JPH11123554A - Method and device for tig welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent damage of a non-consumable electrode and to start an arc smoothly by using an arc generated between a filler wire and a parent metal as a pilot arc and moving the pilot arc to a part between the parent metal and the non-consumable electrode which is applied with no-load voltage in advance. SOLUTION: A non-consumable electrode 1 and a parent metal 2 are fixed with a space L of 2 to 5 mm. A part between the non-consumable electrode 1 and the parent metal 2 is applied with a no-load voltage of a power source 5 for welding. A filler wire 3 and the parent metal 2 are brought into contact with each other and a short-circuit current of 20 to 100 A are applied by using an auxiliary power supply 7 for filler wire energization. After the short-circuit current is detected with a filler wire energization detector 8, the filler wire 3 is separated from the parent metal 2 by inverting a wire feeder 4 and a pilot arc is generated. The pilot arc is moved to between the non-consumable electrode 1 and the parent metal 2 and an arc current is sent. After the arc current is detected with an arc start current detector 6, energization between the filler wire 3 and the parent metal 2 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TIG welding method and a TIG welding apparatus for a metal material structure. The present invention is effectively used particularly in automatic TIG welding.

[0002]

2. Description of the Related Art A conventional arc start method for a TIG welding apparatus is disclosed in, for example, Japanese Unexamined Patent Publication No. Sho 59-101276. There is a method called a touch start method in which a non-consumable electrode is brought into contact with a base material to cause a short-circuit current to flow, and then the arc start is performed by separating the non-consumable electrode from the base material.

On the other hand, in a hot wire TIG welding machine disclosed in Japanese Patent Application Laid-Open No. 58-38674, the filler wire is energized, and the temperature of the filler wire is raised by the resistance heat generation to increase the welding efficiency of the filler wire. ing. However, this method energizes the filler wire in order to increase the welding efficiency, and is not intended for arc start.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the arc start of a TIG welding apparatus.
The method using a high-frequency voltage generates electromagnetic noise due to the use of a high-frequency power supply, which may adversely affect peripheral electronic devices. In particular, the automatic welding apparatus causes a malfunction. In addition, the method of bringing the non-consumable electrode into contact with the base material has a problem in that the timing of contact and separation of the non-consumable electrode is extremely difficult, and furthermore, the non-consumable electrode is easily damaged by welding to the base material. Yes, very inefficient.

The present invention provides a TIG welding method and apparatus that does not require a high-frequency power supply in TIG welding and can start an arc without causing problems such as non-consumable electrode damage and arc generation unlike the touch start method. The purpose is to do.

[0006]

SUMMARY OF THE INVENTION The present inventors have focused on the fact that an arc can be generated between a filler wire and a base material by a method similar to the touch start method. By using the arc as a pilot arc (arc for generating a welding arc) and applying a no-load voltage in advance, by transferring the pilot arc between the non-consumable electrode and the base material, a smooth arc start is possible. The inventors have found the present invention, and the gist thereof is as follows.

(1) A pilot arc is generated between a filler wire and a base material, and a welding arc is generated by transferring the pilot arc between a non-consumable electrode and a base material to which a no-load voltage is applied in advance. A TIG welding method, characterized in that: (2) The TIG welding method according to (1), wherein the distance between the non-consumable electrode and the base material is 5 mm or less.

(3) The pilot arc is generated by bringing the filler wire into contact with the base material and causing a short circuit current of 20 A or more to flow, and then separating the filler wire from the base material. The TIG welding method according to (2). (4) Means for moving the filler wire forward and backward with respect to the base material, an auxiliary power supply for applying a voltage for generating a pilot arc between the filler wire and the base material, and when the filler wire and the base material are short-circuited due to the advance. A short-circuit current detecting means, and a means for detecting an arc current between the non-consumable electrode and the base material, a pilot arc is generated between the filler wire and the base material, and a no-load voltage is applied in advance. A TIG welding apparatus wherein a welding arc is generated by transferring the pilot arc between a non-consumable electrode and a base material.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIG. 3 schematically shows a conventional TIG welding apparatus for performing arc start. The filler wire 3 is supplied by the wire feeder 4 into the welding arc (not shown) formed between the non-consumable electrode 1 and the base material 2 by the welding current from the welding power source 5 to perform TIG welding. Do.

Conventionally, a welding power source 5 capable of generating a high frequency is used. An arc is generated by a high frequency, or the non-consumable electrode 1 and the base material 2 are brought into contact by an arc start method called touch start. The discharge arc was generated by separating the non-consumable electrode from the base material from the state where the short-circuit current was passed by using the method, and the arc start was performed using the discharge arc as a pilot arc.

In the present invention, the filler wire 3 is brought into contact with the base material 2 instead of the non-consumable electrode 1, and the filler wire is separated from the base material in a state where a short-circuit current is flowing, thereby generating a pilot arc. The non-consumable electrode 1 and the base material 2 to which a no-load (open) voltage has been applied in advance
If it is close enough, the arc can be transferred between the non-consumable electrode 1 and the base material 2. The welding arc starts when the pilot arc generated between the filler wire 3 and the base material 2 transfers between the non-consumable electrode 1 and the base material 2.

FIG. 1 schematically shows a TIG welding apparatus for performing the arc start method of the present invention. 3, the non-consumable electrode 1 is supplied by a welding current from a welding power source 5.
The filler wire 3 is supplied by a wire feeder 4 into a welding arc (not shown) formed between the metal and the base material 2 to perform TIG welding. However, the TIG welding apparatus of the present invention has the following features.

That is, the filler wire 3 can be fed and rewound (advanced and retracted with respect to the base material 2) by the wire feeder 4, and the filler wire 3 and the base material 2
Is connected to an auxiliary power supply 7 for generating a pilot arc. A power supply 5 for welding is connected to the non-consumable electrode. In addition, there are provided an energization detection device 8 for detecting energization to the filler wire and an arc current detection device 6 for detecting energization at the time of arc start.

Hereinafter, the arc start procedure of the present invention will be described. 1) A fixed space L is fixed between the non-consumable electrode 1 and the base material 2. 2) Apply no-load voltage V of welding power source 5 between non-consumable electrode 1 and base material 2. The no-load voltage V is a unique value determined by the welding power source 5, and is about 70V to 130V.

3) The filler wire 3 is brought into contact with the base material 2, and a short-circuit current A is caused to flow using the auxiliary power supply 7. 4) After the short-circuit current is detected by the conduction detecting device 8, the wire feeding device 4 is reversed to separate the filler wire 3 from the base material 2. At this time, a pilot arc is generated between the filler wire and the base material.

5) The pilot arc moves between the non-consumable electrode and the base material, and an arc current flows. 6) After the arc current is detected by the arc start detecting device 8, the energization between the filler wire and the base material is stopped.
By performing this procedure using a sequencer or personal computer, arc start is possible,
In order to start the arc stably, it is necessary to limit the short-circuit current A to the filler wire 3 and the distance L between the non-consumable electrode and the base material.

FIG. 2 shows the relationship between the current flowing through the filler wire and the distance between the non-consumable electrode and the base material for performing a stable arc start. The no-load voltage applied between the non-consumable electrode and the base material is 70V. When the current flowing through the filler wire is less than 20 A, no arc is generated, and even when the distance between the non-consumable electrode and the base material exceeds 5 mm, the arc is hardly generated. Therefore, the lower limit of the current flowing through the filler wire is set to 20A. The upper limit of the conduction current is basically not limited, but is set to 100 A in consideration of practicality. The lower limit of the distance between the non-consumable electrode and the base material is set to 2 mm in consideration of practicality, and 2 to 5 m.
m is preferable.

[0018]

EXAMPLE An arc start method according to the present invention was compared with a conventional method using a high frequency voltage and a touch start method using an automatic TIG welding apparatus for automatically controlling the movement of a welding carriage and the height of a torch. Commercially available T power source for welding
A constant current power supply having a maximum current of 30 A was used as the IG welding constant current power supply (no-load voltage 70 V) and the filler wire power supply. A non-consumable electrode was a tungsten electrode containing thoria having a diameter of 3.2 mm, and a general mild steel was used as a base material.

Table 1 shows the results of the arc start using the high-frequency voltage, the results of the touch start, and the results of the arc start method of the present invention. In the method using the high frequency voltage, the controller for controlling the welding bogie was stopped in most cases due to electromagnetic noise at the time of high frequency generation. In the case of an arc length of 5 mm, the arc start sometimes failed.

In the touch start method, the controller for controlling the bogie did not stop, but the non-consumable electrode sometimes welded to the base material, and the arc start failed.
Also, replacement of the non-consumable electrode required a great deal of trouble. On the other hand, according to the arc start method of the present invention, the arc start can be performed without stopping the bogie control controller.

Further, the arc start of the present invention was performed by changing the short-circuit current A to the filler wire and the distance L between the non-consumable electrode and the base material to various values. The success rate was compared depending on how many times the arc start was successful among the five times. As a result, as shown in Table 2, the short-circuit current A was set to 20 A or more,
Furthermore, in the example in which the distance L between the non-consumable electrode and the base material was 5 mm or less, the success rate was 100%, the arc could be started without failure, and the stable arc start was always possible.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

As described above, according to the present invention, no high-frequency voltage is used at the time of arc start, so that malfunction of peripheral control devices does not occur, and there is no need to bring non-consumable electrodes into contact with the base material. Therefore, damage to the non-consumable electrode can be prevented. For this reason, a stable arc start becomes possible, which leads to an improvement in welding quality and an improvement in work efficiency.

[Brief description of the drawings]

FIG. 1 shows a TI performing an arc start according to the present invention.
It is a schematic diagram of a G welding device.

FIG. 2 is a graph showing a relationship between a distance between a non-consumable electrode and a base material for stably performing an arc start according to the present invention, and a short-circuit current flowing through a filler wire.

FIG. 3 is a schematic view of a conventional TIG welding apparatus for performing an arc start.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Non-consumable electrode 2 ... Base material 3 ... Filler wire 4 ... Wire feeder 5 ... Power supply for welding 6 ... Arc start current detector 7 ... Auxiliary power supply for filler wire conduction 8 ... Filler wire conduction detector

Claims (4)

[Claims] 1. A welding arc is generated by generating a pilot arc between a filler wire and a base material and transferring the pilot arc between a non-consumable electrode and a base material to which a no-load voltage is applied in advance. TIG welding method characterized by the above-mentioned. 2. The TIG welding method according to claim 1, wherein the distance between the non-consumable electrode and the base material is 5 mm or less. 3. The method according to claim 1, wherein the filler wire and the base material are brought into contact with each other.
3. The TIG welding method according to claim 1, wherein the pilot arc is generated by separating a filler wire from a base material after a short circuit current of A or more is passed. 4. 4. A means for advancing and retracting a filler wire with respect to a base material, an auxiliary power supply for applying a voltage for generating a pilot arc between the filler wire and the base material, and a short circuit between the filler wire and the base material due to the advance. Means for detecting a short-circuit current at the time of performing, and means for detecting an arc current between the non-consumable electrode and the base material, and a pilot arc is generated between the filler wire and the base material, and a no-load voltage is previously set. A TIG welding apparatus, wherein a welding arc is generated by transferring the pilot arc between the applied non-consumable electrode and the base material.