The cast iron is obtained by remelting pig iron with coke and limestone in a furnace is known as a cupola. It is primarily an alloy of iron and carbon. The carbon content in cast iron radius is from 1.7to 4.5%. It may be present either as free carbon is combined carbon.
Since the cast iron is a brittle material, therefore it cannot be used in those parts which are subjected to shocks. The properties of cast iron that makes it a valuable material for engineering proposed are its low cost, good casting characteristic, high compressive strength, wear-resistance and excellent machinability. The compressive strength of cast iron is much greater than tensile strength.
The car style and also contains a small number of impurities such as silicon, sulphur, MN and phosphorus. The effect of these impurities on cast iron is as follows,…
Cast iron properties
Sulphur:- it makes the cast iron hard and brittle. It must be kept well below 0.1% foremost foundry purpose.
Silicon:- it may be present in cast iron up to 4%. Eat provide that with the formation of free graphite which makes the iron soft and easily machinable.
Manganese:- makes the cast iron white and hard. It is often kept below 0.75%.
Phosphorus:- hit aids fusibility and fluidity in Cast Iron, but induce brittleness. It is really allowed to exceed 1%.
The important types of cast iron are as follows,…..
Grey cast iron:- it is an ordinary commercial iron having 3 to 3.5% carbon. The grey colour is due to the fact that carbon is present in the form of free graphite. It has a low tensile strength, high compressive strength and no ductility. It can be easily machined.
according to Indian standard, grey cast iron is designed by the alphabets FG followed by a figure indicating the minimum tensile strength in MPa or N/mm2. Ford and example FG150 meals grey cast iron with 150 MPa as mean minimum tensile strength.
White cast iron:- it is a particular variety of cast iron on having 1.75 to 2.3% carbon. The white colour is due to the fact that the carbon is in the form of carbide, which is the hardest constituent of iron. White cast iron has a high stencil strength and a low compressive strength.
Chilled cast iron:-. It is a white cast iron produced by quick cooling of molten iron. The quick cooling is generally chilling and the Iron so, produced is known as Child cast iron.
Mottled cast iron:- it is a product in between grey and white cast iron in composition, colour and general properties.
Malleable cast iron:- it is obtained from quiet cast iron by a suitable heat treatment process(i.e. Annealing). According to Indian standard specifications, the malleable cast iron main Bhi Haider white heart, black heart, or pearlitic and are designated by the alphabets WM, BM and PM respectively. This designation is followed by a figure indicating the minimum tensile strength in MPa. For example, WM 350 denotes white heat Malleable cast iron with 350 MPa as minimum tensile strength.
Nodular or spheroidal graphite cast iron:- it is also called it ductile cast iron or high strength cast iron. This type of cast iron is obtained by adding a small amount of magnesium(0.1 to 0.8)% to the grey iron just after tapping. According to Indian standard specification the indicating the minimum tensile strength in MPa and the percentage elongation. For example, SG 400/ 15 means spheroidal graphite cast iron with 400 MPa as minimum tensile strength and 15% elongation.
Alloy cast iron:- it is produced by adding alloying elements like nickel, chromium, Molybdenum, Copper and vanadium in sufficient quantities. The alloy cast iron has special properties like increased strength, higher resistance, corrosion resistance or heat resistance.