JPH0318477A - Pulse welding method for single-sided first layer welding of circumferential butt joints of pipes - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a pulse welding method that controls the shape of the back bead by pulse control in single-sided first layer welding of a circumferential butt joint of a pipe in pipeline construction work. Regarding welding methods.

[Prior art] Figure 7(a). As shown in (b), in circumferential butt joints of pipes, root gap (G) and misalignment (
The occurrence of H) is unavoidable in on-site welding. Generally, the root gap is Max1.
Welding work is required to allow a maximum of 1.6mm of misalignment.

[Problems to be Solved by the Invention] Due to such root gaps and misalignments, conventional welding methods have the following problems.

■The tolerance of the back bead shape against root gap and misalignment decreases as the welding current increases. Therefore, M
a-xl. omm root gap, Maxi, 6mm
If a misalignment is assumed, the applicable welding current and, by extension, the welding speed will be limited.

■Also, in conventional welding technology, the welding speed is as high as 75 cm/min, so torch weaving is not performed, and automatic groove tracing using an arc sensor cannot be performed, so the welding current that can be applied in the same way as in ■ , there was a speed limit.

Due to the factors (1) and (2) above, in the prior art, the welding current for first layer welding of pipes is limited to 20 OA and the welding speed is limited to about 75 cm/min.

The present invention was made to solve the above problems, and aims to improve welding current, ensure stable welding quality, and control the shape of the back bead.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, the rotation speed N of the arc is set to 10 to 150 Hz, and the rotation diameter D of the arc is set to 1 to 150 Hz.
A high-speed rotating arc welding method with a thickness of 4 mm was used.

Furthermore, a control method is adopted that uses pulse welding to synchronize the peak position of the pulse current waveform with an arbitrary position in the rotation of the arc. The synchronous position of rotation is determined by controlling pulse conditions (peak current, pulse waveform).

[Effect] In the conventional method, weaving of the torch is not performed, but
In the present invention, high-speed rotating arc welding method (N-10~150H
z, D=1 to 4 mm), and automatic groove tracing control using an arc sensor can be performed, so the above problem (2) is solved.

Furthermore, in a control method that uses a pulse welding method and synchronizes the peak position of the pulse current waveform with an arbitrary position of the arc rotation, we have developed a control method that uses pulses and rotation to improve the tolerance of the back bead shape against root gaps and mismatches. The synchronization position solves the above problem (2) by controlling the pulse conditions (peak current, pulse waveform).

By the way, in pulse arc welding where the pulse waveform of the welding current is as shown in Fig. 3, in order to accurately perform groove tracing control using a rotary arc sensor, it is necessary to emit pulses symmetrically with respect to the rotation of the arc. be. Peak current 1
As shown in Fig. 4, the pulse period of p is divided by 1 (4th
Figures (a), (b)). Divide by 2 (Figure 4 (c), (d))
．． There is a method of frequency division by 4 (FIGS. 4(e) and 4(f)), and the pulse position can be set at any position in the rotation of the arc. For example, in the case of frequency division by 1, the pulse is at the front position Cr or the rear position C in the welding direction WD of the arc rotation, and in the case of frequency division by 2, the pulse is at the Cr point and the Cr point or between the L point and the R point. can be produced. In addition, in the case of frequency division by 4, C, point, Cr point, L point, and R point,
Or it can be the midpoint between those points.

Therefore, the pulse welding method of the present invention is carried out using a 1-frequency division method and a 2-frequency division method, and pulses are emitted in synchronization with the rotational position of the arc. This is because in the case of frequency division by 4, the position of the peak current 1p is too dispersed, making it difficult and complicated to control the shape of the backwave. Furthermore, from the viewpoint of ease of backwave control, the method shown in FIG. 4(d) is not very suitable even in the case of frequency division by two. Therefore, the most suitable method is the method shown in FIGS. 4(a) to 4(c).

Average welding current ■, peak current a lP, base current shown in Figure 3! , the pulse width tp and the pulse B interval tB can be freely changed depending on the welding conditions, but for example, when the pulse position is set at the Cr point of 1 frequency, the rise current can be reduced by lowering the base current 1, I, is increased, and the degree of increase is determined, for example, by detecting the arc voltage at point C. By controlling the pulses in this manner, the shape of the back bead can be accurately controlled. Of course, due to the action of the high-speed rotating arc sensor, the bead shape of the first layer becomes smooth, making it possible to achieve high-current and high-speed welding. Further, since the filament bath and the cap bath can be successively welded based on the first layer welded in this way, the welding time can be shortened.

[Example] Hereinafter, the present invention will be explained using the drawings.

FIG. 1 is a schematic diagram of a pulse automatic welding machine used for single-sided welding of pipes. The welding machine 1 is installed so as to run by itself along a circumferential guide rail 12 temporarily attached to the outer surface of a pipe 10. ing. A welding torch 2 provided in this welding machine 1 is rotated by a motor 3 via a gear mechanism 4, and is movable in the width direction (X axis) of the groove 14.
It is supported via a shaft slide block 5 and a y-axis slide block 6 that is movable in the direction of the torch (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 the torch 2, and the rotational diameter D of the arc is determined by this eccentric distance. This makes it possible to implement a rotating arc welding method. In addition, 16 is groove 1
This is a backing material such as copper temporary placed opposite to 4.

FIGS. 2(a) and 2(b) are enlarged sectional views of the groove shape according to the present invention, and the groove 14 is formed into a straight annular groove 14b having a V-shaped bottom 14a. bottom 14
The inclination angle θ of a is set to 30'' to 60°. In addition, when the dimension a is 1 to 2 ml and the wall thickness t of the pipe is about 8 to 25 mm, the groove width b is set to 7 to 8 mm or less. In addition,
A small root face 14c may be provided on the inner surface of the pipe of the groove 14 as shown in FIG. 2(b).

By forming the bottom part 14a of the groove 14 in a V-shape in this way, the welding torch 2 shown in FIG. can be made to imitate the external hot bath H (initial layer 1
7) can be circumferentially welded in all positions. Moreover, the above-mentioned pulse control allows the Uranami 18 to be delivered to the main house at the same time as this first layer 17 is welded.

FIG. 5 is a pulse control circuit diagram used in the present invention, and FIG. 6 is a timing chart showing the operating principle of the control waveform.

In FIGS. 5 and 6, the welding current pulse (■) of the pulse welding machine 1 is divided into two, for example, by a frequency divider 22 according to a frequency division command predetermined by a setting device 21, and the frequency division waveform (■) is synchronized with the pulse. The control circuit 23 is manually operated.

On the other hand, the rotational position signal ■ and the rotational speed signal C of the welding torch 2
, is input to the phase adjuster 26 by the rotational position signal generator 24 and encoder 25, and the arc rotation pulse ■ is sent to the pulse synchronization control circuit 23, but the welding current pulse and the arc rotation pulse ■ are not synchronized. Therefore, in order to synchronize them, the setting device 27 commands first to create the waveforms ■' and ■' with adjusted phase and rotation speed, and then to shift the control waveform ■'' using a delay circuit, etc., to obtain the peak current pulse. The position and Cr point are matched.

The rotary driver 28 is controlled by the signal ■1 synchronized in this way, and the rotary motor 3 is driven to drive the welding torch 2.
The rotation speed N is controlled. 29 is a rotation detector of the motor 3, and its signal is fed back to the rotation driver 28.

To explain a specific example, a solid wire of 0.9 mmφ is used, arc rotation speed N-50 Hz, arc rotation diameter D-2 to 3 m1, average welding current Ia - 300 A,
Peak current IP-32OA, base current IB-280
A, pulse period divided by 2, welding speed v=2.0m/
The initial layer was 17 minutes in an atmosphere of 100% C02 gas.
When welded, a good-shaped Uranami 18 as shown in Fig. 2 (C) was obtained. Of course, the first layer 17 also had a smooth bead shape. It is only necessary to sequentially stack and weld the filament bus F and the cap path C based on No. 17, and the butt circumferential welding of the pipes can be performed at a high speed of 300 cm/min at maximum.

[Effects of the Invention] As described above, according to the present invention, it is possible to weld a hot path only from the outer surface of a pipe using the rotary arc sensor method, and moreover, it is possible to normally emit a back wave at the same time as welding. Therefore, it is possible to easily and quickly perform butt circumferential welding of pipes in pipeline construction work.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of an automatic welding machine used for pipe welding of the present invention, Figures 2 (a) and (b) are enlarged sectional views of the groove shape, and Figure 2 (C) is an enlarged cross-sectional view of the groove shape. Figure 3 shows the state of laminated welding, Figure 3 is a pulse waveform diagram of the welding current, Figure 4 (
a) to (f) are diagrams showing the relationship between the pulse position and the arc rotation position, FIG. 5 is a pulse synchronous control circuit diagram used in the control method of the present invention, and FIG. 6 is a diagram showing the operation of the control waveform in FIG. 5. The timing charts of FIGS. 7(a) and 7(b) are explanatory diagrams showing the state of the root gap and misalignment in the conventional groove. 1... Pulse welding machine 2... Welding torch 3... Motor 4... Gear mechanism 5... X-axis slide block 6... Y-axis slide block 7... Welding wire 10... Pipe 12...Circumferential guide rail 14...Bevel 16...Backing material 17...First layer 18...Uranami 21...Setter 22...Frequency divider 23...・Pulse synchronous control circuit 24...Rotation position signal generator 25...Encoder 26...Phase adjuster 27...Setter 28...Rotation driver 29...Rotation detector

Claims (1)

[Claims] In butt circumferential welding of pipes, a bevel in the shape of a V-shape is formed at the bottom of the annular groove on the butt end surfaces of the pipes, a 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. While traveling on the attached circumferential guide rail, the welding current was 200 to 200 Hz while automatic groove tracing control was performed using a high-speed rotating arc welding method with an arc rotation speed of 10 to 150 Hz and an arc rotation diameter of 1 to 4 mm. 500A,
When single-sided welding the first layer from the outer surface of the pipe in all positions at a welding speed of 75 to 300 cm/min, use the pulse welding method and synchronize the peak position of the pulse current waveform to an arbitrary position of the arc rotation. A pulse welding method for single-sided first layer welding of a circumferential butt joint of a pipe, which is characterized by controlling the shape of the back wave.