Hi again everyone
Progress hopefully in rooting 5G - comment whether this sounds promising?
2.5mm 7016 (Filarc 56S) on DCEN.
My pipe looks to be 5inch sched80 (140mmOD, 10mm wall-thk).
Prep is 2mm root-gap, 2mm to 2.5mm root face
From 6o'clock to midday I can get around one side in 3 electrodes.
I am no longer reliant on the Amps setting, but report them as otherwise how would I describe my conditions?
In the lower sector I am at the maximum rating of the rod - which is
85A. So that's maximum burn with a hissing arc. (testing a higher current produced no useful result - between burn-through and lots of poorly keyed-in metal). Rod angle is a drag-angle to keep weld-pool clear of slag. Getting a "flat" penetration bead - in other words it's to the tube surface but no further.
Second middle sector drop to lowest current with mid-range burn at 75A reported on machine dial. That is the vertical-up sector. There is penetration bead. Rod angle is upwards push-angle to square-on to tube.
On the top sector current rises again to "split the difference" - reporting 80A on machine dial. Goes from push to drag angle of rod.
At all times:
Arc must play at least half on weld-pool (no useful result trying equivalent of cellulosic "keyhole"). Which means rod is weld-pool-thickness (should be thin) back from prep.
If prep. is locally wider, hold rod dead steady and build weld-pool up the middle. If it won't go, it won't go. Stop and change something - current? [While U-weave will keep weld going and looking just fine, rocking up and down the alternate side bevels, told don't do this, will get porosity. Not proven this - would be interesting to do test weld and radiograph...]
At all other times, gently jiggle the rod into the bottom of the prep
- observe tiny shake of rod but it is not in any way a weave If it wont' pen, it won't pen. Should have slit prep groove open if it had contracted closer than it should be.
Rod angle is sole control of penetration(???). Pointing to tube centre gives maximum pen.???
There is some complex "falling forward" way of drawing the weld pool onwards - -in the same way that a person unbalances forward to start walking forward. Coming into view as conditions get more consistent, but vague impression so far. Certainly need to get going to avoid huge build-ups leading to burn-through. This aspect is about how you get a flat weld-bead top surface which does not need grinding. I am seeing some of these now.
I've described everything as much as I reckon it to be. It's a question - am I getting it right?
Thanks for all help.
Richard Smith