The flame quenching, heat shrinking, straightening, bending thread

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I would like to start a new thread on flame quenching, heat shrinking, heat bending, heat straightening or whatever you refer to it as.  What I am talking about is the process of either bending or straightening steel by applying heat and then quenching with water to either straighten a bent piece of steel or to bend a straight(er) piece of steel.  I did some searches on this and was dismayed to find a thread started by a member to straighten a slightly curved piece of 2x4x1/2" plate for a table top.  At the end of many attempts suggested by replies posted  he solved the problem by returning the plate to the supplier to exchange it for a flat one.  While exchanging the plate for a flat one is a good solution,  he did not find simple advice to straighten the plate.What I am talking about is the use of heat and cooling (water) to bend or straighten steel without using mechanical force to do so.  Simply put heat is applied to the steel to heat it red hot causing it to expand.  Then water is sprayed on the hot spot to lock the steel in it's expanded position.  I'll give an example.Imagine a 2x2x12 inch square bar, which is not restrained in any way.  Simply put, if you apply a large amount of heat, to the top surface at the mid point to heat it red hot and the red heat penetrates past the middle of the bar towards the bottom, the top will expand and the cooler bottom will restrain it causing the bar to bend in an upwards direction.  Now if the bar is allowed to cool slowly the red hot top will shrink as it cools and return almost to it's original shape.  If instead we quench/cool the red hot top surface with water while it is red hot the bend will be restrained top and bottom and cool in the as bent position.  This can be repeated along the steel bar until the bar is curved to the desired shape.  This is very poweful and can bend the thickest steel if enough heat is available.  I have done this myself, using a rosebud on trailers that were bent.  I have seen lo-boy heavy equipment floats re-arched from a sag to a like new arch.  I have also seen standard I beams curved into arches using this technique.  It can be used to either bend or straighten steel, no mechanical force required.I would like to see others post to this thread with their successful experience doing this, and for others to post questions.  I know it was one of those moments where I knew I had learned something truly amazing the first time I succeeded in doing it myself.  It is not a "black art" and every welder needs to know about this."The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25
Reply:It sure does seem to be a lost art anymore. I've been doing it for over 40-years. Here is a good book on it. 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:Farmersamm has done several good posts on this in the past. Here's links to a few of his best I dug up quick.http://weldingweb.com/vbb/showthread.php?t=28433http://weldingweb.com/vbb/showthread.php?t=32814http://weldingweb.com/vbb/showthread.php?t=27737.No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:By quenching it with water don't you run the risk of hardening the steel or changing the temper? My forman freaks if he sees someone cooling something. Then again he freaks about everything and thinks he know everything and everyone is stupid. He is a horrible person to learn from.
Reply:Heat shrinking..Heat bending...Heat straightening...Heat anything has been beat to death here.Do a search..We are all seasoned veterans here...At least some of us are...How about cold bending before welding to keep flat after welding?That's been done also......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:norite i think if you experiment with this a little more you will find things move more without the water quenching. we straighten things quite often at work and if you let them air cool they move more.
Reply:I recall there being a whole chapter explaining the principles behind this in the Lincoln Bible.It used to be a common practice in auto body sheet metal work, before the new high strength, thin metal came into use. I have a wavy truck bed that wants to be straight some day.
Reply:That 2 by 2 square bar would bend even more if you applied a wet rag or water spray to the cold side while you heated up the red area.  The greater the difference in temperature the greater the shrinkage.  Quenching the red area is self defeating. One should cool the surround area as the red area cools naturally by conduction.  Once the piece is black in colour quenching will not increase or decrease distortion.  The metal upsets when it is red.   Quenching steel when it is red is not wise.  Also flame shrinking can cause grain growth if temperatures are too high.  With the newer structural alloys coming onto the market any flame shrinking is verboten.Last edited by lotechman; 12-08-2010 at 01:19 PM.
Reply:Came across a very good article on flame staightening from an engineering standpoint, has some history of the process, theory behind it and some practical applications.http://www.casperphillips.com/flame_...aightening.htm"The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25
Reply:Originally Posted by Mega Arc 5040DDBy quenching it with water don't you run the risk of hardening the steel or changing the temper?
Reply:Originally Posted by KelvinI don't think mild steel hardens too much. YMMV with medium- and high-carbon steels.
Reply:You all covered that pretty well. I used to work for a fab shop that made steel trusses for industrial buildings all welded together. before the I beams were welded, and some were 24 inch by 8 every one was straightened with a rosebud and a spray bottle. It does take some experience to do. we had an old guy that would walk along and heat the beam and then his welding helper would spray it when he said to. You could sometimes see the beam move over between horses a couple inches. Mac
Reply:See article on flame bending here.
Reply:Originally Posted by zapsterHeat shrinking..Heat bending...Heat straightening...Heat anything has been beat to death here.Do a search..We are all seasoned veterans here...At least some of us are...How about cold bending before welding to keep flat after welding?That's been done also......zap!
Reply:No info on cold bending before welding....?  Maybe just wedge it between some trees and give 'er hell?
Reply:I build tubular boiler products such as waterwalls superhesters etc and flame straightening is a everyday part of our life. Water is a no no for us but when acceptable it does make the process quicker. In my experience your first heat is the easiest to get the metal to move where you want it each time after gets progressively tougher to get the metal to react. Stainless steel is a completely different animal because we can't heat one side of something it has to be heated completely typically an area 2 1/2 times the diameter of the tube. Stainless is typically heated completely then set where is needs to be and held to cool.This is a art not a exact science.
Reply:Originally Posted by DSWFarmersamm has done several good posts on this in the past. Here's links to a few of his best I dug up quick.http://weldingweb.com/vbb/showthread.php?t=28433http://weldingweb.com/vbb/showthread.php?t=32814http://weldingweb.com/vbb/showthread.php?t=27737
Reply:Are you sure the frame isn’t warped? Two ways to go about this. You can start in the middle, and heat lines like I drew on your picture. Heat one line, and cool with water. Before heating the next line make sure the table top is dead cold to the naked hand!Next is remove the table top, and put a straight edge on the frame. If it’s warped heat the frame like drawn on your picture. 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:If the base is fairly flat, I would flip the top over and welding it back down.  Watch as you are welding it back down.  If it needs more pulled down weld a little more there.  Then heat/cool areas as need to get a little better.  If you get it perfectly flat before you weld it down, it will probably look very similar to the way it is now.  I hope this makes a sense.Last edited by OHT; 11-03-2015 at 04:38 PM.
Reply:Put a heavy rectangular tube crossmember in the table, clamp down the high spot and weld it. With those slots it should move fairly easily.
Reply:Thanks for the input guys!  Much appreciated.  I havent given up on the heat yet but this was one idea i had.... Originally Posted by walkerPut a heavy rectangular tube crossmember in the table, clamp down the high spot and weld it. With those slots it should move fairly easily.
Reply:Originally Posted by AKmudI know I'm resurrecting an old thread here, but after a bout with warping this past weekend myself, I'm curious about the "cold bending" before welding that you mentioned Zap...  I built a 10' long ladder/canoe rack for a truck and it warped about 3/4" after welding only two uprights on.  I was able to get it pretty close to straight again by flame straightening, but would like to know how to avoid this in the future.  The problem pieces for me were 10' long 1 1/2" x 2" rectangular tubing.  I welded three uprights to one side and was quite surprised to see the warp when I finished.
Reply:Originally Posted by zapsterHeat shrinking..Heat bending...Heat straightening...Heat anything has been beat to death here.Do a search..We are all seasoned veterans here...At least some of us are...How about cold bending before welding to keep flat after welding?That's been done also......zap!
Reply:My Massachusetts friend, near brother, talked my son into rebuilding a rust bucket dump trailer. The box was essentially a rectangle of 2" channel with more cross members. This floor frame was then covered with 10 gauge steel. My son built the floor frame, and began stitching the sheet to it. All was going well, until Bruce, the owner came along and wanted to MIG weld. He welded the whole perimeter of the sheet in pretty much one continuous bead. It was shaped more a bowl than a table top. Turning it over, I heated the now upper edge of each piece of channel, cooling with an air hose. I got the frame quite flat. the sheet floor though, was too big in the middle. Heat shrinking was going to take a lifetime. I gave in and cut a big X across it with abrasive saw, and welded it back together. I'm not sure I understand how quick cooling increases shrinkage, but it does. Mild, low carbon steel isn't affected much by this.An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.
Reply:IME that table is to flimsy to heat straighten easily, especially for someone's first time.  Not only is the material thin, the slots make the behavior more unpredictable.I would forget about trying to heat straighten the top and weld a strong back to the bottom of the table to both straighten and stiffen the top.I was very successful straightening my 4X5x3/8" top with Farmersamms instructions. I did cut it loose from the frame where the bulges were. You really don't need many welds to hold it to the frame anyway. Once cut free I marked out all the high spots with a Sharpie using numbers to indicate severity. It looked like a topo map when I got it all marked up. Then I clamped down some doubled up 2X2X3/8" angle in two places at a time, with the high spots in between them, starting at the worst areas. Using a cutting torch(preheat), I heated in concentrated, thin lines getting a dull red color, hotter on the higher spots. Sprayed with a heavy mist afterwords and left in the clamped position for a good 1/2 hour each time. Kept re-checking and re-marking with the Sharpie, moving the rig around as needed. After a few hours of work I could not believe how flat I had gotten it! Fine tuned it over several days to near perfect.There is still one tiny spot that would not move, right at the edge of the frame where it is still welded down. Once I cut those welds loose I have no doubt I will be able to straighten that bump easily.Miller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:Originally Posted by bigbThere is still one tiny spot that would not move, right at the edge of the frame where it is still welded down. Once I cut those welds loose I have no doubt I will be able to straighten that bump easily.
Reply:On the bowed table with slots, cutting the top loose and running a heavy beam under the bottom cross members for the legs and using a come-a-long pulling from the slots slots might be all it needs to pull it flat prior to tacking it back to the frame. Might have to pull it a little extra or use a couple small lines of heat on the bottom and leave tension on it till it cools. A while ago I posted pictures of some huge bridge beams (for an Edmonton bridge) that warped all to hell because the contractor didn't put the bracing in as they were installing the individual beams. Most people thought the beams were junk but they were sent out to one of the local structural steel shops and flame straightened. It put the bridge project a year behind schedule. Just last week they decided to delay pouring the concrete because the weather is too cold. It's estimated the contractor will pay about $4,000,000 for their %$#@&*! up. They had to bring in a huge 1200 ton crane to lift the whole bridge down and are paying $11,500/day in late penalties. It would have been even more if they would have needed to fabricate new beams.
Reply:duplicate postMiller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:Originally Posted by CEPHere’s how you fix those spots.