JPH1192837A - Refinement of copper alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refining method which can simultaneously remove high contents of oxygen, hydrogen, and desirably, inclusion in molten copper alloy, at the time of melting and casting the copper alloy in an induction furnace. SOLUTION: In the method for refinement of molten copper in a shifting trough 3, at the time of melting the copper alloy in the induction furnace 2 and supplying the molten copper alloy into a mold 4 through the shifting trough 3, the molten copper alloy surface flowing down the shifting trough 3 is covered with a carbon-base solid reducing agent 8. Further, a nozzle 5 having a rotary blade 6 at the tip part is inserted into the molten copper alloy and fine bubbles 7 of an inert gas is blown into the bottom part of the molten copper alloy flowing down the shifting trough 3 to execute the deoxidation and dehydrogenation, and the oxygen and the hydrogen contained in the copper alloy cast block are reduced to <=20 ppm and <=0.5 ppm, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for refining copper alloys, and more particularly to a method for refining molten copper of copper alloys in a hot water trough provided between a melting furnace and a mold (casting machine). is there.

[0002]

2. Description of the Related Art Copper and copper alloys make use of their excellent properties such as electric and thermal conductivity and workability to make plates and strips,
It is processed into products such as pipes and rods, and is widely used in fields such as electronics, electricity, and heat exchange. Among them, especially the above-mentioned plate or strip of a copper alloy for electronic materials such as a lead frame,
Alternatively, as shown in Fig. 1, for plastic processed or formed products such as heat exchanger tubes, main raw materials 1 such as electric (refined) copper and copper scrap are melted in an induction furnace 2 and the molten copper in the induction furnace 2 is melted. Removes oxygen, hydrogen, and inclusions, and removes Cu-Fe, Cu-Sn, Cu-Mn, Cu-Mg, Cu-Ni
After the components are adjusted to a copper alloy such as a copper alloy or a Cu-Cr alloy, the molten copper is poured into a mold 4 of a casting machine through a hot water gutter 3 to form an ingot (slab). Then, after subjecting the ingot to a homogenizing heat treatment in a soaking furnace, the ingot is subjected to hot working such as hot rolling and cold working such as cold rolling and cold drawing to be processed into the desired product shape and adjusted. Heat treatment for quality and surface treatment such as improvement of corrosion resistance and solderability are performed to make each copper alloy product.

[0003] In the case of a copper alloy to which the present invention is applied, it is necessary to adjust the components of the added alloy elements, and the added alloy elements and the amounts thereof are different. Must be performed in batches, including cleaning of the copper alloy residue of the rod immediately before. Therefore, the melting of copper alloy
The induction furnace (high-frequency induction melting furnace) 2 shown in FIG. 1 is used. On the other hand, in the case of pure copper, there is no need to adjust the components of the added alloy elements. Therefore, instead of the induction furnace 2, a shaft furnace capable of continuous melting is used, and the molten copper is transferred to a hot water gutter. After the oxygen, hydrogen and inclusions are removed in the holding furnace, the molten metal is further poured into a mold through a hot water gutter to form an ingot.

[0004] One of the major factors that determine the quality of such copper alloy products is the quality of the molten copper alloy, and the control of the amount of impurities occupies a large part of the quality of the molten metal. Among these impurities, it is important to control gases such as oxygen and hydrogen and inclusions.

[0005] Among these impurities, first, oxygen adversely affects the mechanical properties and workability of the copper alloy product, and furthermore, the conductivity, and it is desirable that oxygen be reduced as much as possible. Particularly, in a thin copper alloy for electronic materials having a thickness of 1 mm or less such as a lead frame, oxygen may cause cracks and surface defects in the copper alloy during the processing of the copper alloy into the predetermined shape or during use as a product. 20ppm or less, desirably
Low content levels below 10 ppm are required.

[0006] Hydrogen also causes blisters in the copper alloy product during processing of the copper alloy into the predetermined shape or during use as a product, impairing the smoothness of the surface and the plating processability, and causing hydrogen embrittlement. Therefore, it is desirable to reduce as much as possible. In particular, Cu-0.1Fe-0.03P, Cu-1.8Ni-0.4Si-1.0Zn,
Cu-3.2Ni-0.7Si-1.25Sn-0.3Zn, Cu-2.3Fe-0.03P-0.1Z
In thin copper alloys for electronic materials with a thickness of 1 mm or less, such as various lead frame materials with a composition of n, Cu-3.2Ni-0.7Si-1.0Zn, the hydrogen content is as low as 0.5 ppm or less, preferably 0.2 ppm or less. It is necessary to be at the volume level.

Further, inclusions such as oxides or carbides determined by the amount of oxygen in the molten copper cause surface defects of the copper alloy product, which is fatal for applications requiring a uniform surface. Therefore, it is desirable to reduce as much as possible. Especially the thickness of the lead frame material etc. is 1m
In the case of a thin copper alloy material for electronic materials of m or less, it is preferable to set the content of oxide to a low content level of 20 ppm or less, preferably 10 ppm or less, in terms of oxygen content, particularly from the above problem.

On the other hand, the induction furnace used for melting a copper alloy is a crucible type that is difficult to seal unlike a cylindrical shaft furnace which is easy to seal and is likely to be in a reducing atmosphere. It will be done under atmosphere. For this reason, oxygen is easily absorbed into the molten copper from the atmosphere in the melting process, and oxygen contained in the copper raw material (such as water in the raw material or attached to the raw material) is mixed with oxygen in the molten copper. Source. In addition, hydrogen is contained in the copper raw material (such as water adhering to the raw material or attached to the raw material) and water absorbed from the air atmosphere into the molten copper in the melting step, similarly to the oxygen. Becomes

Further, when the molten copper is transferred from the induction furnace to the hot water trough 3, as shown in FIG. 3, there is a head drop between the molten metal outlet of the induction furnace 2 and the hot water trough 3, and the head falls down. The molten copper is transferred to a hot water trough 3. Therefore, due to the entrainment of the atmosphere during the hot water transfer, the absorption from the atmospheric atmosphere during the melting is combined,
In the case of alloy copper, compared to the pure copper, oxygen in the molten copper,
The amount of hydrogen and the amount of oxide-based inclusions inevitably increase. In dissolving the copper alloy, usually, a method of covering the surface of the molten copper with a solid reducing agent such as charcoal to prevent absorption of oxygen from the atmospheric atmosphere into the molten copper in the melting step is adopted. However, although this method is effective in suppressing oxygen, hydrogen inevitably contained in the solid reducing agent is conversely absorbed into the molten copper, resulting in an increase in the amount of hydrogen in the molten copper. . Moreover, the copper alloys are based on the Fe, Sn, M
The alloy contains alloying elements such as n, Mg, Ni, and Cr that are more easily oxidized than pure copper, and accordingly, the amount of oxygen in the molten copper is relatively large. Therefore, in the ordinary melting and casting process of the copper alloy, the amount of impurities in the molten copper in the hot water gutter immediately before casting is oxygen 50 to 500 ppm, hydrogen 5 ppm, oxide 200 to 300 ppm (
However, it is a high amount (in terms of oxygen amount).

Hitherto, refining for reducing impurities in copper or copper alloys has been performed mainly in the induction furnace as the melting furnace. Among these, as a means for reducing oxygen, as described above, usually, a method of covering the surface of the molten copper with a solid reducing agent such as charcoal and preventing absorption of oxygen from the atmospheric atmosphere into the molten copper in the melting step. Has been adopted.

[0011] As a means for reducing hydrogen, a method is usually used in which the amount of oxygen in molten copper is controlled (increased) to, for example, 250 to 500 ppm, and this oxygen is used to oxidize, volatilize, or incorporate hydrogen into slag. There is a method of performing the dissolution in a vacuum to volatilize hydrogen.

The inclusions are mainly removed by filtering the molten copper through a ceramic heat-resistant porous filter provided in the hot water trough.

[0013]

However, each of these prior arts has its own problems. First, the method of covering the surface of molten copper with a solid reducing agent such as charcoal as a means of reducing oxygen has the effect of preventing absorption of oxygen from the air atmosphere into the molten copper in the melting step, but has already been carried out in the molten copper. The effect of actively deoxidizing or reducing existing oxygen is small, and as described above, there is also a problem of promoting the absorption of hydrogen into molten copper.

For this reason, in order to promote deoxidation in molten copper, Japanese Patent Application Laid-Open Nos. 5-25559, 2561986, and 2561987 disclose molten copper in a melting furnace such as an induction furnace. It is disclosed that the surface is coated with charcoal or the like, and an inert gas is blown therein to promote a Boudouard reaction of CO ₂ + C → 2CO to perform deoxidation. However, even if an inert gas is blown in as in the publication, the entire molten copper in the induction furnace is basically in a stationary state, so that the reaction speed of the Boudoir reaction is slow, and sufficient deoxidation is performed on the entire molten copper. To achieve the effect, a processing time of about 20 to 30 minutes is required. In other words, these refining methods can be said to be methods suitable for performing in a melting furnace that can take a sufficient time for the refining process.

Next, the method of increasing the amount of oxygen in the molten copper as a means for reducing hydrogen has the effect of reducing hydrogen, but increases the amount of oxygen in the molten copper by that amount. Also, a method of performing the dissolution in a vacuum to volatilize hydrogen,
There are problems such as a decrease in productivity and an increase in equipment costs for melting the vacuum and melting costs.

Further, a method for removing the inclusions by filtering the molten copper with a heat-resistant filter such as a porous ceramic provided in the hot water gutter is also used. Although it is necessary to make the holes or the mesh fine, the filter tends to be clogged. Therefore, there is a problem that the productivity of melting and casting is hindered due to replacement of the filter and the melting cost is increased.

Therefore, these conventional refining techniques have limitations in the amount of impurities that can be reduced when removing oxygen, hydrogen, and inclusions in molten copper, and inevitably have the potential to cause new adverse effects. . For this reason, in the conventional refining technology, impurities in the copper alloy molten copper are reduced from the above-mentioned high level to oxygen of 20 ppm or less, hydrogen of 0.5 ppm or less, and oxide of 20 pp or less.
m or less, and the molten copper to be cast often contains the above-described level of impurities. Therefore, in the conventional refining technology, it is difficult to avoid the occurrence of the above-mentioned product failure due to the inclusion of these impurities.

The fatal problem of these prior arts is that even if these techniques can reduce the amount of impurities in the molten copper on the exit side of the melting furnace to some extent, the amount of impurities caused by entrapment in the atmosphere during the subsequent hot water transfer will be described. Cannot suppress the increase in Therefore, a high impurity content (50-500ppm of oxygen, 5ppp of hydrogen)
m, oxides of 200 to 300 ppm) to extremely low levels of less than 10 ppm of oxygen, less than 0.3 ppm of hydrogen, and less than 20 ppm of oxides. There is a need to reduce it. Then, in the limited time in the hot water gutter, the above-mentioned Japanese Patent Application Laid-Open
No. 25559, Patent No. 2561986, or Patent No. 2561987
Even if the time-consuming refining method disclosed in the official gazette is applied to the refining method of the hot water gutter, the high impurity amount in the molten copper in the hot water gutter is hardly reduced to the extremely low level. Can not.

As a method for refining molten copper and reducing impurities in this hot water gutter, there is Japanese Patent Application Laid-Open No. 6-212300.
According to the same publication, pure copper-based low-oxygen copper is melted in a shaft furnace that is easily sealed and easily reduced, and then the molten copper is continuously supplied to a mold through a holding furnace and a hot water gutter. A method for refining molten copper in a hot water gutter is disclosed. The refining contents of the hot water gutter are covered by coating the surface of the molten copper flowing down the hot water gutter with a carbon-based solid reducing agent and charging a nozzle having a rotating blade at the tip into the molten copper. This is a technique in which fine bubbles of inert gas are blown into molten copper flowing down a hot water gutter to reduce oxygen and hydrogen contained in the molten copper to 10 ppm or less and hydrogen to 0.3 ppm or less, respectively.

However, as described above, the technique disclosed in the publication is directed to a pure copper system, and has a small amount of oxygen and hydrogen absorbed from the atmosphere and is capable of continuous melting in a reducing atmosphere. -For casting with hot water gutters. Moreover, as described above, the pure copper system targeted by this technique does not contain an element that is easily oxidized as compared with the copper alloy, and accordingly, the amount of oxygen in the molten copper is relatively small. Therefore, the amount of impurities in the molten copper in the hot water gutter immediately before casting is at most 30% oxygen.
-40 ppm, hydrogen 2-3 ppm, and oxide 50-50 ppm, and it is relatively easy to reduce these impurities from the molten copper to the low level.

On the other hand, in the case of the copper alloy targeted by the present invention, as described above, the copper alloy is manufactured by a process in which impurities are easily contained in the molten copper. And for copper alloys, F
e, Sn, Mn, Mg, Ni, Cr, and other elements that are more easily oxidized than pure copper. Therefore, as described above, the amount of impurities in the molten copper in the hot water gutter immediately before casting is at a level several steps higher than in the publication. Therefore, according to the findings of the present inventors, the above-mentioned Japanese Patent Application Laid-Open No.
In the refining technology of pure copper in a hot water gutter disclosed in Japanese Patent Publication No. 00, molten copper alloy containing a high level of impurities is melted within a limited time or volume in the hot water gutter where the molten copper flows down. There is a limit to reducing the amount of impurities in the molten copper to the above-mentioned level uniformly for the entire copper, and particularly for electronic materials such as lead frames.

The present invention has been made in view of these problems of the prior art,
When melting and casting a copper alloy in an induction furnace, high levels of oxygen, hydrogen, and preferably oxide inclusions in the copper alloy molten copper can be removed at the same time, more specifically, the copper alloy after refining 20 ppm or less of oxygen contained in the ingot, preferably 10 ppm
Hereinafter, an object of the present invention is to provide a refining method capable of reducing the amount of hydrogen to 0.5 ppm or less, preferably 0.2 ppm or less.

[0023]

In order to achieve the above object, a method for refining a copper alloy according to the present invention comprises melting a copper alloy in an induction furnace and supplying molten copper to a mold through a hot water gutter. A method of refining molten copper in a hot water gutter, in which the surface of the molten copper flowing down the hot water gutter is coated with a carbon-based solid reducing agent, and a nozzle having a rotating blade at the tip is inserted into the molten copper. Then, fine bubbles of an inert gas are blown into the bottom of the molten copper flowing down the hot water trough to perform deoxidation and dehydrogenation, thereby reducing the oxygen contained in the copper alloy ingot to 20 ppm or less, preferably 10 ppm.
Or less, and 0.5 ppm or less of hydrogen, preferably 0.2 ppm or less, and preferably 20 ppm of oxides as inclusions.
The gist is to reduce the amount to the following (however, converted to the amount of oxygen).

The basic principle of the present invention is to prevent the absorption of oxygen and hydrogen from the atmosphere into the molten copper by coating the surface of the molten copper flowing down the hot water gutter with a solid reducing agent. The contact reaction between the oxygen in the molten copper and the solid reducing agent is promoted by bubbling or stirring of fine bubbles of inert gas and the flow of the molten copper flowing down the hot water trough to reduce oxygen in the molten copper.
(Deacidification). In addition, bubbling of the inert gas microbubbles promotes the contact reaction between the microbubbles and hydrogen in the molten copper, thereby incorporating hydrogen into the microbubbles and reducing the hydrogen in the molten copper. Furthermore, the deoxidation in the molten copper reduces and decomposes oxide-based inclusions such as Cu ₂ O that can be reduced, thereby reducing the inclusions.

According to the present invention, during the refining, a nozzle having a rotating blade at the tip is inserted into the molten copper, and fine bubbles of an inert gas are relatively formed at the bottom of the molten copper flowing down the hot water gutter. A large amount of gas is blown into the molten copper surface to increase the amount of inert gas microbubbles that escape from the bottom of the molten copper to the surface of the molten copper. Then, the reaction rate of deoxidation and dehydrogenation is accelerated and accelerated. In order to accelerate and accelerate the reaction rate of the deoxidation and dehydrogenation, it is necessary to blow fine bubbles of an inert gas as much as possible at the bottom of the molten copper flowing down the hot water trough. JP-A-6-212300
Although the gazette of the present invention shares the basic principle of the present invention, it does not disclose the technical idea of injecting fine bubbles of this inert gas into the bottom of the molten copper. Fine gas bubbles of an inert gas are blown from the upper part to the middle part.

As a result of investigations by the present inventors, the range of the depth of the hot water gutter used for melting and casting of ordinary copper alloys and the range of the molten copper depth differ from the molten copper bottom in the present invention. This is the bottom of the molten copper flow down the hot water gutter. The effect of deoxidation and dehydrogenation of molten copper is greater as the inert gas blowing position is deeper in the molten copper flow. Incidentally, the upper limit of the inert gas injection position is the bottom of the hot water gutter (the bottom surface of the hot water gutter that comes into contact with the molten copper).
From the depth of the molten copper to the height of 1/3 of the depth of the molten copper.When blowing into the upper part of the molten copper beyond this, the amount of fine bubbles of inert gas in the molten copper in the lower part of the molten gas blowing position decreases. However, the reaction rate of deoxidation and dehydrogenation of the lower part or the lower part of the molten copper cannot be accelerated or accelerated, and the effect of uniform and desired impurity reduction of the entire molten copper is lost. Further, the lower limit of the inert gas blowing position is a position where the rotating blade does not contact the bottom of the hot water gutter. If the depth is greater than this, the rotating blades (impellers) will collide with or come into contact with the bottom of the hot water gutter.

Further, in order to exert the effect of the blown-in inert gas, it is preferable to use fine bubbles as fine as possible, specifically, a bubble diameter of 1 mm or less. In order to form the fine bubbles, it is preferable to use a rotary blade provided at the tip of the nozzle charged in the molten copper and to generate fine bubbles by the shearing force of the rotary blade. By using the rotating blades, the effect of bubbling or fluidizing the molten copper by the inert gas is increased, and the efficiency of the contact reaction between oxygen in the molten copper and the solid reducing agent is also increased. Further, the lower the hydrogen partial pressure of the inert gas is, the higher the hydrogen absorption rate is.

The mechanism of deoxidation by the contact reaction between oxygen in the molten copper and the carbon-based solid reducing agent of the present invention is as follows: production of carbon dioxide by the reaction between carbon and oxygen in the molten copper: 2O
Generation of carbon monoxide by the reaction of + C → CO ₂ and generated carbon dioxide and carbon: Deoxidation by a two-stage reaction of CO ₂ + C → 2CO (Boudoir reaction, generated CO is diffused out of molten copper) Progresses. Of these, as described above, in the Baudou reaction, when the molten copper in the refining in the melting furnace is stationary, even if bubbling or stirring with an inert gas or the like, CO ₂ has a high solubility in the molten copper and is dissolved. remaining,
The reaction speed is slow. On the other hand, in the present invention, the contact reaction between the oxygen in the molten copper and the solid reducing agent is carried out by bubbling or stirring fine bubbles from the molten copper bottom of the inert gas and flowing the molten gas down the hot water gutter. Since the flow is promoted by copper, the rate of the Boudouis reaction and deoxidation is remarkably increased as described later.

The mechanism of the dehydrogenation of the present invention is as follows. The bubbling of the microbubbles of the inert gas for deoxidation promotes the contact reaction between these microbubbles and hydrogen in the molten copper. Utilizing the partial pressure difference of hydrogen in active gas microbubbles,
Hydrogen is incorporated into the inert gas microbubbles, and the inert gas incorporating the hydrogen is released into the atmosphere or atmosphere to reduce hydrogen in the molten copper. The mechanism of the dehydrogenation of the present invention is drastically promoted by blowing fine bubbles of an inert gas into the bottom of the molten copper of the hot water gutter, similarly to the deoxidation.

The method of reducing the hydrogen in the molten metal by utilizing the partial pressure difference of the hydrogen in the inert gas microbubbles has already been implemented as a method of reducing the hydrogen in the molten aluminum alloy. However, when the copper alloy, large specific gravity than aluminum alloys, it is also 8 g / m ³ density of molten copper,
The density is 3 to 4 times that of 2 g / m ^{3 of the} molten aluminum alloy, and the floating speed of the inert gas in the molten copper increases accordingly. If the floating speed of the inert gas microbubbles is high, the contact reaction time between the inert gas microbubbles and hydrogen in the molten copper is shortened. It is preferable to make the bubbles as fine as possible, specifically, fine bubbles having a bubble diameter of 1 mm or less, and it is preferable to promote stirring or flow of the molten copper. In order to form the fine bubbles, the stirring or the flow of the molten copper is promoted by using a rotating blade (impeller) inserted into the molten copper, and the inert gas fine bubbles are formed by the shearing force of the rotating blade. is necessary.

As for the rotation speed of the rotary blade for obtaining the fine bubbles, the higher the rotation speed, the finer the bubble of the blown inert gas can be made. Then, in the range of a normal hot water trough having a hot water transfer rate of 1 to 10 tons / hr, the diameter of the rotary blade is set to 100 to 100 mm in order to reduce the substantial amount of the bubble of the inert gas to be blown into the fine bubble of 1 mm or less. When 400 mm φ is used, as described later,
The rotation speed of the rotating blade is preferably 200 rpm or more. Further, in order to make the total amount of the bubble of the inert gas to be blown into the fine bubble of 1 mm or less, it is preferably 400 rpm or more. Incidentally, in the case of the molten aluminum alloy, the required number of rotations of the rotating blades is about 100 to 300 rpm in order to obtain the fine bubbles as described above. Therefore, the miniaturization of the bubble of the inert gas in the present invention is necessary from the technical problems of both the deoxidation and the dehydrogenation, and it is understood that this is a problem peculiar to the copper alloy molten copper. Since it is difficult to actually measure the diameter of the inert gas microbubbles in the molten copper at a high temperature, the measurement of the inert gas microbubble diameter was performed using a water model using water instead of the molten copper. More specifically, the definition of the inert gas microbubble diameter in the present invention is based on, first, the effect of the deoxidation and dehydrogenation of the present invention can be achieved (or not achieved), and the rotation speed of the rotating blades in the molten copper. To
Obtained by the stirring experiment of the molten copper in the actual hot water gutter, visualize the state of the inert gas bubbles when the rotation speed of this rotary blade was reproducibly tested with a water model by experimental equipment simulating the hot water gutter, The measurement is performed by measuring the bubble diameter from the image. The results of this water model correspond well with the bubble diameter estimated from the actual molten copper.

Further, the mechanism of the deintercalation of the present invention is as follows:
Deoxidation of the molten copper is intended to reduce mainly oxide-based inclusions among the inclusions. Usually, oxygen in the molten copper does not exist in the form of dissolved oxygen but in the form of oxide-based inclusions such as Cu ₂ O. Therefore, by the deoxidation of the molten copper, the oxide-based inclusions are reduced and decomposed according to the reaction of Cu ₂ O → Cu + O, and the oxide-based inclusions in the molten copper are reduced to 20% in terms of oxygen amount.
Significantly reduced to below ppm. As a result, when filtering the molten copper by the ceramic filter provided in the hot water gutter to remove inclusions in the molten copper, the load on the filter is greatly reduced. Therefore, the removal efficiency of the carbide-based inclusions and the unreacted oxide-based inclusions that have not been removed by the deoxidation of the molten copper also increases. In addition, as a result of greatly reducing the absolute amount of load on the filter due to the oxide-based inclusions, clogging of the filter is reduced and the life of the filter is extended. As a result, the above-mentioned problems such as the dissolution / casting productivity being hindered due to the replacement of the filter and the increase in the melting cost are greatly improved.

By the refining of the present invention, the molten copper is preferably such that the amount of oxygen contained in the molten copper is 20 ppm or less, preferably 10 ppm or less, and the amount of hydrogen is 0.5 ppm or less, preferably 0.2 ppm or less.
pm or less, it is not necessary to remove oxide inclusions in the molten copper by filtering the molten copper with a filter installed in the hot water gutter, depending on the type of copper or the required characteristics of the product Becomes However, particularly in the case of copper alloys for electronic materials, etc., which have strict product requirements, in other words, for which it is required to purify molten copper, after refining in the hot water gutter, a ceramic filter provided in the hot water gutter further melts the molten copper. It is preferable in terms of quality assurance that oxides in copper, or inclusions from other carbides or refractories be removed. The ceramic filter is made of a ceramic such as alumina, mullite, silicon carbide or the like and has a heat resistance and a strength capable of withstanding the temperature and thermal shock of molten copper, and is made of a noodle or honeycomb-like porous body. It is preferable to use

As described above, in the present invention, the use of a carbon-based solid reducing agent or an inert gas which does not cause secondary contamination of molten metal without using a compound such as flux which easily causes secondary contamination of molten copper. Is also one of the features.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the refining method of the present invention is shown in FIG.
To 3 below. That is, the refining method of the present invention is performed in the hot water trough 3 for transferring the hot water from the induction furnace 2 to the mold 4, and also in the hot water trough 3, the processing time or the time at which the effect of the present refining method can be exhibited. It is preferable that the transfer is performed as soon as possible (downstream of the transfer gutter 3) as much as possible after ensuring the length of the transfer gutter. The inert gas used in the refining method of the present invention is
The nozzle 5 inserted into the bottom of the molten copper from above and the rotating blades 6 provided at the tip of the nozzle 5 cause fine bubbles 7
Is blown into the bottom of the molten copper to perform deoxidation and dehydrogenation. Although only one nozzle 5 is disclosed in FIGS. 1 to 3, a plurality of nozzles 5 may be provided along the longitudinal direction of the hot water gutter 3. Is appropriately selected according to conditions such as the above.

Examples of the carbon-based solid reducing agent in the present invention include charcoal and coke. These carbon-based solid reducing agents do not need to be powders, and may be in the form of a lump in a size generally used. Commonly used solid reducing agents include metal Ca, metal Mg, metal Al, and the like.As described above, these components are liable to cause secondary contamination of molten copper by the components of the solid reducing agent. However, it is permissible to use it supplementally in order to improve the reducing ability of the carbon-based solid reducing agent within a range that does not cause secondary contamination of the molten copper. As shown in FIGS. 1 to 3, the carbon-based solid reducing agent 8 is used to prevent reoxidation of molten copper and re-absorption of hydrogen and to improve the refining efficiency of molten copper.
It is added so as to cover the entire surface of the molten copper in the hot water gutter.

At the tip of the inert gas supply nozzle 5 used in the refining method of the present invention, the tip of the nozzle 5 is viewed from below.
As shown in FIG. 2 (A) and a longitudinal sectional view 2 (B) of the tip of the nozzle 5, the rotating blades 6 provided in a cross shape (four in FIG. 1)
And a slit S provided in the rotary blade 6 is integrally provided. The rotation of the rotary blades 6 by the rotational drive of the nozzle 5 (the drive source is not shown) generates a stirring force for the molten copper, and the inert gas blown into the molten copper through the nozzle 5 and the slit S is The bubbles are sheared by the rotating force of the rotating blades 6 to form fine bubbles 7 and float or move in the molten copper. As described above, in order to reduce the size of the bubble of the inert gas, preferably to the size of the bubble of 1 mm or less, it is preferable that the shearing force of the rotating blade is larger. In order to increase the shearing force, it is preferable that the rotation speed of the rotating blade is higher, and the stirring force of the molten copper is increased as the rotation speed of the rotating blade is higher. Therefore, when the diameter of the rotating blade is 100 to 400 mm φ, the rotating speed of the rotating blade is preferably at least 200 rpm, but if it exceeds 1400 rpm, the flow of molten copper in the hot water gutter may be disturbed. Nature occurs. Therefore, the rotation speed of the rotating blade is preferably 200 to
The range is 1400 rpm, more preferably 400 to 800 rpm. Also, the number of rotating blades is preferably large in order to increase the shearing force and reduce the bubble diameter,
It is preferable in terms of strength and production to provide a sheet. In addition, this nozzle and rotating blades have heat resistance and strength so as to withstand the temperature of molten copper and thermal shock of high-speed rotation, for example,
It is made of ceramics such as graphite and SiC or a mixture or composite of these ceramics.

As the inert gas in the present invention, nitrogen is used.
(N ₂ ), argon (Ar), carbon dioxide (CO ₂ ) and the like. However, since nitrogen is absorbed by the copper alloy molten copper and may deteriorate the mechanical properties of the copper alloy, the inert gas used is preferably argon from this point. The blowing amount of the inert gas is the refining mechanism of the present invention,
A relatively large amount of fine gas of inert gas is blown into the bottom of the molten copper flowing down the hot water gutter to increase the amount of fine gas bubbles of inert gas that escape from the bottom of the molten copper to the surface of the molten copper, thereby increasing In view of accelerating and accelerating the reaction rates of deoxidation and dehydrogenation by promoting mass transfer in the above, it is preferable that the amount is as large as possible. The specific amount varies depending on the amount of molten copper flowing down the hot water gutter, but is set to 20 Nl / min or more in the range of a normal hot water gutter having a hot water flow of 1 to 10 ton / hr. However, an excessively large amount disturbs the flow of molten copper in the hot water gutter, so the upper limit is preferably set to 100 Nl / min.

Further, as shown in FIG.
In the transfer from 2 to the hot water gutter 3, these furnaces are tilted toward the hot water gutter, and the molten copper is transferred from the hot water outlet of the furnace toward the hot water gutter with a drop. Then, in a portion where the molten copper is transferred from the melting furnace to the casting machine with a drop, the molten copper entraps oxygen, moisture, and the like in the air atmosphere and is easily absorbed. Therefore, in order to prevent an increase in the amount of oxygen or hydrogen in the molten copper due to this, it is preferable to seal the molten copper during the hot water transfer with an inert gas. When sealing the molten copper, as shown in Fig. 3, the atmosphere from the furnace inlet to the molten metal dropping point of the hot water gutter is covered with the cover 9, and the cover 9 is inerted into the cover through the inlet 10 of the cover. A preferred embodiment is to introduce a gas, seal the molten copper with this inert gas, and prevent the absorption of oxygen and moisture in the air atmosphere. With this seal, an increase in the amount of oxygen or hydrogen in the molten copper transferred to the hot water gutter can be suppressed, and the load of the refining method of the present invention on the hot water gutter can be reduced.

The refining method of the present invention can be performed in combination with the existing refining method in the melting furnace. As described above, in the refining method of the present invention, the oxygen content of the molten copper is 10 ppm or less, and the hydrogen content is 0.3 ppm or less, preferably 0.
The content can be 2 ppm or less, preferably the amount of inclusions is 20 ppm or less. Basically, the existing refining method in the melting furnace or the holding furnace is not required depending on the type of copper or the required characteristics of the product. However, in particular, the required product characteristics are severe, in other words, for copper alloys for electronic materials and the like, where more purification is required, it is preferable to combine with the existing refining method in the melting furnace or hot water gutter for quality assurance. In addition, it is preferable in that the impurity load on the refining method of the present invention is reduced. Therefore, JP-A-5-25559, JP-A-2561986, or JP-A-5-256559 for promoting deoxidation in the molten copper.
The method disclosed in, for example, Japanese Patent No. 2561987 discloses a method of coating a molten copper surface in an induction furnace with charcoal and blowing an inert gas to perform deoxidation. The method may be appropriately combined with a method of filtering the molten copper through a filter provided to remove inclusions in the molten copper. In particular, the method of removing inclusions in molten copper by providing a porous ceramic filter in a hot water gutter is a method of removing or reducing non-oxide-based inclusions such as carbide-based inclusions that cannot be reduced by the deoxidation of the present invention. It is effective for

[0041]

Next, embodiments of the present invention will be described. Cu-Fe, Cu-Sn
In order to obtain copper alloys of manganese, Cu-Mn, Cu-Mg, Cu-Ni, and Cu-Cr, the melting raw material is heated to the melting point of each alloy + 150 ° C.
(1200-1250 ° C), and the amount of alloy components was adjusted. The Cu-Fe system is Cu-0.1Fe-0.03P, and the Cu-Sn system is Cu-
3.2Ni-0.7Si-1.25Sn-0.3Zn, Cu-Ni system is Cu-1.8Ni-0.4S
i-1.0Zn copper alloy for lead frame material, other Cu-Mn
System, Cu-Mg system, Cu-Cr system, Mn, Mg, Cr 0.2 to 1% each
Containing copper alloy. The melting step was performed by coating the entire surface of the molten copper with charcoal. After the melting, the melting furnace was tilted to transfer each molten copper to a hot water trough. The drop between the melting furnace and the hot water gutter is about 1m, and the hot water flow speed of the hot water gutter (melt speed) 4.5t / h
r, depth of molten copper flow in hot water gutter 100mm, molten copper temperature is 1
150-1200 ° C.

Among the refining conditions of these molten coppers in the hot water transfer gutter, the seal use conditions (with or without argon inert gas seal) shown in FIG. The ingot of the copper alloy was manufactured after variously changing the conditions for blowing the inert gas into the hot water gutter and the conditions for using the molten copper filtration filter after blowing the inert gas. In addition, as a molten copper filtration filter, a 50-mm-thick alumina noodle-shaped porous plate (manufactured by Kobe Steel, Actthermic) was used. The inert gas for molten copper refining was blown with a single nozzle with a nozzle radius of 100 mm (rotary blade diameter 300 mm) with four cross blades at the tip, as shown in Fig. 2, using argon. , Argon gas blowing rate is 20-60Nl /
The rotation speed of the rotary blade was changed within the range of 200 to 1000 rpm. In addition, the argon gas was blown to the bottom of the molten copper 20 mm above the bottom of the hot water gutter (in the depth of 1/3 molten copper from the bottom of the hot water gutter) in the invention example, and in the molten copper bottom or in the comparative example. 50 mm above the bottom of the hot water gutter, from the bottom of the hot water gutter
The upper part of the molten copper exceeded 1/3 molten copper depth (the upper limit of the present invention). Table 1 shows the bubble diameter due to this nozzle blowing.
(Measured by the water model) is described. In the case of a cell having a large bubble diameter, argon gas was blown with a normal lance (a pipe having a hole at the tip) without using the rotating blade. And the molten copper before refining in the hot water gutter,
After refining, oxygen and hydrogen of the slab cast by the mold were measured and compared. Table 1 shows the refining conditions and impurity amounts of the above copper alloys.

As is clear from Table 1, Invention Examples Nos. 1 to 10
Although the amount of impurities in the molten copper in the hot water gutter immediately before copper alloy casting is as high as 200 to 250 ppm oxygen and 3 to 5 ppm hydrogen, the extremely low oxygen content of copper alloy slabs is 10 ppm or less and hydrogen is 0.3 ppm or less. It has been reduced to a lower level. Further, the amount of the oxide-based inclusions is the same as the oxygen amount when converted to the oxygen amount. Therefore, the oxygen amount level in Table 1 is reduced to an extremely low level of 20 ppm or less. In addition, Nos. 2 and 10 in which the head of the melting furnace and the hot water gutter were not sealed with the argon gas shown in FIG. Oxygen in molten copper in hot water gutter,
The amount of hydrogen is relatively high, indicating the sealing effect of argon gas. Furthermore, among the invention examples, the number of revolutions of the rotating blades is comparatively small as No. 1 at 200 rpm, the blowing amount of argon gas is comparatively small as 20 l / min as No. 6, and the bubble diameter of argon gas is 2 mm. In No. 8 which is relatively large and No. 9 in which inclusions were not removed by the filter after refining in the hot water gutter, the level of the amount of impurities in the cast slab was within the scope of the present invention, but compared to other invention examples. It is getting higher. Therefore, the superiority of each preferable condition of the refining method of the present invention can be understood. In addition, from the observation of the clogged state of the filter, the service life of the filter of the invention example was found to be 3 to 10 times longer than that of the filter of the comparative example.

On the other hand, in Comparative Examples Nos. 11 to 14, the copper alloy ingot of the present invention generally exceeded the specified oxygen content of 10 ppm or less and the content of hydrogen of 0.3 ppm or less, and had a high impurity content. In particular, Comparative Examples Nos. 11 and 13 correspond to the hot water gutter refining method of JP-A-6-212300, except for the target copper, and have a diameter of 1 mm.
Despite being within the invention conditions except for the blowing position of argon gas, such as blowing a large amount of the following fine bubble diameter, the blowing position of argon gas is not at the bottom of the molten copper of the present invention, but at the top of the molten copper. Therefore, the impurity amount is out of the range of the present invention. Further, Comparative Examples No. 12 and 14 in which argon gas was simply blown by a nozzle without using a rotating blade
Also, since the bubbles are coarse, the amount of impurities is higher than that of Comparative Examples Nos. 11 and 13. Therefore, the above results show the importance of each requirement of the present invention.

[0045]

[Table 1]

[0046]

As described above, according to the copper alloy refining method of the present invention, when the copper alloy is melted and cast in an induction furnace, oxygen, hydrogen and oxide-based intervening in the copper alloy molten copper. The amount of oxygen contained in the refined copper alloy ingot can be reduced to 20 ppm or less, the amount of hydrogen can be reduced to 0.5 ppm or less, and the amount of inclusions can be reduced to 20 ppm or less in terms of oxygen. Therefore, the quality of a copper alloy for an electronic material such as a lead frame can be significantly improved, and the use of the copper alloy can be expanded.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of the present invention and showing a method of refining molten copper in a hot water gutter.

FIG. 2 shows an inert gas blowing nozzle structure used in the present invention, and FIG. 2 (A) is a view of the tip of the nozzle viewed from below,
2 (B) is a longitudinal sectional view of the tip of the nozzle 5. FIG.

FIG. 3 is an explanatory view showing another embodiment of the present invention and showing a method of refining molten copper in a hot water gutter including a seal at a molten metal drop portion.

[Explanation of symbols]

1: melting raw material 2: induction melting furnace 3: hot water gutter 4: casting machine 5: nozzle 6: rotating blade 7: fine bubbles 8: charcoal 9: cover 10: inert gas inlet S: slit

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shigenobu Yasunaga 1-5-5 Takatsukadai, Nishi-ku, Kobe In Kobe Research Institute, Kobe Steel Co., Ltd. (72) Inventor Yoji Miyagawa 14 Nagafu Minatomachi, Shimonoseki City, Yamaguchi Prefecture No. 1 Inside Kobe Steel's Chofu Works (72) Inventor Hirofumi Okada 14-1 Nagafu Minato-cho, Shimonoseki City, Yamaguchi Prefecture Inside Kobe Steel's Chofu Works, (72) Inventor Eiji Yoshida 14 Nagafu Minato-cho, Shimonoseki City, Yamaguchi Prefecture No. 1 Kobe Steel, Ltd. Chofu Works (72) Inventor Yoshiaki Narishige 14-1, Nagafu Minato-cho, Shimonoseki City, Yamaguchi Prefecture Kobe Steel Co., Ltd., Chofu Works (72) Inventor Kazuhiro Oe, Shimonoseki City, Yamaguchi Prefecture No. 14 No. 1 Kobe Steel, Ltd. Chofu Works

Claims (11)

[Claims] 1. A method for refining molten copper in a hot-water trough when the copper alloy is melted in an induction furnace and the molten copper is supplied to a mold through a hot-water trough, the surface of the molten copper flowing down the hot-water trough. Is coated with a carbon-based solid reducing agent, and a nozzle having a rotating blade at the tip is inserted into the molten copper, and fine gas of inert gas is blown at the bottom of the molten copper flowing down the hot water gutter to deoxidize. A method for refining a copper alloy, comprising reducing oxygen and hydrogen contained in a copper alloy ingot to 20 ppm or less and hydrogen to 0.5 ppm or less, respectively, by performing dehydrogenation. 2. The method for refining a copper alloy according to claim 1, wherein the upper limit of the position at which the fine bubbles of the inert gas are blown is a height from the bottom of the hot water gutter to one third of the molten copper depth. . 3. The method for refining a copper alloy according to claim 1, wherein the blown-in inert gas is formed into fine bubbles having a bubble diameter of 1 mm or less by a shearing force of a rotating blade charged in the molten copper. . 4. The oxygen contained in the copper alloy ingot is reduced to 10 pp.
The copper alloy refining method according to any one of claims 1 to 3, wherein the copper alloy is reduced to m or less. 5. The method according to claim 5, wherein hydrogen contained in said copper alloy ingot is 0.2 p.
The method for refining a copper alloy according to claim 1, wherein the copper alloy is reduced to pm or less. 6. The method for refining a copper alloy according to claim 1, wherein the carbon-based solid reducing agent is charcoal and / or coke. 7. The refining method for a copper alloy according to claim 1, wherein the refining in the hot water gutter is performed immediately before a mold. 8. The method according to claim 1, wherein after the refining in the hot water gutter, the molten copper is filtered by a filter provided in the hot water gutter to remove inclusions in the molten copper. Copper alloy refining method. 9. The method according to claim 1, wherein the molten copper is sealed with an inert gas at a portion where the molten copper is dropped from the induction furnace to the hot water gutter. The refining method of the copper alloy described in the above. 10. The method for refining a copper alloy according to claim 1, wherein the copper alloy is for an electronic material. 11. The method for refining a copper alloy according to claim 1, wherein the copper alloy is used for a lead frame.