Stamping method and stamped part

Abstract

The stamping method of the present invention is a stamping method for stamping a stamped part (1), wherein the stamped part (1) has a top plate portion (3), a longitudinal wall portion (7) continuous from the top plate portion (3) via a punch shoulder portion (5), and a flange portion (11) continuous from the longitudinal wall portion (7) via a die shoulder portion (9), and has a curved portion (13) curved into a concave shape when viewed from above, wherein the bending radius of the punch shoulder portion (5) at the curved portion (13) increases from the central portion of the curve toward the end side.

Description

Technical Field

[0001] The present invention relates to a press forming method and a press-formed part, and more particularly to a press forming method and a press-formed part having a top plate portion, a side wall portion continuous from the top plate portion via a punch shoulder portion, and a flange portion continuous from the side wall portion via a die shoulder portion, and having a curved portion curved into a concave shape when viewed from above. Background Art

[0002] Stamping is a manufacturing method that can produce metal parts at low cost and in a short time, and is used in the manufacture of many automotive parts. In recent years, in order to achieve both improved collision safety and lightweighting of automotive bodies, higher-strength metal sheets have been used for automotive parts. Among the major issues in stamping high-strength metal sheets are the generation of cracks due to reduced ductility and the generation of wrinkles due to increased yield strength.

[0003] For example, Figure 9 As shown in FIG. 1 , in the press forming of the press-formed part 101 in which the longitudinal wall portion 107 is bent into a concave shape when viewed from above and is set as the target shape, the flange portion 111 at the curved portion 113 is stretched in the circumferential direction, which makes it easy to generate cracks. In addition, as a reaction force thereof, deformation (deformation) of contraction in the circumferential direction occurs at the top plate portion 103 and the punch shoulder 105 at the curved portion 113, which makes it easy to generate wrinkles. This deformation is called stretch flange deformation. Therefore, in the press forming of the press-formed part 101, it is important to suppress the generation of cracks and wrinkles in such stretch flange deformation.

[0004] As a technique for suppressing cracks and wrinkles in a stamped part that is curved concavely when viewed from above, Patent Document 1 discloses a stamping method for stamping an L-shaped part from a raw metal sheet. The L-shaped part includes a top plate portion and a vertical wall portion, the vertical wall portion being connected to the top plate portion via a bent portion having an arc-shaped portion and having a flange portion on the side opposite the bent portion. Furthermore, according to this stamping method, a portion of the raw metal sheet corresponding to the top plate portion is pressurized by a pad, and an end portion of a portion of the raw metal sheet corresponding to the lower portion of the L-shaped part is allowed to slide (in-plane movement). The portion corresponding to the lower portion of the L-shaped part is pulled into the vertical wall portion to form the vertical wall portion and the flange portion. This method can suppress the occurrence of cracks in the flange portion and wrinkles in the top plate portion.

[0005] In addition, Patent Document 2 discloses a stamping method for stamping a component having a hat-shaped or U-shaped cross-sectional shape and having a curved portion curved along the longitudinal direction and straight side portions connected to both ends of the curved portion. Moreover, according to this stamping method, by generating material movement that alleviates the tensile deformation (tensile deformation) generated in the circumferential direction of the flange portion of the curved portion, it is possible to suppress the occurrence of cracks caused by the deformation of the extended flange.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 5168429

[0009] Patent Document 2: Japanese Patent No. 6028956 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] In the technology disclosed in Patent Document 1, Figure 10 As shown in FIG. 1 , the direction of movement of the blank (metal plate) flowing out from the top plate 103 to the flange 111 is inconsistent with the direction in which the material is stretched due to the deformation of the flange (circumferential dotted line). Figure 11If the figure is broken down into two vectors, movement from the end of the bend 113 toward the center (the black solid arrow in the figure) is effective in suppressing cracks in the flange 111 caused by extended flange deformation. However, movement from the top plate 103 toward the vertical wall 107 (the black dashed arrow in the figure) does not contribute to suppressing extended flange deformation. Furthermore, even if material moves toward the center of the bend 113, material movement near the center of the bend 113 (the white arrow in the figure) may induce wrinkles near the top plate 103 and the punch shoulder 105.

[0012] In addition, the technology disclosed in Patent Document 1 suppresses wrinkles on the top plate portion by applying pressure to the portion of the raw metal plate corresponding to the top plate portion using a gasket. However, the higher the strength of the steel plate, the greater the gasket load that needs to be applied to pressurize the wrinkles. Therefore, there is a concern that the pressure generating device such as the cylinder installed in the mold will become larger. As a result, there is sometimes a problem of not being able to ensure space for the gasket in the mold, and a problem of increased cost due to the enlargement of the mold. In addition, when applying the technology of Patent Document 1 to Figure 9 In the case of press forming of the illustrated press-formed product 101 , the punch shoulder 105 cannot be pressurized by the spacer, and therefore wrinkles in the punch shoulder 105 cannot be suppressed.

[0013] Furthermore, according to the technology disclosed in Patent Documents 1 and 2, for example, in a stamped part where a rib (bead) shape is required to be given to the top plate portion 103 at the bent portion 113, it is sometimes impossible to use the Figure 11 The material of the portion corresponding to the top plate portion 103 at the bent portion 113 shown moves toward the flange portion 111 causing deformation of the extended flange, making it difficult to suppress wrinkles.

[0014] The present invention is made in view of the above-mentioned problems, and its purpose is to provide a stamping method and a stamping part, which, in a stamping part having a top plate portion, a longitudinal wall portion and a flange portion and being curved into a concave shape when viewed from above, can suppress cracks in the flange portion that produces extended flange deformation, and suppress wrinkles in the top plate portion and the punch shoulder portion on the flange portion side.

[0015] Solutions to Problems

[0016] The first embodiment of the stamping forming method of the present invention is a stamping forming method for stamping a stamped part, wherein the stamped part has a top plate portion, a longitudinal wall portion continuous from the top plate portion via a punch shoulder portion, and a flange portion continuous from the longitudinal wall portion via a die shoulder portion, and has a curved portion that is curved into a concave shape when viewed from above, wherein the bending radius of the punch shoulder at the curved portion increases from the central portion of the bend toward the end side.

[0017] It is preferable that a bending radius of the die shoulder at the bent portion decreases from a central portion toward an end portion of the bend.

[0018] Preferably, the minimum bending radius of the die shoulder is smaller than the minimum bending radius of the punch shoulder.

[0019] Preferably, a rotational motion restricting shape portion for restricting rotational motion of the blank during the press forming process is formed on the top plate portion on the side of the bent end portion.

[0020] Preferably, the flange width of the flange portion at the bent portion is wider at the center of the bend than at the end portions of the bend.

[0021] Preferably, the blank used for stamping the stamped part is a metal plate having a tensile strength of 440 MPa grade to 1600 MPa grade.

[0022] The second embodiment of the stamping forming method of the present invention is a stamping forming method in which a stamped part stamped by the first embodiment of the present invention is used as an intermediate formed product, and the intermediate formed product is further stamped into a target shape, wherein the intermediate formed product makes the bending radius of the punch shoulder on the end side of the bending portion larger than the target shape.

[0023] The stamped part of the present invention has a top plate portion, a longitudinal wall portion continuous from the top plate portion via a punch shoulder portion, and a flange portion continuous from the longitudinal wall portion via a die shoulder portion, and has a curved portion curved into a concave shape when viewed from above, wherein the bending radius of the punch shoulder portion at the curved portion increases from the central portion of the curve toward the end side.

[0024] Preferably, the bending radius of the die shoulder portion at the bent portion decreases from a central portion toward an end portion of the bend.

[0025] Preferably, the minimum bending radius of the die shoulder is smaller than the minimum bending radius of the punch shoulder.

[0026] Preferably, a rotational movement restricting shape portion that restricts rotational movement of the blank during press forming is formed on the top plate portion on the end side of the curve.

[0027] Preferably, the width of the flange portion at the bent portion is wider at a central portion of the bend than at end portions of the bend.

[0028] Preferably, the stamped product is obtained by stamping a metal plate having a tensile strength of 440 MPa to 1600 MPa.

[0029] Effects of the Invention

[0030] According to the present invention, the material can be moved from the top plate portion on the end side of the bend toward the flange portion at the center portion of the bend, thereby suppressing cracks at the flange portion at the bend and suppressing wrinkles on the top plate portion and the punch shoulder portion on the flange portion side at the bend. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 These are diagrams showing an example of a stamped product to be formed in a stamping method according to an embodiment of the present invention ((a) is a perspective view, (b) is a plan view).

[0032] Figure 2 The figures illustrate why cracks can be suppressed by the stamping method according to an embodiment of the present invention ((a) is a top view, (b) is a cross-sectional view of the end side of the bend, and (c) is a cross-sectional view of the central portion of the bend).

[0033] Figure 3 These are diagrams showing an example of a stamped product to be formed in a stamping method according to another aspect of an embodiment of the present invention ((a) is a perspective view, (b) is a plan view).

[0034] Figure 4 These are figures explaining why wrinkles can be suppressed by a stamping method according to another embodiment of the present invention ((a) is a top view, (b) is a cross-sectional view of the end side of the bend, and (c) is a cross-sectional view of the central portion of the bend).

[0035] Figure 5 This is a diagram showing an example of a stamped part having a shape constrained from rotational motion in a horizontal plane parallel to a top plate portion by forming a longitudinal wall portion at an end portion of a blank as a forming object in a stamping method according to an embodiment of the present invention.

[0036] Figure 6 This figure shows another example of a press-formed product in which a rib is used as a forming object in the press-forming method according to the embodiment of the present invention to restrict rotational movement in a horizontal plane parallel to the top plate.

[0037] Figure 7 This is a diagram showing an example of a press-formed product in which the flange width of a flange portion of a bent center portion is increased as a forming target in the press-forming method according to the embodiment of the present invention.

[0038] Figure 8 This is a diagram explaining why cracks can be suppressed in a press-formed product in which the flange width of the flange portion of the bent center portion is increased by the press-forming method according to the embodiment of the present invention.

[0039] Figure 9 The diagram explains cracks and wrinkles generated during press forming of a press-formed product having a portion curved concavely in a plan view.

[0040] Figure 10 This is a diagram explaining the mechanism of cracking during the press forming process of a press-formed product that is curved into a concave shape when viewed from above.

[0041] Figure 11 This is a diagram for explaining material movement during press forming of a press-formed product that is curved concavely in a plan view. DETAILED DESCRIPTION

[0042] The following is based on Figures 1 to 8 A press-formed product and a press-forming method according to an embodiment of the present invention will be described.

[0043] As an example, Figure 1 As shown, the stamping method and stamping part of the present embodiment are stamped to form a stamping part 1, which has a top plate portion 3, a longitudinal wall portion 7 continuous from the top plate portion 3 via a punch shoulder portion 5, and a flange portion 11 continuous from the longitudinal wall portion 7 via a die shoulder portion 9, and has a curved portion 13 curved into a concave shape when viewed from above and two ends of the curve at the curved portion 13 ( Figure 1 A straight portion 15 extending straightly (dashed line in the figure) is formed, wherein the bending radius of the punch shoulder 5 at the bending portion 13 increases from the central portion of the bend toward the end side.

[0044] In the stamping method and stamping part of this embodiment, the reason why cracks in the flange portion 11 at the bent portion 13 of the stamping part 1 and wrinkles in the top plate portion 3 and the punch shoulder portion 5 can be suppressed is based on a schematic diagram showing the movement of the material during the stamping process. Figure 2 It should be noted that Figure 2 The dotted lines in FIG. 1 represent both ends of the bend (the boundaries between the bend portion 13 and the straight portion 15 ).

[0045] The punch shoulder 5 has a bending radius R at the bent end (section A-A') p、1 ( Figure 2 (b)) The bending radius R at the center of the bend (BB' section) p、2 ( Figure 2 (c)) The larger the bending radius, the larger the bending radius becomes from the center to the end. Figure 2 As shown by the black arrow in the figure, the material easily moves along the ridgeline direction (perpendicular to the paper) from the curved end side of the punch shoulder 5 toward the central portion, and is pulled into the flange portion 11 side of the curved central portion. In contrast, the curved central portion of the punch shoulder 5 has a smaller bending radius than the curved end side, so it is difficult for the material to move along the ridgeline direction during the stamping process.

[0046] Therefore, during the stamping process of the stamped part 1, the material can be moved from the top plate portion 3 on the end side of the bend toward the flange portion 11 in the central portion of the bend, thereby suppressing cracks in the flange portion 11 at the bending portion 13 and suppressing wrinkles at the top plate portion 3 and the punch shoulder 5 at the bending portion 13.

[0047] In addition, the stamping method of this embodiment preferably makes the minimum bending radius of the die shoulder 9 smaller than the minimum bending radius of the punch shoulder 5. Here, the minimum bending radius of the die shoulder 9 refers to the minimum bending radius of the die shoulder 9 at the bending portion 13. It should be noted that in the stamping part 1, if Figure 2 As shown, the bending radius R of the die shoulder 9 from the central part to the end side of the bend is d Constant, therefore, the minimum bending radius of the die shoulder 9 is R d On the other hand, the minimum bending radius of the punch shoulder 5 refers to the minimum bending radius of the punch shoulder 5 at the bending portion 13. Moreover, in the stamped part 1, as Figure 2 As shown, the bending radius of the punch shoulder 5 increases from the curved center toward the end side. Therefore, the minimum bending radius of the punch shoulder 5 is the bending radius R of the curved center. p、2 Thus, by making the minimum bending radius of the punch shoulder 9 (=R d ) than the minimum bending radius of the punch shoulder 5 (=R p、2 ) is small, and the movement of the material at the die shoulder 9 is restricted during the stamping process. Accordingly, the material can be strongly pulled from the top plate 3 side to the flange 11 side during the stamping process. As a result, cracks in the flange 11 at the center of the bend and wrinkles in the top plate 3 and punch shoulder 5 can be further suppressed.

[0048] The stamping forming method and stamping formed part of this embodiment are as follows Figure 1 As shown in the stamped part 1, the bending radius of the punch shoulder 5 at the bending part 13 increases from the central part to the end of the bend. Figure 3As in the stamped part 21 shown as an example in the drawing, the bending radius of the punch shoulder 25 at the bending portion 33 is increased from the center of the bend toward the end side, and the bending radius of the die shoulder 29 at the bending portion 33 is reduced from the center of the bend toward the end side.

[0049] Thus, regarding the effect of reducing the bending radius of the die shoulder 29 from the central portion of the bend at the bend portion 33 toward the end side, based on a diagram schematically showing the movement of the material during the stamping process of the stamped part 21, Figure 4 It should be noted that Figure 4 The dotted lines in FIG. 3 represent both ends of the bend (the boundaries between the bend portion 33 and the straight portion 35 ).

[0050] The bending radius R at the curved end side (AA' section) of the die shoulder 29 is d、1 ( Figure 4 (b)) The bending radius R at the center of the bend (BB' section) d、2 ( Figure 4 (c)) is small. Therefore, in the deformation of the extended flange, the Figure 4 (a) shows that the material movement of the flange portion 31 at the bend and the root of the vertical wall portion 27 becomes easy, and the material movement in the circumferential direction of the bend at the flange portion 31 is less likely to occur, which can prevent flange cracks.

[0051] As a result, during the press-forming process of the press-formed product 21 , cracking of the flange portion 31 at the bent portion 33 can be further suppressed.

[0052] In addition, in the stamping forming method and stamping formed part of other aspects of the present embodiment, it is preferable that the minimum bending radius of the die shoulder 29 at the bending portion 33 is smaller than the minimum bending radius of the punch shoulder 25. Here, the minimum bending radius of the die shoulder 29 is the minimum bending radius of the die shoulder 29 at the bending portion 33, as shown in FIG. Figure 4 (b) shows the bending radius R of the curved end side. d、1 On the other hand, the minimum bending radius of the punch shoulder 25 is the minimum bending radius of the punch shoulder 25 at the bending portion 33, such as Figure 4 (c) shows the bending radius R of the central part of the bend. p、2 Thus, by making the minimum bending radius (=R d、1 ) than the minimum bending radius of the punch shoulder 25 (=R p、2 ) is small, the bending radius R of the curved end side of the punch shoulder 25 is p、1 The minimum bending radius R of the punch shoulder 25 (the center of the bend) p、2The larger the punch shoulder 25, the stronger the material can be pulled from the top plate 23 to the flange 31 during the press forming process. As a result, cracks in the flange 31 at the bend 33 and wrinkles in the top plate 23 and punch shoulder 25 can be further suppressed.

[0053] In the above description, if Figure 1 As shown in the figure, the bending radius of the punch shoulder 5 is changed, and then Figure 3 The bending radius of the punch shoulder 25 and the die shoulder 29 can be changed as shown. The stamping forming method and stamping formed part of the present invention can also be changed as shown. Figure 5 As shown in the stamped part 41, a rotational motion restraining shape portion 57 is formed on the end side of the curved portion 53 and the top plate portion 43 at the straight portion 55, and the rotational motion restraining shape portion 57 restrains the rotational motion of the blank in a horizontal plane parallel to the top plate portion 43 during the stamping process.

[0054] The rotational motion restraining shape 57 is a curved shape formed between the vertical wall portion 59 and the top plate portion 43, which is continuous on the side opposite to the vertical wall portion 47 of the straight portion 55. In addition, the punch shoulder 45 is formed in a manner such that the bending radius increases from the center portion of the curve toward the end side, similarly to the punch shoulder 5 of the above-mentioned stamped part 1.

[0055] Thus, by forming the rotational motion restraining shape portion 57 during the stamping process, the rotational motion of the blank in the horizontal plane parallel to the top plate portion 43 can be suppressed during the stamping process, and the material can be moved from the top plate portion 43 on the curved end side and the straight portion 55 to the flange portion 51 in the curved center portion via the punch shoulder 45. In addition, wrinkles on the top plate portion 43 and the punch shoulder 45 at the curved portion 53 can be fully suppressed.

[0056] It should be noted that the present invention is not limited to Figure 5 The rotational motion restraining shape portion 57 of the shape shown, for example, Figure 6 The rotational motion restricting shape portion 63 having a rib shape formed on the top plate portion 43 of the stamped part 61 may be any shape that can restrict the rotational motion of the blank in a horizontal plane parallel to the top plate portion 43 during the stamping process. Furthermore, when a rib is formed on the top plate portion 43, the shape is not limited to a concave shape like the rotational motion restricting shape portion 63, but may also be a convex shape.

[0057] in addition, Figure 5 The rotational motion restraining shape portion 57 shown, Figure 6 The rotational movement restraining shape portion 63 shown is formed from the end of the curved portion 53 to the straight portion 55 , but the position where the rotational movement restraining shape portion is formed does not exclude the possibility of being formed only at the end of the curved portion 53 or only at the straight portion 55 .

[0058] Furthermore, in addition to the bending radius of the punch shoulder and the die shoulder, the stamping forming method and the stamping formed part of the present invention can also be Figure 7 As in the illustrated press-formed product 71 , the flange width of the flange portion 81 at the center of the bent portion 83 is made wider than that at the bent end portions.

[0059] Through Figure 7 The effects of stamping the stamped part 71 are as follows. Figure 8 As shown in (a), the stamped part 1 is obtained by stamping a blank 91 having a shape that will become the shape of the stamped part 1 if stamped. In this case, the flange portion 93 in the blank 91 becomes the flange portion 11 ( Figure 1 ).

[0060] In contrast, Figure 8 As shown in (b), Figure 7 The illustrated press-formed product 71 is press-formed using a blank 95 to which an excess metal (hatched area in the figure) corresponding to a flange portion 97 of the flange portion 81 is added.

[0061] When the stamped part 71 is stamped using such a blank 95, the material of the flange portion 81 at the bent portion 83 is difficult to extend. Accordingly, the material that is insufficient to form the flange portion 81 is pulled in from the top plate portion 73 side through the punch shoulder portion 75 and the vertical wall portion 77. As a result, the material toward the center of the bend at the bent portion 83 increases, and cracks in the flange portion 81 can be further suppressed.

[0062] like Figure 7 As shown in the stamped part 71, when the flange width of the flange portion 81 at the bending portion 83 is made wider in the center of the bend than on the end side of the bend, it is preferred that the maximum width of the flange in the center of the bend is 1.1 to 1.5 times the flange width on the end side.

[0063] If the flange width of the bent central portion is less than 1.1 times, the force pulling the material from the top plate portion 73 toward the flange portion 81 during the press forming process does not increase significantly. On the other hand, if the flange width of the bent central portion is wider than 1.5 times, the flange portion 81 becomes too wide, becoming an obstacle when joining other components. Therefore, in a subsequent process, the flange portion 81 is cut off to narrow the flange width, increasing the number of work steps and further reducing the yield rate.

[0064] It should be noted that the stamping forming method and stamping formed parts according to the embodiment of the present invention are as follows. Figure 1As shown, a stamped part 1 having straight portions 15 extending from both ends of a bend of a bent portion 13 is used as a forming object. The present invention can also be used to stamp a stamped part having only a bent portion or a stamped part having a straight portion extending from only one end of a bend, regardless of whether there is a straight portion.

[0065] In the above description, the bending radius of the punch shoulder portion increases from the curved center portion toward both end portions, but may also increase from the curved center portion toward either end portion.

[0066] Similarly, the radius of curvature of the die shoulder decreases from the center of the curve toward both end portions, but may decrease toward either end portion.

[0067] The above description illustrates the specific aspects of the present invention based on the embodiments of the present invention. However, the present invention also includes, for example, Figure 1 The stamped part 1 shown is used as an intermediate part, and this intermediate part is stamped into a target shape. The stamped part 1 as the intermediate part can have a bend radius of the punch shoulder 5 on the end side of the bend 13 larger than the target shape. In other words, the stamping method includes two steps: a step of stamping the stamped part 1 as the intermediate part, and a step of stamping the stamped part 1 into a stamped part having the target shape.

[0068] Moreover, if the Figure 9 In the example of the previous stamping part 101 with the bending radius of the punch shoulder 105 set as the target shape, even if cracks occur in the flange portion 111 at the bending portion 113 of the stamping part 101 and wrinkles occur in the top plate portion 103 and the punch shoulder 105, according to the stamping method of the present invention, cracks in the flange portion 111 at the bending portion 113 and wrinkles in the top plate portion 103 and the punch shoulder 105 can be suppressed to obtain a stamping part 101 of the target shape.

[0069] Likewise, the present invention will Figure 3 The stamped part 21 shown is used as an intermediate part, and the intermediate part is stamped into a stamped part 101 ( Figure 9 ), the stamped part 21 as the intermediate formed part includes a stamping method in which the bending radius of the die shoulder 29 at the center of the bent portion 33 is larger than the target shape. That is, the stamping method includes two steps: a step of stamping the stamped part 21 as the intermediate formed part and a step of stamping the stamped part 21 into the stamped part 101 of the target shape.

[0070] In this case, if the stamped part 101 in which the bending radius of the die shoulder 109 is set to the target shape is stamped in a single process, cracks in the flange portion 111 at the bending portion 113 and wrinkles in the top plate portion 103 and the punch shoulder 105 will also occur. However, according to the present invention, the cracks in the flange portion 111 at the bending portion 113 and wrinkles in the top plate portion 103 and the punch shoulder 105 can be further suppressed to obtain a stamped part 101 of the target shape.

[0071] The stamping method and stamping part of the present invention are not particularly limited to the type of metal sheet used as the raw material of the blank, but can be preferably applied to the case of using a metal sheet with low ductility. Specifically, it is preferred to use a metal sheet with a tensile strength of 440 MPa or higher and 1600 MPa or lower and a sheet thickness of 0.5 mm or higher and 3.6 mm or lower.

[0072] Metal sheets with a tensile strength below 440 MPa are less susceptible to cracking due to deformation of the stretched flange due to their high ductility, and the advantages of using the present invention are limited. However, for component shapes that are difficult to stamp, the present invention is preferably used even for metal sheets with a tensile strength below 440 MPa. There is no particular upper limit for the tensile strength, but metal sheets exceeding 1600 MPa lack ductility and are therefore more susceptible to cracking in the punch and die shoulders, making stamping difficult.

[0073] In addition, the press forming method and press-formed part of the present invention can prevent cracks in the metal sheet caused by deformation of the extended flange in automobile parts having L-shaped, T-shaped, Y-shaped, or S-shaped parts when viewed from above. As a specific example, the present invention can be preferably applied when forming an A-pillar lower having an L-shaped part, a B-pillar having a T-shaped part, or a rear side member having an S-shaped part.

[0074] Example

[0075] The effects of the stamping method of the present invention will be described below based on specific stamping experiments.

[0076] In the stamping experiment, a steel sheet having the material properties shown in Table 1 was used as a blank, and the stamped part 1 ( Figure 1 )、Stamping parts 21( Figure 3 )、Stamping parts 41( Figure 5 )、Stamping parts 61( Figure 6) was used as the molding object, and an example in which foam molding (crash forming) was performed was used as an inventive example.

[0077] It should be noted that the bending radius of the bending part at the center of the height of the longitudinal wall part of each stamped part is 153 mm, the minimum bending radius of the punch shoulder at the bending part is 7 mm, the minimum bending radius of the die shoulder is 6 mm, the longitudinal wall height in the stamping direction of the longitudinal wall part is 60 mm, and the flange width of the flange part is 30 mm in the center of the bend in the stamped part 1 and 25 mm on the end side of the bend. In the stamped parts 21, 41, and 61, it is 10 mm in the center of the bend and 25 mm on the end side of the bend.

[0078] [Table 1]

[0079] Plate thickness / mm Yield strength / MPa Tensile strength / MPa Elongation / % 1.6 880 1210 13

[0080] Tables 2 and 3 show the bending radius R of the punch shoulder in the stamped parts as the forming objects in the stamping forming experiments. p and the bending radius R of the die shoulder d It should be noted that the bending radius R of the punch shoulder shown in Table 2 and Table 3 is p The ratio is the ratio of the maximum bending radius to the minimum bending radius in the ridgeline direction of the punch shoulder. Similarly, the bending radius R of the die shoulder shown in Table 2 and Table 3 is d The ratio is the ratio of the minimum bending radius to the maximum bending radius in the ridgeline direction of the die shoulder.

[0081] In the press forming experiment, as a comparison object, the method disclosed in Patent Document 1 was used to press the Figure 9 The stamped part 101 shown is a conventional example 1 in which a portion of the stamped part 101 corresponding to the top plate 103 is stamped while allowing the blank to rotate in the horizontal plane parallel to the top plate 103 .

[0082] In Conventional Example 1, the curvature radius of the bend 113, the bend radius of the punch shoulder 109, and the vertical wall height of the vertical wall 107 are the same as those of the press-formed product of the inventive example. Furthermore, in Conventional Example 1, the minimum bend radius of the punch shoulder 105 is constant (=7 mm) in the ridge direction.

[0083] Furthermore, cracks and wrinkles in each stamped part of the invention example and the conventional example were evaluated. Regarding the evaluation of cracks, the thickness of the blank and the tip of the flange portion at the bottom of the concave portion at the bending part (for example, Figure 2 The sheet thickness reduction rate (sheet thickness reduction rate) obtained by dividing the difference in the thickness of the sheet (C portion shown) by the sheet thickness of the blank is evaluated as the sheet thickness reduction rate. The smaller the value, the better the crack suppression is. On the other hand, with respect to the evaluation of wrinkles, a sensory evaluation is performed on the top plate portion and the punch shoulder at the bending portion by visual inspection. The case where there are significant wrinkles is set as "×", the case where there are tiny wrinkles that can be visually confirmed but are tolerable in terms of component performance is set as "△", and the case where wrinkles cannot be visually confirmed is set as "○". The results of evaluating cracks and wrinkles for each stamped part are shown in Tables 2 and 3 above.

[0084] [Table 2]

[0085]

[0086] [Table 3]

[0087]

[0088]

[0089] In Conventional Example 1, the plate thickness reduction rate was as large as 18%, and minute wrinkles were generated.

[0090] Inventive Example 1 is to make the bending radius R of the punch shoulder 5 p An example of press forming of a press-formed product 1 in which the thickness increases from the center of the bend toward the end at a ratio of 1.1. As shown in Table 2, the thickness reduction rate was 17%, which was lower than that of Conventional Example 1, and no wrinkles were observed.

[0091] Inventive Example 2 is to reduce the bending radius R of the punch shoulder 5 to p The ratio of is set to 1.5, which is larger than that of Invention Example 1. As shown in Table 2, the plate thickness reduction rate is 14%, which is smaller than that of Invention Example 1, and the generation of wrinkles is not observed.

[0092] Inventive Example 3 is to reduce the bending radius R of the punch shoulder 5 p The ratio of is set to 2.0, and a larger stamped part 1 than that of Inventive Example 2 is stamped. As shown in Table 2, the plate thickness reduction rate is 12%, which is further reduced than that of Inventive Example 2, and no wrinkles are observed.

[0093] Inventive Example 4 is to make the bending radius R of the punch shoulder 25p The bending radius R of the die shoulder 29 increases from the center of the bend toward the end side at a ratio of 1.5. d The stamped part 21 is obtained by stamping the stamped part 21 with a thickness reduction ratio of 0.9 from the central part to the end side of the bend. As shown in Table 2, the plate thickness reduction ratio is 13%, which is consistent with the bending radius R of the punch shoulder 25. p The ratio of the invention example 2 was smaller than that of the invention example 2, and no wrinkles were observed.

[0094] Inventive Example 5 is to reduce the bending radius R of the die shoulder 29 d The ratio of 0.75 was set to 0.75, and the press-formed product 21 smaller than that of Inventive Example 4 was press-formed. As shown in Table 2, the plate thickness reduction rate was 12%, which was smaller than that of Inventive Example 4, and no wrinkles were observed.

[0095] Inventive Example 6 is to reduce the bending radius R of the die shoulder 29 to d The ratio of is set to 0.5, which is smaller than that of Inventive Example 5. As shown in Table 2, the plate thickness reduction rate is 10%, which is smaller than that of Inventive Example 5, and the generation of wrinkles is not observed.

[0096] Inventive Example 7 is to reduce the bending radius R of the punch shoulder 45 to p The press-formed product 41 was obtained by press-forming the product 41 with the ratio of the die radius to the die shoulder 49 set to 1.5, the ratio of the bending radius to the die shoulder 49 set to 0.75, and the rotational motion restraining shape portion 57 formed between the top plate portion 43 and the vertical wall portion 59. As shown in Table 3, the plate thickness reduction rate was 14%, which was lower than that of Conventional Example 1, and no wrinkles were observed.

[0097] Inventive Example 8 is to make the bending radius R of the punch shoulder 45 p The ratio of the die radius and the bending radius of the die shoulder 49 are equal to those of Inventive Example 7, and a rib-shaped rotational motion restraining portion 63 is formed from the curved end of the top plate 43 to the straight portion. As shown in Table 3, the plate thickness reduction rate is 14%, which is lower than that of Conventional Example 1, and no wrinkles are observed.

[0098] Inventive Example 9 was obtained by press-forming a stamped part 71 using a blank 95 having a shape with excess material added to the flange-equivalent portion 97. The ratio of the bend radius of the punch shoulder 75 was set to 1.5, and the flange width of the flange portion 81 at the center of the bend 83 was set to 1.5 times the flange width at the bent end (=25 mm). As shown in Table 3, the plate thickness reduction rate was reduced to 9%, which is a good result. In addition, no wrinkles were observed.

[0099] Inventive Example 10 is a method for using a blank 95 having a shape in which the flange-equivalent portion 97 is provided with an excess, and the ratio of the bending radius of the punch shoulder 5 is set to 1.5 and the bending radius of the die shoulder is set to d The press-formed product 21 was press-formed with a ratio of 0.75. As shown in Table 3, the plate thickness reduction rate was 7%, which was further reduced compared to Inventive Example 9, and no wrinkles were observed.

[0100] Inventive Example 11 is a case where a blank 95 having a shape in which an excess material is provided in the flange-equivalent portion 97 is used, and the ratio of the bending radius of the punch shoulder 5 is set to 1.5 and the bending radius R of the die shoulder is set to 1.5 as in Inventive Example 7. d The press-formed product 21 was press-formed with a ratio of 0.75 and a rotational motion restraining portion 57. As shown in Table 3, the plate thickness reduction rate was reduced to 9%, which is a good result, and no wrinkles were observed.

[0101] It should be noted that the bending radius R of the punch shoulder 105 is p Table 3 shows an example of a stamped part 101 that is uniformly larger than that of Conventional Example 1. In Comparative Example 1, the bending radius of the entire ridgeline of the punch shoulder 105 of Conventional Example 1 was set to 1.5 times that of the conventional example 1, maintaining it at a constant value of 10.5 mm. As a result, the plate thickness reduction rate was 9%, which was satisfactory, but significant wrinkles were generated, which was problematic.

[0102] As described above, it was confirmed that the press forming method and press formed product of the present invention can suppress cracks in the flange portion at the bent portion and wrinkles in the top plate portion and punch shoulder portion at the bent portion.

[0103] Industrial Applicability

[0104] According to the present invention, a stamping method and a stamping part can be provided. In a stamping part having a top plate portion, a longitudinal wall portion and a flange portion and being curved into a concave shape when viewed from above, cracks in the flange portion resulting from extended flange deformation can be suppressed, and wrinkles in the top plate portion and the punch shoulder portion on the flange portion side can be suppressed.

[0105] Description of Reference Numerals

[0106] 1 Stamping parts

[0107] 3 Top plate

[0108] 5 Punch shoulder

[0109] 7 Vertical wall

[0110] 9 Die shoulder

[0111] 11 Flange

[0112] 13. Bend

[0113] 15 Straight line

[0114] 21 Stamping parts

[0115] 23 Top plate

[0116] 25 Punch shoulder

[0117] 27 longitudinal wall

[0118] 29 Die shoulder

[0119] 31 flange

[0120] 33 bend

[0121] 35 straight line part

[0122] 41 stamped parts

[0123] 43 Top plate

[0124] 45 Punch Shoulder

[0125] 47 longitudinal wall

[0126] 49 Die shoulder

[0127] 51 flange

[0128] 53 bend

[0129] 55 straight line

[0130] 57 Rotational motion constraint shape portion

[0131] 59 longitudinal wall

[0132] 61 stamped parts

[0133] 63 Rotational motion constraint shape portion

[0134] 71 stamped parts

[0135] 73 top plate

[0136] 75 Punch Shoulder

[0137] 77 longitudinal wall

[0138] 79 Die shoulder

[0139] 81 flange

[0140] 83 bend

[0141] 85 straight line

[0142] 91 blank

[0143] 93 flange equivalent

[0144] 95 blank

[0145] 97 flange equivalent

[0146] 101 stamping parts

[0147] 103 top plate

[0148] 105 Punch Shoulder

[0149] 107 longitudinal wall

[0150] 109 die shoulder

[0151] 111 flange

[0152] 113 bend

[0153] 115 straight line part

Claims

1. A stamping method for forming a stamped part by stamping a blank, wherein the stamped part comprises a top plate portion, a longitudinal wall portion continuous from the top plate portion via a punch shoulder portion, and a flange portion continuous from the longitudinal wall portion via a die shoulder portion, and has an L-shaped portion curved in a plan view, the portion being curved into a concave shape, and the flange portion at the curved portion being deformed into an extended flange, wherein: The bending radius of the punch shoulder at the bending portion is increased from the center portion of the bend toward both end portions.

2. The stamping method according to claim 1, wherein: The bending radius of the die shoulder at the bending portion is reduced from the center portion toward the end portion.

3. The stamping method according to claim 1, wherein: The minimum bending radius of the die shoulder is made smaller than the minimum bending radius of the punch shoulder.

4. The stamping method according to any one of claims 1 to 3, wherein: A rotational motion restricting shape portion is formed on the top plate portion on the bent end side to restrict rotational motion of the blank during the press forming process.

5. The stamping method according to any one of claims 1 to 3, wherein: The flange width of the flange portion at the bent portion is made wider in the center portion than on the bent end portions.

6. The stamping method according to any one of claims 1 to 3, wherein: The blank used for stamping the stamped part is a metal plate having a tensile strength of 440 MPa to 1600 MPa.

7. A stamping method, comprising: using a stamped part stamped by the stamping method according to any one of claims 1 to 6 as an intermediate part, and further stamping the intermediate part into a target shape, wherein: The intermediate formed piece has a bending radius of the punch shoulder portion on the end side of the bent portion larger than the target shape.

8. A stamped part comprising a top plate, a longitudinal wall portion continuous from the top plate portion via a punch shoulder portion, and a flange portion continuous from the longitudinal wall portion via a die shoulder portion, and having an L-shaped portion curved in a plan view, the portion curved into a concave shape, and a curved portion where the flange portion is deformed to extend the flange, wherein: The bending radius of the punch shoulder portion at the bending portion increases from the center portion of the bend toward both end portions.

9. The stamped part according to claim 8, wherein: The bending radius of the die shoulder portion at the bending portion decreases from the center portion toward the end portion.

10. The stamped part according to claim 8, wherein The minimum bending radius of the die shoulder is smaller than the minimum bending radius of the punch shoulder.

11. The stamped part according to claim 8, wherein A rotational movement restricting shape portion that restricts rotational movement of the blank during press forming is formed on the top plate portion on the bent end side.

12. The stamped part according to claim 8, wherein The width of the flange portion at the bent portion is wider at the center than at the bent end portions.

13. The stamped part according to any one of claims 8 to 12, wherein: The stamped part is obtained by stamping a metal plate having a tensile strength of 440 MPa to 1600 MPa.

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