5xxx aluminum alloy, and preparation method therefor and use thereof

Abstract

The present invention relates to a 5XXX aluminum alloy, and a preparation method therefor and the use thereof. The 5XXX aluminum alloy comprises, in percentages by mass: 0.1-0.4% of Si, 0.35-0.6% of Fe, 0.05-0.3% of Cu, 0.4-0.9% of Mn, 3.5-5.0% of Mg, 0.05-0.3% of Cr, 0-0.25% of Zn, 0.01-0.15% of Sr, 0.01-0.15% of Mo, 0-0.001% of Be, 0.15% or less of Ti, and 0.15% or less of other impurities, with the balance being Al. The 5XXX aluminum alloy of the present application exhibits high strength and good formability even in the case of a high content of Fe and Mn. The 5XXX aluminum alloy of the present application can be prepared by using a recycled aluminum alloy, and inherently has good recyclability, thereby exhibiting great advantages in the aspect of carbon emission reduction.

Description

A 5XXX aluminum alloy, its preparation method and application Technical Field

[0001] This invention relates to the field of aluminum alloys and aluminum sheet / strip processing, specifically to a 5XXX aluminum alloy, its preparation method, and its applications. Background Technology

[0002] This section is intended to provide background or context for the embodiments of the invention set forth in the claims. The description herein is not an admission that it is prior art simply because it is included in this section.

[0003] 5XXX series aluminum alloys are a class of aluminum alloys with magnesium as the main alloying element, typically containing 3-5% magnesium. They possess good weldability, formability, corrosion resistance, and moderate strength, and are widely used in rail transportation, automobiles, shipbuilding, and other fields.

[0004] There is considerable existing research on 5XXX series aluminum alloys, as detailed below:

[0005] Patent CN106834825A discloses a 5182 aluminum alloy and a process for preparing can lid strip from this aluminum alloy. The alloy is composed of the following components by weight percentage: Si: ≤0.1%, Fe: ≤0.2%, Cu: 0.04–0.07%, Mn: 0.3–0.4%, Mg: 4.5–4.8%, Cr: ≤0.05%, Zn: ≤0.05%, Ti: 0.014–0.04%, with the remainder being Al and some unavoidable impurity elements. High alloying is used to improve alloy strength, while the Fe and Si contents are rationally controlled to suppress the formation of streaks. Continuous air-cushion furnace annealing is employed, and high-temperature short-time annealing is used to regulate grain size, improve strip performance uniformity, and ensure strip surface quality.

[0006] Patent CN118360521A discloses a high-strength, high-elongation 5182 aluminum alloy and its manufacturing method, containing the following chemical elements in the following mass percentages: Si: 0.05–0.15%, Fe: 0.20–0.30%, Cu: 0.05–0.08%, Mn: 0.30–0.40%, Mg: 4.8–5.0%, Cr: 0.02–0.09%, Ti: 0.015–0.025%. Through chemical composition design and optimized manufacturing process, the resulting 5182 aluminum alloy exhibits both high strength and high elongation.

[0007] Patent CN113462936A discloses an aluminum alloy pull tab for beverage cans and its processing technology. The aluminum alloy pull tab is made of 5182 aluminum alloy by stamping. The weight percentage of each element in the 5182 aluminum alloy is as follows: Si: less than or equal to 0.08%, Fe: less than or equal to 0.25%, Cu: less than or equal to 0.1%, Mn: 0.2-0.3%, Mg: 4.4-4.6%, Cr: less than or equal to 0.05%, Zn: less than or equal to 0.15%, other individual impurities less than or equal to 0.03%, total impurities less than or equal to 0.15%, and the balance is Al. It is processed by melting and casting, sawing and milling, hot heating, hot rolling, cold rolling, and stretching and straightening.

[0008] However, none of these patents use recycled aluminum as the main raw material. Aluminum alloys have extremely high recyclability. Compared with electrolytic aluminum, the energy consumption for producing 1 ton of recycled aluminum is only about 5% of that for electrolytic aluminum, which has a significant advantage in reducing carbon footprint.

[0009] However, recycled aluminum alloys inevitably contain large amounts of Fe, Si, and Mn elements. To ensure alloy strength, the Mg content is generally above 3.5 wt.%, further reducing the solubility of impurity elements such as Fe, Mn, and Si in the aluminum matrix. Consequently, large amounts of Fe, Si, and Mn elements form coarse Al deposits in the aluminum alloy. x Secondary phases such as (Fe,Mn), Al(Fe,Mn)Si, and Mg2Si are present, exhibiting complex morphologies such as fishbone and flower-like structures. These coarse secondary phases are extremely difficult to break down or dissolve completely, and remain in the final aluminum alloy product, severely reducing the alloy's strength and formability.

[0010] Currently, the application of recycled aluminum alloys in the field of wrought aluminum alloys is mainly in 8XXX or 1XXX aluminum alloys with a low degree of alloying. It is necessary to add expensive rare earth elements such as La, Ce, and Sc to weaken the reduction in plasticity caused by the coarse iron-rich phase. For example, patent CN1177778821A improves the plasticity of recycled aluminum alloys and refines the morphology of iron-rich phases by adding 0.5% or more of La to recycled aluminum alloys and improving the casting and rolling process.

[0011] Patent CN116790947A discloses a 5086 recycled aluminum alloy automotive sheet metal and its production method. The alloy comprises: Si 0.04%–0.35%, Fe 0.10%–0.35%, Cu ≤0.10%, Mn 0.20%–0.50%, Mg 3.6%–4.1%, Cr ≤0.15%, Zn ≤0.20%, Ti ≤0.10%, other individual impurities ≤0.05%, total other impurities ≤0.15%, and the remainder being Al. However, the Fe content in this patent needs to be controlled below 0.35%, thus requiring the addition of some electrolytic aluminum. Furthermore, the maximum Rm of the O-state 5086 recycled aluminum alloy is 281 MPa. p0.2 The maximum pressure is 131 MPa. The raw materials for its recycled 5086 aluminum alloy come solely from aluminum plants and automotive OEM process waste. This single source and limited market availability, coupled with the long usage cycle of OEM aluminum alloys, undoubtedly prolongs the entire cycle of recycled aluminum alloy from recycling to sheet processing to use and recycling again, making it difficult to meet the needs of large-scale recycling. Furthermore, based on the raw materials used in its recycled aluminum alloy, it can only achieve the grade preservation of automotive aluminum and cannot use lower-quality recycled aluminum alloys such as can stock with higher Fe content.

[0012] In summary, currently, aluminum products manufactured using recycled aluminum can only be used to maintain their grade at best, with most being downgraded. Therefore, there is still a need to develop a 5XXX aluminum alloy that has high tolerance for impurities such as Fe, Mn, and Si, and also possesses good mechanical properties. Summary of the Invention

[0013] The purpose of this invention is to provide a 5XXX aluminum alloy with high tolerance to impurity elements such as Fe, Mn, and Si and good mechanical properties, as well as its preparation method and application.

[0014] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0015] The first aspect of this invention provides a 5XXX aluminum alloy, comprising, by mass percentage: 0.1-0.4% Si, 0.35-0.6% Fe, 0.05-0.3% Cu, 0.4-0.9% Mn, 3.5-5.0% Mg, 0.05-0.3% Cr, 0-0.25% Zn, 0.01-0.15% Sr, 0.01-0.15% Mo, 0-0.001% Be, 0.15% or less Ti, 0.15% or less of other impurities, and the balance being Al.

[0016] According to some specific embodiments, by mass percentage, it includes Si 0.2-0.3%, Fe 0.4-0.55%, Cu 0.05-0.3%, Mn 0.45-0.85%, Mg 3.5-4.5%, Cr 0.05-0.3%, Zn 0-0.25%, Sr 0.01-0.15%, Mo 0.01-0.15%, Be 0-0.001%, Ti 0.15% or less, other impurities 0.15% or less, and the balance being Al.

[0017] According to some specific embodiments, the mass percentage content of Sr is 0.02% to 0.1%, for example, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0018] According to some specific embodiments, the mass percentage content of Mo is 0.02% to 0.1%, for example, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0019] According to some specific embodiments, the mass percentage content of Be is 0.0001% to 0.001%, for example, 0.0001%, 0.0002%, 0.0003%, 0.0004%, 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.0009%, or 0.001%.

[0020] According to some specific embodiments, the Zn mass percentage content is 0.15% to 0.25%.

[0021] According to some specific embodiments, the total mass percentage of Sr and Mo does not exceed 0.15%.

[0022] According to some specific embodiments, the total mass percentage of Mn, Mg and Cu is 4% or more.

[0023] According to some specific embodiments, the total mass ratio of Mn and Cr to Fe is 1:1 to 3:1, for example 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1.

[0024] According to some specific embodiments, the mass ratio of the total mass of Sr and Mo to the mass of Si is 1:20 to 1:1.5. Further, the mass ratio of the total mass of Sr and Mo to the mass of Si is 1:1.5 to 1:5, for example, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2 .5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9, 1:4, 1:4.1, 1:4.2, 1:4.3, 1:4.4, 1:4.5, 1:4.6, 1:4.7, 1:4.8, 1:4.9, 1:5.

[0025] According to some specific embodiments, the mass percentage of each of the other impurities is 0.05% or less.

[0026] According to some specific embodiments, the tensile strength Rm of the 5XXX aluminum alloy is 330MPa or higher, and the specified plastic elongation strength R... p0.2 For a strength of 180 MPa or higher, the elongation after fracture A 50 It is 22% or higher.

[0027] According to some specific embodiments, the average equivalent diameter of the iron-rich phase in the 5XXX aluminum alloy is 1.6 μm or less.

[0028] According to some specific embodiments, the 5XXX aluminum alloy is an O-state aluminum alloy.

[0029] A second aspect of the present invention provides a method for preparing the 5XXX aluminum alloy, comprising the following steps:

[0030] (1) Using scrap aluminum as raw material, one or more of Al-Mn, Al-Cr, Al-Mo, Mg ingot, Al-Sr, and Al-Be master alloys are selectively added, and the aluminum alloy ingots are obtained by smelting, slag removal, alloying, refining, and casting in sequence.

[0031] (2) The aluminum alloy ingot is homogenized, and the temperature of the homogenization treatment is controlled at 420-480℃, and the holding time is 2-12h.

[0032] (3) Hot rough rolling is performed on the homogenized aluminum alloy ingot to control the deformation to be greater than 86%.

[0033] (4) Hot finishing rolling is performed on the hot-rolled material after hot rough rolling, and the deformation is controlled to be greater than 80%.

[0034] (5) The hot-rolled material after hot finishing is cold-rolled, and the deformation is controlled to be 65-93%;

[0035] (6) Anneal the cold-rolled material to obtain the 5XXX aluminum alloy.

[0036] According to some specific implementation methods, the waste aluminum is one or more of the following: recycled aluminum cans, automobile plates, and ship plates.

[0037] Among them, beverage cans are mainly made of 3XXX and 5XXX aluminum alloys, while automotive steel plates and ship plates are mainly made of 5XXX and 6XXX aluminum alloys. In addition to recycled beverage cans, automotive steel plates, ship plates, etc., the scrap aluminum in this application can also be one or more of 3XXX, 5XXX, and 6XXX aluminum alloys from other sources.

[0038] According to some specific implementations, in step (3), the number of rolling passes in the hot roughing is 16 to 22.

[0039] According to some specific implementation methods, in step (4), the final rolling temperature of the hot finishing mill is controlled to be greater than 310°C.

[0040] According to some specific implementations, in step (6), the annealing step is carried out in a box-type annealing furnace or an air-cushion continuous annealing furnace.

[0041] Furthermore, when annealing is carried out in the box-type annealing furnace, the temperature is controlled at 300-380℃ and the holding time is 2-6h; when annealing is carried out in the air-cushion continuous annealing furnace, the temperature is controlled at 440-500℃ and the holding time is 0s-120s.

[0042] According to some specific implementations, in step (1), the percentage of the iron-rich phase area in the aluminum alloy ingot is controlled to be 3.5% or less, and the average equivalent diameter is 3.5 μm or less; the percentage of the Mg2Si phase area is controlled to be 1.6% or less, and the average equivalent diameter is 1.2 μm or less.

[0043] The third aspect of this invention provides the application of the 5XXX aluminum alloy described above, or the 5XXX aluminum alloy prepared by the described method, in automotive body inner panels, structural components, or rail transit structural components.

[0044] The fourth aspect of the present invention provides an inner panel of an automobile body, a structural component or a rail transit structural component, the material of which includes the 5XXX aluminum alloy as described above.

[0045] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0046] Compared with traditional high-strength 5XXX aluminum alloys, the 5XXX aluminum alloy of this application has a high Fe and Mn content, and contains Sr and Mo, and selectively contains Be. That is, by improving the composition of the 5XXX aluminum alloy, especially by adding Sr and Mo, and selectively adding Be, the 5XXX aluminum alloy has high tolerance to impurity elements such as Fe and Mn. Furthermore, the 5XXX aluminum alloy of this application still exhibits high strength and excellent formability even with high Fe and Mn content, and can be used in automotive body panels, structural parts or rail transportation fields.

[0047] The 5XXX aluminum alloy of this application can be prepared using recycled aluminum alloys and has excellent recyclability, which has a great advantage in reducing carbon emissions.

[0048] This application further optimizes and improves the preparation process, which can more fully break down coarse second-phase particles, thereby enabling control over the microstructure and properties of the final product, and thus further improving the product's strength and formability. Attached Figure Description

[0049] Figure 1 shows the as-cast microstructure of the aluminum alloy ingot in Comparative Example 1;

[0050] Figure 2 shows the as-cast microstructure of the aluminum alloy ingot in Comparative Example 3;

[0051] Figure 3 is a diagram of the as-cast microstructure of the aluminum alloy ingot of Example 1;

[0052] Figure 4 shows the as-cast microstructure of the aluminum alloy ingot in Example 2;

[0053] Figure 5 shows the as-cast microstructure of the aluminum alloy ingot in Example 3;

[0054] Figure 6 is a diagram of the as-cast microstructure of the aluminum alloy ingot in Example 4;

[0055] Figure 7 shows the as-cast microstructure of the aluminum alloy ingot in Example 5;

[0056] Figure 8 is a diagram of the as-cast microstructure of the aluminum alloy ingot of Example 6;

[0057] Figure 9 is a diagram of the as-cast microstructure of the aluminum alloy ingot in Example 7;

[0058] Figure 10 shows the statistical results of the area percentage of Fe-rich phase in the as-cast microstructure of the alloy;

[0059] Figure 11 shows the statistical results of the equivalent diameter of the Fe-rich phase in the as-cast microstructure of the alloy.

[0060] Figure 12 shows the statistical results of the area percentage of the Mg2Si phase in the as-cast microstructure of the alloy.

[0061] Figure 13 shows the statistical results of the equivalent diameter of the Mg2Si phase in the as-cast microstructure of the alloy.

[0062] Figure 14 shows the metallographic structure of the ingot after homogenization treatment in Comparative Example 1.

[0063] Figure 15 shows the metallographic structure of the ingot after homogenization treatment in Comparative Example 2.

[0064] Figure 16 shows the metallographic structure of the ingot after homogenization treatment in Comparative Example 3;

[0065] Figure 17 shows the metallographic structure of the ingot after homogenization treatment in Comparative Example 4.

[0066] Figure 18 shows the metallographic structure of the ingot after homogenization treatment in Example 1;

[0067] Figure 19 shows the metallographic structure of the ingot after homogenization treatment in Example 2;

[0068] Figure 20 shows the metallographic structure of the ingot after homogenization treatment in Example 3;

[0069] Figure 21 shows the metallographic structure of the ingot after homogenization treatment in Example 4;

[0070] Figure 22 shows the metallographic structure of the ingot after homogenization treatment in Example 5;

[0071] Figure 23 is a metallographic diagram of the ingot after homogenization treatment in Example 6;

[0072] Figure 24 shows the metallographic structure of the ingot after homogenization treatment in Example 7;

[0073] Figure 25 shows the statistical results of the equivalent diameter of the iron-rich phase in the rolled aluminum alloy. Detailed Implementation

[0074] Existing technologies using recycled aluminum to manufacture aluminum products suffer from limitations: at best, only the grade can be maintained, with most products requiring downgrading. Furthermore, the tolerance for iron content is low, typically requiring the iron content to be limited to below 0.35% to ensure the performance of the manufactured aluminum alloy. Therefore, this application discloses a method for manufacturing a high-Fe, Mn content, high-strength Al-Mg alloy and its sheet, as well as its applications. This alloy exhibits high strength and excellent formability. Moreover, it can be produced using recycled materials such as can stock and possesses recyclable characteristics, offering significant advantages in reducing carbon emissions from aluminum alloys.

[0075] Since the properties of aluminum alloys mainly depend on their composition, which directly determines their most basic characteristics such as mechanical and formability, this application modifies the precipitation behavior of the α-Al matrix and second phase during solidification by controlling the composition, reducing the Mg content, controlling the upper limits of Mn and Cr additions, and adding Sr, Mo, and Be microalloying elements. This allows for the control of grain size and the morphology, quantity, and size of the iron-rich phase. Combined with homogenization treatment, hot rough rolling, hot finish rolling, and cold rolling processes, coarse second-phase particles are thoroughly broken down. The final annealing process further controls the microstructure and properties of the final product. Ultimately, this improves the alloy's tolerance to impurities such as Fe, Mn, and Si, and the alloy exhibits a good balance between strength and plasticity.

[0076] This application utilizes a high proportion of recycled aluminum alloy as raw material, requiring only the use of small amounts of Al-Mn, Al-Cr, Al-Mo, Mg ingots, Al-Sr, and Al-Be master alloys to adjust the mass of each element in the aluminum alloy. In some embodiments, the proportion of recycled aluminum alloy to the total raw material is over 70%.

[0077] As is known to those skilled in the art, recycled scrap aluminum requires pretreatment such as paint stripping before it can be used to prepare 5XXX aluminum alloys. The pretreatment method for recycled scrap aluminum is not the inventive point of this application; it can be performed using conventional techniques in the field.

[0078] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0079] Unless otherwise specified in this article, the preparation methods and process parameters involved in the following examples or comparative examples refer to the prior art, and the raw materials used are commercially available.

[0080] Comparative Example 1

[0081] This example provides an AA5182 alloy and its preparation method. The alloy composition meets the requirements for 5182 alloy composition in the AA standard. By mass percentage, the AA5182 alloy contains 0.15% Si, 0.2% Fe, 0.1% Cu, 0.35% Mn, 0.05% Cr, 4.5% Mg, 0.15% Zn, 0.02% Ti, other unavoidable impurities, and the balance Al.

[0082] The preparation method of this alloy includes the following steps:

[0083] (1) Using electrolytic aluminum ingots or electrolytic aluminum liquid as raw materials, the raw materials are smelted in a smelting furnace at a melting temperature of 760°C. Then, the slag is removed, alloying, refining and casting are carried out in sequence to obtain aluminum alloy ingots with the target aluminum alloy composition.

[0084] (2) The aluminum alloy ingot obtained in step (1) is homogenized, and the temperature of the homogenization treatment is controlled at 460℃ and the holding time is 8h.

[0085] (3) The homogenized ingot is hot rough rolled, and the hot rolling start temperature is controlled at 440℃. After 18 passes of hot rolling, it is rolled to the intermediate billet, and the hot rough rolling deformation is 91%.

[0086] (4) The intermediate billet after hot rough rolling is hot finished rolling, and the hot finished rolling deformation is controlled at 93% and the final rolling temperature is 320℃.

[0087] (5) The hot-rolled coil is cold-rolled to 1.2mm with a cold-rolling deformation of 82%.

[0088] (6) The cold-rolled coil is annealed in a box annealing furnace at a temperature of 340°C for 4 hours to obtain the final product in state O.

[0089] Comparative Example 2

[0090] This example is basically the same as Comparative Example 1, except for the temperature and time of the homogenization process in step (2). The homogenization process in this example is at a temperature of 480℃ and a holding time of 6 hours.

[0091] Comparative Example 3

[0092] This example provides a B1 alloy and its preparation method. The B1 alloy contains, by mass percentage, 0.25% Si, 0.45% Fe, 0.1% Cu, 0.8% Mn, 0.05% Cr, 4.5% Mg, 0.15% Zn, 0.02% Ti, other unavoidable impurities, and the balance Al.

[0093] The preparation method of this alloy includes the following steps:

[0094] (1) Recycled can stock is used as raw material and smelted in a melting furnace at a melting temperature of 760°C. After refining and slag removal, the composition is pre-analyzed. Based on the results of the composition pre-analysis, alloying is carried out by adding Al-Mn, Al-Cr, and Mg ingot master alloys according to the elemental composition described in this invention to obtain an aluminum alloy melt with qualified composition. Then, slag removal, alloying, refining, slag removal, and settling are performed in sequence to obtain an aluminum alloy ingot with the target aluminum alloy composition.

[0095] (2) The aluminum alloy ingot obtained in step (1) is homogenized, and the temperature of the homogenization treatment is controlled at 460℃ and the holding time is 8h.

[0096] (3) The homogenized ingot is hot rough rolled, and the hot rolling start temperature is controlled at 440℃. After 18 passes of hot rolling, it is rolled to the intermediate billet, and the hot rough rolling deformation is 91%.

[0097] (4) The intermediate billet after hot rough rolling is hot finished rolling, and the hot finished rolling deformation is controlled at 93% and the final rolling temperature is 320℃.

[0098] (5) The hot-rolled coil is cold-rolled to 1.2mm with a cold-rolling deformation of 82%.

[0099] (6) The cold-rolled coil is annealed in a box annealing furnace at a temperature of 340°C for 4 hours to obtain the final product in state O.

[0100] Comparative Example 4

[0101] This example is basically the same as Comparative Example 3, except for the temperature and time of the homogenization process in step (2). The homogenization process in this example is at a temperature of 480℃ and a holding time of 6 hours.

[0102] Example 1

[0103] This example provides a B2 alloy and its preparation method. The B2 alloy contains, by mass percentage, 0.25% Si, 0.45% Fe, 0.1% Cu, 0.8% Mn, 0.05% Cr, 4.2% Mg, 0.15% Zn, 0.02% Ti, 0.05% Sr, 0.05% Mo, 0.0005% Be, other unavoidable impurities, and the balance Al.

[0104] The preparation method of this alloy includes the following steps:

[0105] (1) Recycled can stock is used as raw material and smelted in a melting furnace at a melting temperature of 760°C. After refining and slag removal, the composition is pre-analyzed. Based on the results of the composition pre-analysis, alloying is carried out by adding Al-Mn, Al-Cr, Al-Mo, Mg ingots, Al-Sr, and Al-Be master alloys according to the elemental composition described in this invention to obtain an aluminum alloy melt with qualified composition. Then, slag removal, alloying, refining, slag removal, and settling are carried out in sequence before casting to obtain an aluminum alloy ingot with the target aluminum alloy composition.

[0106] (2) The aluminum alloy ingot obtained in step (1) is homogenized, and the temperature of the homogenization treatment is controlled at 420℃ and the holding time is 10h.

[0107] (3) The homogenized ingot is hot rough rolled, and the hot rolling start temperature is controlled at 440℃. After 18 passes of hot rolling, it is rolled to the intermediate billet, and the hot rough rolling deformation is 91%.

[0108] (4) The intermediate billet after hot rough rolling is hot finished rolling, and the hot finished rolling deformation is controlled at 93% and the final rolling temperature is 320℃.

[0109] (5) The hot-rolled coil is cold-rolled to 1.2mm with a cold-rolling deformation of 82%.

[0110] (6) The cold-rolled coil is annealed in a box annealing furnace at a temperature of 340°C for 4 hours to obtain the final product in state O.

[0111] Example 2

[0112] This example is basically the same as Example 1, except for the aluminum alloy composition and the temperature and time of the homogenization treatment in step (2).

[0113] By mass percentage, the B3 alloy provided in this example contains 0.25% Si, 0.45% Fe, 0.15% Cu, 0.8% Mn, 0.05% Cr, 3.5% Mg, 0.15% Zn, 0.02% Ti, 0.05% Sr, 0.1% Mo, 0.0005% Be, other unavoidable impurities, and the balance Al.

[0114] In this example, the homogenization treatment temperature was 430℃, and the holding time was 8 hours.

[0115] Example 3

[0116] This example is basically the same as Example 1, except for the aluminum alloy composition and the temperature and time of the homogenization treatment in step (2).

[0117] By mass percentage, the B4 alloy provided in this example contains 0.25% Si, 0.45% Fe, 0.15% Cu, 0.85% Mn, 0.05% Cr, 4% Mg, 0.2% Zn, 0.02% Ti, 0.05% Sr, 0.05% Mo, 0.0005% Be, other unavoidable impurities, and the balance Al.

[0118] In this example, the homogenization treatment temperature was 440℃, and the holding time was 12h.

[0119] Example 4

[0120] This example is basically the same as Example 1, except for the aluminum alloy composition and the temperature and time of the homogenization treatment in step (2).

[0121] By mass percentage, the B5 alloy provided in this example contains 0.25% Si, 0.4% Fe, 0.15% Cu, 0.8% Mn, 0.1% Cr, 4% Mg, 0.15% Zn, 0.02% Ti, 0.02% Sr, 0.05% Mo, 0.0005% Be, other unavoidable impurities, and the balance Al.

[0122] In this example, the homogenization treatment temperature was 450℃, and the holding time was 10h.

[0123] Example 5

[0124] This example is basically the same as Example 1, except for the aluminum alloy composition and the temperature and time of the homogenization treatment in step (2).

[0125] By mass percentage, the B6 alloy provided in this example contains 0.25% Si, 0.45% Fe, 0.15% Cu, 0.75% Mn, 0.1% Cr, 4% Mg, 0.15% Zn, 0.02% Ti, 0.05% Sr, 0.02% Mo, 0.0005% Be, other unavoidable impurities, and the balance Al.

[0126] In this example, the homogenization treatment temperature was 460℃, and the holding time was 6 hours.

[0127] Example 6

[0128] This example is basically the same as Example 1, except for the aluminum alloy composition and the temperature and time of the homogenization treatment in step (2).

[0129] By mass percentage, the B7 alloy provided in this example contains 0.25% Si, 0.5% Fe, 0.2% Cu, 0.65% Mn, 0.15% Cr, 4% Mg, 0.2% Zn, 0.02% Ti, 0.05% Sr, 0.1% Mo, 0.0005% Be, other unavoidable impurities, and the balance Al.

[0130] In this example, the homogenization treatment temperature was 480℃, and the holding time was 4 hours.

[0131] Example 7

[0132] This example is basically the same as Example 1, except for the aluminum alloy composition and the temperature and time of the homogenization treatment in step (2).

[0133] By mass percentage, the B8 alloy provided in this example contains 0.25% Si, 0.55% Fe, 0.3% Cu, 0.5% Mn, 0.15% Cr, 4% Mg, 0.2% Zn, 0.02% Ti, 0.1% Sr, 0.05% Mo, 0.0005% Be, other unavoidable impurities, and the balance Al.

[0134] In this example, the homogenization treatment temperature was 480℃, and the holding time was 2 hours.

[0135] Performance testing

[0136] According to the microstructure inspection method specified in national standard GB / T3246.1, the aluminum alloy ingots prepared in step (1) of each embodiment and comparative example were tested. Figure 1 shows the as-cast microstructure of the aluminum alloy ingot of Comparative Example 1, Figure 2 shows the as-cast microstructure of the aluminum alloy ingot of Comparative Example 3, Figures 3 to 9 show the as-cast microstructure of the aluminum alloy ingots of Examples 1 to 7, and Figures 10 to 13 show the statistical results of the area percentage and equivalent diameter of the Fe-rich phase and Mg2Si phase in the as-cast microstructure of the alloy. Image analysis software was used to statistically analyze the area percentage of the Fe-rich phase and Mg2Si phase in the metallographic photographs at 200X magnification. To ensure the accuracy of the statistical results, at least five fields of view were selected for statistical analysis, and the average value was taken as the final result. The equivalent diameter of the Fe-rich phase and Mg2Si phase was determined using the same method, by statistically analyzing the area of ​​each second-phase particle, and then calculating the equivalent diameter according to S = πr². 2 The equivalent diameter of each second-phase particle was calculated. To ensure the accuracy of the statistical results, at least 200 second-phase particles were counted, and their average value was taken as the final result.

[0137] This shows that the conventional AA5182 alloy contains only a small amount of Mg2Si phase and iron-rich phase in its as-cast microstructure, which is related to its low Fe, Si, and Mn content. While the B1 alloy, with its high Fe and Mn content, lacks a β-iron phase due to the higher Mn content, its Fe-rich phase content and equivalent diameter increase to approximately 4.2% and 5.6 μm, respectively, compared to the AA5182 alloy. These coarse second-phase particles severely impair the alloy's formability. As for the B2–B8 alloys, although they are prepared from recycled materials like the B1 alloy and therefore contain large amounts of Fe and Mn, their solidification behavior has been altered through alloy composition optimization, particularly by utilizing the synergistic effects of Sr, Mo, and Be with other elements, resulting in a significant change in their as-cast microstructure. The content and equivalent diameter of the Fe-rich and Mg2Si phases in these alloys are significantly reduced compared to the B1 alloy. This invention demonstrates that the high Fe content 5XXX aluminum alloy can effectively reduce and refine the content and size of iron-rich phases and Mg2Si phases in the alloy through alloy composition optimization.

[0138] Figures 14-24 show metallographic photographs of the ingots after homogenization treatment in step (2) of Comparative Examples 1-4 and Examples 1-7, respectively. Although the AA5182 alloy has extremely low Si and Fe contents, the iron-rich phase and Mg2Si phase cannot be completely dissolved after homogenization, and the Mg2Si phase content even tends to increase. The recycled B1 alloy also shows the same trend, and due to the increase in Fe, Mn, and Si element contents, the content and size of the iron-rich phase and Mg2Si phase in the alloy are significantly increased compared to the AA5182 alloy, and homogenization treatment cannot eliminate them. However, the B2-B8 alloys produced by the method of the examples show a significant reduction in the content of the iron-rich phase after homogenization treatment compared to the as-cast alloy, and the Mg2Si phase is fully dissolved.

[0139] Figure 25 shows the statistical results of the equivalent diameter of the iron-rich phase in the rolled aluminum alloys. AA5182-H1 is the rolled aluminum alloy from Comparative Example 1, AA5182-H2 is the rolled aluminum alloy from Comparative Example 2, B1-H1 is the rolled aluminum alloy from Comparative Example 3, B1-H2 is the rolled aluminum alloy from Comparative Example 4, and B2-H to B8-H are the rolled aluminum alloys from Examples 1 to 7, respectively. The large rolling deformation during the rolling process further breaks down the nascent second-phase particles into smaller particles, thereby significantly improving the formability. The average equivalent diameter of the second-phase particles in the rolled B2–B8 alloys produced using the method described in this invention is ≤1.6 μm. Although the B1 alloy also uses the same rolling process, the initial Fe-rich phase and Mg2Si are relatively large, making it extremely difficult to fully break down and retain them during subsequent processing. The alloy described in this invention, through a combination of alloy composition optimization and homogenization and rolling processes, fully breaks down coarse second-phase particles, thereby weakening their impact on strength and plasticity.

[0140] The cold-rolled product of final thickness was annealed to obtain the final product in the O-state. Tensile properties of the final product were tested according to ISO 6892-1:2019 standard, and the results are shown in Table 1. AA5182 is the O-state alloy obtained in Comparative Example 1, and B1 is the O-state alloy obtained in Comparative Example 3. 50 This refers to the elongation after fracture of a standard tensile specimen with a gauge length of 50 mm. Table 1 shows that the B2–B8 alloys produced using the method described in this invention all have higher strength than the AA5182-O alloy, and comparable plasticity. While the B1 alloy from recycled 5XXX series automotive steel sheets has slightly higher strength than the 5182-O alloy, its plasticity is significantly reduced.

[0141] Table 1

[0142] In summary, the high Fe and Mn content Al-Mg aluminum alloy obtained by the embodiments of the present invention, using recycled aluminum cans as raw materials, and produced through alloy composition optimization, casting, homogenization, hot rolling, cold rolling, and annealing processes, exhibits higher strength and better formability than AA5182, meeting the application requirements of automotive body panels, structural components, or rail transportation vehicles with higher performance requirements. Furthermore, the aluminum alloy described in this invention has extremely high recyclability, effectively reducing carbon emissions.

[0143] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A 5XXX aluminum alloy, characterized in that: Based on mass percentage, it includes Si 0.1–0.4%, Fe 0.35–0.6%, Cu 0.05–0.3%, Mn 0.4–0.9%, Mg 3.5–5.0%, Cr 0.05–0.3%, Zn 0–0.25%, Sr 0.01–0.15%, Mo 0.01–0.15%, Be 0–0.001%, Ti 0.15% or less, other impurities 0.15% or less, and the balance being Al.

2. The 5XXX aluminum alloy according to claim 1, characterized in that: Based on mass percentage, it includes Si 0.2–0.3%, Fe 0.4–0.55%, Cu 0.05–0.3%, Mn 0.45–0.85%, Mg 3.5–4.5%, Cr 0.05–0.3%, Zn 0–0.25%, Sr 0.01–0.15%, Mo 0.01–0.15%, Be 0–0.001%, Ti 0.15% or less, other impurities 0.15% or less, and the balance being Al.

3. The 5XXX aluminum alloy according to claim 1 or 2, characterized in that: The Sr content is 0.02-0.1% by mass, the Mo content is 0.02-0.1% by mass, and the Be content is 0.0001-0.001% by mass.

4. The 5XXX aluminum alloy according to claim 1 or 2, characterized in that: The total mass percentage of Sr and Mo does not exceed 0.15%.

5. The 5XXX aluminum alloy according to claim 1 or 2, characterized in that: The total mass percentage of Mn, Mg and Cu is 4% or more.

6. The 5XXX aluminum alloy according to claim 1 or 2, characterized in that: The total mass ratio of Mn and Cr to Fe is 1:1 to 3:

1.

7. The 5XXX aluminum alloy according to claim 1 or 2, characterized in that: The total mass ratio of Sr and Mo to the mass ratio of Si is 1:20 to 1:1.

5.

8. The 5XXX aluminum alloy according to claim 1 or 2, characterized in that: The Zn content is 0.15% to 0.25% by mass.

9. The 5XXX aluminum alloy according to claim 1, characterized in that: The tensile strength Rm of the 5XXX aluminum alloy is 330MPa or higher, and the specified plastic elongation strength R p0.2 For a strength of 180 MPa or higher, the elongation after fracture A 50 It is 22% or higher.

10. The 5XXX aluminum alloy according to claim 1, characterized in that: The average equivalent diameter of the iron-rich phase in the 5XXX aluminum alloy is 1.6 μm or less.

11. The 5XXX aluminum alloy according to claim 1, characterized in that: The 5XXX aluminum alloy is an O-state aluminum alloy.

12. A method for preparing a 5XXX aluminum alloy as described in any one of claims 1 to 11, characterized in that: It includes the following steps: (1) Using scrap aluminum as raw material, one or more of Al-Mn, Al-Cr, Al-Mo, Mg ingot, Al-Sr, and Al-Be master alloys are selectively added, and the aluminum alloy ingots are obtained by smelting, slag removal, alloying, refining, and casting in sequence. (2) The aluminum alloy ingot is homogenized, and the temperature of the homogenization treatment is controlled at 420-480℃, and the holding time is 2-12h. (3) Hot rough rolling is performed on the homogenized aluminum alloy ingot to control the deformation to be greater than 86%. (4) Hot finishing rolling is performed on the hot-rolled material after hot rough rolling, and the deformation is controlled to be greater than 80%. (5) The hot-rolled material after hot finishing is cold-rolled, and the deformation is controlled to be 65-93%; (6) Anneal the cold-rolled material to obtain the 5XXX aluminum alloy.

13. The preparation method according to claim 12, characterized in that: The waste aluminum is one or more of the following: recycled aluminum cans, automotive steel plates, and ship plates.

14. The preparation method according to claim 12, characterized in that: In step (1), the percentage of the iron-rich phase area in the aluminum alloy ingot is controlled to be 3.5% or less, and the average equivalent diameter is 3.5 μm or less; the percentage of the Mg2Si phase area is controlled to be 1.6% or less, and the average equivalent diameter is 1.2 μm or less.

15. The application of a 5XXX aluminum alloy as described in any one of claims 1 to 11, or a 5XXX aluminum alloy prepared by any one of claims 12 to 14, in automotive body inner panels, structural components, or rail transit structural components.

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