แผ่นโลหะผสมอลูมิเนียมสำหรับลำตัวกระป๋องรูปขวดและวิธีการผลิตนั้น

Abstract

The aluminum alloy plate for a bottle-shaped can body contains 0.05-0.60 mass% of Si, 0.05-0.80 mass% of Fe, 0.05-0.25 mass% of Cu, 0.80-1.50 mass% of Mn, 0.80-1.50 mass% of Mg, Al, and incidental impurities. A deep-drawn cup obtained using a blank with a diameter of 57 mm and a drawing ratio of 1.73 has a 45˚ earing ratio of 2.5% or less. The average height value of 0-180˚ earing is smaller than the average height value of 45˚ earing. The yield strength is between 180MPa and 230MPa. A value obtained by subtracting the yield strength from the tensile strength is between 10.0MPa and 28.0MPa. On the surface of the aluminum alloy plate for the bottle-shaped can body, crystal grains arranged orthogonally to the drawing direction have a width of between 10µm and 60µm.

Description

Aluminum alloy sheet for bottle can body and method for producing the same Cross-reference to related applications

[0001] This international application claims priority based on Japanese Patent Application No. 2017-180280 filed with the Japan Patent Office on September 20, 2017, and incorporates the entire contents of Japanese Patent Application No. 2017-180280 by reference into this international application.

[0002] This disclosure relates to an aluminum alloy sheet for a bottle can body and a method for producing the same.

[0003] In recent years, a bottle can, which is a type of aluminum can, is known. A bottle can has a neck portion that is thinner than the body portion. The neck portion is formed by necking. The bottle can has a screw portion near the tip of the neck portion. The screw portion is a portion where a screw for attaching a cap is formed. The bottle can has a curled portion at the tip of the neck portion. The curled portion is a portion that is curled so as to bend to the outer peripheral side (Patent Documents 1 to 5).

[0004] Japanese Unexamined Patent Application Publication No. 2001-114245, Japanese Unexamined Patent Application Publication No. 2001-158436, Japanese Unexamined Patent Application Publication No. 2001-162344, Japanese Unexamined Patent Application Publication No. 2000-191006, Japanese Unexamined Patent Application Publication No. 2004-250790

[0005] When filling the bottle can with contents and tightening the cap, an axial load is applied to the bottle can. In order not to deform even when this load is applied, the bottle can needs to have high axial strength. Axial strength is the strength to withstand an axial load.

[0006] In order to improve the axial strength, it is conceivable to increase the strength of the aluminum alloy sheet constituting the bottle can. However, when an aluminum alloy sheet with high strength is used, generally, the formability in necking, screw forming, and curl forming decreases, and wrinkles, cracks, etc. are likely to occur in the neck portion and the screw portion. Furthermore, a phenomenon in which cracks occur in the curled portion (hereinafter referred to as curl cracking) due to wrinkles, cracks, etc. is likely to occur.

[0007] In one aspect of this disclosure, it is preferable to provide an aluminum alloy sheet for a bottle can body and a method for manufacturing the same, which can realize a bottle can with high axial strength and less susceptibility to curl cracking.

[0008] One aspect of this disclosure is an aluminum alloy sheet for bottle can bodies, containing 0.05 to 0.60 mass% Si, 0.05 to 0.80 mass% Fe, 0.05 to 0.25 mass% Cu, 0.80 to 1.50 mass% Mn, 0.80 to 1.50 mass% Mg, Al, and unavoidable impurities, wherein the 45° ear ratio in a molded cup formed under the conditions of a blank diameter of 57 mm and a drawing ratio of 1.73 is 2. The aluminum alloy sheet for bottle can bodies has a purity of 5% or less, an average value of the 0-180° ear height is less than or equal to the average value of the 45° ear height, a yield strength of 180 MPa or more and 230 MPa or less, a tensile strength minus yield strength of 10.0 MPa or more and 28.0 MPa or less, and a grain width of 10 μm or more and 60 μm or less on the surface of the aluminum alloy sheet for bottle can bodies in a direction perpendicular to the rolling direction.

[0009] One aspect of this disclosure is that a bottle can manufactured using an aluminum alloy sheet for the bottle can body has high axial strength and is less prone to curl cracking. Another aspect of this disclosure is a method for manufacturing an aluminum alloy sheet for a bottle can body, wherein an aluminum alloy ingot containing 0.05 to 0.60 mass% Si, 0.05 to 0.80 mass% Fe, 0.05 to 0.25 mass% Cu, 0.80 to 1.50 mass% Mn, 0.80 to 1.50 mass% Mg, Al, and unavoidable impurities is homogenized, hot-rolled, and cold-rolled without intermediate annealing, wherein in the hot-rolling, the starting temperature for the hot-finishing roll is 400°C or higher and 520°C or lower, in the cold-rolling, the rolling end temperature of the pass preceding the final pass is 130°C or higher and 190°C or lower, and in the cold-rolling, the total reduction ratio is 80.0% or higher and 90.0% or lower.

[0010] Another aspect of this disclosure, the method for manufacturing aluminum alloy sheets for bottle can bodies, allows for the production of aluminum alloy sheets for bottle can bodies. Bottle cans manufactured using these aluminum alloy sheets have high axial strength and are less prone to curl cracking.

[0011] This is an explanatory diagram showing the method for manufacturing the first type of bottle can. This is an explanatory diagram showing the method for manufacturing the second type of bottle can. This is an explanatory diagram showing the method for measuring the grain width.

[0012] 1...Aluminum alloy plate for bottle can body, 3, 9...Neck section, 5, 17...Screw section, 7...Cup, 11...End section, 13...Opening, 15...Bottom, 101...Crystal grain structure photograph, C...Crystal grain, 103...Line segment

[0013] Exemplary embodiments of the present disclosure will be described with reference to the drawings. 1. Composition of the aluminum alloy sheet for bottle can bodies The aluminum alloy sheet for bottle can bodies of the present disclosure contains 0.05 to 0.60 mass% of Si. Si causes a phase transformation in Al-Mn-Fe precipitates, forming a harder Al-Mn-Fe-Si compound. The Al-Mn-Fe-Si compound has a solid lubricating effect. The formation of the Al-Mn-Fe-Si compound improves the ironing formability of the aluminum alloy sheet for bottle can bodies.

[0014] A Si content of 0.05% by mass or more suppresses buildup due to adhesion between the alloy mold and the die when performing DI molding. A Si content of 0.60% by mass or less reduces the edge ratio of aluminum alloy sheets for bottle can bodies.

[0015] The reason why the ear rate can be reduced is as follows: When the Si content is 0.60 mass% or less, the precipitation of fine α-AlMnFeSi phase during hot rolling can be suppressed. The α-AlMnFeSi phase has the effect of inhibiting recrystallization after the completion of hot rolling. By suppressing the precipitation of the α-AlMnFeSi phase, recrystallization after the completion of hot rolling is promoted, and the ear rate can be reduced.

[0016] The aluminum alloy sheet for bottle can bodies of this disclosure contains 0.05 to 0.80 mass% of Fe. The ironing formability of the aluminum alloy sheet for bottle can bodies is improved by containing 0.05 mass% or more of Fe. The reason why the ironing formability is improved by containing 0.05 mass% or more of Fe is that compounds such as Al-Mn-Fe and Al-Mn-Fe-Si precipitate, and these compounds have a solid lubricating effect.

[0017] Furthermore, a Fe content of 0.05% by mass or more results in a finer recrystallized grain size at the end of hot rolling. The reason for this finer recrystallized grain size is as follows: Compounds such as Al-Mn-Fe and Al-Mn-Fe-Si form regions around the matrix phase during hot rolling, where the strain is higher and the dislocation density is higher than that of the matrix phase, becoming recrystallized nuclei at the end of hot rolling. When the Fe content is 0.05% by mass or more, the amount of the compound that acts as a recrystallized nucleus increases, resulting in a finer recrystallized grain size.

[0018] Furthermore, having an Fe content of 0.05% by mass or more eliminates the need to excessively increase the purity of the aluminum ingot, thus reducing costs. Having an Fe content of 0.80% by mass or less suppresses the formation of large Al-Mn-Fe primary crystal compounds that occur when Fe and Mn combine during melting and casting. If large Al-Mn-Fe primary crystal compounds remain after rolling, they can cause cracks and pinholes during DI forming.

[0019] The aluminum alloy sheet for bottle can bodies according to this disclosure contains 0.05 to 0.25 mass% of Cu. A Cu content of 0.05 mass% or more improves the strength of the aluminum alloy sheet for bottle can bodies. Improved strength of the aluminum alloy sheet for bottle can bodies allows for sufficient axial force strength to be obtained in DI forming.

[0020] By keeping the Cu content at 0.25% by mass or less, it is possible to suppress the excessive strength of the aluminum alloy sheet used for the bottle can body. Therefore, it is possible to suppress the excessive hardening of the DI can sidewall. As a result, it is possible to suppress the occurrence of wrinkles during neck forming and the deterioration of curl formability.

[0021] The aluminum alloy sheet for bottle can bodies according to this disclosure contains 0.80 to 1.50% by mass of Mn. A Mn content of 0.80% by mass or more facilitates the formation of Al-Mn-Fe-Si compounds. As a result, the ironing formability of the aluminum alloy sheet for bottle can bodies is improved. Furthermore, a Mn content of 0.80% by mass or more improves the strength of the aluminum alloy sheet for bottle can bodies. Improved strength of the aluminum alloy sheet for bottle can bodies allows for sufficient axial force strength to be obtained in DI forming.

[0022] By keeping the Mn content below 1.50% by mass, it is possible to suppress the formation of large Al-Mn-Fe primary crystal compounds by the bonding of Fe and Mn during melting and casting. If large Al-Mn-Fe primary crystal compounds remain after rolling, they can cause cracks and pinholes during DI molding.

[0023] The aluminum alloy sheet for bottle can bodies of this disclosure contains 0.80 to 1.50% by mass of Mg. A Mg content of 0.80% by mass or more improves the strength of the aluminum alloy sheet for bottle can bodies. Improved strength of the aluminum alloy sheet for bottle can bodies allows for sufficient axial force strength to be obtained in DI forming.

[0024] By having a magnesium content of 1.50% by mass or less, the aluminum alloy sheet for the bottle can body is less prone to work hardening. Therefore, it is possible to suppress the excessive hardening of the side wall of the DI can. As a result, it is possible to suppress the occurrence of wrinkles during neck forming and the deterioration of curl formability.

[0025] The aluminum alloy sheet for bottle can bodies of this disclosure contains Al. Al is the main component of the aluminum alloy sheet for bottle can bodies. In the aluminum alloy sheet, for example, Al is the remainder other than Si, Fe, Cu, Mn, Mg, and unavoidable impurities. The content of unavoidable impurities is preferably 0.5% by mass or less.

[0026] In the aluminum alloy sheet for bottle can bodies of the present disclosure, the 45° ear ratio in a molded cup formed under the conditions of a blank diameter of 57 mm and a drawing ratio of 1.73 is 2.5% or less, and the average value of the 0-180° ear height is less than or equal to the average value of the 45° ear height.

[0027] The 45° ear ratio is a value calculated by the following formula (1). Formula (1) 45° ear ratio (%) = ((Average value of 45° ear height - Average height) / Average height) × 100 In formula (1), "45° ear height" refers to the cup ear height that appears at a position that forms a 45° angle with the rolling direction on the Erichsen cup ear. "Average value of 45° ear height" refers to the average value of the "45° ear height" measured at each of the four "positions that form a 45° angle with the rolling direction" that exist on one cup. The four "positions that form a 45° angle with the rolling direction" are in a symmetrical positional relationship.

[0028] In equation (1), "average height" refers to the following value: The height of the Erichsen cup is measured at 1° intervals from the rolling direction to obtain the cup height at 360 points. The average value of these 360 ​​cup heights is the "average height".

[0029] In equation (1), "average value of 0-180° ear height" means the average value of the cup ear height appearing at a position that forms a 0° angle from the rolling direction and the cup ear height appearing at a position that forms a 180° angle from the rolling direction.

[0030] A 45° edge ratio of 2.5% or less suppresses the thinning of the sidewall plate at the 45° angle from the rolling direction during neck forming of the DI can. This suppresses the occurrence of neck wrinkles and improves curl formability. Neck wrinkles are wrinkles that occur in the neck area during neck forming.

[0031] It is preferable that the 45° ear ratio is 1.0% or more. When the 45° ear ratio is 1.0% or more, it is possible to suppress the 45° ear height from becoming lower than the 0-180° ear height. The average value of the 0-180° ear height is suppressed because the average value of the 0-180° ear height is less than or equal to the average value of the 45° ear height. As a result, it is possible to suppress the thinning of the side wall plate of the neck portion at a position 0-180° from the rolling direction during neck forming of the DI can. As a result, the occurrence of neck wrinkles can be suppressed and curl formability is improved.

[0032] Within the range where the relationship that the average value of the 0-180° ear height is less than or equal to the average value of the 45° ear height is satisfied, a lower 45° ear ratio is preferable. In the aluminum alloy sheet for bottle can bodies of this disclosure, the yield strength is 180 MPa or more and 230 MPa or less. A yield strength of 180 MPa or more allows for high axial strength in the can body after molding. Axial strength refers to the buckling strength in the axial direction of the can. A yield strength of 230 MPa or less prevents the can sidewall from becoming too hard. This suppresses the occurrence of neck wrinkles and improves curl formability.

[0033] In the aluminum alloy sheet for bottle bodies of this disclosure, the difference between tensile strength and yield strength (hereinafter referred to as the difference value) is 10.0 MPa or more and 28.0 MPa or less. Generally, in order to make the difference value less than 10.0 MPa, it is necessary to add heat treatment during cold rolling. In the aluminum alloy sheet for bottle bodies of this disclosure, since the difference value is 10.0 MPa or more, it is not necessarily necessary to add heat treatment during cold rolling. Therefore, the productivity of the aluminum alloy sheet for bottle bodies is increased, manufacturing costs are reduced, energy loss is reduced, and CO2 ２ Emissions can be reduced.

[0034] By keeping the difference value below 28.0 MPa, work hardening in DI forming and neck forming is suppressed, improving curl formability. In the aluminum alloy sheet for bottle bodies of this disclosure, the grain width (hereinafter referred to as grain width) in the direction perpendicular to the rolling direction on its surface is 10 μm or more and 60 μm or less. Generally, in order to make the grain width less than 10 μm, it is necessary to add heat treatment during cold rolling. In the aluminum alloy sheet for bottle bodies of this disclosure, since the grain width is 10 μm or more, it is not necessarily necessary to add heat treatment during cold rolling. Therefore, the productivity of the aluminum alloy sheet for bottle bodies is increased, manufacturing costs are reduced, energy loss is reduced, and CO2 ２ Emissions can be reduced.

[0035] By having a grain width of 60 μm or less, surface roughness defects during cup drawing and neck drawing in the can body manufacturing process are suppressed, and good curl formability can be obtained. One method for reducing the grain width is to add Fe as an alloying element to crystallize Al-Fe-Mn-Si compounds, which serve as recrystallization nuclei after hot rolling is completed. Another method for reducing the grain width is to lower the starting temperature of hot finishing rolling to increase the amount of accumulated strain during hot rolling, thereby increasing the recrystallization driving force after hot rolling is completed and refining the recrystallized grains. The method for measuring the grain width is described in the examples below.

[0036] 2. Method for Manufacturing Aluminum Alloy Sheets for Bottle Can Bodies The aluminum alloy sheets for bottle can bodies of this disclosure can be manufactured, for example, by homogenizing an aluminum alloy ingot, hot rolling it, and then cold rolling it without intermediate annealing. If necessary, final annealing may be performed after cold rolling. The process will be described below step by step.

[0037] (2-1) Cast and homogenized aluminum alloy ingots contain 0.05 to 0.60 mass% Si, 0.05 to 0.80 mass% Fe, 0.05 to 0.25 mass% Cu, 0.80 to 1.50 mass% Mn, 0.80 to 1.50 mass% Mg, Al, and unavoidable impurities.

[0038] Al is the main component of aluminum alloy ingots. For example, in aluminum alloy ingots, Al is the remainder other than Si, Fe, Cu, Mn, Mg, and unavoidable impurities. The content of unavoidable impurities is preferably 0.5% by mass or less. Aluminum alloy ingots can be obtained by melting and casting using conventional methods.

[0039] The temperature during the homogenization process is preferably 580°C or higher and below the melting point of the ingot. If the temperature is 580°C or higher, Al ６From (Fe, Mn), the transformation into the α-phase compound (Al-Mn-Fe-Si system) can be promoted. The α-phase compound (Al-Mn-Fe-Si system) exhibits an anti-seizure effect during ironing. When the temperature of the homogenization treatment is below the melting point of the ingot, it is possible to suppress the occurrence of eutectic melting in a part of the ingot and the deterioration of the quality of the plate surface.

[0040] The time of the homogenization treatment is preferably 1 hour or more and 20 hours or less. When it is 1 hour or more, the transformation from Al ６ (Fe, Mn) into the α-phase compound can be further promoted. When it is 20 hours or less, the economy in the production of the aluminum alloy plate for the bottle can body is improved.

[0041] (2-2) Hot rolling Hot rolling is composed of, for example, hot rough rolling and hot finish rolling. In hot rough rolling, according to the plate thickness to be rolled, the ingot after the homogenization treatment is rolled. Hot rough rolling can be performed, for example, using a reversing mill. The plate thickness after hot rough rolling is, for example, 50 mm or less. In hot finish rolling, for example, it is rolled to a plate thickness of 5 mm or less. Hot finish rolling can be performed, for example, using a tandem mill.

[0042] The starting temperature of the hot finish rolling is preferably 400°C or more and 520°C or less. When the starting temperature of the hot finish rolling is 400°C or more, edge cracking of the plate hardly occurs during hot rolling. When the starting temperature of the hot finish rolling is 520°C or less, the accumulated strain amount during hot rolling increases, and the driving force for recrystallization increases. As a result, the recrystallized grain size is refined, and the grain width on the surface of the final cold-rolled plate is refined.

[0043] The starting temperature of the hot finish rolling is more preferably 420°C or more and 500°C or less. When the starting temperature of the hot finish rolling is 420°C or more and 500°C or less, the grain width can be made into a more appropriate range.

[0044] The finishing temperature of hot rolling is preferably 300°C or higher and 400°C or lower. When the finishing temperature of hot rolling is 300°C or higher, recrystallization after hot rolling can proceed sufficiently, and the 45° ear rate can be lowered. When the finishing temperature of hot rolling is 400°C or lower, the surface of the hot rolled sheet is difficult to oxidize, and the surface quality of the hot rolled sheet is difficult to deteriorate. As a result, it is difficult for streak pattern defects to occur on the outer surface of the can sidewall after DI forming. Streak pattern defects are defects called flow marks. Streak pattern defects may be visually recognized on the outer surface of the can sidewall after DI forming.

[0045] (2-3) If intermediate annealing is performed before cold rolling or during cold rolling, the solid solubility of solute elements increases and the neck formability decreases. Also, when intermediate annealing is performed, the manufacturing cost increases and energy loss occurs. By performing cold rolling without performing intermediate annealing, the above-mentioned adverse effects can be suppressed..

[0046] (2-4) Cold rolling By performing cold rolling, the material strength of the aluminum alloy sheet for bottle can bodies is improved. The total reduction ratio in cold rolling is preferably 80.0% or higher and 99.0% or lower. When the total reduction ratio is 80.0% or higher, the material strength of the aluminum alloy sheet for bottle can bodies is further improved.

[0047] When the total reduction ratio is 90% or lower, it is possible to suppress the excessive development of the rolled texture. As a result, it is possible to suppress the excessive increase in the 45° ear. In addition, when drawing during DI forming, when redrawing a cup, or when forming a neck portion peculiar to a bottle-shaped can, it is possible to suppress variations in the thickness of the can sidewall plate. By suppressing variations in the thickness of the can sidewall plate, wrinkles are less likely to occur. The total reduction ratio in cold rolling is more preferably 85.0% or higher and 90.0% or lower. When the total reduction ratio in cold rolling is within this range, the strength of the aluminum alloy sheet for bottle can bodies is further improved and the ear rate becomes more appropriate.

[0048] In cold rolling, it is preferable that the rolling end temperature of the pass preceding the final pass be between 130°C and 190°C. When the rolling end temperature of the pass preceding the final pass is 130°C or higher, fine precipitation of Mg-Si, Al-Mg-Cu, and Al-Mg-Cu-Si compounds occurs between cold rolling passes, improving the material strength of the aluminum alloy sheet for bottle bodies. Furthermore, when the rolling end temperature of the pass preceding the final pass is 130°C or higher, the amount of solid solution of Cu, Mg, and Si in the matrix phase decreases, suppressing the work hardening of the cold-rolled sheet. As a result, work hardening in DI forming and neck forming is suppressed, improving screw formability and curl formability.

[0049] If the rolling completion temperature of the pass preceding the final pass is 190°C or lower, excessive age hardening due to fine precipitation of Mg-Si, Al-Mg-Cu, and Al-Mg-Cu-Si compounds can be suppressed. As a result, the material strength of the aluminum alloy sheet for bottle bodies is less likely to become excessively high. Consequently, DI formability and neck formability are improved.

[0050] The time from the end of the pass preceding the final pass of cold rolling to the start of the final pass (hereinafter referred to as the inter-pass time) is preferably 1 hour or more and less than 48 hours. When the inter-pass time is 1 hour or more, fine precipitation of Mg-Si, Al-Mg-Cu, and Al-Mg-Cu-Si compounds occurs between cold rolling passes, improving the material strength of the aluminum alloy sheet for bottle bodies. Also, when the inter-pass time is 1 hour or more, the amount of solid solution of Cu, Mg, and Si in the matrix phase decreases, suppressing the work hardening of the cold-rolled sheet. As a result, work hardening in DI forming and neck forming is suppressed, improving screw formability and curl formability. When the inter-pass time is less than 48 hours, the economic efficiency of manufacturing aluminum alloy sheets for bottle bodies is improved.

[0051] (2-5) Final Annealing Final annealing may or may not be performed. Final annealing can be used to adjust the material strength of the aluminum alloy sheet for bottle can bodies. If final annealing is performed, the temperature is preferably 80°C or higher and 250°C or lower, and the time is preferably 0.1 hours or higher and 24 hours or lower. If the final annealing temperature is 80°C or higher, or if the final annealing time is 0.1 hours or longer, the dislocations introduced by cold rolling will recover, and the material strength of the aluminum alloy sheet for bottle can bodies will decrease. If the final annealing temperature is 250°C or lower, the recovery of dislocations introduced by cold rolling will not proceed excessively, and the material strength will not decrease excessively. The final annealing time is preferably 0.1 hours or longer. Even if the final annealing time is longer than 24 hours, the material strength of the aluminum alloy sheet for bottle can bodies will not change significantly compared to when the final annealing time is 24 hours. A final annealing time longer than 24 hours is undesirable from an economic standpoint.

[0052] 3. Method for manufacturing bottle cans Bottle cans can be manufactured using the aluminum alloy sheet for bottle can bodies of the present disclosure.

[0053] (3-1) The manufacturing method of the first bottle can will be explained based on Figure 1 of the manufacturing method of the first bottle can. The first bottle can has a relatively larger opening compared to the second bottle can which will be described later. In S1, an aluminum alloy plate 1 for the bottle can body is prepared. In S2, a blanking process is performed. In S3, a cupping process is performed to form a cup 7. In S4, a DI molding process is performed. In S5, a trimming process is performed. In S6, a necking process is performed. At this time, the neck portion 3 is formed. In S7, a screw forming process is performed. At this time, a screw portion 5 is formed on the neck portion 3. Also, curl forming is performed on the tip of the neck portion 3.

[0054] (3-2) The manufacturing method of the second bottle can will be described based on Figure 2. The second bottle can is a bottle can with a mouth the same size as a PET bottle. Steps S11 to S15 are the same as steps S1 to S5 described above. In step S16, a neck portion 9 is formed on the bottom side of the cup 7 and an end portion 11 is opened. In step S17, a flange process is performed on the side of the opening 13 in the cup 7. In step S18, the bottom portion 15 is rolled up and a screw forming process is performed. At this time, a screw portion 17 is formed on the neck portion 9. Also, curl forming is performed on the tip of the neck portion 9.

[0055] 4. Examples (4-1) Manufacturing of aluminum alloy sheets for bottle can bodies Aluminum alloy sheets for bottle can bodies were manufactured using the manufacturing conditions J1 to J8 shown in Table 1.

[0056] All of J1 to J8 share the same method for manufacturing aluminum alloy plates for bottle can bodies: First, an aluminum alloy ingot is formed by semi-continuous casting. Next, the surface of the ingot is machined, and then a homogenization treatment is performed by holding it at a temperature of 595°C for two hours.

[0057] Next, rough hot rolling is performed using a reversing mill. Then, finish hot rolling is performed using a three-stand tandem mill to obtain a hot-rolled sheet. Next, the obtained hot-rolled sheet is cold-rolled to a thickness of 0.44 mm after it has cooled to room temperature. Finally, a final annealing is performed by holding it at 220°C for 2 hours to obtain an aluminum alloy sheet for bottle bodies. The time between the end of the previous pass of cold rolling and the start of the final pass of cold rolling should be 1 hour or more.

[0058] Table 1 above shows the composition of the aluminum alloy ingots, the starting temperature in hot finishing rolling, the total reduction ratio in cold rolling, and the rolling end temperature of the pass preceding the final pass in cold rolling for J1 to J8.

[0059] (4-2) Evaluation of aluminum alloy plates for bottle can bodies For each of J1 to J8, the aluminum alloy plates for bottle can bodies were evaluated as follows.

[0060] (i) Cup ear characteristics A sample with a blank diameter of 57 mm was cut from an aluminum alloy sheet for bottle can bodies. This sample was deep drawn using an Erichsen testing machine. The punch diameter was 33 mm and the shoulder radius of the punch was 2.5 mm. The wrinkle-holding force was 300 kgf. The cup height was measured at 1° intervals with respect to the rolling direction. The value of the 45° ear ratio, the value of the (average value of ear height from 0-180°), and the value of the (average value of ear height at 45°) were determined. The measurement results are shown in Table 2.

[0061] (ii) Tensile properties: A No. 5 test specimen, as specified in JIS-Z-2201, was prepared by cutting from an aluminum alloy sheet for bottle bodies. This test specimen extends in a direction that forms a 0° angle with respect to the rolling direction.

[0062] Tensile tests were performed on the test specimens in accordance with JIS-Z-2241 to measure the tensile strength and 0.2% yield strength. The yield strength and the value obtained by subtracting the yield strength from the tensile strength (difference value) are shown in Table 2 above. In Table 2, "Yield Strength YS" means yield strength. In Table 2, "Tensile Strength TS - Yield Strength YS Difference" means the difference value.

[0063] (iii) Grain width The grain width of the aluminum alloy sheet for bottle can bodies was measured in accordance with the cutting method of JIS H0501. The specific measurement method is as follows: For each of the five fields of view on the surface of the aluminum alloy sheet for bottle can bodies, a grain structure photograph 101 shown in Figure 3 was obtained. The size of the field of view of this grain structure photograph 101 is 0.7 mm × 0.9 mm. The grain structure photograph 101 is magnified 100 times. In Figure 3, the left-right direction is the rolling direction. Multiple grains C are visible in the grain structure photograph 101.

[0064] Three line segments 103 were drawn in each grain structure photograph 101. Therefore, there are a total of 15 line segments 103 in the five fields of view of the grain structure photograph 101. Each line segment 103 extends in a direction perpendicular to the rolling direction. Each line segment 103 reaches from one end to the other of the grain structure photograph 101. The length of each line segment 103 is 0.7 mm. Since the grain structure photograph 101 is magnified 100 times, the length of each line segment 103 corresponds to a length of 700 μm.

[0065] First, let's focus on a single line segment 103. Let N be the number of crystal grains C that this line segment 103 completely cuts. Completely cutting a crystal grain C means that the line segment 103 passes through the crystal grain C and reaches from one end to the other. In the example shown in Figure 3, the leftmost line segment 103 completely cuts 7 crystal grains C.

[0066] The value obtained by dividing 700 μm by N is taken as the grain width at that line segment 103. The grain width at one line segment 103 is determined in the same way for each of the 15 line segments 103. Finally, the grain width at one line segment 103 is averaged over the 15 line segments 103 to obtain the grain width of the aluminum alloy plate for the bottle can body. The measured grain widths are shown in Table 4 above.

[0067] (iv) A circular disc with a blank diameter of 179 mm was cut from an aluminum alloy sheet for curl-formable bottle can bodies. This disc was die-formed to an inner diameter of 58 mm. Next, trimming, washing, and baking were performed in sequence. The maximum holding temperature during baking was 210°C. Next, necking was performed using the die-neck method until the diameter of the mouth was 26 mm. Next, a bottle can was manufactured by screw curl forming. 100 bottle cans were made using this method, and the occurrence of curl cracks in each bottle can was checked. The curl formability was then evaluated according to the following criteria.

[0068] ○: Curl cracking rate is less than 5%. ×: Curl cracking rate is 5% or more. The evaluation results for curl formability are shown in Table 2 above.

[0069] (v) Axial Force Strength A load was applied from above to the bottle cans manufactured in (iv) above, and the peak load at which the bottle cans underwent plastic deformation was measured. This measurement was performed for each of the five bottle cans, and the average value of the peak loads of the five cans was defined as the axial force strength. The axial force strength was then evaluated according to the following criteria.

[0070] ○: Axial force strength is 1800 N or more. ×: Axial force strength is less than 1800 N. The evaluation results of axial force strength are shown in Table 2 above. Note that 1800 N is the desirable axial force strength when crimping contents with high internal pressure.

[0071] (vi) Evaluation results: J1 and J2 showed good performance in all aspects, including cup lug characteristics, tensile properties, grain width, curl formability, and axial strength.

[0072] In J3, the curl formability was poor. This is presumed to be because the starting temperature for hot finishing rolling was too high, resulting in excessively large grain widths. In J4, plate edge cracking occurred during hot rolling. This is presumed to be because the starting temperature for hot finishing rolling was too low.

[0073] In J5, the curl formability was poor. This is presumed to be because the total reduction ratio during cold rolling was too high, resulting in an excessively high ratio of 45° ears. In J6, both axial strength and curl formability were poor. This is presumed to be because the total reduction ratio during cold rolling was too low, causing the average value of the 0-180° ear height to exceed the average value of the 45° ear height, and also resulting in low yield strength.

[0074] In J7, the curl formability was poor. This is presumed to be because the rolling temperature at the end of the preceding pass before the final pass of cold rolling was too low, resulting in a large difference between tensile strength and yield strength.

[0075] In J8, the curl formability was poor. This is presumed to be because the rolling end temperature of the pass preceding the final pass of cold rolling was too high, resulting in an excessively large yield strength. 5. Other Embodiments Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above and can be implemented with various modifications.

[0076] (1) The function of one component in each of the above embodiments may be divided among multiple components, or the function of multiple components may be performed by one component. Also, a part of the configuration of each of the above embodiments may be omitted. Also, at least a part of the configuration of each of the above embodiments may be added to, substituted for, etc., the configuration of other above embodiments. Any aspect of the technical concept specified by the wording in the claims is an embodiment of the present disclosure.

[0077] (2) In addition to the aluminum alloy plate for the bottle can body described above, this disclosure can also be realized in various forms, such as a bottle can that uses the aluminum alloy plate for the bottle can body as a component, a method for manufacturing a bottle can, etc.

Claims

1. Aluminum alloy sheet for bottle-shaped can body: This aluminum alloy sheet contains Si 0.05-0.60% by mass, Fe 0.05-0.80% by mass, Cu 0.05-0.25% by mass, Mn 0.80-1.50% by mass, Mg 0.80-1.50% by mass, and unavoidable impurities such as Al and foreign matter. The earing rate is 45°. The symbol for the cup forming is drawn into the forming mold under conditions of blank sheet diameter 57 mm. The drawing rate of 1.73 is less than or equal to 2.5% of the average earing height. 0-180° less than or equal to the average of the earing height 45°, proof stress is greater than or equal to 180 MPa and less than or equal to 230 MPa; the value after proof stress from tensile strength is greater than or equal to 10.0 MPa and less than or equal to 28.0 MPa; the grain width of the crystalline structure of the shear direction perpendicular to the rolling direction on the surface of the aluminum alloy sheet for the body of the said bottle-shaped can is greater than or equal to 10 µm and less than or equal to 60 µm².The production method of aluminum alloy sheets for bottle-shaped can bodies involves homogenization, hot rolling, and cold rolling without intermediate annealing to cast aluminum alloy billets containing Si 0.05-0.60% by mass, Fe 0.05-0.80% by mass, Cu 0.05-0.25% by mass, Mn 0.80-1.50% by mass, Mg 0.80-1.50% by mass, and Al, and unavoidable impurities in the hot rolling process. The initial hot rolling finish temperature is greater than or equal to 400°C and less than or equal to 520°C. In the cold rolling process, the finish temperature of the pre-rolling pass to the final rolling pass is greater than or equal to 130°C and less than or equal to 190°C. The total rolling attenuation rate is greater than or equal to 80.0% and less than or equal to 90.0%.The method for producing aluminum alloy sheets for bottle-shaped can bodies specified in Claim 2, in which the aluminum alloy sheets for bottle-shaped can bodies produced have an earring rate of 45° of the forming cup, drawn under conditions of blank sheet diameter of 57 mm, drawing rate of 1.73 is less than or equal to 2.5%, average earring height 0-180° is less than or equal to the average earring height of 45°, proof stress is greater than or equal to 180 MPa and less than or equal to 230 MPa, value minus proof stress from tensile strength is greater than or equal to 10.0 MPa and less than or equal to 28.0 MPa, and the grain width of the crystalline sheath direction perpendicular to the rolling direction at the surface of the said aluminum alloy sheets for bottle-shaped can bodies is greater than or equal to 10 µm and less than or equal to 60 µm;