What is different between gray cast iron and white cast iron?

• Gray cast iron is the most commonly used of all cast irons. It is strong and hard, but brittle under tension. Although gray cast iron is black, it's called "gray," because when it fractures, the fracture surfaces look gray. China started making cast iron plows in the3rd century BC -- many centuries before the first cast iron foundry was built in Britain. Gray cast iron is easy to cast -- to pour into a mold -- but it can't be reheated or reworked after casting.

• White cast iron has a light appearance. It has carbon only as a "carbide," which makes white cast irons extremely hard and resistant to abrasion. However, white cast iron is even more brittle than gray cast iron. According to Professor Carl Koch of North Carolina State University's Materials Science Engineering Department, white cast iron is used for rolling machines for paper manufacturing.

Read more: http://www.ehow.com/list_7600169_types-cast-iron.html#ixzz2kEOOz81m

White Cast Iron has less amount of Silicone than Grey cast Iron, knowing that both have the same amount of Iron in their composition.

what is different between gray cast iron