JPS6086704A - Method of producing nb3sn superconductive wire material using sn-iva group element alloy - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves the production of Nb x8n superconducting wire with improved workability and strong magnetic field characteristics by adding one or more selected from Group A elements titanium, zirconium, and hafnium. It is about law.

Superconducting wires are used as winding materials for electromagnets for generating strong magnetic fields because they allow large currents to flow without consuming power and maintain their superconducting state even in strong magnetic fields. Currently, the most widely used wire rod is Nb
-Ti is a Ti-based alloy wire, but the magnetic field generated by this alloy wire has a limit of 9 Tesla (90,000 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 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, and NbaSn
(Critical temperature: approx. 1 in 1 Critical magnetic field: approx. 21 Tesla) and V=Ga (Critical temperature: approx. 15 K, Critical magnetic field: approx. 22
Tesla's compound-based superconducting wire has come into practical use.

The surface diffusion method is, for example, in the case of NbaSn compound wire, the base niobium tape is continuously passed through a molten tin bath, and then the niobium and tin are caused to undergo a diffusion reaction by heat treatment to generate a Nb3Sn compound layer on the base tape surface. It's a method. For example, in the case of a Nb sSn compound, the composite processing method means that a niobium base and a copper-tin alloy base are compositely integrated, processed into a wire, tape, or tube shape, and then tin and niobium in the copper-tin alloy base are processed by heat treatment. This is a method in which a Nb3Sn compound layer is generated around a niobium substrate by selectively causing a diffusion reaction with the niobium substrate. Using this composite processing method,
It becomes possible to manufacture an ultrafine multifilamentary wire in which a large number of thin niobium cores are embedded in a copper-tin alloy substrate, and stable superconducting properties can be obtained against rapid magnetic field changes. Incidentally, Vs (3a) ultra-fine multifilamentary wire can also be produced by the same method to obtain -C.
Sn, V, and Ga compound wires have already been used as small-sized strong magnetic field magnets for research on physical properties.

On the other hand, the development of Daisei strong magnetic field magnets for use in nuclear fusion reactors, high energy accelerators, superconducting power generation Kaede, etc. is actively progressing, and the superconducting wire used in these has a large criticality in the strong magnetic field region of 15 Tesla or more. 'has a current,
Furthermore, there is an urgent need to commercialize compound-based ultrafine multifilamentary wires that are stable against rapid magnetic field changes. However, the critical current of the conventional Nb, Sn compound wire made from a composite of a niobium base and a copper-tin alloy base decreases rapidly in a magnetic field of about 12 Tesla or more, and this wire can handle a strong magnetic field of 12 Tesla or more. It has been difficult to produce superconducting magnets that can generate On the other hand, V=Ga compound wire has better strong magnetic field characteristics than NbaSn compound wire, but the material price is N
Since it is more expensive than baSn, it cannot be said to be advantageous for large-scale equipment that uses a large amount of wire rods. Therefore, it is better to use a Nb s Sn compound wire with improved strong magnetic field characteristics by adding a small amount of alloying elements. Recently, a method has been invented for producing Nb3Sn compound wires with significantly improved superconducting properties in strong magnetic fields by adding titanium, zirconium, or )-fnium, which are l'%La group elements, to a niobium substrate or a copper-tin alloy substrate. (Patent application 1985-1285)
No. 51, Japanese Patent Application No. 121479/1983).

In these methods, Group A elements added to the niobium substrate or copper-tin alloy substrate promote the diffusion and formation of the Nb5Sn compound, and a portion of it is dissolved in the NbaSn compound layer, resulting in superconductivity in a strong magnetic field. It has the effect of enhancing properties. However, in these manufacturing methods, since the lVa group element is added to the niobium base or the copper-tin alloy base, heavy workability is not excellent and intermediate annealing is required for every 40% reduction in area, making it impractical for practical use. In order to produce a long wire, an extremely large number of annealing operations are required, resulting in a significant increase in manufacturing costs. Furthermore, in the copper-tin alloy substrate used in the conventional composite processing method, the amount of solid solution of tin is limited in order to maintain plastic workability, so the amount of Nb s Sn compound phase that diffuses and forms is small per total area of the wire, and the critical current There was a difficulty in producing a wire rod with a large capacity.

A method for manufacturing Nb and Sn compound wire rods by a composite processing method of a copper alloy base, a tin base, and a niobium base in which group IVa elements are added to pure copper (Japanese Patent Application No. 57-25981) is based on quantitative processing of each base. It solves the above-mentioned problems to some extent, such as having relatively good properties and excellent strong magnetic field critical current characteristics because it contains +Va group elements. However, when producing a practical scale ultra-fine multifilamentary wire made of strong processed metal using this manufacturing method, in order to uniformly draw the wire to the final wire diameter without intermediate annealing, it is necessary to It is necessary to use an extremely small amount of copper alloy. As a result, the content of group (1)a elements in the resulting Nb s Sn compound also decreases, resulting in an unfavorable result of deterioration of the strong magnetic field critical current characteristics.

The present invention improves superconducting properties in strong magnetic fields by adding titanium, zirconium, or hafnium, which are 'f' Ja group elements, to a tin base, which has extremely excellent workability, instead of a copper base. Furthermore, the purpose is to manufacture a Nb3Sn superconducting material with a large critical current capacity.

The present invention is directed to (1) a composite consisting of a tin alloy base, a copper base, and a niobium base containing one or more of the group a elements selected from titanium, zirconium, and hafnium, or the tin alloy body and niobium The method is characterized in that a composite body consisting of the three substrates is prepared, processed into a predetermined shape, and then subjected to diffusion heat treatment to generate an Nb3Sn compound containing Group A elements around the niobium substrate. Further, the tin alloy substrate may contain a small amount of copper in addition to the above-mentioned group ①a elements.

The amount of titanium, zirconium, or hafnium added to the tin substrate should be 0.1 atomic coefficient or more in total of one or more types in order to obtain excellent superconducting properties, and to maintain good workability of the tin alloy substrate. Therefore, it must be in the range of 15 atoms or less. Preferably it is in the range of 1 to 10 atom%.

Copper contained in the copper substrate or the tin alloy substrate assists in the diffusion of tin and group Ⅰa elements during diffusion heat treatment, and is effective in obtaining excellent superconducting properties.

The amount of copper added to the tin alloy substrate must be in the range of 2 atoms or more to be effective in increasing the diffusion rate of tin, and 30 atoms or less in order to maintain good workability of the tin alloy substrate.

The heat treatment performed after processing the composite into a predetermined shape is performed using Nb,
The temperature must be 4001Z' or higher to generate Sn, and 950 C or lower to obtain excellent superconducting properties.

Each substrate constituting the composite body may be in the shape of a solid rod or in the form of a tube having one or more holes into which other substrates are inserted. Further, each substrate may be partially or entirely in the form of powder.

In our invention, we use a composite consisting of a tin alloy base with extremely good workability and a niobium base (and copper base) with good workability, so Compared to this, wire drawing becomes significantly easier, and even practical-scale ultra-fine multifilamentary wires that require strong processing can be processed into thin wires without intermediate annealing, and the cost of wire production is significantly reduced. ■A group elements such as titanium, zirconium, or hafnium added to the tin alloy substrate promote the formation of Nb5Sn compounds, and some of the added elements become solid solutions in the Nb5Sn compounds.
It improves the superconducting critical magnetic field and significantly increases the critical current in strong magnetic fields of 15 Tesla or more. On the other hand, in the heat treatment step, a sufficient amount of tin can be supplied from inside the composite by diffusion, so a wire rod with a large critical current capacity can be produced due to effects such as obtaining a large amount of Nb s Sn compound phase. As a result, it is possible to improve the performance of various superconductor-based devices and reduce manufacturing and cooling costs through miniaturization.

In addition, since the wire produced by the present invention is in the form of an ultra-fine multicore wire, its superconductivity is stably maintained even in the face of rapid magnetic field changes, which is an excellent feature that significantly improves the safety and reliability of equipment used in strong magnetic fields. It has a great effect.

2.5 Insert a tin-5-atom titanium alloy, a tin-5-atom zirconium alloy, or a tin-3-atom titanium-dihafnium alloy rod into the bait hole, and then drill a 1-inch hole around it. A composite body having the cross-sectional structure shown in FIG. 1 was prepared by inserting eight niobium rods. This composite was processed into a long wire of 0.4 Wm by swaging and drawing. In contrast, the conventional composite consisting of a copper-7 atomic percent tin-1 atomic titanium alloy and a niobium core required intermediate annealing approximately 10 times to process the material from 8 to 0.4 m. ,
In processing the samples of this example, intermediate annealing was not necessary at all because the workability of each material was extremely good.

Then, after sealing in a quartz tube in an argon atmosphere, 725
CX diffusion heat treatment was performed for 50 hours. The thickness of the Nt)ssn compound layer of the sample prepared in this way, the critical current (
The measurement results of Ic ) and critical temperature (Tc ) are shown in Table 1. Table 1 also shows l'% for nishiki produced using a similar manufacturing method.
Wire rod without group Ia element added (Comparative Example 1-a) and wire rod in which group ■a element was added to copper instead of tin (Comparative Example 1-a)
The measurement results of b) are also shown.

Table 1 When titanium, zirconium, or hafnium is added to the tin core, the production rate of Nb5Sn compounds is lower than that of the non-additive sample of Comparative Example 1-a, which is a conventional method, and Comparative Example 1-b, in which titanium is added to the copper matrix. Ic1Tc are both elevated. In addition, in the method of Comparative Example 1-b in which group IVa elements are added to copper, in order to obtain superconducting properties equivalent to those of Example 1, it is necessary to add, for example, diatomic Ti to copper. - Composite materials using diatomic titanium alloys have poor workability, and during wire drawing from 8 fins, the wire drawing process is approximately 1.5 +
rm L: It broke at l, and the final wire diameter was 0.4tm1
I couldn't process it until 21'.

As described above, the present invention is a method for manufacturing a Nb5Sn superconducting wire that is much easier to manufacture into a wire than conventional methods.

Tin-5 atom% titanium, tin-3 atom% titanium → 12□,・
Atomic group hafnium or tin-5 atomic group titanium-10
A composite body having the cross-sectional structure shown in FIG. 2 was prepared by inserting seven atomic copper alloy rods. This composite was wire-drawn in the same manner as in Example (1), and Q, 4 ttrm p was obtained without intermediate annealing.
It was made into a long line. Next, after sealing in a quartz tube in an argon atmosphere, diffusion heat treatment was performed at 750C for 50 hours.
We obtained the measurement results shown in . In addition, Table 1 shows wire rods made using the same manufacturing method that do not contain Group A elements (Comparative Example 2).
-a) and ■Measurement results of a wire rod using a tin-copper alloy that does not contain group a elements (Comparative Example 2-b) are also shown. The measurement results show that the Nb z Sn layer thickness and the superconducting properties Ic and Tc of the wire of this example are significantly improved compared to the conventional methods Comparative Example 2-a and Comparative Example 2-b.

Example (3) A niobium tube with an outer diameter of 8 m and an inner diameter of 6 m is filled with copper powder, niobium powder, and tin-5 atomic titanium powder or tin-5 atomic hafnium powder in a ratio of 5:3:1 as shown in Fig. 3. A composite with the cross-sectional structure shown was fabricated.

The powders used each had a size of approximately 100 μm.

This composite was processed into a 0.4 mfl long wire in the same manner as in Examples (1) and (2) without intermediate annealing. Then, after sealing in a quartz tube in an argon atmosphere, 650 U
Diffusion heat treatment was performed for 50 hours. The critical current (Ic) and critical temperature (T
The measurement results of c) are shown in Table 2. Table 2 also shows wire rods produced in the same manner without adding 1'% l'a group elements to tin (
The measurement results of Comparative Example 3) are also shown. The measurement results show that, compared to Comparative Example 3, the wire of this example has significantly improved superconducting characteristics Ic and Tc.

Table 2

[Brief explanation of drawings]

Figures 1, 2 and 3 are examples 1.2 and 3, respectively.
The cross-sectional shape of the uninvented composite material was created in . 1 in the figure is IVa
A tin alloy containing a group element or a tin alloy substrate containing a group a element and copper; 2 indicates a niobium substrate; and 3 indicates a copper substrate.

Claims (1)

[Claims] After producing a composite consisting of a tin alloy base and a niobium base, and processing this into a wire, tape, or tube,
Nb5Sn compound phase containing titanium, zirconium or no-funium is formed around the niobium substrate by diffusion heat treatment at 00 to 950C.
bl Method for manufacturing Sn superconducting wire. (2) As a tin alloy substrate, use a tin alloy containing a total of 0.1 to 15 atoms of one or more selected from titanium, zirconium, and hafnium, and further containing 2 to 30 atoms of copper. A method according to claim 1, characterized in that: