I want to weigh in on the use of copper
1) Copper is a relatively easy metal to work with and has a melting point approx. 1000 degrees LESS than that of iron (iron has to go through a smelting process to make steel)
2) One possible way they "clad" weapons and armor in copper is through electroplating which is a thin enough layer that it doesn't compromise the strength of the steel it coats.
3) Bronze is an alloy of copper and tin which was used the world over for generations, strong but simple.