JPH0349164B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a fiber-dispersed Nb ₃ Sn superconducting wire. More specifically, one or two selected from copper-niobium alloy, which has good workability, and titanium, zirconium, and hafnium, which have good workability.
This invention relates to a method for manufacturing a fiber-dispersed Nb ₃ Sn superconducting wire with improved workability and strong magnetic field properties using a composite of tin alloys containing at least 100% of tin alloys. (Conventional technology and its issues) Superconducting wires allow large currents to flow without consuming power, and the superconducting state is maintained even in strong magnetic fields, so their use as winding materials for electromagnets for generating strong magnetic fields is progressing. It is being Currently, the most widely used wire rod is Nb-Ti alloy wire rod, and the magnetic field generated by this alloy wire rod is 9 Tesla (90,000
Gauss), and if a stronger magnetic field is required, it is necessary to use a compound-based superconductor with a high critical magnetic field. However, compound superconductors lack plasticity, which has been a major obstacle to their practical application. In recent years, methods using diffusion such as surface diffusion method and composite processing method have been invented.
Compound-based superconducting wires of Nb ₃ Sn (critical temperature: approximately 18 K, critical magnetic field: approximately 22 terraces) have come into practical use. For example, in the case of Nb ₃ Sn, the composite processing method involves bonding a niobium base and a copper-tin alloy base, processing them into a wire or tape shape, and then selecting the tin in the copper-tin alloy base through heat treatment. This method is a type of solid-state diffusion method in which a layer of Nb ₃ Sn compound is generated on the interface by reacting with niobium. Using this solid-state diffusion method, a composite consisting of a large number of niobium rods embedded in a copper-tin alloy substrate is processed into a linear shape and heat treated to create an Nb ₃ Sn compound that is stable against changes in the magnetic field. It became possible to manufacture ultra-fine multifilamentary wires. Also,
V ₃ Ga compound ultrafine multifilamentary wires can also be produced using a similar manufacturing method. Nb ₃ Sn or V ₃ Ga compound wires produced by such surface diffusion and combined processing methods are already being used as small-sized strong magnetic field magnets for research on physical properties. However, this composite processing method requires _a complicated process to first prepare the composite, and also
In the case of , the copper-tin alloy substrate is significantly affected by processing, so the tin content in copper is limited to about 8 atomic % or less, making it difficult to generate a large amount of Nb ₃ Sn layer and reducing the cross-sectional reduction rate. Intermediate annealing is required every 40% of the time, and the number of annealing steps is extremely large in order to make a practical long wire rod, resulting in significantly higher manufacturing costs than alloy wire rods. Furthermore, composite processed wire rods have relatively low mechanical strength, and when put into practical use, they have the disadvantage that when combined with reinforcing materials, the critical current capacity per total cross-sectional area becomes low. Recently, a fiber-dispersed wire manufacturing method has been developed that overcomes this difficulty. In this manufacturing method, a copper-niobium alloy substrate is melted by arc melting or high frequency melting to produce an ingot in which fine niobium dendrite particles are uniformly dispersed within a copper matrix. This alloy has excellent workability and can be processed to any diameter without requiring intermediate annealing. Through this processing, the niobium particles are greatly deformed and become elongated fibers, which are closely dispersed in large numbers within the wire. When a desired amount of tin is attached to the surface of this wire by electroplating or the like and heat treatment is performed, the tin diffuses inside and reacts with the niobium fibers, resulting in a wire containing a large number of ultrafine Nb ₃ Sn fibers.
Since the contained fibers have a small diameter and narrow spacing, the fibers themselves serve as reinforcement, increasing the strength of the wire itself and reducing deterioration of superconducting properties due to strain caused by bending, tension, etc. For compound superconducting wires, the practical target value is for the strain at which critical current deterioration begins to be approximately 1% or more.
This wire fully satisfies this condition. In this manufacturing method, if the melted copper-niobium alloy substrate is processed to be as strong as possible, the fiber density will be higher and the superconducting properties and mechanical properties will be improved. Furthermore, recently, a fiber-dispersed type that is made by adding a small amount of titanium, a group A element, to a copper-niobium alloy has been developed.
A method for manufacturing Nb ₃ Sn wire (Japanese Patent Application No. 121478/1982, Japanese Patent Publication No. 12607/1983) and fiber-dispersed Nb ₃ Sn by composite of copper-niobium alloy substrate and niobium-titanium alloy or copper-titanium alloy substrate. Manufacturing method of wire rod (Tokugansho
57-71461 and Special Publication No. 62-62406) were invented successively. In these manufacturing methods, the a-sequential elements are
In addition to promoting the diffusion and formation of Nb ₃ Sn filaments, a portion of them dissolves in the Nb ₃ Sn compound phase and has the effect of significantly increasing the critical current capacity in a strong magnetic field. However, in these manufacturing methods, since group A elements are contained in the copper-niobium alloy, copper, or niobium, their hardness increases, making it difficult to use conventional fiber-dispersed wire rods that do not contain group A elements. In comparison, the processing method for wire rods has deteriorated slightly. (Means for Solving the Problems) The present invention was made to overcome the difficulties of conventional methods, and its purpose is to provide a material that is easy to manufacture and has excellent superconducting properties and mechanical properties in a strong magnetic field. The present invention provides a method for manufacturing a fiber-dispersed Nb ₃ Sn superconducting wire. The present invention consists of a tin alloy base containing one or more selected from Group A elements titanium, zirconium, and hafnium, and a copper matrix in which a large amount of niobium is dispersed. The method is characterized by a method in which a composite consisting of a copper-niobium alloy substrate is prepared, processed into a wire, tape or tube, and then subjected to diffusion heat treatment at 400 to 900°C to produce Nb ₃ Sn compound ultrafine fibers. do. The tin alloy substrate may also contain a small amount of copper in addition to the above elements. Since the diffusion of tin, titanium, zirconium or hafnium in copper is extremely rapid, the tin alloy base composited with the copper-niobium alloy base is simultaneously diffused throughout the wire during the diffusion heat treatment. As a result, the added titanium, zirconium, or hafnium not only promotes the formation of Nb ₃ Sn ultrafine fibers caused by the reaction between the niobium fibers and the diffused tin, but also partially dissolves in the Nb ₃ Sn compound phase. Significantly improves the strong magnetic field properties of Nb ₃ Sn. In addition, titanium, which remained without solid solution in the Nb ₃ Sn layer,
Zirconium or hafnium serves to increase the mechanical strength of the wire after heat treatment. Note that the niobium content in the copper-niobium alloy substrate must be 10 to 60 atomic%; if it is less than 10 atomic%, the niobium fiber density inside the wire becomes small and the fiber spacing increases, resulting in superconductivity. Characteristics deteriorate. Furthermore, if the content exceeds 60 atomic %, the workability of the copper-niobium alloy substrate deteriorates, and it becomes difficult to uniformly diffuse tin throughout the wire, resulting in deterioration of superconducting properties and mechanical properties. The amount of titanium, zirconium, or hafnium added to the tin substrate should be 0.1 atomic % or more in total of one or more types in order to obtain excellent superconducting properties, and in order to maintain good workability of the tin alloy substrate. Must be within the range of atomic percent or less. The preferred range is 1 to 10 at.%. It is preferable to add a small amount of copper to the tin alloy substrate during the diffusion heat treatment in order to assist in the diffusion of tin, titanium, zirconium, and hafnium and to obtain excellent superconducting properties. The amount of copper added to the tin alloy substrate must be in the range of 2 atomic % or more to increase the diffusion rate of tin, and 30 atomic % or less to maintain good workability of the tin alloy substrate. The amount of composite tin alloy substrate is 1 per total cross-sectional area of wire.
A suitable range is from vol.% to 50 vol.%. If it is less than 1 vol.%, it is difficult to produce Nb ₃ Sn ultrafine fibers, and if it exceeds 50 vol. %, compounds other than the Nb ₃ Sn compound phase are produced, which deteriorates superconducting properties and mechanical properties. Unfavorable in terms of characteristics. A temperature range of 400 to 900°C is desirable for the generation of Nb ₃ Sn ultrafine fibers in diffusion heat treatment, and at temperatures lower than 400°C, the generation rate of Nb ₃ Sn ultrafine fibers is extremely slow, and the superconducting properties also deteriorate. When the temperature exceeds 900°C, the crystal grains of the Nb ₃ Sn produced become coarse and the superconducting properties deteriorate. In the present invention, the ingot-produced tin alloy substrate has a metal structure in which the precipitated phases of titanium, zirconium, and hafnium are finely and uniformly distributed in the tin, so its workability is extremely high, comparable to that of dull tin. It is excellent. In addition, the method of the present invention, which is composed of a copper-niobium substrate with a large amount of niobium dispersed in the copper matrix and has good workability, is a method that is similar to the conventional method in which titanium, zirconium, or hafnium is contained in a copper-niobium substrate or a niobium substrate. fiber-dispersed type
Compared to the manufacturing method for Nb ₃ Sn wire, wire drawing is significantly easier, and even practical-scale ultra-fine multifilamentary wires that require strength processing can be processed into thin wires without intermediate annealing, significantly reducing the cost of wire production. Ru. In addition, titanium, etc. as an additive element is
Nb ₃ Sn not only promotes the production of ultrafine fibers, but also
Solid solution in the Nb ₃ Sn compound layer improves the critical magnetic field and significantly increases the critical current above 15 Tesla. In addition, in the diffusion process, a sufficient amount of tin can be diffused and supplied from inside the composite, so a large amount of Nb ₃ Sn ultrafine fibers can be produced and a wire with a large critical current can be produced. In this way, the superconducting and mechanical properties of the wire are improved, which not only improves the performance of various superconducting devices, but also reduces cooling costs due to miniaturization, making it possible to use it in a wide range of areas. Excellent effects such as being able to pave the way can be achieved. (Example) Examples 1 to 4 A copper-30 atomic percent niobium alloy base was melted by arc melting using a rod-shaped consumable electrode made of a composite of copper and niobium, and then machined into a round bar with an outer diameter of 25 mm. . Drill seven holes of 4mmφ on this round bar,
Tin-5 atomic% titanium alloy (Example 1), Tin-5 atomic% zirconium alloy (Example 2), Tin-4 atomic% titanium-3 atomic% hafnium alloy (Example 3)
Alternatively, seven of each of the tin-5 atom% titanium-10 atom% copper alloy rods (Example 4) were inserted to produce a composite as shown in FIG. This composite was processed into a wire with an outer diameter of 0.5 mm by groove rolls and wire drawing without intermediate annealing. These were sealed in a quartz tube in an argon atmosphere and subjected to diffusion heat treatment at 600°C for 100 hours to generate Nb ₃ Sn. In order to compare the present invention with the conventional method, a superconducting wire was produced in the same shape and method as in Example 1 using a blunt tin rod instead of a tin alloy (Comparative Example 1). Also, copper-
A 30 atom% niobium-2 atom% titanium alloy substrate was prepared, seven holes of 4 mmφ were drilled in a round bar with an outer diameter of 25 mm as in Comparative Example 1, and blunt tin rods were inserted into the holes to form a composite body of 1.0 atomic percent. It was processed into a wire of mmφ and heat treated (Comparative Example 2). Furthermore, a 25 mmφ copper-30 at% niobium alloy base was prepared, a 7.2 mmφ blunt tin rod was inserted into the center, and a 1.7 mmφ niobium-50 at% titanium alloy (comparative example 3) or a 2.3 mmφ Six copper-3 atomic% titanium alloy rods (comparative example 4) were inserted into the composite, and the outer diameter was 0.5 in the same manner.
Processing and heat treatment were performed on the mmφ wire. Critical current density, Jc (superconducting current carrying capacity per wire cross-sectional area) of the sample prepared in this way in a strong magnetic field of 12 Tesla
The values are shown in Table 1. From the table, it can be seen that when titanium, zirconium, or hafnium is added to tin, the Jc value in a strong magnetic field of 16 Tesla increases significantly compared to Comparative Example 1 of the conventional method, making it possible to use it in a strong magnetic field of 15 Tesla or more. Recognize. Normally 2A×10 ^4A /
If it has a Jc of cm ² or more, it can be considered a superconducting wire. In the wire of Comparative Example 2, the copper-niobium-titanium alloy base was significantly processed, and wire drawing to a diameter of 1 mm or less was not possible (dashed line). In the case of the wire rods of Comparative Examples 3 and 4, it was possible to draw the wire up to 0.5 mmφ, but according to the cross-sectional observation of the wire rod after processing, the niobium titanium alloy core or copper-titanium alloy core was hardened due to work hardening. The core diameter may become uneven, or
Some cores were broken. As shown in Table 1, the Jc values of Comparative Examples 2 to 4 in a strong magnetic field of 16 Tesla were also considerably inferior to those of the Examples of the present invention. 【table】

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a composite in the method of the present invention, where 1 is a tin alloy core containing titanium, zirconium, or hafnium. 2 is a copper-niobium alloy substrate.

Claims (1)

[Claims] 1. One or more selected from titanium, zirconium, and hafnium in total of 0.1 to 15
A composite consisting of a tin-based alloy substrate containing 10 to 60 atomic percent of niobium and a niobium-dispersed copper-niobium alloy substrate containing 10 to 60 atomic percent of niobium is prepared, processed into a wire, tape, or tube, and then heated at 400 to 900°C. 1. A method for producing a fiber-dispersed Nb ₃ Sn superconducting wire, characterized by performing diffusion heat treatment. 2 Contains a total of 0.1 to 15 atomic percent of one or more selected from titanium, zirconium, and hafnium as a tin alloy base, and further contains 2 to 30 atomic percent of copper.
It is characterized by using a tin alloy containing atomic percent.