An early process used in the production of steel in which one furnace begins as another is finished. Iron is converted to steel in a Bessemer furnace in which the molten product is then transferred to an arc furnace to oxidize the impurities. Duplex is a group of stainless steels that have near-equal amounts of austenite and ferrite. They are noted for their high strength and resistance to corrosion resistance, and are used for process equipment.