flame shrinking

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I thought I would go through my collection of pictures from past years.. some are over 20 years old.  People seem mystified when really it is a straightforward procedure.  Keep in mind that flame shrinking is frowned upon more and more as the strength of alloys goes up.  Regular mild steel is becoming a thing of the past.  Many new alloys are very low carbon but they are stronger than mild steel.  This effect is primarily from the rolling process and if you heat them up to a red heat they change.  First one is a steel storage rack for go-nogo rings that weighed several hundred pounds each.   They made a nice rack and overwelded causing the verticals to bow.  You can see the heats that were applied after the material was removed from the rack.  The rack was  hung by its top shelf about six inches off the floor to give a bit of bending action while it was heated.  A wet rag was used to cool the wedge shaped heats.  I had an underling do this and he wanted one extra heat and it went a bit the other way.  At least the shelves were no longer tipped down.   When you are shrinking something don't get over enthusiastic... put a heat in, cool it off and look to see what you have.  Sometimes these jobs are best done between your regular job so that you don't look silly standing around waiting for it to cool to see if it has worked. Attached Images
Reply:The next pictures are of catwalk frameworks.  They have to be straight or when you put the grating on it would look pretty silly.... this is a strucural shop so all you have to go by is the drawings and the welds required.  The engineers really don't care if it is going to distort... that is your problem simply because they never think about it.   The worst part is we fix the problem and the people who designed the problem continue blinding repeating the errors.  In this case all the welding that joins the huge channel to the wide flange beam has put a sweep in the frame.  Now you would think that you could not straighten that since you have the rectangular framework sticking out on the left.  That stuff is like sphagetti compared to the heavy material and when the fabricator tacked it up it was straight.  I placed shrinkage heats along the flange of the heavy channel and it was enough to pull everything back straight.  This took many hours of heating and cooling until my string line was straight. Attached Images
Reply:I used to love doing that stuff. I worked in a Structural Steel fab shop growing up and used to add cambers to 36" Beams. Sometimes as much as 3" in a 30' beam. This was back before the hydraulic camber presses were popular. It is a great skill to know. There was a seminar my father went to years ago from a father and son who traveled around repairing hangers and buildings ripped apart by tornadoes and hurricanes using nothing but rosebuds and buckets of water.CERTIFICATIONS:7018M- H.V.O10718M- H.V.O11018M- H.V.O9N10- H.V.O71T-1-HYM- H.O.V100S1 PULSE ARC 0,035- H.O.V100S1 PULSE ARC 0.045- H.O.VER70S-3 PULSE ARC 0.035 H.O.VER70S-3 PULSE ARC 0.045 H.O.VER5554- H.O.V
Reply:Ok here is an example of when your best plans can only be solved by the poor machinist.They delivered an 23 inch diameter solid bar and we were to attach slide plates to it.  Us being so smart realized that the plates were going to give us trouble so we set them back to back and welded the ribs to them with full penetration welds.  The shrinkage was stopped and the plates remained flat.  Notice that we welded tabs across the edges.  If you want to make enemies in a shop join items back to back by welding along the edges on the joint.  It is a nightmare of grinding while tabs can be knocked off with a hammer.   We felt pretty foolish when we welded the assemblies to the round bar with full penetration welds and then fillets on top of that.  The plates then shrunk and you can see they are no longer flat.  There was no way to flatten other than spend big dollars and have them machined flat.  The "cotton batting" you see is kaowool insulation.  The assemblies not only have to be preheated but normalized after to to stress relieve. Attached Images
Reply:If you are flame shrinking what works better than wet rags on big stuff is a siphon gun and a bucket of water.  it can be messy on the floor but the combination of air and water cools things quickly.  never aim at the red... you aim beside the red area to maximize shrinkage. Attached Images
Reply:This is a standard shrinkage task on wide flange beam that was split into two tees.  We cut the beam length ways and left it still together skipping on the cut every two ro three feet then cut it apart when cool.  It still sprung so the pieces had to be straightened.  They were for a sign of some sort. Attached Images
Reply:Great information. Thanks for posting up.
Reply:Impressive examples and applications lotechman!Example 1 was pretty clear; I could see where the heat/chill was applied.It would help me more if in your other examples you could illustrate (maybe with arrows) where the heat was applied to correct the bend.Thanks for this thread.Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:Originally Posted by Rick VImpressive examples and applications lotechman!Example 1 was pretty clear; I could see where the heat/chill was applied.It would help me more if in your other examples you could illustrate (maybe with arrows) where the heat was applied to correct the bend.Thanks for this thread.
Reply:Thanks for adding arrows :') Yes the heat marks seem to be wrong..... usually the tee pops with the flange arced on the outside of the curve.  These popped with the flange arced on the inside. (concave)  It just depends on how much residual tension was left in the flange when it was rolled.This next example was canopies hanging from the side of a building.  They wanted seal welds for the little angle iron ledgers. The canopies were hot dipped galvanized.  If you do not seal weld rust will bleed out of any cracks and stain the galvanizing.  As a result a long continuous weld causes problems so we had to shrink the large tubing straight afterwards.  Notice that the heats are approximately pie shaped and extend half way through the section of the tube.  Sometimes I have had to go 3/4  with the heat.  Halfway through the job the foreman convinced the customer to allow stitch welding the angles on.  It saved a lot of time since we did not have to flame shrink.After galvanizing they filled between the stitch welds with silicon caulking that was coloured to match the zinc.  If you are good with laying in the caulking one has trouble seeing the difference between weld and calking bead. Attached ImagesLast edited by lotechman; 12-01-2011 at 11:16 AM.
Reply:Yes we split beam with a track burner...  I have a picture of a slick setup for splitting smaller beams where the burner will not sit inside the beam and you don't want to bother with setting another beam alongside.  I will look for it... found it!   Not my invention but I thought it was handy,.... It saved a trip out to the yard to find another beam.  The bolt on the underside is used to level the support.  This allows you to set the track on the supports and have the burner run outside of the beam.  Obviously you take the assembly off before you snip the places you skipped and split the beam in two. Attached ImagesLast edited by lotechman; 12-01-2011 at 11:10 AM.
Reply:To avoid flame shrinking,,, putting things back to back before welding helps.  I also sprung the assembly by driving wedges in each end after locking in the middle.  I inserted pieces of 1/4 scrap and removed wedges.  You can see the ones tacked together waiting for assembly back to back.  Notice there are scrap strapping across the openings to stop movement also.  The inside fillets were done then let cool and released.   The inside bead was not done in one continuous length.  I skipped around doing about a third at a time.  Afterward the outside was gouged for a partial penetration and welded up on the outside using a bug with a wire feed gun clamped to it.  If you are sharp you will notice that the unit on the horses by itself has the straps tack welded inside the channel... It is not pleasant removing afterward.  Some people work with you and some people ....   Strapped across the top and welded on one side makes removal easy with a large crescent wrench.  Look at closeup. Attached ImagesLast edited by lotechman; 12-02-2011 at 09:53 PM.
Reply:Here is another mistake I made.  I had enough sense to put these plates back to back.  The customer wanted seal welds which guaranteed distortion.  They were loading ramps for a barge.  I set two 2by 4's in the middle and clamped down at the ends then tacked straps across.  I remember the owner coming out and watching me and he asked me if I thought it was enough.  What does he know!!  He is a machinist!  I told him it should be ok... My bad!    In hindsight it would have been better if I had overdone the prebend since it would have been much easier to put some heats on the stiffeners to pull it flat.  Solution was running heats on the plate with a track burner.  That shrunk the face balancing the fillet welds on the other side. Attached Images
Reply:Thanks for sharing your projects/experience Randy, I am sure at some point (on a much smaller scale) some of our approaches will be helpful.GeezerPower Mig 255C185 TIGBlue 175 MIGRanger 8 Kohler 20HP1974 5K Lincoln/Wisconsin Powered (Cherry)Victor/Harris O/AK 487 Spool Gun
Reply:Fascinating stuff! Thank you and feel free to post more.