Influence of Shielding Gas in FCAW Process Welding of UNS S31803 with E2209-T1/4 Wire

Abstract

The present work evaluates the influence of additions between 10 and 25% of CO₂ in argon-based shielded gases on the mechanical properties and corrosion resistance of welded joints by the FCAW process in duplex stainless steel (DSS) UNS S31803 using electrode wire E2209T1-4. Under these conditions the effect of the 2% O₂ addition in the mixture was also taken into account. Mechanical tensile test, Charpy toughness and microhardness in the austenite and ferrite phases were carried out in several places of the joints thus produced. Besides, corrosion tests were carried out to determine the critical pitting temperature (CPT) and mass loss per unit area based on the specifications of ASTM G150 and G48, respectively. The study was complemented with metallographic analyzes using several reagents, quantifying the present phases, as well as revealing microstructural characteristics in the studied conditions. The mechanical properties values obtained in the analyzed joints were satisfactory when compared with normative values as well in recently published works. However, it was also observed a CPT increase value in the joints welded with the use of gases with higher levels of CO₂. Finally, it was observed that, among the welded joints studied, those obtained using the mixture with composition of 73% Ar + 25% CO₂ + 2% O₂, presented the best performance, both with regard to mechanical properties and the corrosion resistance. The results allow determinates the use of other gaseous mixtures in the welding of DSS with the FCAW process, in addition to the normative one, in view of the great demand in the construction and assembly of several components of this stainless steel family in the offshore industry.

Key-words:
Duplex stainless steel; FCAW; Shielding gases; Mechanical properties; Corrosion resistance