Whats the title of the book your currently reading?
This book explains heat shrinking real well, lacks a little on straighten plate tho.
I work with a man here in ga. we use to heat straighten bridge beam after trucks it then. I learn a lot on heating and bending stuff. We couldn't heat them up no higher than 1200 degrees. With some heavy jacks little heat lot of patience you can move the world.
you can buy the AWS publication, but you will learn the most by just trying it out. I bent a 12' piece of 1/8" wall 2"x4" rectangular tube[A500] into a 6' radius in about 12 hours, using a victor #2 brazing tip and a bunch of wet rags. The concept is to establish a steep thermal gradient without getting the base metal above 1200 degrees F. For thicker members a rosebud is required, but for the thin wall stuff a brazing tip works just fine. I put over 400 heat cycles in that tube to get the desired bend, so get yourself a six pack and some tunes, cause it's f***ing boring, but works very well. If you want to know more about the hull bending methods, it is sometimes called the Holt method. I read an article about the use of robotic arms controlling an induction heat source to get very precise shapes in ships hulls.
Mistake No. 1. Heating the Steel Until it is Cherry Red
Mistake Number 2: Cooling the heated area with water while it is heated to temperatures above 1330 degrees F.
I had an interesting project this past summer. The photograph and sketch tells the story better than I can. The stair stringers were fabricated 12x16 inch tubes. They were field welded to the cross members. The welding caused the free ends of the stringers to distort upward on the order of 3-inches. The erector had never flame straightened steel before. I had to write a procedure for the erector and it had to be reviewed and accepted by the owner's engineer and architect before implementation. To say they had little faith in the procedure would be an understatement. To top it off, I could not be on-site when the erector did the flame straightening. I was already committed to teaching a class in another state.
The bottom line was it went a smooth as silk once the erector got the right heating tips. They were sent heating tips for propane when what they needed was heating tips for acetylene.
Best regards - Al
Wow, those engineers sure know what they are talking about. "No chance of success"?, utilizing a decades old technique with well established theory and thousands of successful applications? What a bunch of dumbasses....
I'm surprised that "Flame Straightening Technology for welders" by John P. Stewart wasn't mentioned yet......every shop needs that book in their library.....heat straightening, heat cambering, and all sorts of help can be found in that book.
This is the book I was reading.... A friend of mine gave it to me...It has very limited info on the subject but it had enough to peek my interest in how to bend or straighten steel members...
http://astore.amazon.com/weldingbooks-20/detail/0831131551 Thanks for the info guys.. Im going to read up on this topic for a while..
Its funny how little you know the more you learn...LOL
RC
J.P. Stewart also wrote "Distortion Control", likewise a valuable text no shop should be without....
I haven't read the book you mentioned but what you say from the book sounds right. It's pretty amazing when you think about it.
I've done a fair amount of cambering and straightening but I find that the most satisfying operation for me is when we execute a distortion control plan. (I don't mean nailing the written plan to a post and then shooting it - even though that can be fun too)
It's fun to plan how much a weldment will distort from welding; maybe pre-bend in the opposite direction; then have the weldment come out nice and straight when welding is finished.
There are a lot of variables, it doesn't always go off as we hope (usually it's because part of the plan was skipped over), but it's great when it does work.
I know it's just terminology but I was always taught this was heat shrinking. That word just seems clearer in my mind, although the process involves expanding a segment of metal while it is in it's plastic heat range. The adjacent non expanding metal restrains the heated portion that then plastically deforms, and "shrinks" when it cools.
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