Friction stir welding (FSW) involves temperature, mechanics, metallurgy, and their interactions, which has become a revolutionary green welding technique over the past two decades because of the low peak temperature, severe plastic deformation, and high⁃quality joint. In order to further broaden its application in manufacturing fields, it was necessary to break through the technical barriers of inherent issues. Based on the inherent issues of weld thinning, keyhole and defects quasi⁃equal strength repairing, back⁃supporting and high⁃quality welding of dissimilar materials (such as dissimilar metals and metals/polymers), this paper reviewed the development of FSW innovative technology, which had practical significance for improving joint forming, realizing high⁃reliability joining and expanding engineering application.

Friction stir welding (FSW) is an effective, environment⁃friendly solid state is an efficient and environmentally friendly solid phase bonding method, which has the characteristics of low temperature severe plastic deformation and high joint quality. FSW can effectively solve the problems associated with fusion welding in petroleum tanks and pipelines. However,due to the influence of welding parameters, working conditions and inherent mode of the method, friction stir welding has welding defects, which reduces the service life of the joint. The two major welding defects (global and local welding defects) were summarized in terms of characteristics and causes, while the repairing technologies for various defects were reviewed. This paper has practical significance for joint quality improvement, high⁃efficiency high⁃performance repairing and engineering applications.