Method for manufacturing press-molded article

Abstract

This press-molded article manufacturing method manufactures a press-molded article (100) having a target shape having a top plate portion (101) and a vertical wall portion (105) continuous from the top plate portion (101) via a ridge line portion (103), and in a cross-section orthogonal to the ridge line portion, a recessed stepped portion (109) is formed in the top plate portion (101) along the direction in which the ridge line portion (103) extends. The method for manufacturing a press-molded article includes: a first molding step in which a slab (110) is press-molded into an intermediate molded article (120) having an intermediate top plate section (121) and intermediate vertical wall sections (125) continuous from the intermediate top plate section (121) via intermediate ridge sections (123); and a second molding step for forming a concave step section (109) on the intermediate top plate section (121) of the intermediate molded article (120) to press-mold a press-molded article (100) having a target shape.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a stamping formed part, which has a top plate portion and a longitudinal wall portion continuous from the top plate portion via a ridge line portion, and a stepped portion with a concave shape or a convex shape is formed in the top plate portion along the direction in which the ridge line portion extends. Background Art

[0002] Due to the increasingly strict automotive collision safety standards, in the process of gradually improving the vehicle body collision safety, restricted by current carbon dioxide emissions, it is necessary to lighten the vehicle body. Therefore, in order to balance the improvement of the vehicle body collision safety performance and the lightening of the vehicle body, metal plates with higher strength than before are gradually adopted in the vehicle body. Recently, attempts have been made to apply ultra-high tensile steel plates with a tensile strength of 1.5 GPa or more.

[0003] The stress generated when such a metal plate is stamped and formed becomes larger, and large springback occurs during demolding after stamping and forming, and it is easy to deviate from the target shape. Especially for a stamping formed part having a top plate portion and a longitudinal wall portion continuous from the top plate portion via a ridge line portion, springback occurs where the inner angle formed by the top plate portion and the longitudinal wall portion opens.

[0004] Thus, several techniques for reducing the springback where the inner angle formed by the top plate portion and the longitudinal wall portion opens have been proposed so far. For example, Patent Document 1 discloses a method of expanding the width of the punch in the final stamping after the second time when stamping and forming into a predetermined product size through two or more stamping and forming processes, compared with the first time.

[0005] And Patent Document 2 discloses the following stamping and forming method: with the punch side blank holder protruding outward compared with the pressing surface of the punch, the die side blank holder is pressed against the work material and stamping and forming is performed, and the punch side blank holder is at the same height as the pressing surface of the punch at the forming bottom dead center.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Laid-Open No. 2007-111725

[0009] Patent Document 2: Japanese Patent Laid-Open No. 2010-082660 Summary of the Invention

[0010] Technical Problem to be Solved by the Invention

[0011] As Figure 12In a stamping part 100 having a concave stepped part 109 formed in a top plate part 101 as shown in an example, springback occurs such that an inner angle formed by the top plate part 101 and a vertical wall part 105 opens during demolding. Therefore, the method disclosed in Patent Document 1 or Patent Document 2 is applied to the stamping part 100.

[0012] However, in the method of Patent Document 1, at the part where the vertical wall part 105 (wall part) and the top plate part 101 (bottom part) are first bent and formed, due to the final forming after the second time, the bending is restored. Due to this bending restoration, springback occurs that closes the inner angle between the vertical wall part 105 and the top plate part 101. As a result, the springback that opens the inner angle of the ridge line part can be suppressed by the final forming after the second time. However, the bending angle between the vertical wall part 105 and the top plate part 101 in the first time is larger than the bending angle of the ridge line part in the final forming after the second time. From this, it can be known that compared with the springback in which the inner angle opens due to the final forming after the second time, the springback in which the inner angle closes due to the bending restoration is small, and the springback after forming cannot be sufficiently suppressed.

[0013] Moreover, in the method disclosed in Patent Document 2, when the sectional line length of the workpiece is much longer than the target shape, breakage occurs at the punch shoulder (corresponding to Figure 12 the ridge line part 103 of the stamping part 10). And when the sectional line length of the stamping part 100 is shorter than the target shape, the angle of the ridge line part 103 will not become the target shape.

[0014] Therefore, in the methods disclosed in Patent Document 1 and Patent Document 2, there is a problem that the springback cannot be sufficiently reduced, which affects the appearance of the target shape.

[0015] The present invention is made in view of the above technical problems, and its object is to provide a method for manufacturing a stamping part, which can manufacture a stamping part with a target shape having a concave or convex stepped part formed in the top plate part without affecting the appearance and reducing the springback.

[0016] Technical solution for solving the technical problem

[0017] In order to solve the above technical problems and achieve the above object,

[0018] (1) The method for manufacturing a stamping part of the present invention is a method for manufacturing a stamping part having the following target shape. The target shape of the stamping part has a top plate part and a vertical wall part continuous from the top plate part via a ridge line part. Along the direction in which the ridge line part extends, in a section orthogonal to the ridge line part, a concave or convex stepped part is formed in the top plate part. The method is characterized by including the following steps:

[0019] The slab is stamped into an intermediate formed part having an intermediate top plate part and an intermediate longitudinal wall part continuous from the intermediate top plate part via an intermediate ridge line part, and a bending deformation is imparted to the intermediate ridge line part;

[0020] Next, a stepped part having the concave shape or the convex shape is formed in the intermediate top plate part of the intermediate formed part, and the intermediate formed part is stamped into the stamped formed part having the target shape;

[0021] When forming the stepped part having the concave shape or the convex shape, a bending recovery deformation is imparted to the intermediate ridge line part by pulling the intermediate ridge line part to the intermediate top plate part side.

[0022] (2) The manufacturing method of the stamped formed part of the present invention In the invention of the above (1), it includes a first forming process and a second forming process,

[0023] In the first forming process, the slab is stamped into the intermediate formed part having the intermediate top plate part and the intermediate longitudinal wall part continuous from the intermediate top plate part via the intermediate ridge line part, and a bending deformation is imparted to the intermediate ridge line part;

[0024] In the second forming process, a stepped part having the concave shape or the convex shape is formed in the intermediate top plate part of the intermediate formed part, and the intermediate formed part is stamped into the stamped formed part having the target shape,

[0025] In the second forming process, when forming the stepped part having the concave shape or the convex shape, a bending recovery deformation is imparted to the intermediate ridge line part by pulling the intermediate ridge line part to the intermediate top plate part side.

[0026] (3) The manufacturing method of the stamped formed part of the present invention In the invention of the above (2), in the first forming process, a low stepped part having a stepped height lower than the target shape is formed in the intermediate top plate part,

[0027] In the second forming process, the stepped part is formed by making the low stepped part have the stepped height of the target shape.

[0028] (4) The manufacturing method of the stamped formed part of the present invention In the invention of the above (1), the following processes are performed in one process:

[0029] The slab is stamped into the intermediate formed part, and then, a stepped part having the concave shape or the convex shape is formed in the intermediate top plate part of the intermediate formed part, and the intermediate formed part is stamped into the stamped formed part having the target shape.

[0030] (5) The manufacturing method of the stamped formed part of the present invention includes a stamping process and a dividing process,

[0031] The stamping process stamps the following stamping part by using the manufacturing method of the stamping part of any one of the above inventions 1 to 4. The stamping part includes the top plate part and a pair of longitudinal wall parts that are continuous from both edges of the top plate part via the ridge line part. A step part is formed on the top plate part.

[0032] The dividing process divides the stamping part by cutting the top plate part of the stamping part stamped in the stamping process along the extending direction of the ridge line part.

[0033] Effects of the Invention

[0034] According to the present invention, it is possible to manufacture a stamping part with the following target shape that sufficiently reduces springback without affecting the appearance. The stamping part with the target shape has a top plate part and longitudinal wall parts that are continuous from the top plate part via ridge line parts. Along the extending direction of the ridge line part, in a cross-section orthogonal to the ridge line part, a concave or convex step part is formed on the top plate part. In addition, in the present invention, the top plate part is cut along the extending direction of the ridge line part to divide the stamping part including the top plate part on which a concave or convex step part is formed and a pair of longitudinal wall parts that are continuous from both edges thereof via the ridge line parts. Thus, two stamping parts with a Z-shaped cross-section or an L-shaped cross-section with reduced springback can be obtained from a stamping part with a hat-shaped cross-section or a C-shaped cross-section manufactured by one-time stamping. Therefore, it is preferable because the production cost can be reduced. Description of the Drawings

[0035] Figure 1 FIG. is a diagram for explaining the first forming process of forming an intermediate formed part and the second forming process of forming a stamping part with a target shape in the manufacturing method of the stamping part according to the first embodiment of the present invention ((a) the first forming process, (b) the second forming process).

[0036] Figure 2 FIG. is a cross-sectional view in a direction orthogonal to the ridge line part showing the forming process of the intermediate formed part in the first forming process and the forming process of the stamping part with the target shape in the second forming process in the manufacturing method of the stamping part according to the first embodiment of the present invention ((a) the first forming process, (b) the second forming process).

[0037] Figure 3 FIG. is a diagram for explaining a conventional forming process of stamping a stamping part with a target shape having a concave step part formed on the top plate part in one process.

[0038] Figure 4 FIG. is a cross-sectional view in a direction orthogonal to the ridge line part for explaining a conventional method of stamping a stamping part with a target shape having a concave step part formed on the top plate part in one process.

[0039] Figure 5 It is a contour map showing the stress distribution at the forming bottom dead center of a stamping formed part formed by a conventional method, and a cross-sectional view in a direction orthogonal to the ridge line part of the stamping formed part after demolding and springback ((a) stress distribution, (b) cross-section of the stamping formed part at the forming bottom dead center and after springback).

[0040] Figure 6 It is a contour map showing the stress distribution at the forming bottom dead center of a stamping formed part with a target shape obtained by stamping a middle formed part formed by a first forming process through a second forming process in the manufacturing method of the stamping formed part according to the first embodiment of the present invention, and a cross-sectional view in a direction orthogonal to the ridge line part of the stamping formed part after demolding and springback ((a) stress distribution, (b) cross-section of the stamping formed part at the forming bottom dead center and after springback).

[0041] Figure 7 It is a diagram for explaining the mechanism by which springback is suppressed in a stamping formed part having a stepped part formed in the top plate part in the first and second embodiments of the present invention ((a) before the stepped part is formed, (b) after the stepped part is formed).

[0042] Figure 8 It is a diagram for stamping a stamping formed part with a target shape in one process in the manufacturing method of the stamping formed part according to the second embodiment of the present invention.

[0043] Figure 9 It is a cross-sectional view in a direction orthogonal to the ridge line part for explaining the process of stamping a stamping formed part with a target shape in one process in the manufacturing method of the stamping formed part according to the second embodiment of the present invention.

[0044] Figure 10 It is a contour map showing the stress distribution at the forming bottom dead center of a stamping formed part with a target shape stamped in one process in the manufacturing method of the stamping formed part according to the second embodiment of the present invention, and a cross-sectional view in a direction orthogonal to the ridge line part of the stamping formed part at the forming bottom dead center and after demolding and springback ((a) stress distribution, (b) cross-section of the stamping formed part at the forming bottom dead center and after springback).

[0045] Figure 11 It is a diagram showing the dimensions of a stamping formed part having a hat-shaped cross-sectional shape to be formed in the example.

[0046] Figure 12 It is a diagram of a stamping formed part having a concave shape and a stepped part formed in the top plate part as an example of the stamping formed part targeted in the present invention. Detailed implementation mode

[0047] Before describing the manufacturing methods of the stamping parts in Embodiments 1 and 2 of the present invention, the stamping parts targeted in the present invention and the process of obtaining the present invention will be described.

[0048] <Stamping part>

[0049] Figure 12 An example of the stamping part 100 targeted in the present invention is shown. The stamping part 100 has a hat-shaped cross-sectional shape with a top plate portion 101, a longitudinal wall portion 105 continuous from the top plate portion 101 via a ridge line portion 103, and a flange portion 107 continuous from the longitudinal wall portion 105. Moreover, for the stamping part 100, in a cross-section orthogonal to the ridge line portion, a concave stepped portion 109 is formed in the top plate portion 101 along the extending direction of the ridge line portion 103. Here, the stepped portion 109 is formed covering the entire length in the extending direction of the ridge line portion 103.

[0050] <Process of obtaining the present invention>

[0051] Figure 3 An example of the method of stamping a blank 110 into a stamping part 100 ( Figure 12 ) by a die 30 is shown. The process of stamping the stamping part 100 in a single step in the past will be described based on the cross-sectional view in the direction orthogonal to the ridge line portion shown in Figure 4 . First, a concave stepped portion 109 ( Figure 4 (i)) is formed in the portion corresponding to the top plate portion 101 in the blank 110 ( Figure 4 (ii)), which is a metal plate.

[0052] Next, simultaneously with the formation of the stepped portion 109, both edge sides of the blank 110 are formed into the longitudinal wall portion 105 and the flange portion 107 ( Figure 4 (iii) to Figure 4 (v)).

[0053] In Figure 5 , the process of stamping the stamping part 100 in a single step in the past is analyzed by the finite element method (FEM), and the result of the stress distribution at the forming bottom dead center is obtained. Figure 5 (a) is a contour map showing the stress distribution on the outer side in the plate thickness direction in the three-dimensional view of the stamping part 100 with the target shape, Figure 5 (b) is a cross-sectional view in the direction orthogonal to the ridge line portion of the stamping part 100 showing the overlap of the forming bottom dead center and the part after demolding and springback. Figure 5 (a) shows the stress in the direction orthogonal to the extending direction of the ridge line portion 103.

[0054] As Figure 5As shown in (a), a large tensile stress in the direction orthogonal to the ridge line portion 103 is generated on the outer side in the plate thickness direction in the ridge line portion 103 and its vicinity between the top plate portion 101 and the longitudinal wall portion 105. As a result, as shown in Figure 5 (b), springback occurs when demolding after stamping, and the inner angle between the top plate portion 101 and the longitudinal wall portion 105 of the stamped part 100 becomes larger than the inner angle of the target shape.

[0055] Then, the inventor carefully studied a method for reducing such springback in the stamped part 100. As a result, by changing the stamping sequence, after forming the ridge line portion 103, a stepped portion 109 is formed in the top plate portion 101. Thus, it is conceived to pull the ridge line portion 103 toward the top plate portion 101 side, causing bending recovery in this part and generating a stress that cancels out the stress of the ridge line portion 103 of the target shape. The present invention is an invention based on this concept and will be specifically described in the following embodiments.

[0056] [Embodiment 1]

[0057] The manufacturing method of the stamped part according to Embodiment 1 of the present invention is a manufacturing method for manufacturing the stamped part 100 shown as an example in Figure 12 . Moreover, as shown in Figure 1 , the manufacturing method of the stamped part according to Embodiment 1 includes a first forming process and a second forming process. Hereinafter, the first forming process and the second forming process will be described separately.

[0058] <First forming process>

[0059] As shown in Figure 1 (a) and Figure 2 (a), in the first forming process, the blank 110 is stamped into an intermediate formed part 120 by the first die 10. Here, the intermediate formed part 120 has a hat-shaped cross-sectional shape with an intermediate top plate portion 121, an intermediate ridge line portion 123, an intermediate longitudinal wall portion 125, and an intermediate flange portion 127. Moreover, the intermediate formed part 120 is the shape before the stepped portion 109 ( Figure 2 (b)) is formed in the intermediate top plate portion 121.

[0060] <Second forming process>

[0061] As shown in Figure 1 (b) and Figure 2 (b), the second forming process is a process of stamping the stamped part 100 of the target shape by forming the stepped portion 109 in the intermediate top plate portion 121 of the intermediate formed part 120 using the second die 20. Moreover, in the second forming process, by pulling the part that is the intermediate ridge line portion 123 in the intermediate formed part 120 toward the top plate portion 101 side when forming the stepped portion 109, bending recovery is generated in this part.

[0062] It should be noted that in the second forming process, all or a part of the portion of the intermediate forming member 120 that serves as the intermediate ridge line portion 123 can be pulled into the side of the top plate portion 101.

[0063] <Reason for springback reduction>

[0064] Hereinafter, the reason for the reduction of springback in the stamping formed part 100 manufactured by the manufacturing method of the stamping formed part of the first embodiment will be described.

[0065] For the first forming process and the second forming process of the first embodiment, the stamping forming process is analyzed by the finite element method (FEM). In Figure 6 It shows the stress distribution at the bottom dead center of forming in the second forming process. Figure 6 (a) is a contour map showing the stress distribution on the outer side in the plate thickness direction in the three-dimensional view of the stamping formed part 100 with the target shape, Figure 6 (b) is a cross-sectional view showing the stamping formed part 100 after overlapping the bottom dead center of forming and springback after demolding in the direction orthogonal to the ridge line portion. Figure 6 (a) shows the stress in the direction orthogonal to the direction in which the ridge line portion 103 extends.

[0066] As Figure 6 As shown in (a), it can be seen that on the outer side in the plate thickness direction of the ridge line portion 103, tensile stress is generated in the direction orthogonal to the ridge line portion, and compressive stress is generated on the side of the top plate portion 101 on the outer side in the plate thickness direction near the ridge line portion 103. Here, the tensile stress generated in the ridge line portion 103 and the compressive stress generated in the top plate portion 101 cancel each other out. As a result, even if the stamping formed part 100 with the target shape is demolded, no springback will occur. As a result, as Figure 6 As shown in (b), the inner angle between the top plate portion 101 and the longitudinal wall portion 105 of the demolded stamping formed part 100 is substantially the same as the inner angle at the bottom dead center of forming.

[0067] Based on Figure 7 The method of the first embodiment will be described in detail.

[0068] In the first forming process, as in the cross-section in the direction orthogonal to the ridge line portion shown in Figure 7 (a), in the intermediate ridge line portion 123, tensile stress due to bending is generated on the outer side in the plate thickness direction, and compressive stress is generated on the inner side in the plate thickness direction. In the subsequent second forming process, as in Figure 7As in the cross-section in the direction orthogonal to the ridge line portion shown in (b), when forming the stepped portion 109 on the intermediate top plate portion 121, the portion that becomes the intermediate ridge line portion 123 is pulled from the intermediate longitudinal wall portion 125 side toward the intermediate top plate portion 121 side into the intermediate top plate portion 121. As a result, in the portion of the top plate portion 101 of the press-formed part 100 that becomes the intermediate ridge line portion 123, a compressive stress due to bending recovery is generated on the outer side in the plate thickness direction, and a tensile stress is generated on the inner side in the plate thickness direction.

[0069] As a result, the tensile stress on the outer side in the plate thickness direction of the ridge line portion 103 is offset by the compressive stress on the outer side in the plate thickness direction of the intermediate ridge line portion 123 that is bent and recovered in the top plate portion 101 ( Figure 7 (b)). In addition, the compressive stress on the inner side in the plate thickness direction of the ridge line portion 103 is offset by the tensile stress on the inner side in the plate thickness direction of the intermediate ridge line portion 123 that is bent and recovered in the top plate portion 101 ( Figure 7 (b)). In this way, in the press-formed part 100 of the target shape after demolding, the stress acting on the ridge line portion 103 is offset by the stress generated due to the formation of the stepped portion 109, so the springback is sufficiently reduced.

[0070] As described above, according to the manufacturing method of the press-formed part of the first embodiment, compared with Patent Document 1, in the press-formed part 100 having the concave-shaped stepped portion 109 formed therein, it is possible to sufficiently reduce the springback such as the opening of the inner angle between the top plate portion 101 and the longitudinal wall portion 105.

[0071] And, like the method disclosed in Patent Document 2, in the manufacturing method of the press-formed part of the first embodiment, since the sectional line length of the intermediate formed part 120 does not become too long compared with the target shape, breakage does not occur in the ridge line portion 103. And since the sectional line length of the intermediate formed part 120 does not become too short compared with the target shape, the angle of the ridge line portion 103 can be set to the target shape.

[0072] It should be noted that, as another form of the first embodiment, in the first forming process, a low stepped portion having a stepped height lower than the target shape may be formed on the intermediate top plate portion 121. In this case, in the subsequent second forming process, by setting the low stepped portion formed by the first forming process to the stepped height of the target shape, the stepped portion 109 can be formed while suppressing springback.

[0073] [Second Embodiment]

[0074] Regarding the manufacturing method of the press-formed part of the second embodiment, based on Figure 9 the cross-sectional view in the direction orthogonal to the ridge line portion shown, the process of press-forming the press-formed part 100 of the target shape having the stepped portion 109 formed on the top plate portion 101 in one process (seeFigure 8 is described as follows.

[0075] First, the blank 110 is clamped between the blank holder 59 and the punch 57 of the die 50 ( Figure 9 (i)). Next, the two edge sides of the blank 110 are clamped by the die plate 61 (cam) for compression bending ( Figure 9 (ii)).

[0076] Then, following the formation of the ridge line portion 103, the longitudinal wall portion 105 and the flange portion 107 are formed, and a stepped portion 109 is formed on the top plate portion 101 ( Figure 9 (iii) to Figure 9 (iv)).

[0077] In the second embodiment, the finite element method (FEM) is used to analyze the process of stamping a stamping part 100 with a target shape in one process, and the stress distribution at the forming bottom dead center is as Figure 10 shown.

[0078] Figure 10 (a) is a contour map showing the stress distribution on the outer side in the plate thickness direction in the three-dimensional view of the stamping part 100, Figure 10 (b) is a cross-sectional view in the direction orthogonal to the ridge line portion during the stamping process. Figure 10 (a) shows the stress in the direction orthogonal to the extending direction of the ridge line portion 103. As Figure 10 shown in (a), tensile stress is generated on the outer side in the plate thickness direction of the ridge line portion 103 and its vicinity, and compressive stress is generated on the adjacent top plate portion 101 side. As a result, as Figure 10 shown in (b), these stresses cancel each other out and springback does not occur, and the inner angle between the top plate portion 101 and the longitudinal wall portion 105 of the stamping part 100 is substantially the same as the inner angle at the forming bottom dead center.

[0079] The reason for the reduction in springback is the same as that described above Figure 7 . That is, as Figure 7 shown in (a), during the stamping process before the formation of the stepped portion 109, tensile stress due to bending is generated on the outer side in the plate thickness direction, and compressive stress is generated on the inner side in the plate thickness direction. After that, when the stepped portion 109 is formed near the forming bottom dead center, it is pulled from the ridge line portion 103 toward the top plate portion 101. As a result, as Figure 7 shown in (b), compressive stress due to bending recovery is generated on the outer side in the plate thickness direction, and tensile stress is generated on the inner side in the plate thickness direction.

[0080] As a result, the tensile stress on the outer side in the plate thickness direction of the ridge line portion 103 is offset by the compressive stress on the outer side in the plate thickness direction of the ridge line portion 103 recovered by bending in the top plate portion 101 ( Figure 7(b) Cancellation. Additionally, the compressive stress inside the ridge line portion 103 in the plate thickness direction ( Figure 7 (a)) is cancelled by the tensile stress inside the ridge line portion 103 in the plate thickness direction that is restored by the bending of the top plate portion 101 ( Figure 7 (b)). As a result, in the stamped part 100 of the target shape after demolding, springback is sufficiently reduced.

[0081] As described above, according to the method for manufacturing a stamped part of the second embodiment, in the stamped part 100 formed with the concave-shaped stepped portion 109, the springback of the inner angle opening between the top plate portion 101 and the longitudinal wall portion 105 can be sufficiently reduced. Additionally, similar to the aforementioned first embodiment, the method for manufacturing a stamped part of the second embodiment does not cause poor appearance of the stamped part 100 of the target shape.

[0082] It should be noted that in the second embodiment above, the stepped portion 109 may be formed immediately before the molding of the ridge line portion 103 is completed, or the stepped portion 109 may be formed after the molding of the ridge line portion 103 is completed.

[0083] Moreover, in the present invention, the step height (depth to the bottom surface of the stepped portion) of the concave-shaped stepped portion formed on the top plate portion is preferably set within the range of 1 / 5 to 2 times the sectional length in the direction orthogonal to the ridge line portion. Here, the sectional length in the direction orthogonal to the ridge line portion refers to the length from the bending start portion of the ridge line portion in the top plate portion to the bending stop portion in the longitudinal wall portion.

[0084] If the step height of the stepped portion is less than 1 / 5 of the sectional length in the direction orthogonal to the ridge line portion, it is too small, and the amount of bending recovery by pulling the longitudinal wall portion when forming the stepped portion becomes less, and the expansion of the inner angle between the top plate portion and the longitudinal wall portion due to springback after demolding cannot be sufficiently cancelled. On the other hand, if the step height of the stepped portion exceeds 2 times the sectional length in the direction orthogonal to the ridge line portion, it is too large, and when forming the stepped portion, the amount of pulling the longitudinal wall portion 105 is too large, causing the longitudinal wall portion to be drawn and formed with warping, and it is difficult to become the target shape.

[0085] Moreover, both the first and second embodiments target a stamped part formed with a stepped portion that is recessed in the stamping direction. However, the present invention can also target a stamped part in which a convex-shaped stepped portion extends along the direction of the ridge line portion in a cross section orthogonal to the ridge line portion and is formed on the top plate portion.

[0086] Even in a stamped part having a stepped portion with a convex shape, the stepped portion with a convex shape may be formed in the same manner as in the first or second embodiment. In this case, when the stepped portion with a convex shape is formed, the material is also drawn from the longitudinal wall portion toward the top plate portion side. At this time, bending recovery occurs at the portion serving as the intermediate ridge line portion. As a result, in the stamped part having the target shape after demolding, the springback of the inner angle between the top plate portion and the longitudinal wall portion expanding can be sufficiently reduced.

[0087] It should be noted that the present invention is not limited to the stamped part having a hat-shaped cross-sectional shape, and the springback of the inner angle formed between the top plate portion and the longitudinal wall portion can also be reduced in the stamped parts having a C-shaped cross-sectional shape, a Z-shaped cross-sectional shape, and an L-shaped cross-sectional shape.

[0088] Moreover, a stamped part having a Z-shaped cross-sectional shape with a top plate portion, a longitudinal wall portion, and a flange portion can be manufactured through a stamping process and a splitting process as follows.

[0089] The stamping process is a process of stamping the hat-shaped cross-sectional stamped part 100 shown in Figure 12 by the method of the first or second embodiment described above. The splitting process is a process of cutting the top plate portion of the stamped part 100 after stamping along the direction in which the ridge line portion extends to split the stamped part 100. Thus, two stamped parts having a Z-shaped cross-sectional shape can be obtained.

[0090] In the hat-shaped cross-sectional stamped part stamped by the stamping process, as described above, the springback can be reduced. Therefore, in the subsequent splitting process, the springback of the stamped part having a Z-shaped cross-sectional shape formed by splitting the hat-shaped cross-sectional stamped part can be sufficiently reduced. In this way, two stamped parts having a Z-shaped cross-sectional shape with reduced springback can be obtained from the hat-shaped cross-sectional stamped part manufactured by one-time stamping, so the production cost can be reduced, which is thus preferable.

[0091] In the stamped part having an L-shaped cross-sectional shape, the stamped part having a C-shaped cross-sectional shape is stamped, and the top plate portion is cut by the subsequent splitting process to be split into two stamped parts having an L-shaped cross-sectional shape.

[0092] Examples

[0093] Since the effects of the present invention have been verified, the following will describe them. Stamped parts having a hat-shaped cross-sectional shape, a C-shaped cross-sectional shape, a Z-shaped cross-sectional shape, and an L-shaped cross-sectional shape were manufactured using steel plates with a thickness of 1.0 mm and a tensile strength of 1470 MPa grade or 980 MPa grade.

[0094] Regarding the dimensions of the target shape of the hat-shaped cross-sectional stamped part 100, asFigure 11 As shown, the length is set to 50 mm, the width of the top plate portion 101 is set to 150 mm, the longitudinal wall height of the longitudinal wall portion 105 is set to 55 mm, the inner angle between the longitudinal wall portion and the top plate portion is set to 95°, and the bending radii of the ridge line portion 103 and the step portion 109 are set to R4 mm on the bending inner side respectively. In addition, the width of the step portion 109 is set to 80 mm, and the step height is set to 9 mm (1.4 times the cross-sectional length in the direction orthogonal to the ridge line portion). And the step height of the step portion in the shallow concave shape and shallow convex shape (hereinafter referred to as the low step portion) is set to 5 mm.

[0095] The stamping part with a U-shaped cross-sectional shape is obtained by removing the flange portion 107 from the Figure 11 stamping part 100 with a cap-shaped cross-sectional shape shown, and the dimensions of each part are the same as those of the Figure 11 stamping part 100 shown.

[0096] The stamping part with a Z-shaped cross-sectional shape is obtained by removing one longitudinal wall portion 105 and the flange portion 107 from the Figure 11 stamping part 100 with a cap-shaped cross-sectional shape shown. Moreover, the widths of the top plate portion and the step portion are set to half, i.e., 75 mm and 40 mm respectively, and the dimensions of other parts are the same as those of the stamping part 100.

[0097] The stamping part with an L-shaped cross-sectional shape is obtained by removing one longitudinal wall portion 105 and two flange portions 107 from the Figure 11 stamping part 100 with a cap-shaped cross-sectional shape shown, and the widths of the top plate portion and the step portion are set to half respectively, and the dimensions of other parts are the same as those of the stamping part 100.

[0098] In the embodiment, the product obtained by stamping through the methods described in the foregoing Embodiment 1 and Embodiment 2 is taken as the inventive example. In the inventive example, in the foregoing target shape, the shape of the step portion formed on the top plate portion, the number of processes, and the timing of forming the step portion on the top plate portion are changed. It should be noted that for the number of processes of the stamping part, it is set to two processes as the method of the foregoing Embodiment 1 and one process as the method of the foregoing Embodiment 2.

[0099] Then, the inner angle between the top plate portion and the longitudinal wall portion after demolding and springback of the stamping part of the target shape is measured, and the evaluation is made based on the springback amount. In addition, the product obtained by stamping a stamping product with a concave or convex step portion formed on the top plate portion in one process by the Figure 3 conventional method shown is taken as the conventional example. For the conventional example, the inner angle between the top plate portion and the longitudinal wall portion after demolding and springback of the stamping part of the target shape is measured in the same way as in the inventive example. The results of the inventive example and the conventional example are shown together in Table 1.

[0100] [Table 1]

[0101]

[0102] In Table 1, for No.1 to No.26, a steel plate with a tensile strength of 1470 MPa is used as the slab. For No.1 to No.4, a stamping part 100 with a cap-shaped cross-sectional shape having a concave stepped portion 109 formed in the top plate portion 101 ( Figure 11 ) is stamped.

[0103] No.1 is a product formed by stamping in a single process in the past, with a concave stepped portion 109 formed from the initial stage of forming. The inner angle between the top plate portion 101 and the longitudinal wall portion 105 in No.1 is 111 degrees, and significant springback occurs.

[0104] No.2 is a product of the present invention formed by stamping in a single process, with a concave stepped portion 109 formed near the bottom dead center of forming. The inner angle between the top plate portion 101 and the longitudinal wall portion 105 in No.2 is 102 degrees, and the springback is reduced compared to No.1 of the prior example and is good.

[0105] No.3 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, with a concave stepped portion 109 formed in the second forming process. The inner angle between the top plate portion 101 and the longitudinal wall portion 105 in No.3 is 100 degrees, and the springback is reduced compared to No.1 of the prior example and No.2 of the invention example and is good.

[0106] No.4 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, with a shallow concave and low stepped portion formed in the first forming process and the target stepped height in the second forming process. The inner angle between the top plate portion 101 and the longitudinal wall portion 105 in No.4 is 101 degrees, and the springback is reduced compared to No.1 of the prior example and is good.

[0107] In Table 1, for No.5 to No.8, products are formed by stamping a stamping part (not shown) with a C-shaped cross-sectional shape having a concave stepped portion formed in the top plate portion.

[0108] No.5 is a product formed by stamping in a single process in the past, with a concave stepped portion formed from the initial stage of forming. The inner angle between the top plate portion and the longitudinal wall portion in No.5 is 108 degrees, and significant springback occurs.

[0109] No.6 is a product of the present invention formed by stamping in a single process, with a concave stepped portion formed near the bottom dead center of forming. The inner angle between the top plate portion and the longitudinal wall portion in No.6 is 98 degrees, and the springback is reduced compared to No.5 of the prior example and is good.

[0110] No. 7 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, and having a stepped portion with a concave shape formed in the second forming process. The inner angle between the top plate portion 101 and the vertical wall portion 105 in No. 7 is 98 degrees, and the springback is reduced and good compared with No. 5 of the prior example, similarly to No. 6 of the inventive example.

[0111] No. 8 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, having a low stepped portion with a shallow concave shape formed in the first forming process and a stepped height of the target shape in the second forming process. The inner angle between the top plate portion and the vertical wall portion in No. 8 is 99 degrees, and the springback is reduced and good compared with No. 5 of the prior example.

[0112] In Table 1, No. 9 to No. 12 are products obtained by stamping a stamped part (not shown) having a cap-shaped cross-sectional shape with a convex stepped portion formed on the top plate portion.

[0113] No. 9 is a product of the prior art formed by stamping in one process and having a convex stepped portion formed from the initial stage of forming. The inner angle between the top plate portion and the vertical wall portion in No. 9 is 115 degrees, and significant springback occurs.

[0114] No. 10 is a product of the present invention formed by stamping in one process and having a convex stepped portion formed near the bottom dead center of forming. The inner angle between the top plate portion and the vertical wall portion in No. 10 is 101 degrees, and the springback is reduced and good compared with No. 9 of the prior example.

[0115] No. 11 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, and having a convex stepped portion formed in the second forming process. The inner angle between the top plate portion 101 and the vertical wall portion 105 in No. 11 is 101 degrees, and the springback is reduced and good compared with No. 9 of the prior example, similarly to No. 10.

[0116] No. 12 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, having a low convex stepped portion with a low stepped portion formed in the first forming process and a stepped height of the target shape in the second forming process. The inner angle between the top plate portion and the vertical wall portion in No. 12 is 104 degrees, and the springback is reduced and good compared with No. 9 of the prior example.

[0117] In Table 1, No. 13 to No. 16 are products obtained by stamping a stamped part (not shown) having a C-shaped cross-sectional shape with a convex stepped portion formed on the top plate portion.

[0118] No. 13 is a product formed by stamping in a single process in the past, with a stepped portion having a convex shape formed from the initial stage of forming. The inner angle between the top plate portion and the vertical wall portion in No. 13 is 113 degrees, and significant springback occurs.

[0119] No. 14 is a product of the present invention formed by stamping in a single process, with a stepped portion having a convex shape formed near the bottom dead center of forming. The inner angle between the top plate portion and the vertical wall portion in No. 14 is 101 degrees, and the springback is reduced compared to No. 13 of the conventional example and is good.

[0120] No. 15 is a product of the present invention formed by stamping in two processes, namely the first forming process and the second forming process, with a stepped portion having a convex shape formed in the second forming process. The inner angle between the top plate portion and the vertical wall portion in No. 15 is 101 degrees, and like No. 14 of the invention example, the springback is reduced compared to No. 13 of the conventional example and is good.

[0121] No. 16 is a product of the present invention formed by stamping in two processes, namely the first forming process and the second forming process, with a low stepped portion having a convex shape formed in the first forming process and the stepped height of the target shape formed in the second forming process. The inner angle between the top plate portion and the vertical wall portion in No. 16 is 101 degrees, and like No. 14 and No. 15 of the invention example, the springback is reduced compared to No. 13 of the conventional example and is good.

[0122] In Table 1, No. 17 to No. 21 are products obtained by stamping a stamping formed part (not shown) having a Z-shaped cross-sectional shape.

[0123] No. 17 is a product formed by stamping in a single process without forming a stepped portion on the top plate portion in the past. The inner angle between the top plate portion and the vertical wall portion in No. 17 is 113 degrees, and significant springback occurs.

[0124] No. 18 is a product of the present invention formed by stamping in a single process, with a stepped portion having a concave shape formed on the top plate portion near the bottom dead center of forming. The inner angle between the top plate portion and the vertical wall portion in No. 18 is 102 degrees, and the springback is reduced compared to No. 17 of the conventional example and is good.

[0125] No. 19 is a product of the present invention formed by stamping in a single process, with a stepped portion having a convex shape formed on the top plate portion near the bottom dead center of forming. The inner angle between the top plate portion and the vertical wall portion in No. 19 is 101 degrees, and the springback is reduced compared to No. 17 of the conventional example and is good.

[0126] No.20 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, and in the second forming process, a stepped portion with a concave shape is formed on the top plate portion. The inner angle between the top plate portion and the longitudinal wall portion in No.20 is 100 degrees, and the springback is reduced compared with No.17 of the conventional example and is good.

[0127] No.21 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, and in the second forming process, a stepped portion with a convex shape is formed on the top plate portion. The inner angle between the top plate portion and the longitudinal wall portion in No.21 is 101 degrees, and the springback is reduced compared with No.17 of the conventional example as well as No.19 of the inventive example and is good.

[0128] In Table 1, No.22 to No.26 are products obtained by stamping a stamping part (not shown) with an L-shaped cross-sectional shape.

[0129] No.22 is a conventional product formed by stamping in one process without forming a stepped portion on the top plate portion. The inner angle between the top plate portion and the longitudinal wall portion in No.22 is 108 degrees, and significant springback occurs.

[0130] No.23 is a product of the present invention formed by stamping in one process, and a stepped portion with a concave shape is formed near the bottom dead center of the forming. The inner angle between the top plate portion and the longitudinal wall portion in No.23 is 98 degrees, and the springback is reduced compared with No.22 of the conventional example and is good.

[0131] No.24 is a product of the present invention formed by stamping in one process, and a stepped portion with a convex shape is formed near the bottom dead center of the forming. The inner angle between the top plate portion and the longitudinal wall portion in No.24 is 101 degrees, and the springback is reduced compared with No.22 of the conventional example and is good.

[0132] No.25 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, and a stepped portion with a concave shape is formed in the second forming process. The inner angle between the top plate portion and the longitudinal wall portion in No.25 is 98 degrees, and the springback is reduced compared with No.22 of the conventional example as well as No.23 of the inventive example and is good.

[0133] No.26 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, and a stepped portion with a convex shape is formed in the second forming process. The inner angle between the top plate portion and the longitudinal wall portion in No.26 is 101 degrees, and the springback is reduced compared with No.22 of the conventional example as well as No.24 of the inventive example and is good.

[0134] In Table 1, Nos. 51 to 76 use a steel plate with a tensile strength of 980 MPa as a slab. Nos. 51 to 54 are stamped products of a hat-shaped cross-sectional shape stamping part 100 ( Figure 11 ) having a stepped portion 109 with a concave shape formed in the top plate portion 101.

[0135] No. 51 is a product formed by stamping in a single process in the past, and a stepped portion 109 with a concave shape is formed from the initial stage of forming. The inner angle between the top plate portion 101 and the longitudinal wall portion 105 in No. 51 is 103 degrees, and springback occurs significantly.

[0136] No. 52 is a product of the present invention formed by stamping in a single process, and a stepped portion 109 with a concave shape is formed near the bottom dead center of forming. The inner angle between the top plate portion 101 and the longitudinal wall portion 105 in No. 52 is 99 degrees, and the springback is reduced compared with No. 51 of the prior example and is good.

[0137] No. 53 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, and a stepped portion 109 with a concave shape is formed in the second forming process. The inner angle between the top plate portion 101 and the longitudinal wall portion 105 in No. 53 is 97 degrees, and the springback is reduced compared with No. 51 of the prior example and is good.

[0138] No. 54 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, a low stepped portion is formed in the first forming process, and the stepped height of the target shape is formed in the second forming process. The inner angle between the top plate portion 101 and the longitudinal wall portion 105 in No. 54 is 97 degrees, and the springback is reduced compared with No. 51 of the prior example as well as No. 53 of the inventive example and is good.

[0139] In Table 1, Nos. 55 to 58 are stamped products of a C-shaped cross-sectional shape stamping part (not shown) having a stepped portion with a concave shape formed in the top plate portion.

[0140] No. 55 is a product formed by stamping in a single process in the past, and a stepped portion with a concave shape is formed from the initial stage of forming. The inner angle between the top plate portion and the longitudinal wall portion in No. 55 is 101 degrees, and springback occurs significantly.

[0141] No. 56 is a product of the present invention formed by stamping in a single process, and a stepped portion with a concave shape is formed near the bottom dead center of forming. The inner angle between the top plate portion and the longitudinal wall portion in No. 56 is 96 degrees, and the springback is reduced compared with No. 55 of the prior example and is good.

[0142] No.57 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, and having a stepped portion with a concave shape formed in the second forming process. The inner angle between the top plate portion 101 and the longitudinal wall portion 105 in No.57 is 96 degrees, and the springback is reduced and good compared with No.55 of the prior example, similarly to No.56 of the inventive example.

[0143] No.58 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, having a low stepped portion formed in the first forming process and the stepped height of the low stepped portion being made into a target shape in the second forming process. The inner angle between the top plate portion and the longitudinal wall portion in No.58 is 96 degrees, and the springback is reduced and good compared with No.55 of the prior example, similarly to No.56 and No.57 of the inventive example.

[0144] In Table 1, No.59 to No.62 are products obtained by stamping a stamped part (not shown) having a cap-shaped cross-sectional shape with a convex stepped portion formed on the top plate portion.

[0145] No.59 is a product of the prior art formed by stamping in one process and having a convex stepped portion formed from the initial stage of forming. The inner angle between the top plate portion and the longitudinal wall portion in No.59 is 110 degrees, and significant springback occurs.

[0146] No.60 is a product of the present invention formed by stamping in one process and having a convex stepped portion formed near the bottom dead center of forming. The inner angle between the top plate portion and the longitudinal wall portion in No.60 is 99 degrees, and the springback is reduced and good compared with No.59 of the prior example.

[0147] No.61 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, and having a convex stepped portion formed in the second forming process. The inner angle between the top plate portion 101 and the longitudinal wall portion 105 in No.61 is 98 degrees, and the springback is reduced and good compared with No.59 of the prior example.

[0148] No.62 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, having a low stepped portion formed in the first forming process and the stepped portion being formed to have a stepped height of a target shape in the second forming process. The inner angle between the top plate portion and the longitudinal wall portion in No.62 is 99 degrees, and the springback is reduced and good compared with No.59 of the prior example.

[0149] In Table 1, No.63 to No.66 are products obtained by stamping a stamped part (not shown) having a U-shaped cross-sectional shape with a convex stepped portion formed on the top plate portion.

[0150] No.63 is a product formed by stamping in a single process in the past, with a stepped portion having a convex shape formed from the initial stage of forming. The inner angle between the top plate portion and the longitudinal wall portion in No.63 is 107 degrees, resulting in significant springback.

[0151] No.64 is a product of the present invention formed by stamping in a single process, with a stepped portion having a convex shape formed near the bottom dead center of forming. The inner angle between the top plate portion and the longitudinal wall portion in No.64 is 99 degrees, and the springback is reduced compared to No.63 of the conventional example and is good.

[0152] No.65 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, with a stepped portion having a convex shape formed in the second forming process. The inner angle between the top plate portion and the longitudinal wall portion in No.65 is 98 degrees, and the springback is reduced compared to No.63 of the conventional example and is good.

[0153] No.66 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, with a low stepped portion formed in the first forming process and the stepped portion having the target shape height formed in the second forming process. The inner angle between the top plate portion and the longitudinal wall portion in No.66 is 99 degrees, and the springback is reduced compared to No.63 of the conventional example, similar to No.64 of the invention example, and is good.

[0154] In Table 1, No.67 to No.71 are products obtained by stamping a stamping formed part (not shown) having a Z-shaped cross-sectional shape.

[0155] No.67 is a product of the past formed by stamping in a single process without forming a stepped portion on the top plate portion. The inner angle between the top plate portion and the longitudinal wall portion in No.67 is 106 degrees, resulting in significant springback.

[0156] No.68 is a product of the present invention formed by stamping in a single process, with a stepped portion having a concave shape formed near the bottom dead center of forming. The inner angle between the top plate portion and the longitudinal wall portion in No.68 is 99 degrees, and the springback is reduced compared to No.67 of the conventional example and is good.

[0157] No.69 is a product of the present invention formed by stamping in a single process, with a stepped portion having a convex shape formed near the bottom dead center of forming. The inner angle between the top plate portion and the longitudinal wall portion in No.69 is 100 degrees, and the springback is reduced compared to No.67 of the conventional example and is good.

[0158] No.70 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, with a stepped portion having a concave shape formed in the second forming process. The inner angle between the top plate portion and the longitudinal wall portion in No.70 is 97 degrees, and the springback is reduced compared to No.67 of the conventional example and is good.

[0159] No.71 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, and having a stepped portion with a convex shape formed in the second forming process. The inner angle between the top plate portion and the longitudinal wall portion in No.71 is 99 degrees, and the springback is reduced and is good compared with No.67 of the conventional example.

[0160] In Table 1, Nos.72 to 76 are products obtained by stamping a stamped part (not shown) having an L-shaped cross-sectional shape.

[0161] No.72 is a conventional product formed by stamping in one process without forming a stepped portion on the top plate portion. The inner angle between the top plate portion and the longitudinal wall portion in No.72 is 101 degrees, and significant springback occurs.

[0162] No.73 is a product of the present invention formed by stamping in one process and having a stepped portion with a concave shape formed near the bottom dead center of forming. The inner angle between the top plate portion and the longitudinal wall portion in No.73 is 96 degrees, and the springback is reduced and is good compared with No.72 of the conventional example.

[0163] No.74 is a product of the present invention formed by stamping in one process and having a stepped portion with a convex shape formed near the bottom dead center of forming. The inner angle between the top plate portion and the longitudinal wall portion in No.74 is 99 degrees, and the springback is reduced and is good compared with No.72 of the conventional example.

[0164] No.75 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, and having a stepped portion with a concave shape formed in the second forming process. The inner angle between the top plate portion and the longitudinal wall portion in No.75 is 96 degrees, and the springback is reduced and is good compared with No.72 of the conventional example, similarly to No.73 of the invention example.

[0165] No.76 is a product of the present invention formed by stamping in two processes of a first forming process and a second forming process, and having a stepped portion with a convex shape formed in the second forming process. The inner angle between the top plate portion and the longitudinal wall portion in No.76 is 98 degrees, and the springback is reduced and is good compared with No.72 of the conventional example.

[0166] Industrial Applicability

[0167] As described above, the present invention can provide a method for manufacturing a stamped part, which can manufacture a stamped part having a target shape with a concave or convex stepped portion formed on the top plate portion without affecting the appearance and reducing springback.

[0168] Description of Reference Numerals

[0169] 10. First die;

[0170] 20. Second die;

[0171] 30. Die;

[0172] 50. Mold;

[0173] 59. Blank holder;

[0174] 61. Mold plate;

[0175] 100. Stamped part;

[0176] 101. Top plate part;

[0177] 103. Ridge line part;

[0178] 105. Longitudinal wall part;

[0179] 107. Flange part;

[0180] 109. Step part;

[0181] 110. Slab;

[0182] 120. Intermediate formed part;

[0183] 121. Intermediate top plate part;

[0184] 123. Intermediate ridge line part;

[0185] 125. Intermediate longitudinal wall part;

[0186] 127. Intermediate flange part.

Claims

1. A manufacturing method of a stamping formed part, the stamping formed part having the following target shape: having a top plate portion and a longitudinal wall portion continuously extending from the top plate portion via a ridge line portion, along the direction in which the ridge line portion extends, in a cross section orthogonal to the ridge line portion, a stepped portion with a concave shape or a convex shape is formed in the top plate portion, characterized in that, it includes the following processes: stamping a blank into an intermediate formed part having an intermediate top plate portion and an intermediate longitudinal wall portion continuously extending from the intermediate top plate portion via an intermediate ridge line portion, and imparting a bending deformation to the intermediate ridge line portion; then, forming the stepped portion with the concave shape or the convex shape in the intermediate top plate portion of the intermediate formed part and stamping it into the stamping formed part with the target shape; when forming the stepped portion with the concave shape or the convex shape, by pulling the intermediate ridge line portion to the intermediate top plate portion side, a bending recovery deformation is imparted to the intermediate ridge line portion.

2. The manufacturing method of the stamping formed part according to claim 1, characterized in that, it includes a first forming process and a second forming process, the first forming process stamps the blank into the intermediate formed part having the intermediate top plate portion and the intermediate longitudinal wall portion continuously extending from the intermediate top plate portion via the intermediate ridge line portion, and imparts a bending deformation to the intermediate ridge line portion; the second forming process forms the stepped portion with the concave shape or the convex shape in the intermediate top plate portion of the intermediate formed part and stamps it into the stamping formed part with the target shape, in the second forming process, when forming the stepped portion with the concave shape or the convex shape, by pulling the intermediate ridge line portion to the intermediate top plate portion side, a bending recovery deformation is imparted to the intermediate ridge line portion.

3. The manufacturing method of the stamping formed part according to claim 2, characterized in that, in the first forming process, a low stepped portion with a step height lower than the target shape is formed in the intermediate top plate portion, in the second forming process, the stepped portion is formed by making the low stepped portion have the step height of the target shape.

4. The manufacturing method of the stamping formed part according to claim 1, characterized in that, the following processes are carried out in one process: stamping the blank into the intermediate formed part, and then, forming the stepped portion with the concave shape or the convex shape in the intermediate top plate portion of the intermediate formed part and stamping it into the stamping formed part with the target shape.

5. A manufacturing method of a stamping formed part, characterized in that, it includes a stamping forming process and a dividing process, the stamping forming process stamps the following stamping formed part by the manufacturing method of the stamping formed part according to any one of claims 1 to 4, the stamping formed part includes the top plate portion and a pair of longitudinal wall portions continuously extending from two edges of the top plate portion via the ridge line portion, and the stepped portion is formed in the top plate portion, the dividing process cuts the top plate portion of the stamping formed part stamped in the stamping forming process along the direction in which the ridge line portion extends to divide the stamping formed part.

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