JP2000129458A - Aluminum alloy sheet excellent in press formability and corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve both inconsistent formability and filiform erosion resistance of an alloy sheet by roughening the surface of a Cu-contg. Al-Mg-Si alloy sheet to a specified roughness and providing the surface with an aluminum hydrated oxide film of a specified thickness. SOLUTION: The surface of an Al-Mg-Si aluminum alloy sheet contg., by mass, about 0.2 to 1.8% Si, about 0.2 to 1.6% Mg and 0.3 to 1.5% Cu is roughened so as to control the maximum roughness(RMax) within one inch in the parallel and perpendicular direction to the rolling direction to >=2 μm, and this roughened surface is provided with an aluminum hydrated oxide film of 100 to 3000 Å. As to the roughening of the aluminum alloy sheet surface, the method of executing rolling using cold rolling rolls whose surfaces are roughened to prescribed roughness by shot dulling can easily control the roughening degree and is also effective. The formation of the Al hydrated oxide film is executed, after pretreatment such as degreasing and washing by water for the surface of the roughened Al alloy sheet, by bringing it into contact with high temp. water or water vapor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy (hereinafter, aluminum is simply referred to as Al) excellent in press formability and corrosion resistance. The present invention relates to an Al alloy plate suitable for use as a panel material or various members for a transport machine such as an airplane.

[0002]

2. Description of the Related Art Aluminum alloy plates have been used in place of steel materials for outer panels, structural materials or parts of transport vehicles such as automobiles, ships and vehicles in order to reduce weight. And, among the aluminum alloy sheets, AA from the viewpoint of material properties excellent in moldability and bake hardenability or recyclability
Al alloys of JIS 6000 series (hereinafter simply referred to as 6000 series) have begun to be used.

[0003] This 6000 series Al alloy is basically composed of Si: 0.2-1.
Al-Mg- containing 8% (mass%, the same applies hereinafter), Mg: 0.2-1.6%
It is a Si-based aluminum alloy. The 6000 series Al alloy secures the formability with low proof stress during press forming, and also improves the proof strength by age hardening during baking coating after press forming, thereby ensuring the required strength. Also,
When scrap is reused as a raw material for dissolving Al alloy, the alloy has a relatively small amount of alloy and is excellent in recyclability, such as being easy to obtain the original 6000 series Al alloy ingot. Therefore, the amount of alloy such as Mg that has been conventionally used for transport aircraft is large.
This is more advantageous than the 000 series Al alloy.

On the other hand, a 6000 series Al alloy sheet is inferior in press forming workability and hemming workability (180 ° bending workability) as compared with conventionally used 5000 series Al alloy sheet and the like. Therefore, 60
In order for the 00 series Al alloy plate to be applied to members that are subjected to severe forming processing, such as outer panels of automobiles that are subjected to hem processing after press forming, it is necessary to improve these formability.

Conventionally, as a means of improving the formability of a 6000 series Al alloy sheet, the chemical composition of the 6000 series Al alloy sheet has been controlled. For example, as a basic composition
Controlling the amount and morphology of precipitates such as Si (excess Si amount) and Mg amount, or Mg ₂ Si is disclosed in JP-A-64-65243,
Many have been proposed in 291834, JP-A-7-228939 and the like.

In addition to controlling the amounts of Si and Mg, Cu
It is possible to improve the moldability by adding, for example, JP-A-6-20
No. 64, JP-A-6-136478, JP-A-8-109428, JP-A-9-
Many have been proposed in 209068, JP-A-9-202933 and the like.

[0007] Further, it is disclosed in Japanese Patent Application Laid-Open Nos. 61-46304 and 63-180331 that the surface of an Al alloy plate is roughened to improve lubricity during forming and improve formability. JP 8-
Many have been proposed in 168826, JP-A-9-78169 and the like. Among them, for example, in Japanese Patent Application Laid-Open No. 61-46304, the maximum roughness (Rmax) within 1 inch in the direction parallel and perpendicular to the rolling direction of the Al alloy sheet is 2 μm or more, and
The number of peaks or valleys with a height or depth of 25 inches or more in inches (PPI) is 30 or more, and the surface of the Al alloy plate is roughened to improve overhang and bending workability. Is disclosed.

[0008]

However, in a 6000 series Al alloy plate, the addition of Cu certainly improves the formability, but deteriorates the rust resistance, which is the corrosion resistance after painting. That is, more specifically, it is known that when 0.3% or more of Cu is added, the thread rust resistance is extremely deteriorated as compared with the case where Cu is not added.

Further, the tendency of the deterioration of the thread rust resistance is 6000
In the system Al alloy plate, for improving the formability,
It is also promoted by roughening the surface of the Al alloy plate. In other words, in the 6000 series Al alloy sheet, the issues of improving the formability and improving the thread rust resistance are contradictory issues that if the formability is improved, the thread rust resistance is deteriorated. In fact, there is no means to achieve it.

The present invention has been made in view of such circumstances, and has as its object to provide a 6000 series Al alloy sheet excellent in both contradictory moldability and yarn rust resistance (corrosion resistance). It is intended to provide.

[0011]

In order to achieve this object, the gist of the present invention is that Si: 0.2 to 1.8% (mass%, hereinafter the same)
, Mg: 0.2-1.6%, Cu: 0.3-1.5%, the surface of an Al-Mg-Si based aluminum alloy plate having a maximum roughness (Rmax) of 2 in 1 inch in a direction parallel to and perpendicular to the rolling direction. μm or more and a film thickness of 100 to 3000 mm on the roughened surface.
Is to provide a hydrated oxide film of aluminum.

As a result of repeated studies, the present inventors have found that Al-Mg-
In order to improve the formability of the Si-based Al alloy sheet, even if Cu is actively contained and the surface of the Al alloy sheet is roughened, if a hydrated oxide film of Al is formed on the roughened surface, Even when used in a form in which the hydrated oxide film of Al is directly coated, in other words, even if the coating is performed by omitting a coating base treatment such as a conventional phosphoric acid treatment and a cationic electrodeposition coating treatment, It was found that the thread rust resistance, which is the corrosion resistance after painting, was improved.

If the thickness of the hydrated oxide film of Al is controlled and the thickness of the hydrated oxide film is reduced, and more preferably, the hydrated oxide film of Al Press coating and hemming are sufficiently possible if the coating surface is coated with lubricating oil.
It was found that cracking and peeling of the hydrated oxide film of Al did not occur.

It is known that an Al hydrated oxide film is formed on the surface of an Al alloy plate and that the Al hydrated oxide film has excellent resistance to thread rust. For example,
In JP-A-05-70969 and the like, a boehmite film made of a neutral or weakly alkaline bath having a thickness of 50 to 1.5 μm is formed on the surface of an Al alloy plate after forming as a coating undercoating film instead of the phosphate treatment. In addition, there has been proposed an Al alloy coated plate for an automobile outer panel having excellent thread rust resistance, in which a coated film is formed thereon.

In addition, the metal surface technology Vol. 37, No. 3, 1986
Pages 110 to 114, or Metal Surface Technology Vol. 24, No. 12, 197
3 pages pp. 700-705 show that among the hydrated oxide films of Al, the upper part of the whisker-like coarse part and the dense part of the base layer or the hydrate-rich dense inner layer and the hydroxide-rich Corrosion resistance (CAS test and salt spray test)
Discloses that it is superior to a boehmite film.

However, none of these known examples is directed to an Al alloy plate for forming as in the present invention. That is, in the prior art such as Japanese Patent Application Laid-Open No. 05-70969, a hydrated oxide film of Al is formed on a formed material after forming or on an Al alloy plate that is not formed. .

On the other hand, the Al alloy plate on which the Al hydrated oxide film is formed, which is the object of the present invention, is subjected to forming, and the Al hydrated oxide film together with the Al alloy plate is severe. It is a prerequisite to undergo molding. Usually, the hydrated oxide film of Al is a hard film like the oxide film of Al. Therefore, it has been common technical knowledge that the formability of an Al alloy plate in which the hard coating is positively provided on the surface is inferior, and that there is a high possibility that peeling of the coating or molding failure of the Al alloy plate occurs. On the other hand, in the present invention, if the hydrated oxide film thickness of Al is 3000 mm or less, even an Al alloy plate on which a hydrated oxide film of Al is formed, press forming and hemming are sufficiently possible. Furthermore, they have been made based on the finding that the coated aluminum alloy sheets thus formed have excellent rust resistance when used.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an Al alloy material according to the present invention
Fig. 1 schematically shows the basic structure of a hydrated oxide film of Al.
The hydrated oxide film 2 of Al according to the present invention is formed on the surface of the Al alloy material 1 (material), and is a relatively coarse upper layer film composed of the hydrated oxide 9 of Al in a plate shape (standing plate shape). 3 and a relatively dense lower layer coating 4 made of granular hydrated oxide 10 of Al. Then, in the Al alloy material 8 after the forming and coating, a coating film 5 that does not involve an electrochemical reaction is provided on the hydrated oxide film 2 of Al. And the paint film
Numeral 5 is composed of a coating film (2 coats 2 bake) which does not involve an electrochemical reaction such as, for example, spray coating of intermediate coat 6 and top coat 7. In the same figure, the Al alloy material 8 shows the Al alloy material after forming and coating, and the coating of the lubricant in the pre-coated material of the present invention is used in the forming process and before the coating process. Removed in processing.

(Hydrated oxide film of Al) In the present invention,
The hydrated oxide film of Al is represented by the general formula, Al ₂ O ₃ .XH ₂ O, and refers to a film of a hydrated oxide of Al generated by a hydration reaction of an Al oxide. The hydrated oxide of Al in the present invention is not particularly limited to the type, form, crystal structure, crystallinity, etc. of the hydrated oxide depending on the degree of hydration (the value of X). However, among the hydrated oxides of Al, those of pseudo-boehmite in which the value of X is about 1.5 to 1.9 are generally referred to as boehmite films.

According to the findings of the present inventors, among the hydrated oxide films of Al, a relatively coarse upper layer film 3 in the shape of a standing plate is used.
Is a hydration-rich film in which X of Al ₂ O ₃ .XH ₂ O is 2 or more. Then, as shown in FIG.
Reference numeral 7 denotes a coarse (porous) layer having relatively large spaces or gaps in which standing plate-like crystals are alternately stacked. On the other hand, the dense lower layer film 4 is a relatively dense layer in which X of Al ₂ O ₃ .XH ₂ O is about 1, and granular Al hydrated oxides 8 are dense as shown in FIG. is there.

The identification of these film structures can be carried out by infrared spectroscopy (FT-IR) as described in detail in Examples, in addition to the morphological observation by the scanning electron microscope. . Further, the distinction and film thickness between the upright plate-like coarse upper layer film 3 and the granular dense lower layer film 4 were made by scanning the fracture surface of the Al alloy plate with a scanning electron microscope, as described in detail in Examples. Can be performed with 20,000 times or more observation. In addition,
This magnification, as the thickness of the hydrated oxide of Al becomes thinner,
Higher magnification is required. In addition, identification is possible by X-ray diffraction, and morphological observation is possible by a transmission electron microscope.

The hydrated oxide film of Al in the present invention means not only a film composed of pure Al hydrated oxide of Al ₂ O ₃ .XH ₂ O but also a hydrated oxide of Al. As long as it is mainly composed of a material film, it may be a mixture, that is, a material containing an impurity element which may possibly be mixed in or form an Al hydrated oxide film. However, the allowable amount is in a range that does not impair the properties such as corrosion resistance and adhesion of the hydrated oxide film of Al.

Further, apart from these impurities, the hydrated oxide film of Al is formed of a metal compound having a potential lower than the natural potential of Al, for example, an alkali or alkaline earth metal such as Mg, Li, or Ca. By containing Si and Mn in a total amount and an average content of 1 at% or more in the film, the temperature of the processing solution for forming the hydrated oxide film of Al is lowered, and the hydrated oxide film of Al is formed at a lower temperature. It is possible to do.

Next, the reason why the hydrated oxide film of Al in the present invention has excellent yarn rust resistance will be described. First,
The yarn rust itself is at the corroded portion at the tip of the coating film 5, and the corrosion of the coating film 5 progresses as the pH extremely decreases to about 1 or less. On the other hand, among the hydrated oxide films of Al, the plate-shaped rough upper layer film 3 has a neutralizing effect of increasing the pH under such a strongly acidic environment, and the coating film 5 It has the effect of suppressing the corrosion reaction. Therefore, the effect of improving the rust resistance of the Al alloy sheet according to the present invention is mainly exhibited by the rough (porous) upper layer coating 3 in the shape of a standing plate.

In order to exhibit the effect of improving the yarn rust resistance, the upper coating 3 of the hydrated oxide coating of Al in the present invention is required.
It is preferable that the thickness of the film is 50 ° or more. When the film thickness of the standing plate-like rough upper layer film 3 is smaller than this, the cathode polarization cannot be sufficiently increased, and the corrosion resistance decreases. Further, there is a possibility that a neutralizing effect of increasing the pH in a strongly acidic environment cannot be obtained. on the other hand,
If it is too thick, it will reduce the adhesion with the paint film,
Since there is a possibility that a phenomenon such as peeling of the coating film may occur, the upper limit of the thickness of the upper layer film 3 is preferably 3000 ° or less.

Further, the thickness of the lower layer film is determined by the water resistance of the film. The deterioration of the water resistance is caused by the reaction of the lower film 4 of the hydrated oxide film of Al with water in the present invention. That is, the granular dense underlayer film is made of Al ₂ O
₃ · XH ₂ O in which X is about 1, X is compared with the upper layer coating rich 2 or more hydrated, there is room room to react with moisture, i.e., the X increases. Therefore, along with the deterioration of the paint film during use and the damage of the paint film due to external factors such as chipping, seawater and salt water penetrate the paint film and cause the base material to penetrate the paint film. The hydrated upper coating with X 2 or more does not react with water when it comes into contact with the Al alloy plate, but the dense lower coating positively reacts with water to increase the volume of the coating itself. Occurs. As a result, the coating film swells and peels off, resulting in adhesion at the interface between the base material Al alloy plate surface and the hydrated oxide film of Al and at the interface between the hydrated oxide film of Al and the paint film. And the coating itself is destroyed, thereby deteriorating the water resistance. This phenomenon is
In particular, it becomes remarkable in a seawater or saltwater atmosphere or environment.

The deterioration of the water resistance due to the thickness of the dense underlayer film greatly changes when the film thickness reaches 3000 ° C.
水性 By suppressing the content below, the water resistance is improved. On the other hand, the dense underlayer coating has a poor solubility function to prevent the dissolution of the Al hydrated oxide film by acids and alkalis, and has a general corrosion resistance such as general corrosion of the Al hydrated oxide film. Improve. In order to exhibit this effect, the thickness of the dense lower layer film needs to be 50 ° or more.

The total thickness (total film thickness) of the hydrated oxide film of Al composed of the upper layer film and the lower layer film or the hydrated oxide film of Al composed of any single layer is 100%.
Must be ~ 3000Å. If the total film thickness is less than 100 mm,
Corrosion resistance including the aforementioned rust resistance generally decreases. On the other hand, if the total film thickness exceeds 3,000 mm, the adhesion of the hydrated oxide film of Al to the Al alloy plate, which is necessary for press forming and hemming, is reduced. Even if it does, film peeling and molding failure of the Al alloy sheet occur, and the practicality for molding processing is lost. Further, when the film is peeled off, the corrosion resistance including the water resistance and the rust resistance after coating is generally reduced.

Next, a method for producing a hydrated oxide film of Al in the present invention comprising an upper film and a lower film will be described. First, after an Al alloy plate is formed and welded and joined for a transport machine, an appropriate pretreatment for degrease or washing the Al alloy surface of the formed material with an organic solvent, an alkaline solution or an acidic solution is performed. Among these pretreatments, when pretreatment with an aqueous nitric acid solution, the effect of improving the denseness of the hydrated oxide film of Al formed in a later step, suppressing the penetration of moisture, and further improving the water resistance. Have.

Then, after this pretreatment, a method of directly contacting with high temperature water or steam, or a method of forming an Al oxide layer on the Al alloy surface of a molding material and then performing a hydration reaction to form a hydrated oxide film of Al. Method, further, after providing these hydrated oxide film of Al, a method of adjusting the amount of hydration by heating,
Alternatively, the method of the present invention is appropriately selected by, for example, a method of contacting with a high-temperature neutral or weakly alkaline bath (pure water, tap water, an aqueous solution of triethanolamine or ammonia) as described in JP-A-05-70969 or the like. 2 layers of hydrated oxide film of Al are prepared.

However, even if the main conditions such as the conditions for forming the hydrated oxide film of Al are the same, the two-layered hydrated oxide film of Al of the present invention is not always required. That is, for example,
Even if the main conditions for producing the hydrated oxide film of Al are the same, the surface condition of the Al alloy material, or the pretreatment conditions for producing the hydrated oxide film, If the detailed conditions during production are different, the two-layer hydrated oxide film of Al of the present invention may not be formed. In fact,
In Japanese Patent Application Laid-Open No. 05-70969, the resulting film is a hydrated oxide film consisting of only one layer of boehmite despite contact with a high-temperature neutral or weakly alkaline bath. Therefore, the specific conditions for producing the hydrated oxide film of Al, including the surface conditions of the Al alloy plate and the pretreatment conditions, are those of the present invention.
It is necessary to appropriately select conditions under which two hydrated oxide films of Al are obtained, depending on individual cases.

(Coating) Then, the hydrated oxide film of Al and the organic resin film containing the powdery lubricant of the present invention were provided.
After forming and processing the Al alloy plate, assembling it into used products and parts by welding if necessary, then painting. First, the painting process
Lubricating oil and lubricant during molding of the molding material surface are removed in a degreasing and cleaning process. And at the time of coating, while omitting the conventional undercoating treatment such as phosphate treatment and cationic electrodeposition coating, the Al alloy surface does not fall into the alkaline range,
Apply a coating in the neutral or acidic range. In particular,
A non-cationic electrodeposition coating selected from electrostatic coating, anion electrodeposition coating and spray coating, roll coater coating, and dip coating is selectively performed.

As in the case of a conventional automobile manufacturing line, a coating material having a hydrated oxide film of Al is subjected to a coating base treatment such as a phosphate treatment or a cationic electrodeposition coating, and then subjected to a coating treatment. Is also possible. However, the hydrated oxide film of Al of the present invention can be used as an alternative to conventional undercoating treatments such as phosphate treatment and cationic electrodeposition coating. Possible and excellent in corrosion resistance after painting. Thus, it is possible to omit or reduce the coating base treatment step, which greatly contributes to cost reduction.

Further, when coating is performed by an electrochemical reaction using an Al alloy as a cathode, such as cationic electrodeposition coating, a phenomenon in which the hydrated oxide film is partially damaged by the generated alkaline substance. This causes the rust resistance to deteriorate significantly and the water resistance to deteriorate. Further, by applying the ED coating, the advantage that the ED coating of the present invention can be omitted is also lost.

(Applicable Al Alloy) Next, A in the present invention
The l-alloy plate is a 6000 series Al alloy having mechanical properties such as tensile strength and proof stress, workability, and weldability. In particular, in the case of transport applications, the 6000 series Al alloy, as described above,
At the time of press forming, the formability is ensured by low proof stress, and the proof strength is improved by age hardening at the time of baking coating after press forming, so that the required strength can be secured. Further, when scrap is reused as a raw material for dissolving an Al alloy, there are considerable advantages such as a relatively small amount of alloy and excellent recyclability such as easy acquisition of an original 6000 series Al alloy ingot.

The preferred properties of the 6000 series Al alloy sheet for, for example, an automobile panel are that the Al alloy sheet has a yield strength of 130 N / mm ² or less at the time of forming, and a maximum drawing depth (at the time of deep drawing). LDH ₀ ) is 27mm or more, and the yield strength after painting and paint baking hardening after molding is 2% stretch.
The proof stress after heating at 170 ° C. for 20 minutes is 160 N / mm ² or more.

In order to satisfy these characteristics, the preferable range of the chemical composition is 6000 series Al-Mg-Si series.
Alloy composition standards (6101, 6003, 6151, 6061, 6N01, 6063
Basically, Si: 0.2-1.8%,
Mg: 0.2 to 1.6%, and preferably, Zn: 0.005
~ 1.0%, one or more of Ti: 0.001 ~ 0.1%, B: 1 ~ 3
One or two kinds of 00 ppm, Be: 0.1 to 100 ppm, Mn: 1.0% or less, Cr: 0.3% or less, Zr: 0.15% or less, V: 0.15% or less one or more kinds, selectively totaling 0.01 Al alloy containing up to 1.5%, the balance being Al and unavoidable impurities.

In the present invention, however, it is essential that Cu is contained in an amount of 0.3 to 1.5% in order to improve the moldability, and therefore, it may not always be within the respective AA to JIS component standards. Therefore, in the present invention, the basic component S
Elements other than i and Mg do not comply with each component standard of AA to JIS, as long as they have the basic characteristics described above, to further improve the characteristics and add other characteristics, Changes in component composition are acceptable. In this regard, it is permissible to appropriately contain other elements other than the above, such as Ni, Sc, and Ag, according to more specific applications and required characteristics. In addition, other impurities that are necessarily mixed in from gas components such as H ₂ and O ₂ , dissolved material scrap, and the like are also allowed as long as the quality and characteristics are not impaired.

Next, the content of each element in the Al-Mg-Si-based Al alloy sheet of the present invention will be described in terms of critical significance and preferred range.

Mg: 0.2-1.6%. Mg during artificial aging (molding, baking and curing processes etc. after coating) by, Mg with Si ₂
Precipitated as Si, and in a Cu-containing composition, it is an essential element for forming a compound phase with Cu and Al to impart high strength (proof stress) or bake hardenability during use. Mg 0.
If the content is less than 2%, these effects are insufficient, and sufficient strength cannot be obtained even with artificial aging. On the other hand, if the content exceeds 1.6%, the strength (proof stress) becomes too high, and the moldability is impaired. Therefore, the content of Mg is set in the range of 0.2 to 1.6%.

Si: 0.2-1.8%. Si also precipitates as Mg ₂ Si together with Mg by artificial aging, resulting in high strength during use
(Proof stress) is an essential element for imparting, but if the content is less than 0.2%, sufficient strength cannot be obtained by artificial aging,
If it is contained in excess of 1.8%, it precipitates as coarse particles during casting and quenching, and impairs formability, such as lower elongation. Therefore, the content of Si is set in the range of 0.2 to 1.8%. The precipitation state during baking heating was Mg and
It is greatly affected by the ratio of the Si content. When Mg / Si exceeds 1, the precipitation becomes coarse, and the effect of improving the strength is reduced. Therefore, Mg / Si is preferably set to 1 or less.

Cu: 0.3-1.5%. Cu is Mg when baking and heating,
It forms a compound phase with Al and precipitates, imparts bake hardenability, and improves moldability in a solid solution state during T4 refining. If the Cu content is less than 0.3%, these effects will not be obtained, and if it exceeds 1.5%, the effects will be saturated. If the Cu content exceeds 1.5%, a large amount of Cu precipitates on the surface of the Al alloy plate when the Al alloy plate is etched, and the deposited Cu remains without being removed even by the phosphate treatment. I do. Therefore, Cu adhered to the surface of the Al alloy plate remains at the interface between the coating film and the surface of the Al alloy plate even after electrodeposition coating, deteriorating the corrosion resistance after coating, especially the thread rust resistance. Let it. Therefore, the content of Cu is set to 0.01 to 1.0%.

Next, Zn, Ti, B, Be, Mn, Cr, Zr, V
Is an element selectively contained depending on the purpose.

Zn: 0.005 to 1.0%. Zn achieves high strength by precipitating MgZn ₂ finely and at high density during artificial aging. However, if the content of Zn is less than 0.005%, sufficient strength cannot be obtained by artificial aging, whereas if the content exceeds 1.0%, the corrosion resistance is significantly reduced. Therefore, the content of Zn is preferably in the range of 0.005 to 1.0%.

Ti: 0.001 to 0.1%. Ti is an element added to refine the crystal grains of the ingot and improve press formability. However, if the content of Ti is less than 0.001%, this effect cannot be obtained. On the other hand, if the content of Ti exceeds 0.1%, coarse crystals are formed and the formability is reduced. Therefore, Ti
Is preferably in the range of 0.001 to 0.1%.

B: 1 to 300 ppm. B, like Ti, is an element added to refine the crystal grains of the ingot and improve press formability. However, if the content of B is less than 1 ppm, this effect cannot be obtained, while if the content is more than 300 ppm,
Again, coarse crystals are formed and formability is reduced. Therefore, the content of B is preferably in the range of 1 to 300 ppm.

Be: 0.1 to 100 ppm. Be is an element contained to prevent re-oxidation of the Al melt in the air. However, if the content is less than 0.1 ppm, this effect cannot be obtained, while if the content exceeds 100 ppm, the material hardness increases,
Decreases moldability. Therefore, the content of Be is 0.1 to
It is preferable to be in the range of 100 ppm.

Mn: 1.0% or less, Cr: 0.3% or less, Zr: 0.15% or less, V: 0.15% or less. These elements are used during the homogenizing heat treatment and during the subsequent hot rolling, Al ₂₀ Cu ₂ Mn ₃ , Al ₁₂ Mg ₂ Cr, Al
₃ Zr, and generates dispersed particles such as Al ₂ Mg ₃ Zn _3. Since these dispersed particles have an effect of hindering the movement of the grain boundary after recrystallization, fine crystal grains can be obtained. However, an excessive content tends to generate a coarse intermetallic compound at the time of melting and casting, becomes a starting point of destruction at the time of molding, and causes a decrease in moldability. Further, an excessive content of Zr tends to make the microstructure needle-like, deteriorating fracture toughness and fatigue properties in a specific direction, and further deteriorating formability. Therefore, the content of these elements, respectively, Mn: 1.0% or less, Cr: 0.3% or less, Zr: 0.15% or less,
V: 0.15% or less.

Fe: Fe contained as an impurity is Al ₇ Cu ₂ F
e, Crystallized substances such as Al ₁₂ (Fe, Mn) ₃ Cu ₂ and (Fe, Mn) Al ₆ are generated. These precipitates degrade fracture toughness and fatigue properties, as well as formability. In particular, when the content of Fe exceeds 0.5%, these characteristics are significantly deteriorated.
Preferably, it is 0.5% or less. In addition, crystallized substances generated during casting are, in addition to the above-mentioned Fe system, Al ₂ Cu ₂ Mg, Al ₂ Cu ₂ , Mg ₂ Si
It is preferable that these are dissolved sufficiently in the Al matrix by solution treatment and quenching. In addition, Ni is preferably set to 0.05% or less.

(Method for Producing Al Alloy Plate) Further, an Al alloy plate provided with a hydrated oxide film of Al and an organic resin film is produced as a plate material by rolling or the like by a conventional method. That is, the molten aluminum alloy melted and adjusted within the component specification range is subjected to, for example, a continuous casting rolling method, a semi-continuous casting method (DC
Casting method) and the like are appropriately selected and cast. Next, the aluminum alloy ingot is subjected to a homogenizing heat treatment, and a sheet material product is formed by hot rolling and cold rolling to which rough annealing or intermediate annealing is added as required, and a refining treatment such as quenching.

At this time, the surface of the Al alloy plate was adjusted to have a maximum roughness (Rmax) of 2 μm within 1 inch in a direction parallel and perpendicular to the rolling direction.
It is necessary to roughen the surface to m or more. When Rmax is less than 2 μm, the formability of the Al alloy plate itself is insufficient, and thus, poor forming is likely to occur.

As a method of roughening the surface of the Al alloy plate, the surface of the Al alloy plate may be directly roughened mechanically by shot blasting or the like, or chemically by alkali etching or the like. By cold rolling using a predetermined roughened cold rolling roll, the Rmax of the Al plate surface
Is preferred because it is easy to control and efficient.

[0053]

Next, embodiments of the present invention will be described. As shown in Table 1, with the composition of 6101, 6151, 6061, 6N01 standard, and
Al alloy ingots (only 50 mm thick) adjusted for Cu content only
After melting by DC casting, it was subjected to a homogenizing heat treatment at 470 ° C. for 8 hours and hot-rolled to a thickness of 3.5 mm. Then thickness
The aluminum plate was cold-rolled to 1.0 mm, subjected to a solution treatment at 560 ° C. for 1 hour using a nitrite furnace, and then water-cooled (water-quenched) to prepare an Al plate. Incidentally, the water-cooled test material has a tensile strength of 230 N / m
m ² or more and 120 N / mm ² or more in proof stress, after baking
It had a bake hardenability with a yield strength of 200 N / mm ² or more. The Al plate was roughened by controlling the Rmax of the surface of the Al plate by cold rolling using a cold rolling roll having a predetermined surface roughened by shot dull. Table 2 shows these values.

A hydrated oxide film of Al was provided on these Al alloy plates under the conditions shown below and in Table 2.

(Conditions for Formation of Hydrated Oxide of Al) With respect to the inventive examples Nos. 1 to 3 and 6 to 8 in Table 2, each of the Al alloys containing Cu having the compositions of Nos. 1 to 3 in Table 1 was tested. 2 pieces in 30% nitric acid at 40 ° C
After immersing in water and washing with water, 0.5% triethanolamine (TEA) at 70-90 ° C
The film was immersed in an aqueous solution for 1 to 10 minutes to form two Al hydrated oxide films, and the film thickness was controlled by changing the temperature and the immersion time. For Invention Example No. 5 in Table 2, the test piece was
After immersion in 40% 30% nitric acid for 2 minutes and washing with water, treated with a 90 ° C. aqueous solution containing 4 g / l of nickel acetate for 30 minutes, the Al alloy surface was hydrated with Al hydrated oxide containing 5.7 at% nickel. Composite film (2
Layer). Further, with respect to Invention Example No. 4 in Table 2, the test piece was immersed in 30% nitric acid at 40 ° C for 2 minutes, washed with water, and then washed with a 90 ° C aqueous solution containing 7 g / l of lithium carbonate.
Treated for 20 minutes, Al containing 11at% lithium on Al alloy surface
A composite film with the hydrated oxide (a film consisting of only the upper layer in two layers) was provided. .

For comparison, a hydrated oxide film of Al was provided under the same conditions as those of Comparative Example No. 13 and Inventive Examples Nos. 1 to 3 and 6 to 8 where no Al hydrated oxide film was provided. However, Comparative Example N in which the film thickness was controlled outside the range of the present invention by changing the temperature and the immersion time
o, 9, 10 and the hydrated oxide film thickness of Al are within the scope of the present invention, but 6000 series Al alloy substantially free of Cu (N in Table 1)
Comparative Examples Nos. 11 and 12 using o.4 and 5) were also prepared.

(Identification of hydrated oxide film of Al) As a result of identifying the hydrated oxide film of Al of each of the test pieces by the FT-IR method, AlO ← → H observed near 3000 to 3700 cm ⁻¹ was obtained. stretching vibrations due to absorption spectra, and the absorption spectrum by stretching vibration of 1000~1050cm observed in the vicinity of ^-1 Al ← → OH, at least more of the absorption spectrum due to stretching vibration for allowed OAl ← → O in the vicinity of 800 ~600cm ^-1 of The presence of one or more oxides confirmed the presence of a hydrated oxide film of Al.

Further, the morphological identification of the upper layer coating and the lower layer coating and the measurement of the film thickness were carried out by multiplying the fracture surface of the Al alloy plate specimen by 180 ° bending by 50,000 times (150,000 in the case of a thin film).
The magnification was determined by observation with a scanning electron microscope (SEM).
As a result, Invention Examples Nos. 1-3 and 6-8 and Comparative Example No. 9
12, it was confirmed that the Al hydrated oxide film was composed of an upright plate-like rough upper film and a granular dense lower film as shown in FIG. In addition, Invention Example No. 5 corresponds to FIG.
Among them, it was confirmed that the film consisted only of a rough plate-like upper layer film. In addition, it was confirmed that Invention Example No. 4 was composed of only the upright plate-shaped rough upper layer coating in FIG.

(Molding Test) A U-bending test was performed under the following conditions, and the sliding characteristics were evaluated by measuring the punch load (N / mm ² ) of the test piece. Table 3 shows the results. U The bending test conditions were as follows: each test piece was 25 mm wide x 200 mm long
As a (1.0mmt) blank material, a punch with a shoulder R5.0mm of 50.0mm square and a shoulder R5.0mm of 52.8mm square with a molding height (depth) of 50.0mm
A U-bend was performed using a die of mm with a wrinkle pressing force of 7 kN, and the punch load at this time was measured. As the lubricating oil for forming, a commercially available lubricating oil for forming a steel plate was used.

The interface between the Al hydrated oxide film and the Al alloy plate was observed on the cross section of the side wall of each formed material subjected to the U-bending test, and peeling and cracking of the Al hydrated oxide film were observed. Investigate whether or not a peeling or cracking has occurred. ○: If peeling or cracking has occurred slightly
A sample having a length of 1 mm or more in which remarkable peeling and cracking occurred was evaluated as x. Table 3 shows the results.

(Coating Conditions) The side wall of the molded material subjected to the U-bending test was sampled as a corrosion resistance test piece after coating, and the lubricant on the surface was completely removed in a degreasing and cleaning step.
In each of the invention examples and the comparative examples, a two-coat two-bake coating film was further provided by a spray coating method involving no electrochemical reaction. In addition, only the invention example No. 6 was provided with a coating film in the same manner as the other invention examples after performing cationic electrodeposition coating accompanied by an electrochemical reaction. Further, in Comparative Example No. 13 only, as a normal coating base treatment, a coating film was provided after performing cationic electrodeposition coating after zinc phosphate treatment. Further, only Invention Example No. 2 was provided with a two-coat two-bake coating film by roll coater coating.

2 Coat 2 As a bake coating, more specifically, as a middle coating, a polyester melamine-based coating film having a thickness of 30 μm was provided, observed at 140 ° C. × 20, baked, and further overcoated. A polyester melamine-based paint film with a thickness of 30 μm was
For a minute.

(Corrosion Resistance Test after Painting) The coated test pieces of the invention examples and the comparative examples were all subjected to a rust resistance evaluation test and a water resistance evaluation test under the same conditions. Table 3 also shows the results of these evaluations. The rust resistance evaluation test is performed by applying a 5 cm cross-cut to each of the painted test specimens, then adding 3% HCl at 35 ° C.
After being immersed in the aqueous solution for 2 minutes, it was then left in an atmosphere of constant temperature and humidity of 40 ° C. and 85% RH for 1500 hours, and then the maximum length L (the distance in the vertical direction from the cross cut) of the generated rust was measured. Then, for comparison, the maximum length L of the thread rust generated on the test piece of Comparative Example No. 13 in which the hydrated oxide of Al was not provided in Table 3 was set to 1, and ◎: L ≦ 0.5, ○: 0.5
<L <1, ×: 1 ≦ L

Further, in the water resistance evaluation test, the test piece was heated at 40 ° C.
After 10 days of immersion in ion-exchanged water, a 1 mm width cross cut tape peeling test was performed to measure the residual ratio of the coating film. Then, those in which 100% of the coating film remained were evaluated as ◎, those in which 90% or more remained, and those in which 90% or less were evaluated as x. Table 3 shows the results of the corrosion resistance test.

As is evident from the results in Table 3, Invention Examples Nos. 1 to 8 which are within the scope of the present invention generally have a small punch load in the U-bending test, and show that the formability of the Al alloy sheet is lower than that of Al hydration. Punch load of comparative example No.13 without oxide (formability)
It can be seen that there is no inferiority to. It also has excellent moldability of the hydrated oxide film of Al (crackability and peelability of the hydrated oxide film of Al), and is excellent in both water resistance and yarn rust resistance as corrosion resistance after painting. You can see that there is.

However, among them, in Invention Example No. 3, since the Rmax of the Al plate surface was near the lower limit, the punch load was high, and the Al hydrated oxide had some cracks and the like. The properties are inferior to other invention examples. Also, the hydrated oxide film of Al
Inventive Example No. 5 in which only the upper layered coarse film in the two layers is formed, and Inventive Example in which the hydrated oxide film of Al is only the lower granular dense film in the two layers
No. 4 is excellent in moldability of Al hydrated oxide film, but has two layers of Al hydrated oxide film as either corrosion resistance or water resistance after coating. Is inferior to other invention examples consisting of In addition, Invention Example No. 6 in which cationic electrodeposition coating was performed as a coating base was inferior in both rust resistance and water resistance as well as in corrosion resistance after coating compared to other invention examples not performing cationic electrodeposition coating. I have. In addition, Invention Example No. 7, in which the thickness of the hydrated oxide film of Al is near the upper limit of the present invention, is excellent in corrosion resistance after coating with both rust resistance and water resistance,
As compared with the other invention examples, the punch load is higher, the hydrated oxide of Al has some cracks and the like, and the moldability is poor. In addition, Invention Example No. 8 in which the thickness of the hydrated oxide film of Al is near the lower limit of the present invention has excellent moldability, but has a higher corrosion resistance after painting than the other invention examples. Inferior.

On the other hand, in Comparative Examples Nos. 9 to 12 in which the Rmax of the surface of the Al plate was less than the lower limit, the punch load was generally high, cracks were generated in the hydrated oxide of Al, and the moldability was low. It is significantly inferior to the invention examples. Also, Comparative Example No.13, which is a conventional example not provided with a hydrated oxide film of Al, has a relatively low punch load and is excellent in workability, but has high corrosion resistance after coating, such as yarn rust resistance and water resistance. The properties are remarkably inferior.
Of these, Comparative Example No. 10 provided with a hydrated oxide film of Al that was too thin outside the scope of the present invention had the same results as Comparative Example No. 13. Comparative example further provided with a too thick hydrated oxide film of Al
No. 9 has remarkable workability and cracking or peeling of the hydrated oxide film of Al, and inevitably has particularly poor yarn rust resistance. Furthermore,
Comparative Examples No. 11 and 12 using 6000 series Al alloy containing no Cu
Although the thickness of the hydrated oxide film of Al is within the range of the present invention, the formability of the Al alloy plate itself is extremely poor. In particular, in Comparative Example No. 12, since the Rmax of the Al plate surface was less than the lower limit, the formability was remarkably inferior.

Therefore, the above facts support the critical significance of the present invention and the significance of preferable conditions for achieving excellent corrosion resistance after press molding. In addition, it can be used as a substitute for phosphate treatment + ED coating, has excellent coating properties even without ED coating, and is backed by its suitability as an Al alloy plate for transport equipment.

[0069]

[Table 1]

[0070]

[Table 2]

[0071]

[Table 3]

[0072]

According to the present invention, it is possible to provide an Al alloy plate excellent in both press formability and corrosion resistance, and to provide an Al alloy plate which can replace conventional phosphate treatment + ED coating. . Therefore, it has a great industrial value in that the function of the Al alloy plate can be improved and its use can be expanded.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a basic structure of a hydrated oxide film of Al according to the present invention.

[Explanation of symbols]

1: Al alloy material 1 (material), 2: Al hydrated oxide film, 3: Upper layer film, 4: Lower layer film, 5: Paint film, 6: Middle coat, 7: Top coat,
8: Al alloy material after forming and painting, 9: hydrated oxide of plate-like Al, 10: hydrated oxide of granular Al,

Claims (9)

[Claims] Claims 1. An Al-Mg-Si-based aluminum alloy surface containing Cu: 0.3 to 1.5%, having a maximum roughness (Rmax) of 2 µm or more within 1 inch in a direction parallel to and perpendicular to the rolling direction. An aluminum alloy sheet excellent in press formability and corrosion resistance, characterized in that it has a roughened surface and is provided with a hydrated oxide film of aluminum having a film thickness of 100 to 3000 mm on the roughened surface. 2. The hydrated oxide film of aluminum,
The aluminum alloy sheet having excellent press formability and corrosion resistance according to claim 1, comprising a rough upper layer film and a dense lower layer film, wherein the dense lower layer film has a thickness of 50 to 3000 °. 3. The press formability and corrosion resistance according to claim 1 or 2, wherein the surface of the aluminum alloy plate is treated with a nitric acid aqueous solution before the hydrated oxide film of aluminum is provided. Aluminum alloy plate. 4. The press formability and corrosion resistance according to any one of claims 1 to 3, wherein the aluminum alloy sheet has a yield strength of 160 N / mm ² or more after a forming process and a paint baking hardening process. Aluminum alloy plate. 5. The aluminum alloy sheet having excellent press formability and corrosion resistance according to claim 1, wherein the aluminum alloy sheet is roughened by rolling. 6. The aluminum having excellent press formability and corrosion resistance according to claim 1, wherein the aluminum alloy plate is formed and / or welded and then painted and used. Alloy plate. 7. The aluminum alloy sheet according to any one of claims 1 to 6, wherein the formed material or the welded material of the aluminum alloy plate is directly coated and used without being subjected to a phosphate treatment and a cationic electrodeposition coating treatment. Aluminum alloy plate with excellent press formability and corrosion resistance. 8. The aluminum alloy sheet having excellent press formability and corrosion resistance according to claim 1, wherein the aluminum alloy sheet is for a transport machine. 9. The aluminum alloy sheet having excellent press formability and corrosion resistance according to claim 1, wherein the transporter is for an automobile.