Explanation
Add titanium or niobium elements in excess of ideal chemical ratio into steel with extremely low carbon and nitrogen content (total carbon+nitrogen content is less than 50 * 10 ^ 6) to form carbonitride with carbon and nitrogen atoms in steel, so as to eliminate interstitial carbon and nitrogen atoms, and the room temperature matrix structure is ferrite without interstitial solid solution（ α- Iron).
Classification
Metals -> Steels -> Alloy steels