What is Cast iron?
Cast iron is a group of carbon alloys that contains 2 to 4% of carbon and varying amount of silica and manganese. It also contains impurities such as, phosphorus and sulphur. It is produced by reducing iron ore in a blast furnace and it primary material is pig iron produced from smelted iron ore in a furnace. This iron is made directly from molten pig iron or by remelting pig iron, often along with substantial quantities of iron, limestone, steel, or coke.
It can be melted on a special type of blast furnace called Cupola but it is more often melted in electric induction furnaces or electric arc furnaces.
In this post am going to dissect on what is cast iron?, its types, and applications
As mentioned earlier, cast iron is produced from pig iron, limestone and coke. It manufacturing process takes place in a cupola furnace by remelting those three materials. The cupola furnace is more or less same as blast furnace. It is cylindrical in shape and has diameter of about 1m and height of about 5m. The materials are poured from the top of the furnace and then heated. At this point impurities of pig iron are removed to some extent by oxidation which forms the molten iron. The slag is then removed from the top of the molten iron at regular interval. The molten iron is then poured into a mold to form required shapes.
Types of cast iron
Grey Iron: this types of cast iron are grayish in appearance, caused by it graphitic microstructure which leads to the fractures of the colour. It has less tensile strength and it’s resistance to than steel and it compressive strength is comparable to low and medium carbon steel. These are based on size and shape of the graphite flakes present in the microstructure in the cast iron.
White Iron: white iron shows white fractioned surfaces because it contains an iron carbide which is called “cementite”. Due to low silicon content and faster cooling rate. Carbon in white cast iron precipitates out and allows it to melt as metastable phase cementite, fe3c, rather than graphite. The cementite which precipates from the melt as relatively large particles. As the iron carbide precipates out, it withdraws carbon from the original melt, moving the mixture toward one that is closer to eutectic, and the remaining phase is the lower iron-carbon austenite (which one cooling might transform to martensite).
Malleable Iron: The malleable iron process begins being white casting which is heated at about 950°c (1,740°f) and then cooled for a day or two the carbon in iron carbide then change to graphite and ferrite plus carbon (austenite). The slow process allows the surface tension to form the graphite into spheroidal particles rather than flakes.
Ductile Iron: this types of cast iron is also known as nodular or ductile iron. It was developed in 1948. Ductile types of cast iron have it graphite in form of very tiny nodulus with the graphite in form of concentric layers forming the nodulus. The properties of ductile these irons is that a spongy steel with the stress concentration effect that flakes of graphite would produce – tiny amounts of 0.02 to 0.1% magnesium, and only 0.02 to 0.4% cerium added to these alloys slow the growth of graphite precipates by bonding to the edges of the graphite planes.
Applications of Cast Iron
Cast iron are used in aspect in engineering world such as, mechanical engineering, construction site, wood workshop etc. The following explained below are applications of cast iron.
1. One of its applications is for ornamental casting such as gates, lamppost, bracket, iron column for small coverage.
2. It is used for compression member
3. Its applications o include production of cisterns, water pipes, gas pipes, sewers, sanitary fittings and manhole cover. and
4. It is used for making rail chains, carriage wheels etc.
And that is it for this article, I hopefully believed you now have knowledge on what is cast iron, its types and applications. If you have any questions don’t hesitate to ask via our comment box and don’t forget to share. Thanks for reading!