View Full Version : Penetration vs polarity
05-12-2008, 09:48 AM
Ok fellows, looking for someone to shed some light on this matter. Textbooks say with DC+ that 2/3 of the heat is on the electrode, 1/3 is on the workpiece. DC- 2/3 of the heat is on the workpiece, 1/3 is on the electrode. My question is, using the same rod at the same amperage, which polarity gives the most penetration, and which gives the least? (Rod would have to be something like a 6013, 7014, etc). I've seen textbooks give the answer both ways, which is no help to anyone.
05-12-2008, 11:04 AM
DCEP = highest penetration and slowest burn-off rate.
DCEN = lowest penetration and fastest burn-off rate.
There are so many factors involved that determine which polarity to use that it would not serve to enlighten anyone by trying to explain it in this format.
Maybe 95% of the time, DCEP is the right weapon!
Cary's (sberry) advice is to "set it to DC+ and break off the knob". That pretty much says it all.
05-19-2008, 07:21 AM
Well when I have a problem with "Burnthrough" when putting the stringer bead (first pass) in I change to DCEN and get the bead in then change back to DCEP. When you run NEGATIVE it will lay a bead more on top rather than burn through then when you change back to POSITIVE it burns in. All was on pipeline work. Doing it like this got the bead in and hot passing with POSITIVE would pass API-1104 CODE and also ANSI-B31-1 CODE X-RAYS