JPH0673478A - Aluminum alloy sheet for anodic oxidation treatment and its production - Google Patents

Abstract

PURPOSE:To provide an aluminum allay sheet having a discontinuous vertically striped pattern with a color tone of dark greenish gray and a straight-grained tone as subjected to anodic oxidation treatment in a sulfuric acid bath. CONSTITUTION:This aluminum alloy sheet is the one contg. 0.3 to 1.2% Cr, >0.2 to 1.0% Fe and <=0.5% Si and in which the crystalline grains on the surface after being cast are constituted of wide columnar crystals. As for its producing method, a sheet continuous casting method of executing rapid cooling at >=5 deg.C/sec cooling rate is applied, and after being cast, it is subjected to heating of 400 to 630 deg.Cmu0.5 to 24hr and is thereafter subjected to anodic oxidation treatment to obtain a discontinuous vertically-striped patterns 1 and 2 of dark greenish gray. Moreover, after the casting, cold rolling may be executed, and in this case, before, in the process of or after the cold rolling, the same heating is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy plate for use after being subjected to anodizing treatment, for example, building materials such as curtain walls and outer walls of buildings, roofs, doors, gates, interior materials, and various equipment. The present invention relates to an aluminum alloy plate used for a container, a nameplate, etc. and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, curtain walls and building exterior materials,
Building materials such as interior materials, or rolled materials of aluminum alloy used for vessels, containers, nameplates, etc. are often used after being subjected to anodizing treatment from the viewpoint of corrosion resistance. Many of the aluminum alloys for anodizing treatment for these purposes have a light gray to silver color tone after the anodizing treatment, and as a rolled material of such an alloy, JIS JIS is generally used.
1050 alloy, 1100 alloy, 5005 alloy, etc. are often used. Also, as the gray type, Al-1 ~
A 4% Si alloy is common.

[0003]

Recently, building exterior materials,
In applications such as interior materials, there are increasing demands for diversified color tones and individualization due to design requirements.
Aluminum alloys used after being subjected to anodizing treatment are often required to have various color tones in these applications, and examples thereof include dark green gray tones.

There are secondary electrolysis method, dyeing method, and other coating methods as methods for giving various color tones to the anodized material of aluminum alloy, but these methods have a problem of fading, corrosion resistance and corrosion resistance. There are problems such as cost. Therefore, it is desired to obtain a dark green-gray color tone with the anodizing treatment as it is.

Conventionally, as a method of obtaining a dark green-gray color tone with the anodizing treatment as it is, there is an anodizing treatment with an oxalic acid electrolytic bath.
Compared to the case of sulfuric acid electrolysis bath, which is currently the mainstream, stricter electrolysis conditions and electrolysis bath management are required, and the film characteristics are inferior and the cost is high. It is desirable to obtain a dark green-gray shade at.

However, the fact is that conventionally, a method for obtaining a dark green-gray color tone by the anodic oxidation treatment using a sulfuric acid electrolytic bath has not been established. In particular, when the method of directly casting a plate of about 5 to 50 mm by the plate continuous casting method (continuous casting and rolling method) is applied, a method for obtaining a dark green-gray color tone with the anodizing treatment in the sulfuric acid electrolytic bath as it is The fact is that it was unknown.

In addition, not only the color tone but also the individual appearance pattern is required in the building materials from the viewpoint of design, and one of them is the discontinuous vertical stripes in the grain pattern. Although there is a pattern, in the past, a method for stably obtaining a predetermined discontinuous vertical stripe pattern with the anodizing treatment as it is has not been established.

The present invention has been made in view of the above circumstances, and has a discontinuous vertical stripe pattern in a dark green-gray color tone in a direction parallel to the casting direction or the rolling direction while being anodized in a sulfuric acid electrolytic bath. It is an object of the present invention to provide an aluminum alloy plate that can be reliably and stably obtained.

[0009]

The aluminum alloy sheet for anodizing treatment according to the present invention basically has a component system of Al--
In addition to being Cr-based, a predetermined amount of Fe is added, and the amounts of Ti and B, which are often added to aluminum alloys as grain refiners, are regulated to extremely small amounts or less, and The structure is made of a wide columnar crystal so that a golden color or a dark green gray color having a discontinuous vertical stripe pattern can be obtained with the anodizing treatment in a sulfuric acid electrolytic bath.

Specifically, the aluminum alloy sheet for anodizing treatment according to the first aspect of the present invention comprises Cr 0.3 to 1.2 wt%,
Fe 0.2wt% over 1.0wt%, Si 0.5wt%
It contains the following, the content of Ti is controlled to 0.01 wt% or less, the content of B is regulated to 0.002 wt% or less, and the balance is Al and other unavoidable impurities, and 50% or more of the crystal grains on the surface after casting. Is a columnar crystal having a width of 2 mm or more, and is an aluminum alloy plate for anodizing treatment which exhibits a discontinuous vertical stripe pattern of dark green gray color tone after the anodizing treatment.

The method for producing an aluminum alloy sheet for anodizing according to the present invention limits the composition of the alloy as described above and utilizes the characteristics of rapid solidification by the continuous sheet casting method or the like to make the surface wide. Obtain a cast plate composed of columnar crystals,
Further heat treatment is performed to precipitate fine precipitates that contribute to the darkening of the color tone, and by utilizing the variation of the precipitation for each crystal grain, the surface after the anodizing treatment with a sulfuric acid electrolytic bath has a dark green gray color tone. A discontinuous vertical stripe pattern is generated. Further, it is also intended to provide a plate having a thickness as cast, or a plate having a reduced thickness by performing cold rolling after casting.

[0012] Specifically, the manufacturing method of the invention of claim 2 is as follows: Cr 0.3 to 1.2 wt% Cr 0.3 to 1.2 wt% F
e containing more than 0.2 wt% and 1.0 wt% or less, Si 0.5 wt% or less, Ti amount of 0.01 wt% or less, B amount of 0.002 wt% or less, the balance is Al and other unavoidable Melt of alloy consisting of static impurities at 5 ℃ / sec
Casting is performed at the above cooling rate to obtain a cast plate in which 50% or more of the surface crystal grains are columnar crystals with a width of 2 mm or more, and then the cast plate is heated at 400 to 630 ° C. for 0.5 to 24 hours. It is characterized by doing.

According to the third aspect of the invention, the casting is carried out in the same manner as in the second aspect, and then cold rolling is carried out to obtain a required plate thickness, and between the casting and the cold rolling, or between the cold rolling. 0.5 at 400 to 630 ° C. in the middle of rolling or after cold rolling
It is characterized by heating for up to 24 hours.

[0014]

First, the reasons for limiting the component composition of the aluminum alloy in the present invention will be explained.

Cr: If Cr is present in a solid solution state, a golden color can be developed as a color tone after anodizing treatment. In order to obtain a dark green-gray color tone as the color tone after the anodizing treatment, a golden color of solid solution Cr is essential as the base color tone of the dark green-gray color tone. That is, based on the golden film color, the Al-
As a result of the fine precipitates of the Fe (-Si-Cr) system clouding the golden color, a deep dark green-gray shade is obtained. Therefore, Cr is an alloying element which is basically important in the present invention. The greater the solid solution amount of Cr, the stronger the golden color. However, in order to obtain a sufficient golden color tone, 0.3 wt% or more of Cr is usually required. However, in a usual casting method such as a DC casting method with a slow cooling rate, Cr is 0.3
If it is more than wt%, a huge Cr-based primary intermetallic compound crystallizes out, and not only cannot be manufactured substantially, but also Cr cannot be forcibly solid-dissolved, so that the golden color cannot be clearly developed. On the other hand, by rapid solidification at a cooling rate of 5 ° C./sec or more by a plate continuous casting method or the like, the Cr amount range in which a coarse Cr-based intermetallic compound is not generated can be increased to 1.2 wt%. Moreover, in rapid solidification such as continuous plate casting,
Most of the added Cr can be forced to form a solid solution, so that a sufficiently strong golden color can be developed. However, if Cr exceeds 1.2 wt%, coarse compounds of primary crystals will crystallize even if the plate continuous casting method is applied, and the amount of forced solid solution of Cr will reach the limit, so there is no point in adding more. . Therefore, the Cr amount is set within the range of 0.3 to 1.2 wt%.

Fe: In the present invention, Fe contributes to change the color tone after anodizing from golden to dark green gray by subjecting it to an appropriate heat treatment. That is, if Fe is contained, Al-F can be obtained by performing an appropriate heat treatment.
The e (-Si-Cr) -based precipitates are finely deposited, and the fine precipitates add a dark green-gray turbidity to the golden color tone of the base, thereby providing a deep dark green-gray color tone. . Here, if the Fe content is 0.2 wt% or less,
The amount of Al-Fe (-Si-Cr) -based fine precipitates due to the heat treatment decreases, and it becomes difficult to obtain a dark green-gray color tone. On the other hand, if the Fe content is 1.0 wt% or more, casting becomes difficult. Therefore, the Fe content exceeds 0.2 wt% and becomes 1.0
Must be less than wt%.

Si: If Si is included with Fe,
Fine Al-Fe-Si by appropriate heat treatment
A (-Cr) -based precipitate is deposited. This fine Al-
The Fe-Si (-Cr) -based precipitate contributes to the dark green-gray coloration as described above. Therefore, Si has the effect of promoting the color development of dark green gray. However, if the Si amount exceeds 0.5 wt%, casting becomes difficult, so the Si amount must be 0.5 wt% or less.

Ti, B: In general aluminum alloys, a small amount of Ti is often added alone or a small amount of Ti is combined with a small amount of B in order to refine ingot crystal grains. However, in the case of the present invention, in order to develop a discontinuous vertical stripe pattern on the surface after the anodizing treatment, T
It is necessary to control the content of i or B to be a minute amount or less and to achieve columnar crystallization (coarsening) of ingot crystal grains. That is, in the present invention, a golden color due to solid solution of Cr and Al-Fe (-
Si-Cr) based turbidity due to fine precipitates is synthesized to achieve a dark green-gray color tone. However, according to the study by the present inventors, after casting, an Al-Fe (-Si-Cr) -based color tone is obtained. It was found that the distribution of the fine precipitates varied depending on the crystal orientation when heat treatment was performed to precipitate the fine precipitates.
Therefore, when the crystal grains during casting are coarse columnar crystals,
The precipitation distribution of Al-Fe (-Si-Cr) -based fine precipitates differs for each crystal grain, and as a result, the color tone after anodizing treatment differs for each crystal grain. And since columnar crystals grow along the casting direction, if the plate that has been heat treated for precipitation after casting is subjected to anodization, the color tone will differ for each crystal grain elongated in the casting direction (longitudinal direction). As a result, it is possible to obtain a discontinuous vertical striped pattern having a grain of wood. Here, if the width of the columnar crystals (the maximum width in the direction orthogonal to the casting direction of each columnar crystal grain) is less than 2 mm,
The vertical stripes are so fine that it is hard to say that it is a grainy wood grain, and visually the vertical stripes are too fine and the impression is weak. However,
The width of the crystal grains does not have to be 2 mm or more for all the crystal grains, and even if some of the crystal grains have a width of less than 2 mm,
A wood grain impression can be given, and therefore, in the present invention, 50% or more of the crystal grains on the surface of the cast plate may be columnar crystals having a width of 2 mm or more. Thus, in order to obtain 50% or more of the crystal grains on the surface of the cast plate as coarse columnar crystals and to obtain a discontinuous vertical stripe pattern in a grain pattern, Ti and B which are refined in the ingot crystal grains are obtained. It is necessary to limit the amount. Specifically, Ti is 0.01 wt
If it exceeds%, fine equiaxed crystals are generated and columnar crystals having a width of 2 mm or more cannot be obtained. If B also exceeds 0.002 wt%, equiaxed crystals will be formed. Therefore, Ti is 0.01
wt% or less and B is limited to 0.002 wt% or less.

In addition to the above components, basically Al
And unavoidable impurities other than Ti and B may be used. However, in a usual aluminum alloy, a small amount of Be may be added in order to prevent the oxidation of the molten metal during casting, but in the case of the alloy of the present invention, a small amount of Be may be added. If the amount is about 500 ppm or less, other performance is not particularly deteriorated. In addition, one or more of Cu, Zn, and Mg may be contained for the purpose of improving strength, and Cu is 1.0 wt.
%, Zn is 2.0 wt% or less, and Mg is 2.0 wt% or less, the object of the present invention can be achieved without particularly impairing other performances. However, Cu and Zn are preferably each less than 0.1 wt% from the viewpoint of corrosion resistance, and Mg easily forms an oxide, and inclusions resulting from this adversely affect the surface quality after surface treatment. ,
Mg is also preferably less than 0.1 wt%.

Next, a method for manufacturing the aluminum alloy plate of the present invention will be described.

In the method of the present invention, as a casting method of the molten alloy, a plate continuous casting method or the like in which a plate having a thickness of about 5 to 50 mm is directly cast at a cooling rate of 5 ° C./sec or more is applied. As a typical example of the plate continuous casting method, there is a method of casting a plate by supplying hot water between a pair of rotary cooling rolls, a caterpillar, or a belt, which is, for example, a 3C method or a Hunter method, a caster II, Known as the Hazareth method, it is also called roll casting or strip casting. In such a plate continuous casting method, since the cooling rate is extremely high, a large amount of transition elements such as Cr and Fe can be forcibly solid-dissolved, and a high concentration of Cr is produced without forming a coarse intermetallic compound. Aluminum alloys containing can be cast. In the present invention, by utilizing the solid solution of Cr at such a remarkably high cooling rate and the variation of coarse columnar crystallization and precipitation for each crystal grain due to appropriate selection of the alloy component composition, stable grain-grained grain It was possible to achieve a dark green-gray tone with continuous vertical stripes.

In the method of the present invention, when casting the alloy melt having the above-described composition, the solid solution Cr that contributes to the golden color forming the dark green-gray base is sufficiently secured by anodizing. Therefore, a cooling rate of 5 ° C./sec or more is necessary in order to forcibly dissolve Cr and not form a coarse Cr-based intermetallic compound even if the amount of Cr is 0.3% or more. Cooling rate during such casting,
To obtain a large plate industrially, as mentioned above, a molten metal is supplied between a pair of cooling rolls, a caterpillar, a belt, etc. to directly cast a plate of about 5 to 50 mm. Method) etc.

The cast plate thus obtained by the continuous plate casting method or the like may be subjected to anodizing treatment with the plate thickness as it is, or may be subjected to cold rolling to a required plate thickness and then anodizing treatment. However, as the color tone after the anodizing treatment, the golden color of solid solution Cr is used as a base for Al-
In order to add turbidity due to Fe (-Si-Cr) -based fine precipitates to obtain a deep dark green-gray color tone, and to obtain a discontinuous vertical stripe pattern due to variation of fine precipitates for each crystal grain, casting Immediately after, or in the case of performing cold rolling, it is necessary to perform heat treatment for precipitation at a relatively high temperature during or after cold rolling. If the heating temperature in this case is less than 400 ° C, the precipitation of Al-Fe (-Si-Cr) -based precipitates that contribute to the dark green-gray color development is insufficient, and the golden color is still strong, and the deep dark green-gray color is deep. It can not be said. On the other hand, when the temperature exceeds 630 ° C., the color tone becomes light as a whole, and secondary recrystallization occurs to make it impossible to obtain a wood grain discontinuous vertical stripe pattern. If the heating time is less than 0.5 hours, the precipitation will be insufficient, while if it exceeds 24 hours, the effect will be saturated and the economy will be impaired. Therefore, the heat treatment in this case is performed at a temperature of 400 ° C. or higher and 630 ° C. or lower at 0.5.
Need to heat for ~ 24 hours.

The heat treatment for depositing such fine Al--Fe (--Si--Cr) -based precipitates to obtain a dark green-gray color tone may be carried out after casting when the cast plate is used as it is. When cold rolling is performed, it may be basically before, during, or after cold rolling, but in practice it is desirable to perform heat treatment before cold rolling. That is, when performing cold rolling, the columnar crystals in the cast plate develop a discontinuous vertical stripe pattern due to the difference in precipitation for each crystal grain stretched by rolling, but during the cold rolling Alternatively, when a heat treatment for precipitation is performed after cold rolling, recrystallization occurs prior to precipitation depending on the conditions, and precipitation is performed for a recrystallized structure in which columnar crystals have disappeared. A grain-like discontinuous vertical striped pattern derived from columnar crystals cannot be obtained or is blurred. After casting, recrystallization is less likely to occur in the state before cold rolling, and therefore, in order to achieve a discontinuous vertical stripe pattern in a grain pattern, it is most desirable to perform heat treatment for precipitation before cold rolling. is there. However, in some cases, it may be necessary to perform a heat treatment for precipitation during or after cold rolling.In that case, even if the heat treatment condition range for precipitation as described above is satisfied, precipitation may occur. It is only necessary to select a condition that does not cause recrystallization in advance.

On the other hand, for the purpose of facilitating the cold rolling in the middle of the cold rolling or after the cold rolling after the heat treatment as described above for precipitation or after the cold rolling, or for adjusting the strength. However, it may be necessary to perform annealing. Annealing for such a purpose is generally 300 to 550 ° C. × 0.5 to 24 hours in annealing using a batch furnace in this component system,
Further, in the case of continuous annealing, it is usual to hold at 400 to 650 ° C. or not to hold it for 3 minutes or less. However, in annealing using a batch furnace, recrystallization causes uniform and varied precipitate distribution. The grainy discontinuous vertical stripes may be blurred,
In this case also, it is desirable to select conditions under which recrystallization does not occur, because it may disappear.
The condition for not recrystallizing varies depending on the component composition, the heating condition of the cast plate, the cold working rate, etc., and therefore cannot be uniformly determined, but an appropriate condition may be selected by conducting a test in advance. On the other hand, in continuous annealing, since rapid heating is performed for a short time, even if recrystallization occurs, the distribution of precipitates derived from the original columnar crystals is maintained, and a grain-like discontinuous vertical stripe pattern is also clearly expressed. obtain. Therefore, when it is necessary to perform annealing during or after cold rolling, it is preferable to apply continuous annealing.

Next, the aluminum alloy plate (cast plate or rolled plate) obtained by the above-mentioned method is subjected to anodizing treatment to actually form a discontinuous vertical stripe pattern in a dark green-gray color tone with a wood grain tone. The process for obtaining the plate having is described.

In the anodic oxidation treatment, degreasing and etching are generally performed in order to remove surface stains and surface defects in advance. The etching is usually a caustic soda-based alkali etching. Then, the anodizing treatment itself has a H ₂ SO ₄ concentration of 10
Using a sulfuric acid bath of -25 vol%, the bath temperature is 10 to 30 ° C. and the current density is 1.5 A / dm ² or more and less than 2.5 A / dm ² to form an anodized film having a film thickness of 10 to 30 μm.

Here, the H ₂ SO ₄ concentration of the sulfuric acid bath is 10 v
When it is less than ol%, the porosity of the anodic oxide film formed is decreased and the bath voltage is increased. On the other hand, the H ₂ SO ₄ concentration is 25 vol%
If it exceeds, the surface becomes rough and the anodized film becomes soft. If the bath temperature is lower than 10 ° C, it takes a long time to obtain a required film thickness, which is uneconomical. On the other hand, if the bath temperature exceeds 30 ° C, the corrosion resistance after anodizing is deteriorated. Further, if the current density is 2.5 A / dm ² or more, a large amount of electric power is required for the treatment, which is not practical. On the other hand, if the current density is less than 1.5 A / dm ² , the color tone after anodizing is light and the color is dark green gray. Will not be obtained. Also, the thickness of the anodized film produced is 10
If it is less than μm, sufficient corrosion resistance cannot be obtained, while it is not economical to increase the thickness to more than 30 μm.

A plate having a discontinuous vertical stripe pattern with a dark green-gray color tone can be obtained by the anodizing treatment using the sulfuric acid bath as described above.

The discontinuous vertical striped pattern obtained by the present invention is a striped pattern in a direction substantially parallel to the casting direction and the rolling direction as shown in FIG. Is a striped pattern in which a long striped dark striped portion 1 and a similar striped striped portion 2 are mixed in a state of extending discontinuously in parallel to the casting direction and the rolling direction. However,
Here, the dark-colored striped portion 1 and the light-colored striped portion 2 are uniformly distinguished. However, these dark-colored and light-colored portions are relative ones, and actually, there are various shades of various shades. The parts are mixed. The width of the vertical stripes (distance between the centers of the striped portions 1 and 2) W is about 2 mm or more in the cast plate, like the width of columnar crystals.

[0031]

【Example】

Example 1 Aluminum alloys having compositional compositions shown in alloy numbers 1 to 5 in Table 1 were melted according to a conventional method, and a cast plate having a plate thickness of 7 mm was obtained by a plate continuous casting method in which hot water was supplied between a pair of rolls. . In addition, alloy numbers 1 to 4 do not add Ti and B positively and contain these as impurities,
Alloy No. 5 is a positive addition of Ti and B. Furthermore, the cooling rate during solidification is 200 to 300 ° C /
It was sec. 350 ° C x 1 for each alloy obtained
After heating for 0 hours or 550 ° C. × 10 hours, anodization treatment was performed.

In any of the above cases, the anodic oxidation treatment was performed under the following conditions. That is, first, 10% NaO
After etching with an aqueous solution of H, washing with water, desmutting treatment with nitric acid, and then anodizing treatment using a sulfuric acid bath with a concentration of 15 vol% at a bath temperature of 20 ° C. and a current density of 1.5 A / dm ^2. A 20 μm anodic oxide film was formed.

Table 2 shows the results of visually observing and judging the color tone and the state of discontinuous vertical stripes on the surface of each plate anodized as described above, and the results of examining the surface structure of the cast plate. Are also shown. In Table 2, the circles in the column of discontinuous vertical stripes indicate the case where the wood grain-like discontinuous vertical stripes were clearly developed, the triangle indicates the case where the discontinuous vertical stripes occurred unclearly, and the cross indicates the failure. Represents the case where continuous vertical stripes did not occur.

[0034]

[Table 1]

[0035]

[Table 2]

As is clear from Table 2, in the cast plates (Production Codes A to C) using the alloys (alloy Nos. 1 and 2) having the composition within the range of the present invention, the crystal grains on the surface of the cast plate are all. Columnar crystals with a width of 2 mm or more on average, of which 5
A plate (manufacturing code A, heated at 50 ° C. × 10 hours)
C) was able to develop a dark green gray discontinuous vertical stripe pattern by anodizing treatment, but the plate heated at 350 ° C. (manufacturing code B) had a discontinuous vertical stripe pattern, but had a color tone. Became golden and no dark green gray was obtained. Further, when an alloy (Alloy No. 3) having a small amount of both Cr and Fe (manufacturing code D) was used, columnar crystals were obtained on the cast plate, but discontinuous vertical stripes were observed even after heating at 550 ° C. No pattern was developed and no dark green-gray color tone was obtained. Also, when an alloy having a low Fe content (alloy No. 4) was used (Production Code E), columnar crystals were obtained on the cast plate, but discontinuous vertical stripes were observed even when heated at 550 ° C. Moreover, the color tone was golden. Furthermore, Ti, B
When an alloy (Alloy No. 5) added in an amount exceeding the upper limit specified in the present invention (manufacturing code F) was used, columnar crystals were not obtained on the cast plate and vertical stripes were obtained even if heating was performed at 550 ° C. Not only the pattern did not occur, but a horizontal stripe pattern perpendicular to the casting direction did occur.

FIG. 2 shows a photograph of the surface condition of the plate manufactured by the manufacturing code A using the alloy No. 1 after anodizing. Here, in FIG.
The dimension L _{1 in the} longitudinal direction (casting direction) is 60 mm, and the dimension L ₂ in the lateral direction (direction orthogonal to the casting direction) is 180 mm. From FIG. 2, it can be seen that a dark green gray discontinuous vertical stripe pattern is clearly expressed.

For each of the alloys Nos. 1 and 2 in Table 1, a plate having a thickness of 7 mm was formed by continuous plate casting in the same manner as described above, and each plate was heat-treated at 500 ° C. for 10 hours, and then the plate thickness was 1. Cold rolled to 5 mm. After cold rolling, a part of each plate is anodized as it is, and the others are
Batch furnace 300 ℃ x 5 hours or 500 ℃ x 5
Annealing treatment was performed after annealing for 5 hours at 530 ° C. for 10 seconds using a salt bath assuming continuous annealing. The conditions of the anodizing treatment are the same as those in the first embodiment.

The color tone and discontinuous vertical stripe pattern on the surface after the anodizing treatment were visually observed and judged. The results are shown in Table 3.
Shown in.

[0040]

[Table 3]

As is apparent from Table 3, even when the final annealing is performed after cold rolling and the final annealing in the batch furnace does not cause recrystallization, and when rapid annealing is performed assuming continuous annealing. When annealed by heating for an hour, dark green-gray discontinuous vertical stripe patterns were obtained in all cases. On the other hand, when recrystallization was caused by batch annealing, a discontinuous vertical stripe pattern was not obtained. Therefore, when annealing the cold-rolled sheet, it is understood that it is sufficient not to recrystallize or to apply rapid annealing for heating for a short time.

[0042]

As is apparent from the above-described embodiments, the aluminum alloy sheet of the present invention is dark green gray after anodizing in a sulfuric acid bath by applying the sheet continuous casting method and appropriate heat treatment. It is possible to surely obtain a plate having the above-mentioned color tone and having a stable wood grain (grain) discontinuous vertical stripe pattern.

Further, according to the method for producing an aluminum alloy of the present invention, an aluminum alloy having a dark green-gray color tone and a discontinuous vertical stripe pattern by the anodizing treatment with a sulfuric acid bath as described above is practically mass-produced. It can be obtained reliably and easily on a scale.

Therefore, the present invention is useful when applied to various building material materials, nameplates, various articles, containers, etc., which require diversification of appearance and individuality.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining a horizontal stripe pattern after anodizing treatment of an aluminum alloy plate according to the present invention.

FIG. 2 is a photograph of the metallographic structure of the surface of the aluminum alloy plate of the example after anodizing treatment.

[Explanation of symbols]

 1 Dark stripes 2 Light stripes

[Procedure amendment]

[Submission date] August 11, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

Claims (3)

[Claims] 1. Cr 0.3 to 1.2 wt%, Fe 0.2 wt
%, 1.0 wt% or less, Si 0.5 wt% or less, Ti content is 0.01 wt% or less, B content is 0.002
It is regulated to wt% or less, the balance consists of Al and other unavoidable impurities, and 50% or more of the crystal grains on the surface after casting are columnar crystals with a width of 2 mm or more. An anodizing aluminum alloy plate with a discontinuous vertical stripe pattern in a green-grey color. 2. Cr 0.3-1.2 wt%, Fe 0.2 wt
%, 1.0 wt% or less, Si 0.5 wt% or less, Ti content is 0.01 wt% or less, B content is 0.002
A molten alloy containing Al and other unavoidable impurities, the balance of which is regulated to wt% or less, is cast at a cooling rate of 5 ° C / sec or more, and 50% or more of the crystal grains on the surface are columnar with a width of 2 mm or more. A cast plate made of crystals is obtained, and then the cast plate is
A method for producing an aluminum alloy plate for anodizing treatment, which exhibits a discontinuous vertical stripe pattern of dark green-gray color tone after anodizing treatment, characterized by heating at 400 to 630 ° C for 0.5 to 24 hours. 3. Cr 0.3 to 1.2 wt%, Fe 0.2 wt
%, 1.0 wt% or less, Si 0.5 wt% or less, Ti content is 0.01 wt% or less, B content is 0.002
A molten alloy containing Al and other unavoidable impurities, the balance of which is regulated to wt% or less, is cast at a cooling rate of 5 ° C / sec or more, and 50% or more of the crystal grains on the surface are columnar with a width of 2 mm or more. To obtain a cast plate made of crystals, and then cold rolling to a required plate thickness, and 400 to 400% between the casting and the cold rolling, or during or after the cold rolling.
A method for producing an aluminum alloy plate for anodizing treatment, which exhibits a discontinuous vertical stripe pattern of a dark green-gray color tone after the anodizing treatment, characterized by performing a heat treatment of heating at 630 ° C. for 0.5 to 24 hours.