Aluminum alloy sheet for can lids

Abstract

This aluminum alloy sheet for can lids has a Si content of 0.17-0.40 mass%, an Fe content of 0.30-0.60 mass%, a Cu content of 0.10-0.30 mass%, a Mn content of 0.55-1.0 mass%, and a Mg content of 2.8-4.4 mass%, with the remainder either consisting of Al and unavoidable impurities or comprising Al and unavoidable impurities, wherein a temperature difference ΔT1 obtained by subtracting the melting temperature of Mg2Si from the melting temperature of Al is not less than -1°C, the total content of Fe and Mn is not more than 1.30 mass%, and S represented by expression (1) is not less than 380 MPa. Expression (1): S=σfm / (σ0.2 / σB)

Description

Aluminum alloy plate for can lids Cross-reference of related applications

[0001] This international application claims priority under Japanese Patent Application No. 2024-191930, filed with the Japan Patent Office on 31 October 2024, and the entire contents of Japanese Patent Application No. 2024-191930 are incorporated herein by reference.

[0002] This disclosure relates to an aluminum alloy sheet for can lids.

[0003] In recent years, due to growing environmental awareness, CO2 emissions have been increasing in the manufacturing process. ２ There is a demand for aluminum alloy sheets with low CO emissions. ２ The alloy composition of new aluminum ingots is a major indirect contributor to emissions.

[0004] When manufacturing new aluminum ingots, a large amount of electricity is used in the refining process, and a large amount of CO2 is used. ２ CO2 emissions. Therefore, reducing the amount of new aluminum ingots in the alloy and increasing the horizontal recycling rate will reduce CO2 emissions in the aluminum alloy sheet manufacturing process. ２ This will lead to a reduction in emissions.

[0005] Generally, when aluminum scrap is remelted and used for casting, CO2 is produced. ２ It is said that emissions can be reduced to about 1 / 30th of those generated when manufacturing new aluminum ingots. The production volume of aluminum alloy sheets used for beverage cans is very large worldwide. Further improving the horizontal recycling rate of aluminum alloy sheets used for beverage cans is of great significance in reducing the environmental impact.

[0006] Can lids, which are mainly made of 5182 aluminum alloy (AA5182 alloy), have lower upper limits on the component specifications of Si, Fe, Cu, Mn, etc., compared to can bodies, which are made of 3104 aluminum alloy (AA3104 alloy). Therefore, it is difficult to incorporate scrap raw materials derived from can materials mixed with 3104 aluminum alloy into aluminum alloy sheets for can lids.

[0007] For example, in the case of used beverage cans (UBC) generated from urban areas, the mass ratio of the can body is larger than that of the can lid, and it contains more components of 3104 aluminum alloy. Therefore, in the manufacturing process of the aluminum alloy sheet for can lids, if the scrap raw material derived from the can material is directly blended, the mass ratios of components such as Si, Fe, Cu, and Mn in the aluminum alloy sheet for can lids are likely to exceed the upper limits of the components in the 5182 aluminum alloy.

[0008] Therefore, in the manufacturing process of the aluminum alloy sheet for can lids, compared with the manufacturing process of the aluminum alloy sheet for can bodies, by using more new aluminum ingots, the composition of the aluminum alloy sheet for can lids is adjusted to be close to the composition of the 5182 aluminum alloy. As a result, the recycling rate in the manufacturing process of the aluminum alloy sheet for can lids was low.

[0009] If the aluminum alloy sheet for can lids has a composition that is easy to blend with 3104 aluminum alloy, the usage rate of new aluminum ingots in the manufacturing process of the aluminum alloy sheet for can lids can be significantly reduced. Patent Document 1 discloses an aluminum alloy sheet for can lids that has a composition relatively close to that of 3104 aluminum alloy and is excellent in recyclability.

[0010] Japanese Patent Laid-Open No. Hei 5-263175

[0011] When blending the scrap raw material derived from the can material in the manufacturing process, the composition of the manufactured aluminum alloy sheet for can lids approaches the composition of 3104 aluminum alloy. In this case, there arises a problem that the strength or toughness is likely to decrease.

[0012] In one aspect of the present disclosure, it is desirable to provide an aluminum alloy sheet for can lids that can blend the scrap raw material derived from the can material in the manufacturing process and has high strength and toughness.

[0013] (1) One aspect of the present disclosure is an aluminum alloy sheet for can lids having a silicon (Si) content of 0.17% by mass or more and 0.40% by mass or less, an iron (Fe) content of 0.30% by mass or more and 0.60% by mass or less, a copper (Cu) content of 0.10% by mass or more and 0.30% by mass or less, a manganese (Mn) content of 0.55% by mass or more and 1.0% by mass or less, a magnesium (Mg) content of 2.8% by mass or more and 4.4% by mass or less, with the remainder being aluminum (Al) and unavoidable impurities, or the remainder being aluminum (Al) and unavoidable impurities.

[0014] From the melting point of aluminum (Al) to Mg ２ The temperature difference ΔT obtained by subtracting the melting temperature of Si. １ The temperature is -1°C or higher. The total content of iron (Fe) and manganese (Mn) is 1.30% by mass or less. The S, represented by the following formula (1), is 380 MPa or higher.

[0015] Equation (1) S = σfm / (σ0.2 / σB) In Equation (1), σfm is the average value of σ0.2 and σB. σ0.2 is the 0.2% yield strength. σB is the tensile strength.

[0016] One aspect of this disclosure, the aluminum alloy sheet for can lids, can incorporate scrap raw materials derived from can materials during the manufacturing process, and has high strength and toughness.

[0017] (2) Another aspect of the present disclosure is an aluminum alloy sheet for can lids having a silicon (Si) content of 0.17% by mass or more and 0.40% by mass or less, an iron (Fe) content of 0.30% by mass or more and 0.60% by mass or less, a copper (Cu) content of 0.10% by mass or more and 0.30% by mass or less, a manganese (Mn) content of 0.55% by mass or more and 1.0% by mass or less, a magnesium (Mg) content of 3.3% by mass or more and 4.4% by mass or less, with the remainder being aluminum (Al) and unavoidable impurities, or the remainder being aluminum (Al) and unavoidable impurities.

[0018] From the melting point of aluminum (Al) to Mg ２The temperature difference ΔT obtained by subtracting the melting temperature of Si １ is −1°C or higher. The total content of iron (Fe) and manganese (Mn) is 1.25 mass% or less. S represented by the following formula (1) is 400 MPa or higher.

[0019] Formula (1) S = σfm / (σ0.2 / σB) In formula (1), σfm is the average value of σ0.2 and σB. σ0.2 is the 0.2% proof stress (Yield Strength). σB is the tensile strength (Tensile Strength).

[0020] The aluminum alloy sheet for can lids, which is another aspect of the present disclosure, can incorporate scrap raw materials derived from can materials in the manufacturing process and has high strength and toughness.

[0021] (3) Another aspect of the present disclosure is an aluminum alloy sheet for can lids in which the content of silicon (Si) is 0.17 mass% or more and 0.40 mass% or less, the content of iron (Fe) is 0.30 mass% or more and 0.60 mass% or less, the content of copper (Cu) is 0.10 mass% or more and 0.30 mass% or less, the content of manganese (Mn) is 0.55 mass% or more and 1.0 mass% or less, the content of magnesium (Mg) is 3.3 mass% or more and 4.4 mass% or less, and the balance consists of aluminum (Al) and inevitable impurities, or the balance contains aluminum (Al) and inevitable impurities.

[0022] The temperature difference from the melting temperature of aluminum (Al) to Mg ２ The temperature difference ΔT obtained by subtracting the melting temperature of Si １ is −1°C or higher. The total content of iron (Fe) and manganese (Mn) is 1.25 mass% or less. S represented by the following formula (1) is 400 MPa or higher. The temperature difference ΔT obtained by subtracting the crystallization temperature of AlFeMn from the solidification start temperature of aluminum (Al) ２ is 1°C or higher. The total of the area ratio of AlFeMn with an equivalent circle diameter of 1 μm or more and the area ratio of Mg ２ Si with an equivalent circle diameter of 1 μm or more is 2.5% or less.

[0023] Equation (1) S = σfm / (σ0.2 / σB) In Equation (1), σfm is the average value of σ0.2 and σB. σ0.2 is the 0.2% yield strength. σB is the tensile strength.

[0024] Another aspect of this disclosure, the aluminum alloy sheet for can lids, can incorporate scrap raw materials derived from can materials during the manufacturing process and has high strength and toughness.

[0025] This is an explanatory diagram showing the L-ST cross-section of a test specimen. It is a schematic diagram representing a repeated bending test.

[0026] Exemplary embodiments of the present disclosure will be described with reference to the drawings. <First Embodiment> 1. Composition of Aluminum Alloy Plate for Can Lid (1) Composition of Aluminum Alloy Plate for Can Lid The aluminum alloy plate for can lid of the present disclosure (hereinafter also simply referred to as "alloy plate") contains aluminum (Al), silicon (Si), iron (Fe), copper (Cu), manganese (Mn), and magnesium (Mg).

[0027] The Si content in the alloy sheet is 0.17% by mass or more, and preferably 0.20% by mass or more. If the Si content is less than 0.17% by mass, the amount of Si precipitated due to the processing heat of hot rolling and cold rolling will decrease, which may result in insufficient tensile strength of the alloy sheet.

[0028] The average Si content of 3104 aluminum alloy, as specified in JIS-H-4000:2014, is 0.33 mass%. The average Si content of 5182 aluminum alloy, as specified in JIS-H-4000:2014, is 0.10 mass%. A Si content of 0.17 mass% or more allows for a larger amount of 3104 aluminum alloy scrap to be incorporated during the manufacturing process of the alloy sheet.

[0029] The Si content in the alloy sheet is 0.40% by mass or less, preferably 0.30% by mass or less. If the Si content exceeds 0.40% by mass, Mg crystallizes during casting. ２ The increase in Si makes it difficult to achieve greater solid solution during the homogenization process. Furthermore, in hot rolling, coarse Mg...２ New silicon precipitates. As a result, tensile strength and toughness decrease.

[0030] If the Si content is 0.40% by mass or less, Mg ２ Si can be easily dissolved in the homogenization process. Also, coarse Mg in hot rolling ２ Si precipitation is suppressed, and good tensile strength and toughness can be obtained without performing a heat treatment process after hot rolling.

[0031] The Fe content in the alloy sheet is 0.30% by mass or more, preferably 0.35% by mass or more. The average Fe content standard for 3104 aluminum alloy is 0.40% by mass. The average Fe content standard for 5182 aluminum alloy is 0.18% by mass. By setting the Fe content in the alloy sheet to 0.30% by mass or more, a larger amount of 3104 aluminum alloy scrap can be incorporated in the manufacturing process of the alloy sheet.

[0032] The Fe content in the alloy sheet is 0.60% by mass or less, and preferably 0.45% by mass or less. If the Fe content exceeds 0.60% by mass, the amount of abnormally coarse Al-Fe-Mn or Al-Fe-Mn-Si intermetallic compounds (i.e., giant compounds) increases. As a result, crack propagation paths are created, and the toughness of the alloy sheet decreases.

[0033] By having an Fe content of 0.60 mass% or less, it is possible to suppress the crystallization of the coarse intermetallic compounds mentioned above when a large amount of Mg is added, while also compensating for the tensile strength and toughness of the alloy sheet.

[0034] The Cu content in the alloy sheet is 0.10% by mass or more, preferably 0.12% by mass or more. If the Cu content is less than 0.10% by mass, there will be insufficient Cu to increase strength through solid solution or precipitation, and the tensile strength of the alloy sheet will decrease. Note that the tensile strength of the alloy sheet can be significantly increased by precipitating Cu during hot rolling and cold rolling processes.

[0035] The average Cu content of 3104 aluminum alloy is 0.15 mass%. The average Cu content of 5182 aluminum alloy is 0.075 mass%. By setting the Cu content of the alloy sheet to 0.10 mass% or more, a larger amount of 3104 aluminum alloy scrap can be incorporated in the manufacturing process of the alloy sheet.

[0036] The Cu content in the alloy sheet is 0.30% by mass or less, preferably 0.23% by mass or less. If the Cu content exceeds 0.30% by mass, the amount of coarse precipitates increases, and the toughness of the alloy sheet decreases. By keeping the Cu content at 0.30% by mass or less, the tensile strength can be increased without significantly impairing the toughness of the alloy sheet.

[0037] The Mn content in the alloy sheet is 0.55% by mass or more, and preferably 0.60% by mass or more. If the Mn content is less than 0.55% by mass, there will be insufficient Mn to increase strength through solid solution or precipitation, and the tensile strength of the alloy sheet will decrease.

[0038] The average Mn content of 3104 aluminum alloy is 1.1% by mass. The average Mn content of 5182 aluminum alloy is 0.35% by mass. By setting the Mn content of the alloy sheet to 0.55% by mass or more, a larger amount of 3104 aluminum alloy scrap can be incorporated in the manufacturing process of the alloy sheet.

[0039] The Mn content in the alloy sheet is 1.0% by mass or less, and preferably 0.80% by mass or less. If the Mn content exceeds 1.0% by mass, the amount of abnormally coarse Al-Fe-Mn or Al-Fe-Mn-Si intermetallic compounds increases. As a result, crack propagation paths are formed, and the toughness of the alloy sheet decreases.

[0040] The Mg content in the alloy sheet is 2.8% by mass or more, and preferably 3.3% by mass or more. If the Mg content is less than 2.8% by mass, there will be insufficient Mg to increase strength through solid solution, and the tensile strength of the alloy sheet will decrease. Furthermore, the tensile strength of the alloy sheet can be significantly increased by precipitating Mg during hot rolling and cold rolling processes.

[0041] The Mg content in the alloy sheet is 4.4% by mass or less, preferably 4.2% by mass or less. The average value of the Mg component standard for 3104 aluminum alloy is 1.05% by mass. The average value of the Mg component standard for 5182 aluminum alloy is 4.5% by mass. By setting the Mg content in the alloy sheet to 4.4% by mass or less, preferably 4.2% by mass or less, it is possible to reduce the amount of additional Mg-containing raw materials added during the manufacturing process of the alloy sheet while incorporating a large amount of 3104 aluminum alloy scrap.

[0042] The alloy sheet may contain titanium (Ti). The Ti content is preferably 0.10% by mass or less. When Ti is included, the ingot structure of the alloy sheet is refined. The alloy sheet may also contain zinc (Zn). The Zn content is preferably 0.25% by mass or less. Furthermore, the alloy sheet may contain chromium (Cr). The Cr content is preferably 0.10% by mass or less.

[0043] The alloy sheet may contain unavoidable impurities to the extent that they do not significantly impair the performance of the alloy sheet. In other words, the alloy sheet contains Si, Fe, Cu, Mn, Mg, Ti, Zn, and Cr in the above-mentioned ranges, with the remainder being Al and unavoidable impurities, or the remainder being Al and unavoidable impurities. The total amount of unavoidable impurities is preferably 0.15% by mass or less. The remainder may contain substances other than Al and unavoidable impurities.

[0044] The total content of Fe and Mn in the alloy sheet is 1.30% by mass or less, preferably 1.25% by mass or less. If the Mg content in the alloy sheet is 3.3% by mass or more and 4.4% by mass or less, the total content of Fe and Mn in the alloy sheet is preferably 1.25% by mass or less. A total content of Fe and Mn of 1.30% by mass or less results in a smaller surface area ratio of precipitates, as described later.

[0045] (2) Physical properties of aluminum alloy plate for can lids (2-1) Temperature difference ΔT １ Regarding alloy plates, from the melting temperature of Al to Mg ２ The temperature difference obtained by subtracting the melting temperature of Si is the temperature difference ΔT. １ Let's assume the temperature difference ΔT is...１ The temperature is above -1°C. Temperature difference ΔT １ A temperature difference of -1°C or higher means a negative value, and its absolute value is 1°C or higher. １ When the temperature is above -1°C, Mg is less likely to crystallize coarsely during casting, and as a result, the amount of Mg solid solution increases, which increases the strength of the alloy sheet.

[0046] Temperature difference ΔT １ and the temperature difference ΔT, which will be described later. ２ The method for calculating Mg is as follows: ２ The melting temperature of Si, the solidus temperature of aluminum alloys, the solidification initiation temperature of Al, and the crystallization temperature of AlFeMn-based compounds are uniquely determined by the composition of the aluminum alloy. The method for determining these boundary temperatures from the alloy composition involves calculating the thermodynamic quantities required for each calculation using the CALPHAD method. Such thermodynamic calculations for multi-component alloys are performed using commercially available system software (JMatPro, developed by Sente Software) that combines the necessary thermodynamic database, interface, and phase diagram generation functions.

[0047] Temperature difference ΔT １ This can be controlled by changing the composition of the alloy plate. Mainly, by increasing Si or Mg, Mg ２ The melting temperature of Si shifts to the higher temperature side. Therefore, as the Si and Mg content in the alloy sheet increases, the temperature difference ΔT increases. １ It changes in the negative direction.

[0048] (2-2) Temperature difference ΔT ２ In an alloy sheet, the temperature difference obtained by subtracting the crystallization temperature of the AlFeMn-based compound from the solidification start temperature of Al is called the temperature difference ΔT. ２ Let's assume the temperature difference ΔT is... ２ It is preferable that the temperature is 1°C or higher. Temperature difference ΔT ２ A value of 1°C or greater means that it is a positive value and its absolute value is 1°C or greater. (Temperature difference ΔT) ２ When the temperature is above 1°C, AlFeMn-based compounds are less likely to crystallize. As a result, the toughness of the alloy sheet increases.

[0049] Temperature difference ΔT ２This can be controlled by changing the composition of the alloy sheet. Mainly, increasing the amount of Fe and Mn shifts the crystallization temperature of AlFeMn compounds to a higher temperature. Therefore, as the amount of Fe and Mn in the alloy composition increases, the temperature difference ΔT ２ It changes in the negative direction.

[0050] (2-3) Regarding S, S is expressed by the following equation (1).

[0051] Equation (1) S = σfm / (σ0.2 / σB) In Equation (1), σfm is the average value of σ0.2 and σB. σ0.2 is the 0.2% yield strength. σB is the tensile strength. The measurement methods for σ0.2 and σB are as follows: A No. 5 test specimen as specified in JIS-Z-2241:2011 is prepared by milling. A tensile test is performed on the test specimen in accordance with JIS-Z-2241:2011, and σ0.2 and σB are measured.

[0052] S is a value representing the strength of the alloy plate and corresponds to the pressure resistance strength of the can lid. The larger S is, the stronger the alloy plate. S is 380 MPa or higher, and preferably 400 MPa or higher. When the Mg content in the alloy plate is 3.3% by mass or more and 4.4% by mass or less, and the total Fe and Mn content in the alloy plate is 1.25% by mass or less, S is preferably 400 MPa or higher.

[0053] The higher the Mn and Mg content in the alloy sheet, the larger the S value becomes.

[0054] (2-4) AlFeMn+Mg ２ The total area ratio of Si, the area ratio of AlFeMn-based compounds with an equivalent circle diameter of 1 μm or more, and the area ratio of Mg with an equivalent circle diameter of 1 μm or more. ２ The sum of the area fraction of Si (in the following, AlFeMn + Mg ２ The total area ratio of Si is preferably 2.5% or less. AlFeMn + Mg ２ When the total area ratio of Si is 2.5% or less, the toughness of the alloy sheet becomes even higher. The lower the total content of Fe and Mn in the alloy sheet, the higher the toughness of the AlFeMn+Mg ２ The total area ratio of Si will decrease.

[0055] AlFeMn + Mg ２ The total area ratio of Si can be calculated using the following method. Prepare an alloy plate 1 as shown in Figure 1. In Figure 1, L is the longitudinal direction, ST is the thickness direction, and LT is the width direction. In Figure 1, the L-ST cross section 3 is used for measurement. The L-ST cross section 3 is a plane parallel to the longitudinal direction L and the thickness direction ST. The L-ST cross section 3 is a surface that is created by cutting the alloy plate and is mechanically polished to a mirror-like surface.

[0056] Next, the L-ST section 3 was observed using a scanning electron microscope (SEM), and 10 fields of view were obtained in the central region of the plate thickness. The SEM acceleration voltage was 15 kV, and the magnification was 500x. The area of ​​one field of view was 0.049 mm². ２ The imaging will be performed as follows: COMPO (backscattered electron composition) images will be acquired for each of the 10 fields of view.

[0057] The captured COMPO images are analyzed using the image analysis software "ImageJ". Threshold settings, such as contrast settings during SEM observation, need to be adjusted as appropriate. From the histogram of image brightness at 256 levels, Mg... ２ Determine the threshold for distinguishing between Si particles or Al-Fe-Mn compound particles. ２ In images containing Si particles and Al-Fe-Mn compound particles, three peaks are present in the brightness histogram. The mode peak corresponds to the aluminum matrix peak, and its brightness is denoted as P1. The peaks in the region with lower brightness than the aluminum matrix peak are Mg ２ The peak corresponding to Si particles is denoted as P2, and the brightness of this peak is denoted as P3. The peak located in the region with a brightness higher than the aluminum matrix peak corresponds to the peak of Al-Fe-Mn compound particles, and the brightness of this peak is denoted as P3. Particles with a brightness lower than the average of P1 and P2 are denoted as Mg ２ These particles are identified as Si particles. Additionally, particles with a brightness higher than the average of P1 and P3 are identified as Al-Fe-Mn compound particles.

[0058] Mg ２Even in images where Si particles are not detected and only Al-Fe-Mn compound particles are present, the same method is used to identify the Al-Fe-Mn compound particles. In images where Al-Fe-Mn compound particles are present, two peaks are present in the brightness histogram. The mode peak corresponds to the aluminum matrix peak, and the brightness of this peak is denoted as P1. The peak in the region with a brightness higher than the aluminum matrix peak corresponds to the Al-Fe-Mn compound particle peak, and the brightness of this peak is denoted as P3. Particles with a brightness higher than the average of P1 and P3 are identified as Al-Fe-Mn compound particles.

[0059] Determined Mg ２ The total area s1 of Si particles with an equivalent circular diameter of 1 μm or more is calculated. By dividing the total area s1 by the imaging area of ​​10 fields (i.e., the total area imaged), the Mg ２ The area ratio of Si is calculated.

[0060] The total area s2 of the AlFeMn particles with an area of ​​1 μm or larger in diameter is calculated. The area ratio of AlFeMn is calculated by dividing the total area s2 by the imaging area of ​​10 fields (i.e., the total area captured).

[0061] Mg ２ By adding the area fraction of Si and the area fraction of AlFeMn, we get AlFeMn + Mg ２ The total area ratio of Si is calculated. Note that Mg ２ Area fraction of Si, area fraction of AlFeMn, and AlFeMn + Mg ２ The total area ratio of Si is collectively referred to as the area ratio of precipitated particles.

[0062] 2. Method for Manufacturing Aluminum Alloy Plates for Can Lids The alloy plate of this disclosure can be manufactured, for example, as follows. First, an ingot is produced from an aluminum alloy having the composition of the alloy plate of this disclosure using a semi-continuous casting method (i.e., DC casting) in accordance with a conventional method.

[0063] Next, the four sides of the ingot, excluding the front and rear ends, are machined. After that, the ingot is placed in a soaking furnace for homogenization. The temperature during the homogenization process is preferably 530°C or higher and below the solidus temperature of the Al matrix.

[0064] If the homogenization treatment temperature is 530°C or higher, the homogenization treatment temperature is Mg ２ Because the temperature is sufficiently higher than the solid solution temperature of Si, the second phase particles Mg crystallize or precipitate in the ingot. ２ The amount of Si can be reduced. This improves both the tensile strength and toughness of the alloy sheet. Furthermore, if the homogenization treatment temperature is 550°C or higher, Mg ２ The amount of silicon present can be reduced to an extremely low level.

[0065] When the homogenization temperature is below the solidus temperature of the Al matrix, alloy sheets can be manufactured while suppressing local melting. A homogenization temperature at least 10°C lower than the solidus temperature of the Al matrix is ​​more preferable. In this case, alloy sheets can be produced stably while suppressing local melting.

[0066] Mg ２ The solid solution temperature of Si and the solidus temperature of the Al matrix are uniquely determined by the composition of the alloy sheet. For example, these temperatures can be determined by inputting the composition of the alloy sheet into "JMatPro," a thermodynamic calculation software developed by Sente Software, and calculating the equilibrium phase diagram. The CALPHAD method is used for calculating the thermodynamic model.

[0067] The homogenization treatment time is preferably, for example, 1 hour or more and 20 hours or less. When the homogenization treatment time is 1 hour or more, the temperature of the entire slab becomes uniform, segregation of the ingot structure is easily eliminated, and Mg ２ Si particles are easily redissolved. The longer the homogenization treatment time, the more Mg ２ Si particles can be redissolved. However, if the homogenization treatment time exceeds 20 hours, the effect of the homogenization treatment will saturate.

[0068] After homogenization, the ingot is subjected to hot rolling. The hot rolling process consists of a rough rolling process and a finish rolling process. In the rough rolling process, the ingot is processed into a plate material with a thickness of approximately several tens of millimeters by reverse rolling. In the finish rolling process, for example, by tandem rolling, the thickness of the plate material is reduced to approximately several millimeters, and the plate material is wound into a hot-rolled coil.

[0069] A high total reduction ratio in finish rolling results in a recrystallized structure after winding, increasing the concentration of isotropic cube orientations. A high winding temperature in finish rolling also results in a recrystallized structure after winding, increasing the concentration of cube orientations. The temperature of the sheet material at the end of hot rolling is preferably 300°C or higher.

[0070] Following hot rolling, the sheet material is cold-rolled. In cold rolling, the hot-rolled coil is rolled until the desired product sheet thickness is reached. Cold rolling can be either single-rolling or tandem-rolling. In single-rolling cold rolling, it is preferable to perform the rolling in multiple passes of two or more stages.

[0071] By raising the cold rolling temperature to 120°C or higher in intermediate passes other than the final pass, Si, Cu, and Mg precipitate finely and age harden, thereby increasing the tensile strength of the alloy sheet. Furthermore, raising the temperature to 130°C or higher can further increase the tensile strength of the alloy sheet.

[0072] A cold rolling ratio R of 75% or higher is preferable. A cold rolling ratio R of 75% or higher increases the tensile strength of the alloy sheet. Furthermore, a lower cold rolling ratio R results in more of the cube orientation remaining, therefore a cold rolling ratio R of 95% or lower is preferable. The cold rolling ratio R (%) is calculated as the sheet thickness t before cold rolling. ０ (mm), and the thickness of the product sheet after cold rolling t １ Using (mm), it can be calculated using the following formula (2).

[0073] Formula (2) R=(t ０ -t １ ) / t ０ ×100 In this embodiment, solution treatment is not performed after hot rolling, nor is heat treatment such as solution treatment performed during cold rolling.

[0074] The coils, which have been cold-rolled to the product thickness, may or may not be pre-coated on a painting line or the like. If pre-coating is performed, the cold-rolled coils are degreased, cleaned, and chemically treated on the surface, then the paint is applied and baked.

[0075] In chemical conversion treatment, chromate-based and zirconium-based chemicals are used. Epoxy-based and polyester-based paints are used. These can be selected according to the application. In the paint baking process, the coil is heated to a temperature of 220°C to 270°C (Peak Metal Temperature) for approximately 30 seconds. The lower the PMT, the more the material's recovery is suppressed, allowing the tensile strength of the alloy sheet to be maintained at a higher level.

[0076] 3. Effects of aluminum alloy plates for can lids (1A) The alloy plates of this disclosure can be manufactured by incorporating scrap raw materials derived from can materials.

[0077] (1B) The alloy sheets of the present disclosure have high strength and toughness. <Examples> 1. Manufacturing of aluminum alloy sheets for can lids Alloy sheets S1 to S6 shown in Table 1 were manufactured. The specific manufacturing procedure is described below. First, an ingot was manufactured by semi-continuous casting, with the content of Si, Fe, Cu, Mn, and Mg as shown in the "Component / mass%" column of Table 1, and the remainder consisting of aluminum and unavoidable impurities. The ingot contained 0.10 mass% or less of Ti, 0.25 mass% or less of Zn, 0.10 mass% or less of Cr, and 0.15 mass% or less of unavoidable impurities.

[0078]

[0079] Next, the four sides of the ingot, excluding the front and rear ends, were machined. Then, the ingot was placed in a furnace and subjected to a homogenization treatment. The homogenization treatment temperature (soaking temperature) is shown in Table 1. After the homogenization treatment, the ingot was removed from the furnace and hot rolling was immediately started to produce a rolled sheet. Furthermore, cold rolling was performed on the hot-rolled sheet without solution treatment. The target cold rolling ratio R in the cold rolling process is shown in Table 1.

[0080] Through the above process, alloy sheets S1 to S6 were obtained. Table 1 shows the thickness of the alloy sheets S1 to S6, measured using a microgauge. Table 1 also shows the 3104 blending rate (%) and the temperature difference ΔT for the alloy sheets S1 to S6. １ And, temperature difference ΔT ２ This indicates that.

[0081] The 3104 blending rate is calculated as follows. Assume that an alloy sheet is manufactured using a first material and a second material. The first material is a new aluminum ingot that does not contain Si, Fe, Cu, Mn, and Mg. The second material is a 3104 aluminum alloy. Let the mass ratio of the second material to the total mass of the first and second materials be X (%). This allows us to calculate the mass percentages of each component in the alloy sheet when the 3104 aluminum alloy is included at a specific mass ratio X, as Si(X), Fe(X), Cu(X), Mn(X), and Mg(X). For each of the Si, Fe, Cu, Mn, and Mg in the alloy sheet for which the 3104 blending rate should be calculated, we can individually determine the mass percentage corresponding to a certain mass ratio X of the 3104 aluminum alloy, as Si(X1), Fe(X2), Cu(X3), Mn(X4), and Mg(X5). The smallest value among X1, X2, X3, X4, and X5 (%) will be the possible blending rate of 3104.

[0082] For an alloy sheet with a Si content of 0.40 mass% or less, a Fe content of 0.60 mass% or less, a Cu content of 0.30 mass% or less, a Mn content of 1.0 mass% or less, and a Mg content of 4.4 mass% or less, the mass percentage corresponding to the mass ratio X of 3104 aluminum alloy is determined individually for each of Si (X1), Fe (X2), Cu (X3), Mn (X4), and Mg (X5). The smallest value among X1, X2, X3, X4, and X5 is the possible 3104 blending rate. The higher the possible 3104 blending rate, the more scrap raw materials derived from can materials can be incorporated in the manufacturing process. Temperature difference ΔT １ And, temperature difference ΔT ２ The calculation method was as described above.

[0083] 2. Evaluation of aluminum alloy plates for can lids The following evaluations were performed on alloy plates S1 to S6.

[0084] (1) Tensile Test A tensile test was performed on the alloy plate at 0° to the rolling direction, and YS, TS, and El were measured. Based on the measurement results, (YS + TS) / 2 and S were calculated. The tensile test method was as follows: A No. 5 test specimen as specified in JIS-Z-2241:2011 was prepared by milling. A tensile test was performed on the test specimen in accordance with JIS-Z-2241:2011, and the 0.2% yield strength and tensile strength were measured. The measurement results and calculation results are shown in Table 2.

[0085]

[0086] YS is σ0.2. TS is σB. El is elongation. The method for calculating S was as described above.

[0087] (2) Repeated Bending Test The repeated bending test was performed according to the following procedure. As shown in Figure 2, a test piece 5 cut into a strip shape with a width of 12.5 mm and a length of 200 mm was positioned so that the bending edge R was parallel to the rolling direction D of the alloy sheet. One end 5A of the test piece 5 was fixed with a stationary chuck. The opposite end 5B was fixed with a rotatable chuck. Then, a tension load of 200 N was applied to the test piece 5.

[0088] In this state, a jig with a bending radius of 2.0 mm was placed 150 mm from the end 5A, which was fixed to a stationary chuck, in the longitudinal direction of the test piece 5. By rotating the chuck, to which the end 5B was fixed, 90° to the left LD or right RD, the test piece 5 was bent using the jig as a fulcrum. The operation of bending the test piece 5 as described above was defined as one bending operation. The bending operation was repeated until the test piece 5 broke. The number of bending operations at which the test piece 5 broke was defined as the number of repeated bending operations N.

[0089] If the test specimen 5 fractured during a single bending operation, the bending angle Θ of the test specimen 5 at the time of fracture was read, and the number of repeated bending operations N was calculated using the following formula (3). In formula (3), N0 is the number of bending operations that rotate by 90°. The bending angle Θ is a value between 0° and 90°. The angle Θ at the time when a single bending operation is completed is 0°.

[0090] Equation (3) N = N0 + Θ / 90 The number of repeated bending cycles N decreases as the plate thickness increases when comparing the same alloy plate, so it is necessary to correct for this using a standard plate thickness. Therefore, the normalized number of repeated bending cycles Ns was determined using the following equation (4) with a plate thickness of 0.208 mm as the standard. Note that t (mm) is the plate thickness of test piece 5.

[0091] Equation (4) Ns = N × t / 0.208 The number of repeated bending cycles N and the normalized number of repeated bending cycles Ns are shown in Table 2. The number of repeated bending cycles N and the normalized number of repeated bending cycles Ns are numerical values ​​that represent the toughness of the alloy sheet. The larger the number of repeated bending cycles N and the normalized number of repeated bending cycles Ns, the higher the toughness of the alloy sheet. The higher the toughness of the alloy sheet, the better the formability of the alloy sheet.

[0092] (3) Measurement of the area ratio of precipitates by the method described above, Mg ２ Area fraction of Si, area fraction of AlFeMn, and AlFeMn + Mg ２ The total area ratio of Si was measured. The results are shown in Table 2.

[0093] (4) Evaluation Results In S1 to S4, the proportion of 3104 that could be incorporated was high. In S1 to S4, S was large. In S1 to S3, S was even larger. In S1 to S2, S was particularly large. In S1 to S4, N and Ns were large. In S1 to S2 and S4, N and Ns were even larger. <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 in various modified forms.

[0094] (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, some of the configurations of each of the above embodiments may be omitted. Also, at least some of the configurations of each of the above embodiments may be added to, replaced with, etc., the configurations of other embodiments.

[0095] (2) In addition to the aluminum alloy plate for can lids described above, this disclosure can also be realized in various forms, such as an aluminum alloy plate for tabs, a system using an aluminum alloy plate for can lids as a component, and a method for manufacturing an aluminum alloy plate for can lids.

[0096] 1… Alloy plate, 3… L-ST section, 5… Test piece, 5A, 5B… End piece

Claims

1. The silicon (Si) content is 0.17% by mass or more and 0.40% by mass or less, the iron (Fe) content is 0.30% by mass or more and 0.60% by mass or less, the copper (Cu) content is 0.10% by mass or more and 0.30% by mass or less, the manganese (Mn) content is 0.55% by mass or more and 1.0% by mass or less, the magnesium (Mg) content is 2.8% by mass or more and 4.4% by mass or less, and the remainder consists of aluminum (Al) and unavoidable impurities, or the remainder contains aluminum (Al) and unavoidable impurities, and the Mg content is from the melting point of aluminum (Al) ２ The temperature difference ΔT obtained by subtracting the melting temperature of Si. １ An aluminum alloy sheet for can lids, having a temperature of -1°C or higher, a total content of iron (Fe) and manganese (Mn) of 1.30 mass% or less, and a pressure (S) of 380 MPa or higher, as expressed by the following formula (1): Formula (1) S = σfm / (σ0.2 / σB) (In formula (1), σfm is the average value of σ0.2 and σB. σ0.2 is the 0.2% yield strength. σB is the tensile strength.) 2. The silicon (Si) content is 0.17% by mass or more and 0.40% by mass or less, the iron (Fe) content is 0.30% by mass or more and 0.60% by mass or less, the copper (Cu) content is 0.10% by mass or more and 0.30% by mass or less, the manganese (Mn) content is 0.55% by mass or more and 1.0% by mass or less, the magnesium (Mg) content is 3.3% by mass or more and 4.4% by mass or less, and the remainder consists of aluminum (Al) and unavoidable impurities, or the remainder contains aluminum (Al) and unavoidable impurities, and the Mg content is from the melting point of aluminum (Al) ２ The temperature difference ΔT obtained by subtracting the melting temperature of Si. １ An aluminum alloy sheet for can lids, having a temperature of -1°C or higher, a total content of iron (Fe) and manganese (Mn) of 1.25% by mass or less, and a thermal strength (S) of 400 MPa or higher, as expressed by the following formula (1): Formula (1) S = σfm / (σ0.2 / σB) (In formula (1), σfm is the average value of σ0.2 and σB. σ0.2 is the 0.2% yield strength. σB is the tensile strength.) 3. The silicon (Si) content is 0.17% by mass or more and 0.40% by mass or less, the iron (Fe) content is 0.30% by mass or more and 0.60% by mass or less, the copper (Cu) content is 0.10% by mass or more and 0.30% by mass or less, the manganese (Mn) content is 0.55% by mass or more and 1.0% by mass or less, the magnesium (Mg) content is 3.3% by mass or more and 4.4% by mass or less, and the remainder consists of aluminum (Al) and unavoidable impurities, or the remainder contains aluminum (Al) and unavoidable impurities, and the Mg content is from the melting point of aluminum (Al) ２ The temperature difference ΔT obtained by subtracting the melting temperature of Si. １ The temperature is -1°C or higher, the total content of iron (Fe) and manganese (Mn) is 1.25% by mass or less, the pressure S, represented by the following formula (1), is 400 MPa or higher, and the temperature difference ΔT is obtained by subtracting the crystallization temperature of AlFeMn from the solidification start temperature of aluminum (Al). ２ The temperature is 1°C or higher, and the area ratio of AlFeMn with an equivalent circle diameter of 1 μm or more, and Mg with an equivalent circle diameter of 1 μm or more. ２ An aluminum alloy sheet for can lids, where the total area ratio of Si is 2.5% or less. Equation (1): S = σfm / (σ0.2 / σB) (In equation (1), σfm is the average value of σ0.2 and σB. σ0.2 is the 0.2% yield strength. σB is the tensile strength.)

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