| Summary: | A fully automatic friction welding system was specially developed for the girth friction welding of pipelines with a diameter of up to 400 mm. The friction welding methods were solid-state joining processes based on the generation of heat through the contact and rotation of an intermediate ring placed between two pipes ends. The thermomechanical process used in this non-fusion method generated different welding zones and microstructures. This resulted in the production of defect-free API 5L X46 welded pipes in less than 5 min. The microhardness profile of the welded joints showed an increase in the intermediate ring hardness. A fracture toughness test and fractographic analyses showed reduced values in the centre of the ring, which were associated with dimples nucleated at small inclusions. Keywords: Friction welding system, Pipeline girth welds, API 5L steel
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