High-temperature viscosity of iron‑carbon melts based on liquid structure:The effect of carbon content and temperature

Abstract

Iron-based melts throughout the steel production process. Its viscosity dramatically affects the efficiency of ironmaking, steelmaking, and continuous casting processes. The viscosity was a structure-sensitive physical property and the macroscopic expression of its liquid structure. Molecular dynamics simulations were carried out to study the interaction mechanism between the liquid structure of iron‑carbon melts and its viscosity, to identify the essential factors influencing the viscosity. The results showed that pure iron's liquid structure changed from a thirteen-sided body to a deformed dodecahedron at 1873 K ~ 1923 K. With the increasing of carbon content, the nearest neighbor atomic distance increased from 0.255 nm to 0.261 nm, and the coordination number increased from 13 to 15. While the correlation radius decreasing from 1.450 nm to 0.930 nm, the number of atoms in an atomic cluster decreased from 980 to 300. The liquid structure evolved from medium-range order to short-range order, and the dominant polyhedral structural unit connection transformed. Melts' free volume increased, resulting in a decrease in viscosity. The average influencing degree of carbon content and temperature on iron‑carbon melts viscosity were 15% and 30%, respectively. The short-range structure was largely influenced the temperature. As the temperature increasing, the nearest neighbor atomic distance increased significantly; the correlation radius remained almost unchanged; the coordination number and the number of atoms in an atomic cluster decreased. The increase in free volume and motility of atomic clusters led to a decrease in melt viscosity. Finally, based on kinetic analysis, a quantitative relationship between the viscosity and temperature of pure liquid iron and iron‑carbon melts was constructed.