38
Improving Global Quality of Life
Through Optimum Use and Innovation of Welding and Joining Technologies
The productivity in EB welding has been increased drastically by introducing several chambers for loading
and unloading of work pieces from a separate chamber that is evacuated before the work piece is transferred
into the welding chamber (
Figure 5.4
).
Recently, out-of-vacuum and reduced pressure EB welding has been further developed. Not only heavy
sections are EB-welded but thin sheet parts for the automotive industry e.g. an aluminium hollow section
is welded with 12 m/min in Non-Vacuum EB-system. Such a system is highly recommended when high weld
speeds and short cycle time are required from 1 up to 10 mm in thickness. There are test results showing
that welding speeds for Al and steel with t=1 mm of 60 m/min and 45 m/min respectively are possible to
achieve. EB welding applications will definitely increase thanks to the progress in technology. Currently
there are about 3,000 EB-installations in the world. 800 of these are in USA, 1,300 in Asia, 700 in Europe plus
200
in the former Soviet Union and 22 units installed in Sweden.
5.1.3
Laser beam welding
The laser beam welding process has long been used in various industrial sectors, including automobile, ship-
building and aerospace applications. These applications are driven by cost and weight efficiencies achieved
in the welded structures. Both CO
2
and Nd:YAG welding processes are capable of producing structural welds
with narrow weld and HAZ regions having high quality. Due to the rapid cooling, most structural C-Mn
steels respond with weld zones of high hardness, while austenitic steels provide welds without any hardness
increase.
Recent developments in high-power lasers and robotic control have accelerated the application of the LBW
process for car-body fabrication and assembly, for example through so-called “remote welding”. LBW has
the advantage of single-sided access, high welding speeds and precision while providing consistent weld
integrity and a low heat input which yields reduced distortion. Unlike conventional resistance spot welding,
laser spot welding (LSW) is a single-sided, non-contact process and as a result, LSW can be a very attractive
joining method for automotive mass production. Various factors need to be considered, however, when
replacing one joining method by another.
5.1.4
Laser hybrid welding
The number of laser welding and especially laser hybrid welding applications is growing fast. The laser
welding process is already common in the automotive industry. The most impressive installation with
150
YAG lasers on 4 kW each and one 1 kW at Volkswagen are connected to 250 welding and three cutting
heads. In this line production for the GOLF V, 70 meters are laser welded and brazed while there are only
7
meters of arc welds per car. With the further development and introduction of the laser hybrid process
(
Figure 5.5
),
the possible number of applications for construction will increase significantly.
Figure 5.4
EB welding system with loading
and unloading chambers linked to the
vacuum chamber for welding (Reproduced
courtesy: B. Pekkari)
Loading Evacuating Processing Venting Unloading
