Research and engineering application of continuous-drive friction welding

The friction welding (FW) technology is a kind of solid-phase hot pressing welding method applied to the connection of similar or dissimilar materials. During the FW process, welding heat is generated by the pressure and high-speed relative motion between the joint interfaces of the workpieces. After the joint interfaces and their neighborhood arrive at the thermoplastic state, the workpieces are pressed into a whole by upsetting. FW has a wide range of weldability (e.g., carbon steel, alloy steel, non-ferrous metals, other materials of the same kind, dissimilar metal materials, and metal and non-metal materials with completely different properties) and can obtain welded joints with excellent properties (closed to base metal) and fewer defects (e.g., cracks, pores, and segregation); thus, it has high reliability to welded joints. As its advantages, FW exhibits low energy consumption (i.e., 10%–20% of fusion welding), high efficiency (i.e., only a few seconds to realize an effective joining of the workpieces), and environmental friendliness (i.e., no welding rod, wire, flux, or protective gas and no arc, spatter, smoke, or slag as in fusion welding) and can easily realize automation and large-scale production. FW is widely used in high-tech manufacturing in various industries, including in the automobile, aviation, aerospace, nuclear energy, oil drilling, marine development, and electric power industries. On the basis of the classification and the brief description of FW, the present situation of the research, development, and application of the continuous-drive FW (CDFW) technology was comprehensively sorted out and analyzed in-depth in this paper. This study involved the CDFW process characteristics and main process parameters, process exploration, influence of the process parameters on welded joint properties, numerical analysis, simulations, process parameter optimization, CDFW process innovation for dissimilar metals and non-metallic materials, practical engineering applications, and welding equipment, among others. The aspects of the potential applications of the FW technology, core scientific issues, research and development of the novel FW equipment, numerical analysis and simulation, and combination with emerging technologies associated with the CDFW technology were also reviewed and discussed.