The Constructor

Cast Iron as a Building Material- Manufacturing, Types, Properties and Applications

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What is Cast Iron?

Cast iron is obtained from the pig-iron which is re-melted with coke and limestone. Pig iron is nothing but impure iron which is obtained from the iron ore. Cast iron has lot of engineering properties so, that it can be used in many ways like for sanitary fittings, rail chairs, casting molds etc.

Manufacturing of Cast Iron

Cast iron in manufactured from re-melting process as mentioned above. This process takes place in a furnace called couple furnace. The furnace is 5 meters in height and cylindrical in shape with 1 m diameter. The raw materials pig iron, coke and lime stone are entered from the charging door of chamber which provided at the top. Air blast is introduced into the chamber using air blast inlet which removes the impurities present in the pig iron. Hence, pure cast iron is obtained from the bottom out let and it is poured into molds of required shape. These molds are called as cast iron castings.

Types of Cast Iron used as a Building Material in Construction Works

Following are the types of cast iron used as a building material in construction and their uses:

Grey Cast Iron

As the name suggests, it is grey in color. It has coarse crystalline structure. Its melting point is very low thus it has weak strength and it is only used for casting purposes.

Malleable Cast Iron

Malleability is the property which helps the materials to undergo any shape without breaking or cracking. Hence, malleable cast iron is used for making many types of materials. It has good corrosive resistance. Its manufacturing process involves two steps. In the first step, it is casted and cooled as ordinary cast iron and then again it is heated to 1050oC and soaked in water for long period (several hours or days). Hence, carbon content is slightly reduced and graphite content is precipitated as temper carbon. This reduce the brittleness of cast iron. So, it can be worked easily using machines. It is used for making pipe fittings, fastenings, automobiles etc.

Mottled Cast Iron

Mottled iron is the medium stage cast iron which properties are in between grey cast iron and white cast iron. It has Small amount of graphite in its composition. So, mottled type fractures are developed in its micro structure.

Toughened Cast Iron

Toughened cast iron is the combination of cast iron and wrought iron. To obtain this wrought iron scrap and cast iron melted together. The composition of wrought iron is about 0.15 to 0.25 weight of the cast iron.

White Cast Iron

It is in silver color. Its melting point is high so, strength wise it is better but not used for delicate casting purposes. Because of its heavy strength, it cannot be used easily.

Ductile Cast Iron

Ductile cast iron is also called as spheroidal graphite iron. Its manufacturing process is very easy compared to other types. Its manufacturing process consists manganese treatment which helps to increase the carbon content and opposes the formation of graphite in flaky form. It has very good engineering properties than malleable cast iron. Ductile cast iron has very good corrosion resistance, high strength and durability. So, usage of ductile iron dominates the other types. It is used for making sewer pipes, water conveying pipes etc.

Chilled Cast Iron

Chilled cast iron consists two layers of which one layer has white cast iron properties and other one has grey cast iron properties. This type of iron is used for casting process in which grey cast iron layer is provided in inner surface and white cast iron layer is provided as outer surface. Hence the casting molds serve longer. Machine parts are also made using chilled cast iron.

Composition of Different Types of Cast Iron

Different types of cast iron are composed of different quantities of constituents shown in table below:

Properties of Cast Iron as a Building Material

The properties of cast iron are as follows

Uses of Cast Iron in Building Construction

Cast iron can be used for making different tools, materials etc. as described below. Read More in Building Materials
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