EFFECT OF FILLER MATERIAL SELECTION ON STRESS STRAIN BUILD UP AND STRESS CORROSION CRACKING RESISTANCE OF WELDED SUPERMARTENSITIC STAINLESS STEEL PIPES

摘要

As a cost reducing altemative, supermartensitic stainless steels are increasingly replacing higher alloyed pipeline materials in North Sea oil and gas production. The tubulars are usually connected during pipeline fabrication by orbital tungsten inert gas (TIG) welds. New matching consumables have recently been developed by the intention to replace usually applied duplex and super duplex filler wires and to avoid complex tri-phase microstructures in the heat affected zone (HAZ). In order to investigate the effects of filler material selection in more detail at realistic mechanical and environmental conditions, component tests of welded supermartensitic stainless steel tubulars have been performed. As demonstrated in the present contribution, much lower stresses and strains are produced during welding and cooling by application of supermartensitic instead of duplex stainless steel filler wires, regardless of shrinkage restraint. In both cases the HAZ has been identified as the most crack susceptible region of the joints.