Feasibility of Friction Stir Welding for Sealing the Roller-Expanded Heat Exchanger Tube-To-Tubesheet Joints

In expanded-welded tube-to-tubesheet joints, where welds separate the two transfer fluids, tungsten inert gas (TIG), welding is preferred traditionally. A non-conventional novel technique for sealing the roller-expanded joints using friction stir welding (FSW) instead of TIG welding is proposed. FSW was effective with up to 8% expanded tube-to-tubesheet joints. The minimum leak path of 4%, 8%, and 12% expanded and welded joints were 0.74mm,1.34mm and 0.32mm, respectively. Grains were refined at the stir zone due to dynamic recrystallization and at the expanded zone due to compressive stress imparted by rollers. The results proved that the FSW is a promising technique for producing quality sealed joints.