Whats causing this?

admin

Newbie MIG welder, doing these fishmouth tacks, 2-3 seconds. When I pull out, the puddle starts to bubble and these (what I call) "volcano cones" form. When I grind them, they are hollow. Using C25. Sometimes it does this, sometimes not. I'll do a tack and it won't do it, 5 seconds later I will do another and it will do it. Some days none at all, others it's constant. I'm stumped and annoyed. Gas set to 20 CFH. Last edited by Rockinar; 10-18-2015 at 12:30 AM.
Reply:Just a guess, but "volcano cones" may not be that far off target. Looks like pressure buildup problems from air trapped in your tubing trying for the only way out..Lincoln PrecisionTig 275Miller 251Miller DialArc 250Bridgeport millHossfeld bender & diesLogan shaperJet 14 X 40 latheSouth Bend 9" 'C'Hypertherm 900Ellis 3000 band saw21"Royersford ExcelsiorTwo shops, still too many tools.
Reply:Yeh, volcanoes is what I call them too.  Two possibilities, poor gas coverage, or the most likely is vapors from the inside of  the tube you're closing off."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:Originally Posted by SandyYeh, volcanoes is what I call them too.  Two possibilities, poor gas coverage, or the most likely is vapors from the inside of  the tube you're closing off.
Reply:Swabbing the tube ID clean to remove any paint, oil, etc. also helps.Blackbird
Reply:If you closely examine most fab shop made tube bumpers, guard railings, and whatever, you will often find a small drilled hole or several remaining on the lower sides of the assembly.Those holes were placed there to relieve pressure when assembly got welded up......If you decide to do same and don't want to leave the holes, simply use small holes and once the assembly has cooled to room temps, tack them up and flap disk them smooth.