JP7310777B2 - Press molding method, press molding die for intermediate molding and press molded product - Google Patents

Description

TECHNICAL FIELD The present invention relates to a press-forming method, a press-forming die, and a press-formed product for a metal plate, and in particular, a press-forming method for suppressing the occurrence of wrinkles at specific positions, a press-forming die for intermediate forming, and a press-formed product in which the occurrence of wrinkles is suppressed. It relates to press-molded products.

In recent years, high-strength steel sheets have been widely used for automobile parts in order to reduce the weight of automobile bodies due to environmental concerns. Automobile parts are often manufactured using press molding, which is excellent in terms of manufacturing costs. When a portion having a flange portion is formed by press molding, there is concern that wrinkles may be generated in the portion that shrinks and deforms. Wrinkles in the flange portion are caused by buckling during shrink flanging.

General countermeasures include 1) drawing as deeply as possible in the drawing process, 2) shortening the flange length, 3) changing the wrinkle holding pressure in stages, or 4) partially holding wrinkles. be. 1) In order to draw as deeply as possible in the drawing process, a large forming load is required, which may cause equipment restrictions. In addition, 2) when shortening the flange length, there is a case where the portion is used as a welding point range with other parts, so there is a restriction that it cannot be made smaller than necessary. 3) It is difficult to control the gradual change of the wrinkle holding pressure due to variations and the like.

The following techniques have been disclosed as wrinkle countermeasures in form molding. Patent Document 1 discloses a press forming method for suppressing the occurrence of wrinkles in the vertical wall portion of a press-formed product having a vertical wall portion that does not have a flange portion and is convexly curved outward in a plan view in the longitudinal direction. A form forming technique is disclosed in which the tip of the blank is always in contact with the vertical wall forming part of the die and the vertical wall is formed in a state where there is no restriction other than the contact.

Further, Patent Document 2 discloses a press-formed product having an oblique wall portion without a flange, the press-formed product being convexly curved toward the oblique wall portion in the longitudinal direction of the press-formed product. A technique for performing three-step press molding when molding with a punch is disclosed.

JP 2016-175087 A JP 2016-221558 A

However, the above-described conventional techniques still have the following problems to be solved. The techniques described in Patent Documents 1 and 2 only disclose a foam forming method as a countermeasure against shrinkage wrinkles on vertical walls without flanges, and have a flange portion continuous from the vertical wall, and shrink flange forming on the flange portion. It does not disclose any countermeasures against wrinkles.

The present invention has been made in view of the above circumstances, and proposes a press forming method that suppresses the occurrence of wrinkles in the flange portion, which is a problem in the final shape of a press-formed product having a flange portion. It is an object of the present invention to provide a press-molding die to be used and a press-molded product in which the occurrence of wrinkles is suppressed.

A press forming method of the present invention for solving the above problems and achieving the above objects has a top plate portion, a side wall portion continuous to at least one side of the top plate portion, and a flange portion continuous from the side wall portion. , in a method of forming a press-formed product having two or more continuous bent portions that shrink and deform at the flange portion in a plurality of press processes, the bent portion is formed at a position different from the position of the bent portion of the final molded product. and a second pressing step of forming the intermediate molded product into the final molded product from the intermediate molded product.

Further, the press molding die for intermediate molding of the present invention that achieves the above object has a top plate portion, a side wall portion continuous to at least one side of the top plate portion, and a flange portion continuous from the side wall portion. , a press-molding die for intermediate molding for molding a press-molded product having two or more continuous bent portions that shrink and deform into the flange portion, where the positions of the bent portions are different from the positions of the bent portions of the final molded product. It is characterized in that it is configured to be molded into an intermediate molded product having a flange portion with a bent portion.

Further, the press-formed product of the present invention for achieving the above object has a top plate portion, a side wall portion continuous to at least one side of the top plate portion, and a flange portion continuous from the side wall portion, the flange portion The press-formed product has two or more continuous bent portions that shrink and deform into a flange, and is characterized in that wrinkles around at least one of the bent portions of the flange portion are suppressed.

The press molding method of the present invention has a top plate portion, a side wall portion continuous to at least one side of the top plate portion, and a flange portion continuous from the side wall portion, and the flange portion shrinks and flanges are deformed at two locations. In the above-described method of forming a press-formed product having continuous bent portions in a plurality of pressing steps, an intermediate formed product having a flange portion having a bent portion at a position different from the position of the bent portion in the final molded product is formed. A first pressing step and a second pressing step for forming the final product from the intermediate product.

Therefore, according to the press molding method of the present invention, the first press step forms the intermediate molded product in which the wrinkles of the flange portion are generated at a position different from that of the final molded product, and then the second molded product is formed. By making the flange portion of the intermediate molded product into the shape of the flange portion of the final molded product by the pressing process of 1, for example, when the surrounding of the bent portion where the flange shrinks and the flange deforms becomes the joint with other parts, By suppressing the occurrence of wrinkles at the joint portion of the flange portion, it is possible to facilitate the joining of the parts.

Further, the press molding die for intermediate molding of the present invention has a top plate portion, a side wall portion continuous to at least one side of the top plate portion, and a flange portion continuous from the side wall portion, wherein the flange portion A press-molding die for intermediate molding for molding a press-formed product having two or more continuous bends that undergo shrinkage flange deformation, and which has a bend at a position different from that of the final molded product. It is configured to be molded into an intermediate product having a flange portion.

Therefore, by using the press-molding die for intermediate molding of the present invention in the first press step of the press-molding method of the present invention, the above-described effects of the press-molding method of the present invention can be obtained.

In addition, in the press molding method and the press molding die for intermediate molding of the present invention, the intermediate molded product has a straight bend flange at least one of the bending portions of the final molded product that undergoes shrinkage flange deformation, and the straight bend flange It is preferable to form a preformed portion at a portion that is continuous with the . This is because it is possible to precisely control the position where wrinkles are generated during the final molding.

Furthermore, the press molding method and the press molding die for intermediate molding of the present invention include a wrinkle prediction step of preliminarily grasping the positions of wrinkles to be generated in the flange portion of the final molded product before the first pressing step. , in the intermediate molded product, the relationship between the line length L1 of the wrinkle position predicted in the wrinkle prediction step and the line length L2 of the linearly bent flange satisfies L2>1. 5×L1, the preformed portion has an arc-shaped cross section in side view, the chord length L3 satisfies L3≧L1, and the arrow height H3 is at least twice the plate thickness. It is preferable to design This is because the wrinkle generation position can be controlled more efficiently during the final molding.

In addition, in the press molding method of the present invention, at least one of the first press step and the second press step is preferably foam molding or draw molding. This is because the optimum molding method can be selected according to the material and product shape.

Further, the press-formed product of the present invention is formed using the press-forming method described above, and has a top plate portion, a side wall portion continuous to at least one side of the top plate portion, and a flange portion continuous from the side wall portion. In addition, the press-formed product has two or more continuous bent portions that shrink and deform in the flange portion, and wrinkles around at least one bent portion of the flange portion are suppressed. In addition, the parts can be easily joined together by suppressing the wrinkles at the positions where they are to be joined with other parts, and the product can be manufactured efficiently.

(a1) and (a2) represent a partial side view and a partial top view of the punch, respectively, for explaining the pressing process for forming the final molded product according to the conventional method, and (b1) and (b2) represent the present invention. A press forming method according to an embodiment, showing a partial side view and a partial top view of a punch, respectively, explaining a first pressing step for forming an intermediate product, (c1) and (c2) showing the final Figures 4A-4C depict a partial side view and a partial top view of a punch, respectively, illustrating a second pressing step to form a molded article; (a1) represents a partial side view of the final molded product molded by the conventional method, (a2) represents a cross-sectional view of the final molded product molded by the conventional method, and (a3). represents a partial top view of the final molded product molded by the above conventional method, (b1) represents a partial side view of the intermediate molded product molded by the above embodiment, and (b2) is molded by the above embodiment (b3) is a partial top view of the intermediate molded product molded in the above embodiment. It is a partial side view of an intermediate molded product showing the concept of the above embodiment. It is a contour diagram showing the plate thickness reduction rate of the molded product after press molding according to the conventional method, and (a1) and (a2) are respectively the final press process after molding into the final molded product according to the conventional method. FIG. 4 shows a partial side view of a molded article and a partial top view of a flange portion; It is a contour diagram showing the plate thickness reduction rate of the molded product after press molding according to the above embodiment, and (a1) and (a2) are partial side views of the intermediate molded product molded by the first press step. and a partial top view of the flange portion, and (b1) and (b2) respectively represent a partial side view and a partial top view of the flange portion of the final molded product formed by the second pressing step. FIG. 5A is a side view showing the state of wrinkles in the flange portion after press forming, in which (a) is a cross-sectional view taken along line CC of FIG. 4(a2), and (b) is D of FIG. 5(a2). -D is a cross-sectional view.

A press forming method according to one embodiment of the present invention includes a top plate portion, a side wall portion continuous to at least one side of the top plate portion, and a flange portion continuous from the side wall portion, and a shrink flange portion is formed on the flange portion. In the method of forming a press-formed product having two or more continuous bends that deform in multiple press processes, an intermediate having a flange portion with a bend at a position different from the original position of the bend in the final molded product It includes a first pressing step to form a molded article and a second pressing step to form a final molded article having flanges with bends in situ. By adopting the method of this embodiment, the press-formed product of one embodiment of the present invention is free from wrinkles around at least one bent portion of the flange portion of the press-formed product having the shape described above, which was generated by the conventional method. Suppressed press-formed products can be produced.

Further, the press molding die for intermediate molding used in the first pressing step of the present embodiment is a die for molding the intermediate molded product having the above shape, and the original position of the bent portion of the final molded product is It is configured to be molded into an intermediate product having flanges with bends at different locations.

The details of the present invention will be described below with reference to the drawings. 1(a1) and (a2) show a partial side view and a partial top view of a punch 13, respectively, for explaining the pressing process for forming a final molded product 1 according to the conventional method. FIGS. 1(b1) and 1(b2) are a partial side view and a portion of the punch 13, respectively, for explaining the first press step for forming an intermediate product 101, which is a press forming method according to an embodiment of the present invention. represents a top view. FIGS. 1(c1) and (c2) represent a partial side view and a partial top view of the punch 13, respectively, explaining the second pressing step of forming the intermediate product 101 into the final product 1 in that embodiment. FIGS. 2(a1), (a2) and (a3) respectively show a partial side view, a sectional view taken along the line AA and a partial top view of the final molded product 1 molded by the conventional method. 2(b1), (b2) and (b3) are a partial side view, a BB sectional view and a partial top view, respectively, of the intermediate molded product 101 molded in the first pressing step in the above embodiment. show. As shown in FIGS. 1(c1) and (c2), the second pressing step in this embodiment is the same as the pressing step for forming the final molded product 1 according to the conventional method.

In general, when press-molding a part having a complicated product shape, it is often the case that the part is divided into parts and molded through a plurality of press processes. In the press molding method of the above embodiment, before the second pressing step (FIGS. 1 (c1) and (c2)) for forming the shape of the final molded product 1, the first pressing step ( 1(b1) and (b2)) are performed. The first pressing step may be performed immediately before the second pressing step, or several pressing steps may be interposed therebetween. Also, the second pressing process is not limited to the final pressing process. In the first and second press steps, a die 11, a pad 12 and a punch 13 are used as molds. The blank material 100 and the intermediate molded product 101 are placed on the punch 13, held by the pad 12, sandwiched between the die 11 and the punch 13, pressed down to the bottom dead point, and press-molded.

As shown in FIGS. 2(a1) to 2(a3), the shape of the press-formed product targeted by the present embodiment is a part of the press-formed product 1, a top plate portion 2, and at least one side of the top plate portion 2. and a flange portion 4 continuing from the side wall portion 3 . The flange portion 4 has a plurality of bent portions 5a that are contracted and deformed. In the examples of FIGS. 2(a1) to (a3), the top plate portion 2 is configured to have side wall portions 3 and flange portions 4 on both sides. In the example of FIGS. 2(a1) to (a3), the flange portion 4 configured to extend in the width direction substantially parallel to the top plate portion 2 extends from the bent portion 5a toward the tip of the side wall portion 3. It is formed to gradually decrease in height. When this shape is formed from a flat blank material 100 in one press process, material flows into the flange portion 4 rising from the bending point 5a toward the tip of the part due to the reduction in line length, which is called shrinkage. "Wrinkles" occur due to flange deformation. Therefore, as shown in FIG. 6(a), a wrinkled portion 7 appears on the flange portion 4 from the bent portion 5a to the tip of the component.

In the present embodiment, before the pressing step (second pressing step) for forming the final molded product shape, the pressing step (first pressing step) for forming the intermediate molded product 101 as shown in FIGS. press process). This intermediate molded product 101 is configured to have the bent portion 5 b of the flange portion 4 at a position different from the position of the bent portion 5 a of the final molded product 1 . It is preferable that the bent portions 5b are provided at two locations in the longitudinal direction of the part and configured as straight bending flanges so as to sandwich the positions of the bent portions 5a of the final molded product. Moreover, it is preferable that the flange portion 4 is provided with a preformed portion 6 that is continuous with at least one of the bent portions 5b located at both ends of the straight bent flange. By doing so, the position where wrinkles are generated can be moved toward the front end of the component.

The concept of this embodiment will be described in detail with reference to FIG. In the conventional method of making a final molded product shape from a blank material 100 in one press process, as shown in FIG. A generation point 7 is generated. The wrinkle-occurring portion 7 may be determined in advance by actually measuring a target portion by making a prototype, or by performing calculations through CAE (Computer Aided Engineering) analysis (wrinkle prediction step). FIG. 3 shows the design concept of the intermediate molded product 101 in a side view. The solid line represents the outline of the intermediate molded product 101 in side view, and the dashed line represents the outline of the final molded product 1 in side view. Of the wrinkle generation locations 7 of the final molded product predicted in the wrinkle prediction process, the line length L1 for which wrinkles need to be controlled and the line length L2 between the bent portions 5b at both ends of the straight-bent flanges of the intermediate molded product 101. The relationship is preferably designed such that L2>1.5*L1. The "line length L1 for which wrinkles need to be controlled" refers to the flange portion in the range where wrinkles in the flange portion 4 hinder joining when the corresponding part, which is the final molded product 1, is joined to other parts. 4 line length. Although the upper limit of L2 depends on the range in which wrinkles are to be suppressed and the size of the part, it is preferable to set L2≦3×L1. By doing this, in the intermediate molded product 101, the strain concentrated on the portion (L1) where wrinkles need to be controlled among the wrinkle generation locations 7 near the bent portion 5a can be dispersed, and the generation of wrinkles can be suppressed. be able to.

Further, the preformed portion 6 continuing in the longitudinal direction of the component from one end of the straight bent flange is more preferably arc-shaped in side view, and the chord length L3 of the arc of the preformed portion 6 satisfies L3≧L1. Further, it is more preferable to design so that the arrow height H3 is at least twice the plate thickness. The effect of the preformed portion 6 is to suppress strain concentration on the bent portion 5b near the preformed portion 6, but this effect is too small if the chord length and arrow height are less than the lower limits. The upper limits of the chord length L3 and arrow height H3 are approximately L3≦1.5×L1 and H3≦L1/10, respectively. If it exceeds this, wrinkles may be caused when the preformed portion 6 is returned to the flat shape of the flange portion 4 of the final molded product.

FIG. 4 shows a top view of a contour map of thickness change of a press-formed product after each press process according to the conventional method calculated by CAE analysis. The calculated part shape is approximately 600 mm×150 mm, the top plate portion 2 is approximately 500 mm×70 mm, the side wall portion 3 is approximately 50 mm high, and the flange portion 4 has a projection width of approximately 30 to 40 mm. The material was a 1470 MPa class steel plate with a thickness of 1.2 mm. In the contour diagram, the high brightness side (white) indicates a decrease in plate thickness, and the low brightness side (black) indicates an increase in plate thickness. FIGS. 4(a1) and 4(a2) respectively show a partial side view and a partial top view of the flange portion of the final molded product after the pressing process to obtain the final molded product shape according to the conventional method. As can be seen from the top view of the flange portion 4 (FIG. 4(a2)), the plate thickness increase at the wrinkled portion 7 of the flange portion 4 occurs periodically in the longitudinal direction of the component. That is, when the blank material 100 is press-molded into the final molded product shape in one step as in the conventional method, wrinkles are generated due to the contraction flange effect on the flange portion on the tip side of the part from the bent portion 5a.

FIG. 5 is a top view showing a plate thickness change contour diagram of a press-formed product after each press step according to the present embodiment, which is also subjected to CAE analysis. The representation of the plate thickness decrease/increase in the contour drawing, the calculated part shape and material are the same as in FIG. FIGS. 5(a1) and (a2) respectively show a partial side view of the intermediate molded product 101 formed by the first pressing step and a partial top view of the flange portion 4, and FIGS. 5(b1) and (b2) show , respectively represent a partial side view of the final molded product 1 formed by the second pressing step and a partial top view of the flange portion 4. FIG. Here, assuming that the wrinkle suppression region 8 is approximately half the length in the longitudinal direction of the wrinkle generation location 7 shown in FIG. The intermediate molded product 101 was designed as In the intermediate molded product 101, almost no increase in plate thickness occurs in the wrinkle suppression regions 8 between the bent portions 5b. It can be seen that the periodic increase in plate thickness and wrinkles are concentrated outside the portion sandwiched by the bent portions 5b (on the front end side of the component). This tendency does not change in the final molded product 1 shown in FIGS. 5(b1) and (b2). It can be seen that the application of the press-molding method of the embodiment reduces this.

FIG. 6(a) shows the state of wrinkles in the flange portion 4 after press forming by the conventional method in a cross-sectional view taken along line CC of FIG. 4(a2). FIG. 6(b) shows a wrinkled state of the flange portion 4 of the intermediate molded product 101 according to the above-described embodiment in a cross-sectional view taken along line DD of FIG. 5(a2). In the conventional construction method, wrinkles are generated from the bent portion 5a of the flange portion 4 toward the tip portion side (FIG. 6(a)). On the other hand, the wrinkles of the flange portion of the intermediate molded product 101 to which the present embodiment is applied move toward the tip side (hollow arrow 9 in FIG. 6B), indicating that the occurrence of wrinkles is suppressed. Recognize.

As shown in the above embodiment, the press forming method of the present invention is effective when applied to a part having a shrinkage flange deformation portion. It is preferable to obtain it by analysis or trial production experiment, and to apply it, for example, when wrinkles are expected to occur in joints with other parts. Moreover, the present invention can be applied not only to press molding of automobile parts, but also to all processing methods for press molding plate materials. In addition to steel, iron alloys such as stainless steel, as well as non-ferrous metal materials and non-metal materials can be used as materials for press molding.

As a press working method, form molding or draw molding can be suitably used in either the first press step or the second press step. Form molding is generally performed by bending with the central portion fixed and the outer peripheral portion free, so it is suitable for molding high-strength materials. It is possible to process with a low load, and the energy saving effect is high. However, there is a drawback that wrinkles are likely to occur in the shrinkage flange deformation portion. On the other hand, draw molding is generally a method in which the outer peripheral portion of the material is fixed and the central portion is deep drawn using a mold. Molding with high shape accuracy is possible. However, in the case of a high-strength material, there are cases where it breaks due to its low elongation, or requires a large load for processing. It is suitable for applying to the pressing process of the present invention in accordance with the material and processing shape. A processing method that combines foam molding and draw molding can also be applied to each processed portion.

A part of the press-formed product has a top plate portion, a side wall portion continuous to at least one side of the top plate portion, and a flange portion continuous from the side wall portion, and two or more locations where the flange portion is contracted and flange-deformed. By providing a press-molding method for controlling the wrinkle-generating position when there is a continuous bent portion, a mold for intermediate molding, and a press-molded product formed by the press-molding method, parts as press-molded products can be manufactured. Joining can be performed easily and efficiently.

1 Press molded product (final molded product)
2 Top plate 3 Side wall 4 Flange 5a Bent part of flange of final molded product 5b Bent part of flange of intermediate molded product 6 Preformed part 7 Wrinkle generation point 8 Wrinkle suppression area 9 Wrinkle movement 11 Die 12 Pad 13 Punch 100 Blank material 101 Intermediate molded product L1 Line length of wrinkle control part L2 Line length between bending parts of flange part of intermediate molded part L3 Chord length of arc-shaped preformed part H3 Arrow height of arc-shaped preformed part

Claims (10)

It has a top plate portion, a side wall portion continuous to at least one side of the top plate portion, and a flange portion continuous from the side wall portion. In the method of forming a press-formed product in multiple press steps,
A first pressing step of forming an intermediate molded product having a flange portion having a bent portion at a position different from the position of the bent portion of the final molded product;
a second pressing step for molding from the intermediate product to the final product ;
A press forming method , wherein the flange portion is formed so that the side wall portion gradually decreases in height in one longitudinal direction from the bent portion. 3. The intermediate molded product is characterized in that at least one of the bends of the final molded product that undergoes contraction flange deformation is a linearly bent flange, and a preformed portion is formed in a portion that is continuous with the linearly bent flange. 1. The press molding method according to 1. Furthermore, before the first pressing step, including a wrinkle prediction step of grasping the position of the wrinkle generated in the flange portion of the final molded product in advance,
Of the wrinkle positions predicted in the wrinkle prediction step, the intermediate molded product has a relationship between the line length L1 of the position where wrinkles need to be controlled and the line length L2 of the linearly bent flange is L2>1.5. xL1,
2. The preformed portion is designed to have an arc-shaped cross section in side view, and is designed so that the chord length L3 satisfies L3≧L1 and the arrow height H3 is at least twice the plate thickness. The press molding method described in . The press molding method according to any one of claims 1 to 3, wherein at least one of the first press step and the second press step is performed by form molding. The press molding method according to any one of claims 1 to 3, wherein at least one of the first press step and the second press step is performed by draw molding. It has a top plate portion, a side wall portion continuous to at least one side of the top plate portion, and a flange portion continuous from the side wall portion. A press molding die for intermediate molding for molding a press molded product,
Molding into an intermediate molded product having a flange portion with a bent portion at a position different from the position of the bent portion of the final molded product ,
A press-molding mold for intermediate molding, wherein the side wall portion is configured to form the flange portion so that the height gradually decreases in one longitudinal direction with the bent portion as a boundary. . At least one of the bending portions of the final molded product that undergoes contraction flange deformation is formed as a straight bent flange, and the intermediate molded product is formed to have a preformed portion in a portion that is continuous with the straight bent flange. The press molding die for intermediate molding according to claim 6. The relationship between the line length L1 of the position where wrinkles need to be controlled in the flange portion of the final molded product among the wrinkle positions grasped in advance and the line length L2 of the linearly bent flange is L2>1.5×L1. Configure as
The preformed portion has an arc-shaped cross section in side view, and is configured such that the chord length L3 satisfies L3≧L1 and the arrow height H3 is at least twice the plate thickness. 8. A press molding die for intermediate molding according to Item 7. It has a top plate portion, a side wall portion continuous to at least one side of the top plate portion, and a flange portion continuous from the side wall portion. A press-molded product,
The flange portion is formed such that the side wall portion gradually decreases in height in one longitudinal direction with the bent portion as a boundary,
A press-formed product, wherein wrinkles around the bent portion of at least one portion of the flange portion are suppressed. The press-formed product according to claim 9, which is formed by the press-forming method according to any one of claims 1 to 5.

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