Gas injection rates

The following are some typical values of specific gas injection rates:
Stirring < 5Nl/ (min. t)

Lime steel desulphurization  14Nl/ (min. t)

Vacuum Arc Decarburization < 2Nl/ (min. t)

High gas flow rats though supply large amounts of stirring energy, large freeboards are needed. Large freeboards decrease the molten steel holding capacity of ladle. Lack of large freeboards and splashing often limits rate of gas injection.

Choice of stirring energy

Correct stirring is of utmost importance. It should be known when to stir what, and how vigorously. Vigorous stirring would be required for slag/metal reaction such as desulphurization. Inclusions removal would require weak stirring. Bath homogenization would also require weak stirring.

Vigorous mixing of metal and slag is achieved with gas stirring. Less disturbance at the slag/metal interface can be obtained by induction stirring. Slag carry-over from BOF/EAF must be avoided.  Vigorous stirring in the neighborhood of slag/metal phase boundary activates interfacial mass transfer, leading to reduction of slag by deoxidizing elements, reversion of phosphorus, and oxygen and nitrogen pick up from the atmosphere.