Numerical investigation on melting characteristics of scrap with heat and mass transfers in molten steel

Abstract

Herein, a numerical simulation with simultaneous heat and mass transfers is carried out to investigate the scrap melting characteristics in molten steel after model verification by published experimental data. The numerical results show that the scrap melting stages consist of the frozen shell formation stage, the frozen shell remelting stage and the parent scrap melting stage. The heat transfer coefficient and the carbon mass transfer coefficient between the scrap and the molten steel are, respectively, in the range of 4209–6249 W m⁻² K⁻¹ and 6.4 × 10^–5 m s⁻¹. Meanwhile, the effects of process parameters on scrap melting time were studied. An increase in the scrap preheating temperature $\left( {T_{{{\text{scrap}}}} } \right)$, the molten steel temperature $\left( {T_{{{\text{steel}}}} } \right)$ and the carbon content of molten steel $\left( {C_{{{\text{steel}}}} } \right)$, and a decrease in the scrap thickness $\left( {d_{{{\text{scrap}}}} } \right)$, can reduce the frozen shell existence time, as well as the scrap melting time. On this basis, a quantitative relationship between the aforementioned process parameters and the scrap melting time is obtained to predict the formation of frozen shell (Ψ), which provides process guidance for shortening the scrap melting time. The quantitative relationship is expressed as: $\ln \left( \varPsi \right) = 311.32 - 2.34\ln \left( {T_{{{\text{scrap}}}} } \right) - 39.99\ln \left( {T_{{{\text{steel}}}} } \right) - 0.08\ln \left( {d_{{{\text{scrap}}}} } \right) - 0.57\ln \left( {C_{{{\text{steel}}}} } \right)$.