Structural Welding Code – Steel (D1.1) City Certification Practice Test

The primary gas used for MIG (Metal Inert Gas) welding is carbon dioxide (CO2). This gas is commonly used because it is readily available, cost-effective, and effectively promotes arc stability and good weld penetration. CO2 operates well in the MIG process, particularly when working with certain types of steel, as it can create a good overall weld quality.

While argon and helium are also shielding gases used in various welding processes, they are not the main gases used specifically for MIG welding on materials such as steel. Argon is typically utilized in conjunction with CO2 for a mixed gas application to improve the quality of the weld, while helium is often reserved for specialized applications. Oxygen is generally avoided in MIG welding because it can lead to oxidation and adversely affect the properties of the weld metal. Hence, CO2 remains a preferred choice for many MIG welding applications due to its effectiveness and versatility.