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Removal of impurities in steel making
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Transcript of Removal of impurities in steel making
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ARAVIND GOLI
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The removal phosphrous should be done after the removal silicon only
The one most important removal material during the processes of steel making otherwise it forms a iron phosphide its brittle in nature.
In Ellingham diagrame Fe and p are clos to each other.These lines widely can separated by adding storng basic flux i.e LIME
For effctive removal p ,we have to employ “high basicity”.Basicity incresed by adding lime
Soda ash is 100 times superior to lime but in practise we don’t prefer bcoz of its high corrosive action
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Phosphorous oxidation is Highly exothermic reaction
The low temparatures are best suitable for removal phosphorous bcoz at higher temparatures the Reversion of phosporoustakes place.
Dephosphorising index(DP):it’s the ratio of phophorous content in the slag to phophorous content in the metal.
Its higher for high basicity slag and higher for oxidising of slag.
Dp propotional to basicity & Iron oxide(Feo) and inversely propotional to the TEMPARATURE
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De phophosrization done under oxidising conditions only
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If silicon is less den sulphur content high vice versa in pig iron
If less temp in the blast f/c the silicon reduction decresed,it leads to more viscous slag
Cac2,Cao,Na2o…etc,these are elements mix in pig iron to remove the sulphur
The maximum level of sulphur is 0.020%
Sulphur we have to maintain as low as possible 10ppm(0.001%)
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If the temparature of the blast furnace is high,leads to high silicon content in the pig iron since at high temparature silica reduction is incresed
De-siliconized by
Laddle de-siliconizing by oxygen lancingin a transffer laddle
In active mixer by maintaing a suitable basic salg
In acid bessmer proccesse by partial blowing
We can remove the silicon by adding flux
Now a days removal of silicon takes place by “Tarpedo laddle”
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Hot metal is taken in tarpedo laddle,scarpadded to it the reactions takes place during the processes and forms slag its skimmed off….
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