Aluminum alloy sheet material

Abstract

To provide an aluminum alloy sheet material that can be manufactured by using aluminum alloy waste, and is equipped with bendability.SOLUTION: An aluminum alloy sheet material is made of aluminum alloy which contains 0.50 to 1.50 mass% of Si, 0.35 to 0.80 mass% of Mg, 0.08 to 0.60 mass% of Fe, 0.001 to 0.40 mass% of Cu, 0.01 to 0.25 mass% of Mn, more than 0.00 mass% and 0.09 mass% or less of Ti, and made of the balance Al and inevitable impurities, where the ratio of an intensity integration value (A) of a diffraction peak having a peak top near 2θ=42° for the total of an intensity integration value (A) of a diffraction peak having a peak top near 2θ=42° and an intensity integration value (B) of a diffraction peak having a peak top near 2θ=17°is 10.0% or more, and the integration degree of Cube orientation in the total sheet thickness of an ND-TD surface is 10 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an aluminum alloy sheet material used for automobile body panels and the like. [Background technology]

[0002] Traditionally, to ensure good strength and corrosion resistance when producing aluminum alloys, virgin aluminum ingots have been used as the casting raw material, and elements such as Si and Mg have been added to adjust the chemical composition to the desired range. However, because virgin aluminum ingots consume a large amount of electricity during production, using them as a casting raw material results in high CO2 emissions from the electricity, which increases the environmental impact. In particular, achieving carbon neutrality has become a global social issue in recent years, making it increasingly important to reduce the amount of virgin aluminum used.

[0003] 6000 series aluminum alloy sheets, which have excellent formability and bake hardness (BH), are used for automobile body panels. 6000 series aluminum alloy sheets have a smaller amount of alloying elements than other aluminum alloys, and when reused as an aluminum alloy melting material, the original 6000 series aluminum alloy ingot can be easily obtained, making them suitable for recycling (e.g., Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-116594 Summary of the Invention [Problem to be solved by the invention]

[0005] However, although Patent Document 1 mentions the improvement of bending workability of 6000 series aluminum alloys, it does not mention the specific composition or properties of the aluminum alloy material in terms of recyclability.

[0006] Therefore, there is a demand for an aluminum alloy material of Al-Mg-Si type aluminum alloy such as 6000 series that can be produced using scrap aluminum alloy material and that has excellent bendability and the like.

[0007] Therefore, an object of the present invention is to provide an aluminum alloy sheet material that can be manufactured using scrap aluminum alloy material and has excellent bendability. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have found that, due to the presence of Fe in scrap aluminum alloy material, the ratio of the α-AlFeMnSi phase in the second phase particles of the aluminum alloy produced using this scrap aluminum alloy material is reduced, resulting in reduced performance (bendability).The present inventors have also found that, by appropriately adjusting the composition of the aluminum alloy and optimizing the production method to increase the ratio of the α-AlFeMnSi phase in the second phase particles, and by appropriately adjusting the composition of the aluminum alloy to increase the strength, it is possible to obtain an aluminum alloy sheet material with excellent bendability even when scrap aluminum alloy material containing Fe is used as a production raw material.

[0009] That is, the present invention (1) is an aluminum alloy containing 0.50 to 1.50 mass% Si, 0.35 to 0.80 mass% Mg, 0.08 to 0.60 mass% Fe, 0.001 to 0.40 mass% Cu, 0.01 to 0.25 mass% Mn, and more than 0.00 mass% but not more than 0.09 mass% Ti, and optionally containing one or more elements selected from the group consisting of 0.05 mass% or less Cr, 0.05 mass% or less Zn, and 0.05 mass% or less B, with the remainder being Al and unavoidable impurities; When analyzed by X-ray diffraction, the ratio ((A / (A+B))×100) of the intensity integral (A) of the diffraction peak having a peak top at about 2θ=42° due to the α-AlFeMnSi phase of the second phase particles to the sum of the intensity integral (A) of the diffraction peak having a peak top at about 2θ=42° due to the α-AlFeMnSi phase and the intensity integral (B) of the diffraction peak having a peak top at about 2θ=17° due to the β-AlFeMnSi phase is 10.0% or more, The degree of Cube orientation accumulation across the entire thickness of the ND-TD plane is 10.0 or more. The aluminum alloy sheet material is characterized by the following. The present invention (2) is the aluminum alloy sheet material according to (1), wherein the ratio ((A / (A+B))×100) of the intensity integrated value (A) of the diffraction peak having a peak top at about 2θ=42° and attributed to the α-AlFeMnSi phase of the second phase particles to the sum of the intensity integrated value (A) of the diffraction peak having a peak top at about 2θ=42° and attributed to the β-AlFeMnSi phase, and the intensity integrated value (B) of the diffraction peak having a peak top at about 2θ=17° and attributed to the α-AlFeMnSi phase, is 25.0% or more. The present invention (3) also provides: The tensile strength in the 0°, 45° and 90° directions relative to the rolling direction is 190 MPa or more, The elongation in the 0°, 45° and 90° directions relative to the rolling direction is 23% or more. (1) is an aluminum alloy sheet material characterized by the above. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an aluminum alloy plate material that can be manufactured using scrap aluminum alloy material and has excellent bendability. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an X-ray diffraction chart obtained by analyzing an aluminum alloy plate material by X-ray diffraction. DETAILED DESCRIPTION OF THE INVENTION

[0012] The aluminum alloy sheet material of the present invention is an aluminum alloy containing 0.50 to 1.50 mass% Si, 0.35 to 0.80 mass% Mg, 0.08 to 0.60 mass% Fe, 0.001 to 0.40 mass% Cu, 0.01 to 0.25 mass% Mn, and more than 0.00 mass% but not more than 0.09 mass% Ti, and optionally containing one or more elements selected from the group consisting of 0.05 mass% or less Cr, 0.05 mass% or less Zn, and 0.05 mass% or less B, with the remainder being Al and unavoidable impurities; When analyzed by X-ray diffraction, the ratio ((A / (A+B))×100) of the intensity integral (A) of the diffraction peak having a peak top at about 2θ=42° due to the α-AlFeMnSi phase of the second phase particles to the sum of the intensity integral (A) of the diffraction peak having a peak top at about 2θ=42° due to the α-AlFeMnSi phase and the intensity integral (B) of the diffraction peak having a peak top at about 2θ=17° due to the β-AlFeMnSi phase is 10.0% or more, The degree of Cube orientation accumulation across the entire thickness of the ND-TD plane is 10.0 or more. The aluminum alloy sheet material is characterized by the following.

[0013] The aluminum alloy sheet made of the aluminum alloy of the present invention can be produced from a 6000 series aluminum alloy material, for example, sash scrap containing 0.20 to 0.60 mass% Si, 0.35 mass% or more Fe, 0.10 mass% or less Cu, 0.10 mass% or less Mn, 0.45 to 0.90 mass% Mg, 0.10 mass% or less Cr, 0.10 mass% or less Zn, and 0.10 mass% or less Ti, as a casting raw material. Examples of other aluminum alloy scrap materials that can be used as a casting raw material for the aluminum alloy sheet made of the aluminum alloy of the present invention include scrap metal and other scrap generated during the rolling and slitting processes during the production of aluminum alloy materials. Scrap alloys other than the 6000 series that can be used as a casting raw material for the aluminum alloy sheet made of the aluminum alloy of the present invention may also be mixed metals collected from scrapped vehicles or UBC (used beverage can) scrap.

[0014] The aluminum alloy according to the aluminum alloy sheet of the present invention contains Si, Mg, Fe, Cu, Mn, and Ti as essential elements, and may optionally contain Cr, Zn, and B. The aluminum alloy according to the aluminum alloy sheet of the present invention is composed of the essential elements, optional additional elements added as needed, and aluminum and unavoidable impurities as the balance.

[0015] Since Si is contained in aluminum alloy scrap, the aluminum alloy according to the present invention contains Si. Si improves strength by precipitation of Mg-Si intermetallic compounds. The Si content of the aluminum alloy is 0.50 to 1.50 mass%, preferably 0.55 to 1.25 mass%, and more preferably 0.60 to 1.00 mass%. When aluminum alloy scrap is used as an ingot raw material for producing an aluminum alloy sheet, the Fe content in the aluminum alloy sheet increases, resulting in a decrease in the proportion of the second phase α-AlFeMnSi phase. Furthermore, a decrease in the proportion of the second phase α-AlFeMnSi phase in the aluminum alloy sheet reduces bendability. Therefore, in the aluminum alloy sheet according to the present invention, the Si content is adjusted to the above range, thereby increasing the proportion of the second phase α-AlFeMnSi phase. This results in the aluminum alloy sheet according to the present invention having excellent bendability. Furthermore, Si contributes to improving strength. On the other hand, if the Si content of the aluminum alloy is less than the above range, the effect of improving strength is not sufficiently obtained, and if it exceeds the above range, coarse Si particles and coarse Mg-Si intermetallic compounds are formed, resulting in a decrease in bending workability.

[0016] Since Mg is contained in aluminum alloy scrap, the aluminum alloy according to the present invention contains Mg. Mg improves strength by precipitating Mg-Si intermetallic compounds. The Mg content of the aluminum alloy is 0.35 to 0.80 mass%, preferably 0.40 to 0.75 mass%, and more preferably 0.45 to 0.70 mass%. If the Mg content of the aluminum alloy is less than the above range, the effect of improving strength cannot be sufficiently obtained. On the other hand, if the Mg content exceeds the above range, coarse Mg-Si intermetallic compounds are formed, resulting in a decrease in bending workability.

[0017] Since Fe is contained in aluminum alloy scrap, the aluminum alloy according to the present invention contains Fe. The Fe content of the aluminum alloy is 0.08 to 0.60 mass%, preferably 0.15 to 0.55 mass%, and more preferably 0.20 to 0.50 mass%. When aluminum alloy scrap is used as an ingot raw material for producing an aluminum alloy sheet, the Fe content in the aluminum alloy sheet increases, reducing the proportion of the second phase α-AlFeMnSi phase, and thereby reducing bendability. Therefore, in the aluminum alloy sheet according to the present invention, the Fe content in the aluminum alloy must be limited to the above range. Furthermore, Fe contributes to the refinement of crystal grains. If the Fe content of the aluminum alloy is less than the above range, coarse crystal grains are formed, resulting in rough surfaces during forming. If the Fe content exceeds the above range, coarse intermetallic compounds are formed, resulting in reduced bendability.

[0018] Since Cu is contained in aluminum alloy scrap, the aluminum alloy according to the present invention contains Cu. The Cu content of the aluminum alloy is 0.001 to 0.40% by mass, preferably 0.02 to 0.10% by mass, and more preferably 0.02 to 0.08% by mass. When aluminum alloy scrap is used as an ingot raw material for producing an aluminum alloy sheet, the aluminum alloy scrap often contains Cu, and the inclusion of Cu in the aluminum alloy sheet is unavoidable. However, if the Cu content in the aluminum alloy sheet is too high, the bendability decreases, so in the aluminum alloy sheet according to the present invention, the Cu content in the aluminum alloy must be limited to the above range. Furthermore, Cu contributes to improving strength and formability. If the Cu content of the aluminum alloy is less than the above range, the strength and formability are insufficient, and if it exceeds the above range, the filiformity resistance decreases.

[0019] The aluminum alloy according to the present invention contains Mn. Mn contributes to grain refinement. Mn forms Al-Mn-Si intermetallic compounds, improving strength through dispersion strengthening, and dissolves in the aluminum matrix, improving strength through solid solution strengthening. The Mn content of the aluminum alloy is 0.01 to 0.25 mass%, preferably 0.02 to 0.20 mass%, and more preferably 0.04 to 0.15 mass%. When waste aluminum alloy materials are used as the raw material for ingot production of the aluminum alloy sheet, the waste aluminum alloy materials often contain Mn, and the inclusion of Mn in the aluminum alloy sheet is unavoidable. However, if the Mn content in the aluminum alloy sheet is too high, coarse intermetallic compounds are formed, resulting in a decrease in formability. Therefore, in the aluminum alloy sheet according to the present invention, the Mn content in the aluminum alloy must be limited to the above range. If the Mn content in the aluminum alloy is less than the above range, coarse crystal grains are formed, resulting in rough surfaces during forming. If the content exceeds the above range, coarse intermetallic compounds are formed, causing a decrease in bendability.

[0020] The aluminum alloy according to the present invention contains Ti. Ti has the effect of improving strength through solid solution strengthening and of refining the ingot structure. The Ti content of the aluminum alloy is more than 0.00% by mass and not more than 0.09% by mass, preferably 0.01 to 0.08% by mass, and more preferably 0.02 to 0.07% by mass. If the Ti content of the aluminum alloy exceeds the above range, coarse intermetallic compounds are formed, which adversely affects formability.

[0021] The aluminum alloy material of the present invention may contain, as optional elements, Cr, Zn, and B. The content of each of these optional elements is 0.05 mass % or less.

[0022] The second phase particles (precipitates) of the aluminum alloy according to the aluminum alloy sheet material of the present invention include an α-AlFeMnSi phase and a β-AlFeMnSi phase. In the present invention, attention is focused on the α-AlFeMnSi phase having a body-centered cubic structure and the β-AlFeMnSi phase having a monoclinic structure. Whether the second phase particles are the α-AlFeMnSi phase or the β-AlFeMnSi phase can be analyzed by X-ray diffraction. FIG. 1 shows an X-ray diffraction chart obtained by analyzing the aluminum alloy according to the aluminum alloy material of the present invention by X-ray diffraction. In FIG. 1, the peak having its top at 2θ of approximately 17° on the horizontal axis is a diffraction peak due to the β-AlFeMnSi phase, and the peak having its top at 2θ of approximately 42° is a diffraction peak due to the α-AlFeMnSi phase.

[0023] In the aluminum alloy sheet of the present invention, when the aluminum alloy according to the aluminum alloy sheet of the present invention is subjected to X-ray diffraction analysis, the ratio ((A / (A+B))×100) of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° and attributed to the α-AlFeMnSi phase of the second phase particles to the sum of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° and attributed to the β-AlFeMnSi phase, and the intensity integrated value (B) of the diffraction peak having a peak top near 2θ=17° and attributed to the β-AlFeMnSi phase is 10.0% or more, preferably 15.0% or more. Hereinafter, "the ratio ((A / (A+B))×100) of the intensity integral value (A) of the diffraction peak having a peak top at about 2θ=42° and resulting from the α-AlFeMnSi phase of the second-phase particles to the sum of the intensity integral value (A) of the diffraction peak having a peak top at about 2θ=42° and resulting from the α-AlFeMnSi phase of the second-phase particles and the intensity integral value (B) of the diffraction peak having a peak top at about 2θ=17° and resulting from the β-AlFeMnSi phase" will also be referred to as "the proportion of the α-AlFeMnSi phase in the second-phase particles." By ensuring that the proportion of the α-AlFeMnSi phase in the second-phase particles is 10.0% or more, preferably 15.0% or more, an aluminum alloy sheet can be obtained that combines recyclability, which allows it to be produced using scrap aluminum alloy material, with bendability. That is, the aluminum alloy according to the aluminum alloy sheet of the present invention contains Fe derived from, for example, scrap aluminum alloy material, which reduces the proportion of the α-AlFeMnSi phase in the second-phase particles of the aluminum alloy that forms the aluminum alloy sheet, thereby reducing performance (bendability). Therefore, in the present invention, by appropriately adjusting the composition of the aluminum alloy and optimizing the production method to increase the proportion of the α-AlFeMnSi phase in the second-phase particles, an aluminum alloy sheet with excellent bendability can be obtained. In particular, by setting the Si content to 0.50 to 1.50 mass% and the Fe content to 0.08 to 0.60 mass%, and setting the homogenization treatment temperature in production to 530°C or higher, preferably 540 to 590°C, and more preferably 555 to 590°C, the proportion of the α-AlFeMnSi phase in the second phase particles can be increased, and an aluminum alloy sheet material with excellent bendability can be obtained.

[0024] In the aluminum alloy sheet of the present invention, when the aluminum alloy according to the aluminum alloy sheet of the present invention is subjected to X-ray diffraction analysis, it is more preferable that the ratio ((A / (A+B))×100) of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° attributable to the α-AlFeMnSi phase of the second phase particles to the sum of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° attributable to the α-AlFeMnSi phase of the second phase particles and the intensity integrated value (B) of the diffraction peak having a peak top near 2θ=17° attributable to the β-AlFeMnSi phase is 25.0% or more, since this allows for an aluminum alloy sheet that can be produced using scrap aluminum alloy material and simultaneously achieves strength, toughness, and bendability. By ensuring that the proportion of the α-AlFeMnSi phase in the second-phase particles is within the above range, an aluminum alloy sheet can be obtained that combines recyclability, which allows it to be produced using scrap aluminum alloy material, with strength, toughness, and bendability. In other words, the aluminum alloy according to the aluminum alloy sheet of the present invention contains Fe derived from, for example, scrap aluminum alloy material, which reduces the proportion of the α-AlFeMnSi phase in the second-phase particles of the aluminum alloy that forms the aluminum alloy sheet, thereby reducing performance (toughness and bendability). Therefore, in the present invention, by appropriately adjusting the composition of the aluminum alloy and optimizing the production method to ensure that the proportion of the α-AlFeMnSi phase in the second-phase particles is within the above range, an aluminum alloy sheet with excellent strength, toughness, and bendability can be obtained. In particular, by setting the Si content to 0.50 to 1.50 mass% and the Fe content to 0.08 to 0.60 mass%, and setting the homogenization treatment temperature in production to 530°C or higher, preferably 540 to 590°C, and more preferably 555 to 590°C, the proportion of the α-AlFeMnSi phase in the second phase particles can be increased, and an aluminum alloy sheet material with excellent strength, toughness, and bendability can be obtained.

[0025] Furthermore, in the aluminum alloy sheet of the present invention, when the aluminum alloy according to the aluminum alloy sheet of the present invention is subjected to X-ray diffraction analysis, the upper limit of the ratio ((A / (A+B))×100) of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° and attributed to the α-AlFeMnSi phase of the second phase particles to the sum of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° and attributed to the β-AlFeMnSi phase and the intensity integrated value (B) of the diffraction peak having a peak top near 2θ=17° is not particularly limited, and may be, for example, 95% or less.

[0026] In the present invention, the proportion of the α-AlFeMnSi phase in the second-phase particles is measured using a Cu tube as the X-ray source, manufactured by Rigaku Corporation (trade name: RINT-2500), under the following conditions: 2θ: 10 to 60°, scan speed: 0.2° / min, integration interval: 0.01°, and measurement surface: plate surface, to obtain X-ray diffraction intensity data. Next, the background is removed from the obtained X-ray diffraction intensity data, and the intensity integral value of the diffraction peak in the range of 2θ = 41.6 to 42.3° attributed to the α-AlFeMnSi phase is determined as the intensity integral value (A) of the diffraction peak having a peak top at around 2θ = 42.1° attributed to the α-AlFeMnSi phase. Also, the intensity integral value of the diffraction peak in the range of 2θ = 16.8 to 17.5° attributed to the β-AlFeMnSi phase is determined as the intensity integral value (B) of the diffraction peak having a peak top at around 2θ = 17.2° attributed to the β-AlFeMnSi phase. The proportion of the α-AlFeMnSi phase in the second-phase particles is calculated from the obtained intensity integral values.

[0027] The aluminum alloy sheet of the present invention preferably has a Cube orientation density of 10.0 or more, more preferably 15.0 or more, in a cross section parallel to the rolling direction, i.e., in the ND-TD plane across the entire sheet thickness. The ND-TD plane is a cross section parallel to the rolling direction, and the Cube orientation density is expressed as a ratio to the density of a sample having a random orientation. Having the Cube orientation density within the above range enhances recyclability, which allows production using scrap aluminum alloy, and improves bendability.

[0028] In the aluminum alloy sheet of the present invention, it is more preferable that the degree of integration of Cube orientation in the ND-TD plane across the entire sheet thickness is 20.0 or more, in terms of recyclability, which allows production using scrap aluminum alloy materials, and the effects of improving strength, toughness, and bendability.

[0029] In the aluminum alloy sheet material of the present invention, the upper limit of the degree of accumulation of Cube orientation in the ND-TD plane across the entire sheet thickness is not particularly limited, but may be, for example, 150 or less.

[0030] The aluminum alloy sheet material of the present invention has a tensile strength of 190 MPa or more, preferably 195 MPa or more, and more preferably 200 MPa or more in the 0°, 45°, and 90° directions relative to the rolling direction. When the tensile strengths in all three directions are within the above ranges and the elongation is 23% or more, sufficient formability can be ensured. If the strength and elongation in at least one of the three directions are low, fracture occurs in the direction with low strength and elongation during forming, making it impossible to ensure sufficient formability. Furthermore, having low strength and elongation in at least one direction means anisotropy, which leads to reduced formability.

[0031] The aluminum alloy sheet material of the present invention has elongation of 23% or more, preferably 24% or more, and more preferably 25% or more in the 0°, 45°, and 90° directions relative to the rolling direction. When the elongation in all three directions is within the above range, sufficient formability can be ensured. If the elongation in at least one of the three directions is low, fracture or necking will occur in the direction with low elongation during forming, making it impossible to ensure sufficient formability. Furthermore, having low elongation in at least one direction means anisotropy, which leads to reduced formability.

[0032] The aluminum alloy sheet material of the present invention is used for automobile body panels, hoods, doors, fenders, etc.

[0033] The aluminum alloy sheet material of the present invention has high upper limits for components such as Fe and Cu, and therefore can be easily reused as a part of a casting raw material when it becomes a waste material. Therefore, the aluminum alloy sheet material of the present invention is suitably used as a casting raw material in the following method for producing an aluminum alloy sheet material of the present invention.

[0034] The aluminum alloy sheet material of the present invention is, for example, a casting raw material containing a waste aluminum alloy material is used to cast an aluminum alloy ingot containing 0.50 to 1.50 mass% Si, 0.35 to 0.80 mass% Mg, 0.08 to 0.60 mass% Fe, 0.001 to 0.40 mass% Cu, 0.01 to 0.25 mass% Mn, and more than 0.00 mass% but not more than 0.09 mass% Ti, and optionally containing one or more elements selected from the group consisting of not more than 0.05 mass% Cr, not more than 0.05 mass% Zn, and not more than 0.05 mass% B, with the balance being Al and unavoidable impurities; The aluminum alloy ingot is subjected to a homogenization treatment by heating it to 530°C or higher, The homogenized product is hot-rolled at 300 to 580°C, The hot-rolled product is cold-rolled, and if necessary, intermediate annealing is performed before cold rolling or between cold rolling passes; The cold rolled product can be produced by solution treatment at 500 to 600° C., followed by pre-aging treatment.

[0035] That is, the method for producing an aluminum alloy sheet material of the present invention is as follows: a casting raw material containing a waste aluminum alloy material is used to cast an aluminum alloy ingot containing 0.50 to 1.50 mass% Si, 0.35 to 0.80 mass% Mg, 0.08 to 0.60 mass% Fe, 0.001 to 0.40 mass% Cu, 0.01 to 0.25 mass% Mn, and more than 0.00 mass% but not more than 0.09 mass% Ti, and optionally containing one or more elements selected from the group consisting of not more than 0.05 mass% Cr, not more than 0.05 mass% Zn, and not more than 0.05 mass% B, with the balance being Al and unavoidable impurities; The aluminum alloy ingot is subjected to a homogenization treatment by heating it to 530°C or higher, The homogenized product is hot-rolled at 300 to 580°C, The hot-rolled product is cold-rolled, and if necessary, is subjected to intermediate annealing before cold rolling or between cold rolling passes; The method for producing an aluminum alloy sheet material is characterized in that the cold-rolled product is subjected to a solution treatment at 500 to 600°C, and then subjected to a pre-aging treatment.

[0036] In the method for producing an aluminum alloy sheet of the present invention, first, an aluminum alloy ingot is cast using a casting raw material containing scrap aluminum alloy material. Preferably, the aluminum alloy ingot is cast using a casting raw material in which the proportion of scrap aluminum alloy material used is 10 mass % or more, more preferably 30 mass % or more. That is, in the method for producing an aluminum alloy sheet of the present invention, scrap aluminum alloy material is used as part of the casting raw material. When the proportion of scrap aluminum alloy material used in the casting raw material is within the above range, an aluminum alloy sheet having excellent recyclability and excellent bendability, preferably an aluminum alloy sheet having excellent recyclability and excellent strength, toughness, and bendability, can be obtained.

[0037] In the casting method for producing an aluminum alloy sheet according to the present invention, the aluminum alloy scrap used as the casting raw material includes Mg-containing aluminum alloys, such as Al-Mg-Si aluminum alloy scraps such as 6000-series aluminum alloys, specifically 6000-series aluminum alloy scraps containing 0.20 to 0.60 mass% Si, 0.35 mass% or more Fe, 0.10 mass% or less Cu, 0.10 mass% or less Mn, 0.45 to 0.90 mass% Mg, 0.10 mass% or less Cr, 0.10 mass% or less Zn, and 0.10 mass% or less Ti. Examples of aluminum alloy scrap include scrap metals generated during the rolling and slitting processes used in the production of aluminum alloys, body panels of scrapped or unused automobiles, mixed metals and used beverage cans (UBCs) scraps extracted from scrapped automobiles, etc.

[0038] In the casting in the manufacturing method for an aluminum alloy sheet of the present invention, the average content of each chemical component in the scrap aluminum alloy material used as a casting raw material (the ratio of the total amount of each chemical component contained in the scrap aluminum alloy material to the total mass of the scrap aluminum alloy material used in the casting) can be, for example, the following contents: Si content of 0.20 to 0.60 mass%, Mg content of 0.45 to 0.90 mass%, Fe content of 0.35 mass% or less, Cu content of 0.10 mass% or less, Mn content of 0.10 mass% or less, Ti content of 0.10 mass% or less, Zn content of 0.10 mass% or less, and Cr content of 0.10 mass% or less. The scrap aluminum alloy material used as a casting raw material may contain inevitable impurities.

[0039] In the method for producing an aluminum alloy sheet of the present invention, 0.50 to 1.50 mass%, preferably 0.55 to 1.25 mass%, more preferably 0.60 to 1.00 mass% of Si, 0.35 to 0.80 mass%, preferably 0.45 to 0.75 mass%, more preferably 0.50 to 0.70 mass% of Mg, 0.08 to 0.60 mass%, preferably 0.15 to 0.55 mass%, more preferably 0.20 to 0.50 mass% of Fe, and 0.001 to 0.40 mass%, preferably 0.01 to 0.30 mass%, more preferably 0.02 to 0.20 mass%, more preferably 0.01 to 0.40 mass% of Si. An aluminum alloy ingot is produced, which contains 0.02 to 0.10 mass%, more preferably 0.02 to 0.08 mass%, of Cu, 0.01 to 0.25 mass%, preferably 0.02 to 0.20 mass%, more preferably 0.04 to 0.15 mass%, of Mn, and more than 0.00 mass% but not more than 0.09 mass%, preferably 0.01 to 0.08 mass%, more preferably 0.02 to 0.07 mass%, of Ti, and optionally contains one or more elements selected from the group consisting of 0.05 mass% or less of Cr, 0.05 mass% or less of Zn, and 0.05 mass% or less of B, with the balance being Al and unavoidable impurities.

[0040] The casting method in the method for producing an aluminum alloy sheet material of the present invention is not particularly limited, and a conventional casting method and casting conditions are appropriately selected.

[0041] In the method for producing an aluminum alloy sheet of the present invention, the aluminum alloy ingot is then subjected to a homogenization treatment by heating at 530°C or higher, preferably 540 to 590°C, and more preferably 555 to 590°C, to obtain a homogenized product. The homogenization temperature affects the ratio of the α-AlFeMnSi phase to the β-AlFeMnSi phase in the second phase particles of the aluminum alloy in the aluminum alloy sheet, and by setting the homogenization temperature within the above range, the ratio of the α-AlFeMnSi phase can be increased. In the method for producing an aluminum alloy sheet of the present invention, by setting the chemical composition of the aluminum alloy ingot to be subjected to the homogenization treatment within the above range and setting the homogenization treatment temperature within the above range, the ratio ((A / (A+B))×100) (the ratio of the α-AlFeMnSi phase in the second-phase particles) of the intensity integrated value (A) of the diffraction peak having a peak top at around 2θ=42° and attributable to the α-AlFeMnSi phase of the second-phase particles to the sum of the intensity integrated value (A) of the diffraction peak having a peak top at around 2θ=42° and attributable to the β-AlFeMnSi phase and attributable to the β-AlFeMnSi phase can be set to 10.0% or more, preferably 20.0% or more, and more preferably 25.0%, and an aluminum alloy sheet can be obtained that has recyclability, which can be produced using aluminum alloy waste, and that has bendability, and preferably also strength and toughness. The homogenization time is appropriately selected so as to obtain the effects of the present invention, but is preferably 3 hours or more, more preferably 6 hours or more.

[0042] In the method for producing an aluminum alloy sheet material of the present invention, the homogenized product is then hot rolled at 300 to 580°C to obtain a hot rolled product. The reduction in the hot rolling is preferably 95% or more. The reduction in the hot rolling is determined by the following formula: Hot rolling reduction rate (%) = ((plate thickness before hot rolling - plate thickness after hot rolling) / thickness before hot rolling) × 100 It can be calculated as follows.

[0043] In the method for producing an aluminum alloy sheet of the present invention, the hot-rolled product is then cold-rolled to obtain a cold-rolled product. In cold rolling, cold rolling may be performed in one pass, or two or more passes of cold rolling may be performed. When two or more passes of cold rolling are performed, intermediate annealing may be performed between passes by heating at 250 to 550°C, preferably 300 to 500°C, for 0.5 hours or more. The total rolling reduction in cold rolling is 50% or more, preferably 60% or more. The total reduction in cold rolling is calculated using the following formula: Total reduction rate of cold rolling (%) = ((Thickness before cold rolling in the first pass - Thickness after cold rolling in the last pass) / Thickness before cold rolling in the first pass) × 100 It can be calculated as follows.

[0044] In the method for producing an aluminum alloy sheet of the present invention, the cold-rolled product is then subjected to solution treatment at 500 to 600°C, preferably 520 to 580°C, for 2 to 30 seconds, preferably 5 to 25 seconds. In the solution treatment, the cold-rolled product is held at the above temperature range for the above holding time, and then cooled at a rate of 1°C / second or more. The solution-treated product obtained by the solution treatment is then subjected to pre-aging treatment at 30 to 150°C, preferably 50 to 130°C, to obtain an aluminum alloy sheet.

[0045] In this way, in the method for producing an aluminum alloy sheet of the present invention, the aluminum alloy sheet of the present invention is obtained by using waste aluminum alloy material as part of the casting raw material.

[0046] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples shown below. [Example]

[0047] An aluminum alloy having the alloy composition shown in Table 1 was cast by DC casting. The homogenization temperature shown in Table 2 was set as the target temperature. After reaching the target temperature minus 5°C, the time until the end of heating was defined as the holding time. After the homogenization treatment was completed, hot rolling, cold rolling, intermediate annealing as appropriate, solution treatment and pre-aging treatment were carried out to obtain an aluminum alloy sheet with a thickness of 1 mm. Using the obtained alloy sheet, the ratio of the α-AlFeMnSi phase in the second-phase particles and the degree of aggregation of the Cube orientation were measured. By the aging treatment, the yield strengths in the 0, 45, and 90° directions were increased to the values shown in Table 3, and the bending property was evaluated.

[0048] <X-ray Diffraction Analysis> Using a Cu tube as the X-ray source, measurements were carried out under the conditions of 2θ: 10~60°, scan speed: 0.2° / min, integration interval: 0.01°, and measurement surface: the surface of the plate by Rigaku Corporation (product name RINT-2500) to obtain X-ray diffraction intensity data. Next, regarding the obtained X-ray diffraction intensity data, the background was removed, and the integrated intensity value of the diffraction peak in the range of 2θ = 41.6~42.3° due to the α-AlFeMnSi phase was obtained as the integrated intensity value (A) of the diffraction peak having a peak top near 2θ = 42° due to the α-AlFeMnSi phase. Also, the integrated intensity value of the diffraction peak in the range of 2θ = 16.8~17.5° due to the β-AlFeMnSi phase was obtained as the integrated intensity value (B) of the diffraction peak having a peak top near 2θ = 17° due to the β-AlFeMnSi phase. Then, the value of (A / (A + B))×100 was calculated.

[0049] <Measurement Methods for Tensile Strength, Yield Strength, Elongation, and n Value> From the test material, a No. 5 test piece defined in JIS Z2241 was sampled so that the longitudinal direction and the rolling direction were parallel. Using this test piece, a tensile test was carried out by a method conforming to JIS Z2241 to calculate the tensile strength, 0.2% yield strength, and elongation in the direction parallel to the rolling direction (0° direction). In addition, test pieces No. 5 with an angle of 45° between the longitudinal direction and the rolling direction and test pieces with the longitudinal direction perpendicular to the rolling direction are taken from the test materials, and tensile tests are performed in the same manner as above by the method conforming to JIS Z2241, thereby calculating the tensile strength, 0.2% proof stress, and elongation in the direction inclined 45° with respect to the rolling direction (45° direction) and the direction perpendicular to the rolling direction (90° direction).

[0050] <Method for Measuring the Degree of Cube Orientation Aggregation> The degree of Cube orientation aggregation was obtained by using an X-ray diffractometer (RINT-2000 manufactured by Rigaku Corporation) and measuring the incomplete pole figures of the (111) plane, (z20) plane, and (200) plane by Schulz's reflection method, which is one of the X-ray diffraction measurement methods, in the range where the tilt angle is 15 - 90°. Then, the Cube aggregation degree was determined using pole figure analysis software from the obtained orientation information of the aggregate structure. The aggregation degree is expressed as the ratio of the aggregation degree of the Cube orientation to the aggregation degree of a sample having a random orientation, and is denoted as the random ratio. The measurement plane was the ND-TD plane.

[0051] <Hemming Test> After 10% tensile pre-strain, a 180° bending test was performed with an inner bending radius of 0.5 mm, and then a hemming test was performed on a medium plate with a thickness of 0.9 mm. The surface of the outer periphery of the bend after the test was scored according to the judgment criteria of JIS H7701. A score of 2 or less was considered qualified, and a score of 3 or more was considered unqualified.

[0052]

Table 1

[0053] [[ID=二十三]] [[ID=二十四]] [[ID=二十五]]

Table 2

[0054] [[ID=三十一]] [[ID=三十二]] [[ID=三十三]]

Table 3

[0055] [[ID=三十九]] In Table 3, the integral ratio α (%) is the ratio ((A / (A+B))×100) of the intensity integral value (A) of the diffraction peak having a peak top near 2θ=42° and attributed to the α-AlFeMnSi phase of the second phase particles to the sum of the intensity integral value (A) of the diffraction peak having a peak top near 2θ=42° and attributed to the α-AlFeMnSi phase of the second phase particles and the intensity integral value (B) of the diffraction peak having a peak top near 2θ=17° and attributed to the β-AlFeMnSi phase, when analyzed by X-ray diffraction.

[0056] The above results show that the aluminum alloy sheets of Test Nos. 1 to 3 and 5 to 8, which are invention examples, are excellent in bendability, and also in strength, toughness, and bendability. The average chemical composition of the 6000 series aluminum alloy scrap is usually about: Si content of 0.20 to 0.60 mass%, Mg content of 0.45 to 0.90 mass%, Fe content of 0.35 mass% or less, Cu content of 0.10 mass% or less, Mn content of 0.10 mass% or less, Ti content of 0.10 mass% or less, Zn content of 0.10 mass% or less, and Cr content of 0.10 mass% or less. Then, from the chemical compositions of the aluminum alloy plates of Test Nos. 1 to 3 and 5 to 8, it was found that in the production thereof, scrap 6000 series aluminum alloy material can be used in a maximum of 99 mass% of the casting raw material, and that aluminum alloy plates excellent in bendability, preferably aluminum alloy plates excellent in strength, toughness and bendability, can be produced using the scrap 6000 series aluminum alloy material.

Claims

1. an aluminum alloy containing 0.50 to 1.50 mass% Si, 0.35 to 0.80 mass% Mg, 0.08 to 0.60 mass% Fe, 0.001 to 0.40 mass% Cu, 0.01 to 0.25 mass% Mn, and more than 0.00 mass% but not more than 0.09 mass% Ti, and optionally containing one or more elements selected from the group consisting of 0.05 mass% or less Cr, 0.05 mass% or less Zn, and 0.05 mass% or less B, with the balance being Al and unavoidable impurities; When subjected to X-ray diffraction analysis, the ratio ((A / (A+B))×100) of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° attributable to the α-AlFeMnSi phase of the second phase particles to the sum of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° attributable to the β-AlFeMnSi phase and the intensity integrated value (B) of the diffraction peak having a peak top near 2θ=17° attributable to the α-AlFeMnSi phase is 10.0% or more, The degree of accumulation of Cube orientation in the entire thickness of the ND-TD plane is 10.0 or more, An aluminum alloy plate material characterized by:

2. 2. The aluminum alloy sheet according to claim 1, wherein a ratio ((A / (A+B))×100) of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° due to the α-AlFeMnSi phase of the second phase particles to a sum of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° due to the α-AlFeMnSi phase of the second phase particles and the intensity integrated value (B) of the diffraction peak having a peak top near 2θ=17° due to the β-AlFeMnSi phase is 25.0% or more.

3. The tensile strength in the 0° direction, 45° direction, and 90° direction relative to the rolling direction is 190 MPa or more, The elongation in the 0° direction, 45° direction, and 90° direction relative to the rolling direction is 23% or more.

2. The aluminum alloy sheet material according to claim 1, wherein

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