JP6485423B2 - Manufacturing method of press-molded products - Google Patents

Description

  The present invention relates to a technique for manufacturing a metal plate (blank material) into a product shape having a hat-shaped cross section by press molding.

In recent years, in order to achieve both improvement in collision safety and weight reduction of an automobile body, the application of a high-tensile material of 590 MPa or more has been progressing for vehicle body structural parts. However, since the high tensile strength material has a high yield strength, moldability such as cracking and wrinkling becomes a problem when a metal plate made of the high tensile strength material is press-formed to a structural part.
One of the press-formed products used for vehicle body structural parts is a hat-shaped cross section in which the top plate portion and the flange portion are curved with a predetermined radius of curvature in the longitudinal direction, such as a B-pillar outer, and the curved end of the main body. A product-shaped component having an extending portion extending in a direction perpendicular to the vertical wall surface of the hat-shaped cross section at the portion is given. Such a component is usually formed by draw molding in order to suppress wrinkles generated in the flange portion. However, in the case of molding by draw molding, there is a problem that an opening of the cross section (spring back) occurs.

In order to solve this problem, there is a case where a forming method called step drawing is employed. In molding by this step drawing, a step is provided on the outer periphery of the flange portion, and molding is performed by setting a wrinkle pressing region to be pressed by a wrinkle pressing outside the step. By applying a molding method using this step drawing, tension is applied at the bottom dead center of the molding, so that the opening of the cross section is reduced.
However, in the above-described forming by the step drawing, there is a problem that wrinkles may be generated in the flange portion when a high-tensile material is applied to the metal plate, because wrinkle pressing is not applied to the region inside the step.

Here, in the press molding method described in Patent Document 1, a press method for reducing wrinkles generated in a curved flange in hot press molding has been proposed. In this method, only the curved part where wrinkles are likely to occur is formed by enlarging the blank shape and constraining the material with the wrinkle presser, and forming the other parts with foam. The wrinkle presser restrains the material of the curved part. Since the drawing is performed while reducing the wrinkle, there is an effect of reducing wrinkles.
In the press forming method described in Patent Document 2, a method for reducing wrinkles generated in a curved flange in cold press forming has been proposed. This method is a method of reducing wrinkles by providing a step shape in the flange portion to apply tension in the middle of molding.

Japanese Patent No. 5151784 Japanese Patent No. 5863886

The press molding method described in Patent Document 1 is hot press molding, and is molded at a high temperature during molding to lower the material strength. For this reason, it is difficult to apply to cold press forming, which is the subject of the present invention, and in particular, it is difficult to apply to press working of a metal plate made of a high-strength material such as a high-tensile material.
Further, in the press molding method described in Patent Document 2, since tension is applied by a step in the later stage of molding, it is difficult to sufficiently suppress flange wrinkles generated from the early stage of molding.
The present invention has been made paying attention to the above-described problems, and can greatly reduce the flange wrinkles generated in the hat-shaped cross-section parts, and formability capable of obtaining the hat-shaped cross-section parts without wrinkles. An object of the present invention is to provide a method for producing a press-formed product excellent in.

  In order to solve the problem, a method for manufacturing a press-formed product according to one aspect of the present invention includes a hat-shaped cross section in which a top plate portion and a flange portion are continuous in a width direction through a side wall portion, and the top plate. In the method of manufacturing a press-molded product, the metal plate is press-molded to produce a press-molded product in a product shape having a curved portion that is convexly curved toward the top plate portion along the longitudinal direction of the portion and the flange portion. There is a step drawing process in which a wrinkle holding region for pressing the metal plate with a wrinkle press is set to the outer peripheral part with respect to the outer peripheral portion, and forming with the step drawing, and when forming with the step drawing, the flange portion position An additional area to be pressed with a wrinkle presser is also set in a part of.

According to the aspect of the present invention, it is possible to reduce flange wrinkles in a press-formed product having a hat-shaped cross section. As a result, a part free from molding defects is obtained, leading to an improvement in yield.
Further, for example, when a vehicle body structural component is formed using a hat-shaped cross-sectional component, it is possible to easily assemble the component.
This is particularly effective when the product shape has a hat-shaped cross section, and the top plate portion and the flange portion have a shape curved at least partially convex toward the top plate portion along the longitudinal direction.

It is a figure explaining the example of the product shape of the press-formed product which concerns on embodiment based on this invention, Comprising: (a) is a perspective view, (b) is a side view. It is a figure which shows the example of a flange wrinkle. It is a figure which shows the example of the metal mold | die used by the conventional step-drawing process, Comprising: (a) is a top view which shows the relationship between a punch and a wrinkle press, (b) is a figure which shows the AA 'cross section of (a). It is. It is the schematic which shows the process of the shaping | molding example using the metal mold | die used by the shaping | molding by the conventional step-drawing. It is a figure which shows the example of the metal mold | die used by the step-drawing process based on this invention, Comprising: (a) is a top view which shows the relationship between a punch and a wrinkle presser, (b) is the AA 'cross section of (a). FIG. It is the schematic which shows the process of the example of a shaping | molding using the metal mold | die used at the stage drawing process based on this invention.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
In the present embodiment, a product shape as shown in FIG. 1 will be described as an example of a press-formed product having a hat-shaped cross section. This example assumes a structural component represented by a B-pillar outer.
That is, the product shape of the press-formed product 10 of the present embodiment has a hat-shaped cross section in which both sides in the width direction of the top plate portion 1 are continuous with the flange portion 2 through the side wall portion 3 as shown in FIG. Along with the longitudinal direction, the product is curved so as to be convex toward the top plate 1 side.

  Further, in the product shape of the press-formed product 10 of the present embodiment, the overhanging portions 5 are continuous with both ends in the longitudinal direction of the top plate portion 1. Since the width of each projecting portion 5 is larger in the width direction than the width of the top plate portion 1, the surface of the top plate portion 1 on the end side in the longitudinal direction of the product shape is T-shaped when viewed from above. ing. Further, the lower end portion of the vertical wall portion 6 is continuous with the longitudinal end portion of the flange portion 2. The vertical wall portion 6 rises to the top plate portion 1 side, and its upper end continues to the overhang portion 5. With the shape described above, the main body 4 having a curved end portion extends in the vertical direction with respect to the vertical wall 6. That is, the vertical wall portion 6 rises so as to face the longitudinal direction of the main body portion 4.

Here, the present invention does not require the product shape of the target press-formed product 10 to be a T-shape, and has a hat-shaped cross-sectional shape that may cause wrinkles in the flange portion 2 by step drawing. Any product shape can be applied.
When the metal plate 24 is press-formed into the product shape as described above by step drawing, wrinkles may occur at the curved portion of the flange portion 2 as in the example shown in FIG. This flange wrinkle tends to occur as the material strength increases. In FIG. 2, reference numeral S is an example of a flange wrinkle generation position.

  Here, the mold used for press molding by the above-described step drawing includes a punch 20, a die 21, and a wrinkle presser 23. As shown in FIG. 3 and FIG. 4A, the die 21 and the punch 20 include a hat-shaped cross-section forming portion including a top plate portion forming portion 20a, a side wall portion forming portion 20b, and a flange portion forming portion 20c, and a flange portion. A step forming portion 20d is provided on the outer periphery of the forming portion 20c. As shown in FIG. 3, the wrinkle presser 23 is disposed outside the step forming portion 20d formed on the punch 20, and the metal plate 24 is formed by the wrinkle presser 23 and the die 21 as shown in FIG. It is possible to hold the outer periphery of. Here, the position where the wrinkle presser 23 abuts on the metal plate 24 is a wrinkle presser region S0, and the wrinkle presser region S0 is set on the outer peripheral side of the flange portion 2. A contour line L0 on the flange portion 2 side of the wrinkle holding region S0 is shown in FIG.

Here, press forming by step drawing is an effective processing method for reducing cracks and warping, but the inventors have investigated that wrinkles occur in the flange portion 2 as the material strength of the metal plate 24 increases. The knowledge that there is a possibility of doing. In particular, the inventors have found that wrinkles are likely to occur in the curved flange portion 2.
As a result of examination based on such knowledge, it is possible to reduce wrinkles generated in the flange portion 2 by partially pressing a portion where the wrinkles are generated on the surface of the flange portion 2 and performing molding by step drawing. The knowledge that can be improved.

Based on the above knowledge, in the present embodiment, in addition to the wrinkle holding area S0, an additional area S1 to be pressed by the wrinkle press 23 is set in a part of the flange portion 2 position and molding is performed by step drawing. Then, the metal plate 24 is formed into a desired product shape. Other processing steps may be provided before and after the step drawing step for forming by this step drawing. Another processing step is a step of trimming a blank material, for example.
The additional area S1 is a part of the position of the flange portion 2, and it is estimated that wrinkles are generated when the metal plate 24 is formed by a step drawing without the additional area and formed into a product shape. It is set so as to include a part or all of the generation region S.

The wrinkle generation region S may be determined by experiment. In the present embodiment, CAE analysis is performed in which the metal plate 24 is formed by a step drawing in which there is no additional region in the product shape, and a wrinkle generation region where wrinkles occur in the flange portion 2 is estimated based on the result.
Here, when there are a plurality of wrinkle generation regions, it is not necessary to hold down all of them. For example, the additional region S <b> 1 is set for a region where wrinkles are most greatly generated or a portion that is a joint position where other parts are joined by welding or bolts.
Here, the setting of the additional area S1 does not estimate the wrinkle generation area as described above, and simply includes the position of the additional area S1 so as to include the position of the flange portion 2 set as a joint with other parts. May be set. In this case, the metal plate can be formed into a product shape without reliably generating wrinkles at the joint position. If it is the press-molded product 10 used in a location hidden from the user, it is desired to avoid wrinkles occurring at the joint portion at a minimum. When flange wrinkles are formed at the joint portion, adverse effects such as poor joining accuracy occur when joining with other components.

The wrinkle pressing area S0 and the additional area S1 may be pressed by individual wrinkle pressing areas 23, or the wrinkle pressing area S0 and the additional area S1 may be pressed simultaneously by the integrated wrinkle pressing area 23.
When pressing the metal plate 24 with the individual wrinkle presser 23, it is possible to individually set the pressing force for pressing the wrinkle presser region S0 and the additional region S1, for example, the pressing force of the additional region S1 rather than the wrinkle presser region S0. Can be set relatively weak. However, the mold configuration is complicated accordingly.
Further, the wrinkle holding area S0 and the additional area S1 may be continuous, or the wrinkle holding area S0 and the additional area S1 may be arranged as non-continuous areas.

In the following description, the case where the integrated wrinkle presser 23 is employed and the wrinkle presser region S0 and the additional region S1 are continuous will be described as an example.
In this example, as shown in FIG. 5, the additional region S1 is set by partially expanding the wrinkle holding region S0 toward the flange portion 2 side.
In this example, with respect to the step for step restriction set on the outer periphery of the flange portion 2, the step for step restriction is omitted only at the position covering the region enlarged toward the additional region S1 part of the wrinkle holding region S0. It is an example. That is, a step for step drawing is provided on the outer periphery of the flange portion 2 except for the outer portion of the additional region S1. In this case, since the unevenness due to the step is not formed at the boundary portion between the additional region S1 and the wrinkle pressing region S0, the pressing surface of the wrinkle pressing member 23 is flat. That is, in this example, the case where molding is performed by setting a stepped diaphragm, which is also called a partial stepped diaphragm, in which the step at the outer peripheral position of the flange portion 2 provided with the additional region S1 is omitted is illustrated. Of course, a step may also be formed on the outer periphery of the flange portion 2 provided with the additional region S1. Since this step has a role like a bead with respect to the metal plate 24 (blank material), an unevenness corresponding to the step may be formed on the wrinkle presser 23 according to a request for restraining the outer peripheral portion of the flange.

Even when the wrinkle holding area S0 and the additional area S1 are set to be discontinuous, a step may or may not be provided outside the flange portion 2 where the additional area S1 is set.
It is preferable that the contour line L1 of the additional region S1 is composed of a smooth line having no curvature steep portion with a steep curvature radius and is smoothly connected to the line of the wrinkle holding region S0. By doing in this way, it becomes possible to avoid the occurrence of a stress concentrated portion due to the wrinkle presser 23.
In addition, even when the wrinkle holding area S0 and the additional area S1 are set to be discontinuous, both areas may be pressed by the integrated wrinkle pressing 23.

In forming by step drawing in the present embodiment as described above, in order to reduce flange wrinkles, when forming by step drawing, the region of the wrinkle presser 23 is partially enlarged and the additional region S1 is set separately. Mold into product shape. Thereby, the flange bending part etc. which are easy to generate | occur | produce a wrinkle from an initial stage of shaping | molding are pressed, and a flange wrinkle is suppressed.
Further, in the region where the flange wrinkle is not generated or the wrinkle generated is small, the step drawing is performed, so that a tension is applied in the later stage of molding and the wall opening is suppressed.
The metal plate 24 is particularly effective when it is made of a high tensile material, but a steel plate, an aluminum plate, or the like may be used as the metal plate 24.

Here, as the material strength increases, flange wrinkles are greatly generated. However, if the entire wrinkle wrinkle area is pressed with the wrinkle presser 23, the tension becomes excessive and cracks may occur. Therefore, only a part of the flange wrinkle generation region may be pressed by the wrinkle presser 23 so as not to generate cracks.
As the forming method, step drawing or draw forming may be applied.

In order to confirm the flange wrinkle reduction effect by the press forming method according to the present invention, press forming analysis by a finite element method (FEM) was performed. The results will be described below.
In this embodiment, the case of press-molding into a hat-shaped cross-sectional component curved in the longitudinal direction shown in FIG. The metal plate 24 used for press forming was a plate thickness t = 1.4 mm, a steel plate having a tensile strength of 1470 MPa, and analysis was performed under the condition that the force of the wrinkle presser 23 was 50 tons.
For comparison, an analysis was performed in the case of forming by step drawing using a mold at the time of normal step drawing as shown in FIG. That is, there was a step shape on the entire outer periphery of the flange portion 2, and the analysis was performed under the condition that only the wrinkle holding region S 0 outside the step was pressed with the wrinkle presser 23 and molded.

FIG. 4 shows an overall view and a cross-sectional view in the middle of molding with a mold of such a comparative example. Molding is performed from FIG. 4A to FIG. 4D, and the result of bottom dead center of 30 mmup to 5 mmup is shown. “Mmup” indicates an upper position from the bottom dead center with respect to the bottom dead center. For example, a bottom dead center of 30 mmup indicates a position 30 mm above the bottom dead center.
As can be seen from FIG. 4, in the comparative example, wrinkles started to be generated from 20 mmup, and it can be confirmed that the blank at the stepped portion is swollen by looking at the cross section. Eventually, this bulge becomes wrinkled and remains.

Next, the analysis result of molding based on the present invention will be described.
In the example of the present invention, as shown in FIG. 5, molding is performed by step drawing using a mold in which the wrinkle holding area S0 is partially enlarged and the additional area S1 is set. The analysis was performed under the condition that there is no step shape outside the flange portion 2 where the additional region S1 is set, and the wrinkle presser 23 is disposed from the die R stop.
FIG. 6 shows an overall view and a cross-sectional view in the middle of molding using the mold of the present invention example. Molding is performed from FIG. 6A to FIG. 6D, and the result of bottom dead center of 30 mmup to 5 mmup is shown. As can be seen from FIG. 6, in the example of the present invention, wrinkles of the flange portion are suppressed from the initial stage of molding, and since the material is formed in the flange portion in the middle of molding, a product without flange wrinkles can be obtained. I understand.

DESCRIPTION OF SYMBOLS 1 Top plate part 2 Flange part 3 Side wall part 4 Main body part 5 Overhang part 5 Each overhang part 5 Overhang part 6 Vertical wall part 10 Press molded product 20 Punch 20a Top plate part formation part 20b Side wall part formation part 20c Flange part Forming part 20d Level difference forming part 21 Die 24 Metal plate L0 Outline line L1 Outline line S Wrinkle generation area S0 Wrinkle holding area S1 Additional area

Claims (7)

A curve in which the top plate portion and the flange portion have a hat-shaped cross section that is continuous in the width direction through the side wall portion, and the top plate portion and the flange portion are convexly curved toward the top plate portion side along the longitudinal direction. In the method of manufacturing a press-formed product, in which a metal plate is press-molded into a product shape having a part to manufacture a press-formed product,
It has a step drawing process for setting a wrinkle holding region for pressing the metal plate with a wrinkle press against the outer peripheral part from the flange part position and forming with a step drawing.
A method for manufacturing a press-formed product, characterized in that an additional region to be pressed with a wrinkle presser is set at a part of the flange portion position when forming with the step drawing.   The additional region includes a part or all of a wrinkle generation region that is estimated to generate wrinkles when formed into a product shape by step drawing without the additional region. Item 2. A method for producing a press-formed product according to Item 1.   The additional region is estimated based on a CAE analysis result of forming the metal plate into the product shape, and a wrinkle generation region where wrinkles are generated in the flange portion is estimated and set based on the estimated wrinkle generation region. A method for producing a press-formed product according to claim 1 or 2. The press-molded product is set with a joint part for joining the other part to the flange part,
The method for manufacturing a press-formed product according to any one of claims 1 to 3, wherein the position where the additional region is set includes a part or all of the position of the joint portion.   The method for manufacturing a press-formed product according to any one of claims 1 to 4, wherein the additional region is set by partially expanding the wrinkle holding region toward the flange portion.   The die punch and die used in the step drawing step are characterized in that a step for step drawing is formed on the outer periphery of the flange portion excluding a position outside the flange portion position where the additional region is set. The method for manufacturing a press-formed product according to any one of claims 1 to 5.   The method for producing a press-formed product according to any one of claims 1 to 6, wherein the metal plate has a material strength of 590 MPa or more.

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