How do i keep my frames (square tube) from warping when i weld them?

[MoTiJo2023]

The title should explaing my question. I have tried to make 2 kart frames now, cut all the 4 pieces of square tube exactly to lenght and then MIG weldet them and they warped like sh#t. I have wasted so much time getting the steel cut to lenght (i cut the corners just like in the picture, 45° on both sides) and then this happened, why???? With warping i mean this:
The frames also havent had the 90° angle in all 4 corners that they had before i weldet them, and yes, i tacked them up before welding.
Also: I weldet the frames like they do in this video, i used the same technique (weld outside corner first,....):

 

[Con-Kartist]

Warping happens when too much heat is applied in one spot at one time, and then that spot cools and contracts. When you're working with smaller/ thinner gauge material you'll want to turn the heat down on the welder so not as much heat is displaced into the steel. You did good following the video, alternate welding all 4 corners then all 4 tops etc. IMHO it was probably the heating/ cooling that warped it, either too much heat or the joints cooled too fast.

If you have work bench or a table you're working on you could clamp the frame to the bench while you're welding and while its cooling, that sometimes helps with the warping.

Another idea would be pre-heating the steel before welding, if the whole piece is the same-ish temp it'll cool at the same rate and not warp

 

[Denny]

Tack the whole frame together first then weld it all together skipping around after each weld. Some slight warpage will occur but that is to be expected. One small weld at a time, patience is key!

 

[MoTiJo2023]

Tack the whole frame together first then weld it all together skipping around after each weld. Some slight warpage will occur but that is to be expected. One small weld at a time, patience is key!

I was skipping all around the frame, just like the guy in the video said.... Maybe i should buy a 90° welding clamp, to clamp both pieces in better and secure them...

 

[MoTiJo2023]

Warping happens when too much heat is applied in one spot at one time, and then that spot cools and contracts. When you're working with smaller/ thinner gauge material you'll want to turn the heat down on the welder so not as much heat is displaced into the steel. You did good following the video, alternate welding all 4 corners then all 4 tops etc. IMHO it was probably the heating/ cooling that warped it, either too much heat or the joints cooled too fast.

If you have work bench or a table you're working on you could clamp the frame to the bench while you're welding and while its cooling, that sometimes helps with the warping.

Another idea would be pre-heating the steel before welding, if the whole piece is the same-ish temp it'll cool at the same rate and not warp

Thanks for the ideas, i cant adjust the MIG welder any better because it only has 4 setting to set the amps and one knob that you can turn for wire speed, if i turn the wire speed any lower, its not welding good.

Here is a picture of the same welder that i have, this picture is from google, knobs/switches are the same tho.
The 2 at the top are for amp adjustment and the knob under the 2 switches is for wire speed.
I could buy a better mig welder from the brand Stahlwerk that can be fine adjusted, costs around 350€ (it even has 7 years of guarantee):

 

[Denny]

I always crank up the amperage and wire speed and move fast. Do one side let it cool then do the other side. Patience grasshopper. Just one reason I prefer round tubing.

 

[Master Hack]

Don't waste your time and money on 90 degree clamps. Is EVERYTHING going to be 90? Get some 1/4 plate and good vice grips.
You can clamp pieces at almost any angle and hold them secure while ya tack em. then follow the advice already given.

 

[Rat]

I find beating the weld down as it cools helps it not warp as much because done right you are stretching the weld as it attempts to shrink.

A large flat plate of steel to clamp your work to as a heat sink while welding and leaving until cooled enough to handle it bare handed helps a lot as well, but then again I avoid using anything thin enough to be a problem to begin with.

 

[MoTiJo2023]

I always crank up the amperage and wire speed and move fast. Do one side let it cool then do the other side. Patience grasshopper. Just one reason I prefer round tubing.

Im mostly welding 2-3mm steel, how long do you let it cool?
Also, in the video they say that you should weld them as fast as possible, so the welds pull against eachother.

 

[MoTiJo2023]

I find beating the weld down as it cools helps it not warp as much because done right you are stretching the weld as it attempts to shrink.

A large flat plate of steel to clamp your work to as a heat sink while welding and leaving until cooled enough to handle it bare handed helps a lot as well, but then again I avoid using anything thin enough to be a problem to begin with.

The steel i weld is mostly 3mm, sometimes 2mm

 

[Denny]

Are the m&ms plain, peanut, or almond? Let cool to touch. If round pipe I weld completely around tube one end at a time. If square tubing weld top & bottom let cool then do sides. Clamps are your friends!

 

[Scout]

Don't waste your time and money on 90 degree clamps. Is EVERYTHING going to be 90? Get some 1/4 plate and good vice grips.
You can clamp pieces at almost any angle and hold them secure while ya tack em. then follow the advice already given.

This, and I keep some heavy pieces of angle around to clamp to for 90° welds.