JPH04120257A - Treatment for cu-su alloy for nb3sn superconducting wire - Google Patents

Abstract

PURPOSE:To produce a Cu-Sn alloy sufficiently homogeneous and free from defects by successively subjecting a Cu-Sn alloy for Nb3Sn superconducting wire to homogenizing heat treatment and hot isostatic pressing treatment under respectively specified conditions. CONSTITUTION:Homegenizing heat treatment is applied to a Cu-Sn alloy for Nb3Sn superconducting wire at a temp. in the region between 500 deg.C and the solidus temp. of the average composition of this alloy. Then, hot isostatic pressing treatment is performed at >=350 deg.C under a pressure of >=sigma0.2 of this alloy. By this method, the Cu-Sn alloy capable of producing an extra fine and multiconductor Nb3Sn superconducting wire having a filament diameter of several microns to submicron can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for processing a Cu-Sn alloy for Nb3Sn superconducting wire.

[Prior art]

NtlaSn superconducting wires are usually manufactured by a bronze method. This method uses Cu-3n alloy (bronze).
After drilling many holes in the ingot and inserting Nb rods into each hole,
After a wire drawing process including hot extrusion and intermediate annealing is performed to obtain a composite wire rod of a desired wire diameter, this composite wire rod is subjected to heat treatment to generate Nb3Sn.

〔assignment〕

Recently, however, requirements for the characteristics of superconducting wires have become stricter, and the NtlsSn filaments in superconducting wires are becoming increasingly thinner and more multi-core. However, when Nb3Sn filaments are made ultra-thin and multi-core, problems arise such as the filament becoming more likely to break, making it impossible to obtain the desired characteristics, making it impossible to manufacture long superconducting wires, and reducing product yield. There is.

An object of the present invention is to provide a method for processing a Cu-8n alloy for an Nb3Sn superconducting wire, which makes it possible to manufacture a superconducting wire in which the Nb3Sn filament is made extremely thin and multi-core.

[Means for solving problems]

Disconnection occurs in the Nb3Sn filament in the Nb3Sn superconducting wire because of blowholes and microscopic segregation that exist in the Cu-Sn alloy. The reason is that Cu
- When reducing the area of a composite material of 3n alloy and Nb,
If there is blowhole or segregation in the Cu-3n alloy, the stress field in the vicinity becomes non-uniform, and the N
This is because when the b filament is further processed, constrictions and wire breaks are likely to occur.

In particular, in Cu-Sn alloys for NbaSn superconducting wires, Sn is dissolved in solid solution up to the very limit of solid solution, so Sn segregation tends to occur. It is difficult to completely eliminate segregation and blowholes by improving current melting and casting technology.

Therefore, the present invention applies homogenization heat treatment to a Cu-3n alloy for Nb3Sn superconducting wire at a temperature of 0500°C or higher and below the solidus line of the average composition of the alloy, a temperature of 0350°C or higher, and a σ of the alloy. . , HIP (hot isostatic pressing) treatment is performed at a pressure of 2 or more. Furthermore, σ. ,
, is 0.2% proof stress, that is, a stress value that causes 0.2% permanent strain after stress removal.

The homogenization heat treatment (①) is performed to eliminate segregation of the Cu-3n alloy, and the HIP treatment (②) is performed to eliminate blowholes in the Cu-3n alloy. Which of these two treatments should be performed first? You can go to

The temperature of the homogenization heat treatment was set at 500°C or higher and below the solidus line of the average composition of the Cu-Sn alloy because if it was lower than 500°C, the diffusion rate would be too slow and homogenization would take too long, making it unsuitable for industrial use. This is because the shape of the material to be treated cannot be maintained at temperatures exceeding the solidus line.

In addition, the conditions for HIP treatment were a temperature of 350°C or higher, and σ of the alloy. , the pressure of 2 or more is σ. This is because if the pressure is less than 2, the blowhole of the Cu-3n alloy will not be sufficiently crushed, and if the pressure is less than 350°C, even if the blowhole is crushed, metallurgical bonding will not occur.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A Cu-14, 3wt% Sn-0, 2wt% Ti alloy was melted and cast. As a result of cutting a slice from this ingot and investigating it, a maximum of 5 wt % of Sn was segregated in the blended composition. In addition, the size of 8 to 15μ is spread over the whole slice.
Innumerable circular and polygonal blowholes were observed.

This ingot slice was heat treated at 520±5° C. for 40 hours in a vacuum or an inert gas atmosphere. When the subsequent slices were examined, the blowholes remained as they were, but the segregation had been clearly resolved, especially in the Sn-rich side of the segregation areas.

Next, the alloy ingot 300na + φ
The temperature was raised to 400°C under the temperature increase condition of 00°C/hr, and
HIP treatment was performed at a pressure of 0.00 kgf/cm' for 1 hour. σ at 400℃. , , is 14Kgf/mm".

Afterwards, slices were cut from both ends and the center of the ingot and examined, and it was found that the Sn segregation had been eliminated, and no blowholes were found; the blowholes were completely crushed and metallurgically bonded. was.

Therefore, a superconducting wire was manufactured using the ingot subjected to the above treatment. First, the ingot was forged, and after external cutting to 200mmφ,
Nineteen holes were made and Nb rods were inserted. This composite material was hot-extruded, then cold-worked and annealed repeatedly to obtain a composite wire with a predetermined wire diameter, which was then cut to a regular length.

Next, the same ingot as above which had been subjected to homogenization heat treatment and HIP treatment was subjected to the same forging processing and external cutting as above, and then the composite wire material cut to length in the previous step was inserted. This composite material was hot-extruded, then cold-worked and annealed repeatedly to obtain a composite wire with a predetermined wire diameter, which was then cut to a regular length.

Next, a large number of composite wire rods cut to a fixed length are bundled together, wrapped around a Ta barrier, inserted into a Cu tube, and hot extruded.
Cold working and annealing were repeated until the outer diameter was 3.0 alffl.

The thus obtained wire was heat-treated to generate Nb and Sn to produce a Nb3Sn superconducting wire with a size of 3.0 ml 1φ, a bronze ratio of 3.2, and a number of filaments of 120,000. As a result of investigating this superconducting wire, no filament breakage was found, and Jc (at 16T) was 248^
/mm”.

Example 2 Same as Example 1 Cu-14,3wt%Sn-0,2wt
%Ti alloy ingot was used. As explained in Example 1, in this ingot, a maximum of 5 wt% of Sn segregation was observed based on the composition, and there were countless circular and polygonal blowholes with a size of 8 to 15μ0. be.

This ingot 160 mmφ
HIP treatment was performed at a pressure of 2 for 1 hour. Thereafter, when slices were cut out from both ends and the center of the ingot and examined, the blowhole was completely crushed, and no blowhole was observed. However, the Sn segregation area remained as it was.

Next, the ingot after the HIP treatment was heat treated at 520±5° C. for 40 hours in a vacuum or an inert gas atmosphere.

Thereafter, a slice was cut out from this ingot and examined, and as in Example 1, segregation, especially on the SnlJ side, was clearly eliminated.

Using this ingot, a Nb, Sn superconducting wire was manufactured in the same process as in Example 1. Jc (at 16T) of this superconducting wire
was 245^/mm'', and no filament breakage was observed.

Comparative Example 1 A Nb, Sn superconducting wire was manufactured in the same manner as in Example 1, except that the temperature of the homogenization heat treatment of the bronze ingot was 470°C.

Comparative Example 2 A Nb, Sn superconducting wire was produced in the same manner as in Example 1 except that the temperature of the HIP treatment of the bronze ingot was 330°C. σ at 330°C. , is 14Kgf/city2.

Comparative Example 3 A Nb3Sn superconducting wire was manufactured in the same manner as in Example 1 except that the bronze ingot was not subjected to homogenization heat treatment or HIP treatment.

Table 1 shows the Jc measurement results of the superconducting wires manufactured in Comparative Examples 1 to 3 in comparison with Example 1.2.

Table 1 [Effects of the Invention] As explained above, according to the present invention, it is possible to obtain a sufficiently homogeneous and defect-free Cu-Sn alloy. Multi-centered N
b. It becomes possible to manufacture Sn superconducting wire without causing filament breakage. Therefore, Nb3S
It not only improves the critical current density of the n-superconducting wire, but also improves the product yield and makes it possible to lengthen the length of the superconducting wire, which is an extremely significant industrial effect.

Claims (1)

[Claims] 1. 500% Cu-Sn based alloy for Nb, Sn superconducting wire
After homogenization heat treatment at a temperature of 350°C or higher and below the solidus of the average composition of the alloy, the alloy is heated to a temperature of 350°C or higher and σ_0_. A method for processing a Cu-Sn alloy for Nb_3Sn superconducting wire, characterized by performing HIP (hot isostatic pressing) treatment at a pressure of _2 or more. 2. 350 for Cu-Sn alloy for Nb, Sn superconducting wire
℃ or higher and the alloy's σ_0_. Processing of a Cu-Sn alloy for Nb_3Sn superconducting wire, which is characterized by performing HIP treatment at a pressure of _2 or higher, followed by homogenization heat treatment at a temperature of 500°C or higher and below the solidus line of the average composition of the alloy. Method.