by jared
(raleigh, nc, usa)

i got a quick pipe question for you. i am welding 4" sch 40 carbon steel pipe 6G position. I am having problems with undercut on my cap. i can get the root all the way to the hot pass without any undercut. i am running about 80 amps. using 1/8 tungsten with 1/8 filler walking the cup. also on my root pass i keep having problems on almost 2 out of 3 joints of pipe with suck back. i cant seem to get consistent reinforcement on the inside of the pipe. thanks for your help



suck back is usually from weaving the tungsten on the bottom. try to keep it really narrow. if you are walking the cup, just barely wiggle it...and keep the tungsten angle steeper and almost straight in on the bottom.

undercut sounds like you just need to let it cool for 10 minutes before the cover passes and you might be weaving too wide.



Return to tig forum.