JPS60250512A - Method of producing nb3sn composite superconductive wire - 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 [Technical field to which the invention pertains] The present invention relates to a method for manufacturing a NbBSn-based composite superconductor.

[Prior art and its problems]

As one of the manufacturing methods of Nb38n-based composite superconductor.

The following method (powder method) is known.

That is, NbSn2 powder is included in a Nb tube, the Nb tube is coated with Cu, and then thinned and heated at 675°C.
The inside of the Nb tube is heated to a heat treatment temperature of ~700°C.
A method for manufacturing a Nb 38 n composite superconductor in which a b 38 n layer is formed is known. However, this method has the following disadvantages. In the powder method, it is generally very difficult to process thin wires into long wires (constrictions tend to occur in Nb tubes). (volume ratio~7
0%) We have devised ways to process it. Therefore, the critical current density (overall Jc) of the entire conductor is extremely reduced. Also, since Cu1E is not included in the Nb tube, the temperature at which the Nb2Sn layer is generated becomes higher.
There was a problem that Jc characteristics deteriorated.

We have previously demonstrated the thinning of composite superconductors using Nb tubes.
and disclosed a method for improving the superconducting properties of Nb3Sn (Japanese Patent Publication No. 55-16547). That is, an an coated with Cu is placed inside the Nb tube, and an ann coated with Cu is placed outside the Nb tube.
After bundling multiple u-coated composites and reducing the area,
This is a method for manufacturing a composite superconductor that generates Nb3Sn by applying heat treatment (so-called Nb tube method). In this method, processing problems that are different from those in the case of using a Nb rod using a Nb tube appear as a high degree of surface reduction processing is performed, as in the powder method. However, N
By placing a Cu layer on the inner wall of the b-tube, a high degree of surface reduction can be achieved, and by reacting Nb and Sn through this Cu layer (low-temperature heat treatment is possible), A Nb38n layer with small crystal grain size is generated,
Jc can be improved.

[Purpose of the invention]

This invention eliminates the above-mentioned inconveniences and shortcomings, and
Nb3Sn has good workability without tube filament constriction or core breakage, and has high Jc and high strain resistance.
The object of the present invention is to provide a method for easily manufacturing a composite superconducting wire.

[Summary of the invention]

The composite superconductor according to the present invention is a composite of a Nb3Sn compound superconductor layer produced by the reaction of Nb and an in an Nb tube and a normal conductor made of Cu.

The case of manufacturing a composite superconductor in which this Nb38n superconductor layer is formed will be explained with reference to the drawings.

As shown in FIG. 1(A), through a Cu-based alloy tube 1 (including mesh-shaped tubes) containing Cu as a main component,
A Nb-based alloy tube 2 containing Nb as a main component is placed on the outside.

A composite in which Nb8n2 powder 3 is contained inside and the Nb-based alloy tube 2 is further brought into contact with the Cu matrix 4 is subjected to area reduction processing and heat treated at a temperature of 775° C. or lower to form a composite material as shown in FIG. 1 (B). Nb3Sn superconducting compound 6 as shown in
This is a method for manufacturing a Nb38n composite superconductor 7 that produces the following.

〔Effect of the invention〕

By interposing the KCu alloy tube between the Nb alloy tube and the Nb8n2 powder, the mutual adhesion is very good, and even in high processing conditions during area reduction processing, there is no constriction, thinning, or disconnection of the core wire. lost.

In other words, workability was improved. This resulted in the effects described below.

(Since the 11Nb tube filament is not cut, the internal an does not diffuse into the Cu matrix outside the Nb tube during heat treatment, so Ic is low. Also, the Cu matrix is 8
Since it is not contaminated with n, low resistance can be maintained, resulting in good cooling stability.

(2) Since the integrity of the Nb tube is maintained even at high surface reduction processing, the diameter of the Nb tube can be made small, and the thickness of the Nb38h layer can be made thinner, making it a strong conductor against tension, bending strain, etc.

(3) Since the reaction between Nb and an can be carried out through the presence of Cu, the heat treatment temperature can be relatively low, and as a result, Nb38n with a high Jc value can be produced.・(4) Improved processability allows the proportion of the Cu matrix in the conductor to be reduced, which reduces the Ic per total cross-sectional area of the conductor (overall Jc), which is important for practical purposes.
can be made higher. .

[Embodiments of the invention]

Example 1 As shown in FIG. 1(A), Nb coated on a Cu tube 1
In order to make Sn2 powder 3, Nb with an average particle diameter of ~30#m was placed in a Cu tube with an outer diameter of 185 mφ and an inner diameter of 12+llIφ.
After filling with Sn2 powder, the wire was thinned to have an outer diameter of 5 wm'. This Cu-clad NbSn2 powder wire was installed inside a Nb pipe with an outer diameter of 8 mm and an inner diameter of 5 J, and this combined body was
A 0+m Cu billet is inserted into the Cu' matrix 4, which has 78 8 through-holes, and then processed to reduce its area and made into a thin wire. (including clad Nb8n2 wire) buried wire diameter 0
．． A composite conductor 5 of 2 mm' was formed. No abnormalities were observed in the core wire during the thinning process or at the final wire diameter of 0.2 J.

It was possible to process the core wire to an outer diameter of 16 μmφ and an inner diameter of 10 μmφ (Nb). Processing beyond this is possible, but for the purpose of evaluating the characteristics, we stopped at a wire diameter of 0.2+m+φ. The inner diameter of the Nb core wire, 10 μm6, is less than the value obtained by the conventional method.

For characteristic evaluation, this composite conductor 5 was heat-treated at 625° C. for 50 hours in a vacuum atmosphere to form a Nb 38 n superconducting compound 6 inside the Nb tube 2a, as shown in FIG. 1(B).
Please make sure to generate 1.5μm. The volume fraction of the Cu matrix 4a in this Nb38n composite superconductor 7 was 50%, which was 30% lower than that of the conventional structure.

The critical current (Ic) of the NbB8n composite superconductor 7 thus obtained was determined to be 25.2 A in a magnetic field of 11 T (Tesla). When this value was divided by the total cross-sectional area of the conductor 7 to find the critical current density (Jc), the value was 803 A/mJ. This value is a 934% improvement over conventional conductors. This is due to a decrease in the volume fraction of the Cu matrix and an improvement in Jc due to low temperature heat treatment.

In order to further examine the strain characteristics, after applying bending strain, 4.
2, Ic was measured under the magnetic field of IIT. The results are shown in FIG. In Figure 2, the horizontal axis shows bending strain, and the vertical axis shows Ic under bending strain and I when no bending strain is applied.
The ratio (%) to c is shown. (a) is a conductor for comparison of characteristics, and is a conductor having the same Ic as that of the present invention by using a 4 μm thick Nb38n layer in the Nb core made by a conventional manufacturing method. The above core wire diameter was the upper limit for processing.

(b) shows superconducting wires according to the present invention, and their respective characteristic curves. As is clear from this figure, the superconductor according to the present invention is about twice as strong against strain as the conventional superconductor.

Example 2 Instead of the Cu tube 1 in FIG. 1 (person), a mesh-like Cu tube (the tube is formed in a net shape) was used,
Nb3 with wire outer diameter 0.2 mm' having the same shape as in Example 1 above
A Sn composite conductor was manufactured. For characterization.

Heat treatment was performed in vacuum at 625° C. for 50 hours, and 1.
571 m thick Nb3Sn was produced. Its fi, 4.
2K.

The critical current (Ic) was measured under a magnetic field of 11 T and was 30 OA. This value was further improved by about 20% compared to the conductor of the present invention in Example 1. This is Nb
Because the reaction between and 8n is carried out very efficiently,
This is thought to be due to an improvement in the degree of order of atoms within the generated NbBSn layer.

[Other embodiments of the invention]

The Cu tube in No. 17 (A) is not limited to pure metal K, but may be an alloy to which elements are added within a range that does not impede workability.

NbSn2 instead of Cu mesh tube in Example 2
A Cu wire or the like may be spirally wound around the outer peripheral surface of the sintered powder.

[Brief explanation of the drawing]

FIGS. 1(A) and (B) are partial cross-sectional views showing the structure of a composite superconductor to explain the present invention in detail, and FIG. 2 is a critical current (Ic)-bending diagram of the inventive conductor and comparative conductor. It is a distortion characteristic diagram. 1...Cu-based alloy tube, 2...Nb-based alloy tube, 3...
・Nb8n2 powder, 4...Cu matrix,
5...Composite conductor. 6...Nb3Sn superconducting compound, 7...Nb38n
Composite superconductor, 8... Nb-8n-Cu after reaction
alloy. Representative Patent Attorney Kensuke Norichika (and 1 other person) Figure 1 Figure 2 Hu Qu Ding JLε (phantom)

Claims (1)

[Claims] (1) Cu t- Through the Cu-based alloy tube containing Nb as the main component, and the Nb-based alloy tube containing Nb as the main component on the outside;
2 powder was brought into contact with the inside, and a Nb-based alloy tube was further brought into contact with Cu.
Heat treatment is performed at the following temperature to form a Nb 38n compound.
A method for producing a Nb38n-based composite superconductor, the method comprising producing a superconducting layer. (The method for producing a Nb B S n based composite superconductor according to claim 1, characterized in that a pipe having a mesh shape of a Cu alloy pipe containing 21eu as a main component is used.