AWS WHC-3.04:2008

Resistance Welding Equipment
Scope : Resistance welding includes a group of welding processes that produce coalescence of the faying surfaces with the heat obtained from 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.1, 2 Commonly used resistance welding processes include flash welding, pressure-controlled resistance welding, projection welding, seam welding, spot welding, and upset welding. These processes and allied processes such as resistance soldering, resistance brazing, and hot upsetting are highly important to many industries. Resistance welding provides a fast and economical way to weld all types of steels: coated or uncoated steels, low-carbon and high-carbon steels, dual-phase or heat-treatable steels, and stainless steels. Other materials, including aluminum, titanium, and copper alloys also are commonly joined by resistance welding processes. Resistance spot welding has the advantages of high speed and adaptability to automation for the production of sheet metal components used in automobiles, cabinets, furniture, and other products. Resistance seam welding is used to produce continuous leak-tight joints in sheet assemblies such as hot water tanks, automotive gasoline tanks, and food containers, and also for longitudinal seams in tubular structures. Projection welding contributes valuable design advantages to manufacturers. Fasteners or mounting devices, such as bolts, nuts, pins, brackets, threaded bosses, and handles can be welded to sheet metal with this process. Crossed wires are commonly joined with the projection welding process in a variety of common products, such as concrete reinforcing mats, shopping carts, and wire shelving. Flash welding is used to join products of rod, bar, tube, pipe, and wire made of carbon steels, low-alloy steels, stainless steels, aluminum, nickel, and copper alloys. Upset welding makes end-to-end joints in two components of the same cross section, and makes continuous seams in pipe and tubing and in sheet and strip metals. These resistance welding processes are described in Chapter 1, â??Spot and Seam Welding,â? Chapter 2, â??Projection Welding,â? and Chapter 3, â??Flash and Upset Welding.â? This chapter covers the machines and equipment required to perform the varied joining applications of resistance welding.