Help with TIG welding stainless

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As you surely can see, i am pretty new to this, very green I am looking for some advice for working on stainless steel. I have some experience with stick welding and OA welding and just recently purchased a small little TIG welder. I started to learn how to use the welder with some stainless schedule 40 tubes and sheets and built me cart for a grill. It came out quite ok i liked the welds i produced with and without filler.So i was pretty optimistic for my next project, which was a kitchen counter made out of concrete and that we covered with stainless sheets gauge 18 which we glued on. All i wanted to do is to weld the joints of the sheets; there were like 4 joints, each around 36" long.I thought it would be a breeze to do that, though it came out exactly the opposite.I started to weld some small points along the joint, maybe every 5" apart, so that the sheets would stay nicely together. Then i would go back and add maybe 1-2" also intermediate. But the sheets started to warp like crazy. In the end i had to cut the joint again because it was so ugly and warped that i couldn't leave it.So the next attempt i would only weld 1/2-1" and cool the welding area with a wet rag right after welding.  I was hoping like this to prevent the steel from warping which seemed to work in the beginning, but after some time i had the same problem and it warped. I tried to bolt the sheets down to the concrete but the whole thing came so ugly and after hours of work i have to scrap one piece now and buy a new sheet.My settings were: 1/16" inch Tungsten, cup size 4, pure argon with ca. 11cfh, DC amps. about 50, i tried with filler rod 1/16" and 1/8", welding speed quiet slow, i think to slow.What seems to me one problem is that the heat doesn't really dissipate so good because of the concrete underneath, which enhances the warping.What am i doing wrong or is it just not possible to weld the sheets together with this setup?Any advice would be greatly appreciated.Thanks a lot.
Reply:The 1/8 is definitely too big, so put that away. SS is hard to weld. It uses less heat and dissipates poorly. If you can get a good 1 to 1.5", then let it cool for several minutes between welds. Move down the line a foot or so before beginning a new weld. Most people don't like the wet rag cooling method. Use low heat and let to cool naturally.Best advice I can give you as I'm not a great SS welder myself. I can't imagine the concrete below is doing you any good here. Any chance you can fabricate your top first before attaching to the concrete?__________________
Reply:That is stainless for you....  You may end up clamping or weighing the edge of the sheets down to keep them flat while you weld. If you can, clamp a piece of metal 1-2 "from the edge, parallel to the weld. If you can't get it clamped, try just a piece of heavy, flat metal to hold things together while you weld.  Leave it there the entire time you are welding, not just for tacking.  For 16ga sheet, I've had good luck with a #7 gas lens, 1/16" tungsten, about 20cfm, and 1/16" or 3/32" filler and ran about 45-50A.  Obviously adjust slightly for 18ga.
Reply:I have seen this done once many years ago and did not pay close attention as we were installing cabinets in another part of the house. If I recall correctly they used aluminum heat syncs both sides of the joint top and bottom.
Reply:put some grout in there instead of weldeither that or buy a big sheet so you don't have to weld it. You're gonna have a hard time welding this thin stuff without it warping unless you can clamp it down somehow, but that probably wouldn't work either. You could try heating the backside but you're never gonna get it perfectly flat.you need to just buy a big sheet
Reply:Originally Posted by zekeThe 1/8 is definitely too big, so put that away. SS is hard to weld. It uses less heat and dissipates poorly. If you can get a good 1 to 1.5", then let it cool for several minutes between welds. Move down the line a foot or so before beginning a new weld. Most people don't like the wet rag cooling method. Use low heat and let to cool naturally.Best advice I can give you as I'm not a great SS welder myself. I can't imagine the concrete below is doing you any good here. Any chance you can fabricate your top first before attaching to the concrete?
Reply:Originally Posted by TimmyTIGput some grout in there instead of weldeither that or buy a big sheet so you don't have to weld it. You're gonna have a hard time welding this thin stuff without it warping unless you can clamp it down somehow, but that probably wouldn't work either. You could try heating the backside but you're never gonna get it perfectly flat.you need to just buy a big sheet
Reply:It can definitely be done.  I have read several threads where guys on this site explain how they weld kitchen countertops and sanitary tables in stainless.  There should be some value in the suggestion to back the weld with copper or aluminum,  I have never tried to weld flats of thin stainless so I can't add anything contructive to the discussion other than to say keep looking on weldingweb for your answer.Miller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:If you don't need full penetration welds try lower amps, like 35-40amps. When you see the joint fuse move, anytime wasted going slow is just adding more heat into the stainless causing warping. If you have any copper or aluminum clamping it next to the weld will help pull the heat out of the steel. Sometimes making small circles with the arc can make the joint fuse a little faster when using low amps. Be sure to keep a very tight arc, alot of guys hold too long of an arc and it makes a wide puddle adding alot of heat to the steel.  Also that 1/16" filler may be a little big for 18G stainless, but you should be able to use it. .045" would prob. be a little better.Airco Ac/Dc 300 HeliwelderMillerMatic 200 (stolen)Miller Maxstar 150STLMiller AEAD200LE (welding and generating power) Hobart MIG
Reply:Originally Posted by SquirmyPugIf you don't need full penetration welds try lower amps, like 35-40amps. When you see the joint fuse move, anytime wasted going slow is just adding more heat into the stainless causing warping. If you have any copper or aluminum clamping it next to the weld will help pull the heat out of the steel. Sometimes making small circles with the arc can make the joint fuse a little faster when using low amps. Be sure to keep a very tight arc, alot of guys hold too long of an arc and it makes a wide puddle adding alot of heat to the steel.  Also that 1/16" filler may be a little big for 18G stainless, but you should be able to use it. .045" would prob. be a little better.
Reply:Originally Posted by OscarI was about to post pretty much the same thing until I read your post, lol.  One thing I learned when I was doing my exhaust headers, is use the smallest diameter tungsten you can for the job.  Most of the time I used 0.040" 2%TH since it's good to around 85A.  With the extra short arc-length, you end up getting a weld puddle with a lot less current than a 1/16" tungsten and its corresponding arc-length because the arc doesn't flare out into a wider area.  For filler I used 0.030" or 0.045" mig wire depending on the circumstance, but definitely nothing bigger than 0.045.  OK, maybe a couple times I used 1/16" filler, but it was very rare when I needed it.