Friction stir welding (FSW) offers both economic and technical advantages over conventional fusion welding practices for welding line-pipe. For offshore linepipe construction, the economic savings has been shown to be considerable, approaching a calculated 25%, and for onshore construction, an -7% savings can be realized.[1] However, in prior FSW studies, consistent full penetration in steel linepipe has proved to be a difficult goal when using a portable FSW system capable of operation in the field.[2] That is, in an on-site environment, boundary conditions such as pipe wall tolerances, ovality, etc. can impact the tool position with respect to the joint depth. In the prior studies, post-FSW evaluations demonstrated full penetration through much of the weld length, and, when full penetration is achieved, mechanical properties are excellent.
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