Electro-Slag Remelting (ESR) is a process capable of producing ingots with much lower centre-line
segregation and better internal soundness than conventional ingot casting processes, as well as
lower inclusion and sulfur concentrations. This process is commonly used for alloyed steels intended
for critical applications like components of marine turbines, supercritical powerplants and rocket
motor casings. It involves melting a metal electrode using electrical resistive heating in a slag pool
and re-solidification of the resulting metal droplets beneath the slag layer, forming an ingot.
Conventional ESR fluxes consist primarily of CaF2, Al2O3 and CaO, along with minor concentrations
of SiO2, MgO etc. The emission of fluoride vapour from the molten slag causes several environmental
and health problems, triggering a need to develop and reduce the fluoride content in the ESR flux.
The present study aims to develop low-CaF2 alternatives to commercial ESR fluxes without
compromising on productivity and the surface quality of the refined ingot. Thus, the modification in
chemical composition needs to satisfy properties like electrical resistivity, viscosity and liquidus
temperature, essential for efficient ESR operation. Since electrical resistivity and viscosity are highly
dependent on the ionic structure of the molten slag, it is important to understand the effect of
compositional modification on the structure of the flux. The present study employs Fourier-transform
infrared spectroscopy (FT-IR) and Raman spectroscopy to investigate the structural variations in the
modified fluxes, especially the effect of changing SiO2 concentration, in comparison with
conventional CaF2-rich fluxes. Additionally, thermal analysis (Differential Thermal Analysis (DTA)
and Thermogravimetric Analysis (TGA)) has been carried out to characterise the melting behaviour
of the fluxes. The findings are compared with simulations carried out using the FactSage™ software,
ver 8.3 (GTT Technologies, Aachen, Germany). Simultaneous analysis of liquidus temperature and
the structure is expected to help in identifying the practical suitability of modified ESR flux
compositions for industrial implementation.