AWS WHC-3.03:2008

Flash and Upset Welding
Scope : Flash welding (FW) and upset welding (UW) are resistance welding processes generally used to make butt joints in components of similar cross section by making a weld simultaneously across the entire joint area. Filler metal is not used. To form the solid-state weld characteristic of both processes, upset force is applied during or shortly after the resistive heating cycle is complete. Butt joints between workpieces with similar cross section can be made by both flash welding and upset welding. Upset welding is similar to flash welding except that no flashing action occurs in upset welding. The two variations of upset welding are high-frequency upset welding (UW-HF) and induction upset welding (UW-I). The method of heating, the closing rate, and the timing of the application of force are the distinguishing characteristics of these process variations. The flash welding and upset welding processes are a mainstay of many industries requiring high-integrity welds, such as those used in the automotive, aerospace, railroad, petroleum, and construction industries. Flash welding and upset welding are discussed in separate sections in this chapter. Each section includes the fundamentals of the process, applications, equipment, welding procedures, and process variables. However, both flash welding and upset welding are represented in the sections on weld quality, methods of inspection and examination, and economics. The chapter concludes with a section on safe practices applicable to both processes