JPS6247625B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic welding method for producing beautiful beads in circumferential multi-layer welding of pipes and the like.

When performing fully automatic circumferential welding, the welding method is generally performed while reversing the running direction of the torch every pass in order to prevent twisting of the conduit tube that connects the welding torch and wire feeder. ing.

In this case, when welding the pipe 1 to the flange 2 along the circumference as shown in Fig. 1, when the first pass of welding starts from point a, the end point is set to prevent the bead from being dented by craters etc. Overlaps with starting point △F
is set as point b, and the next second pass uses approximately point b as the welding start point and reverses to end at point a, followed by the third pass.
The pass again starts above point a, turns in the same direction as the first pass, and ends at point b. In this way, the necessary passes of multi-layer welding are performed while alternately reversing.

However, in this method, the positions of the welding start and end points are repeated at the same position for each pass, so
Even if the overlap △F is provided to prevent crater depression,
It is unavoidable that the joint portion of the bead swells, and a crater occurs again at the overlapped portion, resulting in a concave weld as shown in the cross section of FIG. 2, resulting in a weld with a poor weld shape.

The present invention aims to eliminate the above-mentioned defects and provide an automatic welding method that forms a beautiful bead when performing multilayer welding while reversing the circumference every pass by automatic welding. A superior quality welded joint with an improved bead seam will be produced by the i-th (i=
2, 3, .

The present invention will be explained in detail below based on the embodiment shown in FIG. In this example, as in FIG. 1, a pipe 1 is automatically welded to a flange 2 along its circumference.

First, the first pass starts at point a, overlaps ΔF0, and ends at point b. The second pass avoids △F0 of the first pass and moves to point c, that is, △
F=△F0 The first point is around the inverted position as the starting point.
It is reversed in the opposite direction to the path, and ends at point d with an overlap of ΔF0. The following third pass is the first
△F0 of the second pass and △F0 of the second pass
Avoiding point e, that is, the position reversed from point △F = △F0 × (3-1) = 2△F0d, as the starting point, reverse in the opposite direction to the second pass, that is, in the same direction as the first pass. Go, △F0
overlap and end at point f. The same goes for each subsequent pass, and the predetermined n-th pass is performed with the starting point near the position △F=△F0×(n-1) reversed from the end point of the previous pass, and The overlap of ΔF is taken as the end point.

The method of the present invention can be used either in cases where the aiming direction of the wire is the same in each pass and the next bead is layered directly on top of the previous bead, or in cases where the direction of the wire is slightly shifted in each pass. Both are equally effective, and the shape of the bead is made uniform at the seam and at various parts of the circumference. FIG. 4 is a cross-sectional view of a bead connection made by the present method, which does not produce depressions or large protrusions as shown in the cross-section of FIG. 2 obtained by the conventional method.

In fully automatic circumferential welding, there is almost no need to modify conventional equipment in order to set in advance the starting point of the next pass that avoids the bead connection area of the previous pass and automatically reverse the process. Therefore, the present invention can be easily carried out and has a great effect in that not only a beautiful bead shape but also a defect-free welded joint of excellent quality can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the conventional method for circumferential automatic welding, Fig. 2 is a schematic diagram showing the cross-sectional shape of a weld bead connection part according to the conventional method, and Fig. 3 is an explanatory diagram of the method of the present invention for circumferential automatic welding. The explanatory diagram, FIG. 4, is a schematic diagram showing the cross-sectional shape of a weld bead connection part according to the method of the present invention. 1: pipe, 2: flange, 3: weld bead,
a, c, e, f: welding start point, b, d, f, h:
Welding end point.

Claims (1)

[Claims] 1. When performing multi-layer welding while reversing the circumference every pass by automatic welding, the i-th (i=2, 3,...
... n) path from the end point of the i-1th path △
F △F=△F0×(i-1) However, △F0 is the overlap length between the welding start point and end point of each pass.The overlap position of the welding start point and end point of each pass starting from near the reversed position A circumferential automatic welding method characterized by shifting the .