JPH0248351B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for connecting superconducting wires by cold pressure welding with an intermediate metal material interposed therebetween. Generally, as a method for connecting metal wires, a method is known in which two wires to be connected are brought together and cold pressure welded, and this method is widely used for connecting metal wires such as electric wires. However, this method has the drawback that sufficient bonding strength cannot be obtained for metal wires with poor cold weldability, such as composite wires and special alloy wires. The same applies to superconducting wires. Therefore, when connecting metal wires having poor cold weldability, methods that apply heat such as hot pressure welding or brazing are generally used. However, with this method of applying heat, the problems of diffusion layer growth and alloy layer formation cannot be avoided, and the formation of alloy layers is of course difficult for superconducting wires, which extremely dislike the growth of diffusion layers. The problem is that it cannot be applied at all. This is because, in the case of superconducting wires, their properties are affected by heating during connection. An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to easily perform cold welding by interposing a thin intermediate metal material having the same hardness as the superconducting wire. The object of the present invention is to provide a method for connecting superconducting wires, in which the intermediate metal material is also extruded and removed as burrs, thereby forming an extremely sound connection section for superconducting wires. That is, the gist of the present invention is that, in a method for connecting superconducting wires, when the superconducting wires to be connected or the superconducting wire and another metal wire are butted together and cold welded, there is a connection between these butt portions that is similar to the superconducting wire. By interposing a thin intermediate metal material having a certain degree of hardness and made of a material different from that of the wires to be connected, and applying pressure to both wires in the axial direction in this state, the initial protrusion of the intermediate metal material and the wires is removed. A method for connecting superconducting wires, characterized in that mating surfaces are extruded and removed as burrs and cold pressure welding is performed. Next, an embodiment of the method for connecting superconducting wires of the present invention will be described with reference to the accompanying drawings. 1 and 1 are superconducting wires to be connected to each other,
Each is made of solid wire. 2 is the wire rod 1, 1 disposed between the butt portions 3, 3 of the wire rods 1, 1;
Thin intermediate metal members 4, 4 made of materials different from those shown in FIG. Here, in FIG. 1, the pressure welding dies 4, 4 are moved in the direction of the arrows, and the wire rods 1, 4 to be connected are
With the intermediate metal material 2 sandwiched between the abutted portions 3 and 3 of the wire rods 1 and 1, the wire rods 1 and 1 are coldly pressurized in the axial direction, and as shown in FIG. The first abutting surface and the intermediate metal material 2 are extruded and removed as burrs 5, and both wire rods 1, 1 are connected by pressure welding. Here, the intermediate metal material 2 is extruded and removed as a burr during pressure welding, but even if some of the intermediate metal material remains in the pressure welding part, it is not harmful to the connection characteristics of the superconducting wire. No problem. The intermediate metal material is preferably a homogeneous metal having a hardness comparable to that of the superconducting wire.
If it is too hard than the superconducting wire, it will be difficult to extrude it and remove it as burr together with the superconducting wire by applying pressure. In addition, if it is too soft than the superconducting wire, it will easily be extruded and removed as a burr at the tip of the superconducting wire to be connected, so it will resist the burr generated from both wires to be connected, increasing the pressing force and strengthening the connection. It becomes difficult to raise the level. As an intermediate metal material
In the examples described below using BCuP2 and Cu, the hardness of the Cu-based intermediate metal materials is reduced by using work-hardened materials without final annealing. -It is comparable to Ti alloy wire (superconducting wire). As a combination of both wires to be connected, in addition to superconducting wires, a combination of a superconducting wire and another metal wire such as copper may be considered. Next, some specific examples of the present invention will be explained. Example 1 A filament of NbTi alloy wire with an outer diameter of 2.3 mmφ was
When cold welding 1000 Cu-NbTi composite wires whose outer layer is copper, a thickness of 0.1 mm is applied between the butt parts.
A connection part was formed by applying pressure in the axial direction with 0.2 mm and 0.4 mm BCuP2 plates interposed, respectively, to generate sufficient burrs and performing cold pressure welding. Regarding the pressurizing method, the pressurization time was 0.5 to 2.0 seconds per time, and the work was completed by performing the pressurization four times in total with a pressurization time interval of 5 to 10 seconds. In this working method, since the pressurization time interval is the so-called heat radiation time, no particular heat generation occurred during pressurization, and of course no influence of heat on the superconducting wire was observed. In addition, for comparison, we created a joint formed using a pure Cu plate with a thickness of 0.2 mm and a joint formed using the conventional method without using any intervening material, and subjected them to repeated bending tests (bending tests). The joint characteristics were comparatively evaluated using a radius of 30 mm. As shown in the following table, the evaluation results showed that the effect of the interposition of the intermediate metal material was noticeable.

[Table] Example 2 A wire with a thickness of 0.2
A connection part is formed by cold pressure welding with a Cu plate of mm in size interposed (the pressurizing method is the same as in Example 1), and this connection part and a connection part formed by cold pressure welding without intervening a Cu plate. As a result of evaluating and comparing the two through repeated bending tests, it was found that in the former, the characteristics improved by up to 100% in terms of the number of bends before breakage. Example 3 A wire with a thickness of 0.2 mm was placed between the butt part of the same Cu-NbTi composite wire as in Example 1 and a pure copper wire with the same outer diameter.
A connection part was formed by cold pressure welding with a BCuP2 plate interposed (the pressurizing method was the same as in Example 1), and this connection part and a connection part formed without a BCuP2 plate were subjected to repeated bending tests. As a result of the evaluation comparison, it was found that the former had a maximum of 50% improvement in properties in terms of the number of bends before fracture. As is clear from the above embodiments, in the method for connecting superconducting wires of the present invention, when two wires to be connected, at least one of which is a superconducting wire, are abutted and cold-welded, a superconducting wire is inserted between the abutted portions. A thin intermediate metal material having the same hardness as that of the two wires to be connected and made of a different material is interposed, and in this state, both the wires are pressurized in the axial direction. Since this method involves extruding and removing burrs on each butting surface and performing cold pressure welding, cold pressure welding is easily possible by interposing the above intermediate metal material, which allows for a sound connection without being affected by heat. can form a section. In addition, according to the method of the present invention, during cold welding, the intermediate metal material and the first abutting surfaces of both wires to be connected are extruded and removed as burrs, so that the characteristics of the connection part of superconducting wires can be improved. It has the remarkable effect of being able to form an excellent connection in the sense that it can hold the parts completely. Moreover, the present invention allows existing cold pressure welding machines to be used as is, and can be said to have extremely great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a state diagram showing an embodiment of the method of the present invention before pressure welding, and FIG. 2 is a state diagram during pressure welding. 1: Superconducting wire, 2: Intermediate metal material, 3: Butt part, 4: Pressure welding die, 5: Burr.

Claims (1)

[Claims] 1. In the method of connecting superconducting wires, when the superconducting wires to be connected or the superconducting wire and another metal wire are butted together and cold welded, a bond with the same hardness as that of the superconducting wires is made between these butted parts. A thin intermediate metal material made of a different material from the two wire rods to be used is interposed, and in this state, both the wire rods are pressurized in the axial direction, thereby extruding the intermediate metal material and the initial abutting surfaces of the two wire rods as burrs. A method for connecting superconducting wires, characterized by removing the material and performing cold pressure welding.