Effect of the Chemical Composition of the Filler Metal and the Heat Input on the Microstructure and the Mechanical Properties of Duplex Stainless Steel Welded Joints

Duplex stainless steels are characterized by good weldability and mechanical properties; they also present a high resistance to general and localized corrosion. They are the main materials when welding pipes with high requirements in different industries, mainly oil and gas. These steels have a microstructure consisting of two phases: 50% austenite and 50% ferrite, approximately, and their properties depend on the maintenance of this ratio and the total chemical composition. The aim of this work was to study the influence of both the chemical composition of the filler metal and the heat input used when welding, on the microstructure and mechanical properties in welded duplex stainless steel pipes. Base metal used was a duplex stainless steel ASTM A790 - UNS S31803 pipe of 8" in diameter and 8.18 mm in thickness. The filler metals were two tubular wires depositing lean duplex and duplex stainless steels (AWS A5.22: E2209T -1 and E2209T1-G respectively), by semi-automatic welding process under shielding gas, with high and low heat inputs. Samples of each specimen were used to determine chemical composition, to perform the microstructural characterization and to measure mechanical properties (hardness, tensile strength and Charpy-V impact).