hardened iron

This alloy is in fact a hardened copper similar to bronze and not hardened iron.

There is no evidence of steel (hardened iron) production in North, Central, or South America.

At least, that's what Nylan thought smiths called narrowing the cutting edge and adding a thin layer of hardened iron/crude steel.

Around this is a layer of natural uranium to boost the yield and a second layer of hardened iron to keep the core from blowing apart prematurely.