Welding aluminium is a challenge even for the most experienced of welders.
Aluminium has a natural tough oxide layer which protects the metal but unfortunately acts as a barrier for both welding and brazing. Furthermore, aluminium is a great conductor of heat: when the ideal temperature for welding is reached in a particular area on the metal, the heat travels down the metal resulting in blow-holes and preheating of un-welded sections. To counteract this, the metal has to be welded at increasing speeds to keep up with the effect of the conduction of heat; this is known as ‘running away’.
To weld aluminium, the first thing to know is the grade of that particular piece of metal. Grades 1000, 3000, 4000, 5000 and 6000 can be welded however grades 2000 and above 6000 are almost impossible to weld without a much softer filler wire, which lowers the properties of the original material. Once the grade is determined the best process for the job must be decided: either:- laser, Tig or Mig.