Pipe Tig welding carbon steel

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Im an apprentice (in Australia) who is learning pipe welding with TIG.Ive been doing 6G which is the position in between horrizontal & vertial 3 inch diameter, pipe-wall thickness 10mm (0.39370000000000005 of an inch)No problems with the root. Using LW1 wire I am managing to get consistant root penetration inside all the way around. I am using 75 amps for root.Doing the same weld though with 6 inch diameter pipe & pipe-wall thickness 10mm (0.39370000000000005 of an inch) I am struggling with the same techniques. The root is more flat.Any ideas why? Do I need to pump more wire in? Turning the Amps higher seems to flatten the root further more....
Reply:150nb you should be up around 120amps at least, don't worry about the flat root as it will/should push in with the hot pass.I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.
Reply:120 amps for the 6 inch pipe? Seems pretty hot if I weld it that hot. I am new to this so it may be to much at once for me. I want 3 mmm penetration and im not getting it with the larger pipe. I dont get it coz they are the same thickness.
Reply:Well 110 then, but no less. 3mm has you on the maximum edge for the BS31 code. Minimum .5 and max around that 3mm.  Have you got feeding the wire sorted?  Get that right and 120 will be no problem Wait till you get into some bigger bore, then it changes again.I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.
Reply:On your root pass, if you're feeding wire and the puddle isn't growing outward, it's pushing it inward.  That's what I try to keep in mind, and it works good for me.  I burn hot enough that I can push the wire in and not see any more buildup on the outside..and therefore I know it's pushing it inside.