Friction Stir Welding in Pipeline Applications

Friction stir welding (FSW) is a relatively new joining process which has exhibited many advantages over traditional arc welding processes such as the elimination of solidification defects and reduced distortion. With the introduction of new tool material technology such as the use of polycrystalline cubic boron nitride, materials such as steels, stainless steels, and nickel base alloys have successfully been FSW. Though there are many advantages to friction stir welding, there has been very little work in applying the process to out of position welds, such as those found in pipelines. This study outlines the progression from linear friction stir welding to initial work consisting of the rotation of pipe coupons on a turn table and finally to the design of a portable FSW machine able to weld 305 mm (12 inches) diameter line pipe. A brief summary of FSW weld characteristics are given for API grades X65, X80, and X100 steels.