JP2023145315A - Press molding method and method for manufacturing press molded product - Google Patents

Abstract

To provide a press molding method for a press molded product having a corner flange, which method can prevent wrinkles or folding without adding a restriking step, and a method for manufacturing the press molded product.SOLUTION: A press molding method and the method for manufacturing a press molded product are for press-molding a press molded product 1 having a top plate 3, a longitudinal wall 5, a bottom flange 7, a longitudinal flange 9, and a corner flange 11 provided between the longitudinal flange 9 and the bottom flange 7. The methods comprise: a first step of press-molding an intermediate molded product 100 which has the bottom flange 7, the longitudinal flange 9, and the corner flange 11, and an intermediate flange in which an angle between the longitudinal wall 5 and the bottom flange 7 and/or an angle between the longitudinal wall 5 and the longitudinal flange 9 is larger than an angle of a target shape; and a second step of press-molding so as to set the angle with the longitudinal wall 5 in the intermediate flange set larger than the angle of the target shape in the first step equal to the angle of the target shape.SELECTED DRAWING: Figure 1

Description

The present invention provides a top plate portion, a vertical wall portion continuous to the top plate portion, a bottom flange portion continuous to the vertical wall portion and located on the opposite side of the top plate portion, and a longitudinal direction of the vertical wall portion. Press forming of a press-formed product having a vertical flange part continuous to the vertical wall part at the front and/or rear part of the direction, and a corner flange part provided between the vertical flange part and the bottom flange part The present invention relates to a method and a method for manufacturing a press-molded product.

As the collision safety of automobile bodies continues to improve due to stricter collision safety standards for automobiles, it is also necessary to reduce the weight of automobile bodies in order to improve fuel efficiency and shift to electric vehicles in response to carbon dioxide emission regulations. In order to both improve collision safety and reduce weight of these car bodies, the use of high-strength steel plates of 590 MPa or higher (also known as high-tensile steel) is progressing in car body structural parts.

Automotive parts, such as the floor cross member shown in FIG. There is a press-molded product 1 having a hat cross-sectional shape and having a vertical flange portion 9 extending to the front and rear portions of a vertical wall portion 5 in the longitudinal direction.

In such a press-formed product 1, the corner flange portion 11, which is a continuous portion of the bottom flange portion 7 and the vertical flange portion 9, is shrunk and flanged, and when press-formed, large wrinkles and buckling ( fold-in) occurs. Particularly in the case of high-tensile steel materials, increasing the strength tends to cause wrinkles and buckling (folding).

As a technique for suppressing the occurrence of such wrinkles, for example, Patent Document 1 discloses a method for manufacturing a press part that includes bending and forming at least a first surface portion and a flange portion continuous to the first surface portion, which includes at least a wrinkle-generating region. A method of manufacturing a press part is disclosed in which bending is performed using a flange portion as a non-contact area and a mold set in a non-contact shape.

JP2020-093303A

In the method described in Patent Document 1, since the flange portion where wrinkles occur is a region that does not contact the mold, there are cases where the region cannot sufficiently contact the mold and cannot be press-formed into a press-formed product with the target shape. There is. Therefore, in order to achieve the target shape, it was necessary to further add a restriking process and press firmly.
Further, if bending occurs in the non-contact flange portion, there is also a problem that the target shape cannot be obtained even if a restriking process is added.

The present invention has been made to solve such problems, and is a method for press-forming a press-formed product having a corner flange portion, and a method for manufacturing a press-formed product, which eliminates wrinkles and folds without adding a restriking process. It is an object of the present invention to provide a press molding method and a method for manufacturing a press molded product that can prevent clogging.

(1) The press forming method according to the present invention includes a top plate portion, a vertical wall portion continuous to the top plate portion, and a bottom flange portion continuous to the vertical wall portion and located on the opposite side of the top plate portion. a vertical flange portion continuous to the vertical wall portion at the front and/or rear portion of the vertical wall portion in the longitudinal direction; and a corner flange portion provided between the vertical flange portion and the bottom flange portion; A press-forming method for a press-formed product having the following steps:
The bottom flange portion, the vertical flange portion, and the corner flange portion are included, and the angle between the vertical wall portion and the bottom flange portion and/or the angle between the vertical wall portion and the vertical flange portion is an angle of a target shape. a first step of press-molding an intermediate molded product having a larger intermediate flange;
The present invention is characterized by comprising a second step of press-forming the angle between the intermediate flange portion and the vertical wall portion, which was made larger than the angle of the target shape in the first step, to the angle of the target shape.

(2) In the item described in (1) above, in the first step, the interior angle between the top plate portion and the vertical wall portion is press-formed to be larger than the interior angle of the target shape, and in the second step, the interior angle This method is characterized by press-forming the inside corners of the target shape.

(3) Furthermore, in the product described in (1) or (2) above, the press-formed product has vertical wall portions on both sides of the top plate portion, and the bottom flange portion is continuous with the vertical wall portion. It is characterized by having a hat cross-sectional shape.

(4) Furthermore, in the product described in (1) or (2) above, the press-formed product has a vertical wall portion on one side of the top plate portion, and the bottom flange portion is continuous with the vertical wall portion. It is characterized by having a Z-shaped cross-sectional shape.

(5) The method for manufacturing a press-formed product according to the present invention includes a top plate portion, a vertical wall portion continuous to the top plate portion, and a vertical wall portion continuous to the vertical wall portion located on the opposite side to the top plate portion. a bottom flange portion, a vertical flange portion continuous to the vertical wall portion at the longitudinal front and/or rear portion of the vertical wall portion, and a corner flange provided between the vertical flange portion and the bottom flange portion. A method for manufacturing a press-formed product comprising:
The bottom flange portion, the vertical flange portion, and the corner flange portion are included, and the angle between the vertical wall portion and the bottom flange portion and/or the angle between the vertical wall portion and the vertical flange portion is an angle of a target shape. a first step of press-molding an intermediate molded product having a larger intermediate flange;
The present invention is characterized by comprising a second step of press-forming the angle between the intermediate flange portion and the vertical wall portion, which was made larger than the angle of the target shape in the first step, to the angle of the target shape.

According to the present invention, a top plate portion, a vertical wall portion continuous to the top plate portion, a bottom flange portion continuous to the vertical wall portion and located on the opposite side of the top plate portion, and the vertical wall portion Regarding a press-formed product having a vertical flange portion continuous to the vertical wall portion at the front and/or rear portion in the longitudinal direction, and a corner flange portion provided between the vertical flange portion and the bottom flange portion. , wrinkles and folding of the flange portion can be effectively suppressed without adding a restriking process.
As a result, a press-molded product with a good shape can be obtained, which also leads to improved yield in press molding.

FIG. 3 is an explanatory diagram of a mold used in the press molding method of the present embodiment. It is a figure which shows the board thickness increase rate of the flange part in the 1st process and the 2nd process of the press-forming method by this Embodiment. FIG. 2 is an explanatory diagram of a target shape of a press-formed product targeted in this embodiment. FIG. 4 is an explanatory diagram of a conventional mold for molding the press-formed product shown in FIG. 3 in one step. It is a figure which shows the maximum board thickness increase rate by the press forming method of a conventional example. It is an explanatory view explaining the position of the cross section of the intermediate molded article in an example. FIG. 3 is an explanatory diagram of target cross-sectional shapes in the first step and second step of the invention example and the conventional example in the embodiment. It is an explanatory diagram of the analysis result of the invention example and the conventional example in an example.

First, a press-formed product targeted by the press-forming method of this embodiment will be described based on FIG. 3.
As shown in FIG. 3, the target press-formed product 1 includes a top plate part 3, a vertical wall part 5 continuous to the top plate part 3, and a side opposite to the top plate part 3 continuous to the vertical wall part 5. A bottom flange portion 7 located at the bottom flange portion 7, a vertical flange portion 9 continuous to the vertical wall portion 5 at the front and rear portions of the vertical wall portion 5 in the longitudinal direction, and a vertical flange portion 9 provided between the vertical flange portion 9 and the bottom flange portion 7. It is a part having a hat cross-sectional shape and having a corner flange portion 11.

Next, the circumstances leading to the present invention will be explained.
In the conventional press forming method in which the target shape is the press-formed product 1 having the cross-sectional shape of a hat shown in FIG. is shown in Figure 4.
The blank 13 is sandwiched between the pad 15 and the punch 17, and the die 19 is moved relative to the punch 17, thereby aiming at the angle that the bottom flange 7, the vertical flange 9, and the corner flange 11 form with the vertical wall 5. Shape into an angle.

In the press-formed product 1 shown in FIG. 3, the corner flange portion 11, which is a curved portion where the bottom flange portion 7 and the vertical flange portion 9 are continuous, is shrunk and flanged, and the thickness of the corner flange portion 11 increases and wrinkles are eliminated. In severe cases, this can lead to buckling (folding).
FIG. 5 shows the FEM analysis results of the conventional press forming method shown in FIG. 4. FIG. 5 shows the distribution of the plate thickness increase rate of the press-formed product 1 having a hat cross-sectional shape at the bottom dead center of the press-forming, and dark-colored regions indicate that the plate thickness is increasing.

Here, the plate thickness increase rate refers to the difference (plate thickness increase) between the plate thickness after press forming and the plate thickness of the blank 13 before press forming, and the ratio with the plate thickness of the blank 13 before press forming ( It is expressed as a percentage), and the larger the value, the greater the plate thickness.
As shown in FIG. 5, a large increase in thickness has occurred in the corner flange portion 11, and the maximum rate of increase in thickness is as large as 118%, indicating that wrinkles and buckling (folding) occur.

The reason for the large increase in plate thickness is that when a press-formed product 1 with a hat cross-sectional shape as shown in Fig. 3 is press-formed in one step, the material during press-forming shrinks and becomes extremely concentrated in the flange forming area. . The measure in Patent Document 1 does not make it possible to suppress material concentration by keeping the area where wrinkles occur out of contact with the mold, and is not necessarily a sufficient measure.

In order to prevent wrinkles that occur during shrinkage flange forming, it is preferable to suppress the sudden concentration of material at the shrinkage flange forming site. In other words, instead of forming the target shape in one step, it is better to gradually form the material in multiple steps to alleviate the sudden concentration of material.
Further, when molding is performed in multiple steps, a ridge line is formed between the flange portion and the vertical wall portion 5 before the material concentrates on the corner flange portion 11 in the intermediate molded product formed in the first step. By forming this ridgeline, the area is work-hardened, making it difficult for the material to move during shrinkage flange forming in the first and second steps, and material concentration can be alleviated. As a result, wrinkles at the shrinkage flange forming portion of the target press-formed product 1 can be effectively suppressed.

From this point of view, the inventors formed the target shape in multiple steps instead of forming it in one step to prevent sudden material concentration, and also formed a ridge line between the vertical wall portion 5 and the flange portion. In order to suppress shrinkage and flange forming, in the first step, an intermediate molded product 100 (see FIGS. 2(a) and 7(A)(a)) with a bending angle of the flange portion larger than the target shape is press-formed. Then, in the second step, the idea was to press-form it into the target shape.

That is, the press forming method according to the present embodiment has the bottom flange portion 7, the vertical flange portion 9, and the corner flange portion 11, and the angle between the vertical wall portion 5 and the bottom flange portion 7 and the angle between the vertical wall portion 5 and the vertical An intermediate molded product 100 (FIG. 2A, FIG. 7A ) A first step of press-forming (see (a)); and a second step of press-forming the angle between the vertical wall portion 5 of the intermediate flange portion, which was made larger than the angle of the target shape in the first step, to the angle of the target shape. It is equipped with the following.
Here, the intermediate flange section is a general term for the bottom flange section 107, the vertical flange section 109, and the corner flange section 111 in the intermediate molded product 100 formed in the first step.
Note that the angle between the vertical wall portion 105 and the corner flange portion 111 in the intermediate molded product 100 is determined by determining the angle between the vertical wall portion 105 and the bottom flange portion 107 and the angle between the vertical wall portion 105 and the vertical flange portion 109. The portion 107 and the vertical flange portion 109 may be connected smoothly.
Since a press-formed product is manufactured by executing the press-forming method, the invention of the press-forming method can be constituted as an invention of the method of manufacturing a press-formed product. Therefore, the embodiment of the press molding method described below is common to the embodiment of the method of manufacturing a press molded product.

The press molding method of this embodiment will be explained based on FIG. 1, focusing on the mold.
In the first step shown in FIG. 1A, the blank 13 is sandwiched between the pad 20 and the punch 21, and the die 23 is moved relative to the punch 21.
The angle of the bottom shoulder molding part 23c, which is the connecting part between the vertical wall molding part 23a and the bottom flange molding part 23b in the die 23, is made larger than the target angle, and the connection between the vertical wall molding part 23a and the vertical flange molding part 23d is made larger than the target angle. The angle of the vertical shoulder forming portion 23e is made larger than the target angle.

Further, similarly to the die 23, the angle of the bottom shoulder forming part 21c, which is the connecting part between the vertical wall forming part 21a and the bottom flange forming part 21b in the punch 21, is set to be the same angle as the die 23 and larger than the target angle, and further, The angle of the vertical shoulder molding part 21e, which is the connecting part between the vertical wall molding part 21a and the vertical flange molding part 21d, is set at the same angle as the die 23 and larger than the target angle, and the blank 13 is turned into an intermediate molded product 100 (FIG. 2). Press mold.

Thereafter, in the second step shown in FIG. 1(b), press forming is carried out using a die 19 and punch 17 similar to those shown in FIG. 4, in which the bending angle of the flange forming part is set to the target angle. Let it be press-formed product 1. Thereby, while reducing the amount of molding of the shrinkage flange forming portion in each step (first step, second step), it is possible to gradually press-form in a plurality of steps to obtain a wrinkle-free target shape.

Further, in the first step shown in FIG. 1(a), the intermediate molded product 100 is formed by the bottom shoulder molding portion 23c and the vertical shoulder molding portion 23e of the die 23, and the bottom shoulder molding portion 21c and the vertical shoulder molding portion 21e of the punch 21. Bending ridge lines are provided to the bottom ridge line part 117, the vertical ridge line part 119, and the corner ridge line part 121 (see FIG. 2(a)), and the rigidity of the bottom ridge line part and its surroundings, the vertical ridge line part and its surroundings is improved, and the rigidity of the bottom ridge line part and its surroundings is improved. In the second step shown in FIG. 1(b), the material in and around the region becomes difficult to move, and the effect of suppressing wrinkles in the corner flange portion 11 of the target molded product is further increased.

FEM analysis results for press forming of the present invention are shown in FIGS. 2(a) and 2(b). Conventionally, as shown in FIG. 5, the maximum plate thickness increase rate of the corner flange portion 11 was 118%.
On the other hand, in the first step of the present invention, as shown in FIG. 2(a), the maximum plate thickness increase rate of the corner flange portion 111 of the intermediate molded product 100 is significantly reduced to 4.6%, and wrinkles are eliminated. It has not occurred at all. In addition, in the second step, as shown in FIG. 2(b), the maximum plate thickness increase rate of the corner flange portion 11 of the press-formed product 1 having the target shape increased to 13.6%, but the above-mentioned rigidity improvement The impact was significant, reducing wrinkles and preventing buckling (folding).

As described above, according to the press molding method of the present embodiment, wrinkles and buckling of the corner flange portion 11 are prevented when forming the press molded product 1 having a hat cross-sectional shape and having the corner flange portion 11 which is subjected to shrinkage flange molding. can be effectively suppressed.

Note that the above description applies to both the connecting portion between the vertical wall portion 105 and the bottom flange portion 107 and the connecting portion between the vertical wall portion 105 and the vertical flange portion 109 in the intermediate molded product 100 molded in the first step. In this case, the bending angle is larger than that of the press-formed product 1 having the target shape, but the present invention is not limited to this. or only the bending angle of the connection portion between the vertical wall portion 105 and the front and rear vertical flange portions 109 in the longitudinal direction, or the bending angle of the connection portion between the vertical wall portion 105 and one vertical flange portion 109. Even if only the bending angle of the connecting portion is made larger than the target bending angle, there is an effect of preventing wrinkles.

Although the above explanation does not mention the angle (internal angle) formed between the top plate part 3 and the vertical wall part 5, in the first step, the internal angle between the top plate part 3 and the vertical wall part 5 is set to the target shape. It is preferable that the inner angle is press-molded to be larger than the inner angle of the target shape, and in the second step, the inner angle is press-molded to the inner angle of the target shape.
This also has the effect of suppressing springback of the vertical wall portion 5.
Further, regarding the press-molded product having a hat cross-sectional shape obtained by the above-described method, a press-molded product having a Z-shaped cross-section can also be obtained by dividing the top plate portion into two in the ridgeline direction.
In addition, by performing each step of the above-mentioned press molding method, the target press molded product can be manufactured, and the manufactured press molded product has suppressed wrinkles and folding of the flange portion.

In order to demonstrate the effects of the present invention, a high-strength steel plate with a thickness of 1.0 mm and a tensile strength of 980 MPa class is used as a blank 13, and a top plate part 3, a vertical wall part 5 continuous to the top plate part 3, and a vertical wall part 5, a bottom flange part 7 located on the opposite side of the top plate part 3, a vertical flange part 9 continuous to the vertical wall part 5 at the front and rear parts in the longitudinal direction of the vertical wall part 5, and a vertical flange part 9 and a corner flange portion 11 provided between the bottom flange portion 7, a press-molded product 125 (FIGS. 7 and 8) having a hat cross-sectional shape was press-molded as an example of the target shape.

In the embodiment, a conventional example in which press molding is performed in one step is shown, but in this embodiment, an example in which the conventional example is also performed in two steps will be described.
FIG. 6 is a schematic top view of the intermediate molded product 100 after the first step, and AA and BB'-B in FIG. 6 are lines indicating the positions of the cross sections.

FIG. 7 shows AA cross-sectional shapes of the intermediate molded products 100, 127 molded in the first step and the target-shaped press molded product 125 molded in the second step in the invention example and the conventional example.
The molding methods of the invention example and the conventional example are as follows.

<Invention example>
In the invention example, as shown in FIG. 7(A), the outer angle (intermediate outer angle) between the vertical wall portion 105 and the bottom flange portion 107 of the intermediate molded product 100 molded in the first step is β, and in the second step, As shown in FIGS. 7(A) and 7(b), molding was performed so that the outer angle (target outer angle) of the target shape was set to γ, which was smaller than β.
Further, the press-formed product 125 is formed by setting the internal angle (intermediate internal angle) between the top plate portion 103 and the vertical wall portion 105 of the intermediate molded product 100 to α1, and setting the internal angle of the target shape (target internal angle) to α2, which is smaller than α1. Ta.
That is, in the invention example, forming is performed such that both the intermediate external angle (β) and the intermediate internal angle (α1) are larger than the target shape, and in the second step, the intermediate external angle (β) and the intermediate internal angle (α1) are changed to smaller target external angles ( γ) and the target internal angle (α2).
Also, regarding the vertical flange portion 109, in the shape of the BB'-B cross section in FIG. γ) and set it as the target external angle (γ) in the second step.

<Conventional example>
In the conventional example, as shown in FIGS. 7(B), (a), and (b), in the shape of the AA cross section of the intermediate molded product 127 formed in the first step, the intermediate external angle is set to γ, which is the same as the target external angle. .
Further, the relationship between the intermediate interior angle (α1) and the target interior angle (α2) was the same as in the invention example.
Furthermore, regarding the vertical flange portion 9, in the BB'-B cross-sectional shape of FIG. did.

In order to determine the state of wrinkles in shrinkage flange forming in the invention example and the conventional example, the maximum plate thickness increase rate of the corner flange part 111 in the first process and the corner flange part 11 in the second process was determined by FEM analysis. . Note that the larger the maximum plate thickness increase rate, the more likely wrinkles will occur, and if the rate increases further, buckling (folding) will occur.

FIG. 8(A) is an analysis result of the invention example, and as shown in FIG. 8(A)(a), in the first step, the maximum plate thickness increase rate at the corner flange portion 111 of the intermediate molded product 100 is 2. It was only 5%, and no wrinkles occurred.
Further, as shown in FIGS. 8(A) and 8(b), in the second step, the angle between the top plate portion 3 and the vertical wall portion 5 of the press-formed product 125 having the target shape is reduced (α1 → α2), and Even if the intermediate external angle is press-formed to a smaller target external angle (β→γ), the maximum board increase rate of the corner flange portion 11 of the press-formed product 125 in the target shape is as small as 7.2%, and wrinkles do not occur. No defects occurred at all, and a good shape could be obtained.

On the other hand, in the conventional example shown in FIG. 8(B), as shown in FIG. 8(B)(a), the maximum plate thickness increase rate of the corner flange portion 11 of the intermediate molded product 127 has already been achieved in the first step. was significantly large at 19.6%, and not only wrinkles but also buckling (folding) occurred, resulting in product defects. Therefore, it was not possible to proceed to the second step.

As described above, according to the present invention, it has been demonstrated that wrinkles and folds can be effectively prevented without adding a restriking process.

1 Press-formed product 3 Top plate part 5 Vertical wall part 7 Bottom flange part 9 Vertical flange part 11 Corner flange part 13 Blank 15 Pad (conventional example, 2nd process)
17 Punch (conventional example, 2nd process)
19 Die (conventional example, 2nd process)
20 Pad (1st process)
21 Punch (1st process)
21a Vertical wall forming section 21b Bottom flange forming section 21c Bottom shoulder forming section 21d Vertical flange forming section 21e Vertical shoulder forming section 23 Die (first step)
23a Vertical wall molding part 23b Bottom flange molding part 23c Bottom shoulder molding part 23d Vertical flange molding part 23e Vertical shoulder molding part 100 Intermediate molded product (invention example)
103 Top plate part 105 Vertical wall part 107 Bottom flange part 109 Vertical flange part 111 Corner flange part 117 Bottom ridge part 119 Vertical ridge part 121 Corner ridge part 125 Press-formed product (Example)
127 Intermediate molded product (first step of conventional example)

Claims (5)

a top plate part, a vertical wall part continuous to the top plate part, a bottom flange part continuous to the vertical wall part and located on the opposite side of the top plate part, and a longitudinal front part of the vertical wall part. and/or a press-forming method for a press-formed product having a vertical flange portion continuous to the vertical wall portion at the rear, and a corner flange portion provided between the vertical flange portion and the bottom flange portion, ,
The bottom flange portion, the vertical flange portion, and the corner flange portion are included, and the angle between the vertical wall portion and the bottom flange portion and/or the angle between the vertical wall portion and the vertical flange portion is an angle of a target shape. a first step of press-molding an intermediate molded product having a larger intermediate flange;
A press-forming method comprising: a second step of press-molding the angle between the intermediate flange portion and the vertical wall portion, which was made larger than the angle of the target shape in the first step, to an angle of the target shape. In the first step, the interior angle between the top plate portion and the vertical wall portion is press-formed to be larger than the interior angle of the target shape, and in the second step, the interior angle is press-molded to the interior angle of the target shape. Item 1. Press molding method according to item 1. 3. The press-formed product has a hat cross-sectional shape, having vertical wall portions on both sides of a top plate portion, and having the bottom flange portion continuous to the vertical wall portion. Press molding method. According to claim 1 or 2, the press-formed product has a Z-shaped cross section having a vertical wall portion on one side of the top plate portion and the bottom flange portion continuous to the vertical wall portion. Press molding method described. a top plate part, a vertical wall part continuous to the top plate part, a bottom flange part continuous to the vertical wall part and located on the opposite side of the top plate part, and a longitudinal front part of the vertical wall part. and/or a method for manufacturing a press-formed product having a vertical flange portion continuous with the vertical wall portion at the rear, and a corner flange portion provided between the vertical flange portion and the bottom flange portion,
The bottom flange portion, the vertical flange portion, and the corner flange portion are included, and the angle between the vertical wall portion and the bottom flange portion and/or the angle between the vertical wall portion and the vertical flange portion is an angle of a target shape. a first step of press-molding an intermediate molded product having a larger intermediate flange;
A method for producing a press-formed product, comprising a second step of press-forming the angle between the intermediate flange and the vertical wall portion, which is larger than the angle of the target shape in the first step, to the angle of the target shape. .