What Is Ferrous Metal? Its Types, Uses, Properties, and Constituents

Those metals which contain iron as main constituents are defined as ferrous metals. Like pig iron, cast iron, wrought iron, steel, and their alloy. Pig iron is the principal raw material for all ferrous metals.

• Pig iron:- All iron and steel products are derived originally from pig iron. This is the raw material obtained from the chemical reduction of iron ore in the blast furnace. The process of reduction of iron ore to pig iron is called smelting. The main raw material required to produce pig iron is iron ore, coking coal, and flux. Mostly limestone flux is used. The high amount of carbon in pig iron makes it very hard and brittle and unsuitable for making useful articles. Therefore pig iron is refined and remelted to produce other varieties of iron and steel.
• Wrought iron:- This is the purest form of iron. Wrought iron contains less than 0.1% carbon with about 1-3% finely divided stag uniformly distributed in the metal. Wrought iron is produced by the pudding and Auston process. Wrought iron is a very ductile and malleable metal therefore it is very suitable for wire drawing and making sheets. It offers resistance to corrosion. It finds its maximum use in forged articles. The ultimate strength of wrought iron can be increased by a cold working process which is followed by AGEING. It is usually used in the manufacturing of pipes, shipbuilding, cranes, hooks, agricultural equipment, railways coupling,  etc.
• Cast iron:- Cast iron is a general term applied to a large variety of iron-carbon alloys containing 2-4.5% carbon. It has at least 6 elements I.e., iron, carbon, silicon, manganese,  phosphorus, and sulphur. It melts at 1150°C to 1250°C. It can make a good lasting impression.  It is a brittle material with a BEN of 150 to 225. It can be machined easily to required tolerances.

• Classification of cast iron:- 
• Grey cast iron
• White cast iron
• Malleable cast iron
• Spheroidal grey iron or ductile iron
• Inoculated iron
• Alloy cast iron

• Gray cast iron:- it has following composition:-
• Carbon content- 3-3.75%
• Silicon- 1-2.75%
• Manganese- 0.4-1%
• Phosphorus- 0.15-1%
• Sulphur- 0.02-0.15%
• And rest is iron.

               Because of the presence of graphic carbon, it appears grey hence called grey cast iron. Graphite flakes act as stress raisers thus making grey iron brittle in tension. It is strong in compression.  It has negligible ductility. Although it is machinability,  yet machinability varies with the variation of its micro - constituents. Its machinability can be increased by annealing. Grey cast iron can be welded by electric arc welding and gas welding. It has good castability due to its low shrinkage during solidification. It is used in the production of automobile cylinders, pistons, machine casting,  water pipes, etc.

• White cast iron:- It has the following constituents:-
• Carbon content- 1.75-2.3%
• Silicon- 0.85-1.2%
• Manganese- less than 0.4%
• Phosphorus- less than 0.2%
• Sulphur- less than 0.12%
• and the rest is iron.

               White cast iron contains all its carbon as iron carbide which gives the white appearance to the fracture of this iron. It has good casting properties but has poor weldability.  It is produced by the rapid cooling of grey iron by modifying graphitizing elements like silicone.  The rapid cooling rate is called chilling.

• Malleable cast iron:- Malleable cast iron is produced by annealing of white cast iron. Malleable casting is first made of iron which has all of its carbon in the combined form I.e., from white cast iron. The malleable the castings.
• Inoculated cast iron:- When Inoculated ferromagnetic,  calcium silicide,  nickel shots and ferrosilicon are added to molten white cast iron just before casting, Inoculated iron castings are produced with graphite in a flake form. Inoculation increases strength improves uniform properties in varying sections and makes ironable for high duty castings. It is used in lathe beds, light blanking, air-cooled engine cylinders. 
• Alloy cast iron:- Different alloying elements like nickel, chromium,  molybdenum, etc., are used to produce alloy cast iron to increase the mechanical property of cast iron and enable it for a wide range of applications. Nickel is the prime alloying element in cast iron.