What is the purpose of back purge in GTAW?

The purpose of back purge in Gas Tungsten Arc Welding (GTAW) is to prevent oxidation of the weld on the backside of the joint. When welding, especially with materials like aluminum or stainless steel, the rear side of a joint can be exposed to oxygen in the atmosphere, which can lead to oxidation and contamination of the weld metal. This oxidation can compromise the integrity and appearance of the weld, leading to defects such as porosity or a weakened structure.

By applying an inert gas, typically argon, to the back side of the weld, back purging creates a shielding environment that protects the molten weld pool from atmospheric gases. This technique ensures that the weld remains clean and of high quality, which is particularly critical in applications where strength and aesthetic finish are essential.

Understanding this protective role of back purge is vital for achieving optimal results in GTAW, especially in critical welding applications such as in the aerospace, automotive, and manufacturing industries where weld quality is paramount.