JP4569224B2 - Test method for oxide superconducting wire - Google Patents

Description

  The present invention relates to a method for testing a superconducting wire, and more particularly to a method for testing ballooning of a superconducting wire.

When a superconducting device such as a superconducting cable is used, the superconducting device is immersed in a liquid refrigerant such as liquid nitrogen or liquid helium in order to cool the superconducting filament in the superconducting device to a critical temperature ( _Tc ) or lower. , Kept at a very low temperature. On the other hand, at the time of inspection, for example, the superconducting device is taken out from the liquid refrigerant, and the temperature is raised from an extremely low temperature to room temperature by flowing a gas refrigerant at room temperature around the superconducting device. However, when the temperature rises to room temperature after immersion in a liquid refrigerant, the following problems have occurred in conventional superconducting equipment.

  That is, there are many small pinholes on the surface of the oxide superconducting wire constituting the superconducting device. When this oxide superconducting wire is immersed in a liquid refrigerant for a long period of time, the liquid refrigerant enters the voids of the superconductor filament in the oxide superconducting wire through the pinhole. When the temperature rises from this state to room temperature, if the rate of temperature rise is large, the liquid refrigerant that has entered the oxide superconducting wire vaporizes, and the vaporized gas is not released outside. As a result, the pressure inside the oxide superconducting wire increases, and the oxide superconducting wire expands. This phenomenon is called ballooning. When ballooning occurs, there is a problem that the superconductor filament is broken, resulting in a decrease in characteristics such as a decrease in critical current density.

  Therefore, in order to prevent ballooning from occurring in the superconducting cable, the following ballooning test is performed on the oxide superconducting wire used in the production of the superconducting cable. For example, an oxide superconducting wire having a length of 1 km is wound in a pancake shape while applying a tension of 9.8 N or more. Then, the oxide superconducting wire wound in a pancake shape is immersed in liquid nitrogen for a certain time. Here, the reason why the oxide superconducting wire is wound in a pancake shape is to make the oxide superconducting wire compact and to be easily immersed in liquid nitrogen. Thereafter, the oxide superconducting wire is taken out of the liquid nitrogen, thereby rapidly raising the temperature of the oxide superconducting wire to room temperature, and inspecting whether ballooning occurs in the oxide superconducting wire. In this way, the ballooning test is performed, and a superconducting device such as a superconducting cable is manufactured using an oxide superconducting wire that has not been ballooned.

JP-A-10-197468 (Patent Document 1) discloses a conventional superconducting wire testing method.
JP-A-10-197468

  However, the conventional method for ballooning testing of superconducting wires has a problem of low reliability. That is, as a result of the conventional ballooning test, ballooning may occur in a superconducting device manufactured using the superconducting wire even if ballooning does not occur in the superconducting wire.

  Accordingly, an object of the present invention is to provide a highly reliable method for testing a superconducting wire.

One test method of the oxide superconducting wire of the present invention includes a winding step of winding the oxide superconducting wire in a pancake shape while applying a tension of 0.49 N or more and less than 9.8 N to the oxide superconducting wire, It comprises a dipping step of removing by immersing a predetermined time an oxide superconducting wire after line process in a liquid refrigerant, and a step of inspecting the ballooning of the oxide superconducting wire after the immersion step.

  The present inventors have found that the problem that the reliability of the conventional test method is low is due to the following reason. That is, when a superconducting wire is wound in a pancake shape while applying a large tension of 9.8 N or more, a phenomenon of tight tightening occurs in the superconducting wire. When the phenomenon of tightening occurs in the superconducting wire, the superconducting wire does not swell, so even if liquid nitrogen enters the superconducting wire through the pinhole, the superconducting wire does not expand and ballooning does not occur. . However, when it is actually used for a superconducting device, the superconducting wire may be used in a shape having no tightening other than a pancake shape. Thus, when a superconducting wire is used in a state where there is a bulge, ballooning has occurred in the superconducting equipment.

Therefore, according to one test method of the oxide superconducting wire of the present invention, by winding the oxide superconducting wire with a tension less than 9.8 N, which is less than the conventional one, the phenomenon of winding tightening is applied to the oxide superconducting wire. It becomes difficult to occur. Thus, since it is swollen Shi filtered in the oxide superconducting wire, when there is a pinhole in an oxide superconducting wire, the liquid refrigerant may enter the inner oxide superconducting wire through a pin hole, ballooning the oxide superconducting wire Will occur. For this reason, it can be confirmed whether or not the oxide superconducting wire does not generate ballooning, and the reliability of the test can be improved. Further, by winding the oxide superconducting wire in tension of 0.49N or less on, it is possible to reliably winding the oxide superconducting wire.

Other test methods for the oxide superconducting wire of the present invention include a winding process in which a tape and an oxide superconducting wire are overlapped and wound in a pancake shape, a removing process for removing the tape after the winding process, and a removal process. It comprises a dipping process in which the oxide superconducting wire is dipped in a liquid refrigerant for a predetermined time after the process, and a process for inspecting the ballooning of the oxide superconducting wire after the dipping process.

According to another test method of the oxide superconducting wire of the present invention, the tape and the oxide superconducting wire are overlapped and wound once, and then the tape is removed, thereby oxidizing the oxide wound in a pancake shape. A gap can be generated between the superconducting wires. Since the gap is the white blisters of the oxide superconducting wire, when there is a pinhole in an oxide superconducting wire, the liquid refrigerant enters the inner oxide superconducting wire through a pin hole, ballooning in the oxide superconducting wire Will occur. For this reason, it can be confirmed whether or not the oxide superconducting wire does not generate ballooning, and the reliability of the test can be improved.

In the test method, preferably, in the dipping step, the oxide superconducting wire is dipped in a liquid refrigerant in a pressurized atmosphere. As a result, when the oxide superconducting wire has a pinhole, the liquid refrigerant easily enters the oxide superconducting wire through the pinhole. Therefore, it becomes easier to find the oxide superconducting wire in which ballooning occurs, and the reliability of the test is further improved.

According to the method for testing an oxide superconducting wire of the present invention, a bulge can be formed in an oxide superconducting wire wound in a pancake shape. Therefore, if there is a pinhole in an oxide superconducting wire, liquid nitrogen penetrates into the oxide superconducting wire through a pin hole, ballooning is generated in the oxide superconducting wire. Therefore, since it is possible to confirm whether or not the oxide superconducting wire does not generate ballooning, the reliability of the test can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a partial cross-sectional perspective view conceptually showing the configuration of a superconducting wire. With reference to FIG. 1, for example, a multi-conductor superconducting wire will be described. The superconducting wire 1 is, for example, a tape-shaped wire, and has a plurality of superconductor filaments 2 extending in the longitudinal direction and a sheath portion 3 covering them. Each material of the plurality of superconductor filaments 2 has, for example, a Bi—Pb—Sr—Ca—Cu—O-based composition, and in particular, an atomic ratio of (bismuth and lead): strontium: calcium: copper. A material containing the Bi2223 phase expressed approximately in a ratio of 2: 2: 2: 3 is optimal. The material of the sheath part 3 is made of silver, for example. Superconducting wire 1 has a width of 4.3 mm, a thickness of 0.2 mm, and a length of 1 km, for example.

  A pinhole 3a is generated in the superconducting wire 1 in which ballooning occurs. The pinhole 3a is generated, for example, so as to penetrate from the outside to the superconductor filament 2, or generated so as to connect the superconductor filaments 2 to each other.

  In addition, although the multi-core wire was demonstrated in the above, the oxide superconducting wire of the single core wire structure in which the single superconductor filament 2 is coat | covered with the sheath part 3 may be used.

  Next, a test method for the superconducting wire 1 according to the present embodiment will be described with reference to FIGS.

  First, as shown in FIG. 2, the superconducting wire 1 is wound in a pancake shape (coil shape) while applying a tension T to the superconducting wire 1. Specifically, for example, a flat plate 4 having a diameter of 800 mm, for example, having a reel 5 having a diameter of 318 mm at the center is prepared. Then, one end of the superconducting wire 1 is fixed to the reel 5. Then, the reel 5 is rotated in the direction indicated by the arrow A, and the superconducting wire 1 is wound around the reel 5 on the flat plate 4 while applying a tension T of 0.98 N to the superconducting wire 1. The tension T is set to 0.49 N or more and less than 9.8 N, preferably 9.0 N or less. A coil 10 wound with the superconducting wire 1 by this method is shown in FIGS.

  Next, as shown in FIG. 5, a container 7 filled with liquid nitrogen 8 is prepared, and the coil 10 of the superconducting wire 1 is immersed in the liquid nitrogen 8. Thereby, the superconducting wire 1 is cooled. The coil 10 is immersed for 24 hours, for example. While the coil 10 is immersed in the liquid nitrogen 8, the liquid nitrogen 8 is pressurized to 1 MPa, for example. Thereafter, by removing the coil 10 from the liquid nitrogen 8, the superconducting wire 1 is rapidly heated to room temperature.

  Subsequently, the superconducting wire 1 after the temperature rise is inspected for the occurrence of ballooning. At this time, in the case where the pinhole 3a (FIG. 1) is generated in the superconducting wire 1, the liquid nitrogen 8 that has entered through the pinhole 3a is vaporized, so that the swelling (ballooning) as shown in FIG. 11a to 11c are generated. The superconducting wire 1 is tested by the above method.

  The inventors of the present application found the reason why the reliability of the conventional test is low. This will be described in detail below.

  FIG. 7 is an enlarged view of a main part showing a coil wound by a conventional method. Referring to FIG. 7, superconducting wires 101 a to 101 c wound around reel 5 by a conventional method are arranged on flat plate 4. Superconducting wire 101a receives force f3 from superconducting wire 101b present on the inner diameter side than superconducting wire 101a, and receives force f4 from superconducting wire 101c located on the outer diameter side than superconducting wire 101a. In the conventional test method, since the tension applied to the superconducting wire during winding is as large as 9.8 N or more, the phenomenon of tight tightening occurs in the superconducting wire, and the force f3 and force f4 increase. As a result, swelling of superconducting wire 101a is suppressed by force f3 and force f4, and apparently ballooning does not occur.

  FIG. 8 is a cross-sectional view of the superconducting cable. FIG. 9 is an enlarged view of the cable core in FIG. With reference to FIGS. 8 and 9, superconducting cable 30 includes a cable core 31, a heat insulating pipe 38, and a corrosion protection layer 39. A single-core or multiple-core twisted cable core 31 is inserted into the refrigerant flow passage 37 formed inside the heat insulating pipe 38 and the anticorrosion layer 39. Then, the refrigerant flows through the outer periphery of the cable core 31 in the refrigerant flow passage 37.

  The cable core 31 is composed of a former (a plurality of copper strands) 32, a plurality of superconducting wires 1, craft paper 35, and insulating paper 34 in order from the inside. A plurality of superconducting wires 1 are spirally wound around the outer periphery of a former 32 made of a plurality of copper strands having an outer diameter of 20 mm, for example. The former 32 and the plurality of superconducting wires 1 constitute a spiral winding conductor. Each of the plurality of superconducting wires 1 has a laminated structure insulated from each other with the kraft paper 35 interposed therebetween. In the plurality of superconducting wires 1 that are the lower layer (inner diameter side), for example, 13 superconducting wires 1 are arranged at a pitch of 200 mm. Moreover, as for the several superconducting wire 1 which is an upper layer (outer diameter side), for example, 14 superconducting wires 1 are arrange | positioned at 200 mm pitch. The outer periphery of the superconducting wire 1 is covered with an insulating paper 34 made of, for example, polypropylene laminated paper (PPLP (registered trademark)).

  FIG. 10 is a cross-sectional perspective view of a spiral winding conductor. In FIG. 10, the superconducting wire 1 in the upper layer is not shown. As shown in FIG. 10, in the spiral winding conductor 12, each of the plurality of superconducting wires 1 wound in a spiral shape around the outer periphery of the former 32 is arranged without being tightened, and the adjacent superconducting wires 1 are forced from each other. Not receive. For this reason, even when using the superconducting wire 1 in which ballooning did not occur in the conventional test, ballooning may occur in the superconducting cable 30 and the reliability of the test was low.

  On the other hand, in the present embodiment, since the superconducting wire 1 is wound while applying a weaker tension than the conventional one, the reliability of the test is improved. This will be described in detail below.

  FIG. 11 is an enlarged view of a main part of FIG. Referring to FIG. 11, superconducting wire 1 existing at an arbitrary position in superconducting wire 1 is referred to as superconducting wire 1a. Superconducting wire 1a receives force f1 from superconducting wire 1b existing on the inner diameter side of superconducting wire 1a, and receives force f2 from superconducting wire 1c existing on the outer diameter side than superconducting wire 1a. In the present embodiment, the tension applied to superconducting wire 1 at the time of winding is as small as less than 9.8 N, so that force f1 and force f2 are smaller than forces f3 and f4. That is, a swell is formed in the superconducting wire 1. As a result, ballooning occurs in the superconducting wire 1 in which pinholes are generated, and the reliability of the test is improved.

  The superconducting wire 1 that did not swell in the conventional ballooning test was subjected to the ballooning test in the present embodiment. As a result, 30 bulges having a width of 40 μm or more occurred per 1 km of length.

  In the test method for superconducting wire 1 of the present embodiment, superconducting wire 1 is immersed in liquid nitrogen 8 in a pressurized atmosphere. Thereby, when the superconducting wire 1 has a pinhole, the liquid nitrogen 8 is liable to enter the superconducting wire 1 through the pinhole. Therefore, since it becomes easy to find the superconducting wire 1 in which ballooning occurs, the reliability of the test is further improved.

(Embodiment 2)
A method for testing the superconducting wire according to the present embodiment will be described with reference to FIGS.

  First, as shown in FIG. 12, for example, a tape 14 made of polyimide resin having a thickness of 10 μm or more and the superconducting wire 1 are overlapped and wound in a pancake shape (coil shape). Specifically, one end of the superconducting wire 1 and the tape 14 is fixed to the reel 5, the reel 5 is rotated in the direction indicated by the arrow A, and tension is applied to the superconducting wire 1 and the tape 14, while the reel on the flat plate 4. The superconducting wire 1 and the tape 14 are wound around 5. A coil 10 wound with the superconducting wire 1 and the tape 14 by this method is shown in FIG. As the tape 14, for example, Kapton (registered trademark, manufactured by Toray DuPont) is suitable.

  Next, as shown in FIG. 14, a turntable 21 having a rotating shaft 21a for rotatably holding the superconducting wire 1, a guide base 22 having two rollers 22a and 22b, and a rewinding having a roller 23a. The machine 23 is prepared. Then, the coil 10 of the superconducting wire 1 is disposed on the rotating shaft 21 a of the turntable 21. And while rotating the rotating shaft 21a in the direction shown by the arrow E, the other end of the tape 14 is pulled out from the coil 10 and fixed to the roller 23a through the rollers 22a and 22b. Then, each of the rollers 22a, 22b, and 23a is rotated in the directions indicated by arrows B, C, and D, respectively, and the tape 14 is extracted (removed) from the coil 10. The extracted tape 14 is collected in the rewinder 23 and reused. The coil 10 immediately after the tape 14 is removed is shown in FIG.

  FIG. 16 is an enlarged view of a main part of FIG. As shown in FIG. 16, in the coil 10 after the tape 14 is removed, a gap d1 is generated between the adjacent superconducting wire 1a and superconducting wire 1b.

  Thereafter, the coil 10 is dipped in the liquid nitrogen 8 for a predetermined time and taken out by the same method as in the first embodiment shown in FIG. 5 to inspect for the occurrence of ballooning. The superconducting wire is tested by the above method.

  According to the test method for superconducting wire 1 of the present embodiment, tape 14 is superposed on superconducting wire 1 and wound once, and then tape 14 is removed, thereby superconducting wire 1a wound in a coil shape, A gap d1 can be generated between 1b. Since the gap d1 becomes an allowance for the superconducting wire 1, if the superconducting wire 1 has a pinhole 3a (FIG. 1), the liquid nitrogen 8 penetrates into the superconducting wire 1 through the pinhole 3a, and superconducting. Ballooning occurs in the wire 1. For this reason, it can be confirmed whether it is the superconducting wire 1 which does not really generate ballooning, and the reliability of a test can be improved.

  In the first and second embodiments, the case where liquid nitrogen is used as the liquid refrigerant has been described, but the present invention can also use liquid helium as the liquid refrigerant in addition to such a case.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a fragmentary sectional perspective view which shows notionally the composition of a superconducting wire. It is a perspective view which shows the 1st process of the manufacturing method of the superconducting wire in Embodiment 1 of this invention. It is a perspective view which shows the 2nd process of the manufacturing method of the superconducting wire in Embodiment 1 of this invention. It is a top view which shows the 2nd process of the manufacturing method of the superconducting wire in Embodiment 1 of this invention. It is a side view which shows the 3rd process of the manufacturing method of the superconducting wire in Embodiment 1 of this invention. It is a top view which shows typically the superconducting wire which the ballooning generate | occur | produced. It is a principal part enlarged view which shows the coil wound by the conventional method. It is sectional drawing of a superconducting cable. It is an enlarged view of the cable core in FIG. It is a cross-sectional perspective view of a spiral winding conductor. It is a principal part enlarged view of FIG. It is a perspective view which shows the 1st process of the manufacturing method of the superconducting wire in Embodiment 2 of this invention. It is a top view which shows the 2nd process of the manufacturing method of the superconducting wire in Embodiment 2 of this invention. It is a side view which shows the 3rd process of the manufacturing method of the superconducting wire in Embodiment 2 of this invention. It is a top view which shows the 4th process of the manufacturing method of the superconducting wire in Embodiment 2 of this invention. It is a principal part enlarged view of FIG.

Explanation of symbols

  1, 1a to 1c, 101a to 101c Superconducting wire, 2 Superconductor filament, 3 Sheath part, 3a Pinhole, 4 Flat plate, 5 Reel, 7 Container, 8 Liquid nitrogen, 10 Coil, 11a to 11c Swelling, 12 Spiral winding conductor , 14 Tape, 21 Turntable, 21a Rotating shaft, 22 Guide base, 22a, 22b, 23a Roller, 23 Rewinding machine, 30 Superconducting cable, 31 Cable core, 32 Former, 34 Insulating paper, 35 Kraft paper, 37 Refrigerant distribution Road, 38 Insulation pipe, 39 Anticorrosion layer.

Claims (3)

A winding step of winding the oxide superconducting wire in a pancake shape while applying a tension of 0.49 N or more and less than 9.8 N to the oxide superconducting wire;
A dipping step in which the oxide superconducting wire is dipped in a liquid refrigerant for a predetermined time after the winding step; and
A test method for an oxide superconducting wire, comprising a step of inspecting ballooning of the oxide superconducting wire after the dipping step. A winding process in which a tape and an oxide superconducting wire are stacked and wound in a pancake shape;
A removal step of removing the tape after the winding step;
A dipping step in which the oxide superconducting wire is dipped in a liquid refrigerant for a predetermined time after the removing step; and
A test method for an oxide superconducting wire, comprising a step of inspecting ballooning of the oxide superconducting wire after the dipping step. The test method for an oxide superconducting wire according to claim 1 or 2, wherein, in the dipping step, the oxide superconducting wire is immersed in a liquid refrigerant in a pressurized atmosphere.

Images