tig welding aluminum with a DC only tig

[rab]

tig welding aluminum with DC only tig....

i thought i remember reading that you can weld aluminum with a dc only tig with helium?
also if i remember reading right, it will only work for thicker stuff is this true or can you do thinner?

if the above is true, is there anything else you have to do to make it work, ie different rods, more or less gas, switch polarity,ect????

[performance]

Let's just say no you can't.
That question is raised periodically by someone wanting to cheat the system. Techinically you can weld with DC+, but penetration is poor, heat is high, and you need a monster tungsten to only weld the thinnest metal. It is not practical, nor is it cheap to do so. You can dig a 500 year old Live oak out with a tea spoon too...but a bull dozer makes faster and better work of it.

[jp2code]

While on this topic, what properties of AC make it suitable for Aluminum TIG that DC can not do?

In my mind's eye, I've always explained itself to me in this incorrect view: The straight current of DC flowing through the Aluminum that causes the metal to get too hot, whereas the Alternating Current of AC flows only short distances, helping the metal to stay cooler."

Like I said, I know that is wrong. So, what is it?

[performance]

Quite simply: It is the oxidation layer on Aluminum that must be broken up. DCEN will not break it up. DCEP will, but penetration is poor, and heat on the tungsten is extreme because of the reverse flow of electrons. There's plenty of information on the web about it, and a little misinformation as well. The combination of EP and EN allow both penetration and cleaning, without putting too much heat on the tungsten. Only about 30% EP is needed though to maintain adequate cleaning on most aluminum.

[dyethor]

Its the oxidation layer on the top of the aluminum that causes the problem. It melts at a higher temp then the base metal. The back and fourth of the alternating current breaks up this layer to expose the raw aluminum. So the oxide layer is getting beat up from both sides. Then the shielding gas stops the raw aluminum from oxidizing. On DC the oxide layer is only getting punched in one direction.
Wouldn't in Theory if you have aluminum with no oxidation or contaminants in an inert atmosphere you could weld it DCEN?

[Cippee]

The oxide layer on aluminum melts I believe at 2000 F so you don't get a puddle and the aluminum melts under it. Get a small piece and try it you will see. It won't look like anything is happening until the aluminum melts in.

I'm editing this to clear up what I said above. I got this from weldingtipandtricks


"The Skinny" on Welding Aluminum
Or should I say, the real "Skin" on Aluminum??? The thing that makes aluminum different than most other metals is that all Aluminum has an oxide coating that has to be broken down somehow or things go terribly wrong. It is really like a skin like saran wrap or something and unless you can break it down, welding aluminum sucks. Aluminum has a melting point of less than 1200F. The aluminum oxide coating that is on all aluminum melts at around 3600F. To add to this Funk, aluminum even boils at a lower temperature (2880ºF) than this oxide melts. For these reasons, it is easy to see why as much as possible of this oxide "skin" must be removed before welding. Luckily, the reverse polarity half of the A/C arc does an outstanding job of cleaning off most of this oxide ahead of the weld! How does that work? Well the reverse half of the alternating current acts like a sandblasting operation that breaks down the oxides. That’s really all you need to know unless you are a Physics major working on your thesis for a PHD. Besides, I have worked with a few PhD’s that couldn’t find their butt even if you let them use both hands. But that is another story. If you can weld, you already have a leg up on most PhD’s I know. Like uncle Coy used to say: It’s not what you know, it’s what you can do!

[jakeru]

Wouldn't in Theory if you have aluminum with no oxidation or contaminants in an inert atmosphere you could weld it DCEN?

For whatever reason (I don't know, maybe no one has really proved it, I'm sure there are some theories out there...) the aluminum seems to form oxides on the surface at high temperature, even in an inert atmosphere. Maybe the oxygen is being transferred through the metal somehow? I don't know. I hate to say it, but it "just does."

For probably the same reason that oxides form on the front side of the weld (without flux, and without EP), shielding the back side of an aluminum weld joint with an inert gas (like argon) doesn't seem to work to allow full penetration. You can't just backpurge aluminum, like you can, say, stainless steel. Some oxides invariably will form on the back side of the aluminum weld joint, even in an inert/backpurged environment, and impede the flow of the metal on the back side (usually preventing the "weld bead penetration" from going all the way through to the back surface or beyond, like you can effortlessly easily achieve with steels and stainless steels.)

If you had a DC TIG and wanted to weld aluminum, and could clean the back side, I'd look into using some flux. Like, an aluminum stick welding electrode, which is covered in flux. Or alternately, apply some oxy-fuel welding flux to the aluminum before striking your DC arc. Although you won't have the finesse in controlling the front surface of the puddle like you can with AC TIG (since you'll have a layer of molten flux on the surface), and so you wont get the same aesthetic to your weld bead, you sure can make some very solid, and strong welds that won't have oxide inclusions underneath the surface if you use some flux... Even with DC TIG.

The flux does need to be removed! It's basically kind of like a really strong salt. If you leave it on there, it will absorb water right from the atmosphere, and, even over a short period of time, you will see your work getting pretty severely corroded. (If not removed.) Removal typically requires pretty vigorous mechanical scrubbing with preferably pretty hot water. Got a laundry tub and a metal brush? Hot water in there and a metal brush should do the trick. (Or really strong acids like hydrofluoric, that I have not tried, and probably never will. I believe they are strong enough to be able to eat away at glass!)

I used to oxy-fuel weld aluminum, with mixed results. I am so happy I don't need to use flux anymore, due to the availability of the AC TIG welding process that I currently enjoy.

If you had DC TIG however, and wanted to make it weld aluminum though, and could access the back side of the joint for mechanically removing flux (in addition to the front which since you're able to strike an arc, you should likely be able to access well enough for flux removal) , look into using a stick welding electrode with the flux covering it, for the DC TIG process with should allow much better heat control (and less oxidation so you flux will stay cleaner) than stick welding aluminum. Or, look into some kind of separate flux (such as for oxy-fuel aluminum welding) to add to the weld joint before striking the DC TIG arc, to make the aluminum puddle underneath the flux flow.

cheers

[jp2code]

Good stuff, Jake.

I used to have some aluminum arc rods that I used at a welding shop. There were no directions, though, and I noticed after we welded with it ...and did NOT remove the slag! ...that moisture would quickly form beneath the slag and the aluminum bead. I would have described that moisture as very salty. I don't know if I tasted it or some managed to get on my lips or something while trying to remove the slag.

[welderdude]

I remember a guy on WW claiming that he used UHP lab grade helium and DCEN to weld aluminum. Whether or not its really doable or not, I don't know.

[Cippee]

Jody on weldingtipandtricks said he did that exact thing I will find the link and edit this with it. http://www.weldingtipsandtricks.com/...ips-part2.html Here is what he says if you don't want to find it on the page.

Did you know that you can use UHP helium (ultra high purity) and weld aluminum on DCEN? I have not been able to make this work on dirty castings but on something like an injection mold or aluminum fixture made from new fresh aluminum plate that is not heavily oxidized , it works great and does not heat the base metal nearly as much as welding on A/C.. takes a lot less amperage too.

Here is a post from another page of his

And another tip...Did you know that you can do certain aluminum welding jobs with DCEN and straight UHP helium for shielding gas?
UHP stands for "ultra high purity". and thats what you need. Not the stuff they fill balloons with.

I remember one job that this worked great on was an aluminum injection mold.

The pitting that sometimes happens when the A/C does its thing was just not tolerable. All the mold needed was a small fill of a chipped area.

So I Hooked up some UHP helium, increased the flow rate to about double what I would have used with argon, lit up , puddled, added a few drops of filler rod...and done. No pitting, and the mold barely got hot. which was nice because there was a bunch of sealant around the edge that would have needed to be replaced.

[jp2code]

I get Jody's weekly videos emailed to me. Good stuff.

UHP Helium and DCEN for Aluminum, huh? I might have to try this, since I don't have a means to weld Aluminum at all right now.

[Cippee]

I love that sight it really is a fountain of information. It's funny when he was talking about slower pulse settings putting someone in to epileptic shock. I wonder if it has ever happened before.

[welderdude]

I would love to see some good video with arc shots of someone using UHP helium and DCEN. As for the slow pulsing rate, My head started feeling weird just watching the video at home. I would be so dizzy if I had to do that for even a few minutes.

[Wookie]

Dcen on alum is used UHP helium and a oxide free weld zone we use nitric acid with some hydroflouric acid mixed in to clean the alum prior to welding normally used on the thicker stuff but i have done down to 13 gauge on dcen using 4043

Price out UHP helium its not cheap

[jp2code]

Man. Now I want to try DCEN on Aluminum. I'm going to have to get my hands on some UHP Helium, though.

[srp]

With one of the Miller tigs I bought, it came with a tig handbook, on page 75 it says over 1/8 aluminum can be welded on DC with argon or helium/argon. I tried it and it absolutely did not work out for me, in fact may be my worst ever weld.

I have seen where people talk of welding aluminum with DC, but feel for me would only be used in an emergency and if appearance did not mater.

[Rodsmachineshop]

ever weld aluminum with acetylene and oxygen . I do all the time at my machine shop it fun

[jakeru]

Re: oxy-acetylene welding aluminum, I used to before I got the TIG setup. I don't think it's very fun. I hate the flux. Have you ever left it (the uncleaned flux) on a part that you welded and had it destroy the part from corrosion? Nasty stuff. You also have such poor heat control compared to TIG process. Ever melt away an area you didn't intend to melt? Can happen really easily. JMHO... I guess I don't miss it very much!

[Rodsmachineshop]

yes nasty crap . I use a everlast 250ex welds great , I use aluminum arc welding rod with the flux on it works better when gas welding, then you dont have to flux the aluminum your welding also the white flux on the rod dont get nasty