Thursday, May 26, 2011

Seconary steel making 2

There are three properties of slag :
1) Composition
2) Melting point
3) Viscosity

Steel making slags are mostly compared of oxides, fluorides, aluminates & silicates.
Generally CaO, MgO, SiO2, Al2O3, FeO, MnO.

One of other objective for synthetic slag is extending refractory life, so CaF2 is eliminated from the slag making additives. By minimising carryover slag from tapping, we can minimise FeO & MnO.

When CaF2 is added, it crustly & viscous slag, lowers the slag M.P. also weakens the bond.

CaO- Al2O3- SiO2
Hence lower the viscosity.

This is the same mechanism that erode the ladle slag lining. Synthetic slag added with the balance

CaO-Al2O3-SiO2 to achieve a good sulphide capacity, ability to absorve inclusion, lower M.P., lower viscosity & minimal refractory wear.

A premelted synthetic slag having low M.P. for desulphurisation molten steel comprises :

Al2O3 : 44-85%, CaO : 3-35%, MgO : 9-20 %, SiO2 : 0.1-3%, FeO : 0.05-1%

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