Cylinder type structure and manufacturing method of the same

Abstract

To provide a cylinder type structure for a window power generation device which can be easily manufactured, and to provide a manufacturing method of the cylinder type structure.SOLUTION: A cylinder type structure according to one embodiment of the disclosure is used for a window power generation device and includes: a plurality of cylindrical body parts arranged in a longitudinal direction of the cylinder type structure; and a circumferential joint which is a welding joint which extends in a circumferential direction of the cylinder type structure and joins ends of the body parts. The body part has: a plurality of steel plates disposed in a cylindrical form; and a longitudinal joint which is a welding joint which extends the longitudinal direction of the cylinder type structure and joins ends of the steel plates. The longitudinal joint and the circumferential joints form a substantially cross shape at the intersection.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cylindrical structure for a wind turbine generator and a method for manufacturing the cylindrical structure. [Background technology]

[0002] In order to increase the power output of wind power generation equipment, wind turbines, as well as the towers and foundations that support them, are becoming larger. Generally, cylindrical structures made of cylindrical pipes are widely used for the tubular structures that make up the towers and foundations. In the future, tubular structures for wind power generation equipment are expected to become larger, with outer diameters exceeding 10 meters.

[0003] As cylindrical structures become larger, their strength and rigidity must be increased. Therefore, the outer diameter and thickness of the cylindrical structures must also be increased. Various techniques for manufacturing such cylindrical structures have been investigated.

[0004] For example, Patent Document 1 discloses a tower for a wind turbine, the tower having an exterior and an interior, the tower being at least partially constructed of prefabricated metal wall parts, each wall part comprising a substantially rectangular portion having a surface facing outward in the exterior direction of the tower and a surface facing inward in the interior direction of the tower, the portions having a top edge, a bottom edge, a first side edge and a second side edge, the first side edge having a first flange along at least a portion of the length of the first side edge, and the second side edge having a second flange along at least a portion of the length of the second side edge, the first flange of at least one prefabricated metal wall part being attached to the second flange of an adjacent prefabricated metal wall part in a vertical zigzag manner by fastening means so as to connect the prefabricated metal wall parts in a vertical zigzag manner.

[0005] Patent Document 2 discloses a pillar-shaped float that constitutes a floating offshore wind power generation facility, characterized in that it comprises a hollow pillar-shaped pillar body, which is formed by connecting a plurality of facing members with flat plate surfaces in the circumferential direction and has a polygonal cross-sectional shape.

[0006] Patent Document 3 describes a vertical narrow gap gas shielded arc welding method for joining two thick steel sheets each having a plate thickness of 40 mm or more by single layer welding or multi-layer welding using weaving, with a groove angle of 25° or less and a groove gap of 20 mm or less. In the first layer welding, the angle of the welding torch is set to 25° or more and 75° or less with respect to the horizontal, the welding heat input is set to 30 kJ / cm or more and 300 kJ / cm or less, the weaving depth in the plate thickness direction is set to 15 mm or more and 63 mm or less, and the weld bead width in the first layer welding is set to W. In this case, a vertical narrow groove gas-shielded arc welding method is disclosed in which the maximum weaving width in the plate thickness direction and in the direction perpendicular to the weld line is set to be between (W-6) mm and W mm, the welding torch is weaved, the joint depth in the first layer welding is set to be between 20 mm and 65 mm, and during the final layer welding, a cooling plate that can slide in an upward direction is pressed against the thick steel material from the welding torch side as a surface contact material for the groove of the thick steel material, and welding is performed while moving the cooling plate upward in accordance with the upward movement of the welding torch.

[0007] Patent Document 4 discloses a sliding copper welding pad that is disposed opposite a groove between a pair of base materials to form a molten slag bath or a molten metal bath and slides along the groove, the sliding copper welding pad comprising a pad main body and at least one follower member that is provided on at least one side of the pad main body and is movable so that an end portion facing the base material comes into contact with or comes close to the base material.

[0008] Patent Document 5 discloses a sliding copper welding pad that is disposed opposite a groove between a pair of base materials to form a molten slag bath or a molten metal bath, and slides along the groove. The sliding copper welding pad comprises a pad main body and at least one rotating member that is rotatable relative to the pad main body, and the rotating member has a contact surface that can come into contact with the surface of the base material, and the contact surface is rotatable relative to the pad main body so as to be in surface contact with the surface of the base material.

[0009] Patent Document 6 discloses an electroslag welding method for welding members to be welded with a predetermined groove gap, characterized in that steel plates are placed at both ends between opposing surfaces of the members to be welded to maintain the predetermined groove gap, and the members to be welded are electroslag welded while melting the steel plates. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 4708365 [Patent Document 2] Japanese Patent Publication No. 2022-1474 [Patent Document 3] Patent No. 6119949 [Patent Document 4] Japanese Patent Publication No. 2022-102788 [Patent Document 5] Patent Publication No. 2021-53687 [Patent Document 6] Japanese Patent Application Publication No. 2-75483 Summary of the Invention [Problem to be solved by the invention]

[0011] The tower disclosed in Patent Document 1 is obtained by bending steel plates and welding the resulting curved plates together horizontally and vertically. However, there are cases where equipment for bending steel plates cannot be installed at the tower manufacturing site. In such cases, the curved plates must be transported, which reduces the tower manufacturing efficiency. Furthermore, considering the capacity of the bending equipment, the technology disclosed in Patent Document 1 has difficulty in dealing with towers that are larger and thicker.

[0012] The pillar-shaped floating structure disclosed in Patent Document 2 does not have a cylindrical shape. When manufacturing the pillar-shaped floating structure disclosed in Patent Document 2, it is not necessary to bend the steel plates. However, as described in Figures 7 and 10 of Patent Document 2 under the heading "Attachment of Subassemblies," the technology of Patent Document 2 is premised on the use of thin-walled materials as the main structural material and the addition of reinforcing materials. In Patent Document 2, when reinforcing materials are omitted in order to strengthen the tower and improve the efficiency of construction work, thick materials exceeding 50 mm must be used. As shown in Figure 1 of Patent Document 2, the so-called "jointed joint" in which the connection positions (i.e., weld lines) of adjacent segments in the column axis direction are continuous (connected) should be avoided, and a so-called "staggered arrangement" in which the weld lines of adjacent segments in the column axis direction are discontinuous (shifted) should be used. Therefore, when manufacturing the pillar-shaped floating structure disclosed in Patent Document 2, it is also necessary to bend the steel plates at a predetermined bending angle. Therefore, like Patent Document 1, the technology of Patent Document 2 also has issues related to the bending process.

[0013] The techniques disclosed in Patent Documents 3 to 6 disclose welding methods suitable for manufacturing cylindrical structures for wind turbine generators. However, Patent Documents 3 to 6 do not particularly consider the configuration of the cylindrical structures.

[0014] In view of the above circumstances, an object of the present disclosure is to provide a cylindrical structure for a wind turbine generator that is easy to manufacture, and a method for manufacturing the same. [Means for solving the problem]

[0015] The gist of the present disclosure is as follows.

[0016] (1) A cylindrical structure according to one aspect of the present disclosure is a cylindrical structure for a wind power generation device, comprising a plurality of cylindrical body sections arranged in the longitudinal direction of the cylindrical structure, and circumferential joints which are welded joints extending circumferentially of the cylindrical structure and joining the ends of the plurality of body sections, wherein the body sections have a plurality of steel plates arranged in a cylindrical shape, and longitudinal joints which are welded joints extending in the longitudinal direction of the cylindrical structure and joining the ends of the steel plates, and the longitudinal joints and the circumferential joints form an approximately cross shape at their intersection. (2) Preferably, in the cylindrical structure described in (1) above, the cross section of the body perpendicular to the longitudinal direction has a circular shape, and the plurality of steel plates have a shape that is bent into a substantially arc shape. (3) Preferably, in the cylindrical structure described in (1) above, the cross section of the trunk portion perpendicular to the longitudinal direction has a polygonal shape, the plurality of steel plates are flat plates, and in the cross section of the trunk portion, the steel plates are arranged on the sides of the polygon, and the longitudinal joints are arranged at the vertices of the polygon. (4) Preferably, in the cylindrical structure described in any one of (1) to (3) above, the longitudinal joint and the circumferential joint are consumable electrode gas-shielded arc welding (GMAW) joints, shielded metal arc welding (SMAW) joints, submerged arc welding (SAW) joints, electrogas arc welding (EGW) joints, or electroslag welding (ESW) joints. (5) Preferably, in the cylindrical structure described in (4) above, one or more of the plurality of body portions has the longitudinal joint that is the SAW joint, and one or both of the longitudinal joint that is the EGW joint and the longitudinal joint that is the ESW joint. (6) Preferably, in the cylindrical structure described in (4) above, the longitudinal joint is the SAW joint, and the circumferential joint is the GMAW joint or the SMAW joint. (7) Preferably, in the cylindrical structure described in (4) above, the longitudinal joint is the EGW joint or the ESW joint, and the circumferential joint is the GMAW joint or the SMAW joint. (8) Preferably, in the cylindrical structure according to any one of (1) to (7) above, the thickness of the steel plate is 50 mm or more. (9) Preferably, in the cylindrical structure described in any one of (1) to (8) above, the CTOD value at the design temperature at the location where the longitudinal joint and the circumferential joint intersect in a substantially cross shape is 0.1 mm or more.

[0017] (10) A method for manufacturing a cylindrical structure according to another aspect of the present disclosure is a method for manufacturing a cylindrical structure as described in (1) to (9) above, and includes the steps of longitudinally welding a plurality of steel plates at their ends to form a cylindrical body having longitudinal joints, aligning the longitudinal joints of adjacent body sections in approximately the same line, and circumferentially welding the ends of the aligned body sections to form a cylindrical structure. (11) Preferably, the manufacturing method of a cylindrical structure described in (10) above further includes a step of bending the plurality of steel plates into an approximately arc shape before the longitudinal welding, and the longitudinal welding makes the cross section of the body perpendicular to the longitudinal direction circular. (12) Preferably, in the manufacturing method of a cylindrical structure described in (10) above, the plurality of steel plates are flat plates, and in the longitudinal welding, the cross section of the body is polygonal, the steel plates are arranged on the sides of the polygon, and the longitudinal joints are arranged at the vertices of the polygon. (13) Preferably, in the method for manufacturing a cylindrical structure according to any one of (10) to (12) above, one or both of the longitudinal welding and the circumferential welding is performed by one or more methods selected from the group consisting of consumable electrode gas-shielded arc welding (GMAW), shielded metal arc welding (SMAW), submerged arc welding (SAW), electrogas arc welding (EGW), and electroslag welding (ESW). (14) Preferably, in the manufacturing method of a cylindrical structure described in (13) above, when forming one or more of the body portions, first, some of the plurality of steel plates are longitudinally welded to form a plurality of components of the body portion, and then ends of the plurality of components are longitudinally welded to form the body portion, the longitudinal welding of the steel plates is performed by submerged arc welding (SAW), and the longitudinal welding of the components is performed by one or both of electrogas arc welding (EGW) and electroslag welding (ESW). (15) Preferably, in the manufacturing method of a cylindrical structure described in (13) above, the longitudinal welding is performed by submerged arc welding (SAW), and the circumferential welding is performed by consumable electrode gas shielded arc welding (GMAW) or shielded metal arc welding (SMAW). (16) Preferably, in the manufacturing method of a cylindrical structure described in (13) above, the longitudinal welding is performed by electrogas arc welding (EGW) or electroslag welding (ESW), and the circumferential welding is performed by consumable electrode gas shielded arc welding (GMAW) or shielded metal arc welding (SMAW). (17) Preferably, in the method for manufacturing a cylindrical structure according to any one of the above (10) to (16), the thickness of the steel plate is set to 50 mm or more. [Effects of the Invention]

[0018] According to the present disclosure, it is possible to provide a cylindrical structure for a wind turbine generator that is easy to manufacture, and a method for manufacturing the same. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a perspective view of an example of a cylindrical structure. [Figure 2] FIG. 10 is an enlarged view of the intersection of the circumferential joint and the longitudinal joint, which has a generally cross shape. [Figure 3] FIG. 10 is a close-up view of the intersection of the circumferential joint and the longitudinal joint where the butt shift structure is applied. [Figure 4] FIG. 1 is a schematic diagram of longitudinal welding S1 performed in a vertical position with the steel plates standing vertically. [Figure 5]FIG. 1 is a schematic diagram of longitudinal welding S1 performed in a flat position with the steel plate lying on a jig. [Figure 6] FIG. 10 is a schematic diagram of longitudinal joint alignment S2. [Figure 7] This is a schematic diagram of girth welding S3 performed in a horizontal position with the body section held upright. [Figure 8] This is a schematic diagram of circumferential welding S3 performed in a downward position with the body portion laid down. [Figure 9] 1A and 1B are plan and cross-sectional views showing the specimen and the locations where the CTOD test pieces were taken. DETAILED DESCRIPTION OF THE INVENTION

[0020] A cylindrical structure 1 for a wind power generation device according to one aspect of the present disclosure comprises a plurality of cylindrical body sections 11 arranged in the longitudinal direction of the cylindrical structure 1, and circumferential joints 12 which are welded joints joining the ends of the plurality of body sections 11, the body sections 11 having a plurality of steel plates 111 arranged in a cylindrical shape and longitudinal joints 112 which extend in the longitudinal direction of the cylindrical structure 1 and are welded joints joining the ends of the steel plates 111, the longitudinal joints 112 and the circumferential joints 12 forming a substantially cross shape. Details of the cylindrical structure 1 according to this embodiment will be described below.

[0021] 1 is a perspective view schematically showing a part of a cylindrical structure 1 for a wind turbine generator according to this embodiment. Specific examples of the cylindrical structure 1 according to this embodiment include a tower for fixing a rotor made of blades, and a foundation structure for supporting the tower from below.

[0022] The cylindrical structure 1 has a hollow cylindrical shape as shown in Fig. 1. Hereinafter, the longitudinal direction of the cylindrical structure 1 will be simply referred to as the longitudinal direction. Also, the direction along the outer periphery of the cylindrical structure 1 will be referred to as the circumferential direction.

[0023] (Body 11) The cylindrical structure 1 has a plurality of cylindrical body sections 11. The body sections 11 are arranged in the longitudinal direction of the cylindrical structure 1. The central axes of the body sections 11 are approximately collinear. A cross section of the body sections 11 perpendicular to the longitudinal direction has a polygonal or circular shape. The cross section of the body section 11 of the cylindrical structure illustrated in FIG. 1 has a regular octagonal shape. The number of sides and the number of corners of the cross section perpendicular to the longitudinal direction of the body section 11 are designed appropriately depending on the size of the body section 11, etc.

[0024] The trunk 11 has a plurality of steel plates 111 arranged in a cylindrical shape. The ends of adjacent steel plates 111 are joined by longitudinal joints 112. The longitudinal joints 112 are welded joints that extend along the longitudinal direction of the cylindrical structure 1. The welded joints are joined parts that are joined together by welding, and have weld metal and a heat-affected zone formed around the weld metal. The weld metal is also called a weld bead.

[0025] The welded joint constituting the longitudinal joint 112 of the cylindrical structure 1 according to this embodiment is a butt joint or a corner joint. The term "butt joint" is defined in JIS Z 3001-1:2018 "Welding Terminology - Part 1: General" as "a joint in which parts placed on the same plane face each other at an angle of 135°≦α≦180°." The term "corner joint" is defined in JIS Z 3001-1:2018 "Welding Terminology - Part 1: General" as "a joint in which the end faces of two parts are joined at an angle of 30°<α<135°." α is the minor angle formed by the surfaces of the two parts of the butt joint in a cross section perpendicular to the weld line.

[0026] When the cylindrical structure 1 is a rectangular cylindrical structure as exemplified in Fig. 1, the steel plate 111 is a flat plate. In a cross section of the body 11 perpendicular to the longitudinal direction, the steel plate 111 forms the sides of a polygon, and the longitudinal joints 112 form the vertices of the polygon. When the cylindrical structure 1 is a cylindrical structure, the steel plate 111 has a shape curved in a substantially arc shape.

[0027] As illustrated in FIG. 1, the cylindrical structure 1 may have a frustum shape. A frustum is a three-dimensional figure obtained by removing a similarly reduced cone that shares a vertex from a cone. A cone is a general term for a cone-shaped three-dimensional figure formed by a line segment extending from a point in space to a base. A frustum shape is also called a tapered shape. When the cylindrical structure 1 has a frustum shape, the longitudinal direction means the central axis O of the cylindrical structure 1. When the cylindrical structure 1 has a frustum shape, the body 11 also has a frustum shape. The steel plate 111 included in the body 11 is arranged at a slight incline with respect to the longitudinal direction.

[0028] On the other hand, the cylindrical structure 1 may have a columnar shape. A column is a cylindrical spatial figure having two congruent and parallel planar figures as its base. When the cylindrical structure 1 has a columnar shape, the trunk 11 also has a columnar shape. The steel plates 111 included in the trunk 11 are arranged parallel to the longitudinal direction.

[0029] The cylindrical structure 1 may have a shape that combines a frustum and a cylinder. In this case, some of the multiple body portions 11 have a frustum shape, and the remaining portions have a cylinder shape.

[0030] In either case, the steel plates 111 form the surfaces of the frustum and the column. The longitudinal joints 112 and the circumferential joints 12 described later form the sides of the frustum and the column.

[0031] (Circumference joint 12) The ends of the multiple body sections 11 arranged in the longitudinal direction are joined by circumferential joints 12. The circumferential joints 12 are welded joints that extend in the circumferential direction of the cylindrical structure 1. The circumferential joints 12 are obtained by welding the ends of the multiple body sections 11 together. The welded joints that make up the circumferential joints 12 are also butt joints or corner joints.

[0032] (Shape of intersection of longitudinal joint 112 and circumferential joint 12) 2 is an enlarged view of the area surrounded by the dashed line in FIG. 1. FIG. 2 shows an example of an intersection of the longitudinal joint 112 and the circumferential joint 12. In the cylindrical structure 1 according to this embodiment, the longitudinal joint 112 and the circumferential joint 12 have a substantially cross shape at the intersection. That is, at the intersection, the longitudinal joint 112 extending from the circumferential joint 12 toward the tip of the cylindrical structure 1 and the longitudinal joint 112 extending from the circumferential joint 12 toward the base end of the cylindrical structure 1 are substantially collinear. Furthermore, at the intersection, the circumferential joint 12 extending from the longitudinal joint 112 in one circumferential direction of the cylindrical structure 1 and the circumferential joint 12 extending from the longitudinal joint 112 in the other circumferential direction of the cylindrical structure 1 are substantially collinear.

[0033] Typically, circumferential welding for manufacturing the circumferential joint 12 is performed after longitudinal welding for manufacturing the longitudinal joint 112. Therefore, as shown in Figure 2, at the intersection of the longitudinal joint 112 and the circumferential joint 12, the circumferential joint 12 typically extends continuously and is divided by the circumferential joint 12. However, at the intersection of the longitudinal joint 112 and the circumferential joint 12, the longitudinal joint 112 may also extend continuously and be divided by the longitudinal joint 112.

[0034] A butt shift structure is often employed in typical cylindrical structures 1. As shown in FIG. 3, the butt shift structure is a structure in which the intersections of the longitudinal joints 112 and the circumferential joints 12 are T-shaped, avoiding the arrangement of two longitudinal joints 112 on approximately the same line. An example of a butt shift structure is the pressure vessel specified in JIS B 8265:2017, "Construction of Pressure Vessels - General Matters." This pressure vessel requires that "the distance between the centers of the longitudinal joints 112 of adjacent shells shall be at least five times the nominal thickness of the thicker base material." The tower disclosed in Patent Document 1 and the columnar floating structure disclosed in Patent Document 2 also employ a butt shift structure. However, in the cylindrical structure 1 according to this embodiment, a butt shift structure need not be applied to the intersections of the longitudinal joints 112 and the circumferential joints 12.

[0035] (Action and effect) In the cylindrical structure 1 according to this embodiment, the steel plates 111 are joined so that the longitudinal joints 112 and the circumferential joints 12 form a generally cross shape at their intersections. This eliminates the need to bend the steel plates 111 to achieve a butt-shift structure, and makes it possible to manufacture the cylindrical structure 1 by welding flat plates only.

[0036] The butt shift structure can be easily applied to a cylindrical structure. By rotating multiple barrel sections 11 relative to one another, the longitudinal joints 112 formed on each barrel section 11 can be easily separated. Furthermore, even if multiple cylindrical barrel sections 11 are rotated relative to one another, no gaps are created between the multiple barrel sections 11. However, in order to form the cylindrical barrel sections 11, it is necessary to bend the steel plate 111 included in the barrel sections 11 into a substantially arc shape.

[0037] On the other hand, when the multiple body sections 11 are rectangular tubular, rotating the multiple body sections 11 relative to one another to separate the longitudinal joints 112 causes the ends of the multiple body sections 11 to no longer fit together, making it impossible to perform circumferential welding of the body sections 11. In order to apply a butt shift structure to multiple rectangular tubular body sections 11, as illustrated in Fig. 3, it is necessary to bend the steel plate 111 so that the extension direction of the bent section 1111 and the longitudinal direction are approximately aligned, and to position the bent section 1111 of one body section 11 and the longitudinal joint 112 of the other body section 11 on approximately the same line. Therefore, in order to apply a butt shift structure to a rectangular tubular structure, it becomes necessary to bend the steel plate 111 included in the body sections 11.

[0038] 2, when the intersections of the longitudinal joints 112 and the circumferential joints 12 are formed in a substantially cross shape, each of the plurality of steel plates 111 constituting the cylindrical structure 1 can be formed in a flat plate shape. Therefore, the cylindrical structure 1 according to this embodiment can be easily manufactured without bending the steel plates 111.

[0039] Furthermore, even when the cross section of the cylindrical structure 1 is circular, the degree of freedom in welding can be increased by forming the intersections of the longitudinal joints 112 and the circumferential joints 12 into a substantially cross shape. An example of this is given below.

[0040] In a conventional method for manufacturing the circular cylindrical structure 1, one of the following two procedures can be adopted when manufacturing the body portion. (1) First, each of the flat steel plates that make up the trunk is bent. Next, the steel plates are assembled into a tubular shape and welded. The welded joints of the steel plates form longitudinal joints 112. (2) First, all the steel plates that make up the trunk are joined in a row to produce a flat long plate. The welds between the multiple steel plates form longitudinal joints 112. The long plate is then bent into a tubular shape, and the ends of the long plate are welded together. In both of the above steps (1) and (2), the body section does not include the circumferential joint 12. That is, the body sections are manufactured one by one. When joining multiple body sections together, the positions of the longitudinal joints 112 are shifted.

[0041] Here, by using the procedure (2) above for manufacturing the body section 11 and forming the intersections of the longitudinal joints 112 and the circumferential joints 12 into a generally cross shape, it becomes possible to manufacture two or more body sections 11 joined together in a single bending process. Specifically, all of the steel plates that make up the two body sections are joined in two rows to manufacture a flat long plate. This long plate is made by joining the long plates made in the procedure (2) above together with a single circumferential joint. Then, by bending the long plate into a tubular shape, it becomes possible to manufacture two body sections joined by a single circumferential joint in a single bending process.

[0042] Next, a method for manufacturing the cylindrical structure 1 according to this embodiment will be described. The method for manufacturing the cylindrical structure 1 according to this embodiment is as follows: (S1) a step of longitudinally welding a plurality of steel plates 111 at their ends to form a cylindrical body portion 11 having longitudinal joints 112; (S2) a step of aligning the longitudinal joints 112 of adjacent body portions 11 on approximately the same line; (S3) a step of circumferentially welding the ends of the aligned body portions 11 to form a cylindrical structure 1; The method for manufacturing the cylindrical structure 1 will be described in detail below.

[0043] The manufacture of the cylindrical structure 1 may be carried out continuously in one manufacturing facility, or may be carried out in multiple manufacturing facilities for each process. For example, it is expected that the circumferential welding S3 for forming the cylindrical structure 1 is preferably carried out on the land where the cylindrical structure 1 is to be installed. Since the cylindrical structure 1 is very large, it is considered that transportation is difficult. On the other hand, the longitudinal welding S1 for forming the body portion 11 may be carried out in a factory away from the land where the cylindrical structure 1 is to be installed. The body portion 11 formed in the factory may be transported to the land where the cylindrical structure 1 is to be installed, and then the circumferential welding S3 may be carried out.

[0044] (Longitudinal welding S1) In longitudinal welding S1, as shown in Fig. 4 or 5, the ends of a plurality of steel plates 111 are welded together. The steel plates 111 are cut to a predetermined size in advance. The steel plates 111 are then repeatedly welded together while arranging them in the circumferential direction to form a cylindrical body portion 11.

[0045] The steel plate 111 may be a bent plate having a substantially arc-shaped configuration, or may be a flat plate. When the steel plate 111 is a substantially arc-shaped plate, the manufacturing method for the cylindrical structure 1 may further include a step of bending a plurality of steel plates 111 into a substantially arc-shaped configuration before longitudinal welding. Then, the cross section perpendicular to the longitudinal direction of the barrel portion 11 may be made circular by longitudinal welding. On the other hand, when the steel plate 111 is a flat plate, the step of bending the steel plate 111 is ineffective. When the plurality of steel plates 111 are flat plates, the cross section of the barrel portion 11 is made polygonal by longitudinal welding. The steel plates 111 are arranged on the sides of the polygon, and the longitudinal joints 112 are arranged at the vertices of the polygon.

[0046] The welding position and welding method for longitudinal welding are not limited, and can be appropriately selected taking into consideration the size of the steel plate 111 and the equipment for performing longitudinal welding.

[0047] (Alignment S2) The alignment S2 is a step in which the ends of the body sections 11, which are the workpieces to be welded, are positioned so that they can be welded in the subsequent girth welding S3. If the cross-sectional shape of the body sections 11 is polygonal, the sides and vertices of the ends of adjacent body sections 11 are overlapped with each other. Furthermore, as illustrated in Figure 6, the longitudinal joints 112 of adjacent body sections 11 are aligned on approximately the same line.

[0048] (Circumference welding S3) The ends of the aligned body sections 11 are circumferentially welded. By circumferential welding, a circumferential joint 12 is formed that joins the two body sections 11. By repeatedly performing alignment and circumferential welding, multiple body sections 11 are connected along the longitudinal direction, and a cylindrical structure 1 is formed.

[0049] The welding position and welding method for the girth welding are not limited, and can be appropriately selected taking into consideration the size of the steel plate 111 and the equipment for performing the girth welding.

[0050] (Action and effect) In the manufacturing method of the cylindrical structure 1 according to this embodiment, the longitudinal joints 112 of adjacent body portions 11 are aligned on a substantially identical line before circumferential welding. As a result, the longitudinal joints 112 and the circumferential joints 12 form a substantially cross shape at their intersection. Furthermore, it is possible to omit the bending process of the steel plate 111 before circumferential welding, thereby significantly improving productivity.

[0051] The most basic aspect of the cylindrical structure 1 and the manufacturing method thereof according to this embodiment has been described above. A more preferred aspect will now be described.

[0052] (Welding method) The welding method for longitudinal welding and circumferential welding is not particularly limited, but preferred examples include consumable electrode gas-shielded metal arc welding (GMAW), shielded metal arc welding (SMAW), submerged arc welding (SAW), electrogas welding (EGW), and electroslag welding (ESW).

[0053] Consumable electrode gas-shielded arc welding (GMAW) is a metal arc welding method that uses a wire electrode, shielding the arc and molten pool from the atmosphere with externally supplied gas. It is sometimes referred to as gas-shielded metal arc welding. Consumable electrode gas-shielded arc welding is easily automated and can flexibly accommodate larger diameters of cylindrical structures 1. However, consumable electrode gas-shielded arc welding has the limitation that it is difficult to increase the heat input compared to submerged arc welding and other methods. For longitudinal welding using consumable electrode gas-shielded arc welding in the flat position, the upper limit of heat input is considered to be approximately 10 kJ / mm. For longitudinal welding and circumferential welding using consumable electrode gas-shielded arc welding in the vertical position, the upper limit of heat input is considered to be approximately 6.0 kJ / mm.

[0054] Shielded metal arc welding (SMAW) is a manual arc welding method using a shielded electrode, and is also called manual welding. Shielded metal arc welding has the advantages of being applicable to all types of welding, including flat, horizontal, and vertical positions, being easy to work outdoors, and requiring inexpensive equipment. The upper limit of heat input for shielded metal arc welding is approximately 5 kJ / mm, making it less efficient than other welding methods. Furthermore, shielded metal arc welding requires skilled workers. Despite these issues, shielded metal arc welding is effective for applications such as corner welding.

[0055] Submerged arc welding (SAW) is a consumable-electrode arc welding technique performed using one or more electrodes or a strip electrode, with the arc covered by molten slag of granular flux dispersed on the weld joint. Submerged arc welding is typically performed in a flat position, but a vertical position is also possible. Submerged arc welding allows for a large heat input, thereby improving deposition rate and welding efficiency. However, large-scale equipment is required to perform submerged arc welding. Furthermore, as the diameter of the cylindrical structure 1 increases, the submerged arc welding equipment may need to be modified. Therefore, submerged arc welding has the disadvantage of requiring a large capital investment. In conventional longitudinal welding of cylindrical structures 1, the submerged arc welding position is typically a flat position, and the upper limit of heat input is typically approximately 4 kJ / mm. Furthermore, in conventional girth welding of cylindrical structures 1, the welding position for submerged arc welding is a flat position, and the upper limit of the heat input is usually about 40 kJ / mm. However, the inventors believe that it is possible to increase the heat input of submerged arc welding in longitudinal welding up to 20 kJ / mm. It is also believed that girth welding can be performed by submerged arc welding in a vertical position. In this case, the upper limit of the heat input is believed to be about 3.5 kJ / mm.

[0056] Electrogas arc welding (EGW) is a consumable-electrode gas-shielded arc welding process in which a weld pool is supported by a sliding, water-cooled copper backing that advances upward as the welding progresses, and the deposited metal is supplied to the weld pool using a wire or strip electrode. Electroslag welding (ESW) is a fusion welding process in which a welding wire is continuously fed into a molten slag bath, and the welding wire or strip electrode and the base metal are melted primarily by the resistance heat of the molten slag, resulting in a build-up of the deposited metal. Electrogas arc welding and electroslag welding require a vertical upward welding position. On the other hand, electrogas arc welding and electroslag welding allow for very high heat input, resulting in very high welding efficiency. The upper limit of heat input for longitudinal and circumferential welding using electrogas arc welding and electroslag welding is thought to be approximately 80 kJ / mm.

[0057] In this embodiment, a welded joint produced by consumable electrode gas shielded arc welding (GMAW) is referred to as a GMAW joint, a welded joint produced by shielded metal arc welding (SMAW) is referred to as an SMAW joint, a welded joint produced by submerged arc welding (SAW) is referred to as a SAW joint, a welded joint produced by electrogas arc welding (EGW) is referred to as an EGW joint, and a welded joint produced by electroslag welding (ESW) is referred to as an ESW joint. By observing the appearance and cross section of a welded joint, a person skilled in the art can easily determine the type of welded joint. Identifying the type of welded joint based on the welding method corresponds to a case where the structure or characteristics are simply identified by indicating the state.

[0058] (welding position) The various welding methods described above can be applied to both longitudinal welding and circumferential welding. However, the welding position may be limited in the various welding methods described above. Therefore, it is preferable to select a welding position according to the size, manufacturing equipment, and manufacturing location of the cylindrical structure 1, and then select a welding method suitable for this. Examples of welding positions are shown below.

[0059] The longitudinal welding illustrated in FIG. 4 is performed in a vertical position with the steel plate 111 standing vertically. The vertical position refers to a welding position in which a weld line in which the weld surface and weld axis are substantially vertical is welded from the side. Examples of preferred welding methods for longitudinal welding in the vertical position are electrogas arc welding (EGW) or electroslag welding (ESW). Electrogas arc welding or electroslag welding allows welding with a large heat input, thereby realizing high-efficiency manufacturing of the barrel section 11. Furthermore, electrogas arc welding or electroslag welding also allows multiple locations to be welded simultaneously. This is particularly advantageous when the cylindrical structure 1 is large. However, performing longitudinal welding using electrogas arc welding or electroslag welding may require the installation of scaffolding and rails, and the welding worker may need to work at height.

[0060] The longitudinal welding illustrated in FIG. 5 is performed in a flat position with the steel plate 111 laid on a jig. The flat position is a welding position in which a weld line located below is welded from above. An example of a welding method preferred for longitudinal welding in the flat position is submerged arc welding (SAW). Submerged arc welding (SAW) also allows welding with a large heat input, which can achieve high efficiency in manufacturing the body section 11. However, as shown in FIG. 5, in longitudinal welding, the workpieces are not placed flat. In submerged arc welding to manufacture the longitudinal joint 112, it may be necessary to provide a jig on which the workpieces are placed.

[0061] It is also useful to apply GMAW to longitudinal welding, as exemplified in Figure 5. GMAW is often inferior to EGW and ESW in terms of welding efficiency itself. However, the equipment used for GMAW has become smaller, and automation using robots has progressed. Therefore, it is easy to perform GMAW in parallel at multiple locations at a single construction site. Parallel welding of multiple locations can improve the construction efficiency of cylindrical structures.

[0062] In manufacturing the barrel 11, submerged arc welding (SAW), electrogas arc welding (EGW), and electroslag welding (ESW) may be used in combination. For example, the barrel 11 components can be manufactured by submerged arc welding steel plates 111 in a flat position, and then the barrel 11 components can be completed by electrogas arc welding or electroslag welding in a vertical position. The barrel 11 components manufactured by welding two or more steel plates 111 can be easily erected. Once the barrel 11 components are erected, electrogas arc welding or electroslag welding in a vertical upward position can be easily performed. This results in a barrel 11 that combines a longitudinal joint 112 formed by a SAW joint and one or both of a longitudinal joint 112 formed by an EGW joint and a longitudinal joint 112 formed by an ESW joint. By including one or more body portions 11 having two or more types of welded joints in the cylindrical structure 1, the manufacturing efficiency of the body portions 11 is further improved.

[0063] The girth welding illustrated in FIG. 7 is performed in a horizontal position with the body 11 in an upright position, i.e., with the longitudinal direction of the body 11 approximately aligned with the vertical direction. The horizontal position refers to a welding position in which a weld seam is welded from the side with the weld surface approximately vertical and the weld axis approximately horizontal. An example of a preferred welding method for horizontal girth welding is consumable-electrode gas-shielded arc welding (GMAW). Horizontal-position consumable-electrode gas-shielded arc welding can achieve high efficiency in girth welding through automation. Furthermore, horizontal-position consumable-electrode gas-shielded arc welding can simultaneously perform girth welding at multiple locations. However, consumable-electrode gas-shielded arc welding has limitations on heat input. Furthermore, when performing girth welding using horizontal-position consumable-electrode gas-shielded arc welding, the installation of scaffolding and rails and the welding operator's work at height may be required.

[0064] 8 is performed in a flat position with the trunk portion 11 laid down, i.e., with the longitudinal direction of the trunk portion 11 approximately aligned with the horizontal. When performing flat position girth welding, a molten pool is formed at the top of the laid trunk portion 11. Then, by rotating the trunk portion 11 in the circumferential direction, the molten pool is moved in the circumferential direction to create a circumferential joint 12. Examples of welding methods preferred for flat position longitudinal welding are consumable gas-shielded arc welding (GMAW), submerged arc welding (SAW), and shielded metal arc welding (SMAW).

[0065] In addition, by installing multiple portable robots for consumable gas-shielded arc welding (GMAW), the efficiency of girth welding using consumable gas-shielded arc welding can be further improved.

[0066] The combination of welding methods for longitudinal welding and circumferential welding is not particularly limited, but according to the studies of the present inventors, the following combinations are considered to be preferable.

[0067] [Table 1]

[0068] For example, it is preferable to use submerged arc welding (SAW) for the longitudinal welding and gas-shielded arc welding (GMAW) or metal arc welding (SMAW) for the circumferential welding. This results in a cylindrical structure 1 in which the longitudinal joint 112 is a SAW joint and the circumferential joint 12 is a GMAW or SMAW joint. In this case, since welding with an extremely high heat input such as EGW or ESW is not performed, the cost of steel, which is the raw material for the cylindrical structure, can be reduced. Furthermore, longitudinal welding using SAW is more efficient than longitudinal welding using GMAW or SMAW. Furthermore, by using GMAW or SMAW for the circumferential welding, the circumferential welding can be performed as horizontal welding. In this case, the circumferential welding can be performed with the barrel sections stacked vertically. This eliminates the need to rotate the barrel sections during the circumferential welding. Furthermore, horizontal welding can be easily performed efficiently by arranging multiple welding robots around the barrel sections.

[0069] Alternatively, it is preferable to use electrogas arc welding (EGW) or electroslag welding (ESW) for the longitudinal welding and gas-shielded arc welding (GMAW) or metal arc welding (SMAW) for the circumferential welding. This results in a tubular structure 1 in which the longitudinal joint 112 is an EGW joint or an ESW joint, and the circumferential joint 12 is a GMAW joint or an SMAW joint. By using EGW or ESW for longitudinal welding, the welding efficiency of the longitudinal welding can be maximized. For example, longitudinal welding by EGW or ESW can join steel plates 100 mm thick in one pass. Depending on conditions such as the location of the welding workshop, longitudinal welding by EGW or ESW may be more advantageous in terms of cost than longitudinal welding by SAW.

[0070] Alternatively, both the longitudinal welds and the girth welds may be electrogas arc welding (EGW) or electroslag welding (ESW). If girth welding is performed by EGW or ESW, large-scale welding equipment is required. However, by performing both the longitudinal welds and the girth welds by EGW or ESW, welding efficiency can be maximized.

[0071] (Thickness of steel plate 111) In the cylindrical structure 1 and its manufacturing method, it is preferable that the thickness of the steel plate 111 is, for example, 50 mm or more, 55 mm or more, or 60 mm or more. This makes it possible to ensure the strength of the cylindrical structure 1.

[0072] (CTOD) In the cylindrical structure 1 according to this embodiment, it is preferable that the CTOD value at the design temperature at the location where the longitudinal joints 112 and the circumferential joints 12 intersect in a generally cross shape is 0.1 mm or more. The CTOD value is a value used to evaluate the fracture toughness of a metallic material, measured by a test in accordance with WES1108:2016 "Crack Tip Opening Displacement (CTOD) Test Method." The design temperature refers to the temperature of the operating environment. In cylindrical structures for wind power generation equipment, the design temperature is often approximately 0°C to -10°C. By setting the CTOD value at the location where the longitudinal joints 112 and the circumferential joints 12 intersect in a generally cross shape to 0.1 mm or more, fracture of the cylindrical structure 1 originating from this location can be further suppressed.

[0073] An example of a method for measuring the CTOD value is as follows. First, a test specimen simulating the cylindrical structure 1 is created. In the longitudinal joints and circumferential joints of the cylindrical structure 1, the base steel plates may not be on the same plane, but the steel plates that make up the test specimen are arranged on the same plane. In other words, the test specimen is in the shape of a flat plate. Next, a CTOD test specimen is taken from the test specimen. The CTOD test specimen is a full-thickness three-point bending test specimen in accordance with BS7448. Then, a test is performed on the CTOD test specimen at a test temperature of -10°C.

[0074] The location where the CTOD test piece 2 is taken and the location of its notch 21 are as shown in Figure 9, for example. The left side of Figure 9 shows a plan view of the test piece, and the right side of Figure 9 shows a side view of the test piece. The location where the CTOD test piece 2 is taken is indicated by a dashed line in Figure 9. Details of the taking location are as follows: (A) The longitudinal direction of the CTOD test piece 2 is aligned with the extending direction of the longitudinal joint 112. The extending direction of the longitudinal joint 112 corresponds to the longitudinal direction of the cylindrical structure. (B) The depth direction of the notch 21 of the CTOD test piece 2 is aligned with the extension direction of the circumferential joint 12. As a result, on the side of the test piece, the notch 21 extends along the thickness direction of the test piece (see the side view on the right side of Figure 9). (C) When the test specimen is viewed from above, the position where the CTOD test piece 2 is taken is determined so that the bottom of the notch 21 coincides with the toe of the longitudinal joint 112 or an imaginary line along the toe. In the plan view on the left of Figure 9, the bottom of the notch 21 coincides with an imaginary line along the toe of the longitudinal joint 112. (D) Furthermore, the position of the notch 21 is determined so that the length of the weld metal constituting the circumferential joint 12 and the length of the base steel plate are substantially the same at the bottom of the notch 21.

[0075] The above requirement (D) will be explained in detail below. The thickness of the circumferential joint 12 is not uniform on the side of the test specimen. For example, the circumferential joint 12 illustrated in FIG. 9 is obtained by welding an X-groove, and its cross section has a shape resembling two triangles fused at their vertices. Therefore, the length of the area where the notch 21 overlaps with the weld metal varies depending on the location of the notch 21. When the notch 21 is positioned so as to pass through the center of the circumferential joint 12, the bottom of the notch 21 is substantially entirely weld metal. On the other hand, when the notch 21 is positioned so as to pass through the toe of the circumferential joint, the bottom of the notch 21 is substantially entirely base steel plate. Between the toe and center of the circumferential joint, there is a location where the length of the weld metal and the length of the base steel plate are approximately the same at the bottom of the notch 21. This location is identified, and the notch 21 is formed there.

[0076] The term "toe" is defined in JIS Z 3001-7:2018 "Welding terminology - Part 7: Arc welding" as "the point where the surface of the base material and the surface of the weld bead intersect." This definition also applies to the cylindrical structure according to this embodiment.

[0077] By evaluating a CTOD test specimen taken from a position that satisfies the above requirements, the CTOD value of the circumferential joint 12 at the location where the longitudinal joint 112 and the circumferential joint 12 intersect in a roughly cross shape can be obtained. This is because in a cylindrical structure, principal stress occurs in the axial direction and is mainly applied to the circumferential joint 12. It should be noted that this CTOD measurement method differs from that used for existing cylindrical tanks. In toughness evaluation of existing cylindrical tanks, the longitudinal direction of the CTOD test specimen is aligned with the circumferential joint 12 to obtain the CTOD value of the longitudinal joint 112.

[0078] There are no particular limitations on the method for achieving a CTOD value of 0.1 mm or more at the design temperature in the region where the longitudinal joint 112 and the circumferential joint 12 intersect in a generally cross shape. For example, the CTOD value can be maintained within a predetermined range by setting the chemical composition and welding heat input in the region within a predetermined range. The chemical composition of the region can be controlled via the chemical composition of the steel plate, the chemical composition of the filler metal, and the filler metal transfer rate. Specific examples of methods for achieving a CTOD value of 0.1 mm or more in the region are shown in Tables 2 to 5 below.

[0079] Although the embodiment of the present disclosure has been described above, the present disclosure is not limited thereto and can be modified as appropriate within the scope of the technical concept thereof. In the following, a more preferred example of the cylindrical structure 1 according to the present embodiment and the manufacturing method thereof will be described.

[0080] (Size of cylindrical structure 1) The cylindrical structure 1 according to this embodiment is used as a component of a wind turbine generator. Components of the wind turbine generator include, for example, a tower and a foundation. The size of the cylindrical structure 1 can be selected appropriately depending on the installation location and power generation capacity of the wind turbine generator.

[0081] When a wind power generation system is installed offshore, it is preferable to make the wind turbine very large in order to increase the power generation capacity. Therefore, it is also preferable to make the tubular structure 1 that supports the wind turbine large. When a wind power generation system is installed offshore, the diameter of the tubular structure 1 is, for example, 8 to 18 mm, and the length is, for example, 50 to 250 mm. In this case, it is preferable that the thickness of the steel plate 111 included in the tubular structure 1 is 30 to 120 mm. It is also preferable that the longitudinal joints 112 are formed by submerged arc welding, electrogas welding, or electroslag welding, and the circumferential joints 12 are formed by gas metal arc welding or submerged arc welding. Note that when the tubular structure 1 has a polygonal shape, the term "diameter" refers to the diameter of the inscribed circle of the polygon.

[0082] (Types of Steel Plate 111) The type of steel plate 111 included in the cylindrical structure 1 is not particularly limited, but is preferably, for example, SM520, SM570 (JIS Z 3106:2015), rolled steel for building structures SN490 (JIS G 3136:2012), YP385, YP440 for building structures (materials certified by the Minister of Land, Infrastructure, Transport and Tourism), and rolled steel for ship hulls YP355, YP400, YP460, etc. Specific examples of the chemical composition of the steel plate 111 are shown in Table 2 below. [Example]

[0083] The effects of one embodiment of the present disclosure will be explained in more detail using examples. However, the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effects of the present disclosure. The present disclosure is not limited to this example of conditions. Various conditions may be adopted in the present disclosure as long as they do not deviate from the gist of the disclosure and achieve the purpose.

[0084] Various test specimens were prepared to simulate the intersection of longitudinal joints and circumferential joints in a tubular structure. CTOD test specimens were then taken from the test specimens and subjected to CTOD tests. The test specimen preparation method, CTOD test specimen collection method, and CTOD test implementation method were as described above. However, the test temperatures were as shown in Table 4.

[0085] The amounts of alloying elements in the chemical composition of the steel plates constituting the test specimens were as shown in Table 2. The remainder of the chemical composition was iron and impurities. The thickness of all steel plates was 100 mm. The welding conditions for the test specimens were as shown in Table 3.

[0086] The type of base material used in manufacturing the test specimens, the type of longitudinal weld (seam weld) simulating a longitudinal joint, and the type of circumferential weld (girth weld) simulating a circumferential joint were as shown in Table 4. The CTOD test temperatures were also as shown in Table 4. The test temperatures shown in Table 4 correspond to the design temperatures. Table 4 shows the CTOD values ​​of various test specimens obtained by the above-mentioned procedure. The CTOD values ​​shown in Table 4 correspond to the CTOD values ​​at the design temperature at the location where the longitudinal joint and the circumferential joint intersect in a substantially cross shape.

[0087] [Table 2]

[0088] [Table 3]

[0089] [Table 4]

[0090] According to the manufacturing conditions exemplified in Tables 2 to 4, the CTOD value at the design temperature at the location where the longitudinal joints and circumferential joints intersect in a generally cross shape can be made 0.1 mm or more. By applying these manufacturing conditions or similar manufacturing conditions to a manufacturing method for a cylindrical structure, a cylindrical structure with extremely excellent strength can be manufactured. [Explanation of symbols]

[0091] 1 Cylindrical structure 11 Torso 111 Steel plate 1111 Bending part 112 Longitudinal joint 12 Circumference joint

Claims

1. A cylindrical structure for a wind power generation device, A plurality of cylindrical body portions arranged in the longitudinal direction of the cylindrical structure; a circumferential joint that is a welded joint extending in the circumferential direction of the cylindrical structure and joining the ends of the plurality of barrel portions; Equipped with The body portion has a plurality of steel plates arranged in a cylindrical shape and longitudinal joints that are welded joints extending in the longitudinal direction of the cylindrical structure and joining ends of the steel plates, The longitudinal joint and the circumferential joint form a substantially cross shape at their intersection. Cylindrical structure.

2. A cross section of the body portion perpendicular to the longitudinal direction has a circular shape, The plurality of steel plates have a shape bent into a substantially arcuate shape. The cylindrical structure according to claim 1 .

3. A cross section of the body portion perpendicular to the longitudinal direction has a polygonal shape, The plurality of steel plates are flat plates, In the cross section of the body, the steel plates are arranged on the sides of the polygon, and the longitudinal joints are arranged at the vertices of the polygon. The cylindrical structure according to claim 1 .

4. The cylindrical structure according to any one of claims 1 to 3, characterized in that the longitudinal joint and the circumferential joint are consumable electrode gas shielded arc welding (GMAW) joints, covered metal arc welding (SMAW) joints, submerged arc welding (SAW) joints, electrogas arc welding (EGW) joints, or electroslag welding (ESW) joints.

5. One or more of the plurality of body portions, the longitudinal joint being the SAW joint; One or both of the longitudinal joint that is the EGW joint and the longitudinal joint that is the ESW joint; The cylindrical structure according to claim 4, characterized in that it has:

6. the longitudinal joint is the SAW joint, The circumferential joint is the GMAW joint or the SMAW joint. The cylindrical structure according to claim 4 .

7. The longitudinal joint is the EGW joint or the ESW joint, The circumferential joint is the GMAW joint or the SMAW joint. The cylindrical structure according to claim 4 .

8. 4. The cylindrical structure according to claim 1, wherein the thickness of the steel plate is 50 mm or more.

9. The cylindrical structure according to any one of claims 1 to 3, characterized in that the CTOD value at the design temperature at the location where the longitudinal joint and the circumferential joint intersect in an approximately cross shape is 0.1 mm or more.

10. longitudinally welding a plurality of steel plates at their ends to form a tubular body having a longitudinal joint; aligning the longitudinal joints of the adjacent body portions in a substantially collinear manner; a step of circumferentially welding the aligned ends of the plurality of barrel portions to form a cylindrical structure; The method for manufacturing a cylindrical structure according to claim 1, comprising:

11. The method further includes a step of bending the plurality of steel plates into a substantially arc shape before the longitudinal welding, The longitudinal welding forms a circular cross section of the body portion perpendicular to the longitudinal direction. The method for manufacturing a cylindrical structure according to claim 10.

12. The plurality of steel plates are flat plates, In the longitudinal welding, the cross section of the body portion is formed into a polygonal shape, The steel plates are arranged on the sides of the polygon, and the longitudinal joints are arranged at the vertices of the polygon. The method for manufacturing a cylindrical structure according to claim 10.

13. 13. The method for manufacturing a cylindrical structure according to any one of claims 10 to 12, wherein one or both of the longitudinal welding and the circumferential welding are performed by one or more methods selected from the group consisting of consumable electrode gas shielded arc welding (GMAW), covered metal arc welding (SMAW), submerged arc welding (SAW), electrogas arc welding (EGW), and electroslag welding (ESW).

14. When forming the one or more body portions, First, some of the plurality of steel plates are longitudinally welded to form a plurality of parts of the body portion; Then, the ends of the plurality of parts are longitudinally welded to form the body portion; The longitudinal welding of the steel plate is performed by submerged arc welding (SAW), The longitudinal welding of the parts is performed by one or both of the electrogas arc welding (EGW) and the electroslag welding (ESW). The method for manufacturing a cylindrical structure according to claim 13.

15. The longitudinal welding is performed by submerged arc welding (SAW), The girth welding is performed by the consumable gas-shielded arc welding (GMAW) or the shielded metal arc welding (SMAW). The method for manufacturing a cylindrical structure according to claim 13.

16. The longitudinal welding is performed by electrogas arc welding (EGW) or electroslag welding (ESW), The girth welding is performed by the consumable gas-shielded arc welding (GMAW) or the shielded metal arc welding (SMAW). The method for manufacturing a cylindrical structure according to claim 13.

17. The method for manufacturing a cylindrical structure according to any one of claims 10 to 12, characterized in that the thickness of the steel plate is 50 mm or more.

Images