Differances in settings between scratch start TIG and ARC welding

[Mike Pinches]

Hi, I've not got into the garage to practice my TIG welding recently due to college assignments that are due in. At the weekend I needed to make a quick repair to a gate so swapped my Parweld XTI160 back over to stick welding and fixed the gate. I managed to get half an hour free today so thought I would have a quick go at some TIG butt welds and swapped the torch back over. I forgot to flick the switch on the front back over to TIG though.
I noticed that there was absolutely no sticking when scratch starting and that the pool formed really quickly. After tacking I checked the power as I presumed I had it accidently turned up, but it was at 50amps for 2mm steel. At this point I noticed I hadn't flicked the switch so set it back to TIG. When I then scratched to start the ARC there was a very slight sticking as the tungsten made contact and the pool took much longer to form.
I was wondering what internal differences there are in a machine for ARC and TIG welding and how these would affect the starting and speed of weld pool formation? I had always figured that 50amps would have been the same on both ARC and TIG.

 

[Paul.]

It alters the open circuit and arc voltage of the welder, from memory my little Esseti inverter goes from 50 to 85 volts when you put it in tig mode, just makes striking up a bit easier, but the higher voltage may cause problems such as undercut or burn through on thinner materials with some electrodes when stick welding in tig in mode.

 

[Richard.]

^^^
This. It simply changes the OCV
For tig you actually don’t need much more than about 20v
For MMA you need 50 plus ideally.

 

[Mike Pinches]

Thanks for that, good to know that it's normal and the reasons behind it