AWS WHC-3.01:2008

Resistance Spot and Seam Welding
Scope : Spot welding and seam welding are resistance welding processes. Resistance welding includes a group of processes that produce coalescence of the faying surfaces with the heat obtained from the resistance of the workpieces to the flow of the welding current in a circuit of which the workpieces are a part, and by the application of pressure. A resistance spot weld is made between or on overlapping members (workpieces) in which coalescence may start and occur on the faying surfaces, or may proceed from the outer surface of one member. The weld cross section is approximately circular. A seam weld is a continuous weld made between or on overlapping members, in which coalescence may start and occur on the faying surfaces, or may have proceeded from the outer surface of one member. The continuous weld may consist of a single weld bead or a series of overlapping spot welds.1,2 Spot welding and seam welding adapt well to automation. They are mainstay processes in the automotive industry and in other industries that manufacture products involving the welding of similar thicknesses of the same metal. Examples include automobile fuel tanks, catalytic converters, mufflers, and roof joints. Seam welding is an important process for manufacturers of cans and containers of all types. Other products of spot and seam welding are furnace heat exchangers and storage tanks. This chapter covers the fundamental principles of these processes and their variations, equipment, and mechanical systems. The advantages and limitations of the processes are discussed, and welding conditions as applied to various metals are presented. Other topics include joint design, welding schedules, surface preparation, weld quality, and economics. The chapter concludes with a section on safe practices specific to the spot and seam welding processes