American Welding Society Forum
We do welding on a Aluminium piston with two electrode E-1100 and EL-AlSi12 and prehit it up to 200 'C before welding but we observe that many porosity exist in weld.why? How we can solve this problem because we cant use GTAW on it.
as you probably know, Aluminium is very susceptible for porosity due to the behaviour of the self-protecting Aluminium-oxide layer.
This layer is often full of micro-cracks, wich can contain dirt/oil/water/etc. So cleaning is necessary.
Prior to welding, you should also grind the aluminium and weld it directly after grinding. The oxide layer is self-restoring when exposed to air or oxygen.
So watch out when you are pre-heating with a flame : you should regulate your burner to a neutral or reducing flame. An oxidising flame will restore the oxide-layer during pre-heating and will cause problems during welding.
If you have the torch available, use it for the welds. You can apply flux which will make the job easier.
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