<p>A detailed study of shell formation and melt-back around an additive is reported using a novel methodology. A cylindrically shaped manganese rod, representing a Class I additive, is added to a large iron bath and is chosen as a representative system. A 2-dimensional continuum-based conjugate domain model is employed to represent both the additive and the melt. The model initially identifies these materials by specifying their thermo-physical properties—such as density, conductivity, specific heat, and latent heat of fusion—and their state (liquid or solid). This approach removes the need for front tracking and the specification of boundary conditions at the solid/liquid interface. The adopted numerical methodology allows us to capture the asymmetric shell growth around the particle hereto reported uniform using a constant heat transfer coefficient at the solid/liquid interface. The difference in shell dynamics at the top and the bottom is significant. While the shell disappears at the top, it continues to grow at the bottom. Additionally, we demonstrate that convection can develop within the partially molten low-melting-point additives inside the shell, influencing the shell melting process. By accurately accounting for internal convection, we show a 20&#xa0;pct reduction in the shell melting time at the top.</p>