Cast irons

Dr. Dmitri Kopeliovich

Cast irons – iron alloys containing between 2.06 to 4.3% of carbon.

Cast irons are divided onto the following groups:

Chemical compositions of some cast irons
Properties of some cast irons

White cast irons

White cast irons – hard and brittle highly wear resistant cast irons consisting of pearlite and cementite.

White cast irons are produced by chilling some surfaces of the cast mold. Chilling prevents formation of Graphite during solidification of the cast iron.

Applications of white cast irons: brake shoes, shot blasting nozzles, mill liners, crushers, pump impellers and other abrasion resistant parts.

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Grey cast irons

Grey cast irons – cast irons, produced at slow cooling and consisting of ferrite and dispersed graphite flakes.

Grey cast irons possess high compressing strength, fatigue resistance and wear resistance. Presence of graphite in grey cast irons impart them very good vibration dumping capacity.

Applications of grey cast irons: gears, flywheels, water pipes, engine cylinders, brake discs, gears.

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Malleable cast iron

Malleable cast iron – cast irons produced by heat treatment of white cast irons and consisting of ferrite and particles of free graphite.

Malleable cast irons have good ductility and machinability. Ferritic malleable cast irons are more ductile and less strong and hard, than pearlitic malleable cast irons.

Applications of malleable cast irons: parts of power train of vehicles, bearing caps, steering gear housings, agricultural equipment, railroad equipment.

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Nodular (ductile) cast irons – grey cast iron, in which graphite particles are modified by magnesium added to the melt before casting. Nodular cast iron consists of spheroid nodular graphite particles in ferrite or pearlite matrix.

Ductile cast irons possess high ductility, good fatigue strength, wear resistance, shock resistance and high modulus of elasticity.

Applications of nodular (ductile) cast irons: automotive engine crankshafts, heavy duty gears, military and railroad vehicles.

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Chemical compositions of some cast irons

Grade	C,%	Si,%	Mn,%	S,%	P,%
White	1.8…3.6	0.5…1.9	0.25…0.8	0.06…0.2	0.06…0.18
Grey	2.5…4.0	1.0…3.0	0.25…1.0	0.02…0.25	0.05…1.0
ASTM A220	2.0…2.6	0.9…1.6	0.2…1.25	0.04…0.18	0.18 max.
A356	3.0…4.0	1.8…2.8	0.1…1.0	0.03 max.	0.1 max.

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Properties of some cast irons

(Materials Data)

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