BASIC OPEN HEARTH PROCESS OPERATIONAL CHEMISTRY AND STEP INVOLVED


GENERAL PRINCIPLE :   

It involved melting steel scrape on the hearth of reverbratory type furnace. It has regenerate to preheat air and gaseous fuel. The refining is carried out by the reaction between

2FeO + Si = 2Fe + Si
Take care of slag and the metal will take care of itself about operation. A good slag making is a good steel making heat transformer and voluminous.

Acid open hearth process claim quality having P and S content below 0 to 0.05% because these two elements can't be eliminated in AOH process. Hematite grade pig iron only contain low P and S, which is not available chaply and therefore basic open hearth process was developed to treat plenty available basic  pig iron contain P and S more than 0.05% all place in the world. Bath hot metal and cold metal can be refining in BOH process.

The different charge are
1. All steel scrap
2. Pigs + scrap
3. Hot metal + scrap
4. Pre refining metal + scrap
5. Hot metal + pre refining metal
6. All hot metal.
Here the above three are cold charge and bottom three are hot charge practice.


Cold metal practice.

1-Charging :  First scrape is charge in to the hearth and then time and firing is switch on.Then pig are charge when slag starts melting melting pig should not be charged directly on to a basic hearth.

2-Metal-.   Heating is maximized to bring the charge in melting state ,quickly and form a thin slag ever it to protect ever oxidation .1520-1570 *C is maintained depending upon final carbon composition .Most of the 'Si' ,'Mn' are partially oxidised during metal.{Mp to 1650*C}.

3-Mett out-   Complete state of melting and super heating of metal is known as mett out. After melt out a liquid is not quenchant state , the deoxidation to bring it to quenchant state.
Carbon composition is kept 0.3-0.5% is above the specification .If it is less, fresh pigs are added to the melt which is known as pigging .

4-Rifining-.    Iron oxide is added to the bath to the refining of the melt .Vigouriosly boiling is noticed during addition of Iron oxide in the melt is known as oring. During refining basically or v-ratio is maintained to have Semi killed ,killed or rimmed size, for 'P' removal,
'v'-ratio should be 2.5. for high carbon steel product reaction involved are.

                       Si+2FeO=SiO2+2Fe}melting down
                        Mn+PeO=MnO+Fe} renidd

Exothermic}   C+FeO = CO+Fe -------are boil renidd.
Reaction}.      2P+5PeO = P2O5+5Fe
                        CaCO3 = CaO+CO2
                        CO2+C = 2CO
                        CaO+C = CaS+FeO
                        2P+5FeO+CaO = (CaO.P2O5)+5Fe

5-Blocking-.   After refining ,blocking is confirmed out . Deoxidized like Fe & Si Mn are added to stop the carbon drop and block the heat.The block is allow the quenchant period of 20-30 min and helps for tapping.

6-Deoxidation & Finishing -.   Deoxidation of the mett is carried out in Flc maintain v- ratio 3-5 to 4 to avoid 'p'- reversal . Deoxidation (Cu)  also done after tapping the metal in to the laddle .Alloying addition is done after deoxidation.

7- Tapping-    For tapping the melt tap hole is open with oxyacetylene torch after the metal is tapped is tapped to the laddle,which is carried to the cast house for in casting.


Auxiliaries of Open Hearth Furnace :

The supoort O.H steel making process, some other supporting devices are requires these are.
1- charging M/C.
2- Hot metal crane.
3- Mixer -. 1-Active mixer
                   2- Natural mixer
4- Timming fla form.
5- Tar gun.
6- Mould train.
7-  Striffer.
8-  Internal draughting.
9-  Chimney.
10- Blower.

Mixer-.   Mixer is a liquid metal reservoir of an integrated steel palnt. It is made of a large cylindrical steel shell lined inside with chromilec bricks . Diff B.F tapping liquid metal are mixer in the mixer and a homogeneous solution is maintained on the mixer. It also few hundred tonnes of metal in liquid state for long time. Steel mixer Receives the liquid metal of uniform composition for steel making . The mixer are provided with burning to supply heat to the liquid metal and prevant chilled. In an active mixer metal refining & cararied out by adding time.

Share this

Related Posts

Previous
Next Post »

Contact Form

Name

Email *

Message *