CN103374675A - Aluminum alloy plate and manufacturing method for the same - Google Patents

Abstract

The present invention provides an aluminum alloy plate capable of suppressing yellowish color emission as much as possible even when anodized in a sulfuric acid bath, and emitting a greenish-white color without reddish color, and a method for producing the same. An aluminum alloy plate, by mass %, containing 2.0-3.0% of Mg, 0.15-0.25% of Cr, 0.005-0.20% of Ti, or 0.005-0.20% of Ti and 0.0005-0.05% of B, and the rest It is Al and unavoidable impurities, so that Si in the impurities is 0.15% or less, Fe is 0.4% or less, and Mn is 0.06% or less. The above-mentioned Cr content is T _CR %, and the solid solution amount of Cr is S _CR % , P _CR =T _CR -S _CR ≤0.065%. A method for producing an aluminum alloy plate, comprising performing hot rolling after homogenizing an ingot composed of the above-mentioned composition, followed by cold rolling, performing intermediate annealing at a heating and cooling rate of 100° C./second or more, and performing intermediate annealing during cold rolling After rolling, stabilizing annealing is applied at a rate of temperature rise and fall of 100° C./second or more.

Description

Aluminum alloy plate and manufacturing method thereof

This case is a divisional application of a patent application with an application date of March 3, 2011 , an application number of 201110052650.7 , and an invention titled aluminum alloy plate and its manufacturing method.

technical field

The invention relates to an aluminum alloy plate whose anodized film is light green and white and a manufacturing method thereof.

Background technique

The Al—Mg alloy sheet is subjected to intermediate annealing during the sheet manufacturing process, and then cold rolled and annealed to impart desired mechanical properties. However, since this series alloy naturally softens after cold working and the strength becomes unstable, stabilizing annealing may be applied after cold rolling if necessary.

The aluminum alloy plate is anodized in a sulfuric acid bath to give the surface a unique color tone of the alloy. It is used in interior and exterior decorative panels for construction, utensils, home appliances, digital cameras, and electrical and electronic equipment such as PCs. For example, among non-heat-treated alloys, the JIS5052 alloy plate, which has less residual deformation and has high machining accuracy, develops a yellowish tinge in the anodizing treatment in a sulfuric acid bath. The cause of this color tone is considered to be Cr in the alloy added for the purpose of recrystallization grain refinement, etc., and when yellowing is not desired, an aluminum alloy plate without adding Cr is used.

Japanese Patent Application Laid-Open No. 9-143602 discloses an Al—Mg-based alloy sheet containing 0.02% or less of Cr as impurities and 0.10 to 0.30% of Mn.

Patent Document 1: Japanese Patent Application Laid-Open No. 9-143602

Contents of the invention

The present invention provides an Al-Mg-based alloy sheet to which Cr is added for the purpose of refining recrystallized grains and the like. However, if Cr is contained, the anodic oxidation treatment in a sulfuric acid bath will give it a strong yellow color, and an aluminum alloy plate that emits a white color cannot be obtained, and the use of the plate is limited.

That is, an object of the present invention is to provide an aluminum alloy plate capable of suppressing a yellowish color as much as possible even when subjected to an anodizing treatment using a sulfuric acid bath, and emitting a greenish-white color without reddish color, and a method for producing the same. Department of colors.

The inventors of the present invention found that the yellow color in a Cr-containing Al-Mg-based alloy sheet is caused by a Cr-containing intermetallic compound generated in a sheet-making process including casting, and completed the present invention.

That is, the present invention is the following (1) to (4).

(1) An aluminum alloy plate characterized by containing 2.0 to 3.0 mass % of Mg, 0.15 to 0.25 mass % of Cr, 0.005 to 0.20 mass % of Ti, or 0.005 to 0.20 mass % of Ti and 0.0005 to 0.05 mass % The mass % of B, the rest is Al and unavoidable impurities, so that Si in the impurities is 0.15 mass % or less, Fe is 0.4 mass % or less, and Mn is 0.06 mass % or less, and the above-mentioned Cr content is _TCR mass %, when the solid solution amount of Cr is S _CR mass %, the value P _CR of T _CR - S _CR satisfies P _CR ≤ 0.065 mass %.

(2) An aluminum alloy plate having an anodized film, wherein the aluminum alloy plate described in (1) above is covered with a sulfuric acid anodized film of 3 to 12 μm.

(3) A method of manufacturing an aluminum alloy plate, wherein, in the entire annealing process after homogenizing an ingot having the composition described in (1) above, hot rolling, and then cold rolling, The heating and cooling rates are set to be 100° C./second or more.

(4) A method for producing an aluminum alloy plate provided with an anodized film, characterized in that the aluminum alloy plate obtained by the method described in (3) above is covered with a sulfuric acid anodized film of 3 to 12 μm.

That is, the present invention provides: (1) an aluminum alloy plate suitable for sulfuric acid anodizing treatment, (2) an aluminum alloy plate having a sulfuric acid anodized film, (3) a method for manufacturing an aluminum alloy plate suitable for sulfuric acid anodizing treatment, (4) ) A method of manufacturing an aluminum alloy plate having a sulfuric acid anodized film. The effect of the invention

In the Cr-containing Al-Mg alloy sheet of the present invention, since the amount of the Cr-containing intermetallic compound is not more than a predetermined value, even if the anodic oxide film formed by the sulfuric acid bath is covered, yellowishness is suppressed as much as possible and the color is light greenish white. Therefore, the choice of color tone is expanded, and it has the effect that it can be used in preferably white-based interior and exterior decorative panels for buildings, utensils, home appliances, digital cameras, and casings of electrical and electronic equipment such as PCs. In addition, the manufacturing method of the alloy sheet has the effect of being able to easily provide a sheet having the above-mentioned effects through technical application of making the rate of temperature rise and fall at the time of sheet manufacturing rapid.

Detailed ways

The reason for limiting the chemical composition in the present invention will be described.

<Mg: 2.0 to 3.0% by mass>

Mg is the main element of JISA5xxx series alloys, and it is used to impart sufficient strength only by work hardening. If it is less than the lower limit, the strength will be insufficient when processed into panels and utensils. In addition, if it is greater than the upper limit, the formability will be reduced. It's not good.

An Al-Mg alloy containing only Mg develops a light gray surface color in sulfuric acid electrolytic bath system anodizing treatment.

<Cr: 0.15 to 0.25% by mass>

Cr is an element used to refine recrystallized grains during intermediate annealing of JISA 5xxx alloys. When it is less than the lower limit, the effect becomes insufficient. In addition, if it exceeds the upper limit, even if the production method of the present invention is used, the Anodizing treatment will also bring a strong yellow color which is not appropriate.

<Ti: 0.005 to 0.20% by mass> or

<Ti: 0.005 to 0.20% by mass and B: 0.0005 to 0.05% by mass>

Ti or Ti and B are elements used to refine the cast structure and effectively prevent the ingot from cracking during casting. Ti can be added alone, but if Ti and B are added in combination, it can improve the refinement performance of the cast structure and improve the prevention of ingot cracking. Crack performance during casting. When each content is less than the lower limit value, the miniaturization effect is small, and the anti-crack performance of the ingot decreases. If it exceeds the upper limit, crystals of Al—Ti or Ti—B coarse intermetallic compound will precipitate, impairing the workability and formability of the sheet. The content of Ti or Ti and B can be adjusted by the selection of returned materials and the addition of one or more of Ti metal, Al-Ti master alloy or Al-Ti-B.

＜Inevitable impurities＞

Unavoidable impurities refer to elements other than intentionally added alloying elements Mg, Cr, Ti (or Mg, Cr, Ti, and B), which means that in the usual melting method, it is difficult to avoid impurities from raw material, return material, master alloy, etc. Impurities mixed with fixtures, etc. However, in the present invention, if the mixing amount of unavoidable impurities increases, a color peculiar to the element will be emitted, impairing the greenish-white color development with suppressed yellow that is characteristic of the present invention, so it needs to be limited. That is, Si having a large influence is 0.15% by mass or less, Fe is 0.4% by mass or less, and Mn is 0.06% by mass or less. As for other unavoidable impurities, Zn is 0.25% by mass or less, and Cu is 0.1% by mass or less, preferably 0.05% by mass or less. Other elements are preferably limited to 0.05% by mass or less, respectively.

<T _CR -S _CR =P _CR ≤0.065% by mass>

Here, T _CR is the content of Cr (mass %), S _CR is the solid solution amount of Cr (mass %), P _CR is the amount of Cr in the intermetallic compound (mass %), and P _CR =T _CR -S _CR said.

The yellow color is considered to be the reflection of incident light on Cr-containing intermetallic compounds, such as compounds represented by Al ₇ Cr, Al ₁₁ Cr, Al ₁₈ Cr ₂ Mg _3, etc., and the yellow wavelength is preferentially reflected to present a strong yellow color.

"Analysis of Solid Solution Cr"

The Al component was dissolved in hot phenol, the Cr in the solution was analyzed by IPC emission analysis, and the solid solution Cr (S _CR ) was quantified. Since the value of S _CR can be obtained by this method, the value of T _CR −S _CR =P _CR can be calculated according to the Cr content (T _CR ), that is, the amount of Cr in the intermetallic compound (P _CR mass %) can be calculated.

"Mechanism of Yellow Color Suppression"

This P _CR value is the amount of Cr that exists as a compound. A large P _CR value means that there is a large amount of Cr-containing compounds. Therefore, it can be considered that there is a large amount of light with a yellow wavelength that is preferentially reflected in the incident light, thereby showing a strong yellow. It can be considered that if the _PCR value is 0.065% by mass or less, the amount of Cr-containing compounds is also small, and therefore, the amount of light having a yellow wavelength is small, and yellowing can be suppressed.

Next, a preferred method for producing the aluminum alloy plate of the present invention will be described.

A preferred production method of the invention includes the following steps.

<1> Hot rolling is performed after the homogenization treatment of the ingot, and final annealing treatment is performed after the subsequent cold rolling.

<2> After the ingot is homogenized, hot rolling is performed, after the subsequent cold rolling, an intermediate annealing treatment is performed, and then cold rolling is performed, and final annealing is performed. Intermediate annealing can be performed multiple times.

<3> After the homogenization treatment of the ingot, hot rolling is performed, and after the subsequent cold rolling, intermediate annealing treatment is performed, and then cold rolling is performed. The intermediate annealing treatment may be performed multiple times.

<4> After homogenizing the ingot, hot rolling is performed, after the subsequent cold rolling, intermediate annealing is performed, and then cold rolling is performed, and stabilization annealing is performed. The intermediate annealing treatment may be performed multiple times.

<5> After homogenizing the ingot, hot rolling is performed, and after the subsequent cold rolling, temper annealing is performed.

<6> After the ingot is homogenized, hot rolling is performed, after the subsequent cold rolling, an intermediate annealing treatment is performed, then cold rolling is performed, and after the cold rolling, a quenching and tempering annealing treatment is performed. The intermediate annealing treatment may be performed multiple times.

The aluminum alloy plate related to the present invention is based on the composition of the present invention, and the color tone of the anodized film is an L ^* value of 75 to 95, a ^* value of -0.8 to 0, and b ^* value of 0 to 2.0. The production conditions are not limited, but the most preferable production method is exemplified as follows in order to deepen the understanding of the technical relationship.

The step of <1> will be further described.

After melting the molten alloy having the composition of the present invention, it is cast by a semi-continuous casting method (DC casting), preferably through a filter, to obtain an ingot for rolling. The surface of the ingot is preferably shaved by 5 mm to 20 mm to remove the uneven layer on the surface of the ingot, heated at 440-560° C. for 1-24 hours or more, and subjected to homogenization heat treatment. When performing multi-stage homogenization treatment, it is sufficient to satisfy this temperature condition at least in the high-temperature stage. In this treatment, segregation of the β phase (Mg ₂ Al ₃ ) and local microsegregation of Cr and the like are reduced or eliminated.

Next, rolling is performed by hot rolling to a thickness of about 2 to 10 mm. In this hot rolling process, alloy elements are precipitated as fine intermetallic compounds, recrystallized grains are refined in the final annealing treatment, and the hue is made uniform in the subsequent anodizing treatment.

The step of <2> will be further described.

The rolled sheet that has been hot-rolled in the same way as <1> is cold-rolled by the usual method, and then softened by intermediate annealing to become an O material. Then, the rolling ratio is determined and cold-rolled to obtain the required thickness. plate, followed by applying a final anneal. Multiple intermediate annealing treatments may also be applied.

The step of <3> will be further described.

The rolled sheet that has been hot-rolled in the same manner as in <1> is cold-rolled by the usual method, and intermediate annealing is applied to soften it to become an O material. Then, the rolling ratio is determined to be cold-rolled to give the required mechanical properties. Multiple intermediate annealing treatments may also be applied.

The step of <4> will be further described.

Since the Al-Mg alloy naturally softens after cold working and its strength is unstable, when a stable material is required, a stabilization treatment is performed after final cold rolling. That is, the rolled sheet that has been hot-rolled in the same manner as in the step <1> is cold-rolled by the usual method and softened by intermediate annealing to become an O material, and then final cold-rolled and stabilized annealed. Multiple intermediate annealing treatments may also be applied.

The step of <5> will be further described.

If the composition and cold rolling rate of Al-Mg alloys are known, the mechanical properties can be predicted by determining the heating conditions after cold rolling. Therefore, the hot-rolled rolled sheet is obtained by In the cold rolling performed by the usual method, the cold rolling rate is determined, and the rolling is performed, and after the rolling, quenching and tempering annealing treatment is performed.

The step of <6> will be further described.

If the composition and cold rolling rate of Al-Mg alloys are known, the mechanical properties can be predicted by determining the heating conditions after cold rolling. Therefore, the hot-rolled rolled sheet is obtained by The usual method is to perform cold rolling and apply intermediate annealing to make it an O material, then determine the cold rolling rate to perform rolling, and perform quenching and tempering annealing after the rolling. Multiple intermediate annealing treatments may also be applied.

The heating and cooling rate conditions of the intermediate annealing, final annealing, stabilizing annealing, and temper annealing are important for obtaining the color tone of the present invention. That is, the purpose is to suppress the precipitation of Cr-containing intermetallic compounds as much as possible. The condition for the intermediate annealing or final annealing is to keep the temperature at 370-500° C. for 1-100 seconds to produce an O material. When stabilizing annealing treatment is performed after intermediate annealing, it varies depending on the degree of strength imparted. After cold rolling, the temperature is kept at 150 to 250° C. for 1 to 100 seconds to perform stabilizing annealing.

When the cold rolling rate is determined, cold rolling is carried out, and tempering annealing is carried out after the rolling, the conditions are different according to the final required mechanical properties. After cold rolling, the temperature is kept at 250-370°C for 1-100 seconds for tempering Annealing treatment.

Here, the manufacturing method of the present invention is characterized by the following (A) which must be applied or (B) or (C) which is applied as needed.

＜Rapid heating-rapid cooling during intermediate annealing, final annealing, stabilizing annealing and quenching and tempering annealing＞

(A) The rate of temperature rise and fall to 100°C in the temperature range of the above-mentioned intermediate annealing, final annealing, or both annealing is set to 100°C/s or more, and the precipitation of Cr-containing intermetallic compounds generated during the temperature rise and fall process is suppressed and prevent its coarsening.

(B) The rate of temperature rise and fall to 100°C in the stabilization annealing temperature range applied as needed is set to be 100°C/sec or more, and the same as the above (A), suppressing the occurrence of the temperature rise and fall during the temperature rise and fall. Precipitation of Cr intermetallic compounds and prevention of their coarsening.

(C) The rate of temperature rise and fall to 100°C in the above tempering annealing temperature range is set to 100°C/sec or more, and the Cr-containing intermetallic compound generated during the temperature rise and fall is suppressed as in the above (A) precipitation and prevent its coarsening.

For these annealing treatments, for example, the temperature can be raised using an electromagnetic induction heating furnace, and the temperature can be lowered by water cooling.

The aluminum alloy plate obtained by annealing by rapid temperature rise-rapid temperature drop that satisfies the above (A) or the conditions of (B) or (C) that are applied as needed can suppress the formation of Cr-containing intermetallic in the subsequent anodic oxidation treatment. The yellowish color caused by the compound can emit greenish white without yellow.

In addition, hot rolling and cold rolling may be performed as separate steps as described above, or may be performed continuously as a continuous step from the hot rolling temperature range to the cold rolling temperature range. In the case of the latter hot-cold continuous process, in the cold-rolling temperature range, all the matters concerning the above-mentioned cold rolling apply.

＜Conditions for anodizing treatment＞

The aluminum alloy plate obtained by the present invention is subjected to anodizing treatment in a sulfuric acid bath. The conditions are not limited, but the most preferable conditions are as follows. That is, since rolling oil is used in the rolling process during sheet manufacturing, in order to remove oil adhering to the surface of the sheet, it is usually dipped in an acidic aqueous solution containing about 3 to 20% by mass of nitric acid. In order to remove the oxides on the surface, the rolled sheet from which the oil has been removed is subjected to an anodic oxidation treatment using a sulfuric acid bath to uniformly form an anodized film, and after washing with water, it is immersed in an aluminum alloy containing about 5 to 30% by mass of sodium hydroxide. In alkaline aqueous solution, etch to remove the surface layer several μm. After the rolled sheet etched by the alkali treatment is washed with water, the rolled sheet is used as an anode in a sulfuric acid bath containing 10 to 30% by mass of sulfuric acid, at 0.5 to 5A/dm ² , preferably at 1 to 3A/dm An anode current density of ² is applied at an electrolytic bath temperature of 5 to 30° C., preferably 10 to 30° C., for an electrolysis time of 10 to 120 minutes to form a film with a thickness of 3 to 12 μm. In this film thickness range, if expressed according to the UCS expression method, the bright yellow color of the film can be suppressed with L ^* value 75~95, a ^* value -0.8~0, b ^* value 0~2.0 A film that emits a greenish-white natural hair color.

＜Thickness of anodized film: 3～12μm＞

If the thickness of the anodized film is less than 3 μm, the corrosion resistance and scratch resistance will be insufficient. Conversely, if it is more than 12 μm, the yellow color will be enhanced, and the ideal light greenish white cannot be obtained. Therefore, the thickness of the anodized film is limited to a range of 3 to 12 μm.

＜Color tone after anodizing treatment＞

The method of expressing the color tone after anodizing treatment is based on the method of UCS stipulated by JISZ8729 and JISZ8730. That is, JISZ8729 is interpreted by the expression method of the object color obtained by the L ^* a ^* b ^* colorimetric system and the Luv colorimetric system, and JISZ8730 is interpreted by the color difference expression method.

The L ^* value shown in JISZ8730 indicates lightness, and the higher the value, the brighter the hue. The a ^※ value and b ^※ value represent the hue. If the color is reddish, the a ^※ value will increase, and the smaller it is than 0, the more green it will be. On the other hand, if the color is yellowish, the value of b ^* increases, and the smaller it is than 0, the more bluish it is. The color tone of the aluminum alloy plate of the present invention obtained from a sulfuric acid bath has an L ^* value of 75 to 95, an a ^* value of -0.8 to 0, and a b ^* value of 0 to 2.0, and is greenish-white in which yellowness is suppressed as much as possible.

[Example 1]

Further description will be given using the plate produced in the above <2> step.

After the molten alloy having the composition shown in Table 1 was melted, it was passed through a filter, and an ingot for rolling with a thickness of 560 mm was obtained by DC casting. The surface of the ingot was shaved by 10 mm, kept at a temperature of 440° C. for 2 hours, heated, and kept at a temperature of 540° C. for 4 hours to perform a homogenization treatment.

Next, hot rolling of each ingot was started at a temperature of 530° C., and rolled to a thickness of 8 mm. The hot rolled sheet temperature at the end of hot rolling was 360°C.

This 8 mm rolled plate was cold rolled to 3 mm. The heating rate and cooling rate down to 100° C. were varied, and the 3 mm plate was kept at a temperature of 425° C. for 10 seconds, and intermediate annealing was performed to obtain an O material.

Next, it was cold-rolled to a thickness of 1 mm (67% of rolling ratio). The temperature of the 1 mm plate was changed from rising to falling to 100°C, and the temperature was kept at 425°C for 10 seconds to perform final annealing.

Next, the flatness was corrected with a tension leveler, and the sample was cut into 100 mm×100 mm to prepare a sample for the next anodic oxidation film treatment.

The anodic oxidation film treatment process is as follows.

Wash the surface of each sample with an organic solvent, degrease, immerse in an 8% sodium hydroxide aqueous solution at a liquid temperature of 50°C for 2 minutes to treat it with sodium hydroxide, and after washing with water, place it in a 10% by mass nitric acid bath at a liquid temperature of 20°C. Neutralize by dipping for 1 minute. Next, the samples obtained by pretreatment in this way were formed with oxide films of various thicknesses by varying the treatment time with a liquid temperature of 18°C, a 15% by mass sulfuric acid bath, and a current density of 1 A/dm ² . After washing with water, the pores were sealed with warm water at 95°C and dried. Next, the hue was measured with a MINOLTA CM508i device. The results are shown in Table 2.

[Table 1] Alloy composition (unit: mass %)

Alloy serial number Si Fe Cu mn Mg Cr Zn Ti B Remark 1-1 0.08 0.2 0.03 0.05 2.0 0.15 0.10 0.01 - Example of the invention 1-2 0.08 0.2 0.03 0.01 2.5 0.20 0.10 0.02 0.005 Example of the invention 1-3 0.08 0.2 0.03 0.03 3.0 0.25 0.10 0.02 0.005 Example of the invention 1-4 0.08 0.2 0.03 0.02 2.5 0.35 0.10 0.02 0.005 comparative example

Note 1: The rest is Al and unavoidable impurities

Note 2: The - mark indicates the degree of impurities (﹤0.0005)

Note 3: The underline indicates that it is outside the specified range

[Table 2]

Judging from the results in Table 2, in the Al-Mg alloy, if Cr is within the specified range, even if it is contained, the heating and cooling speeds of the intermediate annealing and final annealing treatments are all above the specified speeds (sample number 2- 1, 2-2, 2-3 Invention examples) the color tone of the anodized film is also light greenish white with yellow suppressed. On the other hand, the comparative example (sample No. 2-4) in which the amount of Cr deviates from the specified range was judged to have a high _PCR value even when the heating and cooling rates were both above the specified rate, and turned gray with a strong yellow color.

In addition, it was judged that the comparative examples having a film thickness of 15 μm larger than the predetermined range (sample numbers 2-1, 2-2, and 2-3 had a film thickness of 15 μm) emitted strong green and yellow colors.

It was also judged that even if the chemical composition is the chemical composition of the example of the present invention, when any one of the heating and cooling speeds is slower than the specified range (sample numbers 2-5, 2-6), the _PCR value is also high, and it becomes a strong yellow color. grey.

[Example 2]

Further description will be given using the plate produced in the above step <4>.

After the molten alloy shown in Table 1 was melted, it was passed through a filter, and DC casting was performed to obtain an ingot for rolling with a thickness of 560 mm. The surface of this ingot was shaved by 10 mm, kept at a temperature of 440° C. for 2 hours, heated, and kept at a temperature of 540° C. for 4 hours to perform a homogenization treatment.

Next, hot rolling of each ingot was started at a temperature of 530° C., and rolled to a thickness of 6 mm. The hot rolled sheet temperature at the end of hot rolling was 360°C.

This 6 mm rolled plate was cold rolled to 1.5 mm. The heating rate and the cooling rate down to 100°C were respectively changed, and the 1.5mm plate was kept at a temperature of 425°C for 10 seconds, and intermediate annealing was performed to produce an O material.

Next, it was cold-rolled to a thickness of 1 mm (33% of rolling ratio). The temperature of the 1 mm plate was changed from rising to falling to 100° C., and the temperature was kept at 220° C. for 10 seconds to perform stabilization annealing.

Next, the flatness was corrected with a tension leveler, cut into 100 mm×100 mm, and anodized film treatment was performed in the same manner as in Example 1. Thereafter, the hue was measured in the same manner as in Example 1. The results are shown in Table 3.

[table 3]

Note: The underline indicates that the production conditions deviate from the specified range, and the amount of compound ( _PCR value) is also large, and the result is not ideal.

Judging from the results in Table 3, in the Al-Mg alloy, if Cr is within the specified range, even if it is contained, the heating and cooling rates of the intermediate annealing and stabilizing annealing treatments are all above the specified rate (sample No. The color tone of the anodized film in 3-1, 3-2, and 3-3 of the examples of the present invention) is also light greenish white in which yellow is suppressed.

On the other hand, in the comparative example (Sample No. 3-4) in which the amount of Cr was judged to be deviated from the specified range, even if the heating and cooling rates were both above the specified rate, the _PCR value was high, and it was gray with a strong yellow color.

In addition, it was judged that the comparative examples having a film thickness of 15 μm larger than the predetermined range (sample numbers 3-1, 3-2, and 3-3 had a film thickness of 15 μm) emitted strong green and yellow colors.

It was also judged that even if the chemical composition is the chemical composition of the example of the present invention, when any one of the heating and cooling speeds is slower than the specified range (sample No. 3-5, 3-6), the _PCR value is also high, and it becomes a strong yellow color. grey.

In addition, regarding the composition within the specified range obtained by the process described in the above <1>, <3>, <5> and <6> other than <2> and <4> actually verified in Examples 1 and 2 Aluminum alloy sheet, by making the heating and cooling rate 100°C/sec or more in all annealing treatments after cold rolling, the color tone after anodizing within the specified range can obtain the L ^* value, a ^* value, b within the specified range ^※ For the value, it can be confirmed by visual inspection that there is no yellowish greenish white.

[Example 3]

Among the cold-rolled 1 mm sheets of sample No. 3-2 obtained under the conditions of Example 2, the sheets on the first day after cold-rolling and the sheets on the tenth day after cold-rolling without stabilizing annealing were measured. and the mechanical properties of the plate on the 1st day and the 10th day after the stabilization annealing applied after the cold rolling. The results are shown in Table 4.

[Table 4]

Judging from the results in Table 4, the mechanical properties of the plate with stabilizing annealing (sample No. 4-2) were stable even after 10 days, while the plate without stabilizing annealing (sample No. 1) The mechanical properties will change greatly after 10 days.

Industrial availability

According to the present invention, it is possible to provide an aluminum alloy plate that emits a greenish-white color without reddish color while suppressing yellowish coloring as much as possible even when anodizing in a sulfuric acid bath, and a method for producing the same.

Claims (4)

1. An aluminum alloy plate, characterized in that: Contains 2.0 to 3.0% by mass of Mg, 0.15 to 0.25% by mass of Cr, 0.005 to 0.20% by mass of Ti, or 0.005 to 0.20% by mass of Ti and 0.0005 to 0.05% by mass of B, the remainder being Al and unavoidable Impurities, so that Si in the impurities is 0.15% by mass or less, Fe is 0.4% by mass or less, and Mn is 0.06% by mass or less, the content of Cr is T _CR mass %, and the solid solution amount of Cr is S _CR mass % , the value P _CR of T _CR -S _CR satisfies P _CR ≤0.065% by mass. 2. An aluminum alloy plate with anodized film, characterized in that: The aluminum alloy plate according to claim 1 is covered with a 3-12 μm sulfuric acid anodized film, and the film tone is L ^* value 75-95, a ^* value -0.8-0, b ^* value 0-2.0. 3. A method for manufacturing an aluminum alloy plate, characterized in that: When containing 2.0-3.0 mass % of Mg, 0.15-0.25 mass % of Cr, 0.005-0.20 mass % of Ti, or 0.005-0.20 mass % of Ti and 0.0005-0.05 mass % of B, the rest is Al and Unavoidable impurities, in which Si is 0.15% by mass or less, Fe is 0.4% by mass or less, and Mn is 0.06% by mass or less. After homogenization, the ingot is hot-rolled and then cold-rolled. In the entire annealing treatment, the heating and cooling rate is 100°C/s or more, when the content of Cr is T _CR mass %, and the solid solution amount of Cr is S _CR mass %, the value of T _CR -S _CR is P _CR satisfies P _CR ≤ 0.065% by mass. 4. A method of manufacturing an aluminum alloy plate with an anodic oxidation film, characterized in that: Cover the aluminum alloy plate obtained by the method of claim 3 with a sulfuric acid anodized film of 3 to 12 μm, so that the film tone is L ^* value 75~95, a ^* value -0.8~0, b ^* value 0~2.0 .