Aluminum alloy sheet material

Abstract

Provided is an aluminum alloy sheet material that can be manufactured using a waste material of an aluminum alloy and is bendable. The present invention is an aluminum alloy sheet material comprising an aluminum alloy consisting of 0.50-1.50 mass% Si, 0.35-0.80 mass% Mg, 0.08-0.60 mass% Fe, 0.001-0.40 mass% Cu, 0.01-0.25 mass% Mn, and 0.00 mass% to 0.09 mass% Ti, with the remainder being Al and unavoidable impurities. The ratio of an intensity integral value (A) of a diffraction peak having a peak top in the vicinity of 2θ = 42° to a total of the intensity integral value (A) of the diffraction peak having a peak top in the vicinity of 2θ = 42° and an intensity integral value (B) of a diffraction peak having a peak top in the vicinity of 2θ = 17° is 10.0% or more, and the accumulation degree of cube orientation in the total sheet thickness of an ND-TD plane is 10 or greater.

Description

Aluminum alloy plate

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

[0002] Conventionally, when producing aluminum alloys, in order to ensure good strength and corrosion resistance, new 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 a desired range. However, since new aluminum ingots consume a large amount of electricity during production, using new aluminum ingots as the casting raw material can result in CO2 emissions derived from the electricity. ２ This increases emissions and creates a significant environmental burden. In particular, in recent years, achieving carbon neutrality has become a social issue around the world, making it increasingly important to reduce the amount of virgin metal 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 smaller amounts 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 (see, for example, Patent Document 1).

[0004] JP 2010-116594 A

[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 the 6000 series or other Al-Mg-Si type aluminum alloy 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.

[0008] As a result of extensive research, the present inventors have found that, due to the Fe content of 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). They 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 using scrap aluminum alloy material containing Fe as a production raw material.

[0009] That is, the present invention (1) is an aluminum alloy comprising 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, optionally containing one or more 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; The aluminum alloy sheet is characterized in that, 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° and resulting from the α-AlFeMnSi phase of second phase particles to the sum of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° and resulting from the β-AlFeMnSi phase, and the intensity integrated value (B) of the diffraction peak having a peak top near 2θ=17° and resulting from the α-AlFeMnSi phase, is 10.0% or more; and the degree of accumulation of Cube orientation in the ND-TD plane throughout the entire sheet thickness is 10.0 or more. The present invention (2) is the aluminum alloy sheet according to (1), characterized in 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 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 25.0% or more. The present invention (3) is the aluminum alloy sheet according to (1), characterized in that the tensile strengths in the 0°, 45°, and 90° directions relative to the rolling direction are all 190 MPa or more, and the elongations in the 0°, 45°, and 90° directions relative to the rolling direction are all 23% or more.The present invention also provides a method for producing 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, 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, using a casting raw material containing waste aluminum alloy material; performing a homogenization treatment on the aluminum alloy ingot by heating it to 530°C or higher; hot-rolling the homogenized product at 300 to 580°C; The method for producing an aluminum alloy sheet material is characterized by cold rolling the hot-rolled product, and, if necessary, performing intermediate annealing before cold rolling or between cold rolling passes, and subjecting the cold-rolled product to a solution treatment at 500 to 600°C, followed by a pre-aging treatment.

[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.

[0011] 1 is an X-ray diffraction chart obtained by analyzing an aluminum alloy plate material by X-ray diffraction.

[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, 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; The aluminum alloy sheet is characterized in that, 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° and resulting from the α-AlFeMnSi phase of second phase particles to the sum of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° and resulting from the β-AlFeMnSi phase, and the intensity integrated value (B) of the diffraction peak having a peak top near 2θ=17° and resulting from the α-AlFeMnSi phase, is 10.0% or more; and the degree of accumulation of Cube orientation in the ND-TD plane throughout the entire sheet thickness is 10.0 or more.

[0013] The aluminum alloy sheet made of the aluminum alloy of the present invention can be produced from 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 process and slitting process during the production of aluminum alloy material. 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 used beverage cans (UBCs).

[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, the formation of coarse Mg-Si intermetallic compounds leads to 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 the production of 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. Furthermore, 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 the production of 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 to improve 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 material is used as an ingot raw material for producing the aluminum alloy sheet, the waste aluminum alloy material often contains 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 reduced 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 of 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 refining the ingot structure. The Ti content of the aluminum alloy is more than 0.00 mass% and not more than 0.09 mass%, preferably 0.01 to 0.08 mass%, and more preferably 0.02 to 0.07 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 attributable to the β-AlFeMnSi phase, and the peak having its top at 2θ of approximately 42° is a diffraction peak attributable 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° 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 10.0% or more, preferably 15.0% or more. Hereinafter, "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" will also be referred to as "the α-AlFeMnSi phase proportion in the second-phase particles." When the α-AlFeMnSi phase proportion in the second-phase particles is 10.0% or more, preferably 15.0% or more, an aluminum alloy sheet can be obtained that combines bendability with recyclability, which can be produced using scrap aluminum alloy material. In other words, the aluminum alloy according to the present invention contains Fe, for example, derived from scrap aluminum alloy material, which reduces the proportion of the α-AlFeMnSi phase in the second-phase particles of the aluminum alloy forming 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 manufacturing method, an aluminum alloy sheet with excellent bendability can be obtained by increasing the proportion of the α-AlFeMnSi phase in the second-phase particles. 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 the manufacturing process 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, thereby obtaining an aluminum alloy sheet with excellent bendability.

[0024] In the aluminum alloy sheet of the present invention, when X-ray diffraction analysis is performed on the aluminum alloy according to the present invention, 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 more preferably 25.0% or more, since this allows for an aluminum alloy sheet that combines recyclability, which can be produced using scrap aluminum alloy material, with strength, toughness, and bendability. When the proportion of the α-AlFeMnSi phase in the second-phase particles is within the above range, an aluminum alloy sheet that combines recyclability, which can be produced using scrap aluminum alloy material, with strength, toughness, and bendability can be obtained. In other words, the aluminum alloy according to 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 forming the aluminum alloy sheet, resulting in reduced performance (toughness and bendability). Therefore, in the present invention, by appropriately adjusting the composition of the aluminum alloy and optimizing the manufacturing method so that the proportion of the α-AlFeMnSi phase in the second-phase particles falls 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 by setting the homogenization treatment temperature in the manufacturing process 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, resulting in an aluminum alloy sheet with excellent strength, toughness, and bendability.

[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° 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 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 with an X-ray source manufactured by Rigaku Corporation (product name: RINT-2500) under the conditions of 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, 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 about 2θ = 42° attributed to the α-AlFeMnSi phase, and 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 about 2θ = 17° attributed to the β-AlFeMnSi phase, and 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 an accumulation degree of Cube orientation in a cross section parallel to the rolling direction, i.e., in the ND-TD plane across the entire sheet thickness, of 10.0 or more, more preferably 15.0 or more. The ND-TD plane is a cross section parallel to the rolling direction, and the accumulation degree of Cube orientation is expressed as a ratio to the accumulation degree of a sample having a random orientation. When the accumulation degree of Cube orientation is within the above range, recyclability, which allows production using scrap aluminum alloy, and the effect of improving bendability are enhanced.

[0028] In the aluminum alloy sheet of the present invention, it is more preferable that the degree of accumulation 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 waste aluminum alloy materials, and the effects of improving strength, toughness, and bendability.

[0029] In the aluminum alloy sheet 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 will occur 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 will exhibit anisotropy, leading 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 all of the directions of 0°, 45°, and 90° 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 will exhibit anisotropy, leading 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 can be produced, for example, by using a casting raw material containing waste aluminum alloy material 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 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; homogenizing the aluminum alloy ingot by heating it to 530°C or higher; hot-rolling the homogenized product 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 is solution-treated at 500 to 600°C, and then pre-aged.

[0035] That is, the method for producing an aluminum alloy sheet material of the present invention includes the steps of: using a casting raw material containing a waste aluminum alloy material, casting 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 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; homogenizing the aluminum alloy ingot by heating it to 530°C or more; hot-rolling the homogenized product at 300 to 580°C; The method for producing an aluminum alloy sheet material is characterized by cold rolling the hot-rolled product, and, if necessary, performing intermediate annealing before cold rolling or between cold rolling passes, and subjecting the cold-rolled product to a solution treatment at 500 to 600°C, followed by 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 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, the 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] Examples of aluminum alloy scrap used as a casting raw material in the casting method for producing an aluminum alloy sheet according to the present invention include Mg-containing aluminum alloy scrap, for example, Al-Mg-Si-based aluminum alloy scrap such as 6000-series aluminum alloy scrap, specifically 6000-series aluminum alloy scrap containing, for example, 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 metal and other scrap metal generated during the rolling process or slitting process during the production of aluminum alloy materials, body panels of automobiles that have been scrapped or not used in production, mixed metal and UBC (used beverage can) scrap collected 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 casting) can be, for example, the following contents: Si content: 0.20 to 0.60 mass%, Mg content: 0.45 to 0.90 mass%, Fe content: 0.35 mass% or less, Cu content: 0.10 mass% or less, Mn content: 0.10 mass% or less, Ti content: 0.10 mass% or less, Zn content: 0.10 mass% or less, Cr content: 0.10 mass% or less, and the scrap aluminum alloy material used as a casting raw material may contain unavoidable impurities.

[0039] In the method for producing an aluminum alloy sheet of the present invention, by casting, 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. The present invention provides an aluminum alloy ingot containing 0.02 to 0.10 mass%, more preferably 0.02 to 0.08 mass%, Cu; 0.01 to 0.25 mass%, preferably 0.02 to 0.20 mass%, more preferably 0.04 to 0.15 mass%, 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%, Ti; and optionally 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.

[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 keeping 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 2θ=42° and resulting from 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 resulting from the α-AlFeMnSi phase of the second phase particles and the intensity integrated value (B) of the diffraction peak having a peak top at around 2θ=17° and resulting from 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 scrap aluminum alloy, and 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 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 hot rolling is preferably 95% or more. The reduction in hot rolling can be calculated using the following formula: Hot rolling reduction (%) = ((sheet thickness before hot rolling - sheet thickness after hot rolling) / sheet thickness before hot rolling) x 100.

[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 rolling reduction in cold rolling is calculated by the following formula: Total rolling reduction in cold rolling (%) = ((sheet thickness before cold rolling in the first pass - sheet thickness after cold rolling in the last pass) / sheet thickness before cold rolling in the first pass) × 100.

[0044] In the method for producing an aluminum alloy sheet of the present invention, the cold-rolled product is then subjected to solution treatment by holding it 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. Next, the solution-treated product obtained by the solution treatment is 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.

[0047] An aluminum alloy having the alloy composition shown in Table 1 was cast by DC casting, and the target temperature for the homogenization treatment shown in Table 2 was used. The holding time was the time from reaching the target temperature minus 5°C until the end of heating. After the homogenization treatment was completed, the alloy was hot-rolled, cold-rolled, appropriately intermediate-annealed, solution-treated, and pre-aged to obtain an aluminum alloy sheet with a thickness of 1 mm. The obtained alloy sheet was used to measure the proportion of the α-AlFeMnSi phase in the second-phase particles and the degree of integration of the Cube orientation. The proof stress in the 0, 45, and 90° directions was increased by aging to the values ​​shown in Table 3, and bendability was evaluated.

[0048] <X-ray diffraction analysis> Using a Cu tube as an X-ray source, manufactured by Rigaku Corporation (trade name RINT-2500), 2θ: 10 to 60 °, scan speed: 0.2 ° / min, integration interval: 0.01 °, measurement surface: plate surface conditions, and X-ray diffraction intensity data was obtained. Next, for the obtained X-ray diffraction intensity data, the background was removed, and the intensity integral value of the diffraction peak in the range of 2θ = 41.6 to 42.3 ° due to the α-AlFeMnSi phase was determined as the intensity integral value (A) of the diffraction peak having a peak top near 2θ = 42 ° due to the α-AlFeMnSi phase, and the intensity integral value of the diffraction peak in the range of 2θ = 16.8 to 17.5 ° due to the β-AlFeMnSi phase was determined as the intensity integral value (B) of the diffraction peak having a peak top near 2θ = 17 ° due to the β-AlFeMnSi phase. The value of (A / (A+B))×100 was then calculated.

[0049] <Method of measuring tensile strength, proof stress, elongation, and n value> A No. 5 test piece specified in JIS Z2241 was taken from the test material so that the longitudinal direction was parallel to the rolling direction. A tensile test was performed using this test piece according to JIS Z2241 to calculate the tensile strength, 0.2% proof stress, and elongation in the direction parallel to the rolling direction (0° direction). Furthermore, a No. 5 test piece in which the longitudinal direction forms a 45° angle with the rolling direction and a test piece in which the longitudinal direction is perpendicular to the rolling direction were taken from the test material, and a tensile test was performed similarly according to JIS Z2241 to calculate the tensile strength, 0.2% proof stress, and elongation in the direction inclined at 45° 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 accumulation> The degree of Cube orientation accumulation was measured using an X-ray diffractometer (RINT-2000 manufactured by Rigaku Corporation) by the Schulz reflection method, which is one of the X-ray diffraction measurement methods, at an inclination angle of 15 to 90°, to obtain texture orientation information by measuring incomplete pole figures of the (111), (220), and (200) planes. Then, from the obtained texture orientation information, the Cube accumulation was calculated using pole figure analysis software. The accumulation was expressed as the ratio of the accumulation of Cube orientation to the accumulation of a sample having random orientation, and was referred to as the random ratio. The measurement surface was the ND-TD surface.

[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 the middle plate with a plate thickness of 0.9 mm. After the test, the outer peripheral surface of the bent piece was scored according to the criteria of JIS H7701. A score of 2 or less was considered pass, and a score of 3 or more was considered fail.

[0052]

[0053]

[0054]

[0055] In Table 3, the integral ratio α rate (%) 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 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 near 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 near 2θ=17° and resulting from the β-AlFeMnSi phase, when analyzed by X-ray diffraction.

[0056] From the above results, the aluminum alloy sheets of Test Nos. 1 to 3 and 5 to 8, which are invention examples, are excellent in bendability. Furthermore, the aluminum alloy sheets of Test Nos. 1 to 3 and 5 to 8, which are invention examples, are excellent in strength, toughness, and bendability. The average chemical composition of the scrap 6000 series aluminum alloy material is usually: Si content 0.20 to 0.60 mass%, Mg content 0.45 to 0.90 mass%, Fe content 0.35 mass% or less, Cu content 0.10 mass% or less, Mn content 0.10 mass% or less, Ti content 0.10 mass% or less, Zn content 0.10 mass% or less, and Cr content 0.10 mass% or less. Therefore, Test No. From the chemical compositions of the aluminum alloy plates Nos. 1 to 3 and 5 to 8, it was found that in the production thereof, scrap 6000 series aluminum alloy materials 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 materials.

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; an X-ray diffraction analysis of the aluminum alloy sheet shows that the ratio ((A / (A+B))×100) of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° and resulting from the α-AlFeMnSi phase of second phase particles to the sum of the intensity integrated value (A) of the diffraction peak having a peak top near 2θ=42° and resulting from the β-AlFeMnSi phase, and the intensity integrated value (B) of the diffraction peak having a peak top near 2θ=17° and resulting from the α-AlFeMnSi phase, is 10.0% or more; and the degree of accumulation of Cube orientation in the ND-TD plane throughout the entire sheet thickness is 10.0 or more.

2. The aluminum alloy sheet according to claim 1, wherein 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 25.0% or more.

3. The aluminum alloy sheet material according to claim 1, characterized in that the tensile strength in the 0°, 45° and 90° directions relative to the rolling direction is 190 MPa or more, and the elongation in the 0°, 45° and 90° directions relative to the rolling direction is 23% or more.

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