Graphite nodularization and graphitization of magnesium treated cast irons solidified under argon atmosphere pressure up to 145 atm

Abstract

Argon atmosphere pressure had no effect on the nodularization of graphite in magnesium treated cast iron, while it had considerable influence on the graphitization and graphite nodule number. With increasing argon atmosphere pressure up to 145 atm, the graphitization was retarded and the graphite nodule number reduced. The degree of nodularization became maximum at a magnesium content of about 0.15 mass-% and thereafter decreased as the magnesium content increased. For values >0.15 mass-%Mg, meshlike and flaky graphite was formed in the region adjacent to tiny particles which proved to be magnesium droplets. The effect of magnesium on the graphitization was opposite to that on the nodularization of graphite, i.e. the graphitization was suppressed with increasing magnesium content up to about 0.15 mass-% and was promoted when the magnesium content exceeded 0.15 mass-%.