PIPEWORKS WELDING IN ORBITAL A-TIG PROCESS

摘要

Activating flux TIG (A-TIG) process today appears as a known welding technique but it is not so well documented in shipbuilding and many commercial fluxes exist without a full warranty for the health of welders or welding operators. In the framework of the efficiency improvement of the pipeworks welding for its ships (replacement of manual or orbital TIG processes when possible), DCN decided to assess and validate the orbital A-TIG process using a simple oxyde flux (TiO_2 of 99% purity) by optimization of the welding conditions (welding parameters, flux preparation). Butt-welded joints of pipes up to 6 mm thick made of standard 316L for general use and 316L nuclear grade for pressurized pipeworks have been successfully tested in various positions, with no filler metal or with ferritic insert ring, in accordance with the relevant requirements. Alloy 625 pipes may also be welded with operating conditions close to 316L welding conditions in relationship with their similar thermal dissipation. Orbital A-TIG industrialization is in progress for submarine applications.