JPH09143602A - Aluminum alloy sheet in which anodically oxidized film develops into achromatic light gray - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a balanced, bright and achromatic light gray-colored product excellent in strength and formability with good reproducibility and to produce a sheet product requiring decorativeness such as implements, building materials or the like. SOLUTION: This aluminum alloy sheet has a compsn. contg., by weight, 1.5 to 3.0% Mg, 0.10 to 0.30% Mn, 0.15 to 0.40% Fe and 0.06 to 0.15% Si and furthermore contg. 0.01 to 0.10% Ti or both of 0.01 to 0.10% Ti and 0.0001 to 0.01% B selectively, and the balance Al with inevitable impurities, and in which an anodically oxidized film develops into an achromatic light gray. In this Al base alloy sheet, the content of Cr remaining as the impurity is regulated to <=0.02%.

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 in which an anodic oxide film develops an achromatic light gray color, which is anodized by a sulfuric acid bath to give an achromatic bright film in a light gray color evenly. The present invention relates to an aluminum alloy sheet which is formed with good reproducibility and has excellent strength and formability.

Aluminum alloys, which are often subjected to anodizing treatment for the purpose of imparting decorative properties and improving corrosion resistance and weather resistance, produce a colored film with various color tones on the surface of products such as vessels and building materials. Plates such as pure Al-based 1000 series alloy plates and Al-Si-based 4000 series alloy plates are used. Further, as an aluminum alloy excellent in strength and formability, aluminum alloys such as AA standards 5052, 5083, 5182 can be used as daily necessities, electric parts or door materials.
-Mg-based 5000 series alloy, such as 6061, 6111
Al-Mg-Si 6000 series alloys are used as practical alloys. However, these 5000 series alloys and 600
It is known that the 0 series alloy plate develops a yellowish light gray color by anodizing it with a sulfuric acid bath, but since a uniform color tone cannot be obtained stably, It is rarely used for interior and exterior panels of building materials.

[0003]

However, the diversification of lifestyles in recent years has diversified the demands of users,
A bright light gray color which is a material having corrosion resistance and strength and which is achromatic in color is often preferred because it gives a desirable stability or calmness. Such requirements cannot be properly satisfied because the anodized film of the above-described 5000-series alloy and 6000-series alloy plates, which has been conventionally used, has a yellowish color in the color tone of the anodized film. In other words, there is a great demand for an aluminum alloy plate which is excellent in strength and formability and has an achromatic and bright sensation on its surface even when subjected to anodizing treatment with a sulfuric acid bath, which satisfies this. Such products have not been obtained.

[0004]

Means for Solving the Problems As a result of intensive research on solving the problems in the prior art as described above, the present invention contains Al-Mg containing Fe and Si in specific amounts and Cr in a specific value or less. The present invention has completed the present invention, finding that the color tone of the anodic oxide film formed by the sulfuric acid bath is achromatic and exhibits the original light gray color as it is, and the present invention is completed as follows.

(1) wt%, Mg: 1.5 to 3.0%, Mn:
0.10 to 0.30%, Fe: 0.15 to 0.40%, Si: 0.06
0.1 to 0.15% and Ti: 0.01 to 0.10% or Ti: 0.01 to 0.10% and B: 0.0001 to 0.01%
An aluminum alloy plate containing the above, the balance consisting of Al and unavoidable impurities, and having Cr as an impurity of 0.02% or less, in which an anodized film develops an achromatic light gray color.

(2) wt%, Mg: 1.5 to 3.0%, Mn:
0.10 to 0.30%, Fe: 0.15 to 0.40%, Si: 0.06
.About.0.15%, Cu: 0.01 to 0.15%, and
Ti: 0.01 to 0.10% or Ti: 0.01 to 0.10% and B: 0.0001 to 0.01%, with the balance being Al and inevitable impurities, and Cr as an impurity. Is 0.02% or less, and the aluminum alloy plate whose anodized film develops an achromatic light gray color.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION
More specifically, the present invention, in the impurity element contained in the Al-Mg alloy, suppresses the content of Cr, which adversely affects the hue during anodizing treatment, to below a certain limit, and Fe, Si Is contained in the alloy as a whole so that the anodic oxide film as an entire alloy develops into an achromatic light light gray color. That is, the above-mentioned color tone after the anodizing treatment is based on the color difference formula based on the Lab system shown in JISZ8730, and the color development of the anodized film of the present invention has an L value of 65 to 75 and an a value of -1 to +1. , B values are represented by −1 to +1. Here, the L value indicates lightness, and the higher the value, the brighter the color tone. Further, the a value and the b value show the hue, and when the color is reddish, the value a becomes high, and when the value is smaller than 0, the color is greenish. On the other hand, if it is yellowish, b
The higher the value is and the smaller the value is, the more bluish the color is.
It is -1 to +1 for both a value and b value that it feels achromatic.

Next, the alloy composition according to the present invention will be described in detail. The percentage of the contained element in the present invention is expressed in terms of weight and is as follows. Mg: 1.5 to 3.0% Mg is for imparting strength and formability to the alloy, and if the amount is less than the above lower limit, this action is insufficient, while if it exceeds the upper limit, forming becomes difficult. At the same time, stress corrosion cracking easily occurs, which is not preferable.

Mn: 0.10 to 0.30% Mn is used for making the recrystallized grains fine during the annealing treatment performed during plate making, and imparting strength and formability to the alloy. If it is less than the above range, the effect is insufficient, and if it exceeds the upper limit, the moldability is deteriorated and the hue is slightly reddish, so that the achromatic color as described above cannot be obtained.

Fe: 0.15 to 0.40% Si: 0.06 to 0.15% Fe and Si impart brightness with favorable alkali etching properties when anodizing the alloy and have a color tone. When the amount is less than the lower limit, the effects thereof are insufficient. On the other hand, when the amount exceeds the upper limit, the color tone becomes gray and the molding becomes difficult, which is not preferable.
In addition to the above-mentioned drawbacks, Si exceeds the upper limit, and not only the color tone becomes gray but also yellowish, which is not preferable.

Ti: 0.01 to 0.10%, or Ti: 0.
01 to 0.10% and B: 0.0001 to 0.01% Ti or Ti and B are necessary for refining the cast structure during casting of the molten alloy to prevent casting cracks, and the lower limit If it is less than the value, their actions are insufficient, while if it exceeds the upper limit, coarse intermetallic compound particles are generated and the formability of the plate is impaired.

Cr: 0.02% or less Cr is contained as an impurity from the raw material when the alloy is melted, but since Cr exhibits a yellowish color tone during the anodizing treatment of the alloy, it is below the specified value. . Preferably
It is desired to be 0.01% or less, and more preferably 0.005% or less.

Cu: 0.02 to 0.15% Cu makes the alkali etching property, which is applied as a pretreatment during the anodizing treatment, more uniform, and makes the hue of the film more uniform by the subsequent anodizing treatment using a sulfuric acid bath. To Elements other than the above-mentioned elements contained as unavoidable impurities from the raw materials may cause turbidity in the hue of the anodized film due to the sulfuric acid bath, so Zn is 0.25% or less, and other elements are 0% or less. It is preferable to regulate it to 0.05% or less.

The alloy sheet of the present invention can achieve its technical purpose by satisfying the above-mentioned conditions, and its manufacturing method is not particularly limited, but it facilitates understanding of the technical relationship. An example of the most preferable manufacturing method is as follows.

A molten alloy having the composition of the present invention is cast through a filter by the latter half continuous casting method (DC casting) or the like,
Obtain an ingot for rolling. The ingot thus obtained is chamfered by 5 to 20 mm in order to remove the surface non-uniformity,
Next, in order to reduce or eliminate segregation of alloy elements generated in the ingot during casting, for example, β phase (Mg ₂ Al ₃ ) segregation and local microsegregation, the ingot is heated to 430 to 560 ° C. for about 1 to 20 hours. A multi-stage homogenization treatment is performed by changing the temperature in one step or by changing the temperature. Note that Mn is sufficiently precipitated by heating under this temperature condition, and the recrystallized grains are refined by the subsequent intermediate annealing or final annealing treatment.

After the homogenizing treatment as described above, the ingot is hot-rolled to a thickness of about 2 to 10 mm. In this case, alloy elements are precipitated as fine second-phase particles,
In order to make the hue of the anodic oxide film in the sulfuric acid bath after that uniform, the rolling end temperature is set to 280 ° C. or higher.

After the hot rolling, the rolled plate is cold-rolled to a required plate thickness by a conventional method, and then alloy elements are further precipitated to make the anodized film in the sulfuric acid bath have a uniform hue. In order to do so, the final annealing is performed by heating at 280 to 340 ° C. for about 1 to 5 hours. When a plate with higher strength is required, it is annealed in the middle of cold rolling. In this case, the β phase (Mg ₂ Al ₃ ) gradually precipitates at the grain boundaries with the lapse of time after cold rolling, so as to prevent a so-called softening phenomenon with time that decreases the 0.2% proof stress. It is preferable to heat at a temperature of 180 ° C. for about 1 to 5 hours for stabilization treatment. The cooling rate after the final annealing is up to about 200 ° C., for example, 8
By gradually cooling at a cooling rate of 0 ° C./hour or less, elements such as Cr and Mn can be further precipitated, and the hue of the anodic oxide film formed by the sulfuric acid bath after that can be made achromatic and uniform.

The rolled plate thus obtained is subjected to anodizing treatment in a sulfuric acid bath. The conditions of this anodizing treatment are not particularly limited, but the most preferable examples are as follows. That is, the rolled plate is immersed in an acidic aqueous solution containing about 3 to 20% sulfuric acid in order to remove oil adhering to the surface. The rolled plate from which oil has been removed is washed with water in order to remove oxides on the surface and form an anodized film uniformly by subsequent anodizing treatment with a sulfuric acid bath, and then an alkaline aqueous solution containing ca. 5-30% caustic soda. It is dipped in and etched. The rolled plate etched by this alkali treatment is washed with water and contains 10 to 30% sulfuric acid.
In the contained sulfuric acid bath, the rolled plate was used as an anode, the anode current density was 0.5 to 5 A / dm ² , the bath temperature was 5 to 30 ° C., and the electrolysis time was 1
Electrolyzed in 0 to 120 minutes and the film thickness is 5 to 3
When it is formed to a thickness of 0 μm, an electrolytic color-forming film that is colored in an achromatic, light pale gray color is obtained.

[0019]

EXAMPLE A molten alloy was melted by an ordinary method, and then a semi-continuous casting method was used to obtain ingots for rolling each having a cross section of 560 mm in thickness and 1100 mm in width. The compositions of these ingots are shown as A to F in the following Table 1, and the analysis values of the main elements among the impurity elements other than the indicated elements are Zn 0.015%, Zr
Is 0.001%, V is 0.01%, Ga is 0.005%, and Ni is 0.00%.
005% and Be were 0.008%.

[0020]

[Table 1]

Next, the surface of each of these ingots was chamfered by 10 mm, and then kept at a temperature of 440 ° C. for 2 hours and further heated to 5
The temperature of 30 ° C was maintained for 4 hours. Further, hot rolling of each ingot was started at a temperature of 510 ° C. and rolled to a thickness of 6 mm, but the end temperature of the hot rolling was 300 ° C. The hot-rolled sheet is then cold-rolled to a thickness of 1.5 mm, and after this cold-rolling, it is heated and held at a temperature of 330 ° C. for 3 hours and cooled at a cooling rate of 50 ° C./hour for final annealing. gave. The temper of the material thus produced is called "O material".

The rolled plate subjected to the final annealing as described above was immersed in a 10% sulfuric acid aqueous solution for 10 minutes. After the immersion, it was thoroughly washed with water, immersed in an 8% caustic soda aqueous solution and etched. The rolled plate thus etched was subjected to anodizing treatment under the following conditions to form a colored anodized film on the surface. The results are shown as Test Nos. 1 to 7 in Table 2 below. The mechanical properties and formability were determined using the rolled sheet that was annealed before the anodizing treatment. Electrolyte bath composition Sulfuric acid bath with concentration of 15% Bath temperature 21 ℃ Anode current density 1A / dm ² Counter electrode Cathode Carbon electrode

[0023]

[Table 2]

The moldability shown in Table 2 is as follows.
It was evaluated by R, Er, 180 ° bending test. LDR: Limiting draw ratio This LDR is an index for judging the deep drawability, with the punch diameter kept constant, the blank diameter increased, and the value obtained by dividing the maximum blank diameter that can be squeezed without cracking or tearing by the punch diameter,
It means that the larger the value, the deeper the drawing can be made, and it can be judged that a container deeper than the opening can be manufactured. Testing machine Erichsen deep drawing testing machine Shik pressing pressure 500kg Constant die shoulder curvature 3mm Lubricant One side coating Punch diameter 33mm Er: Erichsen value This is an index to judge the overhang formability, and in this embodiment JIS-A.
According to the law. That is, the ball head punch is pressed against the plate to be measured, and the overhang height (m
m). The larger this value is, the better the stretchability is. However, in this example, the test was conducted under the following conditions. Testing machine Erichsen testing machine made by Nippon Testing Machine Punch diameter 20φ 180 ° Bending: Using a punch with a U-shaped cross section perpendicular to the longitudinal direction and a concave die into which the punch is inserted, press the plate to be measured into the concave die with the above punch. , The minimum inner bending radius that does not cause cracks on the bending surface is shown by the value divided by the plate thickness (mm). The smaller the value, the better the bendability, and it can be determined that a sharp shape can be processed. In this example, the test was conducted under the following conditions. Punch R 0.75-1.5 mm Pressing speed 30-50 mm / min

[0025]

COMPARATIVE EXAMPLE The ingots for rolling shown as G to K in Table 1 were subjected to hot rolling in the same manner as in Example 1, and a cold rolled plate having a thickness of 2 mm was heated to 330 ° C. for 3 days. It was heated and held for a time, cooled at a cooling rate of 50 ° C./hour, subjected to intermediate annealing, and further cold-rolled to obtain a plate having a thickness of 1.5 mm. Next, this plate was subjected to a stabilizing treatment of holding it at a temperature of 150 ° C. for 1 hour, and the tempering of the material thus produced was adjusted to “H34”.
The obtained plate was anodized under the same conditions as in Example 1, and the mechanical properties and formability were measured. The results are shown in Table 2 as test number 8 and below. is there.

According to the results shown in Table 2 as described above,
In each of the aluminum alloy plates (A to F) according to the present invention, the anodized film by the sulfuric acid bath is even and brighter than the comparative alloy plates (G to K), and an achromatic light gray color is obtained. In addition, it was confirmed that it has excellent properties in strength and moldability.

[0027]

As described above, the anodized film of the aluminum alloy sheet according to the present invention is excellent in strength and formability, and is a uniform, bright and achromatic light gray preferable product with good reproducibility and accuracy. Because you can get the equipment,
It is an industrially excellent invention because it has a feature that it can be sufficiently applied to the use of plate products such as building materials that require decorative properties.

Claims (2)

[Claims] 1. Wt%, Mg: 1.5-3.0%, Mn: 0.10
Up to 0.30%, Fe: 0.15 to 0.40%, Si: 0.06 to 0.1
5% and Ti: 0.01 to 0.10% or T
i: 0.01 to 0.10% and B: 0.0001 to 0.01%, the balance consisting of Al and inevitable impurities, and Cr as an impurity was set to 0.02% or less An aluminum alloy plate with an anodized film that develops an achromatic light gray color. 2. In wt%, Mg: 1.5-3.0%, Mn: 0.10
Up to 0.30%, Fe: 0.15 to 0.40%, Si: 0.06 to 0.1
5%, Cu: 0.01 to 0.15%, and Ti: 0.1.
01 to 0.10% or Ti: 0.01 to 0.10% and B: 0.0
001-0.01%, the balance consisting of Al and unavoidable impurities, and the content of Cr as impurities is 0.02% or less, the anodic oxide film is an achromatic light gray colored aluminum. Alloy plate.