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 making an angle formed by the top plate part and the vertical wall part larger than an angle formed by the top plate part and the vertical wall part of the press-formed article, and forming an intermediate formed article having a shape in which the leading end of the vertical wall part of a portion corresponding to the curved shape of the top plate part is bent inward; and a second forming step for forming the vertical wall part of the intermediate formed article and a portion of the vertical wall part bent inward to form the vertical wall part of the press-formed article.

Description

Method for manufacturing a press-formed product and press mold

[0001] The present invention relates to a method for manufacturing a press-formed product having a top plate portion with 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 mold used in the method.

[0002] In recent years, in order to achieve both improved collision safety and weight reduction of automobiles, high-strength steel sheets (hereinafter referred to as high-strength steel sheets) with high yield strength and tensile strength are used for vehicle body components. For example, in the press forming of a vehicle body component having a top plate portion with a curved shape protruding outward and a vertical wall portion continuous with the 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, and 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 occurrence 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 main forming step (see, for example, Patent Document 1 and Patent Document 2). In addition to this, 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 (see, for example, Patent Document 3).

[0004] Japanese Patent Application Laid-Open No. 2013-169578 Japanese Patent Application Laid-Open No. 2023-177203 Japanese Patent Application Laid-Open No. 2016-221558

[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] The present invention provides a method for manufacturing a press-formed product that advantageously solves the above problems, and is characterized by comprising: a first molding step of molding an intermediate molded 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, wherein the angle between the top plate portion and the vertical wall portion is made larger than the angle between the top plate portion and the vertical wall portion of the press-formed product, and the tip of the vertical wall portion in the portion of the top plate portion corresponding to the curved shape is bent inward; and a second molding step of molding the vertical wall portion and the portion of the vertical wall portion bent inward of the intermediate molded product to form the vertical wall portion of the press-formed product.

[0010] Furthermore, the manufacturing method of the press-formed product according to the present invention is more preferably provided by: (a) when the angle between the top plate portion and the vertical wall portion of the press-formed product is θ0, and the angle between the top plate portion and the vertical wall portion of the intermediate molded product is θ1, the ratio θ1 / θ0 is 1.06 or more and 1.94 or less; and (b) when the height from the surface of the top plate portion of the press-formed product to the tip of the vertical wall portion is H0, and the distance from the ridge of the portion of the vertical wall portion of the intermediate molded product that is bent inward to the tip is H, the ratio H / H0 is 0.05 or more and 0.71 or less.

[0011] The present invention provides a press die that advantageously solves the above problems, which processes 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 angle between the top plate portion and the vertical wall portion is made larger than the angle between the top plate portion and the vertical wall portion of the press-formed product, and the tip of the vertical wall portion in the portion corresponding to the curved shape of the top plate portion is bent inward, and the die comprises a first die having a punch and a second die having a pad and a die, the punch having a punch surface on which the metal sheet is placed, and the punch The punch surface is provided with a rounded punch shoulder portion at its edge for forming the ridge portion of an intermediate molded product, and a punch vertical wall portion extending continuously from the punch shoulder portion, wherein the angle between the punch surface and the punch vertical wall portion is greater than the angle between the top plate portion of the press-formed product and the vertical wall portion, and the punch vertical wall portion is provided with a rounded wall-fold shoulder portion at an end of the punch vertical wall portion different from the punch shoulder portion, and a cut-off portion extending continuously from the wall-fold shoulder portion, the pad is positioned opposite the punch surface and is provided with a biasing means for clamping the metal plate, and the die is provided with a die vertical wall portion positioned opposite the punch vertical wall portion, a die shoulder portion at its tip, and a pressing portion positioned opposite the cut-off portion of the punch.

[0012] 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.

[0013] 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 die 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 tip of the wall fold portion of the intermediate molded product in contact with the punch. This is a cross-sectional view showing the die 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] As shown in Figures 3(a) and (b), the intermediate molded product 30 has an angle θ1 between the top plate portion 11 and the vertical wall portion 32 that is greater than the angle θ0 between the top plate portion 11 and the vertical wall portion 12 of the target shape press-formed product 10. Furthermore, it has a wall fold portion 31 formed by folding at least a part of the portion corresponding to the vertical wall portion 12 of the target shape press-formed product 10 inward. The wall fold portion 31 is formed by folding it so that the angle φ with the top plate portion 11 is 90° or more and is smaller than the angle θ1 between the top plate portion 11 and the vertical wall portion 32.

[0020] The vertical wall portion 32 of the intermediate molded product is bent at a ridge portion 34 that corresponds to the ridge portion 13 between the top plate portion 11 and the vertical wall portion 12 in the target shape of the press-molded product 10.

[0021] In the intermediate molded product 30 described above, the angle θ1 between the back surface 11b of the top plate portion 11 and the inner surface 32b of the vertical wall portion 32 is preferably greater than the angle θ0 between the back surface 11b of the top plate portion 11 and the inner surface 12b of the vertical wall portion 12 of the press-formed product 10, which is the target shape, as shown in Figure 3(b), and less than 180°. Hereinafter, the angle θ1 between the back surface 11b of the top plate portion 11 and the inner surface 32b of the vertical wall portion 32 will be simply referred to as the angle θ1 between the top plate portion 11 and the vertical wall portion 32. The angle θ0 between the back surface 11b of the top plate portion 11 and the inner surface 12b of the vertical wall portion 12 will be referred to as the angle θ0 between the top plate portion 11 and the vertical wall portion 12. Figure 3(a) illustrates the case where the angle θ1 between the top plate portion 11 and the vertical wall portion 32 is θ1 = 110°. Figure 3(b) illustrates the case where the angle θ0 between the top plate portion 11 and the vertical wall portion 12 is θ0 = 90°.

[0022] Furthermore, the distance H from the ridge line 33 to the tip 31a of the wall folding portion 31, which is bent inward into the vertical wall portion 32 of the intermediate molded product 30, is set to satisfy, for example, the following equation (1). Hereinafter, the distance H from the ridge line 33 to the tip 31a of the wall folding portion 31 will simply be referred to as the length H of the wall folding portion 31. The position of the ridge line 33 that serves as the reference point for the length H of the wall folding portion 31 is the center of the outer surface arc of the ridge line 33 in the A-A' cross section of Figure 1 shown in Figure 3(a). The distance from this reference point to the tip 31a parallel to the outer surface of the wall folding portion 31 is defined as the length H of the wall folding portion 31. 0.05 ≤ H / H0 ≤ 0.71 ....(1) 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 molded product 10 (see Figure 3(b)). For example, the height H0 is, for instance, H0 = 20 mm.

[0023] In the ridge portion 33 between the vertical wall portion 32 and the wall folding portion 31, when the inner radius of the ridge portion 33 (hereinafter referred to as the inner bending radius) is R and the thickness of the blank material 20 is t, it is preferable that the ratio R / t of the inner bending radius R to the thickness t of the blank material 20 is between a minimum limit value and 20. Here, the minimum limit value 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 decreased. 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.

[0024] Furthermore, the angle φ between the wall-folded portion 31 and the top plate portion 11 must be smaller than the angle θ1 between the top plate portion 11 and the vertical wall portion 32. Preferably, the angle φ between the wall-folded portion 31 and the top plate portion 11 is 90° or more. Within that range, the wall-folded portion 31 can be bent inward relative to the vertical wall portion 32 by press molding without using any special method. In addition, sufficient shape rigidity can be obtained. Here, the angle φ between the wall-folded portion 31 and the top plate portion 11 is the angle between the extending direction from the lower end of the outer surface of the wall-folded portion 31 toward the top plate portion 11 and the extending direction of the surface 11a of the top plate portion 11.

[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 on 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 54 that extends continuously from the punch shoulder portion 52b. The angle between the surface 52a of the punch 52 and the punch vertical wall portion 54 is the angle θ1 described above. The lower part of the punch vertical wall portion 54 is provided with a rounded wall folding shoulder portion 54b for bending the tip of the vertical wall portion 32 of the intermediate molded product 30, and a cut-off portion 54a that extends continuously from the wall folding shoulder portion 54b is provided. The cut-off portion 54a and the wall-folded shoulder portion 54b are provided in a range that corresponds to the curved shape that protrudes outward from the top plate portion of the press-formed 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, by receiving a reaction force from the blank material 20 being bent. As shown in the example in Figure 4, it is preferable that the upper surface of the backup block 53 be positioned above the wall-folded shoulder portion 54b provided on the punch 52. This enhances the effect of the backup block 53 in preventing the die 57 from moving away from the punch 52. Forming can be performed without the backup block 53, but it is preferable to have one.

[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 component that moves vertically and presses the blank material 20 held between the punch 52 and the pad 56. The die vertical wall portion of the die 57, which corresponds to the vertical wall portion 32 of the intermediate molded product 30, is positioned opposite the punch vertical wall portion 54. The angle between the die vertical wall portion and the surface 52a of the punch 52 coincides with the angle θ1 described above. A push-in portion 57b is provided at the bottom of the die 57 to bend the tip of the vertical wall portion 32 of the intermediate molded product 30. A die shoulder portion 57a ​​is provided at the lower end of the push-in portion 57b of the die 57. By providing the die shoulder portion 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. The die 57 also forms a wall-fold portion 31 by clamping the tip of the blank material 20 with the cut-off portion 54a, which corresponds to the wall-fold portion of the punch 52. At that time, the die shoulder portion 57a ​​allows it to descend easily. The indentation portion 57b of the die 57 is provided in a range that corresponds to a curved shape that protrudes outward from the top plate portion of the press-formed product in a plan view.

[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 a metal plate is placed, a rounded punch shoulder 52b at the end of the surface 52a for forming the ridge portion 34 of the intermediate molded product 30, and a punch vertical wall portion 54 that extends continuously from the punch shoulder portion 52b. Preferably, the angle θ1 between the surface 52a of the punch 52 and the punch vertical wall portion 54 is greater than the angle θ0 between the top plate portion 11 and the vertical wall portion 12 of the press molded product 10. Preferably, the punch vertical wall portion 54 has a rounded wall-fold shoulder portion 54b at an end different from the punch shoulder portion 52b, and a cut-off portion 54a that extends continuously from the wall-fold shoulder portion 54b. The pad 56 is preferably positioned opposite the surface 52a of the punch 52 and is provided with a biasing means 58 for gripping a metal plate. The die 57 is preferably provided with a die vertical wall portion positioned opposite the punch vertical wall portion 54, a die shoulder portion 57a ​​at its tip, and a pressing portion 57b positioned opposite the cut-off portion 54a of the punch 52.

[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. Note that the punch 52 used in the first molding process and the punch 72 used in the second molding process differ only in the portion 54 corresponding to the vertical wall. This 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 made common.

[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 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. The punch 72 is also provided with a punch shoulder portion 72b. The inner surface of the ridge portion 34 of the intermediate molded product 30 comes into contact with the punch shoulder portion 72b, and the vertical wall portion 32 of the intermediate molded product 30 is bent.

[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, due to the reaction force from the intermediate molded product 30 being bent.

[0034] The pad 76 moves toward the punch 72, and clamps the top plate 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, which is held between the punch 72 and the pad 76, is pressed, the bending of the vertical wall portion 32 and the flattening of the wall fold portion 31 of the intermediate molded product 30 are facilitated.

[0036] The manufacturing process of the press-formed product 10 shown in this embodiment will now be described. As mentioned 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 34 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 inside of the ridge portion 33, which is the boundary with the wall fold portion, of the part of the blank material 20 corresponding to the vertical wall portion 32, comes into contact with the wall fold shoulder 54b of the punch 52 and bends inward. As a result, an intermediate molded product 30 having a top plate portion 11, a vertical wall portion 32, and a wall folding 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 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 die shoulder portion 77a presses against the vertical wall portion 32 of the intermediate molded product 30, bending it at the ridge portion 13 so that it becomes the vertical wall portion 12 of the press molded product 10. During this process, the tip of the wall-fold portion 31 comes into contact with the side surface of the punch 72 (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 ridge portion 33 is bent back, and the wall folded 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] It was found that the rate of change in sheet thickness Δt of the intermediate molded product 30 produced in the first molding process was within ±10.0%. Furthermore, it was found that the rate of change in sheet thickness Δt of the press-formed product 10 produced in the second molding process was also within ±10.0%.

[0042] The following describes the verification of the plate thickness change rate Δt for the intermediate molded product 30 and the press-formed product 10. For the verification of the plate thickness change rate, the angle θ1, the height H of the wall fold portion 31, and the ratio H / H0 of the height H of the wall fold portion 31 of the intermediate molded product 30 to the height H0 of the vertical wall portion 12 of the press-formed product 10 were varied. The blank material 20 used in the verification of the plate thickness change rate Δt was a steel plate with a plate thickness t = 1.2 mm and a tensile strength of 1180 MPa.

[0043] Table 1 shows the verification results of the thickness change rate for intermediate molded products and press-formed products. Note that if wrinkles occur and are crushed at the bottom dead center of the molding process, a large increase in thickness will occur. If the occurrence of wrinkles can be suppressed, the wrinkles will not be crushed, and therefore the increase in thickness will also be suppressed. A maximum thickness change rate of 10.0% or less is considered acceptable.

[0044]

[0045] In Table 1, for Invention Examples Nos. 3 to 14, in the first forming step, the angle θ1 formed between the top plate portion 11 and the vertical wall portion 32 was changed within the range of θ1 = 95° to 175°. Also, the length H of the wall folding portion 31 was changed within the range of H = 1 to 15 mm. Further, the inner bending radius R of the ridge line portion 33 was set to 3 mm. In the second forming step, the height H0 of the vertical wall portion 12 was set to H0 = 20 mm. In the intermediate molded product 30, the angle φ formed between the top plate portion 11 and the wall folding portion 31 was set to 90°. Also, the angle θ0 formed between the top plate portion 11 and the vertical wall portion 12 of the press-molded product 10 was set to 90°.

[0046] Note that the conventional method of forming the vertical wall portion 12 in one press molding was taken as Conventional Example No. 1. In No. 1, the maximum value of the plate thickness change rate Δt was an increase of 11.1%. No. 2 was taken as a comparative example, and it shows the result when, in the first forming step, the angle θ1 between the top plate portion 11 and the vertical wall portion 32 of the intermediate molded product is set to 95° without providing a wall folding portion, and in the second forming step, the height H0 of the vertical wall portion 12 is formed to be 20 mm. In this case, the plate thickness change rate Δt in the second forming step was a maximum increase of 10.2%. <^

[0047] In Nos. 3 to 5, the case where the angle θ1 between the top plate portion 11 and the vertical wall portion 32 was set to θ1 = 95° in the first forming step is shown. Also, in Nos. 3 to 5, the length H of the wall folding portion 31 was changed within the range of H = 1 to 15 mm respectively. In Nos. 3 to 5, the plate thickness change rate Δt in the first forming step was an increase of 10.0% or less. Also, in these Nos. 3 to 5, the plate thickness change rate in the second forming step was 10.0% or less.

[0048] In Nos. 6 to 8, the case where the angle θ1 between the top plate portion 11 and the vertical wall portion 32 was set to θ1 = 110° in the first forming step is shown. Also, in Nos. 6 to 8, the length H of the wall folding portion 31 was changed within the range of H = 1 to 15 mm respectively. In Nos. 6 to 8, the plate thickness change rate Δt in the first forming step was an increase of 10.0% or less. Also, in these Nos. 6 to 8, the plate thickness change rate in the second forming step was 10.0% or less.

[0049] Cases No. 9 to 11 show the case where the angle θ1 between the top plate portion 11 and the vertical wall portion 32 is θ1 = 150° in the first molding process. Also in cases No. 9 to 11, the length H of the wall fold portion 31 is varied between H = 1 and 15 mm. In cases No. 9 to 11, the rate of change in plate thickness Δt in the first molding process was an increase of 7.0% or less. Furthermore, in cases No. 9 to 11, the rate of change in plate thickness in the second molding process was 9.0% or less.

[0050] In cases No. 12 to 14, the angle θ1 between the top plate portion 11 and the vertical wall portion 32 is set to θ1 = 175° in the first molding process. In cases No. 12 to 14, the length H of the wall fold portion 31 is varied between H = 1 and 15 mm. In cases No. 12 to 14, the rate of change in plate thickness Δt in the first molding process was an increase of 8.0% or less. In cases No. 12 to 14, the rate of change in plate thickness in the second molding process was also 8.0% or less.

[0051] From the above results, it was found that by setting the angle θ1 between the top plate portion 11 and the vertical wall portion 32 to θ1 = 95° to 175° and the length H of the wall fold portion 31 to H / H0 = 0.05 to 0.71 in the first molding process, the rate of increase in plate thickness of the press-molded product 10 is reduced 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 manufacturing method for the press-formed product 10 shown in this embodiment is a manufacturing method for a press-formed product 10 having a top plate portion 11 which has a curved shape with its front end protruding outward in a plan view, and a vertical wall portion 12 which is bent from the front end of the top plate portion 11 in a direction intersecting the top plate portion 11, and includes a first molding step of molding an intermediate molded product 30 having a wall-fold portion 31 in which the tip of the vertical wall portion 32 in the part corresponding to the curved shape of the top plate portion 11 is bent inward, and a second molding step of molding the vertical wall portion 32 and the wall-fold portion 31 bent inward of the intermediate molded product 31 into the vertical wall portion 12 of the press-formed product 10, characterized in that the angle φ between the top plate portion 11 and the wall-fold portion 31 in the intermediate molded product 30 is 90° or more and less than θ1.

[0054] According to the press die 50 shown in this embodiment, 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 outward 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, the angle θ1 between the top plate portion 11 and the vertical wall portion 32 is made larger than the angle θ0 between the top plate portion 11 and the vertical wall portion 12 of the press-formed product 10, and the die 50 is for forming an intermediate molded product 30 having a wall folded 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 inward, the die 50 comprises a first die having a punch 52 and a second die having a pad 56 and a die 57, which are arranged opposite each other, the surface 52a of the punch 52 on which the blank material 20 is placed, and the punch 5 The surface 52a of the punch 52 is provided with a rounded punch shoulder 52b at the end for forming the ridge portion 34 of the intermediate molded product 30, and a punch vertical wall portion 54 that extends continuously from the punch shoulder portion 52b. The angle θ1 between the surface 52a of the punch 52 and the punch vertical wall portion 54 is greater than the angle θ0 between the top plate portion 11 and the vertical wall portion 12 of the press molded product 10. The punch vertical wall portion 54 is provided with a rounded wall-fold shoulder portion 54b at an end different from the punch shoulder portion 52b, and a cut-off portion 54a that extends continuously from the wall-fold shoulder portion 54b. The pad 56 is positioned opposite the surface 52a of the punch 52 and is provided with a biasing means 58 for clamping the blank material 20. The die 57 is provided with a die vertical wall portion positioned opposite the punch vertical wall portion 54, a die shoulder portion 57a ​​at its tip, and a press-in portion 57b positioned opposite the cut-off portion 54a of the punch 52.

[0055] According to these findings, the amount of shrinkage deformation is reduced during the molding of the vertical wall portion 32 and the wall folding portion 31 in the first molding process, thereby reducing the occurrence of an increase in plate thickness. Furthermore, since the wall folding portion 31 is molded in the first molding 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. In addition, because the amount of deformation due to bending is small when the second molding process is performed, 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. Moreover, it is not necessary to use molds with complex shapes as the molds used in the first and second molding processes.

[0056] When the angle between the top plate portion 11 and the vertical wall portion 12 of the press-formed product 10 is defined as θ0, and the angle between the top plate portion 11 and the vertical wall portion 32 of the intermediate molded product 30 is defined as θ1, it is preferable that the ratio θ1 / θ0 of the angle between the top plate portion 11 and the vertical wall portion 12 of the intermediate molded product 30 to the angle θ0 between the top plate portion 11 and the vertical wall portion 12 of the press-formed product 10 is 1.06 or more and 1.94 or less.

[0057] Furthermore, it is preferable that 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 be defined as H0, and the distance from the ridge portion 33 bent inward on the vertical wall portion of the intermediate molded product 30 to the tip of the wall fold portion 31 be defined as H, and that the ratio H / H0 of the distance from the ridge portion 33 bent inward on the vertical wall portion 32 of the intermediate molded product 30 to the tip of the wall fold portion 31 be defined as H0 (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) be defined as 0.05 or more and 0.71 or less.

[0058] According to these methods, 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 increase 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.

[0059] 10 Press-formed product 11 Top plate section 12 Vertical wall section 13 Ridge section 20 Blank material 30 Intermediate molded product 31 Wall folding 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 angle between the top plate portion and the vertical wall portion is made larger than the angle between the top plate portion and the vertical wall portion of the press-formed product, and the tip of the vertical wall portion in the portion of the top plate portion corresponding to the curved shape is bent inward; and a second molding step of molding the vertical wall portion and the portion of the vertical wall portion bent inward of the intermediate molded product to form the vertical wall portion of the press-formed product.

2. The method for manufacturing a press-formed product according to claim 1, wherein when the angle between the top plate portion and the vertical wall portion of the press-formed product is θ0, and the angle between the top plate portion and the vertical wall portion of the intermediate-formed product is θ1, the ratio θ1 / θ0 is 1.06 or more and 1.94 or less.

3. The method for manufacturing a press-formed product according to claim 1 or 2, 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 H is the distance from the ridge of the portion folded inward on the inside of the vertical wall portion of the intermediate molded product to the tip, the ratio H / H0 is 0.05 or more and 0.71 or less.

4. A die for forming an intermediate molded product in which a metal plate is processed 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 angle between the top plate portion and the vertical wall portion is greater than the angle between the top plate portion and the vertical wall portion of the press-formed product, and the tip of the vertical wall portion in the portion corresponding to the curved shape of the top plate portion is bent inward, wherein the die comprises a first die having a punch and a second die having a pad and a die, which are arranged opposite each other, the punch has a punch surface on which the metal plate is placed, a punch shoulder portion having a rounded shape at the end of the punch surface for forming the ridge portion of the intermediate molded product, and a punch vertical wall portion extending continuously from the punch shoulder portion, A press die comprising: an angle between the punch surface and the punch vertical wall portion being greater than the angle between the top plate portion and the vertical wall portion of the press-formed product; a rounded wall-fold shoulder portion and a cut-off portion extending continuously from the wall-fold shoulder portion being provided at an end of the punch vertical wall portion different from the punch shoulder portion; a pad being positioned opposite the punch surface and provided with a biasing means for clamping the metal plate; and a die being provided with a die vertical wall portion positioned opposite the punch vertical wall portion, a die shoulder portion at its tip, and a pressing portion positioned opposite the cut-off portion of the punch.

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