The substance that is used in the steel industry for the removal of carbon, sulphur and phosphorus impurities from pig iron is

The substance used in the steel industry for the removal of carbon, sulphur, and phosphorus impurities from pig iron is oxygen. This process is called "oxidation" and it occurs when oxygen reacts with the impurities in the pig iron, which then form oxides that can be easily removed. During the steelmaking process, pig iron is melted in a furnace and then impurities such as carbon, sulphur, and phosphorus are removed. Oxygen is blown into the furnace, which reacts with the impurities to form oxides. These oxides rise to the surface of the molten metal and form a slag layer, which is removed. This process results in the production of steel with lower impurity levels and higher purity. In summary, oxygen is used in the steel industry for the removal of impurities from pig iron through the process of oxidation, which forms oxides that can be easily removed.