Need Help - TIG Welding Question

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I have an application where I have a 3/8" thick plate, mild carbon steel. One side is painted with an industrial enamel rated around 250 deg F, the other is unpainted. On the unpainted side I am performing some stitch welds running about 200A. Using 1/8 Tungsten, and 3/32 filler. The bead size is between 1/8-3/8" and about 2" long. I am having trouble because the paint on the opposite side is bubbling and distorting from the heat, causing unneeded rework of the paint. I need a method to capture the heat and prevent the paint on the other side from getting ruined. The opposing side must be painted before welding due to our process and limited painting requirements post weld. Thanks so much for any and all advice.
Reply:Having never tried that, it seems like it would be nearly impossible - 250 deg F is pretty low.Have you tried clamping a heat sink to the painted side - like heavy aluminum?May not work since the heat still has to pass through the paint to get to the aluminum - but worth a try.Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Try laying a wet bath towel under the plate. The water in the towel should keep the painted surface from getting damaged. You will also need to weld hot and fast. Weld time puts heat into the metal. You may have to shorten your welds to 1/4 inch at a time. Work around the plate then start over until welds are 2 inch long. Allowing cooling some cooling time at each weld.Does your tig have a pulse mode? Set up right. Pulse will control the heat input and still give you a good puddle. Tungsten type will help with pulse.
Reply:There is a moldable, reusable material called "Heat Fence" that helps to contain the spread of heat, but being as you are welding one side, and the other is painted, I can't see how you could apply it.  You might look it up and see if you can figure out a way to put it to use.  Like others have said, that's a bit of a head scratcher.  Compressed air blast to quickly cool the surface (basically combat the heat at the paint layer until you can get the temps down by some other method)?  You will have to be consider being careful about how you cool the welded surface, as you can cause an insulating effect that drives the heat through the material.  I've felt this when partially quenching a part - the part that is not in the water can have it's temperature raise dramatically when the rest of the part is driven into the water (quite odd, the first time you experience it).Miller Dynasty 200 DXMiller CP-300 with 30A feederHypertherm Powermax 900Oxy-fuel w/Harris torchesScotchman Glide-in bandsawMonarch 10EE latheEmi-Mec Autoturn latheDeckel FP2NC milling machinePro-Tools 105 Bender
Reply:I would go with the wet towel idea. the paint on the other side will have a hard time getting hot with all that water on it. this could be bad if you are welding near the edge of the plate where any steam could screw you up.bosses stuff:trailblazer 325maxstar 200my stuff:sa 200fronius transpocket 180100 amp Lincoln w/f97 f350 DITKevin
Reply:There is only one method I can think of... use a 3/32 tungsten run it on about 88-90 after every pass let it cool down.