Nitrogen porosity during welding
Nitrogen porosity occurs when shielding gas or flux is insufficient to drive oxygen out of the weld. Without this protection, oxygen forms porous spots.
Physical-Chemical Mechanism of Action
Nitrogen porosity occurs when inadequate shielding gas or flux is used during welding. These media exclude oxygen from the weld and thus prevent the formation of pores.
Metallurgical Relevance & Risks in Welding
When shielding gas is missing, oxygen forms in the molten pool, leading to porosity. These pores can severely impair the strength and mechanical properties of the weld metal and result in a poor reliability level of the joint.
Shop Practice & Action Instructions
To avoid nitrogen porosity, use a sufficient volume of shielding gas or flux during welding. For high-strength steels like 1.0472 (X6CrNi18-9), an oxygen content below 5 ppm is required. The amount and time of use depend on the base material and welding technique, but generally, at least 20 liters per kg of weld metal should be used for high-strength steels.