JPH07102464B2 - Method for reducing electrode wear in AC TIG welding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for reducing electrode wear in AC TIG welding.

[Conventional technology]

In TIG welding, in order to prevent air from entering the welding atmosphere, a double shield that surrounds the electrode is provided, and inert gas is ejected from the opening at the tip of this shield to enclose it in the welding location and prevent air from entering. I am trying to do it.

However, in the case of TIG welding using an AC power source, the electrode tungsten is gradually worn down by the impact of electrons from the workpiece during welding and also deforms due to heat,
After welding the work several times in succession, the electrodes must be replaced. Especially when automatic welding is performed by a welding robot or the like, there is a safety problem because the electrode replacement operator must enter the operating area of the automatic machine such as the robot when the electrode is replaced. There is also a problem that the operation rate of the equipment is lowered because the equipment is stopped while the equipment is replaced.

Since the number of exchanges due to electrode wear is greatly affected by electrode wear, many TIG welders have an afterflow function, and argon gas, which is an inert gas, is maintained for a certain period of time after welding is completed. A small amount of helium or helium is ejected to cool the electrode and prevent deformation.

Also, the method of using a device that automatically replaces the electrodes is safe, but the device itself is expensive, and since accessories are attached around the torch, interference between the torch and the work or jig becomes a problem, Further, since the exchange device does not prevent the consumption of the electrodes, the number of times cannot be reduced even if the time for exchanging the electrodes is shortened, and the problem that the operating rate is lowered is
It has the drawback of not being much improved.

[Problems to be Solved by the Invention]

As described above, AC TIG welding consumes more electrode than DC TIG welding, and thus requires replacement of the electrode. Especially in aluminum welding, the AC TI is used to remove the oxide film.
Since it is necessary to perform G welding, the welding conditions change sensitively due to wear and deformation of the electrodes. Therefore, it is necessary to frequently replace the electrodes.
It was a major obstacle to automation of TIG welding.

The present invention has been made in view of such problems in AC TIG welding, and the number of electrode replacements is significantly reduced.
The purpose is to perform stable welding.

[Means for Solving the Problems]

In order to achieve this object, in the AC TIG welding of the present invention, after the welding is finished, an electrode containing an oxygen-containing gas is not blown immediately after the welding is finished, instead of blowing an inert gas by an after flow to cool the electrode. The electrode is cooled and the electrode is oxidized.

[Action]

By cooling the electrode with a gas containing oxygen, the electrode is prevented from being deformed, and the electrode surface, especially the side surface is oxidized to reduce the consumption of the electrode. This principle will be described below.

As a result of detailed observation of the arc generation state in AC TIG welding, the inventor found that the arc generation pattern was different between the positive electrode and the negative electrode as shown in FIGS. 2 (a) and 2 (b). When is negative, the arc has risen to the side surface of the electrode as shown in Fig. 2 (a), and when welding is repeated, the state of rise is gradually increased,
It was found that not only was the electrode consumed and deformed, but the fact that it was lifted up also lengthened the arc length, increasing the arc voltage and changing the welding condition.

The reason why the rising condition becomes severe is considered to be as follows.

(1) Even if the electrode is water-cooled, the temperature gradually rises.

(2) The vicinity where the arc rises is activated and is subjected to the cleaning action, so that the arc tends to be generated from the metal part with the upper oxide like the electrode.

Therefore, in order to eliminate this cause,
Immediately, a gas containing oxygen is blown onto the electrode to cool the electrode, and an oxide film is formed on the electrode surface, especially on the side surface, so that the arc rising to the electrode side surface during repeated welding is reduced.

It should be noted that the oxidation of the electrode makes it difficult for the arc to come out of the electrode in normal DC TIG welding, but in AC TIG welding, the polarity is reversed, so the arc tends to come out at the tip surface, which does not interfere with welding. It didn't happen.

〔Example〕

Hereinafter, the present invention will be specifically described based on the embodiments shown in the drawings.

FIG. 1 is a schematic diagram of a system for accomplishing the method of the present invention. In the figure, 1 is a water-cooled torch for TIG, 2 is a tungsten electrode, 4 is a work, 5 is a robot, 6 is a robot controller, 7 is an AC TIG welder, 8 is a sequencer, and 9 is an air gun.

First, the robot 5 controls the arm by the robot controller 6 and operates the tungsten electrode 2 to weld the work 4. At this time, an inert gas is jetted from the shield nozzle (not shown) around the electrodes. When the welding is completed, the robot controller 6 sends a signal to the sequencer 8 to inform that the welding is completed, and the robot 5 immediately moves the tungsten electrode 2 right above the air gun 9 and receives a command from the sequencer 8. Air is blown onto the tungsten electrode 2 from the air gun 9 for several seconds.

After the tungsten electrode 2 is cooled and oxidized, the next welding spot or another work is welded, and when the welding is completed, air is blown to the tungsten electrode 2. This series of work consumes the electrode and welding is possible. Repeat until it becomes.

According to the experimental results, the electrodes had to be exchanged for every eight workpieces when cooling was not performed with air.
By cooling with air, it became possible to perform sufficient welding by exchanging the electrodes for every 15 workpieces, extending the life of the electrodes by a factor of two.

〔The invention's effect〕

As described above, according to the present invention, since air is blown to the electrode after welding to oxidize it together with cooling, the cooling effect of the electrode is good and deformation can be prevented.
Oxidation can reduce the rising of the arc to the side surface of the electrode during welding, reduce the consumption of the electrode, keep the arc length small, and maintain the welding state evenly.

Also, since the number of electrode conversions is reduced, the operating rate of the automatic machine can be increased, and the number of times a worker enters the operating area of the automatic machine is also reduced, improving safety, especially by using a robot or the like. Effective for automatic welding.

[Brief description of drawings]

FIG. 1 is a system schematic diagram showing a practical example of the present invention.
The figure is an explanatory diagram showing the state of the electrode and arc during welding.
(A) shows the arc state when the electrode is negative, and (b) shows the arc state when the electrode is positive. 1: Torch, 2: Tungsten electrode 3: Arc, 4: Work 5: Robot, 6: Robot controller 7: AC TIG welder, 8: Sequencer 9: Air gun

Claims (2)

[Claims] 1. A method for reducing electrode wear in AC TIG welding, characterized in that a gas containing oxygen is blown to a tungsten electrode immediately after the welding is finished to cool and oxidize the electrode. 2. The gas containing oxygen is air.
A method for reducing electrode wear in the described AC TIG welding.