Welding metal without it bending.

[snipe]

Iv got 2 lengths 6ft long of heavy channel that need welding together. What’s the best way of doing this without bend it. I have an arc welder but would a mig be better. We don’t have any gas bottles so can’t pre heat anything.

 

[davidroberts30]

Weld it with mma or mig
Short sections alternating sides

 

[Phil P]

Iv got 2 lengths 6ft long of heavy channel that need welding together. What’s the best way of doing this without bend it. I have an arc welder but would a mig be better. We don’t have any gas bottles so can’t pre heat anything.

As above, don’t get it to hot and work in sections on both sides.

 

[snipe]

Would clamping it to something like a heavy piece of girder till it’s cooled down help.

 

[startinghandle]

As been said weld alternate sides , if channel is rusty clen first also make sure where you clamp earth is clean
I use arc for welding anything heavy
Not a bad idea clamping to girder

 

[shumungus]

Clamp it together, mark it every six inches. Good tack weld every mark starting at the middle alternating sides work out to ends. Start in middle again weld six inches at a time alternate sides alternate ends of centre keep starting at next tack and work back to main weld. Clear as mud.

 

[snipe]

Thanks for the replies so far.

 

[TechWise]

Are you talking about welding them together to make a box section? Is it not possible to source a bit of box section that would do the job? I would think that even with the precautions outlined above, you'll still get some unpredictable warping that won't be too easy to straighten afterwards. It depends how much deflection you can accept I suppose.

 

[snipe]

Yes making some box as can’t find any near the size I need. A couple of mm of distortion would be ok.

 

[Mc115reed]

Yes making some box as can’t find any near the size I need. A couple of mm of distortion would be ok.

If you can clamp it down tight every metre it’ll not move, clamp it down every metre, plenty of tacks ever metre, wed it up in 6inch intervals spread out not starting at one end and working too the other, then leave it too cool before you unclamp... place I worked at had a 2ft thick steel table that was 20FT square we used too weld stuff like this too it rather than clamping it then cut the welds off next morning and would never distort

 

[shumungus]

Are you talking about welding them together to make a box section? Is it not possible to source a bit of box section that would do the job? I would think that even with the precautions outlined above, you'll still get some unpredictable warping that won't be too easy to straighten afterwards. It depends how much deflection you can accept I suppose.

If its rolled channel section it isn't going to be perfect at starting time anyway.

 

[Forever Fendt]

Used to make lots of drawbars , ram boxes by welding channel together and gate posts run the grinder down the edges and tack together leaving a 2mm gap also put a good run of weld on the inside of the open ends and as far down as you can reach to hold it together then start welding your joint together do as long a run as you can without having to move yourself then go to the opposite side and start the same from the opposite end, It will come out dead straight as both pulling against each other

 

[Hilly]

You need to alternate ends as well as sides

 

[Forever Fendt]

You need to alternate ends as well as sides

Opposite side opposite end

 

[DrWazzock]

I am no expert but I also find that it helps to leave a tiny gap to allow for the weld to cool and contract without bending or cracking something. Sometimes I use bits of offcut MIG wire to set the gap.

 

[Mc115reed]

I am no expert but I also find that it helps to leave a tiny gap to allow for the weld to cool and contract without bending or cracking something. Sometimes I use bits of offcut MIG wire to set the gap.

Doesn’t help with cooling but does help massively with penetration

 

[Rod Dumbreck]

If you find your last weld cracks as you finish the next stitch then swap to hydrogen control rods, they need heating/drying first but it can help.

 

[snipe]

Used to make lots of drawbars , ram boxes by welding channel together and gate posts run the grinder down the edges and tack together leaving a 2mm gap also put a good run of weld on the inside of the open ends and as far down as you can reach to hold it together then start welding your joint together do as long a run as you can without having to move yourself then go to the opposite side and start the same from the opposite end, It will come out dead straight as both pulling against each other

when I have done a weld at one end and turned it over and done a weld at the other end would it help if I let it cool down or should I just keep going

 

[tinman]

last one i done was basically as forever fendt puts it.
9x3 channel with about a 1.5mm gap in it, tacked together, ran a grinding disc down both sides to create a V and welded it 6-8" a time on opposite side and opposite end.
by the time you get back to the other side its cool enough so weld on.