JP2002035806A - Aluminum alloy steel plate for panel stock of air carrier excellent in surface glossiness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al alloy steel for panel stock of an air carrier excellent in surface glossiness that produces no difference of glossiness between the steel plate and the Al alloy steel plate in the surface conditions after painting. SOLUTION: An Al alloy steel characterized by the features that the Al alloy steel is of AA5000 system or AA6000 system aluminum alloy steel used after painting and the oil pits occupancy ratio on the surface is two percent or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy plate (hereinafter, aluminum is simply referred to as Al) for a panel material of a transportation machine, which is excellent in surface glossiness.

[0002]

2. Description of the Related Art Conventionally, non-heat-treated Al-Mg-based AA5000 series, AA6111, AA6022, and AA5022 and AA5023 have been used as panel materials for transportation equipment such as automobiles, ships, and vehicles.
Al-Mg-Si-based AA 6000-based Al alloy sheets are used in heat treatment types such as AA6016.

[0003] However, the 5000 series to 6000 series Al alloy sheets rolled and manufactured by a conventional cold rolling method are used for panel materials of transport equipment, especially when used together with steel sheets in an adjacent state. There is a problem that a difference in gloss is generated between the steel sheet and the steel sheet in a later surface state. When a large difference in gloss from the steel sheet occurs, there is a problem that the appearance and commercial value of the transport device itself are significantly reduced.

[0004] In this regard, many cold rolling techniques using a Cr-plated roll have been conventionally proposed in order to improve the surface quality of an Al alloy plate. For example, JP-A-3-165906
No. and Japanese Patent Application Laid-Open No. 10-263617, AA1000-based Al of pure Al-based
It is disclosed to improve the surface quality of the alloy.

[0005] Japanese Patent Application Laid-Open No. 9-57313 discloses that a roll coated with Cr is used to easily remove a roll coating that impairs the surface quality of an Al alloy plate.

Further, Japanese Patent Application Laid-Open No. 10-99905 discloses that the thickness of a Cr plating is 3 to 12 μm and the roll surface roughness Ra is 0.2 to 0.2 μm.
Use a 0.7 μm Cr-plated roll, 3004 or 5182
It is disclosed to reduce the anisotropy (optical anisotropy) of the light reflection characteristics in the rolling direction and the width direction of such an Al alloy plate. Japanese Patent Application Laid-Open No. 10-328705 discloses that a Cr plating roll has a Cr plating thickness of 3 to 12 μm and a roll surface roughness of
It is also disclosed that Ra is set to 0.2 to 0.7 μm to suppress minute peeling of Cr plating from a roll in rolling of an Al alloy plate.

[0007] However, these prior arts are concerned with the optical anisotropy and surface quality of the surface of the Al alloy plate.
This does not address the difference in gloss after painting between the Al alloy plate and the steel plate. Therefore, for panel materials of transport aircraft,
When used together with a steel sheet, it is inevitable that a difference in gloss will occur between the steel sheet and the surface state after painting.

On the other hand, it has been conventionally proposed to reduce the number of oil pits on the surface of an Al alloy plate in order to improve the surface quality of the Al alloy plate. This oil pit is
Fine recesses or cracks generated on the surface of the Al alloy sheet in a cold rolling step using rolling oil are observed by an optical microscope or the like, and are randomly present on the rolled surface.

For example, JP-A-8-99139 discloses that 3004
In order to prevent black streaks caused by these oil pits from occurring during the coating treatment of the aluminum alloy body such as white,
Oil pits generated on the surface of the alloy plate should be 7% or less of the total surface area, more specifically, the area ratio of the oil pits should be 5.
It is disclosed that the content should be 5 to 6.5% (Example).

In Japanese Patent Application Laid-Open No. 10-296307, a striped pattern caused by the oil pits is generated during surface treatment such as etching or anodic oxidation of a continuously cast pure Al-based AA1000-based Al alloy plate. In order to prevent oil pits generated on the surface of the Al alloy plate to 5% or less of the total surface area,
More specifically, the reduction rate of the final cold rolling is controlled to 60% or more, and the area ratio of oil pits is set to 2 to 4%.
(Example) is disclosed. In this publication, oil pits are defined as recesses or cracks of about 100 μm generated on the surface of the Al alloy plate, but 100 μm is too large, and the size of oil pits is about 10 μm. Yes, it is presumed that this is an error.

[0011]

However, these oil pit control techniques also have a problem of the surface quality of the Al alloy plate itself at the time of surface treatment or painting treatment.
As in the present invention, the difference between the gloss of the 5000-6000 series Al alloy plate for the panel material of the transport machine and the steel plate after coating is not a problem. For this reason, for panel materials of transport aircraft,
When used together with a steel sheet, it is inevitable that a difference in gloss will occur between the steel sheet and the surface state after painting.

Therefore, there has been no technique for controlling the surface gloss of an Al alloy plate so that there is no gloss difference between the steel plate and the steel plate in the surface state after coating.

The present invention has been made in view of such circumstances, and has as its object to provide an excellent surface glossiness such that there is no difference in gloss between the coated steel sheet and the steel sheet. It is an object of the present invention to provide an Al alloy plate for a transport aircraft panel material.

[0014]

In order to achieve this object, the gist of the Al alloy plate for a transport panel material of the present invention is an AA5000 series or 6000 series aluminum alloy sheet to be used after being painted, The oil pit occupancy is to be 2% or less.

The inventors of the present invention have proposed that the Al alloy plate having the composition of AA5000 or 6000 is 5.5 to 6.5% or 2 to 4% as disclosed in JP-A-8-99139 and JP-A-10-296307. %
By setting the oil pit occupancy to a level of 2% or less, instead of the oil pit occupancy level as described above, an Al alloy plate that does not produce a gloss difference with the steel plate in the surface state after painting Was obtained.

Further, in order to make the oil pit occupancy of the Al alloy plate of AA5000 series or 6000 series composition to a level of 2% or less, cold rolling using a Cr plating roll is required. Has been found to be preferable.

Further, when performing cold rolling using a Cr plating roll, the Cr plating thickness is 2 to 20 μm, and the roll surface roughness Ra is 0.01 to 0.5.
It has also been found that a thickness of μm is preferable in order to reduce the oil occupation ratio to 2% or less.

Since the aluminum alloy sheet of the present invention does not show a difference in gloss between the aluminum alloy sheet and the steel sheet in the surface state after coating as described above, the present invention provides an aluminum alloy sheet according to a second aspect of the present invention. It is suitable to be used together with a steel plate as a panel material.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, in the Al alloy plate of the present invention,
The occupancy of oil pits on the surface will be described. In the present invention, as described above, the oil pit occupancy (area ratio) of the Al alloy plate having the AA5000 or 6000 composition is set to 2% or less.

When the oil pit occupancy exceeds 2%, a difference in gloss between the steel sheet and the steel sheet occurs in the surface state after coating, and the surface quality itself of the Al alloy sheet also deteriorates as in the above-mentioned prior art. .

In the present invention, an oil pit is a cold rolling step using a rolling oil, as in the prior art.
AA 5000 series or 6000 series composition is generated on the surface of Al alloy plate, is a concave or crack randomly present on the rolling surface, 10μm
Depressions or cracks of a small degree.

And this oil pit is 500 times SE
Observed by image analysis of M, the oil pit occupancy (%) can be calculated from the ratio of the total oil pit area per field (total oil pit area) to the surface area of the Al alloy plate per field. is there.

Further, in order to reduce the oil pit occupancy of the Al alloy plate having the composition of AA5000 or 6000 to 2% or less, as described above, cold rolling using a Cr plating roll is performed, and the Cr plating is performed. Preferably, the thickness is 2 to 20 μm, and the surface roughness Ra of the roll plated with Cr is 0.01 to 0.5 μm.

If the thickness of the Cr plating is less than 2 μm, the Cr plating becomes non-uniform, and the plating tends to peel off.
There is a high possibility that surface roughness will occur on the Al alloy plate after rolling. On the other hand, if the Cr plating thickness exceeds 20 μm, plating cracks increase, the roll surface becomes rough, the number of oil pits on the Al alloy plate after rolling increases, and the oil pit occupancy is 2% or less. It becomes difficult. Further, the glossiness of the Al alloy plate also decreases.

The surface roughness Ra of the Cr-plated roll is 0.
If the thickness is less than 01 μm, there is a high possibility that the Al alloy sheet will have poor biting or slip during rolling. On the other hand, when the surface roughness Ra of the roll exceeds 0.5 μm, the number of oil pits on the Al alloy sheet after rolling increases, and it becomes difficult to reduce the oil pit occupancy to a level of 2% or less. Further, the glossiness of the Al alloy plate also decreases.

In the case of ordinary cold rolling without using a Cr plating roll, it is difficult to make the oil pit occupancy of the Al alloy plate 2% or less, and the oil pit occupancy is 2% or less. In the case of the level, the roll and the Al alloy plate are likely to slip, and the cold rolling itself may be difficult.

Further, even if the rolling reduction of the final cold rolling is increased to 60% or more as disclosed in Japanese Patent Application Laid-Open No. 10-296307, a pure Al-based Al alloy It is a limit that the area ratio of the oil pits at most is 2 to 4%. Therefore, in combination with the problem of the ordinary cold rolling, only the rolling reduction of the final cold rolling, the object of the present invention, the oil pit occupancy of Al alloy plate of AA5000 series or 6000 series 2% The level cannot be lower.

Next, the chemical composition of the Al alloy of the present invention will be described. The Al alloy sheet of the present invention is an Al alloy sheet having a composition of AA5000 or 6000 series, particularly as a panel material of a transport machine such as an automobile, a ship or a vehicle, and has various basic properties such as formability, strength, and corrosion resistance. It is necessary to satisfy the characteristics. Therefore, selection of Al alloy or composition,
It is carried out as appropriate from the AA to JIS 5000 series or 6000 series Al alloy composition standards according to the use of transport panel materials (required characteristics).

For example, AA5000-based Al alloy sheets such as AA5022 and AA5023, which have been conventionally used as panel materials for transport equipment and have excellent strength and formability, are rolled or tempered, or AA6111 , AA6022, AA6016, and the like, a T4 temper material of AA 6000 series Al alloy sheet excellent in formability and bake hardenability are preferably exemplified.

Incidentally, a preferable chemical composition in the AA 6000 series Al alloy plate will be described below. Mg: 0.2-1.0%. Mg forms a compound phase (aged precipitate) with Si during baking coating (heating) and Cu and Al with Cu-containing composition to precipitate, providing high strength (proof stress) or baking hardenability during use Therefore, it is an essential element. If the content of Mg is less than 0.2%, sufficient bake hardenability (high strength) cannot be secured.
On the other hand, if the content exceeds 1.0%, it is crystallized or precipitated as coarse particles at the time of casting and quenching, and the formability is reduced. Therefore, the content of Mg is preferably in the range of 0.2 to 1.0%.

Si: 0.5 to 1.6%. Si and Mg together with Mg, during baking coating (heating), compound phase
(Aging precipitate) is an essential element that forms and precipitates to impart bake hardenability. If the content of Si is less than 0.5%, sufficient bake hardenability (high strength) cannot be secured.
On the other hand, when the content exceeds 1.6%, it is crystallized or precipitated as coarse particles at the time of casting and quenching, and the formability is reduced. Therefore, the content of Si is set in the range of 0.5 to 1.6%.

Cu: 0.05-1.2%. Cu forms a compound phase (aged precipitate) with Mg and Al during baking coating (heating) and precipitates, resulting in high strength (proof stress) during use
Or bake hardenability. Further, it has the effect of improving the formability in a solid solution state at the time of refining of a solution and quenching treatment of T4 or the like. To demonstrate these effects,
Cu is an element to be selectively contained, but if Cu is less than 0.05%, these effects are reduced. On the other hand, if the content exceeds 1.2%, these effects are saturated and the rust resistance, which is the corrosion resistance after coating, is reduced. Therefore, when Cu is contained, the content of Cu is set to 0.05 to 1.2%.

Fe, Mn, Cr: 0.3% or less. Fe, Mn, and Cr form dispersed particles during homogenization heat treatment, refine crystal grains, and improve formability. In order to exhibit these effects, Fe, Mn, and Cr are elements that selectively contain one or more of them, but if they are contained excessively, they form a coarse compound and lower the formability. For this reason, when Fe, Mn, and Cr are contained, each has an upper limit of 0.
3% or less.

Ti: 0.1% or less, B: 300 ppm or less. If the content of Ti exceeds 0.1% and the content of B exceeds 300 ppm, a coarse crystallized product is formed and moldability is reduced. However, a small amount of Ti and B has the effect of refining the crystal grains of the ingot and improving press formability. Therefore, Ti: 0.1% or less,
B: 300 ppm or less.

In addition, other alloying elements such as Zn, Ni, V, and Zr lead to deterioration of other properties even if one property can be improved in the Al alloy plate of the present invention. As a result, the combination of the above-mentioned various properties of the Al alloy plate is hindered. Therefore, it is desirable to suppress the impurity element as low as possible. However, in the present invention, from the viewpoint of recycling the 6000 series Al alloy, as a melting material, to allow the use of a 6000 series Al alloy or other Al alloy scrap material or low-purity Al ingot as the melting material, These elements may be inevitably contained. Therefore, when these elements are contained, it is permitted to contain them at about AA to JIS standards (upper limit).

The aluminum alloy plate itself of the present invention was prepared by melting, casting, homogenizing heat treatment, hot rolling, and the like, except for controlling the oil pit occupancy by cold rolling using the Cr plating roll.
It can be manufactured by ordinary methods such as intermediate annealing, cold rolling, and tempering.

[0037]

Next, embodiments of the present invention will be described. From the Al alloy sheets having the respective component compositions shown in Table 1, a cold-rolled coil having a width of 75 mm was prepared under standard production conditions for AA5000 series and 6000 series Al alloy sheets.

However, the final pass of the cold rolling of the Al alloy plate is as follows:
Oil pit occupancy was controlled using work rolls having Cr plating or surface roughness under the conditions shown in Table 2. At this time, the other final pass cold rolling conditions were all the same, the entry side plate thickness was 1.34 mm, the rolling reduction was 25%, and the rolling speed was 100 m.
/ Min, and a cold rolling oil for Al alloy having a kinematic viscosity of 3.8 cSt / 40 ° C. was used.

A sample was taken from the cold-rolled coil and subjected to a final annealing treatment at 510 ° C. × 10 seconds for the AA5000 series Al alloy sheet, and 550 ° C. × 10 seconds for the AA6000 series Al alloy sheet.
A second solution treatment was performed.

The oil pit occupancy of the surface (rolled surface) of each of the tempered samples was measured by 〇〇〇〇 magnification SEM observation. Further, the glossiness of the plate surface of each sample was measured by a Gloss value at an incident angle of 60 degrees. Table 2 shows the results. The Al alloy No. in Table 2 is the Al alloy in Table 1.
It corresponds to the alloy number.

Then, each sample of these Al alloy plates was
JIS G313 used for separately prepared car panel materials
3 Low yield point steel sheet samples were combined next to each other to simulate use in combination as an automobile body.

Further, in order to simulate that the Al alloy plate and the steel plate are simultaneously coated on the vehicle body, a sample obtained by combining the above Al alloy plate and the steel plate was treated with zinc phosphate and cationic electrode under the same conditions. The coating process and the coating process were performed.

In the zinc phosphate treatment, a treatment with a colloidal dispersion of titanium phosphate is performed, and then 50 pp of fluorine is added.
By immersing in a zinc phosphate bath containing a low concentration of m 2, a zinc phosphate film was formed on the surface of the molded material. Coating is performed under the same conditions under the same conditions, after performing cationic electrodeposition coating, baking at 170 ° C for 20 minutes, and as a 2 coat 2 bake coat, a 30 µm thick paint film and a 30 µm thick polyester melamine-based paint film. Were baked at 170 ° C. for 20 minutes.

Then, with respect to the coated sample in which the Al alloy plate and the steel plate were combined, the sharpness of the Al alloy plate itself after coating and the color tone difference between adjacent steel plates were visually evaluated. The sharpness of the painted Al alloy plate was determined in three stages (〇, △, ×) of the relative evaluation of the painted sample, and the color tone difference between the adjacent steel plates was determined to be inconspicuous at any angle. When the color tone difference was remarkably noticeable, x was given, and when the angle difference was noticeable, Δ was given.

As is clear from Table 2, Invention Examples A to I in which the final pass of the cold rolling was performed using Cr plating and a work roll having a surface roughness within a preferable range and the oil pit occupancy was 2% or less. Is excellent in surface glossiness of Al alloy plate (base plate). It also has excellent surface sharpness after painting, and characteristically, there is no difference in color tone between adjacent painted steel plates.

Accordingly, it can be seen that the Al alloy plate of the present invention can be suitably used in combination with a steel plate, particularly as a panel material for a transport machine such as an automobile.

On the other hand, in Comparative Examples J to N, since the final pass of the cold rolling deviates from the preferable condition range of the Cr plating of the work roll and the surface roughness, the oil pit occupancy exceeds 2%. It is getting bigger. For this reason, Al alloy plate
The surface glossiness of the (base plate) and the surface sharpness after coating are inferior to those of the invention examples. Characteristically, the color tone difference between adjacent coated steel plates is remarkable. Therefore, the Al alloy sheets of these comparative examples are not suitable for use as a transport panel used together with a steel sheet.

In Comparative Example L, the surface roughness of the work roll was too small, so that a biting defect occurred during cold rolling, and the cold rolling itself could not be performed.

The above results support the critical significance of the requirements of the present invention.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

According to the present invention, in the surface state after painting,
It is possible to provide an Al alloy plate for a transport panel material excellent in surface gloss so that there is no difference in gloss between the steel plate and the steel plate.
Therefore, Al alloy plates, which are used in combination with steel plates, have a great industrial value in that they can be used in a wider range of applications for transportation panel materials such as automobiles, vehicles, and ships. .

Claims (4)

[Claims] 1. AA5000 series or 60 used after being painted
An aluminum alloy sheet for transport equipment panel material excellent in surface glossiness, wherein the oil pit occupancy of the surface is 2% or less, which is a 00 series aluminum alloy sheet. 2. The aluminum alloy sheet according to claim 1, wherein said aluminum alloy sheet is used in combination with a steel sheet. 3. The aluminum alloy sheet for transport equipment panel material having excellent surface glossiness according to claim 1, wherein the oil pit occupancy is controlled by cold rolling using a Cr plating roll. . 4. The Cr plating roll has a Cr plating thickness of 2 to 20 μm and a roll surface roughness Ra of 0.01 to 0.1 μm.
The aluminum alloy plate for a transport panel material according to any one of claims 1 to 3, which has a surface gloss of 5 µm.