What material is commonly used as shielding gas in MIG welding?

In MIG (Metal Inert Gas) welding, the commonly used shielding gas is indeed argon, and it is often mixed with carbon dioxide. Argon, being an inert gas, does not react with the molten metal, providing a stable environment that protects the weld from contamination by atmospheric gases, which can lead to defects such as porosity and oxidation.

The addition of carbon dioxide to argon is popular because it improves the arc stability and penetration, creating a smoother weld bead and better bonding properties, especially when welding mild steel. This combination delivers excellent results across various applications, which is why it is frequently chosen by welders.

Other gases mentioned, such as helium and nitrogen, are less common for this application. Helium can be used in certain cases, particularly when welding thicker materials, as it creates a hotter arc. However, it is not the standard choice. Nitrogen is not typically used as a shielding gas in MIG welding as it can lead to adverse reactions with molten metals. Lastly, oxygen is avoided in MIG welding as it can cause oxidation and result in poor weld quality. Thus, the combination of argon and carbon dioxide strikes a balance between protection and welding performance, making it the favored choice for MIG welding operations.