WO2017187679A1

WO2017187679A1 - Press molding method

Info

Publication number: WO2017187679A1
Application number: PCT/JP2017/002471
Authority: WO
Inventors: 遼揚場; 亮伸石渡
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2016-04-28
Filing date: 2017-01-25
Publication date: 2017-11-02
Also published as: KR20180119672A; CN108778548A; JP2017196646A; KR102105348B1; JP6152911B1; CN108778548B

Abstract

The press molding method pertaining to the present invention comprises molding a press-molded article (70) which is hat-shaped in cross section and has a top plate part, a vertical wall part, and a flange part, the press molding method characterized by having: a first molding step for molding a metallic sheet stock (50) into a temporary molded article (60) using a first mold 1 having top plate molding parts (11, 21), vertical wall molding parts (13, 23), and flange molding parts (15, 25), the vertical wall molding parts (13, 23) molding chevron-shaped vertical wall parts, the cross section of each of which in a molding direction is convex outward in comparison with the target shape of the press-molded article (70); and a second molding step for molding the temporary molded article (60) using a second mold (3) having top plate molding parts (31, 41), vertical wall molding parts (33, 43), and flange molding parts (35, 45) having the same shape as the target shape of the press-molded article (70).

Description

Press forming method

The present invention relates to a press-forming method of a press-forming part (part) having a hat-shaped cross section, and in particular, excellent in shape freezing property that suppresses springback. The present invention relates to a press molding method.

In recent years, high-strength steel sheets have been increasingly used for automobile parts in order to reduce the weight of automobile bodies due to environmental problems. For the production of automobile parts, press molding with excellent production cost is often used. However, a high-strength steel plate has a greater elastic recovery (springback) after press forming than a low-strength steel plate, making it difficult to obtain a target shape part by press forming. Further, increasing the strength of the steel sheet used for the purpose of reducing the weight of the vehicle body is synonymous with reducing the thickness of the sheet. However, the greater the springback of the thinner the steel sheet, the more the above problem is spurred.

Therefore, there is a strong demand for the development of a press molding method for suppressing springback. In particular, in the case of a press-formed part with a cross-sectional hat shape, which is often found in automobile skeletal parts to which high-strength steel sheets are applied, the opening width of the side wall portion of the press-formed part (opening) by springback In many cases, the opening of the wall is deformed so that the width is wider than the opening width of the target shape, and it is significant to suppress the opening of the wall by the spring back.

So far, several press forming methods for suppressing the wall opening due to the spring back of the press-formed part having a hat-shaped cross section have been disclosed.

In Patent Document 1, provisional molding is formed in which the distance between the lateral wall side ends of the vertical wall part in the molding target shape is shorter than the distance between the lateral wall side end parts of the vertical wall part of the molding target shape of the molding member. A technique is disclosed in which a body is drawn and then a vertical wall portion is pushed out in a target shape. According to this technique, the vertical wall portion of the temporary molded body can be reverse-bended and bent back, and the wall camber existing in the vertical wall portion of the temporary molded body. It is said that the wall opening can be suppressed by eliminating the wall warping after releasing the die from the tool of press forming. Yes.

In Patent Document 2, as in Patent Document 1, an intermediate forming part is formed so that the bottom of the punch is smaller than the target shape, and the target shape is formed in the next process. Thus, a technique is disclosed in which the deformation that cancels the wall opening caused by the springback after the mold release is left.

JP 2008-307557 A Japanese Patent No. 4681420

In order to suppress the wall opening of the press-molded part with a hat-shaped cross section, for example, how to relieve the stress caused by the camber applied to the vertical wall part that is bent back in deep drawing, Alternatively, it is important to apply stress and deformation that cancel each other to an appropriate part.

In the press molding methods disclosed in Patent Document 1 and Patent Document 2, the compressive stress applied to the inner side of the vertical wall portion in the first molding process and the tensile stress applied to the outer side are prevented from acting. After forming an intermediate forming part to which stress or deformation that offsets the driving stress (opening stress) of the wall opening is applied, the vertical shape is further extended in the second forming process to achieve the target shape. The cross-section hat-shaped press-molded part is molded, but in the second molding process, the inner compressive stress and the outer tensile stress in the overhang of the vertical wall part are added, and the wall warp cannot be eliminated, Since the angle change with respect to the target shape of the flange part (flange portion) and the vertical wall part of the molded press-molded part is not considered, it joins with other parts via the flange part. There have been cases where Saishi the problem occurs.

The present invention has been made in view of the above problems, and its object is to suppress the opening of the wall due to the spring back and weld it to other parts when a part with a hat-shaped cross section is formed. It is providing the press molding method which can suppress the angle change of the flange part.

In order to solve the above problems and achieve the object, a press molding method according to the present invention includes a top plate portion, a vertical wall portion continuous from the top plate portion, and a continuous from the vertical wall portion. A press-molded part having a hat-shaped cross section having a flange portion, and having a top plate forming portion, a vertical wall forming portion, and a flange forming portion, and the top plate forming portion and the flange forming portion are The top plate portion and the flange portion having the same shape as the target shape of the press-formed part are formed, and the vertical wall forming portion has a cross section in the forming direction that is convex outward compared to the target shape of the press-formed part. A first molding step of molding a metal sheet into a temporary molded part using a first mold for molding a mountain-shaped vertical wall, and a ceiling having the same shape as the target shape of the press-molded part Top plate forming part and vertical wall forming part for forming plate part, vertical wall part and flange part Using a second mold having a flange forming portion, and is characterized in that a second forming step for form molding the temporary molded part.

Further, the press molding method according to the present invention is characterized in that, in the above-mentioned invention, the press-molded part is formed linearly in the longitudinal direction.

The press molding method according to the present invention is characterized in that, in the above-mentioned invention, the first molding step is molded by foam forming.

Further, the press molding method according to the present invention is the length of the ridge line from the punch shoulder (shoulder portion) to the die shoulder in the temporary molded part molded in the first molding step. Is the same as the length of the ridge line from the punch shoulder portion to the die shoulder portion in the press-formed part formed in the second forming step.

In the press molding method according to the present invention, a press-molded part having a cross-sectional hat shape having a top plate portion, a vertical wall portion continuous from the top plate portion, and a flange portion continuous from the vertical wall portion is formed. A top plate forming portion, a vertical wall forming portion, and a flange forming portion, wherein the top plate forming portion and the flange forming portion have the same shape as a target shape of the press-molded part, and the vertical wall A first molding step of molding a temporary molded part using a first mold that molds a vertical wall portion having a convex outer shape in cross section as compared with a target shape of the press molded part; By having a second molding step of molding the temporary molded part using a second mold having a top plate molding part, a vertical wall molding part and a flange molding part having the same shape as the target shape of the press molded part. The temporary molded part with the reverse bend applied to the vertical wall is made the target shape. By forming, the deformation of the vertical wall portion after the release of the press-molded part and the angle change of the punch shoulder portion connecting the top plate portion and the vertical wall portion are offset, and the mold release The deformation of the rear vertical wall portion and the change in the angle of the shoulder portion of the die connecting the vertical wall portion and the flange portion cooperate with each other, so that By changing the radius of curvature (curvature radius), it is possible to adjust the angle of the wall opening and flange of the press-molded part. A molded part can be obtained.

FIG. 1 is a diagram for explaining a press molding method according to an embodiment of the present invention, in which (a) is a first molding step and (b) is a second molding step. FIG. 2 is an external view of a press-molded part to be molded in the embodiment of the present invention. 3A and 3B are diagrams for explaining a mold used for conventional press molding. FIG. 3A is a diagram illustrating a mold used for draw molding, and FIG. 3B is a diagram illustrating a mold used for foam molding. FIG. 4 is an explanatory diagram for explaining a spring back generated in a press-formed part formed by a conventional press-forming method. FIG. 5 is a diagram for explaining a temporary molded part molded by the press molding method according to the present embodiment. FIG. 6 is an explanatory diagram of a mold used in the first molding step of the press molding method according to the present embodiment. FIG. 7 is a diagram for explaining the shape of a press-molded part to be molded in this embodiment. FIG. 8 is a diagram showing a cross-sectional shape of a press-formed part formed by the press-forming method according to the present invention.

The press molding method according to the embodiment of the present invention includes a top plate portion 71, a vertical wall portion 75 continuous from the top plate portion 71, and a flange portion 79 continuous from the vertical wall portion 75, as shown in FIG. As shown in FIG. 1, a metal base plate 50 is temporarily formed using a first die 1 having a die 10 and a punch 20. A first molding step for molding the component 60 and a second molding step for molding the temporary molded component 60 into the press-molded component 70 using the second mold 3 having the die 30 and the punch 40 are included.

Hereinafter, after describing the press-molded part 70 to be molded in the present embodiment, each step of the press-molding method according to the present embodiment will be described in detail.

<Press-formed parts>
As shown in FIG. 2, the press-molded component 70 includes a top plate portion 71, a vertical wall portion 75 that continues from the top plate portion 71 through a punch shoulder portion 73, and a vertical wall portion 75 through a die shoulder portion 77. The cross-sectional hat shape has a continuous flange portion 79 and is linearly formed in the longitudinal direction.

Conventionally, a press-molded part 70 as shown in FIG. 2 is a form using a draw mold (drawing) using a mold 80 shown in FIG. 3 (a) or a mold 90 shown in FIG. 3 (b). It was formed by molding (bending).

In the case of draw molding, the die 80 is composed of a die 81, a punch 83, and a blank holder 85. First, the metal base plate (blank) is held between the die 81 and the blank holder 85 and then punched later. Drawing is performed by moving 83 relative to the die 81.

On the other hand, in the case of foam molding, the mold 90 is composed of a die 91 and a punch 93, and is bent by sandwiching a metal base plate by relative movement of the die 91 and the punch 93.

In any molding method, the molded press-molded part 70 has springs for both the opening of the punch shoulder 73 (increase in the opening angle between the top plate 71 and the vertical wall 75) and the wall warp of the vertical wall 75. By combining the back, a wall opening that deforms so that the opening width of the left and right vertical wall portions 75 is larger than the opening width of the target shape occurs.

Especially, when the metal base plate to be used is a high-strength steel plate or when the plate thickness is thin, the above-described wall opening is remarkable, and the press-formed part 70 greatly deviates from the target shape. *

Further, in order to join the press-molded part 70 having a cross-sectional hat shape to another part by spot welding, it is necessary to match the position and angle of the flange part 79 with respect to the joining surface (flange part) of the other part. However, in the press-formed part 70 in which the wall opening due to the spring back as shown in FIG. 4 occurs, the position of the flange portion 79 is changed and the angle with respect to the joint surface is changed. Some parts could not be joined.

Therefore, the press-molded part 70 is required to be press-molded in which the angle change of the flange portion 79 is suppressed in addition to the wall opening.

<First molding step>
As shown in FIG. 1A, the first molding step uses a first mold 1 having a die 10 and a punch 20, and presses a metal base plate 50 with a pad 17, for example, In this process, the die 10 and the punch 20 have top

plate forming portions

11, 21, vertical

wall forming portions

13 and 23, and

flange forming portions

15 and 25, respectively.

The top

plate forming portions

11 and 21 and the

flange forming portions

15 and 25 are for forming the top plate portion 61 and the flange portion 69 having the same shape as the target shape of the press-formed part 70 (see FIG. 5).

On the other hand, the vertical

wall forming portions

13 and 23 form a mountain-shaped vertical wall portion 65 having a convex section outward in the forming direction as compared with the press-formed part 70 having a target shape (FIG. 5). reference).

In the present embodiment, the vertical wall portion 65 includes an upper flat portion 65a that continues from the top plate portion 61 via the punch shoulder portion 63, and a bent portion 65b that continues from the upper flat portion 65a. And the lower flat surface portion 65c that connects the bent portion 65b and the die shoulder portion 67, the first mold 1 has an upper surface for forming the upper flat surface portion 65a as shown in FIG. It has

plane molding parts

13a and 23a, bending

molding parts

13b and 23b that mold the bending part 65b, and lower

plane molding parts

13c and 23c that mold the lower plane part 65c.

The vertical wall portion 65 formed by the vertical

wall forming portions

13 and 23 is provided with a bending in the direction opposite to the wall warp caused by the springback, which was observed when forming by the conventional press forming method. Also, as shown in FIG. 5, the angle α of the punch shoulder 63 is more open than the punch shoulder of the target shape, and the angle β of the die shoulder 67 is closed than the die shoulder of the target shape. .

<Second molding step>
In the second molding step, the temporary molding part 60 is pressed by the pad 37 using the second mold 3 having the die 30 and the punch 40 as shown in FIG. The die 30 and the punch 40 have top

plate forming portions

31 and 41, vertical

wall forming portions

33 and 43, and

flange forming portions

35 and 45, respectively.

The top

plate forming portions

31, 41, the vertical

wall forming portions

33, 43, and the

flange forming portions

35, 45 are all the same shape as the target shape of the press-formed part 70, and are temporarily formed in the first forming step. The component 60 is molded into a press-molded component 70 having a top plate portion 71, a vertical wall portion 75, and a flange portion 79 having the same shape as the target shape.

The reason why the wall-opening of the press-formed part 70 and the angle change of the flange portion 79 due to the spring back can be suppressed by the press-forming method according to the present embodiment will be described below.

As described above, when the

conventional molds

80 and 90 as shown in FIG. 3 are used for molding, as shown in FIG. A wall opening due to both the angle change at 73 occurs.

This springback is caused by a difference in residual stress (inside: compressive stress, outside: tensile stress) generated between the inside and outside of the vertical wall portion 75 in the forming process in either draw forming or foam forming. To do.

Therefore, for the wall warp in the vertical wall portion 75, a fold remaining (reverse bending) is applied to the vertical wall portion 65 in the opposite direction to the wall warp in the first forming step to form the temporary molded part 60. In the subsequent second molding step, the direction of the residual stress generated on the inner side and the outer side of the vertical wall portion 75 of the press-formed component 70 is formed by forming the vertical wall portion 65 of the temporary molded component 60 into the vertical wall portion 75 of the target shape. (Inside: tensile stress, outside: compressive stress). Thereby, after mold release, the vertical wall part 75 deform | transforms in the direction opposite to the conventional wall curvature, and contributes to reduction of wall opening.

On the other hand, the punch shoulder 73 is further bent in the direction in which the punch shoulder 63 formed in the first forming step is closed in the second forming step (the angle α of the punch shoulder 63 shown in FIG. 5 decreases). Therefore, when the temporary molded part 60 is molded into the target-shaped press-molded part 70 in the second molding step, the punch shoulder 73 is deformed in the direction of opening (increasing angle) by the springback.

This increase in the angle of the punch shoulder 73 contributes to an increase in the wall opening of the portion corresponding to the vertical wall portion 65 of the first molding step in the vertical wall portion 75 of the second molding step, but corresponds to the vertical wall portion 65. Since the deformation of the portion that contributes to the reduction of the wall opening, the wall opening of the press-formed part 70 is suppressed by offsetting these, and the difference between the position of the flange portion 79 and the target shape can be reduced.

Further, the die shoulder portion 67 formed in the first forming step is opened to form the lower plane portion 65c into the vertical wall portion 75 in the second forming step (the angle β of the die shoulder portion 67 shown in FIG. In the second molding step, when the temporary molded component 60 is molded into the press-formed component 70 having the target shape, the die shoulder 77 in the second molding step is closed (the angle is reduced) by the springback. Transforms into

Although the decrease in the angle at the die shoulder 77 affects the increase in the angle from the joint surface of the flange portion 79, the joint surface of the flange portion 79 is formed by the molding of the vertical wall portion 75 and the flange portion 79 described above. Reduce the angle with respect to. Therefore, the decrease in the angle at the die shoulder 77 and the deformation at the vertical wall 75 cooperate to suppress an increase in the angle of the flange 79 with respect to the joint surface.

That is, according to the present invention, by applying reverse bending to the vertical wall portion 75 of the press-molded component 70, the spring back in the vertical wall portion 75 after releasing the press-molded component 70 opens the wall (the position of the flange portion 79). ) And an increase in the angle of the flange portion 79.

Here, the first mold 1 used in the first molding step in the present embodiment is composed of upper planar molded

portions

13a and 23a, bent molded

portions

13b and 23b, and lower planar molded

portions

13c and 23c. Since the vertical molded part 60 has the vertical

wall forming parts

13 and 23, the temporary molded part 60 has an outer side where the upper flat part 65a and the lower flat part 65c of the vertical wall part 65 are connected by a bent part 65b as shown in FIG. A convex mountain shape.

And when the deformation | transformation amount after mold release in the considerable part of the bending part 65b of the press molding component 70 is the same, the position in the shaping | molding height direction from the flange part 69 of the bending part 65b to the top-plate part 61 direction is so high. Since the position change of the lower end of the vertical wall portion 75 (in the vicinity of the flange portion 79 of the vertical wall portion 75) due to the deformation after the mold release in the second molding step becomes large, the bent portion 65b applied in the first molding step is It is considered that the higher the position, the more advantageous for suppressing the wall opening.

Further, the larger the radius of curvature R (fillet radius) of the bent portion 65b is, the wider the range of the vertical wall portion 65 that is subjected to reverse bending in the second forming step is, so that the wall opening of the press-formed part 70 is suppressed. Is considered to be highly effective. On the other hand, if the radius of curvature R of the bent portion 65b is too small, a crease remains in the vertical wall portion 75 of the press-formed part 70, which is not preferable.

Therefore, a press-molded part obtained by molding the temporary molded part 60 in the second molding step by appropriately changing the position H and the radius of curvature R in the molding height direction from the flange 69 to the top plate 61 in the bent part 65b. The wall opening caused by the spring back 70 and the angle change of the flange 79 can be adjusted.

The effect of suppressing the wall opening and the angle change of the flange portion 69 by changing the position H in the molding height direction and the curvature radius R of the bent portion 65b will be demonstrated in Examples described later.

The temporary molded part 60 molded in the first molding step of the press molding method according to the present invention is molded into a shape recessed inward from a temporary line connecting the punch shoulder 63 and the die shoulder 67. Otherwise, there may be no flat portion such as the upper flat portion 65a and the lower flat portion 65c, and the entire vertical wall portion 65 may be curved in a convex mountain shape.

Further, the press-molded part 70 to be molded in the above description is formed linearly in the longitudinal direction, and the longitudinal wall portion 65 of the temporary molded part 60 protrudes outward in the longitudinal direction. However, in the present invention, only a part of the vertical wall portion of the temporary molded part is protruded outward in the first molding step. It does not exclude what is formed into a mountain shape.

Furthermore, in the press molding method according to the present embodiment, the first molding step is molded by foam molding, but the first molding step may be performed by draw molding.

The difference when molded by foam molding or draw molding in the first molding step will be described in Examples described later.

In the above description, the metal base plate 50 is pressed and formed by the pad 17 in the first forming step (see FIG. 6), and the temporary formed part 60 is pressed and formed by the pad 37 in the second forming step. However, the press molding method according to the present invention may perform the first molding process and the second molding process without using the

pads

17 and 37.

Furthermore, in the above description, as shown in FIG. 5, the molding height of the temporary molded part 60 molded in the first molding process is the molding height of the press-molded part 70 having the target shape molded in the second molding process. In this case, the length of the ridge line from the punch shoulder 63 to the die shoulder 67 (see FIG. 5) in the temporary molded part 60 is determined from the punch shoulder 73 in the press-formed part 70. It is longer than the length of the ridge line reaching the die shoulder 77 (see FIG. 7).

However, the press molding method according to the present invention is not limited to the one in which the molding height of the temporary molding part and the molding height of the press molding part of the target shape are the same, but the temporary molding part molded in the first molding step The length of the ridge line from the punch shoulder to the die shoulder in the temporary shape is equal to the length of the ridge line from the punch shoulder to the die shoulder in the target shape of the press-formed part formed in the second forming step. It may be formed (draw molding or foam molding) by setting the molding height of the molded part lower than the molding height of the press molded part.

Then, by setting the length of the ridge line from the punch shoulder to the die shoulder in the temporary molded part and the length of the ridge line from the punch shoulder to the die shoulder in the press-molded part, the molding is performed in the first molding step. Since the molding part (part) of the flange part of the temporary molded part and the flange part of the press-molded part molded in the second molding process coincide with each other, molding closer to the target flange part is possible. Good.

In order to confirm the operational effects of the press molding method according to the present invention, CAE analysis of press molding and spring back was performed, and the results will be described below.

In the present embodiment, a press-molded part 70 having a hat-shaped cross section shown in FIG. 7 is used as a molding target shape, and the metal base plate 50 is temporarily formed by using the first mold 1 as shown in FIG. A press molding analysis is performed between the first molding step of molding into the first molding step and the second molding step of molding the temporary molded part 60 into the press molded part 70 using the second mold 3 as shown in FIG. It was.

Then, a spring back analysis was performed after the mold release of the press-molded part 70 molded to the bottom dead center in the second molding step.

As shown in FIG. 7, the dimensions of the target shape of the press-formed part 70 are as follows. The width of the top plate portion 71 is 60 mm, the molding height is D = 60 mm, the vertical wall angle is 70 °, and the curvature radius of the punch shoulder 73 is set. R = 5 mm.

The metal base plate 50 used for forming the press-formed part 70 was a steel plate having a thickness t = 1.2 mm and a tensile strength of 1180 MPa.

In the press molding analysis of this example, the first molding process was molded by foam molding or draw molding. Further, as shown in FIG. 5, the vertical wall portion 65 of the temporary molded part 60 molded in the first molding step has an outwardly convex mountain shape composed of an upper plane portion 65a, a bent portion 65b, and a lower plane portion 65c. It was. The dimensions of the temporary molded part 60 are such that the angle of the die shoulder 67 is β = 90 °, the molding height is D = 60 mm, the position H and the radius of curvature R (fillet diameter) of the bent portion 65b in the molding height direction. The analysis was performed by changing (see FIG. 5).

In this example, the wall opening by the spring back of the press-formed part 70 and the angle of the flange portion 79 were obtained. The wall opening of the press-formed part 70 was evaluated by the amount of change (wall opening amount ΔW) of the distance Wo between the left and right vertical wall portions 75 at a position 55 mm below the top height from the top plate portion 71 (FIG. 4). FIG. 7). Further, the angle of the flange portion 79 was evaluated by a flange angle θ based on the joint surface of the flange portion 79 having a target shape (see FIG. 4).

FIG. 8 shows a cross-sectional shape obtained by the springback analysis of the press-formed part 70 formed by the press forming analysis using the first forming step as the form forming.

FIG. 8 shows a press-formed part 70 when the position in the molding height direction of the bent portion 65b of the temporary molded part 60 formed in the first forming step is H = 30 mm and the radius of curvature of the bent portion 65b is R = 30 mm. This is an analysis result of the cross-sectional shape. Compared with the target shape of the press-formed part 70, the vertical wall portion 75 has a slightly remaining mountain shape formed in the first forming step, but the position and angle of the flange portion 79 are substantially the same as the target shape. was gotten.

Table 1 shows that the first molding process is foam molding, press molding analysis is performed by changing the position H in the molding height direction and the radius of curvature R of the bent portion 65b of the temporary molded component 60, and the press molding analysis is performed. The results of the wall opening amount ΔW and the flange angle θ obtained by the springback analysis of the press-formed part 70 are shown.

In Table 1, no countermeasure is the result of using the conventional press molding method (conventional example, see FIG. 3B), and conditions a to h are the results of using the press molding method according to the present invention (invention example). It is.
Compared with the conventional example, the invention example was clearly excellent in that the wall opening amount ΔW and the flange angle θ (see FIG. 4) were reduced.

In the invention example, regarding the influence of the difference in the height position H of the bent portion 65b on the wall opening amount ΔW, the position H = 15 mm at the curvature radius R = 30 mm (relative position H / D = 0.25 with respect to the molding height D). When the condition d of position H = 30 mm (relative position H / D = 0.50) and the condition h of position H = 45 mm (relative position H / D = 0.75) are compared, the position H of the bent portion 65b (relative position) It can be seen that the wall opening amount ΔW decreases with an increase in (H / D).

Further, regarding the difference in the curvature radius R of the bent portion 75b, the condition a where the curvature radius R = 5 mm, the condition b where the curvature radius R = 10 mm, the condition c where the curvature radius R = 20 mm, and the condition d where the curvature radius R = 30 mm are compared. Then, it can be seen that as the radius of curvature R increases, both the wall opening amount ΔW and the flange angle θ decrease and approach the target shape. The same applies to the condition e where the radius of curvature R = 10 mm, the condition f where the radius of curvature R = 20 mm, and the condition g where the radius of curvature R = 30 mm.

From these results, within the range of the position H and the radius of curvature R of the bent portion 65b shown in Table 1, the condition that the position H of the bent portion 65b is 30 mm (relative position H / D = 0.50) and the radius of curvature R is 30 mm. As a result, g was the best match with the target shape for both the wall opening amount ΔW and the flange angle θ.

Table 2 shows that the first molding process is draw molding, and the press molding analysis is performed by changing the position H in the molding height direction and the radius of curvature R of the bent portion 65b of the temporary molded part 60. The results of the wall opening amount ΔW and the flange angle θ obtained by the springback analysis of the press-formed part 70 are shown.

In Table 2, no countermeasure is the result of using the conventional press molding method (conventional example, see FIG. 3A), and conditions i to t are the results of using the press molding method according to the present invention (invention example). It is.
From Table 2, it can be seen that, compared with the conventional example, the wall opening amount ΔW and the flange angle θ are clearly reduced in the inventive example, which is a good result.

In the example of the invention, regarding the influence of the difference in the height direction position H of the bent portion 65b on the wall opening amount ΔW, the curvature radius R = 30 mm at H = 15 mm (relative position H / D = 0.25 in the molding height direction). Comparing condition l, condition o with H = 30 mm (relative position H / D = 0.50), and condition r with H = 45 mm (relative position H / D = 0.75), the position H of the bent portion 65b (relative position H / D It can be seen that the wall opening amount ΔW decreases with an increase in).

Further, regarding the difference in the curvature radius R of the bent portion 65b, when the condition i of R = 5 mm, the condition j of R = 10 mm, the condition k of R = 20 mm, and the condition l of R = 30 mm are compared, the curvature radius R becomes larger. It can be seen that both the wall opening amount ΔW and the flange angle θ decrease, and approach the target shape. The same applies to the comparison of the condition m of R = 10 mm, the condition n of R = 20 mm, the condition o of R = 30 mm, the condition p of R = 10 mm, the condition q of R = 20 mm, and the condition r of R = 30 mm. It is.

From these results, within the range of the position H and the radius of curvature R of the bent portion 65b shown in Table 2, the condition o where the position H of the bent portion 65b is 30 mm and the radius of curvature R is 30 mm is the wall opening amount ΔW and the flange. The angle θ was the best match with the target shape.

Further, comparing the case where the first molding process is foam molding (Table 1) and the case where draw molding is performed (Table 2), when the position H of the bent portion 65b and the radius of curvature R are equal, the foam molding method However, both the flange angle θ and the wall opening amount ΔW were better than those obtained by the draw molding.

As described above, in the press molding method according to the present invention, by forming a mountain-shaped temporary molded part that protrudes outward from the target shape, and then molding the target-shaped press molded part, the wall opening by the springback and The angle change of the flange part can be reduced, and the angle of the flange part of the wall opening and the press-formed part can be adjusted by appropriately changing the position and the radius of curvature of the bent part given to the temporary molded part. Indicated. Moreover, it was demonstrated that the spring back can be more effectively suppressed by forming the first forming step by foam forming.

Further, the first molding step is formed as a foam molding, and a temporary molding component 60 (see FIG. 5) is molded. In the second molding step, the length of the ridge line from the punch shoulder 63 to the die shoulder 67 of the temporary molding component 60 is increased. The second mold is changed in the same case where the length of the ridge line from the punch shoulder 73 to the die shoulder 77 of the press-molded part 70 (see FIG. 7) formed in the second molding step is different. And press-molded. The position of the bent portion 65b of the temporary molded part 60 was H = 30 mm, and the radius of curvature was R = 20 mm.

As a result, the length of the ridge line from the punch shoulder 63 to the die shoulder 67 in the temporary molded part 60 molded in the first molding process and the punch shoulder 73 in the press molded part 70 molded in the second molding process. When the length of the ridge line reaching the die shoulder 77 has a difference of Δ5 mm, the flange angle of the press-formed part 70 is 3.6 ° and the wall opening amount ΔW is 1.6 mm, whereas the length of the ridge line is the same. In the case of (a difference of Δ0 mm), the flange angle was 3.0 °, and the wall opening amount ΔW was 1.2 mm.

Therefore, by making the length of the ridge line in the temporary molded part 60 molded in the first molding process the same as the length of the ridge line of the press molded part 70 molded in the second molding process, both the wall opening and the flange angle are set. It was proved that the springback can be more effectively suppressed with good results.

According to the present invention, it is possible to provide a press molding method for suppressing the wall opening of the press molded part due to the spring back when the press molded part having a hat-shaped cross section is press molded.

DESCRIPTION OF SYMBOLS 1 1st metal mold | die 3 2nd metal mold | die 10 Die 11 Top plate shaping | molding part 13 Vertical wall shaping | molding part 13a Upper plane shaping | molding part 13b Bending shaping | molding part 13c Lower side shaping | molding part 15 Flange shaping | molding part 17 Pad 20 Punch 21 Top plate Molding part 23 Vertical wall molding part 23a Upper plane molding part 23b Bending molding part 23c Lower plane molding part 25 Flange molding part 30 Die 31 Top plate molding part 33 Vertical wall molding part 35 Flange molding part 37 Pad 40 Punch 41 Top panel molding Part 43 Vertical wall forming part 45 Flange forming part 50 Metal base plate 60 Temporary forming part 61 Top plate part 63 Punch shoulder part
65 Vertical wall portion 65a Upper flat surface portion 65b Bending portion 65c Lower flat surface portion 67 Die shoulder portion 69 Flange portion 70 Press molded part 71 Top plate portion 73 Punch shoulder portion 75 Vertical wall portion 77 Die shoulder portion 79 Flange portion 80 Mold ( Conventional technology)
81 Die 83 Punch 85 Blank holder 90 Mold (Conventional technology)
91 Die 93 Punch

Claims

A press molding method for molding a press-molded part having a cross-sectional hat shape having a top plate portion, a vertical wall portion continuous from the top plate portion, and a flange portion continuous from the vertical wall portion,
A top plate forming portion, a vertical wall forming portion, and a flange forming portion, and the top plate forming portion and the flange forming portion include a top plate portion and a flange portion having the same shape as a target shape of the press-formed part. The vertical wall forming portion is formed by using a first die that forms a mountain-shaped vertical wall portion having a cross section in the forming direction that is convex outward compared to the target shape of the press-formed part. A first molding step of molding the plate into a temporary molded part;
Using a second mold having a top plate forming portion, a vertical wall forming portion, and a flange forming portion for forming a top plate portion, a vertical wall portion, and a flange portion having the same shape as the target shape of the press-formed part. And a second molding step of foam-molding the temporary molded part.
The press-molding method according to claim 1, wherein the press-molded part is formed in a linear shape in the longitudinal direction.
The press molding method according to claim 1 or 2, wherein the first molding step is performed by foam molding.
The length of the ridge line from the punch shoulder part to the die shoulder part in the temporary molding part molded in the first molding process is changed from the punch shoulder part to the die shoulder part in the press molded part molded in the second molding process. The press molding method according to any one of claims 1 to 3, wherein the length is the same as the length of the ridge line to reach.