I suspect it wasn't so much accidental discovery as a trial and error refinement of their craft. Metalworking began long before they knew the science of it all.
History seems littered with these practical applications of phenomenon without full understanding. You can even say software development is done (programs are built and used) without true understand how to do it "correctly".
http://en.wikipedia.org/wiki/Metalworking http://www.pbs.org/wgbh/nova/samurai/ http://en.wikipedia.org/wiki/Metallurgy