A R C H I V E S of F O U N D R Y E N G I N E E R I N G On modelling of the effect of oxygen on graphite morphology and properties of modified cast irons

Abstract Oxygen in graphitic cast irons substantially influences crystallization. The paper deals with results of experimental works concerning the influence of oxygen activities (a o ) and total oxygen content O OX in cast irons, treated (modified) with master alloys NiMg and FeSiMg, on structural and mechanical properties of modified cast iron. The results show that in castings treated by Mg with subsequent inoculation FeSi strong reduction of total oxygen content in cast iron is observed. It corresponds to increasing residual content of Mg in castings and to the increase of tensile strength. The graphite morphology is connected with oxygen activity and total oxygen content in cast iron too. This decrease changes the morphology of graphite from flake to vermicular and spheroidal morphology. Increase of ultimate tensile strength of modified cast irons in consequence of greater amount of added Mg and consequently higher values of Mg res. too were observed what correlates with decreasing oxygen content in cast iron. This trend expressed by linear dependencies is valid for all melts