Assessment of Specimen Geometry for All-Weld Metal Tensile Test in Narrow Groove Welding

The development of adequate welding procedures for the offshore pipeline industry has required improvement of weld designs due to stringent field operations, e.g., deep and ultra-deep water application, strain-based design, weld overmatching, low temperature toughness, fatigue resistance, etc. Gas-metal arc welding (GMAW) procedures have required the optimization of the groove design, from conventional (wide opening) to narrow-groove (NG) solutions. The assessment of the weld metal tensile properties, based on international codes and specifications, is necessary to deliver full compliance and reliability of requirements for the girth weld performance. However; complexities arise in order to establish weld metal testing procedures, when narrow-groove design is used for welding a heavy-wall (HW) seamless pipe material. The latter requires the assessment of specimen geometry in HW line pipe in order to produce reliable measurements of all-weld metal tensile properties, which can be representative of the weld metal performance. The objective of the present work is to present the assessment in the differences on specimen geometry for all-weld metal tensile test (AWMTT). The work includes the welding of a HW seamless pipe material; 273.1 mm OD × 46 mm WT, X65 steel grade using STT®+GMAW, single-torch, as welding process, with narrow J-bevel, in 2° angle opening. Experiments considered the use of an ER80S-G solid wire as filler material for behavior analysis. The assessment methodology consisted in the machining of three different specimen geometries; strip, round and cross weld specimens were prepared for tensile tests. Efforts were dedicated to extracted tensile specimens avoiding heat affected zone areas in the specimen. Assessment of obtained results is based on tensile tests as well as the analysis of stress-strain data for the yielding behavior regarding the specimen geometry.