JPS58172814A - Method of producing nb3sn superconductive wire - 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] Technical Field of the Invention The present invention relates to a Nb3Sn superconducting wire, particularly a Nb3Sn superconducting wire produced by an external diffusion method.
The present invention relates to a method of manufacturing b5Sn superconducting wire.

[Technical background of the invention and its problems] Conventionally, the method for producing Nb3Sn superconducting wire is to embed a large number of niobium in a bronze (CuSn) matrix, use a wire drawing machine, and react the tin and niobium in the bronze. A so-called bronze method for producing Nb3Sn is known. However, this method has the disadvantage that many intermediate annealing operations are required because bronze is less workable than copper, making the process complicated.

On the other hand, the so-called external diffusion method, in which the outer periphery of a wire with many niobium filaments embedded in a copper matrix is plated with tin and then subjected to diffusion heat treatment, has the advantage that wire drawing is easy and requires fewer steps. On the other hand, there were the following problems.

In other words, if the diffusion heat treatment temperature is below the melting point of tin, the reaction between tin and copper will be slow.On the other hand, if the diffusion heat treatment temperature is above the melting point of tin, the reaction between tin and copper will be very fast. There was a drawback that burn-through occurred and a healthy Nb5Sn superconducting wire could not be obtained.

Note that if the tin plating thickness is 7 μ-゛ or less, diffusion heat treatment at high temperature is possible without causing burn-through, but since the characteristics of Nb3Sn superconducting wire are caused by the tin concentration, the tin plating thickness should be set to 7 μ-゛. The following is not practical.

The inventors of the present invention have carried out intensive research to eliminate the above-mentioned drawbacks of the external diffusion method. After applying and baking a heat-resistant paint mainly composed of polyborosiloxane resin to the outer layer of the tin plating layer, the inventors applied diffusion heat treatment to the outer layer of the tin plating layer. If applied, a coating film that can withstand high-temperature heat treatment is formed on the outer periphery of the tin plating layer, so even if the plating thickness is 7μ or more, tin burn-off can be prevented, and conventionally, tin adheres to the surface. Because of this, stickiness easily occurs between the wires, and it was not possible to heat treat the wires by winding them around a bobbin, so it was only possible to heat treat short lengths. However, they discovered that it is possible to heat treat long lengths by using the method described above. .

[Object of the Invention] The present invention has been made based on the above findings, and an object of the present invention is to manufacture an Nb5Sn superconducting wire that does not show tin burn-off even after diffusion heat treatment at high temperatures.

[Summary of the invention] That is, the method of the present invention is a method for manufacturing Nb5sn superconducting wire by an external diffusion method, in which a heat-resistant paint containing polyborosiloxane resin as a main component is applied and baked on the outer periphery of a tin plating layer, and then a diffusion heat treatment is performed. It is characterized by this.

The heat-resistant paint used in the present invention is obtained by blending a polyborosiloxane resin with a silicone resin and an inorganic filler, and dissolving or dispersing the mixture in an organic solvent such as cresol or N-methyl-2-pyrrolidone (NMP). can be given. The coating film obtained by baking this paint is approximately 800
It can withstand heat treatment at temperatures up to ℃. Note that the baking of this paint is preferably performed at the melting point of tin (232° C. or lower). The polyborosiloxane resins used in heat-resistant paints are (a) S'X4, SIRX3, S
A silane compound represented by I RR'

is an alkyl group or □ is an aryl group;
(b) one or more of boric acid, boric anhydride, boric acid metal salt, boron halide, and boric acid ester; Si
The atomic ratio of diboron is 1 = 10 to 10:1, preferably 5
:1 to 1:5 by heating at 50 to 800°C to perform condensation polymerization.

At this time, organic solvents such as acetylacetone, acetic anhydride, cresol, tetrahydrofuran, xylene, NMP, and dimethylacetamide may be used as necessary.

However, by blending and reacting the following components with the above components (a> and (b)), the flexibility and water resistance of the resulting polyborosiloxane resin can be improved.

(C) Silicone oils such as methysif-1-nyl silicone oil and dimethyl silicone oil (d) Aromatic alcohols, aliphatic polyhydric alcohols, phenols, aromatic carboxylic acids (e) Lead, manganese, cobalt, zinc, calcium, etc. Mixture of organic salts (f) triethanolamine, monoethanolamine,
The blending amounts of nitrogen-containing compounds (C) to (f) such as jetanolamine, phenylenediamine, ethylenediamine, and trimethylenediamine are as follows: (C) Ingredients are 5~
100 parts by weight, (d> components are 5 to 30 parts by weight, (e
) component is 0.05 to 1011 parts, and <f> component is such that the number of N atoms is 5 to 100 per 100 boron atoms in component (b).
It is desirable to set the amount to 200. Above (C) - (
f) Components may be used in short form or in combination of two or more types.

As the silicone resin blended into the resin composition in the present invention, commercially available silicone resins can be used, such as TSR116 manufactured by Toshiba Silicone Co., Ltd. In addition to pure silicone, there are silicone alkyds, silicone polyesters, silicone epoxies, and the like.

The appropriate amount of this compound is 5 to 400 parts by weight, preferably 10 to 200 parts by weight, per 100 parts by weight of the polyborosiloxane resin. If it is less than this range, the flexibility will be poor, and if it exceeds this value, the heat resistance will be reduced.

Furthermore, examples of the inorganic filler include mica, talc, aluminum oxide, zirconium oxide, magnesium oxide, tungsten, aluminum silicate, magnesium silicate, and ceramic frit prepared by mixing and dissolving several metal oxides. These may be used alone or in combination to obtain the same effect. These inorganic fillers may be natural or synthetic, but are preferably fine powders with a particle size of 10 μm or less. The amount of this compound is 5 to 300, preferably 5 to 20, per 100 parts by weight of the total amount of polyborosiloxane resin and silicone resin.
Part of 0m is suitable. Below this value, the heat resistance is poor;
If this value is exceeded, the mechanical properties will deteriorate.

In the present invention, after applying and baking a heat-resistant paint on the outer periphery of the tin plating layer, it is wrapped around a bobbin and subjected to diffusion heat treatment.
200 hours is suitable.

[Embodiments of the invention] Next, examples of the present invention will be described.

(Production method of heat-resistant paint) Diphenyldihydroxysilane 432Q (2 mol)
, boric acid 83o (1,3 mol), viscosity (25°C) 10
Centistokes dimethyl silicone oil 256g
into a flask and stirred in a nitrogen atmosphere from room temperature for 4 hours.
The temperature was raised to 00°C over 6 hours, and the mixture was further heated and stirred at 400°C for 1 hour to carry out a polycondensation reaction. During the reaction process, 66(] of water and 70(+) of unreacted low molecular weight silicone oil were distilled and removed.

The polyborosiloxane resin thus obtained was colorless and solid at room temperature, and the yield was 525 g. The number average molecular weight of this resin was 1500 in terms of polystyrene, and the residual rate after firing up to 700°C was 35%. This was dissolved in NMP to obtain a resin solution with a nonvolatile content of 45.6%.

This polyborosiloxane resin solution 3339 was dissolved in NMP300 (+) together with 300 g of silicone resin (TSR116 manufactured by Toshiba Silicone Co., Ltd.) and 120 g of magnesium oxide to produce a heat-resistant paint.

Example A pure niobium rod was inserted into a copper pipe and drawn into a hexagonal shape. We bundled 295 of these and inserted them into a copper pipe.
When the wire is drawn to 1.0 miφ, the cross-sectional area ratio of copper and niobium is 1,
38 wire rods were obtained. This was electroplated with tin and then wired to produce two samples with a tin plating thickness of 50 μl and a tin plating thickness of 30 μl. Each of these samples was coated with the heat-resistant paint described above, and baked at a baking temperature of 220°C using a baking oven with an oven length of 7.4 m.
, and was baked at a linear speed of 11 IlZ minutes. As a result of repeating coating and baking six times and dry baking four more times, an insulating film with a film thickness of 34 μm was formed. The diameter of 200m of these wires is approximately 35CI.
It was wound around a stainless steel bobbin No. I and heat-treated at 550° C. for 48 hours in an argon gas atmosphere. As a result, we were able to obtain a sound bronze matrix wire with no tin burn-through or adhesion between wires. Furthermore, add this to 725
After heat treatment at ℃ for 6 days, approximately 6 μm of Nb is formed around a 37.7 μm niobium filament when the tin plating thickness is 50 μm, and approximately 4 μm when the tin plating thickness is 30 μm.
A 3Sn layer was produced. When we measured the superelectric properties of this wire, it was 630 A/n2.3 when the plating thickness was 50 μm.
In the case of 0 μm, a critical current density of 500 A/n2 (both 7 T) was obtained.

[Effects of the Invention] As is clear from the above examples, in the production of Nb5sn superconducting wire by the external diffusion method coated with the heat-resistant paint according to the method of the present invention, wire drawing is easier and fewer steps are required than in the bronze method. Furthermore, tin diffusion heat treatment is possible at a higher temperature than the conventional external diffusion method. Furthermore, since adhesion between the wires can be prevented, long lengths can be heat treated, and as a result, there is an advantage that long lengths of Nb3Sn superconducting wire can be supplied in a short time.

Furthermore, since the heat-resistant paint acts as an insulating film after heat treatment, it also has the advantage that there is no need to provide a new insulating layer.

Continuation of page 1 No. 1 Showa Electric Wire and Wire Co., Ltd.

Claims (1)

[Claims] (1) In a method of manufacturing a Nb5Sn superconducting wire by plating tin on the outer periphery of a wire in which many niobium filaments are embedded in a copper-based matrix and subjecting it to diffusion heat treatment, the outer periphery of the tin plating layer is coated with polyborosilicate. A method for producing a Nb3Sn superconducting wire, which comprises applying and baking a heat-resistant paint containing siloxane resin as a main component, and then subjecting it to diffusion heat treatment. (2) A method for producing a Nb5Sn superconducting wire as claimed in the claim, wherein the baking of the heat-resistant paint is carried out at a temperature below the melting point of tin.