Al-mg-si-based aluminum alloy sheet and method for producing same

Abstract

To provide an Al-Mg-Si based aluminum alloy sheet capable of obtaining excellent surface properties and formability even in the case the temperature rising rate and heating temperature at the time of intermediate annealing are made low.SOLUTION: The Al-Mg-Si-based aluminum alloy sheet contains Si: 0.50 mass% or more and 1.60 mass% or less, Mg: 0.25 mass% or more and 1.00 mass% or less, Fe: 0.05 mass% or more and 0.50 mass% or less, Mn: 0.01 mass% or more and 0.30 mass% or less, and Cu: 0.001 mass% or more and 0.30 mass% or less, with the balance being Al and inevitable impurities. When the Mg content is represented by [Mg] in mass%, [Mg] / [Si] is more than 0.50, the area ratio of Cube orientation is 9% or less, and the number densities of compounds having equivalent circle diameters of 1.5 μm or more are 1000 particles / mm2 or more and 10000 particles / mm2 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an Al-Mg-Si aluminum alloy sheet having good surface properties and formability, and a method for producing an Al-Mg-Si aluminum alloy sheet that can reduce CO2 emissions during production. [Background technology]

[0002] In recent years, social demands for weight reduction of automobile bodies have been increasing due to considerations of the global environment, etc. In order to meet such demands, aluminum alloy materials have been used in place of steel materials such as steel sheets for large body panels (outer panels, inner panels) of automobile bodies. Of the large body panels, JIS 6000 series (hereinafter simply referred to as 6000 series) aluminum alloy sheets based on Al-Mg-Si are used, particularly for outer panels (skin panels).

[0003] However, press-formed 6000 series aluminum alloy sheets have a problem in that they are prone to developing streak-like patterns known as ridging marks and surface roughness defects. Patent Document 1, for example, discloses an aluminum alloy sheet in which the composition of the aluminum alloy used as a raw material is controlled, and the values ​​of the Cube orientation density (C), ND rotation Cube orientation density (N), and RD rotation Cube orientation density (G) of the crystal grains present in the sheet, as well as the ratios of (N) to (C) and (G) to (C), are controlled. Patent Document 1 discloses that an aluminum alloy sheet for forming work that has excellent surface roughness resistance and ridging resistance can be obtained.

[0004] Furthermore, Patent Document 2 discloses a method for producing a rolled aluminum alloy sheet for forming work, in which the average cooling rate after homogenization of an ingot made of an aluminum alloy having a predetermined composition, the total cold rolling reduction, the holding conditions before hot rolling, etc. are controlled, and cold rolling is performed without intermediate annealing. Patent Document 2 discloses that a rolled aluminum alloy sheet for forming work that is excellent in bending workability and ridging resistance can be produced.

[0005] On the other hand, because automotive exterior components are generally press-formed, the aluminum alloy sheets used must also have excellent formability. European and American automakers in particular require outer panels with excellent formability, and require materials with small anisotropy (Δr) in the Lankford value (r-value), which is one of the indices used to evaluate the formability of sheet material. However, in the methods for manufacturing aluminum alloy sheets or rolled aluminum alloy sheets described in Patent Documents 1 and 2, the control of orientations other than the Cube orientation is insufficient, and there is a concern that the anisotropy of the r-value may be large or the average r-value may be low.

[0006] Furthermore, Patent Document 3 discloses an aluminum alloy sheet in which the aluminum alloy composition is controlled and the anisotropy of the Lankford value (r-value) and the inner limit bending radius in 180° bending after 15% tensile deformation are specified. Patent Document 3 also describes that it is possible to obtain the aluminum alloy sheet described above, which is excellent in bending workability and paint bake hardenability and is particularly suitable for automobile exterior panels.

[0007] Furthermore, Patent Document 4 describes a method in which the composition of an aluminum alloy sheet is controlled, and after solution treatment and quenching, the maximum diameter of Mg-Si compounds is 10 μm or less, and the number of compounds with diameters of 2 to 10 μm is 1000 / mm 2 and an aluminum alloy sheet having an inner limit bending radius of 0.5 mm under specified conditions is disclosed.

[0008] However, although the aluminum alloy sheet described in Patent Document 3 also exhibits a high r-value, the anisotropy of the r-value is high, and desired formability cannot be obtained. Moreover, Patent Document 4 does not take into consideration the anisotropy of the r-value, and there is a possibility that desired anisotropy of the r-value cannot be obtained.

[0009] Therefore, Patent Document 5 discloses an aluminum alloy sheet in which the aluminum alloy composition is controlled and the Cube orientation density distribution, the average r-value, the absolute value of the in-plane anisotropy index of the r-value, the average grain size, the proof stress after aging, and the proof stress after heating are specified. Patent Document 5 describes that an Al-Mg-Si aluminum alloy sheet for automobile panels can be obtained that is excellent in all of press formability, bending workability that allows flat hemming, shape fixability, paint bake hardenability, and corrosion resistance.

[0010] Furthermore, Patent Document 6 discloses an aluminum alloy sheet in which the aluminum alloy composition is controlled, the total peak intensity of the Cupper orientation, the Brass orientation, the S orientation, the P orientation, and the Q orientation is limited to a predetermined range, and the standard deviation of the Cube orientation area fraction W and the electrical conductivity after being left after final tempering are controlled. Patent Document 6 discloses that a 6000 series aluminum alloy sheet excellent in press formability, ridging mark resistance, and bake hardness (BH) can be obtained. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Patent No. 5415016 [Patent Document 2] Patent No. 6208389 [Patent Document 3] Patent No. 4633993 [Patent Document 4] Patent No. 4175818 [Patent Document 5] Patent No. 6301095 [Patent Document 6] Patent No. 6768568 Summary of the Invention [Problem to be solved by the invention]

[0012] In the intermediate annealing process, for example, rapid heating in a continuous furnace and slow heating in a batch furnace are known. While the batch furnace allows multiple coils to be processed at once, the continuous furnace has the advantage of enabling rapid heating and making it easier to control anisotropy and surface properties.

[0013] In the production of the aluminum alloy sheet described in Patent Document 5, the intermediate annealing temperature is, for example, 350 to 580°C, and the temperature rise rate is fast or the intermediate annealing temperature is relatively high. Also in the aluminum alloy sheet described in Patent Document 6, the intermediate annealing is performed at a temperature rise rate of 5°C / s or more. This makes it possible to control the anisotropy and surface properties of the aluminum alloy sheet in Patent Documents 5 and 6.

[0014] However, in order to produce the aluminum alloy sheets described in Patent Documents 5 and 6, rapid heating or a batch process at a relatively high temperature is required when intermediate annealing is performed, and therefore, the amount of CO2 emissions in the production process is large, which places a burden on the global environment.

[0015] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide an Al-Mg-Si-based aluminum alloy sheet that can obtain excellent surface texture and formability even when the heating rate and heating temperature during intermediate annealing are reduced, and a method for producing an Al-Mg-Si-based aluminum alloy sheet that can reduce CO2 emissions during production by reducing the heating rate and heating temperature during intermediate annealing, and that can obtain an Al-Mg-Si-based aluminum alloy sheet that has excellent surface texture and formability. [Means for solving the problem]

[0016] The above object of the present invention can be achieved by the following configuration [1] or [2] relating to an Al-Mg-Si based aluminum alloy sheet.

[0017] [1] Si: 0.50 mass% or more and 1.60 mass% or less, Mg: 0.25% by mass or more and 1.00% by mass or less, Fe: 0.05% by mass or more and 0.50% by mass or less, Mn: 0.01% by mass or more and 0.30% by mass or less, Cu: 0.001% by mass or more and 0.30% by mass or less, the balance being Al and unavoidable impurities, An Al-Mg-Si-based aluminum alloy sheet, wherein, when the Si content is expressed as [Si] in mass% and the Mg content is expressed as [Mg] in mass%, [Mg] / [Si] exceeds 0.50, The area ratio of Cube orientation is 9% or less, When observing the surface, the number density of compounds with a circle equivalent diameter of 1.5 μm or more is 1000 / mm 2 More than 10000 pieces / mm 2 An Al-Mg-Si based aluminum alloy plate, characterized in that:

[0018] [2] Si: 0.50 mass% or more and 1.60 mass% or less, Mg: 0.25% by mass or more and 1.00% by mass or less, Fe: 0.05% by mass or more and 0.50% by mass or less, Mn: 0.01% by mass or more and 0.30% by mass or less, Cu: 0.001% by mass or more and 0.30% by mass or less, the balance being Al and unavoidable impurities, An Al-Mg-Si-based aluminum alloy sheet, wherein, when the Si content is expressed as [Si] in mass% and the Mg content is expressed as [Mg] in mass%, a ratio of [Mg] / [Si] is 0.50 or less, The area ratio of Cube orientation is 12% or less, When observing the surface, the number density of compounds with a circle equivalent diameter of 1.5 μm or more is 600 / mm 2 More than 10000 pieces / mm 2 An Al-Mg-Si based aluminum alloy plate, characterized in that:

[0019] The above object of the present invention can also be achieved by the following configuration [3] or [4] relating to the method for producing an Al-Mg-Si aluminum alloy sheet.

[0020] [3] Si: 0.50 mass% or more and 1.60 mass% or less, Mg: 0.25% by mass or more and 1.00% by mass or less, Fe: 0.05% by mass or more and 0.50% by mass or less, Mn: 0.01% by mass or more and 0.30% by mass or less, Cu: 0.001% by mass or more and 0.30% by mass or less, the balance being Al and unavoidable impurities, A method for producing an Al-Mg-Si-based aluminum alloy plate according to [1], using an Al-Mg-Si-based aluminum alloy ingot having an [Mg] / [Si] ratio of more than 0.50, where the Si content is expressed as [Si] in mass% and the Mg content is expressed as [Mg] in mass%, wherein The method includes a homogenization heat treatment step, a hot rolling step, a cold rolling step, an intermediate annealing step, and a solution treatment step, A method for producing an Al-Mg-Si aluminum alloy sheet, characterized in that the heat treatment temperature in the intermediate annealing step is less than 500°C and the temperature rising rate is 1°C / second or less.

[0021] [4] Si: 0.50 mass% or more and 1.60 mass% or less, Mg: 0.25% by mass or more and 1.00% by mass or less, Fe: 0.05% by mass or more and 0.50% by mass or less, Mn: 0.01% by mass or more and 0.30% by mass or less, Cu: 0.001% by mass or more and 0.30% by mass or less, the balance being Al and unavoidable impurities, A method for producing an Al-Mg-Si-based aluminum alloy plate according to [2], using an Al-Mg-Si-based aluminum alloy ingot having an [Mg] / [Si] ratio of 0.50 or less, where the Si content is expressed as [Si] in mass% and the Mg content is expressed as [Mg] in mass%, The method includes a homogenization heat treatment step, a hot rolling step, a cold rolling step, an intermediate annealing step, and a solution treatment step, A method for producing an Al-Mg-Si aluminum alloy sheet, characterized in that the heat treatment temperature in the intermediate annealing step is less than 500°C and the temperature rising rate is 1°C / second or less. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide an Al-Mg-Si-based aluminum alloy sheet having good surface properties and formability, and a method for producing an Al-Mg-Si-based aluminum alloy sheet that can reduce CO2 emissions during production. DETAILED DESCRIPTION OF THE INVENTION

[0023] In order to solve the above problems, the present inventors have conducted extensive research into the effects of compounds on the anisotropy and surface properties of aluminum alloy sheets, and have found that by precisely controlling the size and number density of compounds, there exists an effective range for formability and surface properties without significantly impairing elongation or bending. Moreover, the present inventors have found that even when the heating rate or heating temperature during intermediate annealing is reduced, an Al-Mg-Si-based aluminum alloy sheet having excellent surface properties and formability can be obtained. Furthermore, the present inventors have focused on the ratio of the Mg content to the Si content contained in the aluminum alloy sheet, and have found that controlling this ratio makes it possible to widen the allowable ranges of the area ratio of Cube orientation and the number density of specific compounds. The present invention was made based on these findings.

[0024] Hereinafter, embodiments of the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below, and can be implemented with any modifications within the scope of the gist of the present invention.

[0025] [Al-Mg-Si aluminum alloy plate] In this embodiment, an Al-Mg-Si-based aluminum alloy sheet having excellent formability and surface shape can be obtained by controlling the contents of components contained in the Al-Mg-Si-based aluminum alloy sheet and controlling the area fraction of specific Cube orientation and the number density of specific compounds. However, by reducing the ratio of Mg content to Si content in the Al-Mg-Si-based aluminum alloy sheet, the allowable range of the area fraction of Cube orientation and the number density of specific compounds can be widened. Therefore, the case where the ratio of Mg content to Si content is greater than a predetermined value is referred to as "Invention A," and the case where the ratio of Mg content to Si content is equal to or less than a predetermined value is referred to as "Invention B." The chemical compositions of the Al-Mg-Si-based aluminum alloy sheets in Inventions A and B and the reasons for their limitations will be described below, along with the area fraction of Cube orientation and the number density of specific compounds.

[0026] The Al-Mg-Si aluminum alloy sheet in the present invention refers to a rolled sheet such as a hot-rolled sheet or a cold-rolled sheet that has been subjected to tempering treatment such as solution treatment and quenching, and also refers to a base aluminum alloy sheet that has not yet been formed into, for example, an automobile part and has not yet been subjected to artificial aging treatment (artificial aging hardening treatment) such as paint bake hardening. Hereinafter, the Al-Mg-Si aluminum alloy sheet may be simply referred to as an aluminum alloy sheet.

[0027] <Invention A> (Si: 0.50 mass% or more and 1.60 mass% or less) Si, together with Mg, forms Mg-Si precipitate particles that contribute to improving strength during solid solution strengthening and low-temperature artificial aging treatments such as paint baking, thereby demonstrating artificial age hardening (BH) ability. Therefore, Si is an essential element for obtaining the strength (yield strength) required for automotive panel materials such as outer panels. Furthermore, during the casting, soaking, hot rolling, and intermediate annealing processes, Si precipitates and disperses together with Mg as Mg-Si compounds with sizes of 1.5 μm or more. These compounds act as nuclei for recrystallization, effectively contributing to reducing anisotropy and improving surface properties.

[0028] If the Si content in the aluminum alloy sheet is less than 0.50% by mass, the amount of Mg-Si compounds produced after artificial aging heat treatment is insufficient, resulting in poor bake hardening properties and insufficient strength. Furthermore, it becomes difficult to obtain the desired r-value anisotropy and surface texture. Therefore, the Si content in the aluminum alloy sheet is set to 0.50% by mass or more, preferably 0.60% by mass or more, and more preferably 0.65% by mass or more, based on the total mass of the aluminum alloy sheet. On the other hand, if the Si content in the aluminum alloy sheet exceeds 1.60 mass%, coarse Si-based precipitates are formed, resulting in a decrease in ductility. Therefore, the Si content in the aluminum alloy sheet is set to 1.60 mass% or less, preferably 1.50 mass% or less, and more preferably 1.45 mass% or less, based on the total mass of the aluminum alloy sheet.

[0029] (Mg: 0.25 mass% or more and 1.00 mass% or less) As mentioned above, Mg, together with Si, exhibits artificial age hardening ability by forming Mg-Si precipitate particles that contribute to improving strength during solid solution strengthening and low-temperature artificial aging treatments such as paint baking. Therefore, Mg is also an essential element for obtaining the necessary strength for automotive panel materials such as outer panels. Furthermore, during the casting, soaking, hot rolling, and intermediate annealing processes, Mg precipitates and disperses together with Si as Mg-Si compounds with sizes of 1.5 μm or more. These compounds act as nuclei for recrystallization, effectively contributing to reducing anisotropy and improving surface quality.

[0030] If the Mg content in the aluminum alloy sheet is less than 0.25% by mass, the amount of Mg-Si compounds produced will be insufficient, resulting in a significant decrease in bake hardening properties and insufficient strength. Furthermore, it will be difficult to obtain the desired r-value anisotropy and surface texture. Therefore, the Mg content in the aluminum alloy sheet is set to 0.25% by mass or more, preferably 0.27% by mass or more, and more preferably 0.30% by mass or more, based on the total mass of the aluminum alloy sheet. On the other hand, if the Mg content in the aluminum alloy plate exceeds 1.00% by mass, the material strength during forming increases, and the breaking elongation and work hardenability decrease. Therefore, the Mg content in the aluminum alloy plate is set to 1.00% by mass or less, preferably 0.90% by mass or less, and more preferably 0.80% by mass or less, based on the total mass of the aluminum alloy plate.

[0031] (Fe: 0.05 mass% or more and 0.50 mass% or less) Fe and Mn are elements commonly contained in 6000 series aluminum alloys. During the casting process, they form Al-Fe-Mn-Si compounds with a size of 1.5 μm or more. These compounds act as nuclei for recrystallization, effectively contributing to reducing anisotropy and improving surface properties. If the Fe content in the aluminum alloy sheet is less than 0.05% by mass, it becomes difficult to obtain the desired r-value anisotropy and surface quality. Therefore, the Fe content in the aluminum alloy sheet is set to 0.05% by mass or more, preferably 0.10% by mass or more, and more preferably 0.20% by mass or more, based on the total mass of the aluminum alloy sheet. Note that, in Invention A, it is assumed that the value of [Mg] / [Si] described below is greater than 0.50. In this case, if the Fe content in the aluminum alloy sheet is 0.30% by mass or more based on the total mass of the aluminum alloy sheet, relatively large compounds such as Al-Fe-Si compounds can be dispersed during casting, and excellent formability and surface quality can be obtained.

[0032] On the other hand, if the Fe content in the aluminum alloy sheet exceeds 0.50 mass%, the Al-Fe-Mn-Si compounds become coarse and dispersed at high density, which causes deterioration of formability. Therefore, the Fe content in the aluminum alloy sheet is set to 0.50 mass% or less, preferably 0.45 mass% or less, and more preferably 0.40 mass% or less, based on the total mass of the aluminum alloy sheet.

[0033] (Mn: 0.01 mass% or more and 0.30 mass% or less) As described above, Mn forms Al-Fe-Mn-Si compounds with a size of 1.5 μm or more together with Fe during the casting, soaking, and hot rolling processes. These compounds act as nuclei for recrystallization, effectively contributing to reducing anisotropy and improving surface properties. If the Mn content in the aluminum alloy sheet is less than 0.01% by mass, it becomes difficult to obtain the desired r-value anisotropy and surface texture. Therefore, the Mn content in the aluminum alloy sheet is set to 0.01% by mass or more, preferably 0.03% by mass or more, and more preferably 0.05% by mass or more, based on the total mass of the aluminum alloy sheet.

[0034] On the other hand, if the Mn content in the aluminum alloy sheet exceeds 0.30% by mass, Al-Fe-Mn-Si compounds become coarse and dispersed at high density, which causes deterioration of formability. Therefore, the Mn content in the aluminum alloy sheet is set to 0.30% by mass or less, preferably 0.25% by mass or less, and more preferably 0.20% by mass or less, based on the total mass of the aluminum alloy sheet.

[0035] (Cu: 0.001 mass% or more and 0.30 mass% or less) Cu is an element that is generally contained in 6000 series aluminum alloys, and even a trace amount of Cu can improve the strength and formability of the aluminum alloy sheet. If the Cu content in the aluminum alloy sheet is less than 0.001% by mass, the effect of improving the strength and formability of the aluminum alloy sheet cannot be obtained. Therefore, the Cu content in the aluminum alloy sheet is set to 0.001% by mass or more, preferably 0.01% by mass or more, and more preferably 0.1% by mass or more, based on the total mass of the aluminum alloy sheet.

[0036] On the other hand, if the Cu content in the aluminum alloy plate exceeds 0.30 mass%, the corrosion resistance of the aluminum alloy plate decreases. Therefore, the Cu content in the aluminum alloy plate is set to 0.30 mass% or less, preferably 0.25 mass% or less, and more preferably 0.20 mass% or less, relative to the total mass of the aluminum alloy plate.

[0037] (Other ingredients) In addition to the above-mentioned Si, Mg, Fe, Mn, and Cu, the Al-Mg-Si-based aluminum alloy sheet according to this embodiment may contain Cr, Zn, and Ti depending on the required mechanical properties. However, if the content of each of the above components is excessive, the mechanical properties of the aluminum alloy sheet will deteriorate. Therefore, when the aluminum alloy sheet according to this embodiment contains at least one of Cr, Zn, and Ti, the Cr content is set to 0.1 mass% or less, the Zn content is set to 0.25 mass% or less, and the Ti content is set to 0.1 mass% or less, based on the total mass of the aluminum alloy sheet.

[0038] (Remainder: Al and inevitable impurities) The Al-Mg-Si-based aluminum alloy sheet according to this embodiment contains the above-mentioned Si, Mg, Fe, Mn, and Cu, and also contains Cr, Zn, or Ti depending on the required mechanical properties, with the balance being Al and unavoidable impurities. Examples of the unavoidable impurities include B, Zr, Ni, Bi, and Sn. The content of each of these unavoidable impurities is preferably 0.05% by mass or less, and the total content of the unavoidable impurities is preferably 0.15% by mass or less, based on the total mass of the aluminum alloy sheet.

[0039] ([Mg] / [Si]: over 0.50) As a result of investigating various components contained in aluminum alloy sheets, the inventors found that the anisotropy of the r-value changes depending on the numerical range of [Mg] / [Si], even if the Cube orientation area fraction and number density of compounds are the same. Specifically, in Invention A, the Cube orientation {001} <100> The area ratio and number density of compounds with an equivalent circle diameter of 1.5 μm or more are specified as follows. This makes it possible to reduce the anisotropy of the r value even when the [Mg] / [Si] value exceeds 0.50. Here, the above [Si] is the value of the Si content in the aluminum alloy plate expressed in mass %, and the above [Mg] is the value of the Mg content in the aluminum alloy plate expressed in mass %.

[0040] (Cube direction {001} <100> Area ratio: 9% or less) The cube orientation is an orientation in which the r-value is high in the 0 and 90° directions relative to the rolling direction, and low in the 45° direction (Inoue Hiroshi et al., "Evaluation of the γ-Value of Aluminum Alloy Sheets by Quantitative Analysis of Texture," Light Metals, 1994, Vol. 44, No. 2, pp. 97-103). By controlling the area ratio of this cube orientation to a low value, it is possible to increase the r-value in the 45° direction, which generally tends to be low in 6000 series alloys, and to reduce the anisotropy Δr of the r-value. It is also known that Cube orientation is a factor in surface quality (Haruyuki Konishi et al., "Crystal Plasticity Analysis of Ridging Behavior in Al-Mg-Si Alloy Sheets," R&D Kobe Steel Technical Report, October 2012, Vol. 62, No. 2, pp. 39-42). In other words, by controlling the area ratio of Cube orientation to a low level, it is possible to improve surface quality.

[0041] Cube direction {001} <100> If the area ratio of Cube orientation {001} exceeds 9%, the anisotropy Δr of the r value becomes high, the formability deteriorates, and the surface quality also deteriorates. <100> The area ratio is set to 9% or less, and preferably 8% or less.

[0042] Here, the definition of texture and an example of a measurement method will be explained below.

[0043] (Definition of texture) In ordinary aluminum alloys, the following crystal orientation textures are known to exist. Depending on the volume fraction of these crystal orientations, even when equal tensile deformation is applied, the deformation state differs depending on the crystal orientation.

[0044] Cube direction:{001} <100> Goss direction:{011} <100> Cupper bearing:{112} <111> Brass direction:{011} <211> S direction:{123} <634> P direction:{011} <211> Q direction:{130} <312>

[0045] Here, the crystal orientation texture is expressed in terms of the rolling surface and rolling direction in the case of rolled sheet materials. That is, the rolling surface is expressed as {○○○}, and the rolling direction is expressed as <XXX>. ○ and × represent integers (Shinichi Nagashima, "Texture," Maruzen Co., Ltd., 1984; Kunio Ito, "Texture of Aluminum Alloy Sheets," Light Metals, 1993, Vol. 43, No. 5, pp. 285-293).

[0046] (Method for measuring texture) The crystal orientation textures defined in the present invention are evaluated by the SEM-EBSD method using a scanning electron microscope (SEM) or a field emission-scanning electron microscope (FE-SEM). The samples used for the measurements are cold-rolled sheets that have been subjected to final tempering treatment, and the surface of the cold-rolled sheets is mechanically polished, buffed, and then electrolytically polished to remove the oxide film on the surface and otherwise prepare the sheet surface.

[0047] The SEM-EBSD method is widely used as a method for measuring crystal orientation texture, and is a crystal orientation analysis method that uses a field emission scanning electron microscope (e.g., JEOL JSM-7000F) equipped with an Electron Back-Scattered Diffraction Pattern (EBSD) system. In the SEM-EBSD method, an aluminum alloy plate sample placed in the FE-SEM lens barrel is irradiated with an electron beam. The backscattered electron diffraction pattern is then captured in an EBSD instrument (e.g., an EBSD measurement and analysis system, OIM (Orientation Imaging Macrograph) Data & Analysis, manufactured by TSL). The sample surface is scanned every 1 μm while performing crystal orientation analysis. This yields an electron backscatter diffraction pattern (EBSP) at each point, which is then indexed to determine the crystal orientation of the electron beam irradiated area. The obtained crystal orientation measurement data is then rotated 90° around the rolling direction axis and then further rotated 90° in the direction normal to the rolling surface. The crystal orientation distribution function (ODF) and area fraction are then calculated. For details on this crystal orientation analysis method using an EBSD system in an FE-SEM, see, for example, Kobe Steel Technical Report, September 2002, Vol. 52, No. 2, pp. 66-70.

[0048] In this embodiment, the measured deviation of the crystal orientation is the Cube orientation {001} <100> If the angle is within ±15° from the crystal plane, it is defined as belonging to the same orientation factor, and the area ratio is calculated based on this. This is because aluminum alloy sheets exhibit almost the same properties within this range.

[0049] (Number density of compounds with a circular equivalent diameter of 1.5 μm or more: 1000 particles / mm 2 More than 10000 pieces / mm 2 below) As described above, the maximum diameter of the compounds in the aluminum alloy plate is set to 10 μm or less, and the number of compounds with a diameter of 2 to 10 μm is set to 1000 / mm 2Aluminum alloy sheets having improved elongation and bendability are known. On the other hand, in this embodiment, the size and number density of the compounds are precisely controlled, thereby improving anisotropy and surface quality without significantly impairing elongation or bending. This is presumably because recrystallization is promoted around compounds with a circle equivalent diameter of 1.5 μm or more, resulting in a relatively random texture. Since it is difficult to define the randomness of the texture numerically, in this embodiment, the number density of the compounds is used as an index that indirectly indicates the randomness of the texture.

[0050] In the case of Invention A, that is, when the ratio of the Mg content to the Si content ([Mg] / [Si]) exceeds 0.50, the number density of compounds having a circle equivalent diameter of 1.5 μm or more is 1000 particles / mm 2 If the number density is less than 1000 particles / mm, the number of recrystallized grains generated due to particle stimulated nucleation (PSN) is small, making it difficult to obtain a relatively random texture. As a result, it may not be possible to reduce the anisotropy of the r-value, and good surface properties may not be obtained. Therefore, the number density of compounds with a circle equivalent diameter of 1.5 μm or more should be 1000 particles / mm. 2 More than 1200 pieces / mm 2 It is preferable that the number of particles is 1500 or more per mm 2 More preferably, it is equal to or greater than this.

[0051] On the other hand, if the number density of compounds with an equivalent circle diameter of 1.5 μm or more becomes excessive, it will have a negative effect on the strength and elongation of the aluminum alloy sheet. Therefore, the number density of compounds with an equivalent circle diameter of 1.5 μm or more should be 10,000 particles / mm 2 5000 pieces / mm or less 2 It is preferable that the number of particles is 3000 or less per mm 2 More preferably, it is:

[0052] The number density of compounds having a circle-equivalent diameter of 1.5 μm or more can be obtained by calculating the number of compounds having a circle-equivalent diameter of 1.5 μm or more per unit area in 20 visual fields using a scanning electron microscope with a magnification of 500. In this embodiment, an area of ​​about 0.17 mm × about 0.25 mm is observed in one visual field, and the total number of compounds in the 20 visual fields is 0.86 mm. 2 The total number of compounds in the 20 fields of view was then measured within the area of ​​0.86 mm. 2 By dividing by , the number density can be calculated.

[0053] Next, the chemical composition of the Al-Mg-Si aluminum alloy sheet in Invention B will be explained, along with the area ratio of Cube orientation and the number density of specific compounds.

[0054] <Invention B> In Invention B, the ranges of the contents of Si, Mg, Fe, Mn, and Cu contained in the aluminum alloy sheet and the reasons for limiting them are the same as those in Invention A. Therefore, the differences from Invention A, namely, the ratio of the Mg content to the Si content, the area ratio of Cube orientation, and the number density of compounds having a circle-equivalent diameter of 1.5 μm or more, will be explained below.

[0055] ([Mg] / [Si]: 0.50 or less) As mentioned above, the inventors discovered that in materials with a small [Mg] / [Si] ratio, the anisotropy of the r-value is small even when the Cube orientation area fraction and number density of compounds are equivalent. This is presumably because extremely low [Mg] / [Si] ratio changes the recrystallization behavior during intermediate annealing and solution treatment, affecting the formation of orientations other than the Cube orientation. In other words, in Invention B, the [Mg] / [Si] value is controlled to 0.50 or less, which allows the formation of Cube orientation {001} <100> The range of the area ratio and the number density of compounds having an equivalent circle diameter of 1.5 μm or more can be widened. The value of [Mg] / [Si] is preferably 0.45 or less, and more preferably 0.30 or less. As in Invention A, the above [Si] is the value of the Si content in the aluminum alloy plate expressed in mass%, and the above [Mg] is the value of the Mg content in the aluminum alloy plate expressed in mass%.

[0056] In addition, in Invention B in which the value of [Mg] / [Si] is limited to 0.50 or less, when the Fe content in the aluminum alloy plate is 0.20% by mass or more with respect to the total mass of the aluminum alloy plate, relatively large compounds such as Al-Fe-Si compounds can be dispersed during casting, and excellent formability and surface properties can be obtained.

[0057] (Cube direction {001} <100> Area ratio: 12% or less) When the value of [Mg] / [Si] is 0.50 or less, the Cube orientation {001} <100> If the area ratio of Cube orientation {001} exceeds 12%, the anisotropy Δr of the r value becomes high, the formability deteriorates, and the surface quality also deteriorates. <100> The area ratio of the texture is set to 12% or less, preferably 11% or less, and more preferably 10% or less. The method for measuring the texture is the same as in Invention A above.

[0058] (Number density of compounds with a circular equivalent diameter of 1.5 μm or more: 600 particles / mm 2 More than 10000 pieces / mm 2 below) When the value of [Mg] / [Si] is 0.50 or less, the number density of compounds with a circle equivalent diameter of 1.5 μm or more is 600 particles / mm 2 If the number density is less than 1.5 μm, the number of recrystallized grains generated is small, making it difficult to obtain a relatively random texture. As a result, the anisotropy of the r-value cannot be reduced, and good surface properties cannot be obtained. Therefore, the number density of compounds with a circle equivalent diameter of 1.5 μm or more must be 600 particles / mm 2 More than 700 pieces / mm 2 It is preferable that the number of particles is 800 or more per mm 2 More preferably, it is equal to or greater than this.

[0059] On the other hand, if the number density of compounds with an equivalent circle diameter of 1.5 μm or more becomes excessive, it will have a negative effect on the strength and elongation of the aluminum alloy sheet. Therefore, the number density of compounds with an equivalent circle diameter of 1.5 μm or more should be 10,000 particles / mm 2 5000 pieces / mm or less 2 It is preferable that the number of particles is 3000 or less per mm 2 More preferably, it is:

[0060] [Method of manufacturing Al-Mg-Si aluminum alloy sheet] The method for producing an Al-Mg-Si-based aluminum alloy sheet according to this embodiment is the method for producing an Al-Mg-Si-based aluminum alloy sheet according to the above-mentioned Invention A, and the method for producing an Al-Mg-Si-based aluminum alloy sheet according to the above-mentioned Invention B. Specifically, a material having a desired composition is melted and cast to prepare an aluminum alloy ingot having a target composition, and the method includes commonly performed steps of a homogenization heat treatment step, a hot rolling step, a cold rolling step, an intermediate annealing step, and a solution treatment step, in which the heating temperature and the heating rate in the intermediate annealing step are specified.

[0061] In the present embodiment, it is preferable to control the components contained in the aluminum alloy plate and to appropriately control the conditions of the homogenization heat treatment step and the hot rolling step so that relatively large compounds can be dispersed before cold rolling. By dispersing relatively large compounds before cold rolling, recrystallization around the compounds is more likely to occur during intermediate annealing or solution treatment. As a result, the accumulation of Cube orientation, which reduces r45, is reduced, and the crystal orientation tends to become random, which reduces the anisotropy of the r-value and improves surface quality.

[0062] In particular, in this embodiment, the following three methods can be mentioned as methods for dispersing relatively large compounds before cold rolling. (1) The homogenization heat treatment is carried out twice or in two stages. (2) The finishing temperature of the hot rolling is increased and the cooling rate after the hot rolling is slowed. (3) The Fe content in the aluminum alloy sheet is controlled. By using at least one of these methods, an Al-Mg-Si aluminum alloy sheet having good formability and surface properties can be produced. The methods for producing Al-Mg-Si aluminum alloy sheets according to Invention A and Invention B will be described in further detail below.

[0063] <Melting and casting process> An aluminum alloy ingot having a predetermined shape is produced from a molten metal obtained by melting an aluminum alloy material having the desired composition. The method for melting and casting the aluminum alloy material is not particularly limited, and any conventional or known method may be used.

[0064] As described in the section on the Fe content in the aluminum alloy sheet and in (3) above, controlling the Fe content in the aluminum alloy sheet makes it possible to disperse relatively large Al-Fe-Si compounds during casting. That is, when producing the aluminum alloy sheet according to Invention A, it is preferable to set the Fe content in the aluminum alloy ingot to 0.30 mass% or more. Also, when producing the aluminum alloy sheet according to Invention B, it is preferable to set the Fe content in the aluminum alloy ingot to 0.20 mass% or more. In this way, by increasing the Fe content in the aluminum alloy material and the aluminum alloy ingot, it is possible to produce an Al-Mg-Si aluminum alloy sheet with good formability and surface properties.

[0065] <Homogenization heat treatment process> Next, the cast aluminum alloy ingot is subjected to a homogenization heat treatment (soaking treatment). This homogenization heat treatment is performed to homogenize the non-uniform structure that occurs during casting. The homogenization heat treatment temperature is not particularly limited, but if it is less than 480°C, the strength after artificial aging tends to decrease. Therefore, the homogenization heat treatment temperature is preferably 480°C or higher but lower than the melting point, and more preferably 500°C or higher. Regarding the cooling rate after the homogenization heat treatment, the average cooling rate during the cooling from 480°C to 300°C is preferably 500°C / hour or less, and more preferably 100°C / hour or less.

[0066] As described in (1) above, in this embodiment, the soaking treatment is preferably performed twice or in two stages. By performing the soaking treatment twice or in two stages, it becomes possible to distribute a large amount of relatively large Mg-Si compounds during the cooling process after the first soaking treatment or during the temperature increase process in the second soaking treatment. Whether the soaking treatment is performed twice or in two stages can be determined depending on the equipment available.

[0067] <Hot rolling process> After the homogenization heat treatment, the material is hot rolled to a predetermined thickness. As described in (2) above, in this embodiment, it is preferable to increase the end temperature of the hot rolling and to slow the cooling rate after the hot rolling. This allows the cooling process after the hot rolling to be extended, and during this process, it becomes possible to distribute a large amount of relatively large Mg-Si compounds. Therefore, the end temperature of the hot rolling is preferably 370°C or higher, and more preferably 390°C or higher. Regarding the cooling rate after completion of hot rolling, the average cooling rate during cooling from the hot rolling completion temperature to 300°C is preferably 500°C / hour or less, and more preferably 100°C / hour or less.

[0068] <Cold rolling process> The hot-rolled sheet obtained by the hot-rolling step is cold-rolled to obtain a cold-rolled sheet. Note that it is preferable to repeat the cold-rolling step as necessary after the intermediate annealing step described below.

[0069] (Total rolling ratio: 75% or more) In the manufacturing methods of aluminum alloy sheet according to Inventions A and B, increasing the total reduction ratio in cold rolling can reduce the density of Cube orientation, thereby reducing the area ratio of Cube orientation and achieving good formability and surface quality. Therefore, the total reduction ratio in all cold rolling steps from the hot rolling step through the intermediate annealing step to form the sheet to the final thickness is preferably 75% or more, and more preferably 78% or more. The total reduction ratio refers to the reduction ratio of the sheet thickness after all cold rolling steps relative to the sheet thickness after hot rolling.

[0070] <Intermediate annealing process> Since cold-rolled sheets undergo work hardening during the cold rolling process, intermediate annealing is performed to soften the work hardened sheets, improve the efficiency of post-processing, and reduce cracking during processing. In the manufacturing methods of aluminum alloy sheets according to Inventions A and B, intermediate annealing causes repeated recrystallization, making it easier to obtain a relatively random texture and, as a result, making it easier to obtain good surface quality. As described above, increasing the temperature or heating rate of intermediate annealing makes it easier to control the anisotropy and surface quality of the aluminum alloy sheet, but on the other hand, increasing the temperature or heating rate of intermediate annealing places a burden on the environment. In the aluminum alloy sheets according to Inventions A and B, by controlling the area fraction of Cube orientation and the number density of specific compounds, excellent surface quality and formability can be obtained even when the heating rate or heating temperature is low.

[0071] If the heat treatment temperature in the intermediate annealing step is 500°C or higher, or the temperature rise rate exceeds 1°C / second, a large amount of heat is required in the intermediate annealing step, which has a negative impact on the environment. Therefore, the heat treatment temperature in the intermediate annealing step is preferably less than 500°C and 460°C or lower. Furthermore, the temperature rise rate in the intermediate annealing step is preferably 1°C / second or lower, 500°C / hour or lower, and more preferably 100°C / hour or lower. Here, the temperature rise rate is the average temperature rise rate from room temperature to the target temperature.

[0072] <Solution treatment process> After cold rolling, a solution treatment is carried out. The temperature in the solution treatment step is not particularly limited, but it is preferable to hold the temperature at 480° C. or higher and 570° C. or lower for 1 to 120 seconds, for example.

[0073] The aluminum alloy plate according to Invention A and the method for manufacturing the aluminum alloy plate according to Invention B are not limited to the above-mentioned manufacturing methods, and can be arbitrarily modified and implemented within the scope that does not deviate from the gist of the present invention. [Example]

[0074] The present embodiment will be described in more detail below with reference to examples, but the present invention is not limited to these examples, and modifications can be made within the scope of the spirit of the present invention, and all such modifications are included in the technical scope of the present invention.

[0075] <Production of aluminum alloy sheets> Aluminum alloy sheets having various compositions were produced by various production methods. Specific production methods for each aluminum alloy sheet are described below. Examples and comparative examples related to the aluminum alloy sheet according to Invention A are designated Invention Examples Nos. A1 to A3 and Comparative Examples Nos. A4 and A5, and examples and comparative examples related to the aluminum alloy sheet according to Invention B are designated Invention Examples Nos. B1 to B4 and Comparative Example No. B5.

[0076] (Production of aluminum alloy plates of invention examples A1, B1, and B2) Ingots having the compositions shown in Table 1 were produced by a semi-continuous casting method (DC casting: Direct Chill casting process). Next, a two-stage homogenization heat treatment was performed. The first soaking temperature was 560°C, and the temperature was cooled to room temperature by air cooling. After that, the ingots were heated again to 420°C, and then hot-rolled. The hot-rolling was completed at a temperature of 280°C to 420°C, and then slowly cooled. The thicknesses of the aluminum alloy sheets after hot-rolling were 2.3 mm to 6.0 mm. The hot-rolled aluminum alloy sheets were then cold-rolled at various reduction rates, followed by intermediate annealing in a batch-type atmospheric furnace at a heating rate of 40°C / hour (0.011°C / second). After intermediate annealing, the ingots were cold-rolled again at various reduction rates. The final thicknesses after cold-rolling were 0.4 mm to 1.0 mm. Thereafter, the aluminum alloy sheets were heated and held at 560°C for 30 seconds in a salt bath, and then cooled to room temperature by water cooling, for solution treatment. Thereafter, the aluminum alloy sheets were held at room temperature for about one week, thereby producing aluminum alloy sheets of invention examples A1, B1, and B2.

[0077] (Production of aluminum alloy sheets of invention examples Nos. A2, B3, B4 and comparative examples Nos. A4, A5, B5) In the same manner as in the above-described Inventive Example No. A1, an ingot was melted, and subjected to one soaking treatment at a temperature of 560°C, followed by hot rolling, cold rolling, intermediate annealing, a second cold rolling and solution treatment, and then held at room temperature for about one week, thereby producing aluminum alloy sheets of Inventive Examples Nos. A2, B3, and B4 and Comparative Examples Nos. A4, A5, and B5.

[0078] (Production of aluminum alloy plate of invention example No. A3) An ingot was produced in the same manner as in the above-mentioned Invention Example No. A2, and after one soaking treatment, hot rolling was carried out. Next, as additional annealing to verify the effect of compound dispersion after the completion of hot rolling, a solution treatment was carried out at a temperature of 560°C for 4 hours, and then the ingot was held at a temperature of 410°C for 16 hours, followed by quenching. Thereafter, cold rolling, intermediate annealing, a second cold rolling, and a solution treatment were carried out, and the ingot was held at room temperature for about one week, thereby producing an aluminum alloy sheet of Invention Example No. A3.

[0079] The conditions for each step in the production of Invention Examples Nos. A1 to A3, Comparative Examples Nos. A4 to A5, Invention Examples Nos. B1 to B4, and Comparative Example No. B5 are shown in the following Table 2. Note that the composition of the obtained aluminum alloy plates was the same as the composition of the aluminum alloy ingots used as raw materials, and therefore not shown in the table.

[0080] (Texture measurement) The texture of the crystal orientation was measured for the aluminum alloy sheets of the invention examples and comparative examples, and the area ratio of the Cube orientation was calculated. The method for measuring the texture was as described in the above embodiment. Note that the deviation of the measured crystal orientation was calculated based on the area ratio of the Cube orientation {001} <100> The area ratio of Cube orientation was calculated by defining that if the orientation was within ±15° from the crystal plane, it belonged to the same orientation factor.

[0081] (Measurement of the number density of compounds with a circular equivalent diameter of 1.5 μm or more) The number density of compounds having a circle-equivalent diameter of 1.5 μm or more was measured for the obtained aluminum alloy plates of the invention examples and comparative examples. The method for measuring the number density was as described in the above embodiment. The results of measuring the area ratio of Cube orientation and the number density of compounds having a circle-equivalent diameter of 1.5 μm or more are also shown in Table 1 below.

[0082] <Evaluation test> (Plastic strain ratio test) Tensile test specimens were taken from each of the obtained aluminum alloy sheets. Tensile test specimens were prepared by taking No. 13B test specimens (short side: 12.5 mm, gauge length (GL): 50 mm) specified in JIS Z 2241:2011 from each aluminum alloy sheet so that the tensile direction was parallel (0°), 45°, or perpendicular (90°) to the rolling direction, and tensile tests were carried out at room temperature. The tensile test was carried out at 5 mm / min up to the measurement of 0.2% proof stress and 30 mm / min thereafter, and the r-value was measured when 0.2% proof stress and 15% plastic strain were applied. In addition, the in-plane anisotropy Δr was calculated using the following formula (S1), and the average plastic strain ratio r was calculated using the following formula (S2):A was calculated.

[0083] Δr=1 / 2×(r0-2×r45+r90)...Formula (S1) r A =1 / 4×(r0+2×r45+r90)...Formula (S2)

[0084] Each tensile test was measured twice, and the various properties were calculated as the average value.

[0085] (Evaluation criteria for tensile tests) As an evaluation standard for use as an automobile exterior material, an aluminum alloy sheet was judged to have acceptable press formability if its Δr was 0.25 or less and its r-value in the 90° direction (r90) was 0.60 or more.

[0086] (Surface texture test) Test specimens were taken from each of the obtained aluminum alloy plates, and after applying a plastic strain of 15% in a direction perpendicular to the rolling direction, electrodeposition coating (ED) was applied.

[0087] (Evaluation criteria for surface texture test) The test pieces after ED coating were visually evaluated for the presence or absence of surface patterns, and a three-point rating was used: ○ (excellent) for no visible surface patterns, △ (good) for slight surface patterns, and × (poor) for clear surface patterns. A rating of △ or better was considered a pass.

[0088] The measurement results of moldability and surface properties are shown in Table 3 below.

[0089] [Table 1]

[0090] [Table 2]

[0091] [Table 3]

[0092] As shown in Tables 1 to 3, in Invention Examples Nos. A1 to A3 and B1 to B4, the chemical compositions of the aluminum alloy sheets were within the ranges specified in the present invention, and the area ratio of Cube orientation and the number densities of compounds having a circle-equivalent diameter of 1.5 μm or more were also within the ranges specified in the present invention. Therefore, even if the heating rate and heating temperature during intermediate annealing were reduced, aluminum alloy sheets having excellent formability and surface properties could be obtained.

[0093] On the other hand, in Comparative Example No. A4, the area ratio of Cube orientation exceeded the upper limit of the numerical range specified in the present invention, and the number density of compounds having a circle-equivalent diameter of 1.5 μm or more was below the lower limit of the numerical range specified in the present invention, resulting in a large in-plane anisotropy Δr and poor formability. In Comparative Example No. A5, the number density of compounds having a circle-equivalent diameter of 1.5 μm or more was below the lower limit of the numerical range specified in the present invention, resulting in a large in-plane anisotropy Δr and poor formability. In Comparative Example No. B5, the area ratio of Cube orientation exceeded the upper limit of the numerical range specified in the present invention, resulting in a large in-plane anisotropy Δr and poor formability.

Claims

1. Si: 0.50% by mass or more and 1.60% by mass or less, Mg: 0.25% by mass or more and 1.00% by mass or less, Fe: 0.05% by mass or more and 0.50% by mass or less, Mn: 0.01% by mass or more and 0.30% by mass or less, Cu: 0.001% by mass or more and 0.30% by mass or less; the balance being Al and unavoidable impurities; An Al-Mg-Si-based aluminum alloy sheet, in which, when the Si content is expressed as [Si] in mass% and the Mg content is expressed as [Mg] in mass%, a ratio of [Mg] / [Si] exceeds 0.50, The area ratio of the Cube orientation is 9% or less, When observing the surface, the number density of compounds having a circle equivalent diameter of 1.5 μm or more is 1000 / mm ２ More than 10000 pieces / mm ２ An Al-Mg-Si based aluminum alloy plate characterized by the following:

2. Si: 0.50% by mass or more and 1.60% by mass or less, Mg: 0.25% by mass or more and 1.00% by mass or less, Fe: 0.05% by mass or more and 0.50% by mass or less, Mn: 0.01% by mass or more and 0.30% by mass or less, Cu: 0.001% by mass or more and 0.30% by mass or less; the balance being Al and unavoidable impurities; An Al-Mg-Si-based aluminum alloy sheet, wherein, when the Si content is expressed as [Si] in mass% and the Mg content is expressed as [Mg] in mass%, a ratio of [Mg] / [Si] is 0.50 or less, The area ratio of Cube orientation is 12% or less, When observing the surface, the number density of compounds having a circle equivalent diameter of 1.5 μm or more is 600 / mm ２ More than 10000 pieces / mm ２ An Al-Mg-Si based aluminum alloy plate characterized by the following:

3. Si: 0.50% by mass or more and 1.60% by mass or less, Mg: 0.25% by mass or more and 1.00% by mass or less, Fe: 0.05% by mass or more and 0.50% by mass or less, Mn: 0.01% by mass or more and 0.30% by mass or less, Cu: 0.001% by mass or more and 0.30% by mass or less; the balance being Al and unavoidable impurities; A method for producing the Al-Mg-Si-based aluminum alloy plate according to claim 1, using an Al-Mg-Si-based aluminum alloy ingot having an [Mg] / [Si] ratio of more than 0.50, where [Si] is the Si content in mass% and [Mg] is the Mg content in mass%, The method includes a homogenization heat treatment step, a hot rolling step, a cold rolling step, an intermediate annealing step, and a solution treatment step, The method for producing an Al-Mg-Si aluminum alloy sheet is characterized in that the heat treatment temperature in the intermediate annealing step is less than 500°C and the temperature rising rate is 1°C / second or less.

4. Si: 0.50% by mass or more and 1.60% by mass or less, Mg: 0.25% by mass or more and 1.00% by mass or less, Fe: 0.05% by mass or more and 0.50% by mass or less, Mn: 0.01% by mass or more and 0.30% by mass or less, Cu: 0.001% by mass or more and 0.30% by mass or less; the balance being Al and unavoidable impurities; A method for producing the Al-Mg-Si-based aluminum alloy plate according to claim 2, using an Al-Mg-Si-based aluminum alloy ingot having an [Mg] / [Si] ratio of 0.50 or less, where [Si] is the Si content in mass% and [Mg] is the Mg content in mass%, The method includes a homogenization heat treatment step, a hot rolling step, a cold rolling step, an intermediate annealing step, and a solution treatment step, The method for producing an Al-Mg-Si aluminum alloy sheet is characterized in that the heat treatment temperature in the intermediate annealing step is less than 500°C and the temperature rising rate is 1°C / second or less.

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