Method for preparing notebook computer housing using recycled aluminum anodized aluminum strip

Abstract

The application discloses a preparation method of notebook computer shell added with recycled aluminum anodized aluminum strip, and specifically comprises the following steps: raw materials such as recycled aluminum, aluminum ingot and intermediate alloy ingot are subjected to smelting, casting, hot rolling, cold rolling, intermediate annealing, roughening cold rolling and cleaning and straightening to obtain a notebook computer shell added with recycled aluminum 5000 series aluminum plate strip. The average grain size of the aluminum alloy strip is less than 10 microns, the grain aspect ratio is 0.9-1.1, the maximum size of intermetallic compounds is less than 5 microns, the compound proportion difference in unit area is less than 1%, the sand blasting sand type on the surface of the aluminum material is 120-150# iron sand, the roughness Ra after sand blasting is 1.8+ / -0.3 microns, and the anodized surface is fine and free of material lines.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy strip preparation, specifically relating to a method for preparing anodized aluminum strip with added recycled aluminum for laptop casings. Background Technology

[0002] With industrialization, countries are promoting resource recycling, making the preservation and reuse of aluminum alloy scrap an increasingly important issue. The rapid development of the 3C electronics industry has led to an explosive growth in demand for aluminum alloys. The production process generates a large amount of scrap and defective products. To comply with international energy conservation and emission reduction requirements, major electronics companies have joined the ASI system, developing materials produced using recycled aluminum. However, with the addition of recycled aluminum, impurities such as Fe and Si, as well as iron-rich phases, increase, making it easier for discoloration and defects such as streaks to appear after anodizing.

[0003] The quality of anodized films is related not only to the internal grain size, orientation, and second-phase structure of the aluminum material itself, but also to the microstructure of the aluminum surface and the downstream sandblasting and anodizing processes. Overcoming the problem of poor anodized appearance caused by adding recycled aluminum is a key focus and challenge in this field.

[0004] Patent application number 201811260701.3 discloses a 5-series aluminum alloy sheet and strip with good gloss after anodizing and its preparation method. By adjusting the alloying elements Si≤0.04, Fe≤0.05, Cu≤0.05, Mn0.40~0.50, Mg3.0~3.5, Ti0.005~0.012, and Fe / Si≤1.5, and employing a two-stage homogenization treatment at 430~460℃ for 3~5h and 500~530℃ for 4~20h, the hot-rolled coil is cold-rolled at 20~90% and then directly annealed to obtain the finished product; or the cold-rolled coil is cold-rolled to the finished thickness after an intermediate annealing temperature, followed by finished product annealing, stretching and straightening to obtain the finished product. After anodizing with a film thickness of 15~20μm, the gloss Gu value at a 60° measurement angle is ≥120. This method, which employs a high-purity alloy design, not only has high production costs but also faces the challenge of not being able to add recycled aluminum.

[0005] Patent application number 201710548317.2 discloses a mirror-finish anodized aluminum sheet and strip and its preparation method. By adjusting the alloying elements Si≤0.03, Fe≤0.03, Cu0.03~0.08, Mn0.06~0.10, Mg4.0~5.0, Zn0.16~0.25, and Ti0.02~0.03, and employing a three-stage homogenization process, the hot-rolled coil undergoes 50~80% cold rolling followed by intermediate annealing, then cold rolling to the finished thickness with a cold rolling reduction rate of 40~80%. After final annealing at 150~280℃, the finished product is obtained through stretch bending and straightening. This method, employing three-stage homogenization, two annealing processes, and a high-purity composition design, also faces the challenges of high production costs and the inability to add recycled aluminum.

[0006] Patent application number 202311701606.3 discloses an aluminum alloy sheet and strip for anodizing using recycled aluminum as the main material and its preparation method. The alloy composition is designed as follows: Si 0.10-0.15%, Fe 0.15-0.40%, Cu 0.02-0.10%, Mn 0-0.02%, Cr 0.15-0.35%, Mg 1.0-3.0%, Ti 0-0.03%, with the balance being Al and unavoidable impurity elements. The basic process flow is hot rolling to a thickness of 6.0-10.0 mm, followed by multiple cold rollings to the finished thickness, with a total cold rolling rate ≥50%. Finally, the finished product is annealed at 150℃-270℃ for a holding time ≥2 hours. The core objective is to obtain a finished product with a grain size ≤50μm, randomly distributed grain orientation, a rolling texture to recrystallization texture area ratio of 0.9-1.1, and a cube texture ratio of 5-20%. This method is the H2x process. When the cold rolling ratio is ≥50%, it is not conducive to obtaining stable performance by annealing the finished product. Moreover, the design requirements are only made from the perspective of materials, and the downstream matching process is not yet standardized. It is fundamentally different from the H1x process of this invention, which has a reduction ratio of ≥90% before the mid-heating, a reduction ratio of 7.5~9.0% after the mid-heating, and uses EDT texturing Ra0.90~1.10μm rolling.

[0007] Patent application number 202010872694.3 discloses a method for preparing aluminum alloy sheet and strip for anodizing with a roughened surface. It uses high-purity 5252 aluminum alloy, cold-rolled with a processing rate of 70-85%, then continuously annealed, followed by roughening rolling with a cold rolling rate of 5-7%, and finally finished product annealing at 150±10℃. It is actually a two-stage annealing process of H32, which is one more annealing than the H1x process of this invention. At the same time, it is only applicable to high-purity 5252 alloy and is not designed for high-proportion addition of recycled aluminum.

[0008] This invention, through the development of thin-film casting process, combined with rough rolling with low reduction rate after intermediate annealing, and matched with downstream sandblasting and anodizing processes, not only obtains a fine and texture-free surface of anodized aluminum with a high proportion of recycled aluminum, but also only requires one annealing process, simplifying production steps and reducing manufacturing costs, thus conforming to the development trend of emission reduction and carbon reduction in anodized materials. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing anodized aluminum strip with added recycled aluminum for laptop casings. The process flow is reasonable and the production cost is low.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] The preparation method of anodized aluminum strip with added recycled aluminum for laptop casings is as follows: Raw materials such as recycled aluminum, aluminum ingots, and intermediate alloy ingots are processed through smelting, casting, hot rolling, cold rolling, intermediate annealing, texturing cold rolling, cleaning, and straightening to obtain anodized aluminum strip with added recycled aluminum for laptop casings. The specific preparation method includes the following steps:

[0012] (1) The raw materials such as recycled aluminum, aluminum ingots, and intermediate alloy ingots are melted, refined, degassed, filtered and slag removed, and then semi-continuously cast into aluminum alloy flat ingots.

[0013] (2) After homogenization heat treatment, aluminum alloy flat ingots are hot rolled, the hot rolled coils are cold rolled to the intermediate thickness, and then annealed in the intermediate stage. After EDT roughening and cold rolling to the finished thickness, the finished products are directly delivered after cleaning and straightening.

[0014] Preferably, the conditions described in step (1) are: recycled aluminum ratio ≥70wt%, crystallizer thickness 400~520mm, casting temperature 690~720℃, casting speed 45~60mm / min, and water flow rate 100~200m³ / min. 3 / h, the amount of titanium wire added to the heat preservation furnace and the amount of titanium wire added online are 0.040%±0.001% and 0.005%±0.001%, respectively.

[0015] Preferably, the conditions described in step (2) are: ≥90% reduction before intermediate heating, 7.5~9.0% reduction after intermediate heating, and EDT texturing with Ra 0.90~1.10μm rolling.

[0016] Preferably, the chemical composition of the aluminum alloy sheet / strip, by mass fraction, is: Si 0.10~0.14%, Fe 0.25~0.45%, Cu <0.02%, Mn <0.08%, Mg 2.0~4.0%, Ti 0.035~0.045%, with the balance being aluminum and unavoidable impurities.

[0017] Preferably, the downstream process matching it is as follows: after sandblasting the aluminum surface, anodizing is performed. The sandblasting sand type is 120~150# iron sand, the sandblasting pressure is 18~22N, the roughness Ra after sandblasting is 1.8±0.3μm, and the anodized surface is delicate and without material marks.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention addresses the challenge of controlling the quality of anodizing in high-proportion recycled aluminum due to its high impurity content. It achieves a superior original grain structure in the ingot through the development of a thin-film casting process. Combined with a low-reduction roughening rolling process after medium-heat treatment, and downstream sandblasting and anodizing processes, this yields aluminum alloy strips with an average grain size <10μm, a grain aspect ratio of 0.9~1.1, a maximum intermetallic compound size <5μm, and a compound percentage difference of <1% per unit area. The aluminum surface is sandblasted with 120~150# iron sand, resulting in a roughness Ra=1.8±0.3μm. The anodized surface is smooth and free of material marks. This method not only achieves a smooth, mark-free surface from high-proportion recycled aluminum but also requires only one annealing process, simplifying production and reducing manufacturing costs, aligning with the trend of emission reduction and carbon reduction in anodized materials. Attached Figure Description

[0020] Figure 1 For anodizing comparison: a) Example 1 is good; b) Comparative Example 1 shows anodized material texture;

[0021] Figure 2 For comparison of the high-magnification microstructure of the finished products: a) Example 1 has fine and uniform microstructure; b) Comparative Example 1 has coarse and uneven microstructure.

[0022] Figure 3 Microscopic morphology of aluminum surface: a) texturing rolling in Example 2; b) ordinary rolling in Comparative Example 2;

[0023] Figure 4 For anodizing comparison: a) Example 2 is good; b) Comparative Example 2 shows anodized material texture;

[0024] Figure 5 The surface microstructure after sandblasting is as follows: a) Uniform in Example 3; b) Non-uniform in Comparative Example 3. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to these embodiments.

[0026] The quality of anodized films is related not only to the internal grain size, orientation, and second-phase structure of the aluminum material itself, but also to the microstructure of the aluminum surface and the downstream sandblasting and anodizing processes. Overcoming the problem of poor anodized appearance caused by adding a high proportion of recycled aluminum is the focus and challenge of this invention.

[0027] This invention focuses on providing a method for preparing anodized aluminum strip with added recycled aluminum for laptop casings. The mass fraction of the components involved is: Si 0.10-0.14%, Fe 0.25-0.45%, Cu <0.02%, Mn <0.08%, Mg 2.0-4.0%, Ti 0.035-0.045%, with the balance being aluminum and unavoidable impurities.

[0028] A 5000 series aluminum sheet and strip with added recycled aluminum is produced by hot rolling, cold rolling, intermediate annealing, and texturing cold rolling for use in laptop casings.

[0029] Recycled aluminum ratio ≥70wt%, crystallizer thickness 400~520mm, casting temperature 690~720℃, casting speed 45~60mm / min, water flow rate 100~200m³ / min. 3 The titanium wire addition rates in the holding furnace and online titanium wire addition rates were 0.040%±0.001% and 0.005%±0.001%, respectively. This facilitates the production of fine, uniform, and low-segregation casting microstructures, laying a solid foundation for the final product.

[0030] A reduction rate of ≥90% before intermediate annealing yields fine grains. After intermediate annealing, a rough rolling process with a reduction rate of 7.5~9.0% not only ensures good strength and plasticity and equiaxed grains, but also breaks the conventional cold rolling stripes and reduces the risk of subsequent anodizing streaks and discoloration lines.

[0031] To address the high risk of anode damage due to the high recovery rate of impurity elements in this invention, the sand mold is matched with 120~150# iron sand, and the roughness Ra after sandblasting is 1.8±0.3μm. The downstream process further ensures that the anodized surface is delicate and free of material marks.

[0032] The following will illustrate this with specific implementation examples.

[0033] Example 1

[0034] A method for preparing anodized aluminum strip with added recycled aluminum for laptop casings involves processing raw materials such as recycled aluminum, aluminum ingots, and intermediate alloy ingots through smelting, casting, hot rolling, cold rolling, intermediate annealing, texturing cold rolling, cleaning, and straightening to obtain 5000 series anodized aluminum strip with added recycled aluminum for laptop casings. The specific preparation method includes the following steps:

[0035] (1) Recycled aluminum, aluminum ingots, and intermediate alloy ingots are melted, refined, degassed, filtered, and slag removed, and then semi-continuously cast into aluminum alloy flat ingots. The recycled aluminum content is 75 wt%, the crystallizer thickness is 520 mm, the casting temperature is 695 ℃, the casting speed is 60 mm / min, and the water flow rate is 120 m³ / min. 3 / h, the amount of titanium wire added to the holding furnace and the amount of titanium wire added online are 0.040% and 0.005%, respectively, while obtaining Si 0.10%, Fe 0.27%, Cu 0.015%, Mn 0.07%, Mg 2.7%, Ti 0.042%, with the balance being aluminum and unavoidable impurities in the ingot.

[0036] (2) After homogenization heat treatment at 540℃ for 4h, aluminum alloy flat ingots are hot rolled to a thickness of 7.0mm. The final rolling temperature is 300℃. After cold rolling, the thickness is reduced to 0.7mm. Then, intermediate annealing is performed at 440℃ for 30sec. Finally, EDT roughening and cold rolling with a roughness Ra of 0.90μm is performed to a finished thickness of 0.64mm. The final aluminum alloy strip has an average grain size of 8μm, a grain ratio of 0.95, a maximum intermetallic compound size of 4.85μm, a maximum compound ratio difference of 0.89% per unit area, a tensile strength of 220MPa, a yield strength of 190MPa, and an elongation of 10%.

[0037] (3) The downstream process is as follows: after sandblasting, the aluminum material is anodized. The sandblasting sand type is 150# iron sand, the sandblasting pressure is 20N, the roughness Ra after sandblasting is 1.50μm, the anodized surface is delicate and without material marks.

[0038] Example 2

[0039] A method for preparing anodized aluminum strip with added recycled aluminum for laptop casings involves processing raw materials such as recycled aluminum, aluminum ingots, and intermediate alloy ingots through smelting, casting, hot rolling, cold rolling, intermediate annealing, texturing cold rolling, cleaning, and straightening to obtain 5000 series anodized aluminum strip with added recycled aluminum for laptop casings. The specific preparation method includes the following steps:

[0040] (1) Recycled aluminum, aluminum ingots, and intermediate alloy ingots are melted, refined, degassed, filtered, and slag removed, and then semi-continuously cast into aluminum alloy flat ingots. The recycled aluminum content is 80 wt%, the crystallizer thickness is 500 mm, the casting temperature is 710 ℃, the casting speed is 57 mm / min, and the water flow rate is 150 m³ / min. 3 / h, the amount of titanium wire added to the holding furnace and the amount of titanium wire added online are 0.040% and 0.005%, respectively, while obtaining Si 0.14%, Fe 0.35%, Cu 0.015%, Mn 0.055%, Mg 3.0%, Ti 0.042%, with the balance being aluminum and unavoidable impurities in the ingot.

[0041] (2) After homogenization heat treatment at 550℃ for 2h, aluminum alloy flat ingots are hot rolled to a thickness of 8.0mm. The final rolling temperature is 320℃. After cold rolling, the thickness is reduced to 0.75mm. After intermediate annealing at 450℃ for 20sec, the ingots are then roughened by EDT with a roughness of Ra 1.0μm and cold rolled to a finished thickness of 0.68mm. The resulting aluminum alloy strip has an average grain size of 7.5μm, a grain ratio of 1.02, a maximum intermetallic compound size of 4.77μm, a maximum compound percentage difference of 0.76% per unit area, a tensile strength of 230MPa, a yield strength of 208MPa, and an elongation of 9.5%.

[0042] (3) The downstream process is as follows: after sandblasting, the aluminum material is anodized. The sandblasting sand type is 120# iron sand, the sandblasting pressure is 21N, the roughness Ra after sandblasting is 1.70μm, the anodized surface is delicate and without material marks.

[0043] Example 3

[0044] A method for preparing anodized aluminum strip with added recycled aluminum for laptop casings involves processing raw materials such as recycled aluminum, aluminum ingots, and intermediate alloy ingots through smelting, casting, hot rolling, cold rolling, intermediate annealing, texturing cold rolling, cleaning, and straightening to obtain 5000 series anodized aluminum strip with added recycled aluminum for laptop casings. The specific preparation method includes the following steps:

[0045] (1) Recycled aluminum, aluminum ingots, and intermediate alloy ingots are melted, refined, degassed, filtered, and slag removed, and then semi-continuously cast into aluminum alloy flat ingots. The recycled aluminum content is 90 wt%, the crystallizer thickness is 400 mm, the casting temperature is 720 ℃, the casting speed is 60 mm / min, and the water flow rate is 200 m³ / min. 3 / h, the amount of titanium wire added to the holding furnace and the amount of titanium wire added online are 0.040% and 0.005%, respectively, while obtaining Si 0.14%, Fe 0.42%, Cu 0.008%, Mn 0.042%, Mg 3.52%, Ti 0.045%, with the balance being aluminum and unavoidable impurities in the ingot.

[0046] (2) After homogenization heat treatment at 500℃ for 6h, aluminum alloy flat ingots are hot rolled to a thickness of 10.0mm. The final rolling temperature is 310℃. After cold rolling, the thickness is reduced to 0.90mm. Then, intermediate annealing is performed at 400℃ for 60sec. Finally, EDT roughening and cold rolling with a roughness Ra of 1.0μm is performed to a finished thickness of 0.82mm. The final aluminum alloy strip has an average grain size of 5.5μm, a grain ratio of 1.06, a maximum intermetallic compound size of 3.58μm, a maximum compound ratio difference of 0.67% per unit area, a tensile strength of 246MPa, a yield strength of 224MPa, and an elongation of 7.8%.

[0047] (3) The downstream process is as follows: after sandblasting, the aluminum material is anodized. The sandblasting sand type is 150# iron sand, the sandblasting pressure is 20N, the roughness Ra after sandblasting is 2.0μm, the anodized surface is delicate and without material marks.

[0048] Example 4

[0049] A method for preparing anodized aluminum strip with added recycled aluminum for laptop casings involves processing raw materials such as recycled aluminum, aluminum ingots, and intermediate alloy ingots through smelting, casting, hot rolling, cold rolling, intermediate annealing, texturing cold rolling, cleaning, and straightening to obtain 5000 series anodized aluminum strip with added recycled aluminum for laptop casings. The specific preparation method includes the following steps:

[0050] (1) Recycled aluminum, aluminum ingots, and intermediate alloy ingots are melted, refined, degassed, filtered, and slag removed, and then semi-continuously cast into aluminum alloy flat ingots. The recycled aluminum content is 95 wt%, the crystallizer thickness is 400 mm, the casting temperature is 715 ℃, the casting speed is 55 mm / min, and the water flow rate is 200 m³ / min. 3 / h, the amount of titanium wire added to the holding furnace and the amount of titanium wire added online are 0.040% and 0.005%, respectively, while obtaining Si 0.18%, Fe 0.40%, Cu 0.009%, Mn 0.038%, Mg 3.45%, Ti 0.045%, with the balance being aluminum and unavoidable impurities in the ingot.

[0051] (2) After homogenization heat treatment at 520℃ for 5h, aluminum alloy flat ingots were hot rolled to a thickness of 7.0mm. The final rolling temperature was 320℃. After cold rolling, the thickness was reduced to 0.80mm. After intermediate annealing at 380℃ for 60sec, the ingots were roughened by EDT with a roughness of Ra1.0μm and cold rolled to a finished thickness of 0.73mm. The final aluminum alloy strip had an average grain size of 4.9μm, a grain ratio of 1.06, a maximum intermetallic compound size of 3.83μm, a maximum compound percentage difference of 0.68% per unit area, a tensile strength of 242MPa, a yield strength of 221MPa, and an elongation of 7.4%.

[0052] (3) The downstream process is as follows: after sandblasting, the aluminum material is anodized. The sandblasting sand type is 150# iron sand, the sandblasting pressure is 19N, the roughness Ra after sandblasting is 2.0μm, the anodized surface is delicate and without material marks.

[0053] Comparative Example 1

[0054] The preparation method of anodized aluminum strip with added recycled aluminum for laptop casing is the same as that in Example 1, except that the casting temperature is 680°C. The alloy composition of the raw materials, casting, hot rolling, cold rolling, intermediate annealing, texturing cold rolling, and downstream sandblasting anodizing process are the same.

[0055] Measurements showed that the maximum size of the intermetallic compound in Comparative Example 1 was 6.82 μm, with a compound percentage difference of 1.65% per unit area. Anodizing resulted in material streaks and discoloration lines, failing to meet the high surface finish requirements for laptop casings. This indicates that in thin-film casting molds with high cooling intensity, the casting temperature was too low, exacerbating microstructure segregation and surface anodizing quality risks.

[0056] Figure 1 For comparison of anodizing: a) Example 1 is good; b) Comparative Example 1 shows anodized material texture. Figure 2 For comparison of the high magnification structure of the finished products: a) Example 1 has fine and uniform texture; b) Comparative Example 1 has coarse and uneven texture.

[0057] Comparative Example 2

[0058] The method for preparing anodized aluminum strip with recycled aluminum for laptop casings is the same as in Example 2, except that the finished product cold rolling uses ordinary rolling. The alloy composition of the raw materials, casting, hot rolling, cold rolling, intermediate annealing, and downstream sandblasting anodizing processes are identical. However, the anodizing process resulted in material streaks, failing to meet the high surface finish requirements of laptop casings.

[0059] Figure 3 Microscopic morphology of aluminum surface: a) texturized rolling in Example 2; b) ordinary rolling in Comparative Example 2. Figure 4 For comparison of anodizing: a) Example 2 is good; b) Comparative Example 2 shows anodized material texture.

[0060] Comparative Example 3

[0061] The preparation method of anodized aluminum strip with recycled aluminum for laptop casings uses the same alloy composition, casting, hot rolling, cold rolling, intermediate annealing, and texturing cold rolling as in Example 3. However, the downstream sandblasting pressure of 16N is insufficient, resulting in a roughness Ra of only 0.90μm after sandblasting, uneven surface, and material marks appearing during the anodizing process, failing to meet the high surface requirements of laptop casings.

[0062] Figure 5 The surface microstructure after sandblasting is as follows: a) Uniform in Example 3; b) Non-uniform in Comparative Example 3.

[0063] Comparative Example 4

[0064] The preparation method of anodized aluminum strip with added recycled aluminum for laptop casings uses the same alloy composition, casting, hot rolling, intermediate annealing, and texturing cold rolling as in Example 4. However, the intermediate annealing thickness of 0.85 mm and the texturing cold rolling rate of 14.11% are too high, and the anodized texture is obvious, which cannot meet the high surface requirements of laptop casings.

[0065] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing anodized aluminum strip with added recycled aluminum for laptop computer casing, characterized in that: A type of anodized aluminum strip with added recycled aluminum for laptop casings is prepared by smelting, casting, hot rolling, cold rolling, intermediate annealing, texturing cold rolling, cleaning and straightening of recycled aluminum, aluminum ingots and intermediate alloy ingots. The specific preparation method includes the following steps: (1) The recycled aluminum, aluminum ingots and intermediate alloy ingots are melted, refined, degassed and filtered to remove slag and then semi-continuously cast into aluminum alloy flat ingots. (2) After homogenization heat treatment, aluminum alloy flat ingots are hot rolled, the hot rolled coils are cold rolled to the intermediate thickness, and then annealed in the intermediate stage. After EDT roughening and cold rolling to the finished thickness, the finished products are directly delivered after cleaning and straightening. The conditions for step (1) are: recycled aluminum ratio ≥70wt%, crystallizer thickness 400~520mm, casting temperature 690~720℃, casting speed 45~60mm / min, and water flow rate 100~200m³ / min. 3 / h, the titanium wire addition amount in the heat preservation furnace and the online titanium wire addition amount are 0.040%±0.001% and 0.005%±0.001%, respectively; The conditions for step (2) are: ≥90% reduction before intermediate annealing, 7.5~9.0% reduction after intermediate annealing, and EDT texturing with Ra 0.90~1.10μm rolling. The downstream manufacturing process that matches it is as follows: after sandblasting the aluminum surface, anodizing is performed. The sandblasting sand type is 120~150# iron sand, the sandblasting pressure is 18~22N, the roughness Ra after sandblasting is 1.8±0.3μm, and the anodized surface is delicate and without material marks.

2. The preparation method according to claim 1, characterized in that: The chemical composition of the aluminum alloy sheet and strip obtained is as follows (by mass fraction): Si 0.10~0.14%, Fe 0.25~0.45%, Cu<0.02%, Mn<0.08%, Mg 2.0~4.0%, Ti 0.035~0.045%, with the balance being aluminum and unavoidable impurities.

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