JPH05239568A - Method for refining of pure al sheet material by heating - Google Patents

Abstract

PURPOSE:To decrease the contents of Sn, Pb, In, Tl and Ga among the impurities contained in a pure Al sheet material and to improve the corrosion resistance thereof. CONSTITUTION:The pure Al alloy sheet material contg. >=1 kinds among Sn, Pb, In, Tl and Ga as impurities is subjected to a heating treatment, in the state of sheet materials, under the conditions of holding for a prescribed period of time at the prescribed temp. within a range from 200 to 450 deg.C in a nonoxidative atmosphere, by which the above-mentioned Sn, In, Pb, Tl and Ga are diffused, migrated and flocculated to the surface parts. The diffused and flocculated surface parts of the above-mentioned components in the pure Al alloy sheet materials after the above-mentioned heating treatment are then removed, by which the total content of these diffused and flocculated surface parts is decreased to <=0.2ppm.

Description

Detailed Description of the Invention

[0001]

This invention relates to Sn, Pb, In, Tl, and G of impurities contained in a pure Al plate material.
The present invention relates to a method for reducing a by heating and refining a and thereby improving the quality of a pure Al plate material.

[0002]

2. Description of the Related Art Conventionally, for example, purity is generally 99.9%.
The above pure Al plate material is used as a cathode material of an electrolytic capacitor, and the pure Al plate material is used as impurities such as Si and F.
In addition to e and Cu, Sn, Pb, In, T
It is also known to contain one or more of 1 and Ga.

[0003]

On the other hand, the miniaturization and weight reduction of various electric devices in recent years is remarkable, and accordingly, for example, the cathode material of an electrolytic capacitor is required to be further thinned. In the conventional pure Al plate material constituting this, Sn, P contained as impurities as described above
The total content of b, In, Tl, and Ga is 1 ppm.
Approximately (generally, a pure Al plate material having a purity of 99.9% or more, which is used as a cathode material of an electrolytic capacitor, has a total amount of 1 regardless of the purity, that is, 99.9% or 99.99%. Since the corrosion resistance is adversely affected even if it is contained up to about 20 ppm), if the wall thickness is made thin, it is not possible to expect a satisfactory thinning because a through hole that causes deterioration of the cathode characteristics is easily formed. At present, we are trying to reduce the wall thickness.

[0004]

Therefore, the present inventors have
From the above viewpoints, attention is paid to the above-mentioned conventional pure Al plate material, and Sn, Pb, In, Tl, and Ga which adversely affect the corrosion resistance among impurities contained therein are reduced to improve the quality of the pure Al plate material. As a result of conducting research to
The above conventional pure Al plate material, preferably having a purity of 99.9% or more and a thickness of 200 μm or less, and having a total content of Sn, Pb, In, Tl, and Ga of impurities of 1 or less.
200 to 450 ° C. in a vacuum atmosphere or a non-oxidizing atmosphere such as Ar or nitrogen atmosphere on a pure Al plate material of ppm or more
When the heat treatment is performed at a predetermined temperature within the range for a predetermined time, the above Sn, Pb, In, Tl, and Ga positively diffuse and move to the surface of the plate material, and thus aggregate. If the surface portion where the components are diffused and aggregated is removed by an etching means or the like, as a result, the content of the diffusion aggregated component is reduced, and further, the total content of the diffusion aggregated component is reduced to 0.2 ppm or less. According to the research result, the pure Al plate material has a significantly improved corrosion resistance, and even if it is made thin, it does not depend on the use environment and the generation of through holes is prevented.

The present invention has been made based on the above-mentioned research results, and Sn, Pb, and I are used as impurities.
Pure A containing at least one of n, Tl, and Ga
l plate material, preferably with a purity of 99.9% or more and 20
Sn and P of impurities having a thickness of 0 μm or less
A pure Al plate material having a total content of b, In, Tl, and Ga of 1 ppm or more is subjected to a heat treatment under the conditions of maintaining a predetermined temperature within a range of 200 to 450 ° C. for a predetermined time in a non-oxidizing atmosphere. , Sn, Pb, In, Tl, and Ga among the impurities contained in the pure Al plate material are diffused and moved to the surface portion to be aggregated, and then the components are diffused in the pure Al plate material after the heat treatment. The method is characterized by a method for heating and purifying a pure Al plate material by removing the aggregated surface portion and reducing the total content of these diffusion aggregated components to 0.2 ppm or less.

In the method of the present invention, the heat treatment temperature is set to 200 to 450 ° C. because the temperature is 200.
When the temperature is lower than 0 ° C, the diffusion and aggregating component is extremely slow to move to the surface of the plate material, which is not desirable in terms of productivity.
This is because the proportion of solid solution in the l base material is rapidly increased, and the diffusion movement to the surface portion of the plate material is suppressed.

Further, as described above, the corrosion resistance (pitting corrosion resistance) of the pure Al plate material is affected by the diffusion aggregation component,
When the total content of this diffusion aggregation component is 0.2 ppm or less, for example, when it is used as a cathode material of an electrolytic capacitor,
Even if the usage conditions change, it will exhibit excellent corrosion resistance without pitting corrosion, so pure Al after heat treatment
The total content of the diffusing and aggregating components in the plate material is set to 0.2 ppm or less.

[0008]

EXAMPLES Next, the method of the present invention will be specifically described by way of Examples. Impurity contents shown in Table 1, respectively
Pure Al plate materials (hereinafter referred to as conventional pure Al plate materials) a to j of purity and plate thickness are prepared, and these conventional pure Al plate materials a to j are prepared.
The heat treatment is performed under the conditions shown in Table 2, respectively, and subsequently, the plate material surface portion is removed over the thickness shown in Table 2 by using an ordinary etching solution. Was carried out, and the heat-purified pure Al plate material having the impurity contents shown in Table 3 (hereinafter referred to as the pure aluminum plate material of the present invention) 1
10 were produced respectively.

[0009]

[Table 1]

[0010]

[Table 2]

[0011]

[Table 3]

[0012]

[Table 4]

Then, the resulting pure Al plate materials 1 to 10 of the present invention and the above-mentioned conventional pure Al plate materials a to j were subjected to a salt water spray test for 720 hours, and the number of pitting corrosion per unit area and the maximum pitting corrosion were observed. Food depth (appropriate average value at 10 locations)
Was measured. The measurement results are shown in Table 4.

[0014]

From the results shown in Tables 1 to 4, according to the methods 1 to 6 of the present invention, although Si, Fe, and Cu among impurities are slightly reduced, Sn and P among impurities are reduced.
With respect to the diffusion aggregation component composed of b, In, Tl, and Ga, this can be reduced to 0.2 ppm or less,
Therefore, it is clear that the resulting pure Al plate materials 1 to 6 of the present invention all have excellent corrosion resistance as compared with the conventional pure Al plate materials a to f in which the total content of the diffusion aggregation components is 1 ppm or more.

As mentioned above, according to the method of the present invention,
Of the impurities contained in the pure Al plate material, Sn, Pb, I
It is possible to reduce the total content of n, Tl, and Ga to 0.2 ppm or less, which significantly improves the corrosion resistance of the pure Al plate material. Since the occurrence of pitting corrosion is suppressed even when used as a cathode material, industrially useful effects such as excellent performance over a long period of time are brought about.

Claims (1)

[Claims] 1. Sn, Pb, In, Tl as impurities
And a pure Al plate material containing at least one of Ga are subjected to a heat treatment under a condition of maintaining a predetermined temperature within a range of 200 to 450 ° C. for a predetermined time in a non-oxidizing atmosphere to obtain the above pure Al plate material. Of the impurities contained in the above Sn, Pb,
In, Tl, and Ga are aggregated by diffusing and moving to the surface portion, and then the diffusion aggregation surface portion of the above components in the pure Al plate material after the heat treatment is removed, and the total content of these diffusion aggregation components is adjusted to 0. Pure A characterized by reduction to 2ppm or less
Method for heat purification of plate material.