FORMATION BEHAVIOUR OF SPINEL-CaS MULTIPHASE INCLUSIONS IN Ca-TREATED RESULPHURISED STEEL DURING THE LADLE FURNACE PROCESS

Abstract

The formation of multiphase inclusions was investigated in resulphurised steel. Samples were taken at different stages of the steelmaking process, from primary deoxidation through calcium modification and sulphur addition to casting. Chemical analyses were made on all the samples, from which thermodynamic calculations using thermochemical computing software were performed, to determine which phases are stable at any given stage of the steelmaking process. Inclusions were investigated using a scanning electron microscope and automatic inclusion analysis software. The presentation of the automatic inclusion analysis results in the form of ternary diagrams provides an insight into the calcium modification of inclusions and the change of the inclusions' size and chemical composition after sulphur addition. Based on the results from this study, a formation mechanism is proposed for spinel-CaS multiphase inclusions in resulphurised steel.