Method for manufacturing press-molded article, press-molded article, and press-molding method

Abstract

Provided is a technique for suppressing defects and improving productivity during molding of a high-strength steel sheet. This method for manufacturing a press-molded article manufactures a press-molded article by press-molding a blank, the press-molded article comprising: a top plate section having an outer peripheral edge section including a bent section; a vertical wall section that is continuous with the outer peripheral edge section of the top plate section; and a flange section continuous with the vertical wall section, characterized in that the step for forming a curved vertical wall section continuous with the curved section among the vertical wall sections comprises: a pre-forming step for forming a curved vertical wall section having a stepped shape; a lower vertical wall part of the bent vertical wall part from a step part to the flange part, which is arranged at a specified position in the height direction of the bent vertical wall part, extends to the flange part side relative to an upper vertical wall part from the step part to the top plate part; and a main molding step in which a mold having a cam structure is used to flatten the stepped curved vertical wall section into a flat curved vertical wall section.

Description

Technical Field

[0001] This invention relates to a method for manufacturing stamped parts, stamped parts, and a stamping method. Background Technology

[0002] From the perspectives of environmental pollution countermeasures and improved fuel efficiency, there is a demand for lightweight automotive components. As part of this lightweighting effort, efforts have been made to reduce the thickness of the sheet metal or to use high-strength steel sheets with higher strength than previously used. It is known that high-strength steel sheets have less elongation and poorer formability compared to low-strength steel sheets. Therefore, if it is attempted to achieve a component shape that can be formed from conventionally used steel sheets using high-strength steel sheets, forming defects such as cracks and wrinkles may occur. Methods for suppressing defects such as cracks and wrinkles that occur during the forming of such high-strength steel sheets include, for example, Patent Document 1 and Patent Document 2.

[0003] Patent Document 1 discloses a method for improving formability by performing stamping in multiple forming processes. Patent Document 2 discloses a method for manufacturing high-strength, high-design-quality parts by stamping a material softened by heating followed by quenching.

[0004] [Existing technical documents]

[0005] [Patent Literature]

[0006] Patent Document 1: Japanese Patent No. 5867657

[0007] Patent Document 2: Japanese Patent Application Publication No. 5952881 Summary of the Invention

[0008] [The problem the invention aims to solve]

[0009] For example, in a roughly L-shaped component used for the lower part of a front pillar member, wrinkles and cracks are easily generated at the boundary between the top plate and the curved longitudinal wall (hereinafter, the curved longitudinal wall) when forming the curved longitudinal wall. For instance, to suppress cracking on the die shoulder, it is effective to bring the material closer to the die shoulder to suppress elongation along the direction of the die shoulder. Specific countermeasures include deep drawing or adjusting the die shape to promote material rotation during forming. In these countermeasures, the material is brought closer not only to the die shoulder used to form the curved longitudinal wall but also to the punch shoulder, potentially causing wrinkles at the punch shoulder. Especially in forming using high-strength steel sheets, it is necessary to increase the pad pressure to suppress wrinkling. However, considering the shape of the die and the size of the pad material, it is usually difficult to set the pad pressure high. Furthermore, countermeasures against punch shoulder wrinkles have the opposite effect to countermeasures against die shoulder cracks. Therefore, it is difficult to simultaneously adopt countermeasures against wrinkles in the punch head shoulder and cracks in the punch die shoulder.

[0010] However, in the method described in Patent Document 1, the formability can be improved by appropriately designing the shape of each process. However, in the method described in Patent Document 1, as the number of forming processes increases, there is a problem of decreased productivity or increased mold costs. Furthermore, in the method described in Patent Document 2, not only is it necessary to heat the blank above its phase transformation point before stamping, but it is also necessary to quench it after stamping. Therefore, the method described in Patent Document 2 also has limitations in terms of improving productivity.

[0011] The present invention was made in view of the above-mentioned problems, and its object is to provide a technology that can suppress defects such as cracks and wrinkles that occur in the forming of high-strength steel sheets and improve the productivity of stamping.

[0012] [Methods used to solve problems]

[0013] According to one viewpoint, a method for manufacturing a stamped part is a method of manufacturing a stamped part by stamping a blank made of a metal sheet, the stamped part having: a top plate portion having an outer peripheral portion including a curved portion; a longitudinal wall portion continuous with the outer peripheral portion of the top plate portion; and a flange portion continuous with the longitudinal wall portion, characterized in that the process of forming the curved longitudinal wall portion continuous with the curved portion includes: a first forming step, generating a stepped curved longitudinal wall portion, wherein the lower longitudinal wall portion of the curved longitudinal wall portion extending from the step portion at a predetermined position in the height direction of the curved longitudinal wall portion to the flange portion extends toward the flange portion relative to the upper longitudinal wall portion extending from the step portion to the top plate portion; and a second forming step, using a die having a cam structure to flatten the stepped curved longitudinal wall portion into a flat curved longitudinal wall portion.

[0014] Furthermore, preferably, in the top view of the stamped part, the curved portion is arc-shaped. In the second forming process, along the straight line connecting the center point of the curved portion in the top view of the stamped part and the midpoint of the curved portion, the mold having the cam structure abuts against the lower longitudinal wall portion at an angle of 0 degrees or more and 75 degrees or less relative to the surface parallel to the upper surface of the top plate portion, thereby making the stepped curved longitudinal wall portion flat.

[0015] Furthermore, preferably, the process of forming the curved longitudinal wall portion includes a third forming process, which is performed before the first forming process, and forms the boundary portion between the top plate portion and the curved longitudinal wall portion on the blank.

[0016] Alternatively, according to another viewpoint, stamped parts can be manufactured using the stamped part manufacturing method described above.

[0017] Another stamping method, according to another viewpoint, is a method of stamping an intermediate part from a blank sheet by relative movement of a die and a punch. The die includes: a top plate forming surface for forming the intermediate part; a die side longitudinal wall forming surface for forming a longitudinal wall portion connected to the outer periphery of the top plate portion; and a die side flange forming surface for forming a flange portion connected to the longitudinal wall portion. The die side longitudinal wall forming surface has a die side step forming portion in the height direction of the longitudinal wall portion. The die side step forming portion forms a step portion at a predetermined position connected to a curved longitudinal wall portion provided at the outer periphery of the top plate portion. The lower longitudinal wall portion from this predetermined position to the flange portion connected to the longitudinal wall portion is longer than the upper longitudinal wall portion from the top plate portion to the predetermined position. The punch has a flange extending outwards and includes: a punch-side flange forming surface that forms the flange of the intermediate forming part; and a punch-side longitudinal wall forming surface that has a punch-side step forming portion. During relative movement between the punch and the die, the punch-side step forming portion forms the step portion of the curved longitudinal wall between the punch and the die-side longitudinal wall forming surface. Through relative movement between the die and the punch, the blank plate is bent and formed by the top plate forming surface of the die and the die-side longitudinal wall forming surface to form the top plate portion. Then, the blank plate is clamped by the die-side step forming portion and the punch-side step forming portion to form the curved longitudinal wall portion having the step portion. The blank plate is bent and formed by the die-side flange forming surface and the die-side longitudinal wall forming surface to form the flange.

[0018] [Invention Effects]

[0019] According to this disclosure, defects such as cracks and wrinkles can be suppressed when forming high-strength steel sheets, and the productivity of stamping can be improved. That is, according to this disclosure, high-quality parts can be easily formed without reducing productivity. Attached Figure Description

[0020] [ Figure 1 ] Figure 1 This is a schematic perspective view showing an example of a stamped part of the present invention.

[0021] [ Figure 2 ] Figure 2 This is a schematic diagram illustrating the manufacturing process of stamped parts.

[0022] [ Figure 3 ] Figure 3 This is a schematic end view representing the steps of the preforming process.

[0023] [ Figure 4 ] Figure 4 This is a schematic perspective view showing an example of a preform.

[0024] [ Figure 5 ] Figure 5 This is a schematic end view representing the steps of the main forming process.

[0025] [ Figure 6 ] Figure 6 This is a schematic diagram illustrating an example of the direction of movement of a cam mold.

[0026] [ Figure 7 ] Figure 7 This is a schematic diagram illustrating the steps to determine the direction of movement of the cam mold.

[0027] [ Figure 8 ] Figure 8 (a) in the diagram is a schematic representation of the areas of wrinkles and cracks that occur when a stamped part is manufactured through a single stamping process. Figure 8 (b) in the diagram represents the area of ​​cracks that occur when a stamped part is manufactured by performing the main forming process without using a cam die.

[0028] [ Figure 9 ] Figure 9 This is a schematic perspective view of an example of a blank formed by stamping to create the boundary portion between the top and the longitudinal wall.

[0029] [ Figure 10 ] Figure 10 This is a schematic diagram illustrating the flow of material in a stamped part during conventional stamping processes.

[0030] [ Figure 11 ] Figure 11(a) is a schematic end view showing the material flowing from the top plate when the punch moves vertically during the main forming process. Figure 11 (b) is a schematic end view showing the material flowing from the flange during the main forming process. Detailed Implementation

[0031] Hereinafter, this embodiment will be described using the accompanying drawings.

[0032] As an example, the stamped part shown in this embodiment is a stamped part for the lower part of the front pillar lower component of an automobile. The shape of the stamped part in the top view of the stamped part is, for example, approximately L-shaped. It should be noted that the shape of the stamped part in the top view of the stamped part is not limited to an approximately L-shaped shape, and may also be approximately T-shaped or cross-shaped.

[0033] Figure 1 This is a schematic perspective view showing one method of forming a stamped part. The stamped part 10 is produced by stamping a blank. The blank is, for example, a high-strength steel sheet (high-strength material) with a thickness of 1.2 mm and a tensile strength of 1180 MPa or more.

[0034] The stamped part 10 has a top plate portion 20, a longitudinal wall portion 30, and a flange portion 40. The longitudinal wall portion 30 is the portion that connects the top plate portion 20 and the flange portion 40. The longitudinal wall portion 30 has a flat longitudinal wall portion 31 extending in one direction, a flat longitudinal wall portion 32 extending in a direction intersecting the one direction, and a curved longitudinal wall portion 33 connecting these flat longitudinal wall portions 31 and 32. The curved longitudinal wall portion 33 is curved in a convex manner toward the top plate portion 20. That is, the outer periphery of the top plate portion 20 has a curved portion 34 along the curved longitudinal wall portion 33. In addition, when viewed from above, the curved portion 34 is, for example, curved into an arc shape.

[0035] Next, the manufacturing method of the stamped part 10 will be described. For example... Figure 2 As shown, the stamped part 10 is generated by two processes: a preforming process and a main forming process. The preforming process is a process of stamping a blank cut into a specified shape. The main forming process is a process of forming the preform generated in the preforming process using a cam die.

[0036] The preforming process and the main forming process described above are preferably continuous processes. However, the preforming process and the main forming process do not necessarily have to be continuous. For example, the preforming process can be performed in a specific factory, and then the main forming process for the produced preform can be performed in a different factory. Here, the preforming process corresponds to the first forming process described in the technical solution. The main forming process corresponds to the second forming process described in the technical solution.

[0037] (Preforming process)

[0038] The following uses Figure 3 (a) and Figure 3 Section (b) describes the preforming process. The preforming process involves stamping the blank 100 to produce a preformed part 150 (see reference). Figure 4 The process involves forming the preform 150. It should be noted that the stamping process used to produce the preform 150 can include die forming, deep drawing, etc.

[0039] First, the stamping die 120 will be described. The stamping die 120 used in the preforming process consists of a die 121 and a punch 123. The die 121 is provided with a top plate forming surface 121a, a longitudinal wall forming surface 121b, and a flange forming surface 121c. The top plate forming surface 121a forms the top plate portion 151 of the preform 150 between itself and the punch 123. The longitudinal wall forming surface 121b forms the curved longitudinal wall portion 153 of the preform 150 between itself and the punch 123. The flange forming surface 121c forms the flange portion 152 of the preform 150 between itself and the punch 123.

[0040] A step forming portion 121d is provided at a predetermined position in the height direction of the longitudinal wall forming portion 121b. That is, the portion of the longitudinal wall forming portion 121b from the flange forming portion 121c to the step forming portion 121d extends further toward the flange forming portion 121c than the portion from the top plate forming portion 121a to the step forming portion 121d.

[0041] Here, the longitudinal wall forming surface 121b corresponds to the die-side longitudinal wall forming surface described in the technical solution. Similarly, the flange forming surface 121c corresponds to the die-side flange forming surface described in the technical solution. Furthermore, the step forming portion 121d corresponds to the die-side step forming portion described in the technical solution. Additionally, the portion from the top plate forming surface 121a to the step forming portion 121d corresponds to the upper longitudinal wall portion in the technical solution. Moreover, the portion from the flange forming surface 121c to the step forming portion 121d corresponds to the lower longitudinal wall portion in the technical solution.

[0042] The punch 123 is provided with a flange forming surface 123a and a longitudinal wall forming surface 123b. The flange forming surface 123a forms the flange portion 152 of the preform 150 between itself and the die 121. The longitudinal wall forming surface 123b forms the curved longitudinal wall portion 153 of the preform 150 between itself and the die 121.

[0043] Furthermore, a step forming portion 123c is provided at a predetermined position in the height direction of the longitudinal wall forming surface 123b. That is, the portion of the longitudinal wall forming surface 123b from the flange forming surface 123a to the step forming portion 123c is recessed inward compared to other portions.

[0044] Here, the flange forming surface 123a corresponds to the punch-side flange forming surface described in the technical solution. Furthermore, the longitudinal wall forming surface 123b corresponds to the punch-side longitudinal wall forming surface described in the technical solution. Moreover, the step forming portion 123c corresponds to the punch-side step forming portion described in the technical solution.

[0045] like Figure 3 As shown in (a) of the figure, when the preforming process begins, the punch 123 moves in direction B of the figure, pressing the blank 100 held in the die 121. That is, Figure 3 In (a), direction B is the stamping direction in the preforming process. The blank 100 is bent into shape by moving the punch 123 in the stamping direction.

[0046] As described above, the punch 123 is provided with a step forming portion 123c corresponding to the curved longitudinal wall portion 153 of the preform 150. In addition, the die 121 is provided with a step forming portion 121d corresponding to the curved longitudinal wall portion 153 of the preform 150.

[0047] When the punch 123 moves in the stamping direction, the blank 100 is clamped between the die 121 and the punch 123. At this time, it is ensured that the material flows from the flange portion 152 side and the top plate portion 151 side to the curved longitudinal wall portion 153. As a result, it is difficult for cracks to occur, but on the other hand, it becomes a state in which several wrinkles are easily generated in the curved longitudinal wall portion 153.

[0048] like Figure 3 As shown in (b), if stamping continues, the blank 100 is held by the step-forming portion 121d of the die 121 and the step-forming portion 123c of the punch 123. This forms a curved longitudinal wall portion 153 with a step portion 153a. At this time, the remaining material that would cause wrinkles is absorbed by the formation of the step portion 153a. As a result, wrinkles in the step portion 153a can be suppressed.

[0049] Furthermore, as the punch 123 moves in the stamping direction, the blank 100 is clamped by the flange forming surface 121c of the die 121 and the flange forming surface 123a of the punch 123. This forms the flange portion 152. At this time, the boundary portion 153d between the top plate portion 151 and the curved longitudinal wall portion 153 in the stamped part 10 (see reference) Figure 4 A boundary portion 153e is also formed between the flange portion 152 and the curved longitudinal wall portion 153 (see reference). Figure 4 ).

[0050] However, as Figure 4 As shown, in the preform 150, the height H2 of the bent longitudinal wall portion 153 is set to be smaller than the height H1 of the longitudinal wall portions 154 and 155. Furthermore, the height H2 of the bent longitudinal wall portion 153 is set to a height that does not produce wrinkles or cracks. Specifically, the height H2 of the bent longitudinal wall portion 153 is preferably the radius R2 of the shoulder of the punch 123 (see reference). Figure 3 In (b) and above, more preferably the radius R1 of the shoulder of the die 121 (refer to) Figure 3 The sum of (b) and the radius R2 of the shoulder of punch 123 is greater than or equal to the value of (b). Furthermore, the preform 150 corresponds to the intermediate form described in the technical solution.

[0051] Here, the stepped portion 153a of the curved longitudinal wall portion 153 generated in the preforming process is preferably set as follows.

[0052] R1≧R3≧5mm···(1)

[0053] R2≧R4≧5mm···(2)

[0054] R1+R2≧R3+R4+L···(3)

[0055] R1: Radius of curvature of the shoulder of the die (the boundary between the top plate portion 151 and the upper longitudinal wall portion 153b).

[0056] R2: Radius of curvature of the shoulder of the punch (the boundary between the lower longitudinal wall 153c and the flange 152).

[0057] R3: Radius of curvature of the boundary portion (die side) between the stepped section 153a and the upper longitudinal wall section 153b.

[0058] R4: Radius of curvature of the boundary portion (punch side) between the stepped section 153a and the lower longitudinal wall section 153c.

[0059] L: The amount by which the lower longitudinal wall portion 153c extends from the upper longitudinal wall portion 153b

[0060] For example, if the radii of curvature R3 and R4 are less than 5 mm, the risk of cracking during the formation of the step portion 153a increases. Furthermore, if the radii of curvature R3 exceeds the radii of curvature R1, the radii of curvature R4 exceeds the radii of curvature R2, or the sum of the protrusion L, the radii of curvature R3, and the radii of curvature R4 exceeds the sum of the radii of curvature R1 and the radii of curvature R2, the step portion 153a becomes excessively large, increasing the likelihood of wrinkles forming in the upper and lower parts of the step portion 153a, respectively. Therefore, based on these factors, equations (1) to (3) above are defined.

[0061] In addition, generally speaking, the forming height H0 of the curved longitudinal wall can be obtained, for example, according to the following equation (4).

[0062] ε=(R0-tanθ) / (R0-H0 / cosθ) -1 ···(4)

[0063] ε: Elongation along the direction of the curved longitudinal wall

[0064] θ: Inclination of the curved longitudinal wall relative to the direction of movement of the punch

[0065] H0: Forming height of the curved longitudinal wall section

[0066] R0: Radius of curvature of the curved longitudinal wall

[0067] Here, the forming height H0 of the bent longitudinal wall when the elongation ε is equal to the ultimate strain under plane strain of the material is the maximum forming height. It should be noted that the ultimate strain under plane strain can be obtained by known methods such as the Nakajima method and the Marciniak method.

[0068] (Main forming process)

[0069] The main forming process is a process in which the stepped curved longitudinal wall portion 153 of the preform 150 is stamped using a die (hereinafter referred to as a cam die) 162 with a cam mechanism. Through the main forming process, the stepped portion 153a of the curved longitudinal wall portion 153 becomes flat.

[0070] like Figure 5 As shown in (a), the preform 150 is held in the die 160. When the main forming process begins, the cam die 162 moves towards... Figure 5 Move in direction C in (a). Figure 5 In (a), direction C is the stamping direction in the main forming process. When the cam die 162 moves in the stamping direction, the stepped, curved longitudinal wall portion 153 of the preform 150 is clamped between the cam die 162 and the punch 160. As a result, the stepped portion 153a disappears, and the protrusion L of the lower longitudinal wall portion 153c becomes 0 (refer to...). Figure 5 (b) In this context, when the cam die 162 moves in the stamping direction, the inflow of material from the top plate portion 151 to the curved longitudinal wall portion 153 and the inflow of material from the flange portion 152 to the curved longitudinal wall portion 153 are suppressed. As a result, wrinkles can be prevented at the boundary portion 153d between the top plate portion 151 and the curved longitudinal wall portion 153, and cracks can be prevented at the boundary portion 153e between the flange portion 152 and the curved longitudinal wall portion 153.

[0071] Here, the direction of movement (stamping direction) of the cam die 162 in the main forming process will be explained. For example... Figure 6 As shown in (a), the case where the curved longitudinal wall portion 153 is an arc shape when viewed from above the preform 150 will be explained. The stamping direction of the cam die 162 ( Figure 6 In (a), reference numeral C) indicates the direction along the straight line L1 connecting the center point P1 of the curved longitudinal wall portion 153 and the midpoint P2 of the curved longitudinal wall portion 153 when viewed from above the preform 150. Additionally, as... Figure 6 As shown in (b), the stamping direction of the cam die 162 is... Figure 6 The direction of the D-D' section shown in (a) is inclined downward at a specified angle θ1 relative to the plane containing the upper surface of the top plate portion 151.

[0072] The angle θ1 is set as follows. For example, if the angle θ1 is set to around 90°, the step portion 153a of the preform 150 may not be able to elongate properly when forming using the cam mold 162. In this case, material may flow from the flange portion 152 into the step portion 153a, causing cracks. Therefore, the angle θ is preferably in the range of 0° ≤ θ ≤ 75°, and more preferably in the range of 0° ≤ θ1 ≤ 45°.

[0073] In addition, the stamping direction in the main forming process can be determined by the following methods. For example, as... Figure 7 As shown in (a) above, in the top view of the die 160 used in the main forming process, the straight line connecting the midpoint P3 of the bending forming portion 161 of the die 160 and the center point P4 of the bending forming portion 161 of the die 160 is set as straight line L2. Furthermore, as... Figure 7 As shown in (b), the straight line connecting the midpoint P5 of the boundary portion 160c between the side surface 160a and the bottom surface 160b of the die 160 and the center point P6 of the boundary portion 160c is designated as line L3. Furthermore, the intersection of line L2 and line L3 is designated as intersection point P7.

[0074] like Figure 7 As shown in (c), when viewing the die 121 used in the preforming process from above, the straight line connecting the midpoint P8 of the bending forming portion 122 of the die 121 and the center point P9 of the bending forming portion 122 is designated as straight line L4. Additionally, as... Figure 7 As shown in (d), the straight line connecting the midpoint P10 of the boundary portion 121e between the longitudinal wall forming surface 121b and the flange forming surface 121c of the die 121 and the center point P11 of the boundary portion 121e is designated as line L5. Furthermore, the intersection of line L4 and line L5 is designated as intersection point P12.

[0075] like Figure 7As shown in (e), the direction from intersection point P12 to intersection point P7 becomes the moving direction of the cam mold 162 (the stamping direction in the main forming process). Furthermore, when the stamping direction in the main forming process is set as the z-direction, and the two directions perpendicular to the z-direction are set as the x-direction and y-direction, the coordinates of point P12 (x...) are used to determine the direction of movement. P12 y P12 z P12 ) and the coordinates (x) of point P7 P7 y P7 z P7 The vector v from point P12 to point P7 is calculated. Then, the direction of the calculated vector v, within ±30° around the z-axis and y-axis with point P7 or point P12 as the center, is set as the stamping direction in the main forming process. In addition, if the cam mold 162 is moved beyond the ±30° range around the z-axis and y-axis, the forming of the step portion 153a becomes difficult.

[0076] In this embodiment, the direction of movement of the cam mold 162 is defined as ±30° around the z-axis and y-axis, centered at point P7 or point P12, based on the calculated vector direction. However, the direction of movement of the cam mold 162 can also be defined as ±10° around the z-axis and y-axis, centered at point P5 or point P8.

[0077] The following explains the presence or absence of wrinkles and cracks. For example... Figure 8 As shown in (a), in the stamped part 200 produced by a single stamping process, material flows in from the top plate portion 201 toward the curved longitudinal wall portion 202. Additionally, material flows in while extending from the flange portion 204 toward the curved longitudinal wall portion 202. As a result, wrinkles are formed in region 203a of the boundary portion 203 between the top plate portion 201 and the curved longitudinal wall portion 202. Furthermore, cracks are formed in regions 205a and 205b of the boundary portion 205 between the flange portion 204 and the curved longitudinal wall portion 202.

[0078] In addition, such as Figure 8 As shown in (b), if the main forming process is performed without using a cam die after the preforming process, no wrinkles are generated at the boundary portion 253 between the top surface 251 and the curved longitudinal wall portion 252 in the formed stamped part 250. On the other hand, if the main forming process is performed without using a cam die, the material flows in while extending from the flange portion 254 towards the curved longitudinal wall portion 252. As a result, cracks are generated in region 255a of the boundary portion 255 of the flange portion 254.

[0079] In the main forming process of this embodiment, the stepped portion 153a of the preform 150 is stretched by a cam die. Furthermore, in forming using a cam die, material from the top plate portion 20 does not flow into the boundary portion 35 between the top plate portion 20 and the curved longitudinal wall portion 33. Additionally, material from the flange portion 40 does not flow into the boundary portion 36 between the curved longitudinal wall portion 33 and the flange portion 40. As a result, wrinkles at the boundary portion 35 and cracks at the boundary portion 36 can be suppressed.

[0080] In the above-described embodiment, as a method for manufacturing the stamped part 10, a pre-forming process of stamping the pre-formed part 150 and a main forming process of forming the stepped curved longitudinal wall portion 153 of the pre-formed part 150 using a cam die were described. However, the method for manufacturing the stamped part 10 is not limited to this. Figure 9 As shown, for example, the preforming process described above can be performed after the boundary portion 303 between the top plate portion 301 and the curved longitudinal wall portion 302 is pre-formed by stamping the blank 100. In this case, by pre-forming the boundary portion 303 between the top plate portion 301 and the curved longitudinal wall portion 302, during the preforming process described above, when forming the stepped curved longitudinal wall portion, it is possible to suppress the flow of material from the top plate portion 301 into the curved longitudinal wall portion. Therefore, it is possible to suppress the formation of wrinkles at the boundary portion between the top plate portion and the longitudinal wall portion.

[0081] Furthermore, when the curved longitudinal wall portion is formed after the boundary portion 303 between the top plate portion 301 and the curved longitudinal wall portion 302 is formed in advance, the curved longitudinal wall portion can be formed to a higher height compared to the case where the curved longitudinal wall portion is formed without forming the boundary portion 303 between the top plate portion 301 and the longitudinal wall portion.

[0082] <Summary of Results>

[0083] The method for manufacturing a stamped part of the present invention manufactures a stamped part 10 by stamping a blank 100 made of a metal sheet. The stamped part 10 includes: a top plate portion 20 having an outer peripheral portion including a curved portion; a longitudinal wall portion 30 continuous with the outer peripheral portion of the top plate portion 20; and a flange portion 40 continuous with the longitudinal wall portion 30. The method for manufacturing the stamped part is characterized in that a curved longitudinal wall portion 33 continuous with the curved portion is formed in the longitudinal wall portion 30. The process includes: a preforming process, which generates a lower longitudinal wall portion 153c extending from the step portion 153a, which is located at a predetermined position in the height direction of the curved longitudinal wall portion 33, to the flange portion 40, with the upper longitudinal wall portion 153b extending from the step portion 153a to the top plate portion 20, into a stepped curved longitudinal wall portion 153c extending toward the flange portion 40; and a main forming process, which uses a cam mold 162 to smooth the upper longitudinal wall portion 153b and the lower longitudinal wall portion 153c.

[0084] For example, such as Figure 10 As shown, in the case where the stamped part 400 is manufactured through a single forming process, at the ridge portion 401a between the top plate portion 402 and the curved longitudinal wall portion 401, the material of the top plate portion 402 leans against and moves towards the curved longitudinal wall portion 401. Figure 9 (in the H direction) stretching. Additionally, at the ridge portion 401b between the curved longitudinal wall portion 401 and the flange portion 403, the material of the flange portion 403 expands towards the curved longitudinal wall portion 401 (in the H direction). Figure 10 (In the I direction) stretching. Therefore, wrinkles are prone to form at the ridge portion 401a, and cracks are prone to form at the ridge portion 401b.

[0085] On the other hand, in the manufacturing method of the stamped part 10 of this embodiment, firstly, a preformed part 150 having a stepped curved longitudinal wall portion 153 is generated through a preforming process. At this time, the remaining portion, such as the material flowing into the curved longitudinal wall portion 153 from the top plate portion 151 side and the material flowing into the curved longitudinal wall portion 153 from the flange portion 152, is absorbed by the stepped portion 153a. In addition, during the main forming process, when forming the stepped curved longitudinal wall portion 153, the flow of material from the top plate portion 151 and the flange portion 152 into the curved longitudinal wall portion 153 is suppressed. As a result, wrinkles and cracks can be prevented from forming at the boundary portion 35 between the top plate portion 20 and the curved longitudinal wall portion 33, and at the boundary portion 36 between the flange portion 40 and the curved longitudinal wall portion 33.

[0086] Furthermore, when viewed from above, the curved longitudinal wall portion 153 is arc-shaped. In the main forming process, when viewed from above, the cam mold 162 abuts against the lower longitudinal wall portion 153c at an angle of 0 degrees or more and 75 degrees or less relative to the surface parallel to the upper surface of the top plate portion 20, along the straight line connecting the center point P1 and the midpoint P2 of the curved longitudinal wall portion 153, thereby forming the longitudinal wall portion 30.

[0087] For example, in the main forming process, when the cam mold 162 is oriented... Figure 11 In the case of movement in the J direction in (a), sometimes the cam mold 162 has difficulty in smoothly elongating the step portion 153a. In this case, for example, material from the top plate portion 151 flows into the curved longitudinal wall portion 153, causing wrinkles at the boundary between the top plate portion 151 and the curved longitudinal wall portion 153. Additionally, as... Figure 11 As shown in (b), when the cam mold 162 is directed towards Figure 11 When moving in the J direction in (b), the curved longitudinal wall portion 153 hooks onto the cam mold 162 after elongation, and the material of the flange portion 152 flows into the curved longitudinal wall portion 153. In this case, a crack is generated at the boundary between the curved longitudinal wall portion 153 and the flange portion 152.

[0088] On the other hand, in this embodiment, during the main forming process, the cam mold 162 moves towards... Figure 5 The cam mold 162 moves in direction C within (a). Figure 5 In (a), the movement in direction C prevents material from flowing from the top plate portion 151 to the curved longitudinal wall portion 153 and from the flange portion 152 to the curved longitudinal wall portion 153. This prevents wrinkles from forming at the boundary between the top plate portion 151 and the curved longitudinal wall portion 153, and prevents cracks from forming at the boundary between the flange portion 152 and the curved longitudinal wall portion 153.

[0089] In addition, the process of forming the longitudinal wall portion 30 includes a third forming process, which is performed before the preforming process and forms the boundary between the top plate portion 20 and the longitudinal wall portion 30 on the blank 100.

[0090] Therefore, in the third forming process, the blank 100 is stamped to form a boundary portion 303 between the top plate portion 301 and the longitudinal wall portion. When the boundary portion 303 formed in the third forming process is used to form the longitudinal wall portion through stamping, material flow from the top plate portion 301 into the longitudinal wall portion is suppressed. As a result, wrinkles at the boundary portion between the top plate portion 301 and the longitudinal wall portion can be suppressed.

[0091] Furthermore, when the longitudinal wall portion is formed by stamping, material flow from the top plate portion 301 into the longitudinal wall portion is suppressed. As a result, the height of the curved longitudinal wall portion 401 can be greater than the height of the curved longitudinal wall portion 401 when it is formed without forming a boundary portion 303 between the top plate portion 301 and the longitudinal wall portion.

[0092] [Explanation of reference numerals in the attached figures]

[0093] 10 Stamped parts

[0094] 20 Top Plate Section

[0095] 30 Longitudinal wall section

[0096] 33. Curved longitudinal wall section

[0097] 40 Flange portion

[0098] 100 billet

[0099] 150 preform

[0100] 153 Curved longitudinal wall section

[0101] 153a Step section

[0102] 153b Upper longitudinal wall section

[0103] 153c Lower longitudinal wall section

Claims

1. A method for manufacturing a stamped part, comprising manufacturing the stamped part by stamping a blank made of a metal sheet, the stamped part having: a top plate portion having an outer peripheral portion including a curved portion; a longitudinal wall portion continuous with the outer peripheral portion of the top plate portion; and a flange portion continuous with the longitudinal wall portion, characterized in that, The process of forming the curved longitudinal wall portion that is continuous with the curved portion includes: In the first forming process, a stepped curved longitudinal wall portion is formed, wherein the lower longitudinal wall portion of the curved longitudinal wall portion, from the step portion located at a predetermined position in the height direction of the curved longitudinal wall portion to the flange portion, extends toward the flange portion relative to the upper longitudinal wall portion from the step portion to the top plate portion; and In the second forming process, a mold with a cam structure is used to flatten the stepped curved longitudinal wall into a flat curved longitudinal wall.

2. The method for manufacturing a stamped part according to claim 1, characterized in that, In the top view of the stamped part, the bent portion is in the shape of an arc. In the second forming process, along the straight line connecting the center point of the curved portion in the top view of the stamped part and the midpoint of the curved portion, the mold having the cam structure abuts against the lower longitudinal wall portion at an angle of 0 degrees or more and 75 degrees or less relative to the surface parallel to the upper surface of the top plate portion, thereby making the stepped curved longitudinal wall portion flat.

3. The method for manufacturing a stamped part according to claim 1, characterized in that, The process of forming the curved longitudinal wall portion includes a third forming process, which is performed before the first forming process, and forms the boundary portion between the top plate portion and the curved longitudinal wall portion on the blank.

4. A stamped part, manufactured by the method for manufacturing a stamped part according to any one of claims 1 to 3.

5. A stamping forming method, wherein an intermediate formed part is stamped from a blank sheet by the relative movement of a die and a punch, characterized in that, The die includes: a top plate forming surface for forming the top plate portion of the intermediate formed part; a longitudinal wall forming surface for forming the longitudinal wall portion connected to the outer periphery of the top plate portion; and a flange forming surface for forming the flange portion connected to the longitudinal wall portion. The die-side longitudinal wall forming surface has a die-side step forming portion in the height direction of the longitudinal wall portion. The die-side step forming portion forms a step portion at a predetermined position of the curved longitudinal wall portion connected to the curved portion provided on the outer periphery of the top plate portion. The lower longitudinal wall portion extending from the predetermined position to the flange portion connected to the longitudinal wall portion extends towards the flange portion more than the upper longitudinal wall portion extending from the top plate portion to the predetermined position. The punch has: a punch-side flange forming surface that forms the flange portion of the intermediate forming part; and a punch-side longitudinal wall forming surface that has a punch-side step forming portion, wherein during relative movement between the punch and the die, the punch-side step forming portion forms the step portion of the curved longitudinal wall portion between itself and the die-side longitudinal wall forming surface. Through the relative movement of the die and the punch, the blank plate is bent and shaped by the top plate forming surface and the side longitudinal wall forming surface of the die to form the top plate portion. Then, the blank plate is clamped by the die-side step forming portion and the punch-side step forming portion to form a curved longitudinal wall portion having the step portion. The blank plate is bent and shaped by the forming face of the die side flange and the forming face of the die side longitudinal wall to form the flange portion.

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