JPH0116900B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to an aluminum alloy foil for an electrolytic capacitor cathode. In this specification, "%" refers to "% by weight". Conventional technology and its problems In order to improve the performance of electrolytic capacitors,
It is necessary to increase not only the capacitance of the anode foil but also the capacitance of the cathode foil. In order to increase the capacitance of foil, it is effective to increase the surface area of the foil by etching it.
If the etching becomes excessive, the corrosion loss will also be excessive, resulting in a decrease in the capacitance of the foil. Furthermore, in order to reduce the size and weight of capacitors, it is necessary to reduce the thickness of the foil, and to achieve this, the strength of the foil must be increased. Therefore, the conditions that aluminum alloy foil for electrolytic capacitor cathode should meet are as follows:
It has high capacitance, no excessive corrosion loss during etching, and high mechanical strength. Although various aluminum alloy foils for electrolytic capacitor cathodes have conventionally existed, the reality is that there has been no foil that satisfies all of the above three conditions. An object of the present invention is to provide an aluminum alloy foil for an electrolytic capacitor cathode that can satisfy all of the above conditions. Means for Solving the Problems One aluminum alloy foil for an electrolytic capacitor cathode of the present invention is formed from a continuously cast aluminum alloy sheet containing 0.2 to 0.5% silicon, with the remainder being aluminum and unavoidable impurities. Another aluminum alloy foil for an electrolytic capacitor cathode of the present invention contains 0.2 to 0.5% silicon, and further contains 0.1 to 1.0% copper and 0.003% vanadium.
It is formed from a continuously cast aluminum alloy plate containing at least one of ~0.3% and the remainder consisting of aluminum and unavoidable impurities. Silicon has the property of increasing the capacitance of aluminum alloy foil by incorporating it into aluminum, but when the silicon content is
If the silicon content is less than 0.2%, the effect of increasing the capacitance of the foil cannot be obtained, and if the silicon content exceeds 0.5%, a fine etched structure cannot be obtained, the capacitance of the foil becomes small, and corrosion loss occurs. It also becomes excessive. Therefore, the silicon content should be selected within the range of 0.2-0.5%. The reason why the capacitance of aluminum alloy foil increases by containing silicon is as follows. In other words, as is well known, the capacitance of aluminum alloy foil is proportional to the surface area of the foil, but in order to increase the surface area of the foil, etching is applied to create fine recesses uniformly and densely on the surface of the foil. It is necessary to do so. When silicon is contained in aluminum, a structure in which fine silicon is uniformly precipitated in an aluminum matrix can be obtained. This precipitated silicon is electrically nobler than aluminum and has a large electrode potential difference across the aluminum matrix, so during etching the aluminum matrix is preferentially corroded, creating uniform fine depressions on the surface of the foil. and occur in high density. However, the silicon content is 0.5
%, the corrosion weight loss becomes excessive and a fine etched structure cannot be obtained, and the capacitance also decreases. In addition, in continuously cast aluminum alloy sheets containing silicon, silicon is supersaturated in solid solution in the aluminum, and the precipitates are fine and uniform, and iron as an impurity is also present in the aluminum alloy. Since it is possible to prevent the precipitation of coarse Al--Si--Fe compounds even if they are present in the aluminum alloy, etching is applied to the aluminum alloy foil formed by rolling from this continuously cast aluminum alloy sheet. Very fine recesses are generated at a high density, and the above-mentioned effect of increasing the capacitance of the aluminum alloy foil due to the addition of silicon is further improved. In the above, at least one of copper and vanadium is substituted with silicon 0.2
When included in aluminum together with ~0.5%, it lowers the solid solubility limit of silicon and is itself dissolved in the aluminum matrix, improving the etching properties of the matrix and making it possible to contain silicon as described above. It is possible to enhance the effect of However, the content of copper is less than 0.1% and the content of vanadium is 0.003%
If the copper content is less than
If the vanadium content exceeds 1.0% and the vanadium content exceeds 0.3%, etching becomes excessive and the capacitance decreases. Therefore, the copper content should be set to 0.1~
Within the range of 1.0%, vanadium content 0.003-0.3%
Each should be selected within the range. In addition, in continuously cast aluminum alloy sheets, the elements contained in the aluminum are supersaturated in solid solution in the aluminum, and the crystallized substances are fine and uniform, so the strength is increased. There is. Therefore, the strength of the foil formed by rolling from such a continuously cast plate naturally increases. Furthermore, the aluminum alloy foil according to the present invention may contain impurities such as iron that are inevitable during manufacturing. Among impurities, the iron content is particularly
If it exceeds 0.5%, coarse Al-Si will be formed during casting.
- Since Fe compounds may crystallize and inhibit the effects of the aluminum alloy foil according to the present invention, the content of iron among impurities is preferably 0.5% or less. Continuously cast aluminum alloy sheets are obtained by continuous casting and rolling methods such as the 3C method and the Hunter method without going through the usual hot rolling process. The continuously cast aluminum alloy plate is formed to have a thickness of, for example, 25 mm or less. Then, a foil is formed from such a continuously cast aluminum alloy plate through cold rolling and foil rolling. Continuously cast aluminum alloy sheets are sometimes subjected to intermediate annealing before being made into foil. Examples Examples of the present invention will be described below along with comparative examples. Continuously cast plates having a thickness of 25 mm or less were manufactured from alloys A to C and E of the five types of aluminum alloys having the compositions shown in Table 1 by a continuous casting and rolling method at a cooling rate of 1 m/min. These continuously cast plates were then subjected to cold rolling and foil rolling to form two aluminum alloy foils.
Further, a slab was cast from Alloy D by a semi-continuous casting method (cooling rate 0.05 m/min), and two sheets of alloy foil were formed from this slab by a normal foil manufacturing method. Thereafter, the strength of each of the various alloy foils was measured using one of the foils. In addition, another piece of alloy foil was immersed in an aqueous solution of 3% hydrochloric acid and 0.5% oxalic acid at a temperature of 60°C, and etched with alternating current at a current density of 30 A/dm ² for 1 minute and 30 seconds. Capacity was measured.

[Table] The results of the above examples and comparative examples are summarized in Table 2.

[Table] As is clear from Table 2, Alloys A to C have higher capacitance and strength than Alloys D and E. Effects of the Invention One of the aluminum alloy foils for electrolytic capacitor cathodes of the present invention is formed from a continuously cast aluminum alloy plate containing 0.2 to 0.5% silicon, with the remainder being aluminum and unavoidable impurities. It is possible to obtain a structure in which silicon, which is more noble than aluminum, is supersaturated as a solid solution in aluminum, and the precipitates are fine and uniform. Furthermore, even if iron is contained in this aluminum alloy, precipitation of coarse Al--Si--Fe compounds can be prevented. Therefore,
When this aluminum alloy foil is etched,
Extremely fine recesses occur at a high density on the surface of the foil,
Capacitance increases. Furthermore, the mechanical strength also increases. Another aluminum alloy foil for an electrolytic capacitor cathode of the present invention has a silicon content of 0.2
~0.5%, and further contains at least one of 0.1-1.0% copper and 0.003-0.3% vanadium, with the balance being aluminum and inevitable impurities. , at least one of copper and vanadium lowers the silicon solid solubility limit and also
It dissolves in the matrix and improves the etching properties of the matrix. Therefore, the capacitance and strength are greater.

Claims (1)

[Claims] 1. An aluminum alloy foil for an electrolytic capacitor cathode, which is formed from a continuously cast aluminum alloy plate containing 0.2 to 0.5% silicon, with the remainder being aluminum and unavoidable impurities. 2 Contains 0.2 to 0.5% silicon and further 0.1 to 0.1% copper
An aluminum alloy foil for an electrolytic capacitor cathode, which is formed from an aluminum alloy continuous casting sheet containing at least one of 1.0% and 0.003 to 0.3% vanadium, with the balance being aluminum and unavoidable impurities.