Rotation welding method and rotation welding joint

Abstract

The present invention provides a box welding method and box weld joint for a steel structure having a bracket. The box welding method of the present invention involves welding between a vertical plate (2) and a main plate (1), then forming a first weld bead (4) along the short side of the rectangular abutment surface (3a) where the bracket abuts against the main plate, then arranging a weld metal retaining member (7) on the main plate (1) so that the weld bead is adjacent to the first weld bead, and then forming a second weld bead (5) and a third weld bead (6) in order along the long side of the rectangular abutment surface (3a) to cover the end of the first weld bead, and then extending the weld bead onto the main plate (1) so that the second weld bead (5) and the third weld bead (6) are formed along the long side of the rectangular abutment surface (3a) to cover the end of the first weld bead.

Description

[Technical Field]

[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. [Background technology]

[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 meters or deeper.However, because floating offshore wind turbines are exposed to external forces such as waves, there is an issue of reduced fatigue strength at the weld toes of welded joints in floating offshore wind turbines.

[0003] For this reason, various technologies 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, it is possible to obtain a boxing welded joint that can inexpensively and stably improve fatigue strength. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-158380 A [Patent Document 2] Japanese Patent Application Publication No. 2020-055020 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[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, we fabricated a welded joint with a bracket, using a weld metal damming member 7 (hereinafter simply referred to as the "damming member"), a welding auxiliary component that can be removed after welding, as shown in Figure 3 as a guide during welding. For comparison, we also fabricated a welded joint with an extended bead, which was conventionally welded by turning the weld along the bracket. The extended bead spacing M and extended bead length N of the welded joint with the extended weld bead 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 improved fatigue strength of the welded joint with the extended weld bead. As a result, we found that the welded joint with the extended weld bead using the damming member had the extended bead shape and dimensions formed accurately according to the target dimensions, and the fatigue strength of the welded joint was consistently improved.

[0010] The present invention was completed based on these findings and further investigations, and the gist of the present invention is as follows. [1] A turn welding method using a weld metal blocking member for a main plate, a vertical plate, and a bracket, the weld metal damming member has a rectangular bottom surface, and the rectangular bottom surface abuts against the main plate, a first weld bead is formed along a short side of a rectangular contact surface of the bracket that contacts the main plate; Next, the weld metal retaining member is disposed on the main plate so as to be adjacent to the first weld bead; Next, a second weld bead and a third weld bead are sequentially formed along the long sides of the rectangular abutment surface to cover the end of the first weld bead, and further extended onto the main plate so as to follow the weld metal retaining member. Turn welding method. [2] 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; 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. The turn welding method described in [1] above. [3] The shape of the weld metal blocking member is such that the length N of the rectangular bottom surface in the longitudinal direction T is 5.0mm to 60.0mm, The shape of the front side and rear side of the cross section perpendicular to the longitudinal direction of the weld metal blocking member is an inverted trapezoid, and the length of the short side of the rectangular bottom is a bottom width M T is more than 0.0 mm and 10.0 mm or less, The box welding method according to [1] or [2] above. [4] In a cross section perpendicular to the longitudinal direction of the weld metal damming member, the shape of the region where the lateral side surface of the weld metal damming member contacts the weld bead is a curve or a line with an elevation angle θ from the rectangular bottom surface of 60° or less. The box welding method according to any one of the above [1] to [3]. [5] The weld metal blocking member is made of copper or ceramics. The box welding method according to any one of [1] to [4] above. [6] The main plate is a floating 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. The box welding method according to any one of [1] to [5] above. [7] A box weld joint having a main plate, a vertical plate, and a bracket, the box weld 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 a rectangular abutment surface where the bracket abuts against the main plate, the second weld bead and the third weld bead are formed along respective long sides of the rectangular abutment surface, and are formed to cover a part of a start end or a terminal end of the first weld bead and extend onto the main plate, In a cross section perpendicular to the longitudinal direction of the second weld bead and / or the third weld bead formed by extending onto the main plate, the shape of a region where the second weld bead and / or the third weld bead formed by extending onto the main plate and the main plate contact each other has an elevation angle θ from the main plate of 60° or less. Turn welded joint. [8] 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; 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. The box weld joint according to [7] above. [9] The main plate is a floating 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. The boxing weld joint according to [7] or [8]. [Effects of the Invention]

[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 an industrially significant advantage. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view that schematically shows the appearance of an example of a box welded joint obtained by the box welding method according to the present invention. [Figure 2] FIG. 2 is a plan view schematically showing one side of an example of a boxing welded joint obtained by the boxing welding method according to the present invention. [Figure 3] FIG. 3 is a perspective view that schematically shows an example of a weld metal blocking member used in the box welding method according to the present invention. [Figure 4] 4(a) to 4(c) are cross-sectional views that schematically show different cross-sectional shapes (three examples) of the weld metal blocking member used in the box welding method according to the present invention. [Figure 5]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). [Figure 6] FIG. 6 is a plan view schematically showing an example of the procedure of the box welding method according to the present invention. DETAILED DESCRIPTION OF THE 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] [Welded metal blocking member 7] First, the weld metal blocking 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 The length M of the short side is preferably more than 0.0 mm and 10.0 mm or less. T is preferably set and prepared for each welding operation so as to match the target distance M between extension 5a of second weld bead 5 and extension 6a of third weld bead 6 described above. The length of this short side is M 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 7c, the opposite side surface is a rear side surface 7d, and the two side surfaces along the longitudinal direction are lateral side surfaces 7e. It is preferable that the cross-sectional shape perpendicular to the longitudinal direction (i.e., the shapes of the front side surface 7c and the rear side surface 7d) is a substantially inverted trapezoid.

[0019] Examples of the cross-sectional shape (three examples here) are shown in FIG. 4. As shown in FIGS. 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 FIG. 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 FIG. 5. This reduces or avoids stress concentration in the extension. This elevation angle θ is more preferably 10° or more, and more preferably 50° or less. Here, the cross-sectional shapes shown in Figures 4(a) to 4(c) are referred to as inverted trapezoids. This inverted trapezoid includes both a shape in which the lower region of each side surface 7e (i.e., the region on the rectangular bottom surface 7a side) is curved, as in Figures 4(a) and 4(b), and both side surfaces 7e flared upward, as in Figure 4(a), and a shape in which both side surfaces 7e do not flared upward, as in Figure 4(b). It also includes a shape in which the lower region of each side surface 7e is linear, and both side surfaces 7e flared upward, as in Figure 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 based on FIG. 5. The shape of the damming member 7 shown in FIG. 5 is the same as the shape shown in FIGS. 4(a) and 4(b), i.e., the lower region of the lateral side surface 7e is curved, and in FIG. 4(a) the lateral side surfaces 7e on both sides are flared upward, while in FIG. 4(b) they are not flared. FIG. 5(a) is a cross-sectional view of the damming member 7 placed on the main plate 1, and the extension 5a of the second weld bead 5 and the extension 6a of the third weld bead 6 are formed along the lateral side surfaces 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 damming 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 materials include copper and ceramics. Note that examples of ceramics include those containing silica, zirconia, alumina, etc. as their main components.

[0023] [Rotation 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. The 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 members are subjected to the welding process described below. For ease of understanding, Fig. 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 Figs. 1 and 2). Then, the bracket 3 is turn-welded in the following order (a) to (e). This results in a weld bead in the welded joint of the present invention that has the properties described below.

[0026] (a) A first weld bead 4 is formed along one short side (in this example, the side away from the vertical plate 2) of the rectangular contact surface 3a where the bracket 3 contacts the main plate 1 (see (a) in Figure 6). The welding method for forming the weld bead is preferably gas-shielded arc welding, the conditions for which will be described later. (b) Weld metal damming member 7 is disposed on main plate 1 so that center line X of rectangular bottom surface 7a of weld metal damming member 7 is aligned with plate thickness center line Y of bracket 3 and is close to first weld bead 4 formed in (a) above. Here, aligning 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 then 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 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 ratio of the length N of the long side of the rectangular bottom surface 7a of the damming member 7 to the length N of the rectangular bottom surface 7a of the damming member 7. T By making the length shorter than the predetermined length, the shape of the extension portion can be accurately maintained. (d) Similarly, a 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 a third weld bead 6. This results in a uniform bead shape. Here, "covering the end of the first weld bead 4" means that the starting or ending end of the first weld bead 4 is at least partially melted with the third weld bead 6. Furthermore, the length N of the extended portion 6a of the third weld bead 6 is determined by multiplying the length N of the long side of the rectangular bottom surface 7a of the damming member 7 by the length N. T By making the length shorter than the predetermined length, the shape of the extension portion can be accurately maintained. (e) Next, the weld metal retaining member 7 is removed to form a welded joint having the desired shape of the extended bead. Although FIG. 6 mainly shows the area around the bracket on one side of the welded joint, it is preferable to similarly form three weld beads around the bracket on the other side (i.e., the opposite side).

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

[0028] [Steel plate, vertical plate, and bracket box welded joints] Next, we will explain a welded joint obtained by the box welding method according to the present invention. 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 the vertical plate 2 is sandwiched from both sides by two brackets 3. 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 that 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 materials of the standing plate 2 can be the same as those of the main plate 1.

[0031] Bracket 3 is a triangular prism with a right-angled triangular base, and two side surfaces forming a right angle of the triangular prism abut against main plate 1 and upright plate 2. FIG. 2 is a cross-sectional view schematically showing one side of the welded joint, showing rectangular abutment surface 3a of bracket 3 abutting on main plate 1 and rectangular bottom surface 7a of welded metal damming member 7 placed on main plate 1. In one example of the shape of 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 later) of the rectangular abutment surface 3a of 10 mm to 30 mm. It is also preferable that the material of bracket 3 is the same as that of main plate 1 and upright plate 2. The specifications 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 weld bead shape is shown in Figures 1 and 2. Figure 2 is a cross-sectional view of the joint shown 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] First weld bead 4 is a weld bead formed on one short side of rectangular contact surface 3a (that is, the short side not in contact with 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 bead 5 and third weld bead 6, which will be described below, extend onto main plate 1.

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

[0037] In Figure 2, the second weld bead 5 and the third weld bead 6 formed on this long side are formed symmetrically from top to bottom, with the second weld bead 5 on the upper side of rectangular abutment surface 3a and the third weld bead 6 on the lower side, but they may also be arranged upside down.

[0038] As mentioned above, in order to improve the fatigue strength of the welded joint, it is important to adjust the distance M between the extension 5a of the second weld bead 5 and the extension 6a of the third weld bead 6, which are the shapes of the extensions, and the distance N 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.

[0039] [Extension part shape] The following description will be given based on FIGS. As a preferred shape of the extension for improving the fatigue strength of the welded joint, first, the distance N between the tip of second weld bead 5 or the tip of third weld bead 6 and the short side of rectangular abutment surface 3a of bracket 3 is preferably 5.0 mm to 60.0 mm. Here, distance N refers to the shorter distance between the short side of rectangular abutment surface 3a and the tip of second weld bead 5 or the tip of third weld bead 6. The above "distance between the short side of rectangular abutment surface 3a and the tip of second weld bead 5 (or third weld bead 6)" refers to the distance (i.e., the length) from the end of rectangular abutment surface 3a to the tip of second weld bead 5 (or third weld bead 6). If this interval 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 will be too short, making fatigue cracks more likely to propagate, which is undesirable. Furthermore, if the interval N exceeds 60.0 mm, the welding time will be undesirably long. More preferably, the interval N is 5.0 mm to 30.0 mm. Even more preferably, the interval 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 toes 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 above, 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 that is 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 turbines] The swivel welding method according to the present invention can also be applied to welded joints in floating offshore wind power generation facilities.

[0043] Here, an overview of floating offshore wind power generation facilities will be described. 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, with floating offshore wind turbines being used in waters 50 meters or deeper. A floating offshore wind turbine is constructed by attaching a structure carrying the wind turbine to the sea with chains or other means, allowing it to float. The structure consists of a tower section that holds the wind turbine (wind turbine generator) aloft, and a floating section that floats on the sea with the tower section on it. The tower section and the floating section that serves as the base are joined by welding, and improving the fatigue life of this welded joint 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. [Example]

[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 sheet was used as the test material. The test material was fillet welded by gas-shielded arc welding using a shielding gas of 100% CO2 gas at a welding current of 230 A, welding voltage of 30 V, and 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 retaining member. The conventionally welded joints mentioned above refer to welded joints without an extended portion.

[0047] Fatigue tests of welded joints were conducted by fixing the welded joint in a chuck, which is a fixture of the fatigue testing machine, and applying fatigue loads (specifically, tension and compression) to the joint. 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] [Table 1]

[0049] Joints Nos. 1 and 2 are comparative examples, and show test results obtained when conventional fillet welding was performed. 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 Nos. 3 and 4 are comparative examples, showing the test results when 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 longitudinal length of the rectangular base 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] Similarly, joint No. 6 is an example of the present invention, and the length N T is 4.1 mm, and the length M T The test results show that the number of fractures is 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. In addition, similar test results were obtained for fitting No. 18.

[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 fractures 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~60.0mm, length M T The results are from a test in which the weld bead was extended using a weld metal blocking member with a length of more 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 T The error in the distance M between the extension beads measured after the extension bead was formed was within 7.0%. The number of fractures was also greater than that of conventional fillet welding. In addition, fittings No. 19 and 20 also showed similar test results. In addition, the welded joints of these examples of the present invention have the same length (M T、 N T ) was used as a guide for welding. The cross-sectional shapes of the front and rear side surfaces of the damming members used were those shown in Figs. 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 less than the length Q of the short side of the bracket's rectangular abutment surface, the number of fractures is greater than the number of fractures with 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. [Explanation of symbols]

[0057] 1 Main plate 2 Standing board 3 Bracket 3a Rectangular contact surface that contacts the steel plate of the bracket (i.e., bracket rectangular contact surface) 4 First weld bead 5 Second weld bead 5a: Extension of 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 Welded metal blocking member 7a Rectangular bottom surface of weld metal damming member 7b Rectangular top surface of weld metal damming member 7c Front side of welded metal retaining member 7d Rear side of welded metal retaining member 7e Lateral surface of welded metal damming member M: Distance between the extension of the second weld bead and the extension of the third weld bead (unit: mm) N The shorter distance between the short side of the bracket's rectangular contact surface and the tip of the second or third weld bead (unit: mm) Q Length of the short side of the bracket's rectangular contact surface (unit: mm) M TThe length of the short side of the rectangular bottom of the weld metal damming member (i.e., the bottom width) (unit: mm) N T The longitudinal length of the rectangular bottom surface of the weld metal damming member (unit: mm) H T The length (i.e., height) between the rectangular top and bottom surfaces of the weld metal retaining member (unit: mm) X: Center line (longitudinal direction) of the rectangular bottom surface of the weld metal retaining member Y bracket thickness centerline θ Elevation angle (i.e., rise angle) from the rectangular base of the weld metal retaining member (unit: °)

Claims

1. A turn welding method using a weld metal blocking member for a main plate, a vertical plate, and a bracket, the weld metal damming member has a rectangular bottom surface, and the rectangular bottom surface abuts against the main plate, a first weld bead is formed along a short side of a rectangular contact surface of the bracket that contacts the main plate; Next, the weld metal retaining member is disposed on the main plate so as to be adjacent to the first weld bead; Next, a second weld bead and a third weld bead are sequentially formed along the long sides of the rectangular abutment surface to cover the end of the first weld bead, and further extended onto the main plate so as to follow the weld metal retaining member. Turn welding method.

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

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 T is 5.0 mm to 60.0 mm, The shape of the front side and rear side of the cross section perpendicular to the longitudinal direction of the weld metal blocking member is an inverted trapezoid, and the length of the short side of the rectangular bottom is a bottom width M T is more than 0.0 mm and 10.0 mm or less, The box welding method according to claim 1 .

4. The shape of the welded metal damming member is such that the longitudinal length N T of the rectangular bottom surface is 5.0 mm to 60.0 mm, The shape of the front side surface and the rear side surface, which are cross sections perpendicular to the longitudinal direction of the weld metal damming member, is an inverted trapezoid, and a bottom width M T , which is the length of the short side of the rectangular bottom surface, is greater than 0.0 mm and is not greater than 10.0 mm. The box welding method according to claim 2.

5. In a cross section perpendicular to the longitudinal direction of the weld metal damming member, the shape of a region where a lateral side surface of the weld metal damming member contacts the weld bead is a curve or a straight line with an elevation angle θ from the rectangular bottom surface of 60° or less. The box welding method according to any one of claims 1 to 4.

6. The weld metal blocking member is made of copper or ceramics. The box welding method according to any one of claims 1 to 4.

7. The weld metal blocking member is made of copper or ceramics. The box welding method according to claim 5.

8. The main plate is a floating 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. The box welding method according to any one of claims 1 to 4.

9. The main plate is a floating 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. The box welding method according to claim 5.

10. The main plate is a floating 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. The box welding method according to claim 6.

11. The main plate is a floating 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. The box welding method according to claim 7.

12. A box weld joint having a main plate, a vertical plate, and a bracket, the boxing weld 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 a rectangular abutment surface where the bracket abuts against the main plate, the second weld bead and the third weld bead are formed along respective long sides of the rectangular abutment surface, and are formed to cover a part of a start end portion or a terminal end portion of the first weld bead and extend onto the main plate; In a cross section perpendicular to the longitudinal direction of the second weld bead and / or the third weld bead formed by extending onto the main plate, the shape of a region where the second weld bead and / or the third weld bead formed by extending onto the main plate and the main plate contact each other has an elevation angle θ from the main plate of 60° or less. Turn welded joint.

13. a shorter distance N between a short side of the rectangular abutment surface and a tip of the second weld bead or the third weld bead is 5.0 mm to 60.0 mm; When a distance between the extension portion of the second weld bead and the extension portion of the third weld bead is M and a length of a short side of the rectangular abutment surface is Q, M≦10.0 mm and M≦Q.

13. The box weld joint of claim 12.

14. The main plate is a floating 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.

14. A boxing weld joint according to claim 12 or 13.

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