Page 59 - Welding of Aluminium and its Alloys

50 The welding of aluminium and its alloys

• The pure aluminium 1XXX alloys are very soft and wire feeding prob-
lems can be experienced.
• Low magnesium (<2%) 5XXX alloys such as 5251 may suffer hot crack-
ing if matching composition fillers are used. Use Al-Mg5 type instead.
• When welding the 7XXX alloys 5039 filler metal may give more effec-
tive age hardening in low-dilution applications.
• 6XXX alloys exhibit solidification cracking if welded autogenously.
• Titanium and zirconium are sometimes added to filler metals to reduce
the risk of weld metal hot cracking by means of grain refinement.
• 4047 may be used to prevent weld metal cracking in joints involving high
dilution or restraint but remember the first point above.
• The 2XXX series of copper containing alloys were generally regarded
as unweldable until the higher (>4%) copper alloys such as 2219 became
available. If it is necessary to weld the lower copper-containing alloys
then 4047 is the best choice as a filler metal.