Shrinkage When Welding Tubing ???

Gordon Gould · Feb 12, 2016

I am very new to stick welding. Working on my 2nd 5 lb box of 6011. I did a little project to make my learning more interesting. Might be a ahead of my ability but nothing to lose. I have a roll around work/welding cart I built with my O/A torch that I use a lot. Once in a while I wish it had a brake so I made a fold down over the center leg for a brake as a stick learning project.

I used a piece of 1/2" hydraulic tubing with an .065 wall that I had as part of the hinge. I used a 3/8" bolt as the pin thru the tubing so it was a close fit. I did some practice welds with 6013 on the tubing and didn't burn thru but the diameter shrunk so much that I couldn't come close to putting a 3/8" bolt thru it. I ended up braze welding it to keep from deforming it.

My question is this - Did this happen because it was thin walled tubing or do all circular pieces shrink when welded and if so is there a way to predict how much the diameter of the piece will change when welded ?? I was afraid to weld it with the bolt in place in fear that it would never come out.
Thanks.

gg

MMagis · Feb 12, 2016

It's more likely that it warped. All materials can warp, or shrink, when subjected to extreme temps[FONT=&quot], and a thin walled tube like that can warp quite a bit[/FONT]. I would weld it with a throw away bolt in place, and if you can get away with not welding all around it, it would help.

Edit: As mentioned, TIG would work best.

Shield Arc · Feb 12, 2016

Gordon Gould said:
Did this happen because it was thin walled tubing

Yes, and you most likely put too much heat in it when welding. A Tig rig would be very nice for projects like this.

Also tubing, be it square or round. Is very reactive to heat.

MH8675309 · Feb 12, 2016

.065 is pretty shear. Are you sure you didn't burn through a bit?

Gordon Gould · Feb 12, 2016

Thanks for the replies. This is how I learn. For my test welds I used short sections of tubing, 1" or so, and tried welding them over a 3/8 clearance hole in 1/4" bar. After welding I could not get the bolt into the unwelded end of the tube. So it either went out of round or shrunk or both. To my eye it still looked round but that doesn't mean much.

gg

Mysfyt · Feb 13, 2016

I live by the rule 'Where there is weld, there is warp'. Processes will vary, but all welds affect the base metal. I once took a piece of 3" solid square stock x 12" long (cold rolled) and welded a bead with mig across the center of the length and put it on a surface plate to show how that little bit of weld would let it 'rock' on the opposite side from the weld.