clare at snyder.on.ca wrote

The low alloy filler draws some alloy from the base metal (tubing) and
the fillet is thicker than the substrate, so the total strength of the
"low strength" weld is equal to or superior to the base metal. The
base metal is "drawn" - it is less hard, and slightly weaker but less
prone to cracking, so you get a good, solid, reliable joint.
Cracking is extremely rare when the structure is built this way.

Thanks for that explanation. The bit about the drawing makes good sense.

Damns, now I gotta go out and find a tig welder and start practicing! g
--
Jim in NC