the forms of graphite and cast iron types

Graphite is one of the simple forms of carbon, with very low strength, hardness and plasticity. Graphitization refers to the process in which carbon atoms precipitate and form graphite in cast iron. According to the classification of graphite, it can be divided into gray cast iron, malleable cast iron, ductile cast iron, and vermicular graphite cast iron.

Among them, the graphite of gray cast iron is flaky. Gray cast iron has good casting performance and cutting performance, high wear resistance, shock absorption and low notch sensitivity, and it is cheap, so it is widely used. Gray cast iron accounts for more than 80% of total cast iron output. It is often used to make some machine bed, box, frame, machine tool guide rail and cylinder that bear heavy load, complex shape or high precision.



Malleable cast iron is actually not forgeable. Its graphite is in the form of flocculents. High strength, great plasticity and toughness can be obtained by graphitizing annealing, and low temperature toughness is good. The molten iron is relatively simple to handle, stable in quality, and easy to organize flow production. Therefore, it is widely used in automobile, tractor manufacturing and other industries to manufacture small and medium-sized parts such as machine tool wrenches, automobile wheels, crankshafts, connecting rods, gears, etc., with complex shapes and thin walls that can withstand impact loads.

The graphite of nodular cast iron is spherical, it has good mechanical properties and process properties, and can be heat treated (annealing to eliminate internal stress, normalizing to improve strength and wear resistance, and quenching and tempering to obtain good comprehensive mechanical properties). Therefore, it can be substituted Carbon cast steel and malleable cast iron are used to manufacture some parts with complex forces, high strength, hardness, toughness and wear resistance.

The graphite of vermicular graphite cast iron is vermicular; there is a transition form graphite between flake and spherical graphite. It has the properties of nodular cast iron and gray cast iron, and can be used to make steel ingot molds, automobile engines, exhaust pipes, glass molds, diesel engine cylinder heads, brake parts, etc. Nodulizers such as Rare Earth Ferro Silicon Magnesium Alloy, Rare Earth Ferrosilicon, Rare-Earth Calcium Silicon containing rare earth elements are often added to the production of vermicular graphite cast iron in China. This makes the casting products obtain better performance.