From: Grant Erwin <grant@cdac.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: welding and warpage
Date: Thu, 22 Oct 1998 20:44:55 -0700

The best way to control warpage when welding is when doing the
design of the part. Think of a weld as being a shrink zone, that
pulls the part. It is often possible to design a part such that
there are opposing pull forces from the welding, that will offset.

If a flat plate is warped due to being flat welded on one side
to a long member, it will be tough duty to get it flat. Better
to weld a flat plate to a frame around the edges. If it warps
then it can be shrunk, just like tightening a drumhead. This
is very commonly done in shipbuilding.

One difficult thing to do is to put together an angle iron
framework, fit up with small gaps for better penetration, and
to weld it solidly and not have the framework pull out of
square in any direction. I have discovered that this is possible
if you make initial welds that pull frame members free ends
towards each other, then to push them apart using a portapower,
and to clamp the end piece in place and weld up leaving the
portapower in. The first welds pull against the portapower,
the cross piece can't go anywhere, and all of the welding
forces balance each other. Hmm. Harder to write about than to
do.

Grant Erwin
Seattle, Washington