JP2945298B2 - Manufacturing method of aluminum alloy foil for electrolytic capacitor cathode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum alloy foil for an electrolytic capacitor cathode having excellent etching properties.

[0002]

2. Description of the Related Art Aluminum plates which are lightweight and can be miniaturized are frequently used for electrode plates of electrolytic capacitors. Generally, in order to increase the capacitance of an electrolytic capacitor, it is necessary to increase not only the capacitance of an aluminum alloy foil for an anode but also the capacitance of an aluminum alloy foil for a cathode. To increase the capacitance of the alloy foil, the foil must be electrochemically
Alternatively, the surface is roughened by chemical etching to increase the surface area. In most cases, the foil for the cathode is required to have high strength because a foil having a smaller thickness than the foil for the anode is used.

[0003] The aluminum alloy foil for a cathode is, for example, formed into an ingot by semi-continuous casting of molten aluminum, and the ingot is formed into a thickness by hot rolling and cold rolling.
It is manufactured by foil rolling to a thickness of 0.3 to 0.6 mm, and further, foil rolling to a thickness of about 10 to 100 μm. Usually, the ingot is subjected to a homogenizing heat treatment before hot rolling, intermediate annealing is performed as needed during cold rolling, and a foil is annealed to remove distortion before etching. In addition, if the etching is small, the foil is not sufficiently roughened. If the etching is excessive, uneven etching occurs, and in any case, the capacitance is reduced. When the etching is excessive, the strength also decreases. For this reason, it is necessary to appropriately control the etching amount.

[0004]

However, even if the amount of etching is properly controlled, there is a problem that uneven etching occurs and a sufficiently high value such as a capacitance cannot be obtained. The present inventors have conducted various studies on the manufacturing conditions after the melting and casting stage, and found that it is possible to reduce etching unevenness by limiting the slab thermal holding conditions from the homogenization heat treatment to the start of hot rolling. The present inventors have further studied and completed the present invention. An object of the present invention is to provide a method for producing an aluminum alloy foil for an electrolytic capacitor cathode, in which etching is performed uniformly and a cathode having excellent characteristics is obtained.

[0005]

According to the present invention, the purity of aluminum is not less than 98.5% by weight and less than 99.9% by weight, and the content of Fe is not less than 0.9% by weight.
15 wt% or less, Si 0.15 wt% or less, Cu 0.01 to 0.6 wt
% Ingot, the remainder of which is made of inevitable impurities, is subjected to a homogenizing heat treatment at a temperature of 580 ° C or higher for less than 4 hours, and then cooled to a temperature of 420 to 570 ° C. A method for producing an aluminum alloy foil for a cathode of an electrolytic capacitor, comprising: holding for 12 hours or less, thereafter starting hot rolling at the above temperature, and sequentially performing hot rolling and cold rolling according to a conventional method.

[0006]

In the present invention, the reason for limiting the aluminum purity of the aluminum alloy ingot to 98.5 wt% or more and less than 99.9 wt% is that if the purity is 99.9 wt% or more, the strength of the foil for the cathode is insufficient, If the purity is less than 98.5 wt%, the reaction with the etching solution becomes extremely vigorous, and the etching proceeds excessively, so that a normal rough surface cannot be obtained.

[0007] Fe and Si are elements inevitably contained in aluminum ingots, and most of these elements are cast into ingots as coarse intermetallic compounds of about 5 μm when semi-continuous casting of molten aluminum alloy. Crystallizes in. This crystallized substance remains on the foil and impairs the etching property of the foil. In the present invention, these coarse precipitates are divided into about 1 μm by a homogenizing heat treatment at a temperature of 580 ° C. or higher, or form a solid solution in the matrix. As a result, the etching is performed uniformly. In the present invention, the reason why each of Fe and Si is limited to 0.15 wt% or less is that even if any of them exceeds 0.15 wt%, it is sufficient to finely separate or dissolve the intermetallic compound during the homogenization heat treatment. This is due to the fact that etching is uneven due to loss of etching.

[0008] Cu has the effect of increasing the strength of the foil. Cu
If the content is less than 0.01 wt%, the effect cannot be obtained sufficiently. If it exceeds 0.6 wt%, the reaction with the etching solution becomes extremely violent, and the entire surface of the foil rapidly dissolves, resulting in abnormal dissolution. , The capacitance and the strength both decrease.
Therefore, the content of Cu is limited to 0.01 to 0.6 wt%.

In the present invention, the homogenizing heat treatment is performed at a temperature of 580 ° C. or more for less than 4 hours. The reason for limiting the temperature of the homogenizing heat treatment to 580 ° C. or higher is that if the temperature is lower than 580 ° C., it is not sufficient to divide the coarse crystallized product into about 1 μm and re-dissolve it. As the homogenization heat treatment is performed at a higher temperature, the separation and re-dissolution of coarse crystallized substances are completed in a shorter time, and the productivity is improved. Therefore, the homogenization heat treatment is preferably performed at a temperature of 580 ° C or more, more preferably 600 ° C or more.

The treatment time of the above-mentioned homogenization heat treatment at 580 ° C. or more is set to less than 4 hours. If the homogenization heat treatment time is more than 4 hours, the coarse intermetallic compound formed during casting will break up and re-dissolve, but new intermetallic compounds will be generated and deposited, and abnormalities in the foil during etching will occur. Causes dissolution. Therefore, the homogenization heat treatment time is limited to less than 4 hours, and more preferably 1 to 3 hours. The newly precipitated intermetallic compound is considered to be a compound of Si and another element. The retention time of less than 4 hours at 580 ° C. or more means the total time of retention at 580 ° C. or more.

After the homogenizing heat treatment is performed, the temperature is cooled to a temperature of 420 to 570 ° C. When hot rolling is performed immediately after the homogenizing heat treatment, a part of the metal element dissolved in the homogenizing heat treatment precipitates as an extremely fine intermetallic compound of 0.1 μm or less during the hot rolling. As a result, abnormal melting occurs and the capacitance is reduced.
When cooled to a temperature of 420 to 570 ° C after the homogenization heat treatment,
The metal element dissolved by the homogenization heat treatment precipitates, but the precipitation occurs in the form of coarsening the intermetallic compound remaining without being completely dissolved, and thus does not significantly affect the etching property. By this treatment, the amount of solid solution elements is reduced, and the precipitation of many fine compounds of 0.1 μm or less during hot rolling can be suppressed. More preferably, the temperature is maintained at a temperature of from 560 ° C. to 420 ° C. On the other hand, if the cooling temperature after the homogenization heat treatment is too low, such as less than 420 ° C., a large number of dissolved metal elements will precipitate as fine compounds of 0.1 μm or less, which causes abnormal dissolution. Further, the lower limit of the cooling temperature is preferably set to 420 ° C. or more, since the workability is lowered due to an increase in deformation resistance during hot rolling. On the other hand, when the temperature exceeds 570 ° C., the precipitation of new intermetallic compounds that precipitate at high temperatures cannot be suppressed. In addition, in order to sufficiently reduce the amount of solid solution and suppress the precipitation of a large number of fine compounds during hot rolling, it is preferable to maintain the temperature for 30 minutes to 12 hours after cooling to 420 to 570 ° C. The holding time is preferably 30 minutes or more and 12 hours or less from the viewpoint of energy cost in addition to the precipitation of the intermetallic compound.

[0012] The ingot is subjected to the homogenizing heat treatment and 420-57.
After cooling to a temperature of 0 ° C, this temperature (420-570 ° C)
, Hot rolling and cold rolling are sequentially performed according to a conventional method, and the foil is processed. In cold rolling, intermediate annealing is performed as needed. The foil is rolled in a conventional manner. The obtained foil is annealed, if necessary, to remove distortion, and then subjected to an etching treatment and an anodic oxidation treatment in order to be processed into a cathode. According to the above-described manufacturing method, the obtained foil is etched uniformly, and the strength after etching is hardly reduced.

[0013]

The present invention will be described below in detail with reference to examples. (Example 1) An aluminum alloy having the composition shown in Table 1 was cast into a slab (a plate-like ingot having a thickness of 200 mm) by a semi-continuous casting method. The obtained slab was subjected to a homogenizing heat treatment under various conditions as shown in Table 2, and then cooled and held. Then, hot rolling was started at the holding temperature and hot rolled into a 6 mm-thick sheet material by an ordinary method. Next, this hot-rolled material is cold-rolled to a thickness of 0.4
mm foil, and the foil was rolled into a foil having a thickness of 0.04 mm. In the cold rolling, intermediate annealing was appropriately performed depending on the grade. Performing an etching process on each of the obtained foils,
The etching unevenness and tensile strength were investigated. For the etching treatment, the foil was immersed in an etching solution at 55 ° C.
An AC current of z was conducted at a current density of 8 A / dm ² for 3 minutes. Table 3 shows the results.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

As is apparent from Tables 1 to 3, all of the products of the present invention (Nos. 1 to 5) had high tensile strengths both before and after etching. No etching unevenness occurred at all. No. 3 was subjected to intermediate annealing during cold rolling, but no particular difference in properties was observed. On the other hand, in Comparative Examples Nos. 6 and 7, the tensile strength of the foil was low both before and after etching. This is because the former had a high purity of aluminum of 99.95 wt%, and the latter had a low Cu content of less than 0.01 wt%. In No. 8, the tensile strength after etching decreased. This is because the Cu content is 0.6
The reason for this is that, when the content exceeds wt%, the foil reacts very violently with the etching solution during the etching and is abnormally dissolved. No.9
In the sample, unevenness of etching occurred, and the tensile strength after etching was significantly reduced. This is because the purity of aluminum is 98.5wt
% Or less, the foil reacted very violently with the etching solution, the amount of etching became excessive, and a normal rough surface could not be obtained. The effect of intermediate annealing during cold rolling was not particularly observed.

Example 2 An alloy of No. B shown in Table 1 was processed into a 0.04 mm thick foil in the same manner and under the same conditions as in Example 1. In the production, as shown in Table 4, various conditions such as heat treatment for homogenizing the slab were changed. The obtained foil was etched by the same method as in Example 1, and the tensile strength and etching unevenness of the foil before and after etching were examined. The foil after the etching was subjected to anodizing treatment to form a cathode, and the capacitance was measured. The capacitance was measured using an LCR meter. The anodizing treatment was performed by immersing in a 5% ammonium adipate solution heated to 60 ° C. and applying a voltage of 10 V. Table 5 shows the results.

[0019]

[Table 4]

[0020]

[Table 5]

As is clear from Tables 4 and 5, all of the products of the present invention (Nos. 10 to 12) had a high tensile strength of the foil, no uneven etching, and a high capacitance. .
No. 11 is annealed during cold rolling,
No particular difference in properties was observed between those not subjected to annealing. On the other hand, since the homogenizing heat treatment temperature of Comparative Example No. 15 was low, most of the coarse crystals in the ingot remained on the foil. As a result, etching unevenness occurred, and the tensile strength after etching was significantly reduced. Due to uneven etching, the capacitance was also significantly reduced. No.16 and N
In o.17, the time during which the slab was kept at a temperature of 580 ° C or higher from the homogenization heat treatment to the start of hot rolling was long,
The solid solution element was precipitated as a new intermetallic compound, and this precipitate was brought to the foil as it was, and abnormal etching occurred in the foil during etching. As a result, the capacitance and the tensile strength decreased.

[0022]

As described above, according to the present invention, an aluminum alloy ingot having a predetermined composition is subjected to a homogenizing heat treatment at a high temperature for a short period of time under a predetermined condition, and after the homogenizing heat treatment, the aluminum alloy ingot is cooled to a predetermined temperature or less and then heated. Since the foil is rolled, the obtained foil is free of coarse crystals and precipitates.Therefore, the foil obtained by foil rolling this foil has good etching properties and high strength. The electrolytic capacitor used has a high capacitance and the like and is excellent in performance.

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein the purity of the aluminum is 98.5 wt% or more.
Less than 9.9wt%, Fe is 0.15wt% or less, Si is 0.15w
t% or less, containing 0.01 to 0.6 wt% of Cu and the balance being an unavoidable impurity, after subjecting an aluminum alloy ingot to a homogenizing heat treatment at a temperature of 580 ° C or more for less than 4 hours,
Cooling to a temperature of 0 ° C., holding at that temperature for 30 minutes or more and 12 hours or less, then starting hot rolling at the above temperature and sequentially performing hot rolling and cold rolling according to a conventional method. Manufacturing method of aluminum alloy foil for electrolytic capacitor cathode.