JPH06172902A - Aluminum alloy for anodic oxidation and its production - Google Patents

Abstract

PURPOSE:To produce an aluminum alloy for anodic oxidation, used, e.g. for exterior and interior materials for construction and capable of forming a light gray colored anodic oxidation film with stable color tone. CONSTITUTION:This alloy is a one having a composition consisting of, by weight, 0.3-3.0% Si, 0.1-1.0% Fe, 0.1-0.3% Cu, 0.05-0.60% Mn, 0.001-0.10% Ti, and the balance Al with inevitable impurities. It can be produced by subjecting its ingot to homogenizing treatment at 400-600 deg.C and to hot rolling at <=500 deg.C and further performing, at the time of cold rolling, process annealing or final annealing at 300-500 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy for anodic oxidation which forms a light gray anodic oxide film by a sulfuric acid bath anodic oxidation treatment and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, aluminum alloys used for exterior and interior materials for construction, furniture, electrical ornaments, etc. have been subjected to anodizing treatment to improve their corrosion resistance and decorativeness. Therefore, various colors are required for the anodized film. In the case of sulfuric acid bath anodic oxide film, most of the colors develop from silver to gray. Al-Si alloys and Al-Fe alloys are known as light gray anodizing aluminum alloys. The conventional light gray type anodizing aluminum alloy has poor color tone stability, and variations in color tone between lots and before and after the coil were observed. When it is used as an outer plate of a building or the like, it causes a big problem because it impairs the appearance of the building, and a light gray type anodizing aluminum alloy having a stable color tone is required. SUMMARY OF THE INVENTION It is an object of the present invention to provide an anodizing aluminum alloy capable of obtaining an anodized film having a stable color tone and a method for producing the same in order to solve such instability of the color tone.

[0003]

The present invention has been eagerly studied to solve these problems, and by controlling the composition and manufacturing process of an Al--Si alloy, a light gray anodic oxidation with a stable color tone is achieved. This is a development of an aluminum alloy capable of forming a film and a manufacturing method thereof.

That is, the invention according to claim 1 is Si0.3-
3.0%, Fe 0.1-1.0%, Cu 0.1-0.3
%, Mn 0.05 to 0.60%, Ti 0.001 to 0.
An aluminum alloy for anodic oxidation, which comprises 10% and balance Al and unavoidable impurities. The invention according to claim 2 has Si 0.3 to 3.0% and Fe 0.1.
~ 1.0%, Cu 0.1-0.3%, Mn 0.05 ~
An alloy ingot containing 0.60% and Ti of 0.001 to 0.10% and the balance of Al and inevitable impurities was added to an ingot of 400 to 6
After performing homogenization treatment at a temperature of 00 ° C., hot rolling at a temperature of 500 ° C. or less, and further cold rolling at 35 ° C.
A method for producing an aluminum alloy for anodic oxidation, which comprises performing intermediate annealing or final annealing at a temperature of 0 to 500 ° C.

[0005]

First, the alloy composition of the aluminum alloy of the present invention will be described. Si has a function of coloring the sulfuric acid bath anodic oxide film in a light gray color. If the amount of Si is less than 0.3%, the effect is weak and it does not develop a light gray color, and if it exceeds 3.0%, the film thickness must be thin in order to develop a dark color and a light gray color. Spoil. Fe has the effect of increasing the material strength and the effect of stabilizing the color tone. Fe amount is 0.1
If it is less than 1.0%, the material strength is low, and if it exceeds 1.0, the yellow tint becomes strong and the stability of the color tone of light gray is impaired. Cu has the effect of increasing the material strength and improving the alkali etching property before anodizing treatment, obtaining a uniform surface in a short time, and making the color tone uniform. When the amount of Cu is less than 0.1%, the effect of increasing the strength and the effect of improving the etching property are weak, and when the amount of Cu exceeds 0.3%, the color tone becomes more yellowish and the stability of the light gray tone is impaired. Mn has the effect of imparting material strength and suppressing the precipitation of Si-based compounds to increase the stability of color tone. The amount of Mn is 0.
If it is less than 05%, the effect of stability of color tone is weak, and if it exceeds 0.8%, a coarse intermetallic compound is generated to impair the uniformity of color tone, and it affects the uniformity of color tone and the color tone itself, resulting in a uniform light gray color. Will not be obtained. Ti has the effect of refining the structure of the aluminum alloy and homogenizing the color tone of the oxide film. If the Ti content is less than 0.001%, the effect of homogenization is small, and if it exceeds 0.10%, a coarse intermetallic compound is formed, which causes defects such as casting cracks, and also impairs the uniformity of color tone.

In the method for producing an alloy of the present invention, an ingot of a predetermined composition is homogenized at a temperature of 400 to 600 ° C.
This is a method in which hot rolling is performed at 00 ° C. or lower, and cold rolling is further performed to obtain a plate having a final thickness, and during cold rolling, intermediate annealing or final annealing is performed at a temperature of 350 to 500 ° C. This is a homogenization treatment of β-AlFeSi, Al-Fe-Mn.
-Si is deposited as a Si-based compound to control the amount of solid solution of Si, to suppress the precipitation of fine Si in the annealing in the subsequent step, to reduce the color tone change of the anodized film due to the annealing temperature, and to provide a stable and homogeneous light color. This is a method of obtaining a gray anodized film. If the homogenization treatment temperature exceeds 600 ° C., the Si-containing compound forms a solid solution, and Si precipitates in the subsequent annealing. This Si precipitate has the effect of coloring the anodized film in gray, and
Fine Si precipitates give a yellowish tint. For this reason, there is a large change in color tone due to the annealing temperature, the stability of the color tone is poor, and it becomes difficult to match the color of the film. Also, 400 ℃
When it is less than 1, the homogenization of the structure is insufficient and the stability of the color tone is lost. When the hot rolling temperature exceeds 500 ° C., the amount of Si solid solution increases, the amount of fine Si deposited in the annealing step increases, and the stability of color tone is impaired. Annealing temperature is 500 ℃
When it exceeds, the solid solution of Si causes less coloration of the anodic oxide film, and it is necessary to increase the film thickness to obtain a light gray color, which requires a long processing time and is not economical. Fine Si below 350 ° C
However, it is not possible to obtain a uniform light gray anodic oxide film with a large amount of precipitation. For the anodizing treatment of the aluminum alloy of the present invention obtained as described above, a sulfuric acid bath is mainly used, and the conditions such as concentration, current density and treatment temperature are generally applied.

[0007]

EXAMPLES The present invention will now be described in more detail with reference to examples. Example 1 An aluminum alloy having an alloy composition shown in Table 1 was melted and cast to have a width of 1100 mm, a thickness of 500 mm, and a length of 2000 m.
m ingot, homogenizing each ingot at 470 ° C. for 4 hours, hot rolling at a temperature of 430 ° C., and then 1 hour at 400 ° C.
After performing 0 hour intermediate annealing, cold rolling was performed to obtain a rolled sheet having a final sheet thickness of 2.0 mm. The obtained rolled plate was subjected to anodization treatment in a sulfuric acid bath to form an oxide film having a thickness of 20 μm, and the color tone of the anodized film was measured with a color difference meter. The anodizing conditions were a 15% sulfuric acid bath, a treatment temperature of 20 ° C., and a current density of 1.2 A / dm ² . The mechanical properties were also measured.
Table 2 shows the measurement results of the color tone by the color difference meter. The L value in Table 2 indicates the lightness, and the higher the value, the brighter and lighter the color tone is.
The a value and the b value indicate the color tone of the film. The higher the a value, the more reddish, the lower the bish, the higher the b, the more yellowish, the lower the bluish. In the present invention, the light gray tone has a L value of 50 to 75, an a value of -2 to 2, and a b value of 0 to 2.

[0008]

[Table 1]

[0009]

[Table 2]

As is clear from Table 2, the alloy of the present invention develops a light gray color. On the other hand, Comparative Example No.
Comparative Example No. 6 has a small amount of Si and does not develop a light gray color. 7
Had a large amount of Si and became dark gray. Comparative Example No. 8 is Cu
Content and Mn content were small, color unevenness was generated, and strength was low. Comparative Example No. Comparative Example No. 9 has a large amount of Cu and has a yellowish tint. No. 10 had a large amount of Mn and caused color unevenness.

Example 2 An aluminum alloy having the alloy composition shown in Table 3 was melted and cast into the same ingot as in Example 1, and each ingot was 47
After homogenizing treatment at 0 ° C. for 3 hours, hot rolling at a temperature of 450 ° C., intermediate annealing shown in Table 4 was performed, and then cold rolling was performed to obtain a rolled sheet having a final sheet thickness of 2.0 mm. The obtained rolled plate is
The same anodization treatment as in Example 1 was performed, and the color tone of the anodized film was measured with a color difference meter. Table 5 shows the measurement results.

[0012]

[Table 3]

[0013]

[Table 4]

[0014]

[Table 5]

As is clear from Table 5, in the examples of the present invention using the alloy of the present invention, the color tone difference ΔE due to the intermediate annealing temperature was as small as 1 or less, and the color tone of the light gray oxide film was stable. ing. On the other hand, in the comparative example using the comparative alloy, the amount of Cu and Mn was small and the difference in color tone due to the intermediate annealing temperature was Δ.
It shows that the variation of E is large and the stability of the color tone due to the intermediate annealing temperature is small. This means that
This also leads to variations in color tone between lots.
Further, the comparative example in which the intermediate annealing temperature is out of the range of the present invention,
When the intermediate annealing temperature is low, the b value becomes large and the yellowish color becomes strong,
It can be seen that when the intermediate annealing temperature is high, the L value is large and the color development is thin, and the desired light gray oxide film cannot be obtained.

[0016]

As described above, with the aluminum alloy according to the present invention, it is possible to obtain a light gray anodic oxide film with no color unevenness within and between lots, and it is possible to obtain a color difference on the outer panels of buildings and the like. It solves the problem and has a remarkable industrial effect.

Claims (2)

[Claims] 1. Si 0.3 to 3.0% (same as below by weight%), Fe 0.1 to 1.0%, Cu 0.1 to 0.3%,
Mn 0.05 to 0.60%, Ti 0.001 to 0.10.
%, And the balance is Al and unavoidable impurities. An aluminum alloy for anodic oxidation. 2. Si 0.3 to 3.0%, Fe 0.1 to 1.
0%, Cu 0.1 to 0.3%, Mn 0.05 to 0.60
%, Ti 0.001 to 0.10%, the alloy ingot composed of the balance Al and unavoidable impurities is homogenized at a temperature of 400 to 600 ° C., and then hot rolled at a temperature of 500 ° C. or less. And when subjected to cold rolling, 350 to 50
A method for producing an aluminum alloy for anodization, which comprises performing intermediate annealing or final annealing at a temperature of 0 ° C.