Circumferential welding method and circumferential welding joint

Abstract

Provided are a circumferential welding method and a circumferential welding joint for a steel structure having a bracket. A circumferential welding method according to the present invention comprises in sequence: performing welding between an upright plate 2 and a main plate 1; forming a first welding bead 4 along a short side of a rectangular contact surface 3a where a bracket is in contact with the main plate; placing a welding metal dam member 7 on the main plate 1 so that the welding metal dam member 7 is in proximity to the first welding bead; sequentially forming a second welding bead 5 and a third welding bead 6 along long sides of the rectangular contact surface 3a so that the second welding bead 5 and the third welding bead 6 cover end portions of the first welding bead and extend on the main plate 1 along the welding metal dam member 7.

Description

Rotation welding method and rotation welding joint

[0001] The present invention relates to a box welding method using a weld metal retaining member for a main plate, a vertical plate, and a bracket, and in particular to a box welding method that can improve the fatigue strength of the weld between the main plate and the bracket in a steel structure where stress concentration is high by extending the weld bead to a predetermined dimension, and further to a box welded joint with improved fatigue strength obtained by this method.

[0002] In recent years, floating offshore wind turbines have been considered in the field of offshore wind power generation due to their ease of installation, even in waters 50 m or deeper. However, because floating offshore wind turbines are exposed to external forces such as waves, there is a problem of reduced fatigue strength at the weld toes of welded joints in floating offshore wind turbines.

[0003] For this reason, various techniques for improving the fatigue strength of weld toes in welded joints in large structures such as floating offshore wind power generation facilities have been studied. For example, Patent Document 1 discloses a boxing welded joint for a gusset, which has a first weld bead extending from both sides of the short side of the gusset onto the main plate, and second and third weld beads extending along the long side of the gusset, covering the first weld bead, onto the main plate.

[0004] A similar welded joint is also disclosed in Patent Document 2. It states that by controlling the dimensions of the shape of these extended weld beads (hereinafter also referred to as "extended beads"), particularly the spacing between the extended beads and the length of the extended beads, a boxing welded joint can be obtained that can inexpensively and stably improve fatigue strength.

[0005] JP 2018-158380 A JP 2020-055020 A

[0006] However, in on-site welding, visibility is poor due to the need to use a light-shielding surface during welding, and there are no markers to use when welding the extension beads. Therefore, the welded joints and welding methods described in Patent Documents 1 and 2 have a problem in that errors occur in the extension bead spacing M and extension bead length N, which are thought to contribute to improving fatigue strength, making it difficult to control them to the specified dimensions.

[0007] The present invention aims to provide a box welding method and a box welded joint that solves the problems of the prior art and improves the fatigue strength of the welded portion of the bracket by controlling the extension bead spacing M and extension bead length N to specified dimensions.

[0008] As a result of various investigations into achieving the above-mentioned object, the inventors of the present invention have come to realize the need for an auxiliary member for forming the shape of the weld bead with high precision.

[0009] First, welded joints with brackets were fabricated using a weld metal damming member 7 (hereinafter simply referred to as the "damming member"), a welding auxiliary member that can be removed after welding, as shown in Figure 3 as a guide during welding. For comparison, welded joints with extended beads that were conventionally welded by turning the bracket were also fabricated. The extended bead spacing M and extended bead length N of the welded joints with extended weld beads were measured with a vernier caliper, and fatigue tests were then conducted on both welded joints. The fatigue test results were compared to verify the fatigue strength improvement effect of the welded joints with extended weld beads. As a result, we found that the welded joints with extended weld beads using the damming member had the extended bead shape and dimensions formed more accurately according to the target dimensions, and the fatigue strength of the welded joints was consistently improved.

[0010] The present invention was completed based on these findings and through further study, and the gist of the present invention is as follows: [1] A boxing welding method using a weld metal damming member for a main plate, a standing plate, and a bracket, wherein the weld metal damming member has a rectangular bottom surface that abuts against the main plate, a first weld bead is formed along a short side of the rectangular abutment surface where the bracket abuts against the main plate, the weld metal damming member is then disposed on the main plate so as to be adjacent to the first weld bead, and a second weld bead and a third weld bead are then formed in sequence along the long side of the rectangular abutment surface to cover an end of the first weld bead, and further extended onto the main plate so as to follow the weld metal damming member. [2] The box welding method according to [1], wherein the shorter of the distances N between the short sides of the rectangular abutting surface and the tip of the second weld bead or the third weld bead is 5.0 mm to 60.0 mm, and when the distance M between the extension of the second weld bead and the extension of the third weld bead is M and the length of the short sides of the rectangular abutting surface is Q, M≦10.0 mm and M≦Q. [3] The shape of the weld metal blocking member is such that the length N of the rectangular bottom surface in the longitudinal direction is 10.0 mm. T The shape of the front side and rear side, which are cross sections of the weld metal blocking member perpendicular to the longitudinal direction, is an inverted trapezoid, and the bottom width M, which is the length of the short side of the rectangular bottom, is T[4] The box welding method according to any one of [1] to [3], wherein the shape of a region where a lateral side surface of the weld metal damming member contacts the weld bead in a cross section perpendicular to the longitudinal direction of the weld metal damming member is a curve or a line with an elevation angle θ of 60° or less from the rectangular bottom surface. [5] The box welding method according to any one of [1] to [4], wherein the weld metal damming member is made of copper or ceramics. [6] The box welding method according to any one of [1] to [5], wherein the main plate is a floating body member of a floating offshore wind power generation facility, and the upright plate is a tower member of the floating offshore wind power generation facility. [7] A boxing welded joint comprising a main plate, a vertical plate, and a bracket, the boxing welded joint having a first weld bead, a second weld bead, and a third weld bead, the first weld bead being formed along one short side of a rectangular contact surface where the bracket contacts the main plate, the second weld bead and the third weld bead being formed along each long side of the rectangular contact surface and extending onto the main plate to cover a part of a starting end or a terminal end of the first weld bead, and the shape of the region where the second weld bead and / or the third weld bead extending onto the main plate and the main plate contact each other in a cross section perpendicular to the longitudinal direction of the second weld bead and / or the third weld bead formed and extended onto the main plate has an elevation angle θ from the main plate of 60° or less. [8] The boxing welded joint according to [7] above, wherein the shorter distance N between the short side of the rectangular abutment surface and the tip of the second weld bead or the third weld bead is 5.0 mm to 60.0 mm, and wherein, when the distance between the extension of the second weld bead and the extension of the third weld bead is M and the length of the short side of the rectangular abutment surface is Q, M≦10.0 mm and M≦Q. [9] The boxing welded joint according to [7] or [8] above, wherein the main plate is a floater member of a floating offshore wind power generation facility, and the standing plate is a tower member of the floating offshore wind power generation facility.

[0011] According to the present invention, by extending the weld bead on the bracket 3 of the steel structure using the weld metal retaining member 7 as a guide, it is possible to control the distance M between the extensions of the weld bead and the distance N from the rectangular abutment surface 3a to the tip of the weld bead extension to predetermined dimensions. As a result, it is possible to provide a boxing welding method and a boxing welded joint that can improve fatigue strength compared to conventional boxing welded joints, which is of great industrial benefit.

[0012] FIG. 1 is a perspective view schematically showing the appearance of an example of a box welded joint obtained by the box welding method according to the present invention. FIG. 2 is a plan view schematically showing one side of an example of a box welded joint obtained by the box welding method according to the present invention. FIG. 3 is a perspective view schematically showing an example of a weld metal blocking member used in the box welding method according to the present invention. FIGS. 4(a) to 4(c) are cross-sectional views schematically showing different cross-sectional shapes (three examples) of a weld metal blocking member used in the box welding method according to the present invention. FIG. 5 is a cross-sectional view schematically showing the state before and after removal of the weld metal blocking member ((a) during welding and (b) after removal). FIG. 6 is a plan view schematically showing an example of a procedure for the box welding method according to the present invention.

[0013] The present invention provides a boxing welding method for fillet welding between a vertical plate on a main plate and a bracket, in which a weld metal retaining member that can be removed after welding is used as a guide, and the weld bead is extended along the weld metal retaining member. This method improves the dimensional accuracy of the extended bead shape and the fatigue strength of the welded joint, and provides a boxing welded joint with improved fatigue strength.

[0014] [Weld Metal Guard Member 7] First, the weld metal guard member 7, which is an auxiliary member for forming an extended bead, which is important in the box welding method according to the present invention, will be described.

[0015] 3 shows an outline of an example of the weld metal damming member 7. Hereinafter, the weld metal damming member may also be referred to as a "damming member." The shape of the damming member 7 is composed of six flat surfaces.

[0016] The lower surface of the six flat surfaces is a rectangular bottom surface 7a, and the upper surface is a rectangular top surface 7b. The rectangular bottom surface 7a is in contact with the main plate 1, and its longitudinal length N T is a length corresponding to the length of the extensions of the second weld bead 5 and the third weld bead 6 formed by extending on the main plate 1. T From the viewpoint of workability, the length N T It is more preferable that the length N is 5.0 mm to 50.0 mm. T is preferably set to be larger than the interval N, which is the target dimension of the length of the extension portion of the weld bead described above.

[0017] In addition, the length of the short side of the rectangular bottom surface 7a that abuts against the main plate 1 (i.e., the bottom width) M T It is preferable that the length M of the short side is more than 0.0 mm and is not more than 10.0 mm. T It is preferable that the length M of the short side bead 5 coincides with the target distance M between the extension 5 a of the second weld bead 5 and the extension 6 a of the third weld bead 6. T is more preferably 1.0 mm or more, and more preferably 7.0 mm or less.

[0018] Next, one of the two side surfaces perpendicular to the longitudinal direction of the weld metal damming member 7 is a front side surface 7 c, the opposite side surface is a rear side surface 7 d, and the two side surfaces along the longitudinal direction are lateral side surfaces 7 e. It is preferable that the cross-sectional shape perpendicular to the longitudinal direction (i.e., the shapes of the front side surface 7 c and the rear side surface 7 d) be a substantially inverted trapezoid.

[0019] Examples of cross-sectional shapes (three examples here) are shown in Figure 4. As shown in Figures 4(a) and 4(b), the shape of the region where the lateral side surface 7e contacts the weld bead in a cross section perpendicular to the longitudinal direction is preferably formed as a curve with an elevation angle (i.e., rise angle) θ from the rectangular bottom surface 7a of 60° or less. Instead of a curve, as shown in Figure 4(c), a straight line with an elevation angle θ from the rectangular bottom surface 7a of 60° or less may be used. More preferably, θ is 5° or more and 60° or less. If the elevation angle θ from the rectangular bottom surface 7a exceeds 60°, stress concentration at the weld toe deteriorates fatigue properties, resulting in a failure to increase the number of fractures of the welded joint of the present invention. If the elevation angle θ is less than 5°, welding becomes difficult. By using such a curve or straight line, the shape of the weld bead extension, with an elevation angle θ of 60° or less, tends to be close to a semi-ellipse, as shown in Figure 5. This reduces or avoids stress concentration in the extension. The elevation angle θ is more preferably 10° or more, and more preferably 50° or less. Here, the cross-sectional shapes shown in FIGS. 4(a) to 4(c) are referred to as inverted trapezoids. This inverted trapezoid includes, for example, a shape in which the lower region of each lateral side surface 7e (i.e., the region on the rectangular bottom surface 7a side) is curved, as shown in FIGS. 4(a) and 4(b), and both lateral side surfaces 7e flare upward, as shown in FIG. 4(a), and a shape in which both lateral side surfaces 7e do not flare upward, as shown in FIG. 4(b). It also includes, for example, a shape in which the lower region of each lateral side surface 7e is linear, and both lateral side surfaces 7e flare upward, as shown in FIG. 4(c).

[0020] Here, the relationship between the shape of the lower part of the damming member 7 and the weld bead will be explained with reference to FIG. 5 . The shape of the damming member 7 shown in FIG. 5 is the same as that shown in FIGS. 4( a) and 4(b), i.e., the lower region of the lateral side surface 7e is curved, with both lateral side surfaces 7e widening upward in FIG. 4(a) and not widening in FIG. 4(b). FIG. 5(a) is a cross-sectional view of the damming member 7 placed on the main plate 1, with the extension 5a of the second weld bead 5 and the extension 6a of the third weld bead 6 formed along the lateral side surface 7e in the longitudinal direction of the damming member 7. FIG. 5(b) is a cross-sectional view of the damming member 7 after it has been removed. As shown in FIG. 5(b), the shape of the weld bead is formed in the same shape as the lower part of the damming member 7. In other words, the length M of the short side of the rectangular bottom surface 7a of the damming member 7 is 1 / 2. T is equal to the distance M between the extension beads, and the weld toes on the inside of the two weld beads have a rising shape according to the elevation angle θ. Therefore, when welding is performed using the damming member 7 of the present invention, the weld toes of the welded joint have a smooth shape and the distance M between the extension beads is maintained constant, so stress concentration in the extension parts can be reduced or avoided. Note that the shape of the rectangular upper surface 7b of the damming member 7 does not have to be flat.

[0021] Furthermore, the height H of the blocking member 7 T is not particularly limited. T is determined appropriately depending on ease of handling, and is preferably set to 20.0 mm to 60.0 mm.

[0022] Next, the damming member 7 is preferably made of a material that does not bond with the weld metal. By using a material that does not bond with the weld metal, the damming member 7 can be easily removed from its installed position after bead welding. Examples of such a material include copper and ceramics. Note that examples of ceramics include those containing silica, zirconia, alumina, etc. as a main component.

[0023] [Box Welding Method] Next, the box welding method according to the present invention will be described in order with reference to FIG. 6, which shows one embodiment of the procedure.

[0024] In this example, first, as a preparation step before the box welding step, a standing plate 2 is placed on the top surface of the main plate 1, and the standing plate is sandwiched between two brackets 3 on both sides. The brackets are placed so that their two side surfaces contact the main plate 1 and the standing plate 2. Note that Fig. 6 only shows one side of the main plate 1. A rectangular contact surface 3a where the bracket 3 contacts the main plate 1 matches the shape of a rectangular line when the bracket 3 is projected onto the main plate 1. In the following description, the shape of this rectangular line will be referred to as the rectangular contact surface 3a.

[0025] Next, the arranged components are subjected to the welding process described below. For ease of understanding, Figure 6 shows the procedure for box welding to the bracket 3. Prior to welding the bracket 3, fillet welding is performed between the vertical plate 2 and the main plate 1 (see Figures 1 and 2). Then, the bracket 3 is box welded in the following order (a) to (e). This results in a weld bead for the welded joint of the present invention, which has the properties described below.

[0026] (a) A first weld bead 4 is formed along one short side (in this example, the side farther from the upright plate 2) of the rectangular contact surface 3a where the bracket 3 contacts the main plate 1 (see (a) in FIG. 6). The welding method for forming the weld bead is preferably gas-shielded arc welding. The gas-shielded arc welding conditions will be described later. (b) The weld metal damming member 7 is disposed on the main plate 1 such that the center line X of the rectangular bottom surface 7a of the weld metal damming member 7 is aligned with the plate thickness center line Y of the bracket 3 and is adjacent to the first weld bead 4 formed in (a) above. Here, aligning the center lines X and Y means that a deviation of 1 to 2 mm is acceptable. (c) The weld bead formed along one long side of the rectangular abutment surface 3a is covered onto the end of the first weld bead 4, and further extended onto the main plate 1 along the rectangular bottom surface 7a of the weld metal damming member 7 to form the second weld bead 5. Here, "covering the end of the first weld bead 4" means that the starting end or the terminal end of the first weld bead 4 is at least partially melted with the second weld bead 5. The length N of the extended portion 5a of the second weld bead 5 is the sum of the length N of the long side of the rectangular bottom surface 7a of the damming member 7. TBy making the length shorter than , the shape of the extension can be accurately maintained. (d) Similarly, the weld bead formed along the other long side of the rectangular abutment surface 3a is covered over the end of the first weld bead 4, and then extended onto the main plate 1 along the rectangular bottom surface 7a of the weld metal damming member 7 to form the third weld bead 6. This ensures a consistent bead shape. Here, "covering the end of the first weld bead 4" means that the starting end or terminal end of the first weld bead 4 is at least partially melted with the third weld bead 6. Furthermore, the length N of the extension 6a of the third weld bead 6 is determined by the ratio of the length N of the long side of the rectangular bottom surface 7a of the damming member 7 to the length N. T By making the length shorter than , the shape of the extension can be accurately maintained. (e) Next, the weld metal retaining member 7 is removed, thereby forming a weld joint having the desired shape of the extension bead. Note that while Figure 6 mainly shows the area around the bracket on one side of the weld joint, it is preferable to similarly form three weld beads around the bracket on the other side (i.e., the opposite side).

[0027] [Welding conditions for gas-shielded arc welding] Here, an example of welding conditions for gas-shielded arc welding is shown below. Welding current: 200 A to 400 A, welding voltage: 20 V to 50 V, welding speed: 20 cm / min to 40 cm / min Shielding gas: 100% CO2 gas by volume or a mixed gas of CO2 gas and Ar gas (an example of the mixed gas ratio is a mixed gas of 20% CO2 gas by volume and 80% Ar gas by volume). Welding wire diameter: 1.2 mm to 2.4 mm

[0028] [Boxing Welded Joint Between Steel Plate, Vertical Plate, and Bracket] Next, a welded joint obtained by the box welding method according to the present invention will be described. An external perspective view of one example of such a welded joint is shown in Fig. 1. The welded joint of the present invention includes at least a main plate 1, a vertical plate 2, and a bracket 3, and has a weld bead at the joint between them. This boxing welded joint has a rectangular parallelepiped vertical plate 2 placed on the main plate 1, and two brackets 3 sandwiching the vertical plate 2 from both sides. The joint is mainly fillet welded by gas-shielded arc welding, and weld beads including first to third weld beads 4 to 6 are formed.

[0029] The main plate 1 is preferably a steel plate having a thickness (i.e., plate thickness) of 25 mm to 40 mm. Other shape specifications are not particularly limited. Examples of the material for the main plate 1 include YP460 material and YP355 material.

[0030] The standing plate 2 is a rectangular parallelepiped. Other shape specifications are not particularly limited. An example of the standing plate 2 is one in which the long side of the bottom surface (i.e., plate width) is 100 mm to 200 mm, the short side of the bottom surface (i.e., plate thickness) is 50 mm to 60 mm, and the height (i.e., plate length) is 250 mm to 400 mm. The material of the standing plate 2 can be the same as that of the main plate 1.

[0031] The bracket 3 is a triangular prism with a right-angled triangular base, and the two side surfaces forming the right angles of the triangular prism abut against the main plate 1 and the upright plate 2. FIG. 2 is a cross-sectional view schematically illustrating one side of the welded joint, showing the rectangular abutment surface 3a of the bracket 3 abutting against the main plate 1 and the rectangular bottom surface 7a of the weld metal damming member 7 placed on the main plate 1. In one example of the shape of the bracket 3 in the welded joint, the rectangular abutment surface 3a has a long side length of 200 mm to 400 mm and a short side length (Q, described below) of the rectangular abutment surface 3a of 10 mm to 30 mm. The material of the bracket 3 is preferably the same as that of the main plate 1 and the upright plate 2. The dimensions of the shape of an actual steel structure (actual structure) are selected as appropriate.

[0032] [Weld Bead] The weld bead formed primarily by fillet welding consists of a first weld bead 4, a second weld bead 5, and a third weld bead 6, in addition to the weld bead between the upright plate 2 and the main plate 1, in the order formed by the procedure of the welding method described above. The outline of the shape is shown in Figures 1 and 2. Figure 2 is a cross-sectional view of the external appearance of the joint in Figure 1 taken on the surface of one side of the main plate 1, showing the bracket 3 as a rectangular abutment surface 3a that abuts on the main plate 1 and the weld metal retaining member 7 as a rectangular bottom surface 7a. The shape of the weld bead in fillet welding of such a T-joint has a leg length (i.e., the width of the weld) in the range of 7 mm to 18 mm.

[0033] [First Weld Bead 4] The first weld bead 4 is a weld bead formed on one short side of the rectangular contact surface 3a (i.e., the short side not in contact with the standing plate 2).

[0034] The weld toe of the first weld bead 4 formed on the short side is the part where localized stress concentration occurs most and fatigue cracks are likely to occur. Furthermore, as will be described later, in the case of a floating offshore wind power generation facility to which the welding method of the present invention can be applied, fatigue cracks are more likely to occur due to the superposition of structural stress concentration of the wind power generation facility in addition to localized stress concentration.

[0035] In order to suppress the occurrence of such fatigue cracks, it is important that second weld beads 5 and third weld beads 6, which will be described below, extend onto main plate 1.

[0036] [Second Weld Bead 5 and Third Weld Bead 6] The second weld bead 5 is a weld bead formed along one long side of the rectangular abutment surface 3 a of the bracket 3, covering a part of the starting end or terminal end of the first weld bead 4 and extending further onto the main plate 1. The third weld bead 6 is a weld bead formed along the other long side of the rectangular abutment surface 3 a, covering a part of the starting end or terminal end of the first weld bead 4 and extending further onto the main plate 1.

[0037] In FIG. 2, the second weld bead 5 and the third weld bead 6 formed on this long side are formed symmetrically in the up-down direction, with the second weld bead 5 on the upper side of the rectangular contact surface 3a and the third weld bead 6 on the lower side, but they may also be arranged upside down.

[0038] As described above, in order to improve the fatigue strength of the welded joint, it is important to adjust the distance M between the extension portion 5 a of the second weld bead 5 and the extension portion 6 a of the third weld bead 6, which are the shapes of the extension portions, and the distance N between the short side of the rectangular abutment surface 3 a and the tip of the second weld bead 5 or the third weld bead 6.

[0039] [Shape of Extension Portion] The following description will be made based on FIGS. 1 and 2. As a preferred shape of the extension portion for improving the fatigue strength of the welded joint, first, the distance N between the tip of the second weld bead 5 or the tip of the third weld bead 6 and the short side of the rectangular abutment surface 3a of the bracket 3 is preferably 5.0 mm to 60.0 mm. Here, distance N refers to the shorter of the distance between the short side of the rectangular abutment surface 3a and the tip of the second weld bead 5 or the distance between the short side of the rectangular abutment surface 3a and the tip of the third weld bead 6. The above-mentioned "distance between the short side of the rectangular abutment surface 3a and the tip of the second weld bead 5 (or the third weld bead 6)" refers to the distance (i.e., the length) from the end of the rectangular abutment surface 3a to the tip of the second weld bead 5 (or the third weld bead 6). If this distance N is less than 5.0 mm, the length of the extension 5a of the second weld bead 5 or the extension 6a of the third weld bead 6 is too short, which is undesirable because fatigue cracks tend to propagate easily. Furthermore, if the gap N exceeds 60.0 mm, the welding time becomes long, which is undesirable. More preferably, the gap N is 5.0 mm to 30.0 mm. Still more preferably, the gap N is 10.0 mm or more and 20.0 mm or less.

[0040] Next, the distance M between the extension 5a of the second weld bead 5 and the extension 6a of the third weld bead 6 is preferably M≦10.0 mm and M≦Q, where Q is the length of the short side of the bracket's rectangular abutment surface 3a. If M>10.0 mm, the effect of reducing stress concentration begins to decrease, and the effect of improving fatigue strength is reduced, which is not preferable. By satisfying M≦Q, stress concentration at the weld bead toe can be reduced. Note that the distance M here refers to the clearance distance as shown in Figure 2. Note that the boxing welding of this application also includes cases where the second and third beads are straight.

[0041] Furthermore, in a cross section perpendicular to the longitudinal direction of the second weld bead 5 and / or the third weld bead 6 formed and extending onto the main plate 1, the shape of the region where the second weld bead 5 and / or the third weld bead 6 formed and extending onto the main plate 1 contacts the main plate 1 has an elevation angle (i.e., rise angle) θ from the main plate 1 of 60° or less. This is because, as shown in FIG. 5 , when the second weld bead and / or the third weld bead are formed using the damming member 7 of the present invention, the cross-sectional shape of the weld bead is formed so that the elevation angle θ from the rectangular bottom surface 7a of the damming member 7 follows a curve with an elevation angle θ of 60° or less. As a result, the elevation angle θ of the weld toe in the extension from the main plate 1 is 60° or less, thereby reducing or avoiding stress concentration in the extension. The elevation angle θ is preferably 50° or less. From the viewpoint of welding performance, the elevation angle θ is preferably 5° or more, more preferably 10° or more, and even more preferably 15° or more.

[0042] [Welded joints in floating offshore wind power generation facilities] The rotational welding method according to the present invention can also be applied to welded joints in floating offshore wind power generation facilities.

[0043] Here, we will provide an overview of floating offshore wind turbines. Wind power generation is a form of renewable energy, and offshore wind turbines installed on the sea are divided into bottom-fixed and floating types. Floating offshore wind turbines are used in waters 50 meters or deeper. A floating offshore wind turbine is constructed by floating a structure carrying a wind turbine on the sea, connected by chains or the like. The structure consists of a tower section that holds the wind turbine (wind power generator) aloft, and a floating body section that floats on the sea and carries the tower section. The tower section and the floating body section, which serves as the base, are joined by welding, and improving the fatigue life of the welded joints is an important issue.

[0044] Therefore, when the present invention is applied to such a floating offshore wind power generation facility, the present invention is implemented assuming that the main plate is a float member of the floating offshore wind power generation facility and the upright plate is a tower member of the floating offshore wind power generation facility. In other words, by using a weld metal retaining member to extend the weld bead onto the float member, a welded joint with improved fatigue strength can be obtained.

[0045] The present invention will be further described below with reference to examples. However, the following examples are merely intended to illustrate and explain the present invention in more detail, and are not intended to limit the scope of the present invention.

[0046] First, a 100 mm wide YP460 steel plate was used as the test material. The test material was fillet welded by gas-shielded arc welding using a shielding gas of 100% by volume of CO2 gas at a welding current of 230 A, a welding voltage of 30 V, and a welding speed of 34 cm / min to produce a welded joint. The welded joints were either conventionally fillet welded or had the weld bead extended using a weld metal blocking member. The conventionally welded joints referred to above were welded joints without an extension.

[0047] Fatigue tests of the welded joints were carried out by fixing the welded joints in a chuck, which is a fixture of the fatigue testing machine, and applying fatigue loads (specifically, tension and compression) to the joints. The applied stress range was 150 MPa in all cases. The number of cycles until fracture was counted as the fatigue life. The fatigue test results of these welded joints are shown in Table 1.

[0048]

[0049] Joints No. 1 and 2 are comparative examples, showing the test results for conventional fillet welding. Because the weld bead was not stretched, stress concentration occurred at the weld toe on the short side of the gusset, resulting in the number of fractures shown in Table 1.

[0050] Joints No. 3 and No. 4 are comparative examples, showing test results in which an extension bead was formed without using a weld metal blocking member. Because a weld metal blocking member was not used, the specified extension bead length and spacing could not be obtained, and the number of fractures was as shown in Table 1.

[0051] Joint No. 5 is an example of the present invention, and the length in the longitudinal direction of the rectangular bottom surface is N T is 3.1 mm, and the length of the short side of the rectangular base is M T The results are from a test in which a weld bead was extended using a weld metal blocking member with a diameter of 8.3 mm. The number of fractures was improved compared to the comparative example. T However, since this was outside the lower limit (5.0 mm) of the preferred range, the improvement in the number of breaks was slight.

[0052] Joint No. 6 is also an example of the present invention, and has the same length N T is 4.1 mm, and the length M T The results are from a test in which a weld bead was extended using a weld metal blocking member with a length N of 9.7 mm. The number of breaks was improved compared to the comparative example. T However, because this was outside the lower limit of the preferred range (5.0 mm), the improvement in the number of breaks was slight. Note that joint No. 18 also showed similar test results.

[0053] Joint No. 7 is an example of the present invention, and has a length of N T is 5.1 mm and the length M T The results are from a test in which a weld bead was extended using a weld metal blocking member with a length M of 10.6 mm. The number of breaks was improved compared to the comparative example. T However, since this was outside the upper limit (10.0 mm) of the preferred range, the improvement in the number of breaks was slight.

[0054] Joints No. 8 to 15 are examples of the present invention, and the length N T is 5.0mm to 60.0mm, and the length M T The results are from a test in which a weld bead was elongated using a weld metal blocking member with a length greater than 0.0 mm and less than 10.0 mm. T and the error in the length N of the stretched bead measured after the stretched bead is formed, and the length M TThe error in the distance M between the extension beads measured after the extension bead was formed and the distance M between the extension beads measured after the extension bead was formed was within 7.0%. The number of fractures was greater than that of conventional fillet welding. Similar test results were also obtained for joints No. 19 and 20. Note that the welded joints of these examples of the present invention were T、 N T ) was used as a guide for welding. The cross-sectional shapes of the front and rear sides of the damming members used were those shown in Figures 4(a) to 4(c) above. The damming members were made of ceramic.

[0055] From the above results, when the extension bead length N is less than 5.0 mm, the number of fractures is slightly improved compared to conventional fillet welding. Also, when the extension bead spacing M is greater than 10.0 mm, the number of fractures is slightly improved compared to conventional fillet welding. On the other hand, when the extension bead length N is 5.0 mm or more, the extension bead spacing M is 10.0 mm or less, and is equal to or less than the length Q of the short side of the rectangular abutment surface of the bracket, the number of fractures is greater than the number of fractures in conventional fillet welding.

[0056] From the above, it was confirmed that the fatigue strength of the welded joint can be further improved by controlling the spacing and length of the extended beads using the weld metal blocking member of the present invention.

[0057] 1 Main plate 2 Stand plate 3 Bracket 3a Rectangular abutment surface of the bracket that abuts against the steel plate (i.e., bracket rectangular abutment surface) 4 First weld bead 5 Second weld bead 5a Extension of the second weld bead (i.e., second extension bead) 6 Third weld bead 6a Extension of the third weld bead (i.e., third extension bead) 7 Weld metal damming member 7a Rectangular bottom surface of the weld metal damming member 7b Rectangular top surface of the weld metal damming member 7c Front side surface of the weld metal damming member 7d Rear side surface of the weld metal damming member 7e Side side surface of the weld metal damming member M Distance between the extension portion of the second weld bead and the extension portion of the third weld bead (unit: mm) N The shorter of the distances between the short side of the bracket rectangular abutment surface and the tip of the second weld bead or the third weld bead (unit: mm) Q Length of the short side of the bracket's rectangular contact surface (unit: mm) M T Length of the short side of the rectangular bottom of the weld metal damming member (i.e., bottom width) (unit: mm) N T Length of the rectangular bottom surface of the weld metal damming member in the longitudinal direction (unit: mm) H T Length (i.e., height) between the rectangular top surface and rectangular bottom surface of the weld metal damming member (unit: mm) X: Center line (in the longitudinal direction) of the rectangular bottom surface of the weld metal damming member Y: Center line of the plate thickness of the bracket θ: Elevation angle (i.e., rise angle) from the rectangular bottom surface of the weld metal damming member (unit: °)

Claims

1. A box welding method using a weld metal damming member for a main plate, a vertical plate, and a bracket, wherein the weld metal damming member has a rectangular bottom surface that abuts against the main plate, and a first weld bead is formed along the short side of the rectangular abutment surface where the bracket abuts against the main plate, and then the weld metal damming member is disposed on the main plate so as to be adjacent to the first weld bead, and then a second weld bead and a third weld bead are formed in sequence along the long side of the rectangular abutment surface to cover the end of the first weld bead, and then the second and third weld beads are formed by extending them onto the main plate along the weld metal damming member.

2. The box welding method according to claim 1, wherein the shorter distance N between the short side of the rectangular abutting surface and the tip of the second weld bead or the third weld bead is 5.0 mm to 60.0 mm, and when the distance between the extension of the second weld bead and the extension of the third weld bead is M and the length of the short side of the rectangular abutting surface is Q, M≦10.0 mm and M≦Q.

3. The shape of the weld metal damming member is such that the length N of the rectangular bottom surface in the longitudinal direction T The shape of the front side and rear side, which are cross sections of the weld metal blocking member perpendicular to the longitudinal direction, is an inverted trapezoid, and the bottom width M, which is the length of the short side of the rectangular bottom, is T The box welding method according to claim 1 or 2, wherein the welding distance is greater than 0.0 mm and is equal to or less than 10.0 mm.

4. A box welding method according to any one of claims 1 to 3, wherein the shape of the area where the lateral side surface of the weld metal damming member comes into contact with the weld bead in a cross section perpendicular to the longitudinal direction of the weld metal damming member is a curve or a line with an elevation angle θ from the rectangular bottom surface of 60° or less.

5. A box welding method according to any one of claims 1 to 4, wherein the weld metal blocking member is made of copper or ceramics.

6. A box welding method according to any one of claims 1 to 5, wherein the main plate is a floating body member of a floating offshore wind power generation facility, and the standing plate is a tower member of the floating offshore wind power generation facility.

7. A boxing welded joint comprising a main plate, a vertical plate, and a bracket, the boxing welded joint having a first weld bead, a second weld bead, and a third weld bead, the first weld bead being formed along one short side of a rectangular contact surface where the bracket contacts the main plate, the second weld bead and the third weld bead being formed along each long side of the rectangular contact surface and extending onto the main plate to cover a part of the starting end or terminal end of the first weld bead, and the shape of the area where the second weld bead and / or the third weld bead extending onto the main plate and the main plate come into contact in a cross section perpendicular to the longitudinal direction of the second weld bead and / or the third weld bead formed and extended onto the main plate has an elevation angle θ of 60° or less from the main plate.

8. The boxing weld joint according to claim 7, wherein the shorter distance N between the short side of the rectangular abutment surface and the tip of the second weld bead or the third weld bead is 5.0 mm to 60.0 mm, and when the distance between the extension portion of the second weld bead and the extension portion of the third weld bead is M and the length of the short side of the rectangular abutment surface is Q, M≦10.0 mm and M≦Q.

9. A boxing welded joint according to claim 7 or 8, wherein the main plate is a floating body member of a floating offshore wind power generation facility, and the standing plate is a tower member of the floating offshore wind power generation facility.

Images