Construction element and method of manufacturing thereof

Abstract

A manufacturing method of a structural member (10) includes a preparation step of preparing a raw material (M), and a molding step of molding the raw material (M) into the structural member (10) using a mold (20). The structural member (10) includes a member body (11), a first flange (12), and a second flange (13). The mold (20) includes an upper mold (23), a first lower mold (21) for molding the member body (11) and the first flange (12), and a second lower mold (22) for molding the second flange (13). The molding step includes a first step of clamping the raw material (M) with the upper mold (23) and the first lower mold (21) without clamping the raw material (M) with the upper mold (23) and the second lower mold (22), and a second step of molding the second flange (13) by clamping the raw material (M) with the upper mold (23) and the second lower mold (22) after the first step.

Description

Technical Field

[0001] This disclosure relates to structural components for automobiles and methods for manufacturing the same. Background Technology

[0002] Automobiles are composed of many structural components. These structural components include, for example, pillars, longitudinal beams, lower side beams, crossbeams, floor plates, and roof plates. Structural components are manufactured, for example, by pressing metal sheets. For instance, Patent Documents 1-3 disclose manufacturing methods that use a mold comprising an upper die and a lower die to form metal sheets into structural components.

[0003] In the manufacturing method of Patent Document 1, a metal plate is first placed on a lower mold, and pressure is applied to a predetermined area of ​​the metal plate using a pad. Then, an upper mold is brought close to the lower mold, and while one end edge of the metal plate is moved in-plane along its length, the metal plate is clamped by the upper and lower molds to form a structural member. In Patent Document 1, a central column is shown as an example of a structural member manufactured by this method.

[0004] Patent Document 2 discloses a method for manufacturing structural components such as longitudinal beams, lower beams, and cross beams. The structural component to be manufactured in Patent Document 2 has a generally cap-shaped cross-section. That is, the structural component includes a top plate, two longitudinal walls, and two flanges. Outwardly projecting flanges, rising from the top plate and each longitudinal wall, are provided at the ends of the structural component along its length. In Patent Document 2, the outwardly projecting flanges and other portions are formed using a common lower mold. In Patent Document 2, the forming of the structural component begins by separating at least the area of ​​the metal plate that forms the outwardly projecting flange and the area near it from the top surface of the lower mold.

[0005] Patent document 3 discloses a method for manufacturing a structural member (T-shaped component) having a T-shape, such as a beam. The T-shaped component includes a top plate having a T-shape, a longitudinal wall continuous with the top plate, and a flange continuous with the lower end of the longitudinal wall. The top plate includes a longitudinal edge and a transverse edge connected to the longitudinal edge.

[0006] The manufacturing method of Patent Document 3 includes a first forming step of forming a metal sheet into an intermediate shape component, a cutting step of cutting the intermediate shape component to obtain a cut component, and a second forming step of forming the cut component into a T-shaped component using a mold including an upper mold and a lower mold. In the first forming step, a convex shape portion is formed on the portion of the longitudinal edge of the top plate adjacent to the transverse edge. Furthermore, in the first forming step, a curved rounded corner portion is formed to lift the connection portion of the longitudinal wall continuous with the transverse edge of the top plate to the flange. The convex shape portion and the curved rounded corner portion are flattened by the upper mold in the second forming step.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent No. 6436166

[0010] Patent Document 2: Japanese Patent No. 5958644

[0011] Patent Document 3: Japanese Patent Application Publication No. 2019-013952 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] In the structural member of Patent Document 3, a flange continuous to the lower end of the longitudinal wall is used, for example, as a first flange for joining the structural member to the base plate. The transverse edge of the top plate and the portion of the longitudinal wall continuous to the transverse edge of the top plate are used, for example, as a second flange for joining the structural member to the lower side beam. The transverse edge of the top plate and the portion of the longitudinal wall continuous to the transverse edge of the top plate have a generally L-shaped form in the side view of the structural member.

[0014] When manufacturing such structural components by pressing, cracks sometimes occur in the second flange. For example, in the case of a T-shaped joint structure when viewed from above, it is desirable to make the corner rounded corners sharper, which increases the degree of freedom in spatial coordination with other components, reduces dimensional constraints in design, and thus improves the stiffness of the component. However, when the radius of curvature of the corner rounded corner is less than 20.0 mm, cracks are prone to occur at the end edge of the portion of the second flange extending along the height direction of the structural component, and at the connection between the first and second flanges. Cracks in the second flange are particularly prone to occur when the structural component is formed from steel sheet with high tensile strength. Furthermore, when manufacturing the same structural component using 6000 series aluminum alloy sheet with a relatively large total elongation by cold pressing or hot stamping, the aluminum alloy sheet has a small uniform elongation, resulting in a sharp reduction in sheet thickness locally at strain concentration points, which easily leads to cracks.

[0015] The technical problem of this disclosure is to suppress the generation of cracks at the flange when manufacturing structural components for automobiles. Another technical problem of this disclosure is that an intermediate trimming process for the flange is not required when manufacturing structural components for automobiles. A further technical problem of this disclosure is to provide a structural component, such as an integral T-joint structure, which offers high strength and minimizes dimensional constraints in design due to its small radius of curvature at the rounded corners, a feature long desired for automotive structural components.

[0016] Solution for solving the problem

[0017] The manufacturing method disclosed herein is a method for manufacturing structural components for automobiles. This manufacturing method includes a preparation step of preparing raw materials made of sheet metal and a forming step of shaping the raw materials into structural components using a mold. The structural component includes a component body, a first flange, and a second flange. The component body includes a top plate and a longitudinal wall. The top plate has two sides. The two sides extend along the length direction of the structural component. The two sides are opposite each other in the width direction of the structural component. The longitudinal wall is connected to the sides via ridge portions. The first flange is connected to the longitudinal wall on the opposite side of the top plate and extends from the longitudinal wall along the width direction of the structural component. The second flange is continuously disposed at its end in the length direction of the component body. The second flange includes a transverse flange portion and a longitudinal flange portion. The transverse flange portion extends from the top plate along the width direction of the structural component. The longitudinal flange portion is connected to the end of the transverse flange portion near the component body side via ridge portions and extends from the transverse flange portion toward the first flange. The mold includes an upper mold, a first lower mold for forming the component body and the first flange, and a second lower mold for forming the second flange. The first lower mold is disposed opposite to the upper mold. The second lower mold is disposed next to the first lower mold and opposite to the upper mold. The forming process includes a first step in which the raw material is held in place by the upper mold and the first lower mold but not by the upper mold and the second lower mold, and a second step in which the second flange is formed by holding the raw material in place by the upper mold and the second lower mold after the first step.

[0018] The effects of the invention

[0019] According to the manufacturing method of the automotive structural member disclosed herein, crack generation at the flange can be suppressed. Furthermore, according to the manufacturing method of the automotive structural member disclosed herein, an intermediate trimming process for the flange is unnecessary. Moreover, according to this disclosure, a structural member with high strength, a small radius of curvature at the corner fillet, and fewer dimensional constraints in design, such as an integral T-joint structure, can be provided, which is highly desirable for automotive structural members. Attached Figure Description

[0020] Figure 1 This is a perspective view of the structural components of the first embodiment.

[0021] Figure 2 yes Figure 1 The cross-sectional view of the structural component shown.

[0022] Figure 3A This is a schematic diagram illustrating the manufacturing method of the aforementioned structural components.

[0023] Figure 3B This is a schematic diagram illustrating the manufacturing method of the aforementioned structural components.

[0024] Figure 3C This is a schematic diagram illustrating the manufacturing method of the aforementioned structural components.

[0025] Figure 3D This is a schematic diagram illustrating the manufacturing method of the aforementioned structural components.

[0026] Figure 3E This is a schematic diagram illustrating the manufacturing method of the aforementioned structural components.

[0027] Figure 3F This is a schematic diagram illustrating the manufacturing method of the aforementioned structural components.

[0028] Figure 3G This is a schematic diagram illustrating the manufacturing method of the aforementioned structural components.

[0029] Figure 3H This is a schematic diagram illustrating the manufacturing method of the aforementioned structural components.

[0030] Figure 3I This is a schematic diagram illustrating the manufacturing method of the aforementioned structural components.

[0031] Figure 4 yes Figure 1 A partially enlarged view of the structural components shown.

[0032] Figure 5 yes Figure 1 A partially enlarged view of the structural components shown.

[0033] Figure 6 This is a perspective view of the structural components of the second embodiment.

[0034] Figure 7 This is a perspective view of the structural components of a modified example of the second embodiment.

[0035] Figure 8 The chart, obtained through analysis, shows the relationship between the distance from the end of the longitudinal flange portion of the structural member to the end of the transverse flange portion and the reduction rate of the plate thickness. Detailed Implementation

[0036] The manufacturing method described herein is a method for manufacturing a structural component for automobiles. This manufacturing method includes a preparation step of preparing raw materials made of sheet metal and a forming step of shaping the raw materials into a structural component using a mold. The structural component includes a component body, a first flange, and a second flange. The component body includes a top plate and a longitudinal wall. The top plate has two sides. The two sides extend along the length direction of the structural component. The two sides are opposite each other in the width direction of the structural component. The longitudinal wall is connected to the sides via ridge portions. The first flange is connected to the longitudinal wall on the opposite side of the top plate and extends from the longitudinal wall along the width direction of the structural component. The second flange is continuously disposed at its end in the length direction of the component body. The second flange includes a transverse flange portion and a longitudinal flange portion. The transverse flange portion extends from the top plate along the width direction of the structural component. The longitudinal flange portion is connected to the end of the transverse flange portion near the component body side via ridge portions and extends from the transverse flange portion toward the first flange. The mold includes an upper mold, a first lower mold for forming the component body and the first flange, and a second lower mold for forming the second flange. The first lower mold is disposed opposite to the upper mold. The second lower mold is disposed next to the first lower mold and opposite to the upper mold. The forming process includes a first step in which the raw material is held in place by the upper mold and the first lower mold but not by the upper mold and the second lower mold, and a second step (first structure) in which the raw material is held in place by the upper mold and the second lower mold after the first step (first structure).

[0037] In the manufacturing method of the first structure, a structural component is formed from raw material using a first lower die for forming the main body of the component and the first flange, and a second lower die for forming the second flange, which is continuous with the end of the main body of the component along its length. In the first forming step, the raw material is held by the upper die and the first lower die, but not by the upper die and the second lower die. That is, until the middle of the forming process, the portion of the raw material that will become the second flange is not constrained by the die. As a result, material flows into the portion of the raw material that will become the second flange. The material mainly flows from the transverse flange portion, which is continuous with the top plate of the main body of the component, to the longitudinal flange portion, which connects to the transverse flange portion and extends towards the first flange. Therefore, it is possible to suppress the occurrence of cracks at the end edge of the longitudinal flange portion and at the connection between the longitudinal flange portion and the first flange.

[0038] In the manufacturing method of the first structure, the mold may further include a backing plate. In this case, it is preferable that, in the first step, after pressing the raw material with the backing plate, the raw material is clamped by the upper mold and the first lower mold (second structure).

[0039] According to the second structure, in the first forming process, after pressing the raw material with a pad, the raw material is clamped by an upper mold and a first lower mold. Therefore, when forming the raw material into a structural component, misalignment of the raw material can be prevented.

[0040] In the manufacturing method of the first or second structure, a step may be pre-formed between the forming surface of the first lower die and the forming surface of the second lower die, so that in the first step, when the upper die is brought closer to the first and second lower dies, the first lower die clamps the raw material between itself and the upper die before the second lower die. Alternatively, in the second step, by bringing the upper die, which is clamping the raw material together with the first lower die, further closer to the second lower die, the step disappears, and the second lower die clamps the raw material between itself and the upper die. Preferably, the size of the step before the start of the first step is greater than or equal to the thickness of the raw material and less than 5.0 times that thickness (third structure).

[0041] In the third structure, a step is pre-set between the forming surfaces of the first and second lower dies, allowing the first lower die to clamp the raw material between itself and the upper die before the second lower die, which is used to form the second flange. If the step is too small, the portion of the raw material intended to become the second flange is constrained by the second lower die at an early stage, resulting in insufficient material flow. Consequently, cracks are prone to form at the longitudinal flange portion of the second flange and at the connection between the longitudinal flange portion and the first flange. On the other hand, if the step is too large, wrinkles are prone to form at the junction of the transverse flange portion of the second flange and the top plate of the component body. However, in the third structure, the step is set to an appropriate size. That is, the size of the step is greater than or equal to the thickness of the raw material and less than 5.0 times that thickness. Therefore, the generation of cracks and wrinkles in and around the second flange can be suppressed.

[0042] In any of the manufacturing methods of structures 1 to 3, the first lower die can also be configured to be able to rise and fall using a buffer mechanism. In this case, during the forming process, the upper die can be lowered toward the first lower die and the second lower die (structure 4).

[0043] The manufacturing method of any of the structures 1 to 4 may also include a pre-forming step of forming an intermediate molded article from a metal sheet. In this case, during the forming step, the structural component can be formed from the intermediate molded article as raw material (structure 5).

[0044] The manufacturing method of any of the structures 1 to 5 may also include a heating step of heating the raw material. In this case, during the forming step, the raw material heated by the heating step can be formed into a structural component (structure 6).

[0045] In any of the manufacturing methods of structures 1 to 6, the metal plate constituting the raw material may also be a steel plate with a tensile strength of 590 MPa or more (structure 7).

[0046] The structural member described in this embodiment is a structural member for automobiles. The structural member includes a member body, a first flange, and a second flange. The member body includes a top plate and a longitudinal wall. The top plate has two side portions. The two side portions extend along the length direction of the structural member. The two side portions are opposite each other in the width direction of the structural member. The longitudinal wall is connected to the side portions via ridge portions. The first flange is connected to the longitudinal wall on the opposite side of the top plate and extends from the longitudinal wall along the width direction of the structural member. The second flange is continuously disposed at its end in the length direction of the member body. The second flange includes a transverse flange portion and a longitudinal flange portion. The transverse flange portion extends from the top plate along the width direction of the structural member. The longitudinal flange portion is connected to the end of the transverse flange portion near the member body via ridge portions and extends from the transverse flange portion toward the first flange. When the thickness reduction rate based on the thickness of the top plate is set as T[%], the length of the region at the end edge of the longitudinal flange having a thickness reduction rate T that satisfies the following formula (1) is more than 2.0 times and less than 6.0 times the thickness of the top plate (8th structure).

[0047] 0.9×Tmax≤T≤Tmax (1)

[0048] Where Tmax[%] is the maximum value of the reduction rate of plate thickness at the end edge of the longitudinal flange.

[0049] In the structural member of the eighth structure, the length of the region satisfying the above formula (1) at the end edge of the longitudinal flange of the second flange is more than 2.0 times and less than 6.0 times the thickness of the top plate. This means that the thickness distribution at the end edge of the longitudinal flange is relatively uniform. In this case, when using the structural member, stress concentration is less likely to occur at the thickness reduction portion at the end edge of the longitudinal flange, and cracks can be suppressed from the end edge of the longitudinal flange. That is, the structural member can have excellent durability.

[0050] In the construction member of the 8th structure, the length of the region with a Vickers hardness HV[HV] satisfying the following formula (2) at the end edge of the longitudinal flange is more than 5.0 times and less than 10.0 times the thickness of the top plate (the 9th structure).

[0051] HV Tmax -10.0≤HV≤HV Tmax +10.0 (2)

[0052] Among them, HV Tmax [HV] is the Vickers hardness of the portion of the longitudinal flange end edge that has the maximum value Tmax of the reduction rate of plate thickness. HV and HV Tmax This is the Vickers hardness under a test force of 294.2 N.

[0053] When the length of the region satisfying the above formula (2) at the end edge of the longitudinal flange of the second flange, such as in structure 9, is more than 5.0 times but less than 10.0 times the thickness of the top plate, it means that the hardness distribution at the end edge of the longitudinal flange is relatively uniform. In this case, stress concentration is less likely to occur at the end edge of the longitudinal flange, and crack initiation can be suppressed. That is, the structural member can have excellent durability.

[0054] In the structural members of structure 8 or 9, the average Vickers hardness measured at 30 locations on the surface of the longitudinal flange, with a distance between them greater than the thickness of the top plate, is 300.0 Hv or higher, and the standard deviation of this Vickers hardness is 70.0 Hv or lower (structure 10). In this case, the Vickers hardness is the Vickers hardness under a test force of 10 kgf (98.07 N).

[0055] The structural members of any of the structures in 8 to 10 can also be formed from steel plates with a tensile strength of 590 MPa or more (structure 11).

[0056] In any of the structural members of structures 8 to 11, the ridge portion may include a corner portion extending from the top plate toward the transverse flange portion. The corner portion, for example, has a radius of curvature of less than 20.0 mm in the top view of the structural member (structure 12).

[0057] When the radius of curvature at the corner of the edge section is relatively small, less than 20.0 mm, the intersection angle between the longitudinal wall and the longitudinal flange, which are continuous with the edge section, can be set to, for example, approximately right angle. This allows the structural member to excel in spatial efficiency. That is, it increases the degree of freedom in spatial coordination with other components and reduces dimensional constraints in the design of the structural member or other components. Furthermore, even in areas where the structural member is placed, its load-bearing capacity can be ensured. Specifically, when a longitudinal load is applied to a structural member placed in a narrow area, the longitudinal flange can bear the load with its surface, and the load is easily transferred from the longitudinal flange to the main body of the member. Therefore, the structural member can exhibit good load-bearing capacity in the longitudinal direction.

[0058] Embodiments of this disclosure are described below with reference to the accompanying drawings. Identical or equivalent structures are labeled with the same reference numerals in the drawings, and identical descriptions are not repeated.

[0059] <First Embodiment>

[0060] [Structure of the structural components]

[0061] Figure 1This is a perspective view of the structural member 10 according to the first embodiment. The structural member 10 is used as a structural member for automobiles. The structural member 10 is typically a frame extending in the left-right direction of the automobile. The structural member 10 is, for example, a crossbeam disposed on the floor or the back of the floor, or a lateral extension provided at the end of the crossbeam.

[0062] Reference Figure 1 The structural component 10 includes a component body 11, a second flange 13, and two first flanges 12.

[0063] The main body 11 of the component includes a top plate 111 and two longitudinal walls 112. The top plate 111 and each longitudinal wall 112 extend substantially along the length direction (left-right direction of the vehicle) of the structural component 10.

[0064] The top plate 111 includes two side portions 111a. These two side portions 111a extend along the length of the structural member 10. The two side portions 111a are opposite each other in the width direction (rear-to-rear direction of the vehicle) of the structural member 10. Each side portion 111a is connected to a longitudinal wall 112 via a ridge portion 14. The ridge portion 14 extends from the main body 11 to the second flange 13.

[0065] Figure 2 This is a transverse sectional view (section view II-II) of structural member 10. (Refer to...) Figure 2 The two longitudinal walls 112 are opposite each other in the width direction of the structural member 10. In the transverse sectional view of the structural member 10, the longitudinal walls 112 extend approximately along the height direction (vertical direction of the vehicle) of the structural member 10. The ridge portion 14 that is continuous with each longitudinal wall 112 is substantially arc-shaped in the transverse sectional view of the structural member 10.

[0066] The first flange 12 is connected to the longitudinal wall 112 on the opposite side of the top plate 111. The first flange 12 is respectively connected to... Figure 2 The lower end of the longitudinal wall 112 in the paper is connected. Each first flange 12 is connected to the longitudinal wall 112 via a ridge portion 15. The ridge portion 15 is substantially arc-shaped in the transverse cross-sectional view of the structural member 10.

[0067] The first flange 12 extends from the longitudinal wall 112 along the width direction of the structural member 10. The first flange 12 is, for example, fixed to the upper or lower surface of the vehicle's floor. The first flange 12 extends substantially along the length direction of the structural member 10, similar to the top plate 111 and the longitudinal wall 112. Each first flange 12 has an open end edge 12a.

[0068] The second flange 13 is continuously disposed along one end of the main body 11 in the longitudinal direction of the structural member 10. The second flange 13 is also continuous with the two first flanges 12. The second flange 13 is, for example, fixed to the lower side beam of an automobile. The second flange 13 includes a transverse flange portion 131 and two longitudinal flange portions 132.

[0069] Refer again Figure 1 The transverse flange 131 is continuously provided with the top plate 111 of the main body 11. The transverse flange 131 is continuous with one end of the top plate 111 along its length. The transverse flange 131 is substantially or approximately on the same plane as the top plate 111, for example. The transverse flange 131 may be coplanar with the top plate 111, but may also be slightly inclined relative to the top plate 111. The transverse flange 131 extends from the top plate 111 along the width direction of the structural member 10. That is, in the width direction of the structural member 10, the length of the transverse flange 131 is greater than the length of the top plate 111. Therefore, the transverse flange 131 and the top plate 111 form a generally T-shape in the top view of the structural member 10. The transverse flange 131 is connected to the top plate 111 by corner portions 141 included in the edge portions 14 on both sides of the top plate 111. Each corner portion 141 extends from the top plate 111 toward the transverse flange 131. Each corner portion 141 is substantially arc-shaped in the top view of the structural member 10. The radius of curvature of each corner portion 141 in the top view of the structural member 10 is, for example, 20.0 mm or less. The extension amount (flange length) of the transverse flange portion 131 extending from the top plate 111 is, for example, 25.0 mm or less.

[0070] The longitudinal flange portions 132 are connected to the end portions 131a of the transverse flange portions 131 on the side near the main body 11 via the ridge portion 14. The end portion 131a is the end portion of the transverse flange portion 131 that extends from the top plate 111 to both sides in the width direction on the side near the main body 11. Each longitudinal flange portion 132 is connected to the transverse flange portion 131 by the ridge portion 14 extending from the main body 11 to the second flange 13.

[0071] The longitudinal flange portions 132 extend from the transverse flange portions 131 toward the first flange 12. That is, each longitudinal flange portion 132 extends from the end 131a of the transverse flange portion 131 toward the first flange 12 generally along the height direction of the structural member 10. Each longitudinal flange portion 132 is integral with the transverse flange portion 131, the longitudinal wall 112 of the member body 11, and the first flange 12. The corner portions of the longitudinal flange portions 132 and the longitudinal wall 112 have, for example, a radius of curvature of 20.0 mm or less.

[0072] Each longitudinal flange 132 has an open end edge 132a. The end edge 132a extends substantially along the height direction of the structural member 10. The end edge 132a of each longitudinal flange 132 is connected to the side edge 131b of the transverse flange 131 via a connecting edge 161. Furthermore, the end edge 132a of each longitudinal flange 132 is connected to the end edge 12a of the first flange 12 via a connecting edge 162. The connecting edges 161 and 162 are substantially arc-shaped in the side view of the structural member 10.

[0073] [Manufacturing methods for structural components]

[0074] The following is for reference Figures 3A to 3I The manufacturing method of structural component 10 is explained. Figures 3A to 3I This is a schematic diagram illustrating the manufacturing method of the structural component 10. The manufacturing method of the structural component 10 includes a process of preparing raw material M and a process of shaping the raw material M into the structural component 10.

[0075] (Preparation process)

[0076] Reference Figure 3A In the preparation process, raw material M, consisting of a metal sheet, is prepared. Raw material M, for example, is punched to form structural component 10 (… Figure 1 and Figure 2 The billet is an unfolded shape. The metal sheet constituting the raw material M is, for example, a steel sheet. This steel sheet has, for example, a tensile strength of 590 MPa or more. The steel sheet may also have a tensile strength of 780 MPa or more, or even 980 MPa or more. The thickness of the raw material M is, for example, 1.0 mm or more and 5.0 mm or less.

[0077] (Forming process)

[0078] like Figures 3B to 3D As shown, in the forming process, in order to form the raw material M into structural component 10 ( Figure 1 and Figure 2 ), and mold 20 is used. First, the structure of mold 20 will be explained. Figure 3B This is a 3D view of mold 20. Figure 3C This is a cross-sectional view (IIIC-IIIC section view) of mold 20. Figure 3D This is a longitudinal sectional view (IIID-IIID sectional view) of mold 20.

[0079] Reference Figure 3BThe mold 20 includes a first lower mold 21, a second lower mold 22, a backing plate 24, and two upper molds 23. The lower molds 21 and 22 are punches, and the upper molds 23 are dies corresponding to the lower molds 21 and 22. At the start of the forming process, the lower molds 21 and 22 are positioned opposite the upper molds 23 and the backing plate 24. The lower molds 21 and 22 are, for example, positioned below the upper molds 23 and the backing plate 24. The first lower mold 21, the second lower mold 22, the upper molds 23, and the backing plate 24 are, for example, mounted on a known punch press (figure omitted).

[0080] Reference Figure 3C The first lower mold 21 mainly holds the main body 11 and the first flange 12 ( Figure 1 and Figure 2 Forming. The first lower die 21 is configured to be able to rise and fall using the buffer mechanism 25. The buffer mechanism 25 can be a mechanism commonly used in punch presses, such as including a die buffer, a buffer pin, etc.

[0081] The first lower mold 21 has a forming surface 211. The forming surface 211 has an upwardly convex shape. The forming surface 211 includes a top surface 211a, two side surfaces 211b, and two flange surfaces 211c. The top surface 211a is the upward-facing surface opposite to the backing plate 24. The two side surfaces 211b are disposed on both sides of the top surface 211a. The flange surfaces 211c are connected to the lower ends of the side surfaces 211b respectively and protrude laterally from the side surfaces 211b.

[0082] The second lower mold 22 is a mold independent of the first lower mold 21. The second lower mold 22 is positioned next to the first lower mold 21 along the length of the mold 20. The second lower mold 22 mainly houses the second flange 13 ( Figure 1 and Figure 2 Forming. The second lower mold 22 has a forming surface 221.

[0083] Reference Figure 3C and Figure 3D The forming surface 221 of the second lower mold 22 includes a top surface 221a and a side surface 221b. The top surface 221a is the upward-facing surface opposite to the pad 24. The side surface 221b is connected to the top surface 221a on the side of the first lower mold 21 and extends downward from the top surface 221a.

[0084] Before the forming process begins, a step is created between the forming surface 211 of the first lower die 21 and the forming surface 221 of the second lower die 22. Initially, the forming surface 221 of the second lower die 22 is located below the forming surface 211 of the first lower die 21. More specifically, the top surface 221a of the second lower die 22 is located below the top surface 211a of the first lower die 21, thus creating a step between the top surfaces 211a and 221a. Furthermore, the lower end of the side surface 221b of the second lower die 22 is located below the flange surface 211c of the first lower die 21, thus creating a step at the junction of the side surface 221b of the second lower die 22 and the flange surface 211c of the first lower die 21. The size S of the step between the forming surface 211 of the first lower die 21 and the forming surface 221 of the second lower die 22 is preferably greater than or equal to the thickness of the raw material M. The size S of the step is, for example, less than 5.0 times the thickness of the raw material M. The size S of the step is substantially the same as the stroke (buffer stroke) of the buffer mechanism 25.

[0085] Next refer to Figure 3C and Figure 3D The forming surface 231 of the upper die 23 has a shape corresponding to the forming surface 211 of the first lower die 21 and the forming surface 221 of the second lower die 22. A backing plate 24 is disposed between the upper dies 23. The upper dies 23 and the backing plate 24 are mounted, for example, in a punch press (not shown) to a sliding member that can be raised and lowered. The backing plate 24 is connected to the sliding member, for example, via a telescopic elastic member 26.

[0086] In the forming process, a mold 20 configured in this way is used to form the raw material M into a structural component 10. Figure 1 and Figure 2 The forming process includes a first step and a second step. In the first step, the raw material M is held by the upper mold 23 and the first lower mold 21, but not by the upper mold 23 and the second lower mold 22. In the second step, the raw material M is held by the upper mold 23 and the second lower mold 22, and the second flange 13 ( Figure 1 and Figure 2 Forming. The following is a detailed explanation of each process.

[0087] (Step 1)

[0088] like Figure 3C and Figure 3D As shown, at the start of the forming process, the upper die 23 and the backing plate 24 of the sliding component mounted on the punch press (not shown) are at the top dead center. In this state, the raw material M is placed on the top surface 211a of the first lower die 21. Then, the upper die 23 and the backing plate 24, together with the sliding component of the punch press, are lowered toward the lower dies 21 and 22, so that the upper die 23 and the backing plate 24 are close to the lower dies 21 and 22.

[0089] When the upper mold 23 and the backing plate 24 are brought close to the lower molds 21 and 22, such as Figure 3E As shown, the raw material M on the first lower die 21 is first pressed down using the pad 24. That is, the raw material M is clamped by the top surface 211a of the first lower die 21 and the pad 24. On the other hand, since the top surface 221a of the second lower die 22 is located slightly lower than the top surface 211a of the first lower die 21, the raw material M is not clamped between the top surface 221a of the second lower die 22 and the pad 24. At the moment when the raw material M is clamped by the first lower die 21 and the pad 24, there is a gap between the second lower die 22 and the raw material M.

[0090] After pressing the raw material M on the first lower die 21 with the pad 24, the sliding member of the punch press (not shown) is further lowered, causing the upper die 23 to move closer to the lower dies 21 and 22. While maintaining the state of pressing the raw material M on the first lower die 21 with the pad 24, the sliding member is lowered, causing the elastic member 26 connecting the pad 24 to the sliding member to contract, and the upper die 23 to descend relative to the pad 24. Thus, as... Figure 3F and Figure 3G As shown, the raw material M is clamped using the upper mold 23 and the first lower mold 21.

[0091] As described above, a step is pre-formed between the forming surface 211 of the first lower die 21 and the forming surface 221 of the second lower die 22. Therefore, when the upper die 23 is brought close to the lower dies 21 and 22, the first lower die 21 clamps the raw material M together with the upper die 23 before the second lower die 22. At the moment when the raw material M is clamped by the upper die 23 and the first lower die 21, the second lower die 22 does not clamp the raw material M. At this moment, there is a gap between the raw material M and the second lower die 22.

[0092] (Step 2)

[0093] As the upper die 23, which holds the raw material M together with the first lower die 21, moves closer to the second lower die 22, the upper die 23 presses down the first lower die 21, which is supported by the buffer mechanism 25. As a result, the step between the forming surface 211 of the first lower die 21 and the forming surface 221 of the second lower die 22 gradually decreases. (Refer to...) Figure 3H and Figure 3I When the upper die 23 reaches the lower stop point, the step between the first lower die 21 and the second lower die 22 disappears, and the raw material M is clamped (pressed) between the upper die 23 and the second lower die 22. In addition, the raw material M is clamped by the pad plate 24 and the second lower die 22.

[0094] When the upper die 23 reaches its lower stop point, the raw material M is formed into structural component 10. The portion of raw material M that is clamped between the pad 24 and the top surface 211a of the first lower die 21 becomes the top plate 111 of the component body 11. The portion of raw material M that is clamped between the upper die 23 and the side surface 211b of the first lower die 21 becomes the longitudinal wall 112 of the component body 11. The portion of raw material M that is clamped between the flange surface 211c of the upper die 23 and the first lower die 21 becomes the first flange 12. The portion of raw material M that is clamped between the pad 24 and the top surface 221a of the second lower die 22 mainly becomes the transverse flange portion 131 of the second flange 13. The portion of raw material M that is clamped between the upper die 23 and the side surface 221b of the second lower die 22 mainly becomes the longitudinal flange portion 132 of the second flange 13.

[0095] Reference Figure 4 In the structural member 10 after the forming process, the end edge 132a of each longitudinal flange portion 132 includes a deformation region R1. The deformation region R1 is located from the rounded node (on the longitudinal flange portion 132 side) of the connecting edge 161 connecting the transverse flange portion 131 and the longitudinal flange portion 132 to the rounded node (on the longitudinal flange portion 132 side) of the connecting edge 162 connecting the longitudinal flange portion 132 and the first flange 12.

[0096] The deformation region R1 has a thickness reduction rate T[%] that satisfies the following equation (1) over its entire range.

[0097] 0.9×Tmax≤T≤Tmax (1)

[0098] The Tmax[%] in equation (1) above is the maximum value of the thickness reduction rate T of the end edge 132a of each longitudinal flange 132. The thickness reduction rate T is the thickness reduction rate based on the thickness of the top plate 111 of the main body 11. When the thickness of the top plate 111 is set to t0 and the thickness of the end edge 132a of each longitudinal flange 132 is set to t1, the thickness reduction rate T[%] at that position can be obtained by (t0-t1) / t0×100. The thickness t0 of the top plate 111 is the thickness of the portion of the top plate 111 that does not substantially experience strain caused by forming. That is, the thickness t0 is substantially equal to the thickness of the raw material M before forming. The thickness t0 is measured in the central portion of the top plate 111 and is a portion with a flat shape. The plate thickness t0 is, for example, the plate thickness of the top plate 111 measured at a position 5.0 mm or more away from the end of the top plate 111 along its length. When the top plate 111 has a step, a raised portion, or a through hole, the plate thickness t0 is defined as the plate thickness of the top plate 111 measured not only from the end of the top plate 14 and the step, raised portion, or through hole along its length. The plate thickness t0 is, for example, 1.0 mm or more and 5.0 mm or less.

[0099] At the end edge 132a of each longitudinal flange portion 132, the length of the deformation region R1 is more than 2.0 times and less than 6.0 times the plate thickness t0 of the top plate 111.

[0100] [Effect]

[0101] In this embodiment, a first lower die 21 for forming the component body 11 and the first flange 12, and a second lower die 22 for forming the second flange 13 are used to form the structural component 10 from the raw material M. In the first forming process, the raw material M is clamped between the upper die 23 and the pad 24 and the first lower die 21, but not between the upper die 23 and the pad 24 and the second lower die 22. That is, before the forming process is complete, the portion of the raw material M that will become the second flange 13 is not constrained by the die 20. As a result, material flows into the portion of the raw material M that will become the second flange 13. The material mainly flows from the transverse flange portion 131 side to the longitudinal flange portion 132 side. Therefore, it is possible to suppress the occurrence of cracks at the end edges 132a of each longitudinal flange portion 132 and at the connection portion (corner portion) between the longitudinal flange portion 132 and the first flange 12.

[0102] In this embodiment, after the raw material M is pressed by the pad 24 in the first forming step, the raw material M is clamped by the upper mold 23 and the first lower mold 21. That is, the raw material M is formed by the upper mold 23 and the first lower mold 21 while the pad 24 is pressing the raw material M on the top surface 211a of the first lower mold 21. Furthermore, the forming of the second flange 13 in the second forming step is also performed while the raw material M is pressed by the pad 24. As a result, misalignment of the raw material M can be prevented during the forming of the structural member 10. Therefore, the structural member 10 can be formed with high precision.

[0103] In this embodiment, before the forming of the raw material M begins, a step is created between the forming surface 211 of the first lower die 21 and the forming surface 221 of the second lower die 22. The size S of this step is preferably set to be greater than or equal to the thickness of the raw material M and less than 5.0 times that thickness. This suppresses the formation of cracks and wrinkles in and around the second flange 13.

[0104] In the structural member 10 of this embodiment, each longitudinal flange portion 132 of the second flange 13 has a deformation region R1 at its end edge 132a that satisfies the above formula (1). The length of the deformation region R1 is more than 2.0 times and less than 6.0 times the plate thickness t0 of the top plate 111 of the main body 11. This means that the plate thickness distribution at the end edge 132a of each longitudinal flange portion 132 is uniform. In this case, when using the structural member 10, stress concentration at the plate thickness reduction portion at the end edge 132a of the longitudinal flange portion 132 is less likely to occur, and the occurrence of cracks at the end edge 132a of the longitudinal flange portion 132 can be suppressed. That is, the structural member 10 can have excellent durability.

[0105] In the manufacturing method of this embodiment, the forming process can be either a cold forming process or a hot forming process (hot stamping). When the structural member 10 is formed from the raw material M by hot stamping, the manufacturing method of this embodiment also includes a heating process for heating the raw material M. In the forming process, the raw material M, which has been heated to a temperature suitable for hot stamping in the heating process, is simply formed into the structural member 10 using the mold 20. The formed structural member 10 is deheated (quenched) by contacting the mold 20. Therefore, the structural member 10 can be made to have high strength.

[0106] Reference Figure 5When the raw material M is formed into the structural member 10 by hot stamping, the end edge 132a of each longitudinal flange portion 132 includes a low hardness region R2. The low hardness region R2 is located from the rounded node (on the longitudinal flange portion 132 side) of the connecting edge 161 connecting the transverse flange portion 131 and the longitudinal flange portion 132 to the rounded node (on the longitudinal flange portion 132 side) of the connecting edge 162 connecting the longitudinal flange portion 132 and the first flange 12.

[0107] The low-hardness region R2 is the region where the end edge 132a of each longitudinal flange 132 has a lower hardness compared to other parts. The low-hardness region R2 has a Vickers hardness HV[HV] satisfying Equation (2) over its entirety. Tmax [HV] is the Vickers hardness of the portion of the end edge 132a of each longitudinal flange 132 that has the maximum value Tmax of the aforementioned thickness reduction rate. At the end edge 132a of each longitudinal flange 132, the length of the low hardness region R2 is more than 5.0 times and less than 10.0 times the thickness t0 of the top plate 111.

[0108] HV Tmax -10.0≤HV≤HV Tmax +10.0 (2)

[0109] The Vickers hardness of the end edges 132a of each longitudinal flange portion 132 can be investigated as follows. First, a portion including the side edge 131b of the transverse flange portion 131, the connecting edge 161, and the end edges 132a of the longitudinal flange portion 132 is obtained from the structural member 10 by laser cutting. Then, the obtained portion is cut using an underwater cutting tool, and resin is filled and polished so that the end faces of the structural member 10 (the side edges 131b of the transverse flange portion 131, the connecting edge 161, and the end edges 132a of the longitudinal flange portion 132) are disposed on the surface to produce a test piece for hardness investigation. Then, using this test piece and a commercially available measuring instrument (HV-100 fully automatic Vickers hardness tester, manufactured by Mitutoyo Co., Ltd.), a Vickers hardness test is performed according to JIS Z 2244. For example, the Vickers hardness is measured by setting the test force to 294.2 N (the value of HV30) and the holding time of the test force to 15 s.

[0110] In the manufacturing method of this embodiment, when using steel sheet and setting the forming process to hot stamping, a low-hardness region R2 is generated at the end edge 132a of each longitudinal flange portion 132. The length of the low-hardness region R2 is more than 5.0 times and less than 10.0 times the thickness t0 of the top plate 111 of the component body 11. This means that the hardness distribution at the end edge 132a of each longitudinal flange portion 132 is uniform. In this case, stress concentration at the end edge 132a of each longitudinal flange portion 132 is less likely to occur when using the structural member 10, and the generation of cracks can be suppressed. That is, the structural member 10 can have excellent durability.

[0111] When the raw material M is formed into the structural member 10 by hot stamping, each longitudinal flange portion 132 is uniformly strengthened. For example, the average Vickers hardness of the surface of each longitudinal flange portion 132 is 300.0 Hv or more, and the standard deviation is 70.0 Hv or less. The average value and standard deviation of the Vickers hardness of the surface of the longitudinal flange portion 132 can be obtained as follows. That is, the surface of the longitudinal flange portion 132 obtained from the structural member 10 is used as the test surface, and a Vickers test as specified in JIS Z 2244 is performed on any 30 locations on the test surface at a distance from each other that is at least t0 of the thickness of the top plate 111. For example, the Vickers hardness of the surface of the longitudinal flange portion 132 is measured with a test force of 10 kgf (98.07 N) and a test force holding time of 10 s. Then, the average value and standard deviation of the Vickers hardness obtained in the Vickers test can be calculated.

[0112] According to the manufacturing method of this embodiment, when the raw material M is formed into the structural member 10, the occurrence of cracks and wrinkles in and around the second flange 13 can be suppressed. Therefore, high-strength steel sheet can be used as the material for the structural member 10. For example, the structural member 10 can be formed from a steel sheet with a tensile strength of 590 MPa or more. The tensile strength of the steel sheet can also be 780 MPa or more, or even 980 MPa or more. When the structural member 10 is manufactured by hot stamping, the tensile strength of the steel sheet can also be set to 1000 MPa or more, or 2000 MPa or more. By using a high-strength steel sheet in this way, the strength of the structural member 10 is improved, and thus the structural member 10 can be made thinner. This makes the structural member 10 lighter. In addition, when the forming process of the steel sheet is set to hot stamping, the tensile strength of the aforementioned low-hardness region R2 is also 1000 MPa or more.

[0113] In the structural member 10 of this embodiment, the corner portion 141 of the ridge portion 14 has a radius of curvature of, for example, 20.0 mm or less when viewed along a direction perpendicular to the top plate 111. Furthermore, the corner portion between the longitudinal flange portion 132 and the longitudinal wall 112 also has a radius of curvature of, for example, 20.0 mm or less. Therefore, the structural member 10 becomes a member with excellent space efficiency. More specifically, because the radius of curvature of the aforementioned corner portions is relatively small, 20.0 mm or less, the longitudinal flange portion 132 is compactly arranged at a right angle or near-right angle relative to the longitudinal wall 112, thus allowing the structural member 10 to be arranged in a narrow area. As a result, the constraints on the size of the structural member 10 in terms of its spatial arrangement with other components are reduced. Furthermore, when a load in the longitudinal direction is input to the structural member 10 arranged in a narrow area, the longitudinal flange portion 132 can bear the load with its surface, facilitating the transfer of load from the longitudinal flange portion 132 to the member body 11. Therefore, the structural member 10 can exhibit good load transfer capability in the longitudinal direction.

[0114] <Second Implementation>

[0115] Figure 6 This is a perspective view of the structural member 10A according to the second embodiment. The basic structure of the structural member 10A in this embodiment is the same as that of the structural member 10 in the first embodiment. However, the structural member 10A differs from the structural member 10 in the shape of the top plate 111 of the member body 11.

[0116] like Figure 6 As shown, in the top plate 111, the portion 111b near the second flange 13 bulges upwards compared to the other portions. Furthermore, the portion 111b near the second flange 13 in the top plate 111 bulges upwards compared to the transverse flange portion 131 of the second flange 13. The height of the longitudinal wall 112 varies accordingly with the shape of the top plate 111.

[0117] The structural member 10A of this embodiment can also be manufactured using the manufacturing method described in the first embodiment. When manufacturing the structural member 10A, a pre-forming process can be performed before the forming process to form an intermediate product from a sheet metal (blank). In the pre-forming process, for example, the intermediate product is formed from the sheet metal by deep drawing. The intermediate product may, for example, have a raised portion 111b with a top plate 111. The intermediate product may also have a gently sloping shape with a second flange 13. The pre-forming process is typically performed under cold working conditions. The forming process following the pre-forming process can be either a cold forming process or a hot forming process (hot stamping).

[0118] like Figure 7As shown, the structural member 10A may, for example, have a notch 17 at the connection portion of the longitudinal flange portion 132 of the second flange 13 and the first flange 12. The notch 17 in the structural member 10A may be provided only on one side in the width direction or on both sides in the width direction. The notch 17 can be pre-formed in the raw material before being formed into the structural member 10A. Although the figures are omitted, the structural member 10 of the first embodiment (… Figure 1 and Figure 2 It can also have a gap of 17.

[0119] However, to minimize stress concentration when using structural members 10 and 10A, the first flange 12 and the second flange 13 preferably do not have notches. That is, the end edge 12a of the first flange 12, the end edge 132a of the longitudinal flange portion 132, and the side edge 131b of the transverse flange portion 131 are preferably smoothly continuous. In this case, in addition to suppressing stress concentration, the load-bearing capacity of the structural members 10 and 10A during a vehicle collision can also be improved. Furthermore, when the structural members 10 and 10A are provided on the lower surface of the base plate, it is possible to prevent water from seeping into the structural members 10 and 10A through notches, thereby suppressing rusting of the structural members 10 and 10A.

[0120] The embodiments of this disclosure have been described above, but this disclosure is not limited to the above embodiments. Various changes can be made as long as they do not depart from its spirit.

[0121] For example, in the above embodiment, the second flange 13 is provided only at one end of the component body 11 along its length. However, the second flange 13 may also be provided at both ends of the component body 11 along its length. In this case, it is sufficient to prepare two second lower dies 22 for forming the second flange 13 when manufacturing the structural component and to arrange these two second lower dies 22 on both sides of the first lower die 21. The shape of the upper die 23 can be appropriately modified to correspond to the first lower die 21 and the two second lower dies 22.

[0122] When a structural member having a second flange 13 at both ends in the longitudinal direction of the component body 11 is formed, the structural member can also be divided into two after the forming process. Thus, two structural members 10 or structural members 10A having a second flange 13 at only one end in the longitudinal direction of the component body 11 can be manufactured in a single forming process.

[0123] In the above embodiment, the pad 24 has a generally T-shaped form in the top view of the mold 20. In other words, the pad 24 is configured to press the top plate 111 and the transverse flange 131 as a whole during the forming of the structural member 10. However, the shape of the pad 24 is not limited to this. The portion of the structural member 10 that is pressed by the pad 24 during forming can be appropriately modified.

[0124] In the above embodiment, the second lower mold 22 is supported by the buffer mechanism 25 so that it can be raised and lowered. However, the second lower mold 22 is not necessarily supported by the buffer mechanism 25.

[0125] In the above embodiment, before the forming process begins, the forming surface 211 of the first lower die 21 is positioned above the forming surface 221 of the second lower die 22, creating a step between the forming surfaces 211 and 221 of the first lower die 21 and the second lower die 22. However, the positional relationship between the first lower die 21 and the second lower die 22 is not particularly limited thereto. The lower dies 21 and 22 can be configured such that the first lower die 21 clamps the raw material M between itself and the upper die 23 before the second lower die 22. For example, in order to prevent the upper die 23 and the second lower die 22 from clamping the raw material M in the first forming process, the second lower die 22 can be separated from the first lower die 21 in the length direction of the mold 20 in the initial state.

[0126] In the above embodiment, with the die 20 mounted on the punch press, the upper die 23 is positioned above the lower dies 21 and 22. Furthermore, when forming the raw material M into structural components 10 and 10A, the upper die 23 is moved towards the lower dies 21 and 22, bringing them closer together. However, the upper die 23 can also be positioned below the lower dies 21 and 22, contrary to the above embodiment. Additionally, the upper die 23 can be moved towards the upper die 23, bringing it relatively closer to the lower dies 21 and 22.

[0127]

Example

[0128] The present disclosure is described in more detail below through embodiments. However, the present disclosure is not limited to the following embodiments.

[0129] To confirm the effectiveness of this disclosure, commercially available software (JSTAMP ver2.18, a compression molding simulation system manufactured by JSOL Co., Ltd., and LS-DYNA ver971 rev7.12, manufactured by ANSYS Co., Ltd.) was used to test the manufacturing method of the above-described embodiment for the structural member 10 ( Figure 1 and Figure 2 CAE analysis was performed on the compression molding process. The analysis conditions and results are presented in Tables 1-1, 1-2, 2-1, and 2-2.

[0130] Table 1-1

[0131]

[0132] Table 1-2

[0133] Table 1-2

[0134]

[0135] Table 2-1

[0136] Table 2-1

[0137]

[0138] Table 2-2

[0139] Table 2-2

[0140]

[0141] In the embodiments, comparative examples, and reference examples listed in the table above, the forming method is set to hot stamping when the raw material is hot-stamping steel sheet or aluminum alloy sheet, and the forming method is set to cold forming in other cases. Examples 1-31, each comparative example, and each reference example are examples where the forming process is performed while pressing the portion of the metal sheet used as raw material, which forms the top plate 111 and the transverse flange 131, almost entirely using the pad 24. On the other hand, Examples 32-48 are examples where the forming process is performed while pressing the portion of the metal sheet used as raw material, which forms the top plate 111 and the transverse flange 131, partially using the pad 24. That is, in Examples 32-48, the forming member 10 is formed using a pad 24 with a different shape than that used in Examples 1-31.

[0142] In each table, the ridge line R is the radius of curvature in the transverse sectional view of the part of the ridge line portion 14 that connects the transverse flange portion 131 and the longitudinal flange portion 132. The corner R is the radius of curvature of the corner portion between the longitudinal flange portion 132 and the longitudinal wall 112. The corner R is approximately equal to the radius of curvature in the top view of the corner portion 141 of the ridge line portion 14, which is the part extending from the top plate 111 to the transverse flange portion 131. Both the ridge line R and the corner R are radii of curvature measured from the inside (lower mold 21, 22 side) of the structural member 10. The flange length is the extension of the flanges 12, 13 from the main body 11 of the member, and is set as the distance from the rounded corner node (outer side in the width direction) of the corner portion 141 of the ridge line portion 14 to the end of the structural member 10 in the width direction.

[0143] As shown in Table 1, in each embodiment, the size S of the step between the first lower mold 21 and the second lower mold 22 is... Figure 3D The thickness t of the metal sheet used as raw material is ensured to be at least 1.0 times. Therefore, in each embodiment, after the raw material is reliably clamped using the upper die 23 and the first lower die 21, the raw material is clamped using the upper die 23 and the second lower die 22, thereby forming the second flange 13. As a result, in each embodiment, the flow of material at the second flange 13 is facilitated, and no cracks are generated in the second flange 13.

[0144] In each comparative example, the size S of the step between the first lower die 21 and the second lower die 22 is less than 1.0 times the thickness t of the raw material. Therefore, in each comparative example, the raw material is clamped using the upper die 23 and the second lower die 22 before the clamping of the raw material using the upper die 23 and the first lower die 21 is completed. As a result, material flow at the second flange 13 is difficult to achieve in each comparative example, and cracks are generated at the second flange 13.

[0145] Therefore, if a step is pre-formed between the first lower die 21 and the second lower die 22, as long as the size S of the step is set to be greater than or equal to the thickness of the raw material, cracks can be prevented from forming at the second flange 13 during the forming process. This effect can be confirmed not only in the forming of steel sheets, but also in hot stamping using aluminum alloy sheets.

[0146] In Examples 7, 22, and 30, the size S of the step between the first lower die 21 and the second lower die 22 is greater than 5.0 times the thickness t of the raw material. In Examples 7, 22, and 30, wrinkles are generated at or near the second flange 13. On the other hand, in other embodiments where the size S of the step is less than or equal to 5.0 times the thickness t of the raw material, no wrinkles are generated. Therefore, when a step is pre-generated between the first lower die 21 and the second lower die 22, as long as the size S of the step is set to less than or equal to 5.0 times the thickness t of the raw material, the generation of wrinkles at or near the second flange 13 can be suppressed.

[0147] Furthermore, cracks are prone to occur in the second flange 13 when there is no notch in the flange portion, the flange length is relatively small, or the corner radius (R) is relatively small. For example, when the flange length is 0.0 mm or more and 25.0 mm or less, and the corner radius (R) is 20.0 mm or less, deformation tends to concentrate near the rounded corner node of the connecting flange 161 at the end edge 132a of the longitudinal flange portion 132. For example, when manufacturing the structural member 10 using a conventional process that simultaneously forms the main body 11 and the first flange 12 and the second flange 13 using a steel plate with a tensile strength of 590 MPa or more, cracks occur in the second flange 13. Therefore, as in Reference Examples 1 and 4, it is necessary to address cracks by making the flange portion less than specified (represented by a negative flange length in Table 2-1). If the flange portion is less than specified as described above, stress concentration is likely to occur, and the performance of the component will deteriorate, which is undesirable. On the other hand, in cases where the flange length is 50.0 mm or more, as in Reference Example 3, or where the corner radius (R) is greater than 20.0 mm, as in Reference Example 5, cracks in the second flange 13 are less likely to occur even when the structural member 10 is formed using conventional processes. However, from the viewpoint of space constraints and increased component weight, such a shape is undesirable. Furthermore, even if the flange length is shortened by cutting the flange portion after forming, the yield rate deteriorates, leading to increased cutting costs, which is also undesirable.

[0148] Referring to the tables, the conditions for Reference Example 1 are the same as those for Comparative Example 1, except for the flange length. In Comparative Example 1, the flange length is positive and no notch is formed in the flange portion; in Reference Example 1, the flange length is -20.0 mm and a notch is added to the flange portion. The conditions for Reference Example 4 are the same as those for Comparative Example 6, except for the flange length. In Comparative Example 6, the flange length is positive and no notch is formed in the flange portion; in Reference Example 4, the flange length is -15.0 mm and a notch is added to the flange portion. Therefore, unlike Comparative Examples 1 and 6, no crack is generated in the second flange 13 in Reference Examples 1 and 4.

[0149] The conditions for Reference Example 5 are the same as those for Comparative Example 2, except for the corner radius R. The corner radius R in Reference Example 5 is 40.0 mm, which is significantly larger than the corner radius R of Comparative Example 2: 15.0 mm. Therefore, unlike Comparative Example 2, no crack was generated in the second flange 13 in Reference Example 5.

[0150] The manufacturing method disclosed herein suppresses cracks in the second flange 13. Therefore, the manufacturing method of this disclosure is suitable for manufacturing structural members 10 that are prone to cracking in the second flange 13, i.e., structural members 10 with a flange length of 25.0 mm or less, or a radius of curvature of the corner portion 141 of the ridge portion 14, or an angle R between the longitudinal flange portion 132 and the longitudinal wall 112 of 20.0 mm or less. According to the manufacturing method of this disclosure, even if the radius of curvature of the corner portion 141 of the ridge portion 14, or the angle R between the longitudinal flange portion 132 and the longitudinal wall 112 is 20.0 mm or less, cracks in the second flange 13 can be suppressed. Furthermore, even if the flange length is 25.0 mm or less, cracks in the second flange 13 can be suppressed. Therefore, it is not necessary to suppress cracks during forming by pre-increasing the flange length, and it is not necessary to trim the flanges 12 and 13 after forming. That is, an intermediate trimming process for the flanges 12 and 13 is not required.

[0151] Figure 8 This is a graph showing the relationship between the distance from the rounded corner node (on the longitudinal flange 132 side) of the connecting edge 161 connecting the transverse flange 131 and the longitudinal flange 132 to the plate thickness reduction rate T, specifically for the end edge 132a of the longitudinal flange 132. Figure 8 As shown, in Examples 4 and 6, the change in the plate thickness reduction rate T is gradual compared to Comparative Example 1. That is, in Examples 4 and 6, the plate thickness distribution of the end edge 132a of the longitudinal flange portion 132 is more uniform compared to Comparative Example 1.

[0152] like Figure 8 As shown in Tables 1-2, in Examples 4 and 6, the length of the deformation region R1 of the end edge 132a of the longitudinal flange 132, that is, the region satisfying the above formula (1), is longer than that of Comparative Example 1. In Example 4, the length of the deformation region R1 is 4.0 mm, which is 2.0 times the thickness t of the raw material: 2.0 mm. In Example 6, the length of the deformation region R1 is 6.0 mm, which is 3.0 times the thickness t of the raw material: 2.0 mm. On the other hand, in Comparative Example 1, the length of the deformation region R1 is 2.0 mm, which is 1.0 times the thickness t of the raw material: 2.0 mm.

[0153] As shown in Tables 1-2, in embodiments other than Examples 4 and 6, the length of the deformed region R1 is at least 2.0 times the thickness t of the raw material. In each embodiment, the length of the deformed region R1 is less than 6.0 times the thickness t of the raw material. On the other hand, in each comparative example, the length of the deformed region R1 is less than 2.0 times the thickness t of the raw material. Based on this result, if the structural member 10 is manufactured by the manufacturing method of this disclosure, the length of the deformed region R1 is at least 2.0 times and less than 6.0 times the thickness t of the raw material (the thickness t0 of the top plate 111), which means that the thickness distribution of the second flange 13 is uniform.

[0154] Under the conditions of Examples 20, 19, and Comparative Example 5, when the structural member 10 is formed by hot stamping, a low-hardness region R2 satisfying the above formula (2) is generated at the end edge 132a of the longitudinal flange portion 132. In Example 20, the length of the low-hardness region R2 is 10.0 mm, which is 5.0 times the thickness t of the raw material. In Example 19, the length of the low-hardness region R2 is 20.0 mm, which is 10.0 times the thickness t of the raw material. On the other hand, in Comparative Example 5, the length of the low-hardness region R2 is 8.0 mm, which is 4.0 times the thickness t of the raw material. According to this result, if the structural member 10 is formed by hot stamping in the manufacturing method of this disclosure, the length of the low-hardness region R2 is more than 5.0 times and less than 10.0 times the thickness t of the raw material, and it can be said that the hardness distribution of the second flange 13 is uniform.

[0155] Explanation of reference numerals in the attached figures

[0156] 10, 10A, Structural components; 11, Main body of the component; 111, Top plate; 111a, Side part; 112, Longitudinal wall; 12, First flange; 13, Second flange; 131, Transverse flange part; 131a, End; 132, Longitudinal flange part; 132a, End edge; 14, Ridge part; 141, Corner part; 20, Mold; 21, First lower mold; 211, Forming surface; 22, Second lower mold; 221, Forming surface; 23, Upper mold; 24, Pad plate; 25, Buffer mechanism; M, Raw material.

Claims

1. A method for manufacturing a structural component, specifically a method for manufacturing a structural component for automobiles, wherein, The manufacturing method includes: The preparation process involves preparing raw materials made of metal plates; and In the forming process, a mold is used to shape the raw material into the structural component. The structural components include: The main body of the component includes a top plate and longitudinal walls. The top plate has two sides extending along the length direction of the structural component and opposite to each other in the width direction of the structural component. The longitudinal walls are respectively connected to the sides via ridge portions. A first flange, which connects to the longitudinal wall on the opposite side of the top plate, extends from the longitudinal wall along the width direction; and A second flange is continuously disposed at the end of the main body of the component along the length direction. The second flange includes a transverse flange portion and a longitudinal flange portion. The transverse flange portion extends from the top plate along the width direction. The longitudinal flange portion is connected to the end of the transverse flange portion on the side of the main body of the component via the ridge portion and extends from the transverse flange portion toward the first flange. The mold comprises: upper mold; A first lower die, configured opposite to the upper die, is used to form the component body and the first flange; and The second lower die, disposed next to the first lower die and opposite to the upper die, is used to form the second flange. The forming process includes: In the first step, the raw material is held by the upper mold and the first lower mold, but not by the upper mold and the second lower mold; and The second step, after the first step, involves using the upper mold and the second lower mold to clamp the raw material and form the second flange.

2. The manufacturing method according to claim 1, wherein, The mold also includes a backing plate. In the first step, after pressing the raw material with the pad, the raw material is clamped by the upper mold and the first lower mold.

3. The manufacturing method according to claim 1 or 2, wherein, A step is pre-formed between the forming surfaces of the first lower die and the second lower die, so that in the first step, when the upper die is brought closer to the first and second lower dies, the first lower die clamps the raw material between itself and the upper die before the second lower die. In the second step, by bringing the upper die, which is holding the raw material together with the first lower die, closer to the second lower die, the step disappears, and the second lower die holds the raw material between itself and the upper die. The size of the step before the start of the first process is greater than or equal to the thickness of the raw material and less than 5.0 times the thickness of the raw material.

4. The manufacturing method according to claim 3, wherein, The first lower mold is configured to be able to rise and fall using a buffer mechanism. In the forming process, the upper mold is lowered toward the first lower mold and the second lower mold.

5. The manufacturing method according to claim 1, wherein, The manufacturing method also includes a pre-forming process for shaping intermediate molded products from metal sheets. In the forming process, the intermediate molded product is used as the raw material to form the structural component.

6. The manufacturing method according to claim 1, wherein, The manufacturing method also includes a heating step of heating the raw materials. In the forming process, the raw material heated by the heating process is formed into the structural component.

7. The manufacturing method according to claim 1, wherein, The metal plate is a steel plate with a tensile strength of 590 MPa or higher.

8. A structural component, which is a structural component for automobiles, wherein, The structural component includes: The main body of the component includes a top plate and longitudinal walls. The top plate has two sides extending along the length direction of the structural component and opposite to each other in the width direction of the structural component. The longitudinal walls are respectively connected to the sides via ridge portions. The first flange is connected to the longitudinal wall on the opposite side of the top plate and extends from the longitudinal wall along the width direction; as well as A second flange is continuously disposed at the end of the main body of the component along the length direction. The second flange includes a transverse flange portion and a longitudinal flange portion. The transverse flange portion extends from the top plate along the width direction. The longitudinal flange portion is connected to the end of the transverse flange portion on the side of the main body of the component via the ridge portion and extends from the transverse flange portion toward the first flange. When the thickness reduction rate based on the thickness of the top plate is set to T%, the length of the region at the end edge of the longitudinal flange having a thickness reduction rate T satisfying the following formula (1) is more than 2.0 times and less than 6.0 times the thickness of the top plate. 0.9×Tmax≤T≤Tmax (1) Wherein, Tmax% is the maximum value of the plate thickness reduction rate of the end edge of the longitudinal flange portion.

9. The structural member according to claim 8, wherein, The length of the region at the end edge of the longitudinal flange having a Vickers hardness HV satisfying the following formula (2) is more than 5.0 times and less than 10.0 times the thickness of the plate. HW Tmax -10.0≤HV≤HV Tmax +10.0 (2) Among them, HV Tmax It is the Vickers hardness of the portion of the end edge of the longitudinal flange that has the maximum value Tmax of the plate thickness reduction rate.

10. The structural member according to claim 8, wherein, The average Vickers hardness measured at 30 locations on the surface of the longitudinal flange, where the distance between them is greater than or equal to the thickness of the top plate, is 300.0 Hv or more, and the standard deviation of the Vickers hardness is 70.0 Hv or less.

11. The structural member according to claim 8, wherein, The structural component is formed from steel plates with a tensile strength of over 590 MPa.

12. The structural member according to any one of claims 8 to 11, wherein, The ridge portion includes a corner portion that extends from the top plate toward the transverse flange portion and has a radius of curvature of less than 20.0 mm in the top view of the structural member.

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