Weld Distortion

[B R C]

Got a bit of a bend going on, 40mm over 2.3m

Managed to get back fairly well with oxy propane.

 

[milkloss]

I suppose the question would be how do you prevent the distortion due to the welding?

 

[Tonym]

What you have done is weld from one end on the inside edge of the box section which shrinks it and pulls it into a curve. Tack everything together before you start welding to reduce local heat and if necessary weld in braces you can cut off after welding to hold it straight.
When welding fully do it in short welds to avoid too much heat in one place and if possible do one short weld and then do one on the opposite side so as to pull the distortion from the first weld back in the opposite direction.

 

[Bobthebuilder]

Clamp it to another heavy bit of box and weld from each end in turn if possible

 

[B R C]

The 60x40 box was clamped along its full length to my welding table which is 50mm thick! Every bit of 25x50 was then tacked on each corner and top short edge fully welded. Box was then reclamped once cold with 25 x50 in vertical plane. Other short edge then welded, cooled, one long side welded, cooled other long side welded. With that many welds on one side of relatively thin wall, 3mm box I just don’t think there is a way of it not bending. I have always managed to get it back with gas pretty well.
I‘ve just made it up as I’ve gone along, but apparently ’flame straightening’ is an art in itself...

 

[Bob lincs]

A friend of mine welded a new blade on his grain bucket and warped it badly , I watched our local blacksmith straighten it with an oxy torch , bucket of water and a cloth . Heat it and cool it in the right place is the trick but sounds easier that it is .

 

[Pan mixer]

Presumably there would be a top rail on that line of box sections - like for a gate.

When I weld those up I will have all 4 sides of the rectangle clamped and welded and then start with middle upright, then middle again (i.e.quarters) and then half again.

renewing the bottom rail in one of my gates after it has nearly rusted through and the rest of the gate is more or less perfect is a challenge which usually involves a heavy sash cramp to keep things straight in the mean while.

If you were just making a railing with no other side than good luck with the oxy straightening.

 

[fermerboy]

I messed up badly putting new flights on this mobile drier auger.

Cut all the welds off, removed the old flight, new one on welded on the same, with a quick stitch weld every rotatation.
Never thought twice about it till after it was back in the drier and scuffing the centre tube badly.
Pulled it straight by stitch welding on outside side of bend, took a while but got it near perfect that way.
Lesson learned!!!!

 

[B R C]

No top rail, it’s an oar rack similar to this one.

 

[spanners and hammers]

sometimes we use the air line blower do some weld then cool down with the air and repeat not ideal but does help