Hi, could anyone tell me how sucessful it would be to use a mig with alloy wire to weld cast alloy cases off a motorcycle. I have been told that it is near imposible to weld as the cases are made of "the old style" alloy used in the 1950's.
It does depend on what the cases are made from. Could be a standard aluminium/magnesium alloy which should be possible with MIG using aluminium wire. The casings could be zinc based which would need TIG or gas welding (and are trickier). They could even be Nickel based.
Does anyone know how to identify the metal?
One possibility - with a bit of practice you might try easyweld which is like brazing for non-ferrous metals and is applied with a blowtorch.
I have tried similar to easyweld - it is a solder of sorts used to join high voltage cables made of aluminium. It is as the box says 2/3 alloy 1/3 tin it takes to the cases but is a different colour (if that makes sense). As I wish to polish the cases it stands out comes out a bit brighter than the parent alloy. Another maybe silly??? question is if you had a "bath" and filled it with argon (heavier than air) could you use a electric arc welder on the lowest setting with alloy rods to weld?
That sounds like a difficult approach, but assuming you could completely purge the air from the bath, and you could find aluminium rod for a stick welder then I can't see why not.
If it is an aluminium based alloy then you might try MIG with argon shielding. A pure aluminium wire would be reasonably close. No harm giving it a try somewhere where it won't be visible and see if it takes (unless of course the casing turns out to be made from pure Magnesium which is unlikely).
As Malcolm said, its all down to the volume of zinc in the alloy. If its die cast (like a toy car) its neigh on impossible to beld, it just turns to jelly and ends up a big dollop of mess!
If you try the ally rod route, why would you need a 'bath of argon' ?