Effect of nitrogen and activated flux on bead geometry mechanical and corrosion properties of duplex stainless steel gas tungsten arc welds

Abstract

In recent years a number of new stainless steels have been developed among those duplex stainless steels DSS are one of the prominent These steels contain ferrite and austenite in near equal volume DSS have superior tensile strength and enhanced stress corrosion cracking resistance compared to austenitic steels and greater toughness than ferritic stainless steels especially at low temperatures DSS are employed for a wide variety of applications in the oil and gas chemical and petrochemical paper and pulp industries in the form of sheets plates pipes and tubes The outstanding properties of DSS are mainly due to the phase balance ie approximately equal amounts of ferrite and austenite phases Welding of DSS can be carried out by employing any one of the following welding processes MMAW GTAW SAW and FCAW GTAW is the frequently used welding process in fabrication of DSS However the main disadvantage is its relatively low penetration during a single pass welding operation This study focuses on Autogenous GTA welding of Duplex Stainless Steel DSS 2205 6mm thick plates Several variants of Autogenous GTA welding ie Nitrogen addition to shielding gas Activated flux and combination of the above two have been investigated to find their effect on Bead geometry Mechanical and Corrosion properties As a reference welding process DSS 2205 plates of 6mm thickness were multipass welded using 2209 filler alloy which is actually practiced in the industry Effect of Nitrogen addition to shielding gas also has been studied newline