Method for manufacturing press-formed products and molds
The mold configuration with a moving second lower mold minimizes bending and unbending deformation of vertical walls, addressing springback and joint fractures in press-formed products, especially for high-strength materials.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- NIPPON STEEL CORPORATION
- Filing Date
- 2025-09-05
- Publication Date
- 2026-07-30
AI Technical Summary
Press-formed products experience significant springback of vertical walls due to bending and unbending deformation during manufacturing, particularly when using high-strength materials, leading to potential fractures at welded joints.
A method involving a mold configuration with a first and second lower mold, where the second lower mold moves outward in the width direction after forming the top plate and initial ridge lines, reducing bending and unbending deformation of vertical walls by avoiding premature contact with the flange-forming die.
This approach effectively suppresses springback of vertical walls and reduces the likelihood of fractures at welded joints, maintaining product integrity and reducing residual stress.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a method for manufacturing a press-formed product and a mold.
Background Art
[0002] For example, press-formed products are used in the bodies of vehicles such as automobiles. Press-formed products are manufactured by subjecting a blank to press working using a lower mold and an upper mold. Conventionally, various techniques have been proposed regarding methods for manufacturing press-formed products.
[0003] For example, Patent Document 1 discloses a technique for manufacturing a press-formed product using an upper punch and a lower punch (lower mold), and a die (upper mold). The upper punch is provided so as to be separable from and contactable with the lower punch in the height direction. In Patent Document 1, with a predetermined punch gap provided between the upper punch and the lower punch, the top plate and a part of the vertical wall of the press-formed product are formed by the upper punch and the die, and then the die is moved toward the lower punch side, and the remaining part of the vertical wall and the flange are formed in a state where there is no punch gap.
[0004] Patent Document 2 discloses a technique for manufacturing a press-formed product provided with a shape-changing portion at a ridge line portion between a top plate and a vertical wall. In Patent Document 2, the press-formed product is manufactured through a first press working step and a second press working step. In the first press working step, the blank is subjected to press working by a first punch (lower mold), and a first die and a first pad (upper mold), whereby the top plate, the ridge line portion, and a part of the vertical wall are formed. In the second press working step, the remaining part of the vertical wall and the flange are sequentially formed by a main and sub second punch (lower mold), and a second die and a second pad (upper mold).
[0005] Patent Document 3 discloses a technique for manufacturing a press-formed product by hot press working. In Patent Document 3, a punch body, which is a part of the lower mold, is divided into two movable punch portions. These movable punch portions move against the biasing force of a pressurizing member provided between the movable punch portions when the upper mold and the lower mold are clamped, and absorb variations in the plate thickness of the blank. [Prior art documents] [Patent Documents]
[0006] [Patent Document 1] Patent No. 6777053 [Patent Document 2] Patent No. 6369556 [Patent Document 3] Patent No. 6619645 [Overview of the project] [Problems that the invention aims to solve]
[0007] Generally, when manufacturing a press-formed product from a blank using an upper and lower die, including a top plate, vertical walls, and flanges, the vertical walls undergo bending and unbending deformation between the upper and lower dies. Residual stress can be generated in the vertical walls due to this bending and unbending deformation. Therefore, springback of the vertical walls may occur after demolding of the press-formed product. Springback of the vertical walls is particularly likely to occur when the blank is made of a high-strength material.
[0008] The object of this disclosure is to provide a method for manufacturing a press-formed product that can suppress the springback of the vertical wall. [Means for solving the problem]
[0009] The method for manufacturing a press-formed product according to this disclosure comprises a preparation step and a forming step. In the preparation step, a blank is prepared. In the forming step, a mold is used to press-form the blank to obtain a press-formed product. The mold includes a lower mold and an upper mold. The lower mold includes a first lower mold and a second lower mold. The press-formed product includes a top plate, a vertical wall, and a flange. The vertical wall is connected to the top plate via a first ridge. The flange is connected to the vertical wall via a second ridge on the side opposite to the top plate. In the forming step, the upper mold and the first lower mold start forming the top plate and the first ridge with the second lower mold positioned inward in the width direction of the mold relative to the portion of the upper mold corresponding to the flange. Then, the upper mold and the second lower mold form the second ridge and the flange by moving the second lower mold outward in the width direction relative to the first lower mold. [Effects of the Invention]
[0010] According to the method for manufacturing press-formed products described herein, it is possible to suppress the springback of the vertical walls. [Brief explanation of the drawing]
[0011] [Figure 1] Figure 1 is a perspective view of a press-formed product manufactured by the manufacturing method according to each embodiment. [Figure 2] Figure 2 is a cross-sectional view of the press-formed product shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view of the mold according to the first embodiment. [Figure 4A] Figure 4A is a schematic diagram illustrating the manufacturing method of a press-formed product according to the first embodiment. [Figure 4B] Figure 4B is a schematic diagram illustrating the manufacturing method of a press-formed product according to the first embodiment. [Figure 4C] Figure 4C is a schematic diagram illustrating the manufacturing method of a press-formed product according to the first embodiment. [Figure 4D] Figure 4D is a schematic diagram illustrating the manufacturing method of a press-formed product according to the first embodiment. [Figure 4E]FIG. 4E is a schematic diagram for explaining a method of manufacturing a press-formed product according to the first embodiment. [Figure 4F] FIG. 4F is a schematic diagram for explaining a method of manufacturing a press-formed product according to the first embodiment. [Figure 5A] FIG. 5A is a schematic diagram for explaining a method of manufacturing a general press-formed product. [Figure 5B] FIG. 5B is a schematic diagram for explaining a method of manufacturing a general press-formed product. [Figure 6] FIG. 6 is a cross-sectional view of a mold according to the second embodiment. [Figure 7A] FIG. 7A is a schematic diagram for explaining a method of manufacturing a press-formed product according to the second embodiment. [Figure 7B] FIG. 7B is a schematic diagram for explaining a method of manufacturing a press-formed product according to the second embodiment. [Figure 8] FIG. 8 is a cross-sectional view of a mold according to a modification of the first embodiment. [Figure 9] FIG. 9 is a cross-sectional view of a mold according to a modification of the second embodiment.
MODE FOR CARRYING OUT THE INVENTION
[0012] The method of manufacturing a press-formed product according to the embodiment includes a preparation step and a forming step. In the preparation step, a blank is prepared. In the forming step, using a mold, the blank is subjected to press working to obtain a press-formed product. The mold includes a lower mold and an upper mold. The lower mold includes a first lower mold and a second lower mold. The press-formed product includes a top plate, a vertical wall, and a flange. The vertical wall is connected to the top plate via a first ridge line portion. The flange is connected to the vertical wall via a second ridge line portion on the side opposite to the top plate. In the forming step, after starting the forming of the top plate and the first ridge line portion by the upper mold and the first lower mold with the second lower mold disposed inside in the width direction of the mold with respect to the portion of the upper mold corresponding to the flange, the second lower mold is moved outward in the width direction with respect to the first lower mold, whereby the second ridge line portion and the flange are formed by the upper mold and the second lower mold (the first configuration).
[0013] When manufacturing a press-formed product by press working, the upper die and the lower die are relatively approximated, and a blank is clamped between the upper die and the lower die to form a top plate, vertical walls, and a flange. At this time, in the vertical walls, bending deformation occurs during forming when the upper die approaching the lower die makes contact, and then springback deformation occurs when clamped between the lower die and the upper die. After the forming of the ridge line portion between the top plate and the vertical walls is started, if the end of the blank comes into early contact with the portion of the lower die for forming the flange, in the portion of the blank to be formed into the vertical walls, bending by the upper die occurs at a relatively early timing. In this case, the degree of bending deformation and subsequent springback deformation received by the vertical walls increases.
[0014] On the other hand, in the manufacturing method according to the first configuration, after starting the forming of the top plate and the first ridge line portion between the top plate and the vertical walls by the upper die and the first lower die, the second ridge line portion between the vertical walls and the flange, and the flange are formed by the upper die and the second lower die. The second ridge line portion and the flange are formed by moving the second lower die outward in the width direction of the die with respect to the first lower die. In the manufacturing method according to the first configuration, when the forming of the first ridge line portion is started, the second lower die is arranged inward in the width direction of the die with respect to the portion of the upper die corresponding to the flange. Therefore, the end of the blank does not come into early contact with the second lower die for forming the flange, and substantial bending of the vertical walls by the upper die is unlikely to occur during forming. Thereby, the amount of bending and springback deformation in the vertical walls can be reduced. Therefore, springback of the vertical walls due to bending and springback deformation is likely to be suppressed.
[0015] In the manufacturing method according to the first configuration, in the forming process, the second lower die may be moved outward in the width direction by the first lower die (second configuration).
[0016] In the manufacturing method according to the first configuration, in the forming process, the second lower die may be moved outward in the width direction by the upper die (third configuration).
[0017] In a manufacturing method relating to any of the first to third configurations, the blank may include a blank body and a reinforcing material. The reinforcing material is superimposed on the blank body and joined to the blank body by welding. In this case, in the press-formed product, the welded portion between the blank body and the reinforcing material may be located on the vertical wall (fourth configuration).
[0018] In so-called patchwork blanks, heat-affected zone (HAZ) softening may occur during welding between the blank body and the reinforcing material. If the weld containing the HAZ softened area is located on the vertical wall of a press-formed product, bending and unbending deformation may occur at the weld during the vertical wall forming process, potentially causing strain to concentrate on the HAZ softened area and leading to fracture at the weld. Even if HAZ softening does not occur during welding, if bending and unbending deformation occur at the weld, strain may concentrate on the edge of the weld metal, which is relatively hard and has poor ductility, potentially leading to fracture at the weld. However, in the manufacturing method according to this embodiment, when forming the first ridge between the top plate and the vertical wall begins, the second lower die is positioned inward in the width direction of the die relative to the portion of the upper die corresponding to the flange. Therefore, the end of the blank does not come into contact with the second lower die for forming the flange prematurely, and substantial bending of the vertical wall by the upper die is less likely to occur. As a result, the degree of bending and unbending deformation at and near the weld is reduced, making fracture at the weld less likely.
[0019] In a manufacturing method relating to any of the first to fourth configurations, the blank may be formed from a steel plate having a tensile strength of 440 MPa or more (fifth configuration).
[0020] The mold according to the embodiment comprises a lower mold and an upper mold. The lower mold includes a first lower mold and a second lower mold. The first lower mold includes a lower mold top surface and a lower mold side surface. The lower mold side surface is connected to the lower mold top surface via a lower mold shoulder. The second lower mold includes a lower mold flange surface. The upper mold includes an upper mold side surface and an upper mold flange surface. The upper mold side surface corresponds to the lower mold side surface. The upper mold flange surface is connected to the upper mold side surface via an upper mold shoulder. The upper mold flange surface corresponds to the lower mold flange surface. The upper mold is configured to be approachable to the lower mold in the height direction of the mold. The second lower mold is configured to be movable in the width direction of the mold relative to the first lower mold (sixth configuration).
[0021] In the mold according to the sixth configuration, the first lower mold may be configured to be able to approach the second lower mold in the height direction. In this case, the second lower mold may be configured to move in the width direction by the first lower mold which approaches the second lower mold in the height direction (seventh configuration).
[0022] In the mold according to the sixth configuration, the second lower mold may be configured to move in the width direction by an upper mold that approaches the lower mold in the height direction (eighth configuration).
[0023] Embodiments of this disclosure will be described below with reference to the drawings. In these drawings, the same or equivalent components are denoted by the same reference numerals, and the same description will not be repeated.
[0024] <First Embodiment> [Composition of press-formed product] Figure 1 is a perspective view of a press-formed product 10 manufactured by the manufacturing method according to this embodiment. Figure 2 is a cross-sectional view (II-II section) of the press-formed product 10 shown in Figure 1.
[0025] Referring to Figure 1, the press-formed product 10 is, for example, a long-shaped member. The press-formed product 10 includes a top plate 11, vertical walls 12a, 12b, and flanges 13a, 13b.
[0026] The top plate 11 extends in the longitudinal direction of the press-formed product 10. The vertical wall 12a is connected to the top plate 11 via the ridge portion 14a. The vertical wall 12b is connected to the top plate 11 on the opposite side of the vertical wall 12a via the ridge portion 14b. The vertical walls 12a and 12b each extend along the top plate 11. The flange 13a is continuous with one of the vertical walls 12a via the ridge portion 15a on the opposite side of the top plate 11. The flange 13b is continuous with the other vertical wall 12b via the ridge portion 15b on the opposite side of the top plate 11. The flanges 13a and 13b each extend along the vertical walls 12a and 12b.
[0027] Referring to Figure 2, in this embodiment, the press-formed product 10 has a substantially hat shape in its cross-sectional view. Specifically, in the press-formed product 10, the vertical walls 12a and 12b face each other with the top plate 11 in between. The vertical walls 12a and 12b may be parallel or non-parallel. In the cross-sectional view of the press-formed product 10, the vertical walls 12a and 12b may be spaced apart from each other as they move from the top plate 11 side toward the flange 13a and 13b side. The flanges 13a and 13b protrude outward from the vertical walls 12a and 12b toward the outside of the press-formed product 10.
[0028] The ridge portion 14a is positioned between the top plate 11 and one of the vertical walls 12a, and is continuous with both the top plate 11 and the vertical wall 12a. The ridge portion 14b is positioned between the top plate 11 and the other vertical wall 12b, and is continuous with both the top plate 11 and the vertical wall 12b. The ridge portions 14a and 14b are corner portions between the top plate 11 and the vertical walls 12a and 12b, respectively. Each of the ridge portions 14a and 14b may have an arc shape in a cross-sectional view of the press-formed product 10.
[0029] Ridge section 15a is positioned between one vertical wall 12a and flange 13a and is continuous with both the vertical wall 12a and flange 13a. Ridge section 15b is positioned between the other vertical wall 12b and flange 13b and is continuous with both the vertical wall 12b and flange 13b. Ridge section 15a is the corner between the vertical wall 12a and flange 13a, and ridge section 15b is the corner between the vertical wall 12b and flange 13b. Each of the ridge sections 15a and 15b may have an arc shape in a cross-sectional view of the press-formed product 10.
[0030] In this embodiment, the press-formed product 10 is formed from a plurality of metal plates 21 and 22. The metal plate 22 is smaller than the metal plate 21. The metal plate 22 is superimposed on the metal plate 21 to partially reinforce it. In this embodiment, the metal plate 22 is superimposed on the metal plate 21 from the inside of the press-formed product 10. However, the metal plate 22 may also be superimposed on the metal plate 21 from the outside of the press-formed product 10.
[0031] The metal plate 22 reinforces the metal plate 21 in at least a portion of the vertical wall 12a and / or vertical wall 12b. More specifically, the metal plates 21 and 22 are superimposed in at least a portion of the vertical wall 12a and / or vertical wall 12b on the top plate 11 side. In this embodiment, the metal plates 21 and 22 are superimposed in a portion of the vertical walls 12a and 12b and on the top plate 11. More specifically, the metal plates 21 and 22 are superimposed across a portion of each of the vertical walls 12a and 12b, the ridge portions 14a and 14b, and the top plate 11. On the other hand, the metal plate 22 is not superimposed on the metal plate 21 in the flanges 13a and 13b. More specifically, the metal plate 22 is not superimposed on the metal plate 21 in the remaining portions of each of the vertical walls 12a and 12b, the ridge portions 15a and 15b, and the flanges 13a and 13b.
[0032] The metal plates 21 and 22 are joined by welding. In the example in Figure 2, the welded joints 23 of the metal plates 21 and 22 are located on the vertical walls 12a and 12b. The welded joints 23 may also be located on parts other than the vertical walls 12a and 12b. For example, in addition to the vertical walls 12a and 12b, the top plate 11 may also have welded joints 23 of the metal plates 21 and 22.
[0033] [Mold configuration] Next, the configuration of the mold 30 according to this embodiment will be described with reference to Figure 3. The mold 30 is used to form the press-formed product 10. The mold 30 can have an elongated shape corresponding to the press-formed product 10. Figure 3 shows a cross-section (transverse plane) of the mold 30 perpendicular to the longitudinal direction.
[0034] Referring to Figure 3, the die 30 comprises a lower die 40 and an upper die 50. The upper die 50 is configured to be accessible to the lower die 40 in the height direction D1 of the die 30. The lower die 40 and the upper die 50 are used, for example, by being mounted on a known press device. In this case, the pressing direction of the press device is the height direction D1 of the die 30. The pressing direction may also be vertical. In a cross-sectional view of the die 30, the direction perpendicular to the height direction D1 is the width direction D2 of the die 30.
[0035] The lower mold 40 includes the first lower mold 41 and the second lower molds 42a and 42b.
[0036] The first lower die 41 includes a lower die top surface 411 and lower die sides 412a and 412b. The lower die top surface 411 is the surface for forming the top plate 11 (Figures 1 and 2) of the press-formed product 10. The lower die top surface 411 intersects with the height direction D1. The lower die top surface 411 may extend parallel to or non-parallel to the width direction D2 in a cross-sectional view of the die 30. The lower die top surface 411 may have a flat shape overall, but may also have recesses or protrusions in part.
[0037] The lower die sides 412a and 412b are primarily surfaces for forming the vertical walls 12a and 12b (Figures 1 and 2) of the press-formed product 10. The lower die side 412a is connected to the lower die top surface 411 via the lower die shoulder 413a. The lower die side 412b is on the opposite side of the lower die side 412a and is connected to the lower die top surface 411 via the lower die shoulder 413b. The lower die sides 412a and 412b may extend parallel to the height direction D1 in a cross-sectional view of the die 30, or they may extend non-parallel. For example, the lower die sides 412a and 412b may extend from the lower die shoulders 413a and 413b such that they separate in the width direction D2 as they move away from the lower die top surface 411 in a cross-sectional view of the die 30.
[0038] The lower die shoulders 413a and 413b are primarily for forming the ridges 14a and 14b (Figures 1 and 2) of the press-formed product 10. In a cross-sectional view of the mold 30, the lower die shoulders 413a and 413b may have a convex arc shape on the outside of the first lower die 41, for example.
[0039] The second lower molds 42a and 42b are separate from the first lower mold 41. The second lower molds 42a and 42b are arranged side by side in the width direction D2 of the mold 30. One of the second lower molds 42a includes a lower mold flange surface 421a. The other of the second lower molds 42b includes a lower mold flange surface 421b. The lower mold flange surfaces 421a and 421b are mainly for forming the flanges 13a and 13b (Figures 1 and 2) of the press-formed product 10. The lower mold flange surfaces 421a and 421b each intersect the height direction D1 of the mold 30. The lower mold flange surfaces 421a and 421b may extend parallel to or non-parallel to the width direction D2 in a cross-sectional view of the mold 30.
[0040] The first lower mold 41 is configured to be able to approach the second lower molds 42a and 42b in the height direction D1 of the mold 30. In this embodiment, the first lower mold 41 is supported by a support member 43 from the opposite side of the top surface 411 of the lower mold. The support member 43 may be movable in the height direction D1 of the mold 30, such as a cushion pin, or it may be expandable and contractible in the height direction D1 of the mold 30, such as a spring or a fluid pressure cylinder. The movement or expansion / contraction of the support member 43 in the height direction D1 causes the first lower mold 41 to approach or move away from the second lower molds 42a and 42b in the height direction D1.
[0041] The second lower molds 42a and 42b are configured to be movable in the width direction D2 of the mold 30 relative to the first lower mold 41. In this embodiment, the second lower molds 42a and 42b are configured to move in the width direction D2 by the first lower mold 41, which approaches the second lower molds 42a and 42b in the height direction D1 of the mold 30. More specifically, the first lower mold 41 and the second lower molds 42a and 42b constitute a cam mechanism. For example, the first lower mold 41 functions as a cam driver, and the second lower molds 42a and 42b function as cam sliders.
[0042] In this case, the first lower mold 41 may further include inclined surfaces 414a and 414b. The inclined surfaces 414a and 414b are connected, for example, to the lower mold sides 412a and 412b opposite the lower mold top surface 411, respectively. The inclined surface 414a is inclined with respect to the height direction D1 such that the side facing the lower mold side 412a is outward in the width direction D2, and the side opposite the lower mold side 412a is inward in the width direction D2. Similarly, the inclined surface 414b is inclined with respect to the height direction D1 such that the side facing the lower mold side 412b is outward in the width direction D2, and the side opposite the lower mold side 412b is inward in the width direction D2.
[0043] The second lower molds 42a and 42b may further include inclined surfaces 422a and 422b, respectively. The inclined surfaces 422a and 422b are positioned inward in the width direction D2 relative to the lower mold flange surfaces 421a and 421b. The inclined surface 422a is inclined with respect to the height direction D1 at substantially the same angle as the inclined surface 414a of the first lower mold 41. The inclined surface 422b is inclined with respect to the height direction D1 at substantially the same angle as the inclined surface 414b of the first lower mold 41.
[0044] In this embodiment, the upper mold 50 includes a first upper mold 51 and a second upper mold 52.
[0045] The first upper die 51 includes upper die sides 511a, 511b and upper die flange sides 512a, 512b. The upper die sides 511a, 511b correspond to the lower die sides 412a, 412b, respectively. That is, the upper die side 511a is configured to form the vertical wall 12a (Figures 1 and 2) of the press-formed product 10 together with the lower die side 412a. Similarly, the upper die side 511b is configured to form the vertical wall 12b (Figures 1 and 2) of the press-formed product 10 together with the lower die side 412b.
[0046] The upper die flange surfaces 512a and 512b correspond to the lower die flange surfaces 421a and 421b, respectively. That is, the upper die flange surface 512a is configured to form the flange 13a of the press-formed product 10 (Figures 1 and 2) together with the lower die flange surface 421a. Similarly, the upper die flange surface 512b is configured to form the flange 13b of the press-formed product 10 (Figures 1 and 2) together with the lower die flange surface 421b.
[0047] The upper die flange surface 512a is connected to the upper die side surface 511a via the upper die shoulder 513a. The upper die flange surface 512b is connected to the upper die side surface 511b via the upper die shoulder 513b. The upper die shoulders 513a and 513b are primarily for forming the ridges 15a and 15b (Figures 1 and 2) of the press-formed product 10. In a cross-sectional view of the die 30, the upper die shoulders 513a and 513b may have, for example, an arc shape that is convex to the outside of the first upper die 51.
[0048] In the example shown in Figure 3, the first upper die 51 is divided in the width direction D2 of the mold 30. Specifically, the first upper die 51 is divided into a main body portion 51a, which includes the upper die side 511a, the upper die shoulder portion 513a, and the upper die flange surface 512a, and a main body portion 51b, which includes the upper die side 511b, the upper die shoulder portion 513b, and the upper die flange surface 512b. However, in the first upper die 51, the main body portions 51a and 51b may be integrated.
[0049] The second upper die 52 is separate from the first upper die 51. The second upper die 52 is positioned opposite the first lower die 41 in the height direction D1 of the mold 30. The second upper die 52 includes a pressing surface 521. The pressing surface 521 corresponds to the top surface 411 of the lower die. That is, the pressing surface 521 is configured to form the top plate 11 (Figures 1 and 2) of the press-formed product 10 together with the top surface 411 of the lower die.
[0050] [Method for manufacturing press-formed products] In this embodiment, a press-formed product 10 is manufactured using a mold 30. The method for manufacturing the press-formed product 10 according to this embodiment comprises a preparation step and a molding step. The method for manufacturing the press-formed product 10 will be described below with reference to Figures 4A to 4F.
[0051] (preparation process) Referring to Figure 4A, the preparation step involves preparing the blank 20. In this embodiment, the blank 20 is a so-called patchwork blank. The blank 20 includes a blank body, which is a metal plate 21, and a reinforcing material, which is a metal plate 22. The blank body 21 has the shape of, for example, the unfolded press-formed product 10 shown in Figures 1 and 2. The reinforcing material 22 is smaller than the blank body 21 in a plan view of the blank 20. The entire reinforcing material 22 is superimposed on the blank body 21.
[0052] The reinforcing member 22 is joined to the blank body 21 by welding. As a result, a welded joint 23 is formed on the blank 20. The blank body 21 and the reinforcing member 22 are joined, for example, by spot welding. However, the blank body 21 and the reinforcing member 22 may also be joined, for example, by laser welding.
[0053] The blank 20 may be formed from a steel plate. For example, the blank 20 is formed from a steel plate having a tensile strength of 440 MPa or more. The tensile strength of the blank 20 is preferably 780 MPa or more, more preferably 1180 MPa or more. The blank body 21 and the reinforcing material 22 may have the same tensile strength or different tensile strengths. The tensile strength of the blank 20 (blank body 21 and reinforcing material 22) can be measured by performing a tensile test in accordance with, for example, JIS Z 2241:2022. The plate thickness of the blank body 21 and the reinforcing material 22 may be the same or different.
[0054] (molding process) As shown in Figures 4B to 4F, in the molding process, a mold 30 is used to press-form the blank 20 to obtain a press-formed product 10. The press-formed product 10 is typically formed by cold-pressing the blank 20.
[0055] Referring to Figure 4B, at the start of the molding process, the blank 20 is placed between the lower mold 40 and the upper mold 50. If the lower mold 40 is located below the upper mold 50, the blank 20 is placed, for example, on the first lower mold 41. In this embodiment, the blank 20 is placed between the lower mold 40 and the upper mold 50 with the reinforcing material 22 facing the first lower mold 41. In this case, the surface of the first lower mold 41 may be provided with a recess 415 to absorb the step difference between the blank body 21 and the reinforcing material 22. However, if the blank 20 is placed with the reinforcing material 22 facing the upper mold 50, the recess to absorb the step difference between the blank body 21 and the reinforcing material 22 may be provided on the upper mold 50.
[0056] Referring to Figure 4C, with the blank 20 placed between the lower die 40 and the upper die 50, the upper die 50 is brought relatively closer to the lower die 40 in the height direction (pressing direction) D1 of the mold 30. This initiates the forming of the top plate 11 by the upper die 50 and the first lower die 41. Specifically, the blank 20 is held between the lower die top surface 411 of the first lower die 41 and the pressing surface 521 of the second upper die 52, thereby forming the top plate 11. At this time, the second lower dies 42a and 42b are positioned inward in the width direction D2 of the mold 30 with respect to the portion of the upper die 50 corresponding to the flanges 13a and 13b of the press-formed product 10 (Figures 1 and 2). More specifically, the lower die flange surfaces 421a and 421b of the second lower dies 42a and 42b are positioned inward in the width direction D2 compared to the upper die flange surfaces 512a and 512b of the first upper die 51. In this embodiment, the entirety of the lower mold flange surfaces 421a and 421b are positioned inward in the width direction D2 compared to the upper mold flange surfaces 512a and 512b. However, a portion of the lower mold flange surfaces 421a and 421b may overlap with a portion of the upper mold flange surfaces 512a and 512b in the width direction D2.
[0057] Referring to Figure 4D, the molding of the ridges 14a and 14b is then started by the upper die 50 and the first lower die 41. Specifically, with the blank 20 held between the first lower die 41 and the second upper die 52, the first upper die 51 is brought relatively closer to the lower die 40 in the height direction (pressing direction) D1 of the mold 30. As a result, the portion of the blank 20 not held down by the second upper die 52 is pushed towards the lower die 40 by the first upper die 51. The blank 20 is bent along the lower die shoulders 413a and 413b, thus initiating the molding of the ridges 14a and 14b. The molding of the vertical walls 12a and 12b is also started by the lower die sides 412a and 412b of the first lower die 41 and the upper die sides 511a and 511b of the first upper die 51.
[0058] In the molding process, the upper die 50 and the first lower die 41 begin molding the top plate 11 and the ridge portions 14a and 14b with the upper die 50 and the first lower die 41, with the second lower die 42a and 42b positioned inward in the width direction D2 of the mold 30 relative to the upper die 50 with respect to the portions corresponding to the flanges 13a and 13b of the press-formed product 10 (Figures 1 and 2). After the molding of the top plate 11 and the ridge portions 14a and 14b begins, as shown in Figures 4E and 4F, the upper die 50 and the second lower die 42a and 42b move outward in the width direction D2 relative to the first lower die 41, thereby molding the ridge portions 15a and 15b and the flanges 13a and 13b of the press-formed product 10.
[0059] Referring to Figure 4E, in this embodiment, the second lower molds 42a and 42b move outward in the width direction D2 of the mold 30 by the first lower mold 41. More specifically, as the upper mold 50 is pushed toward the lower mold 40, the support member 43 moves or shortens in the height direction D1 of the mold 30, and the first lower mold 41 approaches the second lower molds 42a and 42b in the height direction D1. At this time, in the upper mold 50, the second upper mold 52 may be pressed in the height direction D1 by a part of the first upper mold 51. This increases the load applied from the upper mold 50 to the first lower mold 41. This change in load can be used to push the first lower mold 41 toward the second lower molds 42a and 42b.
[0060] As the first lower die 41 approaches the second lower dies 42a and 42b, the inclined surface 414a of the first lower die 41 slides on the inclined surface 422a of the second lower die 42a, and the inclined surface 414b of the first lower die 41 slides on the inclined surface 422b of the second lower die 42b. As a result, the second lower dies 42a and 42b are pushed outward in the width direction D2 by the first lower die 41.
[0061] Referring to Figure 4F, the blank 20 is bent by the second lower die 42a, 42b, which move outward in the width direction D2 of the die 30. The blank 20 is bent along the upper die shoulders 513a, 513b, forming the ridges 15a, 15b of the press-formed product 10. In addition, the blank 20 is sandwiched between the lower die flange surfaces 421a, 421b of the second lower die 42a, 42b and the upper die flange surfaces 512a, 512b of the first upper die 51, forming the flanges 13a, 13b of the press-formed product 10. For example, when the first upper die 51 reaches the bottom dead center of the press machine, the forming of the ridges 15a, 15b and the flanges 13a, 13b is completed.
[0062] The vertical walls 12a and 12b are formed by the blank 20 being sandwiched between the lower die sides 412a and 412b of the first lower die 41 and the upper die sides 511a and 511b of the first upper die 51. For example, when the first upper die 51 reaches the bottom dead center of the press machine, the blank 20 is sandwiched between the lower die sides 412a and 412b and the upper die sides 511a and 511b, completing the formation of the vertical walls 12a and 12b. Also, when the first upper die 51 reaches the bottom dead center of the press machine, the ridges 14a and 14b are formed by the lower die shoulders 413a and 413b. This completes the production of the press-formed product 10.
[0063] [effect] For example, as shown in Figure 5A, when a blank 20 is press-formed using a general die 90, bending of the blank 20 along the shoulders 911a, 911b of the lower die 91 begins during the forming process. When the blank 20 is pushed towards the lower die 91 by the upper die 92, the ends of the blank 20 come into contact with the flange surfaces 912a, 912b of the lower die 91. As a result, the shoulders 921a, 921b of the upper die 92 are pressed against the blank 20, causing bending to occur in the portions of the blank 20 that become the vertical walls 12a, 12b. Subsequently, as shown in Figure 5B, the vertical walls 12a, 12b are sandwiched between the sides 913a, 913b of the lower die 91 and the sides 922a, 922b of the upper die 92, and undergo deformation as they return to their original shape. In the molding process, if the ends of the blank 20 come into contact with the flange surfaces 912a and 912b of the lower mold 91 and the blank 20 is bent by the shoulders 921a and 921b of the upper mold 92 at an early stage, the amount of bending and unbending deformation in the vertical walls 12a and 12b will be large. As a result, residual stress will be large in the vertical walls 12a and 12b, and springback of the vertical walls 12a and 12b is likely to occur after demolding. Furthermore, if a welded joint 23 is located on the vertical walls 12a and 12b, the bending and unbending deformation experienced by the vertical walls 12a and 12b is likely to cause fracture of the blank 20 at the welded joint 23.
[0064] On the other hand, in the manufacturing method according to this embodiment, the upper die 50 and the first lower die 41 start forming the top plate 11 and the ridge portions 14a and 14b with respect to the portion of the upper die 50 corresponding to the flanges 13a and 13b of the press-formed product 10, with the second lower die 42a and 42b positioned inward in the width direction D2 of the die 30. After the formation of the top plate 11 and the ridge portions 14a and 14b has started, the upper die 50 and the second lower die 42a and 42b move outward in the width direction D2 relative to the first lower die 41, thereby forming the ridge portions 15a and 15b and the flanges 13a and 13b. At the start of forming the ridge sections 14a and 14b, the ends of the blank 20 do not come into contact with the lower die flange surfaces 421a and 421b of the second lower die 42a and 42b, and no substantial bending of the vertical walls 12a and 12b occurs due to the upper die shoulders 513a and 513b. Therefore, the degree of bending of the vertical walls 12a and 12b during the forming process, and the subsequent degree of unbending deformation, can be reduced. As a result, residual stress in the vertical walls 12a and 12b is also reduced, and springback of the vertical walls 12a and 12b after demolding is suppressed. In addition, because the degree of bending and unbending deformation experienced by the vertical walls 12a and 12b is reduced, fracture of the blank 20 at the welded section 23 is less likely to occur.
[0065] In the manufacturing method according to this embodiment, the movement of the second lower molds 42a, 42b outward in the width direction D2, that is, the forming of the ridge portions 15a, 15b and flanges 13a, 13b, may be performed after the forming of the ridge portions 14a, 14b has begun. However, it is preferable that the movement of the second lower molds 42a, 42b be started towards the end of the forming process. For example, the movement of the second lower molds 42a, 42b may be started so that the second lower molds 42a, 42b reach a position where they can form the flanges 13a, 13b together with the first upper mold 51 at the same time as the first upper mold 51 reaches its bottom dead center, or the movement of the second lower molds 42a, 42b may be started after the first upper mold 51 reaches its bottom dead center. By moving the second lower molds 42a and 42b at the end of the molding process, the substantial bending of the vertical walls 12a and 12b by the upper mold shoulders 513a and 513b becomes less likely, and the degree of bending and unbending deformation experienced by the vertical walls 12a and 12b can be further reduced.
[0066] <Second Embodiment> Figure 6 is a cross-sectional view (horizontal view) of the mold 30A according to this embodiment, perpendicular to the longitudinal direction. In the mold 30 according to the first embodiment, the first lower mold 41 is configured to be able to approach the second lower molds 42a and 42b in the height direction D1 of the mold 30, and the second lower molds 42a and 42b are configured to move in the width direction D2 of the mold 30 by the first lower mold 41. On the other hand, in the mold 30A according to this embodiment, the second lower molds 42a and 42b are configured to move in the width direction D2 by the upper mold 50A which approaches the lower mold 40 in the height direction D1.
[0067] Referring to Figure 6, the first upper mold 51A includes a cam driver section 51c in addition to the main body sections 51a and 51b. The cam driver section 51c is arranged, for example, on one or both sides of the main body sections 51a and 51b in the longitudinal direction of the mold 30A (the depth direction in the plane of the paper in Figure 6). The cam driver section 51c may be provided integrally with one or both of the main body sections 51a and 51b.
[0068] The cam driver section 51c includes inclined surfaces 514a and 514b. The inclined surfaces 514a and 514b are provided on the cam driver section 51c corresponding to the inclined surface 422a of the second lower mold 42a and the inclined surface 422b of the second lower mold 42b, respectively. The inclined surface 514a is inclined with respect to the height direction D1 of the mold 30A at substantially the same angle as the inclined surface 422a of the second lower mold 42a. The inclined surface 514b is inclined with respect to the height direction D1 at substantially the same angle as the inclined surface 422b of the second lower mold 42b.
[0069] In this embodiment, the second lower molds 42a and 42b may be configured such that at least a portion of them can be housed within the first lower mold 41. The second lower molds 42a and 42b can extend, for example, through the first lower mold 41 and in the longitudinal direction of the mold 30A to the position of the cam driver portion 51c.
[0070] In this embodiment as well, similar to the first embodiment, in the molding process, the second lower dies 42a and 42b are positioned inward in the width direction D2 of the mold 30A with respect to the portion of the upper die 50A corresponding to the flanges 13a and 13b of the press-formed product 10 (Figures 1 and 2), and the molding of the top plate 11 and the ridge portions 14a and 14b (Figures 1 and 2) is started by the upper die 50 and the first lower die 41. After the molding of the top plate 11 and the ridge portions 14a and 14b has started, the second lower dies 42a and 42b are moved outward in the width direction D2 by the upper die 50A.
[0071] More specifically, as shown in Figure 7A, during the molding process, the first upper die 51A approaches the second lower dies 42a and 42b in the height direction D1 of the mold 30A. Consequently, the inclined surface 514a of the cam driver portion 51c of the first upper die 51A slides on the inclined surface 422a of the second lower die 42a, and the inclined surface 514b of the cam driver portion 51c slides on the inclined surface 422b of the second lower die 42b. As a result, the second lower dies 42a and 42b are pushed outwards in the width direction D2 of the mold 30A by the first upper die 51A. As a result, as shown in Figure 7B, the main body portions 51a and 51b of the first upper die 51A and the second lower dies 42a and 42b form the ridge portions 15a and 15b and flanges 13a and 13b of the press-formed product 10.
[0072] In this embodiment as well, after the molding of the top plate 11 and the ridge portions 14a and 14b begins, the second lower molds 42a and 42b move in the width direction D2 of the mold 30A to form the ridge portions 15a and 15b and the flanges 13a and 13b. Therefore, the manufacturing method and mold 30A according to this embodiment can achieve the same effects as in the first embodiment.
[0073] While embodiments relating to this disclosure have been described above, this disclosure is not limited to the embodiments described above, and various modifications are possible as long as they do not deviate from its spirit.
[0074] In the above embodiment, the second lower molds 42a and 42b are moved in the width direction D2 of the mold 30 or 30A by a cam mechanism. However, the mechanism for moving the second lower molds 42a and 42b is not limited to this. For example, the second lower molds 42a and 42b can also be moved in the width direction D2 by a known actuator or the like. The timing of the actuator's operation can be set, for example, according to the stroke time of the first upper mold 51. However, it is preferable to move the second lower molds 42a and 42b using a cam mechanism as in the above embodiment, since this allows for control of the timing of the movement of the second lower molds 42a and 42b while simplifying the structure of the molds 30 and 30A.
[0075] The molds 30 and 30A according to the above embodiment each include two second lower molds 42a and 42b. However, the molds 30 and 30A do not necessarily have to include either the second lower molds 42a or 42b. For example, if the press-formed product 10 does not include a flange 13b, the molds 30 and 30A may be provided only with the second lower mold 42a, as shown in Figures 8 and 9. Similarly, if the press-formed product 10 does not include a flange 13a, the molds 30 and 30A may be provided only with the second lower mold 42b. The molds 30 and 30A do not necessarily have to be configured symmetrically.
[0076] In the above embodiment, the upper mold 50 includes a separate first upper mold 51 and a second upper mold 52. The upper mold 50A also includes a separate first upper mold 51A and a second upper mold 52. However, the first upper mold 51 or 51A and the second upper mold 52 may be integrated.
[0077] In the above embodiment, the lower mold 40 is positioned below the upper molds 50, 50A. However, the positional relationship between the lower mold 40 and the upper molds 50, 50A is not limited to this. When using molds 30, 30A, the lower mold 40 may be positioned above the upper molds 50, 50A.
[0078] In the above embodiment, the blank 20 is a so-called patchwork blank. That is, the blank 20 includes a blank body 21 and a reinforcing member 22 joined to the blank body 21 by welding. However, the blank 20 does not have to be a patchwork blank. That is, the blank 20 does not have to include the reinforcing member 22.
[0079] In the above embodiment, the press-formed product 10 is substantially straight as a whole. However, the press-formed product 10 may be curved along its longitudinal direction. For example, the press-formed product 10 may have a shape that is partially or entirely curved when viewed from above, or a shape that is partially or entirely curved when viewed from the side. Even a press-formed product 10 with such a shape can be manufactured by the molds 30, 30A and manufacturing method according to the above embodiment. [Explanation of symbols]
[0080] 10: Press-formed product 11: Top plate 12a,12b: Vertical wall 13a, 13b: Flange 14a, 14b: Ridge section (First ridge section) 15a, 15b: Ridge section (Second ridge section) 20: Blank 21: Blank body 22: Reinforcement material 23: Welded section 30,30A: Mold 40: Lower mold 41: Type 1 Lower 411: Bottom mold top surface 412a, 412b: Lower die side 413a, 413b: Lower mold shoulder 42a, 42b: 2nd lower mold 421a, 421b: Lower mold flange surface 50,50A: Upper mold 511a, 511b: Upper mold side 512a, 512b: Upper flange surface 513a, 513b: Upper mold shoulder D1: Height direction D2: Aspect Ratio
Claims
1. A method for manufacturing press-formed products, Preparation process for preparing the blank, A molding process to obtain a press-formed product comprising a blank, a top plate, a vertical wall connected to the top plate via a first ridge, and a flange connected to the vertical wall via a second ridge on the opposite side of the top plate; Equipped with, A manufacturing method comprising the molding process in which, with the second lower mold positioned inward in the width direction of the mold relative to the portion of the upper mold corresponding to the flange, the molding of the top plate and the first ridge portion is started by the upper mold and the first lower mold, and then the second lower mold is moved outward in the width direction relative to the first lower mold, thereby molding the second ridge portion and the flange by the upper mold and the second lower mold.
2. A manufacturing method according to claim 1, A manufacturing method wherein, in the molding process, the second lower mold is moved outward in the width direction by the first lower mold.
3. A manufacturing method according to claim 1, A manufacturing method wherein, in the molding process, the second lower mold is moved outward in the width direction by the upper mold.
4. A manufacturing method according to claim 1, The blank includes a blank body and a reinforcing material superimposed on the blank body and joined to the blank body by welding. A manufacturing method in which, in the press-formed product, the welded portion between the blank body and the reinforcing material is located on the vertical wall.
5. A manufacturing method according to claim 1, A manufacturing method wherein the blank is formed from a steel plate having a tensile strength of 440 MPa or more.
6. A mold used for manufacturing a press-formed product according to Claim 1, A lower mold comprising a first lower mold including a lower mold top surface and a lower mold side surface connected to the lower mold top surface via a lower mold shoulder, and a second lower mold including a lower mold flange surface, An upper mold includes an upper mold side corresponding to the lower mold side, and an upper mold flange surface connected to the upper mold side via an upper mold shoulder and corresponding to the lower mold flange surface, and is configured to be accessible to the lower mold in the height direction of the mold, Equipped with, The second lower mold is configured to be movable in the width direction of the mold relative to the first lower mold.
7. A mold according to claim 6, The first lower mold is configured to be able to approach the second lower mold in the height direction, A mold in which the second lower mold is configured to move in the width direction by the first lower mold which approaches the second lower mold in the height direction.
8. A mold according to claim 6, A mold in which the second lower mold is configured to move in the width direction by the upper mold which approaches the lower mold in the height direction.