AGA-CW-Handbook-A432130-UK

36 Aluminium shielding gases
Aluminium shielding gases.
eral
8.2 Choosing the shielding gas for aluminium
Selection table
8.1 General
Aluminium and aluminium alloys are structural materials with many good
properties, for example lightness, low sensitivity to corrosion, good
machinability, good thermal and electrical conductivity and good lowtemperature
properties.
Due to this, aluminium is used more and more in welded structures and
new applications are found all the time.
Pure aluminium has relatively meagre mechanical characteristics, and it is
hardly used at all in load-bearing structures.
Its strength is improved through alloying and various heat treatments.
The most common aluminium alloys are:
Al-Cu, Al-Mn, Al-Si, Al-Mg, Al-Si-Mg and Al-Zn.
There are several classification systems for aluminium; probably the most
well known is the numerical classification of the Aluminium Association
(AA).
In Finland, wrought aluminium alloys are classified according to the fourdigit
designation system specified in the standard, SFS-EN 573-1.
The standard is identical to the international designation system recommendation
published by the Aluminium Association, USA.
See the table below for some common applications and the weldability of
different aluminium alloys with gas arc methods.
The weldability of pure aluminium is very good.
However, there are large differences in the weldability of different aluminium
alloys, which must be taken into consideration when selecting the
materials for a designed structure.
Structures welded from aluminium may be very large.
Pictured: the world’s largest aluminium catamaran being built at the dockyard of
Finnyards Oy (currently STX Europe).
With regard to choosing the shielding gas, there are no differences between
the classifications.
With aluminium in particular, retaining the purity of the shielding gas all
the way to the welding spot is emphasised.
Even a small amount of moisture entering the molten pool causes porosity
in the weld.
SFS-EN 573-1 Main alloys Example SFS-EN 573-1 Weldability Typical Applivations
1XXX Unalloyed (Al ≥ 99.0%) EN AW-1200 Very good Bus bars, decorative trims, kettles
2XXX Copper EN AW-2011 Possible, not recommended Aircraft industry
3XXX Manganese EN AW-3003 Good General applications, trims
4XXX Silicon EN AW-4045 Good Welding filler materials
5XXX Magnesium EN AW-5005 Good Boats, ships, tank structures, rolling stock
6XXX Magnesium and silicon EN AW-6060 Good Decorative and flashing strips, doors, windows
7XXX Zinc EN AW-7020 Possible, not recommended Aircraft industry, rolling stock
8XXX
Other alloys