JPH02251102A - Method for manufacturing oxide superconducting coil - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a coil using an oxide superconductor that can use liquid nitrogen as a refrigerant.

[Prior art] Oxide superconductors such as the Y Ba-Cu-0 system exhibit a critical temperature exceeding the liquid nitrogen temperature (77K) and are noted as superconductors that can be used at liquid nitrogen temperatures, and are coated with metal. Various prototypes of oxide superconductor shrines coated with silver have been made, and relatively good characteristics have been obtained. Superconducting grades include Y-13a-Cu-0 series, Bj
-Pb/5r-Ca-Cu-0 system or Tl-Ba/5r
Prototypes of Y-based, 13i-based, and Tl-based oxide superconductors, such as -Ca-Cu-0, have been made, and they are 3000 to 12000 A /
A critical current density (Jc) of cJ is obtained.

The method for producing such a metal-coated oxide superconducting wire is usually to fill a metal, such as a silver pipe, with oxide superconductor powder and subject it to surface reduction plastic processing, and if necessary, to form the required number of wires into a silver pipe. A method is adopted in which the material is incorporated into the material, subjected to surface reduction plastic processing, and then subjected to sintering heat treatment. In the case of tape-shaped wire rods, a method is adopted in which a rolling step is added before the sintering heat treatment in the above-mentioned step. However, in the case of a wire produced by this type of powder method, its properties in a magnetic field are poor, so it is necessary to improve the Jc properties in a magnetic field in order to use it as a superconducting coil. As one of the methods to improve the Jc characteristics in a magnetic field, M T G (Melt
It is proposed that a polycrystalline body oriented in one direction be produced by melting and unidirectionally solidifying a bulk material using a method such as , Texture GrawLh). In the case of samples prepared using this method, the Jc characteristics in the magnetic field are greatly improved and there is little deterioration.

The reason for this is that Jc characteristics are said to deteriorate in a magnetic field due to weak links at grain boundaries, but in the case of the sample mentioned above, there are no foreign phases at the grain boundaries, and the joints have a good degree of orientation. It is in what is being done.

[Problems to be Solved by the Invention] The problem with the prior art described above is that even though it is an orientation treatment, it only has a 1-T5 performance with a short and small sample, making it difficult to use it for energetic applications such as superconducting coils. This is not the case. Therefore, an object of the present invention is to provide an oxide superconducting coil that can generate a high magnetic field and can be used at liquid nitrogen temperatures.

[Means for Solving the Problems] The gist of the present invention is to locally heat the vicinity of winding A/1 of an unfired oxide superconducting wire in the process of winding it into a coil, thereby reducing the temperature within the wire. Improving magnetic field characteristics by growing crystals of an oxide superconductor in at least a partially molten state,
This greatly improves the characteristics of oxide superconducting coils.

In this case, as a method for local heating, various means that can perform local heating at the time of winding can be adopted, such as the use of a concentrated furnace with a strong temperature gradient, the use of contact type heating rolls, and the use of high frequency heating.

Note that the oxide superconductor material is not particularly limited.
, Y-Ba-Cu-O, Ln-Ba-Cu-0 system in which Y is replaced with a magnetic element (Ln) such as Er5Ho, Bi
-Pb-5r-Ca-Cu-○ system, Tl-13a/5r
-Ca-Cu-0-based and other oxide superconductors can be applied. Furthermore, the form of the wire rod is not limited to wire rods coated with metal such as silver, but may be any form such as wire rods formed by pressing using an organic binder, wire rods made by spinning, or doctor blade sheets. good. Of course, the core portion may have a multi-core shape.

[Example] Below, an example using a silver-coated tape-shaped wire made of 1'' 1-Ba-Ca-Cu-0 powder will be described.

Tl-Ba-Ca-Cu-0 exhibiting superconductivity as a raw material
A powder with a composition of 22:2:3 was prepared. This powder had an average particle diameter of 5 to 81 tm, and its critical temperature (Tc > on 5et) = 1 was determined by the alternating current magnetic susceptibility method.
I confirmed 20K.

The powder was filled into a silver pipe with an outer diameter of 6 mm, and it was assembled with a swager and a drawing die to reduce the area by 1 mm to an outer diameter of 1 mm. After making a 2m silver Hata wire rod, it is rolled to a thickness of 0.
．． A tape-shaped wire rod with a silver coverage of 50% and a thickness of 2n+m, III 5mm was produced. In the tape-shaped wire material thus produced, the T1 powder without silver coating was in a random state, although slightly oriented, and the powders were almost not in contact with each other.

Next, the tape-shaped wire rod was made into a material with an outer diameter of 50 mm and a length of 80 m.
A solenoid coil was obtained by wrapping an A1□03-based sheet with a thickness of 50 μm around an MgO winding frame with 5 turns as insulation. At this time, as shown in Fig. 1, a heating roll jig 3 with a built-in heater is used to press the tape-shaped wire 2 wound around the winding frame at a temperature of 850 to 920°C in an oxygen atmosphere. A final sintering heat treatment was performed by continuous heating. As a result, wire rod 2
At least the inter-crystal grains of the TI-based superconductor were melted, and the crystals were oriented.

When we looked at the characteristics of the coil manufactured in this way, we found that the wire can carry a current of 18 A in liquid nitrogen, and that there is little deterioration in the magnetic field.

As another example, regarding the tape-shaped wire rod obtained in the previous example, the wire rod is wrapped around an MgO winding frame with an outer diameter of 30 mm.
L2O3 sheet is wrapped in multiple layers as insulation, and the inner diameter is 3.
A pancake coil with an outer diameter of 50 mm was used.

At that time, as shown in Fig. 2, an induction coil 4 is placed in the passage of the wire 2, and the wire 2 to be wound is continuously induced in a temperature range of 820 to 920°C immediately before winding in an oxygen atmosphere. A final sintering heat treatment was performed by heating. In the case of the coil obtained in this way, it was found that a current of 38 A could be passed in liquid nitrogen and the characteristics in a magnetic field were also good.

[Effects of the Invention] As is clear from the above, in the method of the present invention, a superconducting coil with good characteristics can be easily obtained since the method of the present invention performs crystal orientation treatment by local heating during coil winding. In order to wind a crystal-oriented wire into a coil using the R&W method, it is necessary to make the wire thinner due to strain deterioration, which limits the amount of current. Wire rods can also be applied, which has the advantage of allowing large currents and high magnetic fields.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the method according to the present invention, and FIG. 2 is an explanatory diagram showing another example of the present invention. 1: winding frame, 2: wire shrine, 3: heating roll jig, 4: induction coil. Figure 2

Claims (1)

[Claims] (1) When winding an unsintered oxide superconducting wire into a coil, the wire is continuously locally heated at a temperature that at least partially melts the intercrystalline grains of the oxide superconductor near the winding part. 1. A method for producing an oxide superconducting coil, characterized by subjecting it to sintering heat treatment.