Fixing warped frame

admin

Hey guys,I have a problem with a frame I made which warped a bit.They are made of 1.2mm 1 1/2" square hollow sectionyou can see from the pic of both frame lying on each other that the top frame is warped a bit. The bottom frame is not warped.The warp is basically around the middle evenly.I tried clamping them together and even with a 1/4" spacer to no avail.Any suggestions ?Thanks,LMM 180
Reply:Clamp / Heat / Let Cool (with clamps on) That's what I would try. . .
Reply:so clamp both together with no spacer to give it extra bend ?Do I just heat the area marked in red ?Also would a regular propane weedburner torch work or do I need a real torch ?MM 180
Reply:Wrong area to heat, you want the stretched side heated.I was looking at this folder today, and there happens to be a heat shrinking problem in the project.The piece of tubing was bent in the direction with the U facing down.A temp strongback was attached to straighten the U, then heated on the opposite side of the bend (the outside radius of the bend).  Notice the tubing is heated in a relatively small area exactly at the center point of the bend (you can determine the center of the bend using a straightedge).The same was done on the other side of the structureRemember, if it bends, the outside radius has stretched, and you want to shrink it back to size.The cooling after heating causes shrinkage, but remember that opposite force has to be applied (the strongback) to make it work.  You can use water to hurry the process of cooling with mild steel"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Old files, before I saw the light (thanks to SWMBO), and cleaned up the yard"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by lennykso clamp both together with no spacer to give it extra bend ?Do I just heat the area marked in red ?Also would a regular propane weedburner torch work or do I need a real torch ?
Reply:I'd just work it cold with some clamps and spacers.  You can't just bring it back to flat with your clamps and expect it to stay there.  You have to over arch it and let it spring back to flat.Two turn tables and a microphone.
Reply:Agree with Pangea, work it cold.I have a selection of chain, a hydraulic car jack, screw jack, and some large turnbuckles.With those I can expand, pull together, or bend just about anything into shape.Cheers,  Tony._________________________________Transmig 310 + Argoshield LightOxy acetyleneOxy propanePrehistoric stick welder_________________________________
Reply:I just tried heating it but it didn't really change much.I think it will be easier to just weld up a jig to clamp it and fit a car jack in betweengiven that it is 1.2mm thick I might even try standing/jumping on itMM 180
Reply:Originally Posted by lennykI just tried heating it but it didn't really change much.
Reply:Well agreed CEP!  I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:Cooling the spot to be shrunk with water after heating helps too.  Large plates for big boats are flame bent with heat at shipyards using automated OFW torches that have water jets that follow behind to maximize the bending.  You would be surprised how effective it is and pretty darn accurate once you get a feel for it.  Very localized heat will make a sharper bend, while the same heat spread over a larger area will make a more gentle bend.  Mess with some scrap pieces to get the hang of it and good luck!
Reply:DOES ANYONE PAY ATTENTION????? You can heat till the cows come home, AND WITHOUT OPPOSING FORCE IT WON'T WORK.Here it is in 8 simple steps.1.  You have a warped item2. Determine where it bent3. Apply force in the opposite direction from the bend.  IN OTHER WORDS PUT SOME FORCE ON IT IN THE WAY YOU WANT IT TO BEND4.  Apply heat on the outside radius of the warped/distorted bend.  Heat till dull red, but not plastic (ie. don't melt it )5.  Hit it with water for effect"Any day above ground is a good day"http://www.farmersamm.com/
Reply:6, 7, and 8.   Work it till you're happy with it by repeated application of heating and coolingThis isn't rocket science"Any day above ground is a good day"http://www.farmersamm.com/
Reply:.........................."Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by farmersammDOES ANYONE PAY ATTENTION????? You can heat till the cows come home, AND WITHOUT OPPOSING FORCE IT WON'T WORK.
Reply:Sam, you the man!!  Seeing is believing!!  Bob
Reply:Originally Posted by farmersammDOES ANYONE PAY ATTENTION????? You can heat till the cows come home, AND WITHOUT OPPOSING FORCE IT WON'T WORK.
Reply:Sorry Sam,  I too have straightend and bent a lot of steel using heat only.  If your procedures work for you by all means keep doing it.  Your way is not wrong, there are just other options.Dan D.
Reply:First let's look at the original distortion.The weld filler material is molten, and contracts when it cools.  The base metal is locally molten, and cools......but the large mass of the base material is not heated by the weld, doesn't go thru a heat/cool cycle, and the large unheated area is restricted (doesn't want to move with the cooling contraction), so it "pulls".  And we have a heat warped structure.This is something I think we all understand very well.The damage caused by the heat/cool cycle is in the contraction of the weld area, and the stretching of the backside of the welded area.  A good analogy is when you use a pipe bender..... the pipe stretches on the outside radius of the bend, and kinks on the inside radius.  One side is being forced to stretch while the other side is being forced to shrink into a smaller area, thus the kinks.This is my conceptualization of the process.Lincoln explains it in a similar fashion, maybe clearer.http://www.lincolnelectric.com/en-us...on-detail.aspxAnd same with AWS  http://www.aws.org/wj/feb03/feature1.html..................................................  .................................Now I have to find a way to shrink the stretched portion of the base metal.Simply heating, and allowing an unrestrained piece of metal to cool, will result in the metal returning to it's original shape (bent out of shape).  For my purpose it's useless.  I need to shrink the metal.To shrink the metal I need some kind of force.  Either "internal restraint", or "external restraint".  If I understand correctly the internal variety is the thermal mass immediately adjacent to the heated area.  I don't use the internal variety.Instead I introduce external restraint in the form of an opposing force.  THIS IS WHERE THE LINE BLURS.  The FWHA clearly states that my methods approach "heat working" rather than pure "heat straightening".  http://www.fhwa.dot.gov/bridge/steel/02.cfmI introduce more heat, and use positive force rather than pure restraint (although I'd argue that restraint is a form of force keeping the cool metal from moving).  My method is faster I believe.  While probably not appropriate for some steels, it's ok for mild steel.  Mild steel is made to be weld friendly, and the HAZ isn't as finicky if I understand correctly, which makes it an ideal candidate for my method of shrinking.While a lot of people might think that they're using strictly heat to move the metal, it's sometimes different.  Take for instance cambering a beam or piece of tubing, etc.  One method is resting the beam on supports at both ends, and heat shrinking the top portion of the beam to introduce camber.  The weight of the beam is the applied force.As a practical matter I've found that the combination of force with judicious heating is the way to go.This trailer was damaged when a dood hung his front end loader on the azz end while loading hay on it.  He bent the central tube support ( the bend not shown in this pic)I located the point of the bend, jacked up the rear of the trailer enough to apply pressure to the bend, then heated the area to accomplish the heat/cool cycle.  I allowed this job to air cool to make the transition more controllable and slower so's not to ruin it.While I'm not saying you could not have moved it by application of heat alone (providing you could get the beam loading to a neutral state), I'd bet you'd use up quite a bit of time and propane/O2 in the process.  And it would be my assertion that you'd never shrink it back using heat alone."Any day above ground is a good day"http://www.farmersamm.com/
Reply:Here is a 12” x 19# beam that got away from me. I can't remember how far, I brought it back dead nut by using heat only. 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:Ok, I'm sold I don't do it this way, and the few times I've tried I've had no luck at it.I had to go out and try it.Got some 14ga tubing.  Put a straightedge on it.Heated it up 3 times, let it cool 3 times (with water).And was able to induce a pretty good bend.It works.  Simple as that.So let's see if it works on a welded joint......The distortion caused by the welding.SEE FOLLOWING POST FOR CONTINUED STUFF"Any day above ground is a good day"http://www.farmersamm.com/
Reply:ok, enoughUnfortunately I only have a small bottle propane torch which appears to be insufficient when I tried heating it both with and without force.So I ended up using a bottle jack, tried using a scissors jack and twisted it borrowed a small bottle and everything worked out now.MM 180
Reply:Heated it up again, followed by water.And had some good results.  It's as straight as I'd want it.I'm wrong to have said "never".I still will use blocks, jacks, and come alongs, on most stuff.  It simply works best for me on the stuff I do.  But I've seen for myself there's another way to do it.Was a good thing to do the experiment, wouldn't have done it without a nudge. "Any day above ground is a good day"http://www.farmersamm.com/
Reply:Lenny, you started a thread  Gotta take the bad with the good  I certainly enjoyed it, and you should too"Any day above ground is a good day"http://www.farmersamm.com/Here is a really good book on flame straightening. Also what helps with small shapes, is a spray bottle of water. But when doing large beams, you need a garden hose to cool the heated area.I thought of one time I used force. Many, many years ago I was in a crew of weldors, we had to 100% weld 200 4'x8' sheets of 10-GA plates together, for an 80-feet x 80-feet floor. As you can imagine they warped all to he!!. Used a warehouse forklift setting on a 12-feet long piece of 6x6 angle iron. Used a large welding tip, and heated 6 inch long stripes right next to the angle iron, skipped 6-inches and heated another 6-inch strip, cooled each strip soon as the next strip was being heated. Took about a week, but we got it flat as a board. 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:.................................http://www.amazon.com/Metalworking-S.../dp/0831133627Might find it cheaper used, but looks good to me"Any day above ground is a good day"http://www.farmersamm.com/
Reply:one issue with heat shrinking is,how do you know how much heat before you go past your target bend ?MM 180
Reply:Originally Posted by lennykone issue with heat shrinking is,how do you know how much heat before you go past your target bend ?
Reply:Sam and CEP.... Thanks for the info. I don't post much. Do more reading than posting. This bit of info will stay with me forever..
Reply:Great thread guys really enjoyed it! Great to watch both sides of techniques, Have to admit tho Samm you had the upper hand in your first demonstration with a 1/2 plate with a 1/4in undercut. Only kiddin bud   sorry I couldnt resist   Cheers guys!!!I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:yes, thanks for the very informative repliesI had made those frames about 6months ago and I must admit I was rather pissed when I started back work on them yesterday only to find the warp after thinking I could just start back and complete without issues.MM 180
Reply:well the good news is the frames meshed pretty square,the soso news is that in my usual haste there was slight warping at the bottom when those cross pieces were welded in, lolMM 180
Reply:Well, fix it! Look at post #21. Use the same technique, but you'll need a O/A torch. You want a  concentrated flame. Or I should say I've never used anything but O/A for heat shrinking.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:unfortunately I don't have a o/a torch,I might just try running a bead or two insteadcan always grind it off afterMM 180
Reply:That generally works, just more work is all. 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'm kind of an expert on straightening steel and I'll try to clear up a few of the basics. LSU has done a lot of research on this within the past 10 years and it is now considered a science rather than an art as it was previous to that time. 1. Preload the member in the direction that tends to straighen it. About 50% of yield or half the amount of force needed to cold work it is about right.2. For common mild steel, the magic temp is 1150 degrees, give or take 100. In moderate light, you'll just begin to see a little color. Too hot and you'll weaken the steel, under 900 and not much shrinkage will occur. Use a #3 heat tip for 1/4" or less and go up an orifice size for each 1/8" in steel thickness. You want to apply heat to where you want the steel shrink...think like your applying a heat gun to a piece of plastic..sort of.3. Heat where you want the steel to shrink. In a square tube I would put the apex of the vee opposite of the stretched area on each side then a band connected across the open part of the vees. Work an S movement, heating the area once. The widest part of the vee should not be more than the width of the member. The distance between vees should not be closer than the widest part of the vees. 4. Do not quench the steel until it's cool below 600 at least. Better off to just let it cool naturally then release preload pressure and check progress. Reload and repeat heat cycle until it's straight. This is a slow and gradual process. Don't get in a hurry. *You'll need to preload past straight so when you release the pressure after the cooling cycle it will be straight.**This can be done with no preload at all but it just takes a lot more time and you have less controll of the workpiece***A cutting torch is not the right tool for thisLast edited by Ryan937; 02-12-2013 at 10:16 AM.
Reply:Originally Posted by farmersammSimply heating, and allowing an unrestrained piece of metal to cool, will result in the metal returning to it's original shape (bent out of shape).  For my purpose it's useless.  I need to shrink the metal.
Reply:Nice of you guys to comment, but this entire discussion took place nearly a year ago.