Fundamentals and practice for producing low nitrogen steels

Abstract

In general, the refining reactions in steelmaking are well understood and most elements can be controlled by the proper slag practice. However, the nitrogen reaction is complex and its content difficult to control. A recently developed model for computing the removal of nitrogen in OSM is presented along with results quantifying the effect of scrap, stirring gas, and oxygen purity. For the EAF, nitrogen is also removed by CO formation by the carbon-oxygen reaction and a model for the rate is presented. However, recent work shows that the CO evolved from DRI comes off in the slag and is not effective in actually removing nitrogen from the atmosphere. Nitrogen control in ladle processing is discussed, including a new model for vacuum tank or ladle degassing for nitrogen. © 1996 ISIJ.