.cast iron

.types of cast iron

.cast iron types

There are primarily 4 different types of cast iron. Different processing techniques can be used to produce the desired type, which include:

• Grey Cast Iron
• White Cast Iron
• Ductile Cast Iron
• Malleable Cast Iron

Cast Iron is an iron-carbon alloy that typically contains greater than 2% carbon. The iron and carbon are mixed in the desired quantities and smelted together before being cast into a mold.

Grey Cast Iron

Grey Cast iron has a graphite microstructure made up of many small fractures. It is called “grey iron” because the presence of these small cracks creates the appearance of a gray color.

Grey Cast Iron is not as ductile as other cast irons, however high wear resistance, high thermal conductivity, and the excellent damping capacity of Grey Cast Iron makes it ideal for engine blocks, fly wheels, manifolds, and liner.

White Cast Iron

The difference is that white cast iron has features cementite below its surface, while gray cast iron has graphite below its surface. The graphite produces a gray color appearance while the cementite produces a white color appearance. White Cast Iron is used primarily for its wear resistant properties in pump housings, mill linings and rods, crushers and brake shoes.

White cast iron is formed when the carbon in solution is not able to form graphite on solidification. It is a combination of pearlite and cementite cast iron. White cast irons are hard and brittle; they cannot easily be machined.  It is used in drill, taps, dies, files saw blades etc. They are unique in that they are the only member of the cast iron family in which carbon is present only as a carbide.

Ductile Cast Iron

Ductile Cast Iron is produced by adding a small amount of magnesium, approximately 0.2%, which makes the graphite form spherical inclusions that give a more ductile cast iron. It can also withstand thermal cycling better than other cast iron products. Ductile Cast Iron is predominantly used for its relative ductility and can be found extensively in water and sewerage infrastructure. The thermal cycling resistance also makes it a popular choice for crankshafts, gears, heavy duty suspensions and brakes.

Malleable Cast Iron

Malleable Cast Iron is a type of cast iron that is manufactured by heat treating White Cast Iron to break down the iron carbide back into free graphite. This produces a malleable and ductile product that has good fracture toughness at low temperatures. Malleable Cast Iron is used for electrical fittings, mining equipment and machine parts.