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Tig Welding


forteh

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Well me dad just dropped it off at work, it is a (drum roll please.....)

Stel Tig 162H

It looks like this

stel-tig-162h.jpg

Got three disposable bottles of argon, a reactive mask and an arc welding attachment as well (although my dad wasn't sure if this is actually usable with the tig machine but he chucked it in anyways).

So it appears to be a 160amp tig welder, now how do I find more information on it? :D

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How the hell did you find that, couldn't find anything for the 162H on the stel website :(

I wasn't expecting it to be all singing and dancing, enough to learn on hopefully :)

edit: what does the 2t/4t mean? :/

Edited by forteh
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Haha I just watched the same video!
Sort of explains it.

The symbol on the front of the welder has a 35% square step up and then up to full current and then a slope down to 35%

So on 2t...

Press the button and the arc strikes at 35% for a set time and then bangs up to full current (no up slope in effect), release the button and the current ramps down to the 35% for a set time and then breaks the arc.

On 4t...

Press and release the button and this strikes the arc as above and holds a constant current with the button released, press the button again and it ramps down to the 35% and then breaks the arc.

I think that all makes sense :D

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I emailed Stel in Italy and have got the correct user manual for the unit, also asked them what the pre/post gas times and what the ramp down time is, hopefully it should all make sense :)

Whilst the current is ramping down (after releasing the trigger in 2step) should you just hold the torch still at the end of your run until the arc breaks? Also should I be pushing or pulling the torch over the pool?

My dad has added a flow meter to the side of the case so at least I will be able to properly set my gas rate. One of the welders at work has a spare BNIB regulator and has also lent me "The Science and Practise of Welding:7th Edition" for a bit of light reading :D

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Leave the torch hovering a second or two after. Push, as that's the only way you'll see the filler going into it, pulling, the filler would be obscured by the torch hand. And i dont think you can ride the cup backwards, though ive never tried. You'll see what I mean when you have a bash.

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I think I have confused the issue :(

With pull I meant that the torch is in the right hand and is moving from left to right, laying down filler in the back of the pool; with push I meant the torch is in the right hand and moving from right to left laying down filler in the front of the pool.

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Had a fiddle around with the unit last night to try to figure out what connections go where etc.

The gas feed into the welder fits straight onto the flow meter my dad added to the side of the case so it is just a case of connecting a larger bottle (rather than the disposable cylinders) to the back of the flow meter. Got the works buyer talking to BOC to sort out price for rental and refills on a size Y, by my calcs that should do about 18 hours welding :)

Unfortunately stel couldn't tell me the pre/post gas times or the slope up/down times, not the end of the world, would have liked to know though.

I'm assuming that it only welds DC (as there is no AC/DC switch) and for steel/stainless I want to be electrode negative (DCEN), to achieve this I guess I plug the torch into the -ve socket on the unit and the earth into the +ve. Is it possible to weld aluminium with DCEN? I guess it doesn't give such a clean weld as AC because there is no EP to blast the oxide away?

I stripped the torch to check the tungsten, the copper collet has corroded a fair amount, the tungsten is black and green with corrosion. Would I get away with rubbing it down with fine emery paper or should I just pick up a new tungsten and collet?

Sorry for the daft questions :D

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You post sooo many questions in one go smileyvault-chin.gif ...

dc+ is for stick. Dc-is tig, don't recomend trying ally on your machine, but I may be wrong?

You could clean it up but you'll be getting through tips fairly quickly at first so get some spares. 2.4 tips and collet, you can use 1.6 but the weld will be small. Try a few differnt cups too, the technique/material being used means youll probably want a swap it anyway.

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It is a 1.6 tip and collet at the moment, that is also the material I will be welding so wouldn't it make sense to stick with the 1.6 and learn on that? Appreciate at a larger tip will make a larger arc/pool which would help when learning.

Will have a play around and see what happens, I will try to clean up this 1.6 (it's only fairly short anyways, about 4" all in) and see if I can get anything reasonable out of it :)

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One of the videos I watched mentioned an amp per thou of stainless, so 1.6mm would need about 65A as a starting point. After the 130A continuous the 1.6 electrode will start to burn away I guess. So for thicker material you need to use a thicker electrode in order to conduct the current required for penetration.

Got a price for the gas, size Y from BoC £7.52 monthly rental and £62.40 refill, much more expensive than the argoshield we use but then buying a tenth of the volume at a time. Does that sound like a reasonable cost, how long is a 3' tall x Ø8" bottle likely to last? Don't really want to be be stung with months of idle rental, likewise don't want to send a half full bottle back!

On the face of it, it doesn't work out that much more than rental free bottles considering that the VAT will be paid by the company and delivery charge is free, it is however a lot more gas.

edit: the size Y is 4.72m3 which should last 19.6 hours @ 4 l/m and 13.1 hours @ 6 l/m, the smaller size X is half the volume so will do 9.8 and 6.55 hours respectively. I think the X would be a better bottle size to go for, would give me 10 hours to practise and get this pipe welded up - waiting on a price back from BoC now :)

Edited by forteh
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Pre-gas is a few seconds or so to purge the line before the arc strikes and post-gas is again a matter of seconds just to keep the hot weld and electrode shielded from the air till they've cooled down a bit. Slope up is there to help reduce thermal shock on the electrode and give you a bit more life- it just means the arc grows stronger gradually. Perhaps 3-5s or so? Slope out is again to reduce thermal shock but it also gives you a chance to fill the crater at the end of the pool in before the arc goes out (as the arc dies out the crater gets smaller and smaller). Just have a play about and you'll learn alot I'm sure!

I'm assuming that it only welds DC (as there is no AC/DC switch) and for steel/stainless I want to be electrode negative (DCEN), to achieve this I guess I plug the torch into the -ve socket on the unit and the earth into the +ve. Is it possible to weld aluminium with DCEN? I guess it doesn't give such a clean weld as AC because there is no EP to blast the oxide away?

As you and f**kme have already said, stick with DCEN.. Sometimes Al is welded DCEN but it's definitely not common- you can even weld DCEP but that's probably even less common!

I stripped the torch to check the tungsten, the copper collet has corroded a fair amount, the tungsten is black and green with corrosion. Would I get away with rubbing it down with fine emery paper or should I just pick up a new tungsten and collet?

Yeah just give it a clean and try it! Nothing to lose..

I see you have a 1.6mm electrode and came up with 65A on thin sheet- sounds perfectly reasonable to me. Don't get hung up on the leftward/rightward welding thing but usually with tig (for a righthander) it's torch in righthand, filler in left and move from right to left..

ooo and gas flow rate..something like 4-7litres/min would be typical(ish).

Enjoy!

Adam

Edited by Bionic Balls
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The manual for the welder states 4-6l/m, various places on the web have said 12-15 cf/h which equates to max 7l/m; most places have also stated that the least gas possible is better so as to not disturb the shield.

Got to goto my nieces birthday party tomorrow but might try to have a bash with the disposable bottles on Sunday and see how the weld pool behaves :)

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I knew Adam had a metallurgical background, didn't know he was well versed in tig welding.

That said, I'm a mechanical design engineer who designs sewage treatment plant, I can also ride trials bikes, fairly competent riding xc, can sculpt and paint miniatures/models to a reasonable level, additionally I enjoy working on and rebuilding motorcycle engines and hopefully soon I will be able to add a basic tig ability to my hobby skill set :)

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Agree with the least possible approach- too much and the turbulence draws air in. Start low and if you're seeing too much oxidation or porosity (that's what springs to mind anyhow) then turn it up a bit..make sure there's not a draft where you're working either!

I'm a metallurgist/welding engineer so I really should know this by all accounts!

Adam

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