Help With Stainless

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Question for the welding web guru's...I'm welding a 315 stainless tank to a 304 stainless tri-clamp coupler (or visa-versa)... Miller Dynasty 200DX, Argon, 3/32 Ceriated Tungsten, #7 Cup on WP17 torch, regulator at 25 CFM, 120 Amp DC w/ pedal, 316L filler.I'm getting a blackening on top of the weld... almost crystalline looking, which seems to me like there is a problem with the shielding gas.  I checked the regulator by disconnecting it and varying the delivery amounts... listening and checking with my hand... disconnected the argon hose from the front of the machine to check that the solenoid was staying open... I hear gas moving from the torch...Did the spot weld check to verify gas coverage.  Results were iffy.  I need someone with more knowledge than me to help me out here!  I know the weld looks crappy... position was bad.  If I brush the weld, it looks fine.  It's going to be ground down anyhow.  But, I see all these beautiful straw colored stainless welds and... well, something is wrong here!  You can see in teh second photo the brushed weld on the left and the unfinished dark weld on the right.Ahh, trouble shooting.Thanks in advance!!---------------------------------Miller Dynasty 200DXMiller Spectrum 375 Extreme
Reply:You could turn down the gas to 15 cfm and from the looks of it, it looks like your running to hot.  On ss reduce your heat buy 25% over regular cs. Thats all I got.
Reply:Can you try a new cylinder, or try the same one on a different machine?  I have had a brand new tank give me similar results before, it would be wise to make sure you have good gas before anything else.Have we all gone mad?
Reply:Ditto-too hot, too much gas flow--address these for starters,before condemning gas quality. Presumably by #7 cup-you're using a gas lens?....which helps.Excessive electrode stickout and/or torch techniques can contribute to this.What does the electrode look like?Suckholes-the top and bottom pictures show nice craters from abruptstopping of the arc. These are crack generators and can create leaksthru the weld. Practice fading out with the arc, then holding cup in positionfor nice, long post flow--which you don't indicate how long that is.Post flow is way important on SS.Is the tank body being back purged, solar-fluxed or left to oxidize and sugar at it will?Blackbird
Reply:Thanks for the input(s)...Tomorrow I'm going to try the gas lens... don't have one on right now.  Also, I recently switched to ceriated over throiated.  I may switch back until I get this issue worked out.The two welds with pitting were test welds... trying to figure out if I had good gas coverage.  I'll try running at 15 and see how she goes.  I have a 10 second post flow right now... do you think that this is adequate?Right now, the tank is left to sugar at will, but it is 3/32 thick and sugaring hasn't been a problem.  One or two small spots.  The inside of the valve will be ground and blended as well... so I'm not too worried about that.  Do you think that I could be pulling contamination from the back of the weld?Thanks again!---------------------------------Miller Dynasty 200DXMiller Spectrum 375 Extreme
Reply:Originally Posted by szymancpThanks for the input(s)...Tomorrow I'm going to try the gas lens... don't have one on right now.  Also, I recently switched to ceriated over throiated.  I may switch back until I get this issue worked out.The two welds with pitting were test welds... trying to figure out if I had good gas coverage.  I'll try running at 15 and see how she goes.  I have a 10 second post flow right now... do you think that this is adequate?Right now, the tank is left to sugar at will, but it is 3/32 thick and sugaring hasn't been a problem.  One or two small spots.  The inside of the valve will be ground and blended as well... so I'm not too worried about that.  Do you think that I could be pulling contamination from the back of the weld?Thanks again!