My aluminium welding quest - DC Tig

[hotrodder]

I'd imagine the DCEP might give different results.

On paper it should make things worse as around 2/3 of the total heat is at the +ve electrode i.e. for a given amperage etc you're putting more heat into the tungsten and less into the work

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

Would have thought it'd take longer to get a pool. Bead width pretty much tallies with the little play i had today. My kit won't play ball with TIG DCEP (it thinks you're being daft and refuses to work) but out of curiousity i cranked the AC balance as far towards EP as it goes...

Material and wire are both 1.5mm 1050 Al
Tungsten is 2.4mm huntingdon fusion multistrike
68A and 60Hz throughout, i just floored the pedal waited for a weldpool and then shut off the arc after a short bead.


first two pics are tungsten before and after at 35% EN. Started counting after striking an arc, first 5 or 6 secs it was going nuts while the tungsten sorted itself out before stabilising enough to weld. Got to 13 before i had a weldpool that was stable and ready for some wire.

Front and back of beads. One on the left was @ 71%EN (i let the offcut cool back to ambient as it was a good excuse for a cuppa). Initially i tried to use the same tungsten but it wouldn't restrike, probably as the HF is set to min. You can see where the HF was going nuts. Changing HF settings is a bit of a ball ache so i swapped in another 2.4 prepped as in the first post. Weldpool took a couple secs to get going, much nicer and faster as you'd expect. Measuring across the toes the bead on the left ranges from 4-5mm while the one on the right is 7-9mm wide.

 

[Llundberg]

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.

I just find it so hard to believe as it goes against everything I've been taught. But if you did it, good on you.

 

[Tiggy_dorset]

I just find it so hard to believe as it goes against everything I've been taught. But if you did it, good on you.

As with you, I was always under the impression that welding Ali with DC was impossible. It wasnt until I questioned some info on the specs on some filler rods (which now seems to be a typo) that I decided to have a go to see what results I get.

From my own messy but interesting results, the input from other members in this thread and now some snips of information I have sought on the web, I now understand a lot more about the Ali welding process and in particular that DC Ali is possible, although very limited.

At this point It does seem to me that DC =+ limits you to maybe 2 - 2.5mm material thickness. Also, expect wider and flatter welds than you would with AC. I think that perhaps you could weld thicker materials, but that would involve torch upgrades to allow even larger tungstens and possibly the need for a water cooled system. With that and the extra cost of tungstens, it would seem a worthless excercise as the money would be more better spent towards buying an AC outfit.

I am hoping to eventually conclude this thread with showing that for people out there like me,who only have a small DC inverter and are not in the position to afford an AC set, that welding Aluminium can still be done, although limited to thinner material.

 

[matt1978]

Aluminium with DCEP has been around for ages, however it's not widely used in industry compared to ACDC let alone be regarded as practical for DIY/Hobby use.

It's nice to prove that it "can" be done but I still don't think it's practical, but again, I suppose it depends on the application and the weld quality required but even the slightest Tungsten erosion/melting will lead to Tungsten inclusion in the weld pool.

 

[Tiggy_dorset]

Thankyou Hotrodder for your test results, very interesting. Lovely welds by the way I think I might just throw my torch on the ground and get a desk job after seeing them

It does look like the further towards EP you go, the wider and flatter the welds become. Although DCEP welds look reasonably clean, it can clearly be seen that a more balanced AC weld is far cleaner.

I had a little read about those Huntingdon tungstens, very interested. I havnt come across them before. They look the biz.

I also got the same as you with the tungsten needing time to stabalise before forming the puddle, though the ceriated just didnt seem to get there. I have some Lathanated on order now, so will play with them when they arrive.

 

[matt1978]

DCEP should be cleaner than anything because it's the + cycle that "cleans" the Aluminium.

 

[Tiggy_dorset]

DCEP should be cleaner than anything because it's the + cycle that "cleans" the Aluminium.

Yes, I do see your point. It's just how it looks in Hotrodder's pic. Could just be the light/pic quality.

 

[matt1978]

In a "proper" environment, eg, bigger Tungsten, water-cooled torch etc then I am sure you would see a marked difference in the cleanliness.

The discolouration I think you can see on the photos would of been caused from the damage to the tungsten.

It's the same as I'd you weld on ac but have too much EP on the balance or you touch the Tungsten into the pool.

Proper DCEP welding on Alu has no visible damage to the Tungsten, it's a nice shiny ball. But this is only achievable if the Tungsten is much bigger than the amps that you want to weld at.

 

[Tiggy_dorset]

Aluminium with DCEP has been around for ages, however it's not widely used in industry compared to ACDC let alone be regarded as practical for DIY/Hobby use.

It's nice to prove that it "can" be done but I still don't think it's practical, but again, I suppose it depends on the application and the weld quality required but even the slightest Tungsten erosion/melting will lead to Tungsten inclusion in the weld pool.

Im very interested, is there anywhere in the industry where DCEP is prefered over AC?

 

[matt1978]

I am sure there must be some applications. I have only personally seen it once and that was on a Orbital Tig set up, welding very high integrity Alu Tubes.

 

[backpurge]

I used to visit a company that manufactured aluminium road tankers, all the circumferential seams were welded using DC TIG, it was quite a sophisticated auto system. The arc was struck using argon then as soon as it had stabilized the shielding gas changed over to helium, the penetration and deposition rates were phenominal. Apparently it is a process that is quite common on the continent.

The only other time I have seen DC TIG used commercially was by RAF ground crews to carry out small repairs to aircraft, this was back during the "cold war" when aircraft used to sit out on the runways waiting to go, if a minor repair was needed rather than take the aircraft back into the hanger they would plug a small 160 amp DC TIG welder into a generator and use a 75% helium mix, of course with the modern portable inverter sets now available they would use AC nowadays

 

[hotrodder]

I think maybe the odd bit has been messed up/lost in translation but DC TIG aluminium is discussed here including a couple of example pics towards the end... http://aluminium.matter.org.uk/content/html/eng/default.asp?catid=195&pageid=2144416794 The airbag component looks more like DCEN to me.
Only the abstract but talk of welding thin ally with DCEN @ 24m/min here... http://sciencelinks.jp/j-east/article/200303/000020030302A0948943.php A google book preview of Gene Mathers 'the welding of aluminium and it's alloys' here which is a pretty comprehensive book

Thankyou Hotrodder for your test results, very interesting. Lovely welds by the way I think I might just throw my torch on the ground and get a desk job after seeing them

Aluminium has been my 'mild steel' for several years. Can't remember the last time i welded actual mild steel, certainly haven't welded any yet this year. There's always someone that's 'better' (faster and/or neater etc) and as Matt said there's other things going on that effect the result too. If you really want to feel like throwing the torch away google 'marcella manifolds' or 'ztfab' (both are rumured to be robots)

It does look like the further towards EP you go, the wider and flatter the welds become. Although DCEP welds look reasonably clean, it can clearly be seen that a more balanced AC weld is far cleaner.

I had a little read about those Huntingdon tungstens, very interested. I havnt come across them before. They look the biz.

I also got the same as you with the tungsten needing time to stabalise before forming the puddle, though the ceriated just didnt seem to get there. I have some Lathanated on order now, so will play with them when they arrive.

Yes, I do see your point. It's just how it looks in Hotrodder's pic. Could just be the light/pic quality.

Somewhere in the millerwelds TIG resources there'll be a big chart showing the effects AC balance, frequency and the like have on arc and weldpool shape. Tungsten geometry also alters things but is obviously a mute point with DCEP and only properly relevant with DCEN. While personally i think they have the edge over other flavours the huntingdon fusion tungstens aren't night and day better or anything. I switched to them as they were the only alternative from my usual supplier after getting a pack of Parwelds which behaved weirdly... can't remember whether they were supposed to be zirconiated or lanthanated but they behaved like thoriated with AC and ended up in the bin.

The cleanliness thing... again as Matt said DCEP provides more 'cleaning' (as long as you can keep the tungsten in one piece at least ). Me managing to cast a shadow over part of the pic didn't help things but the bead on left is cleaner/brighter. I put that down to the time taken for the weld with lots of EP. Weld ally with too long of an arc length or too slowly and welds typically come out duller just as with stainless etc

 

[steve--o]

well folks an intresting read all this,i too was taught by the green "science and practice " of welding book ,in 1982 when alloy was all AC.
I have been looking for an AC set ,but i have a nice dc new zealand built inverter dc tig ,so this thread has certainly spared me on to rent a bottle of Argon and give it a go on the dc.

 

[Tiggy_dorset]

well folks an intresting read all this,i too was taught by the green "science and practice " of welding book ,in 1982 when alloy was all AC.
I have been looking for an AC set ,but i have a nice dc new zealand built inverter dc tig ,so this thread has certainly spared me on to rent a bottle of Argon and give it a go on the dc.

Please let us know how you get on with the 'experience' Hope to see some pics. Still waiting on my tungsten delivery.