Secondary steelmaking process stream optimization - inclusions, clogging, and segregation

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Micro-particles in steel, also known as inclusions, are highly undesirable. Although modern steelmaking practices have been developed to mitigate most of the deleterious effects, inclusions are detrimental to the properties of the final product, they clog the submerged entry and metering nozzles that transfer molten steel from secondary steelmaking to the continuous casting process stages, and they affect solute segregation / microstructure evolution during casting. At present, these issues are dealt with by (a) dissolving inclusions in a liquid oxide system (slag) during ladle metallurgy, (b) calcium treatment for shape control and (c) frequent replacement of the SENs. Each of these mitigation strategies has their own consequences that negatively impact product quality. Given the impact of inclusions on steel quality, there is need to optimize the secondary steelmaking process stream from the Ladle Metallurgy Furnace (LMF) to the cast product. In this collaborative study with Gerdau and Laurel steel, a suite of fundamental models will be developed that predict steel cleanliness in a wide range of steelmaking practices and products in the LMF, nozzle clogging based on interactions between the melt and the inner surface of the SEN, and subsequent compositional segregation and microstructure development during continuous casting. The models will be verified against plant data and samples taken from the industrial sponsors. Long-term, this set of models will form the basis of an online tool for optimizing the secondary steelmaking process stream. As the models are based on the fundamentals of thermochemistry, transport phenomena, and solidification, a modification procedure will be developed enabling application for any Canadian steel mill.