The process involves converting molten pig iron into steel by blowing oxygen through a lance over the molten pig iron. This is done in a furnace, where pure oxygen initiates a series of chemical reactions. These reactions primarily involve the oxidation of impurities like carbon, silicon, and phosphorus, which are present in the pig iron. The oxygen blowing reduces the carbon content and helps remove other impurities, resulting in steel, which is stronger and more versatile than pig iron.