The Orthosilicate‐Iron Oxide Portion of the System CaO‐“FeO”‐SiO 2

The phase equilibrium diagram has been determined for the liquidus surface of the portion of the system CaO‐“FeO”‐SiO 2 between fayalite, dicalcium silicate, wüstite, and lime. Five ternary peritectic points have been located, but no true eutectics have been found. The primary fields of wuUstite and dicalcium silicate cover most of the area studied (ignoring free iron, which is actually the primary phase in all compositions investigated). The boundaries of smaller fields of olivine solid solution, a parallel‐twinned modification of dicalcium silicate, tri‐calcium silicate, lime, and calciowüstite solid solutions also are delineated. X‐ray data show that lime may contain up to 10%“FeO” in solid solution, whereas wüstite may contain as much as 28% CaO in solid solution. Equilibria involving tricalcium silicate explain earlier observations on open‐hearth slags and furnace‐bottom refractories.