JPH09277052A - Method for controlling arc length in multi-electrode tig welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an electrode from coming into contact with a base material whatever direction a torch may be moved. SOLUTION: In the method for controlling an arc length in multi-electrode TIG welding in which a torch 1 with plural electrodes is used and in which an arc current is applied for each electrode, the electrode 4, 5 is selected that is positioned in front of the advancing direction of the torch 1, with the arc voltage detected for the selected electrode and, on the basis of this arc voltage, the vertical position of the torch 1 is controlled. If an electrode comes close to a groove wall, the torch moves vertically, with the contact of the electrode avoided and with the arc length maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel arc length control method suitable for multi-electrode TIG welding, and more particularly to multi-electrode TIG welding in which the electrode does not come into contact with the welding base metal no matter which direction the torch is moved. The present invention relates to a method for controlling the arc length.

[0002]

2. Description of the Related Art Conventionally, for adjusting the arc length in TIG welding, there is known a technique for automatically adjusting the distance of an electrode to a welding base metal based on the detected arc voltage.

For example, as shown in FIG.
Reference numeral 1 denotes a torch body 52 made of an insulator for supporting the electrodes, and a torch body 5 for supplying gas to the groove.
The gas nozzle 53 is provided in the lower part of the No. 2 and the electrode 54 is protruded from the lower part of the gas nozzle 53 toward the welding base material and is placed in a posture perpendicular to the welding base material. 55 is a torch cap used for attaching and detaching electrodes, 56 is a welding base metal,
57 is a welding wire.

The torch body 52 is supported by a vertical mechanism (not shown) that moves the torch body up and down (a direction perpendicular to the welding base metal 56), and the welding base metal 56 and the electrode 5 are also supported.
4 is provided with a voltage detecting means (not shown) for detecting an arc voltage generated between the voltage and the voltage. Then, the vertical position of the torch 51 is controlled based on the detected voltage. Such a technique or circuit device is called automatic arc length control (AVC).

By the way, a multi-electrode TIG welding method using a plurality of electrodes has been proposed in order to prevent uneven welding (welding defects) in TIG welding and to speed up the welding (Japanese Patent Application No. 6-242242).
-044730). The multi-electrode TIG welding torch according to this method, as shown in FIG.
2, an A torch 63 and a B torch 64, a gas nozzle 6 provided in the lower portion of the torch body 62 for supplying gas to the groove, and a portion protruding from the lower portion of the gas nozzle 6 toward the welding base material 7 One electrode 4, 5 and its electrode 4,
The wire guide (inside the torch main body 62) continuously supplies the welding wire 2 onto the welding base material 7 at the tip of the wire 5. 65
Is a welding wire insertion port, and 66 and 67 are insulators. According to this, a wire guide made of an insulator is sandwiched between two electrodes 4 and 5 which are formed by dividing a cylinder into halves, and the welding wire 2 is supplied through the shaft center. A power source can be separately connected to each of the electrodes 4 and 5 to apply different currents.

[0006]

The conventional arc length control method is based on the assumption that a single electrode is used, and the arc length control method in the case of multiple electrodes is not known. This is because the voltage of each electrode is different, and therefore the electrodes cannot be adjusted based on the arc voltage as in the conventional case.

A particular problem with multi-electrode TIG welding is when performing welding that requires toothiocyanate. The above-mentioned arc length control method (AV
If C) is applied, when the torch moves left and right and the electrode approaches the groove wall, the arc reaches the groove wall, so that the torch rises to adjust the arc length. However, since there is no arc length control method in multi-electrode welding, when the torch moves left and right, the electrode approaches the groove wall and comes into contact with the groove wall as it is, making welding impossible.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to solve the above problems and provide a method for controlling the arc length of multi-electrode TIG welding in which the electrode does not come into contact with the welding base metal no matter which direction the torch is moved.

[0009]

In order to achieve the above object, the present invention uses a torch having a plurality of electrodes and, in an arc length control method for multi-electrode TIG welding in which an arc current is applied to each electrode, the torch is moved. The electrode located on the front side of the direction is selected, the arc voltage of the selected electrode is detected, and the vertical position of the torch is controlled based on this arc voltage.

As the torch is moved to the left and right of the groove, the left and right positions of the torch are detected. When the torch is located on the left side of the groove, the left electrode is selected, and the torch is positioned on the right side of the groove. When doing so, the right electrode may be selected.

[0011]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

The torch for multi-electrode TIG welding shown in FIG. 1 is the same as that already described in FIG. 6, but the internal structure of the torch 1 shown by being broken away will be described in detail. Positioned 2 is a welding wire, and 3 covering the outer periphery thereof is a wire guide made of an insulator, which also serves as an arc control gas introduction part and an interelectrode spacer. Furthermore, 4 and 5 which cover the outer periphery thereof are a first electrode (A electrode) and a second electrode (B electrode) which are divided into two with the wire guide 3 interposed therebetween. The outermost peripheral 6 is a gas nozzle for supplying the torch shield gas.

Further, in detail, the form of the tip portion whose cross section is shown will be described. Reference numeral 7 is a welding base material, 4 and 5 are A electrodes and B electrodes facing the groove, 2 is a welding wire, 3 is a wire guide, and 8 is a wire guide. Is a welding arc by each electrode, 2a is a molten portion of the welding wire 2, and 9 is a molten pool formed at the groove.

The circuit for driving and controlling the torch 1 includes an A power source 10 and a B power source 11 for applying currents to the A electrode 4 and the B electrode 5, respectively, and a wire power source 12 for applying a heating current to the welding wire 2. A progress controller (not shown) that advances a carriage (not shown) equipped with this torch 1 in the longitudinal direction of the groove, and a wire feeder (not shown) that adjusts the supply speed (supply amount) of the welding wire 2. No.) and a torcholate section (not shown) for moving the torch 1 to the left and right in the traveling direction.
A torch horizontal position detection unit (not shown) that detects the horizontal position of the torch 1, voltmeters 13 and 14 that detect the arc voltage of the A electrode 4 and the B electrode 5, and automatic arc length control (A
(VC) built-in welding controller 15 and an electrode selector (switch) 16 for switching the electrodes.

The ground side of each of the power supplies 10 and 11 is the welding base metal 7
, And the application side is connected to the electrodes and is also connected to the electrode selection unit 16 via the voltmeters 13 and 14. In this electrode selection unit 16, any one voltmeter is switched and connected to the ground side.

In addition to incorporating the AVC described in the prior art, the welding control device 15 reads the voltmeters 13 and 14 for the AVC and the means for activating the electrode selector 16 based on the detection result of the left and right positions of the torch. It also has a built-in means, and also has means for driving each of the power sources 10, 11, and 12 in a pulsed manner. The welding control device 15 operates according to the control flow of FIG. 2 according to the present invention.

Next, the operation will be described.

First, welding is started according to the flow of the welding control device 15 shown in FIG. Then AVC is started. In addition, torithiolate is started. In accordance with this torch sylate, the lateral position of the torch is detected by the torch lateral position detector. If the detected position is on the left side of the center, the left end control is performed, and if it is on the right side, the right end control is performed.

The left end control and the right end control will be described with reference to FIG. FIG. 3 is a sectional view of the groove where the torch moves. Reference numeral 31 is a groove wall at the left end, and 32 is a groove wall at the right end. It is assumed that tothiosylation is performed in the range of 33. 34 is a weld bead formed at this time.

The left end control is, as shown by a solid line in FIG. 3, to perform AVC on the A electrode 4 so that the left A electrode 4 does not come too close to the left end groove wall 31.
That is, the electrode selector 16 is switched to the A power source 10 side, and the vertical position of the torch 1 is controlled based on the arc voltage of the A electrode 4 detected by the voltmeter 13. As a result, when the left A electrode 4 approaches the groove wall 31 at the left end, the arc reaches the groove wall 31, so that the torch 1 moves up and down to adjust the arc length.

The right end control is to perform AVC on the B electrode 5 so that the right B electrode 5 does not come too close to the right end groove wall 32, as shown by the broken line in FIG.
That is, the electrode selector 16 is switched to the B power source 11 side, and the vertical position of the torch 1 is controlled based on the arc voltage of the B electrode 5 detected by the voltmeter 14. As a result, when the B electrode 5 on the right side approaches the groove wall 32 at the right end, the arc reaches the groove wall 32, so that the torch 1 moves up and down to adjust the arc length.

Next, a method of applying a current will be described.

The A electrode 4 has an A power source 10 and the B electrode 5 has a B power source 10.
Since the power source 11 is connected and the wire power source 12 is connected to the welding wire 2 and each power source is independent, the welding control device 15 can control them in any combination. FIG. 4 shows an example. The upper row is A power supply 10
The drive waveform of the B power supply 11 is shown in the middle stage, and the drive waveform of the wire power supply 12 is shown in the lower stage. Each power source is pulse-driven to achieve phase synchronization. In this example A
The power source 10 and the wire power source 12 have the same phase, and the B power source 11 has the opposite phase. The voltage of each power supply can be set to the highest or lowest voltage. When using at a constant current, it is advisable to make each voltage setting the same.

The present invention can be applied even when the voltage of each electrode is different as in the example of FIG.

As explained above, the method of the present invention is
The electrode located on the front side in the moving direction of the torch is selected, the arc voltage of the selected electrode is detected, and the vertical position of the torch is controlled based on this arc voltage. Will be controlled,
Contact is avoided. Also, when performing torchoylation, the electrode closer to the groove wall is selected by selecting the electrode depending on the left and right position of the torch, and when the torch moving direction is reversed at the left and right ends of the torchoylation range, The electrode closer to the groove wall will be selected.

[0026]

The present invention exhibits the following excellent effects.

(1) The restrictions on the positional accuracy of attaching the welding device to the work piece are alleviated, and the vertical position adjustment of the torch during welding is automated, which reduces the burden on the welder.

(2) Only one AVC device is required, which is economical.

[Brief description of drawings]

FIG. 1 is a diagram showing the internal structure, tip morphology and circuit configuration of a torch for multi-electrode TIG welding according to the method of the present invention.

FIG. 2 is a control flow chart of a control device to which the method of the present invention is applied.

FIG. 3 is a sectional view of a groove where a torch moves.

FIG. 4 is a diagram of a current pattern of each power supply.

FIG. 5 is a side view of a conventional single electrode torch.

FIG. 6 is a side view of a conventional multi-electrode torch.

[Explanation of symbols]

 1 Torch 2 Welding wire 3 Wire guide 4 Electrode (A electrode) 5 Electrode (B electrode) 16 Electrode selection part

Claims (2)

[Claims] 1. In an arc length control method for multi-electrode TIG welding in which an torch having a plurality of electrodes is used and an arc current is applied to each electrode, an electrode located on the front side in the moving direction of the torch is selected and the selected electrode is selected. The arc length control method for multi-electrode TIG welding is characterized in that the vertical position of the torch is controlled based on the detected arc voltage. 2. The torch lateral position of the torch is detected in accordance with the torch sylate that moves the torch to the left and right of the groove, and when the torch is located on the left side of the groove, the left electrode is selected,
2. The arc length control method for multi-electrode TIG welding according to claim 1, wherein the electrode on the right side is selected when the torch is located on the right side of the groove.