Sulphur elimination:

Until recently refining operations in cast iron were restricted. Essentially all of the cast iron was melted in the acid cupola furnace that permits close control of and silicon and carbon contents however does not eliminate phosphorus or sulphur. Sulphur elimination in cast iron is now accomplished by

 (a) Melting in a basic cupola,

 (b) Melting in a basic electric furnace, or

 (c) Melting in an acid cupola and adding up desulphurizing compounds in the forehearth or ladle.

As phosphorus elimination is not normally accomplished in the cupola it is essential to avoid high phosphorus charge materials for the cupola melting practice; phosphorus and sulphur both might however be eliminated through a double slag electric furnace operation. Desulphurization in the ladle might be accomplished in a variety of ways; two of these being to pour on a sodium oxide slag or to inject powdered desulphurizers such like calcium carbide. Injections are completed by blowing the powders into the metal by a tube immersed in the melt.