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  #11  
Old 11-12-2022, 08:03 AM
sandmanred sandmanred is offline
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The heat of tig welding should anneal the weld line for 1100, 3003 and 5052 alloys. Annealing again after initial planishing should help as well. I've found that 1100 filler doesn't harden up so much as 5356 so I use it where I can
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  #12  
Old 11-13-2022, 12:40 AM
steve.murphy steve.murphy is offline
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Thanks Jeff. I saw a YouTube video recently where the guy said he runs the tig along the backside of his weld joints which helps with the cracking. I think it was cornfield customs.
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  #13  
Old 11-13-2022, 09:44 PM
sandmanred sandmanred is offline
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I agree. There's usually some deep grooves on the backside that could initiate cracking. I try to wash over the back and add filler if needed whenever I can reach the backside of the weld.
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  #14  
Old 11-18-2022, 07:21 PM
billfunk29 billfunk29 is offline
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Default Alum cracking

Back purge with argon if you can. Nice smooth back bead. Or gas weld, if you can tolerate the flux.
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  #15  
Old 11-20-2022, 05:29 AM
crystallographic crystallographic is offline
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It's been generally accepted by (US) aluminum auto/racing/aviation fabricators that tig welding aluminum needs back purge to achieve 100% penetration.
(I have spoken to the tank builders for the KW, Pete, Bulldog, etc over-road freight trucks ..... who were tigging ... cleanroom environs .... backpurge .... cameras inside tanks .... getting leaks constantly ..... another story...)

All that aside, the aluminum tank fabricators (drag/salt/Indy) gas weld the tanks with O/H or O/A, and not usually leak-testing them.

So...a story from a few years back:
I was trading yarns about metalworking with a drag-car owner/builder/driver and he told me a story from his previous season, and a gas-welded aluminum tank -
It was mounted in a tube-cage at the rear of the car, pressurized by the blower.... no fuel pump on the car.
During one race the blower sneezed and so they pushed the car back to the pits, pulled the bodywork off the rear, exposing the tank for pulling and inspecting......
The tank had puffed up a Lot, swelling so much that it quilted through the bars of the cage, making it impossible to extract without cutting the 4130 steel tubing.
So they leak-tested the tank in place - at 14psi - no leaks - and ran it "as is" for the rest of the season.

("if you can tolerate the flux")

- end -
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Last edited by crystallographic; 11-20-2022 at 05:34 AM.
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  #16  
Old 11-20-2022, 08:02 AM
DavidB DavidB is offline
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Quote:
if you can tolerate the flux
Not sure if that's supposed to indicate the flux remaining may be an issue but my experience with aluminium welding with OA here in the UK is that the flux is so deliquescent that after welding I would go away for half an hour or so and when I came back the flux had absorbed so much water from the atmosphere it had dissolved and run off the part so just rinsed and done.
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  #17  
Old 11-20-2022, 11:01 AM
crystallographic crystallographic is offline
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Quote:
Originally Posted by DavidB View Post
Not sure if that's supposed to indicate the flux remaining may be an issue but my experience with aluminium welding with OA here in the UK is that the flux is so deliquescent that after welding I would go away for half an hour or so and when I came back the flux had absorbed so much water from the atmosphere it had dissolved and run off the part so just rinsed and done.
... or hygroscopic ...
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