JPH10219412A - Manufacture of rolled aluminum alloy sheet excellent in external appearance characteristic after forming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of stretcher strain marks of type A at the time of final forming and to obtain the rolled Al alloy sheet of 5000 series by subjecting an Al alloy, having a composition containing specific amounts of Mg, Mn, Fe, and Ti, to final cold rolling at specific draft and then to final heat treatment under respectively specified heating and cooling conditions and specifying the average crystalline grain size in the surface and inner part of the resultant sheet. SOLUTION: An ingot of an Al alloy, having a composition consisting of, by mass, 4-5% Mg, 0.2-0.4% Mn, 0.5-0.35% Fe, 0.01-0.05% Ti, and the balance Al and containing, if necessary, 0.1-0.2% Cu, is subjected to soaking treatment and hot rolling by the ordinary methods, and further, cold rolling is performed, while applying, if necessary, intermediate heat treatment, to prescribed sheet thickness. The draft at the final cold rolling of this alloy sheet is regulated to 8-20%. Then, the alloy sheet is heated at 500-560 deg.C for <=10sec and cooled down to 100 deg.C at <=100 deg.C/sec cooling rate to undergo final heat treatment, by which the average crystalline grain size in the surface and inner part of the sheet can be regulated to 20-50μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a rolled aluminum alloy sheet, and more particularly, to a 5000 series (Al-Mg series) in which the generation of an A type stretcher strain mark, which is liable to occur at the time of final forming, is suppressed. The present invention relates to a method for producing a rolled aluminum alloy sheet.

[0002]

2. Description of the Related Art Aluminum alloy sheets, which are to be finalized by molding, such as for automobile body panels and interior parts, are required to have excellent properties such as formability and strength as well as appearance after molding. It is important.

In particular, for automotive body panels (outer plates such as hood outer, hood inner, front fender, door, etc.), the same press formability and high strength as those of conventional cold-rolled steel sheets, and a paint base treatment such as phosphate treatment. Therefore, an Al-Mg-Cu alloy is used as the aluminum alloy plate. However, recently, inexpensive aluminum alloys have been demanded for cost reduction.

[0004] Therefore, aluminum alloy plates meeting these requirements include 5,000 aluminum alloys such as JIS A5052 based on Al-2.5% Mg and JIS A5182 based on Al-4.5% Mg. Use is being considered.

[0005] Normally, these 5000 series rolled aluminum alloy sheets for forming are formed by ingot melting, then subjected to homogenizing heat treatment (soaking heat treatment) and hot rolling, and if necessary, to intermediate heat treatment. In general, cold rolling is performed to obtain a predetermined final thickness, which is then shipped from a material maker to a processing maker, and is then formed into a final product by the processing maker. As the final forming process, for example, in the case of an automobile body panel, a drawing process and an overhanging process are mainly performed, and are important as the required formability of a rolled aluminum alloy plate. However, in the case of an automobile body panel, in addition to the above, processing such as tension, bending, shearing, and ironing is performed as a final forming process. It will be.

Incidentally, during the above process, 5000
When a rolled aluminum alloy sheet is formed into a final product, non-uniform deformation called stretcher strain mark (hereinafter referred to as SS mark) occurs, which causes flame-like stripes on the surface of the formed product. Because of the pattern, the appearance and aesthetics of the product after the molding process are significantly impaired, and the commercial value may be lost.

[0007] The SS marks include an A type represented by elongation at the yield point and a B type represented by a saw-tooth shape after the yield when expressed in a stress-strain curve shape at the time of a tensile test.
Of these, the A type SS mark is particularly problematic in automobile body panels and the like. When the A-type SS mark is generated, the number of reworking steps such as grinding and polishing is increased and the production cost is increased. When the SS mark is remarkable, the reworking cannot be performed and the product cannot be used in some cases.

[0008] In particular, a 5000 series aluminum alloy is more likely to generate an SS mark because it contains a larger amount of reinforcing elements such as Mn, Fe, and Cr than other aluminum alloys. This is because these reinforcing elements move by diffusion and many atoms are easily fixed to dislocations. In this state, if deformation such as molding to the final product is applied, dislocations are released from the sticking atoms, but once this phenomenon occurs, dislocation movement occurs intensively on the same sliding surface, However, a slip line that can be confirmed is generated. This is the A type S
This is an S mark, and the more the crystal grains are mechanically fine, the more remarkably generated.

[0009] Further, in the method of manufacturing a 5000 series rolled aluminum alloy plate for forming work, the crystal grains of the rolled aluminum alloy plate are necessarily reduced in size, and the SS grains are further reduced.
Marks are likely to occur.

Various techniques have been proposed for suppressing the SS mark on a 5000 series aluminum alloy thin plate for an automobile body. For example,
No. 39500 uses 5000 series aluminum alloy sheets,
There is disclosed a technique of performing high-temperature short-time annealing at 450 to 550 ° C. for 30 to 120 seconds after cold working of 2525%, and then cooling to 100 ° C. or less at an average cooling rate of 80 to 1000 ° C./min.

In order to improve the low yield strength of the aluminum alloy of Japanese Patent Publication No. 59-39500 and the complexity of cold rolling under light pressure, Japanese Patent Publication No. 59-39501 discloses a 5000 series aluminum alloy sheet. After cold working of 25% or more, at 400-550 ° C
Perform high-temperature short-time annealing for 15-120 seconds, then 80-1000 ° C
A technique is disclosed in which after being cooled to 100 ° C. or less at an average cooling rate of / min, bending deformation is repeatedly performed by a leveler having a roll having a specific radius.

As a method similar to that of Japanese Patent Publication No. 59-39501, Japanese Patent Application Laid-Open No. 4-276050 also discloses that a 5000 series aluminum alloy plate is subjected to cold working of 25% or more at 400 to 550 ° C.
High-temperature short-time annealing for 120 seconds or less, then 80 ° C / min
There is disclosed a technique of performing straightening and straightening processing after cooling to 100 ° C. or less at the above average cooling rate and subsequently giving a specified amount of distortion by a roller leveler or the like.

[0013] Japanese Patent Application Laid-Open No. Hei 4-147852 discloses 5000
After the final cold working of 30 to 80%, the aluminum alloy sheet is subjected to solution treatment using a continuous annealing furnace at 450 to 550 ° C, and the average crystal grain size is 10 to 50μ depending on the solution treatment temperature.
Techniques have been disclosed for providing a specific range of particle sizes between m.

Further, Japanese Patent Application Laid-Open Nos. 2-122504 and 2-29
No. 0953 and Japanese Patent Application Laid-Open No. H3-173752 describe squeezed cans (D
As a technology for suppressing the SS mark of 5000 series aluminum alloy sheet for R can), after final cold working of 40% or more, 15
A technique for stabilizing annealing at 0 to 250 ° C. is disclosed.

[0015]

[Problems to be solved by the invention]
No. 59-39500, JP-B-59-39501, JP-A-4-276050
And Japanese Patent Application Laid-Open No. 4-47952, the technology of suppressing the SS mark by continuous annealing after the final cold working is disclosed in
As disclosed in Japanese Patent No. 39501, the yield strength is low, and although high-temperature short-time annealing is performed, the annealing (heating) time is long, and the crystal grains exceeding 50 μm are remarkably coarsened.
Although it has the effect of suppressing the generation of SS marks, the surface is likely to be roughened at the time of final molding.

Also, Japanese Patent Publication No. 59-39501, Japanese Patent Laid-Open No. 4-27
No. 6050, etc., perform high-temperature short-time annealing after cold rolling, and then apply roll bending or tension straightening treatment with a tension leveler or stretcher to repeatedly apply bending deformation or strain. The final moldability itself decreases.

Further, Japanese Patent Application Laid-Open Nos. 2-122504 and 2-29
No. 0953, JP-A-3-17752 and the like are intended for drawn cans (DR cans) such as food cans subjected to deep drawing with a drawing ratio close to 2.0, and ensure this formability. After the final cold working of 40% or more, the steel is annealed at 150-250 ° C in order to gain strength. As a result, the crystal grains are likely to be fine due to a high cold working rate, and the crystal grains are still fine due to a low annealing temperature, and there is no effect of suppressing the generation of SS marks.

[0018] Accordingly, the present invention has been made in view of these conventional problems, and in particular, drawing,
The 5000 series (Al-Mg), which not only has excellent final formability such as overhanging processing, but also suppresses the generation of A-type stretcher strain marks, which are likely to occur during final forming, and has excellent appearance after forming. System) It is an object of the present invention to provide a method for manufacturing a rolled aluminum alloy sheet.

[0019]

[Means for Solving the Problems] As means for achieving this object, in the present invention, Mg: 4 to 5% by mass, M:
n: 0.2 to 0.4%, Fe: 0.15 to 0.35%, Ti: 0.01
The ingot of aluminum alloy containing about 0.05% and the balance of Al and inevitable impurities is subjected to a soaking treatment and a hot rolling by a conventional method, and then to a cold rolling while performing an intermediate heat treatment as necessary. The final cold rolling rate is set to 8 to 20%, including the final sheet thickness.
After heating at a temperature of up to 560 ° C. for 10 seconds or less, a final heat treatment of cooling to a temperature of 100 ° C. at a cooling rate of 100 ° C./sec or more is performed to reduce the average crystal grain size on the plate surface and inside to 20 ° C.
To 50 μm to suppress the generation of A-type stretcher strain marks during the final molding process.

In the present invention, in view of the fact that the roll correction or the tension correction by the tension leveler or the stretcher of the prior art described above after the cold rolling or annealing impairs the final formability, it is preferable to perform the cold rolling or annealing after the cold rolling or annealing. It is preferable that final processing be performed without performing these processings or treatments.

In addition, particularly in the case of an automobile body panel, a rolled aluminum alloy sheet is subjected to a phosphate treatment as a coating base on the same line (condition) as a cold-rolled steel sheet or a Zn-plated steel sheet. The rolled sheet is inferior in phosphatability (phosphate adhesion) to the cold-rolled steel sheet or the Zn-plated steel sheet. Therefore, in such a case, it is necessary to improve the phosphatability of the rolled aluminum alloy sheet. For this purpose, it is preferable that the aluminum alloy further contains Cu as a phosphating property improving element. In addition, in order to improve the phosphatability, the surface of the rolled aluminum alloy plate may be plated with Zn or a Zn alloy similar to the steel plate.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reasons for limiting the chemical components of the aluminum alloy according to the present invention will be described below.

Mg is a basic alloying component of the aluminum alloy in the present invention, and is effective for improving strength, formability, and processability of phosphate (zinc phosphate) as a coating base by solid solution / precipitation hardening. Element. If the content is less than 4%, such effects are poor, while if the content exceeds 5%,
Rollability decreases. Therefore, the Mg content is 4-5%
Range.

Mn is an element that is effective for making crystal grains fine, stabilizing the structure, and improving strength and processability of phosphate (zinc phosphate) as a coating base. If the content is less than 0.2%, these effects cannot be sufficiently obtained. If the content exceeds 0.4%, the crystal grains become too fine, and the SS mark is easily generated. Therefore, the Mn content is in the range of 0.2 to 0.4%.

Fe, like Mn, is an element effective for refining crystal grains, stabilizing the structure, and improving strength and processability of phosphate (zinc phosphate) as a coating base. If the content is less than 0.15%, these effects cannot be sufficiently obtained. On the other hand, if the content exceeds 0.35%, the crystal grains become too fine similarly to Mn, and the SS mark is easily generated. . Therefore, the Fe content is in the range of 0.15 to 0.35%.

Ti is an element that is effective for making the crystal grains of the ingot fine, stabilizing the structure, and improving the strength. Ti is 0.01
If the content is less than 10%, such excellent effects cannot be obtained. However, on the other hand, an excessive content of more than 0.05% of Ti causes a giant product and impairs the formability, and the crystal grains become too fine, so that an SS mark is easily generated.
Therefore, the Ti content is in the range of 0.01 to 0.05%.

Cu is an element effective for improving the processing property of the phosphate, particularly the throwing power of zinc phosphate, and is selectively contained when the property improvement is required. If the content is less than 0.1%, this effect is not obtained, and if it exceeds 0.2%, the effect is saturated, and the corrosion resistance is rather lowered. Therefore, the Cu content when it is positively contained is in the range of 0.1 to 0.2%.

In addition, since impurities such as Si, Zn, and Zr do not adversely affect the properties of the rolled aluminum alloy sheet of the present invention up to 0.15%, the contents of less than 0.15% are permissible.

In the present invention, the average crystal grain size on the surface and inside of the aluminum alloy plate after the final heat treatment needs to be 20 to 50 μm, in addition to specifying the aluminum alloy component. When the average crystal grain size is less than 20 μm, even if the production method of the present invention is applied, A type S
The generation of the S mark cannot be suppressed, and a flame-like stripe pattern is generated on the surface of the molded product, which significantly impairs the appearance.
On the other hand, when the average crystal grain size exceeds 50 μm, the surface is apt to be roughened at the time of final molding, and the appearance is also significantly impaired. Therefore, the average crystal grain size is in the range of 20 to 50 μm over the entire area from the thickness direction to the longitudinal direction, both on the surface and inside of the aluminum alloy plate. The average crystal grain size is measured based on ASTME112.

Next, the reasons for limiting the manufacturing conditions in the present invention will be described. In the present invention, after the aluminum alloy comprising the chemical components is formed into an ingot by melting and casting, it is subjected to a homogenizing heat treatment and a hot rolling, and further to an intermediate heat treatment as necessary, and then to a cold rolling. The final plate thickness. Then, after cold rolling, a final heat treatment of heating to a temperature of 500 to 560 ° C. within 10 seconds and then cooling to a temperature of 100 ° C. at a cooling rate of 100 ° C./sec or more is performed. The diameter is 20 to 50 μm.

In such a production method, the melting casting, the homogenizing heat treatment, the hot rolling, the intermediate heat treatment, and the cold rolling may be performed according to a conventional method. For example, a continuous casting and rolling method and a semi-continuous casting method (DC casting method) are appropriately selected as a method for melting and casting an ingot.

The homogenizing heat treatment removes internal stress during casting of the ingot, reduces segregation and homogenizes the structure. For example, in the case of the 5000-series aluminum alloy of the present invention, for example, 500 to 530 Preferably, it is carried out at a temperature of 2 to 10 hours.

In the hot rolling, the slab after the homogenization heat treatment is
The slab having a thickness of 400 to 600 mm is rolled to a thickness of about 2 to 8 mm by a rough rolling mill and a finishing rolling mill. The sheet after hot rolling is subjected to a heat treatment as it is or, if necessary, in a batch furnace, a continuous annealing furnace or the like, and then cold-rolled.

The cold rolling is performed once or more to obtain a predetermined final product sheet thickness. Intermediate annealing performed between cold rolling and cold rolling is performed as necessary, and is usually performed in a batch furnace or the like to recover the workability of the work-hardened structure.
It is kept at 0 to 400 ° C for 2 to 3 hours to be a completely annealed material.

However, in the present invention, the intermediate annealing is preferably carried out by continuous annealing at a high temperature for a short time. More specifically, by performing continuous annealing at 410 to 510 ° C. for a holding time of 10 seconds or less, workability can be recovered and generation of SS marks can be suppressed. If the temperature is lower than 410 ° C, the effect of suppressing the generation of the SS mark cannot be obtained.
If the diameter exceeds 50, the crystal grain size becomes coarse and the crystal grain size becomes 50
When the thickness exceeds μm, roughening is likely to occur at the time of final molding, and the appearance may be significantly impaired. A holding time of more than 10 seconds reduces production efficiency and is not economical.

After the intermediate annealing, final cold rolling and final heat treatment described below are performed. Here, in the 5000 series alloy targeted in the present invention, elements such as Fe, Mn, and Ti should be suppressed as low as possible in order to suppress SS marks. However, the 5000 series alloy of the present invention, on the contrary,
Rather, since these elements are contained positively and in large amounts, the recrystallized grain size is easily reduced. Therefore, in order to prevent excessive refining of the recrystallized grain size and obtain stable recrystallized grains, the cooling conditions of the final cold rolling and the final heat treatment are extremely important.

That is, the cold rolling reduction of the final cold rolling is 8 to
Must be 20%. Cold rolling before the final heat treatment greatly affects the stabilization of recrystallized grains and the SS mark suppression effect by the final heat treatment. If the cold rolling reduction is less than 8%, coarsening of the recrystallized grain size exceeding 50 μm becomes remarkable, and although there is an effect of suppressing the generation of SS marks, the surface is likely to be roughened at the time of final molding and the appearance may be significantly impaired. There is.
If the cold rolling ratio exceeds 20%, the recrystallization grain size is improved, although it is effective for improving the final formability and preventing skin roughness.
Excessive miniaturization to less than 20μm, SS
Marks are significantly generated.

[0038] The final heat treatment after the final cold rolling is an essential means for dissolving the alloy components or recrystallizing the structure, suppressing the SS mark generation and improving the final formability. Specific conditions are recrystallization temperature (temperature range of 500 to 560 ° C)
It is necessary to rapidly heat the mixture to a maximum of 10 seconds or less and then cool it at a temperature of 100 ° C./sec or more in the temperature range from the recrystallization temperature to 100 ° C. At a cooling rate of less than 100 ° C./sec, the recrystallized grain size becomes excessively fine to less than 20 μm, and the generation of SS marks becomes remarkable at the time of final molding.
If the retention time exceeds 10 sec, the recrystallized
The coarsening exceeding m becomes remarkable, and although there is an effect of suppressing the generation of SS marks, the surface is likely to be roughened at the time of final molding. In addition, the productivity of the heat treatment is reduced, and it is not economical.

The rate of rapid heating up to the recrystallization temperature is preferably 20 ° C./sec or more from the viewpoint of uniform recrystallization, but if the rate is 10 ° C./sec or more, the effect is not significant. Will be maintained.

[0040]

【Example】

[Embodiment 1] Next, the present invention described above will be further described with reference to embodiments.

An aluminum alloy ingot composed of the chemical components shown in Table 1 was produced by DC casting, and after homogenizing heat treatment at 510 ° C. × 4 hours, hot-rolled to a plate thickness of 3.5 mm, and heated to 365 ° C. ×
After rough annealing for 4 hrs, cold rolling was performed to a sheet thickness of 1.45 to 1.05 mm. After that, intermediate annealing at 450 ° C x 0 seconds is performed.
Furthermore, final cold rolling (rolling ratio 30 to 5%) was performed to a thickness of 1 mm. Thereafter, as final annealing, final heat treatment was performed under the respective conditions shown in Table 2.

The mechanical properties and average crystal grain size of the rolled aluminum alloy sheet obtained as described above were measured.
The state of the occurrence of the SS mark and the state of the occurrence of the rough surface during the molding were evaluated. Table 3 shows the results. Alloy No. in Table 3
No. in Table 1 corresponds to No. in the manufacturing process, and No. in the manufacturing process corresponds to No. in Table 2.

In Table 3, the tensile test for examining the mechanical properties of the rolled aluminum alloy plate was performed using a JIS No. 5 test piece in a direction parallel to the rolling direction.
However, the yield elongation, which is a standard for evaluating the A type SS mark, was evaluated in a direction perpendicular to the rolling direction.
Regarding the crystal grain size, a sample was cut out from the plate surface and a cross section parallel to the rolling direction and photographed after micro polishing,
It was measured visually. In addition, the A type SS mark uses an Erichsen tester to apply a slight strain of about 0.1 to 3% to the test piece using a 120 φ blank, 50 mm φ ball-head punch, and a die with a bead. Evaluation was made based on the occurrence or non-occurrence. This evaluation method is excellent in that it corresponds well with the actual situation of the occurrence of the SS mark at the time of molding into an actual automobile panel (outer panel). Further, for rough skin, R = 0.
A 180 degree bending of 5t was performed, and the appearance was judged.

In Table 3, each of the test materials of Comparative Examples was prepared according to the production method shown in Table 2 even though the aluminum alloy component was within the present invention in Table 1 (Nos. 1 and 4). E: the final cold rolling rate exceeds the upper limit of the present invention of 20%, and F: the final heat treatment temperature is lower than the lower limit of the present invention.
C, the cooling rate of the final heat treatment is lower than the lower limit of the present invention.
Below 0 ° C / sec, H;
Below 0 ° C, the heating time exceeds the upper limit of the present invention of 10 seconds, and the cooling rate is lower than the lower limit of the present invention of 100 ° C / sec.
It deviates from the manufacturing method of the present invention.

Therefore, in the evaluation of the properties of the rolled aluminum alloy sheet in Table 3, E to H have a high yield elongation and A type SS marks are generated. D has a coarse average crystal grain size and does not have any SS mark, but has a rough surface and cannot be put to practical use. On the other hand, each of the examples of the present invention has a high level of mechanical properties, and is particularly suitable for an automobile body panel.
It is excellent in final forming workability such as overhanging processing, and has an average crystal grain size within the range, and there is no occurrence of SS mark or rough surface during forming processing.

Example 2 An aluminum alloy ingot having the chemical components shown in Table 1 was produced by DC casting at 510 ° C.
After the homogenizing heat treatment of × 4 hrs, hot rolling was performed to a thickness of 3.5 mm, rough annealing was performed at 365 ° C. × 4 hrs, and then cold rolling was performed (rolling ratio: 15%) to a thickness of 1 mm. Thereafter, as final annealing, a final heat treatment was performed under No. B conditions of the present invention in Table 2.

The mechanical properties and average crystal grain size of the rolled aluminum alloy sheet obtained as described above were measured.
The state of the occurrence of the SS mark and the state of the occurrence of the rough surface during the molding were evaluated. Table 4 shows the results. Alloy No. in Table 4
Corresponds to the Nos. In Table 1, respectively. The evaluation method was the same as that in the examples, but the corrosion resistance was investigated by the intergranular corrosion susceptibility by the anodic electrolytic method.

As is clear from Table 4, the test materials of the comparative examples had aluminum alloy components of No. 5 and No. 5 as shown in Table 1, although the production conditions were the method of the present invention B in Table 2. When the amounts of Fe and Mn are less than the lower limits of 0.15% and 0.2% of the present invention,
6; Mg content exceeds the upper limit of 5% of the present invention; No. 7: Mg content falls below the lower limit of 4% of the present invention; No. 8: Fe and Mn content of the upper limit of 0.35% and 0.4% of the present invention. No. 9; Cu content exceeds the upper limit of 0.2% of the present invention, No. 10; Mn and Mg contents are lower than the lower limit of 0.2% and 4% of the present invention, and the Cr content as an impurity is also higher than that of the present invention. Exceeds the upper limit.

Therefore, No. 5 and No. 8 have a large average crystal grain size, No. 6 has a high yield elongation and SS marks are generated, and No. 7 and No. 10 have a tensile strength and proof stress. Inferior, No. 9 is inferior in corrosion resistance and cannot be put to practical use. On the other hand, each of the examples of the present invention has excellent mechanical properties, and particularly has excellent levels of corrosion resistance as well as excellent final formability such as drawing and overhanging for automobile body panels. Further, when the average crystal grain size is within the range, there is no occurrence of SS mark or rough surface during molding.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

[0053]

[Table 4]

[0054]

According to the present invention, an A-type stretcher strain mark which is excellent in final forming workability such as drawing and overhanging, especially for an automobile body panel, and which is easily generated at the time of final forming. To suppress the occurrence of
5000 series (Al-Mg) with excellent appearance after forming
System) It is possible to provide a method for producing a rolled aluminum alloy plate, and as a result, the industrial value is great in promoting the aluminization of automobile panels.

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Claims (4)

[Claims] (1) In terms of mass%, Mg: 4 to 5%, Mn: 0.2
0.4%, Fe: 0.15 to 0.35%, Ti: 0.01 to 0.05%
, The aluminum alloy ingot consisting of the balance Al and unavoidable impurities is subjected to a homogenizing heat treatment and a hot rolling by a conventional method, and then to a predetermined final sheet by performing a cold rolling while applying an intermediate heat treatment as necessary. Thickness, including the final cold rolling reduction of 8-20%, and then 500-560
After heating at a temperature of 100 ° C for 10 seconds or less,
A final heat treatment of cooling at a cooling rate of 0 ° C./sec or more is performed to set the average crystal grain size on the surface and inside of the plate to 20 to 50 μm, thereby suppressing the generation of the A-type stretcher strain mark at the time of final forming. A method for producing a rolled aluminum alloy sheet having excellent appearance after forming. 2. The method according to claim 2, wherein the aluminum alloy ingot further comprises C
The method for producing a rolled aluminum alloy sheet having excellent appearance after forming according to claim 1, wherein u: 0.1 to 0.2% is contained. 3. The use of the rolled aluminum alloy sheet is as follows:
The method for producing an aluminum alloy rolled sheet having excellent appearance after forming according to claim 1 or 2, which is for an automobile body panel. 4. The rolled aluminum alloy sheet having excellent appearance after forming according to any one of claims 1 to 3, wherein final forming is performed without leveling or stretching after the final cold rolling. Manufacturing method.