For those that tig weld weld stainless steel pipe sch. 80 (any 300 series) and use 1/8 rod for the root and 1/8 for second and 3/32 for the cap.What is you setup as in root gap,root land,purge setting, torch gas setting and amperage that is used. The root and second pass must be run with 1/8 inch rod and the cap can either be 1/8 or 3/32 thats the only must.
On that thickness I like a full 1/8" gap or slightly larger and no land. I run the purge on about 10 cfh on a test coupon. More on production depending on the volume. I run the shielding gas at aropund 20-25 CFH if using a cup Bigger than 1/2". When the cups get smaller I turn the gas down a little. I would probably use about 55 to 60 amps for the root. Maybe more to fill if I continued with GTAW but the same for SMAW with 3/32"
As with many things welding. To each his own!
Best wishes and have a good day
Gerald
Colby, I agree completely with Gerald. We weld an awful lot of stainless pipe in my shop (to nuclear quality standards). I have only one questions regarding your post; why is the 1/8 root & hot pass and the 3/32 cover the must's? As a very, very general rule, we normally set our root opening about the same as the filler or maybe just slightly larger. We normally do not use a land on our piping but if we do, we would try to keep it less than 1/16." We normally run our Argon sheilding gas at 30 - 35 CFH. One thing to beware of; stainless steels move like crazy, so if you have some critical dimensioning requirements you may want to think about that.
Another thing to consider is the thickness. 1/2" Sc 80 will weld different than 4" . As the wall thickness goes down the puddle will become VERY fluid as heat builds up. You may have to adjust your parameters some and allow for cooling or force cool with air or water (Stainless Loves it except for distortion).
Good day
Gerald
I have no idea why they want the root and hot pass being 1/8 and the cap being 3/32 but that is what they want for the x-ray test.For stainless in the past i have always fussed the root and run 1/16 for the fill and .045 for the cap.The only reason i did that was i did not want a gap for the purge to escape from and i like the workablity of the 1/16 and the .045 made a beautiful cap.When i tried running the root with 1/8 i had problems with incomplete penetration and the inside of the root just looking irregular but i was putting a land on the pipe so that may of been why.Personally when you are welding carbon pipe do you put a root land on that or no?
I allow a land of 3/32 to 0" and mostly allow my welders to choose their preference. When welding carbon, we follow the same method. Although I am the welding engineer for my company, it's my opinion that my guy's should be allowed some room for their own personal preferences so long as they don't exceed WPS variables.
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