Inoculated Cast Iron

cast iron into which inoculants are introduced under specific conditions in the liquid state.

Inoculants with a modifying effect (ferrosilicon, calcium-silicon, carbon, aluminum, and alloys of titanium, zirconium, some lanthanides, barium, and strontium) make possible a reduction in the silicon and carbon content of cast iron without chilling and lead to the disintegration of graphite, thus increasing the quantity of pearlite and improving the mechanical properties of gray cast iron.

The introduction of tin, lead, phosphorus, antimony, and nitrogen inoculants facilitates the formation of pearlite gray cast iron. The introduction of bismuth and an increase in the content of sulfur lead to intense chilling. In malleable iron, a number of inoculants bind harmful impurities, such as nitrogen (as A1N and BN) and chromium (as Sb₂Cr₃ atomic segregations). Some inoculants (magnesium, most lanthanides, and yttrium) in specific proportions lead to the separation of spheroidal graphite, which results in the formation of high-strength spheroidal graphite cast iron. This type of inoculation significantly increases the strength of cast iron and sharply increases its malleability and ductility.

Inoculation is usually done in furnace runners, autoclaves, or special hermetic ladles; by injection; by introduction of the inoculants through hardeners or salts; or in the gating of ingot molds.