Kinetics of Scrap Melting in Liquid Steel: Multipiece Scrap Melting

This article extends the study of single-steel bar melting discussed in a previous article[1] to the investigation of two-bar and multibar melting kinetics. Experiments involving multiple bars reveal that the interbar spacing and the initial solid and liquid steel temperatures influence the final melting time by altering the degree of “steel iceberg” formation. Simulations of scrap melting using a recently developed phase-field model of steel scrap melting[1] are shown to follow the trends of the two-bar melting experiments. The phase-field methodology is also extended to examine melting of randomly distributed scrap in the liquid steel bath, a poorly understood situation that is difficult to access experimentally. Two types of simulations were performed. The first type assumed a constant heat-transfer coefficient and liquid steel temperature, corresponding to the limiting case of melting with perfect stirring in the liquid steel bath. Results for this case reveal that the final melting time was controlled by the largest of a group of isolated steel icebergs, which formed in regions of low scrap porosity. The second type examined the case of melting dominated by heat conduction, using an effective thermal conductivity to model low-level natural convection in the liquid steel. In this case, phase-field simulations show that, under certain conditions, melting could be well approximated by a simple one-dimensional (1-D) analytical melting model with effective parameters related to the scrap distribution, scrap preheating, and liquid bath temperatures.