JPS6025841B2 - compound superconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compound superconductor, and particularly to a compound superconductor in which a compound superconducting wire and a reinforcing material are metallically bonded to form an integrated structure.

Niobium 3-tin (N-HiroSn), vanadium 3-gallium (
Compound superconducting materials such as V3Ga) have excellent superconductivity in high magnetic fields and are attracting attention as magnet materials for nuclear fusion devices, but they are weaker than alloy-based superconducting materials such as nickel and titanium. Currently, large, high-field magnets that are subject to strong electromagnetic stress have not been manufactured.

As compound superconductors using compound superconducting materials, structures such as those shown in FIGS. 1 and 2, for example, have been proposed. In these figures, 1 is a reinforcing material, 2 is a superconducting material, 3 is a compound superconducting layer, 4 is a matrix, and 5 is a low melting point metal. That is, in the case shown in Fig. 1, a reinforcing material 1 such as tungsten or stainless steel is placed in the center of the stranded wire where the compound superconducting layer 3 is formed, and in the case shown in Fig. 2, the reinforcing material 1 is made of a compound. It has a structure built inside the superconducting layer 3. However, as a result of research conducted by the present inventors on compound superconductors with various structures, it was found that the strength of the twisted wire structure as shown in Figure 1 is inherently low, and even in magnetic field-current-load weight tests in liquid helium. It has become clear that the critical current begins to deteriorate with a small stress, and the structure in which the reinforcing material is included inside the compound superconducting layer as shown in Figure 2 has extremely poor moldability as a composite, resulting in a large current capacity. It became clear that compound superconductors could not be produced. The present invention aims to eliminate such problems and provide a compound superconductor with high current density and no deterioration of magnetic field current even under strong electromagnetic stress. In a compound superconductor having an integrated structure in which a reinforcing material made of a material having higher strength and higher soaring rate than the compound superconducting wire is metallically bonded, the compound superconducting wire has a niobium tritin compound superconducting layer on the surface. The compound superconductor is made of a plate-like body in which a plurality of compound multi-core wires are embedded in a copper matrix, and the reinforcing material is made of a steel-coated stainless steel plate, and the entire compound superconductor is The cross-sectional area of the reinforcement relative to the cross-sectional area (hereinafter, the total cross-sectional area and the cross-sectional area are referred to as the total cross-sectional area and the cross-sectional area, respectively.

) is characterized by a ratio of 20 to 50%. That is, in order to achieve the purpose of the present invention, it is most suitable to use an integrated structure in which a compound superconducting wire and a reinforcing material made of a material having higher strength and higher elastic modulus than the compound superconducting wire are attached metallically. This was done based on the idea that it is necessary to increase the ratio of the cross-sectional area of the reinforcing material to the total cross-sectional area of the compound superconductor.

Here, there are materials such as stainless steel and tungsten that have higher strength and higher elastic modulus than the compound superconducting wire used as the reinforcing material. Methods such as silver soldering, pressure heating, and welding are used to construct the structure.

With such a structure, the compound superconducting wire and the reinforcing material behave as a compound superconductor with a strong integrated structure without independently deforming in response to large electromagnetic stress.

In order to firmly bond the compound superconducting wire and the reinforcing material metallically, it is preferable to use a composite reinforcing material, such as a cladding material of copper and stainless steel, rather than a single reinforcing material. In addition, the results of measuring the magnetic field-current-force holding property by varying the ratio of reinforcing material (cross-sectional area of reinforcing material/total area of compound superconductor) by the present inventors show that when the ratio of reinforcing material is less than 20%, 20~30k9/The critical current deteriorates due to the stress of the fence, and the effect of reinforcing material insertion is small.Also, when the ratio of reinforcing material is increased to 20% or more, the reinforcing effect becomes noticeable and the stress resistance improves, but , 50% or more, it was clearly shown that the current density of the entire superconductor decreases.

Therefore, although it varies somewhat depending on the material of the reinforcing material, a compound superconductor with a critical current that does not deteriorate against the electromagnetic force applied by a large, high-field magnet and has a high current density is used.
It was found that 0% reinforcement is effective.

Note that simply increasing the ratio of reinforcing material to 20 to 50% has little effect on the stress resistance of the compound superconductor;
The effect of inserting 20 to 50 q○ of reinforcing material can only be exhibited when the compound superconducting wire and the reinforcing material are sufficiently metallically attached to form a structure that can behave as a compound superconductor as one.

Examples will be described below.

FIG. 3 shows the configuration of an example. The compound superconducting wire 6 used here uses Nb and a copper-tin (Cu-Sn) alloy as superconducting materials, and Cu as a stabilizing metal. A matrix 7 made of Nb3Sn compound superconductor, specifically, rectangular Cu with external dimensions of 2.16 x IQ, is covered with Cu-Sn and has an outer diameter of 5 mm.
2 more compound multi-core wires 8 into which 331 Nb wires were pressed
After embedding the 04 wires in combination and molding, heat treatment was performed in a vacuum at 700 qC for 10 hours, and a Nb Su film with a thickness of 1 French was applied to the surface of the Nb wires.
A compound superconducting layer is formed, and the reinforcing material 1 is C
U-coated stainless steel is used, and a compound superconducting wire 6 and a reinforcing material 1 are bonded together with lead-tin (Pb-Sn) solder 9.

In addition, in this example, the ratio to the total cross-sectional area of the line village is 0 to 5.
0% stainless steel reinforcing material was prepared, and the above-mentioned N was bonded to Sn compound superconducting wire with Pb-Sn solder as a sample. , the critical current was determined in a magnetic field of 60 KOe.

Figure 4 shows the results of measuring how the critical current changes with varying stress. The machine axis and the vertical axis respectively show the stress (k9/earth), the critical current under force, and the critical current under no stress. The current ratio (%) is taken, A is when there is no reinforcing material, B is when the ratio of reinforcing material is 20%, C
exemplifies the case where the ratio of reinforcing material is 24%.

As is clear from this figure, as the stress increases, the critical current rapidly deteriorates at a certain stress level. Figure 5 shows the relationship between the cross-sectional area of the reinforcement material and the total cross-sectional area of each sample with the force at this time as the critical force. ), the critical stress (X9/fence) is taken. In this figure, the reinforcement cross-sectional area/total cross-sectional area is 20%.
This indicates that the critical stress increases rapidly when the value exceeds this value. In other words, it is shown that in order to make the reinforcing effect effective, the cross-sectional area of the reinforcing material/total cross-sectional area needs to be 20% or more. Figure 6 shows the critical current when a force of 150k9/fence is applied, and the mechanical and vertical axes are shown, respectively.
Reinforcement material cross-sectional area/total cross-sectional area (%) and critical current (A) are taken.

When the reinforcing material is 24% or more, the critical current is almost the same as 7000-720M, but when the reinforcing material is 20%, the critical current is 68
In the case of 0M and no reinforcing material, it deteriorated to 29 peaks A. Figure 7 is a diagram in which the vertical axis of Figure 6 is rewritten as critical current density (A/Kyo), and this figure shows that the cross-sectional area of the reinforcing material/total cross-sectional area is 30
It shows that the critical current density has a peak around %. In a superconducting magnet, a higher critical current density is more desirable. Therefore, the cross-sectional area/total cross-sectional area of the reinforcing material that has a large reinforcing effect and increases the critical current density is in the range of 20 to 50%. In addition, in Fig. 6, when the cross-sectional area of the reinforcing material/total cross-sectional area is 20% or more and less than 24%, a slight deterioration of the critical current is observed.
Condition without deterioration of critical current, i.e. cross-sectional area of reinforcing material /
More preferably, the total cross-sectional area is 24-36%.
That is, by selecting this range, current deterioration due to stress in the superconductor can be minimized, and furthermore, a decrease in the current density of the entire wire can be suppressed. Further, although this embodiment shows an example in which the reinforcing material is bonded using solder, other methods such as pressure bushing or welding can be similarly used as long as the reinforcing material is bonded metallically to form an integrated structure.

In this way, the compound superconductor described in the examples provides an optimal cross-sectional area of the reinforcing material with respect to the cross-sectional area of the entire wire, so it is possible to produce a wire with high current capacity and stress resistance and high current density. Therefore, a superconducting coil wound with a compound superconductor having a large current capacity can easily be made large and have a high magnetic field, and has a high current density, so it has great economic advantages. As described above, the compound superconductor of the present invention has great industrial effects because it provides a compound superconductor with high current density without deterioration of critical current even under strong electromagnetic force.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of different conventional compound superstring conductors, Figure 3 is a cross-sectional view of an embodiment of the compound superconductor of the present invention, and Figure 4 is the force in the compound superconductor of the present invention. Figure 5 is a characteristic diagram showing the relationship between reinforcement cross-sectional area/total cross-sectional area and critical force, and Figure 6 is a characteristic diagram showing the relationship between reinforcement cross-sectional area/total cross-sectional area and critical force. FIG. 7 is a characteristic diagram showing the relationship between area and critical current, and FIG. 7 is a characteristic diagram showing the relationship between reinforcing material cross-sectional area/total cross-sectional area and critical current density. 1... Reinforcement material, 6... Compound superconducting wire, 7...
Cu matrix, 8... Compound multi-core wire, 9...
・Pb-Sn solder. Hair Figure 2 Figure 3 Figure 4 Tsutomu S Figure 5 Chrysanthemum Figure 7

Claims (1)

[Scope of Claims] 1. In a compound superconductor having an integrated structure in which a compound superconducting wire and a reinforcing material made of a material having higher strength and higher elastic modulus than the compound superconducting wire are metallically bonded, The wire is made of a plate-shaped body in which a plurality of compound multi-core wires, which are a combination of a plurality of niobium wires each having a niobium tri-tin compound superconducting layer formed on the surface thereof, are embedded in a copper matrix, and the reinforcing material is copper-coated stainless steel. A compound superconductor made of a copper plate, characterized in that the ratio of the cross-sectional area of the reinforcing material to the total cross-sectional area of the compound superconductor is 20 to 50 percent. 2 The ratio of the cross-sectional area of the reinforcing material to the total cross-sectional area of the compound superconductor to the cross-sectional area of the reinforcing material is 2.
A compound superconductor according to claim 1, which has a content of 4 to 36 percent.