JPH0129867B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing a Nb ₃ Sn diffused wire, particularly a Nb ₃ Sn diffused wire suitable for generating a strong magnetic field. Conventional technology Nb ₃ Sn compound superconducting wire has superior superconducting properties compared to conventional Nb-Ti alloy wire, and is the most practical material for generating strong magnetic fields of 10 T or more required for nuclear fusion devices. It is known as one of the superconducting materials. As a superconducting application, the demand for large strong magnetic field magnets for nuclear fusion reactors, high energy physics, energy storage, etc. has been increasing recently.
There is great interest in improving the superconducting properties of Nb ₃ Sn wires. In order to increase the magnetic field generated by the magnet, the upper critical magnetic field Hc ₂ (hereinafter referred to as Hc ₂ ) is increased, and the critical current density Jc (hereinafter referred to as Jc) in the high magnetic field is increased.
) is essential.
Note that Jc is the critical current value actually measured in a magnetic field.
It is found by dividing Ic by the cross-sectional area of the superconductor. Conventionally, known methods for producing Nb ₃ Sn diffusion wires include (1) passing an Nb base wire or tape through a heated and molten Sn bath, and heat-treating it to generate an Nb ₃ Sn compound layer on the surface. ing. However, the Jc characteristic of the Nb ₃ Sn compound wire produced by this method in a magnetic field deteriorates rapidly above 15 T, making it difficult to produce a superconducting magnet that can generate a magnetic field of 15 T or above. In addition, (2) the Nb core is replaced with Cu
- It is also known to create a composite wire by embedding it in a Sn alloy, processing it into a wire or tape, and heat-treating this to generate a Nb ₃ Sn compound layer. However, since the wire obtained by this method has an extra portion that does not have superconductivity, it has the disadvantage that the Jc value per total cross-sectional area of the wire is low. OBJECTIVE OF THE INVENTION The present invention seeks to eliminate the drawbacks of conventional methods, and its purpose is to provide a method for manufacturing Nb ₃ Sn diffused wire with high Hc ₂ and excellent Ic and Jc in high magnetic fields. There is something to do. Structure of the Invention In order to achieve the above object, the present inventors conducted extensive research and found that a niobium base wire or tape containing pure niobium or other trace elements was passed through a tin bath heated and melted at 600 to 1200°C. , set this to 800-1000
In the method of generating a Nb ₃ Sn compound layer on the surface by heat treatment at ℃, in the case of pure Nb, in the bath,
In the case of Nb, if a certain amount of Ti is included in either the base wire, the tape, or the bath, or both, the layer thickness of the Nb ₃ Sn compound layer will be increased, and Hc ₂ will be greatly increased. I found it. We also found that by increasing the thickness of the Nb ₃ Sn compound layer, Ic in a total magnetic field can be increased, and furthermore, by increasing Hc ₂ , Ic and Jc in a strong magnetic field can be significantly increased.
Based on this knowledge, the present invention was completed. The gist of the present invention is to pass a pure niobium base line or tape through a tin bath heated and molten at 600 to 1200°C, and then heat-treat it at 800 to 1000°C for 1 minute to 200 hours to form a Nb ₃ Sn compound on the surface. In the layering method, the bath contains 0.1 to 0.3 atomic percent titanium and a niobium underline or tape is used.
Pass through a molten tin bath heated to 600-1200℃,
In the method of heat-treating this at 800-1000℃ for 1 minute to 200 hours to generate a Nb ₃ Sn compound layer on the surface,
Containing 0.1 to 30 atomic percent titanium in the base wire or tape, or in both this and the bath;
Furthermore, for each of the above cases, furthermore,
A method for manufacturing a Nb ₃ Sn diffusion wire characterized by containing 0.1 to 30 at % of lead or indium in the bath. The production method of the present invention is characterized by the addition of Ti to the tin bath or to the base wire or tape.
This has the effect of increasing the layer thickness of the Nb ₃ Sn compound layer, making the crystal grains finer, and greatly increasing its Hc ₂ . The increase in the Nb ₃ Sn compound layer significantly increases the critical current Ic of the wire, and the increase in Hc ₂ significantly increases Ic and Jc of the wire in a strong magnetic field. When the amount of Ti is less than 0.1 at%, almost no effect of Ti addition is obtained, and when it exceeds 30 at%
On the contrary, Hc ₂ decreases, and the workability of the Nb--Ni alloy base also decreases to some extent. The tin bath in the present invention contains 0.1 to 30 atomic % of Ti, and further 0.1 to 30 atomic % of Pb and In as necessary.
Use a solid solution of A solid Ti bath in a tin bath has the same effect as described in the section regarding niobium above. The amount of solid bath is also 0.1
The range of ~30 atom % is necessary for the same reason as above for the influence on _Hc2 . Further, the solid Ti bath may be either the base line, the tape, or the bath, or may be both. When Pb and In are dissolved in solid solution along with Ti solid bath, approx.
Further improve the Ic of the wire in strong magnetic fields of 15T or more. However, on the other hand, it decreases the formation rate of the Nb ₃ Sn compound layer and coarsens the crystal grains of the Nb ₃ Sn compound, so Ic decreases in a magnetic field lower than about 13 T, and in the magnetic field region of 13-15 T. Ic at is not increased. The solid solution amounts of Pb and In are preferably 0.1 to 30 atomic %. If it is less than 0.1 atomic %, little effect will be obtained, and if it exceeds 30 atomic %, the formation of the Nb ₃ Sn compound layer will be inhibited. The temperature of the bath should be 600-1200°C. If the temperature is lower than 600°C, Sn will not be applied uniformly, and if it exceeds 1200°C, Nb will dissolve in the bath, changing the bath composition and deteriorating the superconducting properties. After passing pure niobium or niobium base wire or tape through a tin bath, it is heated at 800 to 1000℃ for 1 minute to 200℃.
Heat treated for an hour. This creates a continuous Nb ₃ Sn compound layer on the surface of the underline or tape.
If the heat treatment temperature is lower than 800°C, the Nb ₃ Sn compound layer will not be formed, and if it exceeds 1000°C, the crystal grains of the Nb ₃ Sn compound will become coarse and the superconducting properties will deteriorate. Furthermore, if the heat treatment time is shorter than 1 minute, the Nb ₃ Sn compound layer will not be formed, and if it exceeds 200 hours, the crystal grains of the Nb ₃ Sn compound will become coarse and the superconducting properties will deteriorate, so it is necessary that the heat treatment time be within the above range. be. Example Pure Nb and a material containing 5 at% Ti mixed with Nb were each melted in an arc melting furnace in an argon atmosphere, and rolled into a material with a width of 3 mm and a thickness of 70 μm.
I made a tape. Each of these tapes was passed through an Sn-based bath (temperature: 950°C) having the composition shown in Table 1, and Sn or Sn-based alloy was applied to the tape surface. Samples with a length of 5 cm were cut from this tape and heated at 950℃ for 10 minutes in an argon gas atmosphere.
Heat treatment was performed for a period of time.

[Table] However, sample numbers 1 and 3 show comparative examples. Moreover, the composition is shown in atomic %. Figures 1 and 2 show the measurement results in liquid helium (4.2K) of H-Ic curves (magnetic field-critical current curves) in a magnetic field of wire rods obtained from samples with sample numbers shown in Table 1. shows. Note that the sample number and the curve number interact with each other. As is clear from Figures 1 and 2, Nb
Wire rod using solid solution of Ti as a base 5
It can be seen that in wire rods 1 to 8, Ic generally increases compared to wire rods 1 to 4 using pure Nb as a base. Also Sn
Wires 2 to 4 with Ti, Pb, and In added to the bath are wire 1.
It can be seen that the decrease in Ic at about 10 T or higher is smaller in samples 6 to 8 than in samples 5 (no Ti, Pb, or In added to the base line, tape, or tin bath) and in comparison to sample 5. Furthermore, in wire rods 4 and 8 obtained by adding Ti to the Nb base and Sn bath and simultaneously adding Pb or In to the Sn bath, the Ic in a strong magnetic field was It can be seen that this has been significantly improved. A wire with Ti added to the Nb base and Ti, Pb, and In added to the Sn bath can withstand use in magnets that generate strong magnetic fields of 17 T or more. Effects of the Invention Compared to the Nb ₃ Sn diffused wire obtained by the method of the present invention, which does not contain Ti, Pb, or In,
Upper critical magnetic field Hc ₂ is high, critical current Ic in strong magnetic field
and critical current density Jc are significantly improved. As a result, it can be used as a wire for superconducting magnets with a generated magnetic field of 17T or more. Further, it has excellent effects such as easy plastic working of the base line or tape.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams showing changes in critical current due to magnetic field in liquid helium (4.2 K) of Nb ₃ Sn superconducting wires obtained with the compositions shown in Table 1. Curve 1 is for the comparative example, and curves 2 to 8 are for the wire produced by the method of the present invention.

Claims (1)

[Claims] 1. Pure niobium base line or tape with a density of 600 to 1200
Pass through a tin bath heated to molten 800 °C.
Heat treated at ~1000℃ for 1 minute ~ 200 hours to create a surface
In the method of generating the Nb ₃ Sn compound layer, the bath is
A method for producing a Nb ₃ Sn diffusion wire characterized by containing 0.1 to 30 atomic % of titanium. 2 Heat the niobium base line or tape to 600 to 1200℃.
Pass it through a tin bath heated and molten to 800~
Heat treated at 1000℃ for 1 minute to 200 hours to form Nb ₃ Sn on the surface.
In the method of producing a compound layer, the base line or tape, or both this and the bath, contains 0.1 to
A method for producing a Nb ₃ Sn diffusion wire characterized by containing 30 atomic percent titanium. 3 Pure niobium base line or tape 600~1200
Pass through a tin bath heated to molten 800 °C.
Heat treated at ~1000℃ for 1 minute ~ 200 hours to create a surface
In the method of producing a Nb ₃ Sn compound layer, 0.1 to 30 at. characterized by containing indium in the bath
Manufacturing method of NB ₃ Sn diffusion wire.