Deoxidation practice

Deoxidation can be carried out during tapping, in ladles runners and even in moulds. Bath stirring is important. During tapping, bath is stirred due to potential energy but this subsides towards the end. When deoxidation is carried out in ladle, it is called ladle deoxidation in industrial practice. Depending on the extent of deoxidation, killed, semi killed and rimming steels are produced. For carbon content less than 0.15% and enough oxygen in steel, rimming steel can be produced.

Alloy steels are fully killed to obtain maximum recovery of alloying additions.

Illustration

Let us take an example of deoxidation of steel with ferromanganese. Manganese is a weak deoxidizer. We intend to reduce the dissolved oxygen in steel from 0.045 wt.% to 0.018 wt.%. How much manganese would be required?

Consider the reaction
(MnO)  = [Mn]  + [O];   

We can write , we have assumed h_Mn= W_Mn and h_o = W_o, where W_o  is weight percent

Substituting the value of K_Mn = 0.0413 1t 1600  and W_o = 0.018 we get



For the deoxidation with manganese, the following reaction must also be considered
(MnO) + [Fe]  = [Mn]  +(FeO);   
By writing equilibrium constant and using the value of  we can find  X_FeO and W_Mn = 2.061 wt. percent.

Total manganese required would be equal to manganese required to remove (0.045% ⎯ 0.018%) oxygen + Manganese required to raise the content of mn from 0.1% to 2.061%

Calculation gives 20.53Kg Mn/ton steel. If the manganese content of ferromanganese is 60%, ferromanganese would be 34 kg/ton of steel

Reference:

A. Ghosh: Principles of secondary processing and casting of steel.

K.W. Lange: Thermodynamics and kinetic aspects of secondary steelmaking. International Materials Reviews, 1988, vol. 33 p 53