JPH049096Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention relates to the structure of tungsten inert gas welding (TIG welding), and in particular to an automatic welding device configured to have a movable electrode.

<Prior art and its problems> TIG welding is widely used for welding high-grade steel and nonferrous metals such as aluminum and titanium because it produces high-quality welds. Traditionally, filler wire had the disadvantage of slow melting speed and poor welding efficiency, but with the advent of the hot wire TIG welding method, which performs welding while heating the filler wire with electricity, this disadvantage has been overcome. The scope of application is becoming more and more expanded.

On the other hand, automation of welding is progressing in order to save labor and obtain welded parts of constant quality, and welding robots are being actively developed. Regarding automation of TIG welding, there is no problem as long as the welding direction is linear, and automatic TIG welding of circumferential welded joints of pipes, for example, is widely used and put into practical use. However, when applying TIG welding to welding where the welding direction changes during welding, there are the following problems. Generally, in the case of TIG welding, as shown in Figure 8, the positional relationship between the tungsten electrode 2 and the filler wire 3 is such that the tungsten electrode 2 is in the front and the filler wire 3 is in the back relative to the welding direction, or vice versa. It is arranged in a straight line with respect to the welding direction. For this reason, as shown in Fig. 9, when the welding direction changes midway, it is necessary to change the direction of the device itself at the course change point 12, or to change the direction of the filler wire, and the control device that rotates them A system becomes necessary.

Moreover, the welding torch is stopped while the device or additive wire is being changed direction, and continuous arc generation not only damages the appearance of the bead but can also cause welding defects such as hot cracking. There is sex. To solve this problem, there is a way to temporarily stop the supply of filler wire when changing direction.
A control device for this purpose is further required. Alternatively, there is a device for changing the direction or a method of stopping the arc itself when the filler wire is rotating, but in this case, a control device is also required, and the point of change of course is the end and start of welding. Therefore, defects such as crater cracks may occur.

<Purpose of the invention> The purpose of the invention is to provide a TIG welding torch that eliminates the above-mentioned drawbacks of the conventional technology, allows for easy direction changes in automatic TIG welding, and provides high-quality welds. .

<Summary of the Means> In short, this invention involves symmetrically arranging three or more tungsten electrodes at the same pitch on a circumference centered on the axis of the supplied wire, and sequentially circling the arc formation and extinction of the electrodes. A rotating electrode TIG characterized by being provided with a current supply means for rotationally moving in the direction
It is a welding device.

<Example 1> An example of the TIG welding torch according to the present invention will be described in detail below with reference to the drawings.

Figure 1 shows a TIG welding torch according to the present invention.
This shows the situation in which welding is performed using TIG welding equipment. In FIG. 1, reference numeral 1 indicates a workpiece to be welded with a groove. The TIG welding device has three tungsten electrodes 2, 2', and 2'', which are supported and fixed on a welding torch 10. A feed roller (not shown) is placed in the center of these three tungsten electrodes. , the filler wire 3 is fed through the contact tip 4. Figure 2 clearly shows the positional relationship between the tungsten electrode and the filler wire. , 2'' form a triangle, and the filler wire 3 is supplied to the center of the three electrodes. The distance between each tungsten electrode 2, 2', 2'' and the filler wire 3 is approximately 3 mm, but for the purpose of unifying the molten pool, it is appropriate for this distance to be in the range of 1 to 5 mm. 2, 2', 2'' and workpiece 1
An arc power supply 6 is connected between the filler wire 3 and the workpiece 1 so that the tungsten electrode is the cathode and the workpiece is the anode, and the filler wire is the anode and the tungsten electrode is the anode. A wire power source 7 is connected so that the wire serves as a cathode. Furthermore, a gate turn-off thyristor (hereinafter referred to as
GTO) 5, 5', 5'' are provided.

The configuration of the TIG welding torch according to the present invention has been described above, and now the current control during welding will be described.

FIG. 3 shows the current waveform during welding by this device. In section a, only the GTO 5 is in the ON state, and therefore an arc is generated only from the tungsten electrode 2. Similarly, in sections b and c, GTO (gate turn-off thyristor) 5
', 5' are ON, and each GTO
Tungsten electrode 2', 2" corresponding to 5', 5"
An arc is generated from. That is, control is performed so that arcs are generated in sequence at the three tungsten electrodes. In Figure 3, while an arc is generated in one tungsten electrode, the current value flowing through the other electrodes is 0, but this does not necessarily have to be 0, and it makes it easier to ignite the arc. Therefore, a small amount of current may be allowed to flow. Also,
The wire current is always in the opposite direction of the arc current. Therefore, the arc current and wire current repel and the arc is deflected outward. This is an effective phenomenon when penetration into the side wall is required, such as in fillet welding, but if the wire current becomes too large, one molten pool is created by the arc generated from three electrodes in turn. This not only impairs the bead appearance but also may cause welding defects. It also has the disadvantage of poor workability. Therefore, a proper wire current value exists. This consists of the filler wire 3 and the respective tungsten electrodes 2, 2',
Although it is related to the distance from 2", as a result of examination at a distance of 3 mm set with this device, the appropriate wire current value was 1/3 to 2/3 of the arc current value.

As described above, the three tungsten electrodes 2,
2' and 2'' in order, causing a phenomenon in which the arc appears to be rotating around the filler wire 3, thereby eliminating the directionality of the electrode with respect to the direction of welding progress. When welding a workpiece 1 having a weld line as shown in FIG. 4, it is only necessary to perform control to change the welding direction at the course change point 12, and there is no need to change the direction of the equipment or the filler wire. Therefore, a smooth bead was formed because the welding was performed at an almost constant speed without reducing the speed at the course change point 12 as in the conventional method.Furthermore, since the arc was generated in sequence, it became a pulse arc shape. This also produces an effect.In other words, it becomes a pulsed arc, and the arcs are generated sequentially as if rotating, so the molten pool is sufficiently stirred, and the crystal grains of the solidified structure become finer.

Note that the arc current was passed through the three tungsten electrodes in sequence, and there was an appropriate frequency range for the arc current. The usable range for simple welding is wide, from a few hertz to several hundred hertz, but the range between 10 hertz and 100 hertz was found to be the most appropriate, especially from the viewpoint of workability and bead appearance.

In this embodiment, the direction of the wire current is opposite to the direction of the arc current, but it goes without saying that if the bead width is desired to be narrowed, the wire current may be the same as the arc current.

The key point of the present invention is to place the filler wire in the center and to generate a phenomenon in which the arc rotates, or appears to rotate, around the filler wire. Therefore, it is sufficient to use a four-electrode structure as shown in FIG. 5 and perform control to sequentially generate arcs in the same manner as in the three-electrode structure. The unique effects in this case are as follows. In the case of three electrodes, when the direction is changed at right angles, which is considered to be the most frequent case, the positional relationship of the electrodes with respect to the traveling direction changes as shown in FIG. The arc occurs in each electrode in turn, creating a single molten pool, so there is almost no effect, but the bead shape changes slightly. However, in the case of four electrodes, the electrodes are at exactly the same position in the direction of travel even after the direction change, so arcs are generated at exactly the same position. That is, the directionality of four electrodes is smaller than that of three electrodes. 4 more
It is also possible to use more electrodes than electrodes.

<Effects of the invention> When welding using the TIG welding torch of the invention, there is no directionality of the electrode with respect to the welding direction, and even when the weld line is not straight, there is no need to change the direction of the device or filler wire. It is possible to change the direction of welding without taking any special measures, and a continuous and good welded area can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the TIG welding device according to the present invention, Fig. 2 is a bottom view of the welding torch section viewed from below, and Fig. 3 shows the arc and wire current waveforms. Fig. 4 is a plan view of a flat plate welded using this device, and Fig. 5 is a plan view of a flat plate welded using this device.
A bottom view of a welding torch in the case of a telephone pole, Figure 6 is a bottom view showing the position of the electrodes due to direction changes for the welding torch which is the bottom plan, A, B are 3 electrodes, C,
D is a drawing showing the case of 4 electrodes, and Fig. 7 is a drawing showing the case of 4 electrodes.
FIG. 8 is a schematic diagram showing the positional relationship between an electrode and a filler wire in TIG welding, and is a plan view of a flat plate having a groove in which the welding direction changes midway. 1... Work to be welded, 3... Filler wire, 5, 5,
5... Gate turn-off thyristor, 6... Arc power supply, 7... Wire power supply, 10... Welding torch.

Claims (1)

[Claims for Utility Model Registration] 1. Three or more tungsten electrodes are arranged symmetrically at the same pitch on a circumference centered on the axis of the supplied wire, and arc formation and extinction of the electrodes are sequentially performed around the circumference. A rotating electrode TIG welding device characterized by being provided with a current supply means for rotationally moving the electrode in a direction. 2 Utility Model Registration Scope of Claim 1. The rotating electrode TIG welding apparatus according to claim 1, characterized in that the rotationally moving supply of the arc current is performed by a gate turn-off thyristor. 3 Utility Model Registration The rotating electrode TIG welding device according to claim 1 or 2, characterized in that the arc formation and ablation operations are made into arc formation and small current supply operations. Device. 4. In the rotating electrode TIG welding device according to any one of claims 1 to 3 of the utility model registration claims, the wire current value is 1/3 to 2/3 of the arc current value.
A rotating electrode TIG welding device characterized by: