JPS5916558B2 - Welding method for base metal edges in butt welding - Google Patents

Description

Detailed Description of the Invention To describe the conventional welding method shown in Figs. 4 and 5, in high current MIG welding (using a constant current power source and constant speed wire feeder), thick plates are welded using high current. When welding two
When the arc a moves from the base metal b to the tab plate c, the minute gap d between the base metal b and the tab plate c becomes a thermal and electrical discontinuity, and the tab plate c side is difficult to melt, so the arc length becomes short, the depth of the connection becomes uneven, and the bead appearance is not only damaged, but in extreme cases, the wire may plunge into the molten pool, stopping the arc and making it impossible to weld.

More specifically, it is a characteristic of high current MIG welding that utilizes constant current characteristics that the arc voltage decreases as the arc length becomes shorter, and this decrease in arc voltage is due to the contact between base material b and tab plate c. Due to the existence of a microgap d which is a contact surface, the welded part conducts to some extent but is thermally and electrically discontinuous, so the arc a penetrates the base material to a depth f. As the base metal B progresses while melting, the base metal B is gradually heated to a high temperature, and the welded part is heated close to the melting temperature, so that at the same time the arc A is blown, the depth f
Therefore, the arc length g does not become short, and therefore the arc voltage does not decrease, and welding can proceed in a stable state at the predetermined depth f of the welding at the base metal part b. .

At the joint between base material B and tab plate C, tab plate C has a very low temperature with almost no heat conduction due to the small gap d, so tab plate C does not melt immediately and the tab plate at the joint part melts. At this point, the arc length g is shortened by 5° to e, and the arc voltage decreases rapidly, and in extreme cases, the arc stops and welding becomes impossible. Even if the arc does not stop, once the voltage suddenly decreases, the arc voltage rapidly decreases → restores, decreases again → restores, and repeats this cycle. Stable penetration depth and bead shape cannot be obtained (see right side of reference photo B). ). Furthermore, the problem can be solved by performing complete entrainment welding between the tab plate and the base metal to form a continuous body, but in the case of thick plates, it is necessary to open the tab plate and the base metal for welding The tip is formed and welding is done in multiple layers, which has disadvantages that are impractical when considering the effort and cost involved.

In order to prevent this, in order to prevent the arc length from becoming short, a slit T is formed in the valley part 6 of the groove groove 4 of the tab plate 5 to have a penetration depth of 8 for the base material 1 and ■O2. The purpose of this J5 joint is to obtain a stable penetration depth and bead shape by eliminating the drop in arc voltage and decrease in arc voltage (right side of reference photo A), and to minimize the increase in the amount of deposited metal due to this. This invention relates to a welding method for base metal edges in welding.

This application solves these problems by providing slits in the tab plate to facilitate the melting of the tab plate when the arc moves to the tab plate, thereby smoothing the melting of the tab plate in the minute gap. This invention relates to a welding method for the end of a base material in butt welding, with the aim of achieving stable arc transition (see right side of reference photo A).

In the present application, although it is not necessary to exclude starting end processing, in reality, problems often occur at the end, so the end processing will be explained.

An example will now be described.

Example 1 A groove 4 having the same shape as the groove 3 formed in the base metals 1 and 2 was provided at the end of the base metals 1 and 2 to be butt welded, and a slit 7 was formed in the valley of the groove groove 4. After that, the groove 3 formed in the base metals 1 and 2 is aligned with the groove groove 4 of the tab plate 5, and the tab plate 5 is temporarily welded (temporarily attached) to the base metals 1 and 2. The tip groove 4 was welded.

Example 2 A tab plate 5 having a groove 4 having the same shape as the groove 3 formed in the base materials 1 and 2 was formed at the end of the base materials 1 and 2 to be butt welded.

After matching the grooves 3 of the base metals 1 and 2 with the groove grooves 4 of the tab plate 5, the tab plate 5 is temporarily welded (tacking) to the base metals 1 and 2. After tacking, the groove of the tab plate 5 A slit 7 is formed in the valley part 6 of the groove 4,
Thereafter, the groove 3 and the groove groove 4 were welded. A macro cross-sectional view of an actual product in which slits were provided in the tab plate and welding was performed as in the above embodiment is shown on the right side of reference photograph A, and is a cross-sectional photograph taken along line X--X in FIG.

The cross-sectional macro of reference photo B is without slits, and in the cross-sectional photo taken along the Y-Y line in Figure 4, a considerable wavy pattern can be seen on the right side of the horizontal center horizontal line, but in the case of photo A, there is a large wavy pattern on the right side of the horizontal center horizontal line. The wavy pattern can hardly be seen on the line. Since this application is as described above, the base material (plate to be welded)
When the arc moves from the tab plate to the tab plate, fluctuations in the arc length are reduced, and the arc length and penetration depth in the base metal are almost uniform with those in the tab plate, resulting in a satisfactory weld bead, and the wire The feature is that there is no possibility that the arc will penetrate into the molten pool and stop welding, making it impossible to continue welding.

[Brief explanation of the drawing]

Figure 1 is a perspective view of the tab plate temporarily welded to the base metal, Figure 2
The figure is a cross-sectional view of a tab plate with slits, Figure 3 is a cross-sectional view of the tab plate temporarily welded to the base metal, and Figures 4 and 5 show the conventional relationship between the base metal and the tab plate. They are a perspective view and a sectional view. 1... Base material, 2... Base material, 3...
...Bevel, 4...Bevel groove, 5...Tab plate, 6...Trough, 7...Slit.

Claims (1)

[Claims] 1. At the ends of the base metals 1 and 2 to be butt welded, a tab plate 5 having a groove groove 4 having the same shape as the groove 3 formed in the base metals 1 and 12, align the groove 3 and the groove groove 4. Temporarily attach it to base materials 1 and 2,
In addition, a slit 7 is provided in the valley of the groove 4 before or after tacking.
A method of welding an end of a base metal in butt welding, which comprises forming a groove 3 and a groove 4 after that.