To analyze the slag adhesion mechanism at the interfaceInterface between RH insertion refractory castablesRefractory castable and refining slagRefining slag, this study conducted interfacial reaction experiments between slag and refractory castablesRefractory castable by combining high-temperatureTemperature static crucible experiments with thermodynamicThermodynamic simulationSimulation calculations. The results show that increasing alkalinity (R), MgO, and CaF2 content reduces viscosityViscosity and activation energy for viscous flow. Lower viscosityViscosity decreases viscous adhesion at the interfaceInterface, demonstrating that adjusting slag composition effectively controls slag adhesion behavior. Significant interfacial interactions occur between slag and refractory castablesRefractory castable, forming a transition layer approximately 20–30 μm thick. This layer becomes thinner with increasing alkalinity, indicating weaker interactions and suggesting elevated alkalinity helps reduce slag adhesion. ThermodynamicThermodynamic calculations confirm that the reaction between the castables and slag produces high-melting-point phases, including Ca2Mg2Al28O46, CAF6, CAF2, and spinel phases. These phases reinforce the anchoring effect on the bonded material under thermal cyclingThermal cycling, promoting the development of slag adhesion.