Which gas is NOT typically categorized as a shielding gas in welding?

Nitrogen is not typically categorized as a shielding gas in welding because its primary function is not to protect the weld pool from contamination or oxidation during the welding process. Shielding gases, like argon and helium, are used to create an inert atmosphere that helps maintain the purity of the weld by preventing the reaction of molten metal with atmospheric elements such as oxygen and nitrogen.

While nitrogen can be present as an impurity in other gases and can even be used in some specialized welding applications, it does not serve the same protective role as argon, helium, or carbon dioxide, which are commonly used to stabilize the arc and improve weld quality. Carbon dioxide, despite being an active gas, is often used in conjunction with argon in MIG welding to enhance arc stability and penetration. In summary, nitrogen does not fit the typical role of shielding gases, which is to provide a protective barrier during the welding process.