Question about keeping thing square when welding

[Eric M.]

I'm new to this welding stuff. I've heard that metal shrinks where it's welded. I'm trying to make a square metal frame. I'm clamping it and even tacking it to the work surface before welding. After I'm done, I pull the clamps and grind the tacks and that's where things go bad. It's no longer square.

How can I prevent this or compensate for it? Do I hammer the welds before letting the clamps loose? Should I wait longer before pulling the clamps? Should I do short welds and wait between them instead of running a complete bead?

Any ideas?

By the way, this is 16 guage, 1" square tube.


Thanks,

Eric M.

 

[LongIslander26]

Welding

Don't put too much heat in one spot for too long, and the metal shouldn't distort. There are also magnets available that are at 90 degree angles that you can use to hold the metal in place. Perhaps the metal is distorting while it's welded to the table, and that's what causing your problems, because it wants to expand with the heat and can't, because it has nowhere to go.

 

[tRustyK5]

Generally if I think it's going to pull I'll brace diagonally (using a square frame as an example). I'll leave the brace on until it has cooled completely. Beyond that you should look to have the 'pull' from one weld cancel out the 'pull' of the next. Weld one inside corner, then weld the diagonal opposite corner...kinda like you're torquing lug nuts.

Lastly, once it's all welded if it ends up a little out of square you can give it a little love with a BFH, or even your own body weight. 16 guage is thin enough tubing that you should be able to push it back to square easily enough. Every bead you make will shrink, so try to envision what that will do and where you can weld next to help cancel that out.

Managing distortion is one of the most diffcult and important parts of welding. You just have to make it work for you rather than against you.

Rene

 

[blazinzuk]

If its thin metal just tack weld until it is one continuous weld other than that, figuring out which way the metal will be pulled and then pulling it back into shape with another weld works wonders

 

[Kyle89K5]

Generally if I think it's going to pull I'll brace diagonally (using a square frame as an example). I'll leave the brace on until it has cooled completely. Beyond that you should look to have the 'pull' from one weld cancel out the 'pull' of the next. Weld one inside corner, then weld the diagonal opposite corner...kinda like you're torquing lug nuts.

Lastly, once it's all welded if it ends up a little out of square you can give it a little love with a BFH, or even your own body weight. 16 guage is thin enough tubing that you should be able to push it back to square easily enough. Every bead you make will shrink, so try to envision what that will do and where you can weld next to help cancel that out.

Managing distortion is one of the most diffcult and important parts of welding. You just have to make it work for you rather than against you.

Rene

To add a little more to what Rene said, check out this article he wrote

Welding Penetration and Distortion

 

[tRustyK5]

I forgot about that article...

Rene

 

[Kyle89K5]

I forgot about that article...

Rene

I didn't. Still a damn good article

 

[Eric M.]

Thanks guys,

I'll give it another try today with some of your suggestions and post up what worked tonight.

Eric M.

 

[Eric M.]

Soo, I lowered my voltage a bit and played with the wire speed. I tacked the inside and outside of the mitres first, then went back and welded a side at a time, but never one after the other on the same mitre, I just kept moving around the frame. I stiched the points of all the mitres. It held it's shape perfectly. I was gonna try preheating if that didn't work, but, no need to.

As for the first frame that was out of square. I clamped it square on the work surface and heated up the corners with an oxy / act. torch. I let it cool about 30 min., pulled the clamps and it kept it's shape.

I had a terrible time trying to figure out how to tack in a set of hinges while fitting a door in a frame ... I kept welding the hinge halfs together!

Thanks for the advice,

Eric M.

 

[Kiwi John]

Welding

Good article Rene.
Eric, welding is good fun. One of the secrets to good welding is the penetration. For good penetration you need heat . So practise, practise. It looks like you have a MIG and gas bottles to play with.
Ask your local fabrication shop for an armful of scrap offcuts of steel from their bin and spend a lot of time just sticking bits together. Try butt joins, T joins, overlap joins, plug weld joins ets.
One of the things i found is that all Mig welders are individual. You have to get to know your machine and understand how it works best. It's a bit like playing a trombone in that there are no fixed notes, just a combination of slider and mouthpiece.
The Mig has a combination of voltage & wire speed and you have to get the hang of what works best for what you're doing.
Like it says in the article, break youir practise joins apart to see how your penetrationgoes. Another good test is to cut the join with a hacksaw and you can see the penetration. Sorry if this is a bit long-winded, but i've seen a lot of poor welding on vehicles. Be very confident if your life depends on what you weld.