Contaminated Tungsten?

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I am hoping someone here can enlighten me on a problem I am having. My tungsten keeps getting contaminated?!? My setup is a Lincoln 185 TIG, 2% Tungsten sharpened to a point, straight Argon. I am welding on old steel, 50's car frame. I will sharpen up a new tungsten, strike an arc and almost immediatly the point foul up with a small halo looking thing on the end. It looks like a tiny washer stabbed onto the end of my tungsten? This has never happened before and it won't happen when I weld on my welding table. This frame has also been sandblasted and before I run a bead I grind it down to bare steel. I don't have a digital camera so I can't take a photo. Any ideas?
Reply:it sounds to me like you aren't getting any shielding gas.  Have you checked the flow to make sure that it is coming out of the gas lens?  What is your flow set at?
Reply:I have set it at 15cfm.
Reply:Do you have the polarity set correctly. For steel it should be DCEN.Hobart TigmateLincoln AC/DC 225 (old buzzbox)Century flux core migCraftsman hand toolsMilwaukee power & cordless toolsfor fun:2003 Crownline 202 w/ 260 hp Mercruiser2500 watt - 10 speaker stereoMy photos page [url]http://s195.photobucket.com/albums/z305/flmeier/
Reply:hmm, sounds like contamination from the steel surface?  A sandblasted surface can have embedded particles which could screw with the arc and the weld, but you would think your grinding of the area would take care of that.Is there an area that has not been sand blasted that you can grind and try a weld on, just as an experiment?
Reply:It is set to DCEN. I have some scrap pieces of the frame that I could test on. I also forgot to mention that sometimes while running a bead a see small particles jumping off the steel. The same thing that happens when you try and weld something that has been plated. I feel that it has to be contamination or gas coverage?
Reply:I am suspect of sandblasting contamination.
Reply:Originally Posted by pulserI am suspect of sandblasting contamination.
Reply:You could try putting a .045 flat on the tungston.  It might handle the stuff better.  It seems to work for me.  Just sharpen as usual and put a little flat on the end so its not sharp to a point.  Otherwise, grind the steel after sandblasting.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:It was the sandblasting. Grinding was not enough I had to wipe it down with acetone. Thanks for all the help. As for tigging the old car frame, I am obsessed with my old cars and it just looks better. Want to be scared, check out the factory welds on old cars!