Which gases are most commonly used for shielding in GTAW?

In Gas Tungsten Arc Welding (GTAW), argon and helium are the most commonly used gases for shielding. Argon, being an inert gas, provides an effective protective atmosphere around the weld zone, preventing contamination through oxidation or reactions with atmospheric elements. Its ability to flow easily and maintain a stable arc makes it ideal for a variety of metals, especially aluminum and stainless steel.

Helium, while also an inert gas, has a higher thermal conductivity than argon, which can be advantageous for welding thicker materials or for applications requiring deeper penetration. The combination of argon and helium can improve arc stability and enhance heat input, making it a favorable choice for certain welding conditions.

The other options listed are typically not used in GTAW shielding. For example, nitrogen and carbon dioxide can introduce unwanted reactions and contaminants into the weld, while oxygen and hydrogen are reactive gases that can severely compromise weld quality. Acetylene and propane are primarily associated with oxy-fuel welding processes rather than GTAW, where maintaining a precise and stable arc in an inert environment is critical.