JPH0242028B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a high-speed tack welding method for continuously performing tack welding at high speed prior to main welding.

(Prior art) When performing tack welding at high speed, as shown in Fig. 2, a leading electrode 1 and a trailing electrode 2 are used.
The arc 5 of the trailing electrode 2 prevents the molten metal 4 generated by the arc 3 from flowing backward while forming a weld bead.

Conventionally, in tack welding using the two electrodes described above, at the start of welding, as shown in FIG. Welding is performed by setting predetermined values I ₁ and D ₁ and adjusting the welding speed V to the predetermined speed V ₁ simultaneously with the start of welding.

According to this conventional tack welding method, when the predetermined welding speed V ₁ is slow, a stable weld bead is formed without any problem.

However, when performing tack welding at high speed, the welding speed V
from 0 m/min to a predetermined welding speed V ₁ , e.g. 10 m/min.
You need to change it to minutes. In this case, if the welding current I of the leading electrode 1 is set to a current value I ₁ to obtain the required amount of welding when the welding speed reaches the maximum predetermined welding speed V ₁ , the molten metal will be It may overflow from within or melt through. In addition, if the flow of molten metal becomes unstable and the throat thickness of tack welding is not average, there will be a discontinuity in the penetration depth during main welding, resulting in weld defects. Ta.

(Objective of the Invention) The object of the present invention is to improve the above-mentioned problems and to propose a high-speed tack welding method that continuously forms a stable bead at high speed with the quickest start-up possible.

(Summary of the Invention) The high-speed tack welding method of the present invention is a welding method that uses a plurality of electrodes and sets the welding current, electrode spacing, and welding speed to predetermined values to perform tack welding of base metals. At the same time, the welding speed is detected, and the welding current of the preceding electrode and the electrode spacing are changed in accordance with the detected change in the welding speed, thereby continuously forming a weld bead with an amount of welding that corresponds to the welding speed.

When performing tack welding in a multi-electrode welding method in which multiple electrodes are used side by side in the joint direction, the amount of welding is determined by the welding current and welding speed of the preceding electrode. Therefore, in order to obtain the required amount of welding, in this method, the welding current of the leading electrode is set to a low value when welding starts at a slow welding speed, and as the welding speed becomes faster, the welding current of the leading electrode is increased. let

Furthermore, the electrode spacing between the leading electrode and the trailing electrode greatly contributes to the continuity of the weld bead. That is, when the welding current of the leading electrode is low, the influence of magnetic blowing is small, so the flow of molten metal is slow, and the position where the trailing electrode is blocked may be close to the leading electrode. However, as the welding speed increases and therefore the welding current of the leading electrode increases, the arc force increases and the flow of molten metal becomes faster, so it is necessary to change the position of the trailing electrode. Therefore, in the present invention, the welding speed is detected and control is performed to change the electrode spacing in accordance with the change in the welding speed to form a continuous weld bead.

(Embodiment of the Invention) FIG. 1 shows the change characteristics of the welding speed V, the welding current I of the leading electrode, and the electrode spacing D in an embodiment of the invention. In the figure, welding speed V ₁ indicates the maximum value of the welding speed, and I ₁ and D ₁ indicate the welding current value of the preceding electrode and the value of the electrode spacing corresponding to the welding speed V ₁ . As shown in Figure 2, the maximum welding speed when performing tack welding at high speed using two electrodes is approximately
The welding current of the leading electrode (wire diameter 2.8 mm) corresponding to this welding speed is approximately 1200 A, the voltage is approximately 22 V, and the electrode spacing is approximately 30 mm. Note that the welding current of the trailing electrode is a constant value necessary to block the molten metal.

When starting welding, set the welding current I ₀ of the preceding electrode at the start of welding and the electrode spacing D ₀ at the start of welding to, for example, I ₀
= 600A, D ₀ = 20mm, and the welding speed V is gradually increased from 0 m/min to the predetermined welding speed V ₁ by moving the trolley or base metal carrying the welding device equipped with the leading electrode and the trailing electrode. Perform tack welding so that the In this case, the changing welding speed V is detected by a tachometer, and the first
As shown in the figure, the welding current I of the preceding electrode and the electrode spacing D are changed to perform tack welding at a high speed. After the welding speed V reaches a predetermined welding speed _V1 , this welding speed _V1
Welding current of the leading electrode corresponding to I ₁ and electrode spacing D ₁
Performs tack welding of the base metal at high speed. Therefore, the required amount of welding can be continuously obtained.

(Effects of the Invention) As explained above, this invention changes the welding current of the preceding electrode and the electrode spacing according to changes in the welding speed, so it is possible to continuously obtain a constant amount of welding, and especially when welding It is possible to prevent the molten metal from overflowing from within the groove at the start, melting through, etc., and it is possible to continuously form a stable bead with a quick start-up. Therefore, during actual welding, it becomes easy to follow the weld line and prevent welding defects from occurring, making it possible to improve vertical seam welding of large-diameter steel pipes, single-sided welding in shipbuilding, etc.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram of changes in welding speed, welding current of the leading electrode, and electrode spacing according to an embodiment of the present invention, Fig. 2 is an electrode arrangement diagram of the two-electrode welding method, and Fig. 3 is a diagram showing the welding speed and the welding current of the leading electrode in the conventional method. FIG. 3 is a characteristic diagram of welding current and electrode spacing. 1... Leading electrode, 2... Trailing electrode, 3, 5... Arc, 4... Molten metal, V... Welding speed, I... Welding current of leading electrode, D... Electrode spacing.

Claims (1)

[Claims] 1. In a welding method that uses multiple electrodes and performs tack welding of the base metal by setting the welding current, electrode spacing, and welding speed to predetermined values, the welding speed is detected at the same time as welding starts, and the welding speed is set to the predetermined value. A high-speed tack welding method characterized by controlling the welding current of the leading electrode and the electrode spacing to be changed according to the speed change until a set value is reached.