The effect of nitrogen on steel is mainly in the area of heat treatment and process properties.
Both nitrogen and carbon can be incorporated into iron as an interstitial linkage to iron, and unlike carbon, nitrogen is a very good austenitic stabilizing substance. And nitrogen can also make a tight connection between high chromium and high chromium-nickel steels. However, when too much nitrogen is present in the steel, inner structure of steel will be loosening or porosity.
Nitrogen enhances the hardenability and high temperature lasting strength of iron, and secondly nitride precipitates hardening and increases the strength of the steel. But the increased strength also means increased brittleness. For example, when steel becomes blue brittle, it is mostly due to nitrogen.
In terms of process properties, when the nitrogen content is higher than 0.0016, the oxidation resistance of the steel becomes weaker and the cold work hardening rate is slightly higher than the average. Nitrogen can also influence the grain growth trend of high chromium ferrite steels, which can be used to improve the weldability of the steel.
