JP2003071546A - Aluminum ingot, and continuous casting method therefor, and manufacturing method for aluminum foil for electrode of electrolytic capacitor using the aluminum ingot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum ingot having metallic structure wherein a cube bearing grain is made clear in the whole area even in forming an ingot into a foil coil, and a continuous casting method therefor, and a manufacturing method for the aluminum foil for an electrode of an electrolytic capacitor using such an ingot. SOLUTION: In the continuous casting method for the aluminum ingot, wherein a molten metal M of aluminum is supplied from the upper end 3 of a cylindrical water cooling mold 2, whose upper end 3 and lower end 4 are opened, into a hollow part 5, and the ingot C cooled and solidified is drawn down from the lower end 4 and a cooling liquid W is added by pouring to continuously cast the ingot C, the pouring side of the molten metal on the upper end 3 of the cooling mold 2 is made of a fire resistant heat insulating material 6, and by controlling at least one or more of the mold length, a casting speed, and the amount of the cooling liquid in the cooling mold 2, the solidification starting point G of the molten metal M of the aluminum occurs in the area of the fire resistant heat insulating material 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum ingot, a continuous casting method therefor, and a method for producing an aluminum foil for an electrode of an electrolytic capacitor using the aluminum ingot. In the present specification, the continuous aluminum casting method includes a semi-continuous aluminum casting method in which the length of the ingot (slab) in the casting direction is 4 to 6 meters at the maximum. Further, aluminum in the present specification includes not only pure aluminum but also various aluminum alloys.

[0002]

2. Description of the Related Art Aluminum foil for electrodes used in medium or high voltage electrolytic capacitors is manufactured by continuously casting ingots (slabs) made of aluminum, homogenizing, hot rolling, cold rolling, and finishing (final) annealing. It is manufactured through each process. Through the steps described above, the obtained aluminum foil for an electrode has a metal structure in which crystal grains having a cubic orientation (001) [100] are sharply exposed.
Further, in order to make the cubic oriented grains more sharply visible, it has been attempted to further perform intermediate annealing and cold rolling between cold rolling and finish annealing. The continuous casting of the ingot is performed by a continuous casting method using a water-cooled mold made entirely of metal. Further, (001) represents the crystal plane parallel to the rolled surface of the crystal grain, and [100] represents the crystal axis parallel to the rolled direction of the crystal grain by the Miller index.

The aluminum foil has a width of about 1000 m.
It is required that the cubic oriented grains are manifested as described above in the entire region of the coil of m. However, as shown in FIG. 4 (A), in an aluminum foil having a width of about 500 mm extending from the center to the edge in the width direction of the coil, the other than the cube orientation (001) [100] near the edge in the width direction. Crystal grains of crystal orientation (non-cubic orientation) may be generated and remain. In addition, FIG. 4 (A) shows a chemical prepared by adjusting the surface of the aluminum foil with hydrochloric acid: nitric acid: hydrofluoric acid at a ratio of 50: 50: 1.
A photograph (schematic drawing) taken with light that is dissolved in (corrosion liquid) and is not perpendicular to the surface is shown. As a result,
In FIG. 4 (A), crystal grains with a cubic orientation are shown as black, and crystal grains with a non-cube orientation are shown as white. The crystal grains in the non-cubic orientation have an inclination of more than 15 degrees from the cubic orientation (001) [100] in either or both of the plane orientation and the axial orientation. As a result, there is a problem in that the level of the above-mentioned manifestation becomes lower near the edge in the width direction of the coil as compared to near the center in the width direction. For this reason, when the aluminum foil for electrodes of the capacitor is subsequently used, the characteristics thereof become non-uniform due to the variation in manifestation in the coil, which may impair the reliability.

As a result of intensive studies by the inventors, it was found that the cause of the generation and retention of the above-mentioned non-cubic crystal grains is the distribution of the texture in the ingot (slab) obtained by continuously casting aluminum. I found it. That is, the ingot obtained by the normal continuous casting method was cut at a right angle to the casting direction, and the exposed cut surface was treated with a chemical (corrosion solution) adjusted to a ratio of hydrochloric acid: nitric acid: hydrofluoric acid of 50: 50: 1. When it was melted and photographed by shining light that was not perpendicular to the cut surface, the columnar crystals that appeared were those in which the [100] axis was parallel to the casting direction were black, and were inclined by more than 15 degrees from the casting direction. Objects appear white. As a result, as shown in FIG. 4 (B), in the cross section orthogonal to the casting direction, columnar crystals that appear white in the widthwise edges (edges) corresponding to the widthwise edges during rolling are compared later. It was found that a large number of columnar crystals that appeared black were relatively developed near the center in the width direction. From this, it was found that the above-mentioned problems were caused by the nonuniformity of the texture in the ingot.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the problems in the prior art described above and provides a metallographic structure in which cubic oriented grains are exposed in all regions even when an ingot is formed into a foil coil. It is an object of the present invention to provide an aluminum ingot and a continuous casting method thereof, and a method for manufacturing an aluminum foil for an electrode of an electrolytic capacitor using the ingot.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors have conducted earnest research and as a result, when continuously casting an aluminum ingot, [100] columnar crystals are generated and grown in all regions. It was made paying attention to that. The [100] columnar crystal is a columnar crystal whose [100] axis is substantially parallel to the casting direction. That is, the aluminum ingot of the present invention (Claim 1) is an ingot which is cooled and solidified while supplying molten metal of aluminum from the upper end of a cylindrical cooling mold whose upper end and lower end are opened. An aluminum ingot which is continuously cast by pulling down and pouring a cooling liquid, in which crystals nucleated in the initial stage of casting grow as columnar crystals substantially along the upper direction and the inner direction, and from the surface of the ingot of the steady part. No new nucleation of crystals has occurred, and the [100] axis of the columnar crystals in the ingot is substantially parallel to the casting direction. The term “substantially parallel” means that the [100] axis of the columnar crystal is parallel to the casting direction or has an inclination within ± 15 degrees from the casting direction.

According to this, the molten aluminum supplied to the cooling mold is not cooled from the inner wall surface of the mold, but is solidified by the cooling liquid poured obliquely downward from the lower end of the mold. In other words, since nucleation does not occur on the surface of the inner wall of the mold, the casting operation is continuously performed, and the cooling liquid is poured into the ingot sequentially drawn from the lower end of the cooling mold, thereby [100] The ingot is an aluminum ingot having columnar crystals whose axes are substantially parallel to the casting direction. That is, in the ingot, among the crystal grains nucleated during solidification in the initial stage of casting, [10
0] axis grows substantially parallel to the casting direction (axial direction of the cooling mold) to form columnar crystals, and the columnar crystals grow as a whole substantially parallel to the casting direction, and
It grows toward the inside (center) of the ingot (slab).

In the present specification, the term "initial stage of casting" refers to the period when casting is carried out under unsteady conditions that do not reach the casting state under steady conditions described later. In addition, the [100] columnar crystal is a crystal grain in which the direction of the [100] axis is parallel to the casting direction (axial direction of the cooling mold) or is inclined within ± 15 degrees around the casting direction. Refers to. In other words,
Those excluding these are non- [100] columnar crystals. Furthermore, the [100] columnar crystal represents the relationship between the axial orientation and the casting direction, which is also the rolling direction described later, and does not specify the plane orientation parallel to the rolling surface during rolling. Further, the steady portion refers to a time when the lowering speed of the lower die (table) that sequentially descends while supporting the tip (lower end) of the ingot (slab) and the supply amount of the cooling liquid are steady conditions.
Further, the above cooling liquid includes cooling oil as well as cooling water. In addition, the aluminum continuous casting method of the present invention may be either an electromagnetic casting method, an OCC process, or a shell-free casting method proposed by the inventors.

Further, in the method for continuously casting an aluminum ingot according to the present invention (claim 2), the molten aluminum is supplied and cooled from the upper end of a cylindrical cooling mold whose upper end and lower end are opened. In the method of pulling down the solidified ingot from the lower end and continuously casting an aluminum ingot by adding a cooling liquid, the molten metal injection side at the upper end of the cooling mold is made of a refractory heat insulating material, and the cooling mold By adjusting at least one of the mold length of the cooling ring, the casting speed, and the amount of the cooling liquid, the solidification start point of the molten aluminum is generated in the region of the refractory heat insulating material. .

According to this, since the molten metal injection side of the cooling mold is made of the refractory heat insulating material, heat removal from the molten aluminum through the mold is suppressed. As a result, the heat removal from the molten metal is directed only to the lower side where it is cooled by the cooling liquid, so that columnar crystals whose [100] axis is substantially parallel to the casting direction can be generated in the entire aluminum ingot. That is,
In order to make the solidification start point of the molten metal within the area (level) of the refractory heat insulating material, shorten the mold length of the cooling ring of the cooling mold, lower the casting speed, and / or increase the cooling liquid amount. By adjusting, the heat removal from the cooling mold can be further suppressed, and it becomes easy to limit only the above heat removal to the lower side.
These suppress nucleation of new crystal grains from the surface of the ingot in the steady part of casting, and thus [100]
It is possible to reliably obtain an ingot in which columnar crystals whose axes are substantially parallel to the casting direction are entirely formed. For the refractory heat insulating material, for example, calcium silicate or the like is used.

Furthermore, according to the present invention, graphite or a mold surface having characteristics equivalent to graphite is formed inside the refractory heat insulating material on the molten metal injection side at the upper end of the cooling mold.
A continuous casting method for aluminum ingots (claim 3) in which the solidification start point of the molten aluminum occurs on the mold surface is also included. According to this, since the mold surface made of graphite or the mold surface having the same solid lubricating property as graphite contacts the surface of the molten aluminum and the ingot, heat removal through the mold while preventing deterioration of the heat insulating material. Can be further suppressed. Moreover, since the starting point of solidification of the molten metal occurs at the level of the mold surface made of the above graphite or the like, nucleation on the surface of the ingot is suppressed and it is almost parallel to the casting direction [1
The growth of columnar crystals from below with the [00] axis is maintained. As a result, it becomes possible to easily control the growth of the columnar crystals whose [100] axis is substantially parallel to the casting direction along the casting direction and the inner direction, and at the same time, the nucleation of non- [100] columnar crystals occurs. Since it is suppressed, it is possible to easily manufacture an aluminum ingot in which columnar crystals each having a [100] axis substantially parallel to the casting direction are formed.

On the other hand, in the method for producing an aluminum foil for electrodes of an electrolytic capacitor according to the present invention (claim 4), the aluminum ingot is homogenized, and then the casting direction of the ingot at the time of the casting is set to the rolling direction. Forming process including hot rolling and cold rolling and heat treatment process including finish annealing. According to this, [100]
Homogenization treatment of the ingot in which the axis is almost parallel to the casting direction and columnar crystals formed in the entire ingot, and then hot rolling and cold rolling in the rolling direction (longitudinal direction) along the casting direction And a heat treatment step such as finish annealing. As a result of the molding process, in all areas of the foil coil,
A uniform rolling texture is formed. Then, during the finish annealing, cubic-oriented crystal grains are generated from the rolling texture, but since the rolling texture is uniform in the entire area of the foil coil, the cubic-oriented crystal grains appear uniformly in the entire area of the coil. Become sharp. Therefore, it is possible to reliably manufacture the aluminum foil for electrodes of the electrolytic capacitor having excellent characteristics such as capacitance. The homogenization treatment includes a case where the heating is simply performed before hot rolling.

Further, according to the present invention, the ingot is further subjected to intermediate annealing and finish cold rolling between the cold rolling and finish annealing, a method for producing an aluminum foil for electrodes of electrolytic capacitors. (Claim 5) is also included. According to this, by further performing intermediate annealing and finish cold rolling, unnecessary non-cube-oriented crystal grains generated during intermediate annealing from the rolling texture of the initial cold rolling are sufficiently formed during finish annealing. It will stop producing and growing. As a result, it becomes possible to reliably manufacture the aluminum foil for electrodes in which the crystal grains in the cubic orientation are sharper (revealed).

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a continuous casting method according to the present invention for obtaining an aluminum ingot of the present invention and a casting apparatus 1 used for the method. The casting apparatus 1 according to the present invention is used exclusively in the shell-free casting method, and as shown in FIG. 1, has a tubular shape having a rectangular shape in plan view and a hollow portion 5 having an open upper end 3 and a lower end 4 inside. A water-cooled mold (cooling mold) 2, a spout (pouring pipe) 10 hanging from above near the central axis of the water-cooled mold 2, and a lower mold 16 positioned below the water-cooled mold 2 so as to be vertically movable. There is. As shown in FIG. 1, the water-cooled mold 2 has an upper end 3
It comprises a refractory heat insulating material 6 which is located nearer to the side where the molten aluminum M is injected and a metal cooling ring 8 which is located nearer the lower end 4 thereof and has a hollow portion 9 having a square cross section. The hollow portion 5 has a rectangular shape in a plan view and has a size of a short side of 300 to 600 mm × a long side of 1000 to 2000 mm.

The heat insulating material 6 is made of, for example, calcium silicate, and a graphite plate 7 is adhered to the entire inner surface of the heat insulating material, which is a mold surface. The graphite plate 7 may be replaced with the heat insulating material 6 up to that region. In this form, molten metal M
Also, a solid lubricant (for example, carbon particles or boron nitride (BN)) may be applied to the portion in contact with the ingot C. Further, the slits s are formed in a square shape inwardly and obliquely downward from the hollow portion 9 of the cooling ring 8, and the high pressure water W supplied to the hollow portion 9 is used as a film of the cooling water (cooling liquid) W in the shape of a quadrangular pyramid. It is possible to inject. Incidentally, a through hole may be used instead of the slit s. Further, as shown in FIG. 1, a horizontal flow dividing plate 12 is arranged near the lower end of the spout 10 and
A ring-shaped float 14 that floats on the molten metal M of aluminum is arranged outside the lower part of the float at regular intervals.

Next, the continuous casting method of the present invention using the casting apparatus 1 will be described. The lower mold 16 is previously inserted in the lower portion of the hollow portion 5 inside the horizontal mold 2.
In such a state, as shown in FIG. 1, pure aluminum molten metal M, which has been purified by removing impurities in advance, is poured into the spout 10 and collided with the flow dividing plate 12, and as shown by an arrow in the upper part of FIG. , The molten metal M is radially supplied into the hollow portion 5 inside the horizontal mold 2. The molten metal M sequentially supplied in the hollow portion 5 and above the lower mold 16 is contacted with the graphite plate 7 and then contacted by the inner surface of the cooling ring 8 to be cooled, and further injected from the cooling ring 8. Since it is forcibly cooled by the cooling water W, it begins to solidify from its outer surface. By such solidification, as shown in FIG. 1, ingots C are sequentially formed below the solidus line K. The solidus line K is highest at the outermost portion in contact with the water-cooled mold 2, and then is cooled by the cooling water W and extends toward the central portion. Therefore, the solidus line K is lowest near the central portion.

Further, as shown in FIG. 1, the distance L from the upper end of the cooling ring 8 for cooling the molten metal M to the injection position of the cooling water W is the effective mold length in the mold apparatus 1.
In addition, the effective mold length L is generally shorter in the casting apparatus 1 of the shell-free casting method using the heat insulating material 6 than in the continuous casting method using a normal metal cooling mold. Furthermore,
By adjusting at least one of shortening the mold length of the cooling ring 8 (length in the vertical direction in FIG. 1), lowering the casting speed, or increasing the amount of cooling water W supplied, A solidification starting point G, which changes from M to the solidified aluminum ingot C of the present invention, can be generated in the region of the refractory heat insulating material 6 as shown in FIG.

As described above, the heat insulating material 6 having the graphite plate 7 adhered therein is arranged near the upper end 3 of the water-cooled mold 2 so that the effective mold length L is relatively short and the solidification starting point G is the heat insulating material. By setting it within the region of the material 6, the heat removal from the molten metal M can be concentrated in the downward direction in which the cooling water W is jetted. As a result, in the aluminum ingot C, nucleation is suppressed in the vicinity of the solidus line K close to the surface of the ingot C, and the direction of the [100] axis is almost parallel to the casting direction (vertical direction in FIG. 1). The growth of columnar crystals can be maintained. Further, as shown in FIG. 1, the solidus line K becomes lower toward the center of the ingot C, but since the columnar crystals of the ingot C grow perpendicularly to the solidus line, The crystal shape follows the inside of the ingot C. However, even in this case, the relationship between the [100] axis and the casting direction is maintained. Therefore, most of the columnar crystals are controlled to have columnar crystals having a [100] axis substantially along the casting direction.

As a result, FIG. 1 shows the entire region of the ingot C which solidifies below the solidus line K and descends with the lower mold 16 along the thick arrow at the bottom of FIG. Is almost parallel to the casting direction (± 1 against the vertical line in Fig. 1).
It is possible to form columnar crystals S having a [100] axis z of 5 degrees or less). The lower mold 16 descends into a pit (not shown) in accordance with the vertical expansion of the aluminum ingot C, and stops when the length in the casting direction reaches, for example, 4 to 6 meters. Further, the aluminum ingot C as described above can be continuously cast also by the electromagnetic casting method or the OCC process by concentrating the heat removal from the molten metal M in the casting direction.

The columnar crystal S having the above-mentioned [100] axis z
A method of manufacturing an aluminum foil for an electrode of an electrolytic capacitor using a cast ingot C having the entire region will be described with reference to FIG. The aluminum ingot C obtained in the above-mentioned continuous casting step S1 is chamfered at an unnecessary peripheral portion and then charged into a soaking furnace (not shown), and as shown in FIG.
First, a homogenization treatment S2 of heating to 0 to 620 ° C. and holding for 48 hours is performed. The chamfering may be performed after the homogenizing process S2. Next, as shown in FIG. 2 (A), hot rolling S3 (forming step) of passing the aluminum ingot C in the above temperature range through a rolling mill is performed. For the hot rolling S3, for example, a tandem type four-high rolling mill is used, and the rolling direction is along the casting direction, the compression ratio is arbitrary, and an arbitrary number of passes are performed to show a thickness of about 7 mm. Do not shape into a coil.

Next, after cooling the coil obtained by the hot rolling S3 to room temperature, as shown in FIG. 2 (A), cold rolling (forming step) S4 is performed. For the cold rolling S4, for example, a 2-tandem 4-high rolling mill or a single 4-high rolling mill is used, and the rolling direction is along the casting direction, and the rolling reduction is about 30 to 70% and 5 to 10 passes are performed. By doing so, an aluminum foil (not shown) having a thickness of about 130 μm is formed. Finally, heat to 300-600 ° C. and for example 24
A finish annealing (heat treatment step) S7 of holding for a time is performed. As a result, it is possible to obtain an aluminum foil in which the processed structure including the strain deformed along the rolling direction by the rolling S3 and S4 is recrystallized into crystal grains having a cubic orientation and having no strain.

As shown in FIG. 2B, cold rolling S4
The subsequent aluminum foil may be subjected to intermediate annealing S5. Such annealing S5 is to heat to 180 to 300 ° C., hold for, for example, 12 hours, and then cool to room temperature. In combination with finish cold rolling S6 and finish annealing S7 described below,
By the rolling S3 and S4, a strain-free cubic oriented crystal can be sharpened from a processed structure including a strain deformed along the rolling direction. Subsequently, as shown in FIG. 2 (B), finish cold rolling S6 is performed in one pass at an extremely low reduction ratio to shape an aluminum foil having a thickness of about 110 μm. Then, by performing the above-mentioned finish annealing S7, it is possible to more reliably obtain the above-mentioned aluminum foil having a sharpened cubic orientation.

[0023]

EXAMPLES Specific examples of the present invention will be described below. The molten aluminum M having the composition shown in Table 1 is
By continuously casting individually using the casting apparatus 1 shown in FIG. 1, aluminum ingots C of Examples 1 to 4 having a thickness of 508 mm and a width of 1080 mm were obtained. Table 1 also shows the effective mold length L, the amount of cooling water, the casting temperature, and the lowering speed of the lower mold 16 in these continuous castings. On the other hand, by continuously casting the molten metal M of pure aluminum shown in Table 1 at the effective mold length L, the cooling water amount, the casting temperature, and the lowering speed of the lower die shown in Table 1, the aluminum casting of the comparative example of the same size was performed. Mass C was obtained. Effective mold length L of the comparative example
However, what is longer than that of Examples 1 to 4 is that the water-cooled mold used in the comparative example is entirely made of metal similar to that used in the conventional continuous casting method described above, and the inside thereof is filled with cooling water. Due to the form.

[0024]

[Table 1]

The aluminum ingot C of Example 2 was cut at a right angle to the casting direction, and the exposed cut surface was dissolved with a chemical (corrosion solution) adjusted to a ratio of hydrochloric acid: nitric acid: hydrofluoric acid of 50: 50: 1. However, it was photographed using non-vertical light. As a result, as shown in FIG. 3 (A), from the edge portion (edge portion) in the width direction to the vicinity of the center, a relatively large amount of [100] columnar crystals appearing in black develop and non- [100] appearing in white. It was found that the growth of columnar crystals was significantly suppressed. The ingot C of Examples 1, 3 and 4 was the same as above. On the other hand, the aluminum ingot C of the comparative example was also cut, treated, and photographed in the same manner as described above, and as a result, similar to FIG. 4B, a non-white image was observed near the edge in the width direction. A relatively large amount of [100] columnar crystals were developed, and a relatively large amount of [100] columnar crystals, which appeared black in the center of the width direction, were developed. As a result of the above, the aluminum ingot C of the present invention
And the effect of the continuous casting method was confirmed.

Further, the aluminum ingots C of Example 2 and Comparative Example were made into an aluminum foil having a thickness of 130 μm by the above-mentioned hot rolling S3 and cold rolling S4, and 2
An aluminum foil having a thickness of 110 μm was obtained by intermediate annealing S5 heating at 60 ° C. for 5 hours and finish cold rolling S6. About these, finish annealing S which is heated at 500 ° C for 1 hour
7 was applied. The surfaces of the obtained aluminum foils of Example 2 and Comparative Example, which had been exposed by melting with the same chemicals as above, were photographed in the same manner as above. As a result, in the aluminum foil of Example 2, as shown in FIG. 3 (B), from the edge portion in the width direction to the vicinity of the center, a relatively large number of cubic-oriented crystal grains appearing in black developed and appeared in white. The development of grains with non-cubic orientation was significantly suppressed. The aluminum foils of Examples 1, 3 and 4 were the same as above.

On the other hand, in the aluminum foil of the comparative example, as in the case of FIG. 4 (A), non-cubic crystal grains which appear white in the vicinity of the edges in the width direction were developed. From the above results,
In the aluminum foil of the example obtained by the manufacturing method of the present invention, the crystal grains in the cubic orientation were sharp in the entire region of the coil.
It was (realized). That is, in the foil, the crystal grains in the cubic orientation are uniformly distributed in the entire region, and thus even when used as the electrode of the electrolytic capacitor, the required characteristics (e.g. capacitance) are stably exhibited. It has also been found that the reliability can be increased. Such an example supports the effect of the method for producing an aluminum foil for an electrode of an electrolytic capacitor according to the present invention.

[0028]

According to the aluminum ingot (Claim 1) of the present invention described above, the molten aluminum supplied to the cooling mold begins to solidify while being cooled by the mold, and the molten aluminum flows from the mold at the stationary portion. Heat removal is suppressed, and among crystals nucleated during solidification in the initial stage of casting, only crystals having a [100] axis substantially parallel to the casting direction grow preferentially. As a result, the [100] axis of most columnar crystals is almost parallel to the casting direction. In addition, since the cooling liquid is poured into the ingots sequentially drawn from the lower end of the water-cooled mold, the aluminum ingots having columnar crystals having [100] axes substantially parallel to each other along the casting direction are formed. Become.

Further, according to the aluminum continuous casting method of the second aspect, since the molten metal injection side of the cooling mold is made of a refractory heat insulating material, heat removal from the molten metal through the mold is suppressed. As a result, the heat removal from the molten metal is directed only to the lower side where it is cooled by the cooling liquid, and columnar crystals having the [100] axis along the casting direction are generated in the entire ingot. Moreover, the mold length of the cooling ring in the cooling mold,
Adjusting either the casting speed or the amount of cooling liquid so that the solidification start point of the molten metal is within the area of the refractory heat insulating material, so that heat removal from the cooling mold is suppressed and only the above heat removal downward is limited. Easier to do. As a result, in the steady part of casting, non- [100]
It is possible to more reliably obtain an ingot in which the nucleation of the columnar crystals is suppressed and the columnar crystals having the [100] axis substantially along the casting direction are entirely formed. Further, according to the continuous casting method for aluminum of claim 3, since the mold surface having a mold surface made of graphite or the like comes into contact with the molten aluminum, deterioration of the heat insulating material is prevented and heat removal through the mold is further improved. Can be suppressed. Moreover, since a solidification start point of the molten metal occurs in the level of the mold surface, new nucleation near the surface is suppressed, and [10]
The growth of columnar crystals from below having the [0] axis can be maintained.
Therefore, it is possible to easily manufacture an aluminum ingot having columnar crystals whose [100] axis is substantially parallel to the casting direction.

On the other hand, according to the method for producing an aluminum foil for an electrode of an electrolytic capacitor according to the present invention (claim 4), the rolling direction (longitudinal direction) along the casting direction is applied to the ingot.
Forming steps such as hot rolling and cold rolling and heat treatment steps such as finish annealing are performed. Therefore, the crystal grains in the cubic orientation are sharpened (revealed) in the entire region, and the aluminum foil for electrodes of the electrolytic capacitor having excellent characteristics such as capacitance can be reliably manufactured. Further, according to the method for producing an aluminum foil for an electrode of an electrolytic capacitor of the fifth aspect, it is possible to more reliably produce an aluminum foil having crystal grains in a cubic orientation which are further sharpened.

[Brief description of drawings]

FIG. 1 is a schematic view showing a continuous casting method of the present invention.

2A and 2B are flow charts showing a method for manufacturing an aluminum foil for electrodes of the present invention.

3 (A) and 3 (B) are schematic drawings showing a structure of an ingot or an aluminum foil of an example.

4A and 4B are schematic drawings showing the structure of a conventional aluminum foil or ingot.

[Explanation of symbols]

2 ... Water-cooled mold (cooling mold), 3 ... Upper end, 4
...... Lower end part, 6 ... Fireproof heat insulating material, 7 ... Graphite plate (mold surface), 8 ... Cooling ring, M ... Molten metal, C ... Aluminum ingot, W ... Cooling water (cooling liquid) , G
…… Solidification starting point, S …… Columnar crystal,
z ... [100] axis S3 ... hot rolling,
S4 ... Cold rolling, S5 ... Intermediate annealing,
S6 ... Finish cold rolling, S7 ... Finish annealing

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B22D 11/059 B22D 11/059 110 110F 120 120A (72) Inventor Yasushi Ishiwata 161, Kambara, Kambara-cho, Anbara-gun, Shizuoka Metal Co., Ltd. in Kambara Electrolysis and Casting Factory (72) Inventor Susumu Nawada 1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Prefecture Nippon Light Metal Co., Ltd. Group Technology Center (72) Inventor Kazumi Higashino Kambara, Anbara-gun, Shizuoka Prefecture 161, Machi Kambara Nippon Light Metal Co., Ltd., Kambara Works (72) Inventor Kiyomi Tsuchiya 1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Prefecture F-term (reference) 4E002 AA08 AD13 BD02 BD09 4E004 AA07 NA02 NC08

Claims (5)

[Claims] 1. An ingot, which is solidified by cooling while supplying a molten aluminum from an upper end of a cylindrical cooling mold whose upper end and lower end are open, is drawn down from the lower end and a cooling liquid is added to continue. In an aluminum ingot to be cast, nucleated crystals at the initial stage of casting grow as columnar crystals substantially along the upper and inner directions, and new crystals nucleate from the surface of the ingot in the steady part. In addition, the aluminum ingot is characterized in that the [100] axis of the columnar crystal in the ingot is substantially parallel to the casting direction. 2. A molten aluminum is supplied from the upper end of a cylindrical cooling mold having an open upper end and a lower end, and a cooled and solidified ingot is drawn down from the lower end and a cooling liquid is added. In the method of continuously casting an aluminum ingot, the molten metal injection side at the upper end of the cooling mold is made of a refractory heat insulating material, and the mold length of the cooling ring in the cooling mold, the casting speed, and at least the cooling liquid amount. A continuous casting method of an aluminum ingot, wherein the solidification start point of the molten aluminum is generated in the region of the refractory heat insulating material by adjusting one or more. 3. A mold surface having the same characteristics as graphite is formed inside the refractory heat insulating material on the molten metal injection side at the upper end of the cooling mold, and the solidification starting point of the molten aluminum is the above. It occurs on the mold surface. The continuous casting method for an aluminum ingot according to claim 2, characterized in that. 4. A forming step and a finish including homogenizing the aluminum ingot according to claim 1, and thereafter including hot rolling and cold rolling in which a rolling direction is a casting direction during the casting of the ingot. A method of manufacturing an aluminum foil for an electrode of an electrolytic capacitor, which comprises performing a heat treatment step including annealing. 5. The electrode of the electrolytic capacitor according to claim 4, wherein the ingot is further subjected to intermediate annealing and finish cold rolling between the cold rolling and the finish annealing. For manufacturing aluminum foil for automobiles.