In the steelmaking process, mold fluxes are essential for ensuring thermal insulation, refining, and
the efficiency of continuous casting. Real-time understanding of the in-service composition of slags
and fluxes are crucial for optimising the steel production process and improving the quality of the
final product. An in situ fibre-optic Raman probe that enables the study of the structure, composition,
and viscosity of molten slags and fluxes at steelmaking temperatures has been developed and
demonstrated both in the lab and in foundry scale experiments. The focus of this study is on the
structural, compositional, and property analysis of molten fluxes in a laboratory setting, with the aim
of applying this technology for in situ monitoring during industrial production. Raman spectra were
successfully collected at various temperatures from 1000°C to 1400°C in real-time and analysed
using a deconvolution algorithm to isolate and quantify peaks in the spectra associated with the
specific structures of molecular components in molten and solidifying flux. The research successfully
combines in situ Raman spectroscopy with high-temperature viscosity data, specifically targeting
CaO-CaF-SiO2-Al2O3 based mould flux systems. Specified ratios of the deconvoluted Raman peaks,
such as Al-O-Al/Si-O-Si ratio, shows good correlation with the flux chemistry, while the Q3/Q0 peak
ratio shows good correlation with viscosity. A ruggedised Raman probe system was also developed
and demonstrated in an 80 kg induction furnace. Ultimately, the goal of this work is to demonstrate
in situ slag and mould flux analysis in industrial processes, such as in the continuous caster or
electric arc furnace (EAF).