JP2008117883A - Superconductive current-carrying member excellent in transformation capability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superconductive current-carrying material using an oxide superconductive material excellent in a transformation capability. <P>SOLUTION: Oxide superconductiors 1, 2 having spiral shapes are connected to a copper electrode 3 in an elastically transformable state, and there is provided a superconductive current-carrying member excellent in the transformation capability in which the oxide superconductors 1, 2 can be deformed when receiving tensile stress and bending stress. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a superconducting current-carrying member excellent in deformability using a superconductor having a spiral shape.

  In recent years, superconducting magnets that do not require a refrigerant for cooling a refrigerator are generally widely used. This is largely due to current leads using high-temperature oxide superconducting materials typified by Y-based and Bi-based materials. Since these oxide superconductors have a critical temperature exceeding the boiling point (77K) of liquid nitrogen, cooling the high temperature end (high temperature region) of the oxide superconductor to about 70K, Thermal intrusion to about 4K (10K or less), which is the cooling temperature range, can be greatly suppressed. Specifically, the low thermal conductivity of oxide superconductors and zero electrical resistance in the superconducting state significantly suppresses heat intrusion from high-temperature regions and heat generation in conductors compared to conventional copper leads. It was because it was done.

  A current-carrying member using such an oxide superconducting material typified by a current lead is disclosed in, for example, Patent Document 1, Non-Patent Document 1, and the like as a material using a Y-based or rare-earth material. Moreover, as a thing using Bi type material, it is disclosed by patent document 2, nonpatent literature 2, etc., for example.

  On the other hand, Patent Document 3 discloses a method for processing a spiral oxide superconducting material. This Patent Document 3 relates to a processing method capable of precision processing a difficult-to-process oxide superconductor and a precision processed oxide superconductor element, and describes a processing method of a superconductor having a spiral shape in Examples and the like. ing. However, as described in the title of the invention of Patent Document 3, the use as a material for a magnet for generating a magnetic field is described instead of a current lead. Patent Document 3 does not describe anything about the elastic deformability of the spiral oxide superconducting material or the deformability of the current-carrying member using the same.

JP 2004-47259 A JP 2002-280212 A JP 2005-191538 A H. Teshima, M. Sawamura and H. Hosei, "Properties of a few hundred A class Y-B-C-O bulk current lead usable in magnetic fields", Physica C, Vol. 378-381 (2002) p.827-832 Proceedings of the 4th International Symposium on Superconductivity (ISS'91) (Advances in Superconductivity IV), October 14-17, 1991, Tokyo, p.621

  In many cases, a current-carrying member represented by a current lead is a component for electrically connecting between devices or terminals, and it is desirable that the current-carrying member itself has flexibility. This is because the flexibility increases the degree of freedom in the device assembly process and improves the work efficiency, as well as reducing the impact caused by movement of the device and the stress generated by thermal contraction due to cooling. The reliability of the incorporated device can be improved.

  However, oxide superconducting materials have poor workability such as ductility, malleability, rigidity and the like, and lack flexibility (deformability) compared to metal materials such as copper.

  In view of the above problems, an object of the present invention is to provide a superconducting current-carrying material having an excellent deformability using an oxide superconducting material.

The gist of the present invention is that the current-carrying member having high deformability as the whole current-carrying member incorporating the oxide superconducting material is given to the oxide superconducting material having poor deformability as a material by giving a shape that is easy to deform. Specifically, it is as follows.
(1) A superconducting current-carrying member excellent in deformability, characterized in that a spiral oxide superconductor is elastically deformed and connected to an electrode.
(2) The deformability according to (1), wherein the elastic deformation rate of the spiral oxide superconductor (the ratio of the maximum displacement to the maximum size of the oxide superconductor) is 3% or more. Superconducting current-carrying member with excellent resistance.
(3) A plurality of spiral oxide superconductors are connected to the electrode, and the spiral direction is arranged in a direction in which the oxide superconductors cancel each other's magnetic field (1) Or a superconducting current-carrying member having excellent deformability as described in (2).
(4) The length of the oxide superconductor in the energization direction or the direction between the electrodes or the distance (D) between the electrodes is the dimension of the oxide superconductor in the direction perpendicular to the energization direction or the direction between the electrodes (width or The superconducting current-carrying member having excellent deformability according to any one of (1) to (3), wherein W> D with respect to thickness (W).
(5) The ratio (width / length: W / D) of the direction (width / thickness) orthogonal to the length of the energizing direction is in the range of 1.5 to 10 in (4) A superconducting current-carrying member having excellent deformability as described.
(6) The superoxide having excellent deformability according to any one of (1) to (5), wherein the spiral oxide superconductor is covered with a member having a deformable shape. Conductive conducting member.
(7) The superconducting current-carrying member having excellent deformability as set forth in (6), wherein the member covering the oxide superconductor has a bellows shape.
(8) The superconducting current-carrying member having excellent deformability according to any one of (1) to (7), wherein the electrode is any one of copper, a copper alloy, silver, or a silver alloy.
(9) The oxide superconductor has a RE ₂ BaCuO ₅ phase in a single-crystal REBa ₂ Cu ₃ O _7-x phase (RE is a rare earth element including Y or a combination thereof, x is an oxygen deficiency amount). The superconducting current-carrying member excellent in deformability according to any one of (1) to (8), characterized in that has a finely dispersed structure.
(10) One or more types of silver or a silver compound are dispersed in the oxide superconductor in an amount of 5 to 25% by volume. .
(11) The superconducting current-carrying member having excellent deformability according to any one of (1) to (10), which has an elastic deformation region of 3% or more with respect to at least one direction.
(12) The superconducting current-carrying member having excellent deformability according to any one of (1) to (10), having an elastic deformation region of 5 ° or more with respect to at least one angle.

  According to the present invention, by providing a superconducting current-carrying member having high deformability, it is easy to design and manufacture superconducting magnets such as metal-based superconducting magnets and oxide-based superconducting magnets, and workability and reliability are improved. In addition to magnets, the same effect can be expected for devices that require a relatively large current in a low temperature region in addition to magnets.

  In view of the above problems, the present invention provides a superconducting energizing member having high flexibility as the entire energizing member while using an oxide superconductor with poor deformability.

  Since the oxide superconducting material is basically a brittle material, cracks and cracks are likely to occur with respect to stress. In particular, since the crystal structure is two-dimensional, cleavage is caused between so-called ab planes. Easy to wake up. In addition, since the oxide superconducting material has a superconducting weak bond at the crystal grain boundary, it is necessary to be a single crystal material or a highly oriented material in order to obtain sufficient critical current density characteristics. Prone to cracking problems. However, depending on the shape to be imparted even in such a brittle material, sufficient deformability can be imparted as a whole.

  Specifically, by processing a thin plate-shaped oxide superconductor into a spiral shape as shown in FIG. 1 by sandblasting or the like, a certain amount of displacement is elastic in the positional relationship between the outer peripheral end and the inner peripheral end. This is possible in the deformation area. That is, by providing a spiral shape, the superconductor can be deformed while maintaining a sufficient critical current density characteristic without causing defects such as cracks and cracks. At this time, FIG. 1 shows a spiral shape close to a circle, but a polygonal spiral shape such as a quadrangle or a hexagon may be used.

For example, in a rare earth (RE) type oxide superconducting material having a critical temperature of 90K class, a QMG material having high critical current density characteristics (RE ₂ BaCuO ₅ is contained in a single-crystal REBa ₂ Cu ₃ O _7-x). The finely dispersed material, RE is a rare earth element including Y or a combination thereof, and x is an oxygen deficiency amount) is reliably cracked or cracked when deformed by 3% even under relatively strong compressive stress. However, characteristic deterioration occurs.

  On the other hand, when it has a spiral shape as shown in FIG. 1, even in the in-plane direction of the spiral, 3% deformation does not cause cracks, cracks, etc., and characteristic deterioration does not occur. Furthermore, in the direction perpendicular to the spiral surface, even when the displacement between the outer peripheral end and the inner peripheral end exceeds 10%, characteristic deterioration does not occur. The elastic deformation rate at this time is calculated as “the ratio of the maximum displacement to the maximum dimension of the oxide superconductor”.

Further, in the case of a 1 mm thick QMG material having a spiral shape as shown in FIG. 1, the maximum elastic deformation rate in a state where no cracks or cracks occurred was 42%. This maximum elastic deformation rate tends to increase as the cross-sectional area of the winding decreases. However, when the cross-sectional area is made extremely thin, it becomes impossible to withstand the load due to its own weight or its own weight during vibration. Therefore, the cross-sectional area of the winding is preferably more than 1 mm ² , and in this case, the maximum elastic deformation rate is about 80%. .

  In a current-carrying member such as a current lead, it is desirable to avoid generation of a magnetic field in the member. This is because the critical current density characteristic is reduced due to the generation of a magnetic field, and it is often necessary on an electric circuit to minimize the inductive component and to use a current-carrying member having only a resistance component. In such a case, a current-carrying member that suppresses the generation of a magnetic field is possible by using a superconductor in which two spiral oxide superconductors are electrically connected so as to cancel the magnetic field generated by the spiral. It becomes.

  In order to reduce the size and weight of the superconducting magnet, it is desirable to improve the thermal insulation characteristics of the current lead that prevents heat from entering and to shorten the length of the superconducting magnet. That is, it is desirable that the length of the energization member in the energization direction is short. Such a situation is made possible by arranging spiral oxide superconductors 1 and 2 between two copper electrodes 3 as shown in FIG. Specifically, it is possible to obtain high thermal insulation by increasing the distance in the direction perpendicular to the energization direction, and at the same time, it is possible to shorten the entire energization member with respect to the energization direction. In such an arrangement, the length (or interelectrode distance) (D) of the oxide superconductor is more than the width (W) of the superconductor in the energizing direction or the direction orthogonal to the direction between the electrodes. It will be large (W> D). On the other hand, when D is extremely small with respect to W, the bending angle cannot be sufficiently obtained. Thus, as a result of extensive studies, it was found that W / D is more preferably in the range of 1.5 to 10.

  The member covering the oxide superconductor in the current-carrying member desirably has a high deformability in itself in order to impart a high deformability to the whole current-carrying member. For example, in the configuration of FIG. 2, the relative position between the copper electrodes 3 can be easily changed by using a bellows pipe 4 made of stainless steel as a material for connecting the copper electrodes 3. By providing a spiral shape to the oxide superconducting material and arranging a cover having a shape that is easily deformed between the copper electrodes 3, while protecting the oxide superconducting material inside, the entire energizing member has high deformability. It becomes possible to grant. The electrode is preferably any one of copper, copper alloy, silver or silver alloy.

Bi-based and RE-based sintered bodies and tape wires can be used as the oxide superconducting material connecting the electrodes 3, but from the viewpoint of critical current density characteristics in a magnetic field and ease of handling, a single crystal A QMG material in which RE ₂ BaCuO ₅ is finely dispersed in a shaped REBa ₂ Cu ₃ O _7-x is desirable. Furthermore, it is desirable that 5 to 25 mass% of silver or silver compound particles are dispersed. This is because the mechanical strength of the oxide superconducting material itself can be improved by the presence of silver or silver compound particles. If it is less than 5%, the effect is insufficient, and if it exceeds 25%, the volume fraction of the superconducting phase itself is lowered, and there is a high possibility that the critical current density characteristic is lowered.

  The current-carrying member such as a current lead having the configuration shown in FIG. 2 is not deteriorated even by deformation caused by pulling of 3% or more of the entire length. Further, even in the cantilever bending deformation, there is no characteristic deterioration even when the bending angle shown in FIG. On the other hand, for example, in a normal current lead in which a rod-shaped superconducting material is arranged between copper electrodes, the characteristic deterioration surely occurs with respect to 3% elongation and 5 ° bending deformation. The maximum elongation rate and bending rate of the entire current-carrying member are not limited by the spiral superconducting deformability, but rather by design constraints such as cover deformability or electrode dimensions. In the case of the energizing member shown in FIG. 3, the rate of elongation is determined by the breaking of the cover or the breaking of the connecting portion between the electrode and the cover. Regarding the maximum bending rate, the contact between the electrodes and the destruction of the connection portion between the electrodes and the cover are the rate-limiting conditions. It is desirable to design the substantial maximum elongation and maximum bending rate to be 15% or less and 30 ° or less, respectively.

(Example 1)
Slice and cut a Gd-based QMG material (a material in which Gd ₂ BaCuO ₅ is finely dispersed in a single crystalline GdBa ₂ Cu ₃ O _7-x ) having a diameter of 50 mm and a thickness of 25 mm to which 10% by mass of silver has been added. A superconducting wafer having a thickness of 50 mm and a thickness of 1 mm was produced. The c-axis almost coincided with the normal of the wafer surface. Then, it processed into the spiral shape of outer diameter 44mm shown in FIG. 1 using the sandblasting method. Similarly, after two sheets were produced, silver was formed on the inner peripheral end and the outer peripheral end by a sputtering method. Thereafter, oxygen annealing treatment was performed, and oxide superconducting materials 1 and 2 having a spiral shape were produced.

  The obtained spiral oxide superconductors 1 and 2 were arranged so as to cancel the magnetic fields generated by energization between the copper electrodes 3 as shown in FIG. At this time, the inner peripheral ends of the coils were soldered together, and the outer peripheral ends (about one turn) were soldered to the copper electrodes 3 respectively. Furthermore, the copper electrode 3 was solder-connected so as to cover the space between the copper electrodes 3 by a bellows pipe 4 made of SUS316L and having a thickness of 0.2 mm.

  The elastic deformation rate of the oxide superconductor in the current-carrying member thus obtained has a maximum displacement of 10 mm with respect to the maximum dimension (44 mm) of one superconductive conductor, and the elastic deformation rate is 22.7. %, Exceeding 3%. The distance between the electrodes was 20 mm, the width of the superconductor was 44 mm, and the W / D was 2.2, which was 1.5 or more.

  Moreover, the obtained electricity supply member was cooled in liquid nitrogen (77K), and it confirmed that it had an electricity supply capacity of 540A.

  Next, the test which pulls the both ends of an electrode with respect to the electricity supply member produced as mentioned above was implemented. A displacement of 2.5 mm was applied to the length of 80 mm in the energizing direction of the energizing member. After such a tensile test, cooling in liquid nitrogen (77K) and measuring the current carrying capacity were the same as 540A before the tensile test.

  Furthermore, a copper electrode on one side was fixed, stress was applied to the electrode on the other end in a direction perpendicular to the energizing direction, and a bending test was performed on the energizing member. As shown in FIG. 3, after bending at 6 °, cooling in liquid nitrogen (77K) and measuring the current carrying capacity, it was the same as 540A before the bending test.

  From these results, it was revealed that this energizing member can withstand 3.1% tensile deformation and 6 ° bending deformation.

  As a comparative material, a current-carrying member produced by replacing a bar-shaped (2.0 mm × 1.0 mm × 40 mm) oxide superconductor (same composition component as in this example) with the spiral oxide superconductor. As shown in FIG. 10 mm each of both end portions of the rod-shaped superconductor 5 was embedded in a hole in the copper electrode 3 and soldered. When the same tensile test and bending test were performed on the obtained current-carrying member, the superconductor in the current-carrying member was destroyed with respect to 0.5% tensile deformation and 1 ° bending deformation, and zero. It was in a state where conduction with resistance was not obtained.

  From this, it was found that the elastic deformation rate of the rod-shaped oxide superconducting material itself was less than 0.5% with respect to tension and less than 1 ° with respect to bending. From these facts, it was confirmed that the current-carrying member having the oxide superconductor provided with the spiral shape has high deformability.

(Example 2)
Gd (50) -Dy (50) -based QMG material having a diameter of 50 mm and a thickness of 25 mm to which 14% by mass of silver has been added (GdDyBaCuO ₅ is fine in single-crystal Gd _0.5 Dy _0.5 Ba ₂ Cu ₃ O _7-x The dispersed material was sliced and a superconducting wafer having a diameter of 50 mm and a thickness of 1.2 mm was produced. The c-axis almost coincided with the normal of the wafer surface. Then, it processed into the spiral shape of outer diameter 44mm shown in FIG. 1 using the sandblasting method. Thereafter, silver was formed on the inner peripheral edge and the outer peripheral edge by sputtering.

  The obtained spiral oxide superconductor was disposed so as to be connected to the silver paste baking connection portion 7 between the silver electrodes 6 as shown in FIG. Thereafter, the inner peripheral end and the outer peripheral end (about one turn) of the coil were respectively connected to the silver electrode 6 by silver paste. The superconductor and silver electrode 6 were baked at about 880 ° C. and then subjected to oxygen annealing. Furthermore, the silver electrodes 6 were soldered so as to cover the space between the silver electrodes 6 by a bellows pipe 4 made of SUS304 having a thickness of 0.3 mm and processed into a bellows. The elastic deformation rate of the oxide superconductor in the current-carrying member thus obtained has a maximum displacement of 10 mm with respect to the maximum dimension (44 mm) of one superconductive conductor, and the elastic deformation rate is 22.7. %, Exceeding 3%. The distance between the electrodes was 10 mm, the width of the superconductor was 44 mm, and the W / D was 4.4, which was 1.5 or more.

  Moreover, the obtained electricity supply member was cooled in liquid nitrogen (77K), and it confirmed that it had an electricity supply capacity of 520A.

  Next, the test which pulls the both ends of the silver electrode 6 with respect to the electricity supply member produced as mentioned above was implemented. A displacement of 2.5 mm was applied to a length of 70 mm in the energizing direction of the energizing member. After such a tensile test, it was cooled in liquid nitrogen (77K), and the current carrying capacity was measured. As a result, it was the same as 520A before the tensile test.

  Furthermore, a silver electrode on one side was fixed, a stress was applied to the electrode on the other end in a direction perpendicular to the energizing direction, and a bending test was performed on the energizing member. After bending at 5.5 ° by the method shown in FIG. 3 and cooling in liquid nitrogen (77K) and measuring the current carrying capacity, it was the same as 520A before the bending test.

  From these facts, it was revealed that this energizing member can withstand 3.5% tensile deformation and 5.5 ° bending deformation.

It is a figure which shows the QMG material (44.0 mm of outer periphery, thickness 1.0mm, inner periphery 14.0mm) which provided the spiral shape. It is a figure which shows the structural example of the electricity supply member which connected two spiral QMG materials and was arrange | positioned between copper electrodes. It is a figure which shows the example of an external appearance of a deformation | transformation of the electricity supply member at the time of application of a bending stress. It is a figure which shows the structural example of the rod-shaped superconducting material used for the comparison material, and an electricity supply member using the same. It is a figure which shows the structural example of the electricity supply member which has arrange | positioned one spiral QMG between silver electrodes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spiral-shaped oxide superconductor 2 Spiral-shaped oxide superconductor 3 Copper electrode 4 Bellows pipe processed into bellows 5 Bar-shaped superconductor 6 Silver electrode 7 Silver paste baking connection part

Claims (12)

  A superconducting current-carrying member excellent in deformability, characterized in that a spiral oxide superconductor is connected to an electrode in an elastically deformed state.   The elastic deformation rate (the ratio of the maximum displacement with respect to the maximum dimension of the oxide superconductor) of the spiral oxide superconductor is 3% or more. Superconducting current-carrying member.   3. A plurality of spiral oxide superconductors are connected to the electrode, and the spiral direction is arranged in a direction in which the oxide superconductors cancel out magnetic fields with each other. A superconducting current-carrying member having excellent deformability as described in 1.   The dimension (width or thickness) of the oxide superconductor in the direction perpendicular to the energizing direction or the direction between the electrodes is the length of the oxide superconductor in the energizing direction or the direction between the electrodes or the interelectrode distance (D). The superconducting conductive member having excellent deformability according to any one of claims 1 to 3, wherein W> D with respect to W).   5. The deformation according to claim 4, wherein the ratio (width / length: W / D) of the direction (width or thickness) orthogonal to the length of the energization direction is in the range of 1.5-10. Superconducting current-carrying member with excellent performance.   The superconducting current-carrying member excellent in deformability according to any one of claims 1 to 5, wherein the spiral oxide superconductor is covered with a member having a deformable shape. .   The superconducting current-carrying member excellent in deformability according to claim 6, wherein the member covering the oxide superconductor has a bellows shape.   The superconducting current-carrying member excellent in deformability according to any one of claims 1 to 7, wherein the electrode is any one of copper, a copper alloy, silver, or a silver alloy. In the oxide superconductor, the RE ₂ BaCuO ₅ phase is finely dispersed in a single-crystal REBa ₂ Cu ₃ O _7-x phase (RE is a rare earth element including Y or a combination thereof, x is an oxygen deficiency amount). The superconducting current-carrying member having excellent deformability according to any one of claims 1 to 8, wherein the conductive material has a deformed structure.   The superconducting current-carrying member excellent in deformability according to claim 9, wherein at least one kind of silver or a silver compound is dispersed in the oxide superconductor in an amount of 5 to 25% by volume.   The superconducting current-carrying member excellent in deformability according to any one of claims 1 to 10, having an elastic deformation region of 3% or more with respect to at least one direction.   The superconducting current-carrying member excellent in deformability according to any one of claims 1 to 10, which has an elastic deformation region of 5 ° or more with respect to at least one angle.

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