Aluminum alloy sheet, method for producing the same, and aluminum member

Abstract

To provide an aluminum alloy sheet having high strength and also exhibiting good color tone even after anodizing treatment, a method for producing the aluminum alloy sheet, and an aluminum member obtained by using the aluminum alloy sheet.SOLUTION: An aluminum alloy sheet has a chemical composition comprising Si: 0.51 mass% or more to 0.68 mass% or less, Fe: 0.17 mass% or more to 0.33 mass% or less, and Mg: 0.49 mass% or more to 0.55 mass% or less, with the remainder consisting of Al and inevitable impurities. The aluminum alloy sheet has a tensile strength of 250 MPa or greater. When the color tone of the surface of the aluminum alloy sheet after anodizing treatment in a sulfuric acid bath is measured using a C light source, the L* value in the CIE 1976 (L*, a*, b*) color space on the surface is 80 or greater, and the b* value is -1.0 or more to less than 1.0.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] 6000 series aluminum alloy sheets have relatively high strength among aluminum alloys, and are therefore used in a variety of applications, such as housings for electronic devices, exterior materials for vehicles, building materials, etc. In recent years, in order to reduce the environmental impact of producing aluminum alloy sheets, studies have been made on the use of recycled materials recovered during the manufacturing, distribution, and disposal of aluminum products, such as aluminum scrap and used aluminum products, as part of the casting raw materials.

[0003] As an aluminum alloy constituting this type of aluminum alloy plate, for example, Patent Document 1 describes an aluminum alloy containing approximately 0.5 to 2.0 wt% Si, 0.2 to 0.4 wt% Fe, a maximum of 0.4 wt% Cu, a maximum of 0.5 wt% Mg, 0.02 to 0.1 wt% Mn, 0.01 to 0.1 wt% Cr, a maximum of 0.15 wt% Sr, a maximum of 0.15 wt% impurities, and Al. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-17976 Summary of the Invention [Problem to be solved by the invention]

[0005] Aluminum alloy sheets are sometimes anodized for purposes such as surface protection and decorativeness. However, when an aluminum alloy sheet made of the aluminum alloy of Patent Document 1 is anodized, the surface color of the aluminum alloy sheet may become dark or yellowish, and the grayish-white color of the aluminum alloy sheet may be lost. In particular, when recycled materials are used as casting raw materials, the concentration of elements other than aluminum in the aluminum alloy sheet is likely to be high due to foreign matter that could not be removed during the preparation and sorting process of the recycled materials and the chemical components of the aluminum alloy contained in the recycled materials. Therefore, as the proportion of recycled materials in the casting raw material increases, the color of the aluminum alloy sheet after anodizing is likely to be lost.

[0006] Moreover, from the viewpoint of using aluminum alloy sheets in applications requiring higher strength, there is a demand for further improvement in the strength of aluminum alloy sheets.

[0007] The present invention has been made in view of the above background, and aims to provide an aluminum alloy sheet having high strength and retaining a good color tone even after anodizing treatment, a method for producing the same, and an aluminum member obtained by using the aluminum alloy sheet. [Means for solving the problem]

[0008] One aspect of the present invention is a sintered body having a chemical composition comprising: Si (silicon): 0.51% by mass or more and 0.68% by mass or less; Fe (iron): 0.17% by mass or more and 0.33% by mass or less; and Mg (magnesium): 0.49% by mass or more and 0.55% by mass or less; and the balance being Al (aluminum) and unavoidable impurities; The tensile strength is 250 MPa or more, The aluminum alloy sheet has the characteristics that, when the color tone of the surface after anodizing in a sulfuric acid bath is measured using a C light source, the L* value of the surface in the CIE1976 (L*, a*, b*) color space is 80 or more and the b* value is -1.0 or more and less than 1.0.

[0009] Another aspect of the present invention is an aluminum member having a base material made of the aluminum alloy plate of the above aspect and an alumite film formed on the surface of the base material.

[0010] Still another aspect of the present invention is a method for manufacturing the aluminum alloy plate of the above aspect, casting an ingot having the chemical composition, holding the ingot at a temperature of 560°C or higher and 600°C or lower for 1 hour or longer to perform homogenization treatment, subsequently, performing hot rolling on the ingot under conditions such that the temperature of the rolled plate at the end of rolling is 300°C or higher and 380°C or lower to produce a rolled plate, performing cold rolling on the rolled plate, subsequently, heating the rolled plate to a temperature of 560°C or higher and then quenching to perform solution treatment, There is a method for manufacturing an aluminum alloy plate in which the rolled plate after the solution treatment is heated and artificial aging treatment is performed so that the heating temperature T and the holding time t satisfy the following Condition 1 or Condition 2. Condition 1: 130°C ≤ T ≤ 150°C and 1 hour ≤ t ≤ 24 hours Condition 2: 150°C < T ≤ 180°C and 1 hour ≤ t ≤ 15 hours

Advantages of the Invention

[0011] The aluminum alloy plate has the specific chemical composition, and has strength within the specific range and characteristics such that the color tone after anodic oxidation treatment is within the specific range. Such an aluminum alloy plate has high strength and also has a good color tone even after anodic oxidation treatment.

[0012] Further, according to the method for manufacturing the aluminum alloy plate, the aluminum alloy plate can be easily obtained.

[0013] Therefore, according to the above-described aspects, it is possible to provide an aluminum alloy sheet having high strength and maintaining a good color tone even after anodizing treatment, a manufacturing method thereof, and an aluminum member obtained by using this aluminum alloy sheet. DETAILED DESCRIPTION OF THE INVENTION

[0014] (aluminum alloy plate) The chemical composition, properties, and reasons for limiting the properties of the aluminum alloy plate will be explained below.

[0015] [Chemical composition] ·Si: 0.51 mass% or more and 0.68 mass% or less The aluminum alloy plate contains 0.51 mass % or more and 0.68 mass % or less of Si as an essential component. By setting the Si content in the aluminum alloy plate within the specific range, the strength of the aluminum alloy plate can be improved and the color tone of the aluminum alloy plate after anodizing treatment can be made closer to grayish white. In this case, even when recycled materials are used as a casting raw material for the aluminum alloy plate, the Si content in the aluminum alloy plate can be easily adjusted to fall within the specific range.

[0016] From the viewpoint of making the color tone of the aluminum alloy sheet after anodizing treatment closer to grayish white, the content of Si in the aluminum alloy sheet is preferably 0.51 mass% or more and 0.68 mass% or less, more preferably 0.51 mass% or more and 0.66 mass% or less, even more preferably 0.51 mass% or more and 0.64 mass% or less, still more preferably 0.52 mass% or more and 0.64 mass% or less, and particularly preferably 0.54 mass% or more and 0.64 mass% or less. If the content of Si in the aluminum alloy sheet is less than 0.51 mass% or more than 0.68 mass%, the color tone of the aluminum alloy sheet after anodizing treatment may become dark and easily take on a yellowish tinge.

[0017] ·Fe: 0.17 mass% or more and 0.33 mass% or less The aluminum alloy sheet contains 0.17% by mass or more and 0.33% by mass or less of Fe as an essential component. By setting the Fe content in the aluminum alloy sheet within the specific range, the color tone of the aluminum alloy sheet after anodizing treatment can be made closer to grayish white. In this case, even when recycled materials are used as a casting raw material for the aluminum alloy sheet, the Fe content in the aluminum alloy sheet can be easily adjusted to fall within the specific range.

[0018] From the viewpoint of making the color tone of the aluminum alloy sheet after anodizing treatment closer to grayish white, the content of Fe in the aluminum alloy sheet is preferably 0.17% by mass or more and 0.32% by mass or less, more preferably 0.17% by mass or more and 0.31% by mass or less, even more preferably 0.17% by mass or more and 0.30% by mass or less, and even more preferably 0.17% by mass or more and 0.29% by mass or less. If the content of Fe in the aluminum alloy sheet exceeds 0.33% by mass, the color tone of the aluminum alloy sheet after anodizing treatment may become dark and may easily become yellowish.

[0019] ·Mg: 0.49 mass% or more and 0.55 mass% or less The aluminum alloy plate contains 0.49% by mass or more and 0.55% by mass or less of Mg as an essential component. By setting the Mg content in the aluminum alloy plate within the specific range, the strength of the aluminum alloy plate can be improved and the color tone of the aluminum alloy plate after anodizing treatment can be made closer to grayish white. In this case, even when recycled materials are used as a casting raw material for the aluminum alloy plate, the Mg content in the aluminum alloy plate can be easily adjusted to fall within the specific range.

[0020] The Mg content in the aluminum alloy sheet is preferably 0.50% by mass or more, more preferably 0.51% by mass or more, and even more preferably 0.52% by mass or more. In this case, the color tone of the aluminum alloy sheet after anodizing treatment can be closer to grayish white. If the Mg content in the aluminum alloy sheet is less than 0.49% by mass, the color tone of the aluminum alloy sheet after anodizing treatment may become dark and yellowish.

[0021] Furthermore, the Mg content in the aluminum alloy sheet is preferably 0.54% by mass or less, and more preferably 0.53% by mass or less. In this case, the color tone of the aluminum alloy sheet after anodizing treatment can be closer to grayish white. If the Mg content in the aluminum alloy sheet exceeds 0.55% by mass, the color tone of the aluminum alloy sheet after anodizing treatment may become dark and yellowish.

[0022] When constituting a preferred range of the Mg content in the aluminum alloy sheet, the above-mentioned upper and lower limits of the Mg content can be combined arbitrarily. For example, the Mg content in the aluminum alloy sheet may be 0.50% by mass or more and 0.55% by mass or less, 0.51% by mass or more and 0.55% by mass or less, 0.52% by mass or more and 0.55% by mass or less, or 0.49% by mass or more and 0.54% by mass or less.

[0023] As described above, by setting the contents of at least Si, Fe, and Mg in the specific ranges, the aluminum alloy sheet can improve its strength and exhibit a color tone close to grayish white after anodizing treatment. From the viewpoint of more reliably obtaining such effects, it is preferable that the content of Si in the aluminum alloy sheet is larger than the content of Mg.

[0024] The reason why high strength and good color tone after anodizing treatment can be achieved by setting the contents of Si, Fe, and Mg in the aluminum alloy sheet within the specific ranges is not necessarily clear, but the following reason is thought to be an example: When Si and Mg coexist in the aluminum alloy sheet, Mg2Si precipitates in the aluminum alloy sheet. The Mg2Si particles precipitated in the aluminum alloy sheet have the effect of improving the strength of the aluminum alloy sheet by precipitation strengthening.

[0025] On the other hand, as the Mg and Si contents in an aluminum alloy sheet increase, the number of Mg2Si particles formed in the aluminum alloy sheet increases, and coarse Mg2Si particles are more likely to form. Similarly, as the Fe content in an aluminum alloy sheet increases, intermetallic compound particles containing Fe, such as Al6Fe, are more likely to precipitate in the aluminum alloy sheet. When an aluminum alloy sheet containing these precipitates is anodized, the precipitates are incorporated into the anodized aluminum film, resulting in a decrease in the transparency of the anodized aluminum film. Therefore, it has been conventionally believed that the Si, Fe, and Mg contents must be reduced to achieve a grayish-white color tone after anodizing.

[0026] In contrast, in the aluminum alloy sheet, by setting the Si, Fe, and Mg contents within the respective specific ranges, it is believed that a portion of the Si reacts with Fe to form α-AlFeSi particles in the aluminum alloy sheet. The α-AlFeSi particles are oxidized during anodizing and become colorless and transparent. Therefore, even when the α-AlFeSi particles are incorporated into the anodized aluminum film, it is believed that the transparency of the anodized aluminum film is unlikely to be impaired. Furthermore, it is believed that the consumption of a portion of the Si in the formation of the α-AlFeSi particles can easily prevent the formation of an excessively large number of Mg2Si particles in the aluminum alloy sheet and the formation of coarse Mg2Si particles.

[0027] For the above reasons, it is considered that, in the aluminum alloy plate, by setting Si, Fe, and Mg within the specific ranges, it is possible to obtain the effect of precipitation strengthening by MgSi particles and avoid deterioration of color tone after anodizing treatment.

[0028] In addition to the essential components Si, Fe, and Mg, the aluminum alloy sheet may contain other elements within a range that does not impair the above-mentioned effects. For example, the aluminum alloy sheet may contain one or more elements selected from the group consisting of 0.08% by mass or less of copper (Cu), 0.08% by mass or less of manganese (Mn), 0.03% by mass or less of chromium (Cr), 0.05% by mass or less of zinc (Zn), and 0.05% by mass or less of titanium (Ti).

[0029] More specifically, the aluminum alloy plate may have a chemical composition containing Si: 0.51% by mass or more and 0.68% by mass or less, Fe: 0.17% by mass or more and 0.33% by mass or less, Mg: 0.49% by mass or more and 0.55% by mass or less, Cu: 0.08% by mass or less, Mn: 0.08% by mass or less, Cr: 0.03% by mass or less, Zn: 0.05% by mass or less, and Ti: 0.05% by mass or less, with the balance being Al and unavoidable impurities.

[0030] The aluminum alloy plate may have a chemical composition including: Si: 0.51% by mass or more and 0.68% by mass or less, Fe: 0.17% by mass or more and 0.33% by mass or less, Mg: 0.50% by mass or more and 0.55% by mass or less, Cu: 0.08% by mass or less, Mn: 0.08% by mass or less, Cr: 0.03% by mass or less, Zn: 0.05% by mass or less, and Ti: 0.05% by mass or less, with the balance being Al and unavoidable impurities.

[0031] The aluminum alloy plate may have a chemical composition that contains Si: 0.51% by mass or more and 0.66% by mass or less, Fe: 0.17% by mass or more and 0.33% by mass or less, and Mg: 0.50% by mass or more and 0.55% by mass or less, and further contains one or more elements selected from the group consisting of Cu: 0.08% by mass or less, Mn: 0.08% by mass or less, Cr: 0.03% by mass or less, Zn: 0.05% by mass or less, and Ti: 0.05% by mass or less, with the balance being Al and unavoidable impurities. Furthermore, the aluminum alloy plate may have a chemical composition that contains Si: 0.51% by mass or more and 0.66% by mass or less, Fe: 0.17% by mass or more and 0.33% by mass or less, and Mg: 0.52% by mass or more and 0.55% by mass or less, and further contains one or more elements selected from the group consisting of Cu: 0.08% by mass or less, Mn: 0.08% by mass or less, Cr: 0.03% by mass or less, Zn: 0.05% by mass or less, and Ti: 0.05% by mass or less, with the balance being Al and unavoidable impurities. Furthermore, the aluminum alloy plate may have a chemical composition that contains Si: 0.51% by mass or more and 0.64% by mass or less, Fe: 0.17% by mass or more and 0.33% by mass or less, and Mg: 0.49% by mass or more and 0.54% by mass or less, and further contains one or more elements selected from the group consisting of Cu: 0.08% by mass or less, Mn: 0.08% by mass or less, Cr: 0.03% by mass or less, Zn: 0.05% by mass or less, and Ti: 0.05% by mass or less, with the balance being Al and unavoidable impurities.

[0032] 〔conductivity〕 The electrical conductivity of the aluminum alloy sheet at a temperature of 15°C or higher and 25°C or lower is preferably 45% IACS or higher and 65% IACS or lower. The electrical conductivity of the aluminum alloy sheet is used as an index of the amount of solute elements dissolved in the Al matrix, and a higher electrical conductivity means a smaller amount of solute elements dissolved in the Al matrix. By setting the electrical conductivity of the aluminum alloy sheet within the specific range, the balance between the amount of solute elements dissolved in the Al matrix and the amount of precipitates such as MgSi particles can be optimized, making it easier to obtain an aluminum alloy sheet that combines high strength and a good color tone after anodizing treatment.

[0033] [Tensile strength and surface color after anodizing treatment] The aluminum alloy sheet has a tensile strength of 250 MPa or more. Furthermore, when the color tone of the surface of the aluminum alloy sheet after anodizing in a sulfuric acid bath is measured using illuminant C, the L* value of the surface in the CIE 1976 (L*, a*, b*) color space is 80 or more, and the b* value is -1.0 or more and less than 1.0. Such an aluminum alloy sheet is suitable for applications requiring both high strength and aesthetic design, such as housings for electronic devices.

[0034] (Method of manufacturing aluminum alloy plate) The aluminum alloy plate is produced, for example, by the following method.

[0035] 〔casting〕 In producing the aluminum alloy plate, first, an ingot having the specific chemical composition is cast. Although the casting method for the ingot is not particularly limited, it is preferable to cast the ingot by, for example, DC casting.

[0036] Casting raw materials can include virgin aluminum, intermediate alloys, and recycled materials. In this specification, "recycled materials" refers to pre-consumer recycled materials and post-consumer materials as defined in UL 2809. Pre-consumer recycled materials include scrap generated as waste during the manufacturing and distribution processes of aluminum products before they reach the end user. More specifically, pre-consumer materials include in-house scrap after rolling, which is made from aluminum material generated in a company's own factory, and scrap generated during the manufacturing process of aluminum products. Note that in-house scrap from casting, which is made from aluminum material before rolling, is not included in pre-consumer recycled materials.

[0037] Post-consumer materials also include aluminum products that can no longer be used for their intended purpose after being delivered to an end user, such as aluminum products that have been discarded after use by the end user.

[0038] In the production method, the ratio of recovered materials to the casting raw materials of the ingot is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. In this case, it is expected that the amount of virgin aluminum used in producing the aluminum alloy plate can be more easily reduced, and the environmental load associated with the production of the aluminum alloy plate can be alleviated.

[0039] In the manufacturing method, various types of aluminum scrap can be used as recovered materials, such as pre-consumer recycled materials derived from aluminum can presses (so-called UBCs) and window sashes, post-consumer materials derived from window sashes, pre-consumer recycled materials derived from computer casings, post-consumer materials derived from computer casings, pre-consumer recycled materials derived from bullet trains, post-consumer materials derived from bullet trains, pre-consumer recycled materials derived from automobiles, and post-consumer materials derived from automobiles. Furthermore, post-consumer materials called "zorba" can also be used as recovered materials. Zorba is specifically a mixture primarily composed of aluminum recovered from scrap generated by crushing scrapped automobiles and home appliances.

[0040] The casting raw material preferably contains one or more recycled materials selected from the group consisting of pre-consumer recycled materials derived from window sashes, post-consumer recycled materials derived from window sashes, pre-consumer recycled materials derived from computer casings, post-consumer recycled materials derived from computer casings, pre-consumer recycled materials derived from bullet trains, post-consumer recycled materials derived from bullet trains, pre-consumer recycled materials derived from automobiles, post-consumer recycled materials derived from automobiles, and Zorba. The chemical compositions of these recycled materials are often similar to those of the aluminum alloy sheet. Therefore, by using the recycled materials as the casting raw material, the proportion of recycled materials in the casting raw material can be more easily increased. As a result, the amount of virgin aluminum used in the production of the aluminum alloy sheet can be more easily reduced, which is expected to reduce the environmental impact associated with the production of the aluminum alloy sheet.

[0041] [Homogenization treatment] Next, the ingot is subjected to a homogenization treatment by being held at a temperature of 560°C or higher and 600°C or lower for one hour or longer. By setting the heating temperature and holding time in the homogenization treatment within the above-mentioned specific ranges, an aluminum alloy sheet exhibiting a grayish-white color after anodizing treatment can be more easily obtained. From the viewpoint of more reliably achieving this effect, the heating temperature in the homogenization treatment is preferably 570°C or higher and 590°C or lower. The reasons for this are thought to be, for example, as follows.

[0042] It is believed that α-AlFeSi particles and β-AlFeSi particles are formed in an ingot having the specific chemical composition. It is also known that β-AlFeSi particles undergo a phase transformation to α-AlFeSi particles at high temperatures, and the temperature at which the phase transformation from β-AlFeSi particles to α-AlFeSi particles begins is 553°C. Therefore, it is believed that by setting the heating temperature in the homogenization treatment of the ingot to 560°C or higher, the β-AlFeSi particles in the ingot can be transformed into α-AlFeSi particles.

[0043] Furthermore, since α-AlFeSi particles are oxidized and become transparent during anodizing as described above, it is believed that even when they are incorporated into an anodized film, they do not impair the transparency of the anodized film. On the other hand, when β-AlFeSi particles are incorporated into an anodized film, the transparency of the anodized film is likely to be impaired, which is thought to lead to a deterioration in the color tone of the aluminum alloy sheet after anodizing. Therefore, by setting the heating temperature during the homogenization treatment of the ingot to 560°C or higher, it is believed that the β-AlFeSi particles in the ingot can be phase-transformed into α-AlFeSi particles, thereby suppressing the decrease in transparency of the anodized film.

[0044] If the heating temperature in the homogenization treatment is too low, the color tone of the surface of the aluminum alloy sheet after the anodizing treatment tends to be dark. If the holding time in the homogenization treatment is too short, the homogenization of the ingot may be insufficient. Moreover, if the heating temperature in the homogenization treatment is too high, the ingot may locally melt during the homogenization treatment.

[0045] [Hot rolling] In the manufacturing method, after the homogenization treatment is completed, the ingot is hot-rolled to produce a rolled plate under conditions such that the temperature of the rolled plate at the end of rolling is 300° C. to 380° C. By setting the temperature of the rolled plate at the end of hot rolling within the specific range, an aluminum alloy plate that exhibits a grayish-white color after anodizing treatment can be more easily obtained.

[0046] [Cold rolling] In the manufacturing method, after the hot rolling is completed, the rolled sheet is subjected to cold rolling to reduce the thickness of the rolled sheet to a desired thickness. The specific mode of cold rolling is not particularly limited, and various modes can be used. For example, in cold rolling, the thickness of the rolled sheet may be reduced to the desired thickness by a single rolling pass, or by multiple rolling passes. Furthermore, if necessary, the rolled sheet may be heated and annealed before and / or during cold rolling.

[0047] [Solution treatment] After the cold rolling is completed, the rolled sheet is heated to a temperature of 560°C or higher and then quenched to perform a solution treatment. By setting the heating temperature of the rolled sheet during the solution treatment within the above-mentioned specific range, an aluminum alloy sheet that exhibits a grayish white color after anodizing can be more easily obtained.

[0048] The reasons for this are thought to be as follows: First, by setting the heating temperature in the solution treatment to 560°C or higher, it is thought that the β-AlFeSi particles present in the rolled sheet can be phase-transformed to α-AlFeSi particles, as in the homogenization treatment. Second, by setting the heating temperature in the solution treatment to 560°C or higher, it is thought that the Mg2Si particles in the rolled sheet can be solid-dissolved in the Al matrix.

[0049] As described above, it is believed that by setting the heating temperature in the solution treatment to 560°C or higher, it is possible to reduce the number of β-AlFeSi particles and coarse Mg2Si particles that affect the transparency of the anodized aluminum film. As a result, it is believed that it is possible to suppress the decrease in transparency of the anodized aluminum film and make the color tone of the aluminum alloy sheet after anodizing treatment closer to grayish white.

[0050] If the heating temperature in the solution treatment is too low, it may be difficult to bring the surface color of the aluminum alloy sheet after the anodizing treatment closer to grayish white. On the other hand, if the heating temperature of the aluminum alloy sheet in the solution treatment is too high, the aluminum alloy sheet may locally melt during the solution treatment. From the viewpoint of more reliably avoiding melting of the aluminum alloy sheet, the heating temperature of the aluminum alloy sheet in the solution treatment is preferably 600°C or less.

[0051] In the solution heat treatment, quenching may be performed immediately after the temperature of the aluminum alloy plate reaches the desired temperature, or after the temperature of the aluminum alloy plate reaches the desired temperature, the temperature above that temperature may be held for a desired time and then quenching may be performed. From the viewpoint of more easily obtaining an aluminum alloy plate that exhibits a grayish white color after anodic oxidation treatment, in the solution heat treatment, it is preferable to perform quenching after holding the aluminum alloy plate at a temperature of 560°C or higher for 20 seconds or longer.

[0052] 〔Artificial aging treatment〕 In the manufacturing method, the rolled plate after the solution heat treatment is heated so that the heating temperature T and the holding time t satisfy the following Condition 1 or Condition 2, and artificial aging treatment is performed. Condition 1: 130°C ≤ T ≤ 150°C and 1 hour ≤ t ≤ 24 hours Condition 2: 150°C < T ≤ 180°C and 1 hour ≤ t ≤ 15 hours

[0053] By setting the heating temperature and the holding time in the artificial aging treatment within the specific range, it is possible to improve the strength of the aluminum alloy plate while avoiding deterioration of the color tone of the aluminum alloy plate after anodic oxidation treatment.

[0054] If the heating temperature in the artificial aging treatment is too low or the holding time is too short, there is a risk of reducing the strength of the aluminum alloy plate. On the other hand, if the heating temperature in the artificial aging treatment is too high or the holding time is too long, there is a risk of deteriorating the color tone of the aluminum alloy plate after anodic oxidation treatment. This is considered to be because when the heating temperature in the artificial aging treatment is too high or the holding time is too long, coarse Mg2Si particles are likely to be formed in the aluminum alloy plate, and the transparency of the alumite film is impaired.

[0055] (Aluminum member)

[0056] An aluminum member can be obtained by anodizing the aluminum alloy plate. The aluminum member thus obtained has a substrate made of the aluminum alloy plate and an anodized aluminum coating formed on the substrate.

[0057] The specific conditions for the anodizing treatment are not particularly limited as long as they are conditions that allow the formation of a porous anodized aluminum film. 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 acidic aqueous solution such as sulfuric acid. Furthermore, before the anodizing treatment of the substrate, pretreatments for the anodizing treatment, such as degreasing, alkaline cleaning, acid cleaning, and chemical polishing, can be performed as necessary.

[0058] From the viewpoint of easily increasing the L* value of the surface of the aluminum member, the temperature of the electrolyte in the anodizing treatment is preferably 10°C or higher. From the same viewpoint, the electrolyte in the anodizing treatment is preferably sulfuric acid with a concentration of 25% or less. In addition, in the anodizing treatment, 2 It is preferable to carry out DC electrolysis at the following current density. [Example]

[0059] Example 1 Examples of the aluminum alloy sheet are described below. The aluminum alloy sheet has a chemical composition containing Si: 0.51% by mass to 0.68% by mass, Fe: 0.17% by mass to 0.33% by mass, and Mg: 0.49% by mass to 0.55% by mass, with the remainder consisting of Al and unavoidable impurities. The tensile strength of the aluminum alloy sheet is 250 MPa or more. When the color tone of the surface of the aluminum alloy sheet is measured after anodizing treatment using a sulfuric acid bath, the surface has a characteristic such that the L* value in the CIE 1976 (L*, a*, b*) color space is 80 or more and the b* value is -1.0 or more and less than 1.0.

[0060] The specific configuration of the aluminum alloy plate of this example and an example of its manufacturing method will be described. In producing the aluminum alloy plate of this example, an ingot having a chemical composition represented by any one of the alloy symbols of alloys A1 to A7 shown in Table 1 is cast by DC casting. In this case, recycled raw materials can be used for at least a part of the casting raw materials. In Table 1, "Bal." is a symbol indicating the remainder.

[0061] Next, the surface of the ingot is chamfered, and then the ingot is subjected to a homogenization treatment by being held at a temperature of 580°C for 10 hours. After the homogenization treatment, the ingot is hot rolled so that the temperature of the rolled plate at the end of rolling is 320°C, and a rolled plate having a thickness of 2.3 mm is produced.

[0062] Next, the rolled plate obtained by hot rolling is cold rolled to reduce the thickness of the rolled plate to 0.8 mm. After cold rolling, the rolled plate is heated to 570°C and held at 570°C for 20 seconds, after which it is quenched for solution treatment. Thereafter, the rolled plate is held at 150°C for 24 hours for artificial aging treatment. Through the above process, test materials S1 to S7 shown in Table 2 can be obtained.

[0063] Test materials R1 to R6 shown in Table 2 are test materials for comparison with test materials S1 to S7. The manufacturing method of test materials R1 to R6 is the same as that of test materials S1 to S7, except that an ingot having a chemical composition represented by the alloy symbol of one of alloys B1 to B6 shown in Table 1 is used.

[0064] The electrical conductivity, mechanical properties, and surface color tone after anodizing treatment of test materials S1 to S7 and test materials R1 to R6 are shown in Table 2. The evaluation methods for these properties are as follows.

[0065] 〔conductivity〕 The test material is placed in a thermostatic chamber maintained at 20°C, and the temperature of the test material is raised to 20°C. Then, the conductivity of the test material at a temperature of 20°C is measured using an eddy current conductivity meter ("SIGMATEST2.069" manufactured by Nippon Foerster Co., Ltd.).

[0066] [Mechanical properties] Three No. 5 test pieces, as specified in JIS Z2241:2011, were taken from each test material so that the rolling direction and the longitudinal direction were parallel. Using these test pieces, a tensile test was conducted based on JIS Z2241:2011, and the tensile strength, 0.2% proof stress, and elongation of each test piece were calculated based on the results of the tensile test. The arithmetic mean values ​​of the tensile strength, 0.2% proof stress, and elongation of the three test pieces were then used to determine the tensile strength, 0.2% proof stress, and elongation of each test material. The tensile strength, 0.2% proof stress, and elongation of each test material obtained in this manner are shown in Table 2.

[0067] [Surface color after anodizing treatment] Three test pieces were taken from each test material. The surfaces of these test pieces were subjected to a blasting treatment, followed by pretreatment for anodizing. In the pretreatment, the test pieces were first immersed in a 100g / L sodium hydroxide solution at 50°C for 60 seconds to etch the surface. Next, a chemical polishing solution was prepared by mixing phosphoric acid and sulfuric acid in a volume ratio of 7:3, and the test pieces were immersed in the chemical polishing solution at 85°C for 60 seconds to chemically polish the test material. After that, the test pieces were immersed in a nitric acid solution at 25°C for 60 seconds to perform a desmutting treatment.

[0068] After the pretreatment described above, the test piece was subjected to anodizing treatment. In the anodizing treatment, the test piece was immersed in a sulfuric acid aqueous solution with a concentration of 18 mass % at a temperature of 25°C, and subjected to a current of 10 mA / cm 2 A porous alumite film is formed on the surface of the test piece by performing direct current electrolysis for 25 minutes at a current density of 1000 kJ / s. After the anodizing treatment is completed, a sealing treatment is performed to close the pores in the alumite film.

[0069] The surface color tone of the test pieces obtained after the anodizing treatment is measured using a spectrophotometer ("Color Meter CC-iS" manufactured by Suga Test Instruments Co., Ltd.), and the L* and b* values ​​of each test piece in the CIE 1976 (L*, a*, b*) color space are calculated. The light source of the spectrophotometer is Illuminant C, and the aperture diameter is φ30 mm.

[0070] The arithmetic mean values ​​of the L* and b* values ​​of the three test pieces were taken as the L* and b* values ​​of the test material. The L* and b* values ​​of the test material obtained in this way are shown in Table 2.

[0071] [Table 1]

[0072] [Table 2]

[0073] As shown in Table 2, test materials S1 to S7 are composed of alloys A1 to A7 having chemical compositions within the above-mentioned specific ranges. Furthermore, the tensile strength and surface color tone after anodizing treatment of test materials S1 to S7 are both within the above-mentioned specific ranges. Therefore, test materials S1 to S7 have high strength and good color tone even after anodizing treatment.

[0074] On the other hand, the Fe content in the test material R1 is higher than the specific range, and therefore the surface color of the test material R1 after anodizing treatment tends to be yellowish. The contents of Si, Fe, Mg, and Zn in test material R2 are greater than the specific ranges, and therefore the surface color of test material R2 after anodizing tends to be dark. The Si content of test material R3 is lower than the specific range. The Fe, Mg, Cu, Mn, and Zn contents of test material R3 are higher than the specific range. Therefore, the surface color of test material R3 after anodizing is dark and tends to be yellowish.

[0075] The Si content of test material R4 is lower than the specific range. The Fe, Mg, Cu, Mn, and Zn contents of test material R4 are higher than the specific range. Therefore, the surface color of test material R4 after anodizing tends to be yellowish. The Si content of test material R5 is lower than the specific range. The Fe, Mg, Cu, Mn, and Zn contents of test material R5 are higher than the specific range. Therefore, the surface color of test material R5 after anodizing tends to be yellowish. The Si content of test material R6 is lower than the specific range. Also, the Mg and Mn contents of test material R6 are higher than the specific range. Therefore, the surface color of test material R6 after anodizing treatment tends to be yellowish.

[0076] Example 2 In this example, various changes in the manufacturing conditions of the aluminum alloy sheet will be described. To produce the aluminum alloy sheet of this example, first, an ingot having a chemical composition represented by alloy symbol A3 in Table 1 of Example 1 is cast. The ingot is then subjected to homogenization treatment, hot rolling, solution treatment, and artificial aging treatment using the same manufacturing method as that for test material S3 of Example 1, except that the treatment conditions for the homogenization treatment, hot rolling, solution treatment, and artificial aging treatment are changed to any of manufacturing conditions C1 to C6 shown in Table 3. Through the above steps, test materials S11 to S16 shown in Table 4 can be obtained.

[0077] Note that test materials R11 to R12 shown in Table 4 are test materials for comparison with test materials S11 to S16. The manufacturing method of test materials R11 to R12 is the same as the manufacturing method of test materials S11 to S16, except that the manufacturing conditions are changed to D1 or D2 shown in Table 3.

[0078] The electrical conductivity, mechanical properties, and surface color tone after anodizing treatment of test materials S11 to S16 and test materials R11 to R12 are shown in Table 4. The evaluation methods for these properties were the same as in Example 1.

[0079] [Table 3]

[0080] [Table 4]

[0081] As shown in Table 4, test materials S11 to S16 were produced by using ingots having the specific chemical compositions and performing the homogenization treatment, hot rolling, solution treatment, and artificial aging treatment under the specific conditions, respectively. Therefore, test materials S11 to S16 have high strength and good color tone even after anodizing treatment.

[0082] On the other hand, the heating temperature of the homogenization treatment for the test material R11 is lower than the specific range, and therefore the surface color of the test material R11 after the anodizing treatment tends to be dark. The heating conditions for the artificial aging treatment of test material R12 did not satisfy either condition 1 or condition 2. Therefore, the surface color of test material R12 after anodizing treatment was dark and prone to yellowish tint.

[0083] Although the aluminum alloy plate, aluminum member, and manufacturing methods thereof have been described above based on Examples 1 and 2, the specific embodiments of the aluminum alloy 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 within the scope that does not depart from the spirit of the present invention.

[0084] For example, the aluminum alloy plate may take the following forms (1) to (3).

[0085] [1] A chemical composition containing Si: 0.51% by mass or more and 0.68% by mass or less, Fe: 0.17% by mass or more and 0.33% by mass or less, and Mg: 0.49% by mass or more and 0.55% by mass or less, with the balance being Al and unavoidable impurities; The tensile strength is 250 MPa or more, An aluminum alloy sheet having the property that, when the color tone of the surface after anodizing in a sulfuric acid bath is measured using Illuminant C, the L* value of the surface in the CIE 1976 (L*, a*, b*) color space is 80 or more and the b* value is -1.0 or more and less than 1.0.

[0086] [2] The aluminum alloy sheet according to [1], further containing one or more elements selected from the group consisting of Cu: 0.08 mass% or less, Mn: 0.08 mass% or less, Cr: 0.03 mass% or less, Zn: 0.05 mass% or less, and Ti: 0.05 mass% or less. [3] The aluminum alloy sheet according to [1] or [2], having a conductivity at a temperature of 15°C or higher and 25°C or lower of 45% IACS or higher and 65% IACS or lower.

[0087] In addition, the aluminum member according to the present invention may take the aspect according to the following [4]. [4] An aluminum member having a base material made of the aluminum alloy sheet according to any one of [1] to [3] and an alumite film formed on the surface of the base material.

[0088] In addition, the manufacturing method of the aluminum alloy sheet according to the present invention may take the aspects according to the following [5] to [7].

[0089] [5] A method for manufacturing the aluminum alloy sheet according to any one of [1] to [3], comprising: casting an ingot having the chemical composition, holding the ingot at a temperature of 560°C or higher and 600°C or lower for 1 hour or more to perform a homogenization treatment, subsequently, performing hot rolling on the ingot under the condition that the temperature of the rolled sheet at the end of rolling is 300°C or higher and 380°C or lower to produce a rolled sheet, performing cold rolling on the rolled sheet, subsequently, heating the rolled sheet to a temperature of 560°C or higher and then quenching to perform a solution treatment, heating the rolled sheet after the solution treatment so that the heating temperature T and the holding time t satisfy the following condition 1 or condition 2 to perform an artificial aging treatment, a method for manufacturing an aluminum alloy sheet. Condition 1: 130°C ≤ T ≤ 150°C and 1 hour ≤ t ≤ 24 hours Condition 2: 150°C < T ≤ 180°C and 1 hour ≤ t ≤ 15 hours

[0090] [6] The method for producing an aluminum alloy sheet according to [5], wherein the ratio of recovered materials to the casting raw materials of the ingot is 50 mass % or more. [7] The method for producing an aluminum alloy sheet according to [6], wherein the casting raw material comprises one or more recovered materials selected from the group consisting of pre-consumer recycled materials derived from sashes, post-consumer materials derived from sashes, pre-consumer recycled materials derived from computer casings, post-consumer materials derived from computer casings, pre-consumer recycled materials derived from Shinkansen trains, post-consumer materials derived from Shinkansen trains, pre-consumer recycled materials derived from automobiles, post-consumer materials derived from automobiles, and Zorba.

Claims

1. The alloy has a chemical composition containing Si: 0.51% by mass or more and 0.68% by mass or less, Fe: 0.17% by mass or more and 0.33% by mass or less, and Mg: 0.49% by mass or more and 0.55% by mass or less, with the balance being Al and unavoidable impurities; The tensile strength is 250 MPa or more, An aluminum alloy sheet having a characteristic that, when the color tone of a surface after anodizing treatment in a sulfuric acid bath is measured using a C illuminant, the L* value of the surface in the CIE 1976 (L*, a*, b*) color space is 80 or more and the b* value is -1.0 or more and less than 1.

0.

2. The aluminum alloy plate according to claim 1, further comprising one or more elements selected from the group consisting of Cu: 0.08% by mass or less, Mn: 0.08% by mass or less, Cr: 0.03% by mass or less, Zn: 0.05% by mass or less, and Ti: 0.05% by mass or less.

3. The aluminum alloy sheet according to claim 1, having an electrical conductivity of 45% IACS or more and 65% IACS or less at a temperature of 15°C or more and 25°C or less.

4. An aluminum member having a substrate made of the aluminum alloy plate according to any one of claims 1 to 3 and an anodized aluminum coating formed on the surface of the substrate.

5. The method for producing an aluminum alloy plate according to any one of claims 1 to 3, Casting an ingot having the chemical composition; The ingot is subjected to a homogenization treatment by holding the ingot at a temperature of 560°C or higher and 600°C or lower for one hour or longer, Thereafter, the ingot is subjected to hot rolling under conditions in which the temperature of the rolled plate at the end of rolling is 300°C or more and 380°C or less to produce a rolled plate; The rolled plate is subjected to cold rolling, Thereafter, the rolled plate is heated to a temperature of 560°C or higher and then quenched to perform a solution treatment, the rolled plate after the solution treatment is heated so that the heating temperature T and the holding time t satisfy the following condition 1 or condition 2, thereby performing an artificial aging treatment. Condition 1: 130°C ≤ T ≤ 150°C and 1 hour ≤ t ≤ 24 hours Condition 2: 150°C < T ≦ 180°C and 1 hour ≦ t ≦ 15 hours

6. The method for producing an aluminum alloy plate according to claim 5, wherein a ratio of the recovered material to the casting raw material of the ingot is 50 mass% or more.

7. 7. The method for producing an aluminum alloy plate according to claim 6, wherein the casting raw material comprises one or more recovered materials selected from the group consisting of pre-consumer recycled materials derived from sashes, post-consumer materials derived from sashes, pre-consumer recycled materials derived from computer casings, post-consumer materials derived from computer casings, pre-consumer recycled materials derived from Shinkansen trains, post-consumer materials derived from Shinkansen trains, pre-consumer recycled materials derived from automobiles, post-consumer materials derived from automobiles, and Zorba.

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