I’ve used it for stainless steel, copper, brass, gold, silver,
palladium, and platinum. Its not as good with brass as it is with
the others, possibly because the zinc has such a low melting point,
but it does work.
This picture http://tinyurl.com/con2fw shows pieces of sheet silver
and 9ct gold butt welded on their edges. The photo shows an area a
little less than 8.2mm square; the silver (its on the left) is 0.57mm
thick, and the gold is 0.43mm thick.
It works, sort of, with aluminium, but the joints are not very
strong. I hope this helps.
Regards, Gary Wooding