Innovations and Optimizations in Tracing Non-Metallic Inclusions in Steel

The steel industry faces a critical shift to reduce CO2 emissions, requiring novel processes and increased recycling while maintaining a high steel quality. A key challenge associated with this is steel cleanness, particularly non-metallic inclusions (NMIs). These mainly microscopic particles are formed and modified during production. Their behavior in the steelmaking process must be monitored, especially in case of implementing new production procedures or higher scrap recycling rates. By applying tracing approaches, such as active tracing, where rare earth elements (REEs) or oxides are directly added to the melt or slag, tracking the path of NMIs is possible. However, the state-of-the-art method for tracing requires optimization concerning automated scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), as REE-traced NMIs appear brighter than conventional deoxidation products. Since this method influences NMI behavior, alternative tracing techniques are needed. A promising approach is REE fingerprinting, a passive method adapted from food chemistry. By analyzing natural REE concentration patterns in potential sources and NMIs, this technique can identify connections between auxiliary materials and NMI formation, offering a non-intrusive way to improve steel cleanness.