JP2001110255A - High strength orientation multicrystal metal substrate and oxide superconductive wire material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multicrystal metal substrate for an oxide superconductive wire material with high strength and high orientation. SOLUTION: A metal substrate for an oxide superconductive wire material is formed of a flexible metal tape which has an internal metal layer with at least a portion formed of iron based alloy and a surface metal layer formed of one type selected out of the groups consisting of nickel, nickel oxide and nickel alloy mainly containing nickel and provided on the outer periphery of the internal metal layer. The aggregate structure show that the 100} planes of crystal grains of nickel, nickel oxide or nickel alloy in the surface metal layer are almost parallel to the surface of the tape and the <001> axes are almost parallel to the rolling direction of the tape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-strength oriented polycrystalline metal substrate and an oxide superconducting wire obtained by forming an oxide superconductor layer on the substrate.

[0002]

2. Description of the Related Art A method for producing a superconducting wire using an oxide superconductor is mainly classified into the following two methods.

In the first method, a metal sheath is filled with an oxide superconductor powder and processed into a wire, and a heat treatment is performed after or during the processing to obtain an oxide superconducting wire. ) Method.

As a typical example of the superconducting wire by this method, a Bi-based oxide superconductor (Bi2121, Bi222) is used.
There is a superconducting tape wire in which 3) is present as many filaments in a silver or silver alloy sheath. The production speed of such a superconducting tape wire, for example, reaches 100 m / h with a Bi2223-based wire, but its critical current density (Jc) is 77 K, 2 to 6 × 10
It is about ⁴ A / cm ² . Further, the sheath material is made of silver or a silver alloy, and the tensile stress that does not lower the critical current density is about 100 MPa.

The second method is a method in which an intermediate layer is provided on a polycrystalline metal substrate by controlling the crystal orientation, and an oxide superconducting thin film is formed thereon to form a wire. In this case, the intermediate layer suppresses the diffusion reaction between the metal substrate and the oxide superconducting layer, and further controls the orientation of the oxide superconducting layer formed thereon, thereby improving the bonding of the crystal grains. It is possible to obtain a high critical current density.

As a typical example of the superconducting wire according to this method, yttrium-stabilized zirconia (YSZ) is formed into an intermediate layer on a Hastelloy alloy tape by ion beam assisted deposition (IBAD) to form an intermediate layer. YBa by laser ablation method
There is also a tape wire obtained by forming a ₂ Cu ₃ O _7-y (Y123) oxide superconducting thin film.

The superconducting tape wire obtained by this method has a Jc of 77 K and 1 × 10 ⁶ A / cm ² under a self-magnetic field.
But the film formation rate of the intermediate layer is 0.001 to 0.1
m / h, which is extremely slow, and there is an industrial problem.

As a similar example, there is a method called RABiTS method. In this method, nickel metal is rolled and heat-treated to form a textured nickel tape, and Pd or the like is then electron-beam evaporated, CeO ₂ or Y
In this method, an intermediate layer is formed by depositing SZ by sputtering or the like, and then a Y123-based superconductor film is formed by laser ablation.

The superconducting wire produced by this method also has a Jc of 77.
K, reaching 1 × 10 ⁶ A / cm ² under a self-magnetic field,
Since the intermediate layer is formed through a plurality of thin film forming processes, there are problems in that the production speed as a wire is low and the cost is low. Furthermore, Ni that has been textured as a polycrystalline metal substrate by heat treatment is annealed and softened, and has a strength (tensile strength) of about 30 MPa. Therefore, there is a problem in strength as an oxide superconducting wire substrate.

There is also a method of forming an oxide superconducting layer directly on a polycrystalline metal substrate. In this method, silver that does not impair the properties of the oxidized superconductor by a diffusion reaction is subjected to rolling and heat treatment to form a texture, which is used as a polycrystalline metal substrate, and a Y123-based superconductor is formed thereon by a laser ablation method. This is a method of forming a film. In the superconducting wire according to this method, 1 × 10
Jc of ⁶ A / cm ² can be obtained.

However, silver is difficult to form a texture, and there is a limit in improving the orientation. Further, silver is annealed by heat treatment and softened. The Young's modulus of silver is about 81 GPa, which is extremely small as compared with the Young's modulus of nickel of 210 GPa, and there is a serious problem in strength. Another problem is that the price of silver is high industrially.

In addition, SOE (Surface Oxid)
A method called the “Epiation method”
The polycrystalline metal tape textured by rolling and heat treatment is oxidized to directly form a highly oriented metal oxide layer, which is then used as an intermediate layer on which a laser ablation method or liquid phase epitaxial method is applied. The oxide superconductor layer is formed by the method.

According to this method, a highly oriented metal surface can be obtained by texture-assembly. However, in order to obtain an oriented oxide layer, selection of a metal material and a heat treatment method thereof is important. If the orientation of the oxide layer serving as the intermediate layer is low, Jc is limited to the order of 10 ⁴ A / cm ² . Further, nickel and copper are typical examples of the metal substrate (metal tape), but both are annealed by a heat treatment for texture formation and are softened, and have a problem in strength.

[0014]

SUMMARY OF THE INVENTION As described above, PIT
According to the method, the obtained superconducting wire has a small Jc at 77K, and thus there is a limit to the use of the superconducting wire at 77K.

On the other hand, regarding the oxide superconducting thin film wire,
In the IBAD method and the RABiTS method, the process of forming the intermediate layer is complicated and the film formation rate is low, and thus there is an industrial problem. Also, the method of omitting the process of forming an intermediate layer using a silver substrate has problems in orientation and wire strength,
In the SOE method, the intermediate layer forming process can be sped up, but there are problems with the strength of the wire and the orientation of the metal oxide.

Furthermore, depending on the material of the metal substrate, there is a problem that the constituent elements react with the superconducting layer by diffusion, deteriorating the characteristics, causing a large magnetization loss due to magnetization, and increasing the AC loss in AC applications. is there.

An object of the present invention is to provide a polycrystalline metal substrate for an oxide superconducting wire having a high strength and a high orientation under the above circumstances.

Another object of the present invention is to provide an oxide superconducting wire having a high Jc in which an oxide superconductor layer is formed on such a polycrystalline metal substrate.

[0019]

Means for Solving the Problems In order to solve the above problems, the present inventors have made intensive studies and as a result, formed a surface metal layer with nickel, nickel oxide, or a nickel alloy containing nickel as a main component, A composite metal material having an internal metal layer formed of a metal that can be diffusion-bonded to nickel can obtain a texture on the substrate surface by rolling and appropriate heat treatment. It has been found that a polycrystalline metal substrate having high strength and high orientation can be obtained by using a high-strength metal material. The present invention is based on such findings.

That is, according to the present invention, at least a part of the inner metal layer is made of an iron-based alloy, and nickel, nickel oxide and a nickel alloy mainly containing nickel are formed on the outer peripheral surface of the inner metal layer. 1 selected from the group
A metal substrate for an oxide superconducting wire comprising a flexible metal tape having a surface metal layer made of a seed, wherein {100} faces of nickel, nickel oxide or nickel alloy crystal grains of the surface metal layer are formed on the tape surface. Is almost parallel to
And a high-strength oriented polycrystalline metal substrate characterized by exhibiting a texture whose <001> axis is substantially parallel to the rolling direction of the tape. Of course, the entire internal metal layer of the metal substrate may be formed of an iron-based metal.

In the metal substrate of the present invention, the strength as a metal substrate is borne by a high-strength metal made of an iron-based alloy constituting the internal metal layer, and the orientation required for the substrate is given by nickel, nickel oxide or nickel on the surface metal layer. The nickel alloy part will play a role.

According to the metal substrate of the present invention configured as described above, since the surface metal layer is made of nickel, nickel oxide or nickel alloy, the oxide layer is directly oxidized on the metal tape by the oxidation treatment as in the SOE method. Also, the formation of the intermediate layer can be accelerated.

Further, since the metal substrate of the present invention uses an iron-based alloy typified by stainless steel as a composite reinforcing material, it has high strength even at a high temperature, and requires a high temperature as in a liquid phase epitaxial method. The present invention can be sufficiently applied to a high-speed film forming process for forming an oxide superconductor thin film.

With respect to the metal constituting the surface metal layer, the orientation is reduced by an orientation treatment, an oxidation treatment, or a diffusion reaction with the internal metal layer during the formation of the oxide superconductor thin film, or the surface metal layer is too thin. It is conceivable that the texture of the orientation is disturbed by the influence of the texture of the internal metal layer, but the thickness of the surface metal layer after rolling is reduced by the metal constituting the internal metal layer during the heat treatment for orientation. Thicker than the spreading distance,
For example, when the thickness is 4 μm or more, a good oriented structure can be obtained by the heat treatment.

However, if the strength of the inner metal layer is to be increased, the smaller the proportion of the surface metal layer in the entire surface metal layer, the better. In this case, for the internal metal layer, a metal having a face-centered cubic structure can easily obtain a high degree of orientation, and an austenitic stainless steel is also preferable.

As the iron-based metal constituting the internal metal layer,
Examples include stainless steel, chromium-molybdenum steel, manganese steel, nickel-chromium steel, chromium-manganese steel, and the like. The thickness of the internal metal layer is 8 to 1 from the thickness of the substrate.
Preferably, the thickness is reduced by 0 μm.

Since austenitic stainless steel is non-magnetic, its magnetism can be reduced in the case of a composite material as compared with pure nickel. In this respect, it is also effective for AC applications.
Furthermore, when an oxide layer is formed at the interface between the internal metal layer and the surface metal layer, the diffusion of the constituent elements of the internal metal layer can be suppressed, so that the reaction between the oxide superconductor layer and the constituent elements of the substrate can be suppressed. Becomes possible.

As described above, according to the present invention, it has a high orientation and a high strength, and can significantly improve the problem of magnetism and the problem of deterioration of superconductivity due to diffusion of constituent elements of a substrate. It is possible to obtain a high strength oriented polycrystalline metal substrate and an oxide superconducting wire.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below.

Example 1 This example shows the effect of increasing the strength when stainless steel is used as the internal metal layer and the effect of lowering the magnetism when using the austenitic stainless steel as the internal metal layer. .

SUS310S, SUH31, SUH30 were placed on a nickel pipe having a diameter of 20 mm and a thickness of 2.5 mm.
9, SUH310, or SUS316 austenitic stainless steel, or SUS430 ferrite stainless steel rods are inserted, and after swaging,
A heat treatment at 800 ° C. was performed in an argon atmosphere.

Subsequently, a thickness of 0.2 mm was obtained by rolling.
Nickel / stainless steel composite tape.

As a comparative example, a metal pipe having the same shape of nickel pipe in which copper and an alloy of 70 wt% of copper and 30 wt% of nickel were inserted, and a pure nickel rod having a diameter of 20 mm were processed in the same manner.

These composite tapes were annealed in an argon atmosphere at 1000 ° C. for 1.0 hour to perform an orientation treatment.

Next, a tensile test was performed on the tape subjected to the orientation treatment at room temperature, and the proof stress was compared. Further, the ratio of nickel {100} plane to the crystal grain surface was determined by X-ray diffraction measurement. Further, the hysteresis of magnetization indicating AC loss was determined by an electromagnetic induction method at liquid nitrogen temperature. The external magnetic field applied at this time is 0.1 Tp-p. Table 1 below shows the results.

[0036]

[Table 1]

From Table 1 above, it can be seen that 80% or more of the crystal grains of each tape are oriented in the nickel {100} plane, and there is no inferiority in the orientation. On the other hand, when compared in terms of proof stress, pure nickel, the nickel / copper composite tape, and the nickel / copper 70 wt% -nickel 30 wt% alloy composite tape are 100 MPa or less smaller than the proof stress of any nickel / stainless steel composite tape. It can be seen that the metal substrate according to (1) shows higher strength.

Hysteresis due to magnetization can be reduced to one-fourth or less when a nonmagnetic material such as copper or austenitic stainless steel is used as the inner metal layer, as compared with Ni ferritic stainless steel. It turns out that it is effective for AC application.

[Embodiment 2] This embodiment is an embodiment relating to the thickness and orientation of the surface metal layer.

A SUS310 rod was inserted into a nickel pipe having a diameter of 20 mm and a thickness of 2.5 mm, and after swaging, heat treatment was performed at 800 ° C. for 1 hour in an argon atmosphere. Thereafter, a nickel / SUS310 steel composite tape having a thickness of 0.3 mm was produced by rolling.

The composite tape was placed in an argon atmosphere at 1000 ° C. for 15 minutes, 30 minutes, 1 hour and 1.
Anneal each for 5 hours to obtain nickel-SUS31
0 composite tape.

The boundary between the outermost layer of nickel and SUS310 was not clear, and there was a gradient in the concentration of iron, nickel and chromium. In particular, as a result of the EPMA observation, the diffusion distance of the iron element to the nickel side of the surface metal layer was the largest as compared with before the heat treatment. The orientation of nickel, which is a surface metal layer, is examined by X-ray diffraction measurement, and the diffusion length of iron element is EP
Observed by MA. The results are shown in Table 2 below.

[0043]

[Table 2]

From Table 2 above, it can be seen that in order to obtain a high degree of orientation of the surface metal layer, a heat treatment of 30 minutes or more is preferable, but when held for 1 hour or more, there is little change in the orientation. On the other hand, since the diffusion of the iron element by the orientation treatment is 2.4 μm in 30 minutes and 30 μm in 1 hour, the thickness of the surface metal layer before the orientation treatment is preferably 3 μm or more. Considering that, it is more preferable that the thickness be 4 μm or more.

Subsequently, the tape which had been subjected to the orientation treatment at 1000 ° C. for 1 hour was subjected to oxidation treatment at 1100 ° C. for 0.5 hour in an oxygen atmosphere to form a NiO layer on the surface. The {100} plane of the obtained NiO crystal is parallel to the underlying nickel surface, and as shown in the X-ray pole figure shown in FIG.
It was confirmed that the 00> axis was oriented highly parallel to the rolling direction.

[Embodiment 3] This embodiment shows an example of fabricating an oriented substrate when a nickel alloy containing nickel as a main component is used for the surface metal layer, and the effect of using a nickel-copper alloy as the surface metal layer. This is an example.

Ni89 having an outer diameter of 20 mm and a thickness of 2.5 mm
wt% -Cr11wt% alloy pipe, Ni90wt%-
V10wt% alloy pipe and Ni84wt% -Cu
A SUS310 rod was inserted into a 16 wt% alloy pipe, and after swaging, heat treatment was performed at 500 ° C. for 1 hour in an argon atmosphere. Thereafter, a nickel alloy / SUS310 steel composite tape having a thickness of 0.3 mm was produced by rolling.

The composite tape was annealed at 920 ° C. for 1.5 hours in an argon-4% hydrogen mixed gas atmosphere to obtain a nickel alloy-SUS310 composite tape.

As a result of EPMA observation, the boundary between SUS310 and the surface metal layer was not clear, and a gradient was formed in the concentration of iron, nickel, and chromium. The orientation of the nickel alloy as the surface metal layer was examined by X-ray diffraction measurement. Further, hysteresis due to magnetization was measured by an electromagnetic induction method in the same manner as in Example 1. The results are shown in Table 3 below.

[0050]

[Table 3]

From Table 3 above, it can be seen that 90% or more of the crystal grains are oriented in the nickel {100} plane, and that the hysteresis is obtained when the surface metal layer is formed of Ni alone (Example 1). This is extremely small, indicating that it is effective for AC applications.

Nickel alloy / SU subjected to the above orientation treatment
The S310 steel composite tape was subjected to an oxide layer forming treatment by changing the oxygen partial pressure at 1050 ° C. However, Ni8
9wt% -Cr11wt% alloy, Ni 90wt% -V1
When a 0 wt% alloy is used as the surface metal layer, the oxygen partial pressure is 5%.
At a pressure of ^10-4 Torr or less, only oxides of Cr and V were formed, and when the oxygen partial pressure was increased, the oxide layer was peeled off.

However, Ni 84 wt% -Cu 16 wt%
When the alloy is used as the surface metal layer, the oxygen partial pressure is set to 5 × 10 ^−4.
From 1 to 10 ³ Torr, a NiO layer could be formed. Note that NiO at this time was NiO as a result of X-ray diffraction.
The (100) plane was oriented approximately 85% parallel to the tape plane. Therefore, the use of a 84 wt% Ni-16 wt% alloy for the surface metal layer is effective in reducing magnetism and forming an oriented oxide layer.

[Embodiment 4] This embodiment shows the superiority of orientation, magnetism and strength of a NiO oxide crystal layer formed by subjecting a composite material to heat treatment.

In the same manner as in Example 1, nickel and SUS
310S, SUH31, SUH309, SUH310,
Using SUS316 austenitic stainless steel and SUS430 ferritic stainless steel, nickel / stainless steel composite tapes each having a thickness of 0.2 mm were produced.

As a comparative example, a metal pipe in which copper and a 70 wt% -copper 30 wt% nickel alloy were inserted into a nickel pipe having the same shape, and a pure nickel rod having a diameter of 20 mm were processed in the same manner.

After annealing this composite tape in an argon atmosphere at 1000 ° C. for 1.0 hour to perform orientation treatment, the nickel / stainless steel composite tape and the nickel tape were heated at 1100 ° C. for 1 hour in an oxygen atmosphere. The heat treatment was performed on the copper or copper alloy composite tape at 1020 ° C. for 1 hour in an oxygen atmosphere to form an oxide crystal layer.

Then, as in Example 1, the proof stress, orientation, and hysteresis due to magnetization were compared. The results are shown in Table 4 below.

[0059]

[Table 4]

From Table 4 above, it can be seen that in each case 80% or more of the crystal grains are oriented in the NiO {100} plane, and there is no inferiority in the orientation. On the other hand, when compared with proof stress, pure nickel, nickel / copper composite tape, nickel / copper 70
It can be seen that the wt% -nickel 30 wt% alloy composite tape shows about half the proof stress of any of the nickel / stainless steel composite tapes, and that the present invention clearly shows higher strength.

The hysteresis caused by magnetization can be obtained by using a nonmagnetic material such as copper or austenitic stainless steel as the inner metal layer, as compared with Ni ferritic stainless steel.
Hysteresis can be reduced to less than one third,
It is effective for AC applications and shows that it is an excellent polycrystalline metal substrate.

[Embodiment 5] This embodiment shows the effect when an oxide of a constituent element of the internal metal layer is formed at the interface between the surface metal layer and the internal metal layer.

As in the case of the first embodiment, SU was added to the nickel pipe.
A nickel / stainless steel composite tape was manufactured by inserting a rod of S310S stainless steel and performing heat treatment and rolling. Subsequently, the composite tape was placed in air and argon,
Each alignment treatment was performed at 900 ° C. for 1 hour in an argon-hydrogen mixed gas.

At this time, the tape heat-treated in the air has a NiO layer having a thickness of about 6 μm on the surface of the tape, and a chromium oxide layer having a thickness of about 3 μm on the interface between nickel and stainless steel. SE is formed
It could be confirmed by M and EPMA observation.

On the other hand, a tape heat-treated in argon or an argon-hydrogen mixed gas has no chromium oxide layer,
Iron or chromium over the surface metal layer Ni
Had diffused to the side. After the NiO layer was polished and removed from the surface of the tape that had been heat-treated in air, all the tapes were subjected to a heat treatment at 1100 ° C. for 30 minutes in oxygen.

Subsequently, the cross section of each tape after the heat treatment was subjected to EP
Observation with MA revealed that the tape subjected to orientation heat treatment in argon or an argon-hydrogen mixed gas showed NiO
It was confirmed that iron was diffused inside. Nickel oxide had a thickness of 5 to 7 μm and was in contact with an iron oxide layer having a thickness of about 3 μm, and the iron oxide layer was in contact with a chromium oxide layer having a thickness of about 3 μm to reach the internal metal layer.

However, when the chromium oxide layer was formed at the interface between nickel and stainless steel, the nickel oxide layer having a thickness of about 5 μm, the chromium oxide layer having a thickness of about 8 μm, The structure was arranged in the order of layers, and it was found that the diffusion of iron was suppressed by the layer of chromium oxide.

When iron is mixed into the superconducting layer, the superconducting characteristics are remarkably reduced. Therefore, the oxide layer for suppressing the diffusion of iron is formed at the interface between the surface metal layer and the internal metal layer.
It is extremely useful for forming an oxide superconducting layer.

[Embodiment 6] This embodiment relates to an oxide superconducting wire. The nickel / stainless steel composite tape described in Example 5 was subjected to orientation treatment at 900 ° C. for 1 hour in argon, and further subjected to 1100 ° C., 30 ° C. in oxygen.
Oxidizing heat treatment for a minute. When the pole figure of the obtained NiO crystal was measured, it was confirmed that the {100} plane was parallel to the tape surface, and that the <001> direction was highly oriented in the rolling direction, exhibiting a texture.

Next, the Y123 oxide superconducting layer and the Nd123 were applied to the high intensity oriented polycrystalline metal substrate by laser ablation using a KrF excimer laser.
Oxide superconducting layer and Bi22 by sol-gel method
A 12 oxide superconducting layer was formed.

In the laser ablation method, the substrate temperature is set to 700 ° C. and the oxygen gas pressure of the atmosphere gas is set to 100 to 20.
0mmTorr, laser energy density is 2J / c
m ² , the laser repetition frequency is 10 Hz, and the film thickness of the Y123 oxide superconducting layer is about 0.3 μm.
It became. In the sol-gel method, a solution of a naphthenic acid solution of a constituent element was applied onto a substrate, and spin-coating and drying at 500 ° C. were repeated to deposit the solution to a thickness of 1 μm.

Subsequently, after partial melting at 900 ° C. in oxygen, heat treatment was performed at 850 ° C. for 5 hours in the air to form an oxide superconducting layer.

Further, an orientation treatment is performed so that the surface of the substrate is Ni
On a {100} <001> -oriented high-strength polycrystalline oriented substrate, a film of MgO is formed to a thickness of 0.4 μm by sputtering, and Y is formed by laser ablation under the above conditions.
A 123 oxide superconducting layer was formed. Jc of this superconducting wire was measured at 77 K under a self-magnetic field, and the results shown in Table 5 below were obtained.

[0074]

[Table 5]

From Table 5 above, it can be seen that the conventional IBAD method and RAB
It can be seen that Jc similar to Jc obtained by the iTS method can be obtained in the Y123 superconductor layer or the Nd123 superconductor layer. In addition, since the Bi-based superconductor has the same Jc as that formed on the silver substrate, it can be seen that the characteristic deterioration due to the diffusion of the constituent elements of the metal substrate can be prevented.

[0076]

As described above in detail, according to the present invention, a high-strength, highly-oriented polycrystalline metal substrate can be obtained, and a metal substrate having a highly-oriented intermediate layer can be obtained by oxidation treatment. It is possible to get. Further, by forming a superconducting layer on such a metal substrate, a superconducting wire having a high Jc can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an X-ray pole figure showing the orientation of a Ni-SUS310 composite tape obtained in Example 2.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshihiko Maeda 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Matsumoto required 1-14-1 Shinonome, Koto-ku, Tokyo (72) Inventor Izumi Hirabayashi 1-14-3 Shinonome, Shintomo, Koto-ku, Tokyo F-term (reference) 5G321 in the Superconductivity Engineering Research Center, International Superconducting Technology Research Center, Tokyo AA01 AA04 AA05 BA01 BA14 CA04 CA21 CA24 CA27 CA28 DB23 DB25 DB38

Claims (9)

[Claims] 1. An internal metal layer at least a part of which is made of an iron-based alloy, and nickel, nickel oxide, and a nickel alloy containing nickel as a main component formed on the outer peripheral surface of the internal metal layer. A metal substrate for an oxide superconducting wire made of a flexible metal tape having a surface metal layer of one kind selected from the group consisting of {100} crystal grains of nickel, nickel oxide or a nickel alloy of the surface metal layer.
The surface is substantially parallel to the tape surface, and its <001>
A high-strength oriented polycrystalline metal substrate characterized by exhibiting a texture whose axis is substantially parallel to the rolling direction of the tape. 2. An iron-based alloy constituting the internal metal layer is stainless steel, and a recrystallization texture is formed on the surface metal layer by performing recrystallization heat treatment, and the surface metal layer is formed by the heat treatment. 2. The high-strength oriented polycrystalline metal substrate according to claim 1, wherein the substrate has a thickness larger than a diffusion distance of an element constituting the internal metal layer. 3. The high-strength oriented polycrystalline metal substrate according to claim 1, wherein the thickness of the surface metal layer is 4 μm or more. 4. The high-strength oriented polycrystalline metal substrate according to claim 1, wherein the iron-based alloy constituting the internal metal layer is austenitic stainless steel. 5. A flexible metal substrate formed by subjecting a high-strength oriented polycrystalline substrate according to claim 1 to a heat treatment to form an oxide crystal layer mainly composed of nickel oxide on the surface thereof. Wherein (10) of crystal grains of the oxide crystal layer
0) A high-strength oriented polycrystalline metal substrate having a crystal orientation in which the plane is substantially parallel to the substrate surface. 6. At least one of metal elements constituting the internal metal layer is provided at an interface between the internal metal layer and the surface metal layer.
The high-strength oriented polycrystalline metal substrate according to claim 5, wherein an oxide layer made of an oxide of one of various kinds of metal elements is formed. 7. The high-strength oriented polycrystalline metal substrate according to claim 1, wherein the nickel alloy constituting the surface metal layer is a nickel-copper alloy, and the surface thereof is mainly made of nickel oxide. The high-strength oriented polycrystalline metal substrate according to claim 5, wherein an oxide crystal layer as a component is formed. 8. A superconductor layer mainly composed of an oxide superconductor is formed on the high-strength oriented polycrystalline metal substrate according to any one of claims 1 to 7 directly or via an intermediate layer. Oxide superconducting wire. 9. An oxide superconductor which is a main component of the superconductor is R
EBa ₂ Cu ₃ O _x (wherein, RE represents a Y or Nd, x is. Indicates the number close to 7) oxidation of claim 8, which is a superconducting material represented by a chemical formula consisting Superconducting wire.