1/4" Plate Warped - Straighten?

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My first welding project and I learned a valuable lesson. I stick welded a ¼” thick mild steel plate 20 inches long to a 2” x 3”  x 6” tall Rectangle tube.  I clamped down the 2x3 to the plate but I didn’t clamp or tack down the ¼” plate to anything.  So the ¼” plate has bowed up like a banana on each end.  I need this to be true so that it sits flat.Any suggestions on how I can straighten this out?Thanks
Reply:How much do you weigh?   Seriously, if the plate is too strong to be manipulated back to flat while welded, you'll probably have to  cut through the weld beads on the sides facing the bow, clamp the plate to a strurdy straight edge and re-weld.   It wouldn't hurt to carry the cuts around the corners a bit also.It will be more of a guess, but if you think the plate will still bow back after the welds cool, you could put a small amount of reverse camber into the plate by putting a spacer between it and the straight edge.    Where I work, we make aluminum forms for poured concrete wall construction.   The form frames are arrow straight until we tack on the 1/8" face sheet, then they banana in all directions.    Our welding tables have spacers permanently installed to put that reverse camber into the form such that when it comes off the table, it's flat.There are no small projects
Reply:how much did it bend on the ends?1/8"?1/4"?next time whatever the "bend" equaled out to try pre bending it the opposite way b-4 weldingif its up 1/8 on each end put a 1/8 rod under the middle and clamp the 2 ends down then weld..when the clamps come off it should be relatively straight..been there done that......zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:What I would try is:  Heat the burn marks on the opposite side as the weld, try to go the approximate the same amount  of heat you applied while welding. As you learned, heat shrinks things, you need to shrink the "long side" of your plate. It would be better to use less at first and go back over it another time, if it looks like your gaining, rather than go overboard, and have to "correct your correction"Just my  opinion, not from a book, just from the road.Howes Welding Inc.www.howesweldinginc.com
Reply:Originally Posted by tessdadWhat I would try is:  Heat the burn marks on the opposite side as the weld, try to go the approximate the same amount  of heat you applied while welding. As you learned, heat shrinks things, you need to shrink the "long side" of your plate. It would be better to use less at first and go back over it another time, if it looks like your gaining, rather than go overboard, and have to "correct your correction"
Reply:next time whatever the "bend" equaled out to try pre bending it the opposite way b-4 weldingif its up 1/8 on each end put a 1/8 rod under the middle and clamp the 2 ends down then weld..when the clamps come off it should be relatively straight..
Reply:I want to thank everyone for all of your advice.  Using the method of heating the burn marks on the opposite side of the weld with my stick I was able to correct all of the warped metal. I used a few 1/8" 6013 rods and allowed the metal to cool for about an hour and then checked to see how much improvement was made. I then ran another bead to correct some more.  After each attempt I used a 90 degree square to check how much improvement there was.I probably ran about 5 beads in all so the whole process took me about 6 hours. I finished up last night at about midnight. Well when I woke up this morning and checked up on my progress I was amazed on how well it came out.Again thanks for your expert advice - without it I would of ended up with an anchor!
Reply:Originally Posted by tapwelderGreat idea.  I will have to remember that and give it a try.  I did 12 stand a few months ago.  All were warped.  I put 1/4" feet at the corners.