JPH0429471B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for automatically welding the abutting portions of large-diameter steel pipes from the inner surface, and more specifically, the present invention relates to a method for automatically welding the abutting portions of large-diameter steel pipes from the inner surface.
A water-coolable copper dowel is used, and welding conditions such as the separation distance from the pipe inner surface of the welding torch used to weld the inner surface of the butt part are changed depending on the circumferential position of the butt part. In particular, we propose an automatic welding method that can improve the quality of welding finish and perform efficient welding. [Prior art] In the construction of large-diameter pipelines with a pipe diameter of approximately 2000 mm, beveled pipe ends are butted against each other, and the butted portion is circumferentially routed along the inner surface of the butted portion. This is done by using a movable welding torch. As such a welding method, a method shown in a partial vertical cross-sectional view in FIG. 5 and a partial cross-sectional view in FIG. 6 is known. As shown in FIG. 5, a steel plate 101 is formed by groove-processing the inner surface so that the groove angle is approximately 30°.
A steel backing metal 31 is placed on the outer periphery of the abutted portion where the steel plate 102 and the steel plate 102 are butted together to perform metal welding.
is welded to the entire circumference, and a cooling copper plate 32 is fitted and fixed on the outer periphery of the backing metal 31. An automatic welding machine (not shown) is installed inside the pipe, and a welding torch 2 of the automatic welding machine is installed at the beveling part.
01 is faced so that it can be moved in the circumferential direction.
Then, the operator determines the position of the welding torch 201, that is, the distance a between the tip of the welding torch 201 as shown in FIG. α
(Arc incident angle, specifically the welding torch 20 relative to the normal to the inner surface of the pipe as shown in FIG.
Welding is carried out by moving the welding torch 201 all around the inner surface of the tube while changing the inclination angle α) of the axis of the nozzle tip 201a in the circumferential direction according to the circumferential position of the abutting portion. It was a method of doing this. [Problems to be Solved by the Invention] Incidentally, in the conventional method as described above, it is necessary to perform fillet welding of the backing metal 31 to the butt portion, and when performing this welding work, for,
Prior to this, it is necessary to align the two tubes 101 and 102. However, in the conventional method, as shown in Fig. 5, the root gap (distance between the bottoms of the beveled parts) was about 8 mm, so both
02 alignment work involves positioning both pipes 101 and 102 in the pipe axis direction, and then temporarily welding a U-shaped "horse" with its legs straddling both pipes 101 and 102. It was carried out by For this reason, the above-mentioned temporary welding and fillet welding are required before the actual welding of the butt parts, and the "horse" needs to be removed after welding the butt parts, which requires a lot of time. As a result, there was a problem in that efficient welding could not be performed. In addition, the backing metal 31 melts during welding of the abutted portions and remains as a large convex portion on the outer surface of the abutted portions, deteriorating the quality of the weld finish. [Means for Solving the Problems] The present invention has been made in view of the above circumstances, and includes a groove for the Uranami bead on the pipe side, and a copper stopper that can be cooled by water. To provide an automatic welding method that is removably attached to the outer surface of a pipe end abutting part to form a smooth uranami bead, has excellent welding finish quality, and can perform efficient welding. purpose. The automatic welding method according to the present invention involves a welding process in which the pipe ends of large-diameter steel pipes are abutted against each other, and a stopper is attached to the outer surface of the abutted portion, so that it can be moved around the inner surface of the abutment. In the method of automatically welding the abutting portion using a torch, two large diameter steel pipes are aligned and butted, temporarily welded, and a groove for the uranami bead is formed on the pipe side, and A water-coolable copper stopper is removably fixed to the abutting portion, and the distance of the tip of the welding torch to the inner surface of the pipe and the inner surface of the welding torch are adjusted according to the circumferential position of the abutting portion. The abutting portion is welded while changing the inclination angle in the tube circumferential direction with respect to the normal line. [Examples] The present invention will be described in detail below based on drawings showing examples thereof. FIG. 1 is a front view showing the implementation state of the automatic welding method according to the present invention, FIG. 2 is an enlarged view of the area around the welding head 15 shown in FIG. 1, and FIG. . The unwelded pipe 2 of the same diameter is aligned with the unwelded side end face of the already welded joint 1 with a diameter of about 2000 mm, which is extended by butt welding the pipe ends to each other, and the pipes are butted together.
The two are connected by temporary welding at appropriate locations within the groove of this abutting portion. Welded pipe 1 and unwelded pipe 2
Each abutting part is beveled on the inner surface side, and the bevel angle at the abutting part is set to be approximately 50°, and the root gap of both pipes 1 and 2 is targeted to be 0 mm. Further, in consideration of the machining accuracy of the flatness of the end face, a tolerance of about +3 mm is allowed. A pair of semi-circular butts 3, 3 of appropriate width and thickness are placed on the outer periphery of the abutting portion, and a pair of convex locking pieces 3c, 3c formed at the respective circumferential ends are provided between the two. By tightening using the lever blocks 4, 4, it is fitted and fixed externally across the abutting portion of both the pipes 1, 2, and when the lever blocks 4, 4 are released, the fittings 3, 3 are tightened. can be easily removed from the abutting portion. As the cross-sectional shape of the deposit 3 is shown in Fig. 3,
The open end of a copper semicircular member 3b having a concave cross section is welded to the outer surface of a semicircular copper plate 3a,
A square hole 3d is formed approximately in the center of the cross section. Both ends in the circumferential direction of the stopper 3 in the square hole 3d are closed. At the center of the inner surface of the copper plate 3a, a curved groove 3e with a center of curvature is formed on the inner surface in order to have a smooth Uranami bead and to position a temporary welding spot.
is formed over its entire circumferential length. A cylindrical feeder is provided on the outer surface side of both ends in the circumferential direction of the stopper 3.
Drain hose connection parts 5 and 6 are attached, and the holes communicate with the square hole 3d. One end portions of a water supply hose 5a and a drainage hose 6a are connected to the water supply hose connection portion 5 and the drainage hose connection portion 6, respectively. The other end of the water supply hose 5a is connected to the discharge side of a water pump (not shown), and is also connected to a drain pump 6a.
The other end is connected to a cooling water tank, and cooling water 7 is circulated and supplied into the square hole 3d by driving a water pump. This allows the money 3 to be cooled. A welding head 15 is provided inside the pipe so as to face the inner surface of the pipe. The welding head 15 is supported by fixed legs (not shown) fixed within the tube so that it can rotate around the center of the tube. An electric motor 17 for driving the welding head 15 is installed at one end of the welding head 15 in the circumferential direction. The electric motor 17 is driven by a signal from a drive control device (not shown) provided outside the tube, and the gear mechanism 1
8, the driving force is applied to a welding head drive wheel 1 mounted at a position near one end of the welding head 15 in the circumferential direction so as to be able to roll in the circumferential direction on the inner surface of the tube.
It is now possible to transmit to 9. When the electric motor 17 is thereby driven, the drive wheel 19 rolls on the inner surface of the pipe, and the welding head 15 moves around the center of the pipe. Note that even when the electric motor 17 is stopped after the welding head 15 has been rotated in the upward direction indicated by the arrow in FIG. There isn't. Note that such circular movement of the welding head 15 may be performed by providing an annular rack concentrically on the inner surface of the pipe and driving a pinion connected to the electric motor 17. On the inner surface of the tube, which is substantially the same circumferentially as the mounting position of the driving wheel 19 of the welding head 15, a cutter shoe 11 is attached along the inner surface of the tube. The cutoff shoe 11 slides on the inner surface of the pipe as the welding head 15 moves. At a position near the other end of the welding head 15 in the circumferential direction of the tube, as shown in FIG. A welding torch 21 is attached to the other end of the welding head 15 in the circumferential direction, and the welding head 15 is made to be able to roll on the grooved surface of the abutting portion and is spaced an appropriate distance apart in the circumferential direction. A pair of copying rollers 20, 20 are attached. welding torch 21
As shown in FIG. 2, the wire 21b is curved toward the normal line 29, and a wire 21b is inserted through the wire 21b with an appropriate length projected therein. Inclination angle α of welding torch 21 and welding torch 2
1, specifically, the distance a between the tip of the wire 21b and the inner surface of the tube is adjustable. As shown in FIG. 2, a guide rail 23 is installed extending from the center of the welding head 15 in the circumferential direction to the other end and curved toward the drive wheel 19. The center of curvature of the guide rail 23 coincides with the tip of the wire 21b. The guide rail 23 includes a holder 24 that supports the welding torch 21 therein, and upper guide rollers 22a and 22 equipped with the holder 24.
a, it is mounted so as to be sandwiched between the lower guide rollers 22b. Guide rollers 22a, 22a, 22
b can roll along a guide rail 23, and by rolling the guide rollers 22a, 22a, 22b, the mounting position of the holder 24, that is, the tilt angle α of the welding torch 21 can be adjusted. It's summery. This adjustment is made by rotating the knob 25 provided on the opposite side of the pipe inner surface of the welding head 15, and
This is carried out by threading a threaded rod 28, which is connected at one end to the holder 24 through a thread and whose other end is screwed to the holder 24, to move the holder 24 along the guide rail 23. In addition, as mentioned above, the center of curvature of the guide rail 24 and the wire 21b
Since the tips of the two coincide with each other, the distance a during this adjustment
remains unchanged. Next, the adjustment of the distance a will be explained. An end portion of the guide rail 24 on the side of the center portion in the circumferential direction of the welding head 15 is attached to a guide rail support member 40 . The guide rail support member 40 can be moved toward and away from the inner surface of the pipe by threading a threaded rod 41 that is threaded thereon, and the distance a can be adjusted by adjusting the amount of feed. Ru. The copying rollers 20, 20 copy the groove in the tube axis direction of the welding head 15, that is, the welding torch 21, which moves around on the inner surface of the tube by the drive of the electric motor 17, so that the welding torch 21 accurately forms the grooved part. Welding is performed to form a weld pool at the front end of the cutlet 11 in the moving direction. Next, the procedure for carrying out the method of the present invention will be explained in detail. The unwelded pipe 2 is suspended by a crane and aligned with the already installed welded pipe 1,
The ends of both tubes 1 and 2 are butted against each other. Next, weld the appropriate places within the groove of this butt part by manual welding,
Temporarily attach both pipes 1 and 2. Next, as described above, the pair of pads 3, 3 are fixed to the outer surface of the abutting portion by tightening the lever blocks 4, 4, and then the cooling water 7 is circulated inside the pads 3, 3 using a water pump. .
Next, the welding head 15 is installed inside the tube, and welding is performed at each circumferential position on the inner surface of the tube shown in FIG. 5 according to the welding conditions shown in Table 1. FIG. 5 is a schematic front view showing the circumferential position of the inner surface of the tube in terms of clock time, and since the tube is symmetrical, the right half is omitted. Table 1 shows the welding conditions (distance a, inclination angle α, groove shape, welding voltage, welding current) when the welding torch 21 is located at the welding position in the circumferential direction of the pipe in comparison with those of the conventional method. It is a table. however,
The welding conditions are the same for the left-right symmetrical positions in the tube circumferential direction, and the right half is omitted. Also,
The steel pipe to be welded has a diameter of 2000 mm and a wall thickness of 20 mm.

〔effect〕

Next, the effects of the present invention will be explained with reference to Table 2 based on Examples. Table 2 shows pipe diameter 2000 obtained by the method of the present invention.
Fig. 2 is a table showing the results of welding of welded pipes and unwelded pipes with a wall thickness of 14 mm to 29 mm, images of welded parts were taken, and the quality of the finished product was inspected using grade 3 X-ray film.

[Table] From Table 2, when the method of the present invention was used, the passing rate of finishing quality was high, and good results were obtained. In addition, it was confirmed that the method of the present invention can improve work efficiency by about 14% compared to the conventional method because the alignment work can be performed quickly and the time required for bead polishing can be shortened. Ta. In the case of the method of the present invention as described above, a copper stopper which is provided with a curved groove for forming a smooth-shaped Uranami bead and is water-coolable is removably fixed to the outer surface of the pipe end abutting part. However, since the pipe end abutting portions are welded according to welding conditions determined in advance through experiments, efficient welding can be performed, and
Good welding finish quality can be obtained. In addition, in the case of the embodiment described above, the root gap is set to substantially 0, the welded pipe and the unwelded pipe are butted against each other, and the grooves of the butted portion are temporarily welded to connect both pipes. Since the pipes are connected in alignment, it is easy to position both pipes in the axial direction, and the alignment work can be done quickly without the need for "horses" as in the conventional method, which further improves the welding work. The present invention has excellent effects, such as greatly improving overall efficiency and resulting in significant cost reductions.

[Brief explanation of drawings]

FIG. 1 is a front view showing the implementation state of the method of the present invention;
Figure 2 is an enlarged view of the area around the welding head, Figure 3 is an enlarged cross-sectional view of the welding metal, Figure 4 is a schematic front view showing the welding position, and Figure 5 is a partial vertical cross-section showing the state of implementation of the conventional method. FIG. 6 is a partial cross-sectional view thereof. 1...Welded pipe, 2...Unwelded pipe, 3,3...
Welding money, 15... welding head, 21... welding torch.

Claims (1)

[Scope of Claims] 1. A welding torch that abuts the ends of large-diameter steel pipes against each other, attaches a stopper to the outer surface of the abutted portion, and is movable around the inner surface of the abutment. In this method, two large-diameter steel pipes are aligned, butted, temporarily welded, and a groove for the uranami bead is formed on the pipe side. A copper stopper is removably fixed to the abutting portion, and the distance of the tip of the welding torch to the inner surface of the pipe and the inner surface of the welding torch are determined depending on the circumferential position of the abutting portion. An automatic welding method characterized by welding abutted portions while changing the inclination angle in the pipe circumferential direction with respect to the normal line. 2. The automatic welding method according to claim 1, wherein the root gap of the abutting portion is substantially zero.