"Gunner" wrote in message ...
Im curious though..when welding on a chunk of mystery steel (likely
12L something) I was getting a brown layer of soot on the work area.
What is it? What was causing it? I recall something about that in a
post before..but cannot find the reference.

This one?
http://groups.google.com/groups?selm...bk%404 ax.com
"If you are welding hot rolled metals/A36 (like angle iron) and do not
remove mill scale there is a substance which looks like rust where the
parent and weld metals join. The shielding gas will also sometimes a
brownish dust around the weld."