JPH0561772B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to an aluminum material for electrolytic capacitor electrodes. Prior Art and Problems Aluminum foil, which is commonly used as an electrode material for aluminum electrolytic capacitors, is generally subjected to electrochemical or chemical etching treatment in order to expand its effective area and increase capacitance per unit area. be done. By the way, aluminum foil is generally manufactured by sequentially performing each process of melting/casting, hot rolling, cold rolling, and final annealing. It is well known that if there are many crystals with a so-called cubic orientation, in which the <001> direction is parallel to the surface of the foil and parallel to the rolling direction, the capacitance will increase when this aluminum foil is etched. It is a fact that Therefore, various studies have been made to improve the occupancy of {100} planes in the recrystallized texture after final annealing, improve etching characteristics, and increase capacitance, but none of them are sufficient. Moreover, there was a large variation in the occupancy of the {100} plane. In view of the above circumstances, the present invention aims to provide an aluminum foil for electrolytic capacitors that improves and stabilizes the occupancy of the {100} plane after final annealing and has a large capacitance, and provides materials for this purpose. This is what I am trying to do. Means for Solving the Problems For the above purpose, the inventor has conducted extensive research and found that
We have discovered that there is a close correlation between the structure after hot rolling in the manufacturing process of aluminum foil and the occupancy rate of {100} planes after final annealing, and based on this knowledge, we have completed this invention. This is what I learned. That is, the method for producing an aluminum material for electrolytic capacitor electrodes according to the present invention includes Fe as impurities,
An aluminum material made of high-purity aluminum with a purity of 99.9% or more for the balance excluding Si and Cu, characterized by a structure after hot rolling in which the length of the minor axis of the crystal grains is at most 10 mm or less That is. In the aluminum material according to the present invention, the purity of the remainder excluding Fe, Si, and Cu as impurities is 99.9.
% or more is limited to less than 99.9% {100}
This is because the variation in the occupancy rate increases and the occupancy rate also decreases. Further, Fe is an element that inhibits the growth of cubic orientation, and if it is contained in an amount exceeding 100 ppm, the {100} occupancy rate itself tends to decrease during final annealing, so it is desirable to limit it to 100 ppm or less. Si is an element that promotes the precipitation of Fe,
If the content exceeds 100 ppm, it tends to inhibit the growth of cubic orientation, so
It is desirable to regulate it to 100ppm or less. Cu is
If the content exceeds 100ppm, problems such as excessive dissolution may occur during etching processing, so
It is desirable to regulate it to 100ppm or less. Due to the hot rolling in the aluminum foil manufacturing process, the aluminum material 1 becomes in a state where its crystal grains 2 are stretched in the rolling direction X, as shown in FIG. Among the length (a) of the long axis of crystal grain 2, the length (b) of short axis 2, and the thickness (C), the short axis length (b) in particular must be at most 10 mm or less. do. If there are grains whose short axis length (b) exceeds 10 mm, the {100}
This is because the surface occupancy rate decreases and the variation within the lot also increases. This is because when the length (b) of the minor axis of grain 2 exceeds 10 mm, the distribution of grain boundaries, which are effective locations for the generation of nuclei such that the rolled surface becomes the {100} plane during recrystallization, becomes uneven. This is thought to be due to the fact that sufficient nucleation and growth of recrystallized grains such that the rolled surface has a {100} plane does not progress during recrystallization that occurs during final annealing because of uniformity. Such a phenomenon becomes particularly noticeable when the rolling reduction in the hot rolling process is about 97% or more. In the structure after hot rolling, the length of short axis b is 10
As a specific method for controlling crystal grains exceeding mm, for example, in hot rolling, a thickness of 10 to 80 mm
Examples include performing a step in which the rolling reduction rate per pass is 40% or more between rolling passes once or twice, and further increasing the holding time between rolling passes to 1 minute or more to advance recrystallization. The above aluminum material is manufactured into an aluminum foil for electrolytic capacitor electrodes by sequentially performing cold rolling, foil rolling, and final annealing. The steps after hot rolling are not limited in any way, and similar conventional conditions may be employed. Further, intermediate annealing may be performed once or twice or more after cold rolling or during cold rolling. After the final annealing, the aluminum foil is then electrochemically or chemically etched.
Used as electrolytic capacitor electrode foil. Effects of the Invention Since the aluminum material for electrolytic capacitor electrodes according to the present invention is as described above, by using the material, {100}
It is possible to improve the surface occupancy rate and to suppress variations depending on the location. the result,
Etching characteristics can be improved, and an electrode foil with excellent capacitance and less variation in capacitance can be obtained. Example [Sample 1] Contains Fe: 25ppm, Si: 10ppm, Cu: 50ppm,
An aluminum ingot containing 10 ppm of impurities other than these was hot rolled at a hot rolling start temperature of 520°C and a total reduction of 98%. Here, as the pass schedule for hot rolling, (a) in Table 1 below was adopted. When the structure of the aluminum material obtained by the hot rolling was examined, the length of the short axis of the crystal grains was at most 180 μm, and the average length was 120 μm. Next, the aluminum material was cold rolled to a thickness of 0.12 mm, followed by intermediate annealing at 250° C. for 10 hours, and then cold rolled to a thickness of 0.1 mm. This aluminum foil was then finally annealed at 550°C for 1 hour. [Sample 2] A test piece was obtained in the same manner as Sample 1 above, except that the hot rolling start temperature was set to 550°C and the pass schedule in the hot rolling was adopted as (b) in Table 1 below. In this case, in the structure of the aluminum material after hot rolling, the short axis length of the crystal grains was at most 20,000 μm (20 mm), and the average value was 900 μm. [Sample 3] Contains Fe: 40ppm, Si: 30ppm, Cu: 30ppm,
An aluminum ingot containing 30 ppm of impurities other than these was hot rolled at a hot rolling start temperature of 580°C and a total reduction of 98%. Here, as the pass schedule for hot rolling, (a) in Table 1 below was adopted. When the weaving of the aluminum material obtained by the above hot rolling was examined, the length of the minor axis of the crystal grains was at most 1800 μm, and the average value was 700 μm. Next, the above aluminum material was cold rolled to a thickness of 0.15 mm, followed by intermediate annealing at 250° C. for 12 hours, and then cold rolled to a thickness of 0.1 mm. This aluminum foil was then finally annealed at 550°C for 1 hour. [Sample 4] A test piece was obtained in the same manner as Sample 3 above, except that the hot rolling start temperature was set to 590°C and the pass schedule in the hot rolling was adopted as (b) in Table 1 below. In this case, in the structure of the aluminum material after hot rolling, the short axis length of the crystal grains was at most 25,000 μm (25 mm), and the average value was 500 μm. [Sample 5] A test piece was obtained in the same manner as Sample 3 except that intermediate annealing was performed at 300° C. for 12 hours. [Sample 6] Contains Fe: 60ppm, Si: 40ppm, Cu: 30ppm,
Hot rolling start temperature of 590℃ for aluminum ingots containing 100ppm of impurities other than these.
Hot rolling was carried out at a total reduction rate of 98%. Here,
For the hot rolling pass schedule, (a) in Table 1 below was adopted. When the structure of the aluminum material obtained by the above-mentioned hot rolling was examined, the length of the short axis of the crystal grains was at most 1200 μm, and the average value was 600 μm. Next, the above aluminum material was cold rolled to a thickness of 0.12 mm, followed by intermediate annealing at 300° C. for 12 hours, and then hot rolled to a thickness of 0.1 mm. This aluminum foil was then finally annealed at 550°C for 1 hour. [Sample 7] Sample 6 above except that (b) in Table 1 below was adopted as the pass schedule in hot rolling.
A test piece was obtained in the same manner as above. In this case, in the structure of the aluminum material after hot rolling, the short axis length of the crystal grains was at most 22,000 μm (22 mm), and the average value was 1,200 μm.

[Table] For the seven types of samples obtained above, the occupancy rate of each {100} plane was investigated at a total of 30 points, 3 points in the width direction and 10 points in the length direction, and the maximum value,
The minimum value and average value were examined. The results are shown in Table 2 below.

【table】

[Table] As can be seen from the above results, it has been confirmed that by using the aluminum material according to the present invention, it is possible to obtain an aluminum foil in which the recrystallized texture has a large occupancy rate of {100} planes and little variation. Therefore, it could be naturally expected that an electrode foil with excellent etching properties, large capacitance, and little variation could be produced.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the grain structure of an aluminum material after hot rolling. 1... Aluminum material, 2... Crystal grain.

Claims (1)

[Scope of Claims] 1. An aluminum material made of high-purity aluminum with a purity of 99.9% or more excluding impurities such as Fe, Si, and Cu, in which the minor axis of crystal grains in the structure after hot rolling is An aluminum material for electrolytic capacitor electrodes characterized by a maximum length of 10 mm or less. 2. The aluminum material for electrolytic capacitor electrodes according to claim 1, wherein the content of Fe, Si, and Cu as impurities is each 100 ppm or less.