The present work was conducted to assess the weldability of duplex stainless steel under hyperbaric conditions relevant for future remote-controlled hot tap welding. This was achieved by horizontal welding with Inconel 625 wire in V-grooves on plates in 2205 duplex steel in chamber pressures of 12 and 35 bar. The highest maximum hardness occurred in the heat-affected zone (HAZ) of the root bead, where HV10 values in the range from 260 to slightly above 280 were measured. The results showed that there is weld metal undermatch with respect to the yield strength (460-490 MPa), while the tensile strength (740 MPa) was at the same level as that of the base plate. The notch toughness at -30 deg C was excellent for all positions tested (weld metal, weld interface, and weld interface +2 mm), and is far beyond current offshore requirements. The HAZ and weld metal were also characterized with respect to their microstructures. Although the welds were quite similar, the 35 bar weld appeared to have a thin zone (0-40 micrometer thickness) of ferrite in the HAZ close to the weld interface. The weld metal microstructure consisted of primary and secondary dendrite arms, which are the first to solidify. During this part of the solidification, solute elements are enriched in the liquid. With falling temperature, the solubility is probably exceeded with subsequent formation of intermetallic phases, as well as nitrides/carbides. Finally, the base metal dilution was subjected to microprobe analysis, showing large variations in weld metal chemical composition between different passes. The implications of the results with respect to corrosion and fracture toughness are discussed.
Hyperbaric GMA welding of duplex stainless steel at 12 and 35 bar
Welding Journal, New York ; 88 , 2 ; 21s-28s
2009
8 Seiten, 13 Bilder, 4 Tabellen, 22 Quellen
Article (Journal)
English
Schweißen in einer Überdruckkammer , MSG-Schweißen , nichtrostender Stahl , Inconel , mechanische Eigenschaft , Mikrogefüge , Schweißeignung , Schweißzusatzwerkstoff , Wärmeeinflusszone , intermetallische Phase , Elektronenmikrosondenanalyse , Korrosionsbeständigkeit , Bruchzähigkeit , Chrom-Nickel-Molybdän-Stahl
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