To Remove Bend in Steel Structures

http://en.wikipedia.org/wiki/Metal_fatigue

This is essentially a one-shot proposition, so I don't think metal fatigue is much at issue. If you heat an outside section of the bent portion to an orange color, and then cool it by applying water spray or wet rags, the heated section will first expand, and then will retract more than it expanded. How much heat, over how large an area, is kind of an art form. There are experienced people who can do this; intuition and familarity seem to figure more than some sort of calculation. Given one or two tries, carbon steel is easier to work than stainless. I'm not very good at it, but I have managed CS decently, whereas I tend to overshoot back and forth with SS. (Once upon a time, I was trying to lay a not-quite-straight SS strip into a channel. That was pretty comical, though finally I got it.)

Without any idea what the structure is, it is impossible to give a sensible answer.
_{(Mind I find it tricky to keep my answers sensible at the best of times).}
Are we talking a steel cake tin or a railway bridge?
Del

Agreed Del, the true answer is "it just depends..." are we talking about mild steel? or are we talking about heat treated beams? if they are heat treated, additional heat will change the material properties, possibly significantly. Further, in corrosive environments, you can potentially have corrosion occurring preferentially in the heat effected zones.

I thought that the preferred method was to re-liquify and re-cast the metal. Doesn't this bring back all of the original properties?

But what do I know? I just like to chase electrons.

Not without the addition of alloys again. Once you re-melt steel, carbons will be lost in the process.

That's one way to look at it. But one could also now say that any alloy is now possible, if you have the recipe. You would also have absolutely no metal fatigue, too.

Heat it.

I assume these are structural shapes since you don't tell us.

Forget metal fatigue, it doesn't apply here.

Hammering in the absence of heat causes embrittlement. I think it is not very effective on shapes anyway.

Heating the outside of an unwanted bend to a dark cherry makes it soften and try to expand at the same time. The unheated side, still full strength, stops it from expanding, in effect making it contract. When it cools it pulls the beam straighter. If this is done at intervals around the bend, the member cam be straightened.

I seem to have repeated what Tornado said, I better give him a GA.

If it's not a cake tin, my preferance is a hydraulic cylinder and chains, or press, or whatever suits the anchorage/support situation. Heating and hitting are too 'hit and miss' in my opinion. Good for panel beating though.

i think hammering is best.. in our site they prefer that than heating...

It's simply IS2062 grade B materials (normally used for structures). Not a alloy and a heat resistant material. i need to know hammering/ heating, which is the best to make the metal straight and why?

It seems to be home work rather then some practical problem.

Wrap it in a heat blanket, then pull on it. Just don't stand under it.

I'll quote from your post http://cr4.globalspec.com/thread/66641

By Lyn "If you take a look at some of OP's other questions, you may discover that he likely doesn't know the answer to your "good answer"".

But we're here to help, if we can. I can put you in touch with "Ivan", give him enough power he can bend any thing, so apply a bit of reverse psychology to him he'll straighten it for you.

Heat till yellow-orange in color and then hammer while still hot just like the blacksmiths used to do. If it worked for them for over a 1000 years why change the recipe.

Heat it and beat it.......I agree with the rest, without knowing size, etc, no answer will be fully correct. I once worked in a shop straightening large beams, etc. We usually just used hydraulic pumps, rams, etc. A lot depends on the composition of the metal, how much it is bent, how perfect do you want to get it back to.

can you suggest me any guide to learn it in detail based on composition and bend size. i want to know that only..

Have even tried to do any research about your question? And then you wanting to know why?, makes sound like it's a home work question. CR4 is good place to find answers, but most of us,_{I think most us here,} would prefer the OP to do some research on their own first. That way, you'll have a better understanding of the "whys" to the replies you receive here.

Hammering is better than heating, but better of both is straightening by an hidraulic cilinder as said before by a contributor. Take care about heating since you can put the steel out of the applicable norm to that shape or flat structural steel. Indeed heating practice for straightening is not allowed everywhere, sorry I can't be more specifyc.

Heating makes the steel metallurgical structure change, increasing the grain size among other parameters, and making the quality certification mechanical properties data change drastically, and in some cases, like when resilience (-20ºC...) is needed you will make it not to comply with the needed parameter.

But you will never get 5 micron accuracy with hammering a piece of steel. It will also take a very big hammer to straighten a 10 meter long IPE 750 x 147 beam.

Hi Redfred, although you want to straighten 10 m, you can always apply the hammer over shorter lengths between supports. It will take longer, but it can be effective if the hammer is capable. We are always considering applying over the x axis (on top of flange tips) of a beam/column.