Tig help!!

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Hello everyone,   Here's my deal, I'm tig welding 1/4 stainless steel and bronze for two 30 foot sculptures.  The sculpture consist's of a inner stainless steel core to provide support for the exterior bronze sheets.   Anyways, I am having problems with my corner welds(60 degree) and butted welds.  They are black in color, and looked scorched, but my fillet welds are wonderfull looking, very even beads and wonderful color (Rainbows).   I assume my problem is from not enough gas sheild around the weld!  Let me tell you what equipment I'm working with and the settings I have tried to fix the problem,Miller 350 XL machine1/4 stainless steel sheets1/8 inch tungsten15 to 25 psi#8 w/gas screen and #10 w/out gas screen150 to 250 ampsPure ARGON GAS1/8 filler rod (3/16 is reccomended but I havent tried any, and maybe that is the issue)Miller reccomends I should be welding with my amps between 225 and 325 for 1/4 stainless steel, but I find that to be way to high, the welds look horrible in that range, and are hard to control.  They begin to look much better around 180 amps and I feel much more in control around that range, but still not perfect.  It seems the less amps the better looking the weld is, but my boss begins to worry about penatration issues, so he tells me to amp it up and step on it.  I hate to do that.  I have tried a # 8 with and without a gas sheild, and a #10 without a gas sheild(I dont have a gas sheild for the #10) and neither seem to make a difference.  Again, my fillet welds are great, but I assume thats because the gas cannot escape.So do I need to keep going up in my cup size until I get  enough gas coverage?  Please any feedback will help! Thanks  James Hemphill New Mexico
Reply:Sounds like the weld is just too hot, because you are trying to penetrate a tight fit joint.  If you need 1/8" of penetration, or whatever, into the 1/4" plate, how about creating a bevel joint that could be filled with less amperage, possible a couple smaller weld passes.
Reply:Try turning your gas down to 7-12 SCFHSometimes you blow the gas away in a corner because it dont know what direction to flow..turbulance.... And corners are tough to begin with..Can you post 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:I'll get some pics of the project tommorrow hopefully.  That should give you a better idea of what I'm dealing with.   I have started beveling the joints, but I havent tried any multiple passes, I like that idea. Because when I run lower amps 120-160 the welds look nice, and maybe the second pass would beef things up enough to pass? Thanks for the quick responses.
Reply:Myself...Thats what I'd be running on that...150 amps.....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:Here are some picturesAnother question I have is, Why does Miller Recommend to weld around 250-325 amps for 1/4 stainless steel plate's.Since Stainless warps so much what is the longest weld I should run over the tacked from?Welding speed - Why are concentric circular beads (overlapped dimes) better then v shaped beads (speed boat wake)? Attached Images
Reply:The fillet welds look good, the corner weld sucks.  If you could shield the corner weld better it would be fine, but with you current shielding it is too hot.The Miller recommendation must be based on trying to achieve maximum penetration on the 1/4" plate with only one pass.Decide what fusion thickness you need for strength.Do you need full penetration, or would 1/2 thickness be OK?Bevel the joint to this depth, use your foot pedal to supply enough current to melt the root plus enough side wall so you can add some filler and have a moderate size (not overheated) weld.Longest weld to prevent warping?  Don't know.  Do you need the assembly to be 100% welded?  Does it require full penetration plus a fillet on the back side?  Probably not, it's a sculpture right, static loads, or is it a rock crusher/earth moving sculpture?  Maybe you don't need huge welds, or continuous welds.  Longest weld for me is dictated by the length of the filler wire and my lack of talent at continuously feeding wire.Welding speed, V shaped boat wake.  Generally speed is not much of a problem with manual welding since it is difficult to smoothly move faster than about 6 inches per minute.One issue with high speed and the V shape solidification pattern is "center line cracking".  This can be a problem in some materials, but probably associated with higher speed automated welding.  The cracking occurs as the metal solidifies, columnar grains grow from the sides walls and converge at the weld centerline.  As the grains form within the molten pool, some elements in the steel solidify first at higher temperatures, and the lower melting point elements such as sulfur are pushed to centerline where they solidify last.  By the time the low melting temperature liquid begins to solidify, there are contraction stresses from the already solid weld that pull the weak centerline open forming a crack.The overlapped dimes looks good, many people like the look, but generally its not metallurgically stronger or what ever.
Reply:Originally Posted by pulserThe fillet welds look good, the corner weld sucks.
Reply:They may be concave, not sure I can tell concave from convex in this photo.I agree, slightly convex is preferred for strength.  Concave welds are more prone to centerline cracks, kind of like when you don't properly fill the crater and you get a crater crack.
Reply:Yaknow..Judging by the size of the project and the stainless involved..If it fit really tight together and all the seams and everything were nice-nice..You could fuse the whole thing with no problem at all..I used to do something like that but diffrent that got all sorts of deep sea cameras and such mounted in it and dragged mercisily on the bottom of the ocean for days collecting data..All fused and never came apart..Done right it works just fine..As far as the "bad" weld pic..Your getting atmosphere from underneeth as you are going along..burn-thru in reverse..Cranking up the argon may help.. but a back purge in those areas works wonders.....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:First off, thanks for all the info!!  I'm been learning alot about Tig welding the last few months, and so far I find it fascinating!Second, could you eloborate on 'Fuse' or fusing, I've not heard of that?And what about back purging?  How do I get gas coverage behind the metal.
Reply:Originally Posted by jhemp_00First off, thanks for all the info!!  I'm been learning alot about Tig welding the last few months, and so far I find it fascinating!Second, could you eloborate on 'Fuse' or fusing, I've not heard of that?And what about back purging?  How do I get gas coverage behind the metal.
Reply:If i cannot get a tube behind the weld, because the area behind it is sealed off, can I fill the area behind it with gas, by maybe drilling a hole a pumping gas into the area?
Reply:Originally Posted by jhemp_00If i cannot get a tube behind the weld, because the area behind it is sealed off, can I fill the area behind it with gas, by maybe drilling a hole a pumping gas into the area?