TIG craters

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Hello everyone,I have a question regarding TIG and contamination. Here is the deal. My skills lie in MIG welding, but I have a TIG machine, and have been doing it for about a year. I usually have excellent results, and I always follow the general rules of cleanliness, grind to shiny metal, and use lots of acetone, but I have been plagued lately with horrible puddle contamination problems, and I cannot figure out what is causing it. I wipe my filler down with acetone, and regrind my tungsten when I need to, but still big problems. Here is what happened today. I was welding a 1/4" npt bung to sheetmeal, and everything was smooth. When I got to the farthest point of travel I could do on that weld in that position, I eased off the pedal slowly, and kept the torch over the weld while it cooled so the post flow was still shielding the hot area. I repositioned the work piece, and started a new puddle, and thats when everything went to crap. As soon as the puddle formed, it started popping and spattering. I eased off the pedal, and a bubble formed and ultimately popped leaving a nasty crater in its place. I tried to salvage the piece, so I ground the bad weld completely out, wire wheeled it, and scrubbed it with acetone. I then took another stab at it, and the same thing happened. Any ideas here guys? Am I missing something?Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:Sounds like a gas problem..Can you hear it hissssssssss when you hit the pedal??...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:The gas is flowing nicely. When welding mild steel I have it set to 20cfh, and  I can hear it coming out of the torch. The other thing I am noticing after I stop the arc from the first weld is there looks to be some smoke around the weld area. I have never seen that before when tigging, but its almost like something is being drawn out of the steel and burning on the surface. I wipe it down with acetone, but after that first pass everything turns to 5h1t.Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:IMHO 20 is way too much..I run mine around 10 generally..Set the flow with the pedal down..Have you tried playing around with a diffrent batch of steel??One more thing...Is it possible to clean the backside of your piece also?Sometimes the oils and crap will rise thru the metal if its thin enough and cause major headaches.....zap!Last edited by zapster; 09-23-2007 at 12:04 PM.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:It is rare, but contaminated argon can do that.  Try changing bottles.  You also need to grind out all the contamination.
Reply:I will turn the gas down, and I will try cleaning the steel even harder. The sheetmetal peice I was welding the bung onto is a brand new (chinese) 20oz oil tank that had a thin coat of oil on the inside for rust protection. I sloshed acetone around inside a few times, and shoved an acetone soaked rag on a stick in it and scrubbed the back side of the weld area with it and then burned off the fumes with a lighter before welding on it.  Maybe its the cheap chinese steel of the tank, I dont know, but the idea of using an oil can as a gas tank is out the window. I will be rolling one out of sheet metal and buying a neck and cap.Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:Riley, this tank of argon has been good to me so far. Ive welded on mild, stainless, and aluminum with no problems before, so I dont want to blame it on the gas just yet. But, that is something I did not know, and will be exploring as a problem should I continue to have cratering problems.Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:Every once in a while, I get a piece of tube that will do this also. It is just a junk spot in the steel, from what I have found. I have welded 3/4 around a tube, with no issues, and then the last little bit of weld is total crap, looks like volcanic rock. All you can do is grind it out, re-weld, grind it out, re-weld. (EDIT) Or, mig it. It seems the mig buries it a little better.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:it does sound like your pulling some kind of crap through the backside of the weld.  Clean it as best you can, or just weld it as cold as possible.Have we all gone mad?
Reply:I'm sure you know this but I can't help but ask...the tank IS vented correct??Miller Dynasty 700Miller 350P with Aluma-pro push-pullMiller 280 Dynasty with expansion card Dynasty 200 DXMigMax 215 Enuff power and hand tools to create one of anything..... but mass produce nothing!!!
Reply:Where was the last place you absolutely remember having your keys? (Sorry, wrong thread.)Is your tungsten grinder being used to grind old, rusty, chipped, hatchet blades?City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Fusion king: I dont know what context you are asking the question, but if you are referring to making sure there is a way for pressure to escape due to the heat expansion during welding, the bung I was welding on to the tank is basically a vent for the time being. If you mean is the tank going to have a vented cap while holding gasoline, the answer to that is yes. Tanglediver: The way I grind my tungsten is I dedicate a 120 grit sanding disc that mounts to my angle die grinder. I chuck the tungsten into the drill, set it as fast as it will go, hold the lever down on the die grinder, and grind. It does a really good job. After that, I wipe down the tungsten with acetone.Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:You need a bench grinder with the guard removed..Stand behind it and grind away from you using the top of the wheel...50$.....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:This maybe out there, but how is the airflow in your work area?  I watched a guy go nuts tigging some aluminum. He kept messing it up, swearing like all get out, clean it up, try again, start cussing. Finally another guy walked over and turned off the fan he had blowing on him.I would suggest trying a new tungsten and cutting back your gas to about 10cfm like Zapster commented.
Reply:I plan on investing in a dedicated tungsten grinder eventually. The method I use was actually shown to me by a guy who gave me the rundown on how to use my machine when I first got it. He said he put both his kids through college as a welder. The method I use does work, if you dont have a dedicated grinding wheel for your tungsten. Ill pick a cheap grinder up next trip to HF. jportale: Air was not a factor. I dont run a fan on me when I MIG or TIG, dont want that shielding gas getting pushed away from the puddle. I think I am going to check this crater mistake off to not having the backside clean enough. While I did put a pretty hard effort into making sure the inside of the tank was clean, the smokey film that kept settling on the HAZ after stopping the arc was just too suspect. The material was pretty thin, and who knows, maybe the junk was wicking through. I hate putting in 15minutes of cleaning time for 4 inches of weld, and screwing up the whole thing in a matter of seconds. People like ZAP make it look easy.Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:this might be a stupid question,,,have you looked at the gas lense?
Reply:I look at it everytime I weld.Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:I've had a lens that someone spattered up....didn't notice it at first and was wondering why I had what appeared to be gas problems. Heard the hiss but still got porosity. Then I looked inside the lens and found a couple of berries that were redirecting/causing turbulence in my gas. New lens, problem gone. Just another option to checkELVIS
Reply:I check it every time I fire up the machine. I will pull the tungsten out of the torch to regrind it, along with about 3 extra, and I make sure its clean. I dont think I have ever seen a dingle berry in it. I do a pretty good job of making sure my workpeice is as clean as possible so there is never really and spatter. Thanks for the suggestions though.Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:Maybe some of the vapor condensed between the pieces and then got into the weld.Miller Dynasty 700Miller 350P with Aluma-pro push-pullMiller 280 Dynasty with expansion card Dynasty 200 DXMigMax 215 Enuff power and hand tools to create one of anything..... but mass produce nothing!!!
Reply:FK, that is a good possibility. All I know is that there was little room for error since the tank I was welding to is so thin. After I reground the weld and it junked a second time, I knew I would have to cut a patch and press on. Rather than think rationally at the time, I just threw the tank, and dented it pretty badly. Theres a big $3 dollars down the drain.Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:Qucifer,Based on your initial description where you stated that you had run an initial bead successfully and the problem started when you tried to restart, I'd say you have contamination coming through from the backside.Sounds as if the initial bead went in pretty well.  I suspect the heat of welding drew the contamination (from backside) to the surface.  As you finished the initial bead (cooling with gas flow) the contamination crystalized near the surface and caused the problem when you tried to restart.Would it be possible to better clean the backside of the weld?  You also may try backgassing the tank.Just my .02Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Sundown, I am settling on the same idea. I put a pretty good effort into getting the inside of the tank as clean as possible, but I am guessing it wasnt enough. The lesson I learned here is, when you think its clean enough, clean it again.Miller Syncrowave 200Hobart Handler 140Thermal Dynamics Cutmaster 38E-Z Tube BenderPlasma Cam DHC2
Reply:If you are not using ER 70S-2, you are using the wrong wire.  S-2 is made to clean the back contamination because of the amount of deoxidisers in the wire.  2% tungsten should be used and tungsted grind marks should go down the tungsten and not around, that has an influence on arc flow.