Welding aluminum

Went by a guys shop I know with another friends outer muffler off his dirt bike, to get it welded. There were several aluminum fuel tanks in the shop getting repaired and new straps getting wrapped around where the tanks are mounted. He makes it look easy. His main welding machine is a Miller Dynasty 300. I thought it was only a 200. He runs it off a 30 amp breaker and can't believe how little power a 300 amp TIG machine uses. It uses less power than his Lincoln Square Wave 175 budget machine.

He does a lot of aluminum motorcycle and sled radiators. I know they are one of the trickiest things to repair. He said the vertical tubes are about the thickness of pop cans and with the Dynasty, he can form a puddle and do almost what ever he wants with it. He said it takes around 20 amps to weld them after he bends the cooling fins out of the way. What was rather neat was that he used all of his welding rods. When the rod got too short to hold, he'd leave it stuck to the weld, tack the next rod onto it with the TIG torch and then resume welding. Most guys would just throw the 2 or 3 inch stub away and get a new rod. Diesel fuel tanks are just rinsed with water but if he does gasoline tanks, he has them steamed out. He mostly just uses a wire brush in a drill or a belt sander to clean the aluminum for welding. Thought some people would be interested to know how an experienced welder does aluminum. Strangely enough, he doesn't have a welding ticket, but says TIG welding just seemed natural to him. He does some pretty impressive work that most welders can't do. He was quite busy earlier in the year building solid stainless steel replica hockey sticks for NHL teams to give as awards and retirement gifts. They are identical to the real stick but pretty heavy. He said goalie sticks are about 20 pounds. Dave

I bought a pack of the alum-alloy sticks you heat up/melt with propane. Fixed a thermostat housing that had a broken off tab. I had to re-drill the hole. That stuff is hard. Put it back on my 351 Ford engine and six years later no problem. I also repaired several storm doors and slider screen frames. That stuff is handy.

It is amazing how nice some guys can make an aluminum weld look. I have been welding since '79 doing mostly stick welding on storage tanks. I started welding in a shop at my current employer and we welded everything from aluminum to tantalum. I was getting pretty good at aluminum but we no longer have that shop and have mostly contractors doing the work. Now I rarely get to weld and am very much out of practice. You definitely have to keep your hand in it to stay good at it.
One of these days I'll get a better machine at home for doing aluminum repairs.

Dave you should have ask if you could try that machine!
I never had the opportunity to do any aluminum welding when working. So when I retired I made up my mind I was going to teach myself to weld aluminum. I had the Miller Gold Star for years, but it was old, and I was lucky enough to have run a Dynasty 300 for a few minutes, I just had to have one. So I bought one! Miller hit the nail right on the head with this Dynasty series! I'm not kidding the machine actually does the welding for you! At the time of these pictures I didn't know anything about aluminum welding. Not great, but not bad for someone who doesn't know what their doing! :wink:

I just got back from the Experimental Aircraft Association convention at Oshkosh. While there I attended a class on gas welding aluminum. I'm going to give it a try, since I don't have a TIG outfit. The instructors could gas weld a bead that puts any TIG-welded bead to shame.

Before we had T.I.G. and M.I.G. all our aluminum was welded with oxyaceteylene. Bare rod & powdered flux. just had to watch your puddle, when it got shiny, you'd better move or you'd have a MUCH larger hole. Really was pretty easy when we didn't know any other way to do it. We also used bare stick electrodes. Now, that'll teach you to keep your arc length the proper distance. LOL. Keith

I've seen some TIG aluminum welds that were done by hand that look like they were done by a robot. With the right person, I'd think the welds would be very similar since the difference is basically the source of heat. Inverter based welding machines like a Dynasty use a different tungsten for aluminum than a conventional machine and it's even ground to a point to give a very fine, pin point arc. Conventional TIG machines use a balled tungsten and the arc is much wider and not nearly as precise. Dave

What little Tig welding I ever did before buying the Dynasty 300 was stainless steel and mild steel. Very little aluminum on my Miller Gold Star. One could say I came from a red and green tungsten world. When I started learning how to use my Dynasty where green (pure) tungsten is not recommended I bought some Lanthanated (Blue) to weld aluminum, but found it couldn't take the heat as well as the Ceriated (orange)! I now use the Ceriated for both aluminum and mild steel. I really like the sharp point for doing aluminum, never did like the ball on the pure tungsten. With 1/8-inch Ceriated tungsten it will hold a sharp point with all 300-amps from my Dynasty.
It is amazing how much control you have of the arc with the Dynasty, just love the AC balance control / frequency. For thin aluminum where you want very little penetration turn it down to 20, for thick or fillet welds turn the balance up to 250. Amazing how Miller figured out how to do this! 8)

One of these days one of those unvented fuel tanks will get him....
Diesel and gasoline vapor have VERY similar LEL's. It will blow.

Rod

Yep. The only reason I don't read every other day about an explosion and death from someone cutting the top off of an oil drum is that they don't hardly sell metal oil drums anymore.

Who said they weren't vented? All the fittings and the fill cap are removed when he welds them. He's done hundreds of them. He even cuts good ends off of banged up tanks and welds them to a new shell. He fills them completely full of water and lets them sit for a while before he drains the water out. He said gasoline tanks are more dangerous than diesel tanks and although he has a done a few doesn't like them too much. Aluminum with TIG is a very fast and versatile process for an experienced welder. He welds cooling fins back on motorcycle engines and even has some old blocks to cut fins off of to weld on to damaged engines. Judging by his work, I'd say he knows what he's doing. Dave

You did...
Unless the tank is charged with CO2 or vented with a large volume of air, it's NOT vented.
He's incorrect in his assumption that a diesel tank is less dangerous.
Washing the tank may remove more diesel residue than you would normally get out of a gasoline tank but that's likely the only thing that's keeping him alive at this point.
Diesel vapor is for all intents and purposes equally explosive to gasoline vapor. I don't have the specs for LEL (lower explosive limit) in front of me right now... but the two are nearly identical.
He's been VERY lucky.

Rod

Considering how many diesel tanks he's done and never had the slightest problem, I'd say he kwows what he's talking about and what he's doing. Dave

I'd say you'll be attending another funeral someday.
The explosive limits of diesel and gasoline vapor are so close it's statistically insignificant... and the day he doesn't get it all out, it will blow.
A lot of people live with the myth that diesel won't explode and a lot are just plain lucky.

Rod

Perhaps if there is some fuel still in the tank, diesel is just as dangerous. I'd say that a guy thats made his living welding aluminum for the last 25 years or so, and probably welded over a thousand diesel fuel tanks, it's not just luck that he hasn't blown up. Dave

He might also use an industrial degreaser in the tanks as well. I never really got too involved asking him how he prepared them for welding. He did say he takes more precautions with gas tanks though. Dave

Diesel vapor.... Fumes... share a very similar LEL with gasoline fumes.
I know this because I've studied it a bit in regard to using gas monitors.
LEL or Lower Explosive Limit is the minimum number of hydrocarbons present required to sustain an explosion.
I'm reluctant to say the actual numbers because I forget them but what stuck in my head was that they are very VERY similar.
What that doesn't account for is how each one produces vapor in a tank. Gasoline is likely to retain more residue in the pores of the tank and produce more vapor... but diesel is still a big chance in my opinion. Gasoline can produce more vapor... but if diesel vapor is there it's equally dangerous.
I've welded LP tanks filled with water... and even after washing those tanks several times in hot water they are still releasing HC as you can see the sheen in the water. I did that once and never again.
Any tank work I ever do again will involve a charge of CO2 or high flow air to either provide an atmosphere that will not support combustion or an atmosphere that is dilute enough that the LEL is below the explosive limit. Anything less is taking a chance in my opinion.

Rod

That aluminum repair rod is great stuff. I welded legs back on aluminum patio furniture that had busted open from trapped water in the extrusions which frooze in the Winter.