Nitrogen (N)

Nitrogen is all around us — air is 78% nitrogen. In welding it appears in two roles. As a shielding gas (backing gas, root gas) it displaces oxygen and is cheaper than argon. As an alloying element in stainless steels it is a strong austenite stabiliser: it raises strength and, crucially, pitting resistance (PREN) without being expensive. The catch: too much nitrogen in the weld metal causes porosity and embrittles the weld.