Method for manufacturing press-formed article, and press die

Abstract

The present invention reduces the occurrence of wrinkles when press forming is performed by using a high-strength steel sheet having high yield strength and high tensile strength. This method for manufacturing a press-formed article, which comprises a top plate part having a curved shape protruding outward in a plan view and a vertical wall part bent in a direction intersecting the top plate part from a portion of the top plate part having the curved shape, includes: a first forming step for forming an intermediate formed article having a shape in which a leading end of the vertical wall part of a portion corresponding to the curved shape of the top plate part is bent outward; and a second forming step for forming a portion of the vertical wall part bent outward of the intermediate formed article into the vertical wall part of the press-formed article. This die for use in the method has a lower die having a projecting portion, which projects outward, at a lower portion where the vertical wall part of the press-formed article is formed.

Description

Method for manufacturing a press-formed product and press die , ,

[0004] ,

[0003] ,

[0005]

[0001] The present invention relates to a method for manufacturing a press-formed product having a top plate portion having a curved shape protruding outward in a plan view and a vertical wall portion bent in a direction intersecting the top plate portion from a portion having the curved shape of the top plate portion, and a die used in the method.

[0002] In recent years, a steel sheet having a high yield strength and tensile strength (hereinafter referred to as a high-strength steel sheet) has been used for vehicle body components for the purpose of achieving both improved collision safety and weight reduction of automobiles. For example, in the press forming of a vehicle body component having a top plate portion having a curved shape protruding outward and a vertical wall portion continuous with a portion having the curved shape of the top plate portion, the ridge line formed between the top plate portion and the vertical wall portion becomes a curved line in a plan view. In addition, the length of the lower end portion of the vertical wall portion changes before and after press forming. This is because material surplus is generated by the inflow of material into the vertical wall portion during press forming. This material surplus causes wrinkles in the vertical wall portion and reduces the product accuracy of the press-formed product. In particular, when the above-described shape is press-formed using a high-strength steel sheet, wrinkles are significantly generated in the vertical wall portion.

[0003] As a method for preventing the generation of wrinkles and the like during press forming, it has been proposed to perform press forming in two steps, a preliminary forming step (intermediate forming step) and a final forming step (for example, see Patent Document 1 and Patent Document 2). In addition, it has also been proposed to sandwich the end portion of the blank material with a die and a punch during the process of performing press forming (for example, see Patent Document 3).

[0004] JP-A-Open 2013-No. 169578, JP-A-Open 2023-No. 177203, JP-A-Open 2016-No.-221558

[0005] In the press forming method disclosed in Patent Document 1 mentioned above, a high-rigidity portion extending along the longitudinal direction is formed at the widthwise end of the blank material in a pre-forming process (intermediate forming process), and in the main forming process, the top surface and side wall portions are formed while leaving the high-rigidity portion intact. This increases the rigidity of the widthwise end of the blank material, making it possible to suppress the occurrence of wrinkles due to excess material caused by the curved shape. However, in Patent Document 1, after the top surface and side wall portions are formed in the main forming process, the high-rigidity portion is crushed to become a flange portion, which presents a problem in that a process is required to remove the flange portion provided on the press-formed product after press forming. In addition, in the press forming method disclosed in Patent Document 1, problems occur in the main forming process such as the position in which the blank material with the formed high-rigidity portion is set being misaligned, and the behavior of the blank material becoming unstable.

[0006] Furthermore, the press forming disclosed in Patent Document 2 is based on press forming used when manufacturing a press-formed product having a top plate portion, a vertical wall portion, and a flange portion. Therefore, when forming a press-formed product that does not have a flange portion, there is a problem that a step is required to remove the flange portion provided on the press-formed product after press forming.

[0007] Furthermore, the press forming disclosed in Patent Document 3 involves forming the inclined wall portion by moving the die towards the punch side to the bottom dead center while the portion of the blank material closer to the end than the portion corresponding to the inclined wall portion is held between the punch-side latch and the die-side latch before the bottom dead center. This makes it possible to suppress the occurrence of wrinkles in the inclined wall portion. However, in the press forming of Patent Document 3, it is necessary to remove the end portion of the blank material held between the punch-side latch and the die-side latch through processes such as restriking or trimming.

[0008] The present invention aims to provide a method for manufacturing a press-formed product that suppresses the occurrence of wrinkles in the vertical wall portion when manufacturing a press-formed product having a top plate portion having a curved shape that protrudes outward in a plan view, and a vertical wall portion that is bent in a direction intersecting the top plate portion from the curved portion of the top plate portion, by press forming using a high-strength steel plate. Another objective is to provide a mold suitable for use in this method of manufacturing a press-formed product.

[0009] A method for manufacturing a press-formed product according to the present invention, which advantageously solves the above problems, is a method for manufacturing a press-formed product having a top plate portion having a curved shape that protrudes outward in a plan view, and a vertical wall portion that is bent in a direction intersecting the top plate portion from the portion of the top plate portion that has a curved shape, characterized in that it includes a first molding step of molding an intermediate molded product having a shape in which the tip of the vertical wall portion in the portion corresponding to the curved shape of the top plate portion is bent outward, and a second molding step of molding the portion of the vertical wall portion that is bent outward from the intermediate molded product into the vertical wall portion of the press-formed product.

[0010] Furthermore, a more preferable solution for the manufacturing method of the press-formed product according to the present invention is that (a) when H0 is the height from the surface of the top plate portion of the press-formed product to the tip of the vertical wall portion, and H1 is the height from the surface of the portion corresponding to the top plate portion of the intermediate molded product to the upper end of the tip of the shape in which the vertical wall portion is bent outward, H1 / H0 is 0.2 or more and 0.9 or less, and (b) the ratio R / t of the inner radius R of the bent ridge of the shape in which the vertical wall portion of the intermediate molded product is bent outward to the plate thickness t is 20 or more and less than or equal to the limit minimum value.

[0011] The press die according to the present invention, which advantageously solves the above problems, is a die for forming an intermediate molded product in which the tip of the vertical wall portion corresponding to the curved shape of the top plate portion is bent outward when processing a metal sheet into a press-formed product having a top plate portion having a curved shape that protrudes outward in a plan view, and a vertical wall portion that is bent in a direction intersecting the top plate portion from the curved portion of the top plate portion, wherein the lower die has a protruding portion that extends outward at the lower part that forms the vertical wall portion of the press-formed product.

[0012] Furthermore, a more preferable solution is that the press die according to the present invention comprises a first die having a punch and a second die having a pad and a die, the first die having a punch and a punch surface on which the metal plate is placed, a rounded punch shoulder portion at the end of the punch surface for forming the ridge of the intermediate molded product, and a punch vertical wall portion extending continuously from the punch shoulder portion, and a protruding portion at an end of the punch vertical wall portion different from the punch shoulder portion for bending the tip of the vertical wall portion of the intermediate molded product, the second die having a die lower surface facing the protruding portion of the punch for bending the tip of the vertical wall portion of the intermediate molded product, and a rounded die shoulder portion at the punch-side end of the die lower surface.

[0013] According to the present invention, when manufacturing a press-formed product having a top plate portion having a curved shape that protrudes outward in a plan view, and a vertical wall portion that is bent in a direction intersecting the top plate portion from the curved portion of the top plate portion by press forming using a high-strength steel plate, it is possible to suppress the occurrence of wrinkles in the vertical wall portion.

[0014] This is a schematic perspective view showing one aspect of a press-formed product according to this embodiment. This is a flowchart showing one aspect of the molding process for a press-formed product. (a) is a cross-sectional view of the intermediate molded product along A-A' shown in Figure 1, and (b) is a cross-sectional view of the press-formed product along A-A'. (a) is a cross-sectional view showing one configuration of a mold used in the first molding process, and (b) is a cross-sectional view showing the state in which the die is at the bottom dead center of the press. (a) is a cross-sectional view showing one configuration of a mold used in the second molding process, and (b) is a cross-sectional view showing the state in which the leading edge of the vertical wall of the intermediate molded product is in contact with the die. This is a cross-sectional view showing the state in which the die is at the bottom dead center of the press. This is a diagram showing the distribution of the rate of change in sheet thickness in an intermediate molded product. This is a diagram showing the distribution of the rate of change in sheet thickness in a press-formed product.

[0015] The embodiments of the present invention will be described in detail below. The following embodiments are illustrative examples of shapes, devices, and methods for realizing the technical concept of the present invention, and do not limit the configuration to those described below. In other words, the technical concept of the present invention can be modified in various ways within the technical scope described in the claims.

[0016] The press-formed product 10 shown in this embodiment and the method for manufacturing the press-formed product 10 will be described with reference to the drawings. In the following description, as shown in Figure 1, the longitudinal direction of the press-formed product 10 is the left-right direction, the short direction of the press-formed product 10 is the front-back direction, and the direction perpendicular to the surface 11a of the top plate portion 11 of the press-formed product 10 is the up-down direction.

[0017] As shown in Figure 1, the press-formed product 10 has a top plate portion 11 with a curved shape whose front end protrudes forward (outward), and a vertical wall portion 12 that is bent downward from the front end of the top plate portion 11. The press-formed product 10 also has a ridge portion 13 between the top plate portion 11 and the vertical wall portion 12. The press-formed product 10 is produced by press forming, which will be described later.

[0018] The blank material 20 used when forming the press-formed product 10 is, for example, a high-strength steel plate with a tensile strength of 440 MPa or more. It is also possible to use mild steel plates or aluminum plates as the blank material 20.

[0019] As shown in Figure 2, the press-formed product 10 is produced by press molding in two processes: a first molding process and a second molding process. Hereinafter, the molded product produced in the first molding process will be referred to as the intermediate molded product 30.

[0020] As shown in Figure 3(a), the intermediate molded product 30 has a top plate portion 11, a vertical wall portion 32, and a bent portion 31 which is a folded portion of at least a part of the vertical wall portion 12 of the press-formed product 10, which is the target shape. The bent portion 31 is provided connected to the part of the vertical wall portion 32 that corresponds to the part of the top plate portion 11 that curves outward in a plan view, and is bent outward from the curved shape.

[0021] The top plate portion 11 of the intermediate molded product 30 and the ridge portion 13 between the top plate portion 11 and the vertical wall portion 32 are the same as the target shape of the press-formed product 10 shown in Figure 3(b).

[0022] In the intermediate molded product 30 described above, the height H1 from the surface 11a of the top plate portion 11 to the upper end 31a of the tip of the bent portion 31 is set to satisfy, for example, the following equation (1). Hereinafter, the height H1 from the surface 11a of the top plate portion 11 to the upper end 31a of the tip of the bent portion 31 will simply be referred to as the bent height H1 of the bent portion 31. 0.2 ≤ H1 / H0 ≤ 0.9 ....(1)

[0023] Here, H0 is the height from the surface 11a of the top plate portion 11 to the lower end 12a of the vertical wall portion 12 in the press-formed product 10, as shown in Figure 3(b). For example, the height H0 is, for example, H0 = 20 mm.

[0024] In the ridge portion 33 between the bent portion 31 and the vertical wall portion 32, let R be the inner radius of the ridge portion 33 (hereinafter referred to as the inner bending radius), and let t be the thickness of the blank material 20. For example, the ratio R / t of the inner bending radius R to the thickness t of the blank material 20 is preferably between a minimum limit value and 20. Here, the minimum limit value of R / t refers to the minimum value of the ratio R / t at which cracks do not occur in the blank material 20 being bent when the thickness t is kept constant and the inner bending radius R is reduced. This minimum limit value is a value that depends on the material of the blank material 20 being press-formed, and is 1.5 as an example.

[0025] Next, the mold used in the first molding process will be described. As shown in Figure 4, the mold 50 used in the first molding process has a lower mold 51 having a punch 52 and a backup block 53, and an upper mold 55 having a pad 56 and a die 57.

[0026] The punch 52 is a member that positions and holds the blank material 20 placed on the surface 52a of the punch 52. The blank material 20 is positioned and held by the punch 52 in a direction in which the back surface 11b of the top plate portion 11 of the intermediate molded product 30 (the back surface 20b of the blank material 20) is in contact with the surface 52a of the punch 52. The punch 52 is provided with a punch shoulder portion 52b necessary for bending and a punch vertical wall portion that extends continuously from the punch shoulder portion 52b. In addition, a protruding portion 54 is provided at the bottom of the punch 52 for bending the tip of the vertical wall portion 32 of the intermediate molded product 30. The protruding portion 54 is provided in the part of the punch 52 corresponding to the vertical wall portion, in a range that corresponds to the curved shape that protrudes outward from the top plate portion of the press molded product in a plan view.

[0027] The backup block 53 prevents the die 57 from moving away from the punch 52 when bending the blank material 20 with the descending die 57, due to the reaction force from the blank material 20 being bent. Forming can be done without the backup block 53, but it is preferable to have it.

[0028] The pad 56 moves toward the punch 52, clamping the blank material 20 between itself and the punch 52. The pad 56 is provided with a biasing means 58, which is, for example, a spring. The biasing means 58 applies a predetermined pressure to the blank material 20 during the bending process.

[0029] The die 57 is a member that moves vertically and presses the blank material held between the punch 52 and the pad 56. A die shoulder 57a is provided at the lower end of the die 57. By providing the die shoulder 57a on the die 57, the bending process performed on the blank material 20 when it is pressed between the punch 52 and the pad 56 is facilitated. In addition, when the bent portion 31 of the intermediate molded product 30 is held between the lower surface 57b of the die and the upper surface 54a of the protruding portion 54 of the punch 52, the die shoulder 57a forms the inner bending radius R of the ridge portion 33 between the bent portion 31 and the vertical wall portion 12.

[0030] Preferably, the mold used in the first molding process comprises a first mold having a punch 52 and a second mold having a pad 56 and a die 57, which are arranged facing each other. Preferably, the punch 52 has a surface 52a on which the metal plate is placed, a rounded punch shoulder 52b at the end of the surface 52a for forming the ridge 13 of the intermediate molded product 30, and a punch vertical wall that extends continuously from the punch shoulder 52b. Preferably, the punch vertical wall has an overhang 54 at an end of the punch vertical wall different from the punch shoulder 52b for bending the tip of the vertical wall 32 of the intermediate molded product 30. Preferably, the pad 56 is arranged facing the surface 52a of the punch 52 and has a biasing means 58 for gripping the metal plate. Preferably, the die 57 is provided with a die lower surface 57b positioned opposite the protruding portion 54 of the punch 52 for bending the tip of the vertical wall portion 32 of the intermediate molded product 30, and a die shoulder portion 57a ​​having a rounded shape at the punch-side end of the die lower surface 57b.

[0031] Next, the mold used in the second molding process will be described. As shown in Figures 5 and 6, the mold 70 used in the second molding process has a lower mold 71 having a punch 72 and a backup block 73, and an upper mold 75 having a pad 76 and a die 77. The upper mold 55 and backup block 53 used in the first molding process can be shared with the upper mold 75 and backup block 73 used in the second molding process. Furthermore, the only difference between the punch 52 used in the first molding process and the punch 72 used in the second molding process is the protruding portion 54. The protruding portion 54 can be prepared separately from the punch 52 body, and the punch 52 body used in the first molding process and the punch 72 used in the second molding process can be shared.

[0032] The punch 72 is a member that positions and holds the intermediate molded product 30 which is placed on the surface 72a of the punch 72. The intermediate molded product 30 is positioned and held on the punch 72 with the back surface 11b of the top plate portion 11 of the intermediate molded product 30 in contact with the surface 72a of the punch 72. The punch 72 is also provided with a punch shoulder portion 72b. The intermediate molded product 30 is placed on the punch 72 such that the inner surface of the ridge portion 13 of the intermediate molded product 30 is in contact with the punch shoulder portion 72b, and the inner surface of the vertical wall portion 32 of the intermediate molded product 30 is in contact with the punch 72.

[0033] The backup block 73 prevents the die 77 from moving away from the punch 72 when the intermediate molded product 30 is bent by the descending die 77, by receiving a reaction force from the intermediate molded product 30 being bent. As shown in Figure 5, it is preferable to position the upper surface of the backup block 73 above the bent portion 31 of the intermediate molded product 30. In other words, the upper surface of the backup block 73 is located between the top plate portion 11 and the bent portion 31 in the direction of movement of the die 77. This ensures that the backup block 73 reliably prevents the die 77 from moving away from the punch 72.

[0034] The pad 76 moves toward the punch 72, clamping the flat portion 11 of the intermediate molded product 30 between itself and the punch 72. The pad 76 is provided with a biasing means 78. The biasing means 78 is, for example, a spring. The biasing means 78 applies a predetermined pressure to the intermediate molded product 30 during the bending process.

[0035] The die 77 is a component that moves vertically and presses the intermediate molded product 30, which is held between the punch 72 and the pad 76. A die shoulder 77a is provided at the lower end of the die 77. By providing the die shoulder 77a on the die 77, when the intermediate molded product 30 held between the punch 72 and the pad 76 is pressed, the bending and flattening of the bent portion 31 of the intermediate molded product 30 is facilitated.

[0036] The method for manufacturing the press-formed product 10 shown in this embodiment will now be described. As described above, the press-formed product 10 is produced by press molding, which has two steps: a first molding step and a second molding step.

[0037] As shown in Figures 4(a) and 4(b), in the first molding process, the blank material 20 is positioned and held in the punch 52 of the mold 50. With the pad 56 protruding from the die 57, the pad 56 of the upper die 55 and the die 57 descend simultaneously. The blank material 20, which is positioned and held in the punch 52, is then clamped between the pad 56 and the punch 52. After that, the die 57 descends. As the die 57 descends, it presses against the blank material 20. As a result, the blank material 20 is bent along the punch shoulder 52b of the punch 52, forming a ridge portion 13 between the top plate portion 11 and the vertical wall portion 32 in the intermediate molded product 30. Subsequently, as the die 57 descends, the tip of the blank material 20 comes into contact with the protruding portion 54 of the punch 52 and bends outward. At the bottom dead center of the die 57, the blank material 20 is bent by the die shoulder 57a, and the tip of the blank material 20 is bent at the bottom surface 57b of the die and the upper surface 54a of the protruding portion 54 of the punch 52, forming the bent portion 31 of the intermediate molded product 30. As a result, an intermediate molded product 30 having a top plate portion 11, a vertical wall portion 32, and a bent portion 31 is produced.

[0038] As shown in Figures 5 and 6, the second molding process is performed on the generated intermediate molded product 30. In the second molding process, the intermediate molded product 30 molded in the first molding process is positioned and held by the punch 72. The intermediate molded product 30 is positioned and held by the punch 72 with the back surface 11b of the top plate portion 11 of the intermediate molded product 30 in contact with the surface 72a of the punch 72 (see Figure 5(a)). With the pad 76 protruding from the die 77, the pad 76 of the upper die 75 and the die 77 descend simultaneously. The intermediate molded product 30, which is positioned and held by the punch 72, is then clamped between the pad 76 and the punch 72. After that, the die 77 descends. As the die 77 descends, the lower surface 77b of the die 77 comes into contact with the upper surface of the bent portion 31 of the intermediate molded product 30 (see Figure 5(b)).

[0039] At this point, the die 77 has not yet moved to the bottom dead center. Therefore, the die 77 continues to descend. As the die 77 descends, the bent portion 31 is flattened. Then, as the die 77 moves to the bottom dead center, the vertical wall portion 12 of the press-formed product 10 is formed (see Figure 6). This produces a press-formed product 10 having a curved top plate portion 11 with its front end protruding outward, and a vertical wall portion 12 bent from the top plate portion 11.

[0040] In manufacturing the press-formed product 10 of this embodiment, the following simulation was performed. Figure 7 shows the distribution of the rate of change of sheet thickness Δt in the intermediate molded product 30 formed in the first molding process. Figure 8 shows the distribution of the rate of change of sheet thickness Δt in the press-formed product 10 formed in the second molding process. Here, the rate of change of sheet thickness Δt is expressed as a percentage obtained by dividing the difference in sheet thickness after molding in each process with respect to the sheet thickness t of the blank material 20 by the sheet thickness t of the blank material 20. The rate of change of sheet thickness Δt was considered positive when it increased from the sheet thickness t of the blank material 20.

[0041] In the intermediate molded product 30 molded in the first molding process, the sheet thickness change rate Δt is at most +5.1% as shown in Fig. 7, and it was found that Δt is within ±10.0%. Also, regarding the sheet thickness change rate Δt in the press-molded product 10 molded in the second molding process, it is at most +6.4% as shown in Fig. 8, and it was found that Δt is within ±10.0%. <​​​​​​​​​​​​​​​As shown in Table 1, Nos. 2 and 3 show the case where the inner bending radius R is 2 mm. In Nos. 2 and 3, the bending height H1 is changed from 18 mm to 4 mm. The sheet thickness change rate Δt in the first forming process decreases from an increase of 5.1% to an increase of 0.4% as the bending height H1 decreases. On the other hand, the sheet thickness change rate Δt in the second forming process is suppressed to an increase of 10.0% or less. In No. 2 where the bending height H1 is 18 mm, the sheet thickness change rate Δt in the second forming process decreased to an increase of 6.5%. Note that the R / t of Nos. 2 and 3 is 1.67, which is greater than 1.5, the limiting minimum value of this steel sheet.

[0048] Nos. 4 to 9 show the case where the inner bending radius R is 4 mm. In Nos. 4 to 9, the bending height H1 is changed from 18 mm to 4 mm. The sheet thickness change rate Δt in the first forming process decreases from an increase of 8.6% to an increase of 0.3% as the bending height H1 decreases. On the other hand, the sheet thickness change rate Δt in the second forming process is suppressed to an increase of 10.0% or less. In No. 6 where the bending height H1 is 14 mm, the increase in the sheet thickness change rate Δt in the second forming process was most suppressed at an increase of 6.1%.

[0049] Nos. 10 and 11 show the case where the inner bending radius R is 12 mm. In Nos. 10 and 11, the bending height H1 is changed from 18 mm to 4 mm. The sheet thickness change rate Δt in the first forming process decreases from an increase of {6.8}% to an increase of 0.2% as the bending height H1 decreases. On the other hand, the sheet thickness change rate Δt in the second forming process is suppressed to an increase of 10.0% or less.

[0050] Nos. 12 and 13 show the case where the inner bending radius R is 20 mm. In Nos. 12 and 13, the bending height H1 is changed from 18 mm to 4 mm. The sheet thickness change rate Δt in the first forming process decreases from an increase of 2.8% to an increase of 0.2% as the bending height H1 decreases. On the other hand, the sheet thickness change rate Δt in the second forming process is suppressed to an increase of 10.0% or less. The R / t of Nos. 12 and 13 is 16.7.

[0051] From the above results, it was found that when the bent portion 31 is formed in the first molding process, setting the inner bending radius R to R = 2 to 20 mm and the height H of the bent portion 31 to H1 / H0 = 0.2 to 0.9 reduces the rate of change in sheet thickness Δt in the press-formed product 10 compared to the conventional molding method.

[0052] This embodiment describes the case of press-forming a press-formed product having a top plate portion having a curved portion that protrudes forward and a vertical wall portion connected to the curved portion. However, it can also be applied to the manufacture of a press-formed product having a U-shaped cross-section perpendicular to the front-to-back direction, having a top plate portion having curved portions that protrude forward and backward, respectively, and vertical wall portions connected to each of these curved portions.

[0053] <Summary of Effects> The method for manufacturing a press-formed product 10 shown in this embodiment is a method for manufacturing a press-formed product 10 having a top plate portion 11 having a curved shape that protrudes outward in a plan view, and a vertical wall portion 12 that is bent from the front end of the top plate portion 11 in a direction intersecting the top plate portion 11, and is characterized by including a first molding step of molding an intermediate molded product 30 having a bent portion 31 in which the tip of the vertical wall portion 32 in the portion corresponding to the curved shape of the top plate portion 11 is bent outward, and a second molding step of molding the bent portion 31 bent outward of the intermediate molded product 30 into the vertical wall portion 12 of the press-formed product 10.

[0054] The press die 50 shown in this embodiment is a die 50 for forming an intermediate molded product 30 in which the tip of the vertical wall portion 32 corresponding to the curved shape of the top plate portion 11 is bent outwards, when processing a blank material 20 made of a flat metal plate into a press-formed product 10 having a top plate portion 11 having a curved shape that protrudes outwards in a plan view, and a vertical wall portion 12 that is bent in a direction intersecting the top plate portion 11 from the curved portion of the top plate portion 11, and the lower die 51 is characterized in that it has an overhang portion 54 that extends outwards to the punch 52 that forms the vertical wall portion 12 of the press-formed product 10.

[0055] According to these findings, the amount of shrinkage deformation during the molding of the bent portion 31 in the first molding process is reduced, thereby reducing the occurrence of an increase in plate thickness. Also, because the bent portion 31 is molded in the first process, the rigidity of the intermediate molded product 30 is improved. As a result, when bending the intermediate molded product 30 in the second molding process, the material is less likely to accumulate in one place. Furthermore, because the amount of deformation due to bending during the second molding process is small, excess material caused by material movement in the vertical wall portion 12 is reduced, preventing the formation of wrinkles in the molded vertical wall portion 12. In addition, it is not necessary to use molds with complex shapes as the molds 50 and 70 used in the first and second molding processes.

[0056] Furthermore, when H0 is the height from the surface of the top plate portion 11 of the press-formed product 10 to the tip of the vertical wall portion 12, and H1 is the height from the surface of the portion corresponding to the top plate portion 11 of the intermediate molded product 30 to the upper end 31a of the tip of the bent portion 31 in which the vertical wall portion 32 is bent outward, it is preferable that the ratio H1 / H0 of the height H0 from the surface of the portion corresponding to the top plate portion 11 of the press-formed product 10 to the tip of the vertical wall portion 12 to the height H1 from the surface 11a of the portion corresponding to the top plate portion 11 of the intermediate molded product 30 to the upper end 31a of the tip of the bent portion 31 in which the vertical wall portion 32 is bent outward is 0.2 or more and 0.9 or less.

[0057] According to this, when the press-formed product 10 is formed, the amount of material that moves in the vertical wall portion 12, i.e., the rate of change in plate thickness, can be reduced. As a result, the load on the mold is reduced when press forming is performed, making it possible to extend the lifespan of the mold.

[0058] Furthermore, it is preferable that the ratio R / t of the inner radius R of the bent ridge line 33 of the bent portion 31 in which the vertical wall portion 32 of the intermediate molded product 30 is bent outward, to the plate thickness t, is between the limit minimum value and 20.

[0059] According to this method, sufficient shape rigidity can be obtained in the bent portion 31 in the first molding process without causing cracks in the ridge portion due to bending, and wrinkles can be sufficiently suppressed in the second molding process.

[0060] 10 Press-formed product 11 Top plate section 12 Vertical wall section 13 Ridge section 20 Blank material 30 Intermediate molded product 31 Bent section

Claims

1. A method for manufacturing a press-formed product having a top plate portion having a curved shape that protrudes outward in a plan view, and a vertical wall portion that is bent in a direction intersecting the top plate portion from the portion of the top plate portion that has a curved shape, comprising: a first molding step of molding an intermediate molded product having a shape in which the tip of the vertical wall portion in the portion corresponding to the curved shape of the top plate portion is bent outward; and a second molding step of molding the portion of the vertical wall portion that is bent outward from the intermediate molded product into the vertical wall portion of the press-formed product.

2. The method for manufacturing a press-formed product according to claim 1, wherein when H0 is the height from the surface of the top plate portion of the press-formed product to the tip of the vertical wall portion, and H1 is the height from the surface of the portion corresponding to the top plate portion of the intermediate molded product to the upper end of the tip of the shape in which the vertical wall portion is bent outward, H1 / H0 is 0.2 or more and 0.9 or less.

3. The method for manufacturing a press-formed product according to claim 1 or 2, wherein the ratio R / t of the inner radius R of the bent ridge of the shape in which the vertical wall portion of the intermediate molded product is bent outward is between a minimum limit value and 20.

4. A press mold for processing a metal plate into a press-formed product having a top plate portion having a curved shape that protrudes outward in a plan view, and a vertical wall portion that is bent in a direction intersecting the top plate portion from the curved portion of the top plate portion, wherein the mold is for forming an intermediate molded product having a shape in which the tip of the vertical wall portion in the portion corresponding to the curved shape of the top plate portion is bent outward, the lower mold having a protruding portion that extends outward at the lower part that forms the vertical wall portion of the press-formed product.

5. The press die according to claim 4, comprising a first die having a punch and a second die having a pad and a die, the die comprising a punch surface on which the metal plate is placed, a rounded punch shoulder portion at the end of the punch surface for forming the ridge of an intermediate molded product, and a punch vertical wall portion extending continuously from the punch shoulder portion, the punch vertical wall portion having a protruding portion at an end of the punch vertical wall portion different from the punch shoulder portion for bending the tip of the vertical wall portion of the intermediate molded product, the pad comprising a pad positioned opposite the punch surface and provided with a biasing means for clamping the metal plate, and the die comprising a die lower surface positioned opposite the protruding portion of the punch for bending the tip of the vertical wall portion of the intermediate molded product, and a die shoulder portion having a rounded die at the punch-side end of the die lower surface.

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