Formed component and forming method

Abstract

The present invention provides: a component formed from a multi-layer steel sheet having a plurality of layers in which delamination of the sheet does not occur; and a forming method. According to an embodiment, the formed component is formed from a multi-layer steel sheet including first and second metal layers and an adhesive layer disposed between the first and second metal layers, and comprises: a flange formed by bending the multi-layer steel sheet; and a bead protruding at a position spaced a first distance inward from the flange, wherein at least one of the first metal layer or the second metal layer is a structural steel.

Description

Molded parts and molding methods

[0001] The present invention relates to a molded part and a molding method, and specifically to a molded part formed from a multi-layer steel plate having multiple layers and a molding method thereof.

[0002] Exterior panel materials in many industrial fields, such as automobiles, structures, and home appliances, are adopting steel plates with excellent strength and rigidity, and technologies are being developed to utilize two steel plates joined by bond, resin, or fusion to lighten products and reduce costs.

[0003] Furthermore, since excellent vibration damping performance can be achieved depending on the characteristics of the bond and resin forming the bonding layer between the steel plates, bonded steel plates are attracting attention in many industries.

[0004] However, due to the reduced strength of the resin forming the bonding interface of these bonded steel plates, the two plates may separate depending on the part shape, making assembly difficult. When the plates delaminate, securing the part shape and assembly stability are compromised, making it difficult to ensure part performance. Furthermore, if the forming amount of the plates, such as the forming depth, is reduced to prevent delamination, it becomes difficult to secure the required rigidity of the part.

[0005] [Prior Art Literature]

[0006] (Patent Document 1) KR 10-2012-0085789 A

[0007] The present invention aims to overcome the limitations of the prior art as described above by providing a formed part and a forming method formed from a multi-layer steel plate having multiple layers in which delamination of the plate material does not occur.

[0008] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall contents of this specification.

[0009] To achieve the above objectives, the present invention provides a part formed from a multi-layer steel plate and a forming method as follows.

[0010] The present invention provides a formed part comprising, in one embodiment, a multilayer steel plate formed from a multilayer steel plate including first and second metal layers and an adhesive layer disposed between the first and second metal layers, wherein the multilayer steel plate is bent and formed into a flange; and a bead formed protruding from a position spaced inward by a first distance from the flange, wherein at least one of the first and second metal layers is a steel material.

[0011] In one embodiment, the first distance may be 20 mm or more, and the height of the bead may be between 200% and 500% of the total thickness of the multilayer steel plate.

[0012] In one embodiment, the beads may be formed continuously along the edge where the flange is formed, or a plurality of beads may be formed spaced apart along the edge where the flange is formed.

[0013] In one embodiment, the bead may be formed in a dot shape when viewed from the first direction in which the second metal layer is bonded to the first metal layer.

[0014] In one embodiment, the bead may be formed such that, when viewed from the first direction in which the second metal layer is bonded to the first metal layer, the length in the circumferential direction of the molded part is longer than the length in the vertical direction perpendicular to the circumferential direction.

[0015] In one embodiment, the first thickness, which is the thickness of the multilayer steel plate at the protruding top portion of the bead, may be smaller than the second thickness, which is the thickness of the multilayer steel plate between the bead and the flange, and the difference between the second thickness and the first thickness may be less than or equal to the thickness of the adhesive layer.

[0016] In one embodiment, the flange includes a first flange disposed on one edge and a second flange disposed on the other edge, and the bead includes a first bead disposed inside the first flange and a second bead disposed inside the second flange, and on a cross-section where the first flange and the second flange are disposed on both sides, the multi-layer steel plate may include a bent portion formed by bending between the first bead and the second bead.

[0017] In one embodiment, the bead may be formed in a semicircular shape in a cross-section perpendicular to the circumferential direction of the molded part.

[0018] The present invention provides a forming method comprising: a preparation step of preparing a multilayer steel plate comprising, in one embodiment, first and second metal layers and an adhesive layer disposed between the first and second metal layers; a bead forming step of forming a bead through a first mold at a position spaced inward by a first distance from a flange formation position at the edge of the multilayer steel plate; and a flange forming step of forming the flange by bending the multilayer steel plate.

[0019] In one embodiment, the method further includes a restrike step performed through a second mold after the bead forming step, wherein in the restrike step, the minimum spacing of the bead forming portion in the second mold may be smaller than the thickness of the multi-layer steel plate.

[0020] In one embodiment, the flange forming step can be performed together with the first mold of the bead forming step.

[0021] In one embodiment, the restrike step may be performed after the flange forming step and the bead forming step are completed.

[0022] In one embodiment, a bending portion forming step for bending the multi-layer steel plate having the flange and bead formed thereon may be further included.

[0023] In one embodiment, the flange forming step may be performed after the bead forming step is performed.

[0024] The present invention can provide a part formed from a multi-layer steel plate having multiple layers that do not cause delamination of the plate material through the above configuration, and a forming method.

[0025] Figure 1 is a schematic diagram of a multilayer steel plate.

[0026] Figure 2 is a schematic diagram of the appearance of a multi-layer steel plate during forming.

[0027] FIG. 3 is a side schematic view of a part formed from a multi-layer steel plate having a flange.

[0028] FIG. 4 is a plan view of a part formed from a multi-layer steel plate according to the first embodiment of the present invention.

[0029] Figure 5 is a front view of the part of Figure 4.

[0030] Figure 6 is a partial cross-sectional view of the part of Figure 4.

[0031] Figure 7 is a graph of the bending experiment results of the first embodiment and comparative example of the present invention.

[0032] FIG. 8 is a perspective view of a part formed from a multi-layer steel plate according to a second embodiment of the present invention.

[0033] FIG. 9 is a perspective view of a part formed from a multi-layer steel plate according to a third embodiment of the present invention.

[0034] FIG. 10 is a perspective view of a part formed from a multi-layer steel plate according to the fourth embodiment of the present invention.

[0035] FIG. 11 is a flowchart of a method for forming a multi-layer steel plate according to an embodiment of the present invention.

[0036] Figure 12 is a schematic diagram of the bead formation step of Figure 11.

[0037] Figure 13 is a schematic diagram of the restrike step of Figure 11.

[0038] Preferred embodiments of the present invention will be described below with reference to the attached drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0039] In addition, embodiments of the present invention are provided to more fully explain the present invention to those with average knowledge in the relevant technical field.

[0040] In drawings, the shapes and sizes of elements may be exaggerated for clearer explanation.

[0041] In describing the embodiments of the present invention, if it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, such definitions should be based on the content throughout this specification. The terms used in the detailed description are merely for describing the embodiments of the present invention and should not be limited in any way. Unless explicitly stated otherwise, expressions in the singular form include the meaning of the plural form.

[0042] In this description, expressions such as “include” or “equipped” are intended to refer to certain characteristics, numbers, steps, actions, elements, parts or combinations thereof, and should not be interpreted to exclude the existence or possibility of one or more other characteristics, numbers, steps, actions, elements, parts or combinations thereof other than those described.

[0043] Unless otherwise specifically defined in the specification of the present invention, % units mean weight %.

[0044] In this specification, terms such as 'top', 'upper', 'upper surface', 'lower', 'lower surface', 'lower surface', and 'side surface' are based on the drawings and may actually vary depending on the direction in which the elements or components are arranged.

[0045] Additionally, throughout the specification, when it is said that one part is 'connected' to another part, this includes not only cases where they are 'directly connected,' but also cases where they are 'indirectly connected' with other elements in between.

[0046] The present invention will be described in detail below through each embodiment or example of the invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may also be combined with other embodiments or examples. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0047] Figure 1 shows a schematic diagram of a multilayer steel plate, Figure 2 shows a schematic diagram of the multilayer steel plate during forming, and Figure 3 shows a side schematic diagram of a part formed from a multilayer steel plate having a flange.

[0048] As shown in FIG. 1, the multilayer steel plate (10) comprises a first metal layer (1), a second metal layer (3), and an adhesive layer (2) disposed between the first metal layer (1) and the second metal layer (3). At least one of the first and second metal layers (1, 3) is a steel plate, and both the first and second metal layers (1, 3) may be steel plates. The adhesive layer (2) is a layer disposed between the first and second metal layers (1, 3) to bond the first and second metal layers (1, 3) to each other. The adhesive layer (2) may be a bond layer, or a resin layer formed by resin, fusion, etc. Depending on the characteristics of the adhesive layer (2), such a multilayer steel plate (10) can be utilized in various industries as it has excellent vibration damping performance.

[0049] In order to make a part from a multi-layer steel plate (10), it must be formed into a suitable shape. FIG. 2 illustrates the bending and forming of a multi-layer steel plate (10) through an upper roll (UR) and a lower roll (BR). By moving the upper roll (UR), which is positioned between the lower roll (BR) in the horizontal direction, downward, the multi-layer steel plate (10) is bent and formed around the upper roll (UR).

[0050] At this time, if we look closely at the part where bending occurs in the multi-layer steel plate (10), compression occurs on the upper side of the first metal layer (1) and tension occurs on the lower side of the first metal layer (1). Likewise, compression occurs on the upper side of the second metal layer (3) and tension occurs on the lower side of the second metal layer (3). Therefore, tension occurs on the lower side of the first metal layer (1), which is on the upper side, and compression occurs on the upper side of the second metal layer (2), which is on the lower side, centered on the adhesive layer (2). Therefore, in order for the first and second metal layers (1, 3) to be properly attached, the adhesive layer (2) must hold the first and second metal layers (1, 3) with sufficient interfacial strength.

[0051] However, as shown in FIG. 3, when a lot of bending is applied to the multi-layer steel plate (10), compression and tension exceeding the interfacial strength of the adhesive layer (2) occur, causing peeling of the adhesive surface of the adhesive layer (2). When the adhesive surface peels off, a peeling region (A) appears in which the first metal layer (1) and the second metal layer (3) are separated from the adhesive layer (2).

[0052] Also, when forming a multi-layer steel plate (10), residual stress and springback occur. Since the first and second metal layers (1, 3) have different forming amounts depending on their position during bending forming, the residual stress and springback amounts of the first and second metal layers (1, 3) differ. If the strength of the adhesive interface of the adhesive layer (2) is weak, peeling of the adhesive surface occurs.

[0053] When high-strength steel plates are used for the first and second metal layers (1, 3), the amount of springback may increase, and when the difference in springback between the first and second metal layers (1, 3) is large, peeling of the adhesive surface is likely to occur.

[0054] A part formed from a multi-layer steel plate (10) may have a flange for joining with other parts rather than a flat shape. However, when the steel plate is bent to form a flange, or when the steel plate with the formed flange is bent again into a desired shape, delamination occurs in a part of the multi-layer steel plate (10), making it difficult to manufacture a part formed from a multi-layer steel plate having a flange.

[0055] In the present invention, a bead is formed on the multi-layer steel plate (10) to prevent slip of the first and second metal layers (1, 3) so that the bonding surface does not peel off due to bending, in a part formed by forming a flange formed by bending. The bead has an uneven structure and performs the role of preventing relative movement of the first metal layer (1) and the second metal layer (30), thereby preventing peeling of the bonding surface.

[0056] FIGS. 4 to 6 illustrate a part formed from a multilayer steel plate according to a first embodiment of the present invention. Specifically, FIG. 4 illustrates a plan view of a part formed from a multilayer steel plate according to a first embodiment of the present invention, FIG. 5 illustrates a front view of the part of FIG. 4, and FIG. 6 illustrates a partial cross-sectional view of the part of FIG. 4.

[0057] A component (100) according to the first embodiment is formed by molding a multi-layer steel plate (10) comprising first and second metal layers (1, 3) and an adhesive layer (2) disposed between the first and second metal layers (1, 3). The first and second metal layers (1, 3) are steel plates, and the adhesive layer (2) may be a resin layer.

[0058] In this embodiment, the multi-layer steel plate (10) is described as having an adhesive layer placed between two metal layers, but in the present invention, the multi-layer steel plate (10) refers to a structure in which one or more adhesive layers are placed between a plurality of metal layers, and the number of metal layers is not limited to two. In addition, in the multi-layer steel plate (10) of this embodiment, the first and second metal layers (1, 3) are made of the same steel, but the present invention is not limited thereto, and the first and second metal layers (1, 3) may be made of different steel, or some of the metal layers may not be made of steel.

[0059] The part (100) includes a flange (30) formed by bending at the edge of a multi-layer steel plate (10) and a bead (20) formed protruding inwardly from the flange (30) by a first distance (l1). In this embodiment, the flange (30) includes a first flange (31) formed on the left edge of the multi-layer steel plate (10) and a second flange (32) formed on the right edge, based on the drawing, and the bead (20) includes a first bead (21) formed protruding from the outer surface of the second metal layer (3) spaced apart from the first flange (31) toward the center and a second bead (22) formed protruding from the outer surface of the second metal layer (3) spaced apart from the second flange (32) toward the center and a bead (22) formed protruding from the outer surface of the second metal layer (3).

[0060] Additionally, the part (100) includes a bent portion (40) formed by bending between the first bead (21) and the second bead (22).

[0061] In the first embodiment of the present invention, the part (100) has a shape in which a bead (20) protrudes by a second distance (l2) at a position spaced apart by a first distance (l1) from the flange (30), and a bend portion (40) is formed between the first bead (21) and the second bead (22). The second distance (l2) may be called the height or protrusion height of the bead (20). In this embodiment, the part (100) is formed by a single multi-layer steel plate (10), and the bend portion (40) or the flange (30) is formed by bending the multi-layer steel plate (10).

[0062] In this embodiment, a bead (20) protruding by a second distance (l2) is formed at a position located at a first distance (l1) away from the flange (30) so as not to cause peeling of the adhesive layer (2) due to bending molding, thereby preventing slipping on the first metal layer (1) or the third metal layer (3) by the bead (20) during the molding of the flange (30) or the bending portion (40). That is, the bead (20) is formed on the multi-layer steel plate (10) before at least one of the flange (30) or the bending portion (40) is formed, and by preventing relative movement of the adhesive layer (2) of the first metal layer (1) or the third metal layer (3) of the multi-layer steel plate (10) during the molding of the flange (30) or the bending portion (40), peeling occurring during bending molding can be prevented. The molding method will be explained again later.

[0063] In addition, in the present invention, the thickness of the multi-layer steel plate (10) at the protruding top portion (21a) of the bead (20) may be smaller than the thickness (30) of the multi-layer steel plate (10) before forming, for example, the thickness of the multi-layer steel plate (10) between the bead (20) and the flange (30) without forming. The difference between the thickness at the protruding top portion (21a) and the thickness before forming may be less than or equal to the thickness of the adhesive layer (2).

[0064] In this embodiment, the bead (20) is formed to protrude in a direction toward the outer surface of the second metal layer (3), but it is of course possible for the bead (20) to protrude in a direction toward the outer surface of the first metal layer (1) rather than the second metal layer (3). In addition, in this embodiment, the direction in which the bead (20) protrudes is opposite to the direction in which the flange (30) is bent to form the flange (30) in the multi-layer steel plate (10) (upward direction in FIG. 5), but the direction in which the flange (30) is bent and the direction in which the bead (20) protrudes may be the same, and in either case, the slip prevention effect caused by the bead (20) can be achieved. However, it may be advantageous for the direction in which the bead (20) protrudes and the direction in which the flange (30) is bent to be different from the forming surface.

[0065] The bead (20) is positioned in the center rather than the flange (30) formed at the edge, and protrudes by a second distance (l2) at a position separated by a first distance (l1). As shown in FIG. 6, the cross-sectional shape of the bead (20) may have a semicircular shape in a cross-section perpendicular to the circumferential direction. Of course, the cross-sectional shape of the bead (20) can vary. Here, the first distance (l1) may be 20 mm or more from the formation position of the flange (30), and the second distance (l2) may be between 200 and 500% of the total thickness of the multi-layer steel plate (10).

[0066] Table 1 discloses the results of experiments on whether peeling occurs depending on the presence or absence of the bead (20) and the first and second distances (l1, l2) of the bead (20). Examples 1 to 6 of Table 1 had the same shape as the first example except for the first and second distances (l1, l2) of the bead (20), and Comparative Example 1 had the same shape as the first example but did not form the bead (20).

[0067] The multilayer steel plate (10) included first and second metal layers (1, 3) of the same steel material having a thickness of 0.4 mm and an adhesive layer (2) with a thickness of 200 μm. Examples 1 to 6 of Table 1 formed the bead (20) first using the multilayer steel plate (10), followed by the flange (30) and the bent portion (40), while Comparative Example 1 formed the flange (30) and the bent portion (40) in that order without forming the bead (20).

[0068] Item Multi-layer steel plate total thickness (mm) 1st distance (l1, mm) 2nd distance (l2, mm) Occurrence of delamination Example 1 0.8 220 2X Example 2 0.8 220 4X Example 3 0.8 230 2X Example 4 0.8 210 2Δ (Delamination between bead and bend) Example 5 0.8 220 5Δ (Delamination around bead) Example 6 0.8 220 1Δ (Flange delamination) Comparative Example 1 0.8 2--O (Delamination at flange and between flange and bend)

[0069] As shown in Table 1, compared to the case where no beads (20) are formed at all as in Comparative Example 1, the degree of peeling is improved in the case where beads (20) are formed as in Examples 1 to 6.

[0070] However, as in Example 4, when the first distance (l1) of the bead (20) is less than 20 mm from the formation position of the flange (30), that is, when the bead (20) is too close to the flange (30), the effect of improving slip is insufficient and delamination occurs between the bead (20) and the bent portion (40); as in Example 5, when the second distance (l2) of the bead (20) exceeds 500% of the total thickness of the multi-layer steel plate (10), delamination of the multi-layer steel plate (10) occurs around the bead (20); and as in Example 6, when the second distance (l2) of the bead (20) is less than 200% of the total thickness of the multi-layer steel plate (10), the effect of preventing slip is not significant and delamination occurs at the flange (30).

[0071] Figure 7 shows a graph of a bending experiment performed on Example 1 of the first embodiment and Comparative Example 1.

[0072] In the graph of FIG. 7, the X-axis represents the angle at which the bend portion (40) is bent, and the Y-axis represents the force. The graph of FIG. 7 is the result of measuring the force according to the forming angle of the bend portion (40) while the bead (20) and flange (30) are formed.

[0073] As shown in part B of FIG. 7, in the case of Comparative Example 1, a decrease in force occurs when the bending angle of the bending part (40) is about 10°, whereas in the case of Example 1, it can be seen that the force increases without a decrease until the bending angle of the bending part (40) increases to the maximum. Here, a decrease in force means that delamination occurs, and from FIG. 7, it can be seen that in the case of Comparative Example 1, delamination occurred even though the bending angle of the bending part (40) was not large, about 10°. On the other hand, in the case of Example 1, it can be seen that delamination did not occur even when the bending angle increased to the maximum measurable size.

[0074] FIGS. 8 to 10 illustrate perspective views of parts formed from multilayer steel plates according to the second to fourth embodiments of the present invention. Specifically, FIG. 8 illustrates a perspective view of a part formed from a multilayer steel plate according to the second embodiment of the present invention, FIG. 9 illustrates a perspective view of a part formed from a multilayer steel plate according to the third embodiment of the present invention, and FIG. 10 illustrates a perspective view of a part formed from a multilayer steel plate according to the fourth embodiment of the present invention.

[0075] As shown in FIG. 8, the part (101) includes a flange (30) formed by bending at the edge of a multi-layer steel plate (10) having a predetermined shape and comprising a first and second metal layer (1, 3; see FIG. 5) and an adhesive layer (2; see FIG. 5) disposed between the first and second metal layer (1, 3), and a bead (20) formed protruding at a position spaced inward by a first distance (l1) from the flange (30).

[0076] In the second embodiment, the bead (20) is formed continuously along the edge where the flange (30) is formed. That is, the bead (20) is formed as a single bead (20) without interruption along the circumferential direction inside the flange (30).

[0077] As shown in FIG. 9, the part (102) of the third embodiment has a shape similar to that of the second embodiment. In the third embodiment, the part (102) is formed by forming a multi-layer steel plate (10) and includes a flange (30) formed by bending at the edge and a plurality of beads (20) protruding from a position spaced inward by a first distance (l1) from the flange (30). At this time, the shape of the beads (20) may be a dot shape when viewed in the thickness direction of the multi-layer steel plate (10).

[0078] In the third embodiment, a plurality of beads (20) are spaced apart along the circumferential direction at a position spaced apart by a first distance (l1) from the flange (30), and the spacing of the beads (20) at the position corresponding to the straight edge of the part (102) is greater than the spacing of the beads (20) at the position corresponding to the bent or curved edge. That is, when the shape of the part edge is complex, the beads (20) are formed relatively densely, and when the shape of the part edge is simple, the beads (20) are formed relatively sparsely.

[0079] As shown in FIG. 10, the part (103) of the fourth embodiment has a shape similar to that of the second and third embodiments. In the fourth embodiment, the part (103) is formed by forming a multi-layer steel plate (10) and includes a flange (30) formed by bending at the edge and a plurality of beads (20) protruding from a position spaced inward by a first distance (l1) from the flange (30). At this time, the shape of the beads (20) may be such that when viewed from the thickness direction of the multi-layer steel plate (10), the length in the perimeter direction of the formed part is longer than the length in the vertical direction perpendicular to the perimeter direction.

[0080] FIG. 11 shows a flowchart of a method for forming a multilayer steel plate according to an embodiment of the present invention, FIG. 12 shows a schematic diagram of the bead forming step of FIG. 11, and FIG. 13 shows a schematic diagram of the restrike step of FIG. 11.

[0081] As shown in FIGS. 11 to 13, the multilayer steel plate forming method according to the present invention comprises: a preparation step (S110) of preparing a multilayer steel plate (10) comprising first and second metal layers (1, 3) and an adhesive layer (2) disposed between the first and second metal layers (1, 3); a bead forming step (S120) of forming a bead (20) through a first mold (200) at a position spaced inward by a first distance from the flange formation position at the edge of the multilayer steel plate (10); a flange forming step (S130) of forming the flange by bending the multilayer steel plate (10); and a restrike step (S140) of reforming the bead after the bead forming step (S120).

[0082] The preparation step (S110) is a step of preparing a multi-layer steel plate (10) by cutting a plurality of metal layers (1, 3) bonded together with an adhesive layer (2).

[0083] The bead forming step (S120) is a step of forming a bead (20) through a first mold (200) at a position that is a first distance from the position of the flange to be formed on the edge of the multi-layer steel plate. As shown in FIG. 12, the first mold (200) includes an upper mold (210) and a lower mold (220), and the bead (20) is formed by pressing through a press while the multi-layer steel plate (10) is positioned between the upper mold (210) and the lower mold (220).

[0084] The flange forming step (S130) can be performed through a bending device and is a step of forming a flange (30; see FIG. 5) by bending the edge around the flange formation position. The flange forming step (S130) may be performed by a separate bending device, but it is also possible to perform it together in the first mold (200). That is, the bead (20) and the flange (30) can be formed at once through the first mold (200).

[0085] The restrike step (S140) is a step of reshaping the bead (20) after forming the bead (20). In this embodiment, the restrike step (S140) is performed by a second mold (300). The second mold (300) includes an upper mold (310) and a lower mold (320) similar to the first mold (200). In the restrike step (S140), the lower mold (320) has a flat surface (321) in the portion corresponding to the protruding top portion (20a). The gap between the upper mold (310) and the lower mold (320) in the flat surface (321) is configured to be smaller than the gap between the upper mold (310) and the lower mold (320) in other portions. That is, as shown in FIG. 13, the lower mold (320) is configured to press the protruding top portion (20a) formed in the bead forming step through the flat surface (321) by a distance (D). By further forming a bead (20) including a flat surface (321) in the lower mold (320), residual stress remaining in the multi-layer steel plate (10) can be removed.

[0086] The above gap (D) can be formed to correspond to the thickness of the adhesive layer (2). In the multi-layer steel plate (10), the thickness of the adhesive layer (2) can be about 60 to 300 μm. The protruding top portion (20a) of the formed bead (20) can be such that the adhesive layer (2) is almost completely removed by pressure.

[0087] However, the restrike step (S140) also includes forming the multi-layer steel plate (10) with the bead (20) formed using the same mold without additional forming, for example, the first mold (200) used in the bead forming step (S120). Even if re-forming with the same mold, it is possible to remove a certain level of residual stress.

[0088] The multilayer steel plate forming method according to the present invention may further include a bending portion forming step for additionally bending the multilayer steel plate having a bead (20) and a flange (30) formed thereon after the bead forming step (S120) and the flange forming step (S130).

[0089] In the case where there is no bending part forming step, the bead forming step (S120) and the flange forming step (S130) are performed first, and then the flange forming step (S130) is performed. However, if there is a bending part forming step, it is also possible to form the flange (30) first and then form the bead (20) and the bending part (40; FIG. 5). That is, in the present invention, if the multi-layer steel plate (10) with the formed bead (20) is bent, the order of bead formation, flange formation, and bending part formation can be changed.

[0090] Although the present invention has been described above with reference to embodiments, it is understood that the invention is not limited thereto and can be implemented with various modifications.

[0091] [Explanation of the symbol]

[0092] 100, 101, 102, 103: Parts

[0093] 1, 3: First and second metal layers 2: Adhesive layer

[0094] 10: Multi-layer steel plate 20: Bead

[0095] 21, 22: 1st and 2nd beads 20a, 21a: Protruding top

[0096] 30: Flange 31, 32: 1st and 2nd flanges

[0097] 200: 1st mold 300: 2nd mold

Claims

1. Formed into a multilayer steel plate comprising a first and second metal layer and an adhesive layer disposed between the first and second metal layers, and A flange formed by bending the above multilayer steel plate; and A bead formed protruding at a position spaced inward by a first distance from the above flange; comprising, A molded part in which at least one of the first and second metal layers is made of steel.

2. In Paragraph 1, A molded part having a first distance of 20 mm or more.

3. In Paragraph 2, A formed part in which the height of the bead is between 200% and 500% of the total thickness of the multilayer steel plate.

4. In Paragraph 3, The above bead is a molded part formed continuously along the edge where the flange is formed.

5. In Paragraph 3, The above beads are molded parts formed spaced apart along the edge where the flange is formed.

6. In Paragraph 5, The above bead is a molded part formed in a dot shape when viewed from the first direction in which the second metal layer is bonded to the first metal layer.

7. In Paragraph 5, The above bead is a molded part in which, when viewed from the first direction in which the second metal layer is bonded to the first metal layer, the length in the circumferential direction of the molded part is longer than the length in the vertical direction perpendicular to the circumferential direction.

8. In Paragraph 3, A formed part in which the first thickness, which is the thickness of the multilayer steel plate at the protruding top portion of the bead, is smaller than the second thickness, which is the thickness of the multilayer steel plate between the bead and the flange.

9. In Paragraph 8, A molded part in which the difference between the second thickness and the first thickness is less than or equal to the thickness of the adhesive layer.

10. In Paragraph 3, The above flange includes a first flange disposed on one edge and a second flange disposed on the other edge, The above bead includes a first bead disposed inside the first flange and a second bead disposed inside the second flange, A formed part comprising a bent portion formed by bending the multi-layer steel plate between the first bead and the second bead on a cross-section in which the first flange and the second flange are arranged on both sides.

11. In Paragraph 10, The above bead is a molded part formed in a semicircular shape in a cross-section perpendicular to the circumferential direction of the molded part.

12. A preparation step for preparing a multilayer steel plate comprising first and second metal layers and an adhesive layer disposed between the first and second metal layers; A bead forming step of forming a bead through a first mold at a position spaced inward by a first distance from the formation position of the edge flange in the multi-layer steel plate; and A forming method comprising a flange forming step of bending the multi-layer steel plate to form the flange.

13. In Paragraph 12, It includes a restorer step performed through a second mold after the above bead forming step, and A forming method in which the minimum spacing of the bead-forming portion in the second mold during the above restrike step is smaller than the thickness of the multi-layer steel plate prior to the above restrike step.

14. In Paragraph 13, A molding method in which the above flange forming step is performed together by the first mold of the above bead forming step.

15. In Paragraph 13, The above restrike step is a molding method performed after the above flange forming step and the above bead forming step are completed.

16. In Paragraph 12, A forming method further comprising a bending portion forming step for bending a multi-layer steel plate having the above-mentioned flange and bead formed.

17. In Paragraph 12, A molding method in which the flange forming step is performed after the bead forming step is performed.

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