The correct answer is A. Cementation process.
The cementation process is a method of manufacturing steel by decarbonising pig iron completely and then adding proper percentage of carbon. The process involves heating pig iron in a furnace with charcoal, which causes the carbon in the charcoal to diffuse into the pig iron. The amount of carbon that diffuses into the pig iron can be controlled by the temperature and duration of the heating process.
The cementation process was developed in the 17th century and was the main method of manufacturing steel until the Bessemer process was developed in the 19th century. The cementation process is still used today, but it is not as common as it once was.
The other options are incorrect because they are not methods of manufacturing steel by decarbonising pig iron completely and then adding proper percentage of carbon.
- The crucible process is a method of manufacturing steel by melting pig iron in a crucible and then adding carbon to it.
- The Bessemer process is a method of manufacturing steel by blowing air through molten pig iron, which causes the carbon in the pig iron to be oxidized and removed.
- The open hearth process is a method of manufacturing steel by heating pig iron in a furnace with air and limestone, which causes the carbon in the pig iron to be oxidized and removed.