Smith, S., R. Fruehan, G.S. Casuccio, M. Potter and T. Lersch, Application of Rapid Inclusion Identification and Analysis, presented at Iron & Steel Technology, AISTech, 2004.
To identify potential problems associated with inclusions in the steelmaking process and final products, techniques are being developed to rapidly identify inclusions in steel. Understanding the origin of inclusions and developing practices to control their composition and content in liquid steel are key to improved castability and quality. The inclusion analysis technique used in this work was based on a computer-controlled scanning electron microscope known as the Automated Steel Cleanliness Assessment Tool (ASCAT). ASCAT can determine the size and composition of hundreds of inclusions in less than 30 minutes. The overall aim of this work is to develop a system that can provide the metallurgist with rapid feedback on inclusion characteristics so that problems can be quickly identified and corrected. In order to develop software and expert systems to analyze the results, a variety of steelmaking issues related to inclusions are being examined. In this paper, three examples of application of this inclusion analysis approach are discussed. In the first example, the very strong influences between late oxidizing alloy additions to Ti-stabilized ultra-low carbon (Ti-ULC) grades and caster clogging is demonstrated. In the second, the impact of degasser circulation time after final alloy addition in Ti-ULC grades on inclusion content is examined. This work was used to determine the rinse circulation time, depending on the product application, which provides the best compromise between cleanliness and productivity. Lastly, some recent understanding on the origin of (MgO)(Al2O3) spinel inclusions in low carbon grades produced through the Ladle Metallurgy Facility (LMF) is discussed. This type of inclusion is known to have a strong influence on clogging. Inclusion analysis has indicated that their formation is promoted by arcing at the LMF and slag with lower levels of reducible oxides, particularly FeO.