Press-formed member and method for manufacturing a press-formed member

Abstract

The present invention provides a press-formed member and a method for manufacturing a press-formed member that can be manufactured using TWB material including an arc-shaped top plate while preventing cracking. [Solution] The press-formed member 1 according to the present disclosure is a press-formed member 1 having a U-shaped cross-section, made of a tailored blank material in which metal plates of different thicknesses and strengths are butted together or overlapped and welded together, comprising an arc-shaped top plate portion 31, flange portions 32 and 33, and bent portions 34 and 35 connecting the top plate portion 31 and the flange portions 32 and 33, wherein the overlap of the metal plates in the top plate portion 31 is equal to the overlap of the metal plates in the flange portions 32 and 33, and the joint of the metal plates in the top plate portion 31 is welded from the front and back surfaces.

Description

Technical Field

[0001] The present disclosure relates to a press-formed member and a method for manufacturing the press-formed member.

Background Art

[0002] Patent Document 1 describes a Tailor Welded Blank (hereinafter referred to as TWB) material in which metal plates having different thicknesses and / or strengths are butt-welded. For a part that presses a TWB material to form a flange, due to the ease of cracking at the welded part, as shown in the figure described in Patent Document 1, it has been difficult to realize a configuration in which there is elongation and contraction in a direction orthogonal to the extending direction of the welded part.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] A method that can have a curvature at least at the bending ridge line of the welded part is desired.

[0005] The present disclosure has been made to solve such problems, and an object thereof is to provide a press-formed member and a method for manufacturing the press-formed member that can manufacture a TWB material including an arcuate top plate portion while preventing cracking.

Means for Solving the Problems

[0006] A press-formed member according to one aspect of the present disclosure is a press-formed member having a U-shaped cross-section, made using a tailored blank material in which metal plates of different thicknesses and strengths are butted together or overlapped and welded together, comprising a top plate portion extending in an arc shape, a flange portion, and a bent portion connecting the top plate portion and the flange portion, wherein the overlap of the metal plates in the top plate portion is equal to the overlap of the metal plates in the flange portion, and the joint portion of the metal plates in the top plate portion is welded from the front and back surfaces.

[0007] A method for manufacturing a press-formed member according to one aspect of the present disclosure is a method for manufacturing a press-formed member having a U-shaped cross-section, comprising a top plate portion extending in an arc shape and a flange portion, and includes the steps of: arranging a first metal plate and a second metal plate having a thickness and / or strength different from the first metal plate, such that at least a portion of the portion corresponding to the inner flange portion located inside the arc from the portion corresponding to the top plate portion overlaps, and the portion corresponding to the outer flange portion located outside the arc from the portion corresponding to the top plate portion does not overlap; welding the portions corresponding to the top plate portion of the first metal plate and the second metal plate together; forming the flange portion by bending; and welding the flange portion of the first metal plate and the flange portion of the second metal plate. [Effects of the Invention]

[0008] This disclosure provides a press-formed member and a method for manufacturing a press-formed member that can be manufactured using a TWB material including an arc-shaped top plate portion while preventing cracking. [Brief explanation of the drawing]

[0009] [Figure 1] (a) is a perspective view illustrating a press-formed member according to Embodiment 1, (b) is a schematic diagram illustrating a butt welding joint, and (c) is a schematic diagram illustrating a lap welding joint. [Figure 2](a) is a cross-sectional view illustrating a press-formed member according to Embodiment 1, showing the cross-section along line II-II in Figure 1(a), and (b) is a diagram illustrating the bending stress distribution. [Figure 3] (a) is a flowchart illustrating a method for manufacturing a press-formed member according to Embodiment 1, and (b) is a perspective view illustrating a state in which the first metal plate and the second metal plate are arranged in the method for manufacturing a press-formed member according to Embodiment 1. [Figure 4] (a) is a perspective view illustrating a state in which the first metal plate and the second metal plate are welded together in the manufacturing method of a press-formed member according to the comparative example, and (b) is a perspective view illustrating a press-formed member in the manufacturing method of a press-formed member according to the comparative example. [Figure 5] (a) and (b) are diagrams illustrating examples of applications of the press-formed member according to Embodiment 1. [Figure 6] This figure illustrates an example of an application of the method for manufacturing a press-formed member according to Embodiment 1. [Modes for carrying out the invention]

[0010] The specific configuration of this embodiment will be described below with reference to the drawings. The following description illustrates preferred embodiments of the disclosure, and the scope of the disclosure is not limited to the following embodiments. Furthermore, not all of the configurations described in this embodiment are necessarily essential as means to solve the problem. For clarity of explanation, the following descriptions and drawings have been omitted and simplified as appropriate. In each drawing, the same elements are denoted by the same reference numerals, and redundant explanations have been omitted as necessary.

[0011] <Embodiment 1> The press-formed member and the method for manufacturing the press-formed member according to this embodiment will be described. Figure 1(a) is a perspective view illustrating a press-formed member 1 according to Embodiment 1, (b) is a schematic diagram illustrating a butt welding joint, and (c) is a schematic diagram illustrating a lap welding joint. Figure 2(a) is a cross-sectional view illustrating a press-formed member 1 according to Embodiment 1, showing the cross-section along line II-II in Figure 1(a), and (b) is a diagram illustrating the bending stress distribution. As shown in Figures 1 and 2, the press-formed member 1 includes a first metal plate 10 and a second metal plate 20. The first metal plate 10 and the second metal plate 20 differ from each other in thickness and / or strength. The press-formed member 1 is formed by butt welding the first metal plate 10 and the second metal plate 20 together or by overlapping them. Therefore, the press-formed member 1 uses TWB material. The press-formed member 1 extends in an arc shape. The cross-section perpendicular to the direction along the arc of the press-formed member 1 has a U-shape. Thus, the press-formed member 1 includes a member with a U-shaped cross-section made of TWB material, which is formed by butting together or overlapping and welding together a first metal plate 10 and a second metal plate 20 having different thicknesses and strengths or both.

[0012] Press-formed member 1 includes a top plate portion 31, a flange portion 32, a flange portion 33, a bent portion 34, and a bent portion 35. The first metal plate 10 includes a top plate portion 11, a flange portion 12, a flange portion 13, a bent portion 14, and a bent portion 15. The second metal plate 20 includes a top plate portion 21, a flange portion 22, a flange portion 23, a bent portion 24, and a bent portion 25. Top plate portion 31 includes top plate portions 11 and 21. Flange portion 32 includes flange portions 12 and 22. Flange portion 33 includes flange portions 13 and 23. Bent portion 34 includes bent portions 14 and 24. Bent portion 35 includes bent portions 15 and 25.

[0013] The top plate portion 31 is plate-shaped. Therefore, the top plate portion 31 has a plate surface 31a (plate surfaces 11a, 21a) and a plate surface 31b (plate surface 11b, plate surface 21b). Plate surface 31b is the surface opposite to plate surface 31a. The top plate portion 31 extends in an arc shape. Specifically, the top plate portion 31 extends in an arc shape within a plane parallel to plate surfaces 31a and 31b.

[0014] Here, for the sake of explaining the press-formed member 1, we introduce an XYZ coordinate system. The direction perpendicular to the plate surfaces 31a and 31b of the top plate portion 31 is defined as the Z direction. The direction from plate surface 31b toward plate surface 31a is defined as the +Z direction. Plate surface 31a is the surface facing the +Z direction, and plate surface 31b is the surface facing the -Z direction. The tangent direction of the arc of the top plate portion 31 is defined as the X direction. Within the plane parallel to the plate surfaces 31a and 31b of the top plate portion 31, the direction perpendicular to the tangent to the arc is defined as the Y-axis direction. The inside of the arc is defined as the -Y direction, and the outside of the arc is defined as the +Y direction. Therefore, an XYZ coordinate system is set for each position on the tangent to the arc.

[0015] The flange portion 32 is positioned on the inside of the arc of the top plate portion 31. The flange portion 32 is a curved plate. The flange portion 32 has plate surfaces 32a (plate surfaces 12a, plate surfaces 22a) and plate surfaces 32b (plate surfaces 12b, 22b). Plate surface 32b is the surface opposite to plate surface 32a. Plate surface 32a faces the inside of the arc. Therefore, plate surface 32a faces the -Y direction. Plate surface 32b faces the outside of the arc. Therefore, plate surface 32b faces the +Y direction. The flange portion 32 curves inward from the arc. Plate surfaces 32a and 32b of the flange portion 32 are perpendicular to the Y direction. The flange portion 32 extends in the -Z direction from the inside edge of the arc of the top plate portion 31.

[0016] The flange portion 33 is positioned on the outer side of the arc of the top plate portion 31. The flange portion 33 is a curved plate. The flange portion 33 has plate surfaces 33a (plate surface 13a, plate surface 23a) and plate surfaces 33b (plate surface 13b, plate surface 23b). Plate surface 33b is the surface opposite to plate surface 33a. Plate surface 33a faces the inner side of the arc. Therefore, plate surface 33a faces the -Y direction. Plate surface 33b faces the outer side of the arc. Therefore, plate surface 33b faces the +Y direction. The flange portion 33 curves inward from the arc. Plate surfaces 33a and 33b of the flange portion 33 are perpendicular to the Y-axis direction. The flange portion 33 extends in the -Z direction from the outer edge of the arc of the top plate portion 31.

[0017] The bending portion 34 connects the top plate portion 31 and the flange portion 32. The bending portion 34 is arranged along the inner edge of the arc of the top plate portion 31. Also, the bending portion 34 is arranged along the edge on the +Z direction side of the flange portion 32.

[0018] The bending portion 35 connects the top plate portion 31 and the flange portion 33. The bending portion 35 is arranged along the outer edge of the arc of the top plate portion 31. Also, the bending portion 35 is arranged along the edge on the +Z direction side of the flange portion 33. The cross section of the press-formed member 1 orthogonal to the X direction is U-shaped.

[0019] The first metal plate 10 and the second metal plate of the press-formed member 1 are butt-welded or lap-welded. When the first metal plate 10 and the second metal plate are butt-welded, the overlapping margin between the first metal plate 10 and the second metal plate 20 in the top plate portion 31, the overlapping margin between the first metal plate 10 and the second metal plate 20 in the flange portion 32, and the overlapping margin between the first metal plate 10 and the second metal plate 20 in the flange portion 33 are equal. For example, the overlapping margin in the top plate portion 31 includes the width of the contact portion between the end face of the top plate portion 11 and the end face of the top plate portion 21. The overlapping margin in the flange portion 32 includes the width of the contact portion between the end face of the flange portion 12 and the end face of the flange portion 22. The overlapping margin in the flange portion 33 includes the width of the contact portion between the end face of the flange portion 13 and the end face of the flange portion 23.

[0020] When the first metal plate 10 and the second metal plate are lap-welded, the overlapping margin between the first metal plate 10 and the second metal plate 20 in the top plate portion 31, the overlapping margin between the first metal plate 10 and the second metal plate 20 in the flange portion 32, and the overlapping margin between the first metal plate 10 and the second metal plate 20 in the flange portion 33 are equal. For example, the overlapping margin in the top plate portion 31 includes the width of the contact portion in the Z direction between the end of the top plate portion 11 and the end of the top plate portion 21. The overlapping margin in the flange portion 32 includes the width of the contact portion in the Y direction between the end of the flange portion 12 and the end of the flange portion 22. The overlapping margin in the flange portion 33 includes the width of the contact portion in the Y direction between the end of the flange portion 13 and the end of the flange portion 23.

[0021] Furthermore, "equal overlap" means not only that the width of the contact area is exactly the same, but also that it is equal within a range that includes unavoidable errors such as alignment during welding the first metal plate 10 and the second metal plate 20 together.

[0022] The joint between the first metal plate 10 and the second metal plate 20 of the top plate portion 31 is welded from both the front and back surfaces. For example, if the first metal plate 10 and the second metal plate are butt-welded together, the end face of the top plate portion 11 and the end face of the top plate portion 21 may be welded together from the +Z direction and the -Z direction. Also, the end face of the flange portion 12 and the end face of the flange portion 22 may be welded together from the +Y direction and the -Y direction. Furthermore, the end face of the flange portion 13 and the end face of the flange portion 23 may be welded together from the +Y direction and the -Y direction.

[0023] Furthermore, when the first metal plate 10 and the second metal plate are overlapped and welded together, the end of the top plate portion 11 and the end of the top plate portion 21 may be welded together from the +Z direction and the -Z direction. Also, the end of the flange portion 12 and the end of the flange portion 22 may be welded together from the +Y direction and the -Y direction. In addition, the end of the flange portion 13 and the end of the flange portion 23 may be welded together from the +Y direction and the -Y direction.

[0024] As shown in Figure 2(b), press-formed members 1 with a U-shaped cross-section are joined by continuous welding such as arc welding to form a member with a square cross-section. In this case, the TWB welded portion will have a square shape. In such a member, bending both sides of the ridge portion generates a large stress on the ridge portion. However, in this embodiment, the joint between the first metal plate 10 and the second metal plate 20 is welded from both the front and back surfaces. Therefore, it is possible to manufacture a TWB material including an arc-shaped top plate portion 31 while preventing cracking.

[0025] Next, a method for manufacturing the press-formed member 1 will be described. The method for manufacturing the press-formed member of this embodiment is a method for manufacturing a press-formed member 1 having a U-shaped cross-section, comprising an arc-shaped top plate portion 31, a flange portion 32 and a flange portion 33.

[0026] Figure 3(a) is a flowchart illustrating a method for manufacturing a press-formed member 1 according to Embodiment 1, and (b) is a perspective view illustrating a state in which the first metal plate 10 and the second metal plate 20 are arranged in the method for manufacturing a press-formed member 1 according to Embodiment 1. As shown in Figure 3, the method for manufacturing a press-formed member 1 according to this embodiment includes a step S11 in which the first metal plate 10 and the second metal plate 20 are arranged, a step S12 in which the portion corresponding to the top plate portion 31 is welded together, a step S13 in which the flange portions 32 and 33 are formed, and a step S14 in which the flange portions 12 and 13 of the first metal plate 10 and the flange portions 22 and 23 of the second metal plate 20 are welded together.

[0027] In step S11, the first metal plate 10 and the second metal plate 20 are arranged in the following manner. That is, the portion corresponding to the inner flange portion 32, which is located inside the arc from the portion corresponding to the top plate portion 31, is made to overlap at least a portion of the first metal plate 10 and the second metal plate 20. For example, the insufficient amount of material is added to at least one of the portions corresponding to the flange portion 32 of the first metal plate 10 and the second metal plate 20. When the portion corresponding to the flange portion 32 is bent by bending, a deficiency occurs in the portion corresponding to the flange portion 32 because the top plate portion 31 is on an arc. In other words, if the deficiency is not compensated for, there will be a gap between the flange portion 12 and the flange portion 22. Therefore, as described above, the insufficient amount of material is added. The portion to which the insufficient amount of material has been added is called the elongated portion 36.

[0028] Furthermore, the portion corresponding to the outer flange portion 33, which is located outside the arc of the portion corresponding to the top plate portion 31, is cut out so that the first metal plate 10 and the second metal plate 20 do not overlap. For example, the portion corresponding to the flange portion 33 of at least one of the first metal plate 10 and the second metal plate 20 is cut out, and the excess material is cut off. When the portion corresponding to the flange portion 33 is bent by bending, excess material is created in the portion corresponding to the flange portion 33 because the top plate portion 31 is on an arc. In other words, if the excess material is not cut off, the flange portion 13 and the flange portion 23 will overlap more than necessary. Therefore, as described above, the excess material is cut off. The portion from which the excess material has been cut off is called the shrinkage portion 37.

[0029] After bending, the size of the elongated portion 36 on the inside of the arc and the contracted portion 37 on the outside of the arc are set so that the overlap of the metal plates in the top plate portion 31 is equal to the overlap of the metal plates in the flange portions 32 and 33.

[0030] In step S12, the portion of the first metal plate 10 and the portion of the second metal plate 20 corresponding to the top plate portion 31 are welded together. In step S12, the portions of the first metal plate 10 and the second metal plate 20 corresponding to the top plate portion 31 may be butt-welded or overlapped. It is preferable to weld TWB up to slightly outside the ridge line on the inside of the bend. It is also preferable that the expansion and contraction of the flange portions 32 and 33 after bending is 10% or less (in the Y direction from the ridge line). Continuous welding such as laser or arc welding is preferred for welding.

[0031] In step S13, the flange portions 32 and 33 are formed by bending. The contracted portion and the expanded portion move during the bending process so that the above-described overlap is formed.

[0032] In step S14, the flange portions 12 and 13 of the first metal plate 10 and the flange portions 22 and 23 of the second metal plate 20 are welded together. For example, after bending, the outer flange portion 33 is continuously welded. For example, continuous welding on both sides increases the strength to twice that of single-sided welding. The welding of the inner flange portion 32 (for example, TWB difference thickness joint) is performed on the tip side of the flange portion 32 beyond the ridge line, within a range of ±10% or less of the bending elongation / contraction rate (from the ridge line in the Y direction).

[0033] Next, before describing the effects of this embodiment, we will describe a comparative example. Then, we will describe the effects of this embodiment in comparison with the comparative example. Figure 4(a) is a perspective view illustrating the state in which the first metal plate 110 and the second metal plate 120 are welded together in the manufacturing method of the press-formed member 101 according to the comparative example, and (b) is a perspective view illustrating the press-formed member 101 in the manufacturing method of the press-formed member 101 according to the comparative example.

[0034] As shown in Figures 4(a) and (b), in the comparative example, the first metal plate 110 and the second metal plate 120 are TWB material that are butt-joined or overlapped and welded together. The first metal plate 110 and the second metal plate 120 in the comparative example do not have portions that extend in an arc shape. The first metal plate 110 and the second metal plate 120 in the comparative example have a rectangular shape. The first metal plate 110 is located on the -X side of the second metal plate 120, and the second metal plate 120 is located on the +X side of the first metal plate 110. The welded portion of the top plate portion 131 extends along the Y direction. The welded portions of the flange portion 132 and flange portion 133 extend in the Z direction.

[0035] The first metal plate 110 includes a top plate portion 111, a flange portion 112, and a flange portion 113. The top plate portion 111, the flange portion 112, and the flange portion 113 extend in the X direction. The second metal plate 120 includes a top plate portion 121, a flange portion 122, and a flange portion 123. The top plate portion 121, the flange portion 122, and the flange portion 123 extend in the X direction.

[0036] As shown in Figures 4(a) and (b), the press-formed member 101 according to the comparative example includes a top plate portion 131, a flange portion 132, and a flange portion 133. The top plate portion 131 includes top plate portions 111 and 121. The flange portion 132 includes flange portions 112 and 122. The flange portion 133 includes flange portions 113 and 123. The bent portion 134 extends along the X direction. The bent portion 135 extends along the X direction. Since the TWB material of the comparative example does not have an arc-shaped portion, the welded portion is perpendicular to the bent portions 134 and 135. Also, no expansion or contraction occurs in the flange portions 132 and 133.

[0037] In contrast, the press-formed member 1 of this embodiment is a press-formed member 1 with a U-shaped cross-section having a top plate portion 31 that extends in an arc shape using a TWB member. In the press-formed member 1, the overlap of the first metal plate 10 and the second metal plate 20 in the top plate portion 31 is equal to the overlap of the first metal plate 10 and the second metal plate 20 in the flange portions 32 and 33. This provides a press-formed member 1 that can suppress cracking.

[0038] Furthermore, Patent Document 2 describes a technique for creating a welded blank material by spot welding the overlapping portions of multiple plate materials, and then press-working this welded blank material. Patent Document 2 also describes a method for manufacturing an automobile part made of TWB material having either an expandable flange portion or a contracted flange portion, or both. The spot welding in Patent Document 2 is performed in the area of ​​the overlapping portion excluding the area that will become either the expandable flange portion or the contracted flange portion, or both.

[0039] The method described in Patent Document 2 involves press-forming the B-pillar portion of the body side member using a single sheet of steel. However, since the method in Patent Document 2 does not require the steel sheets to be the same thickness depending on the product strength, the following steps are proposed: In the first step, two overlapping steel sheets are spot-welded in areas that do not affect the expansion and contraction processes during press-forming. In the second step, press-forming is performed. In the third step, areas that have been press-formed but not spot-welded are spot-welded. However, the spot welding in Patent Document 2 does not ensure strength equivalent to or less than that of a single sheet of steel.

[0040] In contrast, in this embodiment, the press-formed member 1 has the joint between the first metal plate 10 and the second metal plate 20 of the top plate portion 31 welded from both the front and back surfaces. Therefore, the joint strength can be improved to about twice that of single-sided welding.

[0041] Next, an example of an application example of the press-formed member 1 of this embodiment will be described. Note that the application examples of the press-formed member 1 of this embodiment are not limited to this. Figures 5(a) and (b) illustrate an example of an application example of the press-formed member 1 according to Embodiment 1. Figure 6 illustrates an example of an application example of the manufacturing method of the press-formed member 1 according to Embodiment 1. As shown in Figure 5, the press-formed member 1 of this embodiment may be applied to under-chassis parts. The press-formed member 1 may be a continuously welded structure pressed from a thick steel plate (plate thickness 2 to 6 mm). Underbody parts requiring such high strength (ladder frame, front lower arm, etc.) cannot be structurally sound with spot welding. As mentioned above, large bending stresses occur at the edges of the square cross-section of the underbody. For this reason, it is preferable to use a press-formed member 1 with continuous welding on both sides, as in this embodiment.

[0042] Furthermore, as shown in Figure 6, by applying the aforementioned method for manufacturing the press-formed member 1 to the first step: material cutting, the second step: welding the inside of the TWB material, the third step: press bending, and the fourth step: welding the outside of the TWB material, it is possible to manufacture a press-formed member 1 including an arc-shaped top plate portion 31.

[0043] This disclosure is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. For example, combinations of the configurations of Embodiment 1 and the Comparative Examples also fall within the scope of the technical concept of the embodiments. [Explanation of Symbols]

[0044] 1 Press-formed member 10 1st metal plate 11 Top panel 11a, 11b plate surface 12 Flange section 12a, 12b plate surface 13 Flange section 13a, 13b plate surface 14, 15 Bending section 20 Second metal plate 21 Top panel 21a, 21b plate surface 22 Flange section 22a, 22b plate surface 23 Flange section 23a, 23b plate surface 24, 25 Bending section 31 Top panel 31a, 31b plate surface 32 Flange section 32a, 32b plate surface 33 Flange section 33a, 33b plate surface 34, 35 Bending section 36. Extension 37 Shrinkage part 101 Press-formed member 110 1st metal plate 111 Top panel 112, 113 Flange section 120 Second metal plate 121 Top panel 122, 123 Flange section 131 Top panel 132, 133 Flange section 134, 135 Bending section

Claims

1. A press-formed member with a U-shaped cross-section, using a tailored blank material formed by butting or overlapping and welding together metal plates of different thicknesses and strengths, The top plate extends in an arc shape, Flange section and, A bent portion connecting the top plate portion and the flange portion, Equipped with, The overlap of the metal plates in the top plate portion and the overlap of the metal plates in the flange portion are equal, The joint of the metal plate in the top plate is welded from both the front and back surfaces. Press-formed component.

2. A method for manufacturing a press-formed member having a U-shaped cross-section, comprising a top plate portion extending in an arc shape and a flange portion, The steps include: arranging a first metal plate and a second metal plate having a different thickness and strength from the first metal plate, such that at least a portion of the portion corresponding to the inner flange, located arc-inward from the portion corresponding to the top plate, overlaps, while the portion corresponding to the outer flange, located arc-outward from the portion corresponding to the top plate, does not overlap; The steps include welding together the portion of the first metal plate and the second metal plate that corresponds to the top plate portion, The process involves forming the flange portion by bending, The steps include welding the flange portion of the first metal plate and the flange portion of the second metal plate, including, A method for manufacturing press-formed parts.

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