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Old 06-24-2017, 04:11 PM
Rick Mullin Rick Mullin is offline
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Join Date: Mar 2012
Location: Malvern,PA
Posts: 157
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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.

Rick
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