White cast Iron contains carbon exclusively in the form of cementite (Iron Carbide). This is obtained by the presence of relatively large quantities of manganese , a very small amount of silicon, and by rapid cooling. The ordinary rate of cooling in sand produces free graphite while rapid cooling helps to produce cementite. More over, manganese encourages the formation of carbide.
The white cast iron is very hard (the hardness ranges from 400 to 600 BHN) and brittle, and its fractured surface has a silvery metallic appearance. From the engineering point of view, white cast iron has limited application. This is due to its un machinability and to its having , in general , relatively poor mechanical properties. It is widely used in the manufacture of wrought Iron. White cast Iron is also cast as the intermediate material for making malleable cast iron.
White cast iron does not rust so much as the grey kind.
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