GRAPHITE STRUCTURES IN CAST IRONS: GRAPHITE FORMS

GRAPHITE FORMS

Diagrammatic representations of the standard graphite forms in cast irons.

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 Table1: Graphite forms

Form	Description of the form	Main spatial characteristics	Occurrence
I	Lamellar (flake) graphite	Interconnected particles within eutectic cells; lamellar (flake) graphite with sharp ends	·  Principal form in grey cast iron ·  Austenitic cast iron with lamellar/flake graphite ·  Can occur in the rim zone of other cast-iron materials
II	Crab graphite	Aggregate of graphite flakes	·  Can occur in rapidly cooled hypereutectic grey cast irons ·  Can also occur in segregation areas of thick-walled spheroidal-graphite cast-iron castings
III	Compacted (vermicular) Graphite	Usually interconnected particles within eutectic cells; worm-like appearance with rounded ends	·  Principal form in compacted-graphite cast irons ·  Can occur in spheroidal graphite cast irons
IV	Temper carbon Irregular spheroidal graphite*	Isolated particles	Principal form in malleable cast irons
			Can occur on spheroidal-graphite cast iron
V	Slightly irregular spheroidal Graphite	Isolated particles	·  Principal form in thick-walled castings made of spheroidal graphite cast irons ·  Occurs to a specified extent in compacted-graphite cast irons ·  Can occur in malleable cast irons
VI	Spheroidal graphite*	Isolated particles	·  Principal form in castings made of spheroidal-graphite cast irons ·  Occurs to a specified extent in compacted-graphite cast irons

Note: *Spheroidal graphite is sometimes referred to as nodular graphite