JPS5998412A - Manufacturing method of multicore Nb↓3Sn superconducting 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 The present invention relates to an ultrafine multicore compound superconducting wire made of a Nb3Sn superconducting conductor used in a strong magnetic field generator, and a method for manufacturing the same.

Since Nb3Sn compound superconducting materials have excellent superconducting properties such as critical temperature, critical magnetic field, and critical current, they have been put into practical use as magnet windings for generating high magnetic fields. When producing a magnet for generating a high magnetic field, one of the points to be noted is that it is difficult to operate the magnet stably near the critical current value of the material due to the occurrence of flux jumps. As a method for this purpose, a method of forming ultra-fine multifilamentary wires has been used.

Conventionally, the method of making Nb3Sn superconducting material into multifilamentary wires was to embed Nb in a bronze matrix as shown in Figure 1, and then to stretch it and then perform diffusion heat treatment. However, the work hardening rate of bronze was large, and After surface reduction processing of 0 coefficient, it must be softened and annealed at 4.00°C to 600°C for 1 to 2 hours. For example, from 27 mmφ to 1 m+ diameter
When drawing a wire to nφ, approximately 10 times of annealing are required, and this annealing requires a lot of cost and time.

The following method has been used as a conventional method to eliminate the drawbacks of work hardening of bronze, which lengthens the process and increases costs.

Conventional Example 1 As shown in Fig. 2, an Nb wire is placed around a Sn Cu alloy wire, and this is inserted into a Cu tube and stretched to obtain a Sn Cu multifilamentary wire as shown in Fig. 3. A multicore Nb 3 Sn superconducting wire is obtained by diffusion heat treatment at a temperature of 600° C. to 800° C. for several tens of hours.

Conventional example 2゜C where multiple composites made by enlarging Nb particles placed in a Cu vibrator are placed on the outside, and a Cu block is placed in the center.
Both ends of the u-tube are capped with Cu, and the resulting product is electron beam welded and hot extruded to obtain a Cu7 trisox Nl) multicore composite as shown in Figure 4.

After hot extrusion, the central part is hollowed out with a drill, Sn is inserted into that part, and several pieces are stretched and bundled.
. . .: By inserting it into a tube and enlarging it, a composite as shown in FIG. 5 can be obtained.

A Nb 3Sn superconducting wire can be obtained by heat treating this at 600° C. to soo'c for several tens of hours.

Conventional Example 1 has the following drawbacks.

The work hardening characteristics of Nb, 5nCu, and Cu are shown in FIG. 6, where the strength of Nb increases as the working ratio increases, whereas the strength of Sn is extremely weak despite working. Because of this difference in strength, it is difficult to process Sn to a diameter of about 30 μm or less in Conventional Example 1. Therefore, the diameter of Nb3Sn after the diffusion heat treatment becomes 30 μm or more, and when a magnet is made using this wire, the stability of the magnet becomes poor. Also, the diameter of Nb is 30
Since it cannot be made smaller than μm, the time required for the diffusion heat treatment at 600° C. to 750° C. becomes longer, and the critical current density decreases due to the coarsening of Nb3Sn crystal grains due to the long time heat treatment.

In Conventional Example 2, a hole is drilled in the center of the Cu matrix Nb filament composite multifilamentary wire after hot extrusion to insert Sn, but the diameter of this multifilamentary wire must be 30 mm or more. It is extremely difficult to drill a hole with a depth of 1 Oon or more without eccentricity in the center of a multifilamentary wire with a diameter of 30 mm or less, and at a depth of 10 m or less, it is difficult to make a hole in a composite material obtained by stretching after inserting Sn. The amount is so small that it is unsuitable for industrial production. Sn on multifilamentary wire with a diameter of 3Qmm or more
When a hole is drilled for insertion, the diameter of the hole is approximately 10 mm. After enlarging this composite, multiple pieces are bundled together and subjected to area reduction processing. However, when performing composite processing of Sn, Cu, and Nb, the diameter of the hole is approximately 10 mm. Because of the large difference in strength, it is impossible to reduce the surface area to 10,000 or more, and the diameter of Sn cannot be reduced to 100 μm or less.

Therefore, Sn is diffused into the Cu matrix and further S
The heat treatment for reacting n and Nb filament takes time, and the resulting Nb3S
It is difficult to diffuse n crystal grains without making them coarse, and the critical current decreases, resulting in a Jc of at most 800 A/rmn in a 10 Tesla magnetic field.

Due to the large diameter of Nb5sn produced as in Conventional Example 1, the magnet using this wire becomes unstable, and the critical current density decreases due to the large diameter of Nb, and as in Conventional Example 2. The present invention was devised in order to eliminate the drawback that the critical current density decreases due to the large diameter of Sn.

The present invention provides a plurality of Sn or Sn alloy wires and a plurality of C
A composite multifilamentary wire in which u is a matrix and Nb is a filament is tightly bundled and drawn, and the wire is heat-treated to form Nb3.
In a method for manufacturing a Nb3Sn superconducting wire by forming a Sn compound layer, carbon is added around the Sn or Sn alloy wire.
This is a method for producing a multicore Nb3Sn superconducting wire, which is characterized by twisting or bundling a plurality of segments in which composite multifilamentary wires in which U or Cu alloy is the matrix and Nb is the filament are arranged. The compound superconducting wire according to the present invention is usually coated with a metal for stabilization and/or diffusion prevention on the outer periphery of the above-mentioned twisted or bundled wire.

In the manufacturing method of the present invention, first, a composite body as shown in FIG. 7, in which a plurality of Nb pieces are arranged in a Cu or CU gold alloy matrix, is made by hot extrusion, vibrator fitting, or the like. After stretching this, it is twisted or bundled around a rod of Sn, Sr, or alloy as shown in Figure Obtain a wire rod with a cross-sectional shape. Sn
Nb g is diffused into Cu and then heat-treated at 600°C to 800°C to form Nb g around the Nb filament.
Generate a S n layer.

゛ By the manufacturing method according to the present invention, the diameter of the Nb filament can be reduced to 10 μm or less, and the diameter of the Sn filament can be reduced to about 30 μm or less.
As in Conventional Example 1, the diameter of the Nb filament is approximately 30 μm, which deteriorates the stability of the magnet and reduces Jc, and as in Conventional Example 2, Sn
It is possible to prevent a decrease in Jc caused by the large diameter of about 100 μm.

By the manufacturing method according to the present invention, 10 Nb filaments are
The reason for this is that the C
By processing the two types of composite of u and Nb, the Nb filament is made small in advance, and then Sn is included in the process, so the degree of processing of the three types of composite including Sn can be reduced. It is. In the manufacturing method of the present invention, the diameter of Sn can be reduced to about 30 μm because there is no need to drill holes in the Cu and Nb composite as in Conventional Example 2, and the stretched Sn wire is This is because it can be used.

The present invention will be explained below with reference to Examples.

A 10 mmφ Nb rod with an outer diameter of 18 mm and an inner diameter of 10.5
Insert it into a Cu pipe with tt=nφ and after enlarging, use a hexagonal die to make a hexagonal bar with a distance of 3 cities, and cut it into 8 bars every 30 cm.
After cutting 00 pieces, the inner diameter after stretching is 100 cm, and the outer diameter is 120 cm.
into the Cu tube. Both ends of this Cu tube are covered with Cu lids and closed by electron beam welding. After hot extrusion, this wire is drawn to 1.5 μm by drawing processing.

Nb in the complex of Cu and Nb obtained by this
The diameter of the filament is 80 μm. This is placed together with a 1.5-inch Sn wire as shown in Figure 10, and covered with a 0.5-inch Nb sheet with an inner diameter of 18 in and an outer diameter of 24 in.
・When inserted into the Cu vibrator of the gate and enlarged until the outer diameter becomes 0.5mm, the diameter of the Nb filament becomes 0.6μ.
m, and the diameter of Sn is 31 μm. This is 300
By heat treatment at °C for 1 day and 500'C for 3 days, Sn was converted to Ca.
After diffusion into Cu in the complex of Nb and
After 24 hours of heat treatment, Nb3Sni! : Generated around the Nb filament. The critical current of the resulting superconducting wire was measured in the IOT magnetic field and was 143A.
The critical current density of the part excluding the stabilizing material is 140
0 A/-, and an Nb3Sn superconducting wire, which is an ultrafine multifilamentary wire, was obtained at a high current density that could not be obtained by conventional methods.

As mentioned above, the Nb3Sn superconducting wire of the present invention has Sn
Alternatively, a composite multifilamentary wire in which Cu or Cu alloy is the matrix and Nb is the filament is arranged around the Sn alloy wire, so that the Nb filament diameter and S
It is characterized in that the diameter of n can be made small, and as a result, it is electromagnetically stable at a higher critical current density than conventional ones.

[Brief explanation of the drawing]

Figure 1. Conventional Nb3 obtained by injecting Nb into a bronze matrix, stretching and heat treatment.
Fig. 2 is a cross-sectional view of Sn multifilamentary wire, Sn in the conventional method.
Arrangement diagram of Cu wire and Nb wire, Fig. 3, cross-sectional view after Jl stretching of the composite shown in Fig. 2, Fig. 41, cross-sectional view of Cu matrix Nb multicore composite in conventional method, Hollow out the center of the complex shown in Figures 5 and 41, and
Figure 6: Work hardening properties of Nb, 5nCu, Cu Figure 7: Cu matrix Nb multicore composite that can be used in the present invention. 8, a layout diagram of the composite of FIG. 7 and Sn in the present invention, FIG. 9, a cross-sectional view of the composite of the present invention obtained by enlarging the composite of FIG. 8, and FIG. 10. , is a layout diagram of a Cu matrix Nb composite, Sni, Nb sheet, and Cu pipe in an example. In the figure, 1 is bronze, 2 is Nb3Sn 3, 5.8.11.14. , 24.25 is Nb4, 7 is S n Cu 6, 9.12.18.21 is Cu 10 is 5n 11' is 5n Cu tensile strength property 12' is Cu tensile strength property 13' is Nb tensile strength property Strength property 15 is Cu or Cu alloy 16, 19.22 is Sn or Sn alloy 17, 2
0.23 indicates a Cu matrix Nb multicore aggregate. 71 fig. Yoshi 2 fig. 76 fig. W8 flash 19 fig.

Claims (1)

[Claims] (1) Multiple Sn or Sn alloy wires and multiple Ct
q Or in a method for manufacturing an Nb 3 Sn superconducting wire, which is formed by heat-treating a drawn wire made by twisting or bundling composite multifilamentary wires in which a Cu alloy is a matrix and Nb is a filament to generate an NbBSn compound layer, A method for manufacturing a multicore Nb3Sn superconducting wire, which comprises bundling a plurality of segments in which a composite multifilamentary wire having Cu or Cu alloy as a matrix and Nb as a filament is arranged around a Sn or Sn alloy wire.