JPS6331305B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-electrode TIG welding method, and in particular, the welding current is alternately switched to two electrodes to prevent magnetic interference of the arc, and to prevent melting formed by arc heat. This invention relates to a two-electrode TIG welding method in which the distance and angle between the two electrodes are defined so that the pool is integrated.

FIG. 1 shows a conventional two-electrode welding method, in which 1 is a leading torch, 2 is a leading electrode, 3 is a trailing torch, 4 is a trailing electrode, 5 is a filler wire feeding nozzle, and 6 is a trailing torch. is filler wire, 7
a, 7b are arcs, 8a, 8b are molten pools, 9
is the material to be welded, and the arrow indicates the welding direction. 1st
In the conventional two-electrode welding direction shown in the figure, the filler wire 6 is fed from the front of the preceding electrode 2 in the welding direction via the filler wire feeding nozzle 5 into the arc 7a and molten pool 8a of the preceding electrode 2. However, this method had the disadvantage that it was not possible to fully utilize the preheating effect of the leading electrode and the bead forming effect of the trailing electrode, which are the features of two-electrode welding. In addition, in order to increase the welding speed, the distance between the workpiece and the electrode tip (hereinafter referred to as arc length) is generally
However, with this method, if the arc length is shortened to less than the wire diameter, the electrode will come into contact with the wire and welding will not be possible, so it is difficult to shorten the arc length and increase the welding speed. It also had the disadvantage that it was not possible to obtain

In order to eliminate the drawbacks of the conventional two-electrode welding method shown in Fig. 1, a two-electrode welding method as shown in Fig. 2 was disclosed in the Abstracts of the Welding Society of Japan, Vol. 20, pp. 160-161. According to this method, the curved filler wire 6 passes through the filler wire feeding nozzle 5 located between the leading torch 1 and the trailing torch 3 to form an arc 7b of the trailing electrode 4 and a molten pool. 8b. This method shown in Figure 2 increases the amount of welding compared to the method shown in Figure 1, but since conventional two-electrode welding uses a DC power source, if the distance between the electrodes is short, there will be magnetic interference from the arc. The filler wire will be melted by the arc blown up due to interference, making the melting of the wire extremely unstable. Therefore, the electrode spacing must be kept at a distance of 15 mm or more, which will hardly receive any interference from the arc. However, the melt pool could not be integrated.

In addition, if the distance between the electrodes becomes too long, not only will the effect of the leading electrode not be fully utilized, but since the wire is bent, the melting tip of the wire will not be consistent, and molten metal will adhere to the electrode, causing it to become dirty. There were disadvantages such as causing

The purpose of the present invention was to provide a two-electrode TIG welding method that can integrate the molten pool, prevent magnetic interference of the arc, and form a good welding beat. It is on offer.

In order to achieve such an object, the present invention applies a current to two electrodes that constitute a leading electrode and a trailing electrode so that the molten pool formed by the arc heat generated in each electrode becomes one. 2-electrode TIG
In welding, the distance between the two electrodes is 12 mm or less at the tip of the electrode, and the angle between the electrodes is 15 to 40 degrees, and a filler wire is fed into the molten pool located between the electrodes, The present invention is characterized in that welding is performed by alternately passing a welding current to each of the electrodes with equal distribution of each current.

Figure 3 shows the total welding current (the sum of the leading current and trailing current) when the interelectrode angle is 15 degrees, 25 degrees, and 40 degrees, and the welding speed is 30 cm/min. ) is a graph shown in relation to In the figure, indicates the area where the melt pool is integrated;
Curve 1 shows the boundary line between the area where the molten pool separates, and the area where the inter-electrode angle is 15 degrees for curve a, 25 degrees for curve b, and 40 degrees for curve c.
Note that curve d shows the case where the inter-electrode angle is 10 degrees. Next, FIG. 4 is a graph showing the angle between the electrodes at which the molten pool becomes one in relation to the total welding current when the distances between the electrodes are 8 mm, 12 mm, and 13 mm and the welding speed is 30 cm/min. In addition, Figure 4 has a relationship with Figure 3 by swapping the variables on the horizontal axis of coordinates, and the meaning of the entire graph is that both figures show the mutual relationship between the total welding current, the distance between the electrodes, and the angle between the electrodes. They are the same in that they indicate gender. In Figure 4, curves e, f,
g is the boundary line between the area where the molten pool is integrated and the area where the molten pool is separated when the distance between the electrodes is 8 mm, 12 mm, and 13 mm, respectively. That is, the area above each boundary line is the area where the molten pool is integrated.

From these FIGS. 3 and 4, as the distance between the electrodes increases, the total welding current inevitably increases. However, in two-electrode TIG welding, increasing the distance between the electrodes effectively approaches one-electrode welding, and the method of compensating for this by increasing the total welding current reduces the melting efficiency of the weld pool. This will result in a decline. This is because the melting efficiency is higher when the welding pool is integrated with a lower welding current. From this welding efficiency point of view, the total welding current is
It is desirable to set it to 200A or less. Therefore, based on FIG. 4, the distance between the electrodes is set to 12 mm or less.

Further, as shown in FIG. 4, even if the distance between the electrodes is 12 mm, the welding current exceeds 200 A when the angle between the electrodes is less than 15 degrees and more than 40 degrees, and the welding efficiency decreases. Therefore, the angle between the electrodes is set to 15 to 40 degrees. There are other reasons for defining this inter-electrode angle within the above range. First, when the temperature exceeds 40 degrees, the arc force caused by the arc of the trailing electrode of the two electrodes causes the molten pool to float from the rear to the front, making the pool unstable and causing uneven weld beads. is more likely to form. Therefore, a good weld bead cannot be obtained, so the angle between the electrodes should be 40 degrees or less. In addition, if the angle between the electrodes is less than 15 degrees, the arc forces of both the leading and trailing electrodes become isolated and dispersed, which causes the molten pool to be dragged backwards and the arc There is a problem that the amount of melting at lower temperatures is relatively small and humping beads are more likely to occur. Therefore, the temperature should be 15 degrees or higher.

FIG. 5 is a block diagram of an apparatus suitable for carrying out the method of the present invention. In this figure, welding power source 1
The cathode of the welding power source 10 is connected to the leading electrode 2 and the trailing electrode 4 through a switching device 12 constituted by a transistor 11, and the anode of the welding power source 10 is connected to the workpiece 9. Arcs 7a and 7b are generated between the leading electrode 2, the trailing electrode 4, and the workpiece to be welded 9, and a molten pool 13 is formed. Magnetic interference of the arc was prevented by alternately switching the welding current to the leading electrode 2 and the trailing electrode 4 by a switching device 12 controlled by a switching control device 14. The switching frequency was 250Hz. The filler wire 6 is fed into the integral melt pool 13 through a filler wire feed nozzle 5 located between the leading electrode 2 and the trailing electrode 4 . The filler wire feeding device 15 was controlled by a filler wire feeding control device 16.

FIG. 6 is a partial sectional view of the welding torch used in the above embodiment, and this welding torch includes a leading torch 1, a trailing torch 3, and a filler wire feeding nozzle 5.
and a shield nozzle 18. A leading electrode 2 is attached to the leading torch 1 by a collet 19 and a collet holder 20. The trailing torch 3 also has a similar structure to the leading torch 1, and has a trailing electrode 4 attached thereto. The angle between the leading electrode 2 and the trailing electrode 4 is 30 degrees. Further, the distance between the electrode tips of the leading electrode 2 and the trailing electrode 4 was set to 10 mm. The filler wire 6 is fed through the filler wire feed nozzle 5 fixed by a nozzle stop 21 from the middle of the two electrodes. That is, the angle between each electrode 2, 4 and the filler wire feeding nozzle 5 is 15 degrees. Leading torch 1 and trailing torch 3
is water-cooled and has insulation between each torch and nozzle. Each torch is configured to shield the electrodes with a shielding gas. The shielding gas is passed through shielding gas 18 to the weld to shield the weld. The electrode used was a 3.2φ tungsten electrode containing 2% thorium.

For welding, SUS304 was used as the material to be welded, and cometal wire 308 (wire diameter 1.2 mm) was used as the filler wire. Furthermore, Ar gas was used as the shielding gas, and the airflow distribution to each electrode was set at 1:1. Figure 7 is a graph showing the relationship between total welding current and welding speed.
In the figure, C shows the results when the method of the present invention is implemented, and D shows the results when the conventional method shown in FIG. 2 is implemented. As is clear from this figure, the method of the present invention can achieve a welding speed more than twice that of the conventional method shown in FIG. Furthermore, the melting of the filler wire was very stable, and good welding could be performed.

FIG. 8 is a graph showing the relationship between the limit welding speed that does not produce a humping bead and the total welding current. The results of implementing the method are shown. Since the method of the present invention can shorten the arc length regardless of the filler wire,
It has become clear that the limit welding speed can be significantly improved even in filler wire feed welding, and a limit welding speed 2.5 times or more can be obtained compared to the conventional method shown in FIG. Also, because the wire melted stably, a very clean weld bead was obtained. Furthermore, there was much less contamination of the electrodes due to contact with filler wires, etc., than in the conventional method.

As described above, according to the present invention, the arc length can be shortened without being affected by the filler wire, the electrode is less contaminated, and the wire melting is stable, so two-electrode welding is possible. The effect was sufficiently obtained in filler wire feed welding, and the welding speed and welding speed were increased. It is also possible to carry out hidden arc welding in which the tip of the electrode is plunged below the surface of the material to be welded.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the conventional method of feeding filler wire to the leading electrode, Figure 2 is an explanatory diagram of the conventional method of feeding filler wire to the trailing electrode, and Figure 3 is an illustration of the electrode in which the molten pool is integrated. FIG. 4 is a graph showing the relationship between the interelectrode angle at which the molten pool is integrated and the total welding current. FIG. 5 is a graph showing the relationship between the electrode distance and the total welding current. FIG. 6 is a partial sectional view of a welding torch used in carrying out the method of the present invention,
FIG. 7 is a graph showing the relationship between total welding current and welding speed, and FIG. 8 is a graph showing the relationship between total welding current and limit welding speed. DESCRIPTION OF SYMBOLS 1... Leading torch, 2... Leading electrode, 3... Trailing torch, 4... Trailing electrode, 5... Filler wire feeding nozzle, 6... Filler wire, 7a, 7b... Arc,
8a, 8b... molten pool, 9... material to be welded, 10...
Welding power source, 11... Transistor, 12... Switching device, 13... Molten pool, 14... Switching control device, 15... Filler wire feeding device, 1
6... Filler wire feed control device, 17... Torch body, 18... Shield nozzle, 19... Collet, 20... Collet holder, 21... Nozzle stop.

Claims (1)

[Claims] 1 Two electrodes in which a current is passed through the two electrodes that make up the leading electrode and the trailing electrode, so that the molten pool formed by the arc heat generated in each electrode becomes one.
In TIG welding, the two electrodes are arranged with a distance of 12 mm or less at the tip of the electrode and an angle of 15 to 40 degrees, and a filler wire is placed in the molten pool located between each electrode. A two-electrode TIG welding method, characterized in that the welding is carried out by supplying a welding current to each of the electrodes and alternately flowing the welding current to each electrode with the distribution of the current being equal.