Final answer:
For MIG welding steel, an Argon-CO2 mixture is commonly used because it provides a stable arc and good weld quality. Argon's inert characteristic and low heat conductivity make it suitable for welding, while the addition of CO2 stabilizes the arc and improves penetration for thicker steel plates.
Step-by-step explanation:
The type of shielding gas commonly used for MIG welding steel is Argon-CO2. MIG welding, or Metal Inert Gas welding, typically uses a mixture of gases to shield the weld pool from atmospheric contaminants. Pure argon is often used for aluminum and other non-ferrous metals, but when it comes to steel, a combination of argon and carbon dioxide provides a stable arc, good weld penetration, and less spatter. The argon, prized for its inertness and low heat conductivity, is beneficial in preserving the welding tip's life and producing a clean weld. The addition of CO2 helps to stabilize the arc and enables better welding of thicker materials. While options like oxygen, nitrogen, and helium can also be used under certain circumstances, the standardized choice for steel is generally an Argon-CO2 mix, which provides a balance between arc stability, weld quality, and cost effectiveness.