Technology
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Resistance Welding Processes
Resistance welding is a welding technology widely used in
manufacturing industry for joining metal sheets and
components. The weld is made by conducting a strong current
through the metal combination to heat up and finally melt the
metals at localized point(s) predetermined by the design of the
electrodes and/or the workpieces to be welded. A force is always applied
before, during and after the application of current to confine the
contact area at the weld interfaces and, in some applications, to
forge the workpieces.
Depending on the shape of the workpieces and the form of the
electrodes, resistance welding processes can be classified
into several variants as described below:
Resistance Spot Welding
Spot welding is a resistance welding process for joining metal sheets
by directly applying opposing forces with electrodes with pointed
tips. The current and the heat generation are
localized by the form of the electrodes. The weld nugget size is
usually defined by the electrode tip contact area.
Spot welding is the predominant joining process in automotive
industry for assembling the automobile bodies and large
components. It is also widely used for manufacturing of furniture
and domestic euipment etc.
Resistance Projection Welding
Projection welding is a resistance welding process for
joining metal components or sheets with embossments by directly
applying opposing forces with electrodes specially designed to fit
the shapes of the workpieces. The current and the heat
generation are localized by the shape of the workpieces either
with their natural shape or with specially designed projection. Large
deformation or collapse will occur in the projection part of the
workpieces implying high process/machine dynamics.
Projection welding is widely used in electrical, electronics,
automotive and construction industries, and manufacturing of sensors,
valves and pumps etc.
Resistance Seam Welding
Seam welding is a resistance welding process for joining metal
sheets in continuous, often leak tight, seam joints by directly
applying opposing forces with electrodes consisting of rotary
wheels. The current and the heat generation are localized by the
peripheral shapes of the electrode wheels.
Seam welding is mostly applied in manufacturing of containers,
radiators and heat exchangers etc.
Resistance Butt Welding
Butt welding is a resistance welding process for joining thick
metal plates or bars at the ends by directly applying opposing
forces with electrodes clamping the workpieces. A forging operation is
applied after the workpieces are heated up. Often no melt
occurs, thus a solid state weld can be obtained.
Butt welding is applied in manufacturing of wheel
rims, wire joints and railway track joints etc.
Cross wire welding is a resistance welding
process for joining bars or wires in cross joints by
directly applying opposing forces with usually flat electrodes. The
current and the heat generation are localized at the contact points
of the crossed bars or wires. Cross wire welding is widely used in
construction and electrical industry as well as for manufacturing of metal
wire nets and shopping trolleys etc.
Indirect welding is a special resistance
welding process where a single weld is made with one electrode
directly connecting to the weld zone, while the other
electrode is offset at a distance, but still conducts the
current along the workpiece.
Series welding is a special resistance
welding process where two welds are made at the same time with two
electrodes offset at a distance but still conducting the
current along the workpieces between the two welds.
Micro resistance welding refers to the
resistance welding processes for joining micro or
miniaturized components, which in principle can be any of the above
mentioned process variants but in a micro scale.
Parallel gap welding is a special micro
resistance welding process for joining thin foils or thin wires. The
two electrodes are configured in parallel, having a gap between them in
which insulation material is inserted. The weld is made with the
two parallel electrodes accessing the workpieces from the same
side.
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