JPH0429470B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in the first layer welding method.

Conventionally, the groove shape of a butt welded joint has been, for example, as shown in FIGS. 1 and 2. In the figure, 1 and 2 are members to be welded that are butted against each other. Further, 3 to 5 indicate the groove, the welding front side, and the welding back side, respectively. Further, numerals 6 and 7 indicate groove gaps of the welded members 1 and 2, respectively. The widths of these groove gaps 6 and 7 vary depending on the machining of the groove 3 and the accuracy of assembly and attachment, and it is difficult to guarantee that the grooves will be assembled to a small constant amount so that welding is stable. Here, FIG. 3 shows a good cross-sectional shape when the groove 3 shown in FIGS. 1 and 2 is welded in the first layer. 8 and 9 in the figure are weld metal, respectively.
This is a Uranami bead that is melted and formed in a convex shape on the back side.

By the way, in the first layer of butt welding, variations in the groove gaps 6 and 7 are allowed as described above, and the third
In order to obtain a welded joint that forms a good uranami bead 9 as shown in the figure, a non-consumable electrode type gas shielded arc welding (TIG) method is generally employed.

However, TIG welding has poor welding efficiency, and subsequent layers are generally performed using consumable electrode gas-shielded arc welding (MAG). However, when welding the first layer of groove 3 with groove gap 6 (or 7) by MAG welding, if the gap is as large as groove gap 7, the welding wire may penetrate into gap 7 or the molten metal may drip. It is impossible to maintain a stable welding arc molten pool due to
Welding is not possible.

The present invention has been made in view of the above-mentioned circumstances, and even when there are variations in the size of the groove gap of the workpiece to be butt welded, it is possible to perform Uranami welding well, thereby greatly improving welding efficiency. The purpose of this invention is to provide a first layer welding method that can shorten welding time and improve the quality of the welded part.

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 4a and 4b and FIGS. 5 to 8.

FIGS. 4a and 4b show the configurations of a low current shot arc region and a high current spray arc region during welding, respectively. In the same figure, a shows a case where the groove gap of the welded member is large, and b shows a case where the groove gap is small. 11 and 12 in the figure are the advancing directions A with respect to the welding line, respectively.
The part that forms an angle of θ ₁ on the front side of A (low current area), and the part that forms an angle of θ ₂ on the rear side of traveling direction A (high current area)
It is.

5 to 8 show an example of actual welding. Here, 21 and 22 in the figure are members to be welded having grooves 23 and groove gaps 24 which are butted against each other. Further, 25 and 26 indicate the front welding side and the back side of the welding. That is, in this example,
While inserting the wire 28 of the wire guide nozzle 27 into the groove gap 24 of the workpieces 21 and 22, a high current spray arc 31 and a low current shot arc 32 are applied using the energizing tip 29 and the consumable electrode wire 30 in FIG. 4a. As shown in (or b), the welding lines are continuously and alternately moved in a circular manner in the direction of the welding line to form the uranami bead 33. Here, the groove gap 24
If is large, angle θ ₁ is increased as shown in Figure 4 a, and in the opposite case, angle θ ₁ is decreased as shown in Figure 4 b, and the area ratio of angles θ ₁ and θ ₂ is set arbitrarily. At the same time, the moving speed of the arc within each section of angles θ ₁ and θ ₂ is also set arbitrarily. Also,
The moving diameter of the arc is set depending on the size of the groove gap 24. Furthermore, out of each unit circular motion, the high current spray arc 31 causes the welded members 21, 2 to
The wide-angle sides of the second grooves 23, 23 are welded to form a first molten metal 34, and the narrow-angle sides of the same grooves 23, 23 are welded by a low current shot arc 32 to form the first molten metal. A second molten metal 35 is formed preceding 34. Furthermore, the amount of wire 28 added to the wire guide nozzle 27 described above can be changed as appropriate depending on the groove gap 24.
Note that arrow A in the figure indicates the direction of movement with respect to the weld line.

According to the present invention, the member to be welded 21,
A wire guide nozzle 27 is installed in the groove gap 24 between the grooves 22 and 22.
While inserting the wire 28, the high current spray arc 31 and the low current shot arc 32 are continuously and alternately switched at an appropriately set speed to perform circular welding. Therefore, even if there are variations in size between the groove gaps 24 of the welded members 21 and 22, the low current shot arc 32 and the molten metal 3 in the front
The molten metal 34, 35 can be prevented from punching through the grooves 4, 35, and can fill the groove gap 24 by inserting the wire 28 of the wire guide nozzle 27 into the groove gap 24.
can be formed. In addition, at the rear, a high current allows sufficient penetration and the formation of the Uranami bead 33 accurately. From the above, compared to conventional butt welding, MAG is suitable for first layer welding with large and small groove gaps.
Uranami welding can be performed by welding, and it is possible to shorten welding time and improve the quality of the welded part.

As detailed above, the present invention can be applied to all welded structures in which good uranami welding can be performed on large and small groove gaps to shorten welding time and improve the quality of welded parts. It is possible to provide a first layer welding method that is suitable for use in the welding process.

[Brief explanation of drawings]

Figures 1 and 2 are cross-sectional views showing the groove shape of a butt joint, Figure 3 is a cross-sectional view showing the butt joint in Figure 1 or 2 after initial layer welding, and Figure 4
Figures a and b are explanatory diagrams of the first layer welding method according to an embodiment of the present invention, and Figure 5 is a cross-sectional diagram for explaining the state in which the wire of the wire guide nozzle is inserted into the groove gap of the welded member. 6 is a plan view showing a state in which welding is performed according to the present invention, FIG. 7 is a front view of FIG. 6, and FIG. 8 is a perspective view of FIG. 7. 11...Low current area, 12...High current area, 21,
22... Part to be welded, 23... Groove, 24... Groove gap, 25... Welding surface side, 26... Welding back side, 27... Wire guide nozzle, 28... Wire, 29... Energizing Chip, 30...Consumable electrode wire, 31...High current spray arc, 32...Low current shot arc, 33...Uranami bead, 3
4,35...molten metal.

Claims (1)

[Claims] 1 In the first layer welding method, which performs butt welding between parts to be welded by consumable electrode type gas-shielded arc welding, a wire is inserted between the grooves of the parts to be welded, and the amount of wire added is adjusted depending on the size of the gap. At the same time, the high current spray arc and the low current shot arc are continuously and alternately switched to move circularly in the direction of the welding line, and in each unit of circular movement, the gap between the grooves is filled with the low current shot arc on the front side.
An initial layer welding method characterized in that a groove containing molten metal formed by the low current shot arc is welded by a high current spray arc.