JP2007162732A - Coated steel pipe and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated steel pipe in which a leakage test of the coated steel pipe can be easily performed and which is capable of more easily and positively mounting testing ports thereto than before. <P>SOLUTION: In the coated steel pipe 1, band-like members 8 and 9 each covering both ends in the pipe axial direction of coating members 3 to 7 for coating the outer face of a steel pipe 2 are provided annularly in the circumferential direction of the steel pipe 2, and spaces T1 and T2 formed between the inner face of the band-like members 8 and 9, and the outer face of the steel pipe 2, and spaces S1 to S5 formed between the outer face of the steel pipe 2 and the inner faces of the coating members 3 to 7 are communicated. The testing ports 10 and 11 for performing the leakage test of the coated steel pipe 1 are provided on the outer face of the band-like members 8 and 9 so that each communicates with the spaces T1 and T2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coated steel pipe in which the outer surface of a steel pipe of a marine steel structure is covered with a coating material such as a seawater-resistant metal over the entire circumference so as to prevent corrosion of the marine steel structure, and a method for manufacturing the same.

  In steel offshore structures (for example, piers, jackets, etc.), corrosive environments are particularly severe in tidal areas exposed to tidal periods. Corrosion-resistant metal coating technology that improves corrosion resistance by pasting and welding thin metal plates with excellent seawater resistance (such as titanium, stainless steel, etc.) to the entire tidal part of structural materials in recent years. Has been applied.

  As such a coating technique, Patent Document 1 discloses that one or more thin metal sheets as a coating material are wound around the outer surface of a steel pipe (element tube), temporarily welded, and then all the peripheral portions of this coating material. Discloses a coated steel pipe having a structure in which hermetic welding is performed and the coating material and the steel pipe are joined.

  Usually, after the outer surface of the steel pipe is coated with a covering material, a completion inspection is performed on the obtained coated steel pipe. For completion inspection, for example, a foam leak test method according to JISZ2329 (Non-patent document 1), a helium leak test method according to JISZ2331 (Non-patent document 2), or an ammonia leak according to JISZ2333 (Non-patent document 3) A leak test method such as a test method is used. For example, in the pressurization method of the foam leak test method compliant with JISZ2329, a space formed between a coating material and a steel pipe by welding is pressurized and filled from a test port to form a coating that forms the outer surface of this space. Observe the change in the foaming liquid deposited on the surface of the material. Then, by detecting the gas leaking from the space due to foaming of the foaming liquid, it detects a penetration defect such as a hole due to a welding failure or a poor adhesion, and specifies its position.

JP 2004-131843 A JISZ2329: 2002 Japanese Industrial Standard Foam leakage test method JISZ2331: 1992 Japanese Industrial Standard Helium leak test method JISZ2333: 2005 Japanese Industrial Standard Ammonia Leakage Test Method

  In the above-mentioned Patent Document 1, when the peripheral edge of the covering material is hermetically welded, in the portion where the end portions of the covering material overlap each other, only the covering material is hermetically welded, and the covering material and the steel pipe are not welded. A coated steel pipe of construction is described.

  However, in general, a coating material such as stainless steel used for coating the outer surface of a steel pipe has a very thin plate thickness of, for example, about 0.4 mm. When the parts where the ends of the material overlap are sealed by, for example, indirect seam welding, the heat from the welding of the coatings propagates to the steel pipe under the overlapping coating, Since the coating material and the steel pipe are solid-phase bonded by resistance heat generation at the contact surface with the steel pipe, it is difficult to seal and weld only the coating materials.

  For this reason, in the coated steel pipe described in Patent Document 1, the space formed between the coating material and the steel pipe may be unintentionally divided by the joined coating material and the steel pipe. It is cumbersome because it is necessary to conduct a leak test to inspect whether or not there is a penetration defect on the outer surface of the steel pipe individually for each of the spaces formed between each covering material and the steel pipe. . Furthermore, in order to perform the leak test individually on all the spaces, it is necessary to perform a difficult task of attaching test ports communicating with the spaces to a very thin covering material.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a coated steel pipe in which a leak test can be easily performed and the mounting of a test port is made easier than before.

  In order to solve the above-described problems, according to the present invention, a coated steel pipe in which at least a part of an outer surface of a steel pipe is coated with a plurality of coating materials over the entire circumference, the tube shaft of the plurality of coating materials is provided. A strip-shaped member is wound in the circumferential direction of the steel pipe so as to cover both ends in the direction and fixed in an annular shape, and each space formed between the outer surface of the steel pipe and the inner surfaces of the plurality of covering materials is A covered steel pipe is provided which communicates with each other through a space formed between an outer surface of the steel pipe and an inner surface of the belt-like member and forms a closed space.

  In the above-described coated steel pipe, all of the spaces formed between the outer surface of the steel pipe and the inner surfaces of the plurality of coating materials may communicate with each other to form a single closed space.

  In the above-described coated steel pipe, a space formed between the outer surface of the steel pipe and the inner surfaces of the plurality of coating materials may be communicated with each other in any combination to constitute a plurality of closed spaces.

  In the coated steel pipe, the band-shaped member may be provided with a port communicating with the closed space.

  In the coated steel pipe, a port communicating with the closed space may be provided on the inner surface of the steel pipe.

  In the coated steel pipe, the plurality of coating materials may be made of a thin metal plate, and the coating materials may be configured not to overlap each other by three or more.

  In the above-described coated steel pipe, the plurality of coating materials may have lap joint portions that are substantially parallel to the pipe axis direction of the steel pipe, with end portions in the circumferential direction overlapping each other.

  In the coated steel pipe, the convex portion on the surface may be substantially removed.

  In addition, according to the present invention, an indirect seam welding apparatus including a pair of rotatable disc electrodes arranged to face each other substantially in parallel with a predetermined interval is used. A method of manufacturing the coated steel pipe of claim 1, wherein one of the pair of disk electrodes is arranged at a portion where the plurality of coating materials and the steel pipe are joined, and both of the pair of disk electrodes are While being in pressure contact with the outer surface of the coating material, the welding current is passed from one of the pair of disk electrodes to the other while running in parallel along the part to be joined. There is provided a method for producing a coated steel pipe, characterized in that joining by indirect seam welding is performed by generating heat.

  In the method for manufacturing a coated steel pipe, indirect seam welding may be performed by running the pair of disk electrodes in parallel while maintaining a positional relationship shifted in the traveling direction.

  In the method for manufacturing a coated steel pipe, when the pair of disk electrodes are run in parallel in the tube axis direction of the steel pipe, each disk surface of the pair of disk electrodes is parallel to the tube axis direction of the steel pipe. In a state that is present and perpendicular to the outer surface of the covering material, the steel pipes may be run in parallel while being pressed toward the tube axis.

  According to the present invention, in the coated steel pipe, a strip-shaped member that covers both ends in the tube axis direction of a plurality of coating materials covering the outer surface of the steel pipe is provided, and is formed between the outer surface of the steel pipe and the inner surface of each coating material. When the leakage test of the coated steel pipe is performed, the outer surface of the steel pipe and the inner surface of each coating material are used. A plurality of spaces formed between the two can be pressurized and filled at a time, and a leak test can be easily performed. In addition, by attaching a test port for performing a leak test on the coated outer surface of the coated steel pipe to the strip member, it is easier to attach the test port to the coated steel pipe. Therefore, a highly reliable leak test can be performed, and it becomes possible to provide a coated steel pipe of higher quality than before.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a perspective view of a coated steel pipe 1 according to an embodiment of the present invention. As shown in FIG. 1, in this embodiment, the coated steel pipe 1 includes five rectangular sheet-like coating materials 3 to 7 along the circumferential direction on the outer peripheral surface of a steel pipe 2 configured in a circular tube shape. The strips 8 and 9 are joined in the circumferential direction of the steel pipe 2 so that the covering members 3 to 7 are joined to the outer peripheral surface of the steel pipe 2 and further covered at both ends of the pipes 3 to 7 in the pipe axis direction. Wrapped around and joined, and fixed in a ring shape. In the present embodiment, the steel pipe 2 from which the convex portions on the surface that do not include the convex portions having a height exceeding 3 mm on the outer surface is substantially removed is used. Moreover, in this Embodiment, the stainless steel plate is used as the coating materials 3-7, for example. FIG. 2 is a side view of the coated steel pipe 1, in which the joint portions of the steel pipe 2, the covering materials 3 to 7 and the strip-shaped members 8 and 9 are shown in detail. FIG. 3 is a cross-sectional view of the coated steel pipe 1 of FIG.

  As shown in FIGS. 2 and 3, one circumferential end portion 3 U of the covering material 3 overlaps with the circumferential end portion 7 D of the covering material 7, and is substantially parallel to the tube axis direction of the steel pipe 2. A lap joint portion P is formed. Similarly, the other end portion 3D in the circumferential direction of the covering material 3 is overlapped under the circumferential end portion 4U of the covering material 4 to form a lap joint portion P substantially parallel to the tube axis direction of the steel pipe 2. is doing. Similarly, the end portions 4D to 7D in the circumferential direction overlap each other under the end portions 5U to 7U and 3U of the other covering materials 5 to 7 and the steel pipe 2 for the covering materials 4 to 7 as well. A lap joint portion P substantially parallel to the pipe axis direction is formed, and the other end portions 4U to 7U in the circumferential direction of the covering materials 4 to 7 are respectively connected to the end portions 3D to 6D of the other covering materials 3 to 6. Are overlapped with each other to form a lap joint portion substantially parallel to the pipe axis direction of the steel pipe 2. In addition, each coating | covering material 3-7 of the covering steel pipe 1 is arranged side by side only in the circumferential direction of the steel pipe 2, and has the structure by which the some coating | covering material is not arrange | positioned in the pipe-axis direction. That is, the lap joint portion P is formed by overlapping two covering materials 3 to 7 adjacent in the circumferential direction, and is configured not to overlap three or more.

  FIG. 4 is an enlarged view of the vicinity of the lap joint portion P in which the end 3U of the covering material 3 and the end 7D of the covering material 7 are overlapped in FIG. As shown in FIG. 2, in this lap joint portion P, the steel pipe 2 and the covering materials 3 and 7 are indirect seam welded along the tube axis direction of the steel pipe 2, and both ends of the covering material 3 made of stainless steel. 3U and the end portion 7U of the covering material 7 are melt-bonded, and a solid-state bonding portion 21 where the end portion 7D of the covering material 7 made of stainless steel and the steel pipe 2 made of ordinary steel are solid-phase bonded. Is hermetically formed.

  In the above description, the lap joint portion P between the end portion 3U of the covering material 3 and the end portion 7D of the covering material 7 has been described with reference to FIG. 4, but the end portions 4U to 7U and 3D to 6D of the covering materials 3 to 7 are described. Similarly, other lap joint portions P that overlap with each other are also indirect seam welded along the pipe axis direction of the steel pipe 2, and the fusion joints 20 of the covering materials 3 to 7 and the covering materials 3 to 7 A solid phase junction 21 with the steel pipe 2 is hermetically formed.

  In the vicinity of both ends in the pipe axis direction of the steel pipe 2, the covering materials 3 to 7 are indirect seam welded to the outer surface of the steel pipe 2 along the circumferential direction of the steel pipe 2, so that the covering materials 3 and 7 and the steel pipe 2 are fixed to each other. The phase joint portions 22 and 23 are hermetically formed. In addition, as shown in FIG. 2, the circumferential solid-phase joints 22 and 23 by indirect seam welding are discontinuously formed in the circumferential direction of the steel pipe 2 so as to avoid the vicinity of the lap joint P.

  FIG. 5 is an enlarged plan view showing one end of the coating material 3 and the coating material 7 in the tube axis direction of the steel pipe 2. As shown in FIGS. 2 and 5, the belt-like member 8 is an annular ring that wraps around the steel pipe 2 by being wound along the circumferential direction of the steel pipe 2 so as to cover one end in the pipe axis direction of the covering materials 3 to 7. It has a configuration. Both end portions of the strip-shaped member 8 in the tube axis direction are each TIG welded, one end portion is hermetically formed to form an annular TIG welded portion 24 that is melt-bonded to the outer surface of the steel pipe 2, and the other end portion is covered with the covering material 3 An annular TIG welded portion 25 that is melt-bonded to the outer surface of 7 is hermetically formed. Further, as shown in FIG. 2, as with the band-shaped member 9, as with the band-shaped member 9, both end portions in the tube axis direction are each TIG welded, and one end is melted and joined to the steel pipe 2. 26 is hermetically formed, and the other end is hermetically formed as an annular TIG joint 27 that is melt-bonded to the covering materials 3 to 7.

  As shown in FIG. 2 and FIG. 5, between the outer surface of the steel pipe 2 and the inner surfaces of the respective coating materials 3 to 7, a melt-bonded part 20 and a solid phase by indirect seam welding along the pipe axis direction of the steel pipe 2 are provided. Spaces S1 to S5 partitioned by the joint portion 21 are formed. In addition, annular spaces T1 and T2 are formed between the outer surface of the steel pipe 2 and the inner surfaces of the strip members 8 and 9, respectively. As shown in FIG. 5, the spaces S <b> 1 to S <b> 5 are formed by covering materials 3 to 7 and a steel pipe between the solid-phase joint portion 22 in the circumferential direction and the melt-joint portion 20 and the solid-phase joint portion 21 in the tube axis direction. 2 communicates with each of the annular spaces T1 through a portion where 2 is not joined. Similarly, each of the spaces S1 to S5 includes the covering materials 3 to 7 and the steel pipe 2 between the solid-phase joint portion 23 in the circumferential direction and the melt-joint portion 20 and the solid-phase joint portion 21 in the tube axis direction. It communicates with the annular space T2 through a portion that is not joined. As a result, the spaces S1 to S5 communicate with each other via the annular spaces T1 and T2 to form a single closed space.

  In the present embodiment, the strip-shaped member 8 communicates with the space T1 so that a leak test can be performed in accordance with, for example, a foam leak test method defined in JISZ2329 using the coated outer surface of the coated steel pipe 1 as a test surface. Similarly, the strip-shaped member 9 is provided with a test port 11 communicating with the space T2. As described above, the spaces T1, T2, and S1 to S5 communicate with each other to form a single closed space, so that the test ports 10 and 11 communicate with each other. The test ports 10 and 11 are preferably installed at the same position in the circumferential direction of the steel pipe 2. Further, at least one of the test ports 10 and 11 may be maintained even after the coated steel pipe 1 is installed after the test is completed, and a leak test or the like may be performed later as necessary.

  The manufacturing method of the coated steel pipe 1 comprised as mentioned above is demonstrated using FIGS. FIG. 6 is a flowchart for explaining the procedure of the method for manufacturing the coated steel pipe 1. 7-13 is a figure explaining each process at the time of manufacturing the coated steel pipe 1. FIG.

  FIG. 7 is a perspective view of the steel pipe 2 to which the covering materials 3 to 7 are temporarily attached. As shown in FIG. 7, for example, five sheet-like coating materials 3 to 7 are wound around the entire circumference of the steel pipe 2 while being properly positioned along the circumferential direction, for example, by spot welding. Temporarily attach and fix to the steel pipe 2 (step SP1). The positioning at this time is set so that the adjacent covering materials 3 to 7 overlap substantially parallel to the pipe axis direction of the steel pipe 2 so as to appropriately form the lap joint portion P described above.

  Further, spot welding is performed by forming a joint portion between the outer surface of the steel pipe 2 and the inner surfaces of the coating materials 3 to 7 between the outer surface of the steel pipe 2 and the inner surfaces of the coating materials 3 to 7 by spot welding or the like. This is to prevent each of the spaces S1 to S5 from being divided into two or more non-communication spaces. In addition, when a convex part such as a pipe-forming bead exists on the outer surface of the steel pipe 2 as in the case where a UO steel pipe, a bending roll pipe, a spiral steel pipe, or the like is used as the steel pipe 2, this convex part on the surface is previously 3 mm. It is substantially removed by polishing to the following height. The convex portion on the surface of the steel pipe 2 is preferably 1 mm or less.

  FIG. 8 is a configuration diagram illustrating the indirect seam welding apparatus 30. In FIG. 8, a state is shown in which the indirect seam welding 30 is used to apply the coating materials 3 to 7 to the outer surface of the steel pipe 2 and indirect seam welding in the pipe axis direction of the steel pipe 2. As shown in FIG. 8, the indirect seam welding apparatus 30 includes a pair of rotatable disk electrodes 31 and 32 that are opposed to each other substantially in parallel at a predetermined interval. In the present embodiment, the indirect seam welding apparatus 30 is configured to be able to adjust the angle of the disk surfaces of the pair of disk electrodes 31 and 32 that are arranged to face each other. The indirect seam welding apparatus 30 allows a welding current to flow from one of the pair of disk electrodes 31 and 32 to the other in a state where both of the pair of disk electrodes 31 and 32 are in pressure contact with an object to be welded. , It is possible to move in a direction parallel to the disk surfaces of the pair of disk electrodes 31 and 32 (in the case of FIG. 8, the tube axis direction of the steel pipe 2). The indirect seam welding device 30 is arranged in a portion where one of the pair of disc electrodes 31 and 32 brought into pressure contact with an object to be welded is joined, and the portion where the disc electrodes 31 and 32 are joined. Indirect seam welding is performed by causing a welding current to flow from one side to the other while generating parallel heating along the lines, and generating resistance heat at the parts to be joined.

  When the coating materials 3 to 7 are subjected to indirect seam welding on the outer surface of the steel pipe 2 in the tube axis direction, as shown in FIGS. 8 and 9, the indirect seam welding apparatus 30 includes a pair of disk electrodes 31, 32 are arranged so as to be included in a radial plane r passing through the tube axis O, respectively. FIG. 9 is an enlarged view of a pair of disk electrodes 31 and 32 of the indirect seam welding apparatus 30 of FIG. The disc electrode 31 is arranged on the outer surface of the portion where the adjacent covering materials 3 and 7 overlap each other substantially in parallel with the tube axis direction of the steel pipe 2, and the disc electrode 32 is located below the overlapped portion P. It arrange | positions on the outer surface of the coating | covering material 7 of this. These disc electrodes 31 and 32 are arranged in the tube axis direction O of the steel pipe 2 in a state in which their respective disk surfaces are parallel to the tube axis direction O of the steel pipe and perpendicular to the outer surfaces of the covering materials 3 and 7. Press towards. A pair of disk electrodes 31, 32 are rotated while pressing firmly, and are welded between these two disk electrodes 31, 32 while running parallel to the tube axis direction of the steel pipe 2 along the part to be joined. Apply current. As a result, resistance heat is generated in the parts to be joined, and the melt joint part 20 between the covering materials 3 and 7 and the solid phase joint part 21 between the covering materials 3 to 7 and the steel pipe 2 are hermetically formed, and the lap joint part P is formed. (Step SP2). In the present embodiment, since there are five portions where the covering materials 3 to 7 overlap each other, indirect seam welding along the tube axis direction is sequentially performed on each of the five lap joint portions P. Form.

  FIG. 10 is a configuration diagram showing a configuration when indirect seam welding is performed in the circumferential direction on the outer surface of the steel pipe 2 with the end portions in the tube axis direction of the covering materials 3 to 7 using the indirect seam welding apparatus 30. . When the coating materials 3 to 7 are indirect seam welded to the outer surface of the steel pipe 2 in the circumferential direction, as shown in FIG. 10, the indirect seam welding apparatus 30 includes a pair of disk electrodes 31 and 32. It arrange | positions so that a disk surface may become perpendicular | vertical to a pipe-axis direction. The disc electrode 31 is arranged at the end of the steel pipe 2 of the covering materials 3 to 7 in the tube axis direction, and the disc electrode 32 is arranged on the outer surface of the steel pipe 2 where the covering materials 3 to 7 are not arranged. These disc electrodes 31 and 32 are pressed toward the steel pipe 2 in a state where their disc surfaces are perpendicular to the outer surfaces of the covering materials 3 to 7. A pair of disk electrodes 31, 32 are rotated while being pressed firmly, and a welding current is passed between the two disk electrodes 31, 32 while running parallel to the circumferential direction of the steel pipe 2. As a result, resistance heat is generated in the parts to be joined, and the solid-phase joints 22 and 23 between the covering materials 3 to 7 and the steel pipe 2 are hermetically formed (step SP3). In this embodiment, when performing indirect seam welding, the steel pipe 2 is welded discontinuously over the entire circumference except for the vicinity of the lap joint portion P formed in step SP2. Thereby, the solid phase joints 22 and 23 between the outer surface of the steel pipe 2 formed by indirect seam welding and the inner surfaces of the coating materials 3 to 7 are formed between the outer surface of the steel pipe 2 and the inner surfaces of the coating materials 3 to 7. Each of the spaces S1 to S5 formed therebetween is prevented from being divided into two or more non-communication spaces.

  FIG. 11 is a cross-sectional view showing the configuration of the steel pipe 2 and the band-like member 8 to which the covering materials 3 to 7 are joined when performing TIG welding along the circumferential direction of the steel pipe 2. As shown in FIG. 11, the strip-shaped members 8 and 9 are wound around the circumferential direction of the steel pipe 2 so as to cover both ends in the pipe axis direction of the covering materials 3 to 7 joined to the outer surface of the steel material 2. Next, while applying the welding wire 40, both ends of the strip member 8 in the tube axis direction are TIG welded along the circumferential direction of the steel pipe 2 using the TIG welding torch 41, and the strip member 8 and the steel pipe 2 The ring-shaped TIG welded portion 24 to which the material is melt-bonded and the ring-shaped TIG welded portion 25 to which the band-shaped member 8 and the covering materials 3 to 7 are melt-bonded are hermetically formed. Similarly, both end portions of the strip-shaped member 9 in the tube axis direction are each subjected to TIG welding along the circumferential direction of the steel pipe 2 using the TIG welding torch 40, and the annular member 9 and the steel pipe 2 are melt-bonded. The TIG welded portion 26 and the annular TIG welded portion 27 to which the belt-like member 9 and the covering materials 3 to 7 are melt bonded are hermetically formed (step SP4).

  FIG. 12 is a cross-sectional view showing a state in which the tubular test port 10 is attached to the belt-like member 8. In the present embodiment, a thread 50 is formed in the tubular test ports 10 and 11 so that, for example, a pipe for supplying or exhausting gas can be connected by screw connection when performing a foam leak test. Has been. The band-like members 8 and 9 are previously provided with holes 51 having a size suitable for the outer diameter of the test ports 10 and 11 at predetermined positions. The predetermined position may be, for example, a position where the band-shaped members 8 and 9 and the covering material 3 do not overlap and a hollow space is formed between the band-shaped members 8 and 9 and the steel pipe 2. As shown in FIG. 12, the test port 10 is disposed in a hole 51 provided in advance at a predetermined position of the band-shaped member 8, and the test port 10 is hermetically bonded to the band-shaped member 8 by, for example, TIG fillet welding. Similarly to the belt-like member 8, the belt-like member 9 has the test port 11 disposed in a hole 51 provided in advance in a predetermined position of the belt-like member 9, and the test port 11 is formed by TIG fillet welding. 11 is hermetically joined to the belt-like member 9 (step SP5).

  According to the above embodiment, in the coated steel pipe 1, the strip-shaped members 8 and 9 that respectively cover both ends in the tube axis direction of the covering members 3 to 7 that cover the outer surface of the steel pipe 2 are annularly formed in the circumferential direction of the steel pipe 2. Provided, spaces T1 and T2 formed between the inner surfaces of the strip members 8 and 9 and the outer surface of the steel pipe 2, and spaces S1 to S1 formed between the outer surface of the steel pipe 2 and the inner surfaces of the covering materials 3 to 7 Since S5 communicates, the test ports 10 and 11 can be attached to the strip members 8 and 9 instead of the covering materials 3 to 7, and the test ports 10 and 11 can be attached to the coated steel pipe 1. Easier and more secure. In addition, all the spaces S1 to S5 formed between the outer surface of the steel pipe 2 and the inner surfaces of the covering materials 3 to 7 are spaces formed between the inner surfaces of the strip members 8 and 9 and the outer surface of the steel pipe 2. Since a single closed space is formed by communicating with each other via T1 and T2, a test port for performing a leak test on the outer surfaces of the covering materials 3 to 7 and the strip members 8 and 9 of the coated steel pipe 1 It is possible to reduce the number of 10,11.

  Furthermore, in the coated steel pipe 1, the convex portion whose surface height exceeds 3 mm is polished so that the convex portion on the surface of the steel pipe 2 is substantially removed, so that the outer surface of the steel pipe 2 is covered. When winding the materials 3 to 7, the covering materials 3 to 7 are not bulky, and the aesthetic appearance of the coated steel pipe 1 is not impaired. Further, since the lap joint portion P in which the end portions in the circumferential direction of the covering materials 3 to 7 are overlapped with each other is formed substantially parallel to the tube axis direction of the steel pipe 2, the covering materials 3 to 7 are not bulky and the covering steel pipe 1 The beauty of the is not impaired. In addition, since the covering materials 3 to 7 are configured so that three or more sheets do not overlap each other, it is possible to prevent the occurrence of poor welding when the covering materials 3 to 7 are wound around the outer surface of the steel pipe 2 and welded to the steel pipe 2. Is done.

  Further, when the indirect seam welding is performed along the pipe axis direction of the steel pipe 2 when the coated steel pipe 1 is manufactured, the pair of disk electrodes 31 and 32 are arranged so that each disk surface is in the pipe axis direction of the steel pipe. In parallel seam welding, the indirect seam welding is performed by pressing the steel pipe in parallel with the pipe shaft while being parallel to the outer surface of the coating material. It is prevented that 32 shifts | deviates from a welding part to the circumferential direction and improper welding is performed.

  FIG. 13 is a plan view showing the positional relationship between the steel pipe 2 and the covering materials 3 to 7 and the pair of disk electrodes 31 and 32 of the indirect seam welding apparatus 30. As a second embodiment, as shown in FIG. 13, when the lap joint portion P of the coated steel pipe 1 is formed by indirect seam welding along the pipe axis direction of the steel pipe 2, the indirect seam welding apparatus 30 A pair of disk electrodes 31 and 32 are made to run in parallel while maintaining the positional relationship shifted in the traveling direction from the state where the disk surfaces of the pair of disk electrodes 31 and 32 face each other in parallel or substantially in parallel, so that indirect seam welding is performed. It may be.

  In the second embodiment, the disk electrodes 31 and 32 of the indirect seam welding apparatus 30 are maintained in a positional relationship in which the disk electrode 31 is in front of the disk electrode 32 in the direction of travel. Since indirect seam welding is performed by proceeding in the axial direction, when the joint 20 (21) is formed in the lap joint portion P by the disk electrode 31, the center in the tube axial direction is formed from one end of the covering materials 3-7. When the disk electrodes 31 and 32 are stopped when the disk electrode 31 that has started welding from a position close to the other end is reached, the disk electrode 32 is formed at a position other than the lap joint portion P. The joint portion 52 between the outer surface of the steel pipe 2 and the inner surfaces of the covering materials 3 to 7 is formed only from one end portion of the covering materials 3 to 7 to the front of the other end portion. By doing in this way, each space S1-S5 formed between the outer surface of the steel pipe 2 and the inner surface of the coating | covering materials 3-7 is the junction part 20 (21) of the lap joint part P, or indirect seam welding. The joint portion 52 formed at the time prevents the space from being divided into two or more non-communication spaces. That is, as shown in FIG. 13, each of the spaces S <b> 1 to S <b> 5 includes a portion interrupted in the tube axis direction of the joint portion 20 (21) of the lap joint portion P and a portion interrupted in the tube axis direction of the joint portion 52. Via each other.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, this invention is not limited to the example which concerns. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  In the above-described embodiment, the case where the steel pipe 2 is configured in a circular tube shape has been described, but the steel pipe 2 may be configured in a shape other than the circular tube shape.

  In embodiment mentioned above, although the case where the coating | covering materials 3-7 were stainless steel was demonstrated, the coating | covering materials 3-7 may be comprised with the other metal.

  In the above-described embodiment, the case where the coated steel pipe 1 is configured by the five coated materials 3 to 7 has been described. However, the coated steel pipe 1 may be configured by an arbitrary number of coated materials.

  In the above-described embodiment, the spaces S1 to S5 formed between the outer surface of the steel pipe 2 and the inner surfaces of the five coating materials 3 to 7 are formed between the outer surface of the steel pipe 2 and the inner surfaces of the strip members 8 and 9. Although the case where all communicate with each other to form a single closed space through the annular spaces T1 and T2 formed between them, only the space S1 and the space S2 communicate with each other and the other spaces S3 to S5. Constitutes an isolated closed space, or two spaces S1 and S2 communicate with each other to form a first closed space, and the remaining three spaces S3 to S5 communicate with each other. As in the case of configuring a second closed space that does not communicate with each other, the five spaces S1 to S5 may communicate with each other in an arbitrary combination to form a plurality of closed spaces.

  In the above-described embodiment, the case where the covering materials 3 to 7 and the steel pipe 2 are joined by indirect seam welding along the pipe axis direction and TIG welding along the circumferential direction has been described. May be joined. Two or more kinds of welding methods may be applied in combination.

  In the above-described embodiment, the case where the covering materials 3 to 7, the band-like members 8 and 9, and the steel pipe 2 are joined by TIG welding along the circumferential direction has been described, but may be joined by other welding methods. . Two or more kinds of welding methods may be applied in combination.

  In the embodiment described above, the lap joint formed in step SP2 in the circumferential direction of the steel pipe 2 when the end portions in the pipe axis direction of the covering materials 3 to 7 are indirect seam welded to the outer surface of the steel pipe 2 in the circumferential direction. The case of welding discontinuously over the entire circumference excluding the vicinity of the portion P has been described, but a predetermined position other than the lap joint portion P (for example, each coating material) at the end in the tube axis direction of each coating material 3 to 7 You may make it weld discontinuously over the perimeter except the center part vicinity of the circumferential direction of 3-7.

  In the above-described embodiment, the case where the test ports 10 and 11 are joined to the strip-like members 8 and 9 by TIG fillet welding has been described, but they may be joined by other welding methods. Two or more kinds of welding methods may be applied in combination.

  In the embodiment described above, a case has been described in which one test port 10 and 11 is provided in each of the strip members 8 and 9, but the test port may be provided in only one of the strip members 8 and 9. Good. Further, two or more test ports may be provided in each of the belt-like members 8 and 9.

  In the above-described embodiment, the case where the test ports 10 and 11 are provided in the band-shaped members 8 and 9 has been described. From the inner surface side of the steel pipe 2, the outer surface of the steel pipe 2 and the inner surfaces of the five coating materials 3 to 7 are provided. A hole communicating with each of the spaces S1 to S5 formed between them may be formed, and a test port communicating with the spaces S1 to S5 may be provided on the inner surface of the steel pipe 2.

  In the above-described embodiment, the case where the leakage test in accordance with the foam leakage test method specified in JISZ2329 is performed and the coated outer surface of the coated steel pipe 1 is tested as a test surface has been described. The leakage test is described in JISZ2331. It may be performed in accordance with the ammonia leakage test method specified in JIS Z2333 or the helium leakage test method specified in JISZ2333, or may be performed by other methods.

  The present invention can be applied to, for example, a coated steel pipe near a tidal zone in a steel offshore structure, but is also useful for other coated steel pipes.

It is a perspective view of a covering steel pipe concerning an embodiment of the invention. It is a side view of the covering steel pipe which shows the structure of a steel pipe, a coating | covering material, and a strip | belt-shaped member. It is AA arrow sectional drawing of FIG. It is the figure which expanded the lap joint part vicinity of FIG. It is the top view shown about the end of the pipe material direction of a steel pipe of a covering material. It is a flowchart explaining the procedure of the manufacturing method of a coated steel pipe. It is a perspective view of the steel pipe with which the coating | covering material was attached temporarily. It is a block diagram explaining the indirect seam welding apparatus. It is the figure which expanded a pair of disc electrode 31 and 32 of the indirect seam welding apparatus 30 of FIG. FIG. 3 is a configuration diagram showing a configuration when indirect seam welding is performed on the outer surface of a steel pipe 2 in the pipe axial direction end portions of the covering materials 3 to 7 using the indirect seam welding apparatus 30. It is sectional drawing which shows the structure of the steel pipe 2 with which the coating | coated material was joined, and the strip | belt-shaped member at the time of performing TIG welding along the circumferential direction of a steel pipe. It is sectional drawing which shows the state in which the tubular test port was attached to the strip | belt-shaped member. As a second embodiment of the present invention, the positional relationship between a pair of disk electrodes of an indirect seam welding apparatus when forming a lap joint portion of a coated steel pipe by indirect seam welding along the pipe axis direction of the steel pipe FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coated steel pipe 2 Steel pipe 3-7 Coating material 3D-7D, 3U-7U End part of lining material 8,9 Strip member 10,11 Test port 20,22,23 Melt joint part by indirect seam welding 21 Indirect seam Solid-state joints by welding 24-27 TIG welds 30 Indirect seam welding devices 31, 32 Disc electrodes 40 Welding wires 41 TIG welding torches 50 Threads 51 Holes 52 Melt joints generated during indirect seam welding A -A section line O pipe axis P lap joint part S1 to S5, T1, T2 space r radial plane of the steel pipe

Claims (11)

A coated steel pipe in which at least a part of the outer surface of the steel pipe is covered with a plurality of coating materials over the entire circumference,
A band-shaped member is wound in the circumferential direction of the steel pipe so as to cover both ends in the pipe axis direction of the plurality of coating materials, and is fixed in an annular shape,
The spaces formed between the outer surface of the steel pipe and the inner surfaces of the plurality of covering materials communicate with each other via a space formed between the outer surface of the steel pipe and the inner surface of the strip-shaped member; Coated steel pipe, characterized in that it constitutes a closed space. 2. The coated steel pipe according to claim 1, wherein all of the spaces formed between the outer surface of the steel pipe and the inner surfaces of the plurality of coating materials communicate with each other to form a single closed space. . The space formed between the outer surface of the steel pipe and the inner surfaces of the plurality of covering materials communicates with each other in an arbitrary combination to form a plurality of closed spaces. Coated steel pipe. The said steel strip is provided with the port connected to the said closed space, The covering steel pipe in any one of Claims 1-3 characterized by the above-mentioned. The coated steel pipe according to claim 1, wherein a port communicating with the closed space is provided on an inner surface of the steel pipe. The coated steel pipe according to any one of claims 1 to 5, wherein the plurality of coating materials are made of a sheet metal, and each coating material is configured not to overlap each other by three or more. . 7. The coated steel pipe according to claim 6, wherein the plurality of coating materials have circumferential ends overlapped with each other to form a lap joint portion substantially parallel to the pipe axis direction of the steel pipe. . The coated steel pipe according to any one of claims 1 to 7, wherein a convex portion of a surface of the steel pipe is substantially removed. A method for producing a coated steel pipe according to any one of claims 1 to 8, using an indirect seam welding device comprising a pair of rotatable disk electrodes arranged opposite to each other substantially in parallel at a predetermined interval. There,
One of the pair of disk electrodes is disposed at a portion where the plurality of coating materials and the steel pipe are joined, and both the pair of disk electrodes are brought into pressure contact with the outer surfaces of the plurality of coating materials. Indirect seam welding is performed by causing a welding current to flow from one of the pair of disk electrodes to the other while causing them to run parallel to each other along the part to be joined by rotating in a state. A method for manufacturing a coated steel pipe, characterized in that joining is performed by using The method for manufacturing a coated steel pipe according to claim 9, wherein indirect seam welding is performed by causing the pair of disk electrodes to run side by side while maintaining a positional relationship shifted in the traveling direction. When the pair of disk electrodes run in parallel in the tube axis direction of the steel pipe, each disk surface of the pair of disk electrodes is parallel to the tube axis direction of the steel pipe and is on the outer surface of the covering material. 11. The method for manufacturing a coated steel pipe according to claim 9, wherein the pipes are moved in parallel while being pressed toward a pipe axis of the steel pipe.

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