Principle and Practice of High Nitrogen Steel Melting by Blowing Ammonia Gas

During the high nitrogen steel (HNS) melting process, the absorption reaction of nitrogen in the liquid steel by blowing NH3 and N2 was investigated respectively. In order to obtain higher content of nitrogen in steel, the liquid steel should be deoxidized and desulfurized because the oxygen and sulfur as surface activity element are not favorable to the absorption of nitrogen in melting process. Based on the metallurgical thermodynamics, the coupling reaction of NH3 with oxygen can improve the generation of activity nitrogen atom in liquid steel. Nitrogen atom is easier to be absorbed than nitrogen molecule. At the same time, blowing ammonia gas can remove the oxygen from liquid steel and decrease the inclusion in the steel. Experiments of HNS melting were carried out in a 10 kg induction furnace, and the results indicated that for liquid steel containing the same content of alloys and blowing the same mole of nitrogen, the absorption effect of nitrogen by blowing NH3 is obviously higher than that of blowing N2. The technical process of melting HNS by blowing NH3 under normal pressure is feasible in industrial production.