Hot Tensile Properties of Autogenous Pulsed Current Gas Tungsten Arc Welded Super 304HCu Austenitic Stainless Steel Joints

Abstract

.The super 304HCu austenitic stainless steel tubes containing 2.3 to 3 (% wt) of Cu is mainly used in superheaters and reheater of ultra super critical boilers. The addition of Cu to super 304HCu has caused improvement in its corrosion and creep resistance. Austenitic stainless steels welded by constant current gas tungsten arc welding (GTAW) produce coarse columnar grains, increase alloy segregation and may result in low mechanical properties of the weld joint. Hence, autogenous pulsed current GTAW (PC-GTAW) was used to weld super 304HCu tubes of 57.1 mm outer diameter and 3.5 mm thick to control the solidification structure by altering the prevailing thermal gradients in the weld pool. The microstructure, hot tensile properties (550 QC, 600 QC and 650 QC), and fracture surface of the autogenous PC-GTAW welded joint was evaluated. Current pulsing in PC-GTAW joint cannot eliminate segregation in weld metal and exhibited lower tensile strength than the parent metal at all test temperature