JPH01276612A - Aluminum material for electrode of electrolytic capacitor - Google Patents

Abstract

PURPOSE:To enhance an etching characteristic and to increase a static capacitance by setting a maximum length of a short axis of a crystal grain to 10mm or below in a structure after a hot rolling operation. CONSTITUTION:An aluminum material 1 is in a state that its crystal grain 2 is stretched in a rolled direction X. In a structure after a hot rolling operation, it is required that the maximum length especially of a short axis (b) of the crystal grain 2 is 10mm or below. As a concrete method for this, in the hot rolling operation e.g., a process whose rolling-down rate is 40% or above of one pass during a thickness of 10-80mm is executed once or twice, or the retention time between rolling passes is set to one minute or longer in order to promote recrystallization. By this setup, it is possible to obtain an aluminum foil where a rate occupied by a plane 100 is large and its irregularity is small in a recrystallized aggregate structure; an etching characteristic becomes excellent; a static capacitance can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to aluminum materials for electrolytic capacitor electrodes.

Prior Art and Problems Aluminum foil, which is generally 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 the capacitance per unit area. be done.

Incidentally, aluminum foil is generally manufactured by sequentially performing each process of melting/casting, hot rolling, cold rolling, and final annealing, but in the recrystallized texture of the final annealed aluminum foil, (1001 planes 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 aluminum foil is etched. It is a fact.

Therefore, +100 in the recrystallized texture after final annealing.
It is necessary to improve the occupancy of one plane, improve the etching characteristics, and increase the capacitance. Various studies have been made in the past, but none of them are sufficient, and there are large variations in the occupancy of the +1001 plane. It was something.

In view of the above circumstances, this invention has been developed to provide +1001
The purpose of this invention is to provide an aluminum foil for electrolytic capacitors that improves and stabilizes the surface area occupancy and has a large capacitance, and attempts to provide materials for this purpose.

Means for Solving the Problems For the above purpose, as a result of intensive research, the inventor found that there is a close correlation between the structure after hot rolling in the manufacturing process of aluminum foil and the occupancy rate of +1001 plane after final annealing. This invention was completed based on this knowledge.

That is, the method for producing an aluminum material for electrolytic capacitor electrodes according to the present invention uses Fe, Sis Cu as impurities.
An aluminum material made of high-purity aluminum with a purity of 99.996 or higher in the remainder excluding It is something.

In the aluminum material according to the present invention, the purity of the remainder excluding Fe and 5tSCu as impurities is limited to 99.9% or more. This is because it decreases. In addition, Fe is an element that inhibits the growth of cubic orientation, and if it is contained in an amount exceeding 1100 pp, the +
1001 Because the occupancy rate itself tends to decline 1
．． It is desirable to regulate it to 00 ppm or less. Si
is an element that promotes the precipitation of Fe, but if it is contained in an amount exceeding 1100 pp, it tends to inhibit the growth of the cubic orientation, so it is desirable to limit it to <1100 pp or less. If Cu is contained in an amount exceeding 1100 pp, problems such as over-dissolution are likely to occur during the etching process, so it is desirable to limit the Cu content to <1100 pp or less.

Due to hot rolling in the aluminum foil manufacturing process, the aluminum material (1) becomes in a state where its crystal grains (2) are elongated in the rolling direction (X) as shown in FIG.
In this invention, in the structure after hot rolling, crystal grains (2)
Of the long sleeve length (a), short axis length (b), and thickness (C), the short axis length (b) is particularly required to be 10 m or less at maximum. This is because if there are crystal grains with a short axis length (b) exceeding 1.0 m, the occupancy of the +1001 plane after final annealing will decrease and the variation within the lot will also increase. This means that the short axis length (b) of the crystal grain (2) is 1
If it exceeds 0#, the distribution of grain boundaries, which are effective locations for the generation of nuclei, will become uneven so that the rolled surface becomes the +1001 plane during recrystallization, so the rolled surface becomes the +1001 plane during the recrystallization that occurs during final annealing. This is thought to be due to the insufficient nucleation and growth of recrystallized grains that have such a grain. 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 the short axis (b) is 10 m.
As a specific method for controlling crystal grains exceeding m, for example, in hot rolling, a process in which the rolling reduction rate of one bath is 40% or more at a thickness of 10 to 80 m is carried out once or twice. Further, the holding time between rolling baths may be increased to 1 minute or more to promote 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 the same conditions as conventional ones can be adopted. Further, intermediate annealing may be performed once or twice or more after cold rolling or during cold rolling.

The aluminum foil that has undergone final annealing is then electrochemically or chemically etched before being used as an 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, it is possible to improve the occupancy rate of the +1001 plane in the foil after final annealing. Variations can be suppressed.

As a result, it is possible to improve the etching characteristics, and in turn, it is possible to obtain an electrode foil that has excellent capacitance and less variation in its value.

Example [Sample 1] Fe: 25 ppm, Si: 10 ppmSCu
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 rate of 98%. Here, (a) in Table 1 below was adopted as the bus schedule for hot rolling.

When the structure of the aluminum material obtained by the above hot rolling was examined, the length of the short axis of the crystal grains was at most 180 μm, and the average value was 120 μm.

Next, the aluminum material was cold-rolled to a thickness of 0.12 #, followed by intermediate annealing at 250° C. for 10 hours, and then cold-rolled to a thickness o of 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 bus schedule in Table 1 below was adopted. In this case, in the structure of the aluminum material after hot rolling, the short axis length of the crystal grains is at most 20,000 μm.
(20 mm>, and the average value was 900 μm.

[Sample 3] Fe: 40ppm, Si: 30ppm, Cu: 30p
pm, and the content of impurities other than these is 30 ppm
For an aluminum ingot, the hot rolling start temperature is 58
Hot rolling was performed at 0° C. with a total reduction of 98%. Here,
The bus schedule for hot rolling is shown in Table 1 below (
b) was adopted.

When the structure of the aluminum material obtained by the above hot rolling was investigated, the length of the short axis of the crystal grains was at most 1800 μm.
The average value was 700 μm.

Next, the aluminum material was cold rolled to a thickness of 0.1.5 m, followed by intermediate annealing at 250° C. for 12 hours, and then cold rolled to a thickness of 0.11 nIn. 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 590° C. and the bus schedule in Table 1 below was adopted. In this case, in the structure of the aluminum material after hot rolling, the short axis length of the crystal grains is 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] Fe: 60ppm, Si: 40ppm, Cu
: Contains 30 ppm, and the content of impurities other than these is 1
An aluminum ingot having a weight of 100 pp was hot rolled at a hot rolling start temperature of 590° C. and a total reduction rate of 98%. Here, (a) in Table 1 below was adopted as the bus schedule for hot rolling.

When the structure of the aluminum material obtained by the above hot rolling was investigated, the length of the short axis of the crystal grains was at most 1200 μm.
The average value was 600 μm.

Next, the aluminum material was cold-rolled to a thickness of 0.12 mm, followed by intermediate annealing at 300° 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 7] A test piece was obtained in the same manner as Sample 6 above, except that the bus schedule in Table 1 below was adopted as the bus schedule for hot rolling. In this case, in the structure of the aluminum material after hot rolling, the length of the short axis of the crystal grains is at most 220
00 μm (22 mm), and the average value was 1200 μm.

+10 points for each of the 7 types of samples obtained from Table 1 and above for a total of 30 points, 3 points in the width direction and 10 points in the length direction.
The occupancy rate of page 01 was investigated, and its maximum value, minimum value, and average value were investigated. The results are shown in Table 2 below.

[See the margin below.As can be seen from the above results, by using the aluminum material according to the present invention, +
It was confirmed that it was possible to obtain an aluminum foil with a large occupancy of 1001 planes and a small variation, and therefore it was naturally expected that an electrode foil with excellent etching properties and a large capacitance with a small variation could be obtained. It was.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the grain structure of an aluminum material after hot rolling. (1)...Aluminum material, (2)...Crystal grains. that's all

Claims (2)

[Claims] (1) An aluminum material made of high-purity aluminum with a purity of 99.9% or more excluding Fe, Si, and Cu as impurities, and in which the length of the minor axis of the crystal grains is determined in the structure after hot rolling. An aluminum material for electrolytic capacitor electrodes, characterized by a maximum thickness 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.