Burned tig welds

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HelloI have telwin 175 tig machine. Works great, but all of my welds are burned. I tried different flow rates, diffrent amperages even different SS. Welds are grey colour, sometimes little redish.I suspect that I got bad argon bottle. Anybody knows what could be wrong ???There is a picture of sample weld (bad welds I know because I'm used to oxy-acetylen welding). I was welding SS without filler rod.Kevin
Reply:Backpurge???? It really does make a difference..........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:A couple things come to mind.  The red almost looks like dust, or rather rust.  Double check your shielding gas and I would recommend a gas lens for most TIG welding.  15 CFH, #7 cup unless you need better clearance - then smaller cup and slightly smaller flow.  Even with gas lens, hold a close arc - 1/8 of an inch (thick piece of tungsten).  When you finish the weld, and break the arc, keep the torch close, and back up a bit.  Use that post flow of argon not only to protect the red-hot tungsten, but also to protect the stainless (especially at the end).  If you are manually doing post flow, 1 second for ever 10 Amps, then tack 3 seconds on top of that.Please try again, this time sand the metal a bit to make sure all junk is removed, then wipe with a cleaner (something that leaves no residue).Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:Originally Posted by RojodiabloBackpurge???? It really does make a difference..........
Reply:Looks like he's running too hot to me.Mostly indicated by the "reddish" and gray colors and the undercut on the toes.Running hot enough to penetrate through the backside of the parent material will draw in ambient air and contaminate the weld....which is why a back-purge would help.Last edited by ZTFab; 08-27-2010 at 07:06 PM.http://all-a-cart.comWelding Cart Kits and accessories
Reply:Originally Posted by ZTFabRunning hot enough to penetrate through the backside of the parent material will draw in ambient air and contaminate the weld....which is why a back-purge would help.
Reply:Well I tried welding some 5mm thick SS with 60A (without filler rod). Some welds were gray and some blue. Metal was grinded and clean. I'll take my welder to neighbor who have few welders. I will try his argon.I realy suspect argon or leak in the sistem, but the sistem is new and inspected , so I don't think it's a leak.
Reply:That would be a good idea ravselj, also take a couple of small coupons that you have already welded on.Also be patient, TIG welding is a bit of a journey and takes some time and effort to get there. Be sure to post back any good news!Matt