Components of gray cast iron

Gray cast iron has a high carbon content (2.7%~4.0%) and can be regarded as the matrix of carbon steel with flake graphite. Grey cast iron can be divided into three categories based on the different matrix structures: ferritic matrix grey cast iron; Pearlite ferrite matrix gray cast iron; Pearlite matrix gray cast iron.

Ferritic gray cast iron is characterized by numerous and coarse graphite flakes distributed on the ferrite matrix, which have poor strength and hardness and are rarely used;

Pearlite gray cast iron is a type of iron with uniform and fine graphite flakes distributed on a pearlite matrix. It has relatively high strength and hardness and is commonly used in the manufacture of important components such as bed frames and machine bodies;

Pearlite ferrite gray cast iron is a type of gray cast iron with coarse graphite flakes distributed on a mixed matrix of pearlite and ferrite. Although its strength and hardness are lower than the former, it can still meet the requirements of general machine bodies. It has good castability, shock absorption, and is easy to melt, making it the most widely used gray cast iron.

The difference in microstructure of gray cast iron is essentially due to the different forms of carbon present in cast iron. The carbon in gray cast iron is composed of compound carbon (Fe3C) and graphite carbon. When the combined carbon is 0.8%, it belongs to pearlite gray cast iron; When the combined carbon is less than 0.8%, it belongs to pearlite ferrite gray cast iron; When all carbon exists in graphite state, it is ferritic gray cast iron.