Pouring hot steel melt from converter. The converter is employed in the steelmaking process known as BOS, that is Basic Oxygen Steelmaking. During this process a carbon-rich melt know as "pig iron" is converted into pure steel. During the process burnt lime and/or dolomite are added to effect removal of the impurities and to protect the lining of the converter.The burnt lime and dolomite are fluxes of a basic nature, hence the naming (BOS) of the process.