Cast iron is one of the oldest casting techniques in the world. Cast iron is melted and poured into a mold or casting to make part of a product of a certain size and shape. The method of making iron castings is used in many different industries. In the manufacturing process of cast iron, alloying elements determine the type of cast iron. Although both steel and cast iron contain trace amounts of carbon and look similar, there are significant differences between the two metals. The carbon content in the steel is less than 2%, which allows the final product to solidify into a single crystal structure. Cast iron is very suitable for casting due to its high carbon content and the presence of silicon.

Types of cast iron
Cast iron can be divided into several categories, such as gray, ductile iron, white, malleable iron, compacted graphite, etc. Let's take a closer look at each type.

white iron castings
Carbon atoms combine with iron to form iron carbide with a suitable carbon content and a fast cooling rate. This means that the cured material contains only a small amount of free graphite molecules. Due to the absence of graphite, when the white iron is sheared, the cross-section appears white. The cementite microcrystalline structure is hard and brittle, with high compressive strength and good wear resistance. In some special applications, it is necessary to use white iron on the surface of the product. This can be achieved by using a good thermal conductor to make part of the mould. This will quickly extract heat from the molten metal in that particular area, while the rest of the cast iron will cool at a slower rate. One of the most popular white iron grades is Nickel Hard Iron.

advantage:
● High compressive strength
● Difficult to process
● Good hardness
● wear-resistant

Grey cast iron castings
The composition of gray cast iron differs from similar products because it resembles small flakes. When this metal fractures, the fracture occurs with the graphite flakes, which give it a greyish color on the surface of the fractured metal. The name grey iron is derived from this characteristic.
By adjusting the cooling rate and composition, the size and matrix structure of the flakes can be controlled during production. Gray cast iron has lower tensile strength than other cast irons and lower ductility. On the plus side, it's a better heat conductor and has a higher level of vibration damping. Its damping capacity is 20-25 times that of steel and better than all other cast irons. Grey cast iron is also easier to machine than other cast irons, and its wear resistance makes it one of the highest cast iron products.
Inexpensive:
● Good machinability
● Good scratch and abrasion resistance
● High compressive strength

Ductile Iron
Ductile iron or ductile iron gets its special properties by adding magnesium to the alloy. The presence of magnesium causes graphite to form ellipsoids compared to grey cast iron. Ingredient control is very important in the manufacturing process. If impurities react with magnesium, the shape of the graphite molecules can be affected. Different grades of ductile iron are formed by manipulating the crystallite structure. This is achieved by casting or heat treatment.
advantage:
● very high ductility and strength

Compacted graphite cast iron
Compacted graphitic iron has a graphitic structure and related properties and is a mixture of grey iron and white iron. The microcrystalline structure is formed around interconnected passive graphite sheets. Alloys such as titanium are used to suppress the formation of spherical graphite. It has higher tensile strength and higher ductility than grey cast iron. The crystallite structure and properties can be tuned by heat treatment or by adding other alloys.
advantage:
● High tensile strength
● Good extension performance

malleable cast iron
White iron can be further processed into malleable cast iron through a heat treatment process. Prolonged heating and cooling procedures will cause the iron carbide molecules to break down, releasing free graphite molecules into the iron. Different cooling rates and alloy additions will produce malleable cast iron with a microcrystalline structure.
Features:
● High ductility
● Tougher than grey cast iron
● Twist and bend without breaking
● Excellent processing ability
 
The main advantages of cast iron
● Good casting properties
● Good machinability
● low cost
● Stronger compressive strength compared to steel
● Excellent anti-vibration performance
● good sensitivity
● Excellent wear resistance
● Constant mechanical properties between 20 and 350 degrees Celsius
● Low stress concentration
● Durability and resistance to deformation