Apparatus for manufacturing low-oxygen copper

Abstract

An apparatus for manufacturing a copper wire includes a melting furnace in which combustion is performed in a reducing atmosphere so as to produce molten copper; a holding furnace for maintaining a predetermined temperature of the molten copper supplied from the melting furnace; a casting trough for sealing the molten copper supplied from the holding furnace in a non-oxidizing atmosphere and for transferring the molten copper to a tundish; a degasser provided in the casting trough for dehydrogenating the molten copper passing therethrough; a continuous casting machine for continuously producing cast copper from the molten copper supplied from the tundish, and a cutter for cutting the cast copper into a predetermined length. The apparatus permits a dehydrogenating treatment to be performed without requiring a long moving distance of molten copper, and in which the generation of holes in solidification is suppressed, whereby high quality low-oxygen copper wire having superior surface quality can be obtained.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is based on Japanese Application 2000-109827, filed Apr. 11, 2000, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods for continuously manufacturing low-oxygen copper, having a suppressed oxygen content, by continuously casting molten copper produced in a melting furnace.

2. Description of the Background

Low-oxygen copper (called “oxygen-free copper” in some cases) in which the content of oxygen is controlled to 20 ppm or less, and more preferably, to 1 to 10 ppm, is widely used for producing various shapes, e.g., ingot forms such as billets and cakes, rolled sheets, wires and cut forms. As a method for manufacturing low-oxygen copper, molten copper is produced in a high-frequency furnace such as a channel furnace or a coreless furnace, the molten copper is transferred to a continuous casting machine while held in an airtight atmosphere, and the casting is then performed.

When low-oxygen copper is produced by using a high-frequency furnace as described above, there are advantages in that a higher temperature can be easily obtained by a simple operation and the qualities of the products are very uniform since no chemical reaction occurs in production of the molten copper. However there are disadvantages in that the construction cost and the operating cost are high, and productivity is low.

In order to carry out mass production of low-oxygen copper at lower cost, a method using a gas furnace, such as a shaft kiln, is preferably employed. However, when such a gas furnace is used, since combustion is performed in the furnace, oxidation occurs and the oxidized molten copper must be processed by a reducing treatment. This disadvantage of the gas furnace is not observed when a high-frequency furnace is used. As a result, low-oxygen copper cannot be produced unless the amount of oxygen contained in the molten copper is reduced by using a reducing gas and/or an inert gas in a step of transferring the molten copper before the molten copper is fed to a continuous casting machine.

In addition, even when such a deoxidizing step is performed, holes will be formed in the low-oxygen copper and may result in defects such as blisters in some cases. In the case described above, the quality of the low-oxygen copper is degraded. In particular, when a copper wire is manufactured, the holes will cause defects in a rolling step, and hence the copper wire has poor surface qualities. Accordingly, it is generally believed that production of high quality low-oxide copper is difficult to perform using a gas furnace, and hence most low-oxide copper is produced using a high-frequency furnace.

The holes described above are formed by bubbles of steam (H 2 O) produced by combination of hydrogen and oxygen, due to the decease in solubility of the gases in the molten copper when it is solidified. The bubbles are trapped in the molten copper in cooling and solidification and remain in the low-oxide copper, and hence holes are generated. From a thermodynamic point of view, the concentrations of hydrogen and oxygen in molten copper can be represented by the equation shown below.

[H] 2 [O]= p H 2 O K  Equation (A)

In the equation (A), [H] represents the concentration of hydrogen in the molten copper, [O] represents the concentration of oxygen in the molten copper, p H 2 O represents a partial pressure of steam in the ambience, and K represents an equilibrium constant.

Since the equilibrium constant K is a function of temperature and is constant at a constant temperature, the concentration of oxygen in the molten copper is inversely proportional to the concentration of hydrogen. Accordingly, in accordance with the equation (A), the concentration of hydrogen is increased by performing a deoxidizing treatment by reduction, and as a result, holes are easily generated during solidification, whereby only an ingot of low-oxygen copper having poor quality can be manufactured.

On the other hand, molten copper containing hydrogen at a low concentration can be obtained by melting copper in a state near complete combustion using an oxidation-reduction method, which is a general degassing method. However, in a subsequent deoxidizing step, a long moving distance of the molten copper must be ensured, and hence, the method described above cannot be practically used.

SUMMARY OF THE INVENTION

In consideration of the problems described above, an object of the present invention is to provide an apparatus for manufacturing low-oxide copper, in which a dehydrogenating treatment can be performed without requiring a long moving distance of molten copper, the generation of holes in solidification is suppressed, and high quality low-oxide copper can be obtained, having superior surface quality.

An apparatus for continuously manufacturing ingots of low-oxygen copper according to the present invention comprises a melting furnace in which combustion is performed in a reducing atmosphere so as to produce molten copper; a soaking furnace for maintaining a predetermined temperature of the molten copper supplied from the melting furnace; a casting trough for sealing the molten copper supplied from the soaking furnace in a non-oxidizing atmosphere and for transferring the molten copper to a turn-dish; a degasser provided in the casting trough for dehydrogenating the molten copper passing through the casting trough; a continuous casting machine for continuously producing cast copper from the molten copper supplied from the turn-dish; and a cutter for cutting the cast copper into a predetermined length.

An apparatus for continuously manufacturing ingots of low-oxygen copper according to the present invention comprises a melting furnace in which combustion is performed in a reducing atmosphere so as to produce molten copper; a holding furnace for maintaining a predetermined temperature of the molten copper supplied from the melting furnace; a casting trough for sealing the molten copper supplied from the holding furnace in a non-oxidizing atmosphere and for transferring the molten copper to a tundish; a degasser provided in the casting trough for dehydrogenating die molten copper passing through the casting trough; a continuous casting machine for continuously producing cast copper from the molten copper supplied from the tundish; and a cutter for cutting the cast copper into a predetermined length.

In the apparatus for manufacturing ingots of low-oxygen copper described above, the stirrer comprises dikes causing a meandering of the flow path of the molten copper passing through the casting trough.

An apparatus for continuously manufacturing a low-oxygen copper wire according to the present invention comprises a melting furnace in which combustion is performed in a reducing atmosphere so as to produce molten copper; a soaking furnace for maintaining a predetermined temperature of the molten copper supplied from the melting furnace; a casting trough for sealing the molten copper supplied from the soaking furnace in a non-oxidizing atmosphere and for transferring the molten copper to a turn-dish; a degasser provided in the casting trough for dehydrogenating the molten copper passing through the casting trough; a belt caster type continuous casting machine for continuously producing cast copper from the molten copper supplied from the turn-dish; and a rolling machine for rolling the cast copper so as to produce the low-oxygen copper wire.

An apparatus for continuously manufacturing a low-oxygen copper wire according to the present invention comprises a melting furnace in which combustion is performed in a reducing atmosphere so as to produce molten copper; a holding furnace for maintaining a predetermined temperature of the molten copper supplied from the melting furnace; a casting trough for sealing the molten copper supplied from the holding furnace in a non-oxidizing atmosphere and for transferring the molten copper to a tundish; a degasser provided in the casting trough for dehydrogenating the molten copper passing through the casting trough; a belt caster type continuous casting machine for continuously producing cast copper from the molten copper supplied from the tundish; and a rolling machine for rolling the cast copper so as to produce the low-oxygen copper wire.

In the apparatus for manufacturing a low-oxygen copper wire described above, the stirrer comprises dikes causing a meandering of the flow path of the molten copper passing through the casting trough.

An apparatus for continuously manufacturing a wire composed of a low-oxygen copper alloy according to the present invention comprises a melting furnace in which combustion is performed in a reducing atmosphere so as to produce molten copper; a soaking furnace for maintaining a predetermined temperature of the molten copper supplied from the melting furnace; a casting trough for sealing the molten copper supplied from the soaking furnace in a non-oxidizing atmosphere and for transferring the molten copper to a turn-dish; a degasser provided in the casting trough for dehydrogenating the molten copper passing through the casting trough; an adder for adding silver to the dehydrogenated molten copper; a belt caster type continuous casting machine for continuously producing cast copper alloy from the molten copper supplied from the turn-dish; and a rolling machine for rolling the cast copper alloy so as to produce the wire composed of the low-oxygen copper alloy.

An apparatus for continuously manufacturing a wire composed of a low-oxygen copper alloy according to the present invention comprises a melting furnace in which combustion is performed in a reducing atmosphere so as to produce molten copper; a holding furnace for maintaining a predetermined temperature of the molten copper supplied from the melting furnace; a casting trough for sealing the molten copper supplied from the holding furnace in a non-oxidizing atmosphere and for transferring the molten copper to a tundish; a degasser provided in the casting trough for dehydrogenating the molten copper passing through the casting trough; an adder for adding silver to the dehydrogenated molten copper; a belt caster type continuous casting machine for continuously producing cast copper alloy from the molten copper supplied from the tundish; and a rolling machine for rolling the cast copper alloy so as to produce the wire composed of the low-oxygen copper alloy.

In the apparatus for manufacturing a wire composed of a low-oxygen copper alloy described above, the stirrer comprises dikes for causing meandering of the flow path of the molten copper passing through the casting trough.

An apparatus for continuously manufacturing a base low-oxygen copper material containing phosphorus for use in copper plating according to the present invention comprises a melting furnace in which combustion is performed in a reducing atmosphere so as to produce molten copper; a soaking furnace for maintaining a predetermined temperature of the molten copper supplied from the melting furnace; a casting trough for sealing the molten copper supplied from the soaking furnace in a non-oxidizing atmosphere and for transferring the molten copper to a turn-dish; a degasser provided in the casting trough for dehydrogenating the molten copper passing through the casting trough; an adder for adding phosphorus to the dehydrogenated molten copper; a belt caster type continuous casting machine for continuously producing cast base copper material from the molten copper supplied from the turn-dish; and a rolling machine for rolling the cast base copper material so as to produce the base low-oxygen copper material containing phosphorus for use in copper plating.

An apparatus for continuously manufacturing a base low-oxygen copper material containing phosphorus for use in copper plating according to the present invention comprises a melting furnace in which combustion is performed in a reducing atmosphere so as to produce molten copper; a holding furnace for maintaining a predetermined temperature of the molten copper supplied from the melting furnace; a casting trough for sealing the molten copper supplied from the holding furnace in a non-oxidizing atmosphere and for transferring the molten copper to a tundish; a degasser provided in the casting trough for dehydrogenating the molten copper passing through the casting trough; an adder for adding phosphorus to the dehydrogenated molten copper; a belt caster type continuous casting machine for continuously producing cast base copper material from the molten copper supplied from the tundish; and a rolling machine for rolling the cast base copper material so as to produce the base low-oxygen copper material containing phosphorus for use in copper plating.

In the apparatus for manufacturing a base low-oxygen copper material described above, the stirrer comprises dikes causing a meandering of the flow path of the molten copper passing through the casting trough.

The apparatus for manufacturing a base low-oxygen copper material described above further comprises a cutter for cutting the base low-oxygen copper material rolled by the rolling machine into a predetermined length.

The apparatus for manufacturing a base low-oxygen copper material described above further comprises a washer for washing the base low-oxygen copper material having a predetermined length obtained by using the cutter described above.

In the apparatuses for manufacturing the low-oxygen copper described above, the combustion is performed in a melting furnace in a reducing atmosphere, and hence, the molten copper is deoxidized. The deoxidized copper is sealed in a non-oxidizing atmosphere in the casting trough and is then transferred to the turn-dish. Since the concentration of oxygen is inversely proportional to the concentration of hydrogen as described above, the concentration of hydrogen is increased in the molten copper deoxidized in the melting furnace. When the molten copper passes through the casting trough, while containing hydrogen at a high concentration, dehydrogenation is performed by the degasser. Accordingly, the amount of gas evolved in casting is decreased, the generation of holes in a cast copper is suppressed, and as a result, the defects on the surface of the low-oxygen copper are reduced.

In the apparatuses for manufacturing the low-oxygen copper described above, the combustion is performed in a melting furnace in a reducing atmosphere, and hence, the molten copper is deoxidized. The deoxidized copper is sealed in a non-oxidizing atmosphere in the casting trough and is then transferred to the tundish. Since the concentration of oxygen is inversely proportional to the concentration of hydrogen as described above, the concentration of hydrogen is increased in the molten copper deoxidized in the melting furnace. When the molten copper passes through the casting trough, while containing hydrogen at a high concentration, dehydrogenation is performed by the degasser. Accordingly, the amount of gas evolved in casting is decreased, the generation of holes in a cast copper is suppressed, and as a result, the defects on the surface of the low-oxygen copper are reduced.

In addition, when the molten copper is stirred by the degasser, the hydrogen contained in the molten copper is forced out therefrom, whereby dehydrogenation can be performed. That is, since the molten copper stirrer is provided in the casting trough, the molten copper contacting the stirrer is stirred before it reaches the tundish, and as a result the molten copper is well brought into contact with an inert gas blown into the casting trough for forming a non-oxidizing atmosphere. In the step described above, since a partial pressure of hydrogen in the inert gas is very low compared to that in the molten copper, the hydrogen in the molten copper is absorbed in the non-oxidizing atmosphere formed by the inert gas, whereby dehydrogenation of the molten copper can be performed.

In the case described above, the dike provided in the flow path for the molten copper is preferably in the form of a bar, a plate or the like. In addition, a plurality of dikes may be provided along the flow direction of the molten copper or in the direction perpendicular thereto. Furthermore, when dikes are formed of, for example, carbon, the deoxidizing treatment can also be performed efficiently due to the contact between the molten copper and the carbon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the structure of an apparatus for manufacturing an ingot of low-oxygen copper according to a first embodiment of the present invention;

FIG. 2A is an enlarged plan view showing an important portion of a casting trough in FIG. 1 ;

FIG. 2B is an enlarged side view showing an important portion of the casting trough in FIG. 1 ;

FIG. 3 is a schematic view showing the structure of an apparatus for manufacturing a low-oxygen copper wire according to a second embodiment of the present invention;

FIG. 4 is a graph showing the characteristics of gas evolution of the low-oxygen copper wire manufactured in the second embodiment of the present invention compared to those of a low-oxygen copper wire manufactured by a conventional dip forming method;

FIG. 5 is a schematic view showing the structure of an apparatus for manufacturing a wire composed of low-oxygen copper alloy according to a third embodiment of the present invention;

FIGS. 6A to 6 D are charts showing defects on the surface of the wire composed of the low-oxygen copper alloy manufactured in the third embodiment of the present invention;

FIG. 7 is a schematic view showing the structure of an apparatus for manufacturing a base copper material containing phosphorus for use in copper plating according to a fourth embodiment of the present invention; and

FIG. 8 is a schematic enlarged view showing important portions of an apparatus for manufacturing a base low-oxygen copper material according to an example of the fourth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the embodiments of apparatuses for manufacturing low-oxygen copper according to the present invention will be described in detail with reference to the figures. In the embodiments described below, “low-oxygen copper” means copper or an alloy thereof containing oxygen at a concentration of 20 ppm or less, and preferably, of 1 to 10 ppm.

First Embodiment

A first embodiment will first be described with reference to FIGS. 1 , 2 A, and 2 B. This embodiment relates to an apparatus for manufacturing an ingot of low-oxygen copper.

FIG. 1 is a schematic view showing the structure of an apparatus for manufacturing an ingot of low-oxygen copper, which is used in this embodiment of the present invention, and FIGS. 2A and 2B are enlarged plan and side views, respectively, each showing an important portion in FIG. 1 .

An apparatus for manufacturing an ingot of low-oxygen copper (an apparatus for manufacturing low-oxygen copper) 101 is composed of a melting furnace A, a soaking furnace B, a casting trough C, a continuous casting machine D, a cutter E and a transfer device F.

An apparatus for manufacturing an ingot of low-oxygen copper (an apparatus for manufacturing low-oxygen copper) 101 is composed of a melting furnace A, a holding furnace B, a casting trough C, a continuous casting machine D, a cutter E and a transfer device F.

The soaking furnace B temporarily stores the molten liquid supplied from the melting furnace A and supplies the molten liquid to the casting trough C while the temperature of the molten liquid is maintained.

The holding furnace B temporarily stores the molten liquid supplied from the melting furnace A and supplies the molten liquid to the casting trough C while the temperature of the molten liquid is maintained.

The casting trough C seals the molten liquid supplied from the holding furnace B in a non-oxidizing atmosphere and transfers the molten liquid to the tundish 5 a . As shown in FIG. 2B , the upper surface of a flow path (flow path for molten copper) 31 in the casting trough C is covered by a cover 8 , whereby the flow path 31 in the casting trough C is sealed. The non-oxidizing atmosphere is formed by, for example, blowing a mixed gas of nitrogen and carbon monoxide, or an inert gas such as argon, in the casting trough C.

The dikes 33 a are provided at the upper side of the flow path 31 for the molten copper, that is at the cover 8 . In addition, the dikes 33 b are provided at the lower side of the flow path 31 for the molten copper. The dikes 33 c are also provided in the flow path 31 for the molten copper, and the dikes 33 d are provided at the right side of the dikes 33 c in flow path 31 for the molten copper. By the dikes 33 a , 33 b , 33 c , and 33 d provided in the manner described above, the molten liquid flows up and down, and left to right, toward the direction indicated by the arrow in FIG. 2B so as to be vigorously stirred, whereby a degassing treatment can be performed. In FIG. 2B , reference numeral 32 indicates the surface of the molten liquid.

The dikes 33 c and 33 d make the moving distance of the molten liquid longer than the actual flow path 31 for the molten copper, and hence, even if the casting trough C is short, the efficiency of the degassing treatment can be improved. In addition, the dikes 33 a and 33 b serve to prevent gases in the non-oxidizing atmosphere before and after the degassing treatment from being mixed with each other. Similarly, the dikes 33 a and 33 b serve to prevent the molten copper before the degassing treatment from being mixed with the molten copper after the degassing treatment.

The stirrer 33 primarily performs a dehydrogenating treatment; however, the stirrer 33 can also drive out the oxygen remaining in the molten liquid by stirring. That is, in the degassing treatment, the dehydrogenating treatment and a second deoxidizing treatment are performed. When the dikes 33 a , 33 b , 33 c , and 33 d are formed of, for example, carbon, the deoxidizing treatment can be efficiently performed by the contact of the molten copper with the carbon.

The degassing treatment must be performed in a step of transferring the molten copper after it passes the soaking furnace B. The reason for this is that since combustion in a reducing atmosphere or a deoxidizing treatment by using a reducing agent is performed in the soaking furnace B in order to manufacture ingots of low-oxygen copper, the concentration of hydrogen in the molten copper is inevitably increased in the soaking furnace B in accordance with the equilibrium equation (A) described above.

The degassing treatment must be performed in a step of transferring the molten copper after it passes the holding furnace B. The reason for this is that since combustion in a reducing atmosphere or a deoxidizing treatment by using a reducing agent is performed in the holding furnace B in order to manufacture ingots of low-oxygen copper, the concentration of hydrogen in the molten copper is inevitably increased in the holding furnace B in accordance with the equilibrium equation (A) described above.

In addition, the degassing treatment is not preferably performed at the tundish 5 a located just in front of the continuous casting machine D. The reason for this is that when the molten liquid is vigorously stirred, for example by bubbling, the surface of the molten liquid is violently vibrated, a head pressure of the molten liquid flowing from a teeming nozzle varies, and as a result, the molten copper cannot be fed stably to the continuous casting machine D. In contrast, when the surface of the molten liquid is not violently vibrated, the satisfactory effect of the degassing treatment cannot be obtained. Accordingly, the degassing treatment is preferably performed in the transfer step from the holding furnace B to the tundish 5 a .

The tundish 5 a is provided with the teeming nozzle (not shown) at the end of the flow direction of the molten liquid so that the molten liquid is supplied from the tundish 5 a to the continuous casting machine D.

The continuous casting machine D is connected to the holding furnace B via the casting trough C. The continuous casting machine D is a so-called vertical casting machine having a mold 41 and pinch rollers 42 , in which, while the molten copper is cooled, the molten copper is drawn to the lower side in an approximately vertical direction so as to form cast copper 21 a having a predetermined cross-sectional shape. The shapes and the locations of the mold 41 and the pinch rollers 42 are optionally selected in accordance with the shape of an ingot 23 a of low-oxygen copper (low-oxygen copper) obtained as a product. For example, when the ingot 23 a of low-oxygen copper is formed into a billet having an approximately cylindrical form, the mold 41 having a cylindrical cross-sectional shape and the pinch rollers 42 having shapes corresponding thereto may be used. When a cake having an approximately regular cubic shape is formed, the mold 41 having an approximately rectangular shape and the pinch rollers 42 having shapes corresponding thereto may be used. In FIG. 1 , a cake is shown as an example of the ingot 23 a of low-oxygen copper.

The cutter E cuts the cast copper 21 a produced by the continuous casting machine D to a predetermined length. As an example of the cutter E, there may be mentioned a flying saw having a rotary disk blade, although other structures capable of cutting the cast copper 21 a may be used.

The transfer device F is composed of a basket 51 , an elevator 52 , and a conveyor 53 . The basket 51 is located approximately directly under the continuous casting machine D, receives the ingot 23 a of low-oxygen copper having a predetermined length formed by the cutter E, and places the ingot 23 a on the elevator 52 . The elevator 52 lifts the ingot 23 a of low-oxygen copper placed thereon by the basket 51 to the level at which the conveyor 53 is located. The conveyor 53 transfers the ingot 23 a of low-oxygen copper lifted up by the elevator 52 .

Next, a method for manufacturing an ingot of low-oxygen copper will be described using a manufacturing apparatus 101 having the structure described above.

The combustion is first performed in a reducing atmosphere in the melting furnace A so as to produce molten copper while being deoxidized (step of producing molten copper). The deoxidized molten copper transferred to the casting trough C via the soaking furnace B is sealed in a non-oxidizing atmosphere and is then transferred to the turn-dish 5 a (step of transferring molten copper). Since the concentration of oxygen is inversely proportional to that of hydrogen, the concentration of hydrogen in the molten copper deoxidized in the melting furnace A is increased. The molten copper having a high hydrogen concentration is dehydrogenated by the stirrer 33 while passing through the casting trough C (degassing step).

The combustion is first performed in a reducing atmosphere in the melting furnace A so as to produce molten copper while being deoxidized (step of producing molten copper). The deoxidized molten copper transferred to the casting trough C via the holding furnace B is sealed in a non-oxidizing atmosphere and is then transferred to the tundish 5 a (step of transferring molten copper). Since the concentration of oxygen is inversely proportional to that of hydrogen, the concentration of hydrogen in the molten copper deoxidized in the melting furnace A is increased. The molten copper having a high hydrogen concentration is dehydrogenated by the stirrer 33 while passing through the casting trough C (degassing step).

In addition, according to the equilibrium equation (A), since the gas concentration in the molten copper is decreased when the partial pressure of steam is decreased, in the case in which the molten copper before processed by dehydrogenation is ideally separated from the dehydrogenated molten copper, the degassing effect can be further improved. The improved degassing effect described above can be realized by, for example, providing the stirrer 33 described above in the step of transferring the molten copper. That is, the stirrer 33 described above also serves to prevent the gases in the atmospheres before and after the degassing treatment from being mixed with each other and serves to prevent the molten copper before the degassing treatment from being mixed with the molten copper after the degassing treatment.

The molten copper transferred from the melting furnace A to the soaking furnace B is heated and is then supplied to the continuous casting machine D via the casting trough C and the turn-dish 5 a . Subsequently, the molten copper is drawn downward through the mold 41 by the pinch rollers 42 , is cooled and solidified, and is continuously cast so as to produce the cast copper 21 a (continuous casting step).

The molten copper transferred from the melting furnace A to the holding furnace B is heated and is then supplied to the continuous casting machine D via the casting trough C and the tundish 5 a . Subsequently, the molten copper is drawn downward through the mold 41 by the pinch rollers 42 , is cooled and solidified, and is continuously cast so as to produce the cast copper 21 a (continuous casting step).

In the apparatus 101 for manufacturing the ingot of low-oxygen copper according to this embodiment, combustion is performed in a reducing atmosphere in the melting furnace A so that the molten copper is deoxidized, and the deoxidized molten copper is sealed in a non-oxidizing atmosphere in the casting trough C and is then transferred to the turn-dish 5 a . Since the concentration of oxygen in the molten copper is inversely proportional to that of hydrogen, the concentration of hydrogen in the deoxidized molten copper is increased. However, by use of the stirrer 33 in the subsequent degassing step, the molten copper is dehydrogenated. Accordingly, without requiring a long moving distance of the molten copper, the concentration of hydrogen, which is increased by a deoxidizing treatment performed by reduction, can be decreased and hence the generation of holes in the molten copper can be suppressed. As a result, by using a gas furnace in which combustion is performed, the generation of holes can be suppressed in cooling and solidification, and hence mass production of high quality ingots of low-oxygen copper can be continuously performed at lower cost.

In the apparatus 101 for manufacturing the ingot of low-oxygen copper according to this embodiment, combustion is performed in a reducing atmosphere in the melting furnace A so that the molten copper is deoxidized, and the deoxidized molten copper is sealed in a non-oxidizing atmosphere in the casting trough C and is then transferred to the tundish 5 a . Since the concentration of oxygen in the molten copper is inversely proportional to that of hydrogen, the concentration of hydrogen in the deoxidized molten copper is increased. However, by use of the stiffer 33 in the subsequent degassing step, the molten copper is dehydrogenated. Accordingly, without requiring a long moving distance of the molten copper, the concentration of hydrogen, which is increased by a deoxidizing treatment performed by reduction, can be decreased and hence the generation of holes in the molten copper can be suppressed. As a result, by using a gas furnace in which combustion is performed, the generation of holes can be suppressed in cooling and solidification, and hence mass production of high quality ingots of low-oxygen copper can be continuously performed at lower cost.

Furthermore, when the stirrer 33 is composed of the dikes which meander the flow path for the molten copper, the molten copper is automatically stirred by the flow thereof, and hence the dehydrogenating treatment can be efficiently performed by a simple structure without using an additional agitator or the like. In addition, the operation of the apparatus 101 for manufacturing the ingots of low-oxygen copper can be easily controlled, and hence the production cost can be further decreased.

In this connection, the location at which the separation is performed by the stirrer 33 is not limited to one location, and in accordance with the moving distance of the molten copper, a plurality of the stirrers may be optionally provided. In addition, the embodiment is not limited to the production of the ingots of low-oxygen copper and may be applied to the production of ingots of low-oxygen copper alloy by adding an appropriate element.

As the stirrer 33 , the dikes 33 a , 33 b , 33 c , and 33 d are respectively provided at the top and bottom, and the right and left, in the flow path 31 for the molten copper; however, the number and the locations of the dikes may be optionally changed in accordance with the length and the width of the casting trough C.

Furthermore, a so-called vertical continuous casting machine D is used in this embodiment; however, a so-called horizontal continuous casting machine may be used instead. In such a case, a hoist such as the elevator 52 is not required.

Second Embodiment

Next, a second embodiment will be described with reference to FIGS. 3 and 4 . This embodiment relates to a method for manufacturing low-oxygen copper wires.

FIG. 3 is a schematic view showing the structure of an apparatus for manufacturing low-oxygen copper wires, which is used in this embodiment of the present invention. The apparatus for manufacturing low-oxygen copper wires (an apparatus for manufacturing low-oxygen copper) 102 is primarily composed of a melting furnace A, a soaking furnace B, a casting trough C 2 , a belt caster type continuous casting machine G, a rolling machine H, and a coiler I.

FIG. 3 is a schematic view showing the structure of an apparatus for manufacturing low-oxygen copper wires, which is used in this embodiment of the present invention. The apparatus for manufacturing low-oxygen copper wires (an apparatus for manufacturing low-oxygen copper) 102 is primarily composed of a melting furnace A, a holding furnace B, a casting trough C 2 , a belt caster type continuous casting machine G, a rolling machine H, and a coiler I.

In this embodiment, since the melting furnace and the holding furnace have the structures equivalent to those described in first embodiment, respectively, the same reference levels of the elements in first embodiment designate the same constituent elements in this embodiment, and detailed descriptions thereof will be omitted.

The casting trough C 2 seals the molten liquid in a non-oxidizing atmosphere supplied from the holding furnace B and transfers the sealed molten liquid to a tundish 5 b . The tundish 5 b is provided with a teeming nozzle 9 at the downstream end in the flow direction of the molten liquid, so that the molten liquid is supplied from the tundish 5 b to the belt caster type continuous casting machine G.

The casting trough C 2 and the tundish 5 b have shapes and the like which are slightly different from those of first embodiment described above, so as to be applied to the production of low-oxygen copper wires; however, the basic structures thereof are approximately equivalent to those in first embodiment, respectively. That is, the casting trough C 2 is provided with the stirrer 33 shown in FIGS. 2A and 2B .

The belt caster type continuous casting machine G is connected to the holding furnace B via the casting trough C 2 . The belt caster type continuous casting machine G is composed of an endless belt 11 moving around and a casting wheel 13 rotated by the endless belt 11 which is in contact with a part of the casting wheel 13 , in which a cast copper 21 b is continuously produced. The belt caster type continuous casting machine G is also connected to the rolling machine H.

The shear 15 is provided with a pair of rotary blades 16 cuts the cast copper 21 b rolled by the rolling machine H; that is, the shear 15 cuts the low-oxygen copper wire 23 b into wires having shorter lengths. For example, immediately after the belt caster type continuous casting machine G is started, the internal texture of the cast copper 21 b is not stable, and hence, the low-oxygen copper wire 23 b obtained in the case described above cannot be a product having stable quality. Accordingly, in the case described above, the low-oxygen copper wire 23 b supplied from the rolling machine H is sequentially cut by the shear so that the low-oxygen copper wire 23 b is not transferred to the defect detector 19 and to the coiler I until the quality of the cast copper 21 b is stabilized. When the quality of the cast copper material 21 b is stabilizes, the rotary blades 16 are separated from each other so as to permit transfer of the low-oxygen copper wire 23 b to the defect detector 19 and the coiler I.

Next, a method for manufacturing the low-oxygen copper wire will be described, using the apparatus 102 for manufacturing the low-oxygen copper wire having the structure described above.

Combustion is first performed in the melting furnace A in a reducing atmosphere, so as to produce molten copper while being deoxidized (step of producing molten copper). The deoxidized molten copper transferred to the casting trough C 2 via the soaking furnace B is sealed in a non-oxidizing atmosphere and is transferred to the turn-dish 5 b (step of transferring molten copper). Since the concentration of oxygen is inversely proportional to that of hydrogen, the concentration of hydrogen in the molten copper deoxidized in the melting furnace A is increased. The molten copper having a high hydrogen concentration is then dehydrogenated by the stirrer 33 while passing through the casting trough C 2 (degassing step).

Combustion is first performed in the melting furnace A in a reducing atmosphere, so as to produce molten copper while being deoxidized (step of producing molten copper). The deoxidized molten copper transferred to the casting trough C 2 via the holding furnace B is sealed in a non-oxidizing atmosphere and is transferred to the tundish 5 b (step of transferring molten copper). Since the concentration of oxygen is inversely proportional to that of hydrogen, the concentration of hydrogen in the molten copper deoxidized in the melting furnace A is increased. The molten copper having a high hydrogen concentration is then dehydrogenated by the stirrer 33 while passing through the casting trough C 2 (degassing step).

In addition, according to the equilibrium equation (A), since the gas concentration in the molten copper is decreased when the partial pressure of steam is decreased, in the case in which the molten copper before processed by dehydrogenation is ideally separated from the dehydrogenated molten copper, the degassing effect can be further improved. The improved degassing effect described above can be realized by, for example, providing the stirrer 33 described above in the step of transferring the molten copper. That is, the stirrer 33 also serves to prevent the gases in the atmospheres before and after the degassing treatment from being mixed with each other and serves to prevent the molten copper before the degassing treatment from being mixed with the molten copper after the degassing treatment.

The molten copper transferred from the melting furnace A to the soaking furnace B is heated and is then supplied to the belt caster type continuous casting machine G from the teeming nozzle 9 of the turn-dish 5 b via the casting trough C 2 . Subsequently, the molten copper is continuously cast by the belt caster type continuous casting machine G, thereby yielding the cast copper 21 b at the end thereof (continuous casting step).

The molten copper transferred from the melting furnace A to the holding furnace B is heated and is then supplied to the belt caster type continuous casting machine G from the teeming nozzle 9 of the tundish 5 b via the casting trough C 2 . Subsequently, the molten copper is continuously cast by the belt caster type continuous casting machine G, thereby yielding the cast copper 21 b at the end thereof (continuous casting step).

The cast copper 21 a is rolled by the rolling machine H, thereby yielding low-oxygen copper wire 23 b (low-oxygen copper) having a superior surface quality (rolling step). When the low-oxygen copper wire (low-oxygen copper) 23 b has stable quality, and after defects are detected by the defect detector 19 , the low-oxygen copper wire 23 b is wound around the coiler I while a lubricant oil, such as wax, is coated on the wire 23 b , and the low-oxygen copper wire in the wound form is then transferred to a subsequent step.

In the method for manufacturing the low-oxygen copper wire described above, since the content of oxygen in the molten copper is controlled to 20 ppm or less, and the content of hydrogen is controlled to 1 ppm or less prior to the steps of casting and rolling, the amount of gas evolved in casting is decreased, the generation of holes in the cast copper 21 b can be suppressed, and the defects on the surface of the low-oxygen copper wire can be decreased.

In addition, the low-oxygen copper wire manufactured by the method described above has superior characteristics of gas evolution. FIG. 4 shows characteristics of gas evolution of the low-oxygen copper wire manufactured by the method of this embodiment (Curve b) and of a low-oxygen copper wire manufactured by a conventional dip forming method (Curve a). In this figure, the horizontal axis is the time in second elapsed from the start of the evaluation, and the vertical axis is an amount of gas evolved. As shown in the figure, the amount of gas evolved from the low-oxygen copper wire manufactured by the method of this embodiment is very small compared to that of the low-oxygen copper wire manufactured by the dip forming method.

When a low-oxygen copper wire or a low-oxygen copper alloy wire, in which an amount of gas evolved therefrom is large, is used under a high vacuum condition or at a high temperature, the surface quality thereof may be degraded due to the generation of blisters on the surface of the wire, or the gas evolved may be discharged outside so as to pollute the environment in some cases.

Since the amount of gas evolved from the low-oxygen copper wire manufactured by the method according to this embodiment is very small, the wire may be preferably applied to a particle accelerator operated under a high vacuum condition or to a microwave oven in which a temperature is increased.

In the apparatus 102 for manufacturing the low-oxygen copper wire according to this embodiment, combustion is performed in a reducing atmosphere in the melting furnace A so that the molten copper is deoxidized, and the deoxidized molten copper is sealed in a non-oxidizing atmosphere in the casting trough C 2 and is then transferred to the tundish 5 b . Since the concentration of oxygen in the molten copper is inversely proportional to that of hydrogen, the concentration of hydrogen is increased in this molten copper. However, by using the stirrer 33 in the subsequent degassing step, the molten copper is dehydrogenated. Accordingly, without ensuring a long moving distance of the molten copper, the concentration of hydrogen, which is increased by a deoxidizing treatment performed by reduction in accordance with the equilibrium equation (A), can be decreased, and hence the generation of holes in the molten copper can be suppressed. As a result, by using a gas furnace in which combustion is performed, the generation of holes can be suppressed in cooling and in solidification, and hence, production of high quality low-oxygen copper wires can be continuously performed at lower cost.

In addition, since the degassing step is performed by the stirrer 33 for stirring the molten copper, the dehydrogenating treatment can be forcibly performed in a short period, and hence the dehydrogenating treatment can be efficiently performed by using a simple structure.

Furthermore, when the stirrer 33 is composed of dikes which meander the flow path for the molten copper, the molten copper is automatically stirred by the flow thereof, and hence the dehydrogenating treatment can be efficiently performed by a simple structure without using an additional agitator or the like. In addition, the operation of the apparatus 102 for manufacturing the low-oxygen copper wire can be easily controlled.

In this connection, in order to stabilize a temperature of the molten liquid, an electric furnace may be provided between the holding furnace B and the tundish 5 b .

In addition, an adder for adding an element other than copper to the molten copper may be provided at a location from the end of the casting trough C 2 to the end of the tundish 5 b.

Third Embodiment

Next, a third embodiment will be described with reference to FIGS. 5 , and 6 A to 6 D. This embodiment relates to an apparatus for manufacturing a wire composed of a low-oxygen copper alloy containing silver (Ag).

The inventors of the present invention have discovered through intensive research that by adding a small amount of Ag to molten copper, holes generated in the cast copper alloy containing Ag become finely dispersed micro holes, and the micro holes thus formed disappear during rolling and do not cause any defects. Accordingly, the generation of holes which is harmful to the wire composed of the low-oxygen copper alloy can be suppressed. By adding Ag, a decrease in conductivity of the wire composed of the low-oxygen copper alloy can be suppressed.

In the apparatus 103 for manufacturing the wire composed of the low-oxygen copper alloy, a casting trough C 3 is provided instead of the casting trough C 2 in the apparatus 102 for manufacturing the low-oxygen copper wire. In the vicinity of the end of the casting trough C 3 , a Ag adder 3 is provided so that Ag can be added to a molten liquid. By this Ag adder 3 , Ag can be added to the molten liquid which is deoxidized and dehydrogenated, and by the turbulence of the molten copper in a tundish 5 b , generated right after the addition of Ag, the Ag and the molten copper are preferably mixed with each other.

In this embodiment, the location at which the Ag adder 3 is provided is not limited to the vicinity of the end of the casting trough C 3 . That is, so long as the Ag added to the dehydrogenated molten liquid is uniformly diffused therein, the Ag adder 3 may be provided at a location from the end of the casting trough C 3 to the end of the tundish 5 b.

In this embodiment, the location at which the Ag adder 3 is provided is not limited to the vicinity of the end of the casting trough C 3 . That is, so long as the Ag added to the dehydrogenated molten liquid is uniformly diffused therein, the Ag adder 3 may be provided at a location from the end of the casting trough C 3 to the end of the turn-dish 5 b.

In addition, the structure of the casting trough C 3 is equivalent to that of the casting trough C 2 except for the Ag adder 3 . That is, the casting trough C 3 is provided with the stirrer 33 shown in FIG. 2 .

Combustion is first performed in a reducing atmosphere in a melting furnace A so as to produce molten copper while being deoxidized (step of producing molten copper). The deoxidized molten copper transferred to the casting trough C 3 via a holding furnace B is sealed in a non-oxidizing atmosphere and is then transferred to the tundish 5 b (step of transferring molten copper). Since the concentration of oxygen is inversely proportional to that of hydrogen, the concentration of hydrogen in the molten copper deoxidized in the melting furnace A is increased. The molten copper having a high hydrogen concentration is dehydrogenated by the stirrer 33 while passing through the casting trough C 3 (degassing step).

Combustion is first performed in a reducing atmosphere in a melting furnace A so as to produce molten copper while being deoxidized (step of producing molten copper). The deoxidized molten copper transferred to the casting trough C 3 via a soaking furnace B is sealed in a non-oxidizing atmosphere and is then transferred to the turn-dish 5 b (step of transferring molten copper). Since the concentration of oxygen is inversely proportional to that of hydrogen, the concentration of hydrogen in the molten copper deoxidized in the melting furnace A is increased. The molten copper having a high hydrogen concentration is dehydrogenated by the stirrer 33 while passing through the casting trough C 3 (degassing step).

According to the steps described above, the content of oxygen in the molten copper is controlled to 1 to 10 ppm, and the content of hydrogen is controlled to 1 ppm or less. Subsequently, Ag is added to the molten copper, in which the concentrations of oxygen and hydrogen are controlled, by the Ag adder 3 so that the content of the Ag in the molten copper is 0.005 to 0.2 wt % (step of adding Ag).

The molten copper containing Ag transferred from the melting furnace A to the holding furnace B is heated and supplied to a belt caster type continuous casting machine G via the casting trough C 3 and the tundish 5 b . Subsequently, the molten copper containing Ag is continuously cast by the belt caster type continuous casting machine G, thereby yielding a cast copper alloy 21 c at the end thereof (continuous casting step).

The molten copper containing Ag transferred from the melting furnace A to the soaking furnace B is heated and supplied to a belt caster type continuous casting machine G via the casting trough C 3 and the turn-dish 5 b . Subsequently, the molten copper containing Ag is continuously cast by the belt caster type continuous casting machine G, thereby yielding a cast copper alloy 21 c at the end thereof (continuous casting step).

The cast copper alloy 21 c is rolled by a rolling machine H, thereby yielding the wire 23 c composed of the low-oxygen copper alloy (low-oxygen copper) containing a predetermined amount of Ag and having superior surface quality (rolling step). Subsequently, the wire 23 c is wound around a coiler I.

As described above, since the concentrations of oxygen and hydrogen in the molten copper is controlled, and a predetermined amount of Ag is added to the molten copper prior to the steps of casting and rolling, the amount of gas evolved in casting is decreased, the generation of holes in the cast copper alloy 21 c can be suppressed, and the defects on the surface of the wire composed of the low-oxygen copper alloy can be decreased.

The inspection results of defects on the surface of the wire 23 C, composed of the low-oxygen copper alloy obtained by the method using the apparatus 103 described above is shown in FIGS. 6A to 6 D. The inspection of defect in this measurement was performed in accordance with a rotational phase type eddy current method using a defect detector for copper wire (RP-7000 manufactured by Estek K.K.)

FIG. 6A shows the result of a wire containing no Ag, FIG. 6B shows the result of a wire containing 0.01 wt % of Ag, FIG. 6C shows the result of a wire containing 0.03 wt % of Ag, and FIG. 6D shows the result of a wire containing 0.05 wt % of Ag. The vertical axis in each figure is time, and the horizontal axis is a voltage (V) of an eddy current generated in accordance with the number and the size of the defects. As shown in FIGS. 6A to 6 D, when the content of Ag in the wire 23 c composed of the low-oxygen copper alloy is higher, that is, when the amount of Ag added to the molten copper is increased, the number of defects on the surface of the wire 23 c is decreased.

When the number of grain boundaries can be increased by adding an element which forms finer crystal grains of copper, the concentration of a gas component per grain boundary is decreased. Accordingly, when a local equilibrium of hydrogen, oxygen and steam in the cast copper alloy 21 c is considered, an apparent concentration of the gas component in the case described above is significantly decreased compared to the case in which larger grains are formed, and as a result it is believed that large holes are unlikely to be generated.

In the manufacturing apparatus 103 for manufacturing the wire composed of low-oxygen copper alloy according to this embodiment, combustion is performed in the melting furnace A in a reducing atmosphere so that the molten copper is deoxidized, and the molten copper is then sealed in a non-oxidizing atmosphere in the casting trough C 3 and is transferred to the tundish 5 b . Since the concentration of oxygen in molten copper is inversely proportional to that of hydrogen, the concentration of hydrogen in the deoxidized molten copper is increased. However, by using the stirrer 33 in the subsequent degassing step, the molten copper is dehydrogenated. Accordingly, the concentration of hydrogen, which is increased by a degassing treatment performed by reduction in accordance with the equilibrium equation (A), is decreased, and hence the generation of holes in solidification can be suppressed. In addition, Ag is added by the Ag adder 3 to the molten copper in which holes are hardly generated by the deoxidizing and the dehydrogenating treatments, whereby finely dispersed micro holes can be formed.

In the manufacturing apparatus 103 for manufacturing the wire composed of low-oxygen copper alloy according to this embodiment, combustion is performed in the melting furnace A in a reducing atmosphere so that the molten copper is deoxidized, and the molten copper is then sealed in a non-oxidizing atmosphere in the casting trough C 3 and is transferred to the turn-dish 5 b . Since the concentration of oxygen in molten copper is inversely proportional to that of hydrogen, the concentration of hydrogen in the deoxidized molten copper is increased. However, by using the stirrer 33 in the subsequent degassing step, the molten copper is dehydrogenated. Accordingly, the concentration of hydrogen, which is increased by a degassing treatment performed by reduction in accordance with the equilibrium equation (A), is decreased, and hence the generation of holes in solidification can be suppressed. In addition, Ag is added by the Ag adder 3 to the molten copper in which holes are hardly generated by the deoxidizing and the dehydrogenating treatments, whereby finely dispersed micro holes can be formed.

Accordingly, by using the belt caster type continuous casting machine G, long cast copper alloys can be continuously manufactured at lower cost, in which a decrease in conductivity is suppressed and the number of harmful holes is decreased. In addition, even when the degassing step is simplified, a wire composed of low-oxygen copper alloy can be manufactured having excellent surface quality, in which defects on the surface of the wire is significantly reduced. As a result, in order to perform a dehydrogenating treatment, an expensive and specified device such as a vacuum-degassing device is not required, and hence the structure of device can be simplified and a wire composed of low-oxygen copper alloy can be manufactured at lower cost.

In addition, since the degassing step is performed by the stirrer 33 for stirring the molten copper, the dehydrogenating treatment can be forcibly performed in a short period, and hence the dehydrogenating treatment can be efficiently performed by using a simple structure.

Furthermore, when the stirrer 33 is composed of the dikes which meander the flow path of the molten copper, the molten copper is automatically stirred by the flow thereof, and hence the dehydrogenating treatment can be efficiently performed by a simple structure without using an additional agitator or the like. In addition, the operation of the apparatus 103 for manufacturing the wire composed of the low-oxygen copper alloy can be easily controlled.

Since the wire 23 c composed of the low-oxygen copper alloy contains 0.005 to 0.2 wt % of Ag, a decrease in conductivity can be suppressed, and a high quality wire can be manufactured having a small number of defects on the surface, i.e., superior surface quality.

Fourth Embodiment

Next, a fourth embodiment will be described with reference to FIGS. 7 and 8 . This embodiment relates to an apparatus for manufacturing a base low-oxygen copper material containing phosphorus (P) for use in copper plating.

The base low-oxygen copper material is formed into various shapes, such as a bar, a wire and a ball, and is preferably used as, for example, an anode for copper plating forming a wiring pattern on a printed circuit board. That is, a wiring pattern can be preferably formed on a printed circuit board by copper plating, and more preferably by copper sulfate plating. In copper sulfate plating, a copper material containing phosphorus (low-oxygen copper containing approximately 0.04% of phosphorus) is used as an anode. The phosphorus contained in the copper material promotes smooth dissolution of the copper anode, whereas when an anode for copper plating contains no phosphorus, the uniform adhesiveness of a plating film is degraded.

FIG. 7 is a schematic view showing the structure of an apparatus for manufacturing the base copper material containing phosphorus for use in copper plating, which is used in this embodiment of the present invention. In an apparatus (an apparatus for manufacturing low-oxygen copper) 104 for manufacturing the base copper material containing phosphorus for use in copper plating, only the structure of a casting trough differs from that of the apparatus 102 for manufacturing the low-oxygen copper wire in the second embodiment. Accordingly, the same reference labels of the elements in second embodiment designate the same constituent elements in this embodiment, and detailed descriptions thereof will be omitted.

In the vicinity of the end of the casting trough C 4 , a P (phosphorus) adder 4 is provided so that phosphorus can be added to the molten liquid. By this P adder 3 , phosphorus can be added to the molten liquid which is deoxidized and dehydrogenated, the reaction between phosphorus and oxygen is prevented, and by the turbulence of the molten copper in a tundish 5 b generated right after the addition of phosphorus, the phosphorus and the molten copper are preferably mixed with each other.

In this embodiment, the location at which the P adder 4 is provided is not limited to the vicinity of the end of the casting trough C 4 . That is, so long as the P is added to the molten liquid after a dehydrogenating treatment is uniformly diffused therein, the P adder 3 may be provided at any location from the end of the casting trough C 4 to the end of the tundish 5 b.

In this embodiment, the location at which the P adder 4 is provided is not limited to the vicinity of the end of the casting trough C 4 . That is, so long as the P is added to the molten liquid after a dehydrogenating treatment is uniformly diffused therein, the P adder 3 may be provided at any location from the end of the casting trough C 4 to the end of the turn-dish 5 b.

In addition, the structure of the casting trough C 4 is equivalent to that of the casting trough C 2 , except that the P adder 4 is provided. That is, the casting trough C 4 is provided with a stirrer 33 shown in FIG. 2 .

Combustion is first performed in a melting furnace A in a reducing atmosphere so as to produce molten copper while being deoxidized (step of producing molten copper). The deoxidized molten copper, transferred to the casting trough C 4 via a holding furnace B, is sealed in a non-oxidizing atmosphere and is then transferred to the tundish 5 b (step of transferring molten copper). Since the concentration of oxygen is inversely proportional to that of hydrogen, the concentration of hydrogen in the molten copper deoxidized in the melting furnace A is increased. The molten copper having a high hydrogen concentration is dehydrogenated by the stirrer 33 while passing through the casting trough C 4 (degassing step).

Combustion is first performed in a melting furnace A in a reducing atmosphere so as to produce molten copper while being deoxidized (step of producing molten copper). The deoxidized molten copper, transferred to the casting trough C 4 via a soaking furnace B, is sealed in a non-oxidizing atmosphere and is then transferred to the turn-dish 5 b (step of transferring molten copper). Since the concentration of oxygen is inversely proportional to that of hydrogen, the concentration of hydrogen in the molten copper deoxidized in the melting furnace A is increased. The molten copper having a high hydrogen concentration is dehydrogenated by the stirrer 33 while passing through the casting trough C 4 (degassing step).

According to the steps described above, the content of oxygen in the molten copper is controlled to 20 ppm or less, and the content of hydrogen is controlled to 1 ppm or less. Subsequently, to the molten copper in which the concentrations of oxygen and hydrogen are controlled, phosphorus is added by the P adder 4 so that the content of the phosphorus in the molten copper is 40 to 1,000 ppm (step of adding P).

In this embodiment, when the concentration of oxygen, the concentration of hydrogen and the content of phosphorus are out of the range described above, the following problems may occur. That is, when the concentration of oxygen is more than 20 ppm in the molten copper, the workability thereof is poor and cracking may occur in a cast base copper material. When the concentration of hydrogen is more than 1 ppm, the amount of gas evolved is large and cracking may occur in the cast base copper material. When the content of phosphorus is less than 40 ppm, uniform solubility cannot be obtained when the base copper material is used as an anode, and hence the base copper material cannot be a material for forming a copper ball. In addition, when the content of phosphorus is more than 1,000 ppm, the workability is degraded.

As described above, after the molten copper transferred from a melting furnace A to a holding furnace B is heated, the molten copper is supplied to a belt caster type continuous casting machine G via the casting trough C 4 and the tundish 5 b and is then cast by the continuous casting machine G, whereby the cast base copper material 21 d can be obtained at the end of the continuous casting machine G. The cast base copper material 21 d is rolled by a rolling machine H, whereby a base copper material (low-oxygen copper) 23 d containing a predetermined amount of phosphorus for use in copper plating having superior surface quality is formed. The presence of defects in the base copper material 23 d containing phosphorus is inspected by a defect detector 19 , and the base copper material 23 d is then wound by a coiler I while coated by a lubricant such as wax. The base copper material 23 d containing phosphorus is then transferred to another step and is then optionally formed into, for example, copper balls.

In the apparatus 104 for manufacturing the base copper material containing phosphorus for use in copper plating according to this embodiment, the combustion is performed in the melting furnace A in a reducing atmosphere so that the molten copper is deoxidized, and the deoxidized molten copper is sealed in a non-oxidizing atmosphere in the casting trough C 4 and is then transferred to the tundish 5 b . Since the concentration of oxygen is inversely proportional to that of hydrogen, the concentration of hydrogen in the molten copper is increased. However, by the stirrer 33 used in the subsequent degassing step, the molten copper is dehydrogenated. Accordingly, the concentration of hydrogen, which is increased in accordance with the equilibrium equation (A) by a deoxidizing treatment performed by reduction, can be decreased without requiring a long moving distance of the molten copper, and hence the generation of holes in the molten copper can be suppressed. As a result, by using the belt caster type continuous casting machine G, a cast base copper material 21 d can be continuously manufactured at lower cost, having a small number of defects on the surface thereof. In addition, since the amount of gas evolved is small, and the number of defects on the surface can be decreased by suppressing the generation of holes, the cast base copper material 21 d is not cracked, and hence a base copper material 23 d containing phosphorus for use in copper plating can be obtained having excellent surface quality. In addition, since a cast base copper material 21 d can be obtained having high flexural strength, cracking, which occurs when an anode in the form of a ball for use in copper plating is manufactured, can be prevented. Furthermore, since the belt caster type continuous casting machine G is used, hot rolling is performed after casting, and hence, the remaining cast texture, which is produced when an anode for copper plating is formed by direct casting, can be eliminated. In addition, an anode for copper plating having a uniform texture can be obtained by recrystallization. Consequently, mass production of high quality anodes for copper plating can be performed at lower cost.

In the apparatus 104 for manufacturing the base copper material containing phosphorus for use in copper plating according to this embodiment, the combustion is performed in the melting furnace A in a reducing atmosphere so that the molten copper is deoxidized, and the deoxidized molten copper is sealed in a non-oxidizing atmosphere in the casting trough C 4 and is then transferred to the turn-dish 5 b . Since the concentration of oxygen is inversely proportional to that of hydrogen, the concentration of hydrogen in the molten copper is increased. However, by the stirrer 33 used in the subsequent degassing step, the molten copper is dehydrogenated. Accordingly, the concentration of hydrogen, which is increased in accordance with the equilibrium equation (A) by a deoxidizing treatment performed by reduction, can be decreased without requiring a long moving distance of the molten copper, and hence the generation of holes in the molten copper can be suppressed. As a result, by using the belt caster type continuous casting machine G, a cast base copper material 21 d can be continuously manufactured at lower cost, having a small number of defects on the surface thereof. In addition, since the amount of gas evolved is small, and the number of defects on the surface can be decreased by suppressing the generation of holes, the cast base copper material 21 d is not cracked, and hence a base copper material 23 d containing phosphorus for use in copper plating can be obtained having excellent surface quality. In addition, since a cast base copper material 21 d can be obtained having high flexural strength, cracking, which occurs when an anode in the form of a ball for use in copper plating is manufactured, can be prevented. Furthermore, since the belt caster type continuous casting machine G is used, hot rolling is performed after casting, and hence, the remaining cast texture, which is produced when an anode for copper plating is formed by direct casting, can be eliminated. In addition, an anode for copper plating having a uniform texture can be obtained by recrystallization. Consequently, mass production of high quality anodes for copper plating can be performed at lower cost.

When the degassing step is performed by the stirrer 33 for stirring the molten copper, the dehydrogenating treatment can be forcibly performed in a short period, and hence the dehydrogenating treatment can be efficiently performed by a simpler structure.

In addition, when the stirrer 33 is composed of the dikes which meander the flow path for the molten copper, the molten copper is automatically stirred by the flow thereof, and as a result the dehydrogenating treatment can be efficiently performed by a simpler structure without using an additional agitator or the like. Furthermore, the operation of the apparatus 104 for manufacturing the base copper material, containing phosphorus for use in copper plating, can be easily controlled.

In addition to the method described above, a short base copper material 23 e containing phosphorus for use in copper plating may be directly formed by a cutter having a shear 15 . An apparatus used in this manufacturing method will be described as another example of this embodiment according to the present invention.

An apparatus 104 b for manufacturing the base copper material 23 e is composed of the apparatus 104 described above and an alcohol bath 18 provided under the shear 15 . In the manufacturing method using the apparatus 104 b , as shown in FIG. 8 , the continuous and long base copper material 23 d ejected from the rolling machine H is sequentially cut into base copper materials 23 e each having a predetermined length by a cutting portion 16 a of a rotary blade 16 of the shear 15 (cutting step). The base copper materials 23 e are immersed in the alcohol 18 a contained in the alcohol bath 18 , whereby washing is performed by the alcohol 18 a (washing step). That is, in the method described above, a defect detector 19 and a coiler I are not required.

The base copper material 23 d ejected from the rolling machine H is still hot, and the surface thereof is oxidized by air, that is, thin oxide film is formed on the surface. However, since the base copper materials 23 e are immersed in the alcohol 18 a , the surfaces thereof are washed, and in addition the oxide films formed thereon are reduced, whereby the surface quality, and in particular the brilliance thereof, can be improved. As the alcohol 18 a , isopropyl alcohol (IPA) is preferable.

In this example, the rotary blades 16 each have four cutting portions 16 a ; however, the number of the cutting portions 16 a can be optionally changed.

As described above, in the apparatus 104 b for manufacturing the base copper material containing phosphorus for use in copper plating, since the short base copper material 23 e can be directly formed by cutting the base copper material 23 d into a predetermined length, a step of winding the base copper material 23 d around the coiler I, which is a necessary step of manufacturing the long base copper material 23 d , can be eliminated, and hence the number of manufacturing steps can be reduced. As a result, for example, copper balls can be easily manufactured at lower cost.

In addition, since a lubricant is not required which is used when the base copper material 23 d is wound around the coiler I, the risk of significantly decreasing the quality of copper balls can be eliminated, and the quality of anodes for copper plating can be significantly improved, whereby high quality copper balls can be manufactured.

Furthermore, when the base copper material 23 e having a short length is washed by using an alcohol 18 a , such as IPA, a base copper material 23 e having superior surface quality, in particular superior brilliance, can be obtained.

As a washing solution, acids may also be used in addition to alcohols; however, alcohols are preferable due to the easy handling and disposal thereof compared to those of acids.

In the second to fourth embodiments, the belt wheel type continuous casting machine is used as an example of the belt caster type continuous casting machine; however another belt caster type continuous casting machine may also be used. As a belt caster type continuous casting machine, a twin belt type continuous casting machine having two endless belts may also be mentioned.

As has thus been described, according to the apparatus for manufacturing low-oxygen copper of the present invention, a dehydrogenating treatment can be performed without requiring a long moving distance of molten copper, and the generation of holes in solidification is suppressed, whereby high quality low-oxygen copper having superior surface quality can be obtained.

Claims

1. An apparatus for continuously manufacturing a low-oxygen copper wire, comprising:a melting furnace in which combustion may be performed in a reducing atmosphere so as to produce molten copper; a holding furnace connected to receive molten copper supplied from the melting furnace and adapted to maintain a predetermined temperature of the molten copper; a casting trough connected to receive molten copper supplied from the holding furnace and configured to seal the molten copper supplied from the holding furnace in a non-oxidizing atmosphere, and configured for transferring the molten copper to a tundish, wherein said casting trough is covered to have an upper face, a lower face and side faces for a flow path for the molten copper; a degasser provided in the casting trough and adapted for dehydrogenating the molten copper passing through the casting trough, wherein said degasser comprises dikes provided on the upper face, the lower face and the side faces of the trough to cause the molten copper in the trough to meander vertically and side-to-side; a continuous casting machine connected and adapted for continuously producing cast copper from the molten copper supplied from the tundish; and a rolling machine positioned for rolling the cast copper so as to produce the low-oxygen copper wire.

2. An apparatus for continuously manufacturing a low-oxygen copper, comprising:a melting furnace in which combustion may be performed in a reducing atmosphere so as to produce molten copper; a holding furnace connected to receive molten copper supplied from the melting furnace and adapted to maintain a predetermined temperature of the molten copper; a casting trough connected to receive molten copper supplied from the holding furnace and configured to seal the molten copper supplied from the holding furnace in a non-oxidizing atmosphere, and configured for transferring the molten copper to a tundish, wherein said casting trough is covered to have an upper face, a lower face and side faces for a flow path for the molten copper; a degasser provided in the casting trough and adapted for dehydrogenating the molten copper passing through the casting trough, wherein said degasser comprises dikes provided on the upper face, the lower face and the side faces of the trough to cause the molten copper in the trough to meander vertically and side-to-side; a continuous casting machine connected and adapted for continuously producing cast copper from the molten copper supplied from the tundish.