Corner joint, method for manufacturing the same, and closed cross-section member

Abstract

The present invention provides a fillet weld joint and a method for manufacturing the fillet weld joint that can easily and effectively improve the fatigue strength of the joint at low cost. The first metal plate (10) has a bulging portion (13) on the side of the first edge portion (12), and the bulging portion (13) has an internal space (S) of a prescribed size. The second metal plate (20) has a protruding portion (22) that faces the bulging portion (13) and can be inserted into the bulging portion (13). In a state where the protruding portion (22) is inserted into the bulging portion (13), the second edge portion (21) of the first metal plate (10) and the second metal plate (20) is welded to form a first weld bead (30).

Description

Technical Field

[0001] The present invention relates to a corner joint, a method for manufacturing the same, and a closed cross-section member. Background Art

[0002] For structural members of a motor vehicle, not only static strength and rigidity are required, but also high fatigue resistance characteristics are required. In addition, as long as steel plates and aluminum alloy plates are of similar materials, they are mostly joined by welding from the advantages of efficiency and cost. On the other hand, there has always been a demand to reduce the weight of the vehicle body for improving fuel economy. As a countermeasure, recently, thinning due to high-strengthening of steel materials and aluminum alloy materials has been promoted. However, it has become a common understanding that the strength of the welded joint does not increase linearly in conjunction with the strength of the material and does not increase much. The problem of the fatigue strength of the joint is one of the reasons that is difficult to eliminate by high-strength materials and thinning.

[0003] It can be said that there are mainly three reasons why the fatigue of the welded joint is lower than that of the plate material. Hereinafter, as Figure 12 shown, a corner joint 1 in which a first metal plate 10 and a second metal plate 20 overlap and a surface 11 near a edge portion 12 of the first metal plate 10 and an edge portion 21 of the second metal plate 20 are welded by a weld bead 30 will be described as an example.

[0004] The first reason is stress concentration due to the shape. As Figure 13 shown, the boundary between the weld bead 30 as the welded portion and the first metal plate 10 and the second metal plate 20 as the metal members becomes a discontinuous line, so stress concentration occurs at the weld toe portion of the weld bead. The magnitude of this stress concentration is inversely proportional to the smoothness of the weld toe portion of the weld bead.

[0005] The second reason is deterioration of the material. The first metal plate 10 and the second metal plate 20 form a heat-affected zone 31 in which the crystal structure has changed with respect to the original material due to rapid heating and rapid cooling. Along with this, in the heat-affected zone 31, material properties such as hardness, toughness, and elongation change locally.

[0006] The third reason is tensile residual stress. In the vicinity of the welded portion, in addition to a series of heat histories of temperature rise and fall, due to the restraint around the welded portion, tensile residual stress generally remains after cooling at room temperature. This tensile residual stress is an important cause of the reduction in fatigue strength.

[0007] These stress concentrations due to the shape, deterioration of the local member material, and tensile residual stress are superimposed, deteriorating the fatigue characteristics of the joint.

[0008] Against such a background, various designs and studies have been conducted on countermeasures for improving the fatigue strength of welded joints, taking into account their mechanisms. For example, in Patent Document 1, a part of the material is locally thinned to separate the stress concentration part from the weld bead. In Patent Documents 2 and 3, various shot peening treatments are performed after arc welding to impart compressive residual stress to the stress concentration part. In addition, in Patent Document 4, a welding material with a special composition is used and compressive stress is imparted by utilizing martensitic transformation. In Patent Documents 5 and 6, post-weld heat treatment is applied to the periphery of the weld toe using heat sources such as a plasma arc and a laser. In Patent Documents 7 and 8, other welding metals called supplementary rigid beads are provided. In Patent Document 9, a convex pressing bead is provided adjacent to the weld bead. Also, methods such as smoothly forming the weld toe using a grinding mechanism of a grinding machine or annealing the manufactured product itself in a furnace to reduce tensile residual stress have been proposed.

[0009] Prior Art Documents

[0010] Patent Documents

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-30169

[0012] Patent Document 2: Japanese Patent No. 5880260

[0013] Patent Document 3: Japanese Patent No. 3899007

[0014] Patent Document 4: Japanese Patent No. 5450293

[0015] Patent Document 5: Japanese Patent Application Laid-Open No. 2014-4609

[0016] Patent Document 6: Japanese Patent No. 6515299

[0017] Patent Document 7: Japanese Patent No. 5522317

[0018] Patent Document 8: Japanese Patent No. 5843015

[0019] Patent Document 9: Japanese Patent No. 6008072 Summary of the Invention

[0020] Problems to be Solved by the Invention

[0021] However, in the case of thin plates, in addition to the above-mentioned important reasons for the reduction of fatigue strength, there is another important reason for deterioration. This is the deterioration of the plate alignment accuracy and the so-called root gap G, which is the expansion of the gap between plates, due to poor restraint of metal components, deformation of metal components themselves, flexure, and thermal deformation during welding. In the absence of the root gap G, the maximum stress concentration part relative to the joint 1 becomes the weld toe part of the weld bead. However, as Figure 14 and Figure 15 shown, when the root gap G occurs, it is accompanied by a deterioration of rigidity, and the weld toe part does not necessarily become the maximum stress concentration part. The root gap G part becomes the maximum stress concentration part and mostly fractures earlier. The means for improving the fatigue strength of the joints described in Patent Documents 1 to 9 obtained by various designs before do not have the effect of suppressing the expansion of the root gap G, so there is room for further improvement.

[0022] The present invention has been completed in view of the above-mentioned problems, and its object is to provide a fillet weld joint and a method for manufacturing a fillet weld joint that can effectively improve the fatigue strength with a simple structure.

[0023] Solution for Solving the Problem

[0024] Therefore, the above object of the present invention is achieved by the structure of the following (1) of the fillet weld joint.

[0025] (1) A fillet weld joint obtained by overlapping and welding a first metal plate and a second metal plate, wherein

[0026] the first metal plate has at least one bulging portion at the edge on one side as the side welded to the second metal plate, the at least one bulging portion extends along the length direction from the edge on one side of the first metal plate toward the edge on the other side of the first metal plate, and bulges in the direction facing the second metal plate with respect to the flat plate portion,

[0027] the second metal plate has at least one protruding portion at the edge on one side as the side welded to the first metal plate, the at least one protruding portion protrudes in the direction from the edge on the other side of the second metal plate toward the edge on one side of the second metal plate, and can be inserted into the bulging portion,

[0028] the fillet weld joint has a first weld bead obtained by welding the edge on one side of the first metal plate and the second metal plate in a state where the protruding portion is inserted into the bulging portion,

[0029] The bulging portion is formed such that the height in the plate thickness direction of the first metal plate is equal to or greater than the sum of the plate thicknesses of the first metal plate and the second metal plate, and the length in the length direction of the first metal plate exceeds the sum of the leg length of the first weld bead between the first metal plate and the second metal plate and the length of the welding heat affected zone extending from the first weld bead to the other side of the first metal plate.

[0030] According to this structure, the stress concentration at the welded portion is alleviated by a simple structure, and a welded portion with an inhibited root gap is formed, enabling effective improvement of the joint fatigue strength.

[0031] In addition, preferred embodiments of the present invention for the fillet welded joint relate to the following (2) to (8).

[0032] (2) The fillet welded joint according to (1), wherein

[0033] In the second metal plate, the protruding portion is formed between a pair of cuts formed along the length direction from the edge portion on one side of the second metal plate.

[0034] According to this structure, by providing the cuts, the protruding portion can be easily formed.

[0035] (3) The fillet welded joint according to (1) or (2), wherein

[0036] The bulging portion is formed by press forming.

[0037] According to this structure, the bulging portion can be formed with good precision and easily.

[0038] (4) The fillet welded joint according to any one of (1) to (3), wherein

[0039] The fillet welded joint further has a second weld bead obtained by welding the edge portion on one side of the first metal plate at a position corresponding to the bulging portion to the second metal plate.

[0040] According to this structure, the fatigue strength of the fillet welded joint can be further improved.

[0041] (5) The fillet welded joint according to (4), wherein

[0042] The first weld bead and the second weld bead are formed continuously.

[0043] According to this structure, the welding operation of the first weld bead and the second weld bead becomes easy.

[0044] (6) The fillet welded joint according to any one of (1) to (5), wherein

[0045] The first metal plate has at least one cutout portion at the edge portion on one side of the first metal plate.

[0046] The bulging portion is formed at a position corresponding to the cutout portion.

[0047] According to this structure, the area of the overlapping portion between the first metal plate and the second metal plate can be enlarged, and the fatigue strength is further improved.

[0048] (7) The corner joint according to any one of (1) to (6) above, wherein

[0049] The height in the plate thickness direction of the first metal plate in the internal space formed by the bulging portion is substantially the same as the sum of the plate thickness of the first metal plate and the plate thickness of the second metal plate.

[0050] According to this structure, the effect of suppressing the root gap is further improved.

[0051] (8) The corner joint according to any one of (1) to (7) above, wherein

[0052] The bulging portion is formed such that the height in the plate thickness direction of the first metal plate gradually decreases from the entrance side of the protruding portion toward the edge portion on the other side of the first metal plate.

[0053] According to this structure, the protruding portion can be easily inserted into the bulging portion, and the first metal plate and the second metal plate can be constrained without slack.

[0054] In addition, the above object of the present invention is achieved by the structure of the following (9) of the closed cross-section member.

[0055] (9) A closed cross-section member, wherein

[0056] The closed cross-section member applies the corner joint according to any one of (1) to (8) above.

[0057] According to this structure, a closed cross-section member with improved joint fatigue strength can be manufactured.

[0058] In addition, the above object of the present invention is achieved by the structure of the following (10) of the manufacturing method of the corner joint.

[0059] (10) A manufacturing method of a corner joint, which overlaps a first metal plate and a second metal plate and welds them, wherein

[0060] The manufacturing method of the corner joint has the following steps:

[0061] For the first metal plate, at least one bulging portion is formed at an edge portion on one side which is the side welded to the second metal plate. The at least one bulging portion extends along a length direction from the edge portion on the one side of the first metal plate toward the edge portion on the other side of the first metal plate, and bulges in a direction facing the second metal plate with respect to a flat plate portion;

[0062] For the second metal plate, at least one protruding portion is formed at an edge portion on one side which is the side welded to the first metal plate. The at least one protruding portion protrudes in a direction from the edge portion on the other side of the second metal plate toward the edge portion on the one side of the second metal plate, and can be inserted into the bulging portion;

[0063] While inserting the protruding portion into the bulging portion, the first metal plate and the second metal plate are overlapped; and

[0064] Welding is performed on the edge portion on the one side of the first metal plate and the second metal plate to form a first weld bead,

[0065] The bulging portion is formed such that the height in the plate thickness direction of the first metal plate is equal to or greater than the sum of the plate thicknesses of the first metal plate and the second metal plate, and the length in the length direction of the first metal plate exceeds the sum of the leg length of the first weld bead between the first metal plate and the second metal plate and the length of the welding heat affected zone extending from the first weld bead toward the other side of the first metal plate.

[0066] According to this structure, stress concentration at the welded portion is alleviated by a simple structure, and a welded portion with an inhibited root gap is formed, and the joint fatigue strength can be effectively improved.

[0067] In addition, a preferred embodiment of the manufacturing method of the fillet welded joint relates to the following (11) to (16).

[0068] (11) The manufacturing method of the fillet welded joint according to (10), wherein,

[0069] In the second metal plate, the protruding portion is formed between a pair of cutouts formed along the length direction from the edge portion on the one side of the second metal plate.

[0070] According to this structure, by providing the cutouts, the protruding portion can be easily formed.

[0071] (12) The manufacturing method of the fillet welded joint according to (10) or (11), wherein,

[0072] The bulging portion is formed by press forming.

[0073] According to this structure, the bulging portion can be formed accurately and easily.

[0074] (13) The method for manufacturing a fillet welded joint according to any one of (10) to (12), wherein

[0075] The step of forming the first weld bead is performed by any one of an arc welding method, a laser welding method, or a laser-arc hybrid welding method.

[0076] According to this structure, the fatigue strength of the joint can be effectively improved by any one of the welding methods.

[0077] (14) The method for manufacturing a fillet welded joint according to any one of (10) to (13), wherein

[0078] The method for manufacturing the fillet welded joint further includes a step of welding a side edge portion of one side of the first metal plate corresponding to the bulging portion and the second metal plate to form a second weld bead.

[0079] According to this structure, the fatigue strength of the fillet welded joint can be further improved.

[0080] (15) The method for manufacturing a fillet welded joint according to (14), wherein

[0081] The first weld bead and the second weld bead are formed by continuous welding.

[0082] According to this structure, the first weld bead and the second weld bead can be easily formed by continuous welding operation.

[0083] (16) The method for manufacturing a fillet welded joint according to any one of (10) to (15), wherein

[0084] The method for manufacturing the fillet welded joint further includes a step of forming at least one cut portion on a side edge portion of one side of the first metal plate before forming the bulging portion on the first metal plate,

[0085] The bulging portion is formed at a position corresponding to the cut portion.

[0086] According to this structure, the area of the overlapping portion of the first metal plate and the second metal plate can be enlarged, and the fatigue strength is further improved.

[0087] Advantages of the Invention

[0088] According to the fillet welded joint and the method for manufacturing the fillet welded joint of the present invention, the stress concentration at the welded portion is alleviated by a simple structure, and a welded portion with an inhibited root gap is formed, so that the fatigue strength of the joint can be effectively improved. Brief Description of the Drawings

[0089] Figure 1 Figure 1 is a perspective view showing the corner welding joint of the first embodiment of the present invention.

[0090] Figure 2 Figure 2 is showing Figure 1 a perspective view of the manufacturing process of the corner welding joint shown.

[0091] Figure 3 Figure 3 is Figure 2 a C-C cross-sectional view of the corner welding joint shown.

[0092] Figure 4 Figure 4 is Figure 1 a D-D cross-sectional view of the first metal plate shown.

[0093] Figure 5 Figure 5 is a perspective view of the corner welding joint of the first modification of the first embodiment.

[0094] Figure 6 Figure 6 is a perspective view of the corner welding joint of the second modification of the first embodiment.

[0095] Figure 7 Figure 7 is a perspective view of the corner welding joint of the third modification of the first embodiment.

[0096] Figure 8 Figure 8 is a perspective view showing the manufacturing process of the corner welding joint of the second embodiment of the present invention.

[0097] Figure 9 Figure 9 is a perspective view showing the manufacturing process of the corner welding joint of the first modification of the second embodiment.

[0098] Figure 10 Figure 10 is a perspective view of a suspension arm as an example of the corner welding joint of the present invention.

[0099] Figure 11 Figure 11 is a perspective view schematically showing Figure 10 the E-E cross section of.

[0100] Figure 12 Figure 12 is a perspective view of a conventional corner welding joint obtained by overlapping and welding two metal plates. ​​​​​​​​​​​​​​​​​​​​​​​​

[0101] Figure 13 Figure 3 is Figure 12 the A-A cross-sectional view of the corner joint shown in the figure.

[0102] Figure 14 Figure 14 is the perspective view of the conventional corner joint with a gap.

[0103] Figure 15 Figure 15 is Figure 14 the B-B cross-sectional view of the corner joint shown in the figure. Detailed implementation manners

[0104] Hereinafter, each implementation manner of the corner joint of the present invention will be described in detail based on the drawings.

[0105] (First implementation manner)

[0106] Figure 1 is the perspective view showing the corner joint of the first implementation manner of the present invention, Figure 2 is showing Figure 1 the perspective view of the manufacturing process of the corner joint, Figure 3 is Figure 2 the C-C cross-sectional view of. As Figure 2 and Figure 3 shown, the corner joint 1 of the first implementation manner of the present invention has a structure in which the first metal plate 10 and the second metal plate 20 are overlapped, and the second edge portion 21 of the second metal plate 20 is welded to the first metal plate 10.

[0107] It should be noted that, in the following description, the side of the first metal plate 10 where it is welded to the second metal plate 20 is set as one side, the opposite side is set as the other side, and the edge portion on the one side of the first metal plate 10 is set as the first edge portion 12. In addition, the side of the second metal plate 20 where it is welded to the first metal plate 10 is set as one side, the opposite side is set as the other side, and the edge portion on the one side of the second metal plate 20 is set as the second edge portion 21 for description. That is, the first edge portion 12 and the second edge portion 21 face each other, and the one side and the other side of the first metal plate 10 and the second metal plate 20 are opposite to each other.

[0108] In addition, in the present embodiment, the first and second metal plates 10, 20 are flat thin plates of a substantially rectangular shape. The overlapping direction is also called the height direction, the direction along the welding line (each edge portion 12, 21) is called the width direction, and the direction away from the welding line is called the length direction.

[0109] ​​​​​​In the first metal plate 10, a plurality of bulging portions 13 are formed separately along a first edge portion 12 which is a side for welding with the second metal plate 20 and bulges in a direction (surface side) facing the second metal plate 20 with respect to a flat plate portion, and an internal space S is formed on the back side. For example, in Figure 1 the illustrated embodiment, two bulging portions 13 are provided. In the bulging portion 13, the height Xt in the plate thickness direction of the first metal plate 10 is set to be ta + tb or more, which is the sum of the plate thickness ta of the first metal plate 10 and the plate thickness tb of the second metal plate 20. In addition, the length X L in the length direction of the first metal plate 10 is set to be longer than the sum of the leg length L1 of the first weld bead 30 between the first metal plate 10 and the second metal plate 20 and the length L2 of the welding heat affected zone 31 extending from the first weld bead 30 to the other side of the first metal plate 10 (refer to Figure 13 ). That is, the length is L1 + L2.

[0110] On the other hand, the second metal plate 20 includes a plurality of protruding portions 22 formed by notches 23 provided in a second edge portion 21 which is a side for welding with the first metal plate 10 and protruding from the second edge portion 21 toward the first metal plate 10. For example, in Figure 1 the illustrated embodiment, two protruding portions 22 are provided. The two protruding portions 22 are formed corresponding to the intervals of the two bulging portions 13 and can be inserted into the internal space S of the bulging portions 13.

[0111] It should be noted that the bulging portions 13 of the first metal plate 10 can be easily and accurately manufactured by cold pressing or hot pressing the first metal plate 10.

[0112] Then, the protruding portions 22 of the second metal plate 20 are inserted into the internal space S of the bulging portions 13 of the first metal plate 10, and the first metal plate 10 and the second metal plate 20 are overlapped. Thus, the surface of the protruding portion 22 of the second metal plate 20 contacts the back surface of the bulging portion 13, and the portion other than the protruding portion 22 on the back surface of the second edge portion 21 side of the second metal plate 20 contacts the surface 11 of the first metal plate 10, and the second metal plate 20 is clamped by the first metal plate 10.

[0113] It should be noted that the height Xt in the thickness direction of the first metal plate 10 in the internal space S is preferably substantially the same as the sum of the thickness ta of the first metal plate 10 and the thickness tb of the second metal plate 20. However, when they are exactly the same, there is a possibility that the protruding portion 22 cannot enter the internal space S of the bulging portion 13. Therefore, there is actually a slight margin. However, in this case, it is also desirable that at least a part of the surface of the protruding portion 22 of the second metal plate 20 is in physical contact with the back surface of the bulging portion 13, whereby the root gap G between the first metal plate 10 and the second metal plate 20 is suppressed to the minimum gap.

[0114] In addition, in the present embodiment, the surface of the protruding portion 22 of the second metal plate 20 and the back surface of the bulging portion 13 are set to be substantially parallel. However, the bulging portion 13 may be slowly inclined in such a manner that the height gradually decreases from the entrance side of the protruding portion 22 toward the root portion 40 (the edge portion on the other side of the first metal plate 10). Specifically, the height Xt of the opening at the entrance side of the protruding portion 22 of the bulging portion 13 is set to be equal to or greater than the sum of the thickness ta of the first metal plate 10 and the thickness tb of the second metal plate 20, i.e., ta + tb. In addition, in the region where the bulging portion 13 and the protruding portion 22 overlap in the length direction of the first metal plate 10, the height Xt of the bulging portion 13 is set to be less than the sum of the thickness ta of the first metal plate 10 and the thickness tb of the second metal plate 20, i.e., ta + tb. By providing the bulging portion 13 in this way, the insertion of the protruding portion 22 into the bulging portion 13 becomes easy, and in the middle, the protruding portion 22 abuts while being pressed into the bulging portion 13. Therefore, the first metal plate 10 and the second metal plate 20 can be constrained without slack.

[0115] Next, in a state where the protruding portion 22 is inserted into the bulging portion 13, the second edge portion 21 of the second metal plate 20 and a part of the surface 11 of the first metal plate 10 are welded by arc welding or laser-arc hybrid welding to form a first weld bead 30. Here, the part to be welded refers to the second edge portion 21 of the second metal plate 20 exposed on the surface 11 of the first metal plate 10, and the second edge portion 21 of the protruding portion 22 inserted into the bulging portion 13 is not welded. It should be noted that the first weld bead 30 may also be formed in contact with the outer side surface 41 of the bulging portion 13 extending from the first edge portion 12 of the bulging portion 13 toward the other side.

[0116] In the welded joint 1 of the present embodiment, when a load in the thickness direction is applied to the welded joint 1, the root portion 40 of the bulging portion 13 on the side separated from the first edge portion 12 becomes a part of the stress concentration portion, so that the stress concentration can be alleviated from the first weld bead 30 as the welded portion. Therefore, the stress concentration does not act on the heat-affected welding portion 31 whose strength has been reduced due to the welding heat influence (refer to Figure 13 ), and the base metal strengths of the first metal plate 10 and the second metal plate 20 are maintained.

[0117] As a result, the root 40 that becomes the stress concentration part is separated from the first weld bead 30. Therefore, the influence of the weld heat-affected zone 31 whose strength has been reduced due to the welding heat on the fatigue strength of the fillet welded joint 1 is small, and the strength of the first metal plate 10 and the second metal plate 20 as the base materials is maintained.

[0118] It should be noted that, as in the present embodiment, when the first metal plate 10 and the second metal plate 20 are overlapped by the bulging portion 13 of the first metal plate 10 overlapping with the edge portion 21 of the second metal plate 20 through the notch 23 formed in the rectangular second metal plate 20, the length X of the bulging portion 13 in the length direction of the first metal plate 10 L Preferably, the length L3 of the overlapping portion of the first metal plate 10 and the second metal plate 20 is also considered. That is, in the present embodiment, in the bulging portion 13, the length X in the length direction of the first metal plate 10 L is set to exceed the leg length L1 of the first weld bead 30 between the first metal plate 10 and the second metal plate 20, the length L2 of the weld heat-affected zone 31 extending from the first weld bead 30 to the other side of the first metal plate 10, and the total length L1 + L2 + L3 of the overlapping portion of the first metal plate 10 and the second metal plate 20.

[0119] In addition, without using clamping jigs or the like that are usually used to suppress the gap G between the plates, the gap G between the first metal plate 10 and the second metal plate 20 is suppressed to the minimum gap, and the fatigue strength of the welded joint 1 is improved. It should be noted that the more the number of clamping jigs, the higher the suppression effect of the gap G. However, when the number of clamping jigs increases, it brings an increase in the cost of installation work and fixture costs, so it is not preferable.

[0120] In addition, by appropriately setting the length X of the bulging portion 13 alone L , the width X of the bulging portion 13 alone w , the width X of the bulging portion 13 w The total length (∑X w ) and the ratio (∑XW / ∑B) of the total length (∑B; in the example shown in Figure 1 , ∑B = B1 + B2 + B3) of the first weld bead 30, and in addition Figure 4 As shown, the radius Xr of the root 40 of the bulging portion 13 can optimize the strength. It should be noted that since the bulging portion 13 is formed by pressing (press forming), the radius Xr of the root 40 of the bulging portion 13 can be stably formed into a smooth shape.

[0121] Thus, the corner joint 1 according to the present embodiment can suppress the gap G between the first metal plate 10 and the second metal plate 20, so that the welding performance is stable. Moreover, the shape of the bulged portion 13 formed by pressing is not damaged by welding, and the fatigue resistance is improved.

[0122] It should be noted that, in the present embodiment, the front end portion of the protruding portion 22 of the second metal plate 20 protrudes from the second edge portion 21 from the viewpoint of joint rigidity, but it is not limited thereto, and the front end portion of the protruding portion 22 may also be in the same position as the second edge portion 21 in the length direction.

[0123] Figure 5 FIG. is a perspective view of a corner joint according to a first modification of the first embodiment. The second edge portion 21 of the second metal plate 20 and the surface 11 of the first metal plate 10 are welded by laser welding to form a first weld bead 30. It should be noted that, when performing laser welding, a filler wire may also be used additionally.

[0124] Next, with reference to Figure 6 and Figure 7 the corner joints according to the second and third modifications of the first embodiment will be described.

[0125] The welded joint 1 of the second modification is as shown in Figure 6 The protruding portion 22 of the second metal plate 20 is inserted and fitted into the bulged portion 13 of the first metal plate 10. The second edge portion 21 of the second metal plate 20 and the surface 11 of the first metal plate 10 are welded by arc welding or laser-arc hybrid welding to form a first weld bead 30. Further, the first edge portion 14 in the bulged portion 13 and the surface 24 of the second metal plate 20 are welded by arc welding or laser-arc hybrid welding to form a second weld bead 30A. The first weld bead 30 and the second weld bead 30A may also be welded continuously. Thus, compared with the case where the first weld bead 30 and the second weld bead 30A are welded by different processes, the welding man-hours are reduced.

[0126] The corner joint 1 of the third modification is as shown in Figure 7 The protruding portion 22 of the second metal plate 20 is inserted and fitted into the bulged portion 13 of the first metal plate 10. The second edge portion 21 of the second metal plate 20 and the surface 11 of the first metal plate 10 are laser welded to form a first weld bead 30. Further, the first edge portion 14 in the bulged portion 13 and the surface 24 of the second metal plate 20 are laser welded to form a second weld bead 30A. The first weld bead 30 and the second weld bead 30A may also be continuously welded by laser welding.

[0127] (Second Embodiment)

[0128] Figure 8It is a perspective view showing the manufacturing process of the corner joint of the second embodiment of the present invention. As Figure 8 shown, in the first edge portion 12 of the first metal plate 10 of the second embodiment, a plurality of cut portions 15 are formed along the first edge portion 12. For example, in Figure 8 the embodiment shown, two cut portions 15 are provided. And, bulging portions 13 are respectively formed in each cut portion 15.

[0129] Similar to the first metal plate 10 of the first embodiment, the height Xt in the plate thickness direction of the first metal plate 10 is ta + tb, which is the sum of the plate thickness ta of the first metal plate 10 and the plate thickness tb of the second metal plate 20 or more, and has a length X in the direction from the first edge portion 12 toward the other side L of the internal space S (refer to Figure 2 ). The length XI becomes a length exceeding the sum of the leg length L1 of the first weld bead 30 between the first metal plate 10 and the second metal plate 20 and the length L2 of the welding heat affected zone 31 extending from the first weld bead 30 to the other side of the first metal plate 10 (refer to Figure 13 ), that is, L1 + L2.

[0130] On the other hand, the second metal plate 20 has a plurality of protruding portions 22 protruding from the second edge portion 21, which is the side welded to the first metal plate 10, toward the first metal plate 10. The protruding portions 22 are formed corresponding to the intervals of the bulging portions 13 and can be inserted into the internal space S of the bulging portions 13.

[0131] And, the protruding portions 22 of the second metal plate 20 are inserted into and fitted with the bulging portions 13 of the first metal plate 10, and the first metal plate 10 and the second metal plate 20 are overlapped. Thus, the surface of the protruding portion 22 of the second metal plate 20 contacts the back surface of the bulging portion 13, and the portion other than the protruding portions 22 on the back surface on the second edge portion 21 side of the second metal plate 20 contacts the surface 11 of the first metal plate 10, and the second metal plate 20 is clamped by the first metal plate 10. Thus, the gap G between the first metal plate 10 and the second metal plate 20 is suppressed to the minimum gap.

[0132] Next, the edge portion 21 of the second metal plate 20 and a part of the surface 11 of the first metal plate 10 are welded by any one of arc welding, laser welding, and laser - arc hybrid welding to form the first weld bead 30. It should be noted that the first edge portion 14 of the bulging portion 13 and the surface 24 of the second metal plate 20 can also be welded by any one of arc welding, laser welding, and laser - arc hybrid welding to form the second weld bead 30A.

[0133] Figure 9It is a perspective view showing the manufacturing process of the corner joint of the first modification of the second embodiment. In this modification, the corner of the cutout portion 15 formed along the first edge portion 12 of the first metal plate 10 is formed in an R shape, and bulging portions 13 are respectively formed in the cutout portion 15.

[0134] The bulging portion 13 has an internal space S of the same size as the first metal plate 10 of the second embodiment. That is, the height Xt in the thickness direction of the first metal plate 10 is ta + tb or more, which is the sum of the thickness ta of the first metal plate 10 and the thickness tb of the second metal plate 20, and has a length X in the direction from the first edge portion 12 toward the other side L of the internal space S.

[0135] On the other hand, in the second metal plate 20, a plurality of protruding portions 22 protruding toward the first metal plate 10 are formed in the second edge portion 21 overlapping the first metal plate 10 corresponding to the intervals of the bulging portions 13. The shape of the protruding portion 22 is an R shape.

[0136] And, the protruding portion 22 of the second metal plate 20 is inserted and fitted into the bulging portion 13 of the first metal plate 10, the first metal plate 10 and the second metal plate 20 are overlapped, and the second edge portion 21 of the second metal plate 20 and the surface 11 of the first metal plate 10 are welded by any one of arc welding, laser welding, and laser-arc hybrid welding to form the first weld bead 30.

[0137] By forming the cutout portion 15 of the first metal plate 10 and the protruding portion 22 of the second metal plate 20 in an R shape, the overlapping area of the first metal plate 10 and the second metal plate 20 can be enlarged, thereby improving the joint strength.

[0138] Figure 10 It is a perspective view of a suspension arm 100 as an example of the above-mentioned corner joint 1, Figure 11 is a perspective view schematically showing Figure 10 the E-E cross section. In the suspension arm 100, a first member 110 formed in a substantially bowl shape is butted against a second member 120, and the joint surface thereof is welded by any one of arc welding, laser welding, and laser-arc hybrid welding.

[0139] As Figure 11 shown, the cross sections of the first member 110 and the second member 120 are formed in a substantially cylindrical shape that bends inwardly toward each other. Standing portions 111 are provided at both ends in the width direction of the first member 110, and standing portions 121 corresponding to the standing portions 111 are provided at both ends in the width direction of the second member 120. In each standing portion 111 of the first member 110, they are formed separately along the length direction in the first embodiment (refer to Figure 1) The plurality of bulges 13 described in []. In addition, in each erected portion 121 of the second member 120, a plurality of protrusions 22 described in the first embodiment (refer to Figure 1 ) are formed corresponding to the intervals of the bulges 13.

[0140] And, after the bulge 13 of the first member 110 is inserted into the protrusion 22 of the second member 120 and the ends of the erected portion 111 and the erected portion 121 overlap each other, any one of arc welding, laser welding, and laser-arc hybrid welding is used to weld the edge portion 114 of the second member 120 and the erected portion 111 of the first member 110 to form the first weld bead 30. It should be noted that although not shown in the figure, the first edge portion 14 in the bulge 13 and the second member 120 can also be welded by any one of arc welding, laser welding, and laser-arc hybrid welding to form the second weld bead 30A.

[0141] Thus, the corner joint 1 is also applied to a hollow-shaped closed-section member having an arbitrary shape, being lightweight and having a high fatigue resistance.

[0142] It should be noted that the present invention is not limited to the foregoing embodiments and each modification, and can be appropriately deformed, improved, etc.

[0143] For example, in the above-described embodiment, regarding the joining method, any one of arc welding, laser welding, and laser-arc hybrid welding is described, but it is not limited thereto, and brazing, etc. can also be used. In this case, joining between dissimilar materials can also be performed.

[0144] In addition, in the above-described embodiment, in the second metal plate, a protrusion is provided by providing a cut in the edge portion on one side thereof. However, for example, the edge portion on one side can be formed into a waveform shape in which a concave portion and a convex portion are continuous, and the convex portion therein can be set as the protrusion.

[0145] In addition, in the present invention, by bringing the back surface of the second edge portion side of the second metal plate into contact with the surface of the first metal plate, and bringing the back surface of at least one of the plurality of bulges into contact with the surface of at least one of the plurality of protrusions of the second metal plate, the root gap can be suppressed as long as the second metal plate is clamped by the first metal plate.

[0146] As described above, various embodiments have been described with reference to the drawings, but the present invention is of course not limited to this example. Those skilled in the art can clearly conceive of various modification examples or correction examples within the scope described in the technical solution, and these are of course also understood to belong to the technical scope of the present invention. In addition, the constituent elements in the above-described embodiments can be arbitrarily combined without departing from the gist of the invention.

[0147] It should be noted that this application is based on the Japanese patent application (Japanese Patent Application No. 2020-121667) filed on July 15, 2020, the content of which is incorporated herein by reference.

[0148] Description of Reference Numerals

[0149] 1 Butt Welding Joint

[0150] 10 First Metal Plate

[0151] 12 First Edge Portion (Edge Portion on One Side of the First Metal Plate)

[0152] 13 Bulging Portion

[0153] 15 Notch Portion

[0154] 20 Second Metal Plate

[0155] 21 Second Edge Portion (Edge Portion on One Side of the Second Metal Plate, End Face)

[0156] 22 Protruding Portion

[0157] 23 Notch

[0158] 30 First Weld Bead

[0159] 30A Second Weld Bead

[0160] 31 Welding Heat Affected Zone

[0161] 100 Suspension Arm (Closed Cross-Section Member)

[0162] L1 Leg Length of Weld Bead

[0163] L2 Length of Welding Heat Affected Zone

[0164] S Internal Space

[0165] ta Thickness of First Metal Plate

[0166] tb Thickness of Second Metal Plate

[0167] X L Length of Bulging Portion (Length in the Direction from the Edge Portion on One Side of the First Metal Plate to the Edge Portion on the Other Side of the First Metal Plate)

[0168] Xt Height of Bulging Portion in the Plate Thickness Direction (Height in the Plate Thickness Direction of the First Metal Plate)

[0169] X W Width of Bulging Portion.

Claims

1. A corner welding joint obtained by overlapping a first metal plate and a second metal plate and welding them, wherein, the first metal plate has at least one bulging portion at a edge portion on one side which is the side welded to the second metal plate. The at least one bulging portion extends along the length direction from the edge portion on the one side of the first metal plate toward the edge portion on the other side of the first metal plate, and bulges in a direction facing the second metal plate with respect to the flat plate portion, the second metal plate has at least one protruding portion at a edge portion on one side which is the side welded to the first metal plate. The at least one protruding portion protrudes in a direction from the edge portion on the other side of the second metal plate toward the edge portion on the one side of the second metal plate, and can be inserted into the bulging portion, the corner welding joint has a first weld bead obtained by welding the edge portion on the one side of the first metal plate and the second metal plate in a state where the protruding portion is inserted into the bulging portion, the bulging portion is formed such that the height in the plate thickness direction of the first metal plate in the internal space formed by the bulging portion is equal to or more than the total of the plate thickness of the first metal plate and the plate thickness of the second metal plate, and the length in the length direction of the first metal plate exceeds the total of the leg length of the first weld bead between the first metal plate and the second metal plate and the length of the welding heat affected zone extending from the first weld bead toward the other side of the first metal plate.

2. The corner welding joint according to claim 1, wherein, in the second metal plate, the protruding portion is formed between a pair of cutouts formed along the length direction from the edge portion on the one side of the second metal plate.

3. The corner welding joint according to claim 1, wherein, the bulging portion is formed by press forming.

4. The corner welding joint according to claim 2, the bulging portion is formed by press forming.

5. The corner welding joint according to any one of claims 1 to 4, wherein, the corner welding joint further has a second weld bead obtained by welding the edge portion on the one side of the first metal plate at a position corresponding to the bulging portion and the second metal plate.

6. The corner welding joint according to claim 5, wherein, the first weld bead and the second weld bead are formed continuously.

7. The corner welding joint according to any one of claims 1 to 4, wherein, the first metal plate has at least one cutout portion at the edge portion on the one side of the first metal plate, the bulging portion is formed at a position corresponding to the cutout portion.

8. The corner welding joint according to claim 5, wherein, the first metal plate has at least one cutout portion at the edge portion on the one side of the first metal plate, the bulging portion is formed at a position corresponding to the cutout portion.

9. The corner welding joint according to claim 6, wherein, the first metal plate has at least one cutout portion at the edge portion on the one side of the first metal plate, the bulging portion is formed at a position corresponding to the cutout portion.

10. The corner welding joint according to any one of claims 1 to 4, wherein the height in the thickness direction of the first metal plate in the internal space formed by the bulging portion is substantially the same as the sum of the thickness of the first metal plate and the thickness of the second metal plate.

11. The corner welding joint according to any one of claims 1 to 4, wherein the bulging portion is formed such that the height in the thickness direction of the first metal plate in the internal space formed by the bulging portion gradually decreases from the entrance side of the protruding portion toward the other-side edge of the first metal plate.

12. A closed cross-section member, wherein the closed cross-section member applies the corner welding joint according to any one of claims 1 to 4.

13. A method for manufacturing a corner welding joint, which overlaps and welds a first metal plate and a second metal plate, wherein the method for manufacturing the corner welding joint includes the following steps: forming at least one bulging portion at an edge on one side of the first metal plate, which is the side to be welded to the second metal plate, the at least one bulging portion extending along the length direction from the edge on one side of the first metal plate toward the edge on the other side of the first metal plate, and bulging in a direction facing the second metal plate with respect to the flat portion; forming at least one protruding portion at an edge on one side of the second metal plate, which is the side to be welded to the first metal plate, the at least one protruding portion protruding in a direction from the edge on the other side of the second metal plate toward the edge on one side of the second metal plate, and being capable of being inserted into the bulging portion; while inserting the protruding portion into the bulging portion, overlapping the first metal plate and the second metal plate; and welding the edges on one side of the first metal plate and the second metal plate to form a first weld bead, the bulging portion is formed such that the height in the thickness direction of the first metal plate in the internal space formed by the bulging portion is equal to or greater than the sum of the thickness of the first metal plate and the thickness of the second metal plate, and the length in the length direction of the first metal plate exceeds the sum of the leg length of the first weld bead between the first metal plate and the second metal plate and the length of the welding heat-affected portion extending from the first weld bead toward the other side of the first metal plate.

14. The method for manufacturing a corner welding joint according to claim 13, wherein in the second metal plate, the protruding portion is formed between a pair of cuts formed along the length direction from the edge on one side of the second metal plate.

15. The method for manufacturing a corner welding joint according to claim 13, wherein the bulging portion is formed by press forming.

16. The method for manufacturing a corner welding joint according to claim 13, wherein the step of forming the first weld bead is performed by any one of an arc welding method, a laser welding method, or a laser-arc hybrid welding method.

17. The method for manufacturing a corner welding joint according to any one of claims 13 to 16, wherein The manufacturing method of the corner joint further includes a step of welding the edge portion of one side of the first metal plate corresponding to the bulged portion and the second metal plate to form a second weld bead.

18. The manufacturing method of the corner joint according to claim 17, wherein The first weld bead and the second weld bead are formed by continuous welding.

19. The manufacturing method of the corner joint according to any one of claims 13 to 16, wherein The manufacturing method of the corner joint further includes a step of forming at least one cut portion in the edge portion of one side of the first metal plate before forming the bulged portion on the first metal plate, The bulged portion is formed at a position corresponding to the cut portion.

20. The manufacturing method of the corner joint according to claim 17, wherein The manufacturing method of the corner joint further includes a step of forming at least one cut portion in the edge portion of one side of the first metal plate before forming the bulged portion on the first metal plate, The bulged portion is formed at a position corresponding to the cut portion.

21. The manufacturing method of the corner joint according to claim 18, wherein The manufacturing method of the corner joint further includes a step of forming at least one cut portion in the edge portion of one side of the first metal plate before forming the bulged portion on the first metal plate, The bulged portion is formed at a position corresponding to the cut portion.

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