Nitrogen affinity of alloying elements
The nitrogen affinity of alloying elements measures how strongly they react with nitrogen to form stable nitrides. This refines the grain and stabilizes the microstructure.
Physical-Chemical Mechanism of Action
Alloying elements with high nitrogen affinity, such as titanium or aluminum, react strongly with nitrogen in the melt. They form stable nitrides that refine the grain and stabilize the structure.
Metallurgical Relevance & Risks in Welding
High nitrogen affinity can lead to grain refinement, which increases strength. However, over-nitriding can occur if the nitrogen content is too high. This can alter the microstructure and cause cracks or fracture points.
Workshop Practice & Instructions
When welding alloys with high nitrogen affinity, pay attention to the nitrogen content in the melt. Use suitable shielding gas mixtures to control nitrogen levels. For aluminum or titanium, the values are typically set between 0.1 and 0.2 %.