Cast Iron

Cast iron

"Cast iron" is an iron that contains a large amount of carbon (2,1%˜6,7%). Iron containing large amounts of carbon melts at approximately 1400°C and can be poured into moulds and formed with comparative ease.

In case of steel, that has a relatively low carbon content, all of the carbon is dissolves into the iron.

However, due to the high carbon content. the excess carbon precipitates as graphite, Cast iron has high wear resistance as the graphite formed in the cast iron composition works as a lubricant. However, the graphite formed divides the structure of the iron and as such makes the material" brittle".

Gray cast iron, Ductile cast iron

Gray cast iron is another term for normal cast iron. It is named gray cast iron due to the large carbon content that appears as graphite. When looking at the surface of the material it has a gray colouring to it. As previously mentioned cast irons can be cast with relative ease, cast irons also has another property of being able to absorb vibrations and as such it is often used in applications such as machine beds and machine parts.

However, cast iron sometimes does not have enough tensile strength and toughness. There are certain types of cast irons that do have high tensile strength. These are general termed as ductile cast irons. They are also known as "spherodial graphite cast irons" and "nodular cast irons."

In the composition of gray cast iron the graphite is in a linear formation. However for the ductile cast irons the graphite tends to be in a spherodial formation. The spherodial formationof the graphite improves the toughness and reduces problems relating to brittleness.

Gray cast iron can be cast into thin walled components offering comparatively lightweight parts. Therefore gray cast iron is often used for manufacturing of pipes. Ductile cast iron however with it's high tensile strength is more suited for machine parts that going to be exposed to high forces, such as hydraulic cylinder parts and press moulds. The demand for the use of ductile cast irons is expected to increase in the future.