JPH03182014A - Highly stabilized alloy superconducting wire - Google Patents

Abstract

PURPOSE:To provide a superconductive wire satisfactory to the use with a.c. power by compounding a material such as highly pure Al or Ag whose electric resistance decreases to an extreme low at extremely low temperature as a stabilizing agent in an alloy-based superconductive material to give compounded superconductive wires and burying a plurality of the wires in an alloy matrix having high resistance. CONSTITUTION:Core wires 1 of compounded NbTi alloy having highly pure Al 2 in the inside and oxygen-free copper core wires 3 are collectively buried in a CuNi alloy matrix 4 to give a superfine multi-core superconductive wire. In this way, highly pure Al whose resistance at extremely low temperature is about 1/10 of that of the oxygen-free copper exists in the insides of core wires 1 and even in a case that the wire is transformed into a normal conductive state, the Al 2 works sufficiently as a stabilizing material and high stability is obtained. Also, since CuNi alloy with high resistance is used for the matrix 4, bonding loss and eddy current loss among the NbTi alloy core wires are prevented even when the wire is used for a.c. electric power. Ag, which has the same resistance property as Al, may be used instead of Al.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has an electrical resistance that is lower than that of high-purity oxygen-free copper, which has been conventionally used as a stabilizing material, at extremely low temperatures below the superconducting critical temperature. (approximately 1/10 that of high-purity oxygen-free copper) Materials such as high-purity aluminum or silver can be used as a stabilizing material to achieve high stability, and even when used in alternating current or other fluctuating magnetic fields. This invention relates to a highly stabilized alloy superconducting wire with extremely low AC loss.

[Prior art] NbTi series, Nb Ti Zr series or Nb Ti
Alloy-based superconducting wires such as Ta-based wires have a lower critical magnetic field than compound-based superconducting wires such as Nb3Sn-based wires, but they have excellent plastic workability as a characteristic characteristic of alloys, and Cu
It can be processed into &4IM using CuNi alloy, etc. as a matrix, which can be processed into ultra-fine multi-core superconducting alloy wire and formed into superconducting coils, which are actually used in equipment that requires high magnetic fields, and are in practical use as superconducting wires. It has come to dominate the mainstream.

As mentioned above, today most superconducting wires are wound into coils and used as superconducting magnets.
When used as such a magnet, the superconducting state is broken due to movement of the wire due to electromagnetic force or some kind of thermal or electromagnetic disturbance, and a transition to normal conductivity occurs.

In order to prevent this kind of metastasis, and even if it does, to bypass the current flow and prevent the superconducting wire from burning out, the surroundings of the superconducting wire are made of high-purity oxygen-free steel. The so-called ultra-fine multicore superconductor has a structure covered with a material that has extremely low electrical resistance at extremely low temperatures, and many ultra-fine wires such as NbTi alloy are arranged in a matrix made of high-purity oxygen-free copper as a stabilizing material. It is usually used in practical use as an alloy wire.

As mentioned above, the role of the stabilizing material is to bypass the superconducting current when the superconducting material transitions to a normal conductive state, so it is natural to use a material with low electrical resistance as a stabilizing material. is required.

[Problem to be solved by the invention] Conventionally, high-purity oxygen-free copper has been mainly used as a stabilizing material because it is easy to process in combination with NbTi alloy etc. and has low electrical resistance at extremely low temperatures. It has been.

However, recently there has been a growing trend to use superconducting wires for alternating current as well.

In this case, if a superconducting wire using the above-mentioned high-purity oxygen-free copper as a stabilizing matrix is used for alternating current, various alternating current losses will occur.

That is, these include the so-called coupling loss caused by the 'S current flowing between the NbTi core wires via the stabilizing material, and the eddy current loss caused by the eddy current flowing in the stabilizing material. In order to reduce these AC losses, efforts have been made to subdivide the stabilizing material with a high resistance layer such as a CuNi alloy, or to cover the NbTi core wires with a CuNi alloy. However, the use of a high-resistance layer such as CuNi goes against the above-mentioned idea of stabilization, and there is a strong need for a proposal for a superconducting wire that can maintain stability and reduce AC loss.

On the other hand, from the perspective of a material with low electrical resistance at extremely low temperatures, high-purity aluminum has a much lower electrical resistance, with an electrical resistance of only about This high-purity aluminum is more suitable as a material, and in order to achieve the same stability, only 1/10 of the amount is required. Therefore, if high-purity aluminum is used as a stabilizing material, it is possible to reduce the cross-sectional area of the composite superconducting wire, making it possible to obtain a compact wire material. Even if a high-resistance layer is added, the stability is less impaired than that of copper, which is a great feature.

Unfortunately, however, high-purity aluminum is a fairly soft metal, and it is extremely difficult to combine and process high-purity aluminum, high-resistance alloys such as CuNi alloy, and Nb-Ti superelectric wire. However, the current situation is that we have not seen any success stories yet.

In view of the above-mentioned circumstances, it is an object of the present invention to achieve higher stability by using high-purity aluminum as a stabilizing material, and to achieve higher reliability due to the use of high-purity aluminum as a stabilizing material. Provided is a novel highly stabilized alloy-based superconducting wire that makes it possible to use a highly resistive alloy such as a CuNi alloy as a matrix, and can greatly reduce AC loss when used for the above-mentioned AC applications. This is what I am trying to do.

[Means for Solving the Problems] The present invention provides a composite superconducting core wire by combining a material such as high-purity aluminum or silver, which has an extremely low electrical resistance at extremely low temperatures, as a stabilizing material inside an alloy-based superconducting material. A plurality of the composite superconducting core wires are embedded and fixed in a high-resistance alloy matrix, and the composite superconducting core wire having the above structure is further coated with oxygen-free copper,
A plurality of three-layer composite wires constructed in this manner are embedded in a high-resistance matrix, and an oxygen-free steel jacket is provided around the outer periphery of the wire to integrate the entire wire.

[Function] As mentioned above, it is impossible to wire-draw high-purity aluminum as a matrix for alloy-based superconducting wire because the difference in deformation resistance is too large. This allows simultaneous processing with superconducting materials. As a result, the high-purity aluminum inside can sufficiently play the role of a stabilizing material due to its extremely low electrical resistance, and a high-resistance alloy is used as a matrix around the outer periphery of the superconducting core, so that even if it becomes normally conductive, Even if a transition occurs, the high-purity aluminum inside acts as a significant stabilizing material, making it possible to sufficiently avoid unexpected accidents such as burnout.

Furthermore, since the matrix is made of a high-resistance material, the coupling loss and eddy current loss that are conventionally seen are significantly reduced even when used for AC applications, which is sufficient for AC applications. It becomes possible to obtain highly stabilized alloy-based superconducting wires that can be used in

[Example] The present invention will be described below with reference to Examples.

The inventors initially developed the third and fourth AC superconducting wires.
We prototyped a superconducting wire with the configuration shown in the figure.

That is, FIG. 3 shows C, which is a high-resistance material at extremely low temperatures.
A uNi alloy is used as a matrix, and a large number of NbT
The i-alloy core wire 1.1 and the oxygen-free copper core wire 3.3 as a stabilizing material were both appropriately arranged as shown in the figure, and the CuNi matrix and these core wires were drawn into an ultrafine multicore superconducting wire.

However, in this case, the oxygen-free steel core 113.3, which is the stabilizing material,
It was found that the placement of the material was a problem, and that it could not necessarily function as a stabilizing material sufficiently. Oxygen-free copper core wire 3゜3
I tried using high-purity aluminum core wire instead, but there was a difference in deformation resistance, and the aluminum core wire broke and abnormally deformed at various places, making it impossible to draw the wire satisfactorily.

Therefore, next, a superconducting wire having a configuration as shown in FIG. 4 was produced as a prototype.

This is made by applying an oxygen-free steel coating 3 to the outer periphery of a NbTi alloy core wire, embedding such a composite core wire in a CuN alloy matrix 4, and further providing an oxygen-free copper jacket 5 around the outer periphery. be.

With this configuration, N
bSince the oxygen-free copper coating 3 is directly around the Ti alloy core wire, the stabilizing effect is great, but the coating thickness of the oxygen-free copper coating 23 cannot be made large, and the amount of oxygen-free copper is small. It turns out that reliable stabilization cannot be expected.

Therefore, the inventors focused on using high-purity aluminum, which has a significantly lower electrical resistance, as a stabilizing material, and initially attempted to coat the outer periphery of the NbTi alloy wire 1 as shown in FIG. It was found that embedding in the Cu Ni alloy matrix 4 was not possible.

Therefore, the inventors changed their thinking and focused on combining high-purity aluminum inside the Nb-Ti alloy.
When this wire was drawn, it was demonstrated that the wire could be drawn extremely well, and the high-purity aluminum could be drawn to t with the same cross-sectional reduction ratio as the outer NbTi alloy layer without abnormal deformation or wire breakage. It was done.

Figure 1 shows that high-purity aluminum 2
Composite NbTi alloy core wire 1.1 and oxygen-free copper core wire 3 having
.

As already explained, inside each NbTi alloy core wire 1, there is high-purity aluminum 2, which has a very low electrical resistance at extremely low temperatures, about 1/10 that of oxygen-free copper, so in the unlikely event that it becomes normally conductive. Even if the transition occurs, the high-purity aluminum 2 sufficiently plays the role of a stabilizing material, and highly reliable stabilization can be achieved with sufficient margin. In this case, instead of high-purity aluminum, silver or the like having a similar resistance value may be used as the stabilizing material for the troughs.

However, the matrix contains CuN, which is a highly resistive material.
Since CuN alloy is used, even if this superconducting wire is used for AC, the coupling loss between Nb Ti alloy core wires and the eddy current loss seen when oxygen-free copper is used can be avoided.
It was also confirmed that the i-alloy matrix could adequately prevent and significantly reduce AC losses.

FIG. 2 shows another example of the present invention! In this example, high purity aluminum 2 is composited as a stabilizing material inside the NbT + alloy core wire 1, and an oxygen-free copper coating 3 is further provided on the outer periphery. The oxygen-free copper composite layer 3 also serves as a stabilizing material to achieve even higher stability, and a plurality of these three-layer composite wires are combined with a CuNi alloy matrix 4. In addition, an oxygen-free copper jacket 5 is provided to serve as an auxiliary stabilizing material or to maintain good conductivity.

This not only improves the properties of the superconducting wire, but also
Although the oxygen-free copper layer 3 is provided, there is a high-resistance layer made of a CuNi alloy 4 as a matrix between them, so even if it is used for alternating current, the coupling loss can be kept very small. .

[Effects of the Invention] As detailed above, according to the superconducting wire according to the present invention, six parts of each superconducting core wire are composited with a material that has extremely low electrical resistance at extremely low temperatures, such as high-purity aluminum or silver. Therefore, stability can be improved without compromising composite workability, and by using a material such as a highly resistive CuNi alloy for the matrix, even when used for AC, AC loss is significantly lower than in conventional examples. It has become possible to obtain small superconducting wires, and this has immeasurable industrial significance as it will be possible to expand the scope of application of superconducting wires to AC applications.

[Brief explanation of drawings]

1 and 2 are explanatory sectional views showing two types of configuration examples according to the present invention, and FIGS. 3 and 4 are explanatory sectional views showing two types of conventional prototype examples, respectively. 1: Nb Ti core wire, : High purity aluminum, : Oxygen-free copper coating, : CuNi alloy matrix, : Oxygen-free copper jacket.

Claims (2)

[Claims] (1) A composite superconducting core is created by combining a material with extremely low electrical resistance at extremely low temperatures, such as high-purity aluminum or silver, as a stabilizing material inside the alloy-based superconducting material, and multiple composite superconducting cores are Highly stabilized alloy superconducting wire embedded and integrated in a highly resistive alloy matrix. (2) A composite superconducting core wire is created by combining a material with extremely low electrical resistance at extremely low temperatures, such as high-purity aluminum or silver, as a stabilizing material inside the alloy-based superconducting material, and the outer periphery of the composite superconducting core wire is High stability is achieved by providing multiple layers of oxygen-free copper, embedding a plurality of three-layer composite wires configured in this way in a high-resistance matrix, and further integrating the entire structure with an oxygen-free copper sheath around the outer periphery. Alloy superconducting wire.