Method for manufacturing aluminum alloy sheets, hot-rolled aluminum alloy sheets, and aluminum alloy sheets

Abstract

To provide a method for manufacturing an aluminum alloy sheet in which an aluminum alloy sheet with suppressed generation of a burr which has high 0.2% proof stress and excellent DI formability, and has high can body strength after canning can be manufactured without performing process annealing in performing cold rolling, the aluminum alloy sheet, and an aluminum alloy hot-rolled sheet by which the aluminum alloy sheet can be manufactured.SOLUTION: A method for manufacturing an aluminum alloy sheet in which process annealing is not performed in a cold rolling process, an average strain rate and an outlet side temperature in a pass immediately before the final pass are controlled in a hot finish rolling process, and an average strain rate and an outlet side temperature in the final pass are controlled.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for producing an aluminum alloy sheet, a hot-rolled aluminum alloy sheet, and an aluminum alloy sheet.

BACKGROUND ART

[0002] To achieve carbon neutrality, it is necessary to reduce CO₂ emissions even in the production of aluminum cans. By omitting part of the production process, the energy consumption required for manufacturing each can can be reduced. In addition, since the production volume per unit time is improved, the manufacturing cost can be suppressed. In the production of aluminum alloy sheets used for manufacturing aluminum cans, intermediate annealing is generally performed in the cold rolling process in the middle of multiple rolling passes.

[0003] For example, Patent Document 1 discloses a method for producing an aluminum alloy sheet for DR can bodies, which includes: a casting step of casting an aluminum alloy; a homogenization treatment step of subjecting the ingot to homogenization treatment; a hot rolling step of hot rolling the homogenized ingot; a primary cold rolling step for the hot-rolled sheet; an intermediate annealing step of annealing the primary cold-rolled sheet; and a secondary cold rolling step for the intermediate annealed sheet.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0004]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] However, since intermediate annealing is a heat treatment in a high temperature range intended to recrystallize aluminum, it has high energy consumption. If this intermediate annealing can be omitted, it can greatly contribute to the realization of carbon neutrality.

[0006] Omitting intermediate annealing during cold rolling increases the cold rolling rate because there is no process to recrystallize the aluminum after the hot rolling process. This increases the Cu and S orientations, known as the rolling texture. An increase in the rolling texture makes it easier for eaves to form at a 45° angle to the rolling direction during aluminum can manufacturing. Here, eaves refer to the peak-and-valley-like changes that form on the upper edge of an aluminum can when an aluminum alloy sheet is deep drawn or ironed. If eaves are excessively formed at a 45° angle to the rolling direction, they can get caught during transport on the can manufacturing line, requiring removal and thus reducing productivity. If there are high eaves during ironing, the can may come into contact with the body maker (the molding machine for forming DI cans), potentially causing the eaves to chip and allowing foreign matter to enter. Alternatively, foreign matter may get caught in the can wall, potentially causing pinholes. Furthermore, if the eaves cannot be completely removed during the trimming process after ironing, it results in defective cans, leading to a decrease in yield.

[0007] This invention has been made in view of the above circumstances, and aims to provide a method for manufacturing aluminum alloy sheets that can produce aluminum alloy sheets with suppressed edge formation without performing intermediate annealing during cold rolling. Furthermore, it aims to provide a method for manufacturing aluminum alloy sheets that can produce aluminum alloy sheets having high 0.2% yield strength and excellent DI formability, which are characteristics generally required for aluminum alloy sheets used in beverage cans, and that have high can body strength after can manufacturing. Furthermore, the objective is to provide the aforementioned aluminum alloy sheet and to provide an aluminum alloy hot-rolled sheet capable of manufacturing the aforementioned aluminum alloy sheet. [Means for solving the problem]

[0008] (1) A method for manufacturing an aluminum alloy plate according to one aspect of the present invention is: The chemical composition is expressed in mass percent. Si: 0.20~0.35%, Fe: 0.35~0.55%, Cu: 0.15~0.48%, Mn: 0.80~1.15%, Contains Mg: 0.60-1.60%, A casting process in which an aluminum alloy consisting of Al and impurities is melted and a slab is obtained by semi-continuous casting, A homogenization process is performed by holding the material at a temperature range of 560°C or higher and below the melting point for 4 hours or more. A soaking process involves maintaining a temperature range of 520-560°C for more than one hour. A hot rough rolling process is performed to make the plate thickness 15-40 mm, A hot finishing rolling process in which hot finishing rolling is performed so that the plate thickness becomes 2.0 to 4.0 mm, The process includes a cold rolling step in which the sheet is cold-rolled to a thickness of 0.20 to 1.00 mm, and then proceeds to the next step. In the aforementioned cold rolling process, intermediate annealing is not performed. In the aforementioned hot finishing rolling process, In the final pass before the last pass, the average strain rate is set to 10-25 / s, and the exit temperature is set to a temperature range of 300-380°C. In the final pass, the average strain rate is set to 50-160 / s, and the exit temperature is set to a temperature range of 310-380°C. As a result, The plate thickness is 0.20 to 1.00 mm. The cube orientation density is 0.9 or higher. The Cu orientation density is 12.5 or less. The 0.2% yield strength in the rolling direction is 220-340 MPa. An aluminum alloy sheet can be obtained in which the change in 0.2% yield strength after heat treatment at 210°C for 10 minutes is 15% or less. (2) In the method for manufacturing aluminum alloy sheets described in (1) above, a final annealing process may be performed after the cold rolling process, in which the sheet is held at a temperature range of 100 to 210°C for 2 to 10 hours. (3) A hot-rolled aluminum alloy sheet according to another aspect of the present invention is: The chemical composition is expressed in mass percent. Si: 0.20~0.35%, Fe: 0.35~0.55%, Cu: 0.15~0.48%, Mn: 0.80~1.15%, Contains Mg: 0.60-1.60%, The balance consists of Al and impurities, The sheet thickness is 2.0 to 4.0 mm, When EBSD measurement is performed on the ND-RD cross section, the average value of local orientation differences where the local orientation difference is 0 to 5° is 2.0° or less, and the area ratio of the region having a Cube orientation is 10 to 25%. (4) An aluminum alloy sheet according to another aspect of the present invention is The chemical composition, in mass %, is Si: 0.20 to 0.35%, Fe: 0.35 to 0.55%, Cu: 0.15 to 0.48%, Mn: 0.80 to 1.15%, Mg: 0.60 to 1.60%, The balance consists of Al and impurities, The sheet thickness is 0.20 to 1.00 mm, The Cube orientation density is 0.9 or more, The Cu orientation density is 12.5 or less, The 0.2% proof stress in the rolling direction is 220 to 340 MPa, The change ratio of 0.2% proof stress when subjected to heat treatment at 210°C for 10 minutes is 15% or less. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0009] According to the above aspect of the present invention, it is possible to provide a method for producing an aluminum alloy sheet that can produce an aluminum alloy sheet with suppressed earing, high 0.2% proof stress, excellent DI formability, and high can body strength after can making, without performing intermediate annealing during cold rolling. Further, it is possible to provide the aforementioned aluminum alloy sheet, and an aluminum alloy hot-rolled sheet that can produce this aluminum alloy sheet. The method for manufacturing aluminum alloy sheets according to the above embodiment omits intermediate annealing during cold rolling and controls the texture during the hot finishing rolling process, thereby contributing to further energy savings and process simplification. Furthermore, the aluminum alloy sheets according to the above embodiment have a high 0.2% yield strength and excellent DI formability, and have high can body strength after can manufacturing, making them suitable as aluminum alloy sheets for manufacturing beverage cans. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows the relationship between the roll radius r and the mean strain rate ε. [Modes for carrying out the invention]

[0011] The inventors have found that by forming ears in the 0° and 90° directions relative to the rolling direction, it is possible to suppress the formation of ears in the 45° direction relative to the rolling direction (hereinafter sometimes referred to as 45° direction ears).

[0012] The inventors considered that controlling the texture after hot rolling is important in order to control the texture of aluminum alloy sheets without performing intermediate annealing. In order to form ears in the 0° and 90° directions relative to the rolling direction, it is important to control the Cube orientation in the texture. Since the Cube orientation is a recrystallized texture, in order to control the Cube orientation without performing intermediate annealing, it is important to control the texture during hot rolling, that is, to control the texture in the hot-rolled aluminum alloy sheet. Since the 45° ear is caused by the rolling texture, if a rolling texture is formed after hot rolling, it will be a factor in the formation of a 45° ear. Therefore, it is important to reduce the rolling texture in the hot-rolled aluminum alloy sheet.

[0013] The following describes in detail, based on the attached drawings, an example of an embodiment of the present invention: a method for manufacturing an aluminum alloy sheet, a hot-rolled aluminum alloy sheet, and an aluminum alloy sheet.

[0014] The method for manufacturing an aluminum alloy sheet according to this embodiment is as follows: The chemical composition is expressed in mass percent. Si: 0.20~0.35%, Fe: 0.35~0.55%, Cu: 0.15~0.48%, Mn: 0.80~1.15%, Contains Mg: 0.60-1.60%, A casting process in which an aluminum alloy consisting of Al and impurities is melted and a slab is obtained by semi-continuous casting, A homogenization process is performed by holding the material at a temperature range of 560°C or higher and below the melting point for 4 hours or more. A soaking process involves maintaining a temperature range of 520-560°C for more than one hour. A hot rough rolling process is performed to make the plate thickness 15-40 mm, A hot finishing rolling process in which hot finishing rolling is performed so that the plate thickness becomes 2.0 to 4.0 mm, The process includes a cold rolling step in which the sheet is cold-rolled to a thickness of 0.20 to 1.00 mm, and then proceeds to the next step. In the aforementioned cold rolling process, intermediate annealing is not performed. In the aforementioned hot finishing rolling process, In the final pass before the last pass, the average strain rate is set to 10-25 / s, and the exit temperature is set to a temperature range of 300-380°C. In the final pass, the average strain rate is set to 50-160 / s, and the exit temperature is set to a temperature range of 310-380°C. Optionally, the process further includes a final annealing step after the cold rolling step, in which final annealing is performed by holding the machine at a temperature range of 100 to 210°C for 2 to 10 hours. The following describes each step.

[0015] Casting process In the casting process, an aluminum alloy with the desired chemical composition is melted, and a slab is obtained by semi-continuous casting. The chemical composition will be explained in detail below. Note that the numerical ranges indicated below, separated by a "~", include both a lower and upper limit. Numbers indicated as "less than" or "greater than" are not included in the numerical range. In the following explanation, percentages related to chemical composition refer to mass percentages unless otherwise specified.

[0016] Si: 0.20~0.35% Si combines with Mg to precipitate Mg2Si, thereby improving the yield strength of aluminum alloy sheets. If the Si content is less than 0.20%, the amount of Mg2Si precipitated will be small, and the strength of the can body after fabrication will decrease. Therefore, the Si content should be 0.20% or more. Preferably, the Si content is 0.25% or more. On the other hand, if the Si content exceeds 0.35%, the yield strength increases excessively, and the moldability deteriorates. Therefore, the Si content should be 0.35% or less. Preferably, the Si content is 0.32% or less.

[0017] Fe: 0.35~0.55% Fe combines with Al and Mn to form Al-Mn-Fe intermetallic compounds, thereby improving the yield strength of aluminum alloy sheets and preventing sticking to the mold due to die cleaning during ironing. If the Fe content is less than 0.35%, the amount of Al-Mn-Fe intermetallic compounds decreases, reducing the yield strength of the aluminum alloy sheets and lowering the strength of the can body after fabrication. In addition, sticking to the mold occurs during ironing. Therefore, the Fe content should be 0.35% or more. Preferably, the Fe content is 0.40% or more. On the other hand, if the Fe content exceeds 0.55%, the yield strength of the aluminum alloy sheet increases excessively, and the formability deteriorates due to a decrease in elongation. Furthermore, the corrosion resistance of the aluminum alloy sheet deteriorates. For this reason, the Fe content should be 0.55% or less. Preferably, the Fe content is 0.50% or less.

[0018] Cu: 0.15~0.48% Cu improves the yield strength of aluminum alloy sheets through solid solution strengthening. If the Cu content is less than 0.15%, the amount of Cu in solid solution decreases, and the strength of the can body after fabrication decreases in the aluminum alloy sheet. Therefore, the Cu content should be 0.15% or more. Preferably, the Cu content is 0.20% or more. On the other hand, if the Cu content exceeds 0.48%, the yield strength of the aluminum alloy sheet increases excessively, degrading its formability. Furthermore, the corrosion resistance of the aluminum alloy sheet deteriorates. Therefore, the Cu content should be 0.48% or less. Preferably, the Cu content is 0.40% or less.

[0019] Mn: 0.80~1.15% Mn combines with Al and Fe to form Al-Mn-Fe intermetallic compounds, and also with Al, Fe, and Si to form Al-Mn-Fe-Si intermetallic compounds, and is dispersed in the matrix, contributing to dispersion strengthening. This improves the yield strength without degrading the corrosion resistance of the aluminum alloy sheet. If the Mn content is less than 0.80%, the amount of the above intermetallic compounds decreases, and the strength of the can body after fabrication decreases in the aluminum alloy sheet. Therefore, the Mn content should be 0.80% or more. Preferably, the Mn content is 0.90% or more. On the other hand, if the Mn content exceeds 1.15%, the yield strength of the aluminum alloy sheet increases excessively, and its formability deteriorates. Therefore, the Mn content should be 1.15% or less. Preferably, the Mn content is 1.05% or less.

[0020] Mg: 0.60~1.60% Mg improves the yield strength and work hardening properties of aluminum alloy sheets through solid solution strengthening and by precipitation of Mg2Si. If the Mg content is less than 0.60%, the amount of solid solution and Mg2Si will decrease, and the work hardening properties will deteriorate, resulting in a decrease in the strength of the can body after fabrication. Therefore, the Mg content should be 0.60% or more. Preferably, the Mg content is 0.80% or more. On the other hand, if the Mg content exceeds 1.60%, the yield strength of the aluminum alloy sheet increases excessively, and the formability deteriorates due to a decrease in elongation. Furthermore, the work hardening properties increase excessively, making it easier for the sheet to crack during ironing. For this reason, the Mg content should be 1.60% or less. Preferably, the Mg content is 1.50% or less.

[0021] The remainder of the chemical composition consists of Al and impurities. In this embodiment, impurities refer to impurities that are mixed in during the dissolution of the material, and are contained in a range that does not impair the properties of the aluminum alloy sheet according to this embodiment. Examples of impurities include Cr, Zn, Ti, and Zr. If the content of each of these impurities is 0.005% or less, and the total content is 0.015% or less, the properties of the aluminum alloy sheet according to this embodiment will not be impaired.

[0022] Homogenization process In the homogenization process, a homogenization treatment is performed by holding the material at a temperature range of 560°C or higher but below the melting point for at least 4 hours. By controlling the homogenization temperature (heating temperature during the homogenization treatment), the texture and Mg2Si precipitation state in the hot-rolled aluminum alloy sheet can be controlled. If the homogenization temperature is below 560°C, sufficient homogenization cannot be achieved, and the amount of fine precipitates increases. This reduces the area ratio of regions with Cube orientation in the hot-rolled aluminum alloy sheet and increases the average value of the local orientation difference. As a result, excessive 45° oriented edges are formed in the aluminum alloy sheet. Therefore, the homogenization temperature should be 560°C or higher. On the other hand, if the homogenization temperature is above the melting point, the slab will remelt. Therefore, the homogenization temperature should be below the melting point.

[0023] The melting point referred to here is the melting point of the slab (aluminum alloy). The chemical composition of the slab was input into the thermodynamic calculation software JMatPro (manufactured by Sente Software), and a temperature-solid-liquid phase fraction curve was plotted, with the liquid phase proportion being 5 × 10⁻⁶. -4 This can be determined by calculating the temperature at which the percentage becomes less than or equal to %.

[0024] By controlling the homogenization time (holding time at the homogenization temperature) in the homogenization process, the homogenization and productivity of the slab can be controlled. If the homogenization time is less than 4 hours, the microstructure of the hot-rolled aluminum alloy sheet will be non-uniform, and the desired texture cannot be obtained. Therefore, the homogenization time should be 4 hours or longer. On the other hand, if the homogenization time is too long, productivity will decrease, so the homogenization time should be limited to 20 hours or less.

[0025] Soaking process In the soaking process, a soaking treatment is performed by holding the material at a temperature range of 520-560°C for at least one hour. By controlling the soaking temperature in the soaking process (heating temperature during the soaking treatment), the temperature during hot rolling can be controlled. If the soaking temperature is below 520°C, hot rolling will be performed at a low temperature, and the desired texture cannot be obtained in the hot-rolled aluminum alloy sheet. Therefore, the soaking temperature should be 520°C or higher. On the other hand, if the soaking temperature exceeds 560°C, hot rolling will be performed at a high temperature, making it easier for precipitates to form during hot rolling. As a result, the area ratio of regions with a Cube orientation in the hot-rolled aluminum alloy sheet decreases. Consequently, excessive 45° oriented edges are formed in the aluminum alloy sheet. Therefore, the soaking temperature should be 560°C or lower.

[0026] By controlling the soaking time (holding time at the soaking temperature) during the soaking process, the temperature during hot rolling can be controlled. If the soaking time is less than one hour, the temperature of the slab before hot rolling will be uneven, resulting in insufficient or excessive temperature rise for hot rolling. Therefore, the soaking time should be one hour or longer. On the other hand, if the soaking time is too long, productivity will decrease, so the soaking time may be limited to 5 hours or less.

[0027] Hot rough rolling process In the hot rough rolling process, an intermediate plate with a thickness of 15 to 40 mm is obtained by hot rough rolling of the slab. Here, the intermediate plate refers to the plate after hot rough rolling but before hot finish rolling. The method of hot rough rolling is not particularly limited, as long as an intermediate plate with the aforementioned thickness can be obtained.

[0028] Hot finishing rolling process In the hot finishing rolling process, the intermediate sheet is hot-finished to a thickness of 2.0 to 4.0 mm. This hot finishing rolling process yields a hot-rolled aluminum alloy sheet.

[0029] Hot finish rolling may be performed using either a single-reverse hot finish rolling mill or a tandem hot finish rolling mill. In hot finish rolling using a single-reverse hot finish rolling mill, the intermediate plate is passed through in one direction, and then repeatedly passed through in the opposite direction, thereby performing the hot finish rolling. In hot finish rolling using a tandem hot finish rolling mill, the intermediate plate is passed through in only one direction, and the hot finish rolling is performed by multiple rolling mills arranged in a continuous manner.

[0030] By controlling the thickness of the hot-rolled aluminum alloy sheet after hot finish rolling, the hot-rollability and the edge shape after DI forming can be controlled. If the thickness of the hot-rolled aluminum alloy sheet is less than 2.0 mm, there is a risk of adhesion to the roll surface when the sheet is wound up. In addition, it becomes difficult to control the profile of the hot-rolled aluminum alloy sheet. Therefore, hot finish rolling should be performed so that the thickness of the hot-rolled aluminum alloy sheet is 2.0 mm or more. It is also preferable to perform hot finish rolling so that the thickness of the hot-rolled aluminum alloy sheet is 2.5 mm or more. On the other hand, if the thickness of the hot-rolled aluminum alloy sheet exceeds 4.0 mm, excessive 45° edges are formed on the aluminum alloy sheet. Therefore, hot finishing rolling is performed so that the thickness of the hot-rolled aluminum alloy sheet is 4.0 mm or less. Furthermore, it is preferable to perform hot finishing rolling so that the thickness of the hot-rolled aluminum alloy sheet is 3.5 mm or less.

[0031] The thickness of an aluminum alloy hot-rolled sheet after hot finish rolling can be controlled by adjusting the reduction ratio at each stage of the hot finish rolling process, which involves multiple rolling steps.

[0032] In the hot finishing rolling process, controlling the average strain rate in the pass immediately preceding the final pass allows for control of the area ratio of regions with Cube orientation and the average value of the local orientation difference in the hot-rolled aluminum alloy sheet. If the average strain rate in the pass immediately preceding the final pass is less than 10 / s, productivity decreases. Therefore, the average strain rate in the pass immediately preceding the final pass should be 10 / s or higher. On the other hand, if the average strain rate exceeds 25 / s in the pass immediately preceding the final pass, the area ratio of regions with Cube orientation in the hot-rolled aluminum alloy sheet decreases, and the average value of the local orientation difference increases. As a result, excessive 45° oriented edges are formed in the aluminum alloy sheet. Therefore, the average strain rate in the pass immediately preceding the final pass should be 25 / s or less.

[0033] In this context, the pass immediately preceding the final pass refers to the pass immediately before the final pass. For example, in a hot finishing rolling process consisting of 1, 2, 3...10 passes, it refers to the 9th pass.

[0034] Now, let's explain the mean strain rate. Conventionally, in controlling the rolling conditions of hot rolling, two factors were mainly controlled: the rolling speed and the rolling rate (change in plate thickness). The inventors of the present invention have found that it is preferable to control the rolling conditions using the average strain rate, which includes the effect of the roll radius, in addition to the two factors in the conventional control method. In this embodiment, the following equations (1) and (2) are used to calculate the average strain rate ε. Here, in equations (1) and (2) below, t0 is the entry plate thickness, t1 is the exit plate thickness, s is the rolling speed, r is the roll radius, and a is the bite angle.

[0035]

number

[0036]

number

[0037] Figure 1 shows the relationship between the roll radius r and the average strain rate ε. As shown in Figure 1, the average strain rate changes when the roll radius r is changed, suggesting that the roll radius r also affects the texture of the hot-rolled aluminum alloy sheet.

[0038] In the hot finishing rolling process, controlling the exit temperature in the pass immediately preceding the final pass allows for control of the area ratio of regions with Cube orientation and the average value of the local orientation difference in the hot-rolled aluminum alloy sheet. If the exit temperature in the pass immediately preceding the final pass is less than 300°C, the exit temperature in the final pass cannot be controlled favorably as described later. Therefore, the exit temperature in the pass immediately preceding the final pass should be 300°C or higher. On the other hand, if the exit temperature in the pass immediately preceding the final roll exceeds 380°C, the average value of the local orientation difference increases in the hot-rolled aluminum alloy sheet. As a result, excessive 45° oriented edges are formed in the aluminum alloy sheet. Therefore, the exit temperature in the pass immediately preceding the final roll should be kept below 380°C.

[0039] In the hot finishing rolling process, the area ratio of regions with Cube orientation and the average value of local orientation differences in the hot-rolled aluminum alloy sheet can be controlled by controlling the average strain rate in the final pass. If the average strain rate in the final pass is less than 50 / s, the area ratio of regions with Cube orientation in the hot-rolled aluminum alloy sheet decreases. As a result, excessive 45° oriented edges are formed in the aluminum alloy sheet. Therefore, the average strain rate in the final pass should be 50 / s or higher. On the other hand, if the average strain rate in the final pass exceeds 160 / s, productivity decreases due to roll heating. Furthermore, controlling the profile of the hot-rolled aluminum alloy sheet becomes difficult. Therefore, the average strain rate in the final pass should be 160 / s or less. The average strain rate can be calculated using equations (1) and (2) above.

[0040] In the hot finishing rolling process, the area ratio of regions with Cube orientation and the average value of local orientation difference in the hot-rolled aluminum alloy sheet can be controlled by controlling the exit temperature in the final pass. If the exit temperature in the final pass is less than 310°C, the average value of local orientation difference in the hot-rolled aluminum alloy sheet increases. As a result, excessive 45° oriented edges are formed in the aluminum alloy sheet. Therefore, the exit temperature in the final pass should be 310°C or higher. Preferably, it should be 340°C or higher. On the other hand, if the exit temperature in the final pass exceeds 380°C, the area ratio of regions with a Cube orientation in the hot-rolled aluminum alloy sheet decreases. As a result, excessive 45° oriented edges are formed in the aluminum alloy sheet. Furthermore, productivity decreases due to roll heat generation. Therefore, the exit temperature in the final pass should be kept below 380°C.

[0041] Cold rolling process In the cold rolling process, an aluminum alloy sheet with a thickness of 0.20 to 1.00 mm is obtained by cold rolling a hot-rolled aluminum alloy sheet. By controlling the thickness of the aluminum alloy sheet after cold rolling, the DI formability and the edge shape after DI forming can be controlled. If the thickness of the aluminum alloy sheet after cold rolling is less than 0.20 mm, excessive 45° edges are formed on the aluminum alloy sheet. In addition, the strength of the can body after aluminum can forming will be insufficient. Therefore, cold rolling is performed so that the thickness of the aluminum alloy sheet after cold rolling is 0.20 mm or more. On the other hand, if the thickness of the aluminum alloy sheet after cold rolling exceeds 1.00 mm, the ironing rate during DI forming increases, making it more prone to cracking. As a result, the yield decreases. Therefore, cold rolling is performed so that the thickness of the aluminum alloy sheet after cold rolling is 1.00 mm or less.

[0042] The thickness of an aluminum alloy sheet after cold rolling can be controlled by adjusting the reduction ratio at each stage of the cold rolling process, which involves multiple rolling steps.

[0043] In the manufacturing method of aluminum alloy sheets according to this embodiment, intermediate annealing is not performed in the cold rolling process. Therefore, energy consumption can be reduced, and a significant contribution to achieving carbon neutrality can be made. Intermediate annealing, as used here, refers to a heat treatment in cold rolling, where multiple rolling processes are performed, involving heating to a predetermined temperature range between rolling cycles and maintaining that temperature range.

[0044] In the method for manufacturing aluminum alloy sheets according to this embodiment, a final annealing step may be optionally performed on the aluminum alloy sheet after the cold rolling step, in which the sheet is held at a temperature range of 100 to 210°C for 2 to 10 hours. When final annealing is performed, setting the annealing temperature to the 100 to 210°C range and the annealing time to 2 to 10 hours improves the elongation of the aluminum alloy sheet and improves its DI formability. In addition, it is possible to increase the strength of the aluminum alloy sheet.

[0045] Next, the hot-rolled aluminum alloy sheet according to this embodiment will be described. The hot-rolled aluminum alloy sheet according to this embodiment refers to an intermediate product in the manufacturing of an aluminum alloy sheet, and specifically refers to a sheet after the hot finishing rolling process and before the cold rolling process.

[0046] The hot-rolled aluminum alloy sheet according to this embodiment is The chemical composition is expressed in mass percent. Si: 0.20~0.35%, Fe: 0.35~0.55%, Cu: 0.15~0.48%, Mn: 0.80~1.15%, Contains Mg: 0.60-1.60%, The remainder consists of Al and impurities. The plate thickness is 2.0 to 4.0 mm. When EBSD measurements were performed on the ND-RD cross section, the average value of the local orientation difference was 2.0° or less, with local orientation differences ranging from 0 to 5°, and the area ratio of regions with Cube orientation was 10 to 25%. The following explains each of the regulations. Note that the chemical composition is the same as described in the manufacturing method of the aluminum alloy sheet, so the explanation is omitted.

[0047] Plate thickness: 2.0~4.0mm If the thickness of the hot-rolled aluminum alloy sheet is less than 2.0 mm, there is a risk of it adhering to the roll surface when being wound up. Furthermore, controlling the profile of the hot-rolled aluminum alloy sheet becomes difficult. Therefore, the thickness of the hot-rolled aluminum alloy sheet should be 2.0 mm or more. Preferably, it should be 2.5 mm or more. On the other hand, if the thickness of the hot-rolled aluminum alloy sheet exceeds 4.0 mm, excessive 45° edges are formed on the aluminum alloy sheet. Therefore, the thickness of the hot-rolled aluminum alloy sheet should be 4.0 mm or less. Preferably, it should be 3.5 mm or less.

[0048] Average local azimuth difference of 0-5°: 2.0° or less A low average value of local orientation difference, where the local orientation difference is between 0 and 5°, indicates that the recrystallized texture is well-developed. If the recrystallized texture is not well-developed, excessive 45° oriented edges will form in the aluminum alloy plate. Therefore, in this embodiment, the recrystallized texture is sufficiently developed, that is, the average value of the local orientation difference, where the local orientation difference is between 0 and 5°, is controlled to 2.0° or less.

[0049] When EBSD measurements are performed on an ND-RD cross section, if the average value of the local orientation difference between 0 and 5° exceeds 2.0°, excessive 45° edging is formed in the aluminum alloy plate. Therefore, the average value of the local orientation difference between 0 and 5° should be 2.0° or less. Preferably, it should be 1.5° or less, and more preferably 1.2° or less. There is no particular lower limit to the average value of the local azimuth difference when the local azimuth difference is between 0 and 5°, but it may be set to 0.5° or higher or 0.8° or higher.

[0050] Area ratio of regions with Cube orientation: 10-25% When EBSD measurements are performed on an ND-RD cross-section, if the area ratio of the region with Cube orientation is less than 10%, excessive 45° oriented edges are formed in the aluminum alloy plate. Therefore, the area ratio of the region with Cube orientation should be 10% or more. Preferably, it should be 15% or more. On the other hand, if the area ratio of the region having a Cube orientation exceeds 25%, excessive edges are formed in the aluminum alloy sheet in the 0° and 90° directions relative to the rolling direction. Therefore, the area ratio of the region having a Cube orientation should be 25% or less. Preferably, it should be 20% or less.

[0051] The following describes how to measure the average value of local orientation differences (where the local orientation difference is between 0 and 5°) and the area ratio of regions with Cube orientation. A sample is taken from a hot-rolled aluminum alloy sheet so that the ND-RD cross-section (thickness cross-section parallel to the rolling direction) can be observed. The observation surface of the sample is mechanically polished, electrolytically polished, or ion-milled. Next, EBSD (Electron Back Scattering Diffraction) measurement is performed on the observation surface using an EBSD system consisting of a field emission scanning electron microscope (JEOL Ltd. JSM-7900F) and an EBSD detector (TSL Solutions Co., Ltd. DIGIVIEW5) to obtain crystal orientation information. The measurement conditions are as follows: magnification of 200x, measurement area of ​​the entire sheet thickness × 420 μm or more, field of view of 10 or more, acceleration voltage of 15 kV, current value of 6-7 nA, working distance (WD) of 15 mm, and measurement interval of 3.0 μm.

[0052] Using the OIM Software (manufactured by TSL Solutions Co., Ltd.) included with the EBSD analyzer, the orientation difference between adjacent measurement points is calculated for the crystal orientation information, and this orientation difference is considered as the local orientation difference. The average value of local orientation differences between 0 and 5° is calculated to obtain the average value of local orientation differences between 0 and 5°.

[0053] Furthermore, by using the OIM Software (manufactured by TSL Solutions Co., Ltd.) included with the EBSD analyzer, the Cube orientation ((100) <001> The area ratio of regions having orientations with an angular difference of 15° or less from the Cube orientation is calculated. This yields the area ratio of regions having the Cube orientation.

[0054] Next, the aluminum alloy sheet according to this embodiment will be described. The aluminum alloy sheet according to this embodiment refers to a sheet obtained by cold rolling and, if necessary, final annealing of the hot-rolled aluminum alloy sheet described above. The aluminum alloy sheet according to this embodiment has a high 0.2% yield strength and excellent DI formability, and has high can body strength after can manufacturing, making it suitable as an aluminum alloy sheet for manufacturing beverage cans.

[0055] The aluminum alloy plate according to this embodiment is The chemical composition is expressed in mass percent. Si: 0.20~0.35%, Fe: 0.35~0.55%, Cu: 0.15~0.48%, Mn: 0.80~1.15%, Contains Mg: 0.60-1.60%, The remainder consists of Al and impurities. The plate thickness is 0.20 to 1.00 mm. The cube orientation density is 0.9 or higher. The Cu orientation density is 12.5 or less. The 0.2% yield strength in the rolling direction is 220-340 MPa. The change in 0.2% yield strength after heat treatment at 210°C for 10 minutes is 15% or less. The following explains each of the regulations. Note that the chemical composition is the same as described in the manufacturing method of the aluminum alloy sheet, so the explanation is omitted.

[0056] Plate thickness: 0.20~1.00mm If the thickness of the aluminum alloy sheet is less than 0.20 mm, excessive 45° edges will be formed on the aluminum alloy sheet. Furthermore, the strength of the can body after aluminum can molding will be insufficient. Therefore, the thickness of the aluminum alloy sheet should be 0.20 mm or more. On the other hand, if the thickness of the aluminum alloy sheet exceeds 1.00 mm, the ironing rate during DI forming increases, making it more prone to cracking. As a result, the yield decreases. Therefore, the thickness of the aluminum alloy sheet should be 1.00 mm or less.

[0057] Cube orientation density: 0.9 or more If the Cube orientation density is less than 0.9, the valley height in the 90° and 270° directions relative to the rolling direction will be low in the aluminum alloy sheet after deep drawing (DI processing), making it impossible to achieve the appropriate edge ratio as described later. Therefore, the Cube orientation density should be 0.9 or higher. There is no particular upper limit to the cube orientation density, but it may be set to 5.0 or less.

[0058] Cu orientation density: 12.5 or less If the Cu orientation density exceeds 12.5, the peak height in the 45° direction relative to the rolling direction becomes high in aluminum alloy sheets after deep drawing (DI processing), making it impossible to achieve the appropriate edge ratio as described later. Therefore, the Cu orientation density should be 12.5 or less. There is no particular lower limit to the Cu azimuthal density, but it may be set to 6.0 or higher.

[0059] The methods for measuring Cube orientation density and Cu orientation density are described below. A circular sample with a diameter of 40 mm is taken from an aluminum alloy sheet after cold rolling or final annealing, with the sheet surface serving as the measurement surface. Next, Schultz reflection diffractometer (α=20°~90°, β=0°~360°) is used on the measurement surface with an X-ray diffractometer (SmartLab, Rigaku Corporation) to obtain incomplete pole figures for (220), (200), and (111). From the incomplete pole figures, the crystal orientation distribution function f(ψ1, φ, ψ2) is determined using crystal orientation distribution function analysis software (StandardODF, Norm Engineering Co., Ltd.) and a 22nd-order series expansion method. The values ​​for ψ1=0°, φ=0°, and ψ2=0° are defined as the Cube orientation density. The values ​​for ψ1=90°, φ=30°, and ψ2=45° are defined as the Cu orientation density.

[0060] 0.2% yield strength in the rolling direction: 220-340 MPa If the 0.2% yield strength in the rolling direction is less than 220 MPa, the DI formability of the aluminum alloy sheet deteriorates, and the strength of the can body decreases. Therefore, the 0.2% yield strength in the rolling direction should be 220 MPa or higher. Preferably, it should be 250 MPa or higher. On the other hand, if the 0.2% yield strength in the rolling direction exceeds 340 MPa, the DI formability of the aluminum alloy sheet deteriorates. Therefore, the 0.2% yield strength in the rolling direction should be 340 MPa or less. Preferably, it should be 320 MPa or less.

[0061] The 0.2% yield strength in the rolling direction is obtained by performing a tensile test. In accordance with JIS Z 2241:2011, a JIS No. 5 test specimen was prepared, with the tensile axis aligned with the rolling direction of the aluminum alloy sheet, and the initial strain rate set to 6.67 × 10⁻⁶. -4 A tensile test will be performed using the / s setting.

[0062] Change in 0.2% yield strength after heat treatment at 210°C for 10 minutes: 15% or less If the change in 0.2% yield strength of an aluminum alloy sheet after heat treatment at 210°C for 10 minutes exceeds 15%, the balance between the material strength during DI molding and the material strength after baking in the can manufacturing process becomes poor, making it impossible to improve both DI moldability and can body strength simultaneously. Therefore, the change in 0.2% yield strength after heat treatment at 210°C for 10 minutes should be 15% or less. The rate of change in 0.2% yield strength after heat treatment at 210°C for 10 minutes may be considered as 0%.

[0063] The 0.2% yield strength after heat treatment at 210°C for 10 minutes is obtained by heating an aluminum alloy plate to 210°C, holding it at that temperature for 10 minutes, and then performing a tensile test in the same manner as described above. From the 0.2% yield strength after heat treatment and the 0.2% yield strength before heat treatment, the rate of change of the 0.2% yield strength after heat treatment at 210°C for 10 minutes ((|0.2% yield strength before heat treatment - 0.2% yield strength after heat treatment| / 0.2% yield strength before heat treatment) × 100%) is calculated. [Examples]

[0064] Next, the effects of one aspect of the present invention will be described in more detail with reference to examples. However, the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to these examples of conditions. The present invention can adopt various conditions as long as they do not depart from the spirit of the invention and achieve the objectives of the present invention.

[0065] Aluminum alloys having the chemical compositions shown in Tables 1A and 1B were melted and semi-continuous casting was performed to obtain slabs. From the obtained slabs, aluminum alloy hot-rolled plates and aluminum alloy sheets shown in Tables 3A and 3B were obtained under the conditions shown in Tables 2A and 2B. A single-reverse hot finishing mill was used for the hot finishing rolling.

[0066] For the obtained hot-rolled aluminum alloy sheets, the average value of the local orientation difference (where the local orientation difference is between 0 and 5°) and the area ratio of the region having a Cube orientation were determined using the method described above. Furthermore, the Cube orientation density, 0.2% yield strength in the rolling direction, and the rate of change in 0.2% yield strength after heat treatment at 210°C for 10 minutes were determined for the obtained aluminum alloy sheets using the method described above. In addition, the presence or absence of edges, DI formability, and can body strength after fabrication were evaluated for the aluminum alloy sheets using the following method.

[0067] ear rate To evaluate the suppression of edge formation in aluminum alloy sheets, the edge ratio was measured during the can manufacturing process. The edge ratio was calculated from the side wall height of a cup obtained by deep drawing an aluminum alloy sheet using an Erichsen testing machine. The processing conditions were: punch diameter: 33 mm (flat head punch), drawing ratio: 1.75, and wrinkle-holding force: 3 kN. The side wall height of this cup was measured with a digital micrometer, and the edge ratio was calculated using the following formula. (Average peak height - Average valley height) ÷ Average valley height × 100 = Ear rate (%) Furthermore, the average crest heights in the 0° and 180° directions relative to the rolling direction, as well as the average crest heights in the 45°, 135°, 225°, and 315° directions, were determined, and the higher of the two average heights was used as the average crest height in the above formula. In addition, the average valley heights in the 90° and 270° directions were determined and used as the average valley height in the above formula.

[0068] The ear rate was measured for three samples, and the average value was calculated. If the average ear rate obtained was less than 2.5%, it was evaluated as "○", if it was between 2.5% and 3.5%, it was evaluated as "△", and if it was greater than 3.5%, it was evaluated as "×". A rating of "○" or "△" was judged as a pass, and a rating of "×" was judged as a fail.

[0069] DI formability DI moldability was evaluated as follows: "○" for no can breakage during continuous can manufacturing of 10,000 cans, "△" for one can breakage, and "×" for two or more can breakages. A rating of "○" or "△" was judged as passing, and a rating of "×" was judged as failing.

[0070] Can body strength after fabrication A compressed axial load was applied to molded aluminum cans (sample size = 10), and the load at which the aluminum can buckled was measured. The average value of this load was defined as the column strength. A column strength of 1250N or more was marked "○", a value between 1200N and less than 1250N was marked "△", and a value less than 1200N was marked "×". A value of "○" or "△" was judged as a pass, and a value of "×" was judged as a fail.

[0071] [Table 1A]

[0072] [Table 1B]

[0073] [Table 2A]

[0074] [Table 2B]

[0075] [Table 3A]

[0076] [Table 3B]

[0077] As shown in Tables 3A and 3B, the aluminum alloy sheet according to the present invention has suppressed edge formation, high 0.2% yield strength and excellent DI formability, and high can body strength after can manufacturing. On the other hand, it can be seen that the aluminum alloy plate in the comparative example has deteriorated in one or more properties. [Industrial applicability]

[0078] According to the above embodiment of the present invention, it is possible to provide a method for manufacturing an aluminum alloy sheet that suppresses the formation of edges during cold rolling, has a high 0.2% yield strength and excellent DI formability, and has high can body strength after can manufacturing, without performing intermediate annealing during cold rolling. Furthermore, we can provide the aforementioned aluminum alloy sheet and the aluminum alloy hot-rolled sheet capable of manufacturing this aluminum alloy sheet. The method for manufacturing aluminum alloy sheets according to the above embodiment omits intermediate annealing during cold rolling and controls the texture during the hot finishing rolling process, thereby contributing to further energy savings and process simplification. The aluminum alloy sheets according to the above embodiment have a high 0.2% yield strength and excellent DI formability, and also have high can body strength after can manufacturing, making them suitable as aluminum alloy sheets for manufacturing beverage cans.

Claims

1. The chemical composition is expressed in mass percent. Si: 0.20-0.35%, Fe: 0.35-0.55%, Cu: 0.15-0.48%, Mn: 0.80 to 1.15%, Mg: Contains 0.60-1.60%, A casting process in which an aluminum alloy consisting of Al and impurities is melted and a slab is obtained by semi-continuous casting, A homogenization process is performed by holding the material at a temperature range of 560°C or higher and below the melting point for 4 hours or more. A soaking process involves maintaining a temperature range of 520-560°C for at least one hour, A hot rough rolling process is performed to make the plate thickness 15 to 40 mm, A hot finishing rolling process in which hot finishing rolling is performed so that the plate thickness becomes 2.0 to 4.0 mm, The process includes, in sequence, a cold rolling process in which the plate thickness is cold-rolled to 0.20 to 1.00 mm, In the aforementioned cold rolling process, intermediate annealing is not performed. In the aforementioned hot finishing rolling process, In the final pass before the last pass, the average strain rate is set to 10-25 / s, and the exit temperature is set to a temperature range of 300-380°C. In the final pass, by setting the average strain rate to 50-160 / s and the exit temperature to a temperature range of 310-380°C, The plate thickness is 0.20 to 1.00 mm. The cube azimuthal density is 0.9 or higher. The Cu orientation density is 12.5 or less. The 0.2% yield strength in the rolling direction is 220 to 340 MPa. A method for producing an aluminum alloy sheet, characterized by obtaining an aluminum alloy sheet in which the change in 0.2% yield strength after heat treatment at 210°C for 10 minutes is 15% or less.

2. The method for manufacturing an aluminum alloy sheet according to claim 1, characterized in that a final annealing is performed after the cold rolling process, by holding the sheet at a temperature range of 100 to 210°C for 2 to 10 hours.

3. The chemical composition is expressed in mass percent. Si: 0.20-0.35%, Fe: 0.35-0.55%, Cu: 0.15-0.48%, Mn: 0.80 to 1.15%, Mg: Contains 0.60-1.60%, The remainder consists of Al and impurities. The plate thickness is 2.0 to 4.0 mm. A hot-rolled aluminum alloy sheet characterized by having an average value of local orientation differences of 2.0° or less, where the local orientation difference is 0 to 5°, and the area ratio of the region having a cube orientation is 10 to 25% when measured by EBSD on an ND-RD cross section.

4. The chemical composition is expressed in mass percent. Si: 0.20-0.35%, Fe: 0.35-0.55%, Cu: 0.15-0.48%, Mn: 0.80 to 1.15%, Mg: Contains 0.60-1.60%, The remainder consists of Al and impurities. The plate thickness is 0.20 to 1.00 mm. The cube azimuthal density is 0.9 or higher. The Cu orientation density is 12.5 or less. The 0.2% yield strength in the rolling direction is 220 to 340 MPa. An aluminum alloy sheet characterized by having a change in 0.2% yield strength of 15% or less after heat treatment at 210°C for 10 minutes.

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