Press molding method and method for manufacturing press-molded article

Abstract

A press molding method and a method for manufacturing a press-molded article according to the present invention press-mold a press-molded article (210) into a target shape, the press-molded article (210) having a top plate section (211), a vertical wall section (215), and a flange section (219), and having a concave curved portion (221) curved in a concave shape in plan view. The press-molding method and the method for manufacturing the press-molded article comprise: a step (S1) for producing a blank (100) provided with a concave shape (101) corresponding to the bending of a concave bent portion (221); a step (S3) for press-molding the produced blank (100) into an intermediate press-molded article (110) having a top plate section (111), a vertical wall section (115), and a flange section (119), the intermediate press-molded article (110) being provided with a concave curved section (121) that is curved in a concave shape in plan view, and having a cutout section (125) provided in a portion of the flange section (119) and the vertical wall section (115) at a curved center section (121a) of the concave curved section (121); and a step (S5) in which the press-molded article (110) having the intermediate shape is press-molded into the target shape.

Description

Technical Field

[0001] The present invention relates to a stamping method and a method for manufacturing a stamped part, wherein a stamped part is stamped into a target shape, wherein the stamped part has a top plate portion and a longitudinal wall portion continuous from the top plate portion, and has a concave curved portion that is concavely curved when viewed from above. Background Art

[0002] Automobiles or home appliances are composed of multiple stamping parts, which are manufactured by stamping metal sheets, i.e. blanks. In recent years, high-strength metal sheets such as high-tensile steel sheets or aluminum alloy sheets with a tensile strength of 590 MPa or above are used for stamping. However, such metal sheets have low ductility and plastic strain ratio (Lankford value), so there is a problem of easy cracking during stamping.

[0003] As an example of the shape of a stamped part that is prone to cracking, there is a stamped part that has a top plate portion and a longitudinal wall portion that is continuous from the top plate portion via a ridge portion, and has a concave curved portion in which the top plate portion, the ridge portion, and the longitudinal wall portion are concavely curved when viewed from above. If such a stamped part is stamped from a metal plate, i.e., a blank, cracks (stretch flange cracks) are easily generated during the stamping process due to tensile deformation along the bending direction of the blank, which causes poor forming.

[0004] Therefore, currently, a technology for suppressing the occurrence of stretch flange cracks during the press forming process of a press-formed product having a concave curved portion in a plan view has been proposed.

[0005] For example, the following technology is disclosed in Patent Document 1: a sheet metal forming part includes a top plate part having a concave outer peripheral edge part and a flange part (equivalent to the longitudinal wall part of the present application) that is continuously bent from the concave outer peripheral edge part, and when the sheet metal forming part is subjected to stamping, the generation of tensile flange cracks in the flange part is suppressed. In this technology, first, a flange part consisting of a large curvature part having a large curvature and a small curvature part having a small curvature sandwiched between the large curvature parts is formed on a blank to obtain a preform. Here, the curvature of the large curvature part is greater than the curvature part of the flange part constituting the sheet metal forming part, and the curvature of the small curvature part is less than the curvature part of the flange part constituting the sheet metal forming part. In addition, the line length of the flange part of the preform when viewed from above is shorter than the line length of the flange part of the sheet metal forming part when viewed from above. Moreover, by pressing the preform obtained in this way into a target shape again, cracks in the flange part can be suppressed.

[0006] In addition, Patent Document 2 discloses the following technology: a component has a top plate portion and a longitudinal wall portion, the longitudinal wall portion is connected to the top plate portion via a curved portion having an arc-shaped curved portion, and has a flange portion on the side opposite to the curved portion, and the component consisting of the top plate portion, the longitudinal wall portion and the flange portion is formed using a raw material metal plate. In this technology, while at least a portion of the portion of the raw material metal plate corresponding to the top plate portion is pressurized using a gasket, the end of the portion of the raw material metal plate corresponding to the lower side of the L-shape is slid on the portion of the die corresponding to the top plate portion, and the longitudinal wall portion and the flange portion are formed. As a result, cracks in the flange portion can be suppressed.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: (Japanese) Patent Publication No. 2021-159951

[0010] Patent Document 2: (Japan) Patent No. 5168429 Summary of the invention

[0011] Technical problem to be solved by the invention

[0012] However, according to the technology disclosed in Patent Document 1, if a stamped part having a top plate portion and a longitudinal wall portion continuous from the top plate portion via a ridge portion and having a concave curved portion that is concavely curved when viewed from above is stamped, there is a situation where tensile flange cracks are easily generated. In particular, if the radius of curvature of the concave curved portion is small (the curvature is large), the line length of the longitudinal wall portion of the intermediate shape stamped part (the flange portion of the preform of Patent Document 1) is too short, and the tensile strain concentrated in the longitudinal wall portion of the concave curved portion cannot be fully reduced. As a result, the end of the longitudinal wall portion at the concave curved portion is subjected to a large tensile deformation along the bending direction and is formed, so there is a problem of tensile strain concentration, which is easy to generate tensile flange cracks.

[0013] In addition, in the technology disclosed in Patent Document 2, the end of the portion of the raw material metal plate corresponding to the lower side of the L-shape is slid on the portion of the die corresponding to the top plate portion while the vertical wall portion and the flange portion are formed, so the raw material metal plate moves during the press forming. As a result, there is a problem that the shape of the press-formed component changes greatly and the dimensional accuracy fluctuates, and the effect of suppressing tensile flange cracks also changes.

[0014] The present invention is made to solve the technical problems mentioned above, and its purpose is to provide a stamping method and a method for manufacturing a stamped part, which can fully suppress the tensile flange cracks of a stamped part having a top plate portion and a longitudinal wall portion and having a concave curved portion that is concavely curved when viewed from above.

[0015] Technical solutions for solving technical problems

[0016] In order to solve the above technical problems and achieve the purpose, (1) the stamping method of the present invention stamps a stamped part into a target shape, the stamped part has a top plate portion, a longitudinal wall portion continuous from the top plate portion, and a flange portion continuous from the longitudinal wall portion, and has a concave curved portion that is concavely curved when viewed from above, and is characterized in that it includes: a blank making step of making a blank having a concave shape corresponding to the curvature of the concave curved portion of the target shape; an intermediate shape forming step of stamping the made blank into a stamped part of an intermediate shape, the stamped part of the intermediate shape A method of forming a molded product comprising: comprising: providing a top plate portion, a longitudinal wall portion continuous from the top plate portion, and a flange portion continuous from the longitudinal wall portion, and having a concave curved portion which is concavely curved when viewed from above, wherein a notch portion is provided at the flange portion and a part of the longitudinal wall portion, or at the flange portion, the longitudinal wall portion, and a part of the top plate portion at the curved center of the concave curved portion; a target shape forming step of stamping the intermediate shape stamped part into the target shape; in the intermediate shape forming step, stamping is performed in such a manner that a part of the concave shape provided on the blank becomes the notch portion.

[0017] (2) The stamping method of the present invention stamps a stamped part into a target shape, wherein the stamped part has a top plate portion and a longitudinal wall portion continuous from the top plate portion, and has a concave curved portion that is concavely curved when viewed from above, and is characterized in that it includes: a blank making step of making a blank having a concave shape corresponding to the curvature of the concave curved portion; an intermediate shape forming step of stamping the made blank into a stamped part of an intermediate shape, wherein the stamped part of the intermediate shape has a top plate portion and a longitudinal wall portion continuous from the top plate portion, and has a concave curved portion that is concavely curved when viewed from above, and a notch portion is provided in the longitudinal wall portion and a part of the top plate portion at the central part of the curvature of the concave curved portion; a target shape forming step of stamping the stamped part of the intermediate shape into the target shape; in the intermediate shape forming step, the stamping is performed in such a way that a part of the concave shape provided in the blank becomes the notch portion.

[0018] (3) The stamping forming method of the present invention, in the invention of (1) or (2) above, is characterized in that in the intermediate shape forming step, the curvature radius R of the curved end portion of the concave curved portion of the intermediate shape is E The curvature radius R0 of the concave curved portion is greater than the target shape.

[0019] The manufacturing method of the stamped part of the present invention manufactures the stamped part into a target shape, wherein the stamped part has a top plate portion, a longitudinal wall portion continuous from the top plate portion, and a flange portion continuous from the longitudinal wall portion, and has a concave curved portion that is concavely curved when viewed from above, and is characterized in that it includes: a blank manufacturing step of manufacturing a blank having a concave shape corresponding to the curvature of the concave curved portion of the target shape; an intermediate shape forming step of stamping the manufactured blank into a stamped part of an intermediate shape, wherein the stamped part of the intermediate shape has a top plate portion, a longitudinal wall portion continuous from the longitudinal wall portion, and a flange portion continuous from the longitudinal wall portion, and has a concave curved portion that is concavely curved when viewed from above. A longitudinal wall portion continuous with the top plate portion and a flange portion continuous from the longitudinal wall portion, and having a concave curved portion that is concavely curved when viewed from above, a notch portion is provided at the flange portion and a portion of the longitudinal wall portion, or at the flange portion, the longitudinal wall portion and a portion of the top plate portion at the curved center of the concave curved portion; a target shape forming step of stamping the intermediate shape stamped part into the target shape; in the intermediate shape forming step, stamping is performed in such a manner that a portion of the concave shape provided on the blank becomes the notch portion.

[0020] The manufacturing method of the stamped part of the present invention manufactures the stamped part into a target shape, the stamped part has a top plate portion and a longitudinal wall portion continuous from the top plate portion, and has a concave curved portion that is concavely curved when viewed from above, and is characterized in that it includes: a blank making step, making a blank with a concave shape corresponding to the curvature of the concave curved portion; an intermediate shape forming step, stamping the made blank into a stamped part of an intermediate shape, the stamped part of the intermediate shape has a top plate portion and a longitudinal wall portion continuous from the top plate portion, and has a concave curved portion that is concavely curved when viewed from above, and a notch portion is provided in the longitudinal wall portion and a part of the top plate portion at the central part of the curvature of the concave curved portion; a target shape forming step, stamping the stamped part of the intermediate shape into the target shape; in the intermediate shape forming step, the stamping is performed in a manner that a part of the concave shape set in the blank becomes the notch portion.

[0021] The manufacturing method of the stamped part of the present invention is characterized in that, in the invention of (4) or (5) above, in the intermediate shape forming step, the curvature radius R of the curved end portion of the concave curved portion of the intermediate shape is E The press forming is performed so that the curvature radius R0 of the concave curved portion is larger than the target shape.

[0022] Effects of the Invention

[0023] In the stamping method and the method for manufacturing a stamped part of the present invention, a blank having a concave shape corresponding to the bend of a concave curved portion is produced, and the produced blank is stamped into a stamped part of an intermediate shape having a notch portion in the central portion of the bend of the concave curved portion. At this time, stamping is performed so that the concave shape provided in the blank becomes the notch portion. Thus, the tensile stress acting near the notch portion can be reduced, and the tensile stress can be dispersed on both end sides of the bend of the concave curved portion. As a result, when the stamped part of the intermediate shape is stamped into the target shape, tensile flange cracks can be fully suppressed, stable stamping without cracks can be performed, and improved productivity and improved yield can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flowchart showing the process flow in the press forming method according to the embodiment.

[0025] Figure 2 The figures are perspective views showing examples of press-formed products to be formed in the present embodiment ((a) a Z-shaped cross-sectional shape, (b) a U-shaped cross-sectional shape, and (c) a hat-shaped cross-sectional shape).

[0026] Figure 3 This is a diagram for explaining a conventional technique for press-forming a press-formed product having a concave curved portion in a plan view in one process.

[0027] Figure 4 This is a contour diagram showing an example of the results of the thickness reduction rate of a press-formed product that has been press-formed in one process according to the conventional technology.

[0028] Figure 5 The diagrams are for explaining a preform (a press-formed product of an intermediate shape) press-formed in a method of comparative conditions.

[0029] Figure 6 This is a contour diagram showing an example of the results of the plate thickness reduction rate of each of the preform (stamped product of an intermediate shape) and the sheet metal formed product (stamped product of a target shape) which were stamped by the method of comparing the conditions.

[0030] Figure 7 The figures are for explaining a stamped product having an intermediate shape and a target shape which is stamped by the stamping method according to the embodiment.

[0031] Figure 8 The figures are for explaining the process of stamping a stamped part having a concave curved portion when viewed from above by a stamping method according to an embodiment ((a) intermediate shape forming process, (b) target shape forming process).

[0032] Fig. 9 This is a contour diagram showing an example of the results of the plate thickness reduction rate of the stamped product of the intermediate shape and the target shape which are stamped by the stamping method according to the embodiment.

[0033] Fig.10 The figures are for explaining the preferred positions of the ridgeline portions of the concavely curved portions of the intermediate-shaped stamped product to be stamped in the stamping method of the present invention.

[0034] Fig.11 The figures are for explaining a specific example of a notch portion at a concavely curved portion of a press-formed product having an intermediate shape press-formed in the press-forming method of the present invention.

[0035] Fig.12 It is a diagram showing a target shape of a press-formed product having a hat-shaped cross-section as a forming target in the embodiment.

[0036] Fig.13 The figures are diagrams showing the process of stamping an intermediate shape and a target shape of a stamped part respectively by the method of the present invention in an embodiment ((a) intermediate shape forming process, (b) target shape forming process).

[0037] Fig.14 This is a diagram for explaining a conventional example in which a press-formed product having a target shape is press-formed in one step in the embodiment.

[0038] Fig.15 This is a contour diagram of the plate thickness reduction rate obtained in the example for the press-formed product of the target shape in the conventional example.

[0039] Fig.16 The following is a contour diagram of the plate thickness reduction rate obtained for the stamped parts of the intermediate shape and the target shape in the comparative example in the embodiment ((a) stamped part of the intermediate shape, (b) stamped part of the target shape).

[0040] Fig.17 The following is a contour diagram of the plate thickness reduction rate obtained for the stamped parts of the intermediate shape and the target shape in Invention Example 1 in the embodiment ((a) stamped part of the intermediate shape, (b) stamped part of the target shape).

[0041] Fig.18 The following is a contour diagram of the plate thickness reduction rate obtained for the stamped parts of the intermediate shape and the target shape in Invention Example 2 in the embodiment ((a) stamped part of the intermediate shape, (b) stamped part of the target shape). DETAILED DESCRIPTION

[0042] Hereinafter, embodiments of the press forming method and the method for producing a press formed product of the present invention will be described. It should be noted that the present invention is not limited to the embodiments.

[0043] Before describing the press forming method and the method for producing a press-formed product according to the embodiment of the present invention, the press-formed product to be formed in the present invention and the process of obtaining the present invention will be described.

[0044] <Stamping parts>

[0045] Figure 2 It is a perspective view showing a specific example of a press-formed product to be formed in the present invention.

[0046] Figure 2 The stamped part 210 of (a) is an example of a stamped part having a Z-shaped cross-sectional shape, including a top plate 211, a vertical wall 215 continuous from the top plate 211 via a ridge 213, and a flange 219 continuous from the vertical wall 215 via a die shoulder 217. The stamped part 210 includes: a concave curved portion 221, in which the ridge 213, the vertical wall 215, the die shoulder 217, and the flange 219 are concavely curved when viewed from above; and a straight portion 223, which extends straightly from both ends of the curve of the concave curved portion 221.

[0047] in addition, Figure 2 The stamped part 230 of (b) is an example of a stamped part having a U-shaped cross-sectional shape having a top plate portion 231 and a longitudinal wall portion 235 continuous from both ends thereof via a ridge portion 233. The stamped part 230 includes: a concave curved portion 241, in which the ridge portion 233a and the longitudinal wall portion 235a are curved concavely when viewed from above; and a straight portion 243, which extends straightly from both ends of the curved portion 241.

[0048] in addition, Figure 2 The stamped part 250 of (c) is an example of a stamped part having a hat-shaped cross-sectional shape having a top plate portion 251, a longitudinal wall portion 255 continuous from both ends thereof via a ridge portion 253, and a flange portion 259 continuous from the longitudinal wall portion 255 via a die shoulder portion 257. The stamped part 250 includes: a concave curved portion 261, in which the ridge portion 253a, the longitudinal wall portion 255a, the die shoulder portion 257a, and the flange portion 259a are concavely curved when viewed from above; and a straight portion 263, which extends straightly from both ends of the curve of the concave curved portion 261.

[0049] Thus, in the present invention, the stamped parts as the forming object are as long as Figure 2As shown in the example, it has a top plate portion and a longitudinal wall portion continuous from the top plate portion via a ridge portion and a concave curved portion that is concavely curved when viewed from above. Therefore, the stamped part as a forming object is not limited to other specific shapes, such as the cross-sectional shape, the curvature radius of the concave curved portion, the length of the straight portion, etc.

[0050] Below, we will Figure 2 The following description will take as an example a case where a stamped part 210 having a Z-shaped cross-sectional shape shown in (a) is stamped into a target shape.

[0051] <How the present invention was obtained>

[0052] In the past, for Figure 2 For a stamped part 210 having a Z-shaped cross-sectional shape with a concave curved portion 221 when viewed from above as shown in (a), Figure 3 As shown, the die 21 having the concave die 23, the convex die 25 and the gasket 27 is used to press-form the target shape in one process. At this time, the concave curved portion 221 formed by the concave curved portion forming portion 23a on the concave die side and the concave curved portion forming portion 25a on the convex die side becomes a stretch flange.

[0053] For a stamped part 210 that is stamped into a target shape in one process, the inventors of the present application have focused on using Figure 3 The process of stamping by the die 21 shown is subjected to finite element analysis (FEM analysis) to find the thickness reduction rate of the stamped part 210 after stamping. Here, the thickness reduction rate refers to the value obtained by subtracting the thickness of each part after stamping from the thickness of the metal sheet, i.e., the blank 100 before stamping, and then dividing it by the thickness of the blank 100.

[0054] like Figure 4 As shown, it can be seen that in the existing stamped part 210 that is stamped in one process, the maximum plate thickness reduction rate of the end of the flange portion 219 at the concave bending portion 221 is 21.5%, and cracks are easily generated due to stretch flange forming.

[0055] In order to suppress the occurrence of cracks caused by such stretch flange forming, Patent Document 1 proposes a method of performing press forming in two steps, namely, a flange raising step (pre-forming step) and a re-pressing step.

[0056] The method of Patent Document 1 firstly comprises: Figure 5 As shown, a stamped part 170 of an intermediate shape as a preform is obtained. Then, in the next re-pressing step, the preform is re-pressed into a sheet metal formed part, that is, a stamped part 210 of a target shape.

[0057] In the method of Patent Document 1, the intermediate-shaped stamped part 170 has a large curvature (radius of curvature R E The two curved end portions 181b with a small curvature (radius of curvature R C Large) curved central portion 181a.

[0058] Here, as the intermediate shape of the stamped part 170, consider using Figure 5 The condition that the ridge length of the curve of the concave curve portion 181 shown (curve efgh) is shorter than the ridge length of the curve of the concave curve portion 221 of the target shape stamped part 210 (curve pq). This condition satisfies the condition disclosed in Patent Document 1 that "the line length of the flange portion of the preform when viewed from above is shorter than the line length of the flange portion of the sheet metal formed part when viewed from above." At this time, the ridge length of the curve of the concave curve portion 181 of the intermediate shape stamped part 170 (curve efgh) refers to the length from the starting point e to the end point h along the bending direction of the ridge portion 173. In addition, the ridge length of the curve of the concave curve portion 221 of the target shape stamped part 210 (curve pq) refers to the length from the starting point p to the end point q along the bending direction of the ridge portion 213 shown by the dotted line.

[0059] Then, the inventor of the present application Figure 5 Finite element analysis was performed in each process under the conditions shown, and the thickness reduction rate of the stamped part 170 of the intermediate shape and the stamped part 210 of the target shape were obtained.

[0060] like Figure 6 As shown, based on Figure 5 The maximum thickness reduction rate of the stamped part 170 of the intermediate shape under the conditions shown is 24.4%. Furthermore, the maximum thickness reduction rate of the stamped part 210 of the target shape is 25.4%. Figure 5 Under the conditions shown, the stamping process is performed in one step compared to the conventional method ( Figure 4 ) compared to the plate thickness reduction rate, resulting in more tensile flange cracks. Figure 5 There is almost no effect on suppressing tensile flange cracks under the conditions shown.

[0061] Therefore, the inventors of the present application have conducted in-depth research on methods for suppressing such tensile flange cracks. In this research, the inventors of the present application focused on the locations where tensile flange cracks occur in the conventional methods. That is, in a stamped part 210 that is stamped into a target shape by the conventional method, if Figure 4 and Figure 6As shown, the plate thickness reduction rate is large at the curved center portion 221a or its vicinity of the flange portion 219 of the concave curved portion 221. Therefore, attention is paid to the fact that tensile flange cracks are likely to occur at this portion.

[0062] Therefore, the inventors of the present application have conducted in-depth research on the following method: in the stretch flange forming where the tensile stress acts on the concave curved part, the tensile stress acting on the part or the vicinity is reduced, and the tensile stress is dispersed on both ends of the bend of the concave curved part. As a result, it is thought that in the intermediate shape stamping part, by forming a shape in which a part of the concave curved part is cut off, the tensile stress acting on the part or the vicinity is reduced, and the tensile stress is dispersed on both ends of the bend of the concave curved part. It is also found that by reducing the tensile stress in the concave curved part, the tensile flange cracks in the intermediate shape and the target shape stamping parts can be suppressed.

[0063] The present invention has been completed based on the results of the study, and its configuration is as follows.

[0064] <Press forming method>

[0065] The stamping method of the embodiment is to Figure 2 (a) is a method for stamping a stamped part 210 having a concave curved portion 221 that is concavely curved when viewed from above into a target shape. Figure 1 As shown, the stamping method includes a blank making step S1, an intermediate shape forming step S3 and a target shape forming step S5. It should be noted that the stamping part 210 is manufactured by executing the above-mentioned stamping method, so the invention of the stamping method can also become the invention of the method for manufacturing a stamping part. Therefore, the implementation of the stamping method described below is common to the implementation of the method for manufacturing a stamping part. Figure 7 and Figure 8 Each of the above steps will be described.

[0066] 《Blank material production process》

[0067] The blank manufacturing step S1 is to manufacture a blank 100 having a concave shape 101 corresponding to the curvature of the concave curved portion 221 of the press-formed product 210 of the target shape (see Figure 8 (a)) The curvature of the concave curved portion 221 refers to, for example, the curvature of the ridgeline 213 of the concave curved portion 221 .

[0068] 《Intermediate Shape Forming Process》

[0069] The intermediate shape forming step S3 is to press the blank 100 into Figure 7(a) is a process for forming a stamped part 110 of an intermediate shape. Here, the stamped part 110 of the intermediate shape has a top plate portion 111, a longitudinal wall portion 115 continuous from the top plate portion 111 via a continuous ridge portion 113, and a flange portion 119 continuous from the longitudinal wall portion 115 via a die shoulder portion 117. In addition, the stamped part 110 of the intermediate shape has a concave curved portion 121 that is concavely curved when viewed from above, and straight portions 123 that extend linearly from both ends of the curve of the concave curved portion 121. In addition, a notch portion 125 in a shape in which a portion of the flange portion 119 and the longitudinal wall portion 115 are missing is provided in the curved central portion 121a of the concave curved portion 121. Then, stamping is performed in the intermediate shape forming step S3 so that a portion of the concave shape 101 set in the blank 100 becomes the notch portion 125. The cutout 125 provided in the vertical wall 115 of the concave curved portion 121 is a portion of the vertical wall 115 that is originally a portion without material. The height length of the cutout 125 is shorter than the height length of the vertical wall 115 other than the concave curved portion 121.

[0070] In the intermediate shape forming step S3, for example, Figure 8 As shown in (a), a press-formed product 110 having an intermediate shape can be press-formed using an intermediate shape forming die 1 including an intermediate shape forming concave die 3, an intermediate shape forming convex die 5, and a gasket 7.

[0071] The intermediate shape molding die 3 includes a die-side intermediate shape concave curved portion molding part 3a for molding the concave curved portion 121 of the intermediate shape and a die-side intermediate shape straight portion molding part 3b for molding the straight portion 123 of the intermediate shape.

[0072] The intermediate shape forming convex die 5 has a convex-side intermediate shape concave curved portion forming part 5a and a convex-side intermediate shape straight portion forming part 5b. The convex-side intermediate shape concave curved portion forming part 5a cooperates with the concave-side intermediate shape concave curved portion forming part 3a to form the concave curved portion 121 of the intermediate shape. The convex-side intermediate shape straight portion forming part 5b cooperates with the concave-side intermediate shape straight portion forming part 3b to form the straight portion 123 of the intermediate shape.

[0073] The spacer 7 presses the blank 100 toward the intermediate shape forming male die 5 to press the blank 100. In the intermediate shape forming step S3, the intermediate shape forming die 1 does not necessarily need the spacer 7, and the intermediate shape forming female die 3 may have a top plate forming portion.

[0074] 《Target shape forming process》

[0075] The target shape forming step S5 is to form the intermediate shape of the stamped part 110 stamped in the intermediate shape forming step S3 into a target shape. Figure 7 (b) is a process for forming a stamped product 210 into a target shape.

[0076] In the target shape forming step S5, for example, Figure 8 As shown in (b), press forming can be performed using a target shape forming die 11 including a target shape forming concave die 13, a target shape forming convex die 15, and a gasket 17.

[0077] The target shape molding die 13 includes a die-side target shape concave curved portion molding part 13 a that molds the concave curved portion 221 of the target shape and a die-side target shape straight portion molding part 13 b that molds the straight portion 223 of the target shape.

[0078] The target shape molding punch 15 includes a punch side target shape concave curved portion molding part 15a and a punch side target shape straight portion molding part 15b. The punch side target shape concave curved portion molding part 15a cooperates with the die side target shape concave curved portion molding part 13a to mold the concave curved portion 221 of the target shape. The punch side target shape straight portion molding part 15b cooperates with the die side target shape straight portion molding part 13b to mold the straight portion 223 of the target shape.

[0079] The gasket 17 presses the top plate 111 of the intermediate shape stamping part 110 toward the target shape forming convex die 15 to press the stamping part 110. It should be noted that in the target shape forming step S5, the target shape forming die does not necessarily need the gasket 17, and the target shape forming concave die 13 may also have a top plate forming part.

[0080] <Effects>

[0081] The stamping method of the embodiment first manufactures a blank 100 having a concave shape 101 corresponding to the curvature of the concave curved portion 221 of the target-shaped stamped part 210 in a blank manufacturing step S1. Next, the stamping method of the embodiment stamps the manufactured blank 100 into a stamped part 110 of an intermediate shape having a notch 125 in the curved central portion 121a of the concave curved portion 121 in an intermediate shape forming step S3.

[0082] In the intermediate-shaped stamped part 110 stamped in this way, the tensile stress acting near the notch 125 is reduced. In addition, the tensile stress is dispersed on both ends of the bend of the concave curved portion 121. As a result, in the process of stamping the intermediate-shaped stamped part 110 into the stamped part 210 of the target shape, tensile flange cracks can be suppressed and the stamped part of the target shape can be stamped.

[0083] This is through Figure 8 The finite element analysis (FEM analysis) of the stamping process in the stamping method of the embodiment shown as an example is verified. In this verification, the finite element analysis is performed on the process of stamping the blank 100 with the concave shape 101 into the stamping part 110 of the intermediate shape and the process of stamping the stamping part 110 of the intermediate shape into the stamping part 210 of the target shape. Then, the plate thickness reduction rate is calculated for the stamping part 110 of the intermediate shape and the stamping part 210 of the target shape.

[0084] Fig. 9 : is a contour diagram of the thickness reduction rate of the intermediate shape stamping part 110 and the target shape stamping part 210. Here, the intermediate shape stamping part 110 is as shown in FIG. Fig.10 As shown, the ridgeline 113 of the concave curved portion 121 of the intermediate shape is positioned further outward than the ridgeline 213 of the concave curved portion 221 of the target shape. Further outward than the ridgeline 213 of the target shape means being closer to the center side of the bend than the bend pq of the concave curved portion 221 of the target shape. Furthermore, the ridgeline length (e.g., 300 mm) of the ridgeline 113 of the concave curved portion 121 is longer than the ridgeline length (e.g., 250 mm) of the ridgeline 213 of the concave curved portion 221 of the target shape.

[0085] like Fig. 9 As shown in FIG. 1 , the maximum thickness reduction rate of the intermediate-shaped stamped part 110 is 14.8%, and the maximum thickness reduction rate of the target-shaped stamped part 210 is 18.5%. Figure 4 The maximum value (=21.5%) of the thickness reduction rate of the stamped part 210 obtained by the conventional method of performing stamping in one step is smaller than that of the stamped part 210 shown in FIG. Figure 6 The maximum value (=25.4%) of the plate thickness reduction rate of the press-formed product 210 obtained by the method of Patent Document 1 is small.

[0086] These results provide the following suggestion: According to the stamping method of the embodiment, it is possible to stamp a stamped part 210 of a target shape while suppressing the occurrence of stretch flange cracks in the concave curved portion 221 during the stamping process.

[0087] Thus, in the press forming method of the embodiment, first, a blank 100 ( ) having a concave shape 101 corresponding to the curvature of the concave curved portion 221 of the press forming part 210 of the target shape is prepared. Figure 8 (a)). Next, in the stamping method of the embodiment, the produced blank 100 is stamped into a stamped part 110 having an intermediate shape in which a notch 125 is provided in the curved center 121a of the concave curved portion 121 ( Fig. 9 (a)). Furthermore, in the stamping method of the embodiment, the stamping part 110 of the intermediate shape is stamped into the stamping part 210 of the target shape ( Fig. 9 (b)).

[0088] Thus, during the press forming of the intermediate shape press-formed product 110 , the tensile stress acting near the notch 125 of the concave curved portion 121 can be reduced, and the tensile stress can be dispersed to both ends of the curve of the concave curved portion 121 .

[0089] As a result, when the intermediate-shaped stamped part 110 is stamped into the target-shaped stamped part 210, the tensile flange crack can be fully suppressed, and stable stamping without cracks can be performed, which can achieve improved productivity and improved yield.

[0090] Moreover, the stamping method of the embodiment does not need to move the blank 100 during stamping as in the method described in Patent Document 2. Therefore, according to the stamping method of the embodiment, the fluctuation of dimensional accuracy can be suppressed and the stamping part 210 of a good target shape can be obtained, and the productivity and yield can be improved.

[0091] In addition, in the above description, as mentioned above Fig.10 As shown in the figure, the ridgeline 113 of the concavely curved portion 121 of the intermediate shape is positioned outside the ridgeline 213 of the concavely curved portion 221 of the target shape, but the present invention is not limited thereto.

[0092] Of course, if Fig.10 As shown, the present invention preferably makes the ridgeline 113 of the concave curved part 121 of the intermediate shape be located at a position further outward than the ridgeline 213 of the concave curved part 221 of the target shape. In this case, compared with the concave curved part 221 of the target shape, the material is left in the top plate part 111, the ridgeline 113 and the vertical wall part 115 of the concave curved part 121. Thus, even if a part of the vertical wall part 115 and the flange part 119 of the intermediate shape is missing, the stamped part 210 of the target shape having the top plate part 211, the vertical wall part 215 and the flange part 219 can be stamped reliably.

[0093] Furthermore, if the ridgeline 113 of the concave curved portion 121 of the intermediate shape is located outside the ridgeline 213 of the target shape, it is possible to ensure, in the intermediate shape forming step S3, the material that follows the material flow generated in the local stretch flange deformation due to the forming of the concave curved portion 121. Furthermore, in the subsequent target shape forming step S5, the strain generated at the end of the flange portion 219 of the concave curved portion 221 of the target shape formed by stamping can also be widely dispersed and reduced, and the stretch flange crack can be further suppressed.

[0094] In addition, when the ridgeline 113 of the concave curved portion 121 of the intermediate shape is located outside the ridgeline 213 of the target shape, the curvature radius of the concave curved portion 121 may be made constant. Fig.10 As shown, the intermediate concave curved portion 121 may also include a curved central portion 121a (curvature radius R C ) and the curved end portion 121b (curvature radius R E ). In addition, the curvature radius R of the curved end portion 121b of the concave curved portion 121 of the intermediate shape is E There is no restriction on the curvature radius R0 of the concave curved portion 221 of the target shape, R0<R E and R0>R E It can also be set as R0 = R E .

[0095] Furthermore, in the above case, the length (ridge length) of the ridge portion 113 of the concave curved portion 221 of the intermediate shape can be made longer than the length (ridge length) of the ridge portion 213 of the concave curved portion 221 of the target shape. This is preferable because more material can be secured to follow the material flow caused by the local stretch flange deformation by forming the concave curved portion 121 in the intermediate shape forming step.

[0096] The above embodiment uses a stamped part 210 with a Z-shaped cross section as a molding object. Fig.11 As shown in (i) of (a), the flange portion 119 and the longitudinal wall portion 115 of the intermediate-shaped stamped part 110 are partially missing. Of course, in the present invention, the intermediate-shaped stamped part 110 may also be as shown in Fig.11 As shown in (ii) of (a), the flange portion 119 having the concave curved portion 121, the longitudinal wall portion 115, and the notch portion 127 are shaped in such a way that a part of the top plate portion 111 is missing. Thus, the "notch portion" of the stamped part 110 having the intermediate shape of the flange portion 119 refers to a portion that should have been the longitudinal wall portion 115 or the top plate portion 111 and is in a state where there is no material.

[0097] In addition, as described above, the present invention can also be a stamped part 230 ( Figure 2 (b)), L-shaped cross-sectional stamping parts, hat-shaped cross-sectional stamping parts 250 ( Figure 2 (c)) as a molding object.

[0098] When a stamped part with an L-shaped cross section is used as a forming object, first, Fig.11 (b) The stamped part 130 illustrated is stamped into an intermediate shape, and then stamped into a stamped part of a target shape. In this case, the intermediate shape of the stamped part 130 is as follows: Fig.11 As shown in (b), it has a top plate portion 131 and a vertical wall portion 135 that is continuous from the top plate portion 131 via a ridge portion 133. In addition, the intermediate-shaped press-formed product 130 has a concave curved portion 141 that is curved in a concave shape in a plan view.

[0099] Furthermore, the concave shape 101 ( Figure 8 (a)) as part of Fig.11 As shown in (b), the notch 147 of the curved central portion 141a of the concave curved portion 141 is formed by stamping. Fig.11 The notch 147 shown in (b) is a shape in which a part of the vertical wall 135 and the top plate 131 are missing in the curved central portion 141a of the concave curved portion 141. Thus, the "notch" in the stamped part 130 of the intermediate shape in the forming of the stamped part with an L-shaped cross-sectional shape refers to a part that should have been the top plate 131 and is in a state where there is no material.

[0100] In addition, when the stamped part 250 of the hat-shaped cross-section is used as the molding object, the stamped part of the intermediate shape can be stamped in such a way that a part of the concave shape provided in the blank becomes a notch portion of the curved central part of the concave curved part. In this case, the notch portion in the stamped part of the intermediate shape can also be a shape in which a part of the flange portion and the longitudinal wall portion of the curved central part of the concave curved part or a part of the flange portion, the longitudinal wall portion and the top plate portion are missing.

[0101] In order to obtain a stamped part having an intermediate shape of such a notch portion, the curvature radius of the concave shape 101 provided in the blank 100 can be appropriately adjusted in the blank production process (refer to Figure 8 (a)). Specifically, for example, the curvature radius of the concave shape of the blank can be made larger than the curvature radius of the ridgeline of the concave curved portion of the target stamped part when viewed from above (see Fig.10 The radius of curvature R0) in the sample is small.

[0102] Alternatively, the position of the blank 100 in the intermediate shape forming die can be adjusted in the intermediate shape forming step so that the intermediate shape stamping part has a notch. It should be noted that by performing each step of the above-mentioned stamping forming method, a target stamping part can be manufactured, and the manufactured stamping part fully suppresses tensile flange cracks.

[0103] Example

[0104] Since an analysis was conducted to verify the effects of the press forming method and the method for manufacturing a press-formed product according to the present invention, this will be described below.

[0105] In this embodiment, Fig.12 The stamping part 250 of the hat-shaped cross-section shown in the figure is used as the molding object. Here, in the stamping part 250, as shown in the figure, Fig.12 As shown, the forming height is set to 50 mm, the curvature radius of the concave curved portion 261 is set to 150 mm, and the curvature R of the ridge portion 253 and the concave die shoulder 257 are both set to 10 mm. In addition, in the stamped part 250, the length of the curved portion of the ridge portion 253 of the concave curved portion 261 is set to 236 mm.

[0106] First, a blank 100 having a concave shape 101 corresponding to the curvature of the concave curved portion 261 is prepared (see Fig.13 (a) Here, the bending radius of the concave shape 101 is set to 80 mm.

[0107] Then, if Fig.13 As shown in (a), the blank 100 is stamped into an intermediate shape stamped part 150 (see FIG. 1 ) using an intermediate shape forming die 31 having an intermediate shape forming die 33, an intermediate shape forming die 35, and a gasket 37. Fig.13 (b) Here, regarding the intermediate concave curved portion 161, the curved center portion 161a is set to be linear, and the curvature radius R of the curved end portion 161b is set to be E The case where the curvature radius R is set to 80 mm is referred to as Invention Example 1. In Invention Example 1, the ridge length of the concave curved portion 161 of the intermediate shape is set to 273 mm. In addition, regarding the concave curved portion 161 of the intermediate shape, the curved center portion 161a is set to a straight line, and the curvature radius R of the curved end portion 161b is set to E The case of 160 mm is referred to as Invention Example 2. Invention Example 2 is a case in which the curvature radius R of the curved end portion 161 b of the concave curved portion 161 of the intermediate shape is EThe condition that the curvature radius R0 of the concave curved portion 261 of the target shape is greater than that of the concave curved portion 261 of the target shape. In Example 2 of the invention, the ridge length of the concave curved portion 161 of the intermediate shape is set to 322 mm. Fig.13 As shown in (b), the intermediate-shaped stamped part 150 has a concave curved portion 161 that is concavely curved when viewed from above and straight portions 163 extending from both ends thereof. In addition, the intermediate-shaped stamped part 150 is provided with a notch portion 165 at the flange portion 159 of the curved central portion 161a of the concave curved portion 161 and a portion of the vertical wall portion 155.

[0108] Then, if Fig.13 As shown in (b), the press-formed product 150 of the intermediate shape is press-formed into a press-formed product 250 of the target shape using a target shape forming die 41 including a target shape forming concave die 43, a target shape forming convex die 45, and a gasket 47.

[0109] In addition, in this embodiment, as a comparison object, Fig.14 As shown, the blank 100 is stamped into a mold 51 having a concave mold 53, a convex mold 55 and a gasket 57 in one process. Fig.12 The case of the stamped part 250 of the target shape shown in the figure is taken as a conventional example. Figure 5 The conditions of the mold of the shape shown in the figure are used to stamp the stamped product 250 of the target shape in two steps as a comparative example. In the comparative example, regarding the concave curved portion 181 of the intermediate shape, the curved central portion 181a is set to a straight line, and the curvature radius R of the curved end portion 181b is set to E In the comparative example, the ridge length of the concave curved portion 181 of the intermediate shape was set to 211 mm. Then, finite element analysis was performed on the press forming process of the conventional example and the comparative example to find the plate thickness reduction rate.

[0110] Fig.15 It is a contour diagram of the plate thickness reduction rate of the press-formed product 250 having a target shape in the conventional example. Fig.16 It is a contour diagram of the plate thickness reduction rate of the press-formed product 150 of the intermediate shape and the press-formed product 250 of the target shape in the comparative example. Fig.17 It is a contour diagram of the thickness reduction rate of the press-formed product 150 of the intermediate shape and the press-formed product 250 of the target shape in Inventive Example 1. Fig.18 It is a contour diagram of the thickness reduction rate of the intermediate shape stamped part 150 and the target shape stamped part 250 in Inventive Example 2. It should be noted that, regarding the prior art example, since stamping is performed in one process, only the result of the target shape stamped part 250 is shown.

[0111] In the existing example, Fig.15 As shown, the portion where the plate thickness is most reduced is the end portion of the flange portion 259 of the concave curved portion 261, and the maximum value of the plate thickness reduction rate is 20.5%.

[0112] In the comparative example, Fig.16 As shown, the bending line length of the ridgeline portion 193 of the intermediate shape stamped part 190 is shorter, so the plate thickness reduction rate of the bent central portion 201a of the concave curved portion 201 is smaller. However, the maximum value of the plate thickness reduction rate of the bent end portions 201b on both ends of the concave curved portion 201 is 24.4%, which is significantly increased compared to the maximum value (=20.5%) of the plate thickness reduction rate in the target shape stamped part 250 of the prior art. Furthermore, in the stamped part 250 of the target shape that is stamped from the intermediate shape stamped part 190, the maximum value of the plate thickness reduction rate of the bent end portion of the concave curved portion 261 is 25.4%, and the tensile strain is concentrated in this portion, resulting in the easy generation of tensile flange cracks.

[0113] In contrast, in Inventive Example 1, Fig.17 As shown, the maximum value of the plate thickness reduction rate of the intermediate-shaped stamped part 150 is 14.8%, and the plate thickness reduction rate can be reduced by providing the notch 165 compared with the prior art example and the comparative example. Furthermore, in Inventive Example 1, the maximum value of the plate thickness reduction rate in the target-shaped stamped part 250 is 18.3%. This plate thickness reduction rate is a value lower than the maximum value of the plate thickness reduction rate of the target-shaped stamped part 250 of the prior art example and the target-shaped stamped part 250 of the comparative example.

[0114] In addition, in Inventive Example 2, Fig.18 As shown, the maximum value of the plate thickness reduction rate of the intermediate shape stamped part 150 is 13.9%. Compared with the existing example and the comparative example, the plate thickness reduction rate can be reduced by providing the notch portion 165. Furthermore, in Inventive Example 2, the maximum value of the plate thickness reduction rate in the target shape stamped part 250 is 18.8%. This plate thickness reduction rate becomes a value lower than the maximum value of the plate thickness reduction rate of the stamped part 250 of the target shape of the existing example and the stamped part 250 of the target shape of the comparative example. In addition, the maximum plate thickness reduction rate of the two ends of the concave curved portion 261 of Inventive Example 2 is 14.2%, and the plate thickness reduction rate is further reduced compared with the maximum value of 16.2% of the plate thickness reduction rate of the two ends of the concave curved portion 261 of Inventive Example 1.

[0115] Thus, according to the press forming method of the present invention, the curvature radius R of the curved end portion 161b of the concave curved portion 161 of the intermediate shape can be reduced to EThe curvature radius R0 of the concave curved portion 261 of the target shape is set to be larger than that of the concave curved portion 261 of the target shape. E , which can suppress the reduction in plate thickness at both ends of the concave curved portion 261 of the target shape.

[0116] As described above, according to the stamping method of the present invention, a suggestion is given for reducing tensile flange cracks at a concave curved portion during stamping of a stamped part having a target shape having a concave curved portion.

[0117] Industrial Applicability

[0118] The present invention provides a stamping method and a method for manufacturing a stamping-formed part, which can fully suppress tensile flange cracks of a stamping-formed part having a top plate portion and a longitudinal wall portion and a concave curved portion that is concavely curved when viewed from above.

[0119] Description of Reference Numerals

[0120] 1: Die for forming the intermediate shape;

[0121] 3: Concave die for forming the intermediate shape;

[0122] 3a: The concave curved part of the middle shape of the die side;

[0123] 3b: The forming part of the straight line in the middle of the die side;

[0124] 5: Punch for forming the intermediate shape;

[0125] 5a: The concave curved part in the middle of the male die side;

[0126] 5b: The forming part of the straight line in the middle of the punch side;

[0127] 7: Gasket;

[0128] 11: Mold for forming the target shape;

[0129] 13: Concave die for forming the target shape;

[0130] 13a: the target shape concave bending part forming part on the die side;

[0131] 13b: The target shape straight line forming part on the die side;

[0132] 15: Punch for forming the target shape;

[0133] 15a: Target shape concave curved portion forming portion on the male die side;

[0134] 15b: the target shape straight line forming part on the punch side;

[0135] 17: Gasket;

[0136] 21: Mould;

[0137] 23: Concave die;

[0138] 23a: Concave bending forming part of the die side;

[0139] 25: Punch;

[0140] 25a: Concave curved portion forming portion of the male die side;

[0141] 27: Gasket;

[0142] 31: Die for forming the intermediate shape;

[0143] 33: Concave die for forming the intermediate shape;

[0144] 35: Punch for forming the intermediate shape;

[0145] 37: gasket;

[0146] 41: mold for forming the target shape;

[0147] 43: Concave die for forming the target shape;

[0148] 45: a punch for forming a target shape;

[0149] 47: gasket;

[0150] 51: Mould;

[0151] 53: Concave die;

[0152] 55: punch;

[0153] 57: gasket;

[0154] 100: blank;

[0155] 101: concave shape;

[0156] 110: Stamping parts;

[0157] 111: top plate;

[0158] 113: Ridge;

[0159] 115: longitudinal wall;

[0160] 117: die shoulder;

[0161] 119: flange portion;

[0162] 121: concave curvature;

[0163] 121a: curved central part;

[0164] 121b: bent end;

[0165] 123: Straight line part;

[0166] 125: notch;

[0167] 127: notch;

[0168] 130: Stamping parts;

[0169] 131: top plate;

[0170] 133: Ridge;

[0171] 135: longitudinal wall;

[0172] 141: concave curvature;

[0173] 141a: curved central part;

[0174] 147: notch;

[0175] 150: Stamping parts;

[0176] 153: Ridge;

[0177] 155: longitudinal wall;

[0178] 157: die shoulder;

[0179] 159: flange portion;

[0180] 161: concave curvature;

[0181] 161a: curved central part;

[0182] 161b: bent end;

[0183] 163: Straight line part;

[0184] 165: notch;

[0185] 170: Stamping parts;

[0186] 173: Ridge;

[0187] 181: concave curvature;

[0188] 181a: curved central part;

[0189] 181b: bent end;

[0190] 190: Stamping parts;

[0191] 193: Ridge;

[0192] 201: concave curved part;

[0193] 201a: curved central part;

[0194] 201b: bent end;

[0195] 210: Stamping parts;

[0196] 211: top plate;

[0197] 213: Ridge;

[0198] 215: longitudinal wall;

[0199] 217: die shoulder;

[0200] 219: flange portion;

[0201] 221: concave curvature;

[0202] 221a: curved central part;

[0203] 223: Straight line part;

[0204] 230: Stamping parts;

[0205] 231: top plate;

[0206] 233: Ridge;

[0207] 233a: Ridge line;

[0208] 235: longitudinal wall;

[0209] 235a: longitudinal wall;

[0210] 241: concave curvature;

[0211] 243: Straight line part;

[0212] 250: Stamping parts;

[0213] 251: top plate;

[0214] 253: Ridge;

[0215] 253a: Ridge line;

[0216] 255: longitudinal wall;

[0217] 255a: longitudinal wall;

[0218] 257: die shoulder;

[0219] 257a: die shoulder;

[0220] 259: flange portion;

[0221] 259a: flange portion;

[0222] 261: concave curvature;

[0223] 263: Straight line area.

Claims

1. A stamping method for stamping a stamped part into a target shape, wherein the stamped part has a top plate portion, a longitudinal wall portion continuous from the top plate portion, and a flange portion continuous from the longitudinal wall portion, and has a concave curved portion that is concavely curved when viewed from above, characterized in that: include: a blank manufacturing step of manufacturing a blank having a concave shape corresponding to the curvature of the concave curved portion of the target shape; An intermediate shape forming step, wherein the produced blank is formed by stamping into a stamped part of an intermediate shape, wherein the stamped part of the intermediate shape has a top plate portion, a longitudinal wall portion continuous from the top plate portion, and a flange portion continuous from the longitudinal wall portion, and has a concave curved portion that is concavely curved when viewed from above, and a notch portion is provided in the flange portion and a part of the longitudinal wall portion, or in the flange portion, the longitudinal wall portion, and a part of the top plate portion at a curved center of the concave curved portion; A target shape forming step, wherein the stamped part of the intermediate shape is stamped into the target shape; In the intermediate shape forming step, press forming is performed so that a part of the concave shape provided in the blank becomes the notch portion.

2. A stamping method for stamping a stamped part into a target shape, wherein the stamped part has a top plate portion and a longitudinal wall portion continuous from the top plate portion, and has a concave curved portion that is concavely curved when viewed from above, characterized in that: include: a blank manufacturing step of manufacturing a blank having a concave shape corresponding to the curvature of the concave curved portion; an intermediate shape forming step, wherein the produced blank is formed into an intermediate shape stamped part by stamping, wherein the intermediate shape stamped part has a top plate portion and a longitudinal wall portion continuous from the top plate portion, and has a concave curved portion that is concavely curved when viewed from above, and a notch portion is provided in a portion of the longitudinal wall portion and the top plate portion at a curved center of the concave curved portion; A target shape forming step, wherein the stamped part of the intermediate shape is stamped into the target shape; In the intermediate shape forming step, press forming is performed so that a part of the concave shape provided in the blank becomes the notch portion.

3. The stamping method according to claim 1 or 2, characterized in that: In the intermediate shape forming step, the curvature radius R of the curved end portion of the concave curved portion of the intermediate shape is set to E The curvature radius R0 of the concave curved portion is greater than the target shape.

4. A method for manufacturing a stamped part, wherein the stamped part is manufactured into a target shape, wherein the stamped part has a top plate portion, a longitudinal wall portion continuous from the top plate portion, and a flange portion continuous from the longitudinal wall portion, and has a concave curved portion that is concavely curved when viewed from above, wherein: include: a blank manufacturing step of manufacturing a blank having a concave shape corresponding to the curvature of the concave curved portion of the target shape; An intermediate shape forming step, wherein the produced blank is formed by stamping into a stamped part of an intermediate shape, wherein the stamped part of the intermediate shape has a top plate portion, a longitudinal wall portion continuous from the top plate portion, and a flange portion continuous from the longitudinal wall portion, and has a concave curved portion that is concavely curved when viewed from above, and a notch portion is provided in the flange portion and a part of the longitudinal wall portion, or in the flange portion, the longitudinal wall portion, and a part of the top plate portion at a curved center of the concave curved portion; A target shape forming step, wherein the stamped part of the intermediate shape is stamped into the target shape; In the intermediate shape forming step, press forming is performed so that a part of the concave shape provided in the blank becomes the notch portion.

5. A method for manufacturing a stamped part, wherein the stamped part is manufactured into a target shape, wherein the stamped part has a top plate portion and a vertical wall portion continuous from the top plate portion, and has a concave curved portion that is concavely curved when viewed from above, characterized in that: include: a blank manufacturing step of manufacturing a blank having a concave shape corresponding to the curvature of the concave curved portion; an intermediate shape forming step, wherein the produced blank is formed into an intermediate shape stamped part by stamping, wherein the intermediate shape stamped part has a top plate portion and a longitudinal wall portion continuous from the top plate portion, and has a concave curved portion that is concavely curved when viewed from above, and a notch portion is provided in a portion of the longitudinal wall portion and the top plate portion at a curved center of the concave curved portion; A target shape forming step, wherein the stamped part of the intermediate shape is stamped into the target shape; In the intermediate shape forming step, press forming is performed so that a part of the concave shape provided in the blank becomes the notch portion.

6. The method for manufacturing a stamped part according to claim 4 or 5, characterized in that: In the intermediate shape forming step, the curvature radius R of the curved end portion of the concave curved portion of the intermediate shape is set to E The press forming is performed so that the curvature radius R0 of the concave curved portion is larger than the target shape.

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