The construction costs for a northern pipeline will represent approximately half of the project costs and will be extremely challenging with much of the work being carried out in harsh winter conditions at temperatures, as low as −55°C. The welding costs are a major component of the overall construction costs and industry continues to seek future generation pipeline welding technologies to achieve additional improvements in productivity and enable significant cost savings. The current state-of-the-art welding processes for onshore pipelines involve mechanized gas metal arc welding (GMAW). The dual tandem pulse GMAW process provides the greatest productivity to date with four welding arcs operating simultaneously on each welding carriage. Based on the progression of laser welding technology, it is highly likely that the next generation of automated pipeline welding equipment will be built around hybrid laser arc welding (HLAW). The primary objective of this project is to develop, test, and validate a “field ready” HLAW system for full circumferential girth welding of large diameter (NPS30 and above) high strength pipe. The system is based on both robotic and direct clamp-on platforms where potential applications include double jointing operations in pipe mills and as well for onshore and offshore pipeline construction projects. The pipe grades evaluated include both X80 and X100, with wall thicknesses of 10.4mm and 14.3mm, respectively. Lab trials include high speed root pass, high speed root pass with laser assisted GMAW for fill and cap passes, and, single pass complete joint penetration girth welding. This paper discusses the approach to the development of the HLAW system, however at the time the paper was submitted no mechanical testing or system validation trials had been completed. It is expected results will be available for the conference presentation.
Droplet Transfer Induced Keyhole Fluctuation and Its Influence Regulation on Porosity Rate during Hybrid Laser Arc Welding of Aluminum Alloys
