JPH04200975A - One-side welding method for pipes - Google Patents

Abstract

PURPOSE:To perform welding of high quality with high electric current and high speed welding in performing one-side welding of the pipes by carrying out arc sensor automatic groove profile control by the high-speed rotational arc welding process and further, using ceramics backing material on the groove rear. CONSTITUTION:In subjecting the pipes 10 anti 10 to butt welding at the ends thereof, a groove 14 with the V-shaped bottom of an annular channel is formed on the butt end faces and the ceramics backing material 16 is arranged on the interior sides of the pipes 10. An automatic welding machine 1 is made to self-travel along a circumferential, guide rail 12 tack-welded to the exteriors of the pipes 10, a welding torch 2 fitted to the welding machine 1 is rotated by a motor 3 and gas shielded arc welding is performed by a high-speed rotational arc with the arc rotational diameter D of 1.0-4.0mm and the arc rotational speed of >=10Hz. In this case, while groove automatic profile control being carried out by an arc sensor, one-side welding by all positions is performed from the exteriors of the pipes 10 with a welding current of >=300A at the welding speed of >=150cm/min by using a welding wire 7 with 0.8-1.8mm diameter.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a method for welding a pipe on one side.

[Prior art] Conventional methods for single-sided welding of pipes are divided into high-speed welding methods such as the Sbred-E method, which welds 100 pipes per day, and low-speed welding methods of 1 to 2 joints per 8 days. .

In the conventional single-sided welding method for high-speed welding of pipes, a narrow groove is formed on the end surface of the pipe in the shape of a V-shape or a U-shape at the bottom of the annular groove, and a copper backing material is placed on the inside surface of the pipe. MAG welding using a swinging arc with an arc swing speed of 511z or less and an arc swing width of 1.0 to 2.0 mm while running an automatic welding machine on a circumferential guide rail attached to the outer surface of the pipe. Welding current 250-300 A' depending on method
.

A method is known in which the first layer is welded on one side from the outer surface of the pipe at a welding speed of 75 to 10 cm/min.

[Problems to be solved by the invention] In the conventional single-sided welding method for pipes, when high-speed welding is performed by increasing the welding current and welding speed, discontinuous beats may occur, or insufficient welding or cracks may occur in the welded part. There was a problem that defects occurred. In addition, there is a method of tracing the groove width using a contact type sensor that runs a guide roller in contact with the groove, but this method has problems with accuracy and is not suitable for high-speed welding. The current situation is that it has not been put into practical use.

The present invention has been made to solve these problems, and it is possible to speed up the first layer welding in pipe butt welding with stable quality, and to apply high-precision automatic bevel tracing using an arc sensor to one side of the pipe. The purpose is to obtain a welding method.

[Means for Solving the Problems] A method for single-sided welding of pipes according to the present invention includes forming a narrow groove in which the bottom of the annular groove is V-shaped on the abutting end surfaces of the pipes, and forming a ceramic groove on the inner surface of the pipe. While running on a circumferential guide rail with a backing material arranged and an automatic welding machine attached to the outer surface of the pipe, the rotational speed of the arc was set to 1oIIz or more, and the rotational diameter of the arc was set to 1.0 to 4.0mm. Using a gas-n-old arc welding method using a rotating arc and automatically controlling the groove by an arc sensor, the wire diameter was 0.8 to 1.6 mm, the welding current was 300 A or more, and the welding speed was 150 cm/min or more. This method is characterized by single-sided welding of the first layer from the outside of the pipe in all positions.

The reason for using a high-speed rotating arc welding method in which the arc is rotated at high speed in this invention is that the number of oscillations in the conventional method is 10° or more (experimentally MAX 250Hz), compared to 5 hours or less in the conventional method.
) high-speed (rotational) oscillation can be obtained, so even if high-speed welding is performed, welding unevenness and bead shape defects that occur due to a coarse oscillation pitch will not occur. In other words, the high speed limit at which the weld becomes discontinuous in high speed welding is 1.4 to 2.0 times higher in this method than in the conventional welding method. In addition, especially in high-speed welding of the first layer single-sided welding, welding 1--chi, that is, arc groove tracing accuracy, response speed, which greatly influences welding quality, this method uses the circularly moving arc itself and a sensor to perform real-time welding. Highly accurate bevel profile control is possible.

On the other hand, the reason for using a ceramic backing material is that with conventional copper backing materials, the molten pool is rapidly cooled immediately after welding, which tends to cause cracks in the welded area.This also helps speed up welding. This is because we discovered that there is a limit, and using a ceramic backing can be much faster than a copper backing.

[Function] According to the present invention, since a high-speed rotating arc welding method and a ceramic backing material are used on the inner surface of the pipe, the welding speed is 1.4 to 20 times faster than that of the conventional oscillating arc method. Stable penetration and a good weld bead can be obtained with a wire diameter of 08 to 1.8 +++ m and a large welding current of 300 A or more.

In addition, high-precision tracing can be performed in real time by groove tracing control using an arc sensor, which automates welding work and achieves a stable back bead shape and a good front bead shape.

[Example] The welding method of the present invention will be explained below using the drawings.

Figure 1 is a schematic diagram of the automatic welding machine.
is the circumferential guide rail 1 temporarily attached to the outer surface of the pipe 10
It is installed so that it can run on its own along 2. A welding torch 2 provided in this welding machine main body 1 is rotated by a motor 3 via a gear mechanism 4, and is connected to an It is supported via an X-axis slide block 6 that is movable in the y-axis). The rotational speed N of the torch 2 is the rotational speed of the arc, and the rotational speed and rotational position are detected by a rotation detector (not shown). The welding wire 7 is automatically fed to a current-carrying tip having an eccentric hole of l·-chi 2, and the rotational diameter of the arc is determined by this eccentric distance. This allows the rotating arc method to be implemented.

Reference numeral 16 denotes a ceramic backing material disposed opposite to the groove 14.

Figure 2 is a principle diagram of a high-speed rotating arc, and the electrode nozzle 2
1 is rotatably supported by a bearing part 20, 22 is a current-carrying tip screwed to the lower part of the electrode nozzle 21 and has an eccentric wire passing hole, and 7 is a welding wire that passes through the center hole of the electrode nozzle and connects the current-carrying tip 22. Continuously fed from the eccentric hole. 3 is a motor that connects the electrode nozzle 21 to 1 through a gear mechanism.
In other words, the welding tip 22 having an eccentric hole connected to the tip of the electrode nozzle 21 is also rotated, so the welding wire 7 fed from the tip of the energizing tip 22 also moves in a circular motion, making it easy to arc. It can rotate at high speeds.

FIG. 3 is a diagram showing the principle of groove profile control using an arc sensor, and shows the waveform of the arc voltage E that changes in accordance with the position of the rotating welding wire 7, that is, the arc. In the figure, (a) defines the position of the arc, where the front center of the arc that continuously rotates in the right direction is Cr, the rear center is Cr, and the left and right sides are L-R.

In the figure, the waveform indicated by a solid line indicates a case where the center of the rotating arc is shifted toward the R side by ΔX from the center of the groove, as shown in (b) in the figure, and the waveform indicated by a broken line indicates a case where there is no shift. If there is no deviation as shown by the broken line, the waveform is symmetrical with respect to the position Cr, but if it is deviated by ΔX as shown by the solid line, the waveform is asymmetrical.

By detecting and correcting this waveform asymmetry, the deviation amount ΔX in the X-axis direction can be corrected.

That is, the waveform is taken out between the predetermined angles on the left and right with the position Cr as the center, and the waveform area created between the predetermined angles is calculated as SI1. S
Find the areas S and S or equalize RL
By correcting the welding points 1 and 1 in the X-axis direction so that the arc becomes R, the axis of rotation of the arc and the center of the groove can be made to coincide.

Distance control in the height direction of 1-chi, that is, in the X-axis direction, is a method in which the average value of one rotation of the welding current waveform is compared with a reference value, and the y-axis is controlled to move so that the difference becomes zero. It is.

FIGS. 4(a) and 4(b) are enlarged cross-sectional views of the groove shape and the backing material. , the vertical wall has an inclination angle θ of 0° to 3°. Further, the inclination angle α of the bottom portion 14a is 70° to 110°.

Furthermore, the RF dimension is 0.5 to 1.5 mm, and the pipe wall thickness T
In the case of 8 to 16.7 πm, the groove width G of the annular groove 14b is 5 to 10 mm. In addition, the groove 14
A small inner groove 14c may be provided on the inner surface of the flat plate as shown in FIG. The size is 0.5~1. ．． It is 5mm. 16 is pipe 10
This is a ceramic backing material placed on the back side of the groove 14. Note that a grooved ceramic backing material lea or L6b shown in FIGS. 6(a) and 6(b) may also be used.

FIG. 5 shows the laminated state of a cross section of a welded bead. In the figure, the initial layer R has good back bead formation. There were no welding defects such as insufficient welding or cracks. Welding of the laminated layer F1 and the finishing layer C can also be carried out with a large current and high speed by the welding method according to the present invention.

In the specific example described above, welding is performed in an atmosphere of 100% CO2 gas, but it goes without saying that welding can be similarly performed in an atmosphere of mixed gas with 80% inert gas.

[Effects of the Invention] As explained above, the present invention uses a high-speed rotating arc welding method, automatic arc sensor groove tracing control, and furthermore uses a ceramic backing material on the back surface of the groove to perform high-current, high-speed welding. By welding the first layer on one side in all positions, a high quality and good back bead shape can be obtained. The welding method of the present invention can also perform all lamination welding continuously, and has the effect that butt welding of pipes can be performed with high quality and high efficiency.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an automatic welding machine used in the welding method of the present invention, Fig. 2 is a principle diagram of a high-speed rotating arc, Fig. 3 is a principle diagram of arc sensor groove tracing, and Fig. 4 (a),
(b) is an enlarged sectional view of the groove shape and backing material, Figure 5 is an explanatory diagram showing the laminated state of the cross section of the welded bead, and Figures 6 (a) and (b) are the grooved backing material. It is a sectional view showing the material. DESCRIPTION OF SYMBOLS 1... Welding machine main body, 2... Welding torch, 3... Motor, 4... Gear mechanism, 5... X-axis slide block, 6... X-axis slide block, 7... Welding wire, 10... Pipe, I2... Guide rail, 14
...Bevel, 18...Backing material, 20...Bearing part, 2
1... Electrode nozzle, 22... Current-carrying tip.

Claims (1)

[Claims] In butt welding of pipes, a narrow groove in which the bottom of the annular groove is V-shaped is formed on the butt end surfaces of the pipes, a ceramic backing material is placed on the inner surface of the pipe, and an automatic welding machine is applied to the outer surface of the pipe. The groove is automatically traced using an arc sensor using a gas-shielded arc welding method using a high-speed rotating arc with an arc rotation speed of 10 Hz or more and an arc rotation diameter of 1.0 to 4.0 mm while running on the attached circumferential guide rail. Wire diameter 0.8~1.6 while controlling
A method for single-sided welding of pipes, characterized by performing single-sided welding of the first layer from the outer surface of the pipe in all positions at a welding current of 300 A or more and a welding speed of 150 cm/min or more.