How to Remove Sulfur From Molten Steel

Heat metal to the melting point in an electric arc furnace (EAF). In the EAF, scrap iron, pig iron, and iron ore is melted by an electric current generated within the furnace. This is more efficient than the older, basic oxygen furnaces.

Add reactive slag. This can be done either by injection through a refractory lance, or by pouring the molten steel into a ladle containing the slag. Either way, maximize the contact between the slag material and the molten steel. Calcium oxide, or lime, is frequently used, but manganese, magnesium, and iron oxides may be used as well. The calcium or other elements from the oxides interact with the sulfur within the steel to form sulfides, which rise to the surface and can be removed with the slag. The amount of material added should be between 1/20 and 1/40 the weight of the steel being melted, depending upon the degree of purity needed. The reactive material should be added early, before the molten metal has time to cool, to work most efficiently.

Stir the molten steel with induction stirrers, to increase the contact between the steel and the desulfurizing slag. This helps to increase the reaction between the slag and the sulfur contaminants in the steel.

Pour off the sulfides and other residue. Some of the slag can be used for other purposes, such as paving roads.