Cast Iron

Cast irons are iron-carbon alloys generally containing 1,7-6,7% carbon, 1-3% silicon, and small amounts of elements like manganese, phosphorous and Sulphur. These alloys are inexpensive, durable and easy to cast. Depending on their chemical composition and cooling rates, cast irons can be classified into two main groups, namely white cast irons and grey cast irons, according to their fracture characteristics.

White cast iron is obtained by rapid or non-equilibrium cooling during casting. It has slightly lower levels of carbon and silicon than grey cast irons. White cast iron is characterized by a hard microstructure composed of pearlite and cementite (iron carbide). In fact, it is the presence of cementite, an iron carbide (FE3C), that makes the alloy very hard but also fairly brittle. For these reason, white cast iron is particularly intended for wear applications and it is not considered as weldable for its nil ductility.

However, white cast iron can undergo a high temperature annealing, called malleabilization, within a temperature range of 800-860°C (1475-1580°F) for 30 to 40 hours. This treatment transforms the hard white cast iron to a malleable iron with higher ductility. This aims to remedy its fragile structure by breaking down the iron carbides, while instead precipitating graphite nodules (temper graphite) in the matrix. 

Grey cast irons are elaborated from chemical compositions with higher levels of carbon (2,5-4%) and silicon (1-3,0%), using an equilibrium cooling mode. They are called grey cast irons because of their grey fracture surface, caused by almost all of the carbon content crystallizing into graphite.

Contact our metallurgists, to get the right alloy for your welding project.

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