Aluminum alloy plate and its manufacturing method

Abstract

To provide an aluminum alloy sheet having excellent adhesion with a coated film or a resin, vibration-damping property and high strength.SOLUTION: There is provided an aluminum alloy sheet 1 which has a base material 2 having a chemical composition comprising 0.10 mass% or more and 3.0 mass% or less of Fe, 0.10 mass% or more and 3.0 mass% or less of Mn and the balance Al with inevitable impurities and an oxide film 3 which contains an oxide of aluminum and is provided on at least one surface of the base material 2. The adhesive strength of a cellophane tape to the oxide film 3 is 10 N or more. The aluminum alloy sheet 1 has a Young's modulus after heating at a temperature of 100°C or more and 300°C or less for 0.5 hour or more and 10 hours or less of 70 GPa or more, a 0.2% proof stress of 100 MPa or more and a decrement in damped free vibration of 1.5×10-3 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an aluminum alloy sheet and a method for producing the same. [Background technology]

[0002] Steel materials have traditionally been used for automobile bodies. Car bodies are painted for the purposes of rust prevention and improving design. However, in recent years, there has been a strong demand for further weight reduction in automobile bodies to meet the increasing demand for electrification of automobiles and further improvement in fuel efficiency. Therefore, aluminum alloy materials have begun to be used for automobile bodies instead of steel materials.

[0003] As aluminum alloy materials used in automobiles, sheet materials made of Al-Mg alloys (e.g., Patent Document 1) and Al-Mg-Si alloys (e.g., Patent Document 2), which have relatively high strength among aluminum alloys, are widely used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-165538 [Patent Document 2] Japanese Patent Application Publication No. 11-71623 Summary of the Invention [Problem to be solved by the invention]

[0005] While an automobile is running, various vibrations occur, such as those generated by the power source and those caused by uneven road surfaces. If these vibrations are transmitted to various parts of the vehicle via the body, etc., problems may arise due to the vibrations. Therefore, there is a need to further improve the vibration-damping properties of Al-Mg and Al-Mg-Si alloys used in vehicles.

[0006] Furthermore, when an aluminum alloy material is used for a body panel or the like, it is desirable that the coating film has excellent adhesion to the aluminum alloy material. Possible methods for improving adhesion to the coating film include, for example, subjecting the aluminum alloy material to a surface treatment such as chemical conversion treatment or anodizing treatment to modify the surface of the aluminum alloy material. However, when the chemical composition of an aluminum alloy material made of an Al-Mg alloy or an Al-Mg-Si alloy is changed to improve the vibration damping properties, the type of intermetallic compound changes, which may make it difficult to uniformly apply a surface treatment to the surface of the aluminum alloy material.

[0007] The present invention has been made in view of the above background, and aims to provide an aluminum alloy sheet having excellent adhesion to coatings and resins, excellent vibration damping properties, and high strength, and a method for producing the same. [Means for solving the problem]

[0008] One aspect of the present invention is Fe (iron): 1.0 mass% or more and 1.7 mass% or less (excluding Fe: 1.0 mass% or less), Mn (manganese): 0.10% by mass or more 1.0 mass% or less, Si (silicon): 0.10 mass% or more and 0.40 mass% or less, Cu (copper): 0.005 mass% or more and 0.100 mass% or less, Cr (chromium): 0.01 mass% or more and 0.50 mass% or less, Zn (zinc): 0.01 mass% or more and 0.50 mass% or less A substrate having a chemical composition containing the above, with the remainder being Al (aluminum) and unavoidable impurities; an oxide coating including an oxide of aluminum and provided on at least one surface of the substrate; The adhesive strength of the cellophane tape to the oxide film is 10 N or more, 250℃ At a temperature of 3 hours After heating at this temperature for 0.5 to 10 hours, the Young's modulus is 70 GPa or more, the 0.2% proof stress is 100 MPa or more, and the damping ratio in damped free vibration is 1.5 × 10 -3 The aluminum alloy plate has the above properties. [Effects of the Invention]

[0009] The aluminum alloy sheet has a substrate having the specific chemical composition and an oxide film formed on at least one surface of the substrate. By adjusting the chemical composition of the substrate to fall within the specific range, the aluminum alloy sheet can form a uniform oxide film on the substrate. Furthermore, the oxide film formed on the substrate has a property that allows its adhesive strength with cellophane tape to fall within the specific range. By providing an oxide film having such properties on the substrate, the aluminum alloy sheet can improve its adhesion to coatings and resins.

[0010] Furthermore, the aluminum alloy sheet has at least the specific chemical components, and therefore the Young's modulus, 0.2% proof stress, and damping rate of damped free vibration can be set within the specific ranges after heating at a temperature of 100° C. to 300° C. for 0.5 hours to 10 hours. The aluminum alloy sheet having such properties can exhibit high strength and excellent vibration damping properties after undergoing heat treatment, for example, for baking a coating film.

[0011] As described above, according to the above-mentioned embodiment, an aluminum alloy sheet having excellent adhesion to coating films and resins, excellent vibration damping properties, and high strength can be provided. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing a main part of an aluminum alloy plate according to an embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory diagram that schematically shows the attenuation rate measuring device used in the examples. [Figure 3] FIG. 3 is an explanatory diagram showing a method for calculating the attenuation rate in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] (aluminum alloy plate) The aluminum alloy plate has a substrate and an oxide film provided on one or both sides of the substrate.

[0014] [Base material] First, the chemical composition of the substrate of the aluminum alloy plate and the reasons for limiting it will be explained.

[0015] Fe (iron): 1.0 mass% or more and 1.7 mass% or less (excluding Fe: 1.0 mass% or less) The base material contains the following essential components: 1.0 mass% or more and 1.7 mass% or less (excluding Fe: 1.0 mass% or less) The Fe content is 100%. The Fe is mainly present in the Al matrix as second-phase particles such as Al-Fe intermetallic compounds. The Al-Fe intermetallic compounds in the Al matrix improve the vibration damping properties of the aluminum alloy sheet and also improve the strength of the aluminum alloy sheet through dispersion strengthening. The remainder of the Fe is present as a solid solution element in the Al matrix, and also improves the strength of the aluminum alloy sheet.

[0016] The mechanism by which second-phase particles such as Al-Fe intermetallic compounds improve the vibration-damping properties of aluminum alloy sheets is thought to be, for example, as follows. That is, when vibrations are applied to the aluminum alloy sheet from the outside, viscous flow occurs at the interface between the Al matrix and the second-phase particles. It is thought that this viscous flow absorbs the vibration energy, resulting in early damping of the vibrations.

[0017] By setting the Fe content in the substrate to 0.10% by mass or more, the strength and vibration-damping properties of the aluminum alloy sheet can be improved. From the viewpoint of further improving the vibration-damping properties and increasing the strength of the aluminum alloy sheet, the Fe content in the substrate is preferably 0.40% by mass or more, and more preferably 1.0% by mass or more. If the Fe content in the substrate is less than 0.10% by mass, the number of second-phase particles such as Al-Fe-based intermetallic compounds formed in the substrate will be insufficient, which may lead to a decrease in the strength and vibration-damping properties of the aluminum alloy sheet.

[0018] Furthermore, by setting the Fe content in the substrate to 3.0 mass% or less, preferably 2.0 mass% or less, and more preferably 1.7 mass% or less, a uniform oxide film can be easily formed on the substrate. As a result, the adhesion between the aluminum alloy sheet and the coating or resin can be improved. If the Fe content in the substrate is excessively high, coarse Al-Fe intermetallic compounds are likely to be formed in the substrate. If coarse Al-Fe intermetallic compounds are present in the substrate, reactions around the coarse Al-Fe intermetallic compounds are likely to be promoted when forming an oxide film, which may make it difficult to form a uniform oxide film on the substrate.

[0019] Mn (manganese): 0.10% by mass or more 1.0% by mass or less The base material contains 0.10% by mass or more of the essential component 1.0% by mass or less The Mn content is 100%. Mn is mainly present in the Al matrix as second-phase particles such as Al-Mn intermetallic compounds. The Al-Mn intermetallic compounds in the Al matrix, like the Al-Fe intermetallic compounds, have the effect of improving the strength and vibration-damping properties of the aluminum alloy sheet. Mn can also form Al-Fe-Mn intermetallic compounds in the substrate together with Fe. The Al-Fe-Mn intermetallic compounds have a small potential difference with the Al matrix, and therefore have the effect of suppressing local cell reactions during oxide film formation. By suppressing the local cell reactions during oxide film formation, a uniform oxide film can be easily formed on the substrate.

[0020] By setting the Mn content in the substrate to 0.10% by mass or more, preferably 0.20% by mass or more, and more preferably 0.40% by mass or more, the strength and vibration-damping property of the aluminum alloy sheet can be improved and a uniform oxide film can be easily formed on the substrate. If the Mn content in the substrate is less than 0.10% by mass, the number of second-phase particles such as Al-Mn-based intermetallic compounds formed in the substrate will be insufficient, which may lead to a decrease in the strength and vibration-damping property of the aluminum alloy sheet.

[0021] Furthermore, by setting the Mn content in the substrate to 3.0% by mass or less, preferably 2.0% by mass or less, and more preferably 1.0% by mass or less, it is possible to form a uniform oxide film on the substrate. As a result, it is possible to improve the adhesion between the aluminum alloy sheet and the coating film or resin. If the Mn content in the substrate is excessively high, coarse Al-Mn intermetallic compounds are likely to be formed in the substrate. Similar to Al-Fe intermetallic compounds, coarse Al-Mn intermetallic compounds have the effect of accelerating the reaction when forming an oxide film. Therefore, in this case, it may be difficult to form a uniform oxide film on the substrate.

[0022] The base material contains, in addition to the essential components Fe and Mn, Si (silicon), Cu (copper), Cr (chromium), and Zn (zinc). The substrate further comprises It may contain, as an optional component, one or more elements selected from the group consisting of Ti (titanium), B (boron), V (vanadium) and Ni (nickel).

[0023] ·Si: 0.10 mass% or more and 0.40 mass% or less The substrate is Required Contains 0.10 mass% or more and 0.40 mass% or less of Si as a component. There are Si forms second-phase particles such as Si particles in the substrate, and has the effect of improving the strength and vibration-damping properties of the aluminum alloy sheet, similar to Al-Fe intermetallic compounds. Si can also form Al-Si-Mn intermetallic compounds in the substrate together with Mn. Al-Si-Mn intermetallic compounds have a small potential difference with the Al parent phase, so they have the effect of suppressing local cell reactions when forming an oxide film. By suppressing the local cell reactions when forming an oxide film, a uniform oxide film can be easily formed on the substrate.

[0024] By setting the Si content in the substrate to 0.10 mass% or more and 0.40 mass% or less, more preferably 0.15 mass% or more and 0.30 mass% or less, the strength and vibration damping property of the aluminum alloy plate can be further improved, and an oxide film can be more uniformly formed on the substrate.

[0025] ·Cu: 0.005 mass% or more and 0.100 mass% or less The substrate is Required Contains 0.005% by mass or more and 0.100% by mass or less of Cu as a component. There are Cu forms second-phase particles such as Al-Cu intermetallic compounds in the substrate, and has the effect of improving the strength and vibration-damping properties of the aluminum alloy sheet, similar to Al-Fe intermetallic compounds. However, while Al-Cu intermetallic compounds improve vibration-damping properties, they may precipitate at the grain boundaries of the Al matrix upon heat treatment, causing intergranular corrosion. By setting the Cu content in the substrate to 0.005% by mass or more and 0.100% by mass or less, more preferably 0.010% by mass or more and 0.070% by mass or less, it is possible to further improve the strength and vibration-damping properties of the aluminum alloy sheet while suppressing the occurrence of intergranular corrosion.

[0026] ·Cr: 0.01 mass% or more and 1.00 mass% or less The substrate is Required Contains 0.01% by mass or more and 1.00% by mass or less of Cr as a component. There are Cr forms second phase particles such as Al-Cr based intermetallic compounds in the base material, and has the effect of improving the strength and vibration damping properties of the aluminum alloy sheet, similar to Al-Fe based intermetallic compounds.

[0027] On the other hand, if the Cr content in the substrate is excessively high, coarse Al-Cr intermetallic compounds are likely to be formed in the substrate. Since coarse Al-Cr intermetallic compounds have the effect of accelerating the reaction when forming an oxide film, the presence of excessively large coarse Al-Cr intermetallic compounds in the substrate may make it difficult to form a uniform oxide film on the substrate. By setting the Cr content in the substrate to 0.01% by mass or more and 1.00% by mass or less, more preferably 0.10% by mass or more and 0.50% by mass or less, the strength and vibration damping properties of the aluminum alloy sheet can be further improved, and the formation of coarse Al-Cr intermetallic compounds in the substrate can be suppressed, allowing a more uniform oxide film to be formed on the substrate.

[0028] ·Zn: 0.01 mass% or more and 0.50 mass% or less The substrate is Required Contains 0.01% by mass or more and 0.50% by mass or less of Zn as a component. There are A portion of the Zn forms second-phase particles in the Al matrix together with other alloying elements, further improving the strength and vibration-damping properties of the aluminum alloy sheet. The remaining Zn dissolves in the Al matrix, lowering the potential of the substrate and improving the reactivity during oxide film formation. However, an excessively high Zn content may make the substrate more susceptible to corrosion. By setting the Zn content in the substrate to 0.01% by mass or more and 0.50% by mass or less, more preferably 0.10% by mass or more and 0.40% by mass or less, the strength and vibration-damping properties of the aluminum alloy sheet can be further improved, and the potential of the substrate can be appropriately lowered to further promote oxide film formation.

[0029] ·Ti, B and V: Total 0.005 mass% or more and 0.500 mass% or less The substrate may contain, as an optional component, one or more elements selected from the group consisting of Ti, B, and V. These elements have the effect of refining the crystal grains of the ingot during the manufacturing process of the aluminum alloy sheet. By setting the total content of Ti, B, and V within the specific range, the crystal grains of the ingot can be refined and the variation in size of second-phase particles formed in the substrate can be reduced. As a result, the variation in vibration-damping property of the aluminum alloy sheet can be reduced. Furthermore, the reduced variation in size of the second-phase particles reduces the variation in reactivity during oxide film formation, allowing the oxide film to be formed more uniformly on the substrate. From the viewpoint of further enhancing these effects, the total content of Ti, B, and V is more preferably 0.20 mass% or less.

[0030] ·Ni: 0.10% by mass or less The substrate may contain 0.10 mass% or less of Ni as an optional component. Ni forms second-phase particles such as Al-Ni intermetallic compounds in the substrate, and has the effect of improving the strength and vibration-damping properties of the aluminum alloy sheet, similar to Al-Fe intermetallic compounds. However, while Al-Ni intermetallic compounds improve vibration-damping properties, they may become cathode sites when exposed to corrosive substances, accelerating corrosion. Furthermore, since Al-Ni intermetallic compounds have the effect of accelerating reactions when forming an oxide film, if the number of Al-Ni intermetallic compounds present on the surface of the substrate increases, it may become difficult to form a uniform oxide film on the substrate.

[0031] By setting the Ni content in the substrate to 0.10% by mass or less, more preferably 0.05% by mass or less, the strength and vibration-damping properties of the aluminum alloy sheet can be further improved while suppressing the occurrence of corrosion, and in this case, a uniform oxide film can be more easily formed on the substrate.

[0032] Other elements In addition to the elements mentioned above, the base material contains unavoidable impurities that are inevitably mixed in during the manufacturing process. Elements contained as unavoidable impurities include, for example, Zr (zirconium), Pb (lead), Ga (gallium), and Sn (tin). The content of each element as an unavoidable impurity is 0.1% by mass or less for each element, and the total content of the unavoidable impurities is 0.2% by mass or less.

[0033] [Oxide film] An oxide film containing an oxide of aluminum is provided on the substrate. By adjusting the chemical composition of the substrate to fall within the specific range, second-phase particles such as Al-Fe intermetallic compounds can be formed in the substrate. These second-phase particles can improve the strength and vibration-damping properties of the aluminum alloy sheet after heating. Furthermore, the second-phase particles formed in the substrate of the aluminum alloy sheet are unlikely to interfere with the aluminum dissolution reaction and the oxide film growth reaction during oxide film formation. Therefore, by adjusting the chemical composition of the substrate to fall within the specific range, an oxide film can be uniformly formed on the substrate, and the second-phase particles can improve the strength and vibration-damping properties of the aluminum alloy sheet after heating.

[0034] The oxide film also has the property of having an adhesive strength of 10 N or more with cellophane tape measured by the method specified in JIS Z0237:2009. By providing an oxide film having such properties on the substrate, the aluminum alloy sheet can have improved adhesion to coatings and resins. From the viewpoint of further enhancing the effect of improving adhesion to coatings and resins, the thickness of the oxide film is preferably 20 nm or more and 1 μm or less, more preferably 40 nm or more and 700 nm or less, and even more preferably 70 nm or more and 500 nm or less. For measuring the adhesive strength, for example, a 10 mm wide cellophane tape having an adhesive layer made of an acrylic adhesive can be used.

[0035] The oxide film is mainly composed of aluminum oxide. The oxide film is formed, for example, by electrolyzing the substrate in an alkaline electrolyte using an alternating current. The oxide film formed by this method has fine irregularities on the surface and numerous pores. Therefore, it is presumed that the oxide film can improve adhesion to coatings and resins due to its anchoring effect.

[0036] [Physical properties of aluminum alloy sheets] The aluminum alloy plate is 250℃At a temperature of 3 hours After heating, the Young's modulus becomes 70 GPa or more, the 0.2% proof stress becomes 100 MPa or more, and the damping rate in damped free vibration becomes 1.5 × 10 -3 It has the above characteristics. Aluminum alloy sheets with a high Young's modulus and a high damping rate in damped free vibration can efficiently damp externally applied vibrations. Furthermore, aluminum alloy sheets with a high 0.2% yield strength can improve the rigidity of final products such as automobile bodies, and can also suppress the occurrence of cracks and wrinkles during forming processes.

[0037] Therefore, an aluminum alloy sheet having Young's modulus, 0.2% proof stress, and damping rate of damped free vibration each falling within the above-mentioned specific ranges after heating under the above-mentioned specific conditions can exhibit high strength and excellent vibration-damping properties after heat treatment such as baking performed after painting. An aluminum alloy sheet having such properties is particularly suitable for automobile bodies.

[0038] From the viewpoint of further improving the vibration-damping property of the aluminum alloy plate, the aluminum alloy plate is preferably such that the damping rate of damped free vibration after heating at a temperature of 100°C or higher and 300°C or lower for 0.5 hours or higher and 10 hours or lower is 2.0 × 10 -3 The specific method for measuring the damping rate of damped free vibration will be explained in detail in the examples.

[0039] [Application] As described above, the aluminum alloy sheet can improve adhesion to paint films and resins by controlling the chemical composition of the substrate within the specific range and providing an oxide film on the substrate. Furthermore, the aluminum alloy sheet has high strength and excellent vibration damping properties after heating. Therefore, the aluminum alloy sheet is suitable for applications requiring high strength and excellent vibration damping properties after paint baking, such as automobile body panel materials.

[0040] When the aluminum alloy sheet is heated during paint baking or the like, it is preferable that the heating temperature is 300° C. or less and the heating time is 10 hours or less. If the heating temperature of the aluminum alloy sheet is excessively high or the heating time is excessively long, the strength of the aluminum alloy sheet may be reduced.

[0041] (Method of manufacturing aluminum alloy plate) In producing the aluminum alloy plate, a substrate made of an aluminum alloy having the specific chemical composition is cold-rolled to a desired thickness, and then the substrate is electrolyzed in an alkaline electrolyte using an alternating current to form an oxide film.

[0042] The method for producing the substrate is not particularly limited. For example, the substrate may be produced by DC casting an ingot having the specific chemical composition, heating the ingot for homogenization as needed, and then hot rolling the ingot.

[0043] In DC casting, the cooling rate of the ingot after casting is preferably in the range of 0.1°C / sec to 1000°C / sec. When homogenization treatment is performed, the ingot is held at a temperature of 500°C to 650°C for 0.5 hours or more.

[0044] When hot rolling an ingot without homogenizing treatment, it is preferable to start rolling while the temperature of the ingot is in the range of 300°C or higher and 550°C or lower. When hot rolling an ingot after homogenizing treatment, it is preferable to start rolling while the temperature of the ingot is in the range of 300°C or higher and lower than 380°C. In either case, the temperature of the substrate at the end of hot rolling should be 100°C or higher and lower than 380°C.

[0045] Alternatively, a plate material having the specific chemical composition produced by CC casting can be used as the substrate. The cooling rate of the substrate after casting in CC casting is preferably in the range of 0.1°C / sec to 1000°C / sec.

[0046] The substrate thus obtained is subjected to cold rolling to reduce the thickness of the substrate to a desired thickness. The thickness of the substrate after cold rolling may be appropriately set within a range of, for example, 1.0 mm to 2.0 mm. Furthermore, the total rolling ratio in cold rolling, i.e., the ratio of the thickness reduction of the substrate due to cold rolling to the thickness of the substrate before cold rolling, is preferably 10% to 95%.

[0047] Furthermore, when cold rolling the substrate, the substrate can be heated and annealed as necessary. Annealing may be performed before cold rolling or during cold rolling. Annealing may also be performed both before cold rolling and during cold rolling. When performing annealing, a batch annealing furnace or a continuous annealing furnace may be used. For example, when annealing is performed using a batch annealing furnace, it is preferable to hold the substrate at a temperature of 200°C or higher and lower than 380°C for 0.1 hours to 10 hours.

[0048] The cold-rolled substrate is brought into contact with an alkaline electrolyte together with a counter electrode, and an alternating current is passed between the substrate and the counter electrode to electrolyze the substrate, thereby forming an oxide film on the substrate, thereby obtaining the aluminum alloy sheet. When the substrate is electrolyzed in an alkaline electrolyte with an alternating current, an oxide film grows while the substrate serves as the anode, and aluminum dissolves while the substrate serves as the cathode.

[0049] Then, during electrolysis, the oxide film growth reaction and the aluminum dissolution reaction are alternately repeated, resulting in the formation of pores in the oxide film. Furthermore, the surface shape of the oxide film formed in this manner is more complex than that of a typical anodized film, and fine irregularities are formed on the surface of the oxide film. Therefore, an aluminum alloy plate having the oxide film has excellent adhesion to coatings and resins. The surface shape of the oxide film can be controlled to some extent by, for example, the width of the voltage applied between the substrate and the counter electrode.

[0050] Electrolysis of the substrate may be performed at any time between the completion of cold rolling and the coating. For example, electrolysis may be performed by unwinding a coiled substrate from the coil and contacting it with an alkaline electrolyte together with a counter electrode, and passing an alternating current between the substrate and the counter electrode. Alternatively, electrolysis may be performed by contacting a substrate cut to a desired size or a substrate after shaping with an alkaline electrolyte together with a counter electrode, and passing an alternating current between the substrate and the counter electrode. The alkaline electrolyte used for electrolysis may be, for example, an aqueous solution of an alkaline electrolyte such as sodium hydroxide, potassium hydroxide, or sodium pyrophosphate. One type of electrolyte may be dissolved in the alkaline electrolyte, or two or more types of electrolytes may be dissolved in the alkaline electrolyte.

[0051] From the viewpoint of further improving the adhesion between the aluminum alloy sheet and the coating film or resin, the pH of the alkaline electrolyte is preferably 9 or more and 13 or less, and the temperature of the alkaline electrolyte is preferably 35° C. or more and 90° C. or less. From the same viewpoint, the frequency of the alternating current applied between the substrate and the counter electrode is preferably 20 Hz or more and 100 Hz or less, and the current density is preferably 4 A / dm 2 More than 50A / dm 2 The energization time is preferably 5 seconds or more and 600 seconds or less. [Example]

[0052] An example of the aluminum alloy sheet will be described with reference to Figs. 1 to 3. As shown in Fig. 1, the aluminum alloy sheet 1 of this example has a substrate 2 having a chemical composition containing 0.10 to 3.0 mass% of Fe and 0.10 to 3.0 mass% of Mn, with the balance being Al and unavoidable impurities, and an oxide coating 3 containing an oxide of aluminum and provided on at least one surface of the substrate 2. Furthermore, as shown in Table 1, the aluminum alloy sheet 1 of this example has a Young's modulus of 70 GPa or more, a 0.2% proof stress of 100 MPa or more, and a damping ratio in damped free vibration of 1.5 x 10 after heating at a temperature of 100°C to 300°C for 0.5 to 10 hours.-3 It has the above characteristics.

[0053] To produce the aluminum alloy sheet 1 of this example, first, an ingot having the chemical composition shown in Table 1 is produced by DC casting. In Table 1, the symbol "Bal." indicates that the corresponding element is the balance, and the symbol "-" indicates that the corresponding element is not contained. The surface of the ingot is chamfered to remove the surface segregation layer, and then the ingot is held at a temperature of 520°C for 1 hour for homogenization treatment. Thereafter, hot rolling is started while the ingot temperature is 460°C, and a substrate 2 having a thickness of 3.0 mm is produced. The temperature of the substrate 2 at the completion of hot rolling is 280°C. Next, the substrate 2 is cold-rolled to reduce the thickness of the substrate 2 to 1.0 mm.

[0054] After masking one side of the substrate 2 thus obtained, the substrate 2 is immersed together with the counter electrode in an alkaline electrolyte solution at a temperature of 60°C and a pH of 10. Then, a current is applied between the substrate 2 and the counter electrode at a frequency of 50 Hz and a current density of 5 A / dm 2 An alternating current of 1000 kJ / cm 2 is passed through the test piece S1 for 30 seconds to electrolyze the surface of the substrate 2, thereby forming an oxide film 3 on the substrate 2. As a result, the test piece S1 shown in Table 1 can be obtained. The cross section of the test piece S1 was observed using an electron microscope, and the thickness of the oxide film 3 was measured. The results are shown in Table 1.

[0055] Note that test materials R1 and R2 shown in Table 1 are test materials for comparison with test material S1. Test material R1 has the same structure as test material S1, except that the chemical composition of the substrate has been changed as shown in Table 1. Test material R2 has the same chemical composition as the substrate as shown in Table 1. For test material R2, even if electrolysis is performed on the substrate under the same conditions as for test material S1, it is difficult to form a uniform oxide film on the substrate. Therefore, for test material R2, the symbol "-" is entered in the oxide film thickness column in Table 1.

[0056] In the aluminum alloy plate 1 of this example, the adhesive strength of cellophane tape to the oxide film 3, the Young's modulus after heating of the aluminum alloy plate 1, the 0.2% proof stress and the damping rate of damped free vibration were measured as follows.

[0057] Adhesive strength of cellophane tape The adhesive strength of cellophane tape to the oxide film 3 was measured according to the method specified in JIS Z0237:2009. Specifically, a 10-mm-wide cellophane tape with an adhesive layer made of an acrylic adhesive was first applied to the oxide film 3 of the test material. The cellophane tape was then peeled off at a speed of 10 mm / s so that the angle between the peeling direction of the cellophane tape and the cellophane tape on the substrate was 90°. The force required to peel the cellophane tape was then measured, and the average value of the force required to peel the cellophane tape from the start to the end of peeling was taken as the adhesive strength between the aluminum alloy plate and the cellophane tape. Table 1 shows the adhesive strength of the cellophane tape to each test material. Since the adhesive strength of test material R2 was not measured, a "-" was entered in the adhesive strength column.

[0058] ·Young's modulus and damping rate After heat treatment of each test material at the holding temperature and holding time shown in Table 2, strip-shaped test pieces measuring 80 mm in length and 8 mm in width were taken from the test material with the rolling direction and longitudinal direction parallel. These test pieces were attached to a free-resonance internal friction measuring device ("JE-RT" manufactured by Nippon Technoplus Co., Ltd.), and the Young's modulus and damping factor were measured using the damping method. The measuring device 4 used in this example, as shown in Figure 2, has a driving electrode 41 and an amplitude sensor 42 facing the driving electrode 41. The test piece S is horizontally placed between the driving electrode 41 and the amplitude sensor 42, and is fixed with a thin wire 43 at a vibration node position. In this state, an AC current is passed through the driving electrode 41, causing a Coulomb force to act on the test piece S, thereby vibrating the test piece S. The amplitude of the test piece S is then measured using the amplitude sensor 42, thereby obtaining a vibration waveform.

[0059] In this example, an AC current is applied to the driving electrode 41 to forcibly vibrate the test piece S, and then the AC current is stopped, allowing the test piece S to vibrate freely due to its restoring force. The vibration of the test piece S is what is known as damped free vibration, in which the amplitude exponentially decays while oscillating periodically with a period T, as shown in the waveform in Figure 3. In damped free vibration, it is believed that the amplitude decreases exponentially due to losses of vibration energy caused by atmospheric resistance and internal friction due to dislocations and grain boundaries within the test piece.

[0060] The method for calculating the value of the damping rate δ is as follows: First, the nth period (where n is a positive integer) and the n+mth period (where m is an integer of 2 or more) are arbitrarily selected from the waveform of the damped free vibration, and the amplitude a n and the amplitude a of the n+mth period n+m The decay rate δ is the amplitude a k and the amplitude of the next period a k+1 The natural logarithm of the ratio ln(a k / a k+1 ), so the amplitude a n and amplitude a n+m The natural logarithm of the ratio ln(a n / a n+m ) can be expanded as follows: ln(a n / a n+m )=ln{(a n / a n+1 )×(a n+1 / a n+2 )×···×(a n+m-1 / a n+m )}=mδ

[0061] Therefore, the value of the attenuation rate δ is the amplitude a n and the amplitude a of the n+mth period n+m It can be expressed as follows using the value of δ=(1 / m)·ln(a n / a n+m )

[0062] The Young's modulus and damping rate of damped free vibration after heating for each test material are shown in Table 2. Note that for test material R2, the damping rate was not calculated, so the symbol "-" is entered in the damping rate column.

[0063] ·0.2% yield strength Each test material was heat-treated by heating at the holding temperature and holding time shown in Table 2, and then a JIS No. 5 test piece was taken from the test material so that the rolling direction and longitudinal direction were parallel. Using these test pieces, a tensile test was performed using a method in accordance with JIS Z2241:2011. The 0.2% yield strength of each test material was then calculated based on the load-displacement curve obtained from the tensile test. Table 2 shows the 0.2% yield strength of each test material after heating. Note that the 0.2% yield strength of test material R2 was not calculated, so the symbol "-" is entered in the 0.2% yield strength column.

[0064] [Table 1]

[0065] [Table 2]

[0066] As shown in Table 1, test material S1 has a substrate 2 having the specific chemical composition and an oxide coating 3 containing aluminum oxide and provided on the substrate 2. The oxide coating 3 has a property such that the adhesive strength with cellophane tape falls within the specific range. Therefore, test material S1 has excellent adhesion to paint films and resins. Furthermore, test material S1 has properties such that after heat treatment at the temperature and time shown in Table 2, the Young's modulus, 0.2% proof stress, and damping rate of damped free vibration fall within the specific ranges. An aluminum alloy sheet having such properties can exhibit high strength and excellent vibration damping after heating, such as paint baking, and is therefore suitable for use in automobile bodies.

[0067] In test material R1, the Fe content and Mn content in the substrate are lower than the specific ranges, so second-phase particles such as Al-Fe intermetallic compounds and Al-Mn intermetallic compounds are less likely to form in the substrate. As a result, test material R1 has a low Young's modulus and damping rate after heating, and is inferior in vibration damping performance to test material S1.

[0068] In test material R2, the Fe content and Mn content in the substrate are lower than the specific ranges, and the Si content is excessively high, making it difficult to form a uniform oxide film on the substrate during electrolysis.

[0069] The above describes examples of specific configurations of the aluminum alloy plate according to the present invention, but the specific configurations of the aluminum alloy plate according to the present invention are not limited to the configurations of the examples, and the configurations can be changed as appropriate within the scope that does not detract from the spirit of the present invention. [Explanation of symbols]

[0070] 1. Aluminum alloy plate 2 Base material 3. Oxide film

Claims

1. a base material having a chemical composition containing Fe: 1.0 mass % or more and 1.7 mass % or less (excluding Fe: 1.0 mass % or less), Mn: 0.10 mass % or more and 1.0 mass % or less, Si: 0.10 mass % or more and 0.40 mass % or less, Cu: 0.005 mass % or more and 0.100 mass % or less, Cr: 0.01 mass % or more and 0.50 mass % or less, and Zn: 0.01 mass % or more and 0.50 mass % or less, with the balance being Al and unavoidable impurities; an oxide coating including an oxide of aluminum and provided on at least one surface of the substrate; the adhesive strength of the cellophane tape to the oxide film is 10 N or more; After heating at 250°C for 3 hours, the Young's modulus is 70 GPa or more, the 0.2% yield strength is 100 MPa or more, and the damping rate in damped free vibration is 1.5 × 10 －３ An aluminum alloy plate having the above properties.

2. 2. The aluminum alloy plate according to claim 1, wherein the base material further contains one or more elements selected from the group consisting of Ti, B, and V, and the total content of these elements is 0.005% by mass or more and 0.500% by mass or less.

3. The aluminum alloy plate according to claim 1 or 2, wherein the substrate further contains Ni: 0.10 mass % or less.

4. The aluminum alloy plate according to any one of claims 1 to 3, wherein the oxide film has a thickness of 20 nm or more and 1 µm or less.

5. A method for producing an aluminum alloy plate according to any one of claims 1 to 4, comprising: A method for producing an aluminum alloy sheet, comprising electrolyzing a substrate having the above chemical components in an alkaline electrolyte having a pH of 9 to 13 and a temperature of 35°C to 85°C using an alternating current having a frequency of 20 Hz to 100 Hz and a current density of 4 A / dm2 to 50 A / dm2, thereby forming the oxide film on the substrate.

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