The sponge iron or Direct Reduced Iron (DRI) is an important feedstock in the Electric Arc Furnace (EAF). The main sources of iron units for the EAF can be steel scrap, DRI, hot metal and combinations of these materials. The EAF has become a melting reactor and its melting rate plays a key role in furnace productivity. In this work, the melting rate of porous metallic particles is analyzed employing CFD tools, having the computational domain of an industrial size EAF. The molten pool is comprised of two liquid phases, steel and slag. In order to compute the melting rate as a function of particle size and arc length, three sub-models were developed, one computes the instantaneous power delivery as a function of arc voltage and arc length, the second one computes the velocity and temperature fields and finally the third sub-model computes the melting rate. Comparisons of melting rates when the particles are immersed in its own melt and the case where immersion is carried out in the steel/slag system is included in the analysis. A contribution from this work is a more realistic approach to compute the convective heat transfer coefficient using the estimated values of the velocity fields.

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A coupled thermal-microstructural simulation model was developed to estimate the thermal history in a eutectoid steel wire rod under continuous cooling and forced-convection. The model coupled the phenomena of heat transfer, phase transformation and estimation of the cooling boundary condition. The thermal histories were analyzed at different cooling rates to emulate the forced-convection conditions by air-jet as in the controlled cooling conveyor. The thermal histories were acquired and used to calculate the forced-convection heat transfer coefficients through the solution of the Inverse Heat Conduction Problem, while the phase transformation was approximated with the Johnson–Mehl–Avrami–Kolmogorov (JMAK) kinetic model. From the heat transfer coefficients and the kinetic parameters, a user-defined function (UDF) was coded and employed in the ANSYS Fluent® software. The model results were compared and validated with the experimental histories, obtaining a good agreement between both responses, while the microstructural evolution of the pearlite was validated using Scanning Electron Microscopy (SEM) and Vickers microhardness. It was found that specimen diameter and air velocity are the main variables to modify the undercooling and therefore the pearlite interlamellar spacing.

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