Method for manufacturing drawn product

Abstract

This method for manufacturing a drawn product 1 includes forming a bottom corner portion 2a by welding, to a metal blank 10, a metal reinforcing plate 20 made of the same type of metal as the blank 10, and subjecting the welded blank 10 and reinforcing plate 20 to drawing accompanied by deformation in a depth direction and a peripheral direction. The blank 10 and the reinforcing plate 20 are welded together at a plurality of welded portions 6 in the bottom corner portion 2a. The plurality of welded portions 6 are arranged only on a straight line L that bisects the bottom corner portion 2a in the peripheral direction when viewed from the vertical direction.

Description

Manufacturing method for drawn products

[0001] The present disclosure relates to a method for manufacturing a drawn product.

[0002] Reinforcement structures that improve strength by welding a reinforcing plate to a blank are known. Such reinforcement structures are generally referred to as overlapping blank structures or patchwork structures, and are often seen in automobile parts. For example, Patent Document 1 discloses a manufacturing method for a formed member in which a blank and a reinforcing plate are overlapped and joined together, and then bent.

[0003] International Publication No. 2012 / 036262

[0004] When the above-mentioned reinforcement structure is subjected to forming processes such as bending and drawing, cracks may occur starting from the welded portion. While bending deforms the reinforcement structure in one direction, drawing deforms the reinforcement structure in two directions (circumferential and depth directions), so drawing has a higher risk of cracking than bending. Patent Document 1 focuses on bending, but not drawing. Therefore, there is room for improvement in terms of ensuring high crack resistance when drawing the reinforcement structure.

[0005] An object of the present disclosure is to ensure high crack resistance in a manufacturing method for a drawn product having a reinforced structure in which a reinforcing plate material is welded to a blank material.

[0006] The present disclosure provides a method for manufacturing a drawn product, which includes welding a metal blank to a reinforcing plate made of the same type of metal as the blank, and forming a bottom corner by performing drawing on the welded blank and reinforcing plate, which involves deformation in the depth direction and circumferential direction, wherein the blank and the reinforcing plate are welded at the bottom corner by a plurality of welds, and the plurality of welds are only arranged on a straight line that divides the bottom corner into two equal parts in the circumferential direction when viewed from above and below.

[0007] This configuration can suppress cracking during the manufacture of a drawn product having a reinforced structure in which a reinforcing plate is welded to a blank. Specifically, at the bottom corner, the multiple welds are arranged only on a line that bisects the bottom corner in the circumferential direction, preventing them from being arranged side by side in the circumferential direction. If multiple welds were arranged side by side in the circumferential direction at the bottom corner, material would concentrate between the multiple welds in response to a circumferential compressive load, resulting in thickened areas. These thickened areas could become caught in the mold and cause cracks. Therefore, by preventing the multiple welds from being arranged side by side in the circumferential direction, the occurrence of such thickened areas is suppressed. Furthermore, because this line is the circumferential centerline of the bottom corner, the multiple welds can bear the circumferential compressive load evenly at their circumferential centers and can distribute the tensile load generated in the depth direction along this line. Therefore, a high level of crack resistance can be ensured in this method of manufacturing a drawn product having a reinforced structure in which a reinforcing plate is welded to a blank.

[0008] The bottom corner portion may be configured by a main wall extending horizontally and a peripheral side wall extending vertically from an edge of the main wall, and the boundary between the main wall and the peripheral side wall may be a curved surface.

[0009] According to this configuration, stress concentration during drawing can be suppressed compared to when the boundary between the main wall and the peripheral side wall is configured as a sharp corner. The radius of curvature of the curved surface may be 20 mm or more.

[0010] The plurality of welds may be arranged at positions other than on the curved surface.

[0011] With this configuration, the curved surface at the boundary between the main wall and the peripheral side wall is compressed on the inner side and stretched on the outer side during forming. This results in a difference in length between the inner side and the outer side of the curved surface before and after forming. Therefore, in order to avoid restricting this deformation, multiple welds are not provided on the curved surface.

[0012] Each of the plurality of welds may be a point or a line.

[0013] These configurations allow multiple welds to be formed easily and inexpensively.

[0014] The welding between the blank and the reinforcing plate may be seam welding, resistance spot welding, laser welding, or arc welding.

[0015] This configuration allows a plurality of welds to be specifically formed.

[0016] According to the present disclosure, a high resistance to cracking can be ensured in a manufacturing method for a drawn product having a reinforced structure in which a reinforcing plate material is welded to a blank material.

[0017] 1 is a perspective view of an entire drawn product; 2 is a perspective view showing the outside of a bottom corner of the drawn product; 3 is a perspective view showing the inside of a bottom corner of the drawn product; 4 is a perspective view showing a first step of a method for manufacturing a drawn product according to an embodiment of the present disclosure; 5 is a plan view showing a second step of a method for manufacturing a drawn product according to an embodiment of the present disclosure; 6 is a perspective view showing a third step of a method for manufacturing a drawn product according to an embodiment of the present disclosure; 7 is a plan view showing the arrangement of a plurality of welds in an experiment; 8 is a photograph showing experimental results of the present embodiment; 9 is a photograph showing experimental results of a comparative example; 10 is a perspective view showing the inside of a bottom corner of a drawn product in a modified example;

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0019] (First embodiment) Figures 1 to 3 show a drawn product 1 manufactured by a method for manufacturing a drawn product according to one embodiment of the present disclosure. Figure 1 is a perspective view of the entire drawn product 1. Figure 2 is a perspective view showing the outside of a bottom corner 2a of the drawn product 1. Figure 3 is a perspective view showing the inside of the bottom corner 2a of the drawn product 1.

[0020] The drawn product 1 is formed by drawing a welded flat blank material 10 and a reinforcing plate material 20 in the depth direction and circumferential direction. In Fig. 1, the depth direction of the drawing is indicated by the symbol DD, and the circumferential direction is indicated by the symbol CD. As shown in Fig. 3, the reinforcing plate material 20 is attached to the inner surface side of the blank material 10.

[0021] The blank 10 and the reinforcing plate 20 are made of the same type of metal. Here, "made of the same type of metal" refers to metal types that are within a range that can be welded. For example, the blank 10 and the reinforcing plate 20 may both be made of an aluminum alloy. Alternatively, the blank 10 and the reinforcing plate 20 may both be made of steel. Furthermore, the blank 10 and the reinforcing plate 20 may be made of the same type of metal but with different strengths. For example, the blank 10 may be a mild steel plate, and the reinforcing plate 20 may be a high-tensile steel plate.

[0022] The drawn product 1 has a cylindrical drawn portion 2 with a bottom, and a frame-plate-like flange portion 3 extending horizontally outward from the edge of the drawn portion 2. The drawn portion 2 is composed of a main wall 4 that extends horizontally (located in a horizontal plane) and has a rounded rectangular shape in a plan view, and a peripheral side wall 5 that has a rounded rectangular cylindrical shape and extends vertically (in the depth direction DD) from the edge of the main wall 4.

[0023] The peripheral side wall 5 has four linearly extending flat side walls 5a and a curved side wall 5b connecting the flat side walls 5a. Here, the curved side walls 5b and the fan-shaped portions 4a of the main wall 4 extending from the curved side walls 5b are referred to as the base corner portions 2a. The radius of curvature of the curved side walls 5b may be 20 mm or more.

[0024] In this embodiment, four bottom corners 2a are formed in the drawn portion 2. In particular, in the drawing process, the formability of the bottom corners 2a often becomes an issue, and in this embodiment, as will be described in detail later, high formability is ensured by suitably providing a plurality of welds 6 at the bottom corners 2a.

[0025] In this embodiment, the main wall 4 and the peripheral side wall 5 are connected by a curved surface 8a. The curved surface 8a does not have a plurality of welds 6. The radius of curvature of the curved surface 8a may be 6 mm or more. The peripheral side wall 5 and the flange portion 3 are also connected by a curved surface 8b. The peripheral side wall 5 has a rounded rectangular cylindrical shape. Therefore, in this embodiment, the drawn product 1 does not have sharp corners. However, the shape of the drawn product 1 is not particularly limited and may be any shape.

[0026] The reinforcing plate 20 is attached to the inside of the drawn portion 2 of the blank 10. As will be described in detail below, the reinforcing plate 20 is welded to the blank 10 at a plurality of welds 6 at the bottom corners 2a of the drawn product 1. Alternatively, the reinforcing plate 20 may be attached to the outside of the drawn portion 2 of the blank 10.

[0027] An example of a method for manufacturing a drawn product according to this embodiment will be described with reference to FIGS.

[0028] FIG. 4 is a perspective view showing a first step of the method for manufacturing a drawn product according to this embodiment.

[0029] In the first step, a square flat blank material 10 and an octagonal flat reinforcing plate material 20 that is smaller than the blank material 10 are prepared. The octagonal shape of the reinforcing plate material 20 is formed by chamfering the four corners of a square. However, the shapes of the blank material 10 and the reinforcing plate material 20 are not particularly limited.

[0030] FIG. 5 is a plan view showing a second step of the method for manufacturing a drawn product according to this embodiment.

[0031] In the second step, the blank 10 and the reinforcing plate 20 are welded together. In this embodiment, a plurality of welds 6 are provided at the bottom corners 2a of the drawn product 1 (see FIG. 1 ). Strictly speaking, this step is performed before the drawing process, so the bottom corners 2a are not yet formed, and the plurality of welds 6 are provided in the portions corresponding to the bottom corners 2a (see the shaded areas). As shown in the figure, it is sufficient that at least a portion of each of the plurality of welds 6 is provided in the portion corresponding to the bottom corners 2a (see the shaded areas).

[0032] The multiple welds 6 are located only on the diagonal line L of the blank 10. This diagonal line L corresponds to the line L that bisects the bottom corner 2a in the circumferential direction in FIGS. 2 and 3. Note that multiple other welds 7 are also provided in areas other than the bottom corner 2a (specifically, the flat sidewall 5a in FIGS. 1 to 3). In other words, the multiple other welds 7 are not provided in the bottom corner 2a. The multiple other welds 7 are arranged along the edge of the reinforcing plate 20. Furthermore, the diagonal line L can be substituted for the corner bisector. Therefore, even if a shape does not allow for a diagonal line L, as long as a corner bisector can be drawn, the arrangement of the multiple welds 6 can be identified as being on the corner bisector.

[0033] In this embodiment, the plurality of welds 6 and the plurality of other welds 7 are formed by resistance spot welding, and each has a point shape. However, the method of forming the plurality of welds 6 and the plurality of other welds 7 and the shape thereof are not particularly limited.

[0034] FIG. 6 is a perspective view showing a third step of the method for manufacturing a drawn product according to this embodiment.

[0035] In the third step, the welded blank 10 and reinforcing plate 20 are subjected to drawing, which involves deformation in the depth direction and the circumferential direction, to form a drawn product 1 having a bottom corner 2a as shown in FIG.

[0036] In this process, a die 30 is used for drawing. The die 30 has a punch 31, a holder 32, and a die 33.

[0037] The punch 31 presses the blank 10 and the reinforcing plate 20 to form the drawn portion 2. In the illustrated example, the punch 31 has a rounded rectangular prism shape. The upper surface 31a of the punch 31 forms the main wall 4 of the drawn product 1. The side surface 31b of the punch forms the peripheral side wall 5 of the drawn product 1. The upper surface 31a and the side surface 31b of the punch are connected by a curved surface 31c. The curved surface 31c of the punch 31 forms the curved surface 8a connecting the main wall 4 and the peripheral side wall 5 of the drawn product 1, and has a curvature corresponding to the curved surface 8a connecting the main wall 4 and the peripheral side wall 5 of the drawn product 1. The side surface 31b of the punch 31 is provided with a circumferential step 31d having a height corresponding to the thickness of the reinforcing plate 20.

[0038] The holder 32, together with the die 33, holds the blank 10 and the reinforcing plate 20. In the illustrated example, the holder 32 has a rectangular, flat plate shape extending horizontally. The holder 32 has a rounded, rectangular hole 32a through which the punch 31 passes. The holder 32 has a step 32b around the hole 32a, the step 32b having a height corresponding to the thickness of the reinforcing plate 20. The step 32b has an octagonal shape complementary to the reinforcing plate 20. The reinforcing plate 20 is placed on a lower step 32c (inside) of the step 32b, and the blank 10 is placed on an upper step 32d (outside) of the step 32b.

[0039] The die 33, together with the holder 32, presses the blank 10 and the reinforcing plate 20, and together with the punch 31, forms the drawn portion 2. The die has a frame-plate-like flange portion 33a that extends horizontally and has approximately the same shape as the holder 32, and a cylindrical portion 33b that stands up from the flange portion 33a and has a rounded square cylindrical shape. The cylindrical portion 33b has a shape complementary to the punch 31, and is configured so that the punch 31 passes through its interior. The flange portion 33a and the cylindrical portion 33b are connected by a curved surface 33c.

[0040] In this step, first, the blank 10 and the reinforcing plate 20 welded in the second step are sandwiched between the die 33 and the holder 32. Next, the punch 31 is driven to pass through the hole 32a of the holder 32 and the cylindrical portion 33b of the die 33, thereby forming the drawn portion 2.

[0041] 1 to 3, in the drawn product 1 manufactured through the above-described first to third steps, the plurality of welds 6 are arranged only on a line L that bisects the bottom corner 2a in the circumferential direction when viewed from above (in a plan view). In this embodiment, the plurality of welds 6 consists of one weld 6a provided on the circumferential side wall 5 and one weld 6b provided on the main wall 4. Note that the plurality of welds 6 are not arranged on the curved surface 8a connecting the main wall 4 and the circumferential side wall 5.

[0042] The following describes the results of experiments that demonstrate the crack suppression effect of the method for manufacturing a drawn product according to this embodiment.

[0043] FIG. 7 is a plan view showing the arrangement of a plurality of welds in the experiment.

[0044] In the experiment, the presence or absence of cracks was confirmed by comparing the arrangement of the multiple welds 6 at the bottom corner portion 2 a between this embodiment and a comparative example. The blank material 10 and the reinforcing plate material 20 used in the experiment were both made of 5000 series aluminum alloy with a thickness of 1.0 mm.

[0045] In the plan view of Figure 7, regions R2 and R4 in the second and fourth quadrants show the arrangement of the multiple welds 6 of this embodiment, while regions R1 and R3 in the first and third quadrants show the arrangement of the multiple welds 9 of a comparative example that differs from this embodiment. Specifically, in regions R2 and R4 (this embodiment), the multiple welds 6 (two welds 6a and 6b) are arranged only on diagonal line L of the blank 10 (corresponding to the line L that bisects the bottom corner 2a in the circumferential direction in Figure 2). In regions R1 and R3 (comparative example), the multiple welds 9 (three welds 9a, 9b, and 9c) are arranged on diagonal line L of the blank 10 at one point (9a) and two points (9b and 9c) on either side of the diagonal line L.

[0046] Drawing was performed with the arrangement of a plurality of welds 6 and 9 shown in Fig. 7. In the drawing, the drawing depth was set to 30 mm, and the blank holding force was set to 105 kN.

[0047] Fig. 8 is a photograph showing the drawing results in the region R2 (this embodiment), and Fig. 9 is a photograph showing the drawing results in the region R1 (comparative example).

[0048] While no cracks were observed in the photograph of FIG. 8 (present embodiment), cracks were observed in the peripheral side wall 5 in the photograph of FIG. 9 (comparative example) (reference symbol BP). Essentially, as the number of welds increases, the load borne by each weld decreases, making cracks less likely to occur. In this experiment, no cracks were observed in the present embodiment, which has a relatively small number of welds, but cracks were observed in the comparative example, which has a relatively large number of welds, confirming the high usefulness of this embodiment. Furthermore, in the experiment, the number of welds 6 in this embodiment was two (6a, 6b). However, for the reasons mentioned above, it is believed that cracks would not occur even if there were three or more welds.

[0049] According to this embodiment, the following advantageous effects are achieved.

[0050] Cracks can be suppressed during the manufacture of a drawn product 1 having a reinforced structure in which a reinforcing plate 20 is welded to a blank 10. Specifically, at the bottom corner 2a, the multiple welds 6 are arranged only on a line L that bisects the bottom corner 2a in the circumferential direction, preventing them from being arranged side by side in the circumferential direction. If the multiple welds 6 were arranged side by side in the circumferential direction at the bottom corner 2a, material would concentrate between the multiple welds in response to a circumferential compressive load, resulting in thickened areas. These thickened areas could become caught in the mold and cause cracks. Therefore, by preventing the multiple welds 6 from being arranged side by side in the circumferential direction, the occurrence of such thickened areas is suppressed. Furthermore, because the line L is the circumferential centerline of the bottom corner 2a, the multiple welds 6 can bear the circumferential compressive load evenly at the circumferential center and can bear the tensile load generated in the depth direction in a distributed manner along the line L. Therefore, high crack resistance can be ensured in the manufacturing method of a drawn product having a reinforced structure in which a reinforcing plate 20 is welded to a blank 10.

[0051] Furthermore, since the boundary between the main wall 4 and the peripheral side wall 5 is formed by the curved surface 8a, stress concentration during drawing can be suppressed compared to when this boundary is formed by a sharp corner.

[0052] Furthermore, the curved surface 8a at the boundary between the main wall 4 and the peripheral side wall 5 is compressed on the inner side and stretched on the outer side during forming. This results in a difference in length between the inner and outer sides of the curved surface 8a before and after forming. Therefore, in order to avoid restricting this deformation, multiple welds 6 are not provided on the curved surface 8a.

[0053] Furthermore, since the plurality of welds 6 are formed in a dot pattern by resistance spot welding, the plurality of welds can be formed easily and inexpensively.

[0054] Although specific embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments and can be implemented with various modifications within the scope of the present invention.

[0055] FIG. 10 is a perspective view showing the inside of the bottom corner 2a of the drawn product 1 in the modified example.

[0056] In this modification, each of the plurality of welds 6 is linear. The plurality of welds 6 are formed by seam welding, laser welding, or arc welding. Note that other parts are substantially the same as those in the above embodiment.

[0057] The present disclosure may include the following aspects. (Aspect 1) A method for manufacturing a drawn product, comprising: welding a metal blank to a reinforcing plate made of the same metal as the blank; and forming a bottom corner by performing drawing on the welded blank and reinforcing plate, which involves deformation in the depth direction and the circumferential direction, wherein the blank and the reinforcing plate are welded at the bottom corner with a plurality of welds, and the plurality of welds are only located on a line that bisects the bottom corner in the circumferential direction when viewed from above. (Aspect 2) The method for manufacturing a drawn product according to Aspect 1, wherein the bottom corner is formed by a main wall extending horizontally and a peripheral side wall extending vertically from an edge of the main wall, and the boundary between the main wall and the peripheral side wall is a curved surface. (Aspect 3) The method for manufacturing a drawn product according to Aspect 2, wherein the plurality of welds are located at positions other than on the curved surface. (Aspect 4) The method for manufacturing a drawn product according to any one of Aspects 1 to 3, wherein each of the plurality of welds is point-like. (Aspect 5) The method for manufacturing a drawn product according to any one of Aspects 1 to 3, wherein each of the plurality of welds is linear. (Aspect 6) The method for manufacturing a drawn product according to any one of Aspects 1 to 5, wherein the welding between the blank material and the reinforcing plate material is seam welding, resistance spot welding, laser welding, or arc welding.

[0058] This application claims priority from Japanese Patent Application No. 2024-113503, filed July 16, 2024. Japanese Patent Application No. 2024-113503 is incorporated herein by reference.

[0059] REFERENCE SIGNS LIST 1 drawn product 2 drawn portion 2a bottom corner portion 3 flange portion 4 main wall 4a sector portion 5 peripheral side wall 5a flat side wall 5b curved side wall 6, 6a, 6b welded portion 7 welded portion 8a, 8b curved surface 9, 9a, 9b, 9c welded portion 10 blank material 20 reinforcing plate material 30 die 31 punch 31a upper surface 31b side surface 31c curved surface 31d step 32 holder 32a hole portion 32b step 32c lower stage 32d upper stage 33 die 33a flange portion 33b cylindrical portion 33c curved surface

Claims

1. A method for manufacturing a drawn product, comprising: welding a metal blank to a reinforcing plate made of the same metal as the blank; and forming a bottom corner by drawing the welded blank and reinforcing plate, which involves deformation in the depth direction and circumferential direction; wherein the blank and reinforcing plate are welded to the bottom corner at a plurality of welds, and the plurality of welds are only located on a straight line that divides the bottom corner into two equal parts in the circumferential direction when viewed from above and below.

2. A method for manufacturing a drawn product as described in claim 1, wherein the bottom corner portion is composed of a main wall extending horizontally and a peripheral side wall extending vertically from the edge of the main wall, and the boundary between the main wall and the peripheral side wall is a curved surface.

3. The method for manufacturing a drawn product according to claim 2, wherein the plurality of welds are arranged at positions other than on the curved surface.

4. A method for manufacturing a drawn product according to any one of claims 1 to 3, wherein each of the plurality of welds is in the form of a point.

5. A method for manufacturing a drawn product according to any one of claims 1 to 3, wherein each of the plurality of welds is linear.

6. A method for manufacturing a drawn product according to any one of claims 1 to 3, wherein the welding between the blank material and the reinforcing plate material is seam welding, resistance spot welding, laser welding, or arc welding.

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