JPH0512419B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a wrought aluminum alloy that is used for the exterior of buildings and other structures after being anodized, and a method for producing the same. The present invention relates to a wrought aluminum alloy that exhibits a so-called dark gray color tone after oxidation treatment, and a method for producing the same.

Conventional technology Conventionally, aluminum alloys that have been anodized and used for building exteriors are mainly JIS1100 alloy, JIS1050 alloy,
There are JIS5005 alloys, etc., and the typical color tones of these are pale gray due to sulfuric acid bath anodizing treatment, or brownish due to natural coloring anodization treatment or the so-called Asada method coloring. However, recently, from the viewpoint of increasing the appearance of buildings, there has been a strong demand for aluminum alloys that exhibit a dark gray color, that is, a gray to dark gray color tone after being anodized.

As mentioned above, as aluminum alloys for building materials that exhibit a gray or dark gray color tone after anodizing treatment, A-Si based JIS 4343 alloys and alloys improved therefrom are used in some cases.

However, although it is possible to obtain a dark gray tone after anodizing with A-Si based JIS 4343 alloys and alloys improved from it, the gray tone is easily affected by heat, and as a result, the color tone varies between manufacturing lots. It is extremely difficult to produce an alloy plate that stably exhibits the same dark gray color tone, as the color tone may vary even within the same lot. In addition, this type of A-Si alloy is
Compared to JIS 1100 alloy and JIS 5005 alloy, it also has the disadvantage of lower corrosion resistance after anodizing treatment, which also poses a problem for aluminum alloy sheets used for building exteriors.

By the way, JIS1100 alloy, JIS1050 alloy, or
It is known that a pattern called a fir tree structure often occurs in an alloy ingot of a system in which A-Fe intermetallic compounds are crystallized, such as JIS5005 alloy. After anodizing, this fir wood structure exhibits a relatively dark gray color in the inner region and a pale gray color in the outer region, which is due to the presence of A-Fe compounds that crystallize depending on the location of the ingot. It is known that this is due to different types. In other words, the ingot contains AmFe, _A3
Intermetallic compounds of Fe and A ₆ Fe crystallize, but these have different electrochemical properties and
The mFe phase and the A ₃ Fe phase are oxidized during the anodizing treatment and exist as oxides in the oxide film, whereas the A ₆ Fe phase is not oxidized and exists in the film as a metal phase. If this unoxidized A ₆ Fe phase exists in the film, it will absorb the incident light and produce A ₃ Fe,
It exhibits a darker tone of gray than the AmFe phase. Generally, the AmFe phase mainly exists in the outer region of the fir tree structure, and the A ₆ Fe phase and A ₃ Fe phase exist in the inner region.
It is known that the inner region, including the A ₆ Fe phase, exhibits a darker tone of gray than the outer region, which is mainly composed of the AmFe phase.

Therefore, if the internal area of the fir wood structure is expanded so that the entire ingot consists of the structure of the internal area of the fir wood structure, and the ingot is substantially free of the fir wood structure, then
It is believed that it is possible to obtain an aluminum alloy plate that exhibits a gray-dark gray tone after anodizing treatment even if it is not an A-Si alloy as described above.

On the other hand, the present inventors have already proposed in Japanese Patent Publication No. 58-26431 a composition for expanding the internal region of the fir tree structure and making the entire structure into an internal region structure for an A-Fe-Si-Mg-based aluminum alloy. According to this invention, it is certainly possible to obtain an alloy plate having a gray to dark gray color tone after anodizing treatment, and in this type of alloy, the above-mentioned A
-It is possible to obtain better corrosion resistance than Si alloy. However, in accordance with this proposal, it is not always possible to stabilize the gray-dark gray color tone simply by making the entire ingot have a structure in the inner region of the fir wood structure. That is, as mentioned above, not only the dark gray A ₆ Fe phase but also the A ₃ Fe phase crystallizes in the internal region of the fir wood structure, so the ratio of the A ₆ Fe phase to the A ₃ Fe phase changes. For example, even in the structure of the internal region, the gray color tone may change, and the color tone may vary depending on casting conditions and hot working conditions.

Therefore, the inventors of the present application have developed an aluminum alloy that exhibits a stable gray to dark gray color tone after anodizing treatment in an A-Fe-Si-Mg based alloy.
As a result of repeated experiments and studies to develop the ingot and its manufacturing method, we determined that the ratio of Fe and Si was strictly defined in relation to Mg, and at the same time, the casting conditions for the ingot were appropriately set, and the as-cast casting was made. Total A in the part of the ingot that will eventually become the surface of the rolled plate, that is, the part at a depth of 50 mm from the surface of the ingot (skin part)
-At least 70% of the Fe-based intermetallic compounds are A ₆ Fe
It has been found that it is necessary to stably obtain a constant gray to dark gray color tone by occupying a certain phase.
231849).

Problems to be Solved by the Invention According to the proposal of JP-A-61-110741 mentioned above, it is possible to relatively stably crystallize the A ₆ Fe phase and to significantly stabilize the gray to dark gray color tone. is possible. However, the proposed A-Fe-Si-
In the case of Mg-based composition, the mixing ratio of A ₆ Fe phase and A ₃ Fe phase varies depending on the casting conditions.
It has been found that the color tone of the final rolled sheet after anodizing treatment may vary within and between lots.

The present invention was made against the background of the above-mentioned circumstances, and includes an aluminum alloy for wrought use that can exhibit an extremely stable gray to dark gray color tone after anodizing treatment even when manufactured on an industrial scale. The purpose is to provide a manufacturing method.

Means for Solving the Problems The inventors of the present invention have conducted extensive experiments and studies to achieve the above-mentioned objectives. The A ₆ Fe phase is a metastable phase and is relatively easily transformed into the A ₃ Fe phase by heating, but when Mn is added, the metastable A ₆
The Fe phase can be stabilized as the A ₆ Fe (Mn) phase, and by adding a certain amount of Mn, the stable A ₆ Fe (Mn) phase can be uniformly crystallized throughout the ingot. I discovered that. Like this A
₆ If the Fe phase is uniformly crystallized throughout the ingot as a stable A ₆ Fe (Mn) phase, no fir wood structure will occur, so the relationship between the ratio of Fe and Si and the amount of Mg must be strictly controlled. We believe that it is possible to stably make the A ₆ Fe (Mn) phase exist on the surface of the rolled sheet without imposing any restrictions, thereby stably achieving a gray to dark gray color tone after anodizing treatment. It will be done. However, if more than a certain amount of Mn is added, the color tone after anodizing treatment may become reddish. However, as a result of further research by the present inventors, it was found that by adding an appropriate amount of Cu and setting the ingot soaking condition to high temperature heating, the color tone after anodizing treatment becomes reddish. They discovered that it is possible to effectively prevent this and reliably obtain an achromatic color tone ranging from gray to dark gray, leading to the creation of this invention.

Specifically, the aluminum alloy of the first invention is
Weight ratio: Fe0.4~1.5%, Mn0.7~1.5%, Cu0.05~
It is characterized by containing 0.40%, with the remainder consisting of A and inevitable impurities.

Moreover, the aluminum alloy manufacturing method of the second invention includes:
Weight ratio: Fe0.4~1.5%, Mn0.7~1.5%, Cu0.05~
An aluminum alloy containing 0.40% and the balance consisting of A and unavoidable impurities is cast by a semi-continuous casting method, and then the ingot is heated within a temperature range of 550 to 650°C for 0.5 to 12 hours, and then the temperature It is characterized by hot working at a temperature within or below the range.

Function First, the reason for limiting the alloy composition in this invention will be explained.

Fe: If the Fe content is less than 0.4%, the amount of A ₆ Fe (Mn) phase that contributes to the dark gray color after anodizing treatment will decrease and the gray color will become dark;
If it exceeds 0.4~1.5%, the corrosion resistance will decrease.
The range of

Mn: As mentioned above, Mn is an element necessary to stabilize the metastable A ₆ Fe phase as the A ₆ Fe (Mn) phase. A ₆ Fe (Mn) by Mn addition
_{The phase} stabilized as
It has the characteristic that it is less likely to undergo transformation, and therefore less likely to change color tone due to changes in heating conditions.
If 0.7% or more of Mn is added, the color tone after anodizing treatment tends to become reddish, but in this invention, as described later, Cu is added and the ingot soaking temperature is set to 550.
Because the temperature is relatively high at ~650°C, the red color disappears and the desired achromatic gray to dark gray tone is obtained. If the Mn content is less than 0.7%, a fir tree structure may occur during semi-continuous casting, and the color tone tends to fluctuate, resulting in a lack of stability. On the other hand, if Mn exceeds 1.5%, primary crystals of A ₆ Mn may occur.
Therefore, Mn was set within the range of 0.7 to 1.5%.

Cu: Cu is an element necessary to adjust the color tone after anodizing treatment. _A6 if Mn is 0.7% or more
The Fe (Mn) phase is the main component, resulting in a reddish color tone as mentioned above, but if Cu is added and the ingot is soaked at a high temperature, this phenomenon can be suppressed and the color becomes achromatic. A system of gray to dark gray tones is achieved. Here, if Cu is less than 0.05%, the above-mentioned effect cannot be obtained, while if it exceeds 0.40%, corrosion resistance will decrease,
The color becomes yellowish. Therefore
Cu was within the range of 0.05 to 0.40%.

Note that the balance of Fe, Mn, and Cu mentioned above may be substantially A, but in normal A alloys, a small amount of Ti or Ti and B may be added to refine the crystal grains of the ingot. However, the alloy of the present invention includes cases where these are added in small amounts. However, if Ti exceeds 0.10%, primary crystals of TiA ₃ will be generated and cause linear defects called stringers, so Ti should preferably be kept at 0.10% or less, and B should not exceed 0.03%. If B is added, linear defects called stringers are likely to be generated, resulting in poor appearance.
The content is preferably 0.03% or less.

Next, the method for manufacturing the alloy of this invention, that is, the second method.
The conditions of each step in the method of the invention will be explained.

First, an alloy having the above-mentioned composition is cast by semi-continuous casting (DC casting) according to a conventional method. The obtained ingot is heated prior to hot rolling,
This heating temperature must be within the temperature range of 550 to 650°C, and the heating holding time must be 0.5 to 12 hours. The reason why the heating conditions were determined in this manner is as follows. In other words, as mentioned above, at the ingot stage
The addition of Mn thermally stabilizes the A ₆ Fe (Mn) phase, but among the L value, a value, and b value that represent the color tone according to the Hunter color system, the a value that represents reddish saturation is As shown in FIG. 1, the value increases as the Mn content increases in the case without soaking treatment. On the other hand, when the alloy of the present invention to which Cu is added is soaked at a temperature within the range of 550 to 650°C, it has been found that an achromatic color tone occurs when Mn is 0.7% or more. However, if the holding time is less than 0.5 hours, it is difficult to achieve a uniform temperature throughout the ingot, and therefore the above-mentioned effects cannot be obtained sufficiently.
Heating for more than 12 hours is only economically disadvantageous. Therefore, the temperature and time for heating the ingot were specified as described above.

Hot rolling may be carried out according to a conventional method at a temperature at or below the ingot heating temperature, and subsequent cold rolling may be carried out according to a conventional method, and these conditions are the same as those after anodizing treatment. Does not essentially affect surface color tone.

It goes without saying that the method of the present invention can be applied not only to the production of rolled plates but also to the production of extruded materials. That is, when producing an extruded material, the heating temperature and time before hot rolling described above may be applied to the heating temperature and time before hot extrusion.

Example Alloys Nos. 1 to 5 having the chemical composition shown in Table 1 were melted according to a conventional method, and were semi-continuously cast at a casting temperature of 700°C and a casting speed of 65 mm/m.

Claims (1)

[Claims] 1. Fe0.4 to 1.5%, Mn 0.7 to 1.5% by weight,
An aluminum alloy for wrought, which has a gray to dark gray color after anodizing treatment, and is characterized by containing 0.05 to 0.40% of Cu, with the remainder consisting of A and unavoidable impurities. 2 Fe0.4-1.5%, Mn0.7-1.5% by weight,
An aluminum alloy containing 0.05 to 0.40% Cu with the balance consisting of A and unavoidable impurities is cast by a semi-continuous casting method, and then the ingot is heated to 550 to 650°C.
An aluminum alloy for wrought use that has a gray to dark gray color after anodizing treatment, and is characterized by being heated within a temperature range of 0.5 to 12 hours and then hot worked at a temperature within that temperature range or lower. manufacturing method.