6-series aluminum alloy coiled material and preparation method thereof

Abstract

The invention provides a 6-series aluminum alloy coiled material and a preparation method thereof. The preparation method comprises the steps that raw materials of the 6-series aluminum alloy are mixed and then subjected to melt ingot casting, homogenization treatment, hot rolling, cold rolling, solution treatment, quenching treatment, straightening treatment and artificial aging treatment in sequence, and the 6-series aluminum alloy coiled material is obtained; wherein the quenching treatment comprises first-stage quenching treatment (water quenching cooling to 380-450 DEG C at a cooling speed of 30-50 DEG C / s), second-stage quenching treatment (water quenching cooling to 200-250 DEG C at a cooling speed of more than 60 DEG C / s), third-stage quenching treatment (water quenching cooling to 100 DEG C or below at a cooling speed of 20-40 DEG C / s) and fourth-stage quenching treatment (10 DEG C) which are sequentially performed; and air quenching and cooling to the room temperature at the cooling speed of 30 DEG C / s), so that the problem that the 6-series aluminum alloy coiled material cannot simultaneously consider the strength, the bending property and the corrosion resistance is solved.

Description

Technical Field

[0001] This invention relates to the field of 6-series aluminum alloy coil technology, and more specifically, to a 6-series aluminum alloy coil and its preparation method. Background Technology

[0002] With the development of the automotive industry, people have placed higher demands on the safety and lightweighting of automobiles. Aluminum alloys, with their excellent specific strength and specific stiffness, impact resistance, processability, corrosion resistance, and extremely high recyclability, have become the most ideal material for automotive lightweighting.

[0003] 6-series aluminum alloys are commonly used in automotive body panels and structural components. They require excellent formability to meet forming requirements, high strength to meet service strength requirements, excellent bending performance to meet energy absorption requirements during collisions, and excellent corrosion resistance. Conventional automotive 6XXX alloys, such as 6014, 6016, and 6022, are generally supplied in the T4P temper, which has lower strength. This cannot meet the performance requirements of high-strength and high-toughness materials. In recent years, extensive research has been conducted focusing on improving the strength and corrosion resistance of 6-series body panels.

[0004] Chinese patent application CN 1237195 C discloses a weldable high-strength aluminum alloy rolled product and its manufacturing method, but it is mainly used in aircraft skin and is not applicable to the application scenarios involved in automobiles.

[0005] Chinese patent CN 114058885 B discloses a 6XXX series aluminum alloy sheet and its preparation and welding methods. The alloy has high strength and excellent weldability. However, the alloy is supplied in the T4P condition, and its cooling process is not strictly specified.

[0006] Chinese patent application CN 119464850 A discloses a 6-series high-strength aluminum alloy sheet for automobiles and its preparation method. The strength is increased by adding Cr and Zn, and it is supplied in the T4P condition. However, it does not consider properties such as bending resistance and corrosion resistance.

[0007] Chinese patent application CN 118932262 A discloses an aluminum alloy sheet and its preparation method, which optimizes the process of high-Cu 6111 alloy, achieving both high strength and corrosion resistance. However, it does not address bending performance or refine the quenching rate.

[0008] In summary, current technologies for preparing 6-series aluminum alloy sheets cannot simultaneously meet the requirements for strength, bending performance, and corrosion resistance. Therefore, how to further improve the aforementioned properties of 6-series aluminum alloy sheets through simpler processes is a problem that urgently needs to be solved in this field. Summary of the Invention

[0009] The main objective of this invention is to provide a 6-series aluminum alloy coil and its preparation method, so as to solve the problem that the existing 6-series aluminum alloy coil cannot simultaneously achieve strength, bending and corrosion resistance.

[0010] To achieve the above objectives, according to one aspect of the present invention, a method for preparing 6-series aluminum alloy coils is provided. The method includes: step S1, mixing and melting 6-series aluminum alloy raw materials to obtain an aluminum alloy ingot; wherein, by weight percentage, the composition of the 6-series aluminum alloy includes: 0.50~1.00% Si, 0.50~0.90% Mg, 0.40~0.80% Cu, ≤0.50% Fe, 0.10~0.50% Mn, 0.05~0.30% Cr, and 0.02~0.08%... The aluminum alloy ingot is subjected to a series of processes: step S2, homogenization, hot rolling, and cold rolling to obtain a cold-rolled coil; step S3, solution treatment, quenching, and straightening to obtain a straightened coil; step S4, artificial aging treatment to obtain a 6-series aluminum alloy coil; wherein, the quenching process includes sequential first-stage quenching, second-stage quenching, third-stage quenching, and fourth-stage quenching; the first-stage quenching process includes water quenching at a cooling rate of 30~50℃ / s to 380~450℃; the second-stage quenching process includes water quenching at a cooling rate of >60℃ / s to 200~250℃; the third-stage quenching process includes water quenching at a cooling rate of 20~40℃ / s to below 100℃; the fourth-stage quenching process includes air quenching at a cooling rate of 10~30℃ / s to room temperature.

[0011] Furthermore, the amount of plastic deformation during the straightening process is 0.5~2.0%.

[0012] Furthermore, the homogenization treatment temperature is 540~570℃, and the homogenization treatment time is 6~10h.

[0013] Furthermore, the initial rolling temperature during the hot rolling process is 540~570℃, the deformation during hot rolling is 95~99%, and the thickness of the hot-rolled coil is 7.0~10.0 mm.

[0014] Furthermore, the thickness of the coil during cold rolling is 1.5~3.0mm, and the deformation during cold rolling is 70~85%.

[0015] Furthermore, the solution treatment temperature is 540~580℃, and the holding time is 0.5~5min.

[0016] Furthermore, the temperature for artificial aging treatment is 200~250℃, and the holding time is 8~20h.

[0017] Furthermore, by weight percentage, the aluminum alloy composition includes: 0.50~0.9% Si, 0.50~0.80% Mg, 0.40~0.70% Cu, ≤0.40% Fe, 0.10~0.50% Mn, 0.05~0.30% Cr, 0.02~0.08% Ti, and the balance Al.

[0018] According to another aspect of the present invention, a 6-series aluminum alloy coil is provided, which is prepared by the above-described preparation method.

[0019] Furthermore, the 6-series aluminum alloy coil has a flat sheet shape, a yield strength greater than 200 MPa, a bending angle greater than 100°, and a maximum intergranular corrosion depth of less than 250 μm.

[0020] Compared with existing technologies, the innovation and technological advancement of this invention are mainly reflected in the following aspects: 1. Compared with traditional 6-series aluminum alloy automotive coils, this invention changes the aluminum alloy composition, optimizes the content of Mg and Si, adds an appropriate amount of Cu, and, with subsequent processes, allows these elements to interact, achieving the purpose of rationally controlling the precipitation process and fully leveraging the precipitation strengthening effect. By increasing the content of Mn, Cr, and Ti elements, the grains are refined, improving the bending performance and corrosion resistance of the coil. 2. Compared with traditional automotive coils, the coil of this invention is supplied in an artificially aged state, with a strength exceeding 200 MPa. Furthermore, the bending angle is >100°, meeting the requirements for forming and impact energy absorption. 3. This invention employs strict control over the quenching process. The first-stage quenching process is relatively slow to achieve a superior sheet shape; the second-stage quenching process increases the quenching rate to prevent grain boundary phase precipitation that could degrade bending performance and corrosion resistance; the third-stage quenching process slows down the quenching rate to obtain a smoother sheet shape; and the fourth-stage quenching process uses air quenching to maintain a smooth sheet shape while drying any water residue left on the surface from the previous water quenching. 4. This invention eliminates the intermediate annealing process required in the traditional 6-series automotive sheet production, simplifying the production process, improving efficiency, reducing costs, and saving energy and reducing emissions. It is easily implemented in industry and meets the needs of industrial production. In summary, this invention addresses both composition and process aspects through targeted development, effectively controlling grain size and the size and distribution of precipitated phases, thereby developing 6-series aluminum alloy coils that combine strength, toughness, and corrosion resistance. High-strength, high-bending, and corrosion-resistant high-quality 6XXX series aluminum alloy coils can be produced with a simpler production process and can be widely used as automotive 6-series aluminum alloy structural components. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0022] As analyzed in the background section of this application, the existing technology has the problem that 6-series aluminum alloy coils cannot simultaneously achieve strength, bending performance, and corrosion resistance. In order to solve the above problems, this application provides a 6-series aluminum alloy coil and its preparation method.

[0023] In a typical embodiment of this application, a method for preparing 6-series aluminum alloy coils is provided. The method includes: step S1, mixing and melting 6-series aluminum alloy raw materials to obtain an aluminum alloy ingot; wherein, by weight percentage, the composition of the 6-series aluminum alloy includes: 0.50~1.00% Si, 0.50~0.90% Mg, 0.40~0.80% Cu, ≤0.50% Fe, 0.10~0.50% Mn, 0.05~0.30% Cr, and 0.02~0.08% T. The aluminum alloy ingot is subjected to homogenization, hot rolling, and cold rolling in sequence to obtain a cold-rolled coil. In step S3, the cold-rolled coil is subjected to solution treatment, quenching treatment, and straightening treatment in sequence to obtain a straightened coil. In step S4, the straightened coil is subjected to artificial aging treatment to obtain a 6-series aluminum alloy coil. The quenching treatment includes sequential first-stage quenching, second-stage quenching, third-stage quenching, and fourth-stage quenching. The first-stage quenching process includes water quenching at a cooling rate of 30~50℃ / s to 380~450℃. The second-stage quenching process includes water quenching at a cooling rate of >60℃ / s to 200~250℃. The third-stage quenching process includes water quenching at a cooling rate of 20~40℃ / s to below 100℃. The fourth-stage quenching process includes air quenching at a cooling rate of 10~30℃ / s to room temperature.

[0024] Compared to existing technologies, the innovation and technological advancements of this invention are mainly reflected in the following aspects: 1. Compared to traditional 6-series aluminum alloy automotive coils, this invention modifies the aluminum alloy composition, optimizes the content of Mg and Si, adds an appropriate amount of Cu, and, with subsequent processes, allows these elements to interact, achieving the purpose of rationally controlling the precipitation process and fully leveraging the precipitation strengthening effect. By increasing the content of Mn, Cr, and Ti elements, the grain size is refined, improving the bending performance and corrosion resistance of the coil. 2. Compared to traditional automotive coils, the coil of this invention is supplied under artificial aging conditions, with a strength exceeding 200 MPa. Furthermore, the bending angle is >100°, meeting the requirements for forming and impact energy absorption. 3. This invention employs strict control over the quenching process. The first-stage quenching process is relatively slow to achieve a superior sheet shape; the second-stage quenching process increases the quenching rate to prevent grain boundary phase precipitation that could degrade bending performance and corrosion resistance; the third-stage quenching process slows down the quenching rate to obtain a smoother sheet shape; and the fourth-stage quenching process uses air quenching to maintain a smooth sheet shape while drying any water residue left on the surface from the previous water quenching. 4. This invention eliminates the intermediate annealing process required in the traditional 6-series automotive sheet production, simplifying the production process, improving efficiency, reducing costs, and saving energy and reducing emissions. It is easily implemented in industry and meets the needs of industrial production. In summary, this invention addresses both composition and process aspects through targeted development, effectively controlling grain size and the size and distribution of precipitated phases, thereby developing 6-series aluminum alloy coils that combine strength, toughness, and corrosion resistance. High-strength, high-bending, and corrosion-resistant high-quality 6XXX series aluminum alloy coils can be produced with a simpler production process and can be widely used as automotive 6-series aluminum alloy structural components.

[0025] In one embodiment of this application, the amount of plastic deformation in the straightening process is 0.5~2.0%.

[0026] Compared to traditional automotive steel sheets, this invention employs a larger straightening amount, which fully considers the problem of poor sheet shape caused by rapid quenching rate.

[0027] In one embodiment of this application, the homogenization treatment temperature is 540~570℃, and the homogenization treatment time is 6~10h.

[0028] Homogenization treatment, by precisely controlling the temperature and time within the above range, facilitates the full diffusion of atoms within the aluminum ingot, eliminating intragranular segregation and unbalanced low-melting-point phases. This significantly reduces the material's tendency to crack during hot working, improves subsequent plasticity, enhances processing properties such as rolling, and lays the foundation for obtaining a uniform microstructure and excellent final product performance.

[0029] In one embodiment of this application, the initial rolling temperature during the hot rolling process is 540~570℃, the deformation during hot rolling is 95~99%, and the thickness of the hot-rolled coil is 7.0~10.0 mm.

[0030] Controlling the initial rolling temperature within the above range helps ensure that the alloy is in a state of high plasticity and low deformation resistance; the amount of deformation helps control the degree of grain breakage and refinement, and drives recrystallization; the thickness of the coil provides suitable billet for subsequent cold rolling and affects the uniformity of the microstructure, mechanical properties and surface quality of the final product.

[0031] In one embodiment of this application, the thickness of the coil during cold rolling is 1.5~3.0 mm, and the deformation during cold rolling is 70~85%.

[0032] Precise control of the thickness and deformation of the coil during cold rolling is paramount to ensuring product thickness tolerance. Simultaneously, the limited deformation directly influences the material's work hardening degree, texture strength, and mechanical properties, and determines subsequent annealing processes and the final grain structure.

[0033] In one embodiment of this application, the solution treatment temperature is 540~580℃, and the holding time is 0.5~5min.

[0034] Controlling the temperature and time of solution treatment helps alloying elements fully dissolve into the aluminum matrix, forming a supersaturated solid solution. This is a prerequisite for subsequent age hardening, directly determining the quantity and distribution of precipitated phases, thereby maximizing the improvement of the alloy's key mechanical properties such as strength and hardness.

[0035] In one embodiment of this application, the temperature for artificial aging treatment is 200~250℃, and the holding time is 8~20h.

[0036] Using the above artificial aging process helps to eliminate the adverse effects on formability caused by straightening treatment.

[0037] To further control the content of each element and thus enhance their synergistic effect, thereby improving the bending performance and corrosion resistance of the coil, in one embodiment of this application, the preferred aluminum alloy composition by weight percentage includes: 0.50~0.9% Si, 0.50~0.80% Mg, 0.40~0.70% Cu, ≤0.40% Fe, 0.10~0.50% Mn, 0.05~0.30% Cr, 0.02~0.08% Ti, and the balance Al.

[0038] In another typical embodiment of this application, a 6-series aluminum alloy coil is provided, which is prepared by the above-described preparation method.

[0039] According to actual size requirements, the artificially aged coil is processed by shearing or laser cutting to obtain 6-series aluminum alloy coils. The 6-series aluminum alloy coils obtained by the above preparation method of this application have excellent strength, bending properties, and corrosion resistance.

[0040] In one embodiment of this application, the 6-series aluminum alloy coil has a flat shape, a yield strength greater than 200 MPa, a bending angle greater than 100°, and a maximum intergranular corrosion depth of less than 250 μm.

[0041] Specifically, the 6-series aluminum alloy coils of this application can have yield strength, bending angle and maximum intergranular corrosion depth within the above specific numerical ranges, making them particularly suitable for use as high-strength, bending-resistant and corrosion-resistant aluminum alloys.

[0042] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0043] Example 1

[0044] First, pure aluminum and various intermediate alloys are melted according to the composition ratio shown in Table 1. Specific process parameters are shown in Table 2. After refining, the melt is cast into ingots using a semi-continuous casting equipment. The ingots are then cut and milled before being placed in a heat treatment furnace for homogenization. After homogenization, the ingots are directly taken out of the furnace for hot rolling. After hot rolling, the resulting hot-rolled sheet is cold-rolled. The resulting cold-rolled sheet undergoes solution treatment, quenching treatment, straightening treatment, and then artificial aging treatment to obtain the finished coil.

[0045] The specific component ratios in the other embodiments and comparative examples are shown in Table 1, and the process parameters are shown in Table 2.

[0046] Table 1 Chemical composition (wt.%) of high-strength, high-toughness, and corrosion-resistant 6-series aluminum alloys

[0047]

[0048] Table 2 High-strength, high-toughness, and corrosion-resistant 6-series aluminum alloy manufacturing processes

[0049]

[0050] Table 2 (continued)

[0051]

[0052] Performance testing:

[0053] The yield strength, bending angle, and maximum intergranular corrosion depth of the 6-series aluminum alloy coils in the above embodiments and comparative examples were tested respectively, and the test results are listed in Table 3.

[0054] Yield strength: The yield limit of an aluminum alloy when it undergoes yielding. It is defined as the stress value at which 0.2% residual deformation occurs. The stress-strain curve is obtained through a uniaxial tensile test, and the yield strength data is derived from the curve.

[0055] Bending angle: Sample size is 60 mm The bending radius is 60 mm, and the bending direction is perpendicular to the rolling direction. The pressure head stops pressing down when the pressure F decreases by 40 N from its maximum value. The angle between the bent sample and the horizontal direction is the bending angle.

[0056] Maximum intergranular corrosion depth: After mechanical polishing, alkali washing, and acid washing, the samples were immersed in a 30 g / L NaCl + 10 mL / L HCl solution at (30±1)℃ for 24 h. Then, the cross-section of the corroded sample was cut and polished, and the distance from the corroded surface to the corrosion tip was observed and measured using a metallographic microscope. The deepest point was the maximum corrosion depth.

[0057] Table 3 Properties of High-Strength, High-Toughness, and Corrosion-Resistant 6-Series Aluminum Alloys

[0058]

[0059] In Table 3 above, "uneven", "slightly uneven", and "flat" indicate the degree of improvement in the flatness of the sheet type. "Uneven" means that the roll material product is unqualified; "slightly uneven" and "flat" mean that the roll material product is qualified.

[0060] The roll materials prepared in Examples 1-13 met the performance requirements. The roll materials prepared in Comparative Examples 1-13 failed to meet the performance requirements. Details are as follows:

[0061] In Example 7, the homogenization and lower hot rolling temperature resulted in slight precipitation of Mg and Si phases, which worsened the subsequent re-dissolution effect, thereby reducing the strength and bending angle of the coil.

[0062] Compared with Example 3, Example 8 has a reduced straightening amount and a slightly poorer plate shape (slight unevenness).

[0063] Compared with Example 3, Example 9 has an increased straightening amount and a decreased bending angle;

[0064] Compared with Example 4, the artificial aging temperature in Example 10 was lower, resulting in a decrease in the strength of the roll material.

[0065] Compared with Example 5, the artificial aging temperature in Example 11 was higher, the strength of the roll material was lower, and the corrosion resistance was worse.

[0066] Compared with Example 6, Example 12 has a shorter artificial aging time, higher roll strength, lower bending angle, and worse corrosion resistance;

[0067] Compared with Example 6, the artificial aging time in Example 13 is longer, the strength of the roll material is reduced, and the corrosion resistance is worse.

[0068] The excessive Si content in Comparative Example 1 resulted in excessively high strength of the roll material and insufficient bending angle.

[0069] The Mg content in Comparative Example 2 was too low, resulting in insufficient strength.

[0070] The excessive Cu content in Comparative Example 3 resulted in excessively high strength of the roll material, insufficient bending angle, and poor corrosion resistance.

[0071] The low Cr and Ti content in Comparative Example 4 resulted in increased grain size, insufficient bending angle, and poor corrosion resistance.

[0072] The Cu content in Comparative Example 5 was too low, resulting in insufficient strength.

[0073] Comparative Example 6: The first-stage quenching rate was too fast, resulting in poor plate shape;

[0074] Comparative Example 7: The first-stage quenching rate was too slow, resulting in an excessively large temperature difference during the second-stage quenching and poor plate shape.

[0075] Comparative Example 8: The third-stage quenching rate was too fast, resulting in poor plate shape;

[0076] Comparative Example 9: The third and fourth quenching rates were too slow, and the equipment failed to cool to room temperature in time, resulting in damage to the production equipment.

[0077] Comparative Example 10: The second-stage cooling rate was too slow, resulting in the precipitation of grain boundary phases and insufficient bending angle.

[0078] In Comparative Example 11, the first-stage cooling temperature was too low, resulting in a slow cooling rate and precipitation of grain boundary phases, leading to insufficient bending angle.

[0079] Comparative Example 12: The second-stage cooling temperature was too high, and the subsequent cooling rate was too slow, resulting in the precipitation of grain boundary phases and insufficient bending angle.

[0080] Comparative Example 13 uses water quenching in the fourth stage, which results in residual water stains on the coil and poor surface quality.

[0081] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0082] Compared to existing technologies, the innovation and technological advancement of this invention are mainly reflected in the following aspects: 1. Compared to traditional 6-series aluminum alloy automotive coils, this invention modifies the aluminum alloy composition, optimizes the content of Mg and Si, adds an appropriate amount of Cu, and, with subsequent processes, allows these elements to interact, achieving the purpose of rationally controlling the precipitation process and fully leveraging the precipitation strengthening effect. By increasing the content of Mn, Cr, and Ti elements, the grain size is refined, improving the bending performance and corrosion resistance of the coil. 2. Compared to traditional automotive coils, the coil of this invention is supplied under artificial aging conditions, with a strength exceeding 200 MPa. Furthermore, the bending angle is >100°, meeting the requirements for forming and impact energy absorption. 3. This invention employs strict control over the quenching process. The first-stage quenching process is relatively slow to achieve a superior sheet shape; the second-stage quenching process increases the quenching rate to prevent grain boundary phase precipitation that could degrade bending performance and corrosion resistance; the third-stage quenching process slows down the quenching rate to obtain a smoother sheet shape; and the fourth-stage quenching process uses air quenching to maintain a smooth sheet shape while drying any water residue left on the surface from the previous water quenching. 4. This invention eliminates the intermediate annealing process required in the traditional 6-series automotive sheet production, simplifying the production process, improving efficiency, reducing costs, and saving energy and reducing emissions. It is easily implemented in industry and meets the needs of industrial production. In summary, this invention addresses both composition and process aspects through targeted development, effectively controlling grain size and the size and distribution of precipitated phases, thereby developing 6-series aluminum alloy coils that combine strength, toughness, and corrosion resistance. High-strength, high-bending, and corrosion-resistant high-quality 6XXX series aluminum alloy coils can be produced with a simpler production process and can be widely used as automotive 6-series aluminum alloy structural components.

[0083] The above are merely embodiments of the present invention and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing 6-series aluminum alloy coils, characterized in that, The preparation method includes: Step S1: Mix and melt the raw materials of 6-series aluminum alloy to obtain an aluminum alloy ingot; wherein, by weight percentage, the composition of the 6-series aluminum alloy includes: 0.50~1.00% Si, 0.50~0.90% Mg, 0.40~0.80% Cu, ≤0.50% Fe, 0.10~0.50% Mn, 0.05~0.30% Cr, 0.02~0.08% Ti, and the balance Al. Step S2: The aluminum alloy ingot is subjected to homogenization treatment, hot rolling, and cold rolling in sequence to obtain cold-rolled coil. Step S3: The cold-rolled coil is subjected to solution treatment, quenching treatment and straightening treatment in sequence to obtain the straightened coil. Step S4: Perform artificial aging treatment on the straightened coil to obtain the 6-series aluminum alloy coil; The quenching process includes sequentially performing a first-stage quenching process, a second-stage quenching process, a third-stage quenching process, and a fourth-stage quenching process. The first-stage quenching process includes: water quenching at a cooling rate of 30~50℃ / s to 380~450℃; The secondary quenching process includes: water quenching at a cooling rate of >60℃ / s to 200~250℃; The three-stage quenching process includes: water quenching at a cooling rate of 20~40℃ / s to below 100℃; The four-stage quenching process includes: air quenching to room temperature at a cooling rate of 10~30℃ / s.

2. The preparation method according to claim 1, characterized in that, The amount of plastic deformation in the straightening process is 0.5~2.0%.

3. The preparation method according to claim 1 or 2, characterized in that, The homogenization treatment temperature is 540~570℃, and the homogenization treatment time is 6~10h.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The initial rolling temperature during hot rolling is 540~570℃, and the deformation during hot rolling is 95~99%; the thickness of the hot-rolled coil is 7.0~10.0 mm.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The thickness of the coil during cold rolling is 1.5~3.0mm, and the deformation during cold rolling is 70~85%.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The solution treatment temperature is 540~580℃, and the holding time is 0.5~5min.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The temperature for the artificial aging treatment is 200~250℃, and the holding time is 8~20h.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The aluminum alloy composition, by weight percentage, includes: 0.50-0.9% Si, 0.50-0.80% Mg, 0.40-0.70% Cu, ≤0.40% Fe, 0.10-0.50% Mn, 0.05-0.30% Cr, 0.02-0.08% Ti, and the balance Al.

9. A 6-series aluminum alloy coil, characterized in that, The 6-series aluminum alloy coil is prepared by the preparation method described in any one of claims 1 to 8.

10. The 6-series aluminum alloy coil according to claim 9, characterized in that, The 6-series aluminum alloy coil has a flat shape, a yield strength greater than 200 MPa, a bending angle greater than 100°, and a maximum intergranular corrosion depth of less than 250 μm.

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