Aluminum alloy plate for pull ring

Abstract

One aspect of the present disclosure provides an aluminum alloy plate for a tab in which the content of silicon (Si) is 0.20 mass% or more and 0.60 mass% or less, the content of iron (Fe) is 0.30 mass% or more and 0.70 mass% or less, the content of copper (Cu) is 0.11 mass% or more and 0.40 mass% or less, the content of manganese (Mn) is 0.7 mass% or more and 1.2 mass% or less, and the content of magnesium (Mg) is 1.1 mass% or more and 3.0 mass% or less. The plate thickness t (mm) and the tensile strength [sigma] B0 DEG (MPa) in the 0 DEG direction with respect to the rolling direction satisfy the following mathematical formula (1), and the ratio of the total area of Mg2Si particles having an area of 0.3 [mu] m2 or more in the L-ST cross section is 0.2% or less. (2.7 * t-0. 45) * sigma B0 degree > = 67 (1).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This international application claims priority from Japanese Patent Application No. 2023-067405 filed in the Japan Patent Office on April 17, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to an aluminum alloy plate for a pull ring. Background Art

[0004] In recent years, with growing environmental awareness, there has been a demand for aluminum alloy sheets that emit less carbon dioxide during the manufacturing process. The amount of new aluminum matrix metal added during the casting process indirectly impacts carbon dioxide emissions during the aluminum manufacturing process.

[0005] The production of new aluminum matrix metal consumes a lot of electricity in the refining process, resulting in a large amount of carbon dioxide emissions. Therefore, reducing the amount of new aluminum matrix metal mixed in and increasing the same-grade recycling rate can help reduce carbon dioxide emissions in aluminum alloy plate production.

[0006] Generally speaking, the amount of CO2 emitted when aluminum scrap is remelted and cast can be reduced to approximately one-thirtieth of that when new aluminum base metal is produced. Given the enormous volume of aluminum alloy sheet used worldwide for beverage cans, further increasing the recycling rate at this level is crucial for reducing the environmental burden.

[0007] Among them, compared with the can body made of 3104 aluminum alloy (AA3104 alloy), the upper limit of the component specifications of silicon (Si), iron (Fe), copper (Cu), manganese (Mn), etc. in the can cover mainly made of 5182 aluminum alloy (AA5182 alloy) is lower, so it is difficult to mix the scrap derived from the can material containing 3104 aluminum alloy.

[0008] For example, if can scrap (UBC: Used Beverage Can) generated on the market is mixed as is, based on the weight ratio of the can body to the can lid, it will contain more 3104 aluminum alloy components, and therefore will easily exceed the upper limit of the composition of 5182 aluminum alloy, requiring the use of new base metal to dilute the composition.

[0009] Therefore, compared to aluminum alloy sheets for can bodies, aluminum alloy sheets for pull tabs require more new base metal to adjust the composition to that of 5182 aluminum alloy, resulting in a lower recycling rate. Therefore, by changing the pull tab to an alloy whose composition is easily mixed with 3104 aluminum alloy, the use of new base metal in the pull tab can be significantly reduced.

[0010] Patent Document 1 discloses an aluminum alloy plate for a pull ring having a composition relatively close to that of 3104 aluminum alloy having an excellent recycling rate.

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: Japanese Patent Application Laid-Open No. 5-263175. Summary of the Invention

[0014] Problems to be solved by the invention

[0015] Using aluminum alloys with compositions similar to 3104 aluminum alloy for tabs can lead to reduced tab bending strength and toughness. For example, in can opening mechanisms like stay-on tabs that utilize a lever to pry open the notched portion, there is a risk of the tab bending during opening, leading to poor opening.

[0016] The tab bending strength is the maximum load applied to the tab's pull portion in the event of a tab bending due to a can opening failure. It is an indicator of the tab's resistance to bending. Therefore, a high tab bending strength is required to prevent can opening failures.

[0017] Generally speaking, as the thickness of the plate increases and the strength of the material increases, the bending strength of the pull ring increases. Therefore, the high-strength 5182 aluminum alloy containing a large amount of magnesium (Mg) is used in the pull ring.

[0018] In contrast, using conventional 3104 aluminum alloy for the pull tab significantly reduces its bending strength, increasing the risk of can opening failures. Furthermore, increasing the thickness of the sheet to increase the bending strength of the pull tab increases the weight and cost of the tab.

[0019] Furthermore, the material's toughness affects the formability of the pull ring. Low material toughness can lead to cracking, particularly in the bent portion of the pull ring. However, aluminum alloy sheets for pull rings with a composition similar to the conventional 3104 aluminum alloy cannot address either or both of the aforementioned issues: bending strength and toughness (formability).

[0020] One aspect of the present disclosure preferably provides an aluminum alloy plate for a pull ring, which can be mixed with scrap raw materials derived from can materials and can simultaneously achieve high pull ring bending strength and high toughness.

[0021] Solutions to the Problem

[0022] One embodiment of the present disclosure relates to an aluminum alloy plate for a pull ring, wherein a silicon Si content is 0.20 mass% or more and 0.60 mass% or less, an iron Fe content is 0.30 mass% or more and 0.70 mass% or less, a copper Cu content is 0.11 mass% or more and 0.40 mass% or less, a manganese Mn content is 0.7 mass% or more and 1.2 mass% or less, and a magnesium Mg content is 1.1 mass% or more and 3.0 mass% or less, and the remainder consists of aluminum Al and inevitable impurities, or contains aluminum and inevitable impurities, and further, the plate thickness t (mm) and the tensile strength σ in the direction at 0° relative to the rolling direction are B_0 ° (MPa) satisfies the following mathematical formula (1), and on the L-ST cross section, the area is 0.3 μm 2 The total area ratio of the above Mg2Si particles is 0.2% or less.

[0023] (2.7×t-0.45)×σ B_0 °≧67(1)

[0024] The above configuration allows for the mixing of scrap raw materials from can materials while simultaneously achieving high ring-bending strength and high toughness for the aluminum alloy sheet. In other words, a certain amount of scrap 3104 aluminum alloy from can bodies can be mixed in, thereby reducing the use of new base metal and reducing carbon dioxide emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of the repeated bending test.

[0026] Figure 2 This is an explanatory diagram of the L-ST cross section.

[0027] Figure 3 Graph showing the relationship between the value V and the tab bending strength in Examples. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments to which the present disclosure is applied will be described with reference to the accompanying drawings.

[0029] [1. First embodiment]

[0030] [1-1. Structure]

[0031] <Component>

[0032] The aluminum alloy plate for a pull ring of the present disclosure (hereinafter also simply referred to as an "alloy plate") contains aluminum (Al), silicon (Si), iron (Fe), copper (Cu), manganese (Mn), and magnesium (Mg).

[0033] The lower limit of the Si content is 0.20% by mass, preferably 0.27% by mass. If the Si content is less than 0.20% by mass, the amount of Si precipitated during the hot rolling and cold rolling after solution treatment is reduced, which may lead to insufficient tensile strength of the alloy plate.

[0034] Furthermore, the average Si content of 3104 aluminum alloy specified in JIS-H-4000:2014 is 0.30% by mass, and the average Si content of 5182 aluminum alloy specified in JIS-H-4000:2014 is 0.10% by mass. Therefore, by setting the Si content to 0.27% by mass or more, a large amount of 3104 aluminum alloy scrap can be mixed.

[0035] The upper limit of the Si content is 0.60% by mass, preferably 0.39% by mass. If the Si content exceeds 0.60% by mass, the difference between the solid solution temperature of Mg2Si and the solidus temperature of the aluminum matrix decreases, making it difficult to dissolve a large amount of Mg2Si in the aluminum alloy ingot during the homogenization process. In addition, coarse Mg2Si will reprecipitate during hot rolling. As a result, tensile strength and toughness are reduced.

[0036] Furthermore, by setting the Si content to 0.39% by mass or less, Mg2Si can be relatively easily dissolved in the homogenization process. Furthermore, since the precipitation of coarse Mg2Si during hot rolling is suppressed, good tensile strength and toughness can be obtained without the need for a post-hot-rolling heat treatment process.

[0037] The lower limit of the Fe content is 0.30 mass%, preferably 0.35 mass%. The average Fe content of 3104 aluminum alloy is 0.40 mass%, and the average Fe content of 5182 aluminum alloy is 0.18 mass%. Therefore, by setting the Fe content to 0.30 mass% or more, a large amount of 3104 aluminum alloy scrap can be mixed.

[0038] The upper limit of the Fe content is 0.70% by mass, preferably 0.55% by mass. If the Fe content exceeds 0.70% by mass, abnormally coarse Al-Fe-Mn or Al-Fe-Mn-Si intermetallic compounds (i.e., giant compounds) increase. As a result, crack propagation paths are generated, resulting in reduced toughness of the alloy plate.

[0039] Furthermore, by setting the Fe content to 0.55 mass % or less, when the amount of Mg added is increased, the crystallization of the coarse intermetallic compounds can be suppressed while improving the tensile strength and toughness of the alloy plate.

[0040] The lower limit of the content of Cu is 0.11% by mass, preferably 0.17% by mass. If the content of Cu is lower than 0.11% by mass, the Cu that improves tensile strength by solid solution or precipitation is insufficient, thereby causing the tensile strength of the alloy plate to reduce. In addition, by separating out Cu in the cold rolling process after hot rolling and solution treatment, the tensile strength of the alloy plate can be significantly improved.

[0041] Furthermore, the average Cu content of 3104 aluminum alloy is 0.15% by mass, and the average Cu content of 5182 aluminum alloy is 0.075% by mass. Therefore, by setting the Cu content to 0.11% by mass or more, a large amount of 3104 aluminum alloy scrap can be mixed.

[0042] The upper limit of the content of Cu is 0.40% by mass, preferably 0.25% by mass. If the content of Cu exceeds 0.40% by mass, coarse precipitates increase, thereby causing the toughness of the alloy plate to decrease. In addition, by setting the content of Cu to below 0.25% by mass, it is possible to increase the tensile strength without significantly compromising toughness.

[0043] The lower limit of the Mn content is 0.7% by mass, preferably 0.75% by mass. If the Mn content is less than 0.7% by mass, insufficient Mn is present to improve the tensile strength by solid solution or precipitation, resulting in reduced tensile strength of the alloy plate.

[0044] Furthermore, the average Mn content of 3104 aluminum alloy is 1.1% by mass, while the average Mn content of 5182 aluminum alloy is 0.35% by mass. Therefore, by setting the Mn content to 0.75% by mass or more, a larger amount of 3104 aluminum alloy scrap can be mixed compared to the conventional 5182 aluminum alloy.

[0045] The upper limit of the Mn content is 1.2% by mass, preferably 0.95% by mass. If the Mn content exceeds 1.2% by mass, abnormally coarse Al-Fe-Mn or Al-Fe-Mn-Si intermetallic compounds increase. As a result, crack propagation paths are generated, resulting in reduced toughness of the alloy plate.

[0046] The lower limit of the content of Mg is 1.1% by mass, preferably 2.2% by mass. If the content of Mg is less than 1.1% by mass, insufficient Mg is present to improve strength by solid solution, thereby reducing the tensile strength of the alloy plate. In addition, by precipitating Mg during cold rolling after hot rolling and solution treatment, the tensile strength of the alloy plate can be significantly improved.

[0047] The upper limit of the Mg content is 3.0% by mass, preferably 2.8% by mass. The average Mg content of 3104 aluminum alloy is 1.05% by mass, and the average Mg content of 5182 aluminum alloy is 4.5% by mass. Therefore, by setting the Mg content to 3.0% by mass or less, preferably 2.8% by mass or less, it is possible to mix a large amount of 3104 aluminum alloy scrap while reducing the amount of additional Mg-containing raw materials to be mixed.

[0048] The alloy plate may contain titanium (Ti). The upper limit of the content of Ti is preferably 0.10 mass %. By containing Ti, the ingot structure of the alloy plate is refined. In addition, the alloy plate may contain zinc (Zn). The upper limit of the content of Zn is preferably 0.25 mass %. In addition, the alloy plate may contain chromium (Cr). The upper limit of the content of Cr is preferably 0.10 mass %.

[0049] The alloy plate may contain unavoidable impurities within a range that does not significantly impair the performance of the alloy plate. Specifically, the alloy plate contains Si, Fe, Cu, Mn, Mg, Ti, Zn, and Cr within the aforementioned ranges, with the remainder consisting of aluminum and unavoidable impurities, or containing aluminum and unavoidable impurities. The upper limit of the total amount of unavoidable impurities is preferably 0.15% by mass. The remainder may contain substances other than aluminum and unavoidable impurities.

[0050] <Board thickness, material strength, and ring bending strength>

[0051] The relationship between the thickness t (mm) of the aluminum alloy plate disclosed in the present invention and the tensile strength σ in the direction of 0° relative to the rolling direction B_0 °(MPa) satisfies the following mathematical formula (1).

[0052] V=(2.7×t-0.45)×σ B_0 °≧67 (1)

[0053] Empirically, the bending strength of an aluminum alloy pull tab has a strong positive correlation with the value V (i.e., the left side of equation (1)), which is represented by the material strength and thickness of the aluminum alloy plate. Therefore, by setting the value V to 67 or greater, a pull tab having sufficient bending strength can be formed.

[0054] In addition, the tensile strength σ B_0 °Preferably 330 MPa or more. Thus, a pull ring having a sufficient pull ring bending strength value can be formed without significantly increasing the thickness of the alloy plate.

[0055] The mechanical significance of the relationship between the value V and the tab bending strength can be explained as follows. Specifically, when the tab is pulled to open a can, if the tab's resistance is lower than the load applied to the tab, plastic deformation begins due to localized material yielding before the scored portion opens properly. Tab bending occurs when this plastic deformation continues, causing the tab to bend.

[0056] Considering the cross section parallel to the bending ridge line at the position where the pull ring is bent, the resistance to the bending moment applied to the cross section due to pulling up the pull ring increases with the section modulus and 0.2% yield strength σ 0.2 The section modulus is a value inherent to the cross-sectional shape, and the 0.2% yield strength σ 0.2 is the yield strength of the material.

[0057] For example, if the shape of the tab is fixed, such as the common DRT company's stay-on tab, the greater the thickness of the plate, the higher the section modulus of the cross section. Therefore, the thickness and the 0.2% yield strength of the material can be used to determine the cross section modulus. 0.2 To illustrate the degree to which bending is easy to initiate due to the yielding and plastic deformation of the material during the bending of the pull ring.

[0058] In addition, the ring bending is a phenomenon that includes plastic deformation until the ring bending, so it is necessary to consider the work hardening of the material during plastic deformation. 0.2 When the pressure is low and plastic deformation starts early, if the amount of work hardening during plastic deformation is large, the progress of plastic deformation is suppressed, and the pull ring is not easily bent.

[0059] Therefore, the tensile strength σ is introduced B_0 °Replace 0.2% yield strength σ 0.2 As an indicator of material strength including work hardening, the plate thickness t and tensile strength σ B_0 The value V represented by ° can be used to evaluate the ring-bending property of the aluminum alloy plate.

[0060] The tensile strength σ in mathematical formula (1) B_0 °Measure using the method specified in JIS-Z-2241: 2011. For example, use a micrometer to measure the plate thickness t.

[0061] For example, the following steps can be used to measure the bending strength of an aluminum alloy sheet pull ring. A casing formed from an aluminum alloy sheet is subjected to a conversion process other than scoring, thereby forming a can lid with an unscored end. Furthermore, the pull ring formed from the aluminum alloy sheet is attached to the can lid. The can lid is secured to a fixture, and the pull ring is pulled. The maximum load applied to the pulled portion is used as the pull ring bending strength.

[0062] Specifically, for the forming of the pull ring, a pull ring die of the common DRT company type with a retaining pull ring shape is used. For the forming of the shell, for example, (B64) shaped housing mold. For measuring the bending strength of the pull ring, for example, a Pop / Tear Tester manufactured by LEAD Instruments Co., Ltd. is used.

[0063] More specifically, a can lid with a pull ring attached, formed without notches using a dedicated jig, is secured to the jig. A load-applying jig is then attached to the pull ring's raised portion. The jig is then secured perpendicular to the lid's plate, applying a load sufficient to prevent plastic deformation of the pull ring. In this state, the lid is rotated at a speed of 30° / second, lifting and bending the pull ring. The maximum load applied to the pull ring's raised portion is measured within a rotational angle of 90°.

[0064] <Toughness>

[0065] It is known that the toughness of the aluminum alloy sheet affects the formability of the pull ring.

[0066] (Number of repeated bending)

[0067] One of the evaluation indicators of the toughness of aluminum alloy plates is the repeated bending test. For plates of the same thickness, the greater the number of repeated bends, the better the toughness of the aluminum alloy plate.

[0068] The repeated bending test is carried out according to the following steps. Figure 1 As shown, a strip test piece cut into a width of 12.5 mm and a length of 200 mm was arranged so that the direction of the bending ridge line R was parallel to the rolling direction D of the alloy plate. Both ends of the test piece were fixed with chucks, and a tensile force of 200 N was applied.

[0069] In this state, a clamp with a bending radius R of 2.0 mm, which is arranged at a position 150 mm from the end of the specimen fixed on a fixed chuck on one side along the longitudinal direction of the specimen, is used as a fulcrum. The chuck on the other side is rotated 90° to the left and right, and the bending is repeated. The number of bends until the specimen breaks is measured.

[0070] The number of bends is counted as one operation of bending 90° to the left or right and returning to the initial position. If the specimen breaks during bending, the angle θ (0°-90°) is read and the number of repeated bends N is calculated using the following mathematical formula (2). In mathematical formula (2), N0 is the total number of operations of bending 90° to the left or right and returning from the position bent to 90° to the initial 0° position until the specimen breaks.

[0071] N=N0+θ / 90 (2)

[0072] In the repeated bending evaluation, the larger the plate thickness, the more disadvantageous it is, so it is necessary to use the reference plate thickness for correction. Therefore, with the plate thickness of 0.245 mm as the reference, the standardized number of repeated bending times N is calculated by the following mathematical formula (3): s In addition, t t (mm) is the thickness of the specimen.

[0073] N s =N×t t / 0.245 (3)

[0074] The normalized number of repeated bending times of the aluminum alloy plate disclosed herein is preferably 11.7 times or more, and more preferably 15.0 times or more.

[0075] (Second phase particles)

[0076] Toughness is affected by strength and the distribution of second-phase particles. Specifically, higher strength and a higher density of large-area second-phase particles result in lower toughness. In particular, increasing the Mg and Si content increases the likelihood of Mg2Si particles forming. Consequently, these particles become crack initiation points and propagation paths, leading to a decrease in toughness.

[0077] The aluminum alloy plate disclosed in the present invention is Figure 2 The preferred area is 0.3 μm in the central region of the plate thickness of the L-ST cross section indicated by the oblique lines. 2 The total area ratio of the above Mg2Si particles is less than 0.2%. Figure 2 In the figure, L is the longitudinal direction, ST is the plate thickness direction, and LT is the width direction.

[0078] For example, the area ratio of Mg2Si particles can be measured by the following method. First, the measurement sample is cut and the surface to be measured (i.e., L-ST cross section) is mechanically polished to a mirror finish. Next, the polished surface (i.e., L-ST cross section) is observed using an SEM (scanning electron microscope) and 10 fields of view are obtained in the central area of ​​the plate thickness. The acceleration voltage of the SEM is set to 15 kV, the magnification is set to 500 times, and the range of one field of view is set to 0.049 mm. 2 to capture the image and obtain a COMPO (reflected electron component) image.

[0079] The captured COMPO images were analyzed using the image analysis software "ImageJ." Specifically, the brightness value that appeared most frequently among the 256 color levels in the image was set as the background brightness, and particles with a brightness lower than the value obtained by subtracting 30 from the brightness value that appeared most frequently were identified as Mg2Si particles.

[0080] The calculated area of ​​the identified Mg2Si particles is 0.3 μm 2 The total area of ​​the particles above is divided by the photographed area of ​​10 fields of view (i.e., the total area photographed), thereby calculating the area of ​​0.3 μm 2 The ratio of the total area of ​​the above Mg2Si particles in the L-ST cross section.

[0081] <Intensity Anisotropy>

[0082] It is known that the lower the cold rolling reduction ratio (hereinafter referred to as the cold rolling ratio), the higher the toughness of the material. The higher the cold rolling ratio, the higher the 0.2% yield strength σ at 90° to the rolling direction. 0.2 _ 90 ° and 0.2% yield strength σ in the direction of 0° relative to the rolling direction 0.2_0 Therefore, the difference in 0.2% yield strength between the 0° direction and the 90° direction relative to the rolling direction, that is, the strength anisotropy, can be corresponded to the cold rolling rate of the material.

[0083] The alloy plate disclosed in the present invention preferably has a 0.2% yield strength σ in the direction of 0° relative to the rolling direction as calculated by the mathematical formula (4). 0.2_0 ° minus the 0.2% yield strength σ at 90° to the rolling direction 0.2_90 °The obtained value D is -4 MPa or more.

[0084] D=σ 0.2_0 °-σ 0.2_90 ° (4)

[0085] The 0.2% yield strength σ in formula (4) 0.2_0 °、0.2% yield strength σ 0.2_90 °Measured by the method specified in JIS-Z-2241:2011.

[0086] Regarding the 0.2% yield strength σ from the direction of 0° relative to the rolling direction 0.2_0 ° minus the 0.2% yield strength σ at 90° to the rolling direction 0.2_90 The strength anisotropy obtained by ° can be explained as follows in terms of material texture.

[0087] After hot rolling or annealing, the material is in a recrystallized state, with a high concentration of isotropic cube-shaped orientations. Plastic deformation caused by cold rolling then develops a rolling texture deformation toward the cube-shaped orientation, with anisotropy along the rolling direction. Furthermore, as the cold rolling ratio increases, the grains become more elongated in the rolling direction, increasing the grain diameter at 0° relative to the rolling direction. Meanwhile, the change in grain diameter at 90° relative to the rolling direction is smaller than that at 0°.

[0088] The above texture changes caused by the above rolling and the 0.2% yield strength σ 0.2 The relationship between κ and d is expressed as Equation (5) with reference to the Hall-Petch formula. In Equation (5), κ is the resistance of the grain boundary to slip, and d is the grain diameter.

[0089] σ 0.2 ∝κ×d -1 / 2 (5)

[0090] The resistance κ has different values ​​when tensile stress is applied at 0° or 90° relative to the rolling direction. This is because as the cold rolling ratio increases, the concentration of the anisotropic rolled texture increases along the rolling direction, causing the resistance to slip at the grain boundary to change depending on the tensile direction.

[0091] Furthermore, at 0° relative to the rolling direction, the grains elongate and increase in diameter as the cold rolling rate increases, whereas at 90° relative to the rolling direction, the change in grain diameter with the cold rolling rate is relatively small. The cumulative effect of these effects leads to strength anisotropy with increasing cold rolling rate.

[0092] <Method for Manufacturing Aluminum Alloy Plate>

[0093] The aluminum alloy plate of the present disclosure can be manufactured, for example, by the following method: First, an ingot is manufactured from an aluminum alloy having the composition of the aluminum alloy plate of the present disclosure using a semi-continuous casting method (ie, DC casting) according to a conventional method.

[0094] Next, the four surfaces of the ingot, excluding the front and rear ends, are face milled. The ingot is then placed in a soaking furnace for homogenization. The homogenization temperature is preferably above 530°C and below the solidus temperature of the aluminum matrix.

[0095] When the homogenization temperature is 530°C or higher, the amount of Mg2Si, a second-phase particle that crystallizes or precipitates in the ingot, can be reduced because it is sufficiently above the solution temperature of Mg2Si. This improves the tensile strength and toughness of the aluminum alloy sheet. Furthermore, by setting the homogenization temperature to 550°C or higher, the amount of Mg2Si can be significantly reduced.

[0096] Furthermore, by setting the homogenization temperature below the solidus temperature of the aluminum substrate, aluminum alloy sheets can be produced without causing localized melting. Furthermore, the homogenization temperature is preferably at least 10°C lower than the solidus temperature of the aluminum substrate. This allows for stable production of aluminum alloy sheets without causing localized melting.

[0097] The solution temperature of Mg2Si and the solidus temperature of the aluminum matrix are uniquely determined by the composition of the aluminum alloy. For example, the above temperatures can be calculated by inputting the aluminum alloy's composition into the thermodynamic calculation software "JMatPro" developed by Sente Software to calculate a phase equilibrium diagram. The phase diagram calculation (CALPHAD) method is used as a computational thermodynamic model.

[0098] The homogenization treatment time is preferably, for example, 1 hour or longer and 20 hours or shorter. When the homogenization treatment time is 1 hour or longer, the temperature of the entire slab becomes uniform, segregation in the ingot structure is easily eliminated, and the Mg2Si particles are easily re-dissolved. The longer the homogenization treatment time, the more effective the re-dissolution of the Mg2Si particles. However, when the homogenization treatment time exceeds 20 hours, the effect of the homogenization treatment becomes saturated.

[0099] After homogenization, the ingot is hot rolled. The hot rolling process consists of a rough rolling step and a finish rolling step. In the rough rolling step, the ingot is processed into a sheet with a thickness of approximately tens of millimeters through reversible rolling. In the finish rolling step, the sheet is reduced to a thickness of approximately several millimeters through, for example, tandem rolling. The sheet is then wound into a coil to form a hot-rolled coil.

[0100] When the total reduction ratio of the finishing rolling is high, a recrystallized structure is formed after coiling, thereby increasing the concentration of the cube orientation. When the coiling temperature of the finishing rolling is high, a recrystallized structure is formed after coiling, thereby increasing the concentration of the cube orientation.

[0101] Furthermore, by subjecting the hot-rolled coil to intermediate annealing (i.e., solution treatment) to re-solubilize Mg and other elements, an alloy plate with high tensile strength can be obtained. For example, by using a continuous annealing furnace (CAL) to perform a heat treatment (i.e., annealing) at a target solid temperature of 440°C or higher for 30 seconds or longer, followed by forced cooling such as air cooling, the tensile strength of the alloy plate can be effectively improved.

[0102] After hot rolling, the sheet metal is cold rolled. During cold rolling, the hot-rolled coil is rolled until the product thickness is reached. Cold rolling can be performed in a single-stand or continuous rolling mill. In single-stand cold rolling, rolling is preferably performed in multiple passes, two or more.

[0103] In addition, by performing intermediate annealing on the coil during the cold rolling process, Mg and other substances are dissolved again, which can not only improve the tensile strength of the material, but also obtain an alloy plate with a lower final cold rolling rate and suppressed anisotropy of the material. For example, a heat treatment (i.e., annealing) is performed in a continuous annealing furnace to a target solid temperature of 440°C or above, followed by forced cooling by air cooling or other methods, which can effectively improve the tensile strength of the alloy plate. In addition, intermediate annealing of the hot-rolled coil and the coil during the cold rolling process is an optional step.

[0104] Furthermore, by setting the exit temperature of cold rolling in intermediate passes other than the final pass to 120°C or higher, Si, Cu, and Mg are finely precipitated and age-hardened, thereby increasing the tensile strength of the alloy sheet. Further increasing the exit temperature to 130°C or higher further increases the tensile strength of the alloy sheet.

[0105] When solution treatment is not performed during cold rolling, the cold rolling ratio (i.e., the target total reduction) is preferably 75% or higher. A cold rolling ratio of 75% or higher can improve the tensile strength of the alloy sheet. Furthermore, the lower the cold rolling ratio, the more cube orientation remains, so the cold rolling ratio is preferably 92% or lower.

[0106] When solution treatment is performed during cold rolling, the cold rolling ratio (i.e., the target total reduction ratio for solution treatment) is preferably 45% or higher. When the cold rolling ratio is 45% or higher, solution treatment allows for the resolubilization of Mg and other elements, which can both reduce the cold rolling ratio and increase the tensile strength of the alloy sheet. Furthermore, the lower the cold rolling ratio, the more cube orientation remains, so the cold rolling ratio is preferably 80% or lower.

[0107] The cold rolling ratio R (%) is calculated using the plate thickness t0 (mm) after hot rolling or solution treatment and the product plate thickness t1 (mm) after cold rolling using the following mathematical formula (6).

[0108] R=(t0-t1) / t0×100 (6)

[0109] The product plate thickness can be appropriately selected to obtain the desired ring-bending strength. The product plate thickness is selected to satisfy the mathematical formula (1). As described above, according to the aluminum alloy plate disclosed herein, it is possible to suppress the increase in plate thickness for maintaining a high level of ring-bending strength.

[0110] Coils cold rolled to product thickness may or may not be pre-coated in a coating line. In the case of pre-coating, the surface of the cold-rolled coil is degreased, cleaned, and chemically converted, then the coating is applied and the coating is baked.

[0111] Chemical conversion treatments use chemical solutions such as chromates and zirconium. Epoxy and polyester coatings are used. These chemical solutions and coatings can be selected based on the intended application. During the coating bake process, the coil is heated at a peak metal temperature (PMT) between 220°C and 270°C for approximately 30 seconds or less. A lower PMT suppresses material recovery, allowing the alloy sheet's tensile strength to be maintained at a high level.

[0112] [1-2. Effect]

[0113] According to the embodiments described above, the following effects can be obtained.

[0114] (1a) It is possible to combine scrap raw materials from can materials while achieving both high ring-bending strength and high toughness of the aluminum alloy sheet. In other words, a certain amount of scrap 3104 aluminum alloy used for can bodies can be mixed in, thereby reducing the use of new base metal and reducing carbon dioxide emissions.

[0115] [2. Other Implementations]

[0116] The embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above embodiments and can take various embodiments.

[0117] (2a) In addition to the aluminum alloy plate of the above-described embodiment, the present disclosure also includes various aspects such as a component made of the aluminum alloy plate and a method for manufacturing the aluminum alloy plate.

[0118] (2b) The functions of one component in each of the above embodiments may be shared by multiple components, or the functions of multiple components may be integrated into one component. In addition, part of the structure of the above embodiment may be omitted. At least part of the structure of each of the above embodiments may be added to the structure of the other embodiments, or at least part of the structure of each of the above embodiments may be replaced with the structure of the other embodiments. In addition, all the modes included in the technical ideas determined by the statements in the claims are embodiments of the present disclosure.

[0119] [3. Example]

[0120] Hereinafter, the contents of the tests conducted to confirm the effects of the present disclosure and the evaluation results thereof will be described.

[0121] <Manufacturing of Aluminum Alloy Sheets>

[0122] As examples and comparative examples, aluminum alloy plates of S1 to S17 shown in Tables 1 and 2 were produced. Specific production steps are described below.

[0123] First, an ingot containing 0.32 mass% Si, 0.43 mass% Fe, 0.22 mass% Cu, 0.80 mass% Mn, 2.6 mass% Mg, with the remainder consisting of aluminum and inevitable impurities, was produced by a semi-continuous casting method. The ingot contained no more than 0.10 mass% Ti, no more than 0.25 mass% Zn, no more than 0.10 mass% Cr, and no more than 0.15 mass% of inevitable impurities.

[0124] Next, the ingot was face milled on all four surfaces, excluding the front and rear ends. The ingot was then placed in a furnace and homogenized. The homogenization temperatures are shown in Table 1. After homogenization, the ingot was removed from the furnace and immediately hot rolled to form a rolled sheet.

[0125] Then, the hot-rolled sheet of S1-S8 was subjected to cold rolling until the sheet thickness reached the sheet thickness shown in Table 1. After the cold rolling, the sheet was subjected to intermediate annealing. The temperature during the intermediate annealing was shown in Table 1, and the time was 30 seconds. After the intermediate annealing, the sheet was cooled to room temperature by air cooling. After cooling, the sheet was subjected to cold rolling again. The target cold rolling ratio during the cold rolling after the intermediate annealing is shown in Table 1.

[0126] The hot-rolled sheet after S9-S14 is subjected to intermediate annealing. The sheet thickness and temperature during intermediate annealing are shown in Table 1, and the time is 30 seconds. After intermediate annealing, the sheet is cooled to room temperature by air cooling. After cooling, the sheet is cold rolled. The target cold rolling rate during cold rolling is shown in Table 1.

[0127] The rolled sheets after hot rolling in S15-S17 were cold rolled without annealing. The target cold rolling ratios during cold rolling are shown in Table 1.

[0128] The product plate thickness after the cold rolling of S1-S17 (ie, t1 in the mathematical formula (6)) is in the range of approximately 0.330±0.05 mm.

[0129] For S1-S14, S16, and S17, after cold rolling, the coating was applied to the plate surface and a coating baking treatment was performed for 30 seconds. The physical temperature (PMT) during the coating baking is shown in Table 1. No coating or baking treatment was performed for S15. Thus, aluminum alloy plates of S1-S17 were obtained. In addition, the plate thickness (i.e., product plate thickness) of the aluminum alloy plates of S1-S17 measured using a micrometer is shown in Table 1.

[0130] [Table 1]

[0131]

[0132] [Table 2]

[0133]

[0134] <Evaluation of Aluminum Alloy Plate>

[0135] (Tensile properties)

[0136] Two No. 5 test pieces according to JIS-Z-2241: 2011 were produced from aluminum alloy sheets S1 to S17 by milling. The longitudinal directions of the two test pieces extended at angles of 0° and 90° relative to the rolling direction, respectively.

[0137] The above test pieces were subjected to a tensile test according to JIS-Z-2241:2011, and the 0.2% yield strength and tensile strength were measured. Table 2 shows the tensile strength σ in the direction of 0° relative to the rolling direction. B_0 ° measurement results, 0.2% yield strength σ in the direction of 0° relative to the rolling direction 0.2_0 ° and 0.2% yield strength σ at 90° relative to the rolling direction 0.2_90 ° measurement results.

[0138] In addition, the value of the mathematical formula (1) V = (2.7 × t - 0.45) × σ is calculated based on the measurement results of the plate thickness and tensile strength. B_0 °. The calculation results are shown in Table 2.

[0139] (toughness)

[0140] For the aluminum alloy plates of S1 to S17, the measurement method described in the embodiment was used to measure the area of ​​0.3 μm.2 The ratio of the total area of ​​the Mg2Si particles in the L-ST cross section (area ratio) was calculated. The measurement results are shown in Table 2.

[0141] The standardized number of repeated bendings was calculated for the aluminum alloy plates of grades S1 to S17 using the measurement method described in the embodiment and equations (2) and (3). The results are shown in Table 2.

[0142] (Intensity anisotropy)

[0143] The strength anisotropy (ie, the value D) of the aluminum alloy plates of S1 to S17 was calculated according to the mathematical formula (4) described in the embodiment. The results are shown in Table 2.

[0144] (Waste mixing ratio)

[0145] Regarding the compositions of the aluminum alloy plates of S1 to S17, it was determined whether the possible mixing ratio of 3104 aluminum alloy scrap was 50% by mass or more. The results are shown in Table 2.

[0146] In Table 2, the aluminum alloy plate marked "≥50" indicates that 50% by mass or more of 3104 aluminum alloy can be mixed in. Furthermore, Table 3 shows the possible mixing ratio of 3104 aluminum alloy scrap.

[0147] Table 3 shows the correspondence between the mixing ratio and the average value of the composition specifications of 3104 aluminum alloy and 5182 aluminum alloy. The first row of Table 3 shows the average value of the composition specifications of 3104 aluminum alloy, and the second row shows the average value of the composition specifications of 5182 aluminum alloy.

[0148] For example, when the mixing ratio of 3104 aluminum alloy is 50 mass %, the average value of Si is 0.20 mass %, the average value of Fe is 0.29 mass %, the average value of Cu is 0.11 mass %, the average value of Mn is 0.7 mass %, and the average value of Mg is 2.8 mass %.

[0149] Therefore, when the ratios of the various components in the aluminum alloy sheet are equal to or greater than the aforementioned values ​​for Si, Fe, Cu, Mn, and Mg, the possible mixing ratio of the 3104 aluminum alloy sheet is 50% by mass or greater. As the mixing ratio of the 3104 aluminum alloy increases, the Si, Fe, Cu, and Mn contents increase, while the Mg content decreases. Aluminum alloy sheets of grades S1-S17 can contain at least 50% by mass of 3104 aluminum alloy scrap.

[0150] [Table 3]

[0151] alloy Si Fe Cu Mn Mg 3104 0.30 0.40 0.15 1.10 1.05 5182 0.10 0.18 0.08 0.35 4.50 3104 Mixing Ratio Si Fe Cu Mn Mg 5％ 0.11 0.19 0.08 0.4 4.3 10％ 0.12 0.20 0.08 0.4 4.2 15％ 0.13 0.21 0.09 0.5 4.0 20％ 0.14 0.22 0.09 0.5 3.8 25％ 0.15 0.23 0.09 0.5 3.6 30％ 0.16 0.24 0.10 0.6 3.5 35％ 0.17 0.25 0.10 0.6 3.3 40％ 0.18 0.27 0.11 0.7 3.1 45％ 0.19 0.28 0.11 0.7 2.9 50％ 0.20 0.29 0.11 0.7 2.8 55％ 0.21 0.30 0.12 0.8 2.6 60％ 0.22 0.31 0.12 0.8 2.4 65％ 0.23 0.32 0.12 0.8 2.3 70％ 0.24 0.33 0.13 0.9 2.1 75％ 0.25 0.34 0.13 0.9 1.9 80％ 0.26 0.36 0.14 1.0 1.7 85％ 0.27 0.37 0.14 1.0 1.6 90％ 0.28 0.38 0.14 1.0 1.4 95％ 0.29 0.39 0.15 1.1 1.2 100％ 0.30 0.40 0.15 1.1 1.1

[0152] (Pull ring bending strength)

[0153] In addition to the aluminum alloy plates S1 to S17, a plurality of aluminum alloy plates having different plate thicknesses and tensile strengths were prepared, and the ring bending strength of each aluminum alloy plate was measured according to the measurement method described in the embodiment.

[0154] The measurement results, the thickness t of the aluminum alloy plate, the tensile strength σ in the direction of 0° with respect to the rolling direction B_0 °, and the value of mathematical formula (1) V = (2.7 × t - 0.45) × σ B_0 The relationship between ° is shown in Table 4 and Figure 3 In addition, the composition of the aluminum alloy plate for which the ring bending strength was measured is shown in Table 5.

[0155] Depend on Figure 3 It can be confirmed that there is a high correlation between the value V and the bending strength of the pull ring. Figure 3 The results of measurement using a common DRT company-type pull ring with a retaining pull ring shape are shown; however, the same tendency can be obtained using pull rings of other shapes.

[0156] [Table 4]

[0157]

[0158] [Table 5]

[0159]

[0160] As shown in Table 2, it can be confirmed that the value V highly correlated with the ring-bending strength is 67 or greater in all aluminum alloy plates S1 to S17, and that they have a plate thickness and tensile strength that can achieve high ring-bending strength.

[0161] In addition, in all aluminum alloy sheets from S1 to S17, the tensile strength σ B_0 ° are all above 330MPa, which can not only suppress the excessive increase of plate thickness but also maintain high ring bending strength.

[0162] Aluminum alloys S1-S11 and S15-S17, which have higher homogenization temperatures, exhibit higher tensile strength and normalized repeated bending times. For example, aluminum alloys S9-S11 exhibit higher tensile strength and repeated bending times than aluminum alloys S12-S14, even when the process and paint baking temperatures are the same, due to the higher homogenization temperature.

[0163] In addition, the lower the paint baking temperature (PMT), the higher the tensile strength of the alloy sheet. For example, when comparing S1 with S2, S5 with S6, S7 with S8, S9-S11, S12-S14, and S16 with S17, the example with a lower paint baking temperature has a higher 0.2% yield strength σ at 0° relative to the rolling direction. 0.2_0 °, 0.2% yield strength σ in the direction 90° relative to the rolling direction 0.2_90 °, and the tensile strength σ in the direction 0° relative to the rolling direction B_90 ° showed higher values.

[0164] In aluminum alloys S1-S11 and S15-S17, where the homogenization temperature was set at 550°C or higher, the area ratio of Mg2Si particles was lower than in the other examples, at less than 0.2%. Consequently, when comparing aluminum alloy sheets S9-S11 with aluminum alloy sheets S12-S14, while the S9-S11 aluminum alloys had higher tensile strength at 0° relative to the rolling direction than the S12-S14 aluminum alloy sheets, the S9-S11 aluminum alloy sheets had a higher normalized number of repeated bends than the S12-S14 aluminum alloy sheets.

[0165] The number of repeated bending times also varies depending on the tensile strength. Comparing the aluminum alloy plates S9 and S11 with the same cold rolling ratio and a relatively small area ratio of Mg2Si particles, the standardized number of repeated bending times of the aluminum alloy plate S11 with relatively low tensile strength is higher than that of the aluminum alloy plate S9.

[0166] The normalized number of repeated bends also varies depending on the anisotropy of the material texture. For example, when comparing aluminum alloy plates with strength anisotropy of -4 MPa or greater (S1, S2, and S5) with aluminum alloy plates with strength anisotropy less than -4 MPa (S9-S11), despite having similar tensile strengths, the number of repeated bends for S1, S2, and S5 is significantly higher than for S9-S11.

[0167] In addition, when comparing the aluminum alloy plates of S3, S4, S6-S8 with strength anisotropy of more than -4 MPa with the aluminum alloy plates of S15-S17 with strength anisotropy less than -4 MPa, although their tensile strengths are relatively close, the number of repeated bending times of S3, S4, S6-S8 is significantly higher than that of S15-S17.

Claims

1. An aluminum alloy plate for a pull ring, characterized in that: The content of silicon Si is 0.20 mass % or more and 0.60 mass % or less, The content of iron (Fe) is 0.30 mass % or more and 0.70 mass % or less, The content of copper Cu is 0.11 mass % or more and 0.40 mass % or less, The content of manganese Mn is 0.7 mass % or more and 1.2 mass % or less, The content of magnesium Mg is 1.1 mass % or more and 3.0 mass % or less, and The remainder consists of aluminum Al and inevitable impurities, or contains the aluminum and the inevitable impurities. Plate thickness t (mm) and tensile strength σ at 0° relative to the rolling direction B_0 °(MPa) satisfies the following mathematical formula (1), On the L-ST cross section, the area is 0.3 μm 2 The total area ratio of the above Mg2Si particles is less than 0.2%, (2.7×t-0.45)×σ B_0 °≧67(1)。 2. The aluminum alloy plate for pull ring according to claim 1, characterized in that When a strip-shaped test piece cut into a width of 12.5 mm and a length of 200 mm or more and 300 mm or less is repeatedly bent 90° and returned to the 0° position in a direction parallel to the rolling direction until the test piece breaks, the number of bending operations at the time of breakage, i.e., the number of repeated bending times N, is calculated by dividing the thickness t of the test piece by the number of bending operations. t (mm) and the following mathematical formula (2) are used to normalize the normalized repeated bending times N. s More than 11.7 times, The tensile strength σ B_0 ° is 330MPa or more, N s =N×t t / 0.245 (2)。 3. The aluminum alloy plate for pull ring according to claim 2, characterized in that: The standardized repeated bending number N s More than 15.0 times.

4. The aluminum alloy plate for a pull ring according to any one of claims 1 to 3, characterized in that 0.2% yield strength σ from the direction of 0° relative to the rolling direction 0.2_0 ° minus the 0.2% yield strength σ at 90° to the rolling direction 0.2_90 ° and the obtained value is -4MPa or above.

5. The aluminum alloy plate for pull ring according to any one of claims 1 to 3, characterized in that The content of silicon (Si) is 0.27 mass % or more and 0.39 mass % or less, The content of iron (Fe) is 0.35% by mass or more and 0.55% by mass or less, The content of copper Cu is 0.17 mass % or more and 0.25 mass % or less, The content of manganese Mn is 0.75 mass % or more and 0.95 mass % or less, The content of magnesium Mg is 2.2 mass % or more and 2.8 mass % or less.

6. The aluminum alloy plate for pull ring according to claim 4, characterized in that The content of silicon (Si) is 0.27 mass % or more and 0.39 mass % or less, The content of iron (Fe) is 0.35% by mass or more and 0.55% by mass or less, The content of copper Cu is 0.17 mass % or more and 0.25 mass % or less, The content of manganese Mn is 0.75 mass % or more and 0.95 mass % or less, The content of magnesium Mg is 2.2 mass % or more and 2.8 mass % or less.

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