Air carbon arc gouging of austenitic stainless steels prior to arc welding – opportunities and risks
By Koga, Guilherme Yuuki; Ferreira, Tales; Guerra, Ana Paula de Bribean; Cunha, Danilo; Wiezel, Jonas Guilherme Gomes; Bolfarini, Claudemiro
Published in Journal of Materials Processing Technology
2022
Abstract
This paper presents the effect of air carbon arc gouging (ACAG) and submerged arc welding (SAW) on the risk of intergranular corrosion and on the mechanical properties of AISI 304 stainless steel plate, welded with AWS-ER308L wire, and AISI 347H stainless steel plate, welded with AWS-ER347 wire. A high risk of carbon uptake was found for as-gouged surfaces. Different mechanical surface cleaning procedures were evaluated. Brushing was ineffective to remove the carbon-contaminated layer, while grinding was more efficient, as assessed by double-loop electrochemical potentiokinetic reactivation (DL-EPR), but still indicating few remnants carbon-contaminated areas. DL-EPR and oxalic etching tests of gouged and welded 304/ER308L stainless steel indicated the risk of sensitization and suspect etch microstructures regarding intergranular corrosion, while low sensitization risk was found for 347H/ER347 stainless steel welds, highlighting the role of low alloying elements such as Nb, recognized to reduce the risk of intergranular corrosion. Thus, the 304/308L SS weld joints were sensitized, even if no gouging was employed. This indicates a higher susceptibility of sensitization and intergranular attack caused by the thermal cycle induced during the SAW of AISI 304 SS using AWS-ER308L SS wire. Acceptable mechanical behavior of welding onto gouged surfaces was found for both weld joints (i.e., Charpy energy > 90 J and Ultimate Tensile Strength ≥ 600 MPa), revealing that the major risk is the sensitization in the case of 304/ER308L SS welds.