JPH0316725B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a fiber-dispersed V ₃ Ga superconducting wire. For more details, see the fiber dispersion type, which is widely used in electrical equipment, energy storage, nuclear fusion reactors, NMR analyzers, particle accelerators for high-energy physics, etc.
This invention relates to a manufacturing method for improving the strong magnetic field characteristics of V ₃ Ga superconducting wire. Conventional technology Conventionally, Nb-Ti alloy wires have been mainly used as superconducting wires used as winding materials for electromagnets for generating strong magnetic fields, but the limit of the generated magnetic field is 8.5T (85,000 Gauss). If a stronger magnetic field than this is required, it is necessary to use a compound-based superconductor with a high critical magnetic field. However, compound-based superconductors lacked plasticity, which hindered their practical application, but in recent years, methods using diffusion such as surface diffusion methods and composite processing methods have been invented, and V ₃ Ga
(Critical temperature Tc = approx. 15K, critical magnetic field Hc ₂ = approx. 22T),
Nb ₃ Sn (critical temperature Tc = approx. 18K, critical magnetic field Hc ₂ = approx.
21T) compound superconducting wire has come into practical use. Among them, V ₃ Ga wire is manufactured using a composite processing method, in which vanadium and copper-gallium alloy are brought into close contact with each other, processed into a wire, tape or tube shape, and then
A method in which gallium in a copper-gallium alloy is selectively reacted with vanadium through heat treatment to generate a V ₃ Ga compound layer at the interface, or a composite in which a large number of vanadium rods are embedded in a copper-gallium alloy matrix is wired. After processing into shapes etc., heat treatment is performed.
A method has been used in which a V ₃ Ga compound layer is generated at the interface. A similar method was also used for Nb ₃ Sn compounds. However, this composite processing method requires complicated operations to first create the composite, and the copper-gallium alloy undergoes significant work hardening during processing.
Intermediate annealing is required for every % area reduction rate, and the number of annealing operations is extremely large in order to produce a practical long wire rod. Therefore, the manufacturing cost is extremely high and the manufacturing process is also complicated. On the other hand, recently, a so-called in situ method has been developed which overcomes the above drawbacks. In this method, a copper-vanadium binary alloy is melted by arc melting or the like to produce an ingot in which vanadium dendrite particles are uniformly dispersed within a copper matrix. This alloy has excellent workability and can be processed into thin wires of any diameter without requiring intermediate annealing, so it can be processed at low cost. By such wire processing, the vanadium particles undergo large deformation and become elongated fibers that are dispersed in the wire. Gallium is attached to the surface of this wire by electroplating, melt plating, etc., and when it is heat-treated, gallium diffuses into the wire and reacts with the vanadium fibers, forming a wire containing many V ₃ Ga ultrafine discontinuous fibers. Become. The fiber-dispersed V ₃ Ga wire obtained in this way has a superior superconducting critical current density compared to the wire obtained by the composite processing method, and the fibers themselves serve as reinforcements to strengthen the wire. It has the effect of increasing the strength circle and reducing deterioration of superconducting properties such as critical current against strain caused by bending and tension. However, what was obtained with this method was
In a magnetic field of 18T or higher, the critical current density decreases rapidly, making it unsuitable as a wire for strong magnetic field magnets such as NMR analyzers and mirror-type nuclear fusion devices. OBJECTS OF THE INVENTION The present invention aims to eliminate the drawbacks of the conventional methods, and its purpose is to provide a method for manufacturing a fiber-dispersed V ₃ Ga superconducting wire in which the critical current density in a strong magnetic field is significantly improved. There is something to do. Structure of the Invention As a result of research to achieve the above-mentioned object, the present inventors used a material in which vanadium and a specific amount of boron or hafnium were added to copper in place of the copper-vanadium binary alloy in the in-situ method. Then, some of these elements are produced
V ₃ can be dissolved in the Ga phase to increase its critical temperature Tc, thereby increasing the critical magnetic field Hc ₂ and, therefore, significantly increasing the critical current density Jc in a strong magnetic field. Divided. The present invention was completed based on this knowledge. The gist of the present invention is to prepare wires, tapes, or the like by drawing, rolling, or tube-drawing an alloy of copper containing 10 to 70 atomic percent vanadium, 0.03 to 3 atomic percent boron, or 0.01 to 2 atomic percent hafnium. The present invention provides a method for manufacturing a fiber-dispersed V ₃ Ga superconducting wire, which is characterized in that, after being processed into a tubular shape, gallium is attached thereto and heat-treated at 400 to 700°C. In the method of the present invention, boron or hafnium must be added to an extent that does not impair the workability of the wire, and it is desirable that boron be added in an amount of 0.03 to 3 atomic % and hafnium be added as 0.01 to 2 atomic %. Boron is less than 0.03 atomic%, hafnium is 0.01
If it is less than atomic %, it is difficult to obtain the effect of improving the characteristics.
If the boron content exceeds 3 atomic % and the hafnium content exceeds 2 atomic %, the processability into wire rods will be poor, so it is preferable that each of them be within the above ranges. In addition, the content of vanadium in copper-based alloys is 10 to 70
It needs to be in atomic percent. If it is less than 10 atomic %, the vanadium fiber density inside the wire becomes small, the distance between the fibers becomes long, and superconductivity is no longer maintained. Moreover, if it exceeds 70 atomic percent, it becomes difficult for gallium to diffuse uniformly into the wire, and superconductivity and mechanical properties are significantly impaired. These alloys are processed into wires, tapes, or tubes by drawing, rolling, or tube drawing.
Gallium is attached to this processed material by electroplating, melt plating, or the like. This is heat-treated at 400 to 700°C to diffuse gallium and react with vanadium fibers to produce V ₃ Ga. This heat treatment temperature is
If the temperature is lower than 400°C, gallium will not diffuse sufficiently into the interior, and if the temperature exceeds 700°C, the crystal grains of V ₃ Ga will become coarse and the superconducting properties will deteriorate. Heat treatment time is 1~
500 hours is appropriate. Less than 1 hour
When V ₃ Ga is hardly produced and exceeds 500 hours,
The crystal grains of V ₃ Ga become coarser and the superconducting properties deteriorate. Preferably it is 50 to 300 hours. Effects of the Invention According to the method of the present invention, by including a specific amount of boron or hafnium in a copper-based alloy containing vanadium, the critical current density Jc in a strong magnetic field can be increased compared to the conventional in-situ method. Moreover, since it contains V ₃ Ga ultrafine fibers, it has the excellent effect of producing a superconducting wire with excellent mechanical properties. Example 1 An alloy containing vanadium and 0.2, 0.8, and 2 atomic percent boron, respectively, was melted by arc melting and combined with copper to produce a consumable electrode type arc melting electrode rod. For comparison, an electrode rod containing no boron was also made in the same manner. These electrode rods were arc melted to produce ingots with an outer diameter of 40 mmφ and a length of 70 mm.
Expressing the composition of the ingot in atomic percent, it is approximately Cu−
34.9%, V-0.07%B, Cu-34.7%V-0.3%B,
Cu-34.3%V-0.7%B, and Cu-35%V. These ingots are rolled to a width of 4 mm and a thickness of 4 mm without intermediate annealing by using groove rolls, wire drawing, flat rolls, etc.
It was processed into a 100μm tape. The processability of the ingots was as good as in the case of ingots without added boron. This tape was continuously immersed in a Ga melt bath to adhere a gallium film approximately 10 μm thick, and heated at 500℃.
A V ₃ Ga superconducting wire was created by applying diffusion heat treatment for 100 hours. Table 1 shows the critical current density Jc and superconducting transition temperature Tc of this wire for the total cross-sectional area of the wire in magnetic fields of 16T and 20T at 4.2K.

[Table] As shown in this result, the addition of boron improves Jc in the entire magnetic field region, and the rate of increase is particularly large in strong magnetic fields. When used as a wire material for superconducting magnets, Jc is 2×10 ⁴ A/
Since it is desirable that the particle size is at least cm ² , this shows that the present invention can be put to practical use sufficiently. Example 2 In the same manner as in Example 1, vanadium was treated with
An alloy containing 0.2, 0.4, and 1 atomic percent hafnium was produced by arc melting, and this was combined with copper to make a consumable electrode rod for arc melting. These electrolytic rods were arc melted to produce ingots with an outer diameter of 40 mmφ and a length of 70 mm. The composition of the ingot expressed in atomic percent is approximately Cu-34.9%V-0.07%Hf, respectively.
Cu-34.9%V-0.14%Hf and Cu-34.6%V-0.35
%Hf. These ingots were processed into tapes in the same manner as in Example 1. The processability of the ingot was as good as in the case of the ingot without added hafnium. This tape was continuously immersed in a Ga melt bath to adhere a gallium film with a thickness of about 10 μm, and then subjected to diffusion heat treatment at 500°C for 300 hours.
Created V ₃ Ga superconducting wire. Table 2 shows the critical current density Jc and superconducting transition temperature Tc of this wire at 4.2K in magnetic fields of 16T and 20T for the total cross-sectional area of the wire.

[Table] As shown in this result, the addition of hafnium improves Jc in a strong magnetic field.

Claims (1)

[Claims] 1 After processing an alloy of copper containing 10 to 70 atomic percent vanadium and 0.03 to 3 atomic percent boron or 0.01 to 2 atomic percent hafnium into a wire, tape, or tube shape by drawing, rolling, or tube drawing, etc. A method for producing a fiber-dispersed V ₃ Ga superconducting wire, which comprises adhering gallium thereto and heat-treating it at 400 to 700°C.