Estudo da soldagem de tubos de aço inoxidável duplex e superduplex

Abstract

The duplex and superduplex stainless steels have an austeno-ferritic microstructure with an average fraction of each phase of approximately 50%. This duplex microstructure is responsible for the excellent mechanical properties, specially the yield strength and toughness, and for the improved pitting and stress corrosion cracking resistance in chloride environments. Welding of these steels is often a critical operation. One pipe of superduplex stainless steel SAF 2507 were welded by the GTAW process on root pass and the SMAW process on filler passes, and one pipe of duplex SAF 2205 were entirely welded by GTAW process. The toughness and corrosion resistance properties obtained were correlated with the chemical composition, estimated throw welding consumable employed, and microstructure of weld and HAZ. The results obtained from impact Charpy-V tests were satisfactory and do not suggest an intense intermetallics, carbides and nitrides precipitation. The superior corrosion resistance results presented by superduplex stainless steel welded joint, compared to duplex one, were attributed to lower delta ferrite content on weld and HAZ, and weld chemical composition enriched in Cr, Mo, W and N.