What is the function of shielding gas in MIG welding?

In MIG welding, shielding gas plays a critical role primarily by protecting the weld pool from contamination. When welding, the intense heat creates a molten pool of metal that is highly susceptible to impurities from the atmosphere, such as oxygen and nitrogen. These contaminants can lead to defects in the weld, such as oxidation and porosity, which compromise the strength and integrity of the joint.

The shielding gas forms a protective atmosphere around the weld area as it flows out from the nozzle, effectively displacing ambient air and preventing these harmful elements from reacting with the molten metal. This ensures that the weld is of high quality and free from defects that could arise from exposure to atmospheric conditions.

While other options mention effects like additional heat, cooling the metal, or controlling speed, they do not accurately represent the primary function of shielding gas in MIG welding, which focuses on contamination prevention to ensure the quality and durability of the weld.