Thermodynamic modelling of liquid steel tapping process to predict carryover slag amount

Abstract

Control of carryover slag is essential during transfer of liquid steel from basic oxygen furnace to ladle to maintain preferred steel cleanliness. Carryover slag is oxidising in nature and its higher amount will lead to higher refractory wear rate, low alloy recovery and increased secondary steelmaking treatment time. Measuring the amount of carryover slag is essential for evaluating current tapping practices and implementing necessary precautions when needed. In the present study, a kinetic process model has been developed using FactSage macro processing code. Steel lollipop and slag samples were collected between tapping start and onset of ladle refining process for a medium carbon aluminium killed grade. Liquid steel-slag interaction, flux addition to slag, various metallic additions to steel and refractory dissolution to slag were taken into account in the model. Multiple simulations were performed with varying amounts of carryover slag and composition of steel and slag of initial samples from the ladle furnace were equated with the predicted values from FactSage kinetic model to determine the carryover slag amount. Apart from predicting the carryover slag amount, this model can be useful to understand the effect of tapping parameters on variations in liquid steel and slag chemistry during tapping.