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  #11  
Old 06-19-2017, 07:48 AM
elavir elavir is offline
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OK, I guess the flux was too thick, next time I make it more milky like.

Cheers Richard.
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Old 06-19-2017, 12:02 PM
bobadame bobadame is offline
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I wonder if this back fluxing/TIG welding method has any effect on the ductility of the weld.
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  #13  
Old 06-19-2017, 03:31 PM
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The machine should be set on AC...not DC

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Old 06-23-2017, 04:15 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by bobadame View Post
I wonder if this back fluxing/TIG welding method has any effect on the ductility of the weld.
Doubtful that it would / does.
Flux chemistry would not indicate such an occurrence.
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Old 06-23-2017, 04:50 PM
bobadame bobadame is offline
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I don't understand why an oxy acetylene weld is more ductile than a tig weld. (?)
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Old 06-23-2017, 06:32 PM
crystallographic crystallographic is offline
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I don't understand why an oxy acetylene weld is more ductile than a tig weld. (?)
HAZ ++
vs
HAZ--

... and, the filler many TIGboys often choose is that hard, brittle, non-anodizing 4043.
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Old 06-23-2017, 09:09 PM
bobadame bobadame is offline
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Ok, thanks Kent.
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  #18  
Old 06-24-2017, 03:04 AM
elavir elavir is offline
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Originally Posted by crystallographic View Post
Glad to help, Ben.
Aside from the solid smooth penetration there is also the increased weld density. For doing tank welding there will be fewer leaks - something that has plagued the tig forever, and at the highest welding levels.
Hi Kent, these leaks with TIG welding aluminum, is this more relevant to the TIG welding process( eg weld density) or to poor penetration?
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Old 06-24-2017, 09:11 AM
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Hi Kent, these leaks with TIG welding aluminum, is this more relevant to the TIG welding process( eg weld density) or to poor penetration?
Leaks happen in clean-room environments, with excellent back purge, and cameras inside the tanks, as I learned from the guys who build Kenworth and Peterbilt tanks. Perfect appearing TIG welds, inside and out - leak - because of weld density issues. Welds are sliced open along their lengths, and voila! - porosity inside the weld, invisible from outside.

It's a problem that the most expensive tig machines are only just now starting to overcome.
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  #20  
Old 06-24-2017, 04:11 PM
Rick Mullin Rick Mullin is online now
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I would agree with Kent about the density.

When I build an aluminum vessel using TIG, be it for fuel or water, I always double weld. I will first make a proper pass using thin wire and then go back and puddle the weld quickly. It sounds like a lot of work but it happens quickly. The puddle pass is lower current. I find that despite the amount of prep and what appears to be a beautiful weld, there is always a bit of porosity that comes to the surface here and there on the puddle pass. I leak test the tank before the second pass. It is very rare that there is a problem but if there is porosity at all, I figure it can potentially become a leak. I am funny about having to repair a leak later when there has been fluid (especially fuel) in the tank. Repairing a contaminated spot is never a good idea.

Seldom do I have porosity when welding with 1100 wire on 1100 or 3003 sheet metal. 1100 was not the correct wire for the alloy of the tanks I have built so I was using the harder wire as Kent has mentioned (4043 or 5356). I do not know if it would yield a better result if it were done in a chamber or back purged as I have never tried that. Generally my penetration is not an issue although admittedly I often back weld as a precaution on new panels.

I am looking into a new inverter welder from Miller as my machine is an old Syncrowave. I will be taking one for a test drive at the local distributor with the aid of a welding rep. The claims regarding penetration and HAZ are miraculous. Perhaps the back fluxing is the easier and less expensive route.

I have been meaning to try TIG welding with a flux backing. I have Allstate flux that is getting old so it may not be a fair trial. I need to order some of the TM flux. Never seems to be enough time to do all that I would like.

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