aluminium in commercial vehicles - European Aluminium Association

118 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VIII
4. Plasma MIG welding
This process combines the high
melting capacity of the MIG
process with the nearly ideal
shape of the plasma arc and its
very good gas shield for the
welding pool. The result is an
extremely good quality of welds,
especially the absence of porosity.
The plasma arc is maintained
between the plasma ring nozzle
5. Laser welding
Laser welding of aluminium
alloys is developing rapidly parallel
with the development of ever
growing power of laser sources.
There are on one side CO lasers 2
of up to 20 KW and more and
Nd:YAG lasers of 6 KW and
more. With the CO laser, the ori-
2
entation of the beam is limited,
whereas with the Nd:YAG laser
optical fibres allow to bring the
laser beam directly to the weld
zone. This gives high flexibility
especially for robot welding. The
high reflectivity of aluminium
makes it necessary to install the
laser equipment in a separate
of the torch and the work piece,
the MIG arc is in the centre of
the plasma arc. Both arcs have
the same polarity where the high
kinetic energy of the plasma arc
destroys the oxide layer on the
work piece. Mechanical removal
of the oxide layer can be dispensed
with.
room, where during operation of
the equipment, nobody without
adequate eye protection has
access. The sensor which emits
the signals necessary for the
motion control of the laser beam
must be very effective for not
being disturbed by reflections.
The process is mainly used for
thin gauge materials (1 – 4 mm)
and the pieces to be joined must
fit perfectly as is the case e.g. in
the production of tailored blanks
for the car industry.
The process is well suited for
applications with high requirements
for tightness and surface
aspect. It is possible to carry out
butt welds of up to 10 mm thickness
in one pass with the edge
preparation in V. The welding
speed is higher than for MIG
welding.
The achievable welding speeds
are up to 12m/min with thickness
of around 1mm and still
1-3 m/min with thicknesses
between 1.5 and 3 mm.
Compared with standard arc
welding, laser welding allows the
production of components with
reduced geometrical distortions
and residual stresses, as well as
narrower heat affected zone, a
direct consequence of the high
work speed and thus the low
heat input.
The laser welding process is
preferably used with filler wire
for aluminium alloys.