JP2003039124A - Hemming process of aluminum alloy panel stock and aluminum alloy panel stock - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hemming process of an aluminum alloy panel stock and an aluminum alloy panel stock for hemming process capable of simultaneously satisfying hemming workability and artificial aging hardenability under the cryogenic temperature. SOLUTION: A flat hemming process (figure C) characterized by the feature that the process bonds an aluminum alloy outer panel stock 1 having the wall thickness of 0.8 mm or more to an aluminum alloy inner panel stock 2 having the wall thickness of 1.0 mm or less, and when the flat hemming process is conducted in the condition that a clearance exists between the end portion of the inner panel stock 2 inserted into the hemming portion 16 of the outer panel stock 1 and the internal surface of the hemming portion, the outer panel stock 1 includes Si: 0.4-1.3%, Mg: 0.4-1.2%, and Si/Mg is 1 or more, Mn: 0.15% or less and regulates Cu: 0.1% or less, and proof stress is 110-140 MPa and the outer panel stock is a Si excessive type Al-Mg-Si system aluminum alloy and the outer panel stock after the flat hemming process is granted by 2% stretch and then, proof stress after the artificial aging treatment of 150 deg.C×20 minutes is made 170 MPa or more.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for hemming an aluminum alloy panel material and an aluminum alloy panel material for hemming (hereinafter, aluminum is simply referred to as Al).

[0002]

2. Description of the Related Art Conventionally, it has been excellent in moldability (hereinafter simply referred to as "formability") for transportation vehicles such as automobiles, ships or vehicles, home electric appliances, construction and structural members.
5000-series (satisfying the standard) of Al-Mg-based AA to JIS or Al-Mg-Si-based AA to JIS 6000-series with excellent moldability and bake hardenability (hereinafter referred to simply as 5000-series) To 6000 series) Al alloy materials (collectively referred to as rolled aluminum alloy materials such as rolled panel materials, extruded shape materials and forged materials).

In recent years, in response to global environmental problems caused by exhaust gas and the like, improvement in fuel consumption has been pursued by reducing the weight of vehicle bodies of transportation machines such as automobiles. For this reason, in particular, the application of lighter Al alloy materials to the body of automobiles is increasing in place of the steel materials that have been conventionally used.

Among these Al alloy materials, automobile hoods,
For panel materials such as outer panels (outer plates) and inner panels (inner plates) of panel structures such as fenders, doors, roofs, and trunk lids, the thin and high-strength Al alloy panel materials conform to JIS or AA standards. Specified (satisfies JIS or AA standards), excess Si type 6000 series Al alloy panel (plate)
The use of wood is being considered.

This excess Si type 6000 series Al alloy is basically an Al-Mg-Si series aluminum alloy which essentially contains Si and Mg and has Si / Mg of 1 or more. And, since this excess Si type 6000 series Al alloy has a particularly excellent age hardening ability, it secures the formability by low yield strength during press forming and bending, and at the same time, it can be used for baking coating treatment after forming. There is an advantage that the required strength can be ensured by age hardening and increasing yield strength by heating during artificial aging treatment.

Further, these excess Si type 6000 series Al alloy materials are
Compared to other 5000 series Al alloys, which have a large amount of alloys such as Mg, the amount of alloying elements is relatively small. Because of this, these 60
When the scrap of 00 series Al alloy material is reused as the Al alloy melting material (melting raw material), the original 6000 series Al alloy ingot is easily obtained and the recyclability is excellent.

In the outer panel of the automobile panel structure, after the forming process such as pressing in the drawing process or trimming process, the edge of the outer panel is bent (folded 180 degrees) and joined to the edge of the inner panel after the forming process. A hemming process (a folding process, hereinafter referred to as a hemming process) is performed.

An outline of this hemming process is shown in FIGS. 2 (a) to 2 (d). As can be seen from the figure, the hemming process is described in detail below, through the down-flange step of FIG. 2 (a), the pre-hem step of FIG. 2 (b), and the flat hem step of FIG. 2 (c) or FIG. This is basically done by selecting the rope hem process of d).

First, in the down-flange process of FIG. 2 (a), the edge 1a of the outer panel 1 after molding, which is fixed by the die 3a and the plate retainer 5a, is made up to an angle close to a right angle (90 °) by the punch 4a. Fold.

Next, in the prehem step of FIG. 2 (b), the outer panel 1 after the down-flange step is similarly fixed by the die 3b and the plate retainer 5b, and the edge 1b of the outer panel 1 is further reduced by the punch 4b. Bend inwards to 135 °.

In addition, the flat hem process of FIG. 2 (c) and FIG. 2 (d)
In the rope hem process, the edge of the inner panel 2 after the forming process such as the drawing process and the trim process is accommodated (inserted) in the bent portion of the outer panel 1 after the prehem process. Then, the outer panel 1 and the inner panel 2 are fixed by a plate retainer (not shown) and dies 3c, 3d, and the edges 1c, 1d of the outer panel 1 are further fixed by the punches 4c, 4d.
Form a flat hem that folds inward to an angle of °.
In this way, the edge of the inner panel 2 and the outer panel
The flat hem of 1 (folded by 180 degrees) comes into contact, and both ends are joined and adhered.

Of these, the rope hem process of FIG.
Compared with the flat hem process of (c), the shape of the hem curving part (folding part) has a rope-like shape that bulges in an arc shape, and the appearance is not a sharp or flat hem shape. The sex is not good either. In addition, there is a problem that the contact area between the outer panel and the inner panel is small and the bondability and adhesion are poor.

For this reason, particularly in the case of automobile parts and the like where appearance and aesthetics are important, the final step of hem processing is usually performed by the flat hem step of FIG. 2 (c), which is a severe bending step. There is.

In this case, the Al alloy panel material for the outer panel and the inner panel has become thinner and thinner in recent years to a plate thickness of 1.2 mm or less in order to reduce the weight of the panel material. For example, aluminum alloy panel materials for outer panels have a thickness of 0.8 mm or more, and a thickness of 0.9 to 1.2 mm is the mainstream. Al alloy panel material for inner panel is 1.0mm or less, 0.8-1.0mm
The plate thickness of is the mainstream.

However, in these thinned Al alloy panel materials, the thinner the thickness of the inner panel material to be inserted into the curved edge portion of the outer panel material, the more severe the bending condition becomes, and the flat hem processing becomes difficult. .

Therefore, in the flat hem processing of the thinned Al alloy panel material, the edge bend A of the flat hem to be formed has a rough surface X, as shown in order of order in FIG.
Defects such as minute cracks Y 1 and relatively large cracks Z 3 are likely to occur, and it is often impossible to apply them to parts.

Further, in flat hem processing, FIG.
As shown in Fig. 2 (also shown in Fig. 2 (C)), between the end portion 2a of the inner panel material 2 to be inserted into the curved edge portion A of the outer panel material 1 and the inner surface Aa of the curved edge portion A, It is inevitably processed with a slight gap t. If there is this gap t or if this gap t becomes large, the thickness of the edge curved portion A (bent portion) of the outer panel material 1 becomes thin, and the bending conditions become strict, so defects such as cracks Z are likely to occur. This tendency becomes remarkable in the thinned Al alloy panel material described above.

On the other hand, conventionally, on the flat hem processing step side or the material side of the Al alloy plate, the hem portion (curved edge portion,
Various techniques for preventing the occurrence of defects in the bent portion) have been proposed.

For example, in Japanese Patent Publication No. 63-2690,
In flat hem processing of a high-strength Al alloy plate of about 186 MPa, the bending radius of the flange corner formed on the outer panel material in the down-flange process of Fig. 2 (a).
Increase Rd (shoulder radius of die), more specifically, Al
It is disclosed that the bending radius Rd is set to 0.8t to 1.8t (where t is the plate thickness of the Al alloy plate) in relation to the plate thickness of the alloy plate to prevent the occurrence of the defects.

[0020]

However, in the publication,
In flat hem processing, the inner panel material inserted into the curved edge of the outer panel material is relatively thick, about 1.2 mm,
The bending conditions are not severe, and flat hem processing is relatively easy. On the other hand, when a flat hem is processed using a relatively thin inner panel material of about 0.8 to 1.0 mm, even if the bending radius Rd and the like are increased, cracks occur at the edge bend of the flat hem. This is also due to the existence of a gap between the end portion of the inner panel material inserted into the curved edge portion of the outer panel material and the inner surface of the curved edge portion as described above.

For this reason, there are not many practical techniques for improving the flat hem processability of the thin Al alloy panel material described above on the side of the flat hem process. Therefore, on the material side, the proof stress of the 6000 series Al alloy panel material itself has been lowered to improve the flat hem workability.

However, if the proof stress of the 6000 series Al alloy panel material is lowered too much, the proof stress of the Al alloy panel material after the paint baking treatment (artificial age hardening treatment) is inevitably low.

In particular, in recent years, the temperature of the coating and baking treatment of the Al alloy panel material tends to be reduced to a lower temperature and a shorter time due to the demand for energy saving and the improvement of the coating material. Also, from the treatment of 170 ℃ × 20 minutes,
There is a tendency for the temperature to decrease further under conditions such as low temperature short-time treatment conditions of 150 ° C x 20 minutes.

Therefore, when the yield strength of the 6000 series Al alloy panel material is lowered in order to improve the hemming workability under such a low temperature and short time coating baking treatment condition, this type of panel structure application The strength of 170MPa or more required for is not obtained.

As described above, the hem workability and the artificial age hardening ability at low temperature of the thinned 6000 series Al alloy panel material are the same as the conventional problems such as high moldability and high strength. ,
These are technical issues that contradict each other, and it is difficult to make them compatible. For this reason, even with the technology of controlling crystallized substances and precipitates of 6000 series Al alloy panel materials that have been conventionally proposed, and the technology of adding a large amount of Cu etc.
Achieving both the heme processability of an Al alloy panel material and the artificial age hardening ability at low temperature is a very difficult technical issue.

The present invention has been made in view of such circumstances, and an object thereof is a method for hemming an Al alloy panel material which simultaneously satisfies heme machinability and artificial age hardening ability at low temperature. Another object of the present invention is to provide an Al alloy panel material for hemming.

[0027]

To achieve this object, a method for hemming an aluminum alloy panel material of the present invention is provided.
The gist of (Claim 1) is a flat hem processing method for joining an aluminum alloy outer panel material having a plate thickness of 0.8 mm or more to an aluminum alloy inner panel material having a plate thickness of 1.0 mm or less. When performing flat hem processing in a state where there is a gap between the inner panel material end portion to be inserted into the edge bending portion and the inner surface of the edge bending portion, the outer panel material, Si: 0.4 ~ 1.3%, Mg: 0.4 ~ 1.2%, and Si / Mg is 1 or more, Mn: 0.15% or less, Cu: 0.1
2% stretch of the outer panel material after Si-excessive Al-Mg-Si based aluminum alloy with a proof stress of 110% to 140 MPa.
The proof stress after artificial aging treatment at 150 ° C for 20 minutes is 170 MPa or more.

The gist of the aluminum alloy panel material for hemming of the present invention (claim 4) is the Al-Mg-Si system for an outer panel material which is flat hemmed by the method according to any one of claims 1 to 3. Aluminum alloy panel material.

The Al alloy panel material referred to in the present invention is
Hot-rolled sheet material, cold-rolled sheet material, and a sheet material that has been subjected to a tempering treatment (heat treatment) described later, and collectively includes a sheet material for forming.

The present inventors have found that the inner panel material is 1.0 m
Flat hem processing of 6000 series Al alloy panel material thinned to m or less and with a gap between the end of the inner panel material inserted into the edge bend of the outer panel material and the inner surface of the edge bend About 170 hem
Not only under the condition of ℃ × 20 minutes, but also under the condition of artificial aging treatment (paint baking treatment) at 150 ℃ × 20 minutes at low temperature for a short time.
The material conditions for obtaining a strength of 170 MPa or more were examined again.

As a result, if the outer panel material to be flat-hem processed is a Si-excessive Al-Mg-Si-based aluminum alloy having a yield strength in the range of 110 to 140 MPa and a specific component composition range, the inner panel is particularly preferable. The panel material is a 6000 series Al alloy panel material that is thinned to 1.0 mm or less, and there is a gap between the inner panel material end part that is inserted into the edge curved part of the outer panel material and the inner surface of the edge curved part. It was found that even in flat hem processing in a state, it has an effect of improving the hem processing property and simultaneously satisfying the artificial age hardening ability at low temperature.

This effect is particularly great when the 90 ° bending radius of the aluminum alloy panel material in the down-flanging process prior to the flat hem process is in the range of 0.5 to 2.0 as described in claim 2.

Further, since the present invention has such an effect, as described in claim 3, the 6000 series Al alloy plate material is press-formed in advance before the flat hem processing, and strain is introduced to the hem processing. It is suitable to be applied to a hemming method especially for automobile outer panels.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. First, the flat hem processing method according to the present invention is basically the same as the conventional hem processing including the flat hem step described in FIGS. 2 (a) to (c), and the steps and conditions of each step are basically the same. Is.

However, as described above, the object of the flat hem processing in the present invention is that the thickness of the Al alloy outer panel material is 0.8 mm or more and the thickness of the Al alloy inner panel material is 1.0 mm.
The following shall apply. When the plate thickness of the Al alloy outer panel material is thinner than this and the plate thickness of the Al alloy inner panel material is thicker than this, heme workability and artificial age hardening ability at low temperature are simultaneously achieved without using the present invention. It's relatively easy.

The flat hem processing according to the present invention is performed using Al
Whether it is performed on all four sides of the alloy panel material or only on selected sides (side edges) is appropriately selected according to the design of the member.

(Down-Flange Process) First, in the down-flange process of FIG. 2 (a) in the hem processing, the Al alloy outer panel material 1 after the forming process such as the drawing process and the trim process is used as a die 3a as necessary. The plate holder 5a is fixed, and the edge 1a of the outer panel material 1 is bent by the punch 4a to an angle close to a right angle.

At this time, the 90 ° bending radius of the outer panel material 1 is preferably in the range of 0.5 to 2.0. The 90 ° bending radius of the outer panel material 1 is the shoulder radius Rd of the die 3a in Fig. 2 (a).
And the shoulder radius Rp of the punch 4a is adjusted.

When the 90 ° bending radius of the outer panel material is less than 0.5, the inner panel material is a 6000 series Al alloy panel material thinned to 1.0 mm or less, and is inserted into the edge bending portion of the outer panel material. In flat hem processing in the state where there is a gap between the inner panel material end part and the inner surface of the curved edge part, in the flat hem processing step in the flat hem processing step in spite of the proof stress specification of the outer panel material in the present invention, The indicated defects such as cracks are likely to occur.

On the other hand, the 90 ° bending radius of the outer panel material is 2.
When it exceeds 0, the rope hem becomes closer to that shown in FIG. 2 (d), and there is a high possibility that the appearance and aesthetics of the curved edge of the hem will be impaired. In addition, the outer shape line or outer shape line of the original design of the curved edge of the flat hem is shorter than the outer shape line after actual processing, or conversely it is too long, resulting in shape accuracy and dimensional accuracy. The chances of not having one increase.

Next, in the prehem step of FIG. 2 (b), the outer panel material 1 after the down flange step is similarly processed by the die 3b.
And the plate retainer 5b to secure it to the edge 1b of the outer panel material 1.
Is bent inward by a punch 4b to an angle of about 135 °.

Further, in the flat hem process of FIG. 2 (c), the edge of the inner panel 2 after the forming process such as the drawing process and the trim process is inserted into the edge bending portion A of the outer panel material 1 after the prehem process.

At this time, as described above, the gap t formed between the inner panel material end portion 2a and the edge bending portion inner surface Aa shown in FIG. 3 is set so as to reduce the thickness of the edge bending portion A of the outer panel material 1. Since the bending conditions are strict, defects such as cracks Z are likely to occur. Therefore, it is preferable that the gap t is as small as possible in terms of workability in flat hem. However, completely eliminating this gap t is difficult and complicated in terms of hemming. Therefore, in the present invention, a certain amount of the clearance t is allowed within a range that does not cause a defect such as a crack Z of the edge curved portion A 1.

The allowable limit of the gap t in the present invention is the gap
The ratio (t / l) between t and the flange length (circumferential length of the hem edge portion A) l (t / l) shown in Fig. 3 is generally 0.6 or less, although it varies depending on the processing conditions. However, in the conventional hemming, this t / l was about 0.3, which was the allowable limit. That is, in the present invention, by improving the flat hem processability,
It is possible to increase the allowable limit of this gap t which makes the bending condition strict, and this is also one of the effects of the present invention.

Then, the outer panel material 1 and the inner panel 2 are fixed by a plate retainer (not shown) and a die 3c, and the edge 1c of the outer panel 1 is further bent inward by a punch 4c to an angle of 180 degrees. Form a flat hem. In this way, the edge of the inner panel 2 and the flat hem portion (edge curving portion) of the outer panel 1 come into contact with each other, and the two end portions are joined together and brought into close contact with each other.

Therefore, the present invention also has an advantage that the above two effects can be achieved without largely changing the conventional hemming process and conditions.

(Al Alloy Panel Material) Next, according to the present invention, Al
The alloy panel material will be described in detail.

(Proof Strength) First, the yield strength of the Al alloy outer panel material is set in the range of 110 to 140 MPa. FIG. 1 shows the relationship between the proof stress (varied variously) and the hemmability of the AA 6016 Al alloy (composition of the present invention) in the examples described later. In Figure 1, the white circles indicate the inner panel material thickness of 1.0 mm, and the black circles indicate the inner panel material thickness of 0.8 mm. The hemming conditions in Fig. 1 are that the inner panel thickness is 0.8 to 1.0 mm.
The gap t between the end of the inner panel material and the inner surface of the beveled portion is as large as 0.5 at the ratio t / l with the flange length l, and the stricter flatness of the 90 ° bend radius of the down flange process is 0.5. It was hem processed.

As can be seen from FIG. 1, when the yield strength exceeds 140 MPa, the inner panel material is a 6000 series Al alloy panel material thinned to 1.0 mm or less, and under the severe flat hem processing conditions, The thinner the inner panel material is (when the inner panel material thickness is 0.8 mm rather than 1.0 mm), the hem workability deteriorates, and defects such as cracks occur in the edge bent portion of the outer panel material. Therefore, under the severe flat hem processing conditions described above, the excess Si type 6000 series targeted by the present invention is used.
It can be seen that in the Al alloy panel material, there is a criticality in the flat hem workability near a proof stress of 140 MPa.

On the other hand, the yield strength of the Al alloy outer panel material is 110.
If it is less than MPa, the desired low temperature age hardening ability cannot be obtained,
The yield strength during low temperature aging treatment at 150 ℃ × 20 minutes after applying 2% stretch does not exceed 170 MPa, and the strength required as a panel structure cannot be satisfied.

(Plate Thickness) In the present invention, as described above, the plate thickness of the Al alloy outer panel material is equal to the plate thickness of the Al alloy panel material.
The target thickness is 0.8 mm or more and the thickness of the Al alloy inner panel material is 1.0 mm or less. In the case where the plate thickness of the Al alloy outer panel material is thinner than this and the plate thickness of the Al alloy inner panel material is thicker than this, the effect of the plate thickness improves the hem processability, and the problems of the present invention (hem processability and low temperature Achieving the artificial age hardening ability at the same time) is unnecessary.

Also, from the viewpoint of reducing the weight of the panel material or the panel structure, the plate thickness of the Al alloy inner panel material is preferably 1.0 mm or less. In terms of flat hem workability, the thicker the Al alloy inner panel material is,
The thinner the alloy outer panel material, the better the hem processability. However, if the plate thickness of the Al alloy inner panel material is increased, the significance of the adoption of the Al alloy panel material itself for reducing the weight of the panel material or the panel structure is impaired.

(Al Alloy Composition) Next, the chemical composition of the outer panel material of the present invention will be described. The outer panel Al alloy material of the present invention is an excess Si type 6000 series Al alloy material, particularly as a panel structure of a transportation machine such as an automobile, etc., with a yield strength of 110 to 140 MPa, the above-mentioned heme workability and low temperature age hardening. It is necessary to combine (satisfy) the required properties such as press formability, corrosion resistance, and weldability. Therefore, the content of each element such as Si and Mg in the Al alloy panel material of the present invention is specified or included in the standards of AA to JIS, and within the range, it is specified in a preferable range from the viewpoint of exhibiting the above characteristics. less than,
The preferable range and meaning of each element will be described.

Among the alloying elements, other alloying elements such as Cr, Zr, Ti, B, Fe, Zn, Ni and V other than Si, Mg, Cu and Mn are basically impurity elements. Is. However, from the viewpoint of recycling the 6000 series alloy, as a melting material,
Not only high-purity Al ingots, but also 6000 series alloys and other Al
Includes cases where alloy scrap materials, low-purity Al ingots, etc. are used as melting materials. In such a case, these other alloy elements are inevitably included. Therefore, in the present invention, these other alloying elements are allowed to be contained within the JIS or AA standards within a range that does not impair the desired effects of improving the various properties.

Mg: 0.4-1.2%. Mg is a solid solution strengthener and forms a compound phase such as Mg / Si cluster with Si during artificial aging treatment such as paint baking treatment and exerts age hardening ability.As a panel material or panel structure, Mg is 170 MPa or more. Is an essential element for obtaining the required strength of.

When the content of Mg is less than 0.4% (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. Therefore, the required strength of 170 MPa or more cannot be obtained as the panel material or the panel structure.

On the other hand, when the content of Mg exceeds 1.2%, the formability such as press formability and bending workability (hem workability) is significantly impaired. Therefore, the content of Mg is 0.4-1.
It is preferable that the amount is within the range of 2% and the Si / Mg is 1.0 or more.

Si: 0.4 to 1.3%. Si, together with Mg, forms a compound phase such as Mg / Si clusters together with Si during solid solution strengthening and artificial aging treatment such as paint baking treatment, and exerts age hardening ability.As a panel material or panel structure, It is an essential element for obtaining the required strength of 170 MPa or more. Therefore, the present invention excess Si type 60
It is the most important element in the 00-series Al alloy material, in order to combine various characteristics such as press formability, hemmability, corrosion resistance, and weldability required for each application.

Further, in order to exert an excellent low temperature age hardening ability of 170 MPa or more at a low temperature aging treatment of 150 ° C. × 20 minutes after applying 2% stretch, Si / Mg is set to 1.0 or more and Si is set to 1.0 or more. The composition is an excess Si type 6000 series Al alloy composition that is contained in excess of Mg.

When the Si content is less than 0.4%, the age hardening ability and further various characteristics required for each application, such as press formability, hemmability, corrosion resistance and weldability, cannot be combined.

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 0.4-1.3%
The range is preferably

In the outer panel material, since heme workability is particularly important, the Si content is preferably in the lower range of 0.4 to 1.1%.

Cu: 0.1% or less Cu usually has an effect of promoting a compound phase such as Mg / Si clusters in the crystal grains of the Al alloy material structure during the artificial aging treatment such as a paint baking treatment and a solid content. The molten Cu has the effect of improving formability. However, in particular, the inner panel material is a 6000 series Al alloy panel material thinned to 1.0 mm or less, and moreover, between the inner panel material end portion inserted into the edge bent portion of the outer panel material and the inner surface of the edge bent portion. In the flat hem processing in the state where there is a gap, when Cu exceeds 0.1%, the hem workability is deteriorated and defects such as cracks occur in the edge curving portion of the outer panel material. Further, the inclusion of Cu significantly deteriorates the stress corrosion cracking resistance, the thread rust resistance of the corrosion resistance after coating, and the weldability. For this reason, the amount should be as small as 0.1% or less as much as possible, particularly in the case of panel material applications such as automobile outer panels.

Mn: 0.15% or less, Mn produces dispersed particles (dispersed phase) during homogenization heat treatment, and these dispersed particles prevent grain boundary migration after recrystallization,
It has the effect of refining the crystal grains of the Al alloy structure. However, when the content exceeds 0.15%, the inner panel material is 1.0 m
6000 series Al alloy panel material thinned to m or less,
Moreover, the flat hem processing in a state where there is a gap between the inner panel material end portion inserted into the edging portion of the outer panel material and the inner surface of the edging portion reduces the hem processability, resulting in a hem bending portion of the outer panel material. Defects such as cracks occur. Therefore, Mn
Content is regulated to 0.15% or less.

Cr, Zr. Similar to Mn, these transition elements of Cr and Zr have an effect that dispersed particles (dispersed phase) are generated during homogenization heat treatment, and fine crystal grains can be obtained. However, Cr and Zr are also 6000 series Al alloy panel materials in which the inner panel material is thinned to 1.0 mm or less when the content exceeds 0.15%, and moreover, the inner panel inserted into the edge portion of the outer panel material. In the flat hem processing in the state where there is a gap between the material end portion and the inner surface of the edge curved portion, the hem machinability deteriorates, and defects such as cracks occur in the edge curved portion of the outer panel material. Therefore, the Cr and Zr contents are also preferably regulated to 0.15% or less.

Ti, B. If Ti and B are contained in amounts exceeding Ti: 0.1% and B: 300 ppm, respectively, coarse crystallized substances are formed and formability is deteriorated. However, if Ti and B are contained in a small amount, they also have the effect of refining the crystal grains of the ingot and improving the press formability. Therefore, Ti: 0.1% or less and B: 300ppm or less are allowed.

Fe. Fe contained as an impurity by mixing from the melting material is Al₇C
u₂Fe, Al₁₂(Fe, Mn)₃Cu ₂, (Fe, Mn) Al₆Crystallized products such as
To achieve. These crystallized substances have an improved fracture toughness and fatigue properties.
In addition, it significantly deteriorates moldability such as hemmability. Special
In addition, when the Fe content exceeds 0.50%, these characteristics become remarkable.
Therefore, the Fe content (allowable amount) is preferably
It is preferable to use as little as possible, 0.50% or less
Yes.

Zn. If Zn is contained in excess of 0.1%, the corrosion resistance is significantly reduced. Therefore, the content of Zn is preferably set to 0.1% or less, which is as small as possible.

The material of the inner panel material of the present invention may be the same as or different from that of the outer panel material. Use the same material for the outer panel material and the inner panel material.
As the Al alloy material, the same excess Si type 6000 series Al alloy material as the outer panel material is preferable from the viewpoint of uni-alloying for convenience of procurement and recycling. However, it is not necessary for an inner panel material such as a panel structure of a transportation machine such as an automobile to have the strict required characteristics as the outer panel material other than the press formability. Therefore, even if it is not the same as the outer panel material, 3000 of AA or JIS
, Al-Mg series 5000 series, 6000 series, and other Al alloy materials with excellent press formability can be appropriately used.

(Manufacturing Method) The excess Si type 6000 Al alloy outer panel material and inner panel material of the present invention having the above composition can be manufactured by a conventional method. However, as described above, the outer panel material is required to have various required characteristics, and therefore, there are preferable manufacturing conditions even in each step according to the ordinary method, and this point will be described below.

In the melting and casting process, an excessive molten Al alloy melt, which has been melt-adjusted within the composition standard range of the present invention, may be subjected to a normal melt casting method such as a continuous casting rolling method or a semi-continuous casting method (DC casting method). Select and cast.

Then, after subjecting this Al alloy ingot to homogenization heat treatment, hot rolling-cold rolling (if necessary, hot rolling-cold rolling, or cold rolling, intermediate of batch type or continuous type) (Although annealing etc. is also performed), and processed into a panel material shape such as a coil shape or a plate shape.

The Al alloy material after working is first subjected to solution treatment and quenching treatment (T4 treatment) as a refining treatment.
Solution treatment and quenching are important steps for precipitating the compound phases such as Mg / Si clusters and β "phase in the grains sufficiently by the artificial aging treatment such as paint baking and hardening treatment to be performed later. Solution treatment conditions for
It is preferably carried out in the temperature range of 550 ° C.

However, in the case of a panel material for which hemmability is particularly important, the solution treatment condition is preferably at a lower temperature side of 500 to 530 ° C.

During quenching after the solution treatment, the cooling rate is 30
It is preferable to perform rapid cooling at 0 ° C./minute or more. Cooling rate
If it is slower than 300 ° C / min, the strength after quenching will be low, and the age hardening ability will be insufficient, and it will not be possible to secure a high yield strength of 170 MPa or more due to artificial aging treatment such as paint bake hardening treatment later.

In addition, at the time of quenching after solution heat treatment, S
i, MgSi, etc. are likely to be deposited, which easily becomes the starting point of cracks during press molding and hemming, and these moldability are deteriorated. In order to secure this cooling rate, the quenching treatment may be air cooling using a fan or the like, but it is preferable to perform it by selecting from water cooling means such as mist, spraying, dipping and the like.

After the solution hardening treatment, it is preferable to carry out a pre-aging treatment in order to suppress the formation of Si-pores and Si / pore clusters themselves, which cause aging suppression at room temperature. That is, it is preferable to maintain the temperature range of 50 to 100 ° C. for the required time of 1 to 24 hours. The cooling rate after the preliminary aging treatment is preferably 1 ° C./hr or less.

As the preliminary aging treatment, the quenching completion temperature after the solution treatment is increased to 50 to 100 ° C., and then immediately reheated or kept as it is. Alternatively, after the solution treatment, quenching treatment up to room temperature and immediately reheating to 50 to 100 ° C. are performed.

In the case of continuous solution hardening treatment,
The quenching process is completed within the temperature range of the preliminary aging, and the coil is wound around the coil at the high temperature as it is. Note that the coil may be reheated before being wound on the coil, or may be kept warm after being wound. Further, after the quenching treatment up to room temperature, it may be reheated to the above temperature range and wound at a high temperature.

[0080]

EXAMPLES Next, examples of the present invention will be described. (Example 1) First, excess Si type 6000 series Al for outer panel material
As an alloy, an Al alloy plate of AA 6016 Al alloy standard composition, changing the solution treatment conditions, and selectively performing the pre-aging treatment, and a proof stress within the range of the present invention of 110 to 140 MPa, from this range I made it differently from the one that came off. This AA 6
016 Al alloy compositions are shown in Nos. 1 and 2 of Table 1. For comparison, excess Si type or excess Mg of alloy composition outside the scope of the present invention is used.
A type 6000 series Al alloy plate was also prepared. The compositions of these Al alloys are also shown in Nos. 3, 4, and 5 of Table 1. In addition, Al of the invention examples and comparative examples
Table 2 shows the plate thickness of the alloy plate and the yield strength after heat treatment.

The Al alloy plate was prepared under the following conditions. A 50 mm ingot of an Al alloy is melted by a DC casting method, homogenized and heat-treated at 550 ° C for 4 hours, and a thickness of 5 mm at a temperature of 480 ° C or less.
Hot rolled up to. This hot-rolled sheet was heated at a heating rate of 40 ° C / h
Annealing treatment was carried out at r of 500 ° C for 30 seconds, and then cold rolling was performed to a thickness of 0.8 and 1.0 mm. This cold-rolled sheet was further treated in a heat treatment furnace by changing the solution treatment conditions in the range of 500 to 550 ° C., and then immediately subjected to T4 tempering treatment in which quenching was performed by water cooling or air cooling.

The cooling rate during the quenching is 50 to 600 ° C. /
The temperature was adjusted within the range of minutes, the quenching end temperature (quenching temperature) was set to 80 ° C. in common, and pre-aging (cooling rate after holding 1 ° C./hr or less) was performed by holding at this temperature for 2 hours after quenching.

A plurality of strip-shaped test plates (blanks) for hem processing test were cut out from these Al alloy plates, and the blanks were first subjected to drawing and trimming steps of the outer panel of the automobile door prior to hem processing. Simulate the molding process,
Pre-strained with 5%. Then, the flat hem processing allowance of the blank (the distance from the end portion of the outer panel blank after the hem processing that was folded inward to the end portion of the folded portion) was set to 12 mm, and the following hem processing was performed.

First, the edges of the blank (outer panel) which had been pre-strained by the down-flange step shown in FIG. 2 (a) were bent to an angle of 90 degrees. At this time, the 90 ° bending radius of the Al alloy panel material was changed to 0.5 to 1.0. The 90 ° bending radius was adjusted with the shoulder radius Rd of the die 3a. Table 2 shows the 90 ° bend radii of these Al alloy panel materials.

Next, the edges of the blank were further bent inward by an angle of 135 ° by the prehem process shown in FIG. 2 (b).

Then, similarly, the aluminum alloy plate was cut out to obtain a blank as an inner panel (the same panel material as the outer panel material AA 6016 Al alloy, plate thickness 0.8 to 1.0 mm).
The edge of the blank (outer panel) is inserted into the bent portion of the blank (outer panel) to form a gap t between the end of the inner panel material and the inner surface of the bent portion, and by the flat hem process shown in FIG. 2 (c). It has a flat hem. Table 2 shows the plate thickness of the inner panels and the gap t. However, the gap t is shown by the ratio t / l with the flange length l.

Then, the surface condition of the edge bend of the flat hem such as rough skin, minute cracks and large cracks was visually observed. The evaluation is 1; good with no rough skin or fine cracks, 2; no rough cracks, including small ones, 3; fine cracks, 4; large cracks, 5 ; Evaluated in 5 levels, from multiple to multiple large cracks. Good hem processability for this evaluation (usable)
It is judged to be 1 to 2 stages, and heme processability is inferior (unusable) for 3 or more stages.

Further, the Al alloy sheet after production was subjected to artificial age hardening treatment at a low temperature for a short time of 150 ° C. × 20 minutes after applying 2% stretch, and the proof stress (BH proof stress, bake hard proof stress) was measured and the low temperature was measured. The aging capacity was investigated. The results are shown in Table 2 together with the flat hem processability.

As is clear from Table 2, the outer panel material within the proof stress range of the present invention of 110 to 140 MPa and within the excessive Si type 6000 series Al alloy composition range of the present invention (Al alloys No. 1 and 2 in Table 1)
The invention panel Nos. 1 to 6 in which the inner panel thickness is 0.8 mm
It is thin and has a large gap t between the end of the inner panel material and the inner surface of the edge bend, and has excellent hemmability even in the severe hemming with a 90 ° bend radius of 0.5 in the down flange process. Moreover, it can be seen that the BH yield strength after the artificial age hardening treatment at a low temperature of 150 ° C. × 20 minutes for a short time is 170 MPa or more.

However, even with the outer panel materials within the composition range of the excess Si type 6000 Al alloy of the present invention (Al alloys of No. 1 and No. 2 in Table 1), the yield strength is higher than the upper limit of the present invention of 140 MPa and a high comparison is made. Example 7 has a small inner panel thickness of 0.8 mm, a large gap t between the inner panel material edge and the inner surface of the edge bend, and cracks in the severe hemming at 90 ° bend radius of 0.5 in the down flange process. Is occurring. Also, the proof stress is especially 152M
In Comparative Example 8 having a higher Pa, the inner panel plate thickness is as thick as 1.0 mm, the gap t generated between the inner panel material end portion and the edge bending portion inner surface is small, and the 90 ° bending radius of the down flange process is 1.0. Even if the hemming condition is relaxed by increasing the size, cracks occur.

Further, even in the case of the outer panel material within the composition range of the excess Si type 6000 Al alloy of the present invention (Al alloys of No. 1 and No. 2 in Table 1), the yield strength is lower than the lower limit of the present invention of 110 MPa. ,
No. 10 is 150 ℃, although no cracks are generated by hemming
BH proof stress after artificial age hardening treatment at low temperature for a short time of 20 minutes does not satisfy 170 MPa.

Even if the yield strength is within the range of the present invention, it is out of the range of the excess Si type 6000 series Al alloy composition of the present invention (see Table 1).
No.3, 4, 5 Al alloy) Comparative example using outer panel material
Nos. 11, 12, and 13 have a large inner panel thickness of 1.0 mm, a small gap t between the inner panel material edge and the inner surface of the edge bending portion, and a 90 ° bending radius of the down flange process of 1.0
Even if the hemming conditions are relaxed, the cracks are generated.

From the above results, the critical significance of the present invention in the excess Si type 6000 series Al alloy composition of the present invention, the flat heme workability of the yield strength and the low temperature aging treatment ability are understood.

[0094]

[Table 1]

[0095]

[Table 2]

[0096]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a heme processing method for an Al alloy panel material and an Al alloy panel material for heme processing which simultaneously satisfy the heme processability and the artificial age hardening ability at low temperature. . Therefore, it has a great industrial value in that the application of the Al alloy material to transportation machines such as automobiles can be expanded.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the relationship between heme workability and yield strength in down-flange processing of an Al alloy panel material according to the present invention.

FIG. 2 is an explanatory view showing an outline of hemming, (a) is a down-flange process, (b) is a prehem process, (c) is a flat hem process, and (d) is a rope hem process.

FIG. 3 is a perspective view showing a curved edge portion of an outer panel material in flat hem processing.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C22F 1/05 C22F 1/05 // C22F 1/00 602 1/00 602 623 623 630 630A 630K 691 691B 691C 694 694A

Claims (4)

[Claims] 1. A flat hem processing method for joining an aluminum alloy outer panel material having a plate thickness of 0.8 mm or more to an aluminum alloy inner panel material having a plate thickness of 1.0 mm or less, wherein the edge bending portion of the outer panel material is used. When performing flat hem processing in a state where there is a gap between the inner panel material end portion to be inserted and the inner surface of the edge bending portion, the outer panel material, Si: 0.4 ~ 1.3%, Mg: 0.4 ~ 1.2% In addition, Si / Mg is 1 or more, Mn: 0.15% or less, Cu: 0.1% or less, the proof stress range of 110-140MPa
Al-Mg-Si aluminum alloy, and after applying 2% stretch of the outer panel material after the flat hem processing, 150 ° C
A method for hemming an aluminum alloy panel material, which has a yield strength of 170 MPa or more after artificial aging for 20 minutes. 2. The aluminum alloy panel material in the down-flanging process prior to the flat hem process
The method for hemming an aluminum alloy panel material according to claim 1, wherein the bending radius is in the range of 0.5 to 2.0. 3. The aluminum alloy panel material is previously press-formed before the flat hem processing.
Alternatively, the method for hemming an aluminum alloy panel material according to item 2. 4. A Si-excessive Al for an outer panel material, which is flat-hem processed by the method according to any one of claims 1 to 3.
-Mg-Si based aluminum alloy panel material.