Stainless TIG gas consumption

[Corgan]

Hi guys,

finally got around to sorting out my home TIG setup.

I've rented an E sized argon cylinder from air liquide, bought the torch and accessories for use with my little cigweld 170 lift tig/stick inverter

been spending most of the arvo just running beads on random bits of stainless and i'm having some difficulties getting the gas flow right.

i'm getting the dull grey oxidised look of not enough gas coverage, even with my gas turned up to 15 LPM. cant detect any leaks upstream of the torch and it appears to be flowing out of the torch just fine.

turn the gas any higher and i start getting puddle turbulence, turn it down to 10 and it's worse

have tried a variety of heat settings and travel speeds, and i keep the gas flowing over the welds until they stop glowing red.

the only time i achieved an acceptable straw coloured finish was on a fillet weld.

the only thing I can think of that might be causing this, is using 308L filler wire and the only scrap stainless i have atm is 316 grade.

so what do you think? metal still not clean enough? need a gas lens collet body? (using a #6 cup at the moment with the tungsten not poking out very far at all) perhaps the 308 filler on 316 stainless thing?

looking at the pressure guage on the argon cylinder, my wallets going to hate me if i go through argon at that rate :(

thanks lads
corgan

[Corgan]

a bit more info i left out,

am using 2.4mm tungsten, 2.4mm filler and the scrap stainless is 3mm thick

[inverter_weld]

I would run 10 litres/m, a 1.6mm tungsten, make sure it is electrode negative, 90 amps on the display. Stick your tungsten out 5mm past the ceramic and keep it 2-3mm off the job while welding. Push the torch into the gas shield, don't drag it away. Make sure your ceramic is perfectly smooth and not damaged, not even a chip as this can create vortices that suck in atmospheric gases.

Cheers
Pete

[WelderMick]

Hi Corgan,

Is it 100% argon?

I notice you're using post-flow so that's not the problem.

I'm assuming your tungsten is staying clean and bright?

Eliminate the filler question by running a bead without any filler - same symptoms? I doubt this is the issue but it's the obvious test.

Look at the molten weld pool, can you see stuff floating in it? = contamination.

Aside from all that what I reckon is actually happening to you is that you are welding too hot and/or too slow. Even with adequate gas coverage your SS will look grey and not have that shiny smooth finish if you over cook it. Excess heat allows the chromium and carbon in the SS to bind up and result in carbide precipitation. Oddly enough - the fix isn't so much to turn down the amps, but to make sure you're always moving the torch forward so you're not concentrating heat in any one area for too long.

Cheers

- Mick

[WelderMick]

Oh yeah, I agree 15 LPM is too high because of the turbulence - go with Pete's suggestion. For reference, I use 8 LPM with a #7 cup. I also have some gas lenses but they're not necessary for typical work. Cheers - Mick

[Corgan]

thanks guys- i will have another play later on and see if i can move a bit faster. I notice pete recommended 90 amps, I never went any higher than 75-80, so perhaps i'm running too low and having to hang around in one spot too long. will try cranking the amps and running faster.

the gas is pure argon

tungsten contamination is not unlikely as i was sharpening with an old used grinding stone, which i will replace with a new one, and yes no filler runs had the same problem, although the puddle did look quite clean

I'm also thinking i might need a bigger cup, when i was learning at tafe i remember using a #7 at least, the #6 seems very small. i'm quite keen to turn the gas down, the bottle looks like i've used about 1/5th already doing not much at all, and its not cheap stuff!

thanks once again

[Corgan]

Tried a few more things today,

it doesn't seem like heat is changing anything, every weld is getting that grey oxidised look, filler or not. i think i'm going to try a gas lens collet body next and see if it makes any difference.

just wondering, if i'm grinding and dressing all the welds afterwards, is the ugly initial bead going to make any difference ultimately?

[WelderMick]

How about some photos Corgan?

A gas lens won't hurt, but there's no reason your current setup shouldn't get a good weld.

what about your arc length? A long arc will stuff things up too. Keep your arc length tight - say 1-2 mm off the puddle. Get your helmet in nice and close so you can see exactly what is going on.

Cheers

- Mick

[brenton21]

your sure your getting enough gas at the shroud? maybe check your regulator as the gauge maybe reading wrong? or a seal in the torch?

[Corgan]

yeah fairly sure there are no leaks, when i turn the gas up to about 15 l/min i get noticable turbulence at the weld puddle, and i can feel the gas holding my hand at the end of the shroud as well.

it all seems a bit touchy, i welded up some 1.6mm rhs earlier and found 60 amps too hot, and 50amps way too cold, but both dark grey and oxidised

here are some pics of what the beads are looking like on the 3mm stuff:

http://img221.imageshack.us/img221/3384/p8271172k.jpg (http://imageshack.us/photo/my-images/221/p8271172k.jpg/)
http://img35.imageshack.us/img35/656/p8271174.jpg (http://imageshack.us/photo/my-images/35/p8271174.jpg/)

it all looks a bit rusty and messy as the pieces have been out in the rain all day

ive had a few thoughts, possibly 2.4mm tungsten is too thick, and secondly, the grinding wheel i'm using to prep them is fairly coarse, maybe a finer grinding wheel would yield better results?

thanks a ton for the help, ive got a decent grasp on the tig process when things go right, but i never had any of these problems while learning at tafe so not quite sure what to make of it all.

[BenM78]

a bit more info i left out,

am using 2.4mm tungsten, 2.4mm filler and the scrap stainless is 3mm thick

If I was welding this at work I'd be looking around 60 amps, 1.6 filler and 8lpm on a #6 nozzle.

This is about the best you can hope for straight off the torch, mostly welds will have a lot of yellow to blue colouration from the heat. Any time you get the crusty black oxidation will create a porous, potential rusting site and generally poor weld. That said, it can be very difficult to get a outside corner to not have the black oxide on the surface as the gas falls off the corner rather than collects as with a fillet. This weld was around 30A, 2.4mm Lanthanated electrode, 0.9 filler #6 nozzle 8lpm argon. Fillet leg length is around 2mm, material is 1.5mm 316, joint is a 90deg angle and 1.5 sheet.

180191

Have a look in your nozzle, if you have welded a bit of gal or zincanneal you can get blobs of zinc stuck to the inside which can really mess with gas flow.

I'd also like confirmation on your gas - the bottle is all peacock blue? no other colours around the top of the bottle?

[BenM78]

yeah fairly sure there are no leaks, when i turn the gas up to about 15 l/min i get noticable turbulence at the weld puddle, and i can feel the gas holding my hand at the end of the shroud as well.

it all seems a bit touchy, i welded up some 1.6mm rhs earlier and found 60 amps too hot, and 50amps way too cold, but both dark grey and oxidised

here are some pics of what the beads are looking like on the 3mm stuff:


it all looks a bit rusty and messy as the pieces have been out in the rain all day

ive had a few thoughts, possibly 2.4mm tungsten is too thick, and secondly, the grinding wheel i'm using to prep them is fairly coarse, maybe a finer grinding wheel would yield better results?

thanks a ton for the help, ive got a decent grasp on the tig process when things go right, but i never had any of these problems while learning at tafe so not quite sure what to make of it all.

OK, looking at those pics I am sure the gas is argon, if you use a argon/co2 blend on tig the outcome is very crusty on the surface.

2.4 electrode is fine, as is your grinding wheel. so long as you have a sharp point on the end it'll work out fine.

I find that with ER70s-2 the welds on mild are often grey-er, especially if i really pump the amps in (1.6 mild I'd go to 90 amps and feed the filler rather than dip, high travel speed!) if I was after a 'pretty' weld I'd look at around 60-70 amps and dip, resulting weld bead would be quite shiny and yellow to blue like a stainless weld.

[WelderMick]

Hi Corgan,

Geez, there's not much else to try out is there?

That SS looks pretty skanky - you need it to be clean when you start, and it should be clean, although slightly discoloured like Ben's when you finish. Break out a clean flapper disk if you need to.

All the welds look like the amps are too low. Did you try a short arc? A shorter arc means that the amps can be turned up a bit and you can go quicker and cleaner.

Your tungsten is fine, but if you can get some 1.6mm filler then this'll make it easier for you, particularly if you're grinding flush afterwards anyway.

Coarse grinding shouldn't affect the symptoms you're getting - as long as the grinding wheel isn't full of rust from another job.

use some pre-flow gas if you can (BTW is your's a scratch tig?)

I would have the following settings with your #6 cup:
- argon at 7 or 8 LPM
- 60 amps, DCEN
- shiny clean work piece
- sharp clean tungsten. 2.4mm is OK
- torch angle close to vertical (say 80 degrees push angle)
- use some pre-flow as well as post flow gas
- keep your arc short, don't loiter.

If you're visiting the welding shop then I would pick up:
- 1.6mm filler (I find 1.6 the most versatile for a variety of jobs).
- #8 cup (use 10 LPM with this)
- stainless wire brush
- some clean fine flapper disks.

cheers

- Mick

[Corgan]

thanks guys- yeah that particular piece of stainless had some decking oil spilled on parts, none over where i welded, but my results were the same with a fresh clean length of tubing.

i agree the beads are crowned there, that's what i was getting at when i said it all seems a bit touchy- those welds were done on ~ 50 amps, but when i tried with the amps up around 65 the puddle was out of control and the weld was quite undercut.

i always try and keep the arc short as possible, and yes its a lift tig, no HF start or pedal control. there's inevitably always some pre-flow as i have a manual valve on the torch which gets turned on a few seconds before welding.

perhaps when i try some 1.6 filler i will have better results- maybe the 2.4 filler is sucking all the heat out of the puddle when the amps are about right, leading to the cold crowned bead. i'm not exceedingly worried about the crusty grey look as long as it doesn't have any bearing on the weld strength after dressing, so if it's just a cosmetic issue i guess i'm happy to surrender :rolleyes:

anyway, thanks for the support and i'll see how i go tomorrow

[Corgan]

i reckon i've cracked it, i turned the amps down way lower (down to about 45) and had a go without filler, got bright and shiny- then ran some with filler and found i had difficulty keeping the arc tight enough with the 2.4 wire. so i'm gonna get some 1.6 filler and see how i go. the beads with filler were much better today taking into consideration the arc length problems with the thicker filler.

thanks again

[Corgan]

just an update, i've more or less solved the problem and it was a combination of everything- too much heat, too small a cup for the area i was welding (possibly getting some draft or airflow etc), tungsten and filler too big- i've since changed to 1.6 tungsten and filler, size 8 cup and turned the gas down to about 7-8lpm and i'm getting much better results. flat/corner welds are turning out sort of grey but still shiny mid-bead, and coloured on either end, and fillets are turning out shiny silver, golden, blue etc.

now all i have to do is practice my tigging skills as it's been a while, and scratch tig is a different game to the HF start foot pedal controlled machines they have at tafe.

just about finished my first fully tigged project which is a small side/coffee table to match the outdoor table i made last month, tomorrows job is to dress all the visible welds, mitre polish the corners and make the wood slat table

http://img29.imageshack.us/img29/3097/p9011178.jpg (http://imageshack.us/photo/my-images/29/p9011178.jpg/)
http://img4.imageshack.us/img4/2263/p9021183.jpg (http://imageshack.us/photo/my-images/4/p9021183.jpg/)

it's so much easier to hammer/adjust things back to square with tig and 1.6 wall tubing as well, compared to stick welding 3mm tubing :doh: so this table is turning out 100% square and flat in all directions as opposed to the last one

thanks for the help everyone!

[inverter_weld]

Wow, that's awesome. Great looking welds and excellent table. makes me want to whip out a welder and make something :U

[captain_caveman]

Gday
Have you tried turning you gas down to 5 lpm
thanks caveman

[old mate]

isn't the one with a bit of oxy in it the go for stainless ( black band at the top)?

[johncar]

isn't the one with a bit of oxy in it the go for stainless ( black band at the top)?

Yeah I think for MIG process 2% Oxy 98% Argon is good,
TIG process though 100% Argon I think is OK.

[WelderMick]

Nice work Corgan - glad to see you've resolved the problem. Cheers - Mick

[BenM78]

Good stuff.

To clean up your welds get hold of a stainless blending disc. They are a creamy white colour and are cellulose based. Give a very fine grind unlike a flap disc or grind wheel. Have an unusual smell about them. Do the main grind with a grind wheel then blend with the other, they are pricey though.

To clean your stainless all over you can get a chemtech product called aluminium cleaner, it is phosphoric acid based and does a pretty good job. Don't leave it on too long and really wash it off. Wire wheel does a good job of removing the colour too though as you've done.

[Corgan]

thanks for the tips- i've never seen a stainless blending disc, can you elaborate further as to where you can find them etc?

im currently using a 40grit flap disc to get most of the weld ground, then 80grit fiber sanding disc to blend, followed by 120 grit sanding disc then medium then fine non woven type disc before brush finishing with a wheel that chucks in a drill.

i do notice i sometimes have to grind more than i'd like to fully blend which is more likely an issue with my welding or fitup

[BenM78]

I'll find out today what brand they are and where they come from. Normally though just any industrial supply house would have them.

[johncar]

followed by 120 grit sanding disc then medium then fine non woven type disc before brush finishing with a wheel that chucks in a drill.




Hey you probably know but make sure that is a Stainless Steel wire brush, test the bristles with a magnet if not sure. A regular steel wire brush will make your nice SS job rust :(

[Corgan]

yeah, it is a stainless steel 125mm wire wheel for the grinder, as well as a SS hand brush. would hate to be so careful making something look pretty for a month lol

thanks Ben- sounds like a useful product for future projects

[BenM78]

Had a look at the ones at work, all it says is 'Made in USA' and safety/usage info.... no makers name nothing! I am fairly certain they came from Aitkens though so maybe just try a welding place and ask for a stainless blending disc

[19brendan81]

I bet the cup was the main issue. I remember battling away once exactly like you have described, couldnt get anything to work. bumped it up a cup size and bang...welded perfectly at all sorts of combinations of amps and gas flow etc.