Welding SS pipes in a jig to avoid everything move!

admin

So, this week at work i start welding SS pipe together, pipe around 1 1/2 diameter, the project and the pieces need to stay the perfect shape as the layout is draw and everything need to touch the jig stopper when i remove the c-clamps!I use TIG with 1/16 tungsten with argon, people at worj told me to weld the join by fusion first (autogenious TIG welding) and then fill it with the stick, it create a lot of heat and when i remove the clamps some part of the tubing were almost 5/8 off / curved...With success i've solve the probleme by using pry bar and force because the SS was still hot, so it was not a big deal to put it in place!I still have probleme to understand HOW stainless steel work and move with the way im welding it and how to do it right!so all advice are welcome!Calculator > Bevel Square
Reply:I use a spray bottle with water and "shrink" as needed to keep the alignment.Lincoln SA200's... at least 15 - 20. They come and go. Growing partial to the "Short Hoods" in my old age. Last count on Short Hoods was 13 in possession.
Reply:How about a pic of what you are doing. From the sound of it most of the movement can be controlled by manipulating the welding sequence as well as a good rigid fixture.
Reply:I won't draw something because im too lazy, but the piece is really easy to undertsand, im doing some center running hand for a 6 landing staircase, so, the running hand at the wall doesn't need to have any connection at both end so it doesn't matter, but the center one have to connect with an hairline joint at every ''return'' each landing (for people that layout railling often its easy to understand) so for a mental picture, i have about 3000 mm lenght and staight tubing flat to the table, and at both end i have a 90 deg elbow with that connect to a straight part of about 300 mm, so at the end its only a ''L'' shape.should i tack all the pieces together first and then remove it from the jig and weld every part that are face to the table, then clamp it in the jig again and weld everything that is face to me ?Calculator > Bevel Square
Reply:so i draw something finally, the grey rectangle is my table, the black thing is the pipe and the small white part are the jig stopper! Attached ImagesCalculator > Bevel Square
Reply:LayoutManWhen welding in a jig; build the fixture with adjusters, and pre-camber the elements until the weldment comes out of the jig straight.Try to deal with the warpage before, and not after the weld. S/S it the worst, nickel is the culprit.  Nickel is such a poorconductor of heat; all the deformation occurs at the weld.  Mild-steel is more conductive, thus spreading the HAZ much wider, and more easily corrected by post weld desperation. Jet Turbine Fins are made of nickel-alloy's because of nickel's poor heat transfer characteristics.The only thing you can do 'during', is heat-shrink, as forwarded by hobohilton; with post-weld torch 'touch-ups'.Heat shrinking is very effective; read for theory, but for mastery must be taught in person.  Opus