By Joe Escobar
Welding is used in many aircraft applications. One of the most popular methods is gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding. In this article, we will discuss the basic theory of GTAW and cover different equipment setups available.
In gas tungsten arc welding, a non-consumable tungsten electrode is used to establish an arc on the base metal. The heat of the arc melts the base metal and produces a weld pool. In contrast to normal arc welding, in GTAW the weld area is shielded by an inert gas in order to prevent air from contaminating the weld. The gas prevents oxidation of the tungsten electrode, the molten weld puddle, and the heat affected zone adjacent to the weld bead.
In a typical GTAW setup, an AC/DC welding machine is used with a flow of a shielding gas. This shielding gas goes through a regulator and flow meter and on to the torch. The torch has a collet/collet body combination that holds the electrode. A heat-resistant cup or ceramic nozzle surrounds the electrode and controls the gas shield.
Although no metal spatter is produced with GTAW, it still generates intense heat and light. In fact, the clearer atmosphere around the GTAW arcs can cause up to twice the amount of infrared and UV rays compared to normal arc welding. Any exposed skin will be damaged similar to an extreme sunburn. Welders must wear a welding helmet. Welder's protective gloves and clothing should also be used. Fire-resistant cloth and leather clothing and accessories are recommended. Cotton should not be used since it doesn't provide sufficient protection and it deteriorates quickly under the infrared and UV rays produced by the welding process. In addition, dark clothing should be used to reduce reflection of light behind the helmet.
Other safety precautions
The following general precautions need to be observed to protect yourself and co-workers from the dangers associated with GTAW:
- Ensure electrical connection leads are in good condition and tight prior to use. They should be protected to prevent accidental damage from hangar traffic.
- Make sure you have adequate ventilation. Since GTAW uses inert gases during the process, if used in an enclosed area it can displace breathing air and can be harmful without proper ventilation. In addition, ozone is produced during the welding process, and varies with type of electrode used, amperage, and argon flow. In poorly ventilated areas, ozone levels can increase to harmful levels. Whenever possible, draw fumes and contaminated air away when welding.
- Flammable materials should not be carried in clothing pockets.
- Shielding curtains should be placed around all jobs so that workers in the area are not exposed to the welding arcs.