Help, I forgot how to weld aluminum

[donpearsall]

I am fabicating an aluminum tank for my bike and for reasons unknown, I can no longer weld aluminum. I blame the machine! It is a Lincoln precision TIG 185. I am running pure argon with a 1/16" 2% ceriated tungsten. The material is 6061 16 gauge.

For the life of me, I cannot get the puddles to join even when they are touching. No matter what settings I try, hot or cold, the two pieces, including the rod (4043 I think), do not flow into the puddles. The pieces end up melting from the built up heat trying to get them to join.

I have reviewed my settings over and over and am out of ideas. Any suggestions besides taking the parts to a real welder?
Thanks
Don

[jl222]

I am fabicating an aluminum tank for my bike and for reasons unknown, I can no longer weld aluminum. I blame the machine! It is a Lincoln precision TIG 185. I am running pure argon with a 1/16" 2% ceriated tungsten. The material is 6061 16 gauge.

For the life of me, I cannot get the puddles to join even when they are touching. No matter what settings I try, hot or cold, the two pieces, including the rod (4043 I think), do not flow into the puddles. The pieces end up melting from the built up heat trying to get them to join.

I have reviewed my settings over and over and am out of ideas. Any suggestions besides taking the parts to a real welder?
Thanks
Don

 I'am no expert welder but aluminum has to be super clean. Try brushing with a stainless steel brush used only on aluminum if you haven't.

                        JL222

[WhizzbangK.C.]

You probably already know all this, but here's my take on it anyway, LOL.

 From the picture it looks to me like there's too much oxidation on the material. You need to really clean it off good. I can see that you've wire brushed it, but if it's been setting around a while the oxide layer might be thicker than you think. I've had to take sand paper to the sheet a few times when I had welds act like that. I prefer to use the black zirconium grit to remove the layer, since most of the other sand papers are actually made of aluminum oxide abrasive, which is what you're trying to get rid of. Scotch Brite pads also work pretty well. Make sure that you get the oxide off your filler rod also if it's been setting around for a while, a couple of passes through a Scotch Brite works wonders. Don't forget to wipe it down with a clean towel and acetone just before welding to remove any oil and particles too.

The aluminum oxide layer on top of the metal actually has a much higher melt point than the base metal, and will stay solid after the base melts. The dead give away to this is when your puddle looks like it's got a dull gray wrinkled "skin" on it as it slumps away.

[Peter Jack]

Use a stainless brush that's never been used for anything except aluminum to do the cleaning. Abrasive papers can embed contaminants into the base material. Use a final wipe with acetone right before you start to weld. The acetone will disappear almost immediately. Wipe the filler rod with acetone as well.

I normally use tungsten with zirconium, but if your machine is one of the newer technologies the ceriated should work just fine.

Make sure your gas is turned on and the flow should be in the range of 18 / 20.

Make sure the high frequency is on continuous and the current is on AC.

Go for it and good luck!

Pete

[Peter Jack]

Just to add to what I just posted about welding aluminum. Wear a long sleeved shirt with a t-shirt underneath. The long sleeves protect your arms and the t-shirt prevents the nasty v shaped sunburn you get on the front of your neck / upper chest. You don't need the pain of the nasty sunburn you can get from tig welding which may be a good starting point for skin cancer.

My own humble opinion is that all of these chopper and car customizing TV shows that demonstrate most of the unsafe practices available and show them as standard operating procedure should be removed from the air until they can at least demonstrate safe practices. End of Rant!!!

Pete

[Rex Schimmer]

Don,
You cannot be clean enough, everything that Peter and Whizzbang said about cleaning the weld is double true!. Also do not hold the tungsten to close to the weld and if you touch the puddle with the tungsten you need to stop and regrind it. Once it is contaminated from touching the puddle it is straight down hill from there. One of the most difficult welds to make is a 90 degree edge weld like you are trying to do, if you must do it this way make sure the power is just enough to make the weld. I would suggest that you make or buy some tee dollies and then take each side of the tank and radius them over the tee dolly, this will make your weld a but weld which will be much easier and it gives the tank nice radiused corners too.

First and foremost keep it clean!!!


Rex

[octane]

Don, I was given a TON of brilliant advise here:

Any experienced aluminum weldors out there ?

Worth a look !

[Blue]

OK, this reply may get me a bit of trouble with welders who can perform magical feats on impossible joints.

Joint design is the most important thing even before cleaning and back purge.  Never, ever, EVER design a welded joint where the bead pulls away material from both sides of the joint.  If we do, the joint decreases in strength and ability to flow the puddle as the puddle gets bigger.  The opposite should be true.  A joint like this is common and absolutely designed to fail.  If too much heat is used, the bead falls away from one side or both and the gap increases faster than the size of the bead required to span the gap can be created.  If too little is used, the weld bead may look like a stack of dimes, but there's no penetration and the stress concentration at the edges of the bead will lead to cracks in service.

Overlap the joint. Even better, provide a sacrificial feature in the joint that, when melted, becomes the bead.  This is called weld prep joint design.  On a right angle, this means making one part longer by ~1-2X thickness so that the bead melts into position instead of away from it.

Even better than that, don't do outside corner welds.  Bend the material, overlap it with the next face, and do the welds on the flat.

Lack of back purge and proper atmosphere isolation will also create an oxide "skin" on the puddle that prevents any chance of flow.  It needs to be shiny on the back, not just the front.  Welders will hate me for letting this secret out, but anyone worth his helmet has welded an aluminum repair on an oil tank under pathetically contaminated conditions by adding a bead on top of one side of a crack and merging it with material on the other side.  Lesson: material on top of the joint is more important than cleanliness.

Show me a hard to weld joint and I'll show you a joint the welder should have re-designed.

(sorry, this is a real peeve of mine in manufacturing)

[saltfever]

Blue, I agree that joint design is critical. These are quite common edge joints. Is it your opinion they should be re-designed?

[jww36]

Alot of technical talk that I'm not aware of. I'm just a self taught fabricator and I'll tell you what works for me. If you have access to the back side of that 90 degree joint, use a 1" x 1" piece of STEEL or better yet, Stainless Steel angle for tacking only. This does two things. First, it acts as a heat sink during tacking the two pieces. It also allows you to clamp the pieces of aluminum together. If you have the two pieces of aluminum tight together, i.e. touching one another, they almost fuse themselves together with just a small amount of rod.
Good luck,
John

[donpearsall]

Thanks for all the tips everyone. Maybe it is not the machine that is the problem, but ME? Imagine that. I have learned a lot from the help.
Don

[willieworld]

one of the most common mistakes switching to aluminum after welding steel is forgetting to turn up the argon --i run the ball at 10 for steel and 20 for aluminum             willie buchta

[jl222]

Blue, I agree that joint design is critical. These are quite common edge joints. It is your opinion they should be re-designed?

      Saltfever....the air and water tanks on our Procharger intercooler are shaped from one piece of metal, miminizing welded joints.
I've also noticed other intercoolers with added straps or another piece of metal on top of butted welds.

                  JL222

[Blue]

Blue, I agree that joint design is critical. These are quite common edge joints. Is it your opinion they should be re-designed?

Actually, yes.  Every single joint on the end of a box that can be replaced by bending a sheet metal box instead of welding every corner should be.  Either the end cap should be one piece (eliminating two, 2" welds) or the end box should have bent sides (eliminating both long welds and putting the two face welds in shear) and the whole end cap should overlap the cooler to create overlap joint.  Corner welds should be avoided; period.  Pretty? No.  Stronger and less reliant on welder skill? Yes.

A weld that looks like a stack of dimes does not indicate a lack of stress concentration.  Corner welds focus stress even with good joint design.  Two of the welds shown show good overlap or lots of rod was used, one is a fillet weld, and the forth shows rework from the weld pulling away from the joint.  Better design would have been formed corners and overlap welds on the flat.  We can't see the backside of the welds, so we can't judge penetration or backside oxidation, both of which are common for corner welds.  Overlap welds are less critical to these effects.

I once worked for a guy who could weld absolutely any aluminum joint no matter how bad the situation or design.  Because of his torch skill, he tended to make terrible joints in highly stressed corners.  His welds were beautiful.  Every single one failed in service;  sometimes in minutes.

Let's see pictures after it has been in service for 100 to 5,000 hours.  We have a saying in aviation: if it can't last forever, you can't bet your life on it for a minute.

One last note: it is actually illegal on aircraft to have a weld in tension (i.e. an inside corner of a pressure vessel or cooler).  It's done all of the time, but it's still illegal.  Welds should only be used in shear, tension joints should be avoided if at all possible.  This is what leads to many coolers like the one pictured using straps over the joints to allow shear stress from the strap to strengthen the tension and bending weld joints on the cooler ends.  "Common" and "accepted" does not mean "good" practice.  We can do better.

[blackslax]

Blue, I agree that joint design is critical. These are quite common edge joints. Is it your opinion they should be re-designed?

Actually, yes.  Every single joint on the end of a box that can be replaced by bending a sheet metal box instead of welding every corner should be.  Either the end cap should be one piece (eliminating two, 2" welds) or the end box should have bent sides (eliminating both long welds and putting the two face welds in shear) and the whole end cap should overlap the cooler to create overlap joint.  Corner welds should be avoided; period.  Pretty? No.  Stronger and less reliant on welder skill? Yes.

A weld that looks like a stack of dimes does not indicate a lack of stress concentration.  Corner welds focus stress even with good joint design.  Two of the welds shown show good overlap or lots of rod was used, one is a fillet weld, and the forth shows rework from the weld pulling away from the joint.  Better design would have been formed corners and overlap welds on the flat.  We can't see the backside of the welds, so we can't judge penetration or backside oxidation, both of which are common for corner welds.  Overlap welds are less critical to these effects.

I once worked for a guy who could weld absolutely any aluminum joint no matter how bad the situation or design.  Because of his torch skill, he tended to make terrible joints in highly stressed corners.  His welds were beautiful.  Every single one failed in service;  sometimes in minutes.

Let's see pictures after it has been in service for 100 to 5,000 hours.  We have a saying in aviation: if it can't last forever, you can't bet your life on it for a minute.

One last note: it is actually illegal on aircraft to have a weld in tension (i.e. an inside corner of a pressure vessel or cooler).  It's done all of the time, but it's still illegal.  Welds should only be used in shear, tension joints should be avoided if at all possible.  This is what leads to many coolers like the one pictured using straps over the joints to allow shear stress from the strap to strengthen the tension and bending weld joints on the cooler ends.  "Common" and "accepted" does not mean "good" practice.  We can do better.

BLUE,

You know a lot of words.....
 and they are are all worth heading.