Fixing Warped Flame Cut Plate

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I oxy-acetylene cut a 17" disk of 1/4" plate to use as a base for a project and have just noticed that it has quite a convex warp opposite the side the cutting was done from.  I want to correct most of this warp, hopefully there are some smart people here that know how to do it.My thought is to draw some concentric circles on the convex side and use the torch to heat dots along them and then cool them with water to try to induce contraction that will warp it back the other direction.  Would this make sense?  Ideally, the outer heat affected cut area should be stretched/spread to relieve the compression it is putting on the rest of the plate but it seems like heating would just make it contract more.  Obviously I'm new to cutting/welding etc.  Thanks in advance for any help.
Reply:DO NOT DO ANYTHING until we see a pic of it.It may be easier than you think....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:This might help. Attached ImagesDon’t pay any attention to meI’m just a hobbyist!CarlDynasty 300V350-Pro w/pulseSG Spool gun1937 IdealArc-300PowerArc 200ST3 SA-200sVantage 400
Reply:Hi guys, here's a pic of the base.  With a straightedge held across the center, the dip on both sides is about 0.1".  This curve is pretty consistent all the way around.  As you can see there are 4 leg holders welded on the concave side.  Those welds of course increase the curvature locally.FYI, a 2.25" diameter hole will be drilled in the center of the base so flame straightening can't be done there.  Thanks for the help! Attached ImagesLast edited by svenp; 11-08-2012 at 11:25 AM.
Reply:Originally Posted by svenpFYI, a 2.25" diameter hole will be drilled in the center of the base so flame straightening can't be done there
Reply:Originally Posted by KelvinWhy not? Here's an idea: If you're going to flame cut or plasma cut the 2.25" hole, just flip the disk over when you cut it and it'll warp the other way.
Reply:Heat a 3-inch dia circle in the middle of the plate before you drill your 2 1/4-inch dia hole. You may have to heat a circle over each leg too.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:I am in no way an expert in any way, but what I would try first is put it flat side down on a solid surface and peen the edge all the way around with a hammer.  Take it easy and go slow, and watch it.  That should relax the edge and I'll bet it flattens right out.Sent from my C771 using Tapatalk
Reply:Well, now I know what doesn't work.  I tried shrinking the center section (basically no change to the curvature after that) and then I followed the back side of the welds to counteract that local increase in warping.  End result is a significantly greater curvature rather than an improvement.  I think since I'm starting with a dish already, shrinking anything on it seems likely to increase the radial compression and thus increase the dishyness. Ah well.  I may try peening it but it's pretty thick stuff, I don't see that working. Attached Images
Reply:Strange! Did you heat the areas cherry red? Like the one picture I posted? What are you using for heating?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:The methods are not rocket science, the trick is knowing how much heat to use. Remember if you can feel heat with your hand the material is still moving. Attached ImagesDon’t pay any attention to meI’m just a hobbyist!CarlDynasty 300V350-Pro w/pulseSG Spool gun1937 IdealArc-300PowerArc 200ST3 SA-200sVantage 400
Reply:We're talkin' about 1/4" x 17" diameter low-carbon plate?No heat required.That needs to be cribbed up on oak blocks and then  John Henry can plant a few strategic whacks with a sledge to make it flat as a fritter.
Reply:Originally Posted by svenpWell, now I know what doesn't work.  I tried shrinking the center section (basically no change to the curvature after that) and then I followed the back side of the welds to counteract that local increase in warping.  End result is a significantly greater curvature rather than an improvement.
Reply:Originally Posted by denrepWe're talkin' about 1/4" x 17" diameter low-carbon plate?No heat required.That needs to be cribbed up on oak blocks and then  John Henry can plant a few strategic whacks with a sledge to make it flat as a fritter.
Reply:One more time.  Lincolns 'Metals and How to Weld Them', section labeled 'Effects of Expansion and Contraction', about page 164 depending on your version of the book. Steel expands, contracts, compresses, comes out of compression but it can't be shrunk. For straightening flat (this case in this post) stock you heat one side quickly and not all the way through. Other shapes vary in the methods and amount of heat applied but the concepts spelled out are the same.As a side note some of the bowing resulting from flame cutting will relieve itself simply by grinding a bit on the cut edge. Circular pieces like this one would have relaxed quite a bit by cleaning that cut edge off, as long as you don't lean on the grinder so hard you turn the metal blue."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:Hey guys, I just wanted to thank everybody for the info, links and ideas.  This has been a learning experience. I had no idea flame cutting would cause such distortion in the first place but it was an opportunity to learn the mechanics of how flame straightening/bending works.  What ended up working best was heating lines in a radial pattern on the convex side to shrink the inner portion of the disk a little and bow it back the other way.  It wasn't perfect but I got the leg mounts to all point in the same direction...  Heating/shrinking in a circular pattern just made things a lot worse.  If I had to do it all over again I'd cut it a little oversize and grind off the outside first.  and/or find someone with a plasma cutter.
Reply:At least you got the idea. In my experience plate can sometimes be a bear. Shapes are a lot easier. Pipe and box tube being the easiest. Attached ImagesDon’t pay any attention to meI’m just a hobbyist!CarlDynasty 300V350-Pro w/pulseSG Spool gun1937 IdealArc-300PowerArc 200ST3 SA-200sVantage 400
Reply:Originally Posted by svenpIf I had to do it all over again I'd cut it a little oversize and grind off the outside first.  and/or find someone with a plasma cutter.
Reply:Originally Posted by KelvinAre you heating the side you want to shrink? In other words, are you heating the side that is convex? Because that is the side that should shrink and go from being convex to being flat (and then to being concave) if you heat it and cool the other side.Click here, it should help.