Typically used to produce leak-tight joints in sheet
assemblies such as automotive gasoline tanks, resistance
seam welding (RSEW) utilizes the fundamentals of
resistance welding to produce a seam along the length
of the joint. The seam is created with copper wheel-type
electrodes that make a continuous weld by generating
overlapping spot welds, as shown in Figure 1.18, or one
continuous weld (see below).
Because the overlapping of welds causes a shunting
effect (that is, decreased electrical resistance due to weld
overlap), the current and duty cycle required for resistance
seam welding are somewhat higher than those
used in resistance spot welding.
Resistance seam welding machines designed to weld
at high speeds apply a continuous flow of current to the
workpieces. This flow forms a continuously fused weld
(as opposed to overlapping welds) between the lapped
faying surfaces. Another type of resistance spot welding
utilizes current interruptions that are long enough to
form a series of separate spot welds. This type of operation
is known as roll spot welding.