What is the purpose of the back purge in GTAW?

The purpose of the back purge in Gas Tungsten Arc Welding (GTAW) is fundamentally to protect the back side of the weld from oxidation when welding closed joints. In GTAW, the weld pool is highly susceptible to contamination from atmospheric elements, particularly oxygen and nitrogen. When a weld joint is closed, the area behind the weld bead can be exposed to these elements, leading to defects such as porosity or weakened structural integrity.

By applying an inert gas, usually argon or helium, to the back side of the joint—an action known as back purging—the welding environment is significantly improved. This inert gas displaces any atmospheric gases, thereby forming a protective barrier that prevents oxidation and contamination during the welding process. As a result, the quality of the weld is maintained, ensuring that it meets structural and aesthetic requirements.

The other choices do not accurately encompass the primary role of back purging in the context of GTAW. While creating a protective environment and enhancing weld strength could potentially be considered, they do not directly address the oxidation prevention aspect specific to closed joints, which is the primary concern in this welding method.