JPH0543954A - Device for purifying metal - Google Patents

Abstract

PURPOSE:To provide a purifying device for a metal by which a molten metal can be purified at a high speed. CONSTITUTION:Plural sets of unit furnaces 1 composed of a nucleus generating chamber 2 arranged with a nucleus generating device 4 for generating solid phase particles 10 and a nucleus melting chamber 3 for melting the solid phase particles 10 are connected with the nucleus melting chamber 3 in the unit furnace 1 and the nucleus generating chamber 2 in the following unit furnace 1 through a trough 11 in series. The nucleus generating chamber 2 and the nucleus melting chamber 3 in the unit furnace 1 are partitioned with a parting wall 6 provided with a passage 5 at a lower part and molten metal temps. in respective chambers 2, 3 can individually be controlled with a heating body 8 embedded in the furnace wall, and a pair of discharging rolls 7 exposing the roll surfaces rotating downward at the lower part of the nucleus generating chamber 2 are provided. By this method, since the solid phase particles 10 generated in the nucleus generating chamber 2 are forcedly shifted into the nucleus melting chamber 3 by being concentrated with the discharging roll 7, the purifying speed in the molten metal 9 is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal purifying apparatus for producing high-purity metal used as a material for electronic devices such as bonding wires and memory disks.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and refinement of electronic equipment, the metal materials used for this have been found to be conductive, flexible,
Further improvement in surface properties is required, and in response to this, the development of metal materials based on high-purity metals is becoming active year by year. The metal purification methods for obtaining high-purity metals are roughly classified into an electrolysis method and a segregation method, but the segregation method is superior for removing a trace amount of impurities. The segregation method is a purification method that applies a solute distribution law when a molten metal is solidified, and a zone melting method and a solidification method are known.

The above-mentioned distribution law will now be described with reference to the state diagram. FIG. 2 shows partition coefficient K [K = (solute concentration of crystallized solid phase) / (initial solute concentration) when the liquidus temperature is reached]
Is a phase diagram of a metal containing a solute having a value of less than 1, and most of the impurity elements have K <1. Now, when the melt having the solute concentration C ₀ in this state diagram is being cooled and the temperature reaches the liquidus temperature T ₁ , nuclei (solid phase particles) having the C ₁ concentration crystallize first. When the temperature is further lowered, the solute concentration of the solid phase that crystallizes gradually increases, but while the temperature is kept at T ₁ , solid phase particles having the solute concentration C ₁ crystallize out.

By the way, the above-mentioned purification method by the solidification method has been conventionally performed in a batch method and is inferior in productivity, and in order to improve this, the present inventors have succeeded in continuously producing high-purity metal. We have developed a metal purifier that can be manufactured (Japanese Patent Application No. 61-241037). As shown in FIG. 3, this metal purifying apparatus is a nuclear melting chamber that dissolves the nucleation chamber 2 in which the nucleation device 4 for solid phase particle generation is arranged and the solid phase particles 10 generated in the nucleation chamber 2. A plurality of unit furnaces 1 each consisting of a chamber 3 are connected in series via a trough 11 to a nuclear melting chamber 3 of the previous unit furnace 1 and a nucleation chamber of the next unit furnace (not shown). The nucleation chamber 2 and the nucleation chamber 3 are separated by an underflow type partition wall 6, and the floor of the underflow portion between the nucleation chamber 2 and the nucleation chamber 3 is separated from the nucleation chamber 2 to the nucleation chamber. 3 has a structure in which the molten metal temperature can be controlled for each of the chambers 2 and 3 by providing a downwardly sloping slope to the chamber 3 and by using the heating element 8 embedded in the furnace wall.

Next, a method for purifying a molten metal containing a solute having a distribution coefficient K of less than 1 using this apparatus will be described. First
Solid-phase particles 10 generated by the nucleation apparatus 4 in the nucleation chamber 2 of the unit furnace 1 are allowed to flow naturally from the nucleation chamber 2 to the nucleation dissolution chamber 3 along the slope of the floor of the underflow portion, The solid phase particles 10 flowing into the melting chamber 3 are remelted in the nuclear melting chamber 3 to enhance the purity of the molten metal 9 in the nuclear melting chamber 3, and then the molten metal 9 is passed through a trough 11 to produce a second unit furnace (not shown). The same operation as that performed in the first unit furnace 1 is performed again with the set temperature of the molten metal lowered somewhat, and the same operation is repeated until the final unit furnace,
The purity of the molten metal 9 is gradually increased.

[0006]

However, in such a metal purifying apparatus, even if a large amount of solid phase particles are generated in the nucleation chamber, the movement of the solid phase particles to the nucleation melting chamber is caused by gravity flow. Due to the fact that an upward flow occurs in the molten metal in the nucleation chamber due to the effect of the high temperature molten metal in the nuclear melting chamber, and the solid-phase particles are difficult to settle, the generated solid-phase particles undergo nuclear fusion. Even if the solid phase particles do not easily move to the chamber and the production rate of the solid phase particles is increased, the production rate of the high-purity metal is saturated and there is a problem that the required production rate cannot be obtained.

[0007]

The present invention has been made as a result of intensive studies in view of such a situation, and an object thereof is to provide a metal purifying apparatus capable of producing high-purity metal at high speed. To provide. That is, the present invention, a plurality of units of a unit furnace consisting of a nucleation chamber in which a nucleation apparatus for solid phase particle generation is arranged and a nuclear melting chamber for melting solid phase particles generated in the nucleation chamber, The nucleation chamber of the unit furnace and the nucleation chamber of the next unit furnace are connected in series via a gutter, and the nucleation chamber and the nucleation chamber of the unit furnace are partitioned by a partition wall provided with a passage at the bottom, and each chamber In the metal purification device, the temperature of the molten metal was controlled individually by the heating elements embedded in the furnace wall.In the lower part of the nucleation chamber, a pair of discharge rolls with downwardly rotating roll surfaces exposed to the molten metal were installed. It is characterized by having done.

The apparatus of the present invention comprises a pair of solid phase particle discharge rolls (hereinafter referred to as discharges) for solid phase particles generated in the nucleation chamber, the downwardly rotating roll surface of which is exposed to the melt and which is provided in the lower part of the nucleation chamber. This is a metal purifying device in which the metal is concentrated by using a roll) and is forcibly transferred to the nuclear melting chamber through a partition lower passage. Solid phase particles generated in this nucleation chamber refers to particulate crystallized substances or aggregates thereof grown based on nuclei generated by a nucleation device, and in terms of composition, solutes, that is, The concentration of impurities is lower than that of the molten metal.

Next, the device of the present invention will be specifically described with reference to the drawings. FIG. 1 is a side sectional view showing an example of a mode of a unit furnace of the device of the present invention. The unit furnace 1 is composed of a nucleation chamber 2 and a nucleation chamber 3, a nucleation device 4 is arranged in the nucleation chamber 2, and an underflow type in which the nucleation chamber 2 and the nucleation chamber 3 are provided with a passage 5 in the lower part. A partition wall 6 is provided, and a pair of discharge rolls 7 whose downwardly rotating roll surfaces are exposed to the molten metal are provided in the lower part of the nucleation chamber 2. Further, the temperature of the melt 9 in the nucleation chamber 2, the lower passage 5 and the nucleation chamber 3 is controlled by the thermocouples 12 respectively arranged in the nucleation chamber 2, the lower passage 5 and the nucleation chamber 3 and the heating element 8 embedded in the furnace wall. Each can be controlled separately. In the lower part of the nucleation chamber 2, a pair of discharge rolls 7 is provided with the roll surface rotating downward exposed to the molten metal 9. The temperature of the discharge roll 7 can be controlled by passing hot air through the hollow portion inside. Also, for example, engrave a spiral groove on the surface of the discharge roll 7 (knurling)
For example, it is possible to prevent the solid-phase particles from slipping on the roll surface, or to strengthen the downward flow of the molten metal.

Next, a method for purifying an Al molten metal containing a solute having a distribution coefficient K of less than 1 as an impurity by using this metal purifying device will be specifically described with reference to FIG. First, a predetermined amount of a molten metal 9 to be purified is injected into the nucleation chamber 2 and the nucleation melting chamber 3 of the first unit furnace 1, and then the nucleation apparatus 4 of the nucleation chamber 2 is operated to control the molten metal temperature. The liquidus temperature is lowered to and kept at that temperature. During this time, the discharge roll 7 below the nucleation chamber 2 is maintained at the same temperature as the temperature of the molten metal 9 in the nucleation chamber 2. From the molten metal 9 in the nucleation chamber in such a state, solid phase particles 10 having a higher purity than the molten metal 9 are generated according to the above-mentioned distribution law.
Numeral 10 settles in the melt 9 of the nucleation chamber 2 and deposits on a pair of discharge rolls 7 provided in the lower part of the nucleation chamber 2, and the solid-phase particles deposited are concentrated as the discharge roll rotates. Then, it is densified and extruded into the lower passage 5 below the nucleation chamber 2.
The melt 9 in the lower passage 5 and the nuclear melting chamber 3 is kept at a temperature at which the solid-phase particles 10 are melted, and the solid-phase particles 10 are redissolved in the molten metal 9 in the nuclear-melting chamber 3 to obtain the purity of the melt 9. And the molten metal 9 is transferred to the nucleation chamber of the second unit furnace (not shown) through the gutter 11. The nucleation chamber 2 of the first unit furnace 1 is replenished with the raw material Al melt 9 in accordance with the generation rate of the solid phase particles 10. Since the molten metal in the nucleation chamber 2 flows downward due to the rotation of the discharge roll 7, the high-temperature molten metal 9 in the lower passage 5 and the nucleation chamber 3 does not flow back into the nucleation chamber 2, and therefore The solid phase particles 10 in the generation chamber 2 are not prevented from settling.

In the apparatus of the present invention, when the internal water-cooled nucleation apparatus is used as the nucleation apparatus, the amount of solid phase particles S (g / min.) To be produced and the amount of cooling water W (ml /
min.), the empirical formula of S = 1.75 W is established. When the solid phase particles are transferred from the nucleation chamber to the nucleation dissolution chamber by a discharge roll, the peripheral speed of the roll is proportional to the amount of the solid phase particles transferred. Therefore, if the rotation of the discharge roll is sped up more than necessary, a large amount of molten metal with low purity in the nucleation chamber will flow into the nucleation chamber, and if it is too late, a large amount of solid phase particles will accumulate in the nucleation chamber and solidify. Since the generation efficiency of the phase particles decreases, it is necessary to perform a preliminary experiment to determine the optimum rotation speed of the discharge roll in accordance with the nucleation capacity of the nucleation device. In the method of the present invention, the solid-phase particles generated in the nucleation chamber are forcibly fed into the nucleation dissolution chamber by using the discharge roll, so the nucleation device has a high nucleation rate, for example, Japanese Patent Application No. 1-
Proposed in 272228 and Japanese Patent Application No. 1-290720, an internal water-cooled rotary high-performance nucleation method in which the part to be immersed in the molten metal is composed of a mixture of graphite and ceramic materials with different wettability with the molten metal It is preferable to use a device.

[0012]

In the apparatus of the present invention, a pair of discharge rolls having downwardly rotating roll surfaces exposed to the molten metal are provided at the lower part of the nucleation chamber of the unit furnace, and the rolls of the discharge rolls are rotated to move the nucleation chamber. Since the solid-phase particles generated in step 1 are concentrated and are forcibly transferred to the nuclear melting chamber, the production rate of high-purity metal is improved. Further, since the molten metal flows from the nucleation chamber toward the nucleation chamber by the rotation of the roll of the discharge roll, the rising flow of the molten metal in the nucleation chamber caused by the influence of the high temperature molten metal in the nucleation chamber is suppressed. As a result, the solid phase particles generated by the nucleation apparatus rapidly settle in the nucleation chamber and the solid phase particles are efficiently transferred to the nucleation dissolution chamber. If the temperature of the molten metal in the lower passage is raised to the same level as that of the nuclear melting chamber and the solid phase particles extruded by the discharge roll are immediately remelted,
There is no need to provide an inclination for transferring solid phase particles to the floor of the lower passage.

[0013]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 An Al molten metal purification experiment was conducted using a purification apparatus in which five unit furnaces shown in FIG. 1 were connected in series with a gutter. Both the nucleation chamber and the nuclear melting chamber of each unit furnace have a depth of 400 mm,
The vertical and horizontal cross-sections of the inner plane were 60 × 60 mm, the partition wall separating the nucleation chamber and the nucleation chamber was 50 mm in thickness, and the height of the lower passage was 60 mm. A discharge roll made of alumina having a diameter of 100 mm and a face length of 60 mm was used as a discharge roll provided below the nucleation chamber. Two types of discharge rolls are used: one with a smooth roll surface and one with knurled grooves with a depth of 0.1 mm, a width of 0.1 mm and a pitch of 0.2 mm on the entire roll surface. I was there. The roll interval was set to 5 mm. Using a knurled discharge roll, roll peripheral speed V (cm /
min.) and the discharge amount N (g / min.) of solid phase particles were obtained, and an empirical formula of N = 7.6V was obtained. As the raw material molten metal, an Al molten metal having a purity of 99.7% was used. This Al
The molten metal contained elements of Cu, Fe, Mg, Mn, Ni, Si, and Zn as impurities, and all of these elements had a distribution coefficient K of less than 1. This raw material melt is the first
5.4 kg was put in the unit furnace of No. 1 and the melt temperature was set to 665 ° C. in the nucleation chamber and 675 ° C. in the nucleation chamber. An internal water-cooled AC electric nucleation device made of a sintered body of graphite mixed with 5% alumina was used as the nucleation device. The tip of this nucleation device was immersed in the molten metal in the nucleation chamber for 30 mm, and water at 15 ° C. was flown inside the nucleation device. An alternating current of 50 Hz was applied to this to give vibration. The roll peripheral speed of the discharge roll was set so that the discharge speed N of the solid phase particles coincided with the generation speed W of the solid phase particles generated by the nucleation device. The discharge roll controlled the temperature to be the same as the molten metal temperature by sending hot air to the inner hollow portion. A SiC heating element was embedded in the furnace wall. In addition, a SiC heating element formed in a U-shaped cross section was used for the gutter after being electrically heated. The molten metal thus purified from the nuclear melting chamber of the first unit furnace is continuously transferred to the nucleation chamber of the second unit furnace through the gutter, and the same operation is performed in the second unit furnace by changing the molten metal temperature to the first unit. The furnace was set at a temperature slightly lower than that of the furnace, and the same operation was sequentially performed up to the fifth unit furnace to produce a high-purity Al melt from the nuclear melting chamber of the fifth unit furnace. The above-mentioned molten aluminum was supplied to the nucleation chamber at the same rate as the nucleation rate of the nucleation apparatus.

Comparative Example 1 An Al molten metal purification experiment was conducted by the same method as in Example 1 using the purification apparatus shown in FIG. The unit furnace had the same dimensions as the unit furnace used in Example 1, and a downward gradient of 30 degrees was formed on the floor surface from the nucleation chamber to the nuclear melting chamber. In this way, the purification experiment was carried out continuously for 10 hours, and the molten metal produced from the nuclear melting chambers of the fourth and fifth unit furnaces was sampled for quantitative analysis of impurities. Further, the production amount of the highly purified molten metal produced from the nuclear melting chamber of the fifth unit furnace was measured. The results are shown in Table 1 together with the solid phase particle generation rate obtained in the preliminary experiment.

[0015]

[Table 1]

As is clear from Table 1, the product of the present invention (N
o. The produced melts 1 to 7) were all high in purity, and the production rate of high-purity Al increased with the production rate of solid phase particles. The fact that No2 has less impurities than No1 and the production rate of high-purity Al is higher is due to the effect of knurling the roll surface. On the other hand, the No. 8
Has a low production rate, and the production rate of highly purified Al did not change even if the solid phase particle production rate was increased (No. 9). This indicates that the moving speed of the solid phase particles from the nucleation chamber to the nucleation chamber was saturated at 35 g / min. Or less. In addition, the amount of impurities was as high as 37 to 39 ppm after leaving the fifth unit furnace. This value exceeds the amount of impurities in the fourth unit furnace of the product of the present invention, and the device of the present invention can reduce the number of unit furnaces by one compared with the device of the comparative example. The reason why the comparative example product has a large amount of impurities is that the comparative example apparatus has an alternating current of the molten metal between the nucleation chamber and the nuclear melting chamber via the lower passage.

Further, in Table 1, No. In the purification experiments of Nos. 1, 2, and 8, the molten metal was sampled also from the trough between the unit furnaces, and each impurity element was analyzed. The results are shown in Table 2.

[Table 2]

As is clear from Table 2, the amount of the impurity element was always No. from the point where it left the first unit furnace. The number was decreased in the order of 2, 1, 8 and the superiority of the device of the present invention was demonstrated. So far, the purification experiment of a melt containing a solute with a distribution coefficient K of less than 1 as an impurity has been described. However, for a melt containing a solute with a K of more than 1 as an impurity, the apparatus proposed in Japanese Patent Application No. 61-241036 can be used. The purification speed can be improved by providing the discharge roll. Needless to say, the same effect can be obtained even if the raw material melt used is not limited to the Al melt, but is applied to other metal melts such as copper.
A plurality of discharge rolls may be used, and the material, shape, etc. of the discharge rolls can be arbitrarily designed according to the structure of the unit furnace and the kind of molten metal. Further, it is possible to carry out purification using only one unit furnace.

[0019]

As described above, according to the apparatus of the present invention, the molten metal can be purified at a high speed, and the industrially remarkable effect can be obtained.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an example of an embodiment of the device of the present invention.

FIG. 2 is a metal state diagram for explaining a distribution law of solute elements.

3A and 3B are front and plan sectional views of a conventional device, respectively.

[Explanation of symbols]

 1 Unit Furnace 2 Nucleation Chamber 3 Nuclear Melting Chamber 4 Nucleation Device 5 Lower Passage 6 Partition 7 Discharge Roll 8 Heating Element 9 Molten Metal 10 Solid Particle 11 Gutter 12 Thermocouple

Claims (1)

[Claims] 1. A plurality of units of a unit furnace comprising a nucleation chamber in which a nucleation device for producing solid phase particles is arranged and a nucleation chamber in which solid phase particles produced in the nucleation chamber are dissolved, The nucleation chamber of the furnace and the nucleation chamber of the next unit furnace are connected in series via a gutter, and the nucleation chamber and the nucleation chamber of the unit furnace are partitioned by a partition wall provided with a passage at the bottom, In the metal purification device, the temperature of the molten metal can be controlled individually by the heating elements embedded in the furnace wall.In the lower part of the nucleation chamber, a pair of discharge rolls with downwardly rotating roll surfaces exposed to the molten metal were installed. A metal purifying device characterized in that