AC TIG - Tungsten Won't Ball Up.....

[FASTdan]

Hi Guys, wonder if anyone can advise. Welding at around 180A (3mm tube to 10mm plate, fillet welds) using grey tip tungsten. For some reason my tungsten no longer wants to ball up properly and I can't work out what has changed or is causing this. Below is a pic of what is happening:

https://www.dropbox.com/s/5e2xubg4njcwy1c/DSC_1073.jpg

Instead of 1 ball I am getting 3 or 4 small balls forming which obviously results in quite an unstable arc. I have changed my back-cap, shroud, collet and holder but to no avail. I have even started messing around with the AC balance (currently around 40%) and frequency (currently around 80%) but not really achieving anything other than having to change the way I am welding.

The welder is an R-tech 250 AC/DC. Torch is WP26 with flexi head and tungstens are 2.4 grey type.

Any suggestions?

 

[hotrodder]

Is it happening with all your tungstens? Have you recently bought a new packet of 'em? I had this happen once with a cheap pack of (supposedly) zirconiated however as the multiple facet thing is typical of thoriated tungsten i suspect they had been painted the wrong colour in China...

Personally i've always hated ceriated... won't stay sharp for as long as other flavours with DCEN and with AC don't ball as well as zirconiated and can't be kept sharpish like 2% lanthanated or the Huntindon Fusion multistrikes i swapped to after the dodgy batch of zirconiated- only tried them as they were the only alternative brand from my usual suppliers but since they performed so well i've stuck with 'em. Fairly sure they're also made in China but sold/marketed on quality rather than price i.e. not cheapnese
IIRC Elmer Wallace only sell Plansee tungsten which'll be better quality than cheap stuff... http://www.diamondground.co.uk/faqs-tungsten.php

I can't see it being anything else other than the tungsten or (far less likely) the machine... a gas problem (leak etc) would mess with other things long before it affected the way the tungsten melts and from the machine side varying the AC balance should change the way/how much the tungsten melts. If you can see a difference in the size of the etched zone it's unlikely to be the machine, had a glitch with my kit a while back with AC balance but resetting it fixed things http://www.mig-welding.co.uk/forum/threads/lincoln-v205t-curiosity-or-omen.18156/#post-204807

 

[zardoz]

For some reason my tungsten no longer wants to ball up properly and I can't work out what has changed or is causing this.

The welder is an R-tech 250 AC/DC. Torch is WP26 with flexi head and tungstens are 2.4 grey type.

you say 'No longer wants to ball up properly' So i assume that it used to be fine. Is that a used tungsten that has just started acting up, and was fine till now. Or is it a fresh one ?

 

[pedrobedro]

It looks like too many amps for the tungsten size you are using, try going up to a 3.2mm.

 

[FASTdan]

Thanks for the replies.

zardoz this has only just (in the last couple of weeks) started being an issue - tungstens used to ball fine, nice and shiney etc. That tungsten is typical after a few minutes welding from being freshly ground. I usually have 3 on the go and have tried new ones etc, results always the same.

Hotrodder your idea of a poor batch might well be worth pursueing, I cannot recall if the opening latest pack of tungstens ties in with when things started going wrong, but I will try another pack to see (purchased seperately to the current ones). I get a definite change in the way it melts when changing AC balance (going up puts much more heat into tungsten and ampage then needs to be reduced to prevent unstable tungsten end). I will report back once I have tried a different pack of tungsten.

pedro, I have always carried out these welds at 170-190A, so I am reluctant to change to 3.2mm. As I understand 2.4 should be ok up to 200?

 

[Jim Davey]

Its the instability and heat that gives you the ball on the tungsten. Set the balance so its heavily biased towards positive, start welding on a piece of scrap and gradually increase power until the tungsten starts to melt and wobble, it should form a ball gradually, once the desired ball size is reached back off on the power, the tungsten should 'freeze' leaving you with a nice tidy ball of the desired size, set the balance back to balanced or slightly negative (r-tech can be backwards with balance markings) but it should be obvious which balance setting works the tungsten hardest and then weld as normal.

 

[pedrobedro]

According to my chart 2.4 is only up to 150 amps with my Stel welder on AC and then different welds like butt or fillet need different tungsten size as well.

 

[hotrodder]

None of the charts ever agree with each other* as balance settings have a huge effect on what the tungsten will put up with... i can melt a 2.4 at 68 amps with 35% EN http://www.mig-welding.co.uk/forum/...welding-quest-dc-tig.32549/page-2#post-356247 or keep it kinda sharpish at 200A with %EN into the 80s. I don't own tungstens bigger than 2.4mm anymore

Bottom line AIUI is that 2.4mm ceriated used to work for Dan and suddenly are behaving like thoriated do with AC despite all the parameters staying the same

* the one in the forums TIG FAQ lists slightly different amperages for different flavours which makes sense whereas the one on Pro-Fusions site ignores flavour but gives different ranges based on balanced or unbalanced (biased towards EN) AC for example. Personally i typically step upto a 2.4mm earlier than either chart suggests but don't bother with anything smaller than a 1.6, for very low or high amperage stuff i just vary the prep. Lots of ways to skin a cat