JPH05309448A - Manufacture of single crystal copper material - Google Patents

Abstract

PURPOSE:To develop the manufacture of single crystal copper material having a composition consisting of high purity copper having relatively high strength with hardly reducing the RRR value. CONSTITUTION:Single crystal copper material is manufactured by drawing the high purity copper with the purity of 6N (>=99.9999%) and containing Ag of 2-50ppm at the casting speed of <=50mm/min. through a mold. This arrangement can produce fine wire or super-fine wire through cold wire drawing. In a vessel (a melting furnace) 1 to store the molten high purity copper M, the casting rod R is drawn through a mold 3 where one end is projected in the molten copper bath, and the other end is abutted on a cooling structure 6. The pulse drawing is preferable. Perfect single crystal copper material can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a single crystal copper material, which is 2 to 50 ppm based on high purity copper having a purity of 6N (99.9999%) or more.
Of Ag is added and withdrawn at a predetermined casting speed. The present invention also relates to a method for producing a single crystal copper material which is used in the form of a fine wire or an ultrafine wire by cold drawing the drawn rod as it is. The obtained single crystal copper material is used, for example, for audio and image signal transmission wiring applications. According to the present invention, an electric signal transmission wire represented by high quality audio and visual cables is provided.

[0002]

2. Description of the Related Art In recent years, audio and visual equipment, such as compact discs and laser discs, for recording and reproducing digitally using light has become widespread. Recording and reproduction of electric signals in such a digital system expands the range and accuracy of recording and reproduction of sound, for example, in comparison with that of the analog system, and has high purity, rich stereoscopic effect and rich presence. Sound is being reproduced.

[0003] In order to maximize the superior capabilities of the digital system, not only the quality of equipment components is improved, but also signal transmission lines connecting them, wiring materials between the components, and signal transmission lines inside the components. Attention has been focused on improving the quality of the. The true advantages of the digital system can be brought out by paying attention to the entire process from the input to the output including the signal transmission line.

Conventionally, such as a speaker cable connecting an amplifier and a speaker in an audio device, an audio pin cable connecting a tape recorder or a compact disc and an amplifier, an audio stereo pin cable, and a visual pin cable used in a visual device. An analog transmission cable was used as the transmission cable, but as described above, noise and distortion were added during the transmission of the signal, resulting in deterioration of sound quality and image quality.

Under these circumstances, proposals have been made for improving electric wires in order to reproduce high quality sound. For example, in JP-A-59-167904, an attempt is made to obtain high-quality sound quality by coarsening crystal grains by annealing oxygen-free copper having oxygen of 50 ppm or less in an inert gas atmosphere of 700 ° C. or more. Met.

Further improvement has been made and attempts have been made to use copper of ultra-high purity, for example, 6N (99.9999%) or higher purity, which has been successful. By thoroughly eliminating impurities and growing large crystal grains, the transmission of information signals became much more straight, loss was reduced, and transmission characteristics were improved. This was particularly effective in realizing high-purity sound quality and image quality with excellent high frequency characteristics.

[0007]

Problems to be Solved by the Invention 6N (99.9999)
%) Or higher high-purity copper is extremely useful as a copper material for audio and image signal transmission wiring. However, they have the drawback of being poor in strength. In such applications, it is often more suitable for use or handling to have a little more strength. In particular, in the production of extra fine wires, disconnection frequently occurs during drawing, which is a major problem in terms of production efficiency. Further, since the copper wire is sometimes used as a coil, it is a serious problem that wire breakage occurs during winding.

An RRR value (residual resistance ratio value) is an index for evaluating a smooth current flow. Where RRR
The value means a ratio of electric resistance value at 273K / electric resistance value at 4.2K. It is desired that the RRR value be made equal to or higher than the strength of normal-purity copper with almost no decrease. For that purpose, it is desired to obtain a single crystal copper material.

An object of the present invention is to develop a method for producing a single crystal copper material made of high-purity copper having a relatively high strength without substantially lowering the RRR value.

[0010]

[Means for Solving the Problems] The RRR value and the strength are basically opposite to each other. Addition of trace elements to improve strength reduces the RRR value. The present inventors
In high-purity copper of 6N or more, as a result of repeated research on an additive effective for single crystallization with almost no decrease in RRR value, as a result, Ag was found and a small amount of high-purity copper having a purity of 6N or more was added. It has been found that a combination of addition of Ag and a predetermined casting speed is useful for solving the problem of producing a single crystal. It was also found that the drawn single-crystal copper material can be made into a fine wire or an ultrafine wire without causing a disconnection.

Based on this finding, the present invention provides (1) 2
A method for producing a single crystal copper material, characterized in that high-purity copper having a purity of 6N (99.9999%) or more containing 50 ppm of Ag is extracted through a mold at a casting speed of 50 mm / min or less, and (2). 6 containing 2 to 50 ppm Ag
High-purity copper having a purity of N (99.9999%) or more is drawn out through a mold at a casting speed of 50 mm / min or less, and then cold drawn to form fine wires or ultrafine wires. A method for manufacturing a crystalline copper material is provided. It is preferred that the mold has a structure in which one end projects into the molten copper bath and the other end is cooled.

In the present invention, the "copper material for audio and image signal transmission wiring" includes wire materials such as internal wiring for audio / image signal transmission equipment represented by compact disks and laser disks and cables between the equipment. It is a thing.

[0013]

By adding 2 to 50 ppm of Ag to copper having a purity of 6 N or more and drawing it through the mold at a slow casting speed of 50 mm / min or less, the Ag-free 6
It was experimentally confirmed that single crystallization is more reliable than N-purity copper. If Ag is not contained, a grain boundary may be partially generated. The low recrystallization temperature, which is a characteristic of 6N-purity copper, and therefore work hardening cannot be expected, eliminates the difficulty of drawing thin wires. Particularly, in 6N-purity copper, peeling and wire drawing were difficult due to the difference in hardness between the grain boundary and the grain, which is a defect of polycrystal, but this is solved by single crystallization.

[0014]

EXAMPLES For example, taking the internal wiring of audio and visual equipment as an example, the purity and purity of copper are set to 6N to 7N, and the impurities and impurities are extremely reduced. Since it can be reduced to 1/10 or less as compared with the oxygen-free copper wire, noise and distortion in the electric signal due to solid solution or precipitation of impurities are reduced.

As described above, when manufacturing the copper material for the above-mentioned applications such as the wiring inside the equipment and the external wire, High purity, 1. 2. Very few internal defects such as foreign matter and pinholes. 3. Long product with uniform quality and less segregation. 4. The crystal growth is controlled by the single crystal structure. What is needed is a method for producing a high-purity single crystal copper material that does not break during wire drawing.

High-purity cast copper material of 6N or more has insufficient strength due to recrystallization after plastic working. Therefore, according to the present invention, Ag is added in an amount of 2 to 50 ppm and the casting speed is reduced to 50 mm / min or less. If it is less than 2 ppm, the required minimum strength is not expressed, and a stable single crystal cannot be obtained. On the other hand, if it exceeds 50 ppm, the adverse effect on the RRR value becomes remarkable, and a single crystal cannot be stably obtained. When the casting speed exceeds 50 mm / min, single crystallization cannot be performed.

For the sake of reference, the production of a 6N or higher high-purity copper continuous cast material will be first described below. In ordinary copper electrorefining, a crude copper purified to a purity of about 98 to 99% is cast to form an anode, and a seed plate made of a rolled copper plate or the like is used to obtain a copper concentration of 40 to 50 g / l and a free sulfuric acid concentration. Electrolytic copper is produced by performing electrolysis in a 90 to 220 g / l electrolytic solution under conditions of a liquid temperature of 50 to 70 ° C. and a cathode current density of 1 to 3 A / dm ² . The obtained electrolytic copper has a purity of about 4N (99.99%), and it must be further purified.

One method of producing high purity copper is re-electrolysis. In general, re-electrolysis is carried out by a diaphragm method using the electrolytic copper as an anode. Free sulfuric acid concentration in re-electrolysis is 9
0 to 220 g / l and the copper concentration is 30 to 50 g / l, which is no different from ordinary electrolysis. If the concentration of free sulfuric acid in the electrolytic solution is lower than 90 g / l, the denseness and smoothness of the surface of the electrodeposited copper will be poor and impurities will be easily trapped. On the other hand, when the concentration of free sulfuric acid exceeds 220 g / l, the solubility of copper sulfate decreases and productivity decreases. The preferred free sulfuric acid concentration is 90 to 150 g / l. The lower the copper concentration in the electrolytic solution is, the better the denseness and smoothness of the surface of the electrodeposited copper are, but the productivity is decreased.
g / l, preferably around 40 g / l.

As re-electrolysis conditions, an electrolysis temperature of 30 to 50 ° C. and a cathode current density of 50 to 150 A / m ² are generally adopted. The lower the electrolysis temperature, the better the denseness and smoothness of the surface of the electrodeposited copper. Therefore, the liquid temperature is preferably set to 50 ° C as the upper limit. If it exceeds 50 ° C, dendrite-like crystals are likely to be formed. If the temperature is lower than 30 ° C., the solubility of sulfate decreases, and suitable electrolytic operation cannot be performed. The preferable liquid temperature is 35 to 45 ° C., and particularly about 40 ° C. The temperature control is important for preventing Ag contamination. The cathode current density is 50 to 150 A / m ^2, preferably 90 to 150 A / m ^{2 in} consideration of the inclusion of impurities due to the denseness and poor smoothness of the electrodeposited copper surface and the productivity.
It is preferably carried out at 150 A / m ² .

The diaphragm is provided in order to prevent copper powder, cuprous oxide powder and impurities generated when electrolytic copper is dissolved from mixing into electrodeposited copper. The diaphragm is an ion exchange membrane, filter cloth,
The filter cloth may be in the form of a box, which is made of ceramics or the like and stretched over a frame, or in the form of a bag. Devon,
It is preferable to use an acid resistant fiber cloth such as Teflon or Tetron.

In the electrolytic solution, glue is 5 per ton of electrolytic copper.
~ 20 g can be added. The addition of glue makes the surface of the electrodeposited copper dense and effectively prevents the inclusion of impurities. Since glue does not contain sulfur, and the amount added is kept small, there is no risk of contamination with sulfur. If the amount of glue is too large, wrinkles may occur and the surface quality may deteriorate. The addition of glue makes a great contribution to the stabilization of impurity quality reduction.

The electrolysis operation is carried out by arranging an anode as electrolytic copper and a cathode arranged in a box-shaped diaphragm in a facing state in an electrolytic cell. A titanium plate, a stainless plate, or a high-purity copper plate is used as the cathode. The electrolytic solution is extracted from the electrolytic cell, sent to the circulation tank, adjusted in composition, and returned to the inside of the diaphragm through the filter. The glue supply is also stored in the diaphragm. To directly supply the electrolyte and the glue to the diaphragm, 1. 1. The electrodeposited surface is constantly exposed to a clean electrolyte solution, which has a great effect of preventing inclusion of impurities. 2. The glue works well on the electrodeposition surface, and the amount of glue added can be reduced. It is extremely useful for high purification because it can reduce the amount of electrolyte circulation.

The above is an example of high-purity copper that can be used as the raw material of the present invention. Of course, high-purity copper produced by a method other than the above can also be a production raw material of the present invention.

The high-purity copper thus obtained is cast into a rod by drawing it from a melting furnace or a vessel through a mold. As a continuous casting method that can be manufactured safely and efficiently without risk of breakout etc., the present applicant has already (1) a method of continuous casting through a mold in which one end is projected into a molten copper bath and the other end is cooled, And (2) the molten copper stored in the first vessel is sucked into the second vessel for vacuum purification, and then one end is projected into the molten copper bath in the first vessel and the other end is passed through a cooled mold. A method of continuous casting is proposed. This way
It is also used beneficially here.

FIG. 1 shows a horizontal continuous casting facility as a typical example of (1). In a vessel or a melting furnace 1 containing a molten high-purity copper M having a purity of 6 N or more containing 2 to 50 ppm of Ag, one end is projected into a molten copper bath and the other end is a cooling structure in order to pull out a casting rod R. The mold 3 which is in contact with 6 is inserted near the bottom of the melting furnace. The rod is drawn through the mold 3 at a casting speed of 50 mm / min or less.

By using a mold having a structure in which one end is projected into the molten copper bath and the other end is brought into contact with the cooling structure, there is no need to use a separate heating means dedicated to the mold, and even if it is used, it is assisted. A general heater is sufficient, and the solidified surface can be held near the inlet side of the mold without fear of excessive heating. This eliminates the risk of breakouts. This also allows easy single crystallization.

2 to 5 show examples of the vacuum refining-continuous casting equipment of (2). Referring to FIG. 2, the apparatus basically comprises a first vessel (melting furnace) 1, a second vessel 2 and a mold 3.
Composed of and. Melting may be performed in the first vessel 1. The molten copper M is held in the first vessel 1.
A heater 7 is installed around the first vessel 1 if necessary. The second vessel 2 installed directly above the first vessel 1
Comprises a conducting tube 4 immersed in the molten copper held in the first vessel 1. A heater 8 is also installed around the second vessel 2 if necessary. Second vessel 2
The upper end of is connected via a valve 10 to a vacuum system for exhausting the upper part of the second vessel and an inert gas system for pressurizing the vacuum system. Here, the conducting tube 4 is a single tube system that serves both suction and descent of the molten copper, and the pressure of the second vessel is reduced (to about 10 ^-2 Torr) by operating the valve 10 according to the raw material purity and the target quality. Repeated pressurization (up to atmospheric pressure) results in refining of the molten copper. For example,
Depressurization and pressurization are repeated 5 to 30 times.

After the predetermined operation, casting is carried out through the mold 3. First, a pure copper rod is inserted into the mold 3 with its insertion end slightly retracted from the molten copper supply side. One end of the mold 3 is inserted into a recess formed in the bottom of the first vessel and heated by heat from the molten copper and the first vessel wall. Auxiliary heater 9 is installed to provide additional heat. The other end of the mold 3 is cooled by the cooling structure 6. An inert gas such as N ₂ is injected into the mold through the passage 15. A gas seal 16 is provided so that the inert gas is released only to the molten copper side. The casting rod R is pulled out by the pinch roll 17.

The atmosphere of the first vessel is controlled by an inert gas such as N ₂ and Ar and a reducing gas such as CO and H ₂ . An inert gas such as N _{2 or} Ar and a reducing gas such as CO or H ₂ may be blown into the conduit. An inert gas such as N ₂ and Ar and a reducing gas such as CO and H ₂ may be blown into the first vessel molten copper.

By using a mold having a structure in which one end is projected into the molten copper bath and the other end is brought into contact with the cooling structure, there is no need to use a separate heating means dedicated to the mold, and even if it is used, it can be assisted. A general heater is sufficient, and the solidified surface can be held near the inlet side of the mold without fear of excessive heating. This eliminates the risk of breakouts. This also allows easy single crystallization.

The mold is preferably made of a refractory material having a good thermal conductivity such as silicon nitride, silicon carbide or graphite.

Pulse withdrawal is useful in casting. Pulse withdrawal is to withdraw for a certain period of time with a withdrawal stop interposed in between, for example, 2 to
This is an intermittent withdrawal method in which the withdrawal is stopped for 10 seconds and the withdrawal is repeated for 0.1 to 1 second.

"Casting speed" is a value obtained by dividing the drawing length by the drawing time. When pulse drawing is adopted, it is the value obtained by dividing the drawing length by the total time of the stop time and the drawing time. is there.

By blowing the inert gas into the vicinity of the solidification interface, the temperature gradient in the vicinity of the interface can be further increased, and single crystallization can be further facilitated. Also, passage 1
Introducing an inert gas in the middle of the mold through 5, and jetting the inert gas into the molten copper bath while covering the surface of the casting with the inert gas, the inert gas stirs the molten copper bath, It acts to eliminate variations in temperature and impurity components.

Alternatively, as shown in FIG. 3, horizontal drawing can be performed by installing a mold in the horizontal direction at the bottom of the first vessel. The configuration itself is the same as in FIG.

FIG. 4 shows an example of another vacuum refining-continuous casting apparatus. Elements that are the same as in FIG. 2 are labeled with the same reference numbers. Here, unlike FIG. 2, the conducting pipe is shown as a circulating double pipe system in which suction and lowering are performed separately. The conduit pipe 4 is a suction pipe, and the conduit pipe 5 is a downcomer pipe. The molten copper is sucked up through the conducting tube 4, exposed to vacuum in the second vessel, and then descends by its own weight through the conducting tube 5. The oxygen inlet 20 is shown in the second vessel,
The conduit tube 4 is provided with an inert gas tuyere 21.
No. 23 shows an additive input port.

Further, in this example, the mold 3 is completely embedded in the first vessel wall, and one end of the mold 3 projects into the molten copper. Therefore, the mold is sufficiently heated and the auxiliary heater is unnecessary.

FIG. 5 shows the case of the horizontal extraction shown in FIG. 4, and a description thereof will be omitted.

6 and 7 show a continuous vacuum refining continuous casting apparatus. Similar to FIGS. 4 and 5, the conducting tube is a circulating double tube system in which suction and lowering are performed separately, and a partition wall 24 is provided between the two. Conducting tube 4 as a suction tube
Is composed of, for example, three here. Molten copper is continuously supplied from the supply port 26, sucked up through the conducting tube 4 before the partition wall, exposed to vacuum in the second vessel, and then descends behind the partition wall by its own weight through the conducting tube 5. The second vessel is provided with an oxygen blowing port 20, and the conduit tube 4 is provided with an inert gas tuyere 21. Furthermore, a tuyere 30 for blowing a reducing gas into the molten copper bath of the first vessel
Is also equipped.

By combining such a vacuum gas suction or circulation degassing method and a casting method with a mold having one end protruding into molten copper and the other end in contact with a cooling structure, high purity and internal defect Safe and stable castings can be obtained.

Thus, a single crystal copper rod is obtained by using the above-mentioned equipment and drawing it through the mold 3 at a casting speed of 50 mm / min or less. This single crystal rod can be made into a fine wire or an ultrafine wire as it is by cold drawing without breaking.

Example A horizontal type continuous casting facility shown in FIG. 1 was used in which a horizontal graphite mold having one end protruding into a molten copper bath and the other end abutting a cooling structure was inserted near the bottom of a melting furnace. did. The pore size of the graphite mold was 8 mm.

S: 0.05 ppm or less, Fe: 0.05
Dissolves 6N grade copper with extremely high purity, such as ppm or less,
20 ppm of Ag was added, and an outer diameter of 7.
A 6 mm pure copper rod was placed 1 cm inside from the molten metal supply side. The molten high-purity copper in the furnace was heated and maintained at 1250 ° C. Water was passed at 8 l / min through the cooling structure installed on the side opposite to the molten metal supply side, and the solidification position of high-purity copper was set near the molten metal supply side in the mold.

The high-purity copper rod was pulled out by 1 mm in 0.5 seconds and then continuously pulled out by pulse withdrawal stopped for 2.5 seconds. (Average drawing speed: 20 mm / min)

The high-purity copper rod obtained as a result was a long single crystal having no grain boundaries. This rod was cold-drawn as it was, and processed into an ultrafine wire having a diameter of 20 μm without annealing. As a result, 2.5 kg of unbroken wire was obtained.

Further, when a wire having a diameter of 0.6 mm was completely annealed and used for an audio wire, it was well received.
Its RRR value was about 4000.

(Comparative Example 1) A rod was pulse-extracted at an average extraction linear velocity of 20 mm / min in the same manner as in the above-mentioned example except that the added amount of Ag was increased to 100 ppm and 500 ppm. At 100 ppm, some grain boundaries were generated.
At 500 ppm, more crystal grain boundaries were generated.

With the added amount of Ag kept constant at 20 ppm,
The rods were pulled out in the same manner as in the examples, with the average drawing line speed increased to 70 mm / min and 150 mm / min. The rod was completely polycrystalline.

Ag addition amount is 100 ppm and 500 pp
m and the average drawing line speed is 70 mm / min and 1
When increased to 50 mm / min, both combinations were also fully polycrystalline.

It can be seen that the amount of Ag and the casting speed have a great influence on the single crystallization.

(Comparative Example 2) 20 p of In was used instead of Ag.
pm was added and the rod was pulse-extracted at an average drawing linear velocity of 20 mm / min, but some grain boundaries were generated. In is A
It did not have the same single crystallization effect as g. In addition amount of 2
While keeping 0 ppm constant, the average drawing line speed is 70 mm /
Min and 150 mm / min, more grain boundaries were generated when the In addition amount was increased to 100 ppm and 500 ppm with the average drawing linear velocity kept constant at 20 mm / min. In addition was increased to 100 ppm and 500 ppm and average drawing line speed was 70 mm / min and 150
Both were completely polycrystalline when increased to mm / min.

[0052]

EFFECTS OF THE INVENTION A reliable method for producing a single crystal copper material has been established. A thin wire or an ultrafine wire can be manufactured by cold drawing the drawn rod as it is. INDUSTRIAL APPLICABILITY The present invention provides a wire rod for internal wiring of equipment for audio / video signal transmission, which is excellent in strength and RRR value. Particularly, this material does not cause disconnection in the production of extra fine wires and coil production, and is efficient and easy to produce. Will bring a significant cost reduction.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a horizontal continuous casting facility that can be used to practice the invention with a horizontal mold having one end protruding into a molten copper bath and the other end abutting a cooling structure.

FIG. 2 is a schematic vertical cross-sectional view of a single pipe type vertical extraction type refining and casting apparatus.

3 is a cross-sectional view of a mold portion of the apparatus shown in FIG. 2 which is changed to a horizontal extraction type.

FIG. 4 is a schematic vertical sectional view of a vertical extraction type refining and casting apparatus of a double pipe circulation system.

5 is a cross-sectional view of a mold portion of the apparatus of FIG. 4 changed to a horizontal extraction type.

FIG. 6 is a schematic vertical sectional view of a continuous horizontal extraction type refining and casting apparatus.

FIG. 7 is a horizontal cross-sectional view through the first vessel of FIG.

[Explanation of symbols]

 1 1st Vessel (Smelting Furnace) 2 2nd Vessel 3 Mold 4 Conducting Tube 5 Conducting Tube 6 Cooling Structure M Molten Copper R Casting Rod

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication C30B 29/02 7821-4G H01B 1/02 A 7244-5G

Claims (3)

[Claims] 1. A 6N (9) containing 2 to 50 ppm of Ag.
A high-purity copper having a purity of 9.9999% or more is drawn out through a mold at a casting speed of 50 mm / min or less, and a method for producing a single crystal copper material. 2. A 6N (9) containing 2 to 50 ppm of Ag.
9.999%) or more of high-purity copper is drawn out through a mold at a casting speed of 50 mm / min or less and then cold drawn to form a fine wire or an ultrafine wire. .. 3. The method for producing a single crystal copper material according to claim 1, wherein the mold has a structure in which one end projects into the molten copper bath and the other end is cooled.