JP5975014B2 - Press forming method - Google Patents

Description

  The present invention relates to a press forming method for forming a shrink flange by press forming a metal plate.

  By press forming by sandwiching a metal thin plate with a metal mold, the metal plate may be subjected to compressive deformation and shrinkage may occur. This is called shrink flange molding. In the case of a lightly contracted flange, a phenomenon that the plate thickness increases occurs. However, if the amount of the contracted flange is increased, wrinkles are generated during the molding, and the wrinkles remain after the molding. This wrinkle is undesirable because it causes a shape defect of the molded product and wear of the mold. In particular, if this wrinkle is generated strongly, it may cause a forming crack of the metal plate.

Various methods are used as a method for avoiding such a problem caused by the contracted flange.
For example, Patent Document 1 discloses a method of facilitating compressive deformation by thinning a metal plate in advance or by making a hole.
Patent Documents 2 and 3 also disclose a plurality of methods for reducing the generation of wrinkles by devising a molding die.
Further, in Patent Document 4, at least a part of the material metal plate is slid on a portion corresponding to the top plate portion of the die mold in a state where the pad is in proximity to or in contact with the material metal plate. On the other hand, a method for forming a press part having an L-shape for forming a vertical wall portion and a flange portion is disclosed.

JP 2007-253173 A JP-A-7-39954 JP 2010-2014486 A JP 2012-245536 A

Each of the conventional wrinkle countermeasures described above in the shrinkage flange portion has the following problems.
For example, in the method described in Patent Document 1, since non-uniform pre-processing is performed on a metal plate, the appearance, strength, and sealability of the final product are affected, and furthermore, when the material is a surface-treated steel plate, the rust prevention property is affected. Therefore, the application site is limited.
In the method described in Patent Document 2, the mold structure becomes complicated because the periphery of the shrinkage flange portion is constrained, and it is estimated that there is a problem in terms of mold creation and maintenance costs.
The method disclosed in Patent Document 3 is a method of dispersing the deformation by devising the shape of the tip of the bending die, which may be effective when the forming bending angle of the steel sheet is close to 90 °, but the bending angle is If it is small, it is considered that the shape of the bending die tip does not act effectively, and in such a case, it cannot be applied.
Further, in the method disclosed in Patent Document 4, since at least a part of the material metal plate is slid on the portion corresponding to the top plate portion of the die mold, the material metal is interposed between the pad and the die die. It is supposed to provide a gap that is greater than or equal to the plate thickness but not more than 1.1 times the plate thickness, and it is necessary to strictly define the gap. Therefore, there is a problem that it is difficult to maintain the accuracy of the gap.

  The present invention has been made to solve the various problems as described above, and does not depend on the bending angle without pre-processing the metal plate or complicating the mold structure, Furthermore, it aims at obtaining the press molding method which can perform shrinkage flange shaping | molding with the high processing precision without the complication of operation and the fall of productivity.

(1) The press molding method according to the present invention includes a top plate portion having a convex outer peripheral edge portion in which a part of the outer peripheral edge protrudes outward, and bending forming along the convex outer peripheral edge portion of the top plate portion. A press molding method for press-molding a molded part having a vertical wall portion, a plate pressing step for pressing a part of a portion corresponding to the top plate portion in a blank material by a plate press, and the vertical wall portion It comprises a first forming step for bending forming and a second forming step for forming the top plate portion flatly, and the plate pressing step starts from the R stop of the convex outer peripheral edge portion of the top plate portion. The plate pressing is performed along the convex outer peripheral edge at a distance of 10 times to 100 times the plate thickness before processing the material, and the second forming step is the top plate in the first forming step. The part that is not pressed by the plate It is an butterfly.

In the present invention, the plate pressing step performs plate pressing by separating a distance of 10 to 100 times the plate thickness before processing of the blank material from the R stop of the convex outer peripheral edge portion of the top plate portion. The molding process can effectively prevent the occurrence of wrinkles without concentrating the shrinkage on the bent part of the vertical wall part by molding the part of the top plate part that is not pressed in the first molding process, The processing accuracy of the top plate can also be improved.
In addition, since the metal plate and the mold structure used in the present invention are almost the same as general press molding, there is no concern that the manufacturing cost increases by using the press molding method of the present invention.

It is explanatory drawing of the press molding method which concerns on one embodiment of this invention. It is explanatory drawing of the press molded component shape | molded by the press molding method which concerns on one embodiment of this invention. It is explanatory drawing of the principal part of the press molding die used for the press molding method which concerns on one embodiment of this invention. It is a graph of the experimental result used as the basis of the board clamp gap distance L in the board pressing process of the press molding method in this Embodiment. It is a graph of the experimental result of an Example, and is a graph which shows the relationship between the board thickness increase rate of a top-plate part, and the board pressing gap distance L. It is explanatory drawing of the principal part of the other aspect of the press molding die of FIG.

A press molding method according to an embodiment of the present invention is a press molding method for press molding a molded part 1 (see FIG. 2) having a top plate portion 5 and a vertical wall portion 7, and a top plate in a blank material 9. A plate pressing step (see FIG. 1 (a)) for pressing a part of the portion corresponding to the portion 5 with the plate pressing member 17, a first forming step (see FIG. 1 (b)) for forming the vertical wall portion 7, A second molding step (see FIG. 1C) for flatly molding the plate portion 5 is provided.
1A shows the state after the blank material 9 is installed, FIG. 1B shows the state immediately after the first molding step, and FIG. 1C shows the bottom dead center state. Next to FIG. 1 (b) and FIG. 1 (c), in order to show the state of the blank material 9 at that time, the illustration of the punch 15 is omitted {FIG. 1 (b-1) and FIG. -1)}.
Hereinafter, the molded part 1, the press mold 11 to be used, and the press molding method according to the present invention will be described in detail with reference to FIGS.

<Molded parts>
As shown in FIG. 2, a molded part 1 which is a target shape of press molding in the present embodiment includes a top plate portion 5 having a convex outer peripheral edge portion 3 with a part of the outer peripheral edge protruding outward, The vertical wall portion 7 is bent along the convex outer peripheral edge portion 3 of the plate portion 5.
In the molded part 1 having such a shape, the vertical wall portion 7 is contracted to form a flange deformation, the contraction is concentrated on the bent portion 7a of the vertical wall portion 7, and wrinkles are likely to occur in the portion.

<Press mold>
As shown in FIG. 3, the press molding die 11 includes a die 13 serving as a lower die, a punch 15 that moves downward from above the die 13, and a plate presser 17 that presses the blank material 9.
The shape of the punch 15 includes a top plate forming part 15 a for forming the top plate part 5 of the molded part 1 and a vertical wall forming part 15 b for forming the vertical wall part 7 of the molded part 1.
The die 13 has a shape corresponding to the shape of each forming part of the punch 15.
As shown in FIGS. 1 (b-1) and 1 (c-1), the end portion of the plate retainer 17 has a shape in which the central portion protrudes outward in the same manner as the convex outer peripheral edge portion 3 of the molded part 1. I am doing.
The pressing force that presses the blank material 9 against the die 13 by the plate presser 17 is a sufficiently strong pressure that does not cause deformation in the portion of the top plate portion 5 that is holding the plate presser during molding by the downward movement of the punch 15. It is desirable.

<Press molding method>
Next, the plate pressing process, the first molding process, and the second molding process described above will be described in detail for the press molding method using the press molding die 11 described above.

≪Plate holding process≫
The plate pressing step is a step of placing the blank material 9 on the upper surface of the die 13 and pressing it with the plate pressing 17 as shown in FIG.
The blank material 9 is arranged so that a portion corresponding to the vertical wall portion 7 can be pushed and bent by the punch 15.
The plate retainer 17 has a distance L that is 10 times or more and 100 times or less the plate thickness before processing of the blank material 9 from the portion corresponding to the R stop of the convex outer peripheral edge 3 of the top plate portion 5 at the end of the plate retainer 17. (See FIG. 1B-1). That is, in FIG. 1 (b-1), the end of the plate presser 17 is separated by a distance L from the convex position of the end shape of the plate presser 17 and the R stop of the center 8 of the convex outer peripheral edge 3 of bending. And R stop are arranged so as to be substantially parallel.
In the conventional method (ordinary shrinkage flange molding), the plate retainer 17 is arranged along the portion corresponding to the R stop of the convex outer peripheral edge portion 3 to hold down the entire top plate portion 5. In the present invention, as described above, the plate retainer 17 is disposed at a predetermined distance L from the portion corresponding to the R stop of the convex outer peripheral edge portion 3 so as to hold a part of the top plate portion 5. By carrying out like this, in the 1st fabrication process, the part which is not carrying out board press of blank material 9 can be freely deformed to some extent during fabrication. Details of this point will be described later.
The distance L (hereinafter referred to as “plate pressing gap distance L”) from the R stop of the convex outer peripheral edge 3 to the end of the plate presser 17 is set to be 10 times or more and 100 times or less the plate thickness of the blank material 9 before processing. The reason will be described later.

≪First molding process≫
The first forming step is a step of bending the punch 15 as shown in FIG. 1B by moving the punch 15 downward from the state shown in FIG. In this step, the top plate is not pressed for the portion of the distance L from 10 times to 100 times the plate thickness before processing of the blank material 9 from the R stop of the convex outer peripheral edge portion 3 in the top plate portion 5. The other parts in the part 5 are pressed and pressed.
The convex outer peripheral edge 3 and the vertical wall 7 are formed by the first molding step (see FIG. 1B-1).

If the method of pressing the entire top plate portion 5 as in the conventional method, the deformation of the blank material 9 occurs only in the convex outer peripheral edge portion 3 and the vertical wall portion 7, and the top plate portion 5 has a plate press load. If it is sufficient to suppress wrinkles, there will be little deformation except for slight in-plane deformation.
On the other hand, in the case of the present invention, the deformation of the blank material 9 also occurs in a portion where the top plate portion 5 is not pressed in addition to the convex outer peripheral edge portion 3 and the vertical wall portion 7.
Specifically, from the convex outer peripheral edge portion 3 to the top plate portion 5, in the vicinity of the bending center 8 of the convex outer peripheral edge portion 3 (in FIG. In the enclosed part), deformation occurs in the direction of lifting from the die 13. When such a deformation occurs in the top plate part 5, the deformation of the vertical wall part 7 becomes smaller than that of the conventional method and shrinks to the bent part 7a (see FIG. 2) in the vertical wall part 7 as described above. The effect of preventing the generation of wrinkles due to concentration of water is obtained.

Such an effect can be obtained by appropriately setting the plate pressing gap distance L. If the plate retainer gap distance L is too short, that is, if the end of the plate retainer 17 is too close to the R stop of the convex outer peripheral edge 3, the top plate 5 cannot be deformed, and the above-described effects are sufficiently obtained. On the other hand, if it is too far, the effect of the plate presser 17 is reduced.
Therefore, when this point was examined, it is appropriate to express the plate holding gap distance L as a ratio between the rigidity of the blank material 9 and the plate thickness having a very high correlation, specifically, 10 times the plate thickness. As mentioned above, it is desirable that it is 100 times or less (for example, if the plate thickness is 1 mm, the plate holding gap distance L is 10 mm or more and 100 mm or less). The reason for this will be described in detail in the embodiments described later.

≪Second molding process≫
In the second molding step, as shown in FIG. 1 (c), the punch 15 is further moved down from the state shown in FIG. 1 (b), and the top plate portion 5 is not pressed in the first molding step. That is, it is a step of forming the portion of the top plate portion 5 that is at the plate holding gap distance L from the R stop of the convex outer peripheral edge portion 3.
The portion of the top plate portion 5 that is not pressed by the plate is molded by being sandwiched between the die 13 and the punch 15 at the bottom dead center of the molding. In this way, a product having the same shape as the mold can be obtained (see FIG. 1 (c-1)).

  In the first molding step, the deformation (see FIG. 1 (b-1)) that occurs in the portion of the top plate portion 5 where the plate is not pressed is formed flat just before the bottom dead center. 7 undergoes compression deformation. However, since the deformation is widely dispersed throughout the vertical wall portion 7, no wrinkles are generated compared to the conventional method.

The present embodiment has the following effects.
In the first molding step, the plate holder 5 is not pressed for the portion of the distance L from 10 times to 100 times the plate thickness before processing of the blank material 9 from the R stop of the convex outer peripheral edge portion 3. Since the other parts are formed by pressing the plate, deformation can be caused in the part that is not pressed and the increase in the thickness of the vertical wall portion 7 can be reduced. Generation of wrinkles can be effectively prevented without concentrating the shrinkage on the bent portion 7a of the vertical wall portion 7 where the increase is maximum.

  In addition, since the molding is performed for the part that is not pressed in the second molding process, the floating deformation of the top plate part 5 generated in the first molding process is made flat, and the top plate part 5 is also shaped. The molded part 1 with excellent accuracy can be easily manufactured.

  Further, since the process and the mold structure are almost the same as those of general press molding, there is no concern that the manufacturing cost increases by using this method.

  In the present embodiment, since deformation occurs in the portion of the top plate portion 5 where the plate is not pressed, it occurs in the mold when the blank material 9 is taken out from the mold after the bottom dead center of the molding. There is a concern that the shape return due to the springback caused by the generated stress will occur, and the shape accuracy of the top plate part 5 will deteriorate, but as a countermeasure against this shape return, an uneven shape is provided on the top plate part 5 This can be done by adjusting the stress distribution. It is also possible to provide a shape opposite to the generated spring back in the mold in advance and obtain a desired shape after the spring back.

In the above description, the shape of the punch 15 is such that the end of the top plate forming portion 15a extends along the end of the plate retainer 17 as shown in FIG. 3, but the shape of the punch is not limited thereto. Instead, for example, as shown in FIG. 6, a stepped portion may be provided so as not to buffer the plate retainer 17. Specifically, the punch 19 shown in FIG. 6 has an extending portion 19d extending from the top plate forming portion 19a through the step portion 19c, and the top plate forming portion 19a and the die 13 are formed at the bottom dead center. When the blank material 9 is clamped by this, the plate presser 17 is positioned in the gap formed between the extending portion 19d and the die 13, so that the punch 19 is not buffered with the plate presser 17. In addition, it is possible for the punch 19 to pinch the blank material 9 through the plate presser 17 at the bottom dead center of the molding, and the pinching pressure of the top plate portion 5 can be made more reliable.
The punch 19 in FIG. 6 is a modification of the punch 15 in FIG. Therefore, in FIG. 6, the same symbols are attached to the same components as those in FIG. 3, and the same suffixes are attached to the punches 19 that are the same as the punch 15.
Moreover, although the top plate part 5 is flat in the said figure, the top plate part 5 may have some uneven | corrugated shape, and it can prevent the bending part 7a from being wrinkled similarly to the above.

In the press molding method of the present invention, an experiment for confirming the effect of setting the plate presser gap distance L to 10 times or more and 100 times or less the plate thickness before processing of the blank material was performed. Explained.
In the experiment, press forming is performed by changing the plate presser gap distance L (mm), and the wrinkle tendency is evaluated. The molding target was the molded part 1 shown in FIG. Further, the end of the plate retainer 17 was made parallel to the R stop of the convex outer peripheral edge 3 of the molded part 1.
The plate retainer clearance distance L was set to nine levels of 0 mm, 20 mm, 30 mm, 40 mm, 50 mm, 75 mm, 100 mm, 125 mm, and 150 mm. A plate press gap distance L of 0 mm is a conventional press forming method, and was performed for comparison.
Press forming was performed by computer analysis calculation using the finite element method. As the analytical calculation program, a dynamic explicit solver of LS-DYNA version 971 manufactured by LSTC was used.

The press molding conditions other than the plate retainer gap distance L are the same. The shape of the molded part 1 has a convex angle θ (see FIG. 2) of 140 °, a vertical wall height of 30 mm, and a convex outer peripheral edge R. The blank 9 was a high-tensile steel plate with a thickness of 1.2 mm and a tensile strength of 590 MPa.
As the press molding die 11, the one shown in FIGS. 1 and 3 was used.
For the evaluation of the wrinkle tendency, the maximum value (maximum plate thickness increase rate (%)) of the plate thickness increase rate at the bottom dead center was used. Further, a plate thickness increase rate (top plate thickness increase rate) (%), which is an index of flatness of the top plate portion 5, was also obtained.
Table 1 shows the results of press molding.

In Table 1, the maximum plate thickness increase rate means that if the value is large, the vertical wall portion 7 is shrunk during processing and the tendency to generate wrinkles (wrinkle tendency) is strong. The increase rate means that if the value is large, the top plate part 5 has a strong tendency to wrinkle.
The graph created about the maximum plate thickness increase rate of Table 1 and the top plate | board part plate thickness increase rate is shown in FIG.4 and FIG.5.
FIG. 4 is a graph for the maximum plate thickness increase rate. In FIG. 4, the vertical axis represents the maximum plate thickness increase rate (%). The horizontal axis is shown in two stages, and represents the plate holding gap distance L (mm) and the plate holding gap distance L / plate thickness.
FIG. 5 is a graph of the rate of increase in the top plate thickness. In FIG. 5, the vertical axis represents the top plate thickness increase rate (%). The horizontal axis is shown in two stages, and similarly to FIG. 4, the plate holding gap distance L (mm) and the plate holding gap distance L / plate thickness are respectively shown.

As shown in FIG. 4, the maximum plate thickness increase rate is reduced by setting the plate pressing gap distance L to 10 times (12 mm) or more of the plate thickness (1.2 mm). In particular, the plate press gap distance L is remarkably reduced at 40 mm or more, and the wrinkle tendency is improved.
On the other hand, when the plate retainer gap distance L exceeds 100 times (up to 120 mm) the plate thickness (1.2 mm), the maximum plate thickness increase rate increases again. Therefore, it is preferable that the plate pressing gap distance L is 10 to 100 times the plate thickness.
As can be seen from FIG. 5, in the range where the plate retainer gap distance L is from 12 mm to 120 mm, the top plate thickness increase rate is suppressed to 30% or less, and there is no problem of wrinkling.

  From the above, it was demonstrated that the wrinkle tendency is improved by setting the plate-clamping gap distance L to 10 times or more and 100 times or less the plate thickness before processing the blank material.

Next, by setting the plate presser gap distance L within the range of the present invention, parameters other than the plate presser gap distance L (plate thickness, material, convex outer peripheral edge R, convex shape angle θ, vertical wall height, An experiment was conducted to confirm that the effect of the present invention can be obtained even if the plate presser shape is changed. For comparison, the conventional method (plate pressing gap distance L = 0 mm) was also press-formed under the same conditions.
Hereinafter, each changed parameter will be described.

First, a case where the plate thickness is changed will be described.
The plate thickness was set at two levels of 0.6 mm and 1.8 mm. The plate retainer clearance distance L was set to four levels of 0 mm, 10 mm, 50 mm, and 100 mm. In the case of 0.6 mm, the plate retainer clearance distance L is 6 to 60 mm within the scope of the present invention (Invention Examples 1 to 3), and in the case of 1.8 mm, 18 to 180 mm is within the scope of the present invention (Invention). Example 4 and Invention Example 5). Other parameters are the same as in the above embodiment.
Table 2 shows the results of press molding.

As shown in Table 2, the maximum plate thickness increase rate is lower than Comparative Example 1 in the case of Invention Example 1 to Invention Example 3, and in the case of Invention Example 4 and Invention Example 5, Comparative Example 2 and Comparison Reduced compared to the case of Example 3. That is, in the present invention example 1 to the present invention example 5, the wrinkle tendency could be improved as compared with the conventional method.
The top plate thickness increase rate is 30% or less in any of the present invention examples 1 to 5, and there is no problem of wrinkling.
Thus, even when the plate thickness is changed, it has been proved that press forming can be more suitably performed by setting the plate pressing gap distance L within the range of the present invention.

The case where the material is changed will be described below.
The material was set to two levels, 270 MPa class and 980 MPa class. The plate retainer gap distance L was set to two levels of 0 mm and 50 mm. Other parameters are the same as in the above embodiment. The plate thickness is 1.2 mm, and the plate holding gap distance L corresponds to the range of 12 mm to 120 mm in the present invention.
Table 3 shows the results of press molding.

As shown in Table 3, Inventive Example 6 and Inventive Example 7 were able to reduce the maximum thickness increase rate more than the conventional method in any case.
Further, the rate of increase in the thickness of the top plate portion was suppressed to 30% or less in both cases of Invention Example 6 and Invention Example 7, which was suitable for preventing wrinkles.
Thus, even when the material is changed, it has been proved that press forming can be more suitably performed by setting the plate pressing gap distance L within the range of the present invention.

Below, the case where the convex outer periphery R is changed will be described.
The convex outer peripheral edge R has two levels of 2.5 mm and 10 mm. The plate retainer gap distance L was set to two levels of 0 mm and 50 mm. Other parameters are the same as in the above embodiment. The plate thickness is 1.2 mm, and the plate holding gap distance L corresponds to the range of 12 mm to 120 mm in the present invention.
Table 4 shows the results of press molding.

As shown in Table 4, even if the convex outer peripheral edge R was changed, the wrinkle tendency was improved by setting the plate pressing gap distance L within the range of the present invention.
The top plate thickness increase rate is 30% or less in both cases of Invention Example 9 and Invention Example 10, and there is no problem in preventing wrinkles.
Thus, even when the convex outer peripheral edge R is changed, it has been proved that press molding can be performed more suitably by setting the plate pressing gap distance L within the range of the present invention.

The case where the convex shape angle θ is changed will be described below.
The convex shape angle θ was set at two levels of 120 ° and 160 °. The plate-holding gap distance L is set to three levels of 0 mm, 50 mm, and 100 mm when the convex shape angle θ is 120 °, and is set to two levels of 0 mm and 50 mm when the convex shape angle θ is 160 °. Other parameters are the same as in the above embodiment. The plate thickness is 1.2 mm, and the plate holding gap distance L corresponds to the range of 12 mm to 120 mm in the present invention.
Table 5 shows the results of press molding.

  As shown in Table 5, even if the convex shape angle θ was changed, the wrinkle tendency was improved by keeping the plate pressing gap distance L within the range of the present invention. There is no particular problem with the top plate thickness increase rate.

The case where the vertical wall height is changed will be described below.
The vertical wall height was set at two levels of 20mm and 40mm. The plate retainer clearance distance L is 7 levels of 0mm, 5mm, 10mm, 20mm, 30mm, 50mm and 100mm when the vertical wall height is 20mm, and 4mm of 0mm, 10mm, 20mm and 50mm when the vertical wall height is 40mm. Standard level. Other parameters are the same as in the above embodiment. The plate thickness is 1.2 mm, and the plate holding gap distance L corresponds to the range of 12 mm to 120 mm in the present invention.
Table 6 shows the results of press molding.

  As shown in Table 6, even when the height of the vertical wall was changed, the maximum plate thickness increase rate was reduced and the wrinkle tendency was improved by setting the plate pressing gap distance L within the range of the present invention. There is no particular problem with the top plate thickness increase rate.

Hereinafter, a case where the plate presser shape is changed will be described.
In the above embodiment, the plate retainer 17 has a shape whose end is along the convex outer peripheral edge 3 of the molded part 1. In this example, the plate retainer 17 is press-molded using a straight end. Went. In the case of the present embodiment, the plate retainer gap distance L ′ is a distance from the R stop of the center 8 of the convex outer peripheral edge 3 of the top plate 5 to the center of the plate retainer 17 in the width direction. Standard level. Other parameters are the same as in the above embodiment. The plate thickness is 1.2 mm, and the plate pressing gap distance L ′ corresponds to the range of 12 mm to 120 mm in the present invention.
Table 7 shows the results of press molding.

As shown in Table 7, even if the plate presser 17 end shape was changed, the maximum plate thickness increase rate was reduced and the wrinkle tendency was improved.
Further, the top plate thickness increase rate of Example 20 of the present invention is 30% or less, and there is no particular problem in preventing wrinkles.
Thus, it was proved that press forming can be suitably performed even when the plate presser shape is changed.

  As explained based on Tables 2 to 7 above, the plate pressing gap distance is set within the range of 10 times or more and 100 times or less of the plate thickness, the first forming step is performed, and the second forming step is performed. Even if parameters other than the presser gap distance (plate thickness, material, convex outer peripheral edge R, convex angle θ, vertical wall height, plate presser shape) are changed, the tendency to wrinkle is suppressed compared to the conventional method. It has been demonstrated that

DESCRIPTION OF SYMBOLS 1 Molding part 3 Convex outer peripheral part 5 Top plate part 7 Vertical wall part 7a Bending part 8 Bending center of convex outer peripheral part 9 Blank material 11 Press molding die 13 Die 15 Punch 15a Top plate forming part 15b Vertical wall Forming part 17 Plate presser 19 Punch 19a Top plate forming part 19b Vertical wall forming part 19c Step part 19d Extension part

Claims (1)

Pressing a molded part having a top plate portion having a convex outer peripheral edge portion in which a part of the outer peripheral edge protrudes outward, and a vertical wall portion bent and formed along the convex outer peripheral edge portion of the top plate portion A press molding method for molding,
A plate pressing step for pressing a part of the blank material corresponding to the top plate portion with a plate press, a first forming step for bending the vertical wall portion, and a second forming for flatly forming the top plate portion. With a process,
In the plate pressing step, a distance of 10 times or more and 100 times or less of the plate thickness before processing of the blank material is separated from the R stop of the convex outer peripheral edge portion of the top plate portion and along the convex outer peripheral edge portion. And press the plate so that
The second molding step is a press molding method characterized in that molding is performed on a portion of the top plate portion that is not pressed in the first molding step.