"Waynemak" wrote in message
...
I was told that pipe is often welded seam, while tubing is extruded as
one,
with no welds

That has nothing to do with what distinguishes tubing from pipe. Tubing
comes seamless, drawn over a mandrel, drawn over a mandrel- special smooth
ID, cold drawn butt welded and electric resistance welded. Some of these
descriptions match pipe perfectly.

It's the size of the material that determines what it is, not the method by
which it is manufactured. Both tubing and pipe are available in steel,
stainless steel and aluminum, too.

Harold