Manufacturing method for molded product

Abstract

To provide a manufacturing method for a molded product that can suppress joint parts in two welded plate materials from cracking.SOLUTION: A manufacturing method for a molded product comprises a step of overlapping an inner metallic plate with an outer metallic plate and welding the plates to form a first joint part. Further the manufacturing method for a molded product comprises a step of bending the outer metallic plate together with the inner metallic plate by pressing after forming the first joint part. By the pressing, a first surface, a second surface expanding in a direction crossing the first surface and a bent part connecting the first surface to the second surface, which the inner metallic plate is overlapped with are formed on the outer metallic plate. The first joint part is a site where the inner metallic plate is welded to a region which is a first surface of the outer metallic plate. The inner metallic plate is arranged inside the bent part, which is larger in spring back than the outer metallic plate.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a molded article. [Background technology]

[0002] In the drawing and bending of metal sheets, a reinforcing plate (i.e., a patch) is layered and welded to the base metal sheet to increase its strength, and then pressed. In this type of processing, a difference in the elongation caused by pressing occurs between the reinforcing plate located on the inside of the bend and the base material located on the outside. As a result, shear stress occurs in the welded part of the reinforcing plate, which may cause cracking.

[0003] Here, Patent Document 1 discloses a method for manufacturing a U-shaped molded product having a top plate, two vertical wall portions, and bent portions located between the top plate and each vertical wall portion by stacking and welding a main component and a secondary component, and then pressing the stacked components. In this manufacturing method, welded joints are provided on the portions corresponding to the top plate and the vertical wall portions before pressing. Then, in order to disperse the shear stress generated at each joint by pressing, a plurality of joints are provided on the portions corresponding to the vertical wall portions, aligned in a direction from the end of the vertical wall portions on the bent portion side toward the end on the opposite side. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-131226 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the manufacturing method of the above-mentioned cited document 1, depending on the hardness of the members and the type of pressing, particularly when high tensile steel plate material is cold pressed, the shear stress generated at the joint is difficult to disperse and the stress is likely to be insufficiently relieved, resulting in a problem that cracks are likely to occur at the joint.

[0006] An object of one aspect of the present disclosure is to provide a manufacturing method for a molded product that can suppress cracks at the joint between two welded plate materials. [Means for solving the problem]

[0007] One aspect of the present disclosure is a method for manufacturing a molded product, comprising overlapping and welding an inner metal plate to an outer metal plate to form a first joint. The method for manufacturing a molded product also comprises bending the outer metal plate together with the inner metal plate by pressing after forming the first joint. In the pressing, a first surface, a second surface extending in a direction intersecting the first surface, and a bent portion connecting the first surface and the second surface and overlapping the inner metal plate are formed on the outer metal plate. The first joint is a portion where the inner metal plate is welded to a region of the outer metal plate that becomes the first surface. The inner metal plate is disposed inside the bent portion and has a larger springback than the outer metal plate.

[0008] In this configuration, even if the outer metal plate is bent together with the inner metal plate by pressing, causing a difference in elongation length between the outer metal plate and the inner metal plate, stress is unlikely to concentrate at the first joint portion, and therefore cracks at the first joint portion of the welded outer metal plate and inner metal plate can be suppressed.

[0009] In one aspect of the present disclosure, the inner metal plate may have a greater tensile strength than the outer metal plate. In such a configuration, the springback of the inner metal plate is likely to be larger than the springback of the outer metal plate, which makes it easier for the inner metal plate to be pressed against the outer metal plate after pressing, thereby promoting adhesion between the outer metal plate and the inner metal plate after pressing.

[0010] In one aspect of the present disclosure, the inner metal plate may have a thickness smaller than that of the outer metal plate. In such a configuration, the springback of the inner metal plate is likely to be larger than the springback of the outer metal plate, which makes it easier for the inner metal plate to be pressed against the outer metal plate after pressing, thereby promoting adhesion between the outer metal plate and the inner metal plate after pressing.

[0011] One embodiment of the present disclosure may further include welding the outer metal plate and the inner metal plate after pressing to form a second joint portion at which the inner metal plate is welded to the second surface. In this configuration, the second joint is formed in a state where it is less susceptible to the effect of the difference in elongation length between the outer metal plate and the inner metal plate due to pressing. This makes it possible to make the second joint less susceptible to cracking. In addition, the second joint is formed in a state where the outer metal plate and the inner metal plate are encouraged to come into close contact with each other. This makes it easy to form the second joint.

[0012] In one embodiment of the present disclosure, the molded product may have a hat-shaped or L-shaped cross-sectional shape along a direction in which the first surface, the bent portion, and the second surface are aligned. The inner metal plate may be made of high-tensile steel having a tensile strength of 590 MPa or more. In this configuration, the inner metal plate is easily pressed against the outer metal plate after pressing, which can promote close contact between the outer metal plate and the inner metal plate after pressing. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a perspective view showing a molded product. [Diagram 2] FIG. 2 is a side view showing a schematic diagram of the molded product. [Diagram 3] Fig. 3A is a schematic cross-sectional view along the short side at the position of the first welded portion of the blank after the pre-welding process, Fig. 3B is a schematic cross-sectional view along the short side at the position of the first welded portion of the blank after the bending process, and Fig. 3C is a schematic cross-sectional view along the short side at the positions of the first welded portion and the second welded portion of the molded product completed after the post-welding process. [Figure 4]FIG. 1 is a flow diagram showing a manufacturing method of a molded product. [Diagram 5] Fig. 5A is a schematic cross-sectional view along the short side at the position of the second welded portion of the blank after the pre-welding step of the manufacturing method of the first modified example. Fig. 5B is a schematic cross-sectional view along the short side at the position of the second welded portion of the blank after the bending step of the manufacturing method of the first modified example. Fig. 5C is a schematic cross-sectional view along the short side at the positions of the first welded portion and the second welded portion of the molded product completed after the post-welding step of the manufacturing method of the first modified example. [Figure 6] FIG. 13 is a perspective view showing a molded product of a second modified example. [Figure 7] 7 is a perspective view of the molded product of the second modified example of FIG. 6, seen from a different direction. FIG. [Figure 8] FIG. 13 is a schematic cross-sectional view taken along the short side direction of a molded product of a third modified example. [Figure 9] FIG. 13 is a schematic cross-sectional view taken along the short side direction of a molded product of a fourth modified example. [Figure 10] FIG. 13 is a schematic cross-sectional view taken along the short side direction of a molded product of a fifth modified example. [Figure 11] FIG. 13 is a schematic cross-sectional view taken along the short side direction of a molded product of a sixth modified example. [Figure 12] FIG. 13 is a schematic cross-sectional view taken along the short side direction of a molded product of a seventh modified example. [Figure 13] FIG. 13 is a schematic cross-sectional view taken along the short side direction of a molded product of an eighth modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. [1. Composition of molded product] The molded product 100 shown in Figures 1 and 2 is formed by welding and pressing a blank material (hereinafter simply referred to as the blank material), which is a sheet material made by overlapping a first metal plate 1 and a second metal plate 2.

[0015] The molded product 100 is a plate-like part that extends linearly in the longitudinal direction L, and has a number of corners 10. The corners 10 are formed by pressing and squeezing a blank material in the thickness direction. In this embodiment, the molded product 100 has a hat-shaped cross-sectional shape (hereinafter simply referred to as the cross-sectional shape) along the short direction S perpendicular to the longitudinal direction L. The hat shape is a shape that includes two opposing side walls, a top wall that connects the two side walls at first ends, and two flanges that extend away from each other from second ends of the side walls opposite the first ends.

[0016] The molded product 100 is used, for example, as a component part of an automobile body. In this embodiment, the molded product 100 is a locker provided on the lower part of the side of an automobile. The molded product 100 includes a first metal plate 1, a second metal plate 2, a plurality of first bonding portions 3, and a plurality of second bonding portions 4.

[0017] <First metal plate> The first metal plate 1 is made of, for example, a steel plate. In this embodiment, the first metal plate 1 has a hat-shaped cross section. The first metal plate 1 has a top wall 11, two side walls 12, two bent portions 13, and two flange portions 14.

[0018] The plate surface of the top wall 11 extends in a direction intersecting with the plate surfaces of the two side walls 12 that face each other with a gap between them. The top wall 11 has a first surface 111. The side walls 12 have a second surface 121 that extends in a direction intersecting with the first surface 111. The first surface 111 is a surface of the plate surface of the top wall 11 that continues to the inner surface of a bending portion 13 that will be described later. The second surface 121 is a surface of the plate surface of the side walls 12 that continues to the inner surface of the bending portion 13 that will be described later. The bent portion 13 is a region between the top wall 11 and the side wall 12, and is bent by bending the first metal plate 1. The bent portion 13 constitutes a corner portion 10 of the molded product 100. The bent portion 13 connects a first surface 111 of the top wall 11 and a second surface 121 of the side wall 12.

[0019] The flange portion 14 is formed by bending the end portion of the side wall 12 opposite to the top wall 11 by bending the first metal plate 1. The plate surface of the flange portion 14 extends in a direction intersecting with the plate surface of the side wall 12.

[0020] <Second metal plate> The second metal plate 2 is made of, for example, a steel plate, similar to the first metal plate 1. The materials of the first metal plate and the second metal plate are not particularly limited. The first metal plate and the second metal plate may be made of different materials. In this embodiment, the second metal plate 2 has an L-shaped cross section.

[0021] The second metal plate 2 is overlapped and welded to the first metal plate 1. The second metal plate 2 is arranged across the top wall 11, one side wall 12, and the bent portion 13 located between the top wall 11 and the side wall 12 of the first metal plate 1. In this embodiment, the second metal plate 2 overlaps the first surface 111, one second surface 121, and the inner surface of the bent portion 13 located between the first surface 111 and the second surface 121 of the first metal plate 1. That is, the second metal plate 2 is arranged inside the bent portion 13 of the first metal plate 1 and is welded to the first metal plate 1 so as to overlap the bent portion 13 from the inside. In this embodiment, the second metal plate 2 has a shorter length in the longitudinal direction L than the first metal plate 1, and overlaps only a part of the first metal plate 1 along the longitudinal direction L. The second metal plate may have substantially the same length in the longitudinal direction L as the first metal plate, and may overlap the first metal plate over the entire range along the longitudinal direction L from end to end.

[0022] The second metal plate 2 has a first cover portion 21, a second cover portion 22, and a third cover portion . The first cover portion 21 overlaps with the first surface 111 of the first metal plate 1 .

[0023] The second cover portion 22 overlaps with the second surface 121 of the first metal plate 1 . The third cover portion 23 is a portion that overlaps the inner surface of the bent portion 13 of the first metal plate 1, and connects the first cover portion 21 and the second cover portion 22. The third cover portion 23, together with the bent portion 13 of the first metal plate 1, constitutes the corner portion 10 of the molded product 100.

[0024] In this embodiment, the tensile strength of the second metal plate 2 is greater than that of the first metal plate 1, and the plate thickness of the second metal plate 2 is smaller than that of the first metal plate 1. As an example, the second metal plate 2 has a tensile strength of 1470 MPa and a plate thickness of 1.0 mm. As another example, the first metal plate 1 has a tensile strength of 270 MPa and a plate thickness of 2.6 mm. The tensile strengths and plate thicknesses of the first metal plate and the second metal plate are not limited to the above-mentioned numerical values. The second metal plate 2 is preferably formed of high tensile steel having a tensile strength of 590 MPa or more, and more preferably formed of high tensile steel having a tensile strength of 980 MPa or more.

[0025] Here, the greater the tensile strength of the plate material, the greater the springback after the plate material is press-bent. Also, the thinner the plate material is, the greater the springback after the plate material is press-bent. Therefore, in this embodiment, the springback of the second metal plate 2 is greater than the springback of the first metal plate 1.

[0026] <1st joint> As shown in FIG. 1, the first joint 3 is a portion where the first cover portion 21 of the second metal plate 2 is welded to the first surface 111 of the first metal plate 1 in the molded product 100. Details will be described later, but in this embodiment, the first joint 3 is formed before bending the blank. For this reason, as shown in FIG. 3A, the first joint 3 is a portion where the portion 21A of the blank material that becomes the first cover portion 21 of the second metal plate 2 is welded to the first region 111A that becomes the first surface 111 of the first metal plate 1 in the blank material. A plurality of first joints 3 are provided. As shown in FIG. 1, the plurality of first joints 3 are arranged at intervals from each other in the longitudinal direction L. Note that a plurality of first joints may be provided so as to be arranged in the lateral direction S.

[0027] <Second joint> The second joint 4 is a portion of the molded product 100 where the second cover portion 22 of the second metal plate 2 is welded to the second surface 121 of the first metal plate 1. Note that, unlike the first joint 3, in this embodiment, the second joint 4 is formed after bending of the blank material, as will be described in detail later. A plurality of second joints 4 are provided. The plurality of second joints 4 are arranged at intervals from each other in the longitudinal direction L. Note that a plurality of second joints may be provided so as to be arranged in the lateral direction S.

[0028] The first joint 3 and the second joint 4 are each formed of a nugget formed at a welding point of spot welding, for example. Each joint may penetrate the first metal plate 1 or the second metal plate 2.

[0029] [2. Manufacturing method of molded products] Next, a method for manufacturing the above-mentioned molded product 100 will be described with reference to Figures 3A to 3C and 4. The method for manufacturing the molded product 100 includes a pre-welding step S10, a bending step S20, and a post-welding step S30.

[0030] <Pre-welding process> First, as shown in Fig. 3A, a flat first metal plate 1 is overlapped with a flat second metal plate 2 and welded to form a first joint 3. Specifically, the second metal plate 2 is overlapped so as to straddle a first portion 11A that will become the top wall 11, a second portion 12A that will become one side wall 12, and a portion 13A that will become the bent portion 13 located between the first portion 11A and the second portion 12A, of the first metal plate 1 before bending. Thereafter, the portion 21A that will become the first cover portion 21 of the second metal plate 2 before bending is, for example, spot-welded to a first region 111A that will become the first surface 111 of the first metal plate 1, to form the first joint 3.

[0031] <Bending process> 3B, after the above-mentioned first joint portion 3 is formed, the first metal plate 1 is bent together with the second metal plate 2 to form a corner portion 10. Specifically, the corner portion 10 is formed by cold pressing the welded blank material obtained in the pre-welding process S10 using a die (not shown).

[0032] This results in the first metal plate 1 being drawn, forming a top wall 11 (i.e., the first surface 111), two side walls 12 (i.e., the two second surfaces 121), two bent portions 13 and two flange portions 14 on the first metal plate 1.

[0033] Furthermore, the second metal plate 2 is bent along the top wall 11, the side wall 12, and the bent portion 13. As a result, a first cover portion 21, a second cover portion 22, and a third cover portion 23 are formed on the second metal plate 2.

[0034] That is, in this embodiment, when bending is performed on a blank, with respect to the ridgeline R of the bent portion 13 of the first metal plate 1 formed by the bending, only the plate surface located on the first side (i.e., first surface 111) is joined to the second metal plate 2 by the first joint portion 3. On the other hand, the plate surface located on the second side opposite the first side with respect to the ridgeline R of the bent portion 13 (i.e., second surface 121) is not joined to the second metal plate 2.

[0035] <Post-welding process> 3C, after the above-mentioned bending process by cold press, the first metal plate 1 and the second metal plate 2 are further welded to form a second joint 4. That is, the second joint 4 is formed on the blank material after bending obtained in the bending step S20. Specifically, the second cover portion 22 of the second metal plate 2 after bending is, for example, spot-welded to the second surface 121 of the first metal plate 1 to form the second joint 4.

[0036] As described above, in this embodiment, the molded product 100 is obtained by manufacturing in the order of the pre-welding step S10, the bending step S20, and the post-welding step S30.

[0037] [3. Effects] According to the embodiment described above in detail, the following effects can be obtained.

[0038] (3a) In this embodiment, when bending is performed on a blank, with respect to a ridgeline R of a bent portion 13 of a first metal plate 1 formed by the bending, only a first surface 111 located on a first side is joined to the second metal plate 2 by a first joint portion 3. On the other hand, a second surface 121 located on a second side with respect to the ridgeline R of the bent portion 13 is not joined to the second metal plate 2.

[0039] As a result, even if the first metal plate 1 is bent together with the second metal plate 2 by pressing, and a difference occurs in the elongation length of the bent portion 13 along the bending direction B shown in FIG. 3B between the first metal plate 1 and the second metal plate 2, the second metal plate 2 is unlikely to be restrained by the second surface 121 of the first metal plate 1. This makes it difficult for stress to concentrate at the first joint portion 3. As a result, it is possible to suppress cracks at the first joint portion 3 in the welded first metal plate 1 and second metal plate 2.

[0040] (3b) In this embodiment, the second metal plate 2 located inside the bent portion 13 of the first metal plate 1 has a higher tensile strength than the first metal plate 1 and is thinner than the first metal plate 1. Therefore, the second metal plate 2 is more likely to have a large springback after bending by pressing than the first metal plate 1. As a result, the second metal plate 2 is more likely to be pressed against the first metal plate 1 after bending. This can promote adhesion between the first metal plate 1 and the second metal plate 2 after bending. In other words, even if the second metal plate 2 is not joined to the second surface 121 of the first metal plate 1 as in this embodiment, it is possible to suppress the second metal plate 2 from being separated from the second surface 121 in the blank material after bending.

[0041] (3c) In this embodiment, the second joint portion 4 is formed after bending. As a result, the second joint portion 4 is formed in a state in which it is less susceptible to the effect of the difference in elongation length along the bending direction B between the first metal plate 1 and the second metal plate 2 due to bending. This makes it possible to make the second joint portion 4 less susceptible to cracking.

[0042] In addition, in this embodiment, the springback of the second metal plate 2 is configured to be larger than the springback of the first metal plate 1, so that the second joint portion 4 is formed in a state in which the first metal plate 1 and the second metal plate 2 are brought into close contact with each other. This makes it easy to form the second joint portion 4.

[0043] In this embodiment, the first metal plate 1 corresponds to an example of an outer metal plate, and the second metal plate 2 corresponds to an example of an inner metal plate. The first surface 111 of the top wall 11 corresponds to an example of a first surface, the second surface 121 of the side wall 12 corresponds to an example of a second surface, and the first region 111A of the first metal plate 1 corresponds to an example of a region that becomes the first surface of the outer metal plate.

[0044] [4. Other embodiments] Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments and can take various forms.

[0045] (4a) In the above embodiment, in the pre-welding step, the portion 21A of the second metal plate 2 before bending, which becomes the first cover portion 21, is welded to the first region 111A of the first metal plate 1, which becomes the first surface 111 of the first metal plate 1, to form the first joint 3. Then, in the post-welding step, the second cover portion 22 of the second metal plate 2 after bending is welded to the second surface 121 of the first metal plate 1 to form the second joint 4. However, the welds formed in the pre-welding step and the post-welding step are not limited to this.

[0046] For example, the molded product 100 may be manufactured by a manufacturing method of a first modified example shown in FIGS. 5A to 5C. <Pre-welding process> 5A, the second metal plate 2 is overlapped so as to straddle the first portion 11A of the first metal plate 1 before bending, which will become the top wall 11, the second portion 12A of the first metal plate 1 before bending, which will become one side wall 12, and the portion 13A of the first metal plate 2 before bending, which will become the bent portion 13 located between the first portion 11A and the second portion 12A. Then, the portion 22A of the second metal plate 2 before bending, which will become the second cover portion 22, is welded to the second region 121A of the first metal plate 1 before bending, which will become the second surface 121, to form the second joint portion 4.

[0047] <Bending process> 5B, after the second joint portion 4 is formed, the first metal plate 1 is bent together with the second metal plate 2 by cold pressing to form a corner portion 10. Note that the bending process in the manufacturing method of the first modified example is the same as that in the manufacturing method of the above embodiment, and therefore a detailed description thereof will be omitted.

[0048] That is, in the manufacturing method of the first modified example, when bending is performed on a blank, with respect to the ridgeline R of the bent portion 13 of the first metal plate 1 formed by the bending, only the second surface 121 located on the second side is joined to the second metal plate 2 by the second joint portion 4. On the other hand, the first surface 111 located on the first side with respect to the ridgeline R of the bent portion 13 is not joined to the second metal plate 2.

[0049] <Post-welding process> 5C, the first joint portion 3 is formed on the blank material after bending by the above-mentioned cold press. Specifically, the first cover portion 21 of the second metal plate 2 after bending is welded to the first surface 111 of the first metal plate 1 to form the first joint portion 3. The molded product 100 obtained by the manufacturing method of the first modification also provides the same effects as those (3a) to (3c) of the above embodiment.

[0050] (4b) In the above embodiment, the molded product 100 has a configuration in which the cross-sectional shape of the first metal plate 1 is hat-shaped and the cross-sectional shape of the second metal plate 2 is L-shaped. However, the shapes of the first metal plate and the second metal plate in the molded product are not limited to this. For example, the first metal plate and the second metal plate may be hat-shaped, U-shaped, and L-shaped, respectively. Also, for example, the first metal plate and the second metal plate may be a combination of the same shape or a combination of different shapes.

[0051] For example, as in the molded product 100a of the second modified example shown in FIG. 6 and FIG. 7, the first metal plate 1a may have a hat-shaped cross-sectional shape, and the second metal plate 2a may have a U-shaped cross-sectional shape. The molded product 100a is an L-shaped plate-shaped part that extends in the longitudinal direction L and has one end of the molded product 100a in the longitudinal direction S, and has multiple corners 10a as in the above embodiment. The molded product 100a is, for example, a front pillar provided at the front lower part of the side of an automobile. The molded product 100a includes a first metal plate 1a, a second metal plate 2a, multiple first joint parts 3a, and multiple second joint parts 4a. The material, tensile strength, plate thickness, etc. of the first metal plate 1a and the second metal plate 2a are the same as those of the first metal plate 1 and the second metal plate 2 in the above embodiment, so detailed description will be omitted.

[0052] <First metal plate> The first metal plate 1a has a top wall 11a, two side walls 12a, two bent portions 13a, and two flange portions 14a. Note that these configurations are similar to the top wall 11, the two side walls 12, the two bent portions 13, and the two flange portions 14 of the above embodiment, so detailed description will be omitted.

[0053] <Second metal plate> The second metal plate 2a is disposed across the top wall 11a, the two side walls 12a, and the two bent portions 13a of the first metal plate 1a. In the molded product 100a, the second metal plate 2a overlaps the first surface 111a of the top wall 11a, the second surfaces 121a of the side walls 12a, and the inner surfaces of the bent portions 13a of the first metal plate 1a.

[0054] The second metal plate 2a has a first cover portion 21a, two second cover portions 22a, and two third cover portions 23a. Note that these configurations are similar to the first cover portion 21, the second cover portion 22, and the third cover portion 23 of the above embodiment, so detailed description will be omitted.

[0055] <1st joint> The first joint portion 3a is a portion of the molded product 100a where the first cover portion 21a of the second metal plate 2a is welded to the first surface 111a of the first metal plate 1a. A plurality of first joint portions 3a are provided so as to be aligned at intervals from each other in the longitudinal direction L and the lateral direction S.

[0056] <Second joint> The second joint portions 4a are portions of the molded product 100a where the second cover portions 22a of the second metal plate 2a are welded to the second surfaces 121a of the first metal plate 1a. A plurality of second joint portions 4a are provided on each of the second cover portions 22a so as to be aligned at intervals from each other in the longitudinal direction L.

[0057] The above-mentioned molded product 100a is manufactured by the method described below. In the manufacturing method of the molded product 100a of the second modification, in the pre-welding step, first, the second metal plate 2a is overlapped so as to straddle the portion of the first metal plate 1a before bending that will become the top wall 11a, the portions of the first metal plate 1a that will become the two side walls 12a, and the portions of the first metal plate 1a that will become the two bent portions 13a. Then, the portion of the second metal plate 2a before bending that will become the first cover portion 21a is welded to the region that will become the first surface 111a of the first metal plate 1a to form the first joint portion 3a.

[0058] Next, in the bending process, after the first joint portion 3a is formed, the first metal plate 1a is bent together with the second metal plate 2a by cold pressing to form the corner portion 10. That is, the first metal plate 1a is bent so that the cross-sectional shape thereof becomes hat-shaped, and the second metal plate 2a is bent so that the cross-sectional shape thereof becomes U-shaped.

[0059] Next, in a post-welding step, the second joints 4a are formed on the blank material after bending by the above-mentioned cold press. Specifically, the second cover parts 22a of the second metal plate 2a after bending are welded to the second surfaces 121a of the first metal plate 1a to form the second joints 4a. The molded product 100a obtained by this manufacturing method also has the same effects as those of the above-mentioned embodiments (3a) to (3c).

[0060] In the molded product 100a, in the pre-welding step, first, only one of the two second cover parts 22a of the second metal plate 2a before bending may be welded to one of the two second surfaces 121a of the first metal plate 1a to form the second joint part 4a. After that, in the post-welding step, the unjoined second cover part 22a of the second metal plate 2a after bending may be welded to the second surface 121a of the first metal plate 1a to form the second joint part 4a. In the post-welding step, the first cover part 21a of the second metal plate 2a after bending may be welded to the first surface 111a of the first metal plate 1a to form the first joint part 3a. The molded product 100a obtained by this manufacturing method also has the same effects as those of (3a) to (3c) of the above embodiment.

[0061] Also, for example, like a molded product 100b of a third modified example shown in FIG. 8, the first metal plate 1b may have a U-shaped cross section, and the second metal plate 2b may have an L-shaped cross section.

[0062] Also, for example, like a molded product 100c of a fourth modified example shown in FIG. 9, a first metal plate 1c may have a U-shaped cross section, and a second metal plate 2c may have a U-shaped cross section.

[0063] Also, for example, like a molded product 100d of a fifth modified example shown in FIG. 10, a first metal plate 1d may have an L-shaped cross section, and a second metal plate 2d may have an L-shaped cross section.

[0064] Also, for example, like a molded product 100e of a sixth modified example shown in FIG. 11, a first metal plate 1e may have a hat-shaped cross section, and a second metal plate 2e may have a hat-shaped cross section.

[0065] (4c) In the above embodiment, the second metal plate 2 is disposed inside the bent portion 13 of the first metal plate 1, and is welded to the first metal plate 1 so as to overlap the bent portion 13 from the inside. However, for example, as in the molded product 100f of the seventh modification shown in FIG. 12, the second metal plate 2f may be disposed outside the bent portion 13f of the first metal plate 1f and welded to the first metal plate 1f so as to overlap the bent portion 13f from the outside. That is, the second metal plate 2f may be overlapped on the outer surface of the bent portion 13f. The cross-sectional shape of the first metal plate 1f is hat-shaped, and the cross-sectional shape of the second metal plate 2f is L-shaped. In the case of the molded product 100f shown in FIG. 12, the first metal plate 1f corresponds to an example of an inner metal plate, and the second metal plate 2f corresponds to an example of an outer metal plate. Also, the inner surface of the first cover portion 21f corresponds to an example of a first surface, the inner surface of the second cover portion 22f corresponds to an example of a second surface, the third cover portion 23f corresponds to an example of a bent portion, and the region of the second metal plate 2f that becomes the inner surface of the first cover portion 21f corresponds to an example of a region of the outer metal plate that becomes the first surface.

[0066] Furthermore, for example, as in the molded product 100g of the eighth modified example shown in Figure 13, the cross-sectional shape of the second metal plate 2g that is superimposed on the outer surface of the bent portion 13g of the first metal plate 1g having a hat-shaped cross-sectional shape may be U-shaped.

[0067] (4d) In the above embodiment, the second metal plate 2 has a tensile strength greater than that of the first metal plate 1 and a thickness less than that of the first metal plate 1. This makes the springback of the second metal plate 2 greater than that of the first metal plate 1. However, the tensile strength and thickness of each metal plate may be configured as follows so that the springback of the second metal plate 2 is greater than that of the first metal plate 1. For example, when the second metal plate 2 has a tensile strength greater than that of the first metal plate 1, the second metal plate 2 may have a thickness greater than that of the first metal plate 1 or the same thickness as that of the first metal plate 1. That is, the springback of the second metal plate 2 may be greater than that of the first metal plate 1 only because the tensile strength of the second metal plate 2 is greater than that of the first metal plate 1. Furthermore, for example, when the second metal plate 2 is thinner than the first metal plate 1, the second metal plate 2 may have a smaller tensile strength than the first metal plate 1 or may have the same tensile strength as the first metal plate 1. In other words, the springback of the second metal plate 2 may be larger than the springback of the first metal plate 1 simply because the thickness of the second metal plate 2 is thinner than the thickness of the first metal plate 1.

[0068] In the configuration shown in Fig. 12 and Fig. 13 where the second metal plate overlaps the outside of the bent portion of the first metal plate, the tensile strength and thickness of each metal plate may be configured as follows so that the springback of the first metal plate 1f, 1g is larger than the springback of the second metal plate 2f, 2g. For example, the first metal plate 1f, 1g may have a tensile strength larger than the second metal plate 2f, 2g and a thickness smaller than the second metal plate 2f, 2g. Also, for example, when the first metal plate 1f, 1g has a tensile strength larger than the second metal plate 2f, 2g, the first metal plate 1f, 1g may have a thickness larger than the second metal plate 2f, 2g or the same thickness as the second metal plate 2f, 2g. Furthermore, for example, when the first metal plates 1f, 1g are thinner than the second metal plates 2f, 2g, the first metal plates 1f, 1g may have a smaller tensile strength than the second metal plates 2f, 2g or may have the same tensile strength as the second metal plates 2f, 2g. The first metal plates 1f, 1g are preferably made of high tensile steel having a tensile strength of 590 MPa or more, and more preferably made of high tensile steel having a tensile strength of 980 MPa or more.

[0069] (4e) The function of one component in the above embodiments may be distributed among multiple components, or the functions of multiple components may be integrated into one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0070] [5. Technical Concepts Disclosed in This Specification] [Item 1] A method for manufacturing a molded product, comprising the steps of: overlapping and welding the inner metal plate to the outer metal plate to form a first joint; After the first joint portion is formed, bending the outer metal plate together with the inner metal plate by pressing; Equipped with In the pressing, a first surface, a second surface extending in a direction intersecting the first surface, and a bent portion connecting the first surface and the second surface and overlapping the inner metal plate are formed in the outer metal plate, the first joint portion is a portion where the inner metal plate is welded to a region of the outer metal plate that becomes the first surface, A method for manufacturing a molded product, wherein the inner metal plate is positioned inside the bent portion and has a greater springback than the outer metal plate.

[0071] [Item 2] A method for producing the molded product according to item 1, A method for manufacturing a molded product, wherein the inner metal plate has a greater tensile strength than the outer metal plate.

[0072] [Item 3] A method for producing a molded product according to item 1 or 2, A method for manufacturing a molded product, wherein the inner metal plate has a thickness thinner than that of the outer metal plate.

[0073] [Item 4] A method for producing a molded product according to any one of items 1 to 3, The method for manufacturing a molded product further comprises welding the outer metal plate and the inner metal plate together after the pressing, to form a second joint at which the inner metal plate is welded to the second surface.

[0074] [Item 5] A method for producing a molded product according to any one of items 1 to 4, The molded product has a hat-shaped or L-shaped cross-sectional shape along a direction in which the first surface, the bent portion, and the second surface are aligned, A method for manufacturing a molded product, wherein the inner metal plate is formed from high-tensile steel having a tensile strength of 590 MPa or more. [Explanation of symbols]

[0075] 1,1a-1g...first metal plate, 2,2a-2g...second metal plate, 3,3a...first joint, 4,4a...second joint, 10,10a...corner, 11,11a...top wall, 12,12a...side wall, 13,13a,13f,13g...bent portion, 14,14a...flange portion, 21,21a,21f...first cover portion, 22,22a,22f...second cover portion, 23,23a,23f...third cover portion, 100,100a-100g...molded product, 111,111a...first surface, 111A...first region, 121,121a...second surface, 121A...second region, R...ridge line.

Claims

1. A method for manufacturing a molded product, comprising the steps of: overlapping and welding the inner metal plate to the outer metal plate to form a first joint; bending the outer metal plate together with the inner metal plate by pressing after forming the first joint portion; Equipped with In the pressing, a first surface, a second surface extending in a direction intersecting the first surface, and a bent portion connecting the first surface and the second surface and overlapping the inner metal plate are formed in the outer metal plate, the first joint portion is a portion where the inner metal plate is welded to a region of the outer metal plate that becomes the first surface, A method for manufacturing a molded product, wherein the inner metal plate is positioned inside the bent portion and has a greater springback than the outer metal plate.

2. A method for producing the molded product according to claim 1, A method for manufacturing a molded product, wherein the inner metal plate has a greater tensile strength than the outer metal plate.

3. A method for producing the molded product according to claim 1 or 2, comprising the steps of: A method for manufacturing a molded product, wherein the inner metal plate has a thickness thinner than that of the outer metal plate.

4. A method for producing the molded product according to claim 1 or 2, comprising the steps of: The method for manufacturing a molded product further comprises welding the outer metal plate and the inner metal plate together after the pressing to form a second joint portion where the inner metal plate is welded to the second surface.

5. A method for producing the molded product according to claim 1 or 2, comprising the steps of: The molded product has a hat-shaped or L-shaped cross-sectional shape along a direction in which the first surface, the bent portion, and the second surface are aligned, A method for manufacturing a molded product, wherein the inner metal plate is formed from high-tensile steel having a tensile strength of 590 MPa or more.

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