A new issue for me; tig over stick.

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Well, a lot of guys know I have been working at a pipeline/ refinery shop. In the field, guys will fix stuff with whatever it takes to finish out the day, then bring it back to me to do something permanent to repair the tool or part.Had an interesting one Friday; a stud used for adjusting a big guillotine saw had sheared off. So, they cleaned it up a bit, and welded it to hold for the day.I got to do the real repair. The part was welded with 3/32 7018 stick in the field. I ground down, got to very clean material and then proceeded to run a bead with 70 s2. The reaction between the 70 S2 and the 7018 was really interesting; the puddle formed on the 7018 bubbled and argued like it had porosity in it. After a cook off pass with a little filler, it did not look too good- on a lot of it, but not all of it. I cleaned it with a wire brush well, and ground it a little bit, and went for another pass. Brought up less gunk, and was now acting a lot like a weld on cast material, the way you can 'wash out' the weld and get it to come clean after a couple passes.In the end, 2 full passes, and it was a very good weld, and I was happy enough.To test the theory, I had one of our guys do a test piece for me. And, then I cleaned up the 7018 cap, and tried to tig it. Same issue; it argues with being reheated via tig torch.Wondering what the property is in 7018 that makes the 7018 filler act up so much??Welds were power wheeled, and VERY clean. 3/32 tungsten, 3/32 filler, DC, 20CFH argon (Good bottle, hitting SS and alum. every day last week on it, no issues) Ideas??And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:I don't know what causes it either but in the past I have had to tig over 7018 tacks and the same thing happened when I got to run over the tacks..Bubbling.. spitting..all around mess...So what I did was tig tack next to the 7018 then ground the old tacks off.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:I am taking a guess here, but I think the 7018 is boiling off because it melts at a lower temperature. Depending on the make up of the rod and flux, I have run some 7018 1/8" at 95 amps and some will take 135 amps to get the same weld. Like I said it is just a guess.www.georgesplasmacuttershop.comPlasma Cutter and Welder Sales and Repairs--Ebay storeTec.Mo. Dealer Consumables for the PT and IPT torch's
Reply:Originally Posted by zapsterI don't know what causes it either but in the past I have had to tig over 7018 tacks and the same thing happened when I got to run over the tacks..Bubbling.. spitting..all around mess...So what I did was tig tack next to the 7018 then ground the old tacks off.....zap!
Reply:TIG welding everything for the last 10+ years I have seen all kinds of stuff resist. From trying to go over MIG welds to like mentioned stick welds. Most all of them don't like to be TIGed after. Same with torch, plasma, or lazer cut pieces. But then stainless and aluminum flow together like nothing is wrong.
Reply:I also have had this problem with stick, and mig welds. Leads to alot of head scratching and wasting time.I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:Glad I am not alone. On a side note, this can serve as a learning lesson for others who might run into having to weld onto parts that were previously welded.As to porosity in the weld, I seriously doubt it. These guys weld x ray beads all the time, and we have a less than 1% reject rate. But to say the material itself has elements that do not like tig???? I am now certain of it! Thanks for chiming in guys!!!And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Rojodiablo  -  In normal industrial welding [root and fill] you Stick/Wire weld over TIG; and life is good.  If you are TIG/ing over Stick/Wire, it usually means that you are trying to shortcut a fix on an existingproblem.  The welders skill and their general practices is the usual cause, specifically surface prep.Virtually no one preps. their metal for Stick/Wire, and that is why S/W is used for production.  Less work,and it welds "good enough".  Unpreped S/W beads still have mill-scale on the margins, E7018 will commonly have flux inclusions in the 'cold-lap' underbelly margins, and general S/W practices produce porosity in the weld bead itself at surprisingly high, but acceptable levels.TIG/ing virgin carbon steel requires superior preparation to be successful.  I believe the problems cited on S/W beads are a result of: crud on the bottom, crud in the middle, and crud on top; all incompatiblewith TIG.   A TIG puddle reaches deep, and up come all the rabbits.  I TIG over Stick/Wire regularly without any of the aforementioned problem, because I am repairing my own S/W work.  TIG repairs are easy because I prepared the S/W surfaces as if I were TIG welding tobegin with.  I produce a flux-core welded product that has to have cosmeticly perfect welds, and TIG repair is my Bondo.     Because of the S/W conditions cited there isn't a panacea for the problems posted.  In the hierarchy of weld purity, TIG over S/W [by others] will always produced surprises and problem beyond your control.    Grind on.   OpusLast edited by OPUS FERRO; 07-30-2012 at 04:28 AM.Reason: Context