Aluminum alloy foil for packaging material and method for producing same

Abstract

The objective of the present invention is to provide a packaging material of an aluminum alloy foil, the packaging material having high moldability while having sufficient corrosion resistance. This aluminum alloy foil for a packaging material comprises Fe and Si, with the balance consisting of Al and other trace elements including inevitable impurities, wherein the Fe content is 0.60 mass% to 0.80 mass% (exclusive of 0.80 mass%), the Si content is 0.50 mass% or less, the number density of second phase particles having a predetermined size and present on the surface of the aluminum alloy foil has a predetermined relationship, and the 0.2% proof stress, tensile strength, and breaking elongation fall within predetermined ranges.

Description

Aluminum alloy foil for packaging materials and method for manufacturing the same

[0001] This invention relates to aluminum alloy foil for packaging materials, and more particularly to aluminum alloy foil for packaging materials that has excellent formability and corrosion resistance.

[0002] Aluminum foil or aluminum alloy foil (hereinafter, "aluminum foil or aluminum alloy foil" will simply be referred to as "aluminum alloy foil") is used as part of packaging materials for food, pharmaceutical tablets, lithium-ion batteries, etc. In the aforementioned fields, it is often used as a structure in which a resin film layer is laminated on one or both sides of aluminum alloy foil for the purpose of protecting the contents.

[0003] These structures, which consist of laminated aluminum alloy foil and resin film layers, require various molding processes to accommodate their contents. The aluminum alloy foil needs to have good formability, and 1000-series aluminum alloys such as A1N30 and 8000-series aluminum alloys such as A8079 and A8021 are used.

[0004] The thickness of the aluminum alloy foil used in the aforementioned packaging material is generally 50 μm or less, and since it is necessary to suppress the occurrence of cracks and pinholes during molding, the aluminum alloy foil is required to have high strength, high ductility, or both. Patent Document 1 proposes a high-strength aluminum-iron alloy foil with excellent formability. Patent Document 2 proposes a highly ductile aluminum-iron alloy foil with excellent formability.

[0005] Pamphlet WO2014 / 021170, Japanese Patent Publication No. 2023-161183

[0006] Incidentally, in recent years, from the perspective of reducing environmental impact, there has been a desire for monomaterial packaging materials. However, when molding is carried out using only aluminum alloy foil, the possibility of cracks and pinholes increases if the thickness of the aluminum alloy foil is thin. Furthermore, when used as packaging material for chemicals or foods containing salt, for example, the aluminum alloy foil itself is required to have excellent corrosion resistance. However, while Patent Documents 1 and 2 show excellent formability, corrosion resistance has not been considered. Therefore, the present invention aims to provide an aluminum alloy foil packaging material that has sufficient corrosion resistance while also having high formability.

[0007] The present inventors, after diligent research to solve the aforementioned problems, have found that by adjusting each element added to aluminum within a predetermined composition range, applying homogenization heat treatment to the aluminum alloy ingot within the said composition range within a predetermined temperature range, and controlling the number density and size of the second-phase particles present in the aluminum alloy foil, the objective can be achieved for the aluminum alloy foil after final annealing, thus completing the present invention. That is, the present invention relates to the following aluminum alloy foil for packaging materials and a method for manufacturing the same.

[0008] [1] An aluminum alloy foil containing Fe and Si, with the remainder being Al and other trace elements including unavoidable impurities, wherein the Fe content is 0.60% by mass or more and less than 0.80% by mass, and the Si content is 0.50% by mass or less, and the number density (particles / mm²) of second-phase particles present on the surface of the aluminum alloy foil with equivalent circle diameters of 0.2 μm or more and less than 1 μm, 1 μm or more and less than 2 μm, 2 μm or more and less than 3 μm, 3 μm or more and less than 4 μm, and 4 μm or more. ２ When the elements are designated as [A], [B], [C], [D], and [E] respectively, the result of [A] + [B] + [C] + [D] + [E] is 9000 units / mm². ２ More than 50000 pieces / mm ２ The following applies: [D] + [E] = 200 units / mm ２ The following conditions must be met: ([B] + [C] + [D] + [E]) / ([A] + [B] + [C] + [D] + [E]) is 0.1 or greater, and the 0.2% proof stress is 20 N / mm². ２ 35N / mm or more２ The following is true, and the tensile strength is 60 N / mm². ２ 90N / mm or more ２ The following is an aluminum alloy foil for packaging materials, characterized by having a break elongation of 25% or more.

[0009] [2] The aluminum alloy foil for packaging materials according to [1], characterized in that its thickness is 50 μm or more and 150 μm or less. [3] A method for manufacturing aluminum alloy foil for packaging materials, characterized in that it comprises: a casting step of producing an ingot by casting molten aluminum alloy whose composition is adjusted to have an Fe content of 0.60 mass% or more and less than 0.80 mass%, a Si content of 0.50 mass% or less, and the remainder being Al and other trace elements including unavoidable impurities; a homogenization heat treatment step of subjecting the ingot to homogenization heat treatment at 550°C or more and less than 650°C; a rolling step of producing an aluminum alloy foil by rolling the ingot that has undergone the homogenization heat treatment; and a final annealing step of subjecting the aluminum alloy foil to final annealing.

[0010] The aluminum alloy foil for packaging materials according to the present invention can have high formability while possessing sufficient corrosion resistance.

[0011] Backscattered electron image of the aluminum alloy foil surface in Example 1

[0012] Embodiments of the present invention will be described in detail below. The aluminum alloy foil for packaging materials according to the present invention is characterized by containing Fe (iron) and Si (silicon), with the remainder consisting of Al (aluminum) and other trace elements such as unavoidable impurities.

[0013] <Fe (Iron)> The aluminum alloy foil for packaging materials according to the present invention contains Fe. By including Fe, the strength and ductility can be improved. In addition, Al-Fe second-phase particles are formed, and fine second-phase particles of less than 1 μm hinder the movement of grain boundaries during annealing, while coarser second-phase particles of 1 μm or more become nuclei for recrystallization during annealing. The Fe content is preferably 0.60 mass% or more, and more preferably 0.65 mass% or more. Furthermore, it is preferably less than 0.80 mass%, and more preferably less than 0.75 mass%. If the Fe content is less than 0.60 mass%, the number density of these second-phase particles decreases, making it easier for recrystallized grains to grow during annealing, which leads to a decrease in ductility due to the increase in grain size. In contrast, by setting the Fe content to 0.60 mass% or more, the number density of second-phase particles increases, and the number of fine second-phase particles less than 1 μm increases. This hinders the movement of grain boundaries during annealing, thereby inhibiting the growth of recrystallized grains and suppressing the decrease in ductility due to the increase in grain size. This characteristic becomes even more pronounced when the Fe content is 0.65 mass% or more. On the other hand, when the Fe content is 0.80 mass% or more, the number density of second-phase particles acting as cathode sites increases, and the corrosion resistance of the aluminum alloy foil in a weakly acidic environment decreases. In contrast, by setting the Fe content to less than 0.80 mass%, the increase in the number density of second-phase particles acting as cathode sites can be suppressed, and the corrosion resistance of the aluminum alloy foil in a weakly acidic environment can be improved. This characteristic becomes even more pronounced when the Fe content is less than 0.75 mass%.

[0014] <Si (Silicon)> The aluminum alloy foil for packaging materials according to the present invention contains Si. Adding Si to an Al-Fe alloy promotes the crystallization and precipitation of Al-Fe second-phase particles. The Si content is preferably 0.50 mass% or less, more preferably 0.30 mass% or less, and more preferably 0.20 mass% or less. The lower limit of the Si content is not particularly limited, but if it is less than 0.01 mass%, there is a risk that the ductility will decrease due to coarsening of the microstructure during final annealing. If the Si content is greater than 0.50 mass%, the number density of coarse second-phase particles and elemental Si particles increases, and the corrosion resistance of the aluminum alloy foil in a weakly acidic environment decreases. By setting the Si content to 0.50 mass% or less, the increase in the number density of coarse second-phase particles and elemental Si particles can be suppressed, and the corrosion resistance of the aluminum alloy foil in a weakly acidic environment can be improved. In particular, this characteristic becomes even clearer when the Si content is less than 0.30 mass%.

[0015] <Other Trace Elements> The aluminum alloy foil for packaging materials according to the present invention contains other trace elements such as unavoidable impurities in addition to Fe and Si. Examples of trace elements including the aforementioned unavoidable impurities include Mn (manganese), Mg (magnesium), Cu (copper), Zn (zinc), Ti (titanium), Zr (zirconium), Cr (chromium), Ni (nickel), Ca (calcium), V (vanadium), B (boron), Ga (gallium), Bi (bismuth), Sn (tin), Na (sodium), Pb (lead), Sb (antimony), As (arsenic), In (indium), etc. Preferably, the content of each of the above elements is less than 0.1% by mass for each individual and less than 0.2% by mass in total.

[0016] <Thickness of Aluminum Alloy Foil for Packaging Material> The thickness of the aluminum alloy foil for packaging material according to the present invention is preferably 50 μm or more, more preferably 55 μm or more. It is also preferably 150 μm or less, and more preferably 120 μm or less. Within the above range, and especially within the preferred range, it can be suitably used as a packaging material. If it is less than 50 μm, good formability cannot be obtained during the forming process of the aluminum alloy foil, which may cause cracks and pinholes. If it is thicker than 150 μm, polymerization rolling, which is performed at the end of the rolling process, may become difficult.

[0017] <Molded Body> The aluminum alloy foil for packaging materials according to the present invention can be manufactured as a molded body by known molding methods. For example, press molding using known molds can be employed. The resulting molded body can be used as a packaging material. Examples include packaging materials for food, pharmaceutical tablets, and lithium-ion batteries.

[0018] <Method for Manufacturing Aluminum Alloy Foil> [1. Ingot Production Process] The aluminum alloy foil for packaging materials according to the present invention first involves the production of an ingot containing Fe in a proportion within the aforementioned range, Si in a proportion within the aforementioned range, with the remainder being Al and other trace elements including unavoidable impurities. This process can be performed, for example, by melting aluminum ingot and solidifying the molten metal obtained by adding Fe or Al-Fe matrix alloy and Si or Al-Si matrix alloy to cast it. The casting method is not particularly limited and can include semi-continuous casting, continuous casting, and die casting.

[0019] [2. Homogenization Heat Treatment Process] Next, it is important to perform homogenization heat treatment on the obtained ingot. Specifically, in order to eliminate microsegregation during casting or to control the size and number density of the second phase particles, it is necessary to perform homogenization heat treatment at a temperature of 550°C or higher but less than 650°C. If the temperature of the homogenization heat treatment is below 550°C, the size and number density of the second phase particles cannot be controlled, and the desired properties may not be obtained. If the temperature of the homogenization heat treatment is above 650°C, the temperature will exceed the solidus temperature, and the ingot may melt due to the mixing of liquid and solid phases. For production efficiency, the heat treatment time for homogenization is preferably 30 hours or less.

[0020] [3. Rolling Process] A process of rolling the ingot after the above homogenization heat treatment to obtain a foil is included. As a method for performing this rolling, known rolling methods can be widely adopted and are not particularly limited. Further, hot rolling or cold rolling may be performed on the ingot after the above homogenization heat treatment or a cast plate obtained by appropriately rolling the ingot. From the viewpoint of increasing the rolling efficiency, it is preferable to provide a hot rolling process before the cold rolling process. The hot rolling is a method of heating the ingot after the above homogenization heat treatment or a cast plate obtained by appropriately rolling the ingot to about 300°C to 500°C and then performing rolling. The thickness after hot rolling is not particularly limited, but it is preferably 4 to 8 mm.

[0021] The cold rolling is a method of rolling the material at room temperature. By performing cold rolling on the obtained ingot, a cast plate obtained by appropriately rolling the ingot, or a cast plate obtained by performing hot rolling on the ingot after the above homogenization heat treatment or a cast plate obtained by appropriately rolling the ingot, a rolled foil with a predetermined thickness can be obtained. Further, intermediate annealing may be performed as necessary during the cold rolling. Also, the number of cold rolling passes may be appropriately set according to the target final thickness, and the last cold rolling performed is preferably tandem rolling.

[0022] [4. Intermediate Annealing] It is preferable to perform intermediate annealing for the purpose of improving rolling properties and controlling the structure in the above rolling process. The temperature of the intermediate annealing is preferably carried out at 200°C or higher and lower than 500°C. When the temperature of the intermediate annealing is 500°C or higher, the ductility decreases due to the coarsening of the structure. When it is less than 200°C, the rolling properties are not sufficiently improved. The intermediate annealing time is preferably 30 hours or less in terms of production efficiency. By performing intermediate annealing, the thickness of the aluminum alloy foil can be easily adjusted.

[0023] [5. Final Annealing Process] In the method for manufacturing an aluminum alloy foil for packaging materials according to the present invention, after cold rolling to the final thickness, it is important to perform a final annealing for the purpose of improving ductility. The temperature of the final annealing is preferably carried out at 200 °C or higher and less than 400 °C. When the temperature of the final annealing is less than 200 °C, in addition to insufficient annealing resulting in insufficient improvement in ductility, there is a risk of adversely affecting the forming process because the rolling oil adhering to the surface of the aluminum alloy foil cannot be completely removed. When the temperature of the final annealing is 400 °C or higher, there is a risk that the desired strength and ductility cannot be obtained due to coarsening of the structure. The final annealing time is preferably 100 hours or less in terms of production efficiency.

[0024] <Properties of Aluminum Alloy Foil> The 0.2% proof stress, tensile strength, elongation at break, and number density of second-phase particles of the aluminum alloy foil obtained in the present invention will be described below. The 0.2% proof stress, tensile strength, and elongation at break can basically be measured by a method conforming to the tensile test method specified in JIS Z 2241 (2011 edition). The test piece (sample) used in the test is in a strip shape, with a length in the rolling direction of 200 mm and a length in the direction perpendicular to the rolling direction of 15 mm. The tensile test speed is 10 mm / min. At the gauge length (distance between chucks), which is the length of the part where elongation is measured in the rolling direction of the test piece (sample), the original gauge length (distance between chucks before the test), which is the gauge length measured before the test, is 100 mm, and the final gauge length measured after breakage is taken as the distance between chucks at breakage.

[0025] [0.2% Proof Stress] The aluminum alloy foil for packaging materials according to the present invention has a 0.2% proof stress in the tensile test in the rolling direction of 20 N / mm ２ or more and 35 N / mm ２ or less, and preferably 20 N / mm ２ or more and 32 N / mm ２ or less. By setting it to 35 N / mm ２ or less, the packaging material made of aluminum alloy foil can exhibit the characteristic of suppressing breakage or crack generation during the forming process, and 32 N / mm ２This characteristic can be further clearly demonstrated by the following: On the other hand, the 0.2% yield strength is 35 N / mm². ２ If the yield strength exceeds 20 N / mm², packaging materials made of aluminum alloy foil will fracture or crack prematurely during the molding process. The detailed mechanism is not clear, but it is presumed to be as follows: When aluminum alloy foil is molded, it changes from elastic deformation to plastic deformation as it deforms during the molding process. If the yield strength is high, the force it can withstand in the elastic deformation range is too great, so when it changes to plastic deformation, it is accompanied by a large impact, causing cracks or pinholes to occur prematurely. ２ It is difficult to soften it to a degree less than this.

[0026] [Tensile Strength] The aluminum alloy foil for packaging materials according to the present invention has a tensile strength of 60 N / mm² in a tensile test in the rolling direction. ２ 90N / mm or more ２ It has the following characteristics and 60 N / mm ２ More than 85N / mm ２ The following is preferable: 90 N / mm ２ By doing the following, it is possible to suppress the occurrence of cracks and pinholes in the packaging material made of aluminum alloy foil during the molding process, resulting in a load capacity of 85 N / mm ２ This characteristic can be made even clearer by doing the following. On the other hand, the tensile strength is 90 N / mm ２ If the tensile strength exceeds 60 N / mm², packaging materials made of aluminum alloy foil will develop cracks or pinholes prematurely during the molding process. The detailed mechanism is not clear, but it is presumed to be as follows: When aluminum alloy foil is molded, it reaches the plastic deformation region as it deforms during the molding process. If the tensile strength of aluminum is high in the plastic deformation region, it resists deformation, causing cracks or pinholes to develop prematurely. ２ It is difficult to soften it to a degree less than this.

[0027] [Elongation at Break] The aluminum alloy foil for packaging materials according to the present invention is characterized by having an elongation at break of 25% or more in the rolling direction, and preferably 28% or more. By setting the elongation at break to 25% or more, it is possible to suppress the occurrence of cracks and pinholes in the packaging material made of aluminum alloy foil during molding, and it is possible to expect high formability. By setting the elongation at break to 28% or more, this characteristic can be further clearly demonstrated. On the other hand, if the elongation at break is lower than 25%, there is a risk that cracks or pinholes will occur early in the packaging material made of aluminum alloy foil during molding. The thickness when measuring the elongation at break is not particularly limited, but it is sufficient if the above characteristics are obtained at a commonly used thickness, specifically a predetermined thickness in the range of 50 to 150 μm, preferably 55 to 120 μm (for example, 70 μm).

[0028] [Number Density of Second-Phase Particles] Generally, second-phase particles exist in aluminum alloy foil. Below, we will examine the number density of second-phase particles of a predetermined size range present on the surface of the aluminum alloy foil according to the present invention. The number density of these second-phase particles of a predetermined size range can be calculated using a backscattered electron image obtained by observing with a field emission scanning electron microscope (FE-SEM) under conditions of an acceleration voltage of 15 kV, a working distance of 10 mm, and a magnification of 500x. The backscattered electron image is captured, second-phase particles of a predetermined size range are extracted, and the number density within the rectangle is calculated using image processing software.

[0029] Furthermore, regarding the second-phase particles present on the surface of the aluminum alloy foil according to the present invention, the number density of second-phase particles with an equivalent circular diameter of 0.2 μm or more and less than 1 μm (particles / mm²) ２ ) is denoted as [A], and similarly, the number density (particles / mm²) of second-phase particles with an equivalent circular diameter of 1 μm or more and less than 2 μm. ２ ) is [B], and the number density of second-phase particles with an equivalent circular diameter of 2 μm or more and less than 3 μm (particles / mm²) ２ ) is [C], and the number density of second-phase particles with an equivalent circular diameter of 3 μm or more and less than 4 μm (particles / mm²) ２ ) is [D], and the number density of second-phase particles with an equivalent circular diameter of 4 μm or more (particles / mm²) ２ ) is denoted as [E].

[0030] [[[A]+[B]+[C]+[D]+[E]]] The [A]+[B]+[C]+[D]+[E] of the aluminum alloy foil for packaging materials according to the present invention (i.e., the number density (particles / mm²) of second-phase particles with an equivalent circular diameter of 0.2 μm or more present on the foil surface) ２ )) is 9000 pieces / mm ２ More than 50000 pieces / mm ２ It has the following characteristics, and 11,000 pieces / mm ２ More than 25000 pieces / mm ２ The following is preferable: 9000 pieces / mm ２ More than 50000 pieces / mm ２ As described below, the number density of second-phase particles acting as cathode sites is reduced, improving the corrosion resistance of aluminum alloy foil in weakly acidic environments, improving formability, suppressing the growth of recrystallized grains during annealing, maintaining grain size, and preserving ductility, resulting in a density of 11,000 particles / mm². ２ More than 25000 pieces / mm ２ This characteristic can be made even clearer by doing the following. On the other hand, if [A] + [B] + [C] + [D] + [E] is 50,000 units / mm ２ If the number of particles is higher, the number density of the second phase particles acting as cathode sites increases, which reduces the corrosion resistance of the aluminum alloy foil in a weakly acidic environment, as well as its formability. ２ If the value is less than this, recrystallized grains grow more easily during annealing, leading to a decrease in ductility due to the increased grain size.

[0031] [[[D] + [E]]] The [D] + [E] of the aluminum alloy foil for packaging materials according to the present invention (i.e., the number density (particles / mm²) of second-phase particles with an equivalent circular diameter of 3 μm or more present on the foil surface) ２ )) is 200 pieces / mm ２ It has the following characteristics, and produces 150 pieces / mm ２ The following is preferable: 200 pieces / mm ２ As described below, the coarse second-phase particles that act as cathode sites are suppressed, resulting in improved corrosion resistance of aluminum alloy foil in weakly acidic environments, with a density of 150 particles / mm². ２This characteristic can be made even clearer by doing the following. On the other hand, if [D] + [E] is 200 units / mm ２ If the amount is greater, there will be more coarse second-phase particles that act as cathode sites, reducing the corrosion resistance of aluminum alloy foil in a weakly acidic environment.

[0032] [[([B] + [C] + [D] + [E]) / ([A] + [B] + [C] + [D] + [E])]] The ([B] + [C] + [D] + [E]) / ([A] + [B] + [C] + [D] + [E]) of the aluminum alloy foil for packaging materials according to the present invention (that is, the number density of second phase particles with an equivalent circular diameter of 0.2 μm or more present on the foil surface (particles / mm²) ２ The number density (particles / mm²) of second-phase particles with an equivalent circular diameter of 1 μm or more relative to ) ２ The ratio of the material is characterized by being 0.1 or higher, preferably 0.21 or higher, and more preferably 0.25 or higher. Since the ratio is 0.1 or higher, moldability can be improved, and this characteristic can be made even clearer by setting it to 0.21 or higher. On the other hand, when the ratio is less than 0.1, moldability tends to decrease.

[0033] The present invention will be further clarified by providing examples and comparative examples below. First, the test method used in this example is shown below.

[0034] (Test Method) <Measurement of Aluminum Alloy Foil Composition> The alloy composition of the aluminum alloy foil was measured by inductively coupled plasma atomic emission spectrometry. The measuring instrument used was the ICPS-8100 manufactured by Shimadzu Corporation. The detection limit for each element using the above measurement method is 0.01%. Therefore, in Table 1 below, values ​​below the detection limit are indicated as "<0.01".

[0035] <Tensile Test> A tensile testing machine (Strograph VES5D, manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used to measure the 0.2% yield strength, tensile strength, and elongation at break of aluminum alloy foil at a thickness of 70 μm. The tensile test was conducted at a speed of 10 mm / min and a chuck distance of 100 mm. The aluminum alloy foil was cut to a size of 15 mm wide x 200 mm long so that the tensile direction was the rolling direction, and this was used as the sample. Each test was performed three times, and the average value of the elongation at break at the chuck distance was calculated. For foils with a thickness other than 70 μm, the elongation at break was measured by manufacturing aluminum alloy foil with a thickness of 70 μm under the same conditions, and the elongation at break was measured using this foil. Therefore, the elongation at break values ​​for Examples 1-4, 6-10, 12-14, 16, and Comparative Examples 1, 2, 4-6, 8, 9, and 11-15 represent the values ​​of foil manufactured under the same conditions, except that the thickness was 70 μm.

[0036] <Erichsen Test> An Erichsen test was conducted to measure the plastic deformation characteristics, i.e., formability, of aluminum alloy foil during stretching. An Erichsen test machine (516-M, manufactured by Yasuda Seiki Seisakusho Co., Ltd.) was used to measure the Erichsen value of the aluminum alloy foil. The test was conducted at a test speed of 15 mm / min, with a hemispherical punch tip of 20 mm in diameter, and the forming depth at which a crack occurred in the aluminum alloy foil sample was measured. As the grease applied to the sample during the test, spray-type high grease: NX20 (manufactured by Ichinen Chemicals Co., Ltd.) was used, and the grease was applied only to the sample surface that came into contact with the test punch. As a result, samples with an Erichsen value of 6.50 mm or higher were evaluated as having sufficient formability. Each test was performed three times, and the average value was calculated.

[0037] <Corrosion Resistance Evaluation Test in a Weakly Acidic Environment> The corrosion resistance evaluation of the aluminum alloy foil according to the present invention was carried out in a weakly acidic environment. A sample of aluminum alloy foil cut to a size of 40 mm x 40 mm was immersed in an aqueous solution containing 3% by mass of sodium chloride and 3% by mass of acetic acid at 40°C for 2 days (48 hours). The mass was measured before and after immersion, and the loss of dissolution per unit surface area was calculated. As a result, the loss of dissolution per unit surface area of ​​the sample was 3.60 μg / mm². ２Materials below a certain threshold were evaluated as having sufficient corrosion resistance. Each test was conducted twice, and the average value was calculated.

[0038] <Distribution of Second Phase Particles on the Aluminum Alloy Foil Surface> To measure the number density of second phase particles present on the aluminum alloy foil surface according to the present invention, backscattered electron images obtained by observation with a field emission scanning electron microscope (FE-SEM) were used. Backscattered electron images were taken under the conditions of an acceleration voltage of 15 kV, a working distance of 10 mm, and a magnification of 500x. Specifically, backscattered electron images were first obtained for 10 randomly selected rectangular fields on the surface of the aluminum alloy foil sample. Each rectangular field was 0.04287 mm. ２ A rectangular field of view (179.3 μm × 239.1 μm) was used. The backscattered electron images of each rectangular field of view were binarized using image processing software (WinROOF2023, manufactured by Mitani Corporation) under the condition of brightness between 100 and 255, thereby extracting second-phase particles with equivalent circle diameters of 0.2 μm to less than 1 μm, 1 μm to less than 2 μm, 2 μm to less than 3 μm, 3 μm to less than 4 μm, and 4 μm or more. The number density within the rectangle was calculated for the extracted second-phase particles using the aforementioned image processing software, and the average value of the calculation results obtained from 10 rectangular fields of view was used as the evaluation result. As an example of a backscattered electron image before the aforementioned binarization process, the backscattered electron image of the aluminum alloy foil surface of Example 1 is shown in Figure 1. The backscattered electron image before binarization was captured by adjusting the contrast so that the aluminum matrix was black and the second phase particles were white, as shown in Figure 1. After that, binarization was performed using the aforementioned image processing software.

[0039] (Examples 1-16, Comparative Examples 1-15) Aluminum alloys adjusted to the alloy compositions shown in Table 1 were melted, and ingots were obtained by casting. After surface machining of the ingot surface, homogenization heat treatment was performed under the conditions described in Table 2, and then cold rolling was carried out. When the thickness after cold rolling was 0.45 mm, intermediate annealing was performed at 390°C for 3 hours. After that, cold rolling was carried out to the final thickness shown in Table 3, and final annealing was performed under the conditions described in Table 2 to obtain aluminum alloy foil. The above tests were performed on the obtained aluminum alloy foil. The evaluation results are shown in Table 3.

[0040]

[0041]

[0042]

[0043] (Results) Examples 1 to 16 obtained excellent moldability and corrosion resistance because the Fe and Si content was within the specified range and the distribution of second-phase particles was controlled. Comparative Examples 1, 2, and 4 did not obtain sufficient moldability and corrosion resistance because the Fe content exceeded the specified range and the distribution of second-phase particles was outside the specified range. Comparative Examples 3 and 15 did not obtain sufficient corrosion resistance because the Fe content exceeded the specified range and the distribution of second-phase particles was outside the specified range. Comparative Examples 5, 6, and 7 did not obtain sufficient corrosion resistance because the Fe content exceeded the specified range. Comparative Examples 8 and 9 had Fe and Si content within the specified range, but did not obtain sufficient moldability and corrosion resistance because the distribution of second-phase particles was outside the specified range. Comparative Example 10 did not obtain sufficient moldability because the Fe content was below the specified range, resulting in low elongation at break. Comparative Example 11 had an Fe content below the specified level, the distribution of second-phase particles was outside the specified range, and the elongation at break was low, resulting in insufficient moldability. Comparative Example 12 had a Si content above the specified level and the distribution of second-phase particles was outside the specified range, resulting in insufficient corrosion resistance. Comparative Examples 13 and 14 had low elongation at break, resulting in insufficient moldability.

Claims

1. An aluminum alloy foil containing Fe and Si, with the remainder being Al and other trace elements including unavoidable impurities, wherein the Fe content is 0.60% by mass or more and less than 0.80% by mass, and the Si content is 0.50% by mass or less, and the number density (particles / mm²) of second-phase particles present on the surface of the aluminum alloy foil with equivalent circle diameters of 0.2 μm or more and less than 1 μm, 1 μm or more and less than 2 μm, 2 μm or more and less than 3 μm, 3 μm or more and less than 4 μm, and 4 μm or more. ２ When these are denoted as [A], [B], [C], [D], and [E] respectively, then [A] + [B] + [C] + [D] + [E] equals 9000 units / mm². ２ More than 50000 pieces / mm ２ The following applies: [D] + [E] = 200 units / mm ２ The following conditions must be met: ([B] + [C] + [D] + [E]) / ([A] + [B] + [C] + [D] + [E]) is 0.1 or greater, and the 0.2% proof stress is 20 N / mm². ２ 35N / mm or more ２ The following is true, and the tensile strength is 60 N / mm². ２ 90N / mm or more ２ The following aluminum alloy foil for packaging materials, characterized by having a break elongation of 25% or more.

2. The aluminum alloy foil for packaging materials according to claim 1, characterized in that its thickness is 50 μm or more and 150 μm or less.

3. A method for producing aluminum alloy foil for packaging materials, comprising: a casting step of producing an ingot by casting molten aluminum alloy whose composition is adjusted to have an Fe content of 0.60% by mass or more and less than 0.80% by mass, a Si content of 0.50% by mass or less, and the remainder consisting of Al and other trace elements including unavoidable impurities; a homogenization heat treatment step of subjecting the ingot to homogenization heat treatment at 550°C or more and less than 650°C; a rolling step of producing aluminum alloy foil by subjecting the homogenization heat-treated ingot to rolling; and a final annealing step of subjecting the aluminum alloy foil to final annealing.

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