Consumables for welding high strength pipeline steel

Some problems in applying traditional welding methods to modern high strength steels are described. Because of its potential for good penetration, submerged arc welding can allow relatively heavy sections to be welded with low consumable consumption. However, the high dilution that this implies means that when welding lean parent materials, ever higher wire alloy contents must be used to generate the high strength sought in the weld metal, and an investigation into new, high-alloy compositions is described. Consumable development must also go hand in hand with process development, in pipe mills and in the field, and some tests with synergic cold wire welding are reported. Mainline girth welding with mechanized gas metal-arc systems can make use of downhill welding in very narrow compound bevel joint preparations, which extract heat from the weld so fast that lean weld metals can be produced for very high strength steels. Tie-ins are another matter. In this case, beveling and fit-up are less precise and uphill welding must often be used. Combining good weldability with strength, toughness and resistance to hydrogen cracking is not easy but great progress has been made over the last few years. New developments such as laser and hybrid laser welding for pipes may be closer to commercialization than we think, and consumable manufacturers have been busy for some years working on consumables for these. (AU)