JPS594235B2 - Circumferential electroslag welding method for steel pipes - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for circumferential electroslag welding of steel pipes,
In detail, the end faces of a pair of steel pipes are butted together, and while the pipes are rotated, the butt groove is formed with high efficiency and without being affected by the meandering even if there is a meandering in the groove. Relating to a method of electroslag welding.

Conventionally, electroslag welding (hereinafter referred to as slag welding) has been used for circumferential butt welding of steel pipes.

That is, as shown in FIGS. 1 and 2, the end surfaces of the pair of pipes to be welded 5a and 5b are butted against each other, and the water-cooled copper pad 1 for the outer peripheral surface of the groove is pressed against that portion using a pressure means, and welding is performed. Welding is performed using 15 electrodes 2 held by a device 3 and with the wire 9 held in a vertical position 4.

For example, a groove 6 between a pair of steel pipes 5a and 5b to be welded is surrounded by a backing metal 7 and a water-cooled copper metal fitting 1, and a wire 9 is fed into the molten slag 8 floating therein while welding progresses. At the same time, the pipes to be welded 05a and 5b are connected to the turning roller 3a,
There is a method of circumferential welding while rotating on 3b. This type of slag welding is extremely efficient compared to other welding methods such as submerged welding, as it can perform circumferential welding in l-bus construction, but it has the following drawbacks,25 and at present it is not put into practical use. Not yet.

l) In the groove formed between the end faces of the pipe to be welded, the groove line meanderes during bevel processing, assembly, etc. When the tube to be welded is rotated as welding progresses, the rotation causes the tube to be welded to move laterally, that is, in a direction perpendicular to the 30 axis. Therefore, in the above example, the water-cooled copper pad is pressed against the outer circumferential surface of the pipe to be welded using a pressure means, but since it is pressed at a fixed position, it may open due to meandering of the groove line or lateral movement of the pipe. When the leading line is blurred, the pressing position of the 35-karat gold water-cooled copper pad does not change, making it difficult to keep the water-cooled copper pad in the correct position at all times. 2) In the above example, welding is performed with the wire held vertically at a horizontal position in the radial direction of the end surface of the pipe to be welded.

For this reason, when the penetration width on the bead surface side is larger than the width of the reinforcement forming groove provided in the water-cooled copper butt, the cooling effect of the water-cooled copper butt allows the welding between this weld and the outer circumferential surface of the pipe to be welded. The molten slag solidifies between the two, and undercuts etc. occur continuously. The present invention aims to solve the above-mentioned drawbacks, and in particular, it is possible to perform slag welding reliably and efficiently along the groove line even if the groove line is meandering or lateral movement occurs when the workpiece is rotated, and the resulting bead has an undercut. We propose a circumferential electroslag welding method for steel pipes that does not cause such welding defects.

That is, in the method of the present invention, ten pairs of tubes to be welded with their end surfaces butted together are placed horizontally and rotated by a turning roller, etc., and when the circumferences are butted and electroslag welded, a A water-cooled copper pad for the outer circumferential surface of the groove having an upper groove is attached to a carriage that runs along a guide rail fixed to the outer circumferential surface of the pipe to be welded at equal intervals along the groove line. While holding the tube in a freely traveling state, welding is started with a constant welding position set at a point 10 to 15 diameters lower than the horizontal position in the radial direction of the end surface of the pipe to be welded, and after that, the welding speed is Weld at the fixed welding position while rotating the pipe to be welded according to the timing, and when welding has progressed about half a circumference, weld the welding start part of the defective welding part together with the upper groove of the water-cooled copper pad for the outer circumferential surface of the groove. In order to form a finishing groove, stop the rotation of the tube to be welded when the welding has completed one complete turn, and while gradually pulling the welding electrode upward, insert the upper groove of the water-cooled copper pad for the outer circumferential surface. The welding completion groove is filled with weld metal to complete the welding process.

The method of the present invention will be explained in detail below.

First, when welding a pair of steel pipes 5a and 5b together, we start from the states shown in FIGS. 3a and 3b.
That is, each end surface of the pair of steel pipes 5a, 5b is butted,
A groove 6 is formed by applying a backing metal 7 and a water-cooled copper metal fitting 1 to that part. As described later, the water-cooled copper pad 1 is attached to the guide rail 1 parallel to the groove 6 as shown in Figures 7 to 9.
Installed so that it can run freely along 0. When starting slag welding along this circumferential groove 6, each steel pipe 5a95b is rotated clockwise in accordance with the welding speed.
Welding is performed from a point that is about 10-15 degrees lower than -X in the direction of the hour hand at the center angle θ, and thereafter welding is continued with this position as the fixed position. When forming this welding start position, as shown in FIGS. Temporarily attach it to rough spots to form a smooth arc strike and prevent molten slag from falling off. In addition, in order to prevent molten slag from flowing out from the groove for overfilling of the water-cooled copper pad at the start of welding, the back surface of the arc starting hardware 30 is filled with a welding putty 31. Ku. As mentioned above, when slag welding is started from a position 10-15X below the horizontal position at the central angle θ, instead of at the horizontal position XX as in the conventional example, molten slag It does not solidify, and defects such as undercuts can be prevented. That is, in the prior art, the welding starts at a horizontal position XX and the welding is carried out at this position, with the wire being held perpendicular to the position XX and in a vertical position. Therefore, when the penetration width of the bead surface is larger than the width of the reinforcement forming groove of the water-cooled copper pad, the molten slag is cooled by the water-cooled copper pad and the water-cooled copper pad and the steel pipe surface are connected. A solidified slag layer is formed during this period, causing undercuts and the like. In contrast, the method of the present invention starts 10 to 15 center angles down from the X--X position, where the welding takes place, and the wire is held perpendicular to this radial position. In this state, in the conventional example, the molten slag that produces solidified slag is pushed up by the molten metal of high temperature and high specific gravity and floats above it, so that undercuts and the like can be completely prevented. Next, slag welding is started as described above, and is allowed to proceed in that state. When the slag welding has progressed approximately half the circumference of the circumferential groove, Fig. 4 a and b1
In particular, as shown in Fig. 5b, the welding start part 32 (note, indicated by a dotted line) is a welding defect (in slag welding, the welding start part?
Therefore, defects such as poor fusion are likely to occur. ), for example, by arc air gouging, etc., and at this time, it is removed so that a groove for finishing welding, which will be described later, is formed as shown by line 33.
In other words, this adjustment is not only for removing defective welding parts, but also for making adjustments so that the work immediately before welding, which will be described later, can be carried out smoothly.In general, the groove depth is continuously increased as shown by the solid line 33. Adjust so that it becomes shallower. There is no need to stop this work and it can be done in progress. Next, when the slag welding is nearing the end,
As shown in the figure, the electrode 2 is gradually pulled up in the direction of arrow A while the steel pipes 5a and 5b are kept rotating, and when it reaches just before the end, the rotation of each steel pipe 5a and 5b is stopped as shown in Fig. 6, and the electrode 2 is 2 will still be raised.

In this way, while supplying the welding wire 9, welding is carried out inside the welding termination groove formed by the upper groove 34 and the deletion line 33 of the water-cooled copper pad 1. Continue until molten slag overflows. In this case, when pulling up the electrode 2 in the A direction, do not short-circuit it with the water-cooled copper pad 1, and do not change the molten slag depth too much as the molten slag 8 rises (if the slab depth becomes too large, On the other hand, if the bead is too shallow, an arc will occur and welding will be difficult.) Furthermore, it is necessary to form the bead reinforcement at the end sufficiently so that it can be easily repaired later. Incidentally, it is preferable that the upper groove 34 of the water-cooled copper pad 1 be formed into a tapered shape having the same dimension as the width of the bead.

As described above, electroslag welding is performed in the method of the present invention, and by the way, this method produces 32t x 80W! When LΦ steel pipes were butted and circumferentially welded, the welding conditions were: average root gap 12TIUn welding current 450A, voltage 4
5V, power supply DC constant lightning voltage characteristics, solid wire 1.6Φ,
Although it was a molten type flux, a good welded part with no welding defects was obtained in a required welding time of about 37 minutes.

Further, as described above, when slag welding is performed while keeping the water-cooled copper pad movable, a welding apparatus having the following configuration is preferable.

That is, FIG. 7, FIG. 8, and FIG. 9 show a side view, a front view, and a plane of each welding device, and as is clear from these drawings, a guide is provided on the outer periphery of the steel pipe 5b parallel to the groove line 6. A rail 10 is attached, and a carrier 11 is provided so as to be movable along the guide rail 10. Further, the water-cooled copper pad 1 is held by the carrier 11. Therefore, when the steel pipes 5a, 5b are rotated on the turning rollers 3a, 3b, the position of the water-cooled copper pad 1 accurately and reliably follows the groove 6, which eliminates the problem/l as in the conventional example. In order to reliably prevent leakage of the molten slag 8 and perform slag welding smoothly, the water-cooled copper pad 1 must be pressurized by the pressurizing device 12, and the electrode 2 must be firmly held. An electrode holding aim adjusting device 13 is attached so that the aiming position can be finely adjusted. The following is a description of each of these devices.

First, as shown in FIGS. 10 and 11, the guide rail 10 of the water-cooled pad guide device is constructed by connecting at least four arc-shaped divided pieces 10a with a connecting port 14. Tighten and secure around the outer circumference of the steel pipe.

Therefore, even if the groove line is meandering, the guide rail can be set accordingly, and errors in the circumferential length of the steel pipe (which naturally occur during manufacturing) are possible.

) can be absorbed by the connecting bolt 14. Furthermore, since the steel pipe moves laterally due to rotation, the water-cooled copper pad 1 can be accurately pressed against the groove 6. Further, it is preferable to attach the guardrail 10 via a metal sleeper 15. The metal sleeper 15 can secure a space for the wheels 16 of the carriage 11, which will be described later, and block welding heat, thereby preventing thermal expansion of the guide rail 10. (loosening of the extending guide rail) can be prevented. The water-cooled copper pad 1 is held by the carrier 11, and the carrier 11 runs along the guide rail 10 in accordance with the welding speed. It is attached via metal fittings 17 and 18 as shown in FIGS. 13 and 14.

The wheels 16 of the carrier 11 are attached via coil springs 19, and the changes in the outer diameter of the steel pipe and the guide rail 10
The structure is such that the carriage edge can run without trouble even when the curvature changes. Further, the pressurizing device 12 is used to press the water-cooled copper pad 1 and prevent a gap from occurring between the water-cooled copper pad 1 and the steel pipes 5a and 5b.

In this device 12, a lever 20 is rotatably supported at a pivot point 20a as shown in FIG. give. What $? The repulsive force of the spring may be used instead of the weight 21. Further, the electrode aim adjustment device 13 fixes the electrode 2 by tightening it with a bolt 23 as shown in FIGS.
It is configured such that it can be adjusted in the vertical direction 27 with a dial 26, and in the horizontal direction 29 with a dial 28.

As explained in detail above, in the method of the present invention, a guide rail is provided on the outer periphery of the pipe to be welded, such as a steel pipe, and is parallel to the groove line, so that the water-cooled copper pad can run along this guide rail. Even if there is meandering of the tip or lateral movement when the pipe to be welded rotates, the water-cooled copper pad can always be accurately positioned and applied to the groove, ensuring reliable slag welding. I can do it.

In addition, since the welding position is always at a position 10 to 15 degrees lower in the center angle than the horizontal position in the radial direction, a beautiful and stable bead appearance can be obtained that can completely prevent undercuts on the bead surface.

[Brief explanation of drawings]

Fig. 1 is a front view showing a partial cross section when steel pipes are generally circumferentially electroslag welded, Fig. 2 is a plan view thereof, and Figs. 4a and 4b are explanatory diagrams of the mode of adjustment of the welding start part and an enlarged view of a part thereof; FIG. 5 is an explanatory diagram when approaching the end of welding; FIG. 6 is an explanatory diagram immediately before the end of welding, FIGS. 7, 8, and 9 are a side view, a front view, and a plan view of an example of an apparatus for carrying out the method of the present invention, respectively, and FIG. 10 is an illustration of a guide rail. A side view of an example, Figure 11 is an enlarged view of a part of it, Figures 12 and 13.
The figure and FIG. 14 are a front view, a top view, and a side view of an example of a carrier tool, FIG. 15 is a layout diagram of an example of a padding device, and FIGS. 16 and 17 are an example of an electrode holding aim adjustment device. They are a side view and a front view. Code 1...Water-cooled copper pad, 2...Battery, 3a, b...Turning roller, 3...
...Welding device, 4...Welding position, 5a, b...
... Steel pipe to be welded, 6 ... Bevel, 7 ...
... Backing gold, 8... Molten slag, 9...
...Welding wire, 10...Guide rail, 11
...Carrier, 12... Gold pressure device, 13... Electrode holding aim adjustment device, 14.
...Connecting bolt, 15 ... Pillow hardware, 1
6... Wheels, 17, 18... Metal fittings, 1
9...Coil spring, 20...Lever, 2
0a... Pivotal point, 21... Weight, 22
...pressure force, 23 ... bolt, 24,
26, 28... Dial, 25... Front/back direction, 27... Up/down direction, 29...
Left and right direction, 30... Arc start hardware, 3
1... Welding fatigue agent, 32... Welding start part, 33... Solid line, 34... Tapered upper groove.

Claims (1)

[Claims] 1 When a pair of pipes to be welded with their end faces butted together are placed horizontally and rotated by a turning roller, etc., and the circumferences are butted and electroslag welded, a groove outer periphery having an upper groove of the same size as the excess width at the upper part is used. The surface water-cooled copper pads are attached to a carriage that runs along guide rails fixed to the outer circumferential surface of the pipe to be welded at equal intervals along the groove line, so that it can move freely against the pipe to be welded. After holding it, the center angle from the horizontal position in the radial direction of the end surface of the pipe to be welded is 10~
Start welding by setting the position lowered by 15 degrees as the fixed welding position.
After that, welding is performed at the welding position while rotating the pipe to be welded according to the welding speed, and when welding has progressed about half a circumference, the welding start part of the welding defective part is placed on the water-cooled copper pad for the outer peripheral surface of the groove. Along with the upper groove, a bevel for finishing the weld is formed.
When welding has completed one complete turn, stop the rotation of the pipe to be welded, and while gradually pulling the welding electrode upward, insert it into the welding end groove in the upper groove of the water-cooled copper pad for the outer circumferential surface. A method for circumferential electroslag welding of steel pipes, characterized by filling the weld metal to complete the welding.