Nitrogen Deoxidation
Nitrogen deoxidation binds free nitrogen in the weld pool with nitride-forming elements such as aluminum or titanium. This prevents aging and brittle phases, and increases strength.
Physicochemical mechanism of action
Nitrogen deoxidation is a process where free nitrogen in the melt zone is bound by nitride-forming elements like aluminum or titanium. This affinity reaction forms nitrides that hold the free nitrogen molecules in the lattice and prevent them from escaping.
Metallurgical relevance & risks in welding
Binding nitrogen suppresses the formation of brittle phases like martensite and prevents strain aging embrittlement. Without adequate deoxidation, free nitrogen can cause hot cracking and deformation issues, endangering the service life of the weld.
Workshop practice & instructions
To ensure effective nitrogen deoxidation, the following measures must be taken:
• Use deoxidizers like silicon or aluminum in the melt zone.
• Keep the melt zone clean and free of unwanted substances.
• Control the temperature and cooling time to avoid brittle phases.
• Use suitable shielding gases like argon or helium in the welding zone.