JP7386635B2 - High purity metal manufacturing method and manufacturing equipment - Google Patents

Description

More specifically, regarding the manufacturing method and manufacturing equipment for high-purity metals, the content of eutectic impurities is determined based on the content of eutectic impurities from metals such as aluminum, magnesium, lead, and zinc that contain eutectic impurities using the principle of segregation solidification method. The present invention relates to a method and apparatus for producing high-purity metals in a quantity lower than that of other metals.

Among the methods for producing high-purity metals from metals with a high concentration of impurity elements, the refining method that utilizes the segregation phenomenon during solidification (segregation method) is widely used industrially due to its cost advantage over other production methods. . In the segregation method, the target metal is first melted and then partially solidified to discharge impurity elements that form a eutectic with the target metal into the molten metal. Subsequently, by taking out this solidified portion from the molten metal, it can be sorted into a higher purity portion and a lower purity portion, and the original target metal can be refined into a high purity metal. How to extract these high-purity metal crystals with a high degree of purity is the lifeblood of the manufacturing process. When evaluating the purification performance of a purification process such as the segregation method, the impurity element concentration reduction rate before and after purification, that is, the purification efficiency expressed by the following formula, is used.
Purification efficiency = impurity element concentration after purification / impurity element concentration before purification From the viewpoint of quality improvement and production cost, it is extremely important to improve this purification efficiency without reducing the recovery rate of high-purity metal crystals. is important. Improving purification efficiency has been a top priority for many years, and various technological improvements have been made.

For example, among metal refining methods using segregation methods, a typical technique is a technique characterized by slow cooling while rotating a cooling body immersed in the metal at high speed (Patent Document 1 and others). In this technique, the faster the cooling body rotates relative to the molten metal, the thinner the concentration boundary layer near the solidification interface becomes, and the higher the refining efficiency. Therefore, it has been customary for the circumferential speed of rotation on the outer surface of the cooling body to be extremely high in the range of 1,000 to 10,000 mm/s (Patent Document 2).

However, if the cooling body rotates at a higher speed, the centrifugal force felt by the grown metal crystals will increase, and there is a risk that the metal crystals will peel off from the outer circumferential surface of the cooling body. Loss when peeling occurs includes a decrease in productivity due to a decrease in the amount of solidification growth (refined amount) for a given refining time. When a metal crystal peels off, when new metal crystals are crystallized from the peeled part, crystallization occurs from a molten metal whose purity has further deteriorated.

In that case, even if the relative rotational circumferential speed is the same, it is equivalent to crystal growth from a state where the concentration boundary layer thickness is thicker, so the purification efficiency decreases. In addition, when the peeled metal crystals remelt, the temperature of the entire molten metal decreases. Temperature fluctuations in the molten metal lead to temporal or spatial fluctuations in the growth rate of metal crystals, which has a significant impact on the final crystal purity. Therefore, in Patent Document 2, the circumferential speed of the rotary cooling body is limited to a range of 1600 to 8000 mm/s.

Against the above background, attempts have been made for many years to develop techniques that can improve purification efficiency while avoiding crystal exfoliation. In particular, many techniques have been proposed for improving refining efficiency by increasing the relative rotational peripheral speed by reducing the swirling flow velocity of the following molten metal while maintaining the cooling body rotation (Patent Document 3, Patent Document 4). ). For example, in Patent Document 3, high refining efficiency is obtained with a method of suppressing swirling of molten metal by arranging a baffle plate on the inner surface of a crucible. However, there was room for improvement in terms of ease of installation, such as the need for maintenance of the baffle plates at a certain frequency. Patent Document 4 also proposes a technique for reducing the swirling flow velocity and improving refining efficiency by applying rotation in the opposite direction to the swirling flow of molten metal. In particular, it is known that applying reverse rotation using an external magnetic field has a very high flow velocity reduction effect. However, in this case, if there are metal materials in the structural members around the refining device, eddy current loss is unavoidable, so there are certain restrictions on layout design. Although various studies have been attempted, no purification method that can be easily implemented has been proposed for a long time.

Japanese Unexamined Patent Publication No. 57-82437 Special Publication No. 61-03385 Special Publication No. 62-235433 Patent No. 498831

As described above, in the conventional technology, there is room for improvement in obtaining high-purity metals with high purification efficiency using simple methods and equipment.

An object of the present invention is to provide a method and apparatus for producing high-purity metals that further improves purification efficiency while solving the problems of the segregation refining method described above.

In order to achieve the above object, the present invention immerses a cooling body in a molten metal containing a metal to be purified, and while rotating at least one of the cooling body or a crucible, the surface of the cooling body is coated with high-purity metal. In the manufacturing method of high-purity metals that crystallizes, a crucible whose inner surface has an uneven shape is used to expand the contact surface area with the molten metal. By reducing the swirling flow velocity of the molten metal, the relative rotational circumferential velocity near the solidification interface is increased and the refining efficiency is improved. Here, the unevenness refers to vertical grooves, annular grooves formed around the entire circumference, spiral grooves, many scattered depressions (dimples), and combinations thereof.

That is, the high-purity metal manufacturing method and the high-purity metal manufacturing apparatus of the present invention have the following configurations.
(1) A molten metal obtained by melting the metal to be purified is placed in a crucible, a cooling body is immersed in the molten metal, and while at least one of the cooling body or the crucible is rotated, high-purity metal is applied to the surface of the cooling body. A method for producing a high-purity metal in which the crucible has an uneven inner surface.
(2) The method for producing high-purity metal according to item 1, wherein the relative rotational circumferential speed of the cooling body and the molten metal is in the range of 1000 to 10000 mm/s.
(3) The crucible has the uneven shape on at least a part of the contact portion with the molten metal, and the surface area of the inner surface of the crucible is more than 1.05 times the surface area when the crucible does not have the uneven shape. A method for producing a high purity metal according to item 1 or item 2 above.
(4) The crucible has the uneven shape on at least a part of the contact portion with the molten metal, and the surface area of the inner surface of the crucible is not more than twice the surface area when the crucible does not have the uneven shape. A method for producing a high purity metal according to any one of the preceding clauses 1 to 3.
(5) The method for producing a high-purity metal according to any one of items 1 to 4, wherein the height of the unevenness in the uneven portion is 15% or less of the wall thickness of the crucible.
(6) The method for producing a high-purity metal according to any one of items 1 to 5, wherein the uneven shape is formed by grooves and/or edges.
(7) The method for manufacturing a high-purity metal according to item 6, wherein the groove is a vertical groove.
(8) The method for manufacturing a high-purity metal according to any one of items 1 to 5, wherein the uneven shape is formed by dimples.
(9) The method for producing a high-purity metal according to item 8, wherein the dimple has one or more shapes of a hemisphere, a spherical crown, a prism, a pyramid, and a truncated pyramid.
(10) The method for producing a high-purity metal according to any one of Items 1 to 9, wherein the metal is aluminum. (11) A crucible containing a molten metal containing a metal to be purified; A cooling body immersed in a contained molten metal, and a rotational drive device for rotating at least one of the cooling body or the crucible in order to crystallize high-purity metal on the surface of the cooling body. A high-purity metal manufacturing apparatus, wherein the crucible has an uneven inner surface.
(12) The high-purity metal manufacturing apparatus according to item 11, wherein the relative rotational circumferential speed of the cooling body and the molten metal, at least one of which is rotated by the rotary drive device, is in the range of 1000 to 10000 mm/s.
(13) The crucible has the uneven shape on at least a part of the contact portion with the molten metal, and the surface area of the inner surface of the crucible is more than 1.05 times the surface area when the crucible does not have the uneven shape. The high-purity metal manufacturing apparatus according to item 11 or 12 above.
(14) The crucible has the uneven shape on at least a part of the contact portion with the molten metal, and the surface area of the inner surface of the crucible is not more than twice the surface area when the uneven shape does not exist. The high purity metal manufacturing apparatus according to any one of the preceding clauses 11 to 13.
(15) The high-purity metal manufacturing apparatus according to any one of items 11 to 14, wherein the height of the unevenness in the uneven portion is 15% or less of the wall thickness of the crucible.
(16) The high-purity metal manufacturing apparatus according to any one of items 11 to 15, wherein the uneven shape is formed by grooves and/or edges.
(17) The high-purity metal manufacturing apparatus according to item 16, wherein the groove is a vertical groove.
(18) The high-purity metal manufacturing apparatus according to any one of items 11 to 15, wherein the uneven shape is formed by dimples.
(19) The high-purity metal manufacturing apparatus according to item 18, wherein the dimple has one or more shapes of a hemisphere, a spherical crown, a prism, a pyramid, and a truncated pyramid.
(20) The high-purity metal manufacturing apparatus according to any one of items 11 to 19 above, wherein the metal is aluminum.

According to the invention described in the preceding sections (1) and (11), the following effects can be obtained. That is, when attempting to reduce the swirling flow velocity of molten metal using the prior art, large-scale auxiliary equipment was required, such as installing baffles and installing coils for applying an external magnetic field, as described above. . In contrast, in the present invention, since the crucible has an uneven shape on its inner surface, a sufficient effect of reducing swirling flow velocity can be obtained with a simple configuration without the need for large-scale auxiliary equipment, and an improvement in purification efficiency can be achieved. can do. Therefore, the present invention is very advantageous in terms of introduction cost compared to the conventional technology, and can also be maintenance-free in terms of post-installation management.

According to the inventions described in the preceding sections (2) and (12), the larger the swirling flow velocity of the molten metal, the more remarkable the flow velocity reduction effect due to the uneven shape of the inner surface of the crucible. By setting the rotational circumferential speed in the higher range of 1,000 to 10,000 mm/s, it is possible to reliably reduce the flow velocity and thereby improve purification efficiency.

According to the inventions described in the preceding sections (3) and (13), the crucible has an uneven shape on at least a part of the contact portion with the molten metal, and the surface area of the inner surface of the crucible has an uneven shape. Since the surface area is more than 1.05 times the surface area when the crucible is not used, the surface area can be expanded beyond the effect of the natural surface roughness of the crucible, and the effect of reducing the swirling flow velocity of the molten metal and thereby improving the refining efficiency can be reliably obtained. .

According to the invention described in the preceding sections (4) and (14), the crucible has an uneven shape on at least a part of the contact portion with the molten metal, and the surface area of the inner surface of the crucible has an uneven shape. Since the surface area is less than twice that of the case where the surface area is not formed, it is possible to reduce the cost required for forming the uneven shape while achieving a high effect of reducing the swirling flow velocity of the molten metal and thereby improving the refining efficiency.

According to the inventions described in the preceding sections (5) and (15), the height of the unevenness in the uneven portion is 15% or less of the wall thickness of the crucible, so that the durability of the crucible or the uneven portion itself is not impaired. , it is possible to reliably obtain the effect of expanding the surface area by providing the uneven shape and the effect of improving the purification efficiency thereby.

According to the inventions described in the preceding sections (6) and (16), since the uneven shape is formed by grooves and/or ridges, it is possible to form the uneven shape by a simple method, and furthermore, the uneven shape can prevent melting. It is possible to reliably obtain the effect of reducing the swirling flow velocity of metal and the effect of improving refining efficiency thereby.

According to the inventions described in the preceding sections (7) and (17), since the grooves are vertical grooves, it is possible to suppress the cost required for forming the uneven shape, and the effect of reducing the swirling flow velocity of molten metal due to the uneven shape is also achieved. As a result, the effect of improving purification efficiency can be reliably obtained.

According to the inventions described in (8) and (18) above, since the uneven shape is formed by dimples, the swirling flow velocity of the molten metal is higher than that of a crucible having grooves or ridges with the same surface area ratio. It is possible to obtain a reduction effect and a purification efficiency improvement effect thereby.

According to the inventions described in the preceding sections (9) and (19), the dimple has one or more shapes of a hemisphere, a spherical crown, a prism, a pyramid, and a truncated pyramid, so that the uneven shape can be easily formed. This makes it possible to easily obtain a crucible with a higher surface area ratio.

According to the inventions described in the preceding sections (10) and (20), the metal is aluminum, and most of the impurity elements that are generally contained in aluminum form a eutectic with aluminum (for example, iron, silicon, copper, etc.). ), high purification efficiency can be easily achieved.

1 is a longitudinal cross-sectional view of a high-purity metal manufacturing apparatus according to an embodiment of the present invention. (A) to (C) are cross-sectional views showing examples of grooves. FIG. 2 is a cross-sectional view of a crucible with longitudinal grooves formed therein. (A) to (C) are cross-sectional views showing examples of edges. (A) to (D) are cross-sectional views showing examples of dimples. FIG. 2 is a cross-sectional view of a crucible with dimples formed on its inner surface. (A) to (D) are diagrams for explaining grooves or dimples formed on the inner surfaces of the crucibles of Examples 1 to 4.

Hereinafter, one embodiment of the present invention will be described in detail.

FIG. 1 is a longitudinal cross-sectional view of a high-purity metal manufacturing apparatus according to an embodiment of the present invention. This manufacturing apparatus has a crucible 1, and a molten metal 2 is accommodated and held in the hollow interior of the crucible 1. The crucible 1 has an open top and an arcuate bottom in cross section, and a vertical cooling body 3 is disposed in the hollow part of the crucible 1 with its tip immersed in the molten metal 2. The cooling body 3 is arranged to be movable vertically and horizontally, and during metal refining, the cooling body 3 moves downward and is immersed in the molten metal 2 in the crucible 1, as shown in FIG. ing. Although not shown, a refined metal scraping device is installed near the side of the crucible 1, and the refined metal scraping device removes the crystallized metal from the molten metal 2 of the crucible 1 onto the cooling body 3 that has been moved. It is designed to be able to be scraped off and recovered using a dropping device. Further, the molten metal 2 in the crucible 1 is heated from the outside of the crucible 1 so as to maintain a constant temperature.

A rotational drive device 4 such as a motor is connected to the upper end of the cooling body 3 via a rotating shaft 31, so that rotational force can be applied to the cooling body 3. Furthermore, the cooling body 3 can be moved vertically and horizontally by a moving device (not shown).

Furthermore, a refrigerant circulation path was formed inside the cooling body 3, and during refining, the refrigerant that had descended through the center of the cooling body 3 flowed radially outward at the bottom, as shown by the arrow X in Figure 1. Afterwards, the cooling body 3 is configured to be cooled while rotating by ascending and circulating inside the surface of the cooling body 3.

In this embodiment, the crucible 1 has a concavo-convex shape 100 on the inner surface of its lower part, particularly at the part that contacts the molten metal 2. By rotating the cooling body 3 immersed in the molten metal during metal refining, a swirling flow is generated in the molten metal 2 in the direction of rotation of the cooling body 3. By increasing the frictional resistance, the swirling flow is suppressed and the relative rotation peripheral speed of the cooling body 3 with respect to the swirling flow velocity is increased.

The uneven shape 100 is realized by forming recesses and/or projections on the inner surface of the crucible 1. The position where the uneven shape 100 is provided is preferably at least a part of the contact portion with the molten metal 2. Although the inner bottom surface of the crucible 1 may be used, the inner surface is preferable from the viewpoint of increasing frictional resistance more efficiently. It may be formed on either the inner surface or the inner bottom surface. In addition to machining, laser processing and blasting may be used as a method for providing the uneven shape 100. Another method is to add an uneven shape to the crucible while it is still soft, not in the final process of manufacturing the crucible 1, but in a preforming process such as a casting process or cold isostatic pressing (CIP). Can be mentioned.

The frictional resistance against the flow field of the molten metal 2 on the inner surface of the crucible 1 becomes stronger as the swirling flow velocity of the molten metal 2 increases. In other words, unless the rotational speed of the cooling body 3 is set to a sufficiently high speed, there is a possibility that the effect of reducing the swirling flow velocity due to the uneven shape 100 on the inner surface of the crucible 1 will not be sufficiently obtained. Therefore, it is desirable that the peripheral speed of rotation of the cooling body 3 with respect to the molten metal 2 in this embodiment is 1000 mm/s or more. On the other hand, if the peripheral speed of rotation of the cooling body 3 becomes too high, the risk of crystal separation from the cooling body 3 increases. Therefore, it is desirable that the peripheral speed of rotation of the cooling body 3 relative to the molten metal 2 does not exceed 10,000 mm/s.

Furthermore, in general, due to the surface roughness of the crucible 1, the surface area of the inner surface of the crucible 1 is slightly larger by about 1 to 2% than that of a completely flat surface. Therefore, for this range, by using a crucible whose surface area of the inner surface of the crucible 1 after the application of the uneven shape 100 is more than 1.05 times, the effect of reducing the flow velocity due to the application of the uneven shape 100 to the inner surface of the crucible 1 can be ensured. can be obtained.

The larger the contact area between the inner surface of the crucible 1 and the molten metal 2, the stronger the frictional resistance against the molten metal flow field, and the higher the effect of improving refining efficiency. Therefore, as for the uneven shape 100 on the inner surface of the crucible, the height of the unevenness needs to be sufficiently higher than the original surface roughness of the inner surface of the crucible 1. Furthermore, in order to obtain higher purification efficiency improvement performance, it is preferable to arrange a large number of concave portions and/or convex portions at high density. However, when performing high-density uneven processing, processing with high dimensional accuracy is required, so the cost required to provide the uneven shape 100 becomes extremely high. Therefore, the upper limit of the surface area expansion ratio is preferably twice.

At this time, it is necessary to pay attention to the height of the unevenness of the uneven portion to be applied, that is, the difference H between the depressions and the protrusions. In particular, when the uneven shape 100 is formed by forming recesses, the thickness of the crucible 1 itself decreases accordingly, and the durability of the crucible 1 decreases. On the other hand, when the uneven shape 100 is formed by forming protrusions, there is an unavoidable risk of damage and deterioration due to interference between the protrusions on the inner surface of the crucible 1 and the metal crystals grown on the surface of the cooling body 3. Therefore, it is desirable that the unevenness height H be 15% or less of the wall thickness of the crucible 1.

As another constraint, it is desirable to consider the aspect ratio H/D of the concave portion or convex portion itself to be formed. As will be described later, D is the width of the groove or ridge when the recess or protrusion is a groove, and the diameter of the hole when it is a dimple. If the aspect ratio is too large, insufficient strength may become a problem in the case of convex portions. In the case of a recessed portion, the flow field of the molten metal may not sufficiently penetrate into the inside of the uneven shape, which may cause a problem of decreased flow velocity reduction performance. On the other hand, if the aspect ratio is too small, it may not be possible to arrange the concave portions or convex portions at a high density, making it difficult to expand the surface area. For the above reasons, it is desirable that the aspect ratio of the concave or convex portions themselves be in the range of 0.5 to 1.5.

Examples of the recesses for providing the uneven shape 100 include grooves, dimples, and the like. An example of a convex portion is a ridge. In the case of grooves, the cross-sectional shape may be any shape, but examples of grooves that are easy to obtain industrially are, for example, as shown in FIG. Examples include grooves 103 (FIG. 2C) with a square cross section, and other grooves with a polygonal cross section of pentagon or more. The direction in which the grooves are provided may be either vertical (vertical) or horizontal (horizontal), and the grooves may be arranged in any manner such as annular, spiral, or lattice shapes. The example in FIG. 1 shows a case where a plurality of annular grooves each having a rectangular cross section are vertically formed on the inner surface of the crucible 1. Further, as shown in FIG. 3, the uneven shape 100 may be formed by forming a plurality of vertical grooves 104 having a rectangular cross section at intervals in the circumferential direction.

In the case of a ridge, the cross-sectional shape may be any shape, but as shown in FIG. 4, for example, a ridge 105 with a semicircular cross-section (FIG. 4A) and a ridge 106 with a triangular cross-section (FIG. 4B) are suitable for industrial use. , a rectangular cross-sectional edge 107 (FIG. 4C), and other polygonal cross-sectional edges having a pentagonal shape or more. The direction in which the ridges are provided may be either vertical (vertical) or horizontal (horizontal), and the arrangement may be in any shape, such as a ring, a spiral, or a lattice.

On the other hand, in the case of dimples, their shapes are, for example, as shown in FIG. 5: hemispherical dimples 108 (FIG. 5A), spherical dimples 109 (FIG. 5B), pyramidal dimples 110 (FIG. 5C), and truncated pyramidal dimples 111 (FIG. 5D). , prismatic dimples, etc. can be used. FIG. 6 shows an example of a crucible 1 having an uneven shape 100 in which a large number of hemispherical dimples 108 are formed in an annular shape and in the vertical direction.

In addition, when providing the uneven shape 100 with the dimples 108 to 111, by inducing a minute vortex movement in the flow field of the molten metal 2, in addition to the flow velocity reducing effect by expanding the surface area of the inner surface of the crucible 1, theoretically At the same time, the effect of reducing the flow velocity due to the increase in eddy viscosity can also be obtained. Therefore, as shown in Examples described below, the purification efficiency improvement performance by adding dimples is higher than when adding grooves (or ridges) with the same surface area expansion rate. In addition to the recesses and projections, a combination of grooves (or ridges) and dimples may be used. However, in the case of a combination, each concave portion and convex portion must be provided in separate steps, which is economically disadvantageous and increases the cost. Therefore, basically, the uneven shape 100 may be provided by providing each crucible 1 with a single-shaped concave portion or convex portion.

Next, a method for manufacturing high-purity metal using the high-purity metal manufacturing apparatus shown in FIG. 1 will be described.

As shown in FIG. 1, the cooling body 3 is immersed in the molten metal 2 in the crucible 1, and the cooling body 3 is rotated while supplying a refrigerant thereinto, and the refined metal 5 is slowly poured onto the circumferential surface of the cooling body 1. Let it crystallize. This order is not particularly limited, and there is no problem even if the cooling body 3 is immersed in the molten metal 2 while rotating. The eutectic impurities are discharged into the liquid phase and an impurity concentration layer of eutectic impurities is formed in the liquid phase near the solidification interface, but due to the relative speed between the cooling body 3 and the molten metal 2, the impurities in the impurity concentration layer are are dispersed throughout the liquid phase.

Further, due to the rotation of the cooling body 3 relative to the crucible 1, a swirling flow is generated in the molten metal 2 in the same direction as the rotational direction of the cooling body 3, but at least one part of the inner surface of the crucible 1 is in contact with the molten metal 2. Since the molten metal 2 has the concavo-convex shape 100, a frictional force due to the concavo-convex effect of the concave-convex shape 100 acts on the molten metal 2, suppressing swirling flow, and exerting an effect of reducing the flow velocity on the cooling body 3. That is, the circumferential speed of the cooling body 3 relative to the molten metal 2 increases, impurities can be efficiently removed, and the effect of improving purification efficiency can be reliably obtained.

If solidification is allowed to proceed in this state, refined metal 5 with much higher purity than the original molten metal 2 will be obtained on the circumferential surface of the cooling body 3.

In this embodiment, the cooling body 3 is rotated, but the crucible 1 may be rotated, or the cooling body 3 and the crucible 1 may be rotated together. It only needs to be rotated relative to.

The cooling body 3 is preferably made of graphite, ceramics, etc., but is not limited thereto. Since the cooling body 3 also reaches a high temperature due to contact with the high-temperature molten metal 2, the cooling body 3 may be made of metal as long as it does not melt at this high temperature and does not significantly reduce its strength.

The refrigerant for cooling the cooling body 3 is not particularly limited, and nitrogen gas, carbon dioxide gas, argon gas, compressed air, etc. can be used, but compressed air is recommended from the viewpoint of cost.

The metals to be refined may include metals such as aluminum, silicon, magnesium, lead, zinc, etc. that contain eutectic impurities. In particular, when refining aluminum, most of the impurity elements that are commonly contained in aluminum form eutectics with aluminum (for example, iron, silicon, and copper), so high refining efficiency can be easily achieved.

The refined metal 5 crystallized on the circumferential surface of the cooling body 3 is pulled up together with the cooling body 3 from the molten metal 2 after a certain period of time has elapsed, and is scraped off from the cooling body 3 and recovered. Thereafter, the cooling body 3 is again immersed in the molten metal 2 in the crucible 1 and used for metal refining. This step is repeated to continuously refine the metal.

The metals refined as described above can exhibit excellent properties and functions by being used in various processing and applications. For example, a refined metal may be used for casting to produce a cast product, or this cast product may be rolled and used as various metal plates and metal foils. Further, this metal foil may be used, for example, as an electrode material for an aluminum electrolytic capacitor.

An example will be shown in which this embodiment is applied using aluminum (Al) as a refining raw material.

The crucible 1 used was made of graphite and had a diameter of 300 mm, a height of 600 mm, and a wall thickness of 55 mm. In Example 1, an annular groove 101 having a semicircular cross section with a width D: 10 mm and an uneven height (depth) H: 5 mm is formed in the vertical direction on the inner surface of the crucible 1, as shown in FIG. 7(A). A plurality of concavo-convex shapes 100 were formed. In Example 2, as shown in FIG. 7B, a plurality of annular grooves 101 having a semicircular cross section with a width D: 16 mm and an uneven height (depth) H: 8 mm are provided in the vertical direction to form an uneven shape 100. Formed. In Example 3, as shown in FIG. 7(C), a spherical dimple 109 with a diameter D: 10 mm and an uneven height (depth) H: 5 mm was provided in the circumferential direction and the vertical direction to form an uneven shape 100. . In Example 4, as shown in FIG. 7(D), a spherical dimple 109 with a diameter D: 16 mm and an uneven height (depth) H: 8 mm was provided in the circumferential direction and the vertical direction to form an uneven shape 100. .

Furthermore, for comparison, a crucible having no uneven shape was prepared as Comparative Example 1, and a total of five types of crucibles were prepared. Here, the annular grooves 101 of Examples 1 and 2 were processed by turning, and the spherical dimples 109 of Examples 3 and 4 were processed by YAG laser, respectively, on crucibles having no uneven shape. It is. The ratio of the inner surface area of the crucible of Examples 1 to 4 to the inner surface area of the crucible without unevenness, and the ratio of the unevenness height (H) to the crucible wall thickness (T) (H/T) are respectively It was as shown in Table 1.

The Al raw materials used were adjusted to have Fe: 500wt.ppm and Si: 400wt.ppm, respectively. This Al raw material was placed in each of the crucibles of Examples 1 to 4 and Comparative Example 1 and heated and melted while adjusting the amount of melting so that the liquid level height after melting was 250 mm. The obtained molten Al was heated and maintained in the range of 660 to 670°C and used for purification.

The high-purity Al crystal was purified in accordance with the method described in Japanese Patent Publication No. 61-03385. That is, a hollow rotary graphite cooling body (diameter 150 mm) was immersed in the molten Al (molten metal) in each crucible while rotating, and held at a position where the immersion depth relative to the liquid level was 200 mm. At the same time as the immersion, compressed air was supplied as a refrigerant into the cooling body to grow Al crystals on the surface of the cooling body. At this time, the compressed air temperature was 10°C, the refrigerant supply time was 7 min, the cooling body rotation speed was 600 rpm (rotational speed on the cooling body surface: approximately 4700 mm/s), and the crystal growth rate in the radial direction of the cooling body was 2.5. The refrigerant supply conditions (pressure, flow rate) were adjusted to ~3.0 mm/min. The grown Al crystals were pulled out of the molten metal as soon as the coolant supply ended, and their chemical compositions were analyzed using optical emission spectroscopy.

Table 2 shows the chemical compositions of the raw material Al and the grown Al crystals, as well as the purification efficiency calculated using these values. As described in the Background Art section, the method for calculating the purification efficiency is based on the ratio of the Al crystal concentration after purification to the molten Al concentration before purification.

As can be understood from the results in Table 2, for both Fe and Si elements, Example 4, Example 3, Example 2, Example 1, and Comparative Example 1 have the lowest chemical composition, that is, the purification efficiency. The results were high. This confirmed that purification efficiency could be improved by using the crucible 1 having the uneven shape 100 on the inner surface.

1 Crucible 2 Molten metal 3 Cooling body 4 Rotation drive and movement device 5 Crystallized metal 100 Uneven shape 101-104 Groove 105-107 Edge 108-111 Dimple

Claims (26)

A molten metal obtained by melting the metal to be purified is placed in a crucible, a cooling body is immersed in the molten metal, and high-purity metal is crystallized on the surface of the cooling body while rotating at least one of the cooling body or the crucible. In the method for producing high-purity metal,
The crucible has an uneven shape on at least a part of the inner surface that contacts the molten metal,
The surface area of the inner surface of the crucible is more than 1.05 times the surface area when the crucible does not have an uneven shape,
A method for producing a high-purity metal, wherein the height of the unevenness in the uneven portion is 15% or less of the wall thickness of the crucible. A molten metal obtained by melting the metal to be purified is placed in a crucible, a cooling body is immersed in the molten metal, and high-purity metal is crystallized on the surface of the cooling body while rotating at least one of the cooling body or the crucible. In the method for producing high-purity metal,
The crucible has an uneven shape on at least a part of the inner surface that contacts the molten metal,
The surface area of the inner surface of the crucible is more than 1.05 times the surface area when the crucible does not have an uneven shape,
A method for manufacturing high-purity metal, characterized in that the uneven shape is formed by vertical grooves. A molten metal obtained by melting the metal to be purified is placed in a crucible, a cooling body is immersed in the molten metal, and high-purity metal is crystallized on the surface of the cooling body while rotating at least one of the cooling body or the crucible. In the method for producing high-purity metal,
The crucible has an uneven shape on at least a part of the inner surface that contacts the molten metal,
The surface area of the inner surface of the crucible is more than 1.05 times the surface area when the crucible does not have an uneven shape,
A method for manufacturing a high-purity metal, characterized in that the uneven shape is formed by dimples. A molten metal obtained by melting the metal to be purified is placed in a crucible, a cooling body is immersed in the molten metal, and high-purity metal is crystallized on the surface of the cooling body while rotating at least one of the cooling body or the crucible. In the method for producing high-purity metal,
The crucible has an uneven shape formed by at least one of a groove, a ridge, and a dimple having a circular hole with an aspect ratio of 0.5 to 1.5 on at least a part of the inner surface that contacts the molten metal. and
The surface area of the inner surface of the crucible is more than 1.05 times the surface area when the crucible does not have an uneven shape ,
A method for producing a high-purity metal , wherein the height of the unevenness in the uneven portion is 15% or less of the wall thickness of the crucible . A molten metal obtained by melting the metal to be purified is placed in a crucible, a cooling body is immersed in the molten metal, and high-purity metal is crystallized on the surface of the cooling body while rotating at least one of the cooling body or the crucible. In the method for producing high-purity metal,
The crucible has an uneven shape with dimples having grooves and/or circular holes having an aspect ratio of 0.5 to 1.5 on at least a part of the inner surface of the crucible in contact with the molten metal,
A method for producing a high-purity metal, characterized in that the surface area of the inner surface of the crucible is more than 1.05 times the surface area when the crucible does not have an uneven shape.. The method for producing high-purity metal according to any one of claims 1 to 5 , wherein the relative rotational circumferential speed of the cooling body and the crucible is in the range of 1000 to 10000 mm/s. 7. The method for manufacturing a high-purity metal according to claim 1, wherein the surface area of the inner surface of the crucible is not more than twice the surface area when the crucible does not have an uneven shape. 6. The method for manufacturing a high-purity metal according to claim 2 , wherein the height of the unevenness in the uneven portion is 15% or less of the wall thickness of the crucible. 2. The method for manufacturing high-purity metal according to claim 1, wherein the uneven shape is formed by grooves and/or edges. The method for manufacturing high-purity metal according to any one of claims 4, 5, and 9, wherein the groove is a vertical groove. 2. The method of manufacturing a high-purity metal according to claim 1 , wherein the uneven shape is formed by dimples. 12. The method for manufacturing a high-purity metal according to claim 3, wherein the dimple has one or more shapes of a hemisphere, a spherical crown, a prism, a pyramid, and a truncated pyramid. The method for producing a high-purity metal according to any one of claims 1 to 12 , wherein the metal is aluminum. a crucible containing molten metal containing the metal to be refined;
a cooling body immersed in the molten metal contained in the crucible;
a rotational drive device that rotates at least one of the cooling body or the crucible in order to crystallize high-purity metal on the surface of the cooling body;
In high-purity metal manufacturing equipment equipped with
The crucible has an uneven shape on at least a part of the inner surface that contacts the molten metal,
The surface area of the inner surface of the crucible is more than 1.05 times the surface area when the crucible does not have an uneven shape,
A high-purity metal manufacturing apparatus, wherein the height of the unevenness in the uneven portion is 15% or less of the wall thickness of the crucible. a crucible containing molten metal containing the metal to be refined;
a cooling body immersed in the molten metal contained in the crucible;
a rotational drive device that rotates at least one of the cooling body or the crucible in order to crystallize high-purity metal on the surface of the cooling body;
In high-purity metal manufacturing equipment equipped with
The crucible has an uneven shape on at least a part of the inner surface that contacts the molten metal,
The surface area of the inner surface of the crucible is more than 1.05 times the surface area when the crucible does not have an uneven shape,
A high-purity metal manufacturing apparatus, wherein the uneven shape is formed by vertical grooves. a crucible containing molten metal containing the metal to be refined;
a cooling body immersed in the molten metal contained in the crucible;
a rotational drive device that rotates at least one of the cooling body or the crucible in order to crystallize high-purity metal on the surface of the cooling body;
In high-purity metal manufacturing equipment equipped with
The crucible has an uneven shape on at least a part of the inner surface that contacts the molten metal,
The surface area of the inner surface of the crucible is more than 1.05 times the surface area when the crucible does not have an uneven shape,
A high-purity metal manufacturing apparatus characterized in that the uneven shape is formed by dimples. a crucible containing molten metal containing the metal to be refined;
a cooling body immersed in the molten metal contained in the crucible;
a rotational drive device that rotates at least one of the cooling body or the crucible in order to crystallize high-purity metal on the surface of the cooling body;
In high-purity metal manufacturing equipment equipped with
The crucible has an uneven shape formed by at least one of a groove, a ridge, and a dimple having a circular hole with an aspect ratio of 0.5 to 1.5 on at least a part of the inner surface that contacts the molten metal. and
The surface area of the inner surface of the crucible is more than 1.05 times the surface area when the crucible does not have an uneven shape ,
A high-purity metal manufacturing apparatus , wherein the height of the unevenness in the uneven portion is 15% or less of the wall thickness of the crucible . a crucible containing molten metal containing the metal to be refined;
a cooling body immersed in the molten metal contained in the crucible;
a rotational drive device that rotates at least one of the cooling body or the crucible in order to crystallize high-purity metal on the surface of the cooling body;
In high-purity metal manufacturing equipment equipped with
The crucible has an uneven shape formed by dimples having grooves and/or circular holes with an aspect ratio of 0.5 to 1.5 on at least a part of the inner surface of the contact portion with the molten metal,
A high-purity metal manufacturing apparatus characterized in that the surface area of the inner surface of the crucible is more than 1.05 times the surface area when the crucible does not have an uneven shape. The high-purity metal manufacturing apparatus according to any one of claims 14 to 18 , wherein the relative rotational circumferential speed of the cooling body and the crucible is in the range of 1000 to 10000 mm/s. The high-purity metal manufacturing apparatus according to any one of claims 14 to 19 , wherein the surface area of the inner surface of the crucible is not more than twice the surface area when there is no uneven shape. 19. The high-purity metal manufacturing apparatus according to claim 15 , wherein the height of the unevenness in the uneven portion is 15% or less of the wall thickness of the crucible. 15. The high-purity metal manufacturing apparatus according to claim 14 , wherein the uneven shape is formed by grooves and/or edges. 23. The high-purity metal manufacturing apparatus according to claim 17, wherein the groove is a vertical groove. 15. The high-purity metal manufacturing apparatus according to claim 14 , wherein the uneven shape is formed by dimples. 25. The high-purity metal manufacturing apparatus according to claim 16 or 24 , wherein the dimple has one or more shapes of a hemisphere, a spherical crown, a prism, a pyramid, and a truncated pyramid. The high purity metal manufacturing apparatus according to any one of claims 14 to 25 , wherein the metal is aluminum.

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