Nitrogen (N2)
Nitrogen (N2) protects high-alloy chromium-manganese steels from hardening and ignition caused by oxygen. It increases the strength of the weld.
Physicochemical Mechanism of Action
Nitrogen (N2) is an inert gas that is present in air at about 78 %. When welding high-alloy chromium-manganese steels, it prevents hardening and sparking caused by oxygen. This happens because N2 shields the steel surface and prevents oxygen from entering the weld zone.
Metallurgical Relevance & Risks in Welding
Without sufficient nitrogen, the weld can be prone to hardening and sparking, which can lead to cracks and loss of mechanical properties. This is especially critical in high-alloy steels, as they can harden strongly when exposed to oxygen.
Workshop Practice & Action Guidelines
To protect the weld, the nitrogen pressure during welding should be set to at least 90 %. This can be ensured by adequate ventilation and the use of shielding gases like argon or helium. For high-alloy chromium-manganese steels, it is important to maintain the nitrogen pressure throughout the entire welding time to preserve the mechanical properties of the weld.