Pin holes with 7018 and other newbie questions...

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I picked up welding as a hobby a few years ago, and since then have added quite a bit of welding stuff for the shop.  My stick welder is a Lincoln Invertec V250-s stick/TIG machine, and I love burning 7018 with the machine.  Here's my question.  I was recently running some on 3/16 and 1/4" mild steel, and I am having a few problems with pin holes in the bead.  Amperage is around 120, and I am curious is maybe the metal isn't clean enough for 7018.  Some of the metal is new, but some has some paint that I have knocked off with a wire wheel.  Is it possible some contaminate is causing the pin holes, or is it user error?  I am not having any problems maintaining or starting an arc, and the majority of the bead looks great.  Its just there is apparently some porosity/pin holes, and I haven't figured out what I am doing wrong.  Any ideas?  Here are a few other questions.  When running 7018 or even flux core through a wire welder, how long should you wait before chipping/brushing off slag?  Also, how long until you can make additional passes over the root/initial bead?  Thanks!
Reply:In my experience with 7018, I have only noticed porosity when there was porosity in the metal underneath (like from porosity in a tig root that was overlooked). As far as chipping slag, I like to wait untill its not red hot anymore, if everything is set perfectly, the slag peels up really nice into whats commonly referred to as the "scorpion tail."  As far as additional passes go, It varies from project to project, but usually once I've got the slag all cleaned off and wire brushed I keep on welding.- If you can jump across it you can weld it!  - anonymous old boilermaker
Reply:porosity in a 7018 comes from the rods not being stored properly.  Any low hydrogen rods needs to be stored in a rod oven.  Anytime you see porosity it is usually due to mosture in the rods.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Interesting.  I've had these rods for at least 18 months, and they have been kept in a cylindrical rod box in the shop.  Now, I don't get the pin holes all the time, but I may have to try a new box.
Reply:He's rightReasonably fresh rod, period of high humidity, and the resultsFirst Pic.......Before oven dryout of 7018.  Stuff everywhere, no control of puddle to speak of, sputtering splattering mess.Pic Two.....  After drying in oven, and storage in portable oven while using.  A resonably decent weld(for me).  7018 is very sensitive to moisture.I thought it was all a bunch of crap until I experienced it.  Humidity was running around 70% and higher at the time. Attached Images"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Other than MOGAMBO IMPURITIES, the rods (most rods!!!!) will run well if properly handled.The flux handles most of the impurities pretty well.  It's part of the reason it's there"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Farmer,Thanks for the pics.  That's similar to what I am running into, just not quite to that extreme.  Humidity is a serious issue in Georgia, so it does make a lot of sense.
Reply:Jason what part of GA are you located?  A 7018 or any low hydrogen rod is very acceptable to moisture.  Anytime they are used they need to be either out of rod oven, or within 8 hours of opening a hermetically sealed can, NOT a cardboard box.  If not then porosity and or hydrogen embrittlement can occur.  If ya do a search on the forums there is a wealth of information about this issue. Good Luck.  ~JacksonI'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:INtermittent porosity can also occurr with 7018 if you pull too long of an arc length.  Even with properly stored rod, too long an arc will cause problems...Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Dab is on the money too.  7018 is a short arc rod, and needs to be kept in the puddle.Do anything different, and you gotta mess"Any day above ground is a good day"http://www.farmersamm.com/
Reply:7018 can also leave a bit of porosity at your starts.I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.
Reply:Found a good way to get rid of the porosity at the start is to let the arc go long for a few seconds, then get it in close after some metal has transferred.Read a Lincoln tutorial, and followed it, and doggone if it didn't work.Any problems you have can generally be addressed by a reputable supplier/manufacturer.  It's why I swear by Lincoln, Miller, and Hobart.  They're there when you need them."Any day above ground is a good day"http://www.farmersamm.com/
Reply:Porosity at the start was explained as too low of a temp to cook the gasses out of the weld.  The additional time at the start, per their research, allowed the pool to heat up enough to cook the bad stuff out.Cool stuff, all available on the Lincoln website"Any day above ground is a good day"http://www.farmersamm.com/
Reply:3/16" rod at 120 A sounds a little cold.I burn 1/8" at thatG
Reply:He was talking about 3/16-1/4 parent metal thickness, not the rod"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by farmersammHe was talking about 3/16-1/4 parent metal thickness, not the rod
Reply:Originally Posted by gordfraserOh!i see, sorry...carry on
Reply:I was just told that around 135-140 was good for 1/8. I know when I was running 1/8 7018 at 125A it was to cold.
Reply:remember to grind your metal too if there are traces of rust. 7018 and rust dont play well together.25 years of age.Been welding since Feb 23rd 2009.LU1007 Millwright (A1)
Reply:Originally Posted by farmersammFound a good way to get rid of the porosity at the start is to let the arc go long for a few seconds, then get it in close after some metal has transferred
Reply:Thankfully I don't do much with pipe unless its for hinges.I'ts a whole different world as far as I knowProbably mess it up in a heartbeat"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by weldbeadsince you stirred the mud..isnt 120A a little cold for 1/8 ?
Reply:My max DC on the little crackerbox is 125.  It seems to run ok, but I sure wish I could get up into a higher range.  I was worried at first, then saw the penetration at the lower amps(with a lower travel speed), and I was ok with it.I don't have anything going right now, I have to get off my butt and use the portable for some welds.  It has a ton more power than the little machine.  Won't be any welding here until sometime after July unless something breaks in the field"Any day above ground is a good day"http://www.farmersamm.com/
Reply:I'd just feel better if I could run hotter.  Might discover that it's about the same, but with a higher travel rate.  Dunno"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Hell, gonna do some welds on Monday just to find out.  This'll bug me unless I do it  Guess I'm gonna burn some gasoline"Any day above ground is a good day"http://www.farmersamm.com/1/8 is that 3.2mm?   If it is 120amps is fine, hell go all positional and I'm only running 100amps with that size.....I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.
Reply:Originally Posted by gordfrasernot on my machinessee for your self
Reply:The only thing I'd add is, The length and condition of your lead, plus the number of quick-connects will change you amperage at the stinger.  Maybe one of you other fellas remember the amount of amperage lost due to quick-connects and whats lost in the length. If I recall it was somethin like 10 amps per quick connect. don't recall the loss on length.   I guess the point I'm tryin to make is, just because the dial says 120amps, don't mean thats what you're gettin at the stinger.        Good luckDon't let that iron in your lungs, turn to lead in your @$$!!!!
Reply:Originally Posted by IronmowerThe only thing I'd add is, The length and condition of your lead, plus the number of quick-connects will change you amperage at the stinger.  Maybe one of you other fellas remember the amount of amperage lost due to quick-connects and whats lost in the length. If I recall it was somethin like 10 amps per quick connect. don't recall the loss on length.   I guess the point I'm tryin to make is, just because the dial says 120amps, don't mean thats what you're gettin at the stinger.        Good luck
Reply:Depends on the brand of the rod tooSome run hot, some run cool.  Lincoln is on the cool sideTidal pull of the Moon on certain periods during the month???  Higher altitude and it's effects on boiling point??"Any day above ground is a good day"http://www.farmersamm.com/
Reply:I have done a few jobs on gas plants. While working on the down wind side of the cooling towers you run into this quite often. Never seen anybody with a rod oven or anything. Just dont scratch an arc and start welding till you first jab the rod against what you are welding and hold for the rod to heat up some, old Indian trick. Ha. It will drive out the moisture and you will be porosity free. Hope this helps you. Try it. The pic looks like you ran the first one down hill. Thats not good. Maybe thats just the way the camera made it look.
Reply:Originally Posted by weldbeadlooks good, thick steel too..what machines do you have?
Reply:Originally Posted by IronmowerThe only thing I'd add is, The length and condition of your lead, plus the number of quick-connects will change you amperage at the stinger.  Maybe one of you other fellas remember the amount of amperage lost due to quick-connects and whats lost in the length. If I recall it was somethin like 10 amps per quick connect. don't recall the loss on length.   I guess the point I'm tryin to make is, just because the dial says 120amps, don't mean thats what you're gettin at the stinger.        Good luck
Reply:Interesting information. My leads are around 40' each, and the weld was downhill.  Would I be better off pushing the puddle with 7018, and maybe bumping the amperage to 130?  I guess I may need to get a new box and run some test beads.Also, short of using a rod oven, can you store 7018 in a sealed container and avoid moisture?
Reply:7018 runs uphill always, always.I passed all my structural certs all position without breaking 90 amps with 1/8" rod.  Now that I think about it, I was welding some 1"+ steel for a few other things with the welder set at 105.  Just enough to run smooth and still freeze fast enough to stay where you put it. If you have the knob and pointer type adjustment then you need to put a meter on it and see if the pointer needs adjusted.  We had a welder at work that always had to be set 50 amps hotter than the others.  That was the problem, out of adjustment pointer.Last edited by Boostinjdm; 06-29-2009 at 04:23 AM.