Superposed blank, molding method, and method for manufacturing press-molded article

Abstract

The present invention provides a superposed blank which can be molded without causing damage or local deformation of a joint part, by suppressing generation of an excessive load in the joint part. Provided is a superposed blank for press-forming a molded article in which an L-shaped cross-sectional reinforcing component constituted by a top plate part, a vertical wall part, and a ridge part connecting the top plate part and vertical wall part is superposed at the inner portion of a body component comprising at least the top plate part, the vertical wall part, and the ridge part connecting the top plate part and vertical wall part. The superposed blank has a structure of which a second blank made of metal, which constitutes the reinforcing component, is superposed on a first blank made of metal, which constitutes the body component. The structure has a joint part of which two blanks are joined, at the vertical wall corresponding region of the second blank.

Description

Overlapped Blank, Forming Method, and Method for Manufacturing a Press-formed Product

[0001] The present invention relates to an overlapped blank for press-forming a molded product in which a reinforcing part is overlapped inside a main body part, a method for forming the blank, and a method for manufacturing a press-formed product.

[0002] From the viewpoint of protecting the occupants of an automobile body and protecting the battery space, there is a demand for improving the crash safety of automobile parts, such as absorbing crash energy and suppressing deformation. As a means for improving such part performance, there is a method of overlapping a reinforcing part on a part of the main body part that particularly needs to be strengthened.

[0003] On the other hand, when using a reinforcing part, there is a concern that the number of parts increases and the manufacturing cost rises. Therefore, it is required to perform effective reinforcement while suppressing an increase in the number of parts. Thus, a manufacturing method applying a patchwork blank in which a plurality of blanks are overlapped has been proposed. This method has an advantage that it is not necessary to manufacture a reinforcing part separately from the main body part as in the conventional manufacturing method, and thus can suppress and reduce manufacturing costs such as die costs and production preparation periods.

[0004] For example, Patent Document 1 proposes an overlapped blank in which the vicinity along the contour line of the overlapping portion of two blanks is joined by seam welding. By doing so, it is said to have excellent performance in terms of strength, formability, and corrosion resistance compared to joining by spot welding.

[0005] Further, Patent Document 2 proposes an overlapped blank in which a plurality of welding points are arranged in the vicinity of the contour line along the contour line of the overlapping portion of two blanks to form a row in order to avoid breakage of the welded portion during forming.

[0006] Further, Patent Document 3 proposes an overlapped part in which the position that becomes the top plate part is joined first after forming, and the vertical wall part is joined after integral forming. In this invention, by selecting a combination of the strength grade and the plate thickness of the blank, the problem that the wall surfaces of the main body part and the reinforcing part are separated due to springback after integral forming is solved.

[0007] Japanese Patent Publication No. 2000-197969, Japanese Patent Publication No. 2023-501962, Japanese Patent Publication No. 2024-113864

[0008] However, in the methods described in Patent Documents 1 and 2, the joint is formed along the contour line of the overlapping portion of the two blanks. Therefore, it is not possible to fundamentally eliminate the excessive load generated on the joint due to the displacement of the two blanks during bending. Consequently, there remains a risk of damage to the joint and local deformation. In addition, because the joint is formed along the contour line, a large welding length and welding area are required, raising concerns about increased manufacturing costs.

[0009] Furthermore, the method described in Patent Document 3 has a narrow range of applicable conditions. Outside of this applicable range, if the wall lengths of the two blanks are different, their behavior during molding will not match, raising concerns that a gap may form after springback.

[0010] The present invention aims to provide an overlapping blank that can be molded without causing damage or local deformation to the joint by suppressing the generation of excessive load at the joint. Furthermore, the present invention aims to propose a molding method using the overlapping blank and a method for manufacturing press-molded products.

[0011] The overlapping blank according to the present invention, which advantageously solves the above problems, is an overlapping blank for press-molding a molded product in which a reinforcing part having an L-shaped cross section, composed of a top plate portion, a vertical wall portion, and a connecting ridge portion, is overlapped inside a main body component having at least a top plate portion, a vertical wall portion, and a ridge portion connecting them. The overlapping blank has a structure in which a second metal blank, which constitutes the reinforcing part, is overlapped on a first metal blank, which constitutes the main body component. The structure has a joint portion where the two blanks are joined in the region corresponding to the vertical wall of the second blank.

[0012] Furthermore, the molding method according to the present invention, which advantageously solves the above problems, is a molding method for manufacturing a member in which a reinforcing part having an L-shaped cross section composed of a top plate portion, a vertical wall portion, and a ridge portion connecting them is superimposed inside a main body component having at least a top plate portion, a vertical wall portion, and a ridge portion connecting them. The molding method includes a first step of preparing a superimposed blank and a second step of bending the superimposed blank at the ridge portion by press molding. In the first step, a first metal blank constituting the main body component and a second metal blank constituting the reinforcing part are joined at the region corresponding to the vertical wall of the second blank. In the second step, the load generated at the joint is reduced by the relative movement of the two blanks during molding caused by the difference in radius of curvature, by the two blanks moving relative to each other parallel to the contact surface in at least the region corresponding to the top plate among the non-joined regions in the first step.

[0013] Furthermore, the present invention provides a method for manufacturing a press-formed product that advantageously solves the above problems, and involves manufacturing a press-formed product in which a reinforcing part having an L-shaped cross-section, composed of a top plate portion, a vertical wall portion, and a ridge portion connecting them, is superimposed inside a main body component having at least a top plate portion, a vertical wall portion, and a ridge portion connecting them. This manufacturing method includes a first step of preparing a superimposed blank and a second step of bending the superimposed blank at the ridge portion by press forming. In the first step, a first metal blank constituting the main body component and a second metal blank constituting the reinforcing part are joined at the region corresponding to the vertical wall of the second blank. In the second step, the load generated at the joint is reduced by the relative movement of the two blanks during forming caused by the difference in radius of curvature, by the two blanks moving relative to each other parallel to the contact surface in at least the region corresponding to the top plate among the non-joined regions in the first step.

[0014] In this invention, the first blank and the second blank are integrally molded with a joint applied only in the vertical wall-equivalent region that will become the vertical wall portion of the reinforcing part after molding, and the portion on the top plate-equivalent region side of the joint is not joined. Therefore, the excessive load generated on the joint due to the displacement of the two blanks during bending can be reduced by the relative parallel displacement of the two blanks in at least the top plate-equivalent region during molding. Consequently, the risk of damage to the joint and local deformation caused by this can be eliminated. In addition, it is possible to prevent the formation of a gap in the vertical wall portion of the main body part and the reinforcing part after springback. As a result, when an impact load is applied, the main body part and the reinforcing part can undergo integrated deformation behavior to absorb impact energy, thereby improving the impact performance of the members.

[0015] Preferably, when press forming the overlapping blanks, a pad form is used in which the overlapping blanks are compressed between a die mold having a pad and a punch mold facing it. During forming, the pad biases the top plate-equivalent region of the first blank to the punch mold in the area where the second blank is not present, while the top plate-equivalent region of the second blank is not biased by the pad and can move freely parallel to the contact surface with the top plate-equivalent region of the first blank. This effectively absorbs the relative movement of the two blanks during forming caused by the difference in the radius of curvature at the ridges of the main body part and the reinforcing part.

[0016] Furthermore, preferably, a clearance is provided between the punch die and the surface of the pad in the area where the second blank exists, such that the clearance is at least the sum of the thicknesses of the first blank and the second blank plus 0.15 mm. This promotes the relative parallel movement of the top plate-equivalent area, which eliminates the relative movement of the two blanks during molding caused by the difference in the radius of curvature at the ridges of the main body part and the reinforcing part. Therefore, the load generated at the joint can be further reduced.

[0017] (a) is a perspective view of an overlapping blank according to one embodiment of the present invention, and (b) is a perspective view showing a molded product of the overlapping blank. This is a schematic cross-sectional diagram illustrating the method for forming the overlapping blank according to the above embodiment. This is a schematic cross-sectional diagram showing an enlarged view of the bent portion of a reinforcing part, illustrating the method for forming the overlapping blank according to the above embodiment. This is a graph showing the effect of the added distance in the clearance between the punch die and the pad in the range where the second blank exists on the magnitude of the shear load at the joint when forming the overlapping blank according to the above embodiment. This is a perspective view of the overlapping blank of Invention Example 1. This is a schematic cross-sectional diagram in the process of forming the overlapping blank of Invention Example 1. This is a schematic cross-sectional diagram after springback of a press-formed product formed from the overlapping blank of Invention Example 1. This is a perspective view of the overlapping blank of Comparative Example 1. This is a schematic cross-sectional diagram in the process of forming the overlapping blank of Comparative Example 1. This is a schematic cross-sectional diagram after springback of a press-formed product formed from the overlapping blank of Comparative Example 1. This is a schematic cross-sectional diagram of Invention Example 2 showing the clearance between the surface of the punch die and the pad in the range where the second blank exists. This is a schematic cross-sectional view showing the clearance between the punch die and the surface of the pad in the area where the second blank exists in Invention Example 3. This is a schematic cross-sectional view showing the clearance between the punch die and the surface of the pad in the area where the second blank exists in Invention Example 4.

[0018] The following describes, with reference to the drawings, an embodiment of the present invention, including an overlapping blank, a molding method, and a method for manufacturing a press-formed product. Note that the embodiments described below are illustrative examples of apparatus and methods for realizing the technical concept of the present invention, and do not limit the materials, shapes, structures, arrangements, etc., of the components to those embodiments. Furthermore, the drawings are schematic; therefore, it should be noted that the relationship and ratios between thickness and planar dimensions may differ from those in reality. There are also parts where the dimensional relationships and ratios differ between drawings.

[0019] Figure 1(a) is a perspective view of the overlapping blank B according to this embodiment. Figure 1(b) is a perspective view of the molded product P of the overlapping blank B. The overlapping blank B has a structure in which two metal blanks B2 and B3, which constitute the reinforcing part, are superimposed on a first metal blank B1 that constitutes the main part. In this structure, the vertical wall equivalent regions B2b and B3b of the second blanks B2 and B3, which become the vertical wall portion of the reinforcing part after molding, have joint portions WS between the two blanks B1 and B2 (or B1 and B3). On the other hand, this structure does not have joint portions in the top plate equivalent regions B1a, B2a and B3a, which become the top plate portion of the reinforcing part after molding.

[0020] The molded product P has a structure in which L-shaped reinforcing parts P2 and P3 are superimposed on the inside of a hat-shaped main part P1. The main part P1 consists of a top plate portion P1a, a vertical wall portion P1b, a connecting ridge portion P1d, and a flange portion P1c. The reinforcing parts P2 and P3 have top plate portions P2a and P3a, vertical wall portions P2b and P3b, and connecting ridge portions P2d and P3d. The joint portion WS is present in the vertical wall portions P2b and P3b of the reinforcing parts P2 and P3. The top plate portions P2a and P3a and the vertical wall portions P2b and P3b of the reinforcing parts P2 and P3 are superimposed on the main part P1 from the inside. There are areas in the top plate portion P1a and vertical wall portion P1b of the main part P1 where the reinforcing parts P2 and P3 are not superimposed. In this embodiment, the main body component P1 has vertical wall portions P1b on both sides in the width direction of the top plate portion P1a, and reinforcing components P2 and P3 are provided on both sides in the width direction, but it is not limited to this. The present invention can also be applied, for example, when the main body component P1 has a vertical wall portion P1b on only one side in the width direction of the top plate portion P1a, and only one reinforcing component P2 is provided.

[0021] Figure 2 is a schematic cross-sectional view illustrating the molding method according to this embodiment. Figure 2 shows only one side from the widthwise center of the molds (1, 2) and the overlapping blank B. The same applies to Figures 3, 6, 7, etc., where only one side is shown. Figure 2 shows the overlapping blank B placed on the top plate-equivalent portion of the punch die 2 and clamped by the pad 3. As the die die 1, which has a lifting device, descends, the overlapping blank B is compressed into the narrow space between the die die 1 and the punch die 2, thereby forming the shape of the molded product P. The die die 1 is fitted with a pad 3, which suppresses deformation of the top plate-equivalent region during molding, by a spring mechanism 4 as a biasing means. The pad 3 presses the top plate-equivalent region B1a of the first blank B1 against the punch die 2 in the area where the second blanks B2 and B3 are not present. The punch die 2 is provided with a recess 21 where the second blanks B2 and B3 are arranged.

[0022] Figure 3 is an enlarged schematic cross-sectional view of the vicinity of the reinforcing part P2, showing the state after the die mold 1 has been lowered from the state in Figure 2 and the molded product P has been formed from the overlapping blanks B. The pad 3 faces the top plate-equivalent area B1a of the first blank B1 over almost the entire width direction. In this embodiment, the clearance CL between the surface of the punch mold 2 and the surface of the pad 3 in the area where the second blanks B2 and B3 exist during molding is set to a predetermined value. The clearance CL is greater than the sum of the plate thickness of the first blank B1 that constitutes the main body part P1 and the plate thicknesses of the second blanks B2 and B3 that constitute the reinforcing parts P2 and P3. Preferably, the clearance CL is set so that the added distance to the sum of the plate thicknesses of these two blanks is 0.15 mm or more. This promotes relative movement parallel to the contact surface of the top plate-equivalent area (parallel movement of B1a and B2a and parallel movement of B1a and B3a) to eliminate the relative movement of the two blanks during molding caused by the difference in radius of curvature at the edges of the main body part P1 and the reinforcing parts P2 and P3 (difference in radius of curvature between P1d and P2d, difference in radius of curvature between P1d and P3d). This reduces the load generated on the joint WS during molding. From the viewpoint of preventing deformation of the top plate-equivalent areas B1a, B2a, and B3a during molding and ensuring smoothness, the upper limit of the added distance is preferably less than or equal to the thickness of the first blank B1, and more preferably less than or equal to half the thickness of the first blank B1. A recess 31 is formed in the pad 3 of this embodiment to set the clearance CL. The distance between the bottom surface of the recess 31 of the pad 3 and the bottom surface of the recess 21 of the punch die 2 corresponds to the clearance CL. In this embodiment, both the recess 21 and the recess 31 are formed to a certain depth.

[0023] Figure 4 shows a graph illustrating the effect of the clearance CL between the punch die 2 and pad 3 in the area where the second blanks B2 and B3 exist on the magnitude of the shear load at the joint WS. This graph was obtained from simulation analysis results. The magnitude of the shear load is expressed as a percentage, with 100% representing the case where the clearance CL is the sum of the thicknesses of the two blanks, i.e., when the summing distance is 0.00 mm. This graph shows that when the summing distance is 0.15 mm or more, the shear load generated at the joint WS can be reduced to 60% or less compared to the case where the summing distance is 0.00 mm.

[0024] The following describes each step of the method for forming the overlapping members and the method for manufacturing the press-formed product according to this embodiment.

[0025] (First step) In this step, the overlapping blank B is prepared. As shown in Figure 1(a), a first metal blank B1 that constitutes the main body part P1 and second metal blanks B2 and B3 that constitute the reinforcing parts P2 and P3 are prepared. The first blank B1 and the second blanks B2 and B3 are placed in predetermined positions, and a joint WS is formed between the two blanks B1 and B2 (or B1 and B3) in the vertical wall equivalent regions B2b and B3b of the second blanks B2 and B3.

[0026] (Second Process) In this process, the blanks B are bent and formed by press molding so that they form ridge sections (P1d, P2d, P3d) (Figure 3). The relative movement of the two blanks during molding, which occurs due to the difference in the radius of curvature at the ridge sections of the main body part P1 and the reinforcing parts P2 and P3, is absorbed by the relative movement of the first blank B1 and the second blanks B2 and B3 in at least the top plate equivalent areas B1a, B2a, and B3a in the non-joined area of ​​the first process.

[0027] This process preferably involves forming a pad form by compressing a blank B by overlapping it between a die mold 1 having a pad 3 and a punch mold 2 facing it. During forming, the top plate equivalent region B1a of the first blank B1 is biased to the punch mold 2 by the pad 3 using a spring mechanism 4 as a biasing means, in the area where the second blanks B2 and B3 are not present. At this time, the top plate equivalent region B1a of the second blanks B2 and B3 and the top plate equivalent regions B2a and B3a of the second blanks B2 and B3 are not biased by the pad 3. Therefore, the top plate equivalent regions B2a and B3a of the second blanks B2 and B3 are allowed to move freely relative to the top plate equivalent region B1a of the first blank B1, which is constrained by the pad 3 and the punch mold 2, regardless of the biasing force of the pad 3 pressing down on the top plate equivalent region B1a. It is preferable that these top plate equivalent regions B2a and B3a are freely movable parallel to the contact surface with the top plate equivalent region B1a of the first blank B1. Before molding, the first blank B1 and the second blanks B2 and B3 are joined at the vertical wall equivalent regions of the second blanks B2 and B3. Therefore, during molding, the relative movement of the two blanks (B1 and B2, or B1 and B3) caused by the difference in the radius of curvature at the ridge portions P1d, P2d, and P3d of the main body component P1 and the reinforcing components P2 and P3 is absorbed by the relative parallel movement of the first blank B1 and the second blanks B2 and B3 on the top plate side. Depending on the specific deformation behavior during molding, the top plate equivalent regions B2a and B3a of the second blanks B2 and B3 can be displaced either towards the center in the width direction of the top plate or outward relative to the top plate equivalent region B1a of the first blank B1. An example of the deformation behavior of blank B is shown in Figure 6. As the first blank B1 is pressed and bent between the die mold 1 and the punch mold 2, the second blanks B2 and B3 deform inside the first blank B1, conforming to the shape of the first blank B1, and undergo relative displacement along the contact surface with the first blank B1 from the joint WS to the top plate equivalent regions B2a and B3a.As shown in Figure 6, from the viewpoint of absorbing more of the relative movement of the two blanks caused by the difference in radius of curvature due to the relative displacement of the first blank B1 and the second blanks B2 and B3 in the region on the top plate side of the joint WS, it is preferable that the joint WS be provided at a position further away from the top plate equivalent regions B2a and B3a in the vertical wall equivalent regions B2b and B3b, for example, near one end B2e and B3e in the width direction.

[0028] In this process, it is preferable to provide a clearance CL between the punch die 2 and the pad 3 in the area where the second blanks B2 and B3 exist, such that the clearance CL is at least the sum of the thickness of the first blank B1 and the thickness of the second blank B2 plus 0.15 mm. The relative movement of the two blanks that occurs during molding due to the difference in radius of curvature is facilitated by providing the above-mentioned clearance CL.

[0029] <Examples> Examples (inventive examples) and comparative examples conducted to confirm the effects of the overlapping blank, molding method, and press-molded product manufacturing method of this embodiment are described below.

[0030] <Confirmation of the effects and benefits related to the joining region of the overlapping blanks> (Example 1 of the invention) Figure 5 shows a perspective view of the overlapping blank B of Example 1 of the invention according to an embodiment of the present invention. The first blank B1 made of metal that constitutes the main body part P1 is a steel plate with a width of 300 mm, a length of 300 mm, and a thickness of 1.4 mm, with a tensile strength of 980 MPa. The second blanks B2 and B3 made of metal that constitute the reinforcing parts P2 and P3 are steel plates with a width of 50 mm, a length of 300 mm, and a thickness of 1.4 mm, with a tensile strength of 1470 MPa. The first blank B1 and the second blanks B2 and B3 were joined by performing spot welding WS at 40 mm intervals in the vertical wall equivalent regions B2b and B3b.

[0031] Figure 6 shows a cross-sectional view of the molding process of the above-described embodiment 1. The overlapping blanks B are compressed by a die mold 1 and a punch mold 2, which have a lifting device, to form the shape of the molded product P. A pad 3 is attached to the die mold 1 by a spring mechanism 4. The load applied by the pad 3 to the overlapping blanks B is set to 300 kN. The punch mold 2 is provided with recesses 21 in which the second blanks B2 and B3 are placed. The pad 3 is also provided with recesses 31. The clearance CL between the surfaces of the punch mold 2 and the pad 3 is greater than the sum of the thickness of the first blank B1 and the thicknesses of the second blanks B2 and B3, as in the above embodiment. Since the vertical wall regions of the first blank B1 and the second blanks B2 or B3 are joined to each other, they remain joined together even during molding.

[0032] Figure 7 shows a cross-sectional view of the above-described example 1 after springback. After springback, there are no gaps between the main body part P1 and the reinforcing parts P2 and P3, including between the vertical wall portions P1b and P2b, and between the vertical wall portions P1b and P3b. The top plate portions P2a and P3a of the reinforcing parts P2 and P3 are pressed against the inside of the top plate portion P1a of the main body part P1, fixing their position.

[0033] (Comparative Example 1) Figure 8 shows the superimposed blank B of Comparative Example 1 relating to the conventional method. ＰＲ A perspective view is shown. The first metal blank B1, which constitutes the main body component, is a steel plate with a width of 300 mm, a length of 300 mm, and a thickness of 1.4 mm, with a tensile strength of 980 MPa. The second metal blanks B2 and B3, which constitute the reinforcing component, are steel plates with a width of 50 mm, a length of 300 mm, and a thickness of 1.4 mm, with a tensile strength of 1470 MPa. The first blank B1 and the second blanks B2 and B3 are joined to the top plate equivalent areas B2a and B3a of the reinforcing component by performing spot welding WS at 40 mm intervals.

[0034] Figure 9 shows a cross-sectional view of Comparative Example 1 during the molding process. Overlap blank B ＰＲThe blanks are formed into the shape of a component by being compressed by a die mold 1 and a punch mold 2, which have a lifting device. A pad 3 is attached to the die mold 1 by a spring mechanism 4 to suppress deformation of the top plate-equivalent area during molding. The load applied by the pad 3 to the overlapping blank B is set to 300 kN. The pad 3 presses the top plate-equivalent area of ​​the blank B against the punch mold 2 across its entire width. The punch mold 2 is provided with recesses 21 in which the second blanks B2 and B3, which constitute the reinforcing parts of the overlapping blank B, are placed. The vertical wall-equivalent areas of the first blank B1 and the second blanks B2 and B3 are not joined to each other. Therefore, during molding, the vertical wall-equivalent areas of the second blanks B2 and B3 separate from the first blank B1.

[0035] Figure 10 shows the molded product P of Comparative Example 1 after springback. ＰＲ A cross-sectional view is shown. After springback, a gap 5 is created between the main body part P1 and the reinforcing part P2, extending from the vertical wall to the ridge, and the vertical wall portions of the main body part P1 and the reinforcing part P2 are separated.

[0036] <Confirmation of the effect of clearance between the punch die and the pad surface> (Example 2 of Invention) Figure 11 shows the clearance CL between the punch die 2 and the pad 3 in the area where the second blanks B2 and B3 exist for Example 2 of Invention. The blanks B1, B2 and B3 used were the same as in Example 1 of Invention. The clearance CL between the punch die 2 and the pad 3 was designed by adding various addition distances to the combined thickness of two blanks, 2.8 mm, which is the sum of the thickness of the first blank B1 (1.4 mm) and the thickness of the second blanks B2 and B3 (1.4 mm). The shear load generated at the joint WS during molding under various clearance CL conditions was calculated by simulation analysis and is shown in Table 1. In Example 2 of Invention, the depth of the recess 21 of the punch die 2 is approximately equivalent to the thickness of the second blanks B2 and B3. The pad 3 is provided with a recess 31 with a depth corresponding to the addition distance in the clearance CL.

[0037]

[0038] Table 1 shows that when the added distance is 0.15 mm or more, the shear load generated at the joint WS can be reduced to 60% or less compared to when no added distance is used (added distance 0.00 mm).

[0039] (Example 3 of Invention) Figure 12 shows the clearance CL between the punch die 2 and the surface of the pad 3 in the area where the second blanks B2 and B3 exist, according to Example 3 of Invention. When designing the clearance CL, the surface of the pad 3 may be made an inclined surface 32 with respect to the surface of the punch die 2, as shown in Figure 12, so that the area near the edge is widened. In this case, the minimum value of the clearance CL CL1 may be equal to the sum of the plate thickness of the first blank B1 and the plate thickness of the second blank B2 (or B3). During the bending process, the two blanks may be bent while lifting away from the punch die 2 near the area near the edge. Therefore, if the clearance CL is wide near the area of ​​the edge of the two blanks, the top plate-equivalent areas of the first blank B1 and the second blanks B2 and B3 are more likely to be displaced relative to each other.

[0040] (Example 4 of Invention) Figure 13 shows the clearance CL between the punch die 2 and the surface of the pad 3 in the area where the second blanks B2 and B3 exist, according to Example 4 of Invention. When designing the clearance CL, the recess 21 of the punch die 2 may be designed to be more deeply recessed relative to the surface of the pad 3 compared to the embodiment (Figure 3), as shown in Figure 13. In this case, even if the pad 3 does not have a recess 31 formed in it, as shown in Figure 13, the clearance CL is greater than the sum of the thickness of the first blank B1 and the thickness of the second blank B2 (or B3), so, similar to the embodiment described above, the top plate equivalent areas of the two blanks (B1 and B2, or B1 and B3) are easily moved in parallel relative to each other in the area where the second blanks B2 and B3 exist.

[0041] Thus, according to the present invention, the overlapping blank, molding method, and press-formed product manufacturing method have a structure in which a blank constituting a reinforcing part is overlapped with a blank constituting a main part, and this structure has a joint in the region corresponding to the vertical wall of the second blank constituting the reinforcing part. Therefore, the risk of damage to the joint or local deformation caused by excessive load on the joint due to the displacement of the two blanks during bending can be eliminated.

[0042] B (Overlapping) Blank B1 First blank (Constituting the main body part) B1a Top plate equivalent area (of the first blank) B2, B3 Second blank (Constituting the reinforcing part) B2a, B3a Top plate equivalent area (of the second blank) B2b, B3b Vertical wall equivalent area (of the second blank) B2e, B3e One end (of the second blank) P (Pressed) molded product P1 Main body part (Hat-shaped cross section) P1a Top plate portion (of the main body part) P1b Vertical wall portion (of the main body part) P1c Flange portion (of the main body part) P1d Ridge portion (of the main body part) P2, P3 Reinforcing part (L-shaped cross section) P2a, P3a Top plate portion (of the reinforcing part) P2b, P3b Vertical wall portion (of the reinforcing part) P2d, P3d Ridge (of the reinforcing part) CL Clearance (between the surface of the punch die and the pad in the area where the reinforcing part is present) CL1 Minimum value (of the clearance) WS Joint (spot weld) 1 Die die 2 Punch die 3 Pad 4 Spring mechanism 5 Gap (between the main body part and the reinforcing part due to springback) 21 Recess 31 Recess 32 Inclined surface

Claims

1. A superimposed blank for press-forming a molded product in which a reinforcing part having an L-shaped cross section, composed of a top plate, a vertical wall, and a ridge connecting them, is superimposed inside a main body part having at least a top plate, a vertical wall, and a ridge connecting them, wherein the superimposed blank has a structure in which a second metal blank constituting the reinforcing part is superimposed on a first metal blank constituting the main body part, and the structure has a joint portion where the two blanks are joined in a region corresponding to the vertical wall of the second blank.

2. A molding method for manufacturing a member in which a reinforcing part having an L-shaped cross section composed of a top plate, a vertical wall, and a ridge connecting them is superimposed inside a main body part having at least a top plate, a vertical wall, and a ridge connecting them, comprising: a first step of preparing a superimposed blank; and a second step of bending the superimposed blank at the ridge by press molding, wherein in the first step, a first metal blank constituting the main body part and a second metal blank constituting the reinforcing part are joined at the region corresponding to the vertical wall of the second blank; and in the second step, the load generated at the joint due to the relative movement of the two blanks during molding caused by the difference in radius of curvature is reduced by the relative movement of the two blanks during molding caused by the difference in radius of curvature, wherein the two blanks move relative to each other parallel to the contact surface in at least the region corresponding to the top plate among the non-joined regions in the first step.

3. The molding method according to claim 2, wherein the second step is to form a pad foam by compressing the overlapping blanks between a die mold having a pad and a punch mold facing it, wherein during molding, the pad biases the top plate-equivalent region of the first blank to the punch mold in the area where the second blank is not present, and the top plate-equivalent region of the second blank is freely movable parallel to the contact surface with the top plate-equivalent region of the first blank without being biased by the pad.

4. The molding method according to claim 2 or 3, wherein in the second step, a clearance is provided between the punch die and the surface of the pad in the area where the second blank exists, such that the clearance is at least the sum of the thickness of the first blank and the thickness of the second blank plus 0.15 mm, thereby promoting the relative parallel movement of the area equivalent to the top plate.

5. The molding method according to claim 4, wherein the punch die has recesses formed in which the top plate-equivalent region and the vertical wall-equivalent region of the second blank are arranged, and the pad has recesses formed in which the clearance is set.

6. A method for manufacturing a press-formed product in which a reinforcing part having an L-shaped cross section composed of a top plate, vertical wall, and ridge connecting them is superimposed inside a main body part having at least a top plate, vertical wall, and ridge connecting them, comprising: a first step of preparing a superimposed blank; and a second step of bending the superimposed blank at the ridge by press forming, wherein in the first step, a first metal blank constituting the main body part and a second metal blank constituting the reinforcing part are joined at the region corresponding to the vertical wall of the second blank; and in the second step, the load generated at the joint due to the relative movement of the two blanks during forming caused by the difference in radius of curvature is reduced by the relative movement of the two blanks during forming, at least in the region corresponding to the top plate among the non-joined regions in the first step.

7. The method for manufacturing a press-formed product according to claim 6, wherein the second step involves compressing the overlapping blanks between a die mold having a pad and a punch mold facing it to form a pad form, and during molding, the pad biases the top plate-equivalent region of the first blank to the punch mold in the area where the second blank is not present, while the top plate-equivalent region of the second blank is freely movable parallel to the contact surface with the top plate-equivalent region of the first blank without being biased by the pad.

8. The method for manufacturing a press-formed product according to claim 6 or 7, wherein in the second step, a clearance is provided between the punch die and the surface of the pad in the area where the second blank exists, such that the clearance is at least the sum of the thickness of the first blank and the thickness of the second blank plus 0.15 mm, thereby promoting the relative parallel movement of the area equivalent to the top plate.

9. The method for manufacturing a press-formed product according to claim 8, wherein the punch die has recesses formed in which the top plate-equivalent region and the vertical wall-equivalent region of the second blank are arranged, and the pad has recesses formed in which the clearance is set.

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