JPH0794063B2 - High-purity copper ingot manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a high-purity copper ingot.

[0002]

2. Description of the Related Art Conventionally, high-purity copper has been used not only for electronics such as bonding wires and metal / semiconductor contacts, but also for conductive materials such as superconductivity, ultra-high voltage, ultra-high vacuum or acoustic equipment, and cooling media for cryogenic equipment. Or in many advanced technology fields such as high-proof laser mirrors,
It has been widely used as one of the materials that control its performance. In recent years, the demand for high-purity copper materials used for such applications has significantly increased, and accordingly, the shapes required for high-purity copper materials have irregularities from simple ones such as plates and tubes. It is diversifying to complex things.

Conventionally, a continuous casting method in vacuum or in an inert gas atmosphere has been established as a method for producing a high-purity copper ingot using high-purity copper having a purity of 99.999% or more as a raw material. In the case of a simple shape such as a plate or tube, this method can be said to be a suitable method because it can be manufactured at a low cost while maintaining the purity of the raw material. However, the continuous casting method cannot produce a high-purity copper ingot having a complicated shape, and even if the shape is simple, if the molded product does not require a length, the cost is rather high. There was a problem.

Since it is difficult to manufacture a high-purity copper product having a complicated shape by a continuous casting method, first, a high-purity copper ingot having a simple shape is produced by a batch casting method, and then this is processed by cutting or cutting. It is formed into a desired shape by processing. Therefore, in addition to the possibility of contamination with impurities, there is a problem in that the yield is poor because cutting chips and cut pieces are produced during processing, and the use of expensive high-purity copper significantly increases the production cost.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and can produce a high-purity copper ingot of a desired shape which maintains the high-purity characteristics of the raw material at low cost. The purpose of the present invention is to provide a new method for producing a high-purity copper ingot.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems and found that high-purity copper is melted by high-frequency heating in a crucible under high vacuum.
After pouring the melt into the mold placed under the crucible through the hole opened at the bottom of the crucible, the high-frequency heating region at the crucible position moves up and down between the crucible and the bottom of the mold at a predetermined speed. By moving the high frequency coil as described above, it was found that the above problems could be solved, and the present invention could be achieved.

That is, according to the present invention, high purity copper having a total content of silver and sulfur of 1 ppm or less and a purity of 99.999% or more is used as a raw material, and is molded and cast in a high vacuum while maintaining the high purity characteristics of the raw material. In the method, first, the above-mentioned high-purity copper, which is a raw material, is put into a crucible having a hole in the bottom for dropping the molten metal. At that time, there is no problem even if the granular raw material copper falls into the mold. Next, the raw material copper inside is melted by high-frequency heating the crucible in a high vacuum, and the molten metal is dropped from a hole at the bottom of the crucible into a mold shaped into a desired shape. At that time, the raw material copper in the crucible does not have to be completely melted down. When the molten metal stopped falling from the crucible, set the high frequency heating area at the crucible position to 1 ~.
At a speed of 10 mm / min, the crucible is moved to the mold position provided in the lower part of the crucible, lowered toward the bottom of the crucible, and stopped at the bottom of the mold for a predetermined time. After confirming that the raw material copper at the bottom of the mold was completely melted by the thermocouple equipped at the bottom of the mold, the heating area was raised again toward the crucible at the above speed to remove the raw material copper in the mold. Completely melt-molds one by one. Further, when the heating region reaches the crucible position, the heating is stopped again for a predetermined time, and the raw material copper remaining in the crucible is completely melted down.

In many cases, it is sufficient for the high-frequency heating region to move at least one reciprocation between the crucible and the bottom of the mold, but in the case of producing a high-purity copper ingot with a particularly complicated shape, If you move it back and forth several times, you can get higher quality. However, the operation of moving the heating region must be completed by the ascending movement from the bottom of the mold to the upper part of the ingot, and the high frequency heating must be completed above the ingot. This is because molten copper causes a shrinkage of 4.1% in body expansion coefficient during solidification, so that it may form cavities when rapidly cooled. After the operation of moving the heating region is completed, the molten metal in the mold can be gradually cooled to obtain a high-purity copper ingot having a desired shape.

In the method for producing a high-purity copper ingot of the present invention, an apparatus equipped with a movable high-frequency coil for heating and melting raw material copper in a crucible and a mold is used. The device is
It consists of a vertical quartz bell jar connected to a vacuum exhaust device that can make a high vacuum inside, and inside the bell jar, there is a mold fixed to a support, and a crucible placed above it. Has a hole at the bottom for dropping the melted raw material copper into the mold.

There are roughly two types of molds used in the above apparatus, one is an integral mold and the other is a split mold. The integral mold is used when manufacturing an ingot having a simple shape in which the molded ingot can be taken out from the upper opening of the mold, and the split mold is an ingot having a complicated shape that cannot be taken out from the opening. It is used when manufacturing.

[0011]

According to the method for producing a high-purity copper ingot of the present invention, when the molten metal of the raw material copper does not fall from the crucible, the high-frequency heating region at the crucible position is transferred to the bottom of the mold at a speed of 1 to 10 mm / min. It is descending. This is done in order to completely melt the molten metal dropped into the mold from the crucible and solidified in the mold in the mold together with the descending high-frequency heating region. Further, the movement is stopped for a predetermined time when the heating region reaches the bottom position of the mold. This is because in order to dissolve the granular mass that has been moved to the bottom of the mold as described above, and the granular mass that has fallen from the crucible hole to the bottom of the mold when the raw material copper is put into the crucible, It is stopped until it is confirmed that they are completely melted by a thermocouple equipped at the bottom of the mold. By this operation, the granular solids collected at the bottom of the mold are melted, and at the same time, the molten metal at the bottom of the mold is completely filled and melt-molded as the mold.

After that, the heating region is raised again from the bottom of the mold toward the crucible. This is because, depending on the capacity of the heating source and the melting width of the mold, there may be a part where the granular mass remains and the molten metal is not completely filled in the mold. This is because. Further, when the heating area reaches the crucible position, the movement is stopped again for a predetermined time. This is because the raw material copper remaining in the crucible is completely melted down in the mold.

That is, the moving operation of the high-frequency heating region is carried out in order to uniformly melt-form the molten metal in the mold.

Further, since the present invention is formed and cast by a batch method, ingots having various shapes can be obtained, and cutting wastes and cutting pieces are not generated, resulting in very little loss of raw material.

Further, according to the present invention, the high-purity copper raw material is melted by high-frequency heating in a high vacuum and is molded and cast in a high vacuum. Purity characteristics can be retained.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited by the following examples.

[0017]

Example 1 A method for producing a high-purity copper ingot of the present invention using the high-purity copper ingot production apparatus shown in FIG. 1 will be described below.

FIG. 1 is a cross-sectional view showing the apparatus used in the present embodiment, in which a graphite mold 1 formed in conformity with the shape of the ingot to be manufactured is fixed by a supporting base 2, and the upper part thereof has a bottom part. An integral graphite crucible 3 having a hole for dropping the molten metal is placed on. The entire device is covered with a bell jar 4 made of quartz, and the bell jar 4 made of quartz is directly connected to a vacuum exhaust device, so that the inside thereof can be made to have a high vacuum. Further, a high-frequency coil 5 is provided outside the quartz bell jar 4, and the high-frequency coil 5 is movable so as to heat from the crucible 3 inside the quartz bell jar 4 to the bottommost position of the mold 1. It has a structure. In addition, graphite mold 1
A PR thermocouple 6 is provided at the bottom of the graphite mold 1, so that the temperature of the bottom of the graphite mold 1 can be measured.

In this embodiment, first, about 1 kg of high-purity copper having a total content of silver and sulfur of 1 ppm or less and a purity of 99.999% or more is used.
Put it in the crucible 3 and place it on top of the graphite mold 1,
These were covered with a quartz bell jar 4 and connected to a vacuum exhaust device. Next, the degree of vacuum inside the quartz bell jar 4 is raised to 10 ⁻³ to 10 ⁻⁵ Torr by an evacuation device and held, and the high frequency coil 5 is set at a position where the crucible 3 is placed and heated. Then, the high-purity copper contained in the crucible 3 was dissolved.

The molten high-purity copper drops into the graphite mold 1 through the hole formed in the bottom of the crucible, and when the molten metal does not fall from the crucible, the high-frequency coil 5 is heated to 5 mm / min. I lowered it at a speed. When the high-frequency coil 5 reaches the bottom of the graphite mold 1, the movement is stopped in a heated state, and after the PR thermocouple 6 confirms that the copper at the bottom of the graphite mold 1 is completely melted, it is 5 mm / min again. The heating was completed by raising the temperature to the upper part of the mold at the speed of.

After the heating was completed, the molten metal in the graphite mold 1 was gradually cooled to obtain an ingot having a diameter of 22 mm and a length of 300 mm.

The obtained ingot did not lose its high-purity characteristics at the time of raw material, and had no loss such as cutting chips.

[0023]

Example 2 A method for producing a high-purity copper ingot according to the present invention using the high-purity copper ingot production apparatus shown in FIG. 2 will be described below.

FIG. 2 is a cross-sectional view showing the apparatus used in this example, and the apparatus used in Example 1 except that the mold formed in conformity with the shape of the ingot to be manufactured is a split mold. It is a device similar to.

In this example, 2 kg of high-purity copper as a raw material was used, and the high-frequency coil 5 was made to reciprocate between the position where the crucible was installed and the bottom of the mold twice, and the same procedure as in Example 1. A high-purity copper ingot was manufactured.

The obtained ingot did not lose its high-purity characteristics at the time of raw material, and had no loss such as cutting chips.

[0027]

As a result of the development of the present invention, it has become possible to manufacture a homogeneous high-purity copper ingot having a desired shape while maintaining the high-purity characteristics of the raw material. Further, according to the present invention, even if expensive high-purity copper is used as a raw material, the high-purity characteristics of the raw material can be maintained and loss is extremely small, so that a high-purity copper ingot can be produced at low cost. became. Furthermore, the present invention can be easily implemented using a simple device, and therefore has an extremely high industrial value.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a high-purity copper ingot manufacturing apparatus used in the method for manufacturing a high-purity copper ingot of the present invention.

FIG. 2 is a sectional view showing another example of a high-purity copper ingot manufacturing apparatus used in the method for manufacturing a high-purity copper ingot of the present invention.

[Explanation of symbols]

 1 ... Graphite mold 2 ... Support base 3 ... Crucible 4 ... Quartz bell jar 5 ... High frequency coil 6 ... PR thermocouple 7 ... Split mold

Claims (1)

[Claims] 1. A method of forming and casting in high vacuum while using a high-purity copper having a total content of silver and sulfur of 1 ppm or less and a purity of 99.999% or more as a raw material while maintaining the high-purity characteristics of the raw material. Then, put the above-mentioned raw material copper into a crucible having a hole for dropping the molten metal in the bottom part, and melt the raw material copper by high-frequency heating in a high vacuum, and then melt the molten metal into a desired internal shape from the hole in the bottom part of the crucible. The step of dropping into the mold with the high frequency heating area at the crucible position
At a speed of 1 to 10 mm / min, it is lowered toward the bottom of the mold equipped at the bottom of the crucible, stopped at the bottom of the mold for a predetermined time, and then raised again toward the crucible at the above speed, and the crucible position In the method for producing a high-purity copper ingot, the step of gradually cooling the molten metal in the mold after performing the operation of stopping for a predetermined time at least once.