Welding square tubing - Warping!

Hi guys, this week I finally started the summer project of building a workbench and a couple of stands for the lathe and mill. Cut all the material to size and started welding the frames up.

I'm using 50x50x2mm square tubing for all three benches. I tacked all the pieces together all round the corners (I'm tig welding) - so far so good every thing nice and square, then I started doing the full welds, and that's were it started going wrong...I tried to balance the welds doing opposite runs but still ended with a limp bench ( three legs touch the floor and one is 5mm short)

Still have two benches to go, is there anything I can do to limit warping?

Edited By ChrisB on 22/07/2017 10:33:48

FWIW... have you tried triangular fillet pieces across all corners ?...

George.

Good to know for any future projects! Will have to make do with what I have now that the rest of the material is cut and tacked!

Did not, thought about it tbh, but I reasoned the more welds I put the more heat so more chances of warping. When I tacked the whole bench together all the angles were right and it was pretty rigid. Problems started when I did the full welds. Don't know, maybe there's a sequence of how and where to weld.

I think for the next benches I will not weld all round the tube, will do but joints only and leave the corner welds out where possible as those seem to take the most heat to weld.

Edited By ChrisB on 22/07/2017 13:09:45

Welcome to the club ! Been there,done that,ruined a good tee shirt !

When I made my welding trolley, opposite sides were clamped to the substantial steel plate, that would end up on top when finished. Sash clamps were then used to hold the two sides whilst the inter-connecting pieces were installed. This seemed to minimise the amount of distortion. At least all the wheels touch the floor, (if I find a level bit )

Pete

I was given a bare 40mm box frame, effectively 4 legs going up to a pair of parallel 40mm box bars, which presumably at one time, would have held a wooden top.

It's actually very versatile left without the worktop, as I've a selection of short bits of Unistrut and associated brackets.

Since I have limited space, I've effectively got a big boys Meccano skeleton bench, to which I can attach a metal plate as an anvil, a flypress, a big vice, hydraulic ram, etc.

When you weld box section on one side only, it will pull out of shape. If you need to weld on one side only, it is best to clamp the box section to a steel beam with a packing piece under the middle of the box section so when its welded it will pull straight.

Preventing distortion is one of the biggest problems in making a weldment. Location and sequence of welding have a lot to do with how the parts will move. Unfortunately you will not know if you got it right until you are finished. If I were to make the same weldment I would add temporary diagonal bracing to prevent racking. When I put on diagonals use a small angle. Probable 1" for the size weldment you did. I would attach it with short welds, say 1" long along one leg of the angle. Even with the bracing you need to plan the sequence of welding so nthat each weld tends to distort equal and opposite to the previous weld. Once all welds are done use a crescent wrench (adjustable spanner) to twist the angle iron to break the welds. When you twist it to put the root of the wels in tension it breaks quite easily.

When I welded up the stand for my Tormach CNC mill I used 50x50x2. It was welded using oxy-acetylene. I don't recall any particular problems with distortion on the frame itself. Welding the sheet metal tanks was a different story. The fact that I've got bracing diagonals may have helped reduce distortion.

Irrepective of possible distortion adding some diagonals to your frame will effectively make the sides a truss and will considerable stiffen the frame. That means you can probably miss out some of the welds, further helping with distortion.

Andrew

You have the number 1 problem problem with welding, distortion caused by the heat from welding. Tack weld the frame first, getting it square as you tack.

Then weld it in small sections to minimize heat distortion, welding opposite corners, allowing each welding area to cool, before doing any more welding in that area.

The lighter weight the steel the greater the distortion. You will see distortion in welding steel any size. It is a Boilermakers art to minimize distoration. This may be followed by heat treatment to minimize the stresses.

Just don't rush.

Peter

Provide levelling feet. You can say they are there to account for an irregular floor. You won't have to admit to a warped weldment.

Without triangulation a welded rectangular structure is very likely to distort during welding, break out the tape measure and Porto-Power and straighten it afterwards

Thanks all for the advice, tomorrow will go at it again and do some cross bracing and take my time welding it, maybe I'll do a bench over two days rather than in one day like I did the first.

I'll have to remember to wear long sleeves next time - tig gave me quite a nasty sunburn on my arms...and the torch, it gets real hot after continuous use, so might as well let it cool down and the welds as well - should help reducing distortion! Not having had any experience with tig welding before I found it relatively easy when compared to stick or mig to produce a neat weld - I'm happy with the results so far.

Added feet to the bench afterwards, so at least the bench is no longer wobbly 

Edited By ChrisB on 23/07/2017 21:31:57

Edited By ChrisB on 23/07/2017 21:35:13

ChrisB,A number of guys mostly American produce videos on welding processes. You say you are Tig welding and using box section you may find this video useful.

http://www.weldingtipsandtricks.com/welding-distortion-tips.html

This guy has many videos which some have been useful to me.

Carl

Found the pics I wanted,

Back in 2012 I decided to scrap a 2 meters between centers TOS lathe for a few reasons the main ones being it was taking a lot of space up, it had some wear and it was attracting the wrong sort of work [ 1 tonne armatures etc ] when it was working which wasn't often.

Once I had started on the project it soon became obvious what the "it will come in handy one day" was.

Virtually all this had been there that long I had no idea it was there so it got skipped.

Machine dragged out and loaded up for a trip to its new home.

The scrapyard.

Which left this.

So once the cupboards had been scrapped, racks moved,  we got to the relevant part for this post.

3 metre long bench out of 40 x 40 x 3 stick welded with a crappy buzzbox as I couldn't get any of the hard wired Migs into this shop.

And I finished up with this,

Laser cutter on one end, bolt rack on the other and space for two working small CNC's with the keyboards on slide out trays on top of the toolboxes. Various metal short end drawers at one end, wall painted and all new electrics plumbed in. Unfortunately it has got to come out in the grand down size and it won't go in the new shed in one piece so I reckon a quick chop with a 1mm slitting wheel where it changes from cupboards to open space where the tool boxes fit, move in two pieces and stitch back together again and a swift repaint to credit a brand new workshop

Edited By John Stevenson on 24/07/2017 21:13:14

John,

Why have your pictures been censored?

bear..

Nice work there John, hope mine will look something similar when ready! Took a day off the workshop today - too hot to work with 34+ temperatures (now how am I to convince the miss we need ac in the garage!  

Good tips on that clip Carl will definitely take them on. At the moment I don't have much to work with, the workshop/garage is empty so I'm working on a make shift bench (aka Lidl foldable ladders) and basic tooling. Although the first bench warped a bit, I'm not to worried about it as its just the workbench, but the others will take the lathe and mill, so I'd like to keep distortion to a minimum, hopefully I'll manage if I do it slowly and space out the welds.

A question re Tig, on most photos I see shiny nice welds, where as mine are all dull blue grey in colour, am I doing something wrong? I'm using 1.6mm red tungsten with a no 6 nozzle at 7L/m argon flow and a 2mm filler rod where the gap is a bit wide. Where there's no gap I just fuse the base metals.

I can see them pictures... 

Edited By ChrisB on 24/07/2017 21:38:33

So can I, I reckon Grizzly bear has done himself a favour if he can't