TYPES OF STEEL MAKING


COMMERCIAL STEEL MAKING PROCESS


Due to high demand in domestic, commercial and industrial sector it is essential to produce steel in large scale. The large scale commercial steel making process have been developed time to time in the past. The major commercial process are 

LD Converter
Basic oxygen furnace
1. Bessemer Process
2. Open hearth Process 
3. Electrical Arc Process 
4. L.D Converter Process
5. Kaldo Process
6. Rotor Process

The top above three process have called Conventional process and bottom three called Oxygen process.

BESSEMER PROCESS / THOMAS PROCESS :


In Bessemer process air is used for refining the liquid pig iron.The process of refining is carried out in a speared shape converter lined in side with refractory brick with perforated bottom.
                   
                     Cold air or oxygen enriched blast is forced through the metal from below during passage of oxygen in to the converter then oxygen react with the impurities present in the liquid metal and refining is carried out.
                      Refining is completed in about 15-20 mins. Tap to tap time is 30-35 mins are required.
This is a autogeneous process has no external heat is needed. The head required for this process is generated with in the metallic bath by exothermic reaction of impurities like carbon,silicon,phosphorous.

Chemistry of bessemer process 

Bessemer furnace
Bessemer furnace
During the first stage of the operation "Si"and "Mn" 
are oxidise.
2Fe+O2 = 2FeO
2FeO+Si = 2Fe+SiO2
FeO+Mn = Fe+MnO
The Sio2, MnO and some FeO combine from the slag.
FeO+SiO2 = FeO.SiO2
MnO+SiO2 = MnO.SiO2
After most of the "Mn" and "Si"are goes the carbon
beging to burn.
FeO+C = Fe+C
FeO+Fe3C = 4Fe+CO. 


OPEN HEARTH PROCESS :

Open hearth furnace
Open hearth furnace

The furnace in this process is fairly shallow basic lined vessel and hence the name. It is heated by either liquid and or gaseous fuel using the heat generation principle. So as to attend steel making temperature of about 1600 to 1700*C. 

In this process the charge is mixture of scrap and liquid pig iron. The scrap is initially heated to near its softening point and molten pig iron from the blast furnace is poured on to it. The metal charge is heated by conduction and radiation process. During this passage of the flame and tap
ta tap time iks 6-10 hrs.  

This two process are very old process and taking more time so that now a days this process are 
discontinue and modern L.D and Electric arc process are in operate in all steel plants. 


ELECTRIC ARC FURNACE PROCESS :



Electric furnace
Electric arc furnace
In tis process current is utilized to
generate required heat for refining of pig iron. Three electrode type arc
furnace are employed for this
purpose. Cold charge are used for melting. Someting a part of hot metal is include in this process of charging. There is form between the electrode and cold charge provides required heat for the process. Both oxidizing and reducing atmosphere can be maintain in electric arc process. During refining iron ores are uesd as refining agents. The process cycle is logner like open hearth process. Mostly stainless steels are manufacture by this process.

KALDO  PROCESS :


It construction is quite similar to L.D Converter
It kept inclined to horizontal at an angle of about 20 degree and rotate around its own axis at about 30rpm speed.
The oxygen Lance is also inclined to the horizontal and the angle is adjustable.
It's refine time is longer than L.D and tap to tap time is 60 - 70 mins.

Advantages                     Disadvantages

KALDO furnace
Kaldo furnace
1. It produces low.         1. Low productivity
phosphorus steel.

2. It is suitable for all.   2. Higher maintainace
Grade steel making.       Cost because of
                                       rotating components.
3. Nitrogen problem .
 Can be reduce               3. High consumption
                                      Of refractory.
4. Impurities are get
Get easily remove.


ROTOR PROCESS :


ROTOR furnaceIn this process a long durm like furnace is used for liquid metal refining. The hearth of the furnace is shallower like open hearth f/c. After charging the liquid metal two lance are inserted in the furnace. The primary lance deep in to the metal bath and secondary one kept just above the bath surface. Oxygen is pass at a higher pressure in primary lance and low pressure in secondary lance. The furnace is rotate during the lunching for better gas metal and slag contact. The refining is efficient in this process and tap to tap time is 1.5 - 2 hrs.

                                                                                                   

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