JPS6025842B2 - Method for manufacturing compound superconducting wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrafine multicore superconducting wire made of an intermetallic compound having a 31W type crystal structure.

Intermetallic compounds having an 8-W type crystal structure have excellent superconducting properties such as criticality, critical magnetic field, and critical current, and have already been put into practical use as magnet windings for generating strong magnetic fields.

Its typical body structure is a tape-like structure as shown in FIG. 1, which is made of Nb3Sn, V30a, etc. In Figure 1, 1 is a Nb or V core, around which is a N, Sn or V3 Ga compound layer 2, and outside of which is a C
Covered with u layer 3. If a magnet is made using such a tape-shaped conductor, it will be difficult to operate the magnet stably near the material's critical current value due to the occurrence of flux jumps, so special measures are required to prevent this. becomes. Therefore, research is underway to create ultra-fine multifilamentary wires that are essentially stable and do not cause flux jumps. In other words, as the diameter of the superconducting wire is made thinner, even if instability occurs and heat is generated, the heat capacity of the superconducting wire in that area absorbs this heat and does not lead to a transition to a normal conducting state. It was revealed that a similar diameter exists.

It is believed that qualitative stabilization is possible with this technology. It is said that the diameter of a superconductor to be essentially stable is several tens of meters. Therefore, in order to make a wire with a large flow, it is necessary to bundle hundreds to thousands of superconducting wires.
An example of what has been adopted to achieve this is Cu-
After drawing a composite of a 2t% Ga alloy and a large number of V cores into a pongee line and heat-treating it at about 625qo, Cu-○a
A V3Ga layer is generated at the interface between the alloy matrix and V.

In the case of Nb3Sn, Cu-Sn alloy and a large number of Nb
N et Sn wires are obtained by drawing the composite with the core and then heat-treating it at 700 ○, and in the case of V3Sj, after drawing the composite of the Cu-Si alloy and the V core, the wire is heated to about 800 ○. A V3Si wire can be obtained by heat treatment. These methods differ depending on the material, but basically, a composite of a solid solution alloy, which is a normal conductive metal with added elements for compound formation, and a Nb or V core is heated at 600° to 85°C.
This method generates a compound by heating at about 0 qo, and its cross-sectional structure is as shown in FIG. (This method is called the solid-state diffusion method). In Figure 2, 4 is Nb
or a V core, 5 is an alloy prepared by adding an element for compound generation to a normal conducting metal, and 6 is the generated compound superconducting layer.

Such a method can be said to be an excellent method for converting essentially hard and brittle compound superconducting materials into green materials. However, in this method of inserting Nb (or V) into a Cu-Sn (or Cu-Ga) alloy matrix and drawing it, the work hardening of this matrix is severe, and the matrix is softened many times during the process. It has the disadvantage that it requires heat treatment and cannot be said to be an industrially or economically advantageous method.

In addition, as a method to eliminate this drawback, a large number of Nb pieces are inserted into the Cu matrix and wire drawn (Nb and C strands alone have good processability), and even if the wire is processed to a specified size, the surface will be melted and bonded. Coated with Sn and heated to 650o ~ 800o
A method of making a multi-core NQSn wire by heat-treating with 00 is proposed (Appl. Phys. Let
t. Vol. 20, Noll, 1972).

(This is called the external diffusion method). The disadvantage of this method is that Sn is supplied only from the outer surface, so the reaction between the Nb placed in the center and the Nb on the outer periphery is non-uniform, and the reaction with Sn is uneven across the cross section and diameter. In addition, the quality of the N
Inability to supply a sufficient amount of Sn for b, 650~
During the heat treatment at 800oC, the Sn coated on the surface melts off, evaporation loss, etc., resulting in the inconvenience that it is difficult to produce a homogeneous wire on an industrial scale.

The present invention aims to eliminate these drawbacks of the external diffusion method and provide a method for easily producing ultrafine multifilamentary compound wire having a large number of cores with uniform quality.

The first name of the present invention is that a Cn tape is continuously placed along a bundle of multiple composite wires in which a Nb core is coated with Cu and further coated with Sn. A process of forming a composite material by continuously seam-welding the seam parts.A process of drawing the composite material into a composite wire of a predetermined size, and a process of heat-treating the composite wire to generate a superconducting compound. This is a method of manufacturing an ultrafine multicore compound superconducting wire.

The second invention of the present invention is that in the first invention of Joki, a Cu tape is further continuously placed along the bundle of the above-mentioned stretched composite wires, and the multi-composite material is formed while being formed into a pipe shape. This is a method for producing an ultra-fine multicore compound superconducting wire, which comprises a step of manufacturing, a step of stretching the multicomposite material to a predetermined size, and a step of finally subjecting the multicomposite wire to heat treatment to generate a superconducting compound. .

In the present invention, Cu means copper with good conductivity and good workability, such as oxygen-free copper, deoxidized copper, tough pitch copper, etc., and Nb means pure Nb, or Zr, Si, or Ti. Sn means pure Sn or a Sn alloy containing Zr or Si. In addition, as a method of covering a bundle of the above-mentioned Qin wires or the above-mentioned compound wires with pipe-shaped Cu, extrusion C is applied around the slits of the bundle.
You may explore either a method of covering a small fip, or a method of continuously running a Cu tape along the bundle, forming it into a pipe shape, closing the east end, and continuously welding the sheath part. . The invention will be described below with reference to the drawings.

FIG. 3 is a cross-sectional view showing an example of the wire used in the present invention.
To produce this wire, first place the Nb rod 7 into the Cu pipe 8.
is inserted and thinned to a predetermined size by wire drawing, and then the surface is coated with Sn9 by melt plating or fin plating to produce a continuous composite millet wire.

After that, a Cu tape is continuously placed along the bundle of a plurality of composite Qin wires to form a pipe shape, enclosing the above-mentioned east side, and the seam portion is continuously welded. This composite material is finished into a predetermined size by cold stretching. If more cores are required, the process of bundling a plurality of composite wires and enlarging them with Cu coating is repeated one or more times. Thereafter, by finally performing a heat treatment to form N-wide Sn, an ultrafine multicore N-Sn superconducting wire having a structure similar to that shown in FIG. 2, for example, can be manufactured.

Next, examples of the present invention will be described. Example 1 A N material ratio of 0 on the 5 side was inserted into a Cu pipe with an inner diameter of 5.3 and a wall thickness of 0.5 ribs, and expanded and contracted to 0.77 skin 0 without performing any intermediate softening heat treatment.

350q0 After 30 minutes of softening treatment, 350qo
The surface was coated with 30 μm of Sn.

61 of these strands were supplied to an apparatus as shown in FIG. 4, and pipe-shaped Cu was continuously competed. FIG. 4 is an explanatory diagram showing an example of an apparatus for covering a plurality of composite wires bundled with pipe-shaped Cu in the present invention.

In the figure, the required number of composite Qin wires 12 is the wire supply 11
The pipe is fed out from the pipe, passes through a guide plate 13 having a collection and alignment hole, and enters a pipe forming device 16 in an easterly state.

At the same time, the Cu tape 15 is connected to the tape supply 14.
Pipe forming equipment 1 is brought out at the same time as Qin wire 12 group.
6. Here, the Cu tape 15 is continuously formed into a pipe shape so as to grip the wire group 12. Next, the wire group 12 wrapped in the pipe-shaped Cu tape 15 is welded at the seam portion of the metal tape 15 by a torch 20 attached to a die 18 for shape retention or adjustment. The wire group 12 and the Cu tape 15 from the pipe forming device to the welding part are prevented from oxidation etc. by the inert gas supplied from the gas pipe 17 and the torch 20. Composite material 22 after welding
While being molded through one or more dies 21, it is drawn out by a caterpillar, capstan 24, etc., and further processed to a desired diameter by a die 25 as necessary, and wound up by a winder 23. Next, this complex 12
The wire was further drawn in the cold to a diameter of 0.12 ◇.

The Nb core at this time was about 12 mm on average. This is 75
By applying heat treatment in a vacuum at 0.000, 40 o'clock,
Approximately one mountain of N-wide Sn superconducting layer could be uniformly formed on the surface of the Nb core. The obtained ultrafine multicore N-wide Sn superconducting layer wire had a critical current value of 21 A in a 42 K, 5-thigh G magnetic field, and it was confirmed that a healthy N-wide Sn compound layer was generated. Example 2 In the same process as in Example 1, 61 composite wires inserted into a pipe-shaped cu were drawn to a size of 0.77 mm, and the 61 composite wires were then drawn with the apparatus shown in FIG. A material in which a total of 3,721 Nb cores were embedded was fabricated by continuous iron bonding in a pipe-shaped Cu tape using a similar device.
．． The wire was drawn to the 95th side.

The Nb core at this time has about 10 peaks, which are 750oo,
As a result of performing heat treatment in a vacuum for 4 feeding hours and observing the cross section under a microscope, it was confirmed that an Nbbn compound layer with a thickness of less than 1 French similar to that in Example 1 had been formed. As is clear from the examples, the composite material in which many Nb cores are embedded is
It can be easily stretched without heat treatment, and furthermore, Sn uniformly distributed in advance in the composite material acts effectively on heat treatment at high temperatures, making it possible to economically produce ultrafine multifilamentary N-wide Sn superconducting wires.

Also, the inconvenience of Sn melting off or evaporation loss during heat treatment can be eliminated. In addition, as mentioned above, by inserting a large number of thin superconducting layers, we expect essential stability, but we also twist these superconducting layers to make the wire stable against changing magnetic fields and alternating current. If this is also required, in the manufacturing method of the present invention, such a request can be met by twisting N at high temperature before the Sn-forming heat treatment, if necessary.

As described above, the method of the present invention creates a compound superconducting material that is essentially hard and brittle because Cu, Nb, and Sn, which are easy to process, are not mutually in a solid solution or compound state during stretching processing. Nevertheless, it has the advantage that long objects can be easily manufactured using normal enlarging techniques.

Moreover, by repeating the process of bundling a large number of wires, wrapping them with a pipe, and stretching them, it is possible to manufacture a wire in which hundreds to tens of thousands of cores are embedded. In addition, in the method of the present invention, since each strand is coated with Sn, sufficient S is coated on a large number of Nb cores.
Sn can be supplied evenly, and since Sn is surrounded by Cu during heat treatment and is not exposed on the wire surface, there is no melting of Sn or evaporation loss, making it possible to economically achieve uniform quality. There is an advantage that an N Sn layer can be generated.

In summary, the method of the present invention has the advantage of being able to easily and economically produce the longest homogeneous ultrafine multifilamentary compound superconducting wire.
In the above description of the present invention, a multi-core Nbn compound superconductor has been described, but it is clear that a multi-core V3Ga compound superconductor can also be manufactured by the same method.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conductor structure of a compound superconducting material. FIG. 2 is a diagram showing a cross-sectional structure of a multicore compound superconducting wire. FIG. 3 is a sectional view showing an embodiment of the plain twill used in the present invention. FIG. 4 is an explanatory diagram showing an example of a device for covering the east of a composite strand with pipe-shaped Cu in the present invention. 1,4...
...Nb or V core, 2...NGSn or V3G
a Compound layer, 3... Cu layer, 5... Alloy in which an element for compound generation is added to a normal conducting metal, 6.
...Compound superelectric layer, 7...Nb rod, 8...
・Cu pipe, 9...Sn, 11...Wire supply, 12
...Composite wire, 13...Guide plate, 14...
...Tape supply, 15...Cu tape, 16
... Pipe forming device, 17 ... Gas pipe, 18 ... Shape retention or adjustment die, 1
9...Welding machine, 20...Torch, 21
... Dice, 22 ... Composite material, 23.
...Maki Keiki. Gar figure 2 figure spear 3 figure figure size woman

Claims (1)

[Claims] 1. Cu is coated around the Nb core, and Sn is further coated on top of it.
A process of continuously wrapping a Cu tape around a bundle of multiple composite wires coated with copper and wrapping the bundle while forming it into a pipe shape. A method for producing an ultrafine multifilamentary compound superconducting wire, which comprises the steps of drawing a composite wire and subjecting the composite wire to heat treatment to produce a superconducting compound. 2 Coating Cu around the Nb core, and then coating Sn on top of it.
A pipe-shaped Cu
A step of stretching the composite material into a composite wire of a predetermined size, a step of stretching the composite wire into a composite wire of a predetermined size, and continuously running a Cu tape along the bundle of the stretched composite wires to form a pipe shape. The method consists of the following steps: grasping the bundle while forming it, continuously welding the seam portion, stretching the composite material into a composite wire of a predetermined size, and heat-treating the composite wire to form a superconducting compound. A method for manufacturing ultrafine multicore compound superconducting wire.