JPH11229102A - Production of aluminum alloy rolled sheet showing gray color tone after anodic oxidation treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy rolled sheet for anodic oxidation treatment stably showing gray even in the case of a thin anodically oxidized film of about 10 μm, further excellent in bending workability and moreover having strength equal to that of the conventional material. SOLUTION: An Al alloy ingot contg., by weight, 1.3 to 1.5% Mn, 0.4 to 1.2% Mg, 0.1 to 0.2% Fe and 0.05 to 0.15% Si is subjected to heating treatment at 580 to 630 deg.C, then, hot rolling is started at the ingot heating temp. or below and is finished at <=300 deg.C, if required, cold rolling is executed, and thereafter, it is subjected to process annealing of 400 to 600 deg.C×<=10 min under the conditions of rapid temp. raising and rapid cooling and is moreover subjected to cold rolling. In this way, a rolled sheet in which Al-Mn series acicular precipitates of 2 to 8 μm are precipitated at a density of 2000 to 8000 pieces/mm<2> , further having <=80 μm average grain size and >=95 N/mm<2> proof stress is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolled aluminum alloy plate to be used after being subjected to an anodic oxidation treatment, in particular, a building material such as a building interior material, a container, a housing of various electric devices and measuring instruments, The present invention relates to a method for producing a rolled aluminum alloy plate used for a panel of a mechanical device, a decorative article, and the like.

[0002]

2. Description of the Related Art Generally, a rolled aluminum alloy plate used for building materials is usually subjected to an anodic oxidation treatment from the viewpoint of corrosion resistance. In such applications, a gray color tone is often required as a color tone after anodizing for aesthetics. In order to satisfy such a demand, a method for manufacturing an aluminum alloy rolled plate capable of obtaining a grayish color tone with ordinary anodic oxidation treatment has already been disclosed in Japanese Patent No.
The invention of "Aluminum alloy having a bluish gray color after anodizing treatment and a method for producing the same" disclosed in JP-A-44233 has been proposed, and "The color tone after anodizing treatment is yellowish" described in JP-A-9-71831. And a method of manufacturing the same with a reddish gray aluminum alloy plate.

[0003]

Among construction materials, curtain walls and other exterior materials are required to have high corrosion resistance.
The anodic oxide film is formed to be relatively thick as about m, but when used for interior materials, etc., it is not required to be as corrosion-resistant as exterior materials.
An anodic oxide film thickness of about 10 μm is sufficient. However, when a relatively thick anodic oxide film having a thickness of about 20 μm is formed, even a rolled aluminum alloy plate obtained by each of the above-mentioned proposed methods can stably obtain a gray color by applying a normal anodic oxidation treatment. Although it is possible to obtain an anodic oxide film, when a thin anodic oxide film having a thickness of about 10 μm is formed on a rolled aluminum alloy sheet obtained by each of the above-mentioned proposed methods by ordinary anodic oxidation treatment, It is difficult to obtain a stable gray color tone as the color tone after the oxidation treatment, and at most it exhibits only a light gray (light gray) color. Therefore, in order to obtain a stable gray color tone, the thickness of the anodic oxide film should be originally 1
In the case of interior materials that are sufficient at about 0 μm,
Actually, a thick anodic oxide film of about m was formed.

[0004] In addition, in the use of interior materials, a finer and more three-dimensional design is often required as compared with exterior materials and the like. Severe bending is often required. When the rolled aluminum alloy sheet obtained by each of the above-mentioned proposed methods is applied to applications requiring such severe bending, the strength may be insufficient or cracking or rough surface may occur during bending. is there. In addition, in the use of interior materials, it is often required that the appearance quality be higher than that of exterior materials, but in the rolled aluminum alloy plate obtained by the above-mentioned proposed methods, The point was also insufficient.

That is, in the case of the rolled aluminum alloy sheet obtained by each of the above-mentioned proposed methods, relatively large Al-Mn needle-like precipitates are non-uniformly deposited in a region where the ingot heat treatment temperature is low, and Due to this, a streak-like pattern, that is, a poor appearance called so-called “streak defect” occurs on the surface after the anodizing treatment, and in a region where the amount of Mg is small, crystal grains become large and rough surface failure occurs during bending. Depending on the magnitude of the cold rolling reduction after the intermediate annealing, the balance between strength and elongation may be lost, resulting in insufficient strength or, conversely, cracking during bending under severe bending conditions.

The present invention has been made in view of the above circumstances. Even when a thin anodic oxide film having a thickness of less than 20 μm, for example, about 10 μm, is formed, the color tone of the anodic oxide film is stably gray and the streaks are poor. Less likely to occur,
It is still another object of the present invention to provide a method of manufacturing a rolled aluminum alloy plate having a bending workability substantially equal to or higher than that of a conventional material and having significantly improved bending workability.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive experiments and researches. As a result, the present inventors have determined that the composition of the alloy is appropriately set, and at the same time, the manufacturing process conditions, especially the ingot By appropriately selecting heating conditions, hot rolling conditions, intermediate annealing conditions, and final cold rolling conditions, and by making the metal structure state in the final sheet appropriate, it has been found that the above-described problems can be solved. The present invention has been accomplished.

More specifically, the method for producing an aluminum alloy rolled sheet having a gray color after anodizing according to the first aspect of the present invention comprises: Mn 1.3 to 1.5%; Mg 0.4 to 1.2%; F
e into an ingot of Al alloy containing 0.1-0.2%, Si 0.05-0.15%, the balance being Al and unavoidable impurities, at a temperature in the range of 580-630 ° C, 1-24
A heat treatment for holding for a time is performed, then hot rolling is started at a processing temperature or lower in the heat processing, and the hot rolling is completed at 300 ° C. or lower, and thereafter, at a heating rate of 1 to 50 ° C./sec. Heated to a temperature in the range of
After holding for 10 minutes, intermediate annealing for cooling at a cooling rate of 1 to 50 ° C./sec is performed, and further cold rolling is performed at a rolling rate of 2 to 30%, whereby an Al—Mn based material having a size of 2 to 8 μm is obtained. It is characterized in that a rolled aluminum alloy plate is obtained in which needle-like precipitates are precipitated at a density in the range of 2,000 to 8,000 / mm ² and the average crystal grain size is 80 μm or less and the yield strength is 95 N / mm ² or more. Things.

According to a second aspect of the present invention, there is provided the method for manufacturing a rolled aluminum alloy plate according to the first aspect, wherein the ingot of the aluminum alloy further comprises 0.1% in addition to the above components.
003 to 0.15% Ti alone or 0.000%
It is characterized by using what is contained in combination with 1 to 0.01% of B.

According to a third aspect of the present invention, there is provided the method for producing a rolled aluminum alloy plate according to the first aspect, wherein the ingot of the aluminum alloy further contains 0.0001 to 0.05% of each of the above-mentioned components. It is characterized by using a material containing Be.

The invention of claim 4 is characterized in that, in the method for producing a rolled aluminum alloy plate according to claim 1, primary cold rolling is performed after hot rolling and before intermediate annealing. .

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the reasons for limiting the composition of the aluminum alloy used in the production method of the present invention will be described.

Mn: Mn is an important element for forming an Al-Mn intermetallic compound precipitate to determine the color tone after anodizing. That is, Mn dissolves in the matrix of the ingot during casting, and Al
-Precipitates as a Mn-based intermetallic compound, and the precipitate remains up to the final plate, remains in the film even after the anodizing treatment, and contributes to exhibiting a gray color tone. Here, in an anodic oxide film having a thickness of about 10 μm, A having a size of 2 to 8 μm is used.
If the density of the l-Mn needle-like precipitates is less than 2000 particles / mm ² , the grayish color will not be sufficient gray and will be light gray.
When the number of pieces / mm ² is exceeded, the gray becomes too dark and becomes dark gray to black.
The density of Al-Mn based needle-like precipitates having a size of
It is necessary to be within the range of 000 to 8000 pieces / mm ² . The density of the Al-Mn-based acicular precipitates having a size of ^{2 to 8} µm is less than 2000 / mm ² when the Mn content in the alloy is less than 1.3%. Exceeds 8000 / mm ^{2 because} Mn in the alloy
When the amount exceeds 1.5%, the density of the Al-Mn-based needle-like precipitate having a size of 2 to 8 µm is set to 2000 to 800 in order to make the color tone after the anodizing treatment stable gray.
In order to obtain 0 / mm ² , the amount of Mn is set to 1.3 to 1.5.
%.

Mg: Mg is an element that contributes to improving strength. If the Mg content is less than 0.4%, the bending workability is good, but sufficient strength cannot be obtained, while if it exceeds 1.2%, the strength is too high and the bending workability becomes insufficient. Therefore M
The g amount was in the range of 0.4 to 1.2%.

Fe: Fe has a beneficial effect of refining the recrystallized grains during the intermediate annealing. On the other hand, Fe forms an Al—Mn—Fe intermetallic compound during casting to form the alloy in the ingot matrix. It also has a detrimental effect of reducing the amount of Mn solid solution, thereby preventing the precipitation of Al-Mn-based precipitates during heating of the ingot. In particular, if the Fe content exceeds 0.2%, the precipitation of Al-Mn-based precipitates during the heating of the ingot is significantly reduced, and the anodic oxide film having a thickness of about 10 µm hardly becomes gray. On the other hand, if the Fe content is less than 0.1%, the color tone after the anodic oxidation treatment is not essentially affected, but the cost of Al metal is increased, which is not economically preferable. Therefore, the amount of Fe was set in the range of 0.1 to 0.2%.

Si: Si is also an element that affects the color tone after anodizing, and if the Si content exceeds 0.15%, S
It is not preferable because a large amount of the i-type intermetallic compound is generated and the color tone after the anodizing treatment becomes yellowish-red and deviates from the target gray. On the other hand, when the Si content is less than 0.05%, the color tone after the anodizing treatment is not affected, but the cost of the Al base metal increases, which is not economically preferable. Therefore, the amount of Si is set in the range of 0.05 to 0.15%.

In general, inevitable impurities of Al alloy include Cr, Cu, Zn, Zr, and V.
Among them, Cr and Cu have some influence on the color tone after the anodizing treatment, so that it is preferable to restrict them to a small amount. That is, if the content of Cr exceeds 0.05% and the content of Cu exceeds 0.1%, the color tone after anodizing becomes yellowish, so that the Cr content as an impurity is 0.05% or less and the Cu content is 0.1%. It is preferable to regulate as follows. On the other hand, Zn, Zr, and V do not substantially affect the color tone after the anodizing treatment. However, if Zn exceeds 1.0%, the corrosion resistance is reduced, and Zr and V each become 0.3%. If the ratio exceeds the above range, a coarse intermetallic compound is generated and the bending workability is impaired. Therefore, it is preferable that the Zn content as impurities is regulated to 1.0% or less, and the Zr content and V content are each regulated to 0.3% or less. .

Further, in general, in an Al alloy, Ti alone or Ti is added in order to refine the ingot structure.
And Be added to prevent oxidation of molten metal
May be added, but also in the case of the present invention, these may be added. However, if the Ti content is less than 0.003%, the effect of refining the ingot structure cannot be obtained, while the Ti content is 0.15%.
%, A coarse intermetallic compound of TiAl ₃ is generated and the bending workability is impaired. Therefore, when Ti is added, the amount of Ti is set in the range of 0.003 to 0.15%. When B is added together with Ti, the amount of B is 0.0001.
%, The effect of refining the ingot structure cannot be obtained.
Since 0.1% of being coarse TiB ₂ is generated if exceeds bending workability is inhibited, B amount in the case of adding B in combination with Ti is in the range of from 0.0001 to 0.01%. If the amount of Be in the case of adding Be is less than 0.0001%, the effect of preventing the molten metal from being oxidized cannot be obtained.
If Be is added beyond that amount, the above effect is only saturated and the economy is wasted. Therefore, the amount of Be in the case of adding Be is set in the range of 0.0001 to 0.05%.

Further, in the present invention, the structure conditions and characteristic values of the final plate (plate before anodizing treatment) finally obtained are defined, and these will be described below.

In the final plate, the density of Al—Mn needle-like precipitates having a size of ² to 8 μm is 2,000 / mm ² to
It is necessary to be within the range of 8000 particles / mm ² , and by selecting the density range of the Al—Mn-based needle-like precipitates having a size of 2 to 8 μm, as described above, 10 μm
A gray color tone can be obtained stably with an anodic oxide film having a small thickness. Here, in the final plate, Al-
As the Mn-based precipitate, Al-M having a size of 2 to 8 μm is used.
In addition to the n-based needle-like precipitates, there are also precipitates of less than 2 μm, particularly fine fine-grained precipitates of about 1 μm or less. Such fine fine-grained precipitates have a gray color tone. Hardly contributes. Large precipitates having a size exceeding 8 μm are substantially absent within the range of the component composition and the ingot heat treatment conditions specified in the present invention. Therefore, according to the present invention, in particular, A having a size in the range of 2 to 8 μm.
That is, the density of the 1-Mn-based acicular precipitate was specified. Here, the “size” of the Al—Mn-based acicular precipitate means the length in the maximum length direction.

The average crystal grain size in the final plate is 80 μm.
m. The average crystal grain size affects the occurrence of surface roughness during bending, and the smaller the value is, the less likely it is for the surface roughness to occur. In particular, by setting the average crystal grain size to 80 μm or less, the 1
The occurrence of rough skin can be reliably prevented even in severe bending at a temperature of 00 to 180 °.

The proof stress of the final plate is 95 N / mm.
Must be at least ² . That is, the proof stress is 95N
If it is at least / mm ² , the strength will be the same as that of the conventional material, and it will be possible to apply it to the same use as the conventional material.

Next, each process in the manufacturing method of the present invention will be described.

First, an aluminum alloy having the above-described composition is cast to obtain an ingot. This casting method is not particularly limited, and may be in accordance with an ordinary method, but DC casting (semi-continuous casting) is usually preferred.

The ingot is subjected to a heat treatment. This ingot heat treatment is a treatment for precipitating Al-Mn-based precipitates necessary for obtaining a gray color by anodizing the final plate. The temperature of this ingot heat treatment is 580 ° C
If it is less than 1, fine granular precipitates having a diameter of about 1 μm or less and relatively large needle-like precipitates having a size of about 2 to 8 μm exist in the state of the final plate, and among them, particularly large needle-like precipitates are present. There is a possibility that a non-uniform distribution is exhibited and a streak defect occurs after the anodizing treatment. If the temperature of the ingot heat treatment is 580 ° C. or higher, the distribution of the needle-like precipitates having a size of 2 to 8 μm is uniformed, and streak defects are less likely to occur. If the temperature of the ingot heat treatment exceeds 630 ° C., eutectic melting may occur. Therefore, in order to prevent the occurrence of defective streaks, the ingot heat treatment temperature must be within the range of 580 to 630 ° C. The holding temperature of the ingot heat treatment is 1
If less than the time, Al-Mn-based precipitates are not sufficiently deposited,
On the other hand, even if heating and holding for more than 24 hours, Al-M
Precipitation of the n-type precipitates becomes saturated and only impairs economic efficiency. Therefore, the heat holding time of the ingot heat treatment is 1
２４24 hours. Here, in order to obtain a stable gray color in a relatively thin anodic oxide film of about 10 μm, as described above, the distribution density of needle-like precipitates having a size of 2 to 8 μm in the final plate is 2,000 to 8,000 / mm ² is required, but the Mn content of the alloy is 1.3 to 1.
By performing the ingot heat treatment under the above conditions at 5%, the distribution density condition of the Al-Mn-based acicular precipitate can be satisfied.

After the ingot heating treatment as described above, hot rolling is performed. The hot rolling starts at a temperature equal to or lower than the ingot heating temperature and ends at a temperature equal to or lower than the recrystallization temperature. In the case of the alloy used in the present invention, since the recrystallization temperature is approximately 300 ° C., the hot rolling end temperature is set to 300 ° C. or less. When the hot rolling end temperature exceeds 300 ° C., partially recrystallized grains or coarse recrystallized grains remain in the hot-rolled sheet after the hot rolling, and it is difficult to obtain a fine uniform recrystallized structure by subsequent intermediate annealing. In this case, the surface after the anodizing treatment is liable to cause streaking defects due to the non-uniform crystal structure.
It is necessary to end at or below ° C.

After the completion of the hot rolling, intermediate annealing may be performed immediately, or if necessary, cold rolling (primary cold rolling) may be performed before intermediate annealing. That is, in the case where the thickness accuracy of the final sheet in the sheet width direction and the length direction is strictly required, the intermediate annealing may be performed after performing the primary cold rolling after the hot rolling. The previous cold rolling has no substantial effect on the purpose of the present invention.

Intermediate annealing after hot rolling, or after hot rolling and primary cold rolling, is a step required to recrystallize the structure finely and uniformly to prevent the occurrence of rough surface during bending. It is. Average crystal grain size defined by the present invention 8
In order to obtain a fine recrystallized grain structure of 0 μm or less, it is necessary to perform intermediate annealing under conditions of rapid temperature rise and rapid cooling. Specifically, if the heating rate and the cooling rate are less than 1 ° C./sec, it becomes difficult to obtain a fine recrystallized grain structure having an average crystal grain size of 80 μm or less, and the surface is likely to be roughened during bending. It is necessary that both the rate of temperature rise and the rate of cooling be 1 ° C./sec or more. On the other hand, if the heating rate and the cooling rate are higher, it is possible to obtain a fine recrystallized grain structure having an average crystal grain size of 80 μm or less, but if it exceeds 50 ° C./sec, the sheet tends to be deformed during annealing. In addition, industrial implementation on a mass production scale becomes difficult. Therefore, both the temperature rising rate and the cooling rate of the intermediate annealing were set in the range of 1 to 50 ° C./sec. In addition, such a rapid temperature rise of 1 to 50 ° C./sec,
The rapid cooling intermediate annealing can be performed by a continuous annealing furnace. In the annealing in a batch furnace, the rate of temperature rise and the rate of cooling are both as extremely slow as 20 to 60 ° C./hr, so that a fine recrystallized grain structure having an average crystal grain size of 80 μm or less cannot be obtained, and surface roughening may occur during bending. Is high. On the other hand, since intermediate annealing by continuous annealing is heating for a short time, recrystallization is not sufficiently performed when the intermediate annealing temperature is less than 400 ° C.
If the temperature exceeds ℃, coarse recrystallized grains are generated and bending workability is impaired. Therefore, the intermediate annealing temperature is set in the range of 400 to 600 ℃. Also, holding at a heating temperature of 400 to 600 ° C. is 10
If the time exceeds minutes, the productivity decreases, so the holding time is set to 10 minutes or less. Needless to say, the holding may be performed for 0 minute, that is, without holding.

After the intermediate annealing, cold rolling is performed to obtain a final sheet thickness. This cold rolling is a necessary step for improving the strength. If the cold rolling ratio is less than 2%, the yield strength of the final sheet is less than 95 N / mm ² , while if it exceeds 30%, the balance between strength and bending workability is lost, and although bending strength is increased, strength is reduced, In any case, the object of the present invention cannot be achieved. Therefore, the cold rolling reduction after the intermediate annealing is 2
３０30%.

When the rolled sheet having the final thickness after cold rolling obtained as described above is used as an interior material or the like, anodizing treatment is performed. The conditions of this anodizing treatment are not particularly limited, but it is desirable to use the most common sulfuric acid electrolytic bath from the viewpoint of economy and the like. Specifically, for example, H ₂
Using a sulfuric acid bath having an SO ₄ concentration of about 10 to 25 vol%,
Bath temperature about 10 to 30 ° C, current density 1.5 to 2.5 A / d
Anodizing treatment may be performed under the condition of about m ² . The thickness of the film by the anodizing treatment is not particularly limited, but the method of the present invention is characterized in that a gray color tone can be stably obtained even with a film thickness as thin as about 10 μm. The effect of the present invention can be maximized when the film thickness is large, especially when the film thickness is 6 to 15 μm.

Here, the color tone after the anodizing treatment can be evaluated by the value of the lightness index L and the chromaticness indices a and b according to the Hunter's color difference formula (see JIS Z8730). In other words, the higher the L value of the lightness index, the whiter the color index is, while the chromaticness index is about the degree of coloring, and the higher the a value, the stronger the redness,
The higher the b value, the stronger the yellow color.

In the present invention, the color tone in which the anodic oxide film has a small thickness of about 10 μm and has a stable gray color means that the L value is in the range of 57 to 74 when the film thickness is 6 to 15 μm, Moreover, when the film thickness is constant, the variation range of the L value is within 5 and both the a value and the b value are -2 to
The target is an achromatic color within the range of +2. If the target values of the L value, a value, and b value of the color tone at each film thickness are shown in more detail, when the film thickness is 6 μm, L value: 69 to 74, a value and b value: -2 to +2, film thickness 9 μm L value: 65 to 70, a value and b value: -2 to +2 L value: 57 to 62, a value and b value: -2 to +2 when the film thickness is 15 μm. When the aluminum alloy rolled sheet according to the production method of the present invention is subjected to anodizing treatment in a normal sulfuric acid bath, the above-described target value is easily achieved, and a stable gray anodized film having a thickness of 6 to 15 μm is obtained. A film can be obtained.

[0033]

EXAMPLE A melt of each of the alloy symbols A to L shown in Table 1 was melted according to a conventional method, and 550 m was cast by DC casting.
A slab of mx 1200 mm x 4000 mm was cast.
After facing each obtained slab, ingot heat treatment is performed under each condition as shown in production condition numbers 1 to 19 in Table 2, and then hot rolling is started at a temperature not higher than the intermediate heating temperature,
Hot rolling was completed at the temperatures shown in Table 2 to obtain a hot-rolled sheet having a thickness of 4 mm. Production condition No. 18,1
In the case of manufacturing condition numbers 1 to 17 excluding 9, the plate thickness is 2.2 m.
m, and then subjected to intermediate annealing. In the case of Production Condition Nos. 18 and 19, intermediate annealing was directly performed on the hot-rolled sheet without performing primary cold rolling. Intermediate annealing is
In the case of Production Condition Nos. 1 to 11, 13 to 19, the heating and cooling rates were performed at 500 ° C. in a continuous annealing furnace in the range of 1 to 50 ° C./sec without holding. In this case, batch annealing at 400 ° C. for 2 hours was applied as a comparative example. After these intermediate annealings, production condition numbers 1 to
In the case of 12, 15 to 17, cold rolling is performed to a sheet thickness of 2.0 mm to obtain a final sheet, and in the case of the production condition 14, the sheet thickness is 1.3.
mm, and the final sheet was produced by cold rolling to a thickness of 0.1 mm, and in the case of Production Condition No. 13, the intermediate sheet was subjected to intermediate annealing without cold rolling. In addition, in the case of the manufacturing condition No. 18, up to 3.6 mm after the intermediate annealing, and in the case of the manufacturing condition No. 19, it is 3.2 mm
Until the final plate was subjected to cold rolling.

For each final plate, the proof stress was measured by a tensile test, and the bendability was evaluated by a 135 ° bending test (tip radius 0.1 ^R ) under severe conditions for bending.
Further, regarding the crystal grain size, the average crystal grain size was determined by examining the crystal grains on the surface by a cutting method. Furthermore, the maximum length 2-8
The density of the Al-Mn-based acicular precipitates having a thickness of μm was examined by using both a transmission electron microscope and an optical microscope.

Further, for each final plate, 10% NaOH
After etching with an aqueous solution, washing with water and desmutting with nitric acid, an anodic oxidation treatment was performed under the following conditions. That is, using a sulfuric acid bath having a H ₂ SO ₄ concentration of 15 vol%, anodizing treatment was performed at a bath temperature of 20 ° C. and a current density of 1.5 A / dm ² to form anodized films of 9 μm each.

Regarding the surface tone of the anodized film on each plate, a multi-spectrophotometer MSC-IS-2DH manufactured by Suga Test Instruments was used.
The color tone was evaluated by a lightness index L and a chromaticness index a and b according to a Hunter's color difference formula, and the streak was visually evaluated. Table 3 shows the results. In Table 3, the evaluation of 135 ° bending was as follows: ○ indicates no crack (pass);
The mark “Δ” indicates occurrence of rough skin (fail), and the mark “X” indicates occurrence of crack (fail).

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

The individual results will be described below.

Each of the materials of Production Condition Nos. 1, 4, 5, 15 to 19 is an invention example in which both the component composition and the production process satisfy the conditions specified in the present invention. Shows a strength equal to or higher than that of the conventional material of 95 N / mm ² or more, while the bending property is a severe 135.
° No cracking or roughening in bending test, and 9μm
It is clear that this is an excellent material that can obtain a stable gray tone even with a thin anodized film.

On the other hand, the materials of Production Condition Nos. 2, 3, 6 to 9 are comparative examples which satisfy the production process conditions defined in the present invention but do not satisfy the component composition conditions. Among them, Production Condition No. 2 used Alloy B whose Mn content was lower than the component range specified in the present invention, and Production Condition No. 3
Is the alloy C having an Mn content higher than the component range specified in the present invention. In the former case, the density of the 2 to 8 μm Al-Mn needle-like precipitate is too low because the Mn content is small. The L value exceeds the target range, and in the latter case, Mn
Due to the large amount, the density of the Al-Mn-based acicular precipitate of 2 to 8 µm was too high, and the L value was below the target range. On the other hand, Production Condition No. 6 uses Alloy F whose Mg content is lower than the component range specified in the present invention, and Manufacturing Condition No. 7 uses Alloy G whose Mg content is higher than the component range specified in the present invention. In the former case, the yield strength is 95 because the amount of Mg is small.
The strength was as low as N / mm ² or less, and in the latter case, the yield was too high due to the large amount of Mg, and the bending workability was reduced. Further, the manufacturing condition No. 8 uses alloy H whose Fe content is higher than the component range specified in the present invention, and the manufacturing condition No. 9 uses alloy I whose Si content is higher than the component range specified in the present invention.
In the former case, since the amount of Fe is large, A
The l-Mn-Fe-based intermetallic compound increases and the density of the Al-Mn-based needle-like precipitate of 2 to 8 µm decreases, and the L value exceeds the target range. In the latter case, the amount of Si decreases. Due to the large amount, a large amount of the Si-based intermetallic compound was generated, and the b value exceeded the target range.

On the other hand, the manufacturing condition Nos. 10 to 14 use the alloy A satisfying the component composition conditions specified in the present invention (the alloy D is used only in the manufacturing condition number 12), but the manufacturing process conditions are specified in the present invention. This is a comparative example that deviates from the conditions of the above. Among them, the production condition No. 10 was such that the ingot heating temperature was too low, and the Al-Mn-based needle-like precipitates of 2 to 8 µm were unevenly distributed and the density thereof was lowered, so that the L value exceeded the target range, A poor streak occurred. In production condition No. 11, the hot rolling end temperature is too high, and partial recrystallization occurs at the end of hot rolling, which also affects the recrystallized grains of the intermediate annealing, resulting in a mixed grain structure, resulting in poor streaks. Occurred. Further, in the production condition No. 12, since the intermediate annealing was performed in a batch furnace, the recrystallized grains became coarse and the rough surface occurred during bending. In the case of production condition No. 13, the cold rolling was not performed after the intermediate annealing, so that the yield strength was as low as 95 N / mm ² or less. On the other hand, in production condition No. 14, since the cold rolling reduction was too high and the yield strength was high, it was broken by bending.

[0044]

As is clear from the above-mentioned embodiment, according to the manufacturing method of the present invention, the bending workability is particularly good and the strength is 95 N / mm ² or more, which is equivalent to that of the conventional material and 10 μm. Even with a thin anodic oxide film, a rolled aluminum alloy plate that exhibits a stable gray color can be obtained.
Then, the rolled aluminum alloy plate obtained by the method of the present invention is used for gray building materials subjected to anodizing treatment, particularly for interior materials, other objects, housings and panels of various electric instruments and measuring instruments, decorative articles and the like. For example, it becomes possible even with a severe bending work design, and since a thin anodic oxide film stably exhibits a gray color, it is possible to reduce the anodizing treatment cost.

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[Procedure amendment]

[Submission date] January 14, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

According to a third aspect of the present invention, there is provided the method for producing a rolled aluminum alloy plate according to the first aspect, wherein the ingot of the aluminum alloy further contains 0.0001 to 0.05% of each of the above-mentioned components. It is characterized by using a material containing Be.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction contents]

[0039]

[Table 3]

────────────────────────────────────────────────── ⁶ Continuation of the front page (51) Int.Cl. 694A

Claims (4)

[Claims] 1. Mn 1.3 to 1.5% (% by weight, the same applies hereinafter), Mg 0.4 to 1.2%, Fe 0.1 to 0.2%,
An ingot of Al alloy containing 0.05 to 0.15% of Si and the balance consisting of Al and unavoidable impurities is 580 to 6
A heat treatment is performed at a temperature within a range of 30 ° C. for 1 to 24 hours, then hot rolling is started at a temperature lower than the processing temperature in the heat treatment, and the hot rolling is completed at 300 ° C. or lower, and then 400 to 600 at a heating rate of ５０50 ° C./sec.
After heating to a temperature in the range of ° C. and holding for 0 to 10 minutes,
Intermediate annealing is performed at a cooling rate of 50 ° C./sec, and cold rolling is performed at a rolling rate of 2 to 30%.
Al-Mn needle-like precipitates having a size of ~ 8 µm
Precipitated at a density within the range of ０００8000 / mm ² , and have an average crystal grain size of 80 μm or less and a proof stress of 95 N / mm 2.
^A method for producing a rolled aluminum alloy plate having a gray color after anodizing, wherein ^two or more rolled aluminum alloy plates are obtained. 2. The method for producing a rolled aluminum alloy plate according to claim 1, wherein the ingot of the aluminum alloy further contains 0.003 to 0.15% in addition to the above components.
Of Ti alone or 0.0001-0.01% of B
A method for producing a rolled aluminum alloy plate having a gray color after anodizing treatment, wherein the rolled aluminum alloy sheet contains a combination of the above. 3. The method for producing a rolled aluminum alloy plate according to claim 1, wherein the ingot of the aluminum alloy further comprises 0.0001 to 0.05 in addition to the above components.
% Of aluminum alloy rolled plate having a gray color after anodizing, using a material containing Be. 4. The method for producing an aluminum alloy rolled sheet according to claim 1, wherein after the hot rolling, primary cold rolling is performed before the intermediate annealing, and the color tone of the aluminum alloy rolled sheet after anodizing is gray. Manufacturing method.