porosity when fusing carbon sheetmetal

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When tig fusing carbon sheet metal edges I have lots of porosity spots. I've tried everything; wire brushing, sand/grinding edges, gas lense, various argon cfh. What am I missing?Miller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:Post some pics.....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 gauge sheet metal and what type of joint configuration are you using?http://all-a-cart.comWelding Cart Kits and accessories
Reply:The current project is 14ga.. The config. is edge to 90deg. joints. I'm posting pics in a few minutes.Miller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:A few pics. Sorry for the poor quality. I'm using my cell. Attached ImagesMiller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:Looks like hot rolled sheet yes?tig doesn't  like millscale much, try flapwheeling it back from the edges say 1/2"
Reply:Hot rolled yes. I thought the mill scale was the problem. I cleaned the weld side but not the inside. with it being a edge joint I think the inside scale my be drawing into weld.Miller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:Looks like you're running a little hot as well. That can cause ambient air draw from the back side as well as the potential for mill scale contamination when you penetrate all the way through.Any reason you are just fusing it and not adding filler? The deoxidizers would help some...http://all-a-cart.comWelding Cart Kits and accessories
Reply:I was fusing it in attempt to acheive a seamless finished appearence. Just playing around mostly. I tiger disced the mill scale back 1/4" or so on both surfaces and it tig much better. I grew tired of tinkering and miged the remaining seams. Turned out nice. Thanks for all the help.Miller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:its the mill scale.  the first few days after i got my tig welder i just threw stuff together and started welding.  In all the excitement of finally getting a new welder, i only wiped with a paper towel but didn't bother to sand the mill scale off.  Anyway, the arc wondered around, the puddle snap-crackle and popped, bead profile was all out of wack.  after i grind off mill scales, everything improved.
Reply:wagin  -  All of the prep and tech-tips mentioned are mandatory for good results. After proper prep, ZT's "a little hot" observation is the heart of your poor result.For a weld puddle to hold, the heat input and heat dissipation rates must be balanced.  It appeared that you tacked your sections corner-to-corner, aka edge-to-edge.  This joint works well for MIG, but not at all for a TIG fuse welds.  With TIG the corners drop out ahead of your weld puddle.  In effect, you are over-driving your headlights; your thermal gradient is exceeding your weld travel speed and preheating the metal ahead of the weld.  The solution is in the joint configuration.  Instead of corner-to-corner, half lap the edges.  Orient the the outside corner of the lapping section on top [weld flat] and focus the tungsten point on this corner and it will fuse [drop] wonderfully into the bottom lappedsection and give you a corner that looks like it came out of a brake.   OPUS