JP2785908B2 - Method of manufacturing copper tube for superconductivity - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a copper tube for superconductivity. 2. Description of the Related Art Copper tubing containing superconducting wire such as tantalum niobium has an RRR value (residual resistance ratio) of 4N.
(99.99%) about 200 for copper, and an RRR value of about 500 has been commercialized by special treatment. [0003] As a result of intensive studies, the present inventors have made the following invention on a method of manufacturing a copper pipe having a higher RRR value. That is, the present invention provides (1) a continuous casting apparatus having a structure in which one end of a mold protrudes into a molten metal bath and the other end is in contact with a cooling structure. A method for producing a copper tube for super electric use, characterized in that a molten metal made of high-purity copper of 0.5 ppm or less is continuously cast and solidified in one direction to obtain a tube having an RRR value of 6000 or more;
(2) One end of the mold protrudes into the molten metal bath, and the other end is made of high-purity copper containing 1 ppm or less of silver and 0.5 ppm or less of sulfur by using a continuous casting apparatus having a structure in contact with a cooling structure. A method for producing a copper tube for super electric motor, characterized in that a molten metal is continuously cast and single-crystallized to obtain a tube having an RRR value of 9000 or more. (3) After the tube is cast, drawing and / or annealing is performed ( 1) or the production method of (2),
(4) The above-mentioned (1) to which casting is performed by pulse drawing
(3) Production method, (5) Casting speed is 5 to 150 mm /
(6) The molten metal is made of electrolytic copper previously obtained by electrolysis or electrolytic copper obtained by electrolyzing an equivalent product in a mineral acid electrolytic solution. The above (1)
To (5), (7) the method of (6) above, wherein the desilvering of the electrolytic solution is brought into contact with the electrolytic solution discharged from the anode side and metallic copper, and / or chloride ion is used, (8) (7) The method according to the above (7), wherein the anode and the cathode are separated by a diaphragm, and the effluent from the anode is desilvered and then circulated and supplied to the cathode chamber.
(9) The method according to (8), wherein the electrolyte after desilvering is filtered through a member having a pore size of 0.1 to 2 μ, and (10) the method according to (7) to (9), wherein nitric acid is used as the mineral acid in the electrolyte. Method, (1
1) The method according to any one of the above (6) to (10), wherein short-period PR electrolysis is performed using sulfuric acid as an electrolyte. The present invention comprises high-purity copper containing 1 ppm or less of silver and 0.5 ppm or less of sulfur, preferably 0.1 ppm or less of silver and 0.01 ppm or less of sulfur, and more preferably unidirectionally. In order to produce a solidified or single-crystallized superconducting high-purity copper tube, one end of the mold protrudes into the molten metal bath, and the other end uses a continuous casting device having a structure in contact with the cooling structure, In this method, a molten metal made of high-purity copper containing 1 ppm or less of silver and 0.5 ppm or less of sulfur is continuously cast to obtain a cast body, which is drawn and / or annealed as necessary. [0006] In this method, since one end of the mold is protruded into the molten high-purity copper bath, it is not necessary to use another heating means.
A solidified surface can be maintained near the molten metal inlet side. In addition, unidirectional solidification or single crystallization can be easily performed, and a single crystal can be produced by reducing the casting speed. Since the other end of the mold is in contact with the cooling structure, there is no molten metal at the exit of the mold. This enables continuous casting without breakout. Further, if the casting is performed by pulse drawing in order to obtain a cast having large crystal grains without breakout, a product of stable operation and stable quality can be obtained. The pulse extraction is a method in which the extraction is stopped for a certain period of time and then the extraction is repeated. For example, the drawing is stopped in 2 to 10 seconds, and 0.
This is an intermittent drawing method in which the drawing is performed in 1 to 1 second. When pulse drawing is used, a unidirectionally solidified or single crystallized mold can be obtained even when the mold partially projects into a molten metal furnace having a shape as shown in FIG. 5 described later. The preferred casting speed is 5 to 150 mm / min.
Particularly preferably, it is 10 to 70 mm / min. This is because a copper material having very few grain boundaries can be obtained. The casting speed is a value obtained by dividing the drawing length by the drawing time. In the case of employing pulse drawing, the casting speed is a value obtained by dividing the drawing length by the total time of the stopping time and the drawing time. In the continuous casting described above, by blowing an inert gas or a neutral gas into the vicinity of the solidification interface of the molten metal, the temperature gradient near the solidification interface can be increased, and unidirectional solidification is preferably performed. The molten metal used in the continuous casting of the present invention is made of electrolytic copper obtained by electrolysis or a high-purity electrolytic copper obtained by electrolyzing an equivalent product in an electrolytic solution as described below. In order to more preferably perform the above continuous casting, it is preferable to use a refractory of a good conductor as a material of the mold. For example, silicon nitride, silicon carbide, graphite, or the like is used.
When graphite is used, the oxygen concentration of the product decreases to around 3 ppm. [0014] The casting apparatus used in the present invention may be either a mold provided on a side wall of a melting furnace or a holding furnace or a mold provided vertically in a melting furnace or a holding furnace. The size of the product in the present invention is as follows:
Large diameters are not suitable. This is because a product size in a range in which the temperature of the mold is transmitted to the molten metal or semi-solid metal enables unidirectional solidification or single crystallization. The high-purity copper used for the continuous casting melt is
Electrocopper obtained by electrolysis of electrolytic copper or an equivalent product in a mineral acid electrolytic solution in advance is used. Nitric acid or sulfuric acid is used as the mineral acid of the electrolytic solution. In the case of an electrolytic bath of nitric acid, sulfur is hardly mixed into the product, but in the case of a sulfuric acid electrolytic bath, sulfur is easily mixed, so that, for example, a short cycle PR is used.
It is preferable to carry out by electrolysis. The current density during electrodeposition is 0.
^{2 to} 10 A / dm ² , retention time 10 μsec to 2000
msec, current density during melting of electrodeposited copper is 0.05-5A
/ Dm ² , and the holding time is preferably 10 μsec to 1000 msec. More preferably, the current density at the time of electrodeposition is 1 to 6 A / dm ² , and the holding time is 0.1 to 60 msec.
c, current density at the time of melting of electrodeposited copper is 0.2 to 3 A / dm
^{2. The} holding time is 0.1 to 60 msec. In the case of the treatment using a nitric acid electrolytic bath, the concentration of nitric acid is adjusted so as to be maintained at pH: 3 or less. Preferably, the pH is adjusted to 1.5 to 2.0. During electrolysis, it is preferable that the anode and the cathode are separated by a diaphragm. The main purpose of the diaphragm is to isolate the cathode from impurities caused by dissolution of the anode. The impurities are roughly classified into sedimented solids, suspended solids and dissolved substances. Examples of the membrane material include an ion-exchange membrane, a cloth, and a ceramic, and an acid-resistant cloth such as a woven cloth such as Tevilon or Tetron is preferable. The effluent from the anode side is brought into contact with metallic copper and / or the presence of chloride ions such as hydrochloric acid to remove silver from the liquor. Further, the discharged liquid may be passed through an activated carbon tank as needed. After desilvering, impurities can be more preferably removed by filtering the solution with a filter medium having a pore size of 0.1 to 2 μm. The silver obtained by performing such a re-electrolysis treatment is 1 ppm or less and sulfur is 0.5 ppm or less.
In the following, if high-purity copper having an oxygen content of about 6 ppm is cast by the above-mentioned casting method, if necessary, it is further drawn and / or annealed to obtain excellent properties as a copper tube material for superconductivity. As described above, the copper tube for superconductivity in the present invention has a silver content of 1 ppm or less and a sulfur content of 0.1 ppm.
It is made of high-purity copper of 5 ppm or less, which is refined by electrolytic treatment of electrolytic copper using, for example, an apparatus as shown in FIG. 1 and obtained by casting using the continuous casting apparatus as described above. The RRR value is 4000 for a normal polycrystal, 6000 for unidirectional solidification, and around 9000 for a single crystal. The present invention will be described in detail below with reference to the drawings. In FIG. 1, 1 is an electrolytic cell, 2 is an anode made of electrolytic copper, 3 is a cathode, and is immersed in an electrolytic solution 5 mainly containing nitric acid. The cathode 3 is surrounded by a diaphragm 4. Reference numeral 6 denotes a stirring tank, and the electrolytic solution pumped out of the electrolytic tank 1 enters the stirring tank 6, where a certain amount of new liquid is supplied if necessary.
to go into. In the filtration tank 7, silver is removed from the solution by bringing the electrolytic solution into contact with metallic copper in the presence of chloride ions such as hydrochloric acid. 8 is an activated carbon tank. As a specific example, electrolytic copper (component grade, Ag: 13.9 ppm, S: 11.0 ppm, A
s: 0.5 ppm, Sb: 0.3 ppm, Pb: 0.7
ppm, O: 10 ppm) as the anode 2 and Ti as the cathode 3
Around the cathode 3 tetron (TR84501,
The electrolyte solution (trade name, manufactured by Kitamura Seisakusho) was divided into an anode chamber and a cathode chamber, and a diaphragm 4 for isolating the cathode 3 was formed. Electrolyte 5
The impure electrolyte discharged from the anode chamber was desilvered and continuously supplied to the cathode chamber. Desilvering treatment is performed by adding chlorine concentration to the electrolyte 1000 ± 10m by adding hydrochloric acid.
g / liter, and the electrolytic solution was added to the metallic copper in the filtration tank 7.
The contact was performed for 0 hour. After the desilvering treatment, the solution is
And the solution was supplied to the cathode chamber. The amount of liquid supply per cathode surface area was 1.65 cm / hour. The electrolytic bath is a copper 50g / liter nitric acid bath.
H was maintained at 1.7. The electrolytic bath temperature was 22 to 27 ° C. The current density was 1.0 A / dm ² , anode 2 and cathode 3
The distance between them was 40 mm. After energizing for 10 consecutive days, the cathode 3 was pulled up, the electrodeposited copper was peeled off from the Ti plate, washed and dried to obtain the desired high-purity copper. This high purity copper is sulfur:
0.05 ppm or less, silver: 0.3 ppm, Fe: 0.0
It was extremely high in purity, such as 5 ppm or less and O: 6 ppm. This high-purity copper was unidirectionally solidified by a casting apparatus shown in FIG. In FIG. 2, reference numeral 9 denotes a melting furnace, in which a graphite mold 10 is provided on the bottom side wall so that one end protrudes into the molten metal bath 11, and a cooling structure 12 is provided on the other end of the graphite mold 10. First, a pure copper rod 13 having an outer diameter of 10.6 mm is inserted into a hole having a diameter of 11 mm provided in the graphite mold 10 so that an end thereof is drawn in by 1 cm from a molten metal supply side. The above-mentioned high-purity copper is melted and put into a melting metal bath 11 in the melting furnace 9, and the temperature is raised to 1250 ° C. and held. The solidification position of the high-purity copper was set at the molten metal supply side in the mold by passing 8 liters / minute of water through the cooling structure 12. And
The solidified tube is continuously withdrawn 1.5 mm in 0.5 seconds,
Thereafter, pulse extraction was performed to stop for 4 seconds. The resulting tube of high purity copper (sulfur:
0.05 ppm or less, silver: 0.3 ppm or less, O: 3p
pm) was close to a single crystal having almost no crystal grain boundaries. This was filled with a Ta ₃ Nb wire and drawn to obtain a superconductor. The RRR value of the copper tube was as high as 9000. FIG. 3 shows another example of a continuous casting apparatus which is of a type which is drawn out in a vertical direction.
During the continuous casting process, an inert gas was introduced, and an inert gas was introduced into the molten metal bath while covering the surface of the casting tube with the inert gas. Then, the molten metal bath was agitated, and worked to eliminate variations in temperature and impurity components. In addition, the gas seal 16 was provided on the outlet side of the casting tube such that the inert gas was released only to the molten metal bath side. The solidified tube was continuously pulled out with a pinch roll at 20 mm / min. The supply of the inert gas may be performed at the solidification interface of the molten metal in the graphite mold 10 as shown in FIG. The resulting high-purity copper tube was unidirectionally solidified and had a very large crystal grain size of 2 to 5 mm and a smooth surface. The thus obtained copper tube was filled with a Ta ₃ Nb wire and subjected to drawing to produce a superconductor. The RRR value of the copper tube was as high as 6000. FIG. 5 shows another example of a continuous casting apparatus in which a mold 10 partially projects into a molten metal bath 11, in which case the above-described pulse drawing is particularly effective. is there. In addition, 17 in FIG. 5 is a heating element for heat retention provided in order to reduce the influence of the outside air temperature.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing an example of an apparatus for obtaining high-purity electrolytic copper as a starting material of the present invention. FIG. 2 is an explanatory view showing an example of a continuous casting apparatus used in the present invention. FIG. 3 is an explanatory view showing an example of a continuous casting apparatus. FIG. 4 is an explanatory view showing an example of a continuous casting apparatus. FIG. 5 is an explanatory view showing an example of a continuous casting apparatus. [Description of Signs] 1 electrolytic cell 2 anode 3 cathode 4 diaphragm 5 electrolytic solution 6 stirring tank 7 filtration tank 10 graphite mold 11 molten metal bath 15 inert gas introduction pipe 16 gas seal

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C25C 1/12 ZAA C25C 1/12 ZAA C30B 21/02 ZAA C30B 21/02 ZAA (56) References JP-A-61-230209 ( JP, A) JP-A-61-169149 (JP, A) JP-A-61-176454 (JP, A) JP-A-62-107844 (JP, A) JP-A-62-70589 (JP, A) 62-67188 (JP, A) JP-B 38-22111 (JP, B1) JP-B 55-30599 (JP, B2)

Claims (1)

(57) [Claims] One end of the mold protrudes into the molten metal bath, and the other end uses a continuous casting device having a structure in contact with the cooling structure to continuously feed a molten metal of high-purity copper with silver of 1 ppm or less and sulfur of 0.5 ppm or less. A method for producing a copper tube for super electric motor, wherein the tube is cast and unidirectionally solidified to obtain a tube having an RRR value of 6000 or more. 2. 2. The method for producing a copper tube for superconductivity according to claim 1, wherein the tube is drawn and / or annealed after casting. 3. 3. The method according to claim 1, wherein the casting is performed by pulse drawing. 4. The method for producing a copper tube for superconductivity according to any one of claims 1 to 3, wherein the casting speed is 5 to 150 mm / min. 5. 5. The method according to claim 1, wherein the molten metal is made of electrolytic copper obtained by electrolysis of an electrolytic copper or an equivalent thereof in a mineral acid electrolytic solution in advance. 6. Manufacturing method of copper tube for superconductivity. 6. The method for producing a copper tube for superconductivity according to claim 5, wherein desilvering in the electrolytic solution is performed by bringing the electrolytic solution discharged from the anode side into contact with metallic copper and / or using chlorine ions. 7. 7. The method for producing a copper tube for superconducting material according to claim 6, wherein the anode and the cathode are separated by a diaphragm, and the effluent from the anode is desilvered and then circulated and supplied to the cathode chamber. 8. 8. The method for producing a copper tube for superconductivity according to claim 7, wherein the electrolytic solution after desilvering is filtered through a member having a pore size of 0.1 to 2 [mu] m. 9. The method for producing a copper tube for superconductivity according to any one of claims 6 to 8, wherein nitric acid is used as a mineral acid of the electrolytic solution. 10. The method for producing a copper tube for superconductivity according to any one of claims 5 to 9, wherein short-period PR electrolysis is performed using sulfuric acid as an electrolytic solution. 11. One end of the mold protrudes into the molten metal bath, and the other end uses a continuous casting device having a structure in contact with the cooling structure to continuously feed a molten metal of high-purity copper with silver of 1 ppm or less and sulfur of 0.5 ppm or less. A method for producing a copper tube for super electric motor, wherein the tube is cast and single-crystallized to obtain a tube having an RRR value of 9000 or more. 12. The method for producing a copper tube for superconductivity according to claim 11, wherein the tube is cast and / or annealed after casting. 13. 13. The method for producing a superconducting copper tube according to claim 11, wherein the casting is performed by pulse drawing. 14． The method for producing a copper tube for superconductivity according to any one of claims 11 to 13, wherein the casting speed is 5 to 150 mm / min. 15. 15. The method according to claim 11, wherein the molten metal comprises electrolytic copper obtained by electrolysis in advance or electrolytic copper obtained by electrolyzing an equivalent product in a mineral acid electrolytic solution.
The method for producing a superconducting copper pipe material according to the above item. 16. The method for producing a copper tube for superconductivity according to claim 15, wherein desilvering in the electrolytic solution is performed by bringing the electrolytic solution discharged from the anode side into contact with metallic copper and / or using chlorine ions. 17． 17. The method for producing a copper tube for superconducting material according to claim 16, wherein the anode and the cathode are separated by a diaphragm, and the effluent from the anode is desilvered and circulated and supplied to the cathode chamber. 18. 18. The method for producing a copper tube for superconductivity according to claim 17, wherein the electrolytic solution after desilvering is filtered through a member having a pore size of 0.1 to 2 [mu] m. 19. The method for producing a copper tube for superconductivity according to any one of claims 16 to 18, wherein nitric acid is used as a mineral acid of the electrolytic solution.