Tig burning mild steel?

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My welding instructor has suggested that some of the problems with my tig welds are from mild steel's tendency to "burn" when tig welded too hot. Several of my welds have been porous, had small (non-round) holes between ripples, and I've noticed a frequent bubbling-up of the puddle at the end of welding. Is this "burning" a real phenomenon? Could any of these problems have been caused by such burning, perhaps of the steel's carbon content? Argon flow is fine, though I think I do have a habit of taking the filler out of the gas shield from time to time.
Reply:I have seen metal that wasn't clean do that.  What kind of prep are you using before welding?I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:No cleaning at all, actually. I've been doing lazy practice welds for the most part. Sometimes these problems come up, and sometimes they don't, but my metal has always seemed to be uniformly dirty. Also, my tungsten is frequently less than perfect, but I haven't noticed a definite connection to that issue. I'll go in today and grind down to bare steel for some trial runs. I'd sure like to know that I can control certain known flaws when I need to before I buy my own machine, rather than have the problem be this obscure (to me) "burning" thing.
Reply:Tungston must be clean too.  I had my family all do some tig welding this weekend.  I have  PILE of tungstons to sharpen.  As soon as the tip is contaminated, the arc looses its focus and wanders.  Then you needmore heat to get a puddle, then......DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:"Burning the steel", this implies that oxygen is reacting with the molten steel, which would only occur is your inert shielding is inadequate or if oxides (rust or scale) on the base react in the weld/arc.  Clean the base metal, remove all rust and scale to bright metal, and remove all oils.  For critical welds, clean your filler wire with Acetone and handle the filler and your base metal with clean gloves.Shielding a cold weld is easier than shielding a big old overheated hot weld, so part of the issue may be that you are "too hot". Check the gas system for leaks by plugging the torch at the cup, pressurize the system and bubble check, a leak can allow air to enter the inert gas stream.  Excessive flow can cause turbulence and introduce air in the arc.  A gas lens will help with shielding.If you try all the above and the weld bubbles and forms porosity, it could be that the base metal is crap and contains alot of oxides.
Reply:If your steel isn't clean it will bubble.Me and a friend were tig welding some mild steel once that was all rusty.  We cleaned it up and ran some passes.  Looked good.  My friend's brother comes in and wants to give it a try so we let him try it while we went into the backyard to tend to the BBQ.  We came back and he didn't clean the metal.  There were holes everywhere and it looked like crap.  Tungsten was all burned up too.  Heh, funny thing is he says "It'll hold a fender on!".  Ya, until you reach 25mph.  :PTry cleaning it up a bunch, you will see a difference.
Reply:As said before with a tig, and I mean on any material, you have to clean the crap out of it.  The cleaner the material is the better the weld will be.  I am honestly suprised that your instructor did not make that known to you guys.  I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:There is no such thing  as clean enough when it comes to welding anything with any process.. So if you continue to have trouble with dirty oily contaminated metals of any kind while attempting to weld them...I don't want to hear it.. ...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:What kind of filler rod are you using?  I ask because I was having the same problem a while back.  Turns out I grabbed a bunch of cheap filler for gas welding by mistake and had never ending porosity/bubbling problems.  Tried everything before I thought of looking at the filler type and BINGO! Switched to good filler, problem solved.