Manufacturing method of steel plate member

Abstract

To provide a manufacturing method of a steel plate member which is excellent in moldability of inner walls in curved parts when U-bending is performed to steel plates each having the curved part.SOLUTION: A manufacturing method of a steel plate member according to one embodiment of the disclosure includes: a step in which U-bending is performed to a pair of steel plates each having a curved part curved in an arc form along a longitudinal direction; a step in which the pair of steel plates to which U-bending has been performed is placed so that concave surfaces face each other to be welded and form a cylindrical body; and a step in which a pipe is welded to one end of the cylindrical body. Before the step in which U-bending is performed, the curved parts in the pair of steel plates are locally heated.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a steel plate member. [Background technology]

[0002] Patent Document 1 discloses a suspension that uses a trailing arm. As described in Patent Document 1, a pipe for press-fitting a bushing is welded to the end of the trailing arm. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-001898 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors have been studying a method for manufacturing a trailing arm in which a pair of steel plates with a U-shaped cross section are welded together so that their concave surfaces face each other to form a tubular body, and the pipe is welded to one end of the tubular body. Here, the tubular body has a curved portion that is curved in an arc shape along the longitudinal direction, and before welding the pair of steel plates together to form the tubular body, the pair of steel plates with the curved portion are each subjected to a bending process (hereinafter referred to as a U-bending process) to form a U-shaped cross section.

[0005] When U-bending a steel sheet having a curved portion, the radius of curvature Ri of the radially inner side wall (referred to as the "inner wall") of the curved portion is smaller than the radius of curvature Ro of the radially outer side wall (referred to as the "outer wall"). Therefore, the inner wall of the curved portion is difficult to form, and wrinkles, for example, are likely to occur. Furthermore, as the U-bending height H increases, the inner wall becomes even more difficult to form. In other words, when U-bending a steel sheet having a curved portion, the larger H / Ri becomes, the more difficult it is to form the inner wall of the curved portion.

[0006] The present disclosure has been made in consideration of these circumstances, and provides a method for manufacturing a steel plate member that has excellent formability of the inner wall at the curved portion when U-bending is performed on a steel plate having a curved portion. [Means for solving the problem]

[0007] A method for manufacturing a steel plate member according to one embodiment of the present disclosure includes: A step of U-bending each of a pair of steel plates having curved portions curved in an arc shape along the longitudinal direction; a step of welding the concave surfaces of the pair of steel plates that have been U-bent so as to face each other, thereby forming a cylindrical body; and welding a pipe to one end of the cylindrical body. Prior to the step of performing the U-bending, the curved portions of the pair of steel plates are locally heated.

[0008] In a method for manufacturing a steel plate member according to one aspect of the present invention, a pair of steel plates each having a curved portion curved in an arc shape along the longitudinal direction are locally heated at the curved portion before being U-bent. This makes it possible to provide a method for manufacturing a steel plate member that has excellent formability of the inner wall at the curved portion when U-bending the steel plate having the curved portion.

[0009] The bending portion may be locally heated by induction heating. The bending portion can be locally heated by a simple configuration.

[0010] In the step of welding the pipe, an arc-shaped notch may be formed in one end of the cylindrical body so as to straddle the weld between the pair of steel plates, and the side of the pipe may be fitted into the notch, and the pipe may be welded to one end of the cylindrical body so that the central axis of the pipe and the central axis of one end of the cylindrical body are perpendicular to each other. The steel plate member may be a trailing arm. [Effects of the Invention]

[0011] The present disclosure makes it possible to provide a manufacturing method for a steel plate member that has excellent formability of the inner wall of a curved portion when U-bending a steel plate having a curved portion. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a partial plan view of the steel plate member according to the first embodiment. [Figure 2] FIG. 2 is a partial side view of the steel plate member according to the first embodiment. [Figure 3] FIG. 2 is a cross-sectional view taken along the line III-III in FIG. [Figure 4] 3 is a flowchart showing a method for manufacturing a steel plate member according to the first embodiment. [Figure 5] 2 is a partial plan view schematically showing a first steel plate 10 before and after U-bending. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, specific embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to the following embodiments. In addition, the following description and drawings have been simplified appropriately for clarity of explanation.

[0014] (First embodiment) <Structure of steel plate components> First, the configuration of a steel plate member according to a first embodiment will be described with reference to Figures 1 to 3. Figure 1 is a partial plan view of the steel plate member according to the first embodiment. Figure 2 is a partial side view of the steel plate member according to the first embodiment. Figure 3 is a cross-sectional view taken along the line III-III in Figure 1. The steel plate member shown in Figures 1 to 3 is, but is not limited to, a suspension arm for an automobile, and more specifically, a trailing arm.

[0015] The steel plate member shown in FIGS. 1 to 3 includes a first steel plate 10, a second steel plate 20, and a pipe 30, as shown in FIG. Naturally, the right-handed XYZ Cartesian coordinate system shown in Figures 1 to 3 is for the sake of convenience in explaining the positional relationships of the components. In Figure 1 and other figures, the positive direction of the Z axis is vertically upward, and the XY plane is the horizontal plane, which is common to all the figures.

[0016] As shown in FIG. 1, the first steel plate 10 and the second steel plate 20 each have a curved portion that is curved in an arc shape along the longitudinal direction. On the other hand, as shown in Figures 2 and 3, the first steel plate 10 and the second steel plate 20 are both formed with a U-shaped cross section, and are welded so that the concave surfaces of the first steel plate 10 and the second steel plate 20 face each other, forming a square cylindrical body.

[0017] As will be described in detail later, the first steel plate 10 and the second steel plate 20 are each subjected to U-bending, which is a type of press forming, and then welded to each other. Figures 2 and 3 show a schematic representation of the welded portion WP.

[0018] The first steel plate 10 and the second steel plate 20 are not particularly limited, but may be, for example, high-strength steel plates having a thickness of about 0.5 to 10 mm and a tensile strength of 440 MPa or more. 3, both widthwise end portions of the first steel plate 10 and the second steel plate 20 are overlapped and welded, but this is not particularly limited. For example, both widthwise end portions of the first steel plate 10 and the second steel plate 20 may be butt-welded.

[0019] The pipe 30 is a pipe for press-fitting a bushing. That is, a bushing (not shown) is press-fitted into the pipe 30. As shown in Figs. 1 and 2, the pipe 30 is welded to one end of a cylindrical body made of a first steel plate 10 and a second steel plate 20. Here, as shown in Fig. 1, the pipe 30 is welded to one end of the cylindrical body so that the central axis C1 of one end of the cylindrical body, indicated by the dashed dotted line, and the central axis C2 of the pipe 30 are perpendicular to each other.

[0020] <Method of manufacturing steel plate members> Next, a method for manufacturing a steel plate member according to the first embodiment will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the method for manufacturing a steel plate member according to the first embodiment.

[0021] First, as shown in Fig. 4, the curved portions of a pair of steel plates, a first steel plate 10 and a second steel plate 20, each having a curved portion curved in an arc shape along the longitudinal direction, are locally heated (step ST1). For example, by locally heating the curved portions by induction heating, the curved portions can be locally heated with a simple configuration. Heating conditions are, for example, a heating temperature of about 500 to 830°C and a heating time of 10 seconds or less. However, the heating time may exceed 10 seconds.

[0022] Next, as shown in Fig. 4, the first steel plate 10 and the second steel plate 20 whose curved portions have been heated are each subjected to U-bending (step ST2). Fig. 5 is a partial plan view schematically showing the first steel plate 10 before and after U-bending. In Fig. 5, the solid line indicates the first steel plate 10 before U-bending, and the two-dot chain line indicates the first steel plate 10 after U-bending.

[0023] In step ST2, as shown in Fig. 5, the flat first steel plate 10 and the flat second steel plate 20 having curved portions are each subjected to U-bending, which is a type of press forming. As a result, as shown in Fig. 3, the first steel plate 10 and the second steel plate 20 are formed into a U-shaped cross section.

[0024] 1, the radius of curvature Ri of the inner wall of the curved portion is smaller than the radius of curvature Ro of the outer wall, making it difficult to form the inner wall of the curved portion in step ST2, and wrinkles, for example, are likely to occur.

[0025] 3, as the U-bending heights H1 and H2 of the first steel plate 10 and the second steel plate 20 at the curved portion increase, it becomes more difficult to form the inner wall. That is, in U-bending of the first steel plate 10 and the second steel plate 20 having the curved portion, the larger H1 / Ri and H2 / Ri, respectively, the more difficult it becomes to form the inner wall at the curved portion. For example, if H1 / Ri and H2 / Ri are greater than 0.6 at the curved portion of the first steel plate 10 and the second steel plate 20, it becomes more difficult to form the inner wall at the curved portion.

[0026] In the method for manufacturing a steel plate member according to this embodiment, before step ST2, the curved portions of the first steel plate 10 and the second steel plate 20 are locally heated in step ST1. This improves the workability of the curved portions of the first steel plate 10 and the second steel plate 20, and allows the radius of curvature Ri of the inner wall to be smaller than in the comparative example shown by the two-dot chain line in Fig. 1. As a result, the pipe 30 can be made shorter than in the comparative example shown by the two-dot chain line in Fig. 1, thereby reducing the weight of the steel plate member and reducing manufacturing costs.

[0027] Next, as shown in Fig. 4, the concave surfaces of the first steel plate 10 and the second steel plate 20 that have been U-bent are opposed to each other and welded to form a cylindrical body (step ST3). Fig. 3 shows how both widthwise ends of the first steel plate 10 and the second steel plate 20, each with a U-shaped cross section, are welded to each other at a welded part WP to form a rectangular cylindrical body.

[0028] Finally, as shown in Fig. 4, a pipe is welded to one end of the tubular body made up of the first steel plate 10 and the second steel plate 20 (step ST4). More specifically, as shown in Fig. 2, a pair of arc-shaped cutouts (not shown) are formed in one end of the tubular body made up of the first steel plate 10 and the second steel plate 20 so as to straddle the welded part WP. Then, the side of the pipe 30 is fitted into the cutouts, and the pipe 30 is welded to one end of the tubular body so that the central axis C1 of one end of the tubular body, indicated by the dashed dotted line, and the central axis C2 of the pipe 30 are perpendicular to each other, as shown in Fig. 1.

[0029] The notch for fitting the pipe 30 is formed, for example, after U-bending (step ST2) and before welding the first steel plate 10 and the second steel plate 20 together (step ST3). The notch is formed at one end of each of the first steel plate 10 and the second steel plate 20 by, for example, punching or the like.

[0030] As described above, in the method for manufacturing a steel plate member according to this embodiment, step ST1 of locally heating the curved portion is performed before step ST2 of U-bending each of a first steel plate 10 and a second steel plate 20 having a curved portion that is curved in an arc shape along the longitudinal direction. This improves the formability of the curved portion of the first steel plate 10 and the second steel plate 20, and can provide a method for manufacturing a steel plate member that has excellent formability of the inner wall of the curved portion when U-bending the first steel plate 10 and the second steel plate 20.

[0031] Furthermore, with this configuration, the radius of curvature Ri of the inner wall can be made smaller than in the comparative example shown by the two-dot chain line in Fig. 1. As a result, the pipe 30 can be made shorter than in the comparative example shown by the two-dot chain line in Fig. 1, which allows for a reduction in the weight of the steel plate member and a reduction in manufacturing costs.

[0032] The present disclosure is not limited to the above-described embodiments, and can be modified as appropriate within the scope of the present disclosure. [Explanation of symbols]

[0033] 10 First Steel Plate 20 Second Steel Plate 30 Pipe WP weld

Claims

1. A step of U-bending each of a pair of steel plates having curved portions curved in an arc shape along the longitudinal direction; a step of welding the pair of steel plates that have been U-bent so that the concave surfaces face each other to form a cylindrical body; and welding a pipe to one end of the cylindrical body. and locally heating the curved portions of the pair of steel plates prior to the step of performing the U-bending process. Manufacturing method of steel plate components.

2. locally heating the curved portion by induction heating; The method for manufacturing a steel plate member according to claim 1 .

3. In the step of welding the pipe, An arc-shaped notch is formed at one end of the cylindrical body so as to straddle the welded portion between the pair of steel plates, a side surface of the pipe is fitted into the notch, and the pipe is welded to one end of the cylindrical body so that the central axis of the pipe and the central axis of the one end of the cylindrical body are perpendicular to each other; The method for manufacturing a steel plate member according to claim 1 or 2.

4. The steel plate member is a trailing arm. The method for manufacturing a steel plate member according to claim 1 or 2.

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