What is the purpose of postflow in gas tungsten arc welding?

Postflow serves a critical purpose in gas tungsten arc welding by ensuring the protection of the molten weld pool and the tungsten electrode from oxidation. After the arc is extinguished, the inert shielding gas continues to flow for a set period, which helps to create a barrier between the hot, exposed metal and the surrounding atmosphere. This is particularly important because the weld pool can remain exceptionally hot for a duration after the arc has ceased, and any exposure to oxygen can lead to defects such as porosity or oxidation in the weld.

The continued flow of inert gas during postflow is essential for maintaining the quality and integrity of the weld. It allows the molten metal to solidify without contamination and prevents the tungsten electrode from oxidizing, which is crucial for maintaining a stable arc in future welding operations. Overall, postflow plays a vital role in ensuring that the weld is clean, strong, and free from impurities.