GMAW process, ER70S-6 filler, running open butt,3/32" root face, 3/32" root opening, 60 degree included, downward progression, tacks at 12-3-6-9 feathered lead in and lead out, WFS 160, Background current 55, Peak Amps 385, no tailout,2.0 on hot start, LOP at tie ins any suggestions? 10" A588 pipe 1/4" wall.
I don't have programming advice other than possiby increasing the peak amperage or the time on "hot start"
but one "technique" that helps with traditional short circuit open roots is to clip your wire end on your restart, just long enough to contact the "back" of the inside of your stop point.
It's a little different than running down a feathered edge.. But putting the wire under the end of that edge and beginning the restart there, effectivly putting that arc strike on the inside of the pipe.... I've see this technique work really well with restarts on GMAW-S when running in any position you can run a drag angle.
Again it's a little different, but GMAW of pipe is a little different eh?
Are you running 12/6 o'clock or are you rotating the pipe?
Keep us informed on your progress... It's an interesting problem
Running Fixed 6 GR position, Downward progression with STT. Cap E81T1-Ni1 Vertical progression, Not sure what to think about STT process yet , Would just as soon Key hole a 5p up cap LO/HI or use my original Tig procedures for the root, but noooo to slow for production
I bet you will work the bugs out with a few more trials...
The people I know running STT on steel pipe are pretty happy they made the switch... I just haven't squeezed their secrets..."yet"
I don't think STT is any faster than short circuit mig for pipe, but it does have the cool CC/CV behavior that takes out some of the risk of operator bobbles when they make slight changes in stickout in a 6G weld..
What shielding gas are you using?
Back Purge?
Just curious.
Tim
100% CO2, no purge needed,so they say.
If you are able to do some experimentation, I would think that using an Argon/CO2 mix would help the bead wet in or fuse much better.
Tim
You have to grind your stops and starts to a feathered edge and start back about 1/4" from the edge of where you want the complete penetration tie-in - BOTH. No shortcuts will produce consistant results. The reason you always start back on the pevious section of root pass at least 1/4" is so that the base metal and previously deposited weld metal of the root pass will have a chance to heat up and allow for the penetration at that point. With SMAW you long arc, lower the electrode to the keyhole heating up that area - stuff the rod in and go. With GTAW you hold the arc at the edge, build up the heat then add filler. You don't have these luxuries with GMAW-S (or STT or RMD or whatever fronius calls it). When then root pass is complete you will need to remove all of the re-starts that crept back 1/4". If you do switch from 100% CO2 to an Argon mix you will want a slightly larger gap. The Argon blend will promote better arc stability and paramatere variances but has less depth of fusion into the root face. Therefore if you have any misalignment issues it will be less consistant on the CP. Or run a wider gap than the 3/32". Both work fine if adjusted for this issue.
Topic American Welding Society Services / Technical Standards & Publications / Surface Tension Transfer
