JP2002282952A - Method for press forming aluminum alloy panel molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for press forming capable of restraining both flange end crack and corner crack on a molded product when a panel molded product is press-formed by the partial stretch-flanging deformation of a panel material with a metal mold having a draw bead. SOLUTION: The panel material is subjected to the partial stretch-flanging deformation with the metal mold having the draw bead 9 to manufacture the panel molded product 1 by press forming. The passage resistance of the panel material and the quantity of the thickness reduction of the passing panel material are controlled, so that the panel molded product is formed while preventing a crack (flange end crack) X at a stretch-flanging deformed part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for press-forming an aluminum alloy panel molded product having a large curved portion at a side wall and / or a flange.

[0002]

2. Description of the Related Art As is well known, panel materials (materials) such as aluminum alloy plates and steel plates are used for various panel members (parts) such as transportation machines such as automobiles, vehicles, ships, etc., structures, machines, and home electric appliances. A panel molded product (press molded product) obtained by press-molding with a die is used.

In recent years, as these panel members have become larger,
The mold radius, panel molded product radius, or panel molded product height is increasing. Along with this, the panel material (material) that flows into the mold during the press forming of the panel material
And the amount of inflow increases, so that wrinkles are easily generated in the panel molded product. When such wrinkles are formed, the appearance of the panel molded product as a panel member is adversely affected, the shape accuracy is deteriorated, and the cost in the assembling process is increased.

[0004] For this reason, in order to prevent wrinkles from occurring in a panel molded product, it is common to provide a drawing bead called a draw bead in a mold at a portion where a material easily flows.

Conventionally, an optimum design method of the draw bead has been studied. For example, Japanese Patent Application Laid-Open No. H11-290961 discloses a design diagram showing the relationship between the distortion of the panel material after passing the draw bead and the draw bead pull-out resistance. It is proposed to design the draw bead by determining the strain of the panel material and the draw bead pull-out resistance under various conditions from the design diagram.

In recent years, various large-sized panel members, such as automobile parts such as doors, seat pans and oil pans, have been replaced with the AA or JIS standards instead of the steel plates conventionally used for weight reduction. Specified 3000 series, 5000 series, 60
The use of aluminum alloy sheets of the 00 series, the 7000 series, etc. has begun to be studied.

However, since the aluminum alloy plate is inferior in formability to a steel plate, the aluminum alloy plate is used as a panel material and press-formed into various large-sized panel molded products by a mold provided with the draw bead. In such a case, a phenomenon often occurs in which cracks (hereinafter, referred to as corner cracks) occur at corners of a panel molded product.

[0008] In order to solve the problem of corner cracking, it is general to form the draw bead by reducing the passage resistance of the panel material and increasing the inflow of the panel material.

[Problems to be solved by the invention]

On the other hand, in the case of a large panel molded product having largely curved side walls and flanges, corners are prevented from cracking when molded by reducing the draw resistance of the draw bead and increasing the inflow of panel material. However, there is a new problem that a crack (hereinafter, referred to as a flange end crack) is likely to occur at a flange end portion corresponding to the curved side wall portion or the flange portion.

[0010] The tendency of the flange end portion cracking is that the shape of the aluminum alloy panel molded product (panel member) becomes larger and more complicated. For example, the curvature and scale of the side wall portion and the flange portion such as a 90-degree bent side wall portion are reduced. It becomes particularly strong when it gets bigger. This is because a stretch flange deformation occurs partially in the aluminum alloy panel material in the bent portion of the press-formed product. Accordingly, the flange end crack is more remarkable in a panel molded product in which the stretch flange deformation is partially generated.

The flange end cracks, contrary to the usual corner cracks, decrease the draw resistance of the draw bead by increasing the passage resistance of the panel material and decreasing the flow rate of the panel material. Therefore, preventing both flange end cracks and normal corner cracks is a contradictory problem.

The problem of the flange end crack will be described more specifically with reference to FIG. FIG. 3 is a perspective view showing an example of a large panel molded product having greatly curved side walls and flanges, such as the automobile parts. In FIG. 3, the panel molded product 1 is a product part 2 having a relatively large height h.
And a flange portion (surplus portion) 4 having a width w which becomes a part of the panel molded product or is selectively cut off later. Characteristically, the product side wall portion 3 has large curved portions 3a and 3b and curved flange portions 4a and 4b.

FIG. 4 shows a method for press-molding such a panel molded product. First, a mold (die) 6 has a forming part 6a of the product part 2 of the panel molded product 1 and a die face 6b forming a flange part 4 around the product part.
Are provided with draw bead portions 9a and 9b. The draw bead portions 9a and 9b are composed of a pair of male and female draw bead protrusions (projections) 10 and draw bead recesses 11, as shown in an enlarged manner in FIG.

The panel material 5 made of an aluminum alloy plate is formed with a blank holder 8 to give a wrinkle-repressing force during molding, and is provided with a material passing resistance by the draw beads 9a and 9b. It flows into the part 6a.

At this time, in FIG.
1, the curved portions 3a and 3b are provided with a flange curved portion 4 on the front surface thereof.
It is formed by material inflow (inflow direction indicated by arrow A) from a and 4b through the draw bead portion 9. Up to this point, the same applies to other parts of the panel molded product 1.

However, the deformation from the flange bending parts 4a, 4b to the product bending parts 3a, 3b is different from the two-dimensional deformation of other parts, and is a three-dimensional deformation of a fan-shaped part (shown by oblique lines). A certain stretch flange deformation occurs. In the case of this stretch flange deformation, as the flange curved portions 4a, 4b move toward the product curved portions 3a, 3b in the direction of arrow a, the end 4c of the flange curved portion moves in the direction of arrow b, which is a direction perpendicular to arrow a. And it will grow.

The greater the degree of curvature and scale of the side wall and the flange of the panel molded product, the greater the amount of movement of the flange curved end 4c, and therefore the greater the extension flange deformation. As a result, the amount of strain applied to the material in this portion increases, and the stretch flange is broken (stretch flange crack at the blank end).
Flange end cracks (cracked flange bent ends 4c) X shown in FIG. 3 are likely to occur.

When the shape of the aluminum alloy panel molded product becomes larger and more complicated, and the degree of curvature and scale of the side wall portion and the flange portion are increased, the tendency of occurrence of cracks at the flange end is particularly increased. That's why.

When the flange end part becomes a part of the panel molded product, the flange end crack becomes a crack defect of the panel molded product flange end 4c as it is,
Even when 4c is cut off, it easily leads to a crack defect in the product bending portion 3a.

[0020] On the other hand, there is a limit in preventing the flange end cracks by improving the stretch flangeability on the aluminum alloy material side. For this reason, it is common to suppress the inflow of a material from a panel molded product having a larger degree of curvature or a larger scale in the side wall portion and the flange portion in order to prevent the flange end portion from cracking. For this reason, it is necessary to use a draw bead having a sharp shoulder radius or to increase the wrinkle holding force of the blank holder.

However, as a result, the tensile stress applied to the material of the product portion in FIG. 3 is increased, and ordinary corner cracks, which tend to be the opposite of the flange end cracks, tend to occur.

Therefore, at present, especially in the case of a panel material made of an aluminum alloy, there are great restrictions on the degree of curvature and the scale of the side wall portion and the flange portion of the panel molded product that can be molded. For this reason, the only reality was to use a material with good formability at the expense of strength (low strength) or to change the design of the panel member.

The present invention has been made in view of such circumstances, and an object thereof is to press-mold a panel material into a panel molded product by partially expanding a panel material and deforming a flange by a mold provided with a draw bead. It is an object of the present invention to provide a press molding method capable of suppressing both a flange end crack and a corner crack of a molded product.

[0024]

In order to achieve this object, the gist of the press forming method according to the present invention is that a panel material is partially stretched by a mold provided with a draw bead as described in claim 1. When the flange is deformed and press-formed into a panel molded product, the draw resistance of the stretch flange deformed portion is controlled by controlling the passage resistance of the panel material and the amount of reduction in the thickness of the passed panel material, and the stretch flange deformed portion of the panel molded product is controlled. Molding while preventing cracks in the flange (flange end cracks).

The present inventors press-formed a panel molded product having a large degree of curvature or scale of the side wall portion and the flange portion into a panel molded product by partially expanding the panel material and deforming the panel material with a die provided with a draw bead. In forming, in addition to controlling the passage resistance of the panel material in the draw bead, which is conventionally performed, the amount of reduction in the thickness of the panel material when passing through the draw bead is determined by the thickness accuracy of the panel molded product and the product. If it is controlled so as to be relatively large within a range that does not affect the cracking of the part, it is possible to prevent the flange end crack (the crack X of the flange curved end 4c in FIG. 3) and to prevent the corner of the panel molded product from being cracked. It was found that molding was possible while preventing cracks and wrinkles from occurring.

Hereinafter, the present invention will be conceptually described with reference to the drawings. First, FIG. 1 shows the relationship between the flange end crack X and the corner crack Y of the panel molded product 1 in FIG. 3 and the passage resistance of the panel material when passing through the draw bead (pass resistance of the draw bead). In the figure, the vertical axis indicates the degree of each crack (dotted line C indicates the limit of the crack), and the horizontal axis indicates the draw resistance of the draw bead. A1 and A2 each indicate a flange end crack limit curve, where A1 indicates a case where the thickness reduction is large and A2 indicates a case where the thickness reduction is small. B indicates a corner crack limit curve.

As can be seen from FIG. 1, the corner cracks of the panel molded product, which usually become a problem, have a high draw-bead resistance.
(The smaller the inflow of the panel material), the larger it becomes. Therefore, as described above, in the case of a panel molded product having a simple shape in which the stretch flange deformation does not occur, the molded product is usually formed by reducing the draw resistance of the draw bead and increasing the inflow of panel material from the flange. You.

On the other hand, the flange end crack which is the main object of the present invention, on the contrary, becomes larger as the draw resistance of the draw bead is smaller (the inflow of panel material is larger).

Therefore, in order to suppress both flange end cracks and corner cracks of a panel molded product and to press-mold a panel molded product having a large degree of curvature or scale of the side wall and the flange, it is necessary to use a draw bead. In this case, the passing resistance of the panel molded product should be smaller than the limit value at which corner cracking of the panel molded product occurs, and should be larger than the limit value causing the flange end crack of the panel molded product. In other words, the figure
Fig. 1 Flange end crack limit curve A1 and corner crack limit curve B
What is necessary is to select a draw bead passage resistance below the dotted line of C, which is the absolute limit of cracking.

However, the flange end crack limit curve shown in FIG.
In the case of A2 or the like, the intersection with the corner crack limit curve B exceeds the crack limit point C. For this reason, there is no or undetermined optimum value (range) of the pass resistance of the draw bead for preventing both the flange end crack and the corner crack.

From this, it can be seen that the optimum value (range) of the pass resistance of the draw bead may not be determined only from the viewpoint of the relationship between the flange end crack or the corner crack and the pass resistance of the draw bead. . In other words,
It can be seen that the control of the draw bead passage resistance alone may not prevent the flange end cracks and corner cracks. Forming a panel molded product having a large degree of curvature or scale of the side wall portion or the flange portion corresponds to such a case.

Thus, it can be seen from FIG. 1 that the flange end crack limit curves A1 and A2 greatly change depending on the thickness reduction of the panel material. When compared with the same draw bead passage resistance, the flange end crack limit curve A1 with a large thickness reduction is more likely to be below the crack limit point C than the flange end crack limit curve A2 with a small thickness reduction, It can be seen that there is little danger of occurrence of part cracking.

That is, in the case of the forming conditions such as the flange end crack limit curve A2 in which the reduction in plate thickness is small, the amount of reduction in the thickness of the panel material is controlled to be increased to become the flange end crack limit curve A1. If the molding conditions are changed as described above, the intersection with the corner crack limit curve B becomes less than the crack limit point C, and the optimum value of the draw bead passage resistance can be determined. In other words, it can be understood that both the flange end crack and the corner crack can be prevented by controlling the amount of reduction in the thickness of the panel material in addition to controlling the passage resistance of the draw bead.

The reason why the larger the amount of reduction in the thickness of the panel material is, the less the occurrence of cracks at the end of the flange is reduced. The larger the amount of reduction in the thickness of the panel material is, the longer the line length of the panel material becomes. This is because an increase occurs. When the wire length of the panel material increases, the product bending portion of the end portions 4c of the flange bending portions 4a and 4b, which are the stretch flange deformation portions in FIG.
The movement to the 3a and 3b sides is reduced. As a result,
The amount of strain applied to the material in this portion is reduced, and the flange end crack X is suppressed or prevented.

In other words, as described in claim 2, the pass resistance of the draw bead is kept at a low value within a range that does not affect the shape accuracy of the panel molded product and the crack of the product portion. It can be seen that if the draw bead is designed and controlled so that the amount of reduction in the thickness of the panel material becomes large, both flange end cracks and corner cracks can be prevented.

However, the flange end crack of the panel molded product is governed by both the penetration resistance of the draw bead and the thickness reduction of the panel material in the draw bead. Further, corner cracks of the panel molded product are also governed by the draw-bead resistance. For this reason, in order to prevent the cracking of the two, it is necessary to select an appropriate combination of the passage resistance of the draw bead and the reduction in the thickness of the panel material in the draw bead.

This will be described with reference to FIG. Figure 2 shows
This is a conceptual diagram showing how the flange end cracks and corner cracks change depending on the draw-bead (drawing) resistance on the horizontal axis and the thickness strain ε _t after passing the draw bead on the vertical axis. is there. In Fig. 2, A is the limit curve of the flange end crack, B is the limit line of the corner crack, and D is the allowable limit line of the thickness reduction in the draw bead.

In FIG. 2, corner cracks occur in a region to the right of the corner crack limit line B where the draw bead passage resistance is large. In the region to the left of the flange end crack limit curve A, a flange end crack occurs. Further, in a region below the allowable limit line D of the thickness reduction in the draw bead, the crack in the draw bead occurs in a region where the thickness reduction in the draw bead is large. Therefore, by setting the penetration resistance of the draw bead and the thickness reduction of the panel material in the draw bead in the area surrounded by these three curves, both the flange end crack and the corner crack can be prevented.

Then, the optimum area surrounded by the three curves, which the present inventors have found, is the area shown in FIG. 6 obtained from the embodiment described later. That is, the thickness distortion after passing through the draw bead is ε _t , and the pass resistance of the draw bead per unit panel material width, which is made dimensionless by the proof stress of the passing panel material, is T / T _y (where T: draw bead resistance per unit width, _Ty ; the product of the thickness of the panel material and the proof stress), and as shown in claim 3, the flange end crack limit curve A in FIG. 6 (FIG. 2) and the optimal area on the right side are expressed by (Equation 1) ε _t <−0.178 (T / T
_y ) ² +0.6408 (T / T _y ) -0.5767, as shown in Fig. 6 (Fig. 2)
Optimum area of the corner crack limit line B and the left, (Equation 2) epsilon _t
> −0.3, and the crack limit line D of the thickness reduction in the draw bead in FIG. 6 (FIG. 2) and the upper optimal region are expressed by (Equation 3) T / T
It is represented by _y <1.8.

On the other hand, in the present invention, if the amount of the material flowing into the product section is set within an appropriate range, the original function of the draw bead is fulfilled, and there is an effect that wrinkles generated in the molded article are suppressed.
That is, by setting the penetration resistance of the draw bead and the thickness reduction of the panel material in the draw bead in the area surrounded by the three curves in FIG. 2, the crack at the end of the flange and the crack at the corner as well as the crack at the end of the flange are prevented. Occurrence can also be suppressed.

Also in the above-mentioned Japanese Patent Application Laid-Open No. 11-290961, the relationship between the reduction in the thickness of the material and the resistance to the passage of the draw bead is grasped in consideration of the distortion of the material after passing through the draw bead, that is, the reduction in the thickness of the material. ing.

However, in this technique, as specified in the gazette, the bead shape, lubrication conditions, bead holding force, etc.
Understand how it affects the bead passage resistance and the amount of strain (thickness reduction) applied to the material, create a design diagram, and from this design diagram, strain the material under various conditions and pass through the draw bead. It determines the resistance and designs the draw bead.

Therefore, Japanese Patent Application Laid-Open No. H11-290961 intends to design a draw bead only within the range of a normal press forming method in which a panel material is press-formed into a normal panel molded product by a mold provided with a draw bead. Absent. That is, this prior art provides a panel molded product having a large curvature or scale of the side wall and the flange, which is a main problem of the present invention.
When a panel material is partially stretched and flange deformed by a mold with a draw bead and press-formed into a panel molded product, the panel molded product is prevented from cracking at the corners of the panel molded product and at the flange end. There is no disclosure at all about molding while preventing wrinkles from occurring. In addition, from this viewpoint, neither the passing resistance of the draw bead nor the reduction in the thickness of the panel material in the draw bead is controlled.

However, once the optimum draw bead passage resistance and the amount of reduction in the thickness of the panel material in the draw bead are determined by the present invention, the bead shape, lubrication conditions, bead holding force, and the like are determined using this conventional technique. In consideration of the bead passage resistance and the like, it is possible to design a draw bead for achieving the optimum material thickness reduction rate.

Also, when the panel material is press-molded into a panel molded product using a mold provided with a normal draw bead, a decrease in the thickness of the panel material when passing through the draw bead can naturally occur. However, in normal press forming, in consideration of the thickness accuracy of the panel molded product, it is necessary to form the panel material so that the thickness of the panel material does not decrease, or in a range where the thickness of the panel material does not significantly decrease. Was common sense. For this reason, unlike the present invention, there is no viewpoint of actively reducing the thickness of the panel material when passing through the draw bead and preventing a flange end crack of the panel material or a molded product crack due to this. It is a thing.

According to the present invention, since the panel material has an excellent effect of preventing wrinkles together with cracks at the corners of the molded product of the panel material and at the ends of the flanges, the cracks and wrinkles are easily generated as described in claim 4. It is suitably applied to the molding of a panel molded product having a curved portion on the side wall and / or the flange, which is difficult to mold.

According to the present invention, as described in claim 5,
The panel moldings that are difficult to form are made from series AA to JIS, JIS 5000 series,
It is suitably applied to an aluminum alloy selected from the 00 series, the 7000 series, and the like. By applying the aluminum alloy to the panel molded product, the weight of the panel member can be further reduced.

[0048]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Applied Panel Molded Product) In the press molding method of the present invention, when a panel material is press-molded by a mold provided with a draw bead, inevitably a partial stretch flange deformation occurs. Applied to panel molded products. Such panel molded products include automobile parts such as doors, seat pans and oil pans, as well as hat-shaped products.
A panel molded product having a C-shaped cross section and a shape that is greatly curved or bent, or a shape in which the degree of curvature or the scale of the side wall portion or the flange portion in FIG. 3 is large is exemplified.

On the other hand, in the case of a panel molded product in which such a partial stretch flange deformation does not occur, for example, in a deep draw molding of a beverage can having a simple shape such as an ordinary cylindrical shape, the molded product itself has a flange curved end portion. There is no flange curved end itself that would cause cracking. For this reason, it is not regarded as a panel molded product to be applied in the present invention.

(Press Forming Method) The press forming method of the present invention basically comprises
The press forming method of the conventional or ordinary panel molded product and the forming condition range such as the die 6, the draw bead portion 9, and the wrinkle pressing force shown in FIG. 4 are used.

(Optimum amount of thickness reduction) The optimum amount of thickness reduction in the present invention depends on the mechanical properties of the panel material and the condition of the panel molded product.
(Especially, the degree of curvature of the side wall and the flange) and the molding conditions and draw bead conditions. For this reason,
The relationship between the corner crack Y and the flange end crack X of the panel molded product 1 shown in FIG. 3, the draw resistance of the draw bead, and the reduction (rate) of the thickness of the panel material when passing through the draw bead is shown in FIG. is obtained in advance as 2, a molded article corner cracking and flange end crack or wrinkle can be suppressed, flow resistance and optimal decrement in plate thickness or the optimum thickness reduction rate of drawbead (t ₁ -t ₂ of Fig. 5 Alternatively, select t ₁ / t ₂ ).

Then, from this range, as described above, an optimum thickness reduction amount that does not affect the thickness accuracy of the panel molded product is selected. In addition, in order to compensate for this optimum thickness reduction in advance, the thickness of the formed panel material is increased,
The thickness of the panel material may be selected according to the reduction in the thickness.

It should be noted that, even when the above-mentioned optimum thickness reduction amount is selected, although it depends on the molding conditions, the part passing through the draw bead moves to the product part of the press-formed product. According to it does not happen.

Further, a method such as that described in Japanese Patent Application Laid-Open No.
The bead shape such as the radius r ₁ , r ₂ , r ₃ of the draw bead convex (protrusion) 10 and the draw bead concave 11 of the draw bead portion 9 of FIG. 5, lubrication conditions, bead holding force, etc. Design draw-beads and dies to achieve a reduction in thickness.

Further, an aluminum alloy plate having material properties such that the thickness reduction rate of the optimum material is obtained under the conditions of the draw bead or the mold or in advance in accordance with the required properties of the panel member is obtained. The selection is made including the production method and conditions such as rolling and heat treatment conditions.

(Type of Applicable Metal Plate) As the metal plate used in the present invention, an aluminum alloy plate having high strength, elongation value, etc. as material characteristics is appropriately selected according to the required characteristics of the panel member.

Aluminum alloy sheets are generally used for this kind of structural member, and are specified in AA to JIS standards.
Al alloys such as 00 series, 5000 series, 6000 series, and 7000 series are preferably used. These Al alloys have relatively good formability. The mechanical properties such as tempering or strength of these Al alloys are appropriately selected according to the required characteristics of the panel member.

[0058]

Embodiments of the present invention will be described below. The figure above
A large panel molded product 1 having a greatly curved side wall portion and a flange portion shown in FIG. 3 was molded using the mold 6 shown in FIG.
Panel molded product 1 obtained by press-forming with various changes in the thickness of the panel material (t ₁ −t _{2 in} FIG. 5) and the draw bead passage resistance (constraining force) when the draw bead portions 9a and 9b pass through the draw bead. Were visually inspected for cracks in the corners, cracks in the curved ends of the flanges, and the occurrence of wrinkles in panel molded products.

The pass resistance of the draw bead and the thickness reduction of the panel material in the draw bead were changed by changing the wrinkle holding force, the tool shape, and the friction coefficient. In addition, the passage resistance and the reduction rate of the thickness of the panel material are difficult to measure in the above-mentioned press molding test. For this reason, the same draw bead as the above-mentioned press molding is formed, the pass resistance per unit width of the above-mentioned press molding and the passing panel material is made the same, and a sliding test using a gripping jig correlated with the above-mentioned press molding is separately performed. Carried out. That is, the plate was clamped between the gripping jigs, and the plate was pulled out. At this time, the passage resistance per unit width of the passing panel material and the reduction rate of the thickness of the panel material were measured as those in the press molding. . Table 1 shows the measurement results of the passage resistance and the reduction rate of the thickness of the panel material, and the results of the press molding. In Table 1, the sheet thickness reduction is indicated by the sheet thickness reduction rate (%), and the pass resistance of the draw bead is indicated by the pass resistance per unit width of the pass panel material (N / mm ² ).

With respect to the cracks at the corners of the panel molded product, those without cracks were evaluated as Δ, those with fine necking as a pre-crack stage were evaluated as Δ, and those with cracks were evaluated as x. did. Similarly, regarding the crack at the curved end portion of the flange, the case where no crack occurred was evaluated as 〇, the case where fine necking occurred as a stage before the crack was evaluated as Δ, and the case where cracks occurred was evaluated as ×. Furthermore,
Regarding the occurrence of wrinkles on panel molded products, 〇 indicates that there is no vertical wrinkle in the product part, △ indicates that vertical wrinkles of 0.05 mm or less have occurred, and △ indicates that vertical wrinkles exceeding 0.05 mm have occurred Was evaluated as x, and each was evaluated. These results are tabulated.
1 and Figure 6.

The conditions for the panel material are as follows.
A blank (550 mm × 450 mm) cut out from a rolled plate of a 5182-O Al alloy (tensile strength: 270, yield strength: 130, elongation: 26%) was used. The conditions for panel molded product 1 are as follows: product part 2 is 50 mm high, 400 mm long (horizontal direction in the figure), 350 mm long (right side in the vertical direction in the figure), and 250 mm short (left side in the vertical direction in the figure) , Curved parts 3a, 3b
Has a radius of curvature R of 200 mm.

The mold (die) conditions are adapted to the conditions of the panel molded product, and the length of the plate sandwiched between the die faces 6a and 6b forming the flange portion 4 (excess portion) at the start of molding is 150 mm each. Draw bead convex 10 shown in FIG.
R ₁ , r ₂ , and r ₃ of the concave mold 11 were set to 5 mm.

As is clear from Table 1, in Invention Examples Nos. 1 to 3 in which the pass resistance of the draw bead and the amount of reduction in the thickness of the panel material in the draw bead were controlled to the optimum ranges, cracks occurred at the flange curved end. In addition, no corner cracks or wrinkles of the panel molded product were generated.

On the other hand, in Comparative Examples Nos. 4 and 6, where the draw bead passage resistance was large irrespective of the amount of reduction in the thickness of the panel material when passing through the draw bead, although cracks did not occur at the curved end of the flange, The corner crack of the panel molded product has occurred.

Further, in Comparative Examples Nos. 7 and 8, where the amount of reduction in the thickness of the panel material when passing through the draw bead was small, the corners of the panel molded product did not crack, but cracks occurred at the curved end of the flange. ing.

Further, in Comparative Example No. 5, where the amount of reduction in the thickness of the panel material when passing through the draw bead was too large, cracks did not occur at the curved end of the flange, but cracks due to the reduction in the thickness of the draw bead portion occurred. Has occurred.

These results are expressed in the form of the thickness strain and the dimensionless draw bead passing resistance, and the optimum area surrounded by the three curves in FIG. 2 is obtained. As shown in claim 3, the flange end crack limit curve A in FIG. 2 and the area on the right side are ε _t <−0.178 (T / T
_y ) ² +0.6408 (T / T _y ) −0.5767 (Formula 1)
In Figure 2, the corner cracking limit line B and the area on the left are ε _t > −0.3
The area below the crack limit line D of the amount of thickness reduction in the draw bead in FIG. 2 and the lower region is expressed by T / T _y <1.8 (Equation 3). The numbers in FIG. 6 correspond to the numbers of the invention examples and comparative examples in Table 1, respectively.

Therefore, the significance of the molding method of the present invention is clear from these examples. In this embodiment,
The case of JIS 5182-O Al alloy was described, but other 3000
The same can be said for Al alloys such as a series, 5000 series, 6000 series, and 7000 series. Of course, mechanical properties such as tensile strength, proof stress, elongation, etc., differ depending on the Al alloy and tempering (heat treatment) conditions. However, when the draw bead passage resistance is made dimensionless by the strength of the Al alloy material, the relational expression between the draw bead passage resistance and the plate thickness strain value is JI even if it is another Al alloy.
It is almost equal to that of S 5182-O Al alloy. Therefore, the condition described in claim 3 can be applied to other Al alloys.

[0069]

[Table 1]

[0070]

According to the present invention, when a panel material is partially stretched and flange-deformed by a mold provided with a draw bead and pressed into a panel molded product, a flange end crack and a corner crack of the molded product are cracked. And a press molding method capable of suppressing wrinkles. For this reason, the use of a high-strength Al alloy sheet, which is difficult to form, is greatly expanded to the use of a panel molded product, and has great industrial value.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a relationship between a flange end crack or a corner crack of a panel molded product, a passage resistance in a draw bead, and a thickness reduction of a panel material.

FIG. 2 is an explanatory diagram showing a relationship between a flange end crack or a corner crack of a panel molded product, a passage resistance in a draw bead, and a plate thickness distortion.

FIG. 3 is a perspective view showing an example of a panel molded product.

FIG. 4 is a cross-sectional view showing an example of a mold used for press molding of a panel molded product.

FIG. 5 is a sectional view showing an example of a draw bead used for the mold of FIG. 4;

FIG. 6 is an explanatory view showing an optimum relationship between a passage resistance in a draw bead and a reduction in thickness of a panel material, which prevents a crack at a flange end or a corner at a panel molded product.

Claims (5)

[Claims] 1. An aluminum alloy panel material is partially stretch-flange-deformed by a mold provided with a draw bead, and press-formed into a panel molded product. And control the thickness reduction of the passing panel material,
A press forming method for an aluminum alloy panel molded product, wherein the molding is performed while preventing a flange end crack of a stretch flange deformed portion of the panel molded product and a corner crack of the panel molded product. 2. The method according to claim 1, wherein the amount of reduction in the thickness of the panel material when passing through the draw bead is controlled in a direction in which the reduction in the thickness of the panel molded product does not affect the accuracy of the thickness of the panel molded product or cracks in the product portion. Press molding method for an aluminum alloy panel molded article according to the above. 3. The draw bead of the stretched flange deformed portion, the thickness strain ε _t after passing through the draw bead, and the pass resistance of the draw bead per unit panel material width T / T _y ( 3. The press of an aluminum alloy panel molded product according to claim 2, wherein T: draw bead resistance per unit width, T _y : product of panel thickness and proof stress) satisfy the following three equations. Molding method. (Equation 1) ε _t <−0.178 (T / T _y ) ² +0.6408 (T / T _y ) −0.5767 (Equation 2) ε _t > −0.3 (Equation 3) T / T _y <1.8 4. The panel molded product has a side wall and / or
4. The method of press-forming an aluminum alloy panel molded product according to claim 1, further comprising a curved portion in the flange portion. 5. 5. The panel according to claim 1, wherein the panel material is an aluminum alloy selected from 3000 series, 5000 series, 6000 series, and 7000 series specified in AA to JIS standards. Press forming method for aluminum alloy panel molded products.