Thermodynamic Analysis of the Deoxidation Ability of Alkaline-Earth Metals in the Presence of Aluminum

The phase boundaries in the Fe–Mg–Al–O, Fe–Ca–Al–O, Fe–Sr–Al–O, and Fe–Ba–Al–O systems at 1600°C are determined using the theory of construction of solubility surfaces of components in a metal. The equilibrium constants of the formation of alkaline-metal aluminates from the components of a metallic melt are estimated. The compositions of the nonmetallic inclusions formed upon melt deoxidation and equilibrated with liquid iron are determined. A complex mechanism of deoxidation with the formation of oxide compounds containing aluminum and alkaline-earth metal is found to take place in all systems at 0.01 wt % aluminum dissolved in a metallic melt and an alkaline-earth metal concentration of 0.001 wt %. The deoxidation ability curves of the alkaline-earth metals are constructed for a fixed aluminum concentration [Al] = 0.01 wt %.