Abstract
Duplex stainless steels have been extensively used in parts that are subject to corrosive environments and that have high mechanical strength requirements. Welding usually distorts the well-balanced austenite-ferrite ratio, and can produce brittle intermetallic phases; therefore, post-welding heat treatments are usually required. For applications where post-welding treatments are not possible, low heat input methods, such as micro-tungsten inert gas welding (TIG) and laser beam welding (LBW), can be used. The present investigation analyzed the microstructure, mechanical, and corrosion properties of 2507-classduplex steel tubes after welding. The microstructures of the heat-affected zones and the fusion zones contained variable amounts of ferrite and austenite. In the heat-affected and fusion zones in the TIG samples, the microstructures were primarily composed of ferrite grains with allotriomorphic austenite at the grain boundaries, intragranular Widmanstatten needles and plate-like precipitates. The LBW samples showed much finer microstructures, which contained austenite in the grain boundaries and fine austenite precipitates in the ferrite grains. Deleterious intermetallic phases, such as σ-phases, were not observed using X-ray diffraction. The tensile strength properties were very similar for the TIG and LBWsamples, reaching tensile strengths of approximately 840 MPa and total elongations between 61 and 87%. The heat-affected zone of the TIG welds were particularly susceptible to corrosion (0.05 mm/year) compared to the base metal (0.007 mm/year) and the laser welds (0.01 mm/year). Therefore, laser welding is a promising technique for the welding of 2507-class duplex tubes.
Highlights
Duplex stainless steels (DSS), referred to as ferriticaustenitic steels, combine many of the beneficial properties of ferritic and austenitic steels
The heat input for the laser was higher than tungsten inert gas welding (TIG) because of the use of a CO2 laser source, which is not recommended for this type of material[9]
It can be concluded that, SAF2507 is recommended for mildly oxidizing conditions, the addition of suitable depolarizing substances allows the transition from active to passive states to be efficiently controlled
Summary
Duplex stainless steels (DSS), referred to as ferriticaustenitic steels, combine many of the beneficial properties of ferritic and austenitic steels Due to their high chromium and nitrogen contents (often including molybdenum), these steels offer good resistance to pitting and uniform corrosion. According to American Society for Metals[1] DSShave better stress-corrosion cracking resistance and appreciably higher yields and tensile strength than austenitic stainless steels and are currently used as alternatives when the operating temperature is below 260 °C. This temperature, intermetallic phases appear, such as σ-phase, which result in low toughness[2]. The almost 50/50% austenite/ferrite content in modern DSS is optimized for good mechanical and corrosion properties
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
