Aluminum alloy foil

Abstract

Providing an aluminum alloy foil having high formability. 【Solution means】An aluminum alloy foil characterized by containing Fe: 0.8 to 2.0% by mass, and the balance: Al and unavoidable impurities, and satisfying the following formula (1): R×E×T≧10 …(1) However, each symbol in the above formula is represented by the following formulas (2) to (4), respectively, R=r45 - 0.5 …(2) E=e - 5.0 …(3) T=t - 20 …(4) The above R, E, and T are greater than 0, r45 in the above formula (2) is the r value in the direction of 45° with respect to the rolling direction, e in the above formula (3) is the Erichsen value (mm), t in the above formula (4) is the thickness (μm) of the aluminum alloy foil.

Description

【Technical Field】 【0001】 The present invention relates to an aluminum alloy foil. 【Background Art】 【0002】 Aluminum alloy foils used as packaging materials for foods, lithium-ion batteries, etc. are processed into product shapes by applying large deformations through press forming or the like. Therefore, aluminum alloy foils used as packaging materials are required to have high formability. Also, from the perspective of weight reduction, the thickness of aluminum alloy foils is being reduced, and it is also required that high formability can be maintained even when the thickness is reduced. 【0003】 For example, Patent Document 1 discloses an aluminum alloy foil containing 0.05% by mass or more and less than 2.5% by mass of Mn, 0.081% by mass or more and less than 1.7% by mass of Fe, less than 1.5% by mass of Si, less than 1.0% by mass of Cu, with the balance being Al and unavoidable impurities, the total of the Mn, Fe, Si, and Cu contents being less than 3.0% by mass, and the number of second-phase particles having a circle equivalent diameter exceeding 1.5 μm present on the surface of the aluminum alloy foil being less than 1000 per mm 2 The following, and the ratio of the <100> crystal orientation measured by the EBSD method on the surface of the aluminum alloy foil being 0.01 or less, and the ratio of the <101> crystal orientation being 0.05 or more, is disclosed. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2022-63563 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 However, when the inventors evaluated the formability of aluminum alloy foils with a small average grain size, such as conventional aluminum alloy foils, they found that, depending on the product shape, the formability could not be achieved, and pinholes or cracks may occur in the aluminum alloy foil. In particular, when the aluminum alloy foil is thin, there are many product shapes in which the occurrence of pinholes or cracks cannot be prevented simply by controlling the grain size or increasing the elongation. Therefore, there is a concern that the demand for lightweight aluminum alloy foil cannot be adequately met. Thus, the inventors have found that simply using aluminum alloy foil with a small average grain size and high elongation in uniaxial tensile tests may not be sufficient to achieve high formability for the various product shapes required in recent years. 【0006】 This invention has been made in view of the above circumstances, and aims to provide an aluminum alloy foil with high formability. [Means for solving the problem] 【0007】 The gist of this invention is as follows: [1] Fe: 0.8~2.0 mass%, and The remainder contains Al and unavoidable impurities. Aluminum alloy foil characterized by satisfying the following formula (1): R×E×T≧10 …(1) However, each symbol in the above formula (1) is represented by the following formulas (2) to (4), R = r45 - 0.5 …(2) E = e-5.0 …(3) T = t - 20 …(4) The aforementioned R, E, and T are greater than 0. In equation (2) above, r45 is the r value in the direction 45° with respect to the rolling direction. In the above formula (3), e is the Erichsen value (mm), In equation (4) above, t is the thickness (μm) of the aluminum alloy foil. [2] The aluminum alloy foil according to [1], characterized in that the 0.2% yield strength in a uniaxial tensile test at a 45° angle to the rolling direction is 100 MPa or less. [3] The aluminum alloy foil according to [1] or [2], characterized in that the local elongation in a uniaxial tensile test at a 45° angle to the rolling direction is 1.0% or more. [Effects of the Invention] 【0008】 According to the present invention, it is possible to provide an aluminum alloy foil with high formability. [Brief explanation of the drawing] 【0009】 [Figure 1] This is a plan view showing an example of an aluminum alloy foil according to the present invention. [Figure 2] This figure shows the planar shape of a square punch used in square tube forming tests. [Modes for carrying out the invention] 【0010】 In order to obtain an aluminum alloy foil with high formability, the inventors conducted research and found that when the thickness of the aluminum alloy foil, the Erichsen value (known as one of the formability evaluation methods), and the r value (Lankford value) in the direction 45° to the rolling direction satisfy a specific formula, an aluminum alloy foil that can accommodate various shapes can be obtained. 【0011】 Hereinafter, an example of an aluminum alloy foil according to an embodiment of the present invention will be described in detail based on the attached drawings. Note that, for convenience, the drawings used in the following description may show enlarged portions of key features to make them easier to understand. 【0012】 Figure 1 is a plan view showing an example of an aluminum alloy foil according to this embodiment. The aluminum alloy foil 1 shown in Figure 1 is a foil obtained by hot rolling and cold rolling of an ingot obtained by a casting method. In Figure 1, it is depicted as a strip-shaped body with a constant width and its length oriented from left to right. 【0013】 The rolling direction of the aluminum alloy foil 1 is the left-right direction (the length direction of the strip-shaped foil) shown in FIG. 1. For the sake of convenience, the direction of 0° with respect to the rolling direction means the left-right direction in FIG. 1, the direction of 45° with respect to the rolling direction means the direction of the arrow marked 45° in FIG. 1, and the direction of 90° with respect to the rolling direction means the direction of the arrow marked 90° in FIG. 1. In the aluminum alloy foil 1, the direction of 90° with respect to the rolling direction, in other words, means the width direction of the strip-shaped aluminum alloy foil 1 (the up-down direction of the paper surface in FIG. 1). 【0014】 Hereinafter, the aluminum alloy foil 1 according to the present embodiment will be described in detail. In the following description, the reference numerals in the drawings may be omitted. In addition, in the numerical limitation range described with "~" sandwiched therebetween, the lower limit value and the upper limit value are included in that range. The numerical values indicated by "less than" and "more than" do not include those values in the numerical range. 【0015】 First, the composition of the aluminum alloy foil will be described. The aluminum alloy foil contains Fe: 0.8 to 2.0% by mass, and the balance: Al and inevitable impurities. 【0016】 Fe: 0.8 to 2.0% by mass Fe crystallizes as an Al-Fe-based intermetallic compound during casting. When the size of the Al-Fe-based intermetallic compound is in a preferable range, this Al-Fe-based intermetallic compound becomes a recrystallization site during annealing, and thus has the effect of refining the recrystallized grains. When the Fe content is less than 0.8% by mass, the distribution density of the Al-Fe-based intermetallic compound becomes low, the effect of refining the recrystallized grains becomes low, and the finally obtained recrystallized grains become coarse. As a result, the formability of the aluminum alloy foil deteriorates. Therefore, the Fe content should be 0.8% by mass or more. The Fe content is preferably 1.0% by mass or more or 1.2% by mass or more. On the other hand, when the Fe content exceeds 2.0% by mass, the effect of grain refinement saturates or decreases, and furthermore, the size of the Al-Fe intermetallic compound generated during casting becomes very large, resulting in a decrease in the elongation, formability, and rolling property of the aluminum alloy foil. Therefore, the Fe content should be 2.0% by mass or less. The Fe content is preferably 1.8% by mass or less or 1.6% by mass or less. 【0017】 The remainder of the composition of the aluminum alloy foil according to the present embodiment consists of Al and inevitable impurities. In the present embodiment, inevitable impurities refer to elements that are inevitably mixed during the production of the aluminum alloy foil. The inevitable impurities may be included within a range that does not affect the characteristics of the aluminum alloy foil according to the present embodiment. Examples of the inevitable impurities include elements such as silicon (Si), magnesium (Mg), chromium (Cr), manganese (Mn), copper (Cu), zinc (Zn), titanium (Ti), vanadium (V), gallium (Ga), nickel (Ni), boron (B), zirconium (Zr), etc. Si may be included at 0.150% by mass or less. Also, the other elements may each be included at 0.0500% by mass or less in one or more kinds. Also, the total amount of the inevitable impurities is preferably 0.5% by mass or less. 【0018】 The aluminum alloy foil according to the present embodiment satisfies the following formula (1). R×E×T≧10.0 …(1) However, each symbol in the above formula (1) is represented by the following formulas (2) to (4) respectively, R=r45-0.5 …(2) E=e-5.0 …(3) T=t-20 …(4) The above R, E, and T are greater than 0, r45 in the above formula (2) is the r value in the direction of 45° with respect to the rolling direction, e in the above formula (3) is the Erichsen value (mm), t in the above formula (4) is the thickness (μm) of the aluminum alloy foil. 【0019】 When evaluating the formability of aluminum alloy foil, evaluation using the Erichsen value obtained by the Erichsen test is generally well known. The inventors also confirmed that the formability of aluminum alloy foil can be evaluated to some extent using the Erichsen value. However, with products of complex shapes, localized concentration of plastic deformation occurs, and many phenomena were observed where the Erichsen value, which evaluates the formability of the entire material, does not correlate. In response to this, the inventors found that the r value in the direction 45° to the rolling direction is important when forming into complex shapes. Furthermore, they found that aluminum alloy foil exhibiting higher formability than conventional foils satisfies a relational expression that includes thickness, Erichsen value, and r value. Equation (1) above was derived based on these findings. 【0020】 If the above formula (1) is not satisfied, that is, if the left side of the above formula (1) is less than 10.0, high formability cannot be obtained in the aluminum alloy foil. For this reason, the left side of the above formula (1) should be 10.0 or more. Preferably, the left side of the above formula (1) is 12.0 or more, 13.0 or more, or 15.0 or more. The upper limit of the left side of equation (1) above is not particularly limited, but it may be set to 220.0 or less, 80.0 or less, or 70.0 or less. 【0021】 In order to obtain the desired formability in aluminum alloy foil, it is necessary that the above formula (1) is satisfied, and furthermore, that R, E, and T in formula (1) are greater than 0. That is, r45 in formula (2) is greater than 0.5, e in formula (3) is greater than 5.0, and t in formula (4) is greater than 20. The following explains each of these points. 【0022】 r45:0.5 In equation (2) above, r45, which is the r value in the direction 45° to the rolling direction, is greater than 0.5. The r value (Rankford value) is a numerical value that represents the ease with which aluminum alloy foil is thinned, and is known as an important value for evaluating formability. The inventors have found that for forming aluminum alloy foil, increasing the r value in the direction 45° to the rolling direction can improve the formability of products with complex shapes. Therefore, r45 is greater than 0.5. Preferably, r45 is 0.9 or more, or 1.1 or more. 【0023】 r45 is calculated from the degree of thinning at the fracture point after performing a tensile test on the aluminum alloy foil at a 45° angle to the rolling direction. Specifically, it is obtained by determining the ratio of the true strain in the width direction to the true strain in the thickness direction of a test piece obtained by applying uniaxial tensile stress at a 45° angle to the rolling direction to a test piece taken from the aluminum alloy foil. The tensile test is performed in accordance with JIS Z 2241:2022, using a universal tensile testing machine (Shimadzu Corporation, AGS-X 10kN) and a tensile speed of 5 mm / min. The strain change during the test is measured by the digital image correlation method (DIC method), and the r value is calculated from the strain in the tensile and width directions within the range of uniform elongation of 0.2% yield strength or higher. 【0024】 e: More than 5.0mm Aluminum alloy foil can be molded into various products, and their shapes vary widely depending on the application and product. While the Erichsen test is generally well-known for evaluating formability, the inventors have found that an Erichsen value of 5.0 mm or more is the minimum condition for aluminum alloy foil to exhibit a certain level of formability in various molding methods. If the Erichsen value is 5.0 mm or less, formability may be drastically reduced in some molding methods. Therefore, the Erichsen value, e in formula (3) above, is set to be greater than 5.0 mm. Preferably, e is 6.0 mm or more, or 7.0 mm or more. There is no particular upper limit for e, but it may be 10.0 mm or less, or 8.0 mm or less. 【0025】 The Erichsen test is measured by performing the Erichsen test using the following method. An Erichsen tester is used to deep draw aluminum alloy foil, and the height of the cup's sidewall before cracking occurs is measured. The processing conditions are as follows: punch diameter of 33 mm (flat-head punch), die inner diameter of 33.7 mm, drawing ratio of 1.75, clearance between punch and die of 0.35 mm, and wrinkle suppression pressure of 5 kN. The cup's sidewall height is measured with a digital micrometer. The sidewall height before cracking occurs is defined as the Erichsen value. The Erichsen value is obtained by measuring the Erichsen value for at least three or more aluminum alloy foils and calculating the average value. 【0026】 t: more than 20μm Thinner aluminum alloy foil contributes to weight reduction. However, if the thickness is too thin, the areas thinned after molding become weaker against external impacts. Considering the current practical usage environment, a thickness of more than 20 μm is considered necessary. Therefore, the thickness t of the aluminum alloy foil is set to more than 20 μm. Preferably, t is 30 μm or more, or 40 μm or more. There is no particular upper limit to the thickness t of the aluminum alloy foil, but it may be 150 μm or less, or 100 μm or less. The thickness t of the aluminum alloy foil is obtained by embedding the aluminum alloy foil in resin, exposing the surface perpendicular to the rolling direction, and accurately measuring it with a microscope. 【0027】 0.2% yield strength in uniaxial tensile test at a 45° angle to the rolling direction: 100 MPa or less While the 0.2% yield strength in aluminum alloy foil does not have a clear correlation with formability, a high 0.2% yield strength may indicate that recrystallization is not complete and that strain introduced during rolling remains. If recrystallization is not complete, the foil may lack flexibility and may not exhibit sufficient formability. Based on the inventors' research, it can be determined that recrystallization is sufficiently complete in aluminum alloy foil if the 0.2% yield strength in a uniaxial tensile test at a 45° angle to the rolling direction is 100 MPa or less. Therefore, it is preferable that the 0.2% yield strength in a uniaxial tensile test at a 45° angle to the rolling direction be 100 MPa or less. More preferably, the 0.2% yield strength is 80 MPa or less. 【0028】 Local elongation in a uniaxial tensile test at a 45° angle to the rolling direction: 1.0% or greater In tensile testing, the elongation is defined as total elongation (elongation from the start of the test to fracture), uniform elongation (elongation from the start of the test to maximum strength), and local elongation (elongation from maximum strength to fracture). Generally, total elongation is considered the most important characteristic, and in other materials, fracture almost always occurs near the maximum strength, so uniform elongation is often equivalent to total elongation. In aluminum alloy foil, deformability against local deformation is considered important, and the inventors have found that local elongation in tensile testing is important for this local deformability. Therefore, it is preferable that the local elongation in a uniaxial tensile test at a 45° angle to the rolling direction be 1.0% or more. More preferably, the local elongation is 3.0% or more. 【0029】 The 0.2% yield strength and local elongation of aluminum alloy foil are measured by tensile testing. A JIS No. 5 test specimen will be punched out from aluminum alloy foil at a 45° angle to the rolling direction (using Super Dumbbell®, manufactured by Dumbbell Co., Ltd.), and a tensile test will be performed in accordance with JIS Z 2241:2022. A universal tensile testing machine (AGS-X 10kN, manufactured by Shimadzu Corporation) will be used, and the tensile speed will be 5 mm / min. 【0030】 Before the tensile test, two lines are marked at 50 mm intervals (gauge length) along the longitudinal center of the test specimen. After the tensile test, the fracture surfaces are joined together and the distance l (mm) between the marks is measured. The total elongation is then calculated by dividing the elongation (mm) by the gauge length (l0: 50 mm) ((l-l0) / l0 × 100). Total elongation is the same as "elongation at fracture" as defined in JIS Z 2241:2022. 【0031】 Local elongation is calculated by subtracting the amount of strain at the point of maximum stress from the total elongation in the nominal stress-nominal strain curve obtained from the tensile test; that is, by subtracting the "total elongation at maximum test force" from the "elongation at fracture" in JIS Z 2241:2022. Furthermore, the 0.2% proof stress is defined as the stress at which a 0.2% strain occurs in the nominal stress-nominal strain curve obtained from the tensile test. 【0032】 Next, a preferred manufacturing method for producing aluminum alloy foil according to this embodiment will be described. The aluminum alloy foil according to this embodiment can be manufactured by known manufacturing methods, for example, by appropriately adjusting the composition of the aluminum alloy, rolling conditions, thickness, etc. 【0033】 The composition of the aluminum alloy can be adjusted by controlling the presence or absence and amount of at least one metal other than aluminum (for example, iron, copper, nickel, silicon, manganese, magnesium, chromium, zinc, titanium, etc.). The composition of the aluminum alloy is preferably as described above. 【0034】 Rolling conditions such as rolling rate, heating temperature, and heating time can be adjusted. For example, a method may include a process of homogenizing an aluminum or aluminum alloy ingot at approximately 500-600°C for 1-2 hours, a hot rolling process, a cold rolling process, an intermediate annealing process where the ingot is held at approximately 300-450°C for 1-10 hours, a cold rolling process where the rolling rate from the intermediate annealing to the final rolling is 80% or more, more preferably 90% or more, and a final annealing process where the ingot is held at approximately 250-400°C for 30-100 hours. Furthermore, in cold rolling after intermediate annealing, if processing heat is generated during rolling, recrystallization will proceed during rolling, causing a decrease in the r value and Erichsen value, which may make it impossible to satisfy equation (1). Therefore, it is preferable to suppress the rolling temperature to 115°C or below by adjusting the rolling speed and reduction ratio. [Examples] 【0035】 Next, the effects of one aspect of this disclosure will be described in more detail by reference to examples. However, the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effectiveness of this disclosure, and this disclosure is not limited to these examples of conditions. This disclosure may adopt various conditions as long as they do not depart from the gist of this disclosure and achieve the objectives of this disclosure. 【0036】 Aluminum alloy ingots were obtained by casting, and these ingots were subjected to a homogenization treatment by holding them at a temperature range of 500-600°C for 1-2 hours. Subsequently, hot rolling, cold rolling with intermediate annealing, and final annealing by holding them at a temperature range of 250-400°C for approximately 30-100 hours were performed. The cumulative reduction ratio from intermediate annealing to the final cold rolling was set at 80% or more. Furthermore, during cold rolling after intermediate annealing, the rolling temperature was kept below 115°C. However, for samples No. 11, 12, 14, and 15, the rolling temperature was set above 115°C. This yielded aluminum alloy foils with the compositions shown in Table 1. 【0037】 Underlined values ​​in Table 1 indicate that the value is outside the scope of the present invention or that the characteristic value is undesirable. Furthermore, the composition of the aluminum alloy foil included Al and unavoidable impurities as the remainder. 【0038】 For the aluminum alloy foil, the r value (r45), Erichsen value (e), thickness of the aluminum alloy foil (t), 0.2% yield strength in a uniaxial tensile test at 45° to the rolling direction, and local elongation were measured using the method described above. Furthermore, R, E, and T were calculated using the obtained r value (r45), Erichsen value (e), and thickness of the aluminum alloy foil (t) at 45° to the rolling direction, along with equations (2), (3), and (4) above, and the left side of equation (1) (R × E × T) was calculated. The results obtained are shown in Table 1. 【0039】 The formability of the aluminum alloy foil was evaluated by measuring the limiting form height. The limiting forming height was measured by a rectangular tube forming test. The rectangular tube forming test was performed on 40 μm thick aluminum alloy foil using a universal thin sheet forming tester (ERICHSEN Model 142 / 20) and a rectangular punch 2 (side length D=37 mm, corner chamfer diameter R=4.5 mm) as shown in Figure 2. The test conditions were: wrinkle suppression force: 10 kN, punch upward speed (forming speed) scale: 1, and mineral oil was applied as a lubricant to one side of the aluminum alloy foil (the side that the punch struck). A punch rising from the bottom of the device strikes the aluminum alloy foil, forming the foil. The maximum punch height achieved during three consecutive forming attempts without cracks or pinholes was defined as the limiting forming height (mm) for that aluminum alloy foil. The punch height was varied in 0.1mm increments. If the limit molding height was 8.0 mm or higher, it was judged to have particularly high moldability and was judged to pass, with "A" indicated in the table. If the limit molding height was 7.0 mm or higher but less than 8.0 mm, it was judged to have high moldability and was judged to pass, with "B" indicated in the table. If the limit molding height was less than 7.0 mm, it was judged to lack high moldability and was judged to fail, with "C" indicated in the table. 【0040】 [Table 1] 【0041】 As shown in Table 1, the aluminum alloy foil according to the example, which contains Fe: 0.8 to 2.0 mass%, with the remainder being Al and unavoidable impurities, and satisfies the following formula (1), exhibits high formability. 【0042】 On the other hand, the aluminum alloy foil in the comparative example does not exhibit high formability. In samples No. 8-14, the composition fell outside the above range or did not satisfy formula (1), resulting in poor moldability. [Explanation of symbols] 【0043】 1…Aluminum alloy foil 2... Punch

Claims

[Claim 1] Fe: 0.8 to 2.0 mass%, and The remainder contains Al and unavoidable impurities. Aluminum alloy foil characterized by satisfying the following formula (1): R × E × T ≥ 10 … (1) However, each symbol in formula (1) above is represented by the following formulas (2) to (4), R=r45-0.5...(2) E=e-5.0...(3) T=t-20...(4) The aforementioned R, E, and T are greater than 0. In the above equation (2), r45 is the r value in the direction 45° with respect to the rolling direction. In the above formula (3), e is the Erichsen value (mm), In formula (4) above, t is the thickness (μm) of the aluminum alloy foil. [Claim 2] The aluminum alloy foil according to claim 1, characterized in that the 0.2% yield strength in a uniaxial tensile test at a 45° angle to the rolling direction is 100 MPa or less. [Claim 3] The aluminum alloy foil according to claim 1 or 2, characterized in that the local elongation in a uniaxial tensile test at a 45° angle to the rolling direction is 1.0% or more.

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