Welded joint and method for producing same

Abstract

The present invention provides a welded joint for a floating offshore wind power generation device comprising a tower member, a floating member, and a bracket, the welded joint being configured so that the fatigue strength of a welded portion is improved by extending a weld bead toward the floating member, and a method for manufacturing the welded joint. This welded joint has a first bead formed along one short side of a rectangular contact surface where a bracket and a floating body member are in contact, a second bead formed along two long sides of the rectangular contact surface, and a third bead formed along two long sides of the rectangular contact surface. The floating body member is formed so as to extend on the floating body member so as to cover either a starting end or a terminating end of the first bead. It is preferable that M / N, which represents the ratio of the interval M between the tip of the second bead and the tip of the third bead to the length N of the extension of the second bead or the third bead, is 2.0 or less.

Description

Technical Field

[0001] This invention relates to welded joints and their manufacturing methods, and more particularly to welded joints with excellent fatigue strength, such as the welded joint of a floating offshore wind power generation device, which are subjected to gas-shielded arc welding of floating components with the aid of a support, and their manufacturing methods. Background Technology

[0002] In recent years, floating offshore wind power generation has been studied due to its ease of installation even in waters deeper than 50 meters. Since floating offshore wind power units are exposed to external forces such as waves, the research focus is on improving the fatigue life of the weld toes at the welded joints of these units.

[0003] Therefore, various studies have been conducted on techniques to improve the fatigue strength of welded joints in large structures such as offshore wind power plants. For example, Patent Document 1 discloses a welded beam structure consisting of ribs and panels, wherein the ends of the ribs are respectively attached to structural members by fillet welds, forming a pair of extended weld beads with the structural members. These extended weld beads are formed by slightly extending the fillet weld beads on the structural members. Furthermore, Patent Document 1 also discloses that panels are respectively attached to both sides of the side edges of the ribs by fillet welds, forming a pair of extended weld beads with the ribs. These extended weld beads are formed by slightly extending the fillet weld beads on both sides of the side edges of the ribs. It is claimed that these extended weld beads can suppress the initiation of fatigue cracks at the weld toe.

[0004] Patent Document 2 discloses a weld structure comprising: two side weld portions formed by corner welding one side of one plate to the end face of another plate; and two side extended weld portions formed by welding the two side weld portions from the end of the other plate toward one side. Furthermore, Patent Document 2 also describes an end weld portion formed by additional welding the ends of one plate and the other plate together between the two side extended weld portions. This moves the weld toe away from the high-stress portion where defects are prone to occur in the weld, thereby improving the durability of the weld.

[0005] Furthermore, Patent Document 3 discloses a welded joint, which is a welded joint between a node plate and a main plate, having: a first weld bead extending from both sides of the short side of the node plate toward the main plate; and second and third weld beads extending from the long side of the node plate, covering the first weld bead and toward the main plate. It is claimed that this provides a welded joint that can inexpensively and reliably improve fatigue strength.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 8-155634

[0009] Patent Document 2: Japanese Patent Application Publication No. 9-253843

[0010] Patent Document 3: Japanese Patent Application Publication No. 2018-158380 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] The methods described in the aforementioned patent documents are claimed to be effective in improving the fatigue strength of welded joints. However, it remains unclear whether these methods are effective in improving the fatigue strength of welded joints in large structures such as offshore wind turbines, where structural stress concentrations are compounded in addition to localized stress concentrations, such as those in the tower, floating body, and support structures of floating offshore wind turbines.

[0013] Therefore, the inventors explored a method to improve the fatigue strength of welded joints in floating offshore wind power generation devices that suffer from both localized stress concentration and structural stress concentration. The results showed that fatigue strength can be improved by controlling the shape and configuration of the weld beads.

[0014] This invention aims to address the problems of the prior art and relates to welded joints of large structures, such as welded joints of floating offshore wind power generation devices comprising tower components, floating body components, and supports, wherein the weld bead extends to the floating body component. Therefore, the object of this invention is to provide a welded joint with improved fatigue strength and a method for manufacturing the same.

[0015] Methods for solving problems

[0016] To achieve the aforementioned objective, the inventors first fabricated a simulated structure of the weld joints of an actual floating offshore wind power generation device. As weld joints for the simulated structure, two types were fabricated: one with conventional fillet welds along the component and another with extended weld beads. Fatigue tests were then conducted. By comparing the results of these fatigue tests, it was observed that the fatigue strength of the weld joint with extended weld beads was improved.

[0017] This invention is based on the above insights and further research, and the key points of this invention are as follows.

[0018] [1] A welding joint comprising a first member, a second member facing the first member, and a support member contacting the first member and the second member, wherein, The welded joint has a first weld bead, a second weld bead, and a third weld bead. The first weld bead is formed along a short side of the first rectangular contact surface where the support member abuts against the first member. The second weld and the third weld are formed along the long sides of the first rectangular abutment surface and extend toward the first member in such a way that they cover either a portion of the beginning or end of the first weld.

[0019] [2] According to the welding joint described in [1] above, wherein M / N, which represents the ratio of the distance M between the front end of the second weld bead and the front end of the third weld bead to the length N of the extension of the second weld bead or the extension of the third weld bead, is 2.0 or less.

[0020] [3] According to the welding joint described in [1] or [2] above, the length N of the extension of the second weld bead and the extension of the third weld bead is in the range of 4.0 mm to 60.0 mm.

[0021] [4] According to the welding joint described in [1] or [2] above, the welding joint further has a fourth weld bead formed along the long side and the short side of the second rectangular abutment surface that abuts the support member and the second member.

[0022] [5] According to the welding joint described in [1] or [2] above, wherein the welding joint is used as a welding joint for a floating offshore wind power generation device. The first component is a floating component, the second component is a tower structure component, and the supporting component is a bracket.

[0023] [6] A method for manufacturing a welded joint, comprising a first component, a second component facing the first component, and a support component in contact with the first component and the second component, wherein, The welded joint has a first weld bead, a second weld bead, and a third weld bead. The first weld bead is formed along one short side of the first rectangular contact surface where the supporting member abuts against the first member. The second and third welds are formed along the long sides of the first rectangular abutment surface and extending toward the first member in such a way that they cover either the start or end of the first weld bead.

[0024] [7] In the method for manufacturing a welded joint as described in [6] above, the ratio M / N, which represents the ratio of the distance M between the front end of the second weld bead and the front end of the third weld bead to the length N of the extension of the second weld bead or the extension of the third weld bead, is 2.0 or less.

[0025] [8] In the method for manufacturing the welded joint according to [6] or [7] above, the length N of the extension of the second weld bead and the extension of the third weld bead is in the range of 4.0 mm to 60.0 mm.

[0026] [9] According to the manufacturing method of the welded joint described in [6] or [7] above, the welded joint further comprises a fourth weld pass. A fourth weld bead is formed along the long and short sides of the second rectangular contact surface where the support member abuts against the second member.

[0027]

[10] The method for manufacturing a welded joint according to [6] or [7] above, wherein the welded joint is used as a welded joint for a floating offshore wind power generation device, The first component is a floating component, the second component is a tower structure component, and the supporting component is a bracket.

[0028] Invention Effects

[0029] According to the present invention, in the welded joints of large structures, such as welded joints of floating offshore wind power generation devices comprising tower components, floating body components, and supports, by extending the weld bead to the floating body component, it is possible to provide welded joints with improved fatigue strength and a method for manufacturing the same. Furthermore, the present invention has significant industrial advantages. Attached Figure Description

[0030] Figure 1 This is a perspective view schematically representing the overall structure of the welded joint (simulated structure) of the floating offshore wind power generation device involved in this invention.

[0031] Figure 2 (a) and Figure 2 (b) indicates Figure 1 A schematic diagram of the overall structure of the welded joint (simulated structure). Figure 2 (a) is a top view. Figure 2 (b) is the front view.

[0032] Figure 3 It is an enlarged schematic representation Figure 1 A top view of a portion of the welded joint (simulated structure).

[0033] Figure 4 (a)~ Figure 4 (d) indicates Figure 1 A schematic diagram illustrating an example of the steps in a method for manufacturing a welded joint (simulated structure).

[0034] Figure 5 It means Figure 1 A schematic diagram of the fixed state during fatigue testing of the welded joint (simulated structure). Detailed Implementation

[0035] like Figure 1 As shown, the present invention relates to a welded joint and a method for manufacturing the same, the welded joint comprising a first member, a second member mating with a surface (e.g., a surface) of the first member, and a support member in contact with the first member and the second member. The second member is held by a pair of support members. The welded joint of the present invention is preferably used, for example, as a welded joint for a floating offshore wind power generation device. Hereinafter, a welded joint for a floating offshore wind power generation device will be described as an example. In this example, the first member is the floating member 3 described later, the second member is the tower member 2 described later, and the support member is the bracket 4 described later.

[0036] The present invention relates to a welded joint for a floating offshore wind power generation device and a method for manufacturing the same, wherein fatigue strength is improved by extending the weld bead to the floating component.

[0037] The embodiments of the present invention will be described below.

[0038] [Floating offshore wind power generation device]

[0039] First, a general overview of floating offshore wind power generation devices will be provided.

[0040] Wind power is a renewable energy source. Offshore wind turbines are available in two types: bed-mounted and floating. Floating offshore wind turbines are used in waters deeper than 50 meters. The structure of a floating offshore wind turbine involves connecting a structure carrying a windmill using chains or similar means, allowing it to float on the sea. This structure consists of a tower that supports and holds the windmill (wind turbine), and a floating section that supports the tower and floats on the sea. Improving the fatigue life of the welded joints between the tower and the floating section, which serves as the base, is an important issue.

[0041] [Simulated structure of welded joints for floating offshore wind power generation devices]

[0042] To investigate joint improvements in fatigue life for the welded joints of the aforementioned floating offshore wind turbine, a simulated welded joint of the actual floating offshore wind turbine structure was fabricated, and simulation tests were conducted to improve fatigue life. The simulated welded joint structure used herein is shown in [Figure / Image / Description]. Figure 1 The welded joint (i.e., the simulated structure) 1 has the following structure: a cuboid tower component 2 is placed on a floating component 3, and the tower component 2 is held in place from both sides by two supports 4. In addition, the joints of the components are mainly filled by gas-shielded arc welding, forming weld beads 5 at each boundary.

[0043] Tower component 2 is a cuboid. Its shape is not particularly limited; as an example of a simulated structure, for instance, the long side (plate width) of the base is 100mm–200mm, the short side (plate thickness) is 50mm–60mm, and the height (plate length) is 250mm–400mm. Examples of materials for tower component 2 include YP460 and YP355.

[0044] The floating component 3 is a plate with thickness. Its shape is not particularly limited; as an example of a simulated structure, the plate width (plate width) is 100mm to 200mm, the plate thickness (plate thickness) is 25mm to 40mm, and the plate length (plate length) is 800mm to 1000mm. The material of the floating component 3 can also be the same as that of the tower structure component 2.

[0045] The support 4 is a triangular prism with a right-angled triangle base, and the two sides forming the right angle of the triangular prism abut against the tower structure component 2 and the floating body component 3. Figure 2 (a) is a top view of the simulated structure 1 from above. Figure 2 (a) shows the rectangular contact surface 4a (hereinafter sometimes referred to as the "first rectangular contact surface") where the support 4 abuts against the floating body component 3. The shape of the support 4 is not particularly limited; as an example of a simulated structure, for instance, the length of the long side of the rectangular contact surface 4a of the support 4 is 200mm to 400mm, and the length of the short side of the rectangular contact surface 4a is 30mm to 40mm. The material of the support 4 is preferably the same as that of the tower structure component 2 and the floating body component 3.

[0046] [Weld Bead 5]

[0047] In one embodiment, the weld bead 5, primarily formed by fillet welding, consists of a first weld bead 5a, a second weld bead 5b, and a third weld bead 5c formed according to the welding sequence described later. Preferably, a fourth weld bead 5d is further provided in the weld bead 5. Its structure is shown in… Figure 2 (a) Top view and Figure 2 (b) Front view. Figure 2 (a) and Figure 2 (b) shows weld 5, which consists of the first to fourth weld passes.

[0048] It should be noted that, in Figure 2 In (a), the support is shown with its rectangular contact surface (first rectangular contact surface) 4a abutting against the floating body component 3. (The following will be discussed...) Figure 3 , Figure 4 (a)~ Figure 4 (d) The same applies.

[0049] In addition, gas-shielded arc welding is the preferred welding method.

[0050] [First weld pass 5a]

[0051] The first weld bead 5a is a weld bead formed along one short side of the rectangular abutment surface 4a of the support 4 (see reference). Figure 4 (a) etc.

[0052] The weld toe of the weld bead formed on the short side (i.e., the first weld bead 5a) is the part most prone to local stress concentration and fatigue cracking. Furthermore, in the case of the floating offshore wind power generation device to which this invention is aimed, in addition to local stress concentration, structural stress concentration of the wind power generation is also superimposed, making fatigue cracking more likely. In order to suppress the generation of fatigue cracks, it is important to form the second weld bead 5b and the third weld bead 5c, which are described below, and to extend these weld beads to the floating body member 3.

[0053] [Second weld pass 5b and third weld pass 5c]

[0054] The second weld 5b is formed along one long side of the rectangular abutment surface 4a of the support 4 and extends further onto the float member 3 in a manner that covers either the starting or ending end of the first weld 5a (see reference). Figure 4 (b) etc. Additionally, the third weld 5c is formed along the other long side of the rectangular abutment surface 4a and extends further onto the float member 3 in a manner that covers either the terminating end or the starting end of the first weld 5a (see reference). Figure 4 (c) etc.

[0055] It should be noted that, for example, when the second weld bead 5b covers the starting end of the first weld bead 5a, the third weld bead 5c is formed in such a way that it covers the ending end of the first weld bead 5a.

[0056] exist Figure 2 In (a), the second weld 5b and the third weld 5c are formed symmetrically from top to bottom. Their arrangement is such that the second weld 5b is on the upper side of the rectangular abutment surface 4a and the third weld 5c is on the lower side, but it is also fine if the arrangement is reversed.

[0057] The phrase "covering any part of the terminating or starting end of the first weld bead" includes not only the case of covering any part of the terminating or starting end of the first weld bead, but also the case of overlapping welding on a portion of the first weld bead after "covering". For example... Figure 2 As shown in (a), the second weld 5b and the third weld 5c are not straight, but the stress concentration on the short side of the weld is reduced by shortening the weld interval.

[0058] [The distance M between the front end of the second weld bead and the front end of the third weld bead]

[0059] like Figure 3 As shown, the distance between the front end of the second weld 5b and the front end of the third weld 5c is M. Here, the distance M between the front ends refers to the distance between the weld toes at the front ends of the second and third welds, respectively. To improve the fatigue strength of the welded joint, the ratio M / N of this distance M to the length N of the extension of the second or third weld (described later) is preferably 2.0 or less. This is because if the ratio M / N exceeds 2.0, fatigue cracks may sometimes occur, and the fatigue strength may not be improved as much. The ratio M / N of this distance M to the length N of the extension is more preferably 1.8 or less.

[0060] Furthermore, even when the interval M is 0 mm or less, i.e., when the two leading ends of the second and third welds are in contact or when the two welds overlap, an improvement in fatigue strength can be observed. Therefore, the lower limit of the ratio M / N of the interval M to the length N of the extension is not specifically set. That is, the ratio M / N of the interval M to the length N of the extension is preferably 0.0 or more, and more preferably 1.0 or more.

[0061] [Length N of the second and third weld bead extensions]

[0062] like Figure 3 As shown, the length of the extension of the second weld 5b and the extension of the third weld 5c is N. This length N is the length from the weld toe of the first weld 5a to the weld termination end at the leading edge of the second and third welds. This length N is preferably 4.0 mm to 60.0 mm in both the second weld 5b and the third weld 5c. If it is less than 4.0 mm, the improvement in fatigue life cannot be observed. On the other hand, if it exceeds 60.0 mm, excessive weld formation will occur, leading to high welding construction costs, which is therefore undesirable. This length N is preferably 10.0 mm or more, and more preferably 50.0 mm or less.

[0063] [Fourth weld pass 5d]

[0064] like Figure 2 (a) and Figure 2 As shown in (b), the fourth weld bead 5d is formed along the long and short sides of the rectangular abutment surface (hereinafter sometimes referred to as the "second rectangular abutment surface") where the support 4 abuts against the tower component 2. It is used to join the entire boundary between the support 4 and the tower component 2. It should be noted that the welding along the long side of the rectangular abutment surface (second rectangular abutment surface) is vertical welding. This fourth weld bead 5d is preferably provided to improve the overall strength of the welded joint.

[0065] Furthermore, from the viewpoint of more effectively obtaining the aforementioned effects, the ratio d5 / a4, which represents the ratio of the short side length a4 of the first rectangular abutment surface 4a of the bracket 4 to the outer edge length d5 ​​of the short side direction of the second rectangular abutment surface in the fourth weld 5d, is more preferably in the range of 1.2 to 1.5. For example, the long side length of the second rectangular abutment surface of the bracket 4 is 100 mm to 300 mm, and the short side length of the second rectangular abutment surface is 10 mm to 50 mm.

[0066] [Manufacturing method of welded joint]

[0067] Next, regarding the welding method that is the method for manufacturing the welded joint involved in this invention, based on... Figure 4 (a)~ Figure 4 (d) One implementation method for a specific welding construction procedure is described. Welding from Figure 4 (a) Implemented sequentially.

[0068] First, the second component (here, tower component 2) is brought into face-to-face contact with the first component (here, floating component 3), and the support component (here, bracket 4) is configured to contact the first component and the second component.

[0069] Next, gas-shielded arc welding is performed between the configured components. It should be noted that if welding is performed in the order of (a) to (c), a weld bead of the welded joint of the present invention possessing the aforementioned characteristics can be obtained. As described above, when a fourth weld bead is provided to improve the overall strength of the welded joint, welding in (d) can be performed immediately after welding in (c).

[0070] (a) A first weld bead 5a is formed along one short side (the side away from the tower frame component 2) of the rectangular abutment surface 4a where the support 4 abuts against the floating body component 3 (refer to...). Figure 4 (a)).

[0071] (b) A second weld 5b is formed along one long side of the rectangular abutment surface 4a, and covering the first weld 5a, extending further toward the floating body member 3 (see reference). Figure 4 (b)).

[0072] (c) Similarly, a third weld 5c extending further toward the float member 3 is formed along the other long side of the rectangular abutment surface 4a and covering the first weld 5a (see reference). Figure 4 (c)).

[0073] (d) Furthermore, as needed, a fourth weld bead 5d is formed along the long and short sides of the rectangular contact surface between the support 4 and the tower frame component 2. That is, it is formed along the two longitudinal long sides on both sides of the rectangular contact surface with the tower frame component and the upper short side (see reference). Figure 4 (d)).

[0074] It should be noted that, in Figure 4 (a)~ Figure 4 In (d), only one side of the simulated structure 1 of the welded joint is shown, but for the other side (i.e. the opposite side), it is also preferable to form four weld passes around the support.

[0075] [Welding conditions for gas-shielded arc welding]

[0076] An example of welding conditions for gas shielded arc welding is shown.

[0077] • Welding current: 200A~400A, welding voltage: 20V~50V, welding speed: 20cm / min~40cm / min

[0078] • Protective gas: A mixture of 80% by volume CO2 or Ar gas and 20% by volume CO2 gas.

[0079] • Welding wire diameter: 1.0mm~2.0mm

[0080] Example

[0081] The present invention will be further described below based on embodiments. However, the following embodiments are merely illustrative of the present invention in more detail and do not limit the scope of the invention.

[0082] First, a simulated welded joint (i.e., a simulated structure) was fabricated to resemble the actual structure related to the welded joint of the floating offshore wind turbine. The test material used was YP470 material with a plate width of 100 mm. This test material was used as the floating body component of the floating offshore wind turbine, and tower components and supports made of the same material were prepared. Here, the dimensions of the floating body component were set as follows: plate width 100 mm, plate thickness 25 mm, plate length 800 mm; the dimensions of the tower component were set as: plate width 100 mm, plate thickness 50 mm, plate length 100 mm; the dimensions of the support were set as follows: the long side of the first rectangular abutment surface 200 mm, the short side of the first rectangular abutment surface 25 mm, and the long side of the second rectangular abutment surface 250 mm. These components were filled in using gas-shielded arc welding at a current of 230 A, a voltage of 30 V, and a speed of 34 cm / min, resulting in six different welded joints. These six types are: joints welded using standard fillet welding (Joint No. 1) and five joints with extended weld beads (Joints No. 2 to No. 6). The characteristics of the welded joints, namely Young's modulus and Poisson's ratio, were determined according to ASTM E8M "Metallic Materials, Tensile Testing Method". All six joints have a Young's modulus E of 206000 MPa and a Poisson's ratio v of 0.3.

[0083] Fatigue tests of welded joints, such as Figure 5As shown, the welded joint specimen is fixed by the clamps (clamps) of a fatigue testing machine (e.g., a fatigue load testing device), and fatigue loads (specifically tensile and compressive) are applied to the specimen as indicated by the arrows in the figure. The applied stress range is set to 150 MPa. The number of cycles until fracture is recorded as the fatigue life.

[0084] The results of these experiments are shown in Table 1.

[0085]

[0086] Joint No. 1 is a test result performed conventionally as a comparative example when fillet welding is carried out. Joint No. 2 is a test result performed as an example of the present invention when the weld bead is extended and the ratio M / N of the extended weld bead spacing M to the length N of the extended portion is 2.1. Joint No. 3 is a test result performed as an example of the present invention when the weld bead is extended and the ratio M / N of the extended weld bead spacing M to the length N of the extended portion is 0.3. Joint No. 4 is a case where the weld bead is extended and the ratio M / N of the extended weld bead spacing M to the length N of the extended portion is 0.0 as an example of the present invention. Joint No. 5 is a case where the weld bead is extended and the ratio M / N of the extended weld bead spacing M to the length N of the extended portion is 2.0 as an example of the present invention. Joint No. 6 is a case where the weld bead is extended and the ratio M / N of the extended weld bead spacing M to the length N of the extended portion is 1.0 as an example of the present invention.

[0087] It should be noted that joints No. 2 and thereafter are all composed of the first to fourth weld passes, and tests were conducted.

[0088] Regarding the number of fractures, compared to the case of a conventional fillet weld (joint No. 1), the fatigue strength was slightly improved when the ratio of the extended weld bead spacing M to the extension length N, M / N, was 2.1 (joint No. 2). On the other hand, the number of fractures was higher for cases where the ratio of the extended weld bead spacing M to the extension length N, M / N, was 2.0 or less (joints No. 3 to No. 6). Therefore, by extending the weld bead to the floating body component, the effect of improving the fatigue strength of the welded joint was confirmed. Furthermore, by reducing the spacing M of the extended weld bead, making the ratio of the extended weld bead spacing M to the extension length N, M / N, 2.0 or less, a further improvement in fatigue strength was confirmed.

[0089] Symbol Explanation

[0090] 1. Welded joint (simulated structure)

[0091] 2. Tower components

[0092] 3 floating body components

[0093] 4 brackets

[0094] 4a Rectangular contact surface where the support and the floating body component abut.

[0095] 5 Weld bead

[0096] 5a First weld pass

[0097] 5b Second weld pass

[0098] 5c Third weld pass

[0099] 5d Fourth weld pass

[0100] 6. Clamps (gauges) of the fatigue load testing apparatus

[0101] M is the distance between the leading ends of the second and third weld passes (mm).

[0102] N Length of the extension of the second weld pass and the extension of the third weld pass (mm)

Claims

1. A welded joint comprising a first member, a second member facing the first member, and a support member contacting the first member and the second member, wherein, The welded joint has a first weld bead, a second weld bead, and a third weld bead. The first weld bead is formed along a short side of the first rectangular contact surface where the support member abuts against the first member. The second weld and the third weld are formed along the long sides of the first rectangular abutment surface and extend toward the first member in such a way that they cover either a portion of the beginning or end of the first weld.

2. The welded joint according to claim 1, wherein, The ratio M / N, which indicates that the distance M between the front end of the second weld bead and the front end of the third weld bead is 2.0 or less, is the ratio of the length N of the extension of the second weld bead or the extension of the third weld bead.

3. The welded joint according to claim 1 or 2, wherein, The length N of the extension of the second weld bead and the extension of the third weld bead is in the range of 4.0 mm to 60.0 mm.

4. The welded joint according to claim 1 or 2, wherein, The welded joint also has a fourth weld bead formed along the long and short sides of the second rectangular abutment surface that abuts the support member and the second member.

5. The welded joint according to claim 1 or 2, wherein, The welded joint is used as a welded joint for floating offshore wind power generation devices. The first component is a floating component, the second component is a tower structure component, and the supporting component is a bracket.

6. A method for manufacturing a welded joint, comprising a first component, a second component facing the first component, and a support component contacting both the first component and the second component, wherein... The welded joint has a first weld bead, a second weld bead, and a third weld bead. The first weld bead is formed along one short side of the first rectangular contact surface where the supporting member abuts against the first member. The second and third welds are formed along the long sides of the first rectangular abutment surface and extending toward the first member in such a way that they cover either the start or end of the first weld bead.

7. The method for manufacturing a welded joint according to claim 6, wherein, The ratio M / N, which indicates that the distance M between the front end of the second weld bead and the front end of the third weld bead is 2.0 or less, is the ratio of the length N of the extension of the second weld bead or the extension of the third weld bead.

8. The method for manufacturing a welded joint according to claim 6 or 7, wherein, The length N of the extension of the second weld bead and the extension of the third weld bead is in the range of 4.0 mm to 60.0 mm.

9. The method for manufacturing a welded joint according to claim 6 or 7, wherein, The welded joint also has a fourth weld pass. A fourth weld bead is formed along the long and short sides of the second rectangular contact surface where the support member abuts against the second member.

10. The method for manufacturing a welded joint according to claim 6 or 7, wherein, The welded joint is used as a welded joint for floating offshore wind power generation devices. The first component is a floating component, the second component is a tower structure component, and the supporting component is a bracket.

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