JP2021095605A - Aluminum alloy foil for molding and manufacturing method thereof - Google Patents

Abstract

To inhibit a development of an aggregate structure, to reduce an anisotropy in mechanical properties, and to prevent a crease or a crack at molding by an aluminum alloy foil having a fine and even grain structure.SOLUTION: An aluminum alloy foil for molding has a composition including 0.2-1.2 mass% Si, 0.5-1.5 mass% Fe, 0.05-0.20 mass% Cu, and the balance Al with inevitable impurities. As an aggregate structure, a Cube orientation density is 8.0 or less, a Cu orientation density is 5.0 or less, an R orientation density is 5.0 or less, and a difference of the maximum orientation density and the minimum orientation density of these aggregate structures is 4.0 or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to an aluminum alloy foil for molding used in a molding process and a method for producing the same.

Aluminum alloy foil is mainly used as a container for foods and chemicals manufactured by deep drawing. In that case, the aluminum foil is required to have high moldability, "ears" which are irregularities generated by deep drawing, and anisotropy of mechanical properties.
For example, Patent Document 1 states that the moldability is improved by defining the component range, the particle size of the crystal grains, and the area ratio of the Cube orientation.
Further, Patent Document 2 states that the moldability for defining the ratio of each diffraction intensity indicating each of the (111) plane, the (100) plane, the (110) plane, and the (311) plane is enhanced.

Japanese Unexamined Patent Publication No. 2018-115376 Japanese Unexamined Patent Publication No. 2012-052158

However, it cannot be said that the conventional aluminum alloy foil has sufficient moldability, and wrinkles occur during molding and the crystal grain size becomes coarse due to the development of the texture, especially the 0-90 ° ear accompanying the development of the Cube orientation. Moreover, since it is non-uniform, there is a problem that rough skin occurs during molding and cracks occur during molding.
Against the background of the above circumstances, the present invention suppresses the development of texture, reduces the anisotropy of mechanical properties, and prevents wrinkles and cracks during molding by using an aluminum alloy foil having a fine and uniform grain structure. The purpose is.

That is, among the molding aluminum alloy foils of the present invention, the first form is Si: 0.2 to 1.2% by mass, Fe: 0.5 to 1.5% by mass, Cu: 0.05 to 0. .20% by mass, the balance is composed of Al and other unavoidable impurities, and the texture is Cube orientation density 8.0 or less, Cu orientation density 5.0 or less, R orientation density 5.0 or less. It is characterized in that the difference between the maximum azimuth density and the minimum azimuth density of these textures is within 4.0.

The invention of the aluminum alloy foil for molding of the second aspect is characterized in that, in the invention of the said aspect, the composition further contains Mn: 0.0020 to 0.010% by mass.

The invention of the aluminum alloy foil for molding of the third embodiment is characterized in that, in the invention of the above-described embodiment, the average crystal grain size is 25 μm or less and the maximum crystal grain size is 40 μm or less.

In the invention of the fourth aspect of the aluminum alloy foil for molding, in the invention of the above-described aspect, the elongation rate per foil thickness (elongation rate / foil thickness) at the elongation in the 0 °, 45 ° and 90 ° directions with respect to the rolling direction. The difference between the maximum value and the minimum value is 0.1 or less.

Among the methods for producing an aluminum alloy foil for molding of the present invention, the first form is the method for producing an aluminum alloy foil according to each of the above-described forms.
An ingot of an aluminum alloy having the composition of the invention of the above-described embodiment is subjected to a homogenization treatment in which it is held at 480 to 540 ° C. for 4 hours or more, and after the homogenization treatment, hot rolling is performed so that the rolling finish temperature becomes 230 to 320 ° C. Then, intermediate annealing is performed in the middle of cold rolling, the cold rolling ratio from after hot rolling to intermediate annealing is set to 20 to 80%, and the cold rolling ratio from after intermediate annealing to the final product is 75 to 99. %, The final annealing is performed after cold rolling.

Another invention of the method for producing an aluminum alloy foil for molding is that in the invention of the above-mentioned embodiment, the final annealing has a temperature rising rate of 40 ° C./sec or more, and the holding temperature is 220 to 450 ° C. and 100 seconds or less. It is characterized by being done in.

Hereinafter, the technical matters specified in the present invention will be described below.

Si: 0.2 to 1.2% by mass
Si is an element that slightly improves the strength of the aluminum foil, suppresses the texture development of the Al—Fe alloy foil, and is also effective in reducing the ear ratio. If the Si content is less than 0.2%, the effect is poor, and if it exceeds 1.2%, the material strength becomes high, and an Al-Fe-Si-based coarse intermetallic compound is generated, resulting in formability and foil rollability. Causes a decrease in.
For the same reason, it is desirable that the lower limit of the Si content is 0.4% and the upper limit is 0.7%.

Fe: 0.5 to 1.5% by mass
Fe is an element that can improve the strength of aluminum foil. Further, since the Al—Fe-based second phase particles are distributed at high density, the crystal grains become finer, which is effective in improving the moldability and suppressing the rough skin at the time of deep drawing. If the Fe content is less than 0.5%, these effects are poor, and if it exceeds 1.5%, coarse Al-Fe-based intermetallic compounds are formed, which not only lowers the moldability but also develops the texture. As a result, the anisotropy of mechanical properties and the ear ratio increase.
For the same reason, it is desirable that the lower limit of the Fe content is 0.6% and the upper limit is 1.0%.

Cu: 0.05 to 0.20% by mass
Cu is an element that greatly improves the strength of aluminum foil, contributes to texture, and affects the anisotropy of mechanical properties and ear ratio. If the Cu content is less than 0.05%, the Cube orientation density increases, and the anisotropy of mechanical properties and the ear ratio increase. If the Cu content exceeds 0.20%, the material strength becomes too high and the moldability and foil rollability are greatly reduced.
For the same reason, it is desirable that the lower limit of the Cu content is 0.10% and the upper limit is 0.15%.

Mn: 0.0020 to 0.010% by mass
Since Mn is an element that improves the strength of the aluminum foil and strongly inhibits the recrystallization of the aluminum foil, it is contained as desired. If the Mn content is less than 0.0020%, the risk of strength reduction increases in the Al-Fe alloy, which easily recovers and recrystallizes during cold rolling, and it is necessary to use high-purity aluminum bullion, so the manufacturing cost. Will increase. On the other hand, when the Mn content exceeds 0.010%, the material strength becomes high and the moldability and rollability deteriorate.
For the same reason, it is desirable that the lower limit of the Mn content is 0.0025% and the upper limit is 0.005%.
When Mn is not positively contained, Mn may be contained as an unavoidable impurity in an amount of less than 0.0020%.

Cube orientation density 8.0 or less, Cu orientation density 5.0 or less, R orientation density 5.0 or less, and the difference between the maximum orientation density and the minimum orientation density of these textures is 4.0 or less Mechanical development is mechanical. It increases the anisotropy of the property and causes an increase in the ear ratio during deep drawing and the generation of wrinkles due to the generation of ears. Control the Cube azimuth density that contributes to the ears generated in the 0 and 90 degrees directions with respect to the rolling direction of the foil during deep drawing, and the Cu azimuth and R azimuth densities that contribute mainly to the ears generated in the 45 degree direction below the specified value. However, by setting the difference between the maximum azimuth density and the minimum azimuth density (maximum azimuth density-minimum azimuth density) of these aggregates to 4.0 or less, the ear ratio can be reduced and the mechanical properties are different. It is possible to obtain an aluminum alloy foil having a small property.

If the average crystal grain size is 25 μm or less and the maximum crystal grain size is 40 μm or less and the average crystal grain size exceeds 25 μm, the risk of cracking during molding due to rough skin increases.
The average crystal grain size can be varied mainly by selecting the chemical composition and the manufacturing process. Fe has a strong effect of refining crystal grains, and the higher the cold rolling ratio from intermediate annealing to the final thickness, the finer the crystal grains. Further, it is also important for the crystal grain refinement that the temperature rising rate of the final annealing is at least a certain level, and it is possible to prevent the formation of coarse crystal grains and obtain a uniform and fine crystal grain structure. By these optimizations, an average crystal grain size of 25 μm or less and a maximum crystal grain size of 40 μm or less can be achieved. However, since the crystal grain size is also affected by the presence of Fe and the intermediate annealing conditions, it may change even if the amount of Fe added is the same and the cold rolling ratio is the same.

The difference between the maximum and minimum elongation rates per foil thickness ((maximum elongation rate / foil thickness)-(minimum elongation rate / foil thickness)) at elongations in the 0 °, 45 °, and 90 ° directions with respect to the rolling direction. 0.1 or less When the variation in the elongation in each direction is large, the anisotropy of the mechanical properties becomes large, which leads to an increase in the ear ratio and wrinkles during molding. By controlling the difference in elongation rate per foil thickness to 0.1 or less in all directions, the occurrence of these problems can be suppressed.
The above conditions can be achieved by texture control, as described above.

Homogenization treatment step: Homogenization treatment of holding at 480 to 540 ° C. for 4 hours or more By performing the homogenization treatment at a temperature at which Fe is likely to precipitate, the solid solution amount of Fe is reduced and the Cube orientation is developed in the subsequent manufacturing process. Can be urged. Further, increasing the density of Al—Fe-based second-phase particles of 1 μm or more leads to miniaturization of crystal grains.
When the homogenization treatment temperature is less than 480 ° C., a large amount of fine second-phase particles are precipitated, and the effect of grain refinement is poor. When the homogenization treatment temperature exceeds 540 ° C., the amount of solid solution Fe increases, the recrystallization behavior changes, the Cube orientation density decreases, and the Cu orientation density and the R orientation density tend to increase. For the above reasons, the homogenization treatment temperature is preferably 500 to 520 ° C. The holding time is preferably 4 hours or more. Fe is an element that is extremely difficult to diffuse in the aluminum matrix, and the homogenizing effect cannot be sufficiently obtained in less than 4 hours. There is no particular upper limit, but 20 hours or less is desirable from the viewpoint of economy.

Hot rolling process: Rolling finish temperature is 230-320 ° C
When hot rolling the ingot after the homogenization treatment, the finished temperature is important. If the temperature exceeds 320 ° C., recrystallization occurs in a part of the plate after hot rolling, and it becomes difficult to obtain an ideal texture in the final product. Further, the non-uniform structure in which the fiber grains and the recrystallized grains are mixed also contributes to the non-uniformity of the crystal grain structure in the final product, which may lead to a decrease in moldability. In order to finish the rolling at a finished temperature of less than 230 ° C., the temperature during hot rolling is also extremely low, so that there is a concern that cracks may occur on the side of the plate and the productivity may be significantly reduced.

Cold rolling, intermediate annealing, final cold rolling In general, cold rolling develops Cu orientation and S orientation called rolling texture, and recrystallization occurs during intermediate annealing, which is a recrystallized texture. It is known that the orientation develops. Controlling the cold rolling ratio and intermediate annealing conditions is extremely important for obtaining an ideal texture. The cold rolling ratio from hot rolling to intermediate annealing is preferably 20 to 80% in order to suppress the development of texture after intermediate annealing. If the cold rolling ratio exceeds 80%, the Cube orientation does not develop even after intermediate annealing and the rolling texture is maintained, and if the cold rolling ratio is less than 20%, the strain introduced in cold rolling The amount becomes low, which leads to excessive development of Cube orientation, coarsening of recrystallized grains during intermediate annealing, and non-uniform size.

In intermediate annealing, industrial intermediate annealing methods generally include batch annealing (Batch Annealing, BATCH) in which the coil is placed in a furnace and held for a certain period of time, and continuous annealing line (Continuous Annealing Line, CAL). There are two known methods, CAL annealing, in which the material is rapidly heated and cooled.
In the present invention, the intermediate annealing method is not particularly limited, but CAL annealing is desirable for the purpose of suppressing the growth of cube-oriented grains. In the case of batch annealing, a temperature of 300 to 400 ° C. can be preferably selected, and in the case of CAL annealing, a temperature of 420 to 470 ° C. can be selected. In batch annealing, if the annealing temperature is less than 300 ° C., recrystallization is not completed, and if it exceeds 400 ° C., the coarsening of recrystallized grains and Fe precipitation may be insufficient. Even in CAL annealing, recrystallization is not completed when the annealing temperature is less than 420 ° C., and when it exceeds 470 ° C., the amount of solid solution Fe increases, which may promote the development of Cu orientation and R orientation in the final product. Intermediate annealing can be performed multiple times.

By setting the final cold rolling ratio from the intermediate annealing to the final product to 75 to 99%, an ideal texture and a fine crystal grain structure can be obtained. If the final cold rolling ratio is less than 75%, the recrystallized grains become coarse and the Cube orientation density increases, and if it exceeds 99%, the Cu orientation and the R orientation density increase.

Final annealing Final annealing is performed for the purpose of softening the foil, improving moldability, and balancing the density of each crystal orientation by recrystallization. In addition, if the temperature rise rate during final annealing is high, recovery of strain accumulated by cold rolling can be suppressed, and the crystal grain size after recrystallization becomes uniform and fine. Therefore, the condition for final annealing is the temperature rise rate. It is necessary that the temperature is 40 ° C./sec or more, and the holding is performed at a temperature of 220 to 450 ° C. and 100 seconds or less. If the rate of temperature rise is less than 40 ° C./sec, the recrystallization particle size becomes coarse. If the temperature is less than 220 ° C., recrystallization is not completed, and if it exceeds 450 ° C., the amount of solid solution Fe increases, and the formability is impaired by the decrease in elongation as the strength increases. It is desirable to limit the time because it hinders productivity when it exceeds 100 seconds.

According to the present invention, it is possible to suppress an increase in ear ratio and occurrence of wrinkles during molding, and further improve the molding height and prevent cracking. Further, there is an effect that the yield of the product can be improved by reducing the trimming amount at the time of molding.

The flow chart of the manufacturing process in one Embodiment of this invention is shown.

Hereinafter, an aluminum alloy foil for molding according to an embodiment of the present invention and a method for producing the same will be described.
The ingot of the aluminum alloy used as the material of the aluminum alloy foil for molding of the present embodiment can be cast by a conventional method, and is obtained, for example, by adjusting the composition so as to be within the composition range of the present invention and casting. be able to.

Next, as shown in FIG. 1, the ingot of the obtained aluminum alloy is subjected to homogenization treatment and subsequent steps. The homogenization treatment is performed under the conditions of, for example, 480 to 540 ° C. × 4 hours or more, and after the homogenization treatment, hot rolling is performed.
The hot rolling conditions are controlled, for example, between 230 and 320 ° C. as the hot finish temperature.
In the hot rolling, it is preferable that the finished plate thickness of the aluminum alloy plate is 3 to 8 mm. Further, it is desirable to set the finished plate thickness so that the cold rolling ratio from the hot rolling to the first intermediate annealing is 20 to 80%.

After the hot rolling, the hot rolled material is cold rolled.
Further, in the middle of cold rolling, at least one intermediate annealing is performed.
A continuous annealing furnace or a batch furnace is used as the annealing furnace for intermediate annealing. As for the annealing conditions, in the case of a batch furnace, the temperature is raised at a heating rate of 25 to 50 ° C./hour and held at 300 to 400 ° C. for 3 hours or more. It is desirable to carry out cooling at a cooling rate of 20 to 40 ° C./hour, and in the case of a continuous annealing furnace, the temperature is raised at a heating rate of 50 to 300 ° C./sec and at 420 to 470 ° C. for 1 to 5 seconds. After holding, it is desirable to carry out cooling at a cooling rate of 20 to 200 ° C./sec.
When intermediate annealing is performed during cold rolling, it is desirable that cold rolling be performed so that the cold rolling ratio after the hot rolling finish and before the first intermediate annealing is 20 to 80%, and the final intermediate annealing is performed. After that, the final cold rolling ratio up to the final plate thickness is set to 75 to 99%. All cold rolling ratios are based on the plate thickness before cold rolling.
By the cold rolling, for example, an aluminum alloy foil for molding having a plate thickness of 40 to 200 μm is obtained. In the present invention, the thickness of the aluminum alloy foil for molding is not limited to a specific one.

It is desirable to perform final annealing after the completion of cold rolling. It is desirable that the final annealing conditions are, for example, a heating rate of 40 ° C./sec or more and holding at 220 to 450 ° C. × 100 seconds or less. The cooling after the end of holding is not particularly limited, but the cooling rate can be set to 30 to 300 ° C./sec or the like. It is difficult to obtain a high temperature rise rate in the final annealing by conventional batch annealing. For example, there are methods such as IR irradiation on an aluminum alloy foil, injection of superheated steam, and a method of bringing the aluminum alloy foil into contact with a high temperature heat roll. .. In this patent, test materials were prepared using superheated steam, heat rolls and IR as the heating method, and various characteristics were evaluated.
Although the method for producing the aluminum alloy foil for molding has been described above, the method for producing the aluminum alloy foil for molding is not limited to the above steps in the present invention.

The aluminum alloy foil for molding of the present invention can obtain an aluminum alloy foil having extremely small anisotropy of mechanical properties by optimizing its chemical composition and texture.
The aluminum alloy foil for molding can be used for molding such as deep drawing and overhanging, and molding can be performed while suppressing the occurrence of ears and wrinkles.
For example, it can be used for packaging foods and the exterior of batteries. In this case, a resin may be laminated on the surface of the aluminum foil and used as a composite material.

Next, Examples of the present invention will be described while comparing with Comparative Examples.
An alloy having the composition shown in Table 1 (the balance is Al and unavoidable impurities) is melted, and under the conditions shown in Table 1, homogenization treatment, hot rolling, cold rolling, intermediate annealing, and final annealing are performed to prepare the test material. Obtained.

The obtained test materials were evaluated for each of the following items, and the evaluation results are shown in Table 2.

Crystal orientation density The Cube orientation was {001} <100>, the Cu orientation was {112} <111>, and the R orientation was {123} <634>. For each azimuth density, the incomplete pole map of {111}, {200}, and {220} is measured by the X-ray diffractometry, and the result is used to calculate the three-dimensional azimuth distribution function (ODF). Then, each crystal orientation density was evaluated.
Further, among the obtained directional densities of the Cube azimuth, Cu azimuth, and R azimuth, the difference between the maximum and the minimum was calculated and evaluated.

Average crystal grain size and maximum crystal grain size The surface of the sample material of the aluminum foil after final annealing was electrolytically polished at a voltage of 20 V using a mixed solution of 20% by volume perchloric acid + 80% by volume ethanol, and then in Mr. Barker's solution. The anodization treatment was carried out under the condition of a voltage of 30 V. For the test material after the treatment, crystal grains in the range of 300 μm × 300 μm were observed with an optical microscope. The average crystal grain size was calculated from the photograph taken by the cutting method. The maximum crystal grain size at the time of measurement by the cutting method was defined as the maximum crystal grain size.

Elongation rate Elongation rate was measured by a tensile test. JIS No. 5 test pieces in each direction of 0 °, 45 °, and 90 ° with respect to the rolling direction were sampled, and a tensile speed of 5 mm / min was used with a universal tensile tester (AGS-X 10 kN manufactured by Shimadzu Corporation). The test was conducted at. Using the obtained elongation rate, the elongation rate per foil thickness was obtained by calculating (elongation rate (%) / foil thickness (μm)). If the elongation rate per foil thickness is 0.1 or less, the anisotropy is small and there is no problem in moldability, but if it is more than 0.1, the moldability is impaired by the anisotropy, so it was judged as undecidable.

Evaluation of moldability Deep drawing was performed at a drawing ratio of 1.75, and the ear ratio was measured and whether or not wrinkles were formed on the flange of the molding cup was evaluated. Regarding the determination of wrinkles, a stereomicroscope was used to observe the wrinkles generated on the flange portion having a width of 5 mm, and if the length of the wrinkles was less than 2 mm, there was no problem, and if it was 2 mm or more, it was judged to be impossible.
In addition, the ear ratio was measured by the following formula after measuring the uneven shape of the entire circumference of the molded cup.
Ear rate = {average height of mountains-average height of valleys} / {(average height of mountains + average height of valleys) / 2} x 100 (%)
When the ear ratio was 3% or more, the ears became prominent in the shape of the flange, so it was judged as undecidable.

Although the present invention has been described above based on the above-described embodiments and examples, the technical scope of the present invention is not limited to the contents of the above-mentioned description, and is described above as long as it does not deviate from the scope of the present invention. Appropriate changes to the embodiments are possible.

Claims (6)

Composition containing Si: 0.2 to 1.2% by mass, Fe: 0.5 to 1.5% by mass, Cu: 0.05 to 0.20% by mass, and the balance consisting of Al and other unavoidable impurities. Cube orientation density is 8.0 or less, Cu orientation density is 5.0 or less, R orientation density is 5.0 or less, and the difference between the maximum orientation density and the minimum orientation density of these textures is 4. An aluminum alloy foil for molding, which is characterized by being 0 or less. The aluminum alloy foil for molding according to claim 1, further comprising Mn: 0.0020 to 0.010% by mass in the composition. The aluminum alloy foil for molding according to claim 1 or 2, wherein the average crystal grain size is 25 μm or less and the maximum crystal grain size is 40 μm or less. A claim characterized in that the difference between the maximum value and the minimum value of the elongation rate (elongation rate / foil thickness) per foil thickness is 0.1 or less in the elongations in the 0 °, 45 ° and 90 ° directions with respect to the rolling direction. Item 3. The aluminum alloy foil for molding according to any one of Items 1 to 3. The method for producing an aluminum alloy foil according to any one of claims 1 to 3.
An ingot of an aluminum alloy having the composition according to claim 1 or 2 is subjected to a homogenization treatment in which the ingot is held at 480 to 540 ° C. for 4 hours or more, and after the homogenization treatment, heat is applied so that the rolling finish temperature becomes 230 to 320 ° C. Inter-rolling is performed, intermediate annealing is performed during cold rolling, the cold rolling ratio from after hot rolling to intermediate annealing is set to 20 to 80%, and the cold rolling ratio from after intermediate annealing to the final product is set. A method for producing an aluminum alloy foil for molding, which comprises 75 to 99% and is subjected to final annealing after cold rolling. The method for producing an aluminum alloy foil for molding according to claim 5, wherein the final annealing is performed at a temperature rising rate of 40 ° C./sec or more, holding at a temperature of 220 to 450 ° C. and 100 seconds or less.

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