向金属基板の配向性のわずかな乱れがシード層、ひいては、超電導層の配向性に大きな影響を及ぼすため、このような曲線が得られることがわかっている。 That is, as the area ratio (%) of the biaxially oriented structure in the oriented metal substrate improves, the orientation of the seed layer also improves, thereby improving the orientation of the superconducting layer, and the tilt angle of the crystal flow field in the superconducting layer. Becomes smaller and the critical current is greatly improved. From previous studies, it has been found that such a curve can be obtained because a slight disturbance in the orientation of the oriented metal substrate has a great influence on the orientation of the seed layer and thus the superconducting layer.
従来の配向金属基板は、Cu、Ni、Agなどの純金属あるいはその合金に90%以上の強圧延加工を施し、その後、再結晶熱処理をすることによって得られる立方体集合組織と呼ばれる2軸配向組織を用いている。これまでは、比較的完全な2軸配向組織を得やすい組成を選択して基板としてきたが、近年では、超電導線材の強度を向上させるため、あるいは、交流損失を低減するために、合金元素を多く添加した金属基板や、別途強化材を複合した複合基板の開発が行われている。 A conventional oriented metal substrate is a biaxially oriented structure called a cubic texture obtained by subjecting a pure metal such as Cu, Ni, Ag or the like to a strong rolling process of 90% or more and then performing a recrystallization heat treatment. Is used. Until now, the substrate has been selected by selecting a composition that makes it possible to obtain a relatively complete biaxially oriented structure. However, in recent years, in order to improve the strength of the superconducting wire or to reduce the AC loss, the alloy element is used. Developments have been made on metal substrates with a large amount of addition and composite substrates with separate reinforcements.
しかし、こうした高濃度合金基板では、純〜希薄合金金属に比べ、積層欠陥エネルギーが著しく低くなることから、また、複合基板においてもその複雑な構造による応力状態や元素の拡散などの問題から、単純な圧延加工と再結晶熱処理を行っても、完全な立方体集合組織を得ることは非常に困難である。
本発明は、以上のような事情の下になされ、基板の表面特性を改善して、優れた臨界電流特性を示す超電導線材を具現化するための超電導線材用基板及びその製造方法を提供することを目的とする。 The present invention has been made under the circumstances as described above, and provides a substrate for a superconducting wire for realizing a superconducting wire exhibiting excellent critical current characteristics by improving the surface characteristics of the substrate and a method for manufacturing the same. With the goal.
上記課題を解決するため、本発明の第1の態様は、少なくとも表面がNi,WからなるNi合金からなる基板に対して、板厚減少率80%以上の圧延を行う第1の圧延工程と、前記第1の圧延工程を経た前記基板を、前記Ni合金の融点(℃)の0.2〜0.5倍の温度で熱処理を行う第1の熱処理工程と、前記第1の熱処理工程を経た前記基板に対して、板厚減少率10〜50%の圧延を行う第2の圧延工程と、前記第2の圧延工程を経た前記基板に対して、還元性雰囲気中において前記Ni合金の融点(℃)に対して0.5〜0.8倍の温度で熱処理を行う第2の熱処理工程とを具備することを特徴とする超電導線用基板の製造方法を提供する。 In order to solve the above-mentioned problem, the first aspect of the present invention includes a first rolling step in which rolling is performed at a thickness reduction rate of 80% or more on a substrate made of a Ni alloy having at least a surface made of Ni and W. The first heat treatment step of heat treating the substrate that has undergone the first rolling step at a temperature 0.2 to 0.5 times the melting point (° C.) of the Ni alloy , and the first heat treatment step. A second rolling step for rolling the substrate having undergone a sheet thickness reduction rate of 10 to 50%, and a melting point of the Ni alloy in a reducing atmosphere with respect to the substrate that has undergone the second rolling step. And a second heat treatment step of performing a heat treatment at a temperature 0.5 to 0.8 times that of (° C.) . A method for manufacturing a substrate for a superconducting wire is provided.
前記第1の圧延工程前に、前記基板に対して圧延および焼鈍を行う工程を更に具備することができる。 A step of rolling and annealing the substrate can be further included before the first rolling step.
前記金属としては、Ni、Cu、及びAgからなる群から選ばれた金属の1種またはそれを含む合金を用いることが出来る。 As the metal, one kind of metal selected from the group consisting of Ni, Cu, and Ag or an alloy containing the metal can be used.
前記基体の表面の金属を少なくともNiを含むものとし、前記第1の熱処理工程における熱処理温度を450〜700℃とし、前記第2の熱処理工程における熱処理温度を800〜1200℃とすることが出来る。 The metal on the surface of the substrate may contain at least Ni, the heat treatment temperature in the first heat treatment step may be 450 to 700 ° C., and the heat treatment temperature in the second heat treatment step may be 800 to 1200 ° C.
本発明の第2の態様は、少なくとも一方の表面が金属からなる超電導線用基板において、前記表面における{001}<100>方向を有する結晶の面積率が80%以上であって、前記金属の基板の長手方向における結晶粒の長さが基板の幅方向の結晶粒の長さの1.1〜2倍であることを特徴とする超電導線用基板を提供する。 According to a second aspect of the present invention, in the superconducting wire substrate having at least one surface made of metal, an area ratio of crystals having a {001} <100> direction on the surface is 80% or more, the length of the crystal grains in the longitudinal direction of the substrate to provide a substrate for a superconducting wire, which is a 1.1 to 2 times the grain length in the width direction of the substrate.
前記金属として、Ni、Cu、及びAgからなる群から選ばれた金属の1種またはそれを含む合金を用いることが出来る。 As the metal, one kind of metal selected from the group consisting of Ni, Cu, and Ag, or an alloy containing the metal can be used.
本発明によると、基板表面の金属結晶の方位が揃い、かつ、該結晶のほとんどが長手方向に1を超えるアスペクト比を有することにより、優れた超電導特性を示す超電導線を可能にする超電導線材用基板およびその製造方法が提供される。 According to the present invention, the orientation of metal crystals on the substrate surface is aligned, and most of the crystals have an aspect ratio exceeding 1 in the longitudinal direction, thereby enabling a superconducting wire exhibiting excellent superconducting properties. A substrate and a method for manufacturing the same are provided.
以下、本発明の実施形態について説明する。 Hereinafter, embodiments of the present invention will be described.
本発明の第1の実施形態に係る超電導線材用基板の製造方法では、2度の熱処理工程とその間に行う圧延工程により、第1の熱処理により生じた立方体集合組織が第1の圧延工程により歪みを受け、さらに第2の熱処理工程による歪み粒界移動により他方位の結晶粒を浸食しながら再結晶化が生じ、より配向性に優れた表面組織を有する超電導線材用基板を得ることができる。また、第1の熱処理で生じた立方体集合組織を有する結晶粒は、圧延工程により長手方向に1を超えるアスペクト比を有することなり、電流パスとなる結晶界面距離を大きくとることができる。 In the method for manufacturing a substrate for a superconducting wire according to the first embodiment of the present invention, the cube texture generated by the first heat treatment is distorted by the first rolling step due to the two heat treatment steps and the rolling step performed therebetween. In addition, recrystallization occurs while eroding the crystal grains on the other side due to the movement of the strain grain boundaries in the second heat treatment step, and a substrate for a superconducting wire having a surface structure with more excellent orientation can be obtained. Further, the crystal grains having a cubic texture generated by the first heat treatment have an aspect ratio exceeding 1 in the longitudinal direction by the rolling process, and a crystal interface distance serving as a current path can be increased.
このように、基板の表面金属が、歪み粒界移動を用いて形成されることで、基板表面の結晶が高度に2軸配向し、各結晶粒界の傾角は小さくなり、粒界での臨界電流密度の低下が抑制され、通電する超電導層側となる基板表面で、より多くの電流を結晶から結晶へ流すことが可能となる。 In this way, the surface metal of the substrate is formed using strain grain boundary movement, so that the crystal on the substrate surface is highly biaxially oriented, the tilt angle of each crystal grain boundary is reduced, and the criticality at the grain boundary is reduced. A decrease in current density is suppressed, and more current can flow from crystal to crystal on the substrate surface on the superconducting layer side to be energized.
第1の圧延工程で、板厚減少率を80%以上とすることで、第1の熱処理工程において立方体方位結晶を十分に析出させることができる。また、板厚減少率が80%未満の場合には、第1の熱処理工程において立方体方位結晶が十分に析出せず、続く第2の圧延工程と第2の熱処理工程を施しても立方体方位の高い集積を得ることができないという問題点がある。 By setting the plate thickness reduction rate to 80% or more in the first rolling step, the cubic orientation crystals can be sufficiently precipitated in the first heat treatment step. Further, when the plate thickness reduction rate is less than 80%, the cubic orientation crystals are not sufficiently precipitated in the first heat treatment step, and the cube orientation is not affected even if the second rolling step and the second heat treatment step are performed. There is a problem that high accumulation cannot be obtained.
また、第2の圧延工程で、板厚減少率が10〜50%とすることで、立方体方位が歪み粒界移動により優先成長させることができる。また、板厚減少率が10%未満の場合には、立方体方位が優先成長するに充分な歪みが与えられないという問題点があり、板厚減少率が50%を超えた場合には、歪みが大きくなりすぎ他方位の結晶が優先成長するという問題点が生ずる。 In addition, in the second rolling step, by setting the sheet thickness reduction rate to 10 to 50%, the cube orientation can be preferentially grown by the strain grain boundary movement. In addition, when the plate thickness reduction rate is less than 10%, there is a problem in that sufficient strain is not given for the cube orientation to preferentially grow, and when the plate thickness reduction rate exceeds 50%, there is a strain. This causes a problem that the crystal on the other side is preferentially grown.
第1の熱処理工程における熱処理温度は、前記金属の融点に対して0.2〜0.5倍の温度であることが望ましい。このように、第1の熱処理工程の熱処理温度を基板の金属の融点に対して0.2〜0.5倍の温度で行うことによって、必要な立方体方位結晶を実用上好適な時間で析出させることができる。また、熱処理温度が金属の融点に対して0.2倍未満の場合には、立方体方位結晶が十分に析出しない、または、非常に長時間の熱処理を行わないと十分な析出が得られないという問題点があり、熱処理温度が金属の融点に対して0.5倍を超えた場合には、必要以上に再結晶が進んでしまう、あるいは、必要な立方体方位結晶を析出させるための時間が非常に短時間であり、実用上実施できないという問題点がある。 The heat treatment temperature in the first heat treatment step is preferably 0.2 to 0.5 times the melting point of the metal. In this way, by performing the heat treatment temperature in the first heat treatment step at a temperature 0.2 to 0.5 times the melting point of the metal of the substrate, the necessary cubic orientation crystals are precipitated in a practically suitable time. be able to. In addition, when the heat treatment temperature is less than 0.2 times the melting point of the metal, cubic orientation crystals are not sufficiently precipitated, or sufficient precipitation cannot be obtained unless heat treatment is performed for a very long time. There is a problem, and if the heat treatment temperature exceeds 0.5 times the melting point of the metal, recrystallization proceeds more than necessary, or the time required for precipitating the necessary cubic orientation crystals is very long However, it is a short time and cannot be implemented practically.
第2の熱処理工程における熱処理温度は、前記金属の融点に対して0.5〜0.8倍の温度であることが望ましい。このように、第2の熱処理工程の熱処理温度を基板の金属の融点に対して0.5〜0.8倍の温度で行うことによって、立方体方位を有する再結晶集合組織とすることができる。また、熱処理温度が金属の融点に対して0.5倍未満の場合には、温度が低く立方体方位を十分に集積できない、あるいは、十分な立方体方位を有する再結晶集合組織とするためには、非常に長い熱処理時間を必要となる問題点があり、熱処理温度が金属の融点に対して0.8倍を超えた場合には、温度が高すぎるため、非常に短い時間で熱処理を行わないと2次再結晶がすすみ、結晶粒が粗大化し、立方体集合組織が崩れてしまうという問題点がある。 The heat treatment temperature in the second heat treatment step is preferably 0.5 to 0.8 times the melting point of the metal. Thus, by performing the heat treatment temperature in the second heat treatment step at a temperature 0.5 to 0.8 times the melting point of the metal of the substrate, a recrystallized texture having a cubic orientation can be obtained. When the heat treatment temperature is less than 0.5 times the melting point of the metal, the temperature is low and the cube orientation cannot be sufficiently accumulated, or in order to obtain a recrystallized texture having a sufficient cube orientation, There is a problem that requires a very long heat treatment time. If the heat treatment temperature exceeds 0.8 times the melting point of the metal, the temperature is too high, so the heat treatment must be performed in a very short time. There is a problem that secondary recrystallization proceeds, crystal grains become coarse, and the cubic texture collapses.
第1の圧延工程前に、基板に対して圧延および焼鈍を行うことが望ましい。第1の圧延工程前に圧延および焼鈍を行う工程を入れることで、どんな形状の材料からも、所望の最終形状(厚さ)において、必要な第1の加工と第2の加工を行うことができるように初期形状(厚さ)を調整することができる。 It is desirable to perform rolling and annealing on the substrate before the first rolling step. By including a rolling and annealing step before the first rolling step, the necessary first and second processing can be performed from any shape of material in the desired final shape (thickness). The initial shape (thickness) can be adjusted as possible.
金属としては、Ni、Cu、及びAgからなる群から選ばれた金属の1種またはそれを含む合金を用いるのが望ましい。これらの金属を用いることにより、これらの金属は面心立方晶であるため、再結晶集合組織として2軸配向した立方体集合組織を得やすいからである。 As the metal, it is desirable to use one type of metal selected from the group consisting of Ni, Cu, and Ag or an alloy containing the same. This is because, by using these metals, these metals are face-centered cubic crystals, so that it is easy to obtain a biaxially oriented cubic texture as a recrystallized texture.
なお、基体の表面の金属が少なくともNiを含んだ場合には、前記第1の熱処理工程の熱処理温度は450〜700℃であり、かつ、前記第2の熱処理工程の温度は800〜1200℃であることが望ましい。基体の表面の金属がNiを含むことにより、Niを含む金属の融点1400〜1550℃であることに対して、第1の熱処理工程の熱処理温度を450〜700℃とすることで、必要な立方体方位結晶を実用上好適な時間で析出させることができ、また、第2の熱処理工程の温度を800〜1200℃とすることで高度に立方体方位に配向した結晶を実用上好適な時間で析出させることができる。 When the metal on the surface of the substrate contains at least Ni, the heat treatment temperature in the first heat treatment step is 450 to 700 ° C., and the temperature in the second heat treatment step is 800 to 1200 ° C. It is desirable to be. When the metal on the surface of the substrate contains Ni, the melting point of the metal containing Ni is 1400 to 1550 ° C., whereas the heat treatment temperature in the first heat treatment step is 450 to 700 ° C. An orientation crystal can be precipitated in a practically suitable time, and a crystal having a highly cubic orientation is precipitated in a practically suitable time by setting the temperature of the second heat treatment step to 800 to 1200 ° C. be able to.
第1の熱処理工程の熱処理温度を450℃未満とした場合には、必要な立方体方位結晶を析出させることができない、あるいは、必要な結晶粒を得るために長時間熱処理が必要となるため、好ましくない。また、700℃を超えた場合には、必要以上に再結晶が進んでしまう、あるいは、必要な立方体方位結晶を析出させるための時間が非常に短時間であり、実用上実施できないという問題がある。 When the heat treatment temperature of the first heat treatment step is less than 450 ° C., it is preferable because a necessary cubic orientation crystal cannot be precipitated or a long time heat treatment is required to obtain necessary crystal grains. Absent. In addition, when the temperature exceeds 700 ° C., recrystallization proceeds more than necessary, or the time required for precipitating a necessary cubic orientation crystal is very short, and there is a problem that it cannot be carried out practically. .
また、第2の熱処理工程の熱処理温度を800℃未満とした場合には、度が低く立方体方位を十分に集積できない、あるいは、十分な立方体方位を有する再結晶集合組織とするためには、非常に長い熱処理時間を必要となるため、好ましくなく、1200℃を超えた場合には、温度が高すぎるため、非常に短い時間で熱処理を行わないと2次再結晶がすすみ、結晶粒が粗大化し、立方体集合組織が崩れてしまうという問題がある。 In addition, when the heat treatment temperature in the second heat treatment step is less than 800 ° C., in order to obtain a recrystallized texture having a low degree, the cube orientation cannot be sufficiently accumulated, or having a sufficient cube orientation, It is not preferable because a long heat treatment time is required. When the temperature exceeds 1200 ° C., the temperature is too high. If the heat treatment is not performed in a very short time, secondary recrystallization proceeds and the crystal grains become coarse. There is a problem that the cube texture collapses.
本発明の第2の実施形態に係る超電導線用基板は、少なくとも一方の表面が金属からなり、前記表面における{001}<100>方向を有する結晶の面積率が80%以上であって、金属の結晶粒の長手方向長さが幅方向長さに対して1.1〜2倍であることを特徴とする。 The substrate for superconducting wires according to the second embodiment of the present invention has at least one surface made of metal, and the area ratio of crystals having the {001} <100> direction on the surface is 80% or more, The length in the longitudinal direction of the crystal grains is 1.1 to 2 times the length in the width direction.
このように、基板の表面金属が{001}<100>方向を有する結晶の面積率が80%以上の2軸配向組織を有することで、各結晶粒界の傾角は小さくなり、粒界での臨界電流密度の低下が抑制され、更に、長手方向に1.1以上のアスペクト比を有することにより、電流パスとなる結晶界面距離を大きくとることができることから、通電する超電導層側となる基板表面で、より多くの電流を結晶から結晶へ流すことが可能となる。同様の配向性(粒界傾角)を持つなら、アスペクト比が大きい方が、より大きな臨界電流を流すことができるが、アスペクト比を大きくするために強加工を施すと表面金属の配向性が著しく低下して粒界の傾角が大きくなり、超電導層において粒界をまたいで超電導電流がほとんど流れなくなるために、アスペクト比が大きくなった効果がほとんど現れない。なお、基板の表面金属の{001}<100>方向を有する結晶の面積率は、より好ましくは85%以上である。 Thus, since the surface metal of the substrate has a biaxially oriented structure in which the area ratio of crystals having the {001} <100> direction is 80% or more, the tilt angle of each crystal grain boundary becomes small, and The reduction of the critical current density is suppressed, and further, the crystal interface distance serving as a current path can be increased by having an aspect ratio of 1.1 or more in the longitudinal direction. Therefore, the substrate surface on the superconducting layer side to be energized Thus, a larger amount of current can be passed from crystal to crystal. If the aspect ratio is the same (grain boundary tilt angle), the larger the aspect ratio, the larger the critical current can be made to flow. As the angle is lowered and the tilt angle of the grain boundary is increased, and the superconducting current hardly flows across the grain boundary in the superconducting layer, the effect of increasing the aspect ratio hardly appears. The area ratio of the crystal having the {001} <100> direction of the surface metal of the substrate is more preferably 85% or more.
基板の表面を構成する金属としては、Ni、Cu、及びAgからなる群から選ばれた金属の1種またはそれを含む合金を用いることが出来る。 As the metal constituting the surface of the substrate, one kind of metal selected from the group consisting of Ni, Cu, and Ag or an alloy containing the same can be used.
このように、基板の表面金属を、Ni、Cu、及びAgからなる群から選ばれた金属の1種またはそれを含む合金からなるものとすることで、これらの金属は面心立方晶のため、再結晶集合組織として2軸配向した立方体集合組織を得やすいことから、基板の製造が容易となる。 As described above, the surface metal of the substrate is made of one kind of metal selected from the group consisting of Ni, Cu, and Ag or an alloy containing the same, so that these metals are face-centered cubic crystals. Since it is easy to obtain a biaxially oriented cubic texture as a recrystallized texture, it is easy to manufacture the substrate.
以上説明した本発明の第1及び第2の実施形態は、その基板上に形成される超電導層の超電導特性を改善するために、基板の金属表面の結晶粒の配向性に注目してなされた。 The first and second embodiments of the present invention described above have been made paying attention to the orientation of crystal grains on the metal surface of the substrate in order to improve the superconducting properties of the superconducting layer formed on the substrate. .
本実施形態において、基板の少なくとも表面は、ニッケルまたはその合金、銅またはその合金、銀またはその合金であるものが望ましい。ニッケルまたはその合金としては、例えばNi−3at%W、Ni−5at%W、Ni−7at%WなどのNi−W合金、Ni−Co、Ni−Fe、Ni−Mn、Ni−Cr、Ni−Vなどを挙げることができる。銅またはその合金としては、例えばCu−Cr、Cu−Mo、Cu−W、Cu−V、Cu−Snなどを挙げることができる。また、銀またはその合金としては、例えばAg−Mn、Ag−Mg、Ag−Mo、Ag−Crなどを挙げることができる。 In this embodiment, it is desirable that at least the surface of the substrate is nickel or an alloy thereof, copper or an alloy thereof, silver or an alloy thereof. Examples of nickel or an alloy thereof include Ni-W alloys such as Ni-3 at% W, Ni-5 at% W, Ni-7 at% W, Ni-Co, Ni-Fe, Ni-Mn, Ni-Cr, Ni- V etc. can be mentioned. Examples of copper or an alloy thereof include Cu—Cr, Cu—Mo, Cu—W, Cu—V, and Cu—Sn. Examples of silver or an alloy thereof include Ag-Mn, Ag-Mg, Ag-Mo, and Ag-Cr.
これら金属基板の表面金属は、結晶系が面心立方結晶系に属し、強圧延加工を行い易いという利点がある。このような強圧延加工と熱処理により、表面が立方体集合組織と呼ばれる2軸配向した結晶粒の集合体となり、超電導層の形成のための下地として好適に用いることができる。 The surface metal of these metal substrates has the advantage that the crystal system belongs to the face-centered cubic crystal system and is easy to perform strong rolling. By such strong rolling process and heat treatment, the surface becomes an aggregate of biaxially oriented crystal grains called a cubic texture, and can be suitably used as a base for forming a superconducting layer.
また、金属基板の強度や耐熱性を高めることや、金属基板の磁性を低くするなどのために、基板の芯となる部分に表面層と異なる金属を用いることもできる。ここで表面層と異なる芯材として、Ni−W合金、Ni−Fe合金、Ni−Mn合金、Ni−Co合金、Ni−Mg合金、Ni−V合金、Ni−Coなどの耐熱性と高強度と低磁性の特性を有する金属であればその種類を問わない。 Further, in order to increase the strength and heat resistance of the metal substrate, or to lower the magnetism of the metal substrate, a metal different from the surface layer can be used for the core portion of the substrate. Here, as a core material different from the surface layer, Ni-W alloy, Ni-Fe alloy, Ni-Mn alloy, Ni-Co alloy, Ni-Mg alloy, Ni-V alloy, Ni-Co, etc. heat resistance and high strength Any metal having low magnetic properties can be used.
これら芯材としての金属は、表面金属よりも高い強度を有しているので、複合則から、例えば同じ厚さの基板に対して、組み合わせない基板よりも強度を向上させることができる。 Since the metal as the core material has higher strength than the surface metal, it is possible to improve the strength, for example, with respect to substrates having the same thickness as compared with a substrate not combined with a substrate having the same thickness.
以上のような金属基板は、表面金属を2軸配向させるために、従来は90%以上の板厚減少率で圧延加工し、ついで還元性雰囲気で融点の40〜90%の温度で熱処理していたが、本発明においては、まず80%以上の板厚減少率で圧延加工し、融点の20〜50%の温度で熱処理を施して再結晶核を生成した後に、更に10〜50%の板厚減少率の圧延加工を施し、加えて、還元性雰囲気で融点の50〜80%の温度で熱処理を施して2軸配向組織を得るものである。 In order to make the surface metal biaxially oriented, the metal substrate as described above is conventionally rolled at a thickness reduction rate of 90% or more, and then heat-treated at a temperature of 40 to 90% of the melting point in a reducing atmosphere. However, in the present invention, first, rolling is performed at a sheet thickness reduction rate of 80% or more, heat treatment is performed at a temperature of 20 to 50% of the melting point, and recrystallized nuclei are generated. A biaxially oriented structure is obtained by performing a rolling process with a thickness reduction rate and additionally performing a heat treatment at a temperature of 50 to 80% of the melting point in a reducing atmosphere.
ここで、Ni合金において、特に望ましい熱処理は、アルゴンガスに水素を3%から7%程度混合した還元ガスを熱処理炉に流し、1回目の熱処理温度を450℃〜700℃、2回目の熱処理温度を800℃から1200℃の間とし、基板がその熱処理温度にさらされている時間は、配向率と配向度と表面結晶粒径の大きさの兼ね合いから選ぶが、取り扱い上の観点から、少なくとも10分以上とすることである。 Here, in the Ni alloy, a particularly desirable heat treatment is that a reducing gas in which about 3% to 7% of hydrogen is mixed with argon gas is supplied to a heat treatment furnace, and the first heat treatment temperature is 450 ° C. to 700 ° C. The second heat treatment temperature. Is set between 800 ° C. and 1200 ° C., and the time during which the substrate is exposed to the heat treatment temperature is selected from the balance between the orientation rate, the degree of orientation, and the size of the surface crystal grain size. It should be more than minutes.
なお、90%以上の板厚減少率の「板厚減少率」とは、圧延における「板厚減少率」のことであり、圧延前と圧延後の厚みの差を圧延前の厚みで除して100を乗じた値である。 Note that the “thickness reduction rate” of the thickness reduction rate of 90% or more is the “thickness reduction rate” in rolling, and the difference between the thickness before and after rolling is divided by the thickness before rolling. And multiplied by 100.
このような圧延加工及び熱処理の繰り返しにより、金属基板の表面を{100}<001>に2軸配向あるいはほぼ2軸配向させることができる。このように、電流を流す方向(金属基板の圧延方向)の結晶配向を揃えることにより、その上に形成される超電導層に電流が流れやすくなり、臨界電流を向上させることができる。 By repeating such rolling and heat treatment, the surface of the metal substrate can be biaxially or almost biaxially oriented to {100} <001>. Thus, by aligning the crystal orientation in the direction in which the current flows (the rolling direction of the metal substrate), the current can easily flow through the superconducting layer formed thereon, and the critical current can be improved.
実施例
以下に本発明の実施例及び比較例を示し、本発明について具体的に説明する。
Examples Hereinafter, examples and comparative examples of the present invention will be shown, and the present invention will be specifically described.
実施例1
純度3N(99.9%)以上のNi、Wを用いて真空鋳造することにより、Ni−5at%W合金を得た。この合金を必要に応じて鈍しを行いつつ、熱間および/または冷間加工することにより、幅約15mm、初期厚さ0.65〜2.8mmのテープ材を得た。このテープ材に対し、600℃×1時間の焼鈍熱処理を行った後、このテープ材を下記表1に示す第1の熱処理工程時の厚さになるように圧延加工(第1の圧延工程)を行い、更に600℃で、1時間の熱処理(第1の熱処理工程)を行った。なお、第1の圧延工程板厚減少率は、初期厚さに対する第1の熱処理工程時の厚さの減少率を意味する。
Example 1
A Ni-5 at% W alloy was obtained by vacuum casting using Ni and W with a purity of 3N (99.9%) or higher. This alloy was subjected to hot and / or cold working while being blunted as necessary to obtain a tape material having a width of about 15 mm and an initial thickness of 0.65 to 2.8 mm. The tape material is subjected to an annealing heat treatment at 600 ° C. for 1 hour, and then the tape material is rolled so as to have a thickness at the first heat treatment step shown in Table 1 below (first rolling step). Further, a heat treatment (first heat treatment step) was performed at 600 ° C. for 1 hour. The first rolling process plate thickness reduction rate means the thickness reduction rate during the first heat treatment step with respect to the initial thickness.
その後、下記表1に示す最終厚さとなるように、圧延加工(第2の圧延工程)を行い、続いてスリット加工を行うことによって、最終厚さ0.1mm、幅10mmのテープ材を得た。更にこのテープ材を還元雰囲気(Ar/3%H2雰囲気)中で、400〜1075℃の温度で1時間の熱処理(第2の熱処理工程)を行うことにより、超電導線用基板とした。 Then, a tape material having a final thickness of 0.1 mm and a width of 10 mm was obtained by performing a rolling process (second rolling process) so as to have the final thickness shown in Table 1 below, followed by slitting. . Further, this tape material was subjected to a heat treatment (second heat treatment step) for 1 hour at a temperature of 400 to 1075 ° C. in a reducing atmosphere (Ar / 3% H 2 atmosphere) to obtain a superconducting wire substrate.
得られた超電導線用基板に対し、表面金属に対して、X線回折により結晶方位解析を行い、立方体方位{100}<001>からのずれが10°以内の結晶の面積率を2軸配向した結晶の面積率として評価した。また、結晶粒のアスペクト比は、得られた超電導線用基板の表面を、走査型電子顕微鏡(SEM)を用いて観察を行い、30個の結晶粒に対して、基板の長手方向における結晶粒の長さをl、基板の幅方向における長さをwとし、l/wとしてそれぞれ求めた値を平均したものである。 The obtained superconducting wire substrate is subjected to crystal orientation analysis by X-ray diffraction with respect to the surface metal, and the crystal area ratio within 10 ° from the cube orientation {100} <001> is biaxially oriented. The area ratio of the obtained crystals was evaluated. Further, the aspect ratio of the crystal grains is determined by observing the surface of the obtained superconducting wire substrate using a scanning electron microscope (SEM), and the crystal grains in the longitudinal direction of the substrate with respect to 30 crystal grains. 1 is the length in the width direction of the substrate, and w is the length in the width direction of the substrate.
次に、この基板上に電子ビーム蒸着法により、基板温度800℃程度で、CeO2膜を100nm程度堆積させた。更に、マグネトロンスパッタリングにより、YSZおよびCeO2層を約100nmずつ堆積させ、NiW基板/CeO2層/YSZ層/CeO2層の構造を持つ、Y系超電導線用基体を得た。更にその上に、パルスレーザアブレーション法により、YBCO超電導層を2μmの厚さまで堆積した。 Next, about 100 nm of a CeO 2 film was deposited on the substrate by an electron beam evaporation method at a substrate temperature of about 800 ° C. Further, a YSZ and CeO 2 layer was deposited by about 100 nm by magnetron sputtering to obtain a Y-based superconducting wire substrate having a structure of NiW substrate / CeO 2 layer / YSZ layer / CeO 2 layer. Further thereon, a YBCO superconducting layer was deposited to a thickness of 2 μm by pulsed laser ablation.
このようにして得た超電導体に更に保護層となる銀層を約20μmの厚さに成膜し、酸素中500℃で3時間の焼鈍をおこなった後、液体窒素に浸漬して自己磁場中で1μV/cmの定義を用いて4端子法によりIcを測定した。これらの評価結果を下記表1に示す。
実施例2
純度3N(99.9%)以上のNi、Wを用いて真空鋳造することにより、Ni-7at%W合金を得た。初期厚さ1.8mmのテープ材とする以外は実施例1と同様な方法により、超電導線用基板および超電導線を作製し、実施例1と同様の評価を行った。その評価結果を下記表2に示す。
A silver layer serving as a protective layer is further formed on the superconductor thus obtained to a thickness of about 20 μm, annealed in oxygen at 500 ° C. for 3 hours, and then immersed in liquid nitrogen in a self-magnetic field. Ic was measured by the 4-terminal method using the definition of 1 μV / cm. The evaluation results are shown in Table 1 below.
Example 2
A Ni-7 at% W alloy was obtained by vacuum casting using Ni and W having a purity of 3N (99.9%) or higher. A superconducting wire substrate and a superconducting wire were produced in the same manner as in Example 1 except that the tape material had an initial thickness of 1.8 mm, and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 2 below.
実施例3
純度3N(99.9%)以上のNi、Wを用いて真空鋳造することにより、Ni−5at%W合金を得た。この合金を必要に応じて鈍しを行いつつ、熱間および/または冷間加工することにより、幅約15mm、初期厚さ2.8mmのテープ材を得た。このテープ材に対し、600℃×1時間の熱処理を行った後、このテープ材を、板厚減少率95.4%の圧延加工により、厚さ0.13mmまで圧延加工し(第1の圧延工程)、更に下記表3に示す第1の熱処理条件(熱処理温度:340〜790℃、熱処理時間:0.1〜100時間)で熱処理を行った(第1の熱処理工程)。
Example 3
A Ni-5 at% W alloy was obtained by vacuum casting using Ni and W with a purity of 3N (99.9%) or higher. This alloy was subjected to hot and / or cold working while being blunted as necessary to obtain a tape material having a width of about 15 mm and an initial thickness of 2.8 mm. The tape material was heat treated at 600 ° C. for 1 hour, and then the tape material was rolled to a thickness of 0.13 mm by rolling with a plate thickness reduction rate of 95.4% (first rolling) Step) and further heat treatment was performed under the first heat treatment conditions (heat treatment temperature: 340 to 790 ° C., heat treatment time: 0.1 to 100 hours) shown in Table 3 below (first heat treatment step).
その後、板厚減少率23.1%の圧延加工を行い(第2の圧延工程)、続いてスリット加工を行うことによって、厚さ0.1mm、幅10mmのテープ基材を得た。この基板についてEBSD法により配向性を評価した。更にこのテープ材を還元雰囲気(Ar/3%H2雰囲気)中で、下記表3に示す第2の熱処理条件(熱処理温度:600〜1290℃、熱処理時間:0.05〜30時間)の熱処理を行う(第2の熱処理工程)ことにより、超電導線用基板とした。また、実施例1と同様な方法により、超電導線を作製し、実施例1と同様の評価を行った。その評価結果を下記表3に示す。 Then, the tape base material of thickness 0.1mm and width 10mm was obtained by performing the rolling process of 23.1% of plate | board thickness reduction | decrease rates (2nd rolling process), and performing a slit process succeedingly. The orientation of this substrate was evaluated by the EBSD method. Furthermore, the tape material was heat-treated in a reducing atmosphere (Ar / 3% H 2 atmosphere) under the second heat treatment conditions (heat treatment temperature: 600 to 1290 ° C., heat treatment time: 0.05 to 30 hours) shown in Table 3 below. (Second heat treatment step) to obtain a superconducting wire substrate. In addition, a superconducting wire was produced by the same method as in Example 1, and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 3 below.
0.8Tmを超える温度では、2次再結晶粒と思われる粗大な粒が出現し、2軸配向結晶の面積率にバラツキが多くなり、安定した製造には向かないと考えられる。また、0.5Tmを下回る温度では、100時間を超えるような熱処理が必要にも関わらず、面積率が低く、これもまた実用に向かない。 At a temperature exceeding 0.8 Tm, coarse grains that appear to be secondary recrystallized grains appear, and the area ratio of the biaxially oriented crystals increases, which is not suitable for stable production. Further, at a temperature lower than 0.5 Tm, the area ratio is low despite the necessity of heat treatment exceeding 100 hours, which is also not suitable for practical use.
従来例1
厚さ2.8mmで600℃×1時間の熱処理後、熱処理せずに厚さ0.1mmまで加工したことをのぞけば、実施例1と同様の工程で、超電導線を作製し、Icを評価した。その評価結果を下記表1に示す。
Conventional Example 1
A superconducting wire was fabricated and evaluated according to the same process as in Example 1 except that after a heat treatment at a thickness of 2.8 mm and a heat treatment of 600 ° C. × 1 hour, and then processed to a thickness of 0.1 mm without the heat treatment, Ic was evaluated. did. The evaluation results are shown in Table 1 below.
従来例2
厚さ1.8mmで600℃×1時間の熱処理後、熱処理せずに厚さ0.1mmまで加工したことをのぞけば、実施例2と同様の工程で、超電導線を作製し、Icを評価した。その評価結果を下記表2に示す。
Conventional example 2
A superconducting wire was fabricated and evaluated according to the same process as in Example 2 except that after a heat treatment at a thickness of 1.8 mm at 600 ° C. × 1 hour and then processed to a thickness of 0.1 mm without the heat treatment. did. The evaluation results are shown in Table 2 below.
比較例1
テープ材の初期厚さを0.43〜2.8mmとし、第1及び第2の圧延工程における板厚減少率、及び第1及び第2の熱処理温度の少なくともいずれかを本発明の範囲外としたことを除いて、実施例1と同様と同様の工程で、超電導線を作製し、Icを評価した。その評価結果を下記表1に示す。
Comparative Example 1
The initial thickness of the tape material is 0.43 to 2.8 mm, and at least one of the sheet thickness reduction rate in the first and second rolling steps and the first and second heat treatment temperatures is out of the scope of the present invention. A superconducting wire was prepared and Ic was evaluated in the same process as in Example 1 except for the above. The evaluation results are shown in Table 1 below.
比較例2
第1及び第2の圧延工程における板厚減少率、及び第1及び第2の熱処理温度の少なくともいずれかを本発明の範囲外としたことを除いて、実施例2と様と同様の工程で、超電導線を作製し、Icを評価した。その評価結果を下記表2示す。
Comparative Example 2
In the same process as in Example 2, except that at least one of the sheet thickness reduction rate and the first and second heat treatment temperatures in the first and second rolling processes is out of the scope of the present invention. A superconducting wire was prepared and Ic was evaluated. The evaluation results are shown in Table 2 below.
比較例3
第1及び第2の熱処理温度を本発明の範囲外としたことを除いて、実施例3と同様の工程で、超電導線を作製し、Icを評価した。その評価結果を下記表3示す。
A superconducting wire was prepared and Ic was evaluated in the same manner as in Example 3 except that the first and second heat treatment temperatures were outside the scope of the present invention. The evaluation results are shown in Table 3 below.
上記表1〜3に示すように、板厚減少率80%以上の圧延を行う第1の圧延工程、第1の圧延工程に引き続き、熱処理を行う第1の熱処理工程、板厚減少率10〜50%の圧延を行う第2の圧延工程、及び還元性雰囲気中で第1の熱処理工程の温度よりも高い温度で熱処理を行う第2の熱処理工程からなる処理を行う実施例1(1−1〜1−7)、実施例2(2−1〜2−5)、及び実施例3(3−1〜3−10)により得た超電導線用基板は基板表面の前記表面における{001}<100>方向を有する結晶の面積率および再結晶粒の平均アスペクト比は適正であり、この超電導線用基板を用いた超電導線は、高いIcを示した。 As shown in Tables 1 to 3 above, the first rolling process for rolling at a sheet thickness reduction rate of 80% or more, the first heat treatment process for heat treatment following the first rolling process, the sheet thickness reduction ratio of 10 to 10%. Example 1 (1-1) in which a second rolling step in which 50% rolling is performed and a second heat treatment step in which heat treatment is performed at a temperature higher than that of the first heat treatment step in a reducing atmosphere are performed. ˜1-7), Example 2 (2-1 to 2-5), and Example 3 (3-1 to 3-10), the superconducting wire substrate was {001} < The area ratio of crystals having a 100> direction and the average aspect ratio of recrystallized grains were appropriate, and the superconducting wire using this superconducting wire substrate showed high Ic.
これに対し、1回の熱処理と1回の圧延処理を行う従来例1及び2により得た超電導線用基板は、再結晶粒の平均アスペクト比は1であり、この超電導線用基板を用いた超電導線は、満足するIcとはならなかった。 On the other hand, the superconducting wire substrate obtained by the conventional examples 1 and 2 in which one heat treatment and one rolling process are performed has an average aspect ratio of recrystallized grains, and this superconducting wire substrate was used. The superconducting wire did not satisfy Ic.
また、2回の熱処理と2回の圧延処理を行ったが、その熱処理温度及び板厚減少率の少なくとも一方が本発明の範囲外である比較例1(1−1〜1−6)、比較例2(2−1〜2−6)、及び比較例3(3−1〜3−8)により得た超電導線用基板は、基板表面の前記表面における{001}<100>方向を有する結晶の面積率および/または再結晶粒の平均アスペクト比が適正な範囲ではなく、この超電導線用基板を用いた超電導線は、低いIcを示した。 Moreover, although the heat processing of 2 times and the rolling process of 2 times were performed, the comparative example 1 (1-1 to 1-6) and at least one of the heat processing temperature and sheet thickness reduction | decrease rate are outside the scope of the present invention, comparison Superconducting wire substrates obtained in Example 2 (2-1 to 2-6) and Comparative Example 3 (3-1 to 3-8) are crystals having a {001} <100> direction on the surface of the substrate surface. The area ratio and / or the average aspect ratio of the recrystallized grains were not in an appropriate range, and the superconducting wire using this superconducting wire substrate showed low Ic.
以下、実施例および比較例について、詳細に述べる。 Hereinafter, Examples and Comparative Examples will be described in detail.
表1において、第1の圧延工程における板厚減少率が80%以上であり、第2の圧延工程における板厚減少率が10〜50%の範囲内である実施例1−1〜1−7においては、2軸配向組織の面積率がほぼ90%以上であり、かつ、結晶粒のアスペクト比は1.1〜2.0の範囲内となり、平均Icが200A以上の超電導線が得られている。実施例1−5では2軸配向結晶の面積率が85%と従来例と同程度に低いものの、結晶粒のアスペクト比が1.8と大きいために、粒界長の増加によって高いIcを得られたものと考えられる。 In Table 1, Examples 1-1 to 1-7 in which the plate thickness reduction rate in the first rolling step is 80% or more and the plate thickness reduction rate in the second rolling step is in the range of 10 to 50%. , The area ratio of the biaxially oriented structure is approximately 90% or more, the aspect ratio of the crystal grains is in the range of 1.1 to 2.0, and a superconducting wire having an average Ic of 200 A or more is obtained. Yes. In Example 1-5, although the area ratio of the biaxially oriented crystal is 85%, which is as low as that of the conventional example, the aspect ratio of the crystal grains is as large as 1.8. Therefore, a high Ic is obtained by increasing the grain boundary length. It is thought that it was done.
一方、第1の圧延工程での板厚減少率が80%未満である比較例1−1では、アスペクト比は適正であるが、基板表面における{001}<100>方向を有する結晶の面積率が比較的に低いために、平均Icが150Aを下回っている。また、第2の圧延工程での板厚減少率が10%未満である比較例1−2では、再結晶化のために十分な歪みが与えられず基板表面における{001}<100>方向を有する結晶の面積率は適正であるが、アスペクト比が1.1未満のために、平均Icが150Aを下回っている。更に、第2の圧延工程での板厚減少率が50%を超えている比較例1−3では、アスペクト比は2を超えるものの、加工量(歪み量)が大きすぎて基板表面における{001}<100>方向を有する結晶の面積率が低下したために、平均Icが150Aを下回り、極端に低くなっている。 On the other hand, in Comparative Example 1-1 in which the plate thickness reduction rate in the first rolling process is less than 80%, the aspect ratio is appropriate, but the area ratio of crystals having the {001} <100> direction on the substrate surface Is relatively low, the average Ic is below 150A. Further, in Comparative Example 1-2 in which the plate thickness reduction rate in the second rolling process is less than 10%, sufficient strain for recrystallization is not given, and the {001} <100> direction on the substrate surface is set. Although the area ratio of the crystal is appropriate, the average Ic is less than 150 A because the aspect ratio is less than 1.1. Further, in Comparative Example 1-3 in which the plate thickness reduction rate in the second rolling process exceeds 50%, although the aspect ratio exceeds 2, the processing amount (distortion amount) is too large and {001 on the substrate surface } Since the area ratio of the crystals having the <100> direction was lowered, the average Ic was less than 150 A and extremely low.
また、比較例1−4〜1−6のように、第1の熱処理温度が第2の熱処理温度よりも低くなっていない場合には、アスペクト比は適正であるが、基板表面における{001}<100>方向を有する結晶の面積率が比較的に低いために、平均Icが150Aを下回り、ほとんど電流が流れなかった。 Also, as in Comparative Examples 1-4 to 1-6, when the first heat treatment temperature is not lower than the second heat treatment temperature, the aspect ratio is appropriate, but {001} on the substrate surface. Since the area ratio of the crystal having the <100> direction was relatively low, the average Ic was less than 150 A, and almost no current flowed.
表1と同様に、表2においても、第1の圧延工程における板厚減少率が80%以上であり、第2の圧延工程における板厚減少率が10〜50%の範囲内である実施例2−1〜2−5においては、2基板表面における{001}<100>方向を有する結晶の面積率が高く、かつ、結晶粒のアスペクト比が1.1〜2.0の範囲内で1より大きく、平均Icが150A以上の超電導線が得られた。 As in Table 1, also in Table 2, the thickness reduction rate in the first rolling process is 80% or more, and the thickness reduction rate in the second rolling process is in the range of 10 to 50%. In 2-1 to 2-5, the area ratio of the crystals having the {001} <100> direction on the surfaces of the two substrates is high, and the aspect ratio of the crystal grains is 1 to 2.0 within the range of 1.1 to 2.0. A larger superconducting wire having an average Ic of 150 A or more was obtained.
一方、第1の圧延工程での板厚減少率が80%未満であり、第2の圧延工程においても板厚減少率が50%を超えている比較例2−1では、アスペクト比は2.0よりも大きくなるが、基板表面における{001}<100>方向を有する結晶の面積率が低いために、平均Icが150Aを下回り、極端に低くなっている。また、第2の圧延工程での板厚減少率が10%未満である比較例2−2では、基板表面における{001}<100>方向を有する結晶の面積率は従来例と同程度であり、あつ、アスペクト比が1.1未満と小さく電流パスが長くならないために、平均Icが150Aを下回っている。更に、第2の圧延工程での板厚減少率が50%を超えている比較例2−3では、アスペクト比が2.0よりも大きくなるが、基板表面における{001}<100>方向を有する結晶の面積率が低下したために、平均Icが150Aを下回り、極端に低くなっている。 On the other hand, in Comparative Example 2-1, in which the plate thickness reduction rate in the first rolling step is less than 80% and the plate thickness reduction rate in the second rolling step exceeds 50%, the aspect ratio is 2. Although it is larger than 0, since the area ratio of the crystal having the {001} <100> direction on the substrate surface is low, the average Ic is less than 150 A and extremely low. Further, in Comparative Example 2-2 in which the plate thickness reduction rate in the second rolling process is less than 10%, the area ratio of crystals having the {001} <100> direction on the substrate surface is similar to that of the conventional example. The aspect ratio is less than 1.1 and the current path is not long, so the average Ic is less than 150A. Furthermore, in Comparative Example 2-3 in which the plate thickness reduction rate in the second rolling process exceeds 50%, the aspect ratio is larger than 2.0, but the {001} <100> direction on the substrate surface is Since the area ratio of the crystals contained is reduced, the average Ic is less than 150 A and extremely low.
また、比較例2−4〜2−6のように、第1の熱処理温度が第2の熱処理温度よりも低くなっていない場合には、アスペクト比は適正であるが、基板表面における{001}<100>方向を有する結晶の面積率が比較的に低いために、平均Icが150Aを下回り、ほとんど電流が流れなかった。 Further, as in Comparative Examples 2-4 to 2-6, when the first heat treatment temperature is not lower than the second heat treatment temperature, the aspect ratio is appropriate, but {001} on the substrate surface. Since the area ratio of the crystal having the <100> direction was relatively low, the average Ic was less than 150 A, and almost no current flowed.
以上のように、基板表面が配向率の高い2軸配向組織を有し、アスペクト比が1.1〜2.0の再結晶粒を有ししていることで、平均Icが十分に高い超電導線材を得ることができる。このとき、基板表面の2軸配向組織としては、{001}<100>方向を有する結晶の面積率が80%以上であることが望ましい。 As described above, the substrate surface has a biaxially oriented structure with a high orientation ratio and has recrystallized grains having an aspect ratio of 1.1 to 2.0, so that the average Ic is sufficiently high. A wire can be obtained. At this time, as a biaxially oriented structure of the substrate surface, it is desirable that the area ratio of crystals having a {001} <100> direction is 80% or more.
表3の実施例3−1〜3−10では、第1および第2の熱処理工程における熱処理温度の融点に対する割合をそれぞれ変化させたところ、次のような結果となった。 In Examples 3-1 to 3-10 in Table 3, when the ratio of the heat treatment temperature to the melting point in the first and second heat treatment steps was changed, the following results were obtained.
第1の熱処理温度を融点(Tm)に対して、0.2〜0.5とし、第2の熱処理温度を融点(Tm)に対して0.5〜0.9とした実施例3−1〜3−10では、基板表面における{001}<100>方向を有する結晶の面積率が高く、平均Icも高い。 Example 3-1 in which the first heat treatment temperature was 0.2 to 0.5 with respect to the melting point (Tm) and the second heat treatment temperature was 0.5 to 0.9 with respect to the melting point (Tm) In ~ 3-10, the area ratio of the crystals having the {001} <100> direction on the substrate surface is high, and the average Ic is also high.
第1の熱処理温度を融点に対して0.2未満とした比較例3−6では、基板表面における{001}<100>方向を有する結晶の面積率および超電導線としたときの平均Icについては従来例1と同等であり、かつ、基板表面の結晶のアスペクト比も従来例1と同等の1で、第1の熱処理の効果が全く見られない。すなわち、熱処理温度が低すぎるために、その効果が現れなかったと考えられる。また、第1の熱処理温度を融点に対して0.5よりも大きい比較例3−7および3−8では、基板表面における{001}<100>方向を有する結晶の面積率が低く、平均Icが低下した。熱処理時間を短くした比較例3−8では比較例3−7に比べ基板表面における{001}<100>方向を有する結晶の面積率は向上しており、第1の熱処理温度が高い場合には、熱処理時間を短くすることによって、面積率の向上が期待できるが、これ以上熱処理時間を短くすることは熱処理のばらつきという観点から好ましくない。 In Comparative Example 3-6 in which the first heat treatment temperature was less than 0.2 with respect to the melting point, the area ratio of the crystals having the {001} <100> direction on the substrate surface and the average Ic when the superconducting wire was used The aspect ratio of the crystal on the substrate surface is the same as in Conventional Example 1, and the same as in Conventional Example 1, and the effect of the first heat treatment is not seen at all. That is, it is considered that the effect did not appear because the heat treatment temperature was too low. In Comparative Examples 3-7 and 3-8 in which the first heat treatment temperature is higher than 0.5 with respect to the melting point, the area ratio of crystals having the {001} <100> direction on the substrate surface is low, and the average Ic Decreased. In Comparative Example 3-8 in which the heat treatment time was shortened, the area ratio of the crystals having the {001} <100> direction on the substrate surface was improved as compared with Comparative Example 3-7, and when the first heat treatment temperature was high Although the area ratio can be improved by shortening the heat treatment time, shortening the heat treatment time beyond this is not preferable from the viewpoint of variation in heat treatment.
第2の熱処理温度を融点に対して0.5未満とした比較例3−5では、基板表面における{001}<100>方向を有する結晶の面積率が低く、超電導線としたときの平均Icが低い。第2の熱処理温度を融点に対して0.8よりも大きい比較例3−4では、2次再結晶粒と思われる粗大結晶粒が随所に観察され、基板表面における{001}<100>方向を有する結晶の面積率が低く、平均Icが低い。 In Comparative Example 3-5 in which the second heat treatment temperature was less than 0.5 with respect to the melting point, the area ratio of crystals having the {001} <100> direction on the substrate surface was low, and the average Ic when a superconducting wire was used. Is low. In Comparative Example 3-4 in which the second heat treatment temperature is higher than 0.8 with respect to the melting point, coarse crystal grains that are thought to be secondary recrystallized grains are observed everywhere, and the {001} <100> direction on the substrate surface The area ratio of crystals having low is low, and the average Ic is low.
以上のように、第1の熱処理工程における熱処理温度を、金属の融点の0.2〜0.5倍の温度とし、第2の熱処理工程における熱処理温度を、金属の融点に対して0.5〜0.8倍の温度とすることで、2次再結晶を抑えつつ、実用的な時間範囲内において、面積率の高い2軸配向組織を形成することが可能となる。 As described above, the heat treatment temperature in the first heat treatment step is set to 0.2 to 0.5 times the melting point of the metal, and the heat treatment temperature in the second heat treatment step is set to 0.5 with respect to the metal melting point. By setting the temperature to ˜0.8 times, it is possible to form a biaxially oriented structure with a high area ratio within a practical time range while suppressing secondary recrystallization.
Claims (5)
前記第1の圧延工程を経た前記基板を、前記Ni合金の融点(℃)の0.2〜0.5倍の温度で熱処理を行う第1の熱処理工程と、
前記第1の熱処理工程を経た前記基板に対して、板厚減少率10〜50%の圧延を行う第2の圧延工程と、
前記第2の圧延工程を経た前記基板に対して、還元性雰囲気中において前記Ni合金の融点(℃)に対して0.5〜0.8倍の温度で熱処理を行う第2の熱処理工程と
を具備することを特徴とする超電導線用基板の製造方法。 A first rolling step of rolling at a thickness reduction rate of 80% or more on a substrate made of a Ni alloy having at least a surface of Ni and W;
A first heat treatment step of heat-treating the substrate that has undergone the first rolling step at a temperature of 0.2 to 0.5 times the melting point (° C.) of the Ni alloy ;
A second rolling step for rolling the substrate having undergone the first heat treatment step with a thickness reduction rate of 10 to 50%;
A second heat treatment step for heat-treating the substrate that has undergone the second rolling step at a temperature 0.5 to 0.8 times the melting point (° C.) of the Ni alloy in a reducing atmosphere; The manufacturing method of the board | substrate for superconducting wires characterized by comprising.
前記表面における{001}<100>方向を有する結晶の面積率が80%以上であって、前記金属の基板の長手方向における結晶粒の長さが基板の幅方向の結晶粒の長さの1.1〜2倍であることを特徴とする超電導線用基板。 In the substrate for superconducting wires, at least one surface of which is made of metal,
The area ratio of crystals having the {001} <100> direction on the surface is 80% or more, and the length of the crystal grains in the longitudinal direction of the metal substrate is 1 of the length of the crystal grains in the width direction of the substrate. A substrate for a superconducting wire, characterized in that it is 1 to 2 times.
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