What is the purpose of the shielding gas in the MIG welding process?

In the MIG (Metal Inert Gas) welding process, the primary purpose of the shielding gas is to protect the weld pool from atmospheric contaminants, particularly oxygen and moisture, which can lead to oxidation. When the molten metal is exposed to the atmosphere, it can react with these elements, resulting in defects such as porosity or poor weld quality. Shielding gases, typically inert gases such as argon or a mixture of argon and carbon dioxide, create an envelope around the weld area that effectively prevents these reactions. This protective atmosphere ensures that the weld solidifies without contamination, thereby improving the integrity and strength of the weld joint.