JP2000355724A - Aluminum alloy sheet for press forming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent press formability by allowing the alloy sheet to have an Al oxidized film having a specified thickness on the surface and allowing an Mg component in the Al oxidized film to exist by a specified amt. by the ratio between Mg and Al (Mgat%/Alat%). SOLUTION: This is an Al-Mg-Si aluminum alloy sheet contg., by mass, 0.2 to 1.6% Si and 0.2 to 1.6% Mg and having an Al oxidized film of 40 to 100 Å thickness on the surface, and in which the Mg component in the oxidized film is allowed to exist by 0.1 to 0.4 by the ratio between Mg and Al (Mgat%/Alat%). Preferably, the aluminum alloy sheet is the one subjected to solution treatment and quenching by a continuous heat treating furnace, contg. 0.6 to 1.3% Si and 0.2 to 1.0% Mg and having >=1.0 Si/Mg. This aluminum alloy preferably contains one or >= two kinds among 0.01 to 0.2% Mn, 0.01 to 0.2% Cr, 0.01 to 0.2% Zr and 0.01 to 0.15% V as well.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al-Mg-Si-based aluminum alloy sheet having excellent press formability (hereinafter, aluminum is simply referred to as Al).

[0002]

2. Description of the Related Art Molding is used for outer panels and structural materials or parts of transport vehicles such as automobiles, ships and vehicles, for structural materials and parts of home electric appliances, and for building and structural members such as roofing materials. AA to JIS 5000 series excellent in formability and AA to JIS 6000 series excellent in formability and bake hardenability (hereinafter simply referred to as 50
(Referred to as 00 series to 6000 series) Al alloys. Among them, especially, for panel materials or wheels such as car doors, fenders and bonnets,
In view of the material properties and recyclability, use of a 6000 series Al alloy has been studied.

[0003] This 6000 series Al alloy is basically composed of Si: 0.2-1.
Al-M containing 6% (mass%, the same applies hereinafter), Mg: 0.2-1.6%
It is a g-Si based aluminum alloy. And this 6000 series Al
The alloy secures the formability with low proof stress during press forming, and improves the proof strength by age hardening during baking coating after press forming, thereby ensuring the required strength. Further, when scrap is reused as an Al alloy melting raw material, the amount of alloy is relatively small, and it is easy to obtain the original 6000 series Al alloy ingot. Therefore, it is more advantageous than a 5000 series Al alloy which has a large amount of alloy such as Mg, which has been conventionally used for transportation.

On the other hand, in order to make the Al alloy plate into a panel for a transport machine, etc.,
Press forming such as deep drawing, overhang, bending, and stretch flange is performed. At this time, it is necessary to ensure high deep drawability and high shape freezing property in deep drawing, overhanging, or stretch flange forming. With the complication of products or member shapes, press forming conditions are becoming increasingly severe.

[0005] Therefore, in order for the 6000 series Al alloy sheet to be used as a panel material for the transport machine, higher press formability, and particularly, in press forming, the critical draw height is used as an index of deep draw formability. Needs to be high. In recent years, the required limit drawing height in the deep drawing is increasing more and more, and therefore, the 6000 series Al alloy sheet needs to have formability satisfying these.

On the other hand, when manufacturing a 6000 series Al alloy sheet for press formability, after the final solution treatment and quenching treatment, an acid or alkali solution or a combination thereof is used to wash the sheet. . This washing step removes rolling oil and dirt attached to the surface of the Al alloy plate by cold rolling or solution treatment, which is the previous step, or degreasing in zinc phosphate treatment in an automobile production line, This is for removing the oxide film containing MgO, which inhibits the adhesiveness after molding.

However, if the amount of etching in this cleaning step is too large, the press formability of the Al alloy plate is rather deteriorated as described in JP-A-8-92773. This is because it is recognized that the oxide film containing MgO inhibits the chemical conversion property, but on the other hand, contributes to the improvement of lubricity in press molding.

For this reason, in the above publication, when an oxide film containing MgO is etched by a cleaning step, the amount of etching is controlled so that the oxide film remaining amount is determined by the balance between phosphatability and formability. It has been proposed to. That is, in Japanese Patent Application Laid-Open No. 8-92773, the oxide film containing MgO, which contributes to the press formability of the Al alloy plate, is not completely removed by the washing step but is left in a range that does not impair the phosphatability. Is intended.

[0009]

However, it has been found by the present inventors that when the oxide film containing MgO is subjected to the above-mentioned cleaning with ordinary etching, Al
MgO dissolves preferentially over oxides of Therefore, even if the aluminum oxide film is left, the content of MgO in the oxide film is significantly reduced. The oxide film with reduced MgO 2 has a significantly lower formability than the oxide film before etching containing a large amount of MgO.

The reduction of MgO in the oxide film due to the etching and the degree of reduction in press formability due to the reduction of MgO are more remarkable in the Al-Mg-Si-based Al alloy sheet than in the Al-Mg-based Al alloy. Occurs. That is, the Al-Mg-Si-based Al alloy plate having a low Mg content according to the present invention is more remarkable than the Al-Mg-based Al alloy containing 2.0% or more of Mg directly intended by JP-A-8-92773. Occurs. In particular, in the case of an Al-Mg-Si-based Al alloy plate, the amount of Mg contained in the oxide film is 0.8 to 1.5 times that of the oxide film, which is the optimum etching amount described in JP-A-8-92773.
The press formability significantly decreases due to the decrease of O 2.

[0011] This is because the oxide film of an Al-Mg-based Al alloy plate containing a large amount of Mg contains a large amount of MgO, and even if the MgO is preferentially dissolved and reduced by etching, a large amount of MgO still remains. This is because they remain in the oxide film. Therefore, in the Al-Mg-based Al alloy sheet, the phenomenon of the decrease in press formability is not so remarkable as in the Al-Mg-Si-based Al alloy sheet. On the other hand, in an Al-Mg-Si-based Al alloy plate with a low Mg content, MgO in the oxide film is originally small, and if MgO is preferentially dissolved and reduced by etching, the MgO remaining in the oxide film is It extremely lowers, and significantly affects press formability.

That is, JP-A-8-92773 discloses Al-M
Although it can include g-Si Al alloy plate in the range,
The knowledge and recognition of the etching behavior of the oxide film containing MgO is based solely on the behavior of the oxide film of the Al-Mg-based Al alloy sheet. And the examples are also Al-Mg based
Only for Al alloy plates. Therefore, inevitably, the MgO 2 of the oxide film of the Al-Mg-Si-based Al alloy plate
There is no recognition of a behavior different from that of the alloy plate.

The present invention has been made in view of such circumstances, and an object thereof is to provide an Al-Mg-Si-based Al alloy sheet having excellent press formability.

[0014]

In order to achieve this object, the gist of the Al alloy of the present invention is as follows: Si: 0.2 to 1.6% (mass%, the same applies hereinafter); Mg: Al-Mg containing 0.2 to 1.6%. -Si-based aluminum alloy plate with an aluminum oxide film with a thickness of 40 ~ 100mm (angstrom) on the surface,
The Mg content in the aluminum oxide film was calculated as the ratio of Mg to Al.
(Mgat% / Alat%) 0.1 to 0.4.

As described above, the present inventors have proposed an Al-Mg-Si based Al alloy sheet for press forming, particularly an Al-Mg-Si based alloy having a high Si / Mg ratio of 1.0 or more. It was found that the washing process after the solution treatment and quenching of the Al alloy plate by the continuous heat treatment furnace affected the press formability of the Al alloy plate. In other words, it has been found that the abundance ratio of MgO in the oxide film on the surface of the Al-Mg-Si-based Al alloy sheet affects the press formability of the Al alloy sheet.

That is, when the oxide film is etched by this washing, MgO is preferentially dissolved over Al oxide as described above, which contributes to improvement in lubricity in press molding. MgO content is reduced. As a result, an Al-Mg-Si-based Al alloy plate having an oxide film with reduced MgO has an oxide film before etching containing a large amount of MgO due to differences in the oxide film structure or composition, even if the oxide film thickness is the same. The formability is lower than that of the Al-Mg-Si-based Al alloy sheet.

The phenomenon of the decrease in press formability due to the decrease in MgO in the oxide film in this etching or the degree of the decrease in press formability is caused by the fact that Al-Mg containing 2.0% or more of Mg.
Al-Mg-Si Al with lower Mg content according to the present invention than Al alloy
It occurs more prominently in alloy sheets. For example, Al-Mg-Si system
In the case of an Al alloy plate, there is a difference of 1.0 to 1.5 mm in the limit drawing height depending on the etching method.

[0018]

Therefore, in the present invention, Al-M
The thickness of the Al oxide film on the surface of the g-Si-based Al alloy plate is specified to be 40 to 100 mm, and the Mg content in the oxide film is 0.1 to 0.1 in the ratio of Mg to Al (Mgwt% / Alwt%). Be present in the range of 0.4.

(Thickness of Al Oxide Film) When the thickness of the Al oxide film on the surface of the Al alloy plate is less than 40 mm, the amount of Mg in the oxide film is reduced, and the press formability of the plate is reduced. Is significantly reduced. In addition, during press forming, the Al alloy material under the oxide film is deformed, so that the die or punch and Al
The contact area with the alloy plate increases, the sliding resistance increases, and the press formability also decreases significantly.

On the other hand, when the thickness of the Al oxide film exceeds 100 mm, the Al oxide film becomes rather difficult to dissolve (etch) during the chemical conversion treatment, and the adhesion of the chemical conversion coating such as zinc phosphate deteriorates. Become. Therefore, the thickness of the Al oxide film on the surface of the Al alloy plate is in the range of 40 to 100 mm.

(Mg content in oxide film) In the present invention, Al-Mg-
The Mg content in the oxide film on the surface of the Si-based Al alloy plate is the main component
It means not only MgO (most quantitatively) but also all Mg compounds including other Mg compounds such as MgOH and metal Mg present in the oxide film. And, Al in the oxide film means Al ₂ O
_It refers to all Al compounds including ₃ and Al (OH) ₃ .

Due to the presence of Mg in the oxide film, particularly MgO, an increase in the contact area due to local and minute deformation of the plate surface on the sliding surface with the die or punch during press molding is suppressed. You. In particular, MgO is more brittle than Al ₂ O ₃ and preferentially falls or falls off from the oxide film during press formability, and exists as a fine powder at the sliding interface and plays a role in reducing sliding resistance. . As a result, an increase in sliding resistance is suppressed, and the formability of the plate is improved.

(Mgat% / Alat% in Oxide Film) The ratio of Mg to Al in the oxide film as referred to in the present invention means the at% ratio of Mg to Al.
(Mgat% / Alat%), which was measured by X-ray photoelectron spectroscopy (XPS).
From 3 points in the plane of the oxide film on the surface of the Al alloy plate
It refers to the average at% measured at 5 points and converted to Mg and Al or metal elements of these compounds.

If Mgat% / Alat% is less than 0.1, the amount of MgO in the oxide film on the surface of the Al-Mg-Si-based Al alloy plate is too small, and the press formability of the plate is significantly reduced. Also,
The higher the Mgat% / Alat%, the better the press formability of the plate.However, if the Mgat% / Alat% exceeds 0.4, other problems such as a decrease in degreasing and adhesion in zinc phosphate treatment may occur. Occurs. Therefore, Mgat% / Alat% is in the range of 0.1 to 0.4.

The amount of Mg in the Al oxide film on the surface of the Al alloy plate is greatly affected by the Mg content of the original Al alloy plate and the production conditions of the plate (solution treatment and quenching conditions, etc.). Therefore, in the present invention, the control of Mgat% / Alat% in the Al oxide film is performed in accordance with the Mg content of the original Al alloy plate, the temperature and the time of the final solution treatment and quenching, and the subsequent time. The cleaning is performed by controlling the conditions for cleaning the plate using an acid, an alkali solution, a detergent, or the like (etching conditions such as the concentration, temperature, and cleaning time of the cleaning solution).

Further, as another embodiment of the present invention, a zinc-based plating (plating containing zinc as a main component such as pure zinc and a zinc alloy) is further performed on the surface of an Al alloy material provided with an Al oxide film on the surface.
By carrying out, the chemical conversion treatment property such as phosphate treatment can be made more excellent.

Next, the chemical composition of the Al alloy of the present invention will be described. The Al alloy of the present invention needs to satisfy the properties for transportation equipment such as automobiles and ships, structural materials and parts. Among them, particularly panels and the frame members of automobiles, essentially tensile strength and to be excellent in press formability has a 90 N / mm ² or more 200 N / mm ² or more and yield strength, painting after press forming It must be excellent in properties such as bake hardenability, which increases proof stress during baking, and recyclability. For this, among Al alloys
Al-Mg-Si 6000 series Al alloy is good.

The preferred composition of the 6000 series Al alloy will be described below. In order to satisfy the above-mentioned required properties, the component standard of the Al-Mg-Si-based 6000 series Al alloy (6101, 600
(3, 6151, 6061, 6N01, 6063, etc.), basically contains 0.2 to 1.6% of Si: 0.2 to 1.6% of Mg, and others, Fe, Cu, Mn, Cr, Zn, Ti And so on to the extent of the AA to JIS standards. However, even if each component of the 6000 series Al alloy does not conform to the standard, as long as it has the above-mentioned basic properties of the 6000 series Al alloy, a component for further improving properties and adding other properties, Changes in the composition are appropriately permitted. For example, positively containing each of the above elements, or, in addition,
It is permissible to include Ni, V, Zr, Sc, Ag, etc.

Next, the preferable range and critical significance of the content of each element will be described.

Mg: 0.2-1.6%. Mg forms a compound phase (Mg ₂ Si, etc.) together with Si by artificial aging (paint baking treatment, etc.). It is an essential element for imparting strength (proof stress) or baking hardenability. 0.2% of Mg
If the content is less than 10%, the tensile strength may decrease, and cracking may occur during press molding. Further, sufficient strength cannot be obtained even by artificial aging. On the other hand, when the content is more than 1.6%, more preferably more than 1.0%, the proof stress is too high,
It inhibits formability such as bending. Therefore, the content of Mg is in the range of 0.2 to 1.6%, preferably 0.2 to 1.0%.

Si: 0.2-1.6%. Si, together with Mg, is an essential element for forming a compound phase (Mg ₂ Si, etc.) by artificial aging treatment and imparting high strength (proof stress) during use, but less than 0.2%, more strictly If the content is less than 0.6%, sufficient strength cannot be obtained by artificial aging. On the other hand, over 1.6%
More desirably, when the content exceeds 1.3%, it precipitates as coarse particles at the time of casting and quenching, and impairs formability. Therefore, the content of Si is set in the range of 0.2 to 1.6%, preferably 0.6 to 1.3%. The state of formation of the compound phase during the artificial aging treatment is greatly affected by the ratio between the contents of Mg and Si. When Si / Mg is less than 1.0, the formation of the compound phase (eg, Mg ₂ Si precipitation) becomes coarse, and the effect of improving the strength is reduced. Therefore, Si / Mg is preferably set to 1.0 or more.

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

Cu: 0.01-1.0%. Cu is heated during baking
It forms and precipitates a compound phase with Mg and Al, imparts bake hardenability, and improves moldability in a solid solution state during T4 refining. When the Cu content is less than 0.01%, these effects are not obtained, and when the Cu content exceeds 1.0%, the effects are saturated. Also,
If the Cu content exceeds 1.0%, the corrosion resistance after coating, particularly the yarn rust resistance, is rather deteriorated. Therefore, the content of Cu is set to 0.01 to 1.0%.

Zn: 0.005 to 1.0%. Zn has an effect of improving yarn rust resistance. However, if the content of Zn is less than 0.005%, a sufficient effect cannot be obtained. On the other hand, if the content exceeds 1.0%, the corrosion resistance decreases. Therefore, the content of Zn is preferably in the range of 0.005 to 1.0%.

Ti: 0.0001 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,
The content of Ti is preferably in the range of 0.0001 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.

Although not related to the performance of the Al product, in order to prevent re-oxidation of the Al molten metal in the air, Be: 0.1
-100 ppm may be contained. When the content is less than 0.1 ppm, this effect cannot be obtained. On the other hand, when the content exceeds 100 ppm, the material hardness increases and the moldability decreases.

Mn: 0.01 to 0.2%, Cr: 0.01 to 0.2%, Zr: 0.0
1 to 0.2%, V: 0.01 to 0.15%. These elements are used during the homogenizing heat treatment and during the subsequent hot rolling, in the case of 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. If the content is less than each lower limit, this effect cannot be obtained.On the other hand, an excessive (exceeding the upper limit) content tends to form a coarse intermetallic compound at the time of melting and casting, and becomes a starting point of breakage at the time of molding. It may cause a decrease in performance. 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 contents of these elements are respectively Mn: 0.01 to 0.2%, Cr: 0.01%
-0.2%, Zr: 0.01-0.2%, V: 0.01-0.15%.

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.

The Al alloy plate itself in the present invention can be manufactured by a conventional method. For example, a molten Al alloy melt-adjusted within the standard range of the 6000 series Al alloy component is cast by appropriately selecting a normal melting casting method such as a continuous casting rolling method and a semi-continuous casting method (DC casting method). Next, after subjecting this Al alloy ingot to a homogenizing heat treatment, by a plastic working method such as hot rolling and cold rolling (intermediate annealing as necessary), the shape of the desired Al alloy plate such as a coil or a plate is obtained. It is plastically processed. And
The rolled material subjected to plastic working is subjected to T4 treatment (quenching after solution treatment) or, in order to further enhance seizure hardening (BH property), see JP-A-2-205660 and JP-A-62-177143.
As described in Japanese Patent Application Laid-Open No. H10-264, heat treatment is performed after quenching to 50 to 130 ° C. and holding at that temperature or after quenching to maintain the temperature at 40 to 120 ° C. to obtain desired mechanical properties.

However, in order to further improve the press formability of the 6000 series Al alloy sheet and to further improve the age hardening ability during baking coating after press forming, as described above,
It is preferable to increase the amount of Si by setting the amount to 0.6 to 1.3% and Si / Mg to 1.0 or more. However, when the amount of Si is increased, the problem of deterioration in formability due to precipitation of Si at the grain boundaries during the tempering treatment increases. Therefore, to prevent this, it is necessary to heat and rapidly cool the plate in a short time, and in this respect, especially the final solution treatment and quenching treatment (water cooling, mist cooling, air cooling, etc.) It is preferable to use a continuous heat treatment furnace capable of rapidly cooling at a heating and cooling rate of 40 ° C./sec or more by passing a plate continuously from a coil instead of a batch type.

After this tempering treatment, the surface of the Al alloy plate is appropriately cleaned. These washings include acid solutions such as nitric acid and sulfuric acid,
An alkaline solution such as caustic soda or a commercially available detergent is appropriately combined to control the amount of Mg in the Al oxide film. In addition, there is no problem of rolling oil and dirt on the surface of the Al alloy plate until the tempering treatment,
Cleaning is not required for those whose Mg content is within the scope of the present invention.

In order to suppress a change in the composition of the Al oxide film when the manufactured Al alloy plate is stored until pressed, a rust-preventive oil is applied to the surface of the Al alloy plate. Is also effective. By performing the above-described countermeasures in the production of the Al alloy plate, long-term storage in which the composition change of the Al oxide film on the side where the Al alloy plate is used is suppressed becomes possible.

[0044]

Next, embodiments of the present invention will be described. After ingot casting of an aluminum alloy ingot having the composition shown in Table 1 by the DC casting method,
A homogenizing heat treatment was applied within a range of × 8 hours, and hot rolling was performed to a thickness of 3.5 mm. Next, the aluminum plate was cold-rolled to a thickness of 1.0 mm, subjected to a solution treatment at 550 ° C. for several seconds in a continuous heat treatment furnace, and then quenched by water cooling (cooling rate of 40 ° C./sec or more) to prepare an Al plate. Then, control of the thickness of the Al oxide film on the surface of the Al plate and the amount of Mg in the Al oxide film is performed by changing the cleaning conditions of the Al plate, including not performing the cleaning of the Al plate,
Al plates with various Mg contents in the Al oxide film were manufactured.

Then, from these various Al plates, those having remarkably different thicknesses of the Al oxide film on the surface of the Al plate and the amount of Mg in the Al oxide film were selected and sampled. Surface Al
The thickness of the oxide film was measured by a capacitance method. In addition, the ratio of Mg to Al in the Al oxide film was measured by X-ray photoelectron analysis (XPS method) for the surface layer and the inside of the oxide film at three points at both ends and the center of the Al alloy plate. hand,
Mgat / Alat% was calculated by calculating the average at% of Mg and Al or the metal elements of these compounds. Table 2 shows the results.

Then, after simulating that the Al alloy plate was left for a long period of time and aged at room temperature, and then press-molded as the outer panel of an automobile, after the solution treatment and quenching, the aluminum alloy plate was left at room temperature for 90 days. Using the test material as a blank, two forming tests were performed: ball head bulging and rectangular tube drawing, and the forming limit height was determined. Table 2 also shows these results. The ball head overhang test conditions were as follows: a ball head punch with a diameter of 50.0 mmφ and a die with a bead with an inner diameter of 60 mmφ with a shoulder of R5.0 mm and a diameter of 120 mm.
A commercially available rust preventive oil was applied to a test piece processed to mφ, and the forming limit height at which cracking occurred was determined under the condition of applying a 4.0 ton wrinkle holding pressure to the die. The square cylinder drawing test was performed using a 40 × 40 mm square cylinder punch with a shoulder R5.0 mm and a corner R10 mm, and a 42.5 × 42.5 mm die with a shoulder R3.0 mm.
A commercially available rust preventive oil was applied to a test piece processed to 90 mm, and a molding limit height at which cracking occurred was determined under a condition of applying a 2.0-ton wrinkle holding pressure to the die. Table 2 shows these results.
Shown in

Further, in order to evaluate the degreasing property of the Al alloy plate, a commercially available rust-preventive oil was applied to the test material after the solution treatment and quenching, and then left at room temperature for 90 days. Degreasing was performed by immersing in a soda-based degreasing solution (40 ° C) for 2 minutes. Evaluation of the degreasing property was performed based on the water wettability of the surface of the test material after degreasing.
% Or less was evaluated as x. Table 2 also shows these results.

The tensile strength (σ _0.2 ) of the test material left for 90 days at room temperature after the solution quenching was measured by performing a tensile test according to the JIS Z2241 method. Made
(Note that the tensile direction is LT = 90 ° direction to the rolling direction). Furthermore, as a characteristic of the Al plate corresponding to the paint after baking hardening, the proof stress (σ _0.
2 ) was also measured. Table 2 also shows these results.

As is evident from Table 2, the thickness of the Al oxide film is 40 to 100 mm, and the ratio of Mg to Al in the Al oxide film is 0.
Inventive Examples Nos. 1 to 6 in the range of 1 to 0.4, even if the yield strength (σ _0.2 ) of the Al alloy plate to be formed is high, the forming limit height in ball head overhang is 30 mm or more, In addition, the forming limit height in the rectangular tube drawing is 11.0 mm or more, which indicates that the press formability is excellent. It is also excellent in degreasing properties assuming pretreatment of phosphate treatment.

In contrast, Comparative Example No. 7 in which the ratio of Mg to Al in the Al oxide film exceeded the upper limit of 0.4, and Comparative Example No. 9 in which the thickness of the Al oxide film exceeded the upper limit of 100 mm. As compared with the invention examples, the press moldability is almost the same, but the degreasing property assuming the pretreatment of the phosphate treatment is remarkably inferior. Further, Comparative Examples Nos. 8 and 10 in which the ratio of Mg to Al in the Al oxide film was less than the lower limit of 0.1 and the thickness of the Al oxide film was less than the lower limit of 40 mm were less degreased than the invention examples. Are equivalent, but the press formability is remarkably inferior.

Therefore, these results support the critical significance of the definition of the thickness of the Al oxide film and the ratio of Mg to Al in the Al oxide film in the present invention. Further, the Al alloy material of the present invention has mechanical properties such as excellent strength and proof stress, including moldability and seizure hardenability, and can be suitably used particularly as panels and frames of automobiles. I understand.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

According to the present invention, a 6000 series Al alloy having excellent press formability and yarn rust resistance, and excellent in both formability and yarn rust resistance, for reducing the weight of a transport machine. Boards can be provided. Accordingly, the use of the Al alloy plate for transportation equipment such as automobiles, vehicles, ships, etc., has a great industrial value in that it can be expanded.

Claims (12)

[Claims] 1. Si: 0.2 to 1.6% (mass%, the same applies hereinafter), M
g: an Al-Mg-Si-based aluminum alloy plate containing 0.2 to 1.6%, having an aluminum oxide film having a thickness of 40 to 100 mm (angstrom) on the surface, and containing Mg in the aluminum oxide film. Minute, the ratio of Mg and Al (Mgat% / Ala
(t%) in an amount of 0.1 to 0.4. 2. The aluminum alloy sheet for press forming according to claim 1, wherein the aluminum alloy sheet has been subjected to solution treatment and quenching in a continuous heat treatment furnace. 3. The method according to claim 1, wherein the aluminum alloy plate has a Si content of 0.6 to 1.
The aluminum alloy sheet for press forming according to claim 1 or 2, which contains 3%, Mg: 0.2 to 1.0%, and has Si / Mg of 1.0 or more. 4. The method according to claim 1, wherein the aluminum alloy further comprises Mn: 0.0
1 to 0.2%, Cr: 0.01 to 0.2%, Zr: 0.01 to 0.2%, V: 0.01 to
The aluminum alloy sheet for press forming according to any one of claims 1 to 3, comprising one or more of 0.15%. 5. The method according to claim 1, wherein the aluminum alloy further comprises Zn: 0.0
The aluminum alloy sheet for press forming according to any one of claims 1 to 4, wherein the aluminum alloy sheet contains one or two of 0.05 to 1.0% and Cu: 0.005 to 1.0%. 6. The aluminum alloy further comprises Ti: 0.0
The aluminum alloy sheet for press forming according to any one of claims 1 to 5, wherein the aluminum alloy sheet contains one or two kinds of one or two kinds of 01 to 0.1% and B: 1 to 300 ppm. 7. The aluminum alloy sheet for press forming according to claim 1, wherein the yield strength (σ _0.2 ) of the aluminum alloy sheet to be press-formed is 90 N / mm ² or more. 8. The aluminum alloy sheet for press forming according to claim 1, wherein a rust-preventive oil and / or a lubricant is applied to the surface of the aluminum alloy sheet after the cleaning. 9. The aluminum alloy sheet for press forming according to claim 1, wherein the surface of the aluminum alloy sheet after the cleaning is coated with zinc-based plating. 10. The method according to claim 1, wherein the aluminum alloy plate is subjected to a phosphate treatment and coating after press forming.
10. The aluminum alloy plate for press forming according to any one of claims 9 to 9. 11. The aluminum alloy sheet for press forming according to claim 1, wherein the aluminum alloy sheet is for a transport machine. 12. The aluminum alloy sheet for press forming according to claim 1, wherein the aluminum alloy sheet is for an automobile panel.