JPH06223647A - Manufacture of nbti superconducting billet - Google Patents

Abstract

PURPOSE:To provide a method of manufacture of an NbTi superconducting billet excellent in machinability. CONSTITUTION:An NbTi alloy rod is packed in a pipe made of a metal serving as a stabilizer, with Nb metal layers each of thickness 10mum or more interposed in one layer, and the end portions of the metallic pipe are vacuum sealed to obtain a composite filler. The composite filler is subjected to HIP process at temperatures in the range of 500 to 1000 deg.C and at pressures of 500atm. or higher for three minutes or longer. Since the HIP process is carried out at high temperatures and at high pressures for a long time, the adhesion property of the different materials in this NbTi superconducting billet is improved so that a subsequent drawing process is good. Since the Nb metal layers are thickly interposed, the Ti does not diffuse into a stabilizing metal layer to deteriorate the machinability and heat and electric conductivity of the stabilizing metal layer. Since the Nb metal layers are interposed in one layer, deterioration of machinability is avoided that could be caused by imperfect bonding between the Nb metal layers.

Description

Detailed Description of the Invention

[0001]

The present invention relates to NbT having excellent workability.
The present invention relates to a method for manufacturing a superconducting billet.

[0002]

2. Description of the Related Art NbTi superconducting wires are used as conductors for large particle research accelerators, industrial small accelerators (SOR, medical), wiggler magnets, tokamak fusion reactors, generators, power storage devices (SMES), etc. It's being used. By the way, as the NbTi superconducting wire, a multi-core NbTi superconducting wire in which a large number of NbTi filaments are embedded in a copper matrix which is usually a stabilizer is used. And, in the manufacturing, first, a NbTi alloy rod is filled in a copper pipe with a required layer of Nb metal layer interposed, and then the end portion is vacuum-sealed to form a composite filler. 1500 atm
Cold isostatic pressing (CIP) treatment at a degree or 450 ℃ ×
Hot isostatic pressing (HIP) treatment at about 1500 atm is performed to increase the packing density inside to form an NbTi superconducting billet. This superconducting billet is subjected to drawing processing such as hot extrusion and wire drawing to obtain a single core. An NbTi superconducting wire is produced.
Next, a large number of this single-core NbTi superconducting wire is refilled in a copper pipe and the end portion is vacuum-sealed to form a multi-core filling material. The same processing and processing as in the above case was performed to form a multi-core NbTi superconducting wire.

[0003]

However, the multi-core NbTi superconducting wire manufactured by the above-mentioned method has the following problems.
If the internal NbTi filament is thinned to 20 μmφ or less, there is a problem that the superconducting wire is easily broken during wire drawing. Observing this disconnection site, it is often the case that, in the disconnection site, there are many sausage-like filaments 1 with a narrow diameter as shown in FIG. It has been found that the sausage-like filament 1 having a large diameter, which is constricted in places, is caused by uneven deformation between different materials in the superconducting wire.

[0004]

The present invention has conducted intensive studies in view of such a situation, and the cause of non-uniform deformation is Nb.
The inventors have found that there is a cause of defective bonding between dissimilar materials in a Ti superconducting billet, and have conducted further research to complete the present invention. That is, according to the present invention, after a NbTi alloy rod is filled in a metal tube serving as a stabilizer with an Nb metal layer interposed, the end is vacuum-sealed to form a composite filler. NbT for hot isostatic pressing
i In the method of manufacturing a superconducting billet, an Nb metal layer to be interposed between a metal tube used as a stabilizing material and an NbTi alloy rod is formed with a thickness of 10 μm or more to form a single layer, and hot isostatic pressing is performed at 500 It is characterized in that a pressure of 500 atm or more is applied for 3 minutes or more in a temperature range of to 1000 ° C.

According to the method of the present invention, the HIP treatment of the composite filler is carried out at high temperature, high pressure and for a long time so that sufficient diffusion reaction can be achieved at each interface of the stabilizing metal layer / Nb metal layer / NbTi alloy layer of the composite filler. By raising the bondability of each interface by causing the phenomenon, the sausaging phenomenon of the filament during the subsequent drawing process is prevented, and the disconnection frequency of the superconducting wire is reduced accordingly. In addition, in preparation for HIP treatment at high temperature, high pressure, and long time, the Nb metal layer was made thicker so that the diffusion to the stabilizing metal layer was surely suppressed. The reason why the Nb metal layer is provided in one layer is that the Nb metal has a high melting point, so that the Nb metal layers are not diffusion-bonded to each other and the deformation is not uniformly transmitted between the Nb metal layers.

In the present invention, the HIP processing condition is set to 500
The reason why the pressure of 500 atm or more is applied for 3 minutes or more in the temperature range of up to 1000 ° C is that the HIP treatment is performed at a temperature of less than 500 ° C, a pressure of less than 500 atm, or a time of less than 3 minutes even if the NbTi superconducting billet is used. This is because the diffusion bonding between dissimilar materials in the inside is not sufficient, and the superconducting property of the obtained superconducting wire is deteriorated when the HIP treatment temperature exceeds 1000 ° C.

In the present invention, the reason why the Nb metal layer is limited to a thickness of 10 μm or more is that when the Nb metal layer has a thickness of less than 10 μm, it is stabilized through the Nb metal layer during diffusion bonding between different materials. Ti diffuses into the metal pipe, and, for example, (C
This is because a brittle intermetallic compound such as u, Nb) Ti is generated to reduce the workability, and also the thermal / electrical conductivity of the stabilizing metal is reduced. In the present invention, when the superconducting wire is processed until the filament diameter becomes 10 μm or less, HI
P treatment conditions are preferably in the temperature range of 700 to 1000 ° C. and high temperature and high pressure conditions of 1000 atm or more. Suitable stabilizing metals include oxygen-free copper, copper nickel alloys, copper manganese alloys, copper silicon alloys, and the like. Generally, a Nb metal pipe is used for the Nb metal layer.
b A method of winding the metal foil in one layer and welding the ends, or a method of simply winding the Nb plate is also applicable.

[0008]

According to the method of the present invention, NbTi alloy rods are filled in a metal tube serving as a stabilizing material with an Nb metal layer interposed, and then the ends are vacuum-sealed to form a composite filler. Since the filler is subjected to HIP treatment under high temperature, high pressure and long time under predetermined conditions, Nb, Cu, and N are formed at the interfaces of the stabilizing metal layer and the Nb metal layer, and the Nb metal layer and the NbTi alloy rod.
The alloy layers of b and Ti are each formed to have a sufficient thickness to improve the bondability between dissimilar materials, and the subsequent stretching process is made uniform.
The Ti filament will not be deformed abnormally and the superconducting wire will not be broken. Further, since the Nb metal layer is thickly formed to have a thickness of 10 μm or more, Ti does not diffuse and penetrate into the stabilizing metal layer and hinder the workability and thermal / electrical conductivity of the stabilizing metal layer. In addition, since the Nb metal layer is interposed in one layer, deterioration of workability due to defective bonding between the Nb metal layers can be avoided.

[0009]

EXAMPLES The present invention will be described in detail below with reference to examples. Oxygen-free copper pipes with an outer diameter of 210 mmφ and an inner diameter of 157 mmφ are made of Nb
A Ti alloy rod was filled with one Nb metal layer interposed to form a composite filler, and the composite filler was subjected to HIP treatment to manufacture a single-core NbTi superconducting billet. Next, this billet is subjected to wire drawing after hot extrusion, and the opposite side length is 2.96 mm.
A single core NbTi hexagonal superconducting wire of φ was used. In the above, when the Nb metal layer was thick, the pipe was covered, and when it was thin, the foil was welded and interposed. The thickness of the Nb metal layer was variously changed at a thickness of 10 μm or more. Also, the HIP process is performed at a temperature of 500
Within the range of up to 1000 ° C., the pressure was 500 atm or more, and the treatment time was 3 minutes or more, and various treatments were performed. In the HIP process, temperature increase and pressure increase were performed simultaneously. Next, the single core NbTi
4150 superconducting wires are filled into an oxygen-free copper pipe with an outer diameter of 294 mmφ and an inner diameter of 227.5 mmφ to form a multi-core filler, and then this multi-core filler is subjected to HIP treatment, hot extrusion and wire drawing. Sequentially applied, wire diameter 0.65mmφ, copper ratio 1.8, filament diameter 6
A multi-core NbTi superconducting wire of μm was manufactured.

For comparison, a single-core NbTi superconducting billet was manufactured under conditions other than the manufacturing conditions of the present invention, and this billet was processed into a multi-core NbTi superconducting wire under the same conditions as in the above-mentioned embodiment. For each of the superconducting wires thus obtained, the number of breaks, the unit length of break and the n value were determined. The n value is an index of the relational expression of V = AI ⁿ established between the critical current value I and the voltage V at both ends at that time, and the larger the n value is, the less the NbTi filament is broken. In addition, another single-core superconducting billet was manufactured under the same conditions, and the bonding state between different materials was investigated. For joining the dissimilar materials, the single-core superconducting billet is sliced to cut out the disc-shaped body shown in FIG.
From this disk-shaped body, a length of about 50 mm, a width of 12 mm, and a thickness including the respective bonding interfaces of the copper stabilizing material 2 and the Nb metal layer 3, and the Nb metal layer 3 and the NbTi alloy rod 4 shown in FIG. A strip-shaped sample having a length of 3 mm was cut out, pulled in the direction of the arrow, and judged by its breaking strength. The results are shown in Table 1 along with the fracture points.
It was shown to.

[0011]

[Table 1] Tensile strength: unit kg / mm ² , fracture mode: fracture in A to copper, B to joint interface between Nb metal layer and NbTi alloy rod,
C-Nb interlaminar fracture, * Superconducting property deterioration.

As is clear from Table 1, in the products of the present invention (Nos. 1 to 8), the number of disconnection was small and the unit length of disconnection was 20 km or more. This is because the bondability between dissimilar materials was improved, as can be seen from the tensile test results of the single core billet. On the other hand, Comparative Examples No. 9, 10 and 11 are HI
Since the temperature, pressure, and time of the P treatment conditions were lower or shorter than the limit values of the present invention, the single core NbTi superconducting billet was not sufficiently bonded between the dissimilar materials, resulting in frequent disconnection. No12 is N
bBecause the metal layer was thin, N was added to the copper stabilizer during HIP processing.
The Ti of the bTi alloy rod was diffused, and the wire drawability and the superconducting property of the copper stabilizer deteriorated. No13 has 3 Nb metal layers
Since the Nb metal layers were intervened as layers, the Nb metal layers were not joined to each other and disconnection frequently occurred. In addition, No. 14 is HIP treatment of single core billet at 1100 ℃
Since it was applied at a high temperature, the superconducting properties deteriorated.

[0013]

As described above, according to the method of the present invention, Nb
Since the bondability between dissimilar materials in the Ti superconducting billet is improved, abnormal deformation such as sausage does not occur in the NbTi filament. Therefore, the wire drawing workability of the NbTi superconducting wire is improved and the breaking unit strip length is increased. , Has a remarkable industrial effect.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a sausage filament found in a disconnection portion of a NbTi superconducting wire.

FIG. 2 is a plan view of a disk-shaped body obtained by cutting a single-core superconducting billet into slices.

FIG. 3 is a plan view of a strip-shaped tensile test piece cut out from a disk-shaped body obtained by cutting a single-core superconducting billet into a circle.

[Explanation of symbols]

 1 Thick sausage filaments that are narrowed in places 2 Copper stabilizer 3 Nb metal layer 4 NbTi alloy rod

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takuya Suzuki 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (2)

[Claims] 1. A stabilizer is filled with NbTi alloy rods with a Nb metal layer interposed between them, and the ends are vacuum-sealed to form a composite filler. The composite filler is heat-treated. In a method of manufacturing an NbTi superconducting billet that is subjected to hydrostatic compression treatment, an Nb metal layer interposed between a metal tube used as a stabilizer and an NbTi alloy rod is 10 μm or more in thickness.
A method for producing an NbTi superconducting billet, which is characterized in that a hot tube hydrostatic compression treatment is performed in a layer and a pressure of 500 atm or more is applied for 3 minutes or more in a temperature range of 500 to 1000 ° C. 2. The metal material of the metal tube used as the stabilizing material is any one of oxygen-free copper, copper-nickel alloy, copper-manganese alloy and copper-silicon alloy. Of NbTi superconducting billet.