Introduction

Synthetic slag practice is employed to obtain clean steels and to desulphurize molten steel. Synthetic slag practice is adopted to meet the following objectives

i)    To cover molten steel for cutting down heat losses.

ii)    To avoid reoxidation of steel from atmospheric oxygen because the molten steel        transfer operations are done under atmospheric condition.

iii)    To remove inclusions from molten steel.

iv)    Using slag of desired basicity and sulphide capacity, deoxidized steel can be        desulphurized  to as low as 0.005%

v)    Synthetic slag practice is attractive due to low capital cost on equipment.

 Desulphurization of steel

Synthetic slag practice can desulphurize steel up to 50% to 60% of original sulphur in steel. The following properties are desirable in synthetic slag:

i)    Slag should have high sulphide capacity

ii)    Basic slag is required

iii)    Slag should be fluid to obtain faster reaction rates.

iv)    Slag should not cause excessive refractory wear.

For efficient desulphurization , steel should be deoxidized and slag carry-over should be minimized. Fireclay ladles are not suitable if low sulphur steel is to be produced. Instead, dolomite or other basic refractory lined materials should be used. Argon bubbling is done.