TIG question on Al

[arftist]

Jose, thankyou for your exellent explantion of tungsten selection.

[Rutterbush]

Everyone has great input about welding aluminum. I'm gonna stir the cooking pot just a little more. Can never have too many chefs.

Grinding aluminum and power brushing aluminum look as if it gets it super clean just like steel, but there's a catch. As soon as the grinding disc or wire wheel clean the surface the oxide rapidly reforms faster and slightly thicker than normal due to the air turbulence created by the rotating wheel. Only a hand held wire brush should be used. The brush should be pushed or pulled in only one direction just like using a file. The reason being not to drag particles of oxides back into the weld area. This information was passed to me by two of AlcoTecs field technicians who helped me when I started the boat propeller repair business. Called them up and they drove down to my shop and worked closely with me welding cast aluminum propellers.

Castings are full of hydrocarbons in the porous areas between the grain. Just like any gases they tend to expand when heated. Doesn't matter how clean you think you got it. It has oxide and hydrocarbon working against you. A crack that can't be hand brushed or filed is a nasty waiting to happen. I understand that what you're working with is not a crack,

One reason that your weld bead won't fuse with the metal is as stated earlier, there's oxide or hydrocarbon built up on the edge. Sorta like cleaning the weld area then painting over it to get ready to weld. Ain't gonna happen.

The idea is to clean it so that oxygen will hopefully not mix too rapidly, hand brush or file.

Use as large a cup as possible and have a low steady flow of pure argon, a small cup and high pressure will start a venturi affect and suck air into the weld area. a #8 cup and 25 to 35 cfh.

Keep the end of the tungsten a maximum of 1/8" above the puddle. Doesn't matter if it's balled or pointy (technical term).

Yes, you do need the higher starting heat, but back off asap or preheat and weld. Weld with the lowest weldable heat. Just like any other metal too much heat does strange things to the grain.

Another thought is since aluminum is red short (won't support itself at high heat) use a piece of stainless steel to support the weld area. Keeps it from falling through, keeps it flat on the back side and won't weld together. Don't use copper. Copper particles will alloy with the aluminum. Not good.

One final note. Never pull the filler wire out of the argon shielding gas. It only takes a split second to oxidize the hot end of the wire, then put it back into the puddle.

I hope you've got it finished by now and can tell me how full of it I am.

Of course, I'd mig weld that sucker and be done with it. ;0)

[Tigman]

Might want to try 75 % Helium and 25 % argon for welding on thick nasty castings! 20 years welding cylinder heads and intake manifolds in winston cup shops.

[arftist]

Tigman, I've used pure helium, care to elaborate on the properties/benefits of the 75/25 mix? Thankyou.

[HWooldridge]

I bought some 4043 rod, a couple of 3/32" pure tungsten electrodes and a 1/2" gas lens then cranked the argon flow to 25 CFH. The welding got much easier but was still pockmarked by areas that simply would not weld together. I assume this trouble was because this repair was a casting and likely oil soaked. However, by stopping to sandblast periodically, I was able to finish the job. I also welded a piece of material across the ends of the broken fragments so they are all joined by a homogenous piece. After milling away the excess, the piece looked fresh from the factory. The maintenance guys at the plant were suitably impressed (especially since none of them were willing to fix it).

Thanks to all who answered, this forum is a real blessing to all of us who participate and contribute.