Welding Aluminium box. Help!

[julianthegypsy]

I have a project where I want to basically chop up box section ali and weld a plate on each end but I've done nothing with ali and don't know what is possible. I have an a/c arc welder and a mig welder but don't have tig. The mig is pretty old, but sound, 3 phase fronius. The box will be 3mm and 5mm. I also have oxy, but know enough not to even think about trying to go near it with that. All advice welcome. Oh, and the other important bit, the welds must be waterproof haha.
Many thanks in advance.

 

[FranV8]

Hmm, well the arc won't do it. The MIG can with the right liner and ally wire, although I think it can be frustrating - I've never tried. A spool gun is best for it to prevent bird-nesting.

Gas, I think it can be done, and I think it is mentioned in the Performance Welding Handbook, I'll have a look later perhaps.

I've done it with TIG, as that's the machine I have - do you have to do much? can you find a friend/local college who can do it for you or at least allow you use of the equipment?

Out of interest, how thick will the plate be? I had fun welding 3mm ally channel to 5mm strip in a similar manner, you need to be careful if you're welding a thinner section to a thicker base/plate, it can be a bit frustrating, albeit not impossible though.

 

[julianthegypsy]

Thanks. I have two jobs, one will be a 5mm plate filling in the end of a 3mm box and the other a 5mm plate on a 5mm box. It doesn't need to be particularly strong, it's a water jacket, hence the waterproof requirement, but it's not under pressure either, it's in a vented system. I did wonder whether it might be possible to bronze weld it or even glue it with something strong.

 

[pedrobedro]

You can gas weld aluminium with the correct flux but you could also silver solder it which is strong and watertight and only needs a propane torch.

 

[julianthegypsy]

You can gas weld aluminium with the correct flux but you could also silver solder it which is strong and watertight and only needs a propane torch.

Thanks, I knew it was possible to gas weld it, but I also know how hard it is, and that the chances of me doing a smart enough job to give it to a customer are slim to fag paper thin. I hadn't thought of silver solder, that sounds like a good solution. Presumably, if I drilled a hole though it and wanted to run a steel tube into it that would also work for fixing the pipe in place? Or would I just melt everything?