Press forming blanks and press forming parts

Abstract

To prevent cracking during press forming using materials with poor ductility. [Solution] The press-formed blank of the present invention comprises a first blank formed during press forming, which includes a first top plate component that is continuous with a first top plate component provided in a first straight section, and a first vertical wall component that is continuous with the first curved line of the first top plate component via a first ridge section; a second blank formed during press forming, which includes a second top plate component that overlaps with the first top plate component, a second ridge section that is continuous with the second curved line of the second top plate component and overlaps with the first ridge section, a second vertical wall component that is continuous with the second top plate component via the second ridge section and overlaps with the first vertical wall section, and a first flange section that is continuous with the second vertical wall section via a base section. The first blank and the second blank are joined together in a state where the first top plate component and the region of the second top plate component that is continuous with the second top plate component in the second straight section overlap.

Description

Technical Field

[0001] The present invention relates to a press-forming blank and a press-formed part.

Background Art

[0002] From the viewpoint of occupant protection, automotive bodies are required to have collision safety performance such as absorbing collision energy to suppress deformation of the vehicle body. In addition, in line with this, it is also required to reduce the weight of automotive bodies to reduce carbon dioxide emissions. In order to meet such requirements, applying high-strength materials to automotive bodies is an effective measure.

[0003] By the way, among the press-formed products used for the above-described automotive bodies, there are press-formed parts having two or more intersecting linear portions, for example, a substantially L-shape or a substantially T-shape. When such a press-formed part is produced by a single press forming operation, cracks under the influence of stretch-flange deformation are prone to occur at the flange portion provided at the curved portion.

[0004] As a method for preventing cracks that occur during press forming, it is disclosed to perform press forming with the gap between a pad and a die set to be equal to or greater than the sheet thickness and 1.03 times or less of the sheet thickness (see Patent Document 1). By performing such press forming, the steel sheet can be sufficiently moved in-plane inside the die unit during pressing. Therefore, even when excess material occurs in the top plate portion and a force causing out-of-plane deformation of the steel sheet acts, the out-of-plane deformation of the steel sheet is restrained by the pad. As a result, in press forming, the occurrence of cracks and wrinkles under the influence of stretch-flange deformation can be suppressed. Further, Patent Document 2 proposes to avoid the occurrence of cracks in the flange portion by increasing the radius of curvature of the die shoulder portion (ridge line portion) provided between the vertical wall portion and the flange portion in press forming of a blank.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Patent No. 5796560 [Patent Document 2] Patent No. 6966729 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, in the molding method disclosed in Patent Document 1, for example, in the case of a press-formed part with a hat-shaped cross-section in which vertical wall portions and flange portions are continuous at both ends of the top plate portion, it is difficult to move the blank sufficiently in-plane within the mold unit due to the ridges formed on the top plate portion and vertical wall portions, and the ridges formed between the vertical wall portions and flange portions.

[0007] Furthermore, in the molding method disclosed in Patent Document 2, when the flange portion is joined to other parts, it is necessary to ensure a flat area, which presents a problem in that the radius of curvature of the ridge portion cannot be increased.

[0008] The objective of the present invention is to provide a press-forming blank and a press-formed part that can prevent cracking in the flange portion when press-forming using materials with poor ductility, such as high-strength materials. [Means for solving the problem]

[0009] A press-formed blank from one perspective is a blank used for press-forming a press-formed part in which a concave curved portion is formed at the intersection of a first straight portion and a second straight portion, and comprises a first blank formed by press-forming a first top plate component that is continuous with a first top plate component provided in the first straight portion and is provided at the intersection, and a first vertical wall portion that is continuous with the first concave curved line provided in the first top plate component via a first ridge portion, and a second top plate component that overlaps with the first top plate component, and provided in the second top plate component The first blank is formed by press forming a second curved line that curves in a concave shape and is continuous with the second curved line that overlaps with the first curved line during press forming, a second vertical wall that is continuous with the second top plate component via the second curved line and overlaps with the first vertical wall during press forming, and a first flange that is continuous with the second vertical wall via the base line. The first blank and the second blank are joined together in a state in which the first top plate component and a region of the second top plate component provided in the second straight portion that is continuous with the second top plate are overlapped.

[0010] Furthermore, the first blank has a rectangular first region that forms the first straight section, and a second region that forms the first top plate component, with one of the four corners of the rectangle cut out in a curved shape, and it is preferable that the end of the first vertical wall in the direction of extension of the first curved line is continuous with the third vertical wall provided in the first straight section.

[0011] Furthermore, it is preferable that the second blank has a rectangular third region that forms the second straight portion, and a curved fourth region that protrudes from the third region and forms the second top plate component, the second ridge portion, the second vertical wall portion, and the first flange portion.

[0012] Furthermore, it is preferable that the second blank further comprises a fifth region which is superimposed on the first straight portion by press forming.

[0013] Furthermore, the first blank and the second blank are preferably steel plates with a tensile strength of 980 MPa or more and 1600 MPa or less.

[0014] Furthermore, press-formed parts from other perspectives are produced by press forming using the press-forming blanks described above.

[0015] Furthermore, it is preferable that the portions that overlap in the first blank and the second blank by press molding are joined together. [Effects of the Invention]

[0016] According to this disclosure, it is possible to prevent cracking in press forming using materials with poor ductility, such as high-strength materials. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1(a) is a schematic perspective view of the press-formed part in this embodiment as seen from the curved side, and Figure 1(b) is a schematic perspective view of the press-formed part as seen from the opposite side of the curved section. [Figure 2] Figure 2(a) is a schematic perspective view of the first component forming the press-formed part as seen from the curved side, and Figure 2(b) is a schematic perspective view of the first component as seen from the opposite side of the curved section. [Figure 3] Figure 3(a) is a schematic perspective view of the second component forming the press-formed part as seen from the curved side, and Figure 3(b) is a schematic perspective view of the second component as seen from the opposite side of the curved section. [Figure 4] This is a schematic perspective view showing an example of the structure of a press-formed blank. [Figure 5] This is a schematic perspective view showing an example of the configuration of the first blank. [Figure 6] This is a schematic perspective view showing an example of the configuration of the second blank. [Figure 7] This is a flowchart showing the production process of press-formed parts. [Figure 8] This is a plan view showing the movement of the blank during press forming. [Figure 9] This is a plan view of a blank and a press-formed part used as a comparative example when verifying the presence or absence of cracks generated by press forming. [Figure 10] This is a perspective view showing one embodiment of a press-formed part in which the overlapping state of the upper constituent member and the lower constituent member is changed.

Mode for Carrying Out the Invention

[0018] Hereinafter, the blank for press forming and the press-formed part according to the present embodiment will be described with reference to the drawings. Figure 1(a) is a schematic perspective view of the press-formed part in the present embodiment when viewed from the curved portion side, and Figure 1(b) is a schematic perspective view of the press-formed part when viewed from the side opposite to the curved portion.

[0019] As shown in Figure 1(a) and Figure 1(b), the press-formed part 10 is, as an example, a substantially L-shaped part used for the vehicle body of an automobile. The press-formed part 10 is produced, for example, by performing press forming on the blank 100 for press forming (see Figure 4) composed of two blanks. Details of the blank 100 for press forming will be described later.

[0020] In the present embodiment, a substantially L-shaped press-formed part is taken as an example, but the present invention can be applied to any press-formed part in which at least two or more linear portions intersect, such as a T-shape or a Y-shape.

[0021] The press-formed part 10 is a substantially L-shaped press-formed part in which two linear portions 20, 30 intersect, and a curved portion C1 is formed between these two linear portions 20, 30. Hereinafter, the portion where the linear portions 20, 30 intersect is referred to as the intersecting portion 40.

[0022] In Figure 1, the boundary between the straight section 20 and the intersecting section 40 is shown by the dashed line L1. The boundary between the straight section 30 and the intersecting section 40 is shown by the dashed line L2. Here, the straight section 20, the straight section 30, and the intersecting section 40 correspond to the first straight section, the second straight section, and the intersecting section, respectively, as described in the claim.

[0023] The straight section 20 has vertical wall sections 24 and 25 that are continuous from the top plate section 21 via ridge sections 22 and 23, and flange sections 28 and 29 that are continuous from the vertical wall sections 24 and 25 via base sections 26 and 27. That is, the shape of the straight section 20 in a cross section perpendicular to the top plate section 21, including the dashed line L1 in Figure 1, is hat-shaped. Here, the top plate section 21 corresponds to the first top plate section described in the claim.

[0024] Similarly, the straight portion 30 has vertical wall portions 34 and 35 that are continuous from the top plate portion 31 via the ridge portions 32 and 33, and flange portions 38 and 39 that are continuous from the vertical wall portions 34 and 35 via the base portions 36 and 37. That is, the shape of the straight portion 30 in a cross section perpendicular to the top plate portion 31, including the dashed line L2 in Figure 1, is hat-shaped. The top plate portion 31 corresponds to the second top plate portion described in the claim.

[0025] The ridge section 23, vertical wall section 25, base section 27, and flange section 29 that constitute the straight section 20 may be omitted. Similarly, the ridge section 33, vertical wall section 35, base section 37, and flange section 39 that constitute the straight section 30 may be omitted.

[0026] The intersection portion 40 includes a top plate portion 41, a ridge portion 42 formed along the curved line 41a of the top plate portion 41, a vertical wall portion 43 connected to the ridge portion 42, a base portion 44 connected to the lower end of the vertical wall portion 43, and a flange portion 45 connected to the base portion 44. The top plate portion 41 constituting the intersection portion 40 is generated by superimposing the top plate component 61 of the first component 60 (see Figure 2(a)) and the top plate component 81 of the second component 80 (see Figure 3(a)), which will be described later. Here, the curved line 41a corresponds to the second curved line described in the claim. The ridge portion 42, the vertical wall portion 43, and the flange portion 45 correspond to the second ridge portion, the second vertical wall portion, and the first flange portion, respectively, described in the claim.

[0027] The intersection portion 40 has ridge portions 46 and 47 connected to two straight lines 41b and 41c arranged at a predetermined angle, vertical wall portions 48 and 49 continuous via these ridge portions 46 and 47, and flange portions 52 and 53 continuous from the vertical wall portions 48 and 49 via base portions 50 and 51. A gap G is provided between the vertical wall portions 48 and 49. By providing a gap G between the vertical wall portions 48 and 49, cracks that occur in that portion when the vertical wall portions 48 and 49 are installed continuously are prevented.

[0028] In the press-formed part 10 described above, the position indicated by symbol P1 is the position where two overlapping blanks are fixed together by spot welding or the like when generating the press-formed blanks described later. The position indicated by symbol P2 is the position where the blanks are fixed together by spot welding or the like after press forming.

[0029] As described above, the press-formed part 10 is produced by press-forming a press-forming blank generated from two blanks. That is, the press-formed part 10 is composed of two components. Hereinafter, the component having the straight portion 20 will be referred to as the first component 60, and the component having the straight portion 30 will be referred to as the second component 70. In explaining the configuration of the first component 60 and the second component 70, Figures 2 and 3 show these components individually. Hereinafter, at the intersection, parts other than the top plate portion 21 will be denoted by the same reference numerals as the press-formed part 10.

[0030] As shown in Figures 2(a) and 2(b), the first component 60 is a component that is superimposed on the second component 70. Furthermore, the hatched area A0 shown in Figures 2(a) and 2(b) is the area in which the second component 70 is superimposed on the first component 60.

[0031] The first component 60 includes a straight section 20. More specifically, the first component 60 has ridge sections 22, 23, vertical wall sections 24, 25, base sections 26, 27, and flange sections 28, 29. The first component 60 also has ridge sections 46, 47, vertical wall sections 48, 49, base sections 50, 51, and flange sections 52, 53 that constitute the intersection section 40. Furthermore, the intersection section 40 has a top plate component 61 that constitutes the top plate section 41 of the intersection section 40.

[0032] The top plate component 61 described above has a concave curved line L3. A vertical wall portion 63 is continuous with the curved line L3 via a ridge portion 62. The ridge portion 62 is continuous with the ridge portion 22. The vertical wall portion 63 is continuous with the vertical wall portion 24. Here, the curved line L3 corresponds to the first curved line described in the claim. The top plate component 71 corresponds to the first top plate component described in the claim. Furthermore, the vertical wall portions 62 and 63 correspond to the first ridge portion and the first vertical wall portion described in the claim.

[0033] When the height H1 of the vertical wall portion 24 is used as a reference, the height H2 of the vertical wall portion 63 is set to be less than or equal to the height H1 of the vertical wall portion 24. Furthermore, in press-formed parts 10, the configuration of the vertical wall portion 63 is necessary when considering the strength of the intersection portion 40; if the vertical wall portion 63 is absent, it is excluded from this embodiment.

[0034] As shown in Figures 3(a) and 3(b), the second component 70 has a top plate portion 31, ridge portions 32, 33, vertical wall portions 34, 35, base portions 36, 37, and flange portions 38, 39 which constitute the straight portion 30.

[0035] The second component 70 has a top plate component 71 that is roughly V-shaped, in addition to the configuration of the straight portion 30. The top plate component 71 is superimposed on the top plate component 61 of the first component 60. Here, the top plate component 71 corresponds to the second top plate component described in the claim.

[0036] The top plate component 71 has one piece 71a that is connected to the top plate component 31 of the straight portion 30, and another piece 71b whose tip curves outward from the piece 71a. Here, the other piece 71b has a curved curved line 41a. A vertical wall portion 43 is continuous with the curved line 41a via a curved ridge portion 42. Furthermore, a flange portion 45 is continuous with the vertical wall portion 43 via a ridge portion 44. Here, the top plate component 61 corresponds to the second top plate component described in the claim.

[0037] One piece 71a of the top plate component 71 has a vertical wall portion 73 connected to it via a ridge portion 72. Furthermore, a flange portion 75 is connected to the vertical wall portion 73 via a base portion 74. Here, the ridge portion 72 is connected to the ridge portion 33 of the straight portion 30, and the vertical wall portion 73 is connected to the vertical wall portion 35. Also, the base portion 74 is connected to the base portion 37, and the flange portion 75 is connected to the flange portion 39. The ridge portion 72, vertical wall portion 73, base portion 74, and flange portion 75 are superimposed on the ridge portion 46, vertical wall portion 48, base portion 50, and flange portion 52 of the first component member 60.

[0038] A top plate component 76 is further provided at the tip of the other piece 71b of the top plate component 71 that constitutes the second component 70. A vertical wall component 78 is continuous with the top plate component 76 via a ridge component 77. Furthermore, a flange component 80 is continuous with the vertical wall component 78 via a base component 79. Here, the ridge component 77 is continuous with the ridge component 42, and the vertical wall component 78 is continuous with the vertical wall component 43. Also, the ridge component 79 is continuous with the ridge component 44, and the flange component 80 is continuous with the flange component 45. The ridge component 77, vertical wall component 78, base component 79, and flange component 80 are superimposed on the ridge component 22, vertical wall component 24, base component 26, and flange component 28 of the first component 60.

[0039] Next, the press-forming blank 100 used to produce the press-formed part 10 will be described. As shown in Figure 4, the press-forming blank 100 is produced by overlapping and fixing two blanks 110 and 120, with parts of them overlapping. The symbol P1 indicates the part that is fixed by spot welding or the like when producing the press-forming blank 100. Here, blanks 110 and 120 correspond to the first blank and the second blank described in the claim.

[0040] The blanks 110 and 120 used to produce the press-formed blank 100 are, for example, 1.4 mm thick. Furthermore, the blanks 110 and 120 are made of steel sheets with a tensile strength of, for example, 980 MPa to 1600 MPa. While steel sheets are used as examples for blanks 110 and 120, it is also possible to use metal sheets with the same tensile strength.

[0041] As shown in Figure 5, the blank 110 has a roughly rectangular cutout at one corner of the rectangular blank 130 (the area indicated by reference numeral 131 in Figure 5). Furthermore, at the corner opposite the roughly rectangular cutout, the blank 110 is cut out in a shape that combines a rectangular area 133 and a fan-shaped area 134. The size of the fan-shaped area 134 is determined based on the radius of curvature of the ridge portion 62 and the height of the vertical wall portion 63 that is continuous with the ridge portion 62.

[0042] The blank 110 is divided into seven regions A1 to A7. Region A1 is a rectangular region that forms the top plate portion 21 of the straight portion 20 by press forming. Region A1 is continuous with each of regions A2 to A4.

[0043] Region A2 is a rectangular region formed by press molding, which creates the ridge portion 22, vertical wall portion 24, base portion 26, and flange portion 28 of the straight portion 20. Region A2 is continuous with both region A1 and region A7.

[0044] Region A3 is a rectangular region formed by press molding, which creates the ridge portion 23, vertical wall portion 25, base portion 27, and flange portion 29 of the straight portion 20. Region A3 is continuous with regions A1 and A6.

[0045] Area A4 is the area that forms the top plate component 61 of the intersection 40. Area A4 is a region in which one of the four corners that make up the rectangle is cut out along the curved line L3. Area A4 is continuous with areas A1, A5, A6 and A7.

[0046] Region A5 is a rectangular region formed by press molding, which creates the ridge portion 46, vertical wall portion 48, base portion 50, and flange portion 52 of the intersection portion 40. Region A5 is continuous with region A4.

[0047] Region A6 is a rectangular region formed by press molding, which creates the ridge portion 47, vertical wall portion 49, base portion 51, and flange portion 53 of the intersection portion 40. Region A6 is continuous with regions A3 and A4.

[0048] Region A7 is a curved region formed by press molding, which creates the ridge line portion 62 and vertical wall portion 63 of the intersection portion 40. Region A7 is continuous with regions A2 and A4.

[0049] Of the regions A1 to A7 described above, regions A1, A2, and A3 are the regions that form the linear portion 20. Therefore, regions A1, A2, and A3 correspond to the first region described in the claim. Region A4 corresponds to the second region described in the claim.

[0050] As shown in Figure 6, the blank 120 has a rectangular blank body 121 and a protruding piece 122 that curves outward from the blank body 121. The blank 110 is divided into eight regions A11 to A18. The width of the protruding piece 122 is set based on the configuration of the curved portion C1 in the press molded part 10.

[0051] Region A11 is a rectangular region that forms the top plate portion 31 of the straight portion 30 by press forming. Region A11 is continuous with regions A12, A13, and A15.

[0052] Region A12 is a rectangular region formed by press forming, which creates the ridge portion 32, vertical wall portion 34, base portion 36, and flange portion 38 of the straight portion 30. Region A12 is continuous with regions A11 and A16.

[0053] Region A13 is a rectangular region formed by press forming, which creates the ridge portion 33, vertical wall portion 35, base portion 37, and flange portion 39 of the straight portion 30. Region A13 is continuous with regions A11 and A14.

[0054] Region A14 is a rectangular region comprising the ridge section 72, the vertical wall section 73, the base section 74, and the flange section 75. Region A14 is continuous with regions A13 and A15.

[0055] Region A15 is a roughly V-shaped region formed spanning from the blank body 121 to the protruding piece 122. Region A15 has region A15-1 along region A11 and region A15-2 along region A16. Region A15 is the region that forms the top plate component 71 by press molding. Region A15 is continuous with regions A11, A14, A16 and A17.

[0056] Region A16 is the region where the ridge portion 42, vertical wall portion 43, ridge portion 44, and flange portion 45 are formed by press forming. Region A16 is continuous with regions A12, A15, and A18.

[0057] Region A17 is a rectangular area that forms the top plate component 76 by press molding. Region A17 is superimposed on the top plate portion 21 of the straight section 20. Region A17 is continuous with regions A15 and A18.

[0058] Region A18 is the region where the ridge portion 77, vertical wall portion 78, base portion 79, and flange portion 80 are formed by press forming. Region A18 overlaps the ridge portion 22, vertical wall portion 24, base portion 26, and flange portion 28 of the straight portion 20. Region A18 is continuous with regions A16 and A17.

[0059] Of the regions that make up the blank 120, regions A14, A15, A16, A17, and A18 are regions that are superimposed on regions A1, A2, A4, and A5 of the blank 110 by press forming.

[0060] Of the regions A11 to A18 described above, regions A11, A12, and A13 are regions that form the linear portion 30. That is, regions A11, A12, and A13 correspond to the third region described in the claim. Regions A15 and A16 correspond to the fourth region described in the claim. Regions A17 and A18 correspond to the fifth region described in the claim.

[0061] Next, the process for producing the press-formed parts shown in this embodiment will be explained using the flowchart in Figure 7.

[0062] First, in step S101, a blank generation process is carried out. In the blank generation process, blank 110 shown in Figure 5 and blank 120 shown in Figure 6 are generated by, for example, shearing or laser processing of a steel plate.

[0063] In step S102, the blanks 110 and 120 generated in step S101 are fixed together in an overlapping state. For example, when fixing by spot welding, spot welding is performed at multiple positions P1 in region A15-1 of blank 120. This forms the press-formed blank shown in Figure 4.

[0064] In step S103, press forming is performed on the press forming blank 100 to produce a press-formed part.

[0065] Although not shown in the diagram, in press forming, for example, regions A1 and A4 of blank 110 and regions A11 and A15-1 of blank 120 are held between the punch and pad of the mold and formed by adjacent punches and dies.

[0066] At this time, region A2 of the blank 110 forms the ridge portion 22, vertical wall portion 24, base portion 26, and flange portion 28 of the straight portion 20. Simultaneously, region A7 of the blank 110 forms the ridge portion 62 and vertical wall portion 63 of the intersection portion 40. As described above, regions A2 and A7 are continuous. Therefore, when the first component 60 is generated, the ridge portion 22 of the straight portion 20 and the ridge portion 62 of the intersection portion 40 are continuous. Also, the vertical wall portion 24 of the straight portion 20 and the vertical wall portion 63 of the intersection portion 40 are continuous.

[0067] Furthermore, region A3 of the blank 110 forms the ridge portion 23, vertical wall portion 25, base portion 27, and flange portion 29 of the straight portion 20. Simultaneously, region A6 of the blank 110 forms the ridge portion 47, vertical wall portion 49, base portion 51, and flange portion 53 of the intersecting portion 40. Therefore, the ridge portion 23 of the straight portion 20 is continuous with the ridge portion 47 of the intersecting portion 40. Also, the vertical wall portion 25 of the straight portion 20 is continuous with the vertical wall portion 49 of the intersecting portion 40. Also, the base portion 27 of the straight portion 20 is continuous with the base portion 51 of the intersecting portion 40. Furthermore, the flange portion 29 of the straight portion 20 is continuous with the flange portion 53 of the intersecting portion 40.

[0068] Furthermore, region A5 of the blank 110 forms the ridge portion 46, vertical wall portion 48, base portion 50, and flange portion 52 of the intersection portion 40.

[0069] Meanwhile, region A12 of the blank 120 forms the ridge portion 32, vertical wall portion 34, base portion 36, and flange portion 38 of the straight portion 30.

[0070] Furthermore, region A13 of the blank 120 forms the ridge portion 33, vertical wall portion 35, base portion 37, and flange portion 38 of the straight portion 30. Also, region A14 forms the upper curved portion 72, vertical wall portion 73, base portion 74, and flange portion 75. Regions A13 and A14 are continuous. Therefore, the ridge portion 33 of the straight portion 30 and the upper curved portion 72 are continuous. Also, the vertical wall portion 35 and the vertical wall portion 73 of the straight portion are continuous. Also, the base portion 73 and the base portion 74 of the straight portion 30 are continuous. Furthermore, the flange portion 38 and the flange portion 75 of the straight portion 30 are continuous.

[0071] Furthermore, region A16 forms a ridge portion 42, a vertical wall portion 43, a base portion 44, and a flange portion 45 that are connected to one piece 71b of the top plate component 71. In addition, region A18 forms a ridge portion 77, a vertical wall portion 78, a base portion 79, and a flange portion 80 that are connected to the top plate component 76.

[0072] As shown in Figure 8, in press forming using the press forming blank 100, the protruding piece 122 of the blank 120 is bent along the curved line 21a. Therefore, the tip of the protruding piece 122 deforms while moving in the direction D1 in Figure 8. At this time, the protruding piece 122 is pulled in the direction D2 in Figure 8 at its base. On the other hand, since the tip of the protruding piece 122 is a free end, when the protruding piece 122 deforms, it moves in the direction D1 in Figure 8. Therefore, no stress is generated at the tip of the protruding piece 122 in the opposite direction to the direction D2 in Figure 8. As a result, cracking is prevented in the flange portion 45 provided in the curved portion C1.

[0073] In the press forming described above, region A16 of the blank 120 forms a ridge portion 42, a vertical wall portion 43, a ridge portion 44, and a flange portion 45. At this time, the ridge portion 42 and the vertical wall portion 43 are superimposed on the ridge portion 62 and the vertical wall portion 63 of the first component member 60. Furthermore, the top plate component 76, the ridge portion 77, the vertical wall portion 78, the base portion 79, and the flange portion 80 are superimposed on the top plate portion 21, the ridge portion 22, the vertical wall portion 24, the base portion 26, and the flange portion 28 that constitute the straight portion 20 of the first component member 60. Similarly, the top plate component 71a, the ridge portion 72, the vertical wall portion 73, the base portion 74, and the flange portion 75 are superimposed on the top plate component 61, the ridge portion 46, the vertical wall portion 48, the base portion 50, and the flange portion 52 that constitute the first component member 60.

[0074] Finally, in step S104, the overlapping portions of the first component 60 and the second component 70, which are produced by press forming, are spot-welded at multiple positions P2. Specifically, the top plate component 61 and the top plate component 71 are spot-welded. The vertical wall portion 63 and the vertical wall portion 43 are also spot-welded. The top plate component 76 and the top plate portion 21 of the straight portion 20 are also spot-welded. The flange portion 45 and the flange portion 28 of the straight portion 20 are also spot-welded. Furthermore, the flange portion 52 and the flange portion 39 of the straight portion 30 are spot-welded.

[0075] The following describes the verification of whether or not cracks occur in press-formed parts produced by press forming. Example 1 is the case where a 1.4 mm thick, 980 MPa class steel material is used to produce a press-formed part using the press-forming blank 100 shown in this embodiment. Example 2 is the case where a 1.4 mm thick, 14700 MPa class steel material is used. Hereafter, corresponding parts will be denoted with "A" in the description.

[0076] Furthermore, as shown in Figure 9(a), when a press-formed part 10A (see Figure 9(b)) is produced using a single blank 150, the case where a 1.4 mm thick, 980 MPa class steel material is used is designated as Conventional Example 1. The case where a 1.4 mm thick, 1470 MPa class steel material is used is designated as Conventional Example 2.

[0077] Furthermore, as shown in Figures 9(c), 9(e), and 9(g), we also verified the case of press forming using a blank made by combining two blanks. In this case as well, we verified using steel material with a thickness of 1.4 mm and a pressure of 980 MPa, and steel material with a thickness of 1.4 mm and a pressure of 1470 MPa.

[0078] For example, Figure 9(c) shows a blank 160 in which two blanks 161 and 162 are superimposed at the boundary between a straight section 30B and an intersecting section 40B to produce a press-formed part 10B (see Figure 9(d)). Comparative Example 1 is when the blank 160 shown in Figure 9(c) is produced using steel with a thickness of 1.4 mm and a pressure of 980 MPa, and Comparative Example 2 is when it is produced using steel with a thickness of 1.4 mm and a pressure of 1470 MPa.

[0079] Furthermore, Figure 9(e) shows a blank 170 in which two blanks 171 and 172 are stacked together so as to be divided by a plane perpendicular to the top plate portion 21C and the edge portion 22C, as shown in Figure 9(f), to produce a press-formed part 10C (see Figure 9(f)). Comparative Example 3 is the case where the blank 170 shown in Figure 9(e) is produced using steel material with a thickness of 1.4 mm and a pressure of 980 MPa, and Comparative Example 4 is the case where it is produced using steel material with a thickness of 1.4 mm and a pressure of 1470 MPa.

[0080] Furthermore, Figure 9(g) illustrates a case in which a press-formed part 10D (see Figure 9(h)) is produced by stacking two blanks 181 and 182 such that the press-formed part 180 is divided by a plane perpendicular to the top plate portion 21D and the edge portion 42D, and parallel to the edge portion 22D of the straight portion 20D. Comparative Example 5 is the case in which the blank 180 shown in Figure 9(g) is produced using steel material with a thickness of 1.4 mm and a pressure of 980 MPa, and Comparative Example 6 is the case in which it is produced using steel material with a thickness of 1.4 mm and a pressure of 1470 MPa.

[0081] The verification results are shown in Table 1 below.

[0082] [Table 1]

[0083] In Conventional Examples 1 and 2, it was found that cracks occurred at the base line portion 24A of the press-formed part 10A. This is thought to be due to elongation flange deformation.

[0084] Furthermore, in Comparative Example 1, cracks occurred at the base line 44B of the first component 60B, but no cracks occurred at the joint between the first component 60B and the second component 70B. On the other hand, in Comparative Example 2, cracks occurred not only at the base line 44B of the first component 60B, but also at the joint between the first component 60B and the second component 70B. In Comparative Example 2, it is thought that cracks occurred at the joint because the steel material used was less ductile than the steel material used in Comparative Example 1.

[0085] Furthermore, in Comparative Examples 3 and 4, cracks occurred not only at the ridge portion 42C of the first component 60C, but also at the joint portion between the first component 60C and the second component 70C.

[0086] In Comparative Example 5, the protruding piece 183 formed on the blank 182 is pulled and moved during press forming, similar to the blank in this embodiment. Therefore, no cracks occur at the ridge portion 42D or the base portion 44D of the second component 70D. On the other hand, cracks occur at the joint portion between the first component 60D and the second component 70D.

[0087] In Comparative Example 6, cracks occurred not only at the base line portion 44D of the second component 70D, but also at the joint between the first component 60D and the second component 70D. This is thought to be because the movement of the blank that becomes the second component 70D is restricted, causing the cracks to occur.

[0088] On the other hand, in Examples 1 and 2 of this embodiment, it was found that no cracks occurred. In other words, in Examples 1 and 2, it was found that the movement of the protruding piece 122 during press forming suppressed the occurrence of cracks. Thus, in this embodiment, it was found that even when using high-strength steel material with poor ductility, the occurrence of cracks during press forming can be prevented.

[0089] In this embodiment, an example is given of a press-formed part 10 in which a second component 70 is partially overlapped on the upper surface of a first component 60. However, as shown in Figure 10, it may also be a case where a press-formed part 200 is formed in which a first component 201 is partially overlapped on a second component 202. [Explanation of Symbols]

[0090] 10 Press-formed parts 20. Straight section (First straight section) 21 Top panel (First top panel) 24 Vertical wall part (3rd vertical wall part) 30. Straight section (second straight section) 40. Intersecting points (points where points intersect) 41a Curved line (second curved line) 42. Ridge section (Second ridge section) 43 Vertical wall part (second vertical wall part) 44. Foot of the line 45 Flange section (first flange section) 61. Tabletop component (First tabletop component) 62 Ridge section (First ridge section) 63 Vertical wall part (first vertical wall part) 71. Top panel component (second top panel component) 100 blanks for press forming 110 Blank (First Blank) 120 Blank (Second Blank) 121 Blank Body 122 Projecting piece 134 Notch A1,A2,A3 area (first area) A4 area (second area) A11,A12,A13 area (3rd area) A15,A16 area (4th area) A17,A18 area (5th area) C1 Curved section L3 curved line (first curved line)

Claims

1. A blank used for press forming of a press-formed part, wherein a concave curved portion is formed at the intersection of a first straight portion and a second straight portion, A first blank formed by press molding, comprising: a first top plate portion provided in the first straight portion and continuous with the first top plate portion provided in the intersecting portion; and a first vertical wall portion continuous with the first curved line provided in the first top plate portion via a first ridge portion; A second blank formed by press forming, comprising: a second top plate component that overlaps with the first top plate component; a second ridge portion that is continuous with a concave curved second curved line provided on the second top plate component and overlaps with the first ridge portion during press forming; a second vertical wall portion that is continuous with the second top plate component via the second ridge portion and overlaps with the first vertical wall portion during press forming; and a first flange portion that is continuous with the second vertical wall portion via the base portion. It has, A press-formed blank characterized in that the first blank and the second blank are joined together in a state in which the first top plate component and a region of the second top plate component that is continuous with the second top plate component provided on the second straight portion are superimposed.

2. The first blank has a rectangular first region that forms the first straight portion, and a second region that forms the first top plate component, with one of the four corners of the rectangle cut out in a curved shape. The press-formed blank according to claim 1, characterized in that the end of the first vertical wall portion in the direction of extension of the first curved line is continuous with the third vertical wall portion provided in the first straight portion.

3. The second blank comprises a rectangular third region that forms the second straight portion, The press-formed blank according to claim 1, characterized in that it protrudes from the third region and has a curved fourth region that forms the second top plate component, the second ridge line portion, the second vertical wall portion, and the first flange portion.

4. The press-formable blank according to claim 3, characterized in that the second blank further comprises a fifth region which is superimposed on the first straight portion by press forming.

5. The press-formed blank according to claim 1, characterized in that the first blank and the second blank are steel plates having a tensile strength of 980 MPa or more and 1600 MPa or less.

6. A press-formed part characterized by being produced by press forming using a press-forming blank described in any one of claims 1 to 5.

7. The press-formed part according to claim 6, characterized in that the portions that are superimposed by press forming are joined in the first blank and the second blank.

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