JP2643632B2 - Aluminum alloy wrought material for forming colored oxide film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wrought aluminum alloy having a light gray colored oxide film formed on its surface by anodic oxidation and a method for producing the same.

[0002]

2. Description of the Related Art Aluminum alloy wrought materials are used for building materials, objects,
When used as a decorative article or the like, an oxide film is formed on the surface by anodic oxidation treatment in order to impart decorativeness and improve corrosion resistance. The oxide film formed on the surface of the wrought aluminum alloy has various colors depending on the type of the alloy. Therefore, in order to respond to the purpose of use and the needs of the user,
Different types of alloys are used.

However, a colored oxide film formed by a conventional anodic oxidation treatment often tends to have an uneven color tone. Further, there is a disadvantage that coloring is unstable and a color tone changes for each lot.

[0004] For example, in the case of wrought A1100 series aluminum alloy containing Fe and Si as main components of coloring, an oxide film based on gray is formed by ordinary anodic oxidation treatment. However, when casting an aluminum alloy of this type, Al ₃ Fe, Al ₆ Fe, β-AlFeSi, α-
Fe and Si are crystallized as intermetallic compounds such as AlFeSi and α-Al (FeM) Si. M represents a transition metal contained as an impurity in the aluminum alloy. The type and abundance of these crystallized materials vary depending on the alloy composition, casting conditions, homogenizing heat treatment that is subsequently performed, and drawing conditions. In some cases, it is oxidized by anodizing treatment or remains in the oxide film without being oxidized.

[0005] The coexistence of these various crystallized substances causes mottled color and unstable color tone of the oxide film formed by the anodic oxidation treatment. For example, the color tone of the oxide film changes slightly,
A stable colored oxide film cannot be obtained.

[0006] In order to suppress crystallized substances which cause coloring instability, for example, in Japanese Patent Application Laid-Open No. 60-82642, an aluminum alloy ingot is subjected to a heat treatment at a high temperature for a long time.
Transformation of an Al-Fe based intermetallic compound into stable Al ₃ Fe is introduced. Further, by subjecting an aluminum alloy ingot containing a large amount of Fe to a low-temperature soaking treatment, transformation of an intermetallic compound of Al ₆ Fe → Al ₃ Fe is prevented, and only an intermetallic compound mainly containing Al ₆ Fe Have been proposed to obtain an aluminum material having a dark gray anodic oxide film formed thereon.

[0007]

However, a method of subjecting an aluminum alloy ingot to high-temperature and long-time soaking treatment has a high production cost industrially. In addition, productivity is significantly reduced by the soaking. In addition, the oxide film obtained by the anodizing treatment has a yellowish color tone far from pure gray. Further, since the color tone changes for each lot even with a slight change in conditions, it is necessary to strictly control the heating conditions for the ingot. As a result, there has been a problem in the color matching of the obtained product.

On the other hand, soaking at a low temperature can suppress transformation of an Al—Fe intermetallic compound, but cannot sufficiently homogenize a cast structure. For this reason, a material having a fine and uniform crystal structure cannot be obtained, and a band-like stripe pattern easily occurs in the oxide film after the anodic oxidation treatment. In this respect, the method using the low-temperature soaking heat treatment cannot be applied particularly to an application requiring a uniform color tone.

The present invention has been devised to solve such a problem. By producing a stable intermetallic compound at the casting stage which is not affected by processing conditions, heat treatment conditions, and the like, An object of the present invention is to provide an aluminum alloy wrought material capable of stably producing an anodized film having a uniform light gray color tone without color mixture such as yellowish color.

[0010]

The wrought aluminum alloy of the present invention comprises 0.08 to 0.50% by weight of Si and F
e: 0.15 to 0.90% by weight, and Fe / S
An aluminum alloy having a composition in which the content ratio of i is 1.4 to 2.2, wherein α-AlFeSi and / or α-Al
It has a structure in which Al-Fe-Si based intermetallic compound mainly composed of (FeM) Si is dispersed, and a light gray colored oxide film is formed by anodizing treatment. Here, M represents a transition metal contained as an impurity in the aluminum alloy.

The aluminum alloy used here is T
i: 0.001 to 0.10% by weight and if necessary B:
0.0001 to 0.02% by weight can be contained. Moreover, you may contain 0.005-0.1 weight% of Mg.

The wrought aluminum alloy is made of Si:
0.08 to 0.50% by weight and Fe: 0.15 to 0.9
0% by weight, and the Fe / Si content ratio is 1.4.
Α-AlFeSi and / or α
An aluminum alloy ingot having a structure in which Al-Fe-Si intermetallic compound mainly composed of -Al (FeM) Si is dispersed is heated and held at 450 to 590 ° C for 1 hour or more, and then hot and cold expanded. Manufactured by stretching.

[0013]

The conventional soaking heat treatment at a high temperature for a long time and the soaking heat treatment at a low temperature have both been developed with the aim of precipitating a stable intermetallic compound by adjusting the heat treatment conditions. Therefore, it is practically impossible to change the intermetallic compound to a completely stable form, and the intermetallic compound which adversely affects the color tone cannot be avoided.

Therefore, the present inventors have proposed to produce a stable intermetallic compound by controlling the alloy composition, which is as simple as possible in the casting stage and which is not affected by the subsequent processing conditions and heat treatment conditions. It was considered that an anodized product film having a uniform color tone would be formed if this was achieved. As a result of various investigations and studies based on this consideration, it was found that the Fe content, the Si content, and the Fe / Si content ratio of the aluminum alloy have a great influence on the type and the precipitation form of the intermetallic compound. I found it.

That is, the content of Si, the content of Fe, and the content of Fe / Si of the aluminum alloy ingot were set to 0.08 to 0.50% by weight and 0.15 to 0.90% by weight, respectively.
And between 1.4 and 2.2, the Al-Fe-Si intermetallic precipitates in the ingot when casting an aluminum alloy by a semi-continuous casting method which is very generally adopted. The compound is mainly limited to those mainly composed of α-AlFeSi, α-Al (FeM) Si or a mixture thereof. In the following description, these intermetallic compounds are collectively referred to as “α-type compounds”.

The α-type compound is a relatively stable compound. In other words, when soaking heat treatment, hot working, heat treatment during working, etc. of the ingot subsequent to casting are performed within the range of conditions generally used for this kind of alloy, less strict condition control is required. , Α-type compounds are stably present without any transformation. When the Al-Fe-Si intermetallic compound is an α-type compound, the color tone of the oxide film obtained when anodized aluminum alloy is subjected to anodizing treatment is a mixed color of other colors such as yellow. It is homogeneous and pale gray with no color.

The components of the aluminum alloy used in the present invention will be described below. Si: an element contained in the aluminum alloy as an unavoidable impurity,
It greatly affects the color tone of the anodic oxide film. When the Si content exceeds 0.5% by weight, coarse precipitates of elemental Si are easily generated. When this simple Si exists in the alloy,
The oxide film formed by the anodic oxidation treatment develops a black-gray color and cannot obtain a stable light gray color tone.
Therefore, the upper limit of the Si content is set to 0.50% by weight. On the other hand, when the Si content is less than 0.08% by weight,
Color development by anodizing treatment becomes insufficient.

Fe: α-AlFeSi, α-Al (F
eM) It is an important element in forming an α-type compound such as Si and giving a light gray color tone to the oxide film formed by the anodic oxidation treatment. However, when the Fe content exceeds 0.90% by weight, Al-Fe-based intermetallic compounds such as Al ₆ Fe and Al ₃ Fe other than the α-type compound easily precipitate in the alloy structure. As a result, the oxide film obtained by the anodic oxidation treatment has an unstable color tone. On the other hand, if the Fe content is less than 0.15% by weight, it is not possible to precipitate an α-type compound in the alloy in an amount sufficient to cause the oxide film to develop a light gray color by anodizing treatment. Therefore, the Fe content is set in the range of 0.15 to 0.90% by weight.

Fe / Si content ratio: Crystallized Al—
This is an important factor for making most of the Fe-Si based intermetallic compound an α-type compound. Fe / Si content ratio is 2.
If it exceeds 2, Al—Fe such as Al ₆ Fe and Al ₃ Fe
The system intermetallic compound is easily crystallized. As a result, the color of the oxide film formed by the anodic oxidation treatment changes according to the type and the mixture ratio of the intermetallic compound, and a colored alloy material having a uniform light gray oxide film cannot be obtained. Conversely, F
When the content ratio of e / Si becomes less than 1.4, β-AlF
β-type compounds such as eSi and β-Al (FeM) Si and free simple Si are easily precipitated. These deposits cause the anodic oxide film to develop a relatively dark gray color, making it difficult to stably obtain a light gray colored oxide film.

Ti and B: Ti added as an optional component has a function of refining the cast structure of the aluminum alloy and making the coloring of the oxide film uniform. This effect of Ti becomes even more remarkable when B is added. Ti
If it is less than 0.001% by weight and B is less than 0.0001% by weight, the effect is small. Conversely, if the contents of Ti and B exceed 0.10% by weight and 0.02% by weight, respectively, the effect of further refinement of the crystal structure cannot be obtained, and the Al—Ti,
Coarse intermetallic compounds such as Ti-B and Al-Ti-B are easily formed. These intermetallic compounds cause defects such as casting cracks. Therefore, the contents of Ti and B are set to 0.001 to 0.10% by weight and 0.0
It was specified in the range of 001 to 0.02% by weight.

Mg: The addition of a small amount of Mg does not affect the color tone of the anodic oxide film, and has the effect of suppressing the growth of the fir tree structure formed on the surface of the ingot during casting. The fir tree structure is formed by a cooling effect in which the molten metal in contact with the inner wall of the mold has intermittent strength,
-It is generated because the Fe-based intermetallic compound is crystallized near the surface of the ingot. This causes a change in the color tone of the oxide film after the anodizing treatment. Therefore, in order to ensure the surface properties, the fir tree structure is removed from the surface of the ingot by chamfering before the hot rolling process is started. When an aluminum alloy is cast under normal conditions, a fir tree structure may grow from the surface of the ingot with a thickness exceeding 10 mm. As a result, the amount of chamfering increases with the growth of the fir tree structure, the yield decreases, and the product cost increases. The growth of the fir tree tissue can be enhanced by adding 0.005 to 0.1% by weight of Mg.
It can be suppressed within 5 mm from the surface of the ingot. Therefore, the amount of facing can be reduced to less than half of the conventional case. However, when the Mg content exceeds 0.1% by weight, Mg ₂ Si
Is observed, and a color tone change occurs in the anodic oxide film.

Other impurities that may be present in the aluminum alloy raw material or mixed during the smelting include Cu, Zn,
There are Ni, Cr, Mn, Co and the like. The content of these impurities does not adversely affect the color tone of the anodic oxide film as long as it is maintained in the range normally contained. In particular,
0.2% by weight or less of Cu, 0.2% by weight or less of Zn,
0.02% by weight or less of Ni, 0.02% by weight or less of C
r, Mn of 0.02% by weight or less, and Co of 0.02% by weight or less.

In some cases, these impurity elements are effective in improving the strength of the alloy. In addition, Ni, Cr, Mn, Co
Transition elements such as α- formed partially in the alloy
Α-Al (FeM) S combined with AlFeSi compound
Forms an i-based compound. This compound does not change the color tone of the colored oxide film.

FIG. 1 shows the contents of Fe and Si, which are main components of the aluminum alloy used in the present invention, and Fe / S
FIG. 6 shows the results of an experiment in which the effect of the content ratio of i on the formation of intermetallic compounds formed in an alloy was investigated.

In the experiments, predetermined amounts of Fe and Si
Is added, and the ingot obtained by semi-continuous casting of the molten alloy having a changed Fe / Si content ratio is subjected to soaking at 530 ° C. for 1 hour, followed by hot rolling and cold rolling. A rolled sheet obtained by applying intermediate annealing at 390 ° C. for 1 hour during cold rolling was used. X-ray diffraction of a test piece cut out from this rolled plate gave an α-type compound, Al ₃ F
e, peaks of Al ₆ Fe, β-type compound, etc. were measured. Most of the α-type compound in this case is α-Al (Fe
M) Si.

In FIG. 1, a circle indicates a peak in which only the α-type compound was detected, and a cross indicates the α-type compound, Al
₃ that the three peaks of Fe and Al ₆ Fe are detected, △ mark α-type compound, beta-AlFeSi and free Si
Indicates that the peak was detected. As is clear from FIG. 1, the Si content is 0.08 to 0.50% by weight, the Fe content is 0.15 to 0.90% by weight, and the Fe / Si content ratio is 1.4 to 2.2. In the shaded region, a peak of only the α-type compound is detected. However, those outside of this range, in addition to the α-type compound, β-type compound, Al ₃ Fe,
Al ₆ Fe, free Si and the like were detected.

The wrought aluminum alloy of the present invention is made into an ingot by a known casting method such as a semi-continuous casting method, and a soaked aluminum alloy having the above-mentioned composition is subjected to a soaking treatment under appropriate heat treatment conditions. After application, it is formed into a desired shape by hot and cold drawing.

In the soaking process, the aluminum alloy ingot was 4
It is kept for 1 hour or more in the temperature range of 50 to 590 ° C. If the treatment temperature exceeds 590 ° C., a part of the α-type compound is easily transformed into Al ₃ Fe due to the separation of Si, and the color tone of the oxide film formed by the anodic oxidation treatment becomes unstable. On the other hand, if the processing temperature is lower than 450 ° C., the homogenization of the cast structure is not sufficiently performed, and coarse crystal grains and grain streaks tend to be generated during hot spreading. In order to achieve sufficient tissue homogenization, holding for 1 hour or more is required. Retention time 1
If the time is not enough, an inhomogeneous cast structure remains. Heating and holding for about 5 hours at the longest is sufficient. Even if the ingot is kept longer than that, the effect of homogenization is saturated and the energy consumption increases, which is economically disadvantageous.

As the stretching, general processing means such as extrusion, rolling, and forging can be employed.

The anodic oxidation treatment applied to the wrought material after processing is performed under ordinary conditions using an electrolytic bath mainly containing sulfuric acid in the anodic oxidation treatment of this kind of aluminum material. .

[0031]

EXAMPLE An alloy melt corresponding to A1100 having compositions A to G shown in Table 1 was formed by a semi-continuous casting method to a thickness of 508 mm.
And a belt-shaped ingot having a width of 1050 mm.

[0032]

[Table 1]

Each of the alloy ingots was subjected to soaking under the four types of heat treatment conditions a to d shown in Table 2, and then subjected to hot rolling. Further, after performing an intermediate annealing at 390 ° C. for 1 hour,
It was cold rolled to a thickness of 2 mm.

[0034]

[Table 2]

A test piece cut out from the obtained cold-rolled sheet was subjected to anodizing treatment using sulfuric acid as an electrolytic solution to form an oxide film having a thickness of 18 μm. The color tone of the oxide film was measured using a colorimeter. Table 3 shows the measurement results. The anodic oxidation treatment was performed under the following conditions. Electrolysis bath: 15% sulfuric acid solution Electrolysis bath temperature: 25 ° C. Current density: 1.2 A / dm ²

[0036]

[Table 3]

The L value in Table 3 represents the lightness of the film, and the higher the value, the lighter the color tone. The b value is a value representing the hue of the oxide film. The higher the value, the more yellow the color becomes, and the lower the value, the more bluish. Then, as the b value approaches 0, the color becomes light gray without color mixture.
The ΔL value indicates a difference in lightness, and indicates a variation in the L value due to a difference in heat treatment conditions of each ingot.

As is clear from Table 3, in the alloys A to D containing the components falling within the range specified in the present invention, even when the heating temperature of the ingot is changed, the ΔL value showing the color variation is small. , And the b values indicating the hues are all within 0.9.
This indicates that the oxide film has no yellow color mixture.

On the other hand, in the alloys E to G of the comparative examples, when the heating conditions of the ingot were changed, even if the same alloy was used, the variation in color tone became large. As the heating temperature of the ingot increases, the L value also increases, and the variation in ΔL increases. This indicates that the heating temperature of the ingot needs to be strictly controlled in a narrow temperature range in order to obtain a colored anodic oxide film having the same color tone. Further, the b value representing the hue is generally higher than the value of the embodiment of the present invention. This indicates that a yellow color mixture has occurred in the formed oxide film, and indicates that a light gray oxide film without color mixture such as the colored oxide film of the example of the present invention has not been obtained. .

From the results of the X-ray diffraction test for investigating the state of formation of the intermetallic compound, all the alloys A to D of the present invention showed a high intensity peak in α-Al (FeM) Si. I have. Moreover, this situation does not change at all due to a change in the heating temperature of the ingot. On the other hand, in the alloys E to G of the comparative examples, the type of the formed intermetallic compound was not constant, and in addition to the α-type compound, Al ₃ Fe, Al ₆
Peaks were simultaneously detected for Fe, free Si, and the like. In addition, the peak intensity of each precipitate changes variously depending on the heating temperature of the ingot.

From the above, when anodizing is performed using the wrought aluminum alloy of the present invention, the obtained oxide film has a pure and homogeneous light gray color tone without multicolor mixture. Further, it is clear that the color tone does not change depending on the soaking temperature of the ingot. On the other hand, in the case where the alloy wrought material of the comparative example having a component and composition deviating from the range specified in the present invention is subjected to anodizing treatment, an oxide film exhibiting a gray color mixed with a yellow color is formed, Moreover, the degree of color mixture and the degree of gray are slightly different depending on the processing temperature. Therefore, it is found that an oxide film having a stable color tone is hardly formed.

Further, Table 3 shows the overall evaluation of the colored oxide film products. The overall evaluation was ◎ for those with a completely uniform pale gray appearance of the colored oxide film, ○ for those with a nearly completely homogeneous light gray color, △ for those with a slightly heterogeneous color tone and slightly yellowish color, Those having an inhomogeneous color tone and exhibiting a yellow color were represented by x. The marks ○ and ○ indicate that the test passed, and the marks Δ and X indicate that the test failed.

Example 2 An alloy having the composition shown in Table 4 was cast and rolled in the same manner as in Example 1 to form a cold-rolled sheet having a thickness of 2 mm.

[0044]

[Table 4]

A test piece was cut out from the obtained cold-rolled sheet, anodized under the same conditions as in Example 1, and the color tone of the formed oxide film was measured. Table 5 shows the measurement results. Further, the fir tree structure generated in the ingot produced by semi-continuous casting was examined, and the thickness of the structure, that is, the distance at which the fir tree structure was generated from the surface layer of the ingot was measured. Then, if the distance from the surface layer is 5 mm or less,
Tables 5 to 20 mm were evaluated as Δ, and those exceeding 20 mm were evaluated as ×.

[0046]

[Table 5]

As can be seen from Table 5, the alloys H and I according to the present invention containing more than 0.005% by weight of Mg.
In, growth of the fir tree structure is sufficiently suppressed to within 5 mm from the surface of the ingot. On the other hand, in alloys J to L having a small Mg content, growth of a fir tree structure exceeding 20 mm from the surface layer was detected in a large alloy. As a result, prior to hot rolling, the surface of the alloy ingot had to be chamfered with a large amount of chamfering, and the yield decreased accordingly.

[0048]

As described above, in the wrought aluminum alloy for forming a colored oxide film of the present invention, the Fe content, the Si content and the Fe / Si content ratio are adjusted. , Α-AlFeS in the alloy
A stable α-type compound such as i, α-Al (FeM) Si is formed at the casting stage. The α-type compound is stably present in the wrought material after cold rolling without being affected by the subsequent processing conditions and heat treatment conditions. As a result, the oxide film formed by the anodic oxidation treatment has a uniform light gray color without color mixture. Moreover, since this color tone can be obtained with good reproducibility, it is possible to provide a colored aluminum material of the same quality without necessity for color matching or the like.
In addition, since the amount of facing can be reduced by adding Mg, the yield is improved and the manufacturing cost is reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing the effects of Fe content and Si content on the form of precipitates in an aluminum alloy.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akito Nishizawa 1-11-1 Koike, Inazawa-shi, Aichi Japan Light Metal Co., Ltd. Nagoya Plant (56) References JP-A-60-82642 (JP, A)

Claims (4)

(57) [Claims] 1. Si: 0.08 to 0.50% by weight and F
e: 0.15 to 0.90% by weight, and Fe / S
an aluminum alloy having a composition in which the content ratio of i is from 1.4 to 2.2, wherein α-AlFeSi, α-Al (Fe
Α-type Al such as M) Si [where M represents a transition metal]
-An aluminum alloy wrought material having a structure in which an Fe-Si-based intermetallic compound is dispersed and having a light gray colored oxide film formed by anodic oxidation treatment. 2. The method according to claim 1, wherein the aluminum alloy is T
i: 0.001 to 0.10% by weight and B: 0.0001
A wrought aluminum alloy material containing from 0.02% by weight. 3. The wrought aluminum alloy according to claim 1, wherein the aluminum alloy contains 0.005 to 0.1% by weight of Mg. 4. Si: 0.08 to 0.50% by weight and F
e: 0.15 to 0.90% by weight, and Fe / S
i has a composition with a content ratio of 1.4 to 2.2, and α-Al
FeSi, α-Al (FeM) Si [where M is a transition
[Indicating metal]], an aluminum alloy ingot having a structure in which α-type Al-Fe-Si-based intermetallic
A method for producing a wrought aluminum alloy material for forming a colored film, wherein the wrought material is subjected to hot and cold drawing after heating and holding at 590 ° C. for 1 hour or more.