Influence of the silicon content on the high temperature oxidation of a spheroidal graphite cast iron. part 1: Preparation of SG cast iron with various SI contents

Author(s): Mamadou Saidou Diallo, Patrice Berthod

Spheroidal graphite (SG) cast irons sometimes solidify too rapidly to be really constituted of only ferrite and graphite at room temperature. In such cases a heat-treatment of graphitization is compulsory, applying it necessarily induces high temperature oxidation for the pieces surfaces. In not alloyed cast irons the single element possibly limiting this deterioration is silicon. In this study it is wished to start establishing qualitative relationship between the silicon content in a given SG cast iron and the amount of deterioration by hot oxidation provoked by a same thermal cycle. In this first part it was tried to re-melt parts of a same SG cast-iron in order to modify its Si content, but by preserving the spheroidal character of graphite. This was here successfully realized by using a high frequency induction furnace under argon atmosphere for a duration short enough to avoid the fading phenomenon. SG cast iron ingots were thus obtained with different contents in silicon, with graphite particles still spheroidal, but with also a global finer microstructure, notably much higher nodules counts and much smaller nodules.

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