What is the most common inert gas used when welding stainless steel?

The most common inert gas used when welding stainless steel is argon. Its effectiveness in providing a stable shielding environment during the welding process is crucial for preventing oxidation and contamination of the weld pool. Argon has excellent thermal conductivity, which enhances the control over the welding arc, allowing for smoother and more consistent welds.

When welding stainless steel, the use of argon helps to maintain the integrity of the material by protecting it from the atmospheric gases that can lead to defects such as porosity or oxidation. While other inert gases, such as helium, can be used in certain applications to increase heat input or to modify the characteristics of the welding arc, argon remains the primary choice due to its reliability, availability, and cost-effectiveness for stainless steel welding.

This understanding of argon's role and advantages in the welding process illustrates why it is the correct choice compared to other gases like krypton and neon, which are less commonly employed in welding applications.