JP4694770B2 - Aluminum alloy plate with excellent bending workability - Google Patents

Description

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【発明の効果】
本発明によれば、厳しい条件でのフラットヘム加工などの曲げ加工性に特に優れ、プレス成形性や低温時効硬化能などの、パネル化に際して要求される他の諸特性にも優れたAl-Mg-Si系Al合金板を提供することができる。したがって、Al合金板のパネル用途への拡大を図ることができる点で、多大な工業的な価値を有するものである。[0001]
BACKGROUND OF THE INVENTION
The present invention is excellent in bending workability such as hem processing even when room temperature aging has progressed after plate production, and is excellent in other properties required for paneling such as press formability and low temperature aging hardening ability. In addition, the present invention relates to an Al-Mg-Si aluminum alloy plate (hereinafter, aluminum is also simply referred to as Al).
[0002]
[Prior art]
Conventionally, Al-Mg-based AA to JIS with excellent processability (hereinafter simply referred to as formability) for automobiles, ships, vehicles and other transport equipment, home appliances, buildings, and structural members and parts. 5000 series (satisfying the standard) specified in the standard, Al-Mg-Si series AA to JIS 6000 series (hereinafter simply referred to as 5000 series to 6000 series) with excellent formability and bake hardenability Alloy materials (a general term for each aluminum alloy wrought material such as a rolled plate material, an extruded shape material, and a forged material) are used.
[0003]
In recent years, with respect to global environmental problems caused by exhaust gas and the like, improvement in fuel efficiency has been pursued by reducing the weight of the body of a transport aircraft such as an automobile. For this reason, in particular, the application of lighter Al alloy materials instead of steel materials that have been used in the past is increasing for automobile bodies.
[0004]
Among these Al alloy materials, panels such as the outer panel (outer plate) and inner panel (inner plate) of panel structures such as automobile hoods, fenders, doors, roofs, and trunk lids are thin and high-strength Al. As an alloy plate, use of an excess Si type 6000 series Al alloy plate has been studied.
[0005]
This excess Si type 6000 series Al alloy is basically an Al—Mg—Si series aluminum alloy containing Si and Mg as essential elements and having Si / Mg of 1 or more. And this excess Si type 6000 series Al alloy has excellent age-hardening ability, so at the time of press molding and bending processing, it secures formability by reducing the yield strength, and paint baking treatment of the panel after molding etc. It is age-hardened by heating at the time of relatively low-temperature artificial aging treatment to improve proof stress, and has age-hardening ability that can secure the required strength.
[0006]
Further, these excess Si type 6000 series Al alloy materials have a relatively small amount of alloy elements as compared with other 5000 series Al alloys having a large amount of alloy such as Mg. For this reason, when the scraps of these 6000 series Al alloy materials are reused as an Al alloy melting material (melting raw material), the original 6000 series Al alloy ingot is easily obtained, and the recyclability is also excellent.
[0007]
However, these excess Si-type 6000 series Al alloy materials have a large aging effect at room temperature (room temperature) after the production of the Al alloy material itself until it is used in the above-mentioned applications because of its excellent age-hardening ability. There's a problem. This tendency of room temperature aging is particularly strong in the excess Si type 6000 series Al alloy material which is the subject of the present invention.
[0008]
For example, due to this room temperature aging, even after two weeks have passed since the production of excess Si type 6000 series Al alloy material itself, the yield strength increases by about 20% or more, and conversely the elongation decreases by about 10% or more. .
[0009]
And when such room temperature aging occurs, immediately after manufacturing, even if the excess Si type 6000 series Al alloy plate satisfies the required characteristics of each application, it will be used for actual applications after a certain period of time. In this case, there arises a problem that the required characteristics cannot be satisfied. That is, the bending workability such as hem workability is remarkably reduced, and other properties such as the press formability and the age-hardening property at a relatively low temperature are also reduced, and the necessary shape accuracy as a panel is reduced. Strength will not be obtained.
[0010]
In response to the problems of room temperature aging suppression and low temperature aging hardenability improvement of 6000 series Al alloy materials including excess Si type, after solution treatment and quenching treatment of 6000 series Al alloy sheet, at a low temperature of 70-150 ℃ It has been proposed to improve by applying a heat treatment (aging treatment) for about 0.5 to 50 hours (see Patent Documents 1 and 2).
[0011]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-219382
[Patent Document 2]
JP 2000-273567 A
[0012]
In these Patent Documents 1 and 2, the factor inhibiting the low-temperature age-hardening ability of the 6000 series Al alloy material containing excess Si type is the Mg-Si cluster formed during standing at room temperature after solution treatment and quenching treatment. It is said that. That is, the formed Mg-Si clusters are dissolved again at the time of coating baking, so that heat energy is consumed and the precipitation on the side of the GP zone contributing to the strength increase is inhibited.
And in patent document 1, in order to regulate the production | generation amount of Mg-Si cluster which inhibits low temperature age hardening ability, and patent document 2, Mg-Si cluster which contributes to a moldability improvement is made into low temperature age hardening ability. In order to allow a certain amount to exist (utilize) in a range that does not inhibit the above, after solution treatment and quenching to room temperature, low-temperature heat treatment is performed at 70 to 150 ° C. for about 0.5 to 50 hours. As a result, the room temperature aging suppression effect is that the elongation of the Al alloy panel material after standing for 100 days after production is 30% or more, the Erichsen value is 10 mm or more, and the formability is good and the room temperature aging is suppressed.
[0013]
[Problems to be solved by the invention]
However, the actual low-temperature age-hardening ability of these Patent Documents 1 and 2 is about 168 MPa at the maximum even under the baking condition of 170 ° C. × 30 minutes. Therefore, in these patent documents, only an excess Si type 6000 series Al alloy plate of 170 Pa or less can be obtained even under artificial aging treatment conditions of 170 ° C. × 30 minutes.
[0014]
On the other hand, in recent years, the paint baking treatment of the automobile panel after the molding tends to be performed at a low temperature and a short time such as 170 ° C. × 20 minutes or 160 ° C. × 20 minutes. Even under these low-temperature and short-time paint baking conditions (artificial aging treatment conditions), the panel is required to have a high strength of 170 MPa or more.
[0015]
In addition, press formability and flat hem processing conditions tend to become more and more difficult in recent years, and there are cases where conventional improvements from the molding process side and improvements from the material plate side cannot be handled. First, the outer panel shape to be stretched tends to be complicated, for example, the height and the area of the stretch are increased, and the shape has a curved portion with stretched flange deformation. For this reason, molding defects such as cracks and rough skin are likely to occur even when improvements are made from the conventional molding side or the material plate side.
[0016]
Next, the flat hem processing conditions and the shape of the end of the processed outer panel tend to be complicated shapes such as arc shapes or corner portions, not linear simple shapes. In addition, the inner panel inserted into the flat hem portion (curved edge portion) of the outer panel is apt to be thinned to a thickness of 1.0 mm or less, for example, about 0.5 mm, in order to reduce the weight. All of these conditions make the flat hem processing conditions stricter.
[0017]
Thus, in excess Si type 6000 series Al alloy plate, room temperature aging suppression of Al alloy plate, press formability and hem workability, and further improvement in low temperature age hardening ability are contradictory technical issues, It is difficult to achieve both. For example, when flat hem workability is improved by reducing the proof strength of an Al alloy plate, problems such as reduced press formability and insufficient proof strength after artificial age hardening at low temperatures occur.
[0018]
For this reason, it is a very difficult technical problem to achieve these characteristics at the same time even with various techniques for controlling crystallized substances and precipitates that have been proposed in the past and techniques for adding a large amount of Cu or the like.
[0019]
The present invention was made paying attention to such circumstances, and its purpose is particularly excellent in bending workability such as hem processing even if it is aged at room temperature, such as press formability and low-temperature age-hardening ability, It is intended to provide a 6000 series Al alloy plate that is excellent in other properties required for paneling.
[0020]
[Means for Solving the Problems]
  In order to achieve this object, the gist of the aluminum alloy sheet of the present invention is as follows:It is composed of Si: 0.4 to 1.3%, Mg: 0.2 to 1.2%, Mn: 0.01 to 0.65%, Cu: 0.001 to 1.0%, and the balance being Al and inevitable impurities.In Al-Mg-Si based aluminum alloy sheet, as a characteristic after room temperature aging of the manufactured sheet, 0.2% proof stress in the direction parallel to the rolling direction of the sheet is in the range of 120 to 170 MPa, and the rolling of the sheet Elongation in the direction of 45 degrees to the direction δ₁Is over 30% and this δ₁And elongation in the direction parallel to the rolling direction of the plate₂Ratio δ with₁/ δ₂Is 1.2 or more.
[0021]
The Al alloy sheet referred to in the present invention refers to a sheet (rolled sheet) aged at room temperature after being subjected to a tempering treatment after cold rolling. Therefore, each of the above requirements is not immediately after the tempering treatment (immediately after the plate production), but any period from the tempering treatment (after the plate production) to the press molding or bending (for example, one month or more after the plate production). This refers to the state of an Al alloy plate sufficiently aged at room temperature. In addition, the tempering treatment referred to here mainly refers to solution treatment and quenching treatment, but various tempering treatments such as a subsequent arbitrary heat treatment, for example, a pre-aging treatment described later, and an aging treatment further applied as necessary. Indicates that includes.
[0022]
The following description will be focused on an excess Si type 6000 series Al alloy plate. In the present invention, Al—Mg—Si to 6000 series Al alloy plates other than the excess Si type are not as severe as the problem, but can be included in the scope of the present invention. Similarly, the following description of bending workability will be made mainly on hem processing such as flat hem. However, if the hem workability is good, other hat-type bends that have the same processing (deformation) mechanism are used. Bending workability such as processing and 90 degree bending is also improved. Therefore, the present invention can be applied to bending processing other than hem processing and can be included in the scope of the present invention.
[0023]
The present inventors preferably suppress the room temperature aging of the excess Si type 6000 series Al alloy plate itself, but even if it is aged at room temperature after the production of the Al alloy plate, the press formability and bending of flat hem, etc. It was an object to obtain an excess Si type 6000 series Al alloy plate excellent in processing and low temperature age hardening ability. For this reason, the present inventors have reexamined the relationship between press formability and hem workability and the structure of the excess Si-type 6000 series Al alloy plate. As a result, the elongation δ in the direction of 45 degrees with respect to the rolling direction of the excess Si type 6000 series Al alloy sheet₁It has been found that the anisotropy of the correlates closely with both the stretch formability and the flat hemmability.
[0024]
That is, δ₁Is raised above a certain level, and this δ₁The elongation in the other direction of the Al alloy sheet (elongation in the direction parallel to the rolling direction of the sheet δ₂), Even if the excess Si type 6000 series Al alloy sheet is aged at room temperature after manufacturing, it is a contradictory property, stretchability and flat hem workability Both of them were found to be improved. It should be noted that this press formability and flat hem processing can further improve other press formability such as drawing and other hem processing such as roped hem.
[0025]
Also, even if the excess Si type 6000 series Al alloy sheet is aged at room temperature after production, it can be applied at a lower temperature and shorter time for painting baking (artificial aging treatment conditions), such as 170 ° C × 20 minutes or 160 ° C × 20 minutes. However, high strength of 170 MPa or more can be obtained as a panel.
[0026]
In the field of excess Si-type 6000 series Al alloy sheets, improving the hemmability such as press formability and flat hem by improving the elongation, r value, n value, etc. of the Al alloy sheet itself has been conventional. Is also known.
[0027]
However, by giving the excess Si type 6000 series Al alloy sheet anisotropy of elongation in the 45 degree direction with respect to the rolling direction, even if it is aged at room temperature after the production of the Al alloy sheet, it is a contradictory characteristic. It is not known to improve both press formability and hemmability. Similarly, it is not known that high strength of 170 MPa or more can be obtained under low-temperature and short-time artificial aging treatment conditions.
[0028]
This is because, until now, mechanical properties such as elongation and proof stress of ordinary excess Si type 6000 series Al alloy sheets are anisotropic as in the present invention in order to improve press forming including overhang forming. It is common sense that each mechanical property in the direction parallel to the rolling direction of the plate, the 45 degree direction, and the 90 degree direction is as isotropic and uniform as possible without having a structure having there were. It was also common sense that imparting anisotropy to mechanical properties is rather harmful to press formability.
[0029]
Therefore, the mechanical properties of ordinary excess Si-type 6000 series Al alloy sheets obtained up to now by conventional methods are not isotropic and uniform, except for manufacturing variations. It was. For this reason, when referring to the mechanical properties such as elongation and proof stress of the Al alloy plate, it was usually represented by either the parallel or perpendicular mechanical properties to the rolling direction of the Al alloy plate. .
[0030]
Further, in order to obtain an Al alloy sheet structure having elongation anisotropy as in the present invention, it is necessary to add special process conditions as in the manufacturing method described in detail later. However, in the present invention, the addition of the above special process conditions does not complicate the production of the Al alloy plate itself, and does not significantly increase the production cost. Therefore, this point is also an advantage of the Al alloy plate of the present invention.
[0031]
In the present invention, even if aged at room temperature, in order to guarantee at least the various properties of the plate such as hemmability, press formability, and low-temperature age-hardening ability, the above-mentioned δ₁And δ₂And elongation δ in the direction perpendicular to the rolling direction of the plate_Three(2 × δ₁+ Δ₂+ Δ_Three) / 4 is preferably 25% or more.
[0032]
Further, in order to make the various properties of the plate more excellent, the δ of the excess Si type 6000 series Al alloy plate is used.₁/ δ₂Is preferably 1.5 or more.
[0033]
In the present invention, in order to exhibit the above characteristics, from the viewpoint of the composition of the Al alloy plate, the Al alloy plate is Si: 0.4 to 1.3%, Mg: 0.2 to 1.2%, Mn: 0.01 to 0.65%, Cu: 0.001 It is preferable that the composition is composed of ˜1.0%, Si / Mg is 1 or more by mass, and the balance is Al and inevitable impurities.
[0034]
Further, in order to further improve the flat heme workability without reducing other properties such as press formability, the Si content of the Al alloy plate is set to 0.6 to 1.0%, and the Mg content is set to 0.2 to 0.8. % Is preferable.
[0035]
In the present invention, for the purpose of further ensuring artificial age hardening ability at a low temperature in a short time, in order to ensure an appropriate amount of precipitates in the Al alloy plate structure, the conductivity of the Al alloy plate is further in the range of 43 to 47 IACS%. It is preferable that Moreover, in order to prevent rough skin such as poor orange peel when the Al alloy plate is formed into a panel by press molding, the crystal grain size of the Al alloy plate is preferably 50 μm or less.
[0036]
In the present invention, the hem workability such as flat hem and the stretch formability are particularly excellent even if the 0.2% proof stress in the direction parallel to the rolling direction of the Al alloy sheet is not as low as 140 MPa or less as in the prior art. As a result, the 0.2% proof stress of the Al alloy sheet after aging at room temperature can be increased to a high strength exceeding 140 MPa, and even at a low temperature artificial age hardening treatment at 160 ° C. × 20 minutes in the panel coating process after forming, etc. High-strength panels exceeding the above can be obtained.
[0037]
In addition, the Al alloy plate of the present invention is particularly excellent in bending workability such as hem processing, and is also excellent in other properties required for panel formation such as press formability and low-temperature age-hardening ability. It is preferably applied when hem processing is performed after the stretch forming.
[0038]
Similarly, the Al alloy sheet of the present invention is preferably applied in severe conditions where the hemming is flat hemming.
[0039]
Since the present invention has the effects as described above, it is suitable for being applied to an automobile outer panel, in particular, which is hemmed after stretch forming, and has a demand for flat hemm processing as well as stretch formability.
[0040]
DETAILED DESCRIPTION OF THE INVENTION
  First, the structural requirements of the Al alloy plate of the present invention will be described below.
  In the present invention, the elongation δ in the direction of 45 degrees with respect to the rolling direction of the excess Si type 6000 series Al alloy sheet.₁Is 30% or more and the elongation δ in the direction parallel to the rolling direction of the plate₂Ratio δ with₁/ δ₂Is 1.2 or more, more preferably 1.5 or more. By providing such anisotropy of elongation, both the press formability and hem workability can be improved even if the excess Si type 6000 series Al alloy plate is aged at room temperature after production.The
[0041]
Elongation in the 45 ° direction relative to the rolling direction of the plate δ₁If it is less than 30%, there is no effect of improving hem workability such as flat hem and press formability such as overhang when aged at room temperature after production.
[0042]
And more importantly, the elongation δ in the direction parallel to the rolling direction of the plate₂Ratio δ with₁/ δ₂Is less than 1.5, the mechanical properties of each of the parallel direction, 45 degree direction and 90 degree direction in the rolling direction of the sheet are made as uniform as possible, and there is a large difference from the isotropic structure of the conventional or normal Al alloy sheet. In particular, there is no effect of improving hem workability such as flat hem and press formability such as overhang when aged at room temperature after production. In addition, it is not possible to increase the strength under low-temperature and short-time artificial aging treatment conditions when aging at room temperature after production.
[0043]
Note that δ₁And δ₁/ δ₂Is better as it is higher or higher, and there is no upper limit from the effect of improving the hemmability and the stretchability. However, due to the chemical composition of the 6000 series Al alloy plate and the metallurgical restrictions of the manufacturing process, the δ₁And δ₁/ δ₂However, there are limits to the numbers that can be set high.
[0044]
In addition, even when aged at room temperature, in order to guarantee at least the various properties of the plate such as hemmability, press formability, and low-temperature age-hardening ability,₁And δ₂And elongation δ in the direction perpendicular to the rolling direction of the plate_Three(2 × δ₁+ Δ₂+ Δ_Three) / 4 is preferably 25% or more. If this average is less than 25%, δ₂Or δ_ThreeThis means that the elongation value is extremely low, and even if the elongation anisotropy is given, for the hem processing and press molding that can be processed from various directions with respect to the rolling direction of the plate, respectively. There is a possibility that good workability cannot be exhibited.
[0045]
In the present invention, the conductivity of the Al alloy plate surface is preferably in the range of 43 to 47 IACS%. By setting this conductivity range, the amount of the compound phase such as the GP zone in the crystal grains formed during the artificial aging treatment is secured, and the required strength of 170 MPa or more is obtained during the artificial aging treatment at the low temperature and short time. Guarantee. The Al alloy plate to be measured for electrical conductivity is mechanically polished to 0.05 to 0.1 mm and then subjected to electrolytic etching, and the electrical conductivity of the surface is measured.
[0046]
If the conductivity is less than 43 IACS%, the flat heme workability may be reduced. In addition, press formability such as overhang may be reduced. Therefore, it is preferable to define the lower limit of conductivity as 43 IACS%.
[0047]
On the other hand, when the conductivity exceeds 47 IACS%, the amount of compound phase such as GP zone in the crystal grains formed during the artificial aging treatment may be reduced. For this reason, the artificial age hardening ability is lowered, and in particular, the artificial aging treatment at a low temperature for a short time of the panel after the molding process may not provide a yield strength of 170 MPa or more. Therefore, even for thin plates with a thickness of 1.0 mm or less, the upper limit of conductivity should be specified as 47 IACS% in order to guarantee rigidity and strength such as dent resistance as panel outer plates for automobiles etc. Is preferred.
[0048]
In the present invention, it is preferable that the crystal grain size of the Al alloy plate is specified to be 50 μm or less. By making the crystal grain size fine or small within this range, flat hem workability and press formability are ensured or improved. When the crystal grain size exceeds 50μm and becomes coarse, press formability such as flat hem workability and overhang is remarkably deteriorated, resulting in defects such as cracks in the hem part and rough skin during press molding. easy.
[0049]
The crystal grain size referred to here is the maximum diameter of crystal grains in the longitudinal (L) direction of the plate. The crystal grain size is measured by the line intercept method in the L direction by observing the surface of the Al alloy plate that has been mechanically polished by 0.05 to 0.1 mm and then electrolytically etched using an optical microscope. 1 The measurement line length was 0.95mm, and the total measurement line length was 0.95 x 15mm by observing a total of 5 fields with 3 lines per field.
[0050]
In the Al alloy sheet of the present invention, the 0.2% yield strength in the direction parallel to the rolling direction of the sheet when aged at room temperature after production is in the range of 120 to 170 MPa. Conventionally, in the case of a panel for which flat hem workability is particularly important, or in the case of the severe flat hem processing conditions, the solution treatment temperature is set to a lower temperature side, and the 0.2% proof stress is as low as possible. I was doing.
[0051]
However, in the present invention, even when the low proof stress is not achieved, the hem workability such as flat hem and the press formability such as bulging are excellent when aged at room temperature after production. For this reason, in the present invention, the 0.2% proof stress in the direction parallel to the rolling direction of the plate after aging at room temperature can be increased to 120 MPa or more.
[0052]
However, when the 0.2% proof stress after aging at room temperature exceeds 170 MPa, even the Al alloy sheet of the present invention has too high strength, and again, hem workability such as flat hem is deteriorated. On the other hand, when the 0.2% proof stress is less than 120 MPa, it is difficult to obtain a required strength of 170 MPa or more during the artificial aging treatment at the low temperature and short time necessary for the dent characteristics of the outer panel.
[0053]
Next, an embodiment of the chemical composition of the Al alloy sheet of the present invention will be described below.
The basic composition of the Al alloy sheet of the present invention is an Al—Mg—Si (6000 series) Al alloy in order to ensure the above-mentioned definition of elongation and structure and various properties. If it is not within the range of the Al-Mg-Si (6000 series) Al alloy, the elongation and structure specified in the present invention will not be achieved, and various properties will not be exhibited.
[0054]
In addition, in order to ensure the above specifications such as elongation and structure and necessary properties as a plate, Si: 0.4 to 1.3%, Mg: 0.2 to 1.2%, Mn: 0.01 to 0.65%, Cu: 0.001 to 1.0% An excess Si-type Al—Mg—Si-based Al alloy containing Si / Mg at a mass ratio of 1 or more is preferable. In order to ensure the definition and various characteristics of the structure, more strictly, the remainder other than the specified components is preferably Al and inevitable impurities. In the present invention, the percentage display of the chemical component composition means the mass%, including the percentage display in the above claims.
[0055]
In addition to the above alloy elements, other alloy elements such as Cr, Zr, Ti, B, Fe, Zn, Ni, and V are basically impurity elements. However, from the viewpoint of recycling, not only high-purity Al ingots but also 6000 series alloys and other Al alloy scrap materials, low-purity Al ingots, etc. are used as melting raw materials as melting materials. In the case of melting, these other alloy elements are necessarily included. Accordingly, the present invention allows these other alloy elements to be contained within a range not impairing the intended effect of the present invention.
[0056]
The preferable content range and significance of each element, or the allowable amount will be described below.
Si: 0.4 to 1.3%.
Si forms a compound phase such as GP zone with Mg at the time of artificial aging treatment at a low temperature in a short time, such as solid solution strengthening and paint baking treatment, and exhibits age-hardening ability. It is an essential element for obtaining the required strength. Therefore, it is the most important element for combining various characteristics such as press formability and hemmability in the excess Si type 6000 series Al alloy plate of the present invention.
[0057]
In addition, the proof stress at the time of artificial aging treatment at a low temperature and short time (paint baking treatment after molding to a panel, as a evaluation test, 160 ° C. × 20 minutes low temperature aging treatment after applying 2% stretch) is 170 MPa or more, In order to exhibit excellent low-temperature age-hardening ability, it is preferable to have an excess Si type 6000-based Al alloy composition in which Si / Mg is 1.0 or more by mass and Si is excessively contained with respect to Mg.
[0058]
When the Si content is less than 0.4%, the age-hardening ability and further various properties such as press formability and hemmability required for each application cannot be obtained. On the other hand, when Si exceeds 1.3%, heme workability and bending workability are significantly impaired. Furthermore, weldability is significantly impaired. Therefore, Si is preferably in the range of 0.4 to 1.3%. In the outer panel, hem workability is particularly emphasized, so that the Si content is 0.6 to 1.0% in order to further improve the flat hem workability without degrading other properties such as press formability. A lower range is preferable.
[0059]
Mg: 0.2-1.2%.
Mg forms a compound phase such as a GP zone with Si during solid solution strengthening and artificial aging treatment such as paint baking treatment, and exhibits age-hardening ability to obtain the required strength of 170 MPa or more as a panel Is an essential element.
[0060]
If the Mg content is less than 0.2% (mass%, the same applies hereinafter), the absolute amount is insufficient, so that the compound phase cannot be formed during the artificial aging treatment, and the age hardening ability cannot be exhibited. For this reason, the required strength required for the panel cannot be obtained.
[0061]
On the other hand, if the Mg content exceeds 1.2%, moldability such as press formability and bending workability (hem workability) is remarkably impaired. Therefore, the Mg content is in the range of 0.2 to 1.2% and Si / Mg is 1.0 or more. In order to further improve the flat heme workability, when the Si content is set to a lower range of 0.6 to 1.0%, in order to obtain an excess Si type 6000 series Al alloy composition correspondingly, Further, the Mg content is preferably set to a low range of 0.2 to 0.8%.
[0062]
Cu: 0.001 to 1.0%
Cu has the effect of promoting precipitation of a compound phase such as a GP zone in the crystal grains of the Al alloy material structure under the conditions of artificial aging treatment at a relatively low temperature and short time of the present invention. Moreover, Cu dissolved in the aging treatment state also has an effect of improving formability. This effect is not obtained when the Cu content is less than 0.001%. On the other hand, if it exceeds 1.0%, the stress corrosion cracking resistance, the thread rust resistance of the corrosion resistance after coating, and the weldability are significantly deteriorated. For this reason, it is 0.8% or less for structural material applications where corrosion resistance is important, and 0.1% or less for the appearance of yarn rust resistance in panel applications such as automotive exterior panels. It is preferable to do.
[0063]
Mn: 0.01 to 0.65%
Mn produces dispersed particles (dispersed phase) during the homogenization heat treatment, and these dispersed particles have the effect of preventing grain boundary movement after recrystallization, so that fine crystal grains can be obtained. . As described above, the press formability and hem workability of the Al alloy plate of the present invention improve as the crystal grains of the Al alloy structure become finer. In this respect, when the Mn content is less than 0.01%, these effects are not obtained.
[0064]
On the other hand, if the Mn content increases, coarse Al-Fe-Si- (Mn, Cr, Zr) -based intermetallic compounds and crystal precipitates are likely to be generated during melting and casting, which is likely to be the starting point of fracture. This causes a decrease in the mechanical properties of the Al alloy sheet. In particular, in flat hem processing where the processing conditions are severe due to the complicated shape, thinning, or the presence of a gap between the inner panel edge and the inner edge of the outer panel edge, the Mn content is 0.25%. When it exceeds, heme workability will fall. For this reason, Mn is set in the range of 0.01 to 0.65%, and more preferably in the range of 0.01 to 0.25% in the flat hem processing in which the processing conditions are severe.
[0065]
Cr, Zr.
These Cr and Zr transition elements, like Mn, have the effect of producing dispersed particles (dispersed phase) during homogenization heat treatment and obtaining fine crystal grains. However, if Cr and Zr are contained in an amount exceeding 0.15%, the hemmability is lowered in flat hem processing in which the processing conditions are severe. Therefore, the Cr and Zr contents are preferably regulated to 0.15% or less.
[0066]
Ti, B.
When Ti and B are contained in amounts exceeding Ti: 0.1% and B: 300 ppm, coarse crystallized substances are formed and formability is lowered. However, Ti and B are contained in a very small amount, and have the effect of reducing the crystal grains of the ingot and improving the press formability. Therefore, the content of Ti: 0.1% or less and B: 300ppm or less is allowed.
[0067]
Fe.
Fe mixed in from the melting raw material and contained as impurities is Al₇Cu₂Fe, Al₁₂(Fe, Mn)_ThreeCu₂, (Fe, Mn) Al₆A crystallized product such as These crystallized substances serve as nuclei of recrystallized grains, and when Fe is contained in an amount of 0.08% or more, the crystal grains are prevented from coarsening and the crystal grains are reduced to a fine grain of 50 μm or less. However, on the other hand, these crystallized materials significantly deteriorate the fracture toughness and fatigue characteristics, and further, the flat hem workability and press formability in which the processing conditions are severe. These deterioration characteristics become significant when the Fe content exceeds 0.50%. For this reason, the content of Fe when contained is preferably 0.08 to 0.50%.
[0068]
Zn.
When Zn exceeds 0.5%, the corrosion resistance is remarkably lowered. Therefore, the Zn content is preferably 0.5% or less.
[0069]
(Molding)
The hemming targeted by the Al alloy sheet of the present invention is particularly intended for flat hemming. That is, the edge of the outer panel is folded down to an angle close to 90 ° with a tool such as a punch, and the edge of the outer panel is further folded inward to about 135 °, and the inner panel end is accommodated in the bent portion of the outer panel. (Insert) and the edge of the outer panel is further bent inward by a tool to an angle of 180 ° to form a flat hem. In this flat hem, the inner panel and the 180 ° bent portion of the outer panel are joined and brought into close contact with each other to have a flat bent portion shape.
[0070]
However, since the Al alloy sheet of the present invention is excellent in flat hem workability, which is a severe condition, the condition is one step looser than that, such as a rope hem having a rope-like cross-sectional shape in which the bent portion swells in an arc shape. Naturally, it is excellent in workability. In addition, the other work-type (deformation) mechanisms, such as the above-mentioned hat-shaped bending and 90-degree bending, and other bending workability, or in general, V-bending, U-bending, end bending, wave bending, tensile bending, etc. It is also excellent in bending workability called Therefore, the present invention is also intended for hem processing such as other rope hems, and also for bending processing other than hem processing.
[0071]
In addition, the hem processing is not only the normal hem processing performed by the above-described down flange process, pre-hem process, flat hem or rope hem process, but a process such as a roller hem as long as hem is finally formed. Also, those with different process conditions are targeted and applicable as hem processing.
[0072]
In addition, hem processing such as flat hem is performed on all four sides of the Al alloy plate of the present invention, or only on selected sides (side edges), or an outer panel to be hemmed Whether the shape of the end portion is a linear shape, a circular arc shape, or a complicated shape having corners is appropriately selected according to the design of a member such as an outer panel.
[0073]
The Al alloy sheet of the present invention is also intended for press forming such as the above-described overhanging as well as hem workability. In press molding, in particular, it is intended for overhang molding when the above-described shape is enlarged and complicated in an outer panel or the like. However, these excellent stretch-formability means that the processing conditions are relatively gentle and that other drawability is excellent. Therefore, the Al alloy sheet of the present invention is also intended for particularly stretch forming and other press forming that can be represented by stretch forming.
[0074]
(Production method)
  The manufacturing method of the above Al alloy plate of the present invention will be described.
  As described above, the elongation δ in the direction of 45 degrees with respect to the rolling direction of the excess Si type 6000 series Al alloy sheet₁Is 30% or more and the elongation δ in the direction parallel to the rolling direction of the plate₂Ratio δ with₁/ δ₂In order to obtain a structure having an anisotropy of elongation such that is 1.2 or more, more preferably 1.5 or more, in addition to the above component composition, the following cold rolling conditionsAnd coldIt is necessary to add special processes and process conditions such as annealing after hot rolling. In this respect, as described above, a normal Al alloy sheet obtained by a conventional method basically has no elongation anisotropy as in the present invention, and an elongation anisotropy cannot be obtained.
[0075]
In order to obtain a structure having the elongation anisotropy, first, cold rolling is performed at a reduction ratio as high as possible of 70% or more. By increasing the rolling reduction in cold rolling in this way, sufficient strain energy can be accumulated in the cold rolled sheet. As a result, a structure having anisotropy of the elongation can be obtained by tempering treatment including annealing and solution treatment, which will be described later. If the rolling reduction in cold rolling is low, it will not be different from ordinary materials, and the structure having the elongation anisotropy cannot be accumulated by the tempering treatment described later. On the other hand, the higher the rolling reduction in cold rolling, the more difficult the processing itself, such as the occurrence of ear cracks, so the upper limit of the rolling reduction is preferably about 95%.
[0076]
  Next, the cold-rolled sheet is used to obtain a structure having the elongation anisotropy.30It is preferable that annealing is performed at a temperature of 0 ° C. or lower, preferably 150 to 250 ° C., for 1 to 50 hours, for example. By this annealing, a structure having the elongation anisotropy is easily developed in the final solution treatment, and the hem workability is remarkably improved together with the press formability. When the annealing temperature is less than 150 ° C., this effect is not obtained, and the structure having the elongation anisotropy cannot be obtained. As a result, there is no great difference from the crystal grain structure of the conventional Al alloy plate, and there is no effect of improving hem workability such as flat hem as well as press formability.
[0077]
On the other hand, if the annealing temperature exceeds 300 ° C (more severely 250 ° C), the crystal grains are likely to become coarse, and rough skin is likely to occur during press forming and hem processing. Press formability is significantly reduced. This annealing can be performed using a batch furnace or a continuous annealing furnace.
[0078]
Other process conditions can be used in a conventional manner, but there are also preferable conditions for improving the flat hem workability and other characteristics of the outer panel and the like, which will be described below.
[0079]
First, in the melting and casting process, an excess aluminum alloy melt adjusted within the specification range of the present invention is appropriately selected from ordinary melting and casting methods such as a continuous casting rolling method and a semi-continuous casting method (DC casting method). And cast.
[0080]
  Next, the Al alloy ingot is subjected to a homogenization heat treatment, followed by hot rolling and cold rolling at the above-described high reduction ratio, and processing into a plate shape such as a coil shape or a plate shape. ThatBeforeAnnealing under the conditions described is also applied.
[0081]
The processed Al alloy plate is first subjected to solution treatment and quenching treatment as a tempering treatment. The solution treatment and quenching treatment are important steps for sufficiently depositing the compound phase such as the GP zone in the grains by an artificial age hardening treatment such as a subsequent paint bake hardening treatment. The solution treatment conditions for producing this effect are preferably performed in a temperature range of 500 to 560 ° C.
[0082]
Conventionally, in the case of a panel for which flat hemmability is particularly important, or in the case of the severe flat hemming condition, the solution treatment temperature is set to a lower temperature side of 500 to 530 ° C. However, in the present invention, as described above, the hem workability such as flat hem and the press formability are particularly excellent even if the 0.2% proof stress of the Al alloy plate is not as low as 140 MPa or less as in the prior art.
[0083]
For this reason, the solution treatment temperature is set on the high temperature side in the range of 530 to 560 ° C, the 0.2% proof stress of the Al alloy plate is set to a high strength exceeding 140 MPa, and the panel is subjected to GP by artificial age hardening treatment after the subsequent plate forming. It is preferable that a compound phase such as a zone is sufficiently precipitated in the grains, and a high-strength panel exceeding 170 MPa is obtained even in the low-temperature and short-time artificial age hardening treatment in the coating process after molding.
[0084]
In quenching after the solution treatment, the cooling rate is preferably 50 ° C./min or higher. When the cooling rate is slow at less than 50 ° C./min, the strength after quenching is low, the age hardening ability is insufficient, and the high proof stress of 170 MPa or more cannot be ensured by the artificial aging treatment at a low temperature for a short time.
[0085]
In addition, Si, MgSi and the like are likely to precipitate on the grain boundaries, which is likely to be the starting point of cracks during press molding and flat hem processing, and these moldability is reduced. In order to ensure this cooling rate, the quenching process may be air cooling such as a fan, but there is a high possibility that the cooling rate will be slow, and it is preferable to perform the quenching process by selecting from water cooling means such as mist, spray, and immersion.
[0086]
In the present invention, as described above, room temperature aging itself is allowed, but room temperature aging may be suppressed. That is, after the solution hardening treatment, a preliminary aging treatment may be performed to suppress the formation of clusters that cause room temperature aging and promote the precipitation of the GP zone. This preliminary aging treatment is preferably held in a temperature range of 50 to 100 ° C., preferably 60 to 90 ° C., for a required time of 1 to 24 hours. The cooling rate after the pre-aging treatment is preferably 1 ° C./hr or less.
[0087]
As the preliminary aging treatment, the quenching end temperature after the solution treatment is increased to 50 to 100 ° C., and then immediately reheated or kept as it is. Alternatively, it is immediately reheated to 50 to 100 ° C. after quenching to room temperature after solution treatment.
[0088]
Further, in the case of continuous solution quenching, the quenching process is completed within the temperature range of the preliminary aging, and the coil is wound around a coil at the same high temperature. In addition, you may reheat before winding up to a coil, and you may heat-retain after winding. Moreover, after the quenching process to room temperature, it may be reheated to the above temperature range and wound at a high temperature.
[0089]
Furthermore, in order to suppress aging at room temperature, a GP zone may be generated by performing sub-aging treatment at a relatively low temperature without time delay after the preliminary aging treatment. When the time delay is present, room temperature aging (natural aging) occurs with time even after the preliminary aging treatment, and after this room temperature aging occurs, the effect of the sub-aging treatment is hardly exhibited.
[0090]
In order to obtain these effects, in the composition range of the Al alloy material, the aging treatment temperature is set to a sub-aging treatment range of 80 to 120 ° C., and the aging treatment time is set to a necessary time, preferably 1 to 24 hours, From this range, it is preferable to select a temperature and a time at which an aging treatment effect is obtained according to the composition. The cooling rate after the sub-aging treatment is preferably 1 ° C./hr or less. If the aging treatment temperature is less than 80 ° C. and the holding time is too short, the GP zone cannot be generated. For this reason, the room temperature aging inhibitory effect and the low temperature age hardening ability cannot be obtained. On the other hand, when the temperature exceeds 120 ° C, it is not much different from the normal aging treatment, the β "phase is precipitated and aging progresses too much, and the strength becomes too high. This is the same even if the aging treatment holding time is too long. The preliminary aging treatment temperature may be set as high as the aging treatment described later, or a heat treatment combined with or continuous with the aging treatment.
[0091]
In addition to this, it is of course possible to further increase the strength by performing aging treatment or stabilization treatment at a higher temperature according to the application or required characteristics.
[0092]
【Example】
Next, examples of the present invention will be described. For the Al alloy sheets of each 6000 series composition range shown in Table 1, the elongation δ in the direction of 45 degrees with respect to the rolling direction of the Al alloy sheet₁Is 30% or more and the elongation δ in the direction parallel to the rolling direction of the plate₂Ratio δ with₁/ δ₂In order to obtain a structure with an elongation anisotropy of 1.2 or more, as shown in Table 2, by changing the rolling reduction of cold rolling and the annealing temperature after cold rolling, An alloy plate was created. Furthermore, the conductivity and the crystal grain size were variously changed by changing the solution treatment temperature.
[0093]
The production of Al alloy sheets other than the cold rolling reduction ratio and annealing conditions after cold rolling, and the solution treatment temperature, except for the thickness of the hot rolled sheet to change the following cold rolling reduction ratio Performed under almost the same conditions. In other words, 400mm-thick ingots of each composition range shown in Table 1 were melted by DC casting method and then subjected to homogenization heat treatment at 540 ° C x 4 hours to a thickness of 2.3-8mmt at an end temperature of 300 ° C. Were hot rolled with various changes. This hot-rolled sheet was further cold-rolled to various thicknesses of 1.0 mm with various reduction ratios.
[0094]
These cold rolled sheets were tempered under the following conditions. First, after cutting into each test piece size, it was put into an air furnace maintained at 570 ° C, and when each test piece reached the solution treatment temperature of 550 ° C (holding time 0 second), it was baked in hot water at 70 ° C. The process to put in. The cooling rate during the quenching process is 200 ° C / second, the quenching end temperature (quenching temperature) is 70 ° C in common, and pre-aging treatment is held at this temperature for 2 hours after quenching (cooling rate 0.6 ° C after holding) (Slow cooling at / hr). Table 2 shows the cold rolling reduction ratio, annealing conditions after cold rolling, and solution treatment temperature in each example.
[0095]
A plurality of test plates (blanks) 500 mm wide x 500 mm long for testing were cut out from these Al alloy plates, and parallel to the rolling direction of the original Al alloy plate of the Al alloy plate immediately after tempering treatment (L direction) Tensile strength (σ)_B), Yield strength (σ_0.2) Was measured. The elongation (%) is the elongation δ in the direction of 45 degrees with respect to the rolling direction of the Al alloy sheet.₁, Elongation in the direction parallel to the rolling direction of the plate δ₂, Elongation perpendicular to the rolling direction of the plate δ_ThreeAnd were measured respectively. And in order to see the anisotropy of elongation in the 45 degree direction,₁/ δ₂Asked. Furthermore, δ₁And δ₂And δ_ThreeΔ = (2 × δ₁+ Δ₂+ Δ_Three) / 4. These results are shown in Table 3.
[0096]
Then, assuming and considering that Al alloy sheets sufficiently aged at room temperature after tempering treatment are press-formed and hemmed, each test after aging at room temperature for 4 months (120 days) after the tempering treatment was performed. Sheet conductivity (IACS%), grain size, and tensile strength parallel to rolling direction (σ_B) And yield strength (σ_0.2) And the elongation of the Al alloy plate as δ₁, Δ₂, Δ_ThreeAnd were measured respectively. And δ₁/ δ₂And δ₁, Δ₂, Δ_ThreeIs the average value of δ = (2 × δ₁+ Δ₂+ Δ_Three) / 4. These results are shown in Table 4.
[0097]
The tensile test was performed according to JIS Z 2201 and the shape of the test piece was a JIS No. 5 test piece. The crosshead speed was 5 mm / min, and the test piece was run at a constant speed until the test piece broke.
[0098]
In addition, the test plate after the room temperature aging was subjected to a molding test by simulating press molding or hem processing using an Al alloy plate aged at room temperature as an automobile panel. More specifically, a stretch forming test and a flat hem processing test after the stretch forming were performed to evaluate the formability. These results are shown in Table 4.
[0099]
First, the conditions of the stretch forming test were as follows: a plurality of square test plates (blanks) each having a side of 500 mm were cut out from the Al alloy plate after aging at room temperature, and the side was 300 mm on one side and the height was as high as 30 mm. A hat-shaped panel having a rectangular tubular projecting portion and flat flange portions (width 30 mm) around the four portions of the projecting portion was stretch-molded by a mechanical press using a die with a bead.
[0100]
In the overhang forming test, the wrinkle holding force is 49 kN, the lubricating oil is general rust preventive oil, and the forming speed is 3 times under the same conditions of 20 mm / min. Examples where there were no defects and were able to be molded normally were evaluated as x.
[0101]
Appearance evaluation at the time of molding is performed according to the occurrence of orange peel on the surface of the molded hat panel, and the surface of the molded hat panel is observed three times. What produced was evaluated as x.
[0102]
Next, the flat hem processing test was as follows. Simulating that the press-formed Al alloy panel is hem-processed as an outer panel, the entire end face (width 130 mm) of the flange portion parallel to the rolling direction of the flat flange portion of the panel is as follows: The flat hem was processed under the conditions.
[0103]
First, the flat hemming allowance of the Al alloy panel (distance from the end folded to the end of the panel after hemming to the end of the bent portion) is set to 12 mm, the down flange process is simulated, and the edge of the Al alloy panel is simulated. Was bent to a 90 degree angle. At this time, the 90 ° bend radius of the Al alloy panel was set to 0.8. Next, by simulating a prehem process, the edge of the Al alloy panel was further bent inward to an angle of 135 °.
[0104]
Then, simulating severe flat hem processing conditions, flat hem processing was performed in which the inner panel was not inserted into the bent portion of the Al alloy panel, but the bent portion was bent inward by 180 degrees and adhered to the panel surface. The flat hem processing direction was made to coincide with the rolling direction of the original Al alloy sheet.
[0105]
Then, the surface state of the flat hem, such as rough skin, minute cracks, and large cracks, was visually observed. Evaluation: 1; good with no rough skin or fine cracks, 2; rough skin, but no cracks including fine ones, 3; small cracks occurred, 4; large cracks occurred, 5 ; Evaluated in 5 grades from multiple or large cracks. In this evaluation, it is judged that heme workability is good (usable) in 1 to 2 stages, and that heme workability is inferior in 3 stages or more (unusable).
[0106]
Furthermore, in order to investigate the low temperature aging treatment ability, a test plate was collected from the press-formed Al alloy panel and subjected to artificial aging hardening treatment at a low temperature of 160 ° C x 20 minutes for a short time. Tensile strength (ABσ) parallel to the rolling direction (in the L direction) of the plate (of the original Al alloy plate)_B) And yield strength (ABσ_0.2). These results are shown in Table 5.
[0107]
  Invention Example 1 using excess Si-type 6000 series Al alloys 1 to 3 (Table 1) within the composition range of the 6000 series Al alloy and having a Si / Mg mass ratio of 1 or more~ 7 isAs shown in Tables 3 and 4, the Al alloy plate has a predetermined anisotropy with respect to elongation in the 45 ° direction, and the average value of elongation (2 × δ₁+ Δ₂+ Δ_Three) / 4 is also more than 25%. As a result, in comparison with Tables 3 and 4, after the above four months (120 days) aging at room temperature, the yield strength was higher than immediately after tempering, and the conditions were disadvantageous for formability and age hardening. However, as is clear from Table 5, it is excellent in flat hem processability, stretch formability, and age hardening.
[0108]
Moreover, the test conditions and evaluation of the flat hem workability lead to the evaluation of the flat hem workability under actual severe processing conditions such as an automobile outer panel. Therefore, Invention Examples 1 to 9 indicate that sufficient processing can be performed even by hem processing such as actual flat hem.
[0109]
In addition, the test conditions and evaluation of the stretch forming lead to the evaluation of the stretch forming under actual severe processing conditions such as an automobile outer panel. Therefore, Invention Examples 1 to 11 show that even if the overhang height, the overhang area, etc. are increased in press forming such as actual overhang forming or draw forming, the overhang formability is excellent and can be sufficiently processed. Yes.
[0110]
  Furthermore, Invention Example 1~ 7 isEven in the case of artificial age hardening at 160 ° C. × 20 minutes for a short time, the AB yield strength is 170 MPa or more. This means that an AB proof stress of 200 MPa or more can be obtained in the current mainstream 170 ° C x 20 minutes paint baking process, such as in the automobile body manufacturing process.
[0111]
Of these invention examples, Invention Example 6 having a higher annealing temperature after cold rolling has a relatively large crystal grain size and can be stretched under the above-mentioned severe conditions, but is shown in Table 5. As described above, the other examples of the invention did not cause rough skin, while some rough skin (orange peel) occurred.
[0112]
  On the other hand, invention example10 and 12As shown in Tables 3 and 4, Invention Example 1 above~ 7Similarly, the Al alloy plate has a predetermined anisotropy with respect to elongation in the 45 ° direction, and the average value of elongation (2 × δ₁+ Δ₂+ Δ_Three) / 4 is also more than 25%. Therefore invention example10 and 12Invention Example 1~ 7As well as, it is excellent in flat hem workability and stretch formability.
[0113]
  However, invention examples10 and 12The Al alloy 4 in which the Si content and the Mg content are balanced even within the composition range of the present invention 6000 series Al alloy,Al alloy with less Si content of less than 0.4%6 (In each case, Table 1) is used.
[0114]
  For this reason, the invention example10 and 12In comparison with Tables 3 and 4, Invention Example 1 above~ 7In comparison with the above, the increase in yield strength with time after aging at room temperature for 4 months is relatively small. However, under the conditions where the yield strength was increased by room temperature aging and was disadvantageous for age hardening, as shown in Table 5, the invention example 1~ 7Compared to JIS, the AB yield strength after artificial age hardening at a low temperature for a short time is as low as less than 170 MPa. In particular, invention examples with low Si content of less than 0.4%12 isThe AB proof strength is 160MPa level. Therefore, in order to make the AB yield strength after artificial age hardening treatment at a low temperature for a short time to 170 MPa or more, Si / Mg is an excess Si type 6000 series Al alloy with a mass ratio of 1 or more, and the Si content is 0.4%. In addition, the Mg content is preferably 0.2% or more.
[0115]
In contrast to these inventive examples, Comparative Examples 14, 15, 16, and 17 in which the cold rolling rate is too low are the same alloy compositions corresponding to the inventive examples, respectively, but in Table 4, room temperature aging is performed for 4 months. Later, δ₁And δ₁/ δ₂However, the result is out of the range of the present invention. Therefore, as is apparent from Table 5, Comparative Examples 14, 15, 16, and 17 have remarkably lower flat hem processability than the inventive examples. Of the comparative examples, in particular, Comparative Examples 14 and 15 which can be said to be plates produced by a conventional method are δ₁/ δ₂Is 1.0 and there is almost no anisotropy of elongation.
[0116]
And interestingly, the δ of these comparative examples₂And δ_ThreeThe value of δ in the above invention example₂And δ_ThreeDespite being rather high, the flat hem processability of the comparative example is significantly lower than the inventive example. Therefore, from these results, the definition of elongation anisotropy in the present invention (δ₁And δ₁/ δ₂) And the significance of manufacturing conditions such as the cold rolling rate to produce a structure that satisfies the anisotropy of elongation.
[0117]
[Table 1]

[0118]
[Table 2]

[0119]
[Table 3]

[0120]
[Table 4]

[0121]
[Table 5]

[0122]
【The invention's effect】
According to the present invention, Al-Mg is particularly excellent in bending workability such as flat heme processing under severe conditions, and excellent in other properties required for panel formation, such as press formability and low-temperature age-hardening ability. -Si based Al alloy sheet can be provided. Therefore, it has a great industrial value in that the Al alloy plate can be expanded to panel applications.

Claims (9)

Al-Mg- consisting of a composition containing Si: 0.4 to 1.3%, Mg: 0.2 to 1.2%, Mn: 0.01 to 0.65%, Cu: 0.001 to 1.0% with the balance being Al and inevitable impurities In the Si-based aluminum alloy plate, as a characteristic after the room temperature aging of the manufactured plate, the 0.2% proof stress in the direction parallel to the rolling direction of the plate is in the range of 120 to 170 MPa, and the rolling direction of the plate with 45-degree direction elongation [delta] ₁ is 30% or more, the ratio [delta] ₁ / [delta] ₂ of the [delta] ₁ and elongation [delta] ₂ in the parallel direction to the rolling direction of the plate is equal to or 1.2 or more Aluminum alloy plate with excellent bending workability. _2. The average value of the δ ₁ and δ ₂ and the elongation δ _{3 in the} direction perpendicular to the rolling direction of the plate is (2 × δ ₁ + δ ₂ + δ ₃ ) / 4 is 25% or more. Aluminum alloy plate with excellent bending workability. The aluminum alloy sheet having excellent bending workability according to claim 1 or 2, wherein the δ ₁ / δ ₂ is 1.5 or more.   The aluminum alloy plate contains Si: 0.4 to 1.3%, Mg: 0.2 to 1.2%, Mn: 0.01 to 0.65%, Cu: 0.001 to 1.0%, and Si / Mg is 1 or more by mass, and the balance The aluminum alloy plate excellent in bending workability according to any one of claims 1 to 3, wherein the aluminum alloy plate is composed of Al and inevitable impurities.   The aluminum alloy plate excellent in bending workability according to claim 4, wherein the Si content is 0.6 to 1.0% and the Mg content is 0.2 to 0.8%.   The aluminum alloy plate excellent in bending workability according to any one of claims 1 to 5, wherein the conductivity of the aluminum alloy plate is in a range of 43 to 47 IACS% and the crystal grain size is 50 µm or less.   The aluminum alloy plate excellent in bending workability according to any one of claims 1 to 6, wherein the aluminum alloy plate is hemmed after bulge forming. The aluminum alloy plate excellent in bending workability according to claim 7, wherein the hem processing is flat hem processing.   The aluminum alloy plate excellent in bending workability according to any one of claims 1 to 8, wherein the aluminum alloy plate is for an automobile outer panel.