The paper considers best practice to realise the optimum combination of strength, toughness,
corrosion resistance and radiographic integrity in UNS S32760 pipe girth welds made using the
GTAW process.
Aspects of fit up, tacking, root gap are considered. The effect of weld heat input and heat input
control through the thickness of the joint, welding technique, inter pass temperature control and
the use of different combinations of shielding and backing gasses on corrosion resistance of
joints is presented. Current specification, procedure and welder qualification requirements are
discussed, as is the need for supplementary testing, in particular quantitative microstructural
evaluation.

Friction stir welding procedure development was initiated on steel grades S460 G2+M and S690QL1 in plate wall thicknesses of 10 and 15mm. In order to tackle the challenges of the high mechanical loads on the tool as well as its premature wear, a combination of preheating and optimized weld backing set-up was implemented. The inductive preheating allowed a 28% reduction in welding torque and a significant reduction of the tool wear, particularly during the critical initial plunge of the tool within the base material. A comparison of Mo-based and W-based tool was performed, allowing identifying the W-based tool as having a better combination of high temperature strength and wear resistance. Different backing arrangements and materials were investigated. Ceramic backing inlays were used in order to reduce the heat loss at the root area and maintain an acceptable stirring of this zone to achieve full penetration welds. The welds quality was assessed via metallurgical examination, bend tests, and confirmed the possibility to perform sound full-penetration, one-sided welds. The contribution of the preheating to the process as well as the quality and mechanical properties of the welds will be discussed here.

Piping and pipeline are considered to be 60-70% of the oil and gas industry equipment. One of the most crucial factors to complete high quality projects within planned schedules is to focus on the quality of welding activities. Furthermore, the non-skilled welder is considered as a main parameter to produce welds with imperfections beyond the acceptable limits. Welders should have the required welding skills to perform the welding activities and produce sound welds, resulting in low weld rejection. On the other hand, poor welder’s performance produces low quality welds which affect the integrity of the welds and contribute to project delay and increase costs. This paper addresses methods to qualify welders and monitor their performance throughout the project lifecycle. The paper will study ISO 9606 approval testing of welders, American Welding Society (AWS) and American Society of Mechanical Engineers (ASME) Sec IX minimum requirements to qualify and certify welders. It will also illustrate the main variables that may contribute to high welding rejection rate, that are directly associated with the welders’ qualification and performance. Moreover, it will study the method of qualifying welders for different levels to properly assign welders based on load and criticality to avoid high welding rejection rate. The study shows that welders’ skill is the main parameter to produce high quality welds. Focusing on the causes of common welding defects, then educate and train the welders on the main factors causing these welding defects, will leave an influence to prevent defect recurrence