[en] Austenitic stainless steels are increasingly being replaced by duplex grades that can offer similar corrosion resistance with far higher strength. This increased strength makes it possible to reduce material consumption whilst also decreasing transport and construction costs. Although established welding methods used for austenitic steels can be used for duplex steels, modification of the procedures can lead to improved results. This paper reviews the welding of duplex stainless steel and examines precautions that may be required. The advantages and disadvantages of different welding methods are highlighted and some high productivity solutions are presented. The application of a more efficient process with a high deposition rate (e.g. flux- cored arc welding) can decrease labour costs. Further close control of heat input and interpass temperature can result in more favourable microstructures and final properties. Although welding adversely affects the corrosion resistance of austenitic and duplex stainless steels, particularly the pitting resistance, relative to the parent material, this problem can be minimised by proper backing gas protection and subsequent pickling.

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No abstract available

[en] A technology of pulsed-arc butt welding with periodic wire feed to the welding zone has been developed. The pulsed arc is suitable both for submerged and gas-shielded weldings. The technology proposed has some advantages over the stationary-arc welding. Control of the amplitude-frequency characteristics of the process enables one to affect melting and crystallization conditions of the welding crater, weld shape, relation between melting and deposited metal section areas, etc., as well as to reduce heat contribution to the base metal. The new process is shown to be applicable in power engineering. Automatic submerged welding conditions are given for low-carbon and pearlitic heat-resistant steels

[en] The first of two studies reported examines the ultrasonic properties of welds made by the submerged arc (SA) and the metal inert gas (MIG) processes and compares them with the properties of welds made by the manual metal arc (MMA) process, which has previously been well researched. The symmetry of the SA and MIG welds was found to be transversely isotropic, which is the same as that for MMA welds. A geometrical model of the columnar grain structure of the SA and MIG welds has been used to accurately simulate the compression wave velocity characteristics of these welds. Velocity data for MMA weld metal were used in the model. It was also found that a linear relationship exists between the ultrasonic attenuation of weld metal and the average cross-sectional area of the weld beads; welds with small beads have a higher attenuation than welds with large beads. The second study reports on the ultrasonic inspectability of austenitic T-butt and cruciform joints in 50 mm thick plate. It is concluded that T-butt joints can be given a searching volumetric examination from the side opposite the weld, but further technique development is required to perform a satisfactory examination when access is limited to the weld side. (author)

[en] The two principal modes of the vacuum arc arc the multi-cathode spot and the anode spot vacuum arc discharges. In both cases the current is conducted in plasma that is generated on relatively small areas on the relevant electrode surface. The hot anode vacuum arc (HAVA) is another mode of the vacuum arc in which the plasma is produced by material evaporation over the whole surface of a high temperature anode heated by the arc itself. In the present work, a model of a new type of the HAVA, recently discovered in the Electrical Discharges and Plasma Laboratory of TAU, is considered. In this mode of the HAVA the anode is made of a thermally isolated refractory material (graphite), whereas the water cooled cathode is fabricated from a more volatile material (copper). The discharge starts in the multi-cathode spot mode and after a transition period, during which the anode is heated by the arc, re-evaporated cathode material is released from the hot anode surface and becomes the main source of the arc plasma. At steady state, anode temperature exceeds a certain critical value. No evaporation of anode refractory material occurs during arc operation. This arc mode is labeled Hot Refractory Anode Vacuum Arc (HRAVA). The theoretical description of the HRAVA is accomplished by a plasma model that includes equations of mass, momentum, energy, and electrical current conservation, and by an anode thermal model that describes the anode thermal balance. The plasma model also considers radial expansion of the plasma from the interelectrode region. A self-consistent solution of the plasma and anode models was obtained. Plasma electron temperature, plasma density, plasma energy flux to the anode, and anode temperature distribution were calculated for several arc currents in the range 175 - 500 A. In the steady-state arc operation, anode surface temperature was calculated to be in the range 1800 - 2600 degree K, electron temperature is about 1 eV, effective anode voltage is about 6 V, and anode sheath potential drop is 2.2 to 3 V. Calculated plasma and anode parameters agreed well with observed data

[en] The characteristics of SCC crack propagation in duplex stainless steel weldment made by SMAW, GTAW and GMAW processes were investigated in 42% MgCl₂ 142 deg C boiling solution. From these experiments, it could be concluded that the structure anisotropy of γ phase as well as the phase ratio played an important role in SCC resistance. GTA and GMA weld metal showed higher SCC resistance than base metal because of randomly distributed γ phase. The crack in weld metal had same opportunity of receiving keying effect as that in base metal, but it had less possibility of intersecting γ phase. The SCC resistance of the SMA weld metal and the HAZ was lower than that of the base metal because their phase ratio deviated from the proper phase ratio. (Author)

[en] Procedure WPS-1009 is qualified under Section IX of the ASME Boiler and Pressure Vessel Code for manual gas tungsten arc (DC) and semiautomatic gas metal arc (DC) welding of aluminum alloys 6061 and 6063 (P-23), in thickness range 0.187 to 2 in.; filler metal is ER4043 (F-23); shielding gases are helium (GTAW) and argon (GMAW)

[en] The effects of temperature, composition, and weld-process variations on the fracture toughness behavior for Types 308 and 16-8-2 stainless steel (SS) welds were examined using the multiple-specimen J-resistance-curve procedure. Fracture characteristics were found to be dependent on temperature and weld process, but not on filler material. Gas-tungsten-arc (GTA) welds exhibited the highest fracture toughness, a shielded-metal-arc (SMA) weld exhibited an intermediate toughness, and submerged-arc (SA) welds yielded the lowest toughness. Minimum expected fracture properties were defined from lower bound fracture toughness and tearing modulus values generated here and in previous studies. Fractographic examination revealed that microvoid coalescence was the operative fracture mechanism for all welds. Second-phase particles of manganese silicide were found to be detrimental to ductile fracture behavior because they separated from the matrix during the initial stages of plastic straining. In SA welds, the high density of inclusions resulting from silicon pickup from the flux promoted premature dimple rupture

[en] A method is described for repairing low alloy steel steam turbine or generator rotors, the method comprising: a. machining mating attachments on a replacement end and a remaining portion of the original rotor; b. mating the replacement end and the original rotor; c. welding the replacement end to the original rotor by narrow-gap gas metal arc or submerged arc welding up to a depth of 1/2-2 inches from the rotor surface; d. gas tungsten arc welding the remaining 1/2-2 inches; e. boring out the mating attachment and at least the inside 1/4 inch of the welding; and f. inspecting the bore