What is ferrous metals and their constituents

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

  • Pig iron:- All iron and steel products are derived originally fro pig iron. This is the raw material obtained from the 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 are iron iron ore, coking coal and flux. Mostly limestone flux is used. 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 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 it's maximum use in forged articles. Ultimate strength of wrought iron can be increased by cold working process which is followed by AGEING. It is usually used in manufacturing of pipes, ship building, cranes, hooks, agricultural equipments, 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 atleast 6 elements I.e., iron, carbon, silicon, manganese,  phosphorus and sulphur. It melts at 1150°C to 1250°C. It has the ability to take good casting 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:- 
  • Gray cast iron
  • White cast iron
  • Malleable cast iron
  • Spheroidal gray 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 presence of graphic carbon, it appears gray hence called gray cast iron. Graphite flakes act as stress raisers thus making gray iron brittle in tension. It is strong in compression.  It has negligible ductility. Although it is machinability,  yet machinability varies with variation of its micro - constituents. It's machinability can be increased by annealing. Gray 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 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 rest is iron.
               White cast iron contains all its carbon as iron carbide which gives white appearance to the fracture of this iron. It has good casting properties but has poor weldability.  It is produced by rapid cooling of gray iron by modifying graphitezing element like silicone.  Rapid cooling rate is called chilling.

  • Malleable cast iron:- Malleable cast iron is produced by annealing of white cast iron. Malleable casting are first made of an iron which has all of its carbon in the combined form I.e., from white cast iron. The malleabilize the castings.
  • Inoculated cast iron:- When Inoculated like ferromagnetic,  calcium silicide,  nickel shots and ferro-silicon are added to molten white cast iron just before casting, Inoculated iron castings are produced with graphite in flake form. Inoculation increases strength improves uniform properties in varying sections and makes iron able for high duty castings. It is used in lathe beds, light blanking, air cooled engine cylinder. 
  • Alloy cast iron:- Different alloying elements like nickel, chromium,  molybdenum, etc., are used to produce alloy cast iron to increase mechanical property of cast iron and enable it for a wide range of application. Nickel is the prime alloying elements in cast iron.
What is ferrous metals and their constituents What is ferrous metals and their constituents Reviewed by Wikihub on March 18, 2019 Rating: 5

No comments:

Powered by Blogger.