Flux-cored arc welding of 316L austenitic stainless steel: the effect of different shielding gas mixtures on microstructural features and weld performance

ABSTRACT

Double-pass flux cored arc welding (FCAW) of 316 L austenitic stainless steel was performed using different shielding gas mixtures. Microstructural features and weld performance were evaluated. Based on the Cr_eq/Ni_eq ratio of fusion zone and cooling rate, different morphologies of ferrite (skeletal, lathy, and dendritic) and austenite with various volume fractions were produced. An increase in Cr_eq/Ni_eq ratio can increase the strength level because the presence of ferrite in the weld metal acts as a second-phase strengthening agent. On the other hand, ferrite is a suitable place for sigma phase precipitation. Highest joint efficiency resulted in the specimen welded via GTAW. The ductility of welds was ranked as CO₂ +Ar shielded FCAW > GTAW > CO₂ shielded FCAW > self-shielded FCAW. At room temperature, variation of delta-ferrite content (Cr_eq/Ni_eq ratio) does not affect toughness. However, an increased amount of CO₂ in shielding gas will result in decreased toughness values because of the enhanced formation of oxide inclusions. Increasing CO₂ content of shielding gas from 0% to 18% and finally to 100% will result in decreasing toughness values from the highest value of 76J to 40 J and finally the lowest value of 38J.

KEYWORDS:

• Austenitic stainless steel
• flux-cored arc welding
• gas tungsten arc welding
• microstructure
• impact test

Disclosure statement

No potential conflict of interest was reported by the author(s).