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AGA CW Handbook A4_32130-UK
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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 low- temperature 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 four- digit designation system specified in the standard, sfs-en 573-1. the standard is identical to the international designation system recom- mendation 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 alu- minium alloys, which must be taken into consideration when selecting the materials for a designed structure. with regard to choosing the shielding gas, there are no differences be- tween 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. aluminium shielding gases. 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). 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
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