Duplex Stainless Steels: Brief History and Some Recent Alloys

In terms of a common engineering material, modern duplex stainless steels emerged in the early 1980s, developed from cast alloys. Their popularity stems from an attractive combination of properties, including high strength and excellent resistance to chloride stress corrosion cracking. The present paper gives a brief review of the history and some recent developments of duplex stainless steel grades and the improvements made on the standard S32205 DSS lowering the Ni and Mo contents to produce an economical alternative of the well-known grade or in the case of the superduplex S32750 grade increasing the content of Cr, Mo and Nor elevating the content of Cr, N, Cu and W in combination with relatively lower contents of Ni and Mo to improve the strength, toughness and corrosion properties for the oil industry. Parallel to the development of higher-alloy duplex grades for corrosive conditions, there has recently been a great interest in leaner compositions for wider purposes with lower amounts of expensive alloying elements. In this respect, a new patent correspond to the type S32101 DSS has been developed. Finally, the most modern applications in the field of oil and petrochemical industry are described and the major uses of the three main grades, lean, 2205 and 2507, are commented.