GTAW Welding: Touching on the basics

Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding is used in many aircraft applications. GTAW provides a clean, strong weld joint that makes it ideal for assembling and repairing various aircraft components. In this article, we will discuss the basic theory of GTAW and cover some basic welding and setup tips.

Basic Theory

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 an inert gas shields the weld area in order to prevent air from contaminating the weld. This shielding 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 shielding gas. The 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.

Personal Protective Equipment

Although GTAW does not produce the metal spatter that is common with arc or stick welding, it still generates intense heat and light. In fact, the clearer atmosphere around the GTAW arc 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 as 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 should be observed to protect you and co-workers from the hazards 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 it is used in an enclosed area it can displace breathing air and can be hazardous without proper ventilation. In addition, ozone is produced during the welding process. The amount of ozone produced 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 adjacent areas are not exposed to the welding arcs.

Shielding Gas

In GTAW, the gas used to shield the welding arc and hot metals is an inert gas. Inert gases are gases whose atomic structures do not allow them to react with metals or other gases. Argon, helium, or an argon-helium mixture is used as the inert gas in GTAW.

Argon is a relatively heavy gas. It has several benefits when used in GTAW. It requires a lower arc voltage than other shielding gases for a given arc length and current used (ideal for thin metal welding). It also provides easier arc starting. Its heavier weight as compared to helium provides for good shielding with lower flow rates.

In contrast to argon, helium is the lightest of the inert gases. Because of its light weight, about two to three times more helium is needed as compared to argon to shield the weld area. Despite this, helium has an advantage over argon in that it can be used with greater arc voltages. Because of this, helium is preferred when working with thick metal sections.