A Question for our Welder's/Fabricator's Options

[76-914]

I've been trying to figure out how you guy's deal with shrinkage. Not for body panels but just general welding. (And no, I did not shrink my car when I installed the Engman Kit) As an example, let's say I'm welding on a 10' piece of pipe that will become a stair rail. Of course it turns 90' on each end and will have flanged ends that screw to the wall. If the 90' elbows are welded on then the length of the rail will shorten "x" inches. Can this be prevented with pre heating. If so, do you apply heat to the entire piece or just where the weld will be? Do you accept that shrinkage will occur and just do not drill any matching holes until after the weld? Is there a formula that adjusts for this shrinkage? Do you bolt it in place then weld to prevent shrinkage? Also, I don't remember this being a problem with gas welding but that was years ago. My imagination or not? TIA, Kent (IMG:style_emoticons/default/beerchug.gif)

[worn]

I think you heard from the experts. The basic problem is that as the metal is joined part of it is at a high temp and thus expanded. Particularly the puddle. So thinking about it, the smaller the puddle, I.e. Smaller the weld, the less the problem. So you can anticipate it it by starting a bit long. My favorite is little tacks followed by checking measurements. That way the puddles are smaller and as you add more tacks the cooling metal cannot shrink and is forced to stretch. Eventually the majority of the weld is in the correct length and you can fill it all. I did a stair rail for my dad, but I drilled the mounting holes after the fact.