JP2017042825A - Manufacturing method for molded component with stretch flange - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a molded component with a stretch flange which is manufactured together with molding of the stretch flange, at a low molding load while suppressing split of the stretch flange.SOLUTION: The manufacturing method, which manufactures a molded component with a stretch flange which comprises a top plate part 3 having a first concave outer peripheral edge part 3a and a flange part 7 which continues to a vertical wall part 5, bends toward the top plate part 3 and has a second concave outer peripheral edge part 7a, comprises: a first step of drawing-molding a part 5A of the vertical wall part 5 along the first concave outer peripheral edge part 3a and forming at the same time a bent-shape part 8, which has a ridge line 9 extended along the second concave outer peripheral edge part 7a and is bent toward a thickness direction, outside a position becoming flange part 7, by press-molding a blank material: a second step of fixing the position becoming the top plate part 3 and bending-molding the vertical wall part 5 and the flange part 7 after the first step; and a third step of trimming an outer site of the flange part 7.SELECTED DRAWING: Figure 1

Description

  The present invention has a concave outer peripheral edge that is curved so that a part of the outer peripheral edge is indented inward on the top plate, thereby manufacturing an elongated flange-molded part in which the flange is manufactured with stretch flange molding. Regarding technology. As such stretch flange molded parts, for example, press-molded parts used as body frame parts of automobiles, and parts having an L-shaped part or a T-shaped part in plan view can be exemplified. The present invention is a technique that is particularly suitable for production by press molding using a super high tensile material of 980 MPa or more as a raw material.

Parts having an L-shaped part or T-shaped part such as a front pillar reinforcement or a center pillar reinforcement (refer to FIGS. 8 and 9), which are car body skeleton parts, are formed into flat metal plates (blank materials). In the case of manufacturing by press molding, generally drawing or bending is employed.
Drawing is usually performed using a mold consisting of a punch, a die, and a blank holder. The metal plate is made by reducing the distance between the punch and the die while holding the periphery of the metal plate with the die and the blank holder. This is a method of drawing the material. Bending is usually performed by using a die composed of a punch, a pad, and a die, and bending is performed by relatively moving the die while the metal plate is sandwiched between the punch and the pad.

  If a curved portion such as an L-shaped portion or a T-shaped portion that is bent sharply is formed only by drawing as described above, cracks and wrinkles are more likely to occur as the vertical wall portion becomes higher. In particular, in recent years, the strength of a metal plate that is a molding material has been increasing in order to achieve improved safety and weight reduction of an automobile body. Therefore, it is important to take measures against cracking and wrinkling during press forming.

The part where cracks are particularly likely to occur due to the above press molding is the stretch flange molded part of the curved part. In this part, the material end face is deformed in a state where the material flows while being stretched in the peripheral direction during the drawing.
In contrast, there is a technique described in Patent Document 1. In the technology described in Patent Document 1, when a part having an L-shape is press-molded, a vertical wall portion and a flange are formed while sliding a part of a metal material on a portion corresponding to a top plate portion in a die mold. The part is formed.

  And in this patent document 1, since the site | part corresponding to the L-shaped lower part of an L-shaped part is drawn toward a vertical wall part, it is reduced that excessive tension | tensile_strength generate | occur | produces in a flange part, It is described that generation | occurrence | production can be prevented (refer paragraph number 0009 of patent document 1).

JP 2012-245536 A

However, in Patent Document 1, since the metal material corresponding to a part of the top plate portion is slid, a stress concentration portion is formed on the end surface of the metal material. Likely to happen. For this reason, the method of Patent Document 1 is difficult to apply to a steel plate having high strength.
In addition, since the forming load becomes high in the drawing, when an ultra-high tensile material of 980 MPa or more is to be produced only by drawing, there is a possibility that the load of the press is insufficient.

  The present invention has been made paying attention to such a problem, and a stretch flange molded part manufacturing method capable of manufacturing a stretch flange molded part manufactured with stretch flange molding with a low molding load while suppressing stretch flange cracking. It is an object.

  In order to solve the problem, a method of manufacturing an elongated flange molded part according to one aspect of the present invention includes a top plate portion having a concave outer peripheral edge curved so that a part of the outer peripheral edge is recessed inward, and the top plate A stretch flange molded part manufacturing method for manufacturing a stretch flange molded part comprising: a vertical wall portion continuous to the concave outer peripheral edge portion of a portion; and a flange portion bent continuously toward the top plate portion side of the vertical wall portion In the blank material, a part of the vertical wall portion is drawn along the concave outer peripheral edge portion, and the outer peripheral edge portion of the flange portion is positioned outside the position of the flange portion. A first step of forming a bent shape portion extending along the ridge line and bent in the thickness direction, and after the first step, the position of the top plate portion is fixed and the vertical wall portion and the flange portion The second step of bending and forming the frame after the second step Characterized in that it comprises a third step of trimming the outer parts of di-section.

  According to the aspect of the present invention, even if an ultra-high tensile material having a strength level of 980 MPa or higher is used, by forming a part of the vertical wall part by drawing, the vertical wall part is formed by bending in the second step. Can be formed, and it is possible to prevent stretch flange cracking during the bending process in the second step by providing a bent part in advance so as to surround the outer peripheral edge of the flange part where stretch flange cracking is likely to occur. I can do it.

Furthermore, it becomes possible to manufacture with a low molding load by reducing the processing amount of the drawing.
From the above, according to the aspect of the present invention, even when a stretch flange molded part is manufactured with stretch flange molding from an ultra-high tensile material having a strength level of 980 MPa or higher, it is low while suppressing stretch flange cracking. It becomes possible to manufacture with a molding load.
Here, the flange portion is continuous to the first concave outer peripheral edge portion of the top plate portion via the vertical wall, and is bent toward the top plate portion side with respect to the vertical wall portion, so that it extends during manufacture by press molding. With flange forming.

  In addition, since the base plate (blank material) before press forming, which is the molding material, is usually formed by punching or laser processing, burrs and minute scratches remain on the material end face, and deformation is applied. When this happens, local stress concentration is likely to occur. Therefore, cracks called stretch flange cracks occur in the end face of the material during the forming, and in the case of an ultra-high tensile material (high-strength steel sheet having a strength level of 980 MPa or higher), the cracks propagate rapidly and large cracks are likely to occur. .

As a countermeasure against stretch flange cracking, there is a method of uniformly finishing the end face by machining or the like to prevent stress concentration. However, when mass-produced products are press-molded, it is necessary to machine the end faces one by one.
For this reason, in the aspect of the present invention, after the second step, the outer portion of the flange portion is trimmed to form the outer peripheral edge of the flange portion, and at the same time, the bent shape portion provided to suppress the above-mentioned stretch flange crack Has been removed.

It is a perspective view explaining the example of the stretch flange molding component which concerns on embodiment based on this invention. It is a perspective view explaining the intermediate part with a bending shape part which concerns on embodiment based on this invention. It is typical sectional drawing explaining the metal mold | die used at the 1st process concerning embodiment based on this invention. It is typical sectional drawing explaining the intermediate part with a bending shape part after the 1st process which concerns on embodiment based on this invention. It is a schematic diagram which shows the example of the bending shape part which concerns on embodiment based on this invention. It is a perspective view including the partial cross section of the metal mold | die used at the 2nd process concerning embodiment based on this invention. It is explanatory drawing of the 2nd process which concerns on embodiment based on this invention. It is a figure which shows A pillar. It is a figure which shows a center pillar.

Next, embodiments of the present invention will be described with reference to the drawings.
In the present embodiment, an example in which a stretch flange molded part having a portion that becomes a stretch flange molded portion is manufactured using an ultra-high tensile material of 980 MPa or higher as a base plate (blank material) before press molding will be described as an example. To do. The manufacturing method of the present invention can be applied even to a material made of a metal plate having a strength of 980 MPa or less.

In addition, as a flange molding component which has a site | part used as an elongate flange molding part, A pillar (refer FIG. 8) and a center pillar (refer FIG. 9) are mentioned, for example.
Further, in the following, description will be made by paying attention to a portion including a portion that becomes a stretch flange molded portion in a stretch flange molded part, and in each drawing, only the relevant portion is illustrated. Part 1 ". In the mold, only the part for forming the part is shown. Of course, other parts may be molded simultaneously.

  As shown in FIG. 1, the stretch flange molded portion 1 manufactured by the manufacturing method of the present embodiment includes a top plate portion 3 having a concave outer peripheral edge portion 3 a that is curved so that a part of the outer peripheral edge is recessed inward. The vertical wall portion 5 formed along the concave outer peripheral edge portion 3a of the top plate portion 3 is bent to the top plate portion 3 side continuously to the vertical wall portion 5, and a part of the outer peripheral edge is recessed inwardly. The flange portion 7 having the concave outer peripheral edge portion 7a curved as described above is provided, and the flange portion 7 is a portion that is stretched and flange-formed during press molding. In addition, although the shape of the outer periphery of the flange part 7 does not need to be a curved shape so that it may be dented, it is normally processed into the shape along the concave outer periphery 3a.

  Here, in the present embodiment, the concave outer peripheral edge 3a of the top plate portion 3 is also referred to as a first concave outer peripheral edge 3a, and the concave outer peripheral edge 7a of the flange portion 7 is also referred to as a second concave outer peripheral edge 7a. The contour shape of the first concave outer peripheral edge 3a and the contour shape of the second concave outer peripheral edge 7a are usually the same or similar. Of course, the curvature shape of the curve of the contour shape of the first concave outer peripheral edge portion 3a and the contour shape of the second concave outer peripheral edge portion 7a may be different.

The manufacturing method of the stretch flange molded part of the present embodiment includes three steps of a first step, a second step, and a third step, and the molding process is executed in this order.
In the first step, the first concave outer peripheral edge portion 3a of the top plate portion 3 is formed by drawing on a flat plate (blank material) before press forming, and the first concave outer peripheral edge portion 3a is formed on the first concave outer peripheral edge portion 3a. A part 5A of the vertical wall portion 5 is formed along the outer peripheral portion, and an intermediate part with a bent shape portion as shown in FIG. It is a process to do.

In FIG. 2, the material portion outside the bent shape portion 8 is omitted, and the position that becomes the second concave outer peripheral edge portion 7 a is indicated by a one-dot chain line. In other drawings, the material portion outside the bent shape portion 8 is omitted as appropriate for easy viewing.
In the second step, the remaining vertical wall portion 5 and the flange portion 7 are bent to form a second intermediate part.
In the third step, the bent shape portion 8 is trimmed from the second intermediate component, that is, the outer peripheral edge of the flange portion 7 is molded to obtain the above-described stretched flange molded component.
Hereinafter, each step will be described in detail.

[First step]
In the first step, the first concave outer peripheral edge portion 3a and a part 5A of the vertical wall portion 5 continuous to the first concave outer peripheral edge portion 3a are formed by drawing, and as shown in FIG. The bent portion 8 is formed at the outer peripheral position from the position to be. The bent shape portion 8 forms a bent shape portion 8 in which the ridge line 9 extends along the second concave outer peripheral edge portion 7a and is bent in the plate thickness direction. The bent shape part 8 of this embodiment consists of the step-shaped step shape bent in the plate | board thickness direction, for example.

<Mold for the first process>
An example of a mold used in the first step will be described with reference to FIG.
The mold for the first step used in the first step has a die 13 constituting an upper die, a punch 11 constituting a lower die, and a blank holder 12 as shown in FIG.
The shoulder 11a of the punch 11 and the shoulder 13b of the die 13 extend in the same shape as the contour shape of the first concave outer peripheral edge 3a.

Further, the opposing surface of the blank holder 12 and the die 13 extends along the second concave outer peripheral edge portion 7a which is the outer peripheral edge portion of the flange portion, at a portion facing the outer peripheral position of the flange portion 7 and Concave and convex step portions 12a and 13a that can be engaged with each other are formed.
The first process using the mold for the first process as described above will be described.
As shown in FIG. 3, the blank 10 has a plate thickness at the outer peripheral portion where the top plate portion 3 is located, that is, the first concave outer peripheral portion 3 a is located at the punch 11 and the shoulder portions 11 a and 13 b of the die 13. After being arranged between the punch 11 and the die 13 so as to face each other, the die 13 is relatively brought close to the blank holder 12 and the blank material 10 is sandwiched between the blank holder 12 and the die 13.

By holding the blank material 10 between the blank holder 12 and the die 13, the portion of the blank material sandwiched between the step portions 12a and 13a is bent stepwise in the plate thickness direction, and a bent shape portion as shown in FIG. 8 is formed.
The step height (projection height in the plate thickness direction) of the bent shape portion 8 to be molded is preferably 3 mm or more and 10 mm or less.

  In FIG. 2, the bent shape portion 8 is formed so that the ridge line 9 extends along the second concave outer peripheral edge portion 7a in parallel with or substantially parallel to the second concave outer peripheral edge portion 7a or the first concave outer peripheral edge portion 3a. The case is shown as an example. However, the bent shape portion 8 may not have the ridgeline 9 extending in parallel or substantially parallel to the second concave outer peripheral edge portion 7a or the first concave outer peripheral edge portion 3a. Further, the bent portion 8 may be formed intermittently along the second concave outer peripheral edge portion 7a. Moreover, the bent shape part 8 does not need to be formed so that the ridgeline 9 may extend along the entire circumference of the second concave outer peripheral edge part 7a. Of the first concave outer peripheral edge portion 3a, the curved shape portion has a large curvature of curvature, that is, a ridgeline 9 extends only along a portion where a flange flange crack is expected to occur by molding analysis and the vicinity thereof. 8 may be formed.

The bent portion 8 may be formed simultaneously with the drawing, but may be formed by another method separately.
Another example of the shape of the bent portion 8 is shown in FIG. FIG. 5 shows an example in which the bent shape portion 8 is bent so as to protrude downward, but the bent shape portion 8 may be bent so as to protrude upward.

  Next, with the blank material 10 held between the blank holder 12 and the die 13, the blank holder 12 and the die 13 are relatively moved along the punch 11, and the die portion 13 c facing the punch 11 is brought closer to the punch 11. Thus, the blank material 10 is drawn. As a result, the first concave outer peripheral edge 3a of the top plate 3 is formed, and a part 5A of the vertical wall 5 that is continuous with the first concave outer peripheral edge 3a along the first concave outer peripheral edge 3a. Form.

  The height of the part 5A of the vertical wall portion 5 formed in the first step is preferably 30 mm or less. This is because if it is 30 mm or less, it has been confirmed that there is no defect such as cracking even if a 980 MPa class high-tensile material is manufactured. Depending on the strength of the material, it may be formed by drawing until it exceeds 30 mm, but it is preferably 30 mm or less for the purpose of reducing the amount of drawing. However, it is preferable to draw a part 5A of the vertical wall 5 until at least a bend along the first concave outer peripheral edge 3a is formed.

Here, in the first step, when forming the first concave outer peripheral edge portion 3a, the top plate portion of the stretch flange molded part as shown in FIG. 8 or FIG. You may press-work so that the uneven | corrugated shape for the other for reinforcement | strengthening provided to may be formed. However, the uneven shape formed at the position to be the top plate portion 3 may not be the same shape as the shape to be given to the top plate portion of the final product, but is a shape close to the shape to be given to the top plate portion 3 of the final product. It is preferable that Further, the uneven shape may be only a part of the shape to be imparted to the top plate portion 3 of the final product.
Thus, when forming an uneven | corrugated shape in the position used as the top-plate part 3 at a 1st process, the shape corresponding to the uneven | corrugated shape with respect to the surface which clamps the position used as the top-plate part 3 with the metal mold | die of a 2nd process. In this case, the concave-convex shape has an effect of positioning and preventing misalignment when the intermediate part with the bent shape portion is installed in the mold in the second step.

[Second step]
The second step is a step of bending the intermediate part with a bent shape portion formed in the first step and provided with the bent shape portion 8 as shown in FIG. 2 into a second intermediate component.
In this second step, the die 32 is relatively moved along the punch 30 in a state where the top plate portion 3 of the intermediate part with the bent shape portion formed in the first step is sandwiched between the punch 30 and the pad 31. The remaining vertical wall portion 5 is bent and molded, and the flange portion 7 is bent and bent to the top plate portion 3 side.

<Mold for the second process>
The second step mold used in the second step will be described with reference to FIG.
Here, in the following description, the case where the bent portion 8 is bent so as to protrude upward will be described.
As shown in FIG. 6, the second process mold sandwiches the punch 30 constituting the lower die, the die 32 constituting the upper die, and the portion corresponding to the top plate portion 3 in the intermediate part with the bent shape portion. And a pad 31 to be pressed.

<Punch>
The punch 30 has a rising portion 30A for sandwiching the top plate portion and a punch extension portion 30B. The punch extension part 30B may be a separate body from the rising part 30A. The rising portion 30A for sandwiching the top plate portion serves as the first punch, and the punch extension portion 30B constitutes the second punch. The punch extension 30B has a flange-facing surface 30a that is continuous with the lower end portion of the rising portion 30A and can be opposed to at least the flange 7 forming position of the blank material from below.

The upper surface of the rising portion 30 </ b> A is a narrow pressure surface that narrows the top plate portion 3 of the molding material in cooperation with the pad 31.
Further, the side surface 30b of the rising portion 30A is formed with a curved surface having the same curvature as that of the first concave outer peripheral edge portion 3a, and has a shape for forming the vertical wall portion 5 in the stretch flange forming portion. That is, the height of the side surface of the rising portion 30 </ b> A is set to the same height as the vertical wall portion 5.

<Pad>
The pad 31 is provided so as to be detachable from the upper surface of the rising portion 30A of the punch 30. A portion corresponding to the top plate portion 3 in the intermediate part with the bent shape portion is provided in cooperation with the upper surface of the rising portion 30A of the punch 30. It works and can be pinched. That is, the lower surface of the pad 31 has a shape along the first concave outer peripheral edge 3 a of the top plate 3, and at least a portion along the first concave outer peripheral edge 3 a side of the top plate 3 is punched. 30 can be sandwiched together.

  As shown in FIG. 6, the position of the pad 31 of the present embodiment on the side of the first concave outer peripheral edge 3 a is retracted from the side surface 30 b of the rising portion 30 </ b> A of the punch 30 as viewed from above. For this reason, as shown in FIG. 6, when a portion corresponding to the top plate portion 3 is sandwiched between the upper surface of the rising portion 30 </ b> A and the pad 31 in the punch 30, the first concave shape in the portion corresponding to the top plate portion 3. The outer peripheral edge 3a side is exposed upward.

<Die>
The punch side surface of the die 32 is a curved surface that forms the vertical wall portion 5 in cooperation with the side surface 30b of the rising portion 30A. On the punch side surface of the die 32, an overhang portion 32a projecting outward (on the punch 30 side) is formed on the upper side surface, and the overhang portion 32a abuts on the upper surface of the punch 30 via a material. This further restricts the die 32 from moving downward. That is, the restriction position is the position of the molding bottom dead center when the die 32 is lowered. Further, the height of the die side surface from the overhanging portion 32 a to the lower end position is set to the height of the vertical wall portion 5.

  Further, a stepped portion 32b is provided on the lower surface of the die 32 that faces the flange portion 7, so that a concave relief portion 32d is provided, and the die 32 moves to the molding bottom dead center by having the relief portion 32d. In the meantime, the lower surface of the die 32 has a structure in which the bent portion 8 is not narrowed, preferably not in contact. The width of the lower surface 32c of the step portion 32b is equal to or smaller than the width of the flange portion.

The height difference (gap) between the flange-facing surface 30a of the punch 30 and the bottom surface of the relief portion 32d of the die 32 in the state where the die 32 is lowered to the position of the bottom dead center of molding is the bending formed in the intermediate part with the bent shape portion. It is set so as to be equal to or higher than the height of the shape portion 8.
By setting in this way, the bent shape portion 8 is disposed in the gap (recessed portion) formed by the relief portion 32d of the die 32, so that the bent shape portion 8 is restrained and narrowed during the second step of bending. It will not be done. As described above, the portion including the bent portion 8 is freely restrained and deformed during bending, thereby reducing the stress concentration on a specific portion of the flange portion and further preventing cracking. Can do.

When the bent portion 8 is convex toward the flange facing surface 30a side of the punch 30, a recess shape for the relief portion may be set on the flange facing surface 30a side.
Regarding the second step using the second step mold configured as described above, the operation of the second step mold will be described with reference to FIG.
7A shows a state in which the top plate portion 3 of the intermediate part with the bent shape portion is narrowed by the punch 30 and the pad 31, and FIG. 7B relatively moves the die 32 to the press forming bottom dead center. The state at the time of letting it be shown is shown.

First, as shown in FIG. 7A, the top plate portion 3 of the intermediate part with a bent shape portion is placed on the upper surface of the punch 30 and is sandwiched between the punch 30 and the pad 31. The pad 31 is not disposed on the entire surface corresponding to the top plate portion 3 in the stretch flange molding portion, but slightly inward from the side surface having a curvature corresponding to the first concave outer peripheral edge portion 3a of the punch 30. Place it at a shifted position.
In this state, the vertical wall portion 5 and the flange portion 7 are bent by moving the die 32 relative to the flange facing surface 30a along the side surface of the punch 30 to the position shown in FIG.

  At this time, a portion where the bent shape portion 8 is formed in the intermediate part with the bent shape portion (outside from the position to become the flange portion) is stretched flange forming, and tensile stress in the peripheral direction acts. Unlike the end face of the base plate, since the ridge line 9 of the bent shape portion 8 exists in a shape that is continuous in the circumferential direction, there is no crack starting point and cracks are unlikely to occur. In addition, since the ridgeline 9 of the bent shape portion 8 is a continuous shape in the circumferential direction, a uniform tensile stress is applied without concentration of stress. Even in this respect, the stretch flange portion is not easily cracked. .

Furthermore, since the bent shape portion 8 of the present embodiment extends along the second concave outer peripheral edge portion 7a in plan view, the tensile stress acting on the bent shape portion 8 can be made more uniform.
Further, by forming the bent shape portion 8 defined above in the first step at least in the vicinity of the curved portion of the flange portion to be stretch-formed, the portion that becomes the second concave outer peripheral edge portion 7a becomes the stretch flange at the second step. Even when subjected to deformation, the strain is easily dispersed due to the shape rigidity of the bent portion 8, and the strain can be prevented from concentrating on the portion that becomes the second concave outer peripheral edge 7a.

Further, by forming the bent shape portion 8 defined above in the first step, when the second concave outer peripheral edge portion 7a is stretched during the second step and undergoes flange deformation, the bent shape portion 8 has a certain height. By forming with, the part used as the 2nd concave outer periphery part 7a can be planarized, and a line length difference can be earned. Therefore, a strong peripheral tensile stress is unlikely to act on the second concave outer peripheral edge portion 7a.
Thus, by equalizing the tensile stress acting on the portion that becomes the second concave outer peripheral edge portion 7a, the uniformed stress acts also on the outer end surface of the bent shape portion 8, Even if burrs or minute flaws remain on the end face, the stress concentration is relaxed, and a cracking suppression effect can also be exhibited in this respect.

Further, in the middle of molding, the portion including the bent portion 8 is not constrained by the mold and can be freely deformed (moved or escaped) three-dimensionally. It is possible to further relax the tensile stress acting in a concentrated manner.
As described above, the second intermediate part is formed without cracking.
Here, the case where the bent portion 8 protrudes upward has been described. However, when the bent portion 8 protrudes downward, a concave shape that allows the bent portion to escape is formed on the punch extension portion 30B side of the punch 30. May be. Moreover, you may form the recessed part shape for letting a bending-shaped part escape in the both surfaces which the punch extension part 30B of the punch 30 and the die | dies 32 oppose.

[Third step]
In the third step, the outer portion of the flange portion 7 of the second intermediate part is trimmed to form the second concave outer peripheral edge portion 7a. Thus, an elongated flange molded part including the elongated flange molded part is manufactured. The trimmed portion includes a bent portion 8.
As described above, in the present embodiment, the first concave outer peripheral edge portion 3a and the part 5A of the vertical wall portion 5 continuous to the first concave outer peripheral edge portion 3a are drawn and bent in the first step. Since the portion 8 is formed, the intermediate part with the bent portion is bent into the second intermediate part in the second step, and the portion outside the flange portion 7 of the second intermediate part is trimmed in the third step. Even when an ultra-high tensile material of 980 MPa or higher is used as the base plate before press molding, cracking can be suppressed, and a stretch flange molded part including a stretch flange molded portion can be manufactured satisfactorily.

[Effect of this embodiment]
(1) A blank material is formed by drawing a part 5A of the vertical wall portion 5 along the first concave outer peripheral edge portion 3a, and at the outer side of the flange portion 7 along the second concave outer peripheral edge portion 7a. The first step of forming a bent shape portion 8 that extends 9 and bends in the thickness direction, and after the first step, the position of the top plate portion 3 is fixed and the vertical wall portion 5 and the flange portion 7 are bent. A second step of molding.

According to this configuration, even if an ultra-high tensile material having a strength level of 980 MPa or higher is used, the vertical wall portion is formed by bending in the second step by forming a part 5A of the vertical wall portion 5 by drawing. 5 can be formed, and the bent flange portion 8 is provided in advance along the second concave outer peripheral edge portion 7a where the stretch flange crack is likely to occur. Can be suppressed.
Furthermore, it becomes possible to manufacture with a low molding load by reducing the processing amount of the drawing.
From the above, according to the present embodiment, even if a stretch flange molded part is manufactured from an ultra-high tensile material having a strength level of 980 MPa or higher with stretch flange molding, low molding while suppressing stretch flange cracking. It becomes possible to manufacture with a load.

(2) After the second step, a third step of trimming a portion outside the flange portion 7 is provided.
If the base plate (blank material) before press molding is trimmed by punching or laser processing in advance, burrs and minute scratches remain on the material end face, and local stress is applied when deformation is applied. Concentration is likely to occur. Therefore, cracks called stretch flange cracks occur in the end face of the material during the forming, and in the case of an ultra-high tensile material (high-strength steel sheet having a strength level of 980 MPa or higher), the cracks propagate rapidly and large cracks are likely to occur. .
On the other hand, by trimming the outer part of the flange portion 7 after the second step and molding the outer peripheral edge of the flange portion 7, the end surface of the flange portion 7 is further stretched and a flange crack is less likely to occur.

(3) In the first step, the bent material 8 is formed by sandwiching the blank material between the blank holder 12 and the die 13. Further, a part 5 </ b> A of the vertical wall portion 5 is drawn by moving relative to the blank holder 12 and the die 14 with respect to the punch that is in contact with the formation position of the top plate portion 3.
According to this configuration, a part 5 </ b> A of the vertical wall portion 5 can be drawn and the bent shape portion 8 can be applied to the outer position of the flange portion 7.
(4) The height of the said vertical wall part 5 shape | molded by a 1st process shall be 30 mm or less.
By limiting to this range, even if an ultra-high tensile material having a strength level of 980 MPa or higher is used, it is possible to more reliably suppress stretch flange cracking.

(5) In addition, an escape portion 32d for allowing the bent shape portion 8 to escape is provided in the mold for the second step.
According to this configuration, the part including the bent shape portion 8 can be freely deformed (moved or escaped) three-dimensionally during molding because it is not restrained by the mold for the second step. In this respect as well, the tensile stress acting on the end face of the part in the middle of molding can be further relaxed.
(6) The step height of the bent portion 8 is 3 mm or more and 10 mm or less.
By defining the height of the bent portion 8 within this range, even if an ultra-high tensile material having a strength level of 980 MPa or higher is used, it becomes possible to more reliably suppress stretch flange cracks.

<Example 1>
When manufacturing a part having the same shape as the A pillar shown in FIG. 7 using a 980 MPa grade cold-rolled steel plate (plate thickness 1.6 mm) as a blank material, the first step, the second step, The molded product of Example 1 of the present invention was manufactured by a three-stage manufacturing method through three steps.
That is, in the processing step, a part 5A (height 30 mm) of the vertical wall portion 5 was formed and the bent portion 8 was formed in the first step as described above. Next, in the second step, the remaining vertical wall portion 5 and flange portion 7 were bent. Thereafter, as a third step, the outer portion of the flange portion 7 was trimmed to obtain a molded product of Example 1 of the present invention. In addition, the height of the vertical wall part was 100 mm.

On the other hand, the vertical wall portion was formed by only one drawing of the part having the same shape as the A pillar shown in FIG. 8, and then the outer portion of the flange portion was trimmed to produce a molded product of Comparative Example 1. . In Comparative Example 1, no bent molded part was provided.
The stretch flange parts of the molded product of Invention Example 1 and the molded product of Comparative Example 1 were compared. As a result of the evaluation, cracks did not occur at all in the flange portion of the curved portion in Example 1 of the present invention, whereas cracks occurred in the portion shown in FIG. 8 in Comparative Example 1.
As described above, when manufacturing the A pillar, the superiority of the inventive example 1 over the comparative example 1 could be clarified.

<Example 2>
When manufacturing a part having the same shape as the center pillar shown in FIG. 8 using a 1180 MPa class cold-rolled steel plate (plate thickness 1.6 mm) as a blank material, the first step, the second step, The molded product of Example 2 of the present invention was manufactured by a three-stage manufacturing method through three steps.
That is, in the processing step, a part 5A (height 30 mm) of the vertical wall portion 5 was formed and the bent portion 8 was formed in the first step as described above. Next, in the second step, the remaining vertical wall portion 5 and flange portion 7 were bent. Thereafter, as a third step, the outer portion of the flange portion 7 was trimmed to obtain a molded product of Inventive Example 2. In addition, the height of the vertical wall part was 100 mm.

On the other hand, a vertical wall portion was formed by a single step of drawing, with the same shape as the center pillar shown in FIG. 9, and then the outer portion of the flange portion was trimmed to produce a molded product of Comparative Example 2. . In Comparative Example 1, no bent molded part was provided.
The stretch flange parts of the molded product of Invention Example 2 and the molded product of Comparative Example 2 were compared. As a result of the evaluation, cracks did not occur at all in the flange portion of the curved portion in Example 2 of the present invention, whereas cracks occurred in the portion shown in FIG. 9 in Comparative Example 2.
As described above, when the center pillar was manufactured, the superiority of the inventive example 2 over the comparative example 2 could be clarified.

DESCRIPTION OF SYMBOLS 1 Flange molding part 3 Top plate part 3a 1st concave outer peripheral part 5 Vertical wall part 5A Part of vertical wall part 7 Flange part 7a 2nd concave outer peripheral part 8 Bent shape part 9 Edge line 10 Blank material 11 Punch 12 Blank holder 12a Step portion 13 Die 30 Punch 30A Top plate portion for rising pressure (first punch)
30B Punch extension (second punch)
30a Flange facing surface 31 Pad 32 Die 32d Escape part

Claims (3)

A top plate portion having a concave outer peripheral edge curved so that a part of the outer peripheral edge is recessed inward, a vertical wall portion continuous to the concave outer peripheral edge portion of the top plate portion, and continuous to the vertical wall portion. A stretch flange molded part manufacturing method for manufacturing a stretch flange molded part including a flange portion bent toward the top plate part side,
The blank material is formed by drawing a part of the vertical wall portion along the concave outer peripheral edge portion, and a ridge line is formed outside the position that becomes the flange portion along the position that becomes the outer peripheral edge portion of the flange portion. A first step of forming a bent portion extending and bent in the thickness direction;
After the first step, a second step of fixing the position to be the top plate portion and bending the vertical wall portion and the flange portion;
After the second step, a third step of trimming the outer portion of the flange portion;
A method for producing a stretch flange molded part, comprising:   In the first step, the blank material is sandwiched between a blank holder and a die to form the bent portion, and the punch that contacts the top plate forming position is moved relative to the blank holder and the die. The method for manufacturing a stretch flange molded part according to claim 1, wherein a part of the vertical wall portion is drawn. In the second step, the position to be the top plate portion is sandwiched and fixed by a punch and a pad, the vertical wall portion and the flange portion are bent with a die, and the die is opposed to the die with a blank material interposed therebetween. A second punch having a surface to be
The surface of the die and the second punch facing the blank material, and at least the surface on the protruding side of the bent shape portion due to the bending of the bent shape portion can avoid contact with the bent shape portion. A method for manufacturing a stretch flange molded part according to claim 1 or 2, wherein a concave relief portion is formed.

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