Friction Stir Welding of API Garde 65 Steel Pipes

Abstract

Friction stir welding (FSW), a novel solid-state joining process, was applied to girth weld API 5L Grade 65 steel pipes with an outer diameter of 12.75″ (324 mm) and a wall thickness of 0.25″ (6.35 mm). Fully consolidated single pass butt welds were obtained using a specially designed mechanized portable FSW system suitable for on-site pipe construction welding. The friction stir girth weld shows a slightly overmatched strength and superior impact toughness in comparison with the base metal, a very desirable combination of properties for pipeline weld that can be attributed to the wrought microstructure with refined grains in the stir zone (SZ), the thermal-mechanically affected zone (TMAZ), and the heat-affected zone (HAZ).