Pipe welding method

Abstract

To carry out welding work as appropriate at a construction site by suppressing a penetration failure using an automatic welding machine even when a sectional shape of an end joint of a pipe material is opened V at the tip.SOLUTION: When the ends 13a and 14a of pipes 13 and 14 molded V at the tips are connected through welding, welding of at least an initial layer is manually carried out by an operator to form a weld bead B1. Then, welding of a second layer and after is carried out by an automatic welding machine to form a weld bead B2. Through such a process, work of a welder is controlled minimum, and welding work of a pipe material V-shaped at the tip can be carried out as appropriate.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention is Welding method It is related to. [Background technology]

[0002] In the past, when connecting pipes at various construction sites, the ends of the pipes that make up the pipes have been welded together. In recent years, automatic welding machines have been used to reduce the labor required for welding and automate the process.

[0003] An example of an automatic welding machine is disclosed in Patent Document 1, which includes a welding torch for welding piping, a traveling carriage that drives the welding torch three-dimensionally, a weld line detection sensor provided ahead of the welding torch in the direction of travel, and a control device that controls the position of the welding torch by feeding back information detected by the weld line detection sensor. The automatic welding machine also includes a means for storing a difference between welding torch position data that approximates position data obtained by positioning the welding torch at a weld formed around the entire circumference of the piping and sensor position data that approximates position data obtained by positioning the weld line detection sensor, and a control device that corrects the information detected by the sensor using the value stored in the storage means when welding is performed with the welding torch, and controls the welding torch. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3414118 Summary of the Invention [Problem to be solved by the invention]

[0005] When welding the ends of pipe materials together, a method called groove welding is used, in which the ends of the pipe materials are processed before welding, which suppresses deformation of the base material and ensures high strength at the joint after welding.

[0006] In this regard, when welding using an automatic welding machine, if the cross-sectional shape of the joint at the end of the pipe material is a so-called V-groove, poor penetration of the first layer is likely to occur. Therefore, when welding using an automatic welding machine, the cross-sectional shape of the joint at the end of the pipe material is made a so-called U-groove.

[0007] However, processing a U-groove requires high processing precision, which requires the use of specialized machine tools. However, it is practically impossible to bring such machine tools into a small construction site. Therefore, whenever possible, U-groove processing is performed in a separate location away from the construction site, and the processed pipe material is then transported to the welding site. However, because the groove is narrow, there is a risk that the groove will be damaged or deformed during transportation or installation.

[0008] The present invention has been made in consideration of these points, and aims to reduce poor penetration when using an automatic welding machine, even if the cross-sectional shape of the end joint of the pipe material is a so-called V-groove, and to perform welding work efficiently at construction sites. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a welding method for connecting the ends of pipe materials by welding, wherein at least the first layer of welding is performed manually by an operator, and subsequent welding work is performed by an automatic welding machine, and the groove of the pipe material to be welded is a V groove, The automatic welding machine is a welding machine used to weld together the ends of tubular materials, and includes a guide ring attached to the outer periphery of the tubular material, a running section movable in a circumferential direction along the outer periphery of the guide ring, a wire reel provided on the running section, a welding torch provided on the running section, and a wire support section disposed near the welding torch and supporting the welding wire unwound from the wire reel, wherein a side end surface of the wire reel is disposed parallel to the circumferential surface of the guide ring, After the pipe material is hung, the ends of the pipe material are aligned, then tack welding is performed, and then the worker manually performs the first layer welding. The tack welding is performed in the order of lower right, upper left, lower left, and upper right when viewed from the axial direction of the pipe material. It is characterized by the following.

[0010] According to the present invention, at least the first layer of welding is performed manually by a worker, so that poor penetration can be prevented even if the groove of the pipe material to be welded is a V groove. Therefore, subsequent welding work can be performed using an automatic welding machine, which achieves automation and labor savings compared to performing all welding work manually by a worker.

[0011] Furthermore, if the groove of the pipe material to be welded is a V-groove, it can be easily processed at the construction site, and there is no need to make the end of the pipe material into a U-groove, which was previously necessary when using an automatic welding machine, and the end of the pipe material can be easily processed into a V-groove on site.

[0012] The present invention also Used in Automatic welding machines are As mentioned above A welding machine used to weld together the ends of tubular materials, the machine comprising: a guide ring attached to the outer periphery of the tubular material; a running part movable in a circumferential direction along the outer periphery of the guide ring; a wire reel attached to the running part; a welding torch attached to the running part; and a wire support part disposed near the welding torch and supporting the welding wire unwound from the wire reel, the side end surface of the wire reel being disposed parallel to the circumferential surface of the guide ring. It has been done.

[0013] The aboveIn the automatic welding machine, the side end face of the wire reel around which the welding wire is wound, i.e., the surface that is circular in plan view, is arranged parallel to the circumferential surface of the guide ring, so that when the traveling part of the automatic welding machine rotates along the outer periphery of the guide ring, the length in the radial direction from the center of the pipe, i.e., the height, can be reduced, and the range of the rotational orbit of the automatic welding machine during welding can be kept small. Therefore, automatic welding work can be performed effectively even when the work space is narrow due to the tangle of pipes.

[0014] In this case, the center of rotation of the wire reel may be located on the axial rear side of the guide ring, that is, in a direction away from the welding torch.

[0015] By adopting this configuration, the distance between the wire support portion and the portion of the welding wire that is unwound from the wire reel can be increased. Even if the angle of the wire support portion relative to the wire reel is large, the length of the portion of the welding wire that is unwound up to the wire support portion can be increased, thereby increasing the radius of curvature of the trajectory of the welding wire. This allows for smooth and appropriate unwinding of the welding wire. Furthermore, because the running portion itself moves along the outer periphery of the guide ring, its overall height is increased by the thickness of the guide ring. Therefore, by positioning the entire wire reel behind the running portion, it is no longer necessary to position the wire reel above the guide ring. This also reduces the height of the wire reel itself. [Effects of the Invention]

[0016] According to the present invention, even if the cross-sectional shape of the end joint of the pipe material is a so-called V-groove, poor penetration when using an automatic welding machine can be suppressed, and welding work can be carried out efficiently at construction sites. [Brief explanation of the drawings]

[0017] [Figure 1] This is an explanatory diagram of a cross section when the end of a pipe material processed into a V-groove is welded using an automatic welding machine. [Figure 2] FIG. 10 is an explanatory diagram showing a worker manually temporarily attaching the end of a pipe material. [Figure 3] FIG. 10 is an explanatory diagram showing the order of welding points when temporarily attaching the end of a pipe material. [Figure 4] FIG. 10 is an explanatory diagram showing a worker manually welding the first layer of the end of the pipe material after temporary welding. [Figure 5] This is an explanatory diagram of a cross section of the end of a pipe material that has been processed into a V-groove after a worker manually welded the first layer. [Figure 6] FIG. 10 is an illustration showing a worker preparing the end of a pipe for automatic welding after manual welding. [Figure 7] FIG. 10 is an explanatory diagram showing the state in which the end of a pipe material is welded by an automatic welding machine. [Figure 8] 3 is an explanatory diagram of a cross section after welding in FIG. 2 has been performed by an automatic welding machine. [Figure 9] FIG. 1 is a perspective view of an automatic welding machine used in an embodiment. [Figure 10] FIG. 10 is a plan view of the automatic welding machine of FIG. 9. [Figure 11] 10 is a front view of the automatic welding machine of FIG. 9 as seen from the axial direction of the pipe material. [Figure 12] 10 is an explanatory diagram showing the configuration of an automatic welding device including the automatic welding machine of FIG. 9. [Figure 13] 10 is a flowchart of a welding method using the automatic welding machine of FIG. 9. [Figure 14] FIG. 10 is a plan view of an automatic welding machine according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments will be described with reference to the drawings. In the following description, elements having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0019] Figure 1 shows a V-groove, which is created by cutting the joints at the ends of pipe materials 1 and 2 that make up the piping at an angle, so that the space between the ends 1a and 2a of the opposing pipe materials 1 and 2, which are the base materials, has a V-shaped cross section. When the ends of pipe materials 1 and 2 with this V-groove are automatically welded, a weld bead B made of weld metal is formed between the ends 1a and 2a of the V-groove, as shown in Figure 1, but the weld bead B does not reach the tiny gap D on the center side of the pipe between the ends 1a and 2a, resulting in so-called poor penetration.

[0020] Therefore, in the welding method according to the embodiment, welding work is performed through the following steps. This example shows a piping installation process in which an elbow pipe 12 is connected to a vertical pipe 11 rising from a floor surface 10, and a pipe 13 is connected horizontally to the elbow pipe 12, and then a pipe 14 is welded to the pipe 13, thereby extending the pipe horizontally. The ends of the pipes 13 and 14 to be joined by welding are machined into a V-groove, as in the example shown in FIG. 1.

[0021] 2 shows the state in which pipe 14 is being temporarily attached to pipe 13. Worker P1 performing the temporary attachment work performs the work on workbench 16 of aerial work lift 15. On the floor are placed cylinders 17 of various gases (such as argon gas and acetylene gas) required for welding work, and welding equipment and the like are placed on workbench 16.

[0022] In the tack welding work, worker P1 uses a welding rod to weld the ends of pipes 13 and 14 circumferentially at intervals. For example, as shown in Figure 3, tack welding is performed in the order of lower right (a in the figure), upper left (b in the figure), lower left (c in the figure), and upper right (d in the figure) when viewed from the axial direction. The tack welding is performed before the actual welding work. At this time, worker P2 is on the ground (on the floor) monitoring the cylinder 17 and other equipment.

[0023] Once the tacking work is complete, worker P3 performs manual welding work, as shown in Figure 4. Manual pipe welding must be performed by someone with the appropriate knowledge, skill, and experience. For this reason, so-called welders are used. In contrast, worker P1, who performs the tacking work described above, does not need to have the same knowledge, skill, or experience as a welder, so any pipeworker with welding skills can be assigned to the tacking work. Similarly, worker P2 on the ground does not need to have the same knowledge, skill, or experience as a welder; he or she can simply be someone who has taken construction safety courses and training, has the appropriate experience, and is able to manage on-site construction.

[0024] The manual welding by worker P3 is performed sequentially from the bottom indicated by the arrow in Figure 3 upward along the circumferential direction, for example, to prevent the molten bead from dripping.

[0025] The cross-sectional appearance of the pipes 13, 14 after manual welding is completed in this manner is shown in Figure 5. As shown in the figure, a weld bead B1 is formed in the space at the ends 13a, 14a of the pipes 13, 14, and the weld bead B1 also fills the inner gap D. The shape of the space at the ends 13a, 14a of the pipes 13, 14 after manual welding is completed resembles a shallow U-groove due to the weld bead B1 that has been formed.

[0026] 6, worker P4 climbs onto workbench 16 and sets automatic welding machine 21 at the planned welding locations of pipes 13 and 14. This work can be performed by someone other than a welder, for example, a plumber.

[0027] After setting up automatic welding machine 21, worker P5 operates automatic welding machine 21 on the ground (floor). This work can be performed by anyone with general knowledge about welding or who has received appropriate training on operating an automatic welding machine, and there is no need for worker P5 to be a special welder.

[0028] Fig. 5 shows the cross-section of pipes 13, 14 after welding by automatic welding machine 21. In the space between ends 13a, 14a of pipes 13, 14, weld bead B2 is formed by automatic welding on top of weld bead B1 formed by manual welding.

[0029] Considering that automatic welding using an automatic welding machine has traditionally been able to achieve the desired welding in the case of a U-groove, as mentioned above, the spatial shape of the ends 13a, 14a of the pipes 13, 14 after manual welding is completed resembles a shallow U-groove due to the manual weld bead B1 of the first layer, so it is now possible to suitably form a weld bead B2 on top of the weld bead B1 using the torch of the automatic welding machine.

[0030] As described above, the welding method according to this embodiment can prevent poor penetration when using automatic welding machine 21, even if the cross-sectional shape of the end joint of pipes 13, 14 is a so-called V-groove. Furthermore, it is not necessary for welders to perform all welding work; as long as a welder performs at least the first layer of welding, there is no need for a welder to be involved in preliminary tacking work or welding work using automatic welding machine 21. In other words, only worker P3, who performs manual welding, needs to be a welder; the other workers P1, P2, P4, and P5 do not need to be welders. Therefore, in the above-described series of work, the labor of welders can be minimized, allowing welding work at construction sites to be performed optimally.

[0031] For convenience, the workers engaged in the work have been described as P1 to P5. However, in actual work, worker P1, who performs the tacking work, can also be a plumber, and worker P4, who sets up automatic welding machine 21, can also be a plumber. Furthermore, worker P2, who manages safety on the ground, and worker P5, who operates automatic welding machine 21, can also be plumbers. Therefore, the welding method according to the embodiment requires at least one welder and one plumber to perform the work. As a result, when viewed throughout the entire welding work, it is possible to reduce the number of welders required compared to conventional methods, allowing welders, who have become increasingly difficult to secure in recent years, to work more efficiently.

[0032] The automatic welding machine 21 used in the above-described welding method can be any existing automatic welding machine of this type, but in this application, we propose an automatic welding machine 31 suitable for carrying out the present invention, for example, as shown in Figures 9, 10, and 11.

[0033] This automatic welding machine 31 has a traveling unit 32 equipped with a motor and the like. The traveling unit 32 has a pair of ring rails 33a, 33b, and can travel on the outer peripheral surface 33c of an integrated ring-shaped guide rail 33 that can be separated in the radial direction. A plurality of fixing legs 34 are provided on the inner periphery of the guide rail 33 for fixing the guide rail 33 to the outer periphery of a tubular material such as the pipe 14. Fixing to the outer periphery of the tubular material such as the pipe 14 is performed by tightening tightening bolts (not shown).

[0034] Welding torch 35, which performs welding, is fixed to traveling section 32 via an appropriate fixing member 36. Welding wire 41 is successively fed out from the tip of welding torch 35. That is, welding wire 41 is wound around wire reel 42 and is continuously supplied by wire feeding mechanism 43 via wire straightening section 44 to the tip of wire nozzle 45, which serves as a wire support section located directly below welding torch 35. Wire feeding mechanism 43 is fixed to traveling section 32 by an appropriate support member 43a.

[0035] The area directly below welding torch 35, the tip of welding wire 41, and the welding status can be photographed by imaging camera 46. The imaging area is also illuminated by light 47.

[0036] 11, the side end surfaces 42a, 42b of the wire reel 42 are arranged parallel to the peripheral surface 33c of the guide rail 33. Typically, this type of wire reel 42 has the side end surfaces 42a, 42b formed by flat, parallel, opposing disks, with the welding wire 42 wound between them. The lower end of the rotation center 42c of the wire reel 42 itself is supported by a support member 42d, such as a bracket. The support member 42d is fixed to the running part 32.

[0037] Furthermore, the rotation center 42c of the wire reel 42 is positioned on the axial rear side of the guide rail 33, i.e., in the direction away from the running portion 32 (the direction indicated by the arrow U in the figure), as shown in Figure 10.

[0038] This automatic welding machine 31 can be used, for example, as a component of the automatic welding apparatus 51 shown in Figure 12. The automatic welding apparatus 51 has a supply unit 52 that supplies power, gas, etc. and is equipped with a control device that performs various controls. Casters 53 are provided on the underside of the supply unit 52, making it movable. The automatic welding apparatus 51 has a door 54 on the front that can be opened and closed freely, and stores gas cylinders and other items necessary for welding inside. In addition, a remote control device 55 that can be carried by the operator is connected to the supply unit 52, for example, by wire.

[0039] Various cables and hoses necessary for the operation of the automatic welding machine 31 are also connected to the supply unit 52. Specifically, various torch cables, such as an earth wire 60 connected to the piping material serving as the base material, a shielding gas hose 61, a torch cooling water return hose 62, a torch cooling water outlet hose 63, and a power cable 64, are connected to the automatic welding machine 31 via a cable header 65. Furthermore, a control cable 66 for controlling the torch, traveling unit 32, etc. is connected between the supply unit 52 and the automatic welding machine 31. An image signal captured by the imaging camera is output to a monitor 68 of the supply unit 52 via a camera cable 67. Meters 69 that display the current value, gas supply flow rate, etc. are provided on the front of the door 54.

[0040] In this way, a number of different cables and hoses are connected between the supply unit 52 and the automatic welding machine 31. When connecting the various torch cables and control cables mentioned above, it is possible to prevent incorrect connections by color-coding the connection points and terminals of these cables in the supply unit 52, or by color-coding the cables and hoses in the same way as the color-coded connection points and terminals.

[0041] Remote control device 55 is also configured to adjust the travel speed of travel unit 32 of automatic welding machine 31, the feed speed of welding wire 41, and also the output (current value) to welding torch 35 and the position of welding torch 35. Therefore, by setting automatic welding machine 31 around the periphery of the pipe to be welded and connecting the necessary cables and hoses, it is possible to operate automatic welding machine 31 while controlling it from a remote location. Therefore, the person carrying remote control device 55 and performing these tasks does not necessarily have to be a welder; any plumber or other worker who has received the necessary training and is able to operate automatic welding machine 31 can be engaged in automatic welding.

[0042] An example of a welding process using the above-described automatic welding device 51 is shown in the flowchart of Figure 13. First, the pipe to be welded is carried to the welding site (step S1). Next, the end of the pipe is grooved (step S2). As described above, according to the present invention, even with a V-groove, poor penetration can be prevented and welding can be performed favorably, so V-groove preparation, which is easy to perform, can be performed on site.

[0043] Next, the pipes are hung and installed (step S3). Then, the prepared pipes are placed facing each other and the grooves are aligned (step S4). After that, the previously mentioned tack-fitting work is carried out (step S5). After that, the first layer is manually welded (step S6). After the first layer is manually welded, the on-site environment of the pipes to be welded is checked (step S7). This is to reconfirm the installation locations of the automatic welding machine 31 and supply unit 52.

[0044] After checking the environment, supply unit 52 is installed on-site (step S8). Next, the primary power supply in supply unit 52 is connected, cables and hoses are laid and connected, guide rails 33 are attached, and traveling unit 32 is installed (step S9). After these operations are completed, traveling unit 32 is operated once to check the positions of welding torch 35, welding wire 41, etc., before welding begins, and various data is acquired to teach the welding line (step S10). If fine adjustments are necessary, these are made, and then automatic welding work is performed (step S11).

[0045] In the above process, the only work that must be performed by a welder is the first layer welding (step S6); the other work can be performed by a plumber or other person. Therefore, according to the welding method of the embodiment, the work of the welder can be minimized and proper welding work can be performed. Note that the first layer welding does not literally mean only the first welding work when welding the pipes together for the first time. For example, if there is a lack of welding in the first welding, manual welding can be performed subsequently, and when welding by the automatic welding machine 31 becomes possible, subsequent welding work can be performed using the automatic welding machine 31. Therefore, in the present invention, the first layer does not necessarily mean the first welding.

[0046] 11, the side end surfaces 42a, 42b of the wire reel 42 are arranged parallel to the peripheral surface 33c of the guide rail 33. This allows the travel section 32 to rotate along the peripheral surface 33c of the outer periphery of the guide rail 33, thereby reducing the radial length from the center of the pipe, i.e., the height H. This means that the range of the rotational path of the automatic welding machine 31 during welding can be reduced. This allows automatic welding to be performed even in a small working space.

[0047] Furthermore, since the rotation center 42c, which is the center of rotation of the wire reel 42, is located on the rear side in the axial direction of the guide rail 33, i.e., in the direction away from the running portion 32 (the direction indicated by the arrow U in the figure), it is possible to increase the distance between the wire nozzle 45, which is close to the welding torch 35, and the portion of the welding wire 41 that is paid out from the wire reel 42. In other words, referring to Figure 10, even if the angle of the wire nozzle 45 with respect to the wire reel 42 is large, the length of the portion of the welding wire 41 that is paid out up to the wire nozzle 45 can be increased, and the radius of curvature of the trajectory of the welding wire 41 can be increased.

[0048] More specifically, if the rotation center 42c, which is the rotation center of the wire reel 42, is located forward in the axial direction of the guide rail 33, the radius of curvature at the bent portion indicated by R1 in Fig. 10 becomes small, which may cause the welding wire 41 to bend and interfere with the payout of the welding wire 41. In contrast, by positioning the rotation center 42c, which is the rotation center of the wire reel 42, on the rear side in the axial direction of the guide rail 33, i.e., in a direction away from the running portion 32, as in the present embodiment, the radius of curvature at the bent portion indicated by R1 can be increased, and the welding wire 41 can be smoothly paid out to the wire nozzle 45.

[0049] Furthermore, since the running section 32 moves along the peripheral surface 33c of the outer periphery of the guide rail 33, if the wire reel 42 were positioned at the same position as the guide rail 33 in the axial direction of the pipe material, the height of the outer side end surface 42a of the wire reel 42 would inevitably be higher by the thickness of the guide rail 33. In contrast, by positioning the entire wire reel 42 behind the running section 32, it is no longer necessary to position it above the guide rail 33, and the wire reel 42 can be positioned closer to the pipe material to be welded. This makes it possible to reduce the height of the wire reel 42 itself. In such a case, the support member 42d provided on the running section 32 may be, for example, a bracket or the like that is curved or bent downward from the attachment position of the support member 42d.

[0050] The wire reel 42 provided in the automatic welding machine 31 shown in Figures 9 and 10 has a relatively small diameter of about 5 kilograms, but to increase the length of the welding wire that can be wound, it is necessary to attach a larger diameter wire reel, for example, a 10 kilogram reel, to the traveling portion 32.

[0051] The automatic welding machine 31 shown in FIG. 14 shows an example in which such a relatively large diameter wire reel 72 is attached to the traveling portion 32 of the automatic welding machine 31 shown in FIGS.

[0052] 10, and therefore the diameter of the side end surface 72a is larger than that of the wire reel 42. Therefore, the wire reel 72 cannot be placed in the position of the wire reel 42 shown in FIG.

[0053] 14, wire reel 72 is disposed on the opposite side of wire feeding mechanism 43 across travel section 32, and wire reel 72 is supported by support member 72d. In this case, if wire feeding mechanism 43 remains in the position shown in FIG. 10, welding wire 41 unwound from wire reel 72 will have difficulty being introduced linearly into the inlet of wire feeding mechanism 43 and will interfere with travel section 32.

[0054] In this regard, in the automatic welding machine 31 shown in Figure 14, the wire feeding mechanism 43 is configured to rotate relative to the support member 43a, and therefore can be rotated toward the running portion 32 as shown in Figure 14. This allows the welding wire 41 unwound from the wire reel 72 to be introduced linearly into the wire feeding mechanism 43, and also allows the welding wire 41 unwound from the wire reel 72 to be introduced into the wire feeding mechanism 43 without interfering with the running portion 32.

[0055] Even in such a case, by positioning the rotation center 72c of the wire reel 72 axially rearward of the guide rail 33, i.e., in the direction away from the running portion 32 (the direction of the arrow U in the figure), the radius of curvature at the bent portions indicated by R1 and R2 in the figure can be increased, and the welding wire 41 can be smoothly fed to the wire nozzle 45. [Industrial Applicability]

[0056] The present invention is particularly useful for connecting pipes by welding. [Explanation of symbols]

[0057] 1, 2 Piping material 1a, 2a end 10 Floor 11 Vertical pipe 12 Elbow pipe 13, 14 Piping 13a, 14a ends 15. Aerial work lift 16 Workbench 17 Cylinder 21, 31 Automatic welding machine 32 Running part 33 Guide rail 33a, 33b ring rail 34 Fixed leg 35 Torch 41 Welding wire 42, 72 wire reel 43 Wire feeding mechanism 44 Wire straightening unit 45 Wire nozzle 46 Imaging camera 47 Light 51 Automatic welding equipment 52 Supply Unit 55 Remote Control Device 60 Ground wire 61 Shielding gas hose 62 Torch cooling water return hose 63 Torch cooling water outlet hose 64 Power Cable B, B1, B2 weld beads P1~P5 workers

Claims

[Claim 1] A welding method for connecting ends of pipe materials by welding, comprising: At least the first layer of welding is done by hand by workers, The subsequent welding work is carried out by an automatic welding machine. The groove of the pipe material to be welded is a V groove, The automatic welding machine is A welding machine used to weld together the ends of pipe materials, a guide ring attached to the outer periphery of the pipe material; a running portion that is movable in a circumferential direction along an outer periphery of the guide ring; a wire reel provided on the traveling portion; a welding torch provided on the traveling portion; a wire support portion disposed near the welding torch and supporting the welding wire unwound from the wire reel, The side end surface of the wire reel is arranged parallel to the circumferential surface of the guide ring, After the pipe material is hung, the ends of the pipe material are aligned with each other, then temporary welding work is performed, and then the worker manually performs the first layer welding, A welding method characterized in that the tack welding work is performed in the order of lower right, upper left, lower left, and upper right when viewed in the axial direction of the pipe material.

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