Bessemer Converter and Electric Arc Furnace-Methods for Manufacturing of Steel:There are two methods for the manufacturing of steel which are as follows.
2.Electric Arc Furnace
The detailed explanation of Bessemer Converter and Electric Arc Furnace was presented below.
- It was the first industrial process which is inexpensive,used for the mass production of steel from molten pig iron.
- The principle of Bessemer Converter is the removal of impurities from the iron by oxidation and the air is being blown through the molten iron.
- A Bessemer converter is a Pear shaped furnace which is about 20 feet tall and 10 feet dia.
- It is made of steel with fire clay bricks to resist heat.
- There were tuyeres(Air holes) at base and this allows entry of air into the furnace.
- The converter can be rotated horizontally on its axis to enable the entry of molten pig iron(raw material)
- A blast of hot air is to be passed into the converter through the tuyeres.
- The air oxidises the impurities present in the pig iron.
- The impurities manganese(mn) and Silicon(Si) are converted into their respective oxides and that can be expelled out.
Si + O2→ SiO2
2mn + O2→ 2mno
Carbon is oxidised to carbon monoxide which burns with the blue flame at the mouth of the converter.
When all the Carbon monoxide burns out, the blue flame dies out.
The oxides of ‘mn’ and ‘Si’ are react with each other to form a slag.
mno + Sio2→ mnSio3
Here ‘mnSio3’ is a slag .
The slag will be taken out from the converter by tilting it and the rest available is the purest form of steel.
In this way, by the use of Bessemer converter, we can get purest form of steel.
2.Electric Arc Furnace Method:
It is an extremely hot enclosed region, where heat is produced by means of electrodes for melting certain materials such as steel(scrap) without changing the electro-chemical properties of the material(metal).
The electric arc produced between the electrodes and the metal is used for melting the metal(scrap).
Types of Furnace:
- AC electric Arc Furnace
- DC electric Arc Furnace
Here, the AC electric Arc Furnace is used.
1.AC Electric Arc Furnace:
Construction of Electric Arc Furnace:
- The main parts of electric furnace are the roof, hearth (lower part of a furnace, where molten metal is collected), electrodes, and side walls.
- The roof consists of three holes through which the electrodes are inserted. The hearth includes metal and slag.
- The tilting mechanism is used to pour the slag from container before the pure form of iron is to be taken out.
- In AC electric furnace, electrodes are three in number and are in circular cross-section. Graphite is used as electrodes because of its high electrical conductivity.
- The electrodes positioning system helps to raise and lower the electrodes automatically. The electrodes get highly oxidized when the current density is high.
Working of Electric Arc Furnace:
When the power supply is given to the cathode and anode, the ions starts transferring from cathode to anode & anode to cathode simultaneously and due to this, heat is generated which can melts the Pig iron and scrap.
The spark is generated at the electrode due to the collision of ions when transferring between cathode and anode respectively. The spark generated is used to melt the metal quickly.
After the arc is shielded by electrodes, the voltage is increased for speeding up the melting process.
During melting, the impurities present in the molten pool deposits on the surface as a slag. Other impurities will be escaped out from the container. In this process, carbon, silicon, and manganese get oxidized and the reactions are as follows.
Si + O2→ SiO2
2mn + O2→ 2mno
The oxides of Manganese(mn) and Silicon(Si) are react with each other to form a slag and Carbon is reacted with oxygen to form Carbon monoxide(CO).The CO burns in the container itself.
Here mnSiO3 is a slag.
The slag formed is removed from the container by tilting it one side down and the rest of the material is the purest form of steel which is to be taken out from the container.
Thus by the use of Electric Arc Furnace, we can get the purest form of steel.