Experimental investigation of friction stir seal welding of tubetubesheet joints

To ensure heat exchanger tube-tubesheet joints tightness, industrial standards may recommend performing a combination of roller expansion and seal welding, using conventional fusion welding processes. Solid state friction stir welding (FSW) has several advantages over the conventional fusion welding but has not yet proven its usefulness in seal and strength welding of heat exchanger tube-tubesheet joints where the available space is very limited and weld pass is of a relatively complex contour. In this work, a newly designed tool and procedure are applied to friction stir seal weld (FSSW) tube-tubesheet joints. The effects of process conditions such as welding speed and tool offset on dependent process parameters including welding loads and joint quality are investigated on a 600-series aluminum three-tube test cell. The results revealed that the quality of the seal weld of tube-tubesheet joints is affected by the preceding parameters at different levels.