JP6342660B2 - Metal purification apparatus and metal purification method - Google Patents

Description

  The present invention relates to a metal refining apparatus using the principle of segregation solidification and related techniques.

  Conventionally, as a purification method for high-purity metals, a cooling body is immersed in a molten metal containing eutectic impurities placed in a refined molten metal holding container, and the cooling body is rotated while supplying a cooling fluid to the cooling body. A method of crystallizing a purified metal having a purity higher than that of a molten metal around the periphery is known (for example, Patent Document 1).

  In the method described in Patent Document 1, after the metal to be purified is dissolved into a molten metal, the molten metal is always heated and maintained at a temperature exceeding its solidification temperature. The cooling body is immersed, and at that time, the surface temperature of the cooling body is maintained to be equal to or lower than the solidification temperature of the molten metal. This means that a higher-purity metal lump is crystallized and adhered.

  This method uses the principle of segregation in which, when the molten metal is held at a temperature in the region between the liquidus and solidus, it is separated into a higher purity solid phase and a liquid phase with more impurities. .

  First, a solid phase with few impurities is generated on the surface of the cooling body, and a liquid phase with many impurities is discharged to a solidification interface between the solid phase and the molten metal to form a so-called impurity concentrated layer. The metal lump that adheres and grows on the outer peripheral surface of the cooling body diffuses impurities outward by making the progress rate of the solidification interface slower than the diffusion rate to the outside of the impurity concentrated layer, and / or the impurity concentration. By forming the layer into a thin layer by dispersing the formation layer according to the flow rate of the liquid phase, the layer is obtained with less impurities.

  In recent years, higher purity metals are required for some applications.

  For example, in the case of aluminum, the raw material aluminum used for the electrode foil of the electrolytic aluminum capacitor is required to have a high purity of 99.9%. Further, in recent years, the demand for high-voltage electrolytic aluminum capacitors has increased, and as the aluminum foil necessary for such high-capacity aluminum capacitors, a higher purity of 99.99% is required.

  In order to obtain a higher-purity metal mass by a conventional purification method, the purification may be performed a plurality of times. Specifically, once purified products are collected and re-dissolved, the re-dissolved molten metal is purified, and if this is repeated, a high-purity metal mass can be obtained by the number of repetitions. However, this method has a great number of steps, and there is a high possibility that impurities are mixed from the production line during that time. In addition, by re-dissolving many times, the necessary cost and necessary energy increase, and the production efficiency is lowered.

  Therefore, it is desirable to further improve the purification efficiency in the purification process itself, rather than increasing the number of purifications.

  In the conventional method, when the cooling body is immersed and rotating in the molten metal, the surrounding molten metal is not stopped, and is rotating in the same direction as the direction of rotation of the cooling body. Although the rotating speed is lower than the rotational speed of the cooling body, the fact that the molten metal is rotating in the same direction as the cooling body reduces the speed difference between the molten metal and the cooling body. It will be smaller than the rotation speed.

  In order to improve the purification efficiency, it is important how to increase the relative speed which is not actually increased.

As a means for further increasing the relative speed between the cooling body and the molten metal, the following method may be mentioned.
(A) The relative speed with the molten metal is increased by increasing the peripheral speed of the cooling body.
(B) In order to slow down the flow rate of the molten metal, a baffle plate is installed on the inner peripheral surface of the crucible as described in Patent Document 2.

  Further, Patent Document 3 discloses that the concentration of impurities generated at the solidification interface by introducing gas bubbles into the molten metal and efficiently causing the gas bubbles to reach the solidification interface by utilizing the reaction force of centrifugal force acting on the melt. A method for improving the purification efficiency by efficiently removing the chemical layer is disclosed.

  In addition, the applicant forms a portion where the flow width of the molten metal is increased by bringing the immersion position of the cooling body closer to the inner peripheral surface of the crucible, and the relative speed between the cooling body and the molten metal is changed by changing the direction of the molten metal flow. Invented a method to enlarge (Patent Document 4).

  In the purification apparatuses described in these patent documents, a molten metal holding container (such as a crucible) having a circular cross section is used.

Japanese Patent Publication No.61-3385 Japanese Patent Laid-Open No. 61-170527 Japanese Patent No. 3673322 JP 2008-163420 A

  However, in the method of increasing the relative speed with the molten metal by increasing the peripheral speed of the cooling body in (A) above, the point that the molten metal is rotated by the cooling body in the same direction is not solved, There is a problem that it is difficult to increase the relative speed. Also in terms of equipment, the device for rotating the cooling body is larger than the conventional device because the rotation speed has to be further increased, which is not practical. In addition, when the peripheral speed of the cooling body increases, the peripheral speed of the molten metal also increases, thereby increasing the level difference of the liquid level and increasing the fluctuation of the liquid level. There's a problem. Furthermore, since the centrifugal force generated on the outer peripheral surface of the cooling body increases and the metal lump attached to the outer peripheral surface of the cooling body is easily detached, the resulting metal lump is reduced, which is not preferable in terms of production efficiency.

  Further, in the method of installing the baffle plate on the inner peripheral surface of the crucible (B), although the baffle plate has an effect of suppressing the flow rate of the entire molten metal or causing a turbulent flow, an attempt is made to increase the range of the effect. Then, it is necessary to increase the length of the baffle plate, but if the length of the baffle plate is increased, there is a risk that the metal block that adheres and grows on the outer peripheral surface of the cooling body contacts the baffle plate, and the baffle plate is damaged. is there. In addition, in order to obtain a crucible having a baffle plate on the inner peripheral surface of the crucible, there is a method of adhering the baffle plate as a separate part to the inner peripheral surface of the crucible, or a method of manufacturing a crucible having a baffle plate from the beginning. However, it takes time and effort for both production and maintenance.

  The method of introducing gas bubbles into the molten metal of Patent Document 3 is also a method that involves the addition of equipment, and it takes time to manufacture and maintain the equipment.

  The method of changing the immersion position of the cooling body of Patent Document 4 does not require the addition of equipment or the trouble of maintenance.

  In view of the background art described above, the present invention provides a metal refining apparatus that can improve the metal refining efficiency and the related arts without the need for additional facilities or maintenance, as in the technique described in Patent Document 4. For the purpose of provision.

  That is, this invention has the structure as described in following [1]-[11].

[1] A molten metal holding container containing a molten metal to be refined and having at least one corner in a cross section;
A metal refining apparatus, comprising: a cooling body which is immersed in a molten metal in the molten metal holding container and rotates relative to the molten metal holding container.

  [2] The metal refining device according to the above item 1, wherein the corner angle of the corner portion is 120 ° or less.

  [3] The metal refining device according to item 1 or 2, wherein the molten metal holding container has a triangular or quadrangular cross-sectional shape.

[4] The metal refining device according to any one of items 1 to 3, which is formed by two surfaces intersecting the tip of the corner. [5] The tip of the corner is a curved surface. 4. The metal refining device according to any one of the preceding items 1 to 3.

[6] Using the metal purifier according to any one of items 1 to 5,
A cooling body is immersed in a molten metal to be purified contained in a molten metal holding container, and a high purity metal is crystallized on the surface of the cooling body while rotating the cooling body relative to the molten metal holding container. Metal purification method.

  [7] The metal refining method according to the above item 6, wherein the molten metal is aluminum.

  [8] A purified metal purified by the method according to the above item 6 or 7.

  [9] A casting manufactured from the refined metal according to item 8 above.

  [10] A metal product obtained by rolling the casting according to item 9 above.

  [11] An electrolytic capacitor in which the metal product according to item 10 is used as an electrode material.

  According to the invention described in [1], since the molten metal flow generated by the rotation of the cooling body is suppressed by colliding with the corner of the molten metal holding container, the relative speed between the cooling body and the molten metal is increased. As a result, the dispersion of the impurity concentrated layer generated in the vicinity of the solidification interface is promoted, the metal purification efficiency is improved, and a high-purity metal can be obtained. Moreover, since such an effect is obtained by the shape of the molten metal holding container, an additional member such as a baffle plate is not required, and the labor of maintenance does not increase.

  According to the invention described in [2], since the corner angle of the corner portion is 120 ° or less, the effect of suppressing the molten metal flow is particularly great.

  According to the invention described in [3], since the cross section of the molten metal holding container is a quadrangle or a triangle, the corner angle is small, and the effect of suppressing the molten metal flow by the corner portion is great.

  According to the invention described in [4], since the tip end portion of the corner is formed by two intersecting surfaces and has an angular and sharp shape, the effect of suppressing the molten metal flow is great.

  According to the invention described in [5], since the tip of the corner is formed with a curved surface, the flow rate of the molten metal at the corner where the flow velocity of the molten metal tends to become extremely slow is promoted, and bubbles and oxidation are caused. It is possible to avoid stagnation of objects.

  According to the invention described in [6], since the molten metal flow generated by the rotation of the cooling body is suppressed by colliding with the corner of the molten metal holding container, the relative speed between the cooling body and the molten metal is increased. As a result, the dispersion of the impurity concentrated layer generated in the vicinity of the solidification interface is promoted, the metal purification efficiency is improved, and a high-purity metal can be obtained. Moreover, since such an effect is obtained by the shape of the molten metal holding container, an additional member such as a baffle plate is not required, and the labor of maintenance does not increase.

  According to the invention described in [7], high-purity aluminum can be purified.

  According to the invention described in [8], it can be a purified metal with high purity.

  According to the invention described in [9], a cast product with high purity can be obtained.

  According to the invention described in [10], a rolled metal product with high purity can be obtained.

  According to the invention described in [11], an electrolytic capacitor using an electrode material made of high-purity rolled metal can be obtained.

It is a schematic block diagram of the metal purification apparatus which concerns on one Embodiment of this invention. It is the II-II sectional view taken on the line of FIG. It is sectional drawing which shows other embodiment of the molten metal holding | maintenance container used for the metal refinement | purification apparatus of this invention. It is sectional drawing which shows other embodiment of the molten metal holding | maintenance container used for the metal refinement | purification apparatus of this invention. It is sectional drawing which shows other embodiment of the molten metal holding | maintenance container used for the metal refinement | purification apparatus of this invention. It is sectional drawing which shows other embodiment of the molten metal holding | maintenance container used for the metal refinement | purification apparatus of this invention. It is sectional drawing which shows other embodiment of the molten metal holding | maintenance container used for the metal refinement | purification apparatus of this invention. It is sectional drawing which shows other embodiment of the molten metal holding | maintenance container used for the metal refinement | purification apparatus of this invention. It is sectional drawing of the conventional molten metal holding | maintenance container.

  1 and 2 are diagrams for explaining a schematic configuration of a metal purification apparatus according to an embodiment of the present invention and a metal purification method using the same.

[Configuration of metal purification equipment]
The metal refining device (1) includes a molten metal holding container (10) for storing molten metal (M) (hereinafter referred to as “molten metal”), a cooling body (20), and a purified metal scraping device (not shown). It has.

  The molten metal holding container (10) has a bottomed cylindrical shape, and the cross-sectional shape thereof will be described later. The molten metal holding container (10) is placed in a heating furnace and heated from the outside, and is controlled so that the molten metal (M) has a constant temperature.

  The material of the molten metal holding container (10) is not limited. However, since the inner surface is in contact with the molten metal (M) and is heated from the outer surface, the molten metal holding container (10) has heat resistance that does not melt at high temperatures and does not cause an extreme decrease in strength. It is necessary. Specifically, graphite, ceramics, a composite material thereof and the like can be recommended.

  The temperature of the molten metal (M) only needs to exceed the solidification temperature, but is lower than the temperature at which no solid phase exists in the molten metal while the cooling body (20) is immersed in the molten metal (M). Is more desirable.

  The cooling body (20) is formed in a truncated cone shape having a large diameter on the upper end side, and is installed at the lower end of the rotating shaft (21). The rotary shaft (21) is connected to a rotary drive device such as a motor and a moving device, applies a rotational force to the cooling body (20), and can move freely up and down and left and right.

  The shape of the cooling body (20) is not limited, and may be a cylindrical shape or other shapes. The rotating shaft (21) has a tubular shape, and a space is also formed inside the cooling body (20). A refrigerant supply pipe (22) and a refrigerant discharge pipe (23) are inserted into the rotary shaft (21), and the refrigerant is supplied from the refrigerant supply pipe (22). The supplied refrigerant is jetted into the internal space of the cooling body (20) through the refrigerant supply pipe (22) and then discharged through the refrigerant discharge pipe (23) inside the rotating shaft (21). The cooling body (20) can be cooled from the inside.

  The material of the cooling body (20) is preferably a material having high heat resistance and high thermal conductivity because it contacts the high-temperature molten metal (M), and graphite, ceramics, a composite material thereof and the like can be recommended. A metal cooling body can also be used as long as it does not melt at the molten metal temperature and does not cause an extreme decrease in strength. Further, the refrigerant of the cooling body (20) can be either gas or liquid, and nitrogen gas, carbon dioxide gas, argon gas, and compressed air can be used as the gas refrigerant. Among these gaseous refrigerants, compressed air can be recommended in terms of cost.

  A refined metal scraping device (not shown) is installed near the side of the molten metal holding container (10), and is crystallized on the surface of the cooling body (20) that has been pulled up from the molten metal (M) and moved. Scrape and collect the purified metal.

[Shape of molten metal cage]
As shown in FIG. 2, the molten metal holding container (10) has a square cross-sectional shape and has four corners (11). The entrance corner (11) is formed by two planes whose front ends intersect, and has an angular and sharp shape. The corner angle (θ) of the corner portion (11) is 90 °.

[Metal purification method]
As shown in FIGS. 1 and 2, the rotating shaft (21) is moved to immerse the cooling body (20) in the molten metal (M) at an arbitrary position in the molten metal holding container (10), and supply the refrigerant. While rotating in the direction of arrow A, the refined metal is slowly crystallized on the peripheral surface of the rotating cooling body (20). During this crystallization process, the eutectic impurities are discharged into the liquid phase to form an impurity-enriched layer in the vicinity of the solidification interface, but the relative relationship between the cooling body (20) and the molten metal (M). Impurities in the impurity concentrated layer are dispersed throughout the liquid phase by the speed.

  Due to the rotation of the cooling body (20), a tangential flow of the cooling body (20) indicated by an arrow B is generated in the molten metal (M). This molten metal flow B is the corner of the molten metal holding container (10). If it collides with (11), the flow will be suppressed. As a result, the relative speed between the cooling body (20) and the molten metal (M) is increased, the dispersion of impurities in the impurity concentrated layer described above is promoted, the impurities are efficiently removed, and the purification efficiency is improved. The high purity metal can be crystallized on the peripheral surface of the cooling body (20).

  The metal may be crystallized on the bottom surface of the cooling body (20) as long as the purity of the crystallized metal is not greatly affected. The cooling body (20) may start rotating after being immersed in the molten metal (M), or may be immersed in the molten metal (M) while being rotated.

  In contrast to the molten metal holding container (10), the molten metal holding container (50) of FIG. 9 has a circular cross section and is formed of only a curved surface without a corner. In such a molten metal holding container (50), the molten metal (M) flows so as to slide on the curved surface, and a smooth swirling flow in the same rotational direction as the cooling body (20) is formed without stagnation of the flow. Is done. For this reason, the relative speed of the cooling body (20) and the molten metal (M) is slower than the molten metal holding container (10) having the shape having the corner (11).

  In the present invention, the melt flow B generated by the rotation of the cooling body (20) is collided with the corner (11) to suppress the swirling flow, and the smooth swirling flow is prevented to prevent the cooling body (20) and the molten metal. The relative speed with (M) is increased. In addition, since such an effect is obtained not by adding a baffle plate or the like but by the shape of the molten metal holding container, an additional member is not required, and maintenance work is not increased.

  The cooling body (20) is rotated in the molten metal (M) for a predetermined time to crystallize the purified metal on the peripheral surface of the cooling body (20), and then the cooling body (20) is pulled up from the molten metal (M). Move to the purified metal scraping device on the side of the holding container (10). The purified metal is scraped off and recovered from the cooling body (20) by the purified metal scraping device. The method for recovering the purified metal is not limited, and it can be recovered from the cooling body by reheating in addition to scraping off.

  If necessary, the cooling body (20) from which the purified metal has been collected is moved again to the molten metal holding container (10), immersed in the molten metal (M), rotated, and purified, and purification and collection are repeated.

[Other shapes of molten metal cage]
The effect of suppressing the molten metal flow B by the corner (11) of the molten metal holding container (10) described above is larger when the corner angle (θ) is smaller, and the preferable corner angle (θ) is 120 ° or less. Further, the preferred corner angle (θ) is 90 ° or less. Therefore, when the molten metal holding container is polygonal, it is preferable that the number of corners is smaller than that of the hexagon. FIG. 3 shows a regular hexagonal molten metal holding container (30), and the corner angle (θ) of the corner corner (31) is 120 °. FIG. 4 shows an equilateral triangular molten metal holding container (32), and the corner angle (θ) of the corner portion (33) is 60 °. Moreover, since a particularly preferable corner angle (θ) is 90 ° or less, a particularly preferable cross-sectional shape of the molten metal holding container is a quadrangle or a triangle.

  Further, the cross-sectional shape of the molten metal holding container is not limited to a regular polygon, and a rectangular molten metal holding container (34) having a long side and a short side shown in FIG. 5 is also included in the present invention. Furthermore, a cross-sectional shape having corners with different corner angles, for example, a trapezoidal shape for a quadrangle, a parallelogram, an isosceles triangle for a triangle, a right triangle, and an unequal triangle for a molten metal holding container of the present invention. include.

  Moreover, since the inhibitory effect of the molten metal flow B can be obtained if the molten metal holding container has at least one corner, it is not limited to a polygonal shape, but a square shape combining a square shape and a circular shape. A molten metal holding container having a fan-shaped cross section is also included in the present invention. However, if the molten metal flow is suppressed at one place, the molten metal surface fluctuation is increased at the corner of the inlet. Therefore, it is preferable to suppress the molten metal flow at a plurality of places. Also from the viewpoint of dispersing the molten metal flow suppression points, the above-described quadrangular or triangular shape is a preferable shape.

  Moreover, the cross-sectional shape of the molten metal holding container may be an expanded polygon in which each side or a part of sides is formed by a curve. The molten metal holding container (35) of FIG. 6 is a bulging quadrilateral in which all sides are curved in the cross-sectional shape, and the corner (36) is formed by the intersection of two curved surfaces. The tip of the entrance corner (36) has an angular and sharp shape. The molten metal holding container (37) in FIG. 7 is an expanded quadrangle that combines a curve and a straight line in the cross-sectional shape, and the corner (38) is formed by intersecting a plane and a curved surface. The front end of the corner (38) has an angular and sharp shape.

  Therefore, the corner having a sharp and sharp shape is formed by the intersection of two surfaces. Specifically, the corners with a sharp and sharp shape are the intersection of planes (see FIGS. 2 to 4), the intersection of curved surfaces (see FIG. 6), and the intersection of planes and curved surfaces (see FIG. 7). It is formed by either. The molten metal holding container may have any one of the above three types of corners, or may have two or three types of corners. good. Moreover, although the molten metal holding containers (35) and (37) in FIGS. 7 and 8 are quadrangular, even in a polygon such as a triangle and a hexagon, three types of corners can be formed by combining a plane and a curved surface. it can.

  In addition, since the above-mentioned molten metal holding container having a fan-shaped cross section is also a triangle formed by two straight lines and one curved line, two corners by intersecting planes and two by intersecting planes and curved surfaces. With two corners.

[Inner corner shape]
The molten metal in the molten metal holding container is stirred by the rotation of the cooling body, and air is taken into the molten metal by this stirring to generate bubbles and oxides. In the present invention, since the molten metal flow is suppressed at the entrance corner using the melt holding container having the entrance corner, the generated bubbles and oxides are also suppressed at the entrance corner. Since the melt flow velocity is extremely slow in the corner, bubbles and oxides suppressed in the corner may float and remain near the surface of the melt. The molten metal containing a large amount of bubbles and oxides has poorer thermal conductivity than the molten metal not containing them, and the molten metal surface is cooled by the atmosphere, so that the bubbles and oxides remain in the corners without flowing. And the surface of the molten metal is easily solidified. The corners (11), (31), (33), (36), and (38) shown in FIGS. 2 to 4, 6, and 7 have a sharp shape with an angular tip. The corners (11), (31), (33), (36), and (38) having such a shape have a large effect of suppressing molten metal flow, but also have a large effect of suppressing generated bubbles and oxides, and these are liable to stay. Tend.

  With respect to the stay of bubbles and oxides in such a corner, the tip of the corner (12) is formed with a curved surface as in the molten metal holding container (40) shown in FIG. This can be dealt with by preventing it from becoming extremely slow at the corner (12). That is, at the corner (12) where the flow rate of the molten metal (M) tends to become extremely slow, the tip portion is formed with a curved surface to promote the flow of the molten metal, thereby avoiding the retention of bubbles and oxides. The radius of curvature (R) at the tip of the corner (12) is preferably in the range of 10 to 100 mm. When the curvature radius (R) is a small curvature of less than 10 mm, the effect of causing bubbles and oxides to flow is small. In addition, if the radius of curvature (R) is 100 mm, the effect of allowing bubbles and oxides to flow is sufficiently obtained. Therefore, a larger radius of curvature (R) exceeding that is meaningless, and an excessively large radius of curvature (R) is not a molten metal. Since the effect of suppressing flow is reduced, the effect of promoting the dispersion of impurities in the impurity concentrated layer is also reduced.

  The corner (12) in FIG. 8 is formed by forming the tip of the corner corner (11) (see FIG. 2) having a sharp and sharp shape by intersecting planes with a curved surface. The tip portion can be formed with a curved surface also with respect to the entering corner portion (36) (see FIG. 6) due to or the entering corner portion (38) (see FIG. 7) due to the intersection of the plane and the curved surface. However, if the polygons have the same number of corners, the corner (36) due to the intersection between the curved surfaces and the corner (38) due to the intersection between the plane and the curved surface are more than the corner (11) due to the intersection between the planes. In addition, since the corner angle becomes large, the degree of decrease in the melt speed at the tip is small and the amount of bubbles and oxides is small. For this reason, the formation of the curved surface at the tip of the entrance corner has great significance in application to the entrance corner formed by the intersection of planes.

  The radius of curvature (R) can be arbitrarily set according to the cross-sectional dimension of the molten metal holding device, the corner angle of the corner, the degree of retention of bubbles and oxides, and the like.

[Other configurations of metal purification equipment]
In the metal refining device of the present invention, the molten metal holding container and the cooling body may be a single set, or a plurality of sets may be arranged side by side, and adjacent molten metal holding containers may be connected in a continuous manner by a connecting rod at the upper end. good.

  In the case of a single set, since the impurity concentration of the molten metal in the molten metal holding container increases when refining is repeated, the purity of the purified metal may be reduced. For this reason, it is preferable to replace the molten metal when the impurity concentration in the molten metal reaches a certain value.

  In the case of a plurality of sets, a plurality of molten metal holding containers communicate with each other, so if the molten metal is poured into the molten metal holding device at one end, the molten metal containing the high-concentration impurities flows out to the adjacent molten metal holding container. It does not stay in one molten metal holding container. In such an apparatus configuration, it is not necessary to replace the molten metal by batch operation for each molten metal holding container, so that work efficiency is improved. Moreover, since the molten metal which flowed out from the most downstream molten metal holding | maintenance container has high impurity concentration, it processes by discharge | emission etc. Further, even if buoys are generated in the molten metal holding container on the upstream side, if the molten metal is supplied to the molten metal holding container on the downstream side after the buoyant is removed, the buoyant is on the molten metal holding container on the downstream side. It is not carried over to.

  In the present invention, since the cooling body only needs to rotate relative to the molten metal holding container, a configuration in which the cooling body is fixed and the molten metal holding container is rotated, and a configuration in which the cooling body and the molten metal holding container are rotated in the reverse direction are also described. Included in the invention.

[Metal to be refined]
The metal refine | purified by this invention can mention aluminum, a silicon, magnesium, lead, zinc, etc. which contain a eutectic impurity.

In the purification of aluminum, if the aluminum to be purified contains impurity elements that form peritectic crystals with aluminum, such as peritectic elements such as Ti, Zr, and V, boron is added to the molten metal stored in the molten metal holding container. It is preferable to apply the purification method of the present invention after adding and stirring. By adding boron and stirring, boron reacts with peritectic impurities contained in the molten metal, and insoluble borides such as TiB ₂ , VB ₂ , and ZrB ₂ are generated. Since the produced insoluble boride is moved away from the cooling body by the centrifugal force generated by the rotation of the cooling body, it is not contained in the aluminum crystallized on the peripheral surface of the cooling body. Moreover, since excess boron is removed as a eutectic impurity, it is not included in the aluminum crystallized on the peripheral surface of the cooling body.

Boron can be added by, for example, a method of adding an Al—B master alloy to aluminum to be purified and dissolving it together, or blowing BF ₃ gas into the molten metal.

  Further, when a plurality of molten metal holding containers are connected in a continuous manner and the molten metal is sequentially supplied to the molten metal holding container on the downstream side, it is preferable to add boron to the uppermost molten metal holding container to remove insoluble borides. . Alternatively, the uppermost molten metal holding container may be dedicated to the boron reaction, and after removing insoluble borides in the first stage molten metal holding container, purification may be performed by segregation solidification in the second and subsequent molten metal holding containers.

  Since the metal refine | purified by the above is high purity, the outstanding characteristic and function can be exhibited by using for various processes and uses. For example, a refined metal may be used for casting to produce a cast product, or the cast product may be rolled and used as various metal plates or metal foils. Moreover, you may use this metal foil as an electrode material of an aluminum electrolytic capacitor, for example.

  In the metal refining apparatus (1) referred to FIG. 1, a refining test of aluminum was performed using molten metal holding containers having different cross-sectional shapes.

[Mold holding container in each example]
Example 1
Four graphite plates were placed in a circular graphite crucible having an inner diameter of 310 mm to form a molten metal holding space having a square cross section. This molten metal holding space corresponds to the molten metal holding container (10) in the metal refining device (1), and the inner surface shape of the molten metal holding container (10) of this example is a square having a side (S1) of 220 mm. (See FIG. 2). The four corners (11) of the molten metal holding container (10) are formed by two planes intersecting the tip, and have an angular and sharp shape.

(Example 2)
A curved surface was formed by using heat-resistant mortar at the tip of the four corners of the molten metal holding space having a square cross section formed in Example 1, and this was used as the molten metal holding space. This molten metal holding space corresponds to the molten metal holding container (40) in the metal refining device (1), and the inner surface shape of the molten metal holding container (40) of this example is a square whose one side (S1) is 220 mm. The leading end of the corner (12) is a curved surface with a radius of curvature (R) = 10 mm (see FIG. 8).

(Example 3)
A molten metal holding container (40) was formed in the same manner as in Example 2 except that the corner (12) had a curved surface with a radius of curvature (R) = 20 mm (see FIG. 8).

Example 4
A graphite holding vessel (30) made of graphite having a regular hexagonal cross section was used (see FIG. 3). One side (S1) of the inner surface in the cross section of the molten metal holding container (30) is 160 mm, and the corner (31) is formed by two flat surfaces intersecting the tip, and has an angular and sharp shape.

(Example 5)
A graphite holding vessel (32) made of graphite having a regular cross section is used (see FIG. 4). One side (S1) of the inner surface in the cross section of the molten metal holding container (32) is 420 mm, and the corner (33) is formed by two planes intersecting the tip, and has an angular and sharp shape.

(Comparative example)
A graphite holding vessel (50) made of graphite having a circular cross section was used (see FIG. 9). The inner diameter (S2) in the cross section of the molten metal holding container (50) is 310 mm.

[Purification of aluminum]
Each metal refining device (10) (40) (30) (32) (50) was incorporated into the metal refining device (1) of FIG. The purification conditions of each example are the same except that molten metal holding containers having different shapes are used, and details are as follows.

  Aluminum to be purified contains Fe: 520 ppm and Si: 220 ppm as main impurities. The aluminum was melted by electric heating in each molten metal holding container to form a molten metal (M), and maintained at 665 ° C. during the purification.

  The cooling body (20) is made of graphite and is a hollow inverted cone having a maximum outer diameter of 150 mm. When the cooling body (20) was immersed in the molten metal (M), it was heated in advance so that the surface temperature was 550 ° C. Further, the cooling body (20) immersed in the molten metal (M) was rotated at a peripheral speed of 4.7 m / sec, and compressed air was supplied as a refrigerant at a flow rate of 1100 liters / min.

  The purification treatment time, that is, the time for rotating the cooling body (10) in the molten metal (M) was 5 minutes.

After refining for 5 minutes, the cooling body (20) is pulled up from the molten metal (M), and the purified aluminum adhering to the peripheral surface of the cooling body (20) is scraped off and recovered, and Fe, which is an impurity, is recovered. The concentration and Si concentration were examined. Furthermore, the purification efficiency of Fe and Si was calculated by the following formula. Table 1 shows the weight of the recovered purified aluminum, the Fe concentration and Si concentration in the purified aluminum, and the purification efficiency.
Purification efficiency of Fe = Fe concentration in purified aluminum / Fe concentration in molten metal (= 520 ppm)
Si purification efficiency = Si concentration in purified aluminum / Si concentration in molten metal (= 220 ppm)

  In addition, in Examples 1 to 4, when the flow velocity in the corners and the vicinity thereof during the purification was visually observed, Example 3 (square, R = 20 mm) was the fastest, followed by Example 2 (square, R = 10 mm). ) Was fast, followed by Example 3 (regular hexagon, R = 0 mm), and slowest was Example 1 (square, R = 0 mm). In addition, also in Example 1 which is the slowest, the flow of the molten metal (M) did not stop completely, but was flowing though it was extremely slow. Table 1 shows the order of fast flow rate with numbers from 1 (fastest) to 4 (slowest).

  As shown in Table 1, it was confirmed that the purification efficiency could be increased by using a molten metal holding container having a square corner instead of a conventional molten metal holding container having a circular cross section. In addition, it was confirmed that the stay of the molten metal in the corner can be prevented by forming the corner in an arc shape.

  According to the present invention, a high-purity metal can be obtained by efficiently refining the metal, so that it can be used for the production of a high-purity metal such as an electrode material for electrolytic capacitors.

1… Metal refining equipment
10, 30, 32, 34, 35, 37, 40, 50 ... molten metal holding container
11, 12, 31, 33, 36, 38 ... corner
20 ... cooling body
21 ... Rotating shaft M ... Molten metal (molten metal)
θ ... corner angle R ... radius of curvature

Claims (3)

The molten metal to be refined is accommodated, and has at least one, two planes, two curved surfaces, and a corner formed by encountering one of the plane and the curved surface in the cross section, and the tip of the corner A molten metal holding container having a shape formed by a curved surface,
A metal refining apparatus, comprising: a cooling body which is immersed in a molten metal in the molten metal holding container and rotates relative to the molten metal holding container. Using the metal purification apparatus according to claim 1 ,
A cooling body is immersed in a molten metal to be purified contained in a molten metal holding container, and a high purity metal is crystallized on the surface of the cooling body while rotating the cooling body relative to the molten metal holding container. Metal purification method. The metal refining method according to claim 2 , wherein the molten metal is aluminum.

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