Welding Duplex and Super-Duplex Stainless Steel (14036)
By L. van Nassau, H. Meelker and J. Hilkes, reprinted from Welding in the World, Vol. 31, (5), 1993. Industrial conditions, especially involving Cl-containing aqueous fluids, may require materials with improved corrosion and/or strength properties compared to a standard austenitic stainless steel grade (AISI 316L or X2 CrNiMo 1812). To meet this need a duplex stainless steel grade with approximately 18.5% Cr, 5% Ni, 2.7% Mo and 0.1% N was introduced in the 1970s. This grade is no longer promoted by the manufacturers but new low carbon stainless steel grades with 22-27% Cr, 4-8% Ni, 0.1-0.3% N, with or without Mo (1.5-4%), and in some cases with additional elements, have been developed. They form the current families of duplex and super-duplex stainless steels, with the austenite-ferrite structure in common. Early applications, and even today's projects, have frequently been associated with such problems as cracking or preferential corrosion behaviour. Consequently, welding of duplex and super-duplex stainless steel has been subject to fundamental and applied research.