JP6015784B2 - Manufacturing method of stretch flange molded parts - Google Patents

Description

  The present invention relates to a press molding method for molding a part having an L-shaped part or a T-shaped part in plan view, which is a press-molded part used as, for example, a vehicle body frame part of an automobile.

When products with L-shaped parts or T-shaped parts such as front pillar reinforcements and center pillar reinforcements, which are car body skeleton parts, are manufactured from metal plates by press molding, usually the drawing method is adopted. The
Drawing is usually performed using a die consisting of a punch, a die, and a blank holder (wrinkle presser), and the distance between the punch and the die is set with the die and the blank holder all around the metal plate. This is a method of drawing a metal plate close to it.

  In such drawing, cracks and wrinkles are likely to occur in the L-shaped part or the T-shaped part that is bent sharply. In particular, in recent years, the strength of the metal plate used as a molding material has been increasing in order to improve the safety and weight of automobile bodies, and such a high-strength metal plate is as soft as a conventionally used soft steel plate. Therefore, it is important to take measures against cracks and wrinkles during press forming.

FIG. 12 shows an example of a crack 33 generated in the A pillar 31 by drawing, and FIG. 13 shows an example of a crack 37 generated in the center pillar 35 by drawing.
As can be seen from FIGS. 12 and 13, the part where cracks are particularly likely to occur is the stretch flange formed part of the curved part. In this part, it will be in the deformation | transformation state into which material flows in, while a material end surface is extended in the circumferential direction.
Since the base plate before press molding, which is the molding material, is usually formed by punching or laser processing, burrs and minute scratches remain on the material end face, and local deformation occurs when deformation is applied. Stress concentration is likely to occur. Therefore, cracks called stretch flange cracks occur in the end face of the material during molding, and in the case of ultra-high tensile materials (high-strength steel sheets with a strength level of 980 MPa class or higher), the cracks propagate quickly and large cracks are likely to occur. .

As a countermeasure against stretch flange cracking, there is a method to prevent stress concentration by finishing the end face uniformly by machining, etc. However, when pressing a mass-produced product, it is inefficient and economical to machine the end face one by one. Is unreasonable.
Further, in Patent Document 1, when a part having an L-shape is press-molded, a vertical wall portion and a flange portion are placed while sliding a part of a metal material on a portion corresponding to a top plate portion in a die mold. It is to be molded.

JP 2012-245536 A

In patent document 1, since the site | part corresponding to the L-shaped lower side part of an L-shaped shape part is drawn toward a vertical wall part, it is reduced that excessive tension | tensile_strength generate | occur | produces in a flange part, and generation | occurrence | production of cracks is produced. It can be prevented (see paragraph [0009] of Patent Document 1).
However, in Patent Document 1, since the metal material corresponding to a part of the top plate portion is slid, a stress-concentrated portion is formed on the end surface of the metal material. There is a problem that it is difficult to apply to a steel plate that is easy to generate and has high strength.

  The present invention has been made in order to solve the above-described problems. Even when an elongated flange molded part produced with stretch flange molding is manufactured from an ultra-high tensile material having a strength level of 980 MPa or more, stretch flange cracking is achieved. An object of the present invention is to provide a method for producing a stretch flange molded part that can be suppressed.

(1) The manufacturing method of the stretch flange molded part according to the present invention includes a top plate portion having a concave outer peripheral portion curved so that a part of the outer peripheral portion is recessed inward, and a concave outer peripheral portion in the top plate portion. A vertical wall portion formed along the vertical wall portion and a flange portion that bends outward with respect to the vertical wall portion, and a method of manufacturing an elongated flange-molded part manufactured with stretch flange molding,
A first step of manufacturing a blank material with a bent shape portion by forming a bent shape portion bent in the plate thickness direction outside the portion where the flange portion is formed in the base plate before forming;
A portion corresponding to the top plate portion of the blank material with the bent shape portion is placed on the punch, and an inner portion of the bent shape portion of the blank material with the bent shape portion is pressed by a die and a wrinkle presser. A second step of sandwiching and drawing the vertical wall portion and the flange portion;
And a third step of manufacturing the stretched flange molded part by trimming a portion outside the flange portion after the second step.

(2) Further, in the above (1), the bent portion has a shape along the concave outer peripheral edge in a plan view.

  In the present invention, a first step of manufacturing a blank material with a bent shape portion by forming a bent shape portion bent in the plate thickness direction outside a portion where the flange portion of the base plate before forming is formed, and The portion corresponding to the top plate portion in the blank material with a bent shape portion is placed on the punch, and the inner portion of the blank shape portion in the blank material with the bent shape portion is clamped by a die and a wrinkle presser. And a second step of drawing the vertical wall portion and the flange portion, and a third step of trimming the portion outside the flange portion after the second step to manufacture an elongated flange-formed part, thereby providing a strength level. Even when a stretch flange molded part is manufactured with an ultra-high tensile material of 980 MPa class or higher, it can be manufactured while suppressing stretch flange cracking.

It is a perspective view including the partial cross section of the metal mold | die used at the 2nd process of the manufacturing method of the stretch flange molding component which concerns on one embodiment of this invention. It is a one part perspective view of the components manufactured with the manufacturing method of the stretch flange molded component which concerns on one embodiment of this invention. It is a one part perspective view of the blank material with a bent shape part shape | molded at the 1st process of the manufacturing method of the stretch flange molded component which concerns on one embodiment of this invention. It is AA arrow sectional drawing of FIG. It is explanatory drawing of the 2nd process of the manufacturing method of the stretch flange molded component which concerns on one embodiment of this invention. It is a one part perspective view of the intermediate | middle part shape | molded at the 2nd process of the manufacturing method of the stretch flange molded part which concerns on one embodiment of this invention. It is explanatory drawing of the other aspect of the bending shape part formed at the 1st process of the manufacturing method of the stretch flange molding component which concerns on one embodiment of this invention. It is a perspective view including the partial cross section of the metal mold | die used at the 2nd process of the manufacturing method of the stretch flange molded component which concerns on other embodiment of this invention. It is explanatory drawing of the 2nd process of the manufacturing method of the stretch flange molded component which concerns on other embodiment of this invention. It is a perspective view including the partial cross section of the metal mold | die used at the 2nd process of the manufacturing method of the stretch flange molded component which concerns on other embodiment of this invention. It is explanatory drawing of the other aspect of the bending shape part formed at the 1st process of the manufacturing method of the stretch flange molding component of this invention. It is explanatory drawing about the subject in the conventional drawing (the 1). It is explanatory drawing about the subject in the conventional drawing (the 2).

[Embodiment 1]
The manufacturing method of a stretch flange molded part according to an embodiment of the present invention is a stretch flange molded part having a portion to be a stretch flange molded part using a super high tensile material of 980 MPa class or higher as a base plate before press molding ( For example, the present invention relates to a method for manufacturing an A pillar (see FIG. 12) and a center pillar (see FIG. 13).

  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. In FIG. 2, only the portion is illustrated. Part 1 ". In addition, also in a metal mold | die (refer FIG.1 and FIG.5), only the site | part which shape | molds the said site | part is shown in figure.

  As shown in FIG. 2, the stretch flange molding portion 1 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, and a concave outer peripheral edge portion in the top plate portion 3. A vertical wall portion 5 formed along 3a and a flange portion 7 that bends outward with respect to the vertical wall portion 5; is there.

  The manufacturing method of a stretch flange molded part according to an embodiment of the present invention includes forming a bent shape portion 11 (see FIG. 3) that bends in a plate thickness direction on a base plate before forming, and a blank material with a bent shape portion. (See FIG. 3) A first step of manufacturing, a second step of drawing the blank material 9 with a bent portion 9 into an intermediate part 14 (see FIG. 6), and trimming the intermediate part 14 to form an extended flange part ( And a third step of manufacturing (see FIG. 2).

  Hereinafter, each step will be described in detail.

[First step]
A 1st process is a process of manufacturing the blank material 9 with a bent shape part shown in FIG. 3 from the base plate before press molding.
As shown in FIG. 3, the blank material 9 with a bent shape portion is formed with a bent shape portion 11 that is bent in the thickness direction on the end side, and this bent shape portion 11 is a flange portion after the second step described later. 7 (see FIG. 6).
The bent shape portion 11 may be formed by press molding or by another method.
In addition, the bent shape part 11 in this Embodiment has illustrated the thing which consists of a step shape as shown in FIG. 4, If it is such a shape, it can shape | mold by press molding.
In addition, although the bending shape part 11 of this Embodiment has a shape in alignment with the concave outer peripheral edge part 3a in planar view, as shown in FIG. 3, it does not necessarily need to be such a shape.

[Second step]
The second step is a step of drawing the blank material 9 with a bent shape portion into the intermediate part 14 shown in FIG. In FIG. 6, the same components as those in FIG.
In order to draw-form the blank material 9 with the bent shape portion into the intermediate part 14, a portion corresponding to the top plate portion 3 (see FIGS. 2 and 6) in the blank material 9 with the bent shape portion is sandwiched between the punch 15 and the pad 19. In addition, the inner portion of the blank material 9 with the bent shape portion than the bent shape portion 11 is sandwiched between the die 17 and the wrinkle presser 21, and the die 17 and the wrinkle presser 21 are moved along the punch 15 in this state.
Before describing the second step in more detail, the second step mold 13 used in the second step will be described with reference to FIG.

<Mold for the second process>
As shown in FIG. 1, the second process die 13 cooperates with the punch 15, the die 17, and the punch 15 in the stretch flange forming portion 1 of the material to be formed (the blank material 9 with a bent shape portion). It has the pad 19 which clamps the site | part corresponded to the top-plate part 3, and the wrinkle presser 21 which cooperates with the die | dye 17 and clamps a blank material.

≪Punch≫
The upper surface of the punch 15 is a pressing surface for pressing the material to be molded in cooperation with the pad 19.
Further, the side surface of the punch 15 is formed with a curved surface having the same curvature as that of the concave outer peripheral edge portion 3 a, and has a shape for forming the vertical wall portion 5 in the stretch flange forming portion 1. 1 and 5 show only a part thereof.

≪Die≫
The die 17 has a flat surface facing the wrinkle presser 21, and sandwiches the blank material 9 with a bent portion in cooperation with the wrinkle presser 21. Further, the side surface of the die 17 is a curved surface that forms the vertical wall portion 5 in cooperation with the side surface of the punch 15.
A stepped portion 17 a that protrudes toward the punch 15 may be formed on the upper portion of the side surface of the die 17.

≪Pad≫
The pad 19 is provided so as to be detachable from the punch 15 side, and a portion corresponding to the top plate portion 3 (see FIGS. 2 and 6) in the blank material 9 with a bent shape portion is defined as an upper surface of the punch 15. It can be pinched together.

≪Wrinkle presser≫
Like the die 17, the wrinkle presser 21 is provided so as to be movable in the pressing direction, and moves together with the die 17 by the pressing force of the die 17. By doing so, the die 17 and the wrinkle presser 21 cooperate in the press molding so that the blank material 9 with the bent portion can be sandwiched and molded.
In this embodiment, the wrinkle presser 21 has a wrinkle presser portion 21a for sandwiching the blank material 9 with a bent shape portion between the lower surface of the die 17 and a bent shape portion relief portion 21b having a lower height than the wrinkle presser portion 21a. doing.

The wrinkle pressing portion 21a has a shape along the concave outer peripheral edge portion 3a in a plan view, and can clamp a portion inside the bent shape portion 11 in the blank material 9 with a bent shape portion.
The height difference between the wrinkle holding portion 21a and the bent shape portion relief portion 21b is set to be larger than the height of the bent shape portion 11 of the blank material 9 with the bent shape portion. By setting in this way, when the blank material 9 with a bent shape portion is sandwiched between the wrinkle presser 21 and the die 17, the bent shape portion 11 is arranged in a gap formed by the die 17 and the bent shape portion relief portion 21b. The bent portion 11 is not restrained during press molding.
Since the portion including the bent portion 11 is not constrained during the press molding and is freely deformed, stress is not concentrated on a specific portion, and the occurrence of cracking can be prevented.
Note that the wrinkle presser 21 has only a curved portion of the wrinkle presser portion 21 a shown in FIG. 1, and the bent shape portion 11 is free when the blank material 9 with the bent shape portion is sandwiched in cooperation with the die 17. You may make it become a state (state which is not restrained).

The second process using the second process mold 13 configured as described above will be described based on FIG. 5 together with the operation of the second process mold 13.
FIG. 5 is a diagram for explaining the process until the blank material 9 with a bent shape portion is press-molded into the intermediate part 14 through the state of the part 12 being molded. 5 (a) to 5 (c) show a state in the middle of press forming, and FIG. 5 (d) shows a state of press forming bottom dead center.

First, a portion corresponding to the top plate portion 3 (see FIGS. 2 and 6) of the blank material 9 with a bent shape portion is placed on the upper surface of the punch 15 and is sandwiched between the punch 15 and the pad 19 and is pressed against the wrinkles. 21 is moved upward so that the wrinkle holding portion 21a of the wrinkle press 21 and the upper surface of the punch 15 are flush with each other (not shown).
At this time, the blank material 9 with the bent shape portion is arranged so that a sufficient gap is formed between the bent shape portion 11 of the blank material 9 with the bent shape portion and the periphery of the wrinkle holding portion 21a. The reason why such a gap is formed is to prevent the bent shape portion 11 from coming into contact with the wrinkle holding portion 21a even if the bent shape portion 11 moves to the vertical wall portion 5 side due to material inflow during molding. is there.
Further, the pad 19 is not disposed on the entire surface corresponding to the top plate portion 3 in the stretch flange molding portion 1, but may be disposed at a position slightly shifted inward from the curved side surface of the punch 15 (FIG. 5). (See (a)).

  Next, the die 17 is moved to the wrinkle presser 21 side, and the lower portion of the die 17 and the wrinkle presser portion 21a of the wrinkle presser 21 sandwich the portion inside the bent shape portion 11 of the blank material 9 with the bent shape portion. In this state, the vertical wall 5 and the flange 7 are drawn by moving the die 17 along the side surface of the punch 15 (see FIGS. 5A to 5C).

At this time, the portion where the bent shape portion 11 is formed in the blank material 9 with the bent shape portion is stretched flange forming, and the tensile stress in the peripheral direction acts, but unlike the end face of the base plate before press forming, it is bent. Since the ridge line of the shape part 11 is a continuous shape, there is no crack starting point and cracks are unlikely to occur. In addition, since the ridge line of the bent portion 11 is a continuous shape, a uniform tensile stress is applied without concentration of stress, so that cracks are not easily generated.
Furthermore, since the bent shape portion 11 of the present embodiment has a curved shape along the concave outer peripheral edge portion 3a in plan view, the tensile stress acting on the bent shape portion 11 can be made more uniform.

By equalizing the tensile stress acting on the bent shape portion 11, the uniformed stress also acts on the outer end surface of the bent shape portion 11, and burrs and minute scratches remain on the end surface. Even if it does, stress concentration does not occur, and the crack suppression effect can be exhibited also in this respect.
Further, in the part 12 in the middle of molding, the part including the bent shape portion 11 is not constrained by the mold, and therefore can be freely deformed (moved or escaped) three-dimensionally. The tensile stress acting on the 12 end faces can be relaxed.

In the final stage of the second step, the stepped portion 17a of the die 17 contacts the part 12 being molded and presses the vicinity of the portion corresponding to the concave outer peripheral edge 3a of the intermediate part 14 in the part 12 being molded (FIG. 5 (d)).
As described above, the intermediate part 14 (see FIG. 6) is formed without cracking.

[Third step]
The third step is a step of manufacturing an elongated flange molded part including the elongated flange molded part 1 (see FIG. 2) by trimming a portion outside the flange part 7 of the intermediate part 14. The trimmed portion includes a bent portion 11.

As described above, in the present embodiment, the bent shape portion 11 is formed on the unmolded base plate in the first step, and the blank material 9 with the bent shape portion formed in the first step in the second step is used as an intermediate part. 14 and the outer part of the flange part 7 of the intermediate part 14 (including the bent part 11) is trimmed in the third step, so that the base plate before press molding is a super high tensile strength of 980 MPa class or higher. Even when the material is used, cracking can be suppressed, and a stretch flange molded part including the stretch flange molded portion 1 can be manufactured satisfactorily.
In addition, the cross-sectional shape of the bending shape part 11 of the blank material 9 with a bending shape part is not restricted to what is shown in FIG. 4, It can be set as a various aspect as shown in FIG.

As shown in FIGS. 7A to 7C, the cross-sectional shape of the bent shape portion 11 may be a case where the bending direction is downward in the drawing and there is one bent portion. As shown in (t), there may be two bent portions. When two bending portions are provided, the second bending portion (the bending portion close to the tip) may be bent inward as shown in FIGS. Alternatively, as shown in FIGS. 7 (m) to (t), the second bent portion may be bent outward.
Further, as shown in FIGS. 7 (u) and 7 (v), the entire bent portion shape portion may be curved.
In FIG. 7, as an example of forming the bent shape portion 11 from a plurality of bent portions, two examples of the bent portion are shown. However, the number of bends forming the bent shape portion of the present invention is not particularly limited. Absent.

[Embodiment 2]
In the first embodiment, the second process die 13 has the pad 19, and the pad 19 in the second process has the punch 15 and the top plate part 3 of the blank material 9 with the bent shape part (FIG. 2). In the example shown in FIG. 6, the portion corresponding to the blank material 9 with the bent shape is sandwiched between the die and the wrinkle press and the other portion is drawn and formed. In the case where the mounting position of the blank material 9 with the bent portion is difficult to shift during the drawing as in the case, it is not necessary to provide the pad 19 on the punch 15.
In such a case, for example, instead of the die 17 shown in FIG. 1, a die 23 having a pressing portion 23a extending to the punch 15 as shown in FIG. 8 may be used. The die 23 is a modification of the die 17, and the same reference numerals are given to the same components in FIG. 8 as those in FIG. 1.

FIG. 9 is a diagram for explaining the second step performed using the die 23, in which FIGS. 9A to 9C show the state during the press molding, and FIG. 9D shows the bottom dead center of the press molding. Each state is shown.
As shown in FIG. 9 (d), the above-described determination pushing portion 23 a pushes the top plate portion 3 of the intermediate part 14 in cooperation with the punch 15 at the bottom dead center of press forming in the second step. It is. In FIG. 9, the same components as those in FIG.
Even when such a die 23 is used, the intermediate part 14 (see FIG. 6) can be formed without generating cracks as in the case of using the die 17 of the first embodiment.

[Embodiment 3]
In the first and second embodiments described above, as an example of the bent shape portion formed in the blank material with the bent shape portion, the innermost bend, such as the bent shape portion 11 shown in FIG. 3, FIG. 4, FIG. However, the bent shape portion of the present invention is not limited to this, and the innermost bend in the bent shape portion is shown. The direction may be the upper side (the direction opposite to the direction in which the vertical wall is formed) (see FIG. 10).

FIG. 10 is an explanatory diagram of the second process mold 24 when the innermost bending direction of the bent shape portion is the upper side, and the same reference numerals are given to the same portions as FIG.
Since the second process mold 24 of the third embodiment is partially different from the first embodiment in the shapes of the die 25 and the wrinkle presser 26, this point will be described below.

On the lower surface of the die 25, a bent-shaped portion relief portion 25b that is recessed upward from the lower end surface 25a of the vertical wall forming portion is formed. The height difference between the lower end surface 25a of the vertical wall forming portion and the bent shape portion relief portion 25b is set to be larger than the height of the bent shape portion 28 of the blank material 27 with the bent shape portion.
On the other hand, the upper surface of the wrinkle presser 26 is a flat surface.
In this way, when the bent shape portion relief portion 25b is formed on the lower surface of the die 25 and the upper surface of the wrinkle presser 26 is a flat surface, the blank material 27 with the bent shape portion is sandwiched between the wrinkle presser 26 and the die 25. In addition, the bent shape portion 28 is disposed in a gap formed between the wrinkle presser 26 and the bent shape portion relief portion 25b, and the bent shape portion 28 is not restrained during press molding.

As shown in FIGS. 11 (a ′) to (c ′), the cross-sectional shape of the bent shape portion 28 may be the case where the direction of bending is upward in the drawing and the number of bent portions is one. As shown in d ′) to (t ′), there may be two bent portions. When two bending portions are provided, the second bending portion (the bending portion close to the tip) bends inward as shown in FIGS. 11 (d ′) to (l ′). Alternatively, as shown in FIGS. 11 (m ′) to (t ′), the second bent portion may be bent outward.
Further, as shown in FIGS. 11 (u ′) and (v ′), the entire bent portion shape portion may be curved.
In FIG. 11, two examples of the bent portion are shown as an example of forming the bent portion 28 from a plurality of bent portions, but the number of bends forming the bent portion of the present invention is not particularly limited. Absent.

Two types of comparative experiments were conducted to confirm the effect of the manufacturing method of the stretch flange molded part of the present invention, which will be described.
<Comparison experiment 1>
When manufacturing a part having the same shape as the A pillar 31 shown in FIG. 12 using a 980 MPa class cold-rolled steel sheet (plate thickness 1.6 mm), the first to third steps shown in the first embodiment of the present invention are performed. The stretch flange parts manufactured by carrying out the two methods of the method (Invention Example 1) and the conventional drawing method (Comparative Example 1) in one step were compared.
As a result, cracks did not occur at all in Example 1 of the present invention, whereas cracks occurred in the portion indicated by C in FIG. 12 in Comparative Example 1.
Thereby, when manufacturing the A pillar, the superiority of the inventive example 1 over the comparative example 1 could be clarified.

<Comparison experiment 2>
When manufacturing a part having the same shape as the center pillar 35 shown in FIG. 13 using a 1180 MPa class cold-rolled steel sheet (plate thickness 1.6 mm), the first to third steps shown in the second embodiment of the present invention are performed. Stretch flange molded parts manufactured by carrying out the two methods of the method (Invention Example 2) and the conventional drawing method (Comparative Example 2) in one step were compared.
As a result, cracks did not occur at all in Example 2 of the present invention, whereas cracks occurred in the portion indicated by D in FIG. 13 in Comparative Example 2.
Thereby, when manufacturing the center pillar, the superiority of the inventive example 2 over the comparative example 2 could be clarified.

DESCRIPTION OF SYMBOLS 1 Stretch flange molding part 3 Top plate part 3a Concave outer periphery part 5 Vertical wall part 7 Flange part 9 Blank material with a bending shape part 11 Bending shape part 12 Molding part 13 Second process die 14 Intermediate part 15 Punch 17 Die 17a Stepped portion 19 Pad 21 Wrinkle presser 21a Wrinkle presser portion 21b Bent shape portion relief portion 23 Die 23a Decking portion 24 Die for second process 25 Die 25a Lower end surface of vertical wall molding portion 25b Bend shape portion relief portion 26 Wrinkle Presser 27 Blank material with bent portion 28 Bent portion 31 A pillar 33 Warp 35 Center pillar 37 Warp

Claims (2)

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 formed along the concave outer peripheral edge portion of the top plate portion, and the vertical wall portion A method of manufacturing an elongated flange-molded part that has a flange portion that bends outward and is produced with stretch flange molding,
A first step of manufacturing a blank material with a bent shape portion by forming a bent shape portion bent in the plate thickness direction outside the portion where the flange portion is formed in the base plate before forming;
A portion corresponding to the top plate portion of the blank material with the bent shape portion is placed on the punch, and an inner portion of the bent shape portion of the blank material with the bent shape portion is pressed by a die and a wrinkle presser. A second step of sandwiching and drawing the vertical wall portion and the flange portion;
And a third step of manufacturing the stretched flange molded part by trimming a portion outside the flange portion after the second step. The method for manufacturing a stretch flange molded part according to claim 1, wherein the bent portion has a shape along the concave outer peripheral edge in a plan view.

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