Arc gets hotter as you pull it back? How do you find the 'sweet spot'?

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Hi,I am teaching myself how to TIG weld.I have a Thermal Arc 185 AC/DC.I was welding some 16 gauge mild steel 1" square tube. 90 amps, HF start. Pulse.I found that, when I brought the electrode very close to the surface, it was narrow and focussed, but the metal was not heating as much. But if I pulled it back some, it got wider and seemingly, hotter, and I was able to blow holes through the tubing pretty rapidly.  This even though I was holding the control pedal constant.Fortunately I was working on scrap so I could just play with burning holes without wrecking anything.Is this to be expected? It seems counterintuitive. I would think a closer arc would be smaller but more intense, more likely to overheat a small area and blow holes, but instead it seems as though pulling away a bit made it hotter.Or maybe by pulling away the weld area was not being bathed by argon, so was not being cooled and was reacting more with the ambient atmosphere?A reality check/explanation would be much appreciated.Thanks.An odd fellow, but nice enough. I build "interesting" things.
Reply:Originally Posted by ThaddeusHi,I am teaching myself how to TIG weld.I have a Thermal Arc 185 AC/DC.I was welding some 16 gauge mild steel 1" square tube. 90 amps, HF start. Pulse.I found that, when I brought the electrode very close to the surface, it was narrow and focussed, but the metal was not heating as much. But if I pulled it back some, it got wider and seemingly, hotter, and I was able to blow holes through the tubing pretty rapidly.  This even though I was holding the control pedal constant.Fortunately I was working on scrap so I could just play with burning holes without wrecking anything.Is this to be expected? It seems counterintuitive. I would think a closer arc would be smaller but more intense, more likely to overheat a small area and blow holes, but instead it seems as though pulling away a bit made it hotter.Or maybe by pulling away the weld area was not being bathed by argon, so was not being cooled and was reacting more with the ambient atmosphere?A reality check/explanation would be much appreciated.Thanks.
Reply:I think you are correct, that the longer arc blew holes due to lack of shielding and oxidation (burning) of the steel, like OA cutting.  The longer arc does have much higher voltage, which is more power, but the huge increase in arc diameter has a much greater effect in reducing energy density and energy transfer to the workpiece.  In general, you want the shortest possible arc length with TIG to give the most precise, controllable, focused arc, yet allow you to add wire and move along without hitting the tungsten with the wire or dipping the tungsten into the pudddle.
Reply:I'm with Pulser,I'm betting that, as you pulled the tungsten away from the part, you saw a boatload of porosity and bubbling right before you blew through the tube.  Indicative of a lack of gas coverage.  The hole burns through because the lack of shield gas doesn't allow it to flow back into itself.And the sweet spot?  You ask 10 weldors, and you'll get 12 different answers.  There's only one way to find the sweet spot.  Keep looking for it.  Trust me, you'll know when you find it.I r 2 a perfessional
Reply:You have the process down, now its Practice""""""""""""""""""""""""""""""""""""""" JohnSMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :