Tig welding aluminum 6061

[Charley Davidson]

I have a project at my new job that is a big billet block of 6061, it's 2 halves that get bolted together then welded to keep anyone from reverse engineering the part. I have a Syncrowave 350 LX at my disposal for the job. I have never tigged aluminum but have about 5 or 6 days to practice and get up to speed, if I don't feel I can pull it off I'll have a friend do it but would like to do it myself. It will earn me a little more respect at my job with the higher ups. I have plenty of big billet scrap to practice with.

The parts are machined mating surfaces so will be a perfect fit, can they be fusion welded or do I need to use filler rod? Should they be chamfered if so how much? Please give me as much info as you can on this that will get me rolling.

 

[Dr Crankenstein]

If the weld isn't critical, a fusion weld should do. No chamfer, no filler rod. I think it's a good idea to learn how to fusion weld first anyhow. Get a handle on torch control, puddle manipulation, and heat settings before introducing filler rod. When you reach the point where you can run a decent bead, then step up to fillet welds.

How big are the blocks? If you have too much mass, it can be difficult to start a puddle. If that's the case, you might have to preheat the parts.

Keep asking questions if this doesn't get you going.

 

[Charley Davidson]

Parts are about 15" square and about 8" thick assembled the welder is 350 amps.

 

[RPM]

That will most likely have to be preheated. Being these parts are machined, make certain that there is no cutting oil between the parts as the heat will draw it right into the weld area. I find the little scotch brite pads that look like a cookie are great for cleaning before welding on aluminum.

 

[Dr Crankenstein]

Wow, that's some heavy metal. I've been welding aluminum for 15 years, but never something that heavy with a TIG machine.

With that in mind, I would be forced to experiment. Wind that 350 up, see if it will dig a crater in the joint and start a puddle. Starting at an edge or corner will help. Like I said, this is unknown territory for me. Preheating, bevelling and filler rod might be the only way if you can't power your way into the material.

Edit: Yes, what RPM said. Aluminum has to be hospital clean, NO contaminants whatsoever.

 

[Dirtyrat]

One thing I will mention is that aluminum is a very different animal from welding steel. Some things of note: One of the issues with aluminum is the aluminum oxide that is on the surface, it melts at a much higher temp than aluminum, which is why they use AC to weld aluminum to help break up that "skin" of oxide. Also, penetration, is gained from forcing the rod into the puddle, rather than cranking up the heat as you can do with steel.

Blocks THAT thick, you will most likely have issues welding with no filler rod, if I were to attempt it without preheating, I would be starting with a decent bevel, high amps, and a real decent size filler rod.

What size is the tungsten you are using in the torch? if its sized for general welding use, it may not stand up to 350amps, especially using AC, as more amperage is wasted as heat into your tungsten/torch. Also, I think its common practice, but I'll mention it anyway, the non thoriated tungsten is what we use when welding aluminum, it will have the green band painted on the end. When welding aluminum you will end up with a spherical ball end on the tungsten rather than the ground point, and this will form soon after you start welding.

I will 100% agree, the cleaner the better when welding aluminum... the more dirty or old the surface is, the more the clean/penetration dial on the miller will need to be toward cleaning, which I believe actually cycles the ac at a higher rate. (correct me if I am wrong here)

 

[Old Iron]

Parts are about 15" square and about 8" thick assembled the welder is 350 amps.

WOW
Hope it's a water cooled tig

Jim

 

[goose-em]

6061 aluminum, I am assuming in the T6 condition, is prone to weld cracking.

You will most definatley need to add filler metal, if you don't it will carck. Use 4043 filler as it is less likely to crack.

350 amps is really not enough to push that large a piece but that is what you have so you can try.

You will need to run 1/8 inch zirconiated tungsten to push the 350 amps. (this is the grey tungsten) Sharpen it just like you would any other tungsten, the nive thing is it stays sharp so you have better control and less chance that the ball will fall into the weld.

Green tungsten is pure tungsten and will not hold up to the amps. (I hate green tungsten)

Considering that the parts are machined a square butt will not work very well. You will need a beveled edge if you hope to make it work without cracking. Single bevel with a 45 degree angle would work best. That is where you bevel only one side.

Since this weld is not structural I would say that a 1/8" x 1/8" bevel would suffice.

You will need to preheat the aluminum in order to use that 350 amp machine.

Not to hot, just around 150 to 200 degrees should work.

Good luck and practice on some thick stuff.