Discriminating the Fe Peak in Al-Killed Steel Specimens Using an Energy Dispersive Spectrometer: From Matrix or from Oxide Inclusions?

Reoxidation during secondary refining and casting of liquid steel can seriously deteriorate both process stability and the quality control of the final steel product. Unfortunately, detecting reoxidation occurrences is a formidable challenge until process troubles are encountered or product quality issues arise. In the present study, an energy dispersive spectrometer (EDS) was employed to analyze the composition of non-metallic inclusions in Al-killed steel. The specific focus was on deciphering whether the Fe signal within the EDS data originated from the steel (Fe) matrix or from FetO in the inclusions. It was revealed that when reoxidation levels are low, the primary source of the Fe signal is the steel matrix. Conversely, when reoxidation levels are high, a portion of the Fe signal can indeed be attributed to FetO in the inclusions, representing a mixture of signals from the steel matrix and oxide inclusions. A novel method for presenting EDS data was proposed to facilitate the identification of whether the inclusion comprises FetO to some extent. This distinction is critical in assessing whether the liquid steel has undergone reoxidation. To validate the present EDS analysis, a series of Monte Carlo simulations was conducted. It confirmed that EDS analysis of inclusions in steel specimens can effectively signal the presence of reoxidation. This research provides valuable insights for process control and quality assurance in steel production, helping to mitigate the detrimental effects of reoxidation.