JPH05804B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a compound superconducting conductor, and particularly to a compound superconducting conductor having an improved wire reinforcement structure.

[Prior Art] As conventional reinforced superconducting conductors, six types of structures described below have been proposed. The first superconducting conductor has a structure in which a plurality of superconducting strands 2 are twisted around a reinforcing body 1, as shown in FIG. 1a. The second superconducting conductor has a structure in which a plurality of secondary strands 3 in which a plurality of superconducting strands 2 are twisted in advance are stranded around a reinforcing body 1, as shown in FIG. 1b.
The third superconducting conductor has a structure in which a plurality of reinforcing strands 1' and a plurality of superconducting strands 2 are stranded and then wrapped around a tape-shaped reinforcing body 1, as shown in FIG. 1c. . The fourth superconducting conductor is made by twisting a plurality of superconducting strands 2 as shown in FIG. It is a structure. Fifth
As shown in FIG. 1e, the superconducting conductor is composed of a plurality of secondary strands 3 in which a plurality of superconducting strands are twisted in advance, similar to the second conductor, around a reinforcing body 1''. After that, these are housed in a U-shaped reinforcing body 1 with one side open.As shown in FIG. It has a structure in which twisted secondary strands 3 are formed and a plurality of the secondary strands 3 are housed in a tubular reinforcing body 1 having cooling holes 5 on the side surface.

When applying these structures to compound superconducting conductors, there are the following problems.

a In the first and second wire assembly type compound superconducting conductors, the superconducting wire 2 or the secondary wire 3 is located in the outermost layer, so it is subject to external stress and strain during the insulation treatment process, winding process, etc. There's a problem.

b In the third wire assembly type compound superconducting conductor, the reinforcing bodies 1 are arranged discontinuously on the outside of the wire and there are irregularities in the longitudinal direction, so that the irregularities become disordered between adjacent turns of the coil during the winding process. There is a problem in that when the two contacts contact each other, an irregular gap is generated in that part, stress is concentrated, and as a result, the current characteristics are deteriorated.

c The fourth to sixth wire assembly type compound superconducting conductors have a protective function against external stress and distortion, but are thick because the reinforcing bodies are manufactured by machining such as cutting and die extrusion; This cannot be quantified, resulting in an excessive occupancy rate, and the current density of the conductor as a whole decreases accordingly. Further, since the reinforcing body is thick, flexibility during the winding process is poor. Furthermore, there is a limit to how many cooling holes can be densely provided in the reinforcing body through machining, and after winding the coil, there is a low probability that the cooling holes of adjacent conductors will meet each other, so the passages for the refrigerant liquid He or He gas are adjacent to each other. There is a problem that the conductors are not connected and the cooling efficiency is poor.

Incidentally, compound superconducting conductors inherently have excellent superconducting properties such as critical temperature, critical magnetic field, and critical current density. Therefore, it is promising as a winding for high magnetic fields. However, unlike alloy superconducting conductors, compound superconducting conductors are strain-sensitive in that their superconducting properties are significantly degraded when subjected to strain, and they are usually unusable in a strain range of 0.2 to 0.6% or more. On the other hand, the requirements of the users of compound superconducting conductors are that they must be able to be bent to a small radius of curvature, have a large current capacity, be a long continuous large conductor, and have a uniform reinforcement effect in the coil. One example is that there are

Fiber aggregate type compound superconducting conductors are attracting attention as a material that meets these demands. Typical forms of wire assembly type compound superconducting conductors are twisted wires, braided wires, dislocation wires, and compression molded products of these wires.

However, the essential drawbacks of the wire assembly type compound superconducting conductor are that the conductor size changes during winding because it easily stretches in the longitudinal direction and contracts in the radial direction under small tension, and that the conductor size changes during winding. There are many gaps, so the filling rate of the strands is low, and if the strands are locally restrained, such as by tightening the conductor at specified intervals with reinforcements, etc., the strong electromagnetic force generated in the coil will occur. Due to the force, stress and strain are concentrated on the strands of the untightened part, and as a result,
One example of this is that superconductivity characteristics are significantly reduced.

Therefore, there is a need for a reinforced structure for aggregated compound superconducting conductors that overcomes the above-mentioned essential drawbacks and minimizes the concomitant reductions in flexibility, cooling efficiency, and current density.

The present invention was made in order to solve the conventional problems, and aims to provide a compound superconducting conductor having excellent mechanical strength, flexibility, cooling efficiency, and conductor current density.

[Means for Solving the Problems] The present invention provides a wire assembly type compound superconducting conductor formed by combining a superconducting wire having copper on the surface and a reinforcing wire, in which the reinforcing wire is a reinforcing core. After covering the TiNb alloy as a material with copper or a copper alloy, it is heat-treated in a temperature range of 500 to 800°C for 1 to 20 days, so that the interface between the TiNb alloy and the copper or copper alloy is coated.
This is a compound superconducting conductor characterized by using a reinforcing strand in which a Cu-Ti intermetallic compound is formed and whose Young's modulus at 4.2K is 15×10 ³ Kg/mm ² or more.

In the present invention, the combination of superconducting strands and reinforcing strands is not particularly limited, but for example, as shown in FIG. It may be formed by forming and twisting four reinforcing wires 7 provided with a layer 6, or as shown in FIG. The wires 7 and the reinforcing wires 7' may be arranged in a collective form and formed into twisted wires.

The reinforcing wire may have a single reinforcing core material 1 as shown in FIG. 2, or may have a multi-core reinforcing core material embedded in a base material made of copper or copper alloy. good.

A non-magnetic titanium niobium alloy is used as the material for the reinforcing core material. The outside of this reinforcing core material is coated with copper or copper alloy.

Further, the form of the compound superconducting conductor according to the present invention is not particularly limited, and may be a stranded wire, a braided wire, a dislocation wire, or a compressed form line thereof consisting of a plurality of multicore compound superconducting strands, or a compressed form line thereof. The wires may be used as primary strands or secondary strands, and may be made into twisted wires, braided wires, dislocation wires, or compressed wires thereof in the same manner as described above.

[Function] The reason for using a reinforcing core material coated with copper or copper alloy as the reinforcing wire is to achieve the following effects.

(1) Since the surface of the reinforcing wire is made of copper or copper alloy, which is the same as the surface of the superconducting wire, deformation of the wire becomes uniform during shaping and stranding.

(2) Since foreign atoms from the reinforcing core material do not contaminate the copper on the surface of the superconducting wire during diffusion during heat treatment, the residual resistance value is high, and the coil will not burn out even during quenching.

(3) Since the surface of the reinforcing wire is made of copper or copper alloy, heat transfer performance is improved when used in a coolant such as liquid helium.

(4) When soldering or end jointing is performed because the surface of the reinforcing wire is made of copper or copper alloy,
It has the same connection characteristics and workability as superconducting strands.

Further, the reinforcing wire needs to have a Young's modulus of 15×10 ³ Kg/mm ² or more at 4.2K.
The reason for this is that in superconducting magnets that can generate a strong magnetic field of about 10 T using compound-molded stranded wires,
A structure that can withstand electromagnetic pressure of approximately 200 MPa (20.4 Kg/mm ² ) is required. Moreover, it is a compound superconductor.
This is to maximize the conductor current density without giving a strain of 0.5% or more.

Furthermore, it is necessary that the reinforcing wire be heat-treated in a temperature range of 500 to 800°C for 1 to 20 days. The reason for this is that it makes it easier to mechanically form the superconducting strands and reinforcing strands in the collective conductor, and
Such heat treatment is performed in coil design using the normal Wind and React method. By performing this heat treatment, it is possible to form an intermetallic compound between the TiNb alloy serving as the reinforcing core material and the copper or copper alloy covering this core material, thereby improving Young's modulus. For example, by heat-treating a composite base material of Cu and titanium alloy at 500℃ for 6 days, a Cu-Ti alloy with a thickness of approximately 15 μm is produced.
A compound is formed.

In this way, by using a reinforcing core material coated with copper or copper alloy as a reinforcing wire,
In addition to improving the mechanical strength, the processability of the superconducting strands and reinforcing strands can be improved to prevent abnormal deformation of the superconducting strands during forming and stranding processing, thereby improving superconducting properties such as current density. Furthermore, a compound superconducting conductor with improved flexibility, windability, cooling efficiency, and solderability can be obtained. Furthermore, an intermetallic compound is formed at the interface between the reinforcing core material and the copper or copper alloy coating layer by heat treatment to increase the Young's modulus of the reinforcing wire, thereby making it possible to form a conductor using the minimum necessary reinforcing wire. This improves the reinforcing effect of the coil and the current density of the entire coil.

[Examples] Examples of the present invention will be described in detail below.

Example 1 505 Nb in Cu-Su bronze matrix
Embed the core and use the outside as a diffusion barrier layer
A Ta tube was coated, and a high-purity copper tube was coated on the outside as a stabilizing material, and the surface was reduced to obtain a composite wire with an outer diameter of 0.37 mm and a stabilized copper occupancy of 50%.

First, TiCu with a diameter of 50 μm was used as the first reinforcing wire.
A plurality of alloy filaments embedded in a copper wire with an outer diameter of 0.37 mm was prepared. Note that the cross-sectional area ratio of the Cu/TiCu alloy of this reinforcing wire is 1.1/1.0. In addition, as the second reinforcing strand, a diameter of 50 μm was used.
A plurality of TiNb alloy filaments embedded in a copper wire with an outer diameter of 1.1 mm was prepared. The cross-sectional area ratio of the Cu/TiNb alloy of the reinforcing wire is 1.5/1.0.
It is.

Next, the first reinforcing strand is used as a center line,
The six composite wires are twisted around the outer circumference and the outer diameter is 1.1.
A stranded wire of mm was obtained.

Next, the six second reinforcing strands and the stranded wire
18 pieces are twisted together and compression molded using rolls to create an upper base of 2.5 mm.
A keystone shaped stranded wire with a diameter of 1.5 mm, a bottom base of 1.5 mm, and a height of 11.5 mm was obtained.

Keystone molded stranded wire (comparison row Product 1) was obtained.
Further, a keystone molded stranded wire (comparative example product 2) was obtained in the same manner as in the example except that the first and second reinforcing wires described above were not used at all.

These formed strands were subjected to diffusion heat treatment at 650°C for 10 days to form a Nb ₃ Sn compound layer at the interface between the bronze matrix and the Nb core, and at the same time to form an Nb 3 Sn compound layer at the interface between the TiNb alloy of the reinforcing wire and the copper coating layer. A Cu-Ti intermetallic compound was formed, and a coil was further impregnated with resin.

When we conducted an energization experiment on the coil obtained in this way in liquid helium, the value (quench current) was 15,300 A for the product of the present invention, whereas
Comparative example products 1 and 2 are 10000A and 5300A respectively.
And the Young's modulus of the formed stranded wire (product of the present invention) is
The reinforcing effect was confirmed as 18.2×10 ³ Kg/mm ² .

[Effects of the Invention] As detailed above, the present invention has excellent mechanical strength, significantly improves flexibility, winding properties, cooling properties, and soldering properties, and furthermore improves the coil as a whole. It is possible to provide a compound superconducting conductor that has advantages such as being able to significantly improve current density.

[Brief explanation of the drawing]

Fig. 1 shows an example of a conventional reinforced superconducting conductor, Fig. 1 a, b, d, e are cross-sectional views, Fig. 1 c,
f is a perspective view, and FIGS. 2 and 3 are cross-sectional views showing an example of the compound superconducting conductor of the present invention. 1...Reinforcement core material (reinforcement body), 2...Superconducting wire,
3... Superconducting secondary strand, 4... Groove, 5... Cooling hole, 6... Copper coating layer, 7, 7'... Reinforcing strand,
50...Solder.

Claims (1)

[Claims] 1. In a strand assembly type compound superconducting conductor formed by combining a superconducting strand having copper on the surface and a reinforcing strand, the reinforcing strand is coated with a TiNb alloy as a reinforcing core material with copper or a copper alloy. After that,
A Cu-Ti intermetallic compound was generated at the interface between the TiNb alloy and copper or copper alloy by heat treatment at a temperature range of 500 to 800°C for 1 to 20 days, and the Young's modulus at 4.2K was 15 × 10 ³ Kg/ A compound superconducting conductor characterized by using a reinforcing wire having a diameter of mm ² or more.