What is the purpose of using a back purge during TIG welding?

The purpose of using a back purge during TIG welding is to prevent oxidation. In the TIG welding process, the arc produces a significant amount of heat, which can lead to oxidation of the metal surfaces being welded, especially in non-ferrous materials like aluminum or stainless steel. Oxidation occurs when the molten metal is exposed to air, which can result in contamination and weaken the final weld.

A back purge involves introducing an inert gas, typically argon, on the back side of the weld joint. This inert gas displaces the air and creates a protective atmosphere, thus preventing oxygen from coming into contact with the molten weld pool. By ensuring that the underside of the weld joint is shielded from oxidation, the integrity and quality of the weld are significantly improved.

By contrast, alternatives like increasing heat input, enhancing deposition rates, or improving filler metal flow do not directly address the prevention of oxidation. Although those aspects may contribute to the overall welding process, they do not fulfill the specific function of a back purge, which is critical to achieving a clean and strong weld joint.