Arc length

I did a little demo to illustrate the effect arc length has for someone struggling with a fillet weld recently. Thought it may be helpful for anyone new to TIG...

3mm mild steel, 100A, 1 sec slope down, 5L/min argon with a #7 gas lens. After tacking the bits together i added a couple of autogenous tacks using different arc lengths- on the right arc length around 1 - 2mm, on the left had around 5 - 6mm arc length. Too far away to get fusion


Ran short welds keeping the same arc lengths. With a long arc you initially get 2 puddles (unless the juice is cranked way up), adding filler fixes that but the puddle remains crescent shaped. The filler starts to melt before it reaches the puddle and tends to 'wick' towards one side or the other rather than where you aim. Obviously there is a large lack of fusion problem with the long arc weld


Despite staying at 100A the back of the piece (left and right obviously reversed) shows the differences in heat input

Re arc lenth

Both the welds are with a filler rod the one on the right looks great the other not so good what did you do different then

As said in the original post, used 2 different arc lengths

Re arc lenth

When you talk about arc lenth do you meen the tungstone lenth sorry but new to this and your weld on the left looks like my welding so im interested in your point cheers ocean

Very good Hotrodder , the one on the left looks pretty much like mine at the mo .

Arc length is determined by the distance between the tip of the tungsten and the weld puddle- move the torch (and therefore the tip of the tungsten) further away and the arc itself gets longer

The arc itself is sorta cone shaped- as arc length increases it 'fans out' more, heating a larger area inefficiently. This is easily seen in the first pic as the 'long arc' resulted in 2 melted spots away from the root (where the two plates meet) however the shorter arc length melted the very root resulting in a tack weld

Re arc lenth

Can you tell me the tungstone size that you have used . cheers phil

Tungsten and filler were both 1.6mm. A 2.4mm tungsten would be fine too, it just happened to be what was in the torch at the time. Upper limit for 1.6 tungstens is around 120A DCEN

hotrodder said:

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...mind if I step in? I have been gas welding for years and have taken up TIG so that I can weld stainless. The problem is that my welds look like my gas welds rather than the "stack of pennies" look you show at right. Does this matter? I'm so used to dipping my rod in the puddle if you will excuse the expression.

chezqui said:

...mind if I step in? I have been gas welding for years and have taken up TIG so that I can weld stainless. The problem is that my welds look like my gas welds rather than the "stack of pennies" look you show at right. Does this matter? I'm so used to dipping my rod in the puddle if you will excuse the expression.

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if you show us some pictures we could give you a few pointers. are they decrative or for strength.

Hotrodder, did you use inverter or transformer tig plant? Inverters are a bit more forgiving than old trans technology, of course there is a limit where quality is greatly reduced using inverter............

The weld on the bracket.


http://www.paulshakespeare.co.uk/welding/tig.html

chezqui said:

...mind if I step in? I have been gas welding for years and have taken up TIG so that I can weld stainless. The problem is that my welds look like my gas welds rather than the "stack of pennies" look you show at right. Does this matter? I'm so used to dipping my rod in the puddle if you will excuse the expression.

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The stack of dimes/pennies thing is all a bit over rated really... in fact you could argue that a smooth, ripple free weld is better with regards to fatigue strength- less stress raisers. The filler was dipped in the puddle just as with oxy fuel, the heat is far more focused with TIG though so the 'freeze lines' from each addition of filler tend to be more defined than with oxyfuel. The important bits are that the weld 'toes' transition smoothly into the base material and that there's adequate fusion and weld size for the intended usage.

As Scotty said, post some pics (new thread would be better) for more detailed feedback

runnach said:

Hotrodder, did you use inverter or transformer tig plant? Inverters are a bit more forgiving than old trans technology, of course there is a limit where quality is greatly reduced using inverter............

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Hey Runnach, inverter (Lincoln v205t). Been a while since i've used a big 'ol transformer based TIG but part of me prefers the DC arc from a decent transformer... can't quite put my finger on it, just seems 'smoother'. This was the only time i've welded with a long arc (only did it to illustrate the difference it makes to arc focus- someone was being advised that he needed to up the amps to 150A + to fix the lack of fusion issues he was having) but i wouldn't have thought the machine would make much of a difference with regards to loss of focus, maybe an inverter would cope better re. arc voltage?

Oops, wandered off and did something else mid reply and missed a post.

Paul, a small wobble (and maybe a touch cold) at the start but i'd take that over an exaggerated 'stack of dimes' any day. No idea what that weld's holding but i'd have probably bevelled the edge prior to welding

Hi guys. Cant believe I posted that pic it is jut one I had in the computer. Its a new process for me and all a bit of a surprise when the arc fires up compared to the calm that is gas... bless. The other problem is that I have realised I can't focus that close anymore, I need a dioptre (?) or some close focus glasses. Once I have gotten over the shock of the arc and managed to see something I am a "happy chappy" again. Haven't been brave enough to introduce the"pedal" yet.

chezqui said:

The other problem is that I have realised I can't focus that close anymore, I need a dioptre (?) or some close focus glasses.

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I know the feeling Paul, trying to tig (especially ally) wearing glasses AND a 2.25 dioptre (cheater lens) can be a real pain in the harris my eyes seem to zoom in and out all the time, have to really concentrate on focusing.... any one else have similar isssues...

Wheelchairwelder said:

I know the feeling Paul, trying to tig (especially ally) wearing glasses AND a 2.25 dioptre (cheater lens) can be a real pain in the harris my eyes seem to zoom in and out all the time, have to really concentrate on focusing.... any one else have similar isssues...

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Yep, maybe not quite as bad as you. I use a cheater lens for TIG which is OK as long as I maintain the right focal length, trouble starts with positional work or restricted access, when I tend to go boss eyed. Ally is not too bad as everything is generally larger, but trying to hold a 1mm arc length on thin stainless is quite a challenge. W/A