Changing the recipe for hardened steel to require black ice is going to make life for people not living in the snow much harder. Black ice is mostly located in hard-to-reach areas and in extremely cold locations and requires said people to have cold armor and/or gear that they never or very rarely use. Also people that live in the southern areas are probably more than the ones in the north that use hardened steel weapons and gear
This decision is not practical, very limiting, and biased. It favors the north over the south. I suggest you remove this requirement or find an alternative solution.