# Forum Home Renovation Metalwork & Welding  Slight distortion from welding - can I straighten it?

## Led

Hi, I posted a week or two ago about a frame I wanted to make from square steel tube.
Me and a mate got it together, but have got a tiny bend upwards on one side of a horizontal piece
at the bottom of the frame. The left side is about 5mm higher than the right. I could live with it,
but is there any way I could straighten it back down maybe by heating and cooling the outside side of the bend?
Thanks for any advice.
Cheers.

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## ErrolFlynn

Its probably permanent.  Welding light guages is as much an art as skill in estimating how much deformation takes place.  Its something you can learn to work with, but sometimes you just have to throw a job away and start again.  Given that the shrikage is the issue if there is anything else you need to attach to your frame per hpas you could add it so that when you weld it will conter the original bend.  Break it appart and replace the imperfect sections, perhaps even rotating them.  Sometimes clamping to a solid surface works/helps but not guaranteed.  To go out on a limb, something I've never tired, but I've had experience to watch a few panel beaters in my time, and with an oxy they are skilled at shrinking damaged car panels to help bring them back into shape.  If you have the time and equipment you could try that, but car sheet metal is likely to much thiner than your frame.

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## Led

Thanks Errol, yeah it's only 1.6mm steel so the likelyhood of a warp somewhere was on. I don't think it's a big enough issue to chuck it, might just have to live with it...
Cheers

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## CraigandKate

If its only 1.6mm wall you can likely just use mechanical force to bend it back? Sash clamps perhaps? Wouldn't hit it with any heat you are more likely to make it worse!

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## Led

Hi Craig, yeah I was thinking I might just clamp it tomorrow and try to give it a little bend. The horizontal in question is about 950mm long but you only see 25mm at each end, the rest is hidden so wouldn't matter if it was even a little wavey, just long as the two ends line up.
Thanks,

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## PlatypusGardens

Putting a couple of welds on the convex side of the bent piece can straighten it.  
If you lay it on the bench, secure it, put some pressure on the bent end, and set up an "end stop" where you want to bend it to and put a couple of spot welds (or heat with torch) opposite to where the welds which caused it to bend you MIGHT be able to straighten it. 
At the same time it could end up making things worse.  :No:  
Heat distortion is tricky to avoid and even harder to correct for us amateurs.
I've watched pro panelbeaters go over warped sheetmetal with a blowtorch and a wet sponge and all of a sudden it just pops back in to shape.  :Shock:   
When I made these tables I carefully tacked the leg on to the top.
One of them still warped downwards, but popped back in to shape as it cooled down and ended up flat. 
Very unpredictable      :Smilie:

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## ringtail

Can you post a pic Led

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## PlatypusGardens

> Can you post a pic Led

  Agree. 
When will people learn to POST PICTURES of the item in question....?  :Roll Eyes (Sarcastic):    
In the meantime, here's a pic of our dogs.   
Everything is better with dogs.   :Smilie:

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## Marc

Thin kerf disk on grinder. Cut 3 sides, straighten, tack weld in place, let cool down, tack weld a bit more, let cool down. Repeat until finished. Grind flat, admire your handy work.  :2thumbsup:

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## ringtail

That's why I want a pic.

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## Marc

PIC

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## Marc

Some more cheesy suggestions Distortion - corrective techniques - Job knowledge 37 https://www.youtube.com/watch?v=0pf-qQDslhU

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## Led

Hi, thanks for the repliese and pics everyone. I like the dogs, the cheese is good too. I clamped it and gave it a bit of leaning on
and it has lined the opposite sides up enough for me to live with. The edges are the only visible bits and it wasn't too bad to begin with.
I think maybe next time I will use something thicker, maybe 3 mm as I hadn't even considered how the thinner stuff might warp.
Thanks again.
Cheers.

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## Marc

Any size material experiences distortion when welding. The reason for it is usually poorly explained. 
There are two main forces at play when arc or mig welding that could be separated in the following way:
Imagine you take an oxy torch and heat the area to be welded red hot and then leave it to cool down. The area will expand and push the rest of the structure/pipe sideways. Because the rest is cold, it will deform and when the hot area contracts, the force of contraction is not enough to bring the steel back to its original position. 
First distortion.
When you weld you are laying molten metal on top of cold metal. As the molten metal cools down part of the heat goes in the pipe you are welding and pushes the rest the opposite way, yet when the weld cools it contracts and pulls the material the other way. The end result is always an overall distortion towards the weld, but it is never a clean bent. The amount of heat used, the amount of metal deposited and the overall strength/cross section/ thickness of the structure all play a role.

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## Ironlady

Hi Led  
Just backing up what others are saying. When you heat steel it expands, when it cools it shrinks back. but if the steel is heated over a certain temp (600-700 ?) it will shrink back smaller. If I was welding square tube I would tack the 4 corners before welding to try and control the distortion. When building a frame I would (if possible) assemble the frame, tack all corners then balance the welding (weld on one side of frame then the other side and so on (in the same direction). But to much heat in the weld will produce more distortion, not enough failure (not good). More gaps in the weld versus a tight fit up can pull to the gap side. In general weld the tight side first to hold it. Distortion is certain when welding so all you can do is try to control it by clamping, offsetting, pre/post heating, good fit up, correct tacking (as mentioned) etc. Some times you have to straighten after welding by pulling, hitting, heat and shrinking,peening (stretching) etc. Just keep practicing. 
Just some ideas of the top of my head and sorry if I dont respond to any replies at the moment (moving house and business)
Some crackers and a beer or so with that cheese would be ok 
Ironlady

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