Welding flange to pipe

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Here's my process for welding a SS flange (1/2 inch thick, square flange, 4 corner bolt holes) onto schedule 10 pipe. What am I doing wrong?I preheat the flange from the outside in until it's glowing orange. Then I TIG tack the inside of the flange in 4 places. I TIG it out at about 150 amps.Then I immediately get the pipe to the turntable and MIG the outside of the flange with fluxcore at about 240 WFS and 26 volts.When I put a square on the flange when I'm all done, it's warped. The "ears" are bent up. I end up having to beat it flush with a deadblow.What am I doing wrong?Is there a certain way to preheat a flange to avoid warpage?
Reply:Have you tired pre-heating to bend the ears first before welding?Don’t pay any attention to meI’m just a hobbyist!CarlDynasty 300V350-Pro w/pulseSG Spool gun1937 IdealArc-300PowerArc 200ST3 SA-200sVantage 400
Reply:Have you looked at zap post ? http://weldingweb.com/vbb/showthread.php...efore-Weld-101good luck
Reply:It's stainless it's going to pull like crazy. Weld it bend back to square And call it a day. Done this on 2" sched 80 stainless headers with 3 1-1/2 thread owlets put on. A big press helps.
Reply:Are we talking about a slip on flange or a weld neck flange? What pipe diameter and flange measurements? First of all you should not be heating it until it glows orange. Honestly you probably do not need any preheat unless you are working in an environment that is less than 70 degrees or so. If you want to avoid warpage, keeping stainless as cool as possible is critical. Not to mention the fact that you are ruining the properties of the material by overheating it. If it still warps even with low overall heat input, you could consider attaching another flange to it before welding. The extra flange will act as a heat sink and strong back at the same time.IAMAW Local 330Airco 300 AC/DC HeliwelderAirco Dip-Pak 200 with Profax spool gunPowr-Kraft AC225Everlast PowerArc 200stBuffalo Forge No.21 drill pressSpeedglas 9100xxAirco, Oxweld, Purox, Victor torchesLincoln Ranger 8
Reply:You do not need to preheat the pipe or flange, slip the flange on the pipe, pull it back a little leaving enough to back weld it, tack it, square it jump to the other side tack it, square it the other way tack it and check square again tack. If you quarter it when welding 6 o'clock to 9 to o'clock then jump to 3 o'clock to 12 o'clock them 9 o'clock to 12 o'clock and finish. If you just roll it out it will pull every time, you need to balance the shrinking, put your welds in as fast as you can.
Reply:Quote:Austenitic stainless and nickel alloys do NOT harden no matter how fast they cool from welding. So, it is not necessary to preheat stainless, nor to post weld heat treat it. As a matter of fact preheating stainless, beyond what may be necessary to dry it, can be positively harmful. Stress relief 1100-1200°F (600-650°C) as applied to carbon steel is only partially effective with stainless or nickel alloys, and may be damaging to the aqueous corrosion resistancehttp://www.rolledalloys.com/dotAsset...5635c582c7.pdfWhat michaelf said about welding in quarters is also diagramed in the link.Last edited by MinnesotaDave; 01-15-2014 at 11:09 AM.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.