Corrosion of simulated weld HAZ of API X-80 pipeline steel

Parameter optimisation for automatic pipeline girth welding using a new friction welding method

Characterization of fiber laser welds in X100 pipeline steel

The purpose of this work is to develop hot-wire laser welding for narrow-gap joints. Test pieces of ASTM A 304 stainless steel with a gap width of 3 mm were used. With welding by tentative filler rod made of Inconel 600 alloy, melting phenomena of the molten pool and the weld bead formation during welding were investigated by in situ observation using a high-speed camera. Variations in the main welding parameters such as wire current, wire feeding position, laser irradiation angle, and wire feeding angle were investigated to determine appropriate conditions. Experiments showed that under the optimum welding conditions, hot-wire laser welding was able to produce complete weld deposition with very low dilution of the base metal. An experiment on laser beam reflection indicated that the laser beam reflected from the molten pool was a crucial phenomenon to explain the formation of the weld bead, especially in terms of melting the side groove wall of the base metal. Welding parameters as mentioned above significantly affected weld quality. Furthermore, in the case of welding with filler wire ER NiCrCoMo-1, the Vickers hardness distribution along the transverse welding direction was examined to evaluate weld properties and the bonding strength at the fusion interface was examined in a tensile test, and the results showed that there was no great difference in the hardness profile throughout the cross section of the weld plate. Additionally, metallurgical examination of the fracture surface revealed the rupture occurred at the weld metal, probably because the bonding at the fusion interface was stronger than the weld metal. Therefore, the development of laser welding with hot wire can advance the multi-pass weld for an ultra-narrow-gap joint.

Development of a highly efficient hot-wire laser hybrid process for narrow-gap welding—welding phenomena and their adequate conditions

In this paper, a novel swing arc welding system developed for horizontal narrow gap gas metal arc welding (NG-GMAW) which was used in welding and joining heavy plate structures was designed and attempted. Using this welding system, two sound heavy plate beads, i.e., “multi-layer single-pass” welding and “multi-layer double-pass” welding structures, were obtained through adjusting swing amplitude and frequency. Two different welding structures are both without sagged molten pool and interlayer slags, especially obtaining the complete sidewall penetration. All these welding features ensure the bead with higher tensile properties and hardness than the base metal, respectively. This welding system displays considerable flexibility and convenience and possesses a tremendous advantage in the auto-welding industry.

Research on narrow-gap GMAW with swing arc system in horizontal position

Installation of new pipelines is predicted to grow at a rapid rate over the next twenty years, due in part to the increase use worldwide of combined cycle power generation plant using natural gas a fuel. The need to construct large diameter pipelines over long distances has led to an increased demand to improve the productivity of pipeline girth welding. Many novel techniques have been tried in the past to achieve productivity gains, including laser welding, flash butt welding, homopolar welding, and radial friction welding. In spite of the failure to gain wide acceptance, there is still current development aimed at achieving their eventual implementation. Single wire mechanised gas metal arc welding (GMAW) remains the dominant pipe girth welding technique, and has been optimised in the past to produce the maximum productivity possible with this process. Continued development of GMAW with dual torch, tandem GMAW welding and novel techniques for GMAW roots is leading to further significant gains in arc welding productivity. This paper describes a new development, the CAPS project, (Cranfield Automated Pipe-welding System), where tandem GMAW in a narrow groove has been applied to pipeline girth welding with two tandem torches in a single welding head. The CAPS system offers welding productivity three to four times higher than that possible with the conventional single wire GMAW technique, while still producing a weld which is very similar to that generated by single wire welding. The development of the system is described, as well as recent successful trials under field conditions. The development of high power lasers has spurred a current high level of interest in the possibility of application to pipeline welding, and current research is described in which the feasibility of pipeline laser welding has been established.

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Recent developments in high productivity pipeline welding

The hyperbaric GMA welding procedure development carried out for underwater pipeline repair using a fillet welded sleeve is described. The fillet welded sleeve for repair offers greater alignment and installation tolerances than those associated with V-butt welding. In comparison with the hyperbaric TIG process, currently operated offshore with diver-assistance, GMA welding offers a relatively high deposition rate and is well suited to fillet joints. Parameter development enabling the stable deposition necessary for a large fillet weld is described, in addition to the repeatability of the weld quality and results from material property testing. Positional linear fillet welding work has been performed on API 5L X65 pipeline and sleeve material, using a specially developed metal-cored wire at an initial target depth of 360m. Previous work has demonstrated the robust nature of the hyperbaric GMAW process, with results produced at water depths down to 2,500m. The procedure development forms part of the Remote PRS programme, designing, building and testing a diverless underwater hyperbaric GMA welding repair spread, to be operated fully remotely.Copyright © 2004 by ASME

Diverless Underwater GMA Welding for Pipeline Repair Using a Fillet Welded Sleeve

The atmospheric pressure Tungsten Inert Gas (TIG) arc plasma in argon is studied combining results from emission spectroscopy temperature maps with composition data and transport parameters available from literature. Two arc currents are considered and maps are obtained for the Debye number, the number of particle in the Debye sphere, which shows values of the order of 10 or less in the core region of these arcs. This low number puts into serious question the plasma quasi-neutrality. It is striking that this circumstance occurs where Local Thermodynamical Equilibrium (LTE) is usually assumed in these discharges. It is shown that TIG arcs violate the quasi-neutrality requirements and, as such, these discharges are called ‘plasma’ quite improperly. Differently from previously published works, the starting point of the discussion is the experimental two-dimensional temperature maps. Keywords : welding, arc physics, plasma spectroscopy, LTE, Langmuir probes

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Quasi-Neutrality and Local Thermodynamical Equilibrium in Atmospheric Pressure Arc

The atmospheric pressure Tungsten Inert Gas (TIG) arc plasma in argon is studied combining results from emission spectroscopy temperature maps with composition data and transport parameters available from literature. Two arc currents are considered and maps are obtained for the Debye number, the number of particle in the Debye sphere, which shows values of the order of 10 or less in the core region of these arcs. This low number puts into serious question the plasma quasi-neutrality. It is striking that this circumstance occurs where Local Thermodynamical Equilibrium (LTE) is usually assumed in these discharges. It is shown that TIG arcs violate the quasi-neutrality requirements and, as such, these discharges are called 'plasma' quite improperly. Differently from previously published works, the starting point of the discussion is the experimental two-dimensional temperature maps.

Quasi-neutrality and local thermodynamical equilibrium in atmospheric presure arc discharges

Opisan je razvoj hiberbaricnog MAG postupka zavarivanja za reparaturu podvodnih cevovoda koriscenjem ugaono zavarene obujmice. Ugaono zavarena obujmica za reparaturu nudi vecu saoosnost i instalacionu tolerancije nego pri primeni V suceonog spoja. U poređenju sa hiberbaricnim TIG postupkom, koji se sada primenjuje na platformama uz pomoc ronioca, MAG postupak zavarivanja nudi relativno vece brzine nanosenja materijala i veoma je pogodan za ugaone spojeve. Opisan je razvoj parametara potrebnih za stabilno nanosenje dugackih ugaonih spojeva uz dodatni zahtev ponovljivosti kvaliteta spoja kao i rezultati ispitivanja osobina materijala. Pozicionirano linearno zavarivanje ugaonih spojeva izvedeno je na cevovodu i obujmici od materijala API 5L X65 koriscenjem specijalno razvijene metalom punjene žice na dubinama do 2.500 m. Razvijeni postupak cini deo programa za daljinski upravljano reparaturno zavarivanje cevovoda (PRS), projektovanja, izrade i ispitivanja hiberbaricnog podvodnog reparaturnog MAG zavarivanja bez ronioca, koje se odvija sa potpuno daljinskim upravljanjem.

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D. Yapp

Papers

Recent developments in high productivity pipeline welding

Diverless Underwater GMA Welding for Pipeline Repair Using a Fillet Welded Sleeve

Quasi-Neutrality and Local Thermodynamical Equilibrium in Atmospheric Pressure Arc

Quasi-neutrality and local thermodynamical equilibrium in atmospheric presure arc discharges

Diverless underwater GMA welding for pipeline repair using a fillet welded sleeve