Thermodynamic Analysis of the Graphite Flake Formation of Low Manganese and Sulfur Gray Cast Iron

Low manganese and sulfur gray irons were produced by adding inoculant base Fe-Si with small amounts of Al and Ca in the ladle. The effect of the cast thickness, inoculant amount and shakeout time of the green sand molds were studied on the graphite flake formation by microscopically techniques. A thermodynamic analysis was carried out for the cast iron produced with the FactSage 7.2 software. Stability phase diagrams were obtained for both gray cast irons to different manganese (0.1 to 0.9 wt.%) and sulfur (0.01 to 0.12 wt.%) amounts to 1150°C. It was shown that lower amounts of manganese and sulfur allow forming the 3Al2O3·2SiO2, Al2O3, and ZrO2 solid compounds. The thermodynamic results match with those obtained by SEM-EDS. It is possible to form MnS particles in the liquid phase when the solubility product (%Mn) × (%S) equals 0.042 and 0.039 for heats A and B, respectively.