WO2017038579A1

WO2017038579A1 - Method for manufacturing stretch-flange-formed component

Info

Publication number: WO2017038579A1
Application number: PCT/JP2016/074657
Authority: WO
Inventors: 新宮　豊久; 健太郎佐藤; 靖廣岸上; 雄司山▲崎▼
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2015-08-28
Filing date: 2016-08-24
Publication date: 2017-03-09
Also published as: KR102023541B1; CN107921504A; KR20180031764A; JPWO2017038579A1; JP6156608B1; MX2018002445A; CN107921504B; MX367318B

Abstract

Provided is a method for manufacturing, with low formation load and minimized stretch flange cracking, a stretch-flange-formed component manufactured in accompaniment with stretch-flange formation. A method for manufacturing a stretch-flange-formed component provided with: a top plate section (3) having a first concave external peripheral edge section (3a); and a flange section (7) that curves to the top plate section (3) side in continuous fashion to a vertical wall section (5) and that has a second concave external peripheral edge section (7a). The method comprises: a first step for forming a curved-shaped section (8) curved in the plate thickness direction and in which a ridge line (9) extends along the second concave external peripheral edge section (7a) to the outer side of the position of the flange section (7) with respect to a blank material; following the first step, a second step for securing the position of the top plate section (3), and bending and forming the vertical wall section (5) and the flange section (7); and a third step for trimming the outer side locations of the flange section (7).

Description

Manufacturing method of stretch flange molded parts

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 and a center pillar reinforcement (refer to FIGS. 6 and 7), which are car body frame parts, are formed into a flat metal plate (blank material). 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.

When a curved part such as an L-shaped part or a T-shaped part that is bent sharply is formed only by drawing as described above, cracks and wrinkles are more likely to occur as the vertical wall part becomes higher. In particular, in recent years, in order to achieve improvement in safety and weight reduction of the automobile body, the strength of the metal plate as the molding material of the automobile body has tended to increase. Such a high-strength metal plate cannot be expected to be as ductile as a soft steel plate that has been conventionally used. Therefore, it is important to take measures against cracks and wrinkles 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, during the drawing, the material end surface is deformed so that the material flows in while being stretched in the peripheral direction.
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 of the site | part corresponded to a part of top plate part is slid, the location where stress concentrates on the end surface of a metal material is made. As a result, in Patent Document 1, cracks at the end face are likely to occur in addition to the stretch flange cracks at the curved portion. For this reason, the method of patent document 1 is difficult to apply to a steel plate with high strength.
In addition, since the forming load is high in the drawing, when an ultra-high tensile material of 980 MPa or more is to be manufactured only by the drawing, there is a possibility that a shortage of the press machine becomes a problem in the drawing.
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 ridge line extends along a position that becomes the outer peripheral edge portion of the flange portion outside the position that becomes the flange portion, and a bent shape portion that is bent in the plate thickness direction is formed. After the first step, 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, and after the second step, outside the flange portion And a third step of trimming the part of The features.

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, the bent portion is formed so as to surround the outer peripheral edge portion of the flange portion where elongation flange cracking is likely to occur in the first step. By providing in advance, stretch flange cracking during bending in the second step can be suppressed.
Furthermore, in the aspect of the present invention, since the vertical wall portion is formed by bending forming without being processed by drawing, it can be manufactured with a low forming load.
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 blank material with a bent shape part concerning the embodiment based on the present 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. 6) and a center pillar (refer FIG. 7) are mentioned, for example.
In the following, description will be given focusing on a portion including a portion to be a stretch flange molded portion in a stretch flange molded part, and only the portion is illustrated in each drawing. And the said part is called "elongation flange molding part 1." In addition, only the site | part which shape | molds the said site | part also in a metal mold | die is shown in figure. 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. It has the flange part 7 which has the concave outer peripheral part 7a curved in this way. And the flange part 7 is a site | part which becomes stretch flange molding in the case of 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 portion 3a and the contour shape of the second concave outer peripheral edge portion 7a are usually identical or similar. Of course, the curved curvature shape of the contour shape of the first concave outer peripheral edge portion 3a and the curved curvature shape of the contour shape of the second concave outer peripheral edge portion 7a may be different.
Here, the curved profile does not need to have a constant curvature, and it is preferable that there is no curvature steep portion where the curvature is steep along the extending direction.

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 bent portion 8 is applied to the outer peripheral portion at the position to be the flange portion 7 with respect to the flat plate (blank material) before press molding. That is, a 1st process is a process of manufacturing the blank material with a bending shape part as shown in FIG.
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 first concave outer peripheral edge 3a of the top plate 3 is formed, and the vertical wall 5 and the flange 7 are bent along the first concave outer peripheral edge 3a. That is, a 2nd process is a process which uses the blank material with a bending shape part as an intermediate part.
In the third step, the bent portion 8 is trimmed from the intermediate part. That is, a 3rd process is a process of shape | molding the outer periphery of the flange part 7, and setting it as said stretch flange molded component.

Hereinafter, each step will be described in detail.
[First step]
In the first step, as shown in FIG. 2, the bent shape portion 8 is formed at the outer peripheral position from the position to become the flange portion 7 with respect to the flat plate (blank material) before press molding. The bent shape portion 8 is formed such that 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.
The bent shape portion 8 may be formed by press molding using a die and a punch, or may be formed by another processing method.
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.
Another example of the shape of the bent portion 8 is shown in FIG. Although FIG. 3 shows an example in which the bent portion 8 is bent so as to protrude downward, the bent portion 8 may be bent in the thickness direction so as to protrude upward.

Here, in the first step, in conjunction with the formation of the bent shape portion 8, the top plate portion of the stretch flange molded part as shown in FIG. You may press-work so that the uneven | corrugated shape for the other for reinforcement etc. to be provided 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 shape at a position that becomes the top plate portion 3 in the first step, a shape corresponding to the uneven shape is formed on the surface that sandwiches the position that becomes the top plate portion 3 in the mold of the second step. It is good to give it. In this case, the concavo-convex shape imparted in the first step has an effect of positioning and preventing misalignment when the blank material 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 blank material with a bent shape portion formed with the bent shape portion 8 as shown in FIG.
In the second step, the die 32 is relatively moved along the punch 30 while the top plate portion 3 of the blank material with a bent shape portion formed in the first step is sandwiched between the punch 30 and the pad 31. The vertical wall portion 5 is bent and molded so that the flange portion 7 is bent toward the top plate portion 3 side.

<Mold for the second process>
The 2nd process metal mold | die used at a 2nd process is demonstrated with reference to FIG. FIG. 4 shows a state in which a part of the vertical wall portion 5 is formed in the second step so that the position of the first concave outer peripheral edge portion 3a can be seen.
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. 4, the mold for the second process sandwiches a portion corresponding to the top plate portion 3 in the punch 30 constituting the lower die, the die 32 constituting the upper die, and the blank material 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 blank material with a 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. 4, the position of the pad 31 of the present embodiment on the first concave outer peripheral edge 3 a side 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. 4, when the 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 (to the punch 30 side) is formed on the upper side surface. The overhanging portion 32a abuts on the upper surface of the punch 30 through the material, so that the die 32 is further restricted 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, by providing a step portion 32b on the lower surface of the die 32 that faces the flange portion 7, a concave relief portion 32d is provided. By having the relief portion 32d, the lower surface of the die 32 does not compress the bent shape portion 8, and preferably does not contact until the die 32 moves to the bottom dead center. 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 blank material with a 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, the above-described 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.
FIG. 5A shows a state in which the top plate portion 3 of the blank material with a bent shape is narrowed by the punch 30 and the pad 31, and FIG. 5B relatively moves the die 32 to the press forming bottom dead center. The state at the time of making it show is shown.
First, as shown in FIG. 5A, the top plate portion 3 of the blank material with a bent shape portion is placed on the upper surface of the punch 30 and 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 die 32 is moved relative to the flange-facing surface 30a along the side surface of the punch 30 to the position shown in FIG. 5B, whereby the first concave outer peripheral edge portion 3a and the vertical wall portion 5 are moved. , And the flange portion 7 is bent.
That is, by the relative movement of the die 32 in the second step, the first concave outer peripheral edge portion 3a of the blank material with a bent shape portion is first bent. Subsequently, the portion that becomes the vertical wall portion 5 is bent and formed in order from the upper side continuous with the first concave outer peripheral edge portion 3a toward the lower side, and the flange portion 7 side of the blank material is the flange of the punch extension portion 30B. A boundary portion between the lower end portion of the vertical wall portion 5 and the flange portion 7 is bent and formed in contact with the facing surface 30a. Thus, in this embodiment, bending will be added sequentially and continuously from the top plate part side.

At this time, the site | part (outside the position used as a flange part) in which the bent shape part 8 in the blank material with a bent shape part is formed becomes stretch flange molding, and the tensile stress of a peripheral direction acts. However, unlike the end face of the base plate before press molding, the portion is present in a shape in which the ridge line 9 of the bent shape portion 8 is continuous in the circumferential direction, so there is no crack starting point and cracks are unlikely to occur. . In addition, since the ridge line 9 of the bent shape portion 8 has a continuous shape in the circumferential direction, a uniform tensile stress is applied to the portion without stress concentration. Cracks are unlikely to occur.
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 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 part of the flange part 7 of the intermediate part is trimmed to form the second concave outer peripheral edge part 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 bent shape portion 8 is formed in the first step, the blank material with the bent shape portion is bent into the intermediate component in the second step, and the intermediate component in the third step. Since the outer portion of the flange portion 7 is trimmed, cracking can be suppressed even when a 980 MPa class or higher super high tensile material is used as the base plate before press molding, and the stretch flange including the stretch flange molded portion can be satisfactorily included. Molded parts can be manufactured.

[Effect of this embodiment]
(1) A first step of forming 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 at a position outside the flange portion 7 with respect to the blank material; After the first step, the second step of bending the vertical wall portion 5 and the flange portion 7 while fixing the position to be the top plate portion 3 is provided.
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 5 can be formed by bending in the second step, and the second concave shape is likely to cause stretch flange cracks. By providing the bent-shaped portion 8 in advance along the outer peripheral edge portion 7a, it is possible to suppress stretch flange cracking during bending forming in the second step.
Furthermore, since the vertical wall portion is formed by bending without being processed by drawing, it can be manufactured with a low forming load.
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 forming is trimmed by punching or laser processing in advance, burrs and minute scratches remain on the material end face, so local stress concentration when deformation is applied 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) Moreover, the escape part 32d which escapes the bending shape part 8 is provided in the metal mold | die for 2nd processes.
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.
(4) 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.

<Invention 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, the bent portion 8 was formed in the first step as described above. Next, in the second step, the first concave outer peripheral edge portion 3a, the vertical wall portion 5 and the flange portion 7 were successively bent and formed. 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, a vertical wall portion was formed by a single step of drawing, with the same shape as the A pillar shown in FIG. 6, 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 in the flange portion of the curved portion in Example 1 of the present invention, whereas cracks occurred in the portion shown in FIG. 6 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.

<Invention Example 2>
When manufacturing a part having the same shape as the center pillar shown in FIG. 6 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, the bent portion 8 was formed in the first step as described above. Next, in the second step, the first concave outer peripheral edge portion 3a, the vertical wall portion 5 and the flange portion 7 were successively bent and formed. 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 part was formed by a single process of drawing, with the same shape as the center pillar shown in FIG. 7, and then the outer part of the flange part was trimmed to produce a molded product of Comparative Example 2. . In Comparative Example 2, 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 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. 7 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.

As described above, the entire contents of Japanese Patent Application No. 2015-169227 (filed on August 28, 2015) to which the present application claims priority form part of the present disclosure by reference.
Although the present invention has been described with reference to a limited number of embodiments, the scope of rights is not limited thereto, and modifications of each embodiment based on the above disclosure are obvious to those skilled in the art.

DESCRIPTION OF SYMBOLS 1 Flange molding part 3 Top plate part 3a 1st concave outer peripheral part 5 Vertical wall part 7 Flange part 7a 2nd concave outer peripheral part 8 Bent shape part 9 Ridge line 30 Punch 30A Standing part for top plate part clamping (1st punch)
30B Punch extension (second punch)
31 Pad 32 Die 32d Escape part

Claims

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,
A first step of forming, on the blank material, a bent shape portion having a ridge line extending along a position serving as an outer peripheral edge portion of the flange portion outside a position serving as the flange portion and bent in a plate 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 second step, the concave outer peripheral edge portion, the vertical wall portion, and the flange portion are formed by relatively moving the die along the punch while the position of the top plate portion is sandwiched between the punch and the pad. The method for producing an elongated flange-molded part according to claim 1, wherein bending molding is continuously performed in the order of.
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.