JPH02270928A - Aluminum foil for anode of chemical condenser and its manufacture - Google Patents

Abstract

PURPOSE:To obtain the foil in which etching progresses in parallel to the thickness direction even if Al purity is regulated to about 99.98% at relatively low cost by manufacturing Al foil having specified range of compsn. under specified conditions and regulating the cubic azimuthal ratio of crystals to the specified value or above. CONSTITUTION:An ingot constituted of 0.0040 to 0.0100% Si, 0.0035 to 0.0085% Fe, 0.0025 to 0.0100% Cu, 0.0010 to 0.0150% Zn, 0.0010 to 0.0150% Ga, <=0.0010% Ti, <=0.0050% inevitable elements and the balance Al is used. The ingot is subjected to homogenizing treatment and hot rolling, is thereafter subjected to process annealing at 250 to 350 deg.C, is then cold-rolled at 10 to 35% rolling reduction and is thereafter subjected to final annealing at >=500 deg.C. In this way, the Al foil for the anode of a chemical condenser having >=85% cubic azimuthal ratio of crystals can be obtd. At the time of subjecting the Al foil to etching treatment, it can be executed deeply in parallel to the thickness direction of the foil to increase the surface area of the foil surface, by which anode foil having high electrostatic capacity can be obtd.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an aluminum foil suitable for obtaining a high-voltage electrolytic capacitor anode foil used for strobes, etc., and a method for manufacturing the same.

[Conventional technology]

Conventionally, to obtain high voltage electrolytic capacitor anode foil, A
l Aluminum foil with a purity of 99.99% is used. When this aluminum foil is subjected to etching treatment, the etching progresses deeply parallel to the thickness direction of the foil, resulting in an anode foil with high capacitance, which is preferable. However, aluminum foil with an Al purity of 99.99% has the drawback of being expensive. For this reason, attempts have been made to obtain a high-voltage electrolytic capacitor anode foil using a relatively inexpensive aluminum foil with an Al purity of less than 99.99%, for example, an Al purity of about 99.98%. However, even when etching is performed on aluminum foil with an Al purity of about 99.98%, the etching does not proceed deeply parallel to the thickness direction of the foil, and the etching process does not proceed deeply parallel to the thickness direction of the foil.
．． It was not possible to obtain an anode box with a high capacitance equivalent to that obtained using 99% aluminum foil.

[Problem to be solved by the invention]

The inventor of the present invention found that the reason why etching does not proceed deeply parallel to the thickness direction of aluminum foil with Al purity of about 99.98% is that the crystals in this aluminum foil are oriented in various directions. I thought it was because there was a This is A
This is because aluminum foil with a purity of about 99.98% contains a relatively large amount of elements other than Δ1. Therefore, when etching is performed on any of the foils, the etching progresses along the direction of the crystals and does not proceed parallel to the thickness direction of the foil. Therefore, the inventor proposed that if aluminum foil with a specific composition range is manufactured under certain conditions, the Al purity will be 99°9) 3%.
It was discovered that the etching progresses parallel to the thickness direction of the foil, and this led to the present invention.

[Means and effects for solving the problems] That is, the present invention provides Si0.0040 to 0.000. (month()00%Fed, 0
035-0.0085%, Cu0.0025”0.01
00%, Zn0.0010”□0.0150%, Ga0
．． 0010"-0, Ol, 50%, Ti0.0010%
Hereinafter, an aluminum foil consisting of 0.0050% or more of unavoidable elements and the balance Al, characterized in that the i1-plane orientation ratio of the crystals in the aluminum foil is 85% or more. The present invention relates to an aluminum foil for electrolytic capacitor anodes and a method for manufacturing the same. The aluminum foil for electrolytic capacitor anodes according to the present invention contains Si in an amount of 0.040% to 0.0100%. In order to prevent the crystal from taking a certain orientation,
Undesirable. Furthermore, if Si is less than 0.0040%, the purity of the Al wire must be increased, and it is impossible to obtain an aluminum foil with a purity of less than 99.99%, which is the objective of the present invention. Not. Fe is 0.0035-0.008 in aluminum foil
The 5% Agency has also been established. If Fe exceeds 0.0085%, a large amount of precipitates will form in the Ill, which will prevent the crystal from taking a certain orientation, which is not preferable.
If it is less than 0.035%, the purity of the Al wire must be increased, and it is not possible to obtain an aluminum foil with an Al purity of less than 99.99%, which is the object of the present invention. Cu is 0.0025 to 0.010 in aluminum foil
Contains 0%. If Cu exceeds 0.0100%, excessive dissolution will occur during etching, which is not preferred. Further, if Cu is less than 0.0025%, the A1 purity must be increased, and it is not possible to obtain an aluminum foil with an A1 purity of less than 99°99%, which is the object of the present invention, which is not preferable. . Zn is 0.0010 to 0.01 in aluminum foil
Contains 50%. If Zn exceeds 0.0150%, excessive dissolution will occur during etching, which is not preferable. Furthermore, if the Zn content is less than 0.600.10%, the purity of the Al wire must be increased, and it is not possible to obtain an aluminum foil with a purity of less than 99.99%, which is the object of the present invention. Ga is present in the aluminum foil from 0.0010 to 0.0+,
It is 50% irritated. If Ga exceeds 0.0150%, the strength of the aluminum foil decreases, which is not preferable. Moreover, when Ga is less than 0.0010%, A1
Au must have high purity and is the object of the present invention.
This is not preferred because aluminum foil with a purity of less than 99.99% cannot be obtained. Ti is contained in the aluminum foil in an amount of less than 0.0010%. If Ti exceeds 0.0010%, Ti becomes a solid solution in Al and disappears, inhibiting crystal growth, which is preferable. Not. Unavoidable elements include MB+ Mn, Cr, etc., but these must not be mixed in the aluminum foil in an amount of less than 0.0050%. Unavoidable elements are 0, 0
If it exceeds 0.050%, excessive dissolution occurs during etching and crystals do not grow sufficiently, which is not preferable. In the Aluminum A 7A containing the above elemental components, the cubic orientation ratio of the crystal is 85% or more in the present invention. Generally speaking, the cubic orientation ratio refers to the degree to which the crystal planes of the cubic crystals in the aluminum foil are parallel to the surface of the aluminum foil.6 In other words, the crystal orientation of the cubic crystals has positive and negative If ignored, they are (1,00) respectively. It is represented by (010) and (001). These are collectively expressed as (1001). Therefore, the cubic orientation ratio is determined by how much (1001 plane) is observed on the surface of the aluminum foil. The cubic orientation ratio in the present invention is llCl: llN0+:HF=50ml
After immersing the aluminum foil in a chemical etching solution with a volume ratio of 47ml and 1:3ml to reveal the crystal structure, the ratio of the area of the (100) plane to the entire field of view was determined using an optical microscope photograph, and expressed as a percentage. It is expressed. The cubic orientation ratio of the aluminum foil for an electrolytic capacitor anode according to the present invention needs to be 85% or more. If the cubic orientation ratio is less than 85%, there will be many crystal planes other than (100), so even if etching is performed, etching will not proceed deeply parallel to the thickness direction of the foil. Such aluminum foil for electrolytic capacitors can be manufactured by the following method. First, Si0.0040~0.0100%, Fe0.0
035-0.0085%, Cu0.0025-0.01
00%, Zn0.0010-0.0150%, Ga0.
0010=0.0150%, Ti0.0O10% or less,
An ingot containing 0.0050% or less of unavoidable elements and the remainder Al is prepared. Then, this ingot is subjected to homogenization treatment. The homogenization process is
This is done to dissolve elements other than Al into Al. For this reason, it is preferable to perform homogenization treatment at a relatively high temperature for a long time. Specifically, the heating time is preferably about 5 hours or more at 600° C. or higher. After the homogenization treatment, hot rolling is performed to form the ingot into a plate shape. At this time, in order to promote recrystallization, the hot rolling temperature was set at 3.
The temperature is preferably about 30°C or higher. Specifically, the hot rolling start temperature is set to about 550°C or higher, and the hot rolling end temperature is set to 3.
The temperature should be about 30℃ or higher. After hot rolling, intermediate annealing is performed. Note that, of course, before performing intermediate annealing, cold rolling may be performed in order to obtain a desired aluminum plate thickness. In this intermediate annealing, the temperature needs to be 250 to 350°C. If the temperature is less than 250°C, nucleation of crystal grains will not be sufficient and crystal planes parallel to the plate surface will not grow, which is not preferable. Also, when the temperature exceeds 350℃,
The strength of the resulting aluminum foil decreases, which is not preferable. After the intermediate annealing, finish rolling is performed. Finish rolling is performed by cold rolling. However, at this time, finish rolling must not be performed under conditions where the crystal planes grown during intermediate annealing are destroyed or the cubic orientation is changed. For this purpose, the rolling reduction ratio of the aluminum plate must be 10 to 35%. The rolling reduction ratio is [(aluminum plate thickness before finish rolling - aluminum foil thickness after finish rolling)]
/aluminum plate thickness before finish rolling]×100. When the rolling reduction exceeds 35%, changes in crystal planes occur, making it impossible to obtain an aluminum foil with a cubic orientation ratio of 85% or more. Further, if the rolling reduction ratio is less than 10%, the driving force for growth of the (100) crystal plane during final annealing will be reduced, which is not preferable. After finish rolling, final annealing is performed. This final annealing is
This promotes the growth of crystals in aluminum foil. In the present invention, final annealing must be performed at 500°C or higher. If the final annealing is performed at a temperature lower than 500°C, crystal growth will not be sufficient and the number of crystal planes parallel to the aluminum foil surface will not increase, which is not preferable. By the method described above, the aluminum foil for electrolytic capacitor anodes according to the present invention can be obtained.

【Example】

Examples 1 to 7 and Comparative Examples 1 to 4 First, ingots having the compositions shown in Table 1 were prepared. Table 1 This ingot was subjected to homogenization treatment, hot rolling, intermediate annealing, finish rolling and final annealing under the conditions shown in Table 2. Therefore, the j obtained in this way! z-sa10
Table 2 shows the capacitance and capacitance of two frames made of 4μ aluminum foil.
The obtained aluminum foil was immersed in a mixed aqueous solution of 7.0% hydrochloric acid and 7.0% sulfuric acid, and etched for 8 minutes and 20 seconds while applying a DC current of 8 A/d. The foil was immersed in a chemical solution (mixed aqueous solution of 13% boric acid and 0.07% borax) at 85°C and heated to 375V.
After chemical formation, ζ was measured using a capacitance make. :, margin/white) Table 2 (Part 4) As is clear from the above results, the aluminum foil according to the example has a cubic orientation ratio of 85% or more, which indicates that the capacitance is increased. On the other hand, it can be seen that the aluminum foil according to the comparative example has a cubic orientation ratio of less than 85%, and the capacitance is also lower than that according to the example.Reference Example 1 In the method according to Example 5* m, the cubic orientation ratio of the obtained aluminum foil was measured by varying only the rolling reduction during finish rolling.The results are represented by line segment A in Fig. 1.In addition, in Comparative Example 4 In accordance with this method, the cubic orientation ratio of the aluminum foil obtained was measured by varying only the rolling reduction during finish rolling.The results were expressed as line segment B in Figure 1.
It was expressed as Reference Example 2 Based on the method according to Example 5, only the final annealing temperature was varied, and the cubic orientation ratio of the obtained aluminum foil was measured. This result is represented by line segment A in FIG. Further, according to the method according to Comparative Example 4, only the final annealing temperature was varied, and the cubic orientation ratio of the obtained aluminum foil was measured. This result is represented by line segment B in FIG. Further, in accordance with the method of Example 5, only the final annealing temperature was varied without performing intermediate annealing, and the cubic orientation ratio of the obtained aluminum foil was measured. This result is represented by line segment C in FIG. As can be seen from the above, aluminum foil with a constant cubic orientation ratio can be produced by performing intermediate annealing at a constant temperature, finishing rolling at a constant rolling reduction, and final annealing at a constant temperature or higher. This aluminum foil can be etched deeply parallel to the thickness direction of the foil, increasing its capacitance.

【Effect of the invention】

As explained above, the aluminum foil for electrolytic capacitor anodes according to the present invention has a cubic orientation ratio of 85% or more even though the At purity is less than 99.99%. It is possible to perform deep etching parallel to the width direction, increasing the surface area of the foil surface, and thus obtaining a capacitor anode foil with high capacitance. Moreover, if the method according to the present invention is adopted, the A1 purity will be 99.
．． Even if the ingot is less than 99%, the cubic orientation ratio is 85%.
The above aluminum foil can be obtained, and as described above, an anode foil with high capacitance can be obtained. That is, according to the present invention, even if the purity is less than 99.99%, an aluminum foil for electrolytic capacitor anodes can be obtained that has the same performance as aluminum foil with a purity resistance of 99.99% or more. . Therefore, it is possible to provide a high-performance aluminum foil for an anode of an electrolytic capacitor at a low cost.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the rolling reduction during finish rolling and the cubic orientation ratio of the obtained aluminum foil. FIG. 2 is a graph showing the relationship between the final annealing temperature and the cubic orientation ratio of the obtained aluminum foil.

Claims (2)

[Claims] (1) Si0.0040-0.0100%, Fe0.0
035-0.0085%, Cu0.0025-0.01
00%, Zn0.0010-0.0150%, Ga0.
0010 to 0.0150%, Ti 0.0010% or less,
An aluminum foil for an anode of an electrolytic capacitor, characterized in that the aluminum foil is composed of 0.0050% or less of unavoidable elements and the balance is Al, and the cubic orientation ratio of crystals in the aluminum foil is 85% or more. (2) Si0.0040-0.0100%, Fe0.0
035-0.0085%, Cu0.0025-0.01
00%, Zn0.0010-0.0150%, Ga0.
0010 to 0.0150%, Ti 0.0010% or less,
After homogenizing and hot rolling an ingot consisting of 0.0050% or less of unavoidable elements and the balance Al, the ingot was heated to a temperature of 250~250%.
Intermediate annealing is performed at 350°C, followed by a rolling reduction of 10 to 35%.
The method for manufacturing an aluminum foil for an electrolytic capacitor anode according to claim 1, characterized in that cold rolling is carried out within the range of 500°C or higher, and then final annealing is carried out at 500°C or higher.