JP4383039B2 - Method for producing aluminum alloy sheet with excellent bending workability - Google Patents

Description

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【表２】

【０１０８】
【表３】

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【表４】

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【発明の効果】
本発明によれば、フラットヘム加工などの曲げ加工性に優れ、プレス成形性、低温での人工時効硬化能、耐食性など他の要求特性も兼備したAl-Mg-Si系Al合金板の製造方法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。
【図面の簡単な説明】
【図１】フラットヘム加工におけるアウタパネルの縁曲部を示す斜視図である。
【図２】アウタパネルのフラットヘム加工部の形状を模式的に示す説明図である。
【符号の説明】
1:アウタパネル、2:インナパネル、A:折り曲げ部[0001]
BACKGROUND OF THE INVENTION
  The present invention is an Al-Mg-Si-based aluminum alloy plate (hereinafter, aluminum is simply referred to as Al) that has excellent bending workability such as hem processing.)ofIt relates to a manufacturing method.
[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 components and having a Si / Mg ratio of 1 or more in mass ratio. And since this excess Si type 6000 series Al alloy has excellent age-hardening ability, it secures formability by reducing the yield strength during press molding and bending, and artificial aging such as baking coating after molding. There is an advantage that the strength is improved by age hardening by heating at the time of processing, and the necessary strength can be secured.
[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]
On the other hand, in the outer panel of the automobile, etc., after the Al alloy plate is formed by press forming such as overhang, drawing or trim to form an outer panel, the edge of the outer panel is bent (folded 180 degrees) to join the edge of the inner panel. A severe bending process called a hem (other name for hemming) process is performed in combination. In addition, the inner panel is subjected to a combination of severe press molding such as deep drawing.
[0008]
In particular, the outer panel is also required to have high strength (high age hardening), high corrosion resistance, high weldability and the like.
[0009]
The outer panel hem processing is performed by a flat flange process or a rope hem process through a down flange process in which the edge of the outer panel is bent to an angle close to 90 ° with a tool such as a punch, and a prehem process in which the edge of the outer panel is further bent inward to approximately 135 °. Is done.
[0010]
In this flat hem process and rope hem process, as shown in Fig. 1, the end of the inner panel 2 is accommodated (inserted) in the bent part A of the outer panel 1, and the edge 1c of the outer panel 1 is further angled up to 180 ° with a tool. Bend inward to form a hem. Of these, in the flat hem, the edge of the inner panel 2 and the flat hem portion (a 180-degree bent portion) A of the outer panel 1 are in contact with each other, and the two are joined and closely adhered to each other. Has a shape. On the other hand, the rope hem has a rope-like cross-sectional shape in which a bent portion swells in an arc shape, and its appearance is not good as compared with the flat hem shape. In addition, there is a problem that the contact area between the outer panel and the inner panel is small and the bonding property and adhesion are lacking.
[0011]
For this reason, in particular, in automobile parts and the like that place importance on appearance and aesthetics, it is common to perform the final step of hem processing by a flat hem step, which is a severe bending process.
[0012]
However, since the flat hem shape is more flat than the rope hem shape, the processing conditions are more severe because of the flat bent portion shape. For this reason, in flat hem processing of an Al alloy plate, the edge portion (hem portion, bent portion) A of the formed flat hem is shown in the order shown in FIG. Defects such as rough skin X, minute crack Y, and relatively large crack Z are likely to occur. And when such a defect arises, application as an outer panel becomes impossible.
[0013]
Compared to flat hem processing of such Al alloy plates, the flat hem processing process side and the material side of the Al alloy plate prevent the occurrence of defects at the edge bend A and improve flat hem workability. Various techniques have been proposed.
[0014]
From the flat hem processing side, for example, in flat hem processing of a high-strength Al alloy plate of about 186 MPa, the bending radius Rd (the shoulder radius of the die) of the flange corner portion formed in the outer panel in the down flange process is set. It has been proposed to prevent the occurrence of the defect by increasing it to 0.8 t to 1.8 t (where t is the thickness of the Al alloy plate) (see Patent Document 1). Improvements to the processing method itself, such as performing flat hem processing with roller hem, have also been proposed.
[0015]
[Patent Document 1]
Japanese Patent Publication No.63-2690
[0016]
On the other hand, from the raw material side, various proposals or improvements have been made to improve the flat hem workability by regulating the grain boundary precipitates of the Al alloy plate or reducing the proof stress of the Al alloy plate to 140 MPa or less.
[0017]
[Problems to be solved by the invention]
However, flat hem processing conditions tend to become increasingly difficult in recent years. The reason is that the shape (design) of the portion of the outer panel to be flat-hem processed is complicated. If the edge profile of the outer panel processed by flat hem is not a straight simple shape A as shown in Fig. 2, but an arc shape B or corner C, The defect is more likely to occur.
[0018]
Next, the reason is that the Al alloy plate for the outer panel and the inner panel has been increasingly thinned in recent years to a thickness of 1.0 mm or less in order to reduce the weight of the panel. For example, Al alloy plates for outer panels are mainly 1.0 mm or less and 0.8 to 0.9 mm thick. Also, Al alloy plates for inner panels are mainly 1.0 mm or less, 0.5 to 0.8 mm thick. In these thinned Al alloy plates, especially as the thickness of the inner panel inserted into the edge curved portion of the outer panel becomes thinner, the bending process conditions become stricter and flat hem processing tends to be difficult. And this tendency becomes remarkable in the above-described thinned Al alloy plate.
[0019]
Further, in the flat hem processing, there is inevitably a slight gap x between the end 2a of the inner panel 2 inserted into the edge curve A of the outer panel 1 and the inner surface Aa of the edge curve A. It is processed with. This gap x is approximately 0.6 or less, although it varies depending on the processing conditions in terms of the ratio (x / l) to the flange length (peripheral length of the hem edge curved portion A) l shown in FIG. However, if there is this gap x or if this gap x becomes large, the thickness of the edge curved portion A (bending portion) of the outer panel 1 becomes thin and the bending conditions become severe, so that defects such as cracks Z are likely to occur.
[0020]
For such severe flat hemming of an Al alloy plate, there are cases where the conventional improvement techniques on the flat hemming process side or the material side of the Al alloy plate cannot always cope. In addition, the improvement of flat hem processing may decrease the other characteristics of the Al alloy plate. For example, when flat hem workability is improved by lowering the proof stress of the Al alloy plate itself, even if the press formability is reduced or even an excess Si type 6000 series Al alloy plate, the panel coating baking process after plate forming As a result, the yield strength after artificial age-hardening treatment at a low temperature in a short period of time is insufficient, resulting in insufficient dent resistance.
[0021]
  The present invention has been made by paying attention to such circumstances, and the purpose thereof is an Al-Mg-Si-based Al alloy that is particularly excellent in bending workability such as flat hem and has other panel required characteristics.PlankA manufacturing method is to be provided.
[0022]
[Means for Solving the Problems]
  In order to achieve this object, the summary of the method for producing an aluminum alloy sheet of the present invention is, in mass%, Si: 0.4 to 1.3%, Mg: 0.2 to 1.2%, Mn: 0.01 to 0.65%, Cu: 0.001 to An Al-Mg-Si-based aluminum alloy sheet containing 1.0% and the balance being Al and unavoidable impurities is cold-rolled at a reduction rate of 60% or more, and then annealed at a temperature of 350 ° C or less, so Tempering treatment including pouring treatment, the ratio of the integrated strength of {200} plane on the aluminum alloy plate surface is 50% or more, the ratio of the total integrated strength of {200} plane and {400} plane is 60% or more, In addition, the conductivity is in the range of 43 to 47 IACS%, and the crystal grain size is 50 μm or less.
[0024]
The Al alloy plate referred to in the present invention is a plate that has been subjected to tempering treatment (heat treatment) after cold rolling and is aged at room temperature, and is a forming material plate that has not been press-formed or bent. Say. Therefore, each of the above requirements is also the state of the Al alloy plate after the tempering treatment, and after a tempering treatment, from a short period of time to an arbitrary period until press forming and / or bending such as flat hem is performed. This refers to the state of an Al alloy plate aged at room temperature for a long period of time. The tempering treatment referred to here refers to various tempering treatments such as solution treatment and quenching treatment, a preliminary aging treatment described later, and an aging treatment applied if necessary.
[0025]
The inventors of the present invention have reexamined the relationship between the flat heme workability and the structure of the Al—Mg—Si based Al alloy sheet. As a result, the cube orientation (the ratio of the integral strength of the {200} plane and the ratio of the total integral strength of the {200} plane and the {400} plane) of the crystal grain of the Al-Mg-Si Al alloy plate is flat hem. It was found that there was a close correlation with workability. That is, the greater the proportion of crystal grains having a cube orientation, the better the flat heme workability. On the other hand, the smaller the proportion of crystal grains having a cube orientation, the lower the flat hem workability.
[0026]
In the Al alloy sheet field, controlling the ratio of crystal grains having a cube orientation is known per se. For example, in an Al alloy foil for a pure Al electrolytic capacitor electrode, a technology that controls the ratio of the integrated strength of the {200} plane (crystal grains with a cubic orientation) in order to improve the electrode characteristics by increasing the etching pits Are disclosed in Japanese Patent Publication No. 1-333546 and Japanese Patent Application Laid-Open No. 6-287723. In addition, in order to improve the bending workability during press forming in a 5000 series Al alloy plate with a large amount of Mg, a technique for setting the integral strength ratio of the {100} plane to the {110} plane to 1 or more is a special feature. This is disclosed in, for example, Kaihei 10-8176.
[0027]
However, in the case of the Al alloy foil, the purpose is to improve the electrode characteristics described above, and the purpose is completely different from the present invention. In the case of the 5000 series Al alloy plate, although the object is close to the present invention, the integral strength ratio between the {100} plane and the {110} plane is set to 1 or more in order to increase the ultimate deformability. However, in the 6000 series Al alloy plate targeted by the present invention, flat hem processing is possible even if the integral strength ratio between the {100} plane and the {110} plane is 1 or more as disclosed in Japanese Patent Laid-Open No. 10-8176. Sex cannot be improved. This is because the 6000 series Al alloy plate is inferior to the 5000 series Al alloy plate in flat hem workability and press formability, and the flat hem work conditions intended in the present invention are those of the press form intended in the above publication. This is because the processing conditions are more severe than the bending process.
[0028]
As will be described later, a normal Al—Mg—Si-based Al alloy plate obtained by a conventional method has a small proportion of crystal grains having a cube orientation. In other words, in order to obtain an Al alloy sheet structure having a specific amount of crystal grains having a cube orientation as in the present invention, a special process addition or process condition is required as in the manufacturing method described later. .
[0029]
However, in the present invention, the production of the Al alloy plate is not complicated and the production cost is not significantly increased by the special production process. Therefore, this point is also an advantage of the present invention.
[0030]
In the present invention, the hem workability such as flat hem and the press formability are particularly excellent even when the 0.2% proof stress of the Al alloy plate 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 can be increased to 140 MPa or higher, and even at a low-temperature artificial age hardening treatment of 170 ° C x 20 minutes using a paint baking process after molding, etc. A high-strength panel can be obtained.
[0031]
In addition, since the Al alloy plate of the present invention has the above-described effects, it is an outer panel having a thickness of 0.5 mm or more, which is particularly severe even during bending, and a thickness of 1.3 mm or less to 1.0 mm or less. It is preferably applied when hem processing is performed on the inner panel. Similarly, the Al alloy sheet of the present invention is preferably applied to flat hem processing which is a severe bending condition among bending processes. Further, the Al alloy plate of the present invention is suitable for use in an automobile outer panel, in particular, because flat hem processing is widely used and flat hem workability is severely demanded.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
  First, the Al alloy plate of the present invention(Al alloy plate according to the manufacturing method of the present invention, hereinafter the same meaning)The requirements of the organization are described below. In the following description, flat hem processing, which is a severe bending condition in bending, is mainly performed. However, if flat hem processing is improved, other hem workability and other bending workability are also improved.
[0033]
In the present invention, in order to improve the bending workability of flat hem and the like, the ratio of the integrated intensity by X-ray diffraction of the {200} plane of the Al alloy plate surface is set to 50% or more per cube orientation of the Al alloy plate crystal grains. In addition, the ratio of the total integrated intensity by X-ray diffraction between the {200} plane and {400} plane is specified as 60% or more.
[0034]
If the ratio of integrated intensity by X-ray diffraction of {200} plane is less than 50%, or the ratio of total integrated intensity by X-ray diffraction of {200} plane and {400} plane is less than 60%, conventional Al alloy plate There is no significant difference from the crystal grain structure, and there is no improvement effect of bending workability such as flat hem. For this reason, the workability of the Al alloy plate is remarkably lowered particularly in flat hem processing under the above-mentioned severe conditions.
[0035]
On the other hand, when the ratio of the integral strength of the {200} plane exceeds 80%, or when the ratio of the total integral strength of the {200} plane and the {400} plane exceeds 90%, the tension of the Al alloy sheet There is a possibility that press moldability such as extrusion molding or draw molding may be deteriorated. As a result, there is a possibility that the shape accuracy or the shape freezing property, which is particularly important as an outer panel or the like in press molding, may be significantly reduced. For this reason, in order not to deteriorate other properties such as press formability other than hemmability, the ratio of crystal grains having a cube orientation is set to 50 to 50% of the integrated strength of the {200} plane on the Al alloy plate surface. In addition to being in the range of 80%, the ratio of the total integrated intensity of the {200} plane and the {400} plane is preferably in the range of 60% to 90%.
[0036]
Regarding the relationship between the bending direction of the plate with flat hem etc. and the cube orientation (distribution direction) of the plate, make sure that the cube orientation of the plate is parallel to the bending direction of the plate (the bending direction of the plate is When bending is performed so that the cube orientation direction of the plate is perpendicular to the bending direction of the plate (with the bending direction of the plate being perpendicular to the rolling direction of the plate) Similarly, good flat heme workability can be obtained. Even if the cube orientation of the panel is rotated 90 degrees, it has the same structure, so there is no distinction between 0 degrees and 90 degrees. For this reason, even if the bending direction of the plate is parallel or perpendicular to the rolling direction of the material plate, the cube orientation becomes the same structure, and good flat hem workability is obtained. However, the relationship between the bending direction of the plate other than the above two directions and the cube orientation (distribution direction) of the plate, such as the plate's cube orientation being 45 degrees and the bending direction of the plate, the bending of flat hem, etc. Workability may be inferior, and the bending direction of the plate in bending is preferably the above two directions.
[0037]
In the present invention, the degree of development of the cube orientation of the crystal grains of the Al alloy plate is measured by using an X-ray diffractometer (for example, Rigaku RAD-RC) and measuring the surface of the Al alloy plate without any pretreatment. A non-oriented Al sample was used as a standard sample, and {111} plane, {200} plane, {220} plane, {311} plane, {222} plane, {400} plane, {331 to this standard sample }, The sum A of integrated intensities of each of the {420}, {422}, and {422} surfaces is obtained. Then, the integrated intensity I of the {200} plane with respect to A₁Ratio (%), the integrated intensity I of the total of {200} plane and {400} plane I₂Is the ratio (%) of each integrated intensity.
[0038]
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 GP zone formed during the artificial aging treatment such as the panel paint baking process is secured, and corresponding to the press molding and paint baking process, for example, after 2% stretching During the low temperature artificial aging treatment at 170 ° C for 20 minutes, the required strength of 170 MPa or more is guaranteed. 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.
[0039]
If the conductivity exceeds 47IACS%, flat heme workability may be reduced. Moreover, press moldability may also be reduced. Therefore, it is preferable to define the upper limit of conductivity as 47 IACS%.
[0040]
On the other hand, when the electrical conductivity is less than 43 IACS%, the amount of the compound phase such as the GP zone formed during the artificial aging treatment may be reduced. For this reason, the artificial age-hardening ability is lowered, and in particular, the yield strength (σ_0.2) May not be obtained. Therefore, even if the plate thickness is 1.0 mm or less, the lower limit of conductivity should be specified as 43 IACS% in order to guarantee rigidity and strength such as dent resistance as panel outer plates for automobiles and the like. Is preferred.
[0041]
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, flat hem workability and press formability are significantly reduced, such as cracks in the flat hem part, orange peel failure when paneled by press molding, etc. It is easy to cause rough skin.
[0042]
The crystal grain size referred to here is the average diameter of crystal grains in the rolling (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.
[0043]
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 as follows: Si: 0.4-1.3%, Mg: 0.2-1.2%, Mn: 0.01-0.65%, Cu: 0.001-1.0% The remainder is made of Al and Mg-Si (6000 series) Al alloy with 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.
[0044]
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.
[0045]
The content range and significance of each element, or the allowable amount will be described below.
Si: 0.4 to 1.3%.
Si, together with Mg, forms a compound phase such as GP zone at the time of artificial aging treatment at low temperatures such as solid solution strengthening and paint baking treatment, and exhibits age hardening ability, which is necessary as an outer panel of an automobile, for example, It is an essential element for obtaining the required strength of 170 MPa or more. 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.
[0046]
In addition, in order to demonstrate the excellent low-temperature age-hardening ability of 170 MPa or more after the low-temperature paint baking treatment after molding to the panel (at the time of low-temperature aging treatment after applying 2% stretch at 170 ° C × 20 minutes) 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.
[0047]
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%, hemmability and press formability are particularly hindered. Furthermore, weldability is significantly impaired. Therefore, Si is set in the range of 0.4 to 1.3%. In the outer panel, hem workability is particularly important. Therefore, in order to further improve flat hem workability as well as press formability, the Si content is preferably set to a lower range of 0.6 to 1.2%.
[0048]
Mg: 0.2-1.2%.
Mg forms a compound phase such as GP zone together with Si during the above-mentioned artificial aging treatment such as solid solution strengthening and paint baking treatment, and exhibits age-hardening ability, and as a panel, for example, a required strength of 170 MPa or more is obtained. Is an essential element for.
[0049]
If the Mg content is less than 0.2%, 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 of 170 MPa or more necessary for a panel cannot be obtained.
[0050]
On the other hand, if the Mg content exceeds 1.2%, the formability such as press formability and bending workability is significantly inhibited. Therefore, the Mg content is in the range of 0.2 to 1.2%, and the Si / Mg is such that the mass ratio 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 1.2%, in order to obtain an excess Si type 6000 series Al alloy composition correspondingly, Further, the Mg content is preferably in the lower range of 0.2 to 0.7%.
[0051]
Cu: 0.001 to 1.0%
Cu has the effect of promoting GPII and β "phase precipitation 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 according to the present invention. Cu has the effect of improving formability, and if the Cu content is less than 0.001%, this effect is not achieved, while if it exceeds 1.0%, the resistance to stress corrosion cracking and the resistance to yarn after coating are included. This significantly degrades rust and weldability, so that it is 0.8% or less for structural materials where corrosion resistance is important, and yarn rust resistance for panels such as automotive outer panels. The amount is preferably 0.1% or less so that the expression becomes remarkable.
[0052]
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.
[0053]
On the other hand, when the Mn content is increased, coarse Al-Fe-Si- (Mn, Cr, Zr) -based intermetallic compounds and crystal precipitates are easily generated during melting and casting, and the mechanical properties of the Al alloy sheet Causes the properties to deteriorate. In particular, in flat hem processing where the processing conditions have become strict 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 0.15%. 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 0.15%, particularly in flat hem processing in which the processing conditions are severe.
[0054]
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, when Cr and Zr are contained in amounts exceeding 0.15%, the hem workability is deteriorated particularly in flat hem processing in which the processing conditions are severe. Therefore, it is preferable to restrict the Cr and Zr contents to 0.15% or less.
[0055]
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.
[0056]
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 when Fe is contained in an amount of 0.10% or more, and prevent the crystal grains from becoming coarse, and play a role of making the crystal grains fine particles of 50 μm or less. However, on the other hand, these crystallized products significantly deteriorate fracture toughness and fatigue characteristics, and in particular flat hem workability and press formability in which the processing conditions are severe. Since these deterioration characteristics become remarkable when the Fe content exceeds 0.50%, the Fe content (allowable amount) is preferably set to 0.10 to 0.50%.
[0057]
Zn.
When Zn exceeds 0.5%, the corrosion resistance is remarkably lowered. Therefore, the Zn content is preferably as low as possible, preferably 0.5% or less.
[0058]
The bending process targeted by the Al alloy sheet of the present invention is particularly intended for flat hem processing. However, since the Al alloy plate of the present invention is excellent in flat hem workability, which is a severe condition, it is naturally excellent in workability such as the rope hem, which is one step looser than that, and other bending workability. For this reason, not only flat hems but also hem processing such as other rope hems are targeted. In addition, other bending processes are intended for bending of commonly used plates such as V-bending, U-bending and 90-degree bending.
[0059]
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 or process such as a roller hem as long as hem is finally formed. Those with different conditions are also targeted and applicable as hem processing.
[0060]
As described above, the hem processing targeted by the present invention is processed on a thin inner panel Al alloy plate having a plate thickness of 0.5 mm or more as an outer panel and a plate thickness of 1.5 mm or less, particularly 1.0 mm or less. It is preferably applied to harsh processing such as harsh, especially flat hem. If the thickness of the Al alloy plate as the outer panel is thinner than this, and the thickness of the Al alloy inner panel is thicker than this, it is relatively easy to hem.
[0061]
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.
[0062]
In the present invention, as described above, hem workability such as flat hem and 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. As a result, the 0.2% proof stress of the Al alloy sheet can be increased to a high strength exceeding 140 MPa, and a high strength exceeding 180 MPa can be achieved even at a low-temperature artificial age hardening treatment at 170 ° C for 20 minutes in the painting process after molding. You can get a panel. However, when such high strength is not required, the proof stress of the Al alloy plate to be hemmed may be in the range of 110 to 140 MPa.
[0063]
(Production method)
  The manufacturing method of the above Al alloy plate of the present invention will be described. As described above, in order to obtain the Al alloy sheet structure of the present invention in which a specific amount of crystal grains having a cube orientation are present, 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 regard, a normal Al alloy plate obtained by a conventional method has a small proportion of crystal grains having a cube orientation, and an Al alloy plate structure having a specific amount of crystal grains having a cube orientation as in the present invention cannot be obtained. .
[0064]
In order to obtain the Al alloy sheet structure of the present invention in which a specific amount of crystal grains having a cube orientation is present, first, a sheet obtained by hot rolling or continuous casting and rolling, a higher reduction ratio of 60% or more To cold roll. By setting the reduction ratio in cold rolling to a higher reduction ratio of 60% or more, sufficient strain energy can be accumulated in the cold rolled sheet. As a result, a specific amount of crystal grains having a cube orientation can be grown by annealing described later. If the rolling reduction in cold rolling is low, there will be no change from ordinary materials, and it may not be possible to accumulate sufficient strain energy to grow a specific amount of crystal grains with cube orientation by annealing and solution treatment described below. high. 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%.
[0065]
  Next, the cold rolled sheet is used to grow a specific amount of crystal grains having a cube orientation., 35It is preferable that annealing is performed at a temperature of 0 ° C. or lower, preferably 200 to 300 ° C., for 1 to 50 hours, for example. By this annealing, a specific amount of fine recrystallized grains or sub-crystal grains having a cube orientation grows, and the cubic orientation is easily developed in the final solution treatment, and the bending workability is remarkably improved together with the press formability. When the annealing temperature is less than 200 ° C., this effect is not achieved, and the ratio of crystal grains having a cube orientation on the surface of the Al alloy panel is set such that the integral strength ratio of the {200} plane on the Al alloy plate surface is 50% or more. , The ratio of the total integrated intensity of the {200} plane and the {400} plane cannot be 60% or more. 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, under the severe conditions.
[0066]
On the other hand, when the annealing temperature exceeds 350 ° C, the crystal grains are likely to be coarsened, and the skin is likely to be roughened during press forming and hem processing, and the press formability such as the overhang forming and drawing of an Al alloy plate is significantly reduced. . This annealing can be performed using a batch furnace or a continuous annealing furnace.
[0067]
Other process conditions can be used in a conventional manner, but there are also preferable conditions for improving hem workability such as flat hem and other characteristics as an outer panel and the like, which will be described below.
[0068]
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.
[0069]
  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. that time,in frontIt also performs annealing.
[0070]
The processed Al alloy plate is first subjected to solution treatment and quenching treatment as a tempering treatment. The solution treatment and quenching process are important steps for sufficiently depositing the compound phase such as GP zone and β "phase in the grain by the artificial age hardening process such as the subsequent paint bake hardening process. It is preferable to perform the solution treatment conditions in a temperature range of 500 to 540 ° C.
[0071]
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.
[0072]
For this reason, the solution treatment temperature is set on the high temperature side in the range of 530 to 540 ° 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. The compound phase such as the zone and β "phase is sufficiently precipitated in the grains, and the panel has a high strength exceeding 180 MPa even at low-temperature artificial age hardening at 170 ° C for 20 minutes in the coating process after molding. It is preferable.
[0073]
In quenching after the solution treatment, the cooling rate is preferably 50 ° C./min or higher. If the cooling rate is slow, less than 50 ° C / min, the strength after quenching will be low, the age-hardening ability will be insufficient, and the artificial aging, especially at a low temperature of 170 ° C x 20 minutes, such as subsequent paint bake-curing treatment. High yield strength of 170 MPa or more cannot be secured by processing.
[0074]
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.
[0075]
In order to suppress the formation of clusters that cause room temperature aging after the solution hardening treatment, it is preferable to perform preliminary aging treatment. That is, it is preferable that the temperature is maintained at 50 to 100 ° C., preferably 60 to 90 ° C., for 1 to 24 hours. The cooling rate after the pre-aging treatment is preferably 1 ° C./hr or less.
[0076]
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.
[0077]
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.
[0078]
Furthermore, in order to suppress the aging at room temperature, not only to regulate GPI, but also to actively generate GPII, after the preliminary aging treatment, sub-aging treatment at a relatively low temperature without time delay, It is preferable to produce a more stable GPII and β "phase (mainly GPII). When the time delay is present, room temperature aging (natural aging) occurs over time even after the preliminary aging treatment, and this room temperature. After aging has occurred, the effect of the sub-aging treatment is less likely to be exhibited.
[0079]
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 temperature is less than 80 ° C. and if the holding time is too short, a more stable GPII and β ″ phase cannot be generated. Therefore, the room temperature aging inhibitory effect and the low temperature aging hardening ability cannot be obtained. On the other hand, when the temperature exceeds 120 ° C., it is not much different from normal aging treatment, GPII precipitates and aging progresses too much, and the strength becomes too high, even if the aging treatment is held for too long. The preliminary aging treatment temperature may be set to be as high as the aging treatment described later, and may be a heat treatment combined with or continuous with the aging treatment.
[0080]
By using the preliminary aging treatment and the sub-aging treatment together after the solution treatment and quenching treatment, the structure of the Al alloy material is reduced to a micro-structure mainly composed of stable GPII, β "phase and supersaturated solid solution with little or no GPII. As described above, this microstructure has excellent characteristics that it is difficult to cause age hardening at room temperature, while this microstructure is low temperature age hardening treatment at 170 ° C. × 20 minutes. Heating (aging treatment) such as subsequent baking coating, etc. Even at low temperatures, it has the excellent properties of becoming a nucleation site for β "phase and high low temperature aging treatment ability.
[0081]
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.
[0082]
【Example】
Next, examples of the present invention will be described. In order to control the crystal orientation for each 6000 series Al alloy plate of Invention Examples 1 to 5 in the composition range of the present invention and Comparative Examples 6 and 7 of each component composition outside the composition range of the present invention shown in Table 1, As shown in Fig. 2, the ratio of the integrated strength of the {200} plane on the Al alloy sheet surface, the {200} plane and the {400} plane are changed by changing the cold rolling reduction ratio and the annealing conditions and temperature after cold rolling. A 1.0 mm-thick Al alloy plate was produced with various ratios of the total integrated strength. Furthermore, the electrical conductivity and the crystal grain size were variously changed by changing the tempering conditions.
[0083]
Cold rolling conditions and annealing conditions after cold rolling, as well as the production of Al alloy plates other than the solution treatment temperature, except for the thickness of the hot rolled plate to change the rolling reduction of the following cold rolling, The test was performed under almost the same conditions. In other words, 400mm-thick ingots of each composition range shown in Table 1 are melted by DC casting method and then subjected to homogenization heat treatment at 540 ° C x 4 hours, and hot to a thickness of 2.3-8mmt at an end temperature of 300 ° C. Rolled. This hot-rolled sheet was further cold-rolled to a thickness of 1.0 mm and a reduction rate of 55 to 80%.
[0084]
  These cold rolled sheets were tempered under the same conditions as follows. 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). These conditions are shown in Table 2.. MaOnly Comparative Example 17 in Table 2 was subjected to solution treatment at 565 ° C. with the holding temperature of the air furnace being 570 ° C. However, other conditions were the same as above.
[0085]
A plurality of test plates (blanks) having a test width of 50 mm × length of 50 mm were cut out from these Al alloy plates, the ratio of the {200} plane integrated strength on the Al alloy plate surface, the {200} plane and {400 } The ratio of the total integrated intensity with the surface was measured by the X-ray diffraction measurement method described above. In addition, the tensile strength (σ_B), Yield strength (σ_0.2) And elongation (%) were measured. These results are shown in Table 2. Furthermore, considering the room temperature aging of the Al alloy plate, the conductivity (IACS%), crystal grain size, and grain size of each test plate after room temperature aging for 4 months (120 days) after the tempering treatment, The tensile strength (σ_B), Yield strength (σ_0.2) And elongation. These results are shown in Table 3.
[0086]
Furthermore, in order to investigate the low temperature aging treatment ability, the test plate after room temperature aging for 4 months after the tempering treatment was subjected to low temperature artificial aging treatment at 170 ° C. × 20 minutes with 2% strain applied in advance. Tensile strength of test plate (σ_B), Yield strength (σ_0.2) And measured the elongation. These results are also shown in Table 3.
[0087]
The tensile test was performed in accordance with JIS Z 2201, and the shape of the test piece was performed with a JIS No. 5 test piece so that the test piece longitudinal direction coincided with the rolling direction. Therefore, the tensile strength (σ_B), Yield strength (σ_0.2), Elongation was measured in the L direction parallel to the rolling direction. The crosshead speed was 5 mm / min, and the test piece was run at a constant speed until the test piece broke.
[0088]
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, flat hem processing test, plane strain overhang height (LDH₀) A test was conducted to evaluate the moldability. These results are shown in Table 3.
[0089]
The flat hem processing test was as follows. First, a 15% strain was applied to the blank (the test plate after aging at room temperature) by simulating the molding of the outer panel of an automobile. The flat hem processing allowance of the blank (distance from the end of the outer panel blank after hem processing to the end of the bent portion) is set to 12 mm, and the entire width direction of one longitudinal end is reduced. It was bent to an angle of 90 degrees by the flange process. At this time, the shoulder radius Rd of the die was set to 0.8 t (t is the plate thickness). Next, the edge of the blank was further bent inward to an angle of 135 ° by a prehem process.
[0090]
After that, by simulating the flat hem processing conditions, an aluminum alloy plate for an inner panel having a thickness of 1 mm was inserted into the bent portion of the blank (outer panel), and the flat hem processing was performed by bending the blank bent portion inward by 180 degrees. . In these flat hem processes, the longitudinal direction of the blank coincided with the rolling direction of the plate so that the cube orientation was parallel to the bending direction of the flat hem.
[0091]
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 and 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).
[0092]
Also, the plane strain overhang height (LDH₀) The test conditions were such that the test plate test piece after aging at room temperature with a width of 100 mm and a length of 180 mm was used so that the longitudinal direction of the test piece coincided with the direction perpendicular to the rolling direction. Then, using a punch (ball head, 100mmφ) and a die (with bead), it was performed 3 times under the conditions of wrinkle holding force 200kN, lubricating oil R-303, molding speed 20mm / min, and the lowest overhang height. LDH₀Value. This LDH₀A value of 30 mm or more was evaluated as ◯, a value of 25 mm or more and less than 30 mm was evaluated as Δ, and a value of less than 25 mm was evaluated as ×.
[0093]
For the evaluation of the orange peel, the surface of the molding material after the limit drawing ratio test was observed.
[0094]
Further, a post-coating corrosion resistance test piece was collected from the test plate after aging at room temperature, washed, and then subjected to zinc phosphate treatment and coating treatment under the same conditions. The zinc phosphate treatment was performed with a colloidal dispersion of titanium phosphate, and then immersed in a zinc phosphate bath containing fluorine at a low concentration of 50 ppm to form a zinc phosphate coating on the surface of the molding material. In the painting process, after the cationic electrodeposition coating, a coating was applied that was baked at 170 ° C. for 20 minutes, which is a widely used condition at present.
[0095]
Then, a yarn rust resistance evaluation test of these coating test pieces was performed. These evaluation results are also shown in Table 2. In the yarn rust resistance evaluation test, a piece of 7cm cross-cut was applied to the surface of the coating test piece, then immersed in a 1.7% hydrochloric acid solution at 35 ° C for 2 minutes, and then at a constant temperature and humidity of 40 ° C and 85% RH. Was allowed to stand for 1500 hours, and then the maximum length L of thread rust that occurred (the distance in the vertical direction from the crosscut, mm) was measured. The yarn rust having a maximum length of 2.0 mm or less was evaluated as ◯, 2.0 to 4.0 mm as △, and exceeding 4.0 mm as ×. These results are shown in Table 4.
[0096]
  As is clear from Tables 1 to 4, the ratio of the integrated strength of the {200} plane on the Al alloy sheet surface is in the range of 50 to 80% within the alloy composition range of the present invention, and the {200} plane and Invention Example 1 in which the ratio of the total integrated intensity with the {400} plane is in the range of 60% to 90%12Is excellent in flat hem processability. The results of this example show that sufficient processing can be performed even in flat hem processing under the above-mentioned severe conditions such as the complicated shape of the hem processing portion of the outer panel and the thinning of the inner panel.
[0097]
  In this example, the blank was bent so that its cube orientation was parallel to the bending direction of the flat hem (with its longitudinal direction parallel to the rolling direction of the plate).12Similarly, when flat bending is performed so that the cube orientation is perpendicular to the bending direction of the flat hem (the longitudinal direction is perpendicular to the rolling direction of the plate), good flat hem workability is also obtained. Obtained.
[0098]
On the other hand, even within the alloy composition range of the present invention, the ratio of the integral strength of the {200} plane and / or the ratio of the total integral strength of the {200} plane and the {400} plane shown in Table 3 As shown in Table 4, Comparative Examples 16 and 17 outside the scope of the invention have significantly lower flat heme workability under the above-mentioned severe conditions than the invention examples.
[0099]
Further, among the inventive examples, the ratio of the integrated intensity of the {200} plane and / or the ratio of the total integrated intensity of the {200} plane and the {400} plane shown in Table 3 is relatively low. As shown in Table 4, the flat heme workability is relatively low as compared with Invention Examples 1 and 2 having a relatively high integral intensity ratio. Therefore, the above results support the critical significance of the ratio of the integral intensity of the {200} plane and / or the ratio of the total integral intensity of the {200} plane and the {400} plane of the present invention.
[0100]
Further, the invention examples 6 and 9 in which the ratio of the integral intensity of the {200} plane and / or the ratio of the total integral intensity of the {200} plane and the {400} plane are relatively low are as shown in Table 2. The rolling reduction rate is relatively low. In addition, as shown in Table 2, the comparative example 16 in which the ratio of these integrated strengths falls off is also low, and the rolling reduction rate of cold rolling falls off low. Therefore, from the above results, the rolling reduction condition of the cold rolling for obtaining the ratio of the integrated strength of the {200} plane and / or the total integrated intensity of the {200} plane and the {400} plane of the present invention. The critical significance of is supported. In other words, in order to obtain an Al alloy sheet structure having a specific amount of crystal grains having a cube orientation as in the present invention, it is understood that it is necessary to add special conditions for cold rolling.
[0101]
In addition, as is apparent from Tables 1 to 4, the invention examples are LDH except for Invention Example 2 in which the ratio of the integrated strength is the highest in stretch forming.₀No orange peel is produced except for Invention Example 12, which has a high crystal grain size and is excellent in press formability. Furthermore, even with a low-temperature artificial age hardening treatment at 170 ° C. × 20 minutes, the minimum required AB yield strength for an outer panel of an automobile or the like is 170 MPa or more, and the rust resistance is excellent.
[0102]
However, among the inventive examples, as shown in Table 3, Invention Example 12 having a crystal grain size exceeding 50 μm and having a large crystal grain size has some orange peel in the stretch forming. Comparative Example 17 having a large crystal grain size exceeding 50 μm is an LDH₀Is low, and orange peel is also generated. Therefore, the preferable significance of the crystal grain size definition is understood.
[0104]
Further, Comparative Examples 6 and 7 in Table 1 in which Si to Mg are slightly out of the scope of the present invention are compared. Comparative Examples 14 and 15 using the alloy are the ratio of the integral strength of the {200} plane on the Al alloy plate surface, {200} The ratio of the total integrated strength of the plane and the {400} plane is within the range of the present invention, but the AB yield strength is less than 170 MPa in the low-temperature artificial age hardening treatment at 170 ° C. × 20 minutes.
[0105]
From the above results, the present invention, such as the integrated strength range of the present invention, the cold rolling ratio for obtaining these cube orientations, etc. for combining the various characteristics of the outer panel, such as flat hem workability and press workability, etc. Understand the critical significance of requirements.
[0106]
[Table 1]

[0107]
[Table 2]

[0108]
[Table 3]

[0109]
[Table 4]

[0110]
【The invention's effect】
  According to the present invention, an Al-Mg-Si Al alloy that has excellent bending workability such as flat hem processing, and has other required characteristics such as press formability, artificial age hardening at low temperature, and corrosion resistance.PlankA manufacturing method can be provided. Therefore, it has a great industrial value in that the Al alloy plate can be expanded to panel applications.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an edge curved portion of an outer panel in flat hem processing.
FIG. 2 is an explanatory view schematically showing a shape of a flat hem processing portion of an outer panel.
[Explanation of symbols]
1: Outer panel, 2: Inner panel, A: Bending part

Claims (1)

Al-Mg-Si system 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%, the balance being Al and inevitable impurities An aluminum alloy sheet is cold-rolled at a rolling reduction of 60% or more, annealed at a temperature of 350 ° C or less, tempered including solution treatment and quenching, and integrated with the {200} surface on the aluminum alloy sheet surface. Strength ratio is 50% or more, total integrated intensity ratio of {200} face and {400} face is 60% or more, conductivity is in the range of 43 to 47IACS%, and crystal grain size is 50μm or less The manufacturing method of the aluminum alloy plate excellent in bending workability characterized by these.

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