JPS6117897B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a method for manufacturing a Nb ₃ Sn-based compound superconductor used for superconducting wires such as those for superconducting magnets. [Technical Background and Problems of the Invention] The following method called the bronze method is known as a method for manufacturing Nb ₃ Sn-based compound superconductors. That is, after surface reduction processing is performed while the CuSn alloy and Nb or a Nb-based metal such as Nb-based alloy are in contact with each other, heat treatment is performed to generate Nb ₃ Sn at the interface between the CuSn alloy and the Nb-based metal, thereby reducing the Nb ₃ This is a method for manufacturing Sn-based compound superconductors. However, in this method, the area is reduced in a configuration where the CuSn alloy and the Nb-based metal are in direct contact, so for example, if the CuSn alloy is
When a CuSn alloy of 20at% or less is inserted into an Nb pipe and subjected to surface reduction processing, there are differences in mechanical properties between the CuSn alloy and Nb (for example, in terms of hardness, CuSn
Since the Hv of Nb is large (180) compared to the Hv of alloy Hv of 15, the diameter of the Nb pipe tends to become uneven and breaks at thin parts, which limits the area reduction processing.
In the case of a CuSn alloy with a concentration of 20 to 93 at%, its ductility is poor, so if it is inserted into a Nb pipe and subjected to area reduction processing, the CuSn alloy will turn into powder, making it impossible to draw or thin the wire. Therefore, for the above reasons, this method
The Sn concentration could not be increased, and superconductors manufactured by this method could not have a high critical current density. [Object of the Invention] The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to provide a manufacturing method capable of obtaining a Nb ₃ Sn-based compound superconductor with a high critical current density. [Summary of the invention] This invention provides Sn with a Sn or Cu concentration of 8at% or less.
The core is a Sn-based metal rod, which is a CuSn alloy mainly composed of Cu, and is sequentially coated with a Cu-based metal tube, such as a Cu tube, or an Nb-based metal tube, such as an Nb tube. Sn in Cu-based metal rods and Cu-based metal tubes
The ratio of Sn to Cu is 35% to 55% by weight, and specifically the diameter of the Sn-based metal rod and
Nb ₃ Sn was formed by changing the diameter of the Cu-based metal tube so that the weight ratio was within the above range, and then subjected to area reduction processing and heat treatment to generate Nb ₃ Sn.
A method for manufacturing a compound superconductor. [Embodiments of the Invention] Examples of the present invention will be described in detail below. The Nb ₃ Sn-based compound superconductor 1 is manufactured as follows. First, as shown in Figure 1, a 5mm diameter
Rods 6 made of Sn-8at%Cu alloy whose main component is Sn are inserted into Cu tubes 7 having various outside diameters as shown in Table 2, and the wires are each inserted until the outside diameter becomes 5 mm. After drawing the wire, insert this wire into a Nb tube 8 with an outer diameter of 8 mm and an inner diameter of 5 mm, and then
The wire body was inserted into a Cu tube 9 with an outer diameter of 16 mm and an inner diameter of 8 mm so as to be coated with Cu, and then drawn until the outer diameter became 0.5 mm, and then subjected to a prescribed heat treatment. When this is done, the Sn in the rod 6 diffuses through the Cu to the Nb tube 8, and as shown in Fig. 2, it forms on the inner surface of the Nb tube 8.
A Nb ₃ Sn layer 4 is produced, and the Nb ₃ Sn compound superconductor 1 shown in FIG. 2 is obtained. Incidentally, the Sn in the rod 6 whose main component is Sn diffuses during heat treatment and is mostly used to form the Nb ₃ Sn layer, so after the heat treatment the rod 6 and the Cu tube 7 are
becomes CuSn alloy 12, in which most of the Here, the structure in which the rod 6 whose main component is Sn is coated with the Cu tube 7 and further coated with the Nb tube 8 is that the Cu tube is interposed compared to the case where the Nb tube and the CuSn alloy are brought into direct contact. This is to facilitate surface reduction processing. This is Nb, Cu, Sn−
Since the respective hardnesses of 8at% Cu and Sn are shown in Table 1, the difference in hardness changes stepwise by interposing Cu, which prevents the Nb-based metal pipe from becoming thin or breaking the core wire. Therefore, surface reduction processing becomes easier.

[Table] Additionally, Cu is added to the rod 6 whose main component is Sn (8at% in this example) in order to reduce the difference in hardness with the Cu tube, but if the amount of Cu is significantly increased. In CuSn alloys, the ductility deteriorates, so it is not possible to increase Cu much, and as can be seen from Table 1, the hardness cannot be increased that much with the amount of Cu in Sn-8at%Cu alloy. Therefore, adding about 8 at% of Cu to the rod 6 whose main component is Sn does not have much significance. Next, the present inventors changed the weight ratio of Cu and Sn in the Cu tube 7 in the Nb tube 8 and the rod 6 whose main component is Sn as shown in Table 1 to produce an Nb ₃ Sn-based compound superconductor. The critical current density was measured. Specifically, the diameter of the rod 6 whose main component is Sn is constant at 5 mm, and the wall thickness of the Cu tube 7 that covers the rod 6 is varied, that is, the inner diameter is constant and only the outer diameter is changed. The weight ratio of Sn and Cu was changed as shown in Table 2.

〔Effect of the invention〕

As detailed above, according to the present invention, the area of the Nb-based metal tube can be easily reduced without causing any breakage or core wire breakage, and a high critical current value or high critical current density can be obtained. It is industrially superior, as it can be applied to superconducting magnets and other devices to construct high-performance devices. In the above-described embodiments of the present invention, only single-core wires have been described, but the effects of the present invention do not change even if the wires are configured with multi-core wires, and round wires, round wires,
It can be applied to any shape such as a square wire or a flat hollow conductor wire.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the structure of the Nb ₃ Sn-based compound superconductor according to the present invention during the manufacturing process, and FIG. 2 is a cross-sectional view of the Nb ₃ Sn-based compound superconductor obtained by the manufacturing method of the present invention. Figures 3 to 6 show Nb ₃ Sn when the heat treatment temperature and weight ratio of Sn and Cu are changed.
FIG. 2 is a characteristic diagram of a system compound superconductor. 1...Nb ₃ Sn-based compound superconductor, 4...Nb ₃ Sn
Layer, 6... Sn-based metal rod, 7... Cu-based metal tube, 8
...Nb-based metal tube.

Claims (1)

[Claims] 1 A Sn-based metal rod containing Sn as a main component is covered with a Cu-based metal tube containing Cu as a main component, and the outer periphery of this Cu-based metal tube is covered with an Nb-based metal tube containing Nb as a main component, and this Nb Sn-based metal rod and Cu inside metal pipe
Sn is 35% by weight as the proportion of Sn and Cu in the metal pipe.
55% by weight, and then subjected to surface reduction processing,
Characterized by heat treatment to generate Nb ₃ Sn
A method for producing a Nb ₃ Sn-based compound superconductor.