Why is my project warping / managing heat

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Hello All, I'm new to welding and am trying to shorten the learning curve on the effects of heat and managing heat/warping.I've been welding together 1/8" steel scrap to make a lower shelf panel for my table. I have 2.5" wide strips and 1X2" rectangles that I'm welding together (see photo). The first part I made was two of the strips with three of the rectangles between. I tacked it together then went back and welded all of the top side welds without any significant pauses. The piece bowed up from the table about 1/2" as it cooled. Piece was only 24" long. Assumedly this was due to the heat. I clamped down (i.e., in the vertical plane) the next few pieces, took pauses between welds and spritzed them with water after each weld to try to draw off heat. Those pieces have ended up much more flat. On one piece the 1X2" rectangles each retracted up a few degrees after they cooled and I had to bend them. Is this common? How does one minimize heat warpage? Does clamping things help or does it just hold off the inevitable? Should I be pausing to let heat dissipate between welds on this project? Any and all wisdom is welcome.In case it matters, I was using flux-core wire in an Esab EM210 (220 plug) with the recommended settings.Thanks!

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Reply:I would say it is fairly common if you don't constrain in the z-axis (up-down) in the middle where it had a degree of freedom (clamping together does not remove the degree of freedome, only if you clamped to something relatively immovable).  Even if you let the heat dissipate, the effect of the welding is cumulative because each successive tack-weld/bead will still contract as it cools, whether it cools naturally or if you artificially dissipate/wick out the heat.  And you can't arc weld without heat to create the tack/bead in the first place, so the distortion from weld bead contraction is inevitable, unless you either completely constrain the part in 3-axis and/or induce pre-welding stress in the opposite direction, so that the weld bead contraction pulls it flat in the end.

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Reply:Thanks Zod and welcome to the planet. My assumption was that the clamping was the least essential of my attempts to minimize warping. Sounds like if you're going to put X degrees of heat into a piece, it doesn't matter if you do it over 60 seconds or 90 minutes. Heck, maybe it's better to get it all welded together before it starts warping? I guess that's good, though my garage smoke detector will not be happy.Most of my previous clamping has been for gluing woodworking projects. I've been kinda surprised how little clamping I see in the YouTube videos that constitute 99% of my welding education to date. They often just use a grasshopper clamp, but maybe they're working with thicker material.Thanks again,ZLT
Reply:Let's do the weld warp [convo] again!Distortion is a welding fact of life, but it gets pretty intuitive after a while.If you search for this topic it's been covered to death but the quick run down is to minimize heat input (weld time. weld size, number of welds), balance the distortion (match welds on other side,season/grind to taste), and pre bend/positioning so that the shrinkage is pre-accounted for.  Good fitup also helps.In your case I would match the top welds on the underside (since they won't ever be seen and don't need to be ground), and use your friendly neighborhood hammer to scare the rest of the shelf straight.Lookup heat shrinking and it'll give you a great understanding.  If you don't have a torch you can use welds in the same manner.Best of luck, and nice table.