Nickel, as a pure metal, will not harden and is exceptionally resistant to rusting. It was added to steel alloys to increase resistance to rusting before stain resistant (chromium) steels were developed.
Without knowing what metals Livi is using, my guess is that the bright banding could be either a pure nickel or a nickel containing steel that gives a bright finish. If it's pure nickel, welding the patterned stuff to the back of billet and keeping the good steel at the edge is the way to do it.