Press device and press-formed article

Abstract

A press device (20) is provided with punches (21, 22), pads (23, 24), a die (25), and a support mechanism (26). A first punch (21) includes a punch top surface (211). A second punch (22) includes a punch top surface (221), a punch shoulder (222), a punch side surface (223), and a punch flange surface (224). The die (25) includes a die bottom surface (251), a die shoulder (252), a die side surface (253), and a die flange surface (254). The support mechanism (26) supports the second punch (22) such that the punch shoulder (222) is disposed closer to the die bottom surface (251) side than the punch top surface (211). The support mechanism (26) is configured to move the second punch (22) relative to the first punch (21) in a pressing direction (D1).

Description

Press equipment and press-molded products

[0001] The present disclosure relates to a press apparatus and a press-molded product.

[0002] For example, press-formed products are used as parts for automobile bodies. Press-formed products are manufactured by pressing a metal plate material using a mold. When the material is bent during the manufacture of press-formed products, cracks may occur on the outer surface of the bent part.

[0003] In automobiles, high-strength, thin-walled materials are often used as the material for press-formed parts in order to achieve both lightweight body construction and crashworthiness. The higher the material strength, the more likely cracks will occur on the outer surface of the bent part (external bending cracks). To prevent external bending cracks, press-formed parts are sometimes modified in shape, such as by increasing the bending radius of the bent part. However, increasing the bending radius of the bent part reduces the crashworthiness of the press-formed part compared to when the bending radius is smaller.

[0004] Patent Document 1 discloses a method for manufacturing a press-formed product having a bent portion with a small bending radius and suppressing external cracking at bending. The manufacturing method of Patent Document 1 includes a first forming step and a second forming step. In the first forming step, a metal plate as a raw material is press-formed using a die, and a bend radius R １ (mm) and bending angle θ １ In the second forming step, the intermediate product is pressed using a die to form a bend at the position of the bend of the intermediate product with a bending radius R ２ (mm) and bending angle θ ２ The bending radius R in the first forming step is １ is the bending radius R in the second forming step ２ The bending angle θ in the first forming step is larger than １ is the bending angle θ in the second forming step ２ Smaller than bending radius R １ , R ２ and bending angle θ １ , θ ２ is set to satisfy a predetermined relational expression.１ , R ２ and bending angle θ １ , θ ２ By setting the bending radius in this manner, the surface strain in the bent portion is reduced, and therefore, even when a high-strength steel plate having a tensile strength of 590 MPa or more is used as the raw material, the occurrence of cracks is suppressed and a press-formed product having a bent portion with a smaller bending radius can be manufactured.

[0005] International Publication No. 2016 / 121358

[0006] In Patent Document 1, the bent portion of the press-formed product is formed through a first forming step and a second forming step. However, dividing the step of forming the bent portion into two steps increases the number of dies used and the number of steps, which increases the manufacturing cost of the press-formed product.

[0007] An object of the present disclosure is to provide a press device that can form a bent portion of a press-molded product in a single step and can suppress cracks on the outer surface of the bent portion.

[0008] The press apparatus according to the present disclosure includes a first punch, a second punch, a first pad, a die, a support mechanism, and a second pad. The first punch includes a first punch top surface. The first punch top surface intersects with the press direction. The second punch is disposed to the side of the first punch. The second punch includes a second punch top surface, a punch shoulder, a punch side surface, and a punch flange surface. The second punch top surface intersects with the press direction. The punch shoulder is continuous with the second punch top surface on the opposite side of the first punch. The punch side surface is connected to the second punch top surface via the punch shoulder. The punch flange surface is connected to the punch side surface on the opposite side of the punch shoulder. The punch flange surface intersects with the press direction. The first pad faces the first punch top surface in the press direction. The die includes a die bottom surface, a die shoulder, a die side surface, and a die flange surface. The die bottom surface is disposed to the side of the first pad. The die bottom surface faces at least the second punch top surface in the press direction. The die shoulder is continuous with the die bottom surface on the opposite side of the first pad. The die side surface is connected to the die bottom surface via the die shoulder. The die flange surface is connected to the die side surface on the opposite side of the die shoulder. The die flange surface faces the punch flange surface in the pressing direction. The support mechanism supports the second punch so that the punch shoulder is positioned closer to the die bottom surface than the top surface of the first punch. The support mechanism is configured to move the second punch relative to the first punch in the pressing direction. The second pad is positioned between the punch flange surface and the die flange surface.

[0009] According to the press device of the present disclosure, it is possible to form a bent portion of a press-molded product in one step, and to suppress cracks on the outer surface of the bent portion.

[0010] FIG. 1 is a perspective view schematically illustrating a press-formed product according to an embodiment. FIG. 2 is a cross-sectional view of a press apparatus according to an embodiment. FIG. 3A is a schematic view for explaining a method for manufacturing a press-formed product using the press apparatus shown in FIG. 2. FIG. 3B is a schematic view for explaining a method for manufacturing a press-formed product using the press apparatus shown in FIG. 2. FIG. 3C is a schematic view for explaining a method for manufacturing a press-formed product using the press apparatus shown in FIG. 2. FIG. 3D is a schematic view for explaining a method for manufacturing a press-formed product using the press apparatus shown in FIG. 2. FIG. 3E is a schematic view for explaining a method for manufacturing a press-formed product using the press apparatus shown in FIG. 2. FIG. 4 is a cross-sectional view of a press-formed product according to an embodiment. FIG. 5 is a cross-sectional view of a press apparatus according to a modified example of the embodiment. FIG. 6 is a perspective view of a press-formed product according to a modified example of the embodiment. FIG. 7 is a cross-sectional view of a press apparatus according to a modified example of the embodiment. FIG. 8 is a graph showing the distribution of circumferential strain in Examples and Comparative Examples. FIG. 9 is a graph showing the distribution of Vickers hardness in Examples and Comparative Examples.

[0011] The press apparatus according to the embodiment includes a first punch, a second punch, a first pad, a die, a support mechanism, and a second pad. The first punch includes a first punch top surface. The first punch top surface intersects with the press direction. The second punch is disposed to the side of the first punch. The second punch includes a second punch top surface, a punch shoulder, a punch side surface, and a punch flange surface. The second punch top surface intersects with the press direction. The punch shoulder is continuous with the second punch top surface on the opposite side of the first punch. The punch side surface is connected to the second punch top surface via the punch shoulder. The punch flange surface is connected to the punch side surface on the opposite side of the punch shoulder. The punch flange surface intersects with the press direction. The first pad faces the first punch top surface in the press direction. The die includes a die bottom surface, a die shoulder, a die side surface, and a die flange surface. The die bottom surface is disposed to the side of the first pad. The die bottom surface faces at least the second punch top surface in the press direction. The die shoulder is continuous with the die bottom surface on the opposite side of the first pad. The die side surface is connected to the die bottom surface via the die shoulder. The die flange surface is connected to the die side surface on the opposite side of the die shoulder. The die flange surface faces the punch flange surface in the pressing direction. The support mechanism supports the second punch so that the punch shoulder is positioned closer to the die bottom surface than the top surface of the first punch. The support mechanism is configured to move the second punch relative to the first punch in the pressing direction. The second pad is positioned between the punch flange surface and the die flange surface (first configuration).

[0012] A press apparatus according to a first configuration includes a first punch and a second punch disposed to the side of the first punch. The second punch is supported by a support mechanism so that its punch shoulder is positioned closer to the die bottom than the top surface of the first punch. When using this press apparatus to produce a press-formed product from a material, the material is placed between the first punch and the second punch and the first pad and die. The material is first sandwiched between the first pad and the top surface of the first punch. Because the punch shoulder of the second punch is positioned closer to the die bottom than the top surface of the first punch, the portion of the material positioned between the second punch and the die is bent toward the die relative to the portion of the material sandwiched between the first pad and the top surface of the first punch. In this state, by moving the die closer to the second punch in the pressing direction, the die contacts the material, bending it at the punch shoulder of the second punch. Next, the die flange surface presses the punch flange surface of the second punch via the second pad, pushing the second punch and its punch shoulder in the pressing direction. As the punch shoulder is pushed in the pressing direction, it forms a bent portion together with the die.

[0013] When the punch shoulder of the second punch protrudes toward the die bottom surface relative to the top surface of the first punch, the distance from the top surface of the first punch to the punch shoulder is greater than when the punch shoulder is pushed in. Therefore, by protruding the punch shoulder from the top surface of the first punch, the punch shoulder can bend the blank closer to the edge. On the other hand, when the punch shoulder is pushed in the pressing direction, the distance from the top surface of the first punch to the punch shoulder is reduced. This allows the position of the bending caused by the punch shoulder to move toward the inside of the blank. That is, in the press apparatus of the first configuration, the position of the blank bent by the punch shoulder moves during forming. Accordingly, the location where large tensile strain occurs in the blank due to bending also moves, thereby widely distributing the strain and reducing the maximum value of tensile strain. Therefore, when producing a press-formed product from a blank, cracks on the outer surface of the bent portion (external cracking) can be suppressed. By suppressing external cracking, even bends with a relatively small bending radius can be formed.

[0014] When a press-molded product is manufactured using the press apparatus according to the first configuration, there is no need to prepare another press apparatus or mold to prevent outer cracks at bending. The press apparatus according to the first configuration can form the bent portion of the press-molded product in a single process while suppressing outer cracks at bending in the press-molded product.

[0015] The press apparatus according to the first configuration may further include a connecting member, for example, connecting the die flange surface and the second pad. The connecting member is preferably configured to be expandable and contractible in the pressing direction (second configuration).

[0016] In the press apparatus according to the second configuration, the presence of a connecting member connecting the die flange surface and the second pad allows the distance between the punch flange surface of the second punch and the die flange surface in the press direction to be changed during the forming process. For example, at the stage where the punch shoulder of the die and the second punch begin to form a bent portion in the workpiece, the distance between the punch flange surface and the die flange surface in the press direction can be kept relatively large, allowing the workpiece to be bent at a gentle angle. On the other hand, as the second punch and the die approach each other in the press direction, the second pad contacts the punch flange surface and the connecting member begins to contract. This reduces the distance between the punch flange surface and the die flange surface in the press direction, allowing the die flange surface to press against the punch flange surface via the second pad. This makes it easier for the second punch and die to reliably press the workpiece at the bottom dead center of the press apparatus.

[0017] In the press apparatus according to the first or second configuration, the top surface of the second punch may be formed so that the end on the punch shoulder side is positioned closer to the die bottom surface than the end on the first punch side (third configuration).

[0018] In the press apparatus according to any one of the first to third configurations, when the angle between the top surface of the first punch and the side surface of the punch is θ1 and the angle between the top surface of the second punch and the side surface of the punch is θ2, θ2≦θ1 may be satisfied (fourth configuration).

[0019] A press-formed product according to an embodiment includes a top plate, a bent portion, and a vertical wall. The bent portion is continuous with the top plate. The vertical wall is connected to the top plate via the bent portion. When the thickness of the vertical wall is taken as the reference thickness, and the average value of Vickers hardness measured at five points at 0.5 mm intervals from a position 8.0 times the reference thickness toward the vertical wall from the boundary between the top plate and the bent portion is taken as H1, and the average value of Vickers hardness measured at five points at 0.5 mm intervals in a range from a position 2.5 times the reference thickness toward the top plate to a position 4.0 times the reference thickness toward the boundary is taken as H2, H2 / H1≧1.1 (fifth configuration).

[0020] In the press-formed product according to the fifth configuration, the average Vickers hardness H2 of the top plate near the bend is greater than the average Vickers hardness H1 at a position relatively far from the bend toward the vertical wall. That is, in the press-formed product according to the fifth configuration, work hardening during press forming extends not only to the bend but also to the top plate. The widespread presence of such work-hardened portions increases the initial reaction force when a load is input to the press-formed product, allowing the press-formed product to exhibit excellent yield strength.

[0021] In the press-molded product according to the fifth configuration, when the average value of the Vickers hardness of five consecutive points spaced at 0.5 mm intervals beyond a position 7.0 times the standard plate thickness from the boundary toward the top plate is defined as H3, there may be an H3 that satisfies H3 / H1≧1.1 (sixth configuration).

[0022] In the press-formed product according to the sixth configuration, the average Vickers hardness H3 of the top plate at a position farther from the bend is greater than the average Vickers hardness H1 at a position relatively farther from the bend toward the vertical wall. That is, the top plate has work-hardened portions not only near the bend but also at positions farther from the bend. This makes it easier to increase the initial reaction force when a load is input to the press-formed product, making it easier for the press-formed product to exhibit excellent yield strength.

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In these drawings, the same or equivalent components are designated by the same reference numerals, and the same description will not be repeated.

[0024] [Press-formed product] Fig. 1 is a perspective view schematically showing a press-formed product 10 according to this embodiment. The press-formed product 10 is used, for example, in mobile objects such as automobiles and ships. The press-formed product 10 is preferably used as an automobile part. However, the use of the press-formed product 10 is not limited to this.

[0025] 1, a press-formed product 10 has, for example, an elongated shape. The press-formed product 10 may have a straight shape or may be wholly or partially curved. The press-formed product 10 includes a top plate 11, vertical walls 12A, 12B, and bent portions 13A, 13B.

[0026] The top plate 11 extends in the longitudinal direction of the press-formed product 10. The bent portions 13A and 13B are each continuous with the top plate 11. The bent portions 13A and 13B extend along both side edges of the top plate 11. Each of the bent portions 13A and 13B can have a substantially arc shape when viewed in a cross section (transverse cross section) perpendicular to the longitudinal direction of the press-formed product 10. One vertical wall 12A is connected to the top plate 11 via the bent portion 13A. The other vertical wall 12B is connected to the top plate 11 via the bent portion 13B. The vertical wall 12B is disposed on the opposite side of the top plate 11 from the vertical wall 12A. The vertical walls 12A and 12B extend along the bent portions 13A and 13B, respectively. Hereinafter, unless there is a need to distinguish between them, the vertical walls 12A and 12B will be collectively referred to as the vertical wall 12, and the bent portions 13A and 13B will be collectively referred to as the bent portion 13.

[0027] [Pressing Apparatus] The press-formed product 10 can be manufactured using a pressing apparatus 20 shown in Fig. 2. Fig. 2 is a cross-sectional view of the pressing apparatus 20. In this embodiment, the pressing apparatus 20 has the same basic configuration on one side and the other side of the center line in the width direction. Therefore, Fig. 2 shows only a portion of the pressing apparatus 20 on one side of the center line in the width direction. However, the pressing apparatus 20 does not have to be completely symmetrical with respect to the center line in the width direction.

[0028] The press device 20 includes a first punch 21, a second punch 22, a first pad 23, a second pad 24, and a die 25. The press device 20 further includes a support mechanism 26 and connecting members 27 and 28.

[0029] The pads 23, 24 and the die 25 are capable of moving closer to and farther away from the punches 21, 22. The pads 23, 24 and the die 25 are, for example, attached directly or indirectly to a slide (not shown) of the press device 20 and move together with the slide. Alternatively, the punches 21, 22 may be attached directly or indirectly to the slide and move together with the slide. Hereinafter, the direction in which the pads 23, 24 and the die 25 move closer to and farther away from the punches 21, 22 is referred to as the press direction D1. The press direction D1 is, for example, the vertical direction.

[0030] 2 , the first punch 21 includes a punch top surface 211. The punch top surface 211 intersects with the pressing direction D1. The punch top surface 211 may be substantially perpendicular to the pressing direction D1. The punch top surface 211 may have a generally flat shape, or may partially have an uneven shape such as a bead.

[0031] The second punch 22 is separate from the first punch 21. The second punch 22 is disposed to the side of the first punch 21. In this embodiment, the second punch 22 is disposed outward of the first punch 21 in the width direction of the press device 20. The second punch 22 includes a punch top surface 221, a punch shoulder 222, a punch side surface 223, and a punch flange surface 224.

[0032] The punch top surface 221 intersects with the pressing direction D1. The punch shoulder 222 is continuous with the punch top surface 221 on the opposite side of the first punch 21. In a cross-sectional view of the press device 20, the punch shoulder 222 preferably has a substantially arc shape. However, the punch shoulder 222 may also be a non-rounded corner (pin angle). The radius of curvature of the punch shoulder 222 is, for example, 0 mm or more and 10.0 mm or less, preferably 1.0 mm or more and 10.0 mm or less, and more preferably 1.0 mm or more and 6.0 mm or less.

[0033] The punch side surface 223 is connected to the punch top surface 211 via a punch shoulder 222. In a cross-sectional view of the press apparatus 20, the punch side surface 223 extends substantially or generally in the press direction D1 from the punch shoulder 222. In a cross-sectional view of the press apparatus 20, the punch side surface 223 may be parallel to the press direction D1, or may be inclined with respect to the press direction D1.

[0034] In the state of the press apparatus 20 shown in FIG. 2 , the punch shoulder 222 is positioned closer to the die 25 than the punch top surface 211 of the first punch 21. The punch top surface 221 is formed so that the end of the punch shoulder 222 is positioned closer to the die 25 than the end of the punch top surface 221 on the first punch 21 side. In the example of FIG. 2 , the punch top surface 221 is an inclined surface that is inclined with respect to the punch top surface 211 of the first punch 21. The punch top surface 221 approaches the die 25 in the pressing direction D1 as it moves from the first punch 21 toward the punch shoulder 222. However, the punch top surface 221 may be a surface that is substantially parallel to the punch top surface 211 of the first punch 21.

[0035] The punch top surface 221 has, for example, a linear shape when viewed in cross section of the press device 20. Alternatively, the punch top surface 221 may have a curved shape when viewed in cross section of the press device 20. The shape of the punch top surface 221 is not particularly limited.

[0036] The punch top surface 221 forms an angle θ2 with the punch side surface 223. When the punch top surface 221 has a linear shape in the cross-sectional view of the press device 20, the angle θ2 is the angle between the punch top surface 221 itself and the punch side surface 223. When the punch top surface 221 has a curved shape in the cross-sectional view of the press device 20, for example, the angle θ2 is the angle between the tangent to the punch top surface 221 at the boundary between the punch top surface 221 and the punch shoulder 222 and the punch side surface 223. θ2 is, for example, 30° or more and 120° or less, and preferably 45° or more and 90° or less.

[0037] When the punch shoulder 222 has a substantially arcuate shape in the cross-sectional view of the press apparatus 20, the boundary between the punch top surface 221 and the punch shoulder 222 ends at the R on the punch top surface 221 side of the punch shoulder 222. On the other hand, when the punch shoulder 222 is a pin angle, that is, when the apex of the punch top surface 221 and the punch side surface 223 is the punch shoulder 222, the boundary between the punch top surface 221 and the punch shoulder 222 is also that apex.

[0038] The angle θ2 between the punch top surface 221 and the punch side surface 223 is typically equal to or smaller than the angle θ1 between the punch top surface 211 and the punch side surface 223 of the first punch 21 (θ2≦θ1). The angles θ1 and θ2 preferably satisfy θ2<θ1. θ1 is, for example, equal to or larger than 90° and equal to or smaller than 120°.

[0039] The punch flange surface 224 is connected to the punch side surface 223 on the side opposite to the punch shoulder 222. The punch flange surface 224 protrudes from the punch side surface 223 to the side opposite to the first punch 21. The punch flange surface 224 intersects with the press direction D1. The punch flange surface 224 may be a surface that is substantially perpendicular to the press direction D1.

[0040] In this embodiment, the second punch 22 further includes a protrusion 225. The protrusion 225 is provided on the surface of the second punch 22 opposite to the punch side surface 223. The protrusion 225 protrudes from this surface toward the first punch 21. The first punch 21 includes a recess 212 that receives the protrusion 225.

[0041] 2, the first pad 23 is disposed above the first punch 21 and the second punch 22. The first pad 23 faces the punch top surface 211 of the first punch 21 in the press direction D1. The first pad 23 has a sheet pressing surface 231 on the punch top surface 211 side. It is preferable that the sheet pressing surface 231 is substantially parallel to the punch top surface 211. The sheet pressing surface 231 has a shape corresponding to the punch top surface 211.

[0042] The die 25 includes a die bottom surface 251 , a die shoulder 252 , a die side surface 253 , and a die flange surface 254 .

[0043] The die bottom surface 251 is disposed to the side of the first pad 23. In this embodiment, the die bottom surface 251 is disposed outside the first pad 23 in the width direction of the press apparatus 20. The die bottom surface 251 faces at least the punch top surface 221 of the second punch 22 in the press direction D1. In this embodiment, the die bottom surface 251 faces not only the punch top surface 221 of the second punch 22 but also a portion of the punch top surface 211 of the first punch 21 in the press direction D1. It is preferable that the die bottom surface 251 be substantially parallel to the punch top surface 211 of the first punch 21. However, the die bottom surface 251 does not have to be parallel to the punch top surface 221 of the second punch 22.

[0044] The die shoulder 252 is continuous with the die bottom surface 251 on the side opposite to the first pad 23. The die shoulder 252 is disposed at a position corresponding to the punch shoulder 222 of the second punch 22. In a cross-sectional view of the press apparatus 20, the die shoulder 252 preferably has a substantially arcuate shape. However, the die shoulder 252 may also be a non-rounded corner (pin angle).

[0045] The die side surface 253 is connected to the die bottom surface 251 via the die shoulder 252. That is, the die shoulder 252 is a corner portion between the die bottom surface 251 and the die side surface 253. In a cross-sectional view of the press apparatus 20, the die side surface 253 extends from the die shoulder 252 substantially or generally in the press direction D1. The die side surface 253 is disposed at a position corresponding to the punch side surface 223. The die side surface 253 also has a shape corresponding to the punch side surface 223. Like the punch side surface 223, the die side surface 253 may be parallel to the press direction D1 in a cross-sectional view of the press apparatus 20, or may be inclined with respect to the press direction D1.

[0046] The die flange surface 254 is connected to the die side surface 253 on the side opposite to the die shoulder 252. The die flange surface 254 protrudes from the die side surface 253 on the side opposite to the first pad 23. The die flange surface 254 faces the punch flange surface 224 of the second punch 22 in the press direction D1. The second pad 24 is disposed between the die flange surface 254 and the punch flange surface 224.

[0047] The support mechanism 26 supports the second punch 22. For example, when the press device 20 is at the top dead center, the support mechanism 26 supports the second punch 22 so that the punch shoulder 222 of the second punch 22 is positioned closer to the die bottom surface 251 than the punch top surface 211 of the first punch 21. In the example of FIG. 2 , the support mechanism 26 supports the second punch 22 from the side opposite to the punch top surface 221.

[0048] The support mechanism 26 is configured to move the second punch 22 relative to the first punch 21 in the press direction D1. The support mechanism 26 is configured, for example, to be expandable and contractible in the press direction D1. The support mechanism 26 may be a spring such as a compression coil spring, or an actuator such as a hydraulic cylinder or an air cylinder. Operation of the support mechanism 26 allows the second punch 22 to move relative to the first punch 21 in the press direction D1.

[0049] The support mechanism 26 may be capable of controlling the position of the second punch 22 in the press direction D1, or may simply bias the second punch 22 toward the die bottom surface 251. In this case, by bringing the convex portion 225 of the second punch 22 into contact with the surface of the concave portion 212 of the first punch 21, the relative movement of the first punch 21 and the second punch 22 in the press direction D1 can be restricted.

[0050] The connecting member 27 is attached to the first pad 23 on the side opposite to the plate pressing surface 231. The connecting member 27 connects the first pad 23 to the die 25. The connecting member 27 may connect the first pad 23 to the die 25 directly, or may connect the first pad 23 to the die 25 indirectly via, for example, a slide of the press device 20.

[0051] The connecting member 27 is configured to be expandable and contractible in the pressing direction D1. The connecting member 27 may be a spring such as a compression coil spring, or an actuator such as a hydraulic cylinder or an air cylinder. As the connecting member 27 expands and contracts in the pressing direction D1, the first pad 23 can move in the pressing direction D1 relative to the die 25.

[0052] The connecting member 28 connects the die 25 and the second pad 24. More specifically, the connecting member 28 connects the die flange surface 254 and the second pad 24. The connecting member 28 is configured to be expandable and contractible in the pressing direction D1. The connecting member 28 may be a spring such as a compression coil spring, or an actuator such as a hydraulic cylinder or an air cylinder.

[0053] 3A to 3E, an example of a method for manufacturing the press-formed product 10 using the press device 20 will be described. This manufacturing method can include a preparation step and a molding step.

[0054] Referring to FIG. 3A , in the preparation step, a raw material M made of a metal plate is prepared. The raw material M is, for example, a blank having a shape obtained by unfolding the press-formed product 10 ( FIG. 1 ). The metal plate constituting the raw material M may be a steel plate. This steel plate has a tensile strength of, for example, 590 MPa or more, preferably 980 MPa or more, and more preferably 1180 MPa or more. The tensile strength of the steel plate may be 1470 MPa or less. The plate thickness of the raw material M is, for example, 1.0 mm or more. The plate thickness of the raw material M may be 6.0 mm or less.

[0055] 3B , in the forming process, the material M is formed into the press-formed product 10 ( FIG. 1 ) by the press device 20. In the forming process, first, the slide (not shown) of the press device 20 is set to the top dead center, and the first punch 21 and second punch 22 are separated from the first pad 23 and die 25 in the press direction D1. Then, the material M is placed between the first punch 21 and second punch 22 and the first pad 23 and die 25.

[0056] Before the start of forming the material M, the second punch 22 is in standby with its punch shoulder 222 positioned closer to the die bottom surface 251 than the punch top surface 211 of the first punch 21. For example, the convex portion 225 of the second punch 22 catches on the concave portion 212 of the first punch 21, thereby stopping the second punch 22 with the punch shoulder 222 protruding from the punch top surface 211.

[0057] 3C , next, the first pad 23 is moved relatively closer to the first punch 21 in the press direction D1. For example, the connecting member 27 is extended to move the first punch 21 and the first pad 23 relatively closer to each other. Alternatively, the slide of the press device 20 may be moved in the press direction D1 to move the first pad 23 together with the die 25 relatively closer to the first punch 21. As a result, the first pad 23 contacts the material M before the die 25. The first pad 23, together with the first punch 21, clamps a portion of the material M. More specifically, the material M is pressed by the sheet pressing surface 231 of the first pad 23 and the punch top surface 211 of the first punch 21. At this point, the second pad 24 is separated from the punch flange surface 224 of the second punch 22 in the press direction D1.

[0058] When the material M is sandwiched between the first pad 23 and the first punch 21, the material M is pressed down by the first pad 23 at the position of the first punch 21, while the material M is supported by the punch shoulder 222 at the position of the second punch 22. Because the punch shoulder 222 protrudes toward the die 25 relative to the first punch 21, the material M bends at the end of the first pad 23. In other words, the portion of the material M that is not sandwiched between the first pad 23 and the first punch 21 jumps up toward the die 25. As the portion of the material M that is not sandwiched between the first pad 23 and the first punch 21 moves toward the punch shoulder 222, it approaches the die 25 in the pressing direction D1.

[0059] In this state, when the die 25 is brought relatively close to the first punch 21 and the second punch 22 in the pressing direction D1, the connecting member 27 of the first pad 23 contracts and the die 25 comes into contact with the material M, as shown in FIG. 3D. The die 25 first comes into contact with the material M via the die flange surface 254. This causes the material M to bend at the position of the punch shoulder 222. The material M is formed into the preliminary shape shown in FIG. 3D.

[0060] 3E , when the die 25 is further moved relatively closer to the first punch 21 and the second punch 22 in the press direction D1, the second pad 24 comes into contact with the punch flange surface 224 of the second punch 22. As the die 25 and the second punch 22 move relatively closer to each other, the connecting member 28 contracts and the punch flange surface 224 is pressed by the second pad 24. As a result, the second punch 22 moves in the press direction D1 relative to the first punch 21. For example, the support mechanism 26 contracts, causing the second punch 22 to be pressed in the press direction D1 relative to the first punch 21.

[0061] When the second punch 22 is biased toward the die 25 by the support mechanism 26, the second punch 22 is pressed in the press direction D1 when the pressing load from the die 25 and the second pad 24 exceeds the biasing force of the support mechanism 26. The die 25 and the second pad 24 press the second punch 22 until it reaches the bottom dead center of the press device 20. At the bottom dead center of the press device 20, the punch shoulder 222 of the second punch 22 is positioned at substantially the same position as the punch top surface 211 of the first punch 21 in the press direction D1.

[0062] At the bottom dead center of the press device 20, the material M is sandwiched between the punch top surface 211 of the first punch 21 and the first pad 23 and die bottom surface 251 to form the top plate 11. Also, at the bottom dead center of the press device 20, the material M is sandwiched between the punch side surface 223 of the second punch 22 and the die side surface 253 to form the vertical wall 12. Furthermore, the bent portion 13 is formed along the die shoulder 252. In this way, the press-formed product 10 is manufactured.

[0063] Fig. 4 is a cross-sectional view of the press-formed product 10 manufactured by the press device 20. Fig. 4 partially shows a cross section (transverse cross section) of the press-formed product 10 along the plate thickness direction.

[0064] Referring to FIG. 4 , the average value of the Vickers hardness measured at five points at 0.5 mm intervals from position A0, which is 8.0 times the reference plate thickness t0, toward the vertical wall 12 from the boundary 14 between the top plate 11 and the bent portion 13, is designated H1 [HV]. H1 corresponds to the Vickers hardness of the material M before forming. Furthermore, the average value of the Vickers hardness measured at five points at 0.5 mm intervals in the range from position A1 to position A2 on the top plate 11 is designated H2 [HV]. Position A1 is a position 2.5 times the reference plate thickness t0 away from the boundary 14 toward the top plate 11. Position A2 is a position 4.0 times the reference plate thickness t0 away from the boundary 14 toward the top plate 11. H1 and H2 satisfy H2 / H1≧1.1. The reference plate thickness t0 is the plate thickness of the vertical wall 12, and is measured, for example, near the end of the vertical wall 12. Specifically, the reference thickness t0 can be defined as the thickness measured at a position 10.0 mm from the tip (free end) of the vertical wall 12 toward the bent portion 13 along the outer surface of the bent portion of the press-formed product 10. The reference thickness t0 corresponds to the thickness of the material M before forming.

[0065] H3 is the average value of the Vickers hardness at five consecutive points spaced 0.5 mm apart from a position A3 that is 7.0 times the reference plate thickness t0 toward the top plate 11 from the boundary 14. In the press-formed product 10, there exists a point H3 that satisfies H3 / H1 ≥ 1.1. The positions A0, A1, A2, and A3 are all determined by measuring the distance from the boundary 14 along the outer surface of the bent portion of the press-formed product 10.

[0066] H1, H2, and H3 can be obtained as follows. For H1, a test piece including a cross section of the top plate 11, the bent portion 13, and the vertical wall 12 is taken from the press-formed product 10. The Vickers hardness of this cross section (test surface) is measured at five points at 0.5 mm intervals from position A0 toward the end of the vertical wall 12, in accordance with JIS Z 2244:2020, at a position 1 / 4 of the plate thickness from the bent outer surface of the press-formed product 10. The average of the measured Vickers hardness values ​​is then calculated to obtain H1. For H2, the Vickers hardness of the test surface is measured at five arbitrary points at 0.5 mm intervals within the range from position A1 to position A2, in accordance with JIS Z 2244:2020, at a position 1 / 4 of the plate thickness from the bent outer surface of the press-formed product 10. The average of the measured Vickers hardness values ​​is then calculated to obtain H2. For H3, Vickers hardness is measured at a position 1 / 4 of the plate thickness from the outer surface of the bent part of the press-formed product 10 on the test surface, in accordance with JIS Z 2244:2020, starting from position A3 and measuring at 0.5 mm intervals until the center of the width of the top plate 11 is reached. The measurement points are shifted one by one from position A3, and for each measurement point, the average Vickers hardness of the measurement point and the two measurement points on either side of it (five points) is calculated, and each calculated value can be used as H3. The test force for the Vickers hardness test when obtaining H1, H2, and H3 is 1 kgw (9.8 N).

[0067] As described above, H1 corresponds to the Vickers hardness of the raw material M. When H1≧370, it can be determined that a steel plate having a tensile strength of 1180 MPa or more was used as the raw material M. When the radius of curvature on the inner side of the bent portion 13 is R, when H1≧370, the reference plate thickness t0 and the radius of curvature R preferably satisfy R / t0≦1.5, and more preferably satisfy R / t0≦1.0. When H1≧370, it is preferable that the reference plate thickness t0 and the radius of curvature R satisfy R / t0>0.3, and more preferably satisfy R / t0≧0.7. H1 may be 466 or less (H1≦466). When 370≦H1≦466, it can be determined that a steel plate having a tensile strength of 1180 MPa or more and 1470 MPa or less was used as the raw material M. When 308≦H1<370, it can be determined that a steel plate having a tensile strength of 980 MPa or more and less than 1180 MPa was used as the raw material M. When 308≦H1<370, the reference plate thickness t0 and the radius of curvature R preferably satisfy R / t0<1.0, and more preferably R / t0≦0.7. When 308≦H1<370, for example, R / t0>0.1 may be satisfied, and preferably R / t0≧0.3.

[0068] The radius of curvature R of the bent portion 13 is, for example, 0.0 mm or more and 6.0 mm or less, and preferably greater than 0.0 mm and less than 6.0 mm. When the top plate 11 and the vertical wall 12 form an unrounded corner (pin angle), the radius of curvature R is 0.0 mm. On the other hand, when the surface of the bent portion 13 has a substantially arc-shaped cross section, the radius of curvature R is greater than 0.0 mm.

[0069] [Effect] When the press apparatus 20 according to this embodiment is used to manufacture the press-formed product 10, forming of the material M is started with the punch shoulder 222 of the second punch 22 protruding from the punch top surface 211 of the first punch 21 toward the die 25. When the punch shoulder 222 protrudes from the punch top surface 211, the shortest distance from the punch top surface 211 to the punch shoulder 222 is greater than when the punch shoulder 222 is pressed down to a position substantially flush with the punch top surface 211. Therefore, the material M can be bent by the punch shoulder 222 closer to the edge thereof, thereby imparting pre-strain to the material M. Thereafter, by pressing down the punch shoulder 222 protruding from the punch top surface 211, the shortest distance from the punch top surface 211 to the punch shoulder 222 can be reduced. This allows the bending position by the punch shoulder 222 to be shifted toward the inside of the material M.

[0070] In this way, the position of the blank M bent by the punch shoulder 222 moves during the forming process, and the location where large tensile strain occurs in the blank M also moves. This makes it possible to form the bent portion 13 while widely dispersing the strain caused by bending, thereby reducing the maximum value of tensile strain in the bent portion 13. As a result, cracks on the outer surface of the bent portion 13 (outer bending cracks) can be suppressed. By suppressing outer bending cracks, it is possible to form a bent portion 13 even with a relatively small bending radius.

[0071] In the press apparatus 20 according to this embodiment, the second pad 24 presses the punch flange surface 224 of the second punch 22, forcing the second punch 22 in the press direction D1. The second pad 24 can change the distance between the punch flange surface 224 and the die flange surface 254 in the press direction D1 during the forming process. For example, during the stage of preforming a bent portion in the material M with the punch shoulder 222 of the second punch 22 protruding from the punch top surface 221 of the first punch 21, a relatively large distance can be maintained between the punch flange surface 224 and the die flange surface 254. This allows the die 25 and the punch shoulder 222 to bend the material M at a gentle angle. Meanwhile, after preforming, when the second pad 24 contacts the punch flange surface 224, the connecting member 28 contracts, reducing the distance between the punch flange surface 224 and the die flange surface 254, allowing the die flange surface 254 to press the punch flange surface 224 in the press direction D1. This makes it easier for the die 25 and the second punch 22 to reliably press the material M when the press device 20 is at the bottom dead center.

[0072] In the press apparatus 20 according to this embodiment, the punch top surface 221 of the second punch 22 is formed so that the end on the punch shoulder 222 side is positioned closer to the die bottom surface 251 than the end on the first punch 21 side. In this case, by pressing the second punch 22, the end of the punch top surface 221 on the first punch 21 side can be positioned further back from the die 25 than the punch top surface 221 of the first punch 21. In this case, interference between the boundary between the first punch 21 and the second punch 22 and the material M is less likely to occur.

[0073] However, the punch top surface 221 of the second punch 22 may be a surface that is substantially parallel to the punch top surface 211 of the first punch 21. In this case, at the bottom dead center of the press device 20, the punch top surface 221 of the second punch 22, in addition to the punch top surface 211 of the first punch 21, can also press the material M together with the die bottom surface 251.

[0074] In this embodiment, the first punch 21 has a recess 212, and the second punch 22 has a protrusion 225. The protrusion 225 of the second punch 22 is received in the recess 212 of the first punch 21, thereby restricting movement of the second punch 22 in the press direction D1. For example, the protrusion 225 of the second punch 22 abuts against the surface of the recess 212 of the first punch 21, thereby stopping the second punch 22 and positioning the punch shoulder 222 at a desired position before the start of forming. Therefore, the support mechanism 26 of the second punch 22 may simply bias the second punch 22 toward the die 25. In other words, the support mechanism 26 can be simplified.

[0075] When the press-formed product 10 is manufactured using the press apparatus 20 according to this embodiment, strain is widely distributed in the press-formed product 10 as described above, and therefore work hardening also occurs widely. Specifically, the Vickers hardness H2 of the top plate 11 near the bent portion 13 is greater than the Vickers hardness H1 corresponding to the material M before forming. That is, in the press-formed product 10 after forming, work hardening extends not only to the bent portion 13 but also to the top plate 11. The widespread presence of such work-hardened portions makes it easier for a colliding object to come into contact with the work-hardened portion in the event of a collision with the top plate 11, thereby increasing the initial reaction force against the collision load. This allows the press-formed product 10 to exhibit excellent yield strength.

[0076] In the press-formed product 10 according to this embodiment, the top plate 11 is bent and work-hardened by being pressed by the first pad 23 in the early stages of forming. Specifically, the Vickers hardness H3 of the top plate 11 at a position relatively distant from the bent portion 13 is greater than the Vickers hardness H1 corresponding to the material M before forming. This makes it easier for the initial reaction force when a load is input to the press-formed product 10 to be increased, thereby further improving the yield strength of the press-formed product 10.

[0077] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0078] In the above embodiment, the second punch 22 includes a convex portion 225 that protrudes toward the first punch 21. However, the second punch 22 does not necessarily have to include the convex portion 225. If the second punch 22 does not have the convex portion 225, the first punch 21 does not necessarily have to include the concave portion 212.

[0079] In the press apparatus 20 according to the above embodiment, the connecting member 28 is disposed between the die flange surface 254 and the second pad 24, connecting the die flange surface 254 and the second pad 24. However, as shown in FIG. 5 , the connecting member 28 may be disposed between the punch flange surface 224 of the second punch 22 and the second pad 24, connecting the punch flange surface 224 and the second pad 24. Even in this case, the distance between the punch flange surface 224 and the die flange surface 254 in the press direction D1 can be changed during the forming process. For example, in the stage where a bent portion is preformed in the workpiece with the punch shoulder 222 of the second punch 22 protruding from the punch top surface 221 of the first punch 21, a relatively large distance can be ensured between the punch flange surface 224 and the die flange surface 254. This allows the workpiece to be bent at a gentle angle by the die 25 and the punch shoulder 222. On the other hand, after preforming, when the die flange surface 254 comes into contact with the second pad 24, the connecting member 28 contracts, reducing the distance between the punch flange surface 224 and the die flange surface 254, and the punch flange surface 224 can be pressed in the pressing direction D1 by the die flange surface 254. This makes it easier for the die 25 and the second punch 22 to reliably press the material at the bottom dead center of the press device 20.

[0080] The press apparatus 20 according to the above embodiment does not need to include the connecting member 28. The second pad 24 may be directly connected to the die flange surface 254 or the punch flange surface 224. In this case, the second pad 24 is preferably made of an elastic material. By compressing the second pad 24 itself, the distance between the punch flange surface 224 and the die flange surface 254 in the press direction D1 changes, and the die flange surface 254 can press the punch flange surface 224 in the press direction D1.

[0081] The press-formed product 10 according to the above embodiment has a concave cross section. However, the shape of the press-formed product 10 is not limited to this. For example, as shown in Fig. 6, the press-formed product 10 may have a cylindrical burred portion as a vertical wall 12 and a bent portion 13 at the base of the burred portion. In this case, for example, as shown in Fig. 7, the punches 21 and 22 and the die 25 of the press device 20 may have an axisymmetric shape.

[0082] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to the following examples.

[0083] [First Example] To confirm the effects of the manufacturing method according to the present disclosure, a press-molding analysis was performed using commercially available analysis software (LS-DYNA ver. 971, manufactured by Ansys) to form a press-molded product 10 using the press apparatus 20 according to the above embodiment (Example). For comparison, a press-molding analysis was performed using a general punch that was not divided into a first punch 21 and a second punch 22 and a die corresponding to this punch to form the press-molded product 10 by a single pad bending process (Comparative Example). In the Example and Comparative Example, the plate thickness and tensile strength of the material M and the dimensions of the press-molded product 10 after forming (such as the bending angle and curvature radius of the bent portion 13) were the same.

[0084] Fig. 8 is a graph showing the distribution of circumferential strain on the outer surface of the bent portion 13 of the example and the comparative example. The horizontal axis of Fig. 8 is the distance measured along the outer surface of the bent portion 13 from a reference point (zero) on the top plate 11 toward the bent portion 13. Fig. 8 shows the distribution of circumferential strain during forming (preforming stage) in addition to the distribution of circumferential strain after forming is completed for the example.

[0085] In the example, before forming began, the punch shoulder 222 of the second punch 22 was positioned closer to the die 25 than the punch top surface 211 of the first punch 21, increasing the distance from the punch top surface 211 to the punch shoulder 222. Therefore, as shown in Figure 8 , during the preforming stage (during forming), bending due to the punch shoulder 222, i.e., the strain peak, occurred at a position relatively far from the reference point (toward the edge of the material M). In the example, after preforming, the punch shoulder 222 of the second punch 22 was pressed in the press direction D1, shortening the distance from the punch top surface 211 to the punch shoulder 222, and the strain peak shifted closer to the reference point than in the preforming stage. Therefore, in the example, the circumferential strain peak was dispersed over a wide range.

[0086] In contrast, in the comparative example, a general punch that was not divided into the first punch 21 and the second punch 22 was used, resulting in a strain distribution with a peak only at the top of the bent portion 13. The maximum value of the circumferential strain in the comparative example was significantly larger than the maximum value of the circumferential strain in the example. In the example, the circumferential strain was dispersed over a wide range, resulting in a 27% decrease in the maximum value of the circumferential strain compared to the comparative example.

[0087] In this way, when bending is performed using the press device 20, strain on the outer surface of the bent portion 13 is reduced, and cracks on the outer surface of the bent portion 13 can be suppressed.

[0088] FIG. 9 is a graph showing the distribution of Vickers hardness at a position 1 / 4 of the plate thickness for the press-formed product 10 formed in the examples and comparative examples. The horizontal axis of FIG. 9 is the distance along the outer surface of the bend from the boundary 14 between the top plate 11 and the bent portion 13 / reference plate thickness t0. The distance from the boundary 14 (the R end of the bent portion 13 on the top plate 11 side) is set to 0 at the position of the boundary 14, negative on the top plate 11 side, and positive on the vertical wall 12 side. The vertical axis of FIG. 9 is the Vickers hardness measured at a position 1 / 4 of the plate thickness, and is the ratio to the Vickers hardness (base material hardness) of the steel plate used as the raw material M of the press-formed product 10. The base material hardness is substantially equal to the average Vickers hardness H1 [HV] described in the above embodiment.

[0089] 9, in the example, the Vickers hardness measured in the range from position A1, which is 2.5 times the standard plate thickness t0, to position A2, which is 4.0 times the standard plate thickness t0, toward the top plate 11 from the boundary 14 between the top plate 11 and the bent portion 13, was 1.1 times or more the base material hardness H1 as a whole. Therefore, in the example, when five points of the Vickers hardness measured at 0.5 mm intervals from position A1 to position A2 were arbitrarily selected, the average value H2 of these five points satisfied H2 / H1≧1.1. On the other hand, in the comparative example, the Vickers hardness in the range from position A1 to position A2 was the same as the base material hardness H1, and H2 / H1 was 1.0.

[0090] In the example, even beyond position A3, which is 7.0 times the reference plate thickness t0, on the top plate 11 side of the boundary 14 between the top plate 11 and the bent portion 13, there was a region where the Vickers hardness exceeded 1.1 times the base material hardness H1. That is, in the example, when the Vickers hardness was measured at 0.5 mm intervals in the region of the top plate 11 beyond position A3, there was an H3, which was the average value of the Vickers hardness at five consecutive points and satisfied H3 / H1≧1.1. On the other hand, in the comparative example, the Vickers hardness of the top plate 11 beyond position A3 was the same as the base material hardness H1, and there was no H3 that satisfied H3 / H1≧1.1.

[0091] In this way, when bending is performed using the press apparatus 20, work hardening can be widely generated in the top plate 11. This makes it possible to reduce the likelihood of breakage of the press-formed product 10, even when the press-formed product 10 is used in an automobile or the like and is subjected to an impact due to an automobile collision or the like. Specifically, as shown in FIGS. 8 and 9 , even when the curvature radius of the inner side of the bend of the bent portion 13 is the same, in the comparative example, strain (work hardening) is concentrated at the bent portion 13 and the strain peak is large, whereas in the example, strain (work hardening) is widely dispersed around the bent portion 13 and the strain peak is reduced. As the strain is widely dispersed in this way, the strain of the press-formed product 10 is smaller than the limit strain at which breakage occurs. Therefore, even when larger strain occurs during a collision, breakage of the press-formed product 10 is less likely to occur. As a result, the press-formed product 10 is likely to absorb a large amount of energy when subjected to an impact.

[0092] [Second Example] To confirm the effect of R / t0 on cracks during forming, a press forming analysis similar to that of the first example was performed. In this analysis, as an example, a bent portion 13 was formed between the top plate 11 and the vertical wall 12 using the same method as in the first example, and the presence or absence of cracks was determined based on the circumferential strain on the bent outer surface of the bent portion 13. As a comparative example, a bent portion 13 was formed using the same method as in the comparative example in the first example, and the presence or absence of cracks was determined based on the circumferential strain on the bent outer surface of the bent portion 13. In both the example and the comparative example, the raw material was a steel plate with a plate thickness (reference plate thickness) t0 = 2.9 mm.

[0093] Other conditions and results of this analysis are shown in Table 1. In Table 1, R is the radius of curvature on the inside of the bent portion 13 after forming. In this analysis, when the tensile strength of the material M was 980 MPa, it was determined that there was no crack when the circumferential strain on the surface on the outside of the bend of the bent portion 13 was 0.50 or less, and that there was a crack when it exceeded 0.50. When the tensile strength of the material M was 1180 MPa, it was determined that there was no crack when the circumferential strain on the surface on the outside of the bend of the bent portion 13 was 0.35 or less, and that there was a crack when it exceeded 0.35.

[0094]

[0095] As shown in Table 1, when the tensile strength of the material is 980 MPa (when 308≦H1<370), it was determined that cracks would occur in the bent portion 13 when R / t0 was less than 1.0 in the comparative example. On the other hand, when the tensile strength of the material is 980 MPa, it was determined that no cracks would occur in the bent portion 13 in the example even when R / t0 was less than 1.0. In the example, it was determined that no cracks occurred in the bent portion 13 even when R / t0 was 0.7 and 0.3. Therefore, with a method similar to that of the above embodiment, it is possible to form the bent portion 13 without cracks even when the material is a high-strength steel plate with a tensile strength of 980 MPa or more and R / t0 is a relatively small value of less than 1.0.

[0096] As shown in Table 1, when the tensile strength of the material is 1180 MPa (when H1≧370), it was determined that cracks would occur in the bent portion 13 when R / t0 was 1.5 or less in the comparative example. On the other hand, when the tensile strength of the material is 1180 MPa, it was determined that no cracks would occur in the bent portion 13 in the example even when R / t0 was 1.5 or less. In the example, it was determined that no cracks occurred in the bent portion 13 even when R / t0 was 1.0 or less. Therefore, with a method similar to that of the above embodiment, it is possible to form the bent portion 13 without cracks even when the material is a high-strength steel plate with a tensile strength of 1180 MPa or more and R / t0 is a relatively small value of 1.5 or less.

[0097] As described above, in the example, it is possible to form a bent portion 13 with a smaller bending radius (radius of curvature on the inside of the bend) without cracking compared to the comparative example. When the bending radius of the bent portion 13 is small, the distance between the R end of the bent portion 13 on the top plate 11 side and the vertical wall 12 is shortened, so that when the press-formed product receives an impact, the load is more easily transmitted to the vertical wall 12, improving the load transmission efficiency of the press-formed product 10. Therefore, the load (reaction force) of the press-formed product 10 is more likely to be high, and the amount of energy absorption can also be increased.

[0098] 10: Press-molded product 11: Top plate 12, 12A, 12B: Vertical wall 13, 13A, 13B: Bending portion 14: Boundary 20: Press device 21: First punch 211: Punch top surface 212: Recess 22: Second punch 221: Punch top surface 222: Punch shoulder 223: Punch side surface 224: Punch flange surface 225: Convex portion 23: First pad 24: Second pad 25: Die 251: Die bottom surface 252: Die shoulder 253: Die side surface 254: Die flange surface 26: Support mechanism 27, 28: Connecting member

Claims

1. A press device comprising: a first punch including a first punch top surface intersecting with a press direction; a second punch arranged on a side of the first punch, the second punch including a second punch top surface intersecting with the press direction, a punch shoulder continuing with the second punch top surface on the opposite side of the first punch, a punch side surface connected to the second punch top surface via the punch shoulder, and a punch flange surface connected to the punch side surface on the opposite side of the punch shoulder and intersecting with the press direction; a first pad facing the first punch top surface and the press direction; a die arranged on the side of the first pad, including a die bottom surface facing at least the second punch top surface in the press direction, a die shoulder continuing with the die bottom surface on the opposite side of the first pad, a die side surface connected to the die bottom surface via the die shoulder, and a die flange surface connected to the die side surface on the opposite side of the die shoulder and facing the punch flange surface in the press direction; a support mechanism configured to support the second punch so that the punch shoulder is positioned closer to the die bottom surface than the top surface of the first punch and to move the second punch relatively in the pressing direction with respect to the first punch; and a second pad disposed between the punch flange surface and the die flange surface.

2. A press device according to claim 1, further comprising a connection member that connects said die flange surface and said second pad and is configured to be expandable and contractible in said pressing direction.

3. A press device as claimed in claim 1, wherein the top surface of the second punch is formed so that the end on the punch shoulder side is located closer to the bottom surface of the die than the end on the first punch side.

4. A press device as claimed in claim 1, wherein when the angle between the top surface of the first punch and the side surface of the punch is θ1 and the angle between the top surface of the second punch and the side surface of the punch is θ2, θ2≦θ1.

5. A press-molded product comprising: a top plate; a bent portion continuous with the top plate; and a vertical wall connected to the top plate via the bent portion, wherein when the thickness of the vertical wall is taken as a reference thickness, H1 is the average value of Vickers hardness measured at five points at 0.5 mm intervals beyond a position 8.0 times the reference thickness on the vertical wall side from the boundary between the top plate and the bent portion, and H2 is the average value of Vickers hardness measured at five points at 0.5 mm intervals in a range from a position 2.5 times the reference thickness to a position 4.0 times the reference thickness on the top plate side from the boundary, H2 / H1 ≧ 1.

1.

6. A press-formed product according to claim 5, wherein when the average value of the Vickers hardness of five consecutive points spaced at 0.5 mm intervals away from the boundary toward the top plate beyond a position 7.0 times the reference plate thickness is taken as H3, there exists an H3 that satisfies H3 / H1 ≧ 1.1.

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