Method for manufacturing structural member, structural member, and die set

Abstract

A structural member (10, 10A) includes a member body (11) and a continuous flange (12). The member body (11) includes a top plate (111) and a vertical wall (114). The continuous flange (12) includes a top plate (121) and a vertical wall (123). A method for manufacturing the structural member (10, 10A) comprises: a first step for forming the continuous flange (12) by bending a material (30) by using a die (21, 21A); and a second step for further bending the continuous flange (12) by using a die (22) such that the angle between the top plate (121) and the vertical wall (123) becomes smaller than that in the first step when viewed from an end edge (125) of the continuous flange (12). In the end edge (125) of the continuous flange (12) formed in the first step, the top plate (121) is inclined so as to open to the opposite side of a reference horizontal plane (H3) from the vertical wall (123).

Description

Method for manufacturing structural member, structural member, and mold set

[0001] The present disclosure relates to a method for manufacturing a structural member, a structural member, and a mold set.

[0002] For example, a structure such as an automobile body is composed of many structural members. Examples of structural members for automobiles include pillars, side members, side sills (rockers), cross members, floor panels, roof panels, etc. Such structural members are generally manufactured by pressing metal plates (materials).

[0003] For example, Patent Document 1 discloses a method for manufacturing a structural member having an L-shape in a plan view. The structural member includes a top plate, a ridge portion, and a vertical wall connected to the top plate via the ridge portion. The ridge portion includes a corner portion curved along the longitudinal direction of the ridge portion. In the manufacturing method of Patent Document 1, a metal plate is pressed using a mold including an upper mold, a lower mold, and a pad to form the structural member.

[0004] For example, Patent Document 2 discloses a method for manufacturing a structural member having a hat-shaped cross section. A bead portion is formed on a vertical wall of the structural member. In the manufacturing method of Patent Document 2, an intermediate formed body is prepared from a metal plate, and the intermediate formed body is molded into a structural member using a mold including an upper mold, a lower mold, and a sliding mold attached to the upper mold via a cam mechanism. The lower mold includes a center mold and a split mold attached to the center mold via a cam mechanism. In Patent Document 2, the sliding mold and the split mold press the portion corresponding to the vertical wall of the intermediate formed body as the mold is clamped, thereby forming the bead portion of the vertical wall.

[0005] For example, Patent Document 3 discloses a method for manufacturing a structural member having a T-shape in a plan view. The manufacturing method in Patent Document 3 includes a first forming step of forming a metal plate into an intermediate shaped member by drawing, a trimming step of trimming the intermediate shaped member, and a second forming step of forming the trimmed intermediate shaped member into a structural member by forming. In the second forming step, a structural member having a target shape is press-formed using a mold including an upper mold and a lower mold.

[0006] JP 2022-072562 A JP 2011-083807 A Japanese Patent No. 6690605 A

[0007] Some structural components have a flange (continuous flange) that is continuous with the main body of the component. The main body and the continuous flange each include a top plate, a ridge portion, and a vertical wall. A corner portion is provided between the ridge portion of the main body and the ridge portion of the continuous flange.

[0008] When such structural components are formed from metal plates (raw materials), cracks can occur in the continuous flange. In particular, when the radius of curvature of the corners is small, the corners tend to obstruct the flow of material from the top plate to the vertical walls. Therefore, the continuous flange is prone to thinning of the plate thickness, especially in the vertical walls, which can lead to cracks.

[0009] An object of the present disclosure is to provide a method for manufacturing a structural member that can suppress the occurrence of cracks in a continuous flange.

[0010] A manufacturing method according to the present disclosure is a method for manufacturing a structural member including a member body and a continuous flange. The member body includes a first top plate and a first vertical wall. The first vertical wall is connected to the first top plate via a first ridge portion. The continuous flange includes a second top plate and a second vertical wall. The second top plate is continuous with the first top plate. The second vertical wall is connected to the second top plate via a second ridge portion and is continuous with the first vertical wall. The structural member has a corner portion between the first ridge portion and the second ridge portion. The manufacturing method includes a first step of bending a material using a first mold to form a continuous flange, and a second step of further bending the continuous flange using a second mold so that the angle between the second top plate and the second vertical wall, as viewed from the edge of the continuous flange, is smaller than in the first step. At the edge of the continuous flange formed in the first step, when the plane passing through the intersection of the second top plate and the second vertical wall and perpendicular to the opening and closing direction of the first mold is taken as the reference horizontal plane, the second top plate is inclined so as to open to the opposite side of the second vertical wall relative to the reference horizontal plane.

[0011] According to the manufacturing method of a structural member according to the present disclosure, it is possible to suppress the occurrence of cracks in the continuous flange.

[0012] FIG. 1 is a perspective view of a structural member according to the first embodiment. FIG. 2A is a diagram showing a mold set according to the first embodiment. FIG. 2B is a diagram showing a mold set according to the first embodiment. FIG. 3A is a cross-sectional view taken along IIIA-IIIA in FIG. 2A. FIG. 3B is a cross-sectional view taken along IIIB-IIIB in FIG. 2B. FIG. 4A is a schematic diagram for explaining a method for manufacturing a structural member according to the first embodiment. FIG. 4B is a schematic diagram for explaining a method for manufacturing a structural member according to the first embodiment. FIG. 4C is a schematic diagram for explaining a method for manufacturing a structural member according to the first embodiment. FIG. 4D is a schematic diagram for explaining a method for manufacturing a structural member according to the first embodiment. FIG. 4E is a schematic diagram for explaining a method for manufacturing a structural member according to the first embodiment. FIG. 4F is a schematic diagram for explaining a method for manufacturing a structural member according to the first embodiment. FIG. 4G is a schematic diagram for explaining a method for manufacturing a structural member according to the first embodiment. FIG. 4H is a schematic diagram for explaining a method for manufacturing a structural member according to the first embodiment. FIG. 5 is a partially enlarged view of the structural member shown in FIG. 1. FIG. 6 is a diagram for explaining a mold set according to a second embodiment. FIG. 7A is a schematic diagram for explaining a manufacturing method of a structural member according to the second embodiment. FIG. 7B is a schematic diagram for explaining a manufacturing method of a structural member according to the second embodiment. FIG. 7C is a schematic diagram for explaining a manufacturing method of a structural member according to the second embodiment. FIG. 8 is a diagram for explaining a mold set according to a modified example of the second embodiment. FIG. 9 is a perspective view of a structural member according to the third embodiment. FIG. 10 is a graph showing the plate thickness reduction rate measured from the ridge line along the edge of the continuous flange to the top plate side for each example and comparative example. FIG. 11 is a graph showing the plate thickness reduction rate measured from the ridge line along the edge of the continuous flange to the vertical wall side for each example and comparative example.

[0013] The manufacturing method according to the embodiment is a method for manufacturing a structural member including a member body and a continuous flange. The member body includes a first top plate and a first vertical wall. The first vertical wall is connected to the first top plate via a first ridge portion. The continuous flange includes a second top plate and a second vertical wall. The second top plate is continuous with the first top plate. The second vertical wall is connected to the second top plate via a second ridge portion and is continuous with the first vertical wall. The structural member has a corner portion between the first ridge portion and the second ridge portion. The manufacturing method includes a first step of bending a material using a first mold to form a continuous flange, and a second step of further bending the continuous flange using a second mold so that the angle between the second top plate and the second vertical wall, as viewed from the edge of the continuous flange, is smaller than in the first step. At the edge of the continuous flange formed in the first step, when a plane passing through the intersection of the second top plate and the second vertical wall and perpendicular to the opening and closing direction of the first mold is taken as the reference horizontal plane, the second top plate is inclined so as to open to the opposite side of the second vertical wall relative to the reference horizontal plane (first configuration).

[0014] In the manufacturing method according to the first aspect, a material is first bent in a first step to form a continuous flange, and the resulting continuous flange is then further bent in a second step. In the first step, the continuous flange is formed so that the angle between the top plate (second top plate) and the vertical wall (second vertical wall) of the continuous flange is larger than in the second step. In the second step, the continuous flange is bent so that this angle becomes smaller. In the continuous flange formed in the first step, the second top plate is inclined relative to a reference horizontal plane so that it opens toward the opposite side of the second vertical wall. In this case, the flow of material from the second top plate to the second vertical wall can be promoted in the first step, thereby reducing the degree of thickness reduction in the continuous flange. Furthermore, by bending the continuous flange in two stages so that the bending angle in the second step is smaller than in the first step, strain generated in the continuous flange can be dispersed. As a result, cracking in the continuous flange can be suppressed. For example, even when the radius of curvature of the corner between the component body and the continuous flange is small, cracking in the continuous flange is less likely to occur.

[0015] For example, if cracks are expected to occur in the forming process of a continuous flange, particularly at the edge of the continuous flange, the forming process may be performed with excess material provided on the metal plate (blank) in advance to prevent cracks, and then a trimming process may be performed after the forming process to remove the unnecessary excess material. In contrast, the manufacturing method according to the first configuration forms the continuous flange through a two-stage bending process, with the bending angle in the second process being smaller than that in the first process, thereby suppressing cracks in the continuous flange. Therefore, it is not necessary to provide excess material on the material to prevent cracks in the continuous flange, and the trimming process after the forming process can be omitted. When the trimming process of the excess material is omitted, the amount of material input to the forming process can be reduced compared to when the trimming process is performed. This improves the yield in the production of structural components. Furthermore, the reduced amount of material input and the elimination of the trimming process reduce the amount of transportation and electricity required in the production of structural components, thereby also reducing greenhouse gas emissions.

[0016] In the manufacturing method relating to the first configuration, when the angle formed by the second top plate and the second vertical wall at the edge of the continuous flange formed in the first step is θ1 and the angle formed by the second top plate and the second vertical wall at the edge of the continuous flange bent in the second step is θ2, θ1-θ2 may be 10° or more (second configuration).

[0017] In the second configuration, the angle (bending angle) θ1 between the second top plate and the second vertical wall of the continuous flange in the first step is 10° or more larger than the bending angle θ2 in the second step. In this case, the flow of material from the second top plate to the second vertical wall is easily promoted in the first step. This further reduces the degree of thickness reduction in the continuous flange, making it even less likely for cracks to occur in the continuous flange.

[0018] In the manufacturing method relating to the first or second configuration, when the angle formed by the second top plate and the second vertical wall at the edge of the continuous flange formed in the first step is θ1 and the angle formed by the second top plate and the second vertical wall at the edge of the continuous flange bent in the second step is θ2, θ1-θ2 may be 70° or less (third configuration).

[0019] In the manufacturing method according to any one of the first to third configurations, the first mold may include a member body molding section for molding the member body and a continuous flange molding section for molding the continuous flange. The continuous flange molding section may be separate from the member body molding section. In this case, in the first step, the continuous flange molding section can start molding the continuous flange after the member body molding section starts molding the member body (fourth configuration).

[0020] In the fourth configuration, in the first step, the forming of the component body begins prior to the forming of the continuous flange. In this case, the continuous flange is not constrained by the first mold in the initial stage of the first step. This makes it easier for material to flow from the second top plate to the second vertical wall in the continuous flange, further suppressing thickness reduction. This makes it less likely for cracks to occur in the continuous flange.

[0021] The structural member according to the embodiment comprises a member body, a continuous flange, and a corner portion. The member body includes a first top plate and a first vertical wall. The first vertical wall is connected to the first top plate via a first ridge portion. The continuous flange includes a second top plate and a second vertical wall. The second top plate is provided continuous with the first top plate. The second vertical wall is connected to the second top plate via the second ridge portion and is provided continuous with the first vertical wall. The corner portion is provided between the first ridge portion and the second ridge portion. When the maximum value of the thickness reduction rate based on the thickness of the first top plate measured along the edge of the continuous flange in an area 10.0 mm toward the second top plate from the boundary between the second ridge portion and the second top plate is defined as A1, and the maximum value of the thickness reduction rate based on the thickness of the first top plate measured along the edge of the continuous flange in an area 50.0 mm toward the second vertical wall from the boundary between the second ridge portion and the second vertical wall is defined as A2, A1 and A2 satisfy 0.80≦A1 / A2≦1.25 (fifth configuration).

[0022] In the structural member according to the fifth configuration, the maximum thickness reduction rate A1 measured in the region on the top plate (second top plate) side at the edge of the continuous flange and the maximum thickness reduction rate A2 measured in the region on the vertical wall (second vertical wall) side satisfy the relationship 0.80≦A1 / A2≦1.25. This means that thickness reduction occurs in both the region on the second top plate side and the region on the second vertical wall side at the edge of the continuous flange, and the maximum thickness reduction rate in one region is 80% or more of the maximum thickness reduction rate in the other region. In this way, the distribution of the thickness reduction (strain) in both the region on the second top plate side and the region on the second vertical wall side is expected to reduce the maximum thickness reduction amount at the edge of the continuous flange. This reduces the likelihood of cracking in the continuous flange.

[0023] The reduction in thickness in the region on the second top plate side and the region on the second vertical wall side allows the structural member to exhibit good crashworthiness when used in, for example, an automobile body. Specifically, the reduction in thickness in both the region on the second top plate side and the region on the second vertical wall side provides relatively uniform hardness, which helps to suppress concentrated deformation of the continuous flange during a collision. Furthermore, when the structural member is joined to another member with the continuous flange, the improved hardness (strength) of the edge of the continuous flange helps to ensure a strong joint with the other member and facilitates good load transfer between the structural member and the other member.

[0024] The mold set according to the embodiment is used to manufacture a structural member including a member body and a continuous flange. The member body includes a first top plate and a first vertical wall. The first vertical wall is connected to the first top plate via a first ridge portion. The continuous flange includes a second top plate and a second vertical wall. The second top plate is continuous with the first top plate. The second vertical wall is connected to the second top plate via a second ridge portion and is continuous with the first vertical wall. The structural member has a corner portion between the first ridge portion and the second ridge portion. The mold set includes a first mold and a second mold. The first mold includes a first top surface for molding the second top plate, a first shoulder for molding the second ridge portion, and a first side surface for molding the second vertical wall. The first shoulder is continuous with the first top surface. The first side surface is connected to the first top surface via the first shoulder. The second mold includes a second top surface for molding the second top plate, a second shoulder for molding the second ridge portion, and a second side surface for molding the second vertical wall. The second shoulder is provided contiguous with the second top surface. The second side surface is connected to the second top surface via the second shoulder. The angle between the second top surface and the second side surface is smaller than the angle between the first top surface and the first side surface. In the first mold, when a plane that passes through the intersection of the first top surface and the first side surface and is perpendicular to the opening and closing direction of the first mold is defined as a reference horizontal plane, the first top surface is inclined relative to the reference horizontal plane so as to open to the opposite side of the first side surface (sixth configuration).

[0025] 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.

[0026] <First embodiment> [Configuration of structural member] Fig. 1 is a perspective view of a structural member 10 according to a first embodiment. The structural member 10 is typically used in the body of an automobile. Although not particularly limited, the structural member 10 may be, for example, a rocker rear inner.

[0027] 1, the structural member 10 is formed of a metal plate. The structural member 10 is formed of, for example, a steel plate. The thickness of the structural member 10 is, for example, 0.8 mm or more, preferably 1.0 mm or more. The thickness of the structural member 10 is, for example, 4.0 mm or less, preferably 3.0 mm or less.

[0028] The structural member 10 includes a member body 11, a continuous flange 12, and a corner portion 13. The member body 11, the continuous flange 12, and the corner portion 13 are integrally formed.

[0029] The member body 11 has, for example, a generally hat-shaped cross section and includes a top plate 111, ridge portions 112 and 113, and vertical walls 114 and 115. The member body 11 further includes flange portions 116 and 117.

[0030] The top plate 111 includes a flat surface 111a on its surface. The flat surface 111a is a portion of the top plate 111 that serves as a reference surface for work when attaching or assembling the structural member 10 to, for example, the body of an automobile. The flat surface 111a has a flat shape and does not substantially include a curved surface. In the example of this embodiment, the flat surface 111a is the periphery of a through hole 111b that penetrates the top plate 111 in the plate thickness direction.

[0031] The ridges 112 and 113 are provided continuously on both sides of the top plate 111. The ridge 112 extends along the edge of the top plate 111. The ridge 113 extends along the edge of the top plate 111 on the side opposite to the ridge 112. As shown in FIG. 1 , one or both of the ridges 112 and 113 may include a curved portion. In this embodiment, the distance between the ridges 112 and 113 in a plan view of the structural member 10, i.e., the width of the top plate 111, is smaller on one side of the member body 11 in the longitudinal direction and larger on the other side. The ridges 112 and 113 may each have a substantially arc-shaped shape when viewed in a cross section (transverse cross section) perpendicular to their extension direction.

[0032] The vertical wall 114 is connected to the top plate 111 via a ridge portion 112. The vertical wall 115 is connected to the top plate 111 on the opposite side of the vertical wall 114 via a ridge portion 113. The vertical walls 114, 115 may be substantially perpendicular to the flat surface 111a of the top plate 111, or may be inclined with respect to the direction perpendicular to the flat surface 111a. For example, the vertical walls 114, 115 may be spaced apart from each other as they move away from the top plate 111.

[0033] The flange portion 116 is connected to one vertical wall 114 on the opposite side of the top plate 111. The flange portion 117 is connected to the other vertical wall 115 on the opposite side of the top plate 111. The flange portions 116 and 117 protrude from the vertical walls 114 and 115, respectively, toward the outside of the structural member 10. The flange portions 116 and 117 extend along the vertical walls 114 and 115, respectively.

[0034] Continuing to refer to FIG. 1 , the continuous flange 12 is provided continuously with respect to the member body 11 via a corner portion 13. The corner portion 13 has an inwardly concave curved shape in a plan view of the structural member 10. The corner portion 13 may have an arc shape in a plan view of the structural member 10. The radius of curvature of the corner portion 13 is, for example, 100 mm or less. The radius of curvature of the corner portion 13 is preferably 50 mm or less, and more preferably 30 mm or less. Although there is no particular lower limit, the radius of curvature of the corner portion 13 is preferably 1 mm or more.

[0035] The continuous flange 12 includes a top plate 121, a ridge portion 122, and a vertical wall 123. The continuous flange 12 further includes a flange portion 124.

[0036] The top plate 121 is provided continuous with the top plate 111 of the member body 11. The top plate 121 is continuous with the top plate 111 of the member body 11 on the outer side of the bend of the corner portion 13.

[0037] The ridge line portion 122 is provided continuously with the top plate 121. The ridge line portion 122 extends along the edge of the top plate 121. When viewed in a cross section (transverse cross section) perpendicular to the direction in which the ridge line portion 122 extends, the ridge line portion 122 can have a substantially arc shape.

[0038] A corner portion 13 is provided between one ridge portion 112 of the member body 11 and the ridge portion 122 of the continuous flange 12. The ridge portion 122 of the continuous flange 12 is connected to the ridge portion 112 of the member body 11 via the corner portion 13. In a plan view of the structural member 10, the ridge portion 122 of the continuous flange 12 is arranged so as to bend relative to the ridge portion 112 of the member body 11.

[0039] At least the portion of the ridge line 112 of the component body 11 that continues to the corner portion 13 is substantially linear in a plan view of the structural member 10. Similarly, at least the portion of the ridge line 122 of the continuous flange 12 that continues to the corner portion 13 is substantially linear in a plan view of the structural member 10. In this embodiment, "substantially linear" includes not only a completely straight line but also a curve that can be considered a straight line due to its large radius of curvature. For example, a curve that extends with a radius of curvature of 200 mm or more is considered a straight line. Although not particularly limited, the extension length of the ridge line 122 in a plan view of the structural member 10 may be, for example, 15 mm or more.

[0040] The vertical wall 123 is connected to the top plate 121 via a ridge portion 122. The vertical wall 123 is arranged so as to bend relative to one vertical wall 114 of the member body 11. The vertical wall 123 is provided continuous with the vertical wall 114 of the member body 11.

[0041] The flange portion 124 is connected to the vertical wall 123 on the opposite side of the top plate 121. The flange portion 124 protrudes from the vertical wall 123 toward the outside of the structural member 10. The flange portion 124 is provided contiguous with one of the flange portions 116 of the member body 11.

[0042] When the structural member 10 configured as described above is formed from a steel plate, the steel plate preferably has a tensile strength of 590 MPa or more. The steel plate more preferably has a tensile strength of 980 MPa or more, and even more preferably has a tensile strength of 1180 MPa or more. The tensile strength of the structural member 10 can be measured by obtaining a test specimen from the top plate 111 of the member body 11 and performing a tensile test on the test specimen in accordance with JIS Z 2241. The test specimen for the tensile test is obtained from a central portion of the top plate 111 that has a flat shape. The test specimen can be obtained, for example, from the ridge portions 112 and 113 of the top plate 111 and from portions 30.0 mm or more away from the longitudinal ends of the top plate 111. If the top plate 111 has steps, protrusions, or through holes, the test pieces can be obtained not only from the ridges 112, 113, and the longitudinal ends of the top plate 111, but also from parts of the top plate 111 that are at least 30.0 mm away from the steps, protrusions, and through holes.

[0043] If it is not possible to obtain a test specimen for a tensile test from the structural member 10, the tensile strength of the structural member 10 may be obtained by a Vickers hardness test. Specifically, a Vickers hardness test conforming to JIS Z 2244 is performed on the top plate 111 of the structural member 10, with a test force of 0.49 N, to measure the Vickers hardness (HV). The Vickers hardness measurement position on the top plate 111 is the same as the position where the test specimen for the tensile test is obtained. That is, the Vickers hardness measurement can be performed on a flat portion of the top plate 111 that is 30.0 mm or more away from the ridges 112 and 113, the longitudinal ends of the top plate 111, steps, protrusions, and through holes. The tensile strength of the structural member 10 can be determined by multiplying the measured Vickers hardness by 3.3.

[0044] 2A and 2B are diagrams showing a die set 20 for manufacturing the structural member 10. In this embodiment, the description will be mainly directed to a portion of the die set 20 that forms one widthwise side of the structural member 10 (the side of the continuous flange 12). The portion of the die set 20 that forms the other widthwise side of the structural member 10 (the side opposite the continuous flange 12) is not particularly different from a general die used to press-form a structural member having a hat shape in cross section, for example, and therefore will not be described in this embodiment.

[0045] 2A and 2B, the mold set 20 includes a mold 21 and a mold 22. The mold set 20 may further include a mold 23 and a mold 24.

[0046] First, referring to FIG. 2A , the die 21 is typically used in pairs with a die 23. For example, the die 21 is a punch, and the die 23 is a die corresponding to the die 21. The die 23 has a molding surface corresponding to the die 21. When in use, the dies 21 and 23 may be attached to, for example, a known press machine (not shown). The die 21 is capable of moving closer to and away from (opening and closing) the die 23. Hereinafter, for convenience of explanation, the opening and closing direction of the die 21 relative to the die 23 may be referred to as the pressing direction P1.

[0047] The mold 21 includes a member main body molding portion 211 and a continuous flange molding portion 212 .

[0048] The member body molding portion 211 is a portion of the mold 21 that is primarily used to mold the member body 11 (FIG. 1) of the structural member 10. The member body molding portion 211 includes a top surface 211a, a shoulder portion 211b, a side surface 211c, and a flange surface 211d.

[0049] The top surface 211a is provided on the die 21 so as to intersect with the pressing direction P1. The top surface 211a is a surface for forming the top plate 111 ( FIG. 1 ) of the member body 11. The shoulder portion 211b is provided continuous with the top surface 211a. The shoulder portion 211b is a surface for forming the ridge portion 112 ( FIG. 1 ) of the member body 11. The side surface 211c is connected to the top surface 211a via the shoulder portion 211b. The side surface 211c is a surface for forming the vertical wall 114 ( FIG. 1 ) of the member body 11. The flange surface 211d is connected to the side surface 211c on the opposite side of the top surface 211a. The flange surface 211d is a surface for forming the flange portion 116 ( FIG. 1 ) of the member body 11.

[0050] The continuous flange molding portion 212 is a portion of the mold 21 that is primarily used to mold the continuous flange 12 (FIG. 1) of the structural member 10. In the example of FIG. 2A, the continuous flange molding portion 212 is integral with the member main body molding portion 211. The continuous flange molding portion 212 includes a top surface 212a, a shoulder portion 212b, a side surface 212c, and a flange surface 212d.

[0051] The top surface 212a is provided on the die 21 so as to intersect with the pressing direction P1. The top surface 212a is provided adjacent to the top surface 211a of the member main body molding portion 211. The top surface 212a is a surface for molding the top plate 121 (FIG. 1) of the continuous flange 12. The shoulder portion 212b is provided continuous with the top surface 212a. A corner portion 213 is provided between this shoulder portion 212b and the shoulder portion 211b of the member main body molding portion 211. The shoulder portion 212b is a surface for molding the ridge portion 122 (FIG. 1) of the continuous flange 12. The side surface 212c is connected to the top surface 212a via the shoulder portion 212b. The side surface 212c is provided continuous with the side surface 211c of the member main body molding portion 211. The side surface 212c is a surface for molding the vertical wall 123 (FIG. 1) of the continuous flange 12. The flange surface 212d is connected to the side surface 212c on the opposite side of the top surface 212a. The flange surface 212d is provided continuous with the flange surface 211d of the member main body molding portion 211. The flange surface 212d is a surface for molding the flange portion 124 (FIG. 1) of the continuous flange 12.

[0052] 2B , the die 22 is typically used in pairs with a die 24. For example, the die 22 is a punch, and the die 24 is a die corresponding to the die 22. The die 24 has a molding surface corresponding to the die 22. When in use, the dies 22 and 24 may be attached to, for example, a known press machine (not shown). The die 22 can move closer to and away from (open and close) the die 24. Hereinafter, for convenience of explanation, the opening and closing direction of the die 22 relative to the die 24 may be referred to as the pressing direction P2.

[0053] The mold 22 includes a member main body molding portion 221 and a continuous flange molding portion 222 .

[0054] The member body molding portion 221 is a portion of the mold 22 that is primarily used to mold the member body 11 (FIG. 1) of the structural member 10. The member body molding portion 221 includes a top surface 221a, a shoulder portion 221b, a side surface 221c, and a flange surface 221d.

[0055] The top surface 221a is provided on the die 22 so as to intersect with the pressing direction P2. The top surface 221a is a surface for forming the top plate 111 ( FIG. 1 ) of the member body 11. The shoulder portion 221b is provided continuous with the top surface 221a. The shoulder portion 221b is a surface for forming the ridge portion 112 ( FIG. 1 ) of the member body 11. The side surface 221c is connected to the top surface 221a via the shoulder portion 221b. The side surface 221c is a surface for forming the vertical wall 114 ( FIG. 1 ) of the member body 11. The flange surface 221d is connected to the side surface 221c on the opposite side of the top surface 221a. The flange surface 221d is a surface for forming the flange portion 116 ( FIG. 1 ) of the member body 11.

[0056] The continuous flange molding portion 222 is a portion of the mold 22 that is primarily used to mold the continuous flange 12 (FIG. 1) of the structural member 10. In the example of FIG. 2B, the continuous flange molding portion 222 is integral with the member main body molding portion 221. The continuous flange molding portion 222 includes a top surface 222a, a shoulder portion 222b, a side surface 222c, and a flange surface 222d.

[0057] The top surface 222a is provided on the die 22 so as to intersect with the pressing direction P2. The top surface 222a is provided adjacent to the top surface 221a of the member main body molding portion 221. The top surface 222a is a surface for molding the top plate 121 (FIG. 1) of the continuous flange 12. The shoulder portion 222b is provided continuous with the top surface 222a. A corner portion 223 is provided between this shoulder portion 222b and the shoulder portion 221b of the member main body molding portion 221. The shoulder portion 222b is a surface for molding the ridge portion 122 (FIG. 1) of the continuous flange 12. The side surface 222c is connected to the top surface 222a via the shoulder portion 222b. The side surface 222c is provided continuous with the side surface 221c of the member main body molding portion 221. The side surface 222c is a surface for molding the vertical wall 123 (FIG. 1) of the continuous flange 12. The flange surface 222d is connected to the side surface 222c on the opposite side of the top surface 222a. The flange surface 222d is provided continuous with the flange surface 221d of the member main body molding portion 221. The flange surface 222d is a surface for molding the flange portion 124 (FIG. 1) of the continuous flange 12.

[0058] Fig. 3A is a cross-sectional view of mold 21 at the position of continuous flange molding portion 212 (cross-sectional view taken along IIIA-IIIA in Fig. 2A). Fig. 3B is a cross-sectional view of mold 22 at the position of continuous flange molding portion 222 (cross-sectional view taken along IIIB-IIIB).

[0059] 3A , in the mold 21, the top surface 212a of the continuous flange forming portion 212 is inclined with respect to a reference horizontal plane H1. The reference horizontal plane H1 is a plane that passes through the intersection between the top surface 212a and the side surface 212c of the continuous flange forming portion 212 and is perpendicular to the pressing direction P1. The intersection is the point of intersection between an extension line of the top surface 212a and an extension line of the side surface 212c in the cross section of the continuous flange forming portion 212.

[0060] The top surface 212a is inclined relative to the reference horizontal plane H1 so as to open toward the opposite side of the side surface 212c. In other words, the top surface 212a is inclined relative to the reference horizontal plane H1 so that the distance from the reference horizontal plane H1 in the press direction P1 increases with increasing distance from the shoulder portion 212b. The side surface 212c may be substantially perpendicular to the reference horizontal plane H1, or may open toward the opposite side of the top surface 212a from the reference vertical plane V1, as shown in FIG. 3A. The reference vertical plane V1 is a plane that passes through the intersection between the top surface 212a and the side surface 212c of the continuous flange forming portion 212 and is perpendicular to the reference horizontal plane H1. In a cross section of the mold 21 at a position corresponding to the edge of the continuous flange 12 (FIG. 1) of the structural member 10, the angle formed by the top surface 212a and the side surface 212c can be defined as α1.

[0061] 3B , in the mold 22, the top surface 222a of the continuous flange forming portion 222 may be inclined with respect to a reference horizontal plane H2. The reference horizontal plane H2 is a plane that passes through an intersection between the top surface 222a and the side surface 222c of the continuous flange forming portion 222 and is perpendicular to the pressing direction P2. The intersection is the point of intersection between an extension line of the top surface 222a and an extension line of the side surface 222c in the cross section of the continuous flange forming portion 222.

[0062] In the example of FIG. 3B , the top surface 222a is inclined relative to the reference horizontal plane H2 so as to open toward the opposite side of the side surface 222c. In other words, the top surface 222a is inclined relative to the reference horizontal plane H2 so that the distance from the reference horizontal plane H2 in the press direction P2 increases as the top surface 222a moves away from the shoulder portion 222b. However, the top surface 222a may also be substantially parallel to the reference horizontal plane H2. The side surface 222c may be substantially perpendicular to the reference horizontal plane H2, or may open toward the opposite side of the top surface 222a from the reference vertical plane V2, as shown in FIG. 3B . The reference vertical plane V2 is a plane that passes through the intersection between the top surface 222a and the side surface 222c of the continuous flange forming portion 222 and is perpendicular to the reference horizontal plane H2. In a cross section of the mold 22 at a position corresponding to the edge of the continuous flange 12 ( FIG. 1 ) of the structural member 10, the angle formed by the top surface 222a and the side surface 222c can be defined as α2.

[0063] Angle α2 ( FIG. 3B ) between top surface 222 a and side surface 222 c of mold 22 is smaller than angle α1 ( FIG. 3A ) between top surface 212 a and side surface 212 c of mold 21. The difference between angles α1 and α2 when measured at a position corresponding to the edge of continuous flange 12 ( FIG. 1 ) of structural member 10 is, for example, 5° or more, and preferably 10° or more. The difference between angles α1 and α2 when measured at a position corresponding to the edge of continuous flange 12 ( FIG. 1 ) of structural member 10 may be 70° or less.

[0064] The angle β1 ( FIG. 3A ) that the top surface 212 a of the mold 21 makes with the reference horizontal plane H1 is larger than the angle β2 ( FIG. 3B ) that the top surface 222 a of the mold 22 makes with the reference horizontal plane H2. However, the angle γ1 ( FIG. 3A ) that the side surface 212 c of the mold 21 makes with the reference vertical plane V1 may be different from or equal to the angle γ2 ( FIG. 3B ) that the side surface 222 c of the mold 22 makes with the reference vertical plane V2.

[0065] [Method for manufacturing a structural member] A method for manufacturing a structural member 10 using the die set 20 will be described below with reference to Figures 4A to 4H. The method for manufacturing the structural member 10 includes a first step and a second step. The structural member 10 is manufactured by, for example, cold press forming.

[0066] When manufacturing the structural member 10, a material made of a metal plate is first prepared. The material may be a blank. The blank can be formed by punching a metal strip (coil) using a mold of the desired shape. Alternatively, the material may be formed by hollowing out the coil using a laser. The material may be formed from a steel plate having a tensile strength of, for example, 590 MPa or more, preferably 980 MPa or more, and more preferably 1180 MPa or more. The material may also be a preformed body formed by preforming a blank.

[0067] (First Step) As shown in FIGS. 4A and 4B, in the first step, the material is bent using dies 21 and 23 to form the continuous flange 12.

[0068] 4A and 4B show cross sections of the dies 21, 23 at a position corresponding to the continuous flange 12. Referring to Fig. 4A, in the first step, a blank 30 is first placed between the dies 21 and 23. Then, as shown in Fig. 4B, the dies 21 and 23 are moved relatively close to each other in the pressing direction P1, and the blank 30 is sandwiched between the dies 21 and 23 to form the continuous flange 12. Although not shown, portions other than the continuous flange 12 are also formed by sandwiching the blank 30 between the dies 21 and 23.

[0069] (Second Step) The second step is performed after the first step. One or more other steps, such as a step of forming a through hole or a step of removing unnecessary portions, may be performed between the first and second steps. The first and second steps may be included in the manufacturing process until the structural member 10 obtains the shape of the final product. As shown in Figures 4C and 4D , in the second step, the continuous flange 12 is further bent using dies 22 and 24.

[0070] 4C and 4D show cross sections of the dies 22, 24 at a position corresponding to the continuous flange 12. Referring to Fig. 4C, in the second step, the intermediate formed body 40 obtained through the first step is placed between the dies 22, 24. Then, as shown in Fig. 4D, the dies 22 and 24 are brought relatively close to each other in the pressing direction P2, and the intermediate formed body 40 is sandwiched between the dies 22, 24, thereby subjecting the continuous flange 12 to additional bending. Although not shown, the portion of the intermediate formed body 40 other than the continuous flange 12 is also sandwiched between the dies 22, 24.

[0071] Figure 4E is a perspective view showing the intermediate formed body 40 obtained in the first step. Figure 4F is a perspective view showing the structural member 10 obtained in the second step. As shown in Figures 4E and 4F, the structural member 10 after the second step differs from the intermediate formed body 40 after the first step in the shape of the continuous flange 12. In the second step, the continuous flange 12 is bent so that the angle between the top plate 121 and the vertical wall 123 when viewed from the edge of the continuous flange 12 is smaller than in the first step.

[0072] Figure 4G is a view of the intermediate formed body 40 obtained in the first step, viewed from the edge (free end) 125 of the continuous flange 12. Figure 4H is a view of the structural member 10 obtained in the second step, viewed from the edge 125 of the continuous flange 12. Figures 4G and 4H respectively show enlarged views of the continuous flange 12 and its vicinity of the intermediate formed body 40 and the structural member 10.

[0073] Referring to Figure 4G, angle θ1 is the angle between the top plate 121 and the vertical wall 123 at the edge 125 of the continuous flange 12 formed in the first step. Referring to Figure 4H, angle θ2 is the angle between the top plate 121 and the vertical wall 123 at the edge 125 of the continuous flange 12 that has been bent in the second step. Angle θ1 is greater than angle θ2. θ1 - θ2 is, for example, 5° or more, preferably 10° or more. θ1 - θ2 may be 70° or less. By satisfying θ1 > θ2, the radius of curvature of the ridge portion 122 of the continuous flange 12 is also greater in the intermediate formed body 40 after the first step than in the structural member 10 after the second step.

[0074] As shown in Figure 4G, the top plate 121 of the continuous flange 12 formed in the first step is inclined with respect to a reference horizontal plane H3. The reference horizontal plane H3 is a plane that passes through the intersection of the top plate 121 and the vertical wall 123 and is perpendicular to the pressing direction P1 (Figure 2A). The intersection is the intersection between an extension of the inner surface of the top plate 121 and an extension of the inner surface of the vertical wall 123 when viewing the continuous flange 12 from the edge 125. The reference horizontal plane H3 coincides or nearly coincides with the reference horizontal plane H1 (Figure 3A) related to the mold 21.

[0075] At the edge 125 of the continuous flange 12 formed in the first step, the top plate 121 is inclined relative to the reference horizontal plane H3 so as to open toward the opposite side of the vertical wall 123. In other words, the top plate 121 is inclined relative to the reference horizontal plane H3 so that the distance from the reference horizontal plane H3 increases the further it is from the ridge portion 122. When viewing the continuous flange 12 formed in the first step from its edge 125, the vertical wall 123 may be substantially perpendicular to the reference horizontal plane H3, or may open toward the opposite side of the top plate 121 from the reference vertical plane V3. The reference vertical plane V3 is a plane that passes through the intersection of the top plate 121 and the vertical wall 123 and is perpendicular to the reference horizontal plane H3.

[0076] As shown in FIG. 4H , the top plate 121 of the continuous flange 12 bent in the second step may be parallel to the reference horizontal plane H4 or may be inclined relative to the reference horizontal plane H4. The reference horizontal plane H4 is a plane that passes through the intersection between the top plate 121 and the vertical wall 123 and is perpendicular to the pressing direction P2 ( FIG. 2B ). When the continuous flange 12 is viewed from the edge 125, the intersection is the intersection between an extension of the inner surface of the top plate 121 and an extension of the inner surface of the vertical wall 123. The reference horizontal plane H4 coincides with or nearly coincides with the reference horizontal plane H2 ( FIG. 3B ) related to the mold 22. The reference horizontal plane H4 is substantially parallel to the flat surface 111 a ( FIG. 1 ) of the member body 11.

[0077] In the example of Figure 4H, at the edge 125 of the continuous flange 12 formed in the second process, the top plate 121 is inclined relative to the reference horizontal plane H4 so as to open toward the opposite side of the vertical wall 123. In other words, the top plate 121 is inclined relative to the reference horizontal plane H4 so that the distance from the reference horizontal plane H4 increases the further away from the ridge portion 122. When viewing the continuous flange 12 from the edge 125, the vertical wall 123 may be substantially perpendicular to the reference horizontal plane H4, or may open toward the opposite side of the top plate 121 from the reference vertical plane V4. The reference vertical plane V4 is a plane that passes through the intersection of the top plate 121 and the vertical wall 123 and is perpendicular to the reference horizontal plane H4.

[0078] The angle φ1 that the top plate 121 makes with the reference horizontal plane H3 at the edge 125 of the continuous flange 12 formed in the first process is larger than the angle φ2 that the top plate 121 makes with the reference horizontal plane H4 at the edge 125 of the continuous flange 12 formed in the second process. However, the angle λ1 that the vertical wall 123 makes with the reference vertical plane V3 at the edge 125 of the continuous flange 12 formed in the first process may be different from or equal to the angle λ2 that the vertical wall 123 makes with the reference vertical plane V4 at the edge 125 of the continuous flange 12 formed in the second process.

[0079] [Effects] In the manufacturing method according to this embodiment, the blank 30 is first bent in the first step to form the continuous flange 12, and then this continuous flange 12 is further bent in the second step. The angle θ1 between the top plate 121 and the vertical wall 123 of the continuous flange 12 formed in the first step is greater than the angle θ2 between the top plate 121 and the vertical wall 123 of the continuous flange 12 formed in the second step. In this case, the flow of material from the top plate 121 to the vertical wall 123 can be promoted in the first step, thereby reducing thickness loss in the continuous flange 12. Furthermore, by bending the continuous flange 12 in two stages so that the bending angle in the second step is smaller than that in the first step, strain generated in the continuous flange 12 can be dispersed. This can suppress cracking in the vertical wall 123 of the continuous flange 12. For example, even if the radius of curvature of the corner portion 13 between the member body 11 and the continuous flange 12 is small or the structural member 10 has high strength, cracks are less likely to occur in the continuous flange 12.

[0080] In the manufacturing method according to this embodiment, the bending angle θ1 of the continuous flange 12 in the first step is larger than the bending angle θ2 of the continuous flange 12 in the second step. In addition, in at least the first step, the top plate 121 of the continuous flange 12 is inclined relative to the reference horizontal plane H1 so as to open toward the opposite side of the vertical wall 123. Furthermore, because the bending angle θ1 in the first step is large, the radius of curvature of the ridge portion 122 connecting the top plate 121 and the vertical wall 123 can also be increased in the first step. This further promotes the flow of material from the top plate 121 to the vertical wall 123, making it easier to suppress cracking in the continuous flange 12.

[0081] In this embodiment, the difference between the bending angle θ1 of the continuous flange 12 in the first step and the bending angle θ2 of the continuous flange 12 in the second step is preferably 10° or more. In this case, the flow of material from the top plate 121 of the continuous flange 12 to the vertical wall 123 side is more promoted in the first step. This further reduces the degree of thickness reduction in the continuous flange 12, making cracks in the continuous flange 12 even less likely to occur. The difference between the bending angle θ1 of the continuous flange 12 in the first step and the bending angle θ2 of the continuous flange 12 in the second step may be 70° or less.

[0082] In the structural member 10 according to this embodiment, a continuous flange 12 is provided continuously with respect to the member body 11. Providing the continuous flange 12 improves the impact absorption performance of the structural member 10. Furthermore, in this embodiment, the continuous flange 12 is connected to the member body 11 by corner portions 13 having a relatively small radius of curvature, e.g., 100 mm or less. This ensures a relatively large flat surface in the continuous flange 12, making it easier to form spot welds on the continuous flange 12, which is advantageous when joining the continuous flange 12 to other members. However, if the radius of curvature of the corner portions 13 is small, cracks are likely to occur in the continuous flange 12 when the structural member 10 is formed. In contrast, in the manufacturing method according to this embodiment, the continuous flange 12 is formed by a two-stage bending process, which promotes material flow in the continuous flange 12 and disperses strain in the continuous flange 12. Therefore, even when the radius of curvature of the corner portions 13 is small, cracks in the continuous flange 12 can be suppressed.

[0083] FIG. 5 is an enlarged view of the continuous flange 12 of the structural member 10. Referring to FIG. 5, the structural member 10 manufactured through the first and second steps has a characteristic distribution of thickness reduction rates in the continuous flange 12. More specifically, when the maximum thickness reduction rate measured at intervals of, for example, 1.0 mm along the edge 125 of the continuous flange 12 in a region X1 extending 10.0 mm toward the top plate 121 from the R start of the ridgeline 122 is defined as A1, and when the maximum thickness reduction rate measured at intervals of, for example, 3.0 mm along the edge 125 of the continuous flange 12 in a region X2 extending 50.0 mm toward the vertical wall 123 from the R end of the ridgeline 122 is defined as A2, A1 and A2 satisfy the relationship 0.80≦A1 / A2≦1.25. The R start of the ridgeline 122 is the boundary between the substantially arc-shaped ridgeline 122 and the top plate 121. The R end of the ridgeline portion 122 is the boundary between the substantially arc-shaped ridgeline portion 122 and the vertical wall 123. If the length of the vertical wall 123 at the edge 125 of the continuous flange 12 is less than 50.0 mm, the entire area of ​​the vertical wall 123 is defined as an area X2 extending 50.0 mm toward the vertical wall 123 from the R end of the ridgeline portion 122. Here, the entire area of ​​the vertical wall 123 refers to the range at the edge 125 of the continuous flange 12 from the R end of the ridgeline portion 122 to the boundary between the vertical wall 123 and the flange portion 124 (the R start of the ridgeline portion of the flange portion 124 adjacent to the vertical wall 123). The thickness reduction rates of the areas X1 and X2 are based on the thickness of the top plate 111 of the component body 11. For example, when the thickness of the top plate 111 (FIG. 1) of the member body 11 is t0 and the thickness measured in the regions X1 and X2 is t, the thickness reduction rate of the regions X1 and X2 can be obtained by (t0-t) / t0×100.

[0084] The plate thickness t0 is the plate thickness of the top plate 111 ( FIG. 1 ) of the member body 11 at a portion where distortion due to forming is substantially not occurring. In other words, the plate thickness t0 is substantially equal to the plate thickness of the raw material 30 ( FIG. 4A ) before forming. The plate thickness t0 is measured at the center of the top plate 111, at a portion having a flat shape. The plate thickness t0 is, for example, the plate thickness of the top plate 111 measured at positions 30.0 mm or more away from the ridges 112 and 113 ( FIG. 1 ) and the longitudinal ends of the top plate 111. If the top plate 111 has steps, protrusions, or through holes, the plate thickness t0 is the plate thickness of the top plate 111 measured at positions 30.0 mm or more away from the ridges 112 and 113, the longitudinal ends of the top plate 111, as well as the steps, protrusions, and through holes.

[0085] In the structural member 10 according to this embodiment, the maximum thickness reduction rate A1 measured in the region X1 on the top plate 121 side and the maximum thickness reduction rate A2 measured in the region X2 on the vertical wall 123 side at the edge 125 of the continuous flange 12 satisfy the relationship 0.80≦A1 / A2≦1.25. That is, thickness reduction occurs in both the region X1 on the top plate 121 side and the region X2 on the vertical wall 123 side at the edge 125 of the continuous flange 12, and the maximum thickness reduction rate in one region is 80% or more of the maximum thickness reduction rate in the other region. In this way, the thickness reduction (strain) is distributed across both regions X1 and X2, which reduces the maximum thickness reduction at the edge 125 of the continuous flange 12. This reduces the likelihood of cracking in the continuous flange 12.

[0086] The reduction in thickness in both regions X1 and X2 allows the structural member 10 to exhibit good crashworthiness when used in, for example, an automobile body. Specifically, the reduction in thickness occurs in both region X1 on the top plate 121 side and region X2 on the vertical wall 123 side, and the continuous flange 12 becomes relatively uniformly hard, which helps to suppress concentrated deformation of the continuous flange 12 during a collision. Furthermore, when the structural member 10 is joined to another member with the continuous flange 12, the increased hardness (strength) of the edge 125 of the continuous flange 12 helps to ensure a strong joint with the other member, enabling good load transmission between the structural member 10 and the other member.

[0087] Second Embodiment Fig. 6 is a diagram for explaining a mold set 20A according to this embodiment, showing a mold 21A included in the mold set 20A.

[0088] In this embodiment, in the mold 21A used in the first step, the continuous flange forming portion 212 is separate from the member main body forming portion 211. The continuous flange forming portion 212 is separated from the member main body forming portion 211, for example, at the position of a corner portion 213. The continuous flange forming portion 212, which is separate from the member main body forming portion 211, includes at least a top surface 212a, a shoulder portion 212b, and a side surface 212c. In this embodiment, the flange surface 212d is included in the member main body forming portion 211. The continuous flange forming portion 212 can operate independently from the member main body forming portion 211.

[0089] 6, the mold 23A that mates with the mold 21A includes a pad portion 231 and a main body portion 232. A portion of the main body portion 232 is configured to be able to mold the top plate 121, ridge portion 122, and vertical wall 123 (FIG. 4E) of the continuous flange 12, together with the continuous flange molding portion 212 of the mold 21A. The remaining portion of the main body portion 232 and the pad portion 231 are configured to be able to mold the top plate 111, ridge portion 112, vertical wall 114, and flange portion 116 of the member main body 11, as well as the flange portion 124 (FIG. 4E) of the continuous flange 12, together with the member main body molding portion 211 of the mold 21A.

[0090] In the first step, the member body forming portion 211 of the mold 21A starts forming the member body 11 ( FIG. 4E ), and then the continuous flange forming portion 212 can start forming the continuous flange 12 ( FIG. 4E ). For example, first, the blank 30 ( FIGS. 4A and 4B ) is pressed between the member body forming portion 211 and the pad portion 231 of the mold 21A. Then, the member body forming portion 211 of the mold 21A and the main body portion 232 of the mold 23A start forming the member body 11 ( FIG. 4E ). Then, the continuous flange forming portion 212 of the mold 21A and the main body portion 232 of the mold 23A start forming the continuous flange 12 ( FIG. 4E ).

[0091] 7A to 7C are diagrams illustrating the formation of the continuous flange 12 by the continuous flange forming portion 212 of the mold 21A and the main body portion 232 of the mold 23A. FIGS. 7A to 7C show cross sections of the molds 21A and 23A at a position corresponding to the continuous flange 12. As shown in FIG. 7A , when viewed in cross section, the continuous flange forming portion 212 of the mold 21A is positioned away from the member main body forming portion 211 until partway through the first step. When the main body portion 232 of the mold 23A approaches the member main body forming portion 211 of the mold 21A relatively, the member main body forming portion 211 begins to form the member main body 11 ( FIG. 4E ). The member main body forming portion 211 begins to form the member main body 11 when the blank 30 begins to deform along the member main body forming portion 211. The blank 30 is pressed into the die 21A by the body 232 of the die 23A, and is first bent along the shoulder 211b (FIG. 6) of the member main body forming portion 211. At this stage, the continuous flange forming portion 212 is disposed apart from the member main body forming portion 211, and therefore the continuous flange forming portion 212 has not yet started to form the continuous flange 12 (FIG. 4E).

[0092] After the member main body forming section 211 starts forming the member main body 11 (FIG. 4E), the continuous flange forming section 212 starts forming the continuous flange 12 (FIG. 4E). When the continuous flange forming section 212 starts forming the continuous flange 12, this means that the continuous flange forming section 212 starts moving toward a position where it can form the continuous flange 12. After the material 30 starts to deform along the member main body forming section 211, the continuous flange forming section 212 starts moving toward a position where it can form the continuous flange 12, that is, a position where it can clamp the material 30 together with the body section 232 of the mold 23A.

[0093] As shown by the arrow in FIG. 7B , toward the end of the first step, the continuous flange forming portion 212 of the mold 21A is moved by, for example, a cam mechanism 25. The continuous flange forming portion 212 moves toward the flange surface 212d of the member main body forming portion 211 so that the material 30 can be sandwiched between the continuous flange forming portion 212 and the main body portion 232 of the mold 23A. When viewed from a cross section of the mold 21A at the position of the continuous flange 12, the movement direction of the continuous flange forming portion 212 may be perpendicular to the pressing direction P1 or may be inclined within a range of ±30° from the direction perpendicular to the pressing direction P1. As shown in FIG. 7C , for example, at the same time that the mold 23A reaches the bottom dead center, the continuous flange forming portion 212 reaches the position of the member main body forming portion 211 and stops, and the continuous flange forming portion 212 sandwiches the material 30 together with the main body portion 232 of the mold 23A.

[0094] In this embodiment, in the first step, the forming of the member body 11 begins prior to the forming of the continuous flange 12. When viewed in cross section at a position corresponding to the continuous flange 12, the continuous flange forming portion 212 of the mold 21A is pre-positioned in a state spaced apart from the member body forming portion 211. In this case, the continuous flange 12 is not constrained by the mold 21A until partway through the first step. This makes it easier for material to flow from the top plate 121 of the continuous flange 12 to the vertical wall 123 in the first step. This further suppresses thickness reduction in the continuous flange 12, making it less likely for cracks to occur in the continuous flange 12. It is preferable that the continuous flange 12 is not constrained by the mold 21A until the end of the first step.

[0095] Although not shown, the mold 22 used in the second step can have the same configuration as the mold 21A used in the first step. That is, in the mold 22, the continuous flange forming portion 222 may be separate from the member main body forming portion 221 (FIG. 2B). In this case, the mold 24 (FIG. 2B) paired with the mold 22 is also preferably divided into a pad portion and a main body portion, similar to the mold 23A.

[0096] Referring to Fig. 8, even when the member main body molding portion 211 and the continuous flange molding portion 212 of the mold 21 are integrally formed as in the first embodiment, a mold 23A including a pad portion 231 and a main body portion 232 can be used. However, in this case, the dividing positions of the pad portion 231 and the main body portion 232 may differ from those in the example (Fig. 6) described in this embodiment. In the example of Fig. 6, the pad portion 231 is provided in the mold 21A so as to correspond mainly to the top surface 211a of the member main body molding portion 211. The main body portion 232 corresponds to the top surface 212a of the continuous flange molding portion 212. On the other hand, in the example of Fig. 8, the pad portion 231 is provided in the mold 21 so as to correspond to both the top surface 211a of the member main body molding portion 211 and the top surface 212a of the continuous flange molding portion 212.

[0097] Although not shown, a mold 24 (FIG. 2B) used in combination with the mold 22 in the second step may also have a configuration similar to that of the mold 23A shown in Fig. 8. That is, the mold 24 may be divided into a pad portion and a main body portion in the same manner as the mold 23A shown in Fig. 8.

[0098] Third Embodiment Fig. 9 is a perspective view of a structural member 10A according to a third embodiment. Referring to Fig. 9, the structural member 10A according to this embodiment has a configuration similar to that of the structural member 10 according to the other embodiments (Fig. 1). However, the structural member 10A differs from the structural members 10 according to the other embodiments in that the member body 11 does not include the ridge portion 113, the vertical wall 115, or the flange portion 117. In the structural member 10A, the member body 11 includes the ridge portion 112, the vertical wall 114, and the flange portion 116 on the continuous flange 12 side.

[0099] As in the first embodiment, the member body 11 includes a flat surface 111a and a through hole 111b on its top plate 111. However, unlike the first embodiment, the flat surface 111a is concave relative to the other parts of the top plate 111. As in the first embodiment, the flat surface 111a serves as a reference surface for work when attaching or assembling the structural member 10A to, for example, the body of an automobile. The flat surface 111a is a surface that is substantially perpendicular to the pressing directions P1 and P2 (FIGS. 2A and 2B).

[0100] Such a structural member 10A can be manufactured by either of the manufacturing methods described in the first and second embodiments. Furthermore, the structural member 10A has the same characteristics as the structural members 10 according to the other embodiments in terms of the distribution of the thickness reduction rate of the continuous flange 12.

[0101] 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.

[0102] For example, the structural members 10, 10A according to the above embodiments each include a single continuous flange 12. However, the structural members 10, 10A may each include multiple continuous flanges 12. When manufacturing a structural member 10 or 10A including multiple continuous flanges 12, the first and second bending steps can be applied to each of the continuous flanges 12. The structural member 10 or 10A including multiple continuous flanges 12 may be divided after forming.

[0103] In the above embodiment, the molds 21, 21A used in the first step are described as being disposed below their counterpart molds 23, 23A. However, contrary to the above embodiment, the mold 21 or 21A may be disposed above the mold 23 or 23A. The positional relationship between the molds 21, 21A and the molds 23, 23A is not particularly limited. Furthermore, when performing the first step, the molds 21, 21A may be opened and closed relative to the molds 23, 23A. The molds 21, 21A may be opened and closed relative to the molds 23, 23A by moving the mold 23 or 23A, or the molds 21, 21A may be opened and closed relative to the molds 23, 23A by moving the mold 21 or 21A.

[0104] Similarly, the mold 22 used in the second step may be disposed below or above the mating mold 24. The positional relationship between the mold 22 and the mold 24 is not particularly limited. Furthermore, when the second step is carried out, the mold 22 only needs to be able to open and close relative to the mold 24. The mold 22 and the mold 24 may be opened and closed by moving the mold 24, or the mold 22 and the mold 24 may be opened and closed by moving the mold 22.

[0105] 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.

[0106] To confirm the effects of the present disclosure, CAE analysis was performed on the manufacturing method described in the above embodiment using commercially available software (AutoForm Forming R10, manufactured by AutoForm, Inc.). In this analysis, the maximum thickness reduction rate at the edge 125 of the continuous flange 12 after the second process was investigated while changing the relationship between the angle θ1 between the top plate 121 and the vertical wall 123 of the continuous flange 12 formed in the first process and the angle θ2 between the top plate 121 and the vertical wall 123 of the continuous flange 12 formed in the second process. The analysis conditions and results are shown in Table 1.

[0107]

[0108] In Table 1, the top plate angle φ1 is the angle between the top plate 121 of the continuous flange 12 formed in the first process and the reference horizontal plane H3 at the edge 125. The vertical wall top plate angle θ1 is the angle between the top plate 121 and the vertical wall 123 at the edge 125 of the continuous flange 12 formed in the first process. The top plate angle φ2 is the angle between the top plate 121 of the continuous flange 12 formed in the second process and the reference horizontal plane H4 at the edge 125. The vertical wall top plate angle θ2 is the angle between the top plate 121 and the vertical wall 123 at the edge 125 of the continuous flange 12 formed in the second process. In this analysis, the angle (vertical wall angle) between the vertical wall 123 of the continuous flange 12 and the reference vertical plane at the edge 125 was assumed to be the same in the first and second processes. The radius of curvature of the ridge 122 at the edge 125 of the continuous flange 12 after the second process was 10.0 mm, which was the same for all Examples and Comparative Examples. The thickness reduction reduction amount relative to the Comparative Example is the difference between the maximum thickness reduction rate of the continuous flange 12 in the Comparative Example and the maximum thickness reduction rate of the continuous flange 12 in each Example.

[0109] As shown in Table 1, in Examples 1 to 6, the angle between the top plate 121 of the continuous flange 12 and the vertical wall 123 was changed between the first and second processes (θ1-θ2>0°). It was confirmed that the maximum thickness reduction rate of the continuous flange 12 was smaller in Examples 1 to 6 than in the comparative example where θ1-θ2=0°. Therefore, it can be said that cracks are less likely to occur in the continuous flange 12 in Examples 1 to 6.

[0110] In Examples 1 to 5, in which θ1-θ2 was 10° or more, the maximum thickness reduction rate of the continuous flange 12 was 12.1% or less, which was a less severe reduction in thickness than in Example 6, in which θ1-θ2 was 5°. Therefore, it can be said that in Examples 1 to 5, cracks are less likely to occur in the continuous flange 12.

[0111] Figure 10 shows the thickness reduction rate measured along the edge 125 of the continuous flange 12 after the second process, from the beginning of the R of the ridgeline portion 122 toward the top plate 121, for Examples 1 to 3 and the Comparative Example. Figure 11 shows the thickness reduction rate measured along the edge 125 of the continuous flange 12 after the second process, from the end of the R of the ridgeline portion 122 toward the vertical wall 123, for Examples 1 to 3 and the Comparative Example. Figures 10 and 11 show the distribution of thickness reduction rates obtained from the forming analysis results using random element sizes for Examples 1 to 3 and the Comparative Example. Table 2 also shows the maximum value A1 in the region X1, 10.0 mm from the beginning of the R of the ridgeline portion 122 toward the top plate 121, and the maximum value A2 in the region X2, 50.0 mm from the end of the R of the ridgeline portion 122 toward the vertical wall 123.

[0112]

[0113] 10 and 11 , in the comparative example, the thickness reduction rate of the edge 125 of the continuous flange 12 is large from the end of the R of the ridge line 122 toward the vertical wall 123, but is small from the start of the R of the ridge line 122 toward the top plate 121. Therefore, as shown in Table 2, in the comparative example, at the edge 125 of the continuous flange 12, the ratio of the maximum thickness reduction rate A1 in the region X1 on the top plate 121 side to the maximum thickness reduction rate A2 in the region X2 on the vertical wall 123 side is 0.52.

[0114] In contrast, in Examples 1 to 3, as shown in Figures 10 and 11, the thickness reduction of the edge 125 of the continuous flange 12 occurs to the same extent not only from the end of the R of the ridgeline 122 to the vertical wall 123 side, but also from the beginning of the R of the ridgeline 122 to the top plate 121 side. As shown in Table 2, in Examples 1 to 3, A1 and A2 satisfy 0.80 ≦ A1 / A2 ≦ 1.25. That is, in Examples 1 to 3, at the edge 125 of the continuous flange 12, the ratio of the maximum thickness reduction rate A1 in the region X1 on the top plate 121 side to the maximum thickness reduction rate A2 in the region X2 on the vertical wall 123 side to the larger value is 80% or more. Thus, in Examples 1 to 3, the thickness reduction portion (strain) is distributed on both the top plate 121 side and the vertical wall 123 side of the edge 125 of the continuous flange 12, so the maximum thickness reduction rate of the entire continuous flange 12 is significantly smaller than that of the comparative example (Table 1).

[0115] DESCRIPTION OF SYMBOLS 10, 10A: Structural member 11: Member body 111: Top plate (first top plate) 112: Ridge portion (first ridge portion) 114: Vertical wall (first vertical wall) 12: Continuous flange 121: Top plate (second top plate) 122: Ridge portion (second ridge portion) 123: Vertical wall (second vertical wall) 125: Edge 13: Corner portion 20, 20A: Mold set 21, 21A: Mold (first mold) 211: Member body forming portion 212: Continuous flange forming portion 212a: Top surface (first top surface) 212b: Shoulder portion (first shoulder portion) 212c: Side surface (first side surface) 22: Mold (second mold) 221: Member body forming portion 222: Continuous flange forming portion 222a: Top surface (second top surface) 222b: Shoulder (second shoulder) 222c: Side (second side)

Claims

1. A manufacturing method of a structural member including a member body having a first top plate and a first vertical wall connected to the first top plate via a first ridge line portion, a second top plate provided continuously with the first top plate, and a continuous flange including a second vertical wall connected to the second top plate via a second ridge line portion and provided continuously with the first vertical wall, the structural member having a corner portion between the first ridge line portion and the second ridge line portion, the method comprising: a first step of using a first mold to perform a bending process on a material to form the continuous flange; and a second step of using a second mold to further perform a bending process on the continuous flange so that an angle between the second top plate and the second vertical wall as viewed from an edge of the continuous flange is smaller than that in the first step. At an edge of the continuous flange formed in the first step, when a plane perpendicular to an opening / closing direction of the first mold is used as a reference horizontal plane passing through an intersection portion between the second top plate and the second vertical wall, the second top plate is inclined to open on a side opposite to the second vertical wall with respect to the reference horizontal plane.

2. The manufacturing method according to claim 1, wherein when an angle formed by the second top plate and the second vertical wall at an edge of the continuous flange formed in the first step is θ1, and an angle formed by the second top plate and the second vertical wall at an edge of the continuous flange subjected to the bending process in the second step is θ2, θ1 - θ2 is 10° or more.

3. The manufacturing method according to claim 1 or 2, wherein when an angle formed by the second top plate and the second vertical wall at an edge of the continuous flange formed in the first step is θ1, and an angle formed by the second top plate and the second vertical wall at an edge of the continuous flange subjected to the bending process in the second step is θ2, θ1 - θ2 is 70° or less.

4. The manufacturing method according to claim 1, wherein the first mold includes a member body forming portion for forming the member body and a continuous flange forming portion that is separate from the member body forming portion and is for forming the continuous flange. In the first step, after the member body forming portion starts forming the member body, the continuous flange forming portion starts forming the continuous flange.

5. A structural member comprising a member body including a first top plate and a first vertical wall connected to the first top plate via a first ridge line portion, a second top plate continuously provided on the first top plate, and a continuous flange including a second vertical wall connected to the second top plate via a second ridge line portion and continuously provided on the first vertical wall, and a corner portion provided between the first ridge line portion and the second ridge line portion, wherein when a maximum value of a plate thickness reduction rate based on the plate thickness of the first top plate measured in a region of 10.0 mm on the second top plate side from the boundary between the second ridge line portion and the second top plate along the edge of the continuous flange is A1, and a maximum value of a plate thickness reduction rate based on the plate thickness of the first top plate measured in a region of 50.0 mm on the second vertical wall side from the boundary between the second ridge line portion and the second vertical wall along the edge of the continuous flange is A2, A1 and A2 satisfy 0.80 ≦ A1 / A2 ≦ 1.

25.

6. A mold set for manufacturing a structural member including a member body including a first top plate and a first vertical wall connected to the first top plate via a first ridge line portion, a second top plate continuously provided on the first top plate, and a continuous flange including a second vertical wall connected to the second top plate via a second ridge line portion and continuously provided on the first vertical wall, and having a corner portion between the first ridge line portion and the second ridge line portion, the mold set comprising a first mold including a first top surface for forming the second top plate, a first shoulder continuously provided on the first top surface for forming the second ridge line portion, and a first side surface connected to the first top surface via the first shoulder for forming the second vertical wall, and a second mold including a second top surface for forming the second top plate, a second shoulder continuously provided on the second top surface for forming the second ridge line portion, and a second side surface connected to the second top surface via the second shoulder for forming the second vertical wall, wherein an angle between the second top surface and the second side surface is smaller than an angle between the first top surface and the first side surface, and in the first mold, when a plane perpendicular to the opening and closing direction of the first mold passing through an intersection of the first top surface and the first side surface is a reference horizontal plane, the first top surface is inclined to open to the opposite side of the first side surface with respect to the reference horizontal plane.

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