[martinr]

I have made a bit of a breakthrough with my aluminium tig welding, which I thought I’d offer up for your comment and thoughts, and also because possibly it might help others, or at least give suggestions on things to think about. My problem was with the electrode parameters; I hadn’t realised just how important they are.

My aluminium welding has been a bit hit and miss, and the one joint that’s far more miss than hit is the one-inch diameter tube-to-plate. I’m a keen fan of Jody’s aluminium drill but I hit a point where further progress was minimal. So I got some tube and plate and tried to see where I was going wrong. I used 2% lanthanated electrodes and soon realised that arc instability was my problem; I was nearly always fighting to control the arc, especially at lower current settings. Getting a focussed arc was also problematic; increasing the AC frequency helped, but it didn’t solve the problem. So I’d burn through the tube in places, get undercut, and get an inconsistent weld bead.

As arc instability was most evident at low currents, I set current to 25 Amps. My settings were 65% EN, 200 Hz, 25 Amps. I started with a 2.4mm 2% lanthanated electrode. (AC frequency seems to help focus the arc a little, but it’s not like night and day, as Jody would say, so I left it at 200Hz.) I found that:

a. The arc was unstable, and changing the tip angle didn’t help.

b. A 1.6mm electrode was, if anything, worse, and again tip angle made no appreciable difference.

c. A 3.2mm electrode was also unstable until I ground a tip of about 100 degrees - the apex was 2mm from the start of the shoulder of the tip. With this angle I had a rock solid arc at 25 Amps (at 50Hz, too)

electrodes beforehand ceriated left lanth right.JPG (2.07 MiB) Viewed 5061 times

lanth 25 amps.JPG (276.42 KiB) Viewed 5061 times

d. Having read that ceriated tungsten is "best at low amperage range", excellent for arc stability and is recommended for aluminium with inverters or transformers, I tried a 3.2 mm ceriated electrode at 25 Amps, but found the arc unstable. It was unstable at 100 degrees tip angle and even more unstable at a sharper angle. (All electrodes were ground longitudinally with diamond wheels.)

ceriated 25 Amps.JPG (249.23 KiB) Viewed 5061 times

Having now got control of the arc, my next tube-to-plate weld was easy and professional looking - no undercut, no burn-through, and no battling with the arc. (1.5mm tube to 3mm plate - 3.2mm lanthanated tungsten, 100 degree tip angle.) The results of my aluminium drill are now looking a lot more like the results Jody gets.

[martinr]

Arc photos slightly enlarged

lanth 25 amps large.JPG (57.95 KiB) Viewed 5061 times

ceriated 25 Amps large.JPG (81.22 KiB) Viewed 5061 times

[tweake]

nice pic, it really shows that the arc comes off the side of the point. a fine taper makes a wider arc, while a steep taper makes a smaller arc.

[tweake]

what amps are you welding at ? (and material thickness)

obviously 25 amps is just for testing (btw nicely done) but aluminium and low amps generally don't go together.

[martinr]

what amps are you welding at ? (and material thickness)

obviously 25 amps is just for testing (btw nicely done) but aluminium and low amps generally don't go together.

I had the current set probably between 80 and 90 amps, but, of course, as the object (small tube on a small plate) heated up, I would be backing off the pedal. But what this test joint highlighted for me, because I was lowering the current during welding, was where I had been going wrong in general: firstly, I hadn’t really been consciously aware that I wasn’t fully in control of the arc - I just knew that occasionally, my aluminium welds came out really well, and, at other times they didn’t, and I couldn’t work out why.. I suppose I’d taken it for granted that a wandering or unstable arc is something you have to learn to live with; I’m not even sure I was really aware of what the arc was doing, I just knew that welding aluminium could be hit and miss. I’ve learned a valuable lesson:, with the right electrode and tip angle, arc instability isn’t something you have to live with. I guess I got complacent thinking that a 2.4mm lanthanated electrode could do everything - plug and play!

[martinr]

nice pic, it really shows that the arc comes off the side of the point. a fine taper makes a wider arc, while a steep taper makes a smaller arc.

Many thanks.

[martinr]

what amps are you welding at ? (and material thickness)

obviously 25 amps is just for testing (btw nicely done) but aluminium and low amps generally don't go together.

And I forgot to add that I noticed that the hotter the electrode gets, the more unstable the arc can get. That’s why the 3.2mm electrode helped: it runs a lot cooler than a 2.4mm for the same current, so I wasn’t getting a hotspot suddenly forming, say, at the shoulder of the tip with the arc jumping up to a point 3 or 4mm behind the tip.

[tweake]

what amps are you welding at ? (and material thickness)

obviously 25 amps is just for testing (btw nicely done) but aluminium and low amps generally don't go together.

And I forgot to add that I noticed that the hotter the electrode gets, the more unstable the arc can get. That’s why the 3.2mm electrode helped: it runs a lot cooler than a 2.4mm for the same current, so I wasn’t getting a hotspot suddenly forming, say, at the shoulder of the tip with the arc jumping up to a point 3 or 4mm behind the tip.

the 65% en won't be helping as that heats the electrodes a lot.
i try to run as high as i can get away with, typically 70-75%.
90 amps is pretty low (especially at 200hz) to be having heating issues with 2.4mm.

[tweake]

what amps are you welding at ? (and material thickness)

obviously 25 amps is just for testing (btw nicely done) but aluminium and low amps generally don't go together.

I had the current set probably between 80 and 90 amps,

i think your amps is to low.
the 200hz makes it act like lower amps as does the balance setting.

when doing thick to thin you need amps to be higher than what the thin takes to weld. the thick side sucks the heat out and you often end up with cold welds, or you spend so long on the thick side the thin side absorbs the heat and melts through.
so its usually thick side amps (or close to), focus on the thick and wash onto the thin, and keep the travel speed up. quite often people don't have enough amps and travel speed drops to compensate which overheats the parts.

this is where the ac frequency and tungsten angle really helps so you can focus where you need to and focus the heat to get a puddle on marginal amps.

[kiwi2wheels]

Interesting !

What machine are you using and what brand of tungsten ? Were you pulsing the pedal ?

[martinr]

Interesting !

What machine are you using and what brand of tungsten ? Were you pulsing the pedal ?

Thanks. I’m using an RTech 210 inverter. RTech is a UK company. The 3.2mm ceriated tungstens were bought through RTech; they list them as “high quality” (of course they would) but no brand name is given. The lanth. 3.2mm, 2.4mm and 1.6mm electrodes are CK, sourced through a reputable welding supplies firm in the UK.

But I understand your thinking: years ago I bought some EZ Multistrike tungsten electrodes, which claim to be a special recipe of doping elements and suitable for all materials, but I found they would split. I‘ve never had splitting since, I check my electrodes with a x10 and x20 jeweller’s loupe, both after grinding and in use, especially to see that the tip (or ball) is uniform.

As for pulsing the pedal, no. The tests I ran at 25 Amps had the current set to 25, and I depressed the pedal fully. (Just to expand a little, with my 2.4mm lanth. electrode, it was also unstable at 40 Amps but stable at 60 Amps, so I held the current down at 25 Amps when looking at the effect of electrode angle, to make sure I was only seeing the effects, if any, of electrode angle.)

[Oscar]

Based on the pictures, I feel the results are skewed. I knew this contradicted my own observations, but I couldn't tell why, initially. The arc shot with the Ceriated electrode depicts a longer arc length which will in turn affect arc stability. In my eyes, it's pretty clear to see the difference.

[martinr]

Thanks, Oscar. I thought I had set the electrode gaps the same with a 2.9mm thick piece of Al, but possibly I knocked it between setting and running. Anyway, it's an excellent chance to see if I could improve on the photos, which I might have done except that I must have been closer to the ceriated electrode because the ceriated electrode looks wider , and, try as I might, I can't edit the photos to the same size. And even though the ceriated looks hotter than the lanthanted, they were both set to 25 Amps, foot pedal fully down, and same camera settings, same No 9 filter. I guess that I've got a long way to go to match the quality of Jody's arc shots

Here's the lanthanated tungsten 3.2mm at 25 Amps:

lanthanated tungsten CK (2).jpg (21.7 KiB) Viewed 4975 times

and here's the ceriated tungsten 3.2mm 25 Amps

ceriated tungsten CK.jpg (27.94 KiB) Viewed 4975 times

The difference between the 2 electrode types was a bit of an aside, what I was most interested in was the fact that by going to a larger electrode and setting the tip angle to around 100 degrees, I got significantly better results.

[tweake]

Thanks, Oscar. I thought I had set the electrode gaps the same with a 2.9mm thick piece of Al,

imho 2.9mm pretty high especially for low current. i'm interested to hear what the others say on that.
i often just use the filler to set the height, so its often 2.4 mm (tho at 100+ amps). at low amps its lower (1.6mm), especially when using lift arc.
at low amps things get finicky.

[Oscar]

Also, the grind angles are inconsistent. In the last pic both look less than 90°, with one closer to 75°. Even in the first pic, both look acute. With amperage this low, all these seemingly hair-splitting differences play a huge role, IMO. I do salute the effort though.

This is just shy of 100°

[martinr]

Also, the grind angles are inconsistent. In the last pic both look less than 90°, with one closer to 75°. Even in the first pic, both look acute. With amperage this low, all these seemingly hair-splitting differences play a huge role, IMO. I do salute the effort though.

This is just shy of 100°

Here’s the 2 electrodes just before yesterday’s tests:

68803198-E1C5-4F1A-B926-EFBB39EFE55A.jpeg (101.91 KiB) Viewed 4952 times

(Lanthanated on the left)

[martinr]

I wish I hadn’t thrown in the observation of the apparent advantage of lanthanated over ceriated at the test parameters: it’s become a distraction from the main observation i.e. the effect of electrode diameter and tip angle.

[tweake]

is it just me or is the ceriated one ground off centre ??

[martinr]

is it just me or is the ceriated one ground off centre ??

Done by hand on a “medium” diamond disc and then finished off on a very fine diamond wheel, so it could be, I suppose. How do you grind yours?

[Oscar]

Also, the grind angles are inconsistent. In the last pic both look less than 90°, with one closer to 75°. Even in the first pic, both look acute. With amperage this low, all these seemingly hair-splitting differences play a huge role, IMO. I do salute the effort though.

This is just shy of 100°

Here’s the 2 electrodes just before yesterday’s tests:

68803198-E1C5-4F1A-B926-EFBB39EFE55A.jpeg

(Lanthanated on the left)

Confirms my suspicions. Both are acute, and not identical. One has a smaller included angle. That throws off the data.

[martinr]

Today's photos.

This time I decided to grind as obtuse an angle as I reasonably could , by hand, and to compare again ceriated with lanthanated at the same settings.

Lanthanated tungsten:

lanthanated 01.jpg (75.79 KiB) Viewed 4927 times

lanthanated 02.jpg (94.7 KiB) Viewed 4927 times

Ceriated tungsten

ceriated 01.jpg (79.98 KiB) Viewed 4927 times

ceriated 02.jpg (88.66 KiB) Viewed 4927 times

I'm putting this to bed now, you'll be pleased to know; I've got as much as I want out of it - it's cleared up a couple of my misconceptions.

I'd still like to hear how you grind your electrodes - by hand or by dedicated tungsten grinder, such as the Sharpie or something similar, and what difference you'll feel it makes. (When I say 'by hand', I mean by hand on a dedicated tungsten diamond wheel/disc, not on the shop bench grinder that's clogged with all sorts of different metals.)

[tweake]

sadly i don't have a proper tungsten grinder to compare to.
i have dedicated diamond wheel to sharpen by hand. its ok but its still fairly variable. for me it has to be a fair way out to cause issues, but then again i'm not a good welder by any means.

what would be really cool would be to compare different grind angles and more importantly shapes.
one common grind is cut the tip off so you you have a small flat spot on the end (which rounds once in use). it would be interesting to see if it arcs off the bottom or the sides.
same thing with the "crayon" profile grind.

[martinr]

sadly i don't have a proper tungsten grinder to compare to.
i have dedicated diamond wheel to sharpen by hand. its ok but its still fairly variable. for me it has to be a fair way out to cause issues, but then again i'm not a good welder by any means.

what would be really cool would be to compare different grind angles and more importantly shapes.
one common grind is cut the tip off so you you have a small flat spot on the end (which rounds once in use). it would be interesting to see if it arcs off the bottom or the sides.
same thing with the "crayon" profile grind.

Thanks, tweake. I used to put that small flat spot on, but then, after watching one of Jody’s videos, I stopped doing that and let the electrode ball as it wanted to first on a piece of scrap, and if there was any doubt about it, I’d check it with my x10 magnifier. On a certain type of electrode, I’d sometimes see a tiny blow hole or some other irregularly, but I must say that I don’t think I’ve ever had to re-grind and re-ball a CK lanthanated 2% electrode.

I like your ideas for further experimentation; I’ll have a good think about that.

Thanks

[Oscar]

the last set of tests are much more "proper", as things were much more consistent. Awesome 2nd round of testing!

[martinr]

the last set of tests are much more "proper", as things were much more consistent. Awesome 2nd round of testing!

Thanks, Oscar. “Practice makes perfect”, as they say.