JP2015011860A - Oxide superconductive wire rod and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide superconductive wire rod which prevents deterioration of an internal oxide superconductive material by reducing the width dimensional tolerance of the oxide superconductive material to form a structure capable of suppressing invasion of moisture and its production method.SOLUTION: In an oxide superconductive wire rod, a tape-shaped oxide superconductive conductor A is formed by providing a middle layer 4, an oxide superconductive layer 1 and a protective layer 6 on the surface of a tape-like substrate 3, and a metal stabilizing layer 2 composed of a metal tape 2A is formed around the oxide superconductive conductor so as to cover the protective layer side and both side-surface sides of the tape-like oxide superconductive conductor and at least partially the back-surface side of the substrate. An inner low-melting-point metal layer 7a and an outer low-melting-point metal layer 7b are formed on the inner-surface side of the metal stabilization layer, and the metal stabilization layer is joined with the oxide superconductive conductor through the inner low-melting-point metal layer. Both outer surface parts of the metal stabilization layer is polished to remove the outer low-melting-point metal layer partially or entirely so as to form a polished surface in which both outer surface parts of the metal stabilization layer are exposed.

Description

  The present invention relates to an oxide superconducting wire and a method for producing the same.

The RE-123 oxide superconductor (REBa ₂ Cu ₃ O _7-X : RE is a rare earth element) exhibits superconductivity at liquid nitrogen temperature and has low current loss. Therefore, it is processed into a superconducting wire to supply power. For example, a superconducting conductor or a superconducting coil is manufactured. As a method for processing this oxide superconductor into a wire, a structure in which an oxide superconducting layer is formed on a substrate made of metal tape via an intermediate layer, and a metal stabilizing layer is formed on this oxide superconducting layer Is adopted.

  As a conventional general oxide superconducting wire, a thin silver protective layer is formed on the oxide superconducting layer formed on the base material through an intermediate layer, and a thick conductive metal material such as copper is formed thereon. A structure provided with a stable tri-layer is employed. The silver protective layer is also provided for the purpose of adjusting fluctuations in the amount of oxygen when the oxide superconducting layer is subjected to oxygen heat treatment, and the copper protective layer is formed from the superconducting state to the normal conducting state. It is provided in order to function as a bypass for commutating the current flowing in the oxide superconducting layer when trying to change to a state.

  As an example of an oxide superconducting wire configured to cover an oxide superconducting layer with a copper protective layer, a tape-like base material, an oxide superconducting layer and a protective layer thereon are cross-sectionally C-shaped by a reinforcing tape wire made of a metal tape. A structure that is covered so as to be wrapped in a mold has been proposed (see Patent Document 1).

JP2011-3494A

  By the way, the RE-123 oxide superconductor having a specific composition is easily deteriorated by moisture, and when the oxide superconducting wire is stored in an environment with a lot of moisture, or left with the moisture attached to the oxide superconducting wire. In such a case, if moisture enters the oxide superconducting layer, the superconducting characteristics may be deteriorated. Therefore, in order to ensure long-term reliability of the oxide superconducting wire, it is necessary to employ a structure in which the entire circumference of the oxide superconducting layer is protected by some layer.

  In the RE-123 oxide superconducting wire described above, an oxide superconducting layer is laminated on a base material of a metal tape via an intermediate layer, and a thin silver protective layer is laminated. Since it is formed thin so as to be able to adjust the oxygen amount fluctuation, pinholes may exist. Further, since the silver protective layer is formed by a film forming method such as sputtering, there is a problem that peeling or chipping is likely to occur when a long superconducting wire is manufactured. Furthermore, although the surface of the oxide superconducting layer is covered with a silver protective layer, the side of the oxide superconducting layer is not covered with any layer, so measures are taken to prevent moisture from entering from the side. There is a need.

For this reason, a structure in which the oxide superconducting wire is surrounded by a metal tape bent as shown in Patent Document 1 is considered promising. However, if the tape-shaped oxide superconducting wire is surrounded by a metal tape or the like and a solder layer is provided between the oxide superconducting wire and the metal tape to integrate them, the following problems may occur. there were.
In the case of a structure that is fixed with solder, solder adhesion at the interface between the metal tape and the oxide superconducting wire becomes a problem, and if there is even a slight gap in the entire length of the long superconducting wire, moisture will enter through the gap. There is a risk of forgiveness. For this reason, it is necessary to attach a sufficient amount of solder to the metal tape in advance as a solder plating layer, and to bend the metal tape to cover the oxide superconducting wire. However, if the amount of solder formed on the metal tape is too large, it is easy to produce a portion where the solder is bent outward at the bent portion or edge portion of the metal tape. There is a problem that the portion is formed and the width tolerance of the oxide superconducting wire varies greatly.

As the dimensional tolerance normally required for oxide superconducting wires, ± 0.1mm is known as the JIS standard with respect to the width of the original oxide superconducting wire not covered with metal tape. However, when the irregularities are formed by adhering like a flash, there is a problem that it is difficult to keep the dimensional tolerance.
Also, if there are uneven parts due to solder on the edge part of the metal tape, it is difficult to control the shape, which causes problems when attaching electrodes to the surface of the oxide superconducting wire in the subsequent process There is. For example, there is a problem in that solder used for electrode attachment flows to the side surface and the back surface of the oxide superconducting wire due to the solder already attached so as to protrude from the edge portion, resulting in poor soldering workability.
In addition, if the tin that constitutes the solder is thick on both sides of the tape-shaped oxide superconducting wire, tin embrittlement is likely to occur in the oxide superconducting wire that is cooled to a low temperature with liquid nitrogen or the like. The waterproof performance may be reduced.

  The present invention has been made in view of the conventional background as described above. The oxide superconducting wire has a small width tolerance, and has a structure capable of suppressing the ingress of moisture so as not to deteriorate the internal oxide superconducting layer. The object is to provide a superconducting wire. It is another object of the present invention to provide an oxide superconducting wire that hardly causes turbulence when the oxide superconducting wire is wound into a coil for superconducting coils.

  The oxide superconducting wire of the present invention comprises a tape-like oxide superconducting conductor comprising an intermediate layer, an oxide superconducting layer, and a protective layer on the surface of a tape-like substrate, and the oxide superconducting conductor is formed around the oxide superconducting conductor. A metal stabilizing layer made of a metal tape is formed so as to cover the protective layer side and both side surfaces of the tape-shaped oxide superconducting conductor and to cover at least a part of the back surface of the base material, and the inner surface side of the metal stabilizing layer An inner low-melting-point metal layer and an outer low-melting-point metal layer on the outer side, and the metal stabilization layer is joined to the oxide superconducting conductor by the inner low-melting-point metal layer, and both outer side surface portions of the metal stabilization layer Is polished to remove a part or all of the outer low-melting-point metal layer, thereby forming a polished surface exposing both outer surface portions of the metal stabilizing layer.

According to the present invention, since the outer low melting point metal layer on both outer side surfaces of the metal stabilizing layer made of the metal tape surrounding the oxide superconducting conductor is removed to form a polished surface, the oxide superconducting wire Concavities and convexities due to low melting point metal flashes are not formed on both outer side surface portions of the metal stabilizing layer constituting both side surfaces. For this reason, the width | variety tolerance as an oxide superconducting wire can be made small. Therefore, an oxide superconducting wire that is less likely to cause turbulence even when coiled to form a superconducting coil can be provided.
In addition, the inner low melting point metal layer provided between the oxide superconductor and the metal stabilization layer made of the surrounding metal tape covers the periphery of the oxide superconductor. It is possible to provide an oxide superconducting wire that can prevent moisture from entering the oxide superconducting layer located inside the oxide superconducting conductor surrounded by the layer and hardly deteriorate due to moisture.

The oxide superconducting wire of the present invention may be configured such that a residual layer of a low melting point metal layer is formed on the polished surface.
If the outer low-melting-point metal layer is removed by polishing on both sides of the outer side of the metal stabilization layer and remains as a residual layer, it does not affect the width tolerance. Does not occur.

The oxide superconducting wire of the present invention may be configured such that a residual alloy layer made of an alloy of an element constituting the outer low melting point metal layer and an element constituting the metal stabilizing layer is formed on the polished surface.
In the case of a structure in which the outer low-melting-point metal layer is removed by polishing, a part of the outer low-melting-point metal layer may be partly alloyed with the metal constituting the metal stabilizing layer. Even if a part of the residual alloy layer remains when removed by polishing, the residual alloy layer is thin and does not affect the width crossing.

In the oxide superconducting wire of the present invention, the thickness of the outer low melting point metal layer remaining on the polished surface is preferably 2 μm or less.
If the thickness of the outer low-melting-point metal layer remaining on the polished surface on both sides of the metal stabilizing layer is 2 μm or less, the oxide superconducting wire with good dimensional accuracy is less likely to cause turbulence during coil processing. In addition, there is no possibility of embrittlement of the low melting point metal when cooled to a low temperature. In particular, if the low melting point metal is a solder containing tin, even if low temperature embrittlement of tin occurs, it does not propagate to other low melting point metals, so that the progress of embrittlement of the low melting point metal can be suppressed. For this reason, there is no possibility that the low melting point metal layer existing on the inner side of the metal stabilizing layer is affected by low temperature embrittlement.

  In the method for producing an oxide superconducting wire of the present invention, a tape-shaped oxide superconducting conductor comprising an oxide superconducting layer and a protective layer on the surface of a tape-shaped substrate is wider than the oxide superconducting conductor. Using a metal tape having a low melting point metal layer on both sides, the metal tape is bent with this metal tape so as to cover the protective layer side, both side surfaces, and at least the edge side of the substrate back side of the oxide superconductor. After covering the oxide superconductor, the low melting metal layer is heated and melted to join the metal tape to the oxide superconductor, and then the both sides of the oxide superconductor are covered. The both outer surface portions are polished to remove part or all of the low melting point metal layer present on both outer surface portions to form a polished surface to form a metal stabilizing layer.

  According to the manufacturing method of the present invention, it is possible to provide an oxide superconducting wire in which uneven portions due to a low melting point metal flash or the like are not formed on both side portions of the metal stabilizing layer constituting both side surfaces of the oxide superconducting wire. . In addition, since there are no uneven portions made of a low melting point metal on both side surfaces, an oxide superconducting wire that hardly causes turbulence even when coiled can be provided.

In the method for producing an oxide superconducting wire according to the present invention, the low melting point remaining on both outer surface portions of the metal stabilizing layer by removing the low melting point metal layer present on both outer surface portions of the metal tape by polishing. The thickness of the metal layer is preferably 2 μm or less.
If the thickness of the low melting point metal layer present on both outer side surfaces of the metal stabilizing layer is 2 μm or less, an oxide superconducting wire with good dimensional accuracy can be provided with little risk of winding disturbance during coil processing. At the same time, even when the low melting point metal layer becomes brittle when cooled to a low temperature, the embrittlement of the low melting point metal layer does not propagate to other low melting point metal layers.

According to the present invention, the outer low melting point metal layer on both outer side surfaces of the metal stabilizing layer made of a metal tape surrounding the oxide superconducting conductor is removed to form a polished surface, and both sides of the oxide superconducting wire are formed. Width tolerance as an oxide superconducting wire with a structure covered with a metal stabilization layer on a metal tape, because there are no irregularities due to low melting point metal flashes on both outer surface parts of the metal stabilization layer constituting the surface Can be reduced. For this reason, even if it is a case where a coil process is carried out in order to comprise a superconducting coil, the oxide superconducting wire which cannot produce winding disorder easily can be provided.
In addition, since the inner low melting point metal layer provided between the oxide superconductor and the metal stabilization layer made of the metal tape surrounding the oxide superconductor covers the periphery of the oxide superconductor, the metal It is possible to provide an oxide superconducting wire that can prevent moisture from entering from the outside to the oxide superconducting layer positioned inside the oxide superconducting conductor surrounded by the stabilization layer and hardly cause deterioration due to moisture.

The perspective view which made a part of oxide superconducting wire of a 1st embodiment concerning the present invention a cross section. The partial cross section perspective view which shows an example of the oxide superconducting conductor provided in the oxide superconducting wire shown in FIG. FIG. 3A shows a manufacturing method of the oxide superconducting wire shown in FIG. 1. FIG. 3A is a cross-sectional view showing a state in which a copper tape is placed on the oxide superconducting conductor, and FIG. 3B shows the oxide superconducting conductor. Sectional drawing which shows an example of the state which bent the copper tape along which it was along, FIG.3 (c) is sectional drawing which shows the state which soldered the copper tape to the oxide superconducting conductor.

Hereinafter, an oxide superconducting wire according to the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view in which a part of the oxide superconducting wire according to the first embodiment of the present invention is shown in cross section, and the oxide superconducting wire A of this embodiment is a tape-shaped oxide superconducting provided inside. The conductor 1 is covered with a metal stabilization layer 2 made of a metal tape made of a conductive material such as copper.
The oxide superconducting conductor 1 of this example is formed by laminating an intermediate layer 4, an oxide superconducting layer 5, and a protective layer 6 in this order above a tape-shaped base 3 as shown in FIG.
The substrate 3 is preferably in the form of a tape in order to obtain a flexible superconducting wire, and is preferably made of a heat-resistant metal. Among various refractory metals, a nickel alloy is preferable. Especially, if it is a commercial item, Hastelloy (US Haynes Corporation brand name) is suitable. The thickness of the base material 3 is usually 10 to 500 μm. Moreover, as the base material 3, an oriented Ni—W alloy tape base material in which a texture is introduced into a nickel alloy can also be applied.

The intermediate layer 4 can be applied as an example of a diffusion prevention layer, a bed layer, an alignment layer, and a cap layer described below.
The base of the alignment layer can be a multi-layer structure of a diffusion prevention layer and a bed layer, which will be described below, or a structure composed of one of these layers.
When providing the diffusion prevention layer, a single layer structure composed of silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ , also referred to as “alumina”), GZO (Gd ₂ Zr ₂ O ₇ ), or the like. Or the layer of a multilayer structure is desirable, and thickness is 10-400 nm, for example.
In the case of providing a bed layer, the bed layer has high heat resistance, reduces interfacial reactivity, and is used for obtaining the orientation of a film disposed thereon. Such a bed layer is, for example, a rare earth oxide such as yttria (Y ₂ O ₃ ), and more specifically, Er ₂ O ₃ , CeO ₂ , Dy ₂ O ₃ , Ho ₂ O ₃ , La _2. O _{3 and the} like can be exemplified, and a single layer structure or a multilayer structure composed of these materials can be adopted. The thickness of the bed layer is, for example, 10 to 100 nm. Further, the crystallinity of the diffusion preventing layer and the bed layer is not particularly limited, and may be formed by a film forming method such as a normal sputtering method.

The alignment layer functions as a buffer layer for controlling the crystal orientation of the oxide superconducting layer 5 formed thereon, and is preferably made of a metal oxide having good lattice matching with the oxide superconducting layer. Specifically, preferred materials for the alignment layer include Gd ₂ Zr ₂ O ₇ , MgO, ZrO ₂ —Y ₂ O ₃ (YSZ), SrTiO ₃ , CeO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , Gd ₂ O. ₃ , metal oxides such as Zr ₂ O ₃ , Ho ₂ O ₃ and Nd ₂ O ₃ can be exemplified. The alignment layer may be a single layer or a multilayer structure.
If the alignment layer is deposited with a good biaxial orientation by the IBAD (Ion-Beam-Assisted Deposition) method, the crystal orientation of the cap layer can be improved, and the oxide superconductivity formed thereon The crystal orientation of the layer 5 can be improved and excellent superconducting properties can be exhibited.
The cap layer is formed on the surface of the above-described alignment layer and is made of a material that allows crystal grains to self-orient in the in-plane direction. Specifically, CeO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , Gd _{2 O 3, ZrO 2, YSZ,} Ho 2 O 3, Nd 2 O 3, consist of LaMnO ₃ like.
Among them, the CeO ₂ layer can be formed at a high film formation rate by PLD method (pulse laser deposition method), sputtering or the like, and good crystal orientation can be obtained. The cap layer can be formed to a thickness of 50 to 5000 nm, preferably about 300 to 800 nm.

The oxide superconducting layer 5 can be widely applied with an oxide superconductor having a generally known composition, and REBa ₂ Cu ₃ O _y (RE is Y, La, Nd, Sm, Er, Gd, etc.). A material made of a material that represents a rare earth element, specifically, Y123 (YBa ₂ Cu ₃ O _y ) or Gd123 (GdBa ₂ Cu ₃ O _y ) can be exemplified. Further, other oxide superconductors, for _{example, Bi 2 Sr 2 Ca n-} 1 Cu n for _{O 4 + 2n + δ} becomes may be used in compositions such as those made of other oxide superconductors having high critical temperatures representative Of course. The oxide superconducting layer 5 has a thickness of about 0.5 to 5 μm and preferably a uniform thickness.

The oxide superconducting layer 5 may be a known high-temperature superconductor, specifically, REBa ₂ Cu ₃ O _y (RE is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Examples thereof include materials made of Tb, Dy, Ho, Er, Tm, Yb, and Lu (indicating one or more rare earth elements). Examples of the oxide superconducting layer 5 include Y123 (YBa ₂ Cu ₃ O _7-X ) and Gd123 (GdBa ₂ Cu ₃ O _7-X ).
The oxide superconducting layer 5 is laminated by a physical vapor deposition method such as sputtering, vacuum vapor deposition, laser vapor deposition, electron beam vapor deposition, chemical vapor deposition (CVD), or thermal coating decomposition (MOD). In particular, from the viewpoint of productivity, the PLD (pulse laser deposition) method, the TFA-MOD method (organic metal deposition method using trifluoroacetate, coating pyrolysis method) or the CVD method may be used. it can. The oxide superconducting layer 5 has a thickness of about 0.5 to 5 μm and preferably a uniform thickness.

  The protective layer 6 is formed as a layer having good conductivity, such as Ag or an Ag alloy, having a low contact resistance with the oxide superconducting layer 5 and being familiar. The reason why the protective layer 6 is made of Ag or an Ag alloy is that oxygen can be easily transmitted to the oxide superconducting layer 5 side in the oxygen annealing step of doping the oxide superconducting layer 5 with oxygen. The base material of the oxide superconducting layer manufactured by the film formation method is an insulator. However, when oxygen is incorporated by oxygen annealing, the oxide superconducting layer has a well-structured crystal structure and exhibits superconducting properties. In order to form the protective layer 6, a film forming method such as a sputtering method is employed, and the thickness can be formed to about 1 to 30 μm.

In the oxide superconducting conductor 1, the surface and both side surfaces of the protective layer 6, both side surfaces of the underlying oxide superconducting laminate 5, both side surfaces of the intermediate layer 4, and both side surfaces of the base material 3 are covered. A metal stabilization layer 2 made of a metal tape made of a conductive material is provided so as to cover both end portions 3a on the back surface side of the metal plate.
The metal stabilization layer 2 is made of a conductive metal material as an example, and functions as a bypass for commutating current together with the protective layer 6 when the oxide superconducting layer 5 transitions from the superconducting state to the normal conducting state. The material constituting the metal stabilizing layer 2 is not particularly limited as long as it has conductivity, but is not limited to copper, brass (Cu—Zn alloy), copper alloys such as Cu—Ni alloy, Al, Cu— It is preferable to use a material made of a relatively inexpensive material such as an Al alloy. Among them, it is preferable that the material is made of copper because it has high conductivity and is inexpensive. When the oxide superconducting wire A is used for a superconducting fault current limiter, the metal stabilizing layer 2 is made of a high resistance metal material, and is made of, for example, a Ni-based alloy such as Ni—Cr. The thickness of the metal stabilization layer 2 is not particularly limited and can be adjusted as appropriate, but is preferably 50 to 300 μm.

A low melting point metal layer (solder layer) 7 is formed on both the front and back surfaces of the metal stabilizing layer 2.
The metal stabilizing layer 2 and the low melting point metal layer 7 will be described in detail. The metal stabilizing layer 2 is bent into a substantially C-shaped cross section, and includes a front wall 2a, a side wall 2b, and back walls 2c and 2c. The metal superconducting conductor 1 covers the metal stabilizing layer 2 from the protective layer 6 side to the back end portions 3a of the substrate 3. That is, the surface and both sides of the protective layer 6, both sides of the oxide superconducting layer 5, both sides of the intermediate layer 4, both sides of the substrate 3, and both ends 3 a of the back surface of the substrate 3 are covered with the metal stabilizing layer 2. It has been broken.
An inner low melting point metal layer 7a is formed on the entire inner surface of the metal stabilization layer 2, and a portion of the peripheral surface of the oxide superconducting conductor 1 surrounded by the metal stabilization layer 2 is the inner low melting point metal layer. 7a. Also, a first outer low melting point metal layer 7b is formed on the outer surface side of the surface wall 2a of the metal stabilization layer 2, and the low melting point metal layer is removed by polishing on the outer surface side of the side wall 2b of the metal stabilization layer 2. A polished surface 2e exposing the outer surface of the side wall 2b is formed, and a second outer low-melting-point metal layer 7d is formed on the outer surface side of the back wall 2c, 2c of the metal stabilizing layer 2.

Also, a coating portion 7c made of a low melting point metal is formed on the front edge side of the back surface walls 2c, 2c of the metal stabilizing layer 2, and the coating portion 7c is thick so that it slightly bulges from the front edge of the back wall 2c. And is provided so as to close a gap between the tip of the back wall 2c of the metal stabilizing layer 2 and the back surface of the base material 3.
The inner low melting point metal layer 7a is formed between the metal stabilizing layer 2 and the oxide superconducting conductor 1 so as to be filled therebetween. Moreover, since the center part of the back surface side width direction of the said base material 3 is an area | region which is not covered with the back surface walls 2c and 2c of the metal stabilization layer 2, it is on the back surface center part of the base material 3, and is a metal stabilization layer. A groove 2d is provided between the two back walls 2c and 2c.

  The polishing surface 2e is formed as follows. As shown in FIG. 1, a molten solder layer is formed on both the front and back surfaces of the metal tape before bending into a C-shaped cross section to form the metal stabilizing layer 2, and the metal tape is as shown in FIG. After bending into a C-shaped cross section, both sides are polished and the low melting point metal layers on both sides are removed. Therefore, depending on the state of polishing, the low melting point metal layer may partially remain as the residual layer 2f. Further, when the molten solder layer is formed on the outer surface of the metal tape, alloying with the constituent elements on the surface of the metal stabilization layer 2 may be performed depending on the formation temperature of the molten solder layer, and an alloy layer may be formed. . In this case, since a part of the alloy layer may remain on the polished surface 2e, the polished surface 2e on which such a residual alloy layer 2g remains may be used. Of course, the polishing surface may be a polishing surface having no residual layer 2f or residual alloy layer 2g on the polishing surface 2e.

In the tape-shaped oxide superconducting wire A, if the surface portion of the metal stabilizing layer 2 located on both sides of the tape-like oxide superconducting wire A is the polishing surface 2e and the polishing surface 2e is removing the low melting point metal layer, the polishing surface 2e Since uneven portions due to drooping or convex portions due to the low melting point metal residue have already been removed, the oxide superconducting wire A having a small width crossing and high dimensional accuracy in the width direction can be provided.
In this way, when the oxide superconducting wire A having a small width crossing is coiled, a large step does not occur in the formed superconducting coil, and there is a feature that winding disturbance does not easily occur during coil winding.
A method of manufacturing the oxide superconducting wire A by bending the metal tape to form the metal stabilizing layer 2 and then polishing both outer surfaces will be described later.

The low-melting-point metal layer 7 (7a, 7b, 7c, 7d) is formed of solder in this embodiment. As the low-melting-point metal, a metal having a melting point of 150 to 400 ° C., for example, Sn, Sn alloy, It may be made of indium or the like. When using solder, any solder such as Sn—Pb, Pb—Sn—Sb, Sn—Pb—Bi, Bi—Sn, Sn—Cu, Sn—Pb—Cu, Sn—Ag, etc. May be used. In the case where the low melting point metal layer 7 is melted, if the melting point is high, the superconducting properties of the oxide superconducting layer 5 are adversely affected. Therefore, the melting point of the low melting point metal layer 7 is preferably low. A material having a melting point of not higher than ° C., more preferably around 150 to 300 ° C. is desirable.
The thickness of the low melting point metal layer 7 is preferably in the range of 1 μm to 10 μm, and more preferably in the range of 1 μm to 6 μm. If the thickness of the low melting point metal layer 7 is less than 1 μm, the gap between the oxide superconducting conductor 1 and the metal stabilizing layer 2 may not be completely filled, and a gap may be formed. During the process, the constituent elements of the low melting point metal layer 7 may diffuse to form an alloy layer between the metal stabilizing layer 2 and the Ag protective layer 6. Conversely, when the low melting point metal layer 7 is formed to a thickness exceeding 10 μm, the low melting point metal is melted by heating and pressurizing with a roll and integrated with the low melting point metal. The amount of the low melting point metal that protrudes from the tip side to the outside increases, and the thickness of the covering portion 7c becomes larger than necessary. As a result, there is a high possibility of causing turbulence when the oxide superconducting wire A is wound. . In the heating and pressurizing process using a roll, the molten solder may protrude as much as 10 to 20 μm depending on conditions and positions.

In the oxide superconducting wire A having the structure shown in FIG. 1, an inner low melting point metal layer 7 a filled between the oxide superconducting conductor 1 and the metal stabilizing layer 2 around the oxide superconducting conductor 1 has a gap around the oxide superconducting conductor 1. Since it is covered without water, it is possible to prevent moisture from entering the oxide superconducting layer 5 located inside the metal stabilizing layer 2 from the outside.
Further, both end edges of the metal tape 2 are covered with a covering portion 7c formed of a low melting point metal so as to protrude outside from the back wall 2c of the metal stabilizing layer 2 placed on the back surface of the substrate 3. Since the gap with the back surface of the base material 3 is covered, there is an effect that moisture can be surely prevented from entering the inside of the metal stabilizing layer 2 on the edge side of the metal stabilizing layer 2.

  The covering portion 7c made of a low melting point metal that protrudes outside from the edge of the back wall 2c of the metal stabilizing layer 2 slightly protrudes toward the groove 2d between the both edges of the metal stabilizing layer 2. The thickness of the protruding portion is not particularly large compared to the thickness of the metal stabilizing layer 2. Further, even on the polished surface 2e side of the metal stabilizing layer 2, the uneven portion due to the flashing or protruding of the low melting point metal is removed. For this reason, even if it is the oxide superconducting wire A which has the grinding | polishing surface 2e and was equipped with the coating | coated part 7c in the back surface side of the base material 3, when coil winding is carried out, coil winding processing does not produce a big level | step difference. It has a characteristic that it is possible to prevent winding disturbance.

In order to manufacture the oxide superconducting wire A having the structure shown in FIG. 1, a tape-like oxidation in which a substrate 3, an intermediate layer 4, an oxide superconducting layer 5 and a protective layer 6 are laminated as shown in FIG. An object superconducting conductor 1 is prepared, and a metal tape 2 </ b> A is disposed below the protective layer 6 of the oxide superconducting conductor 1. The metal tape 2 </ b> A used here has a low melting point metal layer 8 or 9 formed by plating on the front and back surfaces. These low melting point metal layers 8 and 9 are preferably about 2 μm to 6 μm thick.
If the center portion in the width direction of the metal tape 2A is aligned and arranged at the center lower portion of the oxide superconductor 1, the metal tape 2A is shaped using a forming roll or the like along both end sides of the substrate 3. As shown in FIG. 3B, both ends of the metal tape 2A are bent upward, and further bent along the both ends of the substrate 3 as shown in FIG. A metal stabilizing layer is formed by processing so as to wrap both ends of the back surface and bending the metal tape 2A into a C-shaped cross section.

From this state, the whole is heated to a temperature higher than or equal to the melting temperature of the low melting point metal layers 8 and 9 in a heating furnace, and then heated using a pressure roll heated to a temperature about 50 ° C. lower than the melting temperature of the low melting point metal layers 8 and 9. The metal stabilizing layer 2 and the oxide superconducting conductor 1 bent into a C shape are pressurized. If the melting points of the low melting point metal layers 8 and 9 used here are 150 ° C. to 350 ° C. as an example, a temperature in the range of 100 ° C. to 300 ° C. which is 50 ° C. lower than the melting point can be selected.
By the above processing, the melted low melting point metal layers 8 and 9 are melted and spread so as to completely fill the space between the oxide superconductor 1 and the metal stabilizing layer 2, and the gap between them is filled. . Thereafter, when the whole is cooled to solidify the molten low melting point metal, an oxide superconducting wire A1 having a structure having the low melting point metal layer 7 as shown in FIG. 3C can be obtained.

Once this oxide superconducting wire A1 is obtained, both side surfaces thereof are polished with a polishing tool such as a paper file to remove the low melting point metal layer 7e remaining on both side surfaces to form the polished surface 2e. Thus, the oxide superconducting wire A having the cross-sectional structure shown in FIG. 1 can be obtained. The low melting point metal layer 7e itself has a low hardness and can be easily removed with a polishing tool such as a paper file.
When the low melting point metal layer 7e is removed by a polishing tool, the low melting point metal layer 7e may be removed so that the surface of the underlying metal stabilization layer 2 is exposed and visible. For example, in the case of the metal stabilization layer 2 made of Cu, since the copper color which is clearly different from the low melting point metal layer 7e is exhibited, the polishing may be finished when the copper color is recognized. it can. The means for forming the polished surface 2e is not limited to polishing with a paper file or the like, but a method is adopted in which the oxide superconducting wire A is passed through a die to remove the low-melting point metal layers 7e on both sides to form a polished surface. You may do it.
In addition, as an example of a method of polishing with a paper file, a belt-shaped paper file is spanned in a U-shape or an inverted U-shape so as to straddle both side surfaces from one of the upper surface and the lower surface of the tape-shaped oxide superconducting wire A. A method of simultaneously polishing both surfaces of the oxide superconducting wire A by moving the file up and down can be employed. Of course, the method of polishing with a paper file is not limited to this method, and two paper files are made to face each other and supported by an elastic jig or the like, and the oxide superconducting wire A between the opposed paper files. Any method may be employed, such as polishing by running a plurality of times.

  Thus, if the ground surface 2e is polished until the underlying metal stabilizing layer 2 is exposed, uneven portions made of anyone or convex portions due to the low melting point metal layer are formed on both side surfaces of the oxide superconducting wire A. Since it does not have, the oxide superconducting wire A with a small crossing width and high dimensional accuracy can be obtained. Further, even if the residual layer 2f remains on the polished surface 2e or the residual alloy layer 2g partially remains, the uneven portions on both sides of the oxide superconducting wire A are removed. There is no negative impact on tolerance.

In addition, when the oxide superconducting wire A is wound around a winding frame to form a coil, since tension is not applied to both side portions of the oxide superconducting wire A, if there is a lump of solder containing tin on both side portions, When cooled below the liquid nitrogen temperature, solder containing tin tends to become brittle at low temperatures. As the solder becomes more brittle, there is a risk that the brittleness may propagate to the solder containing tin provided at portions other than both side portions.
For example, when the oxide superconducting wire A is coiled, the front and back surfaces of the oxide superconducting wire A are subjected to compressive stress due to the tension at the time of coiling, so that embrittlement can be suppressed. However, since no tension is applied to the both side surfaces of the oxide superconducting wire A during coiling, there is a high possibility that the solder containing tin becomes brittle. When embrittlement occurs in the solder located on both side surfaces of the oxide superconducting wire A, the embrittlement may propagate to the solder in contact with the embrittled solder.
For example, since Sn expands when embrittled at a low temperature, if embrittlement from β-Sn to α-Sn propagates, it also adversely affects the solder containing Sn formed on the side surfaces of the metal stabilization layer 2. .
If the solder on both outer side surfaces of the oxide superconducting wire A is removed from this surface, the propagation of solder embrittlement can be suppressed. In view of this solder embrittlement, if the thickness of the solder remaining on both outer side surfaces of the oxide superconducting wire A is set in the range of 0 to 2 μm, the influence of low temperature embrittlement of the solder can be eliminated.
When the thickness of the solder is specified to be 2 μm or less, the solder is not uniformly present on the entire outer surface of the metal stabilizing layer 2, but the amount of residual solder remaining in an island shape after polishing. The thickness is 2 μm or less.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to these Examples.
An Al ₂ O ₃ diffusion prevention layer (thickness 80 nm), Y ₂ O on a tape-shaped substrate made of Hastelloy C-276 (trade name of US Haynes Co., Ltd.) having a thickness of 100 μm, a width of 5 mm, and a length of 50 m ₃ bed layer (thickness 30 nm), an intermediate layer of MgO (thickness 10 nm) by ion beam assisted deposition, a CeO ₂ cap layer (thickness 300 nm) by PLD method, and YBa ₂ Cu ₃ O ₇₋ A tape-shaped oxide superconducting conductor was prepared by laminating an oxide superconducting layer (thickness 1 μm) having a composition represented by _x and an Ag protective layer (thickness 10 μm) by DC sputtering.
Further, a metal tape with Sn plating having a thickness of 20 μm, a width of 18 mm, and a length of 50 m and having an Sn plating layer (thickness of 2 to 4 μm) formed on both surfaces was prepared.

  Covering the oxide superconducting conductor in a continuous C-shape while bending the copper tape by roll forming, and covering the tape-shaped oxide superconducting conductor with a metal stabilization layer made of a molded product of copper tape A superconducting conductor was formed. After processing by the roll forming, pressurizing with a heating roll while heating to 250 ° C. with a heater provided at the subsequent stage of the forming roll, melting the Sn plating layer, and crimping a C-shaped copper tape to the oxide superconductor Thereafter, the whole was cooled to obtain an oxide superconducting wire having a structure shown in FIG. 3C, and the oxide superconducting wire was wound on a take-up reel.

Thereafter, the side reel plate of the take-up reel was removed from the reel, and the side portion of the oxide superconducting wire wound around the reel was polished with a # 400 sandpaper (deburred). sample). As a guideline for completing the polishing of the side surface of the oxide superconducting wire, the polishing was completed when the Sn solder layer covering the side surface of the metal stabilizing layer made of copper tape was worn down and the underlying copper color was seen.
The width dimension of the obtained oxide superconducting wire is theoretically 5.04 mm in width because a copper stabilizing layer having a thickness of 20 μm exists on both side surfaces.
Table 1 below shows dimensional analysis data when the width dimension of the oxide superconducting wire with deburring obtained by the above process is measured at intervals of 5 mm.
In addition, the dimensional measurement was similarly performed on a non-deburred oxide superconducting wire sample which was manufactured under the same conditions as described above and was not deburred on both sides by sandpaper. The results are shown in Table 1.

  From the test results shown in Table 1, it is possible to produce an oxide superconducting wire with a small width crossing and a high width dimensional accuracy by deburring and making an oxide superconducting wire having no Sn plating layer on both sides. Became clear.

An accelerated test was conducted to examine the effect of the oxide superconducting wire having the above structure upon cooling at a low temperature.
A plurality of oxide superconducting wires having the same structure as that of Example 1 were prepared, and a plurality of samples were prepared by changing the thickness of the solder layer remaining after polishing on both outer surfaces.
Samples were prepared in which the thickness of the tin solder layer (4NSn layer) formed on the surface side of the copper tape used for manufacturing the oxide superconducting wire was 8 μm, 6 μm, 4 μm, 2 μm, and 0 μm. Samples with Sn solder layer thicknesses of 8 μm, 6 μm, and 4 μm were unpolished samples after the solder layers having the respective thicknesses were formed.
A sample having a solder layer thickness of 2 μm is formed by forming a solder layer having a thickness of 4 μm, and polishing with a paper file so that the solder layer has a thickness of 2 μm. A sample having a solder layer thickness of 0 μm is 4 μm This sample was formed by polishing with a paper file to form a solder layer of 0 μm after the solder layer was formed.

The accelerated test was performed in an environment of −45 ° C. where α-Sn was brought into contact with the solder layer forming portion of each metal stabilizing layer and the progress of embrittlement was considered to be the fastest. When the same acceleration test is performed with 4N—Sn alone, it is generally known that the material becomes brittle in 10 to 15 days, depending on the environment. In the following test results, the determination of embrittlement or not embrittlement was determined by the presence or absence of cracks due to volume expansion and by visual observation of surface discoloration.
Solder layer thickness (0 μm): No embrittlement (after 60 days)
Solder layer thickness (2 μm): No embrittlement (after 60 days)
Solder layer thickness (4 μm): embrittled in 60 days Solder layer thickness (6 μm): embrittled in 30 days Solder layer thickness (8 μm): embrittled in 21 days From this test result, the Sn solder layer was polished If 2 μm or less is left on the surface, it can be assumed that it is not affected by Sn embrittlement.
As the thickness of the tin solder layer on the surface of the metal stabilizing layer was reduced, the progress of Sn embrittlement could be suppressed. For this reason, when a polishing surface is formed on the outer surface side of the metal stabilization layer, the thickness of the remaining solder layer is preferably 2 μm or less in order to suppress Sn embrittlement. When the tin solder layer is thick, it is considered that Cu diffusion does not reach and a portion with high Sn purity occurs, and Sn embrittlement is likely to occur.

  The technology of the present invention can be used for oxide superconducting wires used in various power devices such as superconducting power transmission lines, superconducting motors, and current limiters.

  A ... oxide superconducting wire, 1 ... oxide superconducting conductor, 2 ... metal stabilizing layer, 2A ... metal tape, 2a ... front wall, 2b ... side wall, 2c ... back wall, 2e ... polished surface, 3 ... substrate, 3a ... both ends of the back surface, 4 ... intermediate layer, 5 ... oxide superconducting layer, 6 ... protective layer, 7 ... low melting metal layer (solder layer), 7a ... inner low melting metal layer, 7b, 7d, 7e ... outer low Melting point metal layer, 8, 9... Sn plating layer.

Claims (6)

A tape-shaped oxide superconducting conductor is formed by providing an intermediate layer, an oxide superconducting layer, and a protective layer on the surface of the tape-shaped substrate, and a metal stabilizing layer made of a metal tape is formed around the oxide superconducting conductor. Covering the protective layer side and both side surfaces of the tape-shaped oxide superconducting conductor is formed so as to cover at least a part of the substrate back side,
An inner low melting point metal layer is formed on the inner surface side of the metal stabilization layer, and an outer low melting point metal layer is formed on the outer side, and the metal stabilization layer is joined to the oxide superconducting conductor by the inner low melting point metal layer, The outer side surface portions of the stabilizing layer are polished to remove a part or the whole of the outer low-melting point metal layer, and a polished surface exposing both outer side surface portions of the metal stabilizing layer is formed. Oxide superconducting wire.   2. The oxide superconducting wire according to claim 1, wherein a residual layer of a low melting point metal layer is formed on the polished surface.   The oxide superconductivity according to claim 1 or 2, wherein a residual alloy layer made of an alloy of an element constituting the low melting point metal layer and an element constituting the metal stabilizing layer is formed on the polished surface. wire.   The oxide superconducting wire according to any one of claims 1 to 3, wherein a thickness of the low melting point metal layer remaining on both side surfaces of the metal stabilizing layer is 2 µm or less.   A tape-shaped oxide superconducting conductor comprising an intermediate layer, an oxide superconducting layer, and a protective layer on the surface of a tape-shaped substrate, and having a low melting point metal layer wider than the oxide superconducting conductor and on both sides. Using a metal tape, the metal tape was folded to cover the oxide superconductor with the metal tape so as to cover the protective layer side, both side surfaces, and at least the edge side of the back surface of the base material. Then, the low melting point metal layer is heated and melted to join the metal tape to the oxide superconductor, and then both outer side surfaces of the metal tape covering both side surfaces of the oxide superconductor are polished. A method for producing an oxide superconducting wire, characterized in that a metal stabilizing layer is formed by removing a part or all of a low melting point metal layer present on both outer surface portions to form a polished surface.   The thickness of the low melting point metal layer remaining on both outer side surface portions of the metal stabilizing layer is reduced to 2 μm or less by removing the low melting point metal layer present on both outer side surface portions of the metal tape by polishing. The method for producing an oxide superconducting wire according to claim 5.

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