JPH02282495A - Production of aluminum alloy material forming stable bluish gray anodic oxide film - Google Patents

Abstract

PURPOSE:To form a stable bluish gray oxide film on the surface of an Al alloy ingot, to make the appearance fine and to improve the corrosion resistance by solidifying a molten Al alloy contg. specified amts. of Fe, Si, Cu and Be at a prescribed cooling rate and anodically oxidizing the resulting ingot. CONSTITUTION:An Al alloy consisting of, by weight, 0.3-2.2% Fe, 0.03-0.5% Si, 0.005-0.5% Cu, 0.02-0.1% Be and the balance AC is melted. This molten Al alloy is solidified at 2-50 deg.C/sec cooling rate and the resulting ingot is anodically oxidized with a sulfate bath, etc., to form an anodic oxide film.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to aluminum alloy materials and processed materials thereof that are used after being anodized in a sulfuric acid bath, and are useful for building materials, utensils, ornaments, etc. It makes the appearance beautiful and improves corrosion resistance at the same time.

[Prior Art] At present, Al-Fe and Al-3i alloys are known as alloys that form a gray film through normal anodic oxidation treatment using a sulfuric acid bath.
In the -3t series, it is thought that the Si particles remain in the film after the anodizing treatment and prevent reflection of white light (absorb part of the wavelength), resulting in a gray color.

[Problems to be solved by the invention] At-Fe alloys cause a eutectic reaction when solidifying,
Produces a eutectic compound. Generally cooling rate 1'c/se
The compound produced when solidifying below c is the equilibrium phase Al
It is said that Al6Fe, which is 3Fe and has a solidification rate (cooling rate) of 1 to b, is produced, and when the solidification rate is faster than 10°C/sec, compounds of Al and Fe are produced.

However, when we investigated actual ingots produced by semi-continuous casting, we found that Al3F
A1.e and Al6Fe compounds coexist, and A1. Fe compounds were also observed, suggesting that the cooling rate was non-uniform.

By anodizing treatment in a sulfuric acid bath, Al3Fe%A
The 1mFe compound is oxidized and does not remain as a compound in the film, but the Al6Fe compound remains in the film without being oxidized and appears gray because it does not allow white light to pass through. When a product manufactured from an ingot is anodized, the color of the anodic oxide film becomes uneven due to non-uniformity in the cooling rate, in other words, non-uniformity in the distribution of the Al6Fe compound.

[Means for Solving the Problems] The present invention provides (1) 0.3%≦Fe≦2.2%, 0.3%≦Fe≦2.2%, 0.3%≦Fe≦2.2%;
03%≦Si≦0.5%, 0.005≦Cu≦0.5
% and 0.02%≦Be≦0.10%, with the remainder being Al and inevitable impurities, was melted and solidified at a cooling rate of 2 to 50'C/sec to form an ingot. (2) A method for producing an aluminum alloy ingot that produces a stable bluish-gray anodic oxide film, characterized by This is a method for producing an aluminum alloy material that produces a stable bluish-gray anodic oxide film processed by a processing heat treatment method consisting of a combination.

To stabilize the color of the anodic oxide film on aluminum alloys,
Al3Fe, Al6Fe.

It is necessary to control the type, amount, size, and dispersion of Al, Fe compound (hereinafter referred to as eutectic compound) particles. These compounds are eutectic compounds produced during solidification, and their production is greatly influenced by the components and casting conditions, especially the cooling rate (solidification rate). Therefore, casting conditions, particularly cooling rate (solidification rate), have a large influence on stabilizing the film color. Therefore, in order to stabilize the color of the film, it is convenient to mix ingredients that will make it difficult for the production of eutectic compounds to fluctuate depending on the casting conditions.

Therefore, as a result of adding various elements to the Al-Fe alloy and investigating the relationship between the cooling rate and the color of the anodic oxide film, we found that the addition of Be stabilized the formation of Al6Fe compounds in particular, and the dispersion of the eutectic compounds was fine and uniform. It became clear that the color tone of the film was stabilized due to the Therefore, the present invention has adopted the above configuration.

The reasons for limiting the scope of claims in the present invention are as follows.

Fe: Fe gives an anodic oxide film a wide range of colors from light gray to dark gray depending on its content. However, if the content is less than 0.3%, it will not produce a gray color, and if it is more than 2.2%, coarse primary crystal compounds of Al3Fe will be produced, which will cause surface defects during rolling and extrusion processing, so this is not preferable. do not have. Further, as the Fe content increases, defects in the anodic oxide film increase and the weather resistance of the film also decreases, so it is preferably 2.2% or less.

Be: Addition of Be stabilizes the production of the Al5Fe compound and makes the dispersion of the eutectic compound fine and uniform, thereby stabilizing the color of the anodic oxide film.

However, when Be is less than 0.102%, the formation of eutectic compounds tends to vary depending on the cooling rate, and no effect on suppressing variations in film color can be expected. Also, Be is 0.10
%, the instability of the eutectic structure due to the cooling rate is reduced, but the effect of producing a gray color cannot be obtained.

It is preferable that the content of Si:St is small, and 0
, 596, Al-Fe-Si compounds are likely to be produced, making it impossible to obtain a bluish-gray color. Also,
If the Si content is less than 0.03%, the metal purity must be increased, and the economic advantage is lost.

Cu: The addition of Cu improves etching properties, resulting in a uniform color of the anodic oxide film, but at 0.5%
If it is added in an amount greater than 1, the color of the anodic oxide film will become non-uniform, which is not preferable. Furthermore, reducing Cu to less than 0.005% requires higher metal purity, which loses economic advantages.

Other components: The addition of up to 0.1% Ti and up to 0.05% B, which are often added to improve the crystal structure during alloy melting, has a particular effect on stabilizing the color of the anodic oxide film of the alloy material of the present invention. It doesn't matter since I don't have one.

Cooling rate: Al5F when the cooling rate is less than 1℃/sec
The amount of e produced is extremely small, and most of it becomes Al3Fe, making it difficult to obtain a gray color. Also, 50℃/s
If it exceeds ec, the amount of Al, . . . Fe increases, making it difficult to obtain a gray color.

Processing heat treatment temperature Two metastable phase Al6Fe is 550℃
The above heat treatment results in infiltration or stable phase Al3F.
Because it transforms into compound e, it becomes difficult to obtain a gray color.

[Example code] Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 [Relationship between cooling rate and film color in ingot] The relationship between cooling rate and anodic oxide film color was investigated for the aluminum alloys shown in Table 1.

The cooling rate was determined from the slope of the temperature-time diagram obtained by fixing a thermocouple in the mold and determining the temperature change when the molten metal solidified by /111.

A 15 μl thick anodic oxide film was applied to the produced ingot by measuring the cooling rate under the anodizing treatment conditions shown in Table 2, and the color of the anodic oxide film was measured.

Table 1 Alloy composition (weight %) Table 2 /IP1 color of the anodized film is β0/45° type i'll1
A colorimeter (NDIOID manufactured by Nippon Heavy Industries, Ltd.) was used. The measurement location was the location where the cooling rate of the ingot was measured.

Further, the color was measured from four directions: the casting direction (0', 180°) and the direction perpendicular to the casting direction (90', 270°), and the average value was calculated and used as the embellishment value. The color system was the L''a Tohyo color system.

The Lll value represents the lightness (large; bright, small; dark) aIL
Values represent redness and greenness (+ side: red, - side: green) b value represents yellowness and bluishness (+ side: yellow, - side: blue) Cooling rate and film color of the obtained ingot The relationship is shown in Figure 1.

In the case of sample No. 1 to which Be is not added, the Lll value changes significantly due to a change in the cooling rate. On the other hand, Be
In the material No. 2 in which 0.02% of L was added, the change in the Lll value was small. In addition, No. 1 with 0.10% Be added
, 3, the variation in L* value becomes even smaller. However, in No. 4 with 0.20% addition, although the Llil value is the most stable with respect to the cooling rate, the value is large and no gray color is obtained and there is no coloring effect.

The effect of adding Be is not only to stabilize the Llll value, but also to stabilize the a'' value.The effect on the a value does not change greatly depending on the amount of Be added.
The value increases with increasing amount of Be added, and 0.2%Be
It is difficult to obtain a bluish gray color with additive alloys.

Example 2 [Investigation of film color using rolled plate] N shown in Table 3
An aluminum alloy ingot (500tx 100OW) having main components No. 011 to No. 12 was produced by semi-continuous casting, and after facing 15 mm, heated to 40° C. and hot rolled into a 6ffl11 plate. After forming a 3 mm plate by cold rolling, intermediate annealing was performed at 200 to 500°C, and a 211II plate was obtained by cooling rolling.

This plate was anodized under the same conditions as in Example 1, and the average and variation width of the film color depending on the plate width direction and rolling direction (ALll value, ABit value: Δb* value; ΔL ” -L ” man
-L ” +ml ΔB IK -a” mat
a , 1 △b ” -b ” may-
b'm+n) was investigated.

The results are shown in Table 4.

Alloy components (weight ht%) and intermediate annealing temperature properties 1) Ti is 0.04%, other impurities are 0.01% or less.

Table 4: Anodic oxide film color and its variation [Effects of the invention] The alloy in the present invention and its processed material can provide a stable bluish-gray anodic oxide film.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the cooling rate of the ingot and the color of the anodic oxide film. Nru encounter l (”snake/ki 0)

Claims (2)

[Claims] (1) 0.3%≦Fe≦2.2% (weight%, same below)
, 0.03%≦Si≦0.5%, 0.005≦Cu≦0
．． 5% and 0.02%≦Be≦0.10%, the remainder A
Aluminum that produces a stable bluish-gray anodic oxide film characterized by melting an aluminum alloy consisting of l and inevitable impurities and solidifying it at a cooling rate of 2 to 50°C/sec to form an ingot. Method for manufacturing alloy ingots. (2) A stable bluish-gray anodic oxide film is produced by processing the alloy ingot according to claim (1) using a processing heat treatment method consisting of a combination of rolling, extrusion, and heat treatment at a temperature lower than 550°C. A method for producing aluminum alloy.