Aluminum rolled sheet, aluminum member, and manufacturing methods for these

Abstract

To provide an aluminum rolled sheet capable of exhibiting a wood-grain surface pattern through anodizing treatment, an aluminum member comprising the aluminum rolled sheet, and manufacturing methods for these.SOLUTION: An aluminum rolled sheet A1 is composed of aluminum or an aluminum alloy. The aluminum rolled sheet A1 has, in a cross section perpendicular to the rolling direction, a metal structure containing crystal grains having a length of 200 μm or greater in the direction perpendicular to rolling.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an aluminum rolled plate, an aluminum member, and a method for manufacturing the same. [Background technology]

[0002] Parts used in areas that are visible to consumers, such as building materials, exterior materials for vehicles, housings for electrical appliances, etc., are often required to have design properties in addition to strength. For example, when trying to impart a wood-grain pattern to a metal part, a method is used in which a decorative sheet with a wood-grain pattern printed thereon is attached to the part (e.g., Patent Document 1), or a method is used in which the surface of the part is cut to form a wood-grain groove pattern and then painted (e.g., Patent Document 2).

[0003] Furthermore, for example, Patent Document 3 describes a technology for imparting a wood grain pattern to an aluminum alloy extrusion material having a specific chemical composition by subjecting the aluminum alloy extrusion material to an anodizing treatment and then dyeing the anodized coating. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-80703 A [Patent Document 2] JP 2004-338153 A [Patent Document 3] JP 2023-9409 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a pattern is added to the surface of a part using a decorative sheet or paint as in Patent Documents 1 and 2, the film with the pattern is exposed on the surface of the part. However, the decorative sheet or paint may peel off from the surface of the part for various reasons, such as deterioration during use, which may impair the design of the part.

[0006] In addition, since the aluminum alloy member of Patent Document 3 is an extruded material, the shape of the aluminum alloy member is limited to a shape that can be extruded. Therefore, a technology is desired that can impart a wood grain pattern to the surface of a rolled plate that can be formed into various shapes by bending, pressing, etc.

[0007] The present invention has been made in view of the above background, and aims to provide an aluminum rolled plate capable of imparting a wood grain pattern to its surface by anodizing treatment, an aluminum member made of this aluminum rolled plate, and methods for manufacturing the same. [Means for solving the problem]

[0008] A first aspect of the present invention is an aluminum rolled plate made of aluminum or an aluminum alloy, The aluminum rolled plate contains crystal grains having a length of 200 μm or more in the direction perpendicular to the rolling direction in a cross section perpendicular to the rolling direction.

[0009] A second aspect of the present invention is an aluminum member having a substrate made of the rolled aluminum plate of the above aspect and an anodized aluminum coating formed on the substrate.

[0010] A third aspect of the present invention is a method for producing an aluminum rolled sheet according to the above aspect, A casting step for producing an ingot made of aluminum or an aluminum alloy; a hot rolling step of producing an aluminum rolled plate by hot rolling the ingot; a cold rolling step of cold rolling the aluminum rolled plate; and an annealing step of annealing the aluminum rolled sheet between the hot rolling step and the cold rolling step and / or during the cold rolling step, The heating temperature in the annealing step is 550° C. or higher, and the holding time is 12 hours or longer; The reduction ratio of the aluminum rolled plate after the annealing step is 60% or more. The method lies in the manufacturing method of rolled aluminum sheet.

[0011] A fourth aspect of the present invention is a method for producing a substrate made of an aluminum rolled plate by the method for producing an aluminum rolled plate according to the above aspect, The method for producing an aluminum member further comprises anodizing the base material to form an alumite coating on the base material. Effect of the Invention

[0012] The rolled aluminum sheet has a metal structure containing crystal grains having a length of 200 μm or more in a direction perpendicular to the rolling direction in a cross section perpendicular to the rolling direction. By forming an alumite coating by anodizing the rolled aluminum sheet having such a metal structure, it is possible to impart a wood grain pattern to the surface of the rolled aluminum sheet after the anodizing treatment.

[0013] The aluminum member has a base material made of the rolled aluminum plate and an anodized aluminum coating formed on the base material, so that the surface of the aluminum member has a wood grain pattern.

[0014] Moreover, according to the method for producing an aluminum rolled plate of the above aspect, the aluminum rolled plate can be easily obtained. Similarly, according to the method for producing an aluminum member of the above aspect, the aluminum member can be easily obtained.

[0015] Therefore, according to the above-described aspect, it is possible to provide an aluminum rolled plate capable of imparting a wood grain pattern to the surface by anodizing treatment, an aluminum member made of this aluminum rolled plate, and methods for manufacturing these. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is an enlarged photograph of a cross section perpendicular to the rolling direction of the rolled sheet A1 in Example 1. As shown in FIG. [Diagram 2] FIG. 2 is an enlarged photograph of a cross section of the rolled sheet A1 in Example 1, taken along a line perpendicular to the rolling direction. [Diagram 3] FIG. 3 is a partial cross-sectional view showing a main portion of the aluminum member in the second embodiment. [Figure 4] FIG. 4 is a photograph showing an example of a pattern on the surface of the aluminum member B4 in Example 2. [Diagram 5] FIG. 5 is an explanatory diagram showing the spatial frequency spectrum of the pattern on the surface of the aluminum member B1 in Example 2. [Figure 6] FIG. 6 is an explanatory diagram showing the spatial frequency spectrum of the pattern on the surface of the aluminum member B2 in Example 2. [Figure 7] FIG. 7 is an explanatory diagram showing the spatial frequency spectrum of the pattern on the surface of the aluminum member B3 in Example 2. [Figure 8] FIG. 8 is an explanatory diagram showing the spatial frequency spectrum of the pattern on the surface of the aluminum member B4 in Example 2. [Figure 9] FIG. 9 is an enlarged photograph of a cross section perpendicular to the rolling direction of the rolled sheet C1 in Comparative Example 1. [Figure 10] FIG. 10 is an enlarged photograph of a cross section perpendicular to the rolling direction of the rolled sheet C1 in Comparative Example 1. [Figure 11] FIG. 11 is an explanatory diagram showing the spatial frequency spectrum of the pattern on the surface of the aluminum member D1 in Comparative Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] (rolled aluminum plate) The aluminum rolled plate may be made of aluminum or an aluminum alloy. The chemical components of the aluminum rolled plate can be appropriately selected depending on the application, the required properties, and the like. Specifically, 1000 series aluminum can be used as the aluminum constituting the aluminum rolled plate. In addition, 2000 series alloys, 3000 series alloys, 4000 series alloys, 5000 series alloys, 6000 series alloys, 7000 series alloys, and 8000 series alloys can be used as the aluminum alloy constituting the aluminum rolled plate.

[0018] Among these aluminum and aluminum alloys, the aluminum rolled plate is preferably made of a 6000 series alloy. In this case, it is easier to realize a metal structure containing the specific crystal grains, and it is easier to obtain an aluminum member having a wood grain pattern. In addition, an aluminum rolled plate made of a 6000 series alloy has relatively high strength. Therefore, an aluminum member obtained by using such an aluminum rolled plate is suitable for applications requiring high strength and design, such as building materials and exterior materials for vehicles.

[0019] The 6000 series alloy constituting the aluminum rolled plate may have a chemical composition that includes, for example, 0.20% by mass or more and 1.5% by mass or less of Si (silicon) and 0.25% by mass or more and 1.2% by mass or less of Mg (magnesium), with the balance being Al (aluminum) and unavoidable impurities. From the viewpoint of more reliably obtaining the above-mentioned effects, the content of Mg in the aluminum rolled plate is preferably 0.45% by mass or more and 0.90% by mass or less. That is, the 6000 series alloy constituting the aluminum rolled plate preferably has a chemical composition that includes 0.20% by mass or more and 1.5% by mass or less of Si and 0.45% by mass or more and 0.90% by mass or less of Mg, with the balance being Al and unavoidable impurities.

[0020] Furthermore, the 6000 series alloy may further contain, in addition to Si and Mg, one or more elements selected from the group consisting of Zn (zinc), Fe (iron) and Mn (manganese).

[0021] The rolled aluminum plate is preferably made of an aluminum alloy containing less than 5.0 mass% Zn. By controlling the Zn content in the rolled aluminum plate to fall within the above-mentioned specific range, the appearance of the aluminum member, such as gloss and color tone, after anodizing can be more easily adjusted.

[0022] The aluminum rolled plate is preferably made of an aluminum alloy containing 0.2 mass% or less of Fe. In this case, the metal structure containing the specific crystal grains can be more easily realized. From the same viewpoint, the aluminum rolled plate is preferably made of an aluminum alloy containing less than 0.8 mass% of Mn.

[0023] When the aluminum rolled plate is made of a 6000 series alloy, the 6000 series alloy may have a chemical composition including, for example, Si: 0.20 mass% or more and 1.5 mass% or less, Mg: 0.25 mass% or more and 1.2 mass% or less, and further including one or more elements selected from the group consisting of Zn: less than 5.0 mass%, Fe: 0.2 mass% or less, and Mn: less than 0.8 mass%, with the balance being Al and unavoidable impurities.

[0024] From the viewpoint of more easily realizing a metal structure containing the specific crystal grains, the 6000 series alloy constituting the aluminum rolled plate preferably has a chemical composition containing Si: 0.20% by mass to 1.5% by mass, Mg: 0.45% by mass to 0.90% by mass, and one or more elements selected from the group consisting of Zn: less than 5.0% by mass, Fe: 0.2% by mass or less, and Mn: less than 0.8% by mass, with the balance being Al and unavoidable impurities. Examples of the 6000 series alloy having such a chemical composition include an aluminum alloy having a chemical composition represented by alloy symbol A6063 and an aluminum alloy having a chemical composition represented by alloy symbol A6016.

[0025] The cross section of the rolled aluminum sheet perpendicular to the rolling direction contains crystal grains having a length of 200 μm or more in the direction perpendicular to the rolling direction. That is, when the cross section of the rolled aluminum sheet perpendicular to the rolling direction is observed, at least some of the crystal grains appearing in the cross section have a length of 200 μm or more in the direction perpendicular to the rolling direction. By subjecting the rolled aluminum sheet having such a metal structure to anodizing treatment, an aluminum member having a wood grain pattern can be obtained.

[0026] From the viewpoint of making the surface pattern of the aluminum member more similar to wood grain, the cross section perpendicular to the rolling direction of the aluminum rolled plate preferably contains crystal grains having a length in the direction perpendicular to the rolling direction of 300 μm or more, more preferably contains crystal grains having a length of 400 μm or more, even more preferably contains crystal grains having a length of 500 μm or more, and particularly preferably contains crystal grains having a length of 600 μm or more. From the same viewpoint, it is preferable that the length in the rolling direction of the crystal grains contained in the aluminum rolled plate is longer than the length in the direction perpendicular to the rolling direction.

[0027] The reason why the wood grain pattern appears when the rolled aluminum plate is anodized is not entirely clear, but it is believed that the wood grain pattern appears for the following reasons, for example.

[0028] That is, the aluminum rolled sheet containing the specific crystal grains is composed of coarse crystal grains compared to general rolled sheets. Furthermore, the crystal grains contained in the aluminum rolled sheet are elongated in the rolling direction by rolling, and the crystal orientations of adjacent crystal grains are different from each other.

[0029] Generally, in anodizing an aluminum material, dissolution of the aluminum material and formation of an anodized film proceed simultaneously. The dissolution rate of the aluminum material depends on the crystal orientation of the crystal grains. Therefore, when the aluminum rolled plate is anodized, it is considered that an anodized film of different thickness is formed on the surface of each crystal grain due to the difference in dissolution rate for each crystal orientation. It is also considered that the reflectance on the surface of each crystal grain is different due to the difference in crystal orientation. Therefore, when the aluminum rolled plate having the specific metal structure is anodized, it is considered that a streaky pattern extending in the rolling direction appears on the surface of the aluminum member due to the arrangement of the crystal grains.

[0030] In addition, in the aluminum rolled plate having the specific metal structure, the width of the crystal grains exposed on the surface, i.e., the length of the crystal grains in the direction perpendicular to the rolling direction, is relatively large. Therefore, the period of the streaky pattern that appears when the aluminum rolled plate is anodized tends to be close to the intervals of the wood grain. As a result, it is believed that a wood grain pattern appears on the surface of the aluminum member by anodizing the aluminum rolled plate.

[0031] The average thickness of the crystal grains in the cross section perpendicular to the rolling direction of the aluminum rolled plate is preferably 10 μm or more, more preferably 20 μm or more. In an aluminum rolled plate having an average thickness of the crystal grains within the specific range, the crystal grains are sufficiently stretched in the rolling direction, so that the aluminum member after anodizing can be more reliably imparted with a wood grain pattern. From the viewpoint of obtaining such an effect, the upper limit of the average thickness of the crystal grains is not particularly limited, but the average thickness of the crystal grains in the aluminum rolled plate may be, for example, 100 μm or less, 80 μm or less, or 60 μm or less.

[0032] In addition, the ratio of the average grain width to the average grain thickness in a cross section perpendicular to the rolling direction of the aluminum rolled plate is preferably 250% or more, more preferably 330% or more, and even more preferably 500% or more. In an aluminum rolled plate having an average grain width within the specific range, the grains are sufficiently elongated in the rolling direction, so that a wood grain pattern can be more reliably imparted to the aluminum member after anodizing treatment.

[0033] The method of calculating the average thickness of the crystal grains in the cross section is as follows. First, a cross section perpendicular to the rolling direction of the aluminum rolled plate is exposed, and pretreatment is performed to observe the crystal grains. Then, an enlarged photograph of the cross section is obtained so that the entire range in the thickness direction of the aluminum rolled plate is in the field of view. Five evaluation positions are set on the enlarged photograph, including the center in the direction perpendicular to the rolling of the aluminum rolled plate, and the intervals between adjacent evaluation positions in the direction perpendicular to the rolling are equal to each other. Next, a straight line is drawn through each evaluation position and parallel to the thickness direction of the aluminum rolled plate. Then, the thickness of the aluminum rolled plate at each evaluation position is divided by the number of crystal grains that intersect with the straight line to calculate the average thickness of the crystal grains at each evaluation position. The arithmetic average value of the average thicknesses of the crystal grains at the five evaluation positions obtained as described above is set as the average thickness of the crystal grains of the aluminum rolled plate in the cross section.

[0034] The method of calculating the average width of the crystal grains in the cross section is as follows. First, a cross section perpendicular to the rolling direction of the aluminum rolled plate is exposed, and pretreatment is performed to observe the crystal grains. Then, an enlarged photograph of the cross section is obtained so that the entire range in the thickness direction of the aluminum rolled plate is in the field of view. Five evaluation positions are set on the enlarged photograph, including the center in the thickness direction of the aluminum rolled plate, and the intervals between adjacent evaluation positions in the thickness direction are equal to each other. Next, a straight line is drawn through each evaluation position and parallel to the direction perpendicular to the rolling direction of the aluminum rolled plate. Then, the length of the part where the straight line overlaps with the aluminum rolled plate at each evaluation position is divided by the number of crystal grains that intersect with the straight line to calculate the average width of the crystal grains at each evaluation position. The arithmetic average value of the average widths of the crystal grains at the five evaluation positions obtained as described above is set as the average width of the crystal grains of the aluminum rolled plate in the cross section.

[0035] (Method of manufacturing rolled aluminum sheet) The method for producing the aluminum rolled plate includes a casting step of producing an ingot made of aluminum or an aluminum alloy, a hot rolling step of producing an aluminum rolled plate by hot rolling the ingot; a cold rolling step of cold rolling the aluminum rolled plate; and an annealing step of annealing the aluminum rolled sheet between the hot rolling step and the cold rolling step and / or during the cold rolling step.

[0036] [Casting process] In the casting step of the manufacturing method, the method for producing the ingot is not particularly limited, and various casting methods such as DC casting, continuous casting, etc. From the viewpoint of more easily obtaining an aluminum rolled sheet having the specific metal structure, it is preferable to produce the ingot by DC casting in the casting step.

[0037] [Homogenization process] In the manufacturing method, after producing an ingot, a homogenization treatment step may be performed as necessary before hot rolling, in which the ingot is heated to homogenize it. By performing homogenization treatment on the ingot before hot rolling, segregation of solute elements in the ingot can be eliminated, and a more homogenous ingot can be obtained. As a result, the aluminum rolled plate can be obtained more easily.

[0038] The heating temperature and holding time in the homogenization treatment may be appropriately set depending on the size and chemical composition of the ingot, etc. For example, the holding temperature in the homogenization treatment may be appropriately set within the range of 450° C. to 580° C. The holding time in the homogenization treatment may be appropriately set within the range of 3 hours to 24 hours, for example.

[0039] [Hot rolling process] In the hot rolling process, the ingot is hot-rolled to produce an aluminum rolled plate. The rolling conditions in the hot rolling process may be appropriately set according to the chemical composition of the ingot. For example, the rolling start temperature in the hot rolling process may be appropriately set within a range of, for example, 350°C to 560°C. In addition, the reduction rate in the hot rolling process, that is, the ratio of the thickness reduction amount by hot rolling to the thickness of the ingot, may be appropriately set according to the thickness of the aluminum rolled plate to be finally obtained and the desired reduction rate during cold rolling. For example, when the desired thickness of the aluminum rolled plate is 2.4 mm or less, the reduction rate in hot rolling may be set so that the thickness of the aluminum rolled plate after hot rolling is 6 mm or more.

[0040] [Cold rolling process] In the cold rolling step, the aluminum rolled plate obtained in the hot rolling step is subjected to cold rolling to reduce the thickness of the aluminum rolled plate to a desired thickness. In the cold rolling step, the thickness of the aluminum rolled plate may be reduced to the desired thickness by one rolling step, or may be reduced to the desired thickness by two or more rolling steps.

[0041] [Annealing process] The annealing step is performed between the hot rolling step and the cold rolling step and / or during the cold rolling step. The number of times the annealing step is performed in the manufacturing method may be one or more. That is, in the manufacturing method, the annealing step may be performed between the hot rolling step and the cold rolling step, or between any rolling pass in the cold rolling step and the next rolling pass of the rolling pass. In addition, the annealing step may be performed multiple times between the completion of the hot rolling step and the final rolling pass in the cold rolling step. From the viewpoint of more easily obtaining the aluminum rolled plate, it is preferable to perform the annealing step between the hot rolling step and the cold rolling step.

[0042] The heating temperature in the annealing step may be equal to or lower than the solidus temperature of the rolled aluminum sheet in order to avoid melting of the rolled aluminum sheet. The holding time in the annealing step may be equal to or longer than 12 hours. In the annealing step, the crystal grains of the rolled aluminum sheet are sufficiently grown, so that the rolled aluminum sheet can be easily obtained.

[0043] The heating temperature in the annealing step is preferably 550°C or higher and lower than the solidus temperature of the aluminum rolled sheet, more preferably 560°C or higher and lower than the solidus temperature of the aluminum rolled sheet, and even more preferably 570°C or higher and lower than the solidus temperature of the aluminum rolled sheet. In this way, by heating the aluminum rolled sheet at a relatively high temperature in the annealing step, the size of the crystal grains of the aluminum rolled sheet can be made larger. As a result, it is easier to obtain an aluminum rolled sheet that has a wood grain pattern after anodizing.

[0044] In the manufacturing method, the aluminum rolled sheet is cold-rolled so that the reduction ratio of the aluminum rolled sheet after the annealing step, i.e., the ratio of the reduction amount of the aluminum rolled sheet after the annealing step to the thickness of the aluminum rolled sheet at the time of completing the annealing step, is 60% or more. In this way, by performing cold rolling of the aluminum rolled sheet at a relatively high processing rate after the crystal grains of the aluminum rolled sheet are sufficiently grown in the annealing step, the crystal grains of the aluminum rolled sheet can be sufficiently stretched in the rolling direction. As a result, it is possible to easily obtain an aluminum rolled sheet that has a wood grain pattern after anodizing treatment. From the viewpoint of more reliably obtaining such an effect, the reduction ratio of the aluminum rolled sheet after the annealing step is preferably 70% or more, more preferably 80% or more.

[0045] [Other steps] The aluminum rolled plate obtained by the manufacturing method may be used as it is for the manufacture of an aluminum member. In addition, the aluminum rolled plate obtained in the cold rolling process may be subjected to a heat treatment as long as the metal structure of the aluminum rolled plate is not damaged. For example, the manufacturing method may include a solution treatment process in which the aluminum rolled plate obtained in the cold rolling process is heated to perform a solution treatment, and then quenched. By performing a solution treatment on the aluminum rolled plate, the mechanical properties of the aluminum rolled plate can be adjusted. The heating temperature, heating time, and heating method in the solution treatment may be appropriately set according to the chemical composition of the aluminum rolled plate.

[0046] (Aluminum components and their manufacturing methods) The rolled aluminum plate after the cold rolling process has a metal structure in which a wood grain pattern appears after anodizing. Therefore, by anodizing the rolled aluminum plate after the cold rolling process, an aluminum member having a wood grain pattern can be obtained. The aluminum member thus obtained has a base material made of the rolled aluminum plate and an anodized coating formed on the base material. The shape of the aluminum member is not particularly limited. For example, an aluminum member having a desired shape can be obtained by forming the rolled aluminum plate into a desired shape by bending, pressing, or other forming processes, and then anodizing the aluminum plate.

[0047] The specific treatment conditions for the anodizing treatment are not particularly limited as long as the conditions are such that a porous anodized aluminum film can be formed. For example, in the anodizing treatment, a porous anodized aluminum film can be formed on the surface of the substrate by performing direct current electrolysis in an aqueous sulfuric acid solution. In addition, before the substrate is anodized, pretreatments for the anodizing treatment, such as degreasing, alkaline cleaning, acid cleaning, and chemical polishing, can be performed as necessary.

[0048] From the viewpoint of making the wood grain pattern of the aluminum member more prominent and enhancing the design, it is preferable that the anodized aluminum film is colored. The method of coloring the anodized aluminum film is not particularly limited and may take various forms.

[0049] For example, the anodized film may be colored using a dye. In this case, for example, the pores of the anodized film are impregnated with a dye, and then a sealing treatment is performed to close the pores, thereby coloring the anodized film. The dye used for dyeing the anodized film is not particularly limited, and dyes having various colors such as red dyes, blue dyes, green dyes, purple dyes, orange dyes, brown dyes, brown dyes, and yellow dyes can be used. In addition, the dyed anodized film may contain one type of dye, or may contain two or more types of dyes. From the viewpoint of making the texture of the aluminum member closer to the texture of wood, it is preferable that the dyed anodized film contains a brown dye. As the brown dye, for example, "TAC Orange-LH", "TAC Orange-CH", "TAC Brown-GR" and "TAC Brown-RH" manufactured by Okuno Chemical Industries Co., Ltd. can be used.

[0050] The anodized aluminum film may be colored using a metal compound. In this case, for example, the metal compound is precipitated in the pores of the anodized aluminum film, and then the pores are sealed to color the anodized aluminum film.

[0051] It is preferable that the average value of the amplitude of components having a spatial frequency of 0.2 cycles / mm or more and 2.0 cycles / mm or less in a spatial frequency spectrum obtained by applying Fourier transform processing to a grayscale image of the surface of the aluminum member in a direction perpendicular to the rolling direction is three or more times the average value of the amplitude of components having a spatial frequency of 0.2 cycles / mm or more and 2.0 cycles / mm or less in a spatial frequency spectrum obtained by applying Fourier transform processing to the grayscale image in the rolling direction.

[0052] The distribution of gradation in the rolling direction of the aluminum member in the grayscale image can be expressed as a sum of sine waves having various wavelengths. Therefore, the spatial frequency spectrum obtained by performing fast Fourier transform processing on the grayscale image in the rolling direction shows the average periodicity of the surface pattern of the aluminum member in the rolling direction of the base material. When the surface pattern of the aluminum member changes periodically in the rolling direction, the amplitude of the spatial frequency component corresponding to the period of the change in the pattern in the rolling direction becomes large.

[0053] Similarly, the distribution of gradations in the direction perpendicular to the rolling direction in the grayscale image can be expressed as a sum of sine waves having various wavelengths. Therefore, the spatial frequency spectrum obtained by performing fast Fourier transform processing on the grayscale image in the direction perpendicular to the rolling direction shows the average periodicity of the surface pattern of the aluminum member in the direction perpendicular to the rolling direction of the base material. If the surface pattern of the aluminum member changes periodically in the direction perpendicular to the rolling direction, the amplitude of the spatial frequency component corresponding to the period of the change in the pattern in the direction perpendicular to the rolling direction becomes large.

[0054] Therefore, on the surface of an aluminum member having a ratio of the average values ​​of the spatial frequency components within the above-mentioned specific range, a pattern appears that changes periodically at a relatively short period in the direction perpendicular to the rolling direction of the base material, but the periodic changes are small in the rolling direction of the base material. Therefore, the surface of an aluminum member having such characteristics has a pattern that is closer to that of natural wood grain.

[0055] The method for generating the spatial frequency spectrum is as follows. First, the surface of the aluminum member is imaged to obtain a grayscale image. The method for imaging the aluminum member may be any method that can reproduce the pattern on the surface of the aluminum member. For example, the surface of the aluminum member may be imaged using a scanner or digital camera, and the obtained color image may be converted into a grayscale image. Furthermore, the grayscale image may be subjected to image processing such as smoothing, if necessary.

[0056] On the grayscale image thus obtained, a plurality of measurement areas extending in the direction in which the fast Fourier transform is applied (i.e., either the direction perpendicular to the rolling direction or the rolling direction) are randomly set. The width of each measurement area may be set to, for example, one pixel, and the length may be set so that the length of the actual aluminum member is in the range of 3 mm to 5 mm. A fast Fourier transform process is applied to each of such measurement areas in the extension direction of the measurement area to generate a spatial frequency spectrum in each measurement area. Then, by averaging these spatial frequency spectra, a spatial frequency spectrum in the rolling direction or the direction perpendicular to the rolling direction can be obtained. EXAMPLES

[0057] Example 1 An embodiment of the rolled aluminum sheet and its manufacturing method will be described. The rolled aluminum sheet of this embodiment is made of aluminum or an aluminum alloy. The rolled aluminum sheet has a metal structure including crystal grains having a length of 200 μm or more in a direction perpendicular to the rolling direction in a cross section perpendicular to the rolling direction.

[0058] The aluminum rolled plate of this example (hereinafter referred to as "rolled plate A1") is made of a 6000 series aluminum alloy. More specifically, the 6000 series aluminum alloy constituting the rolled plate A1 has a chemical composition containing 1.0 mass% Si, 0.03 mass% Fe, and 0.53 mass% Mg, with the balance being Al and unavoidable impurities.

[0059] The manufacturing method of the rolled sheet A1 is, for example, as follows: First, an ingot having the above-mentioned chemical composition is produced by DC casting, and then the ingot is held at a temperature of 560° C. for 12 hours for homogenization.

[0060] The ingot that has undergone the homogenization treatment is hot-rolled under conditions where the rolling start temperature is 400°C to produce an aluminum rolled plate with a thickness of 6 mm. The aluminum rolled plate is then annealed by heating at a temperature of 580°C for 25 hours. The annealed aluminum rolled plate is cold-rolled to reduce the thickness of the aluminum rolled plate to 0.8 mm. Through the above steps, the rolled plate A1 can be obtained.

[0061] FIG. 1 shows an enlarged photograph of a cross section perpendicular to the rolling direction of the rolled sheet A1. As shown in FIG. 1, the cross section perpendicular to the rolling direction of the rolled sheet A1 contains crystal grains whose length in the direction perpendicular to the rolling direction is 200 μm or more. In addition, the average thickness of the crystal grains in the cross section perpendicular to the rolling direction of the rolled sheet A1, calculated based on FIG. 1, is 54 μm, and the average width is 680 μm. Therefore, the ratio of the average width to the average thickness of the crystal grains in the rolled sheet A1 is 1259%.

[0062] An enlarged photograph of a cross section perpendicular to the rolling direction of the rolled sheet A1 is shown in Fig. 2. By comparing Fig. 1 with Fig. 2, it can be seen that the crystal grains in the rolled sheet A1 are elongated in the rolling direction.

[0063] The rolled aluminum sheet of this example has a metal structure containing crystal grains having a length of 200 μm or more in the direction perpendicular to the rolling direction in a cross section perpendicular to the rolling direction. By forming an alumite coating by anodizing the rolled aluminum sheet having such a metal structure, it is possible to impart a wood grain pattern to the surface of the rolled aluminum sheet after the anodizing treatment.

[0064] Example 2 In this example, an aluminum member having a wood grain pattern will be described. As shown in Fig. 3, the aluminum member 1 of this example has a base material 2 made of a rolled aluminum plate and an anodized coating 3 formed on the base material 2. The rolled aluminum plate constituting the base material has a metal structure including crystal grains having a length of 200 µm or more in the direction perpendicular to the rolling direction in a cross section perpendicular to the rolling direction.

[0065] The aluminum members of the present example (Table 1, aluminum members B1 to B4) are obtained, for example, by subjecting the rolled sheet A1 of Example 1 to anodizing treatment. The aluminum members of the present example are produced, for example, by the following method.

[0066] Aluminum component B1 After applying a tensile pre-strain of 2% to the rolled sheet A1, the rolled sheet A1 is held at 100°C for 6 hours for heat treatment. The rolled sheet A1 is then pre-treated for anodizing. In the pre-treatment, the rolled sheet A1 is first washed with a 5% aqueous sodium hydroxide solution at 55°C. The rolled sheet A1 is then washed with 30% nitric acid at room temperature. The rolled sheet A1 is then immersed in a chemical polishing solution at 85°C, which is a mixture of phosphoric acid and sulfuric acid in a volume ratio of 3:7, for chemical polishing. The rolled sheet A1 is then washed with 30% nitric acid at room temperature.

[0067] After the above pretreatment, the rolled sheet A1 is subjected to anodizing treatment. In the anodizing treatment, the rolled sheet A1 is immersed in 15% sulfuric acid at a temperature of 20° C. and subjected to a current of 20 mA / cm 2 A porous alumite coating is formed on the surface of the rolled sheet A1 by performing DC electrolysis for 35 minutes at a current density of 1000 .mu.m or more. In this manner, the aluminum member B1 can be obtained.

[0068] Aluminum material B2 After applying a tensile prestrain of 2% to the rolled sheet A1, the rolled sheet A1 is heat-treated by holding it at 100°C for 6 hours. Next, the rolled sheet A1 is immersed in a 10% aqueous sodium hydroxide solution for 40 minutes, and then the aqueous sodium hydroxide solution adhering to the rolled sheet A1 is washed off with 10% nitric acid. Then, the rolled sheet A1 is pretreated for anodizing by the method described above.

[0069] After the pretreatment, the rolled sheet A1 is anodized. In the anodization, the rolled sheet A1 is immersed in 15% sulfuric acid at a temperature of 20°C and is supplied with a current of 10 mA / cm 2 A porous alumite coating is formed on the surface of the rolled sheet A1 by performing DC electrolysis for 35 minutes at a current density of 1000 .mu.m or more. In this manner, the aluminum member B2 can be obtained.

[0070] Aluminum material B3 The manufacturing method of the aluminum member B3 is the same as the manufacturing method of the aluminum member B2, except that before applying tensile prestrain to the rolled sheet A1, the rolled sheet A1 is heated at a temperature of 570°C for 10 seconds to perform a solution treatment, and the time for which the rolled sheet A1 is immersed in the 10% sodium hydroxide aqueous solution is changed to 120 minutes.

[0071] Aluminum material B4 The method for producing the aluminum member B4 is the same as the method for producing the aluminum member B2, except that the time for immersing the rolled plate A1 in the 10% sodium hydroxide aqueous solution is changed to 120 minutes.

[0072] The aluminum members B1 to B4 obtained as described above are immersed in a brown dye to impregnate the pores in the anodized aluminum film with the dye, and then a sealing treatment is performed to close the pores in the anodized aluminum film.

[0073] The surface patterns of the aluminum members B1 to B4 determined by visual observation are shown in Table 1. As an example of the surface patterns of the aluminum members B1 to B4, an enlarged photograph of the surface of the aluminum member B4 is shown in Fig. 4.

[0074] 5 to 8 show spatial frequency spectra obtained by applying Fourier transform processing to the grayscale images of the surfaces of the aluminum members B1 to B4 in the rolling direction and in the direction perpendicular to the rolling direction. The vertical axis of Fig. 5 to Fig. 8 represents the spatial frequency component amplitude, and the horizontal axis represents the spatial frequency.

[0075] The method for creating a spatial frequency spectrum is specifically as follows. First, an image of an aluminum part is captured to obtain a color image of the pattern on the surface of the aluminum part. This color image is converted into a grayscale image, and then smoothed to remove noise. As a filter used for the smoothing process, for example, an averaging filter that averages the gradation of a square area of ​​1 mm length x 1 mm width may be used.

[0076] Next, 20 measurement areas extending in either the direction perpendicular to the rolling direction or the rolling direction are set randomly on the grayscale image. The width of each measurement area may be set to, for example, 1 pixel, and the length may be set to a range of 3 mm to 5 mm in the actual aluminum member. A fast Fourier transform process is performed on each of such measurement areas in the extension direction of the measurement area to generate a spatial frequency spectrum in each measurement area. Then, by averaging these spatial frequency spectra, a spatial frequency spectrum in the rolling direction or the direction perpendicular to the rolling direction can be obtained.

[0077] The average value X1 of the amplitude of the components having a spatial frequency of 0.2 cycles / mm or more and 2.0 cycles / mm or less in the spatial frequency spectrum in the rolling direction, and the average value X2 of the amplitude of the components having a spatial frequency of 0.2 cycles / mm or more and 2.0 cycles / mm or less in the spatial frequency spectrum in the direction perpendicular to the rolling direction, which are calculated based on these spatial frequency spectra, are as shown in Table 1.

[0078] [Table 1]

[0079] As shown in Table 1 and Fig. 4, the surfaces of the aluminum members B1 to B4 have a wood grain pattern that is visually judged to be similar to wood grain. In addition, as shown in Figs. 5 to 8, when the spatial frequency spectrum in the direction perpendicular to the rolling direction of each aluminum member is compared with the spatial frequency spectrum in the rolling direction, the amplitude of a component having a relatively low spatial frequency in the spatial frequency spectrum in the direction perpendicular to the rolling direction is larger than the amplitude of the corresponding component in the spatial frequency spectrum in the rolling direction in each aluminum member. As a result, as shown in Table 1, the ratio X2 / X1 of the average value X1 of the amplitude in the rolling direction to the average value X2 of the amplitude in the direction perpendicular to the rolling direction of the aluminum members B1 to B4 is 3 or more.

[0080] Comparative Example 1 In this example, an example of an aluminum rolled plate that does not have the specific metal structure will be described. The aluminum rolled plate of this example (hereinafter referred to as "rolled plate C1") is made of a 6000 series aluminum alloy. More specifically, the 6000 series aluminum alloy constituting the rolled plate B1 has a chemical composition that includes 0.6 mass% Si, 0.2 mass% Fe, 0.6 mass% Mg, and 0.01 mass% Ti, with the balance being Al and unavoidable impurities.

[0081] The manufacturing method of the rolled sheet C1 is, for example, as follows: First, an ingot having the above-mentioned chemical composition is produced by DC casting, and then the ingot is held at a temperature of 550° C. for 10 hours for homogenization.

[0082] The ingot after the homogenization treatment is hot-rolled at a rolling start temperature of 480°C to produce an aluminum rolled plate with a thickness of 3 mm. The aluminum rolled plate is then cold-rolled without annealing to reduce the thickness of the aluminum rolled plate to 1.0 mm. The above steps produce the rolled plate C1.

[0083] Fig. 9 shows an enlarged photograph of a cross section perpendicular to the rolling direction of the rolled sheet C1. Fig. 10 shows an enlarged photograph of a cross section perpendicular to the rolling direction of the rolled sheet C1. As can be seen from Figs. 9 and 10, the metal structure of the rolled sheet C1 is a fibrous structure, so that the exact values ​​of the length of the crystal grains in the direction perpendicular to the rolling direction and the average thickness of the crystal grains cannot be calculated. However, it is clear that the length of the crystal grains in the direction perpendicular to the rolling direction and the average thickness of the crystal grains in the rolled sheet C1 are sufficiently smaller than those in the rolled sheet A1. Even if an anodizing process is performed on an aluminum rolled sheet having such a metal structure, no woodgrain pattern appears on the surface.

[0084] Comparative Example 2 In this example, an example of an aluminum member that does not have a wood grain pattern will be described. The aluminum member of this example (Table 2, aluminum member D1) is obtained, for example, by subjecting the rolled plate C1 of Comparative Example 1 to anodizing treatment. The manufacturing method of the aluminum member of this example is, for example, as follows.

[0085] First, the rolled sheet C1 is subjected to a pretreatment for anodizing. The pretreatment method is the same as that in Example 2. Then, the rolled sheet C1 is subjected to anodizing. In the anodizing, the rolled sheet C1 is immersed in 15% sulfuric acid at a temperature of 20° C. and is anodized at 10 mA / cm 2 A porous alumite coating is formed on the surface of the rolled sheet C1 by performing DC electrolysis for 35 minutes at a current density of 1000 μm to 1000 μm. In this manner, the aluminum member D1 can be obtained.

[0086] Table 2 shows the surface pattern of the aluminum member D1 judged by visual observation. FIG. 11 shows the spatial frequency spectrum obtained by performing Fourier transform processing on the grayscale image of the surface of the aluminum member D1 in the rolling direction and the spatial frequency spectrum obtained by performing Fourier transform processing in the direction perpendicular to the rolling direction. The vertical axis of FIG. 11 is the spatial frequency component amplitude, and the horizontal axis is the spatial frequency. Table 2 also shows the average value X1 of the amplitude of the component having a spatial frequency of 0.2 cycles / mm or more and 2.0 cycles / mm or less in the spatial frequency spectrum in the rolling direction, which are calculated based on these spatial frequency spectra, and the average value X2 of the amplitude of the component having a spatial frequency of 0.2 cycles / mm or more and 2.0 cycles / mm or less in the spatial frequency spectrum in the direction perpendicular to the rolling direction. The method of creating the spatial frequency spectrum of the aluminum member D1 is the same as in Example 2.

[0087] [Table 2]

[0088] As shown in Table 2, the surface of the aluminum member D1 has a generally uniform color tone and does not have a pattern resulting from differences in surface contrast. In addition, as shown in Fig. 11, when the spatial frequency spectrum of the aluminum member D1 in the direction perpendicular to the rolling direction is compared with the spatial frequency spectrum in the rolling direction, the difference between the amplitude of each spatial frequency component in the spatial frequency spectrum in the direction perpendicular to the rolling direction and the amplitude of the corresponding component in the spatial frequency spectrum in the rolling direction is smaller than that of the aluminum members B1 to B4. As a result, as shown in Table 2, the ratio X2 / X1 of the average value X1 of the amplitude in the rolling direction of the aluminum member D1 to the average value X2 of the amplitude in the direction perpendicular to the rolling direction is less than 3.

[0089] Therefore, from a comparison between Examples 1 and 2 and Comparative Examples 1 and 2, it can be understood that by subjecting a rolled aluminum sheet having the above-mentioned specific metal structure to anodizing treatment, a woodgrain pattern appears on the surface of the aluminum member.

[0090] While the aluminum rolled plate, aluminum member, and manufacturing methods thereof have been described above based on Examples 1 and 2, the specific embodiments of the aluminum rolled plate, aluminum member, and manufacturing methods thereof according to the present invention are not limited to those of Examples 1 and 2, and the configurations can be appropriately changed without departing from the spirit of the present invention.

[0091] For example, the rolled aluminum sheet may have the following aspects (1) to (6).

[0092] [1] An aluminum rolled plate made of aluminum or an aluminum alloy, An aluminum rolled sheet containing crystal grains whose length in the direction perpendicular to the rolling direction is 200 μm or more. [2] The aluminum rolled sheet according to [1], in which the ratio of the average width to the average thickness of crystal grains in a cross section perpendicular to the rolling direction is 250% or more. [3] The aluminum rolled sheet according to [1] or [2], wherein the aluminum rolled sheet is made of an aluminum alloy having a Zn content of less than 5.0 mass%.

[0093] [4] The aluminum rolled sheet according to [3], wherein the content of Fe in the aluminum alloy is 0.2 mass% or less. [5] The aluminum rolled sheet according to [3] or [4], wherein the Mn content in the aluminum alloy is less than 0.8 mass%. [6] The aluminum rolled sheet according to any one of [1] to [5], wherein the aluminum alloy is a 6000 series alloy.

[0094] The aluminum member may have the following aspects according to [7] to [9].

[0095] [7] An aluminum member having a base material made of the rolled aluminum plate according to any one of [1] to [6] and an anodized aluminum coating formed on the base material. [8] The aluminum member according to [7], wherein the anodized coating is colored. [9] The aluminum member according to [8], wherein in a spatial frequency spectrum obtained by applying Fourier transform processing to a grayscale image of the surface of the aluminum member in a direction perpendicular to the rolling direction, the average amplitude of components having a spatial frequency of 0.2 cycles / mm or more and 2.0 cycles / mm or less is at least three times the average amplitude of components having a spatial frequency of 0.2 cycles / mm or more and 2.0 cycles / mm or less in a spatial frequency spectrum obtained by applying Fourier transform processing to the grayscale image in the rolling direction.

[0096] The method for producing the rolled aluminum sheet may take the following aspect

[10] .

[0097]

[10] A method for producing an aluminum rolled sheet according to any one of [1] to [6], A casting step for producing an ingot made of aluminum or an aluminum alloy; a hot rolling step of producing an aluminum rolled plate by hot rolling the ingot; a cold rolling step of cold rolling the aluminum rolled plate; and an annealing step of annealing the aluminum rolled sheet between the hot rolling step and the cold rolling step and / or during the cold rolling step, The heating temperature in the annealing step is 550° C. or higher, and the holding time is 12 hours or longer; The reduction ratio of the aluminum rolled plate after the annealing step is 60% or more. A method for manufacturing rolled aluminum sheets.

[0098] The method for manufacturing the aluminum member may take the following aspect

[11] .

[11] A substrate is produced from an aluminum rolled plate obtained by the method for producing an aluminum rolled plate according to

[10] , The method for manufacturing an aluminum member includes anodizing the base material to form an alumite coating on the base material. [Explanation of symbols]

[0099] 1 Aluminum components 2 Base material 3 Anodized coating

Claims

1. An aluminum rolled plate made of aluminum or an aluminum alloy, An aluminum rolled sheet, the cross section of which perpendicular to the rolling direction contains crystal grains having a length of 200 μm or more in the direction perpendicular to the rolling direction.

2. 2. The aluminum rolled sheet according to claim 1, wherein the ratio of the average width to the average thickness of crystal grains in a cross section perpendicular to the rolling direction is 250% or more.

3. 3. The aluminum rolled sheet according to claim 2, wherein the aluminum rolled sheet is made of an aluminum alloy having a Zn content of less than 5.0 mass%.

4. The aluminum rolled sheet according to claim 3, wherein the aluminum alloy has an Fe content of 0.2 mass% or less.

5. The aluminum rolled sheet according to claim 3, wherein the aluminum alloy has a Mn content of less than 0.8 mass%.

6. 2. The aluminum sheet of claim 1, wherein the aluminum alloy is a 6000 series alloy.

7. An aluminum member having a base material made of the rolled aluminum plate according to any one of claims 1 to 6 and an anodized aluminum coating formed on the base material.

8. The aluminum member according to claim 7 , wherein the anodized coating is colored.

9. 9. The aluminum member according to claim 8, wherein an average value of the amplitude of components having a spatial frequency of 0.2 cycles / mm or more and 2.0 cycles / mm or less in a spatial frequency spectrum obtained by applying Fourier transform processing to a grayscale image of the surface of the aluminum member in a direction perpendicular to the rolling direction is three or more times the average value of the amplitude of components having a spatial frequency of 0.2 cycles / mm or more and 2.0 cycles / mm or less in a spatial frequency spectrum obtained by applying Fourier transform processing to the grayscale image in the rolling direction.

10. A method for producing an aluminum rolled sheet according to any one of claims 1 to 6, A casting step for producing an ingot made of aluminum or an aluminum alloy; a hot rolling step of producing an aluminum rolled plate by hot rolling the ingot; a cold rolling step of cold rolling the aluminum rolled plate; An annealing step of annealing the aluminum rolled sheet between the hot rolling step and the cold rolling step and / or during the cold rolling step, The heating temperature in the annealing step is 550° C. or higher, and the holding time is 12 hours or longer; The reduction ratio of the aluminum rolled plate after the annealing step is 60% or more. A method for manufacturing rolled aluminum sheets.

11. A substrate is produced from the aluminum rolled plate obtained by the method for producing an aluminum rolled plate according to claim 10, The method for manufacturing an aluminum member includes anodizing the base material to form an alumite coating on the base material.

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