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• very carefully grind the area to
be welded to remove all traces of
paint and various residues,
• carefully degrease with suitable
agent
4. MIG and TIG weld repairs
Welding of silo body (Feldbinder)
160
ALUMINIUM IN COMMERCIAL VEHICULES CHAPTER VIII WELDING 160 | 161
4.3. Welding
The rules for repairing are basically
as described in Chapter VII
for forming and as described in
this chapter for welding. When
carrying out repairs it is essential
to:
• hold the components, e.g.
tank, chassis etc., securely in
their relative positions. Clamps
should be adjusted to allow
expansion however, as too much
restriction could aggravate the
adverse effects of contraction. It
is also useful to mark areas of the
structure likely to suffer maximum
stress, referring to the
manufacturer's design calculations
if these are available,
• support built-up parts to control
clearances,
• pay particular attention to the
weld direction. The purpose of
this is to limit deformation and
minimize the risk of hot cracking.
Volume contraction in the weld
bead is approximately 6 %
between the fluid state and the
solid state at ambient temperature.
It is this phenomenon
which causes the risk of cracking,
• change the path of welds in
order to avoid going back over an
original weld (Figure VIII.7),
• perform any necessary tests, e.g.
radiography, dye penetration etc.,
• chose the right welding
process (TIG or MIG). TIG welding
is preferable for minor repairs
where access from behind is not
possible as it is easier to use and
allows better penetration control
than MIG welding.
Compact TIG welding machines
weighing less than 20 kg are
now available on the market
capable of delivering a welding
current of around 160 A. These
machines are easy to carry and
are ideal for small, localized
repairs.
For minor repairs such as a
breach in the skin of a tank, the
patch must be perfectly matched
to the shape of the breach but
should be slightly enlarged by
hammering to compensate for
contraction following welding.
Without this precaution the
residual stress might well cause
systematic cracking. This phenomenon
is more pronounced
the smaller the patch.
WELD REPAIR
FIGURE VIII.4

New weld
161
ACKNOWLEDGEMENTS
Main writers: Jürg Zehnder, Reinhard Pritzlaff, Steinar Lundberg, Bernard Gilmont.
Project team: Asmund Broli, Roald Pedersen, Benoît Lancrenon, Michele Triboldi,
Dietrich Wieser, Ralf Balduck, Klaus Vieregge.
Sponsoring companies: Alcan Engineered Products, Alcoa Europe, Aleris Europe, AMAG,
Elval, Hydro Aluminium, Metra, Novelis, Sapa
The project team is particularly grateful to Alcan Engineered Products for having
authorized to use some texts, tables and figures coming from the following
publications:
• Aluminium in Commercial Vehicles, Pechiney-Rhenalu
• Aluminium and the Sea, Alcan Aerospace, Transportation and Industry
PHOTO AND TABLE CREDITS
Document produced by
European Aluminium Association AISBL
Avenue de Broqueville, 12
BE - 1150 Brussels - Belgium
Telephone: +32 2 775 63 40
Fax: +32 2 775 63 43
www.aluminium.org
Under the Direction of Bernard Gilmont
Designed: Marc Hernu, Plage
Coordination: Pierre Jouhaud, PLJ édition-communication
1 Benalu Benalu
4 Menci EAA library
6, 8 Airbus Airbus
9 Hydro Aluminium Hydro Aluminium
9 Babcock Babcock
10 Alstom, SNCF Alstom, SNCF
11 Mercedes
11 Hydro Aluminium Hydro Aluminium
12 Aluminium-Verlag Aluminium-Verlag
12 Alusuisse Alcan Engineered Products
12 Trailor Trailor
16 Benalu Benalu
17 Tang Fahrzeugbau GmbH Tang Fahrzeugbau GmbH
19 All American Marine All American Marine
20, 36 Stas Stas, IRTE
21 Alcan, Alcoa, Brabant Alucast Alcan, Alcoa, Bernard Gilmont
23 Alcan Engineered Products Alcan Engineered Products
24 Galloo Recycling Bernard Gilmont
25 ATM, PVC Transports Patrick Van Crombrugghe
26 Menci Bernard Gilmont
26 Alcoa Wheel Products Europe Alcoa Wheel Products Europe
27 Benalu Benalu
28 Pezzaioli Pezzaioli
30 Alcoa Europe Alcoa Europe
31 Stas Stas
32 Benalu Benalu
33 Leciñena Leciñena
34 Menci Menci
37 Schrader Schrader
40, 43 Alcan Engineered Products Alcan Engineered Products
44, 45, 47 Various aluminium plants EAA library
48 Menci Bernard Gilmont
　
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