Spiegeleisen:
Spiegeleisen is an alloy of Fe, Mn and C. When air blast is passed into molten pig iron, most of the C is removed as CO and CO2. The required amount of C needed for the formation of steel is added from outside in the form of Spiegeleisen. Some oxides of Fe (FeO) formed during the passage of air blast are reduced to Fe by Spiegeleisen and it also removes O2 if present in molten Fe.