Al-Mg-Si aluminum alloy sheet and method for manufacturing the same.

Abstract

To provide an Al-Mg-Si based aluminum alloy sheet having excellent surface properties and formability even when the temperature increase rate or heating temperature during intermediate annealing is lowered.SOLUTION: There is provided an Al-Mg-Si based aluminum alloy sheet comprising 0.50 mass% or more and 1.60 mass% or less of Si, 0.25 mass% or more and 1.00 mass% or less of Mg, 0.05 mass% or more and 0.50 mass% or less of Fe, 0.01 mass% or more and 0.30 mass% or less of Mn, 0.001 mass% or more and 0.30 mass% or less of Cu and the balance Al with inevitable impurities, wherein when the Si content is represented as [Si] by mass% and the Mg content is represented as [Mg] by mass%, [Mg] / [Si] is more than 0.50, the area ratio of the Cube orientation is 9% or less and further, when the surface is observed, the number density of the compounds having an equivalent diameter of 1.5 μm or more is 1000 pieces / mm2 or more and 10000 pieces / 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 to a method for manufacturing an Al-Mg-Si aluminum alloy sheet that can reduce CO2 emissions during production. [Background technology]

[0002] In recent years, due to concerns about the global environment, there has been an increasing social demand for lighter automobile bodies. To meet this demand, aluminum alloy materials are being used in place of steel plates and other steel materials for large body panels (outer panels and inner panels) of automobile bodies. Of the above-mentioned large body panels, Al-Mg-Si type JIS 6000 series (hereinafter simply referred to as 6000 series) aluminum alloy sheets are used, especially for the outer panels (exterior panels).

[0003] Incidentally, press-formed 6000 series aluminum alloy sheets have the problem of being prone to streaky patterns called rigning marks and surface roughness defects. For example, Patent Document 1 discloses an aluminum alloy sheet in which the composition of the aluminum alloy material is controlled, as well as the values ​​of the Cube orientation density (C), ND rotational Cube orientation density (N), and RD rotational Cube orientation density (G) of the crystal grains present in the sheet, and the ratio of (N) to (C) and the ratio of (G) to (C). According to Patent Document 1, it is stated that an aluminum alloy sheet for forming with excellent resistance to surface roughness and rigning can be obtained.

[0004] Furthermore, Patent Document 2 discloses a method for manufacturing rolled aluminum alloy sheets for forming, which involves controlling the average cooling rate after homogenization treatment of an ingot made of an aluminum alloy having a predetermined composition, the total cold rolling rate, and the holding conditions before hot rolling, and cold rolling without intermediate annealing. According to Patent Document 2, it is possible to manufacture rolled aluminum alloy sheets for forming with excellent bendability and rigning resistance.

[0005] On the other hand, since automotive exterior components are generally press-formed, the aluminum alloy sheets used are required to have excellent formability. In particular, European and American automobile manufacturers are looking for outer panels with excellent formability, and they require materials with low anisotropy (Δr) of the Lankford value (r value), which is one of the indicators for evaluating the formability of sheet materials. However, in the manufacturing methods of aluminum alloy sheets or rolled aluminum alloy sheets described in the above-mentioned Patent Documents 1 and 2, orientation control other than the Cube orientation is insufficient, raising concerns that the anisotropy of the r value is large or the average r value is 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 defined. According to Patent Document 3, it is possible to obtain an aluminum alloy sheet that is excellent in bendability and paint bake hardening, and is particularly suitable for automotive exterior panels.

[0007] Furthermore, Patent Document 4 describes how the composition of the aluminum alloy sheet is controlled, and after solution treatment and quenching, the maximum diameter of the Mg-Si compound is 10 μm or less, and the number of compounds with a diameter of 2 to 10 μm is 1000 / mm². 2 The following is disclosed: an aluminum alloy sheet having an internal limit bending radius of 0.5 mm under predetermined conditions.

[0008] However, even in the aluminum alloy sheet described in Patent Document 3, although the r value is high, the anisotropy of the r value is high, making it impossible to obtain the desired formability. Furthermore, in Patent Document 4, the anisotropy of the r value is not taken into consideration, and there is a possibility that the desired r value anisotropy 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, average value of the r value, absolute value of the in-plane anisotropy index of the r value, average grain size, and the yield strength after aging and after heating are specified. According to Patent Document 5, it is possible to obtain an Al-Mg-Si aluminum alloy sheet for automotive panels that is excellent in all aspects, including press formability, bendability that allows for flat hem processing, shape freezing properties, paint bake hardening properties, 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, Brass, S, P, and Q orientations is limited to a predetermined range, and the standard deviation of the Cube orientation area ratio W and the conductivity after standing after final tempering are controlled. According to Patent Document 6, it is stated that a 6000 series aluminum alloy sheet with excellent press formability, rionic markability, and 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 [Overview of the project] [Problems that the invention aims to solve]

[0012] By the way, in the intermediate annealing step, there are known cases of, for example, rapid heating by a continuous furnace method and low-speed heating by a batch furnace method. In the batch furnace method, a plurality of coils can be processed together, while in the continuous furnace method, rapid heating is possible, which has the advantage of easily controlling anisotropy and surface properties.

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

[0014] However, in order to produce the aluminum alloy sheets described in Patent Documents 5 and 6, both require rapid heating or relatively high-temperature batch treatment when performing intermediate annealing. Therefore, the CO₂ emission amount in the production process is high, which imposes a burden on the global environment.

[0015] The present invention has been made in view of such problems. An object of the present invention is to provide an Al-Mg-Si-based aluminum alloy sheet that can obtain excellent surface properties and formability even when the temperature increase rate and heating temperature during intermediate annealing are lowered, and a method for producing an Al-Mg-Si-based aluminum alloy sheet that can reduce CO₂ emission during production by lowering the temperature increase rate and heating temperature during intermediate annealing, and can obtain an Al-Mg-Si-based aluminum alloy sheet having excellent surface properties and formability. [Means for Solving the Problems]

[0016] The above object of the present invention is achieved by the following configuration [1] or [2] relating to the 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, It contains Cu: 0.001% by mass or more and 0.30% by mass or less. The remainder consists of Al and unavoidable impurities. In an Al-Mg-Si aluminum alloy sheet, where the Si content is expressed as [Si] in mass% and the Mg content is expressed as [Mg] in mass%, the ratio [Mg] / [Si] is greater than 0.50. The area ratio of the cube orientation is 9% or less. When the surface is observed, the number density of compounds with an equivalent circle diameter of 1.5 μm or more is 1000 particles / mm². 2 More than 10000 pieces / mm 2 An Al-Mg-Si aluminum alloy sheet characterized by the following:

[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, It contains Cu: 0.001% by mass or more and 0.30% by mass or less. The remainder consists of Al and unavoidable impurities. An Al-Mg-Si 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%, the ratio [Mg] / [Si] is 0.50 or less, The area ratio of the cube orientation is 12% or less. When the surface is observed, the number density of compounds with an equivalent circle diameter of 1.5 μm or more is 600 particles / mm². 2 More than 10000 pieces / mm 2 An Al-Mg-Si aluminum alloy sheet characterized by the following:

[0019] Furthermore, the above objectives of the present invention are achieved by the following configuration [3] or [4] relating to a method for manufacturing 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, It contains Cu: 0.001% by mass or more and 0.30% by mass or less. The remainder consists of Al and unavoidable impurities. A manufacturing method for producing an Al-Mg-Si aluminum alloy sheet as described in [1], using an Al-Mg-Si aluminum alloy ingot in which, when the Si content is expressed as [Si] in mass%, and the Mg content is expressed as [Mg] in mass%, the ratio [Mg] / [Si] is greater than 0.50, wherein The process includes a homogenization heat treatment process, a hot rolling process, a cold rolling process, an intermediate annealing process, and a solution treatment process. A method for manufacturing 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 heating 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, It contains Cu: 0.001% by mass or more and 0.30% by mass or less. The remainder consists of Al and unavoidable impurities. A manufacturing method for producing an Al-Mg-Si aluminum alloy sheet as described in [2], using an Al-Mg-Si aluminum alloy ingot in which, when the Si content is expressed as [Si] in mass%, and the Mg content is expressed as [Mg] in mass%, the ratio [Mg] / [Si] is 0.50 or less, wherein The process includes a homogenization heat treatment process, a hot rolling process, a cold rolling process, an intermediate annealing process, and a solution treatment process. A method for manufacturing 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 heating 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 aluminum alloy sheet with good surface properties and formability, and a method for manufacturing an Al-Mg-Si aluminum alloy sheet that can reduce CO2 emissions during production. [Modes for carrying out the invention]

[0023] To solve the above problems, the inventors diligently researched the effects of compounds on the anisotropy and surface properties of aluminum alloy sheets. As a result, they found that by precisely controlling the size and number density of the compounds, there is an effective range for formability and surface properties without significantly impairing elongation or bending. Furthermore, the inventors have found that even when the heating rate and heating temperature during intermediate annealing are low, Al-Mg-Si aluminum alloy sheets with excellent surface properties and formability can be obtained. Furthermore, the inventors focused on the ratio of Mg content to Si content in the aluminum alloy plate and found that by controlling this ratio, the allowable range of the area ratio of the Cube orientation and the number density of specific compounds can be broadened. This invention is based on these findings.

[0024] The embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below, and can be modified and implemented as desired without departing from the spirit of the invention.

[0025] [Al-Mg-Si aluminum alloy sheet] In this embodiment, by controlling the content of components contained in the Al-Mg-Si aluminum alloy sheet, as well as controlling the area ratio of a specific Cube orientation and the number density of a specific compound, an Al-Mg-Si aluminum alloy sheet with excellent formability and surface shape can be obtained. However, by reducing the ratio of Mg content to Si content in the Al-Mg-Si aluminum alloy sheet, the allowable range of the area ratio of the Cube orientation and the number density of a specific compound can be widened. Therefore, the case in which the ratio of Mg content to Si content is greater than a predetermined value is referred to as "Invention A," and the case in which the ratio of Mg content to Si content is less than or equal to a predetermined value is referred to as "Invention B." The chemical composition of the Al-Mg-Si aluminum alloy sheet in Invention A and Invention B and the reasons for their limitations will be explained, as well as the area ratio of the Cube orientation and the number density of a specific compound.

[0026] In this invention, the Al-Mg-Si aluminum alloy sheet refers to a rolled sheet, such as a hot-rolled sheet or a cold-rolled sheet, which has been subjected to heat treatment such as solution treatment and quenching, and is a raw aluminum alloy sheet before it is formed into, for example, an automobile component, and before it undergoes artificial aging treatment (artificial aging hardening treatment) such as paint baking hardening treatment. Hereinafter, the Al-Mg-Si aluminum alloy sheet may simply be referred to as an aluminum alloy sheet.

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

[0028] If the Si content in the aluminum alloy sheet is less than 0.50% by mass, the amount of Mg-Si compound formed after artificial aging heat treatment will be insufficient, resulting in reduced BH properties and insufficient strength. Furthermore, it will be difficult to obtain the desired r-value anisotropy and surface properties. Therefore, the Si content in the aluminum alloy sheet should be 0.50% by mass or more, preferably 0.60% by mass or more, and more preferably 0.65% by mass or more, relative to the total mass of the aluminum alloy sheet. On the other hand, if the Si content in the aluminum alloy sheet exceeds 1.60% by mass, coarse Si-based precipitates are formed, reducing ductility. Therefore, the Si content in the aluminum alloy sheet should be 1.60% by mass or less, preferably 1.50% by mass or less, and more preferably 1.45% by mass or less, relative to the total mass of the aluminum alloy sheet.

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

[0030] If the Mg content in the aluminum alloy sheet is less than 0.25% by mass, the amount of Mg-Si compound formed will be insufficient, resulting in a significant decrease in BH properties and insufficient strength. Furthermore, it will be difficult to obtain the desired r-value anisotropy and surface properties. Therefore, the Mg content in the aluminum alloy sheet should be 0.25% by mass or more, preferably 0.27% by mass or more, and more preferably 0.30% by mass or more, relative to the total mass of the aluminum alloy sheet. On the other hand, if the Mg content in the aluminum alloy sheet exceeds 1.00 mass%, the material strength during molding increases, while the elongation at break and work hardening properties decrease. Therefore, the Mg content in the aluminum alloy sheet should be 1.00 mass% or less, preferably 0.90 mass% or less, and more preferably 0.80 mass% or less, relative to the total mass of the aluminum alloy sheet.

[0031] (Fe: 0.05 mass% or more and 0.50 mass% or less) Fe and Mn are elements commonly found in 6000 series aluminum alloys. During the casting process, they form Al-Fe-Mn-Si compounds of 1.5 μm or larger. These compounds act as nuclei for recrystallization, effectively contributing to the reduction of anisotropy and improvement of 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 properties. Therefore, the Fe content in the aluminum alloy sheet should be 0.05% by mass or more, preferably 0.10% by mass or more, and more preferably 0.20% by mass or more, relative to the total mass of the aluminum alloy sheet. Note that Invention A assumes that the [Mg] / [Si] value, described later, is greater than 0.50. In this case, if the Fe content in the aluminum alloy sheet is 0.30% by mass or more relative to the total mass of the aluminum alloy sheet, relatively large Al-Fe-Si compounds can be dispersed during casting, and excellent formability and surface properties 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 coarser and more densely dispersed, which degrades the formability. Therefore, the Fe content in the aluminum alloy sheet should be 0.50 mass% or less, preferably 0.45 mass% or less, and more preferably 0.40 mass% or less, relative to the total mass of the aluminum alloy sheet.

[0033] (Mn: 0.01 mass% or more and 0.30 mass% or less) As described above, during the casting, soaking, and hot rolling processes, Mn forms Al-Fe-Mn-Si compounds of 1.5 μm or larger together with Fe. These compounds act as nuclei for recrystallization, effectively contributing to the reduction of anisotropy and improvement of 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 properties. Therefore, the Mn content in the aluminum alloy sheet should be 0.01% by mass or more, preferably 0.03% by mass or more, and more preferably 0.05% by mass or more, relative to 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 mass%, the Al-Fe-Mn-Si compound becomes coarser and more densely dispersed, which degrades the formability. Therefore, the Mn content in the aluminum alloy sheet should be 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 sheet.

[0035] (Cu: 0.001 mass% or more and 0.30 mass% or less) Cu is an element commonly found in 6000 series aluminum alloys, and even a small amount of Cu can improve the strength and formability of aluminum alloy sheets. 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 should be 0.001% by mass or more relative to the total mass of the aluminum alloy sheet, preferably 0.01% by mass or more, and more preferably 0.1% by mass or more.

[0036] On the other hand, if the Cu content in the aluminum alloy sheet exceeds 0.30 mass%, the corrosion resistance of the aluminum alloy sheet decreases. Therefore, the Cu content in the aluminum alloy sheet should be 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 sheet.

[0037] (Other ingredients) In addition to Si, Mg, Fe, Mn, and Cu, the Al-Mg-Si aluminum alloy sheet according to this embodiment may contain Cr, Zn, and Ti depending on the required mechanical properties. However, if the content of any 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 should be 0.1% by mass or less, the Zn content 0.25% by mass or less, and the Ti content 0.1% by mass or less, relative to the total mass of the aluminum alloy sheet.

[0038] (Remainder: Al and inevitable impurities) The Al-Mg-Si aluminum alloy sheet according to this embodiment contains Si, Mg, Fe, Mn, and Cu, and also contains Cr, Zn, or Ti depending on the required mechanical properties, with the remainder being Al and unavoidable impurities. Examples of 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 of the total mass of the aluminum alloy sheet, and the total amount of unavoidable impurities is preferably 0.15% by mass or less.

[0039] ([Mg] / [Si]: greater than 0.50) The inventors investigated various components contained in aluminum alloy plates and found that the anisotropy of the r value changes depending on the numerical range of [Mg] / [Si], even with equivalent Cube orientation area ratios and compound number densities. Specifically, in Invention A, Cube orientation {001} <100> The number density of compounds with an area fraction and equivalent circle diameter of 1.5 μm or more is defined as follows. This makes it possible to reduce the anisotropy of the r value even when the [Mg] / [Si] value exceeds 0.50. Here, [Si] is the value expressed as mass percent of the Si content in the aluminum alloy sheet, and [Mg] is the value expressed as mass percent of the Mg content in the aluminum alloy sheet.

[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 of the rolling direction, and low in the 45° direction (Hiroshi Inoue et al., "Evaluation of 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 be low, it is possible to increase the r value in the 45° direction, which tends to be low in 6000 series alloys, and to lower the anisotropy Δr of the r value. Furthermore, the Cube orientation is known to be a factor in surface properties (Haruyuki Konishi et al., "Crystal Plasticity Analysis of Ridging Behavior Occurring in Al-Mg-Si Alloy Sheet Materials," R&D Kobe Steel Technical Report, October 2012, Vol.62, No.2, pp.39-42). In other words, by controlling the area ratio of the Cube orientation to a low level, it is possible to improve the surface properties.

[0041] Cube direction {001} <100> When the area ratio exceeds 9%, the anisotropy Δr of the r value increases, resulting in poor moldability and deterioration of the surface properties. Therefore, in Invention A, the Cube orientation {001} <100> The area ratio of is 9% or less, preferably 8% or less.

[0042] Here, we will explain the definition of aggregate organization and an example of a method for measuring it.

[0043] (Definition of collective organization) In typical aluminum alloys, the following crystal orientation textures are known to exist, and even when the same tensile deformation is applied, the deformation state differs depending on the crystal orientation, according to the volume fraction of each 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 method of representing the crystal orientation texture is expressed by the rolling plane and the rolling direction in the case of rolled sheets. That is, the rolling plane is represented by {○○○} and the rolling direction is represented by <×××>. ○ 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 tissue density) Each of the crystal orientation textures defined in the present invention is evaluated by the SEM-EBSD method using a scanning electron microscope (SEM) or a field emission scanning electron microscope (FE-SEM). The sample to be measured is a cold-rolled sheet that has undergone final tempering treatment. The surface of the cold-rolled sheet is then mechanically polished, buffed, and then electropolished to remove the oxide film on the surface, thereby preparing the surface of the sheet.

[0047] This SEM-EBSD method is a widely used method for measuring crystal orientation texture and is a crystal orientation analysis method that incorporates a backscattered electron diffraction pattern (EBSD) system into a field emission scanning electron microscope (for example, JEOL's JSM-7000F). The SEM-EBSD method involves irradiating an aluminum alloy plate sample, set inside the microscope tube of the FE-SEM, with an electron beam. The diffraction pattern of the backscattered electrons is then captured by an EBSD device (for example, an EBSD measurement and analysis system from TSL: OIM (Orientation Imaging Macrograph) Data & Analysis), and the sample surface is scanned every 1 μm while performing crystal orientation analysis. This obtains the EBSP (Electron Back Scatter Diffraction Pattern) at each point, which is then indexed to determine the crystal orientation at the electron beam irradiation site. The obtained crystal orientation measurement data is rotated 90° around the rolling direction axis, and then rotated another 90° in the direction normal to the rolling surface. The crystal orientation distribution function (ODF) and area fraction are then calculated and determined when crystal orientation measurement by EBSD is performed over the entire measurement area. For more information on these crystal orientation analysis methods using FE-SEMs with EBSD systems, see, for example, Kobe Steel Technical Report, September 2002, Vol. 52, No. 2, pp. 66-70.

[0048] In this embodiment, the measured crystal orientation deviation 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 will be calculated accordingly. This is because aluminum alloy plates exhibit almost identical properties within this range.

[0049] (Number density of compounds with an equivalent circle diameter of 1.5 μm or more: 1000 particles / mm²) 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 per mm. 2As described below, aluminum alloy sheets with improved elongation and bendability are known. On the other hand, in the present embodiment, the size and number density of the compounds are precisely controlled, thereby improving anisotropy and surface properties without significantly impairing elongation and bendability. This is presumed to be because recrystallization is promoted around compounds with an equivalent circle diameter of 1.5 µm or more, and as a result, a relatively random texture can be obtained. Since it is difficult to numerically define the randomness of texture, in the present embodiment, the number density of compounds is used as an index indirectly indicating the randomness of texture.

[0050] In the case of Invention A, that is, when the ratio of Mg content to Si content ([Mg] / [Si]) is more than 0.50, the number density of compounds having an equivalent circle diameter of 1.5 µm or more is 1000 pieces / mm 2 If it is less than this value, the amount of recrystallized grains caused by 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 having an equivalent circle diameter of 1.5 µm or more is 1000 pieces / mm 2 or more, preferably 1200 pieces / mm 2 or more, more preferably 1500 pieces / mm 2 or more.

[0051] On the other hand, when the number density of compounds having an equivalent circle diameter of 1.5 µm or more becomes excessive, it adversely affects the strength and elongation of the aluminum alloy sheet. Therefore, the number density of compounds having an equivalent circle diameter of 1.5 µm or more is 10000 pieces / mm 2 or less, preferably 5000 pieces / mm 2 or less, more preferably 3000 pieces / mm 2 or less.

[0052] The number density of compounds with an equivalent circle diameter of 1.5 μm or more is obtained by calculating the number of compounds with an equivalent circle diameter of 1.5 μm or more per unit area in 20 fields of view using a scanning electron microscope at a magnification of 500x. In this embodiment, an area of ​​approximately 0.17 mm × approximately 0.25 mm is observed in one field of view, and the total for 20 fields of view is 0.86 mm. 2 The area is being measured. The total number of the above compounds in 20 fields of view is then calculated based on the area of ​​0.86 mm². 2 By dividing by this, the number density can be calculated.

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

[0054] <Invention B> In Invention B, the range and limitations of the Si, Mg, Fe, Mn, and Cu content in the aluminum alloy plate are the same as in Invention A. Therefore, the differences from Invention A, namely the ratio of Mg content to Si content, the area ratio of the Cube orientation, and the number density of compounds with an equivalent circle diameter of 1.5 μm or more, will be explained below.

[0055] ([Mg] / [Si]: 0.50 or less) As described above, the inventors have found that in materials with a small [Mg] / [Si] ratio, the anisotropy of the r value decreases even with equivalent Cube orientation area fraction and compound number density. This is presumed to be because extremely low [Mg] / [Si] alters the recrystallization behavior during intermediate annealing and solution treatment, affecting orientation formation other than the Cube orientation. In other words, in Invention B, the [Mg] / [Si] value is controlled to 0.50 or less, thereby reducing the Cube orientation {001} <100> The range of number densities for compounds with an area ratio and equivalent circle diameter of 1.5 μm or more can be broadened. The [Mg] / [Si] value is preferably 0.45 or less, and more preferably 0.30 or less. Similar to Invention A, [Si] is the value of the Si content in the aluminum alloy sheet expressed in mass percent, and [Mg] is the value of the Mg content in the aluminum alloy sheet expressed in mass percent.

[0056] Furthermore, in Invention B, where the [Mg] / [Si] value is limited to 0.50 or less, if the Fe content in the aluminum alloy sheet is 0.20% by mass or more relative to the total mass of the aluminum alloy sheet, relatively large Al-Fe-Si compounds can be dispersed during casting, resulting in excellent formability and surface properties.

[0057] (Cube direction {001} <100> Area ratio: 12% or less) If the [Mg] / [Si] value is 0.50 or less, the Cube orientation {001} <100> When the area ratio exceeds 12%, the anisotropy Δr of the r value increases, resulting in poor moldability and deterioration of the surface properties. Therefore, in invention B, the Cube orientation {001} <100> The area ratio 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 an equivalent circle diameter of 1.5 μm or more: 600 particles / mm²) 2 More than 10000 pieces / mm 2 below) When the [Mg] / [Si] ratio is 0.50 or less, the number density of compounds with an equivalent circle diameter of 1.5 μm or more is 600 particles / mm². 2 If the r value is less than 1.5 μm, the amount of recrystallized grains 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 an equivalent circle diameter of 1.5 μm or more should be 600 particles / mm². 2 That's all. 700 pieces / mm 2 Preferably, it is 800 pieces / mm 2 It is more preferable that the above conditions are met.

[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 adversely affects 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 / mm². 2 The following applies: 5000 pieces / mm 2 Preferably, the following: 3000 pieces / mm 2 The following is more preferable:

[0060] [Manufacturing method for Al-Mg-Si aluminum alloy sheets] The method for manufacturing an Al-Mg-Si aluminum alloy sheet according to this embodiment is the method for manufacturing an Al-Mg-Si aluminum alloy sheet according to Invention A and the method for manufacturing an Al-Mg-Si aluminum alloy sheet according to Invention B. Specifically, it involves melting a material having a desired composition and casting it to prepare an aluminum alloy ingot having the desired composition, and includes commonly performed steps such as a homogenization heat treatment step, a hot rolling step, a cold rolling step, an intermediate annealing step, and a solution treatment step, with the heating temperature and heating rate in the intermediate annealing step being specified.

[0061] Furthermore, in this embodiment, it is preferable to control the components contained in the aluminum alloy sheet so that relatively large compounds can be dispersed before cold rolling, and to appropriately control the conditions of the homogenization heat treatment process and the hot rolling process. By dispersing relatively large compounds before cold rolling, recrystallization around the compounds becomes more likely during intermediate annealing or solution treatment. As a result, the accumulation of Cube orientations that reduce r45 is reduced, and the crystal orientations become more random, thereby reducing the anisotropy of the r value and improving the surface properties.

[0062] In particular, in this embodiment, the following three methods can be used to disperse relatively large compounds before cold rolling. (1) The homogenization heat treatment is carried out in two steps or in two separate stages. (2) Increase the final temperature of the hot rolling process and slow down the cooling rate after the hot rolling process. (3) Control the Fe content contained in the aluminum alloy plate. By using at least one of these methods, an Al-Mg-Si aluminum alloy sheet with good formability and surface properties can be manufactured. The methods for manufacturing Al-Mg-Si aluminum alloy sheets according to Inventions A and B will be described in more detail below.

[0063] <Melting and casting process> An aluminum alloy ingot of a predetermined shape is produced from molten aluminum alloy material having the desired composition described above. 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 Fe content in aluminum alloy sheets and in (3) above, controlling the Fe content in aluminum alloy sheets makes it possible to disperse relatively large Al-Fe-Si compounds during casting. Specifically, when manufacturing aluminum alloy sheets according to Invention A, it is preferable to have a Fe content of 0.30 mass% or more in the aluminum alloy ingot. Furthermore, when manufacturing aluminum alloy sheets according to Invention B, it is preferable to have a Fe content of 0.20 mass% or more in the aluminum alloy ingot. In this way, by increasing the Fe content in the aluminum alloy material and aluminum alloy ingot, it is possible to manufacture Al-Mg-Si aluminum alloy sheets with good formability and surface properties.

[0065] <Homogeneity Heat Treatment Process> Next, the cast aluminum alloy ingot is subjected to homogenization heat treatment (soaking treatment). This homogenization heat treatment is performed to make the non-uniform structure from the time of casting uniform. The temperature of the homogenization heat treatment is not particularly limited, but below 480°C, the strength after artificial aging tends to decrease. For this reason, the homogenization heat treatment temperature is preferably 480°C or higher but below the melting point, and more preferably 500°C or higher. Furthermore, regarding the cooling rate after homogenization heat treatment, it is preferable that the average cooling rate during the cooling from 480°C to 300°C be 500°C / hour or less, and more preferably 100°C / hour or less.

[0066] As described in (1) above, in this embodiment, it is preferable that the soaking treatment be carried out in two or two stages. By carrying out the soaking treatment in two or two stages, it is possible to distribute a large amount of relatively large Mg-Si compounds during the cooling process after the first soaking treatment or during the heating process in the second soaking treatment. Whether to carry out the soaking treatment in two or two stages can be determined by the available equipment.

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

[0068] <Cold rolling process> The hot-rolled sheet obtained in the above hot-rolling process is then cold-rolled to obtain a cold-rolled sheet. It is preferable to repeat the cold-rolling process as needed after the intermediate annealing process described later.

[0069] (Total rolling ratio: 75% or more) In the method for manufacturing aluminum alloy sheets according to Inventions A and B, increasing the total rolling ratio in cold rolling reduces the density of Cube orientations, thereby lowering the area ratio of Cube orientations and enabling the acquisition of good formability and surface properties. Therefore, the total rolling ratio in all cold rolling processes from the hot rolling process through the intermediate annealing process to the final sheet thickness is preferably 75% or higher, and more preferably 78% or higher. The total rolling ratio refers to the reduction in sheet thickness after all cold rolling processes with respect to the sheet thickness after hot rolling.

[0070] <Intermediate annealing process> Cold-rolled sheets undergo work hardening during the cold-rolling process described above. Intermediate annealing is performed to soften the sheets, thereby improving the efficiency of post-processing and reducing cracking during processing. In the manufacturing methods of aluminum alloy sheets according to Inventions A and B, intermediate annealing allows for repeated recrystallization, making it easier to obtain a relatively random texture, and as a result, it is easier to obtain good surface properties. As mentioned above, increasing the temperature or heating rate of intermediate annealing makes it easier to control the anisotropy and surface properties of the aluminum alloy sheet. However, increasing the temperature or heating rate of intermediate annealing places a burden on the environment. In aluminum alloy sheets according to Inventions A and B, by controlling the area ratio of Cube orientation and the number density of specific compounds, excellent surface properties 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 process is 500°C or higher, or if the heating rate exceeds 1°C / second, a large amount of heat is required in the intermediate annealing process, which has an adverse effect on the environment. Therefore, it is preferable that the heat treatment temperature in the intermediate annealing process be less than 500°C, and 460°C or lower. Furthermore, it is preferable that the heating rate in the intermediate annealing process be 1°C / second or lower, 500°C / hour or lower, and more preferably 100°C / hour or lower. Here, the heating rate is the average heating rate from room temperature to the target temperature.

[0072] <Solution treatment process> After cold rolling, a solution treatment is performed. The temperature in the solution treatment process is not particularly limited, but it is preferable to maintain a temperature of 480°C to 570°C for 1 to 120 seconds.

[0073] Furthermore, the manufacturing methods for the aluminum alloy plate according to Invention A and the aluminum alloy plate according to Invention B are not limited to the above manufacturing methods and can be modified as appropriate without departing from the spirit of the present invention. [Examples]

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

[0075] <Manufacturing of aluminum alloy sheets> Aluminum alloy sheets with various compositions were manufactured using various manufacturing methods. The specific manufacturing methods for each aluminum alloy sheet are described below. The inventive examples and comparative examples related to the aluminum alloy sheet according to Invention A are designated as Invention Examples No. A1 to A3 and Comparative Examples No. A4 and A5, while the inventive examples and comparative examples related to the aluminum alloy sheet according to Invention B are designated as Invention Examples No. B1 to B4 and Comparative Example No. B5.

[0076] (Manufacturing of aluminum alloy sheets for Invention Examples No. A1, B1, and B2) Ingots of each composition shown in Table 1 were melted using a semi-continuous casting method (DC casting method: Direct Chill casting process). Next, a homogenization heat treatment was performed using a two-stage heat treatment. The first soaking treatment temperature was 560°C, and the material was cooled to room temperature by air cooling. After that, it was heated again to 420°C, and then hot rolling was performed. The final temperature of the hot rolling was 280°C to 420°C, after which slow cooling was performed. The thickness of the aluminum alloy sheet after hot rolling was 2.3 mm to 6.0 mm. Then, the aluminum alloy sheet after hot rolling was cold-rolled at various cold rolling rates, and then intermediate annealing was performed in a batch-type atmospheric furnace at a heating rate of 40°C / hour (0.011°C / second). After the completion of intermediate annealing, cold rolling was performed again at various cold rolling rates. The final sheet thickness after cold rolling was 0.4 to 1.0 mm. Subsequently, a solution treatment was performed using a salt bath, where the material was heated and held at 560°C for 30 seconds, followed by cooling to room temperature using water cooling. After that, the material was held at room temperature for approximately one week to produce aluminum alloy plates of Invention Examples No. A1, B1, and B2.

[0077] (Manufacturing of aluminum alloy sheets for Invention Examples No. A2, B3, B4, and Comparative Examples No. A4, A5, B5) In the same manner as in Invention Example No. A1 described above, an ingot was melted, a soaking treatment was performed once 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 to produce aluminum alloy sheets of Invention Examples No. A2, B3, B4, and Comparative Examples No. A4, A5, B5.

[0078] (Manufacturing of aluminum alloy plate according to Invention Example No. A3) In the same manner as in Invention Example No. A2 described above, an ingot was melted, and after one soaking treatment, hot rolling was performed. Next, as an additional annealing to verify the effect of compound dispersion after hot rolling, a solution treatment was performed at a temperature of 560°C for 4 hours, followed by holding at a temperature of 410°C for 16 hours and then rapid cooling. Subsequently, cold rolling, intermediate annealing, a second cold rolling and solution treatment were performed, and the aluminum alloy sheet of Invention Example No. A3 was manufactured by holding at room temperature for about one week.

[0079] Table 2 below shows the conditions in each step of the manufacturing process for Invention Examples No. A1-A3, Comparative Examples No. A4-A5, Invention Examples No. B1-B4, and Comparative Example No. B5. Note that the composition of the obtained aluminum alloy sheets is the same as that of the raw material aluminum alloy ingot, so its composition is omitted from the table.

[0080] (Measurement of collective organization) The texture of the obtained aluminum alloy plates of the inventive example and comparative example was measured, and the area fraction of the Cube orientation was calculated. The method for measuring the texture was as described in the above embodiment. Note that the measured deviation of the crystal orientation corresponds to the Cube orientation {001}. <100> We defined areas within ±15° of the crystal plane as belonging to the same orientation factor and calculated the area ratio of the Cube orientation.

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

[0082] <Evaluation Test> (Plastic strain ratio test) Tensile test specimens were taken from each obtained aluminum alloy sheet. Tensile test specimens were prepared by taking specimens of type 13B (short side: 12.5 mm, gauge length (GL): 50 mm) as described in JIS Z 2241:2011, with the tensile direction parallel (0°), 45°, and perpendicular (90°) to the rolling direction, from each aluminum alloy sheet, and tensile tests were performed at room temperature. The tensile test was conducted at a rate of 5 mm / min until the 0.2% yield strength measurement, and then at 30 mm / min thereafter. The r value was measured at the 0.2% yield strength and with a 15% plastic strain applied. Furthermore, 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 The result 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 performed twice, and the various properties were calculated using the average value.

[0085] (Evaluation criteria for tensile testing) For use as an automotive exterior material, the evaluation criteria for press formability of aluminum alloy sheets were determined to be acceptable if Δr was 0.25 or less and the r value in the 90° direction (r90) was 0.60 or more.

[0086] (Surface properties test) Test specimens were taken from each obtained aluminum alloy sheet, subjected to a 15% plastic strain in a direction perpendicular to the rolling direction, and then coated with electrodeposition coating (ED).

[0087] (Evaluation criteria for surface texture testing) After ED coating, the presence or absence of surface patterns in the test pieces was visually evaluated. A three-level evaluation was used: ○ (Excellent) for those with no surface patterns at all, △ (Good) for those with slight surface patterns, and × (Poor) for those with clear surface patterns. A score of △ or higher was considered a pass.

[0088] The measurement results for 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 No. A1 to A3 and Invention Examples No. B1 to B4, the chemical composition of the aluminum alloy sheets is within the range defined in this invention, and the area ratio of the cube orientation and the number density of compounds with an equivalent circle diameter of 1.5 μm or more are within the range defined in this invention. Therefore, even when the heating rate and heating temperature during intermediate annealing are low, it was possible to obtain aluminum alloy sheets with excellent formability and surface properties.

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

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, It contains Cu: 0.001% by mass or more and 0.30% by mass or less. The remainder consists of Al and unavoidable impurities. In an Al-Mg-Si aluminum alloy sheet, where the Si content is expressed as [Si] in mass percent and the Mg content is expressed as [Mg] in mass percent, the ratio [Mg] / [Si] is greater than 0.

50. The area ratio of the cube orientation is 9% or less. When the surface is observed, the number density of compounds with an equivalent circular diameter of 1.5 μm or more is 1000 particles / mm². ２ More than 10000 pieces / mm ２ The following: An Al-Mg-Si aluminum alloy sheet characterized by having an in-plane anisotropy Δr of 0.25 or less.

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, It contains Cu: 0.001% by mass or more and 0.30% by mass or less. The remainder consists of Al and unavoidable impurities. An Al-Mg-Si aluminum alloy sheet in which, when the Si content is expressed as [Si] in mass percent and the Mg content is expressed as [Mg] in mass percent, the ratio [Mg] / [Si] is 0.50 or less, The area ratio of the cube orientation is 12% or less. When the surface is observed, the number density of compounds with an equivalent circular diameter of 1.5 μm or more is 600 particles / mm². ２ More than 10000 pieces / mm ２ The following: An Al-Mg-Si aluminum alloy sheet characterized by having an in-plane anisotropy Δr of 0.25 or less.

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, It contains Cu: 0.001% by mass or more and 0.30% by mass or less. The remainder consists of Al and unavoidable impurities. A method for producing an Al-Mg-Si aluminum alloy sheet according to claim 1, using an Al-Mg-Si aluminum alloy ingot in which, when the Si content is expressed as [Si] in mass%, and the Mg content is expressed as [Mg] in mass%, the ratio [Mg] / [Si] is greater than 0.50, wherein The process includes a homogenization heat treatment process, a hot rolling process, a cold rolling process, an intermediate annealing process, and a solution treatment process. A method for manufacturing 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 heating 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, It contains Cu: 0.001% by mass or more and 0.30% by mass or less. The remainder consists of Al and unavoidable impurities. A method for producing an Al-Mg-Si aluminum alloy sheet according to claim 2, using an Al-Mg-Si aluminum alloy ingot in which, when the Si content is expressed as [Si] in mass%, and the Mg content is expressed as [Mg] in mass%, the ratio [Mg] / [Si] is 0.50 or less, the method being used The process includes a homogenization heat treatment process, a hot rolling process, a cold rolling process, an intermediate annealing process, and a solution treatment process. A method for manufacturing 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 heating rate is 1°C / second or less.

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