HELP!! bending 3mm steel

[Floydie]

Hi all,
I'm halfway through making an engine crane from 100x50x3mm steel box section. I have encountered a rather big problem (as i see it), when i welded two uprights onto a 100x50x3mm section about 1000mm long. Due to the heat of the weld, it has bent both sides up! Can anyone reccomend a way of bending them back level? i have asked about heating the section up, but apparently i would'nt be able to fully heat it to bend it!!!
Please help,
Floydie

 

[Hitch]

Who did you ask? You wont need to heat the whole lot to get it back, i doubt it gone that far...?
Any chance of a picture?

 

[Iain Westland]

ooh, Floydie, you got the big boys interested. I'm ok upto about 1mm then get anxiety fits.

iain

 

[weldingscotty803]

big hammer??????? normally works for me

 

[M@tt]

yes B.F.O.H is whats required

 

[gordon stephenson]

I have had good results either heating just the back side of the bend to a dull red and quenching (sometimes more than once) or run a couple of welds in the same area as mentioned and quenching, when satisfied with the results grind off the extra welding,

 

[Mad Mick]

Red hot diamond(s) on the outside of bend,it will initially bend wrong way and then straighten up as it cools.Do not quench.Mick.

 

[Floydie]

Here's a pic

Right, thank you all for your interest and comments, i shall give heating it up a try, i dont really want to go nuts at it with a massive hammer, just in case i bust the steel or the weld. The only slight problem i might come across is fixing it to something while i 'hit' it back into shape when its hot, as its so big!! (as you can see in the pic). I have added a picture of the 3 bars welded together. In the picture, the frame is horizontal because i'm drilling through the two long parts, but the bent bar (as you might see) is standing verticle on a stool, if you look close you can see a slight bend from both sides of where the other steel has been welded. What advice would you give? as i need the part to be flat for the whole thig to work properly.
Many thanks,
Floydie

 

[Paul.]

You shouldn't need to hit it at all, as others have said if you just apply heat opposite to the weld, initially it will expand and make it worse, but as it cools it will contract and straighten the section , don't quench, and be patient , we do this kind of thing all the time in fabrication, rarely is violence required.

 

[Luke]

Why on earth didn't you drill the holes first?!

 

[Hitch]

What you could do, is this, noise free.
Clamp another piece of box section, a bit of that 40x80(?) would be ideal, on its edge, about the same length, but with a packer only in the middle, about 20mm thick. Heat up the outsides of the welded area, and simply screw the clamps up to pull the bow out. Probably wouldnt need to close the gap right up, just eye through after each turn of the clamp.

Is that a school DT workshop by anychance!?

 

[Iain Westland]

knew it, we are sorting out home work

told you these guys know their stuff

iain

 

[Mad Mick]

I think having to hammer big-time (unless pile driving or similar), usually means that you have already lost the battle!Mick

 

[Bsmith]

I use my hydralic pipe bender for the like.

 

[Floydie]

Thank you all for you advice. And yes, that is a DT workshop, this is my A level final project.

 

[Mad Mick]

Good to see something useful and practical being taught at A level these days,good luck mate,regards,Mick

 

[Welderpaul]

As above really, i'd approach it the same way, run a series of welds on the convex side of the bent piece, 1 in the centre, then one either side and so on. Keep looking down it to watch what it does. Remember it can take quite a while for the metal to cool and contract.
Hitting things like that just makes you tired! - theres to much bounce/spring it it to have any effect.
Oh, and drill the holes first

 

[Hitch]

Could be worth noting about distortion control when you do your write up. Doing a similar thing to what i suggested earlier would have virtually eliminated that problem.
Its easy to forget though, i bent some 200x100x6 last week by welding on one side. Luckily we have the gear for sorting that without heat!

 

[Floydie]

So what your suggesting is that i brace the curved base (once heated) with a couple of clamps on each end with steel box section, and then tighten to flatten against the box section?

 

[Hitch]

Yes, but you will need a packer between the two bits to straighten it, to allow the welded piece to move slightly past flat.

Before you welded it, if you had have clamped it to another bit, preferably stronger than the original, with a small packer about 4mm, once welded it would have ended up pretty straight.