New approach to nitrogen control in EAF steelmaking

High grade steels, particularly in flat products are associated with low levels of dissolved nitrogen. For deep drawing steels it is desirable to keep nitrogen levels below 50 ppm, where as a range of 120 to 150ppm is acceptable for high strength structural steels (1). In EAF steelmaking, molten metal is often exposed directly to the air during the melt down. Ionisation of nitrogen by the arc is also thought to accelerate the rate of nitrogen pick up by the steel. In addition, scrap and ferro-alloys can contain significant dissolved nitrogen. As a result, whist steel produced from Oxygen steelmaking contains 30 to 40ppm, nitrogen levels in steel produce from EAF is typically in the range 70 to 100ppm.