Theoretical calculations and thermal experimental study on solid-liquid phase transition processes in metallic iron via VIS-NIR spectroscopy prediction

The melting behavior of scrap steel directly influences the scrap ratio in converters, energy consumption of electric arc furnaces (EAFs), and stability of hot metal pretreatment. Investigating its melting mechanism and detection methods is of great significance for optimizing smelting processes and enhancing resource utilization efficiency. Centering on the high-temperature self-luminescence characteristics of metallic iron—the core component of scrap steel—this study proposes an in-situ measurement method based on visible-near infrared (VIS-NIR) spectroscopy to calculate and analyze the solid-liquid phase transformation process of metallic iron in the molten bath. Through theoretical derivation, the intrinsic correlation between the luminescence intensity of VIS-NIR spectra (during the melting and solidification of metallic iron) and the proportion coefficients of solid-phase and liquid-phase fractions in the molten bath was established. Additionally, a calculation method for determining the liquid-phase fraction proportion in the molten bath via VIS-NIR spectral luminescence intensity was developed, and corresponding experiments were designed to verify the feasibility and calculation accuracy of this method. • A strong correlation between metallic iron's phase transition and its self-luminous spectrum is identified. • By means of VIS-NIR spectral intensity, effective estimation of liquid-phase metallic iron proportion in the molten pool is enabled. • Feasibility of estimating metallic iron melting process via VIS-NIR spectroscopy is verified through theoretical calculations and thermal experiments.