My aluminium welding quest - DC Tig

[Tiggy_dorset]

My experience with aluminium welding is limited, therefore the need to weld up my ali frame bench at home has been good for the chance to experiment.

I have used my AC tig at work on ali with some ok results. Unfortunately at home i currently only own a dc tig inverter (Clarke Tig150). The manual for my inverter gives the impression that it has the ability to weld ali when it states "Welds all metals. (Except aluminium - Tig130) I have a Tig150 so naturally you would think...... Unfortunately my machine has no AC option and the manual has no more information regarding welding ali, so I have never bothered to try welding ali with it (Maybe I should email Clarke)

Anyway, as some may know, I have played around with Mig welding ali, (http://www.mig-welding.co.uk/forum/showthread.php?t=32416) with some success on the first day, but still unhappy with my overall setup. I tried again yesterday, but got frustrated with the birdnesting leaving me now to consider a spool gun.

OK, rolling back to my point.....I brought some ali tig rods from work (sifalumin 15). Checking the specs online: http://www.weldability-sif.com/pages/view_product.asp?product_string=RO155025 in the PDF document it states Current: DC =+
I thought DC =+ means electrode positive please correct me if Im wrong

So... experimenting with this Ali malarky, I pulled my tig out for a play. First tried with DC electrode negative and got exactly what I expected black/grey porous snot. Then swapped leads around, torch positive (according to the welding rod specs). I halved the amps to what I would be using for AC and surprisingly I got some pretty clean welds. Only issue was the tungsten melting away, which I was expecting to happen, but it lasted long enough to allow me to run a bead which looked as clean as an AC weld.

Amps : 45
Tungsten: 2.4 white tip - 0.8% zirconiated
Filler: 1.6 Sifalumin No15

Is there a more ideal tungsten that will last longer with this kind of setup?

I will try and upload pics tomorrow.

 

[hotrodder]

Yep, DC+ is DCEP, electrode +ve. It'll be a typo, someone probably confused MIG with TIG. The EP phase of AC is what provides the 'cleaning'...

Is there a more ideal tungsten that will last longer with this kind of setup?

A really big one http://www.pro-fusiononline.com/tungsten/diameter.htm Zirconiated is as good a flavour as any as they ball up well instead of splitting. 2% lanthanated will take a little more heat but it ain't gonna be night and day or anything. Kinda a mute point as you won't be able to get a tungsten bigger than 3.2 to fit most hand torches and you don't want to know how much a pack of 10 1/4" diameter tungsten costs

The welding all metals bit... could be something lost in translation as if the OCV is good enough there are aluminium stick electrodes (no, they're not nice or easy to use especially on thin material), the other common one is something like 'welds steels, stainless, alloy' which (intentionally or not) catches people out as most metals are 'alloys' and aluminium is one of the few that's also used as a pure metal

 

[Tiggy_dorset]

Thanks for the heads up Hotrodder, it all makes a lot of sense. The chart you provided is quite handy. I guess a 3.2 Lathanated tungstem would give me a little more welding time. I might just bite the bullet and fork out for a half decent AC machine That will be a while yet though.

Once again though, I have learnt and gained some new experience from my experimenting, trying things out and playing around.
Thanks for the info.

 

[200T]

Mmmmmh - sounds interesting... And quite easy; contrary to what I've gathered so far on DC TIG weldinng aluminium...

 

[backpurge]

Ali DC TIG with torch positive and a bigger diameter tungsten is a lot more common than people realise

 

[Tiggy_dorset]

Mmmmmh - sounds interesting... And quite easy; contrary to what I've gathered so far on DC TIG weldinng aluminium...

It was just as easy as using AC if you can keep up with compensating the arc distance due to the melting of the tungsten. That seemed to be the only downside to it, not forgetting the cost of replacing tungstens on a regular basis if you do this often. I might get some bigger tungstens just for the sake of experimenting, I'll think about that one.

 

[Tiggy_dorset]

Ali DC TIG with torch positive and a bigger diameter tungsten is a lot more common than people realise

The fact that the chart supplied by hotrodder had figures relating to DC =+ did lead me to wonder if people actually specifically used this method.

 

[Seano]

Very interested in this post Tiggy, it would be interesting to see what the penetration is like....

 

[penfold]

Ali DC TIG with torch positive and a bigger diameter tungsten is a lot more common than people realise

That's right, the reason you use AC is to give the tungsten an easier time; if you use the biggest tungsten you can fit in the torch, and perhaps try a watercooled torch, there's no reason it won't provide a good weld. It's on my list of things to try this year.

 

[Tiggy_dorset]

Very interested in this post Tiggy, it would be interesting to see what the penetration is like....

I will phone my welding stockist tomorrow and see what he has in stock. I wont hold my breath, hes only a small outfit, otherwise It might not be for a few days before I can have a play with a larger setup. I will have a play with some plate too. Yesterdays practices were done with some box left over from my bench, so you cant see the penetration underneath.

Will post pics after my next practices.

 

[hotrodder]

The bloke that invented TIG (or at least the one that patented what we now call TIG) was apparently working with/for Lockheed on a process for welding magnesium that avoided the drawbacks of oxyfuel- corrosive fluxes and larger HAZ. When the patent was filed the set up was DCEP using helium. At some point Linde took over and named the process Heli-arc, ESAB kept the name when they bought/merged with 'em. Origional patent is here... http://www.ptodirect.com/Results/Patents?query=PN/2274631

As said, AC is easier on the tungsten. I'm guessing that the development of AC (and also variable AC balance, squarewave etc) was as much about efficiency as approx 2/3 of the arcs heat occurs at the +ve electrode (using DCEN you can weld tungsten using a tungsten electrode). Biggest issue for those wanting to use DCEP these days is getting a big enough tungsten in the torch... most DC TIGs are gonna be supplied with a wp17 (upto a 3.2), a wp26 will take a 4mm tungsten but beyond that you'd need to go watercooled and use something like a wp12 which'll let you fit 1/4" tungsten at (from a quick google) around £200 for a pack of 10...

 

[Llundberg]

And here I was thinking that AC is a 110% MUST. To clean off the oxide skin layer before melting the base metal and having it collapse under you. I have been taught that DC welding aluminium is about the same likelyhood as fitting an elephant in to a phone booth or me running 100 meters in 5 seconds - impossible. I tried nevertheless and as expected; 100% failure.

 

[Tiggy_dorset]

Went out and purchased the 3.2 bits today. They didnt have any Lathanated tungstens, so I had to settle with Ceriated. I wish I had gone with the Zirconian.

With the ceriated, I found the arc to be jumping all over the place and wouldnt settle down. It seemed to be taking an age to get any heat into the Ali at 55amps. Would this be due to unstable arc and the bigger tungsten sucking up most of the heat? Also it looks like the ceriated suffered from cracking (see pics below)

Disappointing results for me today. I couldnt do a lot as I only had half a filler rod left and the welding supplier only had a 5k box of rods for over £50
I will get some more rods from work and source some 3.2 lathanated or zirconian tungstens and see if there are any improvements.

Also the box that I have been practicing on is 4mm, not 2.5 as I first thought. I believe I will have better results on thinner material, requiring less amps = less melting of tungsten etc.

My mission :
3.2 tungstens in Lath or Zirc
more filler rods
thinner material to experiment with

Picture below: 2.4 Zirconian (Left), 3.2 Ceriated (Right)
The Zirc balls up lovely and has a stable arc. The Ceri tends to crack and has a wandering arc.


Picture below: A bead with the 2.4 Zirc setup from last night. Not top quality, but it is clean and shows that reasonable results can be possible with DC =+ (from someone who is good at Ali welding in general)


My quest is not over yet!

 

[hotrodder]

I'm amazed you even got a weldpool on 4mm ally with 45A (i assumed it'd be much thinner as you'd typically weld 1.5mm ally at around 65-80A AC). How long did you have to wait for a puddle? Minutes? How wide is the bead?

Bigger tungsten generally = less stable arc everything else being equal. Ceriated really ain't gonna like the treatment your giving them regardless but try sharpening it some. Might encourage it to ball a bit better/split less and should make for a more stable arc, at least until the tungsten self destructs

 

[Tiggy_dorset]

I'm amazed you even got a weldpool on 4mm ally with 45A (i assumed it'd be much thinner as you'd typically weld 1.5mm ally at around 65-80A AC). How long did you have to wait for a puddle? Minutes? How wide is the bead?

Bigger tungsten generally = less stable arc everything else being equal. Ceriated really ain't gonna like the treatment your giving them regardless but try sharpening it some. Might encourage it to ball a bit better/split less and should make for a more stable arc, at least until the tungsten self destructs

I ordered 2.5 box through work. I should know better to check the size when I got it, rather than just to assume. I should have spotted it really but anyhoo... I am feeling confident that I will be able to produce some half decent results with 2mm plate. Lets hope I havn't tempted fate from that statement. I did try with a pointed tip and a blunt tip, but they both produced similar effects. I will try the same when I get some different tungstens.

I doubt I can get back to working on this problem til the middle of next week. Instead I hope to be shifting back to Mig for the weekend assuming my spool gun arrives tomorrow.

 

[Tiggy_dorset]

I'm amazed you even got a weldpool on 4mm ally with 45A (i assumed it'd be much thinner as you'd typically weld 1.5mm ally at around 65-80A AC). How long did you have to wait for a puddle? Minutes? How wide is the bead?

Oh ye....It didnt take long really to get a puddle maybe 10-15 seconds, although the puddle was very wide and flat. Doesnt seem to be much penetration through, when looking inside the box.
Its 50mm box, so looking at the pic, the bead looks about 10mm+ wide

 

[Rick]

I'm amazed you even got a weldpool on 4mm ally with 45A (i assumed it'd be much thinner as you'd typically weld 1.5mm ally at around 65-80A AC). How long did you have to wait for a puddle? Minutes? How wide is the bead?

Bigger tungsten generally = less stable arc everything else being equal. Ceriated really ain't gonna like the treatment your giving them regardless but try sharpening it some. Might encourage it to ball a bit better/split less and should make for a more stable arc, at least until the tungsten self destructs

I'd imagine the DCEP might give different results.

 

[Llundberg]

I don't mean to offend anyone but there is no way I believe those welds were made with DC TIG.

 

[Seano]

I don't mean to offend anyone but there is no way I believe those welds were made with DC TIG.

Oh...Oh.......

 

[Tiggy_dorset]

I don't mean to offend anyone but there is no way I believe those welds were made with DC TIG.

Thankyou, I will take that as a compliment

I am willing for anyone on the forum to come round and vouch for my next lot of welds.