Method for manufacturing molded article

Abstract

The present disclosure provides a method for manufacturing a molded article. The method for manufacturing a molded article includes: forming a first bonding portion by superimposing and welding an inner metal plate on an outer metal plate; after the first joining part is formed, the outer metal plate and the inner metal plate are bent together in the first direction by performing a first press. Further, the method includes bending the outer metal plate and the inner metal plate together in a second direction by performing a second press after performing the first press, and forming a bent portion on the outer metal plate, the bent portion being opposite to the bending direction of the reverse bent portion.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a manufacturing method of a formed product. BACKGROUND

[0002] In the drawing and bending processes of a metal sheet, a reinforcing plate (i.e., a patch) is stacked and welded on a base material of the metal sheet to improve strength, and then the metal sheet is subjected to press working. In the above-mentioned processes, a difference in extension length occurs between the reinforcing plate disposed on the inner side of the bend and the base material disposed on the outer side of the bend due to the press working. This results in the occurrence of a shear stress at the welded portion of the reinforcing plate, and further results in cracking of the welded portion.

[0003] Here, Japanese Patent Application Publication No. 2023-102761 discloses a manufacturing method of a formed product in which a main blank and a reinforcing blank are stacked and welded, and then press working is performed to manufacture the formed product having a ceiling portion, two longitudinal wall portions, and a bend portion between the ceiling portion and each longitudinal wall portion. In the above-mentioned manufacturing method, a joint portion is provided at a portion of the main blank and the reinforcing blank corresponding to each longitudinal wall portion before press working. Further, a convex shape for suppressing cracking of the joint portion is formed on the main blank disposed on the outer side of the bend before welding. Then, the formed product is manufactured in such a manner that the bend portion is formed at a portion provided with the convex shape. SUMMARY

[0004] As another method of suppressing cracking of the joint portion in two sheets welded together, a method in which the joint portion is provided only at a portion corresponding to the ceiling portion in the two sheets, and the joint portion is provided at the longitudinal wall portion after press working of the two sheets can be considered.

[0005] However, in this other method, since the amount of springback of the two sheets after press working is different, there is a possibility that a gap occurs between the two sheets at the longitudinal wall portion. If this gap occurs, there is a problem that the two sheets at the longitudinal wall portion after press working are difficult to weld.

[0006] One aspect of the present disclosure provides a manufacturing method of a formed product that can both suppress cracking of a joint portion in two sheets welded together and easily form the joint portion.

[0007] One aspect of the present disclosure is a method of manufacturing a shaped product. The method includes the following steps: stacking and welding an inner metal plate to an outer metal plate to form a first joining portion; and after forming the first joining portion, bending the outer metal plate and the inner metal plate together in a first direction by performing a first pressing. Further, the method includes the following steps: after performing the first pressing, bending the outer metal plate and the inner metal plate together in a second direction opposite to the first direction by performing a second pressing. In the second pressing, a first surface, a second surface, and a bent portion are formed on the outer metal plate, the second surface extends in a direction intersecting the first surface, the bent portion links the first surface and the second surface to each other, and the bent portion overlaps the inner metal plate. In the first pressing, a reverse bent portion is formed on the outer metal plate, the reverse bent portion is opposite in bending direction to the bent portion, and the reverse bent portion overlaps the inner metal plate. The reverse bent portion is formed to overlap a region that is the bent portion on the outer metal plate. The inner metal plate is located outside the reverse bent portion after performing the first pressing, and is located inside the bent portion after performing the second pressing. The first joining portion is a portion where the inner metal plate is welded to a region that is the first surface in the outer metal plate.

[0008] According to the above configuration, even if the outer metal plate and the inner metal plate are bent together by the first pressing and the second pressing, and a difference in extension length occurs between the outer metal plate and the inner metal plate, stress is not easily concentrated on the first joining portion. Further, since the outer metal plate and the inner metal plate are bent in the first direction before being bent in the second direction, even if the outer metal plate and the inner metal plate spring back due to being bent in the second direction, a gap between the inner metal plate and the second surface of the outer metal plate after the second pressing can be reduced. Thus, both cracking of the first joining portion in the two metal plates that are welded together can be suppressed, and a joining portion that can be formed between the second surfaces of the inner metal plate and the outer metal plate can be easily formed.

[0009] In one aspect of the present disclosure, the following step can be further provided: after performing the second pressing, welding the outer metal plate and the inner metal plate to each other to form a second joining portion, the second joining portion being a portion where the inner metal plate is welded to the second surface.

[0010] According to the above configuration, the second joining portion can be formed in a state where it is not easily affected by a difference in extension length between the outer metal plate and the inner metal plate due to the second pressing. Thus, cracking at the second joining portion can be suppressed. Further, the second joining portion can be formed in a state where a gap between the inner metal plate and the second surface of the outer metal plate after the second pressing is reduced. Thus, the second joining portion can be easily formed.

[0011] In one aspect of the present disclosure, the inner metal plate can have at least one preliminary cover portion that overlaps the reverse bending portion after the first pressing, and the inner metal plate can have at least one cover portion that overlaps the bending portion after the second pressing. The at least one cover portion can have a first end portion on the first surface side and a second end portion on the second surface side. The reverse bending portion can be formed such that a length from a position of the inner metal plate as the first end portion to an end portion of the preliminary cover portion on the side of the region of the outer metal plate as the second surface is longer than a length from the first end portion to the second end portion in the cover portion.

[0012] According to the above configuration, a portion of the preliminary cover portion near the end portion on the side of the region of the outer metal plate as the second surface is bent and deformed toward the first direction at the time of the first pressing, and extends in a substantially straight line after the second pressing. Thus, springback is easily generated, and the inner metal plate is pressed against the second surface of the outer metal plate. Therefore, a gap between the inner metal plate and the second surface of the outer metal plate after the second pressing can be reduced.

[0013] In one aspect of the present disclosure, the reverse bending portion can be formed such that a first bending angle of the reverse bending portion is larger than a second bending angle of the bending portion. The first bending angle can refer to an angle that a first inclined line makes with respect to an intersection line on a cross section along an arrangement direction of the first surface, the bending portion, and the second surface, in which the first inclined line is a line along a preliminary opposite surface of the region of the outer metal plate on the opposite side of the region as the second surface, and the intersection line is a line that intersects the region of the outer metal plate as the first surface in a substantially perpendicular manner. The second bending angle can refer to an angle that a second inclined line makes with respect to the intersection line on the cross section, in which the second inclined line is a line along an opposite surface of the outer metal plate on the opposite side of the second surface.

[0014] According to the above configuration, interference between a portion of the outer metal plate having the region as the second surface after the first pressing and a die for the second pressing can be suppressed when the second pressing is performed.

[0015] In one aspect of the present disclosure, the reverse bending portion can be formed such that an end portion of the reverse bending portion on the side of the region of the outer metal plate as the first surface is located closer to the side of the region of the outer metal plate as the second surface than an end portion of the outer metal plate on the side of the first surface of the bending portion.

[0016] According to the above configuration, because a portion that is not easily bent and deformed at the region of the outer metal plate as the first surface by the first pressing, a tendency to be bent toward the first direction at the first surface can be suppressed when the second pressing is performed.BRIEF DESCRIPTION OF DRAWINGS BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a perspective view schematically showing a molded product.

[0018] Figure 2 is a side view schematically showing a molded product.

[0019] Figure 3A is a schematic cross-sectional view along the lateral direction at the position of the first joint of the blank after a pre-welding process.

[0020] Figure 3B is a schematic cross-sectional view along the lateral direction at the position of the first joint of the blank after the first bending process.

[0021] Figure 3C is a schematic cross-sectional view along the lateral direction at the position of the first joint of the blank after the second bending process.

[0022] Figure 3D is a schematic cross-sectional view along the lateral direction at the positions of the first joint and the second joint of the molded product completed after the post-welding process.

[0023] Figure 4 is a flowchart showing a manufacturing method of a molded product.

[0024] Figure 5 is a view explaining the first bending process.

[0025] Figure 6 is a view explaining the second bending process.

[0026] Figure 7 is a view explaining the relationship between the bending portion and the reverse bending portion.

[0027] Figure 8 is a view explaining the reverse bending portion of the first comparative example.

[0028] Figure 9 is a view explaining the reverse bending portion of the second comparative example.

[0029] Figure 10 is a side view along the lateral direction of a molded product of the first modified example.

[0030] Figure 11 is a side view along the lateral direction of a molded product of the second modified example. DETAILED DESCRIPTION

[0031] An exemplary embodiment of the present disclosure will be described below with reference to the accompanying drawings.

[0032] [1. Configuration of molded product]

[0033] Figure 1 and Figure 2 The molded product 100 is formed by welding processing of a blank and bending processing by press working, where the blank is a sheet material (hereinafter referred to as a blank) in which a first metal sheet 1 and a second metal sheet 2 are stacked.

[0034] The molded product 100 is a plate-shaped member extending along a longitudinal direction L, and has a plurality of corners 10. The corners 10 are formed by press working the blank in a thickness direction. In the present embodiment, the molded product 100 has a hat shape in a cross-sectional shape (hereinafter referred to as a cross-sectional shape) along a transverse direction S orthogonal to the longitudinal direction L. The hat shape refers to a shape having two opposite side walls, a top wall connecting the two side walls at a first end side, and two flange portions extending in a direction away from each other from second ends of the respective side walls on an opposite side of the first end. In addition, the cross section along the transverse direction S can also refer to a cross section along an arrangement direction of the first surface 111, the curved portion 13, and the second surface 121 described below.

[0035] For example, the molded product 100 can be used as a constituent member of a vehicle body. In the present embodiment, the molded product 100 is a side panel provided at a lower portion of a side surface of a vehicle. In addition, the molded product can be a front pillar or a center pillar, or the like. The molded product 100 has the first metal sheet 1, the second metal sheet 2, a plurality of first joining portions 3, and a plurality of second joining portions 4.

[0036] <First Metal Sheet>

[0037] The first metal sheet 1 is constituted by, for example, a steel sheet. In the present embodiment, as shown in FIG. 1, the cross-sectional shape of the first metal sheet 1 is a hat shape. The first metal sheet 1 has a top wall 11, two side walls 12, two curved portions 13, and two flange portions 14. Figure 2

[0038] The top wall 11 has a first surface 111. The side wall 12 has a second surface 121 extending in a direction intersecting the first surface 111. The first surface 111 is a surface of the top wall 11 continuous with an inner surface of the curved portion 13 described below. The second surface 121 is a surface of the side wall 12 continuous with the inner surface of the curved portion 13 described below.

[0039] The curved portion 13 is a portion between the top wall 11 and the side wall 12, and is curved by bending processing of the first metal sheet 1. The curved portion 13 constitutes the corner 10 of the molded product 100. The curved portion 13 links the first surface 111 of the top wall 11 and the second surface 121 of the side wall 12 to each other. ​

[0040] The flange portion 14 is formed by bending end portions of the side walls 12 on the opposite side of the top wall 11 by bending processing of the first metal plate 1. The plate surface of the flange portion 14 extends in a direction intersecting the plate surface of the side wall 12.

[0041] <Second Metal Plate>

[0042] The second metal plate 2 is the same as the first metal plate 1, for example, is configured by a steel plate. In addition, the material of the first metal plate and the second metal plate is not particularly limited. Furthermore, the first metal plate and the second metal plate can be made of different materials. In the present embodiment, the cross-sectional shape of the second metal plate 2 is a U shape.

[0043] The second metal plate 2 is stacked and welded to the first metal plate 1. The second metal plate 2 is arranged so as to straddle the top wall 11, the two side walls 12, and the two bent portions 13 of the first metal plate 1. In the present embodiment, the second metal plate 2 overlaps the first surface 111 of the first metal plate 1, the second surface 121 of each side wall 12, and the inner surface of each bent portion 13. That is, the second metal plate 2 is arranged inside each bent portion 13 of the first metal plate 1 and is welded to the first metal plate 1 in a manner that overlaps each bent portion 13 from the inside. In the present embodiment, the length of the second metal plate 2 in the longitudinal direction L is shorter than the first metal plate 1, and overlaps only a part of the range of the first metal plate 1 in the longitudinal direction L. In addition, the second metal plate can have the same length as the first metal plate in the longitudinal direction L, and can overlap the first metal plate in the entire range from one end to the other end of the first metal plate in the longitudinal direction L.

[0044] The second metal plate 2 has a first cover portion 21, two second cover portions 22, and two third cover portions 23.

[0045] The first cover portion 21 is a portion that overlaps the first surface 111 of the first metal plate 1.

[0046] Each second cover portion 22 is a portion that overlaps each second surface 121 of the first metal plate 1.

[0047] Each third cover portion 23 is a portion that overlaps the inner surface of each bent portion 13 of the first metal plate 1 and links the first cover portion 21 and each second cover portion 22 to each other. The third cover portion 23 cooperates with the bent portion 13 of the first metal plate 1 to constitute the corner portion 10 of the molded product 100.

[0048] In this embodiment, as an example, the molded article 100 is configured such that the tensile strength of the first metal plate 1 is greater than or equal to 980 MPa, and the thickness of the second metal plate 2 located inside the bent portion 13 is greater than the thickness of the first metal plate 1. Furthermore, the tensile strength of the first metal plate is not limited to the aforementioned value. Moreover, the thicknesses of the first and second metal plates are not particularly limited. The thicknesses of the first and second metal plates may be the same or different.

[0049] <First Joint>

[0050] like Figure 1 As shown, the first joint 3 is the part where the first cover 21 of the second metal plate 2 in the molded article 100 is welded to the first surface 111 of the first metal plate 1. As will be described in detail below, in this embodiment, the first joint 3 is formed before the bending process of the blank. Therefore, as... Figure 3A As shown, the first joint 3 is the portion 21A of the second metal plate 2 in the blank, which serves as the first cover 21, and the first region 111A of the first metal plate 1, which serves as the first surface 111, are welded together. Multiple first joints 3 are provided. For example... Figure 1 As shown, the plurality of first joints 3 are arranged at intervals along the longitudinal direction L. Alternatively, the plurality of first joints may be arranged along the transverse direction S.

[0051] <Second Joint>

[0052] The second joint 4 is the part where each of the second cover portions 22 of the second metal plate 2 in the molded article 100 is welded to each of the second surfaces 121 of the first metal plate 1. Furthermore, as will be described in detail below, in this embodiment, unlike the first joint 3, the second joint 4 is formed after the blank is bent. Multiple second joints 4 are provided. The multiple second joints 4 are spaced apart from each other along the longitudinal direction L. Alternatively, the multiple second joints may be arranged along the transverse direction S.

[0053] The first joint 3 and the second joint 4 are each formed by a weld nugget, for example, at the weld point of a spot weld. Furthermore, each joint can penetrate either the first metal plate or the second metal plate.

[0054] [2. Manufacturing method of molded articles]

[0055] Next, refer to Figure 3A to Figure 3D ,as well as Figure 4 to Figure 6 The manufacturing method of the above-mentioned molded article 100 will be described. The manufacturing method of the molded article 100 includes a pre-welding process S10, a first bending process S20, a second bending process S30, and a post-welding process S40.

[0056] <Pre-welding process>

[0057] First, such as Figure 3A As shown, a first flat metal plate 1 and a second flat metal plate 2 are stacked and welded together to form a first joint 3. Specifically, the second metal plate 2 is stacked on the first metal plate such that the second metal plate 2 spans the first portion 11A, which is the top wall 11, the second portion 12A, which is the two side walls 12, and the third portion 13A, which is the two bends 13, of the first metal plate 1 before bending. Then, for example, by spot welding, the portion 21A, which is the first cover 21, of the second metal plate 2 before bending is welded to the first region 111A, which is the first surface 111, of the first metal plate 1, thereby forming the first joint 3.

[0058] <First Bending Process>

[0059] Next, as Figure 3B As shown, after forming the first joint 3, the first metal plate 1 and the second metal plate 2 are bent together in the first direction D1 to form the pre-formed corner 10B. The first direction D1 is the bending direction opposite to the second direction D2, which is the bending direction used in the bending process to form the shape of the molded article 100. As will be explained in detail below, in the first bending process, the first metal plate 1 and the second metal plate 2 are bent in the first direction D1 to the extent that plastic deformation occurs. The pre-formed corner 10B is formed in the same manner as the corner 10 by stamping a blank along the thickness direction.

[0060] Specifically, by using Figure 5 The first mold 5A, the second mold 5B, and the third mold 5C shown are used to perform a first cold pressing on the welded blank obtained in the pre-welding process S10 to form a pre-corner portion 10B. The blank having the pre-corner portion 10B is also called a pre-formed article 101.

[0061] Therefore, the first metal plate 1 is stamped to form a preliminary top wall portion 11B, two preliminary side wall portions 12B, and two reverse bend portions 13B on the first metal plate 1. The majority of the preliminary top wall portion 11B forms the top wall 11 of the formed article 100. The majority of the preliminary side wall portions 12B forms the side wall 12 of the formed article 100. The reverse bend portions 13B are located between the preliminary top wall portions 11B and the preliminary side wall portions 12B, and are bent in the opposite direction to the bend portions 13. The reverse bend portions 13B are formed such that they wholly or partially overlap with the area of ​​the first metal plate 1 that forms the bend portions 13 after bending in the first direction D1. The reverse bend portions 13B constitute the preliminary corner portion 10B of the pre-formed article 101.

[0062] Furthermore, the second metal plate 2 is bent along the prepared top wall portion 11B, the prepared side wall portion 12B, and the reverse bending portion 13B. Thus, a prepared first cover portion 21B, two prepared second cover portions 22B, and two prepared third cover portions 23B are formed on the second metal plate 2. The prepared first cover portion 21B overlaps with the prepared top wall portion 11B. Each prepared second cover portion 22B overlaps with each prepared side wall portion 12B. Each prepared third cover portion 23B overlaps with the outer surface of each reverse bending portion 13B, thereby connecting the prepared first cover portion 21B and each prepared second cover portion 22B to each other. In other words, in the pre-molded article 101, the second metal plate 2 is disposed outside each reverse bending portion 13B of the first metal plate 1 and overlaps with the first metal plate 1 in a manner that overlaps with each reverse bending portion 13B from the outside. The third cover portion 23B and the reverse bending portion 13B together constitute the pre-formed corner portion 10B of the pre-formed article 101.

[0063] like Figure 5 As shown, a first mold 5A is positioned above a second mold 5B, opposite to the second mold 5B. The first mold 5A has a protrusion 51A projecting towards the second mold 5B at its approximately central portion. The protrusion 51A has corresponding surfaces through which the pre-formed top wall portion 11B, two pre-formed side wall portions 12B, and two reverse-bent portions 13B of the pre-formed article 101 can be formed. The second mold 5B has a recess 51B at a position opposite to the protrusion 51A of the first mold 5A, through which the protrusion 51A can be embedded. The recess 51B has corresponding surfaces through which the pre-formed first cover portion 21B, two pre-formed second cover portions 22B, and two pre-formed third cover portions 23B of the pre-formed article 101 can be formed. The second mold 5B has a through hole 52B at a position opposite to the surface of the protrusion 51A used for forming the pre-formed top wall portion 11B, into which the third mold 5C is inserted. That is, the through hole 52B is located approximately at the center of the recess 51B. The third mold 5C is inserted into the through hole 52B of the second mold 5B and is configured to be movable relative to the second mold 5B.

[0064] In this embodiment, the welded blank is placed between the second mold 5B and the first mold 5A while the third mold 5C is inserted into the through hole 52B. Then, the first mold 5A and the second mold 5A are brought close to each other, and the above-mentioned pre-molded article 101 is formed by inserting the protrusion 51A into the recess 51B. At this time, the third mold 5C is pressed downward by the protrusion 51A.

[0065] <Second Bending Process>

[0066] Next, as Figure 3CAfter the bending process in the first direction D1 by the first cold pressing, the first metal sheet 1 and the second metal sheet 2 are bent together in the second direction D2, thereby forming the corner portion 10. Specifically, the first metal sheet 1 and the second metal sheet 2 are bent together in the second direction D2 by using the fourth die 6A, the fifth die 6B, and the sixth die 6C. Figure 6 The fourth die 6A, the fifth die 6B, and the sixth die 6C perform the second cold pressing on the bent blank (i.e., the preliminary shaped product 101) obtained in the first bending process S20, thereby forming the corner portion 10.

[0067] Thus, the first metal sheet 1 after the bending process in the first direction D1 is press-formed, thereby forming the top wall 11 (i.e., the first surface 111), the two side walls 12 (i.e., the two second surfaces 121), the two curved portions 13, and the two flange portions 14 on the first metal sheet 1.

[0068] Further, the second metal sheet 2 after the bending process in the first direction D1 is bent along the top wall 11, the two side walls 12, and the two curved portions 13. Thus, the first cover portion 21, the two second cover portions 22, and the two third cover portions 23 are formed on the second metal sheet 2.

[0069] As shown in FIG. 1, the corner portion 10 is formed by the first metal sheet 1 and the second metal sheet 2. Figure 6 As shown, the fourth die 6A is disposed above the fifth die 6B in an opposite manner to the fifth die 6B. The fifth die 6B has a protruding portion 61B protruding toward the fourth die 6A at a substantially central portion thereof. The protruding portion 61B has respective surfaces through which the first cover portion 21, the two second cover portions 22, and the two third cover portions 23 in the shaped product 100 are shaped. The fourth die 6A has a recessed portion 61A at a position opposite to the protruding portion 61B of the fifth die 6B, into which the protruding portion 61B is fitted. The recessed portion 61A has respective surfaces through which the top wall 11, the two side walls 12, the two curved portions 13, and the two flange portions 14 are shaped. The fourth die 6A has a through-hole 62A at a position opposite to the surface of the protruding portion 61B for shaping the first cover portion 21, into which the sixth die 6C is inserted. That is, the through-hole 62A is located at a substantially central position of the recessed portion 61A. The sixth die 6C is inserted into the through-hole 62A of the fourth die 6A and is configured to be movable relative to the fourth die 6A.

[0070] In this embodiment, the pre-molded article 101 is positioned between the fourth mold 6A and the fifth mold 6B, with the sixth mold 6C inserted into the through hole 62A, such that the pre-molded top wall portion 11B and the pre-molded first cover portion 21B are held by the protrusions 61B of the sixth mold 6C and the fifth mold 6B. At this time, the fourth mold 6A is positioned above the fifth mold 6B with a gap between it and the fifth mold 6B to avoid interference with the pre-molded side wall portion 12B in the pre-molded article 101. Then, the fourth mold 6A and the fifth mold 6B are brought close to each other, and the protrusions 61B are inserted into the recesses 61A to form a blank having the aforementioned corner portion 10.

[0071] In other words, in this embodiment, when a bending process is performed on the blank in the first direction D1, based on the ridge line R0 of the reverse bending portion 13B of the first metal plate 1 formed by the bending process, only the plate surface (the inner surface of the prepared top wall portion 11B) located on the first side of the ridge line R0 is joined to the second metal plate 2 through the first joint portion 3. On the other hand, the plate surface (the inner surface of the prepared side wall portion 12B) located on the second side of the ridge line R0 on the opposite side of the first side, based on the ridge line R0 of the reverse bending portion 13B, is not joined to the second metal plate 2. Furthermore, when a bending process is performed on the blank having the prepared corner portion 10B in the second direction D2, based on the ridge line R of the bending portion 13 of the first metal plate 1 formed by the bending process, only the plate surface located on the first side (i.e., the first surface 111) is joined to the second metal plate 2 through the first joint portion 3. On the other hand, the second side of the plate (i.e., the second surface 121) located on the opposite side of the first side with reference to the ridge line R of the curved portion 13 is not joined to the second metal plate 2.

[0072] <Post-welding process>

[0073] Next, as Figure 3D As shown, after bending in the second direction D2 by the second cold pressing described above, the first metal plate 1 and the second metal plate 2 are further welded together to form the second joint 4. That is, the second joint 4 is formed on the blank obtained in the second bending process S30. Specifically, for example, the second joint 4 is formed by spot welding, whereby each of the second cover portions 22 of the second metal plate 2 after bending in the second direction D2 is welded to each of the second surfaces 121 of the first metal plate 1.

[0074] As described above, in this embodiment, the molded article 100 is manufactured and obtained in the order of pre-welding process S10, first bending process S20, second bending process S30, and post-welding process S40.

[0075] [3. Relationship between the curved section and the reverse curved section]

[0076] Next, the relationship between the curved portion 13 and the reverse curved portion 13B will be described with reference to Figure 7

[0077] As shown in FIG. 1, the curved portion 13 has a first end portion 131 and a second end portion 132, in which the first end portion 131 is located on the side of the top wall 11, and the second end portion 132 is located on the side of the side wall 12. Further, the third cover portion 23 overlapping the curved portion 13 has a first end portion 231 and a second end portion 232, in which the first end portion 231 is located on the side of the first cover portion 21 (i.e., the side of the first surface 111), and the second end portion 232 is located on the side of the second cover portion 22 (i.e., the side of the second surface 121). Figure 7

[0078] Further, the reverse curved portion 13B has a first end portion 131B and a second end portion 132B, in which the first end portion 131B is located on the side of the preliminary top wall portion 11B, and the second end portion 132B is located on the side of the preliminary side wall portion 12B. Further, the preliminary third cover portion 23B overlapping the reverse curved portion 13B has a first end portion 231B and a second end portion 232B, in which the first end portion 231B is located on the side of the preliminary first cover portion 21B (i.e., the side of the region in the first metal plate 1 as the first surface 111), and the second end portion 232B is located on the side of the preliminary second cover portion 22B (i.e., the side of the region in the first metal plate 1 as the second surface 121).

[0079] In the present embodiment, the reverse curved portion 13B is formed in such a manner that the reverse curved portion 13B satisfies the following conditions (A) to (C) with respect to the curved portion 13.

[0080] (A) The length from the position of the first end portion 231 of the third cover portion 23 in the second metal plate 2 to the second end portion 232B of the preliminary third cover portion 23B is longer than the length from the first end portion 231 of the third cover portion 23 to the second end portion 232 of the third cover portion 23.

[0081] In the present embodiment, the center points of the respective end portions 231, 232 of the third cover portion 23 in the plate thickness direction are taken as the midpoints P1, P2, and the center points of the second end portion 232B of the preliminary third cover portion 23B in the plate thickness direction are taken as the midpoints P3, respectively. In this case, the reverse curved portion 13B is formed so that the length from the midpoint P1 to the midpoint P3 in the preliminary shaped product 101 is longer than the length from the midpoint P1 to the midpoint P2 in the shaped product 100. As one example of satisfying the above condition (A), when the radius of curvature of the curved portion 13 in the shaped product 100 is about 5 mm, it is preferable that the radius of curvature of the reverse curved portion 13B in the preliminary shaped product 101 be about 7 mm or more.

[0082] (B) The first bending angle θ1 of the reverse curved portion 13B is larger than the second bending angle θ2 of the curved portion 13.​​

[0083] The first bending angle θ1 is an angle formed by the first inclined line L2 with respect to the intersection line L1 on a cross section along the lateral direction S. The intersection line L1 is a line intersecting a region as the first surface 111 in the first metal plate 1 in a substantially perpendicular manner (in other words, substantially perpendicular to the preliminary top wall portion 11B) on the cross section. The first inclined line L2 is a line along a preliminary opposite surface 122B (in other words, a plate surface of the preliminary side wall portion 12B) on the cross section, where the preliminary opposite surface 122B constitutes a region on the opposite side of the region as the second surface 121 in the first metal plate 1.

[0084] Further, the second bending angle θ2 is an angle formed by the second inclined line L3 with respect to the intersection line L1 on the cross section. The second inclined line L3 is a line along an opposite surface 122 (in other words, a plate surface of the side wall 12) of the first metal plate 1 on the opposite side of the second surface 121 on the cross section.

[0085] For example, if the second bending angle θ2 of the bent portion 13 is about 10°, the gap (hereinafter, simply referred to as a gap) between the outer surface of each second cover portion 22 and the second surface 121 of each side wall 12 formed after the bending process in the second direction D2 with respect to the first bending angle θ1 of the reverse bent portion 13B is as follows. The gap is measured at a substantially middle point in each second cover portion 22 from an end portion on the third cover portion 23 side to an end portion on the opposite side of the third cover portion 23. The middle point is a position where the second joint portion 4 is assumed to be formed.

[0086] When the first bending angle θ1 is about 25°, the gap is about 1.86 mm. Further, when the first bending angle θ1 is about 45°, the gap is about 1.63 mm. Further, when the first bending angle θ1 is about 65°, the gap is about 2.17 mm. Further, when the first bending angle θ1 is about 85°, the gap is about 2.61 mm. In addition, when the first bending angle θ1 is about 0°, that is, when the bending process in the first direction D1 is not performed, the gap is about 3.15 mm. Therefore, when the second bending angle θ2 is 10°, the gap can be reduced by forming the reverse bent portion 13B in such a manner that the first bending angle θ1 is 10° or more. In addition, when the second bending angle θ2 is about 10°, it is more preferable that the first bending angle θ1 is 25° or more and less than 50°.

[0087] (C) The first end portion 131B of the reverse bent portion 13B is located at a position closer to the preliminary side wall portion 12B side with respect to a position of the first end portion 131 of the bent portion 13 in the first metal plate 1.

[0088] [4. Effects]

[0089] According to the above-described embodiments, the following effects can be obtained.

[0090] (4a) In the present embodiment, when the bending process of bending toward the first direction Dl is performed on the blank, only the inner surface of the preliminary top wall portion 1 IB on the first side is joined to the second metal plate 2 by the first joining portion 3 with the ridge line R0 of the reverse bending portion 13B of the first metal plate 1 formed by the bending process as a reference. On the other hand, the inner surface of the preliminary side wall portion 12B on the second side is not joined to the second metal plate 2 with the ridge line R0 of the reverse bending portion 13B as a reference.

[0091] Further, when the bending process of bending toward the second direction D2 is performed on the blank having the preliminary corner portion 10B, only the first surface 111 on the first side of the ridge line R of the bending portion 13 of the first metal plate 1 is joined to the second metal plate 2 by the first joining portion 3 with the ridge line R of the bending portion 13 as a reference. On the other hand, the second surface 121 on the second side is not joined to the second metal plate 2 with the ridge line R of the bending portion 13 as a reference. As described above, in any bending process, the second joining portion 4 is not provided on the blank.

[0092] Thus, even if the first metal plate 1 and the second metal plate 2 are commonly bent by the first cold press and a difference occurs between the first metal plate 1 and the second metal plate 2 along the extension length of the reverse bending portion 13B, the second metal plate 2 is not easily restricted on the region of the first metal plate 1 as the second surface 121. Further, even if the first metal plate 1 and the second metal plate 2 are commonly bent by the second cold press and a difference occurs between the first metal plate 1 and the second metal plate 2 along the extension length of the bending portion 13B, the second metal plate 2 is not easily restricted on the second surface 121 of the first metal plate 1. Therefore, in any cold press process, stress is not easily concentrated on the first joining portion 3.

[0093] Further, in the present embodiment, before the first metal plate 1 and the second metal plate 2 are bent toward the second direction D2, the first metal plate 1 and the second metal plate 2 are first bent toward the first direction Dl. Thus, regardless of the combination of the material strength and the plate thickness of the first metal plate 1 and the second metal plate 2, even if each metal plate 1, 2 is elastically deformed due to bending toward the second direction D2, it is easy to reduce the gap between the first metal plate 1 and the second metal plate 2. As a result, it is easy to form the second joining portion 4.

[0094] Further, in the present embodiment, the second joining portion 4 is formed on the blank after the bending process. Therefore, the second joining portion 4 can be formed in a state in which it is not easily affected by a difference occurring along the extension length of the bending portion between the first metal plate 1 and the second metal plate 2 due to the second cold press.

[0095] Therefore, it can both suppress cracking of the joints 3 and 4 in the first metal plate 1 and the second metal plate 2 welded together, and facilitate the formation of the second joint 4.

[0096] (4b) In this embodiment, the reverse bending portion 13B is formed such that the length from midpoint P1 to midpoint P3 in the pre-molded article 101 is longer than the length from midpoint P1 to midpoint P2 in the molded article 100. That is, the reverse bending portion 13B is formed to satisfy the above condition (A). Therefore, the portion near the second end 232B of the pre-molded third cover portion 23B is subjected to bending deformation in the first direction D1 during the first cold pressing, and extends in a generally straight shape after the second cold pressing. Specifically, as Figure 7 As shown, the midpoint P3 in the pre-formed article 101 is located at the midpoint P4 in the formed article 100 after the second cold pressing. Since the midpoint P4 is located on the sidewall 12, which extends in a generally straight line, the distance from the midpoint P2 to the midpoint P4 in the formed article 100 is approximately straight. This facilitates springback, pressing the second metal plate 2 against the second surface 121 of the first metal plate 1. Therefore, the gap can be further reduced.

[0097] (4c) For example, if the first bending angle of the reverse bending portion is less than or equal to the second bending angle of the bending portion, the warpage of the prepared sidewall portion relative to the prepared top wall portion in the pre-molded article is likely to increase. Therefore, the prepared sidewall portion 12B and the fourth mold 6A used for the second cold pressing are likely to interfere with each other. On the other hand, in this embodiment, the reverse bending portion 13B is formed such that the first bending angle θ1 of the reverse bending portion 13B is greater than the second bending angle θ2 of the bending portion 13. That is, the reverse bending portion 13B is formed to satisfy the above condition (B). As a result, the warpage of the prepared sidewall portion 12B relative to the prepared top wall portion 11B in the pre-molded article 101 is reduced. Therefore, during the second cold pressing, the interference between the prepared sidewall portion 12B in the pre-molded article 101 after the first cold pressing and the fourth mold 6A used for the second cold pressing can be suppressed.

[0098] (4d) In this embodiment, the first end 131B of the reverse bending portion 13B is located near the prepared sidewall portion 12B, relative to the position of the first end 131 of the bending portion 13 in the first metal plate 1. That is, the reverse bending portion 13B is formed to satisfy the above condition (C). As a result, the portion that is less likely to bend and deform in the first region 111A of the first metal plate 1 by the first cold pressing is not easily generated. Therefore, in this embodiment, the tendency for bending in the first direction to remain on the first surface 111 (i.e., the top wall 11) can be suppressed during the second cold pressing.

[0099] In addition, such as Figure 8 and Figure 9When the above condition (B) is satisfied but the condition (C) is not satisfied, a portion where the bending deformation is easily generated at the first region 111A of the first metal plate 1 by the first cold pressing is shown in the reverse bending portion 13C of the first comparative example and the reverse bending portion 13D of the second comparative example shown in a simple form. As shown in Figure 8 and Figure 9 As shown in the first comparative example and the second comparative example, the first end portion 131C of the reverse bending portion 13C and the first end portion 131D of the reverse bending portion 13D are located on the first region 111A side of the first metal plate 1 as the first surface 111 of the bending portion 13, compared to the position of the first end portion 131 of the bending portion 13 of the first metal plate 1. Therefore, when each of the reverse bending portions 13C, 13D is formed as shown in Figure 8 and Figure 9 When the second cold pressing is performed, a tendency to bend in the first direction is easily left on the first surface 111 (i.e., the top wall 11).

[0100] (4e) In the present embodiment, as one example, the shaped product 100 is configured such that the tensile strength of the first metal plate 1 is greater than or equal to 980 MPa, and the thickness of the second metal plate 2 located on the inner side of the bending portion 13 is greater than the thickness of the first metal plate 1. According to the above configuration, if the first bending process S20 is not performed before the second bending process S30, the gap is easily made large. However, in the present embodiment, since the first bending process S20 is performed before the second bending process S30, it is more easily possible to reduce the gap.

[0101] In addition, in the present embodiment, the first metal plate 1 corresponds to one example of the outer side metal plate, and the second metal plate 2 corresponds to one example of the inner side metal plate. Further, the first surface 111 of the top wall 11 corresponds to one example of the first surface, the second surface 121 of the side wall 12 corresponds to one example of the second surface, and the first region 111A of the first metal plate 1 corresponds to one example of the region of the outer side metal plate as the first surface. Further, the preliminary third cover portion 23B corresponds to one example of the preliminary cover portion, and the third cover portion 23 corresponds to one example of the cover portion. Further, the first end portion 231 of the third cover portion 23 corresponds to one example of the first end portion of the cover portion, and the second end portion 232 of the third cover portion 23 corresponds to one example of the second end portion of the cover portion. Further, the second end portion 232B of the preliminary third cover portion 23B corresponds to one example of the end portion of the preliminary cover portion located on the region side of the outer side metal plate as the second surface. Further, the first end portion 131B of the reverse bending portion 13B corresponds to one example of the end portion of the reverse bending portion located on the region side of the outer side metal plate as the first surface.

[0102] [5. Other Embodiments]

[0103] The above describes embodiments of the present disclosure, but the present disclosure is not limited to the above-described embodiments and can take various forms.

[0104] (5a) In the above-described embodiment, the second metal plate 2 has a U-shaped cross-sectional shape, but for example Figure 10 As shown in the formed product 100a of the first modification example, the second metal plate 2a can have an L-shaped cross-sectional shape. In this case, in the first bending process, only the portion of the welded blank in which the second metal plate 2a is stacked is subjected to bending processing in the first direction D1, although not shown, a reverse bending portion can be formed on the first metal plate 1 and a third cover portion can be formed on the second metal plate 2a. That is, the portion of the welded blank in which the second metal plate 2a is not stacked can not be subjected to bending processing in the first direction D1. In this case, the same effects as the effects (4a) to (4d) of the above-described embodiment can be obtained.

[0105] (5b) In the above-described embodiment, the second metal plate 2 is disposed on the inner side of the bending portion 13 of the first metal plate 1 and is welded to the first metal plate 1 in a manner of overlapping the bending portion 13 from the inner side. However, for example Figure 11 As shown in the formed product 100b of the second modification example, the second metal plate 2b can be disposed on the outer side of the bending portion 13 of the first metal plate 1 and can be welded to the first metal plate 1 in a manner of overlapping the bending portion 13 from the outer side. That is, the second metal plate 2b can be stacked on the outer surface of the bending portion 13. In Figure 11 In the formed product 100b, the first metal plate 1 corresponds to one example of an inner side metal plate, and the second metal plate 2b corresponds to one example of an outer side metal plate. Further, the inner surface of the first cover portion 21b corresponds to one example of a first surface, the inner surface of the second cover portion 22b corresponds to one example of a second surface, the third cover portion 23b corresponds to one example of a bending portion, and the region of the second metal plate 2b that is the inner surface of the first cover portion 21b corresponds to one example of a region of the outer side metal plate that is the first surface.

[0106] (5c) In the above embodiment, in the pre-welding process, the portion 21A of the second metal sheet 2 before the bending process, which is the first lid portion 21, is welded to the first region 111A of the first metal sheet 1, which is the first surface 111, thereby forming the first joint portion 3. Then, in the post-welding process, the second lid portion 22 of the second metal sheet 2 after the bending process is welded to the second surface 121 of the first metal sheet 1, thereby forming the second joint portion 4. However, the weld portions formed in the pre-welding process and the post-welding process are not limited thereto. For example, in the pre-welding process, a portion of the second metal sheet 2 before the bending process, which is the second lid portion 22 on one side, can be welded to a region of the first metal sheet 1, which is the second surface, thereby forming the first joint portion. Then, in the post-welding process, the first lid portion 21 of the second metal sheet 2 after the bending process can be welded to the first surface 111 of the first metal sheet 1, and the second lid portion 22 on the other side can be welded to the second surface 121 of the first metal sheet 1, which overlaps the second lid portion 22 on the other side, thereby forming the second joint portion. In this case, the same effects as the effects (4a) to (4D) of the above embodiment can also be obtained.

[0107] (5d) In the above embodiment, the cross-sectional shape of the formed product 100 is in the shape of a hat, however, the cross-sectional shape of the formed product can also be, for example, a U shape or an L shape, or the like.

[0108] (5e) In the above embodiment, the reverse bent portion 13B is formed so as to satisfy all of the above (A) to (C), however, for example, the reverse bent portion can also be formed so as to satisfy at least one of (A) to (C). In this case, the same effects as at least the effect (4a) of the above embodiment can also be obtained.

[0109] (5f) The functions possessed by one constituent element in the above embodiment can be divided and borne by a plurality of constituent elements, or the functions possessed by a plurality of constituent elements can be integrated into one constituent element. Furthermore, a part of the constitution of the above embodiment can be omitted. Furthermore, at least a part of the constitution of the above embodiment can be added to the constitution of the above other embodiment, or at least a part of the constitution of the above embodiment and the constitution of the above other embodiment can be replaced, or the like.

Claims

1. A method for producing a shaped article, characterized by, The process includes the following steps: The inner metal plates are stacked and welded to the outer metal plate to form the first joint. After the first joint is formed, the outer metal plate and the inner metal plate are bent together in the first direction by performing a first stamping; and After the first stamping, a second stamping is performed to bend the outer metal plate and the inner metal plate together in a second direction opposite to the first direction. In the second stamping, a first surface, a second surface, and a curved portion are formed on the outer metal plate. The second surface extends along a direction intersecting the first surface, and the curved portion connects the first and second surfaces and overlaps with the inner metal plate. In the first stamping, a reverse bend is formed on the outer metal plate. There is at least one reverse bend, and its bending direction is opposite to that of the bend in the outer metal plate. The reverse bend overlaps with the inner metal plate. The reverse bending portion is formed such that it overlaps with the region constituting the bending portion on the outer metal plate. The inner metal plate is located outside the reverse bend after the first stamping, and inside the bend after the second stamping. The first joint is the part where the inner metal plate and the area of ​​the outer metal plate that serves as the first surface are welded together.

2. The method for producing a shaped article according to claim 1, characterized by It also has the following processes, After the second stamping, the outer metal plate and the inner metal plate are welded together to form a second joint, which is the part where the inner metal plate is welded to the second surface.

3. The method for manufacturing a molded article according to claim 1 or 2, characterized in that, The inner metal plate has at least one pre-applied cover portion, which overlaps with the reverse bending portion after the first stamping. The inner metal plate also has at least one cover portion, which overlaps with the bending portion after the second stamping. The at least one cover portion has a first end located on one side of the first surface and a second end located on one side of the second surface. The reverse bending portion is formed such that the length from the position of the first end in the inner metal plate to the end of the pre-cover portion is longer than the length from the first end to the second end in the cover portion, wherein the end of the pre-cover portion is located on one side of the region of the second surface in the outer metal plate.

4. The method for manufacturing a molded article according to any one of claims 1 to 3, characterized in that, The reverse bending portion is formed such that the first bending angle of the reverse bending portion is greater than the second bending angle of the bending portion. The first bending angle refers to the angle formed by the first inclined line relative to the intersecting line on a cross section along the arrangement direction of the first surface, the bent portion, and the second surface. The first inclined line is a line along a pre-planned opposite surface of the region in the outer metal plate that constitutes the region opposite to the region of the second surface. The intersecting line is a line that intersects the region of the outer metal plate that constitutes the first surface in a substantially perpendicular manner. The second bending angle refers to the angle formed by the second inclined line relative to the intersecting line on the cross section, wherein the second inclined line is a line along the opposite side of the outer metal plate located on the opposite side of the second surface.

5. The method for manufacturing a molded article according to any one of claims 1 to 4, characterized in that, The reverse bending portion is formed such that the end of the reverse bending portion located on the side of the region that is the first surface of the outer metal plate is located near the side of the region that is the second surface of the outer metal plate, relative to the position of the end of the bending portion on the side of the first surface of the outer metal plate.

Images